[Thermochemistry of dissolving glycine, glycyl-glycine, and diglycyl-glycine in a mixed water-dimethylsulfoxide solvent at 298.15 K].

The enthalpies of dissolving glycine, glycyl-glycine and diglycyl-glycine (deltaH(soln)0) in a mixed water-dimethylsulfoxide (DMSO) solvent was determined by the calorimetric method in the range of concentrations of the organic component 0 < X2 < 0.4 m.d. at 298.15 K. The enthalpies of solvation ((deltaH(solv)0) and transfer ((deltaH(tr)0) of these compounds from water to a mixed solvent were calculated. The dependencies deltaH(tr)0 =f(X2) were found to be extreme, indicating complex intermolecular interactions between the solution components. The influence of the structure and the properties of the substances dissolved and the composition of the mixture and the nature of organic solvent on their thermochemical characteristics was studied. The coefficients of enthalpy for pair interactions of glycine and its oligomers with DMSO molecules were calculated. These have positive values and increase in the order: glycyl-glycine < glycine < diglycyl-glycine. The changes in the thermochemical characteristics of dissolving, transfer, and solvation of glycine and its olygomers were shown to be determined by the energy of the mixed solvent formation, the nature of the organic solvents, and the structure of amino acids and peptides.