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 5.55.5 and the other with a pI of 9.29.2 , 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:

At pH of 3.6, Peptide A and B will bind to the anion-exchange column, while neither peptide will bind to the cation-exchange column.

At pH of 6.6, Peptide A will bind to the cation-exchange column while Peptide B will bind to the anion-exchange column.

At pH of 10.0, Peptide A and B will bind to the cation-exchange column, whereas  neither peptide will bind to the anion-exchange column.

Note: The question is incomplete. A sample complete question is found in the attachment below.

Explanation:

If pH is greater than pI, the net charge on the peptide is negative.

When pH = pI, the net charge is zero

When pH is less than pI, the net charge on the peptide is positive.

A positively charged peptide will bind to an anion-exchange column, whereas a negatively charged peptide will bind to a cation-exchange column.

At pH of 3.6, Peptide A and B will bind to the anion-exchange column, while neither peptide will bind to the cation-exchange column.

At pH of 6.6, Peptide A will bind to the cation-exchange column while Peptide B will bind to the anion-exchange column.

At pH of 10.0, Peptide A and B will bind to the cation-exchange column, whereas  neither peptide will bind to the anion-exchange column.