Anomalous phase behavior of long chain saturated lecithin bilayers.
X-ray scattering has been performed on fully hydrated unoriented multilamellar vesicles of lecithins with even chain lengths n from 16 to 24 as a function of temperature in chain ordered phases. The longer chain lengths, n > or = 20, show anomalous behavior compared to the shorter chain lengths, n < 20. This report concentrates on n = 24. Although the history and time dependence shows that equilibrium was not always achieved, it appears that there is a second gel-like phase G2 below 40 degrees C. The G2 phase has a small tilt angle and opposite hexagonal symmetry breaking from the usual G1 gel phase. Also, as T is raised above 45 degrees C, the wide-angle data suggest the appearance of a phase with hexagonal chain packing and small chain tilt angle.
Sun
W J
WJ
Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
Tristram-Nagle
S
S
Suter
R M
RM
Nagle
J F
JF
D008051:Lipid Bilayers / Q000737:chemistry*; D010713:Phosphatidylcholines / Q000737:chemistry*; D012542:Scattering, Radiation; D013696:Temperature
D008051:Lipid Bilayers; D010713:Phosphatidylcholines