Theoretical study of molecular interactions of amino acids in aqueous carbohydrate solutions by scaled particle theory

Abstract

The scaled particle theory (SPT) has been applied to study solvation thermodynamics of some polar and non-polar amino acids (<em>l-</em>serine, <em>l-</em>threonine, <em>l-</em>asparagine, <em>l-</em>glutamine, glycine, <em>l-</em>alanine, <em>l-</em>valine, <em>l-</em>methionine) in water and in aqueous-glucose (5% <em>d</em>-glucose, <em>w/v</em> in water) at 298.15 K. The solvation free energy (Δ<em>G</em>_Solv), enthalpy (Δ<em>H</em>_Solv) and entropy (Δ<em>S</em>_Solv) of amino acids in aqueous-glucose have been calculated using SPT from various contributions. The results show that the major contribution to thermodynamic parameters is from the interactions between the participating components. While the cavity formation for accommodation of amino acid molecules in aqueous-glucose molecules does not dependent solely on contributions from enthalpy, there is specific contribution from entropy terms. The results also indicate that the interactions in the studied systems follow the order: <em>l</em>-serine < <em>l</em>-threonine < <em>l</em>-asparagine < <em>l</em>-glutamine in the case of polar amino acids; and glycine < <em>l</em>-alanine < <em>l</em>-valine < <em>l</em>-methionine in case of non-polar amino acids.