Effect of copper(II) ions on the γ-radiolysis of uracil

Abstract

Radiation sensitization of uracil (Ura) by Cu^II ions has been investigated using cobalt-60 γ-rays. In N₂O-saturated solution, when no additive is present, the base degradation yield, G(– Ura), is only ca. 3.3, but when Cu^II ions are added in either a free or complexed state to the solution before irradiation, G(– Ura) is found to increase to ca. 5.1. The enhanced degradation of the base is derived from the oxidized transient, e.g. UraOH⁺, although reduction of Cu^II to Cu^I has been ascribed to all the primary adducts, e.g. UraH, UraOH and Ura^–. Glycol and isobarbituric acid constitute the major products of radiolysis, which are derived from the oxidized UraOH⁺ species. Hydroxydihydrouracil and its dimer have also been detected in significant yields when the radiolysis is carried out at comparatively high absorbed doses. The formation of these products has been ascribed to a secondary reaction between UraOH and Cu^I which proceeds through the intermediate formation of a Cu—C bond.