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

Biophys J. 2001 Feb;80(2):822-31. doi: 10.1016/S0006-3495(01)76061-4.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 4-Chloro-7-nitrobenzofurazan / analogs & derivatives*
  • 4-Chloro-7-nitrobenzofurazan / chemistry*
  • Binding Sites
  • Biophysical Phenomena
  • Biophysics
  • Fluorescent Dyes / chemistry*
  • In Vitro Techniques
  • Magnetic Resonance Spectroscopy
  • Membrane Lipids / chemistry*
  • Phosphatidylcholines / chemistry*
  • Spectrometry, Fluorescence
  • Water / chemistry

Substances

  • Fluorescent Dyes
  • Membrane Lipids
  • Phosphatidylcholines
  • Water
  • 1-oleoyl-2-(12-((7-nitro-2,1,3-benzoxadiazol-4-yl)amino)dodecanoyl)phosphatidylcholine
  • 1-palmitoyl-2-(6-(N-(7-nitrobenz)-2-oxa-1,3-diazol-4-yl)aminocaproyl)phosphatidylcholine
  • 4-Chloro-7-nitrobenzofurazan