Interactions between amino acids and alcohols in water at 25° C.

The enthalpies of dilution of ternary aqueous solutions containing an alcohol (ethanol,n-propanol,n-butanol or tert-butanol) and an aminoacid or a peptide (glycine, glycyl-glycine or glycyl-glycyl-glycine), were measured at 25 °C. The results were used to calculate pair cross interaction parameters between solutes. The coefficients of virial expansion of the excess enthalpies are compared with those referring to solutions containing the same alcohols and other structure-breaking solutes (urea, thiourea and biuret). The enthalpic pair parameter for the systems glycine-alcohols shows the same trend, as reported in the literature, for similar structure-breaking solutes, with a maximum in the cross coefficients when reported versus the self pair interaction coefficients of alcohols. The results are interpreted in terms of a prevailing release of water from the cospheres of alcohols