Chemistry 332 - Spring 1996
Elements of Organic Chemistry II


Quiz, Chapter 15 - Amino Acids and Proteins

1. (2 points) Write the structure of tryptophane as it would be expected at pH 7.



2. (2 points) Write the structure of lysine as it would be expected at its isoelectric point.



3. (2 points) Select specific pairs of amino acids that could give rise to the following kinds of interactions that could contribute to a protein's tertiary structure.

example - disulfide linkages Cys - - Cys

a) hydrogen bonding

LOTS OF POSSIBILITIES - basically any two polar side chains, e.g., Thr - - Tyr

b) charge-charge interactions

SEVERAL POSSIBILITIES - an anionic side chain (Asp or Glu) and a cationic side chain (Arg, Lys, or His)

4. (4 points) An unknown tetrapeptide is found to contain one equivalent each of Arg, Cys, Gly, and Leu. Edman degradation releases Gly. Trypsin gives no apparent reaction. Partial hydrolysis in acid gives several dipeptides, including CysArg and LeuCys. Identify the structure of the tetrapeptide. Use the standard abbreviations and give the full name for the tetrapeptide.

Gly-Leu-Cys-Arg

glycylleucylcystylarginine