I'm looking at a (uni) past paper and it has one of those typical Qs - a molecular weight determination has shown that an unknown peptide E is a pentapeptide and that it contains the amino acids glycine, tryptophan, proline, valine and alanine. Treatment of pentapeptide E with carboxypeptidase gives proline as the first free amino acid released. Separate Edman degradations provided the following derivatives: and it shows three compounds, with the first containing tryptophan, second just glycine, third valine. Based upon this analysis, draw the structure of the original pentapeptide and explain how you have arrived at this structure. Show mechanistic detail where appropriate (15 marks). Anyone know?