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Full-Text Articles in Biochemistry, Biophysics, and Structural Biology
The Intermediate Monoclinic Phase Of Phosphatidylcholines, Elizabeth Luna, Harden Mcconnell
The Intermediate Monoclinic Phase Of Phosphatidylcholines, Elizabeth Luna, Harden Mcconnell
Elizabeth J. Luna
Two pure phospholipids, dimyristoyl phosphatidylcholine and dipalmitoyl phosphatidylcholine, have been studied using freeze-fracture electron microscopy and the partitioning of the spin label, TEMPO. It is found that the characteristic band pattern, corresponding to monoclinic symmetry in multilamellar liposomes, is observed only in freeze-fracture electron microphotographs when samples are quenched from temperatures intermediate between the chain melting transition temperature and the pretransition temperature of the membrane. Markings are also observed on fracture faces of samples quenched from below the pretransition, but these "bands" are few in number and are widely and irregularly spaced. The lipid membranes used for freeze-fracture were prepared …
Lateral Phase Separations In Binary Mixtures Of Phospholipids Having Different Charges And Different Crystalline Structures, Elizabeth Luna, Harden Mcconnell
Lateral Phase Separations In Binary Mixtures Of Phospholipids Having Different Charges And Different Crystalline Structures, Elizabeth Luna, Harden Mcconnell
Elizabeth J. Luna
Synthetic dipalmitoyl phosphatidylserine exhibits a sharp chain-melting transition temperature at 51 degrees C as judged by partitioning of the spin label 2,2,6,6-tetramethylpiperidine-1-oxyl. Phase diagrams representing lateral phase separations in binary mixtures of dipalmitoyl phosphatidylserine with dipalmitoyl phosphatidylcholine as well as with dimyristoyl phosphatidylcholine are derived from paramagnetic resonance determinations of 2,2,6,6,-tetramethylpiperidine-1-oxyl partitioning, freeze-fracture electron microscopic studies and theoretical arguments that limit the general form of acceptable phase diagrams. The reported phase diagrams are the first to describe binary mixtures in which one lipid is charged and the second lipid uncharged. These phase diagrams also are the first to include the …
Multiple Phase Equilibria In Binary Mixtures Of Phospholipids, Elizabeth Luna, Harden Mcconnell
Multiple Phase Equilibria In Binary Mixtures Of Phospholipids, Elizabeth Luna, Harden Mcconnell
Elizabeth J. Luna
Approximate phse diagrams describing lateral phase separations are given for binary mixtures of dimyristoyl phosphatidylcholine with dipalmitoyl phosphatidylcholine, distearoyl phosphatidycholine, and dipalmitoyl phosphatidylethanolamine. These diagrams are based in part on freeze-fracture electron microscopic data. These phase diagrams represent an improvement over previous studies in that both solid phses (Pbeta' and Lbeta') of the phosphatidylcholines are included. Further consideration is given to the problem of binary mixtures in which there are two Pbeta' phases that do not form a continuous range of solid solutions.