Chem 336 - Spring 2000
Organic Chemistry III
Dr. Carl C. Wamser

Chapter 27 Quiz

1. (2 points) Write the structure of the dipeptide AspThr as it would appear in aqueous solution at pH 7. Stereochemistry need not be shown.

2. (4 points) Write complete sets of resonance forms to explain the following:

a) why there is restricted rotation around a peptide bond

b) why the side chain of arginine is so basic

3. (4 points) Identify the unknown hexapeptide from the following data:

o complete hydrolysis gives equimolar amounts of Arg, Glu, Lys, Phe, Pro, Tyr
o Edman degradation of the hexapeptide gives labeled Phe
o chymotrypsin cleavage gives a tetrapeptide, Phe, and Glu
o Edman degradation of the tetrapeptide gives labeled Lys
o trypsin cleavage gives three dipeptides
o Edman degradation of the dipeptides gives labeled Phe, Pro, and Tyr

PheLysProArgTyrGlu