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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 34: P6: Biomaterials and Biopolymers

CPP 34.3: Poster

Dienstag, 17. März 2015, 14:00–16:00, Poster C

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 — ¹Physik, Uni Greifswald, 17487 Greifswald, Germany — ²MPI KGF, 14476 Potsdam, Germany — ³Biochemie, Uni Greifswald, 17487 Greifswald, Germany — 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. Combining isotherms, X-ray diffraction, X-ray reflection and IRRAS, we find a partial cleavage of the head group leading to a reduced head group size with negative charge for DPPC monolayers at the air/water interface. Free iron ions are produced by the Fenton reaction, they bind to the head group. Fluorescence microscopy showed immediate nucleation of new domains in the condensed phase, followed by solidifcation. Similar effects are observed with differential scanning calorimetry and confocal microscopy for DMPC liposomes. The use of EDTA in high excess to catch all free iron ions prevents the solidification of the monolayers and liposomes. The chemical changes of the lipids due to radical attack have no direct effect on the phase transition and solidification. Solidification and destruction of the model membranes after the Fenton reaction are attributed to the iron ions, which bind very strongly to the lipids after the radical attack.