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.