Question

A scientist is conducting a Sanger's sequencing experiment to determine the number of polypeptides present in an oligomeric protein. The molecular weight of the protein is 18000 g/mol . After the reaction of 520 mg of the protein with 1‑fluoro‑2,4‑dinitrobenzene, the peptide bonds were hydrolyzed with an acid. As a result, the scientist obtained 39 mg of 2,4‑dinitrophenyl serine. What is the number of the polypeptide chains present in the oligomer?

Answer 1

To determine the number of polypeptide chains present in the oligomeric protein, we need to consider the reaction with Sanger's reagent. The number of polypeptide chains is equal to the number of N-terminal amino acids, which can be calculated based on the amount of 2,4-dinitrophenyl serine obtained in the experiment.

Step-by-step explanation:

Number of Polypeptide Chains

To determine the number of polypeptide chains present in the oligomeric protein, we need to consider the reaction with Sanger's reagent. This reagent reacts with the N-terminal amino acid in proteins. In the given experiment, the scientist obtained 39 mg of 2,4-dinitrophenyl serine after hydrolyzing the peptide bonds. The molecular weight of 2,4-dinitrophenyl serine is 350 g/mol.

We can calculate the number of moles of 2,4-dinitrophenyl serine by dividing its mass by its molecular weight: 39 mg / 350 g/mol = 0.111 mol. Since 1 mole of 2,4-dinitrophenyl serine corresponds to 1 mole of N-terminal amino acid, we can conclude that there are 0.111 moles of N-terminal amino acid in the oligomeric protein.

Each polypeptide chain starts with an N-terminal amino acid. Therefore, the number of polypeptide chains present in the oligomer is equal to the number of N-terminal amino acids. Hence, in this case, there are 0.111 polypeptide chains present in the oligomer.