Radiolytic Decomposition and Radiation Sensitivity of Amino Acids in Aqueous Solution by Gamma Irradiation

Abstract

Radiation sensitivity of amino acids in aqueous solution to γ-rays was investigated by determining a rate of decomposition of amino acids on exposure to various doses of γ-irradiation. From the results the first order rate constants of the decomposition of amino acids were determined to refer the radiation sensitivities. In the aqueous solution, methionine, cystine, threonine, histidine and arginine were proved to be more radiosensitive while cysteic acid, tyrosine, alanine and proline were relatively radioresistant. Tryptophan, cystine, methionine, phenylalanine and tyrosine were more easily decomposed in mixture than in the free solution. Among other amino acids a reciprocal protection was found in the mixture and they were less easily decomposed in mixture than in the free solution. A protective effect of tryptophan, cystine, methionine, tyrosine and phenylalanine was proposed to other amino acids which were more radioresistant, in the γ-irradiated amino acids mixture.