Ionic liquids have recently received significant attention as novel solution environments for biomolecules in various biomedical / biochemical applications. As co-solvent additives, they have been used to inhibit (or promote) amyloid fibril formation and protein aggregation, solubilize biomolecules, and modulate enzyme activity for pharmaceutical applications. The thermodynamic stability of protein structures in ionic liquid environments is an open question. We have quantified the stability of the well-known protein myoglobin in aqueous solutions containing different ionic liquids as co-solvent additives. By performing guanidinium HCl-induced unfolding studies with different concentrations (up to 200 mM) of the ionic liquids ethyl-methyl-imidazalium acetate (EMIAc) and butyl-methyl-imidazolium tetrafluoroborate (BMIBF4) we have quantified the effects of ionic liquids on ?Gunfolding. While EMIAc has minimal effect, BMIBF4 decreases the magnitude of ?Gunfolding by 75%, indicating the BF4 anion is the primary agent affecting protein stability. Temperature-induced unfolding experiments enable quantification of ?Hunfolding and ?Sunfolding and demonstrate how the thermodynamic parameters affecting myoglobin structural stability are affected by ionic liquids in aqueous solution.

Myoglobin unfolding in the presence of ionic liquids in aqueous solution

247th National Meeting (2014)

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