Chem 336 - Spring 2002
Organic Chemistry III
Dr. Carl C. Wamser
Carey, pages 1106 - 1108:
Problems 27.24 - 40
1. Write the structure of the tripeptide alanylprolyllysine, as it would appear at pH 7.
After acid hydrolysis into individual amino acids, show the products as they would appear at pH 1.
2. Show how you might start with a dipeptide, isoleucylglutamine, and specifically add a methionine to the N-terminus. Repeat for the C-terminus.
3. An unknown hexapeptide is determined by complete hydrolysis to have the amino acid composition Ala (2), Lys, Glu, Phe, Cys.
Edman degradation releases Ala followed by Cys.
Chymotrypsin hydrolysis gives two tripeptides, both of which have Ala at their N-termini.
Trypsin hydrolysis gives a pentapeptide plus Glu.
Identify the amino acid sequence of the hexapeptide.
4. Sickle cell anemia is a genetic defect in the structure of hemoglobin, in which just one amino acid is altered. One glutamic acid is replaced by a valine. Describe why this change could be so serious for the protein tertiary structure. Suggest a possible code in the DNA that might have been altered in order to read Val instead of Glu.
5. Some codons can be deduced from simple homopolynucleic acids, e.g., poly-A.
Explain. Identify the four amino acid codes that can be deduced this way.