Refolding of guanidinium hydrochloride denatured bovine serum albumin using pyridinium based ionic liquids as artificial chaperons

Abstract

Herein, the refolding ability of pyridinium based ionic liquids against chemically induced unfolding of bovine serum albumin (BSA) is reported. The study was performed utilizing circular dichroism (CD), steady-state fluorescence, time-resolved fluorescence, and dynamic light scattering (DLS) experiments. Further, ANS (8-Anilinonaphthalene-1-sulfonic acid) binding was performed to study the effect of ionic liquids (ILs) on the hydrophobicity of unfolded protein. The CD results confirmed that the alpha helical content of the denatured protein increased by a significant amount in presence of different concentrations of all the three ILs. The CD results were further supported by steady state fluorescence and ANS binding study. The dynamic light scattering (DLS) results show that the hydrodynamic size of the unfolded protein decreases in presence of all the three ILs. The decrease in hydrodynamic size may be attributed to the increase in compactness and the possible refolding of the protein in presence of ILs. Fluorescence lifetime measurements confirm that the average lifetime of GdmCl treated BSA reached near to the value of native BSA in presence of ILs which again supports the refolding of protein. All the experimental results agreed with each other and suggested that all three ILs have the potential to refold the denatured protein. The 1-butyl pyridinium bromide (BPB), however, proved to be the most effective refolding agent amongst the three ILs utilized for the study.