Principle investigators: Gerald Brezesinski and Christiane A. Helm
Co-supervisor: U. Lendeckel

The effect of ROS/RNS on model membranes in 2D (monolayers at the air/liquid interface) and 3D (supported bilayers and vesicles) will be investigated by different techniques. The work will be conducted in close cooperation with B1 (Helm). IR spectroscopy will be the main method [1,2,3]. Changes in the molecular structure of the used lipids in monolayers at the air/water-interface and in lipid bilayers formed on soft polymer cushions are studied. For the 2-dimensional systems, the changes (position and intensity) of IRRAS bands assigned to vibrations of specific molecular groups are studied under different experimental conditions before and after addition of reactive oxygen and nitrogen species. Changes in the orientation of transition dipole moments are monitored (i.e. the tilt of the alkyl chains) by angle dependent measurements of polarized IR-light. The results are correlated with changes in the structure studied in other projects, especially B1. Additionally, surface potential measurements provide information about the charge of the monolayer, and the corresponding changes during the investigated reactions. To study lipid bilayers, ATR-IR and quartz crystal microbalance (QCM) experiments are combined. Thus the damage to a lipid bilayer is monitored that is correlated to mass loss and changes in the bilayer composition. The advantage of the model system studies is that single lipids or defined lipid mixtures can be used so that the effect of ROS and RNS on individual components of the biological membrane can be studied separately. 
In co-operation with A1 (Lillig), the action of anti-cancer drugs will be studied as a function of the lipid phase state (different packing densities) using defined model lipid layers or binary mixtures. In co-operation with A1 and C2 (Lendeckel), the packing and oxidation of cardiolipins with different chain compositions will be studied in 2D model systems. Interactions between cardiolipin and cytochrome C will be studied in undisturbed single-component or binary systems and after the attack of radicals. In co-operation with projects A2 (Bornscheuer) / A3 (Mayerle/Lerch), we will additionally perform studies of enzymatic reactions in 2D model systems [4,5,6]. The same enzymes or even enzymatic cascades will be used to understand the molecular basis of these interactions. The influence of radicals on the enzymatic activity will be studied in the different model systems. In cooperation with the biological groups A3 and B4 (Lalk/Kahlert), the effect of radical scavengers will also be investigated using the defined model systems.

Literature

1 Hoernke, M., Falenski, J.A., Schwieger, C., Koksch, B., and Brezesinski, G.: Langmuir (2011) 27, 14218.

2 Stefaniu, C., Brezesinski,G., Moehwald‚ H.: Polymer-capped magnetite nanoparticles change the 2D structure of DPPC model membranes, Soft Matter (2012) 8, 7952.

3 Groening, A., Ahrens, H., Ortmann, T., Lawrenz, F., Brezesinski, G., Scholz, F., and Helm, C.A.: Soft Matter (2011) 7, 6467.

4 Estrela-Lopis, I., Brezesinski, G., and Möhwald, H.: Biophys. J. (2001) 80, 749.

5 Wagner, K., and Brezesinski, G.: Biophys. J. (2007) 93, 2373.

6 Wagner, K., and Brezesinski, G.: Curr. Opin. Colloid Interface Sci. (2008) 13, 47.