Regensburg 2016 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 29: Poster: Crystallization, Nucleation, Self Assembly

CPP 29.6: Poster

Dienstag, 8. März 2016, 18:15–21:00, Poster B2

Real-Time BAM Studies of Cardiolipin Monolayers — •Renko Kensbock, Heiko Ahrens, and Christiane A. Helm — Institute of Physics, University of Greifswald, 17487 Greifswald, Germany

We investigate electrostatic interactions within negatively charged cardiolipin monolayers at the water-air interface with isotherms and real-time Brewster angle microscopy (BAM). A non-monotonic dependence for the LE/LC transition surface pressure on salt concentration (NaCl, KCl) is observed with a maximum at 0.1 mol/l. This is in accordance with calculations taking into account head-group interactions. The calculations consist of an electrostatic contribution (Grahame's equation) and counter-ion binding according to the law of mass action. For salt concentrations above 0.1 mol/l the electrostatic repulsion is predominantly screened, whereas for salt concentrations up to 0.1 mol/l the degree of dissociation increases. The electrostatic interaction also determines the surface area of domains as observed with BAM. Depending on line tension and long range electrostatic repulsion, domain nucleation and growth are differently affected by changes in ionic strength. The observed number of domains, compared at fixed molecular area in the LE/LC coexistence region, shows a similar behavior to that observed with the transition surface pressure - fewest observed domains for the pure water subphase, with an increase in number up to 0.1 mol/l NaCl and thereafter a decrease for 1 mol/l NaCl.