Electron Spin Resonance Investigations of Ultra-violet and X-irradiated Methionine

Abstract

WE have already reported¹ that both ultra-violet and X-rays produce the same electron spin resonance signal in cysteine but that in certain other sulphur-containing compounds² the two types of radiation produce electron spin resonance signals which are not identical. On exposing bovine serum albumin, homocysteine and methio-nine to ultra-violet following irradiation with X-rays the X-ray signal was transformed. This change might have occurred because the site of the radical was shifted by additional energy, in which case the intensity of the signal after the delocalization was increased on further ultra-violet irradiation of the sample. Alternatively, ultraviolet absorption by the X-ray-induced radicals may have caused quenching. Examination of the change in radical concentrations should help to elucidate the mechanism, and initial results are now reported.