Drawing Amino Acids (Organic Chem)

Question

Draw the tetrapeptide below out in full chemical structure by attaching the four amino acids from your amino in order (this is an application of the characteristic organic reaction Formation of an Amide. You can use any chemical notation or combination of notations to draw your structure, but all bonds and atoms must be shown.

Tyr-Cys-Met-His

Answer 1

Part one

1. Starting from left of your sequence: Tyr-Cys-Met-His.
2. Use the zip zap chain format, put down the first amino acid structure, Tyrosine. Convention dictates that the amino group to the left and the carboxylic acid to the right.
3. picture of tyrosine.
4. Focus on the amino-acid chain, extend the chain to include all four amino acid.
5. Draw the peptide bonds within the chain - first the carbonyl, then the N peptide bond.
6. Make sure the number of the peptide bond is right - 4 a.a. has 3 peptide bonds, (n-1 for linear peptide, no cyclic or branch)
7. Attach the different side chain for each of the corresponding amino acid, it is up and down and up and down the chain. Do you notice that the peptide has amino group to the left and carboxylic acid group to the right, just like the mono amino acid in step 3 such that you can keep adding more amino acid to the tetrapeptide.
8. Last step is to make sure the stereochemistry of the R groups is correctly indicated. (natural amino acid is L not D.amino acid. And most of them has the S absolute configuration)
9. see the steps in drawing: (step 7 is skipped so you can determine the stereochemistry of the side chain, R for yourself.

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