Regensburg 2010 – scientific programme

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BP: Fachverband Biologische Physik

BP 19: Membranes and Vesicles

BP 19.8: Talk

Wednesday, March 24, 2010, 12:00–12:15, H43

Response of tethered membranes to pH, ionic strength and temperature variations studied by neutron and x-ray reflectometry — •Samira Hertrich, Joachim Rädler, and Bert Nickel — Ludwig-Maximilians-Universität, Department für Physik und CeNS, Geschwister-Scholl-Platz 1, 80539 München

Lipid membranes chemically grafted to a solid surface provide model systems to study membrane-protein interactions. Here, a multi-step chemical reaction is employed to fabricate tethered membranes on silicon oxide by silane chemistry. Reflectometry measurements show that the lipid bilayer is elevated from the surface through a PEG cushion by 7nm. Fluorescent labeled lipids allow for optical characterization by microscopy confirming homogeneity and mobility of the lipid bilayer. The stability of this system has been tested in a wide pH range from 4 to 11. With x-ray reflectivity (D4, HASYLAB) we observe a reversible contraction of the PEG layer at pH > 9.5, originating from a dehydration of the PEG interlayer as is shown by neutron reflectivity (REFSANS and N-Rex, FRM-2). In contrast, temperature changes and variation of the ionic strength of the buffer did not cause significant changes of the PEG interlayer thickness. The tethered membrane system is now used to test for the binding of neural proteins to the membrane. Initial experiments indicate that the effects of protein binding are a thinning of the lipid bilayer and an increase of water in both the head and the chain region of the membrane. Assistance from Martin Haese-Seiller and Adrian Rühm with the neutron experiments is gratefully acknowledged.