Radiation-induced Oxidation of Cytosine and Uracil in Aqueous Solution of Copper (II)

Abstract

BOTH the hydrated electron, e−aq, and the hydroxyl radical, OH, which are formed as the principal intermediates in water radiolysis, react rapidly with the pyrimidine bases through preferential addition to the 5, 6 double bond to give the hydropyrimidyl radical, BH, and the hydroxypyrimidyl radical, BOH, respectively1–4. The yields for base destruction (molecules/100 eV) in oxygen-free solutions under γ-rays are, however, consistently low, G(−B) ⩽ 1 (refs. 5 and 6), when compared with primary yields of the radical species derived from water, Ge−aq = 2.85, GOH = 2.4 (ref. 7); recent work indicates that secondary reactions of BH and BOH lead to regeneration of the parent compound4. In oxygen-saturated solutions, e−aq, is scavenged by oxygen to form O−2(HO2), the regeneration reaction is quenched, and the yield for base destruction increases to G(−B)∼2 through reactions involving the peroxy radical, B(OH)⨀2. Many organic products are formed, however, from the intermediate, B(OH)⨀2, and the overall product stoichiometries have yet to be fully elucidated8.