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

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.