title: Conformational Space and Stability of ETD Charge Reduction Products of Ubiquitin.
abstract: Owing to its versatility, electron transfer dissociation (ETD) has become one of the most commonly utilized fragmentation techniques in both native and non-native top-down mass spectrometry. However, several competing reactions-primarily different forms of charge reduction-occur under ETD conditions, as evidenced by the distorted isotope patterns usually observed. In this work, we analyze these isotope patterns to compare the stability of nondissociative electron transfer (ETnoD) products, specifically noncovalent c/z fragment complexes, across a range of ubiquitin conformational states. Using ion mobility, we find that more extended states are more prone to fragment release. We obtain evidence that for a given charge state, populations of ubiquitin ions formed either directly by electrospray ionization or through collapse of more extended states upon charge reduction, span a similar range of collision cross-sections. Products of gas-phase collapse are, however, less stabilized towards unfolding than the native conformation, indicating that the ions retain a memory of previous conformational states. Furthermore, this collapse of charge-reduced ions is promoted if the ions are 'preheated' using collisional activation, with possible implications for the kinetics of gas-phase compaction. Graphical Abstract ᅟ.
authors: Biomolecular and Analytical Mass Spectrometry Group, Department of Chemistry, University of Antwerp, Antwerpen, Belgium.|Center for Proteomics, University of Antwerp, Antwerpen, Belgium.
authors: Frederik
authors: F
authors: Lermyte
authors: Institute of Informatics, University of Warsaw, Warsaw, Poland.
authors: Mateusz Krzysztof
authors: MK
authors: Łącki
authors: Center for Proteomics, University of Antwerp, Antwerpen, Belgium.|Interuniversity Institute for Biostatistics and Statistical Bioinformatics, Hasselt University, Hasselt, Belgium.|Applied Bio and Molecular Systems, Flemish Institute for Technological Research (VITO), Antwerp, Belgium.
authors: Dirk
authors: D
authors: Valkenborg
authors: Institute of Informatics, University of Warsaw, Warsaw, Poland.
authors: Anna
authors: A
authors: Gambin
authors: Biomolecular and Analytical Mass Spectrometry Group, Department of Chemistry, University of Antwerp, Antwerpen, Belgium. frank.sobott@uantwerpen.be.|Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK. frank.sobott@uantwerpen.be.|School of Molecular and Cellular Biology, University of Leeds, Leeds, LS2 9JT, UK. frank.sobott@uantwerpen.be.
authors: Frank
authors: F
authors: Sobott
mesh_terms: D000818:Animals; D002417:Cattle; D004579:Electron Transport; D004583:Electrons; D007477:Ions / Q000737:chemistry; D007700:Kinetics; D011487:Protein Conformation; D021241:Spectrometry, Mass, Electrospray Ionization; D025801:Ubiquitin / Q000737:chemistry*
chemical_list: D007477:Ions; D025801:Ubiquitin
keywords: Charge reduction; ETD; Ion mobility; PTR; Protein conformation; Ubiquitin