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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 …