Biophysical Society Thematic Meeting

Liposomes, Exosomes, and Virosomes: From Modeling Complex

Membrane Processes to Medical Diagnostics and Drug Delivery

Poster Abstracts

103

27-POS

Board 14

Assembling Double and Multi-layered Lipid Membranes to Study Electron Transfer

Pathways

George R. Heath

, Julea N. Butt

, Lars J. Jeuken

University of Leeds, Leeds, United Kingdom,

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.