|European Journal of Mass Spectrometry|
Volume 4 Issue 4, Pages 287–298 (1998)
Effect of amino acid side-chain on fragmentation of cyclic peptide ions: differences of ESI-MS/CID mass spectra of toxic heptapeptide microcystins containing ADMAdda instead of Adda
Michio Namikoshi and Akira Otsuki*
Department of Ocean Sciences, Tokyo University of Fisheries, Minato-ku, Tokyo 108, Japan. E-mail: email@example.com.
Department of Applied Chemistry and Microbiology, PO Box 56, 00014 University of Helsinki, Finland
Characteristics of collision-induced decomposition (CID) spectra recorded following electrospray ionization (ESI) of toxic heptapeptide microcystins containing (2S,3S,8S,9S)-3-amino-9-acetoxy-2,6,8-trimethyl-10-phenyldeca-4,6-dienoic acid (ADMAdda) have been investigated in detail and compared with those from compounds containing (2S,3S,8S,9S)-3-amino-9-methoxy-2,6,8-trimethyl-10-phenyldeca-4,6-dienoic acid (Adda). A significant difference in their CID spectra was observed in the cleavage of cyclic structures in low-energy CID processes due to the effect of the amino acid side-chain on fragmentation. Microcystins containing ADMAdda produced mostly b-type ions. Fragment ions predicted on the basis of the known fragmentation of cyclic peptides and linear-peptide b- type ions, predicted by the Peptide Matching (PEPM) program, matched well with peaks in the CID spectra. A neutral loss of CH3COOH from the ADMAdda residues was observed in the CID spectra of doubly charged ions, [M + 2H]2+. The present study suggested that the CID spectra of [M + H]+ and [M + 2H]2+ ions can provide their sequence information.
Keywords: two-component signal transduction proteins, on-target proteolysis, structure/function correlation, MALDI-MS, ESI-MS