Redox

About: Redox is a research topic. Over the lifetime, 26853 publications have been published within this topic receiving 862368 citations. The topic is also known as: reduction-oxidation & reduction-oxidation reaction.

Thiol-based antioxidants

Abstract: The thiol redox status of intracellular and extracellular compartments is critical in the determination of protein structure, regulation of enzyme activity, and control of transcription factor activity and binding. Thiol antioxidants act through a variety of mechanisms, including (1) as components of the general thiol/disulfide redox buffer, (2) as metal chelators, (3) as radical quenchers, (4) as substrates for specific redox reactions (GSH), and (5) as specific reductants of individual protein disulfate bonds (thioredoxin). The composition and redox status of the available thiols in a given compartment is highly variable and must play a part in determining the metabolic activity of each compartment. It is generally beneficial to increase the availability of specific antioxidants under conditions of oxidant stress. Cells have devised a number of mechanisms to promote increased intracellular levels of thiols such as GSH and thioredoxin in response to a wide variety of stresses. Exogenous thiols have been used successfully to increase cell and tissue thiol levels in cell cultures, in animal models, and in humans. Increased levels of GSH and other thiols have been associated with increased tolerance to oxidant stresses in all of these systems and in some cases, with disease prevention or treatment in humans. A wide variety of thiol-related compounds have been used for these purposes. These include thiols such as GSH and its derivatives, cysteine and NAC, dithiols such as lipoic acid, which is reduced to the thiol form intracellularly, and "prothiol" compounds such as OTC, which are enzymatically converted to free thiols within the cell. In choosing a thiol for a specific function (e.g., protection of lung from oxidant exposure or protection of organs from ischemia reperfusion injury), the global effects must also be considered. For example, large increases in free thiols in the circulation are associated with toxic effects. These effects may be the result of thiyl radical-mediated reactions but could also be due to destabilizing effects of increases in thiol/disulfide ratios in the plasma, which normally is in a more oxidized state than intracellular compartments. Changes in the thiol redox gradient across cells could also adversely affect any transport or cell signaling processes, which are dependent on formation and rupture of disulfide linkages in membrane proteins. Therapeutic thiol administration has been shown to have great potential, and its efficacy should be increased by selecting compounds and methods of delivery that will minimize perturbations in the thiol status of regions external to the targeted areas.

NAD(H) and NADP(H) Redox Couples and Cellular Energy Metabolism

Abstract: Significance: The nicotinamide adenine dinucleotide (NAD+)/reduced NAD+ (NADH) and NADP+/reduced NADP+ (NADPH) redox couples are essential for maintaining cellular redox homeostasis and fo...

Electrochemical oxidation of phenol at boron-doped diamond electrode. Application to electro-organic synthesis and wastewater treatment.

Abstract: The electrochemical behaviour of a synthetic boron-doped diamond thin film electrode (BDD) has been studied in acid media containing phenol using cyclic voltammetry and bulk electrolysis. The results have shown that in the potential region of water stability direct electron transfers can occur on BDD surface resulting in electrode fouling due to the formation of a polymeric film on its surface. During electrolysis in the potential region of oxygen evolution, complex oxidation reactions can take place due to electrogenerated hydroxyl radicals. Electrode fouling is inhibited under these conditions. Depending on the experimental conditions, the electrogenerated hydroxyl radicals can lead to the combustion of phenol or to the selective oxidation of phenol to benzoquinone. The experimental results have also been compared to a theoretical model that permits the prediction of the evolution with time of phenol concentration, during its combustion, or during its selective oxidation to benzoquinone.

Insights into perovskite-catalyzed peroxymonosulfate activation: Maneuverable cobalt sites for promoted evolution of sulfate radicals

Abstract: Metal-based catalysis has significantly contributed to the chemical community especially in environmental science. However, the knowledge of cobalt-based perovskite for aqueous phase oxidation still remains equivocal and insufficient. In this study, we discovered that Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) perovskite was exclusively effective for peroxymonosulfate (PMS) activation to produce free radicals, whereas the BSCF was inert to activate peroxydisulfate (PDS) and hydrogen peroxide. The BSCF/PMS exhibited superior performance to the benchmark Co3O4 nanocrystals and other classical PMS activators such as α-MnO2 and spinel CoFe2O4, meanwhile achieving an impressive stability with manipulated cobalt leaching in neutral and basic environment. In situ electron paramagnetic resonance (EPR) revealed the evolution of massive sulfate radicals (SO4 −) and hydroxyl radicals ( OH) during the oxidation. A comprehensively comparative study of BSCF and Co3O4 nanocrystals was performed, including electrochemical impedance spectroscopy (EIS) and cyclic voltammograms (CV) in PMS solution as well as hydrogen temperature-programmed reduction (H2-TPR) and oxygen temperature-programmed desorption (O2-TPD) tests. The results unveil that the cobalt-based perovskite, BSCF, exhibited a better electrical conductivity and redox potential than the spinel cobalt oxide to interact with PMS. More importantly, the oxygen vacancies and less-electronegativity A-site metals may secure cobalt sites with a lower valence state for donating electrons to PMS simultaneously for radical generation. This study advances the mechanism of cobalt-based heterogeneous catalysis in environmental remediation.