Shape variation of bilayer membrane daughter vesicles induced by anisotropic membrane inclusions (original) (raw)
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Nonlinear shape perturbations induced by vesicle inclusions
2005
We analyse the effects that a rigid inclusion induces on the stationary shapes of an impermeable three-dimensional vesicle. Our study, performed via a numerical calculation, takes into account shapes which are not close to any reference configuration (neither spherical nor planar). The shape perturbations induced by the embedded inclusions are restricted within distances of the order of the inclusion size. Thus, inclusions do not interfere with global vesicle properties, such as budding transitions. The local character of the inclusion perturbation announces a fast distance decay of the membrane mediated elastic force between different proteins.
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.
Stabilization of Pores in Lipid Bilayers by Anisotropic Inclusions
The Journal of Physical Chemistry B, 2003
Pores in lipid bilayers are usually not stable; they shrink because of the highly unfavorable line tension of the pore rim. Even in the presence of charged lipids or certain additives such as detergents or isotropic membrane inclusions, membrane pores are generally not expected to be energetically stabilized. We present a theoretical model that predicts the existence of stable pores in a lipid membrane, induced by the presence of anisotropic inclusions. Our model is based on a phenomenological free energy expression that involves three contributions: the energy associated with the line tension of the pore in the absence of inclusions, the electrostatic energy of the pore for charged membranes, and the interaction energy between the inclusions and the host membrane. We show that the optimal pore size is governed by the shape of the anisotropic inclusions: saddle-like inclusions favor small pores, whereas more wedgelike inclusions give rise to larger pore sizes. We discuss possible applications of our model and use it to explain the observed dependency of the pore radius in the membrane of red blood cell ghosts on the ionic strength of the surrounding solution.
The European Physical Journal B, 1999
We study the collective behavior of inclusions inducing local anisotropic curvatures in a flexible fluid membrane. The N -body interaction energy for general anisotropic inclusions is calculated explicitly, including multi-body interactions. Long-range attractive interactions between inclusions are found to be sufficiently strong to induce aggregation. Monte Carlo simulations show a transition from compact clusters to aggregation on lines or circles. These results might be relevant to proteins in biological membranes or colloidal particles bound to surfactant membranes.
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.
Theory of self-assembly of lipid bilayers and vesicles
Biochimica et Biophysica Acta (BBA) - Biomembranes, 1977
A simple theory is developed that explains the formation of bilayers and vesicles and accounts quantitatively for many of their physical properties: Properties including vesicle size distributions and bilayer elasticity emerge from a unified theory that links thermodynamics, interaction free energy, and molecular geometry. The theory may be applied to the analysis of more complicated membrane structures and mechanisms.
Physical Review E, 2020
The influence of electrostatic conditions (salt concentration of the solution and vesicle surface charge density) on the size distribution of self-assembled giant unilamellar vesicles (GUVs) is considered. The membranes of GUVs are synthesized by a mixture of dioleoylphosphatidylglycerol and dioleoylphosphatidylcholine in a physiological buffer using the natural swelling method. The experimental results are presented in the form of a set of histograms. The log-normal distribution is used for statistical treatment of results. It is obtained that the decrease of salt concentration and the increase of vesicle surface charge density of the membranes increase the average size of the GUV population. To explain the experimental results, a theory using the Helmholtz free energy of the system describing the GUV vesiculation is developed. The size distribution histograms and average size of GUVs under various conditions are fitted with the proposed theory. It is shown that the variation of the bending modulus due to changing of electrostatic parameters of the system is the main factor causing a change in the average size of GUVs.
Effective line tension and contact angles between membrane domains in biphasic vesicles
The European Physical Journal E, 2011
Inhomogeneities in membranes give rise to localized interactions at the interface between domains in two-component vesicles. The corresponding energy is expressed as a line tension between the two phases. In this paper we study the implications of the thickness mismatch between domains which has been experimentally reported to be of order 20-30% and the conditions under which the induced line tension can destabilize the domains in inhomogeneous vesicles. For asymmetric lipidic membranes we prove an increase of the line tension and the existence of a contact angle. Adsorption of impurities is also examined, our scope being the extension of the Canham-Helfrich model to describe elastic deformations and chemical interactions arising at microscopic scales. This mismatch effect may have important consequences for the stability of very small domains.