Electrochemistry of xanthine oxidase at glassy carbon and mercury electrodes

Rodrigues, Clyde G.; Wedd, Anthony G.; Bond, Alan M.

doi:10.1016/0022-0728(91)85148-i

Cited by 36 publications

(13 citation statements)

References 12 publications

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“…The ratio of the cathodic current over the anodic one is close to 1, suggesting that GOD undergoes a quasi-reversible redox process at the SWNT-modified electrode. The peak potential and the voltammetric characteristics are consistent with reported values for free FAD and the FAD redox center of the flavoenzyme [31,37]. The large background current is attributable to the catalytically active surface of the modified electrode.…”

Section: Direct Electrochemistry Of God At the Swnt-modified Au Electsupporting

confidence: 86%

Direct Electrochemistry of Glucose Oxidase at a Gold Electrode Modified with Single-Wall Carbon Nanotubes

Wang

Zhuo-bin

2003

Sensors

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The direct electrochemistry of glucose oxidase (GOD) was accomplished at a gold electrode modified with single-wall carbon nanotubes (SWNTs). A pair of welldefined redox peaks was obtained for GOD with the reduction peak potential at Ã¢Â€Â“0.465 V and a peak potential separation of 23 mV at pH 7.0. Both FT-IR spectra and the dependence of the reduction peak current on the scan rate revealed that GOD adsorbed onto the SWNT surfaces. The redox wave corresponds to the redox center of the flavin adenine dinucleotide(FAD) of the GOD adsorbate. The electron transfer rate of GOD redox reaction was greatly enhanced at the SWNT-modified electrode. The peak potential was shown to be pH dependent. Verified by spectral methods, the specific enzyme activity of GOD adsorbates at the SWNTs appears to be retained

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Section: Direct Electrochemistry Of God At the Swnt-modified Au Electsupporting

confidence: 86%

Direct Electrochemistry of Glucose Oxidase at a Gold Electrode Modified with Single-Wall Carbon Nanotubes

Wang

Zhuo-bin

2003

Sensors

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“…The FAD cofactor is noncovalently bonded to XO/XDH and may dissociate from the enzyme to give free FAD (which is also electroactive). A thorough and careful study revealed denaturation of bovine XO at a mercury electrode coupled with dissociation of the FAD cofactor . Dissociation of FAD should deactivate XO/XDH so proof of catalytic activity is important but is often overlooked. , Of equal concern are reports of XO/XDH catalytic electrochemistry with unnatural (and unprecedented) substrates, ,, which again cast doubt on whether a native and functional enzyme is being studied.…”

Section: Introductionmentioning

confidence: 99%

Xanthine Dehydrogenase Electrocatalysis: Autocatalysis and Novel Activity

2011

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The enzyme xanthine dehydrogenase (XDH) from the purple photosynthetic bacterium Rhodobacter capsulatus catalyzes the oxidation of hypoxanthine to xanthine and xanthine to uric acid as part of purine metabolism. The native electron acceptor is NAD(+) but herein we show that uric acid in its 2-electron oxidized form is able to act as an artificial electron acceptor from XDH in an electrochemically driven catalytic system. Hypoxanthine oxidation is also observed with the novel production of uric acid in a series of two consecutive 2-electron oxidation reactions via xanthine. XDH exhibits native activity in terms of its pH optimum and inhibition by allopurinol.

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“…Upon addition of 2 mM hypoxanthine in solution, the oxidation peak current of thionine increases, while the reversed reduction peak current decreases (blue curve), suggesting that thionine shuttles electron transfer between FAD centers in XOD and the electrode and thus facilitate the oxidation of hypoxanthine at the electrode through the XODbased catalytic cycle (Scheme 1B, inset). Note that the oxidation observed here could neither be attributed to the direct electrochemistry of XOD nor to the the oxidation of hypoxanthine at the SWNT-modified electrode because the direct electron transfer of FAD/FADH 2 of XOD and the direct oxidation of hypoxanthine at carbon nanotube-modified electrodes or other kinds of electrodes occurred at more negative potentials (approximately −0.40 V vs. Ag/AgCl) [37][38][39][40] and at more positive potentials (usually higher than 0.80 V vs. Ag/AgCl), [41][42][43] respectively.…”

Section: Thionine-mediated Electron Transfer Of Xodmentioning

confidence: 75%

Online electrochemical systems for continuous neurochemical measurements with low-potential mediator-based electrochemical biosensors as selective detectors

Zhang

Hao

Xiao

et al. 2015

Analyst

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This study demonstrates a new strategy to develop online electrochemical systems (OECSs) for continuously monitoring neurochemicals by efficiently integrating in vivo microdialysis with an oxidase-based electrochemical biosensor with low-potential electron mediators to shuttle the electron transfer of the oxidases. By using thionine and xanthine oxidase (XOD) as examples of low-potential mediators and oxidases, respectively, we demonstrate that the use of low-potential mediators to shuttle the electron transfer of oxidases would offer a new approach to the development of oxidase-based biosensors with theoretical and technical simplicity. To construct the XOD-based biosensor, thionine was adsorbed onto carbon nanotubes and used to shuttle the electron transfer of XOD. The XOD-based biosensor was positioned into an electrochemical cell that was directly coupled with in vivo microdialysis to form an online electrochemical system (OECS) for continuous and selective measurements of the substrate of XOD (with hypoxanthine as an example). The OECS based on the low-potential mediators is highly selective against the species endogenously existing in the brain system, which is attributed to the low operation potential benefited from the low redox potentials of the mediators. Moreover, the OECS demonstrated here is stable and reproducible and could thus be envisaged to find some interesting applications in physiological and pathological investigations. This study essentially offers a new strategy to develop online electrochemical systems, which is of great importance in understanding the molecular basis of physiological and pathological events.

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Electrochemistry of xanthine oxidase at glassy carbon and mercury electrodes

Cited by 36 publications

References 12 publications

Direct Electrochemistry of Glucose Oxidase at a Gold Electrode Modified with Single-Wall Carbon Nanotubes

Direct Electrochemistry of Glucose Oxidase at a Gold Electrode Modified with Single-Wall Carbon Nanotubes

Xanthine Dehydrogenase Electrocatalysis: Autocatalysis and Novel Activity

Online electrochemical systems for continuous neurochemical measurements with low-potential mediator-based electrochemical biosensors as selective detectors

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