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

Limiting partial molar volumes, V02, and partial molar heat capacities, C0p, 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 C0p, 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 C0p, 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.