title: Organization of fluorescent cholesterol analogs in lipid bilayers - lessons from cyclodextrin extraction.
abstract: To characterize the structure and dynamics of cholesterol in membranes, fluorescent analogs of the native molecule have widely been employed. The cholesterol content in membranes is in general manipulated by using water-soluble cyclodextrins. Since the interactions between cyclodextrins and fluorescent-labeled cholesterol have not been investigated in detail so far, we have compared the cyclodextrin-mediated membrane extraction of three different fluorescent cholesterol analogs (one bearing a NBD and two bearing BODIPY moieties). Extraction of these analogs was followed by measuring the Förster resonance energy transfer between a rhodamine moiety linked to phosphatidylethanolamine and the labeled cholesterol. The extraction kinetics revealed that the analogs are differently extracted from membranes. We examined the orientation of the analogs within the membrane and their influence on lipid condensation using NMR and EPR spectroscopies. Our data indicate that the extraction of fluorescent sterols from membranes is determined by several parameters, including their impact on lipid order, their hydrophobicity, their intermolecular interactions with surrounding lipids, their orientation within the bilayer, and their affinity with the exogenous acceptor.
authors.affiliation: Department of Biology, Humboldt-University Berlin, Berlin, Germany.
authors.forename: Sigrid
authors.initials: S
authors.lastname: Milles
authors.forename: Thomas
authors.initials: T
authors.lastname: Meyer
authors.forename: Holger A
authors.initials: HA
authors.lastname: Scheidt
authors.forename: Roland
authors.initials: R
authors.lastname: Schwarzer
authors.forename: Lars
authors.initials: L
authors.lastname: Thomas
authors.forename: Magdalena
authors.initials: M
authors.lastname: Marek
authors.forename: Lajos
authors.initials: L
authors.lastname: Szente
authors.forename: Robert
authors.initials: R
authors.lastname: Bittman
authors.forename: Andreas
authors.initials: A
authors.lastname: Herrmann
authors.forename: Thomas
authors.initials: T
authors.lastname: Günther Pomorski
authors.forename: Daniel
authors.initials: D
authors.lastname: Huster
authors.forename: Peter
authors.initials: P
authors.lastname: Müller
mesh_terms: D000818:Animals; D016466:CHO Cells; D002784:Cholesterol / Q000031:analogs & derivatives* / Q000378:metabolism; D006224:Cricetinae; D003505:Cyclodextrins / Q000737:chemistry* / Q000378:metabolism; D031541:Fluorescence Resonance Energy Transfer; D008051:Lipid Bilayers / Q000737:chemistry*; D008563:Membrane Lipids / Q000378:metabolism*; D010713:Phosphatidylcholines / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D013261:Sterols / Q000737:chemistry
chemical_list: D003505:Cyclodextrins; D008051:Lipid Bilayers; D008563:Membrane Lipids; D010713:Phosphatidylcholines; D013261:Sterols; D002784:Cholesterol