Fig. 2.

Mössbauer spectra of as-purified SPL: (A) as-purified with 3 mM SAM (B), photo-reduced with 5-deazariboflavin in the presence of 5 mM DTT (C), and photo-reduced sample with 3 mM SAM (D). The spectra (hatched marks) were recorded at 4.2 K in a magnetic field of 50 mT applied parallel to the γ radiation. The solid lines plotted above the data are simulated spectra for the [2Fe-2S]²⁺ clusters (red), [4Fe-4S]²⁺ clusters (blue), [4Fe-4S]⁺ clusters (cyan), N/O-coordinated Fe²⁺ (green), S- coordinated Fe²⁺ (magenta), and fast relaxing Fe³⁺ (orange). The black lines overlaid with the experimental spectra in C and D are composite spectra. Parameters used for the simulations are given in the text