PRIMARY REDOX EVENTS IN THE RADIOLYSIS OF DNA

This study gathers results found in recent publications concerning the early events that take place in DNA subjected to ionizing radiation. These results bring about a new way of contemplating the behavior of c harges produced initially in this molecule, and lead to the developmen t of a new model describing the fate of these charges. In this model, the reduction of the cytosine (C) base by the electron ejected during the ionization process would induce double-strand breaks. The anion ra dical C--., once formed, is readily protonated by its complementary gu anine (G), to form the radical C(H)(.). The deprotonated guanine, G(-H )(-), can donate its electron to a radical cation, created during the ionizing process, with the formation of the radical G(-H)(.). These tw o coupled free radicals lead to several reactions, one of which being a double-strand break. According to this model, the single-strand brea ks would originate either from the reduced thymine or from oxidation r eactions initiated by the positive charge.