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Relationship between mechanical parameters and behaviour under external stresses in lipid vesicles with modified membranes.

Abstract : The goal of this work was to develop mechanical models of cells based on lipidic giant unilamellar vesicles (GUVs) and to investigate the relationship between mechanical parameters and behaviors under external stresses. Firstly, we succeeded in modifying structural properties of membranes either by coating fluid phase bilayers with polyelectrolytes (chitosan or hyaluronan) or by using the lipid phase transition to obtain membranes in the gel state. The characterization of the coated membrane has revealed the electrostatic origin of the interaction between DOPC bilayers and polyelectrolytes, and that the adsorbed chain conformation at the vesicle surface is controlled by the polymer chemical structure. Concerning membranes in the gel state, a shrewd protocol was proposed to preserve the DMPC GUVs spherical shape upon cooling and transition from the fluid to the gel phase. Secondly, we have demonstrated that the membrane structure highly affects the value of the mechanical parameters and changes the behaviors of these complex GUVs under various applied constraints (e.g. osmotic pressure, pH and salt shocks, compression between two planes (Atomic Force Microscopy) or point-acting force (hydrodynamic membrane tether extrusion)). In particular, AFM experiments have demonstrated that polyelectrolyte coating rigidifies lipid membranes, increasing among others their stretching moduli. As well, the osmotic deflation of gel GUVs have lead to a large panel of concave polyhedron-like shapes, numerically retrieved using a relevant 2D elastic model. Finally, we have proposed an original technique to characterize vesicles by studying their flow in confined geometries.
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https://tel.archives-ouvertes.fr/tel-00615938
Contributor : François Quemeneur <>
Submitted on : Friday, August 19, 2011 - 6:10:56 PM
Last modification on : Wednesday, November 4, 2020 - 1:56:17 PM
Long-term archiving on: : Thursday, March 30, 2017 - 2:12:40 PM

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  • HAL Id : tel-00615938, version 1

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François Quemeneur. Relationship between mechanical parameters and behaviour under external stresses in lipid vesicles with modified membranes.. Data Analysis, Statistics and Probability [physics.data-an]. Université de Grenoble, 2010. English. ⟨tel-00615938⟩

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