FLUOR - Fluorinated Surfactants for Membrane-Protein Research

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Membrane proteins play numerous vital roles in cellular communication and transport processes and represent the majority of drug targets. Still, progress in our knowledge and understanding of membrane-protein structure, dynamics, and function is slow, primarily because of difficulties arising from their very hydrophobic nature. These proteins require a membrane-mimetic environment to keep them both soluble and active during in vitro investigations, which is typically accomplished with the aid of detergents, surface-active compounds that solubilise membrane proteins and lipids. However, many membrane proteins are inactivated when solubilised in detergents, that is, they lose their native structures and functions. This has motivated many efforts at replacing conventional detergents by milder alternatives, among which fluorinated surfactants appear particularly promising. Owing to the weak affinity of fluorocarbons for hydrocarbons and to the larger volume of fluorocarbons, fluorinated surfactants are hypothesised to be less destabilising because they hardly compete with protein-protein and protein-lipid/hydrophobic cofactor interactions. Indeed, it has been shown repeatedly that various membrane proteins are more stable when solubilised in fluorinated surfactants as compared with hydrogenated detergents.Unfortunately, though, neutral fluorinated surfactants are not able to solubilise lipid bilayers and extract membrane proteins directly from membranes. Hence, conventional detergents are still required for solubilisation, and fluorinated surfactants come into play only at a later stage, when labile proteins will already have suffered irreversible damage. We have recently demonstrated that fluorination per se does not exclude detergency, as a fluorinated octyl maltoside derivative retains mild detergent-like activity. In this project, we intend to capitalise on this finding to develop, test, and establish fluorinated detergents that (i) can be synthesised in sufficient quantities and purities for widespread use in membrane-protein research; (ii) display favourable micellar properties such as small and well-defined sizes; (iii) partition into, translocate across, and solubilise membranes in a rapid, thermodynamically controlled manner; (iv) solubilise membrane proteins directly from native or synthetic membranes without requiring harsher, hydrogenated detergents; and (v) offer these proteins a stabilising environment that preserves their native structures and functions for extended periods of time. Such fluorinated detergents will open new possibilities for in vitro studies of physiologically and pharmacologically interesting membrane proteins that have thus far evaded detailed scrutiny.This highly interdisciplinary project shall be accomplished within a consortium that is uniquely qualified to address synthetic, physicochemical, biophysical, biochemical, and structural-biological aspects alike.