A green approach to offset the perturbation action of 1-butyl-3-methylimidazolium iodide on α-chymotrypsin.

Recently, studies have provided evidence for the negative effects of ionic liquids (ILs), "greener solvents," on proteins [Phys. Chem. Chem. Phys., 2014, 16, 5514]. The search to offset the negative effects of ILs on proteins has come into limelight as the maintenance of a "green solvent medium" is a great challenge for chemists and biochemists. As the first step in this search, 1-butyl-3-methylimidazolium bromide ([Bmim][Br]) has been applied to offset the deleterious action of 1-butyl-3-methylimidazolium iodide ([Bmim][I]) on α-chymotrypsin (CT). Fluorescence and circular dichroism (CD) experiments results have indicated that [Bmim][Br] significantly offsets the deleterious action of [Bmim][I] at lower concentrations (0.025 M). Surprisingly, the stabilizing action of [Bmim][Br] turns into a deleterious action for CT at higher concentrations (>0.1 M). On the other hand, [Bmim][I] acted as a destabilizer for CT at all investigated concentrations (0.025-0.6 M). The results obtained from this study lead to valuable insights into the selection of suitable ILs to attenuate the deleterious action of another IL without disturbing the protein structure.