Estimation of partial molar volumes of α-amino acids in water

Abstract

A method of estimating partial molar volumes of α-amino acids in water, starting from the partial molar volume of glycine, is described. For eleven zwitterionic amino acids the estimated partial molar volumes are found to be in very good agreement with the experimental values given in the literature.Amino acids having ionisable side chains can exist in aqueous solution as different ionic species; the partial molar volumes of these obtained from our densitimetric studies have been compared with the estimated values. The method gave good results for the ionic species of lysine and arginine, where the charge centre in the side chain is well separated from [graphic omitted] and α-COO–, but not for all species of aspartic and glutamic acids. However, for the two dicarboxylic amino acids a different procedure, using data for α,ω-amino acids, gave good estimates of the partial molar volumes.