Regensburg 2013 – scientific programme

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BP: Fachverband Biologische Physik

BP 18: Membranes and Vesicles I

BP 18.6: Talk

Wednesday, March 13, 2013, 11:15–11:30, H44

Specific binding of chloride ions to lipid vesicles and implications at molecular scale — •Volker Knecht¹ and Benjamin Klasczyk² — ¹Biomolecular Dynamics, Institute of Physics, Albert Ludwigs University, Hermann-Herder Strasse 3, D-79104 Freiburg — ²MELAG Medical Technology, D-10829 Berlin

Biological membranes comprised of lipids and proteins are in contact with electrolytes like aqueous NaCl solutions. Based on molecular dynamics (MD) simulations it is widely thought that Na⁺ ions specifically bind to POPC bilayers while Cl⁻ ions merely form a diffuse layer of counterions screening the positive membrane charge due to the Na⁺ ions. I will present a comparison of recent data from electrophoresis and isothermal calorimetry experiments indicating that in fact both ion species show very similar affinities. Force field issues with the MD studies are highlighted by our finding that a widely used simulation setup showing asymmetric affinities of Na⁺ and Cl⁻ ions for POPC bilayers overestimates the effect of NaCl on the electrophoretic mobility of a POPC membrane by an order of magnitude. Implications for previous simulation results on the effect of NaCl on the structure of the membrane and the interfacial water are discussed. Our results suggest that a range of published simulation results on the interaction of NaCl with PC bilayers have to be reconsidered and revised.