Insights into the structural changes of bovine serum albumin in ethanolammonium laurate based surface active ionic liquids

Abstract

Abstract Ionic liquids (ILs) owing to their unique and tunable physicochemical properties have found profound applications in the biomedical and pharmaceutical field. Since ILs are widely used as solubilizing and stabilizing agents for biomolecules. It is important to explore their effect on proteins. Surface active ionic liquids (SAILs) due to their higher surface activity and tunable property have emerged as new task specific ILs and found to have superior properties than conventional ionic surfactants. In this work, we have synthesized and characterized two novel ethanolammonium based SAILs, namely, (n-butylethanolammonium laurate [NBEA][LAU] and tert-butylethanolammonium laurate [TBEA][LAU]). The self-assembling behavior of the SAILs in pure water was examined by tensiometry and conductometry. The structural changes occurring in BSA as the consequence of interactions with SAILs at pH\u202f7.4 and T \u202f=\u202f298.15\u202fK were explored using steady-state and life time fluorescence, UV–Visible and far UV circular dichroism(CD) spectroscopy and isothermal titration calorimetry (ITC). The results from surface tension and conductivity measurements give the values of critical micelle concentration (cmc) of the BSA-SAIL complex formation. The CD spectroscopy gives information on the secondary structure alterations of BSA-SAIL complex, which is further confirmed by ITC data. The dynamic quenching effect in tryptophan fluorescence of BSA is significant as evidenced by lifetime measurements. Overall, the present work highlights the conformational changes the protein can undergo upon interacting with SAILs.