Quantitative E.S.R.-measurements of Radiation-induced Radicals in Nucleosides

Abstract

Summary The nucleosides deoxycytidine · HCl, thymidine, deoxyadenosine, deoxyguanosine, deoxyuridine, bromodeoxyuridine and iododeoxyuridine have been irradiated as dry crystalline powders and investigated by electronspin-resonance spectrometry. First derivative spectra of each substance were recorded at 9·4 kMc/sec after x- and gamma-irradiation with a whole range of doses up to 10 Mr. Qualitative results obtained at about 100°k and 300°k include new structural details of spectra. Emphasis has been placed on quantitative determinations. When obtained from the initial linear parts of dose-effect curves, G-values range from 0·4 to 1·4 after irradiation at room temperature. No considerable differences from these values are found at low temperature but on warming up to room temperature about half of the radicals disappear irreversibly. Departure of radical-concentration from a linear dependence on radiation dose occurs above 1 Mr at all temperatures for the nucleosides investigated.