Organic Chemistry 354 Quiz - December 5, 2000

Dr. Sundin

1. A nonapeptide gave the following amino acids on complete hdrolysis:

Ala = 2; Gly = 2; Phe = 1; Pro = 2; and Ser = 2.

Edman degradation gave Gly while carboxypeptidase A gave Ser. Partial hydrolysis gave a complex mixture from which only five tripeptides (see below) were isolated. Give the structure of the nonapeptide.

tripeptides:

Ala-Ala-Pro
Gly-Ser-Pro
Pro-Ala-Ala
Pro-Phe-Ser
Ser-Pro-Ala

Answer

2. Bradykinin, a nonapeptide, is a smooth muscle hypotensive agent. In an attempt to understand its behavior, a number of derivatives were synthesized for a structure-reactivity correlation study.

a. Derivative A had 1/300th the magnitude of the biological activity (rat uterus) of bradykinin. Determine its amino acid sequence based on the analytical data below.

Complete hydrolysis: Ala = 1; Arg = 2; Gly = 1; Phe = 2; Pro = 2; Ser = 1

Both Edman degradation and carboxypeptidase A gave Arg. Partial hydrolysis gave a complex mixture from which only three tripeptides (see below) were isolated in high enough yield and purity to be characterized. They are:

  • Ala-Pro-Gly
  • Pro-Gly-Phe
  • Pro-Phe-Arg

Chymotrypsin hydrolysis gave two oligopeptide fragments which had the following composition:

  • A pentapeptide containing Ala, Arg, Gly, Phe, Pro
  • A tripeptide containing Phe, Pro, Ser

Answer

| Chemistry Home | Dr. Sundin Home | Chemistry 354 | Sample Exams and Quizzes | sundin@uwplatt.edu |