Fast atom bombardment mass spectrometry of some lantibiotics.

Four lantibiotics namely epidermin, gallidermin, lanthiopeptin and mersacidin, have been studied by fast atom bombardment mass spectrometry. The molecular ion clusters of these compounds can be detected with reasonable abundance. The low-mass regions of the spectra show the presence of ions characteristic of the amino acids in the peptides. The mass distribution of the sequence ions provides information about the location of sulphur bridges the occurrence of which is a common feature of these kinds of molecules. The two isomeric compounds epidermin and gallidermin differ only in a leucine/isoleucine exchange at position 6. These two compounds can be distinguished on the basis of the tandem mass spectrum of m/z 86, the immonium ion of leucine and isoleucine.