How does the relationship between pH and pI affect protein migration in an electric field during isoelectric focusing?

• A. Proteins migrate faster when the pH is equal to their pI.
• B. Proteins become denatured when the pH is equal to their pI.
• C. Proteins stop migrating when the pH equals their pI because they have no net charge.
• D. Proteins migrate towards the cathode when the pH is equal to their pI.

Answer: (C)