ROLE OF REDOX POTENTIAL OF HEMOGLOBIN-BASED OXYGEN CARRIERS ON METHEMOGLOBIN REDUCTION BY PLASMA COMPONENTS

AbstractPhotosystem II (PSII) contains Ca2+, which is essential to the oxygen-evolving activity of the catalytic Mn4CaO5 complex. Replacement of Ca2+ with other redox-inactive metals results in a loss/decrease of oxygen-evolving activity. To investigate the role of Ca2+ in this catalytic reaction, we investigate artificial Mn3[M]O2 clusters redox-inactive metals [M] ([M] = Mg2+, Ca2+, Zn2+, Sr2+, and Y3+), which were synthesized by Tsui et al. (Nat Chem 5:293, 2013). The experimentally measured redox potentials (Em) of these clusters are best described by the energy of their highest occupied molecular orbitals. Quantum chemical calculations showed that the valence of metals predominantly affects Em(MnIII/IV), whereas the ionic radius of metals affects Em(MnIII/IV) only slightly.

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Reduction kinetics and carbon deposit for Cu-doped Fe-based oxygen carriers: role of Cu

Chemical Engineering Science ◽

10.1016/j.ces.2021.117406 ◽

2021 ◽

pp. 117406

Author(s):

Guida Li ◽

Wenxing Yao ◽

Yunlei Zhao ◽

Bo Jin ◽

Jianyong Xu ◽

...

Keyword(s):

Carbon Deposit ◽

Reduction Kinetics ◽

Oxygen Carriers

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Quinone-enhanced Ascorbate Reduction of Nitric Oxide: Role of Quinone Redox Potential

Free Radical Research ◽

10.1080/10715760400009852 ◽

2004 ◽

Vol 38 (10) ◽

pp. 1107-1112 ◽

Cited By ~ 11

Author(s):

Antonio E. Alegria ◽

Sheila Sanchez ◽

Ingrid Quintana

Keyword(s):

Nitric Oxide ◽

Redox Potential

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Sediment pH and Redox Potential Affect the Bioavailability of Al, Cu, Fe, Mn, and Zn to Rooted Aquatic Macrophytes

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f93-016 ◽

1993 ◽

Vol 50 (1) ◽

pp. 143-148 ◽

Cited By ~ 46

Author(s):

Leland J. Jackson ◽

Jacob Kalff ◽

Joseph B. Rasnnussen

Keyword(s):

Redox Potential ◽

Metal Content ◽

Aquatic Macrophytes ◽

Organic Content ◽

Trophic Levels ◽

Sediment Organic Content ◽

Sediment Ph ◽

The Relationship ◽

Sediment Metal

We have evaluated the role of sediment pH (4.7–7.1) and redox potential (88–305 mV) in determining the bioavailability of five metals to four species of isoetoid macrophytes. The four species (Eleocharis acicularis, Eriocaulon septangulare With., Isoetes sp., and Sagittaria graminae) did not differ significantly in the relationship between the contents of metals in plants and sediment. When data for all species were pooled, 28–80% of the variation in the log of plant metal content was explained by the log of sediment metal (Al, Fe, and Mn) or by the log of sediment organic content (Cu and Zn). Sediment pH explained 45% (Al), 10% (Cu), 20% (Fe), 5% (Mn), and 12% (Zn) variation over and above that explained by the sediment metal content. These results demonstrate that lower sediment pH, in the presence of mildly oxic redox conditions, increases the bioavailability of these five trace metals to rooted aquatic plants. Rooted macrophytes subject to acidification contain higher metal concentrations which may be transferred by grazing to higher trophic levels.

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The role of physiological elements in future therapies of rheumatoid arthritis. III. The role of the electromagnetic field in regulation of redox potential and life cycle of inflammatory cells*

Reumatologia/Rheumatology ◽

10.5114/reum.2015.54000 ◽

2015 ◽

Vol 4 ◽

pp. 219-224 ◽

Cited By ~ 1

Author(s):

Michał Gajewski ◽

Przemysław Rzodkiewicz ◽

Sławomir Maśliński ◽

Elżbieta Wojtecka-Łukasik

Keyword(s):

Rheumatoid Arthritis ◽

Electromagnetic Field ◽

Life Cycle ◽

Redox Potential ◽

Inflammatory Cells

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The glutathione degrading enzyme, Chac1, is required for calcium signaling in developing zebrafish: redox as an upstream activator of calcium

Biochemical Journal ◽

10.1042/bcj20190077 ◽

2019 ◽

Vol 476 (13) ◽

pp. 1857-1873 ◽

Cited By ~ 1

Author(s):

Shambhu Yadav ◽

Bindia Chawla ◽

Mohammad Anwar Khursheed ◽

Rajesh Ramachandran ◽

Anand Kumar Bachhawat

Keyword(s):

Redox Potential ◽

Calcium Signaling ◽

Reduced Glutathione ◽

Developmental Defects ◽

Degrading Enzyme ◽

Embryonic Lethal ◽

Intracellular Glutathione ◽

Cellular Oxidation ◽

Glutathione Redox

Abstract Calcium signaling is essential for embryonic development but the signals upstream of calcium are only partially understood. Here, we investigate the role of the intracellular glutathione redox potential in calcium signaling using the Chac1 protein of zebrafish. A member of the γ-glutamylcyclotransferase family of enzymes, the zebrafish Chac1 is a glutathione-degrading enzyme that acts only on reduced glutathione. The zebrafish chac1 expression was seen early in development, and in the latter stages, in the developing muscles, brain and heart. The chac1 knockdown was embryonic lethal, and the developmental defects were seen primarily in the myotome, brain and heart where chac1 was maximally expressed. The phenotypes could be rescued by the WT Chac1 but not by the catalytically inactive Chac1 that was incapable of degrading glutathione. The ability of chac1 to alter the intracellular glutathione redox potential in the live animals was examined using Grx1-roGFP2. The chac1 morphants lacked the increased degree of cellular oxidation seen in the WT zebrafish. As calcium is also known to be critical for the developing myotomes, brain and heart, we further investigated if the chac1 knockdown phenotypes were a consequence of the lack of calcium signals. We observed using GCaMP6s, that calcium transients normally seen in the developing embryos were strongly attenuated in these knockdowns. The study thus identifies Chac1 and the consequent change in intracellular glutathione redox potential as important upstream activators of calcium signaling during development.

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Solubility of the nadorite group minerals: implications for mobility of Sb and Bi in oxidised settings

Environmental Chemistry ◽

10.1071/en17076 ◽

2017 ◽

Vol 14 (4) ◽

pp. 224

Author(s):

Adam J. Roper ◽

Peter Leverett ◽

Timothy D. Murphy ◽

Peter A. Williams

Keyword(s):

Redox Potential ◽

Significant Role ◽

Stability Studies ◽

Secondary Minerals ◽

Relative Stabilities ◽

Mineral Phases ◽

Minor Part ◽

A Minor

Environmental contextThe dispersion of antimony in the environment has been misunderstood over the last few decades. Investigating the solubility of naturally forming mineral phases such as nadorite resulted in determination of its limited role in Sb dispersion, providing evidence that nadorite can only limit antimony dispersion in mildly oxidising conditions. Nadorite can only play a significant role in Sb immobilisation in a particular redox window, which forms only a minor part of the framework of Sb dispersion. AbstractAs part of a study of the control that secondary minerals exert on the dispersion of antimony and bismuth in the supergene environment, syntheses and stability studies of nadorite (PbSbO2Cl) and perite (PbBiO2Cl) have been undertaken. Solubilities in aqueous HNO3 were determined at 298.2K and the data obtained used to calculate values of ΔGfθ(298.2K). The ΔGfθ(s, 298.2K) values for PbSbO2Cl (–622.0±2.8kJmol–1) and PbBiO2Cl (–590.0±1.3kJmol–1) have been used in subsequent calculations to determine relative stabilities and relationships with other common secondary Sb and Bi minerals. While the role of nadorite in immobilising Sb is dependent upon the prevailing redox potential such that SbIII is stable, perite may be a significant phase in limiting the dispersion of Bi in certain supergene settings.

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Role of endothelial progenitor cells and redox potential in synovium neovascularisation

Reumatologia/Rheumatology ◽

10.5114/reum.2012.31406 ◽

2012 ◽

Vol 5 ◽

pp. 432-437

Author(s):

Przemysław Rzodkiewicz ◽

Michał Gajewski ◽

Sławomir Maśliński ◽

Elżbieta Wojtecka-Łukasik

Keyword(s):

Redox Potential ◽

Progenitor Cells ◽

Endothelial Progenitor Cells ◽

Endothelial Progenitor

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The role of double covalent flavin binding in chito-oligosaccharide oxidase from Fusarium graminearum

Biochemical Journal ◽

10.1042/bj20071591 ◽

2008 ◽

Vol 413 (1) ◽

pp. 175-183 ◽

Cited By ~ 32

Author(s):

Dominic P. H. M. Heuts ◽

Remko T. Winter ◽

Gerke E. Damsma ◽

Dick B. Janssen ◽

Marco W. Fraaije

Keyword(s):

Redox Potential ◽

Fusarium Graminearum ◽

Covalent Binding ◽

Site Directed Mutagenesis ◽

Wild Type ◽

Covalent Bonds ◽

Regioselective Oxidation ◽

Flavin Binding ◽

High Redox Potential

ChitO (chito-oligosaccharide oxidase) from Fusarium graminearum catalyses the regioselective oxidation of N-acetylated oligosaccharides. The enzyme harbours an FAD cofactor that is covalently attached to His94 and Cys154. The functional role of this unusual bi-covalent flavin–protein linkage was studied by site-directed mutagenesis. The double mutant (H94A/C154A) was not expressed, which suggests that a covalent flavin–protein bond is needed for protein stability. The single mutants H94A and C154A were expressed as FAD-containing enzymes in which one of the covalent FAD–protein bonds was disrupted relative to the wild-type enzyme. Both mutants were poorly active, as the kcat decreased (8.3- and 3-fold respectively) and the Km increased drastically (34- and 75-fold respectively) when using GlcNac as the substrate. Pre-steady-state analysis revealed that the rate of reduction in the mutant enzymes is decreased by 3 orders of magnitude when compared with wild-type ChitO (kred=750 s−1) and thereby limits the turnover rate. Spectroelectrochemical titrations revealed that wild-type ChitO exhibits a relatively high redox potential (+131 mV) and the C154A mutant displays a lower potential (+70 mV), while the H94A mutant displays a relatively high potential of approximately +164 mV. The results show that a high redox potential is not the only prerequisite to ensure efficient catalysis and that removal of either of the covalent bonds may perturb the geometry of the Michaelis complex. Besides tuning the redox properties, the bi-covalent binding of the FAD cofactor in ChitO is essential for a catalytically competent conformation of the active site.

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