Volumetric study of aqueous proline-leucine solutions from 283.15 K to 318.15 K

摘要

Intermolecular interactions in molecules of low molecular weight,taken as molecular models for the more complex polypeptide and protein compounds,have been investigated in the last decades.Thermodynamic properties have been assessed in order to give insight on intra and intermolecular interactions of the different functional groups and on the macroscopic characterization of the hydration.Among these properties the first derivative of volume namely the molar isobaric expansion is one of the most sensitive to' the hydration changes accompanying temperature,and composition variations.Based on the fact that new reliable data is needed either for the thermodynamic characterization of peptides or for the data base needed to pursue the additive models based on small molecules,in this work we determined limiting partial molar volumes and isobaric expansions of proline-leucine dipeptide in water from 283.15 K to 318.15 K.The interpretation of the limiting partial molar volume and isobaric expansion data as a function of temperature,jointly with the trend of the slopes of apparent molar volumes as a function of molality,has been made on the basis of solute-solute-solvent interactions and structure making ability of the solute.