Article Information

• PDF (680 kb)

PubMed

• Articles by E. Farge

Related Articles

• Spontaneous-Curvature Theory of Clathrin-Coated Membranes

  Spontaneous-Curvature Theory of Clathrin-Coated Membranes Biophysical Journal, Volume 74, Issue 6, 1 June 1998, Pages 2862-2875 Robert J. Mashl and Robijn F. Bruinsma Abstract Clathrin-coated membranes are precursors to coated vesicles in the receptor-mediated endocytic pathway. In this paper we present a physical model for the first steps of the transformation of a clathrin-coated membrane into a coated vesicle. The theory is based on in vitro cytoplasmic acidification experiments of Heuser (. . 108:401–411) that suggest the transformation proceeds by changes in the chemical environment of the clathrin lattice, wherein the chemical environment determines the amount of intrinsic, or spontaneous, curvature of the network. We show that a necessary step of the transformation, formation of free pentagons in the clathin network, can proceed via dislocation unbinding, driven by changes in the spontaneous curvature. Dislocation unbinding is shown to favor formation of coated vesicles that are quite small compared to those predicted by the current continuum theories, which do not include the topology of the clathrin lattice. Abstract | Full Text | PDF (595 kb)

• Dynamic Excitations in Membranes Induced by Optical Tweezers...

  Dynamic Excitations in Membranes Induced by Optical Tweezers Biophysical Journal, Volume 75, Issue 1, 1 July 1998, Pages 294-320 Roy Bar-Ziv, Elisha Moses and Philip Nelson Abstract We present the phenomenology of transformations in lipid bilayers that are excited by laser tweezers. A variety of dynamic instabilities and shape transformations are observed, including the pearling instability, expulsion of vesicles, and more exotic ones, such as the formation of passages. Our physical picture of the laser-membrane interaction is based on the generation of tension in the bilayer and loss of surface area. Although tension is the origin of the pearling instability, it does not suffice to explain expulsion of vesicles, where we observe opening of giant pores and creeping motion of bilayers. We present a quantitative theoretical framework to understand most of the observed phenomenology. The main hypothesis is that lipid is pulled into the optical trap by the familiar dielectric effect, is disrupted, and finally is repackaged into an optically unresolvable suspension of colloidal particles. This suspension, in turn, can produce osmotic pressure and depletion forces, driving the observed transformations. Abstract | Full Text | PDF (1497 kb)

• Membrane Remodeling from N-BAR Domain Interactions: Insights...

  Membrane Remodeling from N-BAR Domain Interactions: Insights from Multi-Scale Simulation Biophysical Journal, Volume 92, Issue 10, 15 May 2007, Pages 3595-3602 Gary S. Ayton, Philip D. Blood and Gregory A. Voth Abstract Liposome remodeling processes (e.g., vesiculation and tubulation) due to N-BAR domain interactions with the lipid bilayer are explored with a multi-scale simulation approach. Results from atomistic-level molecular dynamics simulations of membrane binding to the concave face of N-BAR domains are used along with discretized mesoscopic field-theoretic simulations to examine how the spontaneous curvature fields generated by N-BAR domains result in membrane remodeling. It is found that tubulation can be generated by anisotropic N-BAR spontaneous curvature fields, whereas vesiculation is only observed with isotropic N-BAR spontaneous curvature fields at high density. The results of the multi-scale simulations provide insight into recent experimental observations. Abstract | Full Text | PDF (643 kb)

• …more

Abstract

Endocytosis vesiculation consists of local membrane invaginations, continuously generated on the plasma membrane surface of living cells. This vesiculation process was found to be activated in vivo by the generation of a transmembrane surface area asymmetry in the plasma membrane bilayer, after enhancement of transbilayer phospholipid translocation. The observed enhancement was shown to be in good quantitative agreement with a theoretical model of elastic equilibrium describing stabilization of 100-nm vesicles in response to phospholipid redistribution. Very rapid dynamic vesiculation and direct re-fusion of the vesicles, both dependent on the phospholipid translocation activity, were found on a time scale of seconds. Both vesiculation and re-fusion were shown to result in a steady-state population of internal vesicles at long time points. The plasma membrane appears to be a dynamic structure, oscillating between two distinct curvature states, the 10 microns-1 "vesicle" and the 0.1 micron-1 "plasma membrane" curvature states. This dynamic behavior is discussed in terms of an elastic control of the membranes curvature state by the phospholipid translocation activity.