Mechanism and Dynamics of Long-Term Stability of Cytochrome c Conferred by Long-Chain Imidazolium Ionic Liquids at Low Concentration

Protein stability has been a concern for researchers for a long time as they are sensitive toward their environment. Mostly proteins during experiments require medium that keep them stable at room temperature (RT). Recent research utilizing ionic liquids (ILs) to stabilize protein has gained much importance. Although a few ILs have been claimed to suit this requirement, reported studies employ IL concentrations that might produce irreversible denaturation and aggregation. This study demonstrates the first report for long-term stabilization of horse heart cytochrome c (h-cyt c) by long chain imidazolium ILs at far low concentration (1 mM) of IL when stored at RT. Long-chain imidazolium Its until now were less familiar for their stabilizing nature toward protein. A significant increase in the helical content of h-cyt c (dissolved state) was observed with prolonged structural stability (secondary and tertiary) for about 6 months in aqueous solutions of 1-methyl-3-octyl imidazolium chloride [C(8)mim] [Cl] and 1-decyl-3-methylimidazolium chloride [C(10)mim] [Cl]. The in-depth mechanism discussed suggests interaction of ILs with amino acid residues of h-cyt c, which rigidifies the loop regions with reduced mobility; hence, prolonged stability is achieved. The study firmly advocates the use of long-chain imidazolium ILs as the potent inhibitor against denaturation during storage of h-cyt c at RT.