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Tetiana Mukhina, Active Fluctuations and Electrostatic Interactions in Floating Lipid Membranes (2019)

Supervision: Thierry Charitat, Giovanna Fragneto, Yuri Gerelli

The main project of this work was focused on the investigation of out-of-equilibrium fluctuation of phospholipid membranes induced by light-activated transmembrane protein bacteriorhodopsin (BR). A robust protocol for the BR incorporation into the membrane-mimic systems was developed and the induced structural changes caused by BR incorporation and activation with light were probed by means of neutron and X-ray specular and off-specular reflectometry. The reversible effect of light illumination
on the protein activity (on /off) via its effect on the bilayer structure and fluctuation spectrum was demonstrated. These results open the way to investigate the active fluctuation spectrum of a planar membrane-protein system and to access the physical properties of the active membrane.
The aim of the second project was to investigate the interaction between highly negatively charged DPPS lipid bilayers. We fully characterized the structure of the system and clearly demonstrated that attractive interactions existed between charged bilayers, in good agreement with Strong-Coupling theory.

Keywords : membrane, bacteriorhodopsin, membrane fluctuation spectrum, neutron
reflectometry, X-ray reflectometry, membrane interactions, Strong-Coupling theory

PhD manuscript