Berlin 2005 – scientific programme
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CPP: Chemische Physik und Polymerphysik
CPP 13: Selforganized and supramolecular assemblies II
CPP 13.4: Talk
Monday, March 7, 2005, 12:00–12:15, TU C243
Interaction among Charged Membranes — •Beate Klösgen1 and Viveka Alfredsson2 — 1University of Southern Denmark, Phys. Dept. and MEMPHYS, Denmark — 2Lund University, Inst. Phys. Chem., Sweden
Charged membranes exhibit unspecific electrostatic interactions; especially the cationic ones have the potential for binding DNA which suggests an application in gene transfer systems. Yet, the pure electrostatics of composite systems of neutral and charged lipid, counterions and water is not fully understood. Results from interaction studies among charged membranes are presented. Electron microscopy (cryo-TEM, 120kV, Δ z ≃ −1µm) experiments were done on vitrified SUVs ( r ≃ 50nm) of neutral lipid (DOPC) and admixed cationic / anionic lipids of the same chain length (DOPG, E-DOPC), Cl- being the charge counterion. Lipid concentration of 1% (wt/wt) was constant in all vesicle suspensions; charge densities were adjusted to 1% or 10 % (charged lipid/total lipid). A crossover between adhesion and repulsion among adjacend membranes depending on membrane charge density was found. At least two opposing contributions must cause this balance. It may be speculated that the net attractive interaction at low charge density can be attributed to an entropic contribution by counterion release from the aqueous gap in the adhesion site, or to charge dependencies of fluctuation forces.