EPR spectra manifested by CO dehydrogenase under various conditions of 100 μm CO dehydrogenase partially reduced by CO, H2, or dithionite.
A, CO-reduced CO dehydrogenase in 50 mm HEPES, pH 7.2, with simulation in red. B, H2-reduced CO dehydrogenase in 50 mm HEPES, pH 7.2, with simulation in red. C, H2-reduced CO dehydrogenase in 50 mm HEPES, pD 7.2, with simulation in red. D, dithionite-reduced CO dehydrogenase in 50 mm HEPES, pH 7.2. E, dithionite-reduced CO dehydrogenase in 50 mm HEPES, pD 7.2. F, spectrum E minus spectrum D. G, dithionite-reduced CO dehydrogenase in 400 mm bicarbonate, pH 8.0, with simulation in red. Brackets indicate approximate g1,2,3 values (dashed lines) with copper splittings (solid lines). The EPR instrument settings were: 9.45 GHz microwave frequency; 4 milliwatt microwave power; 5 Gauss modulation amplitude; 150 K.