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Accueil du site > Seminars > Séminaires théorie > Theory Club 27 janvier 2016 à 13:00-14:00 (A confirmer) en salle 646A. Guillaume Gueguen: "Mixed lipid bilayers with locally varying spontaneous curvature and bending".

Theory Club 27 janvier 2016 à 13:00-14:00 (A confirmer) en salle 646A. Guillaume Gueguen: "Mixed lipid bilayers with locally varying spontaneous curvature and bending"

Unless otherwise stated, seminars and defences take place at 11:30 in room 454A of Condorcet building.


Mixed lipid bilayers with locally varying spontaneous curvature and bending

Guillaume Gueguen

Abstract: Biological membranes are bidimensional fluids composed of different types of lipids and proteins. It is well known, that the membrane needs to control the spatial organisation of proteins to achieve various biological functions. Here we develop a model of a closed vesicle where the lipid bilayers are modeled as a mixture of two lipids with different average compositions on both leaflets. A Landau hamiltonian describing the lipid-lipid interactions on each leaflet, with two lipidic fields, is coupled to a Helfrich one, accounting for the membrane elasticity, via both a local spontaneous curvature, and a bending modulus.This model allows us to define curved patches as membrane domains where the asymmetry in composition is large, and thick and stiff patches. These thick patches are good candidates for being lipidic rafts, as observed in cell membranes, which are composed primarily of saturated lipids forming a liquid-ordered domain and are known to play the role of signalisation plateform for cells. In the same time we develop a numerical code to extend this study to any shape of vesicle focusing on the local deformation induced by lipid phase separation. First of all, the lipid-lipid structure factors and correlation functions are analytically computed for globally spherical membranes and planar ones and for a whole set of parameters including the surface tension and the coupling in the two leaflet compositions. Phase diagrams are established showing the occurrence of two types of Structure Disordered phases, with correlations between either curved or thick patches, and an Ordered phase. Then, we compare our analytical results to numerical results restrited to quasi-spherical shapes. We extend the simulation to the whole parameter range. Extended phase diagrams of cell shapes as a function of lipid-lipid interactions are draw

27 janvier 2016 à 13:00-14:00 (A confirmer) en salle 646A


Contact : Équipe séminaires / Seminar team - Published on / Publié le 16 December 2015


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