Construction Of A Tethered-bilayer Lipid Membrane By Physiosorption Of Glycolipid GM1 To A Hydrophilically Modified Gold Surface

Abstract

Interactions of membrane-bound molecules with their environment are difficult to study due to the complex and dynamic nature of biological membranes. The development of model membranes can provide insight into the function of membrane proteins in their natural environment. A phospholipid bilayer deposited at a gold surface offers a unique opportunity to investigate the mechanism of voltage-gated ion channel formation induced by surface-active proteins such as Colicin E1. Studies of voltage-gated phenomena involving transmembrane proteins require a model membrane that is supported at a gold electrode and has a water layer on either side of the bilayer. This can be achieved by creating a tethered lipid bilayer membrane (tBLM) with a hydrophilic spacer region separating the gold surface from the bilayer. We describe here the construction of a lipid bilayer membrane which is tethered from the gold surface using glycolipid, GM1. The bilayer is composed of 1,2-dimyristoyl-sn-glycerol-3-phosphocholine (DMPC) and cholesterol. GM1 is physiosorbed to gold by modifying the gold surface with a hydrophilic thiol, 1-thio-D-glucose. Due to the amphiphilic nature of GM1 this is performed at the air/water interface using the Langmuir-Blodgett technique. The outer leaflet of the bilayer is deposited using the Langmuir-Schafer method. The quality of the bilayer formed at the gold surface was characterized using electrochemical methods, in which the capacitance of the tether bilayer is measured on a single crystal gold electrode (Au(111)). The tBLM was further characterized using Atomic Force Microscopy (AFM). The tBLM was depsited on a substrate composed of Au(111) terraces, force-distance curves were measured using AFM, the thickness of the bilayer was than extracted from these curves. These results will be presented for tBLMs constructed with varying GM1 content (10, 20, and 30 mole percent).