Nanomaterials for membrane protein biology

The overall focus of this thesis is investigations into the preferential locations of biomolecules, including membrane proteins, in orientated self-assembled lipid nanostructured materials known as QII phases. The three QII phases, known as the QII G, QII D and QII P , consist of 3 dimensional periodic self-assembled surfaces over which a lipid bilayer is draped. The lipid bilayer in each QII phase consists of regions of flat or high curvature into which it has been hypothesised that guest biomolecules will preferentially partition. Research efforts focus on orientated QII phase domains as more information can be extracted from characteristic Small Angle Scattering (SAS) experiments than from polydomain samples. Different lipid mesophases including the QII phases, were prepared as orientated lipid films and an automated method of 2D Small Angle X-ray Scattering (SAXS) analysis for orientated samples was created. The addition of biomolecules to a QII phase was achieved by co-dissolving with the lipids in an organic solvent before formation of the orientated QII phase, or by addition to an already formed QII phase. Both methods are presented here and the incorporation of various biomolecules into a QII D phase bilayer was monitored in two separate fashions, via SAXS and Raman Spectroscopy. Finally, the addition of biomolecules to orientated QII phases was undertaken and any preferential partitioning into flat or highly curved regions of the bilayer was investigated. It was found via Grazing Incidence Small Angle Neutron Scattering (GISANS) that monopalmitin and cholesterol in a monoolein QII D phase, preferentially partition into the flatter regions of the bilayer. At several instances during my research, variable humidity control was required. Lipid films require particular humidity to maintain specific phase behaviour and for the neutron experiments, the host lipid was contrast matched to a D2O environment. To meet this requirement, two separate humidity control systems were designed and created: the first a low cost, portable, and chamber independent system, the second a fully automated system calibrated to a chamber at Diamond Light Source. A separate study into the relaxed curvature of four lipids, monoolein, monolinolein, phytantriol, and phytantetrol using inverse micelles is also detailed. The relaxed curvature was obtained by calculating the parameters of the neutral surface, or the surface whose area does not change due to bending within a lipid monolayer.