Question

Draw the structure of the N-phenylthiohydantoin formed by initial Edman degradation of each peptide: (a) Ala-Gly-Phe-Phe; (b) Val-Ile-Tyr.

Short answer

a.

b.

Step-by-step solution

Edman Degradation

Edman degradation is a technique to cleave amino acids from the N-terminal of the peptide chain, and the process continues until the whole sequence is known.

There are two products formed by Edman degradation, one is N-phenylthiohydantoin, and the other is a new peptide chain with one less amino acid.

Structure of the N-phenylthiohydantoin formed by initial Edman degradation of Ala-Gly-Phe-Phe.

(a) The initial Edman degradation of Ala-Gly-Phe-Phe is done by cleaving amino acid from N-terminal.

Structure of N-phenylthiohydantoin

Structure of the N-phenylthiohydantoin formed by initial Edman degradation of Val-Ile-Tyr.

(b) The initial Edman degradation of Val-Ile-Tyr is done by removing N-terminal amino acid from the peptide chain.

Structure of N-phenylthiohydantoin