title: Gas-Phase Rearrangement in Lysine Phosphorylated Peptides During Electron-Transfer Dissociation Tandem Mass Spectrometry.
abstract: Tandem mass spectrometry (MS/MS) strategies coupled with collision-induced dissociation (CID) or radical-driven fragmentation techniques such as electron-capture dissociation (ECD) or electron-transfer dissociation (ETD) have been successfully used for comprehensive phosphoproteome analysis. However, the unambiguous characterization of the phosphorylation site remains a significant challenge due to phosphate-related neutral losses and gas-phase rearrangements, which have been observed during CID. In particular, for the analysis of labile N-phosphorylated peptides, ECD and ETD are emerging as a complementary method. In contrast to CID, the phosphorylation site of histidine, arginine, and lysine phosphorylated peptides can be characterized by ETD. Here, we present a study on the application of ETD for analysis of phospholysine (pLys) peptides. We show that, depending on the charge state of the precursor ion as well as the presence of basic amino acid side chains, phosphate transfer reactions during the ETD process can be observed leading to ambiguous fragment ion spectra. Basically, pLys is stable under ETD conditions allowing an unambiguous assignment of the site of phosphorylation, but some factors/parameters have to be considered to avoid gas-phase rearrangement which would lead to false positive results in phosphoproteomic studies.
authors.affiliation: †Leibniz-Institut für Molekulare Pharmakologie (FMP), Robert-Rössle Str. 10, 13125 Berlin, Germany.|§Institut für Chemie und Biochemie, Freie Universität Berlin, Takustrasse 3, 14195 Berlin, Germany.
authors.forename: Jordi
authors.initials: J
authors.lastname: Bertran-Vicente
authors.affiliation: †Leibniz-Institut für Molekulare Pharmakologie (FMP), Robert-Rössle Str. 10, 13125 Berlin, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Schümann
authors.affiliation: †Leibniz-Institut für Molekulare Pharmakologie (FMP), Robert-Rössle Str. 10, 13125 Berlin, Germany.|‡Department Chemie, Humboldt Universität zu Berlin, Brook-Taylor-Strasse 2, 12489 Berlin, Germany.
authors.forename: Christian P R
authors.initials: CP
authors.lastname: Hackenberger
authors.affiliation: †Leibniz-Institut für Molekulare Pharmakologie (FMP), Robert-Rössle Str. 10, 13125 Berlin, Germany.
authors.forename: Eberhard
authors.initials: E
authors.lastname: Krause
mesh_terms: D000595:Amino Acid Sequence; D006801:Humans; D007477:Ions / Q000737:chemistry; D008239:Lysine / Q000737:chemistry*; D010748:Phosphopeptides / Q000032:analysis* / Q000138:chemical synthesis; D053719:Tandem Mass Spectrometry
chemical_list: D007477:Ions; D010748:Phosphopeptides; D008239:Lysine