Binding and Direct Electrochemistry of OmcA, an Outer-Membrane Cytochrome from an Iron Reducing Bacterium, with Oxide Electrodes: A Candidate Biofuel Cell System
Journal Article
·
· Inorganica Chimica Acta, 361(3):769-777
Dissimilatory iron-reducing bacteria transfer electrons to solid ferric respiratory electron acceptors. Outer-membrane cytochromes expressed by these organisms are of interest in both microbial fuel cells and biofuel cells. We use optical waveguide lightmode spectroscopy (OWLS) to show that OmcA, an 85 kDa decaheme outer-membrane c-type cytochrome from Shewanella oneidensis MR-1, adsorbs to isostructural Al2O3 and Fe2O3 in similar amounts. Adsorption is ionic-strength and pH dependent (peak adsorption at pH 6.5–7.0). The thickness of the OmcA layer on Al2O3 at pH 7.0 [5.8 ± 1.1 (2r) nm] from OWLS is similar, within error, to that observed using atomic force microscopy (4.8 ± 2 nm). The highest adsorption density observed was 334 ng cm 2 (2.4 · 1012 molecules cm 2), corresponding to a monolayer or 9.9 nm diameter spheres or submonolayer coverage by smaller molecules. Direct electrochemistry of OmcA on Fe2O3 electrodes was observed using cyclic voltammetry, with cathodic peak potentials of 380 to 320 mV versus Ag/AgCl. Variations in the cathodic peak positions are speculatively attributed to redox-linked conformation change or changes in molecular orientation. OmcA can exchange electrons with ITO electrodes at higher current densities than with Fe2O3. Overall, OmcA can bind to and exchange electrons with several oxides, and thus its utility in fuel cells is not restricted to Fe2O3.
- Research Organization:
- Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 924359
- Report Number(s):
- PNNL-SA-56726; 9593; 6504; 13892; 13890; 13494; 13492; 13302; 13092; 12496; 19842; 19820
- Journal Information:
- Inorganica Chimica Acta, 361(3):769-777, Journal Name: Inorganica Chimica Acta, 361(3):769-777
- Country of Publication:
- United States
- Language:
- English
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