The Partial Molar Volume and Heat Capacity of the Glycyl Group in Aqueous Solution at 25^C

Abstract

The partial molar volumes, V2^, and the partial molar heat capacities, Cp,2^, at infinite dilution have been determined for three new peptides of sequence seryl(glycyl)xglycine, where x=0 to 2, in aqueous solution at 25^C. Values for V2^ at 25°C have also been determined for two neutral peptide derivatives N-acetylglycylglycinamide and N-acetylglycylglycylglycinamide. These V2°; and Cp,2°; results were used to estimate the partial molar volume and heat capacity of the backbone glycyl group, CH2CONH, of proteins in aqueous solution at 25°;C. The results obtained are compared with those calculated using partial molar data for alternative model compounds. The new glycyl group contributions are in excellent agreement with those currently used in our group additivity schemes for the calculation of the partial molar volumes and heat capacities of unfolded proteins.