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Journal of Chemical Physics / Volume 136 / Issue 1 / ARTICLES / Gas Phase Dynamics and Structure: Spectroscopy, Molecular Interactions, Scattering, and Photochemistry

J. Chem. Phys. 136, 014307 (2012); http://dx.doi.org/10.1063/1.3671943 (14 pages)

Photodissociation pathways and lifetimes of protonated peptides and their dimers

G. Aravind1, B. Klærke1, J. Rajput1, Y. Toker1, L. H. Andersen1, A. V. Bochenkova2, R. Antoine3, J. Lemoine4, A. Racaud3, and P. Dugourd3

1Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark
2Chemistry Department, Moscow State University, Moscow 119991, Russia and Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark
3Université de Lyon, F-69622, Lyon, France and Université Lyon 1, Villeurbanne, CNRS, UMR 5579, LASIM, France
4Université de Lyon, F-69622, Lyon, France and Université Lyon 1, Villeurbanne, CNRS, UMR 5180, Sciences Analytiques, France

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(Received 28 September 2011; accepted 3 December 2011; published online 4 January 2012)

Photodissociation lifetimes and fragment channels of gas-phase, protonated YAn (n = 1,2) peptides and their dimers were measured with 266 nm photons. The protonated monomers were found to have a fast dissociation channel with an exponential lifetime of ∼200 ns while the protonated dimers show an additional slow dissociation component with a lifetime of ∼2 μs. Laser power dependence measurements enabled us to ascribe the fast channel in the monomer and the slow channel in the dimer to a one-photon process, whereas the fast dimer channel is from a two-photon process. The slow (1 photon) dissociation channel in the dimer was found to result in cleavage of the H-bonds after energy transfer through these H-bonds. In general, the dissociation of these protonated peptides is non-prompt and the decay time was found to increase with the size of the peptides. Quantum RRKM calculations of the microcanonical rate constants also confirmed a statistical nature of the photodissociation processes in the dipeptide monomers and dimers. The classical RRKM expression gives a rate constant as an analytical function of the number of active vibrational modes in the system, estimated separately on the basis of the equipartition theorem. It demonstrates encouraging results in predicting fragmentation lifetimes of protonated peptides. Finally, we present the first experimental evidence for a photo-induced conversion of tyrosine-containing peptides into monocyclic aromatic hydrocarbon along with a formamide molecule both found in space.

© 2012 American Institute of Physics

Article Outline

  1. INTRODUCTION
  2. EXPERIMENTAL METHOD
  3. COMPUTATIONAL DETAILS
  4. RESULTS AND DISCUSSION
    1. Time-of-flight measurements
    2. Monte-Carlo simulation
    3. Laser-power dependence measurements
    4. Fragment-ion mass analysis
    5. Dissociation mechanisms
  5. CONCLUSION

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KEYWORDS and PACS

Keywords

biochemistry, hydrogen bonds, molecular biophysics, multiphoton processes, photodissociation, proteins, quantum theory, reaction kinetics theory, reaction rate constants, vibrational states

PACS

ARTICLE DATA

Digital Object Identifier
http://dx.doi.org/10.1063/1.3671943

PUBLICATION DATA

ISSN

0021-9606 (print)  
1089-7690 (online)

Publisher

$abstract.society.value is a Member of CrossRef American Institute of Physics

For access to fully linked references, you need to log in.
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