Radiation-induced degradation of DNA bases

Radio-induced degradation of DNA involves radical processes. A series of le sions among the major bases degradation products has been measured in isola ted DNA exposed to gamma radiation in aerated aqueous solution. Degradation can be accounted for by the formation of hydroxyl radicals upon radiolysis of water (indirect effect). The four bases are degraded in high yield. Dir ect effect has been mimicked by photo-induced electron abstraction from the bases producing their radical cation, Quantification of the modified bases showed that guanine is the preferential target. This can be explained by i ts lower oxidation potential and charge transfer phenomena.