Sensitization of thymine and uracil to ionizing radiation by p-nitroacetophenone

p-Nitroacetophenone (PNAP) alters the radiation chemistry of thymine and uracil in de-aerated aqueous solution. In the case of thymine, it increases the yield of radiolysis products by a factor of almost two, and cis glycol of thymine is the major product. With uracil, the yield of the dimeric product, which is the major radiolysis product in de-aerated aqueous solution, is considerably reduced and the yield of cis glycol is increased. When the irradiation is carried out in N2O-saturated solution, PNAP enhances the yeild of glycol by a factor of two. The effects of cupric sulphate on the radiation chemistry of uracil are analogous to those of PNAP. A mechanism, involving a reaction between PNAP and the hydroxyl radical adduct of the pyrimidine proceeding through a one-step process, is postulated for the enhanced formation of glycol.