Fragmentation of α-radical cations of arginine-containing peptides

  • Julia LaskinEmail author
  • Zhibo Yang
  • C. M. Dominic Ng
  • Ivan K. Chu


Fragmentation pathways of peptide radical cations, M, with well-defined initial location of the radical site were explored using collision-induced dissociation (CID) experiments. Peptide radical cations were produced by gas-phase fragmentation of CoIII(salen)-peptide complexes [salen=N,N′-ethylenebis (salicylideneiminato)]. Subsequent hydrogen abstraction from the β-carbon of the side-chain followed by Cα-Cβ bond cleavage results in the loss of a neutral side chain and formation of an α-radical cation with the radical site localized on the α-carbon of the backbone. Similar CID spectra dominated by radical-driven dissociation products were obtained for a number of arginine-containing α-radicals, suggesting that for these systems radical migration precedes fragmentation. In contrast, proton-driven fragmentation dominates CID spectra of α-radicals produced via the loss of the arginine side chain. Radical-driven fragmentation of large M peptide radical cations is dominated by side-chain losses, formation of even-electron a-ions and odd-electron x-ions resulting from Cα-C bond cleavages, formation of odd-electron z-ions, and loss of the N-terminal residue. In contrast, charge-driven fragmentation produces even-electron y-ions and odd-electron b-ions.


Radical Cation Salen Electron Capture Dissociation Electron Detachment Dissociation Arginine Side Chain 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Supplementary material

13361_2011_210400511_MOESM1_ESM.doc (1.2 mb)
Supplementary material, approximately 1295 KB.


  1. 1.
    Zubarev, R. A.; Kelleher, N. L.; McLafferty, F. W. Electron Capture Dissociation of Multiply Charged Protein Cations: A Nonergodic Process. J. Am. Chem. Soc. 1998, 120, 3265–3266.CrossRefGoogle Scholar
  2. 2.
    Zubarev, R. A. Reactions of Polypeptide Ions with Electrons in the Gas Phase. Mass Spectrom. Rev. 2003, 22, 57–77.CrossRefGoogle Scholar
  3. 3.
    Syka, J. E. P.; Coon, J. J.; Schroeder, M. J.; Shabanowitz, J.; Hunt, D. F. Peptide and Protein Sequence Analysis by Electron Transfer Dissociation Mass Spectrometry. Proc. Natl. Acad. Sci. U. S. A. 2004, 101, 9528–9533.CrossRefGoogle Scholar
  4. 4.
    Cooper, H. J.; Hakansson, K.; Marshall, A. G. The Role of Electron Capture Dissociation in Biomolecular Analysis. Mass Spectrom. Rev. 2005, 24, 201–222.CrossRefGoogle Scholar
  5. 5.
    Zubarev, R. A. Electron Capture Dissociation and Other Ion-Electron Fragmentation Reactions. In Principles of Mass Spectrometry Applied to Biomolecules; Laskin, J.; Lifshitz C.; Eds.; John Wiley and Sons: New York, 2006; pp 475–517.CrossRefGoogle Scholar
  6. 6.
    Breuker, K. Protein Structure and Folding in the Gas Phase: Uniquitin and Cytochrome c. In Principles of Mass Spectrometry Applied to Biomolecules; Laskin, J.; Lifshitz, C.; Eds.; John Wiley and Sons., Inc.: Hoboken, NJ, 2006; pp 177–212.CrossRefGoogle Scholar
  7. 7.
    Hopkinson, A. C.; Siu, K. W. M. Peptide Radical Cations. In Principles of Mass Spectrometry Applied to Biomolecules; Laskin, J.; Lifshitz, C.; Eds.; John Wiley and Sons., Inc.: Hoboken, NJ, 2006; pp 301–335.CrossRefGoogle Scholar
  8. 8.
    Gunawardena, H. P.; He, M.; Chrisman, P. A.; Pitteri, S. J.; Hogan, J. M.; Hodges, B. D. M.; McLuckey, S. A. Electron Transfer Versus Proton Transfer in Gas-Phase Ion/Ion Reactions of Polyprotonated Peptides. J. Am. Chem. Soc. 2005, 127, 12627–12639.CrossRefGoogle Scholar
  9. 9.
    Turecek, F.; Chen, X. H.; Hao, C. T. Where Does the Electron Go? Electron Distribution and Reactivity of Peptide Cation Radicals Formed by Electron Transfer in the Gas Phase. J. Am. Chem. Soc. 2008, 130, 8818–8833.CrossRefGoogle Scholar
  10. 10.
    Kjeldsen, F.; Silivra, O. A.; Ivonin, I. A.; Haselmann, K. F.; Gorshkov, M.; Zubarev, R. A. C α-C Backbone Fragmentation Dominates in Electron Detachment Dissociation of Gas-Phase Polypeptide Polyanions. Chem. Eur. J. 2005, 11, 1803–1812.CrossRefGoogle Scholar
  11. 11.
    Antoine, R.; Joly, L.; Tabarin, T.; Broyer, M.; Dugourd, P.; Lemoine, J. Photo-Induced Formation of Radical Anion Peptides: Electron Photodetachment Dissociation Experiments. Rapid Commun. Mass Spectrom. 2007, 21, 265–268.CrossRefGoogle Scholar
  12. 12.
    Pingitore, F.; Wesdemiotis, C. Characterization of Dipeptide Isomers by Tandem Mass Spectrometry of Their Mono- Versus Dilithiated Complexes. Anal. Chem. 2005, 77, 1796–1806.CrossRefGoogle Scholar
  13. 13.
    Hu, P. F.; Loo, J. A. Gas-Phase Coordination Properties of Zn2+, Cu2+, Ni2+, and Co2+ with Histidine-Containing Peptides. J. Am. Chem. Soc. 1995, 117, 11314–11319.CrossRefGoogle Scholar
  14. 14.
    Gatlin, C. L.; Rao, R. D.; Turecek, F.; Vaisar, T. Carboxylate and Amine Terminus Directed Fragmentations in Gaseous Dipeptide Complexes with Copper(II) and Diimine Ligands Formed by Electrospray. Anal. Chem. 1996, 68, 263–270.CrossRefGoogle Scholar
  15. 15.
    Boutin, M.; Bich, C.; Afonso, C.; Fournier, F.; Tabet, J. C. Negative-Charge Driven Fragmentations for Evidencing Zwitterionic Forms from Doubly Charged Coppered Peptides. J. Mass Spectrom. 2007, 42, 25–35.CrossRefGoogle Scholar
  16. 16.
    Turecek, F. Copper-Biomolecule Complexes in the Gas Phase: The Ternary Way. Mass Spectrom. Rev. 2007, 26, 563–582.CrossRefGoogle Scholar
  17. 17.
    Chu, I. K.; Rodriquez, C. F.; Lau, T. C.; Hopkinson, A. C.; Siu, K. W. M. Molecular Radical Cations of Oligopeptides. J. Phys. Chem. B. 2000, 104, 3393–3397.CrossRefGoogle Scholar
  18. 18.
    Chu, I. K.; Rodriguez, C. F.; Rodriguez, F.; Hopkinson, A. C.; Siu, K. W. M. Formation of Molecular Radical Cations of Enkephalin Derivatives Via Collision-Induced Dissociation of Electrospray-Generated Copper (II) Complex Ions of Amines and Peptides. J. Am. Soc. Mass Spectrom. 2001, 12, 1114–1119.CrossRefGoogle Scholar
  19. 19.
    Bagheri-Majdi, E.; Ke, Y. Y.; Orlova, G.; Chu, I. K.; Hopkinson, A. C.; Siu, K. W. M. Copper-Mediated Peptide Radical Ions in the Gas Phase. J. Phys. Chem. B. 2004, 108, 11170–11181.CrossRefGoogle Scholar
  20. 20.
    Chu, I. K.; Siu, S. O.; Lam, C. N. W.; Chan, J. C. Y.; Rodriquez, C. F. Formation of Molecular Radical Cations of Aliphatic Tripeptides from Their Complexes with Cu-II(12-Crown-4). Rapid Commun. Mass Spectrom. 2004, 18, 1798–1802.CrossRefGoogle Scholar
  21. 21.
    Lam, C. N. W.; Ruan, E. D. L.; Ma, C. Y.; Chu, I. K. Non-Zwitterionic Structures of Aliphatic-Only Peptides Mediated the Formation and Dissociation of Gas Phase Radical Cations. J. Mass Spectrom. 2006, 41, 931–938.CrossRefGoogle Scholar
  22. 22.
    Barlow, C. K.; Wee, S.; McFadyen, W. D.; O’Hair, R. A. J. Designing Copper(II) Ternary Complexes to Generate Radical Cations of Peptides in the Gas Phase: Role of the Auxiliary Ligand. J. Chem. Soc. Dalton Trans. 2004, 20, 3199–3204.CrossRefGoogle Scholar
  23. 23.
    Barlow, C. K.; McFadyen, W. D.; O’Hair, R. A. J. Formation of Cationic Peptide Radicals by Gas-Phase Redox Reactions with Trivalent Chromium, Manganese, Iron, and Cobalt Complexes. J. Am. Chem. Soc. 2005, 127, 6109–6115.CrossRefGoogle Scholar
  24. 24.
    Ke, Y.; Zhao, J.; Verkerk, U. H.; Hopkinson, A. C.; Siu, K. W. M. Histidine, Lysine, and Arginine Radical Cations: Isomer Control Via the Choice of Auxiliary Ligand (L) in the Dissociation of [Cu-II(L)(Amino Acid)](·2+) Complexes. J. Phys. Chem. B. 2007, 111, 14318–14328.CrossRefGoogle Scholar
  25. 25.
    Laskin, J.; Yang, Z.; Chu, I. K. Energetics and Dynamics of Electron Transfer and Proton Transfer in Dissociation of MetalIII(Salen)-Peptide Complexes in the Gas Phase. J. Am. Chem. Soc. 2008, 130, 3218–3230.CrossRefGoogle Scholar
  26. 26.
    Masterson, D. S.; Yin, H. Y.; Chacon, A.; Hachey, D. L.; Norris, J. L.; Porter, N. A. Lysine Peroxycarbamates: Free Radical-Promoted Peptide Cleavage. J. Am. Chem. Soc. 2004, 126, 720–721.CrossRefGoogle Scholar
  27. 27.
    Hodyss, R.; Cox, H. A.; Beauchamp, J. L. Bioconjugates for Tunable Peptide Fragmentation: Free Radical Initiated Peptide Sequencing (FRIPS). J. Am. Chem. Soc. 2005, 127, 12436–12437.CrossRefGoogle Scholar
  28. 28.
    Hao, G.; Gross, S. S. Electrospray Tandem Mass Spectrometry Analysis of S- and N-Nitrosopeptides: Facile Loss of NO and Radical-Induced Fragmentation. J. Am. Soc. Mass Spectrom. 2006, 17, 1725–1730.CrossRefGoogle Scholar
  29. 29.
    Wee, S.; Mortimer, A.; Moran, D.; Wright, A.; Barlow, C. K.; O’Hair, R. A. J.; Radom, L.; Easton, C. J. Gas-Phase Regiocontrolled Generation of Charged Amino Acid and Peptide Radicals. Chem. Commun. 2006, 40, 4233–4235.CrossRefGoogle Scholar
  30. 30.
    Ly, T.; Julian, R. R. Tracking Radical Migration in Large Hydrogen Deficient Peptides with Covalent Labels: Facile Movement Does Not Equal Indiscriminate Fragmentation. J. Am. Soc. Mass Spectrom. 2009, 20, 1148–1158.CrossRefGoogle Scholar
  31. 31.
    Ly, T.; Julian, R. R. Residue-Specific Radical-Directed Dissociation of Whole Proteins in the Gas Phase. J. Am. Chem. Soc. 2008, 130, 351–358.CrossRefGoogle Scholar
  32. 32.
    Thompson, M. S.; Cui, W. D.; Reilly, J. P. Fragmentation of Singly Charged Peptide ions by Photodissociation at λ=157 nm. Angew. Chem. Int. Ed. 2004, 43, 4791–4794.Google Scholar
  33. 33.
    Ly, T.; Julian, R. R. Ultraviolet Photodissociation: Developments towards Applications for Mass-Spectrometry-Based Proteomics. Angew. Chem. Int. Ed. 2009, 48, 7130–7137.CrossRefGoogle Scholar
  34. 34.
    Hopkinson, A. C. Radical Cations of Amino Acids and Peptides: Structures and Stabilities. Mass Spectrom. Rev. 2009, 28, 655–671.CrossRefGoogle Scholar
  35. 35.
    Wee, S.; O’Hair, R. A. J.; McFadyen, W. D. Comparing the Gas-Phase Fragmentation Reactions of Protonated and Radical Cations of the Tripeptides GXR. Int. J. Mass Spectrom. 2004, 234, 101–122.CrossRefGoogle Scholar
  36. 36.
    Wee, S.; O’Hair, R. A. J.; McFadyen, W. D. The Role of the Position of the Basic Residue in the Generation and Fragmentation of Peptide Radical Cations. Int. J. Mass Spectrom. 2006, 249, 171–183.CrossRefGoogle Scholar
  37. 37.
    Moran, D.; Jacob, R.; Wood, G. P. F.; Coote, M. L.; Davies, M. J.; O’Hair, R. A. J.; Easton, C. J.; Radom, L. Rearrangements in Model Peptide-Type Radicals Via Intramolecular Hydrogen-Atom Transfer. Helv. Chim. Acta. 2006, 89, 2254–2272.CrossRefGoogle Scholar
  38. 38.
    Leymarie, N.; Costello, C. E.; O’Connor, P. B. Electron Capture Dissociation Initiates a Free Radical Reaction Cascade. J. Am. Chem. Soc. 2003, 125, 8949–8958.CrossRefGoogle Scholar
  39. 39.
    Pingitore, F.; Bleiholder, C.; Paizs, B.; Wesdemiotis, C. Unimolecular Chemistry of Metal Ion-Coordinated α-Dipeptide Radicals. Int. J. Mass Spectrom. 2007, 265, 251–260.CrossRefGoogle Scholar
  40. 40.
    Chu, I. K.; Zhao, J.; Xu, M.; Siu, S. O.; Hopkinson, A. C.; Siu, K. W. M. Are the Radical Centers in Peptide Radical Cations Mobile? The Generation, Tautomerism, and Dissociation of Isomeric α-Carbon-Centered Triglycine Radical Cations in the Gas Phase. J. Am. Chem. Soc. 2008, 130, 7862–7872.CrossRefGoogle Scholar
  41. 41.
    Sun, Q.; Nelson, H.; Ly, T.; Stoltz, B. M.; Julian, R. R. Chain Chemistry Mediates Backbone Fragmentation in Hydrogen Deficient Peptide Radicals. J. Prot. Res. 2009, 8, 958–966.CrossRefGoogle Scholar
  42. 42.
    Zhang, L.; Reilly, J. P. Radical-Driven Dissociation of Odd-Electron Peptide Radical Ions Produced in 157 nm Photodissociation. J. Am. Soc. Mass Spectrom. 2009, 20, 1378–1390.CrossRefGoogle Scholar
  43. 43.
    Laskin, J.; Futrell, J. H.; Chu, I. K. Is Dissociation of Peptide Radical Cations an Ergodic Process? J. Am. Chem. Soc. 2007, 129, 9598–9599.CrossRefGoogle Scholar
  44. 44.
    Laskin, J. Energy and Entropy Effects in Gas-Phase Dissociation of Peptides and Proteins. In Principles of Mass Spectrometry Applied to Biomolecules; Laskin, J.; Lifshitz, C.; Eds.; John Wiley and Sons., Inc.: Hoboken, NJ, 2006.CrossRefGoogle Scholar
  45. 45.
    Laskin, J.; Yang, Z. B.; Lam, C.; Chu, I. K. Charge-Remote Fragmentation of Odd-Electron Peptide Ions. Anal. Chem. 2007, 79, 6607–6614.CrossRefGoogle Scholar
  46. 46.
    Siu, C. K.; Ke, Y.; Orlova, G.; Hopkinson, A. C.; Siu, K. W. M. Dissociation of the N-C-α Bond and Competitive Formation of the [z(n)−H](·+) and [c(n)+2H](+) Product Ions in Radical Peptide Ions Containing Tyrosine and Tryptophan: The Influence of Proton Affinities on Product Formation. J. Am. Soc. Mass Spectrom. 2008, 19, 1799–1807.CrossRefGoogle Scholar
  47. 47.
    Varkey, S. P.; Ratnasamy, C.; Ratnasamy, P. Zeolite-Encapsulated Manganese(III)Salen Complexes. J. Mol. Catal. A Chem. 1998, 135, 295–306.CrossRefGoogle Scholar
  48. 48.
    Wang, P.; Ohanessian, G.; Wesdemiotis, C. Cu(II)-Catalyzed Reactions in Ternary [Cu(AA)(AA-H)](+) Complexes (AA=Gly, Ala, Val, Leu, Ile, t-Leu, Phe). Eur. J. Mass Spectrom. 2009, 15, 325–335.CrossRefGoogle Scholar
  49. 49.
    Yang, Z. B.; Lam, C.; Chu, I. K.; Laskin, J. The Effect of the Secondary Structure on Dissociation of Peptide Radical Cations: Fragmentation of Angiotensin III and Its Analogues. J. Phys. Chem. B. 2008, 112, 12468–12478.CrossRefGoogle Scholar
  50. 50.
    Johnson, R. S.; Martin, S. A.; Biemann, K. Collision-Induced Fragmentation of (M+H)+ ions of peptides: Side-Chain-Specific Sequence Ions. Int. J. Mass Spectrom. Ion Processes. 1988, 86, 137–154.CrossRefGoogle Scholar
  51. 51.
    Chu, I. K.; Lam, C. N. W. Generation of Peptide Radical Dications Via Low-Energy Collision-Induced Dissociation of [CuII(terpy)(M+H)]·3+. J. Am. Soc. Mass Spectrom. 2005, 16, 1795–1804.CrossRefGoogle Scholar
  52. 52.
    Han, H.; Xia, Y.; McLuckey, S. A. Ion Trap Collisional Activation of c and z· Ions Formed Via Gas-Phase Ion/Ion Electron-Transfer Dissociation. J. Proteome Res. 2007, 6, 3062–3069.CrossRefGoogle Scholar
  53. 53.
    Anusiewicz, I.; Jasionowski, M.; Skurski, P.; Simons, J. Backbone and Side-Chain Cleavages in Electron Detachment Dissociation (EDD). J. Phys. Chem. A. 2005, 109, 11332–11337.CrossRefGoogle Scholar
  54. 54.
    Huynh, M. H. V.; Meyer, T. J. Proton-Coupled Electron Transfer. Chem. Rev. 2007, 107, 5004–5064.CrossRefGoogle Scholar
  55. 55.
    Laskin, J.; Bailey, T. H.; Futrell, J. H. Fragmentation Energetics for Angiotensin II and Its Analogs from Time-and Energy-Resolved Surface-Induced Dissociation Studies. Int. J. Mass Spectrom. 2004, 234, 89–99.CrossRefGoogle Scholar
  56. 56.
    Hunt, D. F.; Yates, J. R.; Shabanowitz, J.; Winston, S.; Hauer, C. R. Protein Sequencing by Tandem Mass Spectrometry. Proc. Natl. Acad. Sci. U. S. A. 1986, 83, 6233–6237.CrossRefGoogle Scholar
  57. 57.
    Schwartz, B. L.; Bursey, M. M. Some Proline Substituent Effects in the Tandem Mass-Spectrum of Protonated Penta-Alanine. Biol. Mass Spectrom. 1992, 21, 92–96.CrossRefGoogle Scholar
  58. 58.
    Loo, J. A.; Edmonds, C. G.; Smith, R. D. Tandem Mass Spectrometry of Very Large Molecules. 2: Dissociation of Multiply Charged Proline-Containing Proteins from Electrospray Ionization. Anal. Chem. 1993, 65, 425–438.CrossRefGoogle Scholar
  59. 59.
    Breci, L. A.; Tabb, D. L.; Yates, J. R.; Wysocki, V. H. Cleavage N-Terminal to Proline: Analysis of a Database of Peptide Tandem Mass Spectra. Anal. Chem. 2003, 75, 1963–1971.CrossRefGoogle Scholar
  60. 60.
    Wood, G. P. F.; Moran, D.; Jacob, R.; Radom, L. Bond Dissociation Energies and Radical Stabilization Energies Associated with Model Peptide-Backbone Radicals. J. Phys. Chem. A. 2005, 109, 6318–6325.CrossRefGoogle Scholar

Copyright information

© American Society for Mass Spectrometry 2010

Authors and Affiliations

  • Julia Laskin
    • 1
    Email author
  • Zhibo Yang
    • 1
  • C. M. Dominic Ng
    • 2
  • Ivan K. Chu
    • 2
  1. 1.Chemical and Materials Sciences DivisionPacific Northwest National LaboratoryRichlandUSA
  2. 2.Department of ChemistryUniversity of Hong KongHong KongChina

Personalised recommendations