PARTIAL MOLAR VOLUMES, EXPANSIBILITIES, AND COMPRESSIBILITIES OF OLIGOGLYCINES IN AQUEOUS-SOLUTIONS AT 18-55-DEGREES-C

We have determined the partial molar volumes, expansibilities, and adi abatic compressibilities of glycine, diglycine, triglycine, tetraglyci ne, and pentaglycine over the temperature range 18-55 degrees C. These data were analyzed and interpreted in terms of the hydration of these short oligoglycines and their constituent groups. From our results, w e have estimated the contributions of the peptide group to the partial molar volume and the partial molar adiabatic compressibility of these oligoglycines. Based on these data, we propose that each of the polar atomic groups of the peptide bond forms approximately two hydrogen bo nds with adjacent water molecules. Furthermore, the temperature depend ence of the partial molar volume suggests that water that solvates the polar groups of a peptide linkage behaves more like a ''normal'' liqu id than does bulk water, which exhibits its well-known anomalous liqui d properties. (C) 1994 John Wiley & Sons, Inc.