Interaction of tetradecyltrimethylammonium bromide with bovine serum albumin in different compositions: Effect of temperatures and electrolytes/urea

Herein, the interaction of a protein, bovine serum albumin (BSA), with tetradecyltrimethylammonium bromide (TTAB, a cationic surfactant), has been investigated using the conductivity measurement technique in pure water and some sodium salts (NaCl, Na2SO4, Na2CO3, and Na3PO4) solutions at temperature range of 295.15-320.15 K. Results reveal that, in the plot of specific conductivity versus the concentration of TTAB, only a single critical micelle concentration (cmc) was found for the TTAB + BSA mixed system in all solvents media studied. The addition of BSA in aqueous TTAB solution, the value of cmc undergoes a change fromits pure form, which indicates the presence of strong interaction operating between the BSA and TTAB molecules. In aqueous system, the cmc values of the TTAB + BSA mixtures are obtained higher compared to the values found for single TTAB surfactant. However, the addition of salt decreases the cmc value ofmixed TTAB+ BSA system. The values of cmc of the BSA+ TTABmixed system at 310.15 K and 1.00 mmol.kg (-1) ionic strength of salt followed the order: cmc(Na2CO3) > cmc(Na3PO4) > cmc(NaCl) > cmc(Na2SO4). The cmc values of TTAB+ BSA mixture were found to be lowered in urea solution within the concentrations studied. The values of degree of dissociation (alpha) and fraction of counter ion binding (beta) were found to be dependent on additives and temperature. The free energy of micellization (Delta G(m)(o)) is negative for all the systems, whichmanifests that themicellization phenomenon is energetically spontaneous. The enhancement of the negative value of Delta G(m)(o) in aqueous salt solutions reveals an increase of spontaneity of the TTAB+ BSA micellization process. The values of Delta G(m)(o) also reveal that the spontaneity of micelle formation is enhanced at higher temperatures in allmedia studied. The values of free energy of transfer (Delta G(m)(0),(t)) were also determined for numerous solvent media used in the present study and described with appropriate reasoning. (C) 2020 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd. All rights reserved.

Automated summary

The study investigated the interaction between BSA and TTAB in different solvents, finding changes in critical micelle concentration and spontaneity of micellization process. The addition of salt decreased the cmc value in mixed systems, while temperature and additives influenced the dissociation degree and fraction of ion binding. The free energy of micellization was found to be negative, indicating energetically spontaneous micellization process.