Carboxy-terminal Degradation of Peptides using Perfluoroacyl Anhydrides

An accurate carboxy-terminal sequencing method has long been sought to complement the Edman degradation procedure for ammo-terminal amino acid sequence analysis. The method presented here is a unique and simple method to partly fulfill the needs. Exposure of a polypeptide to perfluoroacyl anhydride vapor at −20°C for 0.5–1 h causes sequential chemical degradation of the molecule from the C-terminus. Fast-atom-bombardment mass spectrometric analysis of the resultant mixture of C-terminally truncated molecules permits the determination of the C-terminal sequence by simple calculation of the mass differences in molecular ions. Experiments suggested that this C-terminal degradation proceeds by active intermediates such as oxazolone at the C-terminal carboxyl residues.