Struktur und Fluktuationen festkörpergestützter Phospholipidmembranen

Abstract

In this work solid supported membranes are studied by X-ray reflectometry. Solid supported phospholipid membranes are model systems for biological membranes and are widely used to study their fundamental physical properties. The development of a new preparation method, allowing for the first time the controlled preparation of stacks of membranes consisting of 3-30 membranes on a substrate, is described. X-ray reflectivity curves of charged and uncharged multilamellar and oligo-membrane stacks have been measured at partial and full hydration. The level of hydration was controlled by the application of osmotic stress. A detailed model for the description of reflectivity measurements including the membrane fluctuations is developed based on kinematic theory. The membrane fluctuations of solid supported membranes are described by a smectic continuous model. The electron density profile of uncharged dmpc (dimyristoylphosphatidylcholine) membranes have been determined from fits to the measured reflectivity curves at varied osmotic pressure. The effects of the osmotic pressure on membrane hydration and fluctuations is beeing discussed in the framework of membrane potentials. By includig the membrane fluctuations in the mathematical model for reflectivity, the elastic properties, like bending rigidity and compression modulus could be derived as a function of osmotic pressure.