Morphology of fast-tumbling bicelles: A small angle neutron scattering and NMR study

Paul A. Luchette, Tatiana N. Vetman, R. Scott Prosser, Robert E.W. Hancock, Mu Ping Nieh, Charles J. Glinka, Susan Krueger, John Katsaras

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138 Citations (Scopus)

Abstract

Bilayered micelles, or bicelles, which consist of a mixture of long- and short-chain phospholipids, are a popular model membrane system. Depending on composition, concentration, and temperature, bicelle mixtures may adopt an isotropic phase or form an aligned phase in magnetic fields. Well-resolved 1H NMR spectra are observed in the isotropic or so-called fast-tumbling bicelle phase, over the range of temperatures investigated (10-40°C), for molar ratios of long-chain lipid to short-chain lipid between 0.20 and 1.0. Small angle neutron scattering data of this phase are consistent with the model in which bicelles were proposed to be disk-shaped. The experimentally determined dimensions are roughly consistent with the predictions of R.R. Vold and R.S. Prosser (J. Magn. Reson. B 113 (1996)). Differential paramagnetic shifts of head group resonances of dimyristoylphosphatidylcholine (DMPC) and dihexanoylphosphatidylcholine (DHPC), induced by the addition of Eu3+, are also consistent with the bicelle model in which DHPC is believed to be primarily sequestered to bicelle rims. Selective irradiation of the DHPC aliphatic methyl resonances results in no detectable magnetization transfer to the corresponding DMPC methyl resonances (and vice versa) in bicelles, which also suggests that DHPC and DMPC are largely sequestered in the bicelle. Finally, 1H spectra of the antibacterial peptide indolicidin (ILPWKWPWWPWRR-NH2) are compared, in a DPC micellar phase and the above fast-tumbling bicellar phases for a variety of compositions. The spectra exhibit adequate resolution and improved dispersion of amide and aromatic resonances in certain bicelle mixtures.

Original languageEnglish
Pages (from-to)83-94
Number of pages12
JournalBiochimica et Biophysica Acta - Biomembranes
Volume1513
Issue number2
DOIs
Publication statusPublished or Issued - 6 Aug 2001
Externally publishedYes

Keywords

  • Bicelle
  • Indolicidin
  • Membrane peptide
  • Model membrane
  • Nuclear magnetic resonance
  • Small angle neutron scattering

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Cell Biology

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