Structural Analysis of Macrotetralide Antibiotic Mixtures Using Collision-Induced Dissociation Mass Spectrometry

Collision-induced dissociation of protonated molecular ions in a mixture of macrotetralide antibiotics has been used to determine the sample make-up, as well as the structures of the components in the mixture. Upon 3 keV gaseous collisional activation the near-tetrameric structure of the macrotetralides is opened and can then fragment further to give oligomeric ions through consecutive losses of monomeric units. The fragment ions generated indicate which monomers are present and also their sequence in the cyclic assembly. The fragmentation mechanism involves cleavage of an ester bond to give an undissociated carboxyl group. This cleavage may take place remote from the charge site.