Question

As part of a purification technique, a mixture of small-protein hormones and peptides are placed in a gel and exposed to an electric field. The gel was prepared using a buffer at pH 2. One peptide in the mixture is the tetrapeptide Ala-Val-Ile-Leu. This peptide will move through the gel toward the _____ terminal.

positive
negative

Answer 1

The correct answer is "negative".

Step-by-step explanation:

At pH 2 the net charge of the R groups of all the amino acids that comprise the peptide in question would be positive. This happens because of the high content of protons in a solution of pH 2, a value that is below the isoelectric point of all the amino acids. Since the peptide would have a positive net charge, it would migrate to the negative terminal of the gel because opposite charges attract each other.