Beyond Saffman-Delbruck approximation: a new regime for 2D diffusion of α-hemolysin complexes in supported lipid bilayer

Eur Phys J E Soft Matter. 2012 Nov;35(11):118. doi: 10.1140/epje/i2012-12118-6. Epub 2012 Nov 21.

Abstract

Cell mechanisms are actively modulated by membrane dynamics. We studied the dynamics of a first-stage biomimetic system by Fluorescence Recovery After Patterned Photobleaching. Using this simple biomimetic system, constituted by α -hemolysin from Staphylococcus aureus inserted as single heptameric pore or complexes of pores in a glass-supported DMPC bilayer, we observed true diffusion behavior, with no immobile fraction. We find two situations: i) when incubation is shorter than 15 hours, the protein inserts as a heptameric pore and diffuses roughly three times more slowly than its host lipid bilayer; ii) incubation longer than 15 hours leads to the formation of larger complexes which diffuse more slowly. Our results indicate that, while the Saffman-Delbruck model adequately describes the diffusion coefficient D for small radii, D of the objects decreases as 1/R(2) for the size range explored in this study. Additionally, in the presence of inserted proteins, the gel-to-fluid transition of the supported bilayer as well as a temperature shift in the gel-to-fluid transition are observed.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Toxins / chemistry*
  • Bacterial Toxins / metabolism
  • Diffusion
  • Dimyristoylphosphatidylcholine / chemistry
  • Dimyristoylphosphatidylcholine / metabolism
  • Hemolysin Proteins / chemistry*
  • Hemolysin Proteins / metabolism
  • Lipid Bilayers / chemistry*
  • Lipid Bilayers / metabolism
  • Temperature

Substances

  • Bacterial Toxins
  • Hemolysin Proteins
  • Lipid Bilayers
  • staphylococcal alpha-toxin
  • Dimyristoylphosphatidylcholine