Thermodynamic denaturation of β-lactoglobulin in the presence of cetylpyridinium chloride

In this work, we determined the stability parameters of bovine β-lactoglobulin, variant A, (BLG-A), in relation to their transition curves induced by cetylpyridinium chloride (CPC) as a cationic surfactant. The experiments took place over the temperature range of 298 K to 358 K. For each transition curve at any specific temperature, the conventional method of analysis, which assumes a linear concentration dependence of the pre- and post-transition base lines, gave the most realistic values for ΔGD(H2O). Results show that the minimum value of ΔGD(H2O) occurs at T = 328 K. Using the Gibbs–Helmholtz equation, the values of enthalpy, ΔHD, and entropy, ΔSD, of denaturation have been calculated considering temperature dependence of ΔGD at any specified concentration of CPC. The values of 12.05 kJ · mol−1, 18.54 kJ · mol−1, and 18.32 J · mol−1 · K−1, were obtained for ΔGD(H2O), ΔHD(H2O), and ΔSD(H2O), respectively. The results show that the enthalpy term dominates the entropy term.