Electrical connection of enzyme redox centers to electrodes

Heller, Adam

doi:10.1021/j100188a007

Cited by 608 publications

(363 citation statements)

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“…Cyclic voltammetry (19,(34)(35)(36)(37) and spectroelectrochemical measurements (38)(39)(40)(41)(42)(43) of actively respiring Geobacter biofilms are consistent with long-range electron transport mediated by sequential electron transfer reactions through a network of bound redox cofactors comprised of ECM c-type cytochromes terminating with electron transfer to the anode surface. This proposed process, analogous to diffusive electron transport observed for redox polymers containing discrete redox moieties (20,(44)(45)(46)(47)(48), is an extension of the normal mode of electron transport in biological systems involving redox proteins (2) to longer length scales (up to 18 μm in the case of biofilms described here).…”

mentioning

confidence: 62%

Long-range electron transport in Geobacter sulfurreducens biofilms is redox gradient-driven

Snider

Glaven

Tsoi

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

234

210

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Geobacter spp. can acquire energy by coupling intracellular oxidation of organic matter with extracellular electron transfer to an anode (an electrode poised at a metabolically oxidizing potential), forming a biofilm extending many cell lengths away from the anode surface. It has been proposed that long-range electron transport in such biofilms occurs through a network of bound redox cofactors, thought to involve extracellular matrix c-type cytochromes, as occurs for polymers containing discrete redox moieties. Here, we report measurements of electron transport in actively respiring Geobacter sulfurreducens wild type biofilms using interdigitated microelectrode arrays. Measurements when one electrode is used as an anode and the other electrode is used to monitor redox status of the biofilm 15 μm away indicate the presence of an intrabiofilm redox gradient, in which the concentration of electrons residing within the proposed redox cofactor network is higher farther from the anode surface. The magnitude of the redox gradient seems to correlate with current, which is consistent with electron transport from cells in the biofilm to the anode, where electrons effectively diffuse from areas of high to low concentration, hopping between redox cofactors. Comparison with gate measurements, when one electrode is used as an electron source and the other electrode is used as an electron drain, suggests that there are multiple types of redox cofactors in Geobacter biofilms spanning a range in oxidation potential that can engage in electron transport. The majority of these redox cofactors, however, seem to have oxidation potentials too negative to be involved in electron transport when acetate is the electron source.microbial fuel cell | bioelectrochemical system | microbial electrochemistry | geomicrobiology | multistep electron hopping

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mentioning

confidence: 62%

Long-range electron transport in Geobacter sulfurreducens biofilms is redox gradient-driven

Snider

Glaven

Tsoi

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

234

210

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“…ET can be achieved directly (direct electron transfer, DET) or by the use of mediators (mediated electron transfer, MET) to shuttle electrons between the redox centre of the enzyme and the electrode. However, mediators are unselective and can also give rise to interfering effects [1][2][3]. DET-based devices offer high selectivity and sensitivity due to the absence of mediators.…”

Section: Introductionmentioning

confidence: 99%

Direct electron transfer of Trametes hirsuta laccase adsorbed at unmodified nanoporous gold electrodes

Salaj-Kośla

Pöller

Schuhmann

et al. 2013

Bioelectrochemistry

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The enzyme Trametes hirsuta laccase undergoes direct electron transfer at unmodified nanoporous gold electrodes, displaying a current density of 28 A/cm 2 . The response indicates that ThLc was immobilised at the surface of the nanopores in a manner which promoted direct electron transfer, in contrast to the absence of a response at unmodified polycrystalline gold electrodes. The bioelectrocatalytic activity of ThLc modified nanoporous gold electrodes was strongly dependent on the presence of halide ions. Fluoride completely inhibited the enzymatic response, whereas in the presence of 150 mM Cl -, the current was reduced to 50% of the response in the absence of Cl -. The current increased by 40% when the temperature was increased from 20°C to 37°C. The response is limited by enzymatic and/or enzyme electrode kinetics and is 30% of that observed for ThLc co-immobilised with an osmium redox polymer. Keywords: Laccase, direct electron transfer, nanoporous gold 2 IntroductionElectron transfer (ET) reactions are ubiquitous in nature. Controlling the rate of these reactions can be of significant benefit in developing biochemical systems that utilise redox proteins and enzymes and in particular, in applications that provide power for implanted or portable electronic devices. ET can be achieved directly (direct electron transfer, DET) or by the use of mediators (mediated electron transfer, MET) to shuttle electrons between the redox centre of the enzyme and the electrode. However, mediators are unselective and can also give rise to interfering effects [1][2][3]. DET-based devices offer high selectivity and sensitivity due to the absence of mediators. In addition, devices based on DET operate at potentials close to the redox potential of the enzyme, maximising the potential difference between the cathode and anode for biofuel cell applications [2]. Moreover, DET can be used to provide detailed information on the kinetics and thermodynamics of the ET process. However, the low stability of the enzyme layer together with the long distances over which ET occurs, represent major obstacles for DET based devices. In addition, the shielding mechanism of the enzymatic redox centre by the protein shell can disrupt DET [2,4]. One approach in optimizing and enabling rapid DET is to design the electrode surface with an architecture which promotes efficient rates of ET. In this way the electrode morphology ensures the most efficient orientation of the enzymatic redox centre and facilitates communication with the electroactive surface. Porous electrodes can be used to encapsulate the enzyme within a network of cavities, shortening the distance for electron transfer to the redox active site, which will promote more efficient and rapid rates of electron transfer [5]. However, the number of redox enzymes capable of interacting directly with the electrode while catalyzing the enzymatic reaction is limited, with estimates of approximately 5% of all enzymes exhibiting such a response [6].DET in enzymes was first described in 1978 fo...

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“…These PBFCs require the immobilization and electrical contacting of the light harnessing components with the electrode supports to the extent that photo-induced electrontransfer processes occur between the photosynthetic RC, thus enabling the generation of photocurrents (or their use for the synthesis of fuel products). The electrical contacting of redox proteins with electrodes attracted substantial research efforts directed to the development of amperometric biosensors [26][27][28][29] or biofuel cell elements [30][31][32][33][34][35] . Different methods to integrate redox proteins with electrodes in electrically contacted configurations were developed, including the modification of the proteins with relay units 36,37 , the reconstitution of the proteins on relay-cofactor units [38][39][40] and the immobilization of the proteins in redox-active polymer matrices 41 .…”

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confidence: 99%

Integrated photosystem II-based photo-bioelectrochemical cells

et al. 2012

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Photosynthesis is a sustainable process that converts light energy into chemical energy. substantial research efforts are directed towards the application of the photosynthetic reaction centres, photosystems I and II, as active components for the light-induced generation of electrical power or fuel products. nonetheless, no integrated photo-bioelectrochemical device that produces electrical power, upon irradiation of an aqueous solution that includes two inter-connected electrodes is known. Here we report the assembly of photobiofuel cells that generate electricity upon irradiation of biomaterial-functionalized electrodes in aqueous solutions. The cells are composed of electrically contacted photosystem II-functionalized photoanodes and an electrically wired bilirubin oxidase/carbon nanotubes-modified cathode. Illumination of the photoanodes yields the oxidation of water to o 2 and the transfer of electrons through the external circuit to the cathode, where o 2 is re-reduced to water.

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Electrical connection of enzyme redox centers to electrodes

Cited by 608 publications

References 6 publications

Long-range electron transport in Geobacter sulfurreducens biofilms is redox gradient-driven

Long-range electron transport in Geobacter sulfurreducens biofilms is redox gradient-driven

Direct electron transfer of Trametes hirsuta laccase adsorbed at unmodified nanoporous gold electrodes

Integrated photosystem II-based photo-bioelectrochemical cells

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