Comparative E.S.R.-measurements of Radical Production in Amino Acids by210Po Alpha- and60Co Gamma-radiation

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Abstract
The spectra and radical yields for eight different amino acids after irradiation with 210Po α-particles were investigated by E.S.R.-spectroscopy, and compared to those for 60Co γ-rays and x-rays. Radical-concentration as a function of dose of α-particles was determined, as well as the effect of storage time on the radical-concentration and amplitude of the first derivative signal. The hyperfine spectra obtained from the aromatic amino acids after α-irradiations were identical with those observed after γ-irradiations, in contrast to our findings for aliphatic amino acids. After α-irradiation, the radical yields of the aliphatic amino acids were about a factor of six less than those obtained with γ-rays, while for the aromatic amino acids the reduction in yield was much smaller. With post-irradiation storage time, a stronger reduction in radical-concentration was observed after α-irradiation than that reported after x-irradiation. the dependence of radical-concentration on radiation dose was compared for α- and x-rays. The typical saturation of radical-concentration was found to occur independently of the actual concentration reached and at nearly equal doses of different radiations.