Cholesterol-induced modulated phase in phospholipid membranes.
We report the observation of a cholesterol-induced modulated phase (Pbeta) in dipalmitoyl phosphatidylcholine bilayers. It occurs below the main transition of the lipid at cholesterol concentrations of around 15 to 20 mol % and is distinct from the ripple (Pbeta') phase found in between the main and pretransitions at lower cholesterol concentrations. An electron density map of this phase, constructed from x-ray diffraction data from oriented multilayers, shows that the bilayers in this phase have a one-dimensional periodic height modulation with an amplitude of about 2.5 A. A partial phase diagram of the system deduced from diffraction data is in broad agreement with earlier studies.
Karmakar
Sanat
S
Raman Research Institute, Bangalore 560 080, India. sanat@rri.res.in
Raghunathan
V A
VA
D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry* / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D002784:Cholesterol / Q000737:chemistry* / Q000378:metabolism; D008051:Lipid Bilayers / Q000737:chemistry* / Q000378:metabolism; D014961:X-Ray Diffraction
D008051:Lipid Bilayers; D015060:1,2-Dipalmitoylphosphatidylcholine; D002784:Cholesterol