Role of Ionic Liquids on Protein stability and Dynamics

Abstract

Environmental conditions such as pH, temperature, and the presence of chemical species are the key factors, which can affect the protein structure, conformations, and dynamics. Nowadays researchers have investigated the effect of ionic liquids (as a co-solvent) as refolding additives and as stabilizing and destabilizing agents depending on their concentrations and types of ions they constitute. By using imidazolium-based, ammonium-based, and morpholinium-based ionic liquid, the conformational stability of commercial proteins (BSA and lysozyme) has been studied. In the case of ammonium-based ionic liquids, hydrophobicity played a key role towards the thermal stability of the protein (in the case of refolding) which is confirmed from far and near-UV CD analysis. Whereas an increase in the concentration of IL shows a better stabilizing effect (without altering the native structure of Bovine Serum Albumin aka BSA), which is further confirmed by fluorescence and circular dichroism spectroscopy. In the case of triethyl octyl ammonium bromide and up to 0.02 M concentration, BSA was found in compact structures other than native one but an increase in concentration causes unfolding. In the case of different imidazolium-based ILs, the hydrophobic cationic part helps in destabilizing the thermal stability of BSA whereas the change in the anionic part also influences the stability along with the increase in the concentration of ILs. In the case of lysozyme (lyz) as a model protein, it was found that the stability and activity of lyz get increased in presence of ionic liquid as compared to the conventional buffer.