Effect of DNA conformation on the hydroxyl radical-induced formation of 8,5'-cyclopurine 2'-deoxyribonucleoside residues in DNA

Reactions of hydroxyl radicals with DNA form a variety of base and sugar products and 8,5'-cyclopurine 2'-deoxyribonucleoside residues in DNA. The effect of DNA conformation is reported on the yields of 8,5'-cyclopurine 2'-deoxynucleosides and the ratios of their (5'R)- and (5'S)-diastereomers. The yields of 8,5'-cyclo-2'-deoxyadenosine and 8,5'-cyclo-2'-deoxyguanosine in single-stranded DNA (ss-DNA) were higher than those in ds-DNA. The (5'R)-diastereomers in ss-DNA. In contrast, the yields of the (5'S)-diastereomers in ds-DNA were slightly higher than those of the (5'R)-diastereomers. The G values of 8,5'-cyclo-2'-deoxyadenosine in ss-DNA and ds-DNA were 0.042 and 0.025, respectively. Those of 8,5'-cyclo-2'-deoxyguanosine in ss-DNA and ds-DNA were 0.038 and 0.017, respectively. (author)