Fig. 3: EPR spectra of Eu(II)–DTPA-reduced CODH and additional Cint states of the C cluster.
From: Metalloradical-driven enzymatic CO2 reduction by a dynamic Ni–Fe cluster
a, EPR spectra of crystals treated with Eu(II)–DTPA under different conditions. The EPR spectra were recorded at 10 K and 0.063 mW. The rhombic signals from Cred2 (blue), Cred2′ (light blue), Bred (dark cyan) and CredΔNi (violet) were simulated. The deconvoluted spectra are presented in Extended Data Fig. 8. b, Structure (left) and electron density map (right) of Eu(II)–DTPA-treated crystals at pH 6.0. The σA-weighted 2Fo − Fc map (blue mesh) is contoured at 3.0σ. Multiple crystals treated in the same way reproduced the shown structure, which has occupancies of 0.78 for both Ni,A and Fe1,i. c, Scheme showing the interconversion of the three observed Cint states, referred to as Cint,o for the OH-bound Cint state, Cint,i for the state with a short Ni–Fe1 distance devoid of an OH ligand and Cint,o–CO for the CO-bound state. d, The inward movement of Fe1 and its coordinating histidine (His261) on transitioning between its ‘in’ and ‘out’ positions. The Ti(III)-reduced pH 8.0 sample (Cint,o state) is shown in violet and the Eu(II)-reduced pH 6.0 sample (Cint,i state) is shown in blue. The σA-weighted 2Fo − Fc maps (blue mesh, Ti(III)-reduced pH 8.0; orange mesh, Eu(II)-reduced pH 6.0) are contoured at 1.0σ. For Eu(II)–DTPA at pH 8.0 and pH 6.0, the crystals were chemically poised at −660 and −632 mV versus SHE, respectively.
