Near-Edge Soft X-ray Absorption Mass Spectrometry of Protonated Melittin |
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| Authors: | Dmitrii Egorov Sadia Bari Rebecca Boll Simon Dörner Sascha Deinert Simone Techert Ronnie Hoekstra Vicente Zamudio-Bayer Rebecka Lindblad Christine Bülow Martin Timm Bernd von Issendorff J. Tobias Lau Thomas Schlathölter |
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| Affiliation: | 1.Zernike Institute for Advanced Materials,University of Groningen,Groningen,Netherlands;2.Deutsches Elektronen-Synchrotron DESY,Hamburg,Germany;3.Institute of X-ray Physics,University of G?ttingen,G?ttingen,Germany;4.Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung,Helmholtz-Zentrum Berlin für Materialien und Energie,Berlin,Germany;5.Abteilung für Hochempfindliche R?ntgenspektroskopie,Helmholtz-Zentrum Berlin für Materialien und Energie,Berlin,Germany;6.Physikalisches Institut,Universit?t Freiburg,Freiburg,Germany;7.Synkrotronljusfysik,Lunds Universitet,Lund,Sweden;8.Institut für Optik und Atomare Physik,Technische Universit?t Berlin,Berlin,Germany |
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| Abstract: | We have investigated the photoionization and photofragmentation yields of gas-phase multiply protonated melittin cations for photon energies at the K-shell absorption edges of carbon, nitrogen, and oxygen. Two similar experimental approaches were employed. In both experiments, mass selected [melittin+qH]q+ (q=2–4) ions were accumulated in radiofrequency ion traps. The trap content was exposed to intense beams of monochromatic soft X-ray photons from synchrotron beamlines and photoproducts were analyzed by means of time-of-flight mass spectrometry. Mass spectra were recorded for fixed photon energies, and partial ion yield spectra were recorded as a function of photon energy. The combination of mass spectrometry and soft X-ray spectroscopy allows for a direct correlation of protein electronic structure with various photoionization channels. Non-dissociative single and double ionization are used as a reference. The contribution of both channels to various backbone scission channels is quantified and related to activation energies and protonation sites. Soft X-ray absorption mass spectrometry combines fast energy deposition with single and double ionization and could complement established activation techniques. |
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