Abstract

Thermodynamic parameters for thermal denaturation of -lactoglobulin (-lg) should account for the dissociation coupled unfolding (DCU) transitions, Dimer&unknown;Monomer&unknown;Unfolded state. Purified -Blg (0.4-4mgml-1 in 50mM glycine-glycine-HCl buffer, pH 2.6) was heated and monitored by UV-difference spectrophotometry. The Monomer&unknown;Unfolded state transition occurred at 65-95oC with Tm equal to 82oC and a Gibbs free energy change (GU0) of 51kJmol-1. Such results were combined with parameters for -Blg dissociation leading to the Gibbs free energy change for DCU (DCU0) of 128 (+/-8.3)kJmol-1. The enthalpy and entropy change for DCU was (HDCU0) equal to 373kJmol-1 and (HDCU0) 824Jmol-1K-1. Thus, the room temperature stability of -Blg is 76kJmol-1 higher than reported previously. The possible significance of such results for protein stability function relations (PSFR) is discussed