Berlin 2012 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 13: Poster: Interfaces and Thin Films
CPP 13.29: Poster
Dienstag, 27. März 2012, 18:15–20:45, Poster A
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 — 1Institut für Physik, Uni Greifswald, 17487 Greifswald, Germany — 2MPI KGF, 14476 Potsdam, Germany — 3Institut für Biochemie, Uni Greifswald, 17487 Greifswald, Germany — 4MPI P, Ackermannweg 10, 55128 Mainz, Germany
The reaction of phosphatidylcholines with hydroxyl radicals is investigated. The radicals are produced by the Fenton reaction. The radical concentration is varied. For DPPC monolayers a decrease in the lateral pressure is used as a measure of the efficiency of the radical attack. Combining isotherms and X-ray diffraction we find that the monolayer can be compressed to smaller molecular areas, with a reduced tilt angle of the alkyl chains. Consistent with this observation IRRAS experiments indicate a partial cleavage of the head group leading to a reduced head group size. X-ray reflectivity demonstrates Fe2+ binding to the head group. Fluorescence microscopy during the radical attack shows that new domains in the condensed phase nucleate immediately.
Furthermore, DMPC liposomes are investigated with differential scanning calorimetry. With increasing radical concentration, the alkyl chain melting transition is shifted to higher temperatures. Summarising, we observe solidification for both monolayers and liposomes which we attribute to a preferential radical attack on the hydrophilic head group region, followed by Fe2+ binding.