Analysis of peptide compounds

The technique of MS/MS is also very promising for the elucidation of the structures of peptides. A large number of examples shows the various applications of this technique, according to a very practical methodology which inevitably leads to the identification of the species studied, the component amino acid residues and the peptide sequence, even in a mixture. 

The presence of metastable peaks in conventional spectra has occasionally been utilized. The ions detected are those which are produced just before the magnetic field in conventional single or conventional double focusing (as E-B configuration) instruments. 

Sun and Lovins [212] studied the elimination of neutral fragments, obtained from amino acids liberated during the Edman degradation, which are transformed into derivatives of methyl- (or phenyl-) thiohydantoin (Fig. 59). 

The data in Table 19 show that, for example, it is possible to distinguish leucine from isoleucine by their methylthiohydantoin derivatives (Fig. 60), as a result of the respective losses of C3H7 and C2H5 from their molecular ions. 

Metastable transitions observed for amino acid derivatives 

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