Radiation-Induced Hydrogen Transfer in Nucleic Acids, Proteins, and Related Substances: Effects of Temperature and Scavengers

Abstract

G values for γ-irradiation-induced hydrogen transfer from exchangeable to carbon-bound sites in dry salmon sperm DNA, D-glucose, ribonuclease, and poly-DL-alanine have been measured and compared with the initial radical yields previously determined by ESR. The effects of temperature, of hydrogen atom scavengers (formate and cupric ions and glucose) and of electron scavengers (cupric and cadmium ions and sulfur hexafluoride) were investigated. Of the scavengers, only cupric ions had a significant effect on the G values, with a decrease of about 90% for DNA and of about 70% for ribonuclease and glucose. Cupric ions may act as scavengers of electrons and/or hydrogen atoms or by quenching triplet states, thus reducing the initial yield of secondary radicals, whose subsequent radiation-induced destruction appears to be responsible for the tritium incorporation. The relationship between radiation-induced hydrogen transfer, the mechanism of radical saturation and the hypothesis that either primary or secondary f...