Curvature-Driven Migration of Colloids on Tense Lipid Bilayers

Scientific reports, 2016

The interplay of membrane proteins is vital for many biological processes, such as cellular transport, cell division, and signal transduction between nerve cells. Theoretical considerations have led to the idea that the membrane itself mediates protein self-organization in these processes through minimization of membrane curvature energy. Here, we present a combined experimental and numerical study in which we quantify these interactions directly for the first time. In our experimental model system we control the deformation of a lipid membrane by adhering colloidal particles. Using confocal microscopy, we establish that these membrane deformations cause an attractive interaction force leading to reversible binding. The attraction extends over 2.5 times the particle diameter and has a strength of three times the thermal energy (-3.3 kBT). Coarse-grained Monte-Carlo simulations of the system are in excellent agreement with the experimental results and prove that the measured interact...

Soft Matter, 2017

Physical interactions on membranes with anisotropic shapes can be exploited by cells to drive macromolecules to preferred regions of cellular or intracellular membranes.

European Biophysics Journal, 1999

We present measurements of the effective spontaneous curvature of fluid lipid bilayers as a function of trans-bilayer asymmetry. Experiments are performed on micrometer-scale vesicles in sugar solutions with varying species across the membrane. There are two effects leading to a preferred curvature of such a vesicle. The spontaneous curvatures of the two monolayers as well as their area difference combine into an effective spontaneous curvature of the membrane. Our technique for measuring this parameter allows us to use vesicle morphology as a probe for general membrane-solute interactions affecting elasticity.

Soft Matter, 2021

Curvature-driven feedback limits the extent of aggregation of the curvature-inducing proteins in the membrane.

Proceedings of the National Academy of Sciences, 2014

The lateral mobility of proteins within cell membranes is usually thought to be dependent on their size and modulated by local heterogeneities of the membrane. Experiments using single-particle tracking on reconstituted membranes demonstrate that protein diffusion is significantly influenced by the interplay of membrane curvature, membrane tension, and protein shape. We find that the curvature-coupled voltage-gated potassium channel (KvAP) undergoes a significant increase in protein mobility under tension, whereas the mobility of the curvature-neutral water channel aquaporin 0 (AQP0) is insensitive to it. Such observations are well explained in terms of an effective friction coefficient of the protein induced by the local membrane deformation.

Physical Review E, 1994

Budding and vesiculation are prominent shape transformations of fluid lipid-bilayer vesicles. We discuss these transitions within the context of a curvature model which contains two types of bending energy. In addition to the usual local curvature elasticity~, we include the effect of a relative areal stretching of the two monolayers. This area-difFerence elasticity leads to an effective nonlocal curvature energy characterized by another parameter K We argue that the two contributions to the curvature energy are typically comparable in magnitude.

Biophysical Journal, 2019

Latest experiments have shown that adherent cells can migrate according to cell-scale curvature variations via a process called curvotaxis. Despite identification of key cellular factors, a clear understanding of the mechanism is lacking. We employ a mechanical model featuring a detailed description of the cytoskeleton filament networks, the viscous cytosol, the cell adhesion dynamics and the nucleus. We simulate cell adhesion and migration on sinusoidal substrates. We show that cell adhesion on three-dimensional curvatures induces a gradient of pressure inside the cell that triggers the internal motion of the nucleus. We propose that the resulting out-of-equilibrium position of the nucleus alters cell migration directionality, leading to cell motility toward concave regions of the substrate, resulting in lower potential energy states. Altogether, we propose a simple mechanism explaining how intracellular mechanics enable the cells to react to substratum curvature, induce a deterministic cell polarization and breakdown cells basic persistent random walk, which correlates with latest experimental evidences.

Physical Review Letters, 1998

We explore the interplay of membrane curvature and nonspecific binding due to excluded-volume effects among colloidal particles inside lipid bilayer vesicles. We trapped submicron spheres of two different sizes inside a pear-shaped, multilamellar vesicle and found the larger spheres to be pinned to the vesicle's surface and pushed in the direction of increasing curvature. A simple model predicts that hard spheres can induce shape changes in flexible vesicles. The results demonstrate an important relationship between the shape of a vesicle or pore and the arrangement of particles within it.

Physical Review A, 1991

According to a model introduced by Helfrich [Z. Naturforsch. 28c, 693 {1973)],the shape of a closed lipid vesicle is determined by minimization of the total bending energy at fixed surface area and enclosed volume. We show that, in the appropriate regime, this model predicts both budding (the eruption of a satellite connected to the parent volume via a neck) and vesiculation (the special case when the neck radius goes to zero). Vesiculation occurs when the minimum is located at a boundary in the space of configurations. Successive vesiculations produce multiplets, in which the minimum-energy configuration consists of several bodies coexisting through infinitesimal necks. We study the sequence of shapes and shape transitions followed by a spherical vesicle of radius Rz, large on the scale Ro set by the spontaneous curvature, as its area A increases at constant volume V =4+R&/3. Such a vesicle periodically sheds excess area into a set of smaller spheres with radii comparable to Ro. We map out this (shape) phase diagram at large volume. In this region the phase diagram is dominated by multiplets and reAects the details of the shedding process. The overall effect of successive vesiculations is to reduce the energy from a quantity of order R v down to zero or near zero when the area reaches 3 V/Ro, however, the decrease is not uniform and the energy E (A, V) is not convex. 'I'he physical origin of the spontaneous curvature under given experimental conditions is a matter of present interest and even controversy. Nonzero values of co may arise, for example, from chemical asymmetry between the interior and exterior of the membrane' or from different areas of the two leaves of the bilayer (the bilayer-couple mechanism). " Whether these mechanisms suffice to explain observed shapes is unclear. In any case, we must keep in mind that the "constant" co may depend on both microscopic (chemical) and macroscopic (geometrical) variables. In what follows, we shall study a model system in which co is taken to be constant. If under laboratory conditions co turns out to depend on the surface area A 43 6843

European Biophysics Journal, 2008

We analyze the motion of colloids propelled by a comet-like tail of polymerizing actin filaments. The curvature of the particle trajectories deviates strongly from a Gaussian distribution, implying that the underlying microscopic processes are fluctuating in a non-independent manner. Trajectories for beads of different size all showed the same non-Gaussian behavior, while the mean curvature decreased weakly with size. A stochastic simulation that includes nucleation, force-dependent dissociation, growth, and capping of filaments, shows that the non-Gaussian curvature distribution can be explained by a positive feedback mechanism in which attached chains under higher tension are more likely to snap.