Tandem Mass Spectrometric Structural Characterization of Cyclic Peptides: Revisited

摘要

Of interest in many fields including natural product chemistry, toxicological and environmental sciences: (1) unique structures and biological activities. (2) resistant to protease/peptidase in general. (3) some can be pharmaceutical candidates. Problematic from MS structural characterization point of views: (1) less fragmentation (at least two bonds have to be cleaved). (2) "head-or-tail" uncertainty (peptide-ring-opening gives linear structures with no C- or N-termini). (3) ring-opening position itself is uncertain (isomeric structures). (4) all makes spectral interpretation difficult.