Regensburg 2004 – scientific programme

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AKB: Biologische Physik

AKB 50: Poster Session "Biological Physics"

AKB 50.66: Poster

Friday, March 12, 2004, 10:30–13:00, B

Structure and Fluctuations of Highly Oriented and Charged Membranes Under Osmotic Stress. — •Guillaume Brotons, Ulrike Mennicke, and Tim Salditt — Institut fuer Roentgenphysik, Universitaet Goettingen

Imposing osmotic pressure to multilamellar membranes is a unique method for studing lipid bilayer interactions [1]. We have extended this approach to charged lamellar phases oriented on flat solid support, which are then probed by interface sensitive X-ray scattering. In this first study we used the anionic phospholipid POPS [2] and synthetic cationic surfactant DDABr [3], at controlled osmotic stress corresponding to water layer thicknesses in the range of a few water molecules up to more than 15 times the bilayer thickness. High-pressures (deshydrated) are obtained by controlled water vapour, while lower pressures (full hydration) are imposed by direct contact with a polyelectrolyte solution of same sign as the lamellar phase under investigation. Under these conditions, specular and non-specular reflectivity can be carried out within the different symmetry axes of the oriented membranes (Fig.1) which opens new routes for establishing the Equations Of State (Pressure-Distance diagram) of bio-molecular assemblies and studing bilayer undulations or compressibility fluctuations as a function of pressure. [1] Parsegian,V.A. et all, Methods in Enzymology; Academic-Press 1986; Vol.127. [2] Mennicke,U., PhD-Dissertation, Göttingen-Universität, 08/2003. [3] Brotons,G. et all, Langmuir 2003, 19, 8235-8244.