Chapter 25, Problem 70PP

Interpretation Introduction

Interpretation:

Two structures of tripeptide that contains glycine, L-alanine and L-phenylalanine which does not react with phenyl isothiocyanate need to be proposed.

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 general scheme for Edman degradation can be shown as,

Please remember that if the amino group in the amino acid is protected or not free means the reaction won’t take place.

To propose : To propose two structures of tripeptides that do not react with phenyl isothiocyanate with the given amino acids.