Journal of the American Society for Mass Spectrometry

, Volume 14, Issue 11, pp 1282–1289

Determination of the activation energy for unimolecular dissociation of a non-covalent gas-phase peptide: Substrate complex by infrared multiphoton dissociation fourier transform ion cyclotron resonance mass spectrometry

  • Mathias Schäfer
  • Carsten Schmuck
  • Martin Heil
  • Helen J. Cooper
  • Christopher L. Hendrickson
  • Michael J. Chalmers
  • Alan G. Marshall
Articles

DOI: 10.1016/S1044-0305(03)00576-2

Cite this article as:
Schäfer, M., Schmuck, C., Heil, M. et al. J Am Soc Mass Spectrom (2003) 14: 1282. doi:10.1016/S1044-0305(03)00576-2

Abstract

The activation energy for the unimolecular dissociation of a non-covalent supramolecular complex between an Artificial Cationic Receptor A ([Gua-Val-Val-Val-Amide]+, in which Gua is guanidiniocarbonyl pyrrole) and an Anionic Tetrapeptide B ([N-Acetyl-Val-Val-Ile-Ala]) has been determined by measurement of the dissociation rate constant as a function of infrared CO2 laser power density. Singly-charged quasimolecular [A+B+H]+ ions are isolated, stored in a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer, and irradiated by IR photons. The rate constant for dissociation of the non-covalent complex is determined at five different laser power densities. A plot of the natural logarithm of the first-order rate constant versus the natural logarithm of the laser power density yields a straight line, the slope of which provides an approximate measure of the activation energy (Ealaser) for dissociation. Ealaser is calculated by a relationship derived earlier by Dunbar and with a newly proposed equation by Paech et al. The results of the two approaches deliver significantly different activation energy values for the unimolecular dissociation of the non-covalent complex. We obtain EaIlaser=0.67 eV (Dunbar approximation) and EaIIlaser=1.12 eV (Paech et al. approximation). Differences between the two approaches are discussed with respect to non-covalent complexes.

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© American Society for Mass Spectrometry 2003

Authors and Affiliations

  • Mathias Schäfer
    • 1
  • Carsten Schmuck
    • 2
  • Martin Heil
    • 2
  • Helen J. Cooper
    • 3
  • Christopher L. Hendrickson
    • 3
    • 5
  • Michael J. Chalmers
    • 3
  • Alan G. Marshall
    • 3
    • 5
  1. 1.Institute of Organic ChemistryUniversity CologneKölnGermany
  2. 2.Institute for Organic ChemistryUniversity WürzburgWürzburgGermany
  3. 3.Ion Cyclotron Resonance Program, National High Magnetic Field LaboratoryFlorida State UniversityTallahasseeUSA
  4. 4.School of BiosciencesUniversity of BirminghamEdgbastonUnited Kingdom
  5. 5.Department of Chemistry and BiochemistryFlorida State UniversityTallahasseeUSA