Question

Can you separate a mixture of the following three proteins using membrane electrophoresis? Protein A has a pI > pH of the run buffer, Protein B has a pI < the pH of the run buffer, and Protein C has a pI = pH of the run buffer. If so, describe the movement of each protein.

Answer 1

pI of a protein is the pH of the protein solution at which there is no net charge on protein. When pH>pI, the protein acquires negative charge and moves towards anode under electric potential.
When pH<pI , the protein acquires positive charge and moves towards cathode.
Thus,protein A has pI>pH and this has positive charge and moves towards cathode..Protein B has pI<pH ,so it has negative charge and moves towards the positive terminal anode. Protein C has no net charge and this does not move under electric potential.
In this way separation can be done.