Effects of ceramics irradiation on dissociation state of L-amino acids

Non-thermal effects of ceramics irradiation on dissociation state of twenty L-amino acids have been investigated. Dissociation constants of the amino acids other than His and Glu varied by a 3-h irradiation under cooling. pK's of alpha-carboxyl group of amino acids having longer side chains on the alpha-carbon were decreased by the irradiation. Although pK's of alpha-amino group of Arg, Lys, Asp, and CySH were decreased by the irradiation and pK of Tyr was increased, pK's of the other fifteen amino acids were not affected. Although the isoelectric points of Lys, Arg, Trp, Asp, and CySH were decreased by the irradiation, those of the other fifteen amino acids were not affected. It was suggested that various changes in pH of amino acids in aqueous solution and dissociation state of the functional groups will be caused from stimulation by the irradiation and stabilization of the hydration layer around amino acids.