Enthalpy parameters of molecular interactions of dl-α-alanyl-dl-α-alanine with polyhydric alcohols in the aqueous solution

Abstract

Integral enthalpies of dissolution Δ_solH^m of DL-α-alanyl-DL-α-alanine in aqueous solutions of glycerol, ethylene glycol, 1,2-propylene glycol, and 1,3-propylene glycol at the concentration of the organic component up to 0.33 molar fraction have been determined by calorimetry. Standard enthalpies of dissolution (Δ_solН⁰) and the transfer (Δ_trН⁰) of the dipeptide from water to aqueous solutions of the polyhydric alcohols have been calculated. The calculated enthalpic coefficients of pairwise interactions of DL-α-alanyl-DL-α-alanine with polyhydric alcohols are positive. The influence of the position of hydroxy groups in the polyhydric alcohol molecule on the enthalpic parameter of the interaction with the dipeptide has been revealed. The effect of various types of the interaction in the solution and structural features of biological molecules and the cosolvent on the enthalpic parameters of the dissolution has been analyzed.