A combined x-ray and neutron diffraction study of selectively deuterated melittin in phospholipid bilayers

Effect of pH

J. P. Bradshaw, C. E. Dempsey, A. Watts

Research output: Contribution to journalArticle

Abstract

In order to study consequences of protonation of the N-terminus upon the interaction of the bee venom melittin with phospholipid bilayers, analogues of melittin, some of which were specifically deuterated at either Ala-12 or 15, were synthesized. These peptides were incorported into bilayers of 1,2-dioleoyl-snglycero-3-phosphocholine at either low pH (N-terminus protonated) or high pH (N-terminus unprotonated). X-ray and neutron diffraction data were collected from ordered stacks of these bilayers and from peptide-free controls. Phase determination was carried out using the swelling series (X-ray) and isomorphous derivative (neutron) methods. The water distribution between adjacent bilayers in the stacks may be described by a pair of Guassians whose position and width change with the protonation state of the melittin. Difference Fourier profiles reveal that the melittin largely incorporates into the phospholipid bilayers. Changes in the water, melittin and deuterium label distributions fit a model in which the melittin lies both at the surface and close to the centre of the bllayer, the distribution of peptide between these locations being pH-dependent, with a larger population of surface melittin when the N-terminus is unprotonated.

Original languageEnglish
Pages (from-to)79-86
Number of pages8
JournalMolecular Membrane Biology
Volume11
Issue number2
DOIs
Publication statusPublished - 1994

Keywords

  • Melittin
  • Neutron diffraction
  • Phospholipid bilayer
  • X-ray diffraction

ASJC Scopus subject areas

  • Molecular Biology
  • Cell Biology

Cite this

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title = "A combined x-ray and neutron diffraction study of selectively deuterated melittin in phospholipid bilayers: Effect of pH",
abstract = "In order to study consequences of protonation of the N-terminus upon the interaction of the bee venom melittin with phospholipid bilayers, analogues of melittin, some of which were specifically deuterated at either Ala-12 or 15, were synthesized. These peptides were incorported into bilayers of 1,2-dioleoyl-snglycero-3-phosphocholine at either low pH (N-terminus protonated) or high pH (N-terminus unprotonated). X-ray and neutron diffraction data were collected from ordered stacks of these bilayers and from peptide-free controls. Phase determination was carried out using the swelling series (X-ray) and isomorphous derivative (neutron) methods. The water distribution between adjacent bilayers in the stacks may be described by a pair of Guassians whose position and width change with the protonation state of the melittin. Difference Fourier profiles reveal that the melittin largely incorporates into the phospholipid bilayers. Changes in the water, melittin and deuterium label distributions fit a model in which the melittin lies both at the surface and close to the centre of the bllayer, the distribution of peptide between these locations being pH-dependent, with a larger population of surface melittin when the N-terminus is unprotonated.",
keywords = "Melittin, Neutron diffraction, Phospholipid bilayer, X-ray diffraction",
author = "Bradshaw, {J. P.} and Dempsey, {C. E.} and A. Watts",
year = "1994",
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pages = "79--86",
journal = "Molecular Membrane Biology",
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AU - Bradshaw, J. P.

AU - Dempsey, C. E.

AU - Watts, A.

PY - 1994

Y1 - 1994

N2 - In order to study consequences of protonation of the N-terminus upon the interaction of the bee venom melittin with phospholipid bilayers, analogues of melittin, some of which were specifically deuterated at either Ala-12 or 15, were synthesized. These peptides were incorported into bilayers of 1,2-dioleoyl-snglycero-3-phosphocholine at either low pH (N-terminus protonated) or high pH (N-terminus unprotonated). X-ray and neutron diffraction data were collected from ordered stacks of these bilayers and from peptide-free controls. Phase determination was carried out using the swelling series (X-ray) and isomorphous derivative (neutron) methods. The water distribution between adjacent bilayers in the stacks may be described by a pair of Guassians whose position and width change with the protonation state of the melittin. Difference Fourier profiles reveal that the melittin largely incorporates into the phospholipid bilayers. Changes in the water, melittin and deuterium label distributions fit a model in which the melittin lies both at the surface and close to the centre of the bllayer, the distribution of peptide between these locations being pH-dependent, with a larger population of surface melittin when the N-terminus is unprotonated.

AB - In order to study consequences of protonation of the N-terminus upon the interaction of the bee venom melittin with phospholipid bilayers, analogues of melittin, some of which were specifically deuterated at either Ala-12 or 15, were synthesized. These peptides were incorported into bilayers of 1,2-dioleoyl-snglycero-3-phosphocholine at either low pH (N-terminus protonated) or high pH (N-terminus unprotonated). X-ray and neutron diffraction data were collected from ordered stacks of these bilayers and from peptide-free controls. Phase determination was carried out using the swelling series (X-ray) and isomorphous derivative (neutron) methods. The water distribution between adjacent bilayers in the stacks may be described by a pair of Guassians whose position and width change with the protonation state of the melittin. Difference Fourier profiles reveal that the melittin largely incorporates into the phospholipid bilayers. Changes in the water, melittin and deuterium label distributions fit a model in which the melittin lies both at the surface and close to the centre of the bllayer, the distribution of peptide between these locations being pH-dependent, with a larger population of surface melittin when the N-terminus is unprotonated.

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