Dresden 2011 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 7: Interfaces and Thin Films II
CPP 7.12: Vortrag
Montag, 14. März 2011, 17:00–17:15, ZEU 114
Phosphocholine Monolayer Solidification due to Oxygen Radicals — •Andreas Gröning1,2, Heiko Ahrens1, Thomas Ortmann1, Frank Lawrenz1, Gerald Brezesinski3, Fritz Scholz2, and Christiane A. Helm1 — 1Inst. für Physik, Uni Greifswald, Felix-Hausdorff-Str. 6, D-17487 Greifswald — 2Inst. für Biochemie, Uni Greifswald, Felix-Hausdorff-Str. 4, D-17487 Greifswald — 3MPI KGF, D-14476 Potsdam
The reaction of 1,2-dipalmitoylphosphatidylcholine (DPPC) with hydroxyl-radicals has been investigated using monolayer techniques: isotherms, infrared absorption reflection spectroscopy (IRRAS), gracing incidence X-ray diffraction (GIXD), X-ray reflection and fluorescence microscopy. The DPPC monolayer undergoes a transition from a liquid-expanded to a liquid-condensed state characterized by a plateau region. The DPPC monolayer is attacked in the coexistence region and in the liquid-condensed state with different Fenton concentrations. With increasing Fenton concentration, the plateau region is shifted to a lower surface pressure; eventually it disappears. With higher Fenton concentration, the molecular area in the liquid-condensed phase is decreased. IRRAS experiments indicate a decomposition of the choline group. After Fenton attack, GIXD shows a decrease of the tilt angle, an increase of translational (by 50%) and orientational order which demonstrates monolayer solidification. The highly compressed monolayer exhibits nearly hexagonal order. Additionally, fluorescence microscopy shows that some DPPC domains fuse and new domains nucleate. At zero pressure, solid domains remain.