Atik, Ahmet EminHernandez, OscarMaitre, PhilippeYalçın, Talat2017-05-302017-05-302014Atik, A.E., Hernandez, O., Maître, P., and Yalçın, T. (2014). Specific rearrangement reactions of acetylated lysine containing peptide bn (n=4-7) ion series. Journal of Mass Spectrometry, 49(12), 1290-1297. doi:10.1002/jms.34621076-51741096-9888https://doi.org/10.1002/jms.3462https://hdl.handle.net/11147/5647Characterization 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 (KAcYAGFLVG and YAKAcGFLVG) 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.eninfo:eu-repo/semantics/openAccessMacrocyclization of b ionsPeptide fragmentationLysine acetylationPeptidesArticle2-s2.0-8491620777310.1002/jms.346210.1002/jms.3462