title: Dynamics of membrane penetration of the fluorescent 7-nitrobenz-2-oxa-1,3-diazol-4-yl (NBD) group attached to an acyl chain of phosphatidylcholine.
abstract: Location and dynamic reorientation of the fluorophore 7-nitrobenz-2-oxa-1,3-diazol-4-yl (NBD) covalently attached to a short (C6) or a long (C12) sn2 acyl chain of a phosphatidylcholine molecule was investigated by fluorescence and solid-state NMR spectroscopy. 2H NMR lipid chain order parameters indicate a perturbation of the phospholipid packing density in the presence of NBD. Specifically, a decrease of molecular order was found for acyl chain segments of the lower, more hydrophobic region. Molecular collision probabilities determined by 1H magic angle spinning nuclear Overhauser enhancement spectroscopy indicate a highly dynamic reorientation of the probe in the membrane due to thermal fluctuations. A broad distribution of the fluorophore in the lipid bilayer is observed with a preferential location in the upper acyl chain/glycerol region. The distribution of the NBD group in the membrane is quite similar for both the long- and the short-chain analog. However, a slight preference of the NBD group for the lipid-water interface is found for C12-NBD-PC in comparison with C6-NBD-PC. Indeed, as shown by dithionite fluorescence assay, the long-chain analog reacts more favorably with dithionite, indicating a better accessibility of the probe by dithionite present in the aqueous phase. Forces determining the location of the fluorophore in the lipid water interface are discussed.
authors.affiliation: Institute of Medical Physics and Biophysics, University of Leipzig, D-04103 Leipzig, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Huster
authors.forename: P
authors.initials: P
authors.lastname: Müller
authors.forename: K
authors.initials: K
authors.lastname: Arnold
authors.forename: A
authors.initials: A
authors.lastname: Herrmann
mesh_terms: D009327:4-Chloro-7-nitrobenzofurazan / Q000031:analogs & derivatives* / Q000737:chemistry*; D001665:Binding Sites; D055592:Biophysical Phenomena; D001703:Biophysics; D005456:Fluorescent Dyes / Q000737:chemistry*; D066298:In Vitro Techniques; D009682:Magnetic Resonance Spectroscopy; D008563:Membrane Lipids / Q000737:chemistry*; D010713:Phosphatidylcholines / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D014867:Water / Q000737:chemistry
chemical_list: D005456:Fluorescent Dyes; D008563:Membrane Lipids; D010713:Phosphatidylcholines; D014867:Water; C067460:1-oleoyl-2-(12-((7-nitro-2,1,3-benzoxadiazol-4-yl)amino)dodecanoyl)phosphatidylcholine; C044745:1-palmitoyl-2-(6-(N-(7-nitrobenz)-2-oxa-1,3-diazol-4-yl)aminocaproyl)phosphatidylcholine; D009327:4-Chloro-7-nitrobenzofurazan