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Lecuyer Sigolène, Fluctuations et déstabilisation d’une bicouche lipidique supportée (2006)

Supervisor: Thierry Charitat

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We study experimentally the dynamical properties of a supported lipid bilayer. The structure and equilibrium properties of single and double bilayers are studied by neutron reflectivity. The submicronic fluctuation spectrum of a "floating" bilayer is studied by off-specular X-ray scattering: its surface tension, bending modulus and, for the first time with this technique, the inter-membrane potential can be determined.Using fluorescence microscopy, we show that this single bilayer can form vesicles. Its destabilisation can occur either at the main gel-fluid transition of the lipids, and can be interpreted in terms of a drop of the bending rigidity, or under an AC low-frequency electric field applied in the fluid phase. In that last case we also study the effect of the electric field at the molecular length scale by neutron reflectivity. In both cases, the detabilisation leads to the formation of relatively monodisperse vesicles, which could give a better understading of the formation mechanism, and eventually allow better control of the preparation process.In a last part, we study the lateral diffusion of lipids in the supported bilayer thanks to fluorescence recovery after photobleaching. Measuring the diffusion coefficient as a function of temperature enables one to spot the gel-fluid transition; our results suggest that it could be lowered by a few degrees for a single bilayer supported on a glass substrate.

PhD Manuscript avalaible here