Determination of the complexation parameters of L-asparagine with some biologically active pyridine derivatives in aqueous solutions from calorimetric results

Abstract

Thermodynamic functions (lgK, ΔcG, ΔcH, ΔcS) were determined by solution calorimetry for the complex formation process of L-asparagine in its zwitterionic form with pharmacologically active ligands, such as pyridoxine, nicotinic acid, isonicotinic acid and picolinic acid in aqueous solutions at 298.15 K. It was found that the complexation affinity of L-asparagine to the pyridine derivatives follows the order picolinic acid < isonicotinic acid < nicotinic acid < pyridoxine. The influence of the presence of hydrophilic substitutes and isomerism of ligands on the stability of amino acid complexes and their thermodynamic quantities was discussed.