Comprehensive examination of mesophases formed by DMPC and DHPC mixtures.
Mixtures of long- and short-chain phospholipids, specifically 14:0 and 6:0 phosphatidylcholines (DMPC and DHPC), have been used successfully in NMR studies as magnetically alignable substrates for membrane-associated proteins. However, recent publications have shown that the phase behavior of these mixtures is much more complex than originally thought. Using polarized light microscopy and small-angle neutron scattering, phase diagrams of DMPC/DHPC mixtures at molar ratios of 2, 3.2, and 5 have been determined. Generally, at temperatures below the main-chain melting transition of DMPC (T(M) = 23 degrees C), an isotropic phase of disk-like micelles is found. At high temperatures (T > 50 degrees C), a lamellar phase consisting of either multilamellar vesicles (MLV) or extended lamellae is formed, which at low lipid concentrations (e.g., MLV) coexists with an excess of water. At intermediate temperatures and lipid concentrations, a chiral nematic phase made up of worm-like micelles was observed.
Harroun
Thad A
TA
Steacie Institute for Molecular Sciences, National Research Council, Chalk River, Ontario K0J 1J0, Canada.
Koslowsky
Martin
M
Nieh
Mu-Ping
MP
de Lannoy
Charles-François
CF
Raghunathan
V A
VA
Katsaras
John
J