Assessing the Compatibility of Mono-, Di-, and Tri-Cholinium Citrate Ionic Liquids for the Stability and Activity of α-Chymotrypsin

In view of the global environmental and economic challenges of conventional organic solvents, most of the ionic liquids (ILs) have proved themselves as a greener group of cosolvents, especially for enzymes. However, there is a lack of fundamental knowledge on the greener aspects of various multicationic IL systems on biomolecules. In this regard, we have synthesized the monocholinium citrate ([ Chn][Cit]), dicholinium citrate ([Chn](2)[Cit]) and tricholinium citrate ([Chn](3)[Cit]) ILs and employed them to explore their suitability for alpha-chymotrypsin (alpha-CT). This study specifically addresses the effect of increased cationic ratio of IL on stability and activity of alpha-CT with the help of various spectroscopic techniques. Various spectroscopic analysis showed that there is improved structural stability and activity of alpha-CT as the cationic ratio of IL increase. We found better structural stability of alpha-CT in [Chn](3)[Cit] and [Chn](2)[Cit] as compared to that in [Chn][Cit]. Interestingly, temperature-dependent fluorescence spectroscopy results explicitly elucidate that transition temperature (T-m) of alpha-CT enhances by 6 degrees C in the presence of [Chn](2)[Cit] when compared to T-m of alpha-CT in buffer solution. Ultimately, these results establish that through an increase in the molar ratio of aqueous cholinium cation in [Chn][Cit] intensifies the capability of ILs to stabilize the alpha-CT structure. Our results suggested that multicationic IL system sensitivity to cosolvent exposure may be utlized in the future as a new approach to explore new biocompatibility toward proven stability studies.

Automated summary

This study synthesized different multicationic IL systems and found that an increase in cationic ratio improved the structural stability and activity of alpha-CT.