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The intermediate monoclinic phase of phosphatidylcholines
Luna Lab Publications
  • Elizabeth J. Luna, University of Massachusetts Medical School
  • Harden M. McConnell, Stanford University
UMMS Affiliation
Department of Cell and Developmental Biology
Document Type
Medical Subject Headings
Electron Spin Resonance Spectroscopy; *Membranes, Artificial; Microscopy, Electron; Myristates; Palmitic Acids; *Phosphatidylcholines; Spin Labels; Temperature
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 using detergent dialysis and are thought to consist of one, two, or some small number of concentric bilayer shells. These observations are in excellent accord with the recent, prior studies of Janiak, M.J., Small, D.M. and Shirley, G.G., ((1976) Biochemistry 15, 4575--4580), who found monoclinic symmetry (Pbeta' structure) in multilamellar liposomes of these phospholipids only when the sample temperature was intermediate between the main, chain melting transition temperature, and the pretransition temperature. The significance of these results for relating freeze-fracture electron microphotographis to phase diagrams derived from spin label or calorimetric data is discussed briefly. 2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO) partitioning data show distinct differences between liposomal preparations of these lipids, and other preparations having fewer bilayers per vesicular structure, with respect to the position, width, and hysteresis of the pretransition.

Citation: Biochim Biophys Acta. 1977 May 2;466(3):381-92. DOI 10.1016/0005-2736(77)90331-5.

At the time of publication, Elizabeth Luna was not yet affiliated with the University of Massachusetts Medical School.

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Link to Article in PubMed
PubMed ID
Citation Information
Elizabeth J. Luna and Harden M. McConnell. "The intermediate monoclinic phase of phosphatidylcholines" Vol. 466 Iss. 3 (1977) ISSN: 0006-3002 (Linking)
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