Expanding the Potential Role of Deep Eutectic Solvents toward Facilitating the Structural and Thermal Stability of α-Chymotrypsin

Since the introduction of deep eutectic solvents (DESs), numerous reports have surfaced describing its tunable properties and environmentally benign nature. Due to such favorable properties of DESs, they have found a wide variety of applications. Moreover, in order to harness the potential of proteins in numerous industries, there is an emergent need to find a suitable cosolvent that is biocompatible with protein and is also environmentally safe. In this context, this work presents a systematic evaluation of effect of two deep eutectic solvents (DESs), namely, choline chloride-urea (ChCl-urea) and choline chloride-glycerol (ChCl-gly) on the structural and thermal stability along with activity of enzyme alpha-chymotrypsin (CT) using circular dichroism (CD), UV-visible, steady state, and thermal fluorescence spectroscopy. It was observed that the presence of DESs does lead to enhancement in the thermal stability of CT along with the preservation of activity. The enzymatic activity was well maintained in both the DESs, and the deleterious effect of urea was overcome by ChCl-urea on the enzyme. Also, desirable results were observed for ChCl-urea, despite having urea as one of its major components. Thus, the negative outcome of urea was overpowered by the combination of ChCl and urea. Furthermore, all the biomolecular studies were also performed with the individual constituents of DESs. It was found that the effect imparted by both the ChCl-based DESs on CT is by the virtue of DES itself rather than its individual constituent. Overall, both the DESs can be described as potential biocompatible, sustainable, and promising cosolvents for CT with enhanced structural and thermal stability along with preservation of its activity.