Abstract
For the elucidation of the biosynthetic relationship between nontoxic peptides and hepatotoxic peptides produced together with hepatotoxic peptides, we applied the high-energy collision FAB MS/MS method to the confirmation and the determination of the peptide structure isolated from cyanobacteria. The structures of the cyanobacterial peptides including the cyclic peptides were definitely elucidated by complementary use of the NMR and MS/MS methods. Furthermore, the MS/MS method is very effective for the structural determination of closely related peptides derived from the difference of a part of the constituent amino acids, and their structures were determined by MS/MS experiments and amino acid analysis without NMR techniques. Additionally, the charge-remote fragmentation was observed in the cases of peptides containing Arg and the sulfate group which facilitated the interpretation of the resulting product ion spectrum. From the present study, the MS/MS method was found to be practicable for the confirmation and determination of the structures of cyanobacterial peptides.