Complexation Behavior of β-Lactoglobulin with Surface Active Ionic Liquids in Aqueous Solutions: An Experimental and Computational Approach.

The nature of functionalization of alkyl chain of imidazolium based surface active ionic liquids (SAILs) with amide- of ester-moiety led to contrasting complexation behavior towards globular protein, bovine serum albumin (BSA). This prompted us to further investigate the SAIL dependent colloidal behavior of another globular protein, -lactoglobulin (LG) to probe the origin of varying structural transformations in globular proteins induced by SAILs. Herein, we investigated the colloidal systems of βLG, rich in β-sheet structure, in the presence of four structurally different SAILs using a multi-technique approach. The complexation behavior, both at air-solution interface as well as in bulk, is supplemented by different techniques. Docking studies has complemented the obtained experimental results. The specificity of structure, H-bonding ability of SAILs and inherent structure of protein is found to govern their complexation behavior in terms of size, shape and polarity of protein-SAIL complexes along with varying degree of structural alterations in globular proteins. The present work is expected to be very useful in establishing a deep understanding of structure-property relationship between the nature of proteins and SAILs for their complexation and colloidal behavior for various biomedical applications.