Molecular Interactions of L-Histidine in an Aqueous Buffer Solution in the Temperature Range of 288–313 K

Abstract

The behavior of L-histidine (His) in an aqueous buffer solution (pH 7.4) is studied via densimetry and differential scanning calorimetry. The densities and specific heat capacities of solutions of the amino acid are determined in the 288.15–313.15 K range of temperatures at His concentrations of 0.00215 to 0.03648 mol kg−1. The apparent and partial molar parameters of L-histidine in the buffer solution are found, and features of the temperature and concentration dependences are identified. It is shown that the partial molar properties of transferring the amino acid from water to the buffer solution (both volume and heat capacity) have positive values in the investigated range of temperatures. Different types of molecular interaction between the solute and the solvent are considered using the Gurney model.