Interaction of Bovine Serum Albumin with Cationic Single Chain plus Nonionic and Cationic Gemini plus Nonionic Binary Surfactant Mixtures

The interaction of bovine serum albumin (BSA) with cetyltrimethylammonium bromide (CTAB), C16C4C16Br2, Brij58, and their binary mixtures has been Studied using tensiometry, spectrofluorometry, and circular dichroism at physiological pH and 25 degrees C. The tensiometric profiles of CTAB and C16C4C16Br2 in the presence of BSA exhibit a single break at a lower surfactant concentration termed as C-1 (concentration corresponding to saturation of the interface) compared to their critical micelle concentration (CMC) in the buffered Solution. However, for Brij58, CTAB+Brij58, and C16C4C16Br2+Brij58, two breaks were observed, first at the critical aggregation concentraion (CAQ, corresponding to onset of interaction with BSA and the second at C, corresponding to saturation of the interface. The interaction of CTAB+Brij58 and C16C4C16Br2+Brij58 mixtures with the BSA Solution is discussed in terms of competition between surfactant-surfactant and surfactant-BSA interactions. CTAB+Brij58 and C16C4C16Br2+Brij58 mixtures show nonideality with respect to mixed micelle formation, which is reflected in their interaction with the BSA. The interaction of CTAB+Brij58 with BSA decreases with increase in the mole fraction of CTAB in the Mixture, whereas in C16C4C16Br2+Brij58 the reverse is the case. The results of the present Study may prove fruitful in optimizing the properties of surfactant-protein Mixtures relevant for many formulations.