Journal of The American Society for Mass Spectrometry

, Volume 29, Issue 9, pp 1826–1834 | Cite as

Radical Anions of Oxidized vs. Reduced Oxytocin: Influence of Disulfide Bridges on CID and Vacuum UV Photo-Fragmentation

  • Luke MacAleeseEmail author
  • Marion Girod
  • Laurent Nahon
  • Alexandre Giuliani
  • Rodolphe Antoine
  • Philippe Dugourd
Focus: Application of Photons and Radicals for MS: Research Article


The nonapeptide oxytocin (OT) is used as a model sulfur-containing peptide to study the damage induced by vacuum UV (VUV) radiations. In particular, the effect of the presence (or absence in reduced OT) of oxytocin’s internal disulfide bridge is evaluated in terms of photo-fragmentation yield and nature of the photo-fragments. Intact, as well as reduced, OT is studied as dianions and radical anions. Radical anions are prepared and photo-fragmented in two-color experiments (UV + VUV) in a linear ion trap. VUV photo-fragmentation patterns are analyzed and compared, and radical-induced mechanisms are proposed. The effect of VUV is principally to ionize but secondary fragmentation is also observed. This secondary fragmentation seems to be considerably enabled by the initial position of the radical on the molecule. In particular, the possibility to form a radical on free cysteines seems to increase the susceptibility to VUV fragmentation. Interestingly, disulfide bridges, which are fundamental for protein structure, could also be responsible for an increased resistance to ionizing radiations.

Graphical Abstract


Electron photo-detachment Photo-fragmentation Two-colors experiment Disulfide bridge Vacuum UV Oxytocin Radical peptide 



We thank the general technical staff of SOLEIL for running the facility.

Funding Information

Research leading to these results received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007–2013 Grant Agreement No. 320659). SOLEIL support is acknowledged under project no. 20120093. This research was supported by the Agence Nationale de la Recherche Scientifique, France, under the project no. BLAN08-1_348053.

Supplementary material

13361_2018_1989_MOESM1_ESM.docx (506 kb)
ESM 1 (DOCX 505 kb)


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Copyright information

© American Society for Mass Spectrometry 2018

Authors and Affiliations

  1. 1.Université de Lyon, CNRS, Université Claude Bernard Lyon 1, Institut Lumière Matière UMR 5306VilleurbanneFrance
  2. 2.Université de Lyon, CNRS, Université Claude Bernard Lyon 1, ENS de Lyon, Institut des Sciences Analytiques UMR 5280VilleurbanneFrance
  3. 3.Synchrotron SOLEILGif Sur YvetteFrance
  4. 4.UAR1008 CEPIA, INRANantesFrance

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