Hard Spheres in Vesicles: Curvature-Induced Forces and Particle-Induced Curvature (original) (raw)
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Wrapping of a spherical colloidal particle, located inside and outside a lipid vesicle, by the membrane which forms the wall of the vesicle is investigated. The process is studied for vesicles of different geometries: prolate, oblate, stomatocytes. We focus on the bending energy change and shape transformations induced by binding the membrane to the spherical particles. The ground-state shapes of vesicles are calculated within the framework of a Helfrich curvature energy functional.
Shape Deformation of Vesicles Containing Hard Spheres
Proceedings of Computational Science Workshop 2014 (CSW2014), 2015
Vesicles containing charged colloids show peculiar shape deformation under certain conditions. However, its physical mechanism is not clear. We have performed Monte Carlo simulation for a model of closed triangulated membrane and encapsulated hard spheres. We analyzed vesicular shapes and encapsulated hard spheres by using diffusion coefficient, change of area difference and volume, and the radial distribution of hard spheres from the membrane. The discussion of our results can be used as the foundation for understanding of the complex behavior of vesicles containing colloids.
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Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2003
In this paper I propose a continuum model to describe the dynamics of a lipid membrane and a bead that are interacting. The bead could represent either a colloidal particle or a peripheral protein. The evolution is governed by a system of nonlinear di¬erential equations. Focusing attention on the case where the membrane is xed gives information about the forces exerted on the bead by the membrane. It turns out that the curvature and the curvature gradient of the membrane play a prominent role in the evolution of the bead, as illustrated by suitable examples.
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EPL (Europhysics Letters), 1998
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Three-Body Interactions of Lipid Membrane-Deforming Colloidal Spheres
arXiv (Cornell University), 2023
Many cell functions require a concerted effort from multiple membrane proteins, for example, for signaling, cell division, and endocytosis. One contribution to their successful self-organization stems from the membrane deformations that these proteins induce. While the pairwise interaction potential of two membrane deforming spheres has recently been measured, membrane-deformation induced interactions have been predicted to be non-additive and hence their collective behavior cannot be deduced from this measurement. We here employ a colloidal model system consisting of adhesive spheres and giant unilamellar vesicles to test these predictions by measuring the interaction potential of the simplest case of three membrane-deforming spherical particles. We quantify their interactions and arrangements and for the first time experimentally confirm and quantify the non-additive nature of membrane-deformation induced interactions. We furthermore conclude that there exist two favorable configurations on the membrane: (1) a linear, and (2) a triangular arrangement of the three spheres. Using Monte Carlo simulation we corroborate the experimentally observed energy minima and identify a lowering of the membrane deformation as the cause for the observed configurations. The high symmetry of the preferred arrangements for three particles suggests that arrangements of many membrane-deforming objects might follow simple rules. SIGNIFICANCE Lipid membrane deforming objects, such as proteins, can interact through the membrane curvature they impose. These interactions have been suggested to be non-additive, that is, one cannot extrapolate from the interaction between two objects the interactions between three or more such objects. In addition, the governing equations are so involved that there are only few and contradicting theoretical and numerical predictions. In this manuscript, this interaction is quantified for the first time for three spherically symmetric deformations on spherical membranes through a series of experiments and Monte Carlo simulations. We find two preferred states: a linear arrangement for smaller distances and an equilateral triangle for slightly larger interparticle distances.
Shape Transformations of Vesicles Induced by Their Adhesion to Flat Surfaces
ACS omega, 2020
The shape transformations of lipid vesicles induced by the adhesion to a flat surface is investigated. We perform the calculations within the framework of the Helfrich spontaneous curvature model. The calculations were performed for a few values of the reduced volume and the spontaneous curvature. The range of stability for different shapes (oblate, prolate, and stomatocyte) of adhered vesicles is determined. New physical phenomena such as budding induced by the adhesion of vesicles are reported.
Faraday Discuss., 2013
Recent experimental studies on supported lipid bilayers and giant vesicles have shown that uni-lamellar membrane systems can undergo spontaneous tubulation, i.e., can form membrane tubules or nanotubes without the application of external forces. In the case of supported lipid bilayers, the tube formation was induced by the adsorption of antimicrobial peptides. In the case of giant vesicles, spontaneous tubulation was observed after the polymer solution inside the vesicles underwent phase separation into two aqueous phases. Here, these processes are studied theoretically and shown to be driven by membrane tension generated by spontaneous curvature. The latter curvature is estimated for different types of adsorbing particles, such as ions, small molecules, and macromolecules, that differ in their size and in their adsorption kinetics. When the two sides of the membranes are exposed to two different concentrations of these particles, the membranes will acquire a spontaneous (or preferred) curvature. Particularly large spontaneous curvatures are induced by the adsorption of amphipathic peptides and BAR domain proteins. Another mechanism that induces spontaneous curvature is provided by different depletion layers in front of the two sides of the membranes. Irrespective of its molecular origin, a spontaneous curvature is predicted to generate a tension in weakly curved membranes, a 'spontaneous' tension that can vary over several orders of magnitudes and can be as high as 1 mJ m À2. The concept of spontaneous tension is first used to explain the spontaneous tubulation of supported lipid bilayers when exposed to adsorbing particles. This tubulation process is energetically preferred when the spontaneous tension exceeds the adhesive strength of the underlying solid support. Furthermore, in the case of giant vesicles, the spontaneous tension can balance the osmotic pressure difference between the interior and exterior aqueous compartment. The vesicles are then able to form stable cylindrical nanotubes that protrude into the vesicle interior as observed recently for membranes in contact with two aqueous polymer phases. In these latter systems, the vesicle membranes are governed by two spontaneous tensions that can be directly measured since they are intimately related to the effective and intrinsic contact angles.
Curvature inducing macroion condensation driven shape changes of fluid vesicles
The Journal of chemical physics, 2015
We study the effect of curvature inducing macroion condensation on the shapes of charged deformable fluid interfaces using dynamically triangulated Monte Carlo simulations. In the weak electrostatic coupling regime, surface charges are weakly screened and the conformations of a vesicle, with fixed spherical topology, depend on the charge-charge interaction on the surface. While in the strong coupling regime, condensation driven curvature induction plays a dominant role in determining the conformations of these surfaces. Condensation itself is observed to be dependent on the induced curvature, with larger induced curvatures favoring increased condensation. We show that both curvature generation and curvature sensing, induced by the interplay of electrostatics and curvature energy, contribute to determination of the vesicle configurations.