Figure 4. Protein film electrochemistry used to probe enzyme-catalysed redox half-reactions.

(A) Work from Elliott et al. demonstrating nitrate reduction by the NarGHI subcomplex of E. coli nitrate reductase in the presence of 1 mM $\mathrm{N}{\mathrm{O}}_3^{-}$ at pH 7, 30°C, adapted with permission from ref. [27]. Copyright 2014 American Chemical Society. (B) Data from Bassegoda et al. showing reversible interconversion of CO₂ and formate by E. coli Mo-containing formate dehydrogenase in the presence of 1 mM CO₂ and 1 mM formate at pH 6.8, 23°C (dark scan recorded first; subsequent scans showing evidence of enzyme desorption are shown in grey) adapted with permission from ref. [28]. (C) Work from Lauterbach et al. showing reversible NAD⁺/NADH cycling by the NAD⁺-reducing HoxFU moiety of R. eutropha soluble hydrogenase in the presence of 1 mM NAD⁺ and 1 mM NADH at pH 8, 30°C, adapted with permission from ref. [29].