Apparent molar volumes of some amino acids and peptides in aqueous urea solutions

Abstract

Densities of solutions of several α-amino acids and peptides in 3 and 6m aqueous urea solvents have been determined at 298.15 K. These data have been used to evaluate the infinite-dilution apparent molar volumes of the solutes and the volume changes due to transfer ( V ⁰_tr) of the α-amino acids and peptides at infinite dilution from water to aqueous urea solutions. The sign and magnitude of the (V ⁰_tr) values have been rationalized in the framework of Friedman's cosphere-overlap model. The V ⁰_tr values for the glycyl group (-CH₂CONH-) and alkyl side chains have been estimated.