Electron spin resonance spectroscopy of irradiated DNA

Abstract

Much work has been done in the last few years to study the effect of ionizing radiation on DNA . In a typical experiment a DNA sample is sealed off under vacuum in a quartz tube and irradiated at one end. The sample is then moved to the other (unirradiated) end and placed in the e. s. r. spectrometer. Results take the form, first, of spectra, which can obviously be obtained under a variety of irradiation and measurement conditions (variation of temperature has been a common procedure) and, secondly, of yield curves, where the area under the absorption curve is taken as a measure of the total free radicals and the radical concentration is plotted against dose. The curves usually show an exponential increase—the free radical concentration levelling off between 10 17 and 10 18 spins/g at a dose of about 1 Mrad. From the initial steep part of the curve the yield or G -value may be estimated as the number of free radicals produced by 100 eV of absorbed energy. Typical values for DNA lie between ½ and 2.