ANYL 83 |
| Five marine cyclic peptides as potential anticancer drugs have been synthesized and their fragmentations induced by multistage collisionally activated decomposition (CAD) have been studied in an ion trap mass spectrometer. Under low-energy CAD, the protonated cyclic peptides mainly dissociate via ring opening pathways and the corresponding bn→ bn-1 pathways to form several sets of b ions as oxazolone rings (and b1 ions as aziridinone rings). Through repeated observation of these b ions in multistage CAD experiments, accurate sequencing and head-to-tail ring structure of cyclic peptides can be determined. However, for a long activation time in an ion trap, a linear b ion can be cyclized to generate another protonated cyclic peptide ion, which induce a bn → cyclo-bn-1 → b*n-1 pathway. These cyclization reactions of b ions that seriously hinder the sequencings were extensively observed in the multistage CAD experiments. Analog syntheses, kinetic studies and quantum chemical calculations have been utilized to provide insight into the proposed dissociation mechanisms.
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General Papers
7:00 PM-9:00 PM, Sunday, 10 September 2006 Moscone Center -- Hall D, Poster
Division of Analytical Chemistry |
