Apparent molal volumes and heat capacities of low molecular weight peptides in water at 25 °C

Abstract

The apparent molal volumes [Formula: see text] and beat capacities [Formula: see text] of oligopeptides of glycine, alanine, and serine have been determined in water at 25 °C by flow densimetry and flow microcalorimetry. The data are reported for the homologous series: glycine to pentaglycine, L-alanine to tetra-L-alanine and L-serine to tri-L-serine. From the limiting [Formula: see text] and [Formula: see text] values of the glycine oligomers, the contributions of the glycyl residue in an extended polypeptide chain has been evaluated as: [Formula: see text] and [Formula: see text] The data for the other peptides are discussed in terms of contributions from the amino acid side chains, i.e. —CH3 and —CH2OH, and end-group hydration effects. Some necessary conditions for obtaining useful additivity schemes for predicting [Formula: see text] and [Formula: see text] of extended polypeptides and proteins are indicated.