Figure 5.

Comparison of the Mössbauer spectra of ⁵⁷Fe-labeled [2Fe-2S] Grx3 and [2Fe-2S] Fra2-Grx3. Samples were ~ 2 mM in [2⁵⁷Fe-2S] clusters. Spectra were recorded at 4.2 K with a magnetic field of 50 mT applied parallel to the γ-radiation. The solid black lines are theoretical simulations of the [2Fe-2S]²⁺ cluster spectra using two unresolved equal-intensity doublets, with the parameters listed in Table 3. Contributions from a minor mononuclear high-spin Fe(II) species (10% of total ⁵⁷Fe for [2Fe-2S] Grx3 and 3% of the total ⁵⁷Fe for [2Fe-2S] Fra2-Grx3) have been removed from the spectra. Parameters used for the Fe(II) species are ΔE_Q = 2.96 mm/s and δ = 1.21 mm/s.