Chapter 25, Problem 75PP

Interpretation Introduction

Interpretation:

The initial PTH derivative formed when Ala-Phe-Val undergoes Edman degradation need to be drawn.

Concept introduction:

Edman degradation is a chemical reaction where the N-terminus amino acid is removed when the peptide is treated with phenyl isothiocyanate followed by treatment with trifluoroacetic acid to form phenylthiohydantoin(PTH) derivative and peptide with one amino acid residue less than the starting peptide.  This method can be used to identify the sequence of the amino acid in peptide as only one amino acid is removed each time forming the PTH derivative. The reaction takes place because the amino group is sufficiently nucleophilic to attack phenyl isothiocyanate.  The general scheme for Edman degradation can be shown as,

Please remember for Edman degradation reaction to take place the N-terminal of the peptides under consideration should be free.