Figure 4. EPR spectra of Fe³⁺ and Fe³⁺–enterobactin bound to FrpB.

EPR spectra are shown of 130 µM ferric-enterobactin (top), 130 µM ferric-enterobactin plus 130 µM FrpB F3-3 (middle) and 150 µM FrpB F3-3 which had been pre-incubated with Fe³⁺, followed by dialysis to remove unbound iron (bottom).