Regensburg 2007 – scientific programme

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BP: Fachverband Biologische Physik

BP 26: Poster Session II

BP 26.30: Poster

Thursday, March 29, 2007, 17:00–19:30, Poster B

Investigation on actin binding to various cationic model membranes — •Lydia Woiterski, Josef Käs, and Carsten Selle — Institut für Exp. Physik I, Linnéstr. 5, 04103 Leipzig

The aim of the present work is to study adsorption of a charged polymer at inflexible and flexible charged surfaces under a two-dimensional confinement. As a polymer, we use actin which is one of major components of the cytoskeleton in eukaryotic cells. The filaments form a quasi-two-dimensional network -- the so-called actin cortex that plays an important role for cellular functions such as motility or adhesion. It is associated with the inner leaflet of the cell membrane, thus, it is of great interest to elucidate the nature of interaction of polymerized actin and lipids. First, this binding process is studied using giant vesicles prepared from mixtures of neutral lipids, the cationic lipid DODAB and cholesterol. The vesicle is trapped with optical tweezers in a micro-fluidic chamber. Filamentous actin is injected into the chamber and the properties of binding are investigated in dependence on the ionic strength and the composition of the model membrane using confocal microscopy. Furthermore, different mixed monolayers are studied to establish a system where liquid domains form and provide binding sites for the adsorption of single polymers. The monolayer/polymer system is a good model to mimic the behavior of polymers near lipid interfaces because it allows to manipulate easily the domain size and permits the observation of lateral diffusion within the model membrane in comparison to curved vesicles.