Labeled nucleotide analogs comprising at least one avidin protein, at least one dye-labeled compound, and at least one nucleotide compound are provided. The analogs are useful in various fluorescence-based analytical methods, including the analysis of highly multiplexed optical reactions in large numbers at high densities, such as single molecule real time nucleic acid sequencing reactions. The analogs are detectable with high sensitivity at desirable wavelengths. They contain structural components that modulate the interactions of the analogs with DNA polymerase, thus decreasing photodamage and improving the kinetic and other properties of the analogs in sequencing reactions. Also provided are nucleotide and dye-labeled compounds of the subject analogs, as well as intermediates useful in the preparation of the compounds and analogs. Compositions comprising the compounds, methods of synthesis of the intermediates, compounds, and analogs, and mutant DNA polymerases are also provided.

The present disclosure provides methods of sequencing polynucleotides and compounds, compositions for sequencing of polynucleotides, and synthesis of such compositions. The chemical compounds include nucleotides and their analogs which possess a sugar moiety comprising a cleavable chemical group capping the 3′-OH group and a base, but without covalently bounded dye. The cleavable chemical group is reactive to form covalent bond(s) with a dye used to confirm the presence of the expected base-pairing. The cleavable chemical group capping the 3′OH group can be removed together with the covalently bounded dye. Furthermore, after the cleavable chemical group is cleaved, the free 3′-OH group can be active in continued elongation. Example chemical compounds according to the present disclosure are shown as Formulas (II) and (V):

##STR00001##

The present disclosure provides methods of sequencing polynucleotides and compounds, compositions for sequencing of polynucleotides, and synthesis of such compositions. The chemical compounds include nucleotides and their analogs which possess a sugar moiety comprising a cleavable chemical group capping the 3′-OH group and a base, but without covalently bounded dye. The cleavable chemical group is reactive to form covalent bond(s) with a dye used to confirm the presence of the expected base-pairing. The cleavable chemical group capping the 3′OH group can be removed together with the covalently bounded dye. Furthermore, after the cleavable chemical group is cleaved, the free 3′-OH group can be active in continued elongation. Example chemical compounds according to the present disclosure are shown as Formulas (II) and (V):

##STR00001##

Embodiments for the synthesis of sensitive oligonucleotides as well as insensitive oligonucleotides are provided. Sulfur-based groups are used for the protection of exo-amino groups of nucleobases, phosphate groups and 2′—OH groups, and as cleavable linker for linking oligonucleotides to a support. Oligonucleotide syntheses are achieved under typical conditions using phosphoramidite chemistry with important modifications. To prevent replacing sulfur-based protecting groups by acyl groups via cap-exchange, special capping agents are used. To retain hydrophobic tag to assist RP HPLC purification, special phosphoramidites are used in the last synthetic cycle. With the sulfur-based groups for protection and linking, oligonucleotide deprotection and cleavage are achieved via oxidation followed by beta-elimination under mild conditions. Therefore, besides for insensitive oligonucleotide synthesis, the embodiments of the invention are capable for the synthesis of oligonucleotide analogs containing sensitive functional groups that cannot survive the harsh conditions used in prior art oligonucleotide synthesis technologies.

Embodiments for the synthesis of sensitive oligonucleotides as well as insensitive oligonucleotides are provided. Sulfur-based groups are used for the protection of exo-amino groups of nucleobases, phosphate groups and 2′—OH groups, and as cleavable linker for linking oligonucleotides to a support. Oligonucleotide syntheses are achieved under typical conditions using phosphoramidite chemistry with important modifications. To prevent replacing sulfur-based protecting groups by acyl groups via cap-exchange, special capping agents are used. To retain hydrophobic tag to assist RP HPLC purification, special phosphoramidites are used in the last synthetic cycle. With the sulfur-based groups for protection and linking, oligonucleotide deprotection and cleavage are achieved via oxidation followed by beta-elimination under mild conditions. Therefore, besides for insensitive oligonucleotide synthesis, the embodiments of the invention are capable for the synthesis of oligonucleotide analogs containing sensitive functional groups that cannot survive the harsh conditions used in prior art oligonucleotide synthesis technologies.

Nucleoside or nucleotide analog compounds having the structure shown below, a method for preparing them, and applications in nucleic acid sequencing are disclosed. The compounds have formula (I): ##STR00001## wherein L.sub.1, L.sub.2, and L.sub.3 are each independently a covalent bond or a covalently linked group; B is a base or a base derivative selected from purines, pyrimidines, or analogs thereof; R.sub.1 is —OH, a phosphate group, or a nucleotide; R.sub.2 as H or a cleavable group; R.sub.3 is a detectable group or a targeting group; R.sub.5 is an inhibitory group; R.sub.4 is H, —NH.sub.2, or —OR.sub.6, wherein R.sub.6 is H or a cleavable group; and C is a cleavable group or a cleavable bond.

Disclosed are a 5′-modified nucleoside and a nucleotide using the same. The nucleoside of the present invention is represented by the formula (I) below. The 5′-modified nucleoside of the present invention is usable as a substitute for a phosphorothioate-modified nucleic acid, which has a risk of, for example, accumulation in a specific organ. The 5′-modified nucleoside also has excellent industrial productivity because a diastereomer separation step is not involved in the production process thereof.

##STR00001##

Disclosed are a 5′-modified nucleoside and a nucleotide using the same. The nucleoside of the present invention is represented by the formula (I) below. The 5′-modified nucleoside of the present invention is usable as a substitute for a phosphorothioate-modified nucleic acid, which has a risk of, for example, accumulation in a specific organ. The 5′-modified nucleoside also has excellent industrial productivity because a diastereomer separation step is not involved in the production process thereof.

##STR00001##

The invention provides various orthogonal nucleotide analogues and methods for using combinations of said various orthogonal nucleotide analogues for sequencing by synthesis.

The invention provides various orthogonal nucleotide analogues and methods for using combinations of said various orthogonal nucleotide analogues for sequencing by synthesis.