The radiation-induced oxidation and reduction of guanine: Electron spin resonance–electron nuclear double resonance studies of irradiated guanosine cyclic monophosphate

Two free radicals are identified by electron spin resonance–electron nuclear double resonance (ESR-ENDOR) spectroscopy in single crystals of guanosine 3′,5′-cyclic monophosphate x irradiated at 4.2 K. The two absorptions are attributed to the anion and cation formed on the guanine moiety. The characteristics of the cation absorption are consistent with those postulated previously for guanine cation presumed to form in irradiated DNA.