title: Specific rearrangement reactions of acetylated lysine containing peptide bn (n = 4-7) ion series.
abstract: Characterization of ε-N-acetylated lysine containing peptides, one of the most prominent post-translational modifications of proteins, is an important goal for tandem mass spectrometry experiments. A systematic study for the fragmentation reactions of b ions derived from ε-N-acetyllysine containing model octapeptides (KAc YAGFLVG and YAKAc GFLVG) has been examined in detail. Collision-induced dissociation (CID) mass spectra of bn (n = 4-7) fragments of ε-N-acetylated lysine containing peptides are compared with those of N-terminal acetylated and doubly acetylated (both ε-N and N-terminal) peptides, as well as acetyl-free peptides. Both direct and nondirect fragments are observed for acetyl-free and singly acetylated (ε-N or N-terminal) peptides. In the case of ε-N-acetylated lysine containing peptides, however, specific fragment ions (m/z 309, 456, 569 and 668) are observed in CID mass spectra of bn (n = 4-7) ions. The CID mass spectra of these four ions are shown to be identical to those of selected protonated C-terminal amidated peptides. On this basis, a new type of rearrangement chemistry is proposed to account for the formation of these fragment ions, which are specific for ε-N-acetylated lysine containing peptides. Consistent with the observation of nondirect fragments, it is proposed that the b ions undergo head-to-tail macrocyclization followed by ring opening. The proposed reaction pathway assumes that bn (n = 4-7) of ε-N-acetylated lysine containing peptides has a tendency to place the KAc residue at the C-terminal position after macrocyclization/reopening mechanism. Then, following the loss of CO, it is proposed that the marker ions are the result of the loss of an acetyllysine imine as a neutral fragment.
authors.affiliation: Department of Chemistry, Faculty of Science, Izmir Institute of Technology, 35430, Urla-Izmir, Turkey.
authors.forename: A Emin
authors.initials: AE
authors.lastname: Atik
authors.forename: Oscar
authors.initials: O
authors.lastname: Hernandez
authors.forename: Philippe
authors.initials: P
authors.lastname: Maître
authors.forename: Talat
authors.initials: T
authors.lastname: Yalcin
mesh_terms: D000107:Acetylation; D000595:Amino Acid Sequence; D003500:Cyclization; D007477:Ions / Q000737:chemistry; D008239:Lysine / Q000032:analysis*; D010455:Peptides / Q000737:chemistry*; D053719:Tandem Mass Spectrometry
chemical_list: D007477:Ions; D010455:Peptides; D008239:Lysine
keywords: lysine acetylation; macrocyclization of b ions; peptide fragmentation