Regensburg 2007 – scientific programme

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BP: Fachverband Biologische Physik

BP 3: Membranes and Interfaces

BP 3.10: Talk

Monday, March 26, 2007, 16:30–16:45, H43

Diffusion of nano-particles in model membranes — •Florian Rückerl, Carsten Selle, and Josef Käs — Universität Leipzig, Institut für Experimentelle Physik I, Abt. PWM

Langmuir monolayers are used as a simple membrane model in which partially charged nano-particles diffuse as model proteins. This system provides good control over obstacle sizes. The condensed domains within liquid phases that are found in the coexistence region exhibit a net dipole moment. The radial dependence of this electric dipolar field changes with the size of the domains from E(|r|)∝1/|r|³ for a single dipole to E(|r|)∝1/|r| for large domains (R>10µ m). The influence of this change on the particle diffusion was investigated by Monte Carlo simulations. The analysis shows that the particles are stronger confined at the domain border of smaller domains and that a change from two to one dimensional diffusion occurs.

We further investigate a more complex system, nano-particles diffusing on the surface of giant unilamellar vesicles composed of either a single lipid or a mixture of lipids: DOPC, DPPC and cholesterol. The latter systems exhibit L_d − L_o coexisting phases which were shown to form curvature gradients in their bilayer surfaces. Therefore, the influence of the local membrane curvature on the diffusive behavior of the nano-particles can be investigated. A variety of lipid compositions and particles, R=34nm−1.6µ m with varying surface modifications, are used in order to to elucidate the interactions between nano-particles and lipids in bilayer membranes.