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Sample records for selective ruthenium-catalyzed redox

  1. Ligand-controlled reactivity, selectivity, and mechanism of cationic ruthenium-catalyzed hydrosilylations of alkynes, ketones, and nitriles: a theoretical study.

    Science.gov (United States)

    Yang, Yun-Fang; Chung, Lung Wa; Zhang, Xinhao; Houk, K N; Wu, Yun-Dong

    2014-09-19

    Density functional theory calculations with the M06 functional have been performed on the reactivity, selectivity, and mechanism of hydrosilylations of alkynes, ketones, and nitriles catalyzed by cationic ruthenium complexes [CpRu(L)(MeCN)2](+), with L = P(i)Pr3 or MeCN. The hydrosilylation of alkynes with L = P(i)Pr3 involves an initial silyl migration mechanism to generate the anti-Markovnikov product, in contrast to the Markovnikov product obtained with L = MeCN. The bulky phosphine ligand directs the silyl group to migrate to Cβ of the alkyne. This explains the anti-Markovnikov selectivity of the catalyst with L = P(i)Pr3. By contrast, the silane additions to either ketone or nitrile proceed through an ionic SN2-Si outer-sphere mechanism, in which the substrate attacks the Si center. The P(i)Pr3 ligand facilitates the activation of the Si-H bond to furnish a η(2)-silane complex, whereas a η(1)-silane complex is formed for the MeCN ligand. This property of the phosphine ligand enables the catalytic hydrosilylation of ketones and nitriles in addition to that of alkynes.

  2. Alkynes as Allylmetal Equivalents in Redox-Triggered C–C Couplings to Primary Alcohols: (Z)-Homoallylic Alcohols via Ruthenium-Catalyzed Propargyl C–H Oxidative Addition

    Science.gov (United States)

    2015-01-01

    The cationic ruthenium catalyst generated upon the acid–base reaction of H2Ru(CO)(PPh3)3 and 2,4,6-(2-Pr)3PhSO3H promotes the redox-triggered C–C coupling of 2-alkynes and primary alcohols to form (Z)-homoallylic alcohols with good to complete control of olefin geometry. Deuterium labeling studies, which reveal roughly equal isotopic compositions at the allylic and distal vinylic positions, along with other data, corroborate a catalytic mechanism involving ruthenium(0)-mediated allene–aldehyde oxidative coupling to form a transient oxaruthenacycle, an event that ultimately defines (Z)-olefin stereochemistry. PMID:25075434

  3. Ruthenium-Catalyzed Dehydrogenative Decarbonylation of Primary Alcohols

    DEFF Research Database (Denmark)

    Mazziotta, Andrea; Madsen, Robert

    2017-01-01

    Dehydrogenative decarbonylation of a primary alcohol involves the release of both dihydrogen and carbon monoxide to afford the one-carbon shorter product. The transformation has now been achieved with a ruthenium-catalyzed protocol by using the complex Ru(COD)Cl2 and the hindered monodentate ligand...... P(o-tolyl)3 in refluxing p-cymene. The reaction can be applied to both benzylic and long chain linear aliphatic alcohols. The intermediate aldehyde can be observed during the transformation, which is therefore believed to proceed through two separate catalytic cycles involving first dehydrogenation...... of the alcohol and then decarbonylation of the resulting aldehyde....

  4. Recent advances in the ruthenium-catalyzed hydroarylation of alkynes with aromatics: synthesis of trisubstituted alkenes.

    Science.gov (United States)

    Manikandan, Rajendran; Jeganmohan, Masilamani

    2015-11-14

    The hydroarylation of alkynes with substituted aromatics in the presence of a metal catalyst via chelation-assisted C-H bond activation is a powerful method to synthesize trisubstituted alkenes. Chelation-assisted C-H bond activation can be done by two ways: (a) an oxidative addition pathway and (b) a deprotonation pathway. Generally, a mixture of cis and trans stereoisomeric as well as regioisomeric trisubstituted alkenes was observed in an oxidative addition pathway. In the deprotonation pathway, the hydroarylation reaction can be done in a highly regio- and stereoselective manner, and enables preparation of the expected trisubstituted alkenes in a highly selective manner. Generally, ruthenium, rhodium and cobalt complexes are used as catalysts in the reaction. In this review, a ruthenium-catalyzed hydroarylation of alkynes with substituted aromatics is covered completely. The hydroarylation reaction of alkynes with amide, azole, carbamate, phosphine oxide, amine, acetyl, sulfoxide and sulphur directed aromatics is discussed.

  5. Ruthenium-catalyzed cyclization of N-carbamoyl indolines with alkynes: an efficient route to pyrroloquinolinones.

    Science.gov (United States)

    Manoharan, Ramasamy; Jeganmohan, Masilamani

    2015-09-21

    A regioselective synthesis of substituted pyrroloquinolinones via a ruthenium-catalyzed oxidative cyclization of substituted N-carbamoyl indolines with alkynes is described. The cyclization reaction was compatible with various symmetrical and unsymmetrical alkynes including substituted propiolates. Later, we performed the aromatization of pyrroloquinolinones into indole derivatives in the presence of 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ).

  6. Ruthenium-catalyzed direct C3 alkylation of indoles with α,β-unsaturated ketones.

    Science.gov (United States)

    Li, Shuai-Shuai; Lin, Hui; Zhang, Xiao-Mei; Dong, Lin

    2015-01-28

    In this paper, a simple and highly efficient ruthenium-catalyzed direct C3 alkylation of indoles with various α,β-unsaturated ketones without chelation assistance has been developed. This novel C-H activation methodology exhibits a broad substrate scope such as different substituted indoles, pyrroles, and other azoles. Further synthetic applications of the alkylation products can lead to more attractive 3,4-fused tricyclic indoles.

  7. Electronic effects of ruthenium-catalyzed [3+2]-cycloaddition of alkynes and azides

    KAUST Repository

    Hou, Duenren

    2010-11-01

    A combined experimental and theoretical study of ruthenium-catalyzed azide-alkyne cycloaddition (RuAAC) reactions is presented and various electronic analyses were conducted to provide a basis in understanding the observed regioselectivity of the 1,2,3-triazole products. Computational studies using density functional theory (DFT) and atoms in molecules quantum theory (AIM) further yield fresh details on the electronic factors that determine the regioselectivity in the RuAAC. It is found that the formation of 1,2,3-triazole products is irreversible and from the Hammett study, the pathway involving a vinyl cationic intermediate is ruled out. The electronic effect favors the formation of 5-electron-donating-group substituted-1,2,3-trizoles. © 2010 Elsevier Ltd. All rights reserved.

  8. Electronic effects of ruthenium-catalyzed [3+2]-cycloaddition of alkynes and azides

    KAUST Repository

    Hou, Duenren; Kuan, Tingchun; Li, YuKai; Lee, Richmond; Huang, Kuo-Wei

    2010-01-01

    A combined experimental and theoretical study of ruthenium-catalyzed azide-alkyne cycloaddition (RuAAC) reactions is presented and various electronic analyses were conducted to provide a basis in understanding the observed regioselectivity of the 1,2,3-triazole products. Computational studies using density functional theory (DFT) and atoms in molecules quantum theory (AIM) further yield fresh details on the electronic factors that determine the regioselectivity in the RuAAC. It is found that the formation of 1,2,3-triazole products is irreversible and from the Hammett study, the pathway involving a vinyl cationic intermediate is ruled out. The electronic effect favors the formation of 5-electron-donating-group substituted-1,2,3-trizoles. © 2010 Elsevier Ltd. All rights reserved.

  9. Ruthenium Catalyzed Diastereo- and Enantioselective Coupling of Propargyl Ethers with Alcohols: Siloxy-Crotylation via Hydride Shift Enabled Conversion of Alkynes to π-Allyls.

    Science.gov (United States)

    Liang, Tao; Zhang, Wandi; Chen, Te-Yu; Nguyen, Khoa D; Krische, Michael J

    2015-10-14

    The first enantioselective carbonyl crotylations through direct use of alkynes as chiral allylmetal equivalents are described. Chiral ruthenium(II) complexes modified by Josiphos (SL-J009-1) catalyze the C-C coupling of TIPS-protected propargyl ether 1a with primary alcohols 2a-2o to form products of carbonyl siloxy-crotylation 3a-3o, which upon silyl deprotection-reduction deliver 1,4-diols 5a-5o with excellent control of regio-, anti-diastereo-, and enantioselectivity. Structurally related propargyl ethers 1b and 1c bearing ethyl- and phenyl-substituents engage in diastereo- and enantioselective coupling, as illustrated in the formation of adducts 5p and 5q, respectively. Selective mono-tosylation of diols 5a, 5c, 5e, 5f, 5k, and 5m is accompanied by spontaneous cyclization to deliver the trans-2,3-disubstituted furans 6a, 6c, 6e, 6f, 6k, and 6m, respectively. Primary alcohols 2a, 2l, and 2p were converted to the siloxy-crotylation products 3a, 3l, and 3p, which upon silyl deprotection-lactol oxidation were transformed to the trans-4,5-disubstituted γ-butyrolactones 7a, 7l, and 7p. The formation of 7p represents a total synthesis of (+)-trans-whisky lactone. Unlike closely related ruthenium catalyzed alkyne-alcohol C-C couplings, deuterium labeling studies provide clear evidence of a novel 1,2-hydride shift mechanism that converts metal-bound alkynes to π-allyls in the absence of intervening allenes.

  10. Ruthenium-catalyzed reactions--a treasure trove of atom-economic transformations.

    Science.gov (United States)

    Trost, Barry M; Frederiksen, Mathias U; Rudd, Michael T

    2005-10-21

    The demand for new chemicals spanning the fields of health care to materials science combined with the pressure to produce these substances in an environmentally benign fashion pose great challenges to the synthetic chemical community. The maximization of synthetic efficiency by the conversion of simple building blocks into complex targets remains a fundamental goal. In this context, ruthenium complexes catalyze a number of non-metathesis conversions and allow the rapid assembly of complex molecules with high selectivity and atom economy. These complexes often exhibit unusual reactivity. Careful consideration of the mechanistic underpinnings of the transformations can lead to the design of new reactions and the discovery of new reactivity.

  11. Direct Vinylation of Alcohols or Aldehydes Employing Alkynes as Vinyl Donors: A Ruthenium Catalyzed C-C Bond Forming Transfer Hydrogenation

    Science.gov (United States)

    Patman, Ryan L.; Chaulagain, Mani Raj; Williams, Vanessa M.; Krische, Michael J.

    2011-01-01

    Under the conditions of ruthenium catalyzed transfer hydrogenation, 2-butyne couples to benzylic and aliphatic alcohols 1a–1i to furnish allylic alcohols 2a–2i, constituting a direct C-H vinylation of alcohols employing alkynes as vinyl donors. Under related transfer hydrogenation conditions employing formic acid as terminal reductant, 2-butyne couples to aldehydes 4a, 4b, and 4e to furnish identical products of carbonyl vinylation 2a, 2b, and 2e. Thus, carbonyl vinylation is achieved from the alcohol or the aldehyde oxidation level in the absence of any stoichiometric metallic reagents. Nonsymmetric alkynes 6a–6c couple efficiently to aldehyde 4b to provide allylic alcohols 2m–2o as single regioisomers. Acetylenic aldehyde 7a engages in efficient intramolecular coupling to deliver cyclic allylic alcohol 8a. PMID:19173651

  12. Ruthenium-Catalyzed Formal Dehydrative [4 + 2] Cycloaddition of Enamides and Alkynes for the Synthesis of Highly Substituted Pyridines: Reaction Development and Mechanistic Study.

    Science.gov (United States)

    Wu, Jicheng; Xu, Wenbo; Yu, Zhi-Xiang; Wang, Jian

    2015-07-29

    Reported herein is a ruthenium-catalyzed formal dehydrative [4 + 2] cycloaddition of enamides and alkynes, representing a mild and economic protocol for the construction of highly substituted pyridines. Notably, the features of broad substrate scope, high efficiency, good functional group tolerance, and excellent regioselectivities were observed for this reaction. Density functional theory (DFT) calculations and experiments have been carried out to understand the mechanism and regiochemistry. DFT calculations suggested that this formal dehydrative [4 + 2] reaction starts with a concerted metalation deprotonation of the enamide by the acetate group in the Ru catalyst, which generates a six-membered ruthenacycle intermediate. Then alkyne inserts into the Ru-C bond of the six-membered ruthenacycle, giving rise to an eight-membered ruthenacycle intermediate. The carbonyl group (which comes originally from the enamide substrate and is coordinated to the Ru center in the eight-membered ruthenacycle intermediate) then inserts into the Ru-C bond to give an intermediate, which produces the final pyridine product through further dehydration. Alkyne insertion step is a regio-determining step and prefers to have the aryl groups of the used alkynes stay away from the catalyst in order to avoid repulsion of aryl group with the enamide moiety in the six-membered ruthenacycle and to keep the conjugation between the aryl group and the triple C-C bond of the alkynes. Consequently, the aryl groups of the used alkynes are in the β-position of the final pyridines, and the present reaction has high regioselectivity.

  13. Metformin selectively targets redox control of complex I energy transduction

    Directory of Open Access Journals (Sweden)

    Amy R. Cameron

    2018-04-01

    Full Text Available Many guanide-containing drugs are antihyperglycaemic but most exhibit toxicity, to the extent that only the biguanide metformin has enjoyed sustained clinical use. Here, we have isolated unique mitochondrial redox control properties of metformin that are likely to account for this difference. In primary hepatocytes and H4IIE hepatoma cells we found that antihyperglycaemic diguanides DG5-DG10 and the biguanide phenformin were up to 1000-fold more potent than metformin on cell signalling responses, gluconeogenic promoter expression and hepatocyte glucose production. Each drug inhibited cellular oxygen consumption similarly but there were marked differences in other respects. All diguanides and phenformin but not metformin inhibited NADH oxidation in submitochondrial particles, indicative of complex I inhibition, which also corresponded closely with dehydrogenase activity in living cells measured by WST-1. Consistent with these findings, in isolated mitochondria, DG8 but not metformin caused the NADH/NAD+ couple to become more reduced over time and mitochondrial deterioration ensued, suggesting direct inhibition of complex I and mitochondrial toxicity of DG8. In contrast, metformin exerted a selective oxidation of the mitochondrial NADH/NAD+ couple, without triggering mitochondrial deterioration. Together, our results suggest that metformin suppresses energy transduction by selectively inducing a state in complex I where redox and proton transfer domains are no longer efficiently coupled. Keywords: Diabetes, Metformin, Mitochondria, NADH, NAD+

  14. Ruthenium-catalyzed alkylation of indoles with tertiary amines by oxidation of a sp3 C-H bond and Lewis acid catalysis.

    Science.gov (United States)

    Wang, Ming-Zhong; Zhou, Cong-Ying; Wong, Man-Kin; Che, Chi-Ming

    2010-05-17

    Ruthenium porphyrins (particularly [Ru(2,6-Cl(2)tpp)CO]; tpp=tetraphenylporphinato) and RuCl(3) can act as oxidation and/or Lewis acid catalysts for direct C-3 alkylation of indoles, giving the desired products in high yields (up to 82% based on 60-95% substrate conversions). These ruthenium compounds catalyze oxidative coupling reactions of a wide variety of anilines and indoles bearing electron-withdrawing or electron-donating substituents with high regioselectivity when using tBuOOH as an oxidant, resulting in the alkylation of N-arylindoles to 3-{[(N-aryl-N-alkyl)amino]methyl}indoles (yield: up to 82%, conversion: up to 95%) and the alkylation of N-alkyl or N-H indoles to 3-[p-(dialkylamino)benzyl]indoles (yield: up to 73%, conversion: up to 92%). A tentative reaction mechanism involving two pathways is proposed: an iminium ion intermediate may be generated by oxidation of an sp(3) C-H bond of the alkylated aniline by an oxoruthenium species; this iminium ion could then either be trapped by an N-arylindole (pathway A) or converted to formaldehyde, allowing a subsequent three-component coupling reaction of the in situ generated formaldehyde with an N-alkylindole and an aniline in the presence of a Lewis acid catalyst (pathway B). The results of deuterium-labeling experiments are consistent with the alkylation of N-alkylindoles via pathway B. The relative reaction rates of [Ru(2,6-Cl(2)tpp)CO]-catalyzed oxidative coupling reactions of 4-X-substituted N,N-dimethylanilines with N-phenylindole (using tBuOOH as oxidant), determined through competition experiments, correlate linearly with the substituent constants sigma (R(2)=0.989), giving a rho value of -1.09. This rho value and the magnitudes of the intra- and intermolecular deuterium isotope effects (k(H)/k(D)) suggest that electron transfer most likely occurs during the initial stage of the oxidation of 4-X-substituted N,N-dimethylanilines. Ruthenium-catalyzed three-component reaction of N-alkyl/N-H indoles

  15. Microfluidic sensor for ultra high redox cycling amplification for highly selective electrochemical measurements

    NARCIS (Netherlands)

    Odijk, Mathieu; Straver, Martin; Olthuis, Wouter; van den Berg, Albert

    2011-01-01

    In this contribution a SU8/glass-based microfluidic sensor is described with two closely spaced parallel electrodes for highly selective measurements using the redox cycling (RC) effect. Using this sensor, a RC amplification of ~2000x is measured using the ferrocyanide redox couple, which is much

  16. Redox Conditions in Selected Principal Aquifers of the United States

    Science.gov (United States)

    McMahon, P.B.; Cowdery, T.K.; Chapelle, F.H.; Jurgens, B.C.

    2009-01-01

    Reduction/oxidation (redox) processes affect the quality of groundwater in all aquifer systems. Redox processes can alternately mobilize or immobilize potentially toxic metals associated with naturally occurring aquifer materials, contribute to the degradation or preservation of anthropogenic contami-nants, and generate undesirable byproducts, such as dissolved manganese (Mn2+), ferrous iron (Fe2+), hydrogen sulfide (H2S), and methane (CH4). Determining the kinds of redox processes that occur in an aquifer system, documenting their spatial distribution, and understanding how they affect concentrations of natural or anthropogenic contaminants are central to assessing and predicting the chemical quality of groundwater. This Fact Sheet extends the analysis of U.S. Geological Survey authors to additional principal aquifer systems by applying a framework developed by the USGS to a larger set of water-quality data from the USGS national water databases. For a detailed explanation, see the 'Introduction' in the Fact Sheet.

  17. Cost-driven materials selection criteria for redox flow battery electrolytes

    Science.gov (United States)

    Dmello, Rylan; Milshtein, Jarrod D.; Brushett, Fikile R.; Smith, Kyle C.

    2016-10-01

    Redox flow batteries show promise for grid-scale energy storage applications but are presently too expensive for widespread adoption. Electrolyte material costs constitute a sizeable fraction of the redox flow battery price. As such, this work develops a techno-economic model for redox flow batteries that accounts for redox-active material, salt, and solvent contributions to the electrolyte cost. Benchmark values for electrolyte constituent costs guide identification of design constraints. Nonaqueous battery design is sensitive to all electrolyte component costs, cell voltage, and area-specific resistance. Design challenges for nonaqueous batteries include minimizing salt content and dropping redox-active species concentration requirements. Aqueous battery design is sensitive to only redox-active material cost and cell voltage, due to low area-specific resistance and supporting electrolyte costs. Increasing cell voltage and decreasing redox-active material cost present major materials selection challenges for aqueous batteries. This work minimizes cost-constraining variables by mapping the battery design space with the techno-economic model, through which we highlight pathways towards low price and moderate concentration. Furthermore, the techno-economic model calculates quantitative iterations of battery designs to achieve the Department of Energy battery price target of 100 per kWh and highlights cost cutting strategies to drive battery prices down further.

  18. Thioredoxin Selectivity for Thiol-based Redox Regulation of Target Proteins in Chloroplasts*

    Science.gov (United States)

    Yoshida, Keisuke; Hara, Satoshi; Hisabori, Toru

    2015-01-01

    Redox regulation based on the thioredoxin (Trx) system is believed to ensure light-responsive control of various functions in chloroplasts. Five Trx subtypes have been reported to reside in chloroplasts, but their functional diversity in the redox regulation of Trx target proteins remains poorly clarified. To directly address this issue, we studied the Trx-dependent redox shifts of several chloroplast thiol-modulated enzymes in vitro and in vivo. In vitro assays using a series of Arabidopsis recombinant proteins provided new insights into Trx selectivity for the redox regulation as well as the underpinning for previous suggestions. Most notably, by combining the discrimination of thiol status with mass spectrometry and activity measurement, we identified an uncharacterized aspect of the reductive activation of NADP-malate dehydrogenase; two redox-active Cys pairs harbored in this enzyme were reduced via distinct utilization of Trxs even within a single polypeptide. In our in vitro assays, Trx-f was effective in reducing all thiol-modulated enzymes analyzed here. We then investigated the in vivo physiological relevance of these in vitro findings, using Arabidopsis wild-type and Trx-f-deficient plants. Photoreduction of fructose-1,6-bisphosphatase was partially impaired in Trx-f-deficient plants, but the global impact of Trx-f deficiency on the redox behaviors of thiol-modulated enzymes was not as striking as expected from the in vitro data. Our results provide support for the in vivo functionality of the Trx system and also highlight the complexity and plasticity of the chloroplast redox network. PMID:25878252

  19. Super-resolution fluorescence imaging of nanoimprinted polymer patterns by selective fluorophore adsorption combined with redox switching

    KAUST Repository

    Yabiku, Y.; Kubo, S.; Nakagawa, M.; Vacha, M.; Habuchi, Satoshi

    2013-01-01

    We applied a super-resolution fluorescence imaging based on selective adsorption and redox switching of the fluorescent dye molecules for studying polymer nanostructures. We demonstrate that nano-scale structures of polymer thin films can

  20. Ruthenium-Catalyzed Aerobic Oxidation of Amines.

    Science.gov (United States)

    Ray, Ritwika; Hazari, Arijit Singha; Lahiri, Goutam Kumar; Maiti, Debabrata

    2018-01-18

    Amine oxidation is one of the fundamental reactions in organic synthesis as it leads to a variety of value-added products such as oximes, nitriles, imines, and amides among many others. These products comprise the key N-containing building blocks in the modern chemical industry, and such transformations, when achieved in the presence of molecular oxygen without using stoichiometric oxidants, are much preferred as they circumvent the production of unwanted wastes. In parallel, the versatility of ruthenium catalysts in various oxidative transformations is well-documented. Herein, this review focuses on aerobic oxidation of amines specifically by using ruthenium catalysts and highlights the major achievements in this direction and challenges that still need to be addressed. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. NAC selectively inhibit cancer telomerase activity: A higher redox homeostasis threshold exists in cancer cells

    Directory of Open Access Journals (Sweden)

    Pengying Li

    2016-08-01

    Full Text Available Telomerase activity controls telomere length, and this plays an important role in stem cells, aging and tumors. Antioxidant was shown to protect telomerase activity in normal cells but inhibit that in cancer cells, but the underlying mechanism is elusive. Here we found that 7721 hepatoma cells held a higher redox homeostasis threshold than L02 normal liver cells which caused 7721 cells to have a higher demand for ROS; MnSOD over-expression in 7721 decreased endogenous reactive oxygen species (ROS and inhibited telomerase activity; Akt phosphorylation inhibitor and NAC both inhibited 7721 telomerase activity. The over-elimination of ROS by NAC resulted in the inhibition of Akt pathway. Our results suggest that ROS is involved in the regulation of cancer telomerase activity through Akt pathway. The different intracellular redox homeostasis and antioxidant system in normal cells and tumor cells may be the cause of the opposite effect on telomerase activity in response to NAC treatment. Our results provide a theoretical base of using antioxidants selectively inhibit cancer telomerase activity. Findings of the present study may provide insights into novel approaches for cancer treatment.

  2. A strategy for selective detection based on interferent depleting and redox cycling using the plane-recessed microdisk array electrodes

    International Nuclear Information System (INIS)

    Zhu Feng; Yan Jiawei; Lu Miao; Zhou Yongliang; Yang Yang; Mao Bingwei

    2011-01-01

    Highlights: → A novel strategy based on a combination of interferent depleting and redox cycling is proposed for the plane-recessed microdisk array electrodes. → The strategy break up the restriction of selectively detecting a species that exhibits reversible reaction in a mixture with one that exhibits an irreversible reaction. → The electrodes enhance the current signal by redox cycling. → The electrodes can work regardless of the reversibility of interfering species. - Abstract: The fabrication, characterization and application of the plane-recessed microdisk array electrodes for selective detection are demonstrated. The electrodes, fabricated by lithographic microfabrication technology, are composed of a planar film electrode and a 32 x 32 recessed microdisk array electrode. Different from commonly used redox cycling operating mode for array configurations such as interdigitated array electrodes, a novel strategy based on a combination of interferent depleting and redox cycling is proposed for the electrodes with an appropriate configuration. The planar film electrode (the plane electrode) is used to deplete the interferent in the diffusion layer. The recessed microdisk array electrode (the microdisk array), locating within the diffusion layer of the plane electrode, works for detecting the target analyte in the interferent-depleted diffusion layer. In addition, the microdisk array overcomes the disadvantage of low current signal for a single microelectrode. Moreover, the current signal of the target analyte that undergoes reversible electron transfer can be enhanced due to the redox cycling between the plane electrode and the microdisk array. Based on the above working principle, the plane-recessed microdisk array electrodes break up the restriction of selectively detecting a species that exhibits reversible reaction in a mixture with one that exhibits an irreversible reaction, which is a limitation of single redox cycling operating mode. The

  3. The intracellular redox stress caused by hexavalent chromium is selective for proteins that have key roles in cell survival and thiol redox control

    International Nuclear Information System (INIS)

    Myers, Judith M.; Antholine, William E.; Myers, Charles R.

    2011-01-01

    Hexavalent chromium [Cr(VI)] compounds (e.g. chromates) are strong oxidants that readily enter cells where they are reduced to reactive Cr intermediates that can directly oxidize some cell components and can promote the generation of reactive oxygen and nitrogen species. Inhalation is a major route of exposure which directly exposes the bronchial epithelium. Previous studies with non-cancerous human bronchial epithelial cells (BEAS-2B) demonstrated that Cr(VI) treatment results in the irreversible inhibition of thioredoxin reductase (TrxR) and the oxidation of thioredoxins (Trx) and peroxiredoxins (Prx). The mitochondrial Trx/Prx system is somewhat more sensitive to Cr(VI) than the cytosolic Trx/Prx system, and other redox-sensitive mitochondrial functions are subsequently affected including electron transport complexes I and II. Studies reported here show that Cr(VI) does not cause indiscriminant thiol oxidation, and that the Trx/Prx system is among the most sensitive of cellular protein thiols. Trx/Prx oxidation is not unique to BEAS-2B cells, as it was also observed in primary human bronchial epithelial cells. Increasing the intracellular levels of ascorbate, an endogenous Cr(VI) reductant, did not alter the effects on TrxR, Trx, or Prx. The peroxynitrite scavenger MnTBAP did not protect TrxR, Trx, Prx, or the electron transport chain from the effects of Cr(VI), implying that peroxynitrite is not required for these effects. Nitration of tyrosine residues of TrxR was not observed following Cr(VI) treatment, further ruling out peroxynitrite as a significant contributor to the irreversible inhibition of TrxR. Cr(VI) treatments that disrupt the TrxR/Trx/Prx system did not cause detectable mitochondrial DNA damage. Overall, the redox stress that results from Cr(VI) exposure shows selectivity for key proteins which are known to be important for redox signaling, antioxidant defense, and cell survival.

  4. Redox Cycling Realized in Paper-Based Biochemical Sensor for Selective Detection of Reversible Redox Molecules Without Micro/Nano Fabrication Process.

    Science.gov (United States)

    Yamamoto, So; Uno, Shigeyasu

    2018-02-28

    This paper describes a paper-based biochemical sensor that realizes redox cycling with close interelectrode distance. Two electrodes, the generator and collector electrodes, can detect steady-state oxidation and reduction currents when suitable potential is held at each electrode. The sensor has two gold plates on both sides of a piece of chromatography paper and defines the interelectrode distance by the thickness of the paper (180 μm) without any micro-fabrication processes. Our proposed sensor geometry has successfully exhibited signatures of redox cycling. As a result, the concentration of ferrocyanide as reversible redox molecules was successfully quantified under the interference by ascorbic acid as a strong irreversible reducing agent. This was possible because the ascorbic acids are completely consumed by the irreversible reaction, while maintaining redox cycling of reversible ferrocyanide. This suggests that a sensor based on the redox cycling method will be suitable for detecting target molecules at low concentration.

  5. Intracellular Diagnostics: Hunting for the Mode of Action of Redox-Modulating Selenium Compounds in Selected Model Systems

    Directory of Open Access Journals (Sweden)

    Dominika Mániková

    2014-08-01

    Full Text Available Redox-modulating compounds derived from natural sources, such as redox active secondary metabolites, are currently of considerable interest in the field of chemoprevention, drug and phytoprotectant development. Unfortunately, the exact and occasionally even selective activity of such products, and the underlying (bio-chemical causes thereof, are often only poorly understood. A combination of the nematode- and yeast-based assays provides a powerful platform to investigate a possible biological activity of a new compound and also to explore the “redox link” which may exist between its activity on the one side and its chemistry on the other. Here, we will demonstrate the usefulness of this platform for screening several selenium and tellurium compounds for their activity and action. We will also show how the nematode-based assay can be used to obtain information on compound uptake and distribution inside a multicellular organism, whilst the yeast-based system can be employed to explore possible intracellular mechanisms via chemogenetic screening and intracellular diagnostics. Whilst none of these simple and easy-to-use assays can ultimately substitute for in-depth studies in human cells and animals, these methods nonetheless provide a first glimpse on the possible biological activities of new compounds and offer direction for more complicated future investigations. They may also uncover some rather unpleasant biochemical actions of certain compounds, such as the ability of the trace element supplement selenite to induce DNA strand breaks.

  6. Super-resolution fluorescence imaging of nanoimprinted polymer patterns by selective fluorophore adsorption combined with redox switching

    Directory of Open Access Journals (Sweden)

    Yu Yabiku

    2013-10-01

    Full Text Available We applied a super-resolution fluorescence imaging based on selective adsorption and redox switching of the fluorescent dye molecules for studying polymer nanostructures. We demonstrate that nano-scale structures of polymer thin films can be visualized with the image resolution better than 80 nm. The method was applied to image 100 nm-wide polymer nanopatterns fabricated by thermal nanoimprinting. The results point to the applicability of the method for evaluating residual polymer thin films and dewetting defect of the polymer resist patterns which are important for the quality control of the fine nanoimprinted patterns.

  7. Super-resolution fluorescence imaging of nanoimprinted polymer patterns by selective fluorophore adsorption combined with redox switching

    KAUST Repository

    Yabiku, Y.

    2013-10-22

    We applied a super-resolution fluorescence imaging based on selective adsorption and redox switching of the fluorescent dye molecules for studying polymer nanostructures. We demonstrate that nano-scale structures of polymer thin films can be visualized with the image resolution better than 80 nm. The method was applied to image 100 nm-wide polymer nanopatterns fabricated by thermal nanoimprinting. The results point to the applicability of the method for evaluating residual polymer thin films and dewetting defect of the polymer resist patterns which are important for the quality control of the fine nanoimprinted patterns. 2013 Author(s).

  8. The influence of supplementation with artichoke (Cynara scolymus L.) extract on selected redox parameters in rowers.

    Science.gov (United States)

    Skarpanska-Stejnborn, Anna; Pilaczynska-Szczesniak, Lucia; Basta, Piotr; Deskur-Smielcka, Ewa; Horoszkiewicz-Hassan, Magorzata

    2008-06-01

    High-intensity physical exercise decreases intracellular antioxidant potential. An enhanced antioxidant defense system is desirable in people subjected to exhaustive exercise. The aim of this study was to investigate the influence of supplementation with artichoke-leaf extract on parameters describing balance between oxidants and antioxidants in competitive rowers. This double-blinded study was carried out in 22 members of the Polish rowing team who were randomly assigned to a supplemented group (n = 12), receiving 1 gelatin capsule containing 400 mg of artichoke-leaf extract 3 times a day for 5 wk, or a placebo group (n = 10). At the beginning and end of the study participants performed a 2,000-m maximal test on a rowing ergometer. Before each exercise test, 1 min after the test completion, and after a 24-hr restitution period blood samples were taken from antecubital vein. The following redox parameters were assessed in red blood cells: superoxide dismutase activity, glutathione peroxidase activity, glutathione reductase activity, reduced glutathione levels, and thiobarbituric-acid-reactive-substances concentrations. Creatine kinase activity and total antioxidant capacity (TAC) were measured in plasma samples, lactate levels were determined in capillary blood samples, and serum lipid profiles were assessed. During restitution, plasma TAC was significantly higher (p artichoke-leaf extract, a natural vegetable preparation of high antioxidant potential, resulted in higher plasma TAC than placebo but did not limit oxidative damage to erythrocytes in competitive rowers subjected to strenuous training.

  9. Evaluation of Selected CYP51A1 Polymorphisms in View of Interactions with Substrate and Redox Partner

    Directory of Open Access Journals (Sweden)

    Tadeja Režen

    2017-06-01

    Full Text Available Cholesterol is essential for development, growth, and maintenance of organisms. Mutations in cholesterol biosynthetic genes are embryonic lethal and few polymorphisms have been so far associated with pathologies in humans. Previous analyses show that lanosterol 14α-demethylase (CYP51A1 from the late part of cholesterol biosynthesis has only a few missense mutations with low minor allele frequencies and low association with pathologies in humans. The aim of this study is to evaluate the role of amino acid changes in the natural missense mutations of the hCYP51A1 protein. We searched SNP databases for existing polymorphisms of CYP51A1 and evaluated their effect on protein function. We found rare variants causing detrimental missense mutations of CYP51A1. Some missense variants were also associated with a phenotype in humans. Two missense variants have been prepared for testing enzymatic activity in vitro but failed to produce a P450 spectrum. We performed molecular modeling of three selected missense variants to evaluate the effect of the amino acid substitution on potential interaction with its substrate and the obligatory redox partner POR. We show that two of the variants, R277L and especially D152G, have possibly lower binding potential toward obligatory redox partner POR. D152G and R431H have also potentially lower affinity toward the substrate lanosterol. We evaluated the potential effect of damaging variants also using data from other in vitro CYP51A1 mutants. In conclusion, we propose to include damaging CYP51A1 variants into personalized diagnostics to improve genetic counseling for certain rare disease phenotypes.

  10. Redox fronts

    International Nuclear Information System (INIS)

    Chapman, N.; McKinley, I.; Shea, M.; Smellie, J.

    1993-01-01

    This article describes the investigations of redox fronts performed at the Osamu Utsumi mine. Results obtained by modelling groups on the rate of movement of the redox fronts and on the chemical reactions involved are discussed. Some of the most important rockwater interactions which occur at redox fronts can be modelled reasonably well but the complex redox chemistry of elements like sulphur is poorly simulated. The observed enrichment of many trace elements close to the redox fronts could be of significance for high-level waste repositories, but cannot be quantified by existing models. (author) 6 figs., 1 tab

  11. Semi-fluorinated sulfonated polyimide membranes with enhanced proton selectivity and stability for vanadium redox flow batteries

    International Nuclear Information System (INIS)

    Li, Jinchao; Liu, Suqin; He, Zhen; Zhou, Zhi

    2016-01-01

    A series of semi-fluorinated sulfonated polyimides (6F-SPIs) are designed and synthesized via a one-step high-temperature polycondensation reaction. The sulfonation degrees of 6F-SPIs are controlled through changing the ratio of sulfonated diamine to non-sulfonated diamine in the casting solution. The physico-chemical properties and single cell performance of 6F-SPI membranes are thoroughly evaluated and compared to a non-fluorinated SPI membrane (6H-SPI-50) and a Nafion 115 membrane. The results show that the designed 6F-SPI membrane with a 50% sulfonation degree (6F-SPI-50) possesses the highest proton selectivity (1.613 × 10 5 S min cm −3 ) among all tested membranes. Besides, the 6F-SPI-50 membrane exhibits a promising performance for vanadium redox flow batteries (VRFBs), showing higher coulombic efficiencies (96.90–99.20%) and energy efficiencies (88.25–64.80%) than the Nafion 115 membrane (with coulombic efficiencies of 90.60–96.70% and energy efficiencies of 81.04–60.10%) at the current densities ranging from 20 to 100 mA cm −2 . Moreover, the 6F-SPI-50 membrane shows excellent chemical stability in the VRFB system. This work paves the way for the development of a new class of 6F-SPI membranes for the VRFB application.

  12. Ruthenium-Catalyzed Alkylation of Oxindole with Alcohols

    DEFF Research Database (Denmark)

    Jensen, Thomas; Madsen, Robert

    2009-01-01

    An atom-economical and solvent-free catalytic procedure for the mono-3-alkylation of oxindole with alcohols is described. The reaction is mediated by the in situ generated catalyst from RuCl3 center dot xH(2)O and PPh3 in the presence of sodium hydroxide, The reactions proceed in good to excellent...... yields with a wide range of aromatic, heteroaromatic, and aliphatic alcohols....

  13. Geochemistry of Natural Redox Fronts

    International Nuclear Information System (INIS)

    Hofmann, B.A.

    1999-05-01

    Redox fronts are important geochemical boundaries which need to be considered in safety assessment of deep repositories for radioactive waste. In most cases, selected host-rock formations will be reducing due to the presence of ferrous minerals, sulphides, etc. During construction and operation of the repository, air will be introduced into the formation. After repository closure, oxidising conditions may persist locally until all oxygen is consumed. In the case of high-level waste, radiolysis of water may provide an additional source of oxidants. Oxidising conditions within a repository are thus possible and potentially have a strong influence on the mobility of many elements. The rate of movement of redox fronts, the boundary between oxidising and reducing environments, and their influence on migrating radionuclides are thus important factors influencing repository performance. The present report is a review of elemental behaviour at natural redox fronts, based on published information and work of the author. Redox fronts are geochemically and geometrically variable manifestations of a global interface between generally oxidising geochemical milieux in contact with the atmosphere and generally reducing milieux in contact with rocks containing ferrous iron, sulphide and/or organic carbon. A classification of redox fronts based on a subdivision into continental near-surface, marine near-surface, and deep environments is proposed. The global redox interface is often located close to the surface of rocks and sediments and, sometimes, within bodies of water. Temperature conditions are close to ambient. A deeper penetration of the global redox front to depths of several kilometres is found in basins containing oxidised sediments (red beds) and in some hydrothermal circulation systems. Temperatures at such deep redox fronts may reach 200 o C. Both near-surface and deep redox fronts are sites of formation of economic deposits of redox-sensitive elements, particularly of

  14. Comparative toxicities of selected rare earth elements: Sea urchin embryogenesis and fertilization damage with redox and cytogenetic effects

    Energy Technology Data Exchange (ETDEWEB)

    Pagano, Giovanni, E-mail: gbpagano@tin.it [“Federico II” University of Naples, Environmental Hygiene, I-80126 Naples (Italy); Guida, Marco; Siciliano, Antonietta [“Federico II” University of Naples, Environmental Hygiene, I-80126 Naples (Italy); Oral, Rahime [Ege University, Faculty of Fisheries, TR-35100 Bornova, İzmir (Turkey); Koçbaş, Fatma [Celal Bayar University, Faculty of Arts and Sciences, Department of Biology, TR-45140 Yunusemre, Manisa (Turkey); Palumbo, Anna; Castellano, Immacolata; Migliaccio, Oriana [Stazione Zoologica Anton Dohrn, Villa Comunale, 80121 Naples (Italy); Thomas, Philippe J. [Environment Canada, Science & Technology Branch, National Wildlife Research Center – Carleton University, Ottawa, Ontario, Canada K1A 0H3 (Canada); Trifuoggi, Marco [“Federico II” University of Naples, Department of Chemical Sciences, I-80126 Naples (Italy)

    2016-05-15

    Background: Broad-ranging adverse effects are known for rare earth elements (REE), yet only a few studies tested the toxicity of several REE, prompting studies focusing on multi-parameter REE toxicity. Methods: Trichloride salts of Y, La, Ce, Nd, Sm, Eu and Gd were tested in Paracentrotus lividus sea urchin embryos and sperm for: (1) developmental defects in either REE-exposed larvae or in the offspring of REE-exposed sperm; (2) fertilization success; (3) mitotic anomalies in REE-exposed embryos and in the offspring of REE-exposed sperm, and (4) reactive oxygen species (ROS) formation, and malondialdehyde (MDA) and nitric oxide (NO) levels. Results: REEs affected P. lividus larvae with concentration-related increase in developmental defects, 10{sup −6} to 10{sup −4} M, ranking as: Gd(III)>Y(III)>La(III)>Nd(III)≅Eu(III)>Ce(III)≅Sm(III). Nominal concentrations of REE salts were confirmed by inductively coupled plasma mass spectrometry (ICP-MS). Significant increases in MDA levels, ROS formation, and NO levels were found in REE-exposed embryos. Sperm exposure to REEs (10{sup −5} to 10{sup −4} M) resulted in concentration-related decrease in fertilization success along with increase in offspring damage. Decreased mitotic activity and increased aberration rates were detected in REE-exposed embryos and in the offspring of REE-exposed sperm. Conclusion: REE-associated toxicity affecting embryogenesis, fertilization, cytogenetic and redox endpoints showed different activities of tested REEs. Damage to early life stages, along with redox and cytogenetic anomalies should be the focus of future REE toxicity studies. - Highlights: • Seven rare earth elements exerted different effects on sea urchin early life stages. • Embryo-, spermio- and mitotoxicity, and oxidative/ nitrosative stress were found. • Nominal vs. analytical REE concentrations were checked. • Comparative toxicities were evaluated for the different REE.

  15. Comparative toxicities of selected rare earth elements: Sea urchin embryogenesis and fertilization damage with redox and cytogenetic effects

    International Nuclear Information System (INIS)

    Pagano, Giovanni; Guida, Marco; Siciliano, Antonietta; Oral, Rahime; Koçbaş, Fatma; Palumbo, Anna; Castellano, Immacolata; Migliaccio, Oriana; Thomas, Philippe J.; Trifuoggi, Marco

    2016-01-01

    Background: Broad-ranging adverse effects are known for rare earth elements (REE), yet only a few studies tested the toxicity of several REE, prompting studies focusing on multi-parameter REE toxicity. Methods: Trichloride salts of Y, La, Ce, Nd, Sm, Eu and Gd were tested in Paracentrotus lividus sea urchin embryos and sperm for: (1) developmental defects in either REE-exposed larvae or in the offspring of REE-exposed sperm; (2) fertilization success; (3) mitotic anomalies in REE-exposed embryos and in the offspring of REE-exposed sperm, and (4) reactive oxygen species (ROS) formation, and malondialdehyde (MDA) and nitric oxide (NO) levels. Results: REEs affected P. lividus larvae with concentration-related increase in developmental defects, 10 −6 to 10 −4 M, ranking as: Gd(III)>Y(III)>La(III)>Nd(III)≅Eu(III)>Ce(III)≅Sm(III). Nominal concentrations of REE salts were confirmed by inductively coupled plasma mass spectrometry (ICP-MS). Significant increases in MDA levels, ROS formation, and NO levels were found in REE-exposed embryos. Sperm exposure to REEs (10 −5 to 10 −4 M) resulted in concentration-related decrease in fertilization success along with increase in offspring damage. Decreased mitotic activity and increased aberration rates were detected in REE-exposed embryos and in the offspring of REE-exposed sperm. Conclusion: REE-associated toxicity affecting embryogenesis, fertilization, cytogenetic and redox endpoints showed different activities of tested REEs. Damage to early life stages, along with redox and cytogenetic anomalies should be the focus of future REE toxicity studies. - Highlights: • Seven rare earth elements exerted different effects on sea urchin early life stages. • Embryo-, spermio- and mitotoxicity, and oxidative/ nitrosative stress were found. • Nominal vs. analytical REE concentrations were checked. • Comparative toxicities were evaluated for the different REE.

  16. Comparison of Selected Parameters of Redox Homeostasis in Patients with Ataxia-Telangiectasia and Nijmegen Breakage Syndrome

    Directory of Open Access Journals (Sweden)

    Barbara Pietrucha

    2017-01-01

    Full Text Available This study compared the antioxidant status and major lipophilic antioxidants in patients with ataxia-telangiectasia (AT and Nijmegen breakage syndrome (NBS. Total antioxidant status (TAS, total oxidant status (TOS, oxidative stress index (OSI, and concentrations of coenzyme Q10 (CoQ10 and vitamins A and E were estimated in the plasma of 22 patients with AT, 12 children with NBS, and the healthy controls. In AT patients, TAS (median 261.7 μmol/L was statistically lower but TOS (496.8 μmol/L was significantly elevated in comparison with the healthy group (312.7 μmol/L and 311.2 μmol/L, resp.. Tocopherol (0.8 μg/mL and CoQ10 (0.1 μg/mL were reduced in AT patients versus control (1.4 μg/mL and 0.3 μg/mL, resp.. NBS patients also displayed statistically lower TAS levels (290.3 μmol/L, while TOS (404.8 μmol/L was comparable to the controls. We found that in NBS patients retinol concentration (0.1 μg/mL was highly elevated and CoQ10 (0.1 μg/mL was significantly lower in comparison with those in the healthy group. Our study confirms disturbances in redox homeostasis in AT and NBS patients and indicates a need for diagnosing oxidative stress in those cases as a potential disease biomarker. Decreased CoQ10 concentration found in NBS and AT indicates a need for possible supplementation.

  17. Pore-Size-Tuned Graphene Oxide Frameworks as Ion-Selective and Protective Layers on Hydrocarbon Membranes for Vanadium Redox-Flow Batteries.

    Science.gov (United States)

    Kim, Soohyun; Choi, Junghoon; Choi, Chanyong; Heo, Jiyun; Kim, Dae Woo; Lee, Jang Yong; Hong, Young Taik; Jung, Hee-Tae; Kim, Hee-Tak

    2018-05-07

    The laminated structure of graphene oxide (GO) membranes provides exceptional ion-separation properties due to the regular interlayer spacing ( d) between laminate layers. However, a larger effective pore size of the laminate immersed in water (∼11.1 Å) than the hydrated diameter of vanadium ions (>6.0 Å) prevents its use in vanadium redox-flow batteries (VRFB). In this work, we report an ion-selective graphene oxide framework (GOF) with a d tuned by cross-linking the GO nanosheets. Its effective pore size (∼5.9 Å) excludes vanadium ions by size but allows proton conduction. The GOF membrane is employed as a protective layer to address the poor chemical stability of sulfonated poly(arylene ether sulfone) (SPAES) membranes against VO 2 + in VRFB. By effectively blocking vanadium ions, the GOF/SPAES membrane exhibits vanadium-ion permeability 4.2 times lower and a durability 5 times longer than that of the pristine SPAES membrane. Moreover, the VRFB with the GOF/SPAES membrane achieves an energy efficiency of 89% at 80 mA cm -2 and a capacity retention of 88% even after 400 cycles, far exceeding results for Nafion 115 and demonstrating its practical applicability for VRFB.

  18. Characterization of redox conditions in pollution plumes

    DEFF Research Database (Denmark)

    Christensen, Thomas Højlund; Bjerg, Poul Løgstrup; Banwart, Steven A.

    2000-01-01

    Evalution of redox conditions in groundwater pollution plumes is often a prerequisite for understanding the behviour of the pollutants in the plume and for selecting remediation approaches. Measuring of redox conditions in pollution plumes is, however, a fairly recent issue and yet relative few...

  19. Monitoring thioredoxin redox with a genetically encoded red fluorescent biosensor.

    Science.gov (United States)

    Fan, Yichong; Makar, Merna; Wang, Michael X; Ai, Hui-Wang

    2017-09-01

    Thioredoxin (Trx) is one of the two major thiol antioxidants, playing essential roles in redox homeostasis and signaling. Despite its importance, there is a lack of methods for monitoring Trx redox dynamics in live cells, hindering a better understanding of physiological and pathological roles of the Trx redox system. In this work, we developed the first genetically encoded fluorescent biosensor for Trx redox by engineering a redox relay between the active-site cysteines of human Trx1 and rxRFP1, a redox-sensitive red fluorescent protein. We used the resultant biosensor-TrxRFP1-to selectively monitor perturbations of Trx redox in various mammalian cell lines. We subcellularly localized TrxRFP1 to image compartmentalized Trx redox changes. We further combined TrxRFP1 with a green fluorescent Grx1-roGFP2 biosensor to simultaneously monitor Trx and glutathione redox dynamics in live cells in response to chemical and physiologically relevant stimuli.

  20. Artesunate-induced testicular injury: Oil from selected spices blend modulates redox homeostasis and exacerbates steroidogenesis in rat models

    Directory of Open Access Journals (Sweden)

    John A. Ajiboye

    2016-12-01

    Full Text Available The therapeutic potential of oil from blends of selected culinary spices against artesunate-induced testicular injury in albino rats was investigated. Two groups of rats each were pretreated with the oil at 1.5 and 3.00 mL respectively for seven days and after which administered artesunate (100 mg/kg bw for seven days; two other groups were administered artesunate for seven days and after which post treated with the oil at both doses respectively for another seven days; another groups were co-administered artesunate and the oil for seven days. A group was administered artesunate only for seven days, while another was fed chows only. After sacrifice, the testicular homogenates of the rats were analysed for GSH, Superoxide Dismutase (SOD, Catalase (CAT, Lipid peroxidation (LPO, 3β-HSD and 17β-HSD activities. LPO and GSH levels, SOD and CAT activities were significantly (p < 0.05 higher in rats administered artesunate only, these were significantly lowered in all treatment groups. Administration of artesunate significantly suppressed steroidogenesis, this was attenuated in all treatment groups. The antioxidant, anti-lipid peroxidative and steriodogenetic effects of the oil indicate its protective potential against artesunate-induced oxidative testicular damage.

  1. Selective extraction of actinides from high level liquid wastes. Study of the possibilities offered by the Redox properties of actinides

    International Nuclear Information System (INIS)

    Adnet, J.M.

    1991-07-01

    Partitioning of high level liquid wastes coming from nuclear fuel reprocessing by the PUREX process, consists in the elimination of minor actinides (Np, Am, and traces of Pu and U). Among the possible processes, the selective extraction of actinides with oxidation states higher than three is studied. First part of this work deals with a preliminary step; the elimination of the ruthenium from fission products solutions using the electrovolatilization of the RuO4 compound. The second part of this work concerns the complexation and oxidation reactions of the elements U, Np, Pu and Am in presence of a compound belonging to the insaturated polyanions family: the potassium phosphotungstate. For actinide ions with oxidation state (IV) complexed with phosphotungstate anion the extraction mechanism by dioctylamine was studied and the use of a chromatographic extraction technic permitted successful separations between tetravalents actinides and trivalents actinides. Finally, in accordance with the obtained results, the basis of a separation scheme for the management of fission products solutions is proposed

  2. The Effect of Acidic and Redox Properties of V2O5/CeO2-ZrO2 Catalysts in Selective Catalytic Reduction of NO by NH3

    DEFF Research Database (Denmark)

    Putluru, Siva Sankar Reddy; Riisager, Anders; Fehrmann, Rasmus

    2009-01-01

    V2O5 supported ZrO2 and CeO2–ZrO2 catalysts were prepared and characterized by N2 physisorption, XRPD, TPR, and NH3-TPD methods. The influence of calcination temperature from 400 to 600 °C on crystallinity, acidic and redox properties were studied and compared with the catalytic activity...... in the selective catalytic reduction (SCR) of NO with ammonia. The surface area of the catalysts decreased gradually with increasing calcination temperature. The SCR activity of V2O5/ZrO2 catalysts was found to be related with the support crystallinity, whereas V2O5/CeO2–ZrO2 catalysts were also dependent...... on acidic and redox properties of the catalyst. The V2O5/CeO2–ZrO2 catalysts showed high activity and selectivity for reduction of NO with NH3....

  3. Organic Redox Species in Aqueous Flow Batteries: Redox Potentials, Chemical Stability and Solubility

    Science.gov (United States)

    Wedege, Kristina; Dražević, Emil; Konya, Denes; Bentien, Anders

    2016-01-01

    Organic molecules are currently investigated as redox species for aqueous low-cost redox flow batteries (RFBs). The envisioned features of using organic redox species are low cost and increased flexibility with respect to tailoring redox potential and solubility from molecular engineering of side groups on the organic redox-active species. In this paper 33, mainly quinone-based, compounds are studied experimentially in terms of pH dependent redox potential, solubility and stability, combined with single cell battery RFB tests on selected redox pairs. Data shows that both the solubility and redox potential are determined by the position of the side groups and only to a small extent by the number of side groups. Additionally, the chemical stability and possible degradation mechanisms leading to capacity loss over time are discussed. The main challenge for the development of all-organic RFBs is to identify a redox pair for the positive side with sufficiently high stability and redox potential that enables battery cell potentials above 1 V. PMID:27966605

  4. Redox behaviors of iron by absorption spectroscopy and redox potential measurement

    International Nuclear Information System (INIS)

    Oh, Jae Yong

    2010-02-01

    This work is performed to study the redox (reduction/oxidation) behaviors of iron in aqueous system by a combination of absorption spectroscopy and redox potential measurements. There are many doubts on redox potential measurements generally showing low accuracies and high uncertainties. In the present study, redox potentials are measured by utilizing various redox electrodes such as Pt, Au, Ag, and glassy carbon (GC) electrodes. Measured redox potentials are compared with calculated redox potentials based on the chemical oxidation speciation of iron and thermodynamic data by absorption spectroscopy, which provides one of the sensitive and selective spectroscopic methods for the chemical speciation of Fe(II/III). From the comparison analyses, redox potential values measured by the Ag redox electrode are fairly consistent with those calculated by the chemical aqueous speciation of iron in the whole system. In summary, the uncertainties of measured redox potentials are closely related with the total Fe concentration and affected by the formation of mixed potentials due to Fe(III) precipitates in the pH range of 6 ∼ 9 beyond the solubility of Fe(III), whilst being independent of the initially prepared concentration ratios between Fe(II) and Fe(III)

  5. Organic Redox Species in Aqueous Flow Batteries: Redox Potentials, Chemical Stability and Solubility

    Science.gov (United States)

    Wedege, Kristina; Dražević, Emil; Konya, Denes; Bentien, Anders

    2016-12-01

    Organic molecules are currently investigated as redox species for aqueous low-cost redox flow batteries (RFBs). The envisioned features of using organic redox species are low cost and increased flexibility with respect to tailoring redox potential and solubility from molecular engineering of side groups on the organic redox-active species. In this paper 33, mainly quinone-based, compounds are studied experimentially in terms of pH dependent redox potential, solubility and stability, combined with single cell battery RFB tests on selected redox pairs. Data shows that both the solubility and redox potential are determined by the position of the side groups and only to a small extent by the number of side groups. Additionally, the chemical stability and possible degradation mechanisms leading to capacity loss over time are discussed. The main challenge for the development of all-organic RFBs is to identify a redox pair for the positive side with sufficiently high stability and redox potential that enables battery cell potentials above 1 V.

  6. The Redox Code.

    Science.gov (United States)

    Jones, Dean P; Sies, Helmut

    2015-09-20

    The redox code is a set of principles that defines the positioning of the nicotinamide adenine dinucleotide (NAD, NADP) and thiol/disulfide and other redox systems as well as the thiol redox proteome in space and time in biological systems. The code is richly elaborated in an oxygen-dependent life, where activation/deactivation cycles involving O₂ and H₂O₂ contribute to spatiotemporal organization for differentiation, development, and adaptation to the environment. Disruption of this organizational structure during oxidative stress represents a fundamental mechanism in system failure and disease. Methodology in assessing components of the redox code under physiological conditions has progressed, permitting insight into spatiotemporal organization and allowing for identification of redox partners in redox proteomics and redox metabolomics. Complexity of redox networks and redox regulation is being revealed step by step, yet much still needs to be learned. Detailed knowledge of the molecular patterns generated from the principles of the redox code under defined physiological or pathological conditions in cells and organs will contribute to understanding the redox component in health and disease. Ultimately, there will be a scientific basis to a modern redox medicine.

  7. Plant redox proteomics

    DEFF Research Database (Denmark)

    Navrot, Nicolas; Finnie, Christine; Svensson, Birte

    2011-01-01

    PTMs in regulating enzymatic activities and controlling biological processes in plants. Notably, proteins controlling the cellular redox state, e.g. thioredoxin and glutaredoxin, appear to play dual roles to maintain oxidative stress resistance and regulate signal transduction pathways via redox PTMs......In common with other aerobic organisms, plants are exposed to reactive oxygen species resulting in formation of post-translational modifications related to protein oxidoreduction (redox PTMs) that may inflict oxidative protein damage. Accumulating evidence also underscores the importance of redox....... To get a comprehensive overview of these types of redox-regulated pathways there is therefore an emerging interest to monitor changes in redox PTMs on a proteome scale. Compared to some other PTMs, e.g. protein phosphorylation, redox PTMs have received less attention in plant proteome analysis, possibly...

  8. Engineered Proteins: Redox Properties and Their Applications

    Science.gov (United States)

    Prabhulkar, Shradha; Tian, Hui; Wang, Xiaotang; Zhu, Jun-Jie

    2012-01-01

    Abstract Oxidoreductases and metalloproteins, representing more than one third of all known proteins, serve as significant catalysts for numerous biological processes that involve electron transfers such as photosynthesis, respiration, metabolism, and molecular signaling. The functional properties of the oxidoreductases/metalloproteins are determined by the nature of their redox centers. Protein engineering is a powerful approach that is used to incorporate biological and abiological redox cofactors as well as novel enzymes and redox proteins with predictable structures and desirable functions for important biological and chemical applications. The methods of protein engineering, mainly rational design, directed evolution, protein surface modifications, and domain shuffling, have allowed the creation and study of a number of redox proteins. This review presents a selection of engineered redox proteins achieved through these methods, resulting in a manipulation in redox potentials, an increase in electron-transfer efficiency, and an expansion of native proteins by de novo design. Such engineered/modified redox proteins with desired properties have led to a broad spectrum of practical applications, ranging from biosensors, biofuel cells, to pharmaceuticals and hybrid catalysis. Glucose biosensors are one of the most successful products in enzyme electrochemistry, with reconstituted glucose oxidase achieving effective electrical communication with the sensor electrode; direct electron-transfer-type biofuel cells are developed to avoid thermodynamic loss and mediator leakage; and fusion proteins of P450s and redox partners make the biocatalytic generation of drug metabolites possible. In summary, this review includes the properties and applications of the engineered redox proteins as well as their significance and great potential in the exploration of bioelectrochemical sensing devices. Antioxid. Redox Signal. 17, 1796–1822. PMID:22435347

  9. The Redox Proteome*

    Science.gov (United States)

    Go, Young-Mi; Jones, Dean P.

    2013-01-01

    The redox proteome consists of reversible and irreversible covalent modifications that link redox metabolism to biologic structure and function. These modifications, especially of Cys, function at the molecular level in protein folding and maturation, catalytic activity, signaling, and macromolecular interactions and at the macroscopic level in control of secretion and cell shape. Interaction of the redox proteome with redox-active chemicals is central to macromolecular structure, regulation, and signaling during the life cycle and has a central role in the tolerance and adaptability to diet and environmental challenges. PMID:23861437

  10. Characterization of redox conditions in groundwater contaminant plumes

    Science.gov (United States)

    Christensen, Thomas H.; Bjerg, Poul L.; Banwart, Steven A.; Jakobsen, Rasmus; Heron, Gorm; Albrechtsen, Hans-Jørgen

    2000-10-01

    Evaluation of redox conditions in groundwater pollution plumes is often a prerequisite for understanding the behaviour of the pollutants in the plume and for selecting remediation approaches. Measuring of redox conditions in pollution plumes is, however, a fairly recent issue and yet relative few cases have been reported. No standardised or generally accepted approach exists. Slow electrode kinetics and the common lack of internal equilibrium of redox processes in pollution plumes make, with a few exceptions, direct electrochemical measurement and rigorous interpretation of redox potentials dubious, if not erroneous. Several other approaches have been used in addressing redox conditions in pollution plumes: redox-sensitive compounds in groundwater samples, hydrogen concentrations in groundwater, concentrations of volatile fatty acids in groundwater, sediment characteristics and microbial tools, such as MPN counts, PLFA biomarkers and redox bioassays. This paper reviews the principles behind the different approaches, summarizes methods used and evaluates the approaches based on the experience from the reported applications.

  11. Redox signaling in plants.

    Science.gov (United States)

    Foyer, Christine H; Noctor, Graham

    2013-06-01

    Our aim is to deliver an authoritative and challenging perspective of current concepts in plant redox signaling, focusing particularly on the complex interface between the redox and hormone-signaling pathways that allow precise control of plant growth and defense in response to metabolic triggers and environmental constraints and cues. Plants produce significant amounts of singlet oxygen and other reactive oxygen species (ROS) as a result of photosynthetic electron transport and metabolism. Such pathways contribute to the compartment-specific redox-regulated signaling systems in plant cells that convey information to the nucleus to regulate gene expression. Like the chloroplasts and mitochondria, the apoplast-cell wall compartment makes a significant contribution to the redox signaling network, but unlike these organelles, the apoplast has a low antioxidant-buffering capacity. The respective roles of ROS, low-molecular antioxidants, redox-active proteins, and antioxidant enzymes are considered in relation to the functions of plant hormones such as salicylic acid, jasmonic acid, and auxin, in the composite control of plant growth and defense. Regulation of redox gradients between key compartments in plant cells such as those across the plasma membrane facilitates flexible and multiple faceted opportunities for redox signaling that spans the intracellular and extracellular environments. In conclusion, plants are recognized as masters of the art of redox regulation that use oxidants and antioxidants as flexible integrators of signals from metabolism and the environment.

  12. Cytotoxicity from coupled redox cycling of autoxidizing xenobiotics and metals: a selective critical review and commentary on work-in-progress

    Energy Technology Data Exchange (ETDEWEB)

    Borg, D C; Schaich, K M

    1984-01-01

    A comprehensive reaction schema for oxidative cytotoxicity is presented, integrating known chemical mechanisms of oxygen radical reactions and observed pathophysiology. The key features of the schema are the coupling of (1) redox cycling of autoxidizable substrates to form the equilibrium pair of superoxide anion (O/sub 2//sup -/)/and its conjugate acid, perhydroxyl radical (HO/sub 2/.); (2) hydrogen peroxide (H/sub 2/O/sub 2/) generation via O/sub 2//sup -/ dimutation; (3) catalytic redox cycling of metals reducing H/sub 2/O/sub 2/ to reactive hydroxyl radicals (OH.); (4) direct reaction of OH. with target molecules, including critical cell macromolecules and polyunsaturated lipids in membranes; (5) transfer of oxidative potential from initial to distant sites via H/sub 2/O/sub 2/ and O/sub 2/-/HO/sub 2/ diffusion, lipid free radical chain peroxidations in membranes, and migration of non-radical lipid oxidation products; and (6) cytotoxic damage at those distant sites mediated by reaction of lipid radical species and other lipid oxidation products with critical target molecules (proteins, DNA, etc.). Although there is a broad consensus of agreement within the cognizant research community concerning many aspects of this schema, there exists considerable controversy and/or misconception about several important issues. Critical analyses of four presently controversial points are presented.

  13. Polyvinylpyrrolidone-based semi-interpenetrating polymer networks as highly selective and chemically stable membranes for all vanadium redox flow batteries

    Science.gov (United States)

    Zeng, L.; Zhao, T. S.; Wei, L.; Zeng, Y. K.; Zhang, Z. H.

    2016-09-01

    Vanadium redox flow batteries (VRFBs) with their high flexibility in configuration and operation, as well as long cycle life are competent for the requirement of future energy storage systems. Nevertheless, due to the application of perfluorinated membranes, VRFBs are plagued by not only the severe migration issue of vanadium ions, but also their high cost. Herein, we fabricate semi-interpenetrating polymer networks (SIPNs), consisting of cross-linked polyvinylpyrrolidone (PVP) and polysulfone (PSF), as alternative membranes for VRFBs. It is demonstrated that the PVP-based SIPNs exhibit extremely low vanadium permeabilities, which contribute to the well-established hydrophilic/hydrophobic microstructures and the Donnan exclusion effect. As a result, the coulombic efficiencies of VRFBs with PVP-based SIPNs reach almost 100% at 40 mA cm-2 to 100 mA cm-2; the energy efficiencies are more than 3% higher than those of VRFBs with Nafion 212. More importantly, the PVP-based SIPNs exhibit a superior chemical stability, as demonstrated both by an ex situ immersion test and continuously cycling test. Hence, all the characterizations and performance tests reported here suggest that PVP-based SIPNs are a promising alternative membrane for redox flow batteries to achieve superior cell performance and excellent cycling stability at the fraction of the cost of perfluorinated membranes.

  14. Organic non-aqueous cation-based redox flow batteries

    Science.gov (United States)

    Jansen, Andrew N.; Vaughey, John T.; Chen, Zonghai; Zhang, Lu; Brushett, Fikile R.

    2016-03-29

    The present invention provides a non-aqueous redox flow battery comprising a negative electrode immersed in a non-aqueous liquid negative electrolyte, a positive electrode immersed in a non-aqueous liquid positive electrolyte, and a cation-permeable separator (e.g., a porous membrane, film, sheet, or panel) between the negative electrolyte from the positive electrolyte. During charging and discharging, the electrolytes are circulated over their respective electrodes. The electrolytes each comprise an electrolyte salt (e.g., a lithium or sodium salt), a transition-metal free redox reactant, and optionally an electrochemically stable organic solvent. Each redox reactant is selected from an organic compound comprising a conjugated unsaturated moiety, a boron cluster compound, and a combination thereof. The organic redox reactant of the positive electrolyte is selected to have a higher redox potential than the redox reactant of the negative electrolyte.

  15. Chloroplast Redox Poise

    DEFF Research Database (Denmark)

    Steccanella, Verdiana

    the redox status of the plastoquinone pool and chlorophyll biosynthesis. Furthermore, in the plant cell, the equilibrium between redox reactions and ROS signals is also maintained by various balancing mechanisms among which the thioredoxin reductase-thioredoxin system (TR-Trx) stands out as a mediator......The redox state of the chloroplast is maintained by a delicate balance between energy production and consumption and is affected by the need to avoid increased production of reactive oxygen species (ROS). Redox power and ROS generated in the chloroplast are essential for maintaining physiological...... metabolic pathways and for optimizing chloroplast functions. The redox poise of photosynthetic electron transport components like plastoquinone is crucial to initiate signaling cascades and might also be involved in key biosynthetic pathways such as chlorophyll biosynthesis. We, therefore, explored...

  16. A Membrane‐Free Redox Flow Battery with Two Immiscible Redox Electrolytes

    OpenAIRE

    Navalpotro, Paula; Palma, Jesus; Anderson, Marc; Marcilla, Rebeca

    2017-01-01

    Abstract Flexible and scalable energy storage solutions are necessary for mitigating fluctuations of renewable energy sources. The main advantage of redox flow batteries is their ability to decouple power and energy. However, they present some limitations including poor performance, short‐lifetimes, and expensive ion‐selective membranes as well as high price, toxicity, and scarcity of vanadium compounds. We report a membrane‐free battery that relies on the immiscibility of redox electrolytes ...

  17. Electrooxidative Ruthenium-Catalyzed C-H/O-H Annulation by Weak O-Coordination.

    Science.gov (United States)

    Qiu, Youai; Tian, Cong; Massignan, Leonardo; Rogge, Torben; Ackermann, Lutz

    2018-05-14

    Electrocatalysis has been identified as a powerful strategy for organometallic catalysis, and yet electrocatalytic C-H activation is restricted to strongly N-coordinating directing groups. The first example of electrocatalytic C-H activation by weak O-coordination is presented, in which a versatile ruthenium(II) carboxylate catalyst enables electrooxidative C-H/O-H functionalization for alkyne annulations in the absence of metal oxidants; thereby exploiting sustainable electricity as the sole oxidant. Mechanistic insights provide strong support for a facile organometallic C-H ruthenation and an effective electrochemical reoxidation of the key ruthenium(0) intermediate. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Understanding LiOH chemistry in a ruthenium-catalyzed Li-O{sub 2} battery

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Tao; Liu, Zigeng; Kim, Gunwoo; Grey, Clare P. [Department of Chemistry, University of Cambridge (United Kingdom); Frith, James T.; Garcia-Araez, Nuria [Department of Chemistry, University of Southampton (United Kingdom)

    2017-12-11

    Non-aqueous Li-O{sub 2} batteries are promising for next-generation energy storage. New battery chemistries based on LiOH, rather than Li{sub 2}O{sub 2}, have been recently reported in systems with added water, one using a soluble additive LiI and the other using solid Ru catalysts. Here, the focus is on the mechanism of Ru-catalyzed LiOH chemistry. Using nuclear magnetic resonance, operando electrochemical pressure measurements, and mass spectrometry, it is shown that on discharging LiOH forms via a 4 e{sup -} oxygen reduction reaction, the H in LiOH coming solely from added H{sub 2}O and the O from both O{sub 2} and H{sub 2}O. On charging, quantitative LiOH oxidation occurs at 3.1 V, with O being trapped in a form of dimethyl sulfone in the electrolyte. Compared to Li{sub 2}O{sub 2}, LiOH formation over Ru incurs few side reactions, a critical advantage for developing a long-lived battery. An optimized metal-catalyst-electrolyte couple needs to be sought that aids LiOH oxidation and is stable towards attack by hydroxyl radicals. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  19. RUTHENIUM-CATALYZED TANDEM OLEFIN MIGRATION-ALDOL AND MANNICH-TYPE REACTIONS IN IONIC LIQUID.

    Science.gov (United States)

    In the presence of a catalytic amount of RuCl2(PPh3)3, a cross-coupling of 3-buten-2-ol with aldehydes and imines was developed via a tandem olefin migration--aldol--Mannich reaction in bmim[PF6]. With In(OAc)3 as a co-catalyst, a-vinylbenzyl alcohol and aldehydes underwent sim...

  20. Ruthenium-Catalyzed Transformations of Alcohols: Mechanistic Investigations and Methodology Development

    DEFF Research Database (Denmark)

    Makarov, Ilya; Madsen, Robert; Fristrup, Peter

    with dimethoxyisopropylidene and pyridilidene ligands could be more active than RuCl2(IiPr)(p-cymene) used in the mechanistic investigation. Two analogs of the calculated complexes were synthesized but were not isolated in a pure form. The amidation reaction catalyzed by a mixture containing the N-ethyl pyridilidene...

  1. Ruthenium-catalyzed self-coupling of primary and secondary alcohols with the liberation of dihydrogen

    DEFF Research Database (Denmark)

    Makarov, Ilya; Madsen, Robert

    2013-01-01

    The dehydrogenative self-condensation of primary and secondary alcohols has been studied in the presence of RuCl2(IiPr)(p-cymene). The conversion of primary alcohols into esters has been further optimized by using magnesium nitride as an additive, which allows the reaction to take place...... at a temperature and catalyst loading lower than those described previously. Secondary alcohols were dimerized into racemic ketones by a dehydrogenative Guerbet reaction with potassium hydroxide as the additive. The transformation gave good yields of the ketone dimers with a range of alkan-2-ols, whereas more...... substituted secondary alcohols were unreactive. The reaction proceeds by dehydrogenation to the ketone, followed by an aldol reaction and hydrogenation of the resulting enone. © 2013 American Chemical Society....

  2. Iridium- and Ruthenium-Catalyzed N-alkylation of Amines with Alcohols and Amines

    DEFF Research Database (Denmark)

    Lorentz-Petersen, Linda Luise Reeh

    -helical propensity. Hereby, it was believed that more stable proteins would be obtained. Folding of the mutants was studied in terms of thermodynamics and kinetics by guanidine hydrochloride denaturation monitored by fluorescence. The results were unfortunately unreliable due to errors in the spectrofluorometer....... in the reaction, as ethyleneglycol and 1,2-ethylenediamine failed to produce piperazine. Introduction of a C-substituent on one or both of the starting materials gave Csubstituted piperazines in high yields. Synthesis of N-benzylpiperazine from ethyleneglycol and N-benzylethylenediamine was also successful. Self...... experiments were conducted and emphasized the importance of the Voigt reaction in the formation of the product. Protein folding During an external stay at The Scripps Research Institute, San Diego, California, USA, folding of the well-known protein CI2 was studied. Several mutants were synthetically prepared...

  3. Redox Species of Redox Flow Batteries: A Review.

    Science.gov (United States)

    Pan, Feng; Wang, Qing

    2015-11-18

    Due to the capricious nature of renewable energy resources, such as wind and solar, large-scale energy storage devices are increasingly required to make the best use of the renewable power. The redox flow battery is considered suitable for large-scale applications due to its modular design, good scalability and flexible operation. The biggest challenge of the redox flow battery is the low energy density. The redox active species is the most important component in redox flow batteries, and the redox potential and solubility of redox species dictate the system energy density. This review is focused on the recent development of redox species. Different categories of redox species, including simple inorganic ions, metal complexes, metal-free organic compounds, polysulfide/sulfur and lithium storage active materials, are reviewed. The future development of redox species towards higher energy density is also suggested.

  4. Redox Species of Redox Flow Batteries: A Review

    Directory of Open Access Journals (Sweden)

    Feng Pan

    2015-11-01

    Full Text Available Due to the capricious nature of renewable energy resources, such as wind and solar, large-scale energy storage devices are increasingly required to make the best use of the renewable power. The redox flow battery is considered suitable for large-scale applications due to its modular design, good scalability and flexible operation. The biggest challenge of the redox flow battery is the low energy density. The redox active species is the most important component in redox flow batteries, and the redox potential and solubility of redox species dictate the system energy density. This review is focused on the recent development of redox species. Different categories of redox species, including simple inorganic ions, metal complexes, metal-free organic compounds, polysulfide/sulfur and lithium storage active materials, are reviewed. The future development of redox species towards higher energy density is also suggested.

  5. Cooperative use of cytochrome cd1 nitrite reductase and its redox partner cytochrome c552 to improve the selectivity of nitrite biosensing

    International Nuclear Information System (INIS)

    Serra, A.S.; Jorge, S.R.; Silveira, C.M.; Moura, J.J.G.; Jubete, E.; Ochoteco, E.; Cabanero, G.; Grande, H.; Almeida, M.G.

    2011-01-01

    In this work, a novel enzymatic biosensor for determination of nitrites constructed on an electrochemical transducing platform is proposed. The sensor is based on cytochrome-cd 1 (cyt-cd 1 ) nitrite reductase from Marinobacter hydrocarbonoclasticus strain 617 as biological recognition element, and its putative physiological redox partner cytochrome-c 552 (cyt-c 552 ), as electron mediator. The proteins were co-immobilized using a photopolymerizable polyvinyl alcohol (PVA) derivative, onto carbon paste screen printed electrodes (CPSPEs); the optimal modification conditions were 100 μM cyt-cd 1 /100 μM cyt-c 552 and 50% PVA, after a 48 h polymerization time. Electrochemical characterization of the mediator was carried out by cyclic voltammetry. The one-electron exchange between cyt-c 552 and the working electrode is a quasi-reversible process, without mass transport limitations. The formal potential of the mediator is 254 ± 2 mV vs NHE and the intermolecular electron transfer rate constant between cytochromes c 552 and cd 1 is 9.9 x 10 3 M -1 s -1 . The analytical parameters of the biosensor response to nitrite as assessed by amperometric measurements were: linear range from 10 to 200 μM; detection and quantification limits of 7 and 24 μM, respectively; sensitivity of 2.49 ± 0.08 A mol -1 cm 2 μM -1 . Catalytic profiles in the presence of possible interfering species were also investigated. The interference from competitive enzymatic reduction of dissolved oxygen could be overcome by tuning the cyclic voltammograms for faster sweep rates.

  6. Cooperative use of cytochrome cd{sub 1} nitrite reductase and its redox partner cytochrome c{sub 552} to improve the selectivity of nitrite biosensing

    Energy Technology Data Exchange (ETDEWEB)

    Serra, A.S.; Jorge, S.R.; Silveira, C.M.; Moura, J.J.G. [REQUIMTE - Dept. de Quimica, CQFB, Faculdade de Ciencias e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Jubete, E.; Ochoteco, E.; Cabanero, G.; Grande, H. [CIDETEC - Centro de Tecnologias Electroquimicas, Parque Tecnologico de San Sebastian, Po Miramon, 196, 20009 Donostia - San Sebastian (Spain); Almeida, M.G., E-mail: mga@dq.fct.unl.pt [REQUIMTE - Dept. de Quimica, CQFB, Faculdade de Ciencias e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Escola Superior de Saude Egas Moniz, Monte de Caparica, 2829-511 Caparica (Portugal)

    2011-05-05

    In this work, a novel enzymatic biosensor for determination of nitrites constructed on an electrochemical transducing platform is proposed. The sensor is based on cytochrome-cd{sub 1} (cyt-cd{sub 1}) nitrite reductase from Marinobacter hydrocarbonoclasticus strain 617 as biological recognition element, and its putative physiological redox partner cytochrome-c{sub 552} (cyt-c{sub 552}), as electron mediator. The proteins were co-immobilized using a photopolymerizable polyvinyl alcohol (PVA) derivative, onto carbon paste screen printed electrodes (CPSPEs); the optimal modification conditions were 100 {mu}M cyt-cd{sub 1}/100 {mu}M cyt-c{sub 552} and 50% PVA, after a 48 h polymerization time. Electrochemical characterization of the mediator was carried out by cyclic voltammetry. The one-electron exchange between cyt-c{sub 552} and the working electrode is a quasi-reversible process, without mass transport limitations. The formal potential of the mediator is 254 {+-} 2 mV vs NHE and the intermolecular electron transfer rate constant between cytochromes c{sub 552} and cd{sub 1} is 9.9 x 10{sup 3} M{sup -1} s{sup -1}. The analytical parameters of the biosensor response to nitrite as assessed by amperometric measurements were: linear range from 10 to 200 {mu}M; detection and quantification limits of 7 and 24 {mu}M, respectively; sensitivity of 2.49 {+-} 0.08 A mol{sup -1} cm{sup 2} {mu}M{sup -1}. Catalytic profiles in the presence of possible interfering species were also investigated. The interference from competitive enzymatic reduction of dissolved oxygen could be overcome by tuning the cyclic voltammograms for faster sweep rates.

  7. Redox active polymers and colloidal particles for flow batteries

    Science.gov (United States)

    Gavvalapalli, Nagarjuna; Moore, Jeffrey S.; Rodriguez-Lopez, Joaquin; Cheng, Kevin; Shen, Mei; Lichtenstein, Timothy

    2018-05-29

    The invention provides a redox flow battery comprising a microporous or nanoporous size-exclusion membrane, wherein one cell of the battery contains a redox-active polymer dissolved in the non-aqueous solvent or a redox-active colloidal particle dispersed in the non-aqueous solvent. The redox flow battery provides enhanced ionic conductivity across the electrolyte separator and reduced redox-active species crossover, thereby improving the performance and enabling widespread utilization. Redox active poly(vinylbenzyl ethylviologen) (RAPs) and redox active colloidal particles (RACs) were prepared and were found to be highly effective redox species. Controlled potential bulk electrolysis indicates that 94-99% of the nominal charge on different RAPs is accessible and the electrolysis products are stable upon cycling. The high concentration attainable (>2.0 M) for RAPs in common non-aqueous battery solvents, their electrochemical and chemical reversibility, and their hindered transport across porous separators make them attractive materials for non-aqueous redox flow batteries based on size-selectivity.

  8. Redox Buffer Strength

    Science.gov (United States)

    de Levie, Robert

    1999-04-01

    The proper functioning of enzymes in bodily fluids requires that the pH be maintained within rather narrow limits. The first line of defense against large pH fluctuations in such fluids is the passive control provided by the presence of pH buffers. The ability of pH buffers to stabilize the pH is indicated by the buffer value b introduced in 1922 by van Slyke. It is equally important for many enzymes that the redox potential is kept within a narrow range. In that case, stability of the potential is most readily achieved with a redox buffer. In this communication we define the redox buffer strength by analogy with acid-base buffer strength.

  9. De Novo Construction of Redox Active Proteins.

    Science.gov (United States)

    Moser, C C; Sheehan, M M; Ennist, N M; Kodali, G; Bialas, C; Englander, M T; Discher, B M; Dutton, P L

    2016-01-01

    Relatively simple principles can be used to plan and construct de novo proteins that bind redox cofactors and participate in a range of electron-transfer reactions analogous to those seen in natural oxidoreductase proteins. These designed redox proteins are called maquettes. Hydrophobic/hydrophilic binary patterning of heptad repeats of amino acids linked together in a single-chain self-assemble into 4-alpha-helix bundles. These bundles form a robust and adaptable frame for uncovering the default properties of protein embedded cofactors independent of the complexities introduced by generations of natural selection and allow us to better understand what factors can be exploited by man or nature to manipulate the physical chemical properties of these cofactors. Anchoring of redox cofactors such as hemes, light active tetrapyrroles, FeS clusters, and flavins by His and Cys residues allow cofactors to be placed at positions in which electron-tunneling rates between cofactors within or between proteins can be predicted in advance. The modularity of heptad repeat designs facilitates the construction of electron-transfer chains and novel combinations of redox cofactors and new redox cofactor assisted functions. Developing de novo designs that can support cofactor incorporation upon expression in a cell is needed to support a synthetic biology advance that integrates with natural bioenergetic pathways. © 2016 Elsevier Inc. All rights reserved.

  10. Simultaneous anionic and cationic redox

    Science.gov (United States)

    Jung, Sung-Kyun; Kang, Kisuk

    2017-12-01

    It is challenging to unlock anionic redox activity, accompanied by full utilization of available cationic redox process, to boost capacity of battery cathodes. Now, material design by tuning the metal-oxygen interaction is shown to be a promising solution.

  11. Redox Regulation of Mitochondrial Function

    Science.gov (United States)

    Handy, Diane E.

    2012-01-01

    Abstract Redox-dependent processes influence most cellular functions, such as differentiation, proliferation, and apoptosis. Mitochondria are at the center of these processes, as mitochondria both generate reactive oxygen species (ROS) that drive redox-sensitive events and respond to ROS-mediated changes in the cellular redox state. In this review, we examine the regulation of cellular ROS, their modes of production and removal, and the redox-sensitive targets that are modified by their flux. In particular, we focus on the actions of redox-sensitive targets that alter mitochondrial function and the role of these redox modifications on metabolism, mitochondrial biogenesis, receptor-mediated signaling, and apoptotic pathways. We also consider the role of mitochondria in modulating these pathways, and discuss how redox-dependent events may contribute to pathobiology by altering mitochondrial function. Antioxid. Redox Signal. 16, 1323–1367. PMID:22146081

  12. Redox Flow Batteries, a Review

    Energy Technology Data Exchange (ETDEWEB)

    Knoxville, U. Tennessee; U. Texas Austin; U, McGill; Weber, Adam Z.; Mench, Matthew M.; Meyers, Jeremy P.; Ross, Philip N.; Gostick, Jeffrey T.; Liu, Qinghua

    2011-07-15

    Redox flow batteries are enjoying a renaissance due to their ability to store large amounts of electrical energy relatively cheaply and efficiently. In this review, we examine the components of redox flow batteries with a focus on understanding the underlying physical processes. The various transport and kinetic phenomena are discussed along with the most common redox couples.

  13. Thermo-Kinetic Investigation of Comparative Ligand Effect on Cysteine Iron Redox Reaction

    Directory of Open Access Journals (Sweden)

    Masood Ahmad Rizvi

    2015-03-01

    Full Text Available Transition metal ions in their free state bring unwanted biological oxidations generating oxidative stress. The ligand modulated redox potential can be indispensable in prevention of such oxidative stress by blocking the redundant bio-redox reactions. In this study we investigated the comparative ligand effect on the thermo-kinetic aspects of biologically important cysteine iron (III redox reaction using spectrophotometric and potentiometric methods. The results were corroborated with the complexation effect on redox potential of iron(III-iron(II redox couple. The selected ligands were found to increase the rate of cysteine iron (III redox reaction in proportion to their stability of iron (II complex (EDTA < terpy < bipy < phen. A kinetic profile and the catalytic role of copper (II ions by means of redox shuttle mechanism for the cysteine iron (III redox reaction in presence of 1,10-phenanthroline (phen ligand is also reported.

  14. Redox-capacitor to connect electrochemistry to redox-biology.

    Science.gov (United States)

    Kim, Eunkyoung; Leverage, W Taylor; Liu, Yi; White, Ian M; Bentley, William E; Payne, Gregory F

    2014-01-07

    It is well-established that redox-reactions are integral to biology for energy harvesting (oxidative phosphorylation), immune defense (oxidative burst) and drug metabolism (phase I reactions), yet there is emerging evidence that redox may play broader roles in biology (e.g., redox signaling). A critical challenge is the need for tools that can probe biologically-relevant redox interactions simply, rapidly and without the need for a comprehensive suite of analytical methods. We propose that electrochemistry may provide such a tool. In this tutorial review, we describe recent studies with a redox-capacitor film that can serve as a bio-electrode interface that can accept, store and donate electrons from mediators commonly used in electrochemistry and also in biology. Specifically, we (i) describe the fabrication of this redox-capacitor from catechols and the polysaccharide chitosan, (ii) discuss the mechanistic basis for electron exchange, (iii) illustrate the properties of this redox-capacitor and its capabilities for promoting redox-communication between biology and electrodes, and (iv) suggest the potential for enlisting signal processing strategies to "extract" redox information. We believe these initial studies indicate broad possibilities for enlisting electrochemistry and signal processing to acquire "systems level" redox information from biology.

  15. Microfluidic redox battery.

    Science.gov (United States)

    Lee, Jin Wook; Goulet, Marc-Antoni; Kjeang, Erik

    2013-07-07

    A miniaturized microfluidic battery is proposed, which is the first membraneless redox battery demonstrated to date. This unique concept capitalizes on dual-pass flow-through porous electrodes combined with stratified, co-laminar flow to generate electrical power on-chip. The fluidic design is symmetric to allow for both charging and discharging operations in forward, reverse, and recirculation modes. The proof-of-concept device fabricated using low-cost materials integrated in a microfluidic chip is shown to produce competitive power levels when operated on a vanadium redox electrolyte. A complete charge/discharge cycle is performed to demonstrate its operation as a rechargeable battery, which is an important step towards providing sustainable power to lab-on-a-chip and microelectronic applications.

  16. Aqueous liquid redox desulfurisation

    Energy Technology Data Exchange (ETDEWEB)

    Reicher, M.; Niemiec, B.; Katona, T.

    1999-12-01

    The LO-CAT II process is an aqueous liquid redox process which uses ferric and ferrous iron catalysts to oxidise hydrogen sulfide (from sour gas) to elemental sulfur: the relevant chemical equations are given. Chelating agents keep the iron in solution. The system is described under the headings of (i) LO-CAT chemistry, (ii) design parameters, (iii) startup challenges, (iv) present situation and (v) anticipated future conditions. Further improvements to the system are anticipated.

  17. Ediacaran Redox Fluctuations

    Science.gov (United States)

    Sahoo, S. K.; Jiang, G.; Planavsky, N. J.; Kendall, B.; Owens, J. D.; Anbar, A. D.; Lyons, T. W.

    2013-12-01

    Evidence for pervasive oxic conditions, and likely even deep ocean oxygenation has been documented at three intervals in the lower (ca. 632 Ma), middle (ca. 580 Ma) and upper (ca. 551 Ma) Ediacaran. The Doushantuo Formation in South China hosts large enrichments of redox-sensitive trace element (e.g., molybdenum, vanadium and uranium) in anoxic shales, which are indicative of a globally oxic ocean-atmosphere system. However, ocean redox conditions between these periods continue to be a topic of debate and remain elusive. We have found evidence for widespread anoxic conditions through much of the Ediacaran in the deep-water Wuhe section in South China. During most of the Ediacaran-early Cambrian in basinal sections is characterized by Fe speciation data and pyrite morphologies that indicate deposition under euxinic conditions with near-crustal enrichments of redox-sensitive element and positive pyrite-sulfur isotope values, which suggest low levels of marine sulfate and widespread euxinia. Our work reinforces an emerging view that the early Earth, including the Ediacaran, underwent numerous rises and falls in surface oxidation state, rather than a unidirectional rise as originally imagined. The Ediacaran ocean thus experienced repetitive expansion and contraction of marine chalcophilic trace-metal levels that may have had fundamental impact on the slow evolution of early animals and ecosystems. Further, this framework forces us to re-examine the relationship between Neoproterozoic oxygenation and metazoan diversification. Varying redox conditions through the Cryogenian and Ediacaran may help explain molecular clock and biomarker evidence for an early appearance and initial diversification of metazoans but with a delay in the appearance of most major metazoan crown groups until close to Ediacaran-Cambrian boundary.

  18. Redox processes in radiation biology and cancer

    International Nuclear Information System (INIS)

    Greenstock, C.L.

    1981-01-01

    Free-radical intermediates, particularly the activated oxygen species OH, O - 2 , and 1 O 2 , are implicated in many types of radiation damage to biological systems. In addition, these same species may be formed, either directly or indirectly through biochemical redox reactions, in both essential and aberrant metabolic processes. Cell survival and adaptation to an environment containing ionizing radiation and other physical and chemical carcinogens ultimately depend upon the cell's ability to maintain optimal function in response to free-radical damage at the chemical level. Many of these feedback control mechanisms are redox controlled. Radiation chemical techniques using selective radical scavengers, such as product analysis and pulse radiolysis, enable us to generate, observe, and characterize individually the nature and reactivity of potentially damaging free radicals. From an analysis of the chemical kinetics of free-radical involvement in biological damage, redox mechanisms are proposed to describe the early processes of radiation damage, redox mechanisms are proposed to describe the early processes of radiation damage, its protection and sensitization, and the role of free radicals in radiation and chemical carcinogenesis

  19. Redox Modulations, Antioxidants, and Neuropsychiatric Disorders

    Directory of Open Access Journals (Sweden)

    Erik A. Fraunberger

    2016-01-01

    Full Text Available Although antioxidants, redox modulations, and neuropsychiatric disorders have been widely studied for many years, the field would benefit from an integrative and corroborative review. Our primary objective is to delineate the biological significance of compounds that modulate our redox status (i.e., reactive species and antioxidants as well as outline their current role in brain health and the impact of redox modulations on the severity of illnesses. Therefore, this review will not enter into the debate regarding the perceived medical legitimacy of antioxidants but rather seek to clarify their abilities and limitations. With this in mind, antioxidants may be interpreted as natural products with significant pharmacological actions in the body. A renewed understanding of these often overlooked compounds will allow us to critically appraise the current literature and provide an informed, novel perspective on an important healthcare issue. In this review, we will introduce the complex topics of redox modulations and their role in the development of select neuropsychiatric disorders.

  20. Redox electrode materials for supercapatteries

    OpenAIRE

    Yu, Linpo; Chen, George Z.

    2016-01-01

    Redox electrode materials, including transition metal oxides and electronically conducting polymers, are capable of faradaic charge transfer reactions, and play important roles in most electrochemical energy storage devices, such as supercapacitor, battery and supercapattery. Batteries are often based on redox materials with low power capability and safety concerns in some cases. Supercapacitors, particularly those based on redox inactive materials, e.g. activated carbon, can offer high power...

  1. Organic non-aqueous cation-based redox flow batteries

    Science.gov (United States)

    Zhang, Lu; Huang, Jinhua; Burrell, Anthony

    2018-05-08

    The present invention provides a non-aqueous redox flow battery comprising a negative electrode immersed in a non-aqueous liquid negative electrolyte, a positive electrode immersed in a non-aqueous liquid positive electrolyte, and a cation-permeable separator (e.g., a porous membrane, film, sheet, or panel) between the negative electrolyte from the positive electrolyte. During charging and discharging, the electrolytes are circulated over their respective electrodes. The electrolytes each comprise an electrolyte salt (e.g., a lithium or sodium salt), a transition-metal free redox reactant, and optionally an electrochemically stable organic solvent. Each redox reactant is selected from an organic compound comprising a conjugated unsaturated moiety, a boron cluster compound, and a combination thereof. The organic redox reactant of the positive electrolyte comprises a tetrafluorohydroquinone ether compound or a tetrafluorocatechol ether compound.

  2. Bifunctional redox flow battery

    International Nuclear Information System (INIS)

    Wen, Y.H.; Cheng, J.; Xun, Y.; Ma, P.H.; Yang, Y.S.

    2008-01-01

    A new bifunctional redox flow battery (BRFB) system, V(III)/V(II)-L-cystine(O 2 ), was systematically investigated by using different separators. It is shown that during charge, water transfer is significantly restricted with increasing the concentration of HBr when the Nafion 115 cation exchange membrane is employed. The same result can be obtained when the gas diffusion layer (GDL) hot-pressed separator is used. The organic electro-synthesis is directly correlated with the crossover of vanadium. When employing the anion exchange membrane, the electro-synthesis efficiency is over 96% due to a minimal crossover of vanadium. When the GDL hot-pressed separator is applied, the crossover of vanadium and water transfer are noticeably prevented and the electro-synthesis efficiency of over 99% is obtained. Those impurities such as vanadium ions and bromine can be eliminated through the purification of organic electro-synthesized products. The purified product is identified to be L-cysteic acid by IR spectrum. The BRFB shows a favorable discharge performance at a current density of 20 mA cm -2 . Best discharge performance is achieved by using the GDL hot-pressed separator. The coulombic efficiency of 87% and energy efficiency of about 58% can be obtained. The cause of major energy losses is mainly associated with the cross-contamination of anodic and cathodic active electrolytes

  3. Redox shuttles for lithium ion batteries

    Science.gov (United States)

    Weng, Wei; Zhang, Zhengcheng; Amine, Khalil

    2014-11-04

    Compounds may have general Formula IVA or IVB. ##STR00001## where, R.sup.8, R.sup.9, R.sup.10, and R.sup.11 are each independently selected from H, F, Cl, Br, CN, NO.sub.2, alkyl, haloalkyl, and alkoxy groups; X and Y are each independently O, S, N, or P; and Z' is a linkage between X and Y. Such compounds may be used as redox shuttles in electrolytes for use in electrochemical cells, batteries and electronic devices.

  4. Organic Redox Species in Aqueous Flow Batteries: Redox Potentials, Chemical Stability and Solubility

    OpenAIRE

    Kristina Wedege; Emil Dražević; Denes Konya; Anders Bentien

    2016-01-01

    Organic molecules are currently investigated as redox species for aqueous low-cost redox flow batteries (RFBs). The envisioned features of using organic redox species are low cost and increased flexibility with respect to tailoring redox potential and solubility from molecular engineering of side groups on the organic redox-active species. In this paper 33, mainly quinone-based, compounds are studied experimentially in terms of pH dependent redox potential, solubility and stability, combined ...

  5. Redox regulation of plant development.

    Science.gov (United States)

    Considine, Michael J; Foyer, Christine H

    2014-09-20

    We provide a conceptual framework for the interactions between the cellular redox signaling hub and the phytohormone signaling network that controls plant growth and development to maximize plant productivity under stress-free situations, while limiting growth and altering development on exposure to stress. Enhanced cellular oxidation plays a key role in the regulation of plant growth and stress responses. Oxidative signals or cycles of oxidation and reduction are crucial for the alleviation of dormancy and quiescence, activating the cell cycle and triggering genetic and epigenetic control that underpin growth and differentiation responses to changing environmental conditions. The redox signaling hub interfaces directly with the phytohormone network in the synergistic control of growth and its modulation in response to environmental stress, but a few components have been identified. Accumulating evidence points to a complex interplay of phytohormone and redox controls that operate at multiple levels. For simplicity, we focus here on redox-dependent processes that control root growth and development and bud burst. The multiple roles of reactive oxygen species in the control of plant growth and development have been identified, but increasing emphasis should now be placed on the functions of redox-regulated proteins, along with the central roles of reductants such as NAD(P)H, thioredoxins, glutathione, glutaredoxins, peroxiredoxins, ascorbate, and reduced ferredoxin in the regulation of the genetic and epigenetic factors that modulate the growth and vigor of crop plants, particularly within an agricultural context.

  6. Ruthenium-catalyzed intramolecular metathesis of dienes and its application in the synthesis of bridged and spiro azabicycles

    Science.gov (United States)

    Kuznetsov, N. Yu; Bubnov, Yu N.

    2015-07-01

    The review presents a historical excursion into catalytic alkene metathesis, covering the problems of history of the discovery of this process, as well as investigations on the properties, structure and reactivity of the most popular ruthenium catalysts for metathesis, mechanism of their action and decomposition. The main part covers studies devoted to the syntheses of bridged azabicyclic and 1-azaspirocyclic compounds comprising the intramolecular metathesis of dienes as the key step. The formation of a bicyclic skeleton of a series of natural bridged (cocaine, ferruginine, calystegines, and anatoxin-a) and spiro (pinnaic acids, halichlorine, hystrionicotoxin, and cephalotaxine) azabicycles, as well as their analogues and compounds with larger rings is demonstrated. The methods for the synthesis of diene precursors and the conditions for final assembling of the bicyclic compounds are considered in detail. The generalization of the literature data allows one to efficiently carry out the mentioned process taking into account the most important features. The bibliography includes 129 references.

  7. Sequential One-Pot Ruthenium-Catalyzed Azide−Alkyne Cycloaddition from Primary Alkyl Halides and Sodium Azide

    KAUST Repository

    Johansson, Johan R.

    2011-04-01

    An experimentally simple sequential one-pot RuAAC reaction, affording 1,5-disubstituted 1H-1,2,3-triazoles in good to excellent yields starting from an alkyl halide, sodium azide, and an alkyne, is reported. The organic azide is formed in situ by treating the primary alkyl halide with sodium azide in DMA under microwave heating. Subsequent addition of [RuClCp*(PPh 3) 2] and the alkyne yielded the desired cycloaddition product after further microwave irradiation. © 2011 American Chemical Society.

  8. Ruthenium-catalyzed intramolecular metathesis of dienes and its application in the synthesis of bridged and spiro azabicycles

    International Nuclear Information System (INIS)

    Kuznetsov, N Yu; Bubnov, Yu N

    2015-01-01

    The review presents a historical excursion into catalytic alkene metathesis, covering the problems of history of the discovery of this process, as well as investigations on the properties, structure and reactivity of the most popular ruthenium catalysts for metathesis, mechanism of their action and decomposition. The main part covers studies devoted to the syntheses of bridged azabicyclic and 1-azaspirocyclic compounds comprising the intramolecular metathesis of dienes as the key step. The formation of a bicyclic skeleton of a series of natural bridged (cocaine, ferruginine, calystegines, and anatoxin-a) and spiro (pinnaic acids, halichlorine, hystrionicotoxin, and cephalotaxine) azabicycles, as well as their analogues and compounds with larger rings is demonstrated. The methods for the synthesis of diene precursors and the conditions for final assembling of the bicyclic compounds are considered in detail. The generalization of the literature data allows one to efficiently carry out the mentioned process taking into account the most important features. The bibliography includes 129 references

  9. ETL 1 kW redox flow cell

    International Nuclear Information System (INIS)

    Nozaki, K.; Ozawa, T.

    1984-01-01

    A 1 kW scale redox flow cell system was set up in the laboratory (ETL), while three different types of batteries were also assembled by private companies in early 1983. In this article, this cell system is described. The concept of a modern type redox flow cell is based on a couple of fully soluble redox ions and a highly selective ion-exchange membrane. In the cell, the redox ion stored in a tank is flowed to and reduced on the electrode, while the other ion is also flowed to and oxidized on the other electrode. This electrochemical reaction produces electronic current in the external circuit and ionic current through the membrane sandwiched as a separator between the two electrodes. The reverse reaction proceeds in the charging process. In ETL, the concept was preliminarily tested, and conceptual design and cost estimation of the redox flow cells were carried out to confirm the feasibility; the R and D started on these bases in 1975

  10. Evaluation of electrolytes for redox flow battery applications

    International Nuclear Information System (INIS)

    Chakrabarti, M.H.; Dryfe, R.A.W.; Roberts, E.P.L.

    2007-01-01

    A number of redox systems have been investigated in this work with the aim of identifying electrolytes suitable for testing redox flow battery cell designs. The criteria for the selection of suitable systems were fast electrochemical kinetics and minimal cross-contamination of active electrolytes. Possible electrolyte systems were initially selected based on cyclic voltammetry data. Selected systems were then compared by charge/discharge experiments using a simple H-type cell. The all-vanadium electrolyte system has been developed as a commercial system and was used as the starting point in this study. The performance of the all-vanadium system was significantly better than an all-chromium system which has recently been reported. Some metal-organic and organic redox systems have been reported as possible systems for redox flow batteries, with cyclic voltammetry data suggesting that they could offer near reversible kinetics. However, Ru(acac) 3 in acetonitrile could only be charged efficiently to 9.5% of theoretical charge, after which irreversible side reactions occurred and [Fe(bpy) 3 ](ClO 4 ) 2 in acetonitrile was found to exhibit poor charge/discharge performance

  11. Redox Couples with Unequal Diffusion Coefficients: Effect on Redox Cycling

    NARCIS (Netherlands)

    Mampallil Augustine, Dileep; Mathwig, Klaus; Kang, Shuo; Lemay, Serge Joseph Guy

    2013-01-01

    Redox cycling between two electrodes separated by a narrow gap allows dramatic amplification of the faradaic current. Unlike conventional electrochemistry at a single electrode, however, the mass-transport-limited current is controlled by the diffusion coefficient of both the reduced and oxidized

  12. The redox-Mannich reaction.

    Science.gov (United States)

    Chen, Weijie; Seidel, Daniel

    2014-06-06

    A complement to the classic three-component Mannich reaction, the redox-Mannich reaction, utilizes the same starting materials but incorporates an isomerization step that enables the facile preparation of ring-substituted β-amino ketones. Reactions occur under relatively mild conditions and are facilitated by benzoic acid.

  13. A catalytic approach to estimate the redox potential of heme-peroxidases

    International Nuclear Information System (INIS)

    Ayala, Marcela; Roman, Rosa; Vazquez-Duhalt, Rafael

    2007-01-01

    The redox potential of heme-peroxidases varies according to a combination of structural components within the active site and its vicinities. For each peroxidase, this redox potential imposes a thermodynamic threshold to the range of oxidizable substrates. However, the instability of enzymatic intermediates during the catalytic cycle precludes the use of direct voltammetry to measure the redox potential of most peroxidases. Here we describe a novel approach to estimate the redox potential of peroxidases, which directly depends on the catalytic performance of the activated enzyme. Selected p-substituted phenols are used as substrates for the estimations. The results obtained with this catalytic approach correlate well with the oxidative capacity predicted by the redox potential of the Fe(III)/Fe(II) couple

  14. Cascade redox flow battery systems

    Science.gov (United States)

    Horne, Craig R.; Kinoshita, Kim; Hickey, Darren B.; Sha, Jay E.; Bose, Deepak

    2014-07-22

    A reduction/oxidation ("redox") flow battery system includes a series of electrochemical cells arranged in a cascade, whereby liquid electrolyte reacts in a first electrochemical cell (or group of cells) before being directed into a second cell (or group of cells) where it reacts before being directed to subsequent cells. The cascade includes 2 to n stages, each stage having one or more electrochemical cells. During a charge reaction, electrolyte entering a first stage will have a lower state-of-charge than electrolyte entering the nth stage. In some embodiments, cell components and/or characteristics may be configured based on a state-of-charge of electrolytes expected at each cascade stage. Such engineered cascades provide redox flow battery systems with higher energy efficiency over a broader range of current density than prior art arrangements.

  15. Thioredoxin-linked redox control of metabolism in Methanocaldococcus jannaschii, an evolutionarily deeply-rooted hyperthermophilic methanogenic archaeon

    Science.gov (United States)

    Thioredoxin (Trx), a small redox protein, controls multiple processes in eukaryotes and bacteria by changing the thiol redox status of selected proteins. We have investigated this aspect in methanarchaea. These ancient methanogens produce methane almost exclusively from H2 plus CO2 carried approxima...

  16. Redox signaling in acute pancreatitis

    Science.gov (United States)

    Pérez, Salvador; Pereda, Javier; Sabater, Luis; Sastre, Juan

    2015-01-01

    Acute pancreatitis is an inflammatory process of the pancreatic gland that eventually may lead to a severe systemic inflammatory response. A key event in pancreatic damage is the intracellular activation of NF-κB and zymogens, involving also calcium, cathepsins, pH disorders, autophagy, and cell death, particularly necrosis. This review focuses on the new role of redox signaling in acute pancreatitis. Oxidative stress and redox status are involved in the onset of acute pancreatitis and also in the development of the systemic inflammatory response, being glutathione depletion, xanthine oxidase activation, and thiol oxidation in proteins critical features of the disease in the pancreas. On the other hand, the release of extracellular hemoglobin into the circulation from the ascitic fluid in severe necrotizing pancreatitis enhances lipid peroxidation in plasma and the inflammatory infiltrate into the lung and up-regulates the HIF–VEGF pathway, contributing to the systemic inflammatory response. Therefore, redox signaling and oxidative stress contribute to the local and systemic inflammatory response during acute pancreatitis. PMID:25778551

  17. Redox signaling in acute pancreatitis

    Directory of Open Access Journals (Sweden)

    Salvador Pérez

    2015-08-01

    Full Text Available Acute pancreatitis is an inflammatory process of the pancreatic gland that eventually may lead to a severe systemic inflammatory response. A key event in pancreatic damage is the intracellular activation of NF-κB and zymogens, involving also calcium, cathepsins, pH disorders, autophagy, and cell death, particularly necrosis. This review focuses on the new role of redox signaling in acute pancreatitis. Oxidative stress and redox status are involved in the onset of acute pancreatitis and also in the development of the systemic inflammatory response, being glutathione depletion, xanthine oxidase activation, and thiol oxidation in proteins critical features of the disease in the pancreas. On the other hand, the release of extracellular hemoglobin into the circulation from the ascitic fluid in severe necrotizing pancreatitis enhances lipid peroxidation in plasma and the inflammatory infiltrate into the lung and up-regulates the HIF–VEGF pathway, contributing to the systemic inflammatory response. Therefore, redox signaling and oxidative stress contribute to the local and systemic inflammatory response during acute pancreatitis.

  18. Redox reaction studies by nanosecond pulse radiolysis

    International Nuclear Information System (INIS)

    Moorthy, P.N.

    1979-01-01

    Free radicals are formed as intermediates in many chemical and biochemical reactions. An important type of reaction which they can undergo is a one electron or redox process. The direction and rate of such electron transfer reactions is governed by the relative redox potentials of the participating species. Because of the generally short lived nature of free radicals, evaluation of their redox potentials poses a number of problems. Two techniques are described for the experimental determination of the redox potentials of short lived species generated by either a nanosecond electron pulse or laser flash. In the first method, redox titration of the short lived species with stable molecules of known redox potential is carried out, employing the technique of fast kinetic spectrophotometry. Conversely, by the same method it is also possible to evaluate the one electron redox potentials of stable molecules by redox titration with free radicals of known redox potential produced as above. In the second method, electrochemical reduction or oxidation of the short lived species at an appropriate electrode (generally a mercury drop) is carried out at different fixed potentials, and the redox potential evaluated from the current-potential curves (polarograms). Full description of the experimental set up and theoretical considerations for interpretation of the raw data are given. The relative merits of the two methods and their practical applicability are discussed. (auth.)

  19. Dissecting Redox Biology Using Fluorescent Protein Sensors.

    Science.gov (United States)

    Schwarzländer, Markus; Dick, Tobias P; Meyer, Andreas J; Morgan, Bruce

    2016-05-01

    Fluorescent protein sensors have revitalized the field of redox biology by revolutionizing the study of redox processes in living cells and organisms. Within one decade, a set of fundamental new insights has been gained, driven by the rapid technical development of in vivo redox sensing. Redox-sensitive yellow and green fluorescent protein variants (rxYFP and roGFPs) have been the central players. Although widely used as an established standard tool, important questions remain surrounding their meaningful use in vivo. We review the growing range of thiol redox sensor variants and their application in different cells, tissues, and organisms. We highlight five key findings where in vivo sensing has been instrumental in changing our understanding of redox biology, critically assess the interpretation of in vivo redox data, and discuss technical and biological limitations of current redox sensors and sensing approaches. We explore how novel sensor variants may further add to the current momentum toward a novel mechanistic and integrated understanding of redox biology in vivo. Antioxid. Redox Signal. 24, 680-712.

  20. Amplified and in situ detection of redox-active metabolite using a biobased redox capacitor.

    Science.gov (United States)

    Kim, Eunkyoung; Gordonov, Tanya; Bentley, William E; Payne, Gregory F

    2013-02-19

    Redox cycling provides a mechanism to amplify electrochemical signals for analyte detection. Previous studies have shown that diverse mediators/shuttles can engage in redox-cycling reactions with a biobased redox capacitor that is fabricated by grafting redox-active catechols onto a chitosan film. Here, we report that redox cycling with this catechol-chitosan redox capacitor can amplify electrochemical signals for detecting a redox-active bacterial metabolite. Specifically, we studied the redox-active bacterial metabolite pyocyanin that is reported to be a virulence factor and signaling molecule for the opportunistic pathogen P. aeruginosa. We demonstrate that redox cycling can amplify outputs from various electrochemical methods (cyclic voltammetry, chronocoulometry, and differential pulse voltammetry) and can lower the detection limit of pyocyanin to 50 nM. Further, the compatibility of this biobased redox capacitor allows the in situ monitoring of the production of redox-active metabolites (e.g., pyocyanin) during the course of P. aeruginosa cultivation. We anticipate that the amplified output of redox-active virulence factors should permit an earlier detection of life-threatening infections by the opportunistic pathogen P. aeruginosa while the "bio-compatibility" of this measurement approach should facilitate in situ study of the spatiotemporal dynamics of bacterial redox signaling.

  1. Engineering redox balance through cofactor systems.

    Science.gov (United States)

    Chen, Xiulai; Li, Shubo; Liu, Liming

    2014-06-01

    Redox balance plays an important role in the production of enzymes, pharmaceuticals, and chemicals. To meet the demands of industrial production, it is desirable that microbes maintain a maximal carbon flux towards target metabolites with no fluctuations in redox. This requires functional cofactor systems that support dynamic homeostasis between different redox states or functional stability in a given redox state. Redox balance can be achieved by improving the self-balance of a cofactor system, regulating the substrate balance of a cofactor system, and engineering the synthetic balance of a cofactor system. This review summarizes how cofactor systems can be manipulated to improve redox balance in microbes. Copyright © 2014 Elsevier Ltd. All rights reserved.

  2. Radii of Redox Components from Absolute Redox Potentials Compared with Covalent and Aqueous Ionic Radii

    Czech Academy of Sciences Publication Activity Database

    Heyrovská, Raji

    2010-01-01

    Roč. 22, č. 9 (2010), s. 903-907 ISSN 1040-0397 Institutional support: RVO:68081707 Keywords : Electrochemistry * Absolute redox potentials * Radii of redox components Subject RIV: BO - Biophysics Impact factor: 2.721, year: 2010

  3. Redox Pioneer: Professor Vadim N. Gladyshev.

    Science.gov (United States)

    Hatfield, Dolph L

    2016-07-01

    Professor Vadim N. Gladyshev is recognized here as a Redox Pioneer, because he has published an article on antioxidant/redox biology that has been cited more than 1000 times and 29 articles that have been cited more than 100 times. Gladyshev is world renowned for his characterization of the human selenoproteome encoded by 25 genes, identification of the majority of known selenoprotein genes in the three domains of life, and discoveries related to thiol oxidoreductases and mechanisms of redox control. Gladyshev's first faculty position was in the Department of Biochemistry, the University of Nebraska. There, he was a Charles Bessey Professor and Director of the Redox Biology Center. He then moved to the Department of Medicine at Brigham and Women's Hospital, Harvard Medical School, where he is Professor of Medicine and Director of the Center for Redox Medicine. His discoveries in redox biology relate to selenoenzymes, such as methionine sulfoxide reductases and thioredoxin reductases, and various thiol oxidoreductases. He is responsible for the genome-wide identification of catalytic redox-active cysteines and for advancing our understanding of the general use of cysteines by proteins. In addition, Gladyshev has characterized hydrogen peroxide metabolism and signaling and regulation of protein function by methionine-R-sulfoxidation. He has also made important contributions in the areas of aging and lifespan control and pioneered applications of comparative genomics in redox biology, selenium biology, and aging. Gladyshev's discoveries have had a profound impact on redox biology and the role of redox control in health and disease. He is a true Redox Pioneer. Antioxid. Redox Signal. 25, 1-9.

  4. Characterization of redox proteins using electrochemical methods

    OpenAIRE

    Verhagen, M.

    1995-01-01

    The use of electrochemical techniques in combination with proteins started approximately a decade ago and has since then developed into a powerfull technique for the study of small redox proteins. In addition to the determination of redox potentials, electrochemistry can be used to obtain information about the kinetics of electron transfer between proteins and about the dynamic behaviour of redox cofactors in proteins. This thesis describes the results of a study, initiated to get a ...

  5. Redox flow batteries having multiple electroactive elements

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Wei; Li, Liyu; Yang, Zhenguo; Nie, Zimin

    2018-05-01

    Introducing multiple redox reactions with a suitable voltage range can improve the energy density of redox flow battery (RFB) systems. One example includes RFB systems utilizing multiple redox pairs in the positive half cell, the negative half cell, or in both. Such RFB systems can have a negative electrolyte, a positive electrolyte, and a membrane between the negative electrolyte and the positive electrolyte, in which at least two electrochemically active elements exist in the negative electrolyte, the positive electrolyte, or both.

  6. Membranes for Redox Flow Battery Applications

    OpenAIRE

    Prifti, Helen; Parasuraman, Aishwarya; Winardi, Suminto; Lim, Tuti Mariana; Skyllas-Kazacos, Maria

    2012-01-01

    The need for large scale energy storage has become a priority to integrate renewable energy sources into the electricity grid. Redox flow batteries are considered the best option to store electricity from medium to large scale applications. However, the current high cost of redox flow batteries impedes the wide spread adoption of this technology. The membrane is a critical component of redox flow batteries as it determines the performance as well as the economic viability of the batteries. Th...

  7. Regulatory redox state in tree seeds

    Directory of Open Access Journals (Sweden)

    Ewelina Ratajczak

    2017-12-01

    Full Text Available Peroxiredoxins (Prx are important regulators of the redox status of tree seeds during maturation and long-term storage. Thioredoxins (Trx are redox transmitters and thereby regulate Prx activity. Current research is focused on the association of Trx with Prx in tree seeds differing in the tolerance to desiccation. The results will allow for better understanding the regulation of the redox status in orthodox, recalcitrant, and intermediate seeds. The findings will also elucidate the role of the redox status during the loss of viability of sensitive seeds during drying and long-term storage.

  8. Zinc and the modulation of redox homeostasis

    Science.gov (United States)

    Oteiza, Patricia I.

    2012-01-01

    Zinc, a redox inactive metal, has been long viewed as a component of the antioxidant network, and growing evidence points to its involvement in redox-regulated signaling. These actions are exerted through several mechanisms based on the unique chemical and functional properties of zinc. Overall, zinc contributes to maintain the cell redox balance through different mechanisms including: i) the regulation of oxidant production and metal-induced oxidative damage; ii) the dynamic association of zinc with sulfur in protein cysteine clusters, from which the metal can be released by nitric oxide, peroxides, oxidized glutathione and other thiol oxidant species; iii) zinc-mediated induction of the zinc-binding protein metallothionein, which releases the metal under oxidative conditions and act per se scavenging oxidants; iv) the involvement of zinc in the regulation of glutathione metabolism and of the overall protein thiol redox status; and v) a direct or indirect regulation of redox signaling. Findings of oxidative stress, altered redox signaling, and associated cell/tissue disfunction in cell and animal models of zinc deficiency, stress the relevant role of zinc in the preservation of cell redox homeostasis. However, while the participation of zinc in antioxidant protection, redox sensing, and redox-regulated signaling is accepted, the involved molecules, targets and mechanisms are still partially known and the subject of active research. PMID:22960578

  9. Crystalization and redox effects in waste vitrification

    International Nuclear Information System (INIS)

    Kim, C.W.; Buechele, A.C.; Muller, I.S.

    1996-01-01

    This is the continuation of a systematic study to determine the effects of redox state and the concentration of certain transition metals on selected properties of a simplified lime-aluminosilicate glass system, similar to one proposed for high temperature (1350 degrees C-1450 degrees C) vitrification of soil and wastes from DOE sites. The solubilities of Cr 2 O 3 , ZnO, NiO, and Fe 2 O 3 in the base glass, and of the first three oxides in higher-iron variants of the base glass are determined at 1350 degrees C, 1400 degrees C, and 1450 degrees C. Enthalpies of solution are calculated from the solubility data for these four transition metal oxides. Different redox ratios, Fe 2+ /Fe total , are induced at 1450 degrees C in a glass containing NiO at about 75% of its solubility limit at this temperature and related to changes in microstructure. A ZnO-SiO 2 -Fe 2 O 3 pseudoternary 1450 degrees C isotherm is determined and plotted over a wide range of compositions for glasses melted in air. Phases appearing are zincite-, hematite- and spinel-type phases. A Time-Temperature-Transformation (TTT) curve is plotted for a ZnO (12 wt%) containing glass using data from heat treatment studies, and the crystal layer growth rate of a melilite-type phase appearing in this glass is measured at several temperatures over the time range in which the rate is found to be linear. Some kinetic parameters of crystal growth are calculated

  10. Preservation of organic matter in nontronite against iron redox cycling.

    Science.gov (United States)

    Zeng, Q.

    2015-12-01

    It is generally believed that clay minerals can protect organic matter from degradation in redox active environments, but both biotic and abiotic factors can influence the redox process and thus potentially change the clay-organic associations. However, the specific mechanisms involved in this process remain poorly understood. In this study, a model organic compound, 12-Aminolauric acid (ALA) was selected to intercalate into the structural interlayer of nontronite (an iron-rich smectite, NAu-2) to form an ALA-intercalated NAu-2 composite (ALA-NAu-2). Shawanella putrefaciens CN32 and sodium dithionite were used to reduce structural Fe(III) to Fe(II) in NAu-2 and ALA-NAu-2. The bioreduced ALA-NAu-2 was subsequently re-oxidized by air. The rates and extents of bioreduction and air re-oxidation were determined with wet chemistry methods. ALA release from ALA-NAu-2 via redox process was monitored. Mineralogical changes after iron redox cycle were investigated with X-ray diffraction, infrared spectroscopy, and scanning and transmission electron microscopy. At the beginning stage of bioreduction, S. putrefaciens CN32 reduced Fe(III) from the edges of nontronite and preferentially reduced and dissolved small and poorly crystalline particles, and released ALA, resulting a positive correlation between ALA release and iron reduction extent (80%). Because bacteria are the principal agent for mediating redox process in natural environments, our results demonstrated that the structural interlayer of smectite can serve as a potential shelter to protect organic matter from oxidation.

  11. Redox reactions in food fermentations

    DEFF Research Database (Denmark)

    Hansen, Egon Bech

    2018-01-01

    involves oxidative steps in the early part of the pathways whereas a multitude of different reactions are used as compensating reductions. Much of the diversity seen between food fermentations arise from the different routes and the different electron acceptors used by microorganisms to counterbalance...... and this contributes to the diversity in flavor, color, texture, and shelf life. The review concludes that these reactions are still only incompletely understood and that they represent an interesting area for fundamental research and also represent a fertile field for product development through a more conscious use...... of the redox properties of strains used to compose food cultures....

  12. Method for producing redox shuttles

    Science.gov (United States)

    Pupek, Krzysztof Z.; Dzwiniel, Trevor L.; Krumdick, Gregory K.

    2015-03-03

    A single step method for producing a redox shuttle having the formula 2,5-di-tert-butyl-1,4-phenylene tetraethyl bis(phosphate) is provided, the method comprising phosphorylating tert butyl hydroquinone with a phosphate-containing reagent. Also provided is method for producing 2,5-di-tert-butyl-1,4-phenylene tetraethyl bis(phosphate), the method comprising solubilizing tert-butyl hydroquinone and tetrabutylammonium bromide with methyltetrahydrofuran to create a mixture; heating the mixture while adding base to the mixture in an amount to turn the mixture orange; and adding diethyl chlorophosphate to the orange mixture in an amount to phosphorylate the hydroquinone.

  13. A Membrane‐Free Redox Flow Battery with Two Immiscible Redox Electrolytes

    Science.gov (United States)

    Navalpotro, Paula; Palma, Jesus; Anderson, Marc

    2017-01-01

    Abstract Flexible and scalable energy storage solutions are necessary for mitigating fluctuations of renewable energy sources. The main advantage of redox flow batteries is their ability to decouple power and energy. However, they present some limitations including poor performance, short‐lifetimes, and expensive ion‐selective membranes as well as high price, toxicity, and scarcity of vanadium compounds. We report a membrane‐free battery that relies on the immiscibility of redox electrolytes and where vanadium is replaced by organic molecules. We show that the biphasic system formed by one acidic solution and one ionic liquid, both containing quinoyl species, behaves as a reversible battery without any membrane. This proof‐of‐concept of a membrane‐free battery has an open circuit voltage of 1.4 V with a high theoretical energy density of 22.5 Wh L−1, and is able to deliver 90 % of its theoretical capacity while showing excellent long‐term performance (coulombic efficiency of 100 % and energy efficiency of 70 %). PMID:28658538

  14. A Membrane-Free Redox Flow Battery with Two Immiscible Redox Electrolytes.

    Science.gov (United States)

    Navalpotro, Paula; Palma, Jesus; Anderson, Marc; Marcilla, Rebeca

    2017-10-02

    Flexible and scalable energy storage solutions are necessary for mitigating fluctuations of renewable energy sources. The main advantage of redox flow batteries is their ability to decouple power and energy. However, they present some limitations including poor performance, short-lifetimes, and expensive ion-selective membranes as well as high price, toxicity, and scarcity of vanadium compounds. We report a membrane-free battery that relies on the immiscibility of redox electrolytes and where vanadium is replaced by organic molecules. We show that the biphasic system formed by one acidic solution and one ionic liquid, both containing quinoyl species, behaves as a reversible battery without any membrane. This proof-of-concept of a membrane-free battery has an open circuit voltage of 1.4 V with a high theoretical energy density of 22.5 Wh L -1 , and is able to deliver 90 % of its theoretical capacity while showing excellent long-term performance (coulombic efficiency of 100 % and energy efficiency of 70 %). © 2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

  15. Information processing through a bio-based redox capacitor: signatures for redox-cycling.

    Science.gov (United States)

    Liu, Yi; Kim, Eunkyoung; White, Ian M; Bentley, William E; Payne, Gregory F

    2014-08-01

    Redox-cycling compounds can significantly impact biological systems and can be responsible for activities that range from pathogen virulence and contaminant toxicities, to therapeutic drug mechanisms. Current methods to identify redox-cycling activities rely on the generation of reactive oxygen species (ROS), and employ enzymatic or chemical methods to detect ROS. Here, we couple the speed and sensitivity of electrochemistry with the molecular-electronic properties of a bio-based redox-capacitor to generate signatures of redox-cycling. The redox capacitor film is electrochemically-fabricated at the electrode surface and is composed of a polysaccharide hydrogel with grafted catechol moieties. This capacitor film is redox-active but non-conducting and can engage diffusible compounds in either oxidative or reductive redox-cycling. Using standard electrochemical mediators ferrocene dimethanol (Fc) and Ru(NH3)6Cl3 (Ru(3+)) as model redox-cyclers, we observed signal amplifications and rectifications that serve as signatures of redox-cycling. Three bio-relevant compounds were then probed for these signatures: (i) ascorbate, a redox-active compound that does not redox-cycle; (ii) pyocyanin, a virulence factor well-known for its reductive redox-cycling; and (iii) acetaminophen, an analgesic that oxidatively redox-cycles but also undergoes conjugation reactions. These studies demonstrate that the redox-capacitor can enlist the capabilities of electrochemistry to generate rapid and sensitive signatures of biologically-relevant chemical activities (i.e., redox-cycling). Published by Elsevier B.V.

  16. Redox properties of small semiconductor particles

    International Nuclear Information System (INIS)

    Liver, N.; Nitzan, A.

    1992-01-01

    The size dependence of electrical and thermodynamic quantities of intermediate-sized semiconductor particles in an electrolyte solution with a given redox pair are studied. The equilibrium constant for this system is then derived based on the relationship of the electrolytic redox components to the size, charges, and concentration of the semiconductor particles. 25 refs., 9 figs., 1 tab

  17. Characterization of redox proteins using electrochemical methods

    NARCIS (Netherlands)

    Verhagen, M.

    1995-01-01

    The use of electrochemical techniques in combination with proteins started approximately a decade ago and has since then developed into a powerfull technique for the study of small redox proteins. In addition to the determination of redox potentials, electrochemistry can be used to obtain

  18. Improving the performance of electrochemical microsensors based on enzymes entrapped in a redox hydrogel

    International Nuclear Information System (INIS)

    Mitala, J.J.; Michael, A.C.

    2006-01-01

    Microsensors based on carbon fiber microelectrodes coated with enzyme-entrapping redox hydrogels facilitate the in vivo detection of substances of interest within the central nervous system, including hydrogen peroxide, glucose, choline and glutamate. The hydrogel, formed by cross-linking a redox polymer, entraps the enzymes and mediates electron transfer between the enzymes and the electrode. It is important that the enzymes are entrapped in their enzymatically active state. Should entrapment cause enzyme denaturation, the sensitivity and the selectivity of the sensor may be compromised. Synthesis of the redox polymer according to published procedures may yield a product that precipitates when added to aqueous enzyme solutions. Casting hydrogels from solutions that contain the precipitate produces microsensors with low sensitivity and selectivity, suggesting that the precipitation disrupts the structure of the enzymes. Herein, we show that a surfactant, sodium dodecyl sulfate (SDS), can prevent the precipitation and improve the sensitivity and selectivity of the sensors

  19. Ruthenium nanocatalysis on redox reactions.

    Science.gov (United States)

    Veerakumar, Pitchaimani; Ramdass, Arumugam; Rajagopal, Seenivasan

    2013-07-01

    Nanoparticles have generated intense interest over the past 20 years due to their high potential applications in different areas such as catalysis, sensors, nanoscale electronics, fuel and solar cells and optoelectronics. As the large fractions of metal atoms are exposed to the surface, the use of metal nanoparticles as nanocatalysts allows mild reaction conditions and high catalytic efficiency in a large number of chemical transformations. They have emerged as sustainable heterogeneous catalysts and catalyst supports alternative to conventional materials. This review focuses on the synthesis, characterization and catalytic role of ruthenium nanoparticles (RuNPs) on the redox reactions of heteroatom containing organic compounds with the green reagent H2O2, a field that has attracted immense interest among the chemical, materials and industrial communities. We intend to present a broad overview of Ru nanocatalysts for redox reactions with an emphasis on their performance, stability and reusability. The growth in the chemistry of organic sulfoxides and N-oxides during last decade was due to their importance as synthetic intermediates for the production of a wide range of chemically and biologically active molecules. Thus design of efficient methods for the synthesis of sulfoxides and N-oxides becomes important. This review concentrates on the catalysis of RuNPs on the H2O2 oxidation of organic sulfides to sulfoxides and amines to N-oxides. The deoxygenation reactions of sulfoxides to sulfides and reduction of nitro compounds to amines are fundamental reactions in both chemistry and biology. Here, we also highlight the catalysis of metal nanoparticles on the deoxygenation of sulfoxides and sulfones and reduction of nitro compounds with particular emphasis on the mechanistic aspects.

  20. Redox kinetics and mechanism in silicate melts

    International Nuclear Information System (INIS)

    Cochain, B.

    2009-12-01

    This work contributes to better understand iron redox reactions and mechanisms in silicate melts. It was conducted on compositions in both Na 2 O-B 2 O 3 -SiO 2 -FeO and Na 2 O-Al 2 O 3 -SiO 2 -FeO systems. The influence of boron-sodium and aluminum-sodium substitutions and iron content on properties and structure of glasses and on the iron redox kinetics has been studied by Raman, Moessbauer and XANES spectroscopies at the B and Fe K-edges. In borosilicate glasses, an increase in iron content or in the Fe 3+ /ΣFe redox state implies a structural rearrangement of the BO 4 species in the glass network whereas the BO 3 and BO 4 relative proportions remain nearly constant. In all studied glasses and melts, Fe 3+ is a network former in tetrahedral coordination, unless for aluminosilicates of ratio Al/Na≥1 where Fe 3+ is a network modifier in five-fold coordination. Near Tg, diffusion of network modifying cations controls the iron redox kinetics along with a flux of electron holes. At liquidus temperatures, oxygen diffusion is considered to be the mechanism that governs redox reactions. This study shows the role played by the silicate network polymerization on the redox kinetics. In borosilicate melts, iron redox kinetics depends on the boron speciation between BO 3 and BO 4 that depends itself on the sodium content. Furthermore, an increase in the network-former/network-modifier ratio implies a decrease in oxygen diffusion that results in a slowing down of the redox kinetics. The obtained results allow a description of the iron redox kinetics for more complex compositions as natural lavas or nuclear waste model glasses. (author)

  1. Feasibility of assessing health state by detecting redox state of human body based on Chinese medicine constitution.

    Science.gov (United States)

    Li, Ling-Ru; Wang, Qi; Wang, Ji; Wang, Qian-Fei; Yang, Ling-Ling; Zheng, Lu-Yu; Zhang, Yan

    2016-08-01

    This article discussed the feasibility of assessing health state by detecting redox state of human body. Firstly, the balance of redox state is the basis of homeostasis, and the balance ability of redox can reflflect health state of human body. Secondly, the redox state of human body is a sensitive index of multiple risk factors of health such as age, external environment and psychological factors. It participates in the occurrence and development of multiple diseases involving metabolic diseases and nervous system diseases, and can serve as a cut-in point for treatment of these diseases. Detecting the redox state of high risk people is signifificantly important for early detection and treatment of disease. The blood plasma and urine could be selected to detect, which is convenient. It is pointed that the indexes not only involve oxidation product and antioxidant enzyme but also redox couple. Chinese medicine constitution reflflects the state of body itself and the ability of adapting to external environment, which is consistent with the connotation of health. It is found that there are nine basic types of constitution in Chinese population, which provides a theoretical basis of health preservation, preventive treatment of disease and personalized treatment. With the combination of redox state detection and the Chinese medicine constitution theory, the heath state can be systemically assessed by conducting large-scale epidemiological survey with classifified detection on redox state of human body.

  2. Flavin-catalyzed redox tailoring reactions in natural product biosynthesis.

    Science.gov (United States)

    Teufel, Robin

    2017-10-15

    Natural products are distinct and often highly complex organic molecules that constitute not only an important drug source, but have also pushed the field of organic chemistry by providing intricate targets for total synthesis. How the astonishing structural diversity of natural products is enzymatically generated in biosynthetic pathways remains a challenging research area, which requires detailed and sophisticated approaches to elucidate the underlying catalytic mechanisms. Commonly, the diversification of precursor molecules into distinct natural products relies on the action of pathway-specific tailoring enzymes that catalyze, e.g., acylations, glycosylations, or redox reactions. This review highlights a selection of tailoring enzymes that employ riboflavin (vitamin B2)-derived cofactors (FAD and FMN) to facilitate unusual redox catalysis and steer the formation of complex natural product pharmacophores. Remarkably, several such recently reported flavin-dependent tailoring enzymes expand the classical paradigms of flavin biochemistry leading, e.g., to the discovery of the flavin-N5-oxide - a novel flavin redox state and oxygenating species. Copyright © 2017 Elsevier Inc. All rights reserved.

  3. Model creation of moving redox reaction boundary in agarose gel electrophoresis by traditional potassium permanganate method.

    Science.gov (United States)

    Xie, Hai-Yang; Liu, Qian; Li, Jia-Hao; Fan, Liu-Yin; Cao, Cheng-Xi

    2013-02-21

    A novel moving redox reaction boundary (MRRB) model was developed for studying electrophoretic behaviors of analytes involving redox reaction on the principle of moving reaction boundary (MRB). Traditional potassium permanganate method was used to create the boundary model in agarose gel electrophoresis because of the rapid reaction rate associated with MnO(4)(-) ions and Fe(2+) ions. MRB velocity equation was proposed to describe the general functional relationship between velocity of moving redox reaction boundary (V(MRRB)) and concentration of reactant, and can be extrapolated to similar MRB techniques. Parameters affecting the redox reaction boundary were investigated in detail. Under the selected conditions, good linear relationship between boundary movement distance and time were obtained. The potential application of MRRB in electromigration redox reaction titration was performed in two different concentration levels. The precision of the V(MRRB) was studied and the relative standard deviations were below 8.1%, illustrating the good repeatability achieved in this experiment. The proposed MRRB model enriches the MRB theory and also provides a feasible realization of manual control of redox reaction process in electrophoretic analysis.

  4. The Deep Thioredoxome in Chlamydomonas reinhardtii: New Insights into Redox Regulation.

    Science.gov (United States)

    Pérez-Pérez, María Esther; Mauriès, Adeline; Maes, Alexandre; Tourasse, Nicolas J; Hamon, Marion; Lemaire, Stéphane D; Marchand, Christophe H

    2017-08-07

    Thiol-based redox post-translational modifications have emerged as important mechanisms of signaling and regulation in all organisms, and thioredoxin plays a key role by controlling the thiol-disulfide status of target proteins. Recent redox proteomic studies revealed hundreds of proteins regulated by glutathionylation and nitrosylation in the unicellular green alga Chlamydomonas reinhardtii, while much less is known about the thioredoxin interactome in this organism. By combining qualitative and quantitative proteomic analyses, we have comprehensively investigated the Chlamydomonas thioredoxome and 1188 targets have been identified. They participate in a wide range of metabolic pathways and cellular processes. This study broadens not only the redox regulation to new enzymes involved in well-known thioredoxin-regulated metabolic pathways but also sheds light on cellular processes for which data supporting redox regulation are scarce (aromatic amino acid biosynthesis, nuclear transport, etc). Moreover, we characterized 1052 thioredoxin-dependent regulatory sites and showed that these data constitute a valuable resource for future functional studies in Chlamydomonas. By comparing this thioredoxome with proteomic data for glutathionylation and nitrosylation at the protein and cysteine levels, this work confirms the existence of a complex redox regulation network in Chlamydomonas and provides evidence of a tremendous selectivity of redox post-translational modifications for specific cysteine residues. Copyright © 2017 The Author. Published by Elsevier Inc. All rights reserved.

  5. Redox-active media for permeable reactive barriers

    International Nuclear Information System (INIS)

    Sivavec, T.M.; Mackenzie, P.D.; Horney, D.P.; Baghel, S.S.

    1997-01-01

    In this paper, three classes of redox-active media are described and evaluated in terms of their long-term effectiveness in treating TCE-contaminated groundwater in permeable reactive zones. Zero-valent iron, in the form of recycled cast iron filings, the first class, has received considerable attention as a reactive media and has been used in about a dozen pilot- and full-scale subsurface wall installations. Criteria used in selecting commercial sources of granular iron, will be discussed. Two other classes of redox-active media that have not yet seen wide use in pilot- or full-scale installations will also be described: Fe(II) minerals and bimetallic systems. Fe(II) minerals, including magnetite (Fe 3 O 4 ), and ferrous sulfide (troilite, FeS), are redox-active and afford TCE reduction rates and product distributions that suggest that they react via a reductive mechanism similar to that which operates in the FeO system. Fe(II) species within the passive oxide layer coating the iron metal may act as electron transfer mediators, with FeO serving as the bulk reductant. Bimetallic systems, the third class of redox-active media, are commonly prepared by plating a second metal onto zero-valent iron (e.g., Ni/Fe and Pd/Fe) and have been shown to accelerate solvent degradation rates relative to untreated iron metal. The long-term effectiveness of this approach, however, has not yet been determined in groundwater treatability tests. The results of a Ni-plated iron column study using site groundwater indicate that a change in reduction mechanism (to catalytic dehydrohalogenation/hydrogenation) accounts for the observed rate enhancement. A significant loss in media reactivity was observed over time, attributable to Ni catalyst deactivation or poisoning. Zero-valent iron systems have not shown similar losses in reactivity in long-term laboratory, pilot or field investigations

  6. Redox sensor proteins for highly sensitive direct imaging of intracellular redox state.

    Science.gov (United States)

    Sugiura, Kazunori; Nagai, Takeharu; Nakano, Masahiro; Ichinose, Hiroshi; Nakabayashi, Takakazu; Ohta, Nobuhiro; Hisabori, Toru

    2015-02-13

    Intracellular redox state is a critical factor for fundamental cellular functions, including regulation of the activities of various metabolic enzymes as well as ROS production and elimination. Genetically-encoded fluorescent redox sensors, such as roGFP (Hanson, G. T., et al. (2004)) and Redoxfluor (Yano, T., et al. (2010)), have been developed to investigate the redox state of living cells. However, these sensors are not useful in cells that contain, for example, other colored pigments. We therefore intended to obtain simpler redox sensor proteins, and have developed oxidation-sensitive fluorescent proteins called Oba-Q (oxidation balance sensed quenching) proteins. Our sensor proteins derived from CFP and Sirius can be used to monitor the intracellular redox state as their fluorescence is drastically quenched upon oxidation. These blue-shifted spectra of the Oba-Q proteins enable us to monitor various redox states in conjunction with other sensor proteins. Copyright © 2015 Elsevier Inc. All rights reserved.

  7. Redox regulation of cell proliferation: Bioinformatics and redox proteomics approaches to identify redox-sensitive cell cycle regulators.

    Science.gov (United States)

    Foyer, Christine H; Wilson, Michael H; Wright, Megan H

    2018-03-29

    Plant stem cells are the foundation of plant growth and development. The balance of quiescence and division is highly regulated, while ensuring that proliferating cells are protected from the adverse effects of environment fluctuations that may damage the genome. Redox regulation is important in both the activation of proliferation and arrest of the cell cycle upon perception of environmental stress. Within this context, reactive oxygen species serve as 'pro-life' signals with positive roles in the regulation of the cell cycle and survival. However, very little is known about the metabolic mechanisms and redox-sensitive proteins that influence cell cycle progression. We have identified cysteine residues on known cell cycle regulators in Arabidopsis that are potentially accessible, and could play a role in redox regulation, based on secondary structure and solvent accessibility likelihoods for each protein. We propose that redox regulation may function alongside other known posttranslational modifications to control the functions of core cell cycle regulators such as the retinoblastoma protein. Since our current understanding of how redox regulation is involved in cell cycle control is hindered by a lack of knowledge regarding both which residues are important and how modification of those residues alters protein function, we discuss how critical redox modifications can be mapped at the molecular level. Crown Copyright © 2018. Published by Elsevier Inc. All rights reserved.

  8. Metabolic Control of Redox and Redox Control of Metabolism in Plants

    Science.gov (United States)

    Fernie, Alisdair R.

    2014-01-01

    Abstract Significance: Reduction-oxidation (Redox) status operates as a major integrator of subcellular and extracellular metabolism and is simultaneously itself regulated by metabolic processes. Redox status not only dominates cellular metabolism due to the prominence of NAD(H) and NADP(H) couples in myriad metabolic reactions but also acts as an effective signal that informs the cell of the prevailing environmental conditions. After relay of this information, the cell is able to appropriately respond via a range of mechanisms, including directly affecting cellular functioning and reprogramming nuclear gene expression. Recent Advances: The facile accession of Arabidopsis knockout mutants alongside the adoption of broad-scale post-genomic approaches, which are able to provide transcriptomic-, proteomic-, and metabolomic-level information alongside traditional biochemical and emerging cell biological techniques, has dramatically advanced our understanding of redox status control. This review summarizes redox status control of metabolism and the metabolic control of redox status at both cellular and subcellular levels. Critical Issues: It is becoming apparent that plastid, mitochondria, and peroxisome functions influence a wide range of processes outside of the organelles themselves. While knowledge of the network of metabolic pathways and their intraorganellar redox status regulation has increased in the last years, little is known about the interorganellar redox signals coordinating these networks. A current challenge is, therefore, synthesizing our knowledge and planning experiments that tackle redox status regulation at both inter- and intracellular levels. Future Directions: Emerging tools are enabling ever-increasing spatiotemporal resolution of metabolism and imaging of redox status components. Broader application of these tools will likely greatly enhance our understanding of the interplay of redox status and metabolism as well as elucidating and

  9. A novel mitochondria-targeted two-photon fluorescent probe for dynamic and reversible detection of the redox cycles between peroxynitrite and glutathione.

    Science.gov (United States)

    Sun, Chunlong; Du, Wen; Wang, Peng; Wu, Yang; Wang, Baoqin; Wang, Jun; Xie, Wenjun

    2017-12-16

    Redox homeostasis is important for maintenance of normal physiological functions within cells. Redox state of cells is primarily a consequence of precise balance between levels of reducing equivalents and reactive oxygen species. Redox homeostasis between peroxynitrite (ONOO - ) and glutathione (GSH) is closely associated with physiological and pathological processes, such as prolonged relaxation in vascular tissues and smooth muscle preparations, attenuation of hepatic necrosis, and activation of matrix metalloproteinase-2. We report a two-photon fluorescent probe (TP-Se) based on water-soluble carbazole-based compound, which integrates with organic selenium, to monitor changes in ONOO - /GSH levels in cells. This probe can reversibly respond to ONOO - and GSH and exhibits high selectivity, sensitivity, and mitochondrial targeting. The probe was successfully applied to visualize changes in redox cycles during ONOO - outbreak and antioxidant GSH repair in cells. The probe will lead to significant development on redox events involved in cellular redox regulation. Copyright © 2017 Elsevier Inc. All rights reserved.

  10. Redox Behavior of Fe2+/Fe3+ Redox Couple by Absorption Spectroscopy and Measurement

    International Nuclear Information System (INIS)

    Oh, J. Y.; Park, S.; Yun, J. I.

    2010-01-01

    Redox behavior has influences on speciation and other geochemical reactions of radionuclides such as sorption, solubility, and colloid formation, etc. It is one of the factors for evaluation of long-term safety assessment under high-level radioactive waste (HLW) disposal conditions. Accordingly, redox potential (Eh) measurement in aquatic system is important to investigate the redox conditions. Eh is usually measured with redox active electrodes (Pt, Au, glassy carbon, etc.). Nevertheless, Eh measurements by general methods using electrodes provide low accuracy and high uncertainty problem. Therefore, Eh calculated from the concentration of redox active elements with a proper complexing reagent by using UV-Vis absorption spectroscopy is progressed. Iron exists mostly as spent nuclear waste container material and in hydro-geologic minerals. In this system, iron controls the redox condition in near-field area and influences chemical behavior and speciation of radionuclides including redox sensitive actinides such as U, Np, and Pu. In the present work, we present the investigation on redox phenomena of iron in aquatic system by a combination of absorption spectroscopy and redox potential measurements

  11. Mitochondrial redox biology and homeostasis in plants.

    Science.gov (United States)

    Noctor, Graham; De Paepe, Rosine; Foyer, Christine H

    2007-03-01

    Mitochondria are key players in plant cell redox homeostasis and signalling. Earlier concepts that regarded mitochondria as secondary to chloroplasts as the powerhouses of photosynthetic cells, with roles in cell proliferation, death and ageing described largely by analogy to animal paradigms, have been replaced by the new philosophy of integrated cellular energy and redox metabolism involving mitochondria and chloroplasts. Thanks to oxygenic photosynthesis, plant mitochondria often operate in an oxygen- and carbohydrate-rich environment. This rather unique environment necessitates extensive flexibility in electron transport pathways and associated NAD(P)-linked enzymes. In this review, mitochondrial redox metabolism is discussed in relation to the integrated cellular energy and redox function that controls plant cell biology and fate.

  12. Symproportionation versus Disproportionation in Bromine Redox Systems

    International Nuclear Information System (INIS)

    Toporek, Marcin; Michałowska-Kaczmarczyk, Anna M.; Michałowski, Tadeusz

    2015-01-01

    Graphical abstract: Display Omitted -- Highlights: • The disproportionation and symproportionation of bromine in different media is presented. • All the redox systems are elaborated according to the principles of the generalized approach to electrolytic redox systems (GATES/GEB). • All physicochemical knowledge is involved in the algorithm applied for this purpose. • The graphical representation of the systems is the basis of gaining the detailed physicochemical knowledge on the systems in question. -- Abstract: The paper refers to dynamic (titration) redox systems where symproportionation or disproportionation of bromine species occur. The related systems are modeled according to principles assumed in the Generalized Approach to Electrolytic Redox Systems (GATES), with Generalized Electron Balance (GEB) concept involved in the GATES/GEB software. The results obtained from calculations made with use of iterative computer programs prepared according to MATLAB computational software, are presented graphically, as 2D and 3D graphs

  13. Polyarene mediators for mediated redox flow battery

    Science.gov (United States)

    Delnick, Frank M.; Ingersoll, David; Liang, Chengdu

    2018-01-02

    The fundamental charge storage mechanisms in a number of currently studied high energy redox couples are based on intercalation, conversion, or displacement reactions. With exception to certain metal-air chemistries, most often the active redox materials are stored physically in the electrochemical cell stack thereby lowering the practical gravimetric and volumetric energy density as a tradeoff to achieve reasonable power density. In a general embodiment, a mediated redox flow battery includes a series of secondary organic molecules that form highly reduced anionic radicals as reaction mediator pairs for the reduction and oxidation of primary high capacity redox species ex situ from the electrochemical cell stack. Arenes are reduced to stable anionic radicals that in turn reduce a primary anode to the charged state. The primary anode is then discharged using a second lower potential (more positive) arene. Compatible separators and solvents are also disclosed herein.

  14. Redox characteristics of the eukaryotic cytosol

    DEFF Research Database (Denmark)

    López-Mirabal, H Reynaldo; Winther, Jakob R

    2007-01-01

    The eukaryotic cytoplasm has long been regarded as a cellular compartment in which the reduced state of protein cysteines is largely favored. Under normal conditions, the cytosolic low-molecular weight redox buffer, comprising primarily of glutathione, is highly reducing and reactive oxygen species...... (ROS) and glutathionylated proteins are maintained at very low levels. In the present review, recent progress in the understanding of the cytosolic thiol-disulfide redox metabolism and novel analytical approaches to studying cytosolic redox properties are discussed. We will focus on the yeast model...... organism, Saccharomyces cerevisiae, where the combination of genetic and biochemical approaches has brought us furthest in understanding the mechanisms underlying cellular redox regulation. It has been shown in yeast that, in addition to the enzyme glutathione reductase, other mechanisms may exist...

  15. Membranes for Redox Flow Battery Applications

    Science.gov (United States)

    Prifti, Helen; Parasuraman, Aishwarya; Winardi, Suminto; Lim, Tuti Mariana; Skyllas-Kazacos, Maria

    2012-01-01

    The need for large scale energy storage has become a priority to integrate renewable energy sources into the electricity grid. Redox flow batteries are considered the best option to store electricity from medium to large scale applications. However, the current high cost of redox flow batteries impedes the wide spread adoption of this technology. The membrane is a critical component of redox flow batteries as it determines the performance as well as the economic viability of the batteries. The membrane acts as a separator to prevent cross-mixing of the positive and negative electrolytes, while still allowing the transport of ions to complete the circuit during the passage of current. An ideal membrane should have high ionic conductivity, low water intake and excellent chemical and thermal stability as well as good ionic exchange capacity. Developing a low cost, chemically stable membrane for redox flow cell batteries has been a major focus for many groups around the world in recent years. This paper reviews the research work on membranes for redox flow batteries, in particular for the all-vanadium redox flow battery which has received the most attention. PMID:24958177

  16. Redox Regulation of Endothelial Cell Fate

    Science.gov (United States)

    Song, Ping; Zou, Ming-Hui

    2014-01-01

    Endothelial cells (ECs) are present throughout blood vessels and have variable roles in both physiological and pathological settings. EC fate is altered and regulated by several key factors in physiological or pathological conditions. Reactive nitrogen species and reactive oxygen species derived from NAD(P)H oxidases, mitochondria, or nitric oxide-producing enzymes are not only cytotoxic but also compose a signaling network in the redox system. The formation, actions, key molecular interactions, and physiological and pathological relevance of redox signals in ECs remain unclear. We review the identities, sources, and biological actions of oxidants and reductants produced during EC function or dysfunction. Further, we discuss how ECs shape key redox sensors and examine the biological functions, transcriptional responses, and post-translational modifications evoked by the redox system in ECs. We summarize recent findings regarding the mechanisms by which redox signals regulate the fate of ECs and address the outcome of altered EC fate in health and disease. Future studies will examine if the redox biology of ECs can be targeted in pathophysiological conditions. PMID:24633153

  17. Membranes for redox flow battery applications.

    Science.gov (United States)

    Prifti, Helen; Parasuraman, Aishwarya; Winardi, Suminto; Lim, Tuti Mariana; Skyllas-Kazacos, Maria

    2012-06-19

    The need for large scale energy storage has become a priority to integrate renewable energy sources into the electricity grid. Redox flow batteries are considered the best option to store electricity from medium to large scale applications. However, the current high cost of redox flow batteries impedes the wide spread adoption of this technology. The membrane is a critical component of redox flow batteries as it determines the performance as well as the economic viability of the batteries. The membrane acts as a separator to prevent cross-mixing of the positive and negative electrolytes, while still allowing the transport of ions to complete the circuit during the passage of current. An ideal membrane should have high ionic conductivity, low water intake and excellent chemical and thermal stability as well as good ionic exchange capacity. Developing a low cost, chemically stable membrane for redox flow cell batteries has been a major focus for many groups around the world in recent years. This paper reviews the research work on membranes for redox flow batteries, in particular for the all-vanadium redox flow battery which has received the most attention.

  18. Membranes for Redox Flow Battery Applications

    Directory of Open Access Journals (Sweden)

    Maria Skyllas-Kazacos

    2012-06-01

    Full Text Available The need for large scale energy storage has become a priority to integrate renewable energy sources into the electricity grid. Redox flow batteries are considered the best option to store electricity from medium to large scale applications. However, the current high cost of redox flow batteries impedes the wide spread adoption of this technology. The membrane is a critical component of redox flow batteries as it determines the performance as well as the economic viability of the batteries. The membrane acts as a separator to prevent cross-mixing of the positive and negative electrolytes, while still allowing the transport of ions to complete the circuit during the passage of current. An ideal membrane should have high ionic conductivity, low water intake and excellent chemical and thermal stability as well as good ionic exchange capacity. Developing a low cost, chemically stable membrane for redox flow cell batteries has been a major focus for many groups around the world in recent years. This paper reviews the research work on membranes for redox flow batteries, in particular for the all-vanadium redox flow battery which has received the most attention.

  19. Biodegradation of NSO-compounds under different redox-conditions

    DEFF Research Database (Denmark)

    Dyreborg, S.; Arvin, E.; Broholm, K.

    1997-01-01

    Laboratory experiments were carried out to investigate the potential of groundwater microorganisms to degrade selected heterocyclic aromatic compounds containing nitrogen, sulphur, or oxygen (NSO-compounds) under four redox-conditions over a period of 846 days. Eight compounds (pyrrole, 1...... anaerobic conditions, even though the microorganisms present in the anaerobic microcosms were active throughout the incubation period. A high variability in the lag period among the NSO-compounds was observed under aerobic conditions. While quinoline, indole, and carbazole were degraded with a lag period...

  20. Redox cycling with facing interdigitated array electrodes as a method for selective detection of redox species

    NARCIS (Netherlands)

    Dam, T.V.A.; Olthuis, Wouter; van den Berg, Albert

    2007-01-01

    A pair of interdigitated ultramicroelectrodes (UMEs) is used to electrochemically detect a weak reductor ( dopamine) in the presence of a stronger one (K-4[ Fe(CN)(6)]). In the mixture of both reductors, one of the two interdigitated electrodes ( the generator electrode) is used to oxidize both

  1. Redox cycling with facing interdigitated array electrodes as a method for selective detection of redox species

    NARCIS (Netherlands)

    Dam, V.A.T.; Olthuis, W.; Berg, van den A.

    2007-01-01

    A pair of interdigitated ultramicroelectrodes (UMEs) is used to electrochemically detect a weak reductor (dopamine) in the presence of a stronger one (K4[Fe(CN)6]). In the mixture of both reductors, one of the two interdigitated electrodes (the generator electrode) is used to oxidize both species at

  2. Redox interplay between mitochondria and peroxisomes

    Directory of Open Access Journals (Sweden)

    Celien eLismont

    2015-05-01

    Full Text Available Reduction-oxidation or ‘redox’ reactions are an integral part of a broad range of cellular processes such as gene expression, energy metabolism, protein import and folding, and autophagy. As many of these processes are intimately linked with cell fate decisions, transient or chronic changes in cellular redox equilibrium are likely to contribute to the initiation and progression of a plethora of human diseases. Since a long time, it is known that mitochondria are major players in redox regulation and signaling. More recently, it has become clear that also peroxisomes have the capacity to impact redox-linked physiological processes. To serve this function, peroxisomes cooperate with other organelles, including mitochondria. This review provides a comprehensive picture of what is currently known about the redox interplay between mitochondria and peroxisomes in mammals. We first outline the pro- and antioxidant systems of both organelles and how they may function as redox signaling nodes. Next, we critically review and discuss emerging evidence that peroxisomes and mitochondria share an intricate redox-sensitive relationship and cooperate in cell fate decisions. Key issues include possible physiological roles, messengers, and mechanisms. We also provide examples of how data mining of publicly-available datasets from ‘omics’ technologies can be a powerful means to gain additional insights into potential redox signaling pathways between peroxisomes and mitochondria. Finally, we highlight the need for more studies that seek to clarify the mechanisms of how mitochondria may act as dynamic receivers, integrators, and transmitters of peroxisome-derived mediators of oxidative stress. The outcome of such studies may open up exciting new avenues for the community of researchers working on cellular responses to organelle-derived oxidative stress, a research field in which the role of peroxisomes is currently highly underestimated and an issue of

  3. A simple method to fabricate electrochemical sensor systems with predictable high-redox amplification

    NARCIS (Netherlands)

    Straver, M.G.; Odijk, Mathieu; Olthuis, Wouter; van den Berg, Albert

    2012-01-01

    In this paper an easy to fabricate SU8/glass-based microfluidic sensor is described with two closely spaced parallel electrodes for highly selective measurements using the redox cycling effect. By varying the length of the microfluidic entrance channel, a diffusion barrier is created for non-cycling

  4. Fluorescence correlation spectroscopy on electron transfer reactions : probing inter- and intramolecular redox processes

    NARCIS (Netherlands)

    Sen, S.

    2016-01-01

    We developed a new FRET-based technique, “Fluredox”, which allows fluorescence readout of the redox state of oxido-reductases at single molecule level. Commercially available red-absorbing fluorophore ATTO655 was selected for labeling Azurin, a small blue mononuclear copper protein. Single molecule

  5. Compartmentation of redox metabolism in malaria parasites.

    Directory of Open Access Journals (Sweden)

    Sebastian Kehr

    Full Text Available Malaria, caused by the apicomplexan parasite Plasmodium, still represents a major threat to human health and welfare and leads to about one million human deaths annually. Plasmodium is a rapidly multiplying unicellular organism undergoing a complex developmental cycle in man and mosquito - a life style that requires rapid adaptation to various environments. In order to deal with high fluxes of reactive oxygen species and maintain redox regulatory processes and pathogenicity, Plasmodium depends upon an adequate redox balance. By systematically studying the subcellular localization of the major antioxidant and redox regulatory proteins, we obtained the first complete map of redox compartmentation in Plasmodium falciparum. We demonstrate the targeting of two plasmodial peroxiredoxins and a putative glyoxalase system to the apicoplast, a non-photosynthetic plastid. We furthermore obtained a complete picture of the compartmentation of thioredoxin- and glutaredoxin-like proteins. Notably, for the two major antioxidant redox-enzymes--glutathione reductase and thioredoxin reductase--Plasmodium makes use of alternative-translation-initiation (ATI to achieve differential targeting. Dual localization of proteins effected by ATI is likely to occur also in other Apicomplexa and might open new avenues for therapeutic intervention.

  6. Characterization of Redox properties of humic materials

    International Nuclear Information System (INIS)

    Choppin, G.R.

    1995-01-01

    An important aspect of humic materials is the presence of stable free radicals as shown by the width of 1 H-NMR lines of humic acid in solution as well as ESR spectra of solid samples. Presumably, these are due to quinohdrone functional groups in the humic structure. These free radicals are assumed to be a source of the redox effects of humics in metal cations. Phenolic groups have also been proposed as a source of reduction potential in these substances. The reduction potential of humic material is 0.5-0.7 V (vs. the normal hydrogen electrode). In addition to this inherent redox property, humics undergo photolysis by sunlight in surface waters which results in the production of hydrogen peroxide. The latter can also result in redox reactions with metal cations. Such direct and indirect redox capability can have significant effects on the migration of reducible cations. Studies of the reduction of hexavalent actinide cations by humic acid showed the reactions Np O 2 2+ -> Np O 2 + (E 1/2 0 = 1.47 V) and Pu O 2 2+ -> Pu +4 (E 1/2 0 = 1.04 V) while U O 2 2+ was not reduced. The reduction of plutonium in sea water by humics is discussed. Evidence of the effects of redox by humic material on metal cations in natural waters and sediments are also reviewed. (authors). 16 refs., 2 figs., 1 tab

  7. Redox-flow battery of actinide complexes

    International Nuclear Information System (INIS)

    Yamamura, Tomoo; Shiokawa, Yoshinobu

    2006-01-01

    Np battery and U battery were developed. We suggested that Np redox-flow battery should be (-)|Np 3+ ,Np 4+ ||NpO 2 + ,NpO 2 2+ |(+), and U battery (-)|[U III T 2 ] - ,[U IV T 2 ] 0 ||[U V O 2 T] - ,[U VI O 2 T] 0 |(+). The electromotive force at 50 % charge of Np and U battery is 1.10 V and 1.04 V, respectively. The energy efficiency of 70 mA/cm 2 of Np and U battery shows 99 % and 98 %, respectively. V redox-flow battery, electrode reactions of An battery, Np battery, U battery and future of U battery are described. The concept of V redox-flow battery, comparison of energy efficiency of Np, U and V battery, oxidation state and ionic species of 3d transition metals and main An, Purbe diagram of Np and U aqueous solution, shift of redox potential of β-diketones by pKa, and specifications of three redox-flow batteries are reported. (S.Y.)

  8. REDOX IMAGING OF THE p53-DEPENDENT MITOCHONDRIAL REDOX STATE IN COLON CANCER EX VIVO

    Science.gov (United States)

    XU, HE N.; FENG, MIN; MOON, LILY; DOLLOFF, NATHAN; EL-DEIRY, WAFIK; LI, LIN Z.

    2015-01-01

    The mitochondrial redox state and its heterogeneity of colon cancer at tissue level have not been previously reported. Nor has how p53 regulates mitochondrial respiration been measured at (deep) tissue level, presumably due to the unavailability of the technology that has sufficient spatial resolution and tissue penetration depth. Our prior work demonstrated that the mitochondrial redox state and its intratumor heterogeneity is associated with cancer aggressiveness in human melanoma and breast cancer in mouse models, with the more metastatic tumors exhibiting localized regions of more oxidized redox state. Using the Chance redox scanner with an in-plane spatial resolution of 200 μm, we imaged the mitochondrial redox state of the wild-type p53 colon tumors (HCT116 p53 wt) and the p53-deleted colon tumors (HCT116 p53−/−) by collecting the fluorescence signals of nicotinamide adenine dinucleotide (NADH) and oxidized flavoproteins [Fp, including flavin adenine dinucleotide (FAD)] from the mouse xenografts snap-frozen at low temperature. Our results show that: (1) both tumor lines have significant degree of intratumor heterogeneity of the redox state, typically exhibiting a distinct bi-modal distribution that either correlates with the spatial core–rim pattern or the “hot/cold” oxidation-reduction patches; (2) the p53−/− group is significantly more heterogeneous in the mitochondrial redox state and has a more oxidized tumor core compared to the p53 wt group when the tumor sizes of the two groups are matched; (3) the tumor size dependence of the redox indices (such as Fp and Fp redox ratio) is significant in the p53−/− group with the larger ones being more oxidized and more heterogeneous in their redox state, particularly more oxidized in the tumor central regions; (4) the H&E staining images of tumor sections grossly correlate with the redox images. The present work is the first to reveal at the submillimeter scale the intratumor heterogeneity pattern

  9. Carbon Redox-Polymer-Gel Hybrid Supercapacitors

    Science.gov (United States)

    Vlad, A.; Singh, N.; Melinte, S.; Gohy, J.-F.; Ajayan, P.M.

    2016-01-01

    Energy storage devices that provide high specific power without compromising on specific energy are highly desirable for many electric-powered applications. Here, we demonstrate that polymer organic radical gel materials support fast bulk-redox charge storage, commensurate to surface double layer ion exchange at carbon electrodes. When integrated with a carbon-based electrical double layer capacitor, nearly ideal electrode properties such as high electrical and ionic conductivity, fast bulk redox and surface charge storage as well as excellent cycling stability are attained. Such hybrid carbon redox-polymer-gel electrodes support unprecedented discharge rate of 1,000C with 50% of the nominal capacity delivered in less than 2 seconds. Devices made with such electrodes hold the potential for battery-scale energy storage while attaining supercapacitor-like power performances. PMID:26917470

  10. MICROSCALE METABOLIC, REDOX AND ABIOTIC REACTIONS IN HANFORD 300 AREA SUBSURFACE SEDIMENTS

    Energy Technology Data Exchange (ETDEWEB)

    Beyenal, Haluk [WSU; McLEan, Jeff [JCVI; Majors, Paul [PNNL; Fredrickson, Jim [PNNL

    2013-11-14

    The Hanford 300 Area is a unique site due to periodic hydrologic influence of river water resulting in changes in groundwater elevation and flow direction. This area is also highly subject to uranium remobilization, the source of which is currently believed to be the region at the base of the vadose zone that is subject to period saturation due to the changes in the water levels in the Columbia River. We found that microbial processes and redox and abiotic reactions which operate at the microscale were critical to understanding factors controlling the macroscopic fate and transport of contaminants in the subsurface. The combined laboratory and field research showed how microscale conditions control uranium mobility and how biotic, abiotic and redox reactions relate to each other. Our findings extended the current knowledge to examine U(VI) reduction and immobilization using natural 300 Area communities as well as selected model organisms on redox-sensitive and redox-insensitive minerals. Using innovative techniques developed specifically to probe biogeochemical processes at the microscale, our research expanded our current understanding of the roles played by mineral surfaces, bacterial competition, and local biotic, abiotic and redox reaction rates on the reduction and immobilization of uranium.

  11. Redox-Mediated and Ionizing-Radiation-Induced Inflammatory Mediators in Prostate Cancer Development and Treatment

    Science.gov (United States)

    Miao, Lu; Holley, Aaron K.; Zhao, Yanming; St. Clair, William H.

    2014-01-01

    Abstract Significance: Radiation therapy is widely used for treatment of prostate cancer. Radiation can directly damage biologically important molecules; however, most effects of radiation-mediated cell killing are derived from the generated free radicals that alter cellular redox status. Multiple proinflammatory mediators can also influence redox status in irradiated cells and the surrounding microenvironment, thereby affecting prostate cancer progression and radiotherapy efficiency. Recent Advances: Ionizing radiation (IR)–generated oxidative stress can regulate and be regulated by the production of proinflammatory mediators. Depending on the type and stage of the prostate cancer cells, these proinflammatory mediators may lead to different biological consequences ranging from cell death to development of radioresistance. Critical Issues: Tumors are heterogeneous and dynamic communication occurs between stromal and prostate cancer cells, and complicated redox-regulated mechanisms exist in the tumor microenvironment. Thus, antioxidant and anti-inflammatory strategies should be carefully evaluated for each patient at different stages of the disease to maximize therapeutic benefits while minimizing unintended side effects. Future Directions: Compared with normal cells, tumor cells are usually under higher oxidative stress and secrete more proinflammatory mediators. Thus, redox status is often less adaptive in tumor cells than in their normal counterparts. This difference can be exploited in a search for new cancer therapeutics and treatment regimes that selectively activate cell death pathways in tumor cells with minimal unintended consequences in terms of chemo- and radio-resistance in tumor cells and toxicity in normal tissues. Antioxid. Redox Signal. 20, 1481–1500. PMID:24093432

  12. Effect of long-term fertilization on humic redox mediators in multiple microbial redox reactions.

    Science.gov (United States)

    Guo, Peng; Zhang, Chunfang; Wang, Yi; Yu, Xinwei; Zhang, Zhichao; Zhang, Dongdong

    2018-03-01

    This study investigated the effects of different long-term fertilizations on humic substances (HSs), humic acids (HAs) and humins, functioning as redox mediators for various microbial redox biotransformations, including 2,2',4,4',5,5'- hexachlorobiphenyl (PCB 153 ) dechlorination, dissimilatory iron reduction, and nitrate reduction, and their electron-mediating natures. The redox activity of HSs for various microbial redox metabolisms was substantially enhanced by long-term application of organic fertilizer (pig manure). As a redox mediator, only humin extracted from soils with organic fertilizer amendment (OF-HM) maintained microbial PCB 153 dechlorination activity (1.03 μM PCB 153 removal), and corresponding HA (OF-HA) most effectively enhanced iron reduction and nitrate reduction by Shewanella putrefaciens. Electrochemical analysis confirmed the enhancement of their electron transfer capacity and redox properties. Fourier transform infrared analysis showed that C=C and C=O bonds, and carboxylic or phenolic groups in HSs might be the redox functional groups affected by fertilization. This research enhances our understanding of the influence of anthropogenic fertility on the biogeochemical cycling of elements and in situ remediation ability in agroecosystems through microorganisms' metabolisms. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Investigation of activity and selectivity of redox catalysts in oxidative ...

    African Journals Online (AJOL)

    Then, the different reaction conditions on this catalyst in a fluidized bed reactor ... In transient state experiments, methane feed without the presence of oxygen in the gas ... and the speed decrease, methane conversion decreases dramatically.

  14. Quantum Dot Nanobioelectronics and Selective Antimicrobial Redox Interventions

    Science.gov (United States)

    Goodman, Samuel Martin

    The unique properties of nanomaterials have engendered a great deal of interest in applying them for applications ranging from solid state physics to bio-imaging. One class of nanomaterials, known collectively as quantum dots, are defined as semiconducting crystals which have a characteristic dimension smaller than the excitonic radius of the bulk material which leads to quantum confinement effects. In this size regime, excited charge carriers behave like prototypical particles in a box, with their energy levels defined by the dimensions of the constituent particle. This is the source of the tunable optical properties which have drawn a great deal of attention with regards to finding appropriate applications for these materials. This dissertation is divided into multiple sections grouped by the type of application explored. The first sectoin investigates the energetic interactions of physically-coupled quantum dots and DNA, with the goal of gaining insight into how self-assembled molecular wires can bridge the energetic states of physically separated nanocrystals. Chapter 1 begins with an introduction to the properties of quantum dots, the conductive properties of DNA, and the common characterization methods used to characterize materials on the nanoscale. In Chapter 2 scanning tunneling measurements of QD-DNA constructs on the single particle level are presented which show the tunable coupling between the two materials and their resulting hybrid electronic structure. This is expanded upon in Chapter 3 where the conduction of photogenerated charges in QD-DNA hybrid thin films are characterized, which exhibit different charge transfer pathways through the constituent nucleobases depending on the energy of the incident light and resulting electrons. Complementary investigations of energy transfer mediated through DNA are presented in Chapter 4, with confirmation of Dexter-like transfer being facilitated through the oligonucleotides. The second section quantifies the use of cadmium telluride quantum dots as light-activated therapeutics for treating multi-drug resistant bacterial infectoins. A review of the physiological effects of cadmium chalcogenide quantum dots is first presented in Chapter 5 which provides a foundation for understanding the inherent toxicity of these materials. The phototoxic effect induced by CdTe quantum dots is then introduced in Chapter 6 showing the reduction in growth of gram-negative bacteria. Additional insight is provided in Chapter 7 which discusses the therapeutic mechanism and the oxygen-centered radical species which are formed by the application of light in aqueous media. The section closes with Chapter 8 describing efforts to improve the stability and bio-compatibility of the dots using various surface treatments, and shows that stability can be improved by the passivation of the quantum dots' anionic facets, though at the cost of overall radical generation.

  15. Electronically Induced Redox Barriers for Treatment of Groundwater

    National Research Council Canada - National Science Library

    Sale, Tom; Gilbert, David

    2006-01-01

    ...) and Colorado State University (CSU). The focus is an innovative electrolytic approach for managing redox-sensitive contaminants in groundwater, referred to as electrically induced redox barrier (e-barriers...

  16. Biogeochemical Barriers: Redox Behavior of Metals and Metalloids

    Science.gov (United States)

    Redox conditions and pH are arguably the most important geochemical parameters that control contaminant transport and fate in groundwater systems. Oxidation-reduction (redox) reactions mediate the chemical behavior of both inorganic and organic chemical constituents by affecting...

  17. Are bioassays useful tools to assess redox processes and biodegradation?

    DEFF Research Database (Denmark)

    Albrechtsen, Hans-Jørgen; Pedersen, Philip Grinder; Ludvigsen, L.

    2002-01-01

    sensitive hydrochemical or geochemical parameters, levels of hydrogen, and redox potential. However, all these approaches have to be evaluated against TEAP-bioassays as the most direct measure. We assessed successfully ongoing microbial-mediated redox processes by TEAP-bioassays in degradation studies...... of aromatic and chlorinated aliphatic compounds in landfill leachate plumes, and of pesticides in aquifers with various redox conditions....

  18. Le reazioni redox: un pasticcio concettuale?

    Directory of Open Access Journals (Sweden)

    Elena Ghibaudi

    2015-10-01

    Full Text Available Le reazioni di ossidoriduzione costituiscono un argomento centrale di qualsiasi corso di base di chimica, sia a livello scolastico che universitario. Il loro apprendimento comporta il superamento di svariati ostacoli concettuali, la cui difficoltà può risultare amplificata da prassi didattiche inadeguate. Gli errori più ricorrenti nel presentare l’argomento sono di due tipi: i fare implicitamente riferimento a modelli esplicativi distinti (es. il numero di ossidazione e il trasferimento elettronico, senza esplicitarli e senza evidenziarne la differente natura e il campo di validità; ii confondere il livello della spiegazione formale con quello della realtà fisica. I fenomeni redox sono normalmente interpretati sulla base di tre distinti modelli empirici, che fanno riferimento al trasferimento di atomi di ossigeno, di atomi di idrogeno, di elettroni; e di un quarto modello, formale, fondato sul cambiamento del numero di ossidazione. La confusione tra questi modelli può generare considerevoli problemi di apprendimento. Il presente lavoro riporta un’analisi critica delle implicazioni concettuali della didattica dei processi redox. L’analisi è articolata in tre sezioni: i disamina della evoluzione storica del concetto di ossidoriduzione; ii analisi dei modelli redox e del loro campo di validità; iii discussione di alcuni aspetti epistemologici inerenti i processi redox che sono rilevanti per la didattica della chimica.

  19. Mitochondrial Energy and Redox Signaling in Plants

    Science.gov (United States)

    Schwarzländer, Markus

    2013-01-01

    Abstract Significance: For a plant to grow and develop, energy and appropriate building blocks are a fundamental requirement. Mitochondrial respiration is a vital source for both. The delicate redox processes that make up respiration are affected by the plant's changing environment. Therefore, mitochondrial regulation is critically important to maintain cellular homeostasis. This involves sensing signals from changes in mitochondrial physiology, transducing this information, and mounting tailored responses, by either adjusting mitochondrial and cellular functions directly or reprogramming gene expression. Recent Advances: Retrograde (RTG) signaling, by which mitochondrial signals control nuclear gene expression, has been a field of very active research in recent years. Nevertheless, no mitochondrial RTG-signaling pathway is yet understood in plants. This review summarizes recent advances toward elucidating redox processes and other bioenergetic factors as a part of RTG signaling of plant mitochondria. Critical Issues: Novel insights into mitochondrial physiology and redox-regulation provide a framework of upstream signaling. On the other end, downstream responses to modified mitochondrial function have become available, including transcriptomic data and mitochondrial phenotypes, revealing processes in the plant that are under mitochondrial control. Future Directions: Drawing parallels to chloroplast signaling and mitochondrial signaling in animal systems allows to bridge gaps in the current understanding and to deduce promising directions for future research. It is proposed that targeted usage of new technical approaches, such as quantitative in vivo imaging, will provide novel leverage to the dissection of plant mitochondrial signaling. Antioxid. Redox Signal. 18, 2122–2144. PMID:23234467

  20. Methods for using redox liposome biosensors

    Science.gov (United States)

    Cheng, Quan; Stevens, Raymond C.

    2002-01-01

    The present invention provides methods and compositions for detecting the presence of biologically-important analytes by using redox liposome biosensors. In particular, the present invention provides liposome/sol-gel electrodes suitable for the detection of a wide variety of organic molecules, including but not limited to bacterial toxins.

  1. Redox regulation in cancer stem cells

    Science.gov (United States)

    Reactive oxygen species (ROS) and ROS-dependent (redox regulation) signaling pathways and transcriptional activities are thought to be critical in stem cell self-renewal and differentiation during growth and organogenesis. Aberrant ROS burst and dysregulation of those ROS-dependent cellular processe...

  2. Redox fluctuations in the Early Ordovician oceans

    DEFF Research Database (Denmark)

    D'Arcy, Joan Mary; Gilleaudeau, Geoffrey Jon; Peralta, Silvio

    2017-01-01

    Chromium (Cr) stable isotopes are a useful tracer of changes in redox conditions because changes in its oxidation state are accompanied by an isotopic fractionation. Recent co-precipitation experiments have shown that Cr(VI) is incorporated into the calcite lattice, suggesting that carbonates......, accompanied by exceptionally low Cr concentrations (runoff or hydrothermal input into the global...

  3. Investigating improvements on redox flow batteries

    CSIR Research Space (South Africa)

    Swartbooi, AM

    2006-09-01

    Full Text Available storage devices coupled to most of their applications. Lead-acid batteries have long been used as the most economical option to store electricity in many small scale applications, but lately more interest have been shown in redox flow batteries. The low...

  4. Redox cycling of potential antitumor aziridinylquinones

    NARCIS (Netherlands)

    Lusthof, Klaas J.; de Mol, Nicolaas J.; Richter, Wilma; Janssen, Lambert H.M.; Butler, John; Hoey, Brigid M.; Verboom, Willem; Reinhoudt, David

    1992-01-01

    The formation of reactive oxygen intermediates (ROI) during redox cycling of newly synthetized potential antitumor 2,5-bis (1-aziridinyl)-1,4-benzoquinone (BABQ) derivatives has been studied by assaying the production of ROI (superoxide, hydroxyl radical, and hydrogen peroxide) by xanthine oxidase

  5. Redox Control of Skeletal Muscle Regeneration.

    Science.gov (United States)

    Le Moal, Emmeran; Pialoux, Vincent; Juban, Gaëtan; Groussard, Carole; Zouhal, Hassane; Chazaud, Bénédicte; Mounier, Rémi

    2017-08-10

    Skeletal muscle shows high plasticity in response to external demand. Moreover, adult skeletal muscle is capable of complete regeneration after injury, due to the properties of muscle stem cells (MuSCs), the satellite cells, which follow a tightly regulated myogenic program to generate both new myofibers and new MuSCs for further needs. Although reactive oxygen species (ROS) and reactive nitrogen species (RNS) have long been associated with skeletal muscle physiology, their implication in the cell and molecular processes at work during muscle regeneration is more recent. This review focuses on redox regulation during skeletal muscle regeneration. An overview of the basics of ROS/RNS and antioxidant chemistry and biology occurring in skeletal muscle is first provided. Then, the comprehensive knowledge on redox regulation of MuSCs and their surrounding cell partners (macrophages, endothelial cells) during skeletal muscle regeneration is presented in normal muscle and in specific physiological (exercise-induced muscle damage, aging) and pathological (muscular dystrophies) contexts. Recent advances in the comprehension of these processes has led to the development of therapeutic assays using antioxidant supplementation, which result in inconsistent efficiency, underlying the need for new tools that are aimed at precisely deciphering and targeting ROS networks. This review should provide an overall insight of the redox regulation of skeletal muscle regeneration while highlighting the limits of the use of nonspecific antioxidants to improve muscle function. Antioxid. Redox Signal. 27, 276-310.

  6. Iron traps terrestrially derived dissolved organic matter at redox interfaces

    Science.gov (United States)

    Riedel, Thomas; Zak, Dominik; Biester, Harald; Dittmar, Thorsten

    2013-01-01

    Reactive iron and organic carbon are intimately associated in soils and sediments. However, to date, the organic compounds involved are uncharacterized on the molecular level. At redox interfaces in peatlands, where the biogeochemical cycles of iron and dissolved organic matter (DOM) are coupled, this issue can readily be studied. We found that precipitation of iron hydroxides at the oxic surface layer of two rewetted fens removed a large fraction of DOM via coagulation. On aeration of anoxic fen pore waters, >90% of dissolved iron and 27 ± 7% (mean ± SD) of dissolved organic carbon were rapidly (within 24 h) removed. Using ultra-high-resolution MS, we show that vascular plant-derived aromatic and pyrogenic compounds were preferentially retained, whereas the majority of carboxyl-rich aliphatic acids remained in solution. We propose that redox interfaces, which are ubiquitous in marine and terrestrial settings, are selective yet intermediate barriers that limit the flux of land-derived DOM to oceanic waters. PMID:23733946

  7. Redox control of molecular motion in switchable artificial nanoscale devices.

    Science.gov (United States)

    Credi, Alberto; Semeraro, Monica; Silvi, Serena; Venturi, Margherita

    2011-03-15

    The design, synthesis, and operation of molecular-scale systems that exhibit controllable motions of their component parts is a topic of great interest in nanoscience and a fascinating challenge of nanotechnology. The development of this kind of species constitutes the premise to the construction of molecular machines and motors, which in a not-too-distant future could find applications in fields such as materials science, information technology, energy conversion, diagnostics, and medicine. In the past 25 years the development of supramolecular chemistry has enabled the construction of an interesting variety of artificial molecular machines. These devices operate via electronic and molecular rearrangements and, like the macroscopic counterparts, they need energy to work as well as signals to communicate with the operator. Here we outline the design principles at the basis of redox switching of molecular motion in artificial nanodevices. Redox processes, chemically, electrically, or photochemically induced, can indeed supply the energy to bring about molecular motions. Moreover, in the case of electrically and photochemically induced processes, electrochemical and photochemical techniques can be used to read the state of the system, and thus to control and monitor the operation of the device. Some selected examples are also reported to describe the most representative achievements in this research area.

  8. Iron oxide redox chemistry and nuclear fuel disposal

    International Nuclear Information System (INIS)

    Jobe, D.J.; Lemire, R.J.; Taylor, P.

    1997-04-01

    Solubility and stability data for iron (III) oxides and aqueous Fe(II) and Fe(III) species are reviewed, and selected values are used to calculate potential-pH diagrams for the iron system at temperatures of 25 and 100 deg C, chloride activities {C1 - } = 10 -2 and 1 mol/kg, total carbonate activity {C T } = 10 -3 mol/kg, and iron(III) oxide/oxyhydroxide solubility products (25 deg C values) K sp = {Fe 3+ }{OH - } 3 = 10 -38.5 , 10 -40 and 10 -42 . The temperatures and anion concentrations bracket the range of conditions expected in a Canadian nuclear fuel waste disposal vault. The three solubility products represent a conservative upper limit, a most probable value, and a minimum credible value, respectively, for the iron oxides likely to be important in controlling redox conditions in a disposal vault for CANDU nuclear reactor fuel. Only in the first of these three cases do the calculated redox potentials significantly exceed values under which oxidative dissolution of the fuel may occur. (author)

  9. Electrochemical redox processes involving soluble cerium species

    International Nuclear Information System (INIS)

    Arenas, L.F.; Ponce de León, C.; Walsh, F.C.

    2016-01-01

    Highlights: • The relevance of cerium in laboratory and industrial electrochemistry is considered. • The history of fundamental electrochemical studies and applications is considered. • The chemistry, redox thermodynamics and electrode kinetics of cerium are summarised. • The uses of cerium ions in synthesis, energy storage, analysis and environmental treatment are illustrated. • Research needs and development perspectives are discussed. - Abstract: Anodic oxidation of cerous ions and cathodic reduction of ceric ions, in aqueous acidic solutions, play an important role in electrochemical processes at laboratory and industrial scale. Ceric ions, which have been used for oxidation of organic wastes and off-gases in environmental treatment, are a well-established oxidant for indirect organic synthesis and specialised cleaning processes, including oxide film removal from tanks and process pipework in nuclear decontamination. They also provide a classical reagent for chemical analysis in the laboratory. The reversible oxidation of cerous ions is an important reaction in the positive compartment of various redox flow batteries during charge and discharge cycling. A knowledge of the thermodynamics and kinetics of the redox reaction is critical to an understanding of the role of cerium redox species in these applications. Suitable choices of electrode material (metal or ceramic; coated or uncoated), geometry/structure (2-or 3-dimensional) and electrolyte flow conditions (hence an acceptable mass transport rate) are critical to achieving effective electrocatalysis, a high performance and a long lifetime. This review considers the electrochemistry of soluble cerium species and their diverse uses in electrochemical technology, especially for redox flow batteries and mediated electrochemical oxidation.

  10. Dual redox catalysts for oxygen reduction and evolution reactions: towards a redox flow Li-O2 battery.

    Science.gov (United States)

    Zhu, Yun Guang; Jia, Chuankun; Yang, Jing; Pan, Feng; Huang, Qizhao; Wang, Qing

    2015-06-11

    A redox flow lithium-oxygen battery (RFLOB) by using soluble redox catalysts with good performance was demonstrated for large-scale energy storage. The new device enables the reversible formation and decomposition of Li2O2 via redox targeting reactions in a gas diffusion tank, spatially separated from the electrode, which obviates the passivation and pore clogging of the cathode.

  11. Redox Biology in Neurological Function, Dysfunction, and Aging.

    Science.gov (United States)

    Franco, Rodrigo; Vargas, Marcelo R

    2018-04-23

    Reduction oxidation (redox) reactions are central to life and when altered, they can promote disease progression. In the brain, redox homeostasis is recognized to be involved in all aspects of central nervous system (CNS) development, function, aging, and disease. Recent studies have uncovered the diverse nature by which redox reactions and homeostasis contribute to brain physiology, and when dysregulated to pathological consequences. Redox reactions go beyond what is commonly described as oxidative stress and involve redox mechanisms linked to signaling and metabolism. In contrast to the nonspecific nature of oxidative damage, redox signaling involves specific oxidation/reduction reactions that regulate a myriad of neurological processes such as neurotransmission, homeostasis, and degeneration. This Forum is focused on the role of redox metabolism and signaling in the brain. Six review articles from leading scientists in the field that appraise the role of redox metabolism and signaling in different aspects of brain biology including neurodevelopment, neurotransmission, aging, neuroinflammation, neurodegeneration, and neurotoxicity are included. An original research article exemplifying these concepts uncovers a novel link between oxidative modifications, redox signaling, and neurodegeneration. This Forum highlights the recent advances in the field and we hope it encourages future research aimed to understand the mechanisms by which redox metabolism and signaling regulate CNS physiology and pathophysiology. Antioxid. Redox Signal. 00, 000-000.

  12. Imaging dynamic redox processes with genetically encoded probes.

    Science.gov (United States)

    Ezeriņa, Daria; Morgan, Bruce; Dick, Tobias P

    2014-08-01

    Redox signalling plays an important role in many aspects of physiology, including that of the cardiovascular system. Perturbed redox regulation has been associated with numerous pathological conditions; nevertheless, the causal relationships between redox changes and pathology often remain unclear. Redox signalling involves the production of specific redox species at specific times in specific locations. However, until recently, the study of these processes has been impeded by a lack of appropriate tools and methodologies that afford the necessary redox species specificity and spatiotemporal resolution. Recently developed genetically encoded fluorescent redox probes now allow dynamic real-time measurements, of defined redox species, with subcellular compartment resolution, in intact living cells. Here we discuss the available genetically encoded redox probes in terms of their sensitivity and specificity and highlight where uncertainties or controversies currently exist. Furthermore, we outline major goals for future probe development and describe how progress in imaging methodologies will improve our ability to employ genetically encoded redox probes in a wide range of situations. This article is part of a special issue entitled "Redox Signalling in the Cardiovascular System." Copyright © 2014 Elsevier Ltd. All rights reserved.

  13. Pseudo-indicator behaviour of platinum electrode explored for the potentiometric estimation of non-redox systems.

    Science.gov (United States)

    Raashid, Syed; Chat, Oyais Ahmad; Rizvi, Masood A; Bhat, Mohsin Ahmad; Khan, Badruddin

    2012-11-15

    A pseudo-indicator electrode based potentiometric method for estimation of non-redox metal ions is presented. In the proposed method, nature and concentration specific impact of analyte over the redox potential of ideally polarisable Pt/pregenerated-redox-couple interface forms the basis of quantification. Utility of the method in estimation of six non-redox metal ions viz. Zn(2+), Cu(2+), Ni(2+), Cd(2+), Pb(2+), Al(3+) in the concentration range of 10(-1)-10(-3) moldm(-3), individually and as binary mixtures is also presented. Three types of potentiometric behaviours, which we ascribe to the nature specific thermodynamic and kinetic aspects of metal-EDTA binding, were observed. While Cu(2+), Ni(2+), Pb(2+) and Al(3+) were found to bind EDTA efficiently, without exchanging Fe(3+); Zn(2+) and Cd(2+) were observed to replace Fe(3+) from EDTA. In contrast, Ca(2+) and Mg(2+) were found to show no binding affinity to EDTA in the pH range employed in the present work. The proposed method was also used to explore the reversibility and the Nernestian behaviour of ferricyanide/ferrocyanide redox couple through spectroelectrochemical titration of Zn(2+) with ferrocyanide. The presented method is presaged to be a reliable and low cost future replacement for costly and delicate ion selective electrodes (ISE) in the estimation of non-redox species like Zn(2+), Cu(2+), etc. Copyright © 2012 Elsevier B.V. All rights reserved.

  14. Mesoporous tungsten oxynitride as electrocatalyst for promoting redox reactions of vanadium redox couple and performance of vanadium redox flow battery

    Science.gov (United States)

    Lee, Wonmi; Jo, Changshin; Youk, Sol; Shin, Hun Yong; Lee, Jinwoo; Chung, Yongjin; Kwon, Yongchai

    2018-01-01

    For enhancing the performance of vanadium redox flow battery (VRFB), a sluggish reaction rate issue of V2+/V3+ redox couple evaluated as the rate determining reaction should be addressed. For doing that, mesoporous tungsten oxide (m-WO3) and oxyniride (m-WON) structures are proposed as the novel catalysts, while m-WON is gained by NH3 heat treatment of m-WO3. Their specific surface area, crystal structure, surface morphology and component analysis are measured using BET, XRD, TEM and XPS, while their catalytic activity for V2+/V3+ redox reaction is electrochemically examined. As a result, the m-WON shows higher peak current, smaller peak potential difference, higher electron transfer rate constant and lower charge transfer resistance than other catalysts, like the m-WO3, WO3 nanoparticle and mesoporous carbon, proving that it is superior catalyst. Regarding the charge-discharge curve tests, the VRFB single cell employing the m-WON demonstrates high voltage and energy efficiencies, high specific capacity and low capacity loss rate. The excellent results of m-WON are due to the reasons like (i) reduced energy band gap, (ii) reaction familiar surface functional groups and (ii) greater electronegativity.

  15. Compromised redox homeostasis, altered nitroso-redox balance, and therapeutic possibilities in atrial fibrillation.

    Science.gov (United States)

    Simon, Jillian N; Ziberna, Klemen; Casadei, Barbara

    2016-04-01

    Although the initiation, development, and maintenance of atrial fibrillation (AF) have been linked to alterations in myocyte redox state, the field lacks a complete understanding of the impact these changes may have on cellular signalling, atrial electrophysiology, and disease progression. Recent studies demonstrate spatiotemporal changes in reactive oxygen species production shortly after the induction of AF in animal models with an uncoupling of nitric oxide synthase activity ensuing in the presence of long-standing persistent AF, ultimately leading to a major shift in nitroso-redox balance. However, it remains unclear which radical or non-radical species are primarily involved in the underlying mechanisms of AF or which proteins are targeted for redox modification. In most instances, only free radical oxygen species have been assessed; yet evidence from the redox signalling field suggests that non-radical species are more likely to regulate cellular processes. A wider appreciation for the distinction of these species and how both species may be involved in the development and maintenance of AF could impact treatment strategies. In this review, we summarize how redox second-messenger systems are regulated and discuss the recent evidence for alterations in redox regulation in the atrial myocardium in the presence of AF, while identifying some critical missing links. We also examine studies looking at antioxidants for the prevention and treatment of AF and propose alternative redox targets that may serve as superior therapeutic options for the treatment of AF. © The Author 2016. Published by Oxford University Press on behalf of the European Society of Cardiology.

  16. A redox-assisted supramolecular assembly of manganese oxide nanotube

    International Nuclear Information System (INIS)

    Tao Li; Sun Chenggao; Fan Meilian; Huang Caijuan; Wu Hailong; Chao Zisheng; Zhai Hesheng

    2006-01-01

    In this paper, we report the hydrothermal synthesis of manganese oxide nanotube from an aqueous medium of pH 7, using KMnO 4 and MnCl 2 as inorganic precursors, polyoxyethylene (10) nonyl phenyl ether (TX-10) a surfactant and acetaldehyde an additive. The characterization of X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and N 2 adsorption at 77 K (BET) reveals that the synthesized manganese oxide nanotube has a mesopore size of ca. 3.65 nm and a wall thickness of ca. 12 nm, with the wall being composed of microporous crystals of monoclinic manganite. The X-ray photoelectron spectroscopy (XPS) result demonstrates a decrease of the binding energy of the Mn 3+ in the manganese oxide nanotube, which may be related to both the nanotubular morphology and the crystalline pore wall. A mechanism of a redox-assisted supramolecular assembly, regulated by acetaldehyde, is postulated

  17. Composite separators and redox flow batteries based on porous separators

    Science.gov (United States)

    Li, Bin; Wei, Xiaoliang; Luo, Qingtao; Nie, Zimin; Wang, Wei; Sprenkle, Vincent L.

    2016-01-12

    Composite separators having a porous structure and including acid-stable, hydrophilic, inorganic particles enmeshed in a substantially fully fluorinated polyolefin matrix can be utilized in a number of applications. The inorganic particles can provide hydrophilic characteristics. The pores of the separator result in good selectivity and electrical conductivity. The fluorinated polymeric backbone can result in high chemical stability. Accordingly, one application of the composite separators is in redox flow batteries as low cost membranes. In such applications, the composite separator can also enable additional property-enhancing features compared to ion-exchange membranes. For example, simple capacity control can be achieved through hydraulic pressure by balancing the volumes of electrolyte on each side of the separator. While a porous separator can also allow for volume and pressure regulation, in RFBs that utilize corrosive and/or oxidizing compounds, the composite separators described herein are preferable for their robustness in the presence of such compounds.

  18. Chronopotentiometric determination of redox states of peptides

    Czech Academy of Sciences Publication Activity Database

    Dorčák, Vlastimil; Paleček, Emil

    2007-01-01

    Roč. 19, č. 23 (2007), s. 2405-2412 ISSN 1040-0397 R&D Projects: GA AV ČR(CZ) IAA500040513; GA ČR(CZ) GA301/07/0490; GA MŠk(CZ) LC06035 Institutional research plan: CEZ:AV0Z50040507; CEZ:AV0Z50040702 Keywords : peptide redox states * constant current chronopotentiometry * catalytic hydrogen evolution Subject RIV: BO - Biophysics Impact factor: 2.949, year: 2007

  19. Redox pioneer:Professor Christine Helen Foyer.

    Science.gov (United States)

    Del Río, Luis A

    2011-10-15

    Dr. Christine Foyer (B.Sc. 1974; Ph.D. 1977) is recognized here as a Redox Pioneer because she has published an article on redox biology that has been cited more than 1000 times, 4 other articles that have been cited more than 500 times, and a further 32 articles that have been each cited more than 100 times. During her Ph.D. at the Kings College, University of London, United Kingdom, Dr. Foyer discovered that ascorbate and glutathione and enzymes linking NADPH, glutathione, and ascorbate are localized in isolated chloroplast preparations. These observations pioneered the discovery of the ascorbate-glutathione cycle, now known as Foyer-Halliwell-Asada pathway after the names of the three major contributors, a crucial mechanism for H(2)O(2) metabolism in both animals and plants. Dr. Foyer has made a very significant contribution to our current understanding of the crucial roles of ascorbate and glutathione in redox biology, particularly in relation to photosynthesis, respiration, and chloroplast and mitochondrial redox signaling networks. "My view is that science…is compulsive and you have to keep with it all the time and not get despondent when things do not work well. Being passionate about science is what carries you through the hard times so that it isn't so much work, as a hobby that you do for a living. It is the thrill of achieving a better understanding and finding real pleasure in putting new ideas together, explaining data and passing on knowledge that keeps you going no matter what!" --Prof. Christine Helen Foyer.

  20. Electrochemical determination of thioredoxin redox states

    Czech Academy of Sciences Publication Activity Database

    Dorčák, Vlastimil; Paleček, Emil

    2009-01-01

    Roč. 81, č. 4 (2009), s. 1543-1548 ISSN 0003-2700 R&D Projects: GA AV ČR(CZ) KAN400310651; GA ČR(CZ) GA301/07/0490; GA MŠk(CZ) LC06035 Institutional research plan: CEZ:AV0Z50040507; CEZ:AV0Z50040702 Keywords : thioredoxin redox states * constant current chronopotentiometric stripping * carbon and mercury electrodes Subject RIV: BO - Biophysics Impact factor: 5.214, year: 2009

  1. Proteostasis and REDOX state in the heart

    Science.gov (United States)

    Christians, Elisabeth S.

    2012-01-01

    Force-generating contractile cells of the myocardium must achieve and maintain their primary function as an efficient mechanical pump over the life span of the organism. Because only half of the cardiomyocytes can be replaced during the entire human life span, the maintenance strategy elicited by cardiac cells relies on uninterrupted renewal of their components, including proteins whose specialized functions constitute this complex and sophisticated contractile apparatus. Thus cardiac proteins are continuously synthesized and degraded to ensure proteome homeostasis, also termed “proteostasis.” Once synthesized, proteins undergo additional folding, posttranslational modifications, and trafficking and/or become involved in protein-protein or protein-DNA interactions to exert their functions. This includes key transient interactions of cardiac proteins with molecular chaperones, which assist with quality control at multiple levels to prevent misfolding or to facilitate degradation. Importantly, cardiac proteome maintenance depends on the cellular environment and, in particular, the reduction-oxidation (REDOX) state, which is significantly different among cardiac organelles (e.g., mitochondria and endoplasmic reticulum). Taking into account the high metabolic activity for oxygen consumption and ATP production by mitochondria, it is a challenge for cardiac cells to maintain the REDOX state while preventing either excessive oxidative or reductive stress. A perturbed REDOX environment can affect protein handling and conformation (e.g., disulfide bonds), disrupt key structure-function relationships, and trigger a pathogenic cascade of protein aggregation, decreased cell survival, and increased organ dysfunction. This review covers current knowledge regarding the general domain of REDOX state and protein folding, specifically in cardiomyocytes under normal-healthy conditions and during disease states associated with morbidity and mortality in humans. PMID:22003057

  2. Tuning of redox regulatory mechanisms, reactive oxygen species and redox homeostasis under salinity stress

    Directory of Open Access Journals (Sweden)

    Hossain eSazzad

    2016-05-01

    Full Text Available Soil salinity is a crucial environmental constraint which limits biomass production at many sites on a global scale. Saline growth conditions cause osmotic and ionic imbalances, oxidative stress and perturb metabolism, e.g. the photosynthetic electron flow. The plant ability to tolerate salinity is determined by multiple biochemical and physiological mechanisms protecting cell functions, in particular by regulating proper water relations and maintaining ion homeostasis. Redox homeostasis is a fundamental cell property. Its regulation includes control of reactive oxygen species (ROS generation, sensing deviation from and readjustment of the cellular redox state. All these redox related functions have been recognized as decisive factors in salinity acclimation and adaptation. This review focuses on the core response of plants to overcome the challenges of salinity stress through regulation of ROS generation and detoxification systems and to maintain redox homeostasis. Emphasis is given to the role of NADH oxidase (RBOH, alternative oxidase (AOX, the plastid terminal oxidase (PTOX and the malate valve with the malate dehydrogenase isoforms under salt stress. Overwhelming evidence assigns an essential auxiliary function of ROS and redox homeostasis to salinity acclimation of plants.

  3. Pyridine nucleotides in regulation of cell death and survival by redox and non-redox reactions.

    Science.gov (United States)

    Novak Kujundžić, Renata; Žarković, Neven; Gall Trošelj, Koraljka

    2014-01-01

    Changes of the level and ratios of pyridine nucleotides determine metabolism- dependent cellular redox status and the activity of poly(ADP-ribose) polymerases (PARPs) and sirtuins, thereby influencing several processes closely related to cell survival and death. Pyridine nucleotides participate in numerous metabolic reactions whereby their net cellular level remains constant, but the ratios of NAD+/NADP+ and NADH/NADPH oscillate according to metabolic changes in response to diverse stress signals. In non-redox reactions, NAD+ is degraded and quickly, afterward, resynthesized in the NAD+ salvage pathway, unless overwhelming activation of PARP-1 consumes NAD+ to the point of no return, when the cell can no longer generate enough ATP to accommodate NAD+ resynthesis. The activity of PARP-1 is mandatory for the onset of cytoprotective autophagy on sublethal stress signals. It has become increasingly clear that redox status, largely influenced by the metabolism-dependent composition of the pyridine nucleotides pool, plays an important role in the synthesis of pro-apoptotic and anti-apoptotic sphingolipids. Awareness of the involvement of the prosurvival sphingolipid, sphingosine-1-phosphate, in transition from inflammation to malignant transformation has recently emerged. Here, the participation of pyridine nucleotides in redox and non-redox reactions, sphingolipid metabolism, and their role in cell fate decisions is reviewed.

  4. Redox Regulation in Amyotrophic Lateral Sclerosis

    Science.gov (United States)

    Parakh, Sonam; Spencer, Damian M.; Halloran, Mark A.; Soo, Kai Y.; Atkin, Julie D.

    2013-01-01

    Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease that results from the death of upper and lower motor neurons. Due to a lack of effective treatment, it is imperative to understand the underlying mechanisms and processes involved in disease progression. Regulations in cellular reduction/oxidation (redox) processes are being increasingly implicated in disease. Here we discuss the possible involvement of redox dysregulation in the pathophysiology of ALS, either as a cause of cellular abnormalities or a consequence. We focus on its possible role in oxidative stress, protein misfolding, glutamate excitotoxicity, lipid peroxidation and cholesterol esterification, mitochondrial dysfunction, impaired axonal transport and neurofilament aggregation, autophagic stress, and endoplasmic reticulum (ER) stress. We also speculate that an ER chaperone protein disulphide isomerase (PDI) could play a key role in this dysregulation. PDI is essential for normal protein folding by oxidation and reduction of disulphide bonds, and hence any disruption to this process may have consequences for motor neurons. Addressing the mechanism underlying redox regulation and dysregulation may therefore help to unravel the molecular mechanism involved in ALS. PMID:23533690

  5. Measurement of Redox Potential in Nanoecotoxicological Investigations

    Directory of Open Access Journals (Sweden)

    Ratna Tantra

    2012-01-01

    Full Text Available Redox potential has been identified by the Organisation for Economic Co-operation and Development (OECD as one of the parameters that should be investigated for the testing of manufactured nanomaterials. There is still some ambiguity concerning this parameter, i.e., as to what and how to measure, particularly when in a nanoecotoxicological context. In this study the redox potentials of six nanomaterials (either zinc oxide (ZnO or cerium oxide (CeO2 dispersions were measured using an oxidation-reduction potential (ORP electrode probe. The particles under testing differed in terms of their particle size and dispersion stability in deionised water and in various ecotox media. The ORP values of the various dispersions and how they fluctuate relative to each other are discussed. Results show that the ORP values are mainly governed by the type of liquid media employed, with little contributions from the nanoparticles. Seawater was shown to have reduced the ORP value, which was attributed to an increase in the concentration of reducing agents such as sulphites or the reduction of dissolved oxygen concentration. The lack of redox potential value contribution from the particles themselves is thought to be due to insufficient interaction of the particles at the Pt electrode of the ORP probe.

  6. Measurement of redox potential in nanoecotoxicological investigations.

    Science.gov (United States)

    Tantra, Ratna; Cackett, Alex; Peck, Roger; Gohil, Dipak; Snowden, Jacqueline

    2012-01-01

    Redox potential has been identified by the Organisation for Economic Co-operation and Development (OECD) as one of the parameters that should be investigated for the testing of manufactured nanomaterials. There is still some ambiguity concerning this parameter, i.e., as to what and how to measure, particularly when in a nanoecotoxicological context. In this study the redox potentials of six nanomaterials (either zinc oxide (ZnO) or cerium oxide (CeO(2))) dispersions were measured using an oxidation-reduction potential (ORP) electrode probe. The particles under testing differed in terms of their particle size and dispersion stability in deionised water and in various ecotox media. The ORP values of the various dispersions and how they fluctuate relative to each other are discussed. Results show that the ORP values are mainly governed by the type of liquid media employed, with little contributions from the nanoparticles. Seawater was shown to have reduced the ORP value, which was attributed to an increase in the concentration of reducing agents such as sulphites or the reduction of dissolved oxygen concentration. The lack of redox potential value contribution from the particles themselves is thought to be due to insufficient interaction of the particles at the Pt electrode of the ORP probe.

  7. Membrane development for vanadium redox flow batteries.

    Science.gov (United States)

    Schwenzer, Birgit; Zhang, Jianlu; Kim, Soowhan; Li, Liyu; Liu, Jun; Yang, Zhenguo

    2011-10-17

    Large-scale energy storage has become the main bottleneck for increasing the percentage of renewable energy in our electricity grids. Redox flow batteries are considered to be among the best options for electricity storage in the megawatt range and large demonstration systems have already been installed. Although the full technological potential of these systems has not been reached yet, currently the main problem hindering more widespread commercialization is the high cost of redox flow batteries. Nafion, as the preferred membrane material, is responsible for about 11% of the overall cost of a 1 MW/8 MWh system. Therefore, in recent years two main membrane related research threads have emerged: 1) chemical and physical modification of Nafion membranes to optimize their properties with regard to vanadium redox flow battery (VRFB) application; and 2) replacement of the Nafion membranes with different, less expensive materials. This review summarizes the underlying basic scientific issues associated with membrane use in VRFBs and presents an overview of membrane-related research approaches aimed at improving the efficiency of VRFBs and making the technology cost-competitive. Promising research strategies and materials are identified and suggestions are provided on how materials issues could be overcome.

  8. Thiol/disulfide redox states in signaling and sensing

    Science.gov (United States)

    Go, Young-Mi; Jones, Dean P.

    2015-01-01

    Rapid advances in redox systems biology are creating new opportunities to understand complexities of human disease and contributions of environmental exposures. New understanding of thiol-disulfide systems have occurred during the past decade as a consequence of the discoveries that thiol and disulfide systems are maintained in kinetically controlled steady-states displaced from thermodynamic equilibrium, that a widely distributed family of NADPH oxidases produces oxidants that function in cell signaling, and that a family of peroxiredoxins utilize thioredoxin as a reductant to complement the well-studied glutathione antioxidant system for peroxide elimination and redox regulation. This review focuses on thiol/disulfide redox state in biologic systems and the knowledge base available to support development of integrated redox systems biology models to better understand the function and dysfunction of thiol-disulfide redox systems. In particular, central principles have emerged concerning redox compartmentalization and utility of thiol/disulfide redox measures as indicators of physiologic function. Advances in redox proteomics show that, in addition to functioning in protein active sites and cell signaling, cysteine residues also serve as redox sensors to integrate biologic functions. These advances provide a framework for translation of redox systems biology concepts to practical use in understanding and treating human disease. Biological responses to cadmium, a widespread environmental agent, are used to illustrate the utility of these advances to the understanding of complex pleiotropic toxicities. PMID:23356510

  9. The redox reaction kinetics of Sinai ore for chemical looping combustion applications

    International Nuclear Information System (INIS)

    Ksepko, Ewelina; Babiński, Piotr; Nalbandian, Lori

    2017-01-01

    Highlights: • Redox reaction kinetics of Fe-Mn-rich Sinai ore was determined by TGA. • The most suitable model for reduction was D3, while R3 for oxidation. • Activation energies 35.3 and 16.70 kJ/mole were determined for reduction and oxidation. • Repetitive redox reactions favor the formation of spinel phases in Sinai ore. • Multiple redox cycles induce formation of extensive porosity of the particles. - Abstract: The objective of this work was to study the use of Sinai ore, a Fe–Mn-based ore from Egypt, as a low-cost oxygen carrier (OC) in Chemical Looping Combustion (CLC). The Sinai ore was selected because it possesses relatively high amounts of iron and manganese oxides. Furthermore, those oxides have low cost, very favorable environmental and thermodynamic properties for the CLC process. The performance of the Sinai ore as an OC in CLC was compared to that of ilmenite (Norway Tellnes mine), the most extensively studied naturally occurring Fe-based mineral. The kinetics of the reduction and oxidation reactions with the two minerals were studied using a thermogravimetric analyzer (TGA). Experiments were conducted under isothermal conditions, with multiple redox cycles, at temperatures between 750 and 950 °C. For the reduction and oxidation reactions, different concentrations of CH_4 (10–25 vol.%) and O_2 (5–20 vol.%) were applied, respectively. The kinetic parameters, such as the activation energy (E_a), pre-exponential factor (A_0), and reaction order (n), were determined for the redox reactions. Furthermore, models of the redox reactions were selected by means of a model-fitting method. For the Sinai ore, the D3 model (3-dimensional diffusion) was suitable for modeling reduction reaction kinetics. The calculated E_a was 35.3 kJ/mole, and the reaction order was determined to be approximately 0.76. The best fit for the oxidation reaction was obtained for the R3 model (shrinking core). The oxidation (regeneration) reaction E_a was equal to 16

  10. Characterisation of the Redox Sensitive NMDA Receptor

    KAUST Repository

    Alzahrani, Ohood

    2016-05-01

    Glucose entry into the brain and its subsequent metabolism to L-lactate, regulated by astrocytes, plays a major role in synaptic plasticity and memory formation. A recent study has shown that L-lactate produced by the brain upon stimulation of glycolysis, and glycogen-derived L-lactate from astrocytes and its transport into neurons, is crucial for memory formation. A recent study revealed the molecular mechanisms that underlie the role of L-lactate in neuronal plasticity and long-term memory formation. L-lactate was shown to induce a cascade of molecular events via modulation of redox-sensitive N-Methyl-D-aspartate (NMDA) receptor activity that was mimicked by nicotinamide adenine dinucleotide hydride (NADH) co-enzyme. This indicated that changes in cellular redox state, following L-lactate transport inside the cells and its subsequent metabolism, production of NADH, and favouring a reduced state are the key effects of L-lactate. Therefore, we are investigating the role of L-lactate in modulating NMDA receptor function via redox modulatory sites. Accordingly, crucial redox-sensitive cysteine residues, Cys320 and Cys87, of the NR2A NMDA receptor subunit are mutated using site-directed mutation, transfected, and expressed in HEK293 cells. This cellular system will then be used to characterise and monitor its activity upon Llactate stimulation, compared to the wild type. This will be achieved by calcium imaging, using fluorescent microscopy. Our data shows that L-lactate potentiated NMDA receptor activity and increased intracellular calcium influx in NR1/NR2A wild type compared to the control condition (WT NR1/NR2A perfused with (1μM) glutamate and (1μM) glycine agonist only), showing faster response initiation and slower decay rate of the calcium signal to the baseline. Additionally, stimulating with L-lactate associated with greater numbers of cells having high fluorescent intensity (peak amplitude) compared to the control. Furthermore, L-lactate rescued the

  11. Analytical redox reactions and redox potentials of tungsten and its concomitants

    Energy Technology Data Exchange (ETDEWEB)

    Wuensch, G.; Mintrop, L.; Tracht, U.

    1985-01-01

    It is demonstrated that tungsten can be more effectively determined by redox titrimetry than by gravimetry. In addition to its inherent greater simplicity the volumetric approach offers to determine several components of the sample from consecutive redox titrations. To provide the necessary information the conditional redox potentials of W, Mo, Fe, V, Ti, Sn, Cu, Cr in HCl, HCl + HF and HCl + H/sub 3/PO/sub 4/ have been determined. Use of HF and/or H/sub 3/PO/sub 4/ allows sample preparations without any precipitation of tungstic acid. The influence of these auxiliary complexing agents on the potentials and kinetics is discussed. The titrations can be performed reductimetrically or more conveniently oxidimetrically using potentiometric or amperometric indication. The use of strongly reducing agents restricts the tolerance interval to +-0.6%, so that the gravimetric determination of tungsten remains superior for high precision analyses.

  12. Analytical redox reactions and redox potentials of tungsten and its concomitants

    International Nuclear Information System (INIS)

    Wuensch, G.; Mintrop, L.; Tracht, U.

    1985-01-01

    It is demonstrated that tungsten can be more effectively determined by redox titrimetry than by gravimetry. In addition to its inherent greater simplicity the volumetric approach offers to determine several components of the sample from consecutive redox titrations. To provide the necessary information the conditional redox potentials of W, Mo, Fe, V, Ti, Sn, Cu, Cr in HCl, HCl + HF and HCl + H 3 PO 4 have been determined. Use of HF and/or H 3 PO 4 allows sample preparations without any precipitation of tungstic acid. The influence of these auxiliary complexing agents on the potentials and kinetics is discussed. The titrations can be performed reductimetrically or more conveniently oxidimetrically using potentiometric or amperometric indication. The use of strongly reducing agents restricts the tolerance interval to +-0.6%, so that the gravimetric determination of tungsten remains superior for high precision analyses. (orig.) [de

  13. Neutral Red and Ferroin as Reversible and Rapid Redox Materials for Redox Flow Batteries.

    Science.gov (United States)

    Hong, Jeehoon; Kim, Ketack

    2018-04-17

    Neutral red and ferroin are used as redox indicators (RINs) in potentiometric titrations. The rapid response and reversibility that are prerequisites for RINs are also desirable properties for the active materials in redox flow batteries (RFBs). This study describes the electrochemical properties of ferroin and neutral red as a redox pair. The rapid reaction rates of the RINs allow a cell to run at a rate of 4 C with 89 % capacity retention after the 100 th  cycle. The diffusion coefficients, electrode reaction rates, and solubilities of the RINs were determined. The electron-transfer rate constants of ferroin and neutral red are 0.11 and 0.027 cm s -1 , respectively, which are greater than those of the components of all-vanadium and Zn/Br 2 cells. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Multiple redox states of multiheme cytochromes may enable bacterial response to changing redox environments

    Science.gov (United States)

    Arbour, T.; Wrighton, K. C.; Mullin, S. W.; Castelle, C.; Luef, B.; Gilbert, B.; Banfield, J. F.

    2013-12-01

    Multiheme c-type cytochromes (MHCs) are key components in electron-transport pathways that enable some microorganisms to transfer electron byproducts of metabolism to a variety of minerals. As a response to changes in mineral redox potential, microbial communities may shift their membership, or individual organisms may adjust protein expression. Alternatively, the ability to respond may be conferred by the innate characteristics of certain electron-transport-chain components. Here, we used potentiostat-controlled microbial fuel cells (MFCs) to measure the timescale of response to imposed changes in redox conditions, thus placing constraints on the importance of these different mechanisms. In the experiments, a solid electrode acts as an electron-accepting mineral whose redox potential can be precisely controlled. We inoculated duplicate MFCs with a sediment/groundwater mixture from an aquifer at Rifle, Colorado, supplied acetate as an electron donor, and obtained stable, mixed-species biofilms dominated by Geobacter and a novel Geobacter-related family. We poised the anode at potentials spanning the range of natural Fe(III)-reduction, then performed cyclic voltammetry (CV) to characterize the overall biofilm redox signature. The apparent biofilm midpoint potential shifted directly with anode set potential when the latter was changed within the range from about -250 to -50 mV vs. SHE. Following a jump in set potential by 200 mV, the CV-midpoint shift by ~100 mV over a timescale of ~30 minutes to a few hours, depending on the direction of the potential change. The extracellular electron transfer molecules, whose overall CV signature is very similar to those of purified MHCs, appear to span a broad redox range (~200 mV), supporting the hypothesis that MHCs confer substantial redox flexibility. This flexibility may be a principle reason for the abundance of MHCs expressed by microorganisms capable of extracellular electron transfer to minerals.

  15. Redox properties of structural Fe in clay minerals: 3. Relationships between smectite redox and structural properties.

    Science.gov (United States)

    Gorski, Christopher A; Klüpfel, Laura E; Voegelin, Andreas; Sander, Michael; Hofstetter, Thomas B

    2013-01-01

    Structural Fe in clay minerals is an important redox-active species in many pristine and contaminated environments as well as in engineered systems. Understanding the extent and kinetics of redox reactions involving Fe-bearing clay minerals has been challenging due to the inability to relate structural Fe(2+)/Fe(total) fractions to fundamental redox properties, such as reduction potentials (EH). Here, we overcame this challenge by using mediated electrochemical reduction (MER) and oxidation (MEO) to characterize the fraction of redox-active structural Fe (Fe(2+)/Fe(total)) in smectites over a wide range of applied EH-values (-0.6 V to +0.6 V). We examined Fe(2+)/Fe(total )- EH relationships of four natural Fe-bearing smectites (SWy-2, SWa-1, NAu-1, NAu-2) in their native, reduced, and reoxidized states and compared our measurements with spectroscopic observations and a suite of mineralogical properties. All smectites exhibited unique Fe(2+)/Fe(total) - EH relationships, were redox active over wide EH ranges, and underwent irreversible electron transfer induced structural changes that were observable with X-ray absorption spectroscopy. Variations among the smectite Fe(2+)/Fe(total) - EH relationships correlated well with both bulk and molecular-scale properties, including Fe(total) content, layer charge, and quadrupole splitting values, suggesting that multiple structural parameters determined the redox properties of smectites. The Fe(2+)/Fe(total) - EH relationships developed for these four commonly studied clay minerals may be applied to future studies interested in relating the extent of structural Fe reduction or oxidation to EH-values.

  16. Electrolyte for stable cycling of high-energy lithium sulfur redox flow batteries

    Science.gov (United States)

    Xiao, Jie; Liu, Jun; Pan, Huilin; Henderson, Wesley A.

    2018-04-24

    A device comprising: a lithium sulfur redox flow battery comprising an electrolyte composition comprising: (i) a dissolved Li2Sx electroactive salt, wherein x.gtoreq.4; (ii) a solvent selected from dimethyl sulfoxide, tetrahydrofuran, or a mixture thereof; and (iii) a supporting salt at a concentration of at least 2 M, as measured by moles of supporting salt divided by the volume of the solvent without considering the volume change of the electrolyte after dissolving the supporting salt.

  17. New tools for redox biology: From imaging to manipulation.

    Science.gov (United States)

    Bilan, Dmitry S; Belousov, Vsevolod V

    2017-08-01

    Redox reactions play a key role in maintaining essential biological processes. Deviations in redox pathways result in the development of various pathologies at cellular and organismal levels. Until recently, studies on transformations in the intracellular redox state have been significantly hampered in living systems. The genetically encoded indicators, based on fluorescent proteins, have provided new opportunities in biomedical research. The existing indicators already enable monitoring of cellular redox parameters in different processes including embryogenesis, aging, inflammation, tissue regeneration, and pathogenesis of various diseases. In this review, we summarize information about all genetically encoded redox indicators developed to date. We provide the description of each indicator and discuss its advantages and limitations, as well as points that need to be considered when choosing an indicator for a particular experiment. One chapter is devoted to the important discoveries that have been made by using genetically encoded redox indicators. Copyright © 2016 Elsevier Inc. All rights reserved.

  18. Nanostructured Electrocatalysts for All-Vanadium Redox Flow Batteries.

    Science.gov (United States)

    Park, Minjoon; Ryu, Jaechan; Cho, Jaephil

    2015-10-01

    Vanadium redox reactions have been considered as a key factor affecting the energy efficiency of the all-vanadium redox flow batteries (VRFBs). This redox reaction determines the reaction kinetics of whole cells. However, poor kinetic reversibility and catalytic activity towards the V(2+)/V(3+) and VO(2+)/VO2(+) redox couples on the commonly used carbon substrate limit broader applications of VRFBs. Consequently, modified carbon substrates have been extensively investigated to improve vanadium redox reactions. In this Focus Review, recent progress on metal- and carbon-based nanomaterials as an electrocatalyst for VRFBs is discussed in detail, without the intention to provide a comprehensive review on the whole components of the system. Instead, the focus is mainly placed on the redox chemistry of vanadium ions at a surface of various metals, different dimensional carbons, nitrogen-doped carbon nanostructures, and metal-carbon composites. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Redox regulation of Rac1 by thiol oxidation

    Science.gov (United States)

    Hobbs, G. Aaron; Mitchell, Lauren E.; Arrington, Megan E.; Gunawardena, Harsha P.; DeCristo, Molly J.; Loeser, Richard F.; Chen, Xian; Cox, Adrienne D.; Campbell, Sharon L.

    2016-01-01

    The Rac1 GTPase is an essential and ubiquitous protein that signals through numerous pathways to control critical cellular processes, including cell growth, morphology, and motility. Rac1 deletion is embryonic lethal, and its dysregulation or mutation can promote cancer, arthritis, cardiovascular disease, and neurological disorders. Rac1 activity is highly regulated by modulatory proteins and posttranslational modifications. Whereas much attention has been devoted to guanine nucleotide exchange factors that act on Rac1 to promote GTP loading and Rac1 activation, cellular oxidants may also regulate Rac1 activation by promoting guanine nucleotide exchange. Herein, we show that Rac1 contains a redox-sensitive cysteine (Cys18) that can be selectively oxidized at physiological pH because of its lowered pKa. Consistent with these observations, we show that Rac1 is glutathiolated in primary chondrocytes. Oxidation of Cys18 by glutathione greatly perturbs Rac1 guanine nucleotide binding and promotes nucleotide exchange. As aspartate substitutions have been previously used to mimic cysteine oxidation, we characterized the biochemical properties of Rac1C18D. We also evaluated Rac1C18S as a redox-insensitive variant and found that it retains structural and biochemical properties similar to those of Rac1WT but is resistant to thiol oxidation. In addition, Rac1C18D, but not Rac1C18S, shows greatly enhanced nucleotide exchange, similar to that observed for Rac1 oxidation by glutathione. We employed Rac1C18D in cell-based studies to assess whether this fast-cycling variant, which mimics Rac1 oxidation by glutathione, affects Rac1 activity and function. Expression of Rac1C18D in Swiss 3T3 cells showed greatly enhanced GTP-bound Rac1 relative to Rac1WT and the redox-insensitive Rac1C18S variant. Moreover, expression of Rac1C18D in HEK-293T cells greatly promoted lamellipodia formation. Our results suggest that Rac1 oxidation at Cys18 is a novel posttranslational modification that

  20. Factors Controlling Redox Speciation of Plutonium and Neptunium in Extraction Separation Processes

    Energy Technology Data Exchange (ETDEWEB)

    Paulenova, Alena [Principal Investigator; Vandegrift, III, George F. [Collaborator

    2013-09-24

    The objective of the project was to examine the factors controlling redox speciation of plutonium and neptunium in UREX+ extraction in terms of redox potentials, redox mechanism, kinetics and thermodynamics. Researchers employed redox-speciation extractions schemes in parallel to the spectroscopic experiments. The resulting distribution of redox species w studied uring spectroscopic, electrochemical, and spectro-electrochemical methods. This work reulted in collection of data on redox stability and distribution of redox couples in the nitric acid/nitrate electrolyte and the development of redox buffers to stabilize the desired oxidation state of separated radionuclides. The effects of temperature and concentrations on the redox behavior of neptunium were evaluated.

  1. Redox homeostasis: The Golden Mean of healthy living.

    Science.gov (United States)

    Ursini, Fulvio; Maiorino, Matilde; Forman, Henry Jay

    2016-08-01

    The notion that electrophiles serve as messengers in cell signaling is now widely accepted. Nonetheless, major issues restrain acceptance of redox homeostasis and redox signaling as components of maintenance of a normal physiological steady state. The first is that redox signaling requires sudden switching on of oxidant production and bypassing of antioxidant mechanisms rather than a continuous process that, like other signaling mechanisms, can be smoothly turned up or down. The second is the misperception that reactions in redox signaling involve "reactive oxygen species" rather than reaction of specific electrophiles with specific protein thiolates. The third is that hormesis provides protection against oxidants by increasing cellular defense or repair mechanisms rather than by specifically addressing the offset of redox homeostasis. Instead, we propose that both oxidant and antioxidant signaling are main features of redox homeostasis. As the redox shift is rapidly reversed by feedback reactions, homeostasis is maintained by continuous signaling for production and elimination of electrophiles and nucleophiles. Redox homeostasis, which is the maintenance of nucleophilic tone, accounts for a healthy physiological steady state. Electrophiles and nucleophiles are not intrinsically harmful or protective, and redox homeostasis is an essential feature of both the response to challenges and subsequent feedback. While the balance between oxidants and nucleophiles is preserved in redox homeostasis, oxidative stress provokes the establishment of a new radically altered redox steady state. The popular belief that scavenging free radicals by antioxidants has a beneficial effect is wishful thinking. We propose, instead, that continuous feedback preserves nucleophilic tone and that this is supported by redox active nutritional phytochemicals. These nonessential compounds, by activating Nrf2, mimic the effect of endogenously produced electrophiles (parahormesis). In summary

  2. Redox homeostasis: The Golden Mean of healthy living

    Directory of Open Access Journals (Sweden)

    Fulvio Ursini

    2016-08-01

    Full Text Available The notion that electrophiles serve as messengers in cell signaling is now widely accepted. Nonetheless, major issues restrain acceptance of redox homeostasis and redox signaling as components of maintenance of a normal physiological steady state. The first is that redox signaling requires sudden switching on of oxidant production and bypassing of antioxidant mechanisms rather than a continuous process that, like other signaling mechanisms, can be smoothly turned up or down. The second is the misperception that reactions in redox signaling involve “reactive oxygen species” rather than reaction of specific electrophiles with specific protein thiolates. The third is that hormesis provides protection against oxidants by increasing cellular defense or repair mechanisms rather than by specifically addressing the offset of redox homeostasis. Instead, we propose that both oxidant and antioxidant signaling are main features of redox homeostasis. As the redox shift is rapidly reversed by feedback reactions, homeostasis is maintained by continuous signaling for production and elimination of electrophiles and nucleophiles. Redox homeostasis, which is the maintenance of nucleophilic tone, accounts for a healthy physiological steady state. Electrophiles and nucleophiles are not intrinsically harmful or protective, and redox homeostasis is an essential feature of both the response to challenges and subsequent feedback. While the balance between oxidants and nucleophiles is preserved in redox homeostasis, oxidative stress provokes the establishment of a new radically altered redox steady state. The popular belief that scavenging free radicals by antioxidants has a beneficial effect is wishful thinking. We propose, instead, that continuous feedback preserves nucleophilic tone and that this is supported by redox active nutritional phytochemicals. These nonessential compounds, by activating Nrf2, mimic the effect of endogenously produced electrophiles

  3. Redox shuttles for safer lithium-ion batteries

    International Nuclear Information System (INIS)

    Chen, Zonghai; Qin, Yan; Amine, Khalil

    2009-01-01

    Overcharge protection is not only critical for preventing the thermal runaway of lithium-ion batteries during operation, but also important for automatic capacity balancing during battery manufacturing and repair. A redox shuttle is an electrolyte additive that can be used as intrinsic overcharge protection mechanism to enhance the safety characteristics of lithium-ion batteries. The advances on stable redox shuttles are briefly reviewed. Fundamental studies for designing stable redox shuttles are also discussed.

  4. Exercise redox biochemistry: Conceptual, methodological and technical recommendations

    Directory of Open Access Journals (Sweden)

    James N. Cobley

    2017-08-01

    Full Text Available Exercise redox biochemistry is of considerable interest owing to its translational value in health and disease. However, unaddressed conceptual, methodological and technical issues complicate attempts to unravel how exercise alters redox homeostasis in health and disease. Conceptual issues relate to misunderstandings that arise when the chemical heterogeneity of redox biology is disregarded: which often complicates attempts to use redox-active compounds and assess redox signalling. Further, that oxidised macromolecule adduct levels reflect formation and repair is seldom considered. Methodological and technical issues relate to the use of out-dated assays and/or inappropriate sample preparation techniques that confound biochemical redox analysis. After considering each of the aforementioned issues, we outline how each issue can be resolved and provide a unifying set of recommendations. We specifically recommend that investigators: consider chemical heterogeneity, use redox-active compounds judiciously, abandon flawed assays, carefully prepare samples and assay buffers, consider repair/metabolism, use multiple biomarkers to assess oxidative damage and redox signalling. Keywords: Exercise, Oxidative stress, Free radical, Antioxidants, Redox signalling

  5. Redox proteomics of tomato in response to Pseudomonas syringae infection

    Science.gov (United States)

    Balmant, Kelly Mayrink; Parker, Jennifer; Yoo, Mi-Jeong; Zhu, Ning; Dufresne, Craig; Chen, Sixue

    2015-01-01

    Unlike mammals with adaptive immunity, plants rely on their innate immunity based on pattern-triggered immunity (PTI) and effector-triggered immunity (ETI) for pathogen defense. Reactive oxygen species, known to play crucial roles in PTI and ETI, can perturb cellular redox homeostasis and lead to changes of redox-sensitive proteins through modification of cysteine sulfhydryl groups. Although redox regulation of protein functions has emerged as an important mechanism in several biological processes, little is known about redox proteins and how they function in PTI and ETI. In this study, cysTMT proteomics technology was used to identify similarities and differences of protein redox modifications in tomato resistant (PtoR) and susceptible (prf3) genotypes in response to Pseudomonas syringae pv tomato (Pst) infection. In addition, the results of the redox changes were compared and corrected with the protein level changes. A total of 90 potential redox-regulated proteins were identified with functions in carbohydrate and energy metabolism, biosynthesis of cysteine, sucrose and brassinosteroid, cell wall biogenesis, polysaccharide/starch biosynthesis, cuticle development, lipid metabolism, proteolysis, tricarboxylic acid cycle, protein targeting to vacuole, and oxidation–reduction. This inventory of previously unknown protein redox switches in tomato pathogen defense lays a foundation for future research toward understanding the biological significance of protein redox modifications in plant defense responses. PMID:26504582

  6. Chemistry of the redox sensitive elements. Literature review

    International Nuclear Information System (INIS)

    Suter, D.

    1991-10-01

    As a part of the safety assessment for a nuclear waste repository, the migration of the radioactive elements from the waste matrix to the biosphere has to be modelled. The geosphere is an important barrier and a consideration of the retention of the radioactive isotopes needs knowledge of sorption coefficients and solubilities. Important long-lived isotopes in the high level radioactive waste are the fission products selenium, technetium, palladium and tin, and the actinide neptunium, which are all redox sensitive elements. A transport model using conservative sorption values predicts mainly doses from these five elements. Since the individual oxidation states of the redox sensitive elements have different and largely unknown sorption properties and solubilities, the realistic doses might be far less. The relevant literature about the chemistry of the five elements is summarized and is planned to serve as the basis for an experimental programme. For every element, the literature about the general chemistry, selected sorption studies, geochemistry, and analytical methods is reviewed. It was found that the knowledge about some of these points is very limited. Even the general chemistry of some of the elements is not well known, because they have only limited applications and research concentrates only on certain aspects. Most of the sorption studies in the context of nuclear waste concentrate on a few of the relevant elements and others have been neglected up to now. The simulation of a realistic system in the laboratory poses some problems, which have to be solved as well. The literature about this subject is also critically reviewed. The elements which are most mobile under realistic far-field conditions are identified and it is recommended to concentrate research on these at the beginning. (author)

  7. Chemistry of the redox sensitive elements. Literature review

    International Nuclear Information System (INIS)

    Suter, D.

    1991-10-01

    As a part of the safety assessment for a nuclear waste repository, the migration of the radioactive elements from the waste matrix to the biosphere has to be modelled. The geosphere is an important barrier and a consideration of the retention of the radioactive isotopes needs knowledge of sorption coefficients and solubilities. Important long-lived isotopes in the high level radioactive waste are the fission products selenium, technetium, palladium and tin, and the actinide neptunium, which are all redox sensitive elements. A transport model using conservative sorption values predicts mainly doses from these five elements. Since the individual oxidation states of the redox sensitive elements have different and largely unknown sorption properties and solubilities, the realistic doses might be far less. The relevant literature about the chemistry of the five elements is summarized and is planned to serve as the basis for an experimental programme. For every element, the literature about the general chemistry, selected sorption studies, geochemistry, and analytical methods is reviewed. It was found that the knowledge about some of these points is very limited. Even the general chemistry of some of the elements in not well known, because they have only limited applications and research concentrates only on certain aspects. Most of the sorption studies in the context of nuclear waste concentrate on a few of the relevant elements and others have been neglected up to now. The simulation of a realistic system in the laboratory poses some problems, which have to be solved as well. The literature about this subject is also critically reviewed. The elements which are most mobile under realistic far-field conditions are identified and it is recommended to concentrate research on these at the beginning. (author) 9 figs., 192 refs

  8. Oxidation of extracellular cysteine/cystine redox state in bleomycin-induced lung fibrosis.

    Science.gov (United States)

    Iyer, Smita S; Ramirez, Allan M; Ritzenthaler, Jeffrey D; Torres-Gonzalez, Edilson; Roser-Page, Susanne; Mora, Ana L; Brigham, Kenneth L; Jones, Dean P; Roman, Jesse; Rojas, Mauricio

    2009-01-01

    Several lines of evidence indicate that depletion of glutathione (GSH), a critical thiol antioxidant, is associated with the pathogenesis of idiopathic pulmonary fibrosis (IPF). However, GSH synthesis depends on the amino acid cysteine (Cys), and relatively little is known about the regulation of Cys in fibrosis. Cys and its disulfide, cystine (CySS), constitute the most abundant low-molecular weight thiol/disulfide redox couple in the plasma, and the Cys/CySS redox state (E(h) Cys/CySS) is oxidized in association with age and smoking, known risk factors for IPF. Furthermore, oxidized E(h) Cys/CySS in the culture media of lung fibroblasts stimulates proliferation and expression of transitional matrix components. The present study was undertaken to determine whether bleomycin-induced lung fibrosis is associated with a decrease in Cys and/or an oxidation of the Cys/CySS redox state and to determine whether these changes were associated with changes in E(h) GSH/glutathione disulfide (GSSG). We observed distinct effects on plasma GSH and Cys redox systems during the progression of bleomycin-induced lung injury. Plasma E(h) GSH/GSSG was selectively oxidized during the proinflammatory phase, whereas oxidation of E(h) Cys/CySS occurred at the fibrotic phase. In the epithelial lining fluid, oxidation of E(h) Cys/CySS was due to decreased food intake. Thus the data show that decreased precursor availability and enhanced oxidation of Cys each contribute to the oxidation of extracellular Cys/CySS redox state in bleomycin-induced lung fibrosis.

  9. Auditable safety analysis for the surveillance and maintenance of the REDOX complex

    International Nuclear Information System (INIS)

    Cuneo, V.J.

    1997-02-01

    The Reduction-Oxidation (REDOX) Complex is an inactive surplus facility that contains two former fuel processing facilities (the 202-S Canyon Building and the 233-S Plutonium Concentration Facility) and a number of ancillary support structures. Deactivation started in 1967 and was completed in 1969 when the plant was transferred to surveillance and maintenance (S ampersand M). This document provides the auditable safety analysis (ASA) for the post-deactivation, long-term S ampersand M phase of the above grade structures of the REDOX Complex. The S ampersand M phase is conducted for the following reasons: (1) Maintain confinement of residual inventories of radioactive materials and other contaminants until the facility is ultimately dispositioned, (2) Prevent deterioration of confinement structures, (3) Respond to potential accident conditions requiring response and mitigation, (4) Provide for the safety of workers involved in the S ampersand M phase, and (5) Provide the basis for evaluation and selection of ultimate disposal alternatives. The ability of the existing facilities to withstand the effects of natural phenomena hazard events is evaluated and the active support systems used to maintain ventilation and/or prevent the spread of contamination are described. This auditable safety analysis document evaluates the routinely required S ampersand M activities (i.e., the S ampersand M of facility barriers, equipment, structures, and postings [including repair and upgrade]; measures to identify, remove, or repair damaged asbestos; measures to identify, remove, or appropriately manage existing containers of hazardous substances; and the performance of spill response measures as needed). For the REDOX Complex, the movement of cell cover blocks is also evaluated, as D-cell cover block was removed a number of years ago and should be replaced. The type and nature of the hazards presented by the REDOX Complex and the REDOX-specific controls required to maintain these

  10. Redox Pioneer: Professor Stuart A. Lipton

    Science.gov (United States)

    2013-01-01

    Abstract Professor Stuart A. Lipton Stuart A. Lipton, M.D., Ph.D. is recognized here as a Redox Pioneer because of his publication of four articles that have been cited more than 1000 times, and 96 reports which have been cited more than 100 times. In the redox field, Dr. Lipton is best known for his work on the regulation by S-nitrosylation of the NMDA-subtype of neuronal glutamate receptor, which provided early evidence for in situ regulation of protein activity by S-nitrosylation and a prototypic model of allosteric control by this post-translational modification. Over the past several years, Lipton's group has pioneered the discovery of aberrant protein nitrosylation that may contribute to a number of neurodegenerative disorders, including Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis (Lou Gehrig's disease). In particular, the phenotypic effects of rare genetic mutations may be understood to be enhanced or mimicked by nitrosative (and oxidative) modifications of cysteines and thereby help explain common sporadic forms of disease. Thus, Lipton has contributed in a major way to the understanding that nitrosative stress may result from modifications of specific proteins and may operate in conjunction with genetic mutation to create disease phenotype. Lipton (collaborating with Jonathan S. Stamler) has also employed the concept of targeted S-nitrosylation to produce novel neuroprotective drugs that act at allosteric sites in the NMDA receptor. Lipton has won a number of awards, including the Ernst Jung Prize in Medicine, and is an elected fellow of the AAAS. Antioxid. Redox Signal. 19, 757–764. PMID:23815466

  11. Redox-active and Redox-silent Compounds: Synergistic Therapeutics in Cancer

    Czech Academy of Sciences Publication Activity Database

    Tomasetti, M.; Santarelli, L.; Alleva, R.; Dong, L.F.; Neužil, Jiří

    2015-01-01

    Roč. 22, č. 5 (2015), s. 552-568 ISSN 0929-8673 R&D Projects: GA MŠk(CZ) ED1.1.00/02.0109 Institutional support: RVO:86652036 Keywords : Apoptosis * autophagy * redox-active agents Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 3.455, year: 2015

  12. Effect of redox conditions on bacterial community structure in Baltic Sea sediments with contrasting redox conditions

    NARCIS (Netherlands)

    Steenbergh, A.K.; Bodelier, P.L.E.; Slomp, C.P; Laanbroek, H.J.

    2014-01-01

    Phosphorus release from sediments can exacerbate the effect of eutrophication in coastal marine ecosystems. The flux of phosphorus from marine sediments to the overlying water is highly dependent on the redox conditions at the sediment-water interface. Bacteria are key players in the biological

  13. Sedimentary cobalt concentrations track marine redox evolution

    Science.gov (United States)

    Swanner, Elizabeth; Planavsky, Noah; Lalonde, Stefan; Robbins, Jamie; Bekker, Andrey; Rouxel, Olivier; Konhauser, Kurt O.; Mojzsis, Stephen J.

    2013-04-01

    Oxygen production by photosynthesis drove the redox evolution of the atmosphere and ocean. Primary productivity by oxygenic photosynthesizers in the modern surface ocean is limited by trace nutrients such as iron, but previous studies have also observed high Co uptake associated with natural cyanobacterial populations. Constraining the size and variation of the oceanic reservoir of Co through time will help to understand the regulation of primary productivity and hence oxygenation through time. In this study, Co concentrations from iron formations (IF), shales and marine pyrites deposited over nearly 4 billion years of Earth's history are utilized to reconstruct secular changes in the mechanisms of Co removal from the oceanic reservoir. The Co reservoir prior to ~2 Ga was dominated by hydrothermal inputs and Fe(III)oxyhydroxides were likely involved in the removal of Co from the water column. Fe(II) oxidation in the water column resulted in the deposition of IF in the Archean and Paleoproterozoic, and the Co inventory of IF records a large oceanic reservoir of Co during this time. Lower Co concentrations in sediments during the Middle Proterozoic signify a decrease in the oceanic reservoir due to the expansion euxinic environments, corresponding to the results of previous studies. A transition to an oxidized deep ocean in the Phanerozoic is evidenced by correlation between Co and manganese (Mn) concentrations in hydrothermal and exhalative deposits, and in marine pyrites. This relationship between Co and Mn, signifying deposition of Co in association with Mn(IV)oxides, does not occur in the Precambrian. Mn(II) oxidation occurs at higher redox potentials than that required for Fe(II) oxidation, and the extent of Mn redox cycling prior to full ventilation of the oceans at the end of the Neoproterozoic was likely limited to spatially restricted oxic surface waters. In this regard, Co is another valuable redox proxy for tracking the growth and decline in oxygenated

  14. Redox Equilibria in SO2 Oxidation Catalysts

    DEFF Research Database (Denmark)

    Rasmussen, Søren Birk; Eriksen, Kim Michael; Boghosian, Soghomon

    1999-01-01

    been carried out regarding the complex and compound formation of V(V) and the formation of V(IV) and V(III) compounds with low solubility causing catalyst deactivation. However, the redox chemistry of vanadium and the complex formation of V(IV) is much less investigated and further information...... on these subjects in pyrosulfate melts is needed to obtain a deeper understanding of the reaction mechanism. The present paper describes our efforts so far to study the V(IV) chemistry using especially spectroscopic and electrochemical methods....

  15. Rebalancing electrolytes in redox flow battery systems

    Science.gov (United States)

    Chang, On Kok; Pham, Ai Quoc

    2014-12-23

    Embodiments of redox flow battery rebalancing systems include a system for reacting an unbalanced flow battery electrolyte with a rebalance electrolyte in a first reaction cell. In some embodiments, the rebalance electrolyte may contain ferrous iron (Fe.sup.2+) which may be oxidized to ferric iron (Fe.sup.3+) in the first reaction cell. The reducing ability of the rebalance reactant may be restored in a second rebalance cell that is configured to reduce the ferric iron in the rebalance electrolyte back into ferrous iron through a reaction with metallic iron.

  16. Aqueous electrolytes for redox flow battery systems

    Science.gov (United States)

    Liu, Tianbiao; Li, Bin; Wei, Xiaoliang; Nie, Zimin; Wang, Wei; Liu, Jun; Sprenkle, Vincent L.

    2017-10-17

    An aqueous redox flow battery system includes an aqueous catholyte and an aqueous anolyte. The aqueous catholyte may comprise (i) an optionally substituted thiourea or a nitroxyl radical compound and (ii) a catholyte aqueous supporting solution. The aqueous anolyte may comprise (i) metal cations or a viologen compound and (ii) an anolyte aqueous supporting solution. The catholyte aqueous supporting solution and the anolyte aqueous supporting solution independently may comprise (i) a proton source, (ii) a halide source, or (iii) a proton source and a halide source.

  17. Fe-V redox flow batteries

    Science.gov (United States)

    Li, Liyu; Kim, Soowhan; Yang, Zhenguo; Wang, Wei; Zhang, Jianlu; Chen, Baowei; Nie, Zimin; Xia, Guanguang

    2014-07-08

    A redox flow battery having a supporting solution that includes Cl.sup.- anions is characterized by an anolyte having V.sup.2+ and V.sup.3+ in the supporting solution, a catholyte having Fe.sup.2+ and Fe.sup.3+ in the supporting solution, and a membrane separating the anolyte and the catholyte. The anolyte and catholyte can have V cations and Fe cations, respectively, or the anolyte and catholyte can each contain both V and Fe cations in a mixture. Furthermore, the supporting solution can contain a mixture of SO.sub.4.sup.2- and Cl.sup.- anions.

  18. Click-PEGylation - A mobility shift approach to assess the redox state of cysteines in candidate proteins.

    Science.gov (United States)

    van Leeuwen, Lucie A G; Hinchy, Elizabeth C; Murphy, Michael P; Robb, Ellen L; Cochemé, Helena M

    2017-07-01

    The redox state of cysteine thiols is critical for protein function. Whereas cysteines play an important role in the maintenance of protein structure through the formation of internal disulfides, their nucleophilic thiol groups can become oxidatively modified in response to diverse redox challenges and thereby function in signalling and antioxidant defences. These oxidative modifications occur in response to a range of agents and stimuli, and can lead to the existence of multiple redox states for a given protein. To assess the role(s) of a protein in redox signalling and antioxidant defence, it is thus vital to be able to assess which of the multiple thiol redox states are present and to investigate how these alter under different conditions. While this can be done by a range of mass spectrometric-based methods, these are time-consuming, costly, and best suited to study abundant proteins or to perform an unbiased proteomic screen. One approach that can facilitate a targeted assessment of candidate proteins, as well as proteins that are low in abundance or proteomically challenging, is by electrophoretic mobility shift assays. Redox-modified cysteine residues are selectively tagged with a large group, such as a polyethylene glycol (PEG) polymer, and then the proteins are separated by electrophoresis followed by immunoblotting, which allows the inference of redox changes based on band shifts. However, the applicability of this method has been impaired by the difficulty of cleanly modifying protein thiols by large PEG reagents. To establish a more robust method for redox-selective PEGylation, we have utilised a Click chemistry approach, where free thiol groups are first labelled with a reagent modified to contain an alkyne moiety, which is subsequently Click-reacted with a PEG molecule containing a complementary azide function. This strategy can be adapted to study reversibly reduced or oxidised cysteines. Separation of the thiol labelling step from the PEG

  19. Redox properties of iron in porous ferrisilicates

    International Nuclear Information System (INIS)

    Lazar, K.; Pal-Borbely, G.; Szegedi, A.; Fejes, P.; Martinez, F.

    2006-01-01

    Insertion of iron into porous ferrisilicates may result in changes of the original structures. For example, this insertion enables the structure to take part in reversible Fe 2+ ↔ Fe 3+ redox process. This process may play an important role e.g. in catalytic procedures. The structure of the host may provide different locations for the iron. In microporous systems (analogous with zeolites, with characteristic pore sizes of 0.5 nm) the framework vs. extra-framework distinction is obvious, since these structures are strictly crystalline (in three dimensions). In contrast, mesoporous structures of 3 - 5 nm characteristic pore dimension, exhibit crystallinity uppermost in two dimensions, since their pore walls are partly amorphous. The appearance of the Fe 2+ ↔ Fe 3+ redox behaviour of iron in micro- and mesoporous systems, its correlation with coordination changes strongly depend on the structure. In general, crystallinity stabilizes the Fe 3+ state, and the Fe 3+ ↔ Fe 2+ change may be correlated with change of the position occupied in the structure. For demonstration, some examples are to be presented by comparing the behaviour of iron located in in microporous (MFI, FER, MCM-22) and mesoporous (MCM-41 and SBA-15) structures. (authors)

  20. Redox regulation of photosynthetic gene expression.

    Science.gov (United States)

    Queval, Guillaume; Foyer, Christine H

    2012-12-19

    Redox chemistry and redox regulation are central to the operation of photosynthesis and respiration. However, the roles of different oxidants and antioxidants in the regulation of photosynthetic or respiratory gene expression remain poorly understood. Leaf transcriptome profiles of a range of Arabidopsis thaliana genotypes that are deficient in either hydrogen peroxide processing enzymes or in low molecular weight antioxidant were therefore compared to determine how different antioxidant systems that process hydrogen peroxide influence transcripts encoding proteins targeted to the chloroplasts or mitochondria. Less than 10 per cent overlap was observed in the transcriptome patterns of leaves that are deficient in either photorespiratory (catalase (cat)2) or chloroplastic (thylakoid ascorbate peroxidase (tapx)) hydrogen peroxide processing. Transcripts encoding photosystem II (PSII) repair cycle components were lower in glutathione-deficient leaves, as were the thylakoid NAD(P)H (nicotinamide adenine dinucleotide (phosphate)) dehydrogenases (NDH) mRNAs. Some thylakoid NDH mRNAs were also less abundant in tAPX-deficient and ascorbate-deficient leaves. Transcripts encoding the external and internal respiratory NDHs were increased by low glutathione and low ascorbate. Regulation of transcripts encoding specific components of the photosynthetic and respiratory electron transport chains by hydrogen peroxide, ascorbate and glutathione may serve to balance non-cyclic and cyclic electron flow pathways in relation to oxidant production and reductant availability.

  1. Dissolution of UO2 in redox conditions

    International Nuclear Information System (INIS)

    Casas, I.; Pablo de, J.; Rovira, M.

    1998-01-01

    The performance assessment of the final disposal of the spent nuclear fuel in geological formations is strongly dependent on the spent fuel matrix dissolution. Unirradiated uranium (IV) dioxide has shown to be very useful for such purposes. The stability of UO 2 is very dependent on vault redox conditions. At reducing conditions, which are expected in deep groundwaters, the dissolution of the UO 2 -matrix can be explained in terms of solubility, while under oxidizing conditions, the UO 2 is thermodynamically unstable and the dissolution is kinetically controlled. In this report the parameters which affect the uranium solubility under reducing conditions, basically pH and redox potential are discussed. Under oxidizing conditions, UO 2 dissolution rate equations as a function of pH, carbonate concentration and oxidant concentration are reported. Dissolution experiments performed with spent fuel are also reviewed. The experimental equations presented in this work, have been used to model independent dissolution experiments performed with both unirradiated and irradiated UO 2 . (Author)

  2. Diglycosyl diselenides alter redox homeostasis and glucose consumption of infective African trypanosomes

    Directory of Open Access Journals (Sweden)

    Jaime Franco

    2017-12-01

    Full Text Available With the aim to develop compounds able to target multiple metabolic pathways and, thus, to lower the chances of drug resistance, we investigated the anti-trypanosomal activity and selectivity of a series of symmetric diglycosyl diselenides and disulfides. Of 18 compounds tested the fully acetylated forms of di-β-D-glucopyranosyl and di-β-D-galactopyranosyl diselenides (13 and 15, respectively displayed strong growth inhibition against the bloodstream stage of African trypanosomes (EC50 0.54 μM for 13 and 1.49 μM for 15 although with rather low selectivity (SI < 10 assayed with murine macrophages. Nonacetylated versions of the same sugar diselenides proved to be, however, much less efficient or completely inactive to suppress trypanosome growth. Significantly, the galactosyl (15, and to a minor extent the glucosyl (13, derivative inhibited glucose catabolism but not its uptake. Both compounds induced redox unbalance in the pathogen. In vitro NMR analysis indicated that diglycosyl diselenides react with glutathione, under physiological conditions, via formation of selenenylsulfide bonds. Our results suggest that non-specific cellular targets as well as actors of the glucose and the redox metabolism of the parasite may be affected. These molecules are therefore promising leads for the development of novel multitarget antitrypanosomal agents. Keywords: Glutathione, Redox biosensor, Selenosugar, Trypanosome inhibition, Selenium NMR

  3. Electrochemistry and electrochemiluminescence from a redox-active metal-organic framework.

    Science.gov (United States)

    Xu, Yang; Yin, Xue-Bo; He, Xi-Wen; Zhang, Yu-Kui

    2015-06-15

    The marriage of metal-organic frameworks (MOFs) and electrochemiluminescence (ECL) can combine their merits together. Designing ECL-active MOF with a high electron transfer capacity and high stability is critical for ECL emission. Here we reported the ECL from a redox-active MOF prepared from {Ru[4,4'-(HO2C)2-bpy]2bpy}(2+) and Zn(2+); a property of MOFs has not been reported previously. The MOF structure is independent of its charge and is therefore stable electrochemically. The redox-activity and well-ordered porous structure of the MOF were confirmed by its electrochemical properties and ECL emission. The high ECL emission indicated the ease of electron transfer between the MOF and co-reactants. Furthermore, the MOF exhibited permselectivity, charge selectivity, and catalytic selectivity along with a stable and concentration-dependent ECL emission toward co-reactants. ECL mechanism was proposed based on the results. The detection and recovery of cocaine in the serum sample was used to validate the feasibility of MOF- based ECL system. The information obtained in this study provides a better understanding of the redox properties of MOFs and their potential electrochemical applications. Copyright © 2014 Elsevier B.V. All rights reserved.

  4. Fenton Redox Chemistry : Arsenite Oxidation by Metallic Surfaces

    NARCIS (Netherlands)

    Borges Freitas, S.C.; Van Halem, D.; Badruzzaman, A.B.M.; Van der Meer, W.G.J.

    2014-01-01

    Pre-oxidation of As(III) is necessary in arsenic removal processes in order to increase its efficiency. Therefore, the Fenton Redox Chemistry is defined by catalytic activation of H2O2 and currently common used for its redox oxidative properties. In this study the effect of H2O2 production catalysed

  5. Silver nanoparticle catalysed redox reaction: An electron relay effect

    International Nuclear Information System (INIS)

    Mallick, Kaushik; Witcomb, Mike; Scurrell, Mike

    2006-01-01

    A silver cluster shows efficient catalytic activity in a redox reaction because the cluster acts as the electron relay centre behaving alternatively as an acceptor and as a donor of electrons. An effective transfer of electrons is possible when the redox potential of the cluster is intermediate between the electron donor and electron acceptor system

  6. "JCE" Classroom Activity #111: Redox Reactions in Three Representations

    Science.gov (United States)

    Nieves, Edgardo L. Ortiz; Barreto, Reizelie; Medina, Zuleika

    2012-01-01

    This activity introduces students to the concept of reduction-oxidation (redox) reactions. To help students obtain a thorough understanding of redox reactions, the concept is explored at three levels: macroscopic, submicroscopic, and symbolic. In this activity, students perform hands-on investigations of the three levels as they work at different…

  7. Exercise redox biochemistry: Conceptual, methodological and technical recommendations.

    Science.gov (United States)

    Cobley, James N; Close, Graeme L; Bailey, Damian M; Davison, Gareth W

    2017-08-01

    Exercise redox biochemistry is of considerable interest owing to its translational value in health and disease. However, unaddressed conceptual, methodological and technical issues complicate attempts to unravel how exercise alters redox homeostasis in health and disease. Conceptual issues relate to misunderstandings that arise when the chemical heterogeneity of redox biology is disregarded: which often complicates attempts to use redox-active compounds and assess redox signalling. Further, that oxidised macromolecule adduct levels reflect formation and repair is seldom considered. Methodological and technical issues relate to the use of out-dated assays and/or inappropriate sample preparation techniques that confound biochemical redox analysis. After considering each of the aforementioned issues, we outline how each issue can be resolved and provide a unifying set of recommendations. We specifically recommend that investigators: consider chemical heterogeneity, use redox-active compounds judiciously, abandon flawed assays, carefully prepare samples and assay buffers, consider repair/metabolism, use multiple biomarkers to assess oxidative damage and redox signalling. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

  8. Visualization of red-ox proteins on the gold surface using enzymatic polypyrrole formation

    International Nuclear Information System (INIS)

    Ramanaviciene, A.; Kausaite-Minkstimiene, A.; Voronovic, J.; Ramanavicius, A.; Oztekin, Y.; Carac, G.; German, N.

    2011-01-01

    We describe a new method for the visualization of the activity of red-ox proteins on a gold interface. Glucose oxidase was selected as a model system. Surfaces were modified by adhesion of glucose oxidase on (a) electrochemically cleaned gold; (b) gold films modified with gold nanoparticles, (c) a gold surface modified with self-assembled monolayer, and (d) covalent immobilization of protein on the gold surface modified with a self-assembled monolayer. The simple optical method for the visualization of enzyme on the surfaces is based on the enzymatic formation of polypyrrole. The activity of the enzyme was quantified via enzymatic formation of polypyrrole, which was detected and investigated by quartz microbalance and amperometric techniques. The experimental data suggest that the enzymatic formation of the polymer may serve as a method to indicate the adhesion of active redox enzyme on such surfaces. (author)

  9. Composition and redox control of waste glasses: Recommendation for process control limit

    International Nuclear Information System (INIS)

    Jantzen, C.M.; Plodinec, M.J.

    1986-01-01

    An electrochemical series of redox couples, originally developed for Savannah River Laboratory glass frit 131 (SRL-131) as a reference composition, has been extended to two other alkali borosilicate compositions that are candidate glasses for nuclear waste immobilization. Since no dramatic differences were ascertained in the redox chemistry of selected multivalent elements in SRL-131 versus that in Savannah River Laboratory glass frit 165 (SRL-165) and in West Valley glass number-sign 205 (WV-205), the comprehensive electrochemical series can readily be applied to a range of nuclear waste glass compositions. In order to alleviate potential problems with foaming and precipitation of insolubles during the processing of the nuclear waste in these glass melts, the [Fe 2+ ]/[Fe 3+ ] ratio of the melt should be between 0.1 and 0.5. 27 refs., 4 figs., 2 tabs

  10. Redox-active cerium oxide nanoparticles protect human dermal fibroblasts from PQ-induced damage

    Directory of Open Access Journals (Sweden)

    Claudia von Montfort

    2015-04-01

    Full Text Available Recently, it has been published that cerium (Ce oxide nanoparticles (CNP; nanoceria are able to downregulate tumor invasion in cancer cell lines. Redox-active CNP exhibit both selective pro-oxidative and antioxidative properties, the first being responsible for impairment of tumor growth and invasion. A non-toxic and even protective effect of CNP in human dermal fibroblasts (HDF has already been observed. However, the effect on important parameters such as cell death, proliferation and redox state of the cells needs further clarification. Here, we present that nanoceria prevent HDF from reactive oxygen species (ROS-induced cell death and stimulate proliferation due to the antioxidative property of these particles.

  11. Development of redox stable, multifunctional substrates for anode supported SOFCS

    DEFF Research Database (Denmark)

    Sudireddy, Bhaskar Reddy; Foghmoes, Søren Preben Vagn; Ramos, Tania

    2017-01-01

    Redox stable solid oxide fuel cells are beneficial in many aspects such as tolerance against system failures e.g fuel cut off and emergency shut down, but also allow for higher fuel utilization, which increases efficiency. State-ofthe-art Ni-cermet based anodes suffer from microstructural changes...... with a multifunctional anode support, the development of a two layer fuel electrode based on a redox stable strontium titanate layer for the electrochemically active layer and a redox stable Ni-YSZ support was pursued. Half-cells with well adhearing strontium titante anode layers on stateof-the-art Ni-YSZ cermet...... supports have been achieved. Redox tolerance of the half-cell depends could be increased by optimizing the redox stability of the cermet support....

  12. Energy storage device including a redox-enhanced electrolyte

    Science.gov (United States)

    Stucky, Galen; Evanko, Brian; Parker, Nicholas; Vonlanthen, David; Auston, David; Boettcher, Shannon; Chun, Sang-Eun; Ji, Xiulei; Wang, Bao; Wang, Xingfeng; Chandrabose, Raghu Subash

    2017-08-08

    An electrical double layer capacitor (EDLC) energy storage device is provided that includes at least two electrodes and a redox-enhanced electrolyte including two redox couples such that there is a different one of the redox couples for each of the electrodes. When charged, the charge is stored in Faradaic reactions with the at least two redox couples in the electrolyte and in a double-layer capacitance of a porous carbon material that comprises at least one of the electrodes, and a self-discharge of the energy storage device is mitigated by at least one of electrostatic attraction, adsorption, physisorption, and chemisorption of a redox couple onto the porous carbon material.

  13. Measuring intracellular redox conditions using GFP-based sensors

    DEFF Research Database (Denmark)

    Björnberg, Olof; Ostergaard, Henrik; Winther, Jakob R

    2006-01-01

    Recent years have seen the development of methods for analyzing the redox conditions in specific compartments in living cells. These methods are based on genetically encoded sensors comprising variants of Green Fluorescent Protein in which vicinal cysteine residues have been introduced at solvent......-exposed positions. Several mutant forms have been identified in which formation of a disulfide bond between these cysteine residues results in changes of their fluorescence properties. The redox sensors have been characterized biochemically and found to behave differently, both spectroscopically and in terms...... of redox properties. As genetically encoded sensors they can be expressed in living cells and used for analysis of intracellular redox conditions; however, which parameters are measured depends on how the sensors interact with various cellular redox components. Results of both biochemical and cell...

  14. Dimensional behavior of Ni-YSZ composites during redox cycling

    DEFF Research Database (Denmark)

    Pihlatie, Mikko; Kaiser, Andreas; Larsen, Peter Halvor

    2009-01-01

    The dimensional behavior of Ni-yttria-stabilized zirconia (YSZ) cermets during redox cycling was tested in dilatometry within the temperature range 600-1000 degrees C. The effect Of humidity oil redox stability was investigated at intermediate and low temperatures. We show that both the sintering...... of nickel depending on temperature of the initial reduction and the operating conditions, and the temperature of reoxidation are very important for the size of the dimensional change. Cumulative redox strain (CRS) is shown to be correlated with temperature. Measured maximum CRS after three redox cycles...... varies within 0.25-3.2% dL/L in dry gas and respective temperature range of 600-1000 degrees C. A high degree of redox reversibility was reached at low temperature. however. reversibility is lost at elevated temperatures. We found that at 850 degrees C, 6% steam and a very high p(H2O)/p(H2) ratio...

  15. Redox-Based Regulation of Bacterial Development and Behavior.

    Science.gov (United States)

    Sporer, Abigail J; Kahl, Lisa J; Price-Whelan, Alexa; Dietrich, Lars E P

    2017-06-20

    Severe changes in the environmental redox potential, and resulting alterations in the oxidation states of intracellular metabolites and enzymes, have historically been considered negative stressors, requiring responses that are strictly defensive. However, recent work in diverse organisms has revealed that more subtle changes in the intracellular redox state can act as signals, eliciting responses with benefits beyond defense and detoxification. Changes in redox state have been shown to influence or trigger chromosome segregation, sporulation, aerotaxis, and social behaviors, including luminescence as well as biofilm establishment and dispersal. Connections between redox state and complex behavior allow bacteria to link developmental choices with metabolic state and coordinate appropriate responses. Promising future directions for this area of study include metabolomic analysis of species- and condition-dependent changes in metabolite oxidation states and elucidation of the mechanisms whereby the redox state influences circadian regulation.

  16. Subcellular Redox Targeting: Bridging in Vitro and in Vivo Chemical Biology.

    Science.gov (United States)

    Long, Marcus J C; Poganik, Jesse R; Ghosh, Souradyuti; Aye, Yimon

    2017-03-17

    Networks of redox sensor proteins within discrete microdomains regulate the flow of redox signaling. Yet, the inherent reactivity of redox signals complicates the study of specific redox events and pathways by traditional methods. Herein, we review designer chemistries capable of measuring flux and/or mimicking subcellular redox signaling at the cellular and organismal level. Such efforts have begun to decipher the logic underlying organelle-, site-, and target-specific redox signaling in vitro and in vivo. These data highlight chemical biology as a perfect gateway to interrogate how nature choreographs subcellular redox chemistry to drive precision redox biology.

  17. Morphology evolution and nanostructure of chemical looping transition metal oxide materials upon redox processes

    International Nuclear Information System (INIS)

    Qin, Lang; Cheng, Zhuo; Guo, Mengqing; Fan, Jonathan A.; Fan, Liang-Shih

    2017-01-01

    Transition metal are heavily used in chemical looping technologies because of their high oxygen carrying capacity and high thermal reactivity. These oxygen activities result in the oxide formation and oxygen vacancy formation that affect the nanoscale crystal phase and morphology within these materials and their subsequent bulk chemical behavior. In this study, two selected earlier transition metals manganese and cobalt as well as two selected later transition metals copper and nickel that are important to chemical looping reactions are investigated when they undergo cyclic redox reactions. We found Co microparticles exhibited increased CoO impurity presence when oxidized to Co_3O_4 upon cyclic oxidation; CuO redox cycles prefer to be limited to a reduced form of Cu_2O and an oxidized form of CuO; Mn microparticles were oxidized to a mixed phases of MnO and Mn_3O_4, which causes delamination during oxidation. For Ni microparticles, a dense surface were observed during the redox reaction. The atomistic thermodynamics methods and density functional theory (DFT) calculations are carried out to elucidate the effect of oxygen dissociation and migration on the morphological evolution of nanostructures during the redox processes. Our results indicate that the earlier transition metals (Mn and Co) tend to have stronger interaction with O_2 than the later transition metals (Ni and Cu). Also, our modified Brønsted−Evans−Polanyi (BEP) relationship for reaction energies and total reaction barriers reveals that reactions of earlier transition metals are more exergonic and have lower oxygen dissociation barriers than those of later transition metals. In addition, it was found that for these transition metal oxides the oxygen vacancy formation energies increase with the depth. The oxide in the higher oxidation state of transition metal has lower vacancy formation energy, which can facilitate forming the defective nanostructures. The fundamental understanding of these metal

  18. Identification of redox-sensitive cysteines in the arabidopsis proteome using OxiTRAQ, a quantitative redox proteomics method

    KAUST Repository

    Liu, Pei

    2014-01-28

    Cellular redox status plays a key role in mediating various physiological and developmental processes often through modulating activities of redox-sensitive proteins. Various stresses trigger over-production of reactive oxygen/nitrogen species which lead to oxidative modifications of redox-sensitive proteins. Identification and characterization of redox-sensitive proteins are important steps toward understanding molecular mechanisms of stress responses. Here, we report a high-throughput quantitative proteomic approach termed OxiTRAQ for identifying proteins whose thiols undergo reversible oxidative modifications in Arabidopsis cells subjected to oxidative stress. In this approach, a biotinylated thiol-reactive reagent is used for differential labeling of reduced and oxidized thiols. The biotin-tagged peptides are affinity purified, labeled with iTRAQ reagents, and analyzed using a paralleled HCD-CID fragmentation mode in an LTQ-Orbitrap. With this approach, we identified 195 cysteine-containing peptides from 179 proteins whose thiols underwent oxidative modifications in Arabidopsis cells following the treatment with hydrogen peroxide. A majority of those redox-sensitive proteins, including several transcription factors, were not identified by previous redox proteomics studies. This approach allows identification of the specific redox-regulated cysteine residues, and offers an effective tool for elucidation of redox proteomes. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Molecular analysis of Ku redox regulation

    Directory of Open Access Journals (Sweden)

    Shatilla Andrea

    2009-08-01

    Full Text Available Abstract Background DNA double-strand breaks (DSBs can occur in response to ionizing radiation (IR, radiomimetic agents and from endogenous DNA-damaging reactive oxygen metabolites. Unrepaired or improperly repaired DSBs are potentially the most lethal form of DNA damage and can result in chromosomal translocations and contribute to the development of cancer. The principal mechanism for the repair of DSBs in humans is non-homologous end-joining (NHEJ. Ku is a key member of the NHEJ pathway and plays an important role in the recognition step when it binds to free DNA termini. Ku then stimulates the assembly and activation of other NHEJ components. DNA binding of Ku is regulated by redox conditions and evidence from our laboratory has demonstrated that Ku undergoes structural changes when oxidized that results in a reduction in DNA binding activity. The C-terminal domain and cysteine 493 of Ku80 were investigated for their contribution to redox regulation of Ku. Results We effectively removed the C-terminal domain of Ku80 generating a truncation mutant and co-expressed this variant with wild type Ku70 in an insect cell system to create a Ku70/80ΔC heterodimer. We also generated two single amino acid variants of Cys493, replacing this amino acid with either an alanine (C493A or a serine (C493S, and over-expressed the variant proteins in SF9 insect cells in complex with wild type Ku70. Neither the truncation nor the amino acid substitutions alters protein expression or stability as determined by SDS-PAGE and Western blot analysis. We show that the C493 mutations do not alter the ability of Ku to bind duplex DNA in vitro under reduced conditions while truncation of the Ku80 C-terminus slightly reduced DNA binding affinity. Diamide oxidation of cysteines was shown to inhibit DNA binding similarly for both the wild-type and all variant proteins. Interestingly, differential DNA binding activity following re-reduction was observed for the Ku70/80

  20. Exercise and Glycemic Control: Focus on Redox Homeostasis and Redox-Sensitive Protein Signaling

    Science.gov (United States)

    Parker, Lewan; Shaw, Christopher S.; Stepto, Nigel K.; Levinger, Itamar

    2017-01-01

    Physical inactivity, excess energy consumption, and obesity are associated with elevated systemic oxidative stress and the sustained activation of redox-sensitive stress-activated protein kinase (SAPK) and mitogen-activated protein kinase signaling pathways. Sustained SAPK activation leads to aberrant insulin signaling, impaired glycemic control, and the development and progression of cardiometabolic disease. Paradoxically, acute exercise transiently increases oxidative stress and SAPK signaling, yet postexercise glycemic control and skeletal muscle function are enhanced. Furthermore, regular exercise leads to the upregulation of antioxidant defense, which likely assists in the mitigation of chronic oxidative stress-associated disease. In this review, we explore the complex spatiotemporal interplay between exercise, oxidative stress, and glycemic control, and highlight exercise-induced reactive oxygen species and redox-sensitive protein signaling as important regulators of glucose homeostasis. PMID:28529499

  1. High energy density redox flow device

    Science.gov (United States)

    Chiang, Yet-Ming; Carter, William Craig; Duduta, Mihai; Limthongkul, Pimpa

    2014-05-13

    Redox flow devices are described including a positive electrode current collector, a negative electrode current collector, and an ion-permeable membrane separating said positive and negative current collectors, positioned and arranged to define a positive electroactive zone and a negative electroactive zone; wherein at least one of said positive and negative electroactive zone comprises a flowable semi-solid composition comprising ion storage compound particles capable of taking up or releasing said ions during operation of the cell, and wherein the ion storage compound particles have a polydisperse size distribution in which the finest particles present in at least 5 vol % of the total volume, is at least a factor of 5 smaller than the largest particles present in at least 5 vol % of the total volume.

  2. Inflammatory and redox reactions in colorectal carcinogenesis.

    Science.gov (United States)

    Guina, Tina; Biasi, Fiorella; Calfapietra, Simone; Nano, Mario; Poli, Giuseppe

    2015-03-01

    It has been established that there is a relationship between chronic inflammation and cancer development. The constant colonic inflammation typical of inflammatory bowel diseases is now considered a risk factor for colorectal carcinoma (CRC) development. The inflammatory network of signaling molecules is also required during the late phases of carcinogenesis, to enable cancer cells to survive and to metastasize. Oxidative reactions are an integral part of the inflammatory response, and are generally associated with CRC development. However, when the malignant phenotype is acquired, increased oxidative status induces antioxidant defenses in cancer cells, favoring their aggressiveness. This contradictory behavior of cancer cells toward redox status is of great significance for potential anticancer therapies. This paper summarizes the essential background information relating to the molecules involved in regulating oxidative stress and inflammation during carcinogenesis. Understanding more of their function in CRC stages might provide the foundation for future developments in CRC treatment. © 2015 New York Academy of Sciences.

  3. Redox signaling during hypoxia in mammalian cells

    Directory of Open Access Journals (Sweden)

    Kimberly A. Smith

    2017-10-01

    Full Text Available Hypoxia triggers a wide range of protective responses in mammalian cells, which are mediated through transcriptional and post-translational mechanisms. Redox signaling in cells by reactive oxygen species (ROS such as hydrogen peroxide (H2O2 occurs through the reversible oxidation of cysteine thiol groups, resulting in structural modifications that can change protein function profoundly. Mitochondria are an important source of ROS generation, and studies reveal that superoxide generation by the electron transport chain increases during hypoxia. Other sources of ROS, such as the NAD(PH oxidases, may also generate oxidant signals in hypoxia. This review considers the growing body of work indicating that increased ROS signals during hypoxia are responsible for regulating the activation of protective mechanisms in diverse cell types.

  4. Hybrid anodes for redox flow batteries

    Science.gov (United States)

    Wang, Wei; Xiao, Jie; Wei, Xiaoliang; Liu, Jun; Sprenkle, Vincent L.

    2015-12-15

    RFBs having solid hybrid electrodes can address at least the problems of active material consumption, electrode passivation, and metal electrode dendrite growth that can be characteristic of traditional batteries, especially those operating at high current densities. The RFBs each have a first half cell containing a first redox couple dissolved in a solution or contained in a suspension. The solution or suspension can flow from a reservoir to the first half cell. A second half cell contains the solid hybrid electrode, which has a first electrode connected to a second electrode, thereby resulting in an equipotential between the first and second electrodes. The first and second half cells are separated by a separator or membrane.

  5. Iron-sulfide redox flow batteries

    Science.gov (United States)

    Xia, Guan-Guang; Yang, Zhenguo; Li, Liyu; Kim, Soowhan; Liu, Jun; Graff, Gordon L

    2013-12-17

    Iron-sulfide redox flow battery (RFB) systems can be advantageous for energy storage, particularly when the electrolytes have pH values greater than 6. Such systems can exhibit excellent energy conversion efficiency and stability and can utilize low-cost materials that are relatively safer and more environmentally friendly. One example of an iron-sulfide RFB is characterized by a positive electrolyte that comprises Fe(III) and/or Fe(II) in a positive electrolyte supporting solution, a negative electrolyte that comprises S.sup.2- and/or S in a negative electrolyte supporting solution, and a membrane, or a separator, that separates the positive electrolyte and electrode from the negative electrolyte and electrode.

  6. Chemistry and Redox Biology of Mycothiol.

    Science.gov (United States)

    Reyes, Aníbal M; Pedre, Brandán; De Armas, María Inés; Tossounian, Maria-Armineh; Radi, Rafael; Messens, Joris; Trujillo, Madia

    2018-02-20

    Mycothiol (MSH, AcCys-GlcN-Ins) is the main low-molecular weight (LMW) thiol of most Actinomycetes, including the human pathogen Mycobacterium tuberculosis that affects millions of people worldwide. Strains with decreased MSH content show increased susceptibilities to hydroperoxides and electrophilic compounds. In M. tuberculosis, MSH modulates the response to several antituberculosis drugs. Enzymatic routes involving MSH could provide clues for specific drug design. Recent Advances: Physicochemical data argue against a rapid, nonenzymatic reaction of MSH with oxidants, disulfides, or electrophiles. Moreover, exposure of the bacteria to high concentrations of two-electron oxidants resulted in protein mycothiolation. The recently described glutaredoxin-like protein mycoredoxin-1 (Mrx-1) provides a route for catalytic reduction of mycothiolated proteins, protecting critical cysteines from irreversible oxidation. The description of MSH/Mrx-1-dependent activities of peroxidases helped to explain the higher susceptibility to oxidants observed in Actinomycetes lacking MSH. Moreover, the first mycothiol-S-transferase, member of the DinB superfamily of proteins, was described. In Corynebacterium, both the MSH/Mrx-1 and the thioredoxin pathways reduce methionine sulfoxide reductase A. A novel tool for in vivo imaging of the MSH/mycothiol disulfide (MSSM) status allows following changes in the mycothiol redox state during macrophage infection and its relationship with antibiotic sensitivity. Redundancy of MSH with other LMW thiols is starting to be unraveled and could help to rationalize the differences in the reported importance of MSH synthesis observed in vitro versus in animal infection models. Future work should be directed to establish the structural bases of the specificity of MSH-dependent enzymes, thus facilitating drug developments. Antioxid. Redox Signal. 28, 487-504.

  7. Redox reactivity and coordination chemistry of uranium

    International Nuclear Information System (INIS)

    Nocton, G.

    2009-09-01

    The study and the understanding of actinides chemistry have important implications in the nuclear field both for the development of new actinides materials and the retreatment of the nuclear wastes. One of the major issues in that chemistry is that the actinides elements are known to undergo redox reaction and to form assemblies of different size and different topologies. In that context uranium can be a good model of the heavier radioelement because it is much less radioactive. So, this work concerns the synthesis and the study of the spectroscopy and the magnetic properties of several uranium based polymetallic assemblies synthesized by taking advantage of the redox properties and the coordination chemistry of uranium. The hydrolysis reactivity of trivalent uranium has been studied in absence of sterically hindered ligands and led to the synthesis of oxo/hydroxo uranium assemblies with different sizes by changing the starting complex or the reaction conditions. By following the same strategy, the controlled oxidation of trivalent uranium complexes led to an original azido/nitrido uranium complex. The coordination chemistry of the pentavalent uranyl polymer {[UO 2 py 5 ][KI 2 py 3 ]} n has also been studied with different ligand and in different conditions and led to several cation-cation complexes for which the stability is sufficient for studying there dismutation by proton NMR. By changing the ancillary ligands stable monomeric complexes of pentavalent uranyl complexes were also obtained. The magnetic properties of all the complexes, monomers and polymetallic complexes were studied and an antiferromagnetic coupling was observed for the cation-cation pentavalent uranyl dimer [UO 2 (dbm) 2 (K 18 C 6 )] 2 . (author)

  8. Polyoxometalate active charge-transfer material for mediated redox flow battery

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, Travis Mark; Hudak, Nicholas; Staiger, Chad; Pratt, Harry

    2017-01-17

    Redox flow batteries including a half-cell electrode chamber coupled to a current collecting electrode are disclosed herein. In a general embodiment, a separator is coupled to the half-cell electrode chamber. The half-cell electrode chamber comprises a first redox-active mediator and a second redox-active mediator. The first redox-active mediator and the second redox-active mediator are circulated through the half-cell electrode chamber into an external container. The container includes an active charge-transfer material. The active charge-transfer material has a redox potential between a redox potential of the first redox-active mediator and a redox potential of the second redox-active mediator. The active charge-transfer material is a polyoxometalate or derivative thereof. The redox flow battery may be particularly useful in energy storage solutions for renewable energy sources and for providing sustained power to an electrical grid.

  9. Arteriovenous oscillations of the redox potential: Is the redox state influencing blood flow?

    Science.gov (United States)

    Poznanski, Jaroslaw; Szczesny, Pawel; Pawlinski, Bartosz; Mazurek, Tomasz; Zielenkiewicz, Piotr; Gajewski, Zdzislaw; Paczek, Leszek

    2017-09-01

    Studies on the regulation of human blood flow revealed several modes of oscillations with frequencies ranging from 0.005 to 1 Hz. Several mechanisms were proposed that might influence these oscillations, such as the activity of vascular endothelium, the neurogenic activity of vessel wall, the intrinsic activity of vascular smooth muscle, respiration, and heartbeat. These studies relied typically on non-invasive techniques, for example, laser Doppler flowmetry. Oscillations of biochemical markers were rarely coupled to blood flow. The redox potential difference between the artery and the vein was measured by platinum electrodes placed in the parallel homonymous femoral artery and the femoral vein of ventilated anesthetized pigs. Continuous measurement at 5 Hz sampling rate using a digital nanovoltmeter revealed fluctuating signals with three basic modes of oscillations: ∼ 1, ∼ 0.1 and ∼ 0.01 Hz. These signals clearly overlap with reported modes of oscillations in blood flow, suggesting coupling of the redox potential and blood flow. The amplitude of the oscillations associated with heart action was significantly smaller than for the other two modes, despite the fact that heart action has the greatest influence on blood flow. This finding suggests that redox potential in blood might be not a derivative but either a mediator or an effector of the blood flow control system.

  10. A multi-electron redox mediator for redox-targeting lithium-sulfur flow batteries

    Science.gov (United States)

    Li, Guochun; Yang, Liuqing; Jiang, Xi; Zhang, Tianran; Lin, Haibin; Yao, Qiaofeng; Lee, Jim Yang

    2018-02-01

    The lithium-sulfur flow battery (LSFB) is a new addition to the rechargeable lithium flow batteries (LFBs) where sulfur or a sulfur compound is used as the cathode material against the lithium anode. We report here our evaluation of an organic sulfide - dimethyl trisulfide (DMTS), as 1) a catholyte of a LFB and 2) a multi-electron redox mediator for discharging and charging a solid sulfur cathode without any conductive additives. The latter configuration is also known as the redox-targeting lithium-sulfur flow battery (RTLSFB). The LFB provides an initial discharge capacity of 131.5 mAh g-1DMTS (1.66 A h L-1), which decreases to 59 mAh g-1DMTS (0.75 A h L-1) after 40 cycles. The RTLSFB delivers a significantly higher application performance - initial discharge capacity of 1225.3 mAh g-1sulfur (3.83 A h L-1), for which 1030.9 mAh g-1sulfur (3.23 A h L-1) is still available after 40 cycles. The significant increase in the discharge and charge duration of the LFB after sulfur addition indicates that DMTS is better used as a redox mediator in a RTLSFB than as a catholyte in a LFB.

  11. Kynurenine pathway metabolites and enzymes involved in redox reactions.

    Science.gov (United States)

    González Esquivel, D; Ramírez-Ortega, D; Pineda, B; Castro, N; Ríos, C; Pérez de la Cruz, V

    2017-01-01

    Oxido-reduction reactions are a fundamental part of the life due to support many vital biological processes as cellular respiration and glucose oxidation. In the redox reactions, one substance transfers one or more electrons to another substance. An important electron carrier is the coenzyme NAD + , which is involved in many metabolic pathways. De novo biosynthesis of NAD + is through the kynurenine pathway, the major route of tryptophan catabolism, which is sensitive to redox environment and produces metabolites with redox capacity, able to alter biological functions that are controlled by redox-responsive signaling pathways. Kynurenine pathway metabolites have been implicated in the physiology process and in the physiopathology of many diseases; processes that also share others factors as dysregulation of calcium homeostasis, mitochondrial dysfunction, oxidative stress, inflammation and cell death, which impact the redox environment. This review examines in detail the available evidence in which kynurenine pathway metabolites participate in redox reactions and their effect on cellular redox homeostasis, since the knowledge of the main factors and mechanisms that lead to cell death in many neurodegenative disorders and other pathologies, such as mitochondrial dysfunction, oxidative stress and kynurenines imbalance, will allow to develop therapies using them as targets. This article is part of the Special Issue entitled 'The Kynurenine Pathway in Health and Disease'. Copyright © 2016 Elsevier Ltd. All rights reserved.

  12. Managing the cellular redox hub in photosynthetic organisms.

    Science.gov (United States)

    Foyer, Christine H; Noctor, Graham

    2012-02-01

    Light-driven redox chemistry is a powerful source of redox signals that has a decisive input into transcriptional control within the cell nucleus. Like photosynthetic electron transport pathways, the respiratory electron transport chain exerts a profound control over gene function, in order to balance energy (reductant and ATP) supply with demand, while preventing excessive over-reduction or over-oxidation that would be adversely affect metabolism. Photosynthetic and respiratory redox chemistries are not merely housekeeping processes but they exert a controlling influence over every aspect of plant biology, participating in the control of gene transcription and translation, post-translational modifications and the regulation of assimilatory reactions, assimilate partitioning and export. The number of processes influenced by redox controls and signals continues to increase as do the components that are recognized participants in the associated signalling pathways. A step change in our understanding of the overall importance of the cellular redox hub to plant cells has occurred in recent years as the complexity of the management of the cellular redox hub in relation to metabolic triggers and environmental cues has been elucidated. This special issue describes aspects of redox regulation and signalling at the cutting edge of current research in this dynamic and rapidly expanding field. © 2011 Blackwell Publishing Ltd.

  13. Unusual thiol-based redox metabolism of parasitic flukes.

    Science.gov (United States)

    Tripathi, Timir; Suttiprapa, Sutas; Sripa, Banchob

    2017-08-01

    Parasitic flukes are exposed to free radicals and, to a greater extent, reactive oxygen species (ROS) during their life cycle. Despite being relentlessly exposed to ROS released by activated immune cells, these parasites can survive for many years in the host. Cellular thiol-based redox metabolism plays a crucial role in parasite survival within their hosts. Evidence shows that oxidative stress and redox homeostasis maintenance are important clinical and pathobiochemical as well as effective therapeutic principles in various diseases. The characterization of redox and antioxidant enzymes is likely to yield good target candidates for novel drugs and vaccines. The absence of active catalase in fluke parasites offers great potential for the development of chemotherapeutic agents that act by perturbing the redox equilibrium of the cell. One of the redox-sensitive enzymes, thioredoxin glutathione reductase (TGR), has been accepted as a drug target against blood fluke infections, and related clinical trials are in progress. TGR is the sole enzyme responsible for Trx and GSH reduction in parasitic flukes. The availability of helminth genomes has accelerated the research on redox metabolism of flukes; however, significant achievements have yet to be attained. The present review summarizes current knowledge on the redox and antioxidant system of the parasitic flukes. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  14. Novel organic redox catalyst for the electroreduction of oxygen to hydrogen peroxide

    International Nuclear Information System (INIS)

    Wang, Andrew; Bonakdarpour, Arman; Wilkinson, David P.; Gyenge, Előd

    2012-01-01

    The organic redox catalysis of O 2 electroreduction to H 2 O 2 in acidic media has been investigated using several quinone and riboflavin catalysts supported on Vulcan XC72 carbon. The synthesis of a novel riboflavinyl–anthraquinone 2-carboxylate ester (RF–AQ) is reported. The activity and selectivity of organic redox catalysts (riboflavin, anthraquinone derivatives and riboflavinyl–anthraquinone 2-carboxylate ester) for the electrosynthesis of H 2 O 2 were investigated by the rotating ring-disk electrode (RRDE) method and potentiostatic electrolysis. Electrodes with 10 wt% RF–AQ loading on Vulcan XC-72 showed excellent electrocatalytic activity toward the two-electron oxygen reduction coupled with very good catalyst layer stability. The reaction mechanism for the organic redox catalysis by RF–AQ is discussed. Electroreduction of O 2 dissolved in 0.5 M H 2 SO 4 under potentiostatic conditions (0.1 V vs. RHE) at 21 °C using the composite RF–AQ/Vulcan XC72 catalyst (total loading 2.5 mg cm −2 ) deposited on unteflonated Toray ® carbon paper, generated H 2 O 2 with an initial rate of 21 μmol h −1 cm geo −2 and a stable current efficiency of 70%.

  15. An Excel Workbook for Identifying Redox Processes in Ground Water

    Science.gov (United States)

    Jurgens, Bryant C.; McMahon, Peter B.; Chapelle, Francis H.; Eberts, Sandra M.

    2009-01-01

    The reduction/oxidation (redox) condition of ground water affects the concentration, transport, and fate of many anthropogenic and natural contaminants. The redox state of a ground-water sample is defined by the dominant type of reduction/oxidation reaction, or redox process, occurring in the sample, as inferred from water-quality data. However, because of the difficulty in defining and applying a systematic redox framework to samples from diverse hydrogeologic settings, many regional water-quality investigations do not attempt to determine the predominant redox process in ground water. Recently, McMahon and Chapelle (2008) devised a redox framework that was applied to a large number of samples from 15 principal aquifer systems in the United States to examine the effect of redox processes on water quality. This framework was expanded by Chapelle and others (in press) to use measured sulfide data to differentiate between iron(III)- and sulfate-reducing conditions. These investigations showed that a systematic approach to characterize redox conditions in ground water could be applied to datasets from diverse hydrogeologic settings using water-quality data routinely collected in regional water-quality investigations. This report describes the Microsoft Excel workbook, RedoxAssignment_McMahon&Chapelle.xls, that assigns the predominant redox process to samples using the framework created by McMahon and Chapelle (2008) and expanded by Chapelle and others (in press). Assignment of redox conditions is based on concentrations of dissolved oxygen (O2), nitrate (NO3-), manganese (Mn2+), iron (Fe2+), sulfate (SO42-), and sulfide (sum of dihydrogen sulfide [aqueous H2S], hydrogen sulfide [HS-], and sulfide [S2-]). The logical arguments for assigning the predominant redox process to each sample are performed by a program written in Microsoft Visual Basic for Applications (VBA). The program is called from buttons on the main worksheet. The number of samples that can be analyzed

  16. Redox chemistry of americium in nitric acid media

    Energy Technology Data Exchange (ETDEWEB)

    Picart, S.; Jobelin, I.; Armengol, G.; Adnet, JM

    2004-07-01

    The redox properties of the actinides are very important parameters for speciation studies and spent nuclear fuel reprocessing based on liquid-liquid extraction of actinides at different oxidation states (as in the Purex or Sesame process). They are also very useful for developing analytical tools including coulometry and redox titration. This study addressed the americium(IV)/americium(III) and americium(VI)/americium(V) redox couples, focusing on exhaustive acquisition of the thermodynamic and kinetic parameters of americium oxidation at an electrode in a complexing nitric acid medium. (authors)

  17. Redox chemistry of americium in nitric acid media

    International Nuclear Information System (INIS)

    Picart, S.; Jobelin, I.; Armengol, G.; Adnet, JM.

    2004-01-01

    The redox properties of the actinides are very important parameters for speciation studies and spent nuclear fuel reprocessing based on liquid-liquid extraction of actinides at different oxidation states (as in the Purex or Sesame process). They are also very useful for developing analytical tools including coulometry and redox titration. This study addressed the americium(IV)/americium(III) and americium(VI)/americium(V) redox couples, focusing on exhaustive acquisition of the thermodynamic and kinetic parameters of americium oxidation at an electrode in a complexing nitric acid medium. (authors)

  18. Study to establish cost projections for production of Redox chemicals

    Science.gov (United States)

    Walther, J. F.; Greco, C. C.; Rusinko, R. N.; Wadsworth, A. L., III

    1982-01-01

    A cost study of four proposed manufacturing processes for redox chemicals for the NASA REDOX Energy Storage System yielded favorable selling prices in the range $0.99 to $1.91/kg of chromic chloride, anhydrous basis, including ferrous chloride. The prices corresponded to specific energy storage costs from under $9 to $17/kWh. A refined and expanded cost analysis of the most favored process yielded a price estimate corresponding to a storage cost of $11/kWh. The findings supported the potential economic viability of the NASA REDOX system.

  19. The Redox Flow System for solar photovoltaic energy storage

    Science.gov (United States)

    Odonnell, P.; Gahn, R. F.; Pfeiffer, W.

    1976-01-01

    The interfacing of a Solar Photovoltaic System and a Redox Flow System for storage was workable. The Redox Flow System, which utilizes the oxidation-reduction capability of two redox couples, in this case iron and titanium, for its storage capacity, gave a relatively constant output regardless of solar activity so that a load could be run continually day and night utilizing the sun's energy. One portion of the system was connected to a bank of solar cells to electrochemically charge the solutions, while a separate part of the system was used to electrochemically discharge the stored energy.

  20. Reaction-based small-molecule fluorescent probes for dynamic detection of ROS and transient redox changes in living cells and small animals.

    Science.gov (United States)

    Lü, Rui

    2017-09-01

    Dynamic detection of transient redox changes in living cells and animals has broad implications for human health and disease diagnosis, because intracellular redox homeostasis regulated by reactive oxygen species (ROS) plays important role in cell functions, normal physiological functions and some serious human diseases (e.g., cancer, Alzheimer's disease, diabetes, etc.) usually have close relationship with the intracellular redox status. Small-molecule ROS-responsive fluorescent probes can act as powerful tools for dynamic detection of ROS and redox changes in living cells and animals through fluorescence imaging techniques; and great advances have been achieved recently in the design and synthesis of small-molecule ROS-responsive fluorescent probes. This article highlights up-to-date achievements in designing and using the reaction-based small-molecule fluorescent probes (with high sensitivity and selectivity to ROS and redox cycles) in the dynamic detection of ROS and transient redox changes in living cells and animals through fluorescence imaging. Copyright © 2017. Published by Elsevier Ltd.

  1. Glutathione redox potential in the mitochondrial intermembrane space is linked to the cytosol and impacts the Mia40 redox state

    Science.gov (United States)

    Kojer, Kerstin; Bien, Melanie; Gangel, Heike; Morgan, Bruce; Dick, Tobias P; Riemer, Jan

    2012-01-01

    Glutathione is an important mediator and regulator of cellular redox processes. Detailed knowledge of local glutathione redox potential (EGSH) dynamics is critical to understand the network of redox processes and their influence on cellular function. Using dynamic oxidant recovery assays together with EGSH-specific fluorescent reporters, we investigate the glutathione pools of the cytosol, mitochondrial matrix and intermembrane space (IMS). We demonstrate that the glutathione pools of IMS and cytosol are dynamically interconnected via porins. In contrast, no appreciable communication was observed between the glutathione pools of the IMS and matrix. By modulating redox pathways in the cytosol and IMS, we find that the cytosolic glutathione reductase system is the major determinant of EGSH in the IMS, thus explaining a steady-state EGSH in the IMS which is similar to the cytosol. Moreover, we show that the local EGSH contributes to the partially reduced redox state of the IMS oxidoreductase Mia40 in vivo. Taken together, we provide a comprehensive mechanistic picture of the IMS redox milieu and define the redox influences on Mia40 in living cells. PMID:22705944

  2. Influence of iron redox transformations on plutonium sorption to sediments

    Energy Technology Data Exchange (ETDEWEB)

    Hixon, A.E.; Powell, B.A. [Environmental Engineering and Earth Sciences, Clemson Univ., Clemson, SC (United States); Hu, Y.J.; Nitsche, H. [Dept. of Chemistry, Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab., Berkeley, CA (United States); Kaplan, D.I. [Savannah River National Lab., Aiken, SC (United States); Kukkadapu, R.K.; Qafoku, O. [Pacific Northwest National Lab., Richland, WA (United States)

    2010-07-01

    Plutonium subsurface mobility is primarily controlled by its oxidation state, which in turn is loosely coupled to the oxidation state of iron in the system. Experiments were conducted to examine the effect of sediment iron mineral composition and oxidation state on plutonium sorption and reduction. A pH 6.3 vadose zone sediment containing iron oxides and iron-containing phyllosilicates was treated with various complexants (ammonium oxalate) and reductants (hydroxylamine hydrochloride and dithionite-citrate-bicarbonate (DCB)) to selectively leach and/or reduce iron oxide and phyllosilicate/clay Fe(III). {sup 57}Fe-Moessbauer spectroscopy was used to identify initial iron mineral composition of the sediment and monitor dissolution and reduction of iron oxides and reduction of phyllosilicate Fe(III). {sup 57}Fe-Moessbauer spectroscopy showed that the Fe-mineral composition of the untreated sediment is: 25-30% hematite, 60-65% small-particle/Al-goethite, and < 10% Fe(III) in phyllosilicate; there was no detectable Fe(II). Upon reduction with a strong chemical reductant (dithionite-citrate-bicarbonate buffer), much of the hematite and goethite was removed. Partial reduction of phyllosilicate Fe(III) was evident in the sediments subjected to DCB treatment. Sorption of Pu(V) was monitored over one week for the untreated and each of five treated sediment fractions. Plutonium oxidation state speciation in the aqueous and solid phases was monitored using solvent extraction, coprecipitation, and XANES. The rate of sorption appears to correlate with the fraction of Fe(II) in the sediment (untreated or treated). Pu(V) was the only oxidation state measured in the aqueous phase, irrespective of treatment, whereas Pu(IV) and much smaller amounts of Pu(V) and Pu(VI) were measured in the solid phase. Surface-mediated reduction of Pu(V) to Pu(IV) occurred in treated and untreated sediment samples; Pu(V) remained on untreated sediment surface for two days before reducing to Pu

  3. Generalized kinetic model of reduction of molecular oxidant by metal containing redox

    International Nuclear Information System (INIS)

    Kravchenko, T.A.

    1986-01-01

    Present work is devoted to kinetics of reduction of molecular oxidant by metal containing redox. Constructed generalized kinetic model of redox process in the system solid redox - reagent solution allows to perform the general theoretical approach to research and to obtain new results on kinetics and mechanism of interaction of redox with oxidants.

  4. Bioelectrochemical probing of intracellular redox processes in living yeast cells—application of redox polymer wiring in a microfluidic environment

    DEFF Research Database (Denmark)

    Heiskanen, Arto; Coman, Vasile; Kostesha, Natalie

    2013-01-01

    utilizing a new double mediator system to map redox metabolism and screen for genetic modifications in Saccharomyces cerevisiae cells. The function of this new double mediator system based on menadione and osmium redox polymer (PVI-Os) is demonstrated. “Wiring” of S. cerevisiae cells using PVI-Os shows...... that microfluidic bioelectrochemical assays employing the menadione–PVI-Os double mediator system provides an effective means to conduct automated microbial assays. FigureMicrofluidic platform for bioelectrochemical assays using osmium redox polymer “wired” living yeast cells...

  5. Modelling sulfamethoxazole degradation under different redox conditions

    Science.gov (United States)

    Sanchez-Vila, X.; Rodriguez-Escales, P.

    2015-12-01

    Sulfamethoxazole (SMX) is a low adsorptive, polar, sulfonamide antibiotic, widely present in aquatic environments. Degradation of SMX in subsurface porous media is spatially and temporally variable, depending on various environmental factors such as in situ redox potential, availability of nutrients, local soil characteristics, and temperature. It has been reported that SMX is better degraded under anoxic conditions and by co-metabolism processes. In this work, we first develop a conceptual model of degradation of SMX under different redox conditions (denitrification and iron reducing conditions), and second, we construct a mathematical model that allows reproducing different experiments of SMX degradation reported in the literature. The conceptual model focuses on the molecular behavior and contemplates the formation of different metabolites. The model was validated using the experimental data from Barbieri et al. (2012) and Mohatt et al. (2011). It adequately reproduces the reversible degradation of SMX under the presence of nitrite as an intermediate product of denitrification. In those experiments degradation was mediated by the transient formation of a diazonium cation, which was considered responsible of the substitution of the amine radical by a nitro radical, forming the 4-nitro-SMX. The formation of this metabolite is a reversible process, so that once the concentration of nitrite was back to zero due to further advancement of denitrification, the concentration of SMX was fully recovered. The forward reaction, formation of 4-nitro SMX, was modeled considering a kinetic of second order, whereas the backward reaction, dissociation of 4-nitro-SMX back to the original compound, could be modeled with a first order degradation reaction. Regarding the iron conditions, SMX was degraded due to the oxidation of iron (Fe2+), which was previously oxidized from goethite due to the degradation of a pool of labile organic carbon. As the oxidation of iron occurred on the

  6. Redox phenomena controlling systems - a 7. framework programme collaborative project (2008-2012)

    International Nuclear Information System (INIS)

    2013-01-01

    The objective of this EURATOM collaborative project is to understand Redox phenomena controlling the long-term release/retention of radionuclides (ReCosy programme) in nuclear waste disposal and to provide tools to apply the results to safety assessment. The project has been organized into 6 task forces: 1) implications of Redox for safety, 2) development of Redox determination methods, 3) Redox response of defined and near-natural systems, 4) Redox reactions of radionuclides, 5) Redox processes in radionuclide transport, and 6) Redox reactions affecting the spent fuel source-term

  7. Redox Stable Anodes for Solid Oxide Fuel Cells

    Directory of Open Access Journals (Sweden)

    Guoliang eXiao

    2014-06-01

    Full Text Available Solid oxide fuel cells (SOFCs can convert chemical energy from the fuel directly to electrical energy with high efficiency and fuel flexibility. Ni-based cermets have been the most widely adopted anode for SOFCs. However, the conventional Ni-based anode has low tolerance to sulfur-contamination, is vulnerable to deactivation by carbon build-up (coking from direct oxidation of hydrocarbon fuels, and suffers volume instability upon redox cycling. Among these limitations, the redox instability of the anode is particularly important and has been intensively studied since the SOFC anode may experience redox cycling during fuel cell operations even with the ideal pure hydrogen as the fuel. This review aims to highlight recent progresses on improving redox stability of the conventional Ni-based anode through microstructure optimization and exploration of alternative ceramic-based anode materials.

  8. Redox mechanisms and superconductivity in layered copper oxides

    International Nuclear Information System (INIS)

    Raveau, B.; Michel, C.; Hervieu, M.; Provost, J.

    1992-01-01

    Redox reactions in high T c superconductors cuprates are complex and play an important role in superconductivity: oxygen non-stoichiometry is influencing the critical temperature, and rock salt layers interact with copper layers. 25 refs., 7 figs

  9. Redox shuttles for overcharge protection of lithium batteries

    Science.gov (United States)

    Amine, Khalil; Chen, Zonghai; Wang, Qingzheng

    2010-12-14

    The present invention is generally related to electrolytes containing novel redox shuttles for overcharge protection of lithium-ion batteries. The redox shuttles are capable of thousands hours of overcharge tolerance and have a redox potential at about 3-5.5 V vs. Li and particularly about 4.4-4.8 V vs. Li. Accordingly, in one aspect the invention provides electrolytes comprising an alkali metal salt; a polar aprotic solvent; and a redox shuttle additive that is an aromatic compound having at least one aromatic ring with four or more electronegative substituents, two or more oxygen atoms bonded to the aromatic ring, and no hydrogen atoms bonded to the aromatic ring; and wherein the electrolyte solution is substantially non-aqueous. Further there are provided electrochemical devices employing the electrolyte and methods of making the electrolyte.

  10. An application of actinide elements for a redox flow battery

    International Nuclear Information System (INIS)

    Shiokawa, Yoshinobu; Yamana, Hajimu; Moriyama, Hirotake

    2000-01-01

    The electrochemical properties of U, Np, Pu and Am were discussed from the viewpoint of cell active materials. From the thermodynamic properties and the kinetics of electrode reactions, it is found that neptunium in the aqueous system can be utilized as an active material of the redox flow battery for the electric power storage. A new neptunium redox battery is proposed in the present article: the galvanic cell is expressed by (-)|Np 3+ , Np 4+ |NpO 2 + , NpO 2 2+ |(+). The neptunium battery is expected to have more excellent charge and discharge performance than the current vanadium battery, whereas the thermodynamic one of the former is comparable to the latter. For the development of a uranium redox battery, the application of the redox reactions in the non-aqueous solvents is essential. (author)

  11. Synthesis, spectroscopic and redox properties of the mononuclear ...

    Indian Academy of Sciences (India)

    Administrator

    magnetic susceptibility measurements, molar conductivity, cyclic voltammetry, mass ... gens donor atoms show DNA binding and antitumor ... trum can be correlated with the strength of the ... ties, the investigation of redox behaviour has a vital.

  12. I. Redox chemistry of bimetallic fulvalene complexes II. Oligocyclopentadienyl complexes

    Energy Technology Data Exchange (ETDEWEB)

    Brown, David Stephen [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Lawrence Berkeley Lab., CA (United States). Chemical Sciences Div.

    1993-11-01

    The electrochemistry of the heterobimetallic complexes (fulvalene)WFe(CO)5 (30) and (fulvalene)WRu(CO)5 (31) has been investigated. Compound 30 is reduced in two one-electron processes, and this behavior was exploited synthetically to prepare a tetranuclear dimer by selective metal reduction. Complex 31 displayed a distinction between the metals upon reoxidation of the dianion, allowing the formation of a dimer by selective metal anion oxidation. The redox behavior of 30 led to an investigation of the use of electrocatalysis to effect metal-specific ligand substitution. It was found that reduction of 30 with a catalytic amount of CpFe(C6Me6) (97) in the presence of excess P(OMe)3 or PMe5 led to the formation of the zwitterions (fulvalene)[W(CO)3-][Fe(CO)PR3+] (107, R = P(OMe)3; 108, R = PMe3). Compound 31 also displayed unique behavior with different reducing agents, as the monosubstituted zwitterion (fulvalene)[W(CO)3-][Ru(CO)2(PMe3+] was obtained when 97 was used while the disubstituted complex (fulvalene) [W(CO)3-] [Ru(CO)(PMe3)2+] was produced when Cp*Fe(C6Me6) was the catalyst. Potential synthetic routes to quatercyclopentadienyl complexes were also explored. Various attempts to couple heterobimetallic fulvalene compounds proved to be unsuccessful. 138 refs.

  13. Accelerated redox reaction between chromate and phenolic pollutants during freezing

    Energy Technology Data Exchange (ETDEWEB)

    Ju, Jinjung; Kim, Jaesung [Department of Environmental Sciences and Biotechnology, Hallym University, Chuncheon, Gangwon-do 24252 (Korea, Republic of); Vetráková, Ľubica [Department of Chemistry and Research Centre for Toxic Compounds in the Environment (RECETOX), Faculty of Science, Masaryk University, Kamenice 5, 625 00 Brno (Czech Republic); Seo, Jiwon [School of Urban and Environmental Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919 (Korea, Republic of); Heger, Dominik [Department of Chemistry and Research Centre for Toxic Compounds in the Environment (RECETOX), Faculty of Science, Masaryk University, Kamenice 5, 625 00 Brno (Czech Republic); Lee, Changha [School of Urban and Environmental Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919 (Korea, Republic of); Yoon, Ho-Il [Korea Polar Research Institute (KOPRI), Incheon 21990 (Korea, Republic of); Kim, Kitae, E-mail: ktkim@kopri.re.kr [Korea Polar Research Institute (KOPRI), Incheon 21990 (Korea, Republic of); Kim, Jungwon, E-mail: jwk@hallym.ac.kr [Department of Environmental Sciences and Biotechnology, Hallym University, Chuncheon, Gangwon-do 24252 (Korea, Republic of)

    2017-05-05

    Highlights: • Redox conversion of 4-CP/Cr(VI) was significantly accelerated during freezing. • Accelerated redox conversion in ice is ascribed to the freeze concentration effect. • 4-CP, Cr(VI), and protons are concentrated in the liquid brine by freezing. • Redox conversions of various phenolic pollutants/Cr(VI) were significant in ice. • Freezing-accelerated redox conversion was observed in real polluted water. - Abstract: The redox reaction between 4-chlorophenol (4-CP) and chromate (Cr(VI)) (i.e., the simultaneous oxidation of 4-CP by Cr(VI) and reduction of Cr(VI) by 4-CP) in ice (i.e., at −20 °C) was compared with the corresponding reaction in water (i.e., at 25 °C). The redox conversion of 4-CP/Cr(VI), which was negligible in water, was significantly accelerated in ice. This accelerated redox conversion of 4-CP/Cr(VI) in ice is ascribed to the freeze concentration effect occurring during freezing, which excludes solutes (i.e., 4-CP and Cr(VI)) and protons from the ice crystals and subsequently concentrates them in the liquid brine. The concentrations of Cr(VI) and protons in the liquid brine were confirmed by measuring the optical image and the UV–vis absorption spectra of cresol red (CR) as a pH indicator of frozen solution. The redox conversion of 4-CP/Cr(VI) was observed in water when the concentrations of 4-CP/protons or Cr(VI)/protons increased by 100/1000-fold. These results corroborate the freeze concentration effect as the reason for the accelerated redox conversion of 4-CP/Cr(VI) in ice. The redox conversion of various phenolic pollutants/Cr(VI) and 4-CP/Cr(VI) in real wastewater was successfully achieved in ice, which verifies the environmental relevance and importance of freezing-accelerated redox conversion of phenolic pollutants/Cr(VI) in cold regions.

  14. Accelerated redox reaction between chromate and phenolic pollutants during freezing

    International Nuclear Information System (INIS)

    Ju, Jinjung; Kim, Jaesung; Vetráková, Ľubica; Seo, Jiwon; Heger, Dominik; Lee, Changha; Yoon, Ho-Il; Kim, Kitae; Kim, Jungwon

    2017-01-01

    Highlights: • Redox conversion of 4-CP/Cr(VI) was significantly accelerated during freezing. • Accelerated redox conversion in ice is ascribed to the freeze concentration effect. • 4-CP, Cr(VI), and protons are concentrated in the liquid brine by freezing. • Redox conversions of various phenolic pollutants/Cr(VI) were significant in ice. • Freezing-accelerated redox conversion was observed in real polluted water. - Abstract: The redox reaction between 4-chlorophenol (4-CP) and chromate (Cr(VI)) (i.e., the simultaneous oxidation of 4-CP by Cr(VI) and reduction of Cr(VI) by 4-CP) in ice (i.e., at −20 °C) was compared with the corresponding reaction in water (i.e., at 25 °C). The redox conversion of 4-CP/Cr(VI), which was negligible in water, was significantly accelerated in ice. This accelerated redox conversion of 4-CP/Cr(VI) in ice is ascribed to the freeze concentration effect occurring during freezing, which excludes solutes (i.e., 4-CP and Cr(VI)) and protons from the ice crystals and subsequently concentrates them in the liquid brine. The concentrations of Cr(VI) and protons in the liquid brine were confirmed by measuring the optical image and the UV–vis absorption spectra of cresol red (CR) as a pH indicator of frozen solution. The redox conversion of 4-CP/Cr(VI) was observed in water when the concentrations of 4-CP/protons or Cr(VI)/protons increased by 100/1000-fold. These results corroborate the freeze concentration effect as the reason for the accelerated redox conversion of 4-CP/Cr(VI) in ice. The redox conversion of various phenolic pollutants/Cr(VI) and 4-CP/Cr(VI) in real wastewater was successfully achieved in ice, which verifies the environmental relevance and importance of freezing-accelerated redox conversion of phenolic pollutants/Cr(VI) in cold regions.

  15. Redox reactions with empirical potentials: Atomistic battery discharge simulations

    OpenAIRE

    Dapp, Wolf B.; Müser, Martin H.

    2013-01-01

    Batteries are pivotal components in overcoming some of today's greatest technological challenges. Yet to date there is no self-consistent atomistic description of a complete battery. We take first steps toward modeling of a battery as a whole microscopically. Our focus lies on phenomena occurring at the electrode-electrolyte interface which are not easily studied with other methods. We use the redox split-charge equilibration (redoxSQE) method that assigns a discrete ionization state to each ...

  16. Complexation Key to a pH Locked Redox Reaction

    Science.gov (United States)

    Rizvi, Masood Ahmad; Dangat, Yuvraj; Shams, Tahir; Khan, Khaliquz Zaman

    2016-01-01

    An unfavorable pH can block a feasible electron transfer for a pH dependent redox reaction. In this experiment, a series of potentiometric titrations demonstrate the sequential loss in feasibility of iron(II) dichromate redox reaction over a pH range of 0-4. The pH at which this reaction failed to occur was termed as a pH locked reaction. The…

  17. Hydrologic influence on redox dynamics in estuarine environments

    Science.gov (United States)

    Michael, H. A.; Kim, K. H.; Guimond, J. A.; Heiss, J.; Ullman, W. J.; Seyfferth, A.

    2017-12-01

    Redox conditions in coastal aquifers control reactions that impact nutrient cycling, contaminant release, and carbon budgets, with implications for water resources and ecosystem health. Hydrologic changes can shift redox boundaries and inputs of reactants, especially in dynamic coastal systems subject to fluctuations on tidal, lunar, and longer timescales. We present two examples of redox shifts in estuarine systems in Delaware, USA: a beach aquifer and a saltmarsh. Beach aquifers are biogeochemical hot spots due to mixing between fresh groundwater and infiltrating seawater. At Cape Henlopen, DE, geochemical measurements identified reactions in the intertidal aquifer that include cycling of carbon, nitrogen, iron, and sulfur. Measurements and modeling illustrate that redox potential as well as the locations of redox reactions shift on tidal to seasonal timescales and in response to changing beach and aquifer properties, impacting overall rates of reactions such as denitrification that reduces N loads to coastal waters. In the St. Jones National Estuarine Research Reserve, tidal fluctuations in channels cause periodic groundwater-surface water exchange, water table movement, and intermittent flooding that varies spatially across the saltmarsh. These changes create shifts in redox potential that are greatest near channels and in the top 20 cm of sediments. The magnitude of redox change depends on hydrologic setting (near channels or in marsh interior), hydrologic conditions (tidal stage, seasonal shifts), as well as prevalence of macropores created by crab burrows that change seasonally with crab activity. These shifts correspond to changes in porewater chemistry that have implications for nutrient cycling and carbon export to the ocean. Understanding hydrologic influence on redox geochemistry is critical for predicting how these systems and their ecosystem services may change in the future in response to anthropogenic and climate change.

  18. A biomimetic redox flow battery based on flavin mononucleotide

    OpenAIRE

    Orita, A; Verde, MG; Sakai, M; Meng, YS

    2016-01-01

    The versatility in design of redox flow batteries makes them apt to efficiently store energy in large-scale applications at low cost. The discovery of inexpensive organic electroactive materials for use in aqueous flow battery electrolytes is highly attractive, but is thus far limited. Here we report on a flow battery using an aqueous electrolyte based on the sodium salt of flavin mononucleotide. Flavins are highly versatile electroactive molecules, which catalyse a multitude of redox reactio...

  19. Fe-phyllosilicate redox cycling organisms from a redox transition zone in Hanford 300 Area sediments

    Directory of Open Access Journals (Sweden)

    Jason eBenzine

    2013-12-01

    Full Text Available Microorganisms capable of reducing or oxidizing structural iron (Fe in Fe-bearing phyllosilicate minerals were enriched and isolated from a subsurface redox transition zone at the Hanford 300 Area site in eastern Washington, USA. Both conventional and in situ i-chip enrichment strategies were employed. One Fe(III-reducing Geobacter (G. bremensis strain R1, Deltaproteobacteria and six Fe(II phyllosilicate-oxidizing isolates from the Alphaproteobacteria (Bradyrhizobium japonicum strains 22, is5, and in8p8, Betaproteobacteria (Cupriavidus necator strain A5-1, Dechloromonas agitata strain is5, and Actinobacteria (Nocardioides sp. strain in31 were recovered. The G. bremensis isolate grew by oxidizing acetate with the oxidized form of NAu-2 smectite as the electron acceptor. The Fe(II-oxidizers grew by oxidation of chemically reduced smectite as the energy source with nitrate as the electron acceptor. The Bradyrhizobium isolates could also carry out aerobic oxidation of biotite. This is the first report of the recovery of a Fe(II-oxidizing Nocardioides, and to date only one other Fe(II-oxidizing Bradyrhizobium is known. The 16S rRNA gene sequences of the isolates were similar to ones found in clone libraries from Hanford 300 sediments and groundwater, suggesting that such organisms may be present and active in situ. Whole genome sequencing of the isolates is underway, the results of which will enable comparative genomic analysis of mechanisms of extracellular phyllosilicate Fe redox metabolism, and facilitate development of techniques to detect the presence and expression of genes associated with microbial phyllosilicate Fe redox cycling in sediments.

  20. Electrode redox reactions with polarizable molecules

    Science.gov (United States)

    Matyushov, Dmitry V.

    2018-04-01

    A theory of redox reactions involving electron transfer between a metal electrode and a polarizable molecule in solution is formulated. Both the existence of molecular polarizability and its ability to change due to electron transfer distinguish this problem from classical theories of interfacial electrochemistry. When the polarizability is different between the oxidized and reduced states, the statistics of thermal fluctuations driving the reactant over the activation barrier becomes non-Gaussian. The problem of electron transfer is formulated as crossing of two non-parabolic free energy surfaces. An analytical solution for these free energy surfaces is provided and the activation barrier of electrode electron transfer is given in terms of two reorganization energies corresponding to the oxidized and reduced states of the molecule in solution. The new non-Gaussian theory is, therefore, based on two theory parameters in contrast to one-parameter Marcus formulation for electrode reactions. The theory, which is consistent with the Nernst equation, predicts asymmetry between the cathodic and anodic branches of the electrode current. They show different slopes at small electrode overpotentials and become curved at larger overpotentials. However, the curvature of the Tafel plot is reduced compared to the Marcus-Hush model and approaches the empirical Butler-Volmer form with different transfer coefficients for the anodic and cathodic currents.

  1. Redox Flow Batteries, Hydrogen and Distributed Storage.

    Science.gov (United States)

    Dennison, C R; Vrubel, Heron; Amstutz, Véronique; Peljo, Pekka; Toghill, Kathryn E; Girault, Hubert H

    2015-01-01

    Social, economic, and political pressures are causing a shift in the global energy mix, with a preference toward renewable energy sources. In order to realize widespread implementation of these resources, large-scale storage of renewable energy is needed. Among the proposed energy storage technologies, redox flow batteries offer many unique advantages. The primary limitation of these systems, however, is their limited energy density which necessitates very large installations. In order to enhance the energy storage capacity of these systems, we have developed a unique dual-circuit architecture which enables two levels of energy storage; first in the conventional electrolyte, and then through the formation of hydrogen. Moreover, we have begun a pilot-scale demonstration project to investigate the scalability and technical readiness of this approach. This combination of conventional energy storage and hydrogen production is well aligned with the current trajectory of modern energy and mobility infrastructure. The combination of these two means of energy storage enables the possibility of an energy economy dominated by renewable resources.

  2. Wine consumption and intestinal redox homeostasis

    Science.gov (United States)

    Biasi, Fiorella; Deiana, Monica; Guina, Tina; Gamba, Paola; Leonarduzzi, Gabriella; Poli, Giuseppe

    2014-01-01

    Regular consumption of moderate doses of wine is an integral part of the Mediterranean diet, which has long been considered to provide remarkable health benefits. Wine׳s beneficial effect has been attributed principally to its non-alcoholic portion, which has antioxidant properties, and contains a wide variety of phenolics, generally called polyphenols. Wine phenolics may prevent or delay the progression of intestinal diseases characterized by oxidative stress and inflammation, especially because they reach higher concentrations in the gut than in other tissues. They act as both free radical scavengers and modulators of specific inflammation-related genes involved in cellular redox signaling. In addition, the importance of wine polyphenols has recently been stressed for their ability to act as prebiotics and antimicrobial agents. Wine components have been proposed as an alternative natural approach to prevent or treat inflammatory bowel diseases. The difficulty remains to distinguish whether these positive properties are due only to polyphenols in wine or also to the alcohol intake, since many studies have reported ethanol to possess various beneficial effects. Our knowledge of the use of wine components in managing human intestinal inflammatory diseases is still quite limited, and further clinical studies may afford more solid evidence of their beneficial effects. PMID:25009781

  3. Redox State of the Neoarchean Earth Environment

    Science.gov (United States)

    Zerkle, Aubrey L.; Claire, Mark W.; Domagal-Goldman, Shawn; Farquhar, James; Poulton, Simon W.

    2011-01-01

    A Titan-like organic haze has been hypothesized for Earth's atmosphere prior to widespread surface oxygenation approx.2.45 billion years ago (Ga). We present a high-resolution record of quadruple sulfur isotopes, carbon isotopes, and Fe speciation from the approx.2.65-2.5 Ga Ghaap Group, South Africa, which suggest a linkage between organic haze and the biogeochemical cycling of carbon, sulfur, oxygen, and iron on the Archean Earth. These sediments provide evidence for oxygen production in microbial mats and localized oxygenation of surface waters. However, this oxygen production occurred under a reduced atmosphere which existed in multiple distinct redox states that correlate to changes in carbon and sulfur isotopes. The data are corroborated by photochemical model results that suggest bi-stable transitions between organic haze and haze-free atmospheric conditions in the Archean. These geochemical correlations also extend to other datasets, indicating that variations in the character of anomalous sulfur fractionation could provide insight into the role of carbon-bearing species in the reducing Archean atmosphere.

  4. Redox environment in stem and differentiated cells: A quantitative approach

    Directory of Open Access Journals (Sweden)

    O.G. Lyublinskaya

    2017-08-01

    Full Text Available Stem cells are believed to maintain a specific intracellular redox status through a combination of enhanced removal capacity and limited production of ROS. In the present study, we challenge this assumption by developing a quantitative approach for the analysis of the pro- and antioxidant ability of human embryonic stem cells in comparison with their differentiated descendants, as well as adult stem and non-stem cells. Our measurements showed that embryonic stem cells are characterized by low ROS level, low rate of extracellular hydrogen peroxide removal and low threshold for peroxide-induced cytotoxicity. However, biochemical normalization of these parameters to cell volume/protein leads to matching of normalized values in stem and differentiated cells and shows that tested in the present study cells (human embryonic stem cells and their fibroblast-like progenies, adult mesenchymal stem cells, lymphocytes, HeLa maintain similar intracellular redox status. Based on these observations, we propose to use ROS concentration averaged over the cell volume instead of ROS level as a measure of intracellular redox balance. We show that attempts to use ROS level for comparative analysis of redox status of morphologically different cells could lead to false conclusions. Methods for the assessment of ROS concentration based on flow cytometry analysis with the use of H2DCFDA dye and HyPer, genetically encoded probe for hydrogen peroxide, are discussed. Keywords: Embryonic stem cells, Differentiated cells, ROS, Redox status, H2DCFDA, HyPer, Flow cytometry, Quantitative redox biology

  5. A study of redox kinetic in silicate melt

    International Nuclear Information System (INIS)

    Magnien, V.

    2005-12-01

    The aim of this thesis is to understand better iron redox reactions and mechanisms in silicate glasses and melts. Particular interest has been paid to the influence of temperature and chemical composition. For this purpose, the influence of alkali element content, iron content and network formers on the kinetics of redox reactions has been determined through XANES and Raman spectroscopy experiments performed either near the glass transition or above the liquidus temperature. As a complement, electrical conductivity and RBS spectroscopy experiments have been made to characterize the diffusivity of the species that transport electrical charges and the reaction morphology, respectively. Temperature and composition variations can induce changes in the dominating redox mechanism. At a given temperature, the parameters that exert the strongest influence on redox mechanisms are the presence or lack of divalent cations and the existing decoupling between the mobility of network former and modifier elements. Near Tg, the diffusion of divalent cations, when present in the melt, controls the kinetics of iron redox reactions along with a flux of electron holes. Composition, through the degree of polymerization and the silicate network structure, influences the kinetics and the nature of the involved cations, but not the mechanisms of the reaction. Without alkaline earth elements, the kinetics of redox reactions are controlled by the diffusion of oxygen species. With increasing temperatures, the diffusivities of all ionic species tend to become similar. The decoupling between ionic fluxes then is reduced so that several mechanisms become kinetically equivalent and can thus coexist. (author)

  6. Electrolyte for stable cycling of high-energy lithium sulfur redox flow batteries

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Jie; Liu, Jun; Pan, Huilin; Henderson, Wesley A.

    2018-04-24

    A device comprising: a lithium sulfur redox flow battery comprising an electrolyte composition comprising: (i) a dissolved Li2Sx electroactive salt, wherein x.gtoreq.4; (ii) a solvent selected from dimethyl sulfoxide, tetrahydrofuran, or a mixture thereof; and (iii) a supporting salt at a concentration of at least 2 M, as measured by moles of supporting salt divided by the volume of the solvent without considering the volume change of the electrolyte after dissolving the supporting salt.

  7. Sunlight mediated synthesis of silver nanoparticles using redox phytoprotein and their application in catalysis and colorimetric mercury sensing.

    Science.gov (United States)

    Ahmed, Khan Behlol Ayaz; Senthilnathan, Rajendran; Megarajan, Sengan; Anbazhagan, Veerappan

    2015-10-01

    Owing to the benign nature, plant extracts mediated green synthesis of metal nanoparticles (NPs) is rapidly expanding. In this study, we demonstrated the successful green synthesis of silver nanoparticles (AgNPs) by utilizing natural sunlight and redox protein complex composed of ferredoxin-NADP(+) reductase (FNR) and ferredoxin (FD). The capping and stabilization of the AgNPs by the redox protein was confirmed by Fourier transform infrared spectroscopy. Light and redox protein is the prerequisite factor for the formation of AgNPs. The obtained result shows that the photo generated free radicals by the redox protein is responsible for the reduction of Ag(+) to Ag(0). Transmission electron microscopy revealed the formation of spherical AgNPs with size ranging from 10 to 15 nm. As-prepared AgNPs exhibit excellent catalytic activity toward the degradation of hazardous organic dyes, such as methylene blue, methyl orange and methyl red. These bio-inspired AgNPs is highly sensitive and selective in sensing hazardous mercury ions in the water at micromolar concentration. In addition, FNR/FD extract stabilized AgNPs showed good antimicrobial activity against gram positive and gram negative bacteria. Copyright © 2015 Elsevier B.V. All rights reserved.

  8. Research Program to Determine Redox Reactions and Their Effects on Speciation and Mobility of Plutonium in DOE Wastes

    Energy Technology Data Exchange (ETDEWEB)

    Choppin, G.R.; Rai, D.

    2000-10-01

    Plutonium in geologic matrices undergoes a variety of complex reactions which complicate its environmental behavior. These complexities in plutonium chemistry whereby a large variety of precipitation, dissolution, adsorption/desorption, and redox reactions control plutonium speciation and concentrations, result in the need for a rather large amount of reliable, fundamental data to predict Pu behavior in geologic media. These data are also needed for evaluation of remediation strategies that involve removing most of the contaminants by selective methods, followed by in situ immobilization of residual contaminants. Two areas were studied during this project: (1) thermodynamic data for Th(IV) and Pu(IV) complexes of EDTA and for Pu(V) interactions with chloride; (2) kinetic data for redox reactions of Pu in the presence of common redox agents (e.g., H{sub 2}O{sub 2}, MnO{sub 2}, and NaOCl) encountered under waste disposal conditions. These studies are relevant to understanding Pu behavior in wastes disposed of in diverse geologic conditions (e.g., at the WIPP and YUCCA Mountain repositories and in contaminated sediments at many different DOE sites) and also for developing effective remediation strategies (e.g., processing of high level waste tanks). These studies have yielded data to address redox reactions of plutonium in the presence of environmentally important agents (e.g. organic and inorganic oxidants/reductants).

  9. Controllable Electrochemical Activities by Oxidative Treatment toward Inner-Sphere Redox Systems at N-Doped Hydrogenated Amorphous Carbon Films

    Directory of Open Access Journals (Sweden)

    Yoriko Tanaka

    2012-01-01

    Full Text Available The electrochemical activity of the surface of Nitrogen-doped hydrogenated amorphous carbon thin films (a-CNH, N-doped DLC toward the inner sphere redox species is controllable by modifying the surface termination. At the oxygen plasma treated N-doped DLC surface (O-DLC, the surface functional groups containing carbon doubly bonded to oxygen (C=O, which improves adsorption of polar molecules, were generated. By oxidative treatment, the electron-transfer rate for dopamine (DA positively charged inner-sphere redox analyte could be improved at the N-doped DLC surface. For redox reaction of 2,4-dichlorophenol, which induces an inevitable fouling of the anode surface by forming passivating films, the DLC surfaces exhibited remarkably higher stability and reproducibility of the electrode performance. This is due to the electrochemical decomposition of the passive films without the interference of oxygen evolution by applying higher potential. The N-doped DLC film can offer benefits as the polarizable electrode surface with the higher reactivity and higher stability toward inner-sphere redox species. By making use of these controllable electrochemical reactivity at the O-DLC surface, the selective detection of DA in the mixed solution of DA and uric acid could be achieved.

  10. Research Program to Determine Redox Reactions and Their Effects on Speciation and Mobility of Plutonium in DOE Wastes

    International Nuclear Information System (INIS)

    Choppin, G.R.; Rai, D.

    2000-01-01

    Plutonium in geologic matrices undergoes a variety of complex reactions which complicate its environmental behavior. These complexities in plutonium chemistry whereby a large variety of precipitation, dissolution, adsorption/desorption, and redox reactions control plutonium speciation and concentrations, result in the need for a rather large amount of reliable, fundamental data to predict Pu behavior in geologic media. These data are also needed for evaluation of remediation strategies that involve removing most of the contaminants by selective methods, followed by in situ immobilization of residual contaminants. Two areas were studied during this project: (1) thermodynamic data for Th(IV) and Pu(IV) complexes of EDTA and for Pu(V) interactions with chloride; (2) kinetic data for redox reactions of Pu in the presence of common redox agents (e.g., H 2 O 2 , MnO 2 , and NaOCl) encountered under waste disposal conditions. These studies are relevant to understanding Pu behavior in wastes disposed of in diverse geologic conditions (e.g., at the WIPP and YUCCA Mountain repositories and in contaminated sediments at many different DOE sites) and also for developing effective remediation strategies (e.g., processing of high level waste tanks). These studies have yielded data to address redox reactions of plutonium in the presence of environmentally important agents (e.g. organic and inorganic oxidants/reductants)

  11. Exercise-intensity dependent alterations in plasma redox status do not reflect skeletal muscle redox-sensitive protein signaling.

    Science.gov (United States)

    Parker, Lewan; Trewin, Adam; Levinger, Itamar; Shaw, Christopher S; Stepto, Nigel K

    2018-04-01

    Redox homeostasis and redox-sensitive protein signaling play a role in exercise-induced adaptation. The effects of sprint-interval exercise (SIE), high-intensity interval exercise (HIIE) and continuous moderate-intensity exercise (CMIE), on post-exercise plasma redox status are unclear. Furthermore, whether post-exercise plasma redox status reflects skeletal muscle redox-sensitive protein signaling is unknown. In a randomized crossover design, eight healthy adults performed a cycling session of HIIE (5×4min at 75% W max ), SIE (4×30s Wingate's), and CMIE work-matched to HIIE (30min at 50% of W max ). Plasma hydrogen peroxide (H 2 O 2 ), thiobarbituric acid reactive substances (TBARS), superoxide dismutase (SOD) activity, and catalase activity were measured immediately post, 1h, 2h and 3h post-exercise. Plasma redox status biomarkers were correlated with phosphorylation of skeletal muscle p38-MAPK, JNK, NF-κB, and IκBα protein content immediately and 3h post-exercise. Plasma catalase activity was greater with SIE (56.6±3.8Uml -1 ) compared to CMIE (42.7±3.2, pexercise plasma TBARS and SOD activity significantly (pexercise protocol. A significant positive correlation was detected between plasma catalase activity and skeletal muscle p38-MAPK phosphorylation 3h post-exercise (r=0.40, p=0.04). No other correlations were detected (all p>0.05). Low-volume SIE elicited greater post-exercise plasma catalase activity compared to HIIE and CMIE, and greater H 2 O 2 compared to CMIE. Plasma redox status did not, however, adequately reflect skeletal muscle redox-sensitive protein signaling. Copyright © 2017 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

  12. Nitroxides as redox probes of melanins: dark-induced and photoinduced changes in redox equilibria

    International Nuclear Information System (INIS)

    Sarna, T.; Korytowski, W.; Sealy, R.C.

    1985-01-01

    The interaction of nitroxide free radicals and their reduced products (hydroxylamines) with synthetic and natural melanins has been studied. Electron spin resonance spectroscopy was used to measure changes in radical concentration in the dark and during irradiation with visible or uv light. Some reduction of nitroxide occurs in the dark, and is reversible: the nitroxide can be completely regenerated by the one-electron oxidant ferricyanide. The kinetics of the process depend strongly on radical charge and pH. For positively charged nitroxides the rate is much faster than for either neutral or anionic radicals. At pH 10 the rate is about 20 times faster than at pH 5. Oxidation of hydroxylamine also can occur so that a redox equilibrium is established. The equilibrium constant has been estimated for the reaction between a nitroxide and melanin from autoxidation of 3,4-dihydroxyphenylalanine. Results are also dependent upon the type of melanin used and chemical modification (oxidation or reduction) of the melanin. Redox equilibria are altered during irradiation with either visible or uv light. Rapid oxidation of hydroxylamine to nitroxide is apparent, together with a slower reduction of nitroxide. Action spectra for these processes are related to those for melanin radical production and oxygen consumption in nitroxide-free melanin systems. Reduction of nitroxide is inhibited by oxygen, suggesting a competition between nitroxide and oxygen for photoinduced reducing equivalents

  13. Redox-Flow Batteries: From Metals to Organic Redox-Active Materials.

    Science.gov (United States)

    Winsberg, Jan; Hagemann, Tino; Janoschka, Tobias; Hager, Martin D; Schubert, Ulrich S

    2017-01-16

    Research on redox-flow batteries (RFBs) is currently experiencing a significant upturn, stimulated by the growing need to store increasing quantities of sustainably generated electrical energy. RFBs are promising candidates for the creation of smart grids, particularly when combined with photovoltaics and wind farms. To achieve the goal of "green", safe, and cost-efficient energy storage, research has shifted from metal-based materials to organic active materials in recent years. This Review presents an overview of various flow-battery systems. Relevant studies concerning their history are discussed as well as their development over the last few years from the classical inorganic, to organic/inorganic, to RFBs with organic redox-active cathode and anode materials. Available technologies are analyzed in terms of their technical, economic, and environmental aspects; the advantages and limitations of these systems are also discussed. Further technological challenges and prospective research possibilities are highlighted. © 2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

  14. Redox Proteomics and Platelet Activation: Understanding the Redox Proteome to Improve Platelet Quality for Transfusion

    Science.gov (United States)

    Sonego, Giona; Abonnenc, Mélanie; Tissot, Jean-Daniel; Prudent, Michel; Lion, Niels

    2017-01-01

    Blood banks use pathogen inactivation (PI) technologies to increase the safety of platelet concentrates (PCs). The characteristics of PI-treated PCs slightly differ from those of untreated PCs, but the underlying reasons are not well understood. One possible cause is the generation of oxidative stress during the PI process. This is of great interest since reactive oxygen species (ROS) act as second messengers in platelet functions. Furthermore, there are links between protein oxidation and phosphorylation, another mechanism that is critical for cell regulation. Current research efforts focus on understanding the underlying mechanisms and identifying new target proteins. Proteomics technologies represent powerful tools for investigating signaling pathways involving ROS and post-translational modifications such as phosphorylation, while quantitative techniques enable the comparison of the platelet resting state versus the stimulated state. In particular, redox cysteine is a key player in platelet activation upon stimulation by different agonists. This review highlights the experiments that have provided insights into the roles of ROS in platelet function and the implications for platelet transfusion, and potentially in diseases such as inflammation and platelet hyperactivity. The review also describes the implication of redox mechanism in platelet storage considerations. PMID:28208668

  15. Redox regulation in metabolic programming and inflammation.

    Science.gov (United States)

    Griffiths, Helen R; Gao, Dan; Pararasa, Chathyan

    2017-08-01

    Energy metabolism and redox state are intrinsically linked. In order to mount an adequate immune response, cells must have an adequate and rapidly available energy resource to migrate to the inflammatory site, to generate reactive oxygen species using NADPH as a cofactor and to engulf bacteria or damaged tissue. The first responder cells of the innate immune response, neutrophils, are largely dependent on glycolysis. Neutrophils are relatively short-lived, dying via apoptosis in the process of bacterial killing through production of hypochlorous acid and release of extracellular NETs. Later on, the most prevalent recruited innate immune cells are monocytes. Their role is to complete a damage limitation exercise initiated by neutrophils and then, as re-programmed M2 macrophages, to resolve the inflammatory event. Almost twenty five years ago, it was noted that macrophages lose their glycolytic capacity and become anti-inflammatory after treatment with corticosteroids. In support of this we now understand that, in contrast to early responders, M2 macrophages are predominantly dependent on oxidative phosphorylation for energy. During early inflammation, polarisation towards M1 macrophages is dependent on NOX2 activation which, via protein tyrosine phosphatase oxidation and AKT activation, increases trafficking of glucose transporters to the membrane and consequently increases glucose uptake for glycolysis. In parallel, mitochondrial efficiency is likely to be compromised via nitrosylation of the electron transport chain. Resolution of inflammation is triggered by encounter with apoptotic membranes exposing oxidised phosphatidylserine that interact with the scavenger receptor, CD36. Downstream of CD36, activation of AMPK and PPARγ elicits mitochondrial biogenesis, arginase expression and a switch towards oxidative phosphorylation in the M2 macrophage. Proinflammatory cytokine production by M2 cells decreases, but anti-inflammatory and wound healing growth factor

  16. Redox behaviour of uranium with iron compounds

    International Nuclear Information System (INIS)

    Ithurbide, A.

    2009-10-01

    An option investigated for the management of long-term nuclear waste is a repository in deep geological formations. It is generally admitted that the release of radionuclides from the spent fuel in the geosphere could occur several thousand years after the beginning of the storage. Therefore, to assess the safety of the long-term disposal, it is important to consider the phenomena that can reduce the migration, and in particular the migration of uranium. The aim of this work is to study if siderite, an iron compound present both in the near - and far -field, can limit this migration as well as the role played by the redox process. Siderite thin layers have been obtained by electrochemistry. The layers are adherent and homogeneous. Their thickness is about 1 μm and they are composed of spherical grains. Analytical characterizations performed show that siderite is free of any impurity and does not exhibit any trace of oxidation. The interactions between siderite and uranium (VI) have been carried out in solutions considered as representative of environmental waters, in terms of pH and carbonate concentration. The retention of uranium on the thin layer is important since, after 24 hours of interaction, it corresponds to retention capacities of several hundreds of uranium micro-moles per gram of siderite. XPS analysis show that, in any studied condition, part of uranium present on the thin layer is reduced into an over stoichiometric uranium dioxide. The process of interaction differs depending on the considered environment, specially on the stability of siderite. (author)

  17. Redox Fluctuations Increase the Contribution of Lignin to Soil Respiration

    Science.gov (United States)

    Hall, S. J.; Silver, W. L.; Timokhin, V.; Hammel, K.

    2014-12-01

    Lignin mineralization represents a critical flux in the terrestrial carbon (C) cycle, yet little is known about mechanisms and environmental factors controlling lignin breakdown in mineral soils. Hypoxia has long been thought to suppress lignin decomposition, yet variation in oxygen (O2) availability in surface soils accompanying moisture fluctuations could potentially stimulate this process by generating reactive oxygen species via coupled biotic and abiotic iron (Fe) redox cycling. Here, we tested the impact of redox fluctuations on lignin breakdown in humid tropical forest soils during ten-week laboratory incubations. We used synthetic lignins labeled with 13C in either of two positions (aromatic methoxyl and propyl Cβ) to provide highly sensitive and specific measures of lignin mineralization not previously employed in soils. Four-day redox fluctuations increased the percent contribution of methoxyl C to soil respiration, and cumulative methoxyl C mineralization was equivalent under static aerobic and fluctuating redox conditions despite lower total C mineralization in the latter treatment. Contributions of the highly stable Cβ to mineralization were also equivalent in static aerobic and fluctuating redox treatments during periods of O2 exposure, and nearly doubled in the fluctuating treatment after normalizing to cumulative O2 exposure. Oxygen fluctuations drove substantial net Fe reduction and oxidation, implying that reactive oxygen species generated during abiotic Fe oxidation likely contributed to the elevated contribution of lignin to C mineralization. Iron redox cycling provides a mechanism for lignin breakdown in soils that experience conditions unfavorable for canonical lignin-degrading organisms, and provides a potential mechanism for lignin depletion in soil organic matter during late-stage decomposition. Thus, close couplings between soil moisture, redox fluctuations, and lignin breakdown provide potential a link between climate variability and

  18. Accelerated redox reaction between chromate and phenolic pollutants during freezing.

    Science.gov (United States)

    Ju, Jinjung; Kim, Jaesung; Vetráková, Ľubica; Seo, Jiwon; Heger, Dominik; Lee, Changha; Yoon, Ho-Il; Kim, Kitae; Kim, Jungwon

    2017-05-05

    The redox reaction between 4-chlorophenol (4-CP) and chromate (Cr(VI)) (i.e., the simultaneous oxidation of 4-CP by Cr(VI) and reduction of Cr(VI) by 4-CP) in ice (i.e., at -20°C) was compared with the corresponding reaction in water (i.e., at 25°C). The redox conversion of 4-CP/Cr(VI), which was negligible in water, was significantly accelerated in ice. This accelerated redox conversion of 4-CP/Cr(VI) in ice is ascribed to the freeze concentration effect occurring during freezing, which excludes solutes (i.e., 4-CP and Cr(VI)) and protons from the ice crystals and subsequently concentrates them in the liquid brine. The concentrations of Cr(VI) and protons in the liquid brine were confirmed by measuring the optical image and the UV-vis absorption spectra of cresol red (CR) as a pH indicator of frozen solution. The redox conversion of 4-CP/Cr(VI) was observed in water when the concentrations of 4-CP/protons or Cr(VI)/protons increased by 100/1000-fold. These results corroborate the freeze concentration effect as the reason for the accelerated redox conversion of 4-CP/Cr(VI) in ice. The redox conversion of various phenolic pollutants/Cr(VI) and 4-CP/Cr(VI) in real wastewater was successfully achieved in ice, which verifies the environmental relevance and importance of freezing-accelerated redox conversion of phenolic pollutants/Cr(VI) in cold regions. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. Redox regulation of the AMP-activated protein kinase.

    Directory of Open Access Journals (Sweden)

    Yingying Han

    2010-11-01

    Full Text Available Redox state is a critical determinant of cell function, and any major imbalances can cause severe damage or death.The aim of this study is to determine if AMP-activated protein kinase (AMPK, a cellular energy sensor, is activated by oxidants generated by Berberine in endothelial cells (EC.Bovine aortic endothelial cells (BAEC were exposed to Berberine. AMPK activity and reactive oxygen species were monitored after the incubation.In BAEC, Berberine caused a dose- and time-dependent increase in the phosphorylation of AMPK at Thr172 and acetyl CoA carboxylase (ACC at Ser79, a well characterized downstream target of AMPK. Concomitantly, Berberine increased peroxynitrite, a potent oxidant formed by simultaneous generation of superoxide and nitric oxide. Pre-incubation of BAEC with anti-oxidants markedly attenuated Berberine-enhanced phosphorylation of both AMPK and ACC. Consistently, adenoviral expression of superoxide dismutase and pretreatment of L-N(G-Nitroarginine methyl ester (L-NAME; a non-selective NOS inhibitor blunted Berberine-induced phosphorylation of AMPK. Furthermore, mitochondria-targeted tempol (mito-tempol pretreatment or expression of uncoupling protein attenuated AMPK activation caused by Berberine. Depletion of mitochondria abolished the effects of Berberine on AMPK in EC. Finally, Berberine significantly increased the phosphorylation of LKB1 at Ser307 and gene silencing of LKB1 attenuated Berberine-enhanced AMPK Thr172 phosphorylation in BAEC.Our results suggest that mitochondria-derived superoxide anions and peroxynitrite are required for Berberine-induced AMPK activation in endothelial cells.

  20. Optical imaging the redox status change during cell apoptosis

    Science.gov (United States)

    Su, Ting; Zhang, Zhihong; Lin, Juqiang; Luo, Qingming

    2007-02-01

    Many cellular events involve the alteration in redox equilibrium, globally or locally. In many cases, excessive reactive oxygen species (ROS) production is the underlying cause. Several green fluoresecence protein based indicators are constructed to measure redox status in cells, e.g, rxYFP and roGFPs, which allow real time detection. reduction and oxidization-sensitive GFP (RoGFPs) are more useful due to ratiometric variation by excitation, making the measurement more accurate. Utilizing one of those roGFPs called roGFP1, we establish a mitochondrial redox state probing platform in HeLa cells with laser scan confocal microscopy (LSCM) as detection system. Control experiments confirmed that our platform could produce stable ratiometric values, which made the data more accurately reflect the real environmental changes of redox status that roGFP1 probed. Using exogenous H IIO II and DTT, we evaluated the reactivity and reversibility of roGFP1. The minimal hydrogen peroxide concentration that roGFP1 could show detectable ratiometric changes in our system was about 200μM. Preliminarily applying our platform to exploring the redox status during apoptosis, we observed an increase in ratiometric, suggesting an excessive ROS production.

  1. Systemic Redox Imbalance in Chronic Kidney Disease: A Systematic Review

    Science.gov (United States)

    Kaltsatou, Antonia; Jamurtas, Athanasios Z.; Koutedakis, Yiannis; Stefanidis, Ioannis; Sakkas, Giorgos K.

    2016-01-01

    Patients with chronic kidney disease (CKD) experience imbalance between oxygen reactive species (ROS) production and antioxidant defenses leading to cell and tissue damage. However, it remains unclear at which stage of renal insufficiency the redox imbalance becomes more profound. The aim of this systematic review was to provide an update on recent advances in our understanding of how the redox status changes in the progression of renal disease from predialysis stages 1 to 4 to end stage 5 and whether the various treatments and dialysis modalities influence the redox balance. A systematic review was conducted searching PubMed and Scopus by using the Cochrane and PRISMA guidelines. In total, thirty-nine studies met the inclusion criteria and were reviewed. Even from an early stage, imbalance in redox status is evident and as the kidney function worsens it becomes more profound. Hemodialysis therapy per se seems to negatively influence the redox status by the elevation of lipid peroxidation markers, protein carbonylation, and impairing erythrocyte antioxidant defense. However, other dialysis modalities do not so far appear to confer advantages. Supplementation with antioxidants might assist and should be considered as an early intervention to halt premature atherogenesis development at an early stage of CKD. PMID:27563376

  2. Systemic Redox Imbalance in Chronic Kidney Disease: A Systematic Review

    Directory of Open Access Journals (Sweden)

    Konstantina P. Poulianiti

    2016-01-01

    Full Text Available Patients with chronic kidney disease (CKD experience imbalance between oxygen reactive species (ROS production and antioxidant defenses leading to cell and tissue damage. However, it remains unclear at which stage of renal insufficiency the redox imbalance becomes more profound. The aim of this systematic review was to provide an update on recent advances in our understanding of how the redox status changes in the progression of renal disease from predialysis stages 1 to 4 to end stage 5 and whether the various treatments and dialysis modalities influence the redox balance. A systematic review was conducted searching PubMed and Scopus by using the Cochrane and PRISMA guidelines. In total, thirty-nine studies met the inclusion criteria and were reviewed. Even from an early stage, imbalance in redox status is evident and as the kidney function worsens it becomes more profound. Hemodialysis therapy per se seems to negatively influence the redox status by the elevation of lipid peroxidation markers, protein carbonylation, and impairing erythrocyte antioxidant defense. However, other dialysis modalities do not so far appear to confer advantages. Supplementation with antioxidants might assist and should be considered as an early intervention to halt premature atherogenesis development at an early stage of CKD.

  3. Dihydroxybenzene/benzoquinone-containing polymers: organic redox polymers

    Energy Technology Data Exchange (ETDEWEB)

    Moulay, S. [Universite de Blida, Lab. de Chimie-Physique Macromoleculaire, Institut de Chimie Industrielle (Algeria)

    2000-08-01

    Polymers containing hydroquinone, catechol or their corresponding benzoquinones are a special class of redox polymers. Three pathways of their syntheses are possible: condensation polymerization of suitable monomers, addition polymerization of vinyl monomers containing redox moiety, and chemical attachment of redox unit onto pre-made polymeric matrix. A range of functionalized matrices have been employed such as polyethers, polyesters, polycarbonates, polyurethanes, polyamides and others. Protection of their phenolic functionality has conducted to chemically interesting redox polymer precursors. The presence of a redox moiety coupled with the extant functionalization of the polymer matrix makes the materials very valuable, of wide properties and consequently of vast applicability. For instance, in the oil field, some polymers such as carboxy-methyl-cellulose (CMC) are often applied as to bring about a viscosity improvement and therefore to facilitate the oil drilling. In this regard, Patel evaluated sulfo-alkylated polymeric catechol, namely sulfo-methylated and sulfo-ethylated resins. Indeed, polymeric catechol chemically modified as such exhibited a marked ability to control the viscosity, the gel strength, as well as the filtrate loss of aqueous oil drilling fluids.

  4. Redox regulation in photosynthetic organisms: signaling, acclimation, and practical implications.

    Science.gov (United States)

    Foyer, Christine H; Noctor, Graham

    2009-04-01

    Reactive oxygen species (ROS) have multifaceted roles in the orchestration of plant gene expression and gene-product regulation. Cellular redox homeostasis is considered to be an "integrator" of information from metabolism and the environment controlling plant growth and acclimation responses, as well as cell suicide events. The different ROS forms influence gene expression in specific and sometimes antagonistic ways. Low molecular antioxidants (e.g., ascorbate, glutathione) serve not only to limit the lifetime of the ROS signals but also to participate in an extensive range of other redox signaling and regulatory functions. In contrast to the low molecular weight antioxidants, the "redox" states of components involved in photosynthesis such as plastoquinone show rapid and often transient shifts in response to changes in light and other environmental signals. Whereas both types of "redox regulation" are intimately linked through the thioredoxin, peroxiredoxin, and pyridine nucleotide pools, they also act independently of each other to achieve overall energy balance between energy-producing and energy-utilizing pathways. This review focuses on current knowledge of the pathways of redox regulation, with discussion of the somewhat juxtaposed hypotheses of "oxidative damage" versus "oxidative signaling," within the wider context of physiological function, from plant cell biology to potential applications.

  5. TEMPOL increases NAD+ and improves redox imbalance in obese mice

    Directory of Open Access Journals (Sweden)

    Mayumi Yamato

    2016-08-01

    Full Text Available Continuous energy conversion is controlled by reduction–oxidation (redox processes. NAD+ and NADH represent an important redox couple in energy metabolism. 4-Hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPOL is a redox-cycling nitroxide that promotes the scavenging of several reactive oxygen species (ROS and is reduced to hydroxylamine by NADH. TEMPOL is also involved in NAD+ production in the ascorbic acid–glutathione redox cycle. We utilized the chemical properties of TEMPOL to investigate the effects of antioxidants and NAD+/NADH modulators on the metabolic imbalance in obese mice. Increases in the NAD+/NADH ratio by TEMPOL ameliorated the metabolic imbalance when combined with a dietary intervention, changing from a high-fat diet to a normal diet. Plasma levels of the superoxide marker dihydroethidium were higher in mice receiving the dietary intervention compared with a control diet, but were normalized with TEMPOL consumption. These findings provide novel insights into redox regulation in obesity.

  6. Anionic Redox Chemistry in Polysulfide Electrode Materials for Rechargeable Batteries.

    Science.gov (United States)

    Grayfer, Ekaterina D; Pazhetnov, Egor M; Kozlova, Mariia N; Artemkina, Sofya B; Fedorov, Vladimir E

    2017-12-22

    Classical Li-ion battery technology is based on the insertion of lithium ions into cathode materials involving metal (cationic) redox reactions. However, this vision is now being reconsidered, as many new-generation electrode materials with enhanced reversible capacities operate through combined cationic and anionic (non-metal) reversible redox processes or even exclusively through anionic redox transformations. Anionic participation in the redox reactions is observed in materials with more pronounced covalency, which is less typical for oxides, but quite common for phosphides or chalcogenides. In this Concept, we would like to draw the reader's attention to this new idea, especially, as it applies to transition-metal polychalcogenides, such as FeS 2 , VS 4 , TiS 3 , NbS 3 , TiS 4 , MoS 3 , etc., in which the key role is played by the (S-S) 2- /2 S 2- redox reaction. The exploration and better understanding of the anion-driven chemistry is important for designing advanced materials for battery and other energy-related applications. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Molecular Orbital Principles of Oxygen-Redox Battery Electrodes.

    Science.gov (United States)

    Okubo, Masashi; Yamada, Atsuo

    2017-10-25

    Lithium-ion batteries are key energy-storage devices for a sustainable society. The most widely used positive electrode materials are LiMO 2 (M: transition metal), in which a redox reaction of M occurs in association with Li + (de)intercalation. Recent developments of Li-excess transition-metal oxides, which deliver a large capacity of more than 200 mAh/g using an extra redox reaction of oxygen, introduce new possibilities for designing higher energy density lithium-ion batteries. For better engineering using this fascinating new chemistry, it is necessary to achieve a full understanding of the reaction mechanism by gaining knowledge on the chemical state of oxygen. In this review, a summary of the recent advances in oxygen-redox battery electrodes is provided, followed by a systematic demonstration of the overall electronic structures based on molecular orbitals with a focus on the local coordination environment around oxygen. We show that a π-type molecular orbital plays an important role in stabilizing the oxidized oxygen that emerges upon the charging process. Molecular orbital principles are convenient for an atomic-level understanding of how reversible oxygen-redox reactions occur in bulk, providing a solid foundation toward improved oxygen-redox positive electrode materials for high energy-density batteries.

  8. Redox rhythm reinforces the circadian clock to gate immune response.

    Science.gov (United States)

    Zhou, Mian; Wang, Wei; Karapetyan, Sargis; Mwimba, Musoki; Marqués, Jorge; Buchler, Nicolas E; Dong, Xinnian

    2015-07-23

    Recent studies have shown that in addition to the transcriptional circadian clock, many organisms, including Arabidopsis, have a circadian redox rhythm driven by the organism's metabolic activities. It has been hypothesized that the redox rhythm is linked to the circadian clock, but the mechanism and the biological significance of this link have only begun to be investigated. Here we report that the master immune regulator NPR1 (non-expressor of pathogenesis-related gene 1) of Arabidopsis is a sensor of the plant's redox state and regulates transcription of core circadian clock genes even in the absence of pathogen challenge. Surprisingly, acute perturbation in the redox status triggered by the immune signal salicylic acid does not compromise the circadian clock but rather leads to its reinforcement. Mathematical modelling and subsequent experiments show that NPR1 reinforces the circadian clock without changing the period by regulating both the morning and the evening clock genes. This balanced network architecture helps plants gate their immune responses towards the morning and minimize costs on growth at night. Our study demonstrates how a sensitive redox rhythm interacts with a robust circadian clock to ensure proper responsiveness to environmental stimuli without compromising fitness of the organism.

  9. Redox-responsive theranostic nanoplatforms based on inorganic nanomaterials.

    Science.gov (United States)

    Han, Lu; Zhang, Xiao-Yong; Wang, Yu-Long; Li, Xi; Yang, Xiao-Hong; Huang, Min; Hu, Kun; Li, Lu-Hai; Wei, Yen

    2017-08-10

    Spurred on by advances in materials chemistry and nanotechnology, scientists have developed many novel nanopreparations for cancer diagnosis and therapy. To treat complex malignant tumors effectively, multifunctional nanomedicines with targeting ability, imaging properties and controlled drug release behavior should be designed and exploited. The therapeutic efficiency of loaded drugs can be dramatically improved using redox-responsive nanoplatforms which can sense the differences in the redox status of tumor tissues and healthy ones. Redox-sensitive nanocarriers can be constructed from both organic and inorganic nanomaterials; however, at present, drug delivery nanovectors progressively lean towards inorganic nanomaterials because of their facile synthesis/modification and their unique physicochemical properties. In this review, we focus specifically on the preparation and application of redox-sensitive nanosystems based on mesoporous silica nanoparticles (MSNs), carbon nanomaterials, magnetic nanoparticles, gold nanomaterials and other inorganic nanomaterials. We discuss relevant examples of redox-sensitive nanosystems in each category. Finally, we discuss current challenges and future strategies from the aspect of material design and practical application. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. Molecular Controls of the Oxygenation and Redox Reactions of Hemoglobin

    Science.gov (United States)

    Henkens, Robert; Alayash, Abdu I.; Banerjee, Sambuddha; Crumbliss, Alvin L.

    2013-01-01

    Abstract Significance: The broad classes of O2-binding proteins known as hemoglobins (Hbs) carry out oxygenation and redox functions that allow organisms with significantly different physiological demands to exist in a wide range of environments. This is aided by allosteric controls that modulate the protein's redox reactions as well as its O2-binding functions. Recent Advances: The controls of Hb's redox reactions can differ appreciably from the molecular controls for Hb oxygenation and come into play in elegant mechanisms for dealing with nitrosative stress, in the malarial resistance conferred by sickle cell Hb, and in the as-yet unsuccessful designs for safe and effective blood substitutes. Critical Issues: An important basic principle in consideration of Hb's redox reactions is the distinction between kinetic and thermodynamic reaction control. Clarification of these modes of control is critical to gaining an increased understanding of Hb-mediated oxidative processes and oxidative toxicity in vivo. Future Directions: This review addresses emerging concepts and some unresolved questions regarding the interplay between the oxygenation and oxidation reactions of structurally diverse Hbs, both within red blood cells and under acellular conditions. Developing methods that control Hb-mediated oxidative toxicity will be critical to the future development of Hb-based blood substitutes. Antioxid. Redox Signal. 18, 2298–2313. PMID:23198874

  11. Recent developments in organic redox flow batteries: A critical review

    Science.gov (United States)

    Leung, P.; Shah, A. A.; Sanz, L.; Flox, C.; Morante, J. R.; Xu, Q.; Mohamed, M. R.; Ponce de León, C.; Walsh, F. C.

    2017-08-01

    Redox flow batteries (RFBs) have emerged as prime candidates for energy storage on the medium and large scales, particularly at the grid scale. The demand for versatile energy storage continues to increase as more electrical energy is generated from intermittent renewable sources. A major barrier in the way of broad deployment and deep market penetration is the use of expensive metals as the active species in the electrolytes. The use of organic redox couples in aqueous or non-aqueous electrolytes is a promising approach to reducing the overall cost in long-term, since these materials can be low-cost and abundant. The performance of such redox couples can be tuned by modifying their chemical structure. In recent years, significant developments in organic redox flow batteries has taken place, with the introduction of new groups of highly soluble organic molecules, capable of providing a cell voltage and charge capacity comparable to conventional metal-based systems. This review summarises the fundamental developments and characterization of organic redox flow batteries from both the chemistry and materials perspectives. The latest advances, future challenges and opportunities for further development are discussed.

  12. Synthesis and characterization of redox-active ferric nontronite

    Energy Technology Data Exchange (ETDEWEB)

    Ilgen, A. G.; Kukkadapu, R. K.; Dunphy, D. R.; Artyushkova, K.; Cerrato, J. M.; Kruichak, J. N.; Janish, M. T.; Sun, C. J.; Argo, J. M.; Washington, R. E.

    2017-10-01

    Heterogeneous redox reactions on clay mineral surfaces control mobility and bioavailability of redox-sensitive nutrients and contaminants. Iron (Fe) residing in clay mineral structures can either catalyze or directly participate in redox reactions; however, chemical controls over its reactivity are not fully understood. In our previous work we demonstrated that converting a minor portion of Fe(III) to Fe(II) (partial reduction) in the octahedral sheet of natural Fe-rich clay mineral nontronite (NAu-1) activates its surface, making it redox-active. In this study we produced and characterized synthetic ferric nontronite (SIP), highlighting structural and chemical similarities and differences between this synthetic nontronite and its natural counterpart NAu-1, and probed whether mineral surface is redox-active by reacting it with arsenic As(III) under oxic and anoxic conditions. We demonstrate that synthetic nontronite SIP undergoes the same activation as natural nontronite NAu-1 following the partial reduction treatment. Similar to NAu-1, SIP oxidized As(III) to As(V) under both oxic (catalytic pathway) and anoxic (direct oxidation) conditions. The similar reactivity trends observed for synthetic nontronite and its natural counterpart make SIP an appropriate analog for laboratory studies. The development of chemically pure analogs for ubiquitous soil minerals will allow for systematic research of the fundamental properties of these minerals.

  13. Anticancer Activity of Metal Complexes: Involvement of Redox Processes

    Science.gov (United States)

    Jungwirth, Ute; Kowol, Christian R.; Keppler, Bernhard K.; Hartinger, Christian G.; Berger, Walter; Heffeter, Petra

    2012-01-01

    Cells require tight regulation of the intracellular redox balance and consequently of reactive oxygen species for proper redox signaling and maintenance of metal (e.g., of iron and copper) homeostasis. In several diseases, including cancer, this balance is disturbed. Therefore, anticancer drugs targeting the redox systems, for example, glutathione and thioredoxin, have entered focus of interest. Anticancer metal complexes (platinum, gold, arsenic, ruthenium, rhodium, copper, vanadium, cobalt, manganese, gadolinium, and molybdenum) have been shown to strongly interact with or even disturb cellular redox homeostasis. In this context, especially the hypothesis of “activation by reduction” as well as the “hard and soft acids and bases” theory with respect to coordination of metal ions to cellular ligands represent important concepts to understand the molecular modes of action of anticancer metal drugs. The aim of this review is to highlight specific interactions of metal-based anticancer drugs with the cellular redox homeostasis and to explain this behavior by considering chemical properties of the respective anticancer metal complexes currently either in (pre)clinical development or in daily clinical routine in oncology. PMID:21275772

  14. Redox Signaling in Diabetic Wound Healing Regulates Extracellular Matrix Deposition.

    Science.gov (United States)

    Kunkemoeller, Britta; Kyriakides, Themis R

    2017-10-20

    Impaired wound healing is a major complication of diabetes, and can lead to development of chronic foot ulcers in a significant number of patients. Despite the danger posed by poor healing, very few specific therapies exist, leaving patients at risk of hospitalization, amputation, and further decline in overall health. Recent Advances: Redox signaling is a key regulator of wound healing, especially through its influence on the extracellular matrix (ECM). Normal redox signaling is disrupted in diabetes leading to several pathological mechanisms that alter the balance between reactive oxygen species (ROS) generation and scavenging. Importantly, pathological oxidative stress can alter ECM structure and function. There is limited understanding of the specific role of altered redox signaling in the diabetic wound, although there is evidence that ROS are involved in the underlying pathology. Preclinical studies of antioxidant-based therapies for diabetic wound healing have yielded promising results. Redox-based therapeutics constitute a novel approach for the treatment of wounds in diabetes patients that deserve further investigation. Antioxid. Redox Signal. 27, 823-838.

  15. Redox-assisted Li+-storage in lithium-ion batteries

    International Nuclear Information System (INIS)

    Huang Qizhao; Wang Qing

    2016-01-01

    Interfacial charge transfer is the key kinetic process dictating the operation of lithium-ion battery. Redox-mediated charge propagations of the electronic (e − and h + ) and ionic species (Li + ) at the electrode–electrolyte interface have recently gained increasing attention for better exploitation of battery materials. This article briefly summarises the energetic and kinetic aspects of lithium-ion batteries, and reviews the recent progress on various redox-assisted Li + storage approaches. From molecular wiring to polymer wiring and from redox targeting to redox flow lithium battery, the role of redox mediators and the way of the redox species functioning in lithium-ion batteries are discussed. (topical review)

  16. New reactions and products resulting from alternative interactions between the P450 enzyme and redox partners.

    Science.gov (United States)

    Zhang, Wei; Liu, Yi; Yan, Jinyong; Cao, Shaona; Bai, Fali; Yang, Ying; Huang, Shaohua; Yao, Lishan; Anzai, Yojiro; Kato, Fumio; Podust, Larissa M; Sherman, David H; Li, Shengying

    2014-03-05

    Cytochrome P450 enzymes are capable of catalyzing a great variety of synthetically useful reactions such as selective C-H functionalization. Surrogate redox partners are widely used for reconstitution of P450 activity based on the assumption that the choice of these auxiliary proteins or their mode of action does not affect the type and selectivity of reactions catalyzed by P450s. Herein, we present an exceptional example to challenge this postulate. MycG, a multifunctional biosynthetic P450 monooxygenase responsible for hydroxylation and epoxidation of 16-membered ring macrolide mycinamicins, is shown to catalyze the unnatural N-demethylation(s) of a range of mycinamicin substrates when partnered with the free Rhodococcus reductase domain RhFRED or the engineered Rhodococcus-spinach hybrid reductase RhFRED-Fdx. By contrast, MycG fused with the RhFRED or RhFRED-Fdx reductase domain mediates only physiological oxidations. This finding highlights the larger potential role of variant redox partner protein-protein interactions in modulating the catalytic activity of P450 enzymes.

  17. Redox-active on-surface polymerization of single-site divalent cations from pure metals by a ketone-functionalized phenanthroline

    Energy Technology Data Exchange (ETDEWEB)

    Skomski, Daniel; Tempas, Christopher D.; Bukowski, Gregory S.; Smith, Kevin A.; Tait, Steven L., E-mail: tait@indiana.edu [Department of Chemistry, Indiana University, 800 E. Kirkwood Ave., Bloomington, Indiana 47405 (United States)

    2015-03-14

    Metallic iron, chromium, or platinum mixing with a ketone-functionalized phenanthroline ligand on a single crystal gold surface demonstrates redox activity to a well-defined oxidation state and assembly into thermally stable, one dimensional, polymeric chains. The diverging ligand geometry incorporates redox-active sub-units and bi-dentate binding sites. The gold surface provides a stable adsorption environment and directs growth of the polymeric chains, but is inert with regard to the redox chemistry. These systems are characterized by scanning tunnelling microscopy, non-contact atomic force microscopy, and X-ray photoelectron spectroscopy under ultra-high vacuum conditions. The relative propensity of the metals to interact with the ketone group is examined, and it is found that Fe and Cr more readily complex the ligand than Pt. The formation and stabilization of well-defined transition metal single-sites at surfaces may open new routes to achieve higher selectivity in heterogeneous catalysts.

  18. Double-membrane triple-electrolyte redox flow battery design

    Science.gov (United States)

    Yushan, Yan; Gu, Shuang; Gong, Ke

    2018-03-13

    A redox flow battery is provided having a double-membrane (one cation exchange membrane and one anion exchange membrane), triple-electrolyte (one electrolyte in contact with the negative electrode, one electrolyte in contact with the positive electrode, and one electrolyte positioned between and in contact with the two membranes). The cation exchange membrane is used to separate the negative or positive electrolyte and the middle electrolyte, and the anion exchange membrane is used to separate the middle electrolyte and the positive or negative electrolyte. This design physically isolates, but ionically connects, the negative electrolyte and positive electrolyte. The physical isolation offers great freedom in choosing redox pairs in the negative electrolyte and positive electrolyte, making high voltage of redox flow batteries possible. The ionic conduction drastically reduces the overall ionic crossover between negative electrolyte and positive one, leading to high columbic efficiency.

  19. Hybrid energy storage systems utilizing redox active organic compounds

    Science.gov (United States)

    Wang, Wei; Xu, Wu; Li, Liyu; Yang, Zhenguo

    2015-09-08

    Redox flow batteries (RFB) have attracted considerable interest due to their ability to store large amounts of power and energy. Non-aqueous energy storage systems that utilize at least some aspects of RFB systems are attractive because they can offer an expansion of the operating potential window, which can improve on the system energy and power densities. One example of such systems has a separator separating first and second electrodes. The first electrode includes a first current collector and volume containing a first active material. The second electrode includes a second current collector and volume containing a second active material. During operation, the first source provides a flow of first active material to the first volume. The first active material includes a redox active organic compound dissolved in a non-aqueous, liquid electrolyte and the second active material includes a redox active metal.

  20. Computational assignment of redox states to Coulomb blockade diamonds.

    Science.gov (United States)

    Olsen, Stine T; Arcisauskaite, Vaida; Hansen, Thorsten; Kongsted, Jacob; Mikkelsen, Kurt V

    2014-09-07

    With the advent of molecular transistors, electrochemistry can now be studied at the single-molecule level. Experimentally, the redox chemistry of the molecule manifests itself as features in the observed Coulomb blockade diamonds. We present a simple theoretical method for explicit construction of the Coulomb blockade diamonds of a molecule. A combined quantum mechanical/molecular mechanical method is invoked to calculate redox energies and polarizabilities of the molecules, including the screening effect of the metal leads. This direct approach circumvents the need for explicit modelling of the gate electrode. From the calculated parameters the Coulomb blockade diamonds are constructed using simple theory. We offer a theoretical tool for assignment of Coulomb blockade diamonds to specific redox states in particular, and a study of chemical details in the diamonds in general. With the ongoing experimental developments in molecular transistor experiments, our tool could find use in molecular electronics, electrochemistry, and electrocatalysis.

  1. Redox electrodes comprised of polymer-modified carbon nanomaterials

    Science.gov (United States)

    Roberts, Mark; Emmett, Robert; Karakaya, Mehmet; Podila, Ramakrishna; Rao, Apparao; Clemson Physics Team; Clemson Chemical Engineering Team

    2013-03-01

    A shift in how we generate and use electricity requires new energy storage materials and systems compatible with hybrid electric transportation and the integration of renewable energy sources. Supercapacitors provide a solution to these needs by combining the high power, rapid switching, and exceptional cycle life of a capacitor with the high energy density of a battery. Our research brings together nanotechnology and materials chemistry to address the limitations of electrode materials. Paper electrodes fabricated with various forms of carbon nanomaterials, such as nanotubes, are modified with redox-polymers to increase the electrode's energy density while maintaining rapid discharge rates. In these systems, the carbon nanomaterials provide the high surface area, electrical conductivity, nanoscale and porosity, while the redox polymers provide a mechanism for charge storage through Faradaic charge transfer. The design of redox polymers and their incorporation into nanomaterial electrodes will be discussed with a focus on enabling high power and high energy density electrodes.

  2. Redox reactions with empirical potentials: atomistic battery discharge simulations.

    Science.gov (United States)

    Dapp, Wolf B; Müser, Martin H

    2013-08-14

    Batteries are pivotal components in overcoming some of today's greatest technological challenges. Yet to date there is no self-consistent atomistic description of a complete battery. We take first steps toward modeling of a battery as a whole microscopically. Our focus lies on phenomena occurring at the electrode-electrolyte interface which are not easily studied with other methods. We use the redox split-charge equilibration (redoxSQE) method that assigns a discrete ionization state to each atom. Along with exchanging partial charges across bonds, atoms can swap integer charges. With redoxSQE we study the discharge behavior of a nano-battery, and demonstrate that this reproduces the generic properties of a macroscopic battery qualitatively. Examples are the dependence of the battery's capacity on temperature and discharge rate, as well as performance degradation upon recharge.

  3. A biomimetic redox flow battery based on flavin mononucleotide.

    Science.gov (United States)

    Orita, Akihiro; Verde, Michael G; Sakai, Masanori; Meng, Ying Shirley

    2016-10-21

    The versatility in design of redox flow batteries makes them apt to efficiently store energy in large-scale applications at low cost. The discovery of inexpensive organic electroactive materials for use in aqueous flow battery electrolytes is highly attractive, but is thus far limited. Here we report on a flow battery using an aqueous electrolyte based on the sodium salt of flavin mononucleotide. Flavins are highly versatile electroactive molecules, which catalyse a multitude of redox reactions in biological systems. We use nicotinamide (vitamin B3) as a hydrotropic agent to enhance the water solubility of flavin mononucleotide. A redox flow battery using flavin mononucleotide negative and ferrocyanide positive electrolytes in strong base shows stable cycling performance, with over 99% capacity retention over the course of 100 cycles. We hypothesize that this is enabled due to the oxidized and reduced forms of FMN-Na being stabilized by resonance structures.

  4. Nrf2 and Redox Status in Prediabetic and Diabetic Patients

    Directory of Open Access Journals (Sweden)

    Angélica S. Jiménez-Osorio

    2014-11-01

    Full Text Available The redox status associated with nuclear factor erythroid 2-related factor-2 (Nrf2 was evaluated in prediabetic and diabetic subjects. Total antioxidant status (TAS in plasma and erythrocytes, glutathione (GSH and malondialdehyde (MDA content and activity of antioxidant enzymes were measured as redox status markers in 259 controls, 111 prediabetics and 186 diabetic type 2 subjects. Nrf2 was measured in nuclear extract fractions from peripheral blood mononuclear cells (PBMC. Nrf2 levels were lower in prediabetic and diabetic patients. TAS, GSH and activity of glutamate cysteine ligase were lower in diabetic subjects. An increase of MDA and superoxide dismutase activity was found in diabetic subjects. These results suggest that low levels of Nrf2 are involved in the development of oxidative stress and redox status disbalance in diabetic patients.

  5. A redox-mediated chromogenic reaction and application in immunoassay.

    Science.gov (United States)

    Yu, Ru-Jia; Ma, Wei; Peng, Mao-Pan; Bai, Zhi-Shan; Long, Yi-Tao

    2016-08-31

    A novel redox-mediated chromogenic reaction was demonstrated based on the reaction between HAuCl4 and 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), which generate various color responses from red to green in the resulting solutions. Various redox substance could be used to mediate the reaction and trigger a distinct color response. We established a sensitive hydrogen peroxide colorimetric sensor based on the redox-mediated chromogenic reaction and depicted the application both in detection of enzyme and in an immunoassay. Combining the traditional chromogenic reagent with gold nanoparticles, our assay has the advantage in short response time (within three minutes), high sensitivity (10(-12) g mL(-1) for HBsAg) and stability. Copyright © 2016. Published by Elsevier B.V.

  6. Linking mitochondrial bioenergetics to insulin resistance via redox biology

    Science.gov (United States)

    Fisher-Wellman, Kelsey H.; Neufer, P. Darrell

    2012-01-01

    Chronic overnutrition and physical inactivity are major risk factors for insulin resistance and type 2 diabetes. Recent research indicates that overnutrition generates an increase in hydrogen peroxide (H2O2) emission from mitochondria, serving as a release valve to relieve the reducing pressure created by fuel overload, as well as a primary signal to ultimately decrease insulin sensitivity. H2O2 is a major input to cellular redox circuits that link to cysteine residues throughout the entire proteome to regulate cell function. Here we review the principles of mitochondrial bioenergetics and redox systems biology and offer new insight as to how H2O2 emission may be linked via redox biology to the etiology of insulin resistance. PMID:22305519

  7. A biomimetic redox flow battery based on flavin mononucleotide

    Science.gov (United States)

    Orita, Akihiro; Verde, Michael G.; Sakai, Masanori; Meng, Ying Shirley

    2016-10-01

    The versatility in design of redox flow batteries makes them apt to efficiently store energy in large-scale applications at low cost. The discovery of inexpensive organic electroactive materials for use in aqueous flow battery electrolytes is highly attractive, but is thus far limited. Here we report on a flow battery using an aqueous electrolyte based on the sodium salt of flavin mononucleotide. Flavins are highly versatile electroactive molecules, which catalyse a multitude of redox reactions in biological systems. We use nicotinamide (vitamin B3) as a hydrotropic agent to enhance the water solubility of flavin mononucleotide. A redox flow battery using flavin mononucleotide negative and ferrocyanide positive electrolytes in strong base shows stable cycling performance, with over 99% capacity retention over the course of 100 cycles. We hypothesize that this is enabled due to the oxidized and reduced forms of FMN-Na being stabilized by resonance structures.

  8. Hydrogen peroxide and central redox theory for aerobic life: A tribute to Helmut Sies: Scout, trailblazer, and redox pioneer.

    Science.gov (United States)

    Jones, Dean P

    2016-04-01

    When Rafael Radi and I wrote about Helmut Sies for the Redox Pioneer series, I was disappointed that the Editor restricted us to the use of "Pioneer" in the title. My view is that Helmut was always ahead of the pioneers: He was a scout discovering paths for exploration and a trailblazer developing strategies and methods for discovery. I have known him for nearly 40 years and greatly enjoyed his collegiality as well as brilliance in scientific scholarship. He made monumental contributions to 20th century physiological chemistry beginning with his first measurement of H2O2 in rat liver. While continuous H2O2 production is dogma today, the concept of H2O2 production in mammalian tissues was largely buried for half a century. He continued this leadership in research on oxidative stress, GSH, selenium, and singlet oxygen, during the timeframe when physiological chemistry and biochemistry transitioned to contemporary 21st century systems biology. His impact has been extensive in medical and health sciences, especially in nutrition, aging, toxicology and cancer. I briefly summarize my interactions with Helmut, stressing our work together on the redox code, a set of principles to link mitochondrial respiration, bioenergetics, H2O2 metabolism, redox signaling and redox proteomics into central redox theory. Copyright © 2015 The Author. Published by Elsevier Inc. All rights reserved.

  9. Redox imbalance and mitochondrial abnormalities in the diabetic lung.

    Science.gov (United States)

    Wu, Jinzi; Jin, Zhen; Yan, Liang-Jun

    2017-04-01

    Although the lung is one of the least studied organs in diabetes, increasing evidence indicates that it is an inevitable target of diabetic complications. Nevertheless, the underlying biochemical mechanisms of lung injury in diabetes remain largely unexplored. Given that redox imbalance, oxidative stress, and mitochondrial dysfunction have been implicated in diabetic tissue injury, we set out to investigate mechanisms of lung injury in diabetes. The objective of this study was to evaluate NADH/NAD + redox status, oxidative stress, and mitochondrial abnormalities in the diabetic lung. Using STZ induced diabetes in rat as a model, we measured redox-imbalance related parameters including aldose reductase activity, level of poly ADP ribose polymerase (PAPR-1), NAD + content, NADPH content, reduced form of glutathione (GSH), and glucose 6-phophate dehydrogenase (G6PD) activity. For assessment of mitochondrial abnormalities in the diabetic lung, we measured the activities of mitochondrial electron transport chain complexes I to IV and complex V as well as dihydrolipoamide dehydrogenase (DLDH) content and activity. We also measured the protein content of NAD + dependent enzymes such as sirtuin3 (sirt3) and NAD(P)H: quinone oxidoreductase 1 (NQO1). Our results demonstrate that NADH/NAD + redox imbalance occurs in the diabetic lung. This redox imbalance upregulates the activities of complexes I to IV, but not complex V; and this upregulation is likely the source of increased mitochondrial ROS production, oxidative stress, and cell death in the diabetic lung. These results, together with the findings that the protein contents of DLDH, sirt3, and NQO1 all are decreased in the diabetic lung, demonstrate that redox imbalance, mitochondrial abnormality, and oxidative stress contribute to lung injury in diabetes. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

  10. Differentiating cancerous from normal breast tissue by redox imaging

    Science.gov (United States)

    Xu, He N.; Tchou, Julia; Feng, Min; Zhao, Huaqing; Li, Lin Z.

    2015-02-01

    Abnormal metabolism can be a hallmark of cancer occurring early before detectable histological changes and may serve as an early detection biomarker. The current gold standard to establish breast cancer (BC) diagnosis is histological examination of biopsy. Previously we have found that pre-cancer and cancer tissues in animal models displayed abnormal mitochondrial redox state. Our technique of quantitatively measuring the mitochondrial redox state has the potential to be implemented as an early detection tool for cancer and may provide prognostic value. We therefore in this present study, investigated the feasibility of quantifying the redox state of tumor samples from 16 BC patients. Tumor tissue aliquots were collected from both normal and cancerous tissue from the affected cancer-bearing breasts of 16 female patients (5 TNBC, 9 ER+, 2 ER+/Her2+) shortly after surgical resection. All specimens were snap-frozen with liquid nitrogen on site and scanned later with the Chance redox scanner, i.e., the 3D cryogenic NADH/oxidized flavoprotein (Fp) fluorescence imager. Our preliminary results showed that both NADH and Fp (including FAD, i.e., flavin adenine dinucleotide) signals in the cancerous tissues roughly tripled to quadrupled those in the normal tissues (pcancerous tissues than in the normal ones (pcancer and non-cancer breast tissues in human patients and this novel redox scanning procedure may assist in tissue diagnosis in freshly procured biopsy samples prior to tissue fixation. We are in the process of evaluating the prognostic value of the redox imaging indices for BC.

  11. A new class of solid oxide metal-air redox batteries for advanced stationary energy storage

    Science.gov (United States)

    Zhao, Xuan

    Cost-effective and large-scale energy storage technologies are a key enabler of grid modernization. Among energy storage technologies currently being researched, developed and deployed, rechargeable batteries are unique and important that can offer a myriad of advantages over the conventional large scale siting- and geography- constrained pumped-hydro and compressed-air energy storage systems. However, current rechargeable batteries still need many breakthroughs in material optimization and system design to become commercially viable for stationary energy storage. This PhD research project investigates the energy storage characteristics of a new class of rechargeable solid oxide metal-air redox batteries (SOMARBs) that combines a regenerative solid oxide fuel cell (RSOFC) and hydrogen chemical-looping component. The RSOFC serves as the "electrical functioning unit", alternating between the fuel cell and electrolysis mode to realize discharge and charge cycles, respectively, while the hydrogen chemical-looping component functions as an energy storage unit (ESU), performing electrical-chemical energy conversion in situ via a H2/H2O-mediated metal/metal oxide redox reaction. One of the distinctive features of the new battery from conventional storage batteries is the ESU that is physically separated from the electrodes of RSOFC, allowing it to freely expand and contract without impacting the mechanical integrity of the entire battery structure. This feature also allows an easy switch in the chemistry of this battery. The materials selection for ESU is critical to energy capacity, round-trip efficiency and cost effectiveness of the new battery. Me-MeOx redox couples with favorable thermodynamics and kinetics are highly preferable. The preliminary theoretical analysis suggests that Fe-based redox couples can be a promising candidate for operating at both high and low temperatures. Therefore, the Fe-based redox-couple systems have been selected as the baseline for this

  12. Highly Sensitive Electrochemical Sensor for the Detection of Anions in Water Based on a Redox-Active Monolayer Incorporating an Anion Receptor.

    Science.gov (United States)

    Kaur, Balwinder; Erdmann, Cristiane Andreia; Daniëls, Mathias; Dehaen, Wim; Rafiński, Zbigniew; Radecka, Hanna; Radecki, Jerzy

    2017-12-05

    In the present work, gold electrodes were modified using a redox-active layer based on dipyrromethene complexes with Cu(II) or Co(II) and a dipodal anion receptor functionalized with dipyrromethene. These modified gold electrodes were then applied for the electrochemical detection of anions (Cl - , SO 4 2- , and Br - ) in a highly diluted water solution (in the picomolar range). The results showed that both systems, incorporating Cu(II) as well as Co(II) redox centers, exhibited highest sensitivity toward Cl - . The selectivity sequence found for both systems was Cl - > SO 4 2- > Br - . The high selectivity of Cl - anions can be attributed to the higher binding constant of Cl - with the anion receptor and the stronger electronic effect between the central metal and anion in the complex. The detection limit for the determination of Cl - was found at the 1.0 pM level for both sensing systems. The electrodes based on Co(II) redox centers displayed better selectivity toward Cl - anion detection than those based on Cu(II) centers which can be attributed to the stronger electronic interaction between the receptor-target anion complex and the Co(II)/Co(III) redox centers in comparison to the Cu(II)/Cu(I) system. Applicability of gold electrodes modified with DPM-Co(II)-DPM-AR for the electrochemical determination of Cl - anions was demonstrated using the artificial matrix mimicking human serum.

  13. Electrochemical redox reactions in solvated silica sol-gel glass

    International Nuclear Information System (INIS)

    Opallo, M.

    2002-01-01

    The studies of electrochemical redox reactions in solvated silica sol-gel glass were reviewed. The methodology of the experiments with emphasis on the direct preparation of the solid electrolyte and the application ultra microelectrodes was described. Generally, the level of the electrochemical signal is not much below that observed in liquid electrolyte. The current depends on time elapsed after gelation, namely the longer time, the smaller current. The differences between electrochemical behaviour of the redox couples in monoliths and thin layers were described. (author)

  14. Solid-phase vibrational redox reactions in coordinated oxides

    International Nuclear Information System (INIS)

    Kostikova, G.P.; Korol'kov, D.V.; Kostikov, Yu.P.

    1996-01-01

    The properties of multicomponent oxides (YBa 2 Cu 3 O 7-x , etc.), incorporating different valency forms of each of two (or more) different elements have been compared with the properties of the known chemical systems, where vibrational (periodic) redox-reactions are realized a fortiori. The essence of the new theoretical concept suggested consists in the following: high-T c superconductivity of the complex oxides and similar compounds originates from vibrational redox reaction proceeding in solid phase and involving different valency atoms of every element

  15. Redox Dysregulation in the Pathophysiology of Schizophrenia and Bipolar Disorder

    DEFF Research Database (Denmark)

    Kulak, Anita; Steullet, Pascal; Cabungcal, Jan-Harry

    2013-01-01

    Abstract Significance: Schizophrenia (SZ) and bipolar disorder (BD) are classified as two distinct diseases. However, accumulating evidence shows that both disorders share genetic, pathological, and epidemiological characteristics. Based on genetic and functional findings, redox dysregulation due...... abnormal prefrontal levels of glutathione (GSH), the major cellular redox regulator and antioxidant. Here we review experimental data from rodent models demonstrating that permanent as well as transient GSH deficit results in behavioral, morphological, electrophysiological, and neurochemical alterations...... hypofunction, elevated glutamate levels, impairment of parvalbumin GABA interneurons, abnormal neuronal synchronization, altered dopamine neurotransmission, and deficient myelination. Critical Issues: Treatment with the GSH precursor and antioxidant N-acetylcysteine normalizes some of those deficits in mice...

  16. Liquid Quinones for Solvent-Free Redox Flow Batteries.

    Science.gov (United States)

    Shimizu, Akihiro; Takenaka, Keisuke; Handa, Naoyuki; Nokami, Toshiki; Itoh, Toshiyuki; Yoshida, Jun-Ichi

    2017-11-01

    Liquid benzoquinone and naphthoquinone having diethylene glycol monomethyl ether groups are designed and synthesized as redox active materials that dissolve supporting electrolytes. The Li-ion batteries based on the liquid quinones using LiBF 4 /PC show good performance in terms of voltage, capacity, energy efficiency, and cyclability in both static and flow modes. A battery is constructed without using intentionally added organic solvent, and its high energy density (264 W h L -1 ) demonstrates the potential of solvent-free organic redox flow batteries using liquid active materials. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Mechanistic studies of cancer cell mitochondria- and NQO1-mediated redox activation of beta-lapachone, a potentially novel anticancer agent

    International Nuclear Information System (INIS)

    Li, Jason Z.; Ke, Yuebin; Misra, Hara P.; Trush, Michael A.; Li, Y. Robert; Zhu, Hong; Jia, Zhenquan

    2014-01-01

    Beta-lapachone (beta-Lp) derived from the Lapacho tree is a potentially novel anticancer agent currently under clinical trials. Previous studies suggested that redox activation of beta-Lp catalyzed by NAD(P)H:quinone oxidoreductase 1 (NQO1) accounted for its killing of cancer cells. However, the exact mechanisms of this effect remain largely unknown. Using chemiluminescence and electron paramagnetic resonance (EPR) spin-trapping techniques, this study for the first time demonstrated the real-time formation of ROS in the redox activation of beta-lapachone from cancer cells mediated by mitochondria and NQO1 in melanoma B16–F10 and hepatocellular carcinoma HepG2 cancer cells. ES936, a highly selective NQO1 inhibitor, and rotenone, a selective inhibitor of mitochondrial electron transport chain (METC) complex I were found to significantly block beta-Lp meditated redox activation in B16–F10 cells. In HepG2 cells ES936 inhibited beta-Lp-mediated oxygen radical formation by ∼ 80% while rotenone exerted no significant effect. These results revealed the differential contribution of METC and NQO1 to beta-lapachone-induced ROS formation and cancer cell killing. In melanoma B16–F10 cells that do not express high NQO1 activity, both NOQ1 and METC play a critical role in beta-Lp redox activation. In contrast, in hepatocellular carcinoma HepG2 cells expressing extremely high NQO1 activity, redox activation of beta-Lp is primarily mediated by NQO1 (METC plays a minor role). These findings will contribute to our understanding of how cancer cells are selectively killed by beta-lapachone and increase our ability to devise strategies to enhance the anticancer efficacy of this potentially novel drug while minimizing its possible adverse effects on normal cells. - Highlights: • Both isolated mitochondria and purified NQO1 are able to generate ROS by beta-Lp. • The differential roles of mitochondria and NQO1 in mediating redox activation of beta-Lp • In cancer cells with

  18. Mechanistic studies of cancer cell mitochondria- and NQO1-mediated redox activation of beta-lapachone, a potentially novel anticancer agent

    Energy Technology Data Exchange (ETDEWEB)

    Li, Jason Z. [Virginia Tech CRC, Blacksburg, VA (United States); Ke, Yuebin [Shenzhen Center for Disease Control and Prevention, Shenzhen 518055 (China); Misra, Hara P. [Virginia Tech CRC, Blacksburg, VA (United States); Trush, Michael A. [Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD (United States); Li, Y. Robert [Campbell University School of Osteopathic Medicine, Buies Creek, NC (United States); Virginia Tech-Wake Forest University SBES, Blacksburg, VA (United States); Department of Biology, University of North Carolina at Greensboro, NC (United States); Zhu, Hong, E-mail: zhu@campbell.edu [Campbell University School of Osteopathic Medicine, Buies Creek, NC (United States); Jia, Zhenquan, E-mail: z_jia@uncg.edu [Department of Biology, University of North Carolina at Greensboro, NC (United States)

    2014-12-15

    Beta-lapachone (beta-Lp) derived from the Lapacho tree is a potentially novel anticancer agent currently under clinical trials. Previous studies suggested that redox activation of beta-Lp catalyzed by NAD(P)H:quinone oxidoreductase 1 (NQO1) accounted for its killing of cancer cells. However, the exact mechanisms of this effect remain largely unknown. Using chemiluminescence and electron paramagnetic resonance (EPR) spin-trapping techniques, this study for the first time demonstrated the real-time formation of ROS in the redox activation of beta-lapachone from cancer cells mediated by mitochondria and NQO1 in melanoma B16–F10 and hepatocellular carcinoma HepG2 cancer cells. ES936, a highly selective NQO1 inhibitor, and rotenone, a selective inhibitor of mitochondrial electron transport chain (METC) complex I were found to significantly block beta-Lp meditated redox activation in B16–F10 cells. In HepG2 cells ES936 inhibited beta-Lp-mediated oxygen radical formation by ∼ 80% while rotenone exerted no significant effect. These results revealed the differential contribution of METC and NQO1 to beta-lapachone-induced ROS formation and cancer cell killing. In melanoma B16–F10 cells that do not express high NQO1 activity, both NOQ1 and METC play a critical role in beta-Lp redox activation. In contrast, in hepatocellular carcinoma HepG2 cells expressing extremely high NQO1 activity, redox activation of beta-Lp is primarily mediated by NQO1 (METC plays a minor role). These findings will contribute to our understanding of how cancer cells are selectively killed by beta-lapachone and increase our ability to devise strategies to enhance the anticancer efficacy of this potentially novel drug while minimizing its possible adverse effects on normal cells. - Highlights: • Both isolated mitochondria and purified NQO1 are able to generate ROS by beta-Lp. • The differential roles of mitochondria and NQO1 in mediating redox activation of beta-Lp • In cancer cells with

  19. A novel redox-based switch: LMW-PTP oxidation enhances Grb2 binding and leads to ERK activation

    International Nuclear Information System (INIS)

    Giannoni, Elisa; Raugei, Giovanni; Chiarugi, Paola; Ramponi, Giampietro

    2006-01-01

    Low molecular weight-PTP has been reported as a redox-sensitive protein during both platelet-derived growth factor and integrin signalling. In response to oxidation the phosphatase undergoes a reversible inactivation, which in turn leads to the increase in tyrosine phosphorylation of its substrates and the properly executed anchorage-dependent proliferation program. Here, we report that an exogenous oxidative stress enhances LMW-PTP tyrosine phosphorylation, through oxidation/inactivation of the enzyme, thus preventing its auto-dephosphorylation activity. In particular, we observed a selective hyper-phosphorylation of Tyr132, that acts as a docking site for the adaptor protein Grb2. The redox-dependent enhancement of Grb2 recruitment to LMW-PTP ultimately leads to an improvement of ERK activation, likely triggering a prosurvival signal against the oxidant environment

  20. Gas-phase ion/ion reactions of peptides and proteins: acid/base, redox, and covalent chemistries.

    Science.gov (United States)

    Prentice, Boone M; McLuckey, Scott A

    2013-02-01

    Gas-phase ion/ion reactions are emerging as useful and flexible means for the manipulation and characterization of peptide and protein biopolymers. Acid/base-like chemical reactions (i.e., proton transfer reactions) and reduction/oxidation (redox) reactions (i.e., electron transfer reactions) represent relatively mature classes of gas-phase chemical reactions. Even so, especially in regards to redox chemistry, the widespread utility of these two types of chemistries is undergoing rapid growth and development. Additionally, a relatively new class of gas-phase ion/ion transformations is emerging which involves the selective formation of functional-group-specific covalent bonds. This feature details our current work and perspective on the developments and current capabilities of these three areas of ion/ion chemistry with an eye towards possible future directions of the field.

  1. Examination of Amine-Functionalised Anion-Exchange Membranes for Possible Use in the All-Vanadium Redox Flow Battery

    International Nuclear Information System (INIS)

    Mallinson, Sarah L.; Varcoe, John R.; Slade, Robert C.T.

    2014-01-01

    The applicability of amine-functionalised anion-exchange membranes (AEMs) for use in the all-vanadium redox flow battery has been studied. A selection of radiation-grafted aminated membranes functionalised with dimethylamine, trimethylamine or diazabicyclo(2,2,2)octane were extensively tested. The success of each grafting process was confirmed by Raman and infrared spectroscopies, titrimetry and ionic conductivity measurements. The amine-functionalised membranes were found to have poor thermo-oxidative stability and high vanadium cation permeabilities. The results highlight the importance of balancing ionic conductivity with vanadium cation permeability and indicate that amine-based functional groups may not be suitably stable for the membranes to remain true AEMs when in use in the all-vanadium redox flow battery

  2. Lateral transport of solutes in microfluidic channels using electrochemically generated gradients in redox-active surfactants.

    Science.gov (United States)

    Liu, Xiaoyang; Abbott, Nicholas L

    2011-04-15

    We report principles for a continuous flow process that can separate solutes based on a driving force for selective transport that is generated by a lateral concentration gradient of a redox-active surfactant across a microfluidic channel. Microfluidic channels fabricated with gold electrodes lining each vertical wall were used to electrochemically generate concentration gradients of the redox-active surfactant 11-ferrocenylundecyl-trimethylammonium bromide (FTMA) in a direction perpendicular to the flow. The interactions of three solutes (a hydrophobic dye, 1-phenylazo-2-naphthylamine (yellow AB), an amphiphilic molecule, 2-(4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s-indacene-3-pentanoyl)-1-hexadecanoyl-sn-glycero-3-phosphocholine (BODIPY C(5)-HPC), and an organic salt, 1-methylpyridinium-3-sulfonate (MPS)) with the lateral gradients in surfactant/micelle concentration were shown to drive the formation of solute-specific concentration gradients. Two distinct physical mechanisms were identified to lead to the solute concentration gradients: solubilization of solutes by micelles and differential adsorption of the solutes onto the walls of the microchannels in the presence of the surfactant concentration gradient. These two mechanisms were used to demonstrate delipidation of a mixture of BODIPY C(5)-HPC (lipid) and MPS and purification of BODIPY C(5)-HPC from a mixture of BODIPY C(5)-HPC and yellow AB. Overall, the results of this study demonstrate that lateral concentration gradients of redox-active surfactants formed within microfluidic channels can be used to transport solutes across the microfluidic channels in a solute-dependent manner. The approach employs electrical potentials (solutions having high ionic strength (>0.1M), and offers the basis of continuous processes for the purification or separation of solutes in microscale systems. © 2011 American Chemical Society

  3. Vegetation-induced spatial variability of soil redox properties in wetlands

    Science.gov (United States)

    Szalai, Zoltán; Jakab, Gergely; Kiss, Klaudia; Ringer, Marianna; Balázs, Réka; Zacháry, Dóra; Horváth Szabó, Kata; Perényi, Katalin

    2016-04-01

    Vegetation induced land patches may result spatial pattern of on soil Eh and pH. These spatial pattern are mainly emerged by differences of aeration and exudation of assimilates. Present paper focuses on vertical extent and temporal dynamics of these patterns in wetlands. Two study sites were selected: 1. a plain wetland on calcareous sandy parent material (Ceglédbercel, Danube-Tisza Interfluve, Hungary); 2. headwater wetland with calcareous loamy parent material (Bátaapáti, Hungary). Two vegetation patches were studied in site 1: sedgy (dominated by Carex riparia) and reedy (dominated by Phragmites australis). Three patches were studied in site2: sedgy1 (dominated by C vulpina), sedgy 2 (C. riparia); nettle-horsetail (Urtica dioica and Equisetum arvense). Boundaries between patches were studied separately. Soil redox, pH and temperature studied by automated remote controlled instruments. Three digital sensors (Ponsell) were installed in each locations: 20cm and 40cm sensors represent the solum and 100 cm sensor monitors the subsoil). Groundwater wells were installed near to triplets for soil water sampling. Soil Eh, pH and temperature values were recorded in each 10 minutes. Soil water sampling for iron and DOC were carried out during saturated periods. Spatial pattern of soil Eh is clearly caused by vegetation. We measured significant differences between Eh values of the studied patches in the solum. We did not find this kinds horizontal differences in the subsoil. Boundaries of the patches usually had more reductive soil environment than the core areas. We have found temporal dynamics of the spatial redox pattern. Differences were not so well expressed during wintertime. These spatial patterns had influence on the DOC and iron content of porewater, as well. Highest temporal dynamics of soil redox properties and porewater iron could be found in the boundaries. These observations refer to importance patchiness of vegetation on soil chemical properties in

  4. Imaging Mitochondrial Redox Potential and Its Possible Link to Tumor Metastatic Potential

    Science.gov (United States)

    Li, Lin Z.

    2012-01-01

    Cellular redox states can regulate cell metabolism, growth, differentiation, motility, apoptosis, signaling pathways, and gene expressions etc. Growing body of literature suggest importance of redox status for cancer progression. While most studies on redox state were done on cells and tissue lysates, it is important to understand the role of redox state in tissue in vivo/ex vivo and image its heterogeneity. Redox scanning is a clinically-translatable method for imaging tissue mitochondrial redox potential with a submillimeter resolution. Redox scanning data in mouse models of human cancers demonstrate a correlation between mitochondrial redox state and tumor metastatic potential. I will discuss the significance of this correlation and possible directions for future research. PMID:22895837

  5. Electron Transfer Reactivity Patterns at Chemically Modified Electrodes: Fundamentals and Application to the Optimization of Redox Recycling Amplification Systems

    Energy Technology Data Exchange (ETDEWEB)

    Bergren, Adam Johan [Iowa State Univ., Ames, IA (United States)

    2006-01-01

    Electroanalytical chemistry is often utilized in chemical analysis and Fundamental studies. Important advances have been made in these areas since the advent of chemically modified electrodes: the coating of an electrode with a chemical film in order to impart desirable, and ideally, predictable properties. These procedures enable the exploitation of unique reactivity patterns. This dissertation presents studies that investigate novel reaction mechanisms at self-assembled monolayers on gold. In particular, a unique electrochemical current amplification scheme is detailed that relies on a selective electrode to enable a reactivity pattern that results in regeneration of the analyte (redox recycling). This regenerating reaction can occur up to 250 times for each analyte molecule, leading to a notable enhancement in the observed current. The requirements of electrode selectivity and the resulting amplification and detection limit improvements are described with respect to the heterogeneous and homogeneous electron transfer rates that characterize the system. These studies revealed that the heterogeneous electrolysis of the analyte should ideally be electrochemically reversible, while that for the regenerating agent should be held to a low level. Moreover, the homogeneous reaction that recycles the analyte should occur at a rapid rate. The physical selectivity mechanism is also detailed with respect to the properties of the electrode and redox probes utilized. It is shown that partitioning of the analyte into/onto the adlayer leads to the extraordinary selectivity of the alkanethiolate monolayer modified electrode. Collectively, these studies enable a thorough understanding of the complex electrode mechanism required for successful redox recycling amplification systems, Finally, in a separate (but related) study, the effect of the akyl chain length on the heterogeneous electron transfer behavior of solution-based redox probes is reported, where an odd-even oscillation

  6. Redox chemistry and natural organic matter (NOM): Geochemists' dream, analytical chemists' nightmare

    Science.gov (United States)

    Macalady, Donald L.; Walton-Day, Katherine

    2011-01-01

    Natural organic matter (NOM) is an inherently complex mixture of polyfunctional organic molecules. Because of their universality and chemical reversibility, oxidation/reductions (redox) reactions of NOM have an especially interesting and important role in geochemistry. Variabilities in NOM composition and chemistry make studies of its redox chemistry particularly challenging, and details of NOM-mediated redox reactions are only partially understood. This is in large part due to the analytical difficulties associated with NOM characterization and the wide range of reagents and experimental systems used to study NOM redox reactions. This chapter provides a summary of the ongoing efforts to provide a coherent comprehension of aqueous redox chemistry involving NOM and of techniques for chemical characterization of NOM. It also describes some attempts to confirm the roles of different structural moieties in redox reactions. In addition, we discuss some of the operational parameters used to describe NOM redox capacities and redox states, and describe nomenclature of NOM redox chemistry. Several relatively facile experimental methods applicable to predictions of the NOM redox activity and redox states of NOM samples are discussed, with special attention to the proposed use of fluorescence spectroscopy to predict relevant redox characteristics of NOM samples.

  7. Redox non-innocent ligands: versatile new tools to control catalytic reactions

    NARCIS (Netherlands)

    Lyaskovskyy, V.; de Bruin, B.

    2012-01-01

    In this (tutorial overview) perspective we highlight the use of "redox non-innocent" ligands in catalysis. Two main types of reactivity in which the redox non-innocent ligand is involved can be specified: (A) The redox active ligand participates in the catalytic cycle only by accepting/donating

  8. Separate effects of flooding and anaerobiosis on soil greenhouse gas emissions and redox sensitive biogeochemistry

    Science.gov (United States)

    Gavin McNicol; Whendee L. Silver

    2014-01-01

    Soils are large sources of atmospheric greenhouse gases, and both the magnitude and composition of soil gas emissions are strongly controlled by redox conditions. Though the effect of redox dynamics on greenhouse gas emissions has been well studied in flooded soils, less research has focused on redox dynamics without total soil inundation. For the latter, all that is...

  9. Redox Modulation by Amaranth Oil in Human Lung Fibroblasts

    NARCIS (Netherlands)

    Semen, K.O.; den Hartog, G.J.M.; Kaminsky, D.V.; Sirota, T.V.; Maij, N.G.A.A.; Yelisyeyeva, O.P.; Bast, A.

    2013-01-01

    Amaranth oil has several health benefits. It has lipid lowering, anti-diabetic, immune modulatory and cytoprotective properties, activates the function of mitochondria and improves heart rate variability. It has been suggested that the effect of amaranth oil on redox status is involved in this

  10. Reductant-dependent electron distribution among redox sites of laccase

    DEFF Research Database (Denmark)

    Farver, O; Goldberg, M; Wherland, S

    1978-01-01

    Rhus laccase (monophenol monooxygenase, monophenol,dihydroxyphenylalanine:oxygen oxidoreductase, EC 1.14.18.1) an O2/H2O oxidoreductase containing four copper ions bound to three redox sites (type 1, type 2, and type 3 Cu pair), was titrated anaerobically with several reductants having various ch...

  11. S-Glutathionylation and Redox Protein Signaling in Drug Addiction.

    Science.gov (United States)

    Womersley, Jacqueline S; Uys, Joachim D

    2016-01-01

    Drug addiction is a chronic relapsing disorder that comes at a high cost to individuals and society. Therefore understanding the mechanisms by which drugs exert their effects is of prime importance. Drugs of abuse increase the production of reactive oxygen and nitrogen species resulting in oxidative stress. This change in redox homeostasis increases the conjugation of glutathione to protein cysteine residues; a process called S-glutathionylation. Although traditionally regarded as a protective mechanism against irreversible protein oxidation, accumulated evidence suggests a more nuanced role for S-glutathionylation, namely as a mediator in redox-sensitive protein signaling. The reversible modification of protein thiols leading to alteration in function under different physiologic/pathologic conditions provides a mechanism whereby change in redox status can be translated into a functional response. As such, S-glutathionylation represents an understudied means of post-translational protein modification that may be important in the mechanisms underlying drug addiction. This review will discuss the evidence for S-glutathionylation as a redox-sensing mechanism and how this may be involved in the response to drug-induced oxidative stress. The function of S-glutathionylated proteins involved in neurotransmission, dendritic spine structure, and drug-induced behavioral outputs will be reviewed with specific reference to alcohol, cocaine, and heroin. Copyright © 2016. Published by Elsevier Inc.

  12. Characterization of redox conditions in groundwater contaminant plumes

    DEFF Research Database (Denmark)

    Christensen, Thomas Højlund; Bjerg, Poul Løgstrup; Banwarth, Steven A.

    2000-01-01

    tools, such as MPN counts, PLFA biomarkers and redox bioassays. This paper reviews the principles behind the different approaches, summarizes methods used and evaluates the approaches based on the experience from the reported applications. C 2000 Elsevier Science B.V. All rights reserved....

  13. TWO IDEAS OF THE REDOX REACTION: MISCONCEPTIONS AND ...

    African Journals Online (AJOL)

    Preferred Customer

    1), or with the reaction of iron and a copper sulfate solution (see Fig. 2). ... Since neither the young people know the historical approach to the explanation of ... everyday life the concept of electron transfer in redox reactions, a good instruction on ..... Improving teaching and learning through chemistry education research: A.

  14. Immobilization of redox mediators on functionalized carbon nanotube

    Indian Academy of Sciences (India)

    Chemical functionalization of single-walled carbon nanotubes with redox mediators, namely, toluidine blue and thionin have been carried out and the performance of graphite electrode modified with functionalized carbon nanotubes is described. Mechanical immobilization of functionalized single-walled nanotube (SWNT) ...

  15. Modelling non-redox enzymes: Anaerobic and aerobic acetylene ...

    Indian Academy of Sciences (India)

    Administrator

    Modelling non-redox enzymes: Anaerobic and aerobic acetylene hydratase. SABYASACHI SARKAR. Department of Chemistry, Indian Institute of Technology, Kanpur 208 016,. India. Acetaldehyde is the first metabolite produced during acetylene degradation by bacteria either aerobically or anaerobically. Conversion of ...

  16. Vanadium and Chromium Redox Behavior in borosilicate Nuclear Waste Glasses

    International Nuclear Information System (INIS)

    McKeown, D.; Muller, I.; Gan, H.; Feng, Z.; Viragh, C.; Pegg, I.

    2011-01-01

    X-ray absorption spectroscopy (XAS) was used to characterize vanadium (V) and chromium (Cr) environments in low activity nuclear waste (LAW) glasses synthesized under a variety of redox conditions. V 2 O 5 was added to the melt to improve sulfur incorporation from the waste; however, at sufficiently high concentrations, V increased melt foaming, which lowered melt processing rates. Foaming may be reduced by varying the redox conditions of the melt, while small amounts of Cr are added to reduce melter refractory corrosion. Three parent glasses were studied, where CO-CO 2 mixtures were bubbled through the corresponding melt for increasing time intervals so that a series of redox-adjusted-glasses was synthesized from each parent glass. XAS data indicated that V and Cr behaviors are significantly different in these glasses with respect to the cumulative gas bubbling times: V 4+ /V total ranges from 8 to 35%, while Cr 3+ /Cr total can range from 15 to 100% and even to population distributions including Cr 2+ . As Na-content decreased, V, and especially, Cr became more reduced, when comparing equivalent glasses within a series. The Na-poor glass series show possible redox coupling between V and Cr, where V 4+ populations increase after initial bubbling, but as bubbling time increases, V 4+ populations drop to near the level of the parent glass, while Cr becomes more reduced to the point of having increasing Cr 2+ populations.

  17. Hemoglobin redox reactions and red blood cell aging.

    Science.gov (United States)

    Rifkind, Joseph M; Nagababu, Enika

    2013-06-10

    The physiological mechanism(s) for recognition and removal of red blood cells (RBCs) from circulation after 120 days of its lifespan is not fully understood. Many of the processes thought to be associated with the removal of RBCs involve oxidative stress. We have focused on hemoglobin (Hb) redox reactions, which is the major source of RBC oxidative stress. The importance of Hb redox reactions have been shown to originate in large parts from the continuous slow autoxidation of Hb producing superoxide and its dramatic increase under hypoxic conditions. In addition, oxidative stress has been shown to be associated with redox reactions that originate from Hb reactions with nitrite and nitric oxide (NO) and the resultant formation of highly toxic peroxynitrite when NO reacts with superoxide released during Hb autoxidation. The interaction of Hb, particularly under hypoxic conditions with band 3 of the RBC membrane is critical for the generating the RBC membrane changes that trigger the removal of cells from circulation. These changes include exposure of antigenic sites, increased calcium leakage into the RBC, and the resultant leakage of potassium out of the RBC causing cell shrinkage and impaired deformability. The need to understand the oxidative damage to specific membrane proteins that result from redox reactions occurring when Hb is bound to the membrane. Proteomic studies that can pinpoint the specific proteins damaged under different conditions will help elucidate the cellular aging processes that result in cells being removed from circulation.

  18. Molecular controls of the oxygenation and redox reactions of hemoglobin.

    Science.gov (United States)

    Bonaventura, Celia; Henkens, Robert; Alayash, Abdu I; Banerjee, Sambuddha; Crumbliss, Alvin L

    2013-06-10

    The broad classes of O(2)-binding proteins known as hemoglobins (Hbs) carry out oxygenation and redox functions that allow organisms with significantly different physiological demands to exist in a wide range of environments. This is aided by allosteric controls that modulate the protein's redox reactions as well as its O(2)-binding functions. The controls of Hb's redox reactions can differ appreciably from the molecular controls for Hb oxygenation and come into play in elegant mechanisms for dealing with nitrosative stress, in the malarial resistance conferred by sickle cell Hb, and in the as-yet unsuccessful designs for safe and effective blood substitutes. An important basic principle in consideration of Hb's redox reactions is the distinction between kinetic and thermodynamic reaction control. Clarification of these modes of control is critical to gaining an increased understanding of Hb-mediated oxidative processes and oxidative toxicity in vivo. This review addresses emerging concepts and some unresolved questions regarding the interplay between the oxygenation and oxidation reactions of structurally diverse Hbs, both within red blood cells and under acellular conditions. Developing methods that control Hb-mediated oxidative toxicity will be critical to the future development of Hb-based blood substitutes.

  19. Differential alkylation-based redox proteomics – Lessons learnt

    Science.gov (United States)

    Wojdyla, Katarzyna; Rogowska-Wrzesinska, Adelina

    2015-01-01

    Cysteine is one of the most reactive amino acids. This is due to the electronegativity of sulphur atom in the side chain of thiolate group. It results in cysteine being present in several distinct redox forms inside the cell. Amongst these, reversible oxidations, S-nitrosylation and S-sulfenylation are crucial mediators of intracellular redox signalling, with known associations to health and disease. Study of their functionalities has intensified thanks to the development of various analytical strategies, with particular contribution from differential alkylation-based proteomics methods. Presented here is a critical evaluation of differential alkylation-based strategies for the analysis of S-nitrosylation and S-sulfenylation. The aim is to assess the current status and to provide insights for future directions in the dynamically evolving field of redox proteomics. To achieve that we collected 35 original research articles published since 2010 and analysed them considering the following parameters, (i) resolution of modification site, (ii) quantitative information, including correction of modification levels by protein abundance changes and determination of modification site occupancy, (iii) throughput, including the amount of starting material required for analysis. The results of this meta-analysis are the core of this review, complemented by issues related to biological models and sample preparation in redox proteomics, including conditions for free thiol blocking and labelling of target cysteine oxoforms. PMID:26282677

  20. Differential alkylation-based redox proteomics--Lessons learnt.

    Science.gov (United States)

    Wojdyla, Katarzyna; Rogowska-Wrzesinska, Adelina

    2015-12-01

    Cysteine is one of the most reactive amino acids. This is due to the electronegativity of sulphur atom in the side chain of thiolate group. It results in cysteine being present in several distinct redox forms inside the cell. Amongst these, reversible oxidations, S-nitrosylation and S-sulfenylation are crucial mediators of intracellular redox signalling, with known associations to health and disease. Study of their functionalities has intensified thanks to the development of various analytical strategies, with particular contribution from differential alkylation-based proteomics methods. Presented here is a critical evaluation of differential alkylation-based strategies for the analysis of S-nitrosylation and S-sulfenylation. The aim is to assess the current status and to provide insights for future directions in the dynamically evolving field of redox proteomics. To achieve that we collected 35 original research articles published since 2010 and analysed them considering the following parameters, (i) resolution of modification site, (ii) quantitative information, including correction of modification levels by protein abundance changes and determination of modification site occupancy, (iii) throughput, including the amount of starting material required for analysis. The results of this meta-analysis are the core of this review, complemented by issues related to biological models and sample preparation in redox proteomics, including conditions for free thiol blocking and labelling of target cysteine oxoforms. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.

  1. Synthesis, spectral characterization and redox properties of iron (II ...

    Indian Academy of Sciences (India)

    Unknown

    Arylazoheterocycles and their chemistry of transition and non-transition metals have been explored for more than two decades.1 Owing to their pH-response, photoactivity, light electron communication, stabilization of low valent metal oxidation state, exhibition of serial redox states of complexes, isolation of anion radicals, ...

  2. Redox Potentials of Ligands and Complexes – a DFT Approach

    African Journals Online (AJOL)

    NICO

    A review of the limited literature concerned with theoretical ways to predict experimentally measured redox potentials of ligands and ... electrode surface, over-potentials and high solvent resistance, ... A correlation coefficient of 0.969 in the linear relation with ... of E0' were performed in two steps, i.e. calculation of the free.

  3. Redox Polymerization of Methyl Methacrylate in the Fluorous Triphasic System

    Institute of Scientific and Technical Information of China (English)

    Shi Zhen CHEN; Yun Peng BAI; Zhao Long LI

    2006-01-01

    Methyl methacrylate (MMA) was polymerized by using of benzoyl peroxide (BPO) and N, N-dimethylaniline (DMA) as an redox initiator in fluorous triphasic system at room temperature.The polymerization was occurred in both initiator layer and monomer layer in a U-tube. It was found that PMMA obtained from the initiator layer with relatively narrow polydispersity.(PDI =1.38)

  4. The Tumorigenic Roles of the Cellular REDOX Regulatory Systems

    Directory of Open Access Journals (Sweden)

    Stéphanie Anaís Castaldo

    2016-01-01

    Full Text Available The cellular REDOX regulatory systems play a central role in maintaining REDOX homeostasis that is crucial for cell integrity, survival, and proliferation. To date, a substantial amount of data has demonstrated that cancer cells typically undergo increasing oxidative stress as the tumor develops, upregulating these important antioxidant systems in order to survive, proliferate, and metastasize under these extreme oxidative stress conditions. Since a large number of chemotherapeutic agents currently used in the clinic rely on the induction of ROS overload or change of ROS quality to kill the tumor, the cancer cell REDOX adaptation represents a significant obstacle to conventional chemotherapy. In this review we will first examine the different factors that contribute to the enhanced oxidative stress generally observed within the tumor microenvironment. We will then make a comprehensive assessment of the current literature regarding the main antioxidant proteins and systems that have been shown to be positively associated with tumor progression and chemoresistance. Finally we will make an analysis of commonly used chemotherapeutic drugs that induce ROS. The current knowledge of cancer cell REDOX adaptation raises the issue of developing novel and more effective therapies for these tumors that are usually resistant to conventional ROS inducing chemotherapy.

  5. Redox potentials of free radicals. III. Reevaluation of the method

    International Nuclear Information System (INIS)

    Rao, P.S.; Hayon, E.

    1974-01-01

    A reevaluation of the method described in ref 1 and 2 to determine the redox potentials of free radicals (.RH) in water using the techniques of pulse radiolysis and absorption spectrophotometry is presented. This method is based on the dependence of the percentage efficiency for the one-electron oxidation (or reduction) of .RH radicals on the redox potentials E 01 of the electron acceptors, A. The reaction .RH + A → .A - + R + H + (kappa/sub ox/) is not reversible for most radicals under the experimental conditions used, and the derived potentials are, therefore, not thermodynamic values. A reinterpretation of the results is made on the basis of the kinetic competition between the above reaction and .RH + A → .RHA (kappa/sub add/) (radical adducts). Based on kappa/ sub ox/ and kappa/sub add/, it is concluded that the observed experimental ''titration'' curves do represent a measure of the redox property of the free radicals. From the midpoint on the curves, the kinetic potential, E/sub kappa/ 01 : of the free radicals can be derived based on the known two-electron redox potentials of the electron acceptors. These and other questions are discussed. (U.S.)

  6. Self-affine roughness influence on redox reaction charge admittance

    NARCIS (Netherlands)

    Palasantzas, G

    2005-01-01

    In this work we investigate the influence of self-affine electrode roughness on the admittance of redox reactions during facile charge transfer kinetics. The self-affine roughness is characterized by the rms roughness amplitude w, the correlation length xi and the roughness exponent H (0

  7. Metathetical Redox Reaction of (Diacetoxyiodo)arenes and Iodoarenes.

    Science.gov (United States)

    Jobin-Des Lauriers, Antoine; Legault, Claude Y

    2015-12-17

    The oxidation of iodoarenes is central to the field of hypervalent iodine chemistry. It was found that the metathetical redox reaction between (diacetoxyiodo)arenes and iodoarenes is possible in the presence of a catalytic amount of Lewis acid. This discovery opens a new strategy to access (diacetoxyiodo)arenes. A computational study is provided to rationalize the results observed.

  8. Chemical Principles Revisited. Redox Reactions and the Electropotential Axis.

    Science.gov (United States)

    Vella, Alfred J.

    1990-01-01

    This paper suggests a nontraditional pedagogic approach to the subject of redox reactions and electrode potentials suitable for freshman chemistry. Presented is a method for the representation of galvanic cells without the introduction of the symbology and notation of conventional cell diagrams. (CW)

  9. Procedures for Decomposing a Redox Reaction into Half-Reaction

    Science.gov (United States)

    Fishtik, Ilie; Berka, Ladislav H.

    2005-01-01

    A simple algorithm for a complete enumeration of the possible ways a redox reaction (RR) might be uniquely decomposed into half-reactions (HRs) using the response reactions (RERs) formalism is presented. A complete enumeration of the possible ways a RR may be decomposed into HRs is equivalent to a complete enumeration of stoichiometrically…

  10. The iodine/iodide redox couple at a platinum electrode

    NARCIS (Netherlands)

    Dane, L.M.; Janssen, L.J.J.; Hoogland, J.G.

    1968-01-01

    The I/iodide redox couple was studied on Pt in 0.5M H2SO4 by measuring the impedance as a function of frequency. From these measurements, the exchange c.d. j0 was derived according to Sluyters. The dependence of j0 on the reversible potential and the I and the iodide concns. was established. By

  11. Electron Transfer in Flavodoxin-based Redox Maquettes

    NARCIS (Netherlands)

    Alagaratnam, S.

    2005-01-01

    Small redox proteins play the role of electron taxis in the cell, picking electrons up at one location and delivering them at another. While it is known that these reactions are the basis for the processes of energy generation by respiration and photosynthesis, the means by which these 'taxis'

  12. Connecting Biology to Electronics: Molecular Communication via Redox Modality.

    Science.gov (United States)

    Liu, Yi; Li, Jinyang; Tschirhart, Tanya; Terrell, Jessica L; Kim, Eunkyoung; Tsao, Chen-Yu; Kelly, Deanna L; Bentley, William E; Payne, Gregory F

    2017-12-01

    Biology and electronics are both expert at for accessing, analyzing, and responding to information. Biology uses ions, small molecules, and macromolecules to receive, analyze, store, and transmit information, whereas electronic devices receive input in the form of electromagnetic radiation, process the information using electrons, and then transmit output as electromagnetic waves. Generating the capabilities to connect biology-electronic modalities offers exciting opportunities to shape the future of biosensors, point-of-care medicine, and wearable/implantable devices. Redox reactions offer unique opportunities for bio-device communication that spans the molecular modalities of biology and electrical modality of devices. Here, an approach to search for redox information through an interactive electrochemical probing that is analogous to sonar is adopted. The capabilities of this approach to access global chemical information as well as information of specific redox-active chemical entities are illustrated using recent examples. An example of the use of synthetic biology to recognize external molecular information, process this information through intracellular signal transduction pathways, and generate output responses that can be detected by electrical modalities is also provided. Finally, exciting results in the use of redox reactions to actuate biology are provided to illustrate that synthetic biology offers the potential to guide biological response through electrical cues. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Redox Biology Course Evaluation Form | Center for Cancer Research

    Science.gov (United States)

    To improve the Redox Biology (RB) course in future years, we would appreciate your feedback by completing this course evaluation. Please score the course elements as poor, fair, average, good or excellent. Please type any comments that you have in response to the questions at the bottom of the form. Remember to include your name as you wish it to appear on the certificate.

  14. Redox Biology Final Examination 2016 | Center for Cancer Research

    Science.gov (United States)

    Numerous registrants have requested a certificate upon completion of the Redox Biology (RB) course. In order to obtain a certificate, you must answer 8 of the 12 questions below correctly. In the final examination, 1 question is derived from each of the 1-hour lectures. It is highly recommended that you have a copy of each PowerPoint presentation prior to taking the

  15. Redox environment in stem and differentiated cells: A quantitative approach.

    Science.gov (United States)

    Lyublinskaya, O G; Ivanova, Ju S; Pugovkina, N A; Kozhukharova, I V; Kovaleva, Z V; Shatrova, A N; Aksenov, N D; Zenin, V V; Kaulin, Yu A; Gamaley, I A; Nikolsky, N N

    2017-08-01

    Stem cells are believed to maintain a specific intracellular redox status through a combination of enhanced removal capacity and limited production of ROS. In the present study, we challenge this assumption by developing a quantitative approach for the analysis of the pro- and antioxidant ability of human embryonic stem cells in comparison with their differentiated descendants, as well as adult stem and non-stem cells. Our measurements showed that embryonic stem cells are characterized by low ROS level, low rate of extracellular hydrogen peroxide removal and low threshold for peroxide-induced cytotoxicity. However, biochemical normalization of these parameters to cell volume/protein leads to matching of normalized values in stem and differentiated cells and shows that tested in the present study cells (human embryonic stem cells and their fibroblast-like progenies, adult mesenchymal stem cells, lymphocytes, HeLa) maintain similar intracellular redox status. Based on these observations, we propose to use ROS concentration averaged over the cell volume instead of ROS level as a measure of intracellular redox balance. We show that attempts to use ROS level for comparative analysis of redox status of morphologically different cells could lead to false conclusions. Methods for the assessment of ROS concentration based on flow cytometry analysis with the use of H 2 DCFDA dye and HyPer, genetically encoded probe for hydrogen peroxide, are discussed. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

  16. Actin filaments – a target for redox regulation

    Science.gov (United States)

    Wilson, Carlos; Terman, Jonathan R.; González-Billault, Christian; Ahmed, Giasuddin

    2016-01-01

    Actin and its ability to polymerize into dynamic filaments is critical for the form and function of cells throughout the body. While multiple proteins have been characterized as affecting actin dynamics through non-covalent means, actin and its protein regulators are also susceptible to covalent modifications of their amino acid residues. In this regard, oxidation-reduction (Redox) intermediates have emerged as key modulators of the actin cytoskeleton with multiple different effects on cellular form and function. Here, we review work implicating Redox intermediates in post-translationally altering actin and discuss what is known regarding how these alterations affect the properties of actin. We also focus on two of the best characterized enzymatic sources of these Redox intermediates – the NADPH oxidase NOX and the flavoprotein monooxygenase MICAL – and detail how they have both been identified as altering actin, but share little similarity and employ different means to regulate actin dynamics. Finally, we discuss the role of these enzymes and redox signaling in regulating the actin cytoskeleton in vivo and highlight their importance for neuronal form and function in health and disease. PMID:27309342

  17. Differential alkylation-based redox proteomics - Lessons learnt

    DEFF Research Database (Denmark)

    Wojdyla, Katarzyna; Rogowska-Wrzesinska, Adelina

    2015-01-01

    Cysteine is one of the most reactive amino acids. This is due to the electronegativity of sulphur atom in the side chain of thiolate group. It results in cysteine being present in several distinct redox forms inside the cell. Amongst these, reversible oxidations, S-nitrosylation and S-sulfenylati......Cysteine is one of the most reactive amino acids. This is due to the electronegativity of sulphur atom in the side chain of thiolate group. It results in cysteine being present in several distinct redox forms inside the cell. Amongst these, reversible oxidations, S-nitrosylation and S......-sulfenylation are crucial mediators of intracellular redox signalling, with known associations to health and disease. Study of their functionalities has intensified thanks to the development of various analytical strategies, with particular contribution from differential alkylation-based proteomics methods. Presented here...... is a critical evaluation of differential alkylation-based strategies for the analysis of S-nitrosylation and S-sulfenylation. The aim is to assess the current status and to provide insights for future directions in the dynamically evolving field of redox proteomics. To achieve that we collected 35 original...

  18. Redox zones of a landfill leachate pollution plume (Vejen, Denmark)

    DEFF Research Database (Denmark)

    Lyngkilde, John; Christensen, Thomas Højlund

    1992-01-01

    Downgradient from an old municipal landfill allowing leachate, rich in dissolved organic carbon, to enter a shallow sandy aerobic aquifer, a sequence of redoxe zones is identified from groundwater chemical analysis. Below the landfill, methanogenic conditions prevail, followed by sulfidogenic...... the fate of reactive pollutants leached from the landfill....

  19. Hunting for low abundant redox proteins in plant plasma membranes.

    Science.gov (United States)

    Lüthje, Sabine; Hopff, David; Schmitt, Anna; Meisrimler, Claudia-Nicole; Menckhoff, Ljiljana

    2009-04-13

    Nowadays electron transport (redox) systems in plasma membranes appear well established. Members of the flavocytochrome b family have been identified by their nucleotide acid sequences and characterized on the transcriptional level. For their gene products functions have been demonstrated in iron uptake and oxidative stress including biotic interactions, abiotic stress factors and plant development. In addition, NAD(P)H-dependent oxidoreductases and b-type cytochromes have been purified and characterized from plasma membranes. Several of these proteins seem to belong to the group of hypothetical or unknown proteins. Low abundance and the lack of amino acid sequence data for these proteins still hamper their functional analysis. Consequently, little is known about the physiological function and regulation of these enzymes. In recent years evidence has been presented for the existence of microdomains (so-called lipid rafts) in plasma membranes and their interaction with specific membrane proteins. The identification of redox systems in detergent insoluble membranes supports the idea that redox systems may have important functions in signal transduction, stress responses, cell wall metabolism, and transport processes. This review summarizes our present knowledge on plasma membrane redox proteins and discusses alternative strategies to investigate the function and regulation of these enzymes.

  20. Towards a thermally regenerative all-copper redox flow battery

    OpenAIRE

    Peljo, Pekka; Lloyd, David; Nguyet, Doan; Majaneva, Marko; Kontturi, Kyosti

    2014-01-01

    An all-copper redox flow battery based on strong complexation of Cu+ with acetonitrile is demonstrated, exhibiting reasonable battery performance. More interestingly, the battery can be charged by heat sources of 100 degrees C, by distilling off the acetonitrile. This destabilizes the Cu+ complex, leading to recovery of the starting materials.

  1. Towards a thermally regenerative all-copper redox flow battery.

    Science.gov (United States)

    Peljo, Pekka; Lloyd, David; Doan, Nguyet; Majaneva, Marko; Kontturi, Kyösti

    2014-02-21

    An all-copper redox flow battery based on strong complexation of Cu(+) with acetonitrile is demonstrated, exhibiting reasonable battery performance. More interestingly, the battery can be charged by heat sources of 100 °C, by distilling off the acetonitrile. This destabilizes the Cu(+) complex, leading to recovery of the starting materials.

  2. Elucidation of the Mechanism of Redox Grafting of Diazotated Anthraquinone

    DEFF Research Database (Denmark)

    Chernyy, Sergey; Bousquet, Antoine; Torbensen, Kristian

    2012-01-01

    . Scanning electrochemical microscopy was used to study the relationship between the conductivity of thefilm and the charging level of the AQ redox units in the grafted film. For that purpose, approach curves were recorded at a platinum ultramicroelectrode for AQ-containing films on gold and glassy carbon...

  3. Effects of Endotoxin and Psychological Stress on Redox Physiology, Immunity and Feather Corticosterone in Greenfinches.

    Directory of Open Access Journals (Sweden)

    Richard Meitern

    Full Text Available Assessment of costs accompanying activation of immune system and related neuroendocrine pathways is essential for understanding the selective forces operating on these systems. Here we attempted to detect such costs in terms of disruption to redox balance and interference between different immune system components in captive wild-caught greenfinches (Carduelis chloris. Study birds were subjected to an endotoxin-induced inflammatory challenge and temporary exposure to a psychological stressor (an image of a predator in a 2*2 factorial experiment. Injection of bacterial endotoxin resulted in up-regulation of two markers of antioxidant protection - erythrocyte glutathione, and plasma oxygen radical absorbance (OXY. These findings suggest that inflammatory responses alter redox homeostasis. However, no effect on markers of oxidative damage to proteins or DNA in erythrocytes could be detected. We found no evidence that the endotoxin injection interfered with antibody production against Brucella abortus antigen or the intensity of chronic coccidiosis. The hypothesis of within-immune system trade-offs as a cost of immunity was thus not supported in our model system. We showed for the first time that administration of endotoxin can reduce the level of corticosterone deposited into feathers. This finding suggests a down-regulation of the corticosterone secretion cascade due to an endotoxin-induced immune response, a phenomenon that has not been reported previously. Exposure to the predator image did not affect any of the measured physiological parameters.

  4. Porphyrin-Based Symmetric Redox-Flow Batteries towards Cold-Climate Energy Storage.

    Science.gov (United States)

    Ma, Ting; Pan, Zeng; Miao, Licheng; Chen, Chengcheng; Han, Mo; Shang, Zhenfeng; Chen, Jun

    2018-03-12

    Electrochemical energy storage with redox-flow batteries (RFBs) under subzero temperature is of great significance for the use of renewable energy in cold regions. However, RFBs are generally used above 10 °C. Herein we present non-aqueous organic RFBs based on 5,10,15,20-tetraphenylporphyrin (H 2 TPP) as a bipolar redox-active material (anode: [H 2 TPP] 2- /H 2 TPP, cathode: H 2 TPP/[H 2 TPP] 2+ ) and a Y-zeolite-poly(vinylidene fluoride) (Y-PVDF) ion-selective membrane with high ionic conductivity as a separator. The constructed RFBs exhibit a high volumetric capacity of 8.72 Ah L -1 with a high voltage of 2.83 V and excellent cycling stability (capacity retention exceeding 99.98 % per cycle) in the temperature range between 20 and -40 °C. Our study highlights principles for the design of RFBs that operate at low temperatures, thus offering a promising approach to electrochemical energy storage under cold-climate conditions. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Room Temperature, Hybrid Sodium-Based Flow Batteries with Multi-Electron Transfer Redox Reactions

    Science.gov (United States)

    Shamie, Jack S.; Liu, Caihong; Shaw, Leon L.; Sprenkle, Vincent L.

    2015-01-01

    We introduce a new concept of hybrid Na-based flow batteries (HNFBs) with a molten Na alloy anode in conjunction with a flowing catholyte separated by a solid Na-ion exchange membrane for grid-scale energy storage. Such HNFBs can operate at ambient temperature, allow catholytes to have multiple electron transfer redox reactions per active ion, offer wide selection of catholyte chemistries with multiple active ions to couple with the highly negative Na alloy anode, and enable the use of both aqueous and non-aqueous catholytes. Further, the molten Na alloy anode permits the decoupled design of power and energy since a large volume of the molten Na alloy can be used with a limited ion-exchange membrane size. In this proof-of-concept study, the feasibility of multi-electron transfer redox reactions per active ion and multiple active ions for catholytes has been demonstrated. The critical barriers to mature this new HNFBs have also been explored. PMID:26063629

  6. Unleashing the Power and Energy of LiFePO4-Based Redox Flow Lithium Battery with a Bifunctional Redox Mediator.

    Science.gov (United States)

    Zhu, Yun Guang; Du, Yonghua; Jia, Chuankun; Zhou, Mingyue; Fan, Li; Wang, Xingzhu; Wang, Qing

    2017-05-10

    Redox flow batteries, despite great operation flexibility and scalability for large-scale energy storage, suffer from low energy density and relatively high cost as compared to the state-of-the-art Li-ion batteries. Here we report a redox flow lithium battery, which operates via the redox targeting reactions of LiFePO 4 with a bifunctional redox mediator, 2,3,5,6-tetramethyl-p-phenylenediamine, and presents superb energy density as the Li-ion battery and system flexibility as the redox flow battery. The battery has achieved a tank energy density as high as 1023 Wh/L, power density of 61 mW/cm 2 , and voltage efficiency of 91%. Operando X-ray absorption near-edge structure measurements were conducted to monitor the evolution of LiFePO 4 , which provides insightful information on the redox targeting process, critical to the device operation and optimization.

  7. The fairytale of the GSSG/GSH redox potential.

    Science.gov (United States)

    Flohé, Leopold

    2013-05-01

    The term GSSG/GSH redox potential is frequently used to explain redox regulation and other biological processes. The relevance of the GSSG/GSH redox potential as driving force of biological processes is critically discussed. It is recalled that the concentration ratio of GSSG and GSH reflects little else than a steady state, which overwhelmingly results from fast enzymatic processes utilizing, degrading or regenerating GSH. A biological GSSG/GSH redox potential, as calculated by the Nernst equation, is a deduced electrochemical parameter based on direct measurements of GSH and GSSG that are often complicated by poorly substantiated assumptions. It is considered irrelevant to the steering of any biological process. GSH-utilizing enzymes depend on the concentration of GSH, not on [GSH](2), as is predicted by the Nernst equation, and are typically not affected by GSSG. Regulatory processes involving oxidants and GSH are considered to make use of mechanistic principles known for thiol peroxidases which catalyze the oxidation of hydroperoxides by GSH by means of an enzyme substitution mechanism involving only bimolecular reaction steps. The negligibly small rate constants of related spontaneous reactions as compared with enzyme-catalyzed ones underscore the superiority of kinetic parameters over electrochemical or thermodynamic ones for an in-depth understanding of GSH-dependent biological phenomena. At best, the GSSG/GSH potential might be useful as an analytical tool to disclose disturbances in redox metabolism. This article is part of a Special Issue entitled Cellular Functions of Glutathione. Copyright © 2012 Elsevier B.V. All rights reserved.

  8. Adaptive changes in renal mitochondrial redox status in diabetic nephropathy

    Energy Technology Data Exchange (ETDEWEB)

    Putt, David A.; Zhong, Qing; Lash, Lawrence H., E-mail: l.h.lash@wayne.edu

    2012-01-15

    Nephropathy is a serious and common complication of diabetes. In the streptozotocin (STZ)-treated rat model of diabetes, nephropathy does not typically develop until 30 to 45 days post-injection, although hyperglycemia occurs within 24 h. We tested the hypothesis that chronic hyperglycemia results in a modest degree of oxidative stress that is accompanied by compensatory changes in certain antioxidants and mitochondrial redox status. We propose that as kidneys progress to a state of diabetic nephropathy, further adaptations occur in mitochondrial redox status. Basic parameters of renal function in vivo and several parameters of mitochondrial function and glutathione (GSH) and redox status in isolated renal cortical mitochondria from STZ-treated and age-matched control rats were examined at 30 days and 90 days post-injection. While there was no effect of diabetes on blood urea nitrogen, measurement of other, more sensitive parameters, such as urinary albumin and protein, and histopathology showed significant and progressive worsening in diabetic rats. Thus, renal function is compromised even prior to the onset of frank nephropathy. Changes in mitochondrial respiration and enzyme activities indicated existence of a hypermetabolic state. Higher mitochondrial GSH content and rates of GSH transport into mitochondria in kidneys from diabetic rats were only partially due to changes in expression of mitochondrial GSH carriers and were mostly due to higher substrate supply. Although there are few clear indicators of oxidative stress, there are several redox changes that occur early and change further as nephropathy progresses, highlighting the complexity of the disease. Highlights: ►Adaptive changes in renal mitochondrial and redox status in diabetic rats. ►Modest renal dysfunction even prior to onset of nephropathy. ►Elevated concentrations of mitochondrial GSH in diabetic kidneys. ►Change in GSH due partly to increased protein expression of transporter.

  9. Adaptive changes in renal mitochondrial redox status in diabetic nephropathy

    International Nuclear Information System (INIS)

    Putt, David A.; Zhong, Qing; Lash, Lawrence H.

    2012-01-01

    Nephropathy is a serious and common complication of diabetes. In the streptozotocin (STZ)-treated rat model of diabetes, nephropathy does not typically develop until 30 to 45 days post-injection, although hyperglycemia occurs within 24 h. We tested the hypothesis that chronic hyperglycemia results in a modest degree of oxidative stress that is accompanied by compensatory changes in certain antioxidants and mitochondrial redox status. We propose that as kidneys progress to a state of diabetic nephropathy, further adaptations occur in mitochondrial redox status. Basic parameters of renal function in vivo and several parameters of mitochondrial function and glutathione (GSH) and redox status in isolated renal cortical mitochondria from STZ-treated and age-matched control rats were examined at 30 days and 90 days post-injection. While there was no effect of diabetes on blood urea nitrogen, measurement of other, more sensitive parameters, such as urinary albumin and protein, and histopathology showed significant and progressive worsening in diabetic rats. Thus, renal function is compromised even prior to the onset of frank nephropathy. Changes in mitochondrial respiration and enzyme activities indicated existence of a hypermetabolic state. Higher mitochondrial GSH content and rates of GSH transport into mitochondria in kidneys from diabetic rats were only partially due to changes in expression of mitochondrial GSH carriers and were mostly due to higher substrate supply. Although there are few clear indicators of oxidative stress, there are several redox changes that occur early and change further as nephropathy progresses, highlighting the complexity of the disease. Highlights: ►Adaptive changes in renal mitochondrial and redox status in diabetic rats. ►Modest renal dysfunction even prior to onset of nephropathy. ►Elevated concentrations of mitochondrial GSH in diabetic kidneys. ►Change in GSH due partly to increased protein expression of transporter.

  10. Enhanced performance of ultracapacitors using redox additive-based electrolytes

    Science.gov (United States)

    Jain, Dharmendra; Kanungo, Jitendra; Tripathi, S. K.

    2018-05-01

    Different concentrations of potassium iodide (KI) as redox additive had been added to 1 M sulfuric acid (H2SO4) electrolyte with an aim of enhancing the capacitance and energy density of ultracapacitors via redox reactions at the interfaces of electrode-electrolyte. Ultracapacitors were fabricated using chemically treated activated carbon as electrode with H2SO4 and H2SO4-KI as an electrolyte. The electrochemical performances of fabricated supercapacitors were investigated by impedance spectroscopy, cyclic voltammetry and charge-discharge techniques. The maximum capacitance ` C' was observed with redox additives-based electrolyte system comprising 1 M H2SO4-0.3 M KI (1072 F g- 1), which is very much higher than conventional 1 M H2SO4 (61.3 F g- 1) aqueous electrolyte-based ultracapacitors. It corresponds to an energy density of 20.49 Wh kg- 1 at 2.1 A g- 1 for redox additive-based electrolyte, which is six times higher as compared to that of pristine electrolyte (1 M H2SO4) having energy density of only 3.36 Wh kg- 1. The temperature dependence behavior of fabricated cell was also analyzed, which shows increasing pattern in its capacitance values in a temperature range of 5-70 °C. Under cyclic stability test, redox electrolyte-based system shows almost 100% capacitance retention up to 5000 cycles and even more. For comparison, ultracapacitors based on polymer gel electrolyte polyvinyl alcohol (PVA) (10 wt%)—{H2SO4 (1 M)-KI (0.3 M)} (90 wt%) have been fabricated and characterized with the same electrode materials.

  11. Multicomponent transport in membranes for redox flow batteries

    Science.gov (United States)

    Monroe, Charles

    2015-03-01

    Redox flow batteries (RFBs) incorporate separator membranes, which ideally prevent mixing of electrochemically active species while permitting crossover of inactive supporting ions. Understanding crossover and membrane selectivity may require multicomponent transport models that account for solute/solute interactions within the membrane, as well as solute/membrane interactions. Application of the Onsager-Stefan-Maxwell formalism allows one to account for all the dissipative phenomena that may accompany component fluxes through RFB membranes. The magnitudes of dissipative interactions (diffusional drag forces) are quantified by matching experimentally established concentration transients with theory. Such transients can be measured non-invasively using DC conductometry, but the accuracy of this method requires precise characterization of the bulk RFB electrolytes. Aqueous solutions containing both vanadyl sulfate (VOSO4) and sulfuric acid (H2SO4) are relevant to RFB technology. One of the first precise characterizations of aqueous vanadyl sulfate has been implemented and will be reported. To assess the viability of a separator for vanadium RFB applications with cell-level simulations, it is critical to understand the tendencies of various classes of membranes to absorb (uptake) active species, and to know the relative rates of active-species and supporting-electrolyte diffusion. It is also of practical interest to investigate the simultaneous diffusion of active species and supports, because interactions between solutes may ultimately affect the charge efficiency and power efficiency of the RFB system as a whole. A novel implementation of Barnes's classical model of dialysis-cell diffusion [Physics 5:1 (1934) 4-8] is developed to measure the binary diffusion coefficients and sorption equilibria for single solutes (VOSO4 or H2SO4) in porous membranes and cation-exchange membranes. With the binary diffusion and uptake measurement in hand, a computer simulation that

  12. The Cr Redox Record of fO2 Variation in Angrites. Evidence for Redox Conditions of Angrite Petrogenesis and Parent Body

    Science.gov (United States)

    Shearer, Charles K.; Bell, Aaron S.; Burger, Paul V.; Papike, James J.; Jones, John; Le, Loan

    2016-01-01

    Angrites represent some of the earliest stages of planetesimal differentiation. Not surprisingly, there is no simple petrogenetic model for their origin. Petrogenesis has been linked to both magmatic and impact processes. Studies demonstrated that melting of chondritic material (e.g. CM, CV) at redox conditions where pure iron metal is unstable (e.g., IW+1 to IW+2) produced angrite-like melts. Alternatively, angrites were produced at more reducing conditions (redox conditions during crystallization (e.g., Fe metal and a Fe-Ti oxide with potential Fe3+. There have been several estimates of fO2 for angrites. Most notably, experiments examined the variation of DEu/DGd with fO2, between plagioclase and fassaitic pyroxene in equilibrium with an angrite melt composition. They used their observations to estimate the fO2 of crystallization to be approximately IW+0.6 for angrite LEW 86010. This estimate is only a "snapshot" of fO2 conditions during co-crystallization of plagioclase and pyroxene. Preliminary XANES analyses of V redox state in pyroxenes from D'Orbigny reported changes in fO2 from IW-0.7 during early pyroxene crystallization to IW+0.5 during latter episodes of pyroxene crystallization [15]. As this was a preliminary report, it presented limited information concerning the effects of pyroxene orientation and composition on the V valence measurements, and the effect of melt composition on valence and partitioning behavior of V. A closer examination of fO2 as recorded by Cr valence state in olivine will allow us to test models for primordial melting of chondritic material to produce the angrite parent melts. Here, we report the our initial stages of examining the origin and conditions of primordial melting on the angrite parent body and test some of the above models by integrating an experimental study of Cr and V valence partitioning between olivine [OL] and an angrite melt, with micro-scale determinations of Cr and V oxidation state in OL in selected "volcanic

  13. Titanium nitride as an electrocatalyst for V(II)/V(III) redox couples in all-vanadium redox flow batteries

    International Nuclear Information System (INIS)

    Yang, Chunmei; Wang, Haining; Lu, Shanfu; Wu, Chunxiao; Liu, Yiyang; Tan, Qinglong; Liang, Dawei; Xiang, Yan

    2015-01-01

    Titanium nitride nanoparticles (TiN NPs) are proposed as a novel catalyst towards the V(II)/V(III) redox pair for the negative electrode in vanadium redox flow batteries (VRFB). Electrochemical properties of TiN NPs were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results show that TiN NPs demonstrate better electrochemical activity and reversibility for the processes of V(II)/V(III) redox couples as compared with the graphite NPs. TiN NPs facilitate the charge transfer in the V(II)/V(III) redox reaction. Performance of a VRFB using a TiN NPs coated carbon paper as a negative electrode is much higher than that of a VRFB with a raw carbon paper electrode. The columbic efficiency (CE), the voltage efficiency (VE) and the energy efficiency (EE) of the VRFB single cell at charge-discharge current density of 30 mA/cm 2 are 91.74%, 89.11% and 81.74%, respectively. During a 50 charge-discharge cycles test, the CE values of VRFB with TiN NPs consistently remain higher than 90%.

  14. Pattern-oriented Agent-based Monte Carlo simulation of Cellular Redox Environment

    DEFF Research Database (Denmark)

    Tang, Jiaowei; Holcombe, Mike; Boonen, Harrie C.M.

    /CYSS) and mitochondrial redox couples. Evidence suggests that both intracellular and extracellular redox can affect overall cell redox state. How redox is communicated between extracellular and intracellular environments is still a matter of debate. Some researchers conclude based on experimental data...... cells. Biochimica Et Biophysica Acta-General Subjects, 2008. 1780(11): p. 1271-1290. 5. Jones, D.P., Redox sensing: orthogonal control in cell cycle and apoptosis signalling. J Intern Med, 2010. 268(5): p. 432-48. 6. Pogson, M., et al., Formal agent-based modelling of intracellular chemical interactions...

  15. Mutagenesis of the redox-active disulfide in mercuric ion reductase: Catalysis by mutant enzymes restricted to flavin redox chemistry

    International Nuclear Information System (INIS)

    Distefano, M.D.; Au, K.G.; Walsh, C.T.

    1989-01-01

    Mercuric reductase, a flavoenzyme that possesses a redox-active cystine, Cys 135 Cys 140 , catalyzes the reduction of Hg(II) to Hg(0) by NADPH. As a probe of mechanism, the authors have constructed mutants lacking a redox-active disulfide by eliminating Cys 135 (Ala 135 Cys 140 ), Cys 14 (Cys 135 Ala 140 ), or both (Ala 135 Ala 140 ). Additionally, they have made double mutants that lack Cys 135 (Ala 135 Cys 139 Cys 140 ) or Cys 140 (Cys 135 Cys 139 Ala 140 ) but introduce a new Cys in place of Gly 139 with the aim of constructing dithiol pairs in the active site that do not form a redox-active disulfide. The resulting mutant enzymes all lack redox-active disulfides and are hence restricted to FAD/FADH 2 redox chemistry. Each mutant enzyme possesses unique physical and spectroscopic properties that reflect subtle differences in the FAD microenvironment. Preliminary evidence for the Ala 135 Cys 139 Cys 14 mutant enzyme suggests that this protein forms a disulfide between the two adjacent Cys residues. Hg(II) titration experiments that correlate the extent of charge-transfer quenching with Hg(II) binding indicate that the Ala 135 Cys 140 protein binds Hg(II) with substantially less avidity than does the wild-type enzyme. All mutant mercuric reductases catalyze transhydrogenation and oxygen reduction reactions through obligatory reduced flavin intermediates at rates comparable to or greater than that of the wild-type enzyme. In multiple-turnover assays which monitored the production of Hg(0), two of the mutant enzymes were observed to proceed through at least 30 turnovers at rates ca. 1000-fold slower than that of wild-type mercuric reductase. They conclude that the Cys 135 and Cys 140 thiols serve as Hg(II) ligands that orient the Hg(II) for subsequent reduction by a reduced flavin intermediate

  16. Organic cofactors participated more frequently than transition metals in redox reactions of primitive proteins.

    Science.gov (United States)

    Ji, Hong-Fang; Chen, Lei; Zhang, Hong-Yu

    2008-08-01

    Protein redox reactions are one of the most basic and important biochemical actions. As amino acids are weak redox mediators, most protein redox functions are undertaken by protein cofactors, which include organic ligands and transition metal ions. Since both kinds of redox cofactors were available in the pre-protein RNA world, it is challenging to explore which one was more involved in redox processes of primitive proteins? In this paper, using an examination of the redox cofactor usage of putative ancient proteins, we infer that organic ligands participated more frequently than transition metals in redox reactions of primitive proteins, at least as protein cofactors. This is further supported by the relative abundance of amino acids in the primordial world. Supplementary material for this article can be found on the BioEssays website. (c) 2008 Wiley Periodicals, Inc.

  17. Engineering redox homeostasis to develop efficient alcohol-producing microbial cell factories.

    Science.gov (United States)

    Zhao, Chunhua; Zhao, Qiuwei; Li, Yin; Zhang, Yanping

    2017-06-24

    The biosynthetic pathways of most alcohols are linked to intracellular redox homeostasis, which is crucial for life. This crucial balance is primarily controlled by the generation of reducing equivalents, as well as the (reduction)-oxidation metabolic cycle and the thiol redox homeostasis system. As a main oxidation pathway of reducing equivalents, the biosynthesis of most alcohols includes redox reactions, which are dependent on cofactors such as NADH or NADPH. Thus, when engineering alcohol-producing strains, the availability of cofactors and redox homeostasis must be considered. In this review, recent advances on the engineering of cellular redox homeostasis systems to accelerate alcohol biosynthesis are summarized. Recent approaches include improving cofactor availability, manipulating the affinity of redox enzymes to specific cofactors, as well as globally controlling redox reactions, indicating the power of these approaches, and opening a path towards improving the production of a number of different industrially-relevant alcohols in the near future.

  18. Loop cleanup with redox decontamination technique

    International Nuclear Information System (INIS)

    Ren Xian Wen; Zhang Yuan

    1998-01-01

    The corrosion rate of stainless steel in nitric acid solution will be enhanced by existence of Ce 4+ . The goal of this study is to develop a circular decontamination process in medium of nitric acid, in order to use it in a loop clean up. That needs a specially designed electrolytic cell to oxidize the Ce 3+ into Ce 4+ . This regenerator's structure should be simple and easy to operate, and can meet the requirements of practical decontamination operation. The concentration of Ce 4+ in the nitric acid solution was selected to provide a suitable corrosion rate to contaminated stainless steel. The total concentration of cerium (III+IV) was also optimized to ensure that the regeneration rate of Ce 4+ could satisfy the consumption rate of Ce 4+ during decontaminating process. The operation parameters were selected strictly on the basis of our experimental results, so that the regeneration rate of Ce 4+ can be higher reasonably in proper operation conditions and not arise any problem related to safety of operation and nuclear aspects. It is considered that this decontamination process could be applied into either decommissioning or maintenance stage of nuclear facilities. The concentration of Ce 4+ and temperature are the main factors for corrosion rate, other factors should also be considered during decision of decontamination process. With the regenerator developed under contract No 7959/RB could obtain sufficient decontamination factors, when use following conditions: concentration of Ce 4+ is higher than 0.2 mol/1, the total concentration of cerium (III+IV) is higher than 0.4 mol/1, concentration of nitric acid is higher than 2 mol/1, temperature of decontamination operation is within 25 deg. C - 40 deg. C and temperature of regeneration is within 40 deg C - 50 deg.C

  19. Characterization of the Redox reaction of V(V) in Ammonia Buffers with Square-Wave Voltammetry

    OpenAIRE

    Mirceski, Valentin; Gulaboski, Rubin; Petrovska-Jovanovic, Simka; Stojanova, Kornelija

    2001-01-01

    The redox reaction of V(V) in ammonia buffers solution with pH = 8.60 was studied by means of square-wave and cyclic voltammetry. The redox reaction studied exhibits properties of a surface redox process in which both the reactant and the product of the redox reaction are immobilized on the electrode surface.

  20. Tuning the Perfluorosulfonic Acid Membrane Morphology for Vanadium Redox-Flow Batteries.

    Science.gov (United States)

    Vijayakumar, M; Luo, Qingtao; Lloyd, Ralph; Nie, Zimin; Wei, Xiaoliang; Li, Bin; Sprenkle, Vincent; Londono, J-David; Unlu, Murat; Wang, Wei

    2016-12-21

    The microstructure of perfluorinated sulfonic acid proton-exchange membranes such as Nafion significantly affects their transport properties and performance in a vanadium redox-flow battery (VRB). In this work, Nafion membranes with various equivalent weights ranging from 1000 to 1500 are prepared and the morphology-property-performance relationship is investigated. NMR and small-angle X-ray scattering studies revealed their composition and morphology variances, which lead to major differences in key transport properties related to proton conduction and vanadium-ion permeation. Their performances are further characterized as VRB membranes. On the basis of this understanding, a new perfluorosulfonic acid membrane is designed with optimal pore geometry and thickness, leading to higher ion selectivity and lower cost compared with the widely used Nafion 115. Excellent VRB single-cell performance (89.3% energy efficiency at 50 mA·cm -2 ) was achieved along with a stable cyclical capacity over prolonged cycling.

  1. Tuning the Perfluorosulfonic Acid Membrane Morphology for Vanadium Redox-Flow Batteries

    Energy Technology Data Exchange (ETDEWEB)

    Vijayakumar, M.; Luo, Qingtao; Lloyd, Ralph B.; Nie, Zimin; Wei, Xiaoliang; Li, Bin; Sprenkle, Vincent L.; Londono, J-David; Unlu, Murat; Wang, Wei

    2016-12-23

    The microstructure of the perfluorinated sulfonic acid proton exchange membranes such as Nafion significantly affects their transport properties and performance in a vanadium redox flow battery (VRB). In this work, Nafion membranes with various equivalent weights (EW) ranging from 1000 to 1500 are prepared and the structure-property-performance relationship is investigated. Nuclear magnetic resonance (NMR) and small-angle X-ray scattering (SAXS) studies revealed their composition and morphology variances, which lead to major differences in key transport properties related to proton conduction and vanadium ion permeation. Their performances are further characterized as VRB membranes. Based on those understanding, a new perfluorosulfonic acid membrane is designed with optimal pore geometry and thickness, leading to higher ion selectivity and lower cost compared with the widely used Nafion® 115. Excellent VRB single-cell performance (89.3% energy efficiency at 50mA∙cm-2) was achieved along with a stable cyclical capacity over prolonged cycling.

  2. Surveillance and Maintenance Plan for the 202-S Reduction Oxidation (REDOX) Facility

    International Nuclear Information System (INIS)

    McGuire, J.J.

    1999-01-01

    This document provides a plan for implementing surveillance and maintenance (S and M) activities to ensure the 202-S Reduction Oxidation (REDOX) Facility is maintained in a safe, environmentally secure, and cost effective manner until subsequent closure during the final disposition phase of decommissioning. Specific objectives of the S and M program are to ensure adequate confinement of hazardous substances, to provide physical safety and security controls, to maintain the facilities in a manner that will minimize potential hazards to the public and workers, to provide adequate frequency of inspections to identify potential hazards, to maintain selected systems or equipment that will be essential for decommissioning activities in a shutdown but standby or operational mode, if economically justified, and to provide a mechanism for the identification and compliance with applicable environmental, safety and health, and safeguard and security requirements

  3. On the activation of Pt/Al2O3 catalysts in HC-SCR by sintering. Determination of redox-active sites using Multitrack

    International Nuclear Information System (INIS)

    Vaccaro, A.R.; Mul, G.; Moulijn, J.A.; Perez-Ramirez, J.

    2003-01-01

    A highly dispersed Pt/Al 2 O 3 catalyst was used for the selective catalytic reduction of NO x using propene (HC-SCR). Contact with the reaction gas mixture led to a significant activation of the catalyst at temperatures above 523K. According to CO chemisorption data and HRTEM analysis, Pt particles on the activated catalyst had sintered. The redox behavior of the fresh and sintered catalysts was investigated using Multitrack, a TAP-like pulse reactor. If Pt particles on the catalyst are highly dispersed (average size below =2nm), only a small part (=10%) of the total number of Pt surface sites as determined by CO chemisorption (Pt surf ) participates in H 2 /O 2 redox cycles (Pt surf,redox ) in Multitrack conditions. For a sintered catalyst, with an average particle size of 2.7nm, the number of Pt surf and Pt surf,redox sites are in good agreement. Similar results were obtained for both catalysts using NO as the oxidant. The low number of Pt surf,redox sites on highly dispersed Pt/Al 2 O 3 is explained by the presence of a kinetically more stable-probably ionic-form of Pt-O bonds on all surface sites of the smaller Pt particles, including corner, edge and terrace sites. When the average particle size shifts to =2.7nm, the kinetic stability of all Pt-O bonds is collectively decreased, enabling the participation of all Pt surface sites in the redox cycles. A linear correlation between the NO x conversion in HC-SCR, and the amount of Pt surf,redox was found. This suggests that redox-active Pt sites are necessary for catalytic activity. In addition, the correlation could be significantly improved by assuming that Pt surf,terrace sites of the particles larger than 2.7nm are mainly responsible for HC-SCR activity in steady state conditions. Implications of these results for the pathway of HC-SCR over Pt catalysts are discussed

  4. Garlic protects the glutathione redox cycle in irradiated rats

    International Nuclear Information System (INIS)

    Abu-Ghadeer, A.R.M.; Osman, S.A.A.; Abbady, M.M.

    1999-01-01

    The aim of the present study is to evaluate the possible radioprotective role of garlic oil on the glutathione redox cycle (GSH, GSH-Px, GR and G6-PD) in blood and tissues (liver, spleen and intestine) of irradiated rats. Garlic oil was orally administered to rats (100 mg/Kg- b.w.) for 7 days before exposure to a fractionated of whole body gamma irradiation up to 9 Gy (3 Gy X 3 at 2 days intervals) and during the whole period of irradiation. The data showed that radiation exposure caused significant inhibition of the biochemical parameters in blood and tissue of irradiated rats all over the investigation periods (3,7 and 15 days). Garlic oil ameliorated the decrease in the tested parameters with noticeable effect on the 15 Th. day after radiation exposure. It is concluded that garlic oil could control the radiation induced changes in the glutathione redox cycle and provided some radioprotective effect

  5. A High-Current, Stable Nonaqueous Organic Redox Flow Battery

    Energy Technology Data Exchange (ETDEWEB)

    Wei, Xiaoliang; Duan, Wentao; Huang, Jinhua; Zhang, Lu; Li, Bin; Reed, David; Xu, Wu; Sprenkle, Vincent; Wang, Wei

    2016-10-14

    Nonaqueous redox flow batteries are promising in pursuit of high-energy storage systems owing to the broad voltage window, but currently are facing key challenges such as poor cycling stability and lack of suitable membranes. Here we report a new nonaqueous all-organic flow chemistry that demonstrates an outstanding cell cycling stability primarily because of high chemical persistency of the organic radical redox species and their good compatibility with the supporting electrolyte. A feasibility study shows that Daramic® and Celgard® porous separators can lead to high cell conductivity in flow cells thus producing remarkable cell efficiency and material utilization even at high current operations. This result suggests that the thickness and pore size are the key performance-determining factors for porous separators. With the greatly improved flow cell performance, this new flow system largely addresses the above mentioned challenges and the findings may greatly expedite the development of durable nonaqueous flow batteries.

  6. TCA Cycle Defects and Cancer: When Metabolism Tunes Redox State.

    Science.gov (United States)

    Cardaci, Simone; Ciriolo, Maria Rosa

    2012-01-01

    Inborn defects of the tricarboxylic acid (TCA) cycle enzymes have been known for more than twenty years. Until recently, only recessive mutations were described which, although resulted in severe multisystem syndromes, did not predispose to cancer onset. In the last ten years, a causal role in carcinogenesis has been documented for inherited and acquired alterations in three TCA cycle enzymes, succinate dehydrogenase (SDH), fumarate hydratase (FH), and isocitrate dehydrogenase (IDH), pointing towards metabolic alterations as the underlying hallmark of cancer. This paper summarizes the neoplastic alterations of the TCA cycle enzymes focusing on the generation of pseudohypoxic phenotype and the alteration of epigenetic homeostasis as the main tumor-promoting effects of the TCA cycle affecting defects. Moreover, we debate on the ability of these mutations to affect cellular redox state and to promote carcinogenesis by impacting on redox biology.

  7. A mathematical model for the iron/chromium redox battery

    Science.gov (United States)

    Fedkiw, P. S.; Watts, R. W.

    1984-01-01

    A mathematical model has been developed to describe the isothermal operation of a single anode-separator-cathode unit cell in a redox-flow battery and has been applied to the NASA iron/chromium system. The model, based on porous electrode theory, incorporates redox kinetics, mass transfer, and ohmic effects as well as the parasitic hydrogen reaction which occurs in the chromium electrode. A numerical parameter study was carried out to predict cell performance to aid in the rational design, scale-up, and operation of the flow battery. The calculations demonstrate: (1) an optimum electrode thickness and electrolyte flow rate exist; (2) the amount of hydrogen evolved and, hence, cycle faradaic efficiency, can be affected by cell geometry, flow rate, and charging procedure; (3) countercurrent flow results in enhanced cell performance over cocurrent flow; and (4) elevated temperature operation enhances cell performance.

  8. Plasmonic tunnel junctions for single-molecule redox chemistry.

    Science.gov (United States)

    de Nijs, Bart; Benz, Felix; Barrow, Steven J; Sigle, Daniel O; Chikkaraddy, Rohit; Palma, Aniello; Carnegie, Cloudy; Kamp, Marlous; Sundararaman, Ravishankar; Narang, Prineha; Scherman, Oren A; Baumberg, Jeremy J

    2017-10-20

    Nanoparticles attached just above a flat metallic surface can trap optical fields in the nanoscale gap. This enables local spectroscopy of a few molecules within each coupled plasmonic hotspot, with near thousand-fold enhancement of the incident fields. As a result of non-radiative relaxation pathways, the plasmons in such sub-nanometre cavities generate hot charge carriers, which can catalyse chemical reactions or induce redox processes in molecules located within the plasmonic hotspots. Here, surface-enhanced Raman spectroscopy allows us to track these hot-electron-induced chemical reduction processes in a series of different aromatic molecules. We demonstrate that by increasing the tunnelling barrier height and the dephasing strength, a transition from coherent to hopping electron transport occurs, enabling observation of redox processes in real time at the single-molecule level.

  9. TCA Cycle Defects and Cancer: When Metabolism Tunes Redox State

    Directory of Open Access Journals (Sweden)

    Simone Cardaci

    2012-01-01

    Full Text Available Inborn defects of the tricarboxylic acid (TCA cycle enzymes have been known for more than twenty years. Until recently, only recessive mutations were described which, although resulted in severe multisystem syndromes, did not predispose to cancer onset. In the last ten years, a causal role in carcinogenesis has been documented for inherited and acquired alterations in three TCA cycle enzymes, succinate dehydrogenase (SDH, fumarate hydratase (FH, and isocitrate dehydrogenase (IDH, pointing towards metabolic alterations as the underlying hallmark of cancer. This paper summarizes the neoplastic alterations of the TCA cycle enzymes focusing on the generation of pseudohypoxic phenotype and the alteration of epigenetic homeostasis as the main tumor-promoting effects of the TCA cycle affecting defects. Moreover, we debate on the ability of these mutations to affect cellular redox state and to promote carcinogenesis by impacting on redox biology.

  10. The NASA Redox Storage System Development project, 1980

    Science.gov (United States)

    1982-12-01

    The technical accomplishments pertaining to the development of Redox systems and related technology are outlined in terms of the task elements: prototype systems development, application analyses, and supporting technology. Prototype systems development provides for a major procurement to develop an industrial capability to take the current NASA Lewis technology and go on to the design, development, and commercialization of iron-chromium Redox storage systems. Application analyses provides for the definition of application concepts and technology requirements, specific definition studies, and the identification of market sectors and their penetration potential. Supporting technology includes both in house and contractual efforts that encompass implementation of technology improvements in membranes, electrodes, reactant processing, and system design. The status of all elements is discussed.

  11. Redox flow batteries based on supporting solutions containing chloride

    Science.gov (United States)

    Li, Liyu; Kim, Soowhan; Yang, Zhenguo; Wang, Wei; Zhang, Jianlu; Chen, Baowei; Nie, Zimin; Xia, Guanguang

    2014-01-14

    Redox flow battery systems having a supporting solution that contains Cl.sup.- ions can exhibit improved performance and characteristics. Furthermore, a supporting solution having mixed SO.sub.4.sup.2- and Cl.sup.- ions can provide increased energy density and improved stability and solubility of one or more of the ionic species in the catholyte and/or anolyte. According to one example, a vanadium-based redox flow battery system is characterized by an anolyte having V.sup.2+ and V.sup.3+ in a supporting solution and a catholyte having V.sup.4+ and V.sup.5+ in a supporting solution. The supporting solution can contain Cl.sup.- ions or a mixture of SO.sub.4.sup.2- and Cl.sup.- ions.

  12. Assessment of redox conditions based on fracture mineralogy

    International Nuclear Information System (INIS)

    Tullborg, E.L.

    1999-01-01

    The frequency and distribution of fracture minerals like calcite, Fe-oxides/hydroxides, and sulphides can be used in performance assessment since their presence reflects the redox processes that are active or have been active in the fractures. The advantage in using fracture minerals is that they undoubtedly represent conditions prior to disturbances caused by drilling or tunnel excavations. In addition, they give a continuous record from the surface to great depth. On the other hand the disadvantage is that the fracture mineral distribution is a result of both past and present processes such that the mineral distribution alone can not discriminate between old and recent processes. Nevertheless it is suggested that the fracture mineral distribution provides important information about the redox capacity in the fracture system. (author)

  13. Fundamental studies of uranium and neptunium redox flow batteries (II)

    International Nuclear Information System (INIS)

    Shiokawa, Y.; Yamamura, T.; Watanabe, N.

    2002-01-01

    The atomic power generation entails production of so-called minor actinides and accumulation of depleted uranium. The theoretical and experimental investigations are underway to transmute minor actinides for minimizing the long-term radiotoxicity and reducing the radioactive waste. The utilization, however, would be alternative means. The actinide redox couples, An(VI)/An(V) and An(IV)/An(III), have excellent properties as battery active materials. Here j the uranium and neptunium redox flow batteries for the electric power storage are discussed from the electrochemical properties of U, Np, Pu and Am [1,2]. One of the required properties for the batteries for electric power storage is high energy efficiency, which is defined by the ratio of the discharge energy to the charge energy. These energies are dependent on the rapidness of kinetics in the electrode reactions, namely the standard rate constants and also the internal resistance of the battery

  14. Multiple-membrane multiple-electrolyte redox flow battery design

    Science.gov (United States)

    Yan, Yushan; Gu, Shuang; Gong, Ke

    2017-05-02

    A redox flow battery is provided. The redox flow battery involves multiple-membrane (at least one cation exchange membrane and at least one anion exchange membrane), multiple-electrolyte (one electrolyte in contact with the negative electrode, one electrolyte in contact with the positive electrode, and at least one electrolyte disposed between the two membranes) as the basic characteristic, such as a double-membrane, triple electrolyte (DMTE) configuration or a triple-membrane, quadruple electrolyte (TMQE) configuration. The cation exchange membrane is used to separate the negative or positive electrolyte and the middle electrolyte, and the anion exchange membrane is used to separate the middle electrolyte and the positive or negative electrolyte.

  15. Redox flow batteries based on supporting solutions containing chloride

    Energy Technology Data Exchange (ETDEWEB)

    Li, Liyu; Kim, Soowhan; Yang, Zhenguo; Wang, Wei; Nie, Zimin; Chen, Baowei; Zhang, Jianlu; Xia, Guanguang

    2017-11-14

    Redox flow battery systems having a supporting solution that contains Cl.sup.- ions can exhibit improved performance and characteristics. Furthermore, a supporting solution having mixed SO.sub.4.sup.2- and Cl.sup.- ions can provide increased energy density and improved stability and solubility of one or more of the ionic species in the catholyte and/or anolyte. According to one example, a vanadium-based redox flow battery system is characterized by an anolyte having V.sup.2+ and V.sup.3+ in a supporting solution and a catholyte having V.sup.4+ and V.sup.5+ in a supporting solution. The supporting solution can contain Cl.sup.- ions or a mixture of SO.sub.4.sup.2- and Cl.sup.- ions.

  16. Redox-active porous coordination polymer based on trinuclear pivalate: Temperature-dependent crystal rearrangement and redox-behavior

    Energy Technology Data Exchange (ETDEWEB)

    Lytvynenko, Anton S. [L.V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, Prospekt Nauki 31, Kiev 03028 (Ukraine); Kiskin, Mikhail A., E-mail: mkiskin@igic.ras.ru [N.S. Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Leninsky Prospect 31, GSP-1, 119991 Moscow (Russian Federation); Dorofeeva, Victoria N.; Mishura, Andrey M.; Titov, Vladimir E.; Kolotilov, Sergey V. [L.V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, Prospekt Nauki 31, Kiev 03028 (Ukraine); Eremenko, Igor L.; Novotortsev, Vladimir M. [N.S. Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Leninsky Prospect 31, GSP-1, 119991 Moscow (Russian Federation)

    2015-03-15

    Linking of trinuclear pivalate Fe{sub 2}NiO(Piv){sub 6} (Piv=O{sub 2}CC(CH{sub 3}){sub 3}) by 2,6-bis(4-pyridyl)-4-(1-naphthyl)pyridine (L) resulted in formation of 1D-porous coordination polymer Fe{sub 2}NiO(Piv){sub 6}(L)·Solv, which was characterized in two forms: DMSO solvate Fe{sub 2}NiO(Piv){sub 6}(L)(DMSO)·2.5DMSO (1) or water solvate Fe{sub 2}NiO(Piv){sub 6}(L)(H{sub 2}O) (2). X-ray structure of 1 was determined. Crystal lattice of 1 at 160 K contained open channels, filled by captured solvent, while temperature growth to 296 K led to the crystal lattice rearrangement and formation of closed voids. Redox-behavior of 2 was studied by cyclic voltammetry for a solid compound, deposited on glassy-carbon electrode. Redox-activity of L preserved upon incorporation in the coordination polymer. The presence of pores in desolvated sample Fe{sub 2}NiO(Piv){sub 6}(L) was confirmed by the measurements of N{sub 2} and H{sub 2} adsorption at 77 K. Potential barriers of the different molecules diffusion through pores were estimated by the means of molecular mechanics. - Graphical abstract: Redox-behavior of 1D-porous coordination polymer Fe{sub 2}NiO(Piv){sub 6}(L)(H{sub 2}O) was studied by cyclic voltammetry in thin film, deposited on glassy-carbon electrode. Redox-activity of L preserved upon incorporation in the coordination polymer. Potential barriers of different molecules diffusion through pores were estimated by the means of molecular mechanics. - Highlights: • Porous 1D coordination polymer was synthesized. • Temperature growth led to pores closing due to crystal lattice rearrangement. • Redox-activity of ligand preserved upon incorporation into coordination polymer. • Redox-properties of solid coordination polymer were studied in thin film. • Diffusion barriers were evaluated by molecular mechanics.

  17. Redox signaling in acute oxygen sensing

    Directory of Open Access Journals (Sweden)

    Lin Gao

    2017-08-01

    Full Text Available Acute oxygen (O2 sensing is essential for individuals to survive under hypoxic conditions. The carotid body (CB is the main peripheral chemoreceptor, which contains excitable and O2-sensitive glomus cells with O2-regulated ion channels. Upon exposure to acute hypoxia, inhibition of K+ channels is the signal that triggers cell depolarization, transmitter release and activation of sensory fibers that stimulate the brainstem respiratory center to produce hyperventilation. The molecular mechanisms underlying O2 sensing by glomus cells have, however, remained elusive. Here we discuss recent data demonstrating that ablation of mitochondrial Ndufs2 gene selectively abolishes sensitivity of glomus cells to hypoxia, maintaining responsiveness to hypercapnia or hypoglycemia. These data suggest that reactive oxygen species and NADH generated in mitochondrial complex I during hypoxia are signaling molecules that modulate membrane K+ channels. We propose that the structural substrates for acute O2 sensing in CB glomus cells are “O2-sensing microdomains” formed by mitochondria and neighboring K+ channels in the plasma membrane. Keywords: Hypoxia, Acute oxygen sensing, Peripheral chemoreceptors, Carotid body, Adrenal medulla, Mitochondrial complex I, Reactive oxygen species (ROS, Pyridine nucleotides

  18. THE STUDY OF REDOX CONDITIONS IN THE DNIESTER RIVER

    Directory of Open Access Journals (Sweden)

    Viorica Gladchi

    2008-06-01

    Full Text Available The work presented in the paper discusses the contribution of the Novodnestrovsc water system to the formation of redox conditions in the lower Dniester. The conclusions were drawn on the basis of a long-term protocol of analyses that included the analysis of the oxygen regime, evaluation of the content of hydrogen peroxide, rH2, biological oxygen demand as well as other additional parameters.

  19. Redox Biology Course Registration Form | Center for Cancer Research

    Science.gov (United States)

    The Redox Biology class is open to all NIH/NCI fellows and staff and will be held Septhember 27 - November 8, 2016. The last day to register is: September 21, 2016. The first 100 registrants will be accepted for the class. Those who plan to participate by Video TeleConference should also register so that you can receive the speaker handouts in advance.

  20. Optimization of a Vanadium Redox Flow Battery with Hydrogen generation

    OpenAIRE

    Wrang, Daniel

    2016-01-01

    We consider the modelling and optimal control of energy storage systems, in this study a Vanadium Redox Flow Battery. Such a battery can be introduced in the electrical grid to be charged when demand is low and discharged when demand is high, increasing the overall efficiency of the network while reducing costs and emission of greenhouse gases. The model of the battery proposed in this study is less complex than the majority of models on batteries and energy storage systems found in literatur...

  1. Redox-active Hybrid Materials for Pseudocapacitive Energy Storage

    Science.gov (United States)

    Boota, Muhammad

    Organic-inorganic hybrid materials show a great promise for the purpose of manufacturing high performance electrode materials for electrochemical energy storage systems and beyond. Molecular level combination of two best suited components in a hybrid material leads to new or sometimes exceptional sets of physical, chemical, mechanical and electrochemical properties that makes them attractive for broad ranges of applications. Recently, there has been growing interest in producing redox-active hybrid nanomaterials for energy storage applications where generally the organic component provides high redox capacitance and the inorganic component offers high conductivity and robust support. While organic-inorganic hybrid materials offer tremendous opportunities for electrochemical energy storage applications, the task of matching the right organic material out of hundreds of natural and nearly unlimited synthetic organic molecules to appropriate nanostructured inorganic support hampers their electrochemical energy storage applications. We aim to present the recent development of redox-active hybrid materials for pseudocapacitive energy storage. We will show the impact of combination of suitable organic materials with distinct carbon nanostructures and/or highly conductive metal carbides (MXenes) on conductivity, charge storage performance, and cyclability. Combined experimental and molecular simulation results will be discussed to shed light on the interfacial organic-inorganic interactions, pseudocapacitive charge storage mechanisms, and likely orientations of organic molecules on conductive supports. Later, the concept of all-pseudocapacitive organic-inorganic asymmetric supercapacitors will be highlighted which open up new avenues for developing inexpensive, sustainable, and high energy density aqueous supercapacitors. Lastly, future challenges and opportunities to further tailor the redox-active hybrids will be highlighted.

  2. Organic chemical degradation by remote study of the redox conditions

    Science.gov (United States)

    Fernandez, P. M.; Revil, A.; Binley, A. M.; Bloem, E.; French, H. K.

    2014-12-01

    Monitoring the natural (and enhanced) degradation of organic contaminants is essential for managing groundwater quality in many parts of the world. Contaminated sites often have limited access, hence non-intrusive methods for studying redox processes, which drive the degradation of organic compounds, are required. One example is the degradation of de-icing chemicals (glycols and organic salts) released to the soil near airport runways during winter. This issue has been broadly studied at Oslo airport, Gardermoen, Norway using intrusive and non-intrusive methods. Here, we report on laboratory experiments that aim to study the potential of using a self-potential, DCresistivity, and time-domain induced polarization for geochemical characterization of the degradation of Propylene Glycol (PG). PG is completely miscible in water, does not adsorb to soil particles and does not contribute to the electrical conductivity of the soil water. When the contaminant is in the unsaturated zone near the water table, the oxygen is quickly consumed and the gas exchange with the surface is insufficient to ensure aerobic degradation, which is faster than anaerobic degradation. Since biodegradation of PG is highly oxygen demanding, anaerobic pockets can exist causing iron and manganese reduction. It is hypothesised that nitrate would boost the degradation rate under such conditions. In our experiment, we study PG degradation in a sand tank. We provide the system with an electron highway to bridge zones with different redox potential. This geo-battery system is characterized by self-potential, resistivity and induced polarization anomalies. An example of preliminary results with self-potential at two different times of the experiment can be seen in the illustration. These will be supplemented with more direct information on the redox chemistry: in-situ water sampling, pH, redox potential and electrical conductivity measurements. In parallel, a series of batch experiments have been

  3. Cynaropicrin targets the trypanothione redox system in Trypanosoma brucei.

    Science.gov (United States)

    Zimmermann, Stefanie; Oufir, Mouhssin; Leroux, Alejandro; Krauth-Siegel, R Luise; Becker, Katja; Kaiser, Marcel; Brun, Reto; Hamburger, Matthias; Adams, Michael

    2013-11-15

    In mice cynaropicrin (CYN) potently inhibits the proliferation of Trypanosoma brucei-the causative agent of Human African Trypanosomiasis-by a so far unknown mechanism. We hypothesized that CYNs α,β-unsaturated methylene moieties act as Michael acceptors for glutathione (GSH) and trypanothione (T(SH)2), the main low molecular mass thiols essential for unique redox metabolism of these parasites. The analysis of this putative mechanism and the effects of CYN on enzymes of the T(SH)2 redox metabolism including trypanothione reductase, trypanothione synthetase, glutathione-S-transferase, and ornithine decarboxylase are shown. A two step extraction protocol with subsequent UPLC-MS/MS analysis was established to quantify intra-cellular CYN, T(SH)2, GSH, as well as GS-CYN and T(S-CYN)2 adducts in intact T. b. rhodesiense cells. Within minutes of exposure to CYN, the cellular GSH and T(SH)2 pools were entirely depleted, and the parasites entered an apoptotic stage and died. CYN also showed inhibition of the ornithine decarboxylase similar to the positive control eflornithine. Significant interactions with the other enzymes involved in the T(SH)2 redox metabolism were not observed. Alongside many other biological activities sesquiterpene lactones including CYN have shown antitrypanosomal effects, which have been postulated to be linked to formation of Michael adducts with cellular nucleophiles. Here the interaction of CYN with biological thiols in a cellular system in general, and with trypanosomal T(SH)2 redox metabolism in particular, thus offering a molecular explanation for the antitrypanosomal activity is demonstrated. At the same time, the study provides a novel extraction and analysis protocol for components of the trypanosomal thiol metabolism. Copyright © 2013 Elsevier Ltd. All rights reserved.

  4. Oxidative Stress, Redox Signaling, and Autophagy: Cell Death Versus Survival

    Science.gov (United States)

    Navarro-Yepes, Juliana; Burns, Michaela; Anandhan, Annadurai; Khalimonchuk, Oleh; del Razo, Luz Maria; Quintanilla-Vega, Betzabet; Pappa, Aglaia; Panayiotidis, Mihalis I.

    2014-01-01

    Abstract Significance: The molecular machinery regulating autophagy has started becoming elucidated, and a number of studies have undertaken the task to determine the role of autophagy in cell fate determination within the context of human disease progression. Oxidative stress and redox signaling are also largely involved in the etiology of human diseases, where both survival and cell death signaling cascades have been reported to be modulated by reactive oxygen species (ROS) and reactive nitrogen species (RNS). Recent Advances: To date, there is a good understanding of the signaling events regulating autophagy, as well as the signaling processes by which alterations in redox homeostasis are transduced to the activation/regulation of signaling cascades. However, very little is known about the molecular events linking them to the regulation of autophagy. This lack of information has hampered the understanding of the role of oxidative stress and autophagy in human disease progression. Critical Issues: In this review, we will focus on (i) the molecular mechanism by which ROS/RNS generation, redox signaling, and/or oxidative stress/damage alter autophagic flux rates; (ii) the role of autophagy as a cell death process or survival mechanism in response to oxidative stress; and (iii) alternative mechanisms by which autophagy-related signaling regulate mitochondrial function and antioxidant response. Future Directions: Our research efforts should now focus on understanding the molecular basis of events by which autophagy is fine tuned by oxidation/reduction events. This knowledge will enable us to understand the mechanisms by which oxidative stress and autophagy regulate human diseases such as cancer and neurodegenerative disorders. Antioxid. Redox Signal. 21, 66–85. PMID:24483238

  5. Uranium redox transition pathways in acetate-amended sediments

    Science.gov (United States)

    Bargar, John R.; Williams, Kenneth H.; Campbell, Kate M.; Long, Philip E.; Stubbs, Joanne E.; Suvorova, Elenal I.; Lezama-Pacheco, Juan S.; Alessi, Daniel S.; Stylo, Malgorzata; Webb, Samuel M.; Davis, James A.; Giammar, Daniel E.; Blue, Lisa Y.; Bernier-Latmani, Rizlan

    2013-01-01

    Redox transitions of uranium [from U(VI) to U(IV)] in low-temperature sediments govern the mobility of uranium in the environment and the accumulation of uranium in ore bodies, and inform our understanding of Earth’s geochemical history. The molecular-scale mechanistic pathways of these transitions determine the U(IV) products formed, thus influencing uranium isotope fractionation, reoxidation, and transport in sediments. Studies that improve our understanding of these pathways have the potential to substantially advance process understanding across a number of earth sciences disciplines. Detailed mechanistic information regarding uranium redox transitions in field sediments is largely nonexistent, owing to the difficulty of directly observing molecular-scale processes in the subsurface and the compositional/physical complexity of subsurface systems. Here, we present results from an in situ study of uranium redox transitions occurring in aquifer sediments under sulfate-reducing conditions. Based on molecular-scale spectroscopic, pore-scale geochemical, and macroscale aqueous evidence, we propose a biotic–abiotic transition pathway in which biomass-hosted mackinawite (FeS) is an electron source to reduce U(VI) to U(IV), which subsequently reacts with biomass to produce monomeric U(IV) species. A species resembling nanoscale uraninite is also present, implying the operation of at least two redox transition pathways. The presence of multiple pathways in low-temperature sediments unifies apparently contrasting prior observations and helps to explain sustained uranium reduction under disparate biogeochemical conditions. These findings have direct implications for our understanding of uranium bioremediation, ore formation, and global geochemical processes.

  6. Redox Biology Course Evaluation Form | Center for Cancer Research

    Science.gov (United States)

    To improve the Redox Biology (RB) course in future years, we would appreciate your feedback by completing this course evaluation. Please score the course elements as poor, fair, average, good or excellent. Please type any comments that you have in response to the questions at the bottom of the form. Remember to include your name as you wish it to appear on the certificate. Thank you for your feedback.

  7. Thermal Coefficient of Redox Potential of Alkali Metals

    Science.gov (United States)

    Fukuzumi, Yuya; Hinuma, Yoyo; Moritomo, Yutaka

    2018-05-01

    The thermal coefficient (α) of redox potential (V) is a significant physical quantity that converts the thermal energy into electric energy. In this short note, we carefully determined α of alkali metals (A = Li and Na) against electrolyte solution. The obtained α is much larger than that expected from the specific heat (CpA) of solid A and depends on electrolyte solution. These observations indicate that the solvent has significant effect on α.

  8. Redox, iron, and nutritional status of children during swimming training.

    Science.gov (United States)

    Kabasakalis, Athanasios; Kalitsis, Konstantinos; Nikolaidis, Michalis G; Tsalis, George; Kouretas, Dimitris; Loupos, Dimitris; Mougios, Vassilis

    2009-11-01

    Effects of exercise training on important determinants of children's long-term health, such as redox and iron status, have not been adequately investigated. The aim of the present study was to examine changes in markers of the redox, iron and nutritional status of boy and girl swimmers during a prolonged period of training. 11 boys and 13 girls, aged 10-11 years, were members of a swimming club. They were assessed at the beginning of the training season, at 13 weeks and at 23 weeks through blood sampling and recording of the diet. Reduced glutathione increased at 13 and 23 weeks, whereas oxidised glutathione decreased at 13 weeks, resulting in an increase of the reduced/oxidised glutathione ratio at 13 and 23 weeks. Total antioxidant capacity, catalase, thiobarbituric acid-reactive substances, hemoglobin, transferrin saturation and ferritin did not change significantly. Carbohydrate intake was below 50% of energy and fat intake was above 40% of energy. Intakes of saturated fatty acids and cholesterol were excessive. Iron intake was adequate but intakes of folate, vitamin E, calcium and magnesium did not meet the recommended daily allowances. No significant differences were found between sexes in any of the parameters measured. In conclusion, child swimmers improved the redox status of glutathione during training, although the intake of antioxidant nutrients did not change. The iron status was not impaired by training. Suboptimal intake of several nutrients suggests the need for nutritional monitoring and education of children athletes.

  9. Numerical modeling of an all vanadium redox flow battery.

    Energy Technology Data Exchange (ETDEWEB)

    Clausen, Jonathan R.; Brunini, Victor E.; Moffat, Harry K.; Martinez, Mario J.

    2014-01-01

    We develop a capability to simulate reduction-oxidation (redox) flow batteries in the Sierra Multi-Mechanics code base. Specifically, we focus on all-vanadium redox flow batteries; however, the capability is general in implementation and could be adopted to other chemistries. The electrochemical and porous flow models follow those developed in the recent publication by [28]. We review the model implemented in this work and its assumptions, and we show several verification cases including a binary electrolyte, and a battery half-cell. Then, we compare our model implementation with the experimental results shown in [28], with good agreement seen. Next, a sensitivity study is conducted for the major model parameters, which is beneficial in targeting specific features of the redox flow cell for improvement. Lastly, we simulate a three-dimensional version of the flow cell to determine the impact of plenum channels on the performance of the cell. Such channels are frequently seen in experimental designs where the current collector plates are borrowed from fuel cell designs. These designs use a serpentine channel etched into a solid collector plate.

  10. Literature survey of redox reactions in the near field

    International Nuclear Information System (INIS)

    Miki, Takahito; Chiba, Tamotsu; Inagaki, Manabu; Sasamoto, Hiroshi; Yui, Mikazu

    2000-01-01

    This report presents a summary of literature survey about geochemical reactions which are important to evaluate the redox conditions in the near field rock mass and buffer. The results of literature survey are summarized as follows; Minerals including ferrous iron and organic materials in the rock mass are important reductants. Initial stage after closure of repository, oxygen will be consumed by pyrite, because the reaction rate between pyrite and oxygen is relatively fast. It is possible to estimate the redox capacity for reductants by rock (mineral)-water interaction experiment in a laboratory. And it is expected that the ferrous iron-rich rock and higher porosity rock may have bigger redox capacity. It is impossible to estimate the oxygen consumption rate by reductants such as minerals including ferrous iron. The rate law and rate constant for the oxidation reaction of ferrous iron in the solution are also determined. As a conclusion, it seems that we can evaluate kinetically the evolution of geochemical conditions in the near field rock mass and buffer by excavation of drifts, based on data derived from these existing literatures. (author)

  11. Online monitoring of Mezcal fermentation based on redox potential measurements.

    Science.gov (United States)

    Escalante-Minakata, P; Ibarra-Junquera, V; Rosu, H C; De León-Rodríguez, A; González-García, R

    2009-01-01

    We describe an algorithm for the continuous monitoring of the biomass and ethanol concentrations as well as the growth rate in the Mezcal fermentation process. The algorithm performs its task having available only the online measurements of the redox potential. The procedure combines an artificial neural network (ANN) that relates the redox potential to the ethanol and biomass concentrations with a nonlinear observer-based algorithm that uses the ANN biomass estimations to infer the growth rate of this fermentation process. The results show that the redox potential is a valuable indicator of the metabolic activity of the microorganisms during Mezcal fermentation. In addition, the estimated growth rate can be considered as a direct evidence of the presence of mixed culture growth in the process. Usually, mixtures of microorganisms could be intuitively clear in this kind of processes; however, the total biomass data do not provide definite evidence by themselves. In this paper, the detailed design of the software sensor as well as its experimental application is presented at the laboratory level.

  12. Glutathione Redox System in β-Thalassemia/Hb E Patients

    Directory of Open Access Journals (Sweden)

    Ruchaneekorn W. Kalpravidh

    2013-01-01

    Full Text Available β-thalassemia/Hb E is known to cause oxidative stress induced by iron overload. The glutathione system is the major endogenous antioxidant that protects animal cells from oxidative damage. This study aimed to determine the effect of disease state and splenectomy on redox status expressed by whole blood glutathione (GSH/glutathione disulfide (GSSG and also to evaluate glutathione-related responses to oxidation in β-thalassemia/Hb E patients. Twenty-seven normal subjects and 25 β-thalassemia/Hb E patients were recruited and blood was collected. The GSH/GSSG ratio, activities of glutathione-related enzymes, hematological parameters, and serum ferritin levels were determined in individuals. Patients had high iron-induced oxidative stress, shown as significantly increased serum ferritin, a decreased GSH/GSSG ratio, and increased activities of glutathione-related enzymes. Splenectomy increased serum ferritin levels and decreased GSH levels concomitant with unchanged glutathione-related enzyme activities. The redox ratio had a positive correlation with hemoglobin levels and negative correlation with levels of serum ferritin. The glutathione system may be the body’s first-line defense used against oxidative stress and to maintain redox homeostasis in thalassemic patients based on the significant correlations between the GSH/GSSH ratio and degree of anemia or body iron stores.

  13. Redox-Dependent Inflammation in Islet Transplantation Rejection

    Directory of Open Access Journals (Sweden)

    Jessie M. Barra

    2018-04-01

    Full Text Available Type 1 diabetes is an autoimmune disease that results in the progressive destruction of insulin-producing pancreatic β-cells inside the islets of Langerhans. The loss of this vital population leaves patients with a lifelong dependency on exogenous insulin and puts them at risk for life-threatening complications. One method being investigated to help restore insulin independence in these patients is islet cell transplantation. However, challenges associated with transplant rejection and islet viability have prevented long-term β-cell function. Redox signaling and the production of reactive oxygen species (ROS by recipient immune cells and transplanted islets themselves are key players in graft rejection. Therefore, dissipation of ROS generation is a viable intervention that can protect transplanted islets from immune-mediated destruction. Here, we will discuss the newly appreciated role of redox signaling and ROS synthesis during graft rejection as well as new strategies being tested for their efficacy in redox modulation during islet cell transplantation.

  14. Redox-Dependent Inflammation in Islet Transplantation Rejection

    Science.gov (United States)

    Barra, Jessie M.; Tse, Hubert M.

    2018-01-01

    Type 1 diabetes is an autoimmune disease that results in the progressive destruction of insulin-producing pancreatic β-cells inside the islets of Langerhans. The loss of this vital population leaves patients with a lifelong dependency on exogenous insulin and puts them at risk for life-threatening complications. One method being investigated to help restore insulin independence in these patients is islet cell transplantation. However, challenges associated with transplant rejection and islet viability have prevented long-term β-cell function. Redox signaling and the production of reactive oxygen species (ROS) by recipient immune cells and transplanted islets themselves are key players in graft rejection. Therefore, dissipation of ROS generation is a viable intervention that can protect transplanted islets from immune-mediated destruction. Here, we will discuss the newly appreciated role of redox signaling and ROS synthesis during graft rejection as well as new strategies being tested for their efficacy in redox modulation during islet cell transplantation. PMID:29740396

  15. Modulation of Erythrocyte Plasma Membrane Redox System Activity by Curcumin

    Directory of Open Access Journals (Sweden)

    Prabhakar Singh

    2016-01-01

    Full Text Available Plasma membrane redox system (PMRS is an electron transport chain system ubiquitously present throughout all cell types. It transfers electron from intracellular substrates to extracellular acceptors for regulation of redox status. Curcumin, isolated from Curcuma longa, has modulatory effects on cellular physiology due to its membrane interaction ability and antioxidant potential. The present study investigates the effect of curcumin on PMRS activity of erythrocytes isolated from Wistar rats in vitro and in vivo and validated through an in silico docking simulation study using Molegro Virtual Docker (MVD. Effects of curcumin were also evaluated on level of glutathione (GSH and the oxidant potential of plasma measured in terms of plasma ferric equivalent oxidative potentials (PFEOP. Results show that curcumin significantly (p<0.01 downregulated the PMRS activity in a dose-dependent manner. Molecular docking results suggest that curcumin interacts with amino acids at the active site cavity of cytochrome b5 reductase, a key constituent of PMRS. Curcumin also increased the GSH level in erythrocytes and plasma while simultaneously decreasing the oxidant potential (PFEOP of plasma. Altered PMRS activity and redox status are associated with the pathophysiology of several health complications including aging and diabetes; hence, the above finding may explain part of the role of curcumin in health beneficial effects.

  16. PHB Biosynthesis Counteracts Redox Stress in Herbaspirillum seropedicae

    Directory of Open Access Journals (Sweden)

    Marcelo B. Batista

    2018-03-01

    Full Text Available The ability of bacteria to produce polyhydroxyalkanoates such as poly(3-hydroxybutyrate (PHB enables provision of a carbon storage molecule that can be mobilized under demanding physiological conditions. However, the precise function of PHB in cellular metabolism has not been clearly defined. In order to determine the impact of PHB production on global physiology, we have characterized the properties of a ΔphaC1 mutant strain of the diazotrophic bacterium Herbaspirillum seropedicae. The absence of PHB in the mutant strain not only perturbs redox balance and increases oxidative stress, but also influences the activity of the redox-sensing Fnr transcription regulators, resulting in significant changes in expression of the cytochrome c-branch of the electron transport chain. The synthesis of PHB is itself dependent on the Fnr1 and Fnr3 proteins resulting in a cyclic dependency that couples synthesis of PHB with redox regulation. Transcriptional profiling of the ΔphaC1 mutant reveals that the loss of PHB synthesis affects the expression of many genes, including approximately 30% of the Fnr regulon.

  17. PHB Biosynthesis Counteracts Redox Stress in Herbaspirillum seropedicae.

    Science.gov (United States)

    Batista, Marcelo B; Teixeira, Cícero S; Sfeir, Michelle Z T; Alves, Luis P S; Valdameri, Glaucio; Pedrosa, Fabio de Oliveira; Sassaki, Guilherme L; Steffens, Maria B R; de Souza, Emanuel M; Dixon, Ray; Müller-Santos, Marcelo

    2018-01-01

    The ability of bacteria to produce polyhydroxyalkanoates such as poly(3-hydroxybutyrate) (PHB) enables provision of a carbon storage molecule that can be mobilized under demanding physiological conditions. However, the precise function of PHB in cellular metabolism has not been clearly defined. In order to determine the impact of PHB production on global physiology, we have characterized the properties of a Δ phaC1 mutant strain of the diazotrophic bacterium Herbaspirillum seropedicae . The absence of PHB in the mutant strain not only perturbs redox balance and increases oxidative stress, but also influences the activity of the redox-sensing Fnr transcription regulators, resulting in significant changes in expression of the cytochrome c -branch of the electron transport chain. The synthesis of PHB is itself dependent on the Fnr1 and Fnr3 proteins resulting in a cyclic dependency that couples synthesis of PHB with redox regulation. Transcriptional profiling of the Δ phaC1 mutant reveals that the loss of PHB synthesis affects the expression of many genes, including approximately 30% of the Fnr regulon.

  18. Chloride supporting electrolytes for all-vanadium redox flow batteries.

    Science.gov (United States)

    Kim, Soowhan; Vijayakumar, M; Wang, Wei; Zhang, Jianlu; Chen, Baowei; Nie, Zimin; Chen, Feng; Hu, Jianzhi; Li, Liyu; Yang, Zhenguo

    2011-10-28

    This paper examines vanadium chloride solutions as electrolytes for an all-vanadium redox flow battery. The chloride solutions were capable of dissolving more than 2.3 M vanadium at varied valence states and remained stable at 0-50 °C. The improved stability appeared due to the formation of a vanadium dinuclear [V(2)O(3)·4H(2)O](4+) or a dinuclear-chloro complex [V(2)O(3)Cl·3H(2)O](3+) in the solutions over a wide temperature range. The all-vanadium redox flow batteries with the chloride electrolytes demonstrated excellent reversibility and fairly high efficiencies. Only negligible, if any, gas evolution was observed. The improved energy capacity and good performance, along with the ease in heat management, would lead to substantial reduction in capital cost and life-cycle cost, making the vanadium chloride redox flow battery a promising candidate for stationary applications. This journal is © the Owner Societies 2011

  19. Single-molecule conductivity of non-redox and redox molecules at pure and gold-mined Au(111)-electrode surfaces

    DEFF Research Database (Denmark)

    Zhang, Jingdong; Chi, Qijin; Ulstrup, Jens

    The structure, two-dimensional organization, and function of molecules immobilized on solid surfaces can be addressed in a degree of detail that has reached the level of the single-molecule. In this context redox molecules are “smart” molecules adding sophisticated electronic function. Redox meta...

  20. The Development of the Redox Concept Inventory as a Measure of Students' Symbolic and Particulate Redox Understandings and Confidence

    Science.gov (United States)

    Brandriet, Alexandra R.; Bretz, Stacey Lowery

    2014-01-01

    This article describes the development of the Redox Concept Inventory (ROXCI) as a measure of students' understandings and confidence of both the symbolic and particulate domains of oxidation-reduction (redox) reactions. The ROXCI was created using a mixed-methods design in which the items were developed based upon themes that emerged from…

  1. Investigation of a redox-sensitive predictive model of mouse embryonic stem cells differentiation using quantitative nuclease protection assays and glutathione redox status

    Science.gov (United States)

    Investigation of a redox-sensitive predictive model of mouse embryonic stem cell differentiation via quantitative nuclease protection assays and glutathione redox status Chandler KJ,Hansen JM, Knudsen T,and Hunter ES 1. U.S. Environmental Protection Agency, Research Triangl...

  2. The Mechanism of Redox Reaction between Palladium(II Complex Ions and Potassium Formate in Acidic Aqueous Solution

    Directory of Open Access Journals (Sweden)

    Wojnicki M.

    2017-06-01

    Full Text Available The kinetics studies of redox reaction between palladium(II chloride complex ions and potassium formate in acidic aqueous solutions was investigated. It was shown, that the reduction reaction of Pd(II is selective in respect to Pd(II complex structure. The kinetic of the process was monitored spectrophotometrically. The influence of chloride ions concentration, Pd(II initial concentration, reductant concentration, ionic strength as well as the temperature were investigated in respect to the process dynamics. Arrhenius equation parameters were determined and are equal to 65.8 kJ/mol, and A = 1.12×1011 s−1.

  3. Metabolic and redox barriers in the skin exposed to drugs and xenobiotics.

    Science.gov (United States)

    Korkina, Liudmila

    2016-01-01

    Growing exposure of human skin to environmental and occupational hazards, to numerous skin care/beauty products, and to topical drugs led to a biomedical concern regarding sustainability of cutaneous chemical defence that is essential for protection against intoxication. Since skin is the largest extra-hepatic drug/xenobiotic metabolising organ where redox-dependent metabolic pathways prevail, in this review, publications on metabolic processes leading to redox imbalance (oxidative stress) and its autocrine/endocrine impact to cutaneous drug/xenobiotic metabolism were scrutinised. Chemical and photo-chemical skin barriers contain metabolic and redox compartments: their protective and homeostatic functions. The review will examine the striking similarity of adaptive responses to exogenous chemical/photo-chemical stressors and endogenous toxins in cutaneous metabolic and redox system; the role(s) of xenobiotics/drugs and phase II enzymes in the endogenous antioxidant defence and maintenance of redox balance; redox regulation of interactions between metabolic and inflammatory responses in skin cells; skin diseases sharing metabolic and redox problems (contact dermatitis, lupus erythematosus, and vitiligo) Due to exceptional the redox dependence of cutaneous metabolic pathways and interaction of redox active metabolites/exogenous antioxidants with drug/xenobiotic metabolism, metabolic tests of topical xenobiotics/drugs should be combined with appropriate redox analyses and performed on 3D human skin models.

  4. The Analgesic Acetaminophen and the Antipsychotic Clozapine Can Each Redox-Cycle with Melanin.

    Science.gov (United States)

    Temoçin, Zülfikar; Kim, Eunkyoung; Li, Jinyang; Panzella, Lucia; Alfieri, Maria Laura; Napolitano, Alessandra; Kelly, Deanna L; Bentley, William E; Payne, Gregory F

    2017-12-20

    Melanins are ubiquitous but their complexity and insolubility has hindered characterization of their structures and functions. We are developing electrochemical reverse engineering methodologies that focus on properties and especially on redox properties. Previous studies have shown that melanins (i) are redox-active and can rapidly and repeatedly exchange electrons with diffusible oxidants and reductants, and (ii) have redox potentials in midregion of the physiological range. These properties suggest the functional activities of melanins will depend on their redox context. The brain has a complex redox context with steep local gradients in O 2 that can promote redox-cycling between melanin and diffusible redox-active chemical species. Here, we performed in vitro reverse engineering studies and report that melanins can redox-cycle with two common redox-active drugs. Experimentally, we used two melanin models: a convenient natural melanin derived from cuttlefish (Sepia melanin) and a synthetic cysteinyldopamine-dopamine core-shell model of neuromelanin. One drug, acetaminophen (APAP), has been used clinically for over a century, and recent studies suggest that low doses of APAP can protect the brain from oxidative-stress-induced toxicity and neurodegeneration, while higher doses can have toxic effects in the brain. The second drug, clozapine (CLZ), is a second generation antipsychotic with polypharmacological activities that remain incompletely understood. These in vitro observations suggest that the redox activities of drugs may be relevant to their modes-of-action, and that melanins may interact with drugs in ways that affect their activities, metabolism, and toxicities.

  5. Redox potentials and kinetics of the Ce 3+/Ce 4+ redox reaction and solubility of cerium sulfates in sulfuric acid solutions

    Science.gov (United States)

    Paulenova, A.; Creager, S. E.; Navratil, J. D.; Wei, Y.

    Experimental work was performed with the aim of evaluating the Ce 4+/Ce 3+ redox couple in sulfuric acid electrolyte for use in redox flow battery (RFB) technology. The solubility of cerium sulfates in 0.1-4.0 M sulfuric acid at 20-60 °C was studied. A synergistic effect of both sulfuric acid concentration and temperature on the solubility of cerous sulfate was observed. The solubility of cerous sulfate significantly decreased with rising concentration of sulfuric acid and rising temperature, while the solubility of ceric sulfate goes through a significant maximum at 40 °C. Redox potentials and the kinetics of the cerous/ceric redox reaction were also studied under the same temperature-concentration conditions. The redox potentials were measured using the combined redox electrode (Pt-Ag/AgCl) in equimolar Ce 4+/Ce 3+ solutions (i.e.[Ce 3+]=[Ce 4+]) in sulfuric acid electrolyte. The Ce 3+/Ce 4+ redox potentials significantly decrease (i.e. shift to more negative values) with rising sulfuric acid concentration; a small maximum is observed at 40 °C. Cyclic voltammetric experiments confirmed slow electrochemical kinetics of the Ce 3+/Ce 4+ redox reaction on carbon glassy electrodes (CGEs) in sulfuric acid solutions. The observed dependencies of solubilities, the redox potentials and the kinetics of Ce 3+/Ce 4+ redox reaction on sulfuric acid concentration are thought to be the result of inequivalent complexation of the two redox species by sulfate anions: the ceric ion is much more strongly bound to sulfate than is the cerous ion. The best temperature-concentration conditions for the RFB electrolytes appear to be 40 °C and 1 M sulfuric acid, where the relatively good solubility of both cerium species, the maximum of redox potentials, and the more or less satisfying stability of CGE s were found. Even so, the relatively low solubility of cerium salts in sulfuric acid media and slow redox kinetics of the Ce 3+/Ce 4+ redox reaction at carbon indicate that the Ce 3+/Ce

  6. Breast Cancer Redox Heterogeneity Detectable with Chemical Exchange Satruation Transfer (CEST) MRI

    Science.gov (United States)

    Cai, Kejia; Xu, He N.; Singh, Anup; Moon, Lily; Haris, Mohammad; Reddy, Ravinder; Li, Lin

    2014-01-01

    Purpose Tissue redox state is an important mediator of various biological processes in health and diseases such as cancer. Previously, we discovered that the mitochondrial redox state of ex vivo tissues detected by redox scanning (an optical imaging method) revealed interesting tumor redox state heterogeneity that could differentiate tumor aggressiveness. Because the noninvasive chemical exchange saturation transfer (CEST) MRI can probe the proton transfer and generate contrasts from endogenous metabolites, we aim to investigate if the in vivo CEST contrast is sensitive to proton transfer of the redox reactions so as to reveal the tissue redox states in breast cancer animal models. Procedures CEST MRI has been employed to characterize tumor metabolic heterogeneity and correlated with the redox states measured by the redox scanning in two human breast cancer mouse xenograft models, MDA-MB-231 and MCF-7. The possible biological mechanism on the correlation between the two imaging modalities was further investigated by phantom studies where the reductants and the oxidants of the representative redox reactions were measured. Results The CEST contrast is found linearly correlated with NADH concentration and the NADH redox ratio with high statistical significance, where NADH is the reduced form of nicotinamide adenine dinucleotide. The phantom studies showed that the reductants of the redox reactions have more CEST contrast than the corresponding oxidants, indicating that higher CEST effect corresponds to the more reduced redox state. Conclusions This preliminary study suggests that CEST MRI, once calibrated, might provide a novel noninvasive imaging surrogate for the tissue redox state and a possible diagnostic biomarker for breast cancer in the clinic. PMID:24811957

  7. pH and redox effects of building materials

    International Nuclear Information System (INIS)

    Van der Sloot, H.A.; Van Zomeren, A.; Meeussen, J.C.L.; De Nie, D.S.

    2007-11-01

    The application of relatively fine grained industrial slags as fill material in industrial terrains and parking lots has led to unacceptably elevated pH values and imposed reducing conditions in ground- and surface water. Based on the Dutch Building Materials Decree the materials applied were classified as category 1 materials (free use). There are no limits set to pH and redox in this regulation. In itself a lower or higher pH and a low redox potential are not necessarily critical. Only when the buffer capacity of the surroundings is exceeded, undesirable situations may develop. In this work, the release of alkaline and reducing substances has been studied to assess if regulatory controls are needed and how such controls could be implemented practically. Both pH and redox potential are unsuitable properties for this purpose as it is the buffer capacity of the releasing material and the buffer capacity of the receiving soil and water bodies that determine whether unacceptable conditions develop. As pH and redox are also affected by gas reactions (O2 and CO2), the evaluation becomes relatively complex. Using the chemical speciation-transport model ORCHESTRA, a scenario description has been developed to assess the release of alkaline and reducing species from slag by infiltration under unsaturated conditions. Proper acid neutralization and redox buffering data for the materials were determined. Based on the sophisticated model results, a simplified model description was applied to link observations to impact. Decision schemes for applications above groundwater and in surface water have been developed based on the buffer capacity and particle size distribution of the material to be used, the infiltration rate, the degree of exposure to O2 and CO2 from the atmosphere or from soil air and the dimensions of the application. This has led to a preliminary guidance on implementing rules for acceptance of materials in specific applications. The modeled release predictions

  8. Redox signaling in the growth and development of colonial hydroids.

    Science.gov (United States)

    Blackstone, Neil W

    2003-02-01

    Redox signaling provides a quick and efficient mechanism for clonal or colonial organisms to adapt their growth and development to aspects of the environment, e.g. the food supply. A 'signature' of mitochondrial redox signaling, particularly as mediated by reactive oxygen species (ROS), can be elucidated by experimental manipulation of the electron transport chain. The major sites of ROS formation are found at NADH dehydrogenase of complex I and at the interface between coenzyme Q and complex III. Inhibitors of complex III should thus upregulate ROS from both sites; inhibitors of complex I should upregulate ROS from the first but not the second site, while uncouplers of oxidative phosphorylation should downregulate ROS from both sites. To investigate the possibility of such redox signaling, perturbations of colony growth and development were carried out using the hydroid Podocoryna carnea. Oxygen uptake of colonies was measured to determine comparable physiological doses of antimycin A(1) (an inhibitor of complex III), rotenone (an inhibitor of complex I) and carbonyl cyanide m-chlorophenylhydrazone (CCCP; an uncoupler of oxidative phosphorylation). Using these doses, clear effects on colony growth and development were obtained. Treatment with antimycin A(1) results in 'runner-like' colony growth, with widely spaced polyps and stolon branches, while treatment with CCCP results in 'sheet-like' growth, with closely spaced polyps and stolon branches. Parallel results have been obtained previously with azide, an inhibitor of complex IV, and dinitrophenol, another uncoupler of oxidative phosphorylation. Perhaps surprisingly, rotenone produced effects on colony development similar to those of CCCP. Assays of peroxides using 2',7'-dichlorofluorescin diacetate and fluorescent microscopy suggest a moderate difference in ROS formation between the antimycin and rotenone treatments. The second site of ROS formation (the interface between coenzyme Q and complex III) may thus

  9. New lab scale approaches for quantification of redox conditions

    Science.gov (United States)

    Fernandez, P. M.; Dathe, A.; Nadeem, S.; Bakken, L. R.; Bloem, E.; French, H. K.; Binley, A. M.

    2013-12-01

    Degradation of organic chemicals in the unsaturated zone is a process highly relevant for developing remediation techniques for protecting groundwater. Degradation causes changes in chemical composition of the water phase and gas releases. These changes can potentially be mapped with electrical resistivity measurements in the bulk soil and gas measurements at the soil surface. The redox potential combined with the local geological conditions determines the composition of available electron acceptors as well as microbial degradation pathways and how the soil system is affected in the long term. After oxygen and nitrate are depleted, manganese and iron should be reduced. However, in experiments conducted in the unsaturated zone at Gardermoen airport, Norway, it was found that for the degradation of the de-icing agent propylene glycol (PG), manganese and iron were preferred over nitrate as electron acceptor. A key hypothesis for the work presented is that for a designated soil, the redox potential affects gas releases and soil solution composition profoundly. As the redox potential decreases, the reactants of the degradation change and therefore the composition of the soil-water system changes. These changes can be quantified dynamically by gas measurements and changes in electrical conductivity of the pore water and electrical resistivity of the bulk soil. Batch experiments were conducted to examine whether nitrate is a preferred electron acceptor over iron and manganese oxides as described in classical redox reaction theory. Gas releases during PG and glutamate degradation were measured in a sandy pristine soil with and without nitrate under anaerobic condition during two weeks of incubation. Chemical reactions were quantified with the modelling tool ORCHESTRA. We are currently investigating whether dynamical measurements of electrical conductivity and bulk resistivity are suited to trace which electron acceptors (nitrate, manganese or iron) are being reduced. First

  10. Sediment phosphorus speciation and mobility under dynamic redox conditions

    Science.gov (United States)

    Parsons, Chris T.; Rezanezhad, Fereidoun; O'Connell, David W.; Van Cappellen, Philippe

    2017-07-01

    Anthropogenic nutrient enrichment has caused phosphorus (P) accumulation in many freshwater sediments, raising concerns that internal loading from legacy P may delay the recovery of aquatic ecosystems suffering from eutrophication. Benthic recycling of P strongly depends on the redox regime within surficial sediment. In many shallow environments, redox conditions tend to be highly dynamic as a result of, among others, bioturbation by macrofauna, root activity, sediment resuspension and seasonal variations in bottom-water oxygen (O2) concentrations. To gain insight into the mobility and biogeochemistry of P under fluctuating redox conditions, a suspension of sediment from a hypereutrophic freshwater marsh was exposed to alternating 7-day periods of purging with air and nitrogen gas (N2), for a total duration of 74 days, in a bioreactor system. We present comprehensive data time series of bulk aqueous- and solid-phase chemistry, solid-phase phosphorus speciation and hydrolytic enzyme activities demonstrating the mass balanced redistribution of P in sediment during redox cycling. Aqueous phosphate concentrations remained low ( ˜ 2.5 µM) under oxic conditions due to sorption to iron(III) oxyhydroxides. During anoxic periods, once nitrate was depleted, the reductive dissolution of iron(III) oxyhydroxides released P. However, only 4.5 % of the released P accumulated in solution while the rest was redistributed between the MgCl2 and NaHCO3 extractable fractions of the solid phase. Thus, under the short redox fluctuations imposed in the experiments, P remobilization to the aqueous phase remained relatively limited. Orthophosphate predominated at all times during the experiment in both the solid and aqueous phase. Combined P monoesters and diesters accounted for between 9 and 16 % of sediment particulate P. Phosphatase activities up to 2.4 mmol h-1 kg-1 indicated the potential for rapid mineralization of organic P (Po), in particular during periods of aeration when the

  11. Electrocatalysis in the vanadium redox flow battery and coupling the redox flow battery with the fuel cell

    OpenAIRE

    Britz, Anette Beata

    2015-01-01

    In den Redox-Fluss-Batterien (RFB) bilden die Funktionskomponenten: Elektrode, Membran und Elektrolyt die limitierenden Faktoren für die Leistung der Batterie. Als Elektrodenmaterial werden kohlenstoffbasierte Materialien verwendet. Durch geeignete Modifizierung dieser Elektroden kann die Stromdichte sowie die Energieeffizienz verbessert werden. Die richtige Wahl der Membran kann einem Kapazitätsverlust während der Lade- und Entladezyklen entgegenwirken. In dieser Arbeit wurden die Funktio...

  12. Inhibitors of nuclease and redox activity of apurinic/apyrimidinic endonuclease 1/redox effector factor 1 (APE1/Ref-1).

    Science.gov (United States)

    Laev, Sergey S; Salakhutdinov, Nariman F; Lavrik, Olga I

    2017-05-01

    Human apurinic/apyrimidinic endonuclease 1/redox effector factor 1 (APE1/Ref-1) is a multifunctional protein which is essential in the base excision repair (BER) pathway of DNA lesions caused by oxidation and alkylation. This protein hydrolyzes DNA adjacent to the 5'-end of an apurinic/apyrimidinic (AP) site to produce a nick with a 3'-hydroxyl group and a 5'-deoxyribose phosphate moiety or activates the DNA-binding activity of certain transcription factors through its redox function. Studies have indicated a role for APE1/Ref-1 in the pathogenesis of cancer and in resistance to DNA-interactive drugs. Thus, this protein has potential as a target in cancer treatment. As a result, major efforts have been directed to identify small molecule inhibitors against APE1/Ref-1 activities. These agents have the potential to become anticancer drugs. The aim of this review is to present recent progress in studies of all published small molecule APE1/Ref-1 inhibitors. The structures and activities of APE1/Ref-1 inhibitors, that target both DNA repair and redox activities, are presented and discussed. To date, there is an urgent need for further development of the design and synthesis of APE1/Ref-1 inhibitors due to high importance of this protein target. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Potential redox behaviour on industrial wastes treatment; Evolucion del potencial redox en tratamiento y depuracion industrial de aguas

    Energy Technology Data Exchange (ETDEWEB)

    Marin Galvin, R.; rodriguez Mellado, J. M.; Ruiz Montoya, M.; Jimenez Gamero, C. [Departamento Quimica Fisica y Termodinamica aplicada, Facultad de ciencias, Universidad de Cordoba (Spain)

    1995-12-31

    A study over the behaviour of redox potential in waters and wastewaters under industrial treatment processes has been carried out. In both cases, the potential-time curves obtained were in a logarithmical shape being more strongly distorted when the waters contained more dissolved and suspended compounds. Oxygen fundamentally leads the redox state in wastewaters, although ozone and chlorine almost oxygen lead the redox potential in raw waters intended to drinking water production. In this way, by increasing 210 m V the E{sub H} value of water or maintaining the rH>21.8 it can be industrially sterilized the drinking water. On the other hand, increases of 350 mV in the EH values from wastewaters influent to plant to the treated waters, allowed discarding 450 mg/l of DQO and 9 mg/l of NH{sub 3} from the former. Finally, the exploitation of the Wastewaters Treatment Plant by regulation of the E{sub H} values can suppose a good practice. (Author) 14 refs.

  14. A study of the Fe(III)/Fe(II)-triethanolamine complex redox couple for redox flow battery application

    International Nuclear Information System (INIS)

    Wen, Y.H.; Zhang, H.M.; Qian, P.; Zhou, H.T.; Zhao, P.; Yi, B.L.; Yang, Y.S.

    2006-01-01

    The electrochemical behavior of the Fe(III)/Fe(II)-triethanolamine(TEA) complex redox couple in alkaline medium and influence of the concentration of TEA were investigated. A change of the concentration of TEA mainly produces the following two results. (1) With an increase of the concentration of TEA, the solubility of the Fe(III)-TEA can be increased to 0.6 M, and the solubility of the Fe(II)-TEA is up to 0.4 M. (2) In high concentration of TEA with the ratio of TEA to NaOH ranging from 1 to 6, side reaction peaks on the cathodic main reaction of the Fe(III)-TEA complex at low scan rate can be minimized. The electrode process of Fe(III)-TEA/Fe(II)-TEA is electrochemically reversible with higher reaction rate constant than the uncomplexed species. Constant current charge-discharge shows that applying anodic active materials of relatively high concentrations facilitates the improvement of cell performance. The open-circuit voltage of the Fe-TEA/Br 2 cell with the Fe(III)-TEA of 0.4 M, after full charging, is nearly 2.0 V and is about 32% higher than that of the all-vanadium batteries, together with the energy efficiency of approximately 70%. The preliminary exploration shows that the Fe(III)-TEA/Fe(II)-TEA couple is electrochemically promising as negative redox couple for redox flow battery (RFB) application

  15. A novel iron-lead redox flow battery for large-scale energy storage

    Science.gov (United States)

    Zeng, Y. K.; Zhao, T. S.; Zhou, X. L.; Wei, L.; Ren, Y. X.

    2017-04-01

    The redox flow battery (RFB) is one of the most promising large-scale energy storage technologies for the massive utilization of intermittent renewables especially wind and solar energy. This work presents a novel redox flow battery that utilizes inexpensive and abundant Fe(II)/Fe(III) and Pb/Pb(II) redox couples as redox materials. Experimental results show that both the Fe(II)/Fe(III) and Pb/Pb(II) redox couples have fast electrochemical kinetics in methanesulfonic acid, and that the coulombic efficiency and energy efficiency of the battery are, respectively, as high as 96.2% and 86.2% at 40 mA cm-2. Furthermore, the battery exhibits stable performance in terms of efficiencies and discharge capacities during the cycle test. The inexpensive redox materials, fast electrochemical kinetics and stable cycle performance make the present battery a promising candidate for large-scale energy storage applications.

  16. A Multi-Parametric Device with Innovative Solid Electrodes for Long-Term Monitoring of pH, Redox-Potential and Conductivity in a Nuclear Waste Repository

    Directory of Open Access Journals (Sweden)

    Jordan Daoudi

    2017-06-01

    Full Text Available We present an innovative electrochemical probe for the monitoring of pH, redox potential and conductivity in near-field rocks of deep geological radioactive waste repositories. The probe is composed of a monocrystalline antimony electrode for pH sensing, four AgCl/Ag-based reference or Cl− selective electrodes, one Ag2S/Ag-based reference or S2− selective electrode, as well as four platinum electrodes, a gold electrode and a glassy-carbon electrode for redox potential measurements. Galvanostatic electrochemistry impedance spectroscopy using AgCl/Ag-based and platinum electrodes measure conductivity. The use of such a multi-parameter probe provides redundant information, based as it is on the simultaneous behaviour under identical conditions of different electrodes of the same material, as well as on that of electrodes made of different materials. This identifies the changes in physical and chemical parameters in a solution, as well as the redox reactions controlling the measured potential, both in the solution and/or at the electrode/solution interface. Understanding the electrochemical behaviour of selected materials thus is a key point of our research, as provides the basis for constructing the abacuses needed for developing robust and reliable field sensors.

  17. A Multi-Parametric Device with Innovative Solid Electrodes for Long-Term Monitoring of pH, Redox-Potential and Conductivity in a Nuclear Waste Repository.

    Science.gov (United States)

    Daoudi, Jordan; Betelu, Stephanie; Tzedakis, Theodore; Bertrand, Johan; Ignatiadis, Ioannis

    2017-06-13

    We present an innovative electrochemical probe for the monitoring of pH, redox potential and conductivity in near-field rocks of deep geological radioactive waste repositories. The probe is composed of a monocrystalline antimony electrode for pH sensing, four AgCl/Ag-based reference or Cl - selective electrodes, one Ag₂S/Ag-based reference or S 2- selective electrode, as well as four platinum electrodes, a gold electrode and a glassy-carbon electrode for redox potential measurements. Galvanostatic electrochemistry impedance spectroscopy using AgCl/Ag-based and platinum electrodes measure conductivity. The use of such a multi-parameter probe provides redundant information, based as it is on the simultaneous behaviour under identical conditions of different electrodes of the same material, as well as on that of electrodes made of different materials. This identifies the changes in physical and chemical parameters in a solution, as well as the redox reactions controlling the measured potential, both in the solution and/or at the electrode/solution interface. Understanding the electrochemical behaviour of selected materials thus is a key point of our research, as provides the basis for constructing the abacuses needed for developing robust and reliable field sensors.

  18. Capacitance enhancement of polyaniline coated curved-graphene supercapacitors in a redox-active electrolyte

    KAUST Repository

    Chen, Wei

    2013-01-01

    We show, for the first time, a redox-active electrolyte in combination with a polyaniline-coated curved graphene active material to achieve significant enhancement in the capacitance (36-92% increase) compared to supercapacitors that lack the redox-active contribution from the electrolyte. The supercapacitors based on the redox-active electrolyte also exhibit excellent rate capability and very long cycling performance (>50 000 cycles). This journal is © The Royal Society of Chemistry.

  19. Thermo-Kinetic Investigation of Comparative Ligand Effect on Cysteine Iron Redox Reaction

    OpenAIRE

    Rizvi, Masood Ahmad; Teshima, Norio; Maqsood, Syed Raashid; Akhoon, Showket Ahmad; Peerzada, Ghulam Mustafa

    2015-01-01

    Transition metal ions in their free state bring unwanted biological oxidations generating oxidative stress. The ligand modulated redox potential can be indispensable in prevention of such oxidative stress by blocking the redundant bio-redox reactions. In this study we investigated the comparative ligand effect on the thermo-kinetic aspects of biologically important cysteine iron (III) redox reaction using spectrophotometric and potentiometric methods. The results were corroborated...

  20. Vascular remodeling: A redox-modulated mechanism of vessel caliber regulation.

    Science.gov (United States)

    Tanaka, Leonardo Y; Laurindo, Francisco R M

    2017-08-01

    Vascular remodeling, i.e. whole-vessel structural reshaping, determines lumen caliber in (patho)physiology. Here we review mechanisms underlying vessel remodeling, with emphasis in redox regulation. First, we discuss confusing terminology and focus on strictu sensu remodeling. Second, we propose a mechanobiological remodeling paradigm based on the concept of tensional homeostasis as a setpoint regulator. We first focus on shear-mediated models as prototypes of remodeling closely dominated by highly redox-sensitive endothelial function. More detailed discussions focus on mechanosensors, integrins, extracellular matrix, cytoskeleton and inflammatory pathways as potential of mechanisms potentially coupling tensional homeostasis to redox regulation. Further discussion of remodeling associated with atherosclerosis and injury repair highlights important aspects of redox vascular responses. While neointima formation has not shown consistent responsiveness to antioxidants, vessel remodeling has been more clearly responsive, indicating that despite the multilevel redox signaling pathways, there is a coordinated response of the whole vessel. Among mechanisms that may orchestrate redox pathways, we discuss roles of superoxide dismutase activity and extracellular protein disulfide isomerase. We then discuss redox modulation of aneurysms, a special case of expansive remodeling. We propose that the redox modulation of vascular remodeling may reflect (1) remodeling pathophysiology is dominated by a particularly redox-sensitive cell type, e.g., endothelial cells (2) redox pathways are temporospatially coordinated at an organ level across distinct cellular and acellular structures or (3) the tensional homeostasis setpoint is closely connected to redox signaling. The mechanobiological/redox model discussed here can be a basis for improved understanding of remodeling and helps clarifying mechanisms underlying prevalent hard-to-treat diseases. Copyright © 2017 Elsevier Inc. All

  1. First-principles molecular dynamics simulation study on electrolytes for use in redox flow battery

    Science.gov (United States)

    Choe, Yoong-Kee; Tsuchida, Eiji; Tokuda, Kazuya; Ootsuka, Jun; Saito, Yoshihiro; Masuno, Atsunobu; Inoue, Hiroyuki

    2017-11-01

    Results of first-principles molecular dynamics simulations carried out to investigate structural aspects of electrolytes for use in a redox flow battery are reported. The electrolytes studied here are aqueous sulfuric acid solutions where its property is of importance for dissolving redox couples in redox flow battery. The simulation results indicate that structural features of the acid solutions depend on the concentration of sulfuric acid. Such dependency arises from increase of proton dissociation from sulfuric acid.

  2. Characterization of plasma thiol redox potential in a common marmoset model of aging

    Directory of Open Access Journals (Sweden)

    James R. Roede

    2013-01-01

    Full Text Available Due to its short lifespan, ease of use and age-related pathologies that mirror those observed in humans, the common marmoset (Callithrix jacchus is poised to become a standard nonhuman primate model of aging. Blood and extracellular fluid possess two major thiol-dependent redox nodes involving cysteine (Cys, cystine (CySS, glutathione (GSH and glutathione disulfide (GSSG. Alteration in these plasma redox nodes significantly affects cellular physiology, and oxidation of the plasma Cys/CySS redox potential (EhCySS is associated with aging and disease risk in humans. The purpose of this study was to determine age-related changes in plasma redox metabolites and corresponding redox potentials (Eh to further validate the marmoset as a nonhuman primate model of aging. We measured plasma thiol redox states in marmosets and used existing human data with multivariate adaptive regression splines (MARS to model the relationships between age and redox metabolites. A classification accuracy of 70.2% and an AUC of 0.703 were achieved using the MARS model built from the marmoset redox data to classify the human samples as young or old. These results show that common marmosets provide a useful model for thiol redox biology of aging.

  3. Redox regulation of peroxiredoxin and proteinases by ascorbate and thiols during pea root nodule senescence.

    Science.gov (United States)

    Groten, Karin; Dutilleul, Christelle; van Heerden, Philippus D R; Vanacker, Hélène; Bernard, Stéphanie; Finkemeier, Iris; Dietz, Karl-Josef; Foyer, Christine H

    2006-02-20

    Redox factors contributing to nodule senescence were studied in pea. The abundance of the nodule cytosolic peroxiredoxin but not the mitochondrial peroxiredoxin protein was modulated by ascorbate. In contrast to redox-active antioxidants such as ascorbate and cytosolic peroxiredoxin that decreased during nodule development, maximal extractable nodule proteinase activity increased progressively as the nodules aged. Cathepsin-like activities were constant throughout development but serine and cysteine proteinase activities increased during senescence. Senescence-induced cysteine proteinase activity was inhibited by cysteine, dithiotreitol, or E-64. Senescence-dependent decreases in redox-active factors, particularly ascorbate and peroxiredoxin favour decreased redox-mediated inactivation of cysteine proteinases.

  4. Development of an investigation method for redox condition of rocks by self potential (SP) method

    International Nuclear Information System (INIS)

    Kubota, Kenji; Inohara, Yoshiki; Oyama, Takahiro

    2012-01-01

    One of the major issues in subsurface disposal of low level radioactive wastes is that long term behaviors of sedimentary rocks can be affected by geochemical factors. Redox conditions can affect to corrosion of metal included in artificial barrier or wastes and adsorption characteristics of a nuclide. Therefore, it is necessary to develop a method for evaluating the redox conditions around natural barrier at waste facilities. In general, geochemical properties are acquired by rock samples or water sampling at a borehole. However, there is a possibility not to acquire data we want to evaluate. If geophysical methods are applied, redox conditions can be evaluated widely and briefly. There is a possibility that self potential (SP) and redox conditions have a correlation. So we have conducted self potential method around test caverns where redox front can be observed at the Rokkasho site. The results demonstrated that self potential decreased around redox front. There was a positive correlation between self potential and pH. One of the factors of self potential change is difference of elevation, however, self potential change around redox front was larger than that expected from elevation difference. Zeta potential is one of the important factors for determination of self potential, and it had a correlation with self potential or pH. Therefore, there is a possibility that self potential change occurs by geochemical condition changes around redox front, and redox condition can be detected by self potential method. (author)

  5. Quantitative proteomic characterization of redox-dependent post-translational modifications on protein cysteines

    Energy Technology Data Exchange (ETDEWEB)

    Duan, Jicheng; Gaffrey, Matthew J.; Qian, Wei-Jun

    2017-01-01

    Protein cysteine thiols play a crucial role in redox signaling, regulation of enzymatic activity and protein function, and maintaining redox homeostasis in living systems. The unique chemical reactivity of thiol groups makes cysteine susceptible to oxidative modifications by reactive oxygen and nitrogen species to form a broad array of reversible and irreversible protein post-translational modifications (PTMs). The reversible modifications in particular are one of the major components of redox signaling and are involved in regulation of various cellular processes under physiological and pathological conditions. The biological significance of these redox PTMs in health and diseases has been increasingly recognized. Herein, we review the recent advances of quantitative proteomic approaches for investigating redox PTMs in complex biological systems, including the general considerations of sample processing, various chemical or affinity enrichment strategies, and quantitative approaches. We also highlight a number of redox proteomic approaches that enable effective profiling of redox PTMs for addressing specific biological questions. Although some technological limitations remain, redox proteomics is paving the way towards a better understanding of redox signaling and regulation in human health and diseases.

  6. Redox front formation in an uplifting sedimentary rock sequence: An analogue for redox-controlling processes in the geosphere around deep geological repositories for radioactive waste

    International Nuclear Information System (INIS)

    Yoshida, H.; Metcalfe, R.; Yamamoto, K.; Murakami, Y.; Hoshii, D.; Kanekiyo, A.; Naganuma, T.; Hayashi, T.

    2008-01-01

    Subsurface redox fronts control the mobilization and fixation of many trace elements, including potential pollutants such as certain radionuclides. Any safety assessment for a deep geological repository for radioactive wastes needs to take into account adequately the long-term redox processes in the geosphere surrounding the repository. To build confidence in understanding these processes, a redox front in a reduced siliceous sedimentary rock distributed in an uplifting area in Japan has been studied in detail. Geochemical analyses show increased concentrations of Fe and trace elements, including rare earth elements (REEs), at the redox front, even though concentrations of reduced rock matrix constituents show little change. Detailed SEM observations revealed that fossilized microorganisms composed of amorphous granules made exclusively of Fe and Si occur in the rock's pore space. Microbial 16S rDNA analysis suggests that there is presently a zonation of different bacterial groups within the redox band, and bacterial zonation played an important role in the concentration of Fe-oxyhydroxides at the redox front. These water-rock-microbe interactions can be considered analogous to the processes occurring in the redox fronts that would develop around geological repositories for radioactive waste. Once formed, the Fe-oxyhydroxides within such a front would be preserved even after reducing conditions resume following repository closure

  7. Redox front formation in an uplifting sedimentary rock sequence: An analogue for redox-controlling processes in the geosphere around deep geological repositories for radioactive waste

    Energy Technology Data Exchange (ETDEWEB)

    Yoshida, H. [Nagoya University Museum, Material Research Section, Furocho, Nagoya 464-8602 (Japan)], E-mail: dora@num.nagoya-u.ac.jp; Metcalfe, R. [Quintessa Japan, Queen' s Tower A7-707, Minatomirai, Yokohama 220-6007 (Japan); Yamamoto, K. [Nagoya University Museum, Material Research Section, Furocho, Nagoya 464-8602 (Japan); Murakami, Y. [Japan Atomic Energy Agency (JAEA), Tono Geoscience Centre (Japan); Hoshii, D.; Kanekiyo, A.; Naganuma, T. [Hiroshima University, Higashi Hiroshima, Kagamiyama 1-4-4 (Japan); Hayashi, T. [Asahi University, Department of Dental Pharmacology, Hozumi, Gifu (Japan)

    2008-08-15

    Subsurface redox fronts control the mobilization and fixation of many trace elements, including potential pollutants such as certain radionuclides. Any safety assessment for a deep geological repository for radioactive wastes needs to take into account adequately the long-term redox processes in the geosphere surrounding the repository. To build confidence in understanding these processes, a redox front in a reduced siliceous sedimentary rock distributed in an uplifting area in Japan has been studied in detail. Geochemical analyses show increased concentrations of Fe and trace elements, including rare earth elements (REEs), at the redox front, even though concentrations of reduced rock matrix constituents show little change. Detailed SEM observations revealed that fossilized microorganisms composed of amorphous granules made exclusively of Fe and Si occur in the rock's pore space. Microbial 16S rDNA analysis suggests that there is presently a zonation of different bacterial groups within the redox band, and bacterial zonation played an important role in the concentration of Fe-oxyhydroxides at the redox front. These water-rock-microbe interactions can be considered analogous to the processes occurring in the redox fronts that would develop around geological repositories for radioactive waste. Once formed, the Fe-oxyhydroxides within such a front would be preserved even after reducing conditions resume following repository closure.

  8. Albumin-bound fatty acids but not albumin itself alter redox balance in tubular epithelial cells and induce a peroxide-mediated redox-sensitive apoptosis

    Science.gov (United States)

    Ruggiero, Christine; Elks, Carrie M.; Kruger, Claudia; Cleland, Ellen; Addison, Kaity; Noland, Robert C.

    2014-01-01

    Albuminuria is associated with metabolic syndrome and diabetes. It correlates with the progression of chronic kidney disease, particularly with tubular atrophy. The fatty acid load on albumin significantly increases in obesity, presenting a proinflammatory environment to the proximal tubules. However, little is known about changes in the redox milieu during fatty acid overload and how redox-sensitive mechanisms mediate cell death. Here, we show that albumin with fatty acid impurities or conjugated with palmitate but not albumin itself compromised mitochondrial and cell viability, membrane potential and respiration. Fatty acid overload led to a redox imbalance which deactivated the antioxidant protein peroxiredoxin 2 and caused a peroxide-mediated apoptosis through the redox-sensitive pJNK/caspase-3 pathway. Transfection of tubular cells with peroxiredoxin 2 was protective and mitigated apoptosis. Mitochondrial fatty acid entry and ceramide synthesis modulators suggested that mitochondrial β oxidation but not ceramide synthesis may modulate lipotoxic effects on tubular cell survival. These results suggest that albumin overloaded with fatty acids but not albumin itself changes the redox environment in the tubules, inducing a peroxide-mediated redox-sensitive apoptosis. Thus, mitigating circulating fatty acid levels may be an important factor in both preserving redox balance and preventing tubular cell damage in proteinuric diseases. PMID:24500687

  9. Pyrazolates advance cerium chemistry: a CeIII/CeIV redox equilibrium with benzoquinone.

    Science.gov (United States)

    Werner, Daniel; Deacon, Glen B; Junk, Peter C; Anwander, Reiner

    2017-05-16

    Two stable cerium(iv) 3,5-dialkylpyrazolate complexes are presented, namely dimeric [Ce(Me 2 pz) 4 ] 2 (Me 2 pz = 3,5-dimethylpyrazolate) and monomeric Ce(tBu 2 pz) 4 (tBu 2 pz = 3,5-di-tert-butylpyrazolate) along with their trivalent counterparts [Ce(Me 2 pz) 3 ] and [Ce(tBu 2 pz) 3 ] 2 . All complexes were obtained from protonolysis reactions employing the silylamide precursors Ce[N(SiHMe 2 ) 2 ] 4 and Ce[N(SiMe 3 ) 2 ] 3 . Treatment of homoleptic Ce IV and Ce III Me 2 pz complexes with 1,4-hydroquinone (H 2 hq) or 1,4-benzoquinone (bq), respectively, ultimately gave the same trimetallic Ce III species via a cerium redox equilibrium. The Ce III complex Ce 3 (Me 2 pz) 5 (pchd) 2 (L) (pchd = 1,4-bis(3,5-dimethylpyrazol-1-yl)cyclohex-2,5-diene-1,4-diolato; L = Me 2 pzH or (thf) 2 ) results from a di-1,4-pyrazolyl attack on pre-coordinated bq. The reduction of bq by [Ce(Me 2 pz) 3 (thf)] 2 , and re-oxidation by the resulting Ce IV species was supported by UV-vis spectroscopic investigations. Comparisons with the redox-innocent complexes [Ln(Me 2 pz) 3 (thf)] 2 (Ln = La and Pr) revealed far less selective reactions with bq, giving hexametallic and octametallic rare-earth metal side products containing 2-Me 2 pz substituted hq ligands.

  10. Salt-Assisted Ultrasonicated De-Aggregation and Advanced Redox Electrochemistry of Detonation Nanodiamond

    Directory of Open Access Journals (Sweden)

    Sanju Gupta

    2017-11-01

    Full Text Available Nanodiamond particles form agglomerates in the dry powder state and this poses limitation to the accessibility of their diamond-like core thus dramatically impacting their technological advancement. In this work, we report de-agglomeration of nanodiamond (ND by using a facile technique namely, salt-assisted ultrasonic de-agglomeration (SAUD. Utilizing ultrasound energy and ionic salts (sodium chloride and sodium acetate, SAUD is expected to break apart thermally treated nanodiamond aggregates (~50–100 nm and produce an aqueous slurry of de-aggregated stable colloidal nanodiamond dispersions by virtue of ionic interactions and electrostatic stabilization. Moreover, the SAUD technique neither has toxic chemicals nor is it difficult to remove impurities and therefore the isolated nanodiamonds produced are exceptionally suited for engineered nanocarbon for mechanical (composites, lubricants and biomedical (bio-labeling, biosensing, bioimaging, theranostic applications. We characterized the microscopic structure using complementary techniques including transmission electron microscopy combined with selected-area electron diffraction, optical and vibrational spectroscopy. We immobilized SAUD produced NDs on boron-doped diamond electrodes to investigate fundamental electrochemical properties. They included surface potential (or Fermi energy level, carrier density and mapping electrochemical (reactivity using advanced scanning electrochemical microscopy in the presence of a redox-active probe, with the aim of understanding the surface redox chemistry and the interfacial process of isolated nanodiamond particles as opposed to aggregated and untreated nanoparticles. The experimental findings are discussed in terms of stable colloids, quantum confinement and predominantly surface effects, defect sites (sp2–bonded C and unsaturated bonds, inner core (sp3–bonded C/outer shell (sp2–bonded C structure, and surface functionality. Moreover, the surface

  11. Investigation of potential analytical methods for redox control of the vitrification process

    International Nuclear Information System (INIS)

    Goldman, D.S.

    1985-11-01

    An investigation was conducted to evaluate several analytical techniques to measure ferrous/ferric ratios in simulated and radioactive nuclear waste glasses for eventual redox control of the vitrification process. Redox control will minimize the melt foaming that occurs under highly oxidizing conditions and the metal precipitation that occurs under highly reducing conditions. The analytical method selected must have a rapid response for production problems with minimal complexity and analyst involvement. The wet-chemistry, Moessbauer spectroscopy, glass color analysis, and ion chromatography techniques were explored, with particular emphasis being placed on the Moessbauer technique. In general, all of these methods can be used for nonradioactive samples. The Moessbauer method can readily analyze glasses containing uranium and thorium. A shielded container was designed and built to analyze fully radioactive glasses with the Moessbauer spectrometer in a hot cell environment. However, analyses conducted with radioactive waste glasses containing 90 Sr and 137 Cs were unsuccessful, presumably due to background radiation problems caused by the samples. The color of glass powder can be used to analyze the ferrous/ferric ratio for low chromium glasses, but this method may not be as precise as the others. Ion chromatography was only tested on nonradioactive glasses, but this technique appears to have the required precision due to its analysis of both Fe +2 and Fe +3 and its anticipated adaptability for radioactivity samples. This development would be similar to procedures already in use for shielded inductively coupled plasma emission (ICP) spectrometry. Development of the ion chromatography method is therefore recommended; conventional wet-chemistry is recommended as a backup procedure

  12. Iron Hydroxide Minerals Drive Organic and Phosphorus Chemistry in Subsurface Redox / pH Gradients

    Science.gov (United States)

    Flores, E.; Barge, L. M.; VanderVelde, D.; Baum, M.

    2017-12-01

    Iron minerals, particularly iron oxides and oxyhydroxides, are prevalent on Mars and may exist in mixed valence or even reduced states beneath the oxidized surface. Iron (II,III) hydroxides, including green rust, are reactive and potentially catalytic minerals that can absorb and concentrate charged species, while also driving chemical reactions. These minerals are highly redox-sensitive and the presence of organics and/or phosphorus species could affect their mineralogy and/or stability. Conversely, the minerals might be able to drive chemical processes such as amino acid formation, phosphorus oxyanion reactions, or could simply selectively preserve organic species via surface adsorption. In an open aqueous sediment column, soluble products of mineral-driven reactions could also diffuse to sites of different chemical conditions to react even further. We synthesized Fe-hydroxide minerals under various conditions relevant to early Earth and ancient Mars (>3.0 Gyr), anoxically and in the presence of salts likely to have been present in surface or ground waters. Using these minerals we conducted experiments to test whether iron hydroxides could promote amino acid formation, and how the reaction is affected by subsurface gradients of redox, pH, and temperature. We also tested the adsorption of organic and phosphorus species onto Fe-hydroxide minerals at different conditions within the gradients. The suite of organic or phosphorus signatures that may be found in a particular mineral system is a combination of what is synthesized there, what is preferentially concentrated / retained there, and what is preserved against degradation. Further work is needed to determine how these processes could have proceeded on Mars and what mineral-organic signatures, abiotic or otherwise, would be produced from such processes.

  13. Redox control of iron biomineralization in Magnetospirillum magneticum AMB-1

    Science.gov (United States)

    Jones, Stephanie Rhianon

    Magnetotactic bacteria have evolved complex subcellular machinery to construct linear chains of magnetite nanocrystals that allow the host cell to sense direction. Each mixed-valent iron nanoparticle is mineralized from soluble iron within a membrane-encapsulated vesicle termed the magnetosome, which serves as a specialized compartment that regulates the iron, redox, and pH environment of the growing mineral. In order to dissect the biological components that control this process, we have carried out genetic and biochemical studies of proteins proposed to function in iron mineralization in Magnetospirillum magneticum AMB-1. As iron biomineralization by magnetotactic bacteria represents a particularly interesting case for understanding how the production of nanomaterials can be programmed at the genetic level, we also apply synthetic biology techniques towards the production of new cellular materials and new cellular functions. As the production of magnetite requires both the formation of Fe(II) and Fe(III), the redox components of the magnetosome play an essential role in this process. Using genetic complementation studies, we show that the redox cofactors or heme sites of the two putative redox partners, MamP and MamT, are required for magnetite biomineralization in vivo and that removal of one or both sites leads to defects in mineralization. We develop and optimize a heterologous expression method in the E. coli periplasm to cleanly isolate fully heme-loaded MamP for biochemical studies. Spectrochemical redox titrations show that the reduction potential of MamP lies in a different range than other c-type cytochrome involved in either Fe(III) reduction or Fe(II) oxidation. Nonetheless, in vitro mineralization studies with MamP and Fe(II) show that it is able to catalyze the formation of mixed-valent Fe(II)/Fe(III) oxides such as green rust. Biomineralization also requires lattice-templating proteins that guide the growth of the functional crystalline material. We

  14. The Comparison of One-Session Intensive Aerobic Exercise Effects on Glutathione Redox State of Red Blood Cells in Professional, Recreational Athletes and Nonathletes

    Directory of Open Access Journals (Sweden)

    Farnaz Seifi-Skishahr

    2015-04-01

    Full Text Available Background & objectives: The “redox” state represents the oxidation/reduction potential within the cell in a way that more “redox” is the marker of health, while the more oxidized reflects predisposition to diseases. Different types of exercise training may change the thiol/disulfide ratio of redox couples such as glutathione and represent a shift in redox balance. This study was assessed the influence of high-intensity aerobic exercise on glutathione redox state in red blood cells in professional, recreational athletes and nonathletes.   Methods: Ten voluntary well trained (WT, moderately trained (MT and untrained men subjectswere randomly selected for this semi-experimental study (mean ages of 21.10±1.72 21.70±1.88 and 20.10±1.44, respectively. Blood samples were collected before, immediately, 10 min and 30 min after acute aerobic exercise with 75%VO2max. The levels of reduced glutathione (GSH, oxidized glutathione (GSSG and (GSH/GSSG in red blood cells (RBCs as well as serum levels of cortisol and creatine kinase (CK were measured.   Results: The results showed reduction, elevation and no changes in RBCs GSH/GSSG ratio in UT, MT and WT groups, respectively. The lowest levels of GSH/GSSG ratio in RBCs and the highest one were detected in the WT and MT groups, respectively. The serum levels of cortisol and creatine kinase were increased following the exercise in three groups.   Conclusion: It is concluded that acute aerobic exercise with high intensity does not change redox balance in well trained subjects, however it is capable to shift redox balance towards more reducing environment in moderately trained subjects and also to more oxidizing one in untrained subjects.

  15. The redox biology network in cancer pathophysiology and therapeutics

    Directory of Open Access Journals (Sweden)

    Gina Manda

    2015-08-01

    Full Text Available The review pinpoints operational concepts related to the redox biology network applied to the pathophysiology and therapeutics of solid tumors. A sophisticated network of intrinsic and extrinsic cues, integrated in the tumor niche, drives tumorigenesis and tumor progression. Critical mutations and distorted redox signaling pathways orchestrate pathologic events inside cancer cells, resulting in resistance to stress and death signals, aberrant proliferation and efficient repair mechanisms. Additionally, the complex inter-cellular crosstalk within the tumor niche, mediated by cytokines, redox-sensitive danger signals (HMGB1 and exosomes, under the pressure of multiple stresses (oxidative, inflammatory, metabolic, greatly contributes to the malignant phenotype. The tumor-associated inflammatory stress and its suppressive action on the anti-tumor immune response are highlighted. We further emphasize that ROS may act either as supporter or enemy of cancer cells, depending on the context. Oxidative stress-based therapies, such as radiotherapy and photodynamic therapy, take advantage of the cytotoxic face of ROS for killing tumor cells by a non-physiologically sudden, localized and intense oxidative burst. The type of tumor cell death elicited by these therapies is discussed. Therapy outcome depends on the differential sensitivity to oxidative stress of particular tumor cells, such as cancer stem cells, and therefore co-therapies that transiently down-regulate their intrinsic antioxidant system hold great promise. We draw attention on the consequences of the damage signals delivered by oxidative stress-injured cells to neighboring and distant cells, and emphasize the benefits of therapeutically triggered immunologic cell death in metastatic cancer. An integrative approach should be applied when designing therapeutic strategies in cancer, taking into consideration the mutational, metabolic, inflammatory and oxidative status of tumor cells, cellular

  16. Arabidopsis redox status in response to caterpillar herbivory

    Directory of Open Access Journals (Sweden)

    Jamuna ePaudel

    2013-05-01

    Full Text Available Plant responses to insect herbivory are regulated through complex, hormone-mediated interactions. Some caterpillar species have evolved strategies to manipulate this system by inducing specific pathways that suppress plant defense responses. Effectors in the labial saliva (LS secretions of Spodoptera exigua caterpillars are believed to induce the salicylic acid (SA pathway to interfere with the jasmonic acid (JA defense pathway; however, the mechanism underlying this subversion is unknown. Since Noctuid caterpillar LS contains enzymes that may affect cellular redox balance, this study investigated rapid changes in cellular redox metabolites within 45 min after herbivory. Caterpillar LS is involved in suppressing the increase in oxidative stress that was observed in plants fed upon by caterpillars with impaired LS secretions. To further understand the link between cellular redox balance and plant defense responses, marker genes of SA, JA and ethylene (ET pathways were compared in wildtype, the glutathione-compromised pad2-1 mutant and the tga2/5/6 triple mutant plants. AtPR1 and AtPDF1.2 showed LS-dependent expression that was alleviated in the pad2-1 and tga2/5/6 triple mutants. In comparison, the ET-dependent genes ERF1 expression showed LS-associated changes in both wildtype and pad2-1 mutant plants and the ORA 59 marker AtHEL had increased expression in response to herbivory, but a LS-dependent difference was not noted. These data support the model that there are SA/NPR1-, glutathione-dependent and ET-, glutathione-independent mechanisms leading to LS-associated suppression of plant induced defences.

  17. Redox regulation of calcium release in skeletal and cardiac muscle

    Directory of Open Access Journals (Sweden)

    CECILIA HIDALGO

    2002-01-01

    Full Text Available In skeletal and cardiac muscle cells, specific isoforms of the Ryanodine receptor channels mediate Ca2+ release from the sarcoplasmic reticulum. These channels are highly susceptible to redox modifications, which regulate channel activity. In this work, we studied the effects of Ca2+ (endogenous agonist and Mg2+ (endogenous inhibitor on the kinetics of Ca2+ release from sarcoplasmic reticulum vesicles isolated from skeletal or cardiac mammalian muscle. Native skeletal vesicles exhibited maximal stimulation of release kinetics by 10-20 µM [Ca2+], whereas in native cardiac vesicles, maximal stimulation of release required only 1 µM [Ca2+]. In 10 µM [Ca2+], free [Mg2+] < 0.1 mM produced marked inhibition of release from skeletal vesicles but free [Mg2+] ­ 0.8 mM did not affect release from cardiac vesicles. Incubation of skeletal or cardiac vesicles with the oxidant thimerosal increased their susceptibility to stimulation by Ca2+ and decreased the inhibitory effect of Mg2+ in skeletal vesicles. Sulfhydryl-reducing agents fully reversed the effects of thimerosal. The endogenous redox species, glutathione disulfide and S-nitrosoglutathione, also stimulated release from skeletal sarcoplasmic reticulum vesicles. In 10 µM [Ca2+], 35S-nitrosoglutathione labeled a protein fraction enriched in release channels through S-glutathiolation. Free [Mg2+] 1 mM or decreasing free [Ca2+] to the nM range prevented this reaction. Possible physiological and pathological consequences of redox modification of release channels on Ca2+ signaling in heart and muscle cells are discussed

  18. Redox control of arsenic mobilization in Bangladesh groundwater

    International Nuclear Information System (INIS)

    Zheng, Y.; Stute, M.; Geen, A. van; Gavrieli, I.; Dhar, R.; Simpson, H.J.; Schlosser, P.; Ahmed, K.M.

    2004-01-01

    Detailed hydrochemical measurements, δ 34 S SO4 and 3 H analyses were performed on 37 groundwater samples collected during February 1999, January and March 2000 from 6 locations in eastern and southeastern Bangladesh to examine redox processes that lead to As mobilization in groundwater. The study sites were chosen based on available nation-wide As surveys to span the entire spectrum of As concentrations in Bangladesh groundwater, and to represent 3 of 5 major geological units of the Ganges-Brahmaputra Delta: uplifted Pleistocene terrace, fluvial flood plain and delta plain. Arsenic was found to be mobilized under Fe-reducing conditions in shallow aquifers ( 4 -reducing conditions, suggesting that authigenic sulfide precipitation does not constitute a significant sink for As in these groundwaters. The redox state of the water was characterized by a variety of parameters including dissolved O 2 , NO 3 - , Mn 2+ , Fe 2+ concentrations, and SO 4 2- /Cl - ratios. High dissolved [As] (> 50 μg/l; or > 0.7 μM ) were always accompanied by high dissolved [HCO 3 - ] (> 4 mM), and were close to saturation with respect to calcite. Groundwater enriched in As (200-800 μg/l; or 2.7-10.7 μM) and phosphate (30-100 μM) but relatively low in dissolved Fe (5-40 μM) probably resulted from re-oxidation of reducing, As and Fe enriched water. This history was deduced from isotopic signatures of δ 34 S SO4 and 3 H 2 O ( 3 H) to delineate the nature of redox changes for some of the reducing groundwaters. In contrast, As is not mobilized in presumed Pleistocene aquifers, both shallow (30-60 m) and deep (150-270 m), because conditions were not reducing enough due to lack of sufficient O 2 demand

  19. Metabolic impact of redox cofactor perturbations in Saccharomyces cerevisiae

    DEFF Research Database (Denmark)

    Hou, Jin; Lages, Nuno; Oldiges, M.

    2009-01-01

    to induce widespread changes in metabolism. We present a detailed analysis of the impact of perturbations in redox cofactors in the cytosol or mitochondria on glucose and energy metabolism in Saccharomyces cerevisiae to aid metabolic engineering decisions that involve cofactor engineering. We enhanced NADH...... oxidation by introducing NADH oxidase or alternative oxidase, its ATP-mediated conversion to NADPH using NADH kinase as well as the interconversion of NADH and NADPH independent of ATP by the soluble, non-proton-translocating bacterial transhydrogenase. Decreasing cytosolic NADH level lowered glycerol...

  20. Synthesis of redox polymer nanobeads and nanocomposites for glucose biosensors.

    Science.gov (United States)

    Wang, Jen-Yuan; Chen, Lin-Chi; Ho, Kuo-Chuan

    2013-08-28

    Redox polymer nanobeads of branched polyethylenimine binding with ferrocene (BPEI-Fc) were synthesized using a simple chemical process. The functionality and morphology of the redox polymer nanobeads were investigated by Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). This hydrophilic redox nanomaterial could be mixed with glucose oxidase (GOx) for drop-coating on a screen-printed carbon electrode (SPCE) for glucose sensing application. Electrochemical properties of the BPEI-Fc/GOx/SPCE prepared under different conditions were studied by cyclic voltammetry (CV). On the basis of these CV results, the synthetic condition of the BPEI-Fc/GOx/SPCE could be optimized. By incorporating conductive poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), the performance of a redox polymer nanobead–based enzyme electrode could be further improved. The influence of PEDOT:PSS on the nanocomposite enzyme electrode was discussed from the aspects of the apparent electron diffusion coefficient (D(app)) and the charge transfer resistance (R(ct)). The glucose-sensing sensitivity of the BPEI-Fc/PEDOT:PSS/GOx/SPCE is calculated to be 66 μA mM(–1) cm(–2), which is 2.5 times higher than that without PEDOT:PSS. The apparent Michaelis constant (K(M)(app)) of the BPEI-Fc/PEDOT:PSS/GOx/SPCE estimated by the Lineweaver–Burk plot is 2.4 mM, which is much lower than that of BPEI-Fc/GOx/SPCE (11.2 mM). This implies that the BPEI-Fc/PEDOT:PSS/GOx/SPCE can catalytically oxidize glucose in a more efficient way. The interference test was carried out by injection of glucose and three common interferences: ascorbic acid (AA), dopamine (DA), and uric acid (UA) at physiological levels. The interferences of DA (4.2%) and AA (7.8%) are acceptable and the current response to UA (1.6%) is negligible, compared to the current response to glucose.

  1. Redox substoichiometry in isotope dilution analysis Pt. 4

    International Nuclear Information System (INIS)

    Kambara, T.; Yoshioka, H.; Ugai, Y.

    1980-01-01

    The oxidation reaction of antimony(III) with potassium dichromate has been investigated radiometrically. The quantitative oxidation of antimony(III) was found to be not disturbed even in large amounts of tin(IV). On the basis of these results the redox substoichiometric isotope dilution analysis using potassium dichromate as the oxidizing agent was proposed for the determination of antimony in metallic tin. An antimony content of 1.22+-0.05 μg in metallic tin (10 mg) was determined without separation of the matrix element. (author)

  2. Redox substoichiometry in isotope dilution analysis Pt. 2

    International Nuclear Information System (INIS)

    Kambara, T.; Suzuki, J.; Yoshioka, H.; Nakajima, N.

    1978-01-01

    Isotope dilution analysis using the redox substoichiometric principle has been applied to the determination of antimony content in metallic zinc. As the substoichiometric reaction, the oxidation of trivalent to pentavalent antimony with potassium permanganate was used, followed by separation of these species by the BHPA extraction of trivalent antimony. Determination of antimony contents less than 0.5 μg was found to be possible with good accuracy, without separation of zinc ions. The antimony content in a metallic zinc sample was determined to be 19.7+-0.8 ppm, in good agreement with the results obtained by the other analytical methods. (author)

  3. Redox protective potential of fruits and vegetables: A review

    Directory of Open Access Journals (Sweden)

    Zainab Tahir

    2015-08-01

    Full Text Available Although oxidation reactions are crucial for life, they can also be damaging to cells and tissues, causing variety of chronic ailments like, aging, cancer, autoimmune problems, cardiovascular and neurodegenerative disorders etc. Redox protective systems are present in body for general immunization against free radicals, which can be supported by antioxidants that we take in our daily diet. Natural antioxidants such as flavonoids, hydrolysable tannins, coumarins, xanthones, phenolics, terpenoids, ascorbic acid, carotenoids and proanthocyanins are found in various plant products, including fruits, leaves, seeds oils, and juices. This review gives a brief account of research reports on fruits and vegetables which provide free radical scavenging compounds to the body.

  4. Redox-Flow-Batterie mit außenliegender Versorgungsleitung

    OpenAIRE

    Seipp, Thorsten; Dötsch, Christian; Berthold, Sascha

    2011-01-01

    A redox flow battery (1, 1') is presented and described, having at least one cell frame (4) surrounding a cell interior space (7) and having at least one supply line (2, 2') provided outside the cell frame (4) for supplying electrolyte to the cell interior space (7) and/or at least one disposal line (3, 3') provided outside the cell frame (4) for removing electrolyte from the cell interior space (4). In order to make greater degrees of freedom available in designing the cell so as to provide ...

  5. Zelle und Zellstack einer Redox-Flow-Batterie

    OpenAIRE

    Seipp, Thorsten; Berthold, Sascha; Burfeind, Jens; Kopietz, Lukas

    2015-01-01

    Source: WO15007543A1 [EN] The invention illustrates and describes a cell (1) of a redox flow battery, having at least one cell frame element (2, 3, 4), a diaphragm (15) and two electrodes (5), wherein the at least one cell frame element (2, 3, 4), the diaphragm (15) and the two electrodes (5) surround two cell interior spaces (10) which are separate from one another, wherein at least four separate channels (6, 7, 8, 9) are provided in the at least one cell frame element (2, 3, 4) such that di...

  6. Redox behaviour of molybdenum in aqueous medium : a potentiometric study

    International Nuclear Information System (INIS)

    Sagi, S.R.; Mohan Rao, P.R.

    1975-01-01

    The nature of the two forms; of Mo(III) cationic-aquomolybdenum(III) (green) and anionic-chloromolybdate(III) (orange-red) has been investigated using various oxidants in hydrochloric acid mdeium, the oxidation steps being detected using a potentiometric method. The two species behave differently towards the various oxidants. The green form is a better reducing agent giving large breaks in potentials during redox titrations. The existence of the intermediate oxidation states Mosup(3.5) and Mosup(4.5) reported earlier has also been confirmed. (author)

  7. Nucleobase modification as redox DNA labelling for electrochemical detection

    Czech Academy of Sciences Publication Activity Database

    Hocek, Michal; Fojta, Miroslav

    2011-01-01

    Roč. 40, č. 12 (2011), s. 5802-5814 ISSN 0306-0012 R&D Projects: GA MŠk(CZ) LC06035; GA MŠk LC512; GA AV ČR(CZ) IAA400040901; GA ČR GA203/09/0317 Institutional research plan: CEZ:AV0Z40550506; CEZ:AV0Z50040507; CEZ:AV0Z50040702 Keywords : nucleotides * oligonucleotides * DNA * electrochemistry * redox labeling Subject RIV: CC - Organic Chemistry Impact factor: 28.760, year: 2011

  8. Systems and methods for rebalancing redox flow battery electrolytes

    Science.gov (United States)

    Pham, Ai Quoc; Chang, On Kok

    2015-03-17

    Various methods of rebalancing electrolytes in a redox flow battery system include various systems using a catalyzed hydrogen rebalance cell configured to minimize the risk of dissolved catalyst negatively affecting flow battery performance. Some systems described herein reduce the chance of catalyst contamination of RFB electrolytes by employing a mediator solution to eliminate direct contact between the catalyzed membrane and the RFB electrolyte. Other methods use a rebalance cell chemistry that maintains the catalyzed electrode at a potential low enough to prevent the catalyst from dissolving.

  9. All-Fullerene-Based Cells for Nonaqueous Redox Flow Batteries.

    Science.gov (United States)

    Friedl, Jochen; Lebedeva, Maria A; Porfyrakis, Kyriakos; Stimming, Ulrich; Chamberlain, Thomas W

    2018-01-10

    Redox flow batteries have the potential to revolutionize our use of intermittent sustainable energy sources such as solar and wind power by storing the energy in liquid electrolytes. Our concept study utilizes a novel electrolyte system, exploiting derivatized fullerenes as both anolyte and catholyte species in a series of battery cells, including a symmetric, single species system which alleviates the common problem of membrane crossover. The prototype multielectron system, utilizing molecular based charge carriers, made from inexpensive, abundant, and sustainable materials, principally, C and Fe, demonstrates remarkable current and energy densities and promising long-term cycling stability.

  10. Monitoring electrolyte concentrations in redox flow battery systems

    Science.gov (United States)

    Chang, On Kok; Sopchak, David Andrew; Pham, Ai Quoc; Kinoshita, Kimio

    2015-03-17

    Methods, systems and structures for monitoring, managing electrolyte concentrations in redox flow batteries are provided by introducing a first quantity of a liquid electrolyte into a first chamber of a test cell and introducing a second quantity of the liquid electrolyte into a second chamber of the test cell. The method further provides for measuring a voltage of the test cell, measuring an elapsed time from the test cell reaching a first voltage until the test cell reaches a second voltage; and determining a degree of imbalance of the liquid electrolyte based on the elapsed time.

  11. Effectively suppressing vanadium permeation in vanadium redox flow battery application with modified Nafion membrane with nacre-like nanoarchitectures

    Science.gov (United States)

    Zhang, Lesi; Ling, Ling; Xiao, Min; Han, Dongmei; Wang, Shuanjin; Meng, Yuezhong

    2017-06-01

    A novel self-assembled composite membrane, Nafion-[PDDA/ZrP]n with nacre-like nanostructures was successfully fabricated by a layer-by-layer (LbL) method and used as proton exchange membrane for vanadium redox flow battery applications. Poly(diallyldimethylammonium chloride) (PDDA) with positive charges and zirconium phosphate (ZrP) nanosheets with negative charges can form ultra-thin nacre-like nanostructure on the surface of Nafion membrane via the ionic crosslinking of tightly folded macromolecules. The lamellar structure of ZrP nanosheets and Donnan exclusion effect of PDDA can greatly decrease the vanadium ion permeability and improve the selectivity of proton conductivity. The fabricated Nafion-[PDDA/ZrP]4 membrane shows two orders of magnitude lower vanadium ion permeability (1.05 × 10-6 cm2 min-1) and 12 times higher ion selectivity than those of pristine Nafion membrane at room temperature. Consequently, the performance of vanadium redox flow batteries (VRFBs) assembled with Nafion-[PDDA/ZrP]3 membrane achieved a highly coulombic efficiency (CE) and energy efficiency (EE) together with a very slow self-discharge rate. When comparing with pristine Nafion VRFB, the CE and EE values of Nafion-[PDDA/ZrP]3 VRFB are 10% and 7% higher at 30 mA cm-2, respectively.

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

    Science.gov (United States)

    Xiao, Wusheng; Wang, Rui-Sheng; Handy, Diane E; Loscalzo, Joseph

    2018-01-20

    The nicotinamide adenine dinucleotide (NAD + )/reduced NAD + (NADH) and NADP + /reduced NADP + (NADPH) redox couples are essential for maintaining cellular redox homeostasis and for modulating numerous biological events, including cellular metabolism. Deficiency or imbalance of these two redox couples has been associated with many pathological disorders. Recent Advances: Newly identified biosynthetic enzymes and newly developed genetically encoded biosensors enable us to understand better how cells maintain compartmentalized NAD(H) and NADP(H) pools. The concept of redox stress (oxidative and reductive stress) reflected by changes in NAD(H)/NADP(H) has increasingly gained attention. The emerging roles of NAD + -consuming proteins in regulating cellular redox and metabolic homeostasis are active research topics. The biosynthesis and distribution of cellular NAD(H) and NADP(H) are highly compartmentalized. It is critical to understand how cells maintain the steady levels of these redox couple pools to ensure their normal functions and simultaneously avoid inducing redox stress. In addition, it is essential to understand how NAD(H)- and NADP(H)-utilizing enzymes interact with other signaling pathways, such as those regulated by hypoxia-inducible factor, to maintain cellular redox homeostasis and energy metabolism. Additional studies are needed to investigate the inter-relationships among compartmentalized NAD(H)/NADP(H) pools and how these two dinucleotide redox couples collaboratively regulate cellular redox states and cellular metabolism under normal and pathological conditions. Furthermore, recent studies suggest the utility of using pharmacological interventions or nutrient-based bioactive NAD + precursors as therapeutic interventions for metabolic diseases. Thus, a better understanding of the cellular functions of NAD(H) and NADP(H) may facilitate efforts to address a host of pathological disorders effectively. Antioxid. Redox Signal. 28, 251-272.

  13. Extracellular redox state: refining the definition of oxidative stress in aging.

    Science.gov (United States)

    Jones, Dean P

    2006-01-01

    Oxidative stress in aging can result from an imbalance of prooxidants and antioxidants with excessive, destructive free radical chemistry. Thiol systems are important in the control of these processes, both by protecting against damage and serving in redox signaling mechanisms to sense danger and repair the damage. Studies by a number of research groups in collaboration with the Emory Clinical Biomarkers Laboratory show that the redox state of the central tissue antioxidant, glutathione (GSH), can be measured in human plasma and provides a quantitative systemic indicator of oxidative stress. Plasma GSH/GSSG redox in humans becomes oxidized with age, in response to chemotherapy, as a consequence of cigarette smoking, and in association with common age-related diseases (e.g., type 2 diabetes, cardiovascular disease). However, the GSH/GSSG redox is not equilibrated with the larger plasma cysteine/cystine (Cys/CySS) pool, and the Cys/CySS redox varies with age in a pattern that is distinct from that of GSH/GSSG redox. Furthermore, in vitro studies show that variation in Cys/CySS redox over the range found in vivo affects signaling pathways, which control cell proliferation and oxidant-induced apoptosis. The results point to the conclusion that free radical scavenging antioxidants are of increased importance when thiol/disulfide redox states are oxidized. Because thiol/disulfide redox states, per se, function in redox signaling and control as well as antioxidant protection, GSH/GSSG and Cys/CySS redox states may provide central parameters to link environmental influences and progression of changes associated with aging.

  14. Rebalancing Redox to Improve Biobutanol Production by Clostridium tyrobutyricum

    Directory of Open Access Journals (Sweden)

    Chao Ma

    2015-12-01

    Full Text Available Biobutanol is a sustainable green biofuel that can substitute for gasoline. Carbon flux has been redistributed in Clostridium tyrobutyricum via metabolic cell engineering to produce biobutanol. However, the lack of reducing power hampered the further improvement of butanol production. The objective of this study was to improve butanol production by rebalancing redox. Firstly, a metabolically-engineered mutant CTC-fdh-adhE2 was constructed by introducing heterologous formate dehydrogenase (fdh and bifunctional aldehyde/alcohol dehydrogenase (adhE2 simultaneously into wild-type C. tyrobutyricum. The mutant evaluation indicated that the fdh-catalyzed NADH-producing pathway improved butanol titer by 2.15-fold in the serum bottle and 2.72-fold in the bioreactor. Secondly, the medium supplements that could shift metabolic flux to improve the production of butyrate or butanol were identified, including vanadate, acetamide, sodium formate, vitamin B12 and methyl viologen hydrate. Finally, the free-cell fermentation produced 12.34 g/L of butanol from glucose using the mutant CTC-fdh-adhE2, which was 3.88-fold higher than that produced by the control mutant CTC-adhE2. This study demonstrated that the redox engineering in C. tyrobutyricum could greatly increase butanol production.

  15. ROS-related redox regulation and signaling in plants.

    Science.gov (United States)

    Noctor, Graham; Reichheld, Jean-Philippe; Foyer, Christine H

    2017-07-18

    As sessile oxygenic organisms with a plastic developmental programme, plants are uniquely positioned to exploit reactive oxygen species (ROS) as powerful signals. Plants harbor numerous ROS-generating pathways, and these oxidants and related redox-active compounds have become tightly embedded into plant function and development during the course of evolution. One dominant view of ROS-removing systems sees them as beneficial antioxidants battling to keep damaging ROS below dangerous levels. However, it is now established that ROS are a necessary part of subcellular and intercellular communication in plants and that some of their signaling functions require ROS-metabolizing systems. For these reasons, it is suggested that "ROS processing systems" would be a more accurate term than "antioxidative systems" to describe cellular components that are most likely to interact with ROS and, in doing so, transmit oxidative signals. Within this framework, our update provides an overview of the complexity and compartmentation of ROS production and removal. We place particular emphasis on the importance of ROS-interacting systems such as the complex cellular thiol network in the redox regulation of phytohormone signaling pathways that are crucial for plant development and defense against external threats. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. Uranium fixation by mineralization at the redox front

    International Nuclear Information System (INIS)

    Isobe, Hiroshi

    1998-01-01

    The behavior of actinide elements including uranium in geomedia is controlled by redox conditions. Under the oxidized conditions, uranium forms uranyl ion (UO 2 2+ ) and its complexes, and dissolves in ground water. Under the reduced conditions, U(IV) has much lower solubility than uranyl ion. In the Koongarra uranium deposit, Australia, lead-bearing uraninite, uranyl lead oxide and uranyl silicate minerals occur in the unweathered, primary ore zone, and uranyl phosphate minerals occur in the weathered, secondary ore zone. Between unweathered and weathered zones, the transition zone exists as a redox front. In the transition zone, graphite and sulfide minerals react as reducing agents for species dissolved in ground water. By SEM, spherical grains of uraninite were observed in veins with graphite. Pyrite had coffinite rim with crystals of uraninite. Calculation based on the ground water chemistry and hydrology at Koongarra shows that the uranium in the transition zone may be fixed from the ground water. In the Koongarra transition zone, recent mineralization of uranium by reduction takes place. Mineralization is much stronger fixation mechanism than adsorption on clay minerals. Pyrite in the buffer materials of possible radioactive waste repositories can fix radionuclides in oxidized ground water by mineralization with reducing reactions. (author)

  17. Effects of rutin on the redox reactions of hemoglobin.

    Science.gov (United States)

    Lu, Naihao; Ding, Yun; Yang, Zhen; Gao, Pingzhang

    2016-08-01

    Flavonoids are widely used to attenuate oxidative damage in vitro and in vivo. In this study, we investigated the influence of rutin (quercetin-3-rhamnosylglucoside) on hemoglobin (Hb)- dependent redox reactions, i.e. oxidative stability of Hb and its cytotoxic ferryl intermediate. It was found that rutin induced generation of H2O2, which in turn oxidized Hb rapidly. Meanwhile, rutin exhibited anti-oxidant effect by effectively reducing ferryl intermediate back to ferric Hb at physiological pH. In comparison with quercetin, rutin had stronger capability on reducing ferryl species while lesser pro-oxidant effect on H2O2 generation, thus it exhibited more protective effect on H2O2-induced Hb oxidation. Circular dichroism spectrum showed no significant change in the secondary structure of Hb after flavonoid addition, while molecular docking revealed different binding modes of quercetin and rutin with Hb. These results might provide new insights into the potential nutritional and physiological implications of rutin and quercetin with redox active heme proteins regarding their ani- and pro-oxidant effects. Copyright © 2016 Elsevier B.V. All rights reserved.

  18. Transient light-induced intracellular oxidation revealed by redox biosensor

    Energy Technology Data Exchange (ETDEWEB)

    Kolossov, Vladimir L., E-mail: viadimer@illinois.edu [Institute for Genomic Biology, University of Illinois at Urbana-Champaign, 1206 W. Gregory Drive, Urbana, IL 61801 (United States); Beaudoin, Jessica N. [Institute for Genomic Biology, University of Illinois at Urbana-Champaign, 1206 W. Gregory Drive, Urbana, IL 61801 (United States); Department of Animal Sciences, University of Illinois at Urbana-Champaign, 1207 W. Gregory Drive, Urbana, IL 61801 (United States); Hanafin, William P. [Institute for Genomic Biology, University of Illinois at Urbana-Champaign, 1206 W. Gregory Drive, Urbana, IL 61801 (United States); DiLiberto, Stephen J. [Institute for Genomic Biology, University of Illinois at Urbana-Champaign, 1206 W. Gregory Drive, Urbana, IL 61801 (United States); Department of Animal Sciences, University of Illinois at Urbana-Champaign, 1207 W. Gregory Drive, Urbana, IL 61801 (United States); Kenis, Paul J.A. [Institute for Genomic Biology, University of Illinois at Urbana-Champaign, 1206 W. Gregory Drive, Urbana, IL 61801 (United States); Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, 600 S. Mathews Avenue, Urbana, IL 61801 (United States); Rex Gaskins, H. [Institute for Genomic Biology, University of Illinois at Urbana-Champaign, 1206 W. Gregory Drive, Urbana, IL 61801 (United States); Department of Animal Sciences, University of Illinois at Urbana-Champaign, 1207 W. Gregory Drive, Urbana, IL 61801 (United States); Department of Pathobiology, University of Illinois at Urbana-Champaign, 2001 S. Lincoln Avenue, Urbana, IL 61801 (United States); Division of Nutritional Sciences, University of Illinois at Urbana-Champaign, 905 S. Goodwin Avenue, Urbana, IL 61801 (United States)

    2013-10-04

    Highlights: •Time-resolved live cell imaging revealed light-induced oxidation. •Only the roGFP probe fused with glutaredoxin reveals photooxidation. •The transient oxidation is rapidly reduced by the cytosolic antioxidant system. •Intracellular photooxidation is media-dependent. •Oxidation is triggered exclusively by exposure to short wavelength excitation. -- Abstract: We have implemented a ratiometric, genetically encoded redox-sensitive green fluorescent protein fused to human glutaredoxin (Grx1-roGFP2) to monitor real time intracellular glutathione redox potentials of mammalian cells. This probe enabled detection of media-dependent oxidation of the cytosol triggered by short wavelength excitation. The transient nature of light-induced oxidation was revealed by time-lapse live cell imaging when time intervals of less than 30 s were implemented. In contrast, transient ROS generation was not observed with the parental roGFP2 probe without Grx1, which exhibits slower thiol-disulfide exchange. These data demonstrate that the enhanced sensitivity of the Grx1-roGFP2 fusion protein enables the detection of short-lived ROS in living cells. The superior sensitivity of Grx1-roGFP2, however, also enhances responsiveness to environmental cues introducing a greater likelihood of false positive results during image acquisition.

  19. Targeting the Redox Balance in Inflammatory Skin Conditions

    Directory of Open Access Journals (Sweden)

    Ditte M. S. Lundvig

    2013-04-01

    Full Text Available Reactive oxygen species (ROS can be both beneficial and deleterious. Under normal physiological conditions, ROS production is tightly regulated, and ROS participate in both pathogen defense and cellular signaling. However, insufficient ROS detoxification or ROS overproduction generates oxidative stress, resulting in cellular damage. Oxidative stress has been linked to various inflammatory diseases. Inflammation is an essential response in the protection against injurious insults and thus important at the onset of wound healing. However, hampered resolution of inflammation can result in a chronic, exaggerated response with additional tissue damage. In the pathogenesis of several inflammatory skin conditions, e.g., sunburn and psoriasis, inflammatory-mediated tissue damage is central. The prolonged release of excess ROS in the skin can aggravate inflammatory injury and promote chronic inflammation. The cellular redox balance is therefore tightly regulated by several (enzymatic antioxidants and pro-oxidants; however, in case of chronic inflammation, the antioxidant system may be depleted, and prolonged oxidative stress occurs. Due to the central role of ROS in inflammatory pathologies, restoring the redox balance forms an innovative therapeutic target in the development of new strategies for treating inflammatory skin conditions. Nevertheless, the clinical use of antioxidant-related therapies is still in its infancy.

  20. Identification of Redox and Glucose-Dependent Txnip Protein Interactions

    Directory of Open Access Journals (Sweden)

    Benjamin J. Forred

    2016-01-01

    Full Text Available Thioredoxin-interacting protein (Txnip acts as a negative regulator of thioredoxin function and is a critical modulator of several diseases including, but not limited to, diabetes, ischemia-reperfusion cardiac injury, and carcinogenesis. Therefore, Txnip has become an attractive therapeutic target to alleviate disease pathologies. Although Txnip has been implicated with numerous cellular processes such as proliferation, fatty acid and glucose metabolism, inflammation, and apoptosis, the molecular mechanisms underlying these processes are largely unknown. The objective of these studies was to identify Txnip interacting proteins using the proximity-based labeling method, BioID, to understand differential regulation of pleiotropic Txnip cellular functions. The BioID transgene fused to Txnip expressed in HEK293 identified 31 interacting proteins. Many protein interactions were redox-dependent and were disrupted through mutation of a previously described reactive cysteine (C247S. Furthermore, we demonstrate that this model can be used to identify dynamic Txnip interactions due to known physiological regulators such as hyperglycemia. These data identify novel Txnip protein interactions and demonstrate dynamic interactions dependent on redox and glucose perturbations, providing clarification to the pleiotropic cellular functions of Txnip.