Quantitative determination of N-terminal amino acids of peptides and proteins with cobalt(III) chelates.

Quantitative N-terminal peptide-bond hydrolysis with the cis-beta-hydroxyaquo(triethylenetetramine) cobal (III) ion, i.e. beta-[Co(trien)(OH)(OH2)]2+, is reported. The method has been demonstrated with 20 small peptides, a hexapeptide, bradykinin, insulin A chain (oxidized), glucagon and insulin. The procedure involves no acidic hydrolysis step and thus no destruction of labile amino acids.