Nonlinear shape perturbations induced by vesicle inclusions (original) (raw)
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Attractive forces between anisotropic inclusions in the membrane of a vesicle
The European Physical Journal B, 1999
The fluctuation-induced interaction between two rod-like, rigid inclusions in a fluid vesicle is studied by means of canonical ensemble Monte Carlo simulations. The vesicle membrane is represented by a triangulated network of hard spheres. Five rigidly connected hard spheres form rod-like inclusions that can leap between sites of the triangular network. Their effective interaction potential is computed as a function of mutual distance and angle of the inclusions. On account of the hard-core potential among these, the nature of the potential is purely entropic. Special precaution is taken to reduce lattice artifacts and the influence of finite-size effects due to the spherical geometry. Our results show that the effective potential is attractive and short-range compared with the rod length L. Its well depth is of the order of κ/10, where κ is the bending modulus.
Membrane-mediated interactions of rod-like inclusions
European Physical Journal E, 2002
Inclusions embedded in lipid membranes undergo a mediated force, due to the tendency of the membrane to relax its excess of elastic energy. In this paper we determine the exact shape of a two-dimensional vesicle hosting two different inclusions, and we analyse how the inclusion conformation influences the mediated interaction. We find non-trivial equilibrium configurations for the inclusions along the hosting membrane, and we derive the complete phase diagram of the mediated interaction. In particular, we find a non-vanishing mediated force even when the distance between the inclusions is much greater than their size. Our model can be applied to describe the mediated interactions of parallel, elongated inclusions embedded in three-dimensional membranes.
Curvature effects on membrane-mediated interactions of inclusions
Journal of Mathematical Biology, 2002
We study the static, long-range interactions of inclusions embedded in lipid membranes. By using a two-dimensional model, we are able to determine explicitly the closed equilibrium shape of the membrane for any value of the distance between the inclusions; our results show that these shapes cannot be obtained by linearizing the equilibrium equations near a referential shape. Moreover, by computing the membrane-mediated force between the inclusions in given static conditions, we also detect the effects on the interactions due to the curvature and the closed geometry of the membrane.
Shape variation of bilayer membrane daughter vesicles induced by anisotropic membrane inclusions
Cellular & Molecular Biology Letters, 2006
A theoretical model of a two-component bilayer membrane was used in order to describe the influence of anisotropic membrane inclusions on shapes of membrane daughter micro and nano vesicles. It was shown that for weakly anisotropic inclusions the stable vesicle shapes are only sligthly out-of-round. In contrast, for strongly anisotropic inclusions the stable vesicle shapes may significantly differ from spheres, i.e. they have a flattened oblate shape at small numbers of inclusions in the membrane, and an elongated cigar-like prolate shape at high numbers of inclusions in the vesicle membrane.
Numerical investigations of the dynamics of two-component vesicles
Journal of Physics: Condensed Matter, 2011
We examined the dynamics of the deformation and phase separation of two-component vesicles. First, we numerically investigated the effects of (i) thermal noise, (ii) hydrodynamic flow induced by the line tension of the domain boundary and (iii) composition-dependent bending rigidity on the coarsening dynamics of a phase-separated pattern on the surfaces of vesicles with fixed shapes. The dynamical exponent z (NDB ∼ t −z , the total length of the domain boundaries) of the coarsening of phase-separated pattern was found to decrease from z = 1/3 under no thermal noise to 1/5 < z < 1/4 when including the effects of thermal noise. We also found that the hydrodynamic effect enhances the coarsening in a bicontinuous phase separation for a spherical vesicle. In phase separations of a shape-fixed tubular vesicle, a band-like phase separation with periodicity along the longer axis of the tube occurs because of the composition-dependent bending rigidity and the higher curvatures at the tube end-caps. Second, we also explored the dynamics of shape deformation coupled with phase separation through the bending rigidity of the membrane which depends on the local composition in lipid, and found that the composition-dependent bending rigidity crucially influences the phase separation and deformation of the vesicle. The results of simulations are in good agreement with experimentally observed behaviors known as "shape convergence" [
arXiv: Soft Condensed Matter, 2019
We investigate the mechanics of heterogeneous vesicles having a collection of phase-separated domains with different preferred curvatures. We develop approaches to study at the coarse-grained level and continuum level the role of phase separation, elastic mechanics, and vesicle geometry. We investigate the elastic responses of vesicles both from passive shape fluctuations and from active deformations. We develop spectral analysis methods for analyzing passive shape fluctuations and further probe the mechanics through active deformations compressing heterogeneous vesicles between two flat plates or subjecting vesicles to insertion into slit-like channels. We find significant domain rearrangements can arise in heterogeneous vesicles in response to deformations. Relative to homogeneous vesicles, we find that heterogeneous vesicles can exhibit smaller resisting forces to compression and larger insertion times into channels. We introduce quantitative approaches for characterizing heterog...
The equilibria of vesicles adhered to substrates by short-ranged potentials
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2013
In equilibrium, a vesicle that is adhered to a horizontal substrate by a long-range attractive, short-range repulsive force traps a thin layer of fluid beneath it. In the asymptotic limit that this layer is very thin, there are quasi-two-dimensional boundary-layer structures near the edges of the vesicle, where the membrane's shape is governed by a balance between bending and adhesive stresses. These boundary layers are analysed to obtain corrections to simpler models that instead represent the adhesive interaction by a contact potential, thereby resolving apparent discontinuities that arise when such models are used. Composite expansions of the shapes of two-dimensional vesicles are derived. When, in addition, the adhesive interaction is very strong, there is a nested boundary-layer structure for which the adhesive boundary layers match towards sharp corners where bending stresses remain important but adhesive stresses are negligible. Outside these corners, bending stresses are...