Probing the energy landscape and thermodynamics of biomolecules for drug design.

The increasing requirement to produce platform chemicals and fuels from renewable sources means advances in biocatalysis are rapidly becoming a necessity. Biomass is widely used in nature as a source of energy and as chemical building blocks. However, recalcitrance towards traditional chemical processes and solvents provides a significant barrier to widespread utility. Here, by optimizing enzyme solubility in ionic liquids, we have discovered solvent-induced substrate promiscuity of glucosidase, demonstrating an unprecedented example of homogeneous enzyme bioprocessing of cellulose. Specifically, chemical modification of glucosidase for solubilization in ionic liquids can increase thermal stability to up to 137 °C, allowing for enzymatic activity 30 times greater than is possible in aqueous media. These results establish that through a synergistic combination of chemical biology (enzyme modification) and reaction engineering (solvent choice), the biocatalytic capability of enzymes can be intensified: a key step towards the full-scale deployment of industrial biocatalysis.

In this work we experimentally investigate solvent and temperature induced conformational transitions of proteins and examine the role of ion-protein interactions in determining the conformational preferences of avidin, a homotetrameric...

Ionic liquids offer exciting possibilities for biocatalysis as solvent properties provide rare opportunities for customizable, energy-efficient bioprocessing. Unfortunately, proteins and enzymes are generally unstable in ionic liquids and several attempts have been made to explain why; however, a comprehensive understanding of the ionic liquid–protein interactions remains elusive. Here, we present an analytical framework (circular dichroism (CD), fluorescence, ultraviolet-visible (UV/Vis) and nuclear magnetic resonance (NMR) spectroscopies, and small-angle X-ray scattering (SAXS)) to probe the interactions, structure, and stability of a model protein (green fluorescent protein (GFP)) in a range (acetate, chloride, triflate) of pyrrolidinium and imidazolium salts. We demonstrate that measuring protein stability requires a similar holistic analytical framework, as opposed to single-technique assessments that provide misleading conclusions. We reveal information on site-specific ionic liquid–protein interactions, revealing that triflate (the least interacting anion) induces a contraction in the protein size that reduces the barrier to unfolding. Robust frameworks such as this are critical to advancing non-aqueous biocatalysis and avoiding pitfalls associated with single-technique investigations.

Thermally-stable ionic liquids (ILs) have limited structural possibilities and lack coordinating anions or functional groups. Thermal stability effectively incurs a tunability penalty, limiting ionic liquid function to render them as simple heat-stable fluids. In this work, a series of new thermally-stable dicationic ionic liquids with pyridine functional groups, abbreviated [(C8ImC1)2Py]­[A]2, are presented and compared to nonfunctional geminal dicationic ILs. All ILs have been thermally characterized to understand their elevated temperature stabilities and the processes that lead to their decomposition. Importantly, functional [(C8ImC1)2Py]­[A]2 with noncoordinating anions (i.e., [NTf2]−) have thermal stabilities comparable to those of geminal dicationic ILs, with the added advantage of a functional pyridine moiety. Dissolution of Zn­[NTf2]2 in [(C8ImC1)2Py]­[NTf2]2 is demonstrated, and the resulting solutions are characterized to show their liquid properties, high thermal stabilities, and the coordination of the metal center to the functional group. This is the first example of a thermally-stable functional IL with the potential to reclaim the tunable, task-specific nature of ILs at elevated temperatures. Importantly, these properties open new avenues for high-temperature applications of IL by extending their operational ranges; catalysis, metal remediation, and separation-based applications are potential key areas of improvement.