High-yield process for preparing calcium superoxide
Pressure and temperature are controlled precisely and water is rapidly removed to inhibit back reaction in process.
Wydeven, T. J.↗
SEARCH · Engineering Papers
Results for “superoxide”
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Comment on: An ab initio study of the ionization of sodium superoxide
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Partridge, Harry↗
The Purification and Characterization of Superoxide Dismutase from Chloroflexus aurantiacus and the Effects of UV Radiation on the Activity of SOD and Catalase in Hydrothermal Mats of Yellowstone National Park
Chloroflexus aurantiacus is a thermotolerant anoxygenic green phototrophic bacterium that is prominent in alkaline hot springs at temperatures between 52 and 60 C. This species often grows in the hyperoxic environment beneath cyanobacterial mats at higher temperatures up to 70 - 72 C. Cf. aurantiacus is an evolutionarily important organism since it is in the earliest branch of the eubacteria that are capable of photosynthesis and many of its characteristics can be found in other diverse groups of phototrophic bacteria. Additional information is contained in the original extended abstract.
Lancaster, Vanessa↗
Evidence that the reactivity of the martian soil is due to superoxide ions
The Viking Landers were unable to detect evidence of Life on Mars but, instead, found a chemically reactive soil capable of decomposing organic molecules.
Oxide↗
Lithium-oxygen batteries incorporating lithium superoxide
A composition includes LiO.sub.2, reduced graphene oxide, and a metal catalyst or residue thereof.
25 ENERGY STORAGE↗
High capacity lithium ion batteries having oxides, peroxides, or superoxides as cathode active material
Described herein is an electrochemical device including a cathode containing an electroactive material including LO.sub.2 or L.sub.2O.sub.2, wherein each L is independently selected from Li, Na, K, Be, Mg, Ca, and Al; the electroactive material is carbon-coated, metal-coated, metal oxide-coated, nano-sized, or doped; and the electroactive material is substantially free of transition metal catalyst.
Lu, Jun↗
Mechanism of Catalytic O2 Reduction by Iron Tetraphenylporphyrin
The catalytic reduction of O2 to H2O is important for energy transduction in both synthetic and natural systems. Herein, we report a kinetic study of O2 reduction catalyzed by iron tetraphenylporphyrin in N,N-dimethylformamide using decamethylferrocene as a soluble reductant and para-toluenesulfonic acid (pTsOH) as the proton source. Reduction of the ferric porphyrin, [FeIII(TPP)]+ , forms the ferrous porphyrin, FeII(TPP), which binds O2 reversibly to form the ferric-superoxide porphyrin complex, FeIII(TPP)(O2 •?). The temperature dependence of both the electron transfer and O2 binding equilibrium constants have been determined. Kinetic studies over a range of concentrations and temperatures show that the catalyst resting state changes during the course of each catalytic run, necessitating the use of global kinetic modeling to extract rate constants and kinetic barriers. The rate-determining step in oxygen reduction is protonation of FeIII(TPP)(O2•?) by pTsOH, which proceeds with a substantial kinetic barrier. Computational studies indicate that this barrier for proton transfer arises from an unfavorable pre-association of the proton donor with the superoxide adduct and a transition state that requires significant desolvation of the proton donor. Together, these results are the first example of oxygen reduction by iron tetraphenylporphyrin where the pre-equilibria between ferric, ferrous, and ferric-superoxide intermediates have been quantified under catalytic conditions. This work gives a generalizable model for the mechanism of iron porphyrin-catalyzed ORR and provides an unusually complete mechanistic study of an ORR reaction. More broadly, this study also highlights the kinetic challenges for proton transfer to catalytic intermediates in organic media.
Pegis, Michael L.↗
Scoparone attenuates RANKL-induced osteoclastic differentiation through controlling reactive oxygen species production and scavenging
Scoparone, one of the bioactive components of Artemisia capillaris Thunb, has various biological properties including immunosuppressive, hepatoprotective, anti-allergic, anti-inflammatory, and antioxidant effects. This study aims at evaluating the anti-osteoporotic effect of scoparone and its underlying mechanism in vitro. Scoparone demonstrated potent cellular antioxidant capacity. It was also found that scoparone inhibited the receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast differentiation and suppressed cathepsin K and tartrate-resistant acid phosphatase (TRAP) expression via c-jun N-terminal kinase (JNK)/extracellular signal-regulated kinase (ERK)/p38-mediated c-Fos–nuclear factor of activated T cells, cytoplasmic 1 (NFATc1) signaling pathway. During osteoclast differentiation, the production of general reactive oxygen species (ROS) and superoxide anions was dose-dependently attenuated by scoparone. In addition, scoparone diminished NADPH (nicotinamide adenine dinucleotide phosphate) oxidase 1 (Nox1) expression and activation via the tumor necrosis factor receptor-associated factor 6 (TRAF6)–cSrc–phosphatidylinositol 3-kinase (PI3k) signaling pathway and prevented the disruption of mitochondrial electron transport chain system. Furthermore, scoparone augmented the expression of superoxide dismutase 1 (SOD1) and catalase (CAT). The overall results indicate that the inhibitory effect of scoparone on RANKL-induced osteoclast differentiation is attributed to the suppressive effect on ROS and superoxide anion production by inhibiting Nox1 expression and activation and protecting the mitochondrial electron transport chain system and the scavenging effect of ROS resulting from elevated SOD1 and CAT expression. - Highlights: • Scoparone dose-dependently inhibited RANKL-induced osteoclast differentiation. • Scoparone diminished general ROS and superoxide anions in a dose-dependent manner. • Scoparone inhibited Nox1 expression and activation. • Scoparone prevented the disruption of mitochondrial electron transport chain system. • Scoparone augmented superoxide dismutase and catalase expression.
60 APPLIED LIFE SCIENCES↗
The oxidation of dehydroascorbic acid and 2,3-diketogulonate by distinct reactive oxygen species
l -Ascorbate, dehydro- l -ascorbic acid (DHA), and 2,3-diketo- l -gulonate (DKG) can all quench reactive oxygen species (ROS) in plants and animals. The vitamin C oxidation products thereby formed are investigated here. DHA and DKG were incubated aerobically at pH 4.7 with peroxide (H 2 O 2 ), ‘superoxide’ (a ~50:50 mixture of O 2 and HO 2 ), hydroxyl radicals ( • OH, formed in Fenton mixtures), and illuminated riboflavin (generating singlet oxygen, 1 O 2 ). Products were monitored electrophoretically. DHA quenched H 2 O 2 far more effectively than superoxide, but the main products in both cases were 4- O -oxalyl- l -threonate (4-OxT) and smaller amounts of 3-OxT and OxA + threonate. H 2 O 2 , but not superoxide, also yielded cyclic-OxT. Dilute Fenton mixture almost completely oxidised a 50-fold excess of DHA, indicating that it generated oxidant(s) greatly exceeding the theoretical • OH yield; it yielded oxalate, threonate, and OxT. 1 O 2 had no effect on DHA. DKG was oxidatively decarboxylated by H 2 O 2 , Fenton mixture, and 1 O 2 , forming a newly characterised product, 2-oxo- l - threo -pentonate (OTP; ‘2-keto- l -xylonate’). Superoxide yielded negligible OTP. Prolonged H 2 O 2 treatment oxidatively decarboxylated OTP to threonate. Oxidation of DKG by H 2 O 2 , Fenton mixture, or 1 O 2 also gave traces of 4-OxT but no detectable 3-OxT or cyclic-OxT. In conclusion, DHA and DKG yield different oxidation products when attacked by different ROS. DHA is more readily oxidised by H 2 O 2 and superoxide; DKG more readily by 1 O 2 . The diverse products are potential signals, enabling organisms to respond appropriately to diverse stresses. Also, the reaction-product ‘fingerprints’ are analytically useful, indicating which ROS are acting in vivo .
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
PCB153 reduces telomerase activity and telomere length in immortalized human skin keratinocytes (HaCaT) but not in human foreskin keratinocytes (NFK)
Polychlorinated biphenyls (PCBs), ubiquitous environmental pollutants, are characterized by long term-persistence in the environment, bioaccumulation, and biomagnification in the food chain. Exposure to PCBs may cause various diseases, affecting many cellular processes. Deregulation of the telomerase and the telomere complex leads to several biological disorders. We investigated the hypothesis that PCB153 modulates telomerase activity, telomeres and reactive oxygen species resulting in the deregulation of cell growth. Exponentially growing immortal human skin keratinocytes (HaCaT) and normal human foreskin keratinocytes (NFK) were incubated with PCB153 for 48 and 24 days, respectively, and telomerase activity, telomere length, superoxide level, cell growth, and cell cycle distribution were determined. In HaCaT cells exposure to PCB153 significantly reduced telomerase activity, telomere length, cell growth and increased intracellular superoxide levels from day 6 to day 48, suggesting that superoxide may be one of the factors regulating telomerase activity, telomere length and cell growth compared to untreated control cells. Results with NFK cells showed no shortening of telomere length but reduced cell growth and increased superoxide levels in PCB153-treated cells compared to untreated controls. As expected, basal levels of telomerase activity were almost undetectable, which made a quantitative comparison of treated and control groups impossible. The significant down regulation of telomerase activity and reduction of telomere length by PCB153 in HaCaT cells suggest that any cell type with significant telomerase activity, like stem cells, may be at risk of premature telomere shortening with potential adverse health effects for the affected organism. -- Highlights: ► Human immortal (HaCaT) and primary (NFK) keratinocytes were exposed to PCB153. ► PCB153 significantly reduced telomerase activity and telomere length in HaCaT. ► No effect on telomere length and telomerase activity was found in NFK. ► Increased intracellular superoxide levels and reduced cell growth was seen in both. ► PCB153 may damage telomerase expressing cells like stem cells.
60 APPLIED LIFE SCIENCES↗
Gold core/ceria shell-based redox active nanozyme mimicking the biological multienzyme complex phenomenon
Catalytically active individual gold (Au) and cerium oxide (CeO2) nanoparticles are well known to exhibit specific enzyme-like activities, such as natural catalase, oxidase, superoxide dismutase, and peroxidase enzymes. These activities have been maneuvered to design several biological applications such as immunoassays, glucose detection, radiation and free radical protection and tissue engineering. A functional nanozyme depicting multienzyme like properties that functions as a synthetic super enzyme has eluded the researchers in the nanoscience community for past decade. In current report, we have designed a functional multienzyme in the form of Gold (core)-CeO2 (shell) nanoparticles (Au@CeO2 CSNPs) exhibiting excellent peroxidase, catalase and superoxide dismutase enzyme-like activities that are controlled simply by tuning the pH. The reaction kinetic parameters reveal that the peroxidase-like activity of this core shell nanozyme is comparable to natural HRP enzyme. Unlike peroxidase-like activity exhibited by other nanomaterials, Au@CeO2 CSNPs showed decrease in hydroxyl radical formation, suggesting that the bio catalytic reactions are performed by efficient electron transfers. A significant enzyme-like activity of this core shell nanoparticle was conserved at extreme pH (2 – 11) and temperatures (up to 90 °C), clearly suggesting the superiority over natural enzymes. Further, the utility of peroxidase-like activity of this core shell nanoparticles was extended for the detection of glucose, which showed a linear range of detection between (100 µM – 1 mM). It is hypothesized that the proximity of the redox potentials of Au+/Au and Ce (III)/Ce (IV) may result in a redox couple promoting the multienzyme activity of core shell nanoparticles. Au@CeO2 CSNPs may open new directions for development of single platform sensors in multiple biosensing applications.
Environmental Molecular Sciences Laboratory↗
Genomic instability induced by mutant succinate dehydrogenase subunit D (SDHD) is mediated by O 2 -• and H 2 O 2
SDHD mutations are associated with human cancers but the mechanisms that may contribute to transformation are unknown. The hypothesis that mutations in SDHD increase levels of superoxide leading to genomic instability was tested using site-directed mutagenesis to generate a truncated SDHD cDNA that was expressed in Chinese hamster fibroblasts. Stable expression of mutant SDHD resulted in 2-fold increases in steady-state levels of superoxide that were accompanied by a significantly increased mutation rate as well as a 70-fold increase in mutation frequency at the hprt locus. Overexpression of MnSOD or treatment with polyethylene glycol conjugated (PEG)-catalase suppressed mutation frequency in SDHD mutant cells by 50% (Pb0.05). Simultaneous treatment with PEG-catalase and PEG-SOD suppressed mutation frequency in SDHD mutant cells by 90% (Pb0.0005). Finally, 95% depletion of glutathione using L-buthionine-[S,R]-sulfoximine (BSO) in SDHD mutant cells caused a 4-fold increase in mutation frequency (Pb0.05). These results demonstrate that mutations in SDHD cause increased steady-state levels of superoxide which significantly contributed to increases in mutation rates and frequency mediated by superoxide and hydrogen peroxide. These results support the hypothesis that mutations in SDHD may contribute to carcinogenesis by increasing genomic instability mediated by increased steady-state levels of reactive oxygen species.
59 BASIC BIOLOGICAL SCIENCES↗
Manganoporphyrin-Polyphenol Multilayer Capsules as Radical and Reactive Oxygen Species (ROS) Scavengers
Local modulation of oxidative stress is crucial for a variety of biochemical events including cellular differentiation, apoptosis, and defense against pathogens. Currently employed natural and synthetic antioxidants exhibit a lack of biocompatibility, bioavailability, and chemical stability, resulting in limited capability to scavenge reactive oxygen species (ROS). To mediate these drawbacks, we have developed a synergistic manganoporphyrin-polyphenol polymeric nanothin coating and hollow microcapsules with efficient antioxidant activity and controllable ROS modulation. These materials are produced by multilayer assembly of a natural polyphenolic antioxidant, tannic acid (TA), with a synthesized copolymer of polyvinylpyrrolidone containing a manganoporphyrin modality (MnP-PVPON) which mimics the enzymatic antioxidant superoxide dismutase. The redox activity of the copolymer is demonstrated to dramatically increase the antioxidant response of MnP-PVPON/TA capsules versus unmodified PVPON/TA capsules through reduction of a radical cationic dye and to significantly suppress the proliferation of superoxide via cytochrome C competition. Inclusion of MnP-PVPON as an outer layer enhances radical-scavenging activity as compared to localization of the layer in the middle or inner part of the capsule shell. In addition, we demonstrate that TA is crucial for the synergistic radical-scavenging activity of the MnP-PVPON/TA system which exhibits a combined superoxide dismutase-like ability and catalase-like activity in response to the free radical superoxide challenge. The MnP-PVPON/TA capsules exhibit a negligible, 8% loss of shell thickness upon free radical treatment, while PVPON/TA capsules lose 39% of their shell thickness due to the noncatalytic free-radical-scavenging of TA, as demonstrated by small angle neutron scattering (SANS). Finally, we have found the manganoporphyrin-polyphenol capsules to be nontoxic to splenocytes from NOD mice after 48 h incubation. In conclusion, our study illustrates the strong potential of combining catalytic activity of manganoporphyrins with natural polyphenolic antioxidants to design efficient free-radical-scavenging materials that may eventually be used in antioxidant therapies and as free radical dissipating protective carriers of biomolecules for biomedical or industrial applications.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Exploiting algal NADPH oxidase for biophotovoltaic energy
Summary Photosynthetic microbes exhibit light‐dependent electron export across the cell membrane, which can generate electricity in biological photovoltaic (BPV) devices. How electrons are exported remains to be determined; the identification of mechanisms would help selection or generation of photosynthetic microbes capable of enhanced electrical output. We show that plasma membrane NADPH oxidase activity is a significant component of light‐dependent generation of electricity by the unicellular green alga Chlamydomonas reinhardtii . NADPH oxidases export electrons across the plasma membrane to form superoxide anion from oxygen. The C. reinhardtii mutant lacking the NADPH oxidase encoded by RBO1 is impaired in both extracellular superoxide anion production and current generation in a BPV device. Complementation with the wild‐type gene restores both capacities, demonstrating the role of the enzyme in electron export. Monitoring light‐dependent extracellular superoxide production with a colorimetric assay is shown to be an effective way of screening for electrogenic potential of candidate algal strains. The results show that algal NADPH oxidases are important for superoxide anion production and open avenues for optimizing the biological component of these devices.
59 BASIC BIOLOGICAL SCIENCES↗
A long-life lithium-oxygen battery via a molecular quenching/mediating mechanism
The advancement of lithium-oxygen (Li-O 2 ) batteries has been hindered by challenges including low discharge capacity, poor energy efficiency, severe parasitic reactions, etc. We report an Li-O 2 battery operated via a new quenching/mediating mechanism that relies on the direct chemical reactions between a versatile molecule and superoxide radical/Li 2 O 2 . The battery exhibits a 46-fold increase in discharge capacity, a low charge overpotential of 0.7 V, and an ultralong cycle life >1400 cycles. Featuring redox-active 2,2,6,6-tetramethyl-1-piperidinyloxy moieties bridged by a quenching-active perylene diimide backbone, the tailor-designed molecule acts as a redox mediator to catalyze discharge/charge reactions and serves as a reusable superoxide quencher to chemically react with superoxide species generated during battery operation. The all-in-one molecule can simultaneously tackle issues of parasitic reactions associated with superoxide radicals, singlet oxygen, high overpotentials, and lithium corrosion. The molecular design of multifunctional additives combining various capabilities opens a new avenue for developing high-performance Li-O 2 batteries.
25 ENERGY STORAGE↗
Development and characterization of a hydrogen peroxide-resistant cholangiocyte cell line: A novel model of oxidative stress-related cholangiocarcinoma genesis
Oxidative stress is a cause of inflammation–related diseases, including cancers. Cholangiocarcinoma is a liver cancer with bile duct epithelial cell phenotypes. Our previous studies in animal and human models indicated that oxidative stress is a major cause of cholangiocarcinoma development. Hydrogen peroxide (H{sub 2}O{sub 2}) can generate hydroxyl radicals, which damage lipids, proteins, and nucleic acids, leading to cell death. However, some cells can survive by adapting to oxidative stress conditions, and selective clonal expansion of these resistant cells would be involved in oxidative stress-related carcinogenesis. The present study aimed to establish H{sub 2}O{sub 2}-resistant cell line from an immortal cholangiocyte cell line (MMNK1) by chronic treatment with low-concentration H{sub 2}O{sub 2} (25 μM). After 72 days of induction, H{sub 2}O{sub 2}-resistant cell lines (ox-MMNK1-L) were obtained. The ox-MMNK1-L cell line showed H{sub 2}O{sub 2}-resistant properties, increasing the expression of the anti-oxidant genes catalase (CAT), superoxide dismutase-1 (SOD1), superoxide dismutase-2 (SOD2), and superoxide dismutase-3 (SOD3) and the enzyme activities of CAT and intracellular SODs. Furthermore, the resistant cells showed increased expression levels of an epigenetics-related gene, DNA methyltransferase-1 (DNMT1), when compared to the parental cells. Interestingly, the ox-MMNK1-L cell line had a significantly higher cell proliferation rate than the MMNK1 normal cell line. Moreover, ox-MMNK1-L cells showed pseudopodia formation and the loss of cell-to-cell adhesion (multi-layers) under additional oxidative stress (100 μM H{sub 2}O{sub 2}). These findings suggest that H{sub 2}O{sub 2}-resistant cells can be used as a model of oxidative stress-related cholangiocarcinoma genesis through molecular changes such as alteration of gene expression and epigenetic changes. - Highlights: • An H{sub 2}O{sub 2}-resistant ox-MMNK1-L cells was established from immortalized cholangiocytes. • The resistance was acquired by daily treatment of low H{sub 2}O{sub 2} (25 μM) for 15 passages. • The cells highly expressed catalase, SODs and DNMT1 with rapid cell proliferation. • Pseudopodia and the loss of cell-to-cell adhesion appeared by 100 μM H{sub 2}O{sub 2} treatment. • The resistant cells can be used as a model of oxidative stress-related carcinogenesis.
60 APPLIED LIFE SCIENCES↗