Sequencing of Tentoxin by Using Fast‐Atom‐Bombardment (FAB)/High‐Resolution (HR)/Tandem Mass Spectrometry (MSMS). Scope and Limitation of a Novel Strategy

The recently developed FAB/MSMS methodology ( i.e. ) ionization of an underivatized peptide by using fast‐atom‐bombardment (FAB) combined with tandem mass spectrometry (MSMS) is applied for the sequencing of the cyclotetrapeptide tentoxin ( 12 ). The scope and limitation of the strategy is discussed in detail. Possible resolutions to overcome problems related to ( i ) the resolution of isobaric fragment ions and ( ii ) the distinction of sequence vs. retro ‐sequence are investigated. The novel strategy is compared with conventional techniques. Significant improvement of the presently used FAB/MSMS methodology can be achieved by combining this approach with accurate mass measurements.