Organic Chemistry III
	Professor Carl C. Wamser
Chem 336 - Spring 2008	Quiz 27

1. (2 points) Write the structure of the dipeptide Ser-Pro as it would be at pH = 7, including stereochemistry.

2. (2 points) Write the expected structures, including stereochemistry, of each amino acid as it would exist at its pI:

a) Tyr ( pI = 5.66 )

b) Arg ( pI = 10.76 )

3. (3 points) Write out the complete side chain structures to illustrate the following types of interactions:

a) H-bonding between Gln and Thr

b) covalent bonding between Cys and Cys

c) Coulombic (charge) attraction between Lys and Asp

4. (3 points) Identify the unknown pentapeptide based on the following observations.

Complete hydrolysis releases Ala, Ile, Lys, Trp, Val .
Edman analysis releases Ile .
Carboxypeptidase releases Ala .
Trypsin generates a dipeptide (A) and a tripeptide (B).
Chymotrypsin generates a dipeptide (C) and a tripeptide (D).
Both A and D are shown to have Ile at their N-terminus.

Ile - Lys - Trp - Val - Ala