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BP: Fachverband Biologische Physik

BP 48: Membranes and Vesicles II

BP 48.4: Vortrag

Donnerstag, 23. März 2017, 10:30–10:45, HÜL 386

Influence of Mono- and Divalent Ions on Cardiolipin Monolayers — •Renko Kensbock, Heiko Ahrens, and Christiane A. Helm — Inst. of Physics, Greifswald University, Germany

We investigate electrostatic interactions within negatively charged cardiolipin monolayers at the air-water interface with isotherms and real-time Brewster angle microscopy (BAM). A non-monotonic dependence for the LE/LC transition surface pressure on monovalent salt concentration (NaCl, KCl, CsCl) is observed with a maximum at around 0.1 M. No specificity for monovalent cations is detectable, which points to the prevalence of electrostatics. For subphases of 0.15 M NaCl with different divalent cations, the transition surface pressure decreases upon increase of their concentration. This indicates binding of divalent cations to the monolayer and an increase in electrostatic screening. The mono- and divalent salt effects are in accordance with electrostatic model calculations accounting for the head-group interactions: an electrostatic contribution (Grahame's equation) and counter-ion binding (law of mass action) are considered. The divalent binding constant assumes a 1:1 divalent cation to cardiolipin binding and is specific for the divalent cations used.