Biophysical Society Thematic Meeting | Ascona, Switzerland

Liposomes, Exosomes, and Virosomes: From Modeling Complex Membrane Processes to Medical Diagnostics and Drug Delivery

Poster Abstracts

27-POS Board 14 Assembling Double and Multi-layered Lipid Membranes to Study Electron Transfer Pathways George R. Heath 1 , Julea N. Butt 2 , Lars J. Jeuken 1 . 1 University of Leeds, Leeds, United Kingdom, 2 University of East Anglia, Norwich, United Kingdom. Multilayer lipid membranes perform many important functions in biology, such as electrical isolation (myelination of axons), increased surface area for biocatalytic purposes (thylakoids and mitochondria), and sequential processing (golgi cisternae). Here we develop a simple layer-by- layer methodology to form lipid multilayers via vesicle rupture onto existing supported lipid membranes using poly-l-lysine (PLL) as an electrostatic polymer linker. The assembly process was monitored at the macroscale by quartz crystal microbalance with dissipation (QCM-D) and the nanoscale by atomic force microscopy (AFM) for up to six lipid bilayers. By varying buffer pH and PLL chain length, we show we can control the separation between the membranes. By incorporating functional membrane proteins into these multilayers using either protein reconstitution into proteoliposomes or by mixing vesicles with membrane extracts we show how this technique can be used to multiply the function of membrane proteins normally limited to a single bilayer. We demonstrate this using cyclic voltammetry of lipid multilayers on gold using two different membrane proteins, a hydrogenase that catalyzes the oxidation of H2 and Cytochrome bo3 which catalyzes O2, both to produce protons. This approach also provides a route to creating complex gram negative bacterial membrane mimics, allowing the study of the electron transfer pathways between a number of inner and outer membrane proteins. Our study focuses on Shewanella oneidensis MR-1, a bacterium which can reduce poisonous heavy metal ions, a better understanding of which may further microbial biotechnologies such as microbial fuel cells and electrosynthesis. By reconstituting the membrane proteins thought to be key to the MR-1 electron transfer pathway and assembling the double membrane on gold we show how this still not fully understood pathway can be investigated for the first time using a bottom up appraoch.

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