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 radiation on thymine residues in DNA. We report NMR and molecular modeling studies on a DNA duplex structure which contains guanine opposite formamide residue. 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 globally a B form structure for the two isomers. Conformational changes are observed between the two isomers.