Dansyl-Edman technique

The Edman degradation, a process by which amino acids are removed stepwise from the NH 2-terminus of peptides and proteins, has evolved since its introduction (Edman, 1950) to the point where it is currently the most valuable tool for protein sequence analysis. Several innovations have led to its widespread use. One of the first was the dansyl Edman technique (Gray, 1967), which is useful for sequencing at the nanomole level. Accelerated manual procedures have been developed by Niall and Potts (1970) and Tarr (1975). During the past decade the rate of sequencing has been... 

These techniques have been used successfully in the micro-Zdman degradation of the enzyme mouse sarcoma dihydrofolate reductase to obtain the amino acid sequence of the first 25 amino acids 455). Similarly, RPC has been used in coqjunction with the automated Edman technique for sequencing 32 residues of myoglobin 456). Methionine and its oxidation products, methionine sulfoxide and methionine sulfone, in methionine fortified foods have been analyzed as their dansyl derivatives 457). Lysine has been determined as its dansyl derivative in a study in which the stability of lysine in fortified wheat flour was evaluated (458). 

Today s sequence techniques have achieved 9-10 orders of magnitude higher detection limit for PTH-amino acid than Edman s first report, in which he described the sequence of Ala-Leu-Gly with 100 pmol. Matsuo et al. succeeded in determing the structure of FSH-RH (LH-RH), a decapeptide hormone, in 1971 by using the Dansyl Edman method.83 This historical work used 200 nmol of FSH-RH purified from 165,000 porcine hypothalami and led a principal investigator, A. Schally, to win the Nobel Prize. Today, we would only need less than one hundred porcine hypothalami to complete the same job on a state-of-art sequencer. Those who plan the structural analysis of even barely detectable amounts of a peptide or protein are urged to start the plan such study could open up a new area in biochemistry. 

Improved methods for end group analysis have become available, notably the use of dansyl chloride (5-dimethylaminonaphthalene-l-sulphonyl chloride) for labelling iV-terminal amino acids and the Edman technique. Dansyl-amino acids fluoresce strongly in ultraviolet light and can be detected in very small amounts so that the method is much more sensitive than Sanger s original DNP technique. 

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