Solvation of lysozyme and β-lactoglobulin in aqueous guanidine hydrochloride solutions

Abstract

The preferential interaction of the solvent components with lysozyme and β-lactoglobulin was determined in aqueous guanidine·HCl solutions by means of equilibrium dialysis and differential refractometry. It has been found that on the molal scale at all concentrations studied the denaturant was preferentially bound. Using a modified equilibrium dialysis technique the total denaturant binding to the two proteins was also estimated. The binding increases with increasing denaturant concentration. In 6 M guanidine·HCl where both proteins are completely denatured one denaturant molecule is bound per three amino acid residues. An attempt is also made to correlate the observed values of total binding for lysozyme with volume and enthalpy changes determined in previous studies.