Role of (single/double chain surfactant) micelles on the protein aggregation

To investigate the interaction between the bovine serum albumin (BSA) and cationic surfactants (monomeric, cetyltrimethylammonium bromide, CTAB) and dimeric/gemini, 1, 6 bis (N, N-hexadecyl dimethyl ammonium bromide, 16-6-16) and to find out the role of micelles in the aggregation of the protein using spectroscopic (UV-visible, fluorescence, fluorescence lifetime measurements, circular dichroism (CD), etc.) and microscopic (atomic force microscope (AFM)) techniques. The different surfactant has an effect on the polarity of the microenvironment of the protein shows in all the spectroscopic technique at below and above the critical micelle concentration (CMC). The far-UV CD spectra show that BSA is more disrupted by the dimeric surfactant compared to the monomeric CTAB above the CMC. The binding of the surfactant induce changes in the microenvironment around the aromatic amino acids residues and disulfide bond of the BSA at different pHs. The binding constant values were found to be 20.278×10³M and 8.443M for the BSA-CTAB complex and BSA-16-6-16 complex, respectively. Atomic force microscope indicates the aggregation is more in case of dimeric (16-6-16) surfactant compared to the monomeric (CTAB) surfactant at the higher concentration (above their CMCs). Below and above the CMC, all changes are noticeable.