ENGINEERED POLYMERASES

WITH IMPROVED THERMAL STABILITY

[0001] Throughout this application various publications, patents, and/or patent applications are referenced. The disclosures of the publications, patents and/or patent applications are hereby incorporated by reference in their entireties into this application in order to more fully describe the state of the art to which this disclosure pertains.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and benefit of U.S. Provisional Application Nos.: 63/351,294, filed June 10, 2022; 63/422,855, filed November 4, 2023; and 63/491,374, filed March 21, 2023; the entire disclosures of which are hereby incorporated by reference in their entireties.

SEQUENCE LISTING

[0003] The instant application contains a Sequence Listing, which has been submitted electronically in XML format and is hereby incorporated by reference in its entirety. Said XML copy, created on June 7, 2023, is named 55744WO_CRF_sequencelistingand is 5,651 kilobytes in size.

TECHNICAL FIELD

[0004] The present disclosure provides mutant polymerases that are engineered for improved thermal stability, exhibit improved binding of nucleotide reagents and/or improved binding and incorporation of nucleotide reagents, improved uracil-tolerance and/or reduced sequence-specific sequencing errors. Exemplary nucleotide reagents include detectably labeled nucleotides, non-labeled nucleotides, nucleotides comprising a 3’ chain terminating moiety, phosphate chain-labeled nucleotides, and multivalent molecules. In some embodiments, the engineered polymerases exhibit reduced transitioning from nucleotide polymerization conformation to exonuclease conformation. The mutant polymerases exhibit increased incorporation rate, compared to wild type polymerases.

BACKGROUND

[0005] Next-generation sequencing (NGS) techniques have become a powerful tool for acquiring sequencing data used in molecular biology techniques, taxonomy, agriscience, medical diagnostics, and the development of new therapies. The present disclosure provides engineered polymerase that are useful for conducting any nucleic acid sequencing method that employs labeled or non-labeled chain terminating nucleotides, where the chain terminating nucleotides include a 3’-O-azido group (or 3’-O-methylazido group) or any other type of bulky blocking group at the sugar 3’ position. For example, the engineered polymerases can be used to conduct sequencing-by-avidity methods (SB A) using labeled multivalent molecules and non-labeled chain terminating nucleotides. Additionally, the engineered polymerases can be used for conducting sequencing-by-synthesis (SBS) methods which employ labeled chain-terminating nucleotides, and for conducting sequencing-by- binding methods (SBB) which employ non-labeled chain-terminating nucleotides.

[0006] The addition of a single nucleotide to a strand of DNA alone does not produce enough signal to easily detect. Currently available SBS technologies overcome this problem by increasing the signal to noise of the nucleotide addition coupled to a detection method with sufficient sensitivity to make an accurate base call. The most commercially successful platforms employ monoclonal template DNA amplification in a spatially constrained matrix to generate discrete DNA islands that contain multiple copies of a sequence to interrogate. The result of this amplification is a “colony” of DNA copies such that addition of a single DNA base on all of the copies concentrates the detection modality in a manner sufficient to overcome the signal to noise problem. The sequencing of multiple spatially constrained identical copies of DNA further increases the reliance on a controlled stepping mechanism to ensure that one, and only one, nucleotide bases can be added to ensure that all of the copies within a DNA colony remain at the same position (N, N+l, N+2, N+3,etc. . .) relative to each other.

[0007] The molecular engine needed to perform SBS is a DNA polymerase. In vivo, this class of enzymes is responsible for DNA replication and maintaining genome integrity. Under native conditions DNA dependent DNA polymerases (dDdP’s) catalyze the addition of deoxynucleotide triphosphates (dNTP) to DNA in a 5’ to 3’ direction creating phosphodiester bonds between the 3’ hydroxyl of the primer DNA terminus and the 5’ alpha phosphate of the incoming nucleotide. This chemistry occurs with high fidelity for the correct Watson-Crick base pair due to hydrogen bonding between the correct incoming dNTP and the templating base. This “correct” base pairing induces a conformational change in the enzyme that aligns catalytic amino acids to efficiently perform phosphodiester bond formation. The newly added dNTP also possesses a 3 ’OH which is used in the next round of catalysis to further extend the DNA strand. [0008] To ensure that only a single dNTP is added to the growing strands of DNA per SBS cycle a reversibly terminated dNTP is employed. These bases contain modifications to the 3’ hydroxyl of the dNTP that block subsequent rounds of incorporation. The most commercially successful reversible terminator is the 3’ methylazido, however others including 3 ’-aminoallyl, and 3’ oxyamine has also been used. Each of these reversibly terminated dNTPs function in the same manner; once incorporated the bulky 3’ block inhibits addition of the next nucleotide because no 3’ hydroxyl is present. When exposed to a catalyst, the 3’ block reacts to re-generate a 3’ hydroxyl capable of forming a new phosphodiester bond during the next cycle. While effective, these bulky 3’ modifications present a challenge for the polymerase.

[0009] The evolutionary need for high fidelity genome replication and stability has resulted in polymerases that only incorporate a non-Watson-Crick base pair in every 10 ⁴ - 10 ⁷ incorporation events. Polymerases often also need to discriminate between vast excesses of nucleotides in the cellular environment. Discrimination between nucleotides is typically done through a steric gate where the presence of a 2’hydroxyl sterically clashes with an amino acid side chain at the nucleotide binding site to select against nucleotide binding and catalysis. Additionally, damage or modification to the 3’ hydroxyl of the nucleotide is also sensed by the enzyme because bases containing non-viable 3’ hydroxyls can act as chain terminators that inhibit DNA synthesis. Discrimination of these unwanted bases occurs through a kinetic pathway where incorrect nucleotide substrates bind with a weaker overall affinity and phosphodiester bond formation occurs at rates 10 ² - 10 ⁴ orders of magnitude more slowly. This occurs due to the lack of an induced fit that would properly align catalytic amino acids for bond formation. As a result, naturally evolved polymerases incorporate reversible chainterminator nucleotides poorly.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The novel advantages and features of the compositions and methods disclosed herein are set forth with particularity in the appended claims. A better understanding of the features and advantages of the compositions and methods of the present disclosure will be obtained by reference to the following detailed description that sets forth illustrative embodiments and the accompanying drawings of which:

[0011] FIG. 1 is a schematic of an exemplary low binding support comprising a glass substrate and alternating layers of hydrophilic coatings which are covalently or non- covalently adhered to the glass, and which further comprises chemi cally-reactive functional groups that serve as attachment sites for oligonucleotide primers (e.g., capture oligonucleotides). In an alternative embodiment, the support can be made of any material such as glass, plastic or a polymer material.

[0012] FIG. 2 is a schematic of various exemplary configurations of multivalent molecules. Left (Class I): schematics of multivalent molecules having a “starburst” or “helter-skelter” configuration. Center (Class II): a schematic of a multivalent molecule having a dendrimer configuration. Right (Class III): a schematic of multiple multivalent molecules formed by reacting streptavidin with 4-arm or 8-arm PEG-NHS with biotin and dNTPs. Nucleotide units are designated ‘N’, biotin is designated ‘B’, and streptavidin is designated ‘SA’.

[0013] FIG. 3 is a schematic of an exemplary multivalent molecule comprising a generic core attached to a plurality of nucleotide-arms.

[0014] FIG. 4 is a schematic of an exemplary multivalent molecule comprising a dendrimer core attached to a plurality of nucleotide-arms.

[0015] FIG. 5 shows a schematic of an exemplary multivalent molecule comprising a core attached to a plurality of nucleotide-arms, where the nucleotide arms comprise biotin, spacer, linker and a nucleotide unit.

[0016] FIG. 6 is a schematic of an exemplary nucleotide-arm comprising a core attachment moiety, spacer, linker and nucleotide unit.

[0017] FIG. 7 shows the chemical structure of an exemplary spacer (TOP), and the chemical structures of various exemplary linkers, including an 11 -atom Linker, 16-atom Linker, 23 -atom Linker and an N3 Linker (BOTTOM)

[0018] FIG. 8 shows the chemical structures of various exemplary linkers, including Linkers 1-9.

[0019] FIG. 9A shows the chemical structures of various exemplary linkers joined/ attached to nucleotide units.

[0020] FIG. 9B shows the chemical structures of various exemplary linkers joined/attached to nucleotide units.

[0021] FIG. 9C shows the chemical structures of various exemplary linkers joined/attached to nucleotide units.

[0022] FIG. 9D shows the chemical structures of various exemplary linkers joined/attached to nucleotide units. [0023] FIG. 10 shows the chemical structure of an exemplary biotinylated nucleotide-arm. In this example, the nucleotide unit is connected to the linker via a propargyl amine attachment at the 5 position of a pyrimidine base or the 7 position of a purine base.

[0024] FIG. 11 is the amino acid sequence of a wild DNA polymerase having a backbone sequence from RLF 89458.1 (SEQ ID NO:1).

[0025] FIG. 12 is the amino acid sequence of a wild DNA polymerase having a backbone sequence from RLF 78286.1 (SEQ ID NO:2).

[0026] FIG. 13 is the amino acid sequence of a wild DNA polymerase having a backbone sequence from NOZ 58130.1 (SEQ ID NO: 1714).

[0027] FIG. 14 is the amino acid sequence of a wild type DNA polymerase having a backbone sequence from RMF 90817.1 (SEQ ID NO:2789).

[0028] FIG. 15 is the amino acid sequence of a wild type DNA polymerase having a backbone sequence from MBC 7218772.1 (SEQ ID NO:2790).

[0029] FIG. 16 is the amino acid sequence of a wild type DNA polymerase having a backbone sequence from WP 175059460.1 (SEQ ID NO:2791).

[0030] FIG. 17 is the amino acid sequence of a wild type DNA polymerase having a backbone sequence from KUO 42443.1 (SEQ ID NO:2792).

[0031] FIG. 18 is the amino acid sequence of a wild DNA polymerase having a backbone sequence from NOZ 77387.1 (SEQ ID NO:2793).

[0032] FIG. 19 is the amino acid sequence of a wild type DNA polymerase having a backbone sequence from Geobacillus stearotherm ophilus (Bst polymerase) (SEQ ID NO:2794).

[0033] FIG. 20 is the amino acid sequence of a 9 °N polymerase (SEQ ID NO:2795).

[0034] FIG. 21 is the amino acid sequence of a 9 °N polymerase UniProt Q56366 (SEQ ID NO:2796).

[0035] FIG. 22 is the amino acid sequence of THERMINATOR polymerase (SEQ ID NO:2797).

[0036] FIG. 23 is the amino acid sequence of a VENT polymerase UniProt P30317 (SEQ ID NO:2798).

[0037] FIG. 24 is the amino acid sequence of a DEEP VENT polymerase UniProt Q51334 (SEQ ID NO:2799).

[0038] FIG. 25 is the amino acid sequence of a Pfu polymerase UniProt P61875 (SEQ ID N0:2800). [0039] FIG. 26 is the amino acid sequence of a Pyrococcus abyssi polymerase UniProt P0CL77 (SEQ ID NO:2801).

[0040] FIG. 27 is the amino acid sequence of an RB69 polymerase (SEQ ID NO:2802). [0041] FIG. 28 is the amino acid sequence of a Phi29 polymerase (SEQ ID NO:2803). [0042] FIG. 29 shows the amino acid sequences of domains of an RLF 89458.1 polymerase.

[0043] FIG. 30 shows the amino acid sequences of domains of a NOZ 58130.1 polymerase.

[0044] FIG. 31 (115 sheets) is Table 1 which lists the protein unfolding transition temperature of Tml and Tm2 (in °C), and activity, of mutant variants (SEQ ID NOS:3-1713) having a backbone sequence of RLF 89458.1 and carrying mutation substitution sites. In Table 1, a truncation is designated with a “ ^A ”. In Table 1, a deleted amino acid is designated with an “X”. In Table 1, in inserted amino acid is designated with “[insert X after P411]” where X is a single letter amino acid code.

[0045] FIG. 32 (68 sheets) is Table 2 which lists the protein unfolding transition temperature of Tml and Tm2 (in °C), and activity, of mutant variants (SEQ ID NOS: 1715- 2787) having a backbone sequence of NOZ 58130.1 and carrying mutation substitution sites. In Table 2, a truncation is designated with a “ ^A ”. In Table 2, a deleted amino acid is designated with an “X”. In Table 2, a deleted portion is designated with “[delete . . .]” where the deleted portion is indicated with a single letter amino acid code.

[0046] FIG. 33 (5 sheets) shows amino acid sequence alignments of DNA polymerases from: RLF 89458.1 (SEQ ID NO:1); WP 175059460 (SEQ ID NO:2791); MBC 7218772 (SEQ ID NO:2790); KUO 42443 (SEQ ID NO:2792); NOZ 58130 (SEQ ID NO: 1714); RMF 90817 (SEQ ID NO:2789); and NOZ 77387 (SEQ ID NO:2793).

[0047] FIG. 34 (5 sheets) shows amino acid sequence alignments of DNA polymerases from: RLF 89458.1 (SEQ ID NO: 1); Geobacillus stearothermophilus (Bst polymerase) (SEQ ID NO:2794); 9°N (SEQ ID NO:2795); Pfu polymerase (SEQ ID N0:2800); and Pyrococcus abyssi polymerase (SEQ ID NO:2801).

[0048] FIG. 35 (5 sheets) shows amino acid sequence alignments of DNA polymerases from: NOZ 58130 (SEQ ID NO: 1714); Geobacillus stearothermophilus (Bst polymerase) (SEQ ID NO:2794); 9°N (SEQ ID NO:2795); Pfu polymerase (SEQ ID N0:2800); and Pyrococcus abyssi polymerase (SEQ ID NO:2801).

[0049] FIG. 36 (5 sheets) shows amino acid sequence alignments of DNA polymerases from: RMF 90817 (SEQ ID NO:2789); Geobacillus stearothermophilus (Bst polymerase) (SEQ ID NO:2794); 9°N (SEQ ID NO:2795); Pfu polymerase (SEQ ID N0:2800); and Pyrococcus abyssi polymerase (SEQ ID NO:2801).

[0050] FIG. 37 (5 sheets) shows amino acid sequence alignments of DNA polymerases from: MBC 7218772 (SEQ ID NO:2790); Geobacillus stearothermophilus (Bst polymerase) (SEQ ID NO:2794); 9°N (SEQ ID NO:2795); Pfu polymerase (SEQ ID N0:2800); and Pyrococcus abyssi polymerase (SEQ ID NO:2801).

[0051] FIG. 38 (5 sheets) shows amino acid sequence alignments of DNA polymerases from: WP 175059460 (SEQ ID NO:2791); Geobacillus stearothermophilus (Bst polymerase) (SEQ ID NO:2794); 9°N (SEQ ID NO:2795); Pfu polymerase (SEQ ID N0:2800); and Pyrococcus abyssi polymerase (SEQ ID NO:2801).

[0052] FIG. 39 (5 sheets) shows amino acid sequence alignments of DNA polymerases from: KUO 42443 (SEQ ID NO:2792); Geobacillus stearothermophilus (Bst polymerase) (SEQ ID NO:2794); 9°N (SEQ ID NO:2795); Pfu polymerase (SEQ ID N0:2800); and Pyrococcus abyssi polymerase (SEQ ID NO:2801).

[0053] FIG. 40 (5 sheets) shows amino acid sequence alignments of DNA polymerases from: NOZ 77387 (SEQ ID NO:2793); Geobacillus stearothermophilus (Bst polymerase) (SEQ ID NO:2794); 9°N (SEQ ID NO:2795); Pfu polymerase (SEQ ID N0:2800); and Pyrococcus abyssi polymerase (SEQ ID NO:2801).

[0054] FIG. 41 is a schematic showing a predicted three-dimensional ribbon model of wild type polymerase RLF 89458.1 (SEQ ID NO: 1) with an N-terminal His-tag. The ribbon model includes predicted positions of post-translational modification at certain amino acid residues. The ribbon model is based on mass spectrometry data.

[0055] FIG. 42 is a schematic showing a predicted three-dimensional ribbon model of wild type polymerase NOZ 58130.1 (SEQ ID NO: 1714) with an N-terminal His-tag. The ribbon model includes predicted positions of post-translational modification at certain amino acid residues. The ribbon model is based on mass spectrometry data.

[0056] FIG. 43 is a graph showing the % error for a 150 cycle sequencing run of a nucleic acid library prepared from E. coli DNA.

[0057] FIG. 44 is a schematic of an exemplary immobilized nucleic acid template molecule hybridized to a first and a second nucleic acid primer. The nucleic acid template molecule shown in FIG. 44 comprises a concatemer which is hybridized with a plurality of nucleic acid primers.

[0058] FIG. 45 is a schematic of exemplary complexed polymerases indicated by the dashed circles, where individual complexed polymerases comprise a DNA polymerase bound to nucleic acid duplex, where each duplex comprises a nucleic acid template hybridized to a nucleic acid primer.

[0059] FIG. 46 is a schematic of an exemplary first binding complex (e.g., indicated by a dashed circle) comprising a first nucleic acid primer, a first DNA polymerase, and a first multivalent molecule bound to a first portion of a concatemer template molecule thereby forming a first binding complex. FIG. 46 also shows a plurality of multivalent molecules that are not part of the first binding complex.

[0060] FIG. 47 is a schematic of an exemplary avidity complex (e.g., indicated by a dashed circle) comprising (i) a first binding complex which comprises a first nucleic acid primer, a first DNA polymerase, and a first multivalent molecule bound to a first portion of a concatemer template molecule thereby forming a first binding complex, wherein a first nucleotide unit of the multivalent molecule is bound to the first DNA polymerase, and (ii) the second binding complex which comprises a second nucleic acid primer, a second DNA polymerase, and the same first multivalent molecule bound to a second portion of the same concatemer template molecule thereby forming a second binding complex, wherein a second nucleotide unit of the multivalent molecule is bound to the second DNA polymerase, and wherein the first and second binding complexes which include the same multivalent molecule forms an avidity complex.

DETAILED DESCRIPTION

[0061] Definitions:

[0062] The headings provided herein are not limitations of the various aspects of the disclosure, which aspects can be understood by reference to the specification as a whole. [0063] Unless defined otherwise, technical and scientific terms used herein have meanings that are commonly understood by those of ordinary skill in the art unless defined otherwise. Generally, terminologies pertaining to techniques of molecular biology, nucleic acid chemistry, protein chemistry, genetics, microbiology, transgenic cell production, and hybridization described herein are those well-known and commonly used in the art. Techniques and procedures described herein are generally performed according to conventional methods well known in the art and as described in various general and more specific references that are cited and discussed throughout the instant specification. For example, see Sambrook et al., Molecular Cloning: A Laboratory Manual (Third ed., Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y. 2000). See also Ausubel et al., Current Protocols in Molecular Biology, Greene Publishing Associates (1992). The nomenclatures utilized in connection with, and the laboratory procedures and techniques described herein are those well-known and commonly used in the art.

[0064] Unless otherwise required by context herein, singular terms shall include pluralities and plural terms shall include the singular. Singular forms “a”, “an” and “the”, and singular use of any word, include plural referents unless expressly and unequivocally limited on one referent.

[0065] It is understood the use of the alternative term (e.g., “or”) is taken to mean either one or both or any combination thereof of the alternatives.

[0066] The term “and/or” used herein is to be taken mean specific disclosure of each of the specified features or components with or without the other. For example, the term “and/or” as used in a phrase such as “A and/or B” herein is intended to include: “A and B”; “A or B”; “A” (A alone); and “B” (B alone). In a similar manner, the term “and/or” as used in a phrase such as “A, B, and/or C” is intended to encompass each of the following aspects: “A, B, and C”; “A, B, or C”; “A or C”; “A or B”; “B or C”; “A and B”; “B and C”; “A and C”; “A” (A alone); “B” (B alone); and “C” (C alone).

[0067] As used herein and in the appended claims, terms “comprising”, “including”, “having” and “containing”, and their grammatical variants, as used herein are intended to be non-limiting so that one item or multiple items in a list do not exclude other items that can be substituted or added to the listed items. It is understood that wherever aspects are described herein with the language “comprising,” otherwise analogous aspects described in terms of “consisting of’ and/or “consisting essentially of’ are also provided.

[0068] As used herein, the terms “about” and “approximately” refer to a value or composition that is within an acceptable error range for the particular value or composition as determined by one of ordinary skill in the art, which will depend in part on how the value or composition is measured or determined, i.e., the limitations of the measurement system. For example, “about” or “approximately” can mean within one or more than one standard deviation per the practice in the art. Alternatively, “about” or “approximately” can mean a range of up to 10% (i.e., ±10%) or more depending on the limitations of the measurement system. For example, about 5 mg can include any number between 4.5 mg and 5.5 mg.

Furthermore, particularly with respect to biological systems or processes, the terms can mean up to an order of magnitude or up to 5-fold of a value. When particular values or compositions are provided in the instant disclosure, unless otherwise stated, the meaning of “about” or “approximately” should be assumed to be within an acceptable error range for that particular value or composition. Also, where ranges and/or subranges of values are provided, the ranges and/or subranges can include the endpoints of the ranges and/or subranges.

[0069] The terms "peptide", "polypeptide" and "protein" and other related terms used herein are used interchangeably and refer to a polymer of amino acids and are not limited to any particular length. Polypeptides may comprise natural and non-natural amino acids. Polypeptides include recombinant or chemically-synthesized forms. Polypeptides also include precursor molecules that have not yet been subjected to post-translation modification such as proteolytic cleavage, cleavage due to ribosomal skipping, hydroxylation, methylation, lipidation, acetylation, SUMOylation, ubiquitination, glycosylation, phosphorylation and/or disulfide bond formation. These terms encompass native and artificial proteins, protein fragments and polypeptide analogs (such as muteins, variants, chimeric proteins and fusion proteins) of a protein sequence as well as post-translationally, or otherwise covalently or non- covalently, modified proteins.

[0070] The term “polymerase” and its variants, as used herein, comprises any enzyme that can catalyze polymerization of nucleotides (including analogs thereof) into a nucleic acid strand. Typically but not necessarily such nucleotide polymerization can occur in a templatedependent fashion. Typically, a polymerase comprises one or more active sites at which nucleotide binding and/or catalysis of nucleotide polymerization can occur. In some embodiments, a polymerase includes other enzymatic activities, such as for example, 3' to 5' exonuclease activity or 5' to 3' exonuclease activity. In some embodiments, a polymerase has strand displacing activity. A polymerase can include without limitation naturally occurring polymerases and any subunits and truncations thereof, mutant polymerases, variant polymerases, recombinant, fusion or otherwise engineered polymerases, chemically modified polymerases, synthetic molecules or assemblies, and any analogs, derivatives or fragments thereof that retain the ability to catalyze nucleotide polymerization (e.g., catalytically active fragment). In some embodiments, a polymerase can be isolated from a cell, or generated using recombinant DNA technology or chemical synthesis methods. In some embodiments, a polymerase can be expressed in prokaryote, eukaryote, viral, or phage organisms. In some embodiments, a polymerase can be post-translationally modified proteins or fragments thereof. A polymerase can be derived from a prokaryote, eukaryote, virus or phage. A polymerase comprises DNA-directed DNA polymerase and RNA-directed DNA polymerase. [0071] As used herein, the term “fidelity” refers to the accuracy of DNA polymerization by template-dependent DNA polymerase. The fidelity of a DNA polymerase is typically measured by the error rate (the frequency of incorporating an inaccurate nucleotide, i.e., a nucleotide that is not complementary to the template nucleotide). The accuracy or fidelity of DNA polymerization is maintained by both the polymerase activity and the 3 '-5' exonuclease activity of a DNA polymerase.

[0072] As used herein, the term “binding complex” refers to a complex formed by binding together a nucleic acid duplex, a polymerase, and a free nucleotide or a nucleotide unit of a multivalent molecule, where the nucleic acid duplex comprises a nucleic acid template molecule hybridized to a nucleic acid primer. In the binding complex, the free nucleotide or nucleotide unit may or may not be bound to the 3’ end of the nucleic acid primer at a position that is opposite a complementary nucleotide in the nucleic acid template molecule. A “ternary complex” is an example of a binding complex which is formed by binding together a nucleic acid duplex, a polymerase, and a free nucleotide or nucleotide unit of a multivalent molecule, where the free nucleotide or nucleotide unit is bound to the 3’ end of the nucleic acid primer (as part of the nucleic acid duplex) at a position that is opposite a complementary nucleotide in the nucleic acid template molecule.

[0073] The term “persistence time” and related terms refers to the length of time that a binding complex remains stable without dissociation of any of the components, where the components of the binding complex include a nucleic acid template and nucleic acid primer, a polymerase, a nucleotide unit of a multivalent molecule or a free (e.g., unconjugated) nucleotide. The nucleotide unit or the free nucleotide can be complementary or non- complementary to a nucleotide residue in the template molecule. The nucleotide unit or the free nucleotide can bind to the 3’ end of the nucleic acid primer at a position that is opposite a complementary nucleotide residue in the nucleic acid template molecule. The persistence time is indicative of the stability of the binding complex and strength of the binding interactions. Persistence time can be measured by observing the onset and/or duration of a binding complex, such as by observing a signal from a labeled component of the binding complex. For example, a labeled nucleotide or a labeled reagent comprising one or more nucleotides may be present in a binding complex, thus allowing the signal from the label to be detected during the persistence time of the binding complex. One exemplary label is a fluorescent label. The binding complex (e.g., ternary complex) remains stable until subjected to a condition that causes dissociation of interactions between any of the polymerase, template molecule, primer and/or the nucleotide unit or the nucleotide. For example, a dissociating condition comprises contacting the binding complex with any one or any combination of a detergent, EDTA and/or water. [0074] The terms “nucleic acid”, "polynucleotide" and "oligonucleotide" and other related terms used herein are used interchangeably and refer to polymers of nucleotides and are not limited to any particular length. Nucleic acids include recombinant and chemically- synthesized forms. Nucleic acids include DNA molecules (e.g., cDNA or genomic DNA), RNA molecules (e.g., mRNA), analogs of the DNA or RNA generated using nucleotide analogs (e.g., peptide nucleic acids and non-naturally occurring nucleotide analogs), and chimeric forms containing DNA and RNA. Nucleic acids can be single-stranded or doublestranded. Nucleic acids comprise polymers of nucleotides, where the nucleotides include natural or non-natural bases and/or sugars. Nucleic acids comprise naturally-occurring internucleosidic linkages, for example phosphdiester linkages. Nucleic acids comprise nonnatural internucleoside linkages, including phosphorothioate, phosphorothiolate, or peptide nucleic acid (PNA) linkages. In some embodiments, nucleic acids comprise a one type of polynucleotides or a mixture of two or more different types of polynucleotides.

[0075] The term “primer” and related terms used herein refers to an oligonucleotide, either natural or synthetic, that is capable of hybridizing with a DNA and/or RNA polynucleotide template to form a duplex molecule. Primers may have any length, but typically range from 4-50 nucleotides. A typical primer comprises a 5’ end and 3’ end. The 3’ end of the primer can include a 3’ OH moiety which serves as a nucleotide polymerization initiation site in a polymerase-mediated primer extension reaction. Alternatively, the 3’ end of the primer can lack a 3’ OH moiety, or can include a terminal 3’ blocking group that inhibits nucleotide polymerization in a polymerase-mediated reaction. Any one nucleotide, or more than one nucleotide, along the length of the primer can be labeled with a detectable reporter moiety. A primer can be in solution (e.g., a soluble primer) or can be immobilized to a support (e.g., a capture primer).

[0076] The term “template nucleic acid”, “template polynucleotide”, “target nucleic acid” “target polynucleotide”, “template strand” and other variations refer to a nucleic acid strand that serves as the basis nucleic acid molecule for generating a complementary nucleic acid strand. The sequence of the template nucleic acid can be partially or wholly complementary to the sequence of the complementary strand. The template nucleic acid can be obtained from a naturally-occurring source, recombinant form, or chemically synthesized to include any type of nucleic acid analog. The template nucleic acid can be linear, circular, or other forms. The template nucleic acids can be isolated in any form, including chromosomal, genomic, organellar (e.g., mitochondrial, chloroplast or ribosomal), recombinant molecules, cloned, amplified, cDNA, RNA such as precursor mRNA or mRNA, oligonucleotides, whole genomic DNA, obtained from fresh frozen paraffin embedded tissue, needle biopsies, cell free circulating DNA, or any type of nucleic acid library. The template nucleic acid molecules may be isolated from any source including from organisms such as prokaryotes, eukaryotes (e.g., humans, plants and animals), fungus, and viruses; cells; tissues; normal or diseased cells or tissues, body fluids including blood, urine, serum, lymph, tumor, saliva, anal and vaginal secretions, amniotic samples, perspiration, and semen; environmental samples; culture samples; or synthesized nucleic acid molecules prepared using recombinant molecular biology or chemical synthesis methods. The template nucleic acid can be subjected to nucleic acid analysis, including sequencing and composition analysis.

[0077] When used in reference to nucleic acid molecules, the terms “hybridize” or “hybridizing” or “hybridization” or other related terms refers to hydrogen bonding between two different nucleic acids to form a duplex nucleic acid. Hybridization also includes hydrogen bonding between two different regions of a single nucleic acid molecule to form a self-hybridizing molecule having a duplex region. Hybridization can comprise Watson-Crick or Hoogstein binding to form a duplex double-stranded nucleic acid, or a double-stranded region within a nucleic acid molecule. The double-stranded nucleic acid, or the two different regions of a single nucleic acid, may be wholly complementary, or partially complementary. Complementary nucleic acid strands need not hybridize with each other across their entire length. The complementary base pairing can be the standard A-T or C-G base pairing, or can be other forms of base-pairing interactions. Duplex nucleic acids can include mismatched base-paired nucleotides.

[0078] The term “nucleotides” and related terms refers to a molecule comprising an aromatic base, a five carbon sugar (e.g., ribose or deoxyribose), and at least one phosphate group. Canonical or non-canonical nucleotides are consistent with use of the term. The phosphate in some embodiments comprises a monophosphate, diphosphate, or triphosphate, or corresponding phosphate analog. In some embodiments, the nucleotide comprises 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 phosphate groups. The term “nucleoside” refers to a molecule comprising an aromatic base and a sugar.

[0079] Nucleotides (and nucleosides) typically comprise a hetero cyclic base including substituted or unsubstituted nitrogen-containing parent heteroaromatic ring which are commonly found in nucleic acids, including naturally-occurring, substituted, modified, or engineered variants, or analogs of the same. The base of a nucleotide (or nucleoside) is capable of forming Watson-Crick and/or Hoogstein hydrogen bonds with an appropriate complementary base. Exemplary bases include, but are not limited to, purines and pyrimidines such as: 2-aminopurine, 2,6-diaminopurine, adenine (A), ethenoadenine, N ⁶ -A ² - isopentenyladenine (6iA), N ⁶ -A ² -isopentenyl-2-methylthioadenine (2ms6iA), N ⁶ - methyladenine, guanine (G), isoguanine, N ² -dimethylguanine (dmG), 7-methylguanine (7mG), 2-thiopyrimidine, 6-thioguanine (6sG), hypoxanthine and O ⁶ -methylguanine; 7- deaza-purines such as 7-deazaadenine (7-deaza-A) and 7-deazaguanine (7-deaza-G); pyrimidines such as cytosine (C), 5-propynylcytosine, isocytosine, thymine (T), 4- thiothymine (4sT), 5,6-dihydrothymine, O ⁴ -methylthymine, uracil (U), 4-thiouracil (4sU) and 5,6-dihydrouracil (dihydrouracil; D); indoles such as nitroindole and 4-methylindole; pyrroles such as nitropyrrole; nebularine; inosines; hydroxymethylcytosines; 5-methycytosines; base (Y); as well as methylated, glycosylated, and acylated base moieties; and the like. Additional exemplary bases can be found in Fasman, 1989, in “Practical Handbook of Biochemistry and Molecular Biology”, pp. 385-394, CRC Press, Boca Raton, Fla.

[0080] Nucleotides (and nucleosides) typically comprise a sugar moiety, such as carbocyclic moiety (Ferraro and Gotor 2000 Chem. Rev. 100: 4319-48), acyclic moieties (Martinez, et al., 1999 Nucleic Acids Research 27: 1271-1274; Martinez, et al., 1997 Bioorganic & Medicinal Chemistry Letters vol. 7: 3013-3016), and other sugar moieties (Joeng, et al., 1993 J. Med. Chem. 36: 2627-2638; Kim, et al., 1993 J. Med. Chem. 36: 30-7; Eschenmosser 1999 Science 284:2118-2124; and U.S. Pat. No. 5,558,991). The sugar moiety comprises: ribosyl; 2'-deoxyribosyl; 3 '-deoxyribosyl; 2', 3 '-dideoxyribosyl; 2', 3'- didehydrodideoxyribosyl; 2'-alkoxyribosyl; 2'-azidoribosyl; 2'-aminoribosyl; 2'-fluororibosyl; 2'-mercaptoriboxyl; 2'-alkylthioribosyl; 3 '-alkoxyribosyl; 3 '-azidoribosyl; 3 '-aminoribosyl; 3'- fluororibosyl; 3'-mercaptoriboxyl; 3 '-alkylthioribosyl carbocyclic; acyclic or other modified sugars.

[0081] In some embodiments, nucleotides comprise a chain of one, two or three phosphorus atoms where the chain is typically attached to the 5’ carbon of the sugar moiety via an ester or phosphoramide linkage. In some embodiments, the nucleotide is an analog having a phosphorus chain in which the phosphorus atoms are linked together with intervening O, S, NH, methylene or ethylene. In some embodiments, the phosphorus atoms in the chain include substituted side groups including O, S or BH3. In some embodiments, the chain includes phosphate groups substituted with analogs including phosphoramidate, phosphorothioate, phosphordithioate, and O-methylphosphoroamidite groups.

[0082] When used in reference to nucleic acids, the terms “extend”, “extending”, “extension” and other variants, refers to incorporation of one or more nucleotides into a nucleic acid molecule. Nucleotide incorporation comprises polymerization of one or more nucleotides into the terminal 3’ OH end of a nucleic acid strand, resulting in extension of the nucleic acid strand. Nucleotide incorporation can be conducted with natural nucleotides and/or nucleotide analogs. Typically, but not necessarily, nucleotide incorporation occurs in a template-dependent fashion. Any suitable method of extending a nucleic acid molecule may be used, including primer extension catalyzed by a DNA polymerase or RNA polymerase. [0083] The term “reporter moiety”, “reporter moieties” or related terms refers to a compound that generates, or causes to generate, a detectable signal. A reporter moiety is sometimes called a “label”. Any suitable reporter moiety may be used, including luminescent, photoluminescent, electroluminescent, bioluminescent, chemiluminescent, fluorescent, phosphorescent, chromophore, radioisotope, electrochemical, mass spectrometry, Raman, hapten, affinity tag, atom, or an enzyme. A reporter moiety generates a detectable signal resulting from a chemical or physical change (e.g., heat, light, electrical, pH, salt concentration, enzymatic activity, or proximity events). A proximity event includes two reporter moieties approaching each other, or associating with each other, or binding each other. It is well known to one skilled in the art to select reporter moieties so that each absorbs excitation radiation and/or emits fluorescence at a wavelength distinguishable from the other reporter moieties to permit monitoring the presence of different reporter moieties in the same reaction or in different reactions. Two or more different reporter moieties can be selected having spectrally distinct emission profiles, or having minimal overlapping spectral emission profiles. Reporter moieties can be linked (e.g., operably linked) to nucleotides, nucleosides, nucleic acids, enzymes (e.g., polymerases or reverse transcriptases), or support (e.g., surfaces).

[0084] A reporter moiety (or label) comprises a fluorescent label or a fluorophore. Exemplary fluorescent moieties which may serve as fluorescent labels or fluorophores include, but are not limited to fluorescein and fluorescein derivatives such as carboxyfluorescein, tetrachlorofluorescein, hexachlorofluorescein, carboxynapthofluorescein, fluorescein isothiocyanate, NHS-fluorescein, iodoacetamidofluorescein, fluorescein maleimide, SAMSA-fluorescein, fluorescein thiosemicarbazide, carbohydrazinomethylthioacetyl-amino fluorescein, rhodamine and rhodamine derivatives such as TRITC, TMR, lissamine rhodamine, Texas Red, rhodamine B, rhodamine 6G, rhodamine 10, NHS-rhodamine, TMR-iodoacetamide, lissamine rhodamine B sulfonyl chloride, lissamine rhodamine B sulfonyl hydrazine, Texas Red sulfonyl chloride, Texas Red hydrazide, coumarin and coumarin derivatives such as AMCA, AMCA-NHS, AMCA-sulfo- NHS, AMCA-HPDP, DCIA, AMCE-hydrazide, BODIPY and derivatives such as BODIPY FL C3-SE, BODIPY 530/550 C3, BODIPY 530/550 C3-SE, BODIPY 530/550 C3 hydrazide, BODIPY 493/503 C3 hydrazide, BODIPY FL C3 hydrazide, BODIPY FL IA, BODIPY 530/551 IA, Br-BODIPY 493/503, Cascade Blue and derivatives such as Cascade Blue acetyl azide, Cascade Blue cadaverine, Cascade Blue ethylenediamine, Cascade Blue hydrazide, Lucifer Yellow and derivatives such as Lucifer Yellow iodoacetamide, Lucifer Yellow CH, cyanine and derivatives such as indolium based cyanine dyes, benzo-indolium based cyanine dyes, pyridium based cyanine dyes, thiozolium based cyanine dyes, quinolinium based cyanine dyes, imidazolium based cyanine dyes, Cy 3, Cy5, lanthanide chelates and derivatives such as BCPDA, TBP, TMT, BHHCT, BCOT, Europium chelates, Terbium chelates, Alexa Fluor dyes, DyLight dyes, Atto dyes, LightCycler Red dyes, CAL Flour dyes, JOE and derivatives thereof, Oregon Green dyes, WellRED dyes, IRD dyes, phycoerythrin and phycobilin dyes, Malachite green, stilbene, DEG dyes, NR dyes, near-infrared dyes and others known in the art such as those described in Haugland, Molecular Probes Handbook, (Eugene, Oreg.) 6th Edition; Lakowicz, Principles of Fluorescence Spectroscopy, 2nd Ed., Plenum Press New York (1999), or Hermanson, Bioconjugate Techniques, 2nd Edition, or derivatives thereof, or any combination thereof. Cyanine dyes may exist in either sulfonated or non-sulfonated forms, and consist of two indolenin, benzo-indolium, pyridium, thiozolium, and/or quinolinium groups separated by a polymethine bridge between two nitrogen atoms. Commercially available cyanine fluorophores include, for example, Cy3, (which may comprise 1 - [6-(2, 5-dioxopyrrolidin- 1 -yloxy)-6-oxohexyl]-2-(3 - { 1 - [6-(2, 5-dioxopyrrolidin- 1 - yloxy)-6-oxohexyl]-3,3-dimethyl-l,3-dihydro-2H-indol-2-ylide ne}prop-l-en-l-yl)-3,3- dimethyl-3H-indolium or l-[6-(2,5-dioxopyrrolidin-l-yloxy)-6-oxohexyl]-2-(3-{ l-[6-(2,5- dioxopyrrolidin-l-yloxy)-6-oxohexyl]-3,3-dimethyl-5-sulfo-l, 3-dihydro-2H-indol-2- ylidene}prop-l-en-l-yl)-3,3-dimethyl-3H-indolium-5-sulfonate ), Cy5 (which may comprise l-(6-((2,5-dioxopyrrolidin-l-yl)oxy)-6-oxohexyl)-2-((lE,3E)- 5-((E)-l-(6-((2,5- dioxopyrrolidin-l-yl)oxy)-6-oxohexyl)-3,3-dimethyl-5-indolin -2-ylidene)penta-l,3-dien-l- yl)-3 ,3 -dimethyl-3H-indol- 1 -ium or 1 -(6-((2, 5-dioxopyrrolidin- 1 -yl)oxy)-6-oxohexyl)-2- ((lE,3E)-5-((E)-l-(6-((2, 5-dioxopyrrolidin- l-yl)oxy)-6-oxohexyl)-3,3-dimethyl-5- sulfoindolin-2-ylidene)penta-l,3-dien-l-yl)-3,3-dimethyl-3H- indol-l-ium-5-sulfonate), and Cy7 (which may comprise l-(5-carboxypentyl)-2-[(lE,3E,5E,7Z)-7-(l-ethyl-l,3-dihydro- 2H- indol-2-ylidene)hepta- 1 ,3 , 5-trien- 1 -yl]-3H-indolium or 1 -(5-carboxypentyl)-2- [(lE,3E,5E,7Z)-7-(l-ethyl-5-sulfo-l,3-dihydro-2H-indol-2-yli dene)hepta-l,3,5-trien-l-yl]- 3H-indolium-5-sulfonate), where “Cy” stands for 'cyanine', and the first digit identifies the number of carbon atoms between two indolenine groups. Cy2 which is an oxazole derivative rather than indolenin, and the benzo-derivatized Cy3.5, Cy5.5 and Cy7.5 are exceptions to this rule.

[0085] In some embodiments, the reporter moiety can be a FRET pair, such that multiple classifications can be performed under a single excitation and imaging step. As used herein, FRET may comprise excitation exchange (Forster) transfers, or electron-exchange (Dexter) transfers.

[0086] Many pH buffering agents are known to the skilled artisan. The full name of the pH buffering agents is listed herein. The term “Tris” refers to a pH buffering agent Tris(hydroxymethyl)-aminomethane. The term “Tris-HCl” refers to a pH buffering agent Tri s(hydroxymethyl)-aminom ethane hydrochloride. The term “Tris-acetate” refers to a pH buffering agent comprising an acetate salt of Tris (hydroxymethyl)-aminomethane. The term “Tricine” refers to a pH buffering agent N-[tris(hydroxymethyl)methyl]glycine. The term “Bicine” refers to a pH buffering agent N,N-bis(2-hydroxyethyl)glycine. The term “Bis-Tris propane” refers to a pH buffering agent 1,3 Bis[tris(hydroxymethyl)methylamino]propane. The term “HEPES” refers to a pH buffering agent 4-(2-hy droxy ethyl)- 1- piperazineethanesulfonic acid. The term “MES” refers to a pH buffering agent 2-(N- morpholino)ethanesulfonic acid). The term “MOPS” refers to a pH buffering agent 3-(N- morpholino)propanesulfonic acid. The term “MOPSO” refers to a pH buffering agent 3-(N~ morphoLino)-2-hydroxypropanesulfonic acid. The term “BES” refers to a pH buffering agent N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic add. The term “TES” refers to a pH buffering agent 2-[(2 -Hydroxy- l,lbis(hydroxymethyl)ethyl)amino]ethanesulfonic acid). The term “CAPS” refers to a pH buffering agent 3 -(cyclohexylamino)- 1-propanesuhinic acid. The term “TAPS” refers to a pH buffering agent N-[Tris(hydroxymethyl)methyl]-3-amino propane sulfonic acid. The term “TAPSO” refers to a pH buffering agent N- [Tris(hydroxymethyl)methy1]-3-amino-2-hyidroxypropansulfonic acid. The term “ACES” refers to a pH buffering agent A-(2-Acetamido)-2-aminoethanesulfonic acid. The term “PIPES” refers to a pH buffering agent piperazine- l,4-bis(2-ethanesulfonic acid. The term “ethanolamine” refers to a pH buffering agent that is also known as 2-aminoethanol .

[0087] The terms “linked”, “joined”, “attached”, and variants thereof comprise any type of fusion, bond, adherence or association between any combination of compounds or molecules that is of sufficient stability to withstand use in the particular procedure. The procedure can include but are not limited to: nucleotide transient-binding; nucleotide incorporation; de-blocking; washing; removing; flowing; detecting; imaging and/or identifying. Such linkage can comprise, for example, covalent, ionic, hydrogen, dipole- dipole, hydrophilic, hydrophobic, or affinity bonding, bonds or associations involving van der Waals forces, mechanical bonding, and the like. In some embodiments, such linkage occurs intramolecularly, for example linking together the ends of a single-stranded or doublestranded linear nucleic acid molecule to form a circular molecule. In some embodiments,, such linkage can occur between a combination of different molecules, or between a molecule and a non-molecule, including but not limited to: linkage between a nucleic acid molecule and a solid surface; linkage between a protein and a detectable reporter moiety; linkage between a nucleotide and detectable reporter moiety; and the like. Some examples of linkages can be found, for example, in Hermanson, G., “Bioconjugate Techniques”, Second Edition (2008); Aslam, M., Dent, A., “Bioconjugation: Protein Coupling Techniques for the Biomedical Sciences”, London: Macmillan (1998); Aslam, M., Dent, A., “Bioconjugation: Protein Coupling Techniques for the Biomedical Sciences”, London: Macmillan (1998). [0088] The term “operably linked” and “operably joined” or related terms as used herein refers to juxtaposition of components. The juxtapositioned components can be linked together covalently. For example, two nucleic acid components can be enzymatically ligated together where the linkage that joins together the two components comprises phosphodiester linkage. A first and second nucleic acid component can be linked together, where the first nucleic acid component can confer a function on a second nucleic acid component. For example, linkage between a primer binding sequence and a sequence of interest forms a nucleic acid library molecule having a portion that can bind to a primer. In another example, a transgene (e.g., a nucleic acid encoding a polypeptide or a nucleic acid sequence of interest) can be ligated to a vector where the linkage permits expression or functioning of the transgene sequence contained in the vector. In some embodiments, a transgene is operably linked to a host cell regulatory sequence (e.g., a promoter sequence) that affects expression of the transgene. In some embodiments, the vector comprises at least one host cell regulatory sequence, including a promoter sequence, enhancer, transcription and/or translation initiation sequence, transcription and/or translation termination sequence, polypeptide secretion signal sequences, and the like. In some embodiments, the host cell regulatory sequence controls expression of the level, timing and/or location of the transgene.

[0089] In some embodiments, the support is solid, semi-solid, or a combination of both. In some embodiments, the support is porous, semi-porous, non-porous, or any combination of porosity. In some embodiments, the support can be substantially planar, concave, convex, or any combination thereof. In some embodiments, the support can be cylindrical, for example comprising a capillary or interior surface of a capillary. [0090] In some embodiments, the surface of the support can be substantially smooth. In some embodiments, the support can be regularly or irregularly textured, including bumps, etched, pores, three-dimensional scaffolds, or any combination thereof.

[0091] In some embodiments, the support comprises a bead having any shape, including spherical, hemi-spherical, cylindrical, barrel-shaped, toroidal, disc-shaped, rod-like, conical, triangular, cubical, polygonal, tubular or wire-like.

[0092] The support can be fabricated from any material, including but not limited to glass, fused-silica, silicon, a polymer (e.g., polystyrene (PS), macroporous polystyrene (MPPS), polymethylmethacrylate (PMMA), polycarbonate (PC), polypropylene (PP), polyethylene (PE), high density polyethylene (HDPE), cyclic olefin polymers (COP), cyclic olefin copolymers (COC), polyethylene terephthalate (PET)), or any combination thereof. Various compositions of both glass and plastic substrates are contemplated.

[0093] In some embodiments, the surface of the support is coated with one or more compounds to produce a passivated layer on the support. In some embodiments, the support comprises a low non-specific binding surface that enable improved nucleic acid hybridization and amplification performance on the support. In general, the support may comprise one or more layers of a covalently or non-covalently attached low-binding, chemical modification layers, e.g., silane layers, polymer films, and one or more covalently or non-covalently attached oligonucleotides that may be used for immobilizing a plurality of nucleic acid template molecules to the support.

[0094] In some embodiments, the degree of hydrophilicity (or “wettability” with aqueous solutions) of the surface coatings may be assessed, for example, through the measurement of water contact angles in which a small droplet of water is placed on the surface and its angle of contact with the surface is measured using, e.g., an optical tensiometer. In some embodiments, a static contact angle may be determined. In some embodiments, an advancing or receding contact angle may be determined. In some embodiments, the water contact angle for the hydrophilic, low-binding support surfaced disclosed herein may range from about 0 degrees to about 30 degrees. In some embodiments, the water contact angle for the hydrophilic, low-binding support surfaced disclosed herein may no more than 50 degrees, 40 degrees, 30 degrees, 25 degrees, 20 degrees, 18 degrees, 16 degrees, 14 degrees, 12 degrees, 10 degrees, 8 degrees, 6 degrees, 4 degrees, 2 degrees, or 1 degree. In many cases the contact angle is no more than 40 degrees. Those of skill in the art will realize that a given hydrophilic, low-binding support surface of the present disclosure may exhibit a water contact angle having a value of anywhere within this range. [0095] The present disclosure provides a plurality (e.g., two or more) of nucleic acid templates immobilized to a support. In some embodiments, the immobilized plurality of nucleic acid templates have the same sequence or have different sequences. In some embodiments, individual nucleic acid template molecules in the plurality of nucleic acid templates are immobilized to a different site on the support. In some embodiments, two or more individual nucleic acid template molecules in the plurality of nucleic acid templates are immobilized to a site on the support. In some embodiments, the support comprises a plurality of sites arranged in an array. The term “array” refers to a support comprising a plurality of sites located at pre-determined locations on the support to form an array of sites. The sites can be discrete and separated by interstitial regions. In some embodiments, the predetermined sites on the support can be arranged in one dimension in a row or a column, or arranged in two dimensions in rows and columns. In some embodiments, the plurality of predetermined sites is arranged on the support in an organized fashion. In some embodiments, the plurality of pre-determined sites is arranged in any organized pattern, including rectilinear, hexagonal patterns, grid patterns, patterns having reflective symmetry, patterns having rotational symmetry, or the like. The pitch between different pairs of sites can be that, same or can vary . In some embodiments, the support can have nucleic acid template molecules immobilized at a plurality of sites at a surface density of about 10 ² - 10 ¹⁵ sites per mm’, or more, to form a nucleic acid template array. In some embodiments, the support comprises at least 10 ² sites, at least 10 ³ sites, at least 10 ⁴ sites, at least 10 ⁵ sites, at least 10 ⁶ sites, at least 10 ⁷ sites, at least 10 ⁸ sites, at least 10 ⁹ sites, at least IO ¹⁰ sites, at least 10 ¹¹ sites, at least 10 ¹² sites, at least 10 ¹³ sites, at least 10 ¹⁴ sites, at least 10 ¹⁵ sites, or more, where the sites are located at pre-determined locations on the support. In some embodiments, a plurality of pre-determined sites on the support (e.g., 10 ² - 10 ¹⁵ sites or more) are immobilized with nucleic acid templates to form a nucleic acid template array. In some embodiments, the nucleic acid templates that are immobilized at a plurality of pre-determined sites by hybridization to immobilized surface capture primers, or the nucleic acid templates are covalently attached to the surface capture primers. In some embodiments, the nucleic acid templates that are immobilized at a plurality of pre-determined sites, for example immobilized at 10 ² - 10 ¹⁵ sites or more. In some embodiments, the nucleic acid templates that are immobilized at a plurality of sites on the support comprise linear or circular nucleic acid template molecules or a mixture of both linear and circular molecules. In some embodiments, the immobilized nucleic acid templates are clonally-amplified to generate immobilized nucleic acid polonies at the plurality of pre-determined sites. In some embodiments, individual immobilized nucleic acid template molecules comprise one copy of a target sequence of interest, or comprise concatemers having two or more tandem copies of a target sequence of interest.

[0096] In some embodiments, a support comprising a plurality of sites located at random locations on the support is referred to herein as a support having randomly located sites thereon. The location of the randomly located sites on the support are not pre-determined. The plurality of randomly-located sites is arranged on the support in a disordered and/or unpredictable fashion. In some embodiments, the support comprises at least 10 ² sites, at least 10 ³ sites, at least 10 ⁴ sites, at least 10 ⁵ sites, at least 10 ⁶ sites, at least 10 ⁷ sites, at least 10 ⁸ sites, at least 10 ⁹ sites, at least IO ¹⁰ sites, at least 10 ¹¹ sites, at least 10 ¹² sites, at least 10 ¹³ sites, at least 10 ¹⁴ sites, at least 10 ¹⁵ sites, or more, where the sites are randomly located on the support. In some embodiments, a plurality of randomly located sites on the support (e.g., 10 ² - 10 ¹⁵ sites or more) are immobilized with nucleic acid templates to form a support immobilized with nucleic acid templates. In some embodiments, the nucleic acid templates that are immobilized at a plurality of randomly located sites by hybridization to immobilized surface capture primers, or the nucleic acid templates are covalently attached to the surface capture primer. In some embodiments, the nucleic acid templates that are immobilized at a plurality of randomly located sites, for example immobilized at 10 ² - 10 ¹⁵ sites or more. In some embodiments, the nucleic acid templates that are immobilized at a plurality of sites on the support comprise linear or circular nucleic acid template molecules or a mixture of both linear and circular molecules. In some embodiments, the immobilized nucleic acid templates are clonally-amplified to generate immobilized nucleic acid polonies at the plurality of randomly located sites. In some embodiments, individual immobilized nucleic acid template molecules comprise one copy of a target sequence of interest, or comprise concatemers having two or more tandem copies of a target sequence of interest.

[0097] In some embodiments, with respect to nucleic acid template molecules immobilized to pre-determined or random sites on the support, the plurality of immobilized nucleic acid template molecules on the support are in fluid communication with each other to permit flowing a solution of reagents (e.g., enzymes including polymerases, multivalent molecules, nucleotides, divalent cations and/or buffers and the like) onto the support so that the plurality of immobilized nucleic acid template molecules on the support can be reacted with the reagents in a massively parallel manner. In some embodiments, the fluid communication of the plurality of immobilized nucleic acid template molecules can be used to conduct nucleotide binding assays and/or conduct nucleotide polymerization reactions (e.g., primer extension or sequencing) on the plurality of immobilized nucleic acid template molecules, and to conduct detection and imaging for massively parallel sequencing. In some embodiments, the term “immobilized” and related terms refer to nucleic acid molecules or enzymes (e.g., polymerases) that are attached to the support at pre-determined or random locations, where the nucleic acid molecules or enzymes are attached directly to a support through covalent bond or non-covalent interaction, or the nucleic acid molecules or enzymes are attached to a coating on the support.

[0098] As used herein, the term “clonally amplified” and it variants refers to a nucleic acid template molecule that has been subjected to one or more amplification reactions either insolution or on-support. In the case of in-solution amplified template molecules, the resulting amplicons are distributed onto the support. Prior to amplification, the template molecule comprises a sequence of interest and at least one universal adaptor sequence. In some embodiments, clonal amplification comprises the use of a polymerase chain reaction (PCR), multiple displacement amplification (MDA), transcription-mediated amplification (TMA), nucleic acid sequence-based amplification (NASBA), strand displacement amplification (SDA), real-time SDA, bridge amplification, isothermal bridge amplification, rolling circle amplification (RCA), circle-to-circle amplification, helicase-dependent amplification, recombinase-dependent amplification, single- stranded binding (SSB) protein-dependent amplification, or any combination thereof.

[0099] As used herein, the term “sequencing” and its variants comprise obtaining sequence information from a nucleic acid strand, typically by determining the identity of at least some nucleotides (including their nucleobase components) within the nucleic acid template molecule. While in some embodiments, “sequencing” a given region of a nucleic acid molecule includes identifying each and every nucleotide within the region that is sequenced, in some embodiments “sequencing” comprises methods whereby the identity of only some of the nucleotides in the region is determined, while the identity of some nucleotides remains undetermined or incorrectly determined. Any suitable method of sequencing may be used. In an exemplary embodiment, sequencing can include label-free or ion based sequencing methods. In some embodiments, sequencing can include labeled or dye-containing nucleotide or fluorescent based nucleotide sequencing methods. In some embodiments, sequencing can include polony -based sequencing or bridge sequencing methods. In some embodiments, sequencing includes massively parallel sequencing platforms that employ sequence-by- synthesis, sequence-by-hybridization or sequence-by-binding procedures. Examples of massively parallel sequence-by-synthesis procedures include polony sequencing, pyrosequencing (e.g., from 454 Life Sciences; U.S. Patent Nos. 7,211,390, 7,244,559 and 7,264,929), chain-terminator sequencing (e.g., from Illumina; U.S. Patent No. 7,566,537; Bentley 2006 Current Opinion Genetics and Development 16:545-552; and Bentley, et al., 2008 Nature 456:53-59, ion-sensitive sequencing (e.g., from Ion Torrent), probe-anchor ligation sequencing (e.g., Complete Genomics), DNA nanoball sequencing, nanopore DNA sequencing. Examples of single molecule sequencing include Heliscope single molecule sequencing, and single molecule real time (SMRT) sequencing. An example of sequence-by- hybridization includes SOLiD sequencing (e.g., from Life Technologies; WO 2006/084132). An example of sequence-by-binding includes Omniome sequencing (e.g., U.S patent No. 10,246,744).

Engineered Polymerases that Exhibit Increased Thermal Stability

[0100] The present disclosure provides compositions comprising mutant polymerases having amino acid substitutions and/or truncated amino acid sequences, nucleic acids encoding the mutant polymerases, and systems and kits comprising mutant polymerases. Further provided herein are methods using the mutant polymerases, including methods for binding a nucleic acid duplex, binding a complementary nucleotide or binding a multivalent molecule having a complementary nucleotide unit, incorporating a complementary nucleotide, extending a primer, and nucleic acid sequencing, where the methods employ any of the mutant polymerases described herein. The mutant polymerases are engineered to exhibit desirable characteristics including exonuclease-minus activity and increased stability, improved uracil-tolerance and/or reduced sequence-specific errors. Additionally, the mutant polymerase can be engineered to express a higher fraction of soluble expressed enzyme.

[0101] The present disclosure provides mutant polymerases that are engineered to reduce post-translational modifications in order to improve protein activity and stability. Post- translational modification of recombinant proteins can reduce protein activity, cause misfolding, increase heterogeneity, reduce thermal stability, and increase protein aggregation. These modifications pose challenges for achieving consistent manufacturability and retaining a long shelf-life. Many recombinant proteins undergo post-translational modification, including phosphorylation, acetylation, ubiquitination, succinylation, methylation, glycosylation (e.g., N-linked, O-linked and C-linked), hydroxylation, oxidation, deamidation, nitro sylati on, sulfation, SUMOylation, disulfide bonding, proteolysis and/or lipidation (e.g., palmitoylation). [0102] Examples of undesirable impacts of post-translational modification include oxidative damage of sulfur-containing amino acids such as cysteine and methionine. Histidine, tryptophan, lysine and serine are also known to be susceptible to oxidative damage. Deamidation of asparagine and glutamine can lead to protein degradation which reduces shelf-life. Acetylation can involve cleavage of the N-terminal methionine and replacement with an acetyl group. In some proteins, the N-terminal methionine plays an important role in enzyme activity and removal of this methionine residue can change enzyme activity. Acetylation can also involve serine and lysine. Methylation can lead to changes in hydrophobicity and side chain charge. Ubiquitination, can lead to protein degradation.

[0103] Analytical techniques such as mass spectrometry and tandem mass spectrometry can be used to detect post-translational modifications, particularly oxidized methionine and lysine residues, which enables rational mutagenesis to improve protein production and stability.

[0104] The present disclosure provides mutant polymerases that are engineered to exhibit reduced editing mode conformation. Many DNA polymerases possess 5’ to 3’ nucleotide polymerization activity, and 3’ to 5’ exonuclease proofreading activity. Generally, the polymerization site in a polymerase is located at a different site from the proofreading site. During polymerization mode, the template and the growing end of the primer strand are located in the polymerization site. In many family B and C polymerases, amino acid residues in the finger, thumb and palm domains form at least a portion of the polymerization site. In proofreading mode, the growing end of the primer is physically transferred from the polymerization site to the exonuclease site, and the mis-incorporated nucleotide at the end of the growing primer strand is excised by the 3’ to 5’ proofreading activity of the polymerase. The transfer of the primer end from the polymerization site to the exonuclease site can involve local unpairing of several base pairs at the primer/template junction which prevents further strand elongation (e.g., polymerization) until the primer end is transferred back to the polymerization site and primer/template pairing is restored. Amino acid residues that play a role in transfer of the primer end are independent from amino acid residues involved in exonuclease activity. The polymerization and exonuclease sites are located in two different domains. Polymerases sometimes undergo this polymerization-to-exonuclease conformational switching unnecessarily when the correct nucleotide is incorporated which stalls primer elongation. In A. coll DNA polymerase III, it has been previously determined that the timescale for primer end transfer and primer/template unpairing is approximately ten milliseconds which is an order of magnitude longer than nucleotide incorporation (Dodd, et al., 2020 Nature Communication 11 :5379, “Polymerization and editing modes of a high- fidelity DNA polymerase are linked by a well-defined path”). Thus, it is desirable to engineer sequencing polymerases that exhibit reduced editing mode conformation when the correct nucleotide is incorporated, or when the correct nucleotide unit from a multivalent molecule is bound at the polymerization site. It is postulated that editing mode mutant polymerases will retain 3’ to 5’ exonuclease activity.

[0105] Protein modeling and mass spectrometry can identify key amino acid residues along the path of transferring the primer end from the polymerization site to the exonuclease site without impacting exonuclease activity. Mutation of at least some of these key amino acid residues can reduce unnecessary polymerization-to-exonuclease conformational switching. For example, mutation of amino acid residues that play a role in guiding the primer end to the exonuclease site, or mutation of amino acid residues that stabilize the transferred primer end at the exonuclease site, may reduce transition to editing mode conformation. In another example, mutation of amino acid residues that interact with and stabilize the template molecule during polymerization may retain the template molecule at the polymerization site.

[0106] The present disclosure provides mutant polymerases that can be used to conduct a two-stage nucleic acid sequencing method. In some embodiments, the first stage generally comprises binding detectably-labeled multivalent molecules to complexed polymerases to form multivalent-complexed polymerases under a condition suitable to inhibit incorporation of a nucleotide unit, and detecting the multivalent-complexed polymerases. The first stage can be conducted using a trapping polymerase. In some embodiments, the second stage generally comprises polymerase-catalyzed nucleotide incorporation using a stepping polymerase.

[0107] The present disclosure provides mutant polymerases that can be used for conducting trapping or stepping events for nucleic acid sequencing. Some of the mutant polymerases can be used for both trapping and stepping events.

[0108] The present disclosure provides mutant polymerases that can be used for trapping a multivalent molecule which comprises a complexed mutant polymerase binding to a multivalent molecule having a complementary nucleotide unit (e.g., exemplary multivalent molecules are shown in Figures 2-5). In some embodiments, the multivalent molecule comprises a central core attached to multiple polymer arms each having a nucleotide unit at the end of the arms. The multivalent molecule can be labeled with a detectable reporter moiety. The complexed mutant polymerase includes a mutant polymerase bound to a template/primer duplex. The mutant polymerases are engineered to exhibit reduced sequencespecific errors that occur after certain motif sequences in the primer strand and/or template strand. The sequence-specific errors for a trapping polymerase may be characterized by a substantial loss of signal intensity which leads to a base miscall (e.g., base substitution) or no call at a specific sequencing cycle. The signal often recovers in the next cycle. The motif sequences that lead to the miscalls are specific to a given polymerase and can occur on either template strand in the forward or reverse sequencing direction.

[0109] The present disclosure provides mutant polymerases that can be used for binding a complementary nucleotide (e.g., a non-conjugated nucleotide) and incorporating the nucleotide into the 3’ end of the primer which is called the stepping event. The mutant polymerases are engineered to exhibit reduced sequence-specific errors which are characterized by substantial loss of nucleotide incorporation that occur after certain motif sequences in the primer strand and/or the template strand. Sequence-specific errors for a stepping enzyme may be characterized by massive phasing after the sequence motif. The motif sequences that lead to phasing are specific to a given polymerase and can occur on either template strand in the forward or reverse sequencing direction.

[0110] Without wishing to be bound by theory, it is postulated that mutant polymerases that exhibit trapping or stepping sequence-specific errors at certain sequence motifs during sequencing switch from a nucleotide incorporation conformation to an editing conformation. During a trapping event, the editing conformation occludes binding of a complementary nucleotide unit from a multivalent molecule which leads to a reduction in signal intensity. During a stepping event, the editing conformation occludes binding and incorporation of a complementary nucleotide or nucleotide analog which leads to a reduction in signal intensity. Designing a trapping and stepping polymerase carrying one or more mutation sites that reduce switching conformations from nucleotide polymerization to editing can reduce trapping sequence-specific errors.

[OHl] In some embodiments, the mutant polymerases comprise polypeptides, or fragments thereof, derived from directed evolution of recently identified novel B-family and A-family polymerases, where the mutant polymerases exhibit improvements in their specificity while maintaining high discrimination for the correct Watson-crick base-pairing. [0112] The present disclosure provides polymerases that have been engineered to include substitution mutations, including polymerases having amino acid sequence backbones of RLF 89458.1 (e.g., from Thermococci archaeon, isolate B13 G1) (SEQ ID NO: 1), RLF 78286.1 (e.g., from Thermococci archaeon, isolate B89 G9) (SEQ ID NO:2), NOZ 58130.1 (e.g., from Euryarchaeota archaeon, isolate M BaxBin.100) (SEQ ID NO: 1714), RMF 90817.1 (e.g., from Euryarchaeota archaeon, isolate J060) (SEQ ID NO:2789), MBC 7218772.1 (e.g., from Hadesarchaea archaeon, isolate MAG-18) (SEQ ID NO:2790), WP 175059460.1 (e.g., from Thermococcus sp. 2319x1) (SEQ ID NO:2791), KUO 42443.1 (e.g., from Candidatus Hadarchaem, yellowstonense, isolate YNP_45) (SEQ ID NO:2792), and NOZ 77387.1 (e.g., from Euryarchaeota archaeon, isolate M_MaxBin.O27) (SEQ ID NO:2793).

[0113] Polypeptides described herein include but are not limited to polypeptides possessing enzymatic activity, such as polymerase activity, and are often described as families. Often, polymerases are DNA polymerases, RNA polymerases, templateindependent polymerases, reverse transcriptases, or other enzymes capable of nucleotide binding and nucleotide incorporation (e.g., primer extension). Many DNA polymerases are known in the art, and such enzymes in some instances are mutated to generate the compositions described herein. Members of the DNA polymerase family are often defined in terms of polymerase activity, active site structure, domain homology/function, or sequence homology to other known DNA polymerase family members. For example, DNA polymerases include but are not limited to E. coli DNA polymerase I, E. coli DNA polymerase II, or other members of the DNA polymerase family. Known thermostable DNA polymerases include Taq polymerase, Pfu polymerase, and 9°N polymerase or other members of the DNA polymerase family. Wild-type DNA polymerases are or may be obtained from any number of origins, such as eukaryotic, prokaryotic, or viral origins, and in some embodiments for purposes of the present disclosure, from archaeal origins. In some embodiments, polymerases comprising amino acid sequences of any of SEQ ID NOS: 1, 2, 1714, 2789-2793 and 2803 are members of a DNA polymerase family.

[0114] The polymerases described herein can include one or more amino acid substitution and/or truncation which increases the thermal stability of the polymerase. In some embodiments, thermal stability of a polymerase can be determined by measuring the temperature at which the polymerase unfolds and/or aggregates. For example, a thermal shift assay using differential scanning fluorimetry can be used to determine the thermal stability of a polymerase. Differential scanning fluorimetry can be used to determine a protein unfolding transition (T(m)) at which approximately 50% of the protein is in its native conformation and approximately 50% of the protein is denatures. The protein unfolding transition (T(m)) can be obtained from a melt peak in which increasing temperature is plotted along the x-axis and the first derivative curve of fluorescence over change in temperature (e.g., dF/dT or dRFU/dT) is plotted along the y-axis. Some proteins exhibit two protein transitions, T(ml) and T(m2). For example the T(ml) temperature is the temperature at which at least 50% of the protein transitions from folded to unfolded. In another example the T(m2) temperature is a temperature which is higher compared to the T(ml) temperature, where at the T(m2) temperature more of the protein transitions from folded to unfolded. Fully denatured protein and protein aggregation (T(agg)) can be obtained from a melt curve in which increasing temperature is plotted along the x-axis and the fluorescence (e.g., RFU) is plotted along the y- axis. For example, Tables 1-2 (e.g., FIGs. 31-32) list Tml and Tm2 of the engineered polymerases.

[0115] In some embodiments, the engineered polymerase exhibits protein unfolding transition at an elevated temperature (e.g., thermal stability) compared to a wild type polymerase or compared to an engineered polymerase having mutations that do not confer increased thermal stability. In some embodiments, the engineered polymerase exhibits increased thermal stability at an elevated temperature of about 72 - 75 °C, or about 75 - 80 °C, or about 80 - 85 °C, or about 85 - 90 °C, or higher temperatures. Many of the engineered polymerases described herein exhibit nucleotide binding and incorporation activity at a temperature range of about 25-50 °C, or about 45-75 °C, or about 65-80°C, or about 80-90°C. Thus, these engineered polymerases are thermal stable at moderately high temperature ranges (e.g., mesothermal polymerase). The engineered polymerases described herein are suitable for conducting nucleotide binding, nucleotide unit binding, nucleotide incorporation and/or nucleic acid sequencing reactions at a temperature range of about 25-50 °C, or about 45-75 °C, or about 65-80 °C, or about 80-90°C, or higher temperatures. In some embodiments, the mutant polymerases exhibit increased thermal stability by about 2-4 °C, or about 4-6 °C, or about 6-8 °C, or about 8-10 °C.

[0116] By contrast, DNA polymerases exhibiting significantly higher thermal stability that exceeds 95 °C include 9°N, THERMINATOR, VENT, DEEP VENT, Pfu and Pyrococcus abyssi. Thermostable polymerases, such as for example 9°N, VENT, DEEP VENT, Pfu and Pyrococcus abyssi polymerases, are suitable for use in a PCR reaction where typical cycling steps are conducted at temperatures that exceed 90-95 °C or higher temperatures, and may not be suitable for use in a nucleotide binding, nucleotide incorporation, and/or nucleic acid sequencing reactions, that are conducted at lower temperature ranges. DNA polymerase from Geobacillus stearothermophilus (e.g., Bst DNA polymerase) is typically stable up to 65 °C.

[0117] Polymerases variously comprise DNA polymerases, RNA polymerases, templateindependent polymerases, reverse transcriptases, or other enzymes capable of catalyzing nucleotide incorporation. Archaeal polymerases are often derived from thermophilic organisms, and thus can represent classes of thermostable or thermotolerant enzymes. Therefore, polypeptide backbones derived from archaeal polymerases provide desirable protein engineering targets to further enhance reversible terminator nucleotide incorporation for applications that may be improved by the application of enzymes with enhanced thermostability or otherwise enhanced resistance to degradation such as by repeated exposure to high temperatures, changes in buffer conditions, and the like.

[0118] The present disclosure provides compositions and methods comprising mutant polymerase enzymes that exhibit improved shelf-life compared to a wild type polymerase or compared to an engineered polymerase having mutations that do not confer improved shelflife. For example, mutant polymerases can retain enzymatic activity after storage for months or years at a give temperature. In some embodiments, the mutant polymerases can retain about 90 - 100 % activity for 2-12 months of storage at a temperature of about 0 - plus 27 °C, or a temperature of about minus 20 °C - minus 45 °C, or a temperature of about minus 45 °C - minus 80 °C. In some embodiments, the mutant polymerases can retain about 80 - 90 % activity for 2-12 months of storage at a temperature of about 0 - plus 27 °C, or a temperature of about minus 20 °C - minus 45 °C, or a temperature of about minus 45 °C - minus 80 °C. In some embodiments, the mutant polymerases can retain about 70 - 80 % activity for 2-12 months of storage at a temperature of about 0 - plus 27 °C, or a temperature of about minus 20 °C - minus 45 °C, or a temperature of about minus 45 °C - minus 80 °C. In some embodiments, the mutant polymerases can retain about 70 - 100 % activity for about 12 - 36 months of storage at a temperature of about 0 - plus 27 °C, or a temperature of about minus 20 °C - minus 45 °C, or a temperature of about minus 45 °C - minus 80 °C.

[0119] In some embodiments, the wild type or engineered polymerase can be stored in a storage buffer comprising a solvent, at least one pH buffering agent, at least one salt, at least one chelating agent, at least one viscosity agent, and at least one detergent. In some embodiments, the solvent comprises water.

[0120] In some embodiments, the buffering agent comprises MES, HEPES, ACES, Tris and/or Tris-HCl, or any other pH buffering agent known to the skilled artisan. In some embodiments, the pH of the pH buffering agent is about 6 - 6.5, or the pH of the pH buffering agent is about 6.5 - 7, or the pH of the pH buffering agent is about 7 - 7.5, or the pH of the pH buffering agent is about 7.5 - 8, or the pH of the pH buffering agent is about 8 - 8.5. In some embodiments, the storage buffer includes at least one pH buffering agent at a concentration of about 10 - 20 mM, or about 20- 30 mM, or about 30 - 40 mM, or about 40 - 50 mM.

[0121] In some embodiments, the salt comprises a monovalent salt comprising NaCl, KC1, NH2SO4 and/or potassium glutamate. In some embodiments, the storage buffer includes at least one monovalent salt at a concentration of about 50 - 100 mM, or about 100 - 200 mM, or about 200 - 300 mM, or about 300 - 400 mM, or about 400 - 500 mM, or about 500

- 600 mM, or about 600 - 800 mM.

[0122] In some embodiments, the chelating agent comprises EDTA (ethylenedi aminetetraacetic acid), EGTA (ethylene glycol tetraacetic acid), HEDTA (hydroxy ethylethylenediaminetriacetic acid), DPTA (diethylene triamine pentaacetic acid), NTA (N,N-bis(carboxymethyl)glycine), citrate anhydrous, sodium citrate, calcium citrate, ammonium citrate, ammonium bicitrate, citric acid, potassium citrate and/or magnesium citrate. In some embodiments, the storage buffer includes at least one chelating at a concentration of about 0.0125 - 0.025 mM, or about 0.025 - 0.05 mM, or about 0.05 - 0.1 mM, or about 0.1 - 0.2 mM.

[0123] In some embodiments, the viscosity agent comprises a saccharide such as trehalose, sucrose, cellulose, xylitol, mannitol, sorbitol and/or inositol. In some embodiments, the viscosity agent comprises glycerol or a glycol compound such as ethylene glycol and/or propylene glycol. In some embodiments, the storage buffer includes at least one viscosity agent at about 20 - 30 %, or about 30 - 40%, or about 40 - 50%, or about 50 - 60%, or about 60 - 70%, or about 70 - 80%.

[0124] In some embodiments, the detergent comprises an ionic detergent such as SDS (sodium dodecyl sulfate). In some embodiments, the detergent comprises a non-ionic detergent such as Triton X-100, Tween 20, Tween 80 or Nonidet P-40. In some embodiments, the detergent comprises a zwitterionic detergent such as CHAPS (3-[(3- cholamidopropyl) dimethylammonio]-l -propanesulfonate) or A-Dodecyl-A, A-di methyl -3- amonio-1 -propanesulfate (DetX). In some embodiments, the detergent comprises LDS ( lithium dodecyl sulfate), sodium taurodeoxycholate, sodium taurocholate, sodium glycocholate, sodium deoxycholate or sodium cholate. In some embodiments, the storage buffer includes at least one detergent at about 0.025 - 0.5%, or about 0.5 - 0.1%, or about 0.1

- 0.2%, or about 0.2 - 0.4%, or about 0.4 - 0.8%, or about 0.8 - 1.6%.

[0125] The present disclosure provides compositions and methods comprising mutant polymerase enzymes that exhibit improved ability to bind complementary nucleotide units of multivalent molecules compared to a wild type polymerase or compared to an engineered polymerase having mutations that do not confer improved binding to complementary nucleotide units of multivalent molecules. Multivalent molecules generally comprises a central moiety (e.g., a core) attached to a plurality of arms where each arm is attached to a nucleotide unit. The multivalent molecules comprise a star, comb, cross-linked, bottle brush, or dendrimer configuration (e.g., see FIG. 2).

[0126] We made the surprising discovery that many of the engineered polymerases described herein exhibit enhanced incorporation rate of nucleotide analogs compared to a wild type polymerase or compared to an engineered polymerase having mutations that do not confer enhanced incorporation rate of nucleotide analogs. Compared to wild type polymerase, some of the engineered polymerases also exhibited one or more desirable characteristics, including increased binding affinity to nucleotide analogs having a 3’ chain terminating group, improved ability to incorporate a dATP nucleotide opposite a uracil-containing template molecule (e.g., uracil -tolerant mutant polymerases), improved ability to bind complementary nucleotide units of multivalent molecules, increased thermal stability up to approximately 90 °C, increased shelf-life, and reduced sequence-specific errors.

[0127] The present disclosure provides compositions and methods comprising mutant polypeptides relating to polymerase enzymes that exhibit increased capacity for binding and discrimination of nucleotide analogs, and improved incorporation of nucleotide analogs compared to a corresponding wild type polymerase. The nucleotide analogs include for example nucleotides comprising a chain terminating group attached to the sugar 2’ or 3’ position. The chain terminating group comprises an azide, azido or azidomethyl group, or another type of chain terminating group. The engineered DNA polymerases exhibit increased incorporation rate of nucleotide analogs, compared to a corresponding wild type polymerase having an amino acid sequence backbone of any of RLF 89458.1 (SEQ ID NO: 1), RLF

78286.1 (SEQ ID NO:2), NOZ 58130.1 (SEQ ID NO: 1714), RMF 90817.1 (SEQ ID NO:2789), MBC 7218772.1 (SEQ ID NO:2790), WP 175059460.1 (SEQ ID NO:2791), KUO

42443.1 (SEQ ID NO:2792), and NOZ 77387.1 (SEQ ID NO:2793).

[0128] The data shown in Tables 1 and 2 provide numerous exemplary mutant polymerases that exhibit increased thermal stability compared to their corresponding wild type polymerases or compared to an engineered polymerase having the same backbone sequence and mutations that do not confer increased thermal stability. Many of these mutant polymerases include mutations at the LYP motif and/or other positions. In some embodiments, the mutant polymerases exhibit increased incorporation rates of nucleotide analogs by about 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 150%, 200%, 250%, 300%, 500%, or 1000% relative to a corresponding wild type enzyme or enzyme variants currently known in the art. Exemplary mutant polymerase that exhibit increased thermal stability are listed in Tables 1 and 2.

[0129] The present disclosure provides compositions and methods comprising mutant polymerases having at least one amino acid residue inserted before or after the LYP motif. In some embodiments, the at least one amino acid residue inserted before or after the LYP motif can move the LYP motif as a unit in the folded polypeptide which may increase or decrease activity of the LYP motif in the mutant enzyme. In some embodiments, insertion of at least one amino acid residue before or after the LYP motif may be more effective in modulating the activity of the LYP motif compared to conventional amino acid substitutions which are designed to change amino acid side chains in and around the LYP motif. In some embodiments, the at least one amino acid residue inserted before or after the LYP motif can modulate (e.g., increase or decrease) the incorporation rate of nucleotide analogs compared to a mutant polymerase that lacks the at least one inserted amino acid residue.

[0130] In some embodiments, a polymerase that binds a nucleotide (or nucleotide analog) or a multivalent molecule under a condition suitable for inhibiting a polymerase-catalyzed nucleotide incorporation reaction comprises at least one amino acid residue inserted before or after the LYP motif. In some embodiments, a polymerase that binds a nucleotide (or nucleotide analog) or a multivalent molecule under a condition suitable for promoting a polymerase-catalyzed nucleotide incorporation reaction comprises at least one amino acid residue inserted before or after the LYP motif.

[0131] In some embodiments, the at least one amino acid residue inserted before or after the LYP motif comprises any of the 20 amino acids (e.g., W, I, M, P, F, G, A, V, L, H, R, K, D, E, N, Y, C, S, T, or Q). In some embodiments, the at least one amino acid residue inserted before or after the LYP motif comprises proline or glycine. Exemplary mutant polymerases comprise amino acid sequences of any of SEQ ID NOS: 1076, 1094, 1197 or 1351.

[0132] In some embodiments, the mutant polypeptide having at least one amino acid residue inserted before or after the LYP motif comprises a backbone sequence of any of RLF 89458.1 (SEQ ID NO: 1), RLF 78286.1 (SEQ ID NO:2), NOZ 58130.1 (SEQ ID NO: 1714), RMF 90817.1 (SEQ ID NO:2789), MBC 7218772.1 (SEQ ID NO:2790), WP 175059460.1 (SEQ ID NO:2791), KUO 42443.1 (SEQ ID NO:2792), and NOZ 77387.1 (SEQ ID NO:2793). [0133] In some embodiments, at least one amino acid residue can be inserted before or after the LYP motif where the LYP motif in RLF 89458.1 (SEQ ID NO: 1) and RLF 78286 (SEQ ID NO:2) are located at positions L409, Y410 and P411.

[0134] In some embodiments, at least one amino acid residue can be inserted before or after the LYP motif where the LYP motif in NOZ 58130 (SEQ ID NO: 1714) is located at positions L440, Y441 and P442.

[0135] In some embodiments, at least one amino acid residue can be inserted before or after the LYP motif where the LYP motif in RMF 90817 (SEQ ID NO:2789) is located at positions L421, Y422 and P423.

[0136] In some embodiments, at least one amino acid residue can be inserted before or after the LYP motif where the LYP motif in MBC 7218772 (SEQ ID NO:2790) is located at positions L451, Y452 and P453.

[0137] In some embodiments, at least one amino acid residue can be inserted before or after the LYP motif where the LYP motif in WP 175059460 (SEQ ID NO:2791) is located at positions L411, Y412 and P413.

[0138] In some embodiments, at least one amino acid residue can be inserted before or after the LYP motif where the LYP motif in KUO 42443 (SEQ ID NO:2792) is located at positions L448, Y449 and P450.

[0139] In some embodiments, at least one amino acid residue can be inserted before or after the LYP motif where the LYP motif in NOZ 77387 (SEQ ID NO:2793) is located at positions L432, Y433 and P434.

[0140] In some embodiments, the mutant polypeptide having at least one amino acid residue inserted before or after the LYP motif comprises a sequence that has at least 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or greater than 99% sequence identity to any of SEQ ID NOs: 1-1713, 1714-2787, 2789, 2790, 2791, 2792, 2793 and 2803.

[0141] Sites that confer certain activities to a polypeptide may be conserved and can be located by aligning the amino acid sequences of various polymerases. For example, certain residues that are associated with polymerase activity (e.g., nucleotide incorporation) can be found at: residues D405, D539 and/or D541 of a polymerase having a backbone sequence of RLF 89458.1 (SEQ ID NO: 1); or at residues D405, D539 and/or D541 of a polymerase having a backbone sequence of RLF 78286.1 (SEQ ID NO:2); or at residues D436, D570 and/or D572 of a polymerase having a backbone sequence of NOZ 58130 (SEQ ID NO: 1714); or at residues D417, D551 and/or D553 of a polymerase having a backbone sequence of RMF 90817 (SEQ ID NO:2789); or at residues D447, D585 and/or D587 of a polymerase having a backbone sequence of MBC 7218772 (SEQ ID NO:2790); or at residues D407, D543 and/or D545 of a polymerase having a backbone sequence of WP 175059460 (SEQ ID NO:2791); or at residues D444, D582 and/or D584 of a polymerase having a backbone sequence of KUO 42443 (SEQ ID NO:2792); or at residues D428, D562 and/or D564 of a polymerase having a backbone sequence of NOZ 77387 (SEQ ID NO:2793). [0142] The skilled artisan can locate these sites and other functional equivalent sites in other polymerase by reviewing the sequence alignments shown in FIG. 33. Such sites are often found at analogous positions in other regions and domains and polypeptides that comprise such domains are consistent with methods and compositions described herein. [0143] Mutations in the polymerases described herein variously comprise one or more changes to amino acid residues present in the polypeptide. Additions, substitutions, deletions and/or truncations are all examples of mutations that are used to generate mutant polypeptides. Substitutions in some embodiments comprise the exchange of one amino acid for an alternative amino acid, and such alternative amino acids differ from the original amino acid with regard to size, shape, conformation, and/or chemical structure. Mutations in some embodiments are conservative or non-conservative. Conservative mutations comprise the substitution of an amino acid with an amino acid that possesses similar chemical properties. Additions often comprise the insertion of one or more amino acids at the N-terminal, C- terminal, or internal positions of the polypeptide. In some cases, additions comprise fusion polypeptides, wherein one or more additional polypeptides is connected to the polypeptide. Such additional polypeptides in some embodiments comprise domains with additional activity, or sequences with additional function (e.g., improve expression, aid purification, improve solubility, attach to a solid support, or other function). Often a polypeptide described herein comprises one or more non-amino acid groups. Fusion polypeptides optionally comprise an amino acid or other chemical linker that connects the one or more proteins. Any number of mutations can be introduced into a polypeptide or portion of a polypeptide described herein such as 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 50, or more than 50 mutations.

[0144] In some embodiments, entire domains (portions of the polypeptide with a defined function) are added, deleted or substituted with domains from other polypeptides. Exemplary domains include DNA/RNA binding domains, nucleotide binding domains, nuclease domains, subcellular localization domains such as nuclear localization domains, or other domains. In some embodiments, the methods and compositions of the present disclosure comprise the attachment of a domain serving as a spacer or label, and/or providing for the attachment of a linker such as a SNAP tag, an avidin moiety, a streptavidin moiety, an epitope tag, a fluorescent protein, an affinity tag, a metal binding (i.e., a His6 (SEQ ID NO: 2850) or polyhistidine tag) or the like. In some embodiments, one or more mutations are present at any location, for example in an exonuclease domain, a nucleic acid binding domain, a nucleotide binding domain and/or a catalytic site. The polypeptide comprises at least one mutation and can be based on a wild type backbone sequence of any one of SEQ ID NOS: 1, 2, 1714, 2789, 2790, 2791, 2792, 2793 or 2803.

[0145] As used herein, the term "surrounding" an amino acid residue or sequence position has its ordinary meaning in the art, including and incorporating modifications such as substitutions, deletions, insertions, or post-translational modifications at residues from 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 or more residues distant from the named residue , i.e., N- terminal or C-terminal from the named residue. In some contexts, a residue greater than 12 residues or sequence positions N or C terminal from the named residue can be considered "surrounding" a named residue based on the sequence or structural (i.e., 3 -dimensional) context as would be understood by one of ordinary skill in the art.

[0146] It is understood that substitutions or modifications of the residues described herein also may incorporate or may include nonstandard amino acids as are known in the art, including but not limited to hydroxyproline, N-formylmethionine, selenomethionine, selenocysteine, phosphotyrosine, phosphohistidine, and the like. The mutations, modifications, truncations, substitutions and the like as described herein may be made by any method as is known in the art, particularly the art of molecular biology and/or protein engineering. Such methods may include site directed mutagenesis using mutagenic and/or partially degenerate primers, in vitro gene assembly, gene editing (such as by CRISPR or related methods) and the like. The mutant or engineered proteins described herein may additionally be expressed, isolated, and/or purified by any such means as is known in the art. Relevant methods are described in: Green, M. and Sambrook, J., Molecular Cloning: A Laboratory Manual (Fourth Edition) which is hereby incorporated by reference in its entirety and especially with respect to its disclosure of methods for modifying, transferring, and expressing, recombinant, modified, and engineered gene sequences as well as extracting, isolating, and/or purifying engineered proteins.

[0147] The polypeptides disclosed herein have been shown to function as nucleotide polymerases that exhibit higher thermostability and higher rates of incorporation of 3’-O- azidomethyl derivatized nucleosides, increased uracil-tolerance and/or improved binding to complementary nucleotide units of a multivalent molecule, compared to their corresponding wild type enzymes. The polypeptides disclosed herein may be used for the elongation of a nucleic acid during replication or synthesis, or may trap/bind a nucleotide at the site of nucleotide addition by, for example, use of a non-incorporable or blocked nucleotide, or can be used under conditions in which a required salt or cofactor is absent. The polypeptides disclosed herein may be utilized, for example, in polynucleotides sequencing applications such as, for example, sequencing by synthesis and sequencing by binding applications. Disclosed herein are mutant polymerases comprising at least 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or greater than 99% sequence identity to any one of SEQ ID NOS: 1, 2, 1714, 2789, 2790, 2791, 2792, 2793 or 2803.

[0148] The present disclosure provides engineered DNA polymerases comprising the amino acid sequence backbone of a family-B or family-A polymerase which typically include replicative polymerases that exhibit high fidelity. Examples of family-B type polymerases include family-B archaeal DNA polymerases and Phi29 polymerase. In some embodiments, engineered DNA polymerases comprise family-B archaeal DNA polymerases which can be selected from Thermococcus, Thermoplasmata, Pyrococcus, Methanococcus, Hadesarchaea, Euryarchaeota, or Candidatus. In some embodiments, engineered DNA polymerases that are family-B polymerases comprise the amino acid sequence backbone from 9°N polymerase (including THERMINATOR polymerase), VENT polymerase, DEEP VENT polymerase, Pfu polymerase or Pyrococcus abyssi polymerase. In some embodiments, engineered DNA polymerases that are family-A polymerases comprise the amino acid sequence backbone of Geobacillus stearothermophilus (e.g., Bst DNA polymerase).

[0149] Engineered DNA polymerases can be designed and prepared by introducing one or more mutations into the amino acid sequence of a DNA polymerase of interest and the resulting phenotype of the engineered polymerase can be determined. Any one or any combination of two or more mutation sites can be transferred from one type of polymerase to a positionally equivalent site (or functionally equivalent site) in a second type of polymerase. For example, any one or any combination of two or more mutation sites from a DNA polymerase comprising any one of SEQ ID NOS: 1, 2, 1714, 2789, 2790, 2791, 2792, 2793 and 2803, or any one of SEQ ID NOS:3-1713 or 1715-2787, can be introduced into a positionally equivalent site (or functionally equivalent site) in a Geobacillus stearothermophilus (e.g., Bst DNA polymerase) (SEQ ID NO:2794), a 9°N polymerase (SEQ ID NOS:2795 or 2796) (including THERMINATOR polymerase; SEQ ID NO:2797), VENT polymerase (SEQ ID NO:2798), DEEP VENT polymerase (SEQ ID NO:2799), Pfu polymerase (SEQ ID N0:2800) and/or Pyrococcus abyssi polymerase (SEQ ID NO:2801), RB69 polymerase (SEQ ID NO:2802) or Phi29 polymerase (SEQ ID NO:2803).

[0150] Exemplary sequence alignments are provided in FIGs. 33-40. The mutations include any one or any combination of two or more amino acid substitutions, insertions, deletions and/or truncations.

[0151] Functional equivalents of a residue comprise one or more amino acid residues that occupy a similar position in the sequence (e.g., sequence alignment) and/or three-dimensional structure of an enzyme (e.g., DNA polymerase), and performs substantially the same function as a known amino acid residue in a known enzyme. A functionally equivalent amino acid substitution includes one or more amino acid residues at a particular position in a basis polypeptide that has the same functional role in another polypeptide. A functionally equivalent amino acid substitution includes any one or any combination of conservative and/or non-conservative amino acid substitutions. Sequence alignments are provided in FIGs. 33-40, which list examples of amino acid residues at sites in a DNA polymerase having a backbone sequence of any one of SEQ ID NOS: 1, 2, 1714, 2789, 2790, 2791, 2792, 2793 and 2803, and functionally equivalent amino acid sites in Geobacillus stearotherm ophilus (e.g., Bst DNA polymerase) (SEQ ID NO:2794), 9°N DNA polymerase (relative to SEQ ID NO:2795 or 2796), THERMINATOR polymerase (relative to SEQ ID NO:2797), VENT polymerase (relative to SEQ ID NO:2798), DEEP VENT polymerase (relative to SEQ ID NO:2799), Pfu DNA polymerase (relative to SEQ ID N0:2800), Pyrococcus abyssi DNA polymerase (relative to SEQ ID NO:2801), RB69 polymerase (relative to SEQ ID NO:2802), or Phi29 polymerase (relative to SEQ ID NO:2803).

[0152] Wild type polypeptide sequences are often starting points for protein or enzyme engineering to generate mutant polypeptides. In some embodiments, a mutant polypeptide differs from a wild-type polypeptide by at least one amino acid residue. Often a mutant polypeptide differs by at least one amino acid residue from the nearest wild-type polypeptide. In some embodiments, a mutant polypeptide differs from a wild-type polypeptide by at least two amino acid residues. In some embodiments, a mutant polypeptide differs from a wildtype polypeptide by at least three, four, five, six or more amino acid residues. Often, a wild type sequence is the closest wild type sequence, identified by aligning the polypeptide comprising at least one mutation within a wild type sequence. In some embodiments, a wild type polypeptide sequence includes a sequence of a naturally-occurring polypeptide.

[0153] An amino acid substitution refers to replacing an amino acid residue at a selected position in a polypeptide with a different amino acid having a similar or different biochemical property, such as similar size, shape, conformation, chemical structure, charge and/or hydrophobicity. The amino acid substitution can be a conservative or non-conservative amino acid replacement. In some embodiments, an amino acid residue at a selected position in a polypeptide can be replaced with an amino acid having a polar side-chain. Examples of amino acids having a polar side-chain include arginine, asparagine, aspartic acid, glutamine, glutamic acid, histidine, lysine, serine and threonine. In some embodiments, an amino acid residue at a selected position in a polypeptide can be replaced with an amino acid having a nonpolar side-chain. Examples of amino acids having a nonpolar side-chain include alanine, cysteine, glycine, isoleucine, leucine, methionine, phenylalanine, prolific, tryptophan, tyrosine and valine. In some embodiments, an amino acid residue at a selected position in a polypeptide can be replaced with an amino acid having a hydrophobic side-chain. Examples of amino acids having a hydrophobic side-chain include glycine, alanine, valine, leucine, isoleucine, proline, phenylalanine, methionine, tyrosine and tryptophan. In some embodiments, an amino acid residue at a selected position in a polypeptide can be replaced with an amino acid having an uncharged side-chain. Examples of amino acids having an uncharged side-chain include glycine, serine, cysteine, asparagine, glutamine, tyrosine, and threonine. In some embodiments, an amino acid residue at a selected position in a polypeptide can be replaced with an amino acid having a positive charged side-chain. Examples of amino acids having a positive charged side-chain include arginine, histidine and lysine. In some embodiments, an amino acid residue at a selected position in a polypeptide can be replaced with an amino acid having a negative charged side-chain. Examples of amino acids having a negative charged side-chain include aspartic acid and glutamic acid.

[0154] Exemplary polypeptide mutants described herein are listed in Tables 1-2 (FIGs. 31-32).

[0155] In some embodiments, a polypeptide comprises a backbone sequence of RLF

89458.1 and having a sequence that has at least 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or greater than 99% sequence identity to any of SEQ ID NOS: 1 or 2 and the polypeptide comprises at least one of the mutations listed in Table 1, FIG. 31 (e g., SEQ ID NOS:3-1713).

[0156] In some embodiments, a polypeptide comprises a backbone sequence of NOZ

58130.1 and having a sequence that has at least 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or greater than 99% sequence identity to any of SEQ ID NOS: 1714 and the polypeptide comprises at least one of the mutations listed in Table 2, FIG. 32 (e.g., SEQ ID NOS: 1715-2787). [0157] In some embodiments, a polypeptide comprises a backbone sequence of RMF 90817 and having a sequence that has at least 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or greater than 99% sequence identity to SEQ ID NO:2787 and the polypeptide comprises at least one mutation that is positionally equivalent to the mutations listed in Tables 1 and/or 2 (FIGs. 31 and 32, respectively) (e.g., SEQ ID NOS:3- 1713) (e.g., SEQ ID NOS: 1715-2787). In some embodiments, positionally equivalent amino acid positions are shown in FIGs. 33 and 36.

[0158] In some embodiments, a polypeptide comprises a backbone sequence of MBC

7218772.1 and having a sequence that has at least 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or greater than 99% sequence identity to SEQ ID NO:2790 and the polypeptide comprises at least one of the mutations and the polypeptide comprises at least one mutation that is positionally equivalent to the mutations listed in Tables 1 and/or 2 (FIGs. 31 and 32, respectively) (e.g., SEQ ID NOS:3-1713) (e.g., SEQ ID NOS: 1715-2787). In some embodiments, positionally equivalent amino acid positions are shown in FIGs. 33 and 37.

[0159] In some embodiments, a polypeptide comprises a backbone sequence of WP

175059460.1 and having a sequence that has at least 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or greater than 99% sequence identity to SEQ ID NO:2791 and the polypeptide comprises at least one mutation that is positionally equivalent to the mutations listed in Tables 1 and/or 2 (FIGs. 31 and 32, respectively) (e.g., SEQ ID NOS:3-1713) (e.g., SEQ ID NOS: 1715-2787). In some embodiments, positionally equivalent amino acid positions are shown in FIGs. 33 and 38.

[0160] In some embodiments, a polypeptide comprising a backbone sequence of KUO

42443.1 and having a sequence that has at least 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or greater than 99% sequence identity to SEQ ID NO:2792 and the polypeptide comprises at least one mutation that is positionally equivalent to the mutations listed in Tables 1 and/or 2 (FIGs. 31 and 32, respectively) (e.g., SEQ ID NOS:3- 1713) (e.g., SEQ ID NOS: 1715-2787). In some embodiments, positionally equivalent amino acid positions are shown in FIGs. 33 and 39.

[0161] In some embodiments, a polypeptide comprising a backbone sequence of NOZ

77387.1 and having a sequence that has at least 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or greater than 99% sequence identity to SEQ ID NO:2793 and the polypeptide comprises at least one mutation that is positionally equivalent to the mutations listed in Tables 1 and/or 2 (FIGs. 31 and 32, respectively) (e.g., SEQ ID NOS:3- 1713) (e.g., SEQ ID NOS: 1715-2787). In some embodiments, positionally equivalent amino acid positions are shown in FIGs. 33 and 39.

[0162] In some embodiments, a polypeptide comprising a backbone sequence of Phi29 and having a sequence that has at least 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or greater than 99% sequence identity to SEQ ID NO:2803 and the polypeptide comprises at least one mutation that is positionally equivalent to the mutations listed in Tables 1 and/or 2 (FIGs. 31 and 32, respectively) (e.g., SEQ ID NOS:3- 1713) (e.g., SEQ ID NOS: 1715-2787).

[0163] Further described herein are segments, or portions of a larger polypeptide. Optionally, segments have catalytic activity such as nucleotide incorporation and nucleic acid extension activity, particularly in the context of a nucleotide polymerization or exonuclease domain as described herein. Described herein are polypeptides comprising any full-length or segment derived from any one of SEQ ID NOS: 1-1713, 1714-2787, 2789, 2790, 2791, 2792, 2793 and 2803, and at least one additional residue at the N-terminus or C-terminus (e.g., +1 residue). In some embodiments both the N and C terminus has at least an additional residue, two, three four five, six seven, eight, nine, ten 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, or more than 100 additional residues.

[0164] For example, described herein are polypeptides comprising any of one of SEQ ID NOS: 1-1713, 1714-2787, 2789, 2790, 2791, 2792, 2793 and 2803 (+1 residue), such as an adjacent N-terminal aspartic acid, an adjacent C-terminal arginine, or a combination thereof, or additional residues such as residues identified through an alignment of any one of SEQ ID NOS: 1-1713, 1714-2787, 2789, 2790, 2791, 2792, 2793 and 2803. Described herein are polypeptides comprising any one of SEQ ID NOS: 1-1713, 1714-2787, 2789, 2790, 2791, 2792, 2793 and 2803 (+1 residue), such as an adjacent N-terminal glutamine, an adjacent C- terminal histidine, or a combination thereof, or additional residues such as residues identified through an alignment of any one of SEQ ID NOS: 1-1713, 1714-2787, 2789, 2790, 2791, 2792, 2793 and 2803. Described herein are polypeptides comprising any one of SEQ ID NOS: 1-1713, 1714-2787, 2789, 2790, 2791, 2792, 2793 and 2803 (+1 residue), such as an adjacent N-terminal valine, an adjacent C-terminal cysteine, or a combination thereof, or additional residues such as residues identified through an alignment of any one of SEQ ID NOS: 1-1713, 1714-2787, 2789, 2790, 2791, 2792, 2793 and 2803. Described herein are polypeptides comprising any one of SEQ ID NOS: 1-1713, 1714-2787, 2789, 2790, 2791, 2792, 2793 and 2803 (+1 residue), such as an adjacent N-terminal threonine, an adjacent C- terminal cysteine, or a combination thereof, or additional residues such as residues identified through an alignment of any one of SEQ ID NOS: 1-1713, 1714-2787, 2789, 2790, 2791, 2792, 2793 and 2803. Described herein are polypeptides comprising any one of SEQ ID NOS: 1-1713, 1714-2787, 2789, 2790, 2791, 2792, 2793 and 2803 (+1 residue), such as an adjacent N-terminal threonine, an adjacent C-terminal cysteine, or a combination thereof, or additional residues such as residues identified through an alignment of any one of SEQ ID NOS: 1-1713, 1714-2787, 2789, 2790, 2791, 2792, 2793 and 2803. Described herein are polypeptides comprising any one of SEQ ID NOS: 1-1713, 1714-2787, 2789, 2790, 2791, 2792, 2793 and 2803 (+1 residue), such as an adjacent N-terminal aspartic acid, an adjacent C-terminal leucine, or a combination thereof, or additional residues such as residues identified through an alignment of any one of SEQ ID NOS: 1-1713, 1714-2787, 2789, 2790,

2791, 2792, 2793 and 2803. Described herein are polypeptides comprising any of SEQ ID NOS: 1-1713, 1714-2787, 2789, 2790, 2791, 2792, 2793 and 2803 (+1 residue), such as an adjacent N-terminal aspartic acid, an adjacent C-terminal arginine, or a combination thereof, or additional residues such as residues identified through an alignment of any one of SEQ ID NOS: 1-1713, 1714-2787, 2789, 2790, 2791, 2792, 2793 and 2803. Described herein are polypeptides comprising any one of SEQ ID NOS: 1-1713, 1714-2787, 2789, 2790, 2791,

2792, 2793 and 2803 (+1 residue), such as an adjacent N-terminal threonine, an adjacent C- terminal threonine, or a combination thereof, or additional residues such as residues identified through an alignment of any one of SEQ ID NOS: 1-1713, 1714-2787, 2789, 2790, 2791, 2792, 2793 and 2803. Described herein are polypeptides comprising any one of SEQ ID NOS: 1-1713, 1714-2787, 2789, 2790, 2791, 2792, 2793 and 2803 (+1 residue), such as an adjacent N-terminal threonine, an adjacent C-terminal asparagine, or a combination thereof, or additional residues such as residues identified through an alignment of any one of SEQ ID NOS: 1-1713, 1714-2787, 2789, 2790, 2791, 2792, 2793 and 2803. Described herein are polypeptides comprising any one of SEQ ID NOS: 1-1713, 1714-2787, 2789, 2790, 2791, 2792, 2793 and 2803 (+1 residue), such as an adjacent N-terminal threonine, an adjacent C- terminal asparagine, or a combination thereof, or additional residues such as residues identified through an alignment of any one of SEQ ID NOS: 1-1713, 1714-2787, 2789, 2790, 2791, 2792, 2793 and 2803. Described herein are polypeptides comprising any one of SEQ ID NOS: 1-1713, 1714-2787, 2789, 2790, 2791, 2792, 2793 and 2803 (+1 residue), such as an adjacent N-terminal threonine, an adjacent C-terminal serine, or a combination thereof, or additional residues such as residues identified through an alignment of any one of SEQ ID NOS: 1-1713, 1714-2787, 2789, 2790, 2791, 2792, 2793 and 2803. Engineered Polymerases Comprising RLF 89458.1 or RLF 78286.1 Backbone Sequence [0165] The present disclosure provides one or more mutant polymerases comprising a backbone sequence of RLF 89458.1 or RLF 78286.1 and having 100%, at least 99%, at least 98%, at least 97%, at least 95%, at least 90% at least 85%, at least 80%, at least 75%, at least 70%, at least 65%, at least 60%, at least 55%, or at least 50% sequence identity to any of SEQ ID NOS: 1-1713 (Table 1 and FIGs. 11-12). The amino acid sequences of RLF 89458.1 and RLF 78286.1 differ by an amino acid substitution at position 235, where RLF 78286.1 includes D235E.

[0166] In some embodiments, the mutant polymerases having a backbone sequence of RLF 89458.1 (e.g., SEQ ID NO: 1) or RLF 78286.1 (SEQ ID NO:2) comprise various domains.

[0167] In some embodiments, the N-terminal domain comprises amino acid residues 1- 134 (SEQ ID NO:2804) (e.g., FIG. 29).

[0168] In some embodiments, the exonuclease domain (e.g., 3’ to 5’ exonuclease domain) comprises amino acid residues 135-356 (SEQ ID NO:2805) (e.g., FIG. 29).

[0169] In some embodiments, the first palm domain comprises amino acid residues 357- 454 (SEQ ID NO:2806) (e.g., FIG. 29).

[0170] In some embodiments, the finger(s) domain comprises amino acid residues 455- 504 (SEQ ID NO:2807) (e.g., FIG. 29).

[0171] In some embodiments, the second palm domain comprises amino acid residues 505-615 (SEQ ID NO:2808) (e.g., FIG. 29).

[0172] In some embodiments, the thumb domain comprises amino acid residues 616-765 (SEQ ID NO:2809) (e g., FIG. 29).

[0173] The present disclosure provides compositions and methods comprising mutant polymerases have a backbone sequence of RLF 89458.1 (e.g., SEQ ID NO: 1) or RLF 78286.1 (SEQ ID NO:2) and comprise at least one amino acid substitution mutation that reduces 3’ to 5’ exonuclease activity compared to a polymerase that lacks an exo-minus mutation. For example, the mutant polymerases comprise at least one amino acid substitution at positions D141 and/or E143. In some embodiments, the mutant polymerases comprise a mutation D141A, D141V, D141L, D141I, D141F, D141Y, D141N, D141T, D141S, D141R, D141K, D141Q, D141W, D141E, D141M, D141P, D141G, D141H or D141C. In some embodiments, the mutant polymerases comprise a mutation E143A, E143V, E143L, E143I, E143F, E143Y, E143N, E143T, E143S, E143W, E143M, E143P, E143F, E143G, E143H, E143R, E143K, E143D, E143C or E143Q. In some embodiments, position E143 is not mutated. In some embodiments, the mutant polymerases comprise any combination of mutations at the D141 and the E143 sites.

[0174] In some embodiments, the mutant polymerases comprise non-mutated E143E, and a mutation D141A, D141V, D141L, D141I, D141F, D141Y, D141N, D141T, D141S, D141R, D141K, D141Q, D141W, D141E, D141M, D141P, D141G, D141H or D141C.

[0175] The present disclosure provides compositions and methods comprising mutant polymerase enzymes that can be used for sequencing a uracil-containing nucleic acid template molecule. The mutant polymerases can exhibit uracil-tolerance having increased ability to incorporate dATP into the 3’ end of a nucleic acid primer at a position that is opposite a uracil base in a nucleic acid template molecule. The mutant polymerases may also be capable of binding an adenine-bearing nucleotide unit of a multivalent molecule at a position that is opposite a uracil base in the nucleic acid template molecule. The mutant polymerases can exhibit increased uracil-tolerance compared to a wild type polymerase or compared to an engineered polymerase having mutations that do not confer uracil-tolerance. Mutant polymerases having a backbone sequence of RLF 89458 or RLF 78286 (e.g., SEQ ID NOS: 1 or 2 respectively) that are uracil-tolerant may comprise a mutation at position Y7, T9, H89, Q91, V93 and/or R97. In some embodiments, the mutant polymerase comprises a backbone sequence of RLF 89458 or RLF 78286 (e.g., SEQ ID NOS: 1 or 2 respectively) and having an amino acid substitution at position Y7, where the mutations comprise any of Y7A, Y7F, Y7N, Y7D, Y7R, Y7W, Y7H or Y7Q. In some embodiments, the mutant polymerase comprises a backbone sequence of RLF 89458 or RLF 78286 (e.g., SEQ ID NOS: 1 or 2 respectively) and having an amino acid substitution at position T9, where the mutations comprise any of T9N, T9E, T9S, T9L, T9I, T9D, T9A or T9R. In some embodiments, the mutant polymerase comprises a backbone sequence of RLF 89458 or RLF 78286 (e.g., SEQ ID NOS: 1 or 2 respectively) and having an amino acid substitution at position H89, where the mutations comprise any of H89D, H89A, H89Y, H89R, H89N, H89Q, H89K, H89F, H89L or H89V. In some embodiments, the mutant polymerase comprises a backbone sequence of RLF 89458 or RLF 78286 (e.g., SEQ ID NOS: 1 or 2 respectively) and having an amino acid substitution at position Q91, where the mutations comprise any of Q91L, Q91H, Q91R, Q91W, Q91A, Q91K, Q91N, Q91P, Q91V or Q91Y. In some embodiments, the mutant polymerase comprises a backbone sequence of RLF 89458 or RLF 78286 (e.g., SEQ ID NOS: 1 or 2 respectively) and having an amino acid substitution at position V93, where the mutations comprise any of V93A, V93M, V93E, V93F, V93Y, V93G, V93S, V93K, V93T or V93I. In some embodiments, the mutant polymerase comprises a backbone sequence of RLF 89458 or RLF 78286 (e.g., SEQ ID NOS: 1 or 2 respectively) and having an amino acid substitution at position R97, where the mutations comprise any of R97C, R97H, R97S, R97P, R97L, R97A, R97N, R97Q, R97E, R97I, R97K, R97M or R97T.

[0176] Other uracil -tolerant mutant polymerases having a backbone sequence of NOZ

58130 (SEQ ID NO: 1714), RMF 90817 (SEQ ID NO:2789), MBC 7218772 (SEQ ID NO:2790), WP 175059460 (SEQ ID NO:2791), KUO 42443 (SEQ ID NO:2792) or NOZ 77387 (SEQ ID NO:2793) may include a mutation that is positionally equivalent to Y7, T9, H89, Q91, V93 and/or R97 in RLF 89458 (SEQ ID NO: 1). FIG. 33 shows a sequence alignment of these various polymerases and their positionally equivalent amino acid residues. [0177] The present disclosure provides compositions and methods comprising mutant polymerases having a backbone sequence of RLF 89458.1 (e.g., SEQ ID NO: 1) or RLF 78286.1 (SEQ ID NO:2) and comprise at least one amino acid substitution mutations of an LYP motif, for example at positions L409, Y410 and P411. In some embodiments, at least one mutation in the LYP motif can increase the incorporation rate of nucleotide analogs. In some embodiments, any one or any combination of the first, second and/or third positions of the LYP motif can be mutated. For example, mutations of the LYP motif include AAG, AAP, AAV, AAI, AGA, AGG, AGI, AGP, AGV, FAA, FAG, FAI, FAP, FAV, FGA, FGG, FGP, FGV, LAG, LAI, LAP, LGG, LGI, LGV, SAA, SAG, SAI, SAV, SGA, SGG, SGI, YAA, YAG, YAI, YAP, YGA, YGG, YGI, YGP, LAA, LAV, LGP, LGA, FGI, SGV, YAV, YGV, SYP, SAP, AAA, SGP, LFP, IFP, VFP, LMP, VMP, IMP, LLP, VLP, ILP, LDP, VDP, IDP, LTP, VTP, ITP, LIP, TIP, NNP, NDP, NAP, SYG, SSG, SSS, CAG, ASG, SSG, MFG and FTA.

[0178] In some embodiments, the polymerases comprise a backbone sequence of RLF 89458 or RLF 78286 (e.g., SEQ ID NOS: 1 or 2 respectively) and having a substitution mutation at position L409 comprises a nonpolar amino acid or polar non-charged amino acid. In some embodiments, the amino acid substitution mutation at position L409 comprises valine, glycine, threonine, alanine, serine, isoleucine, leucine, phenylalanine, tyrosine or methionine. SEQ ID NOS: 1-1713 comprise exemplary amino acid substitution mutation at position L409.

[0179] In some embodiments, the polymerases comprise a backbone sequence of RLF 89458 or RLF 78286 (e.g., SEQ ID NOS: 1 or 2 respectively) and having a substitution mutation at position Y410 comprises a non-polar amino acid or a polar uncharged amino acid. In some embodiments, the amino acid substitution mutation at position Y410 comprises threonine, serine, glycine, alanine, valine, isoleucine or tyrosine. SEQ ID NOS: 1-1713 comprise exemplary amino acid substitution mutation at position Y410.

[0180] In some embodiments, the polymerases comprise a backbone sequence of RLF 89458 or RLF 78286 (e.g., SEQ ID NOS: 1 or 2 respectively) and having a substitution mutation at position P411 comprises a polar uncharged amino acid, non-polar amino acid or a positively charged amino acid. In some embodiments, the amino acid substitution mutation at position P411 comprises serine, glycine, alanine, valine, cysteine, lysine, isoleucine, threonine or proline. SEQ ID NOS: 1-1713 comprise exemplary amino acid substitution mutation at position P411.

[0181] The present disclosure provides compositions and methods comprising mutant polymerases having a backbone sequence of RLF 89458 or RLF 78286 (e.g., SEQ ID NOS:1 or 2 respectively) and having at least one mutation to reduce post-translational modifications. In some embodiments, the polymerase comprises at least one mutation or any combination of mutations of methionine, lysine, histidine, tryptophan and/or cysteine residue(s). In some embodiments, the polymerases comprise an amino acid substitution at position Ml, M129, M159, M313, M329, M467 and/or M759. In some embodiments, the mutation at position Ml comprises M1F, Mil, MIL, MIS, MIN, MIA, Ml V, Ml Y, M1Q, MIK, Ml V or MIA. In some embodiments, the mutation at position M129 comprises M129I, M129V, M129K, M129L, M129E, M129F, M129N, M129S, M129R or M129Y. In some embodiments, the mutation at position Ml 59 comprises M159W, M159F or M159Y. In some embodiments, the mutation at position M313 comprises M3131, M313K, M313L, M313 V, M313D, M313R, M3 13E, M313 A, M313L or M313N. In some embodiments, the mutation at position M329 comprises M329L, M329S, M329W, M329A, M329R, M329I, M329Q, M329N or M329E. In some embodiments, the mutation at position M467 comprises M467V, M467K, M467D, M467T, M467R, M467E, M467Q or M467L. In some embodiments, the mutation at position M759 comprises M759T, M759S, M759N, M759R, M759E, M759D or M759A.

[0182] In some embodiments, the polymerases comprise a backbone sequence of RLF 89458 or RLF 78286 (e.g., SEQ ID NOS: 1 or 2 respectively) and having an amino acid substitution to reduce post-translational modifications, including a mutation at position K240, K306, K371, K429, K468, K476, and/or K592. In some embodiments, the mutation at position K240 comprises K240S, K240E, K240R, K240D, K240N, K240Q or K240A. In some embodiments, the mutation at position K306 comprises K306R, K306N, K306Q, K306A, K306V, K306I or K306F. In some embodiments, the mutation at position K371 comprises K371R, K371D, K371N, K371Q, K371 Y, K371T, K371 V or K371L. In some embodiments, the mutation at position K429 comprises K429R, K429S, K429M, K429A, K429N, K429D, K429Q, K429H, K429Y, K429V, K429L or K429E. In some embodiments, the mutation at position K468 comprises K468R, K468E, K468Y, K468T or K468L. In some embodiments, the mutation at position K476 comprises K476R, K476D, K476A, K476F or K476R. In some embodiments, the mutation at position K592 comprises K592Q, K592R, K592W, K592Y, K592A, K592F, K592I, K592T, K592N or K592S.

[0183] In some embodiments, the polymerases comprise a backbone sequence of RLF 89458 or RLF 78286 (e.g., SEQ ID NOS: 1 or 2 respectively) and having an amino acid substitution to reduce post-translational modifications, including a mutation at position W299 and/or W767. In some embodiments, the mutation at position W299 comprises W299F, W299E, W299N, W299Q, W299Y, W299A or W299F. In some embodiments, the mutation at position W767 comprises W767H, W767Y, W767F, W767S, W767R, W767D, W767A or W767N.

[0184] In some embodiments, the polymerases comprise a backbone sequence of RLF 89458 or RLF 78286 (e.g., SEQ ID NOS: 1 or 2 respectively) and having an amino acid substitution to reduce post-translational modifications, including a mutation at position H601. In some embodiments, the mutation at position H601 comprises H601R, H601I, H601 A, H601T, H601 V, H601L, H601N or H601K.

[0185] In some embodiments, the polymerases comprise a backbone sequence of RLF 89458 or RLF 78286 (e.g., SEQ ID NOS: 1 or 2 respectively) and having an amino acid substitution to reduce post-translational modifications, including a mutation at position C428. In some embodiments, the mutation at position C428 comprises C428Y.

[0186] The present disclosure provides compositions and methods comprising mutant polymerases having a backbone sequence of RLF 89458 or RLF 78286 (e.g., SEQ ID NOS:1 or 2 respectively) and having at least one mutation to remove unpaired cysteines which may reduce oxidative damage to the polymerases. In some embodiments, removal of at least one unpaired cysteine increases thermal stability of the mutant polymerase and/or reduces protein aggregation. In some embodiments, removal of at least one unpaired cysteine increases the amount of protein in a lysate preparation. In some embodiments, the polymerase comprises at least one mutation or any combination of mutations of cysteines at position 223 and/or 509. In some embodiments, the mutation at position C223 comprises an amino acid substitution C223L, C223M, C223A, C223S, C223P, C223K, C223N, C223D or C223V. In some embodiments, the mutation at position C509 comprises an amino acid substitution C509V, C509Y, C509S, C509M, C509A, C509N, C509D, C509H or C509Q. [0187] In some embodiments, the polymerases comprise a backbone sequence of RLF 89458 or RLF 78286 (e.g., SEQ ID NOS: 1 or 2 respectively) and having an amino acid substitution to remove unpaired cysteines, including an amino acid substitution at positions C509 and V419. In some embodiments, the mutation at C509 comprises any of C509V, C509Y, C509S, C509M, C509A, C509N, C509D, C509H or C509Q. In some embodiments, the mutation at V419 comprises any of V419I, V419L or V419R.

[0188] In some embodiments, the polymerases comprise a backbone sequence of RLF 89458 or RLF 78286 (e.g., SEQ ID NOS: 1 or 2 respectively) and having an amino acid substitution to remove unpaired cysteines, including an amino acid substitution at positions C509 and Q497. In some embodiments, the mutation at C509 comprises any of C509V, C509Y, C509S, C509M, C509A, C509N, C509D, C509H or C509Q. In some embodiments, the mutation at Q497 comprises Q497H, Q497G, Q497M, Q497N, Q497F, Q497L, Q497R, Q497K, Q497T, Q497E, Q497D or Q497Y.

[0189] In some embodiments, the polymerases comprise a backbone sequence of RLF 89458 or RLF 78286 (e.g., SEQ ID NOS: 1 or 2 respectively) and having an amino acid substitution to remove unpaired cysteines, including an amino acid substitution at positions C509 and S512. In some embodiments, the mutation at C509 comprises any of C509V, C509Y, C509S, C509M, C509A, C509N, C509D, C509H or C509Q. In some embodiments, the mutation at S512 comprises S512R, S512D, S512E, S512H, S512F, S512K, S512W or S512D.

[0190] The present disclosure provides compositions and methods comprising mutant polymerases having a backbone sequence of RLF 89458 or RLF 78286 (e.g., SEQ ID NOS:1 or 2 respectively) and having at least one mutation to increase thermal stability of the polymerase compared to a wild type polymerase or compared to an engineered polymerase having mutations that do not confer increased thermal stability. In some embodiments, the polymerase exhibits thermal stability at an elevated temperature of about 72 - 75 °C, or about 75 - 80 °C, or about 80 - 85 °C, or about 85 - 90 °C, or higher temperatures. In some embodiments, a thermal shift assay using differential scanning fluorimetry can be used to determine the thermal stability of a polymerase.

[0191] In some embodiments, the polymerases comprise a backbone sequence of RLF 89458 or RLF 78286 (e.g., SEQ ID NOS: 1 or 2 respectively) and having an amino acid substitution to increase thermal stability comprise an amino acid substitution at one or more positions that also confers exonuclease-minus activity including D141 and/or E143. In some embodiments, polymerases that are engineered to exhibit increased thermal stability comprise an amino acid substitution at position M329 alone or in combination with D141 and/or E143. In some embodiments, polymerases that are engineered to exhibit increased thermal stability comprise an amino acid substitution at position D315 alone or in combination with D141 and/or E143. In some embodiments, polymerases that are engineered to exhibit increased amounts of protein (e.g., polymerase enzyme) in a lysate preparation comprise an amino acid substitution D141N alone or in combination with non-mutated E143 or any amino acid substitution of E143. An increased amount of protein in a lysate preparation can increase the yield of active polymerase in a manufacturing process.

[0192] In some embodiments, the mutation at D141 comprises D141 A, D141 V, D141L, D141I, D141F, D141Y, D141N, D141T, D141S, D141R, D141K, D141Q, D141W, D141E, D141M, D141P, D141G, D141H or D141C.

[0193] In some embodiments, the mutation at E143 comprises E143 A, E143 V, E143L, E143I, E143F, E143Y, E143N, E143T, E143S, E143W, E143M, E143P, E143G, E143H, E143R, E143K, E143D, E143C or E143Q.

[0194] In some embodiments, the mutation at M329 comprises M329L, M329S, M329W, M329A, M329R, M329I, M329Q, M329N or M329E.

[0195] In some embodiments, the mutation at D315 comprises D315A, D315E, D315R, D315W, D315L, D315W, D315F.

[0196] The present disclosure provides compositions and methods comprising mutant polymerases having a backbone sequence of RLF 89458 or RLF 78286 (e.g., SEQ ID NOS:1 or 2 respectively) and having a C-terminus truncation to increase thermal stability of the polymerase compared to a non-truncated polymerase having the same wild type or engineered backbone sequence. The C-terminal region of a polymerase may be disordered and may contribute to protein aggregation. Thus, truncation at a C-terminal region can reduce protein aggregation and improve stability. In some embodiments, the polymerase exhibits thermal stability at an elevated temperature of about 72 - 75 °C, or about 75 - 80 °C, or about 80 - 85 °C, or about 85 - 90 °C, or higher temperatures. In some embodiments, a thermal shift assay using differential scanning fluorimetry can be used to determine the thermal stability of a polymerase.

[0197] In some embodiments, the polymerases comprise a backbone sequence of RLF 89458 or RLF 78286 (e.g., SEQ ID NOS: 1 or 2 respectively) and are engineered to exhibit increased thermal stability, where the polymerases comprise a truncation at an amino acid position including K464(truncated), R465(truncated), E475 (truncated), Y481 (truncated), E616(truncated), E620(truncated), E755 (truncated), Y756(truncated), Q757(truncated), R758(truncated), M759(truncated), T762(truncated), W767(truncated) or M770(truncated). In Table 1 and 2, a truncation is designated with a “ ^A ”.

[0198] The present disclosure provides compositions and methods comprising mutant polymerases having a backbone sequence of RLF 89458 or RLF 78286 (e.g., SEQ ID NOS:1 or 2 respectively) and having an N-terminus truncation to increase thermal stability of the polymerase compared to a non-truncated polymerase having the same wild type or engineered backbone sequence. In some embodiments, the engineered polymerase comprises a deleted methionine at position 1. Table 1 lists various engineered polymerases having deleted methionine at position 1 which is designated “MIX”, and their Tml and Tm2 data. [0199] The present disclosure provides compositions and methods comprising mutant polymerases having a backbone sequence of RLF 89458 or RLF 78286 (e.g., SEQ ID NOS:1 or 2 respectively) and having at least one mutation that reduces polymerization-to- exonuclease conformational switching compared to a wild type polymerase or compared to an engineered polymerase having mutations that do not reduce conformational switching. In some embodiments, protein modeling can identify key amino acid residues that interact with the primer or the primer end, where these amino acid residues may play a role in interacting with the primer, or transferring the primer end from the polymerization site to the exonuclease site. In some embodiments, the polymerases comprise an amino acid substitution at any one or any combination of positions V610, D613, Q664, E668, P677 and/or D671.

[0200] In some embodiments, the mutation at V610 comprises V610D, V610A, V610K, V610S, V610T, V610N, V610R or V610Q.

[0201] In some embodiments, the mutation at D613 comprises D613S, D613E, D613R, D613K, D613N, D613Q, D613A, D613V, D613Y or D613F.

[0202] In some embodiments, the mutation at Q664 comprises Q664A, Q664L, Q664V, Q664F, Q664I, Q664R, Q664K, Q664T, Q664N or Q664M.

[0203] In some embodiments the mutation at E668 comprises E668G, E668K, E668M, E668A, E668P, E668S, E668R, E688N, E688D, E668Y or E668Q.

[0204] In some embodiments, the mutation at P677 comprises P677L, P677R, P677K or P677A.

[0205] In some embodiments, the mutation at D671 comprises D671G, D671R, D671 Y, D671S, D671A, D671K or D671N.

[0206] The present disclosure provides compositions and methods comprising mutant polymerases having a backbone sequence of RLF 89458 or RLF 78286 (e.g., SEQ ID NOS:1 or 2 respectively) and having at least one mutation that reduces protein aggregation by reducing intermolecular interactions compared to a wild type polymerase or compared to an engineered polymerase having mutations that do not confer reduced aggregation. In some embodiments, the mutant polymerase aggregates at an elevated temperature of about 72 - 75 °C, or about 75 - 80 °C, or about 80 - 85 °C, or about 85 - 90 °C, or higher temperatures, compared to a wild type polymerase or compared to an engineered polymerase having mutations that do not confer reduced aggregation. In some embodiments, a thermal shift assay using differential scanning fluorimetry can be used to determine the temperature of aggregation of a protein.

[0207] In some embodiments, the polymerases comprise a backbone sequence of RLF 89458 or RLF 78286 (e.g., SEQ ID NOS: 1 or 2 respectively) and having an amino acid substitution to reduce aggregation comprise an amino acid substitution at one or more positions Ni l, K507, K511 and/or K637.

[0208] In some embodiments, the mutation at position N11 comprises N1 IS, N11A, N11R, N1 IQ, N1 IE, N1 IK, N1 IT or N1 ID.

[0209] In some embodiments, the mutation at position K507 comprises K507L, K507E, K507S, K507A, K507N, K507Q, K507E, K507T or K507D.

[0210] In some embodiments, the mutation at position K511 comprises E51 IK, E511 S, E511A, E511R, E511N, E511T, E511Q, E511L, E511D or E511A.

[0211] In some embodiments, the mutation at position K637 comprises K637M, K637A, K637N, K637Q, K637E, K637S or K637T.

[0212] The present disclosure provides compositions and methods comprising mutant polymerases having a backbone sequence of RLF 89458.1 (e.g., SEQ ID NO: 1) or RLF 78286.1 (SEQ ID NO:2) and comprising amino acid substitution mutations at any one or any combination of positions including Ml, L3, D4, D6, Y7, 18, T9, E 10, Ni l, G12, K13, P14, V15, 116, R17, 118, F19, K20, K21, E22, K23, G24, E25, F26, K27, 128, E29, Y30, D31,R32, N33, F34, E35, P36, Y37, 138, Y39, A40, L41, L42, E43, D44, D45, E46, S47, 148, E49, D50, 151, K52, K53, 154, T55, R58, G56, E57, R58, H59, G60, K61, K62, V63, 165, 166, R67, V68, E69, K70, V71, K72, K73, K74, F75, L76, G77, E78, P79, 180, E81, V82, W83, K84, L85, V86, F87, E88, H89, P90, Q91, D92, V93, P94, A95, 196, R97, D98, A99, 1100, R101, S102, H103, P104, A105, V106, R107, E108, 1109, F110, El 11, Y112, D113, 1114, Pl 15, F116, A117, K118, R119, Y120, L121, 1122, D123, K124, L126, V127, P128, M129, E130, G131, G132, E133, L135, K136, L137, L138, A139, F140, D141, 1142, E143, T144, F145, Y146, H147, E148, D150, E151, E156, M159, S166, W173, K174, 1176, Y180, A190, 1191, K192, L195, L198, R199, Q196, P203, V205, L207, Y209, G211, N213, F214, D215, F216, A217, Y218, 1219, K220, C223, E224, K225, G227, L228, K229, F230, T231, 1232, G233, R234, S237, E238, P239, K240, 1241, Q242, R243, M244, G245, D246, R247, A249, E251, L258, Y261, P262, V264, R265, H266, T267, 1268, R269, L270, P271, T272, Y273, T274, L275, E276, A277, V278, V282, F283, K285, K286, K287, E288, K289, V290, Y291, A292, 1295, E297, A298, W299, K300, S301, E302, L305, K306, R307, V308, A309, Q310, Y311, M313, D315, R317, A318, Y320, E321, P328, V331, M329, E332, L333, A334, 1337, G338, Q339, V341, D343, S345, S347, S348, T349, G350, N351, L352, V353, W355, Y356, L357, R359, V360, Y362, N365, E366, L367, K371, P372, G373, G374, E375, E376, Y377, Q378, M381, S383, S384, Y385, 1386, G388, Y389, E394, K395, G396, E399, S400, A402, Y403, L404, F406, R407, S408, L409, Y410, P411, S412, 1413, V415, H417, V419, P421, D422, T423, L424, E425, E427, C428, K429, N430, Y431, V433, A434, 1436, Y439, R440, K443, K446, G447, F448, 1449, P450, S451, 1452, L453, E454, D455, 1457, T459, K462, V463, K464, R465, M467, K468, T470, 1471, D472, 1474, E475, K476, M478, Y481, R484, A485, L486, K487, 1488, N491, S492, Y493, Y494, G495, Q497, G498, Y499, P500, K501, S506, K507, E508, C509, E511, S512, V513, T514, G517, R518, H519, 1521, T523, A528, E529, K534, V535, Y537, A538, D539, T540, D541, G542, F543, F544, 1547, N549, E550, K551, P552, 1555, S557, K558, A559, K560, K561, L563, K564, H565, E568, K569, G572, M573, E575, E577, L583, G585, F586, V588, T589, K592, Y593, L595, 1596, D599, H601, T604, R605, G606, L607, V609, V610, R611, R612, D613, E616, 1617, K619, E620, T621, Q622, A623, K624, V625, L626, E627, V628, 1629, L630, R631, E632, G633, S634, 1635, E636, K637, A638, A639, G640, 1641, V642, K644, V645, V646, E647, D648, L649, A650, N651, Y652, R653, V654, V656, E657, K658, 1660, H662, E663, Q664, 1665, T666, R667, E668, K670, D671, Y672, K673, A674, T675, G676, P677, H678, V679, A680, 1681, A682, K683, R684, L685, Q686, A687, R688, G689, 1690, K691, V692, K693, P694, T696, 1698, S699, Y700, V701, V702, L703, K704, G705, S706, K707, K708, 1709, D711, R712, V713, 1714, L715, F716, D717, E718, Y719, D720, S721, S722, R723, K725, Y726, P728, Y730, Y731, 1732, H733, N734, Q735, V736, P738, A739, V740, L741, R742, 1743, L744, E745, A746, F747, G748, Y749, K750, E751, K752, D753, L754, E755, Y756, Q757, R758, M759, K760, Q761, T762, G763, L764, G765, A766, W767, L768 and/or M770.

[0213] The present disclosure provides compositions and methods comprising mutant polymerases having a backbone sequence of RLF 89458.1 (e.g., SEQ ID NO:1) or RLF 78286.1 (SEQ ID NO:2) and comprise amino acid substitution mutations at any one or any combination of positions including M1F, Mil, MIL, MIS, MIN, MIA, M1V, M1Y, M1Q, MIK, M1V, MIA, L3I, D4R, D4A, D6S, D6R, Y7A, Y7F, Y7N, Y7D, Y7R, Y7W, Y7H, Y7Q, I8S, T9N, T9E, T9S, T9L, T9I, T9D, T9 A, T9R, E10V, E10D, E10K, E10R, E10A, E10N, N11S, N11A, N11R, N11Q, N11E, N11K, NUT, N11D, G12S, G12D, G12E, K13E, P14Q, P14N, P14S, V15I, I16T, I16N, I16F, R17H, R17C, I18V, I18L, F19Y, F19S, F19I, K20M, K20E, K21E, E22G, E22V, E22K, K23E, K23M, K23R, K23A, K23N, G24S, E25K, F26L,K27M, I28F, I28N, I28T, 128 V, I28F, E29V, E29D, Y3OF, Y30N, Y30D, Y30K, D31V, R32C, R32S, N33S, F34S, F34I, E35K, E35G, E35D, P36L, P36A, P36G, P36V, P36M, P36T, P36K, Y37N, Y37F, I38T, I38N, Y39F, A40G, A40V, A40T, L41P, L41F, L41Y, L41D, L41E, L42P, L42Q, E43V, E43K, E43D, D44N, D44G, D45V, E46V, E46S, S47N, S47G, S47R, S47A, I48V, E49G, E49K, D50V, D50G, D50N, D50E, 15 IK, 15 IF, 15 IV, K52I, K52R, K53E, I54T, I54N, I54F, I54K, I54V, T55I, T55S, T55A, G56D, G56S, G56V, G56A, E57G, E57K, R58C, R58L, R58H, H59L, H59Y, G60S, G60D, K61M, K61T, K62N, K62E, K62R, K62T, K62V, V63A, V63I, V63D, I65T, I65V, I65F, I65N, I66V, I66T, I66N, I66K, R67C, V68M, V68A, E69K, K70I, V71I, K72H, K72R, K72V, K72Q, K73E, K74E, K74R, K74N, K74Q, F75C, L76Q, G77D, G77S, E78K, E78G, E78N, E78S, E78R, P79S, I8OF, I8ON, I8OK, I8OS, I8OR, E81D, E81V, V82A, W83R, K84R, L85V, L85Q, L85A, V86D, V86I, V86A, V86Y, F87I, F87L, F87C, E88K, E88D, E88N, E88T, H89D, H89A, H89Y, H89R, H89N, H89Q, H89K, H89F, H89L, H89V, P90L, P90S, P90D, P90R, P90A, P90G, P90V, P90M, P90T, P90K, Q91L, Q91H, Q91R, Q91W, Q91A, Q91K, Q91N, Q91P, Q91V, Q91Y, D92N, D92V, D92E, D92R, V93A, V93M, V93E, V93F, V93Y, V93G, V93S, V93K, V93T, V93I, V93L, P94L, P94W, P94Y, P94Q, P94F, P94S, A95V, I96T, I96K, I96S, R97C, R97H, R97S, R97P, R97L, R97A, R97N, R97Q, R97E, R97I, R97K, R97M, R97T, D98E, D98N, D98V, A99T, A99K, HOOT, R1O1C, R101H, S102N, S102G, S102E, H103R, H103L, H1O3Q, H103Y, P104T, P104L, A1O5S, V106A, V106T, R107C, R107S, R107V, E108V, I109K, I109N, I109F, Fl 1OL, Fl IOS, Fl 1OY, El 1 IV, El 11G, Y112C, DI 13G, DI 13Y, Il 14T, Il 14A, Il 14G, Il 14V, Il 14M, Il 14T, Il 14K, Pl 15C, P115L, P115S, P115R, P115F, F116L, F116S, F116A, A117T, Al 17V, A117K, K118M, K118R, K118A, K118Q, K118Y, K118N, R119H, R119S, R119C, R119A, R119G, R119V, R119M, R119T, R119K, R119Y, Y120C, Y120N, L121M, I122V, I122F, I122N, I122D, D123G, D123E, D123N, D123V, K124N, K124E, K124R, L126F, L126P, L126Q, V127M, V127I, P128L, P128M, M129I, M129V, M129K, M129L, M129E, M129F, M129N, M129S, M129R, M129Y, E130D, E130G, E130V, E130K, E13OT, G131S, G132S, G132D, E133K, L135M, L135P, L135Q, K136E, K136R, K136L, L137F, L137M, L138P, A139E, F140Y, F140L, F140S, D141A, D141V, D141L, D141I, D141F, D141Y, D141N, D141T, D141S, D141R, D141K, D141Q, D141W, D141E, D141M, D141P, D141G, D141H, D141C, I142V, I142F, I142A, E143A, E143V, E143L, E143I, E143F, E143Y, E143N, E143T, E143S, E143W, E143M, E143P, E143G, E143H, E143R, E143K, E143D, E143C, E143Q, T144F, F145L, Y146C, Y146A, Y146E, Y146S, Y146E, Y146K, Y146T, Y146R, H147E, H147R, H147E, H147D, H147N, H147Q, H147K, H147A, E148S, E148D, E148R, E148A, D150R, D150E, E151R, E156P, M159W, M159F, M159Y, S166E, W173R, W173A, W173Q, W173N, W173H, W173F, K174N, K174D, K174E, K174Q, I176V, Y180F, A190V, A190M, I191L, K192L, L195A, R199H, Q196R, L198I, L198V, P203S, V205A, L207I, L207V, Y209A, Y209E, Y209W, G211S, N213E, N213W, N213Y, F214A, F214E, F214W, F214V, D215A, D215N, D215Q, D215E, D215R, D215K, D215P, F216L, A217N, A217T, A217Q, A217S, Y218H, 1219V, I219L, K220R, K220N, K220Q, K220H, K220I, K220L, K220M, K220Y, C223V, C223E, C223S, C223L, C223M, C223A, C223P, C223K, C223N, C223D, E224V, E224R, E224K, K225E, G227S, L228P, L228I, L228V, K229R, K229N, K229Q, K229H, F230L, T231I, T231P, I232F, G233D, R234C, S237G, S237C, E238S, E238R, P239S, K240S, K240E, K240R, K240D, K240N, K240Q, K240A, I241T, I241Q, I241E, I241N, 1241 A, 1241 S, I241D, I241P, Q242N, Q242S, Q242R, Q242D, Q242E, Q242V, R243E, M244T, M244K, G245D, G245S, G245R, G245A, G245N, G245K, D246R, D246L, D246E, D246V, D246Q, R247E, R247D, R247S, R247H, A249G, A249V, E251S, E251R, E251A, L258I, L258Q, L258F, Y261A, Y261P, Y261T, P262S, P262R, P262L, P262D, P262E, P262Q, V264I, V264A, R265D, R265I, H266F, H266W, H266Y, H266R, H266I, H266L, H266A, H266K, T267A, T267F, T267M, T267V, T267W, T267Y, T267I, T267S, I268A, I268F, I268M, I268V, I268W, I268Y, R269L, R269K, R269S, R269T, R269V, R269N, R269H, R269Y, L270R, P271S, P271F, P271E, P271L, P271Q, P271N, T272A, T272Y, T272V, T272S, T272L, T272E, T272C, T272R, T272W, T272N, T272F, T272H, T272K, Y273A, Y273W, T274E, T274W, T274S, T274D, T274V, T274A, T274R, T274N, L275P, L275M, E276K, A277V, V278M, V282L, V282T, V282G, V282I, F283L, K285I, K285Q, K286E, K286P, K287R, E288G, E288K, K289E, K289Q, K289N, K289I, K289R, V290E, Y291F, Y291N, Y291D, Y291K, Y291R, Y291Q, Y291A, A292N, A292T, A292I, I295N, E297G, A298G, W299F, W299E, W299N, W299Q, W299Y, W299A, W299F, K300S, K300E, S301N, S301T, E302G, L305P, K306R, K306N, K306Q, K306A, K306V, K306I, K306F, R307C, V308I, V308A, A309S, Q310R, Y311A, Y311E, Y311W, Y311F, M3131, M313K, M313L, M313 V, M313D, M313R, M313E, M313 A, M313L, M3 13N, D315 A, D315E, D315R, D315 W, D315L, D315 W, D315F, R317C, R317K, A318V, Y320F, E321L, P328A, M329L, M329S, M329W, M329A, M329R, M329I, M329Q, M329N, M329E, V331A, E332K, E332G, E332Q, L333A, L333V, L333I, L333F, A334S, I337V, G338D, Q339N, V341L, D343E, D343N, D343R, D343A, S345C, S345R, S347N, S347T, S347R, S347A, S348C, T349A, T349E, T349F, T349I, T349L, T349N, T349S, T349Y, G350S, N351S, N351Q, N351R, N351I, N351Y, N351K, N351A, N351E, L352M, V353Q, V353E, W355R, W355F, Y356N, Y356C, Y356L, Y356F, L357P, R359H, V360A, V360D, V360I, V360K, Y362I, Y362E, Y362F, Y362N, Y362D, Y362K, Y362R, Y362T, N365S, E366A, E366D, E366N, E366Q, E366R, L367P, K371R, K371D, K371N, K371Q, K371Y, K371T, K371V, K371L, P372S, P372M, G373S, G373D, G374E, E375R, E375K, E376K, Y377L, Q378R, Q378A, Q378E, Q378K, M381I, M381R, M381V, M381D, M381L, S383G, S383Q, S383E, S383T, S384A, S384R, S384D, S384Q, S384E, S384T, Y385R, Y385S, Y385F, Y385K, Y385H, Y385W, Y385A, Y385M, Y385F, Y385D, I386A, I386N, I386D, I386E, I386K, I386T, I386L, G388S, G388R, Y389R, Y389S, Y389F, Y389N, Y389D, Y389K, Y389A, Y389Q, Y389E, Y389I, E394G, K395R, G396S, E399D, S400N, S400D, A402T, A402V, Y403H, Y403L, Y403D, Y403Q, Y403E, Y403H, Y403K, Y403F, Y403W, Y403R, L404Q, F406Y, F406R, F406I, R407N, R407K, R407A, R407L, R407V, R407I, S408A, S408G, L409S, L409F, L409A, L409Y, L409I, L409V, L409T, L409N, L409C, L409M, Y410A, Y410G, Y410F, Y410M, Y410L, Y410D, Y410T, Y410I, Y410N, Y410V, Y410E, Y410S, Y410L, P411G, P411 A, P41 II, P411 V, P41 IS, P41 IT, P411L, S412N, S412A, S412G, I413F, I413V, V415M, V415K, V415R, V415N, V415T, V415I, H417I, H417R, H417F, H417Y, H417V, V419I, V419L, V419R, P421S, D422V, T423I, T423L, L424Q, E425N, E427G, E427R, C428Y, K429R, K429S, K429M, K429A, K429N, K429D, K429Q, K429H, K429Y, K429V, K429L, K429E, N430E, Y431A, Y431D, V433A, A434V, A434D, A434P, I436T, I436F, I436A, I436R, I436N, I436D, I436Q, I436E, I436H, I436K, I436S, Y439H, R440H, K443R, K446P, G447D, F448I, F448L, I449N, I449F, P450L, S451N, S451T, S451A, S451D, I452L, L453Q, E454D, E454N, E454T, E454G, D455N, I457L, T459E, K462D, V463M, V463I, K464C, R465C, R465T, M467V, M467K, M467D, M467T, M467R, M467E, M467Q, M467L, K468R, K468E, K468Y, K468T, K468L, T470S, T470A, I471K, I471Q, 1471 S, 1471 V, I471K, D472V, D472E, D472N, I474C, I474F, I474V, I474L, E475C, K476R, K476D, K476A, K476F, K476R, M478L, Y481C, Y481A, Y481F Y481T, Y481V, Y481W, R484D, R484N, R484K, R484S, R484T, R484V, R484L, A485S, A485T, A485L, A485V, A485G, A485R, L486I, K487M, K487R, K487N, K487A, K487Q, K487Y, I488A, I488V, I488S, I488T, I488M, I488R, I488N, I488Q, I488E, I488K, I488L, N491T, N491S, N491A, N491I, S492G, S492Y, S492D, S492K, S492T, S492N, S492E, Y493T, Y493S, Y493I, Y493F, Y493W, Y494A, Y494N, Y494G, Y494F, Y494W, G495S, Q497H, Q497G, Q497M, Q497N, Q497F, Q497L, Q497R, Q497K, Q497T, Q497E, Q497D, Q497Y, G498R, G498D, G498E, G498F, G498I, G498S, Y499F, P500A, K501R, K501A, K501Q, K501Y, K501N, S506C, S506R, S506A, S506L, S506T, S506N, S506D, S506H, S506V, K507L, K507E, K507S, K507A, K507N, K507Q, K507E, K507T, K507D, E508Q, E508C, C509V, C509Y, C509S, C509M, C509A, C509N, C509D, C509H, C509Q, E51 IK, E511 S, E511 A, E511R, E51 IN, E51 IT, E51 IQ, E511L, E511D, E511A, S512R, S512D, S512E, S512H, S512F, S512K, S512W, S512D, V513T, V513I, V513L, V513M, V513F, V513A, V513S, T514A, T514G, T514S, T514V, T514I, T514S, G517A, G517S, G517V, G517T, R518C, H519N, H519Y, H519E, H519Q, I521N, I521T, I521E, I521H, T523I, T523A, A528L, A528I, E529N, K534N, K534S, K534R, V535N, V535K, V535S, V535R, Y537H, A538V, A538G, D539A, D539G, D539E, D539V, D539L, D539S, D539N, D539I, T540I, D541A, D541G, D541E, G542S, G542E, G542D, G542N, G542R, G542T, F543L, F544H, F544Y, I547F, I547T, I547P, N549G, E550A, K551D, P552L, 1555 V, S557C, S557K, K558A, K558V, K558Q, K558R, A559K, K561N, K561E, L653M, K564S, K564Q, H565Y, H565S, H565N, E568K, K569E, G572S, M573I, M573V, M573K, M573D, M573A, M573R, M573L, E575K, E577D, L583P, G585D, G585A, G585I, G585V, G585Y, G585F, G585T, F586I, V588E, V588T, T589K, K592Q, K592R, K592W, K592Y, K592A, K592F, K592I, K592T, K592N, K592S, Y593R, Y593N, Y593E, Y593H, Y593K, Y593F, Y593A, L595V, I596T, D599E, H601R, H601I, H601A, H601T, H601V, H601L, H601N, H601K, T604S, R605K, R605N, R605Q, R605H, R605D, R605E, R605S, R605T, R605Y, R605A, G606S, G606R, G606Y, G606Q, G606N, G606E, G606D, L607F, V609I, V609L, V610D, V610A, V610K, V610S, V610T, V610N, V610R, V610Q, R611M, R611E, R612E, R612H, R612F, R612W, R612M, R612S, R612N, R612G, R612L, R612I, D613S, D613E, D613R, D613K, D613N, D613Q, D613A, D613V, D613Y, D613F, E616C, E616G, 1617V, K619R, K619A, K619S, K619T, K619V, E620D, E620K, E620C, E620V, T621I, T621S, Q622L, A623T, A623C, A623K, K624I, K624R, V625F, L626I, E627K, V628L, V628I, V628A, I629F, I629C, L630Q, L630M, R631H, R631C, R631D, R631K, E632G, E632C, E632D, E632H, G633S, G633D, S634C, S634D, I635V, I635N, I635T, E636G, E636K, E636D, K637M, K637A, K637N, K637Q, K637E, K637S, K637T, A638E, A638V, A638T, A639T, A639V, G640D, G640R, I641F, I641V, I641A,V642I, V642A, K644E, V645E, V645I, V645M, V646A, V646D, E647G, E647D, E647K, D648V, D648C, D648L, D648G, L649Q, A650E, A650V, A650T, A650N, A650S, N651S, N651K, Y652H, Y652C, Y652M, Y652L, Y652F, R653C, R653H, R653Y, R653E, V654M, V656I, V656I, E657V, K658R, K658E, K658I, K658L, I660V, H662V, E663K, E663R, E663S, E663M, E663Q, E663V, Q664A, Q664L, Q664V, Q664F, Q664I, Q664R, Q664K, Q664T, Q664N, Q664M, I665V, I665F, I665P, I665M, I665F, T666A, R667E, E668G, E668K, E668M, E668A, E668P, E668S, E668R, E688N, E688D, E668Y, E668Q, K670E, K670I, K670R, K670S, D671G, D671R, D671Y, D671S, D671A, D671K, D671N, Y672F, K673I, K673Y, K673R, K673S, K673E, A674T, A674V, A674S, T675S, T675I, T675A, G676S, G676F, G676E, G676Y, G676R, G676L, G676Q, P677L, P677R, P677K, P677A, H678R, H678K, H678Q, H678F, H678W, V679S, V679M,A680V, A680I, A680D, I681T, I681L, I681F, I681V, A682T, A682S, K683R, R684H, L685E, Q686R, Q686C, Q686L, Q686A, A687C, A687T, A687S, R688S, G689S, G689D, I690V, I690F, I690R, I690N, I690Q, I690K, I690T, I690Y, K691R, K691V, K691T, K691D, K691E, K691Q, K691N, V692I, K693M, K693V, K693Q, K693R, K693A, K693T, K693N, K693Y, K693S, K693E, K693D, P694R, T696S, T696I, T696L, T696M, I698K, I698M, I698F, I698Q, S699I, S699G, Y700W, Y700S, V701I, V702A, V702I, L703P, K704E, K704I, K704N, G705D, S706N, S706C, S706G, K707I, K707G, K707N, K708M, K708R, I709F, I709V, I709L, D711G, R712C, V713I, V713A, I714F, L715P, L715Q, F716L, D717N, E718K, E718V, Y719F, D720V, D720Y, D720E, S721N, S721C, S721G, S721P, S722G, R723H, K725E, K725L, K725R, Y726F, P728S, P728L, P728A, Y730H, Y731H, I732T, I732F, I732N, H733R, H733E, N734Y, N734R, N734P, N734D, N734K, N734T, Q735H, Q735R, V736A, P738L, A739V, V740I, L741A, L741Q, L741E, R742K, R742L, R742C, I743V, I743E, L744A, E745V, E745F, E745R, A746V, A746G, F747L, F747Y, G748V, G748K, Y749F, Y749E, K750N, K750R, E751K, E751D, E751M, K752E, K752L, D753V, D753E, D753G, L754Y, L754S, E755G, E755Q, E755D, E755K, E755Y, E755R, Y756C, Y756F, Y756I, Y756R, Y756Q, Y756K, Q757L, Q757H, Q757S, Q757M, R758H, R758A, R758K, M759T, M759S, M759N, M759R, M759E, M759D, M759A, Q761L, T762N, G765S, G765R, G765L, G765F, G765Y, G765I, G765T, G765D, G765E, W767H, W767Y, W767F, W767S, W767R, W767D, W767A, W767N, M770S, M770T and/or M770N.

[0214] In some embodiments, the mutant polymerases have a backbone sequence of RLF 89458.1 (e.g., SEQ ID NO: 1) or RLF 78286.1 (SEQ ID NO:2) and comprise an amino acid deletion at any one or any combination of positions including Ml (deleted), R58(deleted), V93(deleted) and/or E755 (del eted).

[0215] In some embodiments, the mutant polymerases have a backbone sequence of RLF 89458.1 (e.g., SEQ ID NO:1) or RLF 78286.1 (SEQ ID NO:2) and having a substitution mutation at position ML In some embodiments, the amino acid substitution at position Ml comprises any of the 20 natural amino acids (i.e., W, I, M, P, F, G, A, V, L, H, R, K, D, E, N, C, S, T, or Q) or with non-natural amino acids as are known to those of skill in the art. [0216] In some embodiments, the mutant polymerases have a backbone sequence of RLF

89458.1 (e.g., SEQ ID NO: 1) or RLF 78286.1 (SEQ ID NO:2) and having a substitution mutation at position Y7. In some embodiments, the amino acid substitution at position Y7 comprises any of the 20 natural amino acids (i.e., W, I, M, P, F, G, A, V, L, H, R, K, D, E, N, C, S, T, or Q) or with non-natural amino acids as are known to those of skill in the art.

[0217] In some embodiments, the mutant polymerases have a backbone sequence of RLF

89458.1 (e.g., SEQ ID NO: 1) or RLF 78286.1 (SEQ ID NO:2) and having a substitution mutation at position K74. In some embodiments, the amino acid substitution at position K74 comprises any of the 20 natural amino acids (i.e., W, I, M, P, F, G, A, V, L, H, R, K, D, E, N, C, S, T, or Q) or with non-natural amino acids as are known to those of skill in the art.

[0218] In some embodiments, the mutant polymerases have a backbone sequence of RLF

89458.1 (e.g., SEQ ID NO: 1) or RLF 78286.1 (SEQ ID NO:2) and having a substitution mutation at position E88. In some embodiments, the amino acid substitution at position E88 comprises any of the 20 natural amino acids (i.e., W, I, M, P, F, G, A, V, L, H, R, K, D, E, N, C, S, T, or Q) or with non-natural amino acids as are known to those of skill in the art.

[0219] In some embodiments, the mutant polymerases have a backbone sequence of RLF

89458.1 (e.g., SEQ ID NO: 1) or RLF 78286.1 (SEQ ID NO:2) and having a substitution mutation at position V93. In some embodiments, the amino acid substitution at position V93 comprises any of the 20 natural amino acids (i.e., W, I, M, P, F, G, A, L, H, R, K, D, E, N, Y, C, S, T, or Q) or with non-natural amino acids as are known to those of skill in the art.

[0220] In some embodiments, the mutant polymerases have a backbone sequence of RLF

89458.1 (e.g., SEQ ID NO: 1) or RLF 78286.1 (SEQ ID NO:2) and having a substitution mutation at position A217. In some embodiments, the amino acid substitution at position A217 comprises any of the 20 natural amino acids (i.e., W, I, M, P, F, G, A, L, H, R, K, D, E, N, Y, C, S, T, or Q) or with non-natural amino acids as are known to those of skill in the art.

[0221] In some embodiments, the mutant polymerases have a backbone sequence of RLF

89458.1 (e.g., SEQ ID NO: 1) or RLF 78286.1 (SEQ ID NO:2) and having a substitution mutation at position Y261. In some embodiments, the amino acid substitution at position Y261 comprises any of the 20 natural amino acids (i.e., W, I, M, P, F, G, A, V, L, H, R, K, D, E, N, C, S, T, or Q) or with non-natural amino acids as are known to those of skill in the art.

[0222] In some embodiments, the mutant polymerases have a backbone sequence of RLF

89458.1 (e.g., SEQ ID NO: 1) or RLF 78286.1 (SEQ ID NO:2) and having a substitution mutation at position T267. In some embodiments, the amino acid substitution at position T267 comprises any of the 20 natural amino acids (i.e., W, I, M, P, F, G, A, V, L, H, R, K, D, E, N, Y, C, S or Q) or with non-natural amino acids as are known to those of skill in the art. [0223] In some embodiments, the mutant polymerases have a backbone sequence of RLF

89458.1 (e.g., SEQ ID NO: 1) or RLF 78286.1 (SEQ ID NO:2) and having a substitution mutation at position 1268. In some embodiments, the amino acid substitution at position 1268 comprises any of the 20 natural amino acids (i.e., W, M, P, F, G, A, V, L, H, R, K, D, E, N, Y, C, S, T, or Q) or with non-natural amino acids as are known to those of skill in the art. [0224] In some embodiments, the mutant polymerases have a backbone sequence of RLF

89458.1 (e.g., SEQ ID NO: 1) or RLF 78286.1 (SEQ ID NO:2) and having a substitution mutation at position E366. In some embodiments, the amino acid substitution at position E366 comprises any of the 20 natural amino acids (i.e., W, M, P, F, G, A, V, L, H, R, K, D, E, N, Y, C, S, T, or Q) or with non-natural amino acids as are known to those of skill in the art.

[0225] In some embodiments, the mutant polymerases have a backbone sequence of RLF

89458.1 (e.g., SEQ ID NO: 1) or RLF 78286.1 (SEQ ID NO:2) and having a substitution mutation at position 1436. In some embodiments, the amino acid substitution at position 1436 comprises any of the 20 natural amino acids (i.e., W, M, P, F, G, A, V, L, H, R, K, D, E, N, Y, C, S, T, or Q) or with non-natural amino acids as are known to those of skill in the art.

[0226] In some embodiments, the mutant polymerases have a backbone sequence of RLF

89458.1 (e.g., SEQ ID NO: 1) or RLF 78286.1 (SEQ ID NO:2) and having a substitution mutation at position A485. In some embodiments, the amino acid substitution at position A485 comprises any of the 20 natural amino acids (i.e., W, I, M, P, F, G, V, L, H, R, K, D, E, N, Y, C, S, T, or Q) or with non-natural amino acids as are known to those of skill in the art. [0227] In some embodiments, the mutant polymerases have a backbone sequence of RLF

89458.1 (e.g., SEQ ID NO: 1) or RLF 78286.1 (SEQ ID NO:2) and having a substitution mutation at position T514. In some embodiments, the amino acid substitution at position T514 comprises any of the 20 natural amino acids (i.e., W, I, M, P, F, G, A, V, L, H, R, K, D, E, N, Y, C, S or Q) or with non-natural amino acids as are known to those of skill in the art. [0228] In some embodiments, the mutant polymerases have a backbone sequence of RLF

89458.1 (e.g., SEQ ID NO: 1) or RLF 78286.1 (SEQ ID NO:2) and having a substitution mutation at position D671. In some embodiments, the amino acid substitution at position D671 comprises any of the 20 natural amino acids (i.e., W, I, M, P, F, G, A, V, L, H, R, K, E, N, Y, C, S, T, or Q) or with non-natural amino acids as are known to those of skill in the art. Engineered Polymerases Comprising NOZ 58130.1 Backbone Sequence

[0229] The present disclosure provides compositions and methods comprising mutant polymerases having a backbone sequence of NOZ 58130.1 and having 100%, at least 99%, at least 98%, at least 97%, at least 95%, at least 90% at least 85%, at least 80%, at least 75%, at least 70%, at least 65%, at least 60%, at least 55%, or at least 50% sequence identity to any of SEQ ID NOS: 1714-2787 (Table 2 at FIG. 32, and FIG. 13).

[0230] In some embodiments, the mutant polymerases having a backbone sequence of NOZ 58130.1 (e.g., SEQ ID NO: 1714) comprise various domains.

[0231] In some embodiments, the N-terminal domain comprises amino acid residues 1- 162 (SEQ ID NO:2810) (e.g., FIG. 30).

[0232] In some embodiments, the exonuclease domain (e.g., 3’ to 5’ exonuclease domain) comprises amino acid residues 163-405 (SEQ ID NO:2811) (e.g., FIG. 30). [0233] In some embodiments, the palm domain comprises amino acid residues 406-640 (SEQ ID NO:2812) (e g., FIG. 30).

[0234] In some embodiments, the finger(s) sub-domain within the palm domain comprises amino acid residues 480-527 (SEQ ID NO:2813) (e.g., FIG. 30).

[0235] In some embodiments, the thumb domain comprises amino acid residues 641-792 (SEQ ID NO:2814) (e g., FIG. 30).

[0236] The present disclosure provides compositions and methods comprising mutant polymerases having a backbone sequence of NOZ 58130.1 (SEQ ID NO: 1714) and comprise at least one amino acid substitution mutation that reduces 3’ to 5’ exonuclease activity compared to a polymerase that lacks an exo-minus mutation. For example, the mutant polymerases comprise at least one amino acid substitution at positions D168 and/or E170. In some embodiments, the mutant polymerases comprise a mutation DI 68 A, DI 68V, D168L, D168I, D168F, D168Y, D168N, D168K, D168T, D168S, D168W, D168M, D168P, D168G, D168H, D168R, D168E, D168C or D168Q. In some embodiments, the mutant polymerases comprise a mutation E170A, E170V, E170L, E170I, E170F, E170Y, E170N, E170K, E170T, E170S, E170W, E170M, E170P, E170G, E170H, E170R, E170D, E170C or E170Q. In some embodiments, the mutant polymerases comprise any combination of mutations at the DI 68 and the E170 sites. SEQ ID NOS: 1714-2787 comprise exemplary amino acid substitution mutations at positions DI 68 and El 70.

[0237] The present disclosure provides compositions and methods comprising mutant polymerases having a backbone sequence of NOZ 58130.1 (SEQ ID NO: 1714) and comprise at least one amino acid substitution mutations of an LYP motif, for example at positions L440, Y441 and P442. In some embodiments, at least one mutation in the LYP motif can increase the incorporation rate of nucleotide analogs. In some embodiments, any one or any combination of the first, second and/or third positions of the LYP motif can be mutated. For example, mutations of the LYP motif include YAG, FAG, YGP, YAP, FGP, SAP, AAA, YGA, YAA, FGA, FTA, AAG, AAP, AAV, AAI, AGA, AGG, AGI, AGP, AGV, FAA, FAI, FAP, FAV, FGG, FGV, LAG, LAI, LAP, LGG, LGI, LGV, SAA, SAG, SAI, SAV, SGA, SGG, SGI, YAI, YGG, YGI, LAA, LAV, LGP, LGA, FGI, SGV, YAV, YGV, SYP, SGP, LFP, IFP, VFP, LMP, VMP, IMP, LLP, VLP, ILP, LDP, VDP, IDP, LTP, VTP, ITP, LIP, TIP, NNP, NDP, NAP, MFG and SYG.

[0238] In some embodiments, the polymerases comprise a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a substitution mutation at position L440 comprises a nonpolar amino acid or polar non-charged amino acid. In some embodiments, the amino acid substitution mutation at position L440 comprises valine, glycine, threonine, alanine, serine, isoleucine, leucine, phenylalanine, tyrosine or methionine. SEQ ID NOS: 1714-2787 comprise exemplary amino acid substitution mutation at position L440.

[0239] In some embodiments, the polymerases comprise a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a substitution mutation at position Y441 comprises a non-polar amino acid or a polar uncharged amino acid. In some embodiments, the amino acid substitution mutation at position Y441 comprises threonine, serine, glycine, alanine, valine, isoleucine or tyrosine. SEQ ID NOS: 1715-2787 comprise exemplary amino acid substitution mutation at position Y441.

[0240] In some embodiments, the polymerases comprise a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a substitution mutation at position P442 comprises a polar uncharged amino acid, non-polar amino acid or a positively charged amino acid. In some embodiments, the amino acid substitution mutation at position P442 comprises serine, glycine, alanine, valine, cysteine, lysine, isoleucine, threonine or proline. SEQ ID NOS: 1715-2787 comprise exemplary amino acid substitution mutation at position P442.

[0241] The present disclosure provides compositions and methods comprising mutant polymerases having a backbone sequence of NOZ 58130.1 (SEQ ID NO: 1714) and having at least one mutation to reduce post-translational modifications compared to a wild type polymerase or compared to an engineered polymerase lacking mutations to reduce post- translational modifications. In some embodiments, the polymerase comprises at least one mutation or any combination of mutations of methionine, lysine, tryptophan and/or serine residue(s). In some embodiments, the polymerases are engineered to include any one or any combination of amino acid substitution mutations at W135, M187, W329, K335, M389, S473, M527, K552, M629, W641, K650, K711, M723 and/or W791.

[0242] In some embodiments, the polymerases comprise a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a mutation at position W135 comprising W135 S, W135L, W135R, W135Y, W135F, W135D, W135A, W135V or W135G.

[0243] In some embodiments, the polymerases comprise a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a mutation at position M187 comprising M187S, M187L, M187R, M187Y, Ml 871, M187T, M187A or Ml 87V.

[0244] In some embodiments, the polymerases comprise a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a mutation at position W329 comprising W329Y, W329F, W329L, W329D, W329A or W329V.

[0245] In some embodiments, the polymerases comprise a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a mutation at position K335 comprising K335R, K335L, K335S or K335A.

[0246] In some embodiments, the polymerases comprise a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a mutation at position M389 comprising M389D, M389E, M389L, M389Y, M389S, M389A or M389V.

[0247] In some embodiments, the polymerases comprise a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a mutation at position S473 comprising S473K, S473R, S473T, S473Q or S473A.

[0248] In some embodiments, the polymerases comprise a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a mutation at position M527 comprising M527H, M527G, M527Q, M527L, M527D, M527A or M527V.

[0249] In some embodiments, the polymerases comprise a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a mutation at position M549 comprising M549N, M549Y, M549H, M549T, M549D, M549R, M549A or M549V.

[0250] In some embodiments, the polymerases comprise a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a mutation at position K552 comprising K552R, K552T, K552N, K552Q or K552A.

[0251] In some embodiments, the polymerases comprise a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a mutation at position M629 comprising M629L, M629A, M629D, M629R or M629V. [0252] In some embodiments, the polymerases comprise a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a mutation at position W641 comprising W641R, W641 A, W641L, W641F, W641 Y or W641 V.

[0253] In some embodiments, the polymerases comprise a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a mutation at position K650 comprising K650T, K650C, K650A, K650R or K650S.

[0254] In some embodiments, the polymerases comprise a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a mutation at position K711 comprising K711R, K711L, K711T or K711D.

[0255] In some embodiments, the polymerases comprise a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a mutation at position M723 comprising M723S, M723I, M723T, M723N, M723R, M723L, M723 A or M723C.

[0256] In some embodiments, the polymerases comprise a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a mutation at position W791 comprising W791R, W791Y, W791D, W791S, W791L, W791A or W791V.

[0257] The present disclosure provides compositions and methods comprising mutant polymerases having a backbone sequence of NOZ 58130.1 (SEQ ID NO: 1714) and having at least one mutation to remove unpaired cysteines which may reduce oxidative damage to the polymerases. In some embodiments, removal of at least one unpaired cysteine increases thermal stability of the mutant polymerase and/or reduces protein aggregation. In some embodiments, removal of at least one unpaired cysteine increases the amount of protein in a lysate preparation. In some embodiments, the polymerase comprises at least one mutation or any combination of mutations of cysteines at position 362 and/or 539. In some embodiments, the mutation at position C362 comprises an amino acid substitution C362A, C362L, C362I, C362S, C362F, C362Y, C362V, C362P, C362K, C362N or C362D. In some embodiments, the mutation at position C539 comprises an amino acid substitution C539A, C539V, C539L, C539S, C539Y, C539D, C539K, C539N or C539P.

[0258] In some embodiments, the polymerases comprise a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a non-mutated or mutated C362, and an amino acid substitution R536C.

[0259] In some embodiments, the polymerases comprise a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a non-mutated or mutated C539, and an amino acid substitution R536C. [0260] In some embodiments, the polymerases comprise a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a non-mutated or mutated C362, and an amino acid sub stituti on D451 C .

[0261] The present disclosure provides compositions and methods comprising mutant polymerases having a backbone sequence of NOZ 58130.1 (SEQ ID NO: 1714) and having a C-terminus truncation to increase thermal stability of the polymerase compared to a nontruncated polymerase having the same wild type or engineered backbone sequence. The C- terminal region of a polymerase may be disordered and may contribute to protein aggregation. Thus, truncation at a C-terminal region can reduce protein aggregation and improve stability. In some embodiments, the polymerase exhibits thermal stability at an elevated temperature of about 72 - 75 °C, or about 75 - 80 °C, or about 80 - 85 °C, or about 85 - 90 °C, or higher temperatures. In some embodiments, a thermal shift assay using differential scanning fluorimetry can be used to determine the thermal stability of a polymerase.

[0262] In some embodiments, the polymerases comprise a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a C-terminal truncation for increased thermal stability including M723 (truncated), G773(truncated), D777(truncated), E781 (truncated), T784(truncated), Q785 (truncated), R790(truncated), W791 (truncated) or F792(truncated). In Table 2, a truncation is designated with a “ ^A ”.

[0263] The present disclosure provides compositions and methods comprising mutant polymerases having a backbone sequence of NOZ 58130.1 (SEQ ID NO: 1714) and having at least one mutation that reduces polymerization-to-exonuclease conformational switching compared to a wild type polymerase or compared to an engineered polymerase having mutations that do not reduce conformational switching. In some embodiments, protein modeling can identify key amino acid residues that interact with the primer or the primer end, where these amino acid residues may play a role in interacting with the primer, or transferring the primer end from the polymerization site to the exonuclease site. In some embodiments, the polymerases comprise an amino acid substitution at any one or any combination of positions Q95, 1186, V304, L313 and/or E318.

[0264] In some embodiments, the polymerases comprise a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a mutation at Q95 comprising Q95L, Q95H, Q95R, Q95W, Q95A, Q95K, Q95N or Q95P.

[0265] In some embodiments, the polymerases comprise a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a mutation at 1186 comprising I186R or I186N. [0266] In some embodiments, the polymerases comprise a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a mutation at V304 comprising V304D.

[0267] In some embodiments, the polymerases comprise a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a mutation at L313 comprising L313M, L313D, L313F, L313K, L313R, L313A or L313E.

[0268] In some embodiments, the polymerases comprise a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a mutation at E318 comprising E318V.

[0269] The present disclosure provides compositions and methods comprising mutant polymerases having a backbone sequence of NOZ 58130 (SEQ ID NO: 1714) and having at least one mutation that reduces protein aggregation by reducing intermolecular interactions compared to a wild type polymerase or compared to an engineered polymerase having mutations that do not confer reduced aggregation. In some embodiments, the mutant polymerase aggregates at an elevated temperature of about 72 - 75 °C, or about 75 - 80 °C, or about 80 - 85 °C, or about 85 - 90 °C, or higher temperatures, compared to a wild type polymerase or compared to an engineered polymerase having mutations that do not confer reduced aggregation. In some embodiments, a thermal shift assay using differential scanning fluorimetry can be used to determine the temperature of aggregation of a protein. In some embodiments, the mutant polymerase comprises a sequence that has at least 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or greater than 99% sequence identity to any of SEQ ID NOs: 1714-2787 and includes at least one mutation that reduces protein aggregation by reducing intermolecular interactions.

[0270] In some embodiments, the polymerases comprise a backbone sequence of NOZ 58130 (SEQ ID NO:1714) and having an amino acid substitution to reduce aggregation comprise an amino acid substitution at one or more positions E76, K254, R537, E541 and/or K664.

[0271] In some embodiments, the mutation at position E76 comprises E76N, E76A, E76R, E76K, E76T, E76V, E76S, E76Q, E76D or E76I.

[0272] In some embodiments, the mutation at position K254 comprises K254E, K254D, K254A, K254N, K254T, K254V, K254S, K254Q, K254G, K254I or K254R.

[0273] In some embodiments, the mutation at position R537 comprises R537S, R537T, R537N, R537Q, R537A, R537V, R537D, R537I, R537E, R537G, R537K or R537L.

[0274] In some embodiments, the mutation at position E541 comprises E541 A, E541R, E541N, E541K, E541T, E541V, E541S, E541Q, E541D or E541I. [0275] In some embodiments, the mutation at position K664 comprises K664R, K664A, K664N, K664Q, K664E, K664S, K664T, K664D, K664G, K664V or K664I.

[0276] In some embodiments, the mutant polymerases comprise a backbone sequence of NOZ 58130.1 (SEQ ID NO: 1714) and a deleted portion of any of the domains including the N-terminal domain (SEQ ID NO:2810), exonuclease domain (SEQ ID NO:2811), first palm domain (SEQ ID NO:2812), fingers domain (SEQ ID NO:2813), thumb domain (SEQ ID NO:2814).

[0277] In some embodiments, the mutant deletion polymerase comprises a sequence that has at least 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or greater than 99% sequence identity to any of SEQ ID NOs: 1714-2787 and includes a deleted portion of any of the domains.

[0278] In some embodiments, the mutant deletion polymerase comprises a backbone sequence ofNOZ 58130.1 (SEQ ID NO: 1714) and the deleted portion comprises 1130 - P160 or any sub-region therein. In some embodiments, the deleted portion comprises an N- terminus of any of 1130, T134, L136, L138, R143, G151 or E156. In some embodiments, the deleted portion comprises a C-terminus of any of P160, E156, V152, A147, G145 or L136. [0279] In some embodiments, the deleted portion comprises any of I130-P160, L136- P160, L138-P160, R143-P160, 1130-V152, L136-V152, L138-V152, R143-V152, 1130- A147, L136-A147, L138-A147, R143-A147, 1130-G145, L136-G145, L138-G145, R143- G145, 1130-L136, G151-P160, G151-V152, E156-P160 or T134-E156.

[0280] In some embodiments, the portion that is deleted in the mutant polymerase (e.g., having a backbone sequence ofNOZ 58130.1, SEQ ID NO: 1714) is a sequence or a region that is absent in other Archaea Family B polymerases including RLF 89458 (SEQ ID NO: 1), RLF 78286 (SEQ ID NO:2), WP 175059460 (SEQ ID NO:2791), 9°N (SEQ ID NOS:2795 and 2796), THERMINATOR (SEQ ID NO:2797), VENT (SEQ ID NO:2798), DEEP VENT (SEQ ID NO:2799), Pfu (SEQ ID N0:2800) and P. abyssi (SEQ ID NO:2801). For example, see the sequence alignments in FIGs. 33 and 35 which shows a region that is present in NOZ 58130 but absent in other Archaea Family B polymerases. In some embodiments, the portion that is deleted in the mutant polymerase comprises the amino acid sequence TWLRLEVEERDGRALLRGVEQLE (SEQ ID NO:2788) which is 23 amino acids in length. In some embodiments, the deleted portion is larger or smaller than SEQ ID NO:2788.

[0281] The present disclosure provides compositions and methods comprising mutant polymerases having a backbone sequence ofNOZ 58130.1 (e.g., SEQ ID NO: 1714) and comprising amino acid substitution mutations at any one or any combination of positions including Y14, E15, V17, E18, R20, F26, L25, L27, G29, F34, V35, V36, F41, S42, P43, F45, L48, P49, G50, R55, E58, L61, A62, S63, A65, E67, A68, 169, K71, V72, 174, E76, K77, L79, F80, T82, P83, R84, V85, A86, L87, T90, V91, S92, H93, P94, Q95, D96, V97, P98, R99, 1100, R101, E102, R103, R105, E108, Di l l, L112, 1113, N114, E115, H116, D117, 1118, V121, R122, R123, Y124, 1126, R128, 1130, K131, P132, L133, T134, W135, L136, E139, G145, R150, E153, E156, E157, E158, R163, V164, A165, V167, D168, 1169, E170, V171, Y172, N173T, P174, E184, 1186, M187, V190, T192, S193, E197, L200, V205, G207, E209, Q210, Q215, D216, M220, L222, E226, K229, G231, Y233, 1236, V237, G238, N240, T241, S243, F244, Y248, R252, L253, K254, L260, L265, D266, L269, S272, G275, A276, L277, 1282, A286, V288, L290, Y291, P292, 1293, V294, R295, H297, V298, K299, N301, S302, Y303, V304, S307, V309, L312, L313, G314, E318, K319, L320, D321, G322, R324, L325, F326, T327, W329, D330, E331, K335, R336, L338, L339, A343, Y342, L344, D346, A352, A354, K356, L360, C362, 1367, A376, M378, T379, V384, L387, M389, R390, T393, L398, 1399, P400, E407, Y408, A409, R413, Y416, R422, V429, V434, F435, D436, F437, S439, L440, Y441, P442, S443, 1444, 1445, V446, T454, A465, S473, F479, 1480, R496, D504, F511, A515, S522, F523, Y524, Y526, M527, R536, R537, E538, C539, E541, V543, A544, F546, A547, M549, 1551, K552, M555, A558, E559, F562, L564, E565, V566, D570, D572, V576, V577, 1578, P580, L585, A586, Q587, K588, K592, V593, E595, M597, 1601, F608, L613, V615, T616, R619, L622, L623, K628, M629, V631, F636, V637, R638, R639, D640, W641, A642, K650, 1655, L656, A660, K664, A665, L668, 1673, E674, R675, R677, S682, D685, T687, Y689, T690, Q691, R695, S698, S701, E703, V707, A708, K711, E718, V719, M723, 1724, 1729, T730, K734, G735, S737, Q738, T741, D752, D758, N759, 1761, 1765, R767, 1772, Y774, L779, K780, E781, G782, 1783, T784, Q785, T786, S787, L788, S789, R790, W791 and/or F792.

[0282] The present disclosure provides compositions and methods comprising mutant polymerases having a backbone sequence of NOZ 58130.1 (e.g., SEQ ID NO: 1714) and comprise amino acid substitution mutations at any one or any combination of positions including Y14F, Y14D, Y14I, Y14N, E15I, V17E, E18S, E18N, E18D, R20K, L25F, F26Y, F26S, F26I, L27Q, L27K, G29E, G29K, F34K, V35M, V35K, V36F, V36N, V36T, V36I , V36E, F41S, F41I, F41Y, S42K, S42G, S42D, S42E, P43L, P43A, P43G, P43V, P43M, P43T, P43K, F45T, F45N, F45I, L48D, P49V, P49K, P49D, P49E, P49L, G50K, R55G, R55K, R55E, R55I, E58V, L61I, L61S, L61A, L61T, A62D, A62S, A62V, A62G, S63G, S63K, S63E, A65L, A65Y, A65H, E67M, E67K, E67V, A68R, 169 A, I69D, 169 V, K71T, K71V, K71F, K71N, K71I, V72T, V72N, V72I, I74K, E76Q, E76N, E76A, E76R, E76K, E76T, E76V, E76S, E76D, E76I, K77E, L79F, F80L, T82K, T82G, T82N, T82S, T82E, P83R, R84N, R84K, R84S, V85R, V85E, A86V, L87W, T90D, T90I, T90A, T90V, V91I, V91L, V91C, V91F, H93D, H93A, H93Y, P94L, P94S, P94D, P94R, P94A, P94G, P94V, P94M, P94T, P94K, Q95L, Q95H, Q95R, Q95W, Q95A, Q95K, Q95N, Q95P, D96N, D96V, V97S, V97A, V97F, V97Y, V97Q, P98L, P98W, P98Y, P98Q, P98F, P98S, R99V, R99A, HOOT, HOOK, IlOOS, R101C, R101H, R1O1S, R101P, R101L, E102N, E102V, E102D, R103T, R103A, R105C, R105H, E108N, DI 11C, DI 1 IS, DI 11R, LI 12N, LI 12Q, LI 12T, Il 13K, 1113N, Il 13F, Il 13A, 1113D, Il 13N, Il 13T, LI 14N, LI 14T, El 15V, El 15G, Hl 16C, H116Y, H116L, D117G, D117Y, I118T, I118A, I118G, 1118V, I118M, H 18T, H 18K, V121T, V121K, V121A, R122S, R122M, R122K, R123H, R123S, R123C, R123A, R123G, R123V, R123M, R123T, R123K, R123Y, Y124R, Y124C, H26V, I126F, H26N, I126D, R128K, I13OL, K131I, P132L, P132M, L133I, L133V, L133K, L133L, L133E, L133M, T134E, W135S, W135L, W135R, W135Y, W135F, W135D, W135A, W135V, W135G, L136D, E139V, G145S, R150A, R150V, R150L, R150K, R150F, E153A, E153V, E153L, E153K, E153R, E153F, E156N, E156R, E157A, El 57V, E157L, E157K, E157R, E157F, E157D, E157G, E157T, E158S, E158G, R163E, R163L, R163K, R163H, V164F, V164L, V164M, V164I, A165P, A165L, V167I, V167F, D168A, D168V, D168L, D168I, D168F, D168Y, D168N, D168T, D168S, D168W, D168M, D168P, D168G, D168H, D168R, D168E, D168C, D168K, D168Q, I169V, H69F, I169A, H69R, H69W, E170A, E170V, E170L, E170I, E170F, E170Y, E170N, E170T, E170S, V171F, V171T, V171R, Y172R, Y172T, N173T, P174R, E184N, H86R, H86L, I186N, M187S, M187L, M187R, M187Y, M187I, M187T, M187A, M187V, V190Y, T192D, S193E, E197A, L200I, V205I, G207D, E209P, Q210Y, Q215S, D216T, M220I, L222K, E226R, K229E, G231K, Y233P, I236L, V237I, G238T, N240G, N240T, N240S, T241G, S243N, F244S, Y248D, Y248R, R252A, R252S, L253V, L253E, L253C, K254E, K254R, K254A, K254N, K254Q, K254S, K254T, K254D, K254G, K254V, K254I, L260F, L265D, D266G, L269P, S272Q, G275N, G275K, G275S, G275R, A276M, A276N, A276Q, A276D, L277R, L277M, L277D, I282V, A286I, V288F, L290I, Y291A, Y291P, Y291G, Y291D, Y291N, P292R, I293V, V294M, V294I, R295A, H297F, H297Y, V298I, K299N, N301R, N301P, S302N, S302T, Y303G, Y303D, Y303A, V304D, V304A, V304E, V304H, V304I, V304L, V304M, V304P, V304R, V304T, V304W, V304Y, V304F, V304G, V304K, V304N, V304Q, V304S, S307A, V309Y, L312V, L312I, L313M, L313D, L313F, L313K, L313R, L313A, L313E, G314S, G314D, G314K, G314R, G314E, E318V, K319V, K319R, L320V, D321F, G322D, G322S, R324E, L325R, F326N, F326T, F326A, T327Q, W329Y, W329F, W329L, W329D, W329A, W329V, D330N, D330E, E331N, E331R, K335R, K335L, K335S, K335A, R336L, L338E, L339V, Y342N, Y342A, Y342R, A343S, L344M, D346G, D346A, D346R, A352L, A352E, A352D, A352Q, A354G, K356R, K356D, K356E, L360I, L360Q, L360V, L360M, C362A, C362L, C362I, C362S, C362F, C362Y, C362V, C362P, C362K, C362N, C362D, I367L, A376C, A376R, A376S, M378R, M378T, M378A, T379D, T379K, T379N, T379S, V384Q, V384E, L387N, L387C, L387Y, L387F, M389D, M389E, M389L, M389Y, M389S, M389A, M389V, R390M, L398D, I399A, I399N, I399R, I399F, P400H, P400N, P400S, E407R, Y408R, A409R, A409Q, R413Q, R413T, Y416H, R422V, R422T, R422D, V429W, V434H, V434L, V434Y, F435L, D436T, F437Y, F437R, F437I, S439A, S439G, S439R, L440, L440Y, L440F, L440S, L440A, Y441, Y441A, Y441G, Y441T, P442, P442G, P442A, S443R, S443N, S443A, S443G, I444F, I445L, I445F, V446M, V446K, V446R, V446N, V446T, D451C, T454I, T454L, T454R, A465V, A465D, A465P, S473K, S473R, S473T, S473Q, S473A, F479I, F479L, I480F, I480Y, R496T, R496A, R496G, R496C, D504E, F511Y, F511L, F511V, A515L, A515S, A515T, A515V, A515G, A515R, S522D, S522K, S522T, S522N, S522E, S522G, S522Y, F523A, F523S, F523T, F523V, F523I, F523Y, Y524A, Y524N, Y524G, Y524F, Y524L, Y526C, M527H, M527G, M527Q, M527L, M527D, M527A, M527V, R536C, R537K, R537E, R537G, R537S, R537L, R537A, R537N, R537Q, R537T, R537D, R537V, R537I, E538A, E538C, C539A, C539V, C539L, C539S, C539Y, C539D, C539K, C539N, C539P, E541K, E541S, E541A, E541R, E541N, E541T, E541V, E541Q, E541D, E541I, V543T, V543I, V543A, V543S, V543G, A544G, A544S, A544T, F546W, A547G, M549N, M549Y, M549H, M549T, M549D, M549R, M549A, M549V, 155 IN, 155 IT, 155 IE, 1551H, 155 IL, 155 IV, 1551 A, K552R, K552T, K552N, K552Q, K552A, M555Y, M555I, A558I, E559N, E559K, E559D, F562E, F562N, F562Q, F562R, L564F, E565N, E565K, E565S, E565R, V566N, V566K, V566S, V566R, D570A, D570G, D570E, D570V, D570L, D570S, D572A, D572G, D572E, V576A, V577T, I578F, I578T, I578P, I578R, I578T, I578E, I578N, P580G, L585K, L585S, L585E, L585Q, L585R, L585T, L585V, A586K, K588N, K588Q, K588R, K588S, K592A, K592G, K592R, K592T, K592N, K592S, V593I, V593A, E595K, M597L, I601L, F608Y, L613F, V615E, V615T, T616K, R619E, L622V, L623I, K628R, K628I, K628H, M629L, M629A, M629D, M629R, M629V, M629I, V631T, F636I, V637D, V637N, V637R, R638D, R639D, R639N, D640R, D640K, W641R, W641A, W641L, W641F, W641Y, W641V, A642S, K650T, K650C, K650A, K650R, K650S, I655L, I655V, I655A, L656I, A660G, A665E, A665V, A665T, K664R, K664A, K664N, K664Q, K664E, K664S, K664T, K664D, K664G, K664V, K664I, L668I, I673T, E674G, E674D, E674K, R675V, R675C, R675L, R675D, R677E, R677V, R677T, R677N, R677A, S682P, D685R, D685E, D685I, D685L, D685K, T687V, Y689D, Y689N, T690K, T690R, T690S, T690M, T690Q, T690V, T690E, T690N, Q691S, Q691T, R695K, S698D, S698K, S698R, S698G, S698Y, S698D, S701T, S701V, S701A, S701R, S701E, E703R, E703S, E703K, V707I, V707D, V707A, A708V, K711R, K71 IL, K71 IT, K71 ID, E718R, E718V, E718K, V719I, M723S, M723I, M723T, M723N, M723R, M723L, M723A, M723C, I724D, I724V, I729V, T730L, K734I, K734G, K734N, G735M, G735R, G735K, G735S, G735P, G735T, G735E, S737R, S737E, Q738D, Q738S, Q738E, Q738, Q738R, T741I, D752Q, D752T, D758N, N759P, N759D, N759K, N759T, N759Y, N759R, I761V, I765V, R767E, I772L, I772Y, I772F, Y774F, Y774E, L779G, L779Q, L779D, L779K, L779Y, L779E, K780C, K780F, K780I, K780R, K780Q, K780Y, E781L, E781H, E781S, E781M, E781Q, G782H, G782A, G782K, G782R, Q785L, T786N, S789G, W791R, W791Y, W791D, W791S, W791L, W791A, W79 IV and/or F792R.

[0283] In some embodiments, the mutant polymerases have a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a substitution mutation at position Y14. In some embodiments, the amino acid substitution at position Y14 comprises any of the 20 natural amino acids (i.e., W, I, M, P, F, G, A, V, L, H, R, K, D, E, N, C, S, T, or Q) or with nonnatural amino acids as are known to those of skill in the art.

[0284] In some embodiments, the mutant polymerases have a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a substitution mutation at position L48. In some embodiments, the amino acid substitution at position L48 comprises any of the 20 natural amino acids (i.e., W, I, M, P, F, G, A, V, L, H, R, K, D, E, N, C, S, T, or Q) or with nonnatural amino acids as are known to those of skill in the art.

[0285] In some embodiments, the mutant polymerases have a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a substitution mutation at position E76. In some embodiments, the amino acid substitution at position E76 comprises any of the 20 natural amino acids (i.e., W, I, M, P, F, G, A, V, L, H, R, K, D, E, N, C, S, T, or Q) or with nonnatural amino acids as are known to those of skill in the art.

[0286] In some embodiments, the mutant polymerases have a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a substitution mutation at position V97. In some embodiments, the amino acid substitution at position V97 comprises any of the 20 natural amino acids (i.e., W, I, M, P, F, G, A, L, H, R, K, D, E, N, Y, C, S, T, or Q) or with nonnatural amino acids as are known to those of skill in the art.

[0287] In some embodiments, the mutant polymerases have a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a substitution mutation at position R122. In some embodiments, the amino acid substitution at position R122 comprises any of the 20 natural amino acids (i.e., W, I, M, P, F, G, A, V, L, H, K, D, E, N, Y, C, S, T, or Q) or with nonnatural amino acids as are known to those of skill in the art.

[0288] In some embodiments, the mutant polymerases have a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a substitution mutation at position Y124. In some embodiments, the amino acid substitution at position Y124 comprises any of the 20 natural amino acids (i.e., W, I, M, P, F, G, A, V, L, H, K, D, E, N, Y, C, S, T, or Q) or with nonnatural amino acids as are known to those of skill in the art.

[0289] In some embodiments, the mutant polymerases have a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a substitution mutation at position R150. In some embodiments, the amino acid substitution at position R150 comprises any of the 20 natural amino acids (i.e., W, I, M, P, F, G, A, V, L, H, K, D, E, N, Y, C, S, T, or Q) or with nonnatural amino acids as are known to those of skill in the art.

[0290] In some embodiments, the mutant polymerases have a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a substitution mutation at position K254. In some embodiments, the amino acid substitution at position K254 comprises any of the 20 natural amino acids (i.e., W, I, M, P, F, G, A, V, L, H, K, D, E, N, Y, C, S, T, or Q) or with nonnatural amino acids as are known to those of skill in the art.

[0291] In some embodiments, the mutant polymerases have a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a substitution mutation at position V304. In some embodiments, the amino acid substitution at position V304 comprises any of the 20 natural amino acids (i.e., W, I, M, P, F, G, A, V, L, H, K, D, E, N, Y, C, S, T, or Q) or with nonnatural amino acids as are known to those of skill in the art.

[0292] In some embodiments, the mutant polymerases have a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a substitution mutation at position C362. In some embodiments, the amino acid substitution at position C362 comprises any of the 20 natural amino acids (i.e., W, I, M, P, F, G, A, V, L, H, R, K, D, E, N, Y, S, T, or Q) or with nonnatural amino acids as are known to those of skill in the art.

[0293] In some embodiments, the mutant polymerases have a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a substitution mutation at position R496. In some embodiments, the amino acid substitution at position R496 comprises any of the 20 natural amino acids (i.e., W, I, M, P, F, G, A, V, L, H, K, D, E, N, Y, C, S, T, or Q) or with nonnatural amino acids as are known to those of skill in the art. [0294] In some embodiments, the mutant polymerases have a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a substitution mutation at position A515. In some embodiments, the amino acid substitution at position A515 comprises any of the 20 natural amino acids (i.e., W, I, M, P, F, G, V, L, H, R, K, D, E, N, Y, C, S, T, or Q) or with nonnatural amino acids as are known to those of skill in the art.

[0295] In some embodiments, the mutant polymerases have a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a substitution mutation at position R537. In some embodiments, the amino acid substitution at position R537 comprises any of the 20 natural amino acids (i.e., W, I, M, P, F, G, A, V, L, H, K, D, E, N, Y, C, S, T, or Q) or with nonnatural amino acids as are known to those of skill in the art.

[0296] In some embodiments, the mutant polymerases have a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a substitution mutation at position E559. In some embodiments, the amino acid substitution at position E559 comprises any of the 20 natural amino acids (i.e., W, I, M, P, F, G, A, V, L, H, R, K, D, N, Y, C, S, T, or Q) or with nonnatural amino acids as are known to those of skill in the art.

[0297] In some embodiments, the mutant polymerases have a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and having a substitution mutation at position K664 In some embodiments, the amino acid substitution at position K664 comprises any of the 20 natural amino acids (i.e., W, I, M, P, F, G, A, V, L, H, R, K, D, N, Y, C, S, T, or Q) or with nonnatural amino acids as are known to those of skill in the art.

[0298] In some embodiments, the mutant polymerases have a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and comprise an amino acid deletion at any position including D117(deleted).

[0299] In some embodiments, the mutant polymerases have a backbone sequence of NOZ 58130.1 (SEQ ID NO: 1714) and comprise a truncation at an amino acid position including Q587(truncated), M723 (truncated), G773(truncated), Y774(truncated), D777(truncated), E781 (truncated), G782(truncated), T784(truncated), Q785 (truncated), R790(truncated), W791 (truncated) or F792(truncated). Truncated polymerases can exhibit increase thermal stability compared to a non-truncated polymerase having the same backbone sequence. In Table 2, a truncation is designated with the symbol “ ^A ”.

[0300] In some embodiments, the mutant polymerases have a backbone sequence of NOZ

58130.1 (SEQ ID NO: 1714) and comprise a truncation portion at the C-terminal end. In some embodiments, the truncated mutant polymerase comprises a sequence that has at least 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or greater than 99% sequence identity to any of SEQ ID NOs: 1714-2787 and a truncated portion at the C- terminal end. In some embodiments, the truncated portion can be 2-5, 5-10, 10-15 or 15-20 amino acids in length. In some embodiments, the truncated portion comprises G782 - F792 and is 11 amino acids in length. Truncated polymerases can exhibit increase thermal stability compared to a non-truncated polymerase having the same backbone sequence. In Table 2, a truncated portion is designated with the letter “X”.

Compositions Comprising Engineered Polymerases

[0301] The present disclosure provides polymerases that are mutated at two or more positions to increase thermal stability of the enzyme exhibit improved binding of nucleotide reagents and/or improved binding and incorporation of nucleotide reagents, improved incorporation rate of nucleotide analogs, improved uracil-tolerance and/or reduced sequencespecific errors compared to a wild type polymerase comprising an amino acid sequence of any of SEQ ID NOS: 1, 2, 1714, 2789-2793 and 2803. For example, the mutant polymerases exhibit increased thermal stability at a temperature range of about 25-50 °C, or about 45-75 °C, or about 65-90°C. In another example, the mutant polymerases exhibit increased incorporation rates of nucleotide analogs comprising a chain terminating moiety (e.g., blocking moiety) at the sugar 2’ position and/or at the 3’ sugar position. The mutant polymerases may exhibit increased uracil tolerance. The mutant polymerases may exhibit improved binding to complementary nucleotide units of a multivalent molecule. In some embodiments, the mutant polymerases comprise an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99% identical, or a higher level sequence identity, to any of SEQ ID NOS: 1, 2, 1714, 2789-2793 and 2803.

[0302] In some embodiments, the mutant polymerases comprise the backbone sequence ofRLF 89458.1 or RLF 78286.1 and comprising an amino acid sequence of any of SEQ ID NOS: 1-1713, and includes amino acid substitutions which can confer exonuclease-minus activity including any of D141A, D141V, D141L, D141I, D141F, D141Y, D141N, D141T, D141S, D141R, D141K, D141Q, D141W, D141E, D141M, D141P, D141G, D141H or D141C. In some embodiments, the mutant polymerases comprise the backbone sequence of RLF 89458.1 or RLF 78286.1 and comprising an amino acid sequence of any of SEQ ID NOS: 1-1713, and includes amino acid substitutions which can confer exonuclease-minus activity including a non-mutated E143 or mutated E143A, E143V, E143L, E143I, E143F, E143Y, E143N, E143T, E143S, E143W, E143M, E143P, E143F, E143G, E143H, E143R, E143K, E143D, E143C or E143Q.

[0303] In some embodiments, the mutant polymerases comprise the backbone sequence of NOZ 58130.1 and comprising an amino acid sequence of any of SEQ ID NOS: 1714-2787 and 2249-2479 and includes amino acid substitutions which can confer exonuclease-minus activity including any of DI 68 A, DI 68V, D168L, DI 681, D168F, D168Y, D168N, D168K, D168T, D168S, D168W, D168M, D168P, D168G, D168H, D168R, D168E, D168C or D168Q. In some embodiments, the mutant polymerases comprise the backbone sequence of NOZ 58130 and comprising an amino acid sequence of any of SEQ ID NOS: 1714-2787 and includes amino acid substitutions which can confer exonuclease-minus activity including any of E170A, E170V, E170L, E170I, E170F, E170Y, E170N, E170K, E170T, E170S, E170W, E170M, E170P, E170G, E170H, E170R, E170D, E170C or E170Q.

[0304] The present disclosure provides engineered archaeal family-B DNA or family-A polymerases, including Geobacillus stearothermophilus (e.g., Bst DNA polymerase) (SEQ ID NO:2794), 9°N polymerase (SEQ ID NOS: 2795 or 2796) (including THERMINATOR polymerase; SEQ ID NO:2797), VENT polymerase (SEQ ID NO:2798), DEEP VENT polymerase (SEQ ID NO:2799), Pfu polymerase (SEQ ID N0:2800) and/or Pyrococcus abyssi polymerase (SEQ ID NO:2801) and RB69 polymerase (SEQ ID NO:2802), that are mutated in one or more positions that are positionally equivalent (or functionally equivalent sites) to the amino acid substitutions at any one or any combination of positions of a polymerase having a backbone sequence of RLF 89458.1 (e.g., any of SEQ ID NOS: 1 or 3- 1713) or RLF 78286.1 (SEQ ID NO:2) including Ml, L3, D4, D6, Y7, 18, T9, E10, Ni l, G12, K13, P14, V15, 116, R17, 118, F19, K20, K21, E22, K23, G24, E25, F26, K27, 128, E29, Y30, D31,R32, N33, F34, E35, P36, Y37, 138, Y39, A40, L41, L42, E43, D44, D45, E46, S47, 148, E49, D50, 151, K52, K53, 154, T55, R58, G56, E57, R58, H59, G60, K61, K62, V63, 165, 166, R67, V68, E69, K70, V71, K72, K73, K74, F75, L76, G77, E78, P79, 180, E81, V82, W83, K84, L85, V86, F87, E88, H89, P90, Q91, D92, V93, P94, A95, 196, R97, D98, A99, 1100, R101, S102, H103, P104, A105, V106, R107, E108, 1109, Fl 10, El 11, Y112, D113, 1114, Pl 15, F116, A117, K118, R119, Y120, L121, 1122, D123, K124, L126, V127, P128, M129, E130, G131, G132, E133, L135, K136, L137, L138, A139, F140, D141, 1142, E143, T144, F145, Y146, H147, D150, E151, M159, W173, K174, 1176, Y180, A190, 1191, K192, L195, L198, R199, Q196, P203, V205, L207, Y209, G211, N213, F214, F216, A217, Y218, 1219, C223, E224, G227, L228, F230, T231, 1232, G233, R234, S237, E238, P239, K240, 1241, Q242, R243, M244, G245, D246, R247, A249, E251, L258, Y261, P262, V264, R265, H266, T267, 1268, R269, L270, P271, T272, Y273, T274, L275, E276, A277, V278, V282, F283, K285, K286, K287, E288, K289, V290, Y291, A292, 1295, E297, A298, W299, K300, S301, L305, K306, R307, V308, A309, Y311, M313, D315, R317, A318, Y320, E321, P328, M329, V331, E332, L333, A334, 1337, G338, Q339, V341, D343, S345, S347, S348, T349, G350, N351, L352, V353, W355, Y356, L357, R359, V360, Y362, N365, E366, L367, K371, P372, G373, E376, Q378, M381, S384, Y385, 1386, G388, Y389, E394, G396, A402, Y403, L404, F406, R407, S408, L409, Y410, P411, S412, 1413, V415, H417, V419, P421, D422, T423, L424, E427, C428, K429, A434, 1436, R440, K443, G447, F448, 1449, P450, S451, 1452, L453, E454, D455, 1457, V463, K464, R465, M467, K468, D472, 1474, E475, K476, Y481, R484, A485, L486, K487, 1488, N491, S492, Y493, Y494, G495, Q497, G498, Y499, P500, K501, S506, K507, E508, C509, E511, S512, V513, T514, G517, R518, H519, 1521, T523, A528, E529, K534, V535, A538, E539, D541, G542, 1547, 1555, P552, S557, K558, A559, K560, K561, L563, K564, H565, E568, K569, G572, M573, E575, E577, L583, G585, F586, V588, T589, K592, L595, 1596, H601, T604, G606, V609, V610, R611, R612, D613, E616, 1617, K619, E620, T621, Q622, A623, K624, V625, L626, E627, V628, 1629, L630, R631, E632, G633, S634, 1635, E636, K637, A638, A639, G640, 1641, V642, V645, V646, E647, D648, L649, A650, N651, Y652, R653, V654, V656, E657, K658, 1660, H662, E663, Q664, 1665, T666, R667, E668, K670, D671, Y672, K673, A674, T675, G676, P677, H678, V679, A680, 1681, A682, K683, R684, L685, Q686, A687, R688, G689, 1690, K691, V692, K693, P694, T696, 1698, S699, Y700, V701, V702, L703, K704, G705, S706, K707, K708, 1709, D711, R712, V713, 1714, L715, F716, D717, E718, D720, S721, S722, R723, K725, Y726, P728, Y730, Y731, 1732, H733, N734, Q735, V736, P738, A739, V740, L741, R742, 1743, L744, E745, A746, F747, G748, Y749, K750, E751, K752, D753, L754, E755, Y756, Q757, R758, M759, K760, Q761, T762, G763, L764, G765, A766, W767, L768 and/or M770. From the sequence alignment shown in FIG. 34, the skilled artisan can ascertain positionally equivalent positions (or functionally equivalent sites) in Geobacillus stearothermophilus (e.g., Bst DNA polymerase) (SEQ ID NO:2794), 9°N polymerase (SEQ ID NOS: 2795 or 2796) (including THERMINATOR polymerase; SEQ ID NO:2797), VENT polymerase (SEQ ID NO:2798), DEEP VENT polymerase (SEQ ID NO:2799), Pfu polymerase (SEQ ID N0:2800) and/or Pyrococcus abyssi polymerase (SEQ ID NO:2801) and RB69 polymerase (SEQ ID NO:2802).

[0305] The present disclosure provides engineered archaeal family-B DNA or family-A polymerases, including Geobacillus stearothermophilus (e.g., Bst DNA polymerase) (SEQ ID NO:2794), 9°N polymerase (SEQ ID NOS: 2795 or 2796) (including THERMINATOR polymerase; SEQ ID NO:2797), VENT polymerase (SEQ ID NO:2798), DEEP VENT polymerase (SEQ ID NO:2799), Pfu polymerase (SEQ ID N0:2800) and/or Pyrococcus abyssi polymerase (SEQ ID NO:2801) and RB69 polymerase (SEQ ID NO:2802), that are mutated in one or more positions that are positionally equivalent (or functionally equivalent sites) to the amino acid substitutions at any one or any combination of positions of a polymerase having a backbone sequence ofNOZ 58130.1 (e.g., any of SEQ ID NOS: 1714- 2787) including Y14, E18, F26, L27, G29, F34, V35, V36, F41, S42, P43, F45, L48, P49, R55, L61, A62, S63, A65, E67, 169, K71, V72, E76, K77, T82, P83, R84, V85, T90, V91, S92, H93, P94, Q95, D96, V97, P98, R99, 1100, R101, E102, R103, R105, E108, Di l l, L112, 1113, N114, E115, H116, D117, 1118, V121, R122, R123, Y124, 1126, 1130, P132, L133, W135, G145, R150, E153, E156, E157, E158, R163, V164, A165, V167, D168, 1169, E170, V171, Y172, N173T, P174, E184, 1186, M187, V190, L200, V205, M220, K229, Y233, 1236, V237, G238, N240, F244, Y248, R252, L253, K254, L260, L269, G275, A276, L277, 1282, A286, V288, L290, Y291, P292, 1293, V294, R295, H297, V298, N301, S302, Y303, V304, S307, V309, L312, L313, G314, E318, K319, L320, D321, G322, L325, F326, T327, W329, D330, E331, K335, L338, L339, A343, Y342, L344, D346, A352, A354, K356, L360, C362, 1367, A376, M378, T379, V384, L387, M389, R390, T393, L398, 1399, P400, E407, Y408, A409, R413, Y416, R422, V429, V434, F435, D436, F437, S439, L440, Y441, P442, S443, 1444, 1445, V446, T454, A465, S473, F479, 1480, R496, D504, F511, A515, S522, F523, Y524, Y526, M527, R536, R537, E538, C539, E541, V543, A544, F546, A547, M549, 1551, K552, M555, A558, E559, F562, L564, E565, V566, D570, D572, V576, V577, 1578, P580, L585, A586, Q587, K588, K592, V593, E595, M597, 1601, F608, L613, V615, T616, R619, L622, L623, K628, M629, V631, F636, V637, R638, R639, D640, W641, A642, K650, 1655, L656, A660, K664, A665, L668, 1673, E674, R675, R677, S682, D685, T687, Y689, T690, Q691, R695, S698, S701, E703, V707, A708, K711, E718, V719, M723, 1724, 1729, T730, K734, G735, S737, Q738, T741, D752, D758, N759, 1761, 1765, R767, 1772, Y774, L779, K780, E781, G782, 1783, T784, Q785, T786, S787, L788, S789, R790, W791 and/or F792. From the sequence alignment shown in FIG. 35, the skilled artisan can ascertain positionally equivalent positions (or functionally equivalent sites) in Geobacillus stearothermophilus (e.g., Bst DNA polymerase) (SEQ ID NO:2794), 9°N polymerase (SEQ ID NOS: 2795 or 2796) (including THERMINATOR polymerase; SEQ ID NO:2797), VENT polymerase (SEQ ID NO:2798), DEEP VENT polymerase (SEQ ID NO:2799), Pfu polymerase (SEQ ID N0:2800) and/or Pyrococcus abyssi polymerase (SEQ ID NO:2801) and RB69 polymerase (SEQ ID NO:2802). [0306] The present disclosure provides engineered archaeal family-B DNA or family-A polymerases, including Geobacillus stearothermophilus (e.g., Bst DNA polymerase) (SEQ ID NO:2794), 9°N polymerase (SEQ ID NOS: 2795 or 2796) (including THERMINATOR polymerase; SEQ ID NO:2797), VENT polymerase (SEQ ID NO:2798), DEEP VENT polymerase (SEQ ID NO:2799), Pfu polymerase (SEQ ID N0:2800) and/or Pyrococcus abyssi polymerase (SEQ ID NO:2801) and RB69 polymerase (SEQ ID NO:2802), that are mutated in one or more positions that are positionally equivalent (or functionally equivalent sites) to the amino acid substitutions at any one or any combination of positions of a polymerase having a backbone sequence of RMF 90817.1 (SEQ ID NO:2789) including Y11, D15, F23, K25, 128, L29, F34, Q35, P36, F38, H43, E49, G55, A56, V57, R62, R67, 175, L76, S77, H78, P79, S80, E81, V82, P83, K84, 185, R86, E87, E88, R90, E96, 198, E100, H101, D102, 1103, A106, R108, 1111, P117, L118, E138, G139, R144, V145, M146, D149, 1150, E151, T152, A234, Y272, C307, R312, E333, A357, V365, L368, F374, L390, V415, D417, F418, S420, L421, Y422, P423, 1425, V427, T435, P445, F459, A496, S503, F504, Y505, M508, K518, E519, C520, S523, V524, T525, M530, T532, D551, D553, V559, R566, A567, M568, R576, 1596, T597, N609, Q631, V636, A646, N655, R656, K658, D666, T671, R679, N682, K688, E699, M704, G715, L716, N740, L753, Y755, K761, E762, E763, M764, V765, Q766, G767, S768, L769, Q770, R771, W772 and/or F773. From the sequence alignment shown in FIG. 36, the skilled artisan can ascertain positionally equivalent positions (or functionally equivalent sites) in Geobacillus stearothermophilus (e.g., Bst DNA polymerase) (SEQ ID NO:2794), 9°N polymerase (SEQ ID NOS: 2795 or 2796) (including THERMINATOR polymerase; SEQ ID NO:2797), VENT polymerase (SEQ ID NO:2798), DEEP VENT polymerase (SEQ ID NO:2799), Pfu polymerase (SEQ ID N0:2800) and/or Pyrococcus abyssi polymerase (SEQ ID NO:2801) and RB69 polymerase (SEQ ID NO:2802).

[0307] The present disclosure provides engineered archaeal family-B DNA or family-A polymerases, including Geobacillus stearothermophilus (e.g., Bst DNA polymerase) (SEQ ID NO:2794), 9°N polymerase (SEQ ID NOS: 2795 or 2796) (including THERMINATOR polymerase; SEQ ID NO:2797), VENT polymerase (SEQ ID NO:2798), DEEP VENT polymerase (SEQ ID NO:2799), Pfu polymerase (SEQ ID N0:2800) and/or Pyrococcus abyssi polymerase (SEQ ID NO:2801) and RB69 polymerase (SEQ ID NO:2802), that are mutated in one or more positions that are positionally equivalent (or functionally equivalent sites) to the amino acid substitutions at any one or any combination of positions of a polymerase having a backbone sequence of MBC 7218772.1 (SEQ ID NO:2790) including 110, C468 and/or T560. From the sequence alignment shown in FIG. 37, the skilled artisan can ascertain positionally equivalent positions (or functionally equivalent sites) in Geobacillus stearothermophilus (e.g., Bst DNA polymerase) (SEQ ID NO:2794), 9°N polymerase (SEQ ID NOS: 2795 or 2796) (including THERMINATOR polymerase; SEQ ID NO:2797), VENT polymerase (SEQ ID NO:2798), DEEP VENT polymerase (SEQ ID NO:2799), Pfu polymerase (SEQ ID N0:2800) and/or Pyrococcus abyssi polymerase (SEQ ID NO:2801) and RB69 polymerase (SEQ ID NO:2802).

[0308] The present disclosure provides engineered archaeal family-B DNA or family-A polymerases, including Geobacillus stearothermophilus (e.g., Bst DNA polymerase) (SEQ ID NO:2794), 9°N polymerase (SEQ ID NOS: 2795 or 2796) (including THERMINATOR polymerase; SEQ ID NO:2797), VENT polymerase (SEQ ID NO:2798), DEEP VENT polymerase (SEQ ID NO:2799), Pfu polymerase (SEQ ID N0:2800) and/or Pyrococcus abyssi polymerase (SEQ ID NO:2801) and RB69 polymerase (SEQ ID NO:2802), that are mutated in one or more positions that are positionally equivalent (or functionally equivalent sites) to the amino acid substitutions at any one or any combination of positions of a polymerase having a backbone sequence of WP 175059460.1 (SEQ ID NO:2791) including Y7, Dl l, 151, K61, V93, Al 17, M129, D141, 1142, E143, T144, A223, E302, E323, D407, F408, S410, L411, Y412, P413, R487, A488, S495, Y496, K510, T517, 1524, K562, A563, R564, S572, T593, R605, K652, D675, K695, T700, R712, R759, Y760, Q761, S762, S763, K764, Q765 and/or T766. From the sequence alignment shown in FIG. 38, the skilled artisan can ascertain positionally equivalent positions (or functionally equivalent sites) in Geobacillus stearothermophilus (e.g., Bst DNA polymerase) (SEQ ID NO:2794), 9°N polymerase (SEQ ID NOS: 2795 or 2796) (including THERMINATOR polymerase; SEQ ID NO:2797), VENT polymerase (SEQ ID NO:2798), DEEP VENT polymerase (SEQ ID NO:2799), Pfu polymerase (SEQ ID N0:2800) and/or Pyrococcus abyssi polymerase (SEQ ID NO:2801) and RB69 polymerase (SEQ ID NO:2802).

[0309] The present disclosure provides engineered archaeal family-B DNA or family-A polymerases, including Geobacillus stearothermophilus (e.g., Bst DNA polymerase) (SEQ ID NO:2794), 9°N polymerase (SEQ ID NOS: 2795 or 2796) (including THERMINATOR polymerase; SEQ ID NO:2797), VENT polymerase (SEQ ID NO:2798), DEEP VENT polymerase (SEQ ID NO:2799), Pfu polymerase (SEQ ID N0:2800) and/or Pyrococcus abyssi polymerase (SEQ ID NO:2801) and RB69 polymerase (SEQ ID NO:2802), that are mutated in one or more positions that are positionally equivalent (or functionally equivalent sites) to the amino acid substitutions at any one or any combination of positions of a polymerase having a backbone sequence of KUO 42443.1 (SEQ ID NO:2792) including Y7, D I 70, E172, T557 and/or S558. From the sequence alignment shown in FIG. 39, the skilled artisan can ascertain positionally equivalent positions (or functionally equivalent sites) in Geobacillus stearothermophilus (e.g., Bst DNA polymerase) (SEQ ID NO:2794), 9°N polymerase (SEQ ID NOS: 2795 or 2796) (including THERMINATOR polymerase; SEQ ID NO:2797), VENT polymerase (SEQ ID NO:2798), DEEP VENT polymerase (SEQ ID NO:2799), Pfu polymerase (SEQ ID N0:2800) and/or Pyrococcus abyssi polymerase (SEQ ID NO:2801) and RB69 polymerase (SEQ ID NO:2802).

[0310] The present disclosure provides engineered archaeal family-B DNA or family-A polymerases, including Geobacillus stearothermophilus (e.g., Bst DNA polymerase) (SEQ ID NO:2794), 9°N polymerase (SEQ ID NOS: 2795 or 2796) (including THERMINATOR polymerase; SEQ ID NO:2797), VENT polymerase (SEQ ID NO:2798), DEEP VENT polymerase (SEQ ID NO:2799), Pfu polymerase (SEQ ID N0:2800) and/or Pyrococcus abyssi polymerase (SEQ ID NO:2801) and RB69 polymerase (SEQ ID NO:2802), that are mutated in one or more positions that are positionally equivalent (or functionally equivalent sites) to the amino acid substitutions at any one or any combination of positions of a polymerase having a backbone sequence of NOZ 77387.1 (SEQ ID NO:2793) including Y10, C41, C531 and/or T536. From the sequence alignment shown in FIG. 40, the skilled artisan can ascertain positionally equivalent positions (or functionally equivalent sites) in Geobacillus stearothermophilus (e.g., Bst DNA polymerase) (SEQ ID NO:2794), 9°N polymerase (SEQ ID NOS: 2795 or 2796) (including THERMINATOR polymerase; SEQ ID NO:2797), VENT polymerase (SEQ ID NO:2798), DEEP VENT polymerase (SEQ ID NO:2799), Pfu polymerase (SEQ ID N0:2800) and/or Pyrococcus abyssi polymerase (SEQ ID NO:2801) and RB69 polymerase (SEQ ID NO:2802).

[0311] The present disclosure provides polymerases operably linked to a detectable reporter moiety. Any of the polymerases described herein can be labeled with a detectable reporter moiety, including polymerases having a mutant amino acid sequence backbone of any polymerase described herein, including any of SEQ ID NOS: 1-2787, 2789-2793, Geobacillus stearothermophilus (e.g., Bst DNA polymerase) (SEQ ID NO:2794), 9°N polymerase (SEQ ID NOS: 2795 or 2796) (including THERMINATOR polymerase; SEQ ID NO:2797), VENT polymerase (SEQ ID NO:2798), DEEP VENT polymerase (SEQ ID NO:2799), Pfu polymerase (SEQ ID N0:2800) and/or Pyrococcus abyssi polymerase (SEQ ID NO:2801), RB69 polymerase (SEQ ID NO:2802) and Phi29 (SEQ ID NO:2803). [0312] In some embodiments, the detectable reporter moiety generates a detectable signal resulting from a chemical or physical change (e.g., heat, light, electrical, pH, salt concentration, enzymatic activity, or proximity events such as FRET). In some embodiments, the detectable reporter moiety comprises a luminescent moiety, fluorescent moiety, or quencher. In some embodiment, the detectable moiety comprises a fluorescent moiety that behaves as a FRET donor or acceptor. The detectable reporter moiety can be attached to the polymerase at the N-terminus, C-terminus or any internal location. The detectable reporter moiety is attached to the polymerase in a manner that does not interfere with the ability of the polymerase to bind a nucleic acid template molecule, a nucleic acid primer, or a nucleotide. The detectable reporter moiety is attached to the polymerase in a manner that does not interfere with catalytic activity of the polymerase including nucleotide incorporation.

[0313] The present disclosure provides recombinant fusion polypeptides which include any of the DNA polymerases described herein operably linked to any one or any combination of two or more exogenous amino acid sequences for affinity purification, cleavage and/or solubilization. In some embodiments, the recombinant fusion polypeptides comprise polymerases having a mutant amino acid sequence backbone of any polymerase described herein operably linked to an affinity purification tag, a cleavage tag and/or a solubilization tag, including any of SEQ ID NOS: 1-2787, 2789-2793, Geobacillus stearothermophilus (e.g., Bst DNA polymerase) (SEQ ID NO:2794), 9°N polymerase (SEQ ID NOS: 2795 or 2796) (including THERMINATOR polymerase; SEQ ID NO:2797), VENT polymerase (SEQ ID NO:2798), DEEP VENT polymerase (SEQ ID NO:2799), Pfu polymerase (SEQ ID N0:2800) and/or Pyrococcus abyssi polymerase (SEQ ID NO:2801) and RB69 polymerase (SEQ ID NO:2802) and Phi29 (SEQ ID NO:2803).

[0314] In some embodiments, the recombinant fusion polypeptides comprise any of the wild type and mutant polymerases operably linked at their N- and/or C-terminus end(s) to at least one affinity purification tag sequence, where the affinity purification tag sequence(s) include a Histidine tag (e.g., His-tag), FLAG tag, T7 tag, Strep II tag, S tag (e.g., from pancreatic ribonuclease A), HA tag (e.g., from human influenza hemagglutinin protein) and/or c-Myc tag. In some embodiments, the affinity purification tag sequence comprises a plurality of histidine residues, for example (3-10 histidine residues SEQ ID NO: 2851). In some embodiments, the affinity purification tag sequence comprises a plurality of consecutive histidine residues, for example 3-10 consecutive histidine residues (SEQ ID NO: 2851). [0315] In some embodiments, the wild type and engineered polymerases are recombinant proteins that can be expressed by a host cell harboring a cloned expression vector. It has been previously demonstrated that recombinant proteins carrying an affinity purification His-tag can undergo post-translational by an A", coll expression host cell. An example of post- translational modification includes N-phosphogluconoylation in which a gluconic acid derivative is attached to a His-tag at the N-terminus of the recombinant protein. The N- phosphogluconoylation is catalyzed by an E. coll 6-phosphoglucono-l,5-lactone pathway (Geoghegan 1999 Analytical Biochemistry 267: 169-184; Aon 2008 Applied and Environmental Microbiology 74(4):950-958). Another example of post-translational modification includes N-gluconoylation in which an N-phosphogluconoylated recombinant protein is further modified an E. coll host cell’s phosphatase. N-gluconoylation of recombinant proteins arises from a non-enzymatic acylation modification and is known to reduce protein activity, increases susceptibility to oxidation, and reduce protein crystallization. Thus, N-phosphogluconoylation and/or N-gluoconoylati on are undesirable post-translational modifications which can adversely impact production and shelf-life of recombinant proteins including the engineered polymerases.

[0316] It has been previously demonstrated by others that N-gluconoylation can be decreased by changes in host cell culture conditions, adaptation of modified purification processes or site directed mutagenesis of amino acid residues near the N-terminus in the recombinant protein. For example, recombinant proteins carrying N-terminal His-tags, where the amino acid sequence of the His-tag is modified, exhibit decreased N-gluoconoylati on (Martos-Maldonado, et al., 2018 Nature Communications 9:3307 (doi: 10.1038/s41467-018- 05695-3)).

[0317] In some embodiments, any of the engineered polymerases comprising any of SEQ ID NOS: 1-2787, can be linked at the N-terminal or C-terminal end to a conventional His-tag. In some embodiments, the conventional His-tag comprises the sequence MGSSHHHHHH (SEQ ID NO:2815), MGSSHHHHHHGS (SEQ ID NO:2816) or MGSSHHHHHHSSG (SEQ ID NO:2817).

[0318] In some embodiments, the engineered polymerases can be linked at the N-terminal or C-terminal end to a modified His-tag to generate a tagged polymerase that exhibits reduced N-phosphogluconoylation and/or N-gluoconoylati on when expressed by an expression host cell harboring a cloned expression vector, wherein the modified His-tag comprises the sequence MGSDKIHHHHHH (SEQ ID NO:2818), MAHHHHHH (SEQ ID NO:2819), MHHHHHH (SEQ ID NO:2820), MRGSPHHHHHH (SEQ ID NO:2821), MRGSHHHHHH (SEQ ID NO:2822), MHHHHHHSSG (SEQ ID NO:2823), or GGHHHHHH (SEQ ID NO:2824).

[0319] In some embodiments, the engineered polymerases can be linked at the N-terminal or C-terminal end to a His-tag that is modified by replacing one or more amino acid residues that are susceptible to N-phosphogluconoylation and/or N-gluconoylati on. In some embodiments, the engineered polymerases can be linked at the N-terminal or C-terminal end to a modified N-terminal His-tag, to generate a tagged polymerase that exhibits reduced N- phosphogluconoylation and/or N-gluoconoylation when expressed by an expression host cell harboring a cloned expression vector, wherein the modified His-tag comprises a glycine at position 2 that is replaced with Phenylalanine (F) or proline (P). In some embodiments, the modified His-tag comprises the sequence MFGSDKIHHHHHH (SEQ ID NO:2825), MPGSDKIHHHHHH (SEQ ID NO:2826), MFGSSHHHHHHGS (SEQ ID NO:2827), MPGSSHHHHHHGS (SEQ ID NO:2828), MFRGSPHHHHHH (SEQ ID NO:2829), MPRGSPHHHHHH (SEQ ID NO:2830), MFRGSHHHHHH (SEQ ID NO:2831), MPRGSHHHHHH (SEQ ID NO:2832), MFGSSHHHHHHSSGLVPRGSH (SEQ ID NO:2846), MPGSSHHHHHHSSGLVPRGSH (SEQ ID NO:2847), MPSSHHHHHHSSGLVPRGS (SEQ ID NO:2848) or MPGSSHHHHHHSSGLVPRGS (SEQ ID NO:2849).

[0320] In some embodiments, the tagged polymerase that exhibits reduced N- phosphogluconoylation and/or N-gluoconoylation also exhibits increased enzymatic activity and/or reduced oxidation compared to a tagged polymerase that carries a non-modified His- tag. In some embodiments, the tagged polymerase that exhibits reduced N- phosphogluconoylation and/or N-gluoconoylation also exhibits an increased fraction of active polymerase enzyme in a prepared batch (e.g., manufactured batch) and/or increase shelf-life compared to a tagged polymerase that carries a non-modified His-tag.

[0321] In some embodiments, the engineered polymerases comprises any of SEQ ID NOS: 1-2787 and 2789-2793) operably linked at their N- and/or C-terminus end(s) to at least one polypeptide cleavage sequence, or the polypeptide cleavage sequence can be positioned between an affinity tag sequence and the N-terminus or C-terminus end of the polymerase sequence. In some embodiments, the polypeptide cleavage sequence can be recognized and cleaved with a protease or a reducing condition. In some embodiments, the polypeptide cleavage sequence comprises a thrombin cleavage sequence, TEV cleavage sequence (e.g., from tobacco etch virus including AcTEV and ProTEV), factor Xa cleavage sequence, enterokinase cleavage sequence, and SUMO cleavage sequence (e.g., Small ubiquitin-like modified including Ulpl, Senp2 and SUMOstar).

[0322] In some embodiments, the engineered polymerases can be linked at the N-terminal or C-terminal end to a tag comprising a thrombin cleavage sequence. For example, a conventional thrombin cleavage sequence comprises the sequence LVPRGS (SEQ ID NO:2833), where the cleavage occurs after the arginine (R).

[0323] In some embodiments, the engineered polymerases can be linked at the N-terminal or C-terminal end to a tag comprising a modified thrombin cleavage sequence to generate a tagged polymerase that exhibits reduced N-phosphogluconoylation and/or N-gluoconoylation when expressed by an expression host cell harboring a cloned expression vector, wherein the modified thrombin cleavage sequence comprises an additional amino acid residue inserted after the arginine at position 4. In some embodiments, the modified thrombin cleavage sequence comprises the sequence LVPRAGSH (SEQ ID NO:2834), LVPRGGSH (SEQ ID NO:2835) or LVPRSGSH (SEQ ID NO:2836).

[0324] In some embodiments, the engineered polymerases can be linked at the N-terminal or C-terminal end to a His-tag comprising a thrombin cleavage sequence. In some embodiments, the His-tag which comprises a conventional thrombin cleavage sequence comprises the sequence

[0325] MGSSHHHHHHSSGLVPRGSH (SEQ ID NO:2837) or MGSSHHHHHHSSGLVPRGS (SEQ ID NO:2838). In some embodiments, the His-tag which comprises a thrombin cleavage sequence comprises the sequence MGSSHHHHHHSSGLHHRSGLVPRGSH (SEQ ID NO:2839), MGSSHHHHHHSSGLVPRQS (SEQ ID NO:2840) or MGSSHHHHHHSSGLVPGGSH (SEQ ID NO:2841).

[0326] In some embodiments, the engineered polymerases can be linked at the N-terminal or C-terminal end to a His-tag which comprises a modified thrombin cleavage sequence to generate a tagged polymerase that exhibits reduced N-phosphogluconoylation and/or N- gluoconoylation when expressed by an expression host cell harboring a cloned expression vector, wherein the His-tag which comprises a modified thrombin cleavage sequence comprises the sequence MGSSHHHHHHSSGLVPRAGSH (SEQ ID NO:2842), MGSSHHHHHHSSGLVPRGGSH (SEQ ID NO:2843) or MGSSHHHHHHSSGLVPRSGSH (SEQ ID NO:2844).

[0327] In some embodiments, the recombinant fusion polypeptides comprise any of the wild type and mutant polymerases described herein operably linked at their N- and/or C- terminus end(s) to at least one exogenous amino acid sequence for improving solubilization, including maltose binding protein (MBP), small ubiquitin-like modifier (SUMO) and glutathione S-transferase (GST).

[0328] The present disclosure provides a composition comprising: one or more mutant polymerases and at least one nucleic acid template molecule and at least one nucleic acid primer. In some embodiments, the one or more mutant polymerases may, or may not, be bound to the at least one nucleic acid template molecule and at least one nucleic acid primer. In some embodiments, the primer provides an initiation site for nucleotide polymerization. In some embodiments, the primer comprises a 3’ extendible end for a polymerase-catalyzed nucleotide incorporation reaction, or the primer comprises a 3’ non-extendible end. In some embodiments, the nucleic acid template molecule includes at least one uridine nucleotide or lacks a uridine nucleotide. In some embodiments, the mutant polymerases comprise an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99% identical, or a higher level sequence identity, to any of SEQ ID NOS: 1-2787 and 2789-2793. In some embodiments, the mutant polymerases include amino acid substitutions that confer exonuclease-minus activity. In some embodiments, the polymerases comprise at least one mutation that increases thermal stability of the enzyme, improves binding of nucleotide reagents and/or improved binding and incorporation of nucleotide reagent, improves incorporation rate of nucleotide analogs, improves uracil-tolerance and/or reduced sequence-specific errors compared to their corresponding wild type polymerase.

[0329] The present disclosure provides a composition comprising: one or more mutant polymerases and at least one nucleic acid template molecule having a self-priming 3’ end. In some embodiments, the one or more mutant polymerases may, or may not, be bound to the at least one nucleic acid template molecule having a self-priming 3’ end. In some embodiments, the self-priming 3’ end of the template molecule provides an initiation site for nucleotide polymerization. In some embodiments, the nucleic acid template molecule includes at least one uridine nucleotide or lacks a uridine nucleotide. In some embodiments, the mutant polymerases comprise an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99% identical, or a higher level sequence identity, to any of SEQ ID NOS: 1-2787 and 2789-2793. In some embodiments, the mutant polymerases include amino acid substitutions that confer exonuclease-minus activity. In some embodiments, the polymerases comprise at least one mutation that increases thermal stability of the enzyme, improves incorporation rate of nucleotide analogs and/or improves uracil-tolerance compared to their corresponding wild type polymerase. [0330] In some embodiments, the composition comprises: one or more mutant polymerases bound to nucleic acid duplexes each comprising a nucleic acid template hybridized to a nucleic acid primer, thereby forming a complexed polymerase. In some embodiments, the primer provides an initiation site for nucleotide polymerization. In some embodiments, the mutant polymerase is bound to a nucleic acid template molecule having a self-priming 3’ end to form a complexed polymerase that lacks a separate primer molecule. In some embodiments, the nucleic acid template molecule includes at least one uridine nucleotide or lacks a uridine nucleotide. In some embodiments, the mutant polymerases comprise an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99% identical, or a higher level sequence identity, to any of SEQ ID NOS: 1-2787 and 2789-2793. In some embodiments, the mutant polymerases are recombinant polymerases.

[0331] In some embodiments, the composition comprises one or more mutant polymerases, at least one nucleic acid template molecule, and an initiation site for nucleotide polymerization, wherein the mutant polymerases are in solution, the nucleic acid template molecules are in solution, and the initiation sites (e.g., primers) are in solution. In some embodiments, the composition comprises one or more mutant polymerases, at least one nucleic acid template molecule, and an initiation site for nucleotide polymerization, wherein the composition comprises any combination of mutant polymerases that are in solution, the nucleic acid template molecules that are in solution or immobilized to a support, and the initiation sites (e.g., primers) that are in solution or immobilized to a support. In some embodiments, the composition comprises one or more mutant polymerases, at least one nucleic acid template molecule, and an initiation site for nucleotide polymerization, wherein the composition comprises any combination of mutant polymerases that are in solution or immobilized to a support, the nucleic acid template molecules that are in solution or immobilized to a support, and the initiation sites (e.g., primers) that are in solution or immobilized to a support.

[0332] In some embodiments, the mutant polymerases exhibit increased thermal stability compared to the wild type polymerase or compared to an engineered polymerase having the same backbone sequence including polymerases having the amino acid sequence of any of SEQ ID NOS: 1-2787 and 2789-2793. For example, the mutant polymerases exhibit increased thermal stability at a temperature range of about 25-50 °C or about 45-90 °C.

[0333] In some embodiments, the mutant polymerases exhibit increased incorporation rate of nucleotide analogs compared to a wild type polymerase or compared to an engineered polymerase having the same backbone sequence including polymerases having the amino acid sequence of any of SEQ ID NOS: 1-2787 and 2789-2793, where the nucleotide analogs comprise a chain terminating moiety (e.g., blocking moiety) at the sugar 2’ position and/or at the 3’ sugar position.

[0334] In some embodiments, the mutant polymerases exhibit increased uracil-tolerance compared to a wild type polymerase compared to a wild type polymerase or compared to an engineered polymerase having the same backbone sequence including polymerases having the amino acid sequence of any of SEQ ID NOS: 1-2787 and 2789-2793.

[0335] In some embodiments, the mutant polymerases exhibit increased ability to bind complementary nucleotide units of a multivalent molecule compared to a wild type polymerase or compared to an engineered polymerase having the same backbone sequence including polymerases having the amino acid sequence of any of SEQ ID NOS: 1-2787 and 2789-2793.

[0336] In some embodiments, the mutant polymerases exhibit reduced switching from polymerization conformation to exonuclease conformation (e.g., reduced switching to editing mode) compared to a wild type polymerase or compared to an engineered polymerase having the same backbone sequence including polymerases having the amino acid sequence of any of SEQ ID NOS: 1-2787 and 2789-2793.

[0337] In some embodiments, the composition comprises: one or more mutant polymerases, and a plurality of nucleic acid duplexes each comprising a nucleic acid template hybridized to a nucleic acid primer. In some embodiments, the one or more polymerases and the nucleic acid duplex further comprises nucleotide reagents. The one or more mutant polymerases may or may not be bound to the nucleic acid duplex. The one or more mutant polymerases may or may not be bound to the nucleotide reagents. In some embodiments, the one or mutant polymerases is bound to the nucleic acid duplex comprising a nucleic acid template hybridized to a nucleic acid primer, thereby forming a complexed polymerase. In some embodiments, the complexed polymerase further comprises a nucleotide reagent. In some embodiments, the mutant polymerases comprise an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99% identical, or a higher level sequence identity, to any of SEQ ID NOS: 1-2787 and 2789-2793. In some embodiments, the mutant polymerases are recombinant polymerases.

[0338] In some embodiments, nucleotide reagents comprise any one or any combination of nucleotides and/or multivalent molecules. In some embodiments, the nucleotides comprise canonical nucleotides. In some embodiments, the nucleotides comprise non-labeled nucleotides. In some embodiments, the nucleotides comprise detectably labeled nucleotides each comprising a detectable reporter moiety joined to a nucleo-base or one of the phosphate moieties of the phosphate chain. In some embodiments, the nucleotides comprise nucleotides carrying a removable or non-removable chain terminating moiety. In some embodiments, the reversible chain terminating nucleotides can be detectably labeled or non-labeled. In some embodiments, individual multivalent molecules comprise a central core attached to multiple polymer arms each having a nucleotide unit at the end of the arms.

[0339] In some embodiments, the complexed polymerase further comprises a nucleotide reagent which comprises a nucleotide. In some embodiments, a nucleotide can bind to a complexed polymerase without incorporation. In some embodiments, a complementary nucleotide can bind a complexed polymerase without undergoing polymerase-catalyzed incorporation to form a ternary complex in which the complementary nucleotide binds the 3’ end of the primer at a position that is opposite a complementary nucleotide in the template strand.

[0340] In some embodiments, at least one nucleotide in the plurality of nucleotides comprise a base, sugar and at least one phosphate group. In some embodiments, at least one nucleotide in the plurality comprises an aromatic base, a five carbon sugar (e.g., ribose or deoxyribose), and one or more phosphate groups (e.g., 1-10 phosphate groups). The plurality of nucleotides can comprise at least one type of nucleotide selected from a group consisting of dATP, dGTP, dCTP, dTTP and dUTP. The plurality of nucleotides can comprise at a mixture of any combination of two or more types of nucleotides selected from a group consisting of dATP, dGTP, dCTP, dTTP and/or dUTP.

[0341] In some embodiments, at least one nucleotide in the plurality of nucleotides comprise a chain of one, two or three phosphorus atoms where the chain is typically attached to the 5’ carbon of the sugar moiety via an ester or phosphoramide linkage. In some embodiments, at least one nucleotide in the plurality is an analog having a phosphorus chain in which the phosphorus atoms are linked together with intervening O, S, NH, methylene or ethylene. In some embodiments, the phosphorus atoms in the chain include substituted side groups including O, S or BH3. In some embodiments, the chain includes phosphate groups substituted with analogs including phosphoramidate, phosphorothioate, phosphordithioate, and O-methylphosphoroamidite groups.

[0342] In some embodiments, at least one nucleotide in the plurality of nucleotides comprises a nucleotide analog having a chain terminating moiety (e.g., blocking moiety) at the sugar 2’ position, at the sugar 3’ position, or at the sugar 2’ and 3’ position. In some embodiments, the chain terminating moiety can inhibit polymerase-catalyzed incorporation of a subsequent nucleotide unit or free nucleotide in a nascent strand during a primer extension reaction. In some embodiments, the chain terminating moiety is attached to the 3’ sugar hydroxyl position where the sugar comprises a ribose or deoxyribose sugar moiety. In some embodiments, the chain terminating moiety is removable/cleavable from the 3’ sugar hydroxyl position to generate a nucleotide having a 3 ’OH sugar group which is extendible with a subsequent nucleotide in a polymerase-catalyzed nucleotide incorporation reaction. In some embodiments, the chain terminating moiety comprises an alkyl group, alkenyl group, alkynyl group, allyl group, aryl group, benzyl group, azide group, amine group, amide group, keto group, isocyanate group, phosphate group, thio group, disulfide group, carbonate group, urea group, silyl group or acetal group. In some embodiments, the chain terminating moiety is cleavable/removable from the nucleotide, for example by reacting the chain terminating moiety with a chemical agent, pH change, light or heat. In some embodiments, the chain terminating moieties alkyl, alkenyl, alkynyl and allyl are cleavable with tetrakis(triphenylphosphine)palladium(0) (Pd(PPh3)4) with piperidine, or with 2,3-Dichloro- 5,6-dicyano-l,4-benzo-quinone (DDQ). In some embodiments, the chain terminating moieties aryl and benzyl are cleavable with H2 Pd/C. In some embodiments, the chain terminating moieties amine, amide, keto, isocyanate, phosphate, thio, disulfide are cleavable with phosphine or with a thiol group including beta-mercaptoethanol or dithiothritol (DTT). In some embodiments, the chain terminating moiety carbonate is cleavable with potassium carbonate (K2CO3) in MeOH, with triethylamine in pyridine, or with Zn in acetic acid (AcOH). In some embodiments, the chain terminating moieties urea and silyl are cleavable with tetrabutylammonium fluoride, pyridine-HF, with ammonium fluoride, or with triethylamine trihydrofluoride. In some embodiments, the chain terminating moiety may be cleavable/removable with nitrous acid. In some embodiments, a chain terminating moiety may be cleavable/removable using a solution comprising nitrite, such as, for example, a combination of nitrite with an acid such as acetic acid, sulfuric acid, or nitric acid. In some further embodiments, said solution may comprise an organic acid.

[0343] In some embodiments, at least one nucleotide in the plurality of nucleotides comprises a terminator nucleotide analog having a chain terminating moiety (e.g., blocking moiety) at the sugar 2’ position, at the sugar 3’ position, or at the sugar 2’ and 3’ position. In some embodiments, the chain terminating moiety comprises an azide, azido or azidomethyl group. In some embodiments, the chain terminating moiety comprises a 3’-O-azido or 3’-O- azidomethyl group. In some embodiments, the chain terminating moieties azide, azido and azidomethyl group are cleavable/removable with a phosphine compound. In some embodiments, the phosphine compound comprises a derivatized tri-alkyl phosphine moiety or a derivatized tri-aryl phosphine moiety. In some embodiments, the phosphine compound comprises Tris(2-carboxyethyl)phosphine (TCEP) or bis-sulfo triphenyl phosphine (BS-TPP) or Tri(hydroxyproyl)phosphine (THPP). In some embodiments, the cleaving agent comprises 4-dimethylaminopyridine (4-DMAP). In some embodiments, the chain terminating moiety comprising one or more of a 3’-O-amino group, a 3’-O-aminomethyl group, a 3’-O- methylamino group, or derivatives thereof may be cleaved with nitrous acid, through a mechanism utilizing nitrous acid, or using a solution comprising nitrous acid. In some embodiments, the chain terminating moiety comprising one or more of a 3’-O-amino group, a 3’-O-aminomethyl group, a 3’-O-methylamino group, or derivatives thereof may be cleaved using a solution comprising nitrite. In some embodiments, for example, nitrite may be combined with or contacted with an acid such as acetic acid, sulfuric acid, or nitric acid. In some further embodiments, for example, nitrite may be combined with or contacted with an organic acid such as, for example, formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, or the like. In some embodiments, the chain terminating moiety comprises a 3’-acetal moiety which can be cleaved with a palladium deblocking reagent (e.g., Pd(0)). [0344] In some embodiments, the nucleotide analog comprise a chain terminating moiety which is selected from a group consisting of 3’-deoxy nucleotides, 2’, 3 ’-dideoxynucleotides, 3 ’-methyl, 3 ’-azido, 3 ’-azidomethyl, 3’-O-azidoalkyl, 3’-O-ethynyl, 3’-O-aminoalkyl, 3’-O- fluoroalkyl, 3 ’-fluoromethyl, 3 ’-difluoromethyl, 3 ’-trifluoromethyl, 3 ’-sulfonyl, 3 ’-malonyl, 3’-amino, 3’-O-amino, 3’-sulfhydral, 3 ’-aminomethyl, 3’-ethyl, 3’butyl, 3" -tert butyl, 3’- Fluorenylmethyloxycarbonyl, 3’ /c/V-Butyloxycarbonyl, 3’-O-alkyl hydroxylamino group, 3’- phosphorothioate, and 3-O-benzyl, or derivatives thereof.

[0345] In some embodiments, the plurality of nucleotides comprises a plurality of nucleotides that lack a detectable reporter moiety, for example a fluorophore. In some embodiments, the plurality of nucleotides comprises a plurality of nucleotides labeled with detectable reporter moiety. The detectable reporter moiety comprises a fluorophore. In some embodiments, the fluorophore is attached to the nucleotide base. In some embodiments, the fluorophore is attached to the nucleotide base with a linker which is cleavable/removable from the base.

[0346] In some embodiments, the cleavable linker on the base comprises a cleavable moiety comprising an alkyl group, alkenyl group, alkynyl group, allyl group, aryl group, benzyl group, azide group, amine group, amide group, keto group, isocyanate group, phosphate group, thio group, disulfide group, carbonate group, urea group, or silyl group. In some embodiments, the cleavable linker on the base is cleavable/removable from the base by reacting the cleavable moiety with a chemical agent, pH change, light or heat. In some embodiments, the cleavable moieties alkyl, alkenyl, alkynyl and allyl are cleavable with tetrakis(triphenylphosphine)palladium(0) (Pd(PPh3)4) with piperidine, or with 2,3-Dichloro- 5,6-dicyano-l,4-benzo-quinone (DDQ). In some embodiments, the cleavable moieties aryl and benzyl are cleavable with H2 Pd/C. In some embodiments, the cleavable moieties amine, amide, keto, isocyanate, phosphate, thio, disulfide are cleavable with phosphine or with a thiol group including beta-mercaptoethanol or dithiothritol (DTT). In some embodiments, the cleavable moiety carbonate is cleavable with potassium carbonate (K2CO3) in MeOH, with triethylamine in pyridine, or with Zn in acetic acid (AcOH). In some embodiments, the cleavable moieties urea and silyl are cleavable with tetrabutylammonium fluoride, pyridine- HF, with ammonium fluoride, or with triethylamine trihydrofluoride.

[0347] In some embodiments, the cleavable linker on the base comprises cleavable moiety including an azide, azido or azidomethyl group. In some embodiments, the cleavable moieties azide, azido and azidomethyl group are cleavable/removable with a phosphine compound. In some embodiments, the phosphine compound comprises a derivatized tri-alkyl phosphine moiety or a derivatized tri-aryl phosphine moiety. In some embodiments, the phosphine compound comprises Tris(2-carboxyethyl)phosphine (TCEP) or bis-sulfo triphenyl phosphine (BS-TPP) or Tri(hydroxyproyl)phosphine (THPP). In some embodiments, the cleaving agent comprises 4-dimethylaminopyridine (4-DMAP).

[0348] In some embodiments, the chain terminating moiety (e.g., at the sugar 2’ and/or sugar 3’ position) and the cleavable linker on the base have the same or different cleavable moieties. In some embodiments, the chain terminating moiety (e.g., at the sugar 2’ and/or sugar 3’ position) and the detectable reporter moiety linked to the base are chemically cleavable/removable with the same chemical agent. In some embodiments, the chain terminating moiety (e.g., at the sugar 2’ and/or sugar 3’ position) and the detectable reporter moiety linked to the base are chemically cleavable/removable with different chemical agents. [0349] In some embodiments, the composition comprises: one or more mutant polymerases and a nucleic acid duplex each comprising a nucleic acid template hybridized to a nucleic acid primer. In some embodiments, the one or more polymerases and the nucleic acid duplex further comprises a plurality of nucleotide reagents. In some embodiments, the one or more polymerases and the nucleic acid duplex further comprises a plurality of multivalent molecules. The one or more mutant polymerases may or may not be bound to the nucleic acid duplex. The one or more mutant polymerases may or may not be bound to one or more of the multivalent molecules. In some embodiments, the one or mutant polymerases is bound to the nucleic acid duplex comprising a nucleic acid template hybridized to a nucleic acid primer, thereby forming a complexed polymerase. In some embodiments, the complexed polymerase further comprises at least one nucleotide reagent (e.g., plurality of multivalent molecules). In some embodiments, the mutant polymerases comprise an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99% identical, or a higher level sequence identity, to any of SEQ ID NOS: 1-2787 and 2789-2793. In some embodiments, the mutant polymerases are recombinant polymerases.

[0350] In some embodiments, nucleotide reagents comprise any one or any combination of nucleotides and/or multivalent molecules. In some embodiments, the nucleotides comprise canonical nucleotides. In some embodiments, the nucleotides comprise non-labeled nucleotides. In some embodiments, the nucleotides comprise nucleotide analogs comprise detectably labeled nucleotides and/or nucleotides carrying a removable or non-removable chain terminating moiety. In some embodiments, individual multivalent molecules comprise a central core attached to multiple polymer arms each having a nucleotide unit at the end of the arms.

[0351] In some embodiments, the multivalent molecule generally comprises a central moiety (e.g., a core) attached to a plurality of arms where each arm is attached to a nucleotide unit. The multivalent molecule comprises a star, comb, cross-linked, bottle brush, or dendrimer configuration. In some embodiments, the multivalent molecule may comprise 2-4, 4-10, 10-20, or up to 64 arms. In some embodiments, the arms may radiate from a central moiety.

[0352] In some embodiments, at least one multivalent molecule in the plurality of multivalent molecules comprises: (a) a core; and (b) a plurality of nucleotide arms which comprise (i) a core attachment moiety, (ii) a spacer (e.g., comprising a PEG moiety), (iii) a linker, and (iv) a nucleotide unit, wherein the core is attached to the plurality of nucleotide arms, wherein the spacer is attached to the linker, wherein the linker is attached to the nucleotide unit. In some embodiments, the nucleotide unit comprises a base, sugar and at least one phosphate group, and the linker is attached to the nucleotide unit through the base. In some embodiments, the linker comprises an aliphatic chain or an oligo ethylene glycol chain where both linker chains having 2-6 subunits. In some embodiments, the linker also includes an aromatic moiety. Exemplary multivalent molecules are shown in FIGs. 2-5. An exemplary nucleotide arm is shown in FIG. 6. An exemplary spacer is shown in FIG. 7 (top). Various exemplary linkers are shown in FIG. 7 (bottom) and FIG. 8. Examples of various linkers joined/ attached to nucleotide units are shown in FIGs. 9A-D, where the 5 position of a pyrimidine base or the 7 position of a purine base is attached to the linker via a propargyl amine attachment (see also FIG. 10).

[0353] In some embodiments, the nucleotide-arm is designed so that the nucleotide unit of the nucleotide-arm is capable of interacting with a polymerase enzyme in a manner similar to a free nucleotide. The nucleotide unit of a nucleotide-arm can bind a polymerase which is complexed with a nucleic acid template and nucleic acid primer (e.g., nucleotide association). The nucleotide unit can also dissociate from the complexed polymerase and either re-bind the same complexed polymerase or bind a different complexed polymerase that is proximal to the multivalent molecule. Since a multivalent molecule comprises multiple nucleotide-arms, the nucleotide units of a single multivalent molecule can bind multiple complexed polymerases at the same time. The multivalent molecules effectively increase the local concentration of nucleotides which can enhance signals in a nucleotide binding reaction.

[0354] In some embodiments, a nucleotide unit of the multivalent molecule can bind to a complexed polymerase without incorporation. In some embodiments, a complementary nucleotide unit of a multivalent molecule can bind a complexed polymerase without undergoing polymerase-catalyzed incorporation in which the complementary nucleotide unit binds the 3’ end of the primer at a position that is opposite a complementary nucleotide in the template strand.

[0355] In some embodiments, a nucleotide unit of the multivalent molecule can bind to a complexed polymerase, and undergo primer extension by incorporating into the 3’ end of an extendible primer (e.g., complexed with the polymerase) resulting in primer extension. When the nucleotide unit includes a sugar 3 ’OH then a subsequent nucleotide can be incorporated into the nascent extended primer. When the nucleotide unit includes a sugar 3 ’OH substituted with a blocking group, then a subsequent nucleotide is blocked from being incorporated into the nascent extended primer strand. A nucleotide unit (of a multivalent molecule) can bind the 3’ end of the primer at a position that is opposite a complementary nucleotide in the template strand. The nucleotide unit can undergo nucleotide incorporation in a polymerase- catalyzed reaction, thereby extending the primer by one nucleotide.

[0356] In some embodiments, the core, linker and/or nucleotide unit of the multivalent molecule can be labeled with a detectable reporter moiety (e.g., fluorophore) in a manner that permits distinction between different multivalent molecules carrying a different type of nucleotide unit. For example, the core unit of a first multivalent molecule is labeled with a first fluorophore, where the first multivalent molecule comprises multiple nucleotide-arms with dGTP nucleotide units. The core unit of a second multivalent molecule is labeled with a second fluorophore (which differs from the first fluorophore), where the second multivalent molecule comprises multiple nucleotide-arms with dATP nucleotide units. The binding and incorporating events of the nucleotide unit can be detected, and the specific base of the nucleotide unit (as part of the multivalent molecule) can be identified based on detection and identification of the detectable reporter moiety on the core. In another example, the linker and/or nucleotide unit of a first multivalent molecule is labeled with a first fluorophore, where the first multivalent molecule comprises multiple nucleotide-arms with dGTP nucleotide units. The linker and/or nucleotide unit of a second multivalent molecule is labeled with a second fluorophore (which differs from the first fluorophore), where the second multivalent molecule comprises multiple nucleotide-arms with dATP nucleotide units. The binding and incorporating events of the nucleotide unit can be detected, and the specific base of the nucleotide unit (as part of the multivalent molecule) can be identified based on detection and identification of the detectable reporter moiety on the core. In some embodiments, the core, linker and nucleotide unit are not labeled with a detectable reporter moiety.

[0357] In some embodiments, at least one nucleotide unit attached to the nucleotide arm of the multivalent molecule can be labeled with a detectable reporter moiety (e.g., fluorophore) in a manner that permits distinction between different multivalent molecules carrying a different type of nucleotide unit. For example, the nucleotide unit of a first multivalent molecule is labeled with a first fluorophore, where the first multivalent molecule comprises multiple nucleotide-arms with dGTP nucleotide units. The nucleotide unit of a second multivalent molecule is labeled with a second fluorophore (which differs from the first fluorophore), where the second multivalent molecule comprises multiple nucleotide- arms with dATP nucleotide units. The binding and incorporating events of the nucleotide unit can be detected, and the specific base of the nucleotide unit (as part of the multivalent molecule) can be identified based on detection and identification of the detectable reporter moiety on the nucleotide unit.

[0358] In some embodiments, individual multivalent molecules in the plurality of multivalent molecules comprise a core attached to multiple nucleotide arms, and wherein the multiple nucleotide arms have the same type of nucleotide unit which is selected from a group consisting of dATP, dGTP, dCTP, dTTP and dUTP.

[0359] In some embodiments, the nucleotide unit of the at least one multivalent molecule comprises an aromatic base, a five carbon sugar (e.g., ribose or deoxyribose), and one or more phosphate groups (e.g., 1-10 phosphate groups). The plurality of multivalent molecules can comprise one type multivalent molecule having one type of nucleotide unit selected from a group consisting of dATP, dGTP, dCTP, dTTP and dUTP. The plurality of nucleotides can comprise at a mixture of any combination of two or more types of multivalent molecules, where individual multivalent molecules in the mixture comprise nucleotide units selected from a group consisting of dATP, dGTP, dCTP, dTTP and/or dUTP.

[0360] In some embodiments, the plurality of complexed mutant DNA polymerases further comprise a first and second binding complex and a multivalent molecule which forms an avidity complex, wherein (i) the first binding complex comprises a first nucleic acid primer, a first DNA polymerase, and a first multivalent molecule bound to a first portion of a concatemer template molecule thereby forming a first binding complex (e.g., FIGs. 44-46), wherein a first nucleotide unit of the multivalent molecule is bound to the first DNA polymerase, and (ii) the second binding complex comprises a second nucleic acid primer, a second DNA polymerase, and the first multivalent molecule bound to a second portion of the same concatemer template molecule thereby forming a second binding complex (e.g., FIGs. 44-46), wherein a second nucleotide unit of the multivalent molecule is bound to the second DNA polymerase, wherein the first and second binding complexes which include the same multivalent molecule forms an avidity complex (e.g., FIG. 47). In some embodiments, the first polymerase comprises any mutant polymerase described herein. In some embodiments, the second polymerase comprises any mutant polymerase described herein. The concatemer template molecule comprises tandem repeat sequences of a sequence of interest and at least one universal sequencing primer binding site. The first and second nucleic acid primers can bind to a sequencing primer binding site along the concatemer template molecule.

[0361] In some embodiments, in the system, the plurality of complexed DNA polymerases further comprise a first and second binding complex and a multivalent molecule which forms an avidity complex, wherein (i) the first binding complex comprises a first nucleic acid primer, a first DNA polymerase, and a first multivalent molecule bound to a first template molecule thereby forming a first binding complex, wherein a first nucleotide unit of the multivalent molecule is bound to the first DNA polymerase, and (ii) the second binding complex comprises a second nucleic acid primer, a second DNA polymerase, and the first multivalent molecule bound to a second template molecule thereby forming a second binding complex, wherein a second nucleotide unit of the multivalent molecule is bound to the second DNA polymerase, wherein the first and second binding complexes which include the same multivalent molecule forms an avidity complex. In some embodiments, the first polymerase comprises any mutant polymerase described herein. In some embodiments, the second polymerase comprises any mutant polymerase described herein. In some embodiments, the first and second template molecules are clonally amplified template molecules. In some embodiments, the first and second template molecules are localized in close proximity to each other. For example, the clonally-amplified first and second template molecules comprise linear template molecules that are generated via bridge amplification and are immobilized to the same location or feature on a support. The first and second template molecules comprise a sequence of interest and at least one universal sequencing primer binding site. The first and second nucleic acid primers can bind to a sequencing primer binding site on the first and second template molecules, respectively.

[0362] In some embodiments, at least one multivalent molecule in the plurality of multivalent molecules comprise a nucleotide unit having a chain of one, two or three phosphorus atoms where the chain is typically attached to the 5’ carbon of the sugar moiety via an ester or phosphoramide linkage. In some embodiments, at least one nucleotide unit is a nucleotide analog having a phosphorus chain in which the phosphorus atoms are linked together with intervening O, S, NH, methylene or ethylene. In some embodiments, the phosphorus atoms in the chain include substituted side groups including O, S or BH3. In some embodiments, the chain includes phosphate groups (e.g., 1-10 phosphate groups) substituted with analogs including phosphoramidate, phosphorothioate, phosphordithioate, and O- methylphosphoroamidite groups.

[0363] In some embodiments, individual multivalent molecules in the plurality of multivalent molecule comprise a core attached to multiple nucleotide arms, and wherein individual nucleotide arms comprise a nucleotide unit having a chain terminating moiety (e.g., blocking moiety) at the sugar 2’ position, at the sugar 3’ position, or at the sugar 2’ and 3’ position.

[0364] In some embodiments, at least one multivalent molecule in the plurality of multivalent molecules comprises a nucleotide unit comprising a nucleotide analog having a chain terminating moiety (e.g., blocking moiety) at the sugar 2’ position, at the sugar 3’ position, or at the sugar 2’ and 3’ position. In some embodiments, the chain terminating moiety can inhibit polymerase-catalyzed incorporation of a subsequent nucleotide unit or free nucleotide in a nascent strand during a primer extension reaction. In some embodiments, the chain terminating moiety is attached to the 3’ sugar hydroxyl position where the sugar comprises a ribose or deoxyribose sugar moiety. In some embodiments, the chain terminating moiety is removable/cleavable from the 3’ sugar hydroxyl position to generate a nucleotide having a 3 ’OH sugar group which is extendible with a subsequent nucleotide in a polymerase-catalyzed nucleotide incorporation reaction. In some embodiments, the chain terminating moiety comprises an alkyl group, alkenyl group, alkynyl group, allyl group, aryl group, benzyl group, azide group, amine group, amide group, keto group, isocyanate group, phosphate group, thio group, disulfide group, carbonate group, urea group, or silyl group. In some embodiments, the chain terminating moiety is cleavable/removable from the nucleotide, for example by reacting the chain terminating moiety with a chemical agent, pH change, light or heat. In some embodiments, the chain terminating moieties alkyl, alkenyl, alkynyl and allyl are cleavable with tetrakis(triphenylphosphine)palladium(0) (Pd(PPh3)4) with piperidine, or with 2,3-Dichloro-5,6-dicyano-l,4-benzo-quinone (DDQ). In some embodiments, the chain terminating moieties aryl and benzyl are cleavable with H2 Pd/C. In some embodiments, the chain terminating moieties amine, amide, keto, isocyanate, phosphate, thio, disulfide are cleavable with phosphine or with a thiol group including beta-mercaptoethanol or dithiothritol (DTT). In some embodiments, the chain terminating moiety carbonate is cleavable with potassium carbonate (K2CO3) in MeOH, with triethylamine in pyridine, or with Zn in acetic acid (AcOH). In some embodiments, the chain terminating moieties urea and silyl are cleavable with tetrabutylammonium fluoride, pyridine-HF, with ammonium fluoride, or with triethylamine trihydrofluoride.

[0365] In some embodiments, at least one multivalent molecule in the plurality of multivalent molecules comprises a nucleotide unit comprising a terminator nucleotide analog having a chain terminating moiety (e.g., blocking moiety) at the sugar 2’ position, at the sugar 3’ position, or at the sugar 2’ and 3’ position. In some embodiments, the chain terminating moiety comprises an azide, azido or azidomethyl group. In some embodiments, the chain terminating moiety comprises a 3’-O-azido or 3’-O-azidomethyl group. In some embodiments, the chain terminating moieties azide, azido and azidomethyl group are cleavable/removable with a phosphine compound. In some embodiments, the phosphine compound comprises a derivatized tri-alkyl phosphine moiety or a derivatized tri-aryl phosphine moiety. In some embodiments, the phosphine compound comprises Tris(2- carboxyethyl)phosphine (TCEP) or bis-sulfo triphenyl phosphine (BS-TPP) or Tri(hydroxyproyl)phosphine (THPP). In some embodiments, the cleaving agent comprises 4- dimethylaminopyridine (4-DMAP)..

[0366] In some embodiments, at least one multivalent molecule in the plurality of multivalent molecules comprises a nucleotide unit comprising a chain terminating moiety which is selected from a group consisting of 3’-deoxy nucleotides, 2’, 3 ’-dideoxynucleotides, 3 ’-methyl, 3 ’-azido, 3 ’-azidomethyl, 3’-O-azidoalkyl, 3’-O-ethynyl, 3’-O-aminoalkyl, 3’-O- fluoroalkyl, 3 ’-fluoromethyl, 3 ’-difluoromethyl, 3 ’-trifluoromethyl, 3 ’-sulfonyl, 3 ’-malonyl, 3’-amino, 3’-O-amino, 3’-sulfhydral, 3 ’-aminomethyl, 3’-ethyl, 3’butyl, 3" -tert butyl, 3’- Fluorenylmethyloxycarbonyl, 3’ tert-Butyloxycarbonyl, 3’-O-alkyl hydroxylamino group, 3’- phosphorothioate, and 3-O-benzyl, or derivatives thereof.

[0367] In some embodiments, at least one multivalent molecule in the plurality of multivalent molecules comprises a core attached to multiple nucleotide arms, wherein the core is labeled with detectable reporter moiety. In some embodiments, the detectable reporter moiety comprises a fluorophore.

[0368] In some embodiments, at least one multivalent molecule in the plurality of multivalent molecules comprises a nucleotide unit attached to multiple nucleotide arms, wherein the nucleotide unit is labeled with detectable reporter moiety. In some embodiments, the detectable reporter moiety comprises a fluorophore.

[0369] In some embodiments, at least one multivalent molecule in the plurality of multivalent molecules comprises at least one linker that is part of a nucleotide arm, wherein the linker is labeled with detectable reporter moiety. In some embodiments, the detectable reporter moiety comprises a fluorophore.

[0370] In some embodiments, the core comprises an streptavidin-type or avidin-type moiety and the core attachment moiety comprises biotin. In some embodiments, the core comprises an streptavidin-type or avidin-type moiety which includes an avidin protein, as well as any derivatives, analogs and other non-native forms of avidin that can bind to at least one biotin moiety. Other forms of avidin moieties include native and recombinant avidin and streptavidin as well as derivatized molecules, e.g. nonglycosylated avidin and truncated streptavidins . For example, avidin moiety includes deglycosylated forms of avidin, bacterial streptavidin produced by Streptomyces (e.g., Streptomyces avidinii), as well as derivatized forms, for example, N- acyl avidins, e.g., N-acetyl, N-phthalyl and N-succinyl avidin, and the commercially- available products ExtrAvidin™, Captavidin™, Neutravidin™’ and Neutralite Avidin™. Exemplary multivalent molecules are shown in FIGs. 2-3 and 5 in which a generic core is conjugated to a plurality of nucleotide-arms. An exemplary multivalent molecule is shown in FIG. 4 in which a generic dendrimer core is conjugated to a plurality of nucleotide-arms. An exemplary design for a multivalent molecule is shown in FIG. 5, which shows a core (e.g., streptavidin core) attached/bound to a plurality of nucleotide-arms, where the nucleotide arms comprise a core attachment moiety (e.g., biotin), spacer, linker and nucleotide unit. An exemplary biotinylated nucleotide-arm comprising biotin, spacer, linker and nucleotide unit, is shown in FIG. 6.

[0371] In some embodiments, the composition comprises: one or more mutant polymerases which are bound to nucleic acid duplexes each comprising a nucleic acid template hybridized to a nucleic acid primer, thereby forming a complexed polymerase, and the composition further comprises at least one cation. In some embodiment, the at least one cation is selected from the group consisting of strontium, barium, sodium, magnesium, potassium, manganese, calcium, lithium, nickel and cobalt. In some embodiments, the cation comprises a catalytic divalent cation that promotes polymerase-catalyzed nucleotide incorporation, wherein the catalytic divalent cations comprise magnesium or manganese. In some embodiments, the cation comprises a non-catalytic divalent cation that inhibits polymerase-catalyzed nucleotide incorporation, wherein the non-catalytic divalent cations comprise strontium, barium and/or calcium.

[0372] In some embodiments, the composition comprises: one or more mutant polymerases which are bound to nucleic acid duplexes each comprising a nucleic acid template molecule hybridized to a nucleic acid primer, thereby forming a complexed polymerase. In some embodiments, the nucleic acid template molecule comprises a linear nucleic acid molecule, or a circular nucleic acid molecule, or a mixture of both linear and circular nucleic acid molecules. In some embodiments, the nucleic acid template molecules in the plurality of nucleic acid template molecules comprise the same target sequence of interest or different target sequences of interest. In some embodiments, the nucleic acid template molecule comprises an amplified nucleic acid molecule. In some embodiments, the nucleic acid template molecule comprises a clonally-amplified template molecule or a single nucleic acid template molecule. In some embodiments, the nucleic acid template molecule comprises one copy of a target sequence of interest. In some embodiments, the nucleic acid template molecule comprises two or more tandem copies of a target sequence of interest (e.g., a concatemer). In some embodiments, the nucleic acid template molecules includes at least one uridine nucleotide or lacks a uridine nucleotide. In some embodiments, the primer provides an initiation site for nucleotide polymerization. In some embodiments, the nucleic acid primer comprises an extendible 3’ terminal end or a non-extendible 3’ terminal end. In some embodiments, the mutant polymerases comprise an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99% identical, or a higher level sequence identity, to any of SEQ ID NOS: 1-2787 and 2789-2793. [0373] In some embodiments, the complexed polymerase is immobilized to a support, where any of the nucleic acid template, nucleic acid primer and/or polymerase is/are immobilized to the support. In some embodiments, the composition comprises a plurality of complexed polymerases immobilized to a support. In some embodiments, about 10 ² - 10 ¹⁵ complexed polymerases are immobilized to a support at different sites on the support. In some embodiments, the plurality of complexed polymerases are immobilized to predetermined sites (e.g., locations) on the support. In some embodiments, the plurality of complexed polymerases are immobilized to random sites (e.g., locations) on the support. In some embodiments, the plurality of immobilized complexed mutant DNA polymerases are in fluid communication with each other to permit flowing a solution of reagents (e.g., enzymes including polymerases, multivalent molecules, nucleotides and/or divalent cations, and the like) onto the support so that the plurality of immobilized complexed polymerases on the support can be reacted with the solution of reagents in a massively parallel manner.

[0374] In some embodiments, the support comprises a planar or non-planar support. The support can be solid or semi-solid. In some embodiments, the support can be porous, semi- porous or non-porous. In some embodiments, the surface of the support can be coated with one or more compounds to produce a passivated layer on the support. In some embodiments, the passivated layer forms a porous or semi-porous layer. In some embodiments, the nucleic acid primer or template, or the polymerase, can be attached to the passivated layer to immobilize the primer, template and/or polymerase to the support. In some embodiments, the support comprises a low non-specific binding surface that enable improved nucleic acid hybridization and amplification performance on the support. In general, the support may comprise one or more layers of a covalently or non-covalently attached low-binding, chemical modification layers, e.g., silane layers, polymer films, and one or more covalently or non-covalently attached oligonucleotides that can be used for immobilizing a plurality of nucleic acid template molecules to the support. In some embodiments, the support can comprise a functionalized polymer coating layer covalently bound at least to a portion of the support via a chemical group on the support, a primer grafted to the functionalized polymer coating, and a water-soluble protective coating on the primer and the functionalized polymer coating. In some embodiments, the functionalized polymer coating comprises a poly(N-(5- azidoacet-amidylpentyl)acrylamide-co-acrylamide (PAZAM). In some embodiments, the support comprises a surface coating having at least one hydrophilic polymer coating layer and at least one layer of a plurality of oligonucleotides. The hydrophilic polymer coating layer can comprise polyethylene glycol (PEG). The hydrophilic polymer coating layer can comprise branched PEG having at least 4 branches. In some embodiments, the low nonspecific binding coating has a degree of hydrophilicity which can be measured as a water contact angle, where the water contact angle is no more than 45 degrees.

[0375] In some embodiments, the composition comprises a plurality of complexed polymerases, having at least a first and second complexed polymerase, wherein: (a) the first complexed polymerases comprises a first mutant polymerase bound to a first nucleic acid duplex comprising a first nucleic acid template molecule which is hybridized to a first nucleic acid primer, (b) the second complexed polymerases comprises a second mutant polymerase bound to a second nucleic acid duplex comprising a second nucleic acid template molecule which is hybridized to a second nucleic acid primer. In some embodiments, the first and second nucleic acid template molecule comprise the same or different sequences. In some embodiments, the first and second nucleic acid template molecules are clonally-amplified. In some embodiments, the first and/or the second nucleic acid template molecule includes at least one uridine nucleotide or lacks a uridine nucleotide. In some embodiments, the first and second primers comprise extendible 3’ ends or non-extendible 3’ ends. In some embodiments, the first and second mutant polymerases comprise an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99% identical, or a higher level sequence identity, to any of SEQ ID NOS: 1-2787 and 2789-2793. In some embodiments, the first and second mutant polymerases are recombinant polymerases.

[0376] In some embodiments, the plurality of complexed polymerases (including the first and second complexed polymerases) are immobilized to a support. In some embodiments, the density of the plurality of complexed polymerases comprises about 10 ² - 10 ¹⁵ per mm ² complexed polymerases that are immobilized to the support. In some embodiments, the first and second nucleic acid template molecules are immobilized to a different site on the support. In some embodiments, the support comprises a plurality of sites arranged in an array. In some embodiments, the sites on the support are arranged in one dimension in a row or a column, or arranged in two dimensions in rows and columns. In some embodiments, the plurality of sites is arranged on the support in a random or organized fashion, or a combination of both. In some embodiments, the plurality of sites is arranged in any pattern, including rectilinear or hexagonal patterns. In some embodiments, the support comprises about 10 ² - 10 ¹⁵ sites per mm ² or more that are immobilized with nucleic acid templates to form a nucleic acid template array. In some embodiments, the nucleic acid templates that are immobilized at a plurality of sites, for example the nucleic acid template molecules are immobilized at about 10 ² - 10 ¹⁵ sites per mm ² or more, where the immobilized nucleic acid templates are clonally- amplified to generate immobilized nucleic acid polonies at the plurality of sites. In some embodiment, the plurality of nucleic acid template molecules immobilized on the support are in fluid communication with each other to permit flowing a solution of a reagents (e.g., a plurality of enzymes (e.g., polymerases), a plurality of nucleotides and/or a plurality of multivalent molecules) onto the support so that the plurality of nucleic acid template molecules immobilized on the support can be reacted with the plurality of reagents in a massively parallel manner. In some embodiments, the fluid communication of the plurality of nucleic acid polonies immobilized on the support can be used to conduct nucleotide binding assays and/or conduct nucleotide incorporation assays (e.g., primer extension or sequencing) essentially simultaneously on the plurality of nucleic acid polonies. In some embodiments, the fluid communication of the plurality of nucleic acid polonies immobilized on the support can be used to conduct detection and imaging for massively parallel sequencing. In some embodiments, the term “immobilized” and related terms refer to nucleic acid molecules or enzymes that are attached directly to a support through covalent bond or non-covalent interaction, or attached to a coating on the support. In some embodiments, the low nonspecific binding coating has a degree of hydrophilicity which can be measured as a water contact angle, where the water contact angle is no more than 45 degrees.

[0377] In some embodiments, a binding complex comprises a mutant polymerase, a nucleic acid template molecule duplexed with a primer, and a nucleotide reagent. In some embodiments, a binding complex comprises (i) a mutant polymerase, a nucleic acid template molecule duplexed with a primer, and a nucleotide, or the binding complex comprises (ii) a mutant polymerase, a nucleic acid template molecule duplexed with a primer, and a nucleotide unit of a multivalent molecule. In some embodiments, the mutant polymerase comprises an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99% identical, or a higher level sequence identity, to any of SEQ ID NOS: 1-2787 and 2789-2793. In some embodiments, the binding complex has a persistence time of greater than about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1 second. In some embodiments, the binding complex has a persistence time of 1-30 seconds. The binding complex has a persistence time of greater than about 0.1-0.25 seconds, or about 0.25-0.5 seconds, or about 0.5-0.75 seconds, or about 0.75-1 second, or about 1-2 seconds, or about 2-3 seconds, or about 3-4 second, or about 4-5 seconds, or about 5-10 seconds, or about 10-30 seconds and/or wherein the method is or may be carried out at a temperature of at or above 15 °C, at or above 20 °C, at or above 25 °C, at or above 35 °C, at or above 37 °C, at or above 42 °C at or above 55 °C at or above 60 °C, or at or above 72 °C, or at or above 80 °C, or within a range defined by any of the foregoing. In some embodiments, the binding complexes may have a persistence time of greater than Is, greater than 2s, greater than 3 s, greater than 5s, greater than 10s, greater than 15s, greater than 20s, greater than 30s, greater than 60s, greater than 120s, greater than 360s, greater than 3600s, or more, or for a time lying within a range defined by any two or more of these values. The binding complex (e.g., ternary complex) remains stable until subjected to a condition that causes dissociation of interactions between any of the polymerase, template molecule, primer and/or the nucleotide unit or the nucleotide. For example, a dissociating condition comprises contacting the binding complex with any one or any combination of a detergent, EDTA and/or water. In some embodiments, the present disclosure provides said method wherein the binding complex is deposited on, attached to, or hybridized to, a surface showing a contrast to noise ratio in the detecting step of greater than 20. In some embodiments, the present disclosure provides said method wherein the contacting is performed under a condition that stabilizes the binding complex when the nucleotide or nucleotide unit is complementary to a next base of the template nucleic acid, and destabilizes the binding complex when the nucleotide or nucleotide unit is not complementary to the next base of the template nucleic acid.

[0378] The present disclosure provides a composition comprising a reaction mixture which comprises: (a) one or more mutant polymerases; (b) a nucleic acid template molecule; (c) a nucleic acid primer having a 3’ extendible end or a 3’ non-extendible end; and (d) a plurality of nucleotides or a plurality of multivalent molecules. In some embodiments, the one or more mutant polymerases are not bound to the nucleic acid template molecules. In some embodiments, the one or more mutant polymerases are not bound to the nucleic acid primers. In some embodiments, the one or more mutant polymerases are bound to nucleic acid duplexes comprising a nucleic acid template hybridized to a nucleic acid primer, thereby forming complexed polymerases. In some embodiments, the nucleic acid template molecules includes at least one uridine nucleotide or lacks a uridine nucleotide. In some embodiments, the plurality of nucleotides includes at least one uridine nucleotide or lacks a uridine nucleotide. In some embodiments, the mutant polymerases comprise an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99% identical, or a higher level sequence identity, to any of SEQ ID NOS: 1-2787 and 2789-2793.

[0379] In some embodiments, the reaction mixture further comprises (el) at least one non-catalytic divalent cation that permits binding at least one nucleotide to the complexed polymerase or that permits binding at least one multivalent molecule to the complexed polymerase, but the non-catalytic divalent cation inhibits polymerase-catalyzed incorporation. In some embodiments the non-catalytic divalent cation comprises strontium, barium and/or calcium.

[0380] In some embodiments, the reaction mixture further comprises (e2) at least one catalytic divalent cation that permits binding at least one nucleotide to the complexed polymerase or that permits binding at least one multivalent molecule to the complexed polymerase, and the catalytic divalent cation promotes polymerase-catalyzed incorporation. In some embodiments, the catalytic divalent cation comprises magnesium and/or manganese. In some embodiments, the nucleic acid template and nucleic acid primer are in solution. In some embodiments, the nucleic acid template and/or the nucleic acid primer is immobilized to a support or immobilized to a coating on a support.

[0381] In some embodiments, the reaction mixture is suitable for use in conducting a nucleotide binding reaction (or multivalent molecule binding reaction). In some embodiments, the reaction mixture is suitable for use in conducting a nucleotide incorporation reaction (or incorporation reaction of the nucleotide unit of the multivalent molecule). In some embodiments, the reaction mixture is suitable for use in conducting a primer extension reaction in which the nucleotide incorporates into the 3’ end of the extendible primer (or the nucleotide unit of the multivalent molecule incorporates into the 3’ end of the extendible primer).

Kits

[0382] The present disclosure provides a kit comprising at least one mutant polymerase comprising an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99% identical, or a higher level sequence identity, to any of SEQ ID NOS: 1-2787 and 2789-2793.

[0383] In some embodiments, the kit further comprises at least one cation. In some embodiment, the at least one cation is selected from the group consisting of strontium, barium, sodium, magnesium, potassium, manganese, calcium, lithium, nickel and cobalt. [0384] In some embodiments, the kit further comprises a plurality of nucleic acid primers having an extendible 3’ terminal end or a non-extendible 3’ terminal end. In some embodiments, at least one of the primers can be immobilized to a support. In some embodiments, the immobilized primers (e.g., capture primers) can be used to hybridize to nucleic acid templates. In some embodiments, at least one of the primers comprise a sequencing primer that can hybridize to an adaptor sequence (e.g., universal adaptor sequence) appended to a template molecule. [0385] In some embodiments, the kit further comprises a plurality of nucleotides. In some embodiments, at least one nucleotide in the plurality of nucleotides comprise a base, sugar and at least one phosphate group. In some embodiments, at least one nucleotide in the plurality comprises an aromatic base, a five carbon sugar (e.g., ribose or deoxyribose), and one or more phosphate groups (e.g., 1-10 phosphate groups). The plurality of nucleotides can comprise at least one type of nucleotide selected from a group consisting of dATP, dGTP, dCTP, dTTP and dUTP. The plurality of nucleotides can comprise at a mixture of any combination of two or more types of nucleotides selected from a group consisting of dATP, dGTP, dCTP, dTTP and/or dUTP.

[0386] In some embodiments, in the kit, at least one nucleotide in the plurality of nucleotides comprise a chain of one, two or three phosphorus atoms where the chain is typically attached to the 5’ carbon of the sugar moiety via an ester or phosphoramide linkage. In some embodiments, at least one nucleotide in the plurality is an analog having a phosphorus chain in which the phosphorus atoms are linked together with intervening O, S, NH, methylene or ethylene. In some embodiments, the phosphorus atoms in the chain include substituted side groups including O, S or BH3. In some embodiments, the chain includes phosphate groups substituted with analogs including phosphoramidate, phosphorothioate, phosphordithioate, and O-methylphosphoroamidite groups.

[0387] In some embodiments, in the kit, at least one nucleotide in the plurality of nucleotides comprises a terminator nucleotide analog having a chain terminating moiety (e.g., blocking moiety) at the sugar 2’ position, at the sugar 3’ position, or at the sugar 2’ and 3’ position. In some embodiments, the chain terminating moiety can inhibit polymerase- catalyzed incorporation of a subsequent nucleotide unit or free nucleotide in a nascent strand during a primer extension reaction. In some embodiments, the chain terminating moiety is attached to the 3’ sugar hydroxyl position where the sugar comprises a ribose or deoxyribose sugar moiety. In some embodiments, the chain terminating moiety is removable/cleavable from the 3’ sugar hydroxyl position to generate a nucleotide having a 3 ’OH sugar group which is extendible with a subsequent nucleotide in a polymerase-catalyzed nucleotide incorporation reaction. In some embodiments, the chain terminating moiety comprises an alkyl group, alkenyl group, alkynyl group, allyl group, aryl group, benzyl group, azide group, amine group, amide group, keto group, isocyanate group, phosphate group, thio group, disulfide group, carbonate group, urea group, or silyl group. In some embodiments, the kit can also include a chemical agent that cleaves the chain terminating moieties. For example, the kit comprises any one or any combination of tetrakis(triphenylphosphine)palladium(0) (Pd(PPh3)4) with piperidine, or with 2,3-Dichloro-5,6-dicyano-l,4-benzo-quinone (DDQ), H2 Pd/C, or a phosphine or with a thiol group including beta-mercaptoethanol or dithiothritol (DTT). In some embodiments, the kit includes a chemical agent comprising potassium carbonate (K2CO3) in MeOH, with triethylamine in pyridine, or with Zn in acetic acid (AcOH). In some embodiments, the kit includes a chemical agent comprising tetrabutylammonium fluoride, pyridine-HF, with ammonium fluoride, or with triethylamine trihydrofluoride. In some embodiments, the kit includes a chemical agent comprising nitrous acid. In some embodiments, the kit includes a solution comprising nitrite, such as, for example, a combination of nitrite with an acid such as acetic acid, sulfuric acid, or nitric acid. In some further embodiments, said solution may comprise an organic acid such as for example, formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, or the like. [0388] In some embodiments, in the kit, at least one nucleotide in the plurality of nucleotides comprises a terminator nucleotide analog having a chain terminating moiety (e.g., blocking moiety) at the sugar 2’ position, at the sugar 3’ position, or at the sugar 2’ and 3’ position. In some embodiments, the chain terminating moiety comprises an azide, azido or azidomethyl group. In some embodiments, the chain terminating moiety comprises a 3’-O- azido or 3’-O-azidomethyl group. In some embodiments, the kit can include a chemical agent that cleaves the chain terminating moieties. For example, the kit comprises any one or any combination of a phosphine compound, a phosphine compound comprises a derivatized trialkyl phosphine moiety or a derivatized tri-aryl phosphine moiety. In some embodiments, the phosphine compound comprises Tris(2-carboxyethyl)phosphine (TCEP) or bis-sulfo triphenyl phosphine (BS-TPP) or Tri(hydroxyproyl)phosphine (THPP). In some embodiments, the cleaving agent comprises 4-dimethylaminopyridine (4-DMAP).

[0389] In some embodiments, in the kit, the nucleotide analog comprise a chain terminating moiety which is selected from a group consisting of 3’-deoxy nucleotides, 2’,3’- dideoxynucleotides, 3 ’-methyl, 3 ’-azido, 3 ’-azidomethyl, 3’-O-azidoalkyl, 3’-O-ethynyl, 3’- O-aminoalkyl, 3’-O-fluoroalkyl, 3 ’-fluoromethyl, 3 ’-difluoromethyl, 3 ’-trifluoromethyl, 3’- sulfonyl, 3’-malonyl, 3’-amino, 3’-O-amino, 3’-sulfhydral, 3 ’-aminomethyl, 3’-ethyl, 3’butyl, 3 ’-tert butyl, 3’- Fluorenylmethyloxy carbonyl, 3’ tert-Butyloxycarbonyl, 3’-O-alkyl hydroxylamino group, 3’-phosphorothioate, and 3-O-benzyl, or derivatives thereof.

[0390] In some embodiments, in the kit, the plurality of nucleotides comprises a plurality of nucleotides labeled with detectable reporter moiety. The detectable reporter moiety comprises a fluorophore. In some embodiments, the fluorophore is attached to the nucleotide base. In some embodiments, the fluorophore is attached to the nucleotide base with a linker which is cleavable/removable from the base.

[0391] In some embodiments, in the kit, the cleavable linker on the base comprises a cleavable moiety comprising an alkyl group, alkenyl group, alkynyl group, allyl group, aryl group, benzyl group, azide group, amine group, amide group, keto group, isocyanate group, phosphate group, thio group, disulfide group, carbonate group, urea group, or silyl group. In some embodiments, the kit can also include a chemical agent that cleaves the cleavable linker on the base. For example, the kit comprises any one or any combination of tetrakis(triphenylphosphine)palladium(0) (Pd(PPh3)4) with piperidine, or with 2,3-Dichloro- 5,6-dicyano-l,4-benzo-quinone (DDQ), H2 Pd/C, or a phosphine or with a thiol group including beta-mercaptoethanol or dithiothritol (DTT). In some embodiments, the kit includes a chemical agent comprising potassium carbonate (K2CO3) in MeOH, with triethylamine in pyridine, or with Zn in acetic acid (AcOH). In some embodiments, the kit includes a chemical agent comprising tetrabutylammonium fluoride, pyridine-HF, with ammonium fluoride, or with triethylamine trihydrofluoride.

[0392] In some embodiments, in the kit, the cleavable linker on the base comprises cleavable moiety including an azide, azido or azidomethyl group. In some embodiments, the kit can include a chemical agent that cleaves the cleavable linker on the base. For example, the kit comprises any one or any combination of a phosphine compound, a phosphine compound comprises a derivatized tri-alkyl phosphine moiety or a derivatized tri-aryl phosphine moiety. In some embodiments, the phosphine compound comprises Tris(2- carboxyethyl)phosphine (TCEP) or bis-sulfo triphenyl phosphine (BS-TPP) or Tri(hydroxyproyl)phosphine (THPP). In some embodiments, the cleaving agent comprises 4- dimethylaminopyridine (4-DMAP).

[0393] In some embodiments, in the kit, the chain terminating moiety (e.g., at the sugar 2’ and/or sugar 3’ position) and the cleavable linker on the base have the same or different cleavable moieties. In some embodiments, the chain terminating moiety (e.g., at the sugar 2’ and/or sugar 3’ position) and the detectable reporter moiety linked to the base are chemically cleavable/removable with the same chemical agent. In some embodiments, the chain terminating moiety (e.g., at the sugar 2’ and/or sugar 3’ position) and the detectable reporter moiety linked to the base are chemically cleavable/removable with different chemical agents. [0394] The present disclosure provides a kit comprising at least one mutant polymerase comprising an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99% identical, or a higher level sequence identity, to any of SEQ ID NOS: 1-2787 and 2789-2793, and the kit further comprises a plurality of multivalent molecules. In some embodiments, at least one multivalent molecule in the plurality of multivalent molecules comprises: (a) a core; and (b) a plurality of nucleotide arms which comprise (i) a core attachment moiety, (ii) a spacer (e.g., comprising a PEG moiety), (iii) a linker, and (iv) a nucleotide unit, wherein the core is attached to the plurality of nucleotide arms, wherein the spacer is attached to the linker, wherein the linker is attached to the nucleotide unit. Exemplary multivalent molecules are shown in FIGs. 2-5. An exemplary nucleotide arm is shown in FIG. 6. An exemplary spacer is shown in FIG. 7 (top). Various exemplary linkers are shown in FIG. 7 (bottom) and FIG. 8. Examples of various linkers joined/ attached to nucleotide units are shown in FIGs. 9A-D, where the 5 position of a pyrimidine base or the 7 position of a purine base is attached to the linker via a propargyl amine attachment (see also FIG. 10). In some embodiments, the nucleotide unit comprises a base, sugar and at least one phosphate group, and the linker is attached to the nucleotide unit through the base. In some embodiments, the linker comprises an aliphatic chain or an oligo ethylene glycol chain where both linker chains having 2-6 subunits. In some embodiments, the linkers further include an aromatic moiety.

[0395] In some embodiments, in the kit, individual multivalent molecules in the plurality of multivalent molecules comprise a core attached to multiple nucleotide arms, and wherein the multiple nucleotide arms have the same type of nucleotide unit which is selected from a group consisting of dATP, dGTP, dCTP, dTTP and dUTP.

[0396] In some embodiments in the kit, the nucleotide unit of the at least one multivalent molecule comprises an aromatic base, a five carbon sugar (e.g., ribose or deoxyribose), and one or more phosphate groups (e.g., 1-10 phosphate groups). The plurality of multivalent molecules can comprise one type multivalent molecule having one type of nucleotide unit selected from a group consisting of dATP, dGTP, dCTP, dTTP and dUTP. The plurality of nucleotides can comprise at a mixture of any combination of two or more types of multivalent molecules, where individual multivalent molecules in the mixture comprise nucleotide units selected from a group consisting of dATP, dGTP, dCTP, dTTP and/or dUTP. [0397] In some embodiments, in the kit, at least one multivalent molecule in the plurality of multivalent molecules comprise a nucleotide unit having a chain of one, two or three phosphorus atoms where the chain is typically attached to the 5’ carbon of the sugar moiety via an ester or phosphoramide linkage. In some embodiments, at least one nucleotide unit is a nucleotide analog having a phosphorus chain in which the phosphorus atoms are linked together with intervening O, S, NH, methylene or ethylene. In some embodiments, the phosphorus atoms in the chain include substituted side groups including O, S or BEE. In some embodiments, the chain includes phosphate groups substituted with analogs including phosphoramidate, phosphorothioate, phosphordithioate, and O-methylphosphoroamidite groups.

[0398] In some embodiments, in the kit, individual multivalent molecules in the plurality of multivalent molecule comprise a core attached to multiple nucleotide arms, and wherein individual nucleotide arms comprise a nucleotide unit having a chain terminating moiety (e.g., blocking moiety) at the sugar 2’ position, at the sugar 3’ position, or at the sugar 2’ and 3’ position.

[0399] In some embodiments, in the kit, at least one multivalent molecule in the plurality of multivalent molecules comprises a nucleotide unit comprising a terminator nucleotide analog having a chain terminating moiety (e.g., blocking moiety) at the sugar 2’ position, at the sugar 3’ position, or at the sugar 2’ and 3’ position. In some embodiments, the chain terminating moiety can inhibit polymerase-catalyzed incorporation of a subsequent nucleotide unit or free nucleotide in a nascent strand during a primer extension reaction. In some embodiments, the chain terminating moiety is attached to the 3’ sugar hydroxyl position where the sugar comprises a ribose or deoxyribose sugar moiety. In some embodiments, the chain terminating moiety is removable/cleavable from the 3’ sugar hydroxyl position to generate a nucleotide having a 3 ’OH sugar group which is extendible with a subsequent nucleotide in a polymerase-catalyzed nucleotide incorporation reaction. In some embodiments, the chain terminating moiety comprises an alkyl group, alkenyl group, alkynyl group, allyl group, aryl group, benzyl group, azide group, amine group, amide group, keto group, isocyanate group, phosphate group, thio group, disulfide group, carbonate group, urea group, or silyl group. In some embodiments, the kit can also include a chemical agent that cleaves the chain terminating moi eties of the nucleotide unit of the multivalent molecule. For example, the kit comprises any one or any combination of tetrakis(triphenylphosphine)palladium(0) (Pd(PPh3)4) with piperidine, or with 2,3-Dichloro- 5,6-dicyano-l,4-benzo-quinone (DDQ), H2 Pd/C, or a phosphine or with a thiol group including beta-mercaptoethanol or dithiothritol (DTT). In some embodiments, the kit includes a chemical agent comprising potassium carbonate (K2CO3) in MeOH, with triethylamine in pyridine, or with Zn in acetic acid (AcOH). In some embodiments, the kit includes a chemical agent comprising tetrabutylammonium fluoride, pyridine-HF, with ammonium fluoride, or with triethylamine trihydrofluoride.

[0400] In some embodiments, in the kit, at least one multivalent molecule in the plurality of multivalent molecules comprises a nucleotide unit comprising a terminator nucleotide analog having a chain terminating moiety (e.g., blocking moiety) at the sugar 2’ position, at the sugar 3’ position, or at the sugar 2’ and 3’ position. In some embodiments, the chain terminating moiety comprises an azide, azido or azidomethyl group. In some embodiments, the chain terminating moiety comprises a 3’-O-azido or 3’-O-azidomethyl group. In some embodiments, the kit can include a chemical agent that cleaves the chain terminating moieties of the nucleotide unit of the multivalent molecule. For example, the kit comprises any one or any combination of a phosphine compound, a phosphine compound comprises a derivatized tri-alkyl phosphine moiety or a derivatized tri-aryl phosphine moiety. In some embodiments, the phosphine compound comprises Tris(2-carboxyethyl)phosphine (TCEP) or bis-sulfo triphenyl phosphine (BS-TPP) or Tri(hydroxyproyl)phosphine (THPP). In some embodiments, the cleaving agent comprises 4-dimethylaminopyridine (4-DMAP).

[0401] In some embodiments, in the kit, at least one multivalent molecule in the plurality of multivalent molecules comprises a nucleotide unit comprising a chain terminating moiety which is selected from a group consisting of 3’-deoxy nucleotides, 2’, 3 ’-dideoxynucleotides, 3 ’-methyl, 3 ’-azido, 3 ’-azidomethyl, 3’-O-azidoalkyl, 3’-O-ethynyl, 3’-O-aminoalkyl, 3’-O- fluoroalkyl, 3 ’-fluoromethyl, 3 ’-difluoromethyl, 3 ’-trifluoromethyl, 3 ’-sulfonyl, 3 ’-malonyl, 3’-amino, 3’-O-amino, 3’-sulfhydral, 3 ’-aminomethyl, 3’-ethyl, 3’butyl, 3" -tert butyl, 3’- Fluorenylmethyloxycarbonyl, 3’ /c/V-Butyloxycarbonyl, 3’-O-alkyl hydroxylamino group, 3’- phosphorothioate, and 3-O-benzyl, or derivatives thereof.

[0402] In some embodiments, in the kit, at least one multivalent molecule in the plurality of multivalent molecules comprises a core attached to multiple nucleotide arms. In some embodiments, the core, at least one linker and/or at least one nucleotide unit is labeled with detectable reporter moiety. In some embodiments, the detectable reporter moiety comprises a fluor ophore.

[0403] In some embodiments, in the kit, individual multivalent molecules comprise a core having an avidin-like moiety and the core attachment moiety comprises biotin. In some embodiments, the core comprises an streptavidin-type or avidin-type moiety which includes an avidin protein, as well as any derivatives, analogs and other non-native forms of avidin that can bind to at least one biotin moiety. Other forms of avidin moieties include native and recombinant avidin and streptavidin as well as derivatized molecules, e.g. nonglycosylated avidin and truncated streptavidins . For example, avidin moiety includes deglycosylated forms of avidin, bacterial streptavidin produced by Streptomyces (e.g., Streptomyces avidinii), as well as derivatized forms, for example, N- acyl avidins, e.g., N-acetyl, N-phthalyl and N-succinyl avidin, and the commercially- available products ExtrAvidin™, Captavidin™, Neutravidin™’ and Neutralite Avidin™. [0404] In some embodiments, the kit comprises one or more containers that contain the at least one mutant polymerase, cations, primers, plurality of nucleotides and/or plurality of multivalent molecules. The mutant polymerase, cations, primers, and/or plurality of nucleotides can be combined in any combination and can be contained in a single container, or can be contained in separate container, or any combination thereof. The mutant polymerase, cations, primers, and/or plurality of multivalent molecules can be combined in any combination and can be contained in a single container, or can be contained in separate container, or any combination thereof.

[0405] The kit can include instructions for use of the kit for conducting a nucleotide binding reaction, a nucleotide incorporation reaction and/or a nucleic acid sequencing reaction using a plurality of nucleotides. The kit can include instructions for use of the kit for conducting a multivalent molecule binding reaction, a multivalent molecule incorporation reaction and/or a nucleic acid sequencing reaction using a plurality of multivalent molecules.

Nucleic Acids Encoding Engineered Polymerases., Vectors and Host Cells

[0406] The present disclosure provides nucleic acids encoding any of the mutant polymerases described herein which comprise an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99% identical, or a higher level sequence identity, to any of SEQ ID NOS: 1-2787 and 2789-2793.

[0407] The present disclosure provides a vector operably linked to at least one nucleic acid (e.g., a transgene) encoding any of the mutant polymerases described herein which comprise an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99% identical, or a higher level sequence identity, to any of SEQ ID NOS: 1-2787 and 2789-2793. In some embodiments, the vector comprises at least one host cell regulatory sequence, including a promoter sequence, enhancer, transcription and/or translation initiation sequence, transcription and/or translation termination sequence, polypeptide secretion signal sequences, and the like. The promoter sequence can be a constitutive or inducible promoter sequence. In some embodiments, the promoter sequence in the vector can be operably linked to the at least one nucleic acid encoding the mutant polymerase to control expression of the mutant polymerase by the host cell. In some embodiments, the vector comprises an expression vector. [0408] The present disclosure provides a host cell harboring the vector (e.g., expression vector) which is operably linked to at least one nucleic acid (e.g., a transgene) encoding any of the mutant polymerases described herein which comprise an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99% identical, or a higher level sequence identity, to any of SEQ ID NOS: 1-2787 and 2789-2793. In some embodiments, the vector comprises a promoter sequence which is operably linked to the at least one nucleic acid encoding the mutant polymerase, where the promoter sequence controls expression of the mutant polymerase by the host cell.

[0409] The present disclosure provides a plurality of host cells, wherein individual host cells in the plurality of host cells harbor the vector (e.g., expression vector) which is operably linked to at least one nucleic acid (e.g., a transgene) encoding any of the mutant polymerases described herein which comprise an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99% identical, or a higher level sequence identity, to any of SEQ ID NOS: 1-2787 and 2789-2793. In some embodiments, the vector comprises a promoter sequence which is operably linked to the at least one nucleic acid encoding the mutant polymerase, where the promoter sequence controls expression of the mutant polymerase by the host cell.

Methods

[0410] The present disclosure provides methods for preparing a plurality of mutant polymerases, comprising: culturing the plurality of host cells of, wherein individual host cells in the plurality of host cells harbor the vector (e.g., expression vector) which is operably linked to at least one nucleic acid (e.g., a transgene) encoding any of the mutant polymerases described herein which comprise an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99% identical, or a higher level sequence identity, to any of SEQ ID NOS: 1-2787 and 2789-2793. In some embodiments, the vector in the host cell comprises a promoter sequence which is operably linked to the at least one nucleic acid encoding the mutant polymerase, where the promoter sequence controls expression of the mutant polymerase by the host cell. In some embodiments, the plurality of host cells is cultured under conditions suitable for expressing a plurality of mutant polymerases by the plurality of host cells. In some embodiments, the method further comprises recovering (e.g., isolating/enriching) the plurality of mutant polymerases from the plurality of host cells.

[0411] In some embodiments, the plurality of host cells harbor the vector (e.g., expression vector) which is operably linked to at least one nucleic acid (e.g., a transgene) encoding any of the mutant polymerases described herein which comprise an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99% identical, or a higher level sequence identity, to any of SEQ ID NOS: 1-2787 and 2789-2793, and wherein the transgene that encodes any of the mutant polymerases is operably linked to any one of the His-tags (e.g., SEQ ID NOS :2815-2832) or any one of the His-tags having a thrombin cleavage sequence (e.g., SEQ ID NOS:2833-2849).

[0412] The present disclosure provides methods for binding nucleotide analogs, methods for incorporating nucleotide analogs, and methods for binding nucleotide units of a multivalent molecule. The methods described herein can be used to conduct primer extension reactions and nucleic acid sequencing reactions. Polymerases variously comprise DNA polymerases, RNA polymerases, template-independent polymerases, reverse transcriptases, or other enzymes capable of nucleotide extension. Wild type DNA polymerases generally do not tolerate certain types of nucleotide modifications, such as modifications to the 3' position of the sugar. This property requires that wild type DNA polymerases be significantly modified in order to facilitate reversible or irreversible terminator (removable chemical groups which prevent nucleic acid extension) incorporation for applications such as sequencing. Further provided herein are methods of sequencing employing mutant polymerases that incorporate modified nucleotides. Further, the use of engineered DNA polymerases allows the development of enzymes capable of incorporating modified nucleotides into an elongating nucleic acid chain without sacrificing the thermostability of the enzyme or the ability of the enzyme to function at higher temperatures. This property is especially enhanced when DNA polymerases are engineered based on archaeal polymerase backbones, and more especially backbones derived from the DNA polymerase sequences of thermophilic or thermotolerant archaea.

[0413] Engineered DNA polymerases that exhibit improved thermostability and/or improved ability to incorporation nucleotide analogs may be useful in isothermal sequencing or elongation techniques. Isothermal techniques include SDA, LAMP, SMAP, ICAN, SMART, among others, and may further include additional techniques as disclosed herein. In these techniques, the elongation reaction proceeds at a constant temperature, for example using strand displacement reactions, or in some additional exemplary embodiments, elongating from a primed, single stranded template, especially including a primed polyvalent template. In some embodiments, the engineered DNA polymerases have strand displacement capabilities. In amplification-dependent methods, isothermal amplification can be completed in a single step, by incubating the mixture of samples, primers, DNA polymerase with strand displacement activity, and substrates at a constant temperature. This reduces the number of

I l l steps required, eliminating thermal ramping steps and reducing the total cycle time for each sequencing or elongation cycle, while simultaneously decreasing the reaction time required for each cycle. In amplification-free methods, isothermal methods allow for the binding, detection, and elongation of a nascent nucleic acid strand during a sequencing cycle without lost time due to temperature ramping or additional thermal stress on key components or reagents.

Sequencing Methods Using Engineered Polymerases

[0414] The present disclosure provides engineered polymerase that are useful for conducting any nucleic acid sequencing method that employs labeled or non-labeled chain terminating nucleotides, where the chain terminating nucleotides include a 3’-O-azido group (or 3’-O-methylazido group) or any other type of bulky blocking group at the sugar 3’ position. For example, the engineered polymerases can be used to conduct sequencing-by- avidity methods (SB A) using labeled multivalent molecules and non-labeled chain terminating nucleotides. Additionally, the engineered polymerases can be used for conducting sequencing-by-synthesis (SBS) methods which employ labeled chain-terminating nucleotides, and for conducting sequencing-by-binding methods (SBB) which employ nonlabeled chain-terminating nucleotides. The engineered polymerases can be used for conducting phosphate-chain labeled nucleotide.

[0415] Sequencing-by-avidity (SB A) of DNA ideally requires (a) the detection of the n+1 base and requires 2 or more copies of target nucleic acid sequence, two or more primer nucleic acid molecules that are complementary to one or more regions of said target nucleic acid sequence and two more polymerases contacting said composition with a multivalent molecule (e.g., a polymer-nucleotide conjugate) under conditions sufficient to allow a multivalent binding complex to be formed between said polymer-nucleotide conjugate and said two or more copies of said target nucleic acid sequence in said composition of wherein the polymer-nucleotide conjugate comprises two or more nucleotide moieties; the detection substrates is subsequently washed away and (b) to ensure only a single incorporation occurs, a structural modification (‘blocking group') of the an unlabeled nucleotides is required to ensure a single nucleotide incorporation but which then prevents any further nucleotide incorporation into the polynucleotide chain. The blocking group must then be removable, under reaction conditions which do not interfere with the integrity of the DNA being sequenced. The sequencing cycle can then continue with the N+1 detection of the next multivalent polymerase-conjugate-DNA complex and so on. In order to be of practical use, the avidity step requires both (a) a stable substrate to persist for long enough to image for > 30 s and (b) a stepping step whereby the entire process should consist of high yielding, highly specific chemical and enzymatic steps to facilitate multiple cycles of sequencing.

Sequencing-by-Synthesis

[0416] Sequencing-by-synthesis (SBS) of DNA ideally requires the controlled (i.e. one at a time) incorporation of the correct complementary nucleotide opposite the oligonucleotide being sequenced. This allows for accurate sequencing by adding nucleotides in multiple cycles as each nucleotide residue is sequenced one at a time, thus preventing an uncontrolled series of incorporations occurring. The incorporated nucleotide is read using an appropriate label attached thereto before removal of the label moiety and the subsequent next round of sequencing. In order to ensure only a single incorporation occurs, a structural modification (‘blocking group') of the sequencing nucleotides is required to ensure a single nucleotide incorporation but which then prevents any further nucleotide incorporation into the polynucleotide chain. The blocking group must then be removable, under reaction conditions which do not interfere with the integrity of the DNA being sequenced. The sequencing cycle can then continue with the incorporation of the next blocked, labelled nucleotide. In order to be of practical use, the entire process should consist of high yielding, highly specific chemical and enzymatic steps to facilitate multiple cycles of sequencing.

Sequencing-by-Binding

[0417] Sequencing-by-binding (SBB) requires method for sequencing a nucleic acid that includes the steps of (a) sequentially contacting a primed template nucleic acid with at least two separate mixtures under ternary complex stabilizing conditions, wherein the at least two separate mixtures each include a polymerase and a nucleotide, whereby the sequentially contacting results in the primed template nucleic acid being contacted, under the ternary complex stabilizing conditions, with nucleotide cognates for first, second and third base type base types in the template; (b) examining the at least two separate mixtures to determine whether a ternary complex formed; and (c) identifying the next correct nucleotide for the primed template nucleic acid molecule, wherein the next correct nucleotide is identified as a cognate of the first, second or third base type if ternary complex is detected in step (b), and wherein the next correct nucleotide is imputed to be a nucleotide cognate of a fourth base type based on the absence of a ternary complex in step (b); (d) adding a next correct nucleotide to the primer of the primed template nucleic acid after step (b), thereby producing an extended primer; and (e) repeating steps (a) through (d) at least once on the primed template nucleic acid that comprises the extended primer. Exemplary sequencing-by-binding methods are described in U.S. patent Nos. 10,246,744 and 10,731,141 (where the contents of both patents are hereby incorporated by reference in their entireties).

Methods for Sequencing using Phosphate-Chain Labeled Nucleotides

[0418] The present disclosure provides methods for sequencing using immobilized sequencing polymerases which bind non-immobilized template molecules, wherein the sequencing reactions are conducted with phosphate-chain labeled nucleotides. In some embodiments, the sequencing methods comprise step (a): providing a support having a plurality of sequencing polymerases immobilized thereon. In some embodiments, the sequencing polymerase comprises a processive DNA polymerase. In some embodiments, the sequencing polymerase comprises a wild type or mutant DNA polymerase, including for example a Phi29 DNA polymerase. In some embodiments, the support comprise a plurality of separate compartments and a sequencing polymerase is immobilized to the bottom of a compartment. In some embodiments, the separate compartments comprise a silica bottom through which light can penetrate. In some embodiments, the separate compartments comprise a silica bottom configured with a nanophotonic confinement structure comprising a hole in a metal cladding film (e.g., aluminum cladding film). In some embodiments, the hole in the metal cladding has a small aperture, for example, approximately 70 nm. In some embodiments, the height of the nanophotonic confinement structure is approximately 100 nm. In some embodiments, the nanophotonic confinement structure comprises a zero mode waveguide (ZMW). In some embodiments, the nanophotonic confinement structure contains a liquid.

[0419] In some embodiments, the sequencing method further comprises step (b): contacting the plurality of immobilized sequencing polymerases with a plurality of single stranded circular nucleic acid template molecules and a plurality of oligonucleotide sequencing primers, under a condition suitable for individual immobilized sequencing polymerases to bind a single stranded circular template molecule, and suitable for individual sequencing primers to hybridize to individual single stranded circular template molecules, thereby generating a plurality of polymerase/template/primer complexes. In some embodiments, the individual sequencing primers hybridize to a universal sequencing primer binding site on the single stranded circular template molecule. [0420] In some embodiments, the sequencing method further comprises step (c): contacting the plurality of polymerase/template/primer complexes with a plurality of phosphate chain labeled nucleotides each comprising an aromatic base, a five carbon sugar (e.g., ribose or deoxyribose), and phosphate chain comprising 3-20 phosphate groups, where the terminal phosphate group is linked to a detectable reporter moiety (e.g., a fluorophore). The first, second and third phosphate groups can be referred to as alpha, beta and gamma phosphate groups. In some embodiments, a particular detectable reporter moiety which is attached to the terminal phosphate group corresponds to the nucleotide base (e.g., dATP, dGTP, dCTP, dTTP or dUTP) to permit detection and identification of the nucleo-base. In some embodiments, the plurality of polymerase/template/primer complexes are contacted with the plurality of phosphate chain labeled nucleotides under a condition suitable for polymerase-catalyzed nucleotide incorporation. In some embodiments, the sequencing polymerases are capable of binding a complementary phosphate chain labeled nucleotide and incorporating the complementary nucleotide opposite a nucleotide in a template molecule. In some embodiment, the polymerase-catalyzed nucleotide incorporation reaction cleaves between the alpha and beta phosphate groups thereby releasing a multi-phosphate chain linked to a fluorophore.

[0421] In some embodiments, the sequencing method further comprises step (d): detecting the fluorescent signal emitted by the phosphate chain labeled nucleotide that is bound by the sequencing polymerase, and incorporated into the terminal end of the sequencing primer. In some embodiments, step (d) further comprises identifying the phosphate chain labeled nucleotide that is bound by the sequencing polymerase, and incorporated into the terminal end of the sequencing primer.

[0422] In some embodiments, the sequencing method further comprises step (d): repeating steps (c) - (d) at least once. In some embodiments, sequencing methods that employ phosphate chain labeled nucleotides can be conducted according to the methods described in U.S. patent Nos. 7,170,050; 7,302,146; and/or 7,405,281.

[0423] DNA polymerases which may be used according to the methods and compositions of the present disclosure include viral, bacterial, archaeal and eukaryotic polymerases and homologs and orthologs thereof. In some embodiments, DNA polymerases include but are not limited to archaeal DNA polymerases such as Thermococcus, Thermoplasmata, Pyrococcus, Methanococcus, Hadesarchaea, Euryarchaeota, or Candidatus polymerases and homologs and orthologs thereof and engineered, mutated, and/or truncated variants thereof. Other DNA polymerases and homologous or orthologous polymerases are known in the art and are expressly contemplated within this disclosure.

[0424] Provided herein are methods that employ mutant polypeptides which have enhanced thermostability. In some embodiments, such mutant polypeptides possess polymerase activity (e.g., mutant nucleic acid polymerase). Thermostability in some embodiments includes increased Tm, resistance to degradation, and/or the ability to maintain functional activity (e.g., incorporation of nucleotides) at elevated temperatures relative to a nearest wild-type enzyme, such as a wild-type enzyme comprising a nearest wild-type enzyme sequence. Mutant polymerases in some embodiments comprise Tm that are increased about 1, 2, 5, 10, 15, 20, 25, or about 30 degrees C relative to a nearest wild-type enzyme. Mutant polypeptides in some embodiments comprise a Tm that are increased at least 1, 2, 5, 10, 15, 20, 25, or at least 30 degrees C relative to a nearest wild-type enzyme. Mutant polymerases often comprise a Tm value that are increased at least 1-10, 5-15, 4-20, 2-10, 4- 15, 20-30, 10-60, or 25-35 degrees C relative to a nearest wild-type enzyme. Polymerase activity, in some embodiments, comprises kcat, kcat/Km, or yields of incorporated nucleotides for a given time period. In some embodiments, polymerase activity, in some embodiments, comprises kcat, kcat/Km, or yields of incorporated modified nucleotides, such as 3’-O-azido or 3’-O-azidomethyl modified nucleotides, for a given time period. In some embodiments, mutant polymerases functioning at an elevated temperature maintain at least 99%, 98%, 95%, 90%, 85%, or at least 80% of the optimal activity of a nearest wild-type enzyme functioning at a lower temperature, utilizing unmodified nucleotides. For example, mutant polymerases functioning at about 37 degrees C maintain at least 99%, 98%, 95%, 90%, 85%, or at least 80% of the optimal activity of a nearest wild-type enzyme utilizing unmodified nucleotides. In some embodiments, mutant polymerases functioning at about 42 degrees C maintain at least 99%, 98%, 95%, 90%, 85%, or at least 80% of the optimal activity of a nearest wildtype enzyme utilizing unmodified nucleotides. In some embodiments, mutant polymerases functioning at about 55 degrees C maintain at least 99%, 98%, 95%, 90%, 85%, or at least 80% of the optimal activity of a nearest wild-type enzyme utilizing unmodified nucleotides. In some embodiments, mutant polymerases functioning at about 60 degrees C maintain at least 99%, 98%, 95%, 90%, 85%, or at least 80% of the optimal activity of a nearest wildtype enzyme utilizing unmodified nucleotides. In some embodiments, mutant polymerases functioning at least at 50 degrees C maintain at least 99%, 98%, 95%, 90%, 85%, or at least 80% of the optimal activity of a nearest wild-type enzyme utilizing unmodified nucleotides. In some embodiments, mutant polymerases functioning at least at 60 degrees C maintain at least 99%, 98%, 95%, 90%, 85%, or at least 80% of the optimal activity of a nearest wildtype enzyme utilizing unmodified nucleotides. In some embodiments, mutant polymerases functioning at 37-95 degrees C maintain at least 99%, 98%, 95%, 90%, 85%, or at least 80% of the optimal activity of a nearest wild-type enzyme utilizing unmodified nucleotides. In some embodiments, mutant polymerases functioning at 37-95, 37-60, 37-55, 37-42, 40-60, 50-80, 42-55, 55-60, 55-95, 60-95, or 40-90 degrees C maintain at least 99%, 98%, 95%, 90%, 85%, or at least 80% of the optimal activity of a nearest wild-type enzyme utilizing unmodified nucleotides. In some embodiments, mutant polymerases functioning at 42-95 degrees C maintain at least 99%, 98%, 95%, 90%, 85%, or at least 80% of the optimal activity of a nearest wild-type enzyme utilizing unmodified nucleotides. In some embodiments, mutant polymerases functioning at 40-90 degrees C maintain at least 99%, 98%, 95%, 90%, 85%, or at least 80% of the optimal activity of a nearest wild-type enzyme utilizing unmodified nucleotides. In some embodiments, mutant polymerases functioning at 37-55 degrees C maintain at least 99%, 98%, 95%, 90%, 85%, or at least 80% of the optimal activity of a nearest wild-type enzyme utilizing unmodified nucleotides. In some embodiments, mutant polymerases functioning at 50-95 degrees C maintain at least 99%, 98%, 95%, 90%, 85%, or at least 80% of the optimal activity of a nearest wild-type enzyme utilizing unmodified nucleotides. In some embodiments, Mutant polymerases functioning at 60-95 degrees C maintain at least 99%, 98%, 95%, 90%, 85%, or at least 80% of the optimal activity of a nearest wild-type enzyme utilizing unmodified nucleotides. In some embodiments a mutant polymerase has an increased kcat relative to a nearest related wild-type sequence functioning at a temperature of at least 37 degrees C. In some embodiments a mutant polymerase has an increased kcat relative to a nearest related wild-type sequence functioning at a temperature of at least 42 degrees C. In some embodiments a mutant polymerase has an increased kcat relative to a nearest related wild-type sequence functioning at a temperature of at least 55 degrees C. In some embodiments a mutant polymerase has an increased kcat relative to a nearest related wild-type sequence functioning at a temperature of at least 60 degrees C. In some embodiments a mutant polymerase has an increased kcat relative to a nearest related wild-type sequence functioning at a temperature of at least 80 degrees C. In some embodiments a mutant polymerase has an increased kcat relative to a nearest related wild-type sequence functioning at a temperature of at least 90 degrees C. In some embodiments a mutant polymerase has an increased kcat relative to a nearest related wild-type sequence functioning at a temperature of 37-95, 37-60, 37-55, 37-42, 40-60, 50-80, 42-55, 55-60, 55-95, 60-95, or 40-80 degrees C. In some embodiments a mutant polymerase has an increased kcat relative to a nearest related wild-type sequence functioning at a temperature of 37-55 degrees C. In some embodiments a mutant polymerase has an increased kcat relative to a nearest related wild-type sequence functioning at a temperature of 35-90 degrees C.

Methods for Forming Complexed Polymerases

[0425] The present disclosure provides methods for forming a plurality of complexed polymerases, comprising step (a): contacting a plurality of mutant polymerases with (i) a plurality of nucleic acid template molecules and (ii) a plurality of nucleic acid primers, under a condition suitable to bind the plurality of mutant polymerases to the plurality of nucleic acid template molecules and the plurality of nucleic acid primers, thereby forming a plurality of complexed polymerases each comprising a mutant polymerase bound to a nucleic acid duplex wherein the nucleic acid duplex comprises a nucleic acid template molecule hybridized to a nucleic acid primer. In some embodiments, the plurality of mutant polymerases comprise a DNA polymerase. In some embodiments, the plurality of mutant polymerases comprise a plurality of recombinant mutant polymerases. In some embodiments, the mutant polymerases comprise an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99% identical, or a higher level sequence identity, to any of SEQ ID NOS: 1-2787 and 2789-2793.

[0426] In some embodiments, , in the methods for forming a plurality of complexed polymerases, the mutant polymerases include amino acid substitutions that confer exonuclease-minus activity. In some embodiments, the mutant polymerases exhibit desirable characteristics compared to a polymerase having a wild type amino acid backbone sequence. For example, the mutant polymerases exhibit increased thermal stability (Tm). In another example, the mutant polymerases exhibit increased incorporation rates of nucleotide analogs comprising a chain terminating moiety (e.g., blocking moiety) at the sugar 2’ position and/or at the 3’ sugar position. In yet another example, the mutant polymerases exhibit increased uracil-tolerance. In some embodiments, the mutant DNA polymerases exhibit improved binding to a nucleotide reagent. In some embodiments, the mutant DNA polymerases exhibit improved binding and incorporation of a nucleotide reagent. In some embodiments, the mutant DNA polymerases exhibit reduced sequence-specific sequencing errors. In some embodiments, the mutant DNA polymerases exhibit increased thermal stability at a temperature range of about 25-50 °C or about 45-75 °C compared to corresponding wild type polymerase comprising SEQ ID NO: 1-2787 and 2789-2793. [0427] In some embodiments, in the methods for forming a plurality of complexed polymerases, the nucleotide reagents comprise any one or any combination of nucleotides and/or multivalent molecules. In some embodiments, the nucleotides comprise canonical nucleotides. In some embodiments, the nucleotides comprise non-labeled nucleotides. In some embodiments, the nucleotides comprise nucleotide analogs comprise detectably labeled nucleotides and/or nucleotides carrying a removable or non-removable chain terminating moiety. In some embodiments, individual multivalent molecules comprise a central core attached to multiple polymer arms each having a nucleotide unit at the end of the arms. [0428] In some embodiments, in the methods for forming a plurality of complexed polymerases, the primer comprises a 3’ extendible end or a 3’ non-extendible end. In some embodiments, the plurality of nucleic acid template molecules comprise linear nucleic acid molecules or circular nucleic acid molecules. In some embodiments, the plurality of nucleic acid template molecules comprise amplified template molecules (e.g., clonally amplified template molecules). In some embodiments, the plurality of nucleic acid template molecules comprise one copy of a target sequence of interest. In some embodiments, the plurality of nucleic acid molecules comprise two or more tandem copies of a target sequence of interest (e.g., concatemers). In some embodiments, the nucleic acid template molecules in the plurality of nucleic acid template molecules comprise the same target sequence of interest or different target sequences of interest.

[0429] In some embodiments, in the methods for forming a plurality of complexed polymerases, the plurality of nucleic acid template molecules and/or the plurality of nucleic acid primers are in solution or are immobilized to a support. In some embodiments, when the plurality of nucleic acid template molecules and/or the plurality of nucleic acid primers are immobilized to a support, the binding with the recombinant mutant polymerase generates a plurality of immobilized complexed polymerases. In some embodiments, the plurality of nucleic acid template molecules and/or nucleic acid primers are immobilized to 10 ² - 10 ¹⁵ different sites on a support. In some embodiments, the binding of the plurality of template molecules and nucleic acid primers with the plurality of recombinant mutant polymerases generates a plurality of complexed polymerases immobilized to 10 ² - 10 ¹⁵ different sites on the support. In some embodiments, the plurality of immobilized complexed polymerases on the support are immobilized to pre-determined or to random sites on the support. In some embodiments, the plurality of immobilized complexed polymerases are in fluid communication with each other to permit flowing a solution of reagents (e.g., enzymes including polymerases, multivalent molecules, nucleotides, and/or divalent cations) onto the support so that the plurality of immobilized complexed polymerases on the support are reacted with the solution of reagents in a massively parallel manner.

Forming Complexed Polymerases with Multivalent Molecules

[0430] In some embodiments, the methods for forming a plurality of complexed polymerases generally comprise: (a) contacting a plurality of mutant polymerases with (i) a plurality of nucleic acid template molecules and (ii) a plurality of nucleic acid primers to form a plurality of complexed polymerases; (bl) contacting the plurality of complexed polymerases with a plurality of multivalent molecules to form a plurality of multivalent- complexed polymerases. In some embodiments, the method further comprises step (cl): detecting the multivalent molecules that are bound to the complexed polymerases. In some embodiments, the method further comprises step (dl): identifying the complementary nucleotide unit of the multivalent molecules that are bound to the complexed polymerases. In some embodiments, the mutant polymerases comprise an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99% identical, or a higher level sequence identity, to any of SEQ ID NOS: 1-2787 and 2789-2793.

[0431] In some embodiments, the methods for forming a plurality of complexed polymerases further comprise step (bl): contacting the plurality of complexed polymerases with a plurality of multivalent molecules, wherein individual multivalent molecules in the plurality comprise a core attached to multiple nucleotide arms and each nucleotide arm is attached to a nucleotide (e.g., a nucleotide unit). In some embodiments, the binding of the complementary nucleotide unit of the multivalent molecules to the complexed polymerases forms a plurality of multivalent-complexed polymerases. In some embodiments, the contacting in step (bl) is conducted under a condition suitable for binding a complementary nucleotide unit of at least one of the multivalent molecules to at least one of the complexed polymerases. In some embodiments, the condition is suitable for inhibiting incorporation of the complementary nucleotide units into the primers of the plurality of multivalent- complexed polymerases. In some embodiments, the contacting in step (bl) is conducted under a condition suitable for binding a nucleotide of at least one of the multivalent molecules to at least one of the complexed polymerases but the bound nucleotide does not incorporate into the 3’ end of the nucleic acid primer.

[0432] In some embodiments, in the methods for forming a plurality of complexed polymerases, individual multivalent molecules in the plurality of multivalent molecules comprise: (a) a core; and (b) a plurality of nucleotide arms which comprise (i) a core attachment moiety, (ii) a spacer (e.g., comprising a PEG moiety), (iii) a linker, and (iv) a nucleotide, wherein the core is attached to the plurality of nucleotide arms via their core attachment moiety, wherein the spacer is attached to the linker, and wherein the linker is attached to the nucleotide. In some embodiments, the linker comprises an aliphatic chain having 2-6 subunits or an oligo ethylene glycol chain having 2-6 subunits. Exemplary multivalent molecules are shown in FIGs. 2-5. An exemplary nucleotide arm is shown in FIG. 6. An exemplary spacer is shown in FIG. 7 (top). Various exemplary linkers are shown in FIG. 7 (bottom) and FIG. 8. Examples of various linkers joined/ attached to nucleotide units are shown in FIGs. 9A-D, where the 5 position of a pyrimidine base or the 7 position of a purine base is attached to the linker via a propargyl amine attachment (see also FIG. 10). In some embodiments, the plurality of nucleotide arms attached to a given core have the same type of nucleotide, and wherein the types of nucleotide comprise dATP, dGTP, dCTP, dTTP or dUTP. In some embodiments, the plurality of multivalent molecules comprise one type of a multivalent molecule wherein each multivalent molecule in the plurality has the same type of nucleotide unit selected from a group consisting of dATP, dGTP, dCTP, dTTP and dUTP. In some embodiments, the plurality of multivalent molecules comprise a mixture of any combination of two or more types of multivalent molecules each type having nucleotide units selected from a group consisting of dATP, dGTP, dCTP, dTTP and/or dUTP.

[0433] In some embodiments, in the methods for forming a plurality of complexed polymerases, the binding of the plurality of complexed polymerases with the plurality of multivalent molecules forms at least one avidity complex, the method comprising the steps: (a) binding a first nucleic acid primer, a first DNA polymerase, and a first multivalent molecule to a first portion of a concatemer template molecule thereby forming a first binding complex (e.g., FIGs. 44-46), wherein a first nucleotide unit of the first multivalent molecule binds to the first DNA polymerase; and (b) binding a second nucleic acid primer, a second DNA polymerase, and the first multivalent molecule to a second portion of the same concatemer template molecule thereby forming a second binding complex (e.g., FIGs. 44-46), wherein a second nucleotide unit of the first multivalent molecule binds to the second DNA polymerase, wherein the first and second binding complexes which include the same multivalent molecule forms an avidity complex (e.g., FIG. 47). In some embodiments, the first polymerase comprises any mutant polymerase described herein. In some embodiments, the second polymerase comprises any mutant polymerase described herein. The concatemer template molecule comprises tandem repeat sequences of a sequence of interest and at least one universal sequencing primer binding site. The first and second nucleic acid primers can bind to a sequencing primer binding site along the concatemer template molecule.

[0434] In some embodiments, in the methods for forming a plurality of complexed polymerases, the binding of the plurality of complexed polymerases with the plurality of multivalent molecules forms at least one avidity complex, the method comprising the steps: (a) binding a first nucleic acid primer, a first DNA polymerase, and a first multivalent molecule to a first template molecule thereby forming a first binding complex, wherein a first nucleotide unit of the first multivalent molecule binds to the first DNA polymerase; and (b) binding a second nucleic acid primer, a second DNA polymerase, and the first multivalent molecule to a second template molecule thereby forming a second binding complex, wherein a second nucleotide unit of the first multivalent molecule binds to the second DNA polymerase, wherein the first and second binding complexes which include the same multivalent molecule forms an avidity complex. In some embodiments, the first polymerase comprises any mutant polymerase described herein. In some embodiments, the second polymerase comprises any mutant polymerase described herein. In some embodiments, the first and second template molecules are clonally amplified template molecules. In some embodiments, the first and second template molecules are localized in close proximity to each other. For example, the clonally-amplified first and second template molecules comprise linear template molecules that are generated via bridge amplification and are immobilized to the same location or feature on a support. The first and second template molecules comprise a sequence of interest and at least one universal sequencing primer binding site. The first and second nucleic acid primers can bind to a sequencing primer binding site on the first and second template molecules, respectively.

[0435] In some embodiments, in the methods for forming a plurality of complexed polymerases, at least one of the multivalent molecules in the plurality of multivalent molecules is labeled with a detectable reporter moiety. In some embodiments, the detectable reporter moiety comprises a fluorophore. In some embodiments, the core of the multivalent molecule is labeled with a fluorophore, and wherein the fluorophore which is attached to a given core of the multivalent molecule corresponds to the nucleotide base (e.g., adenine, guanine, cytosine, thymine or uracil) of the nucleotide arm. In some embodiments, at least one of the nucleotide arms of the multivalent molecule comprises a linker and/or nucleotide base that is attached to a fluorophore, and wherein the fluorophore which is attached to a given nucleotide base corresponds to the nucleotide base (e.g., adenine, guanine, cytosine, thymine or uracil) of the nucleotide arm. [0436] In some embodiments, in the methods for forming a plurality of complexed polymerases, the plurality of multivalent molecules comprise at least one multivalent molecule having multiple nucleotide arms each attached with a nucleotide analog (e.g., nucleotide analog unit), where the nucleotide analog includes a chain terminating moiety at the sugar 2’ and/or 3’ position. In some embodiments, the plurality of multivalent molecules comprises at least one multivalent molecule comprising multiple nucleotide arms each attached with a nucleotide unit that lacks a chain terminating moiety.

[0437] In some embodiments, in the methods for forming a plurality of complexed polymerases, the contacting of step (bl) is conducted in the presence of at least one cation selected from a group consisting of strontium, barium, sodium, magnesium, potassium, manganese, calcium, lithium, nickel and cobalt. In some embodiments, the contacting of step (bl) is conducted in the presence of strontium, barium and/or calcium.

[0438] In some embodiments, in the methods for forming a plurality of complexed polymerases, the contacting of step (a) is conducted at a constant temperature which is selected from a temperature range of about 25-90 °C. In some embodiments, the contacting of step (bl) is conducted at a constant temperature which is selected from a temperature range of about 25-90 °C. In some embodiments, the contacting of steps (a) and (bl) are conducted at a constant temperature which is selected from a temperature range of about 25-90 °C (e.g., isothermal temperature).

[0439] In some embodiments, the methods for forming a plurality of complexed polymerases further comprise step (cl): detecting the multivalent molecule which is bound to the complexed polymerase. In some embodiments, the detecting includes detecting the multivalent molecules that are bound to the complexed polymerases, where the complementary nucleotide units of the multivalent molecules are bound to the primers but incorporation of the complementary nucleotide units is inhibited. In some embodiments, the multivalent molecules are labeled with a detectable reporter moiety to permit detection. In some embodiments, the labeled multivalent molecules comprise a fluorophore attached to the core, linker and/or the base of the nucleotide unit of the multivalent molecules.

[0440] In some embodiments, the methods for forming a plurality of complexed polymerases further comprise step (dl): identifying the complementary nucleotide unit of the multivalent molecule which is bound to the complexed polymerase. In some embodiments, the identifying the complementary nucleotide unit of the multivalent molecule can be used to determine the sequence of the nucleic acid template. In some embodiments, the multivalent molecules are labeled with a detectable reporter moiety that corresponds to the particular nucleotide units attached to the nucleotide arms to permit identification of the complementary nucleotide units (e.g., nucleotide base adenine, guanine, cytosine, thymine or uracil) that are bound to the plurality of complexed polymerases. In some embodiments the detecting of step (cl) and the identifying of step (dl) can be used to determine the sequence of the nucleic acid template molecules.

[0441] In some embodiments, in the methods for forming a plurality of complexed polymerases, at least one multivalent molecule in the plurality of multivalent molecules of step (bl) comprises: (a) a core; and (b) a plurality of nucleotide arms which comprise (i) a core attachment moiety, (ii) a spacer (e.g., comprising a PEG moiety), (iii) a linker, and (iv) a nucleotide unit, wherein the core is attached to the plurality of nucleotide arms, wherein the spacer is attached to the linker, wherein the linker is attached to the nucleotide unit. Exemplary multivalent molecules are shown in FIGs. 2-5. An exemplary nucleotide arm is shown in FIG. 6. An exemplary spacer is shown in FIG. 7 (top). Various exemplary linkers are shown in FIG. 7 (bottom) and FIG. 8. Examples of various linkers joined/ attached to nucleotide units are shown in FIGs. 9A-D, where the 5 position of a pyrimidine base or the 7 position of a purine base is attached to the linker via a propargyl amine attachment (see also FIG. 10). In some embodiments, the nucleotide unit comprises a base, sugar and at least one phosphate group, and the linker is attached to the nucleotide unit through the base. In some embodiments, the linker comprises an aliphatic chain or an oligo ethylene glycol chain where both linker chains having 2-6 subunits. In some embodiments, the linker also includes an aromatic moiety.

[0442] In some embodiments, in the methods for forming a plurality of complexed polymerases, individual multivalent molecules in the plurality of multivalent molecules of step (bl) comprise a core attached to multiple nucleotide arms, and wherein the multiple nucleotide arms have the same type of nucleotide unit which is selected from a group consisting of dATP, dGTP, dCTP, dTTP and dUTP.

[0443] In some embodiments, in the methods for forming a plurality of complexed polymerases, the nucleotide unit of the at least one multivalent molecule of step (bl) comprises an aromatic base, a five carbon sugar (e.g., ribose or deoxyribose), and one or more phosphate groups (e.g., 1-10 phosphate groups). The plurality of multivalent molecules can comprise one type multivalent molecule having one type of nucleotide unit selected from a group consisting of dATP, dGTP, dCTP, dTTP and dUTP. The plurality of multivalent molecules can comprise at a mixture of any combination of two or more types of multivalent molecules, where individual multivalent molecules in the mixture comprise nucleotide units selected from a group consisting of dATP, dGTP, dCTP, dTTP and/or dUTP.

[0444] In some embodiments, in the methods for forming a plurality of complexed polymerases, at least one multivalent molecule in the plurality of multivalent molecules of step (bl) comprise a nucleotide unit having a chain of one, two or three phosphorus atoms where the chain is typically attached to the 5’ carbon of the sugar moiety via an ester or phosphoramide linkage. In some embodiments, at least one nucleotide unit is a nucleotide analog having a phosphorus chain in which the phosphorus atoms are linked together with intervening O, S, NH, methylene or ethylene. In some embodiments, the phosphorus atoms in the chain include substituted side groups including O, S or BH3. In some embodiments, the chain includes phosphate groups substituted with analogs including phosphoramidate, phosphorothioate, phosphordithioate, and O-methylphosphoroamidite groups.

[0445] In some embodiments, in the methods for forming a plurality of complexed polymerases, individual multivalent molecules in the plurality of multivalent molecule of step (bl) comprise a core attached to multiple nucleotide arms, and wherein individual nucleotide arms comprise a nucleotide unit having a chain terminating moiety (e.g., blocking moiety) at the sugar 2’ position, at the sugar 3’ position, or at the sugar 2’ and 3’ position.

[0446] In some embodiments, in the methods for forming a plurality of complexed polymerases, at least one multivalent molecule in the plurality of multivalent molecules of step (bl) comprises a nucleotide unit comprising a terminator nucleotide analog having a chain terminating moiety (e.g., blocking moiety) at the sugar 2’ position, at the sugar 3’ position, or at the sugar 2’ and 3’ position. In some embodiments, the chain terminating moiety can inhibit polymerase-catalyzed incorporation of a subsequent nucleotide unit or free nucleotide in a nascent strand during a primer extension reaction. In some embodiments, the chain terminating moiety is attached to the 3’ sugar hydroxyl position where the sugar comprises a ribose or deoxyribose sugar moiety. In some embodiments, the chain terminating moiety is removable/cleavable from the 3’ sugar hydroxyl position to generate a nucleotide having a 3 ’OH sugar group which is extendible with a subsequent nucleotide in a polymerase-catalyzed nucleotide incorporation reaction. In some embodiments, the chain terminating moiety comprises an alkyl group, alkenyl group, alkynyl group, allyl group, aryl group, benzyl group, azide group, amine group, amide group, keto group, isocyanate group, phosphate group, thio group, disulfide group, carbonate group, urea group, or silyl group. In some embodiments, the chain terminating moiety is cleavable/removable from the nucleotide unit, for example by reacting the chain terminating moiety with a chemical agent, pH change, light or heat. In some embodiments, the chain terminating moieties alkyl, alkenyl, alkynyl and allyl are cleavable with tetrakis(triphenylphosphine)palladium(0) (Pd(PPh3)4) with piperidine, or with 2,3-Dichloro-5,6-dicyano-l,4-benzo-quinone (DDQ). In some embodiments, the chain terminating moieties aryl and benzyl are cleavable with H2 Pd/C. In some embodiments, the chain terminating moieties amine, amide, keto, isocyanate, phosphate, thio, disulfide are cleavable with phosphine or with a thiol group including betamercaptoethanol or dithiothritol (DTT). In some embodiments, the chain terminating moiety carbonate is cleavable with potassium carbonate (K2CO3) in MeOH, with triethylamine in pyridine, or with Zn in acetic acid (AcOH). In some embodiments, the chain terminating moieties urea and silyl are cleavable with tetrabutylammonium fluoride, pyridine-HF, with ammonium fluoride, or with triethylamine trihydrofluoride.

[0447] In some embodiments, in the methods for forming a plurality of complexed polymerases, at least one multivalent molecule in the plurality of multivalent molecules of step (bl) comprises a nucleotide unit comprising a terminator nucleotide analog having a chain terminating moiety (e.g., blocking moiety) at the sugar 2’ position, at the sugar 3’ position, or at the sugar 2’ and 3’ position. In some embodiments, the chain terminating moiety comprises an azide, azido or azidomethyl group. In some embodiments, the chain terminating moiety comprises a 3’-O-azido or 3’-O-azidomethyl group. In some embodiments, the chain terminating moieties azide, azido and azidomethyl group are cleavable/removable with a phosphine compound. In some embodiments, the phosphine compound comprises a derivatized tri-alkyl phosphine moiety or a derivatized tri-aryl phosphine moiety. In some embodiments, the phosphine compound comprises Tris(2- carboxyethyl)phosphine (TCEP) or bis-sulfo triphenyl phosphine (BS-TPP) or Tri(hydroxyproyl)phosphine (THPP). In some embodiments, the cleaving agent comprises 4- dimethylaminopyridine (4-DMAP).

[0448] In some embodiments, in the methods for forming a plurality of complexed polymerases, at least one multivalent molecule in the plurality of multivalent molecules of step (bl) comprises a nucleotide unit comprising a chain terminating moiety which is selected from a group consisting of 3’-deoxy nucleotides, 2’,3’-dideoxynucleotides, 3’-methyl, 3’- azido, 3 ’-azidomethyl, 3’-O-azidoalkyl, 3’-O-ethynyl, 3’-O-aminoalkyl, 3’-O-fluoroalkyl, 3’- fluorom ethyl, 3 ’-difluoromethyl, 3 ’-trifluoromethyl, 3 ’-sulfonyl, 3 ’-malonyl, 3 ’-amino, 3’-O- amino, 3’-sulfhydral, 3 ’-aminomethyl, 3 ’-ethyl, 3 ’butyl, 3 ’-tert butyl, 3’- Fluorenylmethyloxycarbonyl, 3’ tert-Butyloxycarbonyl, 3’-O-alkyl hydroxylamino group, 3’- phosphorothioate, and 3-O-benzyl, or derivatives thereof. [0449] In some embodiments, in the methods for forming a plurality of complexed polymerases, at least one multivalent molecule in the plurality of multivalent molecules of step (bl) comprises a core attached to multiple nucleotide arms, wherein the core, linker and/or nucleotide unit is labeled with detectable reporter moiety. In some embodiments, the detectable reporter moiety comprises a fluorophore. In some embodiments, a particular detectable reporter moiety (e.g., fluorophore) that is attached to the multivalent molecule can correspond to the base (e.g., dATP, dGTP, dCTP, dTTP or dUTP) of the nucleotide unit to permit detection and identification of the nucleotide base.

[0450] In some embodiments, in the methods for forming a plurality of complexed polymerases, at least one nucleotide arm of a multivalent molecule in the plurality of multivalent molecules of step (bl) has a nucleotide unit that is attached to a detectable reporter moiety. In some embodiments, the detectable reporter moiety is attached to the nucleotide base. In some embodiments, the detectable reporter moiety comprises a fluorophore. In some embodiments, a particular detectable reporter moiety (e.g., fluorophore) that is attached to the multivalent molecule can correspond to the base (e.g., dATP, dGTP, dCTP, dTTP or dUTP) of the nucleotide unit to permit detection and identification of the nucleotide base.

[0451] In some embodiments, in the methods for forming a plurality of complexed polymerases, the core of a multivalent molecule of step (bl) comprises an avidin-like moiety and the core attachment moiety comprises biotin. In some embodiments, the core comprises an streptavidin-type or avidin-type moiety which includes an avidin protein, as well as any derivatives, analogs and other non-native forms of avidin that can bind to at least one biotin moiety. Other forms of avidin moieties include native and recombinant avidin and streptavidin as well as derivatized molecules, e.g. nonglycosylated avidin and truncated streptavidins . For example, avidin moiety includes deglycosylated forms of avidin, bacterial streptavidin produced by Streptomyces (e.g., Streptomyces avidinii), as well as derivatized forms, for example, N- acyl avidins, e.g., N-acetyl, N-phthalyl and N-succinyl avidin, and the commercially- available products ExtrAvidin™, Captavidin™, Neutravidin™’ and Neutralite Avidin™.

Forming Complexed Polymerases with Nucleotides

[0452] In some embodiments, the methods for forming a plurality of complexed polymerases generally comprise: (a) contacting a plurality of mutant polymerases with (i) a plurality of nucleic acid template molecules and (ii) a plurality of nucleic acid primers to form a plurality of complexed polymerases; (b2) contacting the plurality of complexed polymerases with a plurality of nucleotides to form a plurality of nucleotide-complexed polymerases. In some embodiments, the method further comprises step (c2): detecting the complementary nucleotides which are incorporated into the primers of the nucleotide- complexed polymerases. In some embodiments, the method further comprises step (d2): identifying the bases of the complementary nucleotides which are incorporated into the primers of the nucleotide-complexed polymerases. In some embodiments, the mutant polymerases comprise an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99% identical, or a higher level sequence identity, to any of SEQ ID NOS: 1-2787 and 2789-2793. [0453] In some embodiments, the methods for forming a plurality of complexed polymerases further comprise step (b2): contacting the plurality of complexed polymerases of step (a) with a plurality of nucleotides under a condition suitable for binding a complementary nucleotide from the plurality of nucleotides to a complexed polymerase from the plurality of complexed polymerases thereby forming a nucleotide-complexed polymerase. In some embodiments, the contacting of step (b2) is conducted under a condition that is suitable for promoting incorporation of the bound complementary nucleotides into the primers of the nucleotide-complexed polymerases thereby forming a plurality of nucleotide- complexed polymerases. In some embodiments, the incorporating the nucleotide into the 3’ end of the primer in step (b2) comprises a primer extension reaction. In some embodiments, the contacting of step (b2) is conducted in the presence of at least one cation selected from a group consisting of strontium, barium, sodium, magnesium, potassium, manganese, calcium, lithium, nickel and cobalt. In some embodiments, the contacting of step (b2) is conducted in the presence of magnesium and/or manganese. In some embodiments, individual nucleotides in the plurality comprise an aromatic base, a five carbon sugar, and 1-10 phosphate groups. In some embodiments, the plurality of nucleotides comprises one type of nucleotide selected from a group consisting of dATP, dGTP, dCTP, dTTP and dUTP, or comprise a mixture of any combination of two or more types of nucleotides selected from a group consisting of dATP, dGTP, dCTP, dTTP and/or dUTP. In some embodiments, the plurality of nucleotides comprise native nucleotides (e.g., non-analog nucleotides) or nucleotide analogs. In some embodiments, individual nucleotides in the plurality of nucleotides comprise a chain terminating moiety attached to the 2’ and/or 3’ sugar position. In some embodiments, the plurality of nucleotides comprise a 2’ and/or 3’ chain terminating moiety which is removable or is not removable. In some embodiments, the chain terminating moiety comprises an azide, azido or azidomethyl group. In some embodiments, the azide, azido or azidomethyl group is removable from the nucleotide with a phosphine compound. One skilled in the art will recognize that other removable chain terminating moieties are possible. In some embodiments, the plurality of nucleotides comprises a plurality of nucleotides labeled with detectable reporter moiety. The detectable reporter moiety comprises a fluorophore. In some embodiments, the fluorophore is attached to the nucleotide base. In some embodiments, the fluorophore is attached to the nucleotide base with a linker which is cleavable/removable from the base or is not removable from the base. In some embodiments, at least one of the nucleotides in the plurality is not labeled with a detectable reporter moiety. In some embodiments, a particular detectable reporter moiety (e.g., fluorophore) that is attached to the nucleotide can correspond to the nucleotide base (e.g., dATP, dGTP, dCTP, dTTP or dUTP) to permit detection and identification of the nucleotide base. In some embodiments, the plurality of nucleotides in step (b2) comprise non-labeled nucleotides.

[0454] In some embodiments, in the methods for forming a plurality of complexed polymerases, the contacting of step (a) is conducted at a constant temperature which is selected from a temperature range of about 25-90 °C. In some embodiments, the contacting of step (b2) is conducted at a constant temperature which is selected from a temperature range of about 25-90 °C. In some embodiments, the contacting of steps (a) and (b2) are conducted at a constant temperature which is selected from a temperature range of about 25-90 °C (e.g., isothermal temperature).

[0455] In some embodiments, the methods for forming a plurality of complexed polymerases further comprise step (c2): detecting the complementary nucleotides which are incorporated into the primers of the nucleotide-complexed polymerases. In some embodiments, the plurality of nucleotides are labeled with a detectable reporter moiety to permit detection.

[0456] In some embodiments, the methods for forming a plurality of complexed polymerases further comprises the (d2): identifying the bases of the complementary nucleotides which are incorporated into the 3’ end of the primers of the nucleotide- complexed polymerases. In some embodiments the detecting of step (c2) and the identifying of step (d2) can be used to determine the sequence of the nucleic acid template molecules. [0457] In some embodiments, in the methods for forming a plurality of complexed polymerases, at least one nucleotide in the plurality of nucleotides of step (b2) comprise a base, sugar and at least one phosphate group. In some embodiments, at least one nucleotide in the plurality comprises an aromatic base, a five carbon sugar (e.g., ribose or deoxyribose), and one or more phosphate groups (e.g., 1-10 phosphate groups). The plurality of nucleotides can comprise at least one type of nucleotide selected from a group consisting of dATP, dGTP, dCTP, dTTP and dUTP. The plurality of nucleotides can comprise at a mixture of any combination of two or more types of nucleotides selected from a group consisting of dATP, dGTP, dCTP, dTTP and/or dUTP. In some embodiments, at least one nucleotide in the plurality is not a nucleotide analog. In some embodiments, at least one nucleotide in the plurality comprises a nucleotide analog.

[0458] In some embodiments, in the methods for forming a plurality of complexed polymerases, at least one nucleotide in the plurality of nucleotides of step (b2) comprise a chain of one, two or three phosphorus atoms where the chain is typically attached to the 5’ carbon of the sugar moiety via an ester or phosphoramide linkage. In some embodiments, at least one nucleotide in the plurality is an analog having a phosphorus chain in which the phosphorus atoms are linked together with intervening O, S, NH, methylene or ethylene. In some embodiments, the phosphorus atoms in the chain include substituted side groups including O, S or BH3. In some embodiments, the chain includes phosphate groups substituted with analogs including phosphoramidate, phosphorothioate, phosphordithioate, and O-methylphosphoroamidite groups.

[0459] In some embodiments, in the methods for forming a plurality of complexed polymerases, at least one nucleotide in the plurality of nucleotides of step (b2) comprises a terminator nucleotide analog having a chain terminating moiety (e.g., blocking moiety) at the sugar 2’ position, at the sugar 3’ position, or at the sugar 2’ and 3’ position. In some embodiments, the chain terminating moiety can inhibit polymerase-catalyzed incorporation of a subsequent nucleotide unit or free nucleotide in a nascent strand during a primer extension reaction. In some embodiments, the chain terminating moiety is attached to the 3’ sugar hydroxyl position where the sugar comprises a ribose or deoxyribose sugar moiety. In some embodiments, the chain terminating moiety is removable/cleavable from the 3’ sugar hydroxyl position to generate a nucleotide having a 3 ’OH sugar group which is extendible with a subsequent nucleotide in a polymerase-catalyzed nucleotide incorporation reaction. In some embodiments, the chain terminating moiety comprises an alkyl group, alkenyl group, alkynyl group, allyl group, aryl group, benzyl group, azide group, amine group, amide group, keto group, isocyanate group, phosphate group, thio group, disulfide group, carbonate group, urea group, silyl group or acetal group. In some embodiments, the chain terminating moiety is cleavable/removable from the nucleotide, for example by reacting the chain terminating moiety with a chemical agent, pH change, light or heat. In some embodiments, the chain terminating moieties alkyl, alkenyl, alkynyl and allyl are cleavable with tetrakis(triphenylphosphine)palladium(0) (Pd(PPh3)4) with piperidine, or with 2,3-Dichloro- 5,6-dicyano-l,4-benzo-quinone (DDQ). In some embodiments, the chain terminating moieties aryl and benzyl are cleavable with H2 Pd/C. In some embodiments, the chain terminating moieties amine, amide, keto, isocyanate, phosphate, thio, disulfide are cleavable with phosphine or with a thiol group including beta-mercaptoethanol or dithiothritol (DTT). In some embodiments, the chain terminating moiety carbonate is cleavable with potassium carbonate (K2CO3) in MeOH, with triethylamine in pyridine, or with Zn in acetic acid (AcOH). In some embodiments, the chain terminating moieties urea and silyl are cleavable with tetrabutylammonium fluoride, pyridine-HF, with ammonium fluoride, or with triethylamine trihydrofluoride. In some embodiments, the chain terminating moiety may be cleavable/removable with nitrous acid. In some embodiments, a chain terminating moiety may be cleavable/removable using a solution comprising nitrite, such as, for example, a combination of nitrite with an acid such as acetic acid, sulfuric acid, or nitric acid. In some further embodiments, said solution may comprise an organic acid.

[0460] In some embodiments, in the methods for forming a plurality of complexed polymerases, at least one nucleotide in the plurality of nucleotides of step (b2) comprises a terminator nucleotide analog having a chain terminating moiety (e.g., blocking moiety) at the sugar 2’ position, at the sugar 3’ position, or at the sugar 2’ and 3’ position. In some embodiments, the chain terminating moiety comprises an azide, azido or azidomethyl group. In some embodiments, the chain terminating moiety comprises a 3’-O-azido or 3’-O- azidomethyl group. In some embodiments, the chain terminating moieties azide, azido and azidomethyl group are cleavable/removable with a phosphine compound. In some embodiments, the phosphine compound comprises a derivatized tri-alkyl phosphine moiety or a derivatized tri-aryl phosphine moiety. In some embodiments, the phosphine compound comprises Tris(2-carboxyethyl)phosphine (TCEP) or bis-sulfo triphenyl phosphine (BS-TPP) or Tri(hydroxyproyl)phosphine (THPP). In some embodiments, the cleaving agent comprises 4-dimethylaminopyridine (4-DMAP). In some embodiments, the chain terminating moiety comprising one or more of a 3’-O-amino group, a 3’-O-aminomethyl group, a 3’-O- methylamino group, or derivatives thereof may be cleaved with nitrous acid, through a mechanism utilizing nitrous acid, or using a solution comprising nitrous acid. In some embodiments, the chain terminating moiety comprising one or more of a 3’-O-amino group, a 3’-O-aminomethyl group, a 3’-O-methylamino group, or derivatives thereof may be cleaved using a solution comprising nitrite. In some embodiments, for example, nitrite may be combined with or contacted with an acid such as acetic acid, sulfuric acid, or nitric acid. In some embodiments, the chain terminating moiety comprises a 3 ’-acetal moiety which can be cleaved with a palladium deblocking reagent (e.g., Pd(0)). In some further embodiments, for example, nitrite may be combined with or contacted with an organic acid such as, for example, formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, or the like. [0461] In some embodiments, in the methods for forming a plurality of complexed polymerases, at least one nucleotide in the plurality of nucleotides of step (b2) comprises a chain terminating moiety which is selected from a group consisting of 3 ’-deoxy nucleotides, 2’, 3 ’-dideoxynucleotides, 3’-methyl, 3’-azido, 3 ’-azidomethyl, 3’-O-azidoalkyl, 3’-O- ethynyl, 3’-O-aminoalkyl, 3’-O-fluoroalkyl, 3 ’-fluoromethyl, 3 ’-difluoromethyl, 3’- trifluorom ethyl, 3 ’-sulfonyl, 3 ’-malonyl, 3 ’-amino, 3’-O-amino, 3’-sulfhydral, 3’- aminomethyl, 3 ’-ethyl, 3 ’butyl, 3 ’-tert butyl, 3’- Fluorenylmethyloxy carbonyl, 3’ tert- Butyloxy carbonyl, 3’-O-alkyl hydroxylamino group, 3’-phosphorothioate, 3’-O-benzyl, and 3 ’-acetal moiety, or derivatives thereof.

[0462] In some embodiments, in the methods for forming a plurality of complexed polymerases, at least one nucleotide in the plurality of nucleotides of step (b2) comprises a detectable reporter moiety. In some embodiments, at least one nucleotide in the plurality of nucleotides of step (b2) comprises a labeled nucleotide. In some embodiments, the detectable reporter moiety comprises a fluorophore. In some embodiments, the fluorophore is attached to the nucleotide base. In some embodiments, the fluorophore is attached to the nucleotide base with a linker which is cleavable/removable from the base. In some embodiments, at least one of the nucleotides in the plurality is not labeled with a detectable reporter moiety. In some embodiments, a particular detectable reporter moiety (e.g., fluorophore) that is attached to the nucleotide can correspond to the nucleotide base (e.g., dATP, dGTP, dCTP, dTTP or dUTP) to permit detection and identification of the nucleotide base. In some embodiments, the plurality of nucleotides of step (b2) comprise non-labeled nucleotides.

[0463] In some embodiments, in the methods for forming a plurality of complexed polymerases, at least one nucleotide in the plurality of nucleotides of step (b2) comprises a cleavable linker on the base which comprises a cleavable (e.g., removable) moiety comprising an alkyl group, alkenyl group, alkynyl group, allyl group, aryl group, benzyl group, azide group, amine group, amide group, keto group, isocyanate group, phosphate group, thio group, disulfide group, carbonate group, urea group, silyl or acetal group. In some embodiments, the cleavable linker on the base is cleavable/removable from the base by reacting the cleavable moiety with a chemical agent, pH change, light or heat. In some embodiments, the cleavable moieties alkyl, alkenyl, alkynyl and allyl are cleavable with tetrakis(triphenylphosphine)palladium(0) (Pd(PPh3)4) with piperidine, or with 2,3-Dichloro- 5,6-dicyano-l,4-benzo-quinone (DDQ). In some embodiments, the cleavable moieties aryl and benzyl are cleavable with H2 Pd/C. In some embodiments, the cleavable moieties amine, amide, keto, isocyanate, phosphate, thio, disulfide are cleavable with phosphine or with a thiol group including beta-mercaptoethanol or dithiothritol (DTT). In some embodiments, the cleavable moiety carbonate is cleavable with potassium carbonate (K2CO3) in MeOH, with triethylamine in pyridine, or with Zn in acetic acid (AcOH). In some embodiments, the cleavable moieties urea and silyl are cleavable with tetrabutylammonium fluoride, pyridine- HF, with ammonium fluoride, or with triethylamine trihydrofluoride.

[0464] In some embodiments, in the methods for forming a plurality of complexed polymerases, at least one nucleotide in the plurality of nucleotides of step (b2) comprises a cleavable linker on the base which comprises a cleavable moiety including an azide, azido or azidomethyl group. In some embodiments, the cleavable moieties azide, azido and azidomethyl group are cleavable/removable with a phosphine compound. In some embodiments, the phosphine compound comprises a derivatized tri-alkyl phosphine moiety or a derivatized tri-aryl phosphine moiety. In some embodiments, the phosphine compound comprises Tris(2-carboxyethyl)phosphine (TCEP) or bis-sulfo triphenyl phosphine (BS-TPP) or Tri(hydroxyproyl)phosphine (THPP). In some embodiments, the cleaving agent comprises 4-dimethylaminopyridine (4-DMAP).

[0465] In some embodiments, in the methods for forming a plurality of complexed polymerases, at least one nucleotide in the plurality of nucleotides of step (b2) comprises a chain terminating moiety at the sugar 2’ and/or the sugar 3’ position, and a cleavable linker on the base, wherein the chain terminating moiety on the sugar and the cleavable linker on the base have the same or different cleavable moieties. In some embodiments, the chain terminating moiety (e.g., at the sugar 2’ and/or sugar 3’ position) and the detectable reporter moiety linked to the base are chemically cleavable/removable with the same chemical agent. In some embodiments, the chain terminating moiety (e.g., at the sugar 2’ and/or sugar 3’ position) and the detectable reporter moiety linked to the base are chemically cleavable/removable with different chemical agents.

[0466] The present disclosure provides methods for binding a mutant polymerase to a nucleotide, comprising: (a) contacting a mutant polymerase to (i) a nucleic acid template molecule and (ii) a nucleic acid primer, wherein the contacting is conducted under a condition suitable to bind the mutant polymerase to the nucleic acid template molecule which is hybridized to the nucleic acid primer, wherein the nucleic acid template molecule hybridized to the nucleic acid primer forms the nucleic acid duplex. In some embodiments, the mutant polymerase comprises a recombinant mutant polymerase. In some embodiments, the primer comprises a 3’ extendible end or a 3’ non-extendible end. In some embodiments, the mutant polymerase comprises an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99% identical, or a higher level sequence identity, to any of SEQ ID NOS: 1-2787 and 2789-2793. In some embodiments, the mutant polymerases include amino acid substitutions that confer exonuclease-minus activity. In some embodiments, the mutant polymerase exhibits increased incorporation rate of nucleotide analogs compared to a corresponding wild type polymerase, where the nucleotide analogs comprise a chain terminating moiety (e.g., blocking moiety) at the sugar 2’ position and/or at the 3’ sugar position.

[0467] In some embodiments, the methods for binding a mutant polymerase to a nucleotide further comprise (b) contacting the mutant polymerase with a plurality of nucleotides under a condition suitable for binding at least one nucleotide to the mutant polymerase which is bound to the nucleic acid duplex. In some embodiments, the mutant polymerase is contacted with the plurality of nucleotides in the presence of at least one cation selected from a group consisting of strontium, barium, sodium, magnesium, potassium, manganese, calcium, lithium, nickel and cobalt. In some embodiments, the contacting of step (b) is conducted in the presence of strontium, barium and/or calcium. In some embodiments, the at least one nucleotide binds the mutant polymerase does not incorporate into the 3’ end of the extendible or non-extendible primer. In some embodiments, the plurality of nucleotides comprises at least one nucleotide analog having a chain terminating moiety at the sugar 2’ or 3’ position. In some embodiments, the plurality of nucleotides comprises at least one nucleotide that lacks a chain terminating moiety. In some embodiments, the method further comprises (c) detecting the at least one nucleotide that is bound to the polymerase but has not incorporated into the 3’ end of the primer. In some embodiments, the method further comprises (d) identifying the at least one nucleotide that is bound to the polymerase but has not incorporated into the 3 ’ end of the primer.

[0468] Alternatively, the methods for binding a polymerase to a nucleotide, comprising forming a complexed polymerase: (al) contacting a mutant polymerase to (i) a nucleic acid template molecule and (ii) a nucleic acid primer, wherein the contacting is conducted under a condition suitable to bind the mutant polymerase to the nucleic acid template molecule which is hybridized to the nucleic acid primer, wherein the nucleic acid template molecule hybridized to the nucleic acid primer forms the nucleic acid duplex. In some embodiments, the mutant polymerase comprises a recombinant mutant polymerase. In some embodiments, the primer comprises a 3’ extendible end or a 3’ non-extendible end. In some embodiments, the mutant polymerase comprises an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99% identical, or a higher level sequence identity, to any of SEQ ID NOS: 1-2787 and 2789-2793. In some embodiments, the mutant polymerases include amino acid substitutions that confer exonuclease-minus activity. In some embodiments, the mutant polymerase exhibits increased incorporation rate of nucleotide analogs compared to a corresponding wild type polymerase, where the nucleotide analogs comprise a chain terminating moiety (e.g., blocking moiety) at the sugar 2’ position and/or at the 3’ sugar position.

[0469] The alternative method further comprises step (bl): contacting the plurality of complexed polymerases of step (al) with a plurality of nucleotides under a condition suitable for binding a complementary nucleotide from the plurality of nucleotides to a complexed polymerase from the plurality of complexed polymerases thereby forming a nucleotide- complexed polymerase. In some embodiments, the contacting of step (bl) is conducted under a condition that is suitable for promoting nucleotide binding but inhibiting incorporation of the bound complementary nucleotides to the 3’ end of the primers of the nucleotide- complexed polymerases. In some embodiments, the contacting of step (bl) is conducted in the presence of at least one cation selected from a group consisting of strontium, barium, sodium, magnesium, potassium, manganese, calcium, lithium, nickel and cobalt. The plurality of complexed polymerases can be contacted sequentially with at least two separate mixtures where each mixture comprises an engineered polymerase and a nucleotide. The contacting is conducted under conditions suitable for forming stable ternary complexes with cognates for first, second and third base type base types in the template. The method further comprises step (cl) examining the at least two separate mixtures to determine if a ternary complex formed. The method further comprises step (dl) identifying the next correct nucleotide for the primed template nucleic acid molecule, wherein the next correct nucleotide is identified as a cognate of the first, second or third base type if ternary complex is detected in step (cl), and wherein the next correct nucleotide is imputed to be a nucleotide cognate of a fourth base type based on the absence of a ternary complex in step (cl). The method further comprises step (el) adding a next correct nucleotide to the primer of the primed template nucleic acid after step (c3), thereby producing an extended primer; and step (fl) repeating steps (a) through (el) for the primed template nucleic acid that comprises the extended primer.

[0470] The present disclosure provides methods for incorporating a nucleotide, comprising: (a) contacting a mutant polymerase to (i) a nucleic acid template molecule and (ii) a nucleic acid primer, wherein the contacting is conducted under a condition suitable to bind the mutant polymerase to the nucleic acid template molecule which is hybridized to the nucleic acid primer, wherein the nucleic acid template molecule hybridized to the nucleic acid primer forms the nucleic acid duplex. In some embodiments, the mutant polymerase comprises a recombinant mutant polymerase. In some embodiments, the primer comprises a 3’ extendible end. In some embodiments, the mutant polymerase comprises an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99% identical, or a higher level sequence identity, to any of SEQ ID NOS: 1-2787 and 2789-2793. In some embodiments, the mutant polymerases include amino acid substitutions that confer exonuclease-minus activity. In some embodiments, the mutant polymerase exhibits increased incorporation rate of nucleotide analogs compared to a corresponding wild type polymerase, where the nucleotide analogs comprise a chain terminating moiety (e.g., blocking moiety) at the sugar 2’ position and/or at the 3’ sugar position.

[0471] In some embodiments, the methods for incorporating a nucleotide further comprise (b) contacting the mutant polymerase with a plurality of nucleotides under a condition suitable for binding at least one nucleotide to the mutant polymerase which is bound to the nucleic acid duplex. In some embodiments, the mutant polymerase is contacted with the plurality of nucleotides in the presence of at least one cation selected from a group consisting of strontium, barium, sodium, magnesium, potassium, manganese, calcium, lithium, nickel and cobalt. In some embodiments, the contacting of step (b) is conducted in the presence of strontium, barium and/or calcium. In some embodiments, the plurality of nucleotides comprises at least one nucleotide analog having a chain terminating moiety at the sugar 2’ or 3’ position. In some embodiments, the plurality of nucleotides comprises at least one nucleotide that lacks a chain terminating moiety. In some embodiments, the plurality of nucleotides comprise labeled nucleotides. In some embodiments, the plurality of nucleotides comprise non-labeled nucleotides. In some embodiments, the method further comprises (c) incorporating at least one nucleotide into the 3’ end of the extendible primer under a condition suitable for incorporating the at least one nucleotide. In some embodiments, the suitable conditions for nucleotide binding the mutant polymerase and for incorporation the nucleotide can be the same or different. In some embodiments, conditions suitable for incorporating the nucleotide comprise inclusion of at least one cation selected from a group consisting of strontium, barium, sodium, magnesium, potassium, manganese, calcium, lithium, nickel and cobalt. In some embodiments, the at least one nucleotide binds the mutant polymerase and incorporates into the 3’ end of the extendible primer. In some embodiments, the incorporating the nucleotide into the 3’ end of the primer in step (c) comprises a primer extension reaction. In some embodiments, the method further comprises (d) repeating the incorporating at least one nucleotide into the 3’ end of the extendible primer of step (c) at least once. In some embodiments, the method further comprises detecting the at least one incorporated nucleotide at step (c) and/or (d). In some embodiments, the method further comprises identifying the at least one incorporated nucleotide at step (c) and/or (d). In some embodiments, the sequence of the nucleic acid template molecule can be determined by detecting and identifying the nucleotide that binds the mutant polymerase. In some embodiments, the sequence of the nucleic acid template molecule can be determined by detecting and identifying the nucleotide that incorporates into the 3’ end of the primer. [0472] The present disclosure provides methods for determining the sequence of a nucleic acid template molecule, comprising: (a) contacting a mutant polymerase to (i) a nucleic acid template molecule and (ii) a nucleic acid primer, wherein the contacting is conducted under a condition suitable to bind the mutant polymerase to the nucleic acid template molecule which is hybridized to the nucleic acid primer, wherein the nucleic acid template molecule hybridized to the nucleic acid primer forms the nucleic acid duplex. In some embodiments, the mutant polymerase comprises a recombinant mutant polymerase. In some embodiments, the primer comprises a 3’ extendible end. In some embodiments, the mutant polymerase comprises an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99% identical, or a higher level sequence identity, to any of SEQ ID NOS: 1-2787 and 2789- 2793. In some embodiments, the mutant polymerases include amino acid substitutions that confer exonuclease-minus activity. In some embodiments, the mutant polymerase exhibits increased incorporation rate of nucleotide analogs compared to a corresponding wild type polymerase, where the nucleotide analogs comprise a chain terminating moiety (e.g., blocking moiety) at the sugar 2’ position and/or at the 3’ sugar position.

[0473] In some embodiments, the methods for determining the sequence of a nucleic acid template molecule further comprise contacting the (b) contacting the mutant polymerase with a plurality of nucleotides under a condition suitable for binding at least one nucleotide to the mutant polymerase which is bound to the nucleic acid duplex. In some embodiments, the mutant polymerase is contacted with the plurality of nucleotides in the presence of at least one cation selected from a group consisting of strontium, barium, sodium, magnesium, potassium, manganese, calcium, lithium, nickel and cobalt. In some embodiments, the contacting of step (b) is conducted in the presence of strontium, barium and/or calcium. In some embodiments, the plurality of nucleotides comprises at least one nucleotide analog having a chain terminating moiety at the sugar 2’ or 3’ position. In some embodiments, the plurality of nucleotides comprises at least one nucleotide that lacks a chain terminating moiety. In some embodiments, the plurality of nucleotides comprise labeled nucleotides. In some embodiments, the plurality of nucleotides comprise non-labeled nucleotides. In some embodiments, the method further comprises (c) incorporating at least one nucleotide into the 3’ end of the extendible primer under a condition suitable for incorporating the at least one nucleotide. In some embodiments, the suitable conditions for nucleotide binding the mutant polymerase and for incorporation the nucleotide can be the same or different. In some embodiments, conditions suitable for incorporating the nucleotide comprise inclusion of at least one cation selected from a group consisting of strontium, barium, sodium, magnesium, potassium, manganese, calcium, lithium, nickel and cobalt. In some embodiments, the at least one nucleotide binds the mutant polymerase and incorporates into the 3’ end of the extendible primer. In some embodiments, the incorporating the nucleotide into the 3’ end of the primer in step (c) comprises a primer extension reaction. In some embodiments, the method further comprises (d) repeating the incorporating at least one nucleotide into the 3’ end of the extendible primer of step (c) at least once. In some embodiments, the plurality of nucleotides comprises a plurality of nucleotides labeled with detectable reporter moiety. The detectable reporter moiety comprises a fluorophore. In some embodiments, the fluorophore is attached to the nucleotide base. In some embodiments, the fluorophore is attached to the nucleotide base with a linker which is cleavable/removable from the base. In some embodiments, at least one of the nucleotides in the plurality is not labeled with a detectable reporter moiety. In some embodiments, a particular detectable reporter moiety (e.g., fluorophore) that is attached to the nucleotide can correspond to the nucleotide base (e.g., dATP, dGTP, dCTP, dTTP or dUTP) to permit detection and identification of the nucleotide base. In some embodiments, the method further comprises detecting the at least one incorporated nucleotide at step (c) and/or (d). In some embodiments, the method further comprises identifying the at least one incorporated nucleotide at step (c) and/or (d). In some embodiments, the sequence of the nucleic acid template molecule can be determined by detecting and identifying the nucleotide that binds the mutant polymerase, thereby determining the sequence of the nucleic acid template. In some embodiments, the sequence of the nucleic acid template molecule can be determined by detecting and identifying the nucleotide that incorporates into the 3’ end of the primer, thereby determining the sequence of the nucleic acid template.

[0474] In some embodiments, in the methods for determining the sequence of a nucleic acid template, the plurality of polymerases that are bound to the nucleic acid duplexes comprise a plurality of complexed polymerases, having at least a first and second complexed polymerase, wherein (a) the first complexed polymerases comprises a first polymerase bound to a first nucleic acid duplex comprising a first nucleic acid template which is hybridized to a first nucleic acid primer, (b) the second complexed polymerases comprises a second polymerase bound to a second nucleic acid duplex comprising a second nucleic acid template which is hybridized to a second nucleic acid primer, (c) the first and second nucleic acid templates comprise different sequences, (d) the first and second nucleic acid templates are clonally-amplified, (e) the first and second primers comprise extendible 3’ ends or nonextendible 3’ ends, and (f) the plurality of complexed polymerases are immobilized to a support. In some embodiments, the density of the plurality of complexed polymerases is about 10 ² - 10 ¹⁵ complexed polymerases per mm ² that are immobilized to the support.

[0475] In some embodiments, in the method for binding a nucleotide and in the method for incorporating a nucleotide and in the method for sequencing the nucleic acid template using nucleotides, at least one nucleotide in the plurality of nucleotides comprise a base, sugar and at least one phosphate group. In some embodiments, at least one nucleotide in the plurality comprises an aromatic base, a five carbon sugar (e.g., ribose or deoxyribose), and one or more phosphate groups (e.g., 1-10 phosphate groups). The plurality of nucleotides can comprise at least one type of nucleotide selected from a group consisting of dATP, dGTP, dCTP, dTTP and dUTP. The plurality of nucleotides can comprise at a mixture of any combination of two or more types of nucleotides selected from a group consisting of dATP, dGTP, dCTP, dTTP and/or dUTP. In some embodiments, at least one nucleotide in the plurality is not a nucleotide analog. In some embodiments, at least one nucleotide in the plurality comprises a nucleotide analog.

[0476] In some embodiments, in the method for binding a nucleotide and in the method for incorporating a nucleotide and in the method for sequencing the nucleic acid template, at least one nucleotide in the plurality of nucleotides comprise a chain of one, two or three phosphorus atoms where the chain is typically attached to the 5’ carbon of the sugar moiety via an ester or phosphoramide linkage. In some embodiments, at least one nucleotide in the plurality is an analog having a phosphorus chain in which the phosphorus atoms are linked together with intervening O, S, NH, methylene or ethylene. In some embodiments, the phosphorus atoms in the chain include substituted side groups including O, S or BH3. In some embodiments, the chain includes phosphate groups substituted with analogs including phosphoramidate, phosphorothioate, phosphordithioate, and O-methylphosphoroamidite groups. [0477] In some embodiments, in the method for binding a nucleotide and in the method for incorporating a nucleotide and in the method for sequencing the nucleic acid template, at least one nucleotide in the plurality of nucleotides comprises a terminator nucleotide analog having a chain terminating moiety (e.g., blocking moiety) at the sugar 2’ position, at the sugar 3’ position, or at the sugar 2’ and 3’ position. In some embodiments, the chain terminating moiety can inhibit polymerase-catalyzed incorporation of a subsequent nucleotide unit or free nucleotide in a nascent strand during a primer extension reaction. In some embodiments, the chain terminating moiety is attached to the 3’ sugar hydroxyl position where the sugar comprises a ribose or deoxyribose sugar moiety. In some embodiments, the chain terminating moiety is removable/cleavable from the 3’ sugar hydroxyl position to generate a nucleotide having a 3 ’OH sugar group which is extendible with a subsequent nucleotide in a polymerase-catalyzed nucleotide incorporation reaction. In some embodiments, the chain terminating moiety comprises an alkyl group, alkenyl group, alkynyl group, allyl group, aryl group, benzyl group, azide group, amine group, amide group, keto group, isocyanate group, phosphate group, thio group, disulfide group, carbonate group, urea group, or silyl group. In some embodiments, the chain terminating moiety is cleavable/removable from the nucleotide, for example by reacting the chain terminating moiety with a chemical agent, pH change, light or heat. In some embodiments, the chain terminating moieties alkyl, alkenyl, alkynyl and allyl are cleavable with tetrakis(triphenylphosphine)palladium(0) (Pd(PPh3)4) with piperidine, or with 2,3-Dichloro- 5,6-dicyano-l,4-benzo-quinone (DDQ). In some embodiments, the chain terminating moieties aryl and benzyl are cleavable with H2 Pd/C. In some embodiments, the chain terminating moieties amine, amide, keto, isocyanate, phosphate, thio, disulfide are cleavable with phosphine or with a thiol group including beta-mercaptoethanol or dithiothritol (DTT). In some embodiments, the chain terminating moiety carbonate is cleavable with potassium carbonate (K2CO3) in MeOH, with triethylamine in pyridine, or with Zn in acetic acid (AcOH). In some embodiments, the chain terminating moieties urea and silyl are cleavable with tetrabutylammonium fluoride, pyridine-HF, with ammonium fluoride, or with triethylamine trihydrofluoride. In some embodiments, the chain terminating moiety may be cleavable/removable with nitrous acid. In some embodiments, a chain terminating moiety may be cleavable/removable using a solution comprising nitrite, such as, for example, a combination of nitrite with an acid such as acetic acid, sulfuric acid, or nitric acid. In some further embodiments, said solution may comprise an organic acid. [0478] In some embodiments, in the method for binding a nucleotide and in the method for incorporating a nucleotide and in the method for sequencing the nucleic acid template, at least one nucleotide in the plurality of nucleotides comprises a terminator nucleotide analog having a chain terminating moiety (e.g., blocking moiety) at the sugar 2’ position, at the sugar 3’ position, or at the sugar 2’ and 3’ position. In some embodiments, the chain terminating moiety comprises an azide, azido or azidomethyl group. In some embodiments, the chain terminating moiety comprises a 3’-O-azido or 3’-O-azidomethyl group. In some embodiments, the chain terminating moieties azide, azido and azidomethyl group are cleavable/removable with a phosphine compound. In some embodiments, the phosphine compound comprises a derivatized tri-alkyl phosphine moiety or a derivatized tri-aryl phosphine moiety. In some embodiments, the phosphine compound comprises Tris(2- carboxyethyl)phosphine (TCEP) or bis-sulfo triphenyl phosphine (BS-TPP) or Tri(hydroxyproyl)phosphine (THPP). In some embodiments, the cleaving agent comprises 4- dimethylaminopyridine (4-DMAP). In some embodiments, the chain terminating moiety comprising one or more of a 3’-O-amino group, a 3’-O-aminomethyl group, a 3’-O- methylamino group, or derivatives thereof may be cleaved with nitrous acid, through a mechanism utilizing nitrous acid, or using a solution comprising nitrous acid. In some embodiments, the chain terminating moiety comprising one or more of a 3’-O-amino group, a 3’-O-aminomethyl group, a 3’-O-methylamino group, or derivatives thereof may be cleaved using a solution comprising nitrite. In some embodiments, for example, nitrite may be combined with or contacted with an acid such as acetic acid, sulfuric acid, or nitric acid. In some further embodiments, for example, nitrite may be combined with or contacted with an organic acid such as, for example, formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, or the like.

[0479] In some embodiments, in the method for binding a nucleotide and in the method for incorporating a nucleotide and in the method for sequencing the nucleic acid template, the nucleotide comprises a chain terminating moiety which is selected from a group consisting of 3 ’-deoxy nucleotides, 2’, 3 ’-dideoxynucleotides, 3 ’-methyl, 3 ’-azido, 3 ’-azidomethyl, 3’-O- azidoalkyl, 3’-O-ethynyl, 3’-O-aminoalkyl, 3’-O-fluoroalkyl, 3’-fluoromethyl, 3’- difluoromethyl, 3’-trifluoromethyl, 3’-sulfonyl, 3’-malonyl, 3’-amino, 3’-O-amino, 3’- sulfhydral, 3 ’-aminomethyl, 3’-ethyl, 3’butyl, 3" -tert butyl, 3’- Fluorenylmethyloxy carbonyl, 3’ tert-Butyloxycarbonyl, 3’-O-alkyl hydroxylamino group, 3’-phosphorothioate, 3’-O- benzyl, and 3 ’-acetal moiety, or derivatives thereof. [0480] In some embodiments, in the method for binding a nucleotide and in the method for incorporating a nucleotide and in the method for sequencing the nucleic acid template, the plurality of nucleotides comprises a plurality of nucleotides labeled with detectable reporter moiety. The detectable reporter moiety comprises a fluorophore. In some embodiments, the fluorophore is attached to the nucleotide base. In some embodiments, the fluorophore is attached to the nucleotide base with a linker which is cleavable/removable from the base. In some embodiments, in the method for incorporating a nucleotide and in the method for sequencing the nucleic acid template using nucleotides comprising a fluorophore attached to the nucleotide base, cleavage of the linker to remove the fluorophore generates an extended strand having at least a portion of the linker remaining which creates a scar. In some embodiments, at least one of the nucleotides in the plurality is not labeled with a detectable reporter moiety. In some embodiments, a particular detectable reporter moiety (e.g., fluorophore) that is attached to the nucleotide can correspond to the nucleotide base (e.g., dATP, dGTP, dCTP, dTTP or dUTP) to permit detection and identification of the nucleotide base. In some embodiments, the plurality of nucleotides comprise non-labeled nucleotides. [0481] In some embodiments, in the method for binding a nucleotide and in the method for incorporating a nucleotide and in the method for sequencing the nucleic acid template, the cleavable linker on the base comprises a cleavable moiety comprising an alkyl group, alkenyl group, alkynyl group, allyl group, aryl group, benzyl group, azide group, amine group, amide group, keto group, isocyanate group, phosphate group, thio group, disulfide group, carbonate group, urea group, or silyl group. In some embodiments, the cleavable linker on the base is cleavable/removable from the base by reacting the cleavable moiety with a chemical agent, pH change, light or heat. In some embodiments, the cleavable moieties alkyl, alkenyl, alkynyl and allyl are cleavable with tetrakis(triphenylphosphine)palladium(0) (Pd(PPh3)4) with piperidine, or with 2,3-Dichloro-5,6-dicyano-l,4-benzo-quinone (DDQ). In some embodiments, the cleavable moieties aryl and benzyl are cleavable with H2 Pd/C. In some embodiments, the cleavable moieties amine, amide, keto, isocyanate, phosphate, thio, disulfide are cleavable with phosphine or with a thiol group including beta-mercaptoethanol or dithiothritol (DTT). In some embodiments, the cleavable moiety carbonate is cleavable with potassium carbonate (K2CO3) in MeOH, with triethylamine in pyridine, or with Zn in acetic acid (AcOH). In some embodiments, the cleavable moieties urea and silyl are cleavable with tetrabutylammonium fluoride, pyridine-HF, with ammonium fluoride, or with triethylamine trihydrofluoride. In some embodiments, the chain terminating moiety comprises a 3 ’-acetal moiety which can be cleaved with a palladium deblocking reagent (e.g., Pd(0)).

[0482] In some embodiments, in the method for binding a nucleotide and in the method for incorporating a nucleotide and in the method for sequencing the nucleic acid template, the cleavable linker on the base comprises cleavable moiety including an azide, azido or azidomethyl group. In some embodiments, the cleavable moieties azide, azido and azidomethyl group are cleavable/removable with a phosphine compound. In some embodiments, the phosphine compound comprises a derivatized tri-alkyl phosphine moiety or a derivatized tri-aryl phosphine moiety. In some embodiments, the phosphine compound comprises Tris(2-carboxyethyl)phosphine (TCEP) or bis-sulfo triphenyl phosphine (BS-TPP) or Tri(hydroxyproyl)phosphine (THPP). In some embodiments, the cleaving agent comprises 4-dimethylaminopyridine (4-DMAP).

[0483] In some embodiments, in the method for binding a nucleotide and in the method for incorporating a nucleotide and in the method for sequencing the nucleic acid template, the chain terminating moiety (e.g., at the sugar 2’ and/or sugar 3’ position) and the cleavable linker on the base have the same or different cleavable moieties. In some embodiments, the chain terminating moiety (e.g., at the sugar 2’ and/or sugar 3’ position) and the detectable reporter moiety linked to the base are chemically cleavable/removable with the same chemical agent. In some embodiments, the chain terminating moiety (e.g., at the sugar 2’ and/or sugar 3’ position) and the detectable reporter moiety linked to the base are chemically cleavable/removable with different chemical agents.

[0484] In some embodiments, in the methods for sequencing, the binding complex comprises a mutant polymerase, a nucleic acid template molecule duplexed with a primer, and a nucleotide reagent. In some embodiments, in the methods for forming a binding complex which comprises (i) a mutant polymerase, a nucleic acid template molecule duplexed with a primer, and a nucleotide, or the binding complex comprises (ii) a mutant polymerase, a nucleic acid template molecule duplexed with a primer, and a nucleotide unit of a multivalent molecule. In some embodiments, the mutant polymerase comprises an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99% identical, or a higher level sequence identity, to any of SEQ ID NOS: 1-2787 and 2789-2793. In some embodiments, the binding complex has a persistence time of greater than about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1 second. The binding complex has a persistence time of greater than about 0.1-0.25 seconds, or about 0.25-0.5 seconds, or about 0.5-0.75 seconds, or about 0.75-1 second, or about 1-2 seconds, or about 2-3 seconds, or about 3-4 second, or about 4-5 seconds, or about 5-10 seconds and/or wherein the method is or may be carried out at a temperature of at or above 15 °C, at or above 20 °C, at or above 25 °C, at or above 35 °C, at or above 37 °C, at or above 42 °C at or above 55 °C at or above 60 °C, or at or above 72 °C, or at or above 80 °C, or within a range defined by any of the foregoing. The binding complex (e.g., ternary complex) remains stable until subjected to a condition that causes dissociation of interactions between any of the polymerase, template molecule, primer and/or the nucleotide unit or the nucleotide. For example, a dissociating condition comprises contacting the binding complex with any one or any combination of a detergent, EDTA and/or water. In some embodiments, the present disclosure provides said method wherein the binding complex is deposited on, attached to, or hybridized to, a surface showing a contrast to noise ratio in the detecting step of greater than 20. In some embodiments, the present disclosure provides said method wherein the contacting is performed under a condition that stabilizes the binding complex when the nucleotide or nucleotide unit is complementary to a next base of the template nucleic acid, and destabilizes the binding complex when the nucleotide or nucleotide unit is not complementary to the next base of the template nucleic acid.

[0485] In some embodiments, in the methods for forming a plurality of complexed polymerases, including methods that employ multivalent molecules and/or nucleotides, the support comprises a planar or non-planar support. The support can be solid or semi-solid. In some embodiments, the support can be porous, semi-porous or non-porous. In some embodiments, the surface of the support can be coated with one or more compounds to produce a passivated layer on the support. In some embodiments, the passivated layer forms a porous or semi-porous layer. In some embodiments, the nucleic acid primer, template and/or polymerase, can be attached to the passivated layer to immobilize the primer, template and/or polymerase to the support. In some embodiments, the support comprises a low non-specific binding surface that enable improved nucleic acid hybridization and amplification performance on the support. In general, the support may comprise one or more layers of a covalently or non-covalently attached low-binding, chemical modification layers, e.g., silane layers, polymer films, and one or more covalently or non-covalently attached oligonucleotides that can be used for immobilizing a plurality of nucleic acid template molecules to the support (e.g., FIG. 1). In some embodiments, the support can comprise a functionalized polymer coating layer covalently bound at least to a portion of the support via a chemical group on the support, a primer grafted to the functionalized polymer coating, and a water-soluble protective coating on the primer and the functionalized polymer coating. In some embodiments, the functionalized polymer coating comprises a poly(N-(5- azidoacetamidylpentyl)acrylamide-co-acrylamide (PAZAM). In some embodiments, the support comprises a surface coating having at least one hydrophilic polymer coating layer and at least one layer of a plurality of oligonucleotides. The hydrophilic polymer coating layer can comprise polyethylene glycol (PEG). The hydrophilic polymer coating layer can comprise branched PEG having at least 4 branches. In some embodiments, the low nonspecific binding coating has a degree of hydrophilicity which can be measured as a water contact angle, where the water contact angle is no more than 45 degrees. In some embodiments, the density of the plurality of complexed polymerases immobilized to the support or immobilized to the coating on the support is about 10 ² - 10 ⁶ per mm ² , or about 10 ⁶ - 10 ⁹ per mm ² , or about 10 ⁹ - 10 ¹² per mm ² , or about 10 ¹² - 10 ¹⁵ per mm ² In some embodiments, the plurality of complexed polymerases is immobilized to the support or immobilized to the coating on the support at pre-determined sites on the support (or the coating on the support), or immobilized to the coating on the support at random sites on the support (or the coating on the support).

Methods for Nucleic Acid Sequencing

[0486] The present disclosure provides methods for determining the sequence of one or more nucleic acid template molecules, comprising: (a) contacting a plurality of a first mutant polymerase to (i) a plurality of nucleic acid template molecules and (ii) a plurality of nucleic acid primers, wherein the contacting is conducted under a condition suitable to bind the plurality of first mutant DNA polymerases to the plurality of nucleic acid template molecules and the plurality of nucleic acid primers thereby forming a plurality of first complexed polymerases each comprising a first mutant DNA polymerase bound to a nucleic acid duplex wherein the nucleic acid duplex comprises a nucleic acid template molecule hybridized to a nucleic acid primer. In some embodiments, the plurality of first mutant polymerases comprise a recombinant mutant polymerase. In some embodiments, the plurality of first mutant polymerases comprise a DNA polymerase. In some embodiments, the first mutant polymerases comprise an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99% identical, or a higher level sequence identity, to any of SEQ ID NOS: 1-2787 and 2789-2793. In some embodiments, the first mutant polymerases are recombinant polymerases. In some embodiments, the first mutant polymerases include amino acid substitutions that confer exonuclease-minus activity. In some embodiments, the first mutant polymerases exhibit desirable characteristics compared to a polymerase having a corresponding wild type amino acid backbone sequence (e.g., any of SEQ ID NOS: 1, 2, 1714 or 2789-2793). For example, the first mutant polymerases exhibit increased thermal stability (Tm). In another example, the first mutant polymerases exhibit increased incorporation rates of nucleotide analogs comprising a chain terminating moiety (e.g., blocking moiety) at the sugar 2’ position and/or at the 3’ sugar position. In yet another example, the first mutant polymerases exhibit increased uracil-tolerance. In some embodiments, the mutant DNA polymerases exhibit improved binding to a nucleotide reagent. In some embodiments, the mutant DNA polymerases exhibit improved binding and incorporation of a nucleotide reagent. In some embodiments, the mutant DNA polymerases exhibit reduced sequence-specific sequencing errors.

[0487] In some embodiments, in the methods for determining the sequence of one or more nucleic acid template molecules, the nucleotide reagents comprise any one or any combination of nucleotides and/or multivalent molecules. In some embodiments, the nucleotides comprise canonical nucleotides. In some embodiments, the nucleotides comprise non-labeled nucleotides. In some embodiments, the nucleotides comprise nucleotide analogs comprise detectably labeled nucleotides and/or nucleotides carrying a removable or nonremovable chain terminating moiety. In some embodiments, individual multivalent molecules comprise a central core attached to multiple polymer arms each having a nucleotide unit at the end of the arms.

[0488] In some embodiments, in the methods for determining the sequence of one or more nucleic acid template molecules, the primer comprises a 3’ extendible end or a 3’ nonextendible end. In some embodiments, the plurality of nucleic acid template molecules comprise amplified template molecules (e.g., clonally amplified template molecules). In some embodiments, the plurality of nucleic acid template molecules comprise one copy of a target sequence of interest. In some embodiments, the plurality of nucleic acid molecules comprise two or more tandem copies of a target sequence of interest (e.g., concatemers). In some embodiments, the nucleic acid template molecules in the plurality of nucleic acid template molecules comprise the same target sequence of interest or different target sequences of interest. In some embodiments, the plurality of nucleic acid template molecules and/or the plurality of nucleic acid primers are in solution or are immobilized to a support. In some embodiments, when the plurality of nucleic acid template molecules and/or the plurality of nucleic acid primers are immobilized to a support, the binding with the first recombinant mutant polymerase generates a plurality of immobilized first complexed polymerases. In some embodiments, the plurality of nucleic acid template molecules and/or nucleic acid primers are immobilized to 10 ² - 10 ¹⁵ different sites on a support. In some embodiments, the binding of the plurality of template molecules and nucleic acid primers with the plurality of first recombinant mutant polymerases generates a plurality of first complexed polymerases immobilized to 10 ² - 10 ¹⁵ different sites on the support. In some embodiments, the plurality of immobilized first complexed polymerases on the support are immobilized to predetermined or to random sites on the support. In some embodiments, the plurality of immobilized first complexed polymerases are in fluid communication with each other to permit flowing a solution of reagents (e.g., enzymes including polymerases, multivalent molecules, nucleotides, and/or divalent cations) onto the support so that the plurality of immobilized complexed polymerases on the support are reacted with the solution of reagents in a massively parallel manner.

[0489] In some embodiments, the methods for determining the sequence of one or more nucleic acid template molecules further comprises step (b): contacting the plurality of first complexed polymerases with a plurality of multivalent molecules to form a plurality of multivalent-complexed polymerases. In some embodiments, individual multivalent molecules in the plurality of multivalent molecules comprise a core attached to multiple nucleotide arms and each nucleotide arm is attached to a nucleotide (e.g., nucleotide unit). In some embodiments, the contacting of step (b) is conducted under a condition suitable for binding complementary nucleotide units of the multivalent molecules to at least two of the plurality of first complexed polymerases thereby forming a plurality of multivalent-complexed polymerases. In some embodiments, the condition is suitable for inhibiting incorporation of the complementary nucleotide units into the primers of the plurality of multivalent- complexed polymerases. In some embodiments, the plurality of multivalent molecules comprise at least one multivalent molecule having multiple nucleotide arms each attached with a nucleotide analog (e.g., nucleotide analog unit), where the nucleotide analog includes a chain terminating moiety at the sugar 2’ and/or 3’ position. In some embodiments, the plurality of multivalent molecules comprises at least one multivalent molecule comprising multiple nucleotide arms each attached with a nucleotide unit that lacks a chain terminating moiety. In some embodiments, at least one of the multivalent molecules in the plurality of multivalent molecules is labeled with a detectable reporter moiety. In some embodiments, the detectable reporter moiety comprises a fluorophore. In some embodiments, the contacting of step (b) is conducted in the presence of at least one cation selected from a group consisting of strontium, barium, sodium, magnesium, potassium, manganese, calcium, lithium, nickel and cobalt. In some embodiments, the contacting of step (b) is conducted in the presence of strontium, barium and/or calcium. [0490] In some embodiments, the methods for determining the sequence of one or more nucleic acid template molecules further comprises step (c): detecting the plurality of multivalent-complexed polymerases. In some embodiments, the detecting includes detecting the multivalent molecules that are bound to the complexed polymerases, where the complementary nucleotide units of the multivalent molecules are bound to the primers but incorporation of the complementary nucleotide units is inhibited. In some embodiments, the multivalent molecules are labeled with a detectable reporter moiety to permit detection. In some embodiments, the labeled multivalent molecules comprise a fluorophore attached to the core, linker and/or nucleotide unit of the multivalent molecules.

[0491] In some embodiments, the methods for determining the sequence of one or more nucleic acid template molecules further comprises step (d): identifying the base of the complementary nucleotide units that are bound to the plurality of first complexed polymerases, thereby determining the sequence of the nucleic acid template. In some embodiments, the multivalent molecules are labeled with a detectable reporter moiety that corresponds to the particular nucleotide units attached to the nucleotide arms to permit identification of the complementary nucleotide units (e.g., nucleotide base adenine, guanine, cytosine, thymine or uracil) that are bound to the plurality of first complexed polymerases. [0492] In some embodiments, in the methods for determining the sequence of one or more nucleic acid template molecules, the binding of the plurality of first complexed polymerases with the plurality of multivalent molecules forms at least one avidity complex, the method comprising the steps: (a) binding a first nucleic acid primer, a first DNA polymerase, and a first multivalent molecule to a first portion of a concatemer template molecule thereby forming a first binding complex (e.g., FIGs. 44-46), wherein a first nucleotide unit of the first multivalent molecule binds to the first DNA polymerase; and (b) binding a second nucleic acid primer, a second DNA polymerase, and the first multivalent molecule to a second portion of the same concatemer template molecule thereby forming a second binding complex (e.g., FIGs. 44-46), wherein a second nucleotide unit of the first multivalent molecule binds to the second DNA polymerase, wherein the first and second binding complexes which include the same multivalent molecule forms an avidity complex (e.g., FIG. 47). In some embodiments, the first polymerase comprises any mutant polymerase described herein. In some embodiments, the second polymerase comprises any mutant polymerase described herein. The concatemer template molecule comprises tandem repeat sequences of a sequence of interest and at least one universal sequencing primer binding site. The first and second nucleic acid primers can bind to a sequencing primer binding site along the concatemer template molecule.

[0493] In some embodiments, in the methods for determining the sequence of one or more nucleic acid template molecules, the method includes binding the plurality of first complexed polymerases with the plurality of multivalent molecules to form at least one avidity complex, the method comprising the steps: (a) contacting the plurality of DNA polymerases and the plurality of nucleic acid primers with different portions of a concatemer nucleic acid template molecule to form at least first and second complexed polymerases on the same concatemer template molecule (e.g., FIGs. 44-45); (b) contacting a plurality of multivalent molecules to the at least first and second complexed polymerases on the same concatemer template molecule, under conditions suitable to bind a single multivalent molecule from the plurality to the first and second complexed polymerases, wherein at least a first nucleotide unit of the single multivalent molecule is bound to the first complexed polymerase which includes a first primer hybridized to a first portion of the concatemer template molecule thereby forming a first binding complex (e.g., first ternary complex) (e.g., FIGs. 44-46), and wherein at least a second nucleotide unit of the single multivalent molecule is bound to the second complexed polymerase which includes a second primer hybridized to a second portion of the concatemer template molecule thereby forming a second binding complex (e.g., second ternary complex) (e.g., FIGs. 44-46), wherein the contacting is conducted under a condition suitable to inhibit polymerase-catalyzed incorporation of the bound first and second nucleotide units in the first and second binding complexes, and wherein the first and second binding complexes which are bound to the same multivalent molecule forms an avidity complex (e.g., FIG. 47); and (c) detecting the first and second binding complexes on the same concatemer template molecule, and (d) identifying the first nucleotide unit in the first binding complex thereby determining the sequence of the first portion of the concatemer template molecule, and identifying the second nucleotide unit in the second binding complex thereby determining the sequence of the second portion of the concatemer template molecule. In some embodiments, the plurality of DNA polymerases comprise any mutant polymerase described herein. The concatemer template molecule comprises tandem repeat sequences of a sequence of interest and at least one universal sequencing primer binding site. The plurality of nucleic acid primers can bind to a sequencing primer binding site along the concatemer template molecule.

[0494] In some embodiments, in the methods for determining the sequence of one or more nucleic acid template molecules, the binding of the plurality of first complexed polymerases with the plurality of multivalent molecules forms at least one avidity complex, the method comprising the steps: (a) binding a first nucleic acid primer, a first DNA polymerase, and a first multivalent molecule to a first template molecule thereby forming a first binding complex, wherein a first nucleotide unit of the first multivalent molecule binds to the first DNA polymerase; and (b) binding a second nucleic acid primer, a second DNA polymerase, and the first multivalent molecule to a second template molecule thereby forming a second binding complex, wherein a second nucleotide unit of the first multivalent molecule binds to the second DNA polymerase, wherein the first and second binding complexes which include the same multivalent molecule forms an avidity complex. In some embodiments, the first polymerase comprises any wild type or mutant polymerase described herein. In some embodiments, the second polymerase comprises any wild type or mutant polymerase described herein. In some embodiments, the first and second template molecules are clonally amplified template molecules. In some embodiments, the first and second template molecules are localized in close proximity to each other. For example, the clonally- amplified first and second template molecules comprise linear template molecules that are generated via bridge amplification and are immobilized to the same location or feature on a support. The first and second template molecules comprise a sequence of interest and at least one universal sequencing primer binding site. The first and second nucleic acid primers can bind to a sequencing primer binding site on the first and second template molecules, respectively.

[0495] In some embodiments, in the methods for determining the sequence of one or more nucleic acid template molecules, the method includes binding the plurality of first complexed polymerases with the plurality of multivalent molecules to form at least one avidity complex, the method comprising the steps: (a) contacting the plurality of DNA polymerases and the plurality of nucleic acid primers (which includes a first and second primer) with a first and second template molecule to form at least first and second complexed polymerases on the first and second template molecule, respectively; (b) contacting a plurality of multivalent molecules to the at least first and second complexed polymerases, under conditions suitable to bind a single multivalent molecule from the plurality to the first and second complexed polymerases, wherein at least a first nucleotide unit of the single multivalent molecule is bound to the first complexed polymerase which includes a first primer hybridized to the first template molecule thereby forming a first binding complex (e.g., first ternary complex), and wherein at least a second nucleotide unit of the single multivalent molecule is bound to the second complexed polymerase which includes a second primer hybridized to a second template molecule thereby forming a second binding complex (e.g., second ternary complex), wherein the contacting is conducted under a condition suitable to inhibit polymerase-catalyzed incorporation of the bound first and second nucleotide units in the first and second binding complexes, and wherein the first and second binding complexes which are bound to the same multivalent molecule forms an avidity complex; and (c) detecting the first and second binding complexes on the first and second template molecules, respectively, and (d) identifying the first nucleotide unit in the first binding complex thereby determining the sequence of the first template molecule, and identifying the second nucleotide unit in the second binding complex thereby determining the sequence of the second template molecule. In some embodiments, the plurality of DNA polymerases comprise any wild type or mutant polymerase described herein. The first and second template molecules are clonally amplified template molecules. In some embodiments, the first and second template molecules are localized in close proximity to each other. For example, the clonally-amplified first and second template molecules comprise linear template molecules that are generated via bridge amplification and are immobilized to the same location or feature on a support. The first and second template molecules comprise a sequence of interest and at least one universal sequencing primer binding site. The first and second nucleic acid primers can bind to a sequencing primer binding site on the first and second template molecules, respectively.

[0496] In some embodiments, the methods for determining the sequence of one or more nucleic acid template molecules further comprises step (e): dissociating the plurality of multivalent-complexed polymerases and removing the plurality of first mutant DNA polymerases and their bound multivalent molecules, and retaining the plurality of nucleic acid duplexes.

[0497] In some embodiments, the methods for determining the sequence of one or more nucleic acid template molecules further comprises step (f): contacting the plurality of the retained nucleic acid duplexes of step (e) with a plurality of second recombinant mutant DNA polymerases, wherein the contacting is conducted under a condition suitable for binding the plurality of second mutant DNA polymerases to the plurality of the retained nucleic acid duplexes, thereby forming a plurality of second complexed polymerases each comprising a second mutant DNA polymerase bound to a nucleic acid duplex. In some embodiments, the second mutant polymerases comprise an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99% identical, or a higher level sequence identity, to any of SEQ ID NOS: 1-2787 and 2789-2793. In some embodiments, the second mutant polymerases are recombinant polymerases. In some embodiments, the second mutant polymerases include amino acid substitutions that confer exonuclease-minus activity. In some embodiments, the second mutant polymerases exhibit desirable characteristics compared to a polymerase having a corresponding wild type amino acid backbone sequence (e.g., any of SEQ ID NOS: 1, 2, 1714 or 2789-2793). For example, the second mutant polymerases exhibit increased thermal stability (Tm). In another example, the second mutant polymerases exhibit increased incorporation rates of nucleotide analogs comprising a chain terminating moiety (e.g., blocking moiety) at the sugar 2’ position and/or at the 3’ sugar position. In yet another example, the second mutant polymerases exhibit increased uracil-tolerance.

[0498] In some embodiments, the plurality of first mutant polymerases of step (a) have an amino acid sequence that is 100% identical to the amino acid sequence as the plurality of the second mutant polymerases of step (f). In some embodiments, the plurality of first mutant polymerases of step (a) have an amino acid sequence that differs from the amino acid sequence of the plurality of the second mutant polymerases of step (f).

[0499] In some embodiments, the methods for determining the sequence of one or more nucleic acid template molecules further comprises step (g): contacting the plurality of second complexed polymerases with a plurality of nucleotides, wherein the contacting is conducted under a condition suitable for binding complementary nucleotides from the plurality of nucleotides to at least two of the second complexed polymerases thereby forming a plurality of nucleotide-complexed polymerases. In some embodiments, the contacting of step (g) is conducted under a condition that is suitable for promoting incorporation of the bound complementary nucleotides into the primers of the nucleotide-complexed polymerases thereby forming a plurality of nucleotide-complexed polymerases. In some embodiments, the incorporating the nucleotide into the 3’ end of the primer in step (g) comprises a primer extension reaction. In some embodiments, the contacting of step (g) is conducted in the presence of at least one cation selected from a group consisting of strontium, barium, sodium, magnesium, potassium, manganese, calcium, lithium, nickel and cobalt. In some embodiments, the contacting of step (g) is conducted in the presence of magnesium and/or manganese. In some embodiments, the plurality of nucleotides comprise native nucleotides (e.g., non-analog nucleotides) or nucleotide analogs. In some embodiments, the plurality of nucleotides comprise a 2’ and/or 3’ chain terminating moiety which is removable or is not removable. In some embodiments, the plurality of nucleotides comprises a plurality of nucleotides labeled with detectable reporter moiety. The detectable reporter moiety comprises a fluorophore. In some embodiments, the fluorophore is attached to the nucleotide base. In some embodiments, the fluorophore is attached to the nucleotide base with a linker which is cleavable/removable from the base or is not removable from the base. In some embodiments, at least one of the nucleotides in the plurality is not labeled with a detectable reporter moiety. In some embodiments, the plurality of nucleotides are non-labeled. In some embodiments, a particular detectable reporter moiety (e.g., fluorophore) that is attached to the nucleotide can correspond to the nucleotide base (e.g., dATP, dGTP, dCTP, dTTP or dUTP) to permit detection and identification of the nucleotide base. In some embodiments, individual labeled nucleotides comprise a fluorophore attached to one of the leaving phosphate groups in the phosphate chain, or the fluorophore can be attached to the nucleotide base with a linker which is cleavable/removable from the base. In some embodiments, when a fluorophore is attached to the nucleotide base, after incorporation of the labeled nucleotides, cleavage of the linker to remove the fluorophore generates an extended strand having at least a portion of the linker remaining which creates a scar. In some embodiments, when the plurality of nucleotides comprise non-labeled nucleotides, incorporation of the non-labeled nucleotides generates an extended strand lacking a scar.

[0500] In some embodiments, the methods for determining the sequence of one or more nucleic acid template molecules further comprise step (h): detecting the complementary nucleotides which are incorporated into the primers of the nucleotide-complexed polymerases. In some embodiments, the plurality of nucleotides are labeled with a detectable reporter moiety to permit detection. In some embodiments, in the methods for determining the sequence of one or more nucleic acid template molecules, the detecting step is omitted. [0501] In some embodiments, the methods for determining the sequence of one or more nucleic acid template molecules further comprises step (i): identifying the bases of the complementary nucleotides which are incorporated into the primers of the nucleotide- complexed polymerases. In some embodiments, the identification of the incorporated complementary nucleotides in step (i) can be used to confirm the identity of the complementary nucleotides of the multivalent molecules that are bound to the plurality of first complexed polymerases in step (d). In some embodiments, the identifying of step (i) can be used to determine the sequence of the nucleic acid template molecules. In some embodiments, in the methods for determining the sequence of one or more nucleic acid template molecules, the identifying step is omitted.

[0502] In some embodiments, the methods for determining the sequence of one or more nucleic acid template molecules further comprises step (j): removing the chain terminating moiety from the incorporated nucleotide when step (g) is conducted by contacting the plurality of second complexed polymerases with a plurality of nucleotides that comprise at least one nucleotide having a 2’ and/or 3’ chain terminating moiety.

[0503] In some embodiments, the methods for determining the sequence of one or more nucleic acid template molecules further comprises step (k): repeating steps (a) - (j) at least once. In some embodiments, the sequence of the nucleic acid template molecules can be determined by detecting and identifying the multivalent molecules that bind the mutant polymerases but do not incorporate into the 3’ end of the primer at steps (c) and (d). In some embodiments, the sequence of the nucleic acid template molecule can be determined (or confirmed) by detecting and identifying the nucleotide that incorporates into the 3’ end of the primer at steps (h) and (i).

[0504] In some embodiments, in the methods for determining the sequence of one or more nucleic acid template molecules, at least one multivalent molecule in the plurality of multivalent molecules of step (b) comprises: (1) a core; and (2) a plurality of nucleotide arms which comprise (i) a core attachment moiety, (ii) a spacer (e.g., comprising a PEG moiety), (iii) a linker, and (iv) a nucleotide unit, wherein the core is attached to the plurality of nucleotide arms, wherein the spacer is attached to the linker, wherein the linker is attached to the nucleotide unit. In some embodiments, the nucleotide unit comprises a base, sugar and at least one phosphate group, and the linker is attached to the nucleotide unit through the base. In some embodiments, the linker comprises an aliphatic chain or an oligo ethylene glycol chain where both linker chains having 2-6 subunits. In some embodiments, the linker also includes an aromatic moiety.

[0505] In some embodiments, in the methods for determining the sequence of one or more nucleic acid template molecules, individual multivalent molecules in the plurality of multivalent molecules of step (b) comprise a core attached to multiple nucleotide arms, and wherein the multiple nucleotide arms have the same type of nucleotide unit which is selected from a group consisting of dATP, dGTP, dCTP, dTTP and dUTP.

[0506] In some embodiments, in the methods for determining the sequence of one or more nucleic acid template molecules, the nucleotide unit of the at least one multivalent molecule of step (b) comprises an aromatic base, a five carbon sugar (e.g., ribose or deoxyribose), and one or more phosphate groups (e.g., 1-10 phosphate groups). The plurality of multivalent molecules can comprise one type multivalent molecule having one type of nucleotide unit selected from a group consisting of dATP, dGTP, dCTP, dTTP and dUTP. The plurality of multivalent molecules can comprise at a mixture of any combination of two or more types of multivalent molecules, where individual multivalent molecules in the mixture comprise nucleotide units selected from a group consisting of dATP, dGTP, dCTP, dTTP and/or dUTP.

[0507] In some embodiments, in the methods for determining the sequence of one or more nucleic acid template molecules, at least one multivalent molecule in the plurality of multivalent molecules of step (b) comprise a nucleotide unit having a chain of one, two or three phosphorus atoms where the chain is typically attached to the 5’ carbon of the sugar moiety via an ester or phosphoramide linkage. In some embodiments, at least one nucleotide unit is a nucleotide analog having a phosphorus chain in which the phosphorus atoms are linked together with intervening O, S, NH, methylene or ethylene. In some embodiments, the phosphorus atoms in the chain include substituted side groups including O, S or BH3. In some embodiments, the chain includes phosphate groups substituted with analogs including phosphoramidate, phosphorothioate, phosphordithioate, and O-methylphosphoroamidite groups.

[0508] In some embodiments, in the methods for determining the sequence of one or more nucleic acid template molecules, individual multivalent molecules in the plurality of multivalent molecule of step (b) comprise a core attached to multiple nucleotide arms, and wherein individual nucleotide arms comprise a nucleotide unit having a chain terminating moiety (e.g., blocking moiety) at the sugar 2’ position, at the sugar 3’ position, or at the sugar 2’ and 3’ position.

[0509] In some embodiments, in the methods for determining the sequence of one or more nucleic acid template molecules, at least one multivalent molecule in the plurality of multivalent molecules of step (b) comprises a nucleotide unit comprising a terminator nucleotide analog having a chain terminating moiety (e.g., blocking moiety) at the sugar 2’ position, at the sugar 3’ position, or at the sugar 2’ and 3’ position. In some embodiments, the chain terminating moiety can inhibit polymerase-catalyzed incorporation of a subsequent nucleotide unit or free nucleotide in a nascent strand during a primer extension reaction. In some embodiments, the chain terminating moiety is attached to the 3’ sugar hydroxyl position where the sugar comprises a ribose or deoxyribose sugar moiety. In some embodiments, the chain terminating moiety is removable/cleavable from the 3’ sugar hydroxyl position to generate a nucleotide having a 3 ’OH sugar group which is extendible with a subsequent nucleotide in a polymerase-catalyzed nucleotide incorporation reaction. In some embodiments, the chain terminating moiety comprises an alkyl group, alkenyl group, alkynyl group, allyl group, aryl group, benzyl group, azide group, amine group, amide group, keto group, isocyanate group, phosphate group, thio group, disulfide group, carbonate group, urea group, or silyl group. In some embodiments, the chain terminating moiety is cleavable/removable from the nucleotide unit, for example by reacting the chain terminating moiety with a chemical agent, pH change, light or heat. In some embodiments, the chain terminating moieties alkyl, alkenyl, alkynyl and allyl are cleavable with tetrakis(triphenylphosphine)palladium(0) (Pd(PPh3)4) with piperidine, or with 2,3-Dichloro- 5,6-dicyano-l,4-benzo-quinone (DDQ). In some embodiments, the chain terminating moieties aryl and benzyl are cleavable with H2 Pd/C. In some embodiments, the chain terminating moieties amine, amide, keto, isocyanate, phosphate, thio, disulfide are cleavable with phosphine or with a thiol group including beta-mercaptoethanol or dithiothritol (DTT). In some embodiments, the chain terminating moiety carbonate is cleavable with potassium carbonate (K2CO3) in MeOH, with triethylamine in pyridine, or with Zn in acetic acid (AcOH). In some embodiments, the chain terminating moieties urea and silyl are cleavable with tetrabutylammonium fluoride, pyridine-HF, with ammonium fluoride, or with triethylamine trihydrofluoride. In some embodiments, the chain terminating moiety may be cleavable/removable with nitrous acid. In some embodiments, a chain terminating moiety may be cleavable/removable using a solution comprising nitrite, such as, for example, a combination of nitrite with an acid such as acetic acid, sulfuric acid, or nitric acid. In some further embodiments, said solution may comprise an organic acid.

[0510] In some embodiments, in the methods for determining the sequence of one or more nucleic acid template molecules, at least one multivalent molecule in the plurality of multivalent molecules of step (b) comprises a nucleotide unit comprising a terminator nucleotide analog having a chain terminating moiety (e.g., blocking moiety) at the sugar 2’ position, at the sugar 3’ position, or at the sugar 2’ and 3’ position. In some embodiments, the chain terminating moiety comprises an azide, azido or azidomethyl group. In some embodiments, the chain terminating moiety comprises a 3’-O-azido or 3’-O-azidomethyl group. In some embodiments, the chain terminating moieties azide, azido and azidomethyl group are cleavable/removable with a phosphine compound. In some embodiments, the phosphine compound comprises a derivatized tri-alkyl phosphine moiety or a derivatized triaryl phosphine moiety. In some embodiments, the phosphine compound comprises Tris(2- carboxyethyl)phosphine (TCEP) or bis-sulfo triphenyl phosphine (BS-TPP) or Tri(hydroxyproyl)phosphine (THPP). In some embodiments, the cleaving agent comprises 4- dimethylaminopyridine (4-DMAP). In some embodiments, the chain terminating moiety comprising one or more of a 3’-O-amino group, a 3’-O-aminomethyl group, a 3’-O- methylamino group, or derivatives thereof may be cleaved with nitrous acid, through a mechanism utilizing nitrous acid, or using a solution comprising nitrous acid. In some embodiments, the chain terminating moiety comprising one or more of a 3’-O-amino group, a 3’-O-aminomethyl group, a 3’-O-methylamino group, or derivatives thereof may be cleaved using a solution comprising nitrite. In some embodiments, for example, nitrite may be combined with or contacted with an acid such as acetic acid, sulfuric acid, or nitric acid. In some further embodiments, for example, nitrite may be combined with or contacted with an organic acid such as, for example, formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, or the like. In some embodiments, the chain terminating moiety comprises a 3’-acetal moiety which can be cleaved with a palladium deblocking reagent (e.g., Pd(0)). [0511] In some embodiments, in the methods for determining the sequence of one or more nucleic acid template molecules, at least one multivalent molecule in the plurality of multivalent molecules of step (b) comprises a nucleotide unit comprising a chain terminating moiety which is selected from a group consisting of 3’-deoxy nucleotides, 2’,3’- dideoxynucleotides, 3 ’-methyl, 3 ’-azido, 3 ’-azidomethyl, 3’-O-azidoalkyl, 3’-O-ethynyl, 3’- O-aminoalkyl, 3’-O-fluoroalkyl, 3’-fluoromethyl, 3 ’-difluoromethyl, 3 ’-trifluoromethyl, 3’- sulfonyl, 3’-malonyl, 3’-amino, 3’-O-amino, 3’-sulfhydral, 3 ’-aminomethyl, 3’-ethyl, 3’butyl, 3 ’-tert butyl, 3’- Fluorenylmethyloxy carbonyl, 3’ tert-Butyloxycarbonyl, 3’-O-alkyl hydroxylamino group, 3’-phosphorothioate, 3’-O-benzyl, and 3 ’-acetal moiety, or derivatives thereof.

[0512] In some embodiments, in the methods for determining the sequence of one or more nucleic acid template molecules, at least one multivalent molecule in the plurality of multivalent molecules of step (b) comprises a core attached to multiple nucleotide arms, wherein the nucleotide arms comprise a spacer, linker and nucleotide unit, and wherein the core, linker and/or nucleotide unit is labeled with detectable reporter moiety. In some embodiments, the detectable reporter moiety comprises a fluorophore. In some embodiments, a particular detectable reporter moiety (e.g., fluorophore) that is attached to the multivalent molecule can correspond to the base (e.g., dATP, dGTP, dCTP, dTTP or dUTP) of the nucleotide unit to permit detection and identification of the nucleotide base.

[0513] In some embodiments, in the methods for determining the sequence of one or more nucleic acid template molecules, at least one nucleotide arm of a multivalent molecule in the plurality of multivalent molecules of step (b) has a nucleotide unit that is attached to a detectable reporter moiety. In some embodiments, the detectable reporter moiety is attached to the nucleotide base. In some embodiments, the detectable reporter moiety comprises a fluorophore. In some embodiments, a particular detectable reporter moiety (e.g., fluorophore) that is attached to the multivalent molecule can correspond to the base (e.g., dATP, dGTP, dCTP, dTTP or dUTP) of the nucleotide unit to permit detection and identification of the nucleotide base.

[0514] In some embodiments, in the methods for determining the sequence of one or more nucleic acid template molecules, the core of a multivalent molecule of step (b) comprises an avidin-like moiety and the core attachment moiety comprises biotin. In some embodiments, the core comprises an streptavidin-type or avidin-type moiety which includes an avidin protein, as well as any derivatives, analogs and other non-native forms of avidin that can bind to at least one biotin moiety. Other forms of avidin moieties include native and recombinant avidin and streptavidin as well as derivatized molecules, e.g. nonglycosylated avidin and truncated streptavidins . For example, avidin moiety includes deglycosylated forms of avidin, bacterial streptavidin produced by Streptomyces (e.g., Streptomyces avidinii), as well as derivatized forms, for example, N- acyl avidins, e.g., N-acetyl, N-phthalyl and N-succinyl avidin, and the commercially- available products ExtrAvidin™, Captavidin™, Neutravidin™’ and Neutralite Avidin™. [0515] In some embodiments, in the methods for determining the sequence of one or more nucleic acid template molecules, the each of the steps (a) - (j) are conducted at a temperature which is selected from a temperature range of about 25-90 °C. In some embodiments, the contacting of steps (a) and (b) are conducted at a constant temperature which is selected from a temperature range of about 25-90 °C (e.g., isothermal temperature). In some embodiments, the detecting and identifying of steps (c) and (d) are conducted at a constant temperature which is selected from a temperature range of about 25-90 °C (e.g., isothermal temperature). In some embodiments, the dissociating of step (e) is conducted at a constant temperature which is selected from a temperature range of about 25-90 °C (e.g., isothermal temperature). In some embodiments, the contacting of steps (f) and (g) are conducted at a constant temperature which is selected from a temperature range of about 25- 90 °C (e.g., isothermal temperature). In some embodiments, the detecting and identifying of steps (h) and (i) are conducted at a constant temperature which is selected from a temperature range of about 25-90 °C (e.g., isothermal temperature). In some embodiments, the removing of step (j) is conducted at a constant temperature which is selected from a temperature range of about 25-90 °C (e.g., isothermal temperature). In some embodiments, the steps (a) - (j) are conducted at a constant temperature which is selected from a temperature range of about 25- 90 °C (e.g., isothermal temperature). [0516] In some embodiments, a sequencing reaction or a binding assay can be conducted by binding a plurality of fluorescently-labeled multivalent molecules to a mutant polymerase, and the resulting binding complexes can exhibit reduced error rate, reduced phasing and/or improved signal intensity compared to conducting the same sequencing reaction or assay with a corresponding wild type polymerase or a reference polymerase.

[0517] In some embodiments, the mutant polymerases used to conduct the sequencing reaction or assay comprise an amino acid sequence that is at least 99%, at least 98%, at least 97%, at least 95%, at least 90% at least 85%, at least 80%, at least 75%, at least 70% identical to any of SEQ ID NOS: 1-1713 (e.g., RLF 89458.1 or RLF 78286.1 backbone sequences).

[0518] In some embodiments, the mutant polymerases used to conduct the sequencing reaction or assay comprise an amino acid sequence that is at least 99%, at least 98%, at least 97%, at least 95%, at least 90% at least 85%, at least 80%, at least 75%, at least 70% identical to any of SEQ ID NOS: 1714-2787 (e.g., NOZ 58130 backbone sequence).

[0519] In some embodiments, the mutant polymerases used to conduct the sequencing reaction or assay comprise an amino acid sequence that is at least 99%, at least 98%, at least 97%, at least 95%, at least 90% at least 85%, at least 80%, at least 75%, at least 70% identical to SEQ ID NO: 2789 (e.g., RMF 90817 backbone sequence).

[0520] In some embodiments, the mutant polymerases used to conduct the sequencing reaction or assay comprise an amino acid sequence that is at least 99%, at least 98%, at least 97%, at least 95%, at least 90% at least 85%, at least 80%, at least 75%, at least 70% identical to SEQ ID NO: 2790 (e.g., MBC 7218772 backbone sequence).

[0521] In some embodiments, the mutant polymerases used to conduct the sequencing reaction or assay comprise an amino acid sequence that is at least 99%, at least 98%, at least 97%, at least 95%, at least 90% at least 85%, at least 80%, at least 75%, at least 70% identical to SEQ ID NO: 2791 (e.g., WP 175059460 backbone sequence).

[0522] In some embodiments, the mutant polymerases used to conduct the sequencing reaction or assay comprise an amino acid sequence that is at least 99%, at least 98%, at least 97%, at least 95%, at least 90% at least 85%, at least 80%, at least 75%, at least 70% identical to SEQ ID NO: 2792 (e.g., KUO 42443 backbone sequence).

[0523] In some embodiments, the mutant polymerases used to conduct the sequencing reaction or assay comprise an amino acid sequence that is at least 99%, at least 98%, at least 97%, at least 95%, at least 90% at least 85%, at least 80%, at least 75%, at least 70% identical to SEQ ID NO: 2793 (e.g., NOZ 77387 backbone sequence). [0524] In some embodiments, in the methods for determining the sequence of one or more nucleic acid template molecules, at least one nucleotide in the plurality of nucleotides of step (g) comprise a base, sugar and at least one phosphate group. In some embodiments, at least one nucleotide in the plurality comprises an aromatic base, a five carbon sugar (e.g., ribose or deoxyribose), and one or more phosphate groups (e.g., 1-10 phosphate groups). The plurality of nucleotides can comprise at least one type of nucleotide selected from a group consisting of dATP, dGTP, dCTP, dTTP and dUTP. The plurality of nucleotides can comprise at a mixture of any combination of two or more types of nucleotides selected from a group consisting of dATP, dGTP, dCTP, dTTP and/or dUTP. In some embodiments, at least one nucleotide in the plurality is not a nucleotide analog. In some embodiments, at least one nucleotide in the plurality comprises a nucleotide analog.

[0525] In some embodiments, in the methods for determining the sequence of one or more nucleic acid template molecules, at least one nucleotide in the plurality of nucleotides of step (g) comprise a chain of one, two or three phosphorus atoms where the chain is typically attached to the 5’ carbon of the sugar moiety via an ester or phosphoramide linkage. In some embodiments, at least one nucleotide in the plurality is an analog having a phosphorus chain in which the phosphorus atoms are linked together with intervening O, S, NH, methylene or ethylene. In some embodiments, the phosphorus atoms in the chain include substituted side groups including O, S or BH3. In some embodiments, the chain includes phosphate groups substituted with analogs including phosphoramidate, phosphorothioate, phosphordithioate, and O-methylphosphoroamidite groups.

[0526] In some embodiments, in the methods for determining the sequence of one or more nucleic acid template molecules, at least one nucleotide in the plurality of nucleotides of step (g) comprises a terminator nucleotide analog having a chain terminating moiety (e.g., blocking moiety) at the sugar 2’ position, at the sugar 3’ position, or at the sugar 2’ and 3’ position. In some embodiments, the chain terminating moiety can inhibit polymerase- catalyzed incorporation of a subsequent nucleotide unit or free nucleotide in a nascent strand during a primer extension reaction. In some embodiments, the chain terminating moiety is attached to the 3’ sugar hydroxyl position where the sugar comprises a ribose or deoxyribose sugar moiety. In some embodiments, the chain terminating moiety is removable/cleavable from the 3’ sugar hydroxyl position to generate a nucleotide having a 3 ’OH sugar group which is extendible with a subsequent nucleotide in a polymerase-catalyzed nucleotide incorporation reaction. In some embodiments, the chain terminating moiety comprises an alkyl group, alkenyl group, alkynyl group, allyl group, aryl group, benzyl group, azide group, amine group, amide group, keto group, isocyanate group, phosphate group, thio group, disulfide group, carbonate group, urea group, silyl or acetal group. In some embodiments, the chain terminating moiety is cleavable/removable from the nucleotide, for example by reacting the chain terminating moiety with a chemical agent, pH change, light or heat. In some embodiments, the chain terminating moieties alkyl, alkenyl, alkynyl and allyl are cleavable with tetrakis(triphenylphosphine)palladium(0) (Pd(PPh3)4) with piperidine, or with 2,3-Dichloro-5,6-dicyano-l,4-benzo-quinone (DDQ). In some embodiments, the chain terminating moieties aryl and benzyl are cleavable with H2 Pd/C. In some embodiments, the chain terminating moieties amine, amide, keto, isocyanate, phosphate, thio, disulfide are cleavable with phosphine or with a thiol group including beta-mercaptoethanol or dithiothritol (DTT). In some embodiments, the chain terminating moiety carbonate is cleavable with potassium carbonate (K2CO3) in MeOH, with triethylamine in pyridine, or with Zn in acetic acid (AcOH). In some embodiments, the chain terminating moieties urea and silyl are cleavable with tetrabutylammonium fluoride, pyridine-HF, with ammonium fluoride, or with triethylamine trihydrofluoride. In some embodiments, the chain terminating moiety may be cleavable/removable with nitrous acid. In some embodiments, a chain terminating moiety may be cleavable/removable using a solution comprising nitrite, such as, for example, a combination of nitrite with an acid such as acetic acid, sulfuric acid, or nitric acid. In some further embodiments, said solution may comprise an organic acid.

[0527] In some embodiments, in the methods for determining the sequence of one or more nucleic acid template molecules, at least one nucleotide in the plurality of nucleotides of step (g) comprises a terminator nucleotide analog having a chain terminating moiety (e.g., blocking moiety) at the sugar 2’ position, at the sugar 3’ position, or at the sugar 2’ and 3’ position. In some embodiments, the chain terminating moiety comprises an azide, azido or azidomethyl group. In some embodiments, the chain terminating moiety comprises a 3’-O- azido or 3’-O-azidomethyl group. In some embodiments, the chain terminating moieties azide, azido and azidomethyl group are cleavable/removable with a phosphine compound. In some embodiments, the phosphine compound comprises a derivatized tri-alkyl phosphine moiety or a derivatized tri-aryl phosphine moiety. In some embodiments, the phosphine compound comprises Tris(2-carboxyethyl)phosphine (TCEP) or bis-sulfo triphenyl phosphine (BS-TPP) or Tri(hydroxyproyl)phosphine (THPP). In some embodiments, the cleaving agent comprises 4-dimethylaminopyridine (4-DMAP). In some embodiments, the chain terminating moiety comprising one or more of a 3’-O-amino group, a 3’-O- aminom ethyl group, a 3 ’-O-m ethylamino group, or derivatives thereof may be cleaved with nitrous acid, through a mechanism utilizing nitrous acid, or using a solution comprising nitrous acid. In some embodiments, the chain terminating moiety comprising one or more of a 3’-O-amino group, a 3’-O-aminomethyl group, a 3 ’-O-m ethylamino group, or derivatives thereof may be cleaved using a solution comprising nitrite. In some embodiments, for example, nitrite may be combined with or contacted with an acid such as acetic acid, sulfuric acid, or nitric acid. In some embodiments, the chain terminating moiety comprises a 3’- acetal moiety which can be cleaved with a palladium deblocking reagent (e.g., Pd(0)). In some further embodiments, for example, nitrite may be combined with or contacted with an organic acid such as, for example, formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, or the like.

[0528] In some embodiments, in the methods for determining the sequence of one or more nucleic acid template molecules, at least one nucleotide in the plurality of nucleotides of step (g) comprises a chain terminating moiety which is selected from a group consisting of 3 ’-deoxy nucleotides, 2’, 3 ’-dideoxynucleotides, 3 ’-methyl, 3 ’-azido, 3 ’-azidomethyl, 3’-O- azidoalkyl, 3’-O-ethynyl, 3’-O-aminoalkyl, 3’-O-fluoroalkyl, 3’-fluoromethyl, 3’- difluoromethyl, 3’-trifluoromethyl, 3’-sulfonyl, 3’-malonyl, 3’-amino, 3’-O-amino, 3’- sulfhydral, 3 ’-aminomethyl, 3’-ethyl, 3’butyl, 3" -tert butyl, 3’- Fluorenylmethyloxy carbonyl, 3’ tert-Butyloxycarbonyl, 3’-O-alkyl hydroxylamino group, 3’-phosphorothioate, 3’-O- benzyl, and 3 ’-acetal moiety, or derivatives thereof.

[0529] In some embodiments, in the methods for determining the sequence of one or more nucleic acid template molecules, at least one nucleotide in the plurality of nucleotides of step (g) comprises detectable reporter moiety (e.g., at least one labeled nucleotide). The detectable reporter moiety comprises a fluorophore. In some embodiments, the fluorophore is attached to the nucleotide base. In some embodiments, the fluorophore is attached to the nucleotide base with a linker which is cleavable/removable from the base. In some embodiments, at least one of the nucleotides in the plurality is not labeled with a detectable reporter moiety. In some embodiments, a particular detectable reporter moiety (e.g., fluorophore) that is attached to the nucleotide can correspond to the nucleotide base (e.g., dATP, dGTP, dCTP, dTTP or dUTP) to permit detection and identification of the nucleotide base.

[0530] In some embodiments, in the methods for determining the sequence of one or more nucleic acid template molecules, at least one nucleotide in the plurality of nucleotides of step (g) comprises a cleavable linker on the base which comprises a cleavable (e.g., removable) moiety comprising an alkyl group, alkenyl group, alkynyl group, allyl group, aryl group, benzyl group, azide group, amine group, amide group, keto group, isocyanate group, phosphate group, thio group, disulfide group, carbonate group, urea group, or silyl group. In some embodiments, the cleavable linker on the base is cleavable/removable from the base by reacting the cleavable moiety with a chemical agent, pH change, light or heat. In some embodiments, the cleavable moieties alkyl, alkenyl, alkynyl and allyl are cleavable with tetrakis(triphenylphosphine)palladium(0) (Pd(PPh3)4) with piperidine, or with 2,3-Dichloro- 5,6-dicyano-l,4-benzo-quinone (DDQ). In some embodiments, the cleavable moieties aryl and benzyl are cleavable with H2 Pd/C. In some embodiments, the cleavable moieties amine, amide, keto, isocyanate, phosphate, thio, disulfide are cleavable with phosphine or with a thiol group including beta-mercaptoethanol or dithiothritol (DTT). In some embodiments, the cleavable moiety carbonate is cleavable with potassium carbonate (K2CO3) in MeOH, with triethylamine in pyridine, or with Zn in acetic acid (AcOH). In some embodiments, the cleavable moieties urea and silyl are cleavable with tetrabutylammonium fluoride, pyridine- HF, with ammonium fluoride, or with triethylamine trihydrofluoride.

[0531] In some embodiments, in the methods for determining the sequence of one or more nucleic acid template molecules, at least one nucleotide in the plurality of nucleotides of step (g) comprises a cleavable linker on the base which comprises cleavable moiety including an azide, azido or azidomethyl group. In some embodiments, the cleavable moieties azide, azido and azidomethyl group are cleavable/removable with a phosphine compound. In some embodiments, the phosphine compound comprises a derivatized tri-alkyl phosphine moiety or a derivatized tri-aryl phosphine moiety. In some embodiments, the phosphine compound comprises Tris(2-carboxyethyl)phosphine (TCEP) or bis-sulfo triphenyl phosphine (BS-TPP) or Tri(hydroxyproyl)phosphine (THPP). In some embodiments, the cleaving agent comprises 4-dimethylaminopyridine (4-DMAP).

[0532] In some embodiments, in the methods for determining the sequence of one or more nucleic acid template molecules, at least one nucleotide in the plurality of nucleotides of step (g) comprises a chain terminating moiety on the sugar 2’ and/or sugar 3’ position. In some embodiments, the chain terminating moiety on the sugar and the cleavable linker on the base have the same or different cleavable moieties. In some embodiments, the chain terminating moiety (e.g., at the sugar 2’ and/or sugar 3’ position) and the detectable reporter moiety linked to the base are chemically cleavable/removable with the same chemical agent. In some embodiments, the chain terminating moiety (e.g., at the sugar 2’ and/or sugar 3’ position) and the detectable reporter moiety linked to the base are chemically cleavable/removable with different chemical agents. [0533] In some embodiments, in the methods for sequencing, the binding complex comprises a mutant polymerase, a nucleic acid template molecule duplexed with a primer, and a nucleotide reagent. In some embodiments, in the methods for sequencing which comprises forming a binding complex, where the binding complex comprises (i) a mutant polymerase, a nucleic acid template molecule duplexed with a primer, and a nucleotide, or the binding complex comprises (ii) a mutant polymerase, a nucleic acid template molecule duplexed with a primer, and a nucleotide unit of a multivalent molecule. In some embodiments, the mutant polymerase comprises an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99% identical, or a higher level sequence identity, to any of SEQ ID NOS: 1-2787 and 2789-2793. In some embodiments, the binding complex has a persistence time of greater than about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1 second. In some embodiments, the binding complex has a persistence time of 1-30 seconds. The binding complex has a persistence time of greater than about 0.1-0.25 seconds, or about 0.25-0.5 seconds, or about 0.5-0.75 seconds, or about 0.75-1 second, or about 1-2 seconds, or about 2-3 seconds, or about 3-4 second, or about 4-5 seconds, or about 5-10 seconds, or about 10-30 seconds and/or wherein the method is or may be carried out at a temperature of at or above 15 °C, at or above 20 °C, at or above 25 °C, at or above 35 °C, at or above 37 °C, at or above 42 °C at or above 55 °C at or above 60 °C, or at or above 72 °C, or at or above 80 °C, or within a range defined by any of the foregoing. In some embodiments, the binding complexes may have a persistence time of greater than Is, greater than 2s, greater than 3s, greater than 5s, greater than 10s, greater than 15s, greater than 20s, greater than 30s, greater than 60s, greater than 120s, greater than 360s, greater than 3600s, or more, or for a time lying within a range defined by any two or more of these values. The binding complex (e.g., ternary complex) remains stable until subjected to a condition that causes dissociation of interactions between any of the polymerase, template molecule, primer and/or the nucleotide unit or the nucleotide. For example, a dissociating condition comprises contacting the binding complex with any one or any combination of a detergent, EDTA and/or water. In some embodiments, the present disclosure provides said method wherein the binding complex is deposited on, attached to, or hybridized to, a surface showing a contrast to noise ratio in the detecting step of greater than 20. In some embodiments, the present disclosure provides said method wherein the contacting is performed under a condition that stabilizes the binding complex when the nucleotide or nucleotide unit is complementary to a next base of the template nucleic acid, and destabilizes the binding complex when the nucleotide or nucleotide unit is not complementary to the next base of the template nucleic acid. [0534] In some embodiments, in any of the methods for determining the sequence of one or more nucleic acid template molecules, the support comprises a planar or non-planar support. The support can be solid or semi-solid. In some embodiments, the support can be porous, semi-porous or non-porous. In some embodiments, the surface of the support can be coated with one or more compounds to produce a passivated layer on the support. In some embodiments, the passivated layer forms a porous or semi-porous layer. In some embodiments, the nucleic acid primer, template and/or polymerase, can be attached to the passivated layer to immobilize the primer, template and/or polymerase to the support. In some embodiments, the support comprises a low non-specific binding surface that enable improved nucleic acid hybridization and amplification performance on the support. In general, the support may comprise one or more layers of a covalently or non-covalently attached low-binding, chemical modification layers, e.g., silane layers, polymer films, and one or more covalently or non-covalently attached oligonucleotides that can be used for immobilizing a plurality of nucleic acid template molecules to the support (e.g., FIG. 1). In some embodiments, the support can comprise a functionalized polymer coating layer covalently bound at least to a portion of the support via a chemical group on the support, a primer grafted to the functionalized polymer coating, and a water-soluble protective coating on the primer and the functionalized polymer coating. In some embodiments, the functionalized polymer coating comprises a poly(N-(5-azidoacetamidylpentyl)acrylamide-co- acrylamide (PAZAM). In some embodiments, the support comprises a surface coating having at least one hydrophilic polymer coating layer and at least one layer of a plurality of oligonucleotides. The hydrophilic polymer coating layer can comprise polyethylene glycol (PEG). The hydrophilic polymer coating layer can comprise branched PEG having at least 4 branches. In some embodiments, the low non-specific binding coating has a degree of hydrophilicity which can be measured as a water contact angle, where the water contact angle is no more than 45 degrees. In some embodiments, the density of the plurality of first complexed polymerases immobilized to the support or immobilized to the coating on the support is about 10 ² - 10 ⁶ per mm ² , or about 10 ⁶ - 10 ⁹ per mm ² , or about 10 ⁹ - 10 ¹² per mm ² . In some embodiments, the plurality of first complexed polymerases is immobilized to the support or immobilized to the coating on the support at pre-determined sites on the support (or the coating on the support), or immobilized to the coating on the support at random sites on the support (or the coating on the support).

[0535] In some embodiments, the support is passivated with a low non-specific binding coating. The surface coatings described herein exhibit very low non-specific binding to reagents typically used for nucleic acid capture, amplification and sequencing workflows, such as dyes, nucleotides, enzymes, and nucleic acid primers. The surface coatings exhibit low background fluorescence signals or high contrast-to-noise (CNR) ratios compared to conventional surface coatings.

[0536] The low non-specific binding coating comprises one layer or multiple layers. In some embodiments, the plurality of surface primers are immobilized to the low non-specific binding coating. In some embodiments, at least one surface primer is embedded within the low non-specific binding coating. The low non-specific binding coating enables improved nucleic acid hybridization and amplification performance. In general, the supports comprise a substrate (or support structure), one or more layers of a covalently or non-covalently attached low-binding, chemical modification layers, e.g., silane layers, polymer films, and one or more covalently or non-covalently attached surface primers that can be used for tethering singlestranded nucleic acid library molecules to the support (e.g., FIG. 1). In some embodiments, the formulation of the coating, e.g., the chemical composition of one or more layers, the coupling chemistry used to cross-link the one or more layers to the support and/or to each other, and the total number of layers, may be varied such that non-specific binding of proteins, nucleic acid molecules, and other hybridization and amplification reaction components to the coating is minimized or reduced relative to a comparable monolayer. The formulation of the coating described herein may be varied such that non-specific hybridization on the coating is minimized or reduced relative to a comparable monolayer. The formulation of the coating may be varied such that non-specific amplification on the coating is minimized or reduced relative to a comparable monolayer. The formulation of the coating may be varied such that specific amplification rates and/or yields on the coating are maximized. Amplification levels suitable for detection are achieved in no more than 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, or more than 30 amplification cycles in some cases disclosed herein.

[0537] The support structure that comprises the one or more chemically-modified layers, e.g., layers of a low non-specific binding polymer, may be independent or integrated into another structure or assembly. For example, in some embodiments, the support structure may comprise one or more surfaces within an integrated or assembled microfluidic flow cell. The support structure may comprise one or more surfaces within a microplate format, e.g., the bottom surface of the wells in a microplate. In some embodiments, the support structure comprises the interior surface (such as the lumen surface) of a capillary. In some embodiments, the support structure comprises the interior surface (such as the lumen surface) of a capillary etched into a planar chip.

[0538] The attachment chemistry used to graft a first chemically-modified layer to the surface of the support will generally be dependent on both the material from which the surface is fabricated and the chemical nature of the layer. In some embodiments, the first layer may be covalently attached to the surface. In some embodiments, the first layer may be non-covalently attached, e.g., adsorbed to the support through non-covalent interactions such as electrostatic interactions, hydrogen bonding, or van der Waals interactions between the support and the molecular components of the first layer. In either case, the support may be treated prior to attachment or deposition of the first layer. Any of a variety of surface preparation techniques known to those of skill in the art may be used to clean or treat the surface. For example, glass or silicon surfaces may be acid-washed using a Piranha solution (a mixture of sulfuric acid (H2SO4) and hydrogen peroxide (H2O2)), base treatment in KOH and NaOH, and/or cleaned using an oxygen plasma treatment method.

[0539] Silane chemistries constitute non-limiting approaches for covalently modifying the silanol groups on glass or silicon surfaces to attach more reactive functional groups (e.g., amines or carboxyl groups), which may then be used in coupling linker molecules (e.g., linear hydrocarbon molecules of various lengths, such as C6, Cl 2, Cl 8 hydrocarbons, or linear polyethylene glycol (PEG) molecules) or layer molecules (e.g., branched PEG molecules or other polymers) to the surface. Examples of suitable silanes that may be used in creating any of the disclosed low binding coatings include, but are not limited to, (3 -Aminopropyl) trimethoxy silane (APTMS), (3 -Aminopropyl) tri ethoxy silane (APTES), any of a variety of PEG-silanes (e.g., comprising molecular weights of IK, 2K, 5K, 10K, 20K, etc.), amino-PEG silane (i.e., comprising a free amino functional group), maleimide-PEG silane, biotin-PEG silane, and the like.

[0540] Any of a variety of molecules known to those of skill in the art including, but not limited to, amino acids, peptides, nucleotides, oligonucleotides, other monomers or polymers, or combinations thereof may be used in creating the one or more chemically-modified layers on the support, where the choice of components used may be varied to alter one or more properties of the layers, e.g., the surface density of functional groups and/or tethered oligonucleotide primers, the hydrophilicity /hydrophobicity of the layers, or the three three- dimensional nature (i.e., “thickness”) of the layer. Examples of polymers that may be used to create one or more layers of low non-specific binding material in any of the disclosed coatings include, but are not limited to, polyethylene glycol (PEG) of various molecular weights and branching structures, streptavidin, polyacrylamide, polyester, dextran, polylysine, and poly-lysine copolymers, or any combination thereof. Examples of conjugation chemistries that may be used to graft one or more layers of material (e.g. polymer layers) to the surface and/or to cross-link the layers to each other include, but are not limited to, biotinstreptavidin interactions (or variations thereof), his tag - Ni/NTA conjugation chemistries, methoxy ether conjugation chemistries, carboxylate conjugation chemistries, amine conjugation chemistries, NHS esters, maleimides, thiol, epoxy, azide, hydrazide, alkyne, isocyanate, and silane.

[0541] The low non-specific binding surface coating may be applied uniformly across the support. Alternatively, the surface coating may be patterned, such that the chemical modification layers are confined to one or more discrete regions of the support. For example, the coating may be patterned using photolithographic techniques to create an ordered array or random pattern of chemically-modified regions on the support. Alternately or in combination, the coating may be patterned using, e.g., contact printing and/or ink-jet printing techniques. In some embodiments, an ordered array or random pattern of chemically- modified regions may comprise at least 1, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, or 10,000 or more discrete regions.

[0542] In some embodiments, the low nonspecific binding coatings comprise hydrophilic polymers that are non-specifically adsorbed or covalently grafted to the support. Typically, passivation is performed utilizing poly(ethylene glycol) (PEG, also known as polyethylene oxide (PEO) or polyoxyethylene) or other hydrophilic polymers with different molecular weights and end groups that are linked to a support using, for example, silane chemistry. The end groups distal from the surface can include, but are not limited to, biotin, methoxy ether, carboxylate, amine, NHS ester, maleimide, and bis-silane. In some embodiments, two or more layers of a hydrophilic polymer, e.g., a linear polymer, branched polymer, or multibranched polymer, may be deposited on the surface. In some embodiments, two or more layers may be covalently coupled to each other or internally cross-linked to improve the stability of the resulting coating. In some embodiments, surface primers with different nucleotide sequences and/or base modifications (or other biomolecules, e.g., enzymes or antibodies) may be tethered to the resulting layer at various surface densities. In some embodiments, for example, both surface functional group density and surface primer concentration may be varied to attain a desired surface primer density range. Additionally, surface primer density can be controlled by diluting the surface primers with other molecules that carry the same functional group. For example, amine-labeled surface primers can be diluted with amine-labeled polyethylene glycol in a reaction with an NHS-ester coated surface to reduce the final primer density. Surface primers with different lengths of linker between the hybridization region and the surface attachment functional group can also be applied to control surface density. Example of suitable linkers include poly-T and poly-A strands at the 5’ end of the primer (e.g., 0 to 20 bases), PEG linkers (e.g., 3 to 20 monomer units), and carbon-chain (e.g., C6, C12, C18, etc.). To measure the primer density, fluorescently-labeled primers may be tethered to the surface and a fluorescence reading then compared with that for a dye solution of known concentration.

[0543] In some embodiments, the low nonspecific binding coatings comprise a functionalized polymer coating layer covalently bound at least to a portion of the support via a chemical group on the support, a primer grafted to the functionalized polymer coating, and a water-soluble protective coating on the primer and the functionalized polymer coating. In some embodiments, the functionalized polymer coating comprises a poly(N-(5- azidoacetamidylpentyl)acrylamide-co-acrylamide (PAZAM).

[0544] In order to scale primer surface density and add additional dimensionality to hydrophilic or amphoteric coatings, supports comprising multi-layer coatings of PEG and other hydrophilic polymers have been developed. By using hydrophilic and amphoteric surface layering approaches that include, but are not limited to, the polymer/co-polymer materials described below, it is possible to increase primer loading density on the support significantly. Traditional PEG coating approaches use monolayer primer deposition, which have been generally reported for single molecule applications, but do not yield high copy numbers for nucleic acid amplification applications. As described herein “layering” can be accomplished using traditional crosslinking approaches with any compatible polymer or monomer subunits such that a surface comprising two or more highly crosslinked layers can be built sequentially. Examples of suitable polymers include, but are not limited to, streptavidin, poly acrylamide, polyester, dextran, poly-lysine, and copolymers of poly-lysine and PEG. In some embodiments, the different layers may be attached to each other through any of a variety of conjugation reactions including, but not limited to, biotin-streptavidin binding, azide-alkyne click reaction, amine-NHS ester reaction, thiol-maleimide reaction, and ionic interactions between positively charged polymer and negatively charged polymer. In some embodiments, high primer density materials may be constructed in solution and subsequently layered onto the surface in multiple steps. [0545] Examples of materials from which the support structure may be fabricated include, but are not limited to, glass, fused-silica, silicon, a polymer (e.g., polystyrene (PS), macroporous polystyrene (MPPS), polymethylmethacrylate (PMMA), polycarbonate (PC), polypropylene (PP), polyethylene (PE), high density polyethylene (HDPE), cyclic olefin polymers (COP), cyclic olefin copolymers (COC), polyethylene terephthalate (PET)), or any combination thereof. Various compositions of both glass and plastic support structures are contemplated.

[0546] The support structure may be rendered in any of a variety of geometries and dimensions known to those of skill in the art, and may comprise any of a variety of materials known to those of skill in the art. For example, the support structure may be locally planar (e.g., comprising a microscope slide or the surface of a microscope slide). Globally, the support structure may be cylindrical (e.g., comprising a capillary or the interior surface of a capillary), spherical (e.g., comprising the outer surface of a non-porous bead), or irregular (e.g., comprising the outer surface of an irregularly-shaped, non-porous bead or particle). In some embodiments, the surface of the support structure used for nucleic acid hybridization and amplification may be a solid, non-porous surface. In some embodiments, the surface of the support structure used for nucleic acid hybridization and amplification may be porous, such that the coatings described herein penetrate the porous surface, and nucleic acid hybridization and amplification reactions performed thereon may occur within the pores.

[0547] The support structure that comprises the one or more chemically-modified layers, e.g., layers of a low non-specific binding polymer, may be independent or integrated into another structure or assembly. For example, the support structure may comprise one or more surfaces within an integrated or assembled microfluidic flow cell. The support structure may comprise one or more surfaces within a microplate format, e.g., the bottom surface of the wells in a microplate. In some embodiments, the support structure comprises the interior surface (such as the lumen surface) of a capillary. In some embodiments the support structure comprises the interior surface (such as the lumen surface) of a capillary etched into a planar chip.

[0548] As noted, the low non-specific binding supports of the present disclosure exhibit reduced non-specific binding of proteins, nucleic acids, and other components of the hybridization and/or amplification formulation used for solid-phase nucleic acid amplification. The degree of non-specific binding exhibited by a given support surface may be assessed either qualitatively or quantitatively. For example, exposure of the surface to fluorescent dyes (e.g., cyanins such as Cy3, or Cy5, etc., fluoresceins, coumarins, rhodamines, etc. or other dyes disclosed herein), fluorescently-labeled nucleotides, fluorescently-labeled oligonucleotides, and/or fluorescently-labeled proteins (e.g. polymerases) under a standardized set of conditions, followed by a specified rinse protocol and fluorescence imaging may be used as a qualitative tool for comparison of non-specific binding on supports comprising different surface formulations. In some embodiments, exposure of the surface to fluorescent dyes, fluorescently-labeled nucleotides, fluorescently- labeled oligonucleotides, and/or fluorescently-labeled proteins (e.g. polymerases) under a standardized set of conditions, followed by a specified rinse protocol and fluorescence imaging may be used as a quantitative tool for comparison of non-specific binding on supports comprising different surface formulations — provided that care has been taken to ensure that the fluorescence imaging is performed under conditions where fluorescence signal is linearly related (or related in a predictable manner) to the number of fluorophores on the support surface (e.g., under conditions where signal saturation and/or self-quenching of the fluorophore is not an issue) and suitable calibration standards are used. In some embodiments, other techniques known to those of skill in the art, for example, radioisotope labeling and counting methods may be used for quantitative assessment of the degree to which non-specific binding is exhibited by the different support surface formulations of the present disclosure.

[0549] Some surfaces disclosed herein exhibit a ratio of specific to nonspecific binding of a fluorophore such as Cy3 of at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 35, 40, 50, 75, 100, or greater than 100, or any intermediate value spanned by the range herein. Some surfaces disclosed herein exhibit a ratio of specific to nonspecific fluorescence of a fluorophore such as Cy3 of at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 35, 40, 50, 75, 100, or greater than 100, or any intermediate value spanned by the range herein.

[0550] The degree of non-specific binding exhibited by the disclosed low-binding supports may be assessed using a standardized protocol for contacting the surface with a labeled protein (e.g., bovine serum albumin (BSA), streptavidin, a DNA polymerase, a reverse transcriptase, a helicase, a single-stranded binding protein (SSB), etc., or any combination thereof), a labeled nucleotide, a labeled oligonucleotide, etc., under a standardized set of incubation and rinse conditions, followed be detection of the amount of label remaining on the surface and comparison of the signal resulting therefrom to an appropriate calibration standard. In some embodiments, the label may comprise a fluorescent label. In some embodiments, the label may comprise a radioisotope. In some embodiments, the label may comprise any other detectable label known to one of skill in the art. In some embodiments, the degree of non-specific binding exhibited by a given support surface formulation may thus be assessed in terms of the number of non-specifically bound protein molecules (or nucleic acid molecules or other molecules) per unit area. In some embodiments, the low-binding supports of the present disclosure may exhibit non-specific protein binding (or non-specific binding of other specified molecules, (e.g., cyanins such as Cy3, or Cy5, etc., fluoresceins, coumarins, rhodamines, etc. or other dyes disclosed herein)) of less than 0.001 molecule per pm ² , less than 0.01 molecule per pm ² , less than 0.1 molecule per pm ² , less than 0.25 molecule per pm ² , less than 0.5 molecule per pm ² , less than 1 molecule per pm ² , less than 10 molecules per pm ² , less than 100 molecules per pm ² , or less than 1,000 molecules per pm ² . Those of skill in the art will realize that a given support surface of the present disclosure may exhibit non-specific binding falling anywhere within this range, for example, of less than 86 molecules per pm ² . For example, some modified surfaces disclosed herein exhibit nonspecific protein binding of less than 0.5 molecule/pm ² following contact with a 1 pM solution of Cy3 labeled streptavidin (GE Amersham) in phosphate buffered saline (PBS) buffer for 15 minutes, followed by 3 rinses with deionized water. Some modified surfaces disclosed herein exhibit nonspecific binding of Cy3 dye molecules of less than 0.25 molecules per pm ² . In independent nonspecific binding assays, 1 pM labeled Cy3 SA (ThermoFisher), 1 pM Cy5 SA dye (ThermoFisher), 10 pM Aminoallyl-dUTP-ATTO-647N (Jena Biosciences), 10 pM Aminoallyl-dUTP-ATTO-Rhol 1 (Jena Biosciences), 10 pM Aminoallyl-dUTP-ATTO-Rhol 1 (Jena Biosciences), 10 pM 7- Propargylamino-7-deaza-dGTP-Cy5 (Jena Biosciences, and 10 pM 7-Propargylamino-7- deaza-dGTP-Cy3 (Jena Biosciences) were incubated on the low binding coated supports at 37° C. for 15 minutes in a 384 well plate format. Each well was rinsed 2-3* with 50 ul deionized RNase/DNase Free water and 2-3 x with 25 mM ACES buffer pH 7.4. The 384 well plates were imaged on a GE Typhoon instrument using the Cy3, AF555, or Cy5 filter sets (according to dye test performed) as specified by the manufacturer at a PMT gain setting of 800 and resolution of 50-100 pm. For higher resolution imaging, images were collected on an Olympus 1X83 microscope (e.g., inverted fluorescence microscope) (Olympus Corp., Center Valley, Pa.) with a total internal reflectance fluorescence (TIRF) objective (100x, 1.5 NA, Olympus), a CCD camera (e.g., an Olympus EM-CCD monochrome camera, Olympus XM- 10 monochrome camera, or an Olympus DP80 color and monochrome camera), an illumination source (e.g., an Olympus 100W Hg lamp, an Olympus 75 W Xe lamp, or an Olympus U-HGLGPS fluorescence light source), and excitation wavelengths of 532 nm or 635 nm. Dichroic mirrors were purchased from Semrock (IDEX Health & Science, LLC, Rochester, N.Y.), e.g., 405, 488, 532, or 633 nm dichroic reflectors/beamsplitters, and band pass filters were chosen as 532 LP or 645 LP concordant with the appropriate excitation wavelength. Some modified surfaces disclosed herein exhibit nonspecific binding of dye molecules of less than 0.25 molecules per pm ² . In some embodiments, the coated support was immersed in a buffer (e.g., 25 mM ACES, pH 7.4) while the image was acquired.

[0551] In some embodiments, the surfaces disclosed herein exhibit a ratio of specific to nonspecific binding of a fluorophore such as Cy3 of at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 35, 40, 50, 75, 100, or greater than 100, or any intermediate value spanned by the range herein. In some embodiments, the surfaces disclosed herein exhibit a ratio of specific to nonspecific fluorescence signals for a fluorophore such as Cy3 of at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 35, 40, 50, 75, 100, or greater than 100, or any intermediate value spanned by the range herein.

[0552] The low-background surfaces consistent with the disclosure herein may exhibit specific dye attachment (e.g., Cy3 attachment) to non-specific dye adsorption (e.g., Cy3 dye adsorption) ratios of at least 4: 1, 5: 1, 6: 1, 7: 1, 8:1, 9: 1, 10: 1, 15: 1, 20: 1, 30: 1, 40: 1, 50: 1, or more than 50 specific dye molecules attached per molecule nonspecifically adsorbed. Similarly, when subjected to an excitation energy, low-background surfaces consistent with the disclosure herein to which fluorophores, e.g., Cy3, have been attached may exhibit ratios of specific fluorescence signal (e.g., arising from Cy3-labeled oligonucleotides attached to the surface) to non-specific adsorbed dye fluorescence signals of at least 4: 1, 5: 1, 6: 1, 7: 1, 8: 1, 9: 1, 10: 1, 15: 1, 20: 1, 30:1, 40: 1, 50: 1, or more than 50: 1.

[0553] In some embodiments, the degree of hydrophilicity (or “wettability” with aqueous solutions) of the disclosed support surfaces may be assessed, for example, through the measurement of water contact angles in which a small droplet of water is placed on the surface and its angle of contact with the surface is measured using, e.g., an optical tensiometer. In some embodiments, a static contact angle may be determined. In some embodiments, an advancing or receding contact angle may be determined. In some embodiments, the water contact angle for the hydrophilic, low-binding support surfaced disclosed herein may range from about 0 degrees to about 30 degrees. In some embodiments, the water contact angle for the hydrophilic, low-binding support surfaced disclosed herein may no more than 50 degrees, 40 degrees, 30 degrees, 25 degrees, 20 degrees, 18 degrees, 16 degrees, 14 degrees, 12 degrees, 10 degrees, 8 degrees, 6 degrees, 4 degrees, 2 degrees, or 1 degree. In many cases the contact angle is no more than 40 degrees. Those of skill in the art will realize that a given hydrophilic, low-binding support surface of the present disclosure may exhibit a water contact angle having a value of anywhere within this range.

[0554] In some embodiments, the hydrophilic surfaces disclosed herein facilitate reduced wash times for bioassays, often due to reduced nonspecific binding of biomolecules to the low-binding surfaces. In some embodiments, adequate wash steps may be performed in less than 60, 50, 40, 30, 20, 15, 10, or less than 10 seconds. For example, adequate wash steps may be performed in less than 30 seconds.

[0555] Some low-binding surfaces of the present disclosure exhibit significant improvement in stability or durability to prolonged exposure to solvents and elevated temperatures, or to repeated cycles of solvent exposure or changes in temperature. For example, the stability of the disclosed surfaces may be tested by fluorescently labeling a functional group on the surface, or a tethered biomolecule (e.g., an oligonucleotide primer) on the surface, and monitoring fluorescence signal before, during, and after prolonged exposure to solvents and elevated temperatures, or to repeated cycles of solvent exposure or changes in temperature. In some embodiments, the degree of change in the fluorescence used to assess the quality of the surface may be less than 1%, 2%, 3%, 4%, 5%, 10%, 15%, 20%, or 25% over a time period of 1 minute, 2 minutes, 3 minutes, 4 minutes, 5 minutes, 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, 60 minutes, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 15 hours, 20 hours, 25 hours, 30 hours, 35 hours, 40 hours, 45 hours, 50 hours, or 100 hours of exposure to solvents and/or elevated temperatures (or any combination of these percentages as measured over these time periods). In some embodiments, the degree of change in the fluorescence used to assess the quality of the surface may be less than 1%, 2%, 3%, 4%, 5%, 10%, 15%, 20%, or 25% over 5 cycles, 10 cycles, 20 cycles, 30 cycles, 40 cycles, 50 cycles, 60 cycles, 70 cycles, 80 cycles, 90 cycles, 100 cycles, 200 cycles, 300 cycles, 400 cycles, 500 cycles, 600 cycles, 700 cycles, 800 cycles, 900 cycles, or 1,000 cycles of repeated exposure to solvent changes and/or changes in temperature (or any combination of these percentages as measured over this range of cycles).

[0556] In some embodiments, the surfaces disclosed herein may exhibit a high ratio of specific signal to nonspecific signal or other background. For example, when used for nucleic acid amplification, some surfaces may exhibit an amplification signal that is at least 4, 5, 6, 7, 8, 9, 10, 15, 20, 30, 40, 50, 75, 100, or greater than 100 fold greater than a signal of an adjacent unpopulated region of the surface. Similarly, some surfaces exhibit an amplification signal that is at least 4, 5, 6, 7, 8, 9, 10, 15, 20, 30, 40, 50, 75, 100, or greater than 100 fold greater than a signal of an adjacent amplified nucleic acid population region of the surface. [0557] In some embodiments, fluorescence images of the disclosed low background surfaces when used in nucleic acid hybridization or amplification applications to create polonies of hybridized or clonally-amplified nucleic acid molecules (e.g., that have been directly or indirectly labeled with a fluorophore) exhibit contrast-to-noise ratios (CNRs) of at least 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 20, 210, 220, 230, 240, 250, or greater than 250.

[0558] One or more types of primer may be attached or tethered to the support surface. In some embodiments, the one or more types of adapters or primers may comprise spacer sequences, adapter sequences for hybridization to adapter-ligated target library nucleic acid sequences, forward amplification primers, reverse amplification primers, sequencing primers, and/or molecular barcoding sequences, or any combination thereof. In some embodiments, 1 primer or adapter sequence may be tethered to at least one layer of the surface. In some embodiments, at least 2, 3, 4, 5, 6, 7, 8, 9, 10, or more than 10 different primer or adapter sequences may be tethered to at least one layer of the surface.

[0559] In some embodiments, the tethered adapter and/or primer sequences may range in length from about 10 nucleotides to about 100 nucleotides. In some embodiments, the tethered adapter and/or primer sequences may be at least 10, at least 20, at least 30, at least 40, at least 50, at least 60, at least 70, at least 80, at least 90, or at least 100 nucleotides in length. In some embodiments, the tethered adapter and/or primer sequences may be at most 100, at most 90, at most 80, at most 70, at most 60, at most 50, at most 40, at most 30, at most 20, or at most 10 nucleotides in length. Any of the lower and upper values described in this paragraph may be combined to form a range included within the present disclosure, for example, in some embodiments the length of the tethered adapter and/or primer sequences may range from about 20 nucleotides to about 80 nucleotides. Those of skill in the art will recognize that the length of the tethered adapter and/or primer sequences may have any value within this range, e.g., about 24 nucleotides.

[0560] In some embodiments, the resultant surface density of primers (e.g., capture primers) on the low binding support surfaces of the present disclosure may range from about 100 primer molecules per pm ² to about 100,000 primer molecules per pm ² . In some embodiments, the resultant surface density of primers on the low binding support surfaces of the present disclosure may range from about 1,000 primer molecules per pm ² to about 1,000,000 primer molecules per pm ² . In some embodiments, the surface density of primers may be at least 1,000, at least 10,000, at least 100,000, or at least 1,000,000 molecules per pm ² . In some embodiments, the surface density of primers may be at most 1,000,000, at most 100,000, at most 10,000, or at most 1,000 molecules per pm ² . Any of the lower and upper values described in this paragraph may be combined to form a range included within the present disclosure, for example, in some embodiments the surface density of primers may range from about 10,000 molecules per pm ² to about 100,000 molecules per pm ² . Those of skill in the art will recognize that the surface density of primer molecules may have any value within this range, e.g., about 455,000 molecules per pm ² . In some embodiments, the surface density of target library nucleic acid sequences initially hybridized to adapter or primer sequences on the support surface may be less than or equal to that indicated for the surface density of tethered primers. In some embodiments, the surface density of clonally-amplified target library nucleic acid sequences hybridized to adapter or primer sequences on the support surface may span the same range as that indicated for the surface density of tethered primers. [0561] Local densities as listed above do not preclude variation in density across a surface, such that a surface may comprise a region having an oligo density of, for example, 500,000/pm ² , while also comprising at least a second region having a substantially different local density.

[0562] In some embodiments, the performance of nucleic acid hybridization and/or amplification reactions using the disclosed reaction formulations and low-binding supports may be assessed using fluorescence imaging techniques, where the contrast-to-noise ratio (CNR) of the images provides a key metric in assessing amplification specificity and nonspecific binding on the support. CNR is commonly defined as: CNR=(Signal- Background)/Noise. The background term is commonly taken to be the signal measured for the interstitial regions surrounding a particular feature (diffraction limited spot, DLS) in a specified region of interest (ROI). While signal-to-noise ratio (SNR) is often considered to be a benchmark of overall signal quality, it can be shown that improved CNR can provide a significant advantage over SNR as a benchmark for signal quality in applications that require rapid image capture (e.g., sequencing applications for which cycle times must be minimized), as shown in the example below. At high CNR the imaging time required to reach accurate discrimination (and thus accurate base-calling in the case of sequencing applications) can be drastically reduced even with moderate improvements in CNR. Improved CNR in imaging data on the imaging integration time provides a method for more accurately detecting features such as clonally-amplified nucleic acid colonies on the support surface. [0563] In most ensemble-based sequencing approaches, the background term is typically measured as the signal associated with 'interstitial' regions. In addition to "interstitial" background (Binter ), "intrastitial" background (Bintra) exists within the region occupied by an amplified DNA colony. The combination of these two background signals dictates the achievable CNR, and subsequently directly impacts the optical instrument requirements, architecture costs, reagent costs, run-times, cost/genome, and ultimately the accuracy and data quality for cyclic array-based sequencing applications. The Binter background signal arises from a variety of sources; a few examples include auto-fluorescence from consumable flow cells, non-specific adsorption of detection molecules that yield spurious fluorescence signals that may obscure the signal from the ROI, the presence of non-specific DNA amplification products (e.g., those arising from primer dimers). In typical next generation sequencing (NGS) applications, this background signal in the current field-of-view (FOV) is averaged over time and subtracted. The signal arising from individual DNA colonies (i.e., (Signal)-B(interstial) in the FOV) yields a discernable feature that can be classified. In some embodiments, the intrastitial background (B(intrastitial)) can contribute a confounding fluorescence signal that is not specific to the target of interest, but is present in the same ROI thus making it far more difficult to average and subtract.

[0564] Nucleic acid amplification on the low-binding coated supports described herein may decrease the B(interstitial) background signal by reducing non-specific binding, may lead to improvements in specific nucleic acid amplification, and may lead to a decrease in non-specific amplification that can impact the background signal arising from both the interstitial and intrastitial regions. In some embodiments, the disclosed low-binding coated supports, optionally used in combination with the disclosed hybridization and/or amplification reaction formulations, may lead to improvements in CNR by a factor of 2, 5, 10, 100, 250, 500 or 1000-fold over those achieved using conventional supports and hybridization, amplification, and/or sequencing protocols. Although described here in the context of using fluorescence imaging as the read-out or detection mode, the same principles apply to the use of the disclosed low-binding coated supports and nucleic acid hybridization and amplification formulations for other detection modes as well, including both optical and non-optical detection modes.

[0565] The present disclosure provides methods for determining the sequence of a nucleic acid template molecule, where the multivalent molecules are labeled with fluorophores and the detecting and/or identifying steps comprise use of fluorescence imaging. In some embodiments, the fluorescence imaging comprises dual wavelength excitation/four wavelength emission fluorescence imaging. In some embodiments, four different types of multivalent molecules are employed, each comprising a different nucleotide unit (or nucleotide unit analog). For example, a first type of multivalent molecules comprise dATP nucleotide units, a second type of multivalent molecules comprise dGTP nucleotide units, a third type of multivalent molecules comprise dCTP nucleotide units, and a fourth type of multivalent molecules comprise dTTP nucleotide units. In some embodiments, the four different types of multivalent molecules are labeled with a different fluorophore that corresponds to the nucleotide units attached to a given multivalent molecule to permit identification of the nucleotide units. In some embodiments, the detecting step comprises simultaneous or single excitation at a wavelength sufficient to excite all four fluorophores and imaging of fluorescence emission at wavelengths sufficient to detect each respective fluorophore. In some embodiments, the four labeled multivalent molecules are used to determine the identity of a terminal nucleotide in the nucleic acid template molecule. In some embodiments, the four types of multivalent molecules are labeled with different fluorophores, including for example fluorophores that emit different visible colors such as blue, green, yellow, orange or red. In some embodiments, the four types of multivalent molecules are labeled with different fluorophores, including for example Cy2 or a dye or fluorophore similar in excitation or emission properties, Cy3 or a dye or fluorophore similar in excitation or emission properties, Cy3.5 or a dye or fluorophore similar in excitation or emission properties, Cy5 or a dye or fluorophore similar in excitation or emission properties, Cy5.5 or a dye or fluorophore similar in excitation or emission properties, and Cy7 or a dye or fluorophore similar in excitation or emission properties. In some embodiments, the detecting step comprises simultaneous excitation at any two of 532 nm, 568 nm and 633 nm, and imaging of fluorescence emission at about 570 nm, 592 nm, 670 nm, and 702 nm, respectively. In some embodiments, the fluorescence imaging comprises dual wavelength excitation/dual wavelength emission fluorescence imaging. In some embodiments, the four different types of multivalent molecules are labeled with distinguishable fluorophores (or a set of fluorophores), and the detecting step comprises simultaneous or single excitation at a wavelength sufficient to excite one, two, three, or four fluorophores or sets of fluorophores, and imaging of fluorescence emission at wavelengths is sufficient to detect each respective fluorophore.

[0566] In some embodiments, the sequencing methods can be conducted with three different types of labeled multivalent molecules and one type of unlabeled multivalent molecule (e.g., a “dark” multivalent molecule), where the labeled multivalent molecules are labeled with a different fluorophore that corresponds to the nucleotide units attached to a given multivalent molecule to permit identification of the nucleotide units. In some embodiments, the detecting step comprises simultaneous excitation at a wavelength sufficient to excite the three types of fluorophores and imaging of fluorescence emission at wavelengths is sufficient to detect each respective fluorophore, and detection of the fourth type of multivalent molecule is determined or determinable with reference to the location of “dark” or unlabeled spots.

[0567] In some embodiments, the fluorophores comprise a FRET donor and accepter pair, such that multiple detections and identifications can be performed under a single excitation and imaging step. In some embodiments, a sequencing cycle comprises forming a plurality of complexed polymerases, contacting the complexed polymerases with a plurality of different types of fluorescently-labeled multivalent molecules, and detecting the fluorescently-labeled multivalent molecules that are bound to the complexed polymerases. In some embodiments, a sequencing cycle can be conducted in less than 30 minutes, in less than 20 minutes, or in less than 10 minutes. In some embodiments, conducting sequencing reactions with labeled multivalent molecules gives an average Q-score for base calling accuracy over a sequencing run which is greater than or equal to 30, and/or greater than or equal to 40. In some embodiments, at least 50%, at least 60%, at least 70%, at least 80%, or at least 90% of the base calls have a Q-score of greater than 30 and/or greater than or equal to 40. In some embodiments, the present disclosure provides the method, herein at least 95% of the base calls have a Q-score of greater than 30.

EXAMPLES

[0568] The following examples are meant to be illustrative and can be used to further understand embodiments of the present disclosure and should not be construed as limiting the scope of the present teachings in any way.

[0569] EXAMPLE 1: Clarified Lysate Preparation of Mutant Polymerases

[0570] Mutant polymerases were prepared using site directed mutagenesis. The mutated sites of the mutant polymerases are listed in Table 1 (FIG. 31) and Table 2 (FIG. 32).

[0571] Host cells harboring an expression vector operably linked to a nucleic acid encoding a wild type polymerase or one of the mutant polymerases were prepared. The host cells were cultured under conditions suitable for expressing the wild type or mutant polymerase. The host cells were grown in plate format and centrifuged after expression. Cell pellets were lysed by treatment with lysozyme in buffer (20 mM Tris-HCl (pH 8.8), 10 mM KC1, 10 mM (NHf SCh)) and centrifuged again. The supernatants were transferred to PCR plates and heat shocked at 65 °C for 60 minutes. The heat shocked lysates were then clarified by centrifuge and the supernatants transferred to a new plate for the nucleotide incorporation assay.

[0572] Clarified lysates were mixed with a 4X SDS loading day and run on a 4-12% NuPAGE Bis-Tris SDS polyacrylamide gel. After running the gel, it was stained with Coomassie blue staining buffer and de-stained overnight to resolve the target bands. The protein yield and presence of stable enzyme or heat shock aggregation could be assessed by visual inspection of the de-stained gels. Alternatively, the protein yield and concentration from the lysates was determined using an automated microfluidic chip which was configured in high throughput mode to stain, de-stain and electrophoretically separate the protein (e.g., LABCHIP GXII TOUCH).

[0573] EXAMPLE 2: Nucleotide Incorporation Assay

[0574] Atto dye-labeled DNA templates were used to prepare the DNA duplexes. The labeled DNA templates were annealed with primers in a reaction buffer (Tris-HCl (pH 7.5), NaCl, EDTA). The duplexes were mixed with the clarified lysates (described in Example 1) and allowed to equilibrate to 42 °C. The nucleotide incorporation reaction was started with the addition of a 3’ methylazido nucleotide corresponding to the next base on the template (e.g., dCTP-N3 or dATP-N3). The reaction was allowed to proceed under different temperature and time conditions, for example 42 °C for 150 seconds, or 56 °C for as little as 2 seconds, and quenched with EDTA and formamide. The analysis of the n+1 vs n was performed by capillary electrophoresis.

[0575] The incorporation activity data listed in Table 2 (FIG. 32) represent the relative activity of mutant polymerases in incorporation of 3 ’methylazido nucleotides at the N+1 position of an extending polynucleotide chain at 42°C.

[0576] Numerous mutant polymerases were expressed by recombinant host cells as described in Example 1. Lysates from the expression host cells, which contained mutant polymerases, were subjected to heat shock at 65 °C for 60 minutes. The mutant polymerases in the heat shocked lysates were screened for their ability to incorporate a 3’ methylazido nucleotide as described in Example 2. Analysis of the incorporation reactions were conducted via capillary electrophoresis as described in Example 2. The incorporation activities of the mutant polymerases were assigned a grade of 0 if they exhibited zero or negligible incorporation activity, or assigned a grade of + or ++ if they exhibited moderate or high incorporation activity respectively. It was predicted that approximately 50 - 60% or more of the mutant polymerases would exhibit incorporation activity having a grade of + or higher.

[0577] EXAMPLE 3: Thermal Melt Assays

[0578] Purified wild type and mutant polymerases in a heparin elution buffer was mixed with IX SYPRO Orange Protein Gel Stain and run on a CFX384 thermocycler. The thermal melt data was analyzed using a CFX Maestro software (from Bio-Rad). Thermal melt data including (Tml) and (Tm2) are listed in Tables 1 and 2. The thermal melt data was used to generate melt peaks and melt curves.

[0579] EXAMPLE 4: Thermal Aggregation Assays

[0580] The temperature of aggregation onset (T(agg)) was measured using quartz cuvettes containing polymerases at 1 mg/mL in a buffer. The cuvettes were placed in an UNCLE instrument (from Unchained Labs, Pleasanton, California) and exposed to a temperature ramp of 25 °C to 95 °C, at a rate of 0.5 °C per second. The aggregation temperature was measured using static light scattering and was determined as the temperature where the 266 nm signal increased beyond 10% of the average baseline read. The thermal aggregation T(agg) temperatures were determined from the thermal melt data and melt curves were generated.

[0581] EXAMPLE 5: Uracil incorporation assays

[0582] Primed DNA template molecules in a reaction buffer was mixed with a purified mutant polymerase and allowed to equilibrate to 42 °C. The reaction was started by adding a 3’ methylazido nucleotide corresponding to the next base on the template molecule. The reaction was allowed to proceed at 42 °C and quenched with EDTA and formamide at incremental time points. Analysis of the n+1 versus n was performed by capillary electrophoresis. The incorporation rates of dATP nucleotide analog into a template having a thymine as the next base in the template molecule was assayed. The incorporation rates of dATP nucleotide analog into a template having an adenine as the next base in the template molecule was assayed. The incorporation rates of dATP nucleotide analog into a template having a uracil as the next base in the template molecule was assayed. Some of the mutant polymerases exhibited increased capability for incorporating a dATP nucleotide analog into a uracil-containing template molecule.

[0583] EXAMPLE 6: Assay for binding labeled multivalent molecules

[0584] DNA concatemers were prepared and immobilized to flowcells. A solution of fluorescently-labeled multivalent molecules (e.g., see FIG. 5) and engineered polymerase enzyme was flowed onto the flowcells. Each solution contained multivalent molecules carrying nucleotide units of dATP, dGTP, dCTP or dTTP. The core of the multivalent molecules were labeled with different fluorophores that correspond to the nucleotide units of dATP, dGTP, dCTP or dTTP. The concatemers were reacted with the solution for 10 seconds, then removed using air. The multivalent molecules and polymerase enzyme was removed with a wash buffer. An imaging solution was flowed onto the flowcell and the fluorescent intensity of the multivalent molecules bound to the concatemers was measured. The purity of the bound nucleotide unit was calculated by dividing the fluorescent intensity of the dominant nucleotide unit (e.g., the correct nucleotide unit) by the sum of the intensities of all four nucleotide units.

[0585] In a separate assay, complexed engineered polymerases were reacted with fluorescently labeled multivalent molecules carrying nucleotide units of dATP, dGTP, dCTP or dUTP, under different temperature and time conditions. For example, the temperature tested included 25 - 56 °C, and the time during included 1 - 90 seconds. Images and intensities of multivalent molecules binding the complexed polymerases were acquired.

[0586] The intensity exhibited by the mutant polymerases were assigned a grade of 0 if they exhibited zero or negligible activity, or assigned a grade of + or ++ if they exhibited moderate or high activity respectively. It was predicted that approximately 50 - 60% or more of the mutant polymerases would exhibit intensity having a grade of + or higher. Mutant polymerases with a grade of + or ++ were suitable for forming in sequencing.

[0587] EXAMPLE 7: Binding activity - labeled nucleotide arms

[0588] Labeled nucleotide arms were prepared (e.g., FIG. 6) each carrying a fluorophore, a nucleotide unit, linker, spacer and core attachment moiety. Cell lysates containing mutant polymerases were prepared from different host cells expressing different mutant polymerases. DNA template/primer duplexes were prepared, where the template molecules were fluorescently labeled. The cell lysate, template/primer duplex and the labeled nucleotide arms were mixed together with a non-catalytic cation in the wells of a multi-well plate, under a condition suitable for forming complexed polymerases and under a condition suitable to bind a nucleotide arm to a complexed polymerase. The plates were positioned on a plate read and spectral scanning was conducted at the appropriated excitation wavelength. Emission measurements were obtained. The multivalent binding activity data of the mutant polymerases are listed in Table 1 (FIG. 31).

[0589] EXAMPLE 8: Mass spectrometry and modeling

[0590] Wild type polymerases were prepared. The wild type polymerases comprised a backbone sequence of RLF 89458.1 (SEQ ID NO: 1) or NOZ 58130.1 (SEQ ID NO: 992), and having a His-tag at their N-terminal ends. The His-tag on the RLF 89458.1 polymerase comprised the sequence MGSSHHHHHHSSGLVPRGS (SEQ ID NO:2838) and the His-tag on the NOZ 58130.1 polymerase comprised the sequence MGSSHHHHHHSSGLVPRGSH (SEQ ID NO:2837).

[0591] The His-tagged polymerases were solubilized in a reagent comprising Tris (50 mM, pH 7.5) and NaCl (50 mM), using a 30 kDa cut-off spin filter. The polymerase solutions were concentration to approximately 0.5 - 1 mg/mL as determined using a Bradford assay. 20-50 uL of the polymerase solution was diluted to a final volume of 100 uL using 0.2% Rapigest (e.g., 0.2% Rapigest in 50 mM ammonium bicarbonate). 2.5 uL of DTT (e.g., 200 mM DTT in 50 mM ammonium bicarbonate) was added to the diluted polymerase and vortexed. The polymerase solutions were incubated in a 60 °C oven for 30 minutes to reduce. After reduction, the polymerase solution was equilibrated to room temperature. 7.5 uL of iodoacetamide (IAA) (e.g., 200 mM iodoacetamide in 50 mM ammonium bicarbonate) was added to the reduced polymerase solution. The polymerase solution was vortexed for 30 minutes at room temperature in the dark. Trypsin (e.g., 0.1 ug/uL trypsin in 50 mM ammonium bicarbonate) was added to the polymerase solution at a ratio of 1 :30 trypsin-to- polymerase concentration. The polymerase was digested for at least 4 hours (e.g., overnight) at 37 °C. After digestion, the polymerase solution (e.g., now peptides) was adjusted to about pH 2 with addition of HC1 and kept at 37 °C for 30 minutes. The polymerase solution was vortexed and placed at 4 °C for at least 2 hours. The polymerase solution was centrifuged for 15 minutes and the supernatant was used for mass spectrometry analysis.

[0592] Electrospray ionization was used to conduct the mass spectrometry(MS/MS) analysis. The peptides were analyzed by nano-flow LC tandem mass spectrometry in data- dependent scanning mode using an ion trap mass spectrometer (Thermo Scientific Q Exactive Plus mass spectrometer). The MS/MS data was searched against the predicted fragment ions from theoretical digests of the known protein sequences using Mascot software (Matrix Science Limited). The mass spectrometry data was used generate a predicted three- dimensional ribbon model and to identify sites of post-translational modifications including oxidation and acetylation sites (e.g., FIGs. 41 and 42). The acetylation sites were identified as sites that had undergone N-phosphogluconoylation or N-gluconoylation. The ribbon model in FIG. 41 also shows the predicted structure of the His-tag MGSSHHHHHHSSGLVPRGS (SEQ ID NO:2838), where G-17, S-16, S-15, H-12, and H-11 are the amino acid residues from the His-tag. The ribbon model in FIG. 42 also shows the predicted structure of the His- tag MGSSHHHHHHSSGLVPRGSH (SEQ ID NO:2837), where G-17, H-8, H-7, S-4 and S-3 are the amino acid residues from the His-tag.

[0593] Modeling of the wild type polymerases, RLF 89458.1 and NOZ 58130.1, were conducted using Rosetta software with the standard workflow inputs, including (1) a sequence alignment was generated using ClustalX, and (2) the coordinates of the template structure available from RCSB protein structure database, Protein Data Bank. The alignment and template were input into Rosetta and commanded to thread the target sequence onto the template. Fragments were generated for missing portions. Approximately 10,000 - 15,000 comparative models were generated and the lowest energy models were selected.

[0594] EXAMPLE 9: Accelerated aging studies for engineered polymerases

[0595] Accelerated aging studies were conducted to determine the estimated shelf-life of various purified engineered polymerases, including polymerases comprising RLF89458 (e.g., SEQ ID NOS: 1-1713) or NOZ 58130 (e.g., SEQ ID NOS: 1714-2787) backbone sequences. Engineered polymerases were aged in a sequencing storage buffer lacking nucleotide analogs and multivalent molecules. The accelerated aging studies were conducted at four temperatures including -20 °C, 4 °C, 25 °C or 37 °C.

[0596] The theoretical shelf-life was estimated using the following equation:

Accelerated Aging Time (ATT) = Desired Real Time (RT)

Q10 [(TAA - TRT)/10] wherein Q10 is the reaction rate coefficient, TAA is the oven aging temperature, and TRT is the ambient temperature (e.g., room temperature). The reaction rate coefficient Q10 corresponds to the rate of spoilage when the temperature is raised to 10 °C. Typically, the value for Q10 is set at 2, where the rate of spoilage is doubled for every 10 °C increase in temperature. For example, when applying the accelerated aging time equation, an engineered polymerase stored at 25 °C for 16 days corresponds to 362 days at -20 °C.

[0597] When the engineered polymerases were aged for the desired time, their level of activity was tested by conducting a nucleotide incorporation assay.

[0598] The nucleotide incorporation assay was conducted in a manner similar to the incorporation assay described in Example 2. Dye-labeled DNA templates were annealed with primers in a reaction buffer. The duplexes were mixed with purified engineered polymerase and allowed to equilibrate to 50 °C. The nucleotide incorporation reaction was started with the addition of a 3’ methylazido nucleotide corresponding to the next base on the template. The reaction was allowed to proceed 50 °C, and quenched with EDTA and formamide at incremental times. The analysis of the n+1 vs n was performed by capillary electrophoresis. [0599] EXAMPLE 10: Sequencing using multivalent molecules and nucleotides [0600] A two-stage sequencing reaction was conducted on a flow cell having a plurality of concatemer template molecules immobilized thereon (e.g., immobilized polonies).

[0601] The first-stage sequencing reaction was conducted by hybridizing a plurality of a soluble sequencing primers to concatemer template molecules that were immobilized to a flow cells to form immobilized primer-concatemer duplexes. A plurality of a first sequencing polymerase was flowed onto the flow cell (e.g., contacting the immobilized primer- concatemer duplexes) and incubated under a condition suitable to bind the sequencing polymerase to the duplexes to form complexed polymerases. Exemplary first sequencing polymerases comprise an amino acid backbone sequence of any one of SEQ ID NOS: 1, 2 or 1714. In some embodiments, the mutant polymerase comprises an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99% identical, or a higher level sequence identity, to any of SEQ ID NOS: 1-1713 or 1714-2787. A mixture of fluorescently labeled multivalent molecules (e.g., at different concentrations of about 20-100 nM) was flowed onto the flow cell in the presence of a buffer that included a non-catalytic cation (e.g., strontium, barium and/or calcium) and incubated under conditions suitable to bind complementary nucleotide units of the multivalent molecules to the complexed polymerases to form avidity complexes without polymerase-catalyzed incorporation of the nucleotide units. Various temperature and time conditions were tested, for example 25-56 °C for 5-90 seconds. The fluorescently labeled multivalent molecules were labeled at their cores. The complexed polymerases were washed. An image was obtained of the fluorescently labeled multivalent molecules that remined bound to the complexed polymerases. The first sequencing polymerases and multivalent molecules were removed, while retaining the sequencing primers hybridized to the immobilized concatemers (retained duplexes), by washing with a buffer comprising a detergent.

[0602] The first stage sequencing reaction was suitable for forming a plurality of avidity complexes on the concatemer template molecules (e.g., polonies). For example, the first stage sequencing reaction comprised: (a) binding a first nucleic acid primer, a first polymerase, and a first multivalent molecule to a first portion of a concatemer template molecule thereby forming a first binding complex, wherein a first nucleotide unit of the first multivalent molecule was bound to the first polymerase; and (b) binding a second nucleic acid primer, a second polymerase, and the first multivalent molecule to a second portion of the same concatemer template molecule thereby forming a second binding complex, wherein a second nucleotide unit of the first multivalent molecule was bound to the second polymerase, wherein the first and second binding complexes which included the same multivalent molecule formed a first avidity complex.

[0603] The second-stage sequencing reaction was conducted by contacting the retained duplexes with a plurality of second sequencing polymerases to form complexed polymerases. Exemplary second sequencing polymerases comprise an amino acid backbone sequence of any one of SEQ ID NOS: 1, 2 or 1714. In some embodiments, the mutant polymerase comprises an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99% identical, or a higher level sequence identity, to any of SEQ ID NOS: 1-1713 or 1714-2787. A mixture of non-labeled nucleotide analogs (e.g., 3 ’O-m ethylazido nucleotides) (e.g., at different concentrations of about 1-5 uM) was added to the complexed polymerases in the presence of a buffer that included a catalytic cation (e.g., magnesium and/or manganese) and incubated under conditions suitable to bind complementary nucleotides to the complexed polymerases and promote polymerase-catalyzed incorporation of the nucleotides to generate a nascent extended sequencing primer. Various temperature and time conditions were tested, for example 25-56 °C for 5-180 seconds. The complexed polymerases were washed. No image was obtained. The incorporated non-labeled nucleotide analogs were reacted with a cleaving reagent that removes the 3’ O-methylazido group and generates an extendible 3 ’OH group. [0604] In an alternative second stage sequencing reaction, a mixture of fluorescently labeled nucleotide analogs (e.g., 3 ’O-methylazido nucleotides) (e.g., about 1-5 uM) was added to the complexed polymerases in the presence of a buffer that included a catalytic cation (e.g., magnesium and/or manganese) and incubated under conditions suitable to bind complementary nucleotides to the complexed polymerases and promote polymerase- catalyzed incorporation of the nucleotides to generate a nascent extended sequencing primer. The complexed polymerases were washed. An image was obtained of the incorporated fluorescently labeled nucleotide analogs as a part of the complexed polymerases. The incorporated fluorescently labeled nucleotide analogs were reacted with a cleaving reagent that removes the 3’ O-methylazido group and generates an extendible 3 ’OH group.

[0605] The second sequencing polymerases were removed, while retaining the nascent extended sequencing primers hybridized to the concatemers (retained duplexes), by washing with a buffer comprising a detergent. Recurring sequencing reactions were conducted by performing multiple cycles of first-stage and second-stage sequencing reactions to generate extended forward sequencing primer strands. FIG. 43 shows a 150 cycle sequencing run of immobilized concatemers generated from a nucleic library prepared from E. coli DNA. The X-axis indicates the sequencing cycle number and the Y-axis indicates the % error.