I will describe several years of our efforts to build a model biological membrane at a surface of a gold electrode. In this architecture, the membrane may be exposed to static electric fields on the order of 107 to 108V/m. These fields are comparable in magnitude to the static electric field acting on a natural biological membrane. The field may be conveniently used to manipulate organic molecules within the membrane. By turning a knob on the control instrument one can force phase transitions in the film of organic molecules or force them to disperse or to aggregate at the surface. We use electrochemical techniques to control the physical state of the film while the photon polarization infrared reflection absorption spectroscopy (PMIRRAS), surface imaging by STM and AFM and neutron scattering techniques are employed to study conformational changes of organic molecules and their ordering within the membrane. I will show examples of a membrane build of a simple zwitterionic phospholipid such as DMPC and a mixed membrane composed of DMPC and cholesterol. Our results will illustrate a tremendous effect of cholesterol on the membrane structure. I will also compare two methods of membrane deposition at the electrode surface, namely by unilamellar vesicles fusion and using the Langmuir-Blodgett technique.
Host: Jim Davis