title: Multiple Ionization of Free Ubiquitin Molecular Ions in Extreme Ultraviolet Free-Electron Laser Pulses.
abstract: The fragmentation of free tenfold protonated ubiquitin in intense 70 femtosecond pulses of 90 eV photons from the FLASH facility was investigated. Mass spectrometric investigation of the fragment cations produced after removal of many electrons revealed fragmentation predominantly into immonium ions and related ions, with yields increasing linearly with intensity. Ionization clearly triggers a localized molecular response that occurs before the excitation energy equilibrates. Consistent with this interpretation, the effect is almost unaffected by the charge state, as fragmentation of sixfold deprotonated ubiquitin leads to a very similar fragmentation pattern. Ubiquitin responds to EUV multiphoton ionization as an ensemble of small peptides.
authors.affiliation: Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747, AG, Groningen, The Netherlands. t.a.schlatholter@rug.nl.
authors.forename: Thomas
authors.identifier: 0000-0001-9923-172X
authors.initials: T
authors.lastname: Schlathölter
authors.affiliation: Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747, AG, Groningen, The Netherlands.|Max-Born-Institute, Max Born Strasse 2A, 12489, Berlin, Germany.
authors.forename: Geert
authors.initials: G
authors.lastname: Reitsma
authors.affiliation: Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747, AG, Groningen, The Netherlands.
authors.forename: Dmitrii
authors.identifier: 0000-0002-2734-022X
authors.initials: D
authors.lastname: Egorov
authors.affiliation: Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747, AG, Groningen, The Netherlands.
authors.forename: Olmo
authors.initials: O
authors.lastname: Gonzalez-Magaña
authors.affiliation: European XFEL GmbH, Holzkoppel 4, 22869, Schenefeld, Germany.|DESY, Notkestraße 85, 22607, Hamburg, Germany.
authors.forename: Sadia
authors.identifier: 0000-0003-3985-2051
authors.initials: S
authors.lastname: Bari
authors.affiliation: Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747, AG, Groningen, The Netherlands.|Kapteyn Institute, Landleven 12, 9747, AD, Groningen, The Netherlands.
authors.forename: Leon
authors.initials: L
authors.lastname: Boschman
authors.affiliation: Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747, AG, Groningen, The Netherlands.
authors.forename: Erwin
authors.initials: E
authors.lastname: Bodewits
authors.affiliation: Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117, Heidelberg, Germany.
authors.forename: Kirsten
authors.initials: K
authors.lastname: Schnorr
authors.affiliation: Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117, Heidelberg, Germany.
authors.forename: Georg
authors.initials: G
authors.lastname: Schmid
authors.affiliation: Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117, Heidelberg, Germany.
authors.forename: Claus Dieter
authors.initials: CD
authors.lastname: Schröter
authors.affiliation: Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117, Heidelberg, Germany.
authors.forename: Robert
authors.initials: R
authors.lastname: Moshammer
authors.affiliation: Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747, AG, Groningen, The Netherlands.
authors.forename: Ronnie
authors.identifier: 0000-0001-8632-3334
authors.initials: R
authors.lastname: Hoekstra
keywords: free-electron lasers; mass spectrometry; multiphoton ionization; photoionization; proteins