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Publication Thermotropic lipid clustering in tetrahymena membranes JournalArticle (Originalarbeit in einer wissenschaftlichen Zeitschrift) ID 153139 Author(s) Wunderlich, F; Ronai, A; Speth, V; Seelig, J; Blume, A Author(s) at UniBasel Seelig, Joachim; Year 1975 Title Thermotropic lipid clustering in tetrahymena membranes Journal Biochemistry Volume 14 Number 17 Pages / Article-Number 3730-5 Keywords Animals; Cell Membrane/analysis/enzymology/*ultrastructure; Electron Spin Resonance Spectroscopy; Freeze Etching; Glucose-6-Phosphatase/analysis; Lipids/*analysis; Magnetic Resonance Spectroscopy; Microscopy; Electron; Molecular Conformation; Tetrahymena pyriformis/analysis/enzymology/*ultrastructure The effect of temperature on the core structure of endoplasmic reticulum membranes has been visualized directly in cells of the poikilothermic eukaryote Tetrahymena pyriformis by freeze-etch electron microscopy. Moreover, the effect of temperature on the smooth microsomal membrane vesicles isolated from these cells, as well as on the extracted membrane lipids, has been examined by fluorescence probing, electron spin resonance, proton nuclear magnetic resonance, and calorimetry. Freeze-etch electron microscopy of T. pyriformis cells, equilibrated at different temperatures between 28 and 5 degrees, reveals the emergence of smooth areas on the fracture faces of endoplasmic reticulum membranes at temperatures below similar to 17 degrees. In this temperature range, we also find discontinuities in the glucose 6-phosphatase activity, in the fluorescence intensity of 8-anilino-1-naphthalensulfonate, in the partition of 4-doxyldecane, and in the separation of the outer hyperfine extrema of 5-doxylstearic acid in the microsomal membranes. These membranes apparently contain at least two lipid environments of different fluidity as indicated by the 12doxylstearic acid spin-label. Proton nuclear magnetic resonance of the extracted membrane lipids indicates an abrupt change of the fatty acid chain mobilities at temperatures below similar to 17 degrees. This, however, is not due to a true thermal liquid crystalline in equilibrium crystalline phase transition. Calorimetric measurements also support this conclusion. The thermotropic alterations observed within the membranes are interpreted to be due primarily to a clustering of "rigid" liquid crystalline lipid environments which exclude membrane-intercalating proteins. Publisher American Chemical Society ISSN/ISBN 0006-2960 edoc-URL http://edoc.unibas.ch/dok/A5257558 Full Text on edoc No Digital Object Identifier DOI 10.1021/bi00688a002 PubMed ID http://www.ncbi.nlm.nih.gov/pubmed/169883 ISI-Number WOS:A1975AN14000002 Document type (ISI) Article