Thermodynamic stability and retinol binding property of β-lactoglobulin in the presence of cationic surfactants

In this work the stability parameters of bovine β-lactoglobulin, variant A (BLG-A), with regard to their transition curves induced by dodecyltrimethylammonium bromide (C12TAB), tetradecyltrimethylammonium bromide (C14TAB) and hexadecyltrimethylammonium bromide (C16TAB) as cationic surfactants, were determined at 298 K. For each transition curve, 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). The results represent the increase in the denaturating power of surfactants with an increase in hydrocarbon chain length. The value of about 22.27 kJ · mol−1 was obtained for ΔGD(H2O) from transition curves. Subsequently, the retinol binding property of BLG as its functional indicator was investigated in the presence of these surfactants using the spectrofluorimeter titration method. The results represent the substantial enhancement of retinol binding affinity of BLG in the presence of these surfactants.

► The stability parameters of β-lactoglobulin, BLG, in the presence of CnTAB have been evaluated.
► Rising in hydrocarbon chain length increases the denaturating power of surfactants.
► CnTAB enhances the retinol binding affinity of BLG in all of its concentration range.