Dresden 2009 – scientific programme

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BP: Fachverband Biologische Physik

BP 25: Membranes

BP 25.7: Talk

Friday, March 27, 2009, 12:15–12:30, HÜL 186

Interaction of charged colloids and actin filaments with inhomogeneous lipid membranes — •Florian Rückerl, Lydia Woiterski, Josef Käs, and Carsten Selle — Universität Leipzig, Inst. Exp. Phys. I

Lipid bilayers are simple and controllable mimics of cell membranes. The model membranes used in the experiments are composed of ternary mixtures of lipids (DOPC, cholesterol and DPPC or Sphingomyelin). These compositions can form liquid membranes and exhibit an ordered-disordered phase coexistence.

In giant unilamellar lipid vesicles, electrostatic interactions are screened by the surrounding polar liquid and relatively short-ranged. However, even for supposedly neutral membranes, positively charged colloids show a much higher binding affinity to the bilayer than negatively charged colloids. Further, we see a strong influence of the phase boundary on the diffusional properties of the tracer particle, namely a switch from two- to one-dimensional diffusion. This observation is similar to our previous experiments on monolayer systems [1,2].

The negatively charged semiflexible polymer actin readily binds to lipid membranes containing 10% of the cationic DOTAP. There is an interesting interplay between the size of the domains in which the DOTAP partitions into, and the length of the filaments. Our experiments indicate a lower limit for the domain size below which the binding of the filaments does not occur.

[1] Rückerl et al., Langmuir 2008, 24 (7)

[2] Forstner et al., Phys Rev E 2008, 77