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BP: Fachverband Biologische Physik
BP 21: Membranes and Vesicles II
BP 21.1: Vortrag
Dienstag, 1. April 2014, 14:00–14:15, ZEU 250
Interactions of Radical Oxygen Species with Phosphatidylcholine Monolayers and Liposomes — •Andreas Gröning1, Heiko Ahrens1, Frank Lawrenz1, Thomas Ortmann1, Gerald Brezesinski2, Fritz Scholz3, Doris Vollmer4, and Christiane A. Helm1 — 1Inst. f. Physik, Uni Greifswald, 17487 Greifswald, Germany — 2MPI KGF, 14476 Potsdam, Germany — 3Inst. f. Biochemie, Uni Greifswald, 17487 Greifswald — 4MPIP, 55128 Mainz, Germany
During times of environmental stress (e.g., UV or heat exposure), levels of reactive oxygen species (ROS) can increase. This may result in significant damage to cell structures. Here we focus on the effect of hydroxyl radicals (produced by Fenton reaction) on model membranes.
For DPPC monolayers at the air/water interface a decrease in the lateral pressure is used as a measure of the efficiency of the radical attack. Combining isotherms, X-ray diffraction and IRRAS we find a partial cleavage of the head group leading to a reduced head group size with negative charge. X-ray reflectivity demonstrates Fe2+ binding to the head group, fluorescence microscopy immediate nucleation of new domains in the condensed phase.
The radicals destroy DMPC liposomes, only fragments remain as is observed with confocal microscopy. Differential scanning calorimetry shows that an increasing radical concentration causes a shift of the alkyl chain melting transition to higher temperatures.
Summarising, both monolayers and liposomes solidify on exposure to ROS, consistent with a common molecular mechanism.