Question

Peptides can be separated using an ion-exchange column based on their isoelectric (pl) values. At which pH values would two different peptides, one with a pl of 5.0 and the other with a pl of 9.2, bind to a cation- and anion-exchange column? Each peptide may be capable of binding to each column at more than one pH value. anion-exchange column at pH = 3.0 cation-exchange column at pH = 3.0 Answer Bank peptide B pI = 9.2 peptide A pl = 5.0 pH = 6.9 pH = 6.9 pH = 10.5 pH = 10.5

Answer 1

Solution :

we know that the pH > pl then protein has net negative charge and its get binded to anion exchange coloumn and when the pH < pl then  peptide has net positive charge and peptide gets binded to cation exchange column

Anion exchange for protein A

a) pH = 3.0, Peptide A (pI = 5.0), Positive charge --> no bind

b) pH = 6.9, Peptide A (pI = 5.0), Negative Charge -->  binds

c) pH = 10.5, Peptide A (pI = 5.0), Negative charge --> binds

Canion exchange for protein A

a) pH = 3.0, Peptide A (pI = 5.0), Positive charge --> binds

b) pH = 6.9, Peptide A (pI = 5.0), Negative Charge --> will not bind

c) pH = 10.5, Peptide A (pI = 5.0), Negative charge --> will not bind

For Protein B; Anion Exchanger:

a) pH = 3.0, Peptide B (pI = 9.2), Positive charge --> no bind

b) pH = 6.9, Peptide B (pI = 9.2), Positive charge --> no bind

c) pH = 10.5, Peptide B (pI = 9.2), Negative charge --> will bind

For Protein B; Canion Exchanger:

a) pH = 3.0, Peptide B (pI = 9.2), Positive charge --> binds

b) pH = 6.9, Peptide B (pI = 9.2), Positive charge --> binds

c) pH = 10.5, Peptide B (pI = 9.2), Negative charge --> no bind