Studies on the Mechanism of Action of Ionizing Radiations: XIII. The Effect of X-Irradiation on Some Physico-Chemical Properties of Amino Acids and Proteins

Publisher Website
Google Scholar
Abstract
Dilute aqueous solutions of aromatic amino acids showed marked changes in their absorption spectra after X-irradiation with moderate doses, irradiation of tyrosine increasing light absorption around 2800 A and irradiation of tryptophan decreasing it. Similar changes were observed on irradiation of proteins those with a tyrosine/tryptophan ratio greater than 1 showed an increase in light absorption, whereas those with a ratio less than 1 showed a decrease. Inhibition of enzyme activity of lysozyme seemed to be related to decrease of light absorption in the far UV, about 2400 A. The initial reaction on X-irradiation of amino acids seems to be an oxidative deamination: on X-irradiation of glycine there was equimolar formation of glyoxylic acid and NH3. On X-irradiation of serum albumin with doses insufficient to produce denaturation there was a decrease in the combining power with anionic dyes and an increase in the combining power with Cu++ ions. These effects are explained as the consequence of the loss of NH2 groups in the protein.