Thermodynamic properties of peptide solutions. Part 6.—The amino acid side-chain contributions to the partial molar volumes and heat capacities of some tripeptides in aqueous solution

Abstract

Limiting partial molar volumes, V⁰₂, and partial molar heat capacities, C⁰_{p, 2}, have been determined for the tripeptides glycyl-L-valylglycine, glycyl-DL-serylglycine and the D and L isomers of glycylleucylglycine in aqueous solution at 298.15 K. These V⁰₂ and C⁰_{p, 2} results, in conjunction with those for glycylglycylglycine, were used to estimate the contribution of the side chains to the thermodynamic properties. The results obtained are compared with those estimated using V⁰₂ and C⁰_{p, 2} data for amino acids and dipeptides. The comparison suggests that the tripeptides of sequence glycyl-X-glycine are reasonable models for estimating the contribution to the thermodynamic properties of proteins made by solvent-accessible side chains.