What primarily determines the migration of hemoglobin during electrophoresis?

• A. Molecular weight
• B. Net charge at the pH
• C. Hydrophobicity
• D. Size

Answer: (B)

Migration in electrophoresis is driven by the electric force on charged particles, so at a given buffer pH, the net charge of the molecule determines how fast and in what direction it moves. Hemoglobin variants differ mainly in their net charge because of specific amino acid substitutions, which changes how strongly they are pulled by the electric field. Since their molecular weights and overall sizes are quite similar, those factors have much less influence on their movement in this context. Hydrophobicity isn’t a primary driver for this type of separation. The pH sets the ionization state, and at typical electrophoresis buffers, the net charge dictates the pattern of migration—the more negative the net charge, the faster the migration toward the positive electrode.