Structure of an oligonucleotide containing a N-(2-deoxy-beta-D-erythro-pentofuranosyl)formamide residue facing a guanine

Formamide residue is a major oxidative DNA damage product from ionizing rad iation on thymine residues in DNA. We report NMR and molecular modeling stu dies on a DNA duplex structure which contains guanine opposite formamide re sidue. Formamide residue exists as either the cis and trans isomer. For the trans and the cis isomers, we find that guanine and formamide are stacked inside the helix and are hydrogen bonded. The oligonucleotide adopts global ly a B form structure for the two isomers. Conformational changes are obser ved between the two isomers. (C) 2000 Societe francaise de biochimie et bio logie moleculaire/ Editions scientifiques et medicales Elsevier SAS.