Separation of the human transferrin isoforms by carrier-free high-performance zone electrophoresis and isoelectric focusing.

Human transferrin isoforms, i.e., molecules with different carbohydrate contents which differ from each other by only one negative charge, were resolved by high-performance zone electrophoresis in free solution. The di-, tri-, tetra-, penta-, hexa- and heptasialo transferrins could be assigned in the electrophoretic pattern. The pattern changed when iron-free transferrin was treated with neuraminidase, which splits off the sialic acid from the carbohydrate chains. The final digest contained transferrin molecules without sialic acids, as was confirmed by isoelectric focusing.