SOLVENT INDUCED CHANGES IN THE CONFORMATIONAL STATE OF β-LACTOGLOBULIN AND THE INFLUENCE OF PROTIC IONIC LIQUIDS

Abstract

The protic ionic liquids (pILs), triethylammonium acetate, triethylammonium trifluoroacetate, triethylammonium mesylate and trimethylammonium sulfate were used to induce various native and non-native conformational states of the protein β-lactoglobulin (βLG). Changes in the secondary structure of βLG were observed on moving from a high water content to a high pIL content. We examined the stability of various pIL induced states via thermal unfolding and refolding, where it was found that at a given pIL concentration a highly stable non-native conformation was formed. The βLG non-native conformation was characterized by a high α-helical content. Additionally, pIL conditions that promoted amyloid fibril formation were identified and characterized by CD, a Thioflavin T binding assay and transmission electron microscopy (TEM). This work highlights the use of pILs as solvents in the study of protein folding using βLG as a model system.