Bilirubin oxidase labeling triggers an efficient signaling mechanism of oxygen reduction reaction for smart photocathodic immunoassay

2021 ◽  
Vol 330 ◽  
pp. 129331
Author(s):  
Di Zhang ◽  
Shiting Gu ◽  
Lingbo Zong ◽  
Ze Hu ◽  
Gao-Chao Fan ◽  
...  
Keyword(s):  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Reduction Reaction ◽  
Signaling Mechanism ◽  
Bilirubin Oxidase

scholarly journals Comparison of Direct and Mediated Electron Transfer for Bilirubin Oxidase from Myrothecium Verrucaria. Effects of Inhibitors and Temperature on the Oxygen Reduction Reaction

Catalysts ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 1056 ◽  
Author(s):  
Riccarda Antiochia ◽  
Diego Oyarzun ◽  
Julio Sánchez ◽  
Federico Tasca
Keyword(s):  
Electron Transfer ◽  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Direct Electron Transfer ◽  
Reduction Reaction ◽  
Redox Mediator ◽  
Bilirubin Oxidase ◽  
Myrothecium Verrucaria ◽  
Physiological Conditions ◽  
Mediated Electron Transfer

One of the processes most studied in bioenergetic systems in recent years is the oxygen reduction reaction (ORR). An important challenge in bioelectrochemistry is to achieve this reaction under physiological conditions. In this study, we used bilirubin oxidase (BOD) from Myrothecium verrucaria, a subclass of multicopper oxidases (MCOs), to catalyse the ORR to water via four electrons in physiological conditions. The active site of BOD, the T2/T3 cluster, contains three Cu atoms classified as T2, T3α, and T3β depending on their spectroscopic characteristics. A fourth Cu atom; the T1 cluster acts as a relay of electrons to the T2/T3 cluster. Graphite electrodes were modified with BOD and the direct electron transfer (DET) to the enzyme, and the mediated electron transfer (MET) using an osmium polymer (OsP) as a redox mediator, were compared. As a result, an alternative resting (AR) form was observed in the catalytic cycle of BOD. In the absence and presence of the redox mediator, the AR direct reduction occurs through the trinuclear site (TNC) via T1, specifically activated at low potentials in which T2 and T3α of the TNC are reduced and T3β is oxidized. A comparative study between the DET and MET was conducted at various pH and temperatures, considering the influence of inhibitors like H2O2, F−, and Cl−. In the presence of H2O2 and F−, these bind to the TNC in a non-competitive reversible inhibition of O2. Instead; Cl− acts as a competitive inhibitor for the electron donor substrate and binds to the T1 site.

N and S Co-doped Ordered Mesoporous Carbon: An Efficient Electrocatalyst for Oxygen Reduction Reaction in Microbial Fuel Cells

2020 ◽  
Vol 16 (4) ◽  
pp. 625-638
Author(s):  
Leila Samiee ◽  
Sedigheh Sadegh Hassani
Keyword(s):  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Microbial Fuel Cells ◽  
Carbon Materials ◽  
Reduction Reaction ◽  
Carbon Substrate ◽  
Promising Candidate ◽  
X Ray ◽  
Carbon Framework ◽  
Co Doped

Background: Porous carbon materials are promising candidate supports for various applications. In a number of these applications, doping of the carbon framework with heteroatoms provides a facile route to readily tune the carbon properties. The oxygen reduction reaction (ORR), where the reaction can be catalyzed without precious metals is one of the common applications for the heteroatom-doped carbons. Therefore, heteroatom doped catalysts might have a promising potential as a cathode in Microbial fuel cells (MFCs). MFCs have a good potential to produce electricity from biological oxidization of wastes at the anode and chemical reduction at the cathode. To the best of our knowledge, no studies have been yet reported on utilizing Sulfur trioxide pyridine (STP) and CMK-3 for the preparation of (N and S) doped ordered porous carbon materials. The presence of highly ordered mesostructured and the synergistic effect of N and S atoms with specific structures enhance the oxygen adsorption due to improving the electrocatalytic activity. So the optimal catalyst, with significant stability and excellent tolerance of methanol crossover can be a promising candidate for even other storage and conversion devices. Methods: The physico-chemical properties of the prepared samples were determined by Small Angle X-ray Diffraction (SAXRD), N2 sorption-desorption, Transmission Electron Microscopy (TEM), Field Emission Scanning Electron Microscopy (FESEM) and X-ray Photoelectron Spectroscopy (XPS). The prepared samples were further applied for oxygen reduction reaction (ORR) and the optimal cathode was tested with the Microbial Fuel Cell (MFC) system. Furthermore, according to structural analysis, The HRTEM, and SAXRD results confirmed the formation of well-ordered hexagonal (p6mm) arrays of mesopores in the direction of (100). The EDS and XPS approved that N and S were successfully doped into the CMK-3 carbon framework. Results: Among all the studied CMK-3 based catalysts, the catalyst prepared by STP precursor and pyrolysis at 900°C exhibited the highest ORR activity with the onset potential of 1.02 V vs. RHE and 4 electron transfer number per oxygen molecule in 0.1 M KOH. The high catalyst durability and fuel-crossover tolerance led to stable performance of the optimal cathode after 5000 s operation, while the Pt/C cathode-based was considerably degraded. Finally, the MFC system with the optimal cathode displayed 43.9 mW·m-2 peak power density showing even reasonable performance in comparison to a Pt/C 20 wt.%.cathode. Conclusions: The results revealed that the synergistic effect of nitrogen and sulfur co-doped on the carbon substrate structure leads to improvement in catalytic activity. Also, it was clearly observed that the porous structure and order level of the carbon substrate could considerably change the ORR performance.

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