Singlet oxygen takes part in 8-hydroxydeoxyguanosine formation in deoxyribonucleic acid treated with the horseradish peroxidase-H2O2 system

Treatment of calf thymus deoxyribonucleic acid (DNA) with the horseradish peroxidase-H2O2 system resulted in efficient formation of 8-hydroxydeoxyguanosine (8-OH-dG) residues. It was concluded that singlet oxygen was the reactive species involved, based on experiments using active oxygen scavengers and D2O. For 8-OH-dG formation, a higher-ordered polynucleotide structure seems to be required: double stranded DNA was a better substrate for the reactive species than single stranded DNA, and monomeric deoxyguanosine underwent C8-hydroxylation to a lesser extent.