Luna Lab Publications


The intermediate monoclinic phase of phosphatidylcholines

UMMS Affiliation

Department of Cell and Developmental Biology

Publication Date


Document Type



Electron Spin Resonance Spectroscopy; *Membranes, Artificial; Microscopy, Electron; Myristates; Palmitic Acids; *Phosphatidylcholines; Spin Labels; Temperature


Biochemistry, Biophysics, and Structural Biology | Cell and Developmental Biology


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.

DOI of Published Version



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

Journal/Book/Conference Title

Biochimica et biophysica acta


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