Ionic liquids are fully ionic salts which exist as liquids at room temperature. Ionic liquids are well known to have negligible vapor pressures, are nonflammable, and have a wide range of solvent compatibility. As such, these ionic liquids have garnered much interest from analytical and physical chemists interested in exploiting the ionic properties in applications such as batteries fuel cells, co-solvents, and other electrochemical applications. Recent investigations into the compatibility with biomolecules in aqueous solutions (where the ionic liquids exist as strong electrolytes) have resulted in a range of results including both stabilization and destabilization of proteins, as well as enhancement and inhibition of enzymatic activity. The specific effects on activity are determined both by the cation/anion pair that comprises the ionic liquid as well as the model system it is interacting with. We previously showed that the aqueous solutions supplemented with the ionic liquid BMIBF4 significantly destabilized the folded structure of myoglobin whereas aqueous solutions supplemented with the related ionic liquid EMIAc had minimal effect on the stability of the folded structure when analyzed using traditional GuHCl titration experiments. We've extended these studies to include a number of other denaturation approaches including traditional thermal denaturation as well as other common chemical denaturants such as urea and SDS. We monitored the unfolding of myoglobin using circular dichroism, absorbency, and fluorescence spectroscopy (FRET). Our results show that the inclusion of relatively low concentrations of the ionic liquid BMIBF4to neutral pH solutions of myoglobin similarly destabilized the folded protein structure in thermal and other chaotrope induced denaturations. The destabilization of proteins by these and related ionic liquids will provide routes to studying protein folding intermediates, hard to denature proteins, and gain insights into protein ligand interactions to enhance drug design and accessibility to occluded binding sites.

Effects of ionic liquids on protein folding-unfolding transitions

248th National Meeting (2014)

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