Aggregation and thermodynamic study of bovine serum albumin + cationic surfactant mixture in short chain alcoholic media: Effect of composition and temperature

Abstract

To improve the application of surfactants and polymers, the knowledge of the interaction of surfactant with polymer is essential. Therefore, the interaction of bovine serum albumin (BSA) with a typical cationic surfactant, tetradecyltrimethylammonium bromide (TTAB) was investigated using the conductivity measurement method in aq. alcohols solutions having numerous alcohols concentrations at definite temperature (310.55 K) and the same alcohols concentration at variable temperatures (300.55–323.55 K). The types and extent of interactions between BSA and TTAB have been detected from the variation of critical micelle concentration (CMC) for the studied system. The CMC has been achieved from the plots of conductivity against TTAB concentration. One CMC was achieved for the TTAB + BSA mixture in all aq. alcohols media. The CMC values experience a change with the variation of alcohol contents and temperature of the study medium. The extent of micelle ionization (α), counter ions binding (β), and thermodynamic variables such as free energy (ΔGm0), enthalpy (ΔHm0) and entropy (ΔSm0) of micellization were computed from the standard thermodynamic formulae and demonstrated in detail. The ΔGm0 values were found negative which pointed out the spontaneous attitude of the aggregation process. Here, the intrinsic enthalpy gain (ΔHm0,∗) and the compensation temperature (Tc) were also evaluated and explained. The estimated parameters reveal the presence of interaction among the studied components which is dependent on solvent composition and temperature.