Iron saturation of transferrin following incubation with A. fumigatus siderophores. Purified desferrisiderophores were incubated with holotransferrin (25 μM) at 37°C for 16 h. Desferriferrichrome, desferriferricrocin, and desferritriacetylfusarinine C were serially diluted to final concentrations of 5 μM (lanes 1), 50 μM (lanes 2), 500 μM (lanes 3), and 5 mM (lanes 4). Controls containing holotransferrin alone also were run (lanes 0). holo-Tf, holotransferrin; Fe-Tf, monoferric transferrin; apo-Tf, apotransferrin.