Soaking it up: new lipid sponge phases and their applications

Recent work has demonstrated that cubic lipid systems may be doped with charged lipids, with important consequences for their physical properties. Among others, Tyler et al. have reported some of the largest lipid cubic phases seen to date using this technique\footnote{A. Tyler et al. \textit{Soft Matter}, \textbf{2015}, 11, 3279-3286}. The sponge phase is a disordered bicontinuous phase, formed when the membrane curvature of a cubic phase is reduced through the addition of butane diol\footnote{V. Cherezov et al. \textit{J. Mol. Biol.} \textbf{2006} 357, 1605-1618}. Additionally, it is known that sponge phases may be converted back into highly ordered cubic ones\footnote{A. Seddon et al, \textit{J. Am. Chem. Soc.}, \textbf{2011}, 133, 13860}. Whilst past work has concentrated on sponge phases formed from monoolein, we have investigated the properties and behaviour of a bipartite sponge phase formed of monoolein and DOPG, and their conversion to cubic phases using shear. Furthermore, as both the sponge and cubic phase are of interest with respect to their applications in protein crystallography\footnote{A. W{\"o}hri et al. \textit{Structure} \textbf{2008}, 16, 1003-1009}, we have explored the interaction of the protein light-harvesting complex with the lipid system.