OH-induced free radicals in purine nucleoside monophosphates: e.s.r. and spin-trapping.

Free radicals produced by the reactions of OH radicals with six purine nucleoside monophosphates (3'-AMP, 5'-AMP, 5'-dAMP, 3'-GMP, 5'-GMP and 5'-dGMP) were investigated by a method combining e.s.r. spin-trapping and high-performance liquid chromatography (HPLC). The N2O-saturated aqueous solutions of purine nucleoside monophosphates, containing 2-methyl-2-nitrosopropane as a spin-trap, were X-irradiated and the resulting spin-adducts were separated by reverse-phase HPLC in the ion suppression mode. The separated spin-adducts were characterized by e.s.r. spectrometry and UV spectrophotometry. Consequently, the radicals due to H-abstraction at the C4' position of the sugar moiety were identified arising from 5'-dAMP and 5'-dGMP. In all cases, e.s.r. spectra consisting of a secondary doublet were observed and assigned to the radical due to H-abstraction at the C5' position of the sugar moiety.