Patent ID: 9169510
Filing Date: 2015-10-27
Classification: C12Q,G01N

Abstract:
1. A method for determining the nucleotide sequence of a single-stranded DNA comprising performing the following steps: (a) immobilizing the single-stranded DNA on a solid substrate via an azido linkage, an alkynyl linkage, or a 1,2,3-triazole linkage; (b) contacting the DNA under DNA polymerization-permitting conditions with (i) a 3′-O-blocked dNTP selected from the group consisting of 3′-O-blocked dATP, 3′-O-blocked dCTP, 3′-O-blocked dGTP, and 3′-O-blocked dTTP, wherein each 3′-O-blocked dNTP comprises an unmodified triphosphate group, and wherein each 3′-O-blocked dNTP comprises an unlabeled base, and (ii) 9° N DNA polymerase (exo-) A4851/Y409V, wherein the moiety blocking the 3′-O atom of the dNTP is an allyl moiety or a methoxymethyl moiety; (c) (i) determining whether pyrophosphate is generated as a result of step (b), whereby (1) pyrophosphate generation indicates that polymerization has occurred and the identity of the nucleic acid residue in the DNA is that which is complementary to the 3′-O-blocked dNTP used in part (i) of step (b), and (2) the absence of pyrophosphate generation indicates that the identity of such nucleic acid residue is not that which is complementary to such 3′-O-blocked dNTP; wherein determining whether pyrophosphate is generated is performed by detecting dissociation of a coumarin-derived indicator from a complex between the indicator and a bis-Zn and (ii) if pyrophosphate is not generated, repeating step (b) once, twice or three times as necessary, wherein in each repetition a 3′-O-blocked dNTP is used which is different from any 3′-O-blocked dNTP already used, and determining, after each repetition of step (b), whether pyrophosphate is generated, such generation indicating that polymerization has occurred and the identity of the nucleic acid residue in the DNA is that which is complementary to the 3′-O-blocked dNTP used in part (i) of the repeated step (b); and (d) removing from the 3′-O-blocked dNTP polymerized in step (b) or (c), whichever is applicable, the moiety blocking the 3′-O atom of the dNTP, with the proviso that such removing step is optional in the event that there remains no further nucleic acid residue of the DNA whose identity is to be determined; and (e) iteratively repeating each of steps (b) to (d) for each nucleic acid residue of the single-stranded DNA whose identity is to be determined, thereby determining the sequence of the single-stranded DNA.