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.

Interactions of ionic liquids with hydration layer of poly(N-isopropylacrylamide): comprehensive analysis of biophysical techniques results.

Here, we report comprehensive analysis of biophysical technique results for the influence of ionic liquids (ILs) containing the same cation, 1-butyl-3-methylimidazolium (Bmim(+)), and commonly used anions such as SCN(-), BF4(-), I(-), Br(-), Cl(-), CH3COO(-) and HSO4(-) on the phase transition temperature of poly(N-isopropylacrylamide) (PNIPAM) aqueous solution. Further, the effect of these ILs on bovine serum albumin (BSA) has also been studied. The modulations in UV-visible (UV-vis) absorption spectra, fluorescence intensity spectra, viscosity (η), hydrodynamic diameter (dH), Fourier transform infrared (FTIR) spectra and scanning electron microscopy (SEM) micrographs clearly reflect the change in the hydration state of PNIPAM in the presence of ILs. The observed single phase transition of PNIPAM aqueous solution at higher concentration of IL is the result of weak ion-ion pair interactions in IL.