Excess enthalpies of aqueous solutions of (urea + one of four dipeptides)

Abstract

The excess enthalpies at 298.15 K of aqueous solutions of urea + each of the dipeptides glycylglycine, glycylalanine, alanylglycine, and alanylalanine have been determined by flow microcalorimetry. These results along with enthalpies of dilution for the initial solutions were used to determine the enthalpy interaction coefficients h xy, xyy, etc., that characterize the pair and triplet interactions between urea y and a dipeptide x. The pairwise-interaction coefficients are all negative and show a dependence on the dipeptide side-groups. The results are discussed in terms of the likely solute-solute interactions.