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BP: Fachverband Biologische Physik

BP 38: Electrolytes at Interfaces - Stern Layer (focus session, joint CPP/BP/O)

BP 38.5: Vortrag

Mittwoch, 18. März 2015, 16:15–16:30, C 130

Cardiolipin Monolayers — •Renko Kensbock, Heiko Ahrens, Andreas Gröning, Thomas Ortmann, and Chrisitane A. Helm — Physik, Uni Greifswald, 17487 Greifswald, Germany

Cardiolipin-cytochrome c binding in the inner mitochondrial membrane is pertinent to apoptotic processes involving positively charged cytochrome c, motivating a characterization of cardiolipin membranes. Cardiolipins are negatively charged lipids with four alkyl chains. Our approach is to analyse cardiolipin monolayers at the water-air interface, using isotherms and Brewster angle microscopy. The calculation of the in-plane electrostatic pressure consists of an electrostatic contribution using Grahame's equation and a chemical part reflected by the law of mass action. A nonmonotonic ionic strength dependence with a maximum at 0.1 M (NaCl, KCl) is observed for the phase transition surface pressure. This finding is in accordance with the calculations predicting the dominance of charge screening by monovalent counterions only for concentrations above 0.1 M. For lower salt content, its increase causes an elevation of the degree of dissociation and thus electrostatic repulsion within the cardiolipin membrane. The results will be reported, showing pH, concentration, temperature influences on the surface potential, and thus the ability to bind cytochrome c.