EdmanAbbau

EdmanAbbau, in English Edman degradation, is a chemical method used to determine the amino acid sequence of peptides by sequentially identifying the N-terminal residue. It is a classic technique in protein chemistry and is commonly referred to in German as Edman-Abbau.

In a typical cycle, the N-terminal amino acid reacts with phenylisothiocyanate (PITC) under mildly basic conditions to form a phenylthiocarbamoyl derivative. This derivative is then subjected to acidic cleavage, yielding the N-terminal amino acid in the form of a phenylthiohydantoin (PTH) derivative. The released PTH-amino acid is identified by chromatographic methods, such as high-performance liquid chromatography (HPLC) or electrophoresis. After removal of the first residue, the peptide is ready for the next cycle, which proceeds with the new N-terminus. Repeating cycles produce a stepwise readout of the peptide sequence from the N-terminus.

The method is most effective for relatively short peptides, typically up to about 25–50 residues under practical conditions. It requires an unblocked N-terminus and is less reliable if the N-terminus is chemically modified or blocked. Proline residues at the penultimate position can hinder the efficiency of the cycles, and modifications near the N-terminus or extensive peptide heterogeneity can limit performance. EdmanAbbau has historically been a dominant approach to sequencing but is largely supplanted in modern proteomics by mass spectrometry-based techniques that can analyze longer peptides and intact proteins more rapidly.

Developed by Pehr Edman in the 1950s, the Edman degradation played a foundational role in protein sequencing. While its use has diminished in routine work, it remains a foundational concept in understanding N-terminal sequencing and serves educational and niche applications where short, well-defined peptides are analyzed.