Question

Peptides can be separated using an ion‑exchange column based on their isoelectric (pI) values. At which pH values would two different peptides, one with a pI of 5.5 and the other with a pI of 9.1 , bind to a cation‑ and anion‑exchange column? Each peptide may be capable of binding to each column at more than one pH value.

Answer 1

Answer:

The ansers are in the explanation.

Explanation:

The isoelectric point of a peptide is the pH in which this compound will be electrically neutral. When the pH is lower than pI, the peptide will be a cation. when the pH is higher than pI, the peptide will be as an anion.

Cation‑ and anion‑exchange columns are chromatography columns that allows the separation of substances based in their charges. A cation-exchange column will bind to positively charges molecules and an anion-exchange column will bind with negatively charges molecules.

Thus, the peptide with pI of 5,5 will bind with cation-exchange column at pH's lowers than 5,5 and will bind with anion-exchange column at pH's highers than 5,5.

In the same way, the peptide with pI of 9,1 will bind with cation-exchange column at pH's lowers than 9,1 and will bind with anion-exchange column at pH's highers than 9,1.

I hope it helps!