Membrane coupled to the cytoskeleton: Fluctuations and stability

[摘要] ENGLISH ABSTRACT : In erythrocytes the plasma membrane is coupled to the underlying two dimensional hexagonal network of spectrin filaments through protein node complexes. There are also other protein complexes that link an individual filamentto the bilayer at a random point along its length. This network, together witha repulsive glycocalix, is responsible for large shape changes and shape transformation sequence of these erythrocytes. It has been experimentally shownthat the stiffening of the erythrocytes after infection by malaria Plasmodiumfalciparum parasite, for instance, correlates with the structural transformationin the network.We develop a model to treat the detachment of a membrane from such asubstrate, which might be a model for structural failure of erythrocytes. Weconsider a flexible membrane elastically linked at random points to a substrateunder an applied pressure differential across the membrane. This quenchedrandomness requires the use of the replica formalism, which we investigate fromboth replica symmetric and weakly broken replica symmetry perspectives. Wecompare these results with the continuum and the annealed adhesion modelswe first construct.The fluctuation spectrum as function of the pressure, generally, shows thatthe average square fluctuations increases with the pressure. However, for thediscrete inhomogeneous adhesion, when the position of tethers distributionis quenched the square fluctuation exhibit a non monotonic behavior. Ourmodel characterize the role of the pressure and the disorder in the emergentnon monotonic fluctuation spectrum for the different treatment of the tetherposition distribution randomness.The annealed tether position distribution yields a monotonic relation ofincrease for the square fluctuations with the removal of tethers for nonzeropressure.

[发布机构] Stellenbosch University