PROTON ASSISTED INTRAMOLECULAR ELECTRON-TRANSFER REACTIONS IN DNA - A PROPOSED MECHANISM

The interaction of ionizing radiation with DNA leads to the creation of radicals whose ESR spectra suggest the presence of guanine cation and thymine anion radicals. Later it was suggested that the cytosine anion could be also present. Recent studies on the reduction potentials of the purine and pyrimidine bases of DNA, their reaction with mild reductants and oxidants and the acid/base properties of their reduced and oxidized radicals had confirmed these ESR conclusions. Based on these findings, we review the possibility of internal electron transfer in DNA and discuss the unique role of the cytosine/guanine pair in this transfer.