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Regensburg 2004 – scientific programme

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AKB: Biologische Physik

AKB 50: Poster Session "Biological Physics"

AKB 50.47: Poster

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

Elastic and caloric properties of model membranes at the chain melting transition — •Wolfgang Manglkammer and Jan K. Krüger — Universität des Saarlandes, Experimentalphysik, Postfach 151150, D-66041 Saarbrücken, GERMANY

One remarkable feature of lipid membranes, which often serve as a model for ’real’ biological membranes, is the so-called main transition, but its nature is not yet clear. When the hydrocarbon chains are melting, the lipid bilayer transforms from the gel phase into the fluid Lα phase.
We investigated the hypersonic properties of oriented, solid supported Phosphatidylcholine bilayer stacks of different chain length by Brillouin spectroscopy as a function of hydration and temperature. The elastic moduli show huge steps which accompany several phase transitions. Therefore the transition points can easily be defined, what allows us to draw a temperature-composition phase diagram.
The elastic behaviour near the main transition is related to the specific heat as obtained from multi-lamellar vesicles by quasi-isothermal Temperature Modulated DSC. The heat capacity shows critical behaviour on both sides of the transition. Such pre-critical features were not found for the high frequency elastic moduli, although they were reported in literature for low frequency elastic experiments.

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