Gas-Phase Structure of Amyloid-β (12 – 28) Peptide Investigated by Infrared Spectroscopy, Electron Capture Dissociation and Ion Mobility Mass Spectrometry

  • Thi Nga Le
  • Jean Christophe Poully
  • Frédéric Lecomte
  • Nicolas Nieuwjaer
  • Bruno Manil
  • Charles Desfrançois
  • Fabien Chirot
  • Jerome Lemoine
  • Philippe Dugourd
  • Guillaume van der Rest
  • Gilles GrégoireEmail author
Research Article


The gas-phase structures of doubly and triply protonated Amyloid-β12-28 peptides have been investigated through the combination of ion mobility (IM), electron capture dissociation (ECD) mass spectrometry, and infrared multi-photon dissociation (IRMPD) spectroscopy together with theoretical modeling. Replica-exchange molecular dynamics simulations were conducted to explore the conformational space of these protonated peptides, from which several classes of structures were found. Among the low-lying conformers, those with predicted diffusion cross-sections consistent with the ion mobility experiment were further selected and their IR spectra simulated using a hybrid quantum mechanical/semiempirical method at the ONIOM DFT/B3LYP/6-31 g(d)/AM1 level. In ECD mass spectrometry, the c/z product ion abundance (PIA) has been analyzed for the two charge states and revealed drastic differences. For the doubly protonated species, N – Cα bond cleavage occurs only on the N and C terminal parts, while a periodic distribution of PIA is clearly observed for the triply charged peptides. These PIA distributions have been rationalized by comparison with the inverse of the distances from the protonated sites to the carbonyl oxygens for the conformations suggested from IR and IM experiments. Structural assignment for the amyloid peptide is then made possible by the combination of these three experimental techniques that provide complementary information on the possible secondary structure adopted by peptides. Although globular conformations are favored for the doubly protonated peptide, incrementing the charge state leads to a conformational transition towards extended structures with 310- and α-helix motifs.

Key words

Amyloid peptide Gas phase structure ECD Ion Mobility IRMPD 



The authors thank the CLIO staff for its technical assistance, and the financial support of the CNRS TGE-FTICR program for the ECD experiments and the CNRS GDR 3335 for the IMS experiments. They acknowledge the use of the computing facility Magi cluster of the Université Paris 13.

Supplementary material

13361_2013_722_MOESM1_ESM.doc (3.3 mb)
ESM 1 (DOC 3371 kb)


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Copyright information

© American Society for Mass Spectrometry 2013

Authors and Affiliations

  • Thi Nga Le
    • 1
  • Jean Christophe Poully
    • 1
    • 5
  • Frédéric Lecomte
    • 1
  • Nicolas Nieuwjaer
    • 1
  • Bruno Manil
    • 1
  • Charles Desfrançois
    • 1
  • Fabien Chirot
    • 2
  • Jerome Lemoine
    • 2
  • Philippe Dugourd
    • 3
  • Guillaume van der Rest
    • 4
  • Gilles Grégoire
    • 1
    Email author
  1. 1.Université Paris 13, Sorbonne Paris Cité, Laboratoire de Physique des Lasers, CNRS UMR 7538VilletaneuseFrance
  2. 2.Université Lyon 1, CNRS, UMR 5280, Institut des Sciences AnalytiquesVilleurbanneFrance
  3. 3.Université Lyon 1, CNRS, UMR 5306, Institut Lumière MatièreVilleurbanneFrance
  4. 4.Laboratoire de Chimie Physique, Université Paris Sud, CNRSOrsayFrance
  5. 5.CIMAP, UMR 6252 CEA, CNRS, University of Caen and ENSICAENCAEN Cedex 5France

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