Structure and fluctuations of a single floating lipid bilayer.
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.
Daillant
J
J
Service de Chimie Moléculaire/LIONS, Commissariat à l'Energie Atomique Saclay, Bâtiment 125, F-91191 Gif-sur-Yvette Cedex, France. daillant@dsm-mail.saclay.cea.fr
Bellet-Amalric
E
E
Braslau
A
A
Charitat
T
T
Fragneto
G
G
Graner
F
F
Mora
S
S
Rieutord
F
F
Stidder
B
B
D004583:Electrons; D005782:Gels / Q000737:chemistry; D008051:Lipid Bilayers / Q000737:chemistry* / Q000528:radiation effects; D010713:Phosphatidylcholines / Q000737:chemistry; D010767:Phosphorylcholine / Q000737:chemistry; D012542:Scattering, Radiation; D013057:Spectrum Analysis; D013696:Temperature; D014867:Water / Q000737:chemistry; D014965:X-Rays
D005782:Gels; D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D014867:Water; D010767:Phosphorylcholine; C010942:1,2-distearoyllecithin