Compartmentalisation and Membrane Activity in Protic Ionic Liquids and Deep Eutectic Solvents

Abstract

Ionic liquids and deep eutectic solvents are areas of great interest to non-aqueous reaction systems. They can be fine-tuned for an array of properties and are often less harmful than other, organic, solvents. This research focused specifically on self-assembly in ionic liquids and deep eutectic solvents with an eye to understand self-assembly processes. Not only does this work offer industrial applications, for isolated reaction systems and batteries, it also provides an interesting insight into the possibility of non-aqueous life-forms. If compartmentalisation can occur without water, then perhaps so too can the other requirements of life. Ionic liquid nanostructure significantly affected phospholipid self-assembly with more nanostructure resulting in more curved micellar phases, rather than the lamellar phases observed in water and less structured ILs. This held true for both zwitterionic lipids and ionic surfactants, demonstrated by microscopy, small angle neutron and x-ray scattering. Phospholipids formed swellable lamellar phases in all fourteen of the deep eutectic solvents tested. Examination of lipid transition temperatures by polarising optical microscopy demonstrated that the components of the solvent could influence lipid behaviour and stability, solvents with long alkyl components acted as cosurfactants. Tethered lipid membranes and electrical impedance spectroscopy demonstrated that membranes could exist, and form, in a pure IL environment (ethanolammonium formate). This is the first time such a technique has been used to study membranes in an IL and offers unparalleled opportunities for further research. Furthermore, this technique was used to demonstrate the continued function of a membrane transporter, valinomycin, in ethanolammonium formate. Valinomycin continued to transport potassium with an extremely high selectivity over sodium. These results show that compartmentalisation, and even protein function, can continue even in the absence of water.