Role of Oxygen in the Cross-linking and Degradation of Deoxyribonucleic Acid by Ionizing Radiations

Abstract

WHEN deoxyribonucleic acid in dilute aqueous solutions is irradiated with X-rays, the attack by the free radicals produced in water leads to main-chain scission, and this reaction is essentially the same in the presence as in the absence of oxygen¹. Irradiation of nucleic acid in the solid state and containing less than 25 per cent of water leads to a complex series of reactions which, judged by physico-chemical measurements, were largely unaffected by oxygen. With nucleic acid gels having a water content between these two extremes, oxygen was found to exert a pronounced influence on the changes produced by irradiation with 1-MeV. electrons. Since deoxyribonucleic acid is present in the cells in the form of a relatively concentrated gel, the response to radiation in this form is more likely to be of biological significance than the behaviour of dilute solutions or nearly dry solid.