Department
of Physics and 
Department
of Biological Sciences,
Carnegie Mellon University , Pittsburgh, PA 15213
Cornell High
Energy Synchrotron Source, Ithaca, NY 14853
MacCHESS, Division
of Biochemistry, Molecular and Cell Biology, Ithaca, NY 14853
Ruitian Zhang
,
Stephanie Tristram-Nagle
,
Wenjun Sun
,
R. L. Headrick
,
T. C. Irving
,
Robert M. Suter
,
and John F. Nagle
Fri Oct 4 15:38:11 EDT 1996
Keywords: 
phase,
dipalmitoylphosphatidylcholine, smectic liquid crystal, X-ray line shape,
bilayer structure.
Running title: X-ray scattering of lipid bilayers
X-ray scattering data at high instrumental resolution are reported
for multilamellar vesicles of 
phase lipid bilayers of DPPC at 50 
C
under varying osmotic pressure. The data are fitted to two theories that
account for non-crystalline disorder, paracrystalline theory (PT) and modified
Caillé theory (MCT). The modified Caillé theory provides good fits to the
data, much better than the PT fits. The particularly important characteristic
of MCT is the long power law tails in the scattering. PT fits (as well
as ordinary integration with no attempt to account for the non-crystalline
disorder) increasingly underestimate this scattering intensity as the order
h increases, thereby underestimating the form factors used to obtain electron
density profiles.