Figure 2.

UV–visible spectra of nitrous oxide reductase purified in the presence of oxygen from (a) an aerobic culture; (b) an ‘anaerobic1’ culture and (c) an ‘anaerobic2’ culture. In each panel the spectra of the (i) fully oxidized, (ii) as-isolated, (iii) ascorbate-reduced and (iv) dithionite-reduced forms of the enzyme are presented. (d) Difference spectra between fully oxidized and the ascorbate-reduced forms for the (i) ‘aerobic’ (solid line) (ii) ‘anaerobic1’ (thick line) and (iii) ‘anaerobic2’ (dotted line) N₂OR samples.