Géométrie dans la Nature


Confinement des membranes lipidiques


Publications sur ce thème (en anglais)

  • Flexoelectric fluid membrane vesicles in spherical confinement
    Niloufar Abtahi, Lila Bouzar, Nadia Saidi-Amroun, Martin Michael Müller

    The morphology of spherically confined flexoelectric fluid membrane vesicles in an ex- ternal uniform electric field is studied numerically. Due to the deformations induced by the confinement, the membrane becomes polarized resulting in an interaction with the external field. The equilibrium shapes of the vesicle without electric field can be clas- sified in a geometrical phase diagram as a function of scaled area and reduced volume [1, 2]. When the area of the membrane is only slightly larger than the area of the con- fining sphere, a single axisymmetric invagination appears. A non-vanishing electric field induces an additional elongation of the confined vesicle which is either perpendicular or parallel depending on the sign of the electric field parameter. Higher values of the surface area or the electric field parameter can reduce the symmetry of the system leading to more complex folding. We present the resulting shapes and show that transition lines are shifted in the presence of an electric field. The obtained folding patterns could be of interest for biophysical and technological applications alike.

    EPL, 131(1): 18001, 2020. Cf. aussi arXiv:2006.04475.


  • Confining a fluid membrane vesicle of toroidal topology in an adhesive hard sphere
    Lila Bouzar, Ferhat Menas, Martin Michael Müller

    We discuss how the equilibrium shapes of a confined toroidal fluid membrane vesicle change when an adhesion between membrane and confining sphere is taken into account. The case without adhesion was studied in Ref. [1]. Different types of solution were found and assembled in a phase diagram as a function of area and reduced volume of the membrane. Depending on the degree of confinement the vesicle is either free, in contact along a circle (contact-circle solutions) or on a surface (contact-area solutions). All solutions without adhesion are up-down symmetric. When the container is adhesive, the phase diagram is altered and new kinds of solution without up-down symmetry are found. For increasing values of adhesion the region of contact-circle solutions shrinks until it vanishes completely from the phase diagram.

    IOP Conf. Series: MSE, 186: 012021, 2017.


  • Toroidal membrane vesicles in spherical confinement
    Lila Bouzar, Ferhat Menas, Martin Michael Müller

    We investigate the morphology of a toroidal fluid membrane vesicle confined inside a spherical container. The equilibrium shapes are assembled in a geometrical phase diagram as a function of scaled area and reduced volume of the membrane. For small area the vesicle can adopt its free form. When increasing the area, the membrane cannot avoid contact and touches the confining sphere along a circular contact line, which extends to a zone of contact for higher area. The elastic energies of the equilibrium shapes are compared to those of their confined counterparts of spherical topology to predict under which conditions a topology change is favored energetically.

    Phys. Rev. E, 92: 032721, 2015. Cf. aussi arXiv:1509.00765.


  • Fluid membrane vesicles in confinement
    Osman Kahraman, Norbert Stoop, Martin Michael Müller

    We numerically study the morphology of fluid membrane vesicles with prescribed volume and surface area in confinement. For spherical confinement we observe axisymmetric invaginations that transform into ellipsoidal invaginations a the area of the vesicle is increased, followed by a transition into stomatocyte-like shapes. We provide a detailed analysis of the axisymmetric shapes and investigate the effect of the spontaneous curvature of the membrane as a possible mechanism for shape regulation. We show that the observed morphologies are stable under small geometric deformations of the confinement. The results could help to understand the role of mechanics in the complex folding patterns of biological membranes.

    New J. Phys., 14: 095021, 2012.


  • Morphogenesis of membrane invaginations in spherical confinement
    Osman Kahraman, Norbert Stoop, Martin Michael Müller

    We study the morphology of a fluid membrane in spherical confinement. When the area of the membrane is slightly larger than the area of the outer container, a single axisymmetric invagination is observed. For higher area, self-contact occurs: the invagination breaks symmetry and deforms into an ellipsoid-like shape connected to its outer part via a small slit. For even higher areas, a second invagination forms inside the original invagination. The folding patterns observed could constitute basic building blocks in the morphogenesis of biological tissues and organelles.

    Europhys. Lett., 97(6): 68008, 2012. Cf. aussi arXiv:1201.2518.







     © Martin Michael Müller