The phenyltetraene lysophospholipid analog PTE-ET-18-OMe as a fluorescent anisotropy probe of liquid ordered membrane domains (lipid rafts) and ceramide-rich membrane domains |
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Authors: | Omar Bakht Francisco Amat-Guerri Erwin London |
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Institution: | a Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794-5215, USA b Instituto de Quimica-Fisica “Rocasolano” (CSIC) Serrano 119, E-28006 Madrid, Spain c Instituto de Química Orgánica General (CSIC), Juan de la Cierva 3, E-28006 Madrid, Spain |
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Abstract: | The conjugated phenyltetraene PTE-ET-18-OMe (all-(E)-1-O-(15′-phenylpentadeca-8′,10′,12′,14′-tetraenyl)-2-O-methyl-rac-glycero-3-phosphocholine) is a recently developed fluorescent lysophospholipid analog of edelfosine, (Quesada et al. (2004) J. Med. Chem. 47, 5333-5335). We investigated the use of this analog as a probe of membrane structure. PTE-ET-18-OMe was found to have several properties that are favorable for fluorescence anisotropy (polarization) experiments in membranes, including low fluorescence in water and moderately strong association with lipid bilayers. PTE-ET-18-OMe has absorbance and fluorescence properties similar to those of diphenylhexatriene (DPH) probes, with about as large a difference between its fluorescence anisotropy in liquid disordered (Ld) and ordered states (gel and Lo) as observed for DPH. Also like DPH, PTE-ET-18-OMe has a moderate affinity for both gel state ordered domains and Lo state ordered domains (rafts). However, unlike fluorescent sterols or DPH (Megha and London (2004) J. Biol. Chem. 279, 9997-10004), PTE-ET-18-OMe is not displaced from ordered domains by ceramide. Also unlike DPH, PTE-ET-18-OMe shows only slow exchange between the inner and outer leaflets of membrane bilayers, and can thus be used to examine anisotropy of an individual leaflet of a lipid bilayer. Since PTE-ET-18-OMe is a zwitterionic molecule, it should not be as influenced by electrostatic interactions as are other probes that do not cross the lipid bilayer but have a net charge. We conclude that PTE-ET-18-OMe has some unique properties that should make it a useful fluorescence probe of membrane structure. |
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Keywords: | Fluorescence polarization Fluorescence anisotropy Edelfosine Lipid domain Lipid microdomain Energy transfer FRET Shingomyelin Shingolipid |
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