Lipid structural order parameters (reciprocal of fluidity) in biomembranes derived from steady-state fluorescence polarization measurements |
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Authors: | WJ Van Blitterswijk RP Van Hoeven BW Van Der Meer |
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Institution: | 1. Division of Cell Biology, Antoni Van Leeuwenhoek-Huis, The Netherlands aCancer Institute, 121 Plesmanlaan, 1066 CX Amsterdam, The Netherlands;2. Physiological Laboratory, University of Leiden, 62 Wassenaarseweg, 2300 RC Leiden The Netherlands |
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Abstract: | This paper presents an interpretation of fluorescence polarization measurements in lipid membranes which are labelled with the apolar probe 1,6-diphenyl-1,3,5-hexatriene. The steady-state fluorescence anisotropy, , is resolved into a fast decaying or kinetic component, , and an infinitely slow decaying or static component, . The latter contribution, which predominates in biological membranes, is exclusively determined by the degree of molecular packing (order) in the apolar regions of the membrane; is proportional to the square of the lipid order parameter. An empirical relation between and is presented, which is in agreement with a prediction based on a theory of rotational dynamics in liquid crystals. This relation enabled us to estimate a lipid structural order parameter directly from simple steady-state fluorescence polarization measurements in a variety of isolated biological membranes. It is shown that major factors determining the order parameter in biomembranes are the temperature, the cholesterol and sphingomyelin content and (in a few systems) the membrane intrinsic proteins. |
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Keywords: | Fluidity Fluorescence polarization Order parameter Plasma membrane Membrane lipid DPH 1 6-diphenyl-1 3 5-hexatriene DMPC dimyristoyl DPPC dipalmitoyl DOPC dipalmitoyl dioleoyl-L-α-phosphatidylcholine |
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