University of Oulu

J. Phys. Chem. A 2022, 126, 9, 1496–1503,

X-ray induced fragmentation of protonated cystine

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Author: Gopakumar, Geethanjali1; Lindblad, Rebecka2,3,4,1; Svensson, Pamela H. W.1;
Organizations: 1Department of Physics and Astronomy, Uppsala University, SE-751 20 Uppsala, Sweden
2Abteilung für Hochempfindliche Röntgenspektroskopie, Helmholtz-Zentrum Berlin für Materialien und Energie, DE-12489 Berlin, Germany
3Department of Physics, Lund University, SE-22100 Lund, Sweden
4Department of Chemistry - Ångström Laboratory, Uppsala University, SE-75121 Uppsala, Sweden
5Deutsches Elektronen-Synchrotron DESY, DE-22607 Hamburg, Germany
6Department of Physical Chemistry, University of Vienna, 1090 Vienna, Austria
7Institut für Optik und Atomare Physik, Technische Universität Berlin, DE-10623 Berlin, Germany
8Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, DE-79104 Freiburg, Germany
9Physikalisches Institut, Albert- Ludwigs-Universität Freiburg, DE-79104 Freiburg, Germany
10Nano and Molecular Systems Research Unit, Faculty of Science, University of Oulu, 90570 Oulu, Finland
11Center for Free-Electron Laser Science, Deutsches Elektronen- Synchrotron DESY, DE-22607 Hamburg, Germany
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 2.8 MB)
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Language: English
Published: American Chemical Society, 2022
Publish Date: 2022-05-16


We demonstrate site-specific X-ray induced fragmentation across the sulfur L-edge of protonated cystine, the dimer of the amino acid cysteine. Ion yield NEXAFS were performed in the gas phase using electrospray ionization (ESI) in combination with an ion trap. The interpretation of the sulfur L-edge NEXAFS spectrum is supported by Restricted Open-Shell Configuration Interaction (ROCIS) calculations. The fragmentation pathway of triply charged cystine ions was modeled by Molecular Dynamics (MD) simulations. We have deduced a possible pathway of fragmentation upon excitation and ionization of S 2p electrons. The disulfide bridge breaks for resonant excitation at lower photon energies but remains intact upon higher energy resonant excitation and upon ionization of S 2p. The larger fragments initially formed subsequently break into smaller fragments.

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Series: The journal of physical chemistry. A
ISSN: 1089-5639
ISSN-E: 1520-5215
ISSN-L: 1089-5639
Volume: 126
Issue: 9
Pages: 1496 - 1503
DOI: 10.1021/acs.jpca.1c10158
Type of Publication: A1 Journal article – refereed
Field of Science: 114 Physical sciences
116 Chemical sciences
Funding: Beamtime for this project was granted at the Ion Trap endstation of BESSY II beamline UE52-PGM, operated by the Helmholtz-Zentrum Berlin. This project has received funding from the European Union’s Horizon 2020 research and innovation program under Grant Agreement No. 730872 and by the German Federal Ministry of Education and Research (BMBF) through Grant No. BMBF-05K16Vf2. R.L. acknowledges funding from the Swedish Research Council, Contract 637-2014-6929. C.C. acknowledges the Swedish Research Council (Grant 2018-00740) and the Helmholtz Association through the Center for Free-Electron Laser Science at DESY. O.B. acknowledges funding from the Swedish Research Council (VR) for the project VR 2017-04162. L.S acknowledges funding from the Helmholtz Initiative and Networking Fund through the Young Investigators Group Program (VH-NG-1104). C.-M.S. acknowledges funding from the EU Horizon 2020 program under the Marie Sklodowska-Curie Grant Agreement No. 847693 through the REWIRE program at the University of Vienna.
Copyright information: © 2022 The Authors. Published by American Chemical Society. Published under the Creative Commons Attribution 4.0 International (CC BY 4.0) license.