Detection of new sequences of peptaibol antibiotics trichotoxins A-40 by on-line liquid chromatography-electrospray ionization mass spectrometry

Using high-performance liquid chromatography (HPLC) coupled to electrospray ionization mass spectrometry (ESI-MS) the sequences of the microheterogeneous peptide mixture of the 18-residue "peptaibol" antibiotics trichotoxins A-40, isolated from the mold Trichoderma viride strain NRRL 5242, were reinvestigated. The structures of two major and one minor component [J. Chromatogr., 296 (1984) 236] could be confirmed and hitherto not known sequences of a further major and two minor peptides could be determined. It is demonstrated that ESI-MS in the positive ionization mode is advantageously completed by applying negative ionization. The methods used make possible the sequence determination of components of peptaibols without previous isolation and allow, in certain cases, sequencing of peptides which are incompletely or not resolved by HPLC.