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Methylated DNA: The influence of 7‐deaza‐7‐methylguanine on the structure and stability of oligonucleotides
Author(s) -
Seela Frank,
Chen Yaoming
Publication year - 1997
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19970800406
Subject(s) - chemistry , phosphoramidite , exonuclease , phosphodiester bond , oligonucleotide , stereochemistry , moiety , dna , nuclease , phosphodiesterase , duplex (building) , guanosine , hydrolysis , crystallography , biochemistry , enzyme , dna polymerase , rna , gene
The 7‐deaza‐2′‐deoxy‐7‐methylguanosine ( 2b ) [9], which is the glycosylic‐bond‐stable, noncharged analogue of 2′‐deoxy‐7‐methylguanosine ( 1b ), was incorporated in DNA by solid‐phase synthesis. As building blocks, the protected phosphonatc 3a and the phosphoramidite 3b were prepared. The 7‐methyl group of 2b stabilizes the B‐DNA duplex compared to 7‐deaza‐2′‐deoxyguanosine but does not induce a B‐Z transition as it is known from compound 1b . The stabilization by the 7‐deaza‐7‐methylguanine moiety is sequence‐dependent, and the nearest‐neighbor influence is different from that of 7‐deazaguanine. Homooligonucleotides of 2b show sigmoidal melting indicating a highly ordered single‐stranded structure. In general, Oligonucleotides containing 2b are very stable against hydrolysis with calf‐spleen phosphodiesterase (CS‐PDE, 5′ → 3′ exonuclease), while phosphodiester hydrolysis with snake‐venom phosphodiesterase (SV‐PDE, 3′ → 5′ exonuclease) is only slightly reduced.