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Influence de la composition lipidique sur la résistance de membranes bio-mimétiques au stress oxydant

Abstract : Mitochondrion is both the place of cell energy production and the regulatory center of apoptosis. The efficiency of these functions depends on the oxidation level of inner mitochondrial membranes (IMM). The aim of this work is to decipher the influence of lipids on the membrane resistance to oxidative stress. Experiments are done on IMM-mimicking liposomes. Membrane oxidation is controlled by irradiation of the Ce6, a photosensitizer with high affinity for lipid bilayers. First we quantifiy the binding of Ce6 to membrane by fluorimetry. This measures are used to have a ratio Ce6/lipids equal between membrane compositions. Then we study, by phase contrast microscopy, the influence of the nature of lipid polar head and of the number, position and conformation of aliphatic chains insaturations on the oxidation-induced liposome permeabilization. This permeabilization is due to 2 phenomena : the formation of membrane defects and micrometric pore openings. These latter allow, for IMM-like membranes, a significant leak of liposome inner medium. The presence of cardiolipin, a mitochondrion-specific lipid, delays and decreases the induced permeability. The more insaturations lipids have and the closer to the polar head they have, the more efficient is the permeabilization. Raman spectroscopy allows us to follow chemical scenario of this phenomenon. In particular, membrane oxidation is possible only if the double bonds electron can be delocalized.
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  • HAL Id : tel-02555176, version 1

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Aurélien Bour. Influence de la composition lipidique sur la résistance de membranes bio-mimétiques au stress oxydant. Biophysique [physics.bio-ph]. Sorbonne Université, 2018. Français. ⟨NNT : 2018SORUS394⟩. ⟨tel-02555176⟩

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