An EPR study of the transfer of radical-induced damage from the base to sugar in nucleic acid components: relevance to the occurrence of strand-breakage

Abstract

EPR spectroscopy has been employed, in conjunction with a rapid-flow system and the Ti^III–H₂O₂ and Ti^III–HOOSO₃^– redox couples, to study the reactions of ˙OH and SO₄˙^– with pyrimidine nucleosides. From experiments which complement radiolytic and photolytic studies it is concluded that the formation of base-centred radical-cations (from SO₄˙^– and from ˙OH at low pH) is followed both by hydration and by loss of the C2′-H in the ribose (but not 2-deoxyribose) ring: further fragmentation follows the latter reaction. The crucial role of the C2′-OH group in the transfer of damage is discussed.