Interaction of the functional group and hydrocarbon radicals in the L-alanine and glycine amino acids in aqueous NaCl, KCl, and urea solutions at different temperatures

Abstract

The calorimetric method at temperatures of 288 K, 298 K, and 313 K is used to measure the heats of dissolution of L-α-alanine in aqueous NaCl (m ≤ 5 mol/kg water) and KCl (m ≤ 4 mol/kg water) solutions. The enthalpy and heat capacity coefficients are determined for the pair and triple interactions of alanine with nonaqueous components. Literature data is used to find the contributions from the charged NH₃⁺ and COO^– groups and the hydrocarbon radicals СНСН₃ of L-alanine and СН₂ of glycine in mixtures of water with NaCl, KCl, and urea. A discussion is given of the impact of additives and temperature on the interactions of hydrophilic and hydrophobic amino acids in the said systems.