Edman Degradation: Classic Method for Peptide Amino Acid Sequencing

The Edman degradation is a classic method for determining the amino acid sequence of peptides and proteins. This method was developed by Pehr Edman in the 1950s and is still widely used today, especially for shorter peptide fragments.

 

Principle

1. Edman degradation is based on the principle of sequentially removing amino acids from the N-terminal of a peptide and identifying them.

2. Firstly, the N-terminal of the peptide reacts with the Edman reagent (Phenylisothiocyanate), forming a stable ester compound.

3. Subsequently, under mild acidic conditions, this ester compound will break, releasing the derivatized amino acid formed with the Edman reagent. This process does not damage other parts of the peptide.

4. The released derivatized amino acid can be identified by chromatography or other methods.

5. By repeating the above process, the amino acid sequence of the peptide can be identified one by one.

 

Advantages

1. Specificity

The Edman degradation is very specific, targeting only the N-terminal amino acid.

 

2. Accuracy

Under ideal conditions, this method can provide very accurate sequencing results.

 

Limitations

1. Length Limit

Although this method is very accurate, it is usually only used for shorter peptide fragments, typically within 50-60 amino acids. For longer peptides or proteins, they need to be cut first and then sequenced separately.

 

2. Sensitivity

A sufficient amount of sample is required to ensure the accuracy of sequencing.

 

Applications

Although modern mass spectrometry techniques have become very popular in protein and peptide sequencing, the Edman degradation is still a valuable tool, especially when mass spectrometry methods are not applicable or when mass spectrometry results need to be verified.