Berlin 2012 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 26: Posters: Membranes and Vesicles

BP 26.18: Poster

Donnerstag, 29. März 2012, 17:30–19:30, Poster A

Statics and dynamics of stalks studied by minimal coarse-grained models. — Giovanni Marelli, •Yuliya Smirnova, and Marcus Müller — Institut für theoretische Physik, Georg August Universität Göttingen

The stalk is a lipid bridge between two lipid membranes and a fundamental step in the process of membrane fusion. The formation and evolution of the stalk is a collective phenomenon which involves the interaction and change of conformation of many lipids. We use our coarse-grained solvent-free model to simulate a stalk between two opposed membranes. The absence of solvent molecules avoids the non trivial problem of re-equilibrating the number of solvent molecules between the two bilayers present in explicit solvent models. Depending on the type and architecture of lipids we can change the stability and morphology of the stalk. Radial stalks are mostly metastable and we calculate the average density profile and fluctuations of their thickness. Small hydrophobic chains (oil) added in the hydrophobic layer of the membrane preferentially go to the lower and upper ends of the stalk, where the membrane is slightly indented, and relax the total tension. Linear stalks formed by more asymmetric lipids are stable and span the simulation box over the pbc. We calculate their line tension. In case of mixed lipid membranes we observe the segregation of lipids with different spontaneous curvatures to curved and planar portions of the morphology. Finally we compare the thickness profile and the bilayer repulsion with different models and experimental data.