Micellization, interaction and thermodynamics behavior of BSA + SDS mixture in aqua-organic mixed solvent: Influences of temperature and solvent composition

Abstract

The interaction of bovine serum albumin (BSA) with sodium dodecyl sulphate (SDS) in aqueous medium as well as aqua-organic mixed media has been performed using the conductivity measurement technique at several temperatures. The experiments were performed in the temperature ranges of 298.15–313.15 K with a gap of 5 K. The critical micelle concentration (CMC) and the degree of micelle ionization (α) have been computed from the specific conductivity versus the surfactant concentration plot. The CMC values achieved in the present study are dependent on the concentration of BSA, composition of the mixed solvent, and a variation of experimental temperature. For SDS + BSA mixture, an increase of BSA concentration causes a decrease in the values of CMC. Also, the values of CMC of SDS + BSA system in water-organic solvents were found to follow the order: CMCwater-DMF > CMCwater-AN > CMCwater-DMSO > CMCwater. In every case examined, the association of SDS + BSA mixture was spontaneous (negative ΔG0m). On the basis of observed ΔH0m and ΔS0m values for the SDS + BSA mixed system, it is expected that an electrostatic, hydrophobic, and ion–dipole interactions are in effect between SDS and BSA species, whereas the hydrophobic interaction is believed to be the main driving force for the aggregation process. In each of the case thoroughly detected, a linear relationship between ΔH0m and ΔS0m values was viewed, which is a strong indication in favor of the presence of enthalpy–entropy compensation phenomenon in the overall interaction process.