Sequencing of Cyclosporins by Fast Atom Bombardment and Linked-scan Mass Spectrometry

Article abstract of DOI:10.1002/oms.1210281214

The mass spectrometric sequence determination of amino acid residues in cyclosporins using fast atom bombardment, collisionally activated dissociations in the first field-free region and linked B/E scan is described.The general fragmentation scheme was derived from the spectra of cyclosporins A, B, C, D, F, G, L and 1>CS.The main fragmentation pathways start by primary splitting between amino acids 2-3, 1-11 and 5-6.The corresponding N-terminal b-type ions are common fragment types in the mass spectra.The 1-11 splitting can be enhanced by the introduction of a lactone group into the peptide ring by conversion of cyclosporins into isocyclosporins.The fragmentation scheme was used for amino acid sequence determination on four new natural cyclosporins, 1>CS, 4>CS, 4>CS and 5>CS.