What Does Edman Degradation Reveal About Peptide Sequence?

In summary, the conversation discusses the analysis of an unknown pentapeptide, E, which has been determined to contain the amino acids glycine, tryptophan, proline, valine, and alanine. Treatment with carboxypeptidase reveals proline as the first free amino acid released. Separate Edman degradations of the pentapeptide provide derivatives that confirm the presence of tryptophan, glycine, and valine in the original structure. The conversation also raises questions about the specific flavor of carboxypeptidase used and the definition of "Separate Edman degradations."
  • #1
chem_monkey
3
0
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?
 
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  • #2
Which flavor of Carboxypeptidase are you using? "Separate Edman degradations..." refers to what?
 
  • #3
chemisttree said:
Which flavor of Carboxypeptidase are you using? "Separate Edman degradations..." refers to what?

what flavor?
 

Related to What Does Edman Degradation Reveal About Peptide Sequence?

1. What is Edman degradation?

Edman degradation is a chemical technique used for identifying and sequencing amino acids in a protein. It involves the selective removal of one amino acid at a time from the N-terminus (the end of the protein chain with a free amino group) and then analyzing it to determine its identity.

2. How does Edman degradation work?

Edman degradation works by reacting the protein with a reagent called phenylisothiocyanate, which binds to the N-terminus of the protein. This creates a cyclic thiohydantoin derivative that can be cleaved off and analyzed. The process is repeated multiple times, each time removing one amino acid at a time, until the entire sequence is determined.

3. What are the advantages of using Edman degradation?

Edman degradation is advantageous because it is a relatively simple and efficient method for determining the sequence of amino acids in a protein. It also does not require a large amount of starting material and can be automated for high-throughput analysis.

4. What are the limitations of Edman degradation?

One of the main limitations of Edman degradation is that it can only sequence up to about 50 amino acids before the cyclic derivative becomes too unstable to continue. It is also not suitable for proteins with multiple N-termini or post-translational modifications, and can be affected by impurities or secondary structures in the protein sample.

5. What are some applications of Edman degradation?

Edman degradation has been widely used in protein structure and function studies, as well as in the characterization of peptides and small proteins. It has also been used in the development of new drugs, specifically in the identification and sequencing of peptide hormones and neuropeptides. Additionally, it has been used in forensic science for the identification of proteins in crime scene evidence.

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