Thermodynamics of aromatic amino acid solvation and the solute– Alcohol interactions in the highly aqueous water-tert-butanol binary mixtures

This paper focuses on thermodynamics of solvation of two essential aromatic amino acids, viz. L-phenylalanine and L-tryptophan, in highly aqueous water- tertiary butanol (t-BuOH) mixtures at 298.15 K. The experimental results are used to compute pair and triplet interaction parameters between the amino acid and alcohol molecules in water. The pair interaction is found to be repulsive due to the unfavorable enthalpic term, while the favorable entropy change leads to the attractive amino acid interaction with two alcohol molecules. The most important finding from the information obtained is that many-body correlations between t-BuOH molecules are responsible for alcohol clustering in water and pronounced extrema on the curves of Δ_tY⁰ –vs X_t-BuOH for both aromatic amino acids.