Fig. 1.

Serum transferrin isoelectric focusing (TIEF) gels with the number of terminal sialic acid residues indicated at the left and right side (0 to 5). Lanes 1 and 3: normal pattern; lane 2: CDG-I pattern (elevated asialo- and disialotransferrin bands); lanes 4, 5, 7 and 8: CDG-II pattern (additional increase of monosialo- and trisialotransferrin bands). Lane 6: mild CDG-I profile, resembles mild CDG-II pattern. Lane 7: combined CDG-I and -II profile. Lanes 8 to 11: transferrin before and after neuraminidase treatment (+n) for CDG-II defect MAN1B1-CDG and a polymorphism of transferrin, respectively. Two bands instead of one band will become visible when treating a transferrin polymorphism with neuraminidase