Peptide sequencing with the 2-pyridinecarboxaldehyde schiff base peptide degradation

Dedicated to Professor John C. Sheehan on the occasion of his sixty-fifth birthday. Peptides treated with 2-pyridinecarboxaldehyde are converted to Schiff bases, pyridoimidazoles, α-ketoacyl amino acids and peptide amides, and diketopiperazines. Nitrogen abstraction and condensation with 2-pyridinecarboxaldehyde gives heterocyclic products. The products are separable by gas chromatography and when analyzed by mass spectrometry afford information for sequence assignment. Thus, a nonvolatile peptide can be converted to a mixture of products in one step that by mass spectrometric analysis affords the sequence. Peptides of up to eight and nine amino acids have been analyzed using this degradation as the basis of a one-step procedure.