Regensburg 2004 – wissenschaftliches Programm

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AKB: Biologische Physik

AKB 50: Poster Session "Biological Physics"

AKB 50.68: Poster

Freitag, 12. März 2004, 10:30–13:00, B

Investigation of Lipid Multilayers under Electric Field Using X-Ray Reflectivity — •Doru Constantin, Christoph Ollinger, and Tim Salditt — Institut fuer Roentgenphysik, Universitaet Goettingen

The influence of an external electric field upon lipid bilayers is of paramount importance, both from a practical and a fundamental point of view. Cell electroporation has been long employed for introducing exogenous molecules into cells, while electroformation is the best method to date for obtaining giant unilamellar vesicles. Although very important, these phenomena are still in need of a clear-cut explanation.

We studied the behaviour of solid-supported multilayers of the zwitterionic lipid DMPC under an applied transverse electric field, using specular and non-specular X-ray scattering. As a first step, we determined the kinetics of unbinding under field for various applied voltages, both for thin (tens of bilayers) and thick (thousands of bilayers) samples. Surprising similarities with the previously characterized thermal unbinding kinetics were revealed.

No changes were detected in the diffuse scattering signal, hinting that the unbinding could be a surface phenomenon, not related to instabilities in the bulk, but rather affecting only a few layers at the top of the stack. This hypothesis is reinforced by the fact that the time correlation function of the reflectivity signal from thin samples exhibits a peak at the frequency of the applied field, which does not appear for thick samples.