Electron Transfer Oxidation of DNA Radicals by Paranitroacetophenone

Publisher Website
Google Scholar
Abstract
The reaction of a typical electron-affinity sensitizer, p-nitroacetophenone (PNAP) with the model compounds thymine, thymidine, thymidylic acid, deoxyribose and single and double-standed [calf thymus] DNA was investigated by pulse radiolysis. Radicals formed by 1-electron reduction of the bases and of DNA react rapidly and efficiently with PNAP by electron transfer. A small yield of transfer (< 10%) is also observed arising from oxidation of the radicals formed by the small proportion of OH which react at the sugar moieties in DNA. Electron transfer oxidation by PNAP of radicals formed by the addition of OH to the base moieties, e.g., thymine, is not an efficient process. Addition of the sensitizer to the thymine OH-adduct proceeds at a rate that is too low to measure by pulse radiolysis. Since the major sites of OH reaction with DNA are the heterocyclic bases (> 80%), oxidation of the resultant radicals is unlikely to be a major step in the mechanism of sensitization by this typical hypoxic-cell sensitizer. [Electron-affinity sensitizers have a potential use in radiotherapy, because of their ability to sensitize hypoxic cells differentially in tumors.].

This publication has 1 reference indexed in Scilit: