Schematic structure and mass fragmentation spectrum of anabaenopeptin NP 883. The structure of the peptide (Ile + CO[Lys + Val + Hph + MeHty + MetO]) was deduced on the basis of the following fragments: 866 [M + H − H2O], 856 [M + H − CO], 838 [M + H − CO − H2O], 820 [M + H − CH3SOH (from MetO)], 802 [M + H − CH3SOH − H2O), 771 [M + H − Ile], 753 [M + H − Ile − H2O], 727 [M + H − (Ile + CO)], 723 [M + H − Hph], 707 [M + H − Ile − CH3SOH], 689 [M + H − Ile − CH3SOH − H2O], 624 [M + H − (Hph + Val)], 606 [M + H − (Hph + Val) − H2O], 528 [M + H − Ile − Hph − CH3SOH − H2O], 511 [M + H − Ile − (Hph + Val)], 452 [MeHty + Hph + Val + H], 339 [MetO + MeHty + H], 447 [M + H − Ile − (Hph + Val) − CH3SOH], 164 MeHty, 107 [CH2PhOH], 84 Lys-immonium ion.