Figure 7. UV-VIS light absorption spectra of tyrosyl radical iron cluster formation and reduction.

Light absorption spectra of metal-free EBV R2 before (dashed-line) and after reconstitution of the diferric (Fe³⁺–O²⁻–Fe³⁺) metal site (light-grey line). Representative spectrum obtained under anaerobic conditions for the incubation of reconstituted EBV R2 with 4 mM HU recorded after 200 s (dark grey line) and after 20 min (black line), T = 277 K. The inset shows the resulting spectra obtained at higher temperature (T = 293 K), before (light-grey line) and after anaerobic incubation with HU (200 s, dark grey line; 400 s, black line). The protein concentration was ∼130 µM in a pH 7.5, 50 mM HEPES buffer.