Chemistry 332 - Spring 1996
Elements of Organic Chemistry II
Homework, Chapter 15 - Amino Acids and Proteins
McMurry, pp 469-472:
Problems 15.18-24, 26, 30, 32, 34, 40, 42, 43, 45-47
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 Ala2, Lys, Glu, Phe, Cys.
Edman degradation releases Ala followed by Cys.
(indicates N-terminus is Ala and Cys is next to it)
Chymotrypsin hydrolysis gives two tripeptides, both of which have Ala at
their N-termini.
(indicates the Phe is next to Ala, also the Phe-Ala bond is in the center
of the hexapeptide)
Trypsin hydrolysis gives a pentapeptide plus Glu.
(indicates the Lys is next to Glu, which must be the C-terminus)
Identify the amino acid sequence of the hexapeptide.
Ala-Cys-Phe-Ala-Lys-Glu