Recent interest in the applications of ionic liquids have prompted investigations into their effects on biomolecules. Previous research has shown that ionic liquids can affect protein stability; however, the mechanism of this effect is unknown. The denaturation profile of myoglobin was examined in the presence of aqueous ionic liquids, including 1-butyl-3-methylimidazolium tetrafluoroborate and 1-ethyl-3-methylimidazolium acetate, using the zwitterionic detergent N,N-Dimethyl-N-dodecylglycine betaine (Empigen BB). Detergents traditionally unfold proteins through the disruption of hydrophobic contacts at the interior of the folded structure. The hypothesis was that if the ionic liquids, or some component of the ionic liquids, were reacting through a similar mechanism, the detergent-mediated unfolding would be enhanced. A combination of absorbance, fluorescence, and circular dichroism spectroscopy were used to monitor unfolding. This unfolding process also changes the distance between the heme and tryptophan residues intrinsic to myoglobin, altering its absorbance and fluorescence quenching profile. CD spectroscopy was used to monitor the loss of the heme signal as well as the loss of secondary structure in control experiments. All three types of experiments showed similar denaturation profiles under the same ionic liquid conditions. The ionic liquids did not appear to have a significant impact on unfolding by Empigen BB, indicating their effects on protein stability may be through a different mechanism than that by which Empigen BB unfolds proteins. In all cases examined, the protein denaturation profile remained a traditional, cooperative process.

Influence of ionic liquids on detergent mediated denaturation of myoglobin

254th National Meeting (2017)

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