Study on interactions of cationic gemini surfactants with folded and unfolded bovine serum albumin: Effect of spacer group of surfactants

摘要

AbstractInteractions of three cationic gemini surfactants, 12-4-12, 2Br?12-8-12, 2Br?and 12-4(OH)-12, 2Br?with natured and denatured protein, bovine serum albumin (BSA) have been studied by means of UV–Visible absorption, steady-state and time-resolved fluorescence, and circular dichromism (CD) spectroscopy. CD spectroscopic study shows the change in theα-helix andβ-strand content of protein with the concentration of gemini surfactants. Gemini surfactant with hydroxyl group in the spacer decreases theα-helix of the BSA more efficiently than that without hydroxyl group in the spacer. Efficiency to decrease theα-helix of the protein increases with decreasing the hydrophobicity of the spacer group of the surfactants at lower concentration range following the order, 12-8-12, 2Br?<12-4-12, 2Br?<12-4(OH)-12, 2Br?. However, at higher concentration range of surfactant, the increasing order of providing hydrophobic environment to tryptophan (Trp) and tyrosine (Tyr) residues of the protein is as follows: 12-4(OH)-12<12-4-12<12-8-12. Gemini surfactant with hydrophobic spacer group provides more hydrophobic environment around Trp and Typ residues of the protein forming micelles like structures along the protein chain. In this concentration range, 12-8-12, 2Br?interacts differently as compared to other two surfactants which are evidenced by the data on excited state lifetime of the protein. It is more