Sustainable combination of ionic liquid and deep eutectic solvent for protecting and preserving of the protein structure: The synergistic interaction of enzymes and eco-friendly hybrid ionic fluids.

Hybrid ionic fluids (HIFs) are one of the emerging and fascinating sustainable solvent media, a novel environment-friendly solvent for biomolecules. The HIFs have been synthesized by combining a deep eutectic solvent (DES), an ionic liquid (IL) having a common ion. The stability and activity of hen's egg white lysozyme (Lyz) in the presence of a recently designed new class of biocompatible solvents, HIFs have been explored by UV-visible, steady-state fluorescence, circular dichroism (CD), Fourier transform infrared spectroscopy (FT-IR) along with dynamic light scattering (DLS) measurements. This work emphasizes the effect of DES synthesized by using 1:2 choline chloride and glycerol [Glyn], ILs (1-butly-3-methylimidazolium chloride [BMIM]Cl and choline acetate [Chn][Ac]) and their corresponding HIFs on the structure and functionality of Lyz. Moving forward, we also studied the secondary structure, thermal stability and enzymatic activity and thermodynamic profile of Lyz at pH = 7 in the presence of varying concentrations (0.1 to 0.5) M of [BMIM]Cl, [Chn][Ac] ILs, [Glyn] DES and [Glyn][BMIM]Cl (hybrid ionic fluid) as well as [Glyn][Chn][Ac] (hybrid ionic fluid). Spectroscopic results elucidate that ILs affect the activity and structural stability of Lyz, whereas the stability and activity are increased by DES and are maintained by HIFs at all the studied concentrations. Overall, the experimental results studied elucidate expressly that the properties of Lyz are maintained in the presence of hybrid ionic fluid while these properties are intensified in hybrid ionic fluid. This work has elucidated expressly biocompatible green solvents in protein stability and functionality due to the alluring properties of DES, which can counteract the negative effect of ILs in HIFs.