EdmanAbbauReaktion

The Edman degradation is a method for sequencing amino acids in a peptide. Developed by Pehr Edman in the 1950s, it is a sequential process that systematically removes and identifies the N-terminal amino acid of a peptide chain. The reaction involves treating the peptide with phenylisothiocyanate (PITC) under alkaline conditions. This reaction forms a phenylthiocarbamoyl (PTC) derivative of the peptide.

Following the formation of the PTC derivative, the peptide is treated with a strong acid, such as trifluoroacetic acid. This acidic treatment cleaves the peptide bond between the first and second amino acid, releasing the N-terminal amino acid as an anilinothiazolinone (ATZ) derivative. The rest of the peptide chain remains intact, albeit shortened by one amino acid.

The released ATZ derivative is then extracted into an organic solvent and converted into a more stable phenylthiohydantoin (PTH) derivative by treatment with aqueous acid. This PTH-amino acid can be identified using chromatographic techniques, most commonly high-performance liquid chromatography (HPLC). The remaining peptide, now with a new N-terminus, can then undergo another round of Edman degradation to identify the subsequent amino acid. This cycle is repeated until the entire peptide sequence is determined or a point is reached where the yield is too low for reliable identification. While powerful, the Edman degradation is limited by the length of the peptide that can be sequenced due to cumulative losses and side reactions. It is typically effective for peptides up to 50-60 amino acids long.