Characterization of interactions between β-lactoglobulin with surface active ionic liquids in aqueous medium

Abstract

The interaction of β-lactoglobulin (βLG) with surface active ionic liquids (ILs), 1-dodecyl-3-methylimidazolium bromide [C12mim][Br] and 1-hexyl-3-methylimidazolium dodecylsulfate [C6mim][C12OSO3] has been investigated employing tensiometry, conductivity, fluorescence, dynamic light scattering (DLS), zeta potential and circular dichroism (CD) methods. A significant difference was observed in the nature of interactions present in the βLG-[C12mim][Br] system as compared to βLG-[C6mim][C12OSO3]. The IL, [C12mim][Br] interacted strongly with βLG to form complexes at the interface as compared to weaker interactions observed in case of βLG-[C6mim][C12OSO3] system. The results of intrinsic fluorescence measurements along with CD measurements have provided insights into the unfolding of βLG due to binding of ILs. Turbidity measurements have shown the coacervate formation in case of βLG-[C12mim][Br] which was also supported from DLS and zeta potential measurements. An excellent correlation of results obtained from multiple techniques has been used to characterize the interactional behavior of ILs and βLG in a wide concentration regime. The results of the present studies are expected to contribute in understanding the interactional behavior of βLG with surface active ILs and its effect on functionality of protein.