Structure and fluctuations of a single floating lipid bilayer

Proc Natl Acad Sci U S A. 2005 Aug 16;102(33):11639-44. doi: 10.1073/pnas.0504588102. Epub 2005 Aug 8.

Abstract

A single lipid molecular bilayer of 17 or 18 carbon chain phosphocholines, floating in water near a flat wall, is prepared in the bilayer gel phase and then heated to the fluid phase. Its structure (electron density profile) and height fluctuations are determined by using x-ray reflectivity and non-specular scattering. By fitting the off-specular signal to that calculated for a two-dimensional membrane using a Helfrich Hamiltonian, we determine the three main physical quantities that govern the bilayer height fluctuations: The wall attraction potential is unexpectedly low; the surface tension, roughly independent on chain length and temperature, is moderate (approximately 5 x 10(-4) J.m(-2)) but large enough to dominate the intermediate range of the fluctuation spectrum; and the bending modulus abruptly decreases by an order-of-magnitude from 10(-18) J to 10(-19) J at the bilayer gel-to-fluid transition.

MeSH terms

  • Electrons
  • Gels / chemistry
  • Lipid Bilayers / chemistry*
  • Lipid Bilayers / radiation effects
  • Phosphatidylcholines / chemistry
  • Phosphorylcholine / chemistry
  • Scattering, Radiation
  • Spectrum Analysis
  • Temperature
  • Water / chemistry
  • X-Rays

Substances

  • Gels
  • Lipid Bilayers
  • Phosphatidylcholines
  • Water
  • Phosphorylcholine
  • 1,2-distearoyllecithin