FIG. 3.

EPR spectra of CODH I (A) and CODH II (B). CODH I (3.8 mg ml⁻¹) or CODH II (3.1 mg ml⁻¹) were in 50 mM Tris-HCl (pH 8.0). Traces: (a and e) as-isolated freshly prepared enzyme was frozen under N₂; (b and f) air-oxidized as-isolated enzyme was kept under air for 12 h at 4°C; (c and g) CO-reduced as-isolated enzyme was kept under pure CO for 60 min at 50°C; (d and h) dithionite-reduced as-isolated enzyme was treated with 4 mM dithionite under pure N₂. The relevant g values are indicated in the spectra. General conditions: 10 mW microwave power; 10 G modulation amplitude; 9.47 GHz microwave frequency; temperatures (in degrees K) as indicated.