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Sample records for superoxide anions o2

  1. Ionol (BHT) produces superoxide anion.

    Science.gov (United States)

    Smirnova, E G; Lyubimov, Yu I; Malinina, T G; Lyubimova, E Yu; Alexandrushkina, N I; Vanyushin, B F; Kolesova, G M; Yaguzhinsky, L S

    2002-11-01

    In aqueous medium etiolated wheat seedlings release superoxide anion (O2*-). Interaction of a synthetic antioxidant, butylated hydroxytoluene (BHT, ionol), with oxygen in the aqueous medium is accompanied by O2*- formation. This suggests that under certain conditions BHT behaves as a prooxidant. A natural antioxidant, superoxide dismutase (SOD), and also a wound healing preparation, emulsified denatured placenta (EDP), do not exhibit the prooxidant properties. In contrast to BHT, they reduce O2*- production by the etiolated wheat seedling system.

  2. Superoxide anion radical (O2(-)) degrades methylmercury to inorganic mercury in human astrocytoma cell line (CCF-STTG1).

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    Mailloux, Ryan J; Yumvihoze, Emmanuel; Chan, Hing Man

    2015-09-05

    Methylmercury (MeHg) is a global pollutant that is affecting the health of millions of people worldwide. However, the mechanism of MeHg toxicity still remains somewhat elusive and there is no treatment. It has been known for some time that MeHg can be progressively converted to inorganic mercury (iHg) in various tissues including the brain. Recent work has suggested that cleavage of the carbon-metal bond in MeHg in a biological environment is facilitated by reactive oxygen species (ROS). However, the oxyradical species that actually mediates this process has not been identified. Here, we provide evidence that superoxide anion radical (O2(-)) can convert MeHg to iHg. The calculated second-order rate constant for the degradation of 1μM MeHg by O2(-) generated by xanthine/xanthine oxidase was calculated to be 2×10(5)M(-1)s(-1). We were also able to show that this bioconversion can proceed in intact CCF-STTG1 human astrocytoma cells exposed to paraquat (PQ), a O2(-) generating viologen. Notably, exposure of cells to increasing amounts of PQ led to a dose dependent increase in both MeHg and iHg. Indeed, a 24h exposure to 500μM PQ induced a ∼13-fold and ∼18-fold increase in intracellular MeHg and iHg respectively. These effects were inhibited by superoxide dismutase mimetic MnTBAP. In addition, we also observed that a 24h exposure to a biologically relevant concentration of MeHg (1μM) did not induce cell death, oxidative stress, or even changes in cellular O2(-) and H2O2. However, co-exposure to PQ enhanced MeHg toxicity which was associated with a robust increase in cell death and oxidative stress. Collectively our results show that O2(-) can bioconvert MeHg to iHg in vitro and in intact cells exposed to conditions that simulate high intracellular O2(-) production. In addition, we show for the first time that O2(-) mediated degradation of MeHg to iHg enhances the toxicity of MeHg by facilitating an accumulation of both MeHg and iHg in the intracellular

  3. Ursodeoxycholic acid and superoxide anion

    Institute of Scientific and Technical Information of China (English)

    Predrag Ljubuncic; Omar Abu-Salach; Arieh Bomzon

    2005-01-01

    AIM: To investigate the ability of ursodeoxycholic acid (UDCA) to scavenge superoxide anion (O2-).METHODS: We assessed the ability of UDCA to scavenge (O2-) generated by xanthine-xanthine oxidase (X-XO) in a cell-free system and its effect on the rate of O2--induced ascorbic acid (AA) oxidation in hepatic post-mitochondrial supernatants.RESULTS: UDCA at a concentration as high as 1 mmol/Ldid not impair the ability of the X-XO system to generate O2-, but could scavenge O2- at concentrations of 0.5 and 1 mmol/L, and decrease the rate of AA oxidation at a concentration of 100 μmol/L.CONCLUSION: UDCA can scavenge O2-, an action that may be beneficial to patients with primary biliary cirrhosis.

  4. Competitive Deprotonation and Superoxide [O2 -•] Radical-Anion Adduct Formation Reactions of Carboxamides under Negative-Ion Atmospheric-Pressure Helium-Plasma Ionization (HePI) Conditions

    Science.gov (United States)

    Hassan, Isra; Pinto, Spencer; Weisbecker, Carl; Attygalle, Athula B.

    2016-03-01

    Carboxamides bearing an N-H functionality are known to undergo deprotonation under negative-ion-generating mass spectrometric conditions. Herein, we report that N-H bearing carboxamides with acidities lower than that of the hydroperoxyl radical (HO-O•) preferentially form superoxide radical-anion (O2 -•) adducts, rather than deprotonate, when they are exposed to the glow discharge of a helium-plasma ionization source. For example, the spectra of N-alkylacetamides show peaks for superoxide radical-anion (O2 -•) adducts. Conversely, more acidic amides, such as N-alkyltrifluoroacetamides, preferentially undergo deprotonation under similar experimental conditions. Upon collisional activation, the O2 -• adducts of N-alkylacetamides either lose the neutral amide or the hydroperoxyl radical (HO-O•) to generate the superoxide radical-anion ( m/z 32) or the deprotonated amide [ m/z (M - H)-], respectively. For somewhat acidic carboxamides, the association between the two entities is weak. Thus, upon mildest collisional activation, the adduct dissociates to eject the superoxide anion. Superoxide-adduct formation results are useful for structure determination purposes because carboxamides devoid of a N-H functionality undergo neither deprotonation nor adduct formation under HePI conditions.

  5. Superoxide anion production by human neutrophils activated by Trichomonas vaginalis.

    Science.gov (United States)

    Song, Hyun-Ouk; Ryu, Jae-Sook

    2013-08-01

    Neutrophils are the predominant inflammatory cells found in vaginal discharges of patients infected with Trichomonas vaginalis. In this study, we examined superoxide anion (O2 (.-)) production by neutrophils activated by T. vaginalis. Human neutrophils produced superoxide anions when stimulated with either a lysate of T. vaginalis, its membrane component (MC), or excretory-secretory product (ESP). To assess the role of trichomonad protease in production of superoxide anions by neutrophils, T. vaginalis lysate, ESP, and MC were each pretreated with a protease inhibitor cocktail before incubation with neutrophils. Superoxide anion production was significantly decreased by this treatment. Trichomonad growth was inhibited by preincubation with supernatants of neutrophils incubated for 3 hr with T. vaginalis lysate. Furthermore, myeloperoxidase (MPO) production by neutrophils was stimulated by live trichomonads. These results indicate that the production of superoxide anions and MPO by neutrophils stimulated with T. vaginalis may be a part of defense mechanisms of neutrophils in trichomoniasis.

  6. Superoxide anion production and superoxide dismutase and catalase activities in Coxiella burnetii.

    OpenAIRE

    Akporiaye, E T; Baca, O G

    1983-01-01

    Coxiella burnetii was examined for superoxide anion (O2-) production and superoxide dismutase and catalase activities. The organism generated O2- at pH 4.5 but not at pH 7.4. The rickettsia displayed superoxide dismutase activity distinguishable from that of the host cell (L-929 mouse fibroblast). Catalase activity was maximal at pH 7.0 and diminished at pH 4.5. These enzymes may account, in part, for the ability of this obligate intracellular parasite to survive within phagocytes.

  7. In vitro inhibition of superoxide anion production and superoxide dismutase activity by zinc in human spermatozoa.

    Science.gov (United States)

    Gavella, M; Lipovac, V; Vucić, M; Sverko, V

    1999-08-01

    The in vitro effect of zinc on superoxide anion (O2-) generation and on SOD-like activity in spermatozoa of infertile men was investigated. The formation of superoxide anion was stimulated by NADPH and the level of superoxide anion was measured by the reduction of ferricytochrome c. Both Percoll-isolated (n = 14) and washed spermatozoa (n = 14) exposed to 1 mmol/L zinc (60 min, 37 degrees C), released less (p zinc-untreated spermatozoa. These results implicate a possible role for zinc as a scavenger of excessive superoxide anions produced by defective spermatozoa in semen after ejaculation. Additionally, zinc was found to dose-dependently inhibit superoxide dismutase (SOD)-like activity of spermatozoa in vitro. The inhibition of SOD-like activity by an equal concentration of zinc (1 mmol/L) was less pronounced in oligospermic (p zinc to inhibit SOD-like activity may be relevant to the physiological function of spermatozoa in fertilization. The evidence that zinc may elicit an inhibition of both superoxide anion production and SOD-like activity in human spermatozoa, indicate the existence of novel, zinc-related mechanism(s) involved in the oxidative events occurring after ejaculation, with a possible modulatory effect on germ cell function.

  8. Methylglyoxal as a scavenger for superoxide anion-radical.

    Science.gov (United States)

    Shumaev, K B; Lankin, V Z; Konovalova, G G; Grechnikova, M A; Tikhaze, A K

    2016-07-01

    Methylglyoxal at a concentration of 5 mM caused a significant inhibition of superoxide anion radical (O2 (·-)) comparable to the effect of Tirone. In the process of O2 (·-) generation in the system of egg phosphatidylcholine liposome peroxidation induced by the azo-initiator AIBN, a marked inhibition of chemiluminescence in the presence of 100 mM methylglyoxal was found. At the same time, methylglyoxal did not inhibit free radical peroxidation of low-density lipoprotein particles, which indicates the absence of interaction with methylglyoxal alkoxyl and peroxyl polyenoic lipid radicals. These findings deepen information about the role of methylglyoxal in the regulation of free radical processes.

  9. Superoxide Complex [W4O12(O2')]:A Theoretical Study

    Institute of Scientific and Technical Information of China (English)

    WANG Bin; ZHANG Xian-Hui; HUANG Xin; ZHANG Yong-Fan

    2008-01-01

    Extensive DFT calculations are performed to optimize the geometric structures of O-rich tungsten oxide clusters, to simulate the PES spectra, and to analyze the chemical bonding. The ground-state structure of W4O14- is best considered as W4O12(O2-), containing a side-on bound superoxide ligand. The current study indicates that the extra electron in W4O12- is capable of activating dioxygen by non-dissociative electron transfer (W 5d→O2 π*), and the anionic clusters can be viewed as models for reduced defect sites on tungsten oxide surfaces for the chemisorption of O2.

  10. Superoxide anion production by neutrophils in myelodysplastic syndromes (preleukemia.

    Directory of Open Access Journals (Sweden)

    Takahashi,Isao

    1988-02-01

    Full Text Available Superoxide anion (O2- production by neutrophils from 14 untreated patients with acute nonlymphocytic leukemia (ANLL was significantly less than that of healthy controls (4.93 +/- 1.99 vx 6.20 +/- 1.53 nmol/min/10(6 neutrophils, p less than 0.05. In 10 patients with myelodysplastic syndrome (MDS, however, it was not significantly different from the control level although 6 of the 10 patients had low levels, when individual patients were compared with the lower limit of the control range. An inverse correlation between the O2- production of neutrophils and the percentage of leukemic cells in the marrow existed in ANLL (r = -0.55, p less than 0.01, but not in MDS. Three of 4 MDS patients who died of pneumonia prior to leukemic conversion showed a low level of O2- production. The impaired O2- production by neutrophils from some MDS patients, probably due to the faulty differentiation from leukemic clones, may be one of the causes of enhanced susceptibility to infection.

  11. Mechanism and kinetics for scavenging superoxide anion by progesterone

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The chemical reaction of progesterone with superoxide anion in 0.1 mol/L NaHCO3 medium is studied by polarography. Differing from the indirect inhibition of generation by synthesized glucocorticoids in mechanism, the function that progesterone scavenges is ascribed to that directly oxidizes the C == C double bond conjugated with the carbonyl moiety of progesterone molecule to a free radical, and then is reduced to H2O2. The result obtained in this work gives new evidence for biomedical research. The equation of rate constant of the oxidization reaction is de-duced, and the apparent rate constant obtained is 308 L·mol-1·s-1.

  12. Effect of superoxide anion scavenger on rat hearts with chronic intermittent hypoxia.

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    Pai, Peiying; Lai, Ching Jung; Lin, Ching-Yuang; Liou, Yi-Fan; Huang, Chih-Yang; Lee, Shin-Da

    2016-04-15

    Only very limited information regarding the protective effects of the superoxide anion scavenger on chronic intermittent hypoxia-induced cardiac apoptosis is available. The purpose of this study is to evaluate the effects of the superoxide anion scavenger on cardiac apoptotic and prosurvival pathways in rats with sleep apnea. Forty-two Sprague-Dawley rats were divided into three groups, rats with normoxic exposure (Control, 21% O2, 1 mo), rats with chronic intermittent hypoxia exposure (Hypoxia, 3-7% O2vs. 21% O2per 40 s cycle, 8 h per day, 1 mo), and rats with pretreatment of the superoxide anion scavenger and chronic intermittent hypoxia exposure (Hypoxia-O2 (-)-Scavenger, MnTMPyP pentachloride, 1 mg/kg ip per day; 3-7% O2vs. 21% O2per 40 s cycle, 8 h per day, 1 mo) at 5-6 mo of age. After 1 mo, the protein levels and apoptotic cells of excised hearts from three groups were measured by Western blotting and terminal deoxynucleotide transferase-mediated dUTP nick end labeling (TUNEL) assay. The superoxide anion scavenger decreased hypoxia-induced myocardial architecture abnormalities, left ventricular hypertrophy, and TUNEL-positive apoptosis. The superoxide anion scavenger decreased hypoxia-induced Fas ligand, Fas death receptors, Fas-associated death domain (FADD), activated caspase-8, and activated caspase-3 (Fas-dependent apoptotic pathway) as well as Bad, activated caspase-9 and activated caspase-3 (mitochondria-dependent apoptotic pathway), endonuclease G (EndoG), apoptosis-inducing factor (AIF), and TUNEL-positive apoptosis. The superoxide anion scavenger increased IGF-1, IGF-1R, p-PI3k, p-Akt, p-Bad, Bcl-2, and Bcl-xL (survival pathway). Our findings imply that the superoxide anion scavenger might prevent cardiac Fas-mediated and mitochondrial-mediated apoptosis and enhance the IGF-1-related survival pathway in chronic intermittent hypoxia. The superoxide anion scavenger may prevent chronic sleep apnea-enhanced cardiac apoptotic pathways and enhances

  13. Mechanism of Action of Sulforaphane as a Superoxide Radical Anion and Hydrogen Peroxide Scavenger by Double Hydrogen Transfer: A Model for Iron Superoxide Dismutase.

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    Prasad, Ajit Kumar; Mishra, P C

    2015-06-25

    The mechanism of action of sulforaphane as a scavenger of superoxide radical anion (O2(•-)) and hydrogen peroxide (H2O2) was investigated using density functional theory (DFT) in both gas phase and aqueous media. Iron superoxide dismutase (Fe-SOD) involved in scavenging superoxide radical anion from biological media was modeled by a complex consisting of the ferric ion (Fe(3+)) attached to three histidine rings. Reactions related to scavenging of superoxide radical anion by sulforaphane were studied using DFT in the presence and absence of Fe-SOD represented by this model in both gas phase and aqueous media. The scavenging action of sulforaphane toward both superoxide radical anion and hydrogen peroxide was found to involve the unusual mechanism of double hydrogen transfer. It was found that sulforaphane alone, without Fe-SOD, cannot scavenge superoxide radical anion in gas phase or aqueous media efficiently as the corresponding reaction barriers are very high. However, in the presence of Fe-SOD represented by the above-mentioned model, the scavenging reactions become barrierless, and so sulforaphane scavenges superoxide radical anion by converting it to hydrogen peroxide efficiently. Further, sulforaphane was found to scavenge hydrogen peroxide also very efficiently by converting it into water. Thus, the mechanism of action of sulforaphane as an excellent antioxidant has been unravelled.

  14. Corticosteroids increase superoxide anion production by rat liver microsomes.

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    Nelson, D H; Ruhmann-Wennhold, A

    1975-01-01

    Superoxide anion production by liver microsomes from intact, adrenalectomized, and cortisoltreated adrenalectomized rats has been determined. The amount formed was roughly proportionate to the amount of cortisol given, and a similar response was seen in the activity of NADPH-cytochrome c reductase. The amount of measurable superoxide anion was markedly reduced by the addition of superoxide dismutase. The increased production of this potent free radical with cortisol therapy suggests that its formation may contribute to some of the harmful effects of corticosteroids given in more than physiologic amounts. PMID:239969

  15. The TOM complex is involved in the release of superoxide anion from mitochondria.

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    Budzińska, Małgorzata; Gałgańska, Hanna; Karachitos, Andonis; Wojtkowska, Małgorzata; Kmita, Hanna

    2009-08-01

    Available data indicate that superoxide anion (O(2)(*-) ) is released from mitochondria, but apart from VDAC (voltage dependent anion channel), the proteins involved in its transport across the mitochondrial outer membrane still remain elusive. Using mitochondria of the yeast Saccharomyces cerevisiae mutant depleted of VDAC (Deltapor1 mutant) and the isogenic wild type, we studied the role of the TOM complex (translocase of the outer membrane) in the efflux of O(2)(*-) from the mitochondria. We found that blocking the TOM complex with the fusion protein pb(2)-DHFR decreased O(2)(*-) release, particularly in the case of Deltapor1 mitochondria. We also observed that the effect of the TOM complex blockage on O(2)(*-) release from mitochondria coincided with the levels of O(2)(*-) release as well as with levels of Tom40 expression in the mitochondria. Thus, we conclude that the TOM complex participates in O(2)(*-) release from mitochondria.

  16. Reactions of superoxide dismutases with HS(-)/H2S and superoxide radical anion: An in vitro EPR study.

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    Bolić, Bojana; Mijušković, Ana; Popović-Bijelić, Ana; Nikolić-Kokić, Aleksandra; Spasić, Snežana; Blagojević, Duško; Spasić, Mihajlo B; Spasojević, Ivan

    2015-12-01

    Interactions of hydrogen sulfide (HS(-)/H2S), a reducing signaling species, with superoxide dimutases (SOD) are poorly understood. We applied low-T EPR spectroscopy to examine the effects of HS(-)/H2S and superoxide radical anion O2.- on metallocenters of FeSOD, MnSOD, and CuZnSOD. HS(-)/H2S did not affect FeSOD, whereas active centers of MnSOD and CuZnSOD were open to this agent. Cu(2+) was reduced to Cu(1+), while manganese appears to be released from MnSOD active center. Untreated and O2.- treated FeSOD and MnSOD predominantly show 5 d-electron systems, i.e. Fe(3+) and Mn(2+). Our study provides new details on the mechanisms of (patho)physiological effects of HS(-)/H2S.

  17. Scavenging of superoxide anions by lecithinized superoxide dismutase in HL-60 cells.

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    Ishihara, Tsutomu; Shibui, Misaki; Hoshi, Takaya; Mizushima, Tohru

    2016-01-01

    Superoxide dismutase covalently bound to four lecithin molecules (PC-SOD) has been found to have beneficial therapeutic effects in animal models of various diseases. However, the mechanism underlying these improved therapeutic effects has not yet been elucidated. It has previously been shown that PC-SOD localizes on the plasma membrane and in the lysosomes of cells. In this study, we evaluated the superoxide anion-scavenging activity of PC-SOD in HL-60 human promyelocytic leukemia cells. Compared to SOD, PC-SOD had only 17% scavenging activity in cell-free systems. Nevertheless, by analyzing enzyme activities in cell suspensions containing PC-SOD or SOD, PC-SOD and SOD showed almost equal activity for scavenging extracellular superoxide anions produced by HL-60 cells. Furthermore, the activity for scavenging extracellular superoxide anions increased with increased amount of PC-SOD on the plasma membrane. Moreover, PC-SOD exhibited no obvious inhibitory effect on the scavenging of intracellular superoxide anions. These results suggested that the association of PC-SOD with the plasma membrane plays a key role in its beneficial therapeutic effects. Thus, this finding may provide a rationale for selecting target diseases for PC-SOD treatment.

  18. Iron-mediated induction of sister-chromatid exchanges by hydrogen peroxide and superoxide anion.

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    Larramendy, M; Mello-Filho, A C; Martins, E A; Meneghini, R

    1987-05-01

    When Chinese hamster fibroblasts were exposed to hydrogen peroxide or to a system consisting of xanthine oxidase and hypoxanthine, which generates superoxide anion plus hydrogen peroxide, sister-chromatid exchanges (SCEs) were formed in a dose-dependent manner. When the iron-complexing agent o-phenanthroline was present in the medium, however, the production of these SCEs was completely inhibited. This fact indicates that the Fenton reaction: Fe2+ + H2O2----OH0 + OH- + Fe3+ is responsible for the production of SCEs. When O2- and H2O2 were generated inside the cell by incubation with menadione, the production of SCE was prevented by co-incubation with copper diisopropylsalicylate, a superoxide dismutase mimetic agent. The most likely role of O2- is as a reducing agent of Fe3+: O2- + Fe3+----Fe2+ + O2, so that the sum of this and the Fenton reaction, i.e., the iron-catalyzed Haber-Weiss reaction, provides an explanation for the active oxygen species-induced SCE: H2O2 + O2(-)----OH- + OH0 + O2. According to this view, the OH radical thus produced is the agent which ultimately causes SCE. These results are discussed in comparison with other mechanisms previously proposed for induction of SCE by active oxygen species.

  19. Carbon dioxide suppresses macrophage superoxide anion production independent of extracellular pH and mitochondrial activity

    NARCIS (Netherlands)

    Kuebler, Joachim F.; Kos, Marcin; Jesch, NataLie K.; Metzelder, Martin L.; van der Zee, David C.; Bax, Klaas M.; Vieten, Gertrud; Ure, Benno M.

    2007-01-01

    Background: Superoxide anions released by activated inacrophages during surgery are considered to be responsible for local cellular damage. Application of CO2 prieumoperitoneum during laparoscopy affects superoxide anion release, but the underlying mechanism remains unclear and the data reported are

  20. Nanostructured cobalt phosphates as excellent biomimetic enzymes to sensitively detect superoxide anions released from living cells.

    Science.gov (United States)

    Wang, Min-Qiang; Ye, Cui; Bao, Shu-Juan; Xu, Mao-Wen; Zhang, Yan; Wang, Ling; Ma, Xiao-Qing; Guo, Jun; Li, Chang-Ming

    2017-01-15

    Monitoring superoxide anion radicals in living cells has been attracting much academic and industrial interest due to the dual roles of the radicals. Herein, we synthesized a novel nanostructured cobalt phosphate nanorods (Co3(PO4)2 NRs) with tunable pore structure using a simple and effective micro-emulsion method and explored their potential utilization in the electrochemical sensing of superoxide anions. As an analytical and sensing platform, the nanoscale biomimetic enzymes Co3(PO4)2 NRs exhibited excellent selectivity and sensitivity towards superoxide anion (O2(•-)) with a low detection limit (2.25nM), wide linear range (5.76-5396nM), and long-term stability. Further, the nanoscale biomimetic enzyme could be efficiently applied in situ to electrochemically detect O2(•-) released from human malignant melanoma cells and normal keratinocyte, showing excellent real time quantitative detection capability. This material open up exciting opportunities for implementing biomimetic enzymes in nanoscale transition metal phosphates and designing enzyme-free biosensors with much higher sensitivity and durability in health and disease analysis than those of natural one.

  1. Superoxide anion production by human spermatozoa as a part of the ionophore-induced acrosome reaction process.

    Science.gov (United States)

    Griveau, J F; Renard, P; Le Lannou, D

    1995-04-01

    The involvement of superoxide anion (O2o-) in human sperm capacitation and/or acrosome reaction was investigated. Addition of superoxide dismutase (SOD) to the medium at the beginning of the capacitation process or 15 min before induction of the acrosome reaction, decreased the level of ionophore-induced acrosome reaction. Hyperactivation was unaffected by the presence of SOD during the capacitation process. Addition of calcium ionophore to the sperm suspension increased production of O2o- by the spermatozoa by four to five-fold and induced the acrosome reaction. In the presence of SOD, superoxide anion could not be detected in the medium and the rate of induced-acrosome reaction was decreased greatly. The presence of an inhibitor of protein kinase C inhibited the production of O2o- in the medium and reduced the induced-acrosome reaction. The production of O2o- and the acrosome reaction were also increased by exposure of spermatozoa to 12-myristate 13-acetate phorbol ester, a specific activator of protein kinase C. While the level of spontaneous acrosome reaction was not increased by the direct addition of O2o- to the medium, its presence induced the release of unesterified fatty acids from membrane phospholipids. These findings suggest that the production of O2o- by spermatozoa could be involved in the ionophore-induced acrosome reaction, possibly through the de-esterification of membrane phospholipids. However, this production of superoxide anion is not sufficient on its own to induce the acrosome reaction.

  2. Immobilization of superoxide dismutase on Pt-Pd/MWCNTs hybrid modified electrode surface for superoxide anion detection.

    Science.gov (United States)

    Zhu, Xiang; Niu, Xiangheng; Zhao, Hongli; Tang, Jie; Lan, Minbo

    2015-05-15

    Monitoring of reactive oxygen species like superoxide anion (O2(∙-)) turns to be of increasing significance considering their potential damages to organism. In the present work, we fabricated a novel O2(∙-) electrochemical sensor through immobilizing superoxide dismutase (SOD) onto a Pt-Pd/MWCNTs hybrid modified electrode surface. The Pt-Pd/MWCNTs hybrid was synthesized via a facile one-step alcohol-reduction process, and well characterized by transmission electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction. The immobilization of SOD was accomplished using a simple drop-casting method, and the performance of the assembled enzyme-based sensor for O2(∙-) detection was systematically investigated by several electrochemcial techniques. Thanks to the specific biocatalysis of SOD towards O2(∙-) and the Pt-Pd/MWCNTs - promoted fast electron transfer at the fabricated interface, the developed biosensor exhibits a fast, selective and linear amperometric response upon O2(∙-) in the concentration scope of 40-1550 μM (R(2)=0.9941), with a sensitivity of 0.601 mA cm(-2) mM(-1) and a detection limit of 0.71 μM (S/N=3). In addition, the favorable biocompatibility of this electrode interface endows the prepared biosensor with excellent long-term stability (a sensitivity loss of only 3% over a period of 30 days). It is promising that the proposed sensor will be utilized as an effective tool to quantitatively monitor the dynamic changes of O2(∙-) in biological systems.

  3. The superoxide anion donor, potassium superoxide, induces pain and inflammation in mice through production of reactive oxygen species and cyclooxygenase-2.

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    Maioli, N A; Zarpelon, A C; Mizokami, S S; Calixto-Campos, C; Guazelli, C F S; Hohmann, M S N; Pinho-Ribeiro, F A; Carvalho, T T; Manchope, M F; Ferraz, C R; Casagrande, R; Verri, W A

    2015-04-01

    It is currently accepted that superoxide anion (O2•-) is an important mediator in pain and inflammation. The role of superoxide anion in pain and inflammation has been mainly determined indirectly by modulating its production and inactivation. Direct evidence using potassium superoxide (KO2), a superoxide anion donor, demonstrated that it induced thermal hyperalgesia, as assessed by the Hargreaves method. However, it remains to be determined whether KO2 is capable of inducing other inflammatory and nociceptive responses attributed to superoxide anion. Therefore, in the present study, we investigated the nociceptive and inflammatory effects of KO2. The KO2-induced inflammatory responses evaluated in mice were: mechanical hyperalgesia (electronic version of von Frey filaments), thermal hyperalgesia (hot plate), edema (caliper rule), myeloperoxidase activity (colorimetric assay), overt pain-like behaviors (flinches, time spent licking and writhing score), leukocyte recruitment, oxidative stress, and cyclooxygenase-2 mRNA expression (quantitative PCR). Administration of KO2 induced mechanical hyperalgesia, thermal hyperalgesia, paw edema, leukocyte recruitment, the writhing response, paw flinching, and paw licking in a dose-dependent manner. KO2 also induced time-dependent cyclooxygenase-2 mRNA expression in the paw skin. The nociceptive, inflammatory, and oxidative stress components of KO2-induced responses were responsive to morphine (analgesic opioid), quercetin (antioxidant flavonoid), and/or celecoxib (anti-inflammatory cyclooxygenase-2 inhibitor) treatment. In conclusion, the well-established superoxide anion donor KO2 is a valuable tool for studying the mechanisms and pharmacological susceptibilities of superoxide anion-triggered nociceptive and inflammatory responses ranging from mechanical and thermal hyperalgesia to overt pain-like behaviors, edema, and leukocyte recruitment.

  4. Production of superoxide anions by keratinocytes initiates P. acnes-induced inflammation of the skin.

    Directory of Open Access Journals (Sweden)

    Philippe A Grange

    2009-07-01

    Full Text Available Acne vulgaris is a chronic inflammatory disorder of the sebaceous follicles. Propionibacterium acnes (P. acnes, a gram-positive anareobic bacterium, plays a critical role in the development of these inflammatory lesions. This study aimed at determining whether reactive oxygen species (ROS are produced by keratinocytes upon P. acnes infection, dissecting the mechanism of this production, and investigating how this phenomenon integrates in the general inflammatory response induced by P. acnes. In our hands, ROS, and especially superoxide anions (O2(*-, were rapidly produced by keratinocytes upon stimulation by P. acnes surface proteins. In P. acnes-stimulated keratinocytes, O2(*- was produced by NAD(PH oxidase through activation of the scavenger receptor CD36. O2(*- was dismuted by superoxide dismutase to form hydrogen peroxide which was further detoxified into water by the GSH/GPx system. In addition, P. acnes-induced O2(*- abrogated P. acnes growth and was involved in keratinocyte lysis through the combination of O2(*- with nitric oxide to form peroxynitrites. Finally, retinoic acid derivates, the most efficient anti-acneic drugs, prevent O2(*- production, IL-8 release and keratinocyte apoptosis, suggesting the relevance of this pathway in humans.

  5. Feijoa sellowiana Berg fruit juice: anti-inflammatory effect and activity on superoxide anion generation.

    Science.gov (United States)

    Monforte, Maria T; Fimiani, Vincenzo; Lanuzza, Francesco; Naccari, Clara; Restuccia, Salvatore; Galati, Enza M

    2014-04-01

    Feijoa sellowiana Berg var. coolidge fruit juice was studied in vivo for the anti-inflammatory activity by carrageenin-induced paw edema test and in vitro for the effects on superoxide anion release from neutrophils in human whole blood. The fruit juice was analyzed by the high-performance liquid chromatography method, and quercetin, ellagic acid, catechin, rutin, eriodictyol, gallic acid, pyrocatechol, syringic acid, and eriocitrin were identified. The results showed a significant anti-inflammatory activity of F. sellowiana fruit juice, sustained also by an effective antioxidant activity observed in preliminary studies on 1,1-diphenyl-2-picrylhydrazyl (DPPH) test. In particular, the anti-inflammatory activity edema inhibition is significant since the first hour (44.11%) and persists until the fifth hour (44.12%) of the treatment. The effect on superoxide anion release was studied in human whole blood, in the presence of activators affecting neutrophils by different mechanisms. The juice showed an inhibiting response on neutrophils basal activity in all experimental conditions. In stimulated neutrophils, the higher inhibition of superoxide anion generation was observed at concentration of 10(-4) and 10(-2) mg/mL in whole blood stimulate with phorbol-myristate-13-acetate (PMA; 20% and 40%) and with N-formyl-methionyl-leucyl-phenylalanine (FMLP; 15% and 48%). The significant reduction of edema and the inhibition of O2(-) production, occurring mainly through interaction with protein-kinase C pathway, confirm the anti-inflammatory effect of F. sellowiana fruit juice.

  6. Superoxide anion-induced pain and inflammation depends on TNFα/TNFR1 signaling in mice.

    Science.gov (United States)

    Yamacita-Borin, Fabiane Y; Zarpelon, Ana C; Pinho-Ribeiro, Felipe A; Fattori, Victor; Alves-Filho, Jose C; Cunha, Fernando Q; Cunha, Thiago M; Casagrande, Rubia; Verri, Waldiceu A

    2015-09-25

    Inhibition of tumor necrosis factor-alpha (TNFα) and superoxide anion production reduces inflammation and pain. The present study investigated whether superoxide anion-induced pain depends on TNFα signaling and the role of superoxide anion in TNFα-induced hyperalgesia to clarify the interrelation between these two mediators in the context of pain. Intraplantar injection of a superoxide anion donor (potassium superoxide) induced mechanical hyperalgesia (0.5-5h after injection), neutrophil recruitment (myeloperoxidase activity), and overt pain-like behaviors (paw flinching, paw licking, and abdominal writhings) in wild-type mice. Tumor necrosis factor receptor 1 deficiency (TNFR1-/-) and treatment of wild-type mice with etanercept (a soluble TNFR2 receptor that inhibits TNFα actions) inhibited superoxide anion-induced pain-like behaviors. TNFR1(-/-) mice were also protected from superoxide anion donor-induced oxidative stress, suggesting the role of this pathway in the maintenance of oxidative stress. Finally, we demonstrated that Apocynin (an NADPH oxidase inhibitor) or Tempol (a superoxide dismutase mimetic) treatment inhibited TNFα-induced paw mechanical hyperalgesia and neutrophil recruitment (myeloperoxidase activity). These results demonstrate that TNFα/TNFR1 signaling is important in superoxide anion-triggered pain and that TNFα/TNFR1 signaling amplifies the oxidative stress triggered by superoxide anion, which contributes to sustaining pain and inflammation.

  7. Superoxide anion radicals induce IGF-1 resistance through concomitant activation of PTP1B and PTEN.

    Science.gov (United States)

    Singh, Karmveer; Maity, Pallab; Krug, Linda; Meyer, Patrick; Treiber, Nicolai; Lucas, Tanja; Basu, Abhijit; Kochanek, Stefan; Wlaschek, Meinhard; Geiger, Hartmut; Scharffetter-Kochanek, Karin

    2015-01-01

    The evolutionarily conserved IGF-1 signalling pathway is associated with longevity, metabolism, tissue homeostasis, and cancer progression. Its regulation relies on the delicate balance between activating kinases and suppressing phosphatases and is still not very well understood. We report here that IGF-1 signalling in vitro and in a murine ageing model in vivo is suppressed in response to accumulation of superoxide anions (O2∙-) in mitochondria, either by chemical inhibition of complex I or by genetic silencing of O2∙--dismutating mitochondrial Sod2. The O2∙--dependent suppression of IGF-1 signalling resulted in decreased proliferation of murine dermal fibroblasts, affected translation initiation factors and suppressed the expression of α1(I), α1(III), and α2(I) collagen, the hallmarks of skin ageing. Enhanced O2∙- led to activation of the phosphatases PTP1B and PTEN, which via dephosphorylation of the IGF-1 receptor and phosphatidylinositol 3,4,5-triphosphate dampened IGF-1 signalling. Genetic and pharmacologic inhibition of PTP1B and PTEN abrogated O2∙--induced IGF-1 resistance and rescued the ageing skin phenotype. We thus identify previously unreported signature events with O2∙-, PTP1B, and PTEN as promising targets for drug development to prevent IGF-1 resistance-related pathologies.

  8. Superoxide Anion Radical: Generation and Detection in Cellular and Non-Cellular Systems.

    Science.gov (United States)

    Chiste, Renan Campos; Freitas, Marisa; Mercadante, Adriana Zerlotti; Fernandes, Eduarda

    2015-01-01

    The production of superoxide anion radical (O2•(-)) is essential for the life of aerobic organisms. This free radical acts as a signaling molecule, regulating numerous biological processes including apoptosis, aging, and senescence. Nevertheless, when overproduction of O2•(-) occurs and/or antioxidant defences are deficient, oxidative stress may develop, damaging important biomolecules and altering their physiological function. These effects have been associated to the development of several diseases. Scavenging of O2•(-) has been used as a hallmark to test the antioxidant capacity of several types of compounds in cellular and non-cellular systems. However, despite the pathophysiological importance of O2•(-), the information about its endogenous and/or chemical generation and detection is dispersed and there are no reports that concisely cover the information in an integrated form. This gap can explain the limitations attributed to the currently used systems, namely in what concerns the selectivity, specificity and validation. This review attempts to provide a critical assessment of the available O2•(-) generating and detection, both in endogenous and chemical systems, scrutinizing its advantages and limitations in order to facilitate the choice and implementation of the O2•(-) generator and/or detection method that better fits the researchers' objectives.

  9. Detoxification of superoxide without production of H2O2: antioxidant activity of superoxide reductase complexed with ferrocyanide

    CERN Document Server

    Molina-Heredia, Fernando P; Berthomieu, Catherine; Touati, Danièle; Tremey, Emilie; Favaudon, Vincent; Adam, Virgile; Nivière, Vincent

    2015-01-01

    The superoxide radical O(2)(-.) is a toxic by-product of oxygen metabolism. Two O(2)(-.) detoxifying enzymes have been described so far, superoxide dismutase and superoxide reductase (SOR), both forming H2O2 as a reaction product. Recently, the SOR active site, a ferrous iron in a [Fe(2+) (N-His)(4) (S-Cys)] pentacoordination, was shown to have the ability to form a complex with the organometallic compound ferrocyanide. Here, we have investigated in detail the reactivity of the SOR-ferrocyanide complex with O(2)(-.) by pulse and gamma-ray radiolysis, infrared, and UV-visible spectroscopies. The complex reacts very efficiently with O(2)(-.). However, the presence of the ferrocyanide adduct markedly modifies the reaction mechanism of SOR, with the formation of transient intermediates different from those observed for SOR alone. A one-electron redox chemistry appears to be carried out by the ferrocyanide moiety of the complex, whereas the SOR iron site remains in the reduced state. Surprisingly, the toxic H2O2 s...

  10. Production of superoxide/H2O2 by dihydroorotate dehydrogenase in rat skeletal muscle mitochondria.

    Science.gov (United States)

    Hey-Mogensen, Martin; Goncalves, Renata L S; Orr, Adam L; Brand, Martin D

    2014-07-01

    Dehydrogenases that use ubiquinone as an electron acceptor, including complex I of the respiratory chain, complex II, and glycerol-3-phosphate dehydrogenase, are known to be direct generators of superoxide and/or H2O2. Dihydroorotate dehydrogenase oxidizes dihydroorotate to orotate and reduces ubiquinone to ubiquinol during pyrimidine metabolism, but it is unclear whether it produces superoxide and/or H2O2 directly or does so only indirectly from other sites in the electron transport chain. Using mitochondria isolated from rat skeletal muscle we establish that dihydroorotate oxidation leads to superoxide/H2O2 production at a fairly high rate of about 300pmol H2O2·min(-1)·mg protein(-1) when oxidation of ubiquinol is prevented and complex II is uninhibited. This H2O2 production is abolished by brequinar or leflunomide, known inhibitors of dihydroorotate dehydrogenase. Eighty percent of this rate is indirect, originating from site IIF of complex II, because it can be prevented by malonate or atpenin A5, inhibitors of complex II. In the presence of inhibitors of all known sites of superoxide/H2O2 production (rotenone to inhibit sites in complex I (site IQ and, indirectly, site IF), myxothiazol to inhibit site IIIQo in complex III, and malonate plus atpenin A5 to inhibit site IIF in complex II), dihydroorotate dehydrogenase generates superoxide/H2O2, at a small but significant rate (23pmol H2O2·min(-1)·mg protein(-1)), from the ubiquinone-binding site. We conclude that dihydroorotate dehydrogenase can generate superoxide and/or H2O2 directly at low rates and is also capable of indirect production at higher rates from other sites through its ability to reduce the ubiquinone pool.

  11. Anamperometric superoxide anion radicalbiosensor based on SOD/PtPd-PDARGO modified electrode.

    Science.gov (United States)

    Tang, Jie; Zhu, Xiang; Niu, Xiangheng; Liu, Tingting; Zhao, Hongli; Lan, Minbo

    2015-05-01

    In the present work, a high-performance enzyme-based electrochemical sensor for the detection of superoxide anion radical (O2(●-)) is reported. Firstly, we employed a facile approach to synthesize PtPd nanoparticles (PtPd NPs) on chemically reduced graphene oxide (RGO) coated with polydopamine (PDA). The prepared PtPd-PDARGO composite was well characterized by transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectra, X-ray diffraction, X-ray photoelectron spectroscopy and electrochemical methods. Then the assembled composite was used as a desired electrochemcial interface for superoxide dismutase (SOD) immobilization. Owing to the PDA layer as well as the synergistic effect of PtPd NPs, the fabricated SOD/PtPd-PDARGO sensor exhibited an outstanding sensitivity of 909.7 μA mM(-1) cm(-2) upon O2(●-) in a linear range from 0.016 mM to 0.24 mM (R(2)=0.992), with a low detection limit of 2 μM (S/N=3) and excellent selectivity, good reproducibility as well as favorable long-term stability.

  12. Inhibitory effects of cardols and related compounds on superoxide anion generation by xanthine oxidase.

    Science.gov (United States)

    Masuoka, Noriyoshi; Nihei, Ken-ichi; Maeta, Ayami; Yamagiwa, Yoshiro; Kubo, Isao

    2015-01-01

    5-Pentadecatrienylresorcinol, isolated from cashew nuts and commonly known as cardol (C₁₅:₃), prevented the generation of superoxide radicals catalysed by xanthine oxidase without the inhibition of uric acid formation. The inhibition kinetics did not follow the Michelis-Menten equation, but instead followed the Hill equation. Cardol (C₁₀:₀) also inhibited superoxide anion generation, but resorcinol and cardol (C₅:₀) did not inhibit superoxide anion generation. The related compounds 3,5-dihydroxyphenyl alkanoates and alkyl 2,4-dihydroxybenzoates, had more than a C9 chain, cooperatively inhibited but alkyl 3,5-dihydroxybenzoates, regardless of their alkyl chain length, did not inhibit the superoxide anion generation. These results suggested that specific inhibitors for superoxide anion generation catalysed by xanthine oxidase consisted of an electron-rich resorcinol group and an alkyl chain having longer than C9 chain.

  13. Possible Involvement of NADPH Oxidase in Lanthanide Cation-Induced Superoxide Anion Generation in BY-2 Tobacco Cell Suspension Culture

    Institute of Scientific and Technical Information of China (English)

    Yang Shengchang

    2006-01-01

    A rapid and concentration-dependent generation of superoxide anionO-2), measured with a superoxide-specific Cypridina luciferin-derived chemiluminescent reagent, was observed when two lanthanide salts (LaCl3 and GdCl3) were added to tobacco (Nicotiana tabacum) cell suspension culture.Addition of superoxide dismutase (480 U·ml-1) and Tiron (5 μmol·L-1) to cell culture suspension decreases the level of lanthanide cation-induced ·O-2 generation, suggesting that ·O-2 generation is extra-cellular.Pretreatment of the cell culture suspension with diphenyleneiodonium (10 and 50 μmol·L-1), quinacrine (1 and 5 mmol·L-1) and imidazol (10 mmol·L-1), inhibitors of NADPH oxidase, notably inhibits the generation of superoxide induced by lanthanide cation, implying the possible involvement of activation of NADPH oxidase.In addition, addition of SHAM (1 and 5 mmol·L-1), azide (0.2 and 1 mmol·L-1), inhibitor of peroxidase, has no influence on ·O-2 generation.

  14. Endomorphins 1 and 2 modulate chemotaxis, phagocytosis and superoxide anion production by microglia.

    Science.gov (United States)

    Azuma, Y; Ohura, K; Wang, P L; Shinohara, M

    2001-09-03

    We evaluate the role of endomorphins 1 and 2 on microglial functions. Endomorphins 1 and 2 blocked phagocytosis of Escherichia coli. In addition, both markedly inhibited chemotaxis toward zymosan-activated serum. In contrast, when microglia was preincubated with these endomorphins, followed by incubation with LPS before stimulation with phorbol 12-myristate 13-acetate (PMA) at 200 nM, they potentiated superoxide anion production. Furthermore, when microglia was preincubated with these endomorphins together with PMA at 20 nM, followed by stimulation with PMA at 200 nM, superoxide anion production was potentiated. These results suggest that endomorphins 1 and 2 modulate phagocytosis, chemotaxis and superoxide anion production by microglia.

  15. Bosentan, a mixed endothelin receptor antagonist, inhibits superoxide anion-induced pain and inflammation in mice.

    Science.gov (United States)

    Serafim, Karla G G; Navarro, Suelen A; Zarpelon, Ana C; Pinho-Ribeiro, Felipe A; Fattori, Victor; Cunha, Thiago M; Alves-Filho, Jose C; Cunha, Fernando Q; Casagrande, Rubia; Verri, Waldiceu A

    2015-11-01

    Bosentan is a mixed endothelin receptor antagonist widely used to treat patients with pulmonary arterial hypertension, and the emerging literature suggests bosentan as a potent anti-inflammatory drug. Superoxide anion is produced in large amounts during inflammation, stimulates cytokine production, and thus contributes to inflammation and pain. However, it remains to be determined whether endothelin contributes to the inflammatory response triggered by the superoxide anion. The present study investigated the effects of bosentan in a mouse model of inflammation and pain induced by potassium superoxide, a superoxide anion donor. Male Swiss mice were treated with bosentan (10-100 mg/kg) by oral gavage, 1 h before potassium superoxide injection, and the inflammatory response was evaluated locally and at spinal cord (L4-L6) levels. Bosentan (100 mg/kg) inhibited superoxide anion-induced mechanical and thermal hyperalgesia, overt pain-like behavior (abdominal writhings, paw flinching, and licking), paw edema, myeloperoxidase activity (neutrophil marker) in the paw skin, and leukocyte recruitment in the peritoneal cavity. Bosentan also inhibited superoxide anion-induced interleukin-1 beta (IL-1β) and tumor necrosis factor alpha (TNF-α) production, while it enhanced IL-10 production in the paw skin and spinal cord. Bosentan inhibited the reduction of antioxidant capacity (reduced glutathione, ferric reducing antioxidant power, and ABTS radical scavenging ability) induced by the superoxide anion. Finally, we demonstrated that intraplantar injection of potassium superoxide induces the mRNA expression of prepro-endothelin-1 in the paw skin and spinal cord. In conclusion, our results demonstrated that superoxide anion-induced inflammation, pain, cytokine production, and oxidative stress depend on endothelin; therefore, these responses are amenable to bosentan treatment.

  16. Superoxide Anion Radical Production in the Tardigrade Paramacrobiotus richtersi, the First Electron Paramagnetic Resonance Spin-Trapping Study.

    Science.gov (United States)

    Savic, Aleksandar G; Guidetti, Roberto; Turi, Ana; Pavicevic, Aleksandra; Giovannini, Ilaria; Rebecchi, Lorena; Mojovic, Milos

    2015-01-01

    Anhydrobiosis is an adaptive strategy that allows withstanding almost complete body water loss. It has been developed independently by many organisms belonging to different evolutionary lines, including tardigrades. The loss of water during anhydrobiotic processes leads to oxidative stress. To date, the metabolism of free radicals in tardigrades remained unclear. We present a method for in vivo monitoring of free radical production in tardigrades, based on electron paramagnetic resonance and spin-trap DEPMPO, which provides simultaneous identification of various spin adducts (i.e., different types of free radicals). The spin trap can be easily absorbed in animals, and tardigrades stay alive during the measurements and during 24-h monitoring after the treatment. The results show that hydrated specimens of the tardigrade Paramacrobiotus richtersi produce the pure superoxide anion radical ((•)O2(-)). This is an unexpected result, as all previously examined animals and plants produce both superoxide anion radical and hydroxyl radical ((•)OH) or exclusively hydroxyl radical.

  17. Sources of superoxide/H2O2 during mitochondrial proline oxidation

    Directory of Open Access Journals (Sweden)

    Renata L.S. Goncalves

    2014-01-01

    Full Text Available p53 Inducible gene 6 (PIG6 encodes mitochondrial proline dehydrogenase (PRODH and is up-regulated several fold upon p53 activation. Proline dehydrogenase is proposed to generate radicals that contribute to cancer cell apoptosis. However, there are at least 10 mitochondrial sites that can produce superoxide and/or H2O2, and it is unclear whether proline dehydrogenase generates these species directly, or instead drives production by other sites. Amongst six cancer cell lines, ZR75-30 human breast cancer cells had the highest basal proline dehydrogenase levels, and mitochondria isolated from ZR75-30 cells consumed oxygen and produced H2O2 with proline as sole substrate. Insects use proline oxidation to fuel flight, and mitochondria isolated from Drosophila melanogaster were even more active with proline as sole substrate than ZR75-30 mitochondria. Using mitochondria from these two models we identified the sites involved in formation of superoxide/H2O2 during proline oxidation. In mitochondria from Drosophila the main sites were respiratory complexes I and II. In mitochondria from ZR75-30 breast cancer cells the main sites were complex I and the oxoglutarate dehydrogenase complex. Even with combinations of substrates and respiratory chain inhibitors designed to minimize the contributions of other sites and maximize any superoxide/H2O2 production from proline dehydrogenase itself, there was no significant direct contribution of proline dehydrogenase to the observed H2O2 production. Thus proline oxidation by proline dehydrogenase drives superoxide/H2O2 production, but it does so mainly or exclusively by providing anaplerotic carbon for other mitochondrial dehydrogenases and not by producing superoxide/H2O2 directly.

  18. Sources of superoxide/H2O2 during mitochondrial proline oxidation.

    Science.gov (United States)

    Goncalves, Renata L S; Rothschild, Daniel E; Quinlan, Casey L; Scott, Gary K; Benz, Christopher C; Brand, Martin D

    2014-01-01

    p53 Inducible gene 6 (PIG6) encodes mitochondrial proline dehydrogenase (PRODH) and is up-regulated several fold upon p53 activation. Proline dehydrogenase is proposed to generate radicals that contribute to cancer cell apoptosis. However, there are at least 10 mitochondrial sites that can produce superoxide and/or H2O2, and it is unclear whether proline dehydrogenase generates these species directly, or instead drives production by other sites. Amongst six cancer cell lines, ZR75-30 human breast cancer cells had the highest basal proline dehydrogenase levels, and mitochondria isolated from ZR75-30 cells consumed oxygen and produced H2O2 with proline as sole substrate. Insects use proline oxidation to fuel flight, and mitochondria isolated from Drosophila melanogaster were even more active with proline as sole substrate than ZR75-30 mitochondria. Using mitochondria from these two models we identified the sites involved in formation of superoxide/H2O2 during proline oxidation. In mitochondria from Drosophila the main sites were respiratory complexes I and II. In mitochondria from ZR75-30 breast cancer cells the main sites were complex I and the oxoglutarate dehydrogenase complex. Even with combinations of substrates and respiratory chain inhibitors designed to minimize the contributions of other sites and maximize any superoxide/H2O2 production from proline dehydrogenase itself, there was no significant direct contribution of proline dehydrogenase to the observed H2O2 production. Thus proline oxidation by proline dehydrogenase drives superoxide/H2O2 production, but it does so mainly or exclusively by providing anaplerotic carbon for other mitochondrial dehydrogenases and not by producing superoxide/H2O2 directly.

  19. Induction of Apoptosis by Superoxide Anion and the Protective Effects of Selenium and Vitamin E

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Objective The purpose of this study is to investigate the effect of superoxide anion on the apoptosis of cultured fibroblasts and the protective role of selenium and Vitamin E. Methods Cultured fibroblasts (NIH3T3), with or without selenium or vitamin E in the medium, were treated by superoxide anion produced by xanthine/xanthine oxidase reaction system and changes in cell structure and DNA were observed microscopically and electrophoretically. Results Apoptosis was observed when superoxide anion at a concentration of 5 nmol/L or 10 nmol/L had acted on the fibroblasts for 5-10 h. Selenium and Vitamin E in the medium inhibited the apoptosis significantly when their concentrations reached 1.15 mol/L and 2.3 mol/L respectively. Conclusion Selenium and vitamin E have protective effect against the apoptosis induced by superoxide anion. The effect of selenium is more remarkable than that of vitamin E.

  20. FITC Doped Rattle-Type Silica Colloidal Particle-Based Ratiometric Fluorescent Sensor for Biosensing and Imaging of Superoxide Anion.

    Science.gov (United States)

    Zhou, Ying; Ding, Jie; Liang, Tingxizi; Abdel-Halim, E S; Jiang, Liping; Zhu, Jun-Jie

    2016-03-01

    Fluorescent nanosensors have been widely applied in recognition and imaging of bioactive small molecules; however, the complicated surface modification process and background interference limit their applications in practical biological samples. Here, a simple, universal method was developed for ratiometric fluorescent determination of general small molecules. Taking superoxide anion (O2(•-)) as an example, the designed sensor was composed of three main moieties: probe carrier, rattle-type silica colloidal particles (mSiO2@hmSiO2 NPs); reference fluorophore doped into the core of NPs, fluorescein isothiocyanate (FITC); fluorescent probe for superoxide anion, hydroethidine (HE). In the absence of O2(•-), the sensor just emitted green fluorescence of FITC at 518 nm. When released HE was oxidized by O2(•-), the oxidation product exhibited red fluorescence at 570 nm and the intensity was linearly associated with the concentration of O2(•-), while that of reference element remained constant. Accordingly, ratiometric determination of O2(•-) was sensitively and selectively achieved with a linear range of 0.2-20 μM, and the detection limit was calculated as low as 80 nM. Besides, the technique was also successfully applied for dual-emission imaging of O2(•-) in live cells and realized visual recognition with obvious fluorescence color change in normal conditions or under oxidative stress. As long as appropriate reference dyes and sensing probes are selected, ratiometric biosensing and imaging of bioactive small molecules would be achieved. Therefore, the design could provide a simple, accurate, universal platform for biological applications.

  1. Chemiluminescence Imaging of Superoxide Anion Detects Beta-Cell Function and Mass.

    Science.gov (United States)

    Bronsart, Laura L; Stokes, Christian; Contag, Christopher H

    2016-01-01

    Superoxide anion is produced during normal cellular respiration and plays key roles in cellular physiology with its dysregulation being associated with a variety of diseases. Superoxide anion is a short-lived molecule and, therefore, its homeostatic regulation and role in biology and disease requires dynamic quantification with fine temporal resolution. Here we validated coelenterazine as a reporter of intracellular superoxide anion concentration and used it as a dynamic measure both in vitro and in vivo. Chemiluminescence was dependent upon superoxide anion levels, including those produced during cellular respiration, and concentrations varied both kinetically and temporally in response to physiologically relevant fluctuations in glucose levels. In vivo imaging with coelenterazine revealed that beta cells of the pancreas have increased levels of superoxide anion, which acted as a measure of beta-cell function and mass and could predict the susceptibility of mice to diabetes mellitus. Glucose response and regulation are key elements of cellular physiology and organismal biology, and superoxide anion appears to play a fundamental and dynamic role in both of these processes.

  2. Superoxide radical anion scavenging and dismutation by some Cu2+ and Mn2+ complexes: A pulse radiolysis study

    Science.gov (United States)

    Joshi, Ravi

    2017-10-01

    Copper (Cu) and manganese (Mn) ions are catalytic centers, in complexed form, in scavenging and dismutation process of superoxide radicals anion (O2.-) by superoxide dismutase enzyme. In the present work, fast reaction kinetics and mechanism of scavenging and dismutation of O2.- by Cu2+, Mn2+ and their complexes formed with some natural ligands have been studied using pulse radiolysis technique. Catechol, gentisic acid, tetrahydroxyquinone, tyrosine, tryptophan, embelin and bilirubin have been used as low molecular weight natural ligands for Cu2+ and Mn2+ to understand superoxide radical scavenging and dismutation reactions. These complexes have been found to be efficient scavengers of O2.- (k 107-109 M-1 s-1). The effects of nature of metal ion and ligand, and stoichiometry of complex on scavenging reaction rate constants are reported. Higher scavenging rate constants have been observed with complexes of: (1) Cu2+ as compared to Mn2+, and (2) at [ligand]/[metal] ratio of one as compared to two. A clear evidence of O2.- dismutation by free metal ions and some of the complexes has been observed. The study suggests that complexes of Cu2+ and Mn2+ with small natural ligands can also act as SOD mimics.

  3. Titanium dioxide nanoparticles enhance production of superoxide anion and alter the antioxidant system in human osteoblast cells

    Directory of Open Access Journals (Sweden)

    Niska K

    2015-02-01

    Full Text Available Karolina Niska,1 Katarzyna Pyszka,1 Cecylia Tukaj,2 Michal Wozniak,1 Marek Witold Radomski,3–5 Iwona Inkielewicz-Stepniak1 1Department of Medical Chemistry, 2Department of Electron Microscopy, Medical University of Gdansk, Gdansk, Poland; 3School of Pharmacy and Pharmaceutical Sciences, Trinity Biomedical Sciences Institute, The University of Dublin Trinity College, Dublin, Ireland; 4Kardio-Med Silesia, 5Silesian Medical University, Zabrze, Poland Abstract: Titanium dioxide (TiO2 nanoparticles (NPs are manufactured worldwide for a variety of engineering and bioengineering applications. TiO2NPs are frequently used as a material for orthopedic implants. However, to the best of our knowledge, the biocompatibility of TiO2NPs and their effects on osteoblast cells, which are responsible for the growth and remodeling of the human skeleton, have not been thoroughly investigated. In the research reported here, we studied the effects of exposing hFOB 1.19 human osteoblast cells to TiO2NPs (5–15 nm for 24 and 48 hours. Cell viability, alkaline phosphatase (ALP activity, cellular uptake of NPs, cell morphology, superoxide anion (O2•- generation, superoxide dismutase (SOD activity and protein level, sirtuin 3 (SIR3 protein level, correlation between manganese (Mn SOD and SIR, total antioxidant capacity, and malondialdehyde were measured following exposure of hFOB 1.19 cells to TiO2NPs. Exposure of hFOB 1.19 cells to TiO2NPs resulted in: (1 cellular uptake of NPs; (2 increased cytotoxicity and cell death in a time- and concentration-dependent manner; (3 ultrastructure changes; (4 decreased SOD and ALP activity; (5 decreased protein levels of SOD1, SOD2, and SIR3; (6 decreased total antioxidant capacity; (7 increased O2•- generation; and (8 enhanced lipid peroxidation (malondialdehyde level. The linear relationship between the protein level of MnSOD and SIR3 and between O2•- content and SIR3 protein level was observed. Importantly, the cytotoxic

  4. Stochastic modelling suggests that an elevated superoxide anion - hydrogen peroxide ratio can drive extravascular phagocyte transmigration by lamellipodium formation.

    Science.gov (United States)

    Kundu, Siddhartha

    2016-10-21

    Chemotaxis, integrates diverse intra- and inter-cellular molecular processes into a purposeful patho-physiological response; the operatic rules of which, remain speculative. Here, I surmise, that superoxide anion induced directional motility, in a responding cell, results from a quasi pathway between the stimulus, surrounding interstitium, and its biochemical repertoire. The epochal event in the mounting of an inflammatory response, is the extravascular transmigration of a phagocyte competent cell towards the site of injury, secondary to the development of a lamellipodium. This stochastic-to-markovian process conversion, is initiated by the cytosolic-ROS of the damaged cell, but is maintained by the inverse association of a de novo generated pool of self-sustaining superoxide anions and sub-critical hydrogen peroxide levels. Whilst, the exponential rise of O2(.-) is secondary to the focal accumulation of higher order lipid raft-Rac1/2-actin oligomers; O2(.-) mediated inactivation and redistribution of ECSOD, accounts for the minimal concentration of H2O2 that the phagocyte experiences. The net result of this reciprocal association between ROS/ RNS members, is the prolonged perturbation and remodeling of the cytoskeleton and plasma membrane, a prelude to chemotactic migration. The manuscript also describes the significance of stochastic modeling, in the testing of plausible molecular hypotheses of observable phenomena in complex biological systems.

  5. Superoxide generated by pyrogallol reduces highly water-soluble tetrazolium salt to produce a soluble formazan: a simple assay for measuring superoxide anion radical scavenging activities of biological and abiological samples.

    Science.gov (United States)

    Xu, Chen; Liu, Shu; Liu, Zhiqiang; Song, Fengrui; Liu, Shuying

    2013-09-02

    Superoxide anion radical (O2(˙-)) plays an important role in several human diseases. The xanthine/xanthine oxidase system is frequently utilized to produce O2(˙-). However, false positive results are easily got by using this system. The common spectrophotometric probes for O2(˙-) are nitroblue tetrazolium (NBT) and cytochrome c. Nevertheless, the application of NBT method is limited because of the water-insolubility of NBT formazan and the assay using cytochrome c lacks sensitivity and is not suitable for microplate measurement. We overcome these problems by using 1,2,3-trihydroxybenzene (pyrogallol) as O2(˙-)-generating system and a highly water-soluble tetrazolium salt, 2-(4-iodophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium sodium salt (WST-1) which can be reduced by superoxide anion radical to a stable water-soluble formazan with a high absorbance at 450 nm. The method is simple, rapid and sensitive. Moreover, it can be adapted to microplate format. In this study, the O2(˙-) scavenging activities of superoxide dismutase (SOD), L-ascorbic acid, N-acetyl-L-cysteine (NAC), albumin from human serum, flavonoids and herbal extracts were assessed by using this method. Meanwhile, the activities of tissue homogenates and serum were determined by using this validated method. This method, applicable to tissue homogenates, serum and herbal extracts, proved to be efficient for measuring O2(˙-) scavenging activities of biological and abiological samples.

  6. The changes of serum nitric oxide, angiotensin Ⅱ and superoxide anion in renal artery hypertension rat

    Institute of Scientific and Technical Information of China (English)

    马向红; 杨万松; 黄体钢; 周丽娟; 倪燕平; 樊振旺

    2003-01-01

    Objectives To study the changes of nitric oxide, angiotensin Ⅱ and superoxide anion in renal artery hypertension pathogenesis. Methods Male Wistar rats weighing 256 -285g were divided into 5 groups randomly, 10 rats of each group. Control group:false operation was made and routine diet was given; Ligature group: left renal artery was ligatured uncompletely and routine diet was given; Ligature + Losartan group:left renal artery was ligatured uncompletely and Losartan ture + L -Arg group: left renal artery was ligatured undrinking water; Ligature + L - Arg + Losartan group: left the drinking water. Blood pressure and heart rate were measured before and at the end of the experiment. One week after ligature, blood was drawn to determine angiotensin Ⅱ, cGMP, nitric oxide, nitric oxide synthase (NOS), O2-, superoxide dismutase (SOD). Results Systolic blood pressure was higher in ligature group than that in control group (p<0.05), systolic blood pressure was much lower in ligature + Losartan group than that in ligature group. Heart rate did not change significantly after experiment (p > 0. 05 ). AngⅡ was higher in ligature group than that in control group, even much higher in ligature + Losartan group (p < 0. 01 ). There was no difference of cGMP in each group (p > 0. 05 ). The concentration of NO was lower in ligature group (p < 0. 05 ), NO was higher in ligature + L - Arg + Losartan group than that in ligature group (p < 0. 05). O2' was higher in ligature group and ligature + L - Arg group than that in control group (p < 0. 05), O2- was lower in ligature + Losartan group than that in ligature group (p <0. 05). The level of SOD was lower in ligature group than that in control group (p < 0.05), higher in ligature + L - Arg group and ligature + L - Arg + Losartan group than that in ligature group (p <0.05). Conclusions AnglⅡ,O2- and NO imbalance play an important role in hypertension pathogenesis, L-Arg and losartan may have protective effect.

  7. A novel murrel Channa striatus mitochondrial manganese superoxide dismutase: gene silencing, SOD activity, superoxide anion production and expression.

    Science.gov (United States)

    Arockiaraj, Jesu; Palanisamy, Rajesh; Bhatt, Prasanth; Kumaresan, Venkatesh; Gnanam, Annie J; Pasupuleti, Mukesh; Kasi, Marimuthu

    2014-12-01

    We have reported the molecular characterization including gene silencing, superoxide activity, superoxide anion production, gene expression and molecular characterization of a mitochondrial manganese superoxide dismutase (mMnSOD) from striped murrel Channa striatus (named as CsmMnSOD). The CsmMnSOD polypeptide contains 225 amino acids with a molecular weight of 25 kDa and a theoretical isoelectric point of 8.3. In the N-terminal region, CsmMnSOD carries a mitochondrial targeting sequence and a superoxide dismutases (SOD) Fe domain (28-109), and in C-terminal region, it carries another SOD Fe domain (114-220). The CsmMnSOD protein sequence shared significant similarity with its homolog of MnSOD from rock bream Oplegnathus fasciatus (96%). The phylogenetic analysis showed that the CsmMnSOD fell in the clade of fish mMnSOD group. The monomeric structure of CsmMnSOD possesses 9 α-helices (52.4%), 3 β-sheets (8.8%) and 38.8% random coils. The highest gene expression was noticed in liver, and its expression was inducted with fungal (Aphanomyces invadans) and bacterial (Aeromonas hydrophila) infections. The gene silencing results show that the fish that received dsRNA exhibited significant (P superoxide anion production was determined by calculating the granular blood cell count during infection in murrel. It shows that the infection influenced the superoxide radical production which plays a major role in killing the pathogens. Overall, this study indicated the defense potentiality of CsmMnSOD; however, further research is necessary to explore its capability at protein level.

  8. Ultrasensitive detection of superoxide anion released from living cells using a porous Pt-Pd decorated enzymatic sensor.

    Science.gov (United States)

    Zhu, Xiang; Liu, Tingting; Zhao, Hongli; Shi, Libo; Li, Xiaoqing; Lan, Minbo

    2016-05-15

    Considering the critical roles of superoxide anion (O2(∙-)) in pathological conditions, it is of great urgency to establish a reliable and durable approach for real-time determination of O2(∙-). In this study, we propose a porous Pt-Pd decorated superoxide dismutase (SOD) sensor for qualitative and quantitative detection O2(∙-). The developed biosensor exhibits a fast, selective and linear amperometric response upon O2(∙-) in the concentration scope of 16 to 1,536 μM (R(2)=0.9941), with a detection limit of 0.13 μM (S/N=3) and a low Michaelis-Menten constant of 1.37 μM which indicating a high enzymatic activity and affinity to O2(∙-). Inspiringly, the proposed sensor possesses an ultrahigh sensitivity of 1270 μA mM(-1)cm(-2). In addition, SOD/porous Pt-Pd sensor exhibits excellent anti-interference property, reproducibility and long-term storage stability. Beyond our expectation, the trace level of O2(∙-) released from living cells has also been successfully captured. These satisfactory results are mainly ascribed to (1) the porous interface with larger surface area and more active sites to provide a biocompatible environment for SOD (2) the specific biocatalysis of SOD towards O2(∙-) and (3) porous Pt-Pd nanomaterials fastening the electron transfer. The superior electrochemical performance makes SOD/porous Pt-Pd sensor a promising candidate for monitoring the dynamic changes of O2(∙-)in vivo.

  9. Role of superoxide dismutase enzymes and ascorbate in protection of nitrergic relaxation against superoxide anions in mouse duodenum

    Institute of Scientific and Technical Information of China (English)

    M Ata SECILMIS; Olcay Ergurhan KIROGLU; Nuran OGULENER

    2008-01-01

    Aim: The aim of this study was to investigate whether superoxide dismutase (SOD) enzymes and ascorbate play a role in the protection of the nitrergic relax-ation against superoxide anion inhibition in the mouse duodenum. Methods: The effects of exogenous SOD, N,N'-bis(salicylidene) ethylenediamine chlo-ride (EUK-8; a synthetic cell-permeable mimetic of the manganese SOD [Mn SOD] and ascorbate on relaxant responses induced by nitrergic nerve stimulation), exogenous nitric oxide (NO), and nitroglycerin were investigated in isolated mouse duodenum tissues. Results: Diethyidithiocarbamate (DETCA) inhibited the relaxation to exogenous NO and nitroglycerin, but not relaxation to electri-cal field stimulation (EFS). SOD and ascorbate partially prevented the inhibi-tory effect of DETCA on relaxation to NO, abut not to nitroglycerin. The DETCA-induced inhibition on nitroglycerin was prevented by ELrK-8. Hemoglobin, 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazolinel-oxyl-3-oxide, and hydroxo-cobalamin inhibited the relaxation to NO, but not to EFS and nitroglycerin in the presence of DETCA. Pyrogallol and hydroquinone inhibited the relaxation to NO, but not to EFS and nitroglycerin. This inhibition was prevented by exog-enous SOD and ascorbate, but was not prevented by EUK-8. Pyrogallol and hy-droquinone did not inhibit the EFS-induced relaxation in the presence of DETCA. Duroquinone and 6-anilino-5.8-quinolinedione inhibited the relaxation to EFS, NO, and nitroglycerin, and this inhibition was prevented by EUK-8. Conclusion: These results suggest that the nitrergic neurotransmission in the mouse duode-num is protected by endogenous tissue antioxidants against superoxide anions, and Mn SOD, in addition to copper/zinc SOD, can protect NO from attack from superoxide anion generators intracellularly. Also, the possibility that the endog-enous neurotransmitter may not be the free NO but a NO-containing or NO-generating molecule in the mouse duodenum remains open.

  10. Metal ions induced heat shock protein response by elevating superoxide anion level in HeLa cells transformed by HSE-SEAP reporter gene.

    Science.gov (United States)

    Yu, Zhanjiang; Yang, Xiaoda; Wang, Kui

    2006-06-01

    The aim of this work is to define the relationship between heat shock protein (HSP) and reactive oxygen species (ROS) in the cells exposed to different concentrations of metal ions, and to evaluate a new method for tracing the dynamic levels of cellular reactive oxygen species using a HSE-SEAP reporter gene. The expression of heat shock protein was measured using a secreted alkaline phosphatase (SEAP) reporter gene transformed into HeLa cell strain, the levels of superoxide anion (O(2)(-)) and hydrogen peroxide (H(2)O(2)) were determined by NBT reduction assay and DCFH staining flow cytometry (FCM), respectively. The experimental results demonstrated that the expression of heat shock protein induced by metal ions was linearly related to the cellular superoxide anion level before cytotoxic effects were observed, but not related to the cellular hydrogen peroxide level. The experimental results suggested that metal ions might induce heat shock protein by elevating cellular superoxide anion level, and thus the expression of heat shock protein indicated by the HSE-SEAP reporter gene can be an effective model for monitoring the dynamic level of superoxide anion and early metal-induced oxidative stress/cytotoxicity.

  11. Construction of a highly sensitive non-enzymatic sensor for superoxide anion radical detection from living cells.

    Science.gov (United States)

    Liu, Yuelin; Liu, Xiuhui; Liu, Yidan; Liu, Guoan; Ding, Lan; Lu, Xiaoquan

    2017-04-15

    A novel non-enzymatic superoxide anion (O2•(-)) sensor was fabricated based on Ag nanoparticles (NPs)/L-cysteine functioned carbon nanotubes (Cys-MWCNTs) nanocomposites and used to measure the release of O2•(-) from living cells. In this strategy, AgNPs could be uniformly electrodeposited on the MWCNTs surface with average diameter of about 20nm as exhibited by scanning electronmicroscopy (SEM). Electrochemical study demonstrated that the AgNPs/Cys-MWCNTs modified glassy carbon electrode exhibited excellent catalytic activity toward the reduction of O2•(-) with a super wide linear range from 7.00×10(-11) to 7.41×10(-5)M and a low detection limit (LOD) of 2.33×10(-11)M (S/N=3). Meanwhile, the mechanism for O2•(-) reduction was also proposed for the first time. Importantly, this novel non-enzymatic O2•(-) sensor can detect O2•(-) release from cancer cells under both the external stimulation and the normal condition, which has the great potential application in clinical diagnostics to assess oxidative stress of living cells.

  12. Homocysteine enhances superoxide anion release and NADPH oxidase assembly by human neutrophils. Effects on MAPK activation and neutrophil migration.

    Science.gov (United States)

    Alvarez-Maqueda, Moisés; El Bekay, Rajaa; Monteseirín, Javier; Alba, Gonzalo; Chacón, Pedro; Vega, Antonio; Santa María, Consuelo; Tejedo, Juan R; Martín-Nieto, José; Bedoya, Francisco J; Pintado, Elisabeth; Sobrino, Francisco

    2004-02-01

    Hyperhomocysteinaemia has recently been recognized as a risk factor of cardiovascular disease. However, the action mechanisms of homocysteine (Hcy) are not well understood. Given that Hcy may be involved in the recruitment of monocytes and neutrophils to the vascular wall, we have investigated the role of Hcy in essential functions of human neutrophils. We show that Hcy increased superoxide anion (O2*-) release by neutrophils to the extracellular medium, and that this effect was inhibited by superoxide dismutase and diphenyleneiodonium (DPI), an inhibitor of NADPH oxidase activity. The enzyme from rat peritoneal macrophages displayed a similar response. These effects were accompanied by a time-dependent increased translocation of p47phox and p67phox subunits of NADPH oxidase to the plasma membrane. We also show that Hcy increased intracellular H2O2 production by neutrophils, that Hcy enhanced the activation and phosphorylation of mitogen-activated protein kinases (MAPKs), specifically p38-MAPK and ERK1/2, and that the migration of neutrophils was increased by Hcy. Present results are the first evidence that Hcy enhances the oxidative stress of neutrophils, and underscore the potential role of phagocytic cells in vascular wall injury through O2*- release in hyperhomocysteinaemia conditions.

  13. Superoxide Anion Radical Scavenging Ability of Quaternary Ammonium Salt of Chitosan

    Institute of Scientific and Technical Information of China (English)

    Xiao Yan ZHU; Jian Min WU; Zhi Shen JIA

    2004-01-01

    A series of N-alkyl or N-aryl chitosan quaternary ammonium salt were prepared using 96% deacetylated chitosan. Their scavenging activities against superoxide anion radical were investigated by chemiluminescence. The IC50 values of these compounds range from 280 to 880 μg/mL, which should be attributed to their different substitutes.

  14. Induction of Apoptosis by Superoxide Anion and the Protective Effects of Selenium and Vitamin E

    Institute of Scientific and Technical Information of China (English)

    GUOLING; XUEAN-NA; 等

    2001-01-01

    Objective:The purpose of this study is to investigate the effect of superoxide anion on the apoptosis of cultured fibroblasts and the protective role of seleium and Vitamin E.Methods:Cultured fibroblasts(NIH3T3),with or without selenium or vitamin E in the medium,were treated by superoxide anion produced by xanthine/xanthine oxidase reaction system and changes in cell structure and DNA were observed microscopically and electrophoretically,Results:Apoptosis was observed when superoxide anion at a concentration of 5nmol/L or 10nmol/L had acted on the fibroblasts for 5-10h.Selenium and Vitamin E in the medium inhibited the apoptosis significantly when their concentrations reached 1.15mol/L and 2.3mol/L respectively.Concleusion:selenium and vitamin Ehave protective effect against the apoptosis induced by superoxide anion.The effect of selenium is more remakable than that of vitamin E.

  15. Osmotic stress stimulates generation of superoxide anion by spermatozoa in horses.

    Science.gov (United States)

    Burnaugh, L; Ball, B A; Sabeur, K; Thomas, A D; Meyers, S A

    2010-02-01

    The objective of this study was to examine the interplay between osmotic and oxidative stress as well as to determine mechanisms by which osmotic stress increases superoxide generation in spermatozoa of horses. Superoxide production, as measured by dihydroethidium (DHE), increased when spermatozoa of horses were incubated under either hyperosmotic or hyposmotic conditions. This increase in superoxide production was inhibited by the MAP kinase p38 inhibitor, SB203580, and by the superoxide scavenger, tiron. Incubation of spermatozoa under hyperosmotic conditions increased overall protein tyrosine phosphorylation as measured by western blotting techniques; however, a similar increase was not detected when spermatozoa were incubated under hyposmotic conditions. The general protein kinase C (PKC) and protein tyrosine kinase (PTK) inhibitor staurosporine inhibited (P<0.05) tyrosine phosphorylation in samples from cells under hyperosmotic conditions. In addition, the NADPH oxidase inhibitor diphenyleneiodonium (DPI) also inhibited (P<0.05) protein tyrosine phosphorylation in cells under hyperosmotic conditions. In summary, these data indicate that incubation of equine spermatozoa under both hyposmotic and hyperosmotic conditions can increase superoxide anion generation. Under hyperosmotic conditions, this increased generation of superoxide anion was accompanied by increased protein tyrosine phosphorylation.

  16. Martian Superoxide and Peroxide O2 Release (OR) Assay: A New Technology for Terrestrial and Planetary Applications

    Science.gov (United States)

    Georgiou, Christos D.; Zisimopoulos, Dimitrios; Panagiotidis, Konstantinos; Grintzalis, Kontantinos; Papapostolou, Ioannis; Quinn, Richard C.; McKay, Christopher P.; Sun, Henry J.

    2015-01-01

    This study presents an assay for the detection and quantification of soil metal superoxides and peroxides in regolith and soil. The O2 release (OR) assay is based on the enzymatic conversion of the hydrolysis products of metal oxides to O2, and their quantification by an O2 electrode based on the stoichiometry of the involved reactions: The intermediate product O2 from the hydrolysis of metal superoxides is converted by cytochrome c to O2, and also by superoxide dismutase (SOD) to 1/2 mol O2 and 1/2 mol H2O2, which is then converted by catalase (CAT) to 1/2 mol O2. The product H2O2 from the hydrolysis of metal peroxides and hydroperoxides is converted to 1/2 mol O2 by CAT. The assay-method was validated in a sealed sample chamber using a liquid-phase Clark-type O2 electrode with known concentrations of O2 and H2O2, and with commercial metal superoxide and peroxide mixed with Mars analogue Mojave and Atacama Desert soils. Carbonates and perchlorates, both present on Mars, do not interfere with the assay. The assay lower limit of detection, using luminescence quenching/optical sensing O2-electrodes, is 1 nmol O2 cm(exp. -3) or better. The activity of the assay enzymes SOD and cytochrome c was unaffected up to 6 Gy exposure by gamma-radiation, while CAT retained 100% and 40% of its activity at 3 and 6 Gy, respectively, demonstrating the suitability of these enzymes for planetary missions, e.g., in Mars or Europa.

  17. A new endoplasmic reticulum-targeted two-photon fluorescent probe for imaging of superoxide anion in diabetic mice.

    Science.gov (United States)

    Xiao, Haibin; Liu, Xiao; Wu, Chuanchen; Wu, Yaohuan; Li, Ping; Guo, Xiaomeng; Tang, Bo

    2017-05-15

    Excessive or unfolded proteins accumulation in endoplasmic reticulum (ER) will cause ER stress, which has evolved to involve in various metabolic diseases. In particular, ER stress plays an important role in the pathogenesis of diabetes. Both ER stress and course of diabetes accompany oxidative stress and production of reactive oxygen species (ROS), among which superoxide anion (O2(•-)) is the first produced ROS and has been recognized as cell signaling mediator involved in the physiological and pathological process of diabetes. Hence, the development of effective monitoring methods of O2(•-) in live cells and in vivo is of great importance for ascertaining the onset and progress of related diseases. Herein, a new endoplasmic reticulum-targeted two-photon fluorescent probe termed ER-BZT is designed and synthesized for imaging of O2(•-). The probe ER-BZT shows high sensitivity, selectivity, stability, and low cytotoxicity. Based on these superior properties, the rise of O2(•-) levels in endoplasmic reticulum induced with different stimuli is visualized by one- and two-photon fluorescence imaging. Most importantly, by utilizing ER-BZT, the two-photon fluorescence imaging results demonstrate that the endogenous O2(•-) concentration in abdominal or hepatic tissue of diabetic mice is higher than that in normal mice. Meanwhile, after treated with metformin, a broad-spectrum antidiabetic drug, the diabetic mice exhibit depressed O2(•-) level. The proposed two-photon probe, ER-BZT might serve as perfect tool to image the O2(•-) fluctuations and study the relevance between O2(•-) and various diseases in live cells and in vivo.

  18. Sensitive electrochemical detection of superoxide anion using gold nanoparticles distributed poly(methyl methacrylate)-polyaniline core-shell electrospun composite electrode.

    Science.gov (United States)

    Santhosh, Padmanabhan; Manesh, Kalayil Manian; Lee, Se-Hee; Uthayakumar, Sivaperumal; Gopalan, Anantha Iyengar; Lee, Kwang-Pill

    2011-04-21

    In the present communication, a novel composite nanofibrous electrode is developed for the detection of superoxide anion (O(2)˙(-)) in phosphate buffered saline (PBS). The composite fiber electrode is fabricated by dispersing gold nanoparticles onto poly(methyl methacrylate) (PMMA)-polyaniline (PANI) core-shell electrospun nanofibers. The constructed architecture is proven to be a favorable environment for the immobilization of the enzyme, superoxide dismutase (SOD). Direct electron transfer is achieved between SOD and the electrode with an electron transfer rate constant of 8.93 s(-1). At an applied potential of +300 mV, PMMA/PANI-Au(nano)/SOD-ESCFM shows highly sensitive detection of O(2)˙(-). In addition to this, quantification of different activities of SOD is realized at PMMA/PANI-Au(nano)/SOD-ESCFM. These analytical features offer great potential for construction of the third-generation O(2)˙(-) biosensor.

  19. Signaling Pathways Linked to Serotonin-Induced Superoxide Anion Production: A Physiological Role for Mitochondria in Pulmonary Arteries

    Science.gov (United States)

    Genet, Nafiisha; Billaud, Marie; Rossignol, Rodrigue; Dubois, Mathilde; Gillibert-Duplantier, Jennifer; Isakson, Brant E.; Marthan, Roger; Savineau, Jean-Pierre; Guibert, Christelle

    2017-01-01

    Serotonin (5-HT) is a potent vasoconstrictor agonist and contributes to several vascular diseases including systemic or pulmonary hypertension and atherosclerosis. Although superoxide anion (O2•_) is commonly associated to cellular damages due to O2•_ overproduction, we previously demonstrated that, in physiological conditions, O2•_ also participates to the 5-HT contraction in intrapulmonary arteries (IPA). Here, we focused on the signaling pathways leading to O2•_ production in response to 5-HT in rat IPA. Using electron paramagnetic resonance on rat IPA, we showed that 5-HT (100 μM)-induced O2•_ production was inhibited by ketanserin (1 μM—an inhibitor of the 5-HT2 receptor), absence of extracellular calcium, two blockers of voltage-independent calcium permeable channels (RHC80267 50 μM and LOE-908 10 μM) and a blocker of the mitochondrial complex I (rotenone—100 nM). Depletion of calcium from the sarcoplasmic reticulum or nicardipine (1 μM—an inhibitor of the L-type voltage-dependent calcium channel) had no effect on the 5-HT-induced O2•_ production. O2•_ levels were also increased by α-methyl-5-HT (10 μM—a 5-HT2 receptors agonist) whereas GR127935 (1 μM—an antagonist of the 5-HT1B/D receptor) and citalopram (1 μM—a 5-HT transporter inhibitor) had no effect on the 5-HT-induced O2•_ production. Peroxynitrites were increased in response to 5-HT (100 μM). In isolated pulmonary arterial smooth muscle cells loaded with rhod-2 or mitosox probes, we respectively showed that 5-HT increased both mitochondrial calcium and O2•_ levels, which were both abrogated in absence of extracellular calcium. Mitochondrial O2•_ levels were also abolished in the presence of rotenone (100 nM). In pulmonary arterial smooth muscle cells loaded with TMRM, we showed that 5-HT transiently depolarized the mitochondrial membrane whereas in the absence of extracellular calcium the mitochondrial membrane depolarisation was delayed and sustained in

  20. Inhibitory effects of chitosan on superoxide anion radicals and lipid free radicals

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    With the electron spin resonance (ESR) technique, the inhibitory effects of chitosan on superoxide anion radicals and linoleic acid lipid radicals were found. The inhibitory ratio E for these two kinds of radicals is in proportion to the concentration of chitosan. It was also observed that E for linoleic acid lipid radicals increased with the increase of the degree of deacetylation and decreased with the increase of the molecular weight of chitosan.

  1. Equine digital veins are more sensitive to superoxide anions than digital arteries.

    Science.gov (United States)

    Lapo, Rock Allister; Gogny, Marc; Chatagnon, Gérard; Lalanne, Valérie; Harfoush, Khaled; Assane, Moussa; Desfontis, Jean-Claude; Mallem, Mohamed Yassine

    2014-10-05

    This work was designed to investigate (i) the effect of superoxide dismutase (SOD) inhibition on endothelial function and (ii) the free radical-induced endothelial dysfunction in equine digital veins (EDVs) and equine digital arteries (EDAs) isolated from healthy horses. EDV and EDA rings were suspended in a 5 ml organ bath containing Krebs solution. After a 60 min equilibration period, EDV and EDA rings were contracted with phenylephrine. Then, cumulative concentration-response curves (CCRCs) to acetylcholine were performed. In both EDVs and EDAs, acetylcholine (1 nM to 10 µM) produced concentration-dependent relaxation. We investigated the influence of SOD inhibition by diethyldithiocarbamate (DETC; 100 µM), a CuZnSOD inhibitor, on EDAs and EDVs relaxant responses to acetylcholine. Acetylcholine -mediated relaxation was impaired by DETC only in EDVs. SOD activity assayed by a xanthine-xanthine oxidase method was higher in EDAs compared with EDVs (Psuperoxide anions generating systems showed that in both EDVs and EDAs, the acetylcholine-mediated relaxation was significantly impaired by pyrogallol and homocysteine. This impairment was more pronounced in EDVs than in EDAs. Moreover, the pyrogallol-induced impairment of acetylcholine-mediated relaxation was potentiated by DETC to a greater extent in EDVs. We concluded that due to the lower activity of SOD, EDVs are more sensitive to superoxide anions than EDAs. So, any alteration of superoxide anions metabolism is likely to have a more important impact on venous rather than arterial relaxation.

  2. New TiO2/DSAT Immobilization System for Photodegradation of Anionic and Cationic Dyes

    OpenAIRE

    Wan Izhan Nawawi Wan Ismail; S. K. Ain; R. Zaharudin; Ali H. Jawad; M. A. M. Ishak; Khudzir Ismail; Sudirman Sahid

    2015-01-01

    A new immobilized TiO2 technique was prepared by coating TiO2 solution onto double-sided adhesive tape (DSAT) as a thin layer binder without adding any organic additives. Glass plate was used as support material to immobilized TiO2/DSAT. Two different charges of dyes were applied, namely, anionic reactive red 4 (RR4) and cationic methylene blue (MB) dyes. Photocatalytic degradation of RR4 and MB dyes was observed under immobilized TiO2/DSAT with the degradation rate slightly lower and higher,...

  3. Ratiometric fluorescence detection of superoxide anion based on AuNPs-BSA@Tb/GMP nanoscale coordination polymers.

    Science.gov (United States)

    Liu, Nan; Hao, Juan; Cai, Keying; Zeng, Mulan; Huang, Zhenzhong; Chen, Lili; Peng, Bingxian; Li, Ping; Wang, Li; Song, Yonghai

    2017-08-03

    A novel ratiometric fluorescence nanosensor for superoxide anion (O2(•-) ) detection was designed with gold nanoparticles-bovine serum albumin (AuNPs-BSA)@terbium/guanosine monophosphate disodium (Tb/GMP) nanoscale coordination polymers (NCPs) (AuNPs-BSA@Tb/GMP NCPs). The abundant hydroxyl and amino groups of AuNPs-BSA acted as binding points for the self-assembly of Tb(3+) and GMP to form core-shell AuNPs-BSA@Tb/GMP NCP nanosensors. The obtained probe exhibited the characteristic fluorescence emission of both AuNPs-BSA and Tb/GMP NCPs. The AuNPs-BSA not only acted as a template to accelerate the growth of Tb/GMP NCPs, but also could be used as the reference fluorescence for the detection of O2(•-) . The resulting AuNPs-BSA@Tb/GMP NCP ratiometric fluorescence nanosensor for the detection of O2(•-) demonstrated high sensitivity and selectivity with a wide linear response range (14 nM-10 μM) and a low detection limit (4.7 nM). Copyright © 2017 John Wiley & Sons, Ltd.

  4. Neutrophil superoxide-anion generating capacity in chronic smoking: effect of long-term -tocopherol therapy

    Indian Academy of Sciences (India)

    Lambertus J Hvan Tits; Frouwkje De Waart; Heidi L M Hak-Lemmers; Jacqueline De Graaf; Pierre N M Demacker; Anton F H Stalenhoef

    2003-02-01

    We investigated whether long-term -tocopherol therapy in chronic smoking affects superoxide generating capacity of neutrophils ex vivo. To this purpose, we randomly assigned 128 male chronic smokers (37 ± 21 pack years of smoking) to treatment with placebo ( = 64) or -tocopherol (400 IU dL--tocopherol daily, = 64). After two years of therapy, we measured phorbol 12-myristate 13-acetate-induced superoxide production of isolated neutrophils and of diluted whole blood by monitoring reduction of ferricytochrome and luminolenhanced peroxidase-catalyzed chemiluminescence. Plasma lipids and lipoproteins were not different between the two treatment groups. As expected, concentrations of -tocopherol in plasma and in low-density lipoproteins were markedly elevated in the supplemented group compared to the placebo group (+ 120%, P < 0.0001 and + 83%, < 0.0001, respectively). Consequently, resistance to in vitro oxidation of low-density lipoproteins (reflected by lag time of conjugated diene formation) was higher in the supplemented group than in the placebo group (+ 22%, < 0.0001). Superoxide generating capacity of neutrophils and superoxide production in diluted whole blood did not differ between -tocopherol and placebo group. It is concluded that in chronic smoking long-term supranormal -tocopherol intake does not reduce neutrophil superoxide-anion generating capacity, despite large increases in the concentrations of -tocopherol in plasma and in low-density lipoproteins.

  5. A two-photon fluorescent probe for exogenous and endogenous superoxide anion imaging in vitro and in vivo.

    Science.gov (United States)

    Li, Run-Qing; Mao, Zhi-Qiang; Rong, Lei; Wu, Nian; Lei, Qi; Zhu, Jing-Yi; Zhuang, Lin; Zhang, Xian-Zheng; Liu, Zhi-Hong

    2017-01-15

    Herein, we report a novel quinoline derivative-based two-photon fluorescent probe 6-(dimethylamino)quinoline-2-benzothiazoline (HQ), which is capable of tracking superoxide anion in organisms with specific "turn-on" fluorescence response based on extension of π-conjugations and moderate ICT process. The probe exhibited favorable photophysical properties, a broad linear range and high photostability. It can specifically detect superoxide anion with a significant fluorescence enhancement and great linearity from 0 to 500μM in PBS buffer. Furthermore, HQ shows low cytotoxicity and excellent photostability toward living cells and organisms, which was able to monitor endogenous superoxide anion fluxes in living cells and in vivo. For the first time, endogenous superoxide anion in lung inflammation was visualized successfully by using HQ through two-photon microscopy, and the probe HQ shows great potential for fast in-situ detecting of inflammatory response in live organisms.

  6. Influence of Aqueous Inorganic Anions on the Reactivity of Nanoparticles in TiO2 Photocatalysis.

    Science.gov (United States)

    Farner Budarz, Jeffrey; Turolla, Andrea; Piasecki, Aleksander F; Bottero, Jean-Yves; Antonelli, Manuela; Wiesner, Mark R

    2017-03-21

    The influence of inorganic anions on the photoreactivity and aggregation of titanium dioxide nanoparticles (NPs) was assessed by dosing carbonate, chloride, nitrate, phosphate, and sulfate as potassium salts at multiple concentrations. NP stability was monitored in terms of aggregate morphology and electrophoretic mobility (EPM). Aggregate size and fractal dimension were measured over time by laser diffraction, and the isoelectric point (IEP) as a function of anion and concentration was obtained by measuring EPM versus pH. Phosphate, carbonate, and to a lesser extent, sulfate decreased the IEP of TiO2 and stabilized NP suspensions owing to specific surface interactions, whereas this was not observed for nitrate and chloride. TiO2 NPs were exposed to UV-A radiation, and the photoreactivity was assessed by monitoring the production of reactive species over time both at the NP surface (photogenerated holes) and in the bulk solution (hydroxyl radicals) by observing their reactions with the selective probe compounds iodide and terephthalic acid, respectively. The generation of photogenerated holes and hydroxyl radicals was influenced by each inorganic anion to varying degrees. Carbonate and phosphate inhibited the oxidation of iodide, and this interaction was successfully described by a Langmuir-Hinshelwood mechanism and related to the characteristics of TiO2 aggregates. Chloride and nitrate do not specifically interact with TiO2, and sulfate creates relatively weak interactions with the TiO2 surface such that no decrease in photogenerated hole reactivity was observed. A decrease in hydroxyl radical generation was observed for all inorganic anions. Quenching rate constants for the reaction of hydroxyl radicals with each inorganic anion do not provide a comprehensive explanation for the magnitude of this decrease, which arises from the interplay of several physicochemical phenomena. This work shows that the reactivity of NPs will be strongly influenced by the makeup of

  7. Roles of superoxide and myeloperoxidase in ascorbate oxidation in stimulated neutrophils and H2O2-treated HL60 cells.

    Science.gov (United States)

    Parker, Amber; Cuddihy, Sarah L; Son, Tae G; Vissers, Margreet C M; Winterbourn, Christine C

    2011-10-01

    Ascorbate is present at high concentrations in neutrophils and becomes oxidized when the cells are stimulated. We have investigated the mechanism of oxidation by studying cultured HL60 cells and isolated neutrophils. Addition of H(2)O(2) to ascorbate-loaded HL60 cells resulted in substantial oxidation of intracellular ascorbate. Oxidation was myeloperoxidase-dependent, but not attributable to hypochlorous acid, and can be explained by myeloperoxidase (MPO) exhibiting direct ascorbate peroxidase activity. When neutrophils were stimulated with phorbol myristate acetate, about 40% of their intracellular ascorbate was oxidized over 20 min. Ascorbate loss required NADPH oxidase activity but in contrast to the HL60 cells did not involve myeloperoxidase. It did not occur when exogenous H(2)O(2) was added, was not inhibited by myeloperoxidase inhibitors, and was the same for normal and myeloperoxidase-deficient cells. Neutrophil ascorbate loss was enhanced when endogenous superoxide dismutase was inhibited by cyanide or diethyldithiocarbamate and appears to be due to oxidation by superoxide. We propose that in HL60 cells, MPO-dependent ascorbate oxidation occurs because cellular ascorbate can access newly synthesized MPO before it becomes packaged in granules: a mechanism not possible in neutrophils. In neutrophils, we estimate that ascorbate is capable of competing with superoxide dismutase for a small fraction of the superoxide they generate and propose that the superoxide responsible is likely to come from previously identified sites of intracellular NADPH oxidase activity. We speculate that ascorbate might protect the neutrophil against intracellular effects of superoxide generated at these sites.

  8. Free Superoxide is an Intermediate in the Production of H2O2 by Copper(I)-Aβ Peptide and O2.

    Science.gov (United States)

    Reybier, Karine; Ayala, Sara; Alies, Bruno; Rodrigues, João V; Bustos Rodriguez, Susana; La Penna, Giovanni; Collin, Fabrice; Gomes, Cláudio M; Hureau, Christelle; Faller, Peter

    2016-01-18

    Oxidative stress is considered as an important factor and an early event in the etiology of Alzheimer's disease (AD). Cu bound to the peptide amyloid-β (Aβ) is found in AD brains, and Cu-Aβ could contribute to this oxidative stress, as it is able to produce in vitro H2O2 and HO˙ in the presence of oxygen and biological reducing agents such as ascorbate. The mechanism of Cu-Aβ-catalyzed H2O2 production is however not known, although it was proposed that H2O2 is directly formed from O2 via a 2-electron process. Here, we implement an electrochemical setup and use the specificity of superoxide dismutase-1 (SOD1) to show, for the first time, that H2O2 production by Cu-Aβ in the presence of ascorbate occurs mainly via a free O2˙(-) intermediate. This finding radically changes the view on the catalytic mechanism of H2O2 production by Cu-Aβ, and opens the possibility that Cu-Aβ-catalyzed O2˙(-) contributes to oxidative stress in AD, and hence may be of interest.

  9. Excitation Wavelength Dependent O2 Release from Copper(II)-Superoxide Compounds: Laser Flash-Photolysis Experiments and Theoretical Studies

    Science.gov (United States)

    Saracini, Claudio; Liakos, Dimitrios G.; Zapata Rivera, Jhon E.; Neese, Frank; Meyer, Gerald J.; Karlin, Kenneth D.

    2014-01-01

    Irradiation of the copper(II)-superoxide synthetic complexes [(TMG3tren)CuII(O2)]+ (1) and [(PV-TMPA)CuII(O2)]+ (2) with visible light resulted in direct photo-generation of O2 gas at low temperature (from −40 °C to −70°C for 1 and from −125 °C to −135 °C for 2) in 2-methyltetrahydrofuran (MeTHF) solvent. The yield of O2 release was wavelength dependent: λexc = 436 nm, ϕ = 0.29 (for 1), ϕ = 0.11 (for 2), and λexc = 683 nm, ϕ = 0.035 (for 1), ϕ = 0.078 (for 2), which was followed by fast O2-recombination with [(TMG3tren)CuI]+ (3) and [(PV-TMPA)CuI]+ (4). Enthalpic barriers for O2 re-binding to the copper(I) center (~ 10 kJ mol−1) and for O2 dissociation from the superoxide compound 1 (45 kJ mol−1) were determined. TD-DFT studies, carried out for 1, support the experimental results confirming the dissociative character of the excited states formed upon blue or red light laser excitation. PMID:24428309

  10. Sonochemiluminescence of lucigenin: Evidence of superoxide radical anion formation by ultrasonic irradiation

    Science.gov (United States)

    Matsuoka, Masanori; Takahashi, Fumiki; Asakura, Yoshiyuki; Jin, Jiye

    2016-07-01

    The sonochemiluminescence (SCL) behavior of lucigenin (Luc2+) has been studied in aqueous solutions irradiated with 500 kHz ultrasound. Compared with the SCL of a luminol system, a tremendously increased SCL intensity is observed from 50 µM Luc2+ aqueous solution (pH =11) when small amounts of coreactants such as 2-propanol coexist. It is shown that SCL intensity strongly depends on the presence of dissolved gases such as air, O2, N2, and Ar. The highest SCL intensity is obtained in an O2-saturated solution, indicating that molecular oxygen is required to generate SCL. Since SCL intensity is quenched completely in the presence of superoxide dismutase (SOD), an enzyme that can catalyze the disproportionation of O2 •-, the generation of O2 •- in the ultrasonic reaction field is important in the SCL of Luc2+. In this work, the evidence of O2 •- production is examined by a spectrofluorometric method using 2-(2-pyridyl)benzothiazoline as the fluorescent probe. The results indicate that the yield of O2 •- is markedly increased in the O2-saturated solutions when a small amount of 2-propanol coexists, which is consistent with the results of SCL measurements. 2-Propanol in the interfacial region of a cavitation bubble reacts with a hydroxyl radical (•OH) to form a 2-propanol radical, CH3C•(OH)CH3, which can subsequently react with dissolved oxygen to generate O2 •-. The most likely pathways for SCL as well as the spatial distribution of SCL in a microreactor are discussed in this study.

  11. SK-N-MC cell death occurs by distinct molecular mechanisms in response to hydrogen peroxide and superoxide anions: involvements of JAK2-STAT3, JNK, and p38 MAP kinases pathways.

    Science.gov (United States)

    Moslehi, Maryam; Yazdanparast, Razieh

    2013-07-01

    Oxidative stress plays a vital role in the pathogenesis of neurodegenerative diseases. Nerve cells are incessantly exposed to environmental stresses leading to overproduction of some harmful species like reactive oxygen species (ROS). ROS including hydrogen peroxide and superoxide anion are potent inducers of various signaling pathways encompassing MAPKs and JAK-STAT pathways. In the current study, we scrutinized the effects of hydrogen peroxide and/or menadione (superoxide anion generator) on JNK/p38-MAPKs and JAK2-STAT3 pathways to elucidate the mechanism(s) by which each oxidant modulated the above-mentioned pathways leading to SK-N-MC cell death. Our results delineated that hydrogen peroxide and superoxide anion radical induced distinct responses as we showed that STAT3 and p38 were activated in response to hydrogen peroxide, but not superoxide anion radicals indicating the specificity in ROS-induced signaling pathways activations and behaviors. We also observed that menadione induced JNK-dependent p53 expression and apoptotic death in SK-N-MC cells while H2O2-induced JNK activation was p53 independent. Thus, we declare that ROS type has a key role in selective instigation of JNK/p38-MAPKs and JAK2-STAT3 pathways in SK-N-MC cells. Identifying these differential behaviors and mechanisms of hydrogen peroxide and superoxide anion functions illuminates the possible therapeutic targets in the prevention or treatment of ROS-induced neurodegenerative diseases such as Alzheimer's disease.

  12. New TiO2/DSAT Immobilization System for Photodegradation of Anionic and Cationic Dyes

    Directory of Open Access Journals (Sweden)

    Wan Izhan Nawawi Wan Ismail

    2015-01-01

    Full Text Available A new immobilized TiO2 technique was prepared by coating TiO2 solution onto double-sided adhesive tape (DSAT as a thin layer binder without adding any organic additives. Glass plate was used as support material to immobilized TiO2/DSAT. Two different charges of dyes were applied, namely, anionic reactive red 4 (RR4 and cationic methylene blue (MB dyes. Photocatalytic degradation of RR4 and MB dyes was observed under immobilized TiO2/DSAT with the degradation rate slightly lower and higher, respectively, compared with TiO2 in suspension mode. It was observed that DSAT is able to provide a very strong intact between glass and TiO2 layers thus making the reusability of immobilized TiO2/DSAT be up to 30 cycles. In fact, a better photodegradation activity was observed by number of cycles due to increasing formation of pores on TiO2 surface observed by SEM analysis.

  13. Proton transfer from 1,4-pentadiene to superoxide radical anion: a QTAIM analysis

    Directory of Open Access Journals (Sweden)

    Angela Rodríguez-Serrano

    2014-04-01

    Full Text Available We studied the bis-allylic proton transferreaction from 1,4-pentadiene to superoxideradical anion (O2·־. Minima andtransition state geometries, as well asthermochemical parameters were computedat the B3LYP/6-311+G(3df,2plevel of theory. The electronic wavefunctions of reactants, intermediates,and products were analyzed within theframework of the Quantum Theory ofAtoms in Molecules. The results showthe formation of strongly hydrogen bondedcomplexes between the 1,4-pentadien-3-yl anion and the hydroperoxylradical as the reaction products. Theseproduct complexes (PCs are more stablethan the isolated reactants and muchmore stable than the isolated products.This reaction occurs via pre-reactivecomplexes which are more stable thanthe PCs and the transition states. This isin agreement with the fact that the netproton transfer reaction that leads to freeproducts is an endothermic and nonspontaneousprocess.

  14. Triterpenoids and Steroids from Ganoderma mastoporum and Their Inhibitory Effects on Superoxide Anion Generation and Elastase Release

    Directory of Open Access Journals (Sweden)

    Tran Dinh Thang

    2013-11-01

    Full Text Available The methanol extracts of the fruiting bodies of Ganoderma mastoporum collected in Vietnam was purified to afford eight compounds, including three triterpenoids and five steroids. The purified compounds were examined for their inhibitory effects against superoxide anion generation and elastase release. Among the tested compounds, ergosta-4,6,8(14,22-tetraen-3-one (3 exhibited the most significant inhibition towards superoxide anion generation and elastase release with IC50 values of 2.30 ± 0.38 and 1.94 ± 0.50 µg/mL, respectively.

  15. Kinetics of sonophotocatalytic degradation of anionic dyes with Nano-TiO2.

    Science.gov (United States)

    Vinu, R; Madras, Giridhar

    2009-01-15

    The current research work focuses on the combination of photocatalytic and sonocatalytic (sonophotocatalytic) degradation of anionic dyes, viz., Orange G, Remazol Brilliant Blue R, Alizarin Red S, Methyl Blue, and Indigo Carmine, with solution combustion synthesized TiO2 (CS TiO2) and commercial Degussa P-25 TiO2 (DP-25). The rate of sonophotocatalytic degradation of all the dyes and the reduction of total organic carbon was higher compared to the individual photo- and sonocatalytic processes. The effect of dissolved gases and ultrasonic intensity on the sonophotocatalytic degradation of the dyes was evaluated. A dual-pathway network mechanism of sonophotocatalytic degradation was proposed for the first time, and the rate equations were modeled using the network reduction technique. The kinetic rate coefficients of the individual steps were evaluated for all the systems by fitting the model with experimental data.

  16. Utilization of superoxide anion by indoleamine oxygenase-catalyzed tryptophan and indoleamine oxidation.

    Science.gov (United States)

    Hayaishi, O

    1996-01-01

    The following is our current working hypothesis concerning the biological significance of IDO induction. When tissues are invaded by virus, bacteria, or parasites, leukocytes and lymphocytes will accumulate at the site and interferon will be produced by these cells in the inflammatory loci. The interferon thus produced is released and interacts with the cell surface to trigger IDO induction in the same or other types of cells. As a consequence of inflammation, superoxide anion is liberated and serves as a substrate for IDO. Although it is possible that some trytophan metabolites may activate the immune system or act as bacteriostatic agents, available evidence does not support this hypothesis. We therefore tentatively conclude that tryptophan is degraded by IDO and depleted, whereby the growth of viruses, bacteria and certain parasites is inhibited, because tryptophan is the least available and therefore most important essential amino acid for their growth.

  17. A study on scavenging effects of Chinese medicine on superoxide anion radicals by pulse radiolysis

    Energy Technology Data Exchange (ETDEWEB)

    Li Fengmei; Liu Andong; Gu Hongchun; Di Shaojie (Beijing Normal Univ., BJ (China). Inst. of Low Energy Nuclear Physics)

    A study on scavenging and dismutation effects on superoxide anion radical ([center dot]O[sub 2][sup -]) using two Chinese antiaging medicines - Salvia miltiorrhiza injection (S.M.) and Sulekang capsule (S.C.) was carried out using pulse radiolysis. The absorption spectra of [center dot] OH[sub 2][sup -] was redetermined by radiolysis of an aqueous solution of sodium format. The absorption maximum is at about 250 nm. The results suggested that S.M. and S.C. can dismutate and scavenge [center dot]O[sub 2][sup -]. The experimental scavenging rates of S.M. (150[mu]g/ml) and S.C. (250[mu]g/ml) were 89.6% and 69.5% respectively. (author).

  18. PCL assay application in superoxide anion-radical scavenging capacity of tea Camellia sinensis extracts

    Directory of Open Access Journals (Sweden)

    Anna Gramza-Michałowska

    2015-12-01

    Full Text Available Background. Plant polyphenols are known for their limiting of adverse effects on reactive oxygen species (ROS in biological systems. The photochemiluminescence (PCL assay allows to evaluate the antiradical activity of a compound in the presence of a superoxide anion-radical (O •-, which is one of the ROS directly associated with the human body. In this work, determination of the superoxide anion radical scavenging ac- tivity of different tea extracts using the PCL assay was performed. Material and methods. Investigations were conducted on different tea leaves extracts. The study included five kinds of tea leaves subjected to aqueous and ethanol extraction procedure. Catechins content was evalu- ated using HPLC. Antiradical activity of the samples was conducted with use of Photochem assay. Results. Analysis of total catechins content in tea aqueous extracts enabled them to be arranged as follows: yellow > green > white > red > black, while for ethanol extracts it was: yellow = green > white > red > black. The examined tea extracts were ranked from highest to lowest water-soluble antioxidative capacity (ACW values as follows: yellow > green > white > red > black. The results of lipid-soluble antioxidative capacity (ACL values for aqueous extracts were similar; however, were approximately 50% lower than those pre- sented as ACW. The second examined group were ethanol extracts, which ranked for ACW values: yellow > green = red = white > black, while ACL values ranked as follows: yellow > white = black = red > green. PCL assay results were correlated with total catechin content in aqueous extracts. Conclusions. Antiradical activity of different tea leaves extracts in PCL assay, showed that the highest activ- ity was found in extracts of yellow tea; the lowest, however, was identified in black tea extracts.

  19. Correlation between the circadian rhythm of melatonin, phagocytosis, and superoxide anion levels in ring dove heterophils.

    Science.gov (United States)

    Rodríguez, A B; Marchena, J M; Nogales, G; Durán, J; Barriga, C

    1999-01-01

    A functional role for melatonin is its relationship to circadian timing mechanisms. In addition, there has recently been assumed to be a functional connection between the pineal gland and the immune system in mammals and birds, with some findings showing melatonin to be a free radical scavenger and general antioxidant. The present study investigates the possible relationship between the circadian rhythm of melatonin and the ingestion capacity as well as superoxide anion levels of ring dove (Streptopelia risoria) heterophils. In birds, heterophils, with their ability to ingest and kill different antigens, play a central role in the host defence mechanism. All determinations were made during 24 hr periods at 2 hr intervals. Radioimmunoassay showed an increase of melatonin serum levels during the dark period (from 20:00 to 07:00 hr) with a maximum at 04:00 hr, and a significant decline during the hours of light with a minimum at 16:00 hr. Similarly, the phagocytic index was enhanced during the night, with the maximum at approximately 04:00 hr and the minimum at approximately 18:00 hr. The same was the case in relation to phagocytic percentage. However, the superoxide anion levels were lower during darkness (minimum at 04:00 hr) and higher during the light period (maximum at 14:00 hr). In conclusion, our findings show that one pineal-mediated effect on the immune system may be a direct action of melatonin on phagocytosis and the phagocytic biochemical process, and that this neurohormone might act as an antioxidant.

  20. Effects of Acetosalicylic Acid on Levels of Superoxide Anion and Peroxidation of Membrane Lipid in Rice Seedlings Under Nickel-Stress%乙酰水杨酸对镍胁迫下水稻幼苗中O-2水平和膜脂过氧化的影响

    Institute of Scientific and Technical Information of China (English)

    王海华; 蒋明义; 康健; 彭喜旭; 帕尼古丽

    2001-01-01

    采用室内培养及生理指标测定方法,研究了乙酰水杨酸对镍胁迫下水稻幼苗中部分生理指标的影响。结果表明, 10 μ mol· L- 1和 30 μ mol· L- 1的镍胁迫下,稻苗叶片中 SOD活性明显降低,质外体中的 NADH氧化酶活性显著上升;同时,细胞中总和质外体中产生明显加快,从而导致叶片组织中 MDA含量和质膜透性亦明显增加。同样胁迫条件下,加入 0.05% ASA, SOD活性回升,产生速率回落, MDA含量和质膜透性增加的程度亦减小,但乙酰水杨酸 (ASA)对质外体中 NADH氧化酶活性无明显影响。这些结果提示产生与积累导致的膜脂过氧化作用介导了镍对稻苗的毒害; ASA能降低产生速率,减轻膜脂过氧化损伤程度,因而缓解了镍胁迫对稻苗的毒害%Two stress concentrations of nickel tested (10,30 μ mol· L- 1) significantly decreased superoxide dismutase (SOD) activity in rice leaves, while enhanced NADH oxidase activity significantly in apoplast. Measurement of, malondialdehyde(MDA), relative electric conductivity showed that there was a significantly increase in both totalgeneration rate and that of apoplast, as well as in MDA content and the plasma membrane permeability after nickel treatment. Addition of 0.05 % acetylsalicylic (ASA) to the same nickel stress condition decreased the rate of decline in SOD activity, and that of increase in generation, MDA content and the plasma permeability observed in rice leaves treated with nickel alone. However, no changes in apoplast NADH oxidase activity were observed. The results suggested that accumulation and membrane lipid peroxidation were involved in the toxicity to rice seedlings led by nickel, and the decline in level and membrane lipid peroxidation were the reasons by which ASA mitigated the injuries induced by nickel stress in rice seedlings.

  1. Superoxide anions and hydrogen peroxide induce hepatocyte death by different mechanisms : Involvement of JNK and ERK MAP kinases

    NARCIS (Netherlands)

    Conde de la Rosa, L; Schoemaker, MH; Vrenken, TE; Buist-Homan, M; Havinga, R; Jansen, PLM; Moshage, H

    2006-01-01

    Background/Aims: In liver diseases, reactive oxygen species (ROS) are involved in cell death and liver injury, but the mechanisms are not completely elucidated. To elucidate the mechanisms of hepatocyte cell death induced by the ROS superoxide anions and hydrogen peroxide, primary cultures of hepato

  2. Parthenolide induces superoxide anion production by stimulating EGF receptor in MDA-MB-231 breast cancer cells.

    Science.gov (United States)

    D'Anneo, A; Carlisi, D; Emanuele, S; Buttitta, G; Di Fiore, R; Vento, R; Tesoriere, G; Lauricella, M

    2013-12-01

    The sesquiterpene lactone parthenolide (PN) has recently attracted considerable attention because of its anti-microbial, anti-inflammatory and anticancer effects. However, the mechanism of its cytotoxic action on tumor cells remains scarcely defined. We recently provided evidence that the effect exerted by PN in MDA-MB-231 breast cancer cells was mediated by the production of reactive oxygen species (ROS). The present study shows that PN promoted the phosphorylation of EGF receptor (phospho-EGFR) at Tyr1173, an event which was observed already at 1 h of incubation with 25 µM PN and reached a peak at 8-16 h. This effect seemed to be a consequence of ROS production, because N-acetylcysteine (NAC), a powerful ROS scavenger, prevented the increment of phospho-EGFR levels. In addition fluorescence analyses performed using dihydroethidium demonstrated that PN stimulated the production of superoxide anion already at 2-3 h of incubation and the effect further increased prolonging the time of treatment, reaching a peak at 8-16 h. Superoxide anion production was markedly hampered by apocynin, a well known NADPH oxidase (NOX) inhibitor, suggesting that the effect was dependent on NOX activity. The finding that AG1478, an EGFR kinase inhibitor, substantially blocked both EGFR phosphorylation and superoxide anion production strongly suggested that phosphorylation of EGFR can be responsible for the activation of NOX with the consequent production of superoxide anion. Therefore, EGFR phosphorylation can exert a key role in the production of superoxide anion and ROS induced by PN in MDA-MB-231 cells.

  3. 1,1-Diphenyl-2-picrylhydrazyl radical and superoxide anion scavenging activity of Rhizophora mangle (L. bark

    Directory of Open Access Journals (Sweden)

    Janet Calero Sánchez

    2010-01-01

    Full Text Available Background: Rhizophora mangle (L. produce a variety of substances that possesses pharmacological actions. Although it shown antioxidant properties in some assays, there is no available information about its effect on some free radical species. So the objective of the present research is to evaluate the DPPH radical and superoxide anion scavenging properties of R. mangle extract and its polyphenol fraction. Methods: Rhizophora mangle (L. bark aqueous extract and its major constituent, polyphenols fraction, were investigated for their antioxidant activities employing 2 in vitro assay systems: 1,1-diphenyl-2-picrylhydrazyl (DPPH and superoxide anion radicals scavenging. Results: IC 50 for DPPH radical-scavenging activity was 6.7 μg tannins/mL for extract and 7.6 μg tannins/mL for polyphenolic fraction. The extract showed better activity than its fraction (P < 0.05 in the DPPH radicals reducing power. Polyphenolic fraction exhibited better superoxide anion scavenging ability (IC 50 = 21.6 μg tannins/mL than the extract (IC 50 = 31.9 μg tannins/mL. Antioxidant activities of both samples increased with the rise of tannins concentration. The comparison of regression lines showed significant differences (P < 0.05 between extract and its polyphenolic fraction in both assays, indicating that extract was more effective in DPPH radical scavenging than its fraction at tannin concentrations below the crossing point of both lines, while that fraction was more effective than extract inhibiting the superoxide anions generation. Conclusions: R. mangle aqueous extract showed a potent antioxidant activity, achieved by the scavenging ability observed against DPPH radicals and superoxide anions. Regarding its polyphenolic composition, the antioxidant effects observed in this study are due, most probably, to the presence of polyphenolic compounds.

  4. Discovery of Multiple, Ionization-Created Anions in Gas Mixtures Containing CS2 and O2

    CERN Document Server

    Snowden-Ifft, Daniel P

    2013-01-01

    The use of negative ions in TPCs has several advantages for high-resolution rare- event detection experiments. The DRIFT experiment, for example, has taken full advantage of this technique over the past decade in a directional search for dark matter. This paper focuses on the surprising discovery of multiple species of ionization-created CS2 anions, called minority carriers, in gas mixtures containing electronegative CS2 and O2, identified by their slightly different drift velocities. Measurements of minority carriers in gas mixtures of CS2, CF4 and O2 are reported in an effort to understand the nature of these charge carriers. Regardless of the micro-physics however, this discovery offers significant practical advantages for experiments such as DRIFT, where the difference in arrival time may be used to fiducialize the original ionization event without an external start pulse.

  5. Pyrrolidine dithiocarbamate inhibits superoxide anion-induced pain and inflammation in the paw skin and spinal cord by targeting NF-κB and oxidative stress.

    Science.gov (United States)

    Pinho-Ribeiro, Felipe A; Fattori, Victor; Zarpelon, Ana C; Borghi, Sergio M; Staurengo-Ferrari, Larissa; Carvalho, Thacyana T; Alves-Filho, Jose C; Cunha, Fernando Q; Cunha, Thiago M; Casagrande, Rubia; Verri, Waldiceu A

    2016-06-01

    We evaluated the effect of pyrrolidine dithiocarbamate (PDTC) in superoxide anion-induced inflammatory pain. Male Swiss mice were treated with PDTC and stimulated with an intraplantar or intraperitoneal injection of potassium superoxide, a superoxide anion donor. Subcutaneous PDTC treatment attenuated mechanical hyperalgesia, thermal hyperalgesia, paw oedema and leukocyte recruitment (neutrophils and macrophages). Intraplantar injection of superoxide anion activated NF-κB and increased cytokine production (IL-1β, TNF-α and IL-10) and oxidative stress (nitrite and lipid peroxidation levels) at the primary inflammatory foci and in the spinal cord (L4-L6). PDTC treatment inhibited superoxide anion-induced NF-κB activation, cytokine production and oxidative stress in the paw and spinal cord. Furthermore, intrathecal administration of PDTC successfully inhibited superoxide anion-induced mechanical hyperalgesia, thermal hyperalgesia and inflammatory response in peripheral foci (paw). These results suggest that peripheral stimulus with superoxide anion activates the local and spinal cord oxidative- and NF-κB-dependent inflammatory nociceptive mechanisms. PDTC targets these events, therefore, inhibiting superoxide anion-induced inflammatory pain in mice.

  6. The effect of orexin-A on cardiac dysfunction mediated by NADPH oxidase-derived superoxide anion in ventrolateral medulla.

    Directory of Open Access Journals (Sweden)

    Jun Chen

    Full Text Available Hypocretin/orexin-producing neurons, located in the perifornical region of the lateral hypothalamus area (LHA and projecting to the brain sites of rostral ventrolateral medulla (RVLM, involve in the increase of sympathetic activity, thereby regulating cardiovascular function. The current study was designed to test the hypothesis that the central orexin-A (OXA could be involved in the cardiovascular dysfunction of acute myocardial infarction (AMI by releasing NAD(PH oxidase-derived superoxide anion (O2 (- generation in RVLM, AMI rat model established by ligating the left anterior descending (LAD coronary artery to induce manifestation of cardiac dysfunction, monitored by the indicators as heart rate (HR, heart rate variability (HRV, mean arterial pressure (MAP and left intraventricular pressure. The results showed that the expressions of OXA in LHA and orexin 1 receptor (OX1R increased in RVLM of AMI rats. The double immunofluorescent staining indicated that OX1R positive cells and NAD(PH oxidative subunit gp91phox or p47phox-immunoreactive (IR cells were co-localized in RVLM. Microinjection of OXA into the cerebral ventricle significantly increased O2 (- production and mRNA expression of NAD(PH oxidase subunits when compared with aCSF-treated ones. Exogenous OXA administration in RVLM produced pressor and tachycardiac effects. Furthermore, the antagonist of OX1R and OX2R (SB-408124 and TCS OX2 29, respectively or apocynin (APO, an inhibitor of NAD(PH oxidase, partly abolished those cardiovascular responses of OXA. HRV power spectral analysis showed that exogenous OXA led to decreased HF component of HRV and increased LF/HF ratio in comparison with aCSF, which suggested that OXA might be related to sympathovagal imbalance. As indicated by the results, OXA might participate in the central regulation of cardiovascular activities by disturbing the sympathovagal balance in AMI, which could be explained by the possibility that OXR and NAD(PH-derived O

  7. Inhibitory effects of N-acetylcysteine on superoxide anion generation in human polymorphonuclear leukocytes.

    Science.gov (United States)

    Villagrasa, V; Cortijo, J; Martí-Cabrera, M; Ortiz, J L; Berto, L; Esteras, A; Bruseghini, L; Morcillo, E J

    1997-05-01

    It has been suggested that reactive oxygen species released by activated polymorphonuclear leukocytes (PMN) in man is one mechanism of tissue injury. Therapeutic action aimed at increasing antioxidant defence mechanisms is still a clinical challenge. This study examines the activity of N-acetylcysteine, a known antioxidant, in the protection of PMN exposed in-vitro to the chemoattractant peptide fMet-Leu-Phe (FMLP), the protein kinase C activator phorbol myristate acetate or the lipid peroxidation promoter t-butyl hydroperoxide. FMLP (3-300 nM) and phorbol myristate acetate (160 pm-160 nM) induced concentration-related superoxide anion generation. Pre-treatment with N-acetylcysteine (33-333 microM) resulted in concentration-related inhibition of superoxide production induced by FMLP (30 nM) or phorbol myristate acetate (16 nM);-log IC50 values were 3.97 +/- 0.07 and 3.91 +/- 0.10, respectively. Changes in intracellular calcium ion concentration ([Ca2+]i) induced by FMLP (30 nM) were studied in fura-2-loaded human PMN. FMLP produced a transient calcium response, i.e. a peak followed by decay to a residual value above baseline. N-Acetylcysteine (333 microM) did not affect either basal [Ca2+]i values or changes in [Ca2+]i values after treatment with FMLP. Activation by phorbol myristate acetate caused a reduction in glutathione levels from 5.94 +/- 0.86 (control) to 1.84 +/- 0.51 nmol/3 x 10(6) cells (P 0.05 compared with control). Exposure to t-butyl hydroperoxide (0.5 mM, 30 min) markedly increased malondialdehyde levels (from 0.03 +/- 0.02 to 0.73 +/- 0.07 nmol/10(6) cells), and index of lipid peroxidation. Malondialdehyde levels were significantly reduced in PMN treated with N-acetylcysteine (333 microM; 0.55 +/- 0.04 nmol/10(6) cells; P < 0.05 compared with untreated cells exposed to t-butyl hydroperoxide). In conclusion, N-acetylcysteine reduces superoxide generation in response to FMLP and phorbol myristate acetate and partially protects against lipid

  8. Ferrous Ion Chelating, Superoxide Anion Radical Scavenging and Tyrosinase Inhibitory Properties of Pure and Commercial Essential Oils of Anetrhum Graveolens

    Directory of Open Access Journals (Sweden)

    Sh Darvish Alipour Astaneh

    2013-04-01

    Full Text Available Introduction: Despite slight toxicities of essential oils, they are not under strict control in many countries. Anethum graveolens is widely consumed and its essential oils are at public reach. This study was designed to study essential oils of Anethum graveolens. Methods: The biological properties of pure and commercial essential oils of Anethum graveolens were investigated. In fact, Ferrous ion chelating activity, superoxide anion radical scavenging property, tyrosinase inhibition and total flavonoids of the oils were determined. Results: Chelating activity of 7.8 µg of EDTA was equivalent to 2 µg of the pure oil. The oils had superoxide anion radical scavenging activities which may be related to their total phenol and flavonoid contents. IC50 of ferrous ion chelating, antityrosiase and superoxide anion radical scavenging activities of pure and commercial oils were 1.3, 1.4, 1 and (171.6, 589, 132 µg respectively. Antityrosiase activity of 6.4 µg pure oil was equal to 1000 µg of the commercial oil. Conclusion: Anethum possesses antioxidative and free radical scavenging properties. This oil chelates ferrous ions and superoxide radicals. It is effective in formation of reactive toxic products. Anethum has good potentials regarding its applications in food and drug industries.

  9. [Production of superoxide anion radical and nitric oxide in renal tissues sutured with different surgical suture material].

    Science.gov (United States)

    Kostenko, V O; Tsebrzhins'kii, O I

    2000-01-01

    The generation of superoxide anion radicals (in mitochondria, microsomes and under respiratory burst of leucocytes) and nitric oxide (NO) in renal tissue has been studied in the experiment with white rats, which had been carried out nephrotomy with following usage for suture such absorbable surgical threads as plain and chromic catgut, biofil (of dura mater spinalis of the cattle), Dexon II (polyglycolic acid) and biofil modified with aethonium, succinate and mexidol. The research proves the use of plai and chromic catgut leads to the development longer oxidative stress with increasing of cytotoxic agents production (superoxide anion and NO). The risk of longitudinal oxidative stress decreases under the use of biofil suture modified with biological active compounds (aethonium, succinate and mexidol). In this case, the generation of superoxide anion radicals in mitochondria and microsomes is normalised earlier. The superoxide generation with respiratory burst of leucocytes and NO production decreases in 14 day of postoperative period under the use of biofil suture modified with succinate and mexidol.

  10. Pyrroloquinoline quinone from Gluconobacter oxydans fermentation broth enhances superoxide anion-scavenging capacity of Cu/Zn-SOD.

    Science.gov (United States)

    Ma, Ke; Cui, Jun-Zhu; Ye, Jian-Bin; Hu, Xian-Mei; Ma, Ge-Li; Yang, Xue-Peng

    2017-09-01

    A bioassay-guided fractionation of extract from Gluconobacter oxydans fermentation broth afforded Compound 1, which was identified as pyrroloquinoline quinone (PQQ) by spectroscopic methods. PQQ has been shown to enhance the superoxide anion-scavenging capacity significantly for Cu/Zn-SOD. To illustrate the mechanism, the interaction between PQQ and Cu/Zn-SOD was investigated. The multiple binding sites involving hydrogen bonds and van der Waals force between PQQ and Cu/Zn-SOD were revealed by isothermal titration calorimetry. The α-helix content was increased in the Cu/Zn-SOD structure with the addition of PQQ into the solution through ultraviolet (UV) spectroscopy. These results indicated that PQQ could change the conformation of Cu/Zn-SOD through interaction, which could enhance its superoxide anion-scavenging capacity. Therefore, PQQ is a potential natural antioxidant. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. Modifications in nitric oxide and superoxide anion metabolism induced by fructose overload in rat heart are prevented by (-)-epicatechin.

    Science.gov (United States)

    Calabró, Valeria; Piotrkowski, Barbara; Fischerman, Laura; Vazquez Prieto, Marcela A; Galleano, Monica; Fraga, Cesar G

    2016-04-01

    Fructose overload promotes functional and metabolic derangements in humans and in animal experimental models. Evidence suggests that dietary flavonoids have the ability to prevent/attenuate the development of metabolic diseases. In this work we investigated the effects of (-)-epicatechin on the modifications induced by fructose overload in the rat heart in terms of nitric oxide and superoxide metabolism. Male Sprague Dawley rats received 10% (w/v) fructose in the drinking water for 8 weeks, with or without (-)-epicatechin (20 mg per kg body weight per day) in the rat chow diet. These conditions of fructose overload did not lead to overt manifestations of heart hypertrophy or tissue remodeling. However, biochemical and molecular changes were observed and could represent the onset of functional alterations. (-)-Epicatechin prevented a compromised NO bioavailability and the development of oxidative stress produced by fructose overload essentially acting on superoxide anion metabolism. In this line, the increase in superoxide anion production, the overexpression of NOX2 subunit p47phox and of NOX4, the decrease in superoxide dismutase activity, and the higher oxidized/reduced glutathione ratio installed by fructose overload were absent in the rats receiving (-)-epicatechin. These results support the hypothesis that diets rich in (-)-epicatechin could prevent the onset and progression of heart dysfunctions associated with metabolic alterations.

  12. Superoxide anion production and expression of gp91(phox) and p47(phox) are increased in glomeruli and proximal tubules of cisplatin-treated rats.

    Science.gov (United States)

    Trujillo, Joyce; Molina-Jijón, Eduardo; Medina-Campos, Omar Noel; Rodríguez-Muñoz, Rafael; Reyes, José Luis; Barrera, Diana; Pedraza-Chaverri, José

    2015-04-01

    The chemotherapeutic drug cisplatin has some side effects including nephrotoxicity that has been associated with reactive oxygen species production, particularly superoxide anion. The major source of superoxide anion is nicotinamide adenine dinucleotide phosphate hydrogen (NADPH) oxidase. However, the specific segment of the nephron in which superoxide anion is produced has not been identified. Rats were sacrificed 72 h after cisplatin injection (7.5 mg/kg), and kidneys were obtained to isolate glomeruli and proximal and distal tubules. Cisplatin induced superoxide anion production in glomeruli and proximal tubules but not in distal tubules. This enhanced superoxide anion production was prevented by diphenylene iodonium, an inhibitor of NADPH oxidase. Consistently, this effect was associated with the increased expression of gp91(phox) and p47(phox), subunits of NADPH oxidase. The enhanced superoxide anion production in glomeruli and proximal tubules, associated with the increased expression of gp91(phox) and p47(phox), is involved in the oxidative stress in cisplatin-induced nephrotoxicity.

  13. Traditional Chinese medicine formula Qing Huo Yi Hao as superoxide anion scavenger in high glucosetreated endothelial cells

    Institute of Scientific and Technical Information of China (English)

    Qiong xu; Bin ZHANG; Xiao-mu LI; Xin GAO

    2012-01-01

    Aim:To investigate the effects of a traditional Chinese medicine formula Qing Huo Yi Hao (QHYH)and its components on hydroxyl radical (HO·)production in vitro and the activity of QHYH against free radicals in cultured endothelial cells induced by high glucose.Methods:Hydroxyl radicals (HO·)were generated through Fenton reactions in vitro,and 5,5-dimethyl-1-pyrroline N-oxide (DMPO)was used as a spin trap to form DMPO/HO·adducts detected using electron paramagnetic resonance (EPR).Immortalized mouse cerebral microvascular endothelial (bEnd.3)cells were treated with high glucose (35 mmol/L).The free radical scavenging ability of QHYH in the cells was evaluated using EPR.Superoxide dismutase (SOD)was used to identify the free radicals scavenged by QHYH in the cells.Results:QHYH and its 8 components concentration-dependently reduced DMPO/HO· signaling.The DMPO/HO· adduct scavenging ability of QHYH was 82.2%,which was higher than each individual component.The free radical scavenging ability of 1% QHYH in high glucose-treated bEnd.3 cells was approximately 70%.In these cells,the free radicals were also specifically reduced by SOD (400 U/mL),implying that the free radicals were primarily superoxide anions.Conclusion:The results demonstrate that the QHYH formula is potent antioxidant acting as scavenge of superoxide anions in high glucose-treated endothelial cells.

  14. The formation and stability of the superoxide radical (O2-) on rock-forming minerals: Band gaps, hydroxylation state, and implications for Mars oxidant chemistry

    Science.gov (United States)

    Zent, Aaron P.; Ichimura, Andrew S.; Quinn, Richard C.; Harding, Heather K.

    2008-09-01

    We have examined the generation and stability of O2 - on TiO2 and albite, a common Na feldspar. We were not able to produce thermally stable superoxide on albite, in contrast to the results of Yen et al., who reported the generation of O2 - that was stable up to 200°C on labradorite, another common feldspar. The superoxide radical did form under UV irradiation at 77 K on albite that was not dehydrated but decayed rapidly at room temperature. On dehydrated albite, no superoxide signal was observed. We studied the kinetics of O2 - decomposition on hydrated albite and derived an activation energy, E a = 15.2 kJ/mol. Assuming pseudo first-order kinetics, a simple thermal model of Mars' regolith demonstrates that the surface O2 - population does not go to zero overnight; superoxide extinction at the surface is only complete when the seasonal CO2 cap covers the surface and surface photolysis is inhibited. Depending on the specific quantum efficiency of the e-/h+ generation process, a finite, non-equilibrium population of O2 - should be observable on Martian surface materials throughout the Martian year. However, on the basis of our inability to generate stable O2 - on hydrated albite via direct UV irradiation, we do not believe that this mechanism is capable of explaining the O2 release in the Viking Gas Exchange (GEx) results, since O2 release in that case was observed even after samples had been stored for 143 sols in the dark at 10°C, then heated to 145°C for 3 hours. At least two other potential pathways to the generation of O2 - are identified in this article. The first possibility is that metal oxides common on the Martian surface, particularly hematite, may be photoactive on Mars and play a role analogous to TiO2 in surface catalysis. Secondly, we found that superoxide that formed during the sorption or drying of a 1% H2O2 solution on TiO2, and potentially other oxides seems to be stable indefinitely.

  15. Propylparaben-induced disruption of energy metabolism in human HepG2 cell line leads to increased synthesis of superoxide anions and apoptosis.

    Science.gov (United States)

    Szeląg, S; Zabłocka, A; Trzeciak, K; Drozd, A; Baranowska-Bosiacka, I; Kolasa, A; Goschorska, M; Chlubek, D; Gutowska, I

    2016-03-01

    The effect of propylparaben (in final concentrations 0.4 ng/ml, 2.3 ng/ml and 4.6 ng/ml) on the energy metabolism of HepG2 hepatocytes, superoxide anion synthesis, apoptosis and necrosis is described. Propylparaben can be toxic to liver cells due to the increased production of superoxide anions, which can contribute to a reduced concentration of superoxide dismutase in vivo and impairment of the body's antioxidant mechanisms. Finally, a further reduction in the mitochondrial membrane potential and uncoupling of the respiratory chain resulting in a reduction in ATP concentration as a result of mitochondrial damage may lead to cell death by apoptosis.

  16. The geometry of the chlorine dioxide anion ClO2-: Ab initio calculation and Franck-Condon analysis

    Science.gov (United States)

    Zheng, Haiyan; Zhang, Xiaowei; Li, Renzhong; Liang, Jun; Cui, Zhifeng

    2007-11-01

    Geometry optimization and harmonic vibrational frequency calculations were performed on the XB state of ClO 2 and XA state of ClO2-. The electron affinity energies of ClO 2 were calculated up to CCSD(T) level. Franck-Condon analyses and spectral simulations were carried out on the ClO(XB)-ClO2-(XA) photodetachment process. In addition, the equilibrium geometry parameters, r(ClO) = 1.567 ± 0.002 Å and ∠(OClO) = 116.5 ± 0.5°, of the XA state of ClO2-, were derived in the spectral simulation. Our conclusions regarding the anion geometry suggest a reinterpretation of the results of Gilles et al. [M.K. Gilles, M.L. Polak, W.C. Lineberger, J. Chem. Phys. 96 (1992) 8012].

  17. Effects of PDE4 inhibitors on lipopolysaccharide-induced priming of superoxide anion production from human mononuclear cells

    Directory of Open Access Journals (Sweden)

    Noëlla Germain

    2001-01-01

    Full Text Available Aims: Phosphodiesterase 4 (PDE4 inhibitors have been described as potent anti-inflammatory compounds, involving an increase in intracellular levels of cyclic 3',5'-adenosine monophosphate (AMP. The aim of this study was to compare the effects of selective PDE4 inhibitors, rolipram and RP 73-401 with the cell permeable analogue of cyclic AMP, dibutyryl-cyclic AMP (db-cAMP and the anti-inflammatory cytokine interleukin-10 (IL-10 on superoxide anion production from peripheral blood mononuclear cells preincubated with lipopolysaccharide (LPS.

  18. Poly(vinylidene fluoride) (PVDF) Binder Degradation in Li-O2 Batteries: A Consideration for the Characterization of Lithium Superoxide.

    Science.gov (United States)

    Papp, Joseph K; Forster, Jason D; Burke, Colin M; Kim, Hyo Won; Luntz, Alan C; Shelby, Robert M; Urban, Jeffrey J; McCloskey, Bryan D

    2017-02-27

    We show that a common Li-O2 battery cathode binder, poly(vinylidene fluoride) (PVDF), degrades in the presence of reduced oxygen species during Li-O2 discharge when adventitious impurities are present. This degradation process forms products that exhibit Raman shifts (∼1133 and 1525 cm(-1)) nearly identical to those reported to belong to lithium superoxide (LiO2), complicating the identification of LiO2 in Li-O2 batteries. We show that these peaks are not observed when characterizing extracted discharged cathodes that employ poly(tetrafluoroethylene) (PTFE) as a binder, even when used to bind iridium-decorated reduced graphene oxide (Ir-rGO)-based cathodes similar to those that reportedly stabilize bulk LiO2 formation. We confirm that for all extracted discharged cathodes on which the 1133 and 1525 cm(-1) Raman shifts are observed, only a 2.0 e(-)/O2 process is identified during the discharge, and lithium peroxide (Li2O2) is predominantly formed (along with typical parasitic side product formation). Our results strongly suggest that bulk, stable LiO2 formation via the 1 e(-)/O2 process is not an active discharge reaction in Li-O2 batteries.

  19. Superoxide anions produced by Streptococcus pyogenes group A-stimulated keratinocytes are responsible for cellular necrosis and bacterial growth inhibition.

    Science.gov (United States)

    Regnier, Elodie; Grange, Philippe A; Ollagnier, Guillaume; Crickx, Etienne; Elie, Laetitia; Chouzenoux, Sandrine; Weill, Bernard; Plainvert, Céline; Poyart, Claire; Batteux, Frédéric; Dupin, Nicolas

    2016-02-01

    Gram-positive Streptococcus pyogenes (group A Streptococcus or GAS) is a major skin pathogen and interacts with keratinocytes in cutaneous tissues. GAS can cause diverse suppurative and inflammatory infections, such as cellulitis, a common acute bacterial dermo-hypodermitis with a high morbidity. Bacterial isolation yields from the lesions are low despite the strong local inflammation observed, raising numerous questions about the pathogenesis of the infection. Using an in vitro model of GAS-infected keratinocytes, we show that the major ROS produced is the superoxide anion ([Formula: see text]), and that its production is time- and dose-dependent. Using specific modulators of ROS production, we show that [Formula: see text] is mainly synthesized by the cytoplasmic NADPH oxidase. Superoxide anion production leads to keratinocyte necrosis but incomplete inhibition of GAS growth, suggesting that GAS may be partially resistant to the oxidative burst. In conclusion, GAS-stimulated keratinocytes are able to develop an innate immune response based on the production of ROS. This local immune response limits GAS development and induces keratinocyte cell death, resulting in the skin lesions observed in patients with cellulitis.

  20. TiO2 photocatalysis of naproxen: effect of the water matrix, anions and diclofenac on degradation rates.

    Science.gov (United States)

    Kanakaraju, Devagi; Motti, Cherie A; Glass, Beverley D; Oelgemöller, Michael

    2015-11-01

    The TiO2 photocatalytic degradation of the active pharmaceutical ingredient (API) naproxen (NPX) has been studied using a laboratory-scale photoreactor equipped with a medium pressure mercury lamp. UV/TiO2 photocatalysis proved highly efficient in the elimination of NPX from a variety of water matrices, including distilled water, unfiltered river water and drinking water, although the rate of reaction was not always proportional to TiO2 concentration. However, the NPX degradation rate, which follows first-order kinetics, was appreciably reduced in river water spiked with phosphate and chloride ions, a dual anion system. Addition of chloride into drinking water enhanced the TiO2-photocatalysed degradation rate. Competitive degradation studies also revealed that the NPX degradation was greatly reduced in the presence of increased concentrations of another API, diclofenac (DCF). This was established by (i) the extent of mineralization, as determined by dissolved organic carbon (DOC) content, and (ii) the formation of intermediate NPX by-products, identified using liquid chromatography and electrospray ionization (positive and negative mode) mass spectrometry techniques. This study demonstrates that competition for active sites (anions or DCF) and formation of multiple photoproducts resulting from synergistic interactions (between both APIs) are key to the TiO2-photocatalysed NPX degradation.

  1. The Protective Effects of N-Acetylcysteine on Exogenous Hydrogen Peroxide and Endogenous Superoxide Anion induced DNA Strand Breakage in Human Spermatozoa%`

    Institute of Scientific and Technical Information of China (English)

    徐德祥; 沈汉民; 王俊南

    2001-01-01

    Objective To explore the protective effects of N-Acetylcysteine (NAC) on exogenous hydrogen peroxide and endogenous superoxide anion-induced DNA strand breakage in human spermatozoa by using the single-cell gel electropherosis (SCGE)Methods Sperm cells were exposed to 0. 5 mmol/L of H2O2 or 5. 0 mmol/L of β -NADPH with or without 0. 1, 0. 5, 1. 0 mmol/L of NAC. The percentage of sperm comet cells and the comet tail lengths were measured in the treated sperm cells by using SCGE.Results Both percentage of comet sperm nuclei and mean tail length in sperm cells exposed to 0. 5 mmol/L hydrogen peroxide with different concentrations of NAC decrease significantly in a dose-dependent manner as compared with sperm cells exposed to H2O2 without NAC or catalase. Although mean tail length in sperm cells exposed to 5. 0 mmol/L of β-NADPH with different concentrations of NAC decreases significantly compared with sperm cells exposed to β-NADPH without NAC or SOD,there were no significant differences on the percentage of sperm comet cells between sperm cells exposed to 5. 0 mmol/L of β-NADPH with different concentrations of NAC and sperm cells exposed to 5. 0 mmol/L of β-NADPH without NAC.Conclusion NAC has a protective effect on exogenous hydrogen peroxide-induced DNA damage, while protective effect of NAC against O2- induced DNA strand break age is significant but very weak.

  2. Identifying the sources and sinks of CDOM/FDOM across the Mauritanian Shelf and their potential rolein the decomposition of Superoxide (O2-

    Directory of Open Access Journals (Sweden)

    Maija Iris Heller

    2016-08-01

    Full Text Available Superoxide (O2- is a short lived reactive oxygen species (ROS formed in seawater by photochemical or biological sources, it is important in the redox cycling of trace elements and organic matter in the ocean. The photoproduction of O2- is now thought to involve reactions between O2 and reactive reducing (radical intermediates formed from dissolved organic matter (DOM via intramolecular reactions between excited singlet state donors and ground-state acceptors (Zhang et al., 2012. In seawater the main pathways identified for the decomposition of O2- into H2O2 and O2, involve reactions with Cu, Mn and DOM. In productive regions of the ocean, the reaction between DOM and O2- can be a significant sink for O2-. Thus DOM is a key component of both the formation and decomposition of O2- and formation of H2O2. In the present work we examined the relationships between O2- decay rates and parameters associated with chromophoric dissolved organic matter (CDOM and fluorescent dissolved organic matter (FDOM by using the thermal O2- source SOTS-1. Filtered samples (0.2 µm were run both in the presence, and absence, of the metal chelator diethylenetriaminepentaacetic acid (DTPA to determine the contribution from DOM. Samples were collected along a transect across the continental shelf of the Mauritanian continental shelf during a period of upwelling. In this region we found that reactions with DOM, are a significant sink for O2- in the Mauritanian Upwelling, constituting on average 58 ± 13 % of the O2- loss rates. Superoxide reactivity with organic matter showed no clear correlation with bulk CDOM or FDOM properties (as assessed by PARAFAC analysis suggesting that future work should concentrate at the functional group level to clearly elucidate which molecular species are involved as bulk properties represent a wide spread of chemical moieties with different O2- reactivities. Analysis of FDOM parameters indicates that many of the markers used previously for

  3. Vascular nitric oxide and superoxide anion contribute to sex-specific programmed cardiovascular physiology in mice.

    Science.gov (United States)

    Roghair, Robert D; Segar, Jeffrey L; Volk, Kenneth A; Chapleau, Mark W; Dallas, Lindsay M; Sorenson, Anna R; Scholz, Thomas D; Lamb, Fred S

    2009-03-01

    Intrauterine environmental pertubations have been linked to the development of adult hypertension. We sought to evaluate the interrelated roles of sex, nitric oxide, and reactive oxygen species (ROS) in programmed cardiovascular disease. Programming was induced in mice by maternal dietary intervention (DI; partial substitution of protein with carbohydrates and fat) or carbenoxolone administration (CX, to increase fetal glucocorticoid exposure). Adult blood pressure and locomotor activity were recorded by radiotelemetry at baseline, after a week of high salt, and after a week of high salt plus nitric oxide synthase inhibition (by l-NAME). In male offspring, DI or CX programmed an elevation in blood pressure that was exacerbated by N(omega)-nitro-l-arginine methyl ester administration, but not high salt alone. Mesenteric resistance vessels from DI male offspring displayed impaired vasorelaxation to ACh and nitroprusside, which was blocked by catalase and superoxide dismutase. CX-exposed females were normotensive, while DI females had nitric oxide synthase-dependent hypotension and enhanced mesenteric dilation. Despite the disparate cardiovascular phenotypes, both male and female DI offspring displayed increases in locomotor activity and aortic superoxide production. Despite dissimilar blood pressures, DI and CX-exposed females had reductions in cardiac baroreflex sensitivity. In conclusion, both maternal malnutrition and fetal glucocorticoid exposure program increases in arterial pressure in male but not female offspring. While maternal DI increased both superoxide-mediated vasoconstriction and nitric oxide mediated vasodilation, the balance of these factors favored the development of hypertension in males and hypotension in females.

  4. Enhancing electrochemical intermediate solvation through electrolyte anion selection to increase nonaqueous Li-O$_2$ battery capacity

    CERN Document Server

    Burke, Colin M; Khetan, Abhishek; Viswanathan, Venkatasubramanian; McCloskey, Bryan D

    2015-01-01

    Among the 'beyond Li-ion' battery chemistries, nonaqueous Li-O$_2$ batteries have the highest theoretical specific energy and as a result have attracted significant research attention over the past decade. A critical scientific challenge facing nonaqueous Li-O$_2$ batteries is the electronically insulating nature of the primary discharge product, lithium peroxide, which passivates the battery cathode as it is formed, leading to low ultimate cell capacities. Recently, strategies to enhance solubility to circumvent this issue have been reported, but rely upon electrolyte formulations that further decrease the overall electrochemical stability of the system, thereby deleteriously affecting battery rechargeability. In this study, we report that a significant enhancement (greater than four-fold) in Li-O$_2$ cell capacity is possible by appropriately selecting the salt anion in the electrolyte solution. Using $^7$Li nuclear magnetic resonance and modeling, we confirm that this improvement is a result of enhanced Li...

  5. Depression of alveolar macrophage hydrogen peroxide and superoxide anion release by mineral dusts: correlation with antimony, lead, and arsenic contents.

    Science.gov (United States)

    Gulyas, H; Labedzka, M; Gercken, G

    1990-04-01

    Activated rabbit alveolar macrophages were incubated with airborne dusts from four West German sites (1 to 200 micrograms/10(6) cells) and waste incinerator fly ash fractions (50 to 500 micrograms/10(6) cells). Quartz dust DQ 12 (5 to 200 micrograms/10(6) cells) and Fe2O3 (0.05 to 50 micrograms/10(6) cells) were used as control dusts. The zymosan-stimulated hydrogen peroxide and superoxide anion release of the macrophages were not affected significantly by Fe2O3. All other investigated dusts decreased the two cell functions which were correlated negatively with surfaces, particle numbers, and antimony, lead, and arsenic contents of the dusts. The influence of heavy metal antagonisms and dust surfaces on dust toxicity against alveolar macrophages is discussed.

  6. Peroxynitrite mediates active site tyrosine nitration in manganese superoxide dismutase. Evidence of a role for the carbonate radical anion.

    Science.gov (United States)

    Surmeli, N Basak; Litterman, Nadia K; Miller, Anne-Frances; Groves, John T

    2010-12-08

    carbonate radical anion (•CO3(-)) in MnSOD nitration by PN. We also observed that the nitration of Tyr34 caused inactivation of the enzyme, while nitration of Tyr9 and Tyr11 did not interfere with the superoxide dismutase activity. The loss of MnSOD activity upon Tyr34 nitration implies that the responsible reagent in vivo is peroxynitrite, acting either directly or through the action of •CO3(-).

  7. A novel amperometric biosensor for superoxide anion based on superoxide dismutase immobilized on gold nanoparticle-chitosan-ionic liquid biocomposite film

    Energy Technology Data Exchange (ETDEWEB)

    Wang Lu; Wen Wei; Xiong Huayu; Zhang Xiuhua; Gu Haoshuang [Ministry of Education Key Laboratory for the Synthesis and Application of Organic Functional Molecules and College of Chemistry and Chemical Engineering, Hubei University, Wuhan 430062 (China); Wang Shengfu, E-mail: wangsf@hubu.edu.cn [Ministry of Education Key Laboratory for the Synthesis and Application of Organic Functional Molecules and College of Chemistry and Chemical Engineering, Hubei University, Wuhan 430062 (China)

    2013-01-03

    Graphical abstract: Schematic representation of the assembly process of SOD/GNPs-CS-IL/GCE. Highlights: Black-Right-Pointing-Pointer SOD was immobilized in gold nanoparticles-chitosan-ionic liquid (GNPs-CS-IL) film. Black-Right-Pointing-Pointer The biosensor was constructed by one-step ultrasonic electrodeposition of GNPs-CS-IL onto GCE. Black-Right-Pointing-Pointer The biosensor showed excellent analytical performance for O{sub 2}{center_dot}{sup -} real-time analysis. - Abstract: A novel superoxide anion (O{sub 2}{center_dot}{sup -}) biosensor is proposed based on the immobilization of copper-zinc superoxide dismutase (SOD) in a gold nanoparticle-chitosan-ionic liquid (GNPs-CS-IL) biocomposite film. The SOD-based biosensor was constructed by one-step ultrasonic electrodeposition of GNP-CS-IL composite onto glassy carbon electrode (GCE), followed by immobilization of SOD on the modified electrode. Surface morphologies of a set of representative films were characterized by scanning electron microscopy. The electrochemical performance of the biosensor was evaluated by cyclic voltammetry and chronoamperometry. A pair of quasi-reversible redox peaks of SOD with a formal potential of 0.257 V was observed at SOD/GNPs-CS-IL/GCE in phosphate buffer solution (PBS, 0.1 M, pH 7.0). The effects of varying test conditions on the electrochemical behavior of the biosensor were investigated. Furthermore, several electrochemical parameters were calculated in detail. Based on the biomolecule recognition of the specific reactivity of SOD toward O{sub 2}{center_dot}{sup -}, the developed biosensor exhibited a fast amperometric response (<5 s), wide linear range (5.6-2.7 Multiplication-Sign 10{sup 3} nM), low detection limit (1.7 nM), and excellent selectivity for the real-time measurement of O{sub 2}{center_dot}{sup -}. The proposed method is promising for estimating quantitatively the dynamic changes of O{sub 2}{center_dot}{sup -} in biological systems.

  8. Viral infection correlated with superoxide anion radicals production and natural and synthetic copper complexes.

    Science.gov (United States)

    Tomas, E; Popescu, A; Titire, A; Cajal, N; Cristescu, C; Tomas, S

    1989-01-01

    Studies conducted on asymmetric triazine derivatives synthetized at the Chemical and Pharmaceutical Research Institute showed that products S1, S16, S17, S19, S20 and S22 have a remarkable O2- radical scavenger activity. Among these derivatives, the product S1 is the most efficient as an antiviral agent.

  9. Vibrio vulnificus MO6-24/O Lipopolysaccharide Stimulates Superoxide Anion, Thromboxane B2, Matrix Metalloproteinase-9, Cytokine and Chemokine Release by Rat Brain Microglia in Vitro

    Directory of Open Access Journals (Sweden)

    Alejandro M. S. Mayer

    2014-03-01

    Full Text Available Although human exposure to Gram-negative Vibrio vulnificus (V. vulnificus lipopolysaccharide (LPS has been reported to result in septic shock, its impact on the central nervous system’s innate immunity remains undetermined. The purpose of this study was to determine whether V. vulnificus MO6-24/O LPS might activate rat microglia in vitro and stimulate the release of superoxide anion (O2−, a reactive oxygen species known to cause oxidative stress and neuronal injury in vivo. Brain microglia were isolated from neonatal rats, and then treated with either V. vulnificus MO6-24/O LPS or Escherichia coli O26:B6 LPS for 17 hours in vitro. O2− was determined by cytochrome C reduction, and matrix metalloproteinase-2 (MMP-2 and MMP-9 by gelatinase zymography. Generation of cytokines tumor necrosis factor alpha (TNF-α, interleukin-1 alpha (IL-1α, IL-6, and transforming growth factor-beta 1 (TGF-β1, chemokines macrophage inflammatory protein (MIP-1α/chemokine (C-C motif ligand 3 (CCL3, MIP-2/chemokine (C-X-C motif ligand 2 (CXCL2, monocyte chemotactic protein-1 (MCP-1/CCL2, and cytokine-induced neutrophil chemoattractant-2alpha/beta (CINC-2α/β/CXCL3, and brain-derived neurotrophic factor (BDNF, were determined by specific immunoassays. Priming of rat microglia by V. vulnificus MO6-24/O LPS in vitro yielded a bell-shaped dose-response curve for PMA (phorbol 12-myristate 13-acetate-stimulated O2− generation: (1 0.1–1 ng/mL V. vulnificus LPS enhanced O2− generation significantly but with limited inflammatory mediator generation; (2 10–100 ng/mL V. vulnificus LPS maximized O2− generation with concomitant release of thromboxane B2 (TXB2, matrix metalloproteinase-9 (MMP-9, and several cytokines and chemokines; (3 1000–100,000 ng/mL V. vulnificus LPS, with the exception of TXB2, yielded both attenuated O2− production, and a progressive decrease in MMP-9, cytokines and chemokines investigated. Thus concentration-dependent treatment of

  10. Sono- and photocatalytic activities of SnO2 nanoparticles for degradation of cationic and anionic dyes

    Science.gov (United States)

    Paramarta, Valentinus; Taufik, Ardiansyah; Munisa, Lusitra; Saleh, Rosari

    2017-01-01

    The current research work focuses on the catalytic activity of SnO2 nanoparticles (NPs) against degradation of both cationic dye (methylene blue) and anionic dye (Congo-red). SnO2 NPs were synthesized under the sol-gel method and were characterized by performing X-ray diffraction, Fourier Transform Infrared Spectroscopy (FT-IR), Transmission Electron Microscopy (TEM) Brunauer-Emmet-Teller (BET) surface area analysis and UV-Vis spectroscopy. The results demonstrate that SnO2 NPs has well crystalline structure with the crystallite size of 44 nm. The degradation of dyes was studied under ambient temperature using ultrasonicator and UV light, respectively. The sono- and photocatalytic activities of SnO2 NPs on dyes were analyzed by measuring the change in absorbance of dyes under UV-spectrophotometer. The degradation of the organic dyes has been calculated by monitoring the degradation in the concentration of the dyes before and after irradiation of ultrasonic and light, respectively. The influence of other parameters such as catalyst dosage, pH and scavenger have also been investigated. The catalytic activity is enhanced in the presence of ultrasonic irradiation. The degradation of both dyes follows pseudo-first order kinetics. The reusability tests have also been done to ensure the stability of the used catalysts. A reasonable mechanism of sono- and photocatalysis with SnO2 NPs has been proposed by correlating the active radical species involved with the physical properties of the as-synthesized samples.

  11. Synthesis of calcium superoxide

    Science.gov (United States)

    Rewick, R. T.; Blucher, W. G.; Estacio, P. L.

    1972-01-01

    Efforts to prepare Ca(O2) sub 2 from reactions of calcium compounds with 100% O3 and with O(D-1) atoms generated by photolysis of O3 at 2537 A are described. Samples of Ca(OH) sub 2, CaO, CaO2, Ca metal, and mixtures containing suspected impurities to promote reaction have been treated with excess O3 under static and flow conditions in the presence and absence of UV irradiation. Studies with KO2 suggest that the superoxide anion is stable to radiation at 2537 A but reacts with oxygen atoms generated by the photolysis of O3 to form KO3. Calcium superoxide is expected to behave in an analogous.

  12. Chemical modification of polysulfone: composite anionic exchange membrane with TiO2 nano-particles

    CSIR Research Space (South Africa)

    Nonjola, PT

    2013-04-01

    Full Text Available Synthesis of quaternary polysulfone/Titanium dioxide (QPSf/TiO2) nanocomposite membranes by the recasting procedure as suitable electrolyte in alkaline fuel cells is described. The composite membranes were characterized by ionic conductivity...

  13. Effect of band gap engineering in anionic-doped TiO2 photocatalyst

    Science.gov (United States)

    Samsudin, Emy Marlina; Abd Hamid, Sharifah Bee

    2017-01-01

    A simple yet promising strategy to modify TiO2 band gap was achieved via dopants incorporation which influences the photo-responsiveness of the photocatalyst. The mesoporous TiO2 was successfully mono-doped and co-doped with nitrogen and fluorine dopants. The results indicate that band gap engineering does not necessarily requires oxygen substitution with nitrogen or/and fluorine, but from the formation of additional mid band and Ti3+ impurities states. The formation of oxygen vacancies as a result of modified color centres and Ti3+ ions facilitates solar light absorption and influences the transfer, migration and trapping of the photo-excited charge carriers. The synergy of dopants in co-doped TiO2 shows better optical properties relative to single N and F doped TiO2 with c.a 0.95 eV band gap reduction. Evidenced from XPS, the synergy between N and F in the co-doped TiO2 uplifts the valence band towards the conduction band. However, the photoluminescence data reveals poorer electrons and holes separation as compared to F-doped TiO2. This observation suggests that efficient solar light harvesting was achievable via N and F co-doping, but excessive defects could act as charge carriers trapping sites.

  14. Thermophysical and anion diffusion properties of (U x ,Th1-x )O2.

    Science.gov (United States)

    Cooper, Michael W D; Murphy, Samuel T; Fossati, Paul C M; Rushton, Michael J D; Grimes, Robin W

    2014-11-01

    Using molecular dynamics, the thermophysical properties of the (U x ,Th1-x )O2 system have been investigated between 300 and 3600 K. The thermal dependence of lattice parameter, linear thermal expansion coefficient, enthalpy and specific heat at constant pressure is explained in terms of defect formation and diffusivity on the oxygen sublattice. Vegard's law is approximately observed for solid solution thermal expansion below 2000 K. Different deviations from Vegard's law above this temperature occur owing to the different temperatures at which the solid solutions undergo the superionic transition (2500-3300 K). Similarly, a spike in the specific heat, associated with the superionic transition, occurs at lower temperatures in solid solutions that have a high U content. Correspondingly, oxygen diffusivity is higher in pure UO2 than in pure ThO2. Furthermore, at temperatures below the superionic transition, oxygen mobility is notably higher in solid solutions than in the end members. Enhanced diffusivity is promoted by lower oxygen-defect enthalpies in (U x ,Th1-x )O2 solid solutions. Unlike in UO2 and ThO2, there is considerable variety of oxygen vacancy and oxygen interstitial sites in solid solutions generating a wide range of property values. Trends in the defect enthalpies are discussed in terms of composition and the lattice parameter of (U x ,Th1-x )O2.

  15. Propofol attenuates high glucose-induced superoxide anion accumulation in human umbilical vein endothelial cells.

    Science.gov (United States)

    Wang, Jiaqiang; Jiang, Hui; Wang, Jing; Zhao, Yanjun; Zhu, Yun; Zhu, Minmin

    2016-12-01

    Perioperative hyperglycemia is a common clinical metabolic disorder. Hyperglycemia could induce endothelial apoptosis, dysfunction, and inflammation, resulting in endothelial injury. Propofol is a widely used anesthetic drug in clinical settings. Our previous studies indicated that propofol attenuated high glucose-induced endothelial apoptosis, dysfunction, and inflammation via inhibiting reactive oxygen species (ROS) accumulation. However, the mechanisms by which propofol reduces high glucose-induced endothelial ROS accumulation are still obscure. In this study, we examined how propofol attenuates high glucose-induced endothelial ROS accumulation. Compared with 5 mm glucose treatment, 15 mm glucose upregulated the expression of pin-1, phosphatase A2 (PP2A), p66(shc) and mitochondrial p66(shc) expression, increased p66(shc) -Ser(36) phosphorylation, and O2·- accumulation. More importantly, although propofol had no effect on 15 mm glucose-induced p66(shc) -Ser(36) phosphorylation and pin-1 expression, propofol could downregulated PP2A expression and p66(shc) expression in whole-cell and mitochondrion, resulting in the reduction of O2·- accumulation. Moreover, we demonstrated that the antioxidative effect of propofol was similar to that of calyculin A, an inhibitor of PP2A. In contrast, FTY720, an activator of PP2A, antagonized the effect of propofol. Our data indicated that the antioxidative effect of propofol was achieved by downregulating PP2A expression, resulting in the inhibition of p66(shc) -Ser(36) dephosphorylation and mitochondrial p66(shc) expression. © 2016 Société Française de Pharmacologie et de Thérapeutique.

  16. The activity of 3- and 7-hydroxyflavones as scavengers of superoxide radical anion generated from photo-excited riboflavin

    Energy Technology Data Exchange (ETDEWEB)

    Montana, P.; Pappano, N.; Debattista, N. [Universidad Nacional de San Luis, Area de Quimica Fisica, San Luis (Argentina); Avila, V.; Posadaz, A.; Bertolotti, S.G.; Garcia, N.A. [Universidad Nacional de Rio Cuarto, Dto. de Quimica, Rio Cuarto (Argentina)

    2003-08-01

    The visible-light irradiation of the system Riboflavin plus 3-hydroxyflavone or plus 7-hydroxyflavone, under aerobic conditions, produces a series of competitive processes that depend on the relative concentrations of the pigment and the flavones. The picture comprises photochemical mechanisms that potentially operate in nature. They mainly include the quenching of Rf singlet ({sup 1}Rf*) and triplet ({sup 3}Rf*) excited states (with bimolecular rate constants in the order of 10{sup 9} M{sup -1} s{sup -1}) and superoxide radical anion-mediated reactions. The participation of the oxidative species singlet molecular oxygen was not detected. The overall result shows chemical transformations in both Rf and 3-hydroxyflavone. No experimental evidence was found indicating any chemical reaction involving 7-hydroxyflavone. The fate of the pigment also depends on the amount of the dissolved flavonoid. At 50 mM concentrations of these compounds or higher, practically no photochemistry occurs, owing to the extensive quenching of ({sup 1}Rf*) When the concentration of the flavones is in the mM range or lower, ({sup 3}Rf*) is photogenerated. Then, the excited triplet species can be quenched mainly by the flavones through an electron-transfer process, yielding the semireduced pigment. The latter interacts with dissolved oxygen producing O{sub 2}{sup .-}, which reacts with both the pigment and 3-hydroxyflavone. In summary, 3-hydroxyflavone and 7-hydroxyflavone participate in the generation of superoxide ion in an Rf-sensitized process, and simultaneously 3-hydroxyflavone constitutes a degradable quencher of the oxidative species. (author)

  17. Adsorption of Anionic, Cationic and Nonionic Surfactants on Carbonate Rock in Presence of ZrO 2 Nanoparticles

    Science.gov (United States)

    Esmaeilzadeh, Pouriya; Bahramian, Alireza; Fakhroueian, Zahra

    The adsorption of surfactants at the solid-water interface is important for the control of wetting, lubrication, detergency and in mineral flotation.We have studied the adsorptions of different types of surfactants, cationic (Dodecyl trimethylammonium bromide, DTAB), anionic (sodium dodecyl sulfate, SDS) and non-anionic (lauryl alcohol-7 mole ethoxylate, LA7) on carbonate rock in presence of zirconium oxide spherical nanoparticles (17-19 nm). ZrO2 nanoparticles with tetrahedral structure have significant effect on adsorption of surfactants on the carbonate rock. We have used the measured conductivities to determine the rate of adsorption of surfactants at rock-water interfaces. The conductivity of DTAB in aqueous solutions containing calcite powder decreases more than the other surfactants in contact with ZrO2 nanoparticles. We have also investigated the adsorption of surfactants at the air-water interface. The presence of nanoparticles, as demonstrated by our experiments, enhances the surface activity and surface adsorption of the surfactants through electrostatic forces or formation of nanostructures. Dynamic light structuring data shows similar aggregation number of nanoparticles in presence of nanoparticles.

  18. Functionalized TiO2 nanoparticles for use for in-situ anion immobilization

    Energy Technology Data Exchange (ETDEWEB)

    Mattigod, Shas V.; Fryxell, Glen E.; Alford, Kentin L.; Gilmore, Tyler J.; Parker, Kent E.; Serne, R JEFFREY.; Engelhard, Mark H.

    2005-09-15

    40-60 nm anatase nanoparticles were coated with an organosilane monolayer terminated with an ethylenediamine (EDA) ligand. This functionalized nanoparticle (FNP) was then treated with an aqueous solution of Cu(II) to create a cationic Cu-EDA complex bound to the nanoparticle surface. The Cu-EDA FNP was then studied for its binding affinity for pertechnetate anion from a Hanford groundwater matrix. The Cu-EDA FNP was also evaluated for its injectability into a porous medium for possible application as a subsurface semi-permeable reactive barrier. Injection was readily accomplished, and resulted in a highly uniform distribution of the FNP sorbent in the test column.

  19. A kinetic study of the reactions between H2O2 and Cu,Zn superoxide dismutase; evidence for an electrostatic control of the reaction rate.

    Science.gov (United States)

    Viglino, P; Scarpa, M; Rotilio, G; Rigo, A

    1988-01-04

    H2O2 was shown to reduce the copper ion of native bovine Cu,Zn superoxide dismutase (superoxide:superoxide oxidoreductase, EC 1.15.1.1) (ECu2+) and to oxidize the reduced enzyme (ECu+). The time-course of these processes was monitored by NMR measurement of the longitudinal relaxation rate of the water protons. A steady-state characterized by the same ratio [ECu2+]/[( EC2+] + [ECu+]) was obtained either by starting from the oxidized or the reduced enzyme. The kinetics of these processes appear to be quite complex, since different reactions between H2O2, or its reaction products, and the enzyme-bound copper control the reaction rate. The solution of the differential equations describing the kinetic processes showed that the oxidation and the reduction of the copper ion by H2O2 are first-order with respect to the copper ion itself only when these processes approach the steady-state. The rate constants of the reduction and oxidation reactions were calculated according to these equations and were found to have comparable values which are in the range 5-80 and 5-45 M-1.min-1, respectively, changing the pH from 5.6 to 7 at 0.21 M ionic strength. This result, together with the dependence of the reaction rates on pH and ionic strength, points to HO2- as the reactive species in both processes, and indicates that the electrostatic control of the access of the peroxide to the active site is the rate-determining step of the two redox reactions.

  20. Accumulation of non-superoxide anion reactive oxygen species mediates nitrogen-limited alcoholic fermentation by Saccharomyces cerevisiae.

    Science.gov (United States)

    Mendes-Ferreira, Ana; Sampaio-Marques, Belém; Barbosa, Catarina; Rodrigues, Fernando; Costa, Vítor; Mendes-Faia, Arlete; Ludovico, Paula; Leão, Cecília

    2010-12-01

    Throughout alcoholic fermentation, nitrogen depletion is one of the most important environmental stresses that can negatively affect the yeast metabolic activity and ultimately leads to fermentation arrest. Thus, the identification of the underlying effects and biomarkers of nitrogen limitation is valuable for controlling, and therefore optimizing, alcoholic fermentation. In this study, reactive oxygen species (ROS), plasma membrane integrity, and cell cycle were evaluated in a wine strain of Saccharomyces cerevisiae during alcoholic fermentation in nitrogen-limiting medium under anaerobic conditions. The results indicated that nitrogen limitation leads to an increase in ROS and that the superoxide anion is a minor component of the ROS, but there is increased activity of both Sod2p and Cta1p. Associated with these effects was a decrease in plasma membrane integrity and a persistent cell cycle arrest at G(0)/G(1) phases. Moreover, under these conditions it appears that autophagy, evaluated by ATG8 expression, is induced, suggesting that this mechanism is essential for cell survival but does not prevent the cell cycle arrest observed in slow fermentation. Conversely, nitrogen refeeding allowed cells to reenter cell cycle by decreasing ROS generation and autophagy. Altogether, the results provide new insights on the understanding of wine fermentations under nitrogen-limiting conditions and further indicate that ROS accumulation, evaluated by the MitoTracker Red dye CM-H(2)XRos, and plasma membrane integrity could be useful as predictive markers of fermentation problems.

  1. Gas-phase reactions of molecular oxygen with uranyl(V) anionic complexes-synthesis and characterization of new superoxides of uranyl(VI).

    Science.gov (United States)

    Lucena, Ana F; Carretas, José M; Marçalo, Joaquim; Michelini, Maria C; Gong, Yu; Gibson, John K

    2015-04-16

    Gas-phase complexes of uranyl(V) ligated to anions X(-) (X = F, Cl, Br, I, OH, NO3, ClO4, HCO2, CH3CO2, CF3CO2, CH3COS, NCS, N3), [UO2X2](-), were produced by electrospray ionization and reacted with O2 in a quadrupole ion trap mass spectrometer to form uranyl(VI) anionic complexes, [UO2X2(O2)](-), comprising a superoxo ligand. The comparative rates for the oxidation reactions were measured, ranging from relatively fast [UO2(OH)2](-) to slow [UO2I2](-). The reaction rates of [UO2X2](-) ions containing polyatomic ligands were significantly faster than those containing the monatomic halogens, which can be attributed to the greater number of vibrational degrees of freedom in the polyatomic ligands to dissipate the energy of the initial O2-association complexes. The effect of the basicity of the X(-) ligands was also apparent in the relative rates for O2 addition, with a general correlation between increasing ligand basicity and O2-addition efficiency for polyatomic ligands. Collision-induced dissociation of the superoxo complexes showed in all cases loss of O2 to form the [UO2X2](-) anions, indicating weaker binding of the O2(-) ligand compared to the X(-) ligands. Density functional theory computations of the structures and energetics of selected species are in accord with the experimental observations.

  2. A hybrid density functional theory study of the anion distribution and applied electronic properties of the LaTiO2N semiconductor photocatalyst.

    Science.gov (United States)

    Wang, Xin; Li, Zhaosheng; Zou, Zhigang

    2015-07-15

    Although the crystallographic space group has been determined, detailed first principles calculations of the LaTiO2N semiconductor photocatalyst crystal have not been performed because of the nitrogen/oxygen sosoloid-like anion distribution. In this study, based on the Heyd-Scuseria-Ernzerhof method and experimental anion content, we present the possibility of determining detailed information about the LaTiO2N sosoloid-like anion distribution by dividing the anions into possible primitive cells. The detailed information about the anion distribution based on the characteristics of the energetically acceptable primitive cell structures suggests that the LaTiO2N structure is composed of aperiodic stacks of six building-block primitive cells, the non-vacancy primitive cells are located at the surface as effective photoreaction sites, and vacancy structures are located in the bulk. The surface oxide-rich structures increase the near-surface conduction band minimum rise and strengthen photoelectron transport to the bulk, while the content of the bulk vacancy structures should be balanced because of being out of photoreactions. This study is expected to provide a different perspective to understanding the LaTiO2N sosoloid-like anion distribution.

  3. Thin Film Nanocrystalline TiO2 Electrodes: Dependence of Flat Band Potential on pH and Anion Adsorption.

    Science.gov (United States)

    Minella, M; Maurino, V; Minero, C; Pelizzetti, E

    2015-05-01

    Thin nanocrystalline TiO2 films were produced on ITO conductive glass by dip-coating of a sol-gel TiO2 precursor. The transparent films were characterized from the optical and structural point of view with UV-Vis, Spectroscopic Ellipsometry, Raman and X-ray photoelectron spectroscopies, the roughness of the coating by AFM. The changes in the electrochemical properties features of ITO/TiO2 electrodes were evaluated in the presence of different electrolytes (KCI, Na2SO4 and phosphate buffer) with the aim to clarify the role of the ion adsorption on the structure of the electrical double layer. Electrochemical tests (Cyclic Voltammetry, CV, and Impedance Electrochemical Spectroscopy, EIS) showed a strong influence of the electrolyte properties on the semiconductor band edge position in the electrochemical scale and on band bending. The CV profiles recorded can be explained by considering that the interface capacity is due to the charging of surface states (e.g., Ti(IV) surface sites coordinated by oxygen atoms, ≡Ti-OH or Ti-O-Ti). The surface charge is strongly affected also by the density and nature of adsorbed ions and by dissociation of surficial OH. Of interest the fact that for the produced nanocrystalline electrodes the flat band potential, measured from the Mott-Schottky analysis of the space charge layer capacity obtained with EIS, showed a non Nernstian behavior with the pH probably caused by a change in the surface acidity as a consequence of specific anion adsorption. The modulation of flat band potential with adsorbed ions is of interest for many applications, in particular for photocatalysis (change in the redox potential of photogenerated carriers) and for photovoltaic applications like DSSC (change in the photopotentials).

  4. Inhibition of formyl peptide-stimulated superoxide anion generation by Fal-002-2 occurs mainly through the blockade of the p21-activated kinase and protein kinase C signaling pathways in ratneutrophils.

    Science.gov (United States)

    Tsai, Ya-Ru; Huang, Li-Jiau; Lin, Hui-Yi; Hung, Yun-Jie; Lee, Miau-Rong; Kuo, Sheng-Chu; Hsu, Mei-Feng; Wang, Jih-Pyang

    2013-02-15

    In formyl-Met-Leu-Phe (fMLP)-stimulated rat neutrophils, a synthetic compound, 6-chloro-2-(2-chlorophenyl)-4-oxo-1,4-dihydroquinoline-3-carboxylate (Fal-002-2), inhibited superoxide anion (O2(•-)) generation with an IC50 value of about 11μM, which was not mediated by scavenging the generated O2(•-) or by a cytotoxic effect on neutrophils. Fal-002-2 effectively attenuated the phosphorylation of Ser residues in p47(phox) and the association between p47(phox) and p22(phox) in fMLP-stimulated neutrophils. The interaction of p47(phox) with protein kinase C (PKC) isoforms (α, βI, βII, δ and ζ) was attenuated by Fal-002-2 with a similar IC50 value to that required for inhibition of O2(•-) generation, whereas Fal-002-2 had no prominent effect on PKC isoform membrane translocation and did not affect the kinase activity. Moreover, Fal-002-2 had no effect on the phosphorylation of Akt and downstream glycogen synthase kinase-3β, only slightly affected the intracellular free Ca(2+) concentration, phosphorylation of extracellular signal-regulated kinase and p38 mitogen-activated protein kinase (MAPK), but effectively attenuated the downstream MAPK-activated protein kinase-2 phosphorylation. The interaction of p21-activated kinase (PAK) 1with p47(phox), phosphorylation of PAK1 (Thr423/Ser144) and the membrane recruitment of PAK1 were effectively inhibited by Fal-002-2. Fal-002-2 also blocked the activation of Rac1 and Cdc42 in a concentration range that effectively inhibited PAK activation. Taken together, these results suggest that Fal-002-2 inhibits fMLP-stimulated O2(•-) generation in neutrophils mainly through the blockade of PKC and PAK signaling pathways and partly through p38 MAPK signaling.

  5. The carbonate radical anion-induced covalent aggregation of human copper, zinc superoxide dismutase, and alpha-synuclein: intermediacy of tryptophan- and tyrosine-derived oxidation products.

    Science.gov (United States)

    Zhang, Hao; Andrekopoulos, Christopher; Joseph, Joy; Crow, John; Kalyanaraman, B

    2004-06-01

    In this review, we describe the free radical mechanism of covalent aggregation of human copper, zinc superoxide dismutase (hSOD1). Bicarbonate anion (HCO3-) enhances the covalent aggregation of hSOD1 mediated by the SOD1 peroxidase-dependent formation of carbonate radical anion (CO3*-), a potent and selective oxidant. This species presumably diffuses out the active site of hSOD1 and reacts with tryptophan residue located on the surface of hSOD1. The oxidative degradation of tryptophan to kynurenine and N-formyl kynurenine results in the covalent crosslinking and aggregation of hSOD1. Implications of oxidant-mediated aggregation of hSOD1 in the increased cytotoxicity of motor neurons in amyotrophic lateral sclerosis are discussed.

  6. Mixed cerium-platinum oxides: Electronic structure of [CeO]Ptn (n = 1, 2) and [CeO2]Pt complex anions and neutrals

    Science.gov (United States)

    Ray, Manisha; Kafader, Jared O.; Topolski, Josey E.; Jarrold, Caroline Chick

    2016-07-01

    The electronic structures of several small Ce-Pt oxide complexes were explored using a combination of anion photoelectron (PE) spectroscopy and density functional theory calculations. Pt and Pt2 both accept electron density from CeO diatomic molecules, in which the cerium atom is in a lower-than-bulk oxidation state (+2 versus bulk +4). Neutral [CeO]Pt and [CeO]Pt2 complexes are therefore ionic, with electronic structures described qualitatively as [CeO+2]Pt-2 and [CeO+]Pt2-, respectively. The associated anions are described qualitatively as [CeO+]Pt-2 and [CeO+]Pt2-2, respectively. In both neutrals and anions, the most stable molecular structures determined by calculations feature a distinct CeO moiety, with the positively charged Ce center pointing toward the electron rich Pt or Pt2 moiety. Spectral simulations based on calculated spectroscopic parameters are in fair agreement with the spectra, validating the computationally determined structures. In contrast, when Pt is coupled with CeO2, which has no Ce-localized electrons that can readily be donated to Pt, the anion is described as [CeO2]Pt-. The molecular structure predicted computationally suggests that it is governed by charge-dipole interactions. The neutral [CeO2]Pt complex lacks charge-dipole stabilizing interactions, and is predicted to be structurally very different from the anion, featuring a single Pt-O-Ce bridge bond. The PE spectra of several of the complexes exhibit evidence of photodissociation with Pt- daughter ion formation. The electronic structures of these complexes are related to local interactions in Pt-ceria catalyst-support systems.

  7. An electrochemical DNA biosensor for evaluating the effect of mix anion in cellular fluid on the antioxidant activity of CeO2 nanoparticles.

    Science.gov (United States)

    Zhai, Yanwu; Zhang, Yan; Qin, Fei; Yao, Xin

    2015-08-15

    CeO2 nanoparticles are of particular interest as a novel antioxidant for scavenging free radicals. However, some studies showed that they could cause cell damage or death by generating reactive oxygen species (ROS). Up to now, it is not well understood about these paradoxical phenomena. Therefore, many attentions have been paid to the factors that could affect the antioxidant activity of CeO2 nanoparticles. CeO2 nanoparticles would inevitably encounter body fluid environment for its potential medical application. In this work the antioxidant activity behavior of CeO2 nanoparticles is studied in simulated cellular fluid, which contains main body anions (HPO4(2-), HCO3(-), Cl(-) and SO4(2-)), by a method of electrochemical DNA biosensor. We found that in the solution of Cl(-) and SO4(2-), CeO2 nanoparticles can protect DNA from damage by hydroxyl radicals, while in the presence of HPO4(2-) and HCO3(-), CeO2 nanoparticles lose the antioxidant activity. This can be explained by the cerium phosphate and cerium carbonate formed on the surface of the nanoparticles, which interfere with the redox cycling between Ce(3+) and Ce(4+). These results not only add basic knowledge to the antioxidant activity of CeO2 nanoparticles under different situations, but also pave the way for practical applications of nanoceria. Moreover, it also shows electrochemical DNA biosensor is an effective method to explore the antioxidant activity of CeO2 nanoparticles.

  8. Superoxide Mediates the Toxicity of Paraquat for Chinese Hamster Ovary Cells

    Science.gov (United States)

    Bagley, Ann C.; Krall, Judith; Lynch, Robert E.

    1986-05-01

    The roles of superoxide and H2O2 in the cytotoxicity of paraquat were assessed in Chinese hamster ovary cells. Neither catalase nor superoxide dismutase inhibited the loss of ability to form colonies when added to the medium. When introduced into the cells, superoxide dismutase but not catalase inhibited the toxicity of paraquat. That superoxide dismutase acted by its known catalytic action is shown by the loss of inhibition when the enzyme was inactivated by H2O2 before being introduced into the cells. The lack of inhibition by catalase, by dimethyl sulfoxide, and by desferoxamine suggests that the toxicity is not mediated by a reaction between H2O2 and superoxide to engender the hydroxyl radical. Exposure of Chinese hamster ovary cells to paraquat may be a suitable means to determine the effects of superoxide anion in cultured cells and the ways in which cells can resist this toxic action.

  9. TiO2 coated CuO nanowire array: Ultrathin p-n heterojunction to modulate cationic/anionic dye photo-degradation in water

    Science.gov (United States)

    Scuderi, Viviana; Amiard, Guillaume; Sanz, Ruy; Boninelli, Simona; Impellizzeri, Giuliana; Privitera, Vittorio

    2017-09-01

    We report the photocatalytic efficiency of CuO nanowires covered with a thin TiO2 film, studied by dyes degradation in water. The CuO nanowires were synthesized on Cu foils by thermal oxidation. A subsequent TiO2 deposition (7, 15, 30, 50 nm thick) was performed by atomic layer deposition, developing an ultrathin p-n heterojunction. A structural characterization was obtained by X-ray diffraction analysis, scanning and transmission electron microscopies equipped with energy dispersive x-ray analysis. The photocatalytic activity of the investigated materials was tested by the degradation of a cationic (methylene blue) or anionic (methyl orange). The relevance of the reported results was discussed in relation with the effects of the ultrathin p-n TiO2/CuO heterojunction. The two semiconductors are in intimate connection increasing the exposed surface and only TiO2 is directly in contact with water. This allowed to study systematically the effect of the electric filed generated by the p-n junction on the interface TiO2/liquid and therefore to modulate cationic/anionic dyes photo-degradation in water.

  10. A superoxide anion biosensor based on direct electron transfer of superoxide dismutase on sodium alginate sol-gel film and its application to monitoring of living cells

    Energy Technology Data Exchange (ETDEWEB)

    Wang Xiuhua; Han Min; Bao Jianchun; Tu Wenwen [Jiangsu Key Laboratory of Biofunctional Materials, College of Chemistry and Materials Science, Nanjing Normal University, Nanjing 210097 (China); Dai Zhihui, E-mail: daizhihuii@njnu.edu.cn [Jiangsu Key Laboratory of Biofunctional Materials, College of Chemistry and Materials Science, Nanjing Normal University, Nanjing 210097 (China)

    2012-03-02

    Highlights: Black-Right-Pointing-Pointer The direct electron transfer of SOD was facilitated on SA sol-gel film. Black-Right-Pointing-Pointer O{sub 2}{center_dot}{sup -} sensor has high selectivity, stability and sensitivity. Black-Right-Pointing-Pointer The proposed measurement for O{sub 2}{center_dot}{sup -} can be applied in living cells. - Abstract: The direct electron transfer of superoxide dismutase (SOD) was greatly facilitated by sodium alginate (SA) sol-gel film with the formal potential of 0.14 V, which was just located between O{sub 2}{center_dot}{sup -}/O{sub 2} and O{sub 2}{center_dot}{sup -}/H{sub 2}O{sub 2}. The preparation of the SOD/SA modified electrode was simple without any mediators or promoters. Based on bimolecular recognition for specific reactivity of SOD/SA toward O{sub 2}{center_dot}{sup -}, the SOD modified electrode was utilized to measure O{sub 2}{center_dot}{sup -} with good analytical performance, such as low applied potential (0 V), high selectivity (no obvious interference), wide linear range (0.44-229.88 {mu}M) and low detection limit (0.23 {mu}M) in pH 7.0 phosphate buffer solution. Furthermore, it could be successfully exploited for the determination of O{sub 2}{center_dot}{sup -} released from living cells directly adhered on the modified electrode surface. Thus, the proposed O{sub 2}{center_dot}{sup -} biosensor, combining with the properties of SA sol-gel film, provided a novel approach for protein immobilization, direct electron transfer study of the immobilized protein and real-time determination of O{sub 2}{center_dot}{sup -} released from living cells.

  11. Prion-derived copper-binding peptide fragments catalyze the generation of superoxide anion in the presence of aromatic monoamines

    Directory of Open Access Journals (Sweden)

    Tomonori Kawano

    2007-01-01

    Full Text Available Objectives: Studies have proposed two opposing roles for copper-bound forms of prion protein (PrP as an anti-oxidant supporting the neuronal functions and as a pro-oxidant leading to neurodegenerative process involving the generation of reactive oxygen species. The aim of this study is to test the hypothesis in which putative copper-binding peptides derived from PrP function as possible catalysts for monoamine-dependent conversion of hydrogen peroxide to superoxide in vitro. Materials and methods: Four peptides corresponding to the copper (II-binding motifs in PrP were synthesized and used for analysis of peptide-catalyzed generation of superoxide in the presence of Cu (II and other factors naturally present in the neuronal tissues. Results: Among the Cu-binding peptides tested, the amino acid sequence corresponding to the Cu-binding site in the helical region was shown to be the most active for superoxide generation in the presence of Cu(II, hydrogen peroxide and aromatic monoamines, known precursors or intermediates of neurotransmitters. Among monoamines tested, three compounds namely phenylethylamine, tyramine and benzylamine were shown to be good substrates for superoxide-generating reactions by the Cu-bound helical peptide. Conclusions: Possible roles for these reactions in development of prion disease were suggested.

  12. Two anionically derivatized scandium oxoselenates(IV): ScF[SeO3] and Sc2O2[SeO3

    Science.gov (United States)

    Greiner, Stefan; Chou, Sheng-Chun; Schleid, Thomas

    2017-02-01

    Scandium fluoride oxoselenate(IV) ScF[SeO3] and scandium oxide oxoselenate(IV) Sc2O2[SeO3] could be synthesized through solid-state reactions. ScF[SeO3] was obtained phase-pure, by reacting mixtures of Sc2O3, ScF3 and SeO2 (molar ratio: 1:1:3) together with CsBr as fluxing agent in corundum crucibles embedded into evacuated glassy silica ampoules after firing at 700 °C for seven days. Sc2O2[SeO3] first emerged as by-product during the attempts to synthesize ScCl[SeO3] following aforementioned synthesis route and could later be reproduced from appropriate Sc2O3/SeO3 mixtures. ScF[SeO3] crystallizes monoclinically in space group P21/m with a=406.43(2), b =661.09(4), c=632.35(4) pm, β=93.298(3)° and Z=2. Sc2O2[SeO3] also crystallizes in the monoclinic system, but in space group P21/n with a=786.02(6), b=527.98(4), c=1086.11(8) pm, β=108.672(3)° for Z=4. The crystal structures of both compounds are strongly influenced by the stereochemically active lone pairs of the ψ1-tetrahedral [SeO3]2- anions. They also show partial structures, where the derivatizing F- or O2- anions play an important role. For ScF[SeO3] chains of the composition 2+ ∞ 1[FSc2/2] form from connected [FSc2]5+ dumbbells, while [OSc3]7+ pyramids and [OSc4]10+ tetrahedra units are condensed to layers according to 2+ ∞ 2[O2Sc2 ] in Sc2O2[SeO3].

  13. Anionic or Cationic S-Doping in Bulk Anatase TiO 2 : Insights on Optical Absorption from First Principles Calculations

    KAUST Repository

    Harb, Moussab

    2013-05-02

    Using first principles calculations, we investigate the structural, electronic, optical, and energetic properties of S-doped anatase TiO2 bulk systems. To ensure accurate band gap predictions, we use the HSE06 exchange correlation functional, and the absorption spectra are obtained with density functional perturbation (DFPT) theory by employing HSE06. Various oxidation states (anionic and cationic) of sulfur are considered depending on the location in bulk TiO2: in interstitial position or in substitution for either oxygen or titanium atoms. Among the explored structures, two anionic and one cationic configurations induce an improved optical absorption response in the visible region as observed experimentally. Moreover, we undertake a thermodynamic analysis as a function of the chemical potential of oxygen and considering three relevant sulfur chemical doping agents (S 2, H2S, and thiourea). It highlights that cationic configurations (S4+ and S6+) are strongly stabilized in a wide range of oxygen chemical potential (including standard conditions), whereas anionic species are stabilized only at very low chemical potential of oxygen. The metastable cationic Ti(1-2x)O2S2x system involving the presence of S4+ species in substitution for Ti 4+, with the formation of SO2 units, should offer the best compromise between the thermodynamic conditions and the expected optical properties. © 2013 American Chemical Society.

  14. [Effects and mechanisms of inorganic anions in water on degradation of LAS by UV/H2 O2 combination process].

    Science.gov (United States)

    Pan, Jing; Sun, Tie-Heng; Li, Hai-Bo

    2007-11-01

    Experiments are carried out to study the effects and mechanisms of inorganic anions in water on the degradation of linear alkyl benzene sulfonate (LAS) in UV/H2 O2 process. The results show that UV/H2 O2 process could remove LAS effectively, and the rate of photodegradation follows first-order reaction kinetics model. Under the condition that H2 O2 concentration was 8 mg x L(-1) and a 14 W low pressure mercury vapor discharge lamp irradiated samples, the first-order photodegradation rate constant of LAS in distilled water and tap water were 0.018 0 min(-1) and 0.012 2 min(-1) respectively. NO3-, Cl-, SO4(2-) and HCO3- have inhibitory action on LAS photodegradation. The higher inorganic anions concentration was, the stronger inhibitory action. When their concentrations were 5, 10 and 15 mmol x L(-1) respectively, their inhibitory action order was HCO3- > NO3- > Cl- > SO4(2-) all the time. It was anions synthetical effect that caused photodegradation rate constant of LAS in tap water lower than distilled water.

  15. Synthesis and characterization of ZnO-TiO2 nanopowders doped with fe via sol-gel method and their application in photocatalytic degradation of anionic surfactant

    Science.gov (United States)

    Giahi, M.; Saadat Niavol, S.; Taghavi, H.; Meskinfam, M.

    2015-12-01

    ZnO and 0, 5, and 10 mol % Fe-doped ZnO-TiO2 nanopowders were synthesized by the sol-gel Pechini method. The successful synthesis of coupled ZnO-TiO2 nanopowders was evident by XRD. Scanning electron microscopy (SEM) revealed that the Fe ions were well incorporated into the ZnO-TiO2 crystal lattice. The photocatalytic degradation of anionic surfactant (linear alkylbenzene sulfonate (LABS), was investigated in aqueous solution using ZnO and Fe-doped ZnO-TiO2 nanoparticles. The degradation was studied under different conditions such as the Fe3+ concentration, amount of photocatalyst, irradiation time, pH, initial concentration and presence of electron acceptor. The results showed that photocatalytic degradation of LABS was strongly influenced by these parameters. The best conditions for the photocatalytic degradation of LABS were obtained. It is found that under UV light irradiation, Fe-doping of ZnO-TiO2 increases the efficiency of its photocatalytic activity in degradation of LABS than pure ZnO and ZnO-TiO2.

  16. A Li-O2/CO2 battery.

    Science.gov (United States)

    Takechi, Kensuke; Shiga, Tohru; Asaoka, Takahiko

    2011-03-28

    A new gas-utilizing battery using mixed gas of O(2) and CO(2) was developed and proved its very high discharge capacity. The capacity reached three times as much as that of a non-aqueous Li-air (O(2)) battery. The unique point of the battery is expected to be the rapid consumption of superoxide anion radical by CO(2) as well as the slow filling property of the Li(2)CO(3) in the cathode.

  17. Heterogeneous photo catalytic degradation of anionic and cationic dyes over TiO(2) and TiO(2) doped with Mo(6+) ions under solar light: Correlation of dye structure and its adsorptive tendency on the degradation rate.

    Science.gov (United States)

    Gomathi Devi, L; Narasimha Murthy, B; Girish Kumar, S

    2009-08-01

    Degradation of synthetic dyes like Methyl Orange (MO), p-amino azo benzene (PAAB), Congo Red (CR), Brilliant Yellow (BY), Rhodamine-B (RB) and Methylene Blue (MB) under solar light were carried out using TiO(2) doped with Mo(6+) ions. The rate constant for the degradation of anionic dyes MO, PAAB, CR and BY was high at pH 5.6, while for cationic dyes the highest rate constant was obtained in the alkaline pH 8.0. These differences can be accounted to their adsorption capacity on the catalyst surface at different pH conditions. Among the photocatalyst used, Mo(6+) (0.06%)-TiO(2) showed enhanced activity due to the effective separation of charge carriers.

  18. BPA-toxicity via superoxide anion overload and a deficit in β-catenin signaling in human bone mesenchymal stem cells.

    Science.gov (United States)

    Leem, Yea-Hyun; Oh, Seikwan; Kang, Hong-Je; Kim, Jung-Hwa; Yoon, Juno; Chang, Jae-Suk

    2017-01-01

    Bisphenol A (BPA), used in the manufacture of products based on polycarbonate plastics and epoxy resins, is well known as an endocrine-disrupting monomer. In the current study, BPA increased cytotoxicity in hBMSCs in a dose- and time-dependent manner, concomitantly with increased lipid peroxidation. Increased cell death in BPA-treated cells was markedly blocked by pretreatment with the superoxide dismutase mimetic MnTBAP and MnTMPyP, but not by catalase, glutathione, the glutathione peroxidase mimetic ebselen, the NOS inhibitor NAME, or the xanthine oxidase inhibitor allopurinol. Furthermore, the decline in nuclear β-catenin and cyclin D1 levels in hBMSCs exposed to BPA was reversed by MnTBAP treatment. Finally, treatment of hBMSCs with the GSK3β inhibitor LiCl2 increased nuclear β-catenin levels and significantly attenuated cytotoxicity compared with BPA treatment. Our current results in hBMSCs exposed to BPA suggest that BPA causes a disturbance in β-catenin signaling via a superoxide anion overload. © 2016 The Authors Environmental Toxicology Published by Wiley Periodicals, Inc. Environ Toxicol 32: 344-352, 2017.

  19. Antioxidant protection of NO-induced relaxations of the mouse anococcygeus against inhibition by superoxide anions, hydroquinone and carboxy-PTIO.

    Science.gov (United States)

    Lilley, E; Gibson, A

    1996-09-01

    1. The potential protective effect of several antioxidants [Cu/Zn superoxide dismutase (Cu/Zn SOD), ascorbate, reduced glutathione (GSH), and alpha-tocopherol (alpha-TOC)] on relaxations of the mouse anococcygeus muscle to nitric oxide (NO; 15 microM) and, where appropriate, nitrergic field stimulation (10 Hz; 10 s trains) was investigated. 2. The superoxide anion generating drug duroquinone (100 microM) reduced relaxations to exogenous NO by 54 +/- 6%; this inhibition was partially reversed by Cu/Zn SOD (250 u ml-1), and by ascorbate (500 microM). Following inhibition of endogenous Cu/Zn SOD activity with diethyldithiocarbamate (DETCA), duroquinone (50 microM) also reduced relaxations to nitrergic field stimulation (by 53 +/- 6%) and this effect was again reversed by Cu/Zn SOD and by ascorbate. Neither GSH (500 microM) nor alpha-TOC (400 microM) afforded any protection against duroquinone. 3. Xanthine (20 mu ml-1); xanthine oxidase (100 microM) inhibited NO-induced relaxations by 73 +/- 14%, but had no effect on those to nitrergic field stimulation, even after DETCA treatment. The inhibition of exogenous NO was reduced by Cu/Zn SOD (250 u ml-1) and ascorbate (400 microM), but was unaffected by GSH or alpha-TOC (both 400 microM). 4. Hydroquinone (100 microM) also inhibited relaxations to NO (by 52 +/- 10%), but not nitrergic stimulation. In this case, however, the inhibition was reversed by GSH (5-100 microM) and ascorbate (100-400 microM), although Cu/Zn SOD and alpha-TOC were ineffective. 5. 2-(4-Carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (carboxy-PTIO, 50 microM) inhibited NO-induced relaxations by 50 +/- 4%, but had no effect on nitrergic responses; the inhibition was reduced by ascorbate (2-200 microM) and alpha-TOC (10-200 microM), but not by Cu/Zn SOD or GSH. 6. Hydroxocobalamin (5-100 microM) inhibited, equally, relaxations to both NO (-logIC40 3.14 +/- 0.33) and nitrergic stimulation (-logIC40 3.17 +/- 0.22). 7. Thus, a number of

  20. Synergism between arsenite and proteasome inhibitor MG132 over cell death in myeloid leukaemic cells U937 and the induction of low levels of intracellular superoxide anion

    Energy Technology Data Exchange (ETDEWEB)

    Lombardo, Tomás [Laboratorio de Immunotoxicologia (LaITO), IDEHU-CONICET, Hospital de Clínicas, José de San Martín, Universidad de Buenos Aires (UBA), Buenos Aires (Argentina); Cavaliere, Victoria; Costantino, Susana N. [Laboratorio de Inmunología Tumoral (LIT), IDEHU-CONICET, Facultad de Farmacia y Bioquímica, UBA, Buenos Aires (Argentina); Kornblihtt, Laura [Servicio de Hematología, Hospital de Clínicas, José de San Martín (UBA), Buenos Aires (Argentina); Alvarez, Elida M. [Laboratorio de Inmunología Tumoral (LIT), IDEHU-CONICET, Facultad de Farmacia y Bioquímica, UBA, Buenos Aires (Argentina); Blanco, Guillermo A., E-mail: gblanco@ffyb.uba.ar [Laboratorio de Immunotoxicologia (LaITO), IDEHU-CONICET, Hospital de Clínicas, José de San Martín, Universidad de Buenos Aires (UBA), Buenos Aires (Argentina)

    2012-02-01

    Increased oxygen species production has often been cited as a mechanism determining synergism on cell death and growth inhibition effects of arsenic-combined drugs. However the net effect of drug combination may not be easily anticipated solely from available knowledge of drug-induced death mechanisms. We evaluated the combined effect of sodium arsenite with the proteasome inhibitor MG132, and the anti-leukaemic agent CAPE, on growth-inhibition and cell death effect in acute myeloid leukaemic cells U937 and Burkitt's lymphoma-derived Raji cells, by the Chou–Talalay method. In addition we explored the association of cytotoxic effect of drugs with changes in intracellular superoxide anion (O{sub 2}{sup −}) levels. Our results showed that combined arsenite + MG132 produced low levels of O{sub 2}{sup −} at 6 h and 24 h after exposure and were synergic on cell death induction in U937 cells over the whole dose range, although the combination was antagonistic on growth inhibition effect. Exposure to a constant non-cytotoxic dose of 80 μM hydrogen peroxide together with arsenite + MG132 changed synergism on cell death to antagonism at all effect levels while increasing O{sub 2}{sup −} levels. Arsenite + hydrogen peroxide also resulted in antagonism with increased O{sub 2}{sup −} levels in U937 cells. In Raji cells, arsenite + MG132 also produced low levels of O{sub 2}{sup −} at 6 h and 24 h but resulted in antagonism on cell death and growth inhibition. By contrast, the combination arsenite + CAPE showed high levels of O{sub 2}{sup −} production at 6 h and 24 h post exposure but resulted in antagonism over cell death and growth inhibition effects in U937 and Raji cells. We conclude that synergism between arsenite and MG132 in U937 cells is negatively associated to O{sub 2}{sup −} levels at early time points after exposure. -- Highlights: ► Arsenic combined cytotoxic and anti-proliferative effects by Chou–Talalay method. ► Cytotoxic effect

  1. A superoxide anion-scavenger, 1,3-selenazolidin-4-one suppresses serum deprivation-induced apoptosis in PC12 cells by activating MAP kinase

    Energy Technology Data Exchange (ETDEWEB)

    Nishina, Atsuyoshi, E-mail: nishina@yone.ac.jp [Yonezawa Women' s Junior College, 6-15-1 Tohrimachi, Yonezawa, Yamagata 992-0025 (Japan); Kimura, Hirokazu; Kozawa, Kunihisa [Gunma Prefectural Institute of Public Health and Environmental Sciences, 378 Kamioki, Maebashi, Gunma 371-0052 (Japan); Sommen, Geoffroy [Lonza Braine SA, Chaussee de Tubize 297, B-1420 Braine l' Alleud (Belgium); Nakamura, Takao [Department of Biomedical Information Engineering, Graduate School of Medical Science, Yamagata University, Yamagata 990-9585 (Japan); Heimgartner, Heinz [University of Zuerich, Institut of Organic Chemistry, Winterthurerstrasse 190, CH-8057 Zuerich (Switzerland); Koketsu, Mamoru [Department of Materials Science and Technology, Faculty of Engineering, Gifu University, Gifu 501-1193 (Japan); Furukawa, Shoei [Laboratory of Molecular Biology, Gifu Pharmaceutical University, 5-6-1 Mitahora-higashi, Gifu 502-8585 (Japan)

    2011-12-15

    Synthetic organic selenium compounds, such as ebselen, may show glutathione peroxidase-like antioxidant activity and have a neurotrophic effect. We synthesized 1,3-selenazolidin-4-ones, new types of synthetic organic selenium compounds (five-member ring compounds), to study their possible applications as antioxidants or neurotrophic-like molecules. Their superoxide radical scavenging effects were assessed using the quantitative, highly sensitive method of real-time kinetic chemiluminescence. At 166 {mu}M, the O{sub 2}{sup -} scavenging activity of 1,3-selenazolidin-4-ones ranged from 0 to 66.2%. 2-[3-(4-Methoxyphenyl)-4-oxo-1,3-selenazolidin-2-ylidene]malononitrile (compound b) showed the strongest superoxide anion-scavenging activity among the 6 kinds of 2-methylene-1,3-selenazolidin-4-ones examined. Compound b had a 50% inhibitory concentration (IC{sub 50}) at 92.4 {mu}M and acted as an effective and potentially useful O{sub 2}{sup -} scavenger in vitro. The effect of compound b on rat pheochromocytome cell line PC12 cells was compared with that of ebselen or nerve growth factor (NGF) by use of the MTT [3-(4, 5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide] assay. When ebselen was added at 100 {mu}M or more, toxicity toward PC12 cells was evident. On the contrary, compound b suppressed serum deprivation-induced apoptosis in PC12 cells more effectively at a concentration of 100 {mu}M. The activity of compound b to phosphorylate mitogen-activated protein kinase/extracellular signal-regulated protein kinase (ERK) 1/2 (MAP kinase) in PC12 cells was higher than that of ebselen, and the former at 100 {mu}M induced the phosphorylation of MAP kinase to a degree similar to that induced by NGF. From these results, we conclude that this superoxide anion-scavenger, compound b, suppressed serum deprivation-induced apoptosis by promoting the phosphorylation of MAP kinase. -- Highlights: Black-Right-Pointing-Pointer We newly synthesized 1,3-selenazolidin-4-ones to

  2. Enhancing electrochemical intermediate solvation through electrolyte anion selection to increase nonaqueous Li–O2 battery capacity

    National Research Council Canada - National Science Library

    Colin M. Burke; Vikram Pande; Abhishek Khetan; Venkatasubramanian Viswanathan; Bryan D. McCloskey

    2015-01-01

    Among the "beyond Li-ion" battery chemistries, nonaqueous Li-O2 batteries have the highest theoretical specific energy and, as a result, have attracted significant research attention over the past decade...

  3. 氧脱木素过程中超氧阴离子自由基的控制%Regulation of Superoxide Anion Radical During the Oxygen Delignification Process

    Institute of Scientific and Technical Information of China (English)

    曹石林; 詹怀宇; 付时雨; 陈礼辉

    2007-01-01

    In this study, the superoxide anion radicals were generated by the auto-oxidation of 1,2,3-trihydroxybenzene and determined by UV spectrophotometry, and the reaction was found to be facilitated by anthraquinone-2-sulfonic acid sodium salt. The bamboo kraft pulps were treated by the 1,2,3-trihydroxybenzene auto-oxidation method or the 1,2,3-trihydroxybenzene auto-oxidation combined with anthraquinone-2-suffonic acid sodium salt to show the effect of the superoxide anion radicals during the oxygen delignification of bamboo kraft pulp and the enhancing affect of anthraquinone compounds as an additive on delignification. The results indicated that the superoxide anion radicals could react with lignin and remove it from pulp with negligible damage on cellulose, and the anthraquinone-2-sulfonic acid sodium salt could facilitate the generation of superoxide anion radical to enhance delignification of pulps. The oxygen delignification selectivity could be improved using the 1,2,3-trihydroxybenzene auto-oxidation system combined with anthraquinone-2-sulfonic acid sodium salt.

  4. Hydrotalcite-TiO2 magnetic iron oxide intercalated with the anionic surfactant dodecylsulfate in the photocatalytic degradation of methylene blue dye.

    Science.gov (United States)

    Miranda, Liany D L; Bellato, Carlos R; Milagres, Jaderson L; Moura, Luciano G; Mounteer, Ann H; de Almeida, Marciano F

    2015-06-01

    The new magnetic photocatalysts HT/TiO2/Fe and HT-DS/TiO2/Fe, modified with the anionic surfactant sodium dodecylsulfate (DS) were successfully synthesized in this work. Titanium dioxide (anatase) followed by iron oxide were deposited on the hydrotalcite support. Several catalyst samples were prepared with different amounts of titanium and iron. The photocatalysts were characterized by infrared and Raman spectroscopy, X-ray diffraction, scanning electron microscopy. Photocatalytic performance was analyzed by UV-visible radiation (filter cutoff, λ > 300 nm) of an aqueous solution (24 mg/L) of methylene blue (MB). The most efficient catalyst was obtained at an iron oxide:TiO2 molar ratio of 2:3. This catalyst showed high photocatalytic activity, removing 96% of the color and 61% of total organic carbon from the MB solution after 120 min. It was easily removed from solution after use because of its magnetic properties. The reuse of the HT-DS/TiO2/Fe23 catalyst was viable and the catalyst was structurally stable for at least four consecutive photocatalytic cycles.

  5. Photoelectron angular distributions as probes of cluster anion structure: I(-)·(H2O)2 and I(-)·(CH3CN)2.

    Science.gov (United States)

    Mbaiwa, Foster; Holtgrewe, Nicholas; Dao, Diep Bich; Lasinski, Joshua; Mabbs, Richard

    2014-09-01

    The use of photoelectron angular distributions to provide structural details of cluster environments is investigated. Photoelectron spectra and angular distributions of I(-)·(H2O)2 and I(-)·(CH3CN)2 cluster anions are recorded over a range of photon energies. The anisotropy parameter (β) for electrons undergoes a sharp change (Δβmax) at photon energies close to a detachment channel threshold. I(-)·(H2O)2 results show the relationship between dipole moment and Δβmax to be similar to that observed in monosolvated I(-) detachment. The Δβmax of the 4.0 eV band in the I(-)·(CH3CN)2 photoelectron spectrum suggests a dipole moment of 5-6 D. This is consistent with predictions of a hydrogen bonded conformer of the I(-)·(CH3CN)2 cluster anion [Timerghazin, Q. K.; Nguyen, T. N.; Peslherbe, G. H. J. Chem. Phys. 2002, 116, 6867-6870].

  6. Antioxidative capacity and enzyme activity in Haematococcus pluvialis cells exposed to superoxide free radicals

    Institute of Scientific and Technical Information of China (English)

    刘建国; 张晓丽; 孙延红; 林伟

    2010-01-01

    The antioxidative capacity of astaxanthin and enzyme activity of reactive oxygen eliminating enzymes such as superoxide dismutase (SOD),peroxidase (POD),catalase (CAT) and ascorbate peroxidase (APX) were studied in three cell types of Haematococcus pluvialis exposed to high concentrations of a superoxide anion radical (O2ˉ).The results show that defensive enzymes and astaxanthin-related mechanisms were both active in H.pluvialis during exposure to reactive oxygen species (ROS) such as Oˉ2.Astaxanthin reacte...

  7. [Generation of superoxides during the interaction of melanins with oxygen].

    Science.gov (United States)

    Lapina, V A; Dontsov, A E; Ostrovskiĭ, M A

    1984-10-01

    The rate of nitroblue tetrazolium (NBT) reduction by dihydroxyphenylalanine-melanin, pheomelanin and retinal pigment epithelium melanosomes under aerobic conditions (pH 7.4) is low both in the dark and upon illumination, but increases drastically in the presence of cetyltrimethylammonium bromide (CTAB). Under these conditions, the light insignificantly stimulates NBT reduction (1.3-fold). The reaction is effectively inhibited by superoxide dismutase. This suggests that superoxide anions (O2-. are formed as intermediate reaction products in the course of NBT reduction by melanins. At alkaline values of pH (greater than or equal to 9.0), the O2-.-dependent reduction of NBT can also take place in the absence of CTAB. In contrast with oxidation of photoreduced riboflavin, the melanin oxidation by O2 cannot induce lipid peroxidation. It is concluded that O2-. generation via melanin oxidation of melanosomes occurs only under non-physiological conditions and can hardly take place in vivo.

  8. Application of SiO_2 Nano-particles in Treatment of Raw Water Containing Anionic Surfactant%纳米SiO_2用于含表面活性剂原水的处理

    Institute of Scientific and Technical Information of China (English)

    阮彩群; 李冬梅; 任毅; 李绍秀; 李斌; 李志生

    2009-01-01

    By adding SiO_2 nano-particles into kaolin suspensions with turbidity of 6 NTU in the presence of anionic surfactant--sedium dodeeyl sulphate (SDS), dynamic coagulation experiments and quiescent settling experiments were done. The action efficiency and morphologic properties of SiO_2 nano-particles were discussed using image analysis technology and a quantitative faetor---fractal dimension. The formation and growth of flocs have fractal properties. The fractal structure formation is a main effect factor of particles coagulation, flocs compact degree and settleability. The flocs formation is interfered at the ini-tial flocculation stage in the presence of SDS. Afterwards, the mixture of SDS and the coagulant acta on particles together and enhances the flocculation efficiency. The flocs become larger and compacter, and the settleability is improved. There is competitive adsorption between SDS and SiO_2. When SiO_2 nano-particles are added alone, small and fragile flocs are formed. When PAC serves as a primary coagulant, SiO_2 nano-particles as floeeulant aid are beneficial for PAC flocs structure evolution to more compact con-figurations. The removal rates of turbidity and SDS are improved.%在含表面活性剂十二烷基硫酸钠(SDS)的低浊(6 NTU)高岭土原水中,投加纳米SiO_2进行动态混凝与静沉试验,借助图像分析技术与定量控制参数,探讨了纳米SiO_2的作用效果与形态学特性.结果表明:絮体的形成与生长具有分形特征,分形结构是影响颗粒混凝、絮团密实度与沉降特性的主要因素;SDS的存在对絮凝初期絮体的形成起阻碍作用,随后SDS与混凝剂的混合体共同对粒子作用,促进絮凝,絮体变大且密实,沉降性能改善;SDS和SiO_2对高岭土粒子存在竞争吸附;单独投加纳米SiO_2时形成的絮体小而脆弱,而以纳米SiO_2为助凝剂能促使PAC絮体结构向更密实的构型转变,对浊度和SDS的去除率提高.

  9. 无机阴离子对TiO2-膨润土紫外光降解SDBS的影响%Effect of Inorganic Anion on Degradation of Sodium Dodecyl Benzene Sulfonate by TiO2-bentonite

    Institute of Scientific and Technical Information of China (English)

    温淑瑶; 马占青; 马敏立

    2012-01-01

    Photodegradation of sodium dodecyl benzene sulfonate (SDBS) by TiO2-bentonite is efficient, and the inorganic anions such as Cl-, SO42-, NO3-, HCO3-, H2PO4- which usually exist in water have an effect on photodegradation efficiency of SDBS by TiO2-bentonite. 36 mmol/L sodium salt of these inorganic anions was input into SDBS aqueous solution respectively,and the solutions were irradiated for 2 h with ultraviolet lamp. The difference of photodegradation results with or without the input of inorganic anions in the solution was compared. Results showed that effect of inorganic anion such as Cl-, SO42-, NO3-,HCO3-, H2PO4- on degradation of SDBS by TiO2-bentonite existed. Among which the effect of HCO3- on degradation was the most obvious, followed by H2PO-4 , NO3- , SO42-, Cl- The concentration of SDBS solutions with input of HCO3- , H2PO4- , NO3- ,SO42-, Cl- increased by 2.63, 1.63, 0.73, 0.52 and 0.46 times respectively within 2 h than that without input of the inorganic anions, which mainly depends on the competitions of surface active position between inorganic anions and organic molecules,appearance of high polarity environment near surface of catalyst particle and change of pH of solutions. Effect of inorganic anion on COD of aqueous solutions was different, within 2 h COD of aqueous solutions which had been input Cl-, SO42-,NO3- , HCO3- , HZPO4- , increased 6.62, 0.26, 0.03, 0.29 and 0.45 times respectively than that hadn't been put into.%TiO2-膨润土光催化降解水溶液中阴离子表面活性剂十二烷基苯磺酸钠(SDBS)的效率较高,Cl-、SO42-、NO3-、HC3-、H2PO4-是水体中常见的阴离子,这些阴离子对降解效果的影响直接影响该技术的实际应用.分别投加36 mmol/L上述阴离子的钠盐到SDBS水溶液中,紫外光照射溶液2h,比较投加与不投加的SDBS去除效果差异,结果表明:(1)水溶液中上述阴离子对TiO2-膨润土降解SDBS的效果都有不利影响,其中HCO3影响最大,其次是H2PO4_,

  10. Is the band gap of pristine TiO(2) narrowed by anion- and cation-doping of titanium dioxide in second-generation photocatalysts?

    Science.gov (United States)

    Serpone, Nick

    2006-12-07

    Second-generation TiO(2)-(x)D(x) photocatalysts doped with either anions (N, C, and S mostly) or cations have recently been shown to have their absorption edge red-shifted to lower energies (longer wavelengths), thus enhancing photonic efficiencies of photoassisted surface redox reactions. Some of the studies have proposed that this red-shift is caused by a narrowing of the band gap of pristine TiO(2) (e.g., anatase, E(bg) = 3.2 eV; absorption edge ca. 387 nm), while others have suggested the appearance of intragap localized states of the dopants. By contrast, a recent study by Kuznetsov and Serpone (J. Phys. Chem. B, in press) has proposed that the commonality in all these doped titanias rests with formation of oxygen vacancies and the advent of color centers (e.g., F, F(+), F(++), and Ti(3+)) that absorb the visible light radiation. This article reexamines the various claims and argues that the red-shift of the absorption edge is in fact due to formation of the color centers, and that while band gap narrowing is not an unknown occurrence in semiconductor physics it does necessitate heavy doping of the metal oxide semiconductor, thereby producing materials that may have completely different chemical compositions from that of TiO(2) with totally different band gap electronic structures.

  11. Effect of insulin, the glutathione system, and superoxide anion radical in modulation of lipolysis in adipocytes of rats with experimental diabetes.

    Science.gov (United States)

    Ivanov, V V; Shakhristova, E V; Stepovaya, E A; Nosareva, O L; Fedorova, T S; Ryazantseva, N V; Novitsky, V V

    2015-01-01

    Spontaneous lipolysis was found to be increased in adipocytes of rats with alloxan-induced diabetes. In addition, isoproterenol-stimulated hydrolysis of triacylglycerols was inhibited against the background of oxidative stress and decreased redox-status of cells. A decrease in the ability of insulin to inhibit isoproterenol-stimulated lipolysis in adipocytes that were isolated from adipose tissue of rats with experimental diabetes was found, which shows a disorder in regulation of lipolysis in adipocytes by the hormone in alloxan-induced diabetes. Based on these findings, we concluded that there is an influence of reactive oxygen species, superoxide anion radical in particular, and redox potential of the glutathione system on molecular mechanisms of change in lipolysis intensity in rat adipocytes in alloxan-induced oxidative stress. Activation of spontaneous lipolysis under conditions of oxidative stress might be a reason for the high concentration of free fatty acids in blood plasma in experimental diabetes, and this may play a significant role in development of insulin resistance and appearance of complications of diabetes.

  12. Germination induction of dormant Avena fatua caryopses by KAR(1) and GA(3) involving the control of reactive oxygen species (H2O2 and O2(·-)) and enzymatic antioxidants (superoxide dismutase and catalase) both in the embryo and the aleurone layers.

    Science.gov (United States)

    Cembrowska-Lech, Danuta; Koprowski, Marek; Kępczyński, Jan

    2015-03-15

    Avena fatua L. caryopses did not germinate at 20 °C in darkness because they were dormant. However, they were able to germinate in the presence of karrikinolide (KAR1), a key bioactive compound present in smoke, and also in the presence of gibberellin A3 (GA3), a commonly known stimulator of seed germination. The aim of this study was to collect information on a possible relationship between the above regulators and abscisic acid (ABA), reactive oxygen species (ROS) and ROS scavenging antioxidants in the regulation of dormant caryopses germination. KAR1 and GA3 caused complete germination of dormant A. fatua caryopses. Hydrogen peroxide (H2O2), compounds generating the superoxide (O2(·-)), i.e. menadione (MN), methylviologen (MV) and an inhibitor of catalase activity, aminotriazole (AT), induced germination of dormant caryopses. KAR1, GA3, H2O2 and AT decreased ABA content in embryos. Furthermore, KAR1, GA3, H2O2, MN, MV and AT increased α-amylase activity in caryopses. The effect of KAR1 and GA3 on ROS (H2O2, O2(·-)) and activities of the superoxide dismutase (SOD) and catalase (CAT) were determined in caryopses, embryos and aleurone layers. SOD was represented by four isoforms and catalase by one. In situ localization of ROS showed that the effect of KAR1 and GA3 was associated with the localization of hydrogen peroxide mainly on the coleorhiza. However, the superoxide was mainly localized on the surface of the scutellum. Superoxide was also detected in the protruding radicle. Germination induction of dormant caryopses by KAR1 and GA3 was related to an increasing content of H2O2, O2(·-)and activities of SOD and CAT in embryos, thus ROS homeostasis was probably required for the germination of dormant caryopses. The above regulators increased the content of ROS in aleurone layers and decreased the activities of SOD and CAT, probably leading to the programmed cell death. The presented data provide new insights into the germination induction of A. fatua dormant

  13. Photochemical degradation of an anionic surfactant by TiO2 nanoparticle doped with C, N in aqueous solution

    Science.gov (United States)

    Zamiri, M.; Giahi, M.

    2016-12-01

    Novel C,N-doped TiO2 nanoparticles were prepared by a solid phase reaction. The catalyst was characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX). The results showed that crystallite size of synthesized C,N-doped TiO2 particles were in nanoscale. UV light photocatalytic studies were carried out using sodium naphthalenesulfonate formaldehyde condensate (SNF) as a model pollutant. The effects of initial concentration of surfactant, catalyst amount, pH, addition of oxidant on the reaction rate were ascertained and optimum conditions for maximum degradation was determined. The results indicated that for a solution of 20 mg/L of SNF, almost 98.7% of the substance were removed at pH 4.0 and 0.44 g/L photocatalyst load, with addition of 1 mM K2S2O8 and irradiation time of 90 min. The kinetics of the process was studied, and the photodegradation rate of SNF was found to obey pseudo-first-order kinetics equation represented by the Langmuir-Hinshelwood model.

  14. Surface diffusion control of the photocatalytic oxidation in air/TiO2 heterogeneous reactors

    CERN Document Server

    Tsekov, R

    2015-01-01

    The diffusion of superoxide radical anions on the surface of TiO2 catalysts is theoretically considered as an important step in the kinetics of photocatalytic oxidation of toxic pollutants. A detailed analysis is performed to discriminate the effects of rotation, anion and adsorption bonds vibrations on the diffusion coefficient. A resonant dependence of the diffusivity on the lattice parameters of the TiO2 surface is discovered showing that the most rapid diffusion takes place when the lattice parameters are twice larger than the bond length of the superoxide radical anions. Whereas the rotation and vibrations normal to the catalyst surface are important, the anion bond vibrations do not affect the diffusivity due to their low amplitudes as compared to the lattice parameters.

  15. N-acetylcysteine downregulates phosphorylated p-38 expression but does not reverse the increased superoxide anion levels in the spinal cord of rats with neuropathic pain.

    Science.gov (United States)

    Horst, A; de Souza, J A; Santos, M C Q; Riffel, A P K; Kolberg, C; Ribeiro, M F M; de Fraga, L S; Partata, W A

    2017-02-16

    We determined the effect of N-acetylcysteine (NAC) on the expression of the phosphorylated p38 (p-p38) protein and superoxide anion generation (SAG), two important players in the processing of neuropathic pain, in the lumbosacral spinal cord of rats with chronic constriction injury (CCI)-induced neuropathic pain. The sciatic functional index (SFI) was also measured to assess the functional recovery post-nerve lesion. Thirty-six male Wistar rats were divided equally into the following groups: Naive (rats did not undergo surgical manipulation); Sham (rats in which all surgical procedures involved in CCI were used except the ligature), and CCI (rats in which four ligatures were tied loosely around the right common sciatic nerve), which received 2, 4, or 8 intraperitoneal injections of NAC (150 mg·kg-1·day-1) or saline beginning 4 h after CCI. Rats were sacrificed 1, 3, and 7 days after CCI. The SFI was measured on these days and the lumbosacral spinal cord was used for analysis of p-p38 expression and SAG. CCI induced a decrease in SFI as well as an increase in p-p38 expression and SAG in the spinal cord. The SFI showed a partial recovery at day 7 in saline-treated CCI rats, but recovery was improved in NAC-treated CCI rats. NAC induced a downregulation in p-p38 expression at all time-points evaluated, but did not reverse the increased SAG induced by CCI. Since p-p38 is a mediator in neuropathic pain and/or nerve regeneration, modulation of this protein may play a role in NAC-induced effects in CCI rats.

  16. Inhibition of glutamate receptors reduces the homocysteine-induced whole blood platelet aggregation but does not affect superoxide anion generation or platelet membrane fluidization.

    Science.gov (United States)

    Karolczak, Kamil; Pieniazek, Anna; Watala, Cezary

    2017-01-01

    Homocysteine (Hcy) is an excitotoxic amino acid. It is potentially possible to prevent Hcy-induced toxicity, including haemostatic impairments, by antagonizing glutaminergic receptors. Using impedance aggregometry with arachidonate and collagen as platelet agonists, we tested whether the blockade of platelet NMDA (N-methyl-D-aspartate), AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) and kainate receptors with their inhibitors: MK-801 (dizocilpine hydrogen maleate, [5R,10S]-[+]-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine), CNQX (7-nitro-2,3-dioxo-1,4-dihydroquinoxaline-6-carbonitrile) and UBP-302 (2-{[3-[(2S)-2-amino-2-carboxyethyl]-2,6-dioxo-3,6-dihydropyrimidin 1(2H)-yl]methyl}benzoic acid) may hamper Hcy-dependent platelet aggregation. All the tested compounds significantly inhibited Hcy-augmented aggregation of blood platelets stimulated either with arachidonate or collagen. Hcy stimulated the generation of superoxide anion in whole blood samples in a concentration-dependent manner; however, this process appeared as independent on ionotropic glutamate receptors, as well as on NADPH oxidase and protein kinase C, and was not apparently associated with the extent of either arachidonate- or collagen-dependent platelet aggregation. Moreover, Hcy acted as a significant fluidizer of surface (more hydrophilic) and inner (more hydrophobic) regions of platelet membrane lipid bilayer, when used at the concentration range from 10 to 50 µmol/l. However, this effect was independent on the Hcy action through glutamate ionotropic receptors, since there was no effects of MK-801, CNQX or UBP-302 on Hcy-mediated membrane fluidization. In conclusion, Hcy-induced changes in whole blood platelet aggregation are mediated through the ionotopic excitotoxic receptors, although the detailed mechanisms underlying such interactions remain to be elucidated.

  17. Acute ethanol intake induces superoxide anion generation and mitogen-activated protein kinase phosphorylation in rat aorta: A role for angiotensin type 1 receptor

    Energy Technology Data Exchange (ETDEWEB)

    Yogi, Alvaro; Callera, Glaucia E. [Kidney Research Centre, Ottawa Hospital Research Institute, University of Ottawa, Ontario (Canada); Mecawi, André S. [Department of Physiology, Faculty of Medicine of Ribeirão Preto, University of São Paulo (USP), Ribeirão Preto, SP (Brazil); Batalhão, Marcelo E.; Carnio, Evelin C. [Department of General and Specialized Nursing, College of Nursing of Ribeirão Preto, USP, São Paulo (Brazil); Antunes-Rodrigues, José [Department of Physiology, Faculty of Medicine of Ribeirão Preto, University of São Paulo (USP), Ribeirão Preto, SP (Brazil); Queiroz, Regina H. [Department of Clinical, Toxicological and Food Science Analysis, Faculty of Pharmaceutical Sciences, USP, São Paulo (Brazil); Touyz, Rhian M. [Kidney Research Centre, Ottawa Hospital Research Institute, University of Ottawa, Ontario (Canada); Tirapelli, Carlos R., E-mail: crtirapelli@eerp.usp.br [Department of Psychiatric Nursing and Human Sciences, Laboratory of Pharmacology, College of Nursing of Ribeirão Preto, USP, Ribeirão Preto, SP (Brazil)

    2012-11-01

    Ethanol intake is associated with increase in blood pressure, through unknown mechanisms. We hypothesized that acute ethanol intake enhances vascular oxidative stress and induces vascular dysfunction through renin–angiotensin system (RAS) activation. Ethanol (1 g/kg; p.o. gavage) effects were assessed within 30 min in male Wistar rats. The transient decrease in blood pressure induced by ethanol was not affected by the previous administration of losartan (10 mg/kg; p.o. gavage), a selective AT{sub 1} receptor antagonist. Acute ethanol intake increased plasma renin activity (PRA), angiotensin converting enzyme (ACE) activity, plasma angiotensin I (ANG I) and angiotensin II (ANG II) levels. Ethanol induced systemic and vascular oxidative stress, evidenced by increased plasma thiobarbituric acid-reacting substances (TBARS) levels, NAD(P)H oxidase‐mediated vascular generation of superoxide anion and p47phox translocation (cytosol to membrane). These effects were prevented by losartan. Isolated aortas from ethanol-treated rats displayed increased p38MAPK and SAPK/JNK phosphorylation. Losartan inhibited ethanol-induced increase in the phosphorylation of these kinases. Ethanol intake decreased acetylcholine-induced relaxation and increased phenylephrine-induced contraction in endothelium-intact aortas. Ethanol significantly decreased plasma and aortic nitrate levels. These changes in vascular reactivity and in the end product of endogenous nitric oxide metabolism were not affected by losartan. Our study provides novel evidence that acute ethanol intake stimulates RAS activity and induces vascular oxidative stress and redox-signaling activation through AT{sub 1}-dependent mechanisms. These findings highlight the importance of RAS in acute ethanol-induced oxidative damage. -- Highlights: ► Acute ethanol intake stimulates RAS activity and vascular oxidative stress. ► RAS plays a role in acute ethanol-induced oxidative damage via AT{sub 1} receptor activation.

  18. Oxidation of Hantzsch 1,4-dihydropyridines of pharmacological significance by electrogenerated superoxide.

    Science.gov (United States)

    Ortiz, M E; Núñez-Vergara, L J; Camargo, C; Squella, J A

    2004-03-01

    To study the reaction of a series of Hantzsch dihydropyridines with pharmacological significance such as, nifedipine, nitrendipine, nisoldipine, nimodipine, isradipine and felodipine, with electrogenerated superoxide in order to identify products and postulate a mechanism. The final pyridine derivatives were separated and identified by gas chromatography/mass spectrometry (GC-MS). The intermediates, anion dihydropyridine and the HO2*/HO2- species, were observed from voltammetric studies and controlled potential electrolysis was used to electrogenerate O2*-. The current work reveals that electrogenerated superoxide can quantitatively oxidize Hantzsch dihydropyridines to produce the corresponding aromatized pyridine derivatives. Our results indicate that the aromatization of Hantzsch dihydropyridines by superoxide is initiated by proton transfer from the N1-position on the 1,4-dihydropyridine ring to give the corresponding anion dihydropyridine, which readily undergoes further homogeneous oxidations to provide the final aromatized products. The oxidation of the anionic species of the dihydropyridine is more easily oxidized than the parent compound.

  19. Extracellular production and degradation of superoxide in the coral Stylophora pistillata and cultured Symbiodinium.

    Directory of Open Access Journals (Sweden)

    Eldad Saragosti

    Full Text Available BACKGROUND: Reactive oxygen species (ROS are thought to play a major role in cell death pathways and bleaching in scleractinian corals. Direct measurements of ROS in corals are conspicuously in short supply, partly due to inherent problems with ROS quantification in cellular systems. METHODOLOGY/PRINCIPAL FINDINGS: In this study we characterized the dynamics of the reactive oxygen species superoxide anion radical (O(2(- in the external milieu of the coral Stylophora pistillata. Using a sensitive, rapid and selective chemiluminescence-based technique, we measured extracellular superoxide production and detoxification activity of symbiont (non-bleached and aposymbiont (bleached corals, and of cultured Symbiodinium (from clades A and C. Bleached and non-bleached Stylophora fragments were found to produce superoxide at comparable rates of 10(-11-10(-9 mol O(2(- mg protein(-1 min(-1 in the dark. In the light, a two-fold enhancement in O(2(- production rates was observed in non-bleached corals, but not in bleached corals. Cultured Symbiodinium produced superoxide in the dark at a rate of . Light was found to markedly enhance O(2(- production. The NADPH Oxidase inhibitor Diphenyleneiodonium chloride (DPI strongly inhibited O(2(- production by corals (and more moderately by algae, possibly suggesting an involvement of NADPH Oxidase in the process. An extracellular O(2(- detoxifying activity was found for bleached and non-bleached Stylophora but not for Symbiodinium. The O(2(- detoxifying activity was partially characterized and found to resemble that of the enzyme superoxide dismutase (SOD. CONCLUSIONS/SIGNIFICANCE: The findings of substantial extracellular O(2(- production as well as extracellular O(2(- detoxifying activity may shed light on the chemical interactions between the symbiont and its host and between the coral and its environment. Superoxide production by Symbiodinium possibly implies that algal bearing corals are more susceptible to an

  20. Photoelectron spectroscopy of higher bromine and iodine oxide anions: electron affinities and electronic structures of BrO(2,3) and IO(2-4) radicals.

    Science.gov (United States)

    Wen, Hui; Hou, Gao-Lei; Huang, Wei; Govind, Niranjan; Wang, Xue-Bin

    2011-11-14

    This report details a photoelectron spectroscopy (PES) and theoretical investigation of electron affinities (EAs) and electronic structures of several atmospherically relevant higher bromine and iodine oxide molecules in the gas phase. PES spectra of BrO(2)(-) and IO(2)(-) were recorded at 12 K and four photon energies--355 nm/3.496 eV, 266 nm/4.661 eV, 193 nm/6.424 eV, and 157 nm/7.867 eV--while BrO(3)(-), IO(3)(-), and IO(4)(-) were only studied at 193 and 157 nm due to their expected high electron binding energies. Spectral features corresponding to transitions from the anionic ground state to the ground and excited states of the neutral are unraveled and resolved for each species. The EAs of these bromine and iodine oxides are experimentally determined for the first time (except for IO(2)) to be 2.515 ± 0.010 (BrO(2)), 2.575 ± 0.010 (IO(2)), 4.60 ± 0.05 (BrO(3)), 4.70 ± 0.05 (IO(3)), and 6.05 ± 0.05 eV (IO(4)). Three low-lying excited states along with their respective excitation energies are obtained for BrO(2) [1.69 (A (2)B(2)), 1.79 (B (2)A(1)), 1.99 eV (C (2)A(2))], BrO(3) [0.7 (A (2)A(2)), 1.6 (B (2)E), 3.1 eV (C (2)E)], and IO(3) [0.60 (A (2)A(2)), 1.20 (B (2)E), ∼3.0 eV (C (2)E)], whereas six excited states of IO(2) are determined along with their respective excitation energies of 1.63 (A (2)B(2)), 1.73 (B (2)A(1)), 1.83 (C (2)A(2)), 4.23 (D (2)A(1)), 4.63 (E (2)B(2)), and 5.23 eV (F (2)B(1)). Periodate (IO(4)(-)) possesses a very high electron binding energy. Only one excited state feature with 0.95 eV excitation energy is shown in the 157 nm spectrum. Accompanying theoretical calculations reveal structural changes from the anions to the neutrals, and the calculated EAs are in good agreement with experimentally determined values. Franck-Condon factors simulations nicely reproduce the observed vibrational progressions for BrO(2) and IO(2). The low-lying excited state information is compared with theoretical calculations and discussed with their

  1. A Pd/C-CeO2 Anode Catalyst for High-Performance Platinum-Free Anion Exchange Membrane Fuel Cells.

    Science.gov (United States)

    Miller, Hamish A; Lavacchi, Alessandro; Vizza, Francesco; Marelli, Marcello; Di Benedetto, Francesco; D'Acapito, Francesco; Paska, Yair; Page, Miles; Dekel, Dario R

    2016-05-10

    One of the biggest obstacles to the dissemination of fuel cells is their cost, a large part of which is due to platinum (Pt) electrocatalysts. Complete removal of Pt is a difficult if not impossible task for proton exchange membrane fuel cells (PEM-FCs). The anion exchange membrane fuel cell (AEM-FC) has long been proposed as a solution as non-Pt metals may be employed. Despite this, few examples of Pt-free AEM-FCs have been demonstrated with modest power output. The main obstacle preventing the realization of a high power density Pt-free AEM-FC is sluggish hydrogen oxidation (HOR) kinetics of the anode catalyst. Here we describe a Pt-free AEM-FC that employs a mixed carbon-CeO2 supported palladium (Pd) anode catalyst that exhibits enhanced kinetics for the HOR. AEM-FC tests run on dry H2 and pure air show peak power densities of more than 500 mW cm(-2) .

  2. Vibrio vulnificus MO6-24/O lipopolysaccharide stimulates superoxide anion, thromboxane B₂, matrix metalloproteinase-9, cytokine and chemokine release by rat brain microglia in vitro.

    Science.gov (United States)

    Mayer, Alejandro M S; Hall, Mary L; Holland, Michael; De Castro, Cristina; Molinaro, Antonio; Aldulescu, Monica; Frenkel, Jeffrey; Ottenhoff, Lauren; Rowley, David; Powell, Jan

    2014-03-26

    Although human exposure to Gram-negative Vibrio vulnificus (V. vulnificus) lipopolysaccharide (LPS) has been reported to result in septic shock, its impact on the central nervous system's innate immunity remains undetermined. The purpose of this study was to determine whether V. vulnificus MO6-24/O LPS might activate rat microglia in vitro and stimulate the release of superoxide anion (O₂⁻), a reactive oxygen species known to cause oxidative stress and neuronal injury in vivo. Brain microglia were isolated from neonatal rats, and then treated with either V. vulnificus MO6-24/O LPS or Escherichia coli O26:B6 LPS for 17 hours in vitro. O₂⁻ was determined by cytochrome C reduction, and matrix metalloproteinase-2 (MMP-2) and MMP-9 by gelatinase zymography. Generation of cytokines tumor necrosis factor alpha (TNF-α), interleukin-1 alpha (IL-1α), IL-6, and transforming growth factor-beta 1 (TGF-β1), chemokines macrophage inflammatory protein (MIP-1α)/chemokine (C-C motif) ligand 3 (CCL3), MIP-2/chemokine (C-X-C motif) ligand 2 (CXCL2), monocyte chemotactic protein-1 (MCP-1)/CCL2, and cytokine-induced neutrophil chemoattractant-2alpha/beta (CINC-2α/β)/CXCL3, and brain-derived neurotrophic factor (BDNF), were determined by specific immunoassays. Priming of rat microglia by V. vulnificus MO6-24/O LPS in vitro yielded a bell-shaped dose-response curve for PMA (phorbol 12-myristate 13-acetate)-stimulated O₂⁻ generation: (1) 0.1-1 ng/mL V. vulnificus LPS enhanced O₂⁻ generation significantly but with limited inflammatory mediator generation; (2) 10-100 ng/mL V. vulnificus LPS maximized O₂⁻ generation with concomitant release of thromboxane B2 (TXB2), matrix metalloproteinase-9 (MMP-9), and several cytokines and chemokines; (3) 1000-100,000 ng/mL V. vulnificus LPS, with the exception of TXB2, yielded both attenuated O₂⁻ production, and a progressive decrease in MMP-9, cytokines and chemokines investigated. Thus concentration-dependent treatment of

  3. Screened coulomb hybrid DFT study on electronic structure and optical properties of anionic and cationic Te-doped anatase TiO2

    KAUST Repository

    Harb, Moussab

    2013-06-27

    The origin of the enhanced visible-light optical absorption in Te-doped bulk anatase TiO2 is investigated in the framework of DFT and DFPT within HSE06 in order to ensure accurate electronic structure and optical transition predictions. Various oxidation states of Te species are considered based on their structural location in bulk TiO2. In fact, TiO (2-x)Tex (with isolated Te2- species at Te-Te distance of 8.28 Å), TiO2Tex (with isolated TeO 2- species at Te-Te distance of 8.28 Å), TiO2Te 2x (with two concomitant TeO2- species at Te-Te distance of 4.11 Å), and Ti(1-2x)O2Te2x (with two neighboring Te4+ species at nearest-neighbor Te-Te distance of 3.05 Å) show improved optical absorption responses in the visible range similarly as it is experimentally observed in Te-doped TiO2 powders. The optical absorption edges of TiO(2-x)Tex, TiO 2Tex, and TiO2Te2x are found to be red-shifted by 400 nm compared with undoped TiO2 whereas that of Ti(1-2x)O2Te2x is red-shifted by 150 nm. On the basis of calculated valence and conduction band edge positions of Te-doped TiO2, only TiO(2-x)Tex and Ti (1-2x)O2Te2x show suitable potentials for overall water splitting under visible-light irradiation. The electronic structure analysis revealed narrower band gaps of 1.12 and 1.17 eV with respect to undoped TiO2, respectively, resulting from the appearance of new occupied electronic states in the gap of TiO2. A delocalized nature of the gap states is found to be much more pronounced in TiO (2-x)Tex than that with Ti(1-2x)O 2Te2x due to the important contribution of numerous O 2p orbitals together with Te 5p orbitals. © 2013 American Chemical Society.

  4. Improved Osteoblast and Chondrocyte Adhesion and Viability by Surface-Modified Ti6Al4V Alloy with Anodized TiO2 Nanotubes Using a Super-Oxidative Solution

    Directory of Open Access Journals (Sweden)

    Ernesto Beltrán-Partida

    2015-03-01

    Full Text Available Titanium (Ti and its alloys are amongst the most commonly-used biomaterials in orthopedic and dental applications. The Ti-aluminum-vanadium alloy (Ti6Al4V is widely used as a biomaterial for these applications by virtue of its favorable properties, such as high tensile strength, good biocompatibility and excellent corrosion resistance. TiO2 nanotube (NTs layers formed by anodization on Ti6Al4V alloy have been shown to improve osteoblast adhesion and function when compared to non-anodized material. In his study, NTs were grown on a Ti6Al4V alloy by anodic oxidation for 5 min using a super-oxidative aqueous solution, and their in vitro biocompatibility was investigated in pig periosteal osteoblasts and cartilage chondrocytes. Scanning electron microscopy (SEM, energy dispersion X-ray analysis (EDX and atomic force microscopy (AFM were used to characterize the materials. Cell morphology was analyzed by SEM and AFM. Cell viability was examined by fluorescence microscopy. Cell adhesion was evaluated by nuclei staining and cell number quantification by fluorescence microscopy. The average diameter of the NTs was 80 nm. The results demonstrate improved cell adhesion and viability at Day 1 and Day 3 of cell growth on the nanostructured material as compared to the non-anodized alloy. In conclusion, this study evidences the suitability of NTs grown on Ti6Al4V alloy using a super-oxidative water and a short anodization process to enhance the adhesion and viability of osteoblasts and chondrocytes. The results warrant further investigation for its use as medical implant materials.

  5. Interactions with ATP, DNA Cleavage and Anti-tumor Activities of Complexes with Anions [Mo(V)O2O2CeH4)2]3-, [Mo(Ⅴ)0.5W(Ⅵ)0.5O2O2C6H4)2]2.5- and [W(Ⅵ)O2O2C6H4)2]2-

    Institute of Scientific and Technical Information of China (English)

    鲁晓明; 姜凌; 毛希安; 叶朝晖; 卢景芬; 崔景荣

    2005-01-01

    (NH3CH2CH2NH2)3[Mo(Ⅴ)O2(O2C6H4)2] (1), (NH3CH2CH2NH2)2.5[Mo(Ⅴ)o.sW(Ⅵ)o.502(O2C6H4)2] (2) and(NH3CH2CH2NH2)2[VC(Ⅵ)O2(O2C6H4)2] (3) were synthesized, structurally characterized by X-ray diffraction analysis, and studied on their interactions with ATP, their DNA cleavage activities and antitumor properties. The redox state of molybdenum was not changed on going from crystal to aqueous solutions in complexes 1 and 2, while tungsten underwent reduction from W(VI) to W(V) in complexes 2 and 3. ATP promoted the oxidation of both molybdenum and tungsten from M(Ⅴ) to M(Ⅵ) and the hydrolysis of catecholate ligands in solution consisting of ATP and the complexes. Complex 1 possesses fairly good activity to DNA cleavage and against tumor S180 in mice, and is more effective than the control drug cyclophosphamide under the identical conditions. However, complexes 2 and 3 exhibited marginal effectiveness. The effectiveness of anti-tumor of the complexes was related positively to their DNA cleavage activities and their hydrolysis of catecholate ligands.

  6. Anion-π, lone pair-π and π-π interactions in VO(O2)+ complexes with one dipicolinato(2-)-N,O,O ligand and bearing picolinamidium, nicotinamidium or phenanthrolinium as counterions

    Science.gov (United States)

    Gyepes, Róbert; Pacigová, Silvia; Tatiersky, Jozef; Sivák, Michal

    2013-06-01

    From the V2O5sbnd H2O2sbnd H2dipic-nica/pa/phen-H2O/H2Osbnd CH3CN reaction systems (H2dipic = dipicolinic acid, nica = nicotinamide, pa = picolinamide, phen = 1,10-phenanthroline), three monoperoxidovanadium(V) complexes have been synthesized and structurally characterized: (Hpa)[VO(O2)(dipic)(H2O)]ṡH2O (1), (Hnica)[VO(O2)(dipic)(H2O)] (2) and (Hphen)[VO(O2)(dipic)(H2O)]ṡH2O (3). The organic counterions in 1-3 are protonated on the aromatic nitrogen atoms, whereas the dipicolinato(2-) (=dipic) ligand adopts a tridentate chelating coordination mode in all three complexes. The NOO donor atoms of dipic occupy the three equatorial positions of the characteristic distorted pentagonal bipyramid around the central vanadium atom. The aqua ligand is located in the apical position trans to the short Vtbnd O(oxido) bond. In addition to electrostatic cation-anion interactions, the supramolecular architecture of the title complexes is formed by: (i) a network of Dsbnd H⋯O (D = N, O and C) hydrogen bonds, (ii) π-π interactions between offset pyridine rings of dipic (in 1 and 2) as well as between the rings of Hpa+, Hnica+ or Hphen+, (iii) anion-π interactions (in 1 and 3) between the oxygen atoms of the COO- group and rings of the dipic ligands, and (iv) the rarely recognized lone pair-π interaction between the carboxamide oxygen atoms of Hpa+ and pyridine rings in 1, as well as between the oxygen atoms from crystal water molecules and the pyridine rings of Hphen+ in 3. The anion-π and lone pair-π interactions were studied more in detail by DFT. A common feature for both these interactions was the lack of significant covalent contributions to the attraction between the respective partners. 51V NMR spectra of the acidic aqueous solutions of 1-3 showed that the structure of the complex anion is for 2 and 3 maintained even after dissolution (single shift δV = -597 ppm), whereas 1 partially decomposes with formation of monoperoxidovanadium(V) species: [VO(O2)(H2O

  7. Superoxide anions are involved in mediating the effect of low K intake on c-Src expression and renal K secretion in the cortical collecting duct.

    Science.gov (United States)

    Babilonia, Elisa; Wei, Yuan; Sterling, Hyacinth; Kaminski, Pawel; Wolin, Michael; Wang, Wen-Hui

    2005-03-18

    We previously demonstrated that low K intake stimulated the expression of c-Src and that stimulation of protein tyrosine kinase inhibited ROMK channel activity (Wei, Y., Bloom, P., Lin, D. H., Gu, R. M., and Wang, W. H. (2001) Am. J. Physiol. 281, F206-F212). Decreases in dietary K content significantly increased O(2)(-) levels and the phosphorylation of c-Jun, a transcription factor, in renal cortex and outer medulla. The role of O(2)(-) and related products such as H(2)O(2) in stimulating the expression of protein tyrosine kinase is suggested by the observation that addition of 50-200 microm H(2)O(2) increased the phosphorylation of c-Jun and the expression of c-Src in M1 cells, a mouse collecting duct principal cell line. The effect of H(2)O(2) on c-Src expression was completely abolished with cyclohexamide or actinomycin D. The treatment of animals on a K-deficient (KD) diet with tempol for 7 days significantly decreased the production of O(2)(-), c-Jun phosphorylation, and c-Src expression. Moreover, low K intake decreased the activity of ROMK-like small conductance channels from 1.37 (control K diet) to 0.5 in the cortical collecting duct and increased the tyrosine phosphorylation of ROMK in the renal cortex and outer medulla. In contrast, the tempol treatment not only increased channel activity to 1.1 in the cortical collecting duct but also decreased the tyrosine phosphorylation of ROMK from rats on a KD diet. Finally, suppressing O(2)(-) production with tempol significantly increased renal K excretion measured with metabolic cage and lowered the plasma K concentration in comparison with those on a KD diet alone without tempol. We conclude that O(2)(-) and related products play a role in mediating the effect of low K intake on c-Src expression and in suppressing ROMK channel activity and renal K secretion.

  8. Ab initio studies of O2-(H2O)n and O3-(H2O)n anionic molecular clusters, n≤12

    DEFF Research Database (Denmark)

    Bork, Nicolai Christian; Kurtén, T.; Enghoff, Martin Andreas Bødker

    2011-01-01

    An ab initio study of gaseous clusters of O2− and O2− with water is presented. Based on thorough scans of configurational space, we determine the thermodynamics of cluster growth. The results are in good agreement with benchmark computational methods and existing experimental data. We find...

  9. Superoxide Anions Are Involved in Mediating the Effect of Low K Intake on c-Src Expression and Renal K Secretion in the Cortical Collecting Duct*

    Science.gov (United States)

    Babilonia, Elisa; Wei, Yuan; Sterling, Hyacinth; Kaminski, Pawel; Wolin, Michael; Wang, Wen-Hui

    2010-01-01

    We previously demonstrated that low K intake stimulated the expression of c-Src and that stimulation of protein tyrosine kinase inhibited ROMK channel activity (Wei, Y., Bloom, P., Lin, D. H., Gu, R. M., and Wang, W. H. (2001) Am. J. Physiol. 281, F206–F212). Decreases in dietary K content significantly increased O2·¯ levels and the phosphorylation of c-Jun, a transcription factor, in renal cortex and outer medulla. The role of O2·¯ and related products such as H2O2 in stimulating the expression of protein tyrosine kinase is suggested by the observation that addition of 50–200 µM H2O2 increased the phosphorylation of c-Jun and the expression of c-Src in M1 cells, a mouse collecting duct principal cell line. The effect of H2O2 on c-Src expression was completely abolished with cyclohexamide or actinomycin D. The treatment of animals on a K-deficient (KD) diet with tempol for 7 days significantly decreased the production of O2·¯, c-Jun phosphorylation, and c-Src expression. Moreover, low K intake decreased the activity of ROMK-like small conductance channels from 1.37 (control K diet) to 0.5 in the cortical collecting duct and increased the tyrosine phosphorylation of ROMK in the renal cortex and outer medulla. In contrast, the tempol treatment not only increased channel activity to 1.1 in the cortical collecting duct but also decreased the tyrosine phosphorylation of ROMK from rats on a KD diet. Finally, suppressing O2·¯ production with tempol significantly increased renal K excretion measured with metabolic cage and lowered the plasma K concentration in comparison with those on a KD diet alone without tempol. We conclude that O2·¯ and related products play a role in mediating the effect of low K intake on c-Src expression and in suppressing ROMK channel activity and renal K secretion. PMID:15644319

  10. Literature Review of Research and Application on Superoxide Dismutase%超氧化物歧化酶研究与应用

    Institute of Scientific and Technical Information of China (English)

    张俊艳; 贺阳

    2012-01-01

    Superoxide dismutase is a specific metalloproteinase to clear the superoxide anion radical (O2^**). It could catalyze the disproportionation of superoxide anion radical O2^**- to clear the O2^.**, and it have anti- inflammatory, anti-virus, anti-radiation, anti-aging effect. The source and distribution, purification methods, chemical modification, activity determination and application of the SOD on the article were reviewed, and its production problems and application prospect were analyzed.%超氧化物歧化酶(superoxide dismutase SOD)是一种专一清除超氧阴离子自由基(O2.-)的金属蛋白酶,催化超氧阴离子自由基O2.-发生歧化反应,从而清除O2.-,具有抗炎,抗病毒,抗辐射,抗衰老等作用。对SOD的来源分布、提纯方法、化学修饰、活性测定和生产应用等方面进行了综述,并对其生产问题以及应用前景进行了分析。

  11. Ferric and cupric ions requirement for DNA single-strand breakage by H2O2.

    Science.gov (United States)

    Tachon, P

    1989-01-01

    Hydrogen peroxide (H2O2), was able to nick the replicative form of the phage fd, without the addition of a reducing agent or of a metal. This DNA single-strand breakage decreased with an increase of the ionic strength, suggesting that H2O2 reacted with traces of metal bound to DNA. When cupric of ferric ions were added, the rate of DNA single-strand breakage by H2O2 greatly increased and it was 20-30 times faster with cupric than with ferric ions. The addition of EDTA at an equimolar ratio or in excess of metal prevented partially DNA single-strand cleavage by H2O2 in the presence of ferric ions and completely when cupric ions were used. Superoxide dismutase prevented DNA single-strand breakage by H2O2 and ferric ions. On the contrary, with cupric ions and H2O2, the addition of superoxide dismutase increased the rate of DNA single-strand breakage. That superoxide dismutase was acting catalytically was shown by the loss of its effects after heat inactivation of the enzyme. The results of the present study show that besides its involvement in the Fenton reaction, H2O2 is able to reduce the metal bound to DNA, generating the superoxide anion radical or/and its protonated form, the perhydroxyl radical involved in DNA nicking. On the other hand, the ability of cuprous ions unlike ferrous ions to dismutate the superoxide radical may explain some differences observed between iron and copper in the DNA single-strand breakage by H2O2.

  12. Adsorption and reactions of O2 on anatase TiO2.

    Science.gov (United States)

    Li, Ye-Fei; Aschauer, Ulrich; Chen, Jia; Selloni, Annabella

    2014-11-18

    CONSPECTUS: The interaction of molecular oxygen with titanium dioxide (TiO2) surfaces plays a key role in many technologically important processes such as catalytic oxidation reactions, chemical sensing, and photocatalysis. While O2 interacts weakly with fully oxidized TiO2, excess electrons are often present in TiO2 samples. These excess electrons originate from intrinsic reducing defects (oxygen vacancies and titanium interstitials), doping, or photoexcitation and form polaronic Ti(3+) states in the band gap near the bottom of the conduction band. Oxygen adsorption involves the transfer of one or more of these excess electrons to an O2 molecule at the TiO2 surface. This results in an adsorbed superoxo (O2(-)) or peroxo (O2(2-)) species or in molecular dissociation and formation of two oxygen adatoms (2 × O(2-)). Oxygen adsorption is also the first step toward oxygen incorporation, a fundamental reaction that strongly affects the chemical properties and charge-carrier densities; for instance, it can transform the material from an n-type semiconductor to a poor electronic conductor. In this Account, we present an overview of recent theoretical work on O2 adsorption and reactions on the reduced anatase (101) surface. Anatase is the TiO2 polymorph that is generally considered most active in photocatalysis. Experiments on anatase powders have shown that the properties of photoexcited electrons are similar to those of excess electrons from reducing defects, and therefore, oxygen on reduced anatase is also a model system for studying the role of O2 in photocatalysis. Experimentally, the characteristic Ti(3+) defect states disappear after adsorption of molecular oxygen, which indicates that the excess electrons are indeed trapped by O2. Moreover, superoxide surface species associated with two different cation surface sites, possibly a regular cation site and a cation close to an anion vacancy, were identified by electron paramagnetic resonance spectroscopy. On the

  13. Control of superoxide and nitric oxide formation during human sperm capacitation.

    Science.gov (United States)

    de Lamirande, Eve; Lamothe, Geneviève; Villemure, Michèle

    2009-05-15

    We studied the modulation of superoxide anion (O(2).(-)) and nitric oxide (NO.) generation during human sperm capacitation (changes needed for the acquisition of fertility). The production of NO. (diaminofluorescein-2 fluorescence assay), but not that of O(2).(-) (luminescence assay), related to sperm capacitation was blocked by inhibitors of protein kinase C, Akt, protein tyrosine kinase, etc., but not by those of protein kinase A. Extracellular calcium (Ca(2+)) controlled O(2).(-) synthesis but extra- and intracellular Ca(2+) regulated NO. formation. Zinc inhibited capacitation and formation of O(2).(-) and NO.. Zinc chelators (TPEN and EDTA) and sulfhydryl-targeted compounds (diamide and N-ethylmaleimide) stimulated capacitation and formation of O(2).(-) and NO.; superoxide dismutase (SOD) and nitric oxide synthase inhibitor (L-NMMA) prevented these events. Diphenyliodonium (flavoenzyme inhibitor) blocked capacitation and related O(2).(-) synthesis but promoted NO. formation, an effect canceled by SOD and L-NMMA. NADPH induced capacitation and NO. (but not O(2).(-)) synthesis and these events were blocked by L-NMMA and not by SOD. Integration of these data on O(2).(-) and NO. production during capacitation reinforces the concept that a complex, but flexible, network of factors is involved and probably is associated with rescue mechanisms, so that spermatozoa can achieve successful fertilization.

  14. Effects of superoxide generating systems on muscle tone, cholinergic and NANC responses in cat airway.

    Science.gov (United States)

    Bauer, V; Nakajima, T; Pucovsky, V; Onoue, H; Ito, Y

    2000-02-14

    To study the possible role of reactive oxygen species in airway hyperreactivity, we examined the effects of the superoxide anion radical (O(2)(-)) generating systems, pyrogallol and xanthine with xanthine oxidase, on muscle tone, excitatory and inhibitory neurotransmission in the cat airway. Smooth muscle contraction or non-adrenergic non-cholinergic (NANC) relaxation evoked by electrical field stimulation (EFS) were measured before or after O(2)(-) generating systems with or without diethydithiocarbamic acid (DEDTCA), an inhibitor of endogenous superoxide dismutase (SOD). Resting membrane potential or excitatory junction potential (EJP) were also measured in vitro. Both pyrogallol and xanthine/xanthine oxidase produced biphasic changes in basal and elevated (by 5-HT) muscle tone. After SOD pretreatment, both systems consistently produced a prolonged contraction, thereby indicating that O(2)(-) was converted to H(2)O(2) by the action of SOD and as a result the actions of O(2)(-) were lost but those of H(2)O(2) introduced. The O(2)(-) showed no significant effect on smooth muscle contraction or EJP evoked by EFS, however after DEDTCA pretreatment, it evoked initial enhancement followed by suppression of the contraction and EJP. DEDTCA pretreatment ameliorated the inhibitory action of pyrogallol and xanthine/xanthine oxidase on the NANC relaxation, probably because O(2)(-) could combine with endogenous NO to form peroxynitrite. These results indicate that the O(2)(-) generating systems have multiple actions, presumably due to the presence and simultaneous action of at least two different reactive oxygen species (O(2)(-) and H(2)O(2)). While H(2)O(2) seems to be responsible for elevation of muscle tone and augmentation of smooth muscle contraction by EFS, O(2)(-) inhibits muscle tone, cholinergic and NANC neurotransmission.

  15. One pot synthesis of nanosized anion doped TiO2: Effect of irradiation of sound waves on surface morphology and optical properties

    Science.gov (United States)

    Sharotri, Nidhi; Sud, Dhiraj

    2015-08-01

    Commercialization of AOP's for remediation of pollutants from environmental matrix required the process to be operated by solar light. Semiconductor TiO2 has emerged as an effective and preferred photocatalyst in the field of environmental photocatalysis due to its; (i) biological and chemical inertness (ii) resistance to chemical and photo corrosion, (iii) can absorb natural UV light due to appropriate energetic separation between its valence and conduction band. However, unfortunately the optical band gap of TiO2 (3.0-3.23 eV) with absorption cut off ˜ 380 nm, enables it to harness only a small fraction (˜ 5%) of the entire solar spectrum. One of the current areas of research is modification of TiO2 photocatalyst. In present paper one pot greener synthesis from titanium isopropoxide and hydroxylamine hydrochloride has been used as titanium and nitrogen precursor under ultrasonic waves. The as synthesized TiO2 nanomaterials were dried at 100°C and further calcinated at different temperatures. The effect of reaction parameters such as ultrasonication time on the yield, surface morphology, spectroscopic data and optical properties was also investigated. The results confirm that the anatase phase is a main phase with a crystallite size of 35-77 nm and the calculated band gap of nanomaterials varies from 2.10-3.1 eV.

  16. Assembly of thiometalate-based {Mo16 } and {Mo36 } composite clusters combining [Mo2O2S2 ](2+) cations and selenite anions.

    Science.gov (United States)

    Zang, Hong-Ying; Chen, Jia-Jia; Long, De-Liang; Cronin, Leroy; Miras, Haralampos N

    2013-11-20

    A new family of thiometalate-based composite molecular materials is synthesized and characterized. 1.6 and 1.9 nm-sized clusters are observed in the gas phase utilizing high-resolution ESI-MS. The diversity of the selenite anions as an inorganic ligand is demonstrated by the isolation of the highest nuclearity selenium-based oxothiometalate materials reported so far. The observed proton conductivity of the selenite based oxothiometalate species renders them as promising alternative materials for fuel-cell applications. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Photophysical Properties of SrTaO2N Thin Films and Influence of Anion Ordering: A Joint Theoretical and Experimental Investigation

    KAUST Repository

    Ziani, Ahmed

    2017-04-10

    Converting photon energy into chemical energy using inorganic materials requires the successful capture of photons, exciton dissociation, and the charge carrier diffusion. This study reports a thorough analysis of the optoelectronic properties of visible-light-responsive SrTaON perovskites to quantify their absorption coefficient and the generated charge carriers\\' effective masses, dielectric constants, and electronic structures. The measurements on such intrinsic properties were attempted using both epitaxial and polycrystalline SrTaON films deposited by radiofrequency magnetron sputtering under N reactive plasma. Density functional theory calculations using the HSE06 functional provided reliable values of these optoelectronic properties. Such quantities obtained by both measurements and calculations gave excellent correspondence and provide possible variations that account for the small discrepancies observed. One of the significant factors determining the optical properties was found to be the anion ordering in the perovskite structure imposed by the cations. As a result, the different anion ordering has a noticeable influence on the optical properties and high sensitivity of the hole effective mass. Determination of relative band positions with respect to the water redox properties was also attempted by Mott-Schottky analysis. All these results offer the opportunity to understand why SrTaON possesses intrinsically all the ingredients needed for an efficient water splitting device.

  18. Microglial cells (BV-2) internalize titanium dioxide (TiO2) nanoparticles: toxicity and cellular responses.

    Science.gov (United States)

    Rihane, Naima; Nury, Thomas; M'rad, Imen; El Mir, Lassaad; Sakly, Mohsen; Amara, Salem; Lizard, Gérard

    2016-05-01

    Because of their whitening and photocatalytic effects, titanium dioxide nanoparticles (TiO2-NPs) are widely used in daily life. These NPs can be found in paints, plastics, papers, sunscreens, foods, medicines (pills), toothpastes, and cosmetics. However, the biological effect of TiO2-NPs on the human body, especially on the central nervous system, is still unclear. Many studies have demonstrated that the brain is one of the target organs in acute or chronic TiO2-NPs toxicity. The present study aimed to investigate the effect of TiO2-NPs at different concentrations (0.1 to 200 μg/mL) on murine microglial cells (BV-2) to assess their activity on cell growth and viability, as well as their neurotoxicity. Different parameters were measured: cell viability, cell proliferation and DNA content (SubG1 peak), mitochondrial depolarization, overproduction of reactive oxygen species (especially superoxide anions), and ultrastructural changes. Results showed that TiO2-NPs induced some cytotoxic effects with a slight inhibition of cell growth. Thus, at high concentrations, TiO2-NPs were not only able to inhibit cell adhesion but also enhanced cytoplasmic membrane permeability to propidium iodide associated with a loss of mitochondrial transmembrane potential and an overproduction of superoxide anions. No induction of apoptosis based on the presence of a SubG1 peak was detected. The microscopic observations also indicated that small groups of nanosized particles and micron-sized aggregates were engulfed by the BV-2 cells and sequestered as intracytoplasmic aggregates after 24-h exposure to TiO2-NPs. Altogether, our data show that the accumulation TiO2-NPs in microglial BV-2 cells favors mitochondrial dysfunctions and oxidative stress.

  19. Effects of paramagnetic ferrocenium cations on the magnetic properties of the anionic single-molecule magnet [Mn(12)O(12)(O(2)CC(6)F(5))(16)(H(2)O)(4)]-.

    Science.gov (United States)

    Kuroda-Sowa, T; Lam, M; Rheingold, A L; Frommen, C; Reiff, W M; Nakano, M; Yoo, J; Maniero, A L; Brunel, L C; Christou, G; Hendrickson, D N

    2001-12-03

    The preparation and physical characterization are reported for the single-molecule magnet salts [M(Cp')(2)](n)()[Mn(12)O(12)(O(2)CC(6)F(5))(16)(H(2)O)(4)] (M = Fe, n = 1, Cp' = C(5)Me(5) (2a), C(5)H(5) (2b); M = Co, n = 1, Cp' = C(5)Me(5) (2c), C(5)H(5) (2d); M = Fe, n = 2, Cp' = C(5)Me(5) (2e), C(5)H(5) (2f)) to investigate the effects of paramagnetic cations on the magnetization relaxation behavior of [Mn(12)]- anionic single-molecule magnets. Complex 2a.2H(2)O crystallizes in the orthorhombic space group Aba2, with cell dimensions at 173 K of a = 25.6292(2) A, b = 25.4201(3) A, c = 29.1915(2) A, and Z = 4. Complex 2c.2CH(2)Cl(2).C(6)H(14) crystallizes in the monoclinic space group P2(1)/c, with cell dimensions at 173 K of a = 17.8332(6) A, b = 26.2661(9) A, c = 36.0781(11) A, beta = 92.8907(3) degrees, and Z = 4. These two salts consist of either paramagnetic [Fe(C(5)Me(5))(2)]+ cations or diamagnetic [Co(C(5)Me(5))(2)]+ cations, and [Mn(12)O(12)(O(2)CC(6)F(5))(16)(H(2)O)(4)]- anions. The structures of the anions in the two salts are similar, consisting of a central Mn(4)O(4) cubane moiety, surrounded by a nonplanar ring of eight Mn atoms that are bridged by and connected to the cube via mu(3)-O(2)- ions. The oxidation states of four Mn sites out of eight outer Mn ions in complex 2a were assigned to be +2.75 from the valence bond sum analysis although the disordering of bridging carboxylates prevents more precise determination. On the other hand in complex 2c, one Mn site out of eight outer Mn ions was identified as a Mn(II) ion, accommodating the "extra" electron; this was deduced by a valence bond sum analysis. Thus, the anion in complex 2c has a Mn(II)(1)Mn(III)(7)Mn(IV)(4) oxidation state description. The Jahn-Teller axes of the Mn(III) ions in both anions are roughly aligned in one direction. All complexes studied exhibit a single out-of-phase ac magnetic susceptibility (chi"(M)) signal in the 4.6-4.8 K range for complexes 2a-2d and in the 2.8-2.9 K range

  20. Superoxide dismutase activity of the naturally occurring human serum albumin-copper complex without hydroxyl radical formation.

    Science.gov (United States)

    Kato, Ryunosuke; Akiyama, Matofusa; Kawakami, Hiroyoshi; Komatsu, Teruyuki

    2014-01-01

    The superoxide radical anion (O2(.-)) is biologically toxic and contributes to the pathogenesis of various diseases. Here we describe the superoxide dismutase (SOD) activity of human serum albumin (HSA) complexed with a single Cu(II) ion at the N-terminal end (HSA-Cu complex). The structure of this naturally occurring copper-coordinated blood serum protein has been characterized by several physicochemical measurements. The O2(.-) dismutation ability of the HSA-Cu (1:1) complex is almost the same as that of the well-known SOD mimics, such as Mn(III) -tetrakis(N-methylpyridinium)porphyrin. Interestingly, the HSA-Cu complex does not induce a subsequent Fenton reaction to produce the hydroxyl radical (OH(.)), which is one of the most harmful reactive oxygen species.

  1. Salidroside Stimulates Mitochondrial Biogenesis and Protects against H2O2-Induced Endothelial Dysfunction

    Science.gov (United States)

    Xing, Shasha; Yang, Xiaoyan; Li, Wenjing; Bian, Fang; Wu, Dan; Chi, Jiangyang; Xu, Gao; Zhang, Yonghui; Jin, Si

    2014-01-01

    Salidroside (SAL) is an active component of Rhodiola rosea with documented antioxidative properties. The purpose of this study is to explore the mechanism of the protective effect of SAL on hydrogen peroxide- (H2O2-) induced endothelial dysfunction. Pretreatment of the human umbilical vein endothelial cells (HUVECs) with SAL significantly reduced the cytotoxicity brought by H2O2. Functional studies on the rat aortas found that SAL rescued the endothelium-dependent relaxation and reduced superoxide anion (O2∙−) production induced by H2O2. Meanwhile, SAL pretreatment inhibited H2O2-induced nitric oxide (NO) production. The underlying mechanisms involve the inhibition of H2O2-induced activation of endothelial nitric oxide synthase (eNOS), adenosine monophosphate-activated protein kinase (AMPK), and Akt, as well as the redox sensitive transcription factor, NF-kappa B (NF-κB). SAL also increased mitochondrial mass and upregulated the mitochondrial biogenesis factors, peroxisome proliferator-activated receptor gamma-coactivator-1alpha (PGC-1α), and mitochondrial transcription factor A (TFAM) in the endothelial cells. H2O2-induced mitochondrial dysfunction, as demonstrated by reduced mitochondrial membrane potential (Δψm) and ATP production, was rescued by SAL pretreatment. Taken together, these findings implicate that SAL could protect endothelium against H2O2-induced injury via promoting mitochondrial biogenesis and function, thus preventing the overactivation of oxidative stress-related downstream signaling pathways. PMID:24868319

  2. Salidroside Stimulates Mitochondrial Biogenesis and Protects against H2O2-Induced Endothelial Dysfunction

    Directory of Open Access Journals (Sweden)

    Shasha Xing

    2014-01-01

    Full Text Available Salidroside (SAL is an active component of Rhodiola rosea with documented antioxidative properties. The purpose of this study is to explore the mechanism of the protective effect of SAL on hydrogen peroxide- (H2O2- induced endothelial dysfunction. Pretreatment of the human umbilical vein endothelial cells (HUVECs with SAL significantly reduced the cytotoxicity brought by H2O2. Functional studies on the rat aortas found that SAL rescued the endothelium-dependent relaxation and reduced superoxide anion (O2∙- production induced by H2O2. Meanwhile, SAL pretreatment inhibited H2O2-induced nitric oxide (NO production. The underlying mechanisms involve the inhibition of H2O2-induced activation of endothelial nitric oxide synthase (eNOS, adenosine monophosphate-activated protein kinase (AMPK, and Akt, as well as the redox sensitive transcription factor, NF-kappa B (NF-κB. SAL also increased mitochondrial mass and upregulated the mitochondrial biogenesis factors, peroxisome proliferator-activated receptor gamma-coactivator-1alpha (PGC-1α, and mitochondrial transcription factor A (TFAM in the endothelial cells. H2O2-induced mitochondrial dysfunction, as demonstrated by reduced mitochondrial membrane potential (Δψm and ATP production, was rescued by SAL pretreatment. Taken together, these findings implicate that SAL could protect endothelium against H2O2-induced injury via promoting mitochondrial biogenesis and function, thus preventing the overactivation of oxidative stress-related downstream signaling pathways.

  3. Synthesis and Crystal Structure of One-dimensional Chain Zinc(II) Coordination Polymer:{Na[ZnL(H2O)2]}n(L=2-Hydroxyl-2-hydroxylate-malonate Trivalent Anion)

    Institute of Scientific and Technical Information of China (English)

    石敬民; 朱思成; 吴长举

    2004-01-01

    A one-dimensional chain complex {Na[ZnL(H2O)2]}n was synthesized by sodium 2,2-dihydroxyl-malonate (Na2L′) and hydrate zinc perchlorate. The crystal belongs to the mono- clinic system, space group P21/n with a = 5.936(2), b = 7.203(3), c = 19.356(8) A,Z= 95.264(6)°, V = 824.2(6)A3, Z = 4, C3H5NaO8Zn, Mr = 257.43, Dc = 2.075 g/cm3, F(000) = 512 and ( = 3.045 mm-1. The structure was refined to R = 0.0381 and Wr = 0.0766 for 1188 observed reflections (I>2σ(I)). In the complex the zinc(II) atom is coordinated to six oxygen atoms from two H2O mole- cules, two carboxylate groups, one ionized hydroxyl group and one hydroxyl group. By the coordi- nation of zinc(II) ions and bridging ligand 2-hydroxyl-2-hydroxylate-malonate trivalent anion the one-dimensional chain is constructed.

  4. Superoxide radical production in chicken skeletal muscle induced by acute heat stress.

    Science.gov (United States)

    Mujahid, A; Yoshiki, Y; Akiba, Y; Toyomizu, M

    2005-02-01

    Heat stress is of major concern for poultry, especially in the hot regions of the world because of the resulting poor growth performance, immunosuppression, and high mortality. To assess superoxide (O2*-) production in mitochondria isolated from skeletal muscle of chickens (n = 4 to 8) exposed to acute heat stress, electron spin resonance (ESR) spectroscopy using 5,5-dimethyl-1-pyrroline N-oxide (DMPO) as a spin trap agent and lucigenin-derived chemiluminescence (LDCL) method were applied. ESR spectra of suspensions containing mitochondria from control and acute heat-treated meat-type chickens showed similar hyperfine coupling constants (aN = 1.44 mT, aHbeta = 0.12 mT, and aHbeta = 0.11 mT) to those of DMPO-O2*- adducts observed in a hypoxanthine-xanthine oxidase system. Heat exposure resulted in enhancement of the DMPO-O2*- signal. The results using LDCL showed significantly enhanced superoxide production in heat stress-treated skeletal muscle mitochondria of meat-type chickens, whereas no such increase was observed in laying chickens. The enhancement of superoxide production in the former case was associated with heat-induced increments in rectal and muscle temperatures, leading to significant body weight loss. In contrast, the latter case showed no increase in temperatures, although there was a slight decrease in body weight gain. Percentage increases of superoxide production in the presence of carboxyatractylate, a specific inhibitor of adenine nucleotide translocator (ANT), were the same for skeletal muscle mitochondria from meat- and laying-type chickens from the control or heat stress-treated group. This finding suggests the irrelevance of ANT in the regulation of reactive oxygen species flux under heat stress conditions. The study provides the first evidence of superoxide anion production in the skeletal muscle mitochondria of meat-type chickens in response to acute heat stress.

  5. Copper-catalyzed activation of molecular oxygen for oxidative destruction of acetaminophen: The mechanism and superoxide-mediated cycling of copper species.

    Science.gov (United States)

    Zhang, Yunfei; Fan, Jinhong; Yang, Bo; Huang, Wutao; Ma, Luming

    2017-01-01

    In this study, the commercial zero-valent copper (ZVC) was investigated to activate the molecular oxygen (O2) for the degradation of acetaminophen (ACT). 50 mg/L ACT could be completely decomposed within 4 h in the ZVC/air system at initial pH 3.0. The H2O2, hydroxyl radical (OH) and superoxide anion radical (O2(-)) were identified as the main reactive oxygen species (ROSs) generated in the above reaction; however, only OH caused the decomposition and mineralization of ACT in the copper-catalyzed O2 activation process. In addition, the in-situ generated Cu(+) from ZVC dissolution not only activated O2 to produce H2O2, but also initiated the decomposition of H2O2 to generate OH. Meanwhile, the H2O2 could also be partly decomposed into O2(-), which served as a mediator for copper cycling by reduction of Cu(2+) to Cu(+) in the ZVC/air system. Therefore, OH could be continuously generated; and then ACT was effectively degraded. Additionally, the effect of solution pH and the dosage of ZVC were also investigated. As a result, this study indicated the key behavior of the O2(-) during Cu-catalyzed activation of O2, which further improved the understanding of O2 activation mechanism by zero-valent metals. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. STUDY OF THE ANIONS EFFECT OF THE DEGRADATION OF THE DYE REMAZOL RED RB 133% BY H2O2/UV = ESTUDO DO EFEITO DOS ÂNIONS NA DEGRADAÇÃO DO CORANTE REMAZOL VERMELHO RB 133% POR H2O2/UV

    Directory of Open Access Journals (Sweden)

    Jefferson Pereira Ribeiro

    2014-06-01

    Full Text Available Industrial activities that consume excess water in its manufacturing process, typically generate a high volume of effluents, the textile industry being a typical example. The chemical oxidation is an alternative for the treatment of effluents containing textile dyes, among them stand out from the advanced oxidation processes (AOPs are based on the generation of hydroxyl radicals (. OH in which are highly oxidizing processes and can decompose compounds quickly and non-selective manner, leading to partial or complete mineralization of the contaminant. We studied the effect of anions on the degradation of the dye Remazol Red RB 133% by combined treatment H2O2/UV. The results of the removal efficiencies of color at the end of the process indicated that there was no difference between treatments in the presence of anions in the studied concentration (10 mM compared the degradation without the presence of these anions, because at the end of all treatments the solution was colorless. For the parameter of chemical oxygen demand (COD was no influence on the removal efficiencies of the studied anions, especially for NO3¬-, Cl-, and PO43-. = As atividades industriais que consomem excesso de água no seu processo industrial, normalmente geram um elevado volume de efluentes, sendo a indústria têxtil um exemplo típico. A oxidação química é um dos processos alternativos para o tratamento de efluentes contendo corantes têxteis, entre eles destacam-se os processos oxidativos avançados (POAs que são baseados na geração de radicais hidroxilas (.OH no qual são altamente oxidantes, podendo decompor compostos de maneira rápida e não-seletiva, conduzindo a mineralização parcial ou completa do contaminante. Neste trabalho estudou-se o efeito dos ânions na degradação do corante remazol vermelho RB 133% pelo tratamento combinado H2O2/UV. Os resultados das eficiências de remoção de cor ao final do processo indicaram que não houve diferença entre

  7. Enhanced photodegradation of methyl orange with TiO2 nanoparticles using a triboelectric nanogenerator

    Science.gov (United States)

    Su, Yuanjie; Yang, Ya; Zhang, Hulin; Xie, Yannan; Wu, Zhiming; Jiang, Yadong; Fukata, Naoki; Bando, Yoshio; Wang, Zhong Lin

    2013-07-01

    Methyl orange (MO) can be degraded by a photocatalytic process using TiO2 under UV irradiation. The photo-generated holes and electrons can migrate to the surface of TiO2 particles and serve as redox sources that react with adsorbed reactants, leading to the formation of superoxide radical anions, hydrogen peroxide and hydroxyl radicals involved in the oxidation of dye pollution. Here, we fabricated a polytetrafluoroethylene-Al based triboelectric nanogenerator (TENG) whose electric power output can be used for enhancing the photodegradation of MO with the presence of TiO2 nanoparticles, because the TENG generated electric field can effectively boost the separation and restrain the recombination of photo-generated electrons and holes. Due to the photoelectrical coupling, the degradation percentages of MO for 120 min with and without TENG assistance are 76% and 27%, respectively. The fabricated TENGs have potential applications in wastewater treatment, water splitting, and pollution degradation.

  8. Quantification of superoxide radical production in thylakoid membrane using cyclic hydroxylamines.

    Science.gov (United States)

    Kozuleva, Marina; Klenina, Irina; Mysin, Ivan; Kirilyuk, Igor; Opanasenko, Vera; Proskuryakov, Ivan; Ivanov, Boris

    2015-12-01

    Applicability of two lipophilic cyclic hydroxylamines (CHAs), CM-H and TMT-H, and two hydrophilic CHAs, CAT1-H and DCP-H, for detection of superoxide anion radical (O2(∙-)) produced by the thylakoid photosynthetic electron transfer chain (PETC) of higher plants under illumination has been studied. ESR spectrometry was applied for detection of the nitroxide radical originating due to CHAs oxidation by O2(∙-). CHAs and corresponding nitroxide radicals were shown to be involved in side reactions with PETC which could cause miscalculation of O2(∙-) production rate. Lipophilic CM-H was oxidized by PETC components, reducing the oxidized donor of Photosystem I, P700(+), while at the same concentration another lipophilic CHA, TMT-H, did not reduce P700(+). The nitroxide radical was able to accept electrons from components of the photosynthetic chain. Electrostatic interaction of stable cation CAT1-H with the membrane surface was suggested. Water-soluble superoxide dismutase (SOD) was added in order to suppress the reaction of CHA with O2(∙-) outside the membrane. SOD almost completely inhibited light-induced accumulation of DCP(∙), nitroxide radical derivative of hydrophilic DCP-H, in contrast to TMT(∙) accumulation. Based on the results showing that change in the thylakoid lumen pH and volume had minor effect on TMT(∙) accumulation, the reaction of TMT-H with O2(∙-) in the lumen was excluded. Addition of TMT-H to thylakoid suspension in the presence of SOD resulted in the increase in light-induced O2 uptake rate, that argued in favor of TMT-H ability to detect O2(∙-) produced within the membrane core. Thus, hydrophilic DCP-H and lipophilic TMT-H were shown to be usable for detection of O2(∙-) produced outside and within thylakoid membranes.

  9. Improved Osteoblast and Chondrocyte Adhesion and Viability by Surface-Modified Ti6Al4V Alloy with Anodized TiO2 Nanotubes Using a Super-Oxidative Solution

    OpenAIRE

    Ernesto Beltrán-Partida; Aldo Moreno-Ulloa; Benjamín Valdez-Salas; Cristina Velasquillo; Monica Carrillo; Alan Escamilla; Ernesto Valdez; Francisco Villarreal

    2015-01-01

    Titanium (Ti) and its alloys are amongst the most commonly-used biomaterials in orthopedic and dental applications. The Ti-aluminum-vanadium alloy (Ti6Al4V) is widely used as a biomaterial for these applications by virtue of its favorable properties, such as high tensile strength, good biocompatibility and excellent corrosion resistance. TiO2 nanotube (NTs) layers formed by anodization on Ti6Al4V alloy have been shown to improve osteoblast adhesion and function when compared to non-anodized m...

  10. TiO2 photocatalysis damages lipids and proteins in Escherichia coli.

    Science.gov (United States)

    Carré, Gaëlle; Hamon, Erwann; Ennahar, Saïd; Estner, Maxime; Lett, Marie-Claire; Horvatovich, Peter; Gies, Jean-Pierre; Keller, Valérie; Keller, Nicolas; Andre, Philippe

    2014-04-01

    This study investigates the mechanisms of UV-A (315 to 400 nm) photocatalysis with titanium dioxide (TiO2) applied to the degradation of Escherichia coli and their effects on two key cellular components: lipids and proteins. The impact of TiO2 photocatalysis on E. coli survival was monitored by counting on agar plate and by assessing lipid peroxidation and performing proteomic analysis. We observed through malondialdehyde quantification that lipid peroxidation occurred during the photocatalytic process, and the addition of superoxide dismutase, which acts as a scavenger of the superoxide anion radical (O2·(-)), inhibited this effect by half, showing us that O2·(-) radicals participate in the photocatalytic antimicrobial effect. Qualitative analysis using two-dimensional electrophoresis allowed selection of proteins for which spot modifications were observed during the applied treatments. Two-dimensional electrophoresis highlighted that among the selected protein spots, 7 and 19 spots had already disappeared in the dark in the presence of 0.1 g/liter and 0.4 g/liter TiO2, respectively, which is accounted for by the cytotoxic effect of TiO2. Exposure to 30 min of UV-A radiation in the presence of 0.1 g/liter and 0.4 g/liter TiO2 increased the numbers of missing spots to 14 and 22, respectively. The proteins affected by photocatalytic oxidation were strongly heterogeneous in terms of location and functional category. We identified several porins, proteins implicated in stress response, in transport, and in bacterial metabolism. This study reveals the simultaneous effects of O2·(-) on lipid peroxidation and on the proteome during photocatalytic treatment and therefore contributes to a better understanding of molecular mechanisms in antibacterial photocatalytic treatment.

  11. Sodium selenide toxicity is mediated by O2-dependent DNA breaks.

    Directory of Open Access Journals (Sweden)

    Gérald Peyroche

    Full Text Available Hydrogen selenide is a recurrent metabolite of selenium compounds. However, few experiments studied the direct link between this toxic agent and cell death. To address this question, we first screened a systematic collection of Saccharomyces cerevisiae haploid knockout strains for sensitivity to sodium selenide, a donor for hydrogen selenide (H(2Se/HSe(-/Se(2-. Among the genes whose deletion caused hypersensitivity, homologous recombination and DNA damage checkpoint genes were over-represented, suggesting that DNA double-strand breaks are a dominant cause of hydrogen selenide toxicity. Consistent with this hypothesis, treatment of S. cerevisiae cells with sodium selenide triggered G2/M checkpoint activation and induced in vivo chromosome fragmentation. In vitro, sodium selenide directly induced DNA phosphodiester-bond breaks via an O(2-dependent reaction. The reaction was inhibited by mannitol, a hydroxyl radical quencher, but not by superoxide dismutase or catalase, strongly suggesting the involvement of hydroxyl radicals and ruling out participations of superoxide anions or hydrogen peroxide. The (•OH signature could indeed be detected by electron spin resonance upon exposure of a solution of sodium selenide to O(2. Finally we showed that, in vivo, toxicity strictly depended on the presence of O(2. Therefore, by combining genome-wide and biochemical approaches, we demonstrated that, in yeast cells, hydrogen selenide induces toxic DNA breaks through an O(2-dependent radical-based mechanism.

  12. Cu/Zn-superoxide dismutase from the fungal strain Humicola lutea 103 improves ram spermatozoa functions in vitro.

    Science.gov (United States)

    Stefanov, R; Angelova, M; Stefanova, T; Subev, M; Dolashka, P; Voelter, W; Zachariev, Z

    2004-04-01

    In this study we determined the effect of reactive oxygen species (ROS) generation during incubation in media at 39 degrees C on ram spermatozoa and the protection by exogenously added antioxidant enzyme, superoxide dismutase (SOD). A novel Cu/Zn-SOD, isolated from the fungal strain Humicola lutea 103 (HLSOD), was used. Our results point out that the levels of both, superoxide anion radicals (*O2-) and H2O2, increase approximately 8-10- and 2-3-fold, respectively, during incubation of spermatozoa. Enhanced ROS generation coincided with reduction of motility, independently of the type of diluted medium. Addition of HLSOD (30, 60 and 120 U ml(-1) sperm) improved sperm functions, maintaining almost initial percentages of motile spermatozoa and increasing the values of mean cytochemical coefficient. At the same time, a significant diminution of *O2- and H2O2 content in the presence of antioxidant enzyme was established. The results suggest that HLSOD is an effective *O2- scavenger in semen that leads to protection of sperm functions.

  13. Salicylic acid-induced superoxide generation catalyzed by plant peroxidase in hydrogen peroxide-independent manner.

    Science.gov (United States)

    Kimura, Makoto; Kawano, Tomonori

    2015-01-01

    It has been reported that salicylic acid (SA) induces both immediate spike and long lasting phases of oxidative burst represented by the generation of reactive oxygen species (ROS) such as superoxide anion radical (O2(•-)). In general, in the earlier phase of oxidative burst, apoplastic peroxidase are likely involved and in the late phase of the oxidative burst, NADPH oxidase is likely involved. Key signaling events connecting the 2 phases of oxidative burst are calcium channel activation and protein phosphorylation events. To date, the known earliest signaling event in response to exogenously added SA is the cell wall peroxidase-catalyzed generation of O2(•-) in a hydrogen peroxide (H2O2)-dependent manner. However, this model is incomplete since the source of the initially required H2O2 could not be explained. Based on the recently proposed role for H2O2-independent mechanism for ROS production catalyzed by plant peroxidases (Kimura et al., 2014, Frontiers in Plant Science), we hereby propose a novel model for plant peroxidase-catalyzed oxidative burst fueled by SA.

  14. Magnetoreception through Cryptochrome may involve superoxide

    DEFF Research Database (Denmark)

    Solov'yov, Ilia; Schulten, Klaus

    2009-01-01

    pair-based reaction in the photoreceptor cryptochrome that reduces the protein's flavin group from its signaling state FADH$^bullet$ to the inactive state FADH$^–$ (which reacts to the likewise inactive FAD) by means of the superoxide radical, O2$^$. We argue that the spin dynamics in the suggested...

  15. Antioxidant capacity and angiotensin I converting enzyme inhibitory activity of a melon concentrate rich in superoxide dismutase.

    Science.gov (United States)

    Carillon, Julie; Del Rio, Daniele; Teissèdre, Pierre-Louis; Cristol, Jean-Paul; Lacan, Dominique; Rouanet, Jean-Max

    2012-12-01

    Antioxidant capacity and angiotensin 1-converting enzyme (ACE) inhibitory activity of a melon concentrate rich in superoxide dismutase (SOD-MC) were investigated in vitro. The total antioxidant capacity (TAC) was measured by the Trolox equivalent antioxidant capacity assay (TEAC), the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical assay, and the ferric reducing antioxidant power assay (FRAP). The ability of the extract to scavenge three specific reactive oxygen species (superoxide radical anion (O(2)(-)), hydroxyl radical (HO()) and hydrogen peroxide (H(2)O(2))) was also investigated in order to better evaluate its antioxidant properties. Even if the measures of TAC were relatively low, results clearly established an antioxidant potential of SOD-MC that exhibited the highest radical-scavenging activity towards O(2)(-), with a IC(50) 12-fold lower than that of H(2)O(2) or HO(). This lets hypothesis that the antioxidant potential of SOD-MC could be mainly due to its high level of SOD. Moreover, for the first time, an ACE inhibitory activity of SOD-MC (IC(50)=2.4±0.1mg/mL) was demonstrated, showing that its use as a functional food ingredient with potential preventive benefits in the context of hypertension may have important public health implications and should be carefully considered.

  16. Healing of colonic ischemic anastomoses in the rat: role of superoxide radicals.

    Science.gov (United States)

    Garcia, J G; Criado, F J; Persona, M A; Alonso, A G

    1998-07-01

    The aim of this study was to evaluate the role of superoxide radicals in the healing of ischemic colonic anastomoses in the rat. Adult male Wistar rats were used in a factorial design with two factors (normal or ischemic colonic anastomoses) each having two levels (treatment with saline or allopurinol). Colonic anastomoses were performed either in normal or previously devascularized colons (ischemic anastomoses) at identical locations, using the same technique. On the fourth postoperative day, animals were killed, and specimens were taken for determinations. Ischemic anastomoses displayed significant increases in superoxide radical (assayed as superoxide anion), superoxide dismutase, and glutathione peroxidase concentrations. Bursting strength and hydroxyproline levels were also significantly lower in these anastomoses. Allopurinol administration elicited a significant decrease in superoxide anions and raised both bursting strength and hydroxyproline levels only in ischemic anastomoses. Superoxide radicals are involved in the delay in healing of ischemic anastomoses. Allopurinol lowers superoxide anion production and has beneficial effects on the cicatrization of ischemic anastomoses.

  17. Differential effects of superoxide dismutase and superoxide dismutase/catalase mimetics on human breast cancer cells.

    Science.gov (United States)

    Shah, Manisha H; Liu, Guei-Sheung; Thompson, Erik W; Dusting, Gregory J; Peshavariya, Hitesh M

    2015-04-01

    Reactive oxygen species (ROS) such as superoxide and hydrogen peroxide (H2O2) have been implicated in development and progression of breast cancer. In the present study, we have evaluated the effects of the superoxide dismutase (SOD) mimetic MnTmPyP and the SOD/catalase mimetic EUK 134 on superoxide and H2O2 formation as well as proliferation, adhesion, and migration of MCF-7 and MDA-MB-231 cells. Superoxide and H2O2 production was examined using dihydroethidium and Amplex red assays, respectively. Cell viability and adhesion were measured using a tetrazolium-based MTT assay. Cell proliferation was determined using trypan blue assay. Cell cycle progression was analyzed using flow cytometry. Clonal expansion of a single cell was performed using a colony formation assay. Cell migration was measured using transwell migration assay. Dual luciferase assay was used to determine NF-κB reporter activity. EUK 134 effectively reduced both superoxide and H2O2, whereas MnTmPyP removed superoxide but enhanced H2O2 formation. EUK 134 effectively attenuated viability, proliferation, clonal expansion, adhesion, and migration of MCF-7 and MDA-MB-231 cells. In contrast, MnTmPyP only reduced clonal expansion of MCF-7 and MDA-MB-231 cells but had no effect on adhesion and cell cycle progression. Tumor necrosis factor-alpha-induced NF-κB activity was reduced by EUK 134, whereas MnTmPyP enhanced this activity. These data indicate that the SOD mimetic MnTmPyP and the SOD/catalase mimetic EUK 134 exert differential effects on breast cancer cell growth. Inhibition of H2O2 signaling using EUK 134-like compound might be a promising approach to breast cancer therapy.

  18. Nitric oxide and superoxide dismutase modulate endothelial progenitor cell function in type 2 diabetes mellitus

    Directory of Open Access Journals (Sweden)

    Brenner Benjamin

    2009-10-01

    Full Text Available Abstract Background The function of endothelial progenitor cells (EPCs, which are key cells in vascular repair, is impaired in diabetes mellitus. Nitric oxide (NO and reactive oxygen species can regulate EPC functions. EPCs tolerate oxidative stress by upregulating superoxide dismutase (SOD, the enzyme that neutralizes superoxide anion (O2-. Therefore, we investigated the roles of NO and SOD in glucose-stressed EPCs. Methods The functions of circulating EPCs from patients with type 2 diabetes were compared to those from healthy individuals. Healthy EPCs were glucose-stressed, and then treated with insulin and/or SOD. We assessed O2- generation, NO production, SOD activity, and their ability to form colonies. Results EPCs from diabetic patients generated more O2-, had higher NAD(PH oxidase and SOD activity, but lower NO bioavailability, and expressed higher mRNA and protein levels of p22-phox, and manganese SOD and copper/zinc SOD than those from the healthy individuals. Plasma glucose and HbA1c levels in the diabetic patients were correlated negatively with the NO production from their EPCs. SOD treatment of glucose-stressed EPCs attenuated O2- generation, restored NO production, and partially restored their ability to form colonies. Insulin treatment of glucose-stressed EPCs increased NO production, but did not change O2- generation and their ability to form colonies. However, their ability to produce NO and to form colonies was fully restored after combined SOD and insulin treatment. Conclusion Our data provide evidence that SOD may play an essential role in EPCs, and emphasize the important role of antioxidant therapy in type 2 diabetic patients.

  19. Biological Superoxide In Manganese Oxide Formation

    Science.gov (United States)

    Hansel, C.; Learman, D.; Zeiner, C.; Santelli, C. M.

    2011-12-01

    Manganese (Mn) oxides are among the strongest sorbents and oxidants within the environment, controlling the fate and transport of numerous elements and the degradation of recalcitrant carbon. Both bacteria and fungi mediate the oxidation of Mn(II) to Mn(III/IV) oxides but the genetic and biochemical mechanisms responsible remain poorly understood. Furthermore, the physiological basis for microbial Mn(II) oxidation remains an enigma. We have recently reported that a common marine bacterium (Roseobacter sp. AzwK-3b) oxidizes Mn(II) via reaction with extracellular superoxide (O2-) produced during exponential growth. Here we expand this superoxide-mediated Mn(II) oxidation pathway to fungi, introducing a surprising homology between prokaryotic and eukaryotic metal redox processes. For instance, Stibella aciculosa, a common soil Ascomycete filamentous fungus, precipitates Mn oxides at the base of asexual reproductive structures (synnemata) used to support conidia (Figure 1). This distribution is a consequence of localized production of superoxide (and it's dismutation product hydrogen peroxide, H2O2), leading to abiotic oxidation of Mn(II) by superoxide. Disruption of NADPH oxidase activity using the oxidoreductase inhibitor DPI leads to diminished cell differentiation and subsequent Mn(II) oxidation inhibition. Addition of Cu(II) (an effective superoxide scavenger) leads to a concentration dependent decrease in Mn oxide formation. We predict that due to the widespread production of extracellular superoxide within the fungal and likely bacterial kingdoms, biological superoxide may be an important contributor to the cycling of Mn, as well as other metals (e.g., Hg, Fe). Current and future explorations of the genes and proteins involved in superoxide production and Mn(II) oxidation will ideally lend insight into the physiological and biochemical basis for these processes.

  20. 酶法制备鲽鱼鱼皮胶原蛋白肽及其清除超氧阴离子自由基的研究%Study on the Enzymatic Preparation and Superoxide Anion Radical Scavenging Activity of Collagen Peptide from Plaice Skin

    Institute of Scientific and Technical Information of China (English)

    王群; 郑海涛; 葛尧; 何计国

    2011-01-01

    采用碱性蛋白酶酶解鲽鱼鱼皮胶原蛋白制备胶原蛋白肽,对其清除超氧阴离子自由基的能力进行研究.通过单因素试验和响应面法分析不同酶解条件对超氧阴离子自由基清除率的影响,优化得到最佳酶解工艺条件:pH 9.5,加酶量158l U/g,底物浓度10 mg/mL,酶解时间为6h,酶解温度60℃,最高清除率为75.51%,半数清除浓度(IC5o)为7.98 mg/mL.%Alcalase was used to hydrolyze plaice skin for preparing collagen peptide, and the superoxide anion radical scavenging activity of this collagen peptide was studied. Effect of the different enzymatic hydrolysis conditions on superoxide anion radical scavenging activity were analyzed by single factor experiment and response surface method. The optimal hydrolytic conditions of plaice skin collagen using Alcalase with high scavenging rate were pH=9.5, enzyme dosage 1581 U/g, concentration of substrate 10 mg/mL, hydrolysis time 6 h, temperature 60℃. The maximum scavenging rate of 75.51% and half scavenging concentration (IC50) of 7.98 mg/mL were obtained.

  1. 二氧化铬阴离子光电子能谱的理论研究%Theoretical investigation on the photoelectron spectra of the photodetachmentprocess of the CrO2- anion

    Institute of Scientific and Technical Information of China (English)

    王茹; 崔方; 张浚贤; 梁军; 崔执凤

    2013-01-01

    凭借密度泛函理论,采用不同基组对中性分子CrO2的基态((X)3B1)以及阴离子CrO1-的基态((X)4B1)进行几何优化和振动频率分析;应用量化计算得到的力常数及结构和光谱参数,基于推得的两维四模Franck-Condon重叠积分的代数表示,对CrO2((X)3B1)-CrO2-((X)4B1)的光脱附过程进行Franck-Condon分析和光谱模拟,理论上得到光电子能谱的谱线相对强度及振动结构分布,理论谱与实验测得的二氧化铬阴离子光电子能谱达到一致,并对光电子能谱的振动结构进行归属及热带分析;另外,在光谱模拟过程中通过迭代Franck-Condon分析过程,推得CrO2-((X)4B1)与CrO2((X)3B1)平衡几何结构之差:△R(Cr-O)=0.05A,△∠(O-Cr-O)=12°.%Geometry optimization and harmonic vibrational frequency calculations were performed on the(X)3B1 state of CrO2 and (X)4B1 state of CrO2-by using the Density Functional Theory with various basis sets.The adiabatic electron affinity of CrO2 was investigated by using BPW91 and B3PW91 methods extrapolated to the complete basis set limit.Frank-Condon analyses and spectral simulations were carried out on the CrO2 ((X)3B1)-CrO2-((X)4B1) photodetachment process.The simulated photoelectron spectra of CrO2-are in excellent agreement with the observed ones.While the Duschinsky effect plays a minor role and can be neglected.In addition,the equilibrium geometry differences between the ion and neutral,△R(Cr-O)=0.05 (A) and △ ∠(O-Cr-O)=12°,were deduced by employing an iterative Franck-Condon analysis procedure in the spectral simulation.

  2. In Situ OH Generation from O2- and H2O2 Plays a Critical Role in Plasma-Induced Cell Death.

    Directory of Open Access Journals (Sweden)

    Dehui Xu

    Full Text Available Reactive oxygen and nitrogen species produced by cold atmospheric plasma (CAP are considered to be the most important species for biomedical applications, including cancer treatment. However, it is not known which species exert the greatest biological effects, and the nature of their interactions with tumor cells remains ill-defined. These questions were addressed in the present study by exposing human mesenchymal stromal and LP-1 cells to reactive oxygen and nitrogen species produced by CAP and evaluating cell viability. Superoxide anion (O2- and hydrogen peroxide (H2O2 were the two major species present in plasma, but their respective concentrations were not sufficient to cause cell death when used in isolation; however, in the presence of iron, both species enhanced the cell death-inducing effects of plasma. We propose that iron containing proteins in cells catalyze O2- and H2O2 into the highly reactive OH radical that can induce cell death. The results demonstrate how reactive species are transferred to liquid and converted into the OH radical to mediate cytotoxicity and provide mechanistic insight into the molecular mechanisms underlying tumor cell death by plasma treatment.

  3. Detection of superoxide production in stimulated and unstimulated living cells using new cyclic nitrone spin traps.

    Science.gov (United States)

    Abbas, Kahina; Hardy, Micael; Poulhès, Florent; Karoui, Hakim; Tordo, Paul; Ouari, Olivier; Peyrot, Fabienne

    2014-06-01

    Reactive oxygen species (ROS), including superoxide anion and hydrogen peroxide (H2O2), have a diverse array of physiological and pathological effects within living cells depending on the extent, timing, and location of their production. For measuring ROS production in cells, the ESR spin trapping technique using cyclic nitrones distinguishes itself from other methods by its specificity for superoxide and hydroxyl radical. However, several drawbacks, such as the low spin trapping rate and the spontaneous and cell-enhanced decomposition of the spin adducts to ESR-silent products, limit the application of this method to biological systems. Recently, new cyclic nitrones bearing a triphenylphosphonium (Mito-DIPPMPO) or a permethylated β-cyclodextrin moiety (CD-DIPPMPO) have been synthesized and their spin adducts demonstrated increased stability in buffer. In this study, a comparison of the spin trapping efficiency of these new compounds with commonly used cyclic nitrone spin traps, i.e., 5,5-dimethyl-1-pyrroline N-oxide (DMPO), and analogs BMPO, DEPMPO, and DIPPMPO, was performed on RAW 264.7 macrophages stimulated with phorbol 12-myristate 13-acetate. Our results show that Mito-DIPPMPO and CD-DIPPMPO enable a higher detection of superoxide adduct, with a low (if any) amount of hydroxyl adduct. CD-DIPPMPO, especially, appears to be a superior spin trap for extracellular superoxide detection in living macrophages, allowing measurement of superoxide production in unstimulated cells for the first time. The main rationale put forward for this extreme sensitivity is that the extracellular localization of the spin trap prevents the reduction of the spin adducts by ascorbic acid and glutathione within cells.

  4. Superoxide generation in extracts from isolated plant cell walls is regulated by fungal signal molecules.

    Science.gov (United States)

    Kiba, A; Miyake, C; Toyoda, K; Ichinose, Y; Yamada, T; Shiraishi, T

    1997-08-01

    ABSTRACT Fractions solubilized with NaCl from cell walls of pea and cowpea plants catalyzed the formation of blue formazan from nitroblue tetrazolium. Because superoxide dismutase decreased formazan production by over 90%, superoxide anion (O(2) ) may participate in the formation of formazan in the solubilized cell wall fractions. The formazan formation in the fractions solubilized from pea and cowpea cell walls was markedly reduced by exclusion of NAD(P)H, manganese ion, or p-coumaric acid from the reaction mixture. The formazan formation was severely inhibited by salicylhydroxamic acid and catalase, but not by imidazole, pyridine, quinacrine, and diphenyleneiodonium. An elicitor preparation from the pea pathogen Mycosphaerella pinodes enhanced the activities of formazan formation nonspecifically in both pea and cowpea fractions. The suppressor preparation from M. pinodes inhibited the activity in the pea fraction in the presence or absence of the elicitor. In the cowpea fraction, however, the suppressor did not inhibit the elicitor-enhanced activity, and the suppressor alone stimulated formazan formation. These results indicated that O(2) generation in the fractions solubilized from pea and cowpea cell walls seems to be catalyzed by cell wall-bound peroxidase(s) and that the plant cell walls alone are able to respond to the elicitor non-specifically and to the suppressor in a species-specific manner, suggesting the plant cell walls may play an important role in determination of plant-fungal pathogen specificity.

  5. High glucose impairs superoxide production from isolated blood neutrophils

    DEFF Research Database (Denmark)

    Perner, A; Nielsen, S E; Rask-Madsen, J

    2003-01-01

    Superoxide (O(2)(-)), a key antimicrobial agent in phagocytes, is produced by the activity of NADPH oxidase. High glucose concentrations may, however, impair the production of O(2)(-) through inhibition of glucose-6-phosphate dehydrogenase (G6PD), which catalyzes the formation of NADPH. This study...

  6. Role of active oxidative species on TiO2 photocatalysis of tetracycline and optimization of photocatalytic degradation conditions.

    Science.gov (United States)

    Luo, Zhaohui; Li, Lu; Wei, Chuanlin; Li, Huixin; Chen, Dan

    2015-07-01

    The optimum operating conditions for TiO2 photocatalytic degradation of tetracycline antibiotic (TC) in aqueous solution and the role of active oxidative species (AOS) from UV/TiO2 in its degradation were investigated. Response surface methodology (RSM) and central composite design (CCD) were adopted to optimize three parameters: TiO2 concentration, initial pH and UV irradiation time. Radical scavengers were added to reaction solution to assess the photocatalytic reaction mechanism of TC. The results showed that 93.1% degradation efficiency was obtained under optimum conditions established during experimentation (TiO2 concentration = 2.09 g l(-1), pH = 5.56 and t = 20.95 min). These results agree with the prediction made by the proposed model. Photocatalytic degradation of TC followed a pseudo first-order reaction rate. Photogenerated holes (h+(VB)) with minor participation from superoxide anions (O2*), were responsible for TC oxidation on TiO2, while hydroxyl radicals (*OH) played a negligible role in titania-TC oxidation.

  7. Synthesis, Crystal Structures and Properties of Tetrametallic Complexes: [M2(phen)4(FCA)2](ClO4)2o(H2O)2 (M=Zn or Co, phen= 1,10-phenanthroline, FCA =anion of 3-ferrocenyl-2-crotonic acid)

    Institute of Scientific and Technical Information of China (English)

    YANG Jia-Xiang; HU Zhang-Jun; ZHANG Ze; TIAN Yu-Peng; LIU Qing-Liang; CHANTRAPROMMA Suchada; FUN Hoong-Kun

    2005-01-01

    Two new complexes [Zn2(phen)4(FCA)2](ClO4)2·(H2O)2 (1) and [Co2(phen)4 (FCA)2](ClO4)2·(H2O)2 (2) (FCA =anion of 3-ferrocenyl-2-crotonic acid, phen= 1,10-phenanthroline) have been synthesized, and characterized by elemental analysis, IR, UV-Vis spectra, thermal analyses, and single-crystal X-ray diffraction. Two M(Ⅱ) (M=Zn or Co) ions are bridged by two FCA anions with syn-anti bridging ligands, leading to dimeric cores,[M2(phen)4(FCA)2]2+, and each M(Ⅱ) ion is six-coordinated in a distorted octahedral geometry by two chelate phen ligands and two μ2-carboxylate oxygen atoms from two FCA groups. The M(Ⅱ)…M(Ⅱ) intradimer distances are 0.4391 and 0.4462 nm in 1 and 2, respectively. Electrochemical properties of the complexes have been discussed.

  8. High glucose impairs superoxide production from isolated blood neutrophils

    DEFF Research Database (Denmark)

    Perner, A; Nielsen, S E; Rask-Madsen, J

    2003-01-01

    Superoxide (O(2)(-)), a key antimicrobial agent in phagocytes, is produced by the activity of NADPH oxidase. High glucose concentrations may, however, impair the production of O(2)(-) through inhibition of glucose-6-phosphate dehydrogenase (G6PD), which catalyzes the formation of NADPH. This stud...... measured the acute effects of high glucose or the G6PD inhibitor dehydroepiandrosterone (DHEA) on the production of O(2)(-) from isolated human neutrophils....

  9. Enhanced Cycling Stability of Rechargeable Li-O2 Batteries Using High Concentration Electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Bin; Xu, Wu; Yan, Pengfei; Sun, Xiuliang; Bowden, Mark E.; Read, Jeffrey; Qian, Jiangfeng; Mei, Donghai; Wang, Chong M.; Zhang, Jiguang

    2016-01-26

    The electrolyte stability against reactive reduced-oxygen species is crucial for the development of rechargeable Li-O2 batteries. In this work, we systematically investigated the effect of lithium salt concentration in 1,2-dimethoxyethane (DME)-based electrolytes on the cycling stability of Li-O2 batteries. Cells with high concentration electrolyte illustrate largely enhanced cycling stability under both the full discharge/charge (2.0-4.5 V vs. Li/Li+) and the capacity limited (at 1,000 mAh g-1) conditions. These cells also exhibit much less reaction-residual on the charged air electrode surface, and much less corrosion to the Li metal anode. The density functional theory calculations are conducted on the molecular orbital energies of the electrolyte components and the Gibbs activation barriers for superoxide radical anion to attack DME solvent and Li+-(DME)n solvates. In a highly concentrated electrolyte, all DME molecules have been coordinated with salt and the C-H bond scission of a DME molecule becomes more difficult. Therefore, the decomposition of highly concentrated electrolyte in a Li-O2 battery can be mitigated and both air-cathodes and Li-metal anodes exhibits much better reversibility. As a results, the cyclability of Li-O2 can be largely improved.

  10. Sipunculan celomocytes increase the resistance to H2O2-induced cell death under hypoxia

    Directory of Open Access Journals (Sweden)

    T Lombardo

    2014-03-01

    Full Text Available Themiste petricola is a marine intertidal endolithic worm that experiences transient hypoxia within its habitat, owing to natural sediment movements or increased organic enrichment. We characterized and quantified the cytotoxic effect of H2O2 in celomocytes of the sipunculan Themiste petricola under normoxia and hypoxia (O2 < 0.1 % through the median effect method. The 50 % cell death H2O2 dose at 24 h (EC50 under normoxia was 1.5 mM. The range EC10-EC90 was 0.6 mM - 3.9 mM. The fraction of cells having collapsed mitochondrial membrane potential (MMP was increased dose-dependently after 3 h exposure with 24 h cytotoxic doses of H2O2 from EC10 to EC90. The 24 h cytotoxic dose inducing 50 % of cells with collapsed MMP at 3 h was 3.67 mM. Intracellular superoxide anion production was increased dose-dependently, while reduced glutathione was decreased dose-dependently at 3 h with H2O2 from EC10 to EC90. Exposure to 24 h hypoxia did not cause cell death but induced intracellular acidification. The 24 h EC50 of H2O2 under hypoxia was increased to 4.7 mM while the range EC10-EC90 was increased to 0.9 mM - 25.1 mM. We conclude that hypoxia induces anaerobic metabolism and increases tolerance to H2O2-induced cell death in celomocytes of Themiste petricola preserving the immune functions and providing an advantage to survive under low oxygen tension.

  11. Preparation and Characterization of TiO2 Nanotubes Array by Anodic Oxidation in Anionic Modified Glycerol-Based Electrolyte%阴离子改性甘油溶液中TiO2纳米管阵列的制备和表征

    Institute of Scientific and Technical Information of China (English)

    肖秀峰; 梁建鹤; 汤海贞; 杨小娟; 刘榕芳

    2013-01-01

    本文采用电化学阳极氧化法以含氟的甘油和水混合溶液为电解液在纯钛表面制备了一层排列规整的TiO2纳米管阵列,研究了电解液中额外添加3种2价阴离子、不同的电解时间及不同的添加物浓度等因素对所获得的TiO2纳米管阵列形貌的影响.结果表明,在改性电解液中制备的TiO2纳米管阵列的长度均超过了未改性的电解液中制备的,并随着氧化时间的增长,纳米管管口直径增大,管壁变薄;同时添加的(NH42TiF6浓度在0.025~0.1 mol·L-1范围内均可获得管长更长且形貌较好的TiO2纳米管阵列.%High-order T1O2 nanotube arrays on titanium foils were prepared in glycerol-based electrolyte containing fluorine and water by electrochemical anodic oxidation in this work. The influence of different dianion additives, different oxidation duration and concentration of electrolyte additives on the effect of the morphology of TiO2 nanotube arrays were investigated. Results showed that the length of TiO2 nanotube arrays in the modified electrolyte were longer than the samples in the unmodified electrolyte. And with the growth of oxidation duration, the diameter of the nanotubes increased, the wall were thinner; moreover better and longer TiO2 nanotube arrays can be prepared in the glycerol-based electrolyte with the range of the concentration of (NH4)2TiF6.

  12. Simultaneous monitoring of superoxides and intracellular calcium ions in neutrophils by chemiluminescence and fluorescence: evaluation of action mechanisms of bioactive compounds in foods.

    Science.gov (United States)

    Kazumura, Kimiko; Sato, Yukiko; Satozono, Hiroshi; Koike, Takashi; Tsuchiya, Hiroshi; Hiramatsu, Mitsuo; Katsumata, Masakazu; Okazaki, Shigetoshi

    2013-10-01

    We have developed a measuring system for simultaneous monitoring of chemiluminescence and fluorescence, which indicate respectively, (i) generation of superoxide anion radicals (O2(-•)) and (ii) change in the intracellular calcium ion concentration ([Ca(2+)]i) of neutrophils triggered by the mechanism of innate immune response. We applied this measuring system for establishing a method to distinguish between anti-inflammatory actions and antioxidant actions caused by bioactive compounds. We evaluated anti-inflammatory agents (zinc ion [Zn(2+)] and ibuprofen) and antioxidants (superoxide dismutase [SOD] and ascorbic acid). It was shown that ibuprofen and Zn(2+) were anti-inflammatory while SOD and ascorbic acid were anti-oxidative. We conclude that it is possible to determine the mechanism of action of bioactive compounds using this method.

  13. To what end does nature produce superoxide? NADPH oxidase as an autocrine modifier of membrane phospholipids generating paracrine lipid messengers.

    Science.gov (United States)

    Saran, Manfred

    2003-10-01

    Production of superoxide anion O2*- by the membrane-bound enzyme NADPH oxidase of phagocytes is a long-known phenomenon; it is generally assumed that O2*-helps phagocytes kill bacterial intruders. The details and the chemistry of the killing process have, however, remained a mystery. Isoforms of NADPH oxidase exist in membranes of nearly every cell, suggesting that reactive oxygen species (ROS) participate in intra- and intercellular signaling processes. What the nature of the signal is exactly, how it is transmitted, and what structural characteristics a receptor of a "radical message" must have, have not been addressed convincingly. This review discusses how the action of messengers is in agreement with radical-specific behavior. In search for the smallest common denominator of cellular free radical activity we hypothesize that O2*- and its conjugate acid, HO2*, may have evolved under primordial conditions as regulators of membrane mechanics and that isoprostanes, widely used markers of "oxidative stress", may be an adventitious correlate of this biologic activity of O2*-/HO2*. An overall picture is presented that suggests that O2*-/HO2* radicals, by modifying cell membranes, help other agents gain access to the hydrophobic region of phospholipid bilayers and hence contribute to lipid-dependent signaling cascades. With this, O2*-/HO2* are proposed as indispensable adjuvants for the generation of cellular signals, for membrane transport, channel gating and hence, in a global sense, for cell viability and growth. We also suggest that many of the allegedly O2*- dependent bacterial pathologies and carcinogenic derailments are due to membrane-modifying activity rather than other chemical reactions of O2*-/HO2*. A consequence of this picture is the potential evolution of the "radical theory of ageing" to a "lipid theory of aging".

  14. Is the HO4- anion a key species in the aqueous-phase decomposition of ozone?

    Science.gov (United States)

    Anglada, Josep M; Torrent-Sucarrat, Miquel; Ruiz-Lopez, Manuel F; Martins-Costa, Marilia

    2012-10-15

    The role of the HO(4)(-) anion in atmospheric chemistry and biology is a matter of debate, because it can be formed from, or be in equilibrium with, key species such as O(3) + HO(-) or HO(2) + O(2) (-). The determination of the stability of HO(4)(-) in water therefore has the greatest relevance for better understanding the mechanism associated with oxidative cascades in aqueous solution. However, experiments are difficult to perform because of the short-lived character of this species, and in this work we have employed DFT, CCSD(T) complete basis set (CBS), MRCI/aug-cc-pVTZ, and combined quantum mechanics/molecular mechanics (QM/MM) calculations to investigate this topic. We show that the HO(4)(-) anion has a planar structure in the gas phase, with a very large HOO-OO bond length (1.823 Å). In contrast, HO(4)(-) adopts a nonplanar configuration in aqueous solution, with huge geometrical changes (up to 0.232 Å for the HOO-OO bond length) with a very small energy cost. The formation of the HO(4)(-) anion is predicted to be endergonic by 5.53±1.44 and 2.14±0.37 kcal mol(-1) with respect to the O(3) + HO(-) and HO(2) + O(2)(-) channels, respectively. Moreover, the combination of theoretical calculations with experimental free energies of solvation has allowed us to obtain accurate free energies for the main reactions involved in the aqueous decomposition of ozone. Thus, the oxygen transfer reaction (O(3) + OH(-) → HO(2) + O(2)(-)) is endergonic by 3.39±1.80 kcal mol(-1), the electron transfer process (O(3) + O(2)(-) → O(3)(-) + O(2)) is exergonic by 31.53±1.05 kcal mol(-1), supporting the chain-carrier role of the superoxide ion, and the reaction O(3) + HO(2)(-) → OH + O(2)(-) + O(2) is exergonic by 12.78±1.15 kcal mol(-1), which is consistent with the fact that the addition of small amounts of HO(2)(-) (through H(2)O(2)) accelerates ozone decomposition in water. The combination of our results with previously reported thermokinetic data provides some

  15. Simultaneous photoinduced generation of Fe(2+) and H2O2 in rivers: An indicator for photo-Fenton reaction.

    Science.gov (United States)

    Mostofa, Khan M G; Sakugawa, Hiroshi

    2016-09-01

    The photo-Fenton reaction is a key source of the highly reactive hydroxyl radical (HO) that is produced by the reaction of simultaneous photo-induced generation of Fe(2)(+)-dissolved organic matter (DOM) with H2O2 in sunlit surface waters as well as in the treatment of organic pollutants in the advanced oxidation processes (AOPs). Concentrations of both H2O2 and Fe(2)(+)-DOM were dependent on time and total solar intensity flux, and their levels were highest in the diurnal samples collected at noon compared with the samples collected during the period before sunrise and after sunset. H2O2 and Fe(2)(+)-DOM concentrations during monthly readings were also found higher in comparison with the diurnal samples, shortly before sunrise or after sunset. A π-electron bonding system is formed between Fe and the functional groups in DOM (Fe-DOM), through electron donation from the functional groups of DOM to an empty d-orbital of Fe. The π-electron is loosely bound and is highly susceptible to a rapid excitation upon light exposure that will provide better understanding of the formation of aqueous electrons, superoxide radical anions, H2O2 and finally, photo-Fenton reactions, too. Our results imply that simultaneous generation of H2O2 and Fe(2)(+)-DOM upon sunlight exposure during the daytime is most likely to be the key photo-Fenton reaction pathway, taking place in surface waters.

  16. Reaction Mechanisms for the Limited Reversibility of Li-O2 Chemistry in Organic Carbonate Electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Wu; Xu, Kang; Viswanathan, Vilayanur V.; Towne, Silas A.; Hardy, John S.; Xiao, Jie; Nie, Zimin; Hu, Dehong; Wang, Deyu; Zhang, Jiguang

    2011-11-15

    The Li-O2 chemistry in nonaqueous carbonate electrolytes and the underneath reason of its limited reversibility was exhaustively investigated. The discharge products collected from the air cathode in a Li-O2 battery at different depth of discharge (DOD) were systematically analyzed with X-ray diffraction. It is revealed that, independent of the discharge depth, lithium alkylcarbonate (either lithium propylenedicarbonate - LPDC, or lithium ethylenedicarbonate - LEDC, with other related derivatives) and lithium carbonate (Li2CO3) are always the main products, obviously originated from the electrolyte solvents propylene carbonate (PC) and ethylene carbonate (EC). These lithium alkylcarbonates are obviously generated from the single-electron reductive decomposition of the corresponding carbonate solvents initiated by the attack of superoxide radical anions. On the other hand, neither lithium peroxide (Li2O2) nor lithium oxide (Li2O) is detected. More significantly, from in situ gas chromatography/mass spectroscopy it is found that Li2CO3 and Li2O cannot be oxidized even when charged up to 4.6 V vs. Li/Li+, while LPDC, LEDC and Li2O2 are readily able to, with CO2 and CO released with the re-oxidation of LPDC and LEDC. It is therefore concluded that the quasi-reversibility of Li-O2 chemistry observed hitherto in an organic carbonate-based electrolyte is actually reliant on the formation of lithium alkylcarbonates through the reductive decomposition of carbonate solvents during discharge process and the subsequent oxidation of these same alkylcarbonates during charge process. It is the poor oxidizability of these alkylcarbonate species that constitutes the obstruction to an ideal rechargeable Li-O2 battery.

  17. 溶液中阴离子对UV/H2O2降解十二烷基苯磺酸钠的影响及其机理%Effects of anions on UV/H2O2 oxidation of linear alkyl benzene sulfonate

    Institute of Scientific and Technical Information of China (English)

    潘晶; 陈永强; 索艳丽; 孙铁珩

    2007-01-01

    研究了UV/H2O2工艺对十二烷基苯磺酸钠(LAS)的去除效果、溶液中阴离子对LAS降解的影响及机理.结果表明:UV/H2O2工艺可以有效地去除水中的LAS;在H2O2投加量为8 mg/L,14 W低压汞灯照射下,LAS在蒸馏水和自来水中的反应速率常数分别为0.018 0 、0.012 2 min-1;NO-3、Cl-、SO2-4和HCO-3对LAS光降解有抑制作用,当该4种离子摩尔浓度均分别为5、10、15 mmol/L时,对LAS光降解的抑制程度为HCO-3》NO-3》Cl-》SO2-4,且随着离子摩尔浓度的增大,抑制作用增强;LAS在自来水中的反应速率常数低于在蒸馏水中的反应速率常数是由于水中多种离子影响的结果.

  18. Reduced glomerular filtration rate, inflammation and HDL cholesterol as main determinants of superoxide production in non-dialysis chronic kidney disease patients.

    Science.gov (United States)

    Morena, Marion; Patrier, Laure; Jaussent, Isabelle; Bargnoux, Anne-Sophie; Dupuy, Anne-Marie; Badiou, Stéphanie; Leray-Moragues, Hélène; Klouche, Kada; Canaud, Bernard; Cristol, Jean-Paul

    2011-06-01

    Enhanced oxidative stress partly resulting from an over-production of superoxide anion (O(2)(•-)) represents a novel and particular risk factor in chronic kidney disease (CKD) patients. This study was therefore designed to evaluate O(2)(•-) determinants in this population. O(2)(•-) production was evaluated using chemiluminescence method in 136 CKD patients (79M/57F, median age: 69.5 [27.4-94.6]). Renal function (evaluated by the glomerular filtration rate using modification of diet in renal disease (MDRD)), inflammation, lipids, nutritional and bone mineral as well as clinical parameters were evaluated. Potential relationships between O(2)(•-) and these clinico-biological parameters were investigated to identify main determinants of such a pathological process. Enhanced O(2)(•-) production has been observed at the pre-dialysis phase: stages 4 and 5 of CKD (p = 0.0065). In multivariate analysis, low eGFR (MDRD <30 mL/min/1.73 m(2); p = 0.046), high fibrinogen (≥3.7 g/L; p = 0.044) and abnormal HDL cholesterol (<1.42 mmol/L and ≥ 1.75 mmol/L; p = 0.042) were the main determinants of O(2)(•-) production in CKD patients.

  19. Expanded Bed Recovery of D-2-Chloropropionic Acid Dehalogenase Using TiO2-Densified Cellulose Anion Exchanger%使用纤维素-钛白粉复合扩张床阴离子吸附剂提取D-2-氯丙酸脱卤酶

    Institute of Scientific and Technical Information of China (English)

    雷引林; 金志华; 童微星; 姚善泾; 朱自强

    2006-01-01

    The TiO2-densified cellulose composite beads were activated by epichlorohydrin and coupled with diethylamine, to function as an anion exchanger for expanded bed chromatography. The adsorbent exhibited a favorable performance of expanded bed adsorption for proteins, and therefore was applied to the expanded bed recovery of D-2-chloropropionic acid dehalogenase directly from the unclarified homogenate of Pseudomonas sp. NT21. The binding capacity of the dehalogenase was found to be 8.54U·ml-1 adsorbent, and two active peaks were eluted respectively at 0.15mol· L-1 and 0.3mol· L-1 (NH4)2SO4. The result indicated that the overall enzyme yield was 68%,with a purification factor of 22. In comparison to other recovery processes, the yield of the expanded bed process rises at least 70%, simultaneously saving a great deal of operation time and costs.

  20. A mitochondrial superoxide theory for oxidative stress diseases and aging.

    Science.gov (United States)

    Indo, Hiroko P; Yen, Hsiu-Chuan; Nakanishi, Ikuo; Matsumoto, Ken-Ichiro; Tamura, Masato; Nagano, Yumiko; Matsui, Hirofumi; Gusev, Oleg; Cornette, Richard; Okuda, Takashi; Minamiyama, Yukiko; Ichikawa, Hiroshi; Suenaga, Shigeaki; Oki, Misato; Sato, Tsuyoshi; Ozawa, Toshihiko; Clair, Daret K St; Majima, Hideyuki J

    2015-01-01

    Fridovich identified CuZnSOD in 1969 and manganese superoxide dismutase (MnSOD) in 1973, and proposed "the Superoxide Theory," which postulates that superoxide (O2 (•-)) is the origin of most reactive oxygen species (ROS) and that it undergoes a chain reaction in a cell, playing a central role in the ROS producing system. Increased oxidative stress on an organism causes damage to cells, the smallest constituent unit of an organism, which can lead to the onset of a variety of chronic diseases, such as Alzheimer's, Parkinson's, amyotrophic lateral sclerosis and other neurological diseases caused by abnormalities in biological defenses or increased intracellular reactive oxygen levels. Oxidative stress also plays a role in aging. Antioxidant systems, including non-enzyme low-molecular-weight antioxidants (such as, vitamins A, C and E, polyphenols, glutathione, and coenzyme Q10) and antioxidant enzymes, fight against oxidants in cells. Superoxide is considered to be a major factor in oxidant toxicity, and mitochondrial MnSOD enzymes constitute an essential defense against superoxide. Mitochondria are the major source of superoxide. The reaction of superoxide generated from mitochondria with nitric oxide is faster than SOD catalyzed reaction, and produces peroxynitrite. Thus, based on research conducted after Fridovich's seminal studies, we now propose a modified superoxide theory; i.e., superoxide is the origin of reactive oxygen and nitrogen species (RONS) and, as such, causes various redox related diseases and aging.

  1. Synthesis and the crystal and molecular structure of the silver(I)-germanium(IV) polymeric complex with citrate anions {[Ag2Ge(H Cit)2(H2O)2] • 2H2O} n

    Science.gov (United States)

    Sergienko, V. S.; Martsinko, E. E.; Seifullina, I. I.; Churakov, A. V.; Chebanenko, E. A.

    2016-03-01

    The synthesis and X-ray diffraction study of compound {[Ag2Ge(H Cit)2(H2O)2] • 2H2O} n , where H4 Cit is the citric acid, are performed. In the polymeric structure, the H Cit 3- ligand fulfils the tetradentate chelate-μ4-bridging (3Ag, Ge) function (tridentate with respect to Ge and Ag atoms). The Ge atom is octahedrally coordinated by six O atoms of two H Cit 3-ligands. The coordination polyhedron of the Ag atom is an irregular five-vertex polyhedron [four O atoms of four H Cit 3- ligands and the O(H2O) atom]. An extended system of O-H···O hydrogen bonds connects complex molecules into a supramolecular 3D-framework.

  2. Exploring the microscopic solvation of doubly charged anions: symmetric or asymmetric solvation in the CO 2-(CH 2) 4-CO 22-·(H 2O) 2 dicarboxylate dianion cluster?

    Science.gov (United States)

    Dessent, Caroline E. H.; Rigby, Christopher

    2003-03-01

    Optimised geometries and absolute energies of CO 2-(CH 2) 4-CO 22-·(H 2O) n, n=0,1,2, were determined using density functional methods. The n=1 global minimum was found to contain a bifurcated hydrogen-bond, with the n=2 minimum containing two such bonds. Vertical detachment energies (VDEs) obtained for the n=1,2 global minima at the MP2/6-31+G*//B3LYP/6-31+G* level agree well with experiment, and suggest that the two waters solvate the carboxylate groups separately in CO 2-(CH 2) 4-CO 22-·(H 2O) 2. However, a number of different isomers were identified for both clusters with several isomers producing similar VDEs, indicating that the measured VDEs may contain contributions from multiple isomers. Calculations are presented illustrating that IR predissociation spectra would allow the direct identification of these isomers.

  3. A lithium-oxygen battery based on lithium superoxide.

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Jun; Lee, Yun Jung; Luo, Xiangyi; Lau, Kah Chun; Wen, Jianguo; Wang, Hsien-Hau; Zhai, Dengyun; Miller, Dean; Jeong, Yo-Sub; Park, Jin-Bum; Curtiss, Larry A.; Amine, Khalil

    2016-01-11

    Although the superoxide of lithium (LiO2) is believed to be a key intermediate in Li-O2 batteries leading to the formation of lithium peroxide, LiO2 has never been observed in its pure state. In this work, we provide evidence that use of a cathode based on a reduced graphene oxide with Ir nanoparticles in a Li-O2 battery results in a LiO2 discharge product formed by single electron transfer without further electron transfer or disproportionation to form Li2O2. High energy X-ray diffraction (HE-XRD) patterns indicates the presence of crystalline LiO2 with no evidence of Li2O2 or Li2O. The HEXRD studies as a function of time also show that LiO2 can be stable in its crystalline form after one week of aging in the presence of electrolyte. The results provide evidence that LiO2 is stable enough that it can be repeatedly charged and discharged with a very low charge potential (~3.2 V) and may open the avenue for a lithium superoxide-based battery.

  4. ROLE OF COPPER,ZINC-SUPEROXIDE DISMUTASE IN CATALYZING NITROTYROSINE FORMATION IN MURINE LIVER

    Science.gov (United States)

    The solely known function of Cu,Zn-superoxide dismutase (SOD1) is to catalyze the dismutation of superoxide anion into hydrogen peroxide. Our objective was to determine if SOD1 catalyzed murine liver protein nitration induced by acetaminophen (APAP) and lipopolysaccharide (LPS). Liver and plasma ...

  5. A new formula to calculate activity of superoxide dismutase in indirect assays

    NARCIS (Netherlands)

    Zhang, Chen; Bruins, Marieke E.; Yang, Zhi Qiang; Liu, Shu Tao; Rao, Ping Fan

    2016-01-01

    To calculate superoxide dismutase (SOD) activity rapidly and accurately by indirect SOD assays, a formula based on the ratio of the catalytic speed of SOD to the reaction speed of the indicator with superoxide anion was deduced. The accuracy of this formula was compared with the conventional form

  6. Extra Copper-mediated Enhancement of the DNA Cleavage Activity Supported with Wild-type Cu, Zn Superoxide Dismutase

    Institute of Scientific and Technical Information of China (English)

    ZHOU Ruo-Yu; JIANG Wei; ZHANG Li-Na; WANG Li; LIU Chang-Lin

    2008-01-01

    It is well known that the primary function of wild type Cu, Zn superoxide dismutase (holo SOD) is to catalyze the conversion of the superoxide anion to H2O2 and O2 as an antioxidant enzyme. However, the aberrant copper-mediated oxidation chemistry in the enzyme (including its mutation forms) that damages nucleic acids, proteins including itself and cell membrane has attracted extensive attention in the past decade. The present study examined the hydrogen peroxide-dependent DNA cleavage activity supported with the combinations between holo SOD and extra copper (holo SOD+nCu(Ⅱ)). The results indicate that the presence of extra copper can enhance the DNA cleavage activity and a cooperative effect between holo SOD and the extra Cu(Ⅱ) occurs in DNA cleavage. The relative activity and kinetic assay showed that the DNA cleavage activity of holo SOD+nCu(Ⅱ) was enhanced upon addition of extra Cu(Ⅱ). The favorable pH regions for the DNA cleavage were observed to be 3.6-5.6 and 9.0-10, suggesting the species responsible for the DNA cleavage are different in different pH regions. In addition,to obtain an insight into DNA cleavage pathways, the effect of free radical scavengers and inhibitors on the DNA cleavage activity was probed.

  7. Co-Immobilization of Superoxide Dismutase with Catalase on Soft Microparticles Formed by Self-Assembly of Amphiphilic Poly(Aspartic Acid

    Directory of Open Access Journals (Sweden)

    Siyu Mao

    2017-07-01

    Full Text Available Through genetic engineering technology, catalase (CAT and superoxide dismutase (SOD have been separately fused to an elastin-like polypeptide (ELP. Thus, the enzymes can be purified through phase transition. Hexadecylamine-modified poly(aspartic acid (HPASP is able to self-assemble, forming soft microparticles. The HPASP microparticles were used to co-immobilize SOD-ELP and CAT-ELP through amidation reaction. Circular dichroism (CD confirmed that the secondary structures of the co-immobilized enzymes have been preserved. Fluorescence spectra showed that the co-immobilized enzymes exhibited a higher stability than the free enzymes. Dismutation of superoxide by superoxide dismutase (SOD generates hydrogen peroxide. By using the co-immobilized enzymes (SOD-ELP/CAT-ELP@HPASP, the generated hydrogen peroxide of SOD-ELP can be decomposed in situ by CAT-ELP. Activity assay results demonstrated that the superoxide anion (•O2− scavenging ability is 63.15 ± 0.75% for SOD-ELP/CAT-ELP@HPASP. The advantages of the approach of enzyme co-immobilization include the fact that the soft support HPASP itself is a polypeptide in nature, the stability of immobilized enzymes is improved, and a high activity has been achieved. Potentially SOD-ELP/CAT-ELP@HPASP can be applied in the cosmetic industry.

  8. L -propionyl-carnitine as superoxide scavenger, antioxidant, and DNA cleavage protector.

    Science.gov (United States)

    Vanella, A; Russo, A; Acquaviva, R; Campisi, A; Di Giacomo, C; Sorrenti, V; Barcellona, M L

    2000-01-01

    L-Propionylcarnitine, a propionyl ester of L-carnitine, increases the intracellular pool of L-carnitine. It exhibits a high affinity for the enzyme carnitine acetyltransferase (CAT) and, thus, is readily converted into propionyl-coenzyme A and free carnitine. It has been reported that L-propionylcarnitine possesses a protective action against heart ischemia-reperfusion injury; however, the antioxidant mechanism is not yet clear. L-Propionylcarnitine might reduce the hydroxyl radical production in the Fenton system, by chelating the iron required for the generation of hydroxyl radicals. To obtain a better insight into the antiradical mechanism of L-propionylcarnitine, the present research analyzed the superoxide scavenging capacity of L-propionylcarnitine and its effect on linoleic acid peroxidation. In addition, the effect of L-propionylcarnitine against DNA cleavage was estimated using pBR322 plasmid. We found that L-propionylcarnitine showed a dose-dependent free-radical scavenging activity. In fact, it was able to scavenge superoxide anion, to inhibit the lipoperoxidation of linoleic acid, and to protect pBR322 DNA from cleavage induced by H2O2 UV-photolysis.

  9. NOC/oFQ PKC-dependent superoxide generation contributes to hypoxic-ischemic impairment of NMDA cerebrovasodilation.

    Science.gov (United States)

    Armstead, W M

    2000-12-01

    This study determined whether nociceptin/orphanin FQ (NOC/oFQ) generates superoxide anion (O(2)(-)) in a protein kinase C (PKC)-dependent manner and whether such production contributes to hypoxic-ischemic (H-I) impairment of N-methyl-D-aspartate (NMDA)-induced pial artery dilation in newborn pigs equipped with closed cranial windows. Superoxide dismutase (SOD)-inhibitable nitroblue tetrazolium (NBT) reduction was an index of O(2)(-) generation. Under non-H-I conditions, topical NOC/oFQ (10(-10) M, concentration present in cerebrospinal fluid after I or H-I) increased SOD-inhibitable NBT reduction from 1 +/- 1 to 20 +/- 3 pmol/mm(2). PKC inhibitors staurosporine and chelerythrine (10(-7) M) blunted NBT reduction (1 +/- 1 to 7 +/- 2 pmol/mm(2) for chelerythrine), whereas the NOC/oFQ receptor antagonist [F/G]NOC/oFQ (1-13)-NH(2) (10(-6) M) blocked NBT reduction. [F/G]NOC/oFQ(1-13)-NH(2) and staurosporine also blunted the NBT reduction observed after I or H-I. NMDA (10(-8), 10(-6) M)-induced pial artery dilation was reversed to vasoconstriction after H-I. The NOC/oFQ antagonist staurosporine and free radical scavengers partially prevented this impaired dilation (sham: 9 +/- 1 and 16 +/- 1; H-I: -5 and -10 +/- 1; H-I staurosporine pretreated: 3 +/- 1 and 6 +/- 1%). These data show that NOC/oFQ increased O(2)(-) production in a PKC-dependent manner and contributed to this production after insult and that NOC/oFQ contributed to impaired NMDA-induced pial artery dilation after H-I, suggesting, therefore, that PKC-dependent O(2)(-) generation by NOC/oFQ links NOC/oFQ release to impaired NMDA dilation after H-I.

  10. Effect of superoxide and superoxide-generating systems on the prooxidant effect of iron in oil emulsion and raw turkey homogenates.

    Science.gov (United States)

    Ahn, D U; Kim, S M

    1998-09-01

    Mechanisms of superoxide.O2--generating systems on the pro-oxidant effect of iron from various sources were studied. Reaction mixtures were prepared with distilled water, oil emulsion, or meat homogenates. Free ionic iron (ferrous and ferric), ferritin and hemoglobin (Hb) were used as iron sources, and KO2 and xanthine oxidase (XOD) systems were used to produce .O2-. Thiobarbituric acid reactive substances (TBARS) values and iron contents of the reaction mixtures were determined. Ferric iron and ferritin, in the presence or absence of superoxide-generating systems, had no catalytic effect on the oxidation of oil emulsion but became pro-oxidants when reducing agent (ascorbate) was present. Ferrous iron and Hb had strong catalytic effects on the oxidation of oil emulsion as shown by TBARS values. Superoxide and H2O2, generated from superoxide-generating systems, oxidized ferrous iron and ascorbate, and lowered the pro-oxidant effect of ferrous iron in oil emulsion. Addition of ferric or ferrous iron increased but Hb did not have any effect on the TBARS values of raw meat homogenates. The reaction mechanisms of superoxide and the superoxide-generating systems on the prooxidant effect of various iron sources indicated that .O2- was a strong oxidizer rather than a reducing agent, and the antioxidant effect of XOD system in oil was caused by the oxidation of ferrous iron to the ferric form by .O2- and/or H2O2.

  11. Iron, copper, and manganese complexes with in vitro superoxide dismutase and/or catalase activities that keep Saccharomyces cerevisiae cells alive under severe oxidative stress.

    Science.gov (United States)

    Ribeiro, Thales P; Fernandes, Christiane; Melo, Karen V; Ferreira, Sarah S; Lessa, Josane A; Franco, Roberto W A; Schenk, Gerhard; Pereira, Marcos D; Horn, Adolfo

    2015-03-01

    Due to their aerobic lifestyle, eukaryotic organisms have evolved different strategies to overcome oxidative stress. The recruitment of some specific metalloenzymes such as superoxide dismutases (SODs) and catalases (CATs) is of great importance for eliminating harmful reactive oxygen species (hydrogen peroxide and superoxide anion). Using the ligand HPClNOL {1-[bis(pyridin-2-ylmethyl)amino]-3-chloropropan-2-ol}, we have synthesized three coordination compounds containing iron(III), copper(II), and manganese(II) ions, which are also present in the active site of the above-noted metalloenzymes. These compounds were evaluated as SOD and CAT mimetics. The manganese and iron compounds showed both SOD and CAT activities, while copper showed only SOD activity. The copper and manganese in vitro SOD activities are very similar (IC50~0.4 μmol dm(-3)) and about 70-fold higher than those of iron. The manganese compound showed CAT activity higher than that of the iron species. Analyzing their capacity to protect Saccharomyces cerevisiae cells against oxidative stress (H2O2 and the O2(•-) radical), we observed that all compounds act as antioxidants, increasing the resistance of yeast cells mainly due to a reduction of lipid oxidation. Especially for the iron compound, the data indicate complete protection when wild-type cells were exposed to H2O2 or O2(•-) species. Interestingly, these compounds also compensate for both superoxide dismutase and catalase deficiencies; their antioxidant activity is metal ion dependent, in the order iron(III)>copper(II)>manganese(II). The protection mechanism employed by the complexes proved to be independent of the activation of transcription factors (such as Yap1, Hsf1, Msn2/Msn4) and protein synthesis. There is no direct relation between the in vitro and the in vivo antioxidant activities. Copyright © 2014 Elsevier Inc. All rights reserved.

  12. On the reaction mechanism of the complete intermolecular O2 transfer between mononuclear nickel and manganese complexes with macrocyclic ligands.

    Science.gov (United States)

    Zapata-Rivera, Jhon; Caballol, Rosa; Calzado, Carmen J; Liakos, Dimitrios G; Neese, Frank

    2014-10-01

    The recently described intermolecular O2 transfer between the side-on Ni-O2 complex [(12-TMC)Ni-O2](+) and the manganese complex [(14-TMC)Mn](2+), where 12-TMC and 14-TMC are 12- and 14-membered macrocyclic ligands, 12-TMC=1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane and 14-TMC=1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane, is studied by means of DFT methods. B3LYP calculations including long-range corrections and solvent effects are performed to elucidate the mechanism. The potential energy surfaces (PESs) compatible with different electronic states of the reactants have been analyzed. The calculations confirm a two-step reaction, with a first rate-determining bimolecular step and predict the exothermic character of the global process. The relative stability of the products and the reverse barrier are in line with the fact that no reverse reaction is experimentally observed. An intermediate with a μ-η(1):η(1)-O2 coordination and two transition states are identified on the triplet PES, slightly below the corresponding stationary points of the quintet PES, suggesting an intersystem crossing before the first transition state. The calculated activation parameters and the relative energies of the two transition sates and the products are in very good agreement with the experimental data. The calculations suggest that a superoxide anion is transferred during the reaction.

  13. Cu/Zn superoxide dismutases in developing cotton fibers

    Science.gov (United States)

    Hydrogen peroxide (H2O2) and other reactive oxygen species (ROS) are important signaling molecules in diverse physiological processes. Previously, we discovered superoxide dismutase (SOD) activity in extracellular protein preparations from fiber-bearing cotton (Gossypium hirsutum L.) seeds. We sho...

  14. Extracellular superoxide dismutase of boar seminal plasma.

    Science.gov (United States)

    Kowalowka, M; Wysocki, P; Fraser, L; Strzezek, J

    2008-08-01

    Superoxide dismutase (SOD) is an enzymatic component of the antioxidant defense system that protects spermatozoa by catalysing the dismutation of superoxide anions to hydrogen peroxide and oxygen. Age and season effects on SOD activity in the seminal plasma were measured in boars at the onset of 8 months through a 35-month period. It was found that age-related changes in SOD activity in the seminal plasma were markedly higher in boars less than 2 years of age. However, it appeared that SOD activity was established at the early sexual maturity age (8-12 months). There were variations in SOD activity throughout the season, being significantly higher in spring and autumn than in summer. A secretory extracellular form of SOD (EC-SOD) was purified to homogeneity (350-fold) from boar seminal plasma, using a three-step purification protocol (affinity chromatography followed by ion exchange and ceramic hydroxyapatite chromatography). The molecular properties and specificity of SOD (molecular mass, isoelectric point, optimum pH, thermostability and susceptibility to inhibitors) confirmed that the purified enzyme is an extracellular form of Cu/Zn-superoxide dismutase occurring in boar seminal plasma. The results of this study indicate that EC-SOD is an important antioxidant enzyme of boar seminal plasma, which plays an important physiological role in counteracting oxidative stress in spermatozoa.

  15. H2O2 generated from mitochondrial electron transport chain in thoracic perivascular adipose tissue is crucial for modulation of vascular smooth muscle contraction.

    Science.gov (United States)

    Costa, Rafael M; Filgueira, Fernando P; Tostes, Rita C; Carvalho, Maria Helena C; Akamine, Eliana H; Lobato, Nubia S

    2016-09-01

    The perivascular adipose tissue (PVAT) releases a variety of factors that affect vascular function. PVAT in the thoracic aorta shares characteristics with the brown adipose tissue, including a large amount of mitochondria. PVAT-derived factors influence both endothelial and smooth muscle function via several signaling mechanisms including the release/generation of reactive nitrogen and oxygen species. Considering the importance of reactive oxygen species (ROS) on vascular function and that mitochondria are an important source of ROS, we hypothesized that mitochondria-derived ROS in the PVAT modulates vascular reactivity. Vascular reactivity to norephinephrine (NE) was evaluated in thoracic aortic rings, with or without endothelium and/or PVAT, from male Wistar rats. Mitochondrial uncoupling, as well as hydrogen peroxide (H2O2) removal, increased the contraction in vessels surrounded by PVAT. PVAT stimulated with NE exhibited increased protein expression, determined by Western blot analysis, of manganese superoxide dismutase (Mn-SOD) and decreased protein expression of catalase. Ultimately, NE increased superoxide anion (O2(-)) generation in PVAT via increases in intracellular calcium. These results clearly demonstrate that mitochondrial electron transport chain (mETC) in PVAT contributes to modulation of aortic muscle contraction by generating higher amounts of O2(-) that is, in turn, dismutated to hydrogen peroxide, which then acts as a pivotal signaling molecule regulating vascular smooth muscle contraction.

  16. Rapid reaction of nanomolar Mn(II) with superoxide radical in seawater and simulated freshwater

    Science.gov (United States)

    Hansard, S.P.; Easter, H.D.; Voelker, B.M.

    2011-01-01

    Superoxide radical (O2-) has been proposed to be an important participant in oxidation-reduction reactions of metal ions in natural waters. Here, we studied the reaction of nanomolar Mn(II) with O 2- in seawater and simulated freshwater, using chemiluminescence detection of O2- to quantify the effect of Mn(II) on the decay kinetics of O2-. With 3-24 nM added [Mn(II)] and superoxide could maintain a significant fraction of dissolved Mn in the +III oxidation state. ?? 2011 American Chemical Society.

  17. Superoxide reduction by a superoxide reductase lacking the highly conserved lysine residue.

    Science.gov (United States)

    Pinto, Ana F; Romão, Célia V; Pinto, Liliana C; Huber, Harald; Saraiva, Lígia M; Todorovic, Smilja; Cabelli, Diane; Teixeira, Miguel

    2015-01-01

    Superoxide reductases (SORs) are the most recently identified superoxide detoxification systems, being found in microorganisms from the three domains of life. These enzymes are characterized by a catalytic mononuclear iron site, with one cysteine and four histidine ligands of the ferrous active form. A lysine residue in the -EKHVP- motif, located close to the active site, has been considered to be essential for the enzyme function, by contributing to the positive surface patch that attracts the superoxide anion and by controlling the chemistry of the catalytic mechanism through a hydrogen bond network. However, we show here that this residue is substituted by non-equivalent amino acids in several putative SORs from Archaea and unicellular Eukarya. In this work, we focus on mechanistic and spectroscopic studies of one of these less common enzymes, the SOR from the hyperthermophilic Crenarchaeon Ignicoccus hospitalis. We employ pulse radiolysis fast kinetics and spectroscopic approaches to study the wild-type enzyme (-E23T24HVP-), and two mutants, T24K and E23A, the later mimicking enzymes lacking both the lysine and glutamate (a ferric ion ligand) of the motif. The efficiency of the wild-type protein and mutants in reducing superoxide is comparable to other SORs, revealing the robustness of these enzymes to single mutations.

  18. Theoretical determination of the alkali-metal superoxide bond energies

    Science.gov (United States)

    Partridge, Harry; Bauschlicher, Charles W., Jr.; Sodupe, Mariona; Langhoff, Stephen R.

    1992-01-01

    The bond dissociation energies for the alkali-metal superoxides have been computed using extensive Gaussian basis sets and treating electron correlation at the modified coupled-pair functional level. Our computed D0 values are 61.4, 37.2, 40.6, and 38.4 kcal/mol for LiO2, NaO2, KO2, and RbO2, respectively. These values, which are expected to be lower bounds and accurate to 2 kcal/mol, agree well with some of the older flame data, but rule out several recent experimental measurements.

  19. Pulse radiolysis studies on superoxide reductase from Treponema pallidum

    CERN Document Server

    Nivière, V; Fontecave, M; Houée-Levin, C

    2015-01-01

    Superoxide reductases (SORs) are small metalloenzymes, which catalyze reduction of O2*- to H2O2. The reaction of the enzyme from Treponema pallidum with superoxide was studied by pulse radiolysis methods. The first step is an extremely fast bi-molecular reaction of the ferrous center with O2, with a rate constant of 6 x 10 (8) M(-1) s(-1). A first intermediate is formed which is converted to a second one with a slower rate constant of 4800 s(-1). This latter value is 10 times higher than the corresponding one previously reported in the case of SOR from Desulfoarculus baarsii. The reconstituted spectra for the two intermediates are consistent with formation of transient iron-peroxide species.

  20. Production of superoxide and activity of superoxide dismutase in rabbit epididymal spermatozoa.

    Science.gov (United States)

    Holland, M K; Alvarez, J G; Storey, B T

    1982-12-01

    Mature rabbit spermatozoa from the cauda epididymidis suspended in potassium Tris phosphate buffer at 24 degrees C produced O2.-, as measured by reduction of acetylated ferricytochrome c, with an intrinsic rate of 0.20 nmol/min per 10(8) cells. This rate increased to 1.80 nmol/min per 10(8) cells in the presence of 10 mM cyanide. These spermatozoa contain 2.8 units per 10(8) cells of superoxide dismutase activity, 95% of which is sensitive, and 5% of which is insensitive, to cyanide inhibition. These activities correspond to the cytosolic Cu-Zn form and the mitochondrial Mn form of the dismutase, respectively. Only the cyanide-sensitive form is released from the sperm on hypo-osmotic treatment or sonication. Hypo-osmotically treated rabbit epididymal spermatozoa produced O2.- with an intrinsic rate of 0.24 nmol/min per 10(8) cells, which increased to 0.58 nmol/min per 10(8) cells in the presence of 10 mM cyanide. Both intact and hypo-osmotically treated cells react with O2.- in a second order reaction as inferred from the hyperbolic dependence on cell concentration of O2.- production rate in both the absence and presence of cyanide. The second order rate constant for this reaction with intact cells, kS, was calculated to be 22.9 X 10(-8) (cells/ml)-1 min-1 in its absence. For hypo-osmotically treated cells, the values of kS were 10.8 X 10(-8) (cells/ml)-1 min-1 and 8.2 X 10(-8) (cells/ml) -1 min-1, respectively. Since hypo-osmotically treated cells have lost much of their plasma membrane, the lower value of kS for the treated cells implies that this membrane is one site of reaction of O2.- with the cells. The increase in kS in the presence of cyanide, which inhibits superoxide dismutase and so increases O2.- production, suggests that the cells become more reactive with O2.- as its production rate increase, as would be expected for the occurrence of radical chain oxidation. This in turn suggests that superoxide dismutase plays a major role in protecting rabbit sperm

  1. Superoxide dismutase phenotypes in duodenal ulcers: A genetic marker?

    Directory of Open Access Journals (Sweden)

    Sulekha S

    2006-01-01

    Full Text Available Background:Cu-Zn superoxide dismutases are antioxidative defensive enzymes that catalyze the reduction of superoxide anions to hydrogen peroxide. Aim:The study focuses on the association of electromorph of superoxide dismutase with duodenal ulcers, which result due to an imbalance between aggressive and defensive factors. Materials and Methods:Endoscopically confirmed 210 duodenal ulcer patients and 185 healthy individuals for comparative analysis were considered for the present study. Phenotyping of superoxide dismutase was carried out by subjecting the RBC membranes to polyacrylamide gel electrophoresis, using appropriate staining protocols. Results:Statistical analysis of SOD phenotypes revealed a significant increase of SOD AFNx012 allele and Superoxide dismutases (SOD 2-2 phenotype in duodenal ulcer group. Among these individuals, a predominance of Helicobacter pylori infection was observed. The increased preponderance of homozygotes can be explained on the basis of reduced and altered enzyme activity, which may lead to disturbance in homeostasis of antioxidant/oxidant culminating in high lipid peroxidative gastric mucosal tissue damage and ulceration. No variation in the distribution of SOD phenotypes with respect to Helicobacter pylori indicates the role of Mn-SOD rather than Cu-Zn SOD in the Helicobacter pylori infected cases as reported earlier. Conclusions:Superoxide dismutase as a genetic marker / gene modifier, encoding for an antioxidant enzyme in maintaining tissue homeostasis of the gastric mucosa is discussed.

  2. Constraints on superoxide mediated formation of manganese oxides

    Directory of Open Access Journals (Sweden)

    Deric R. Learman

    2013-09-01

    Full Text Available Manganese (Mn oxides are among the most reactive sorbents and oxidants within the environment, where they play a central role in the cycling of nutrients, metals, and carbon. Recent discoveries have identified superoxide (O2- (both of biogenic and abiogenic origin as an effective oxidant of Mn(II leading to the formation of Mn oxides. Here we examined the conditions under which abiotically produced superoxide led to oxidative precipitation of Mn and the solid-phases produced. Oxidized Mn, as both aqueous Mn(III and Mn(III/IV oxides, was only observed in the presence of active catalase, indicating that hydrogen peroxide, a product of the reaction of O2- with Mn(II, inhibits the oxidation process presumably through the reduction of Mn(III. Citrate and pyrophosphate increased the yield of oxidized Mn but decreased the amount of Mn oxide produced via formation of Mn(III-ligand complexes. While complexing ligands played a role in stabilizing Mn(III, they did not eliminate the inhibition of net Mn(III formation by H2O2. The Mn oxides precipitated were highly disordered colloidal hexagonal birnessite, similar to those produced by biotically generated superoxide. Yet, in contrast to the large particulate Mn oxides formed by biogenic superoxide, abiotic Mn oxides did not ripen to larger, more crystalline phases. This suggests that the deposition of crystalline Mn oxides within the environment requires a biological, or at least organic, influence. This work provides the first direct evidence that, under conditions relevant to natural waters, oxidation of Mn(II by superoxide can occur and lead to formation of Mn oxides. For organisms that oxidize Mn(II by producing superoxide, these findings may also point to other microbially mediated processes, in particular enzymatic hydrogen peroxide degradation and/or production of organic ligand metabolites, that allow for Mn oxide formation.

  3. Models of Superoxide Dismutases

    Energy Technology Data Exchange (ETDEWEB)

    Cabelli, Diane E.; Riley, Dennis; Rodriguez, Jorge A.; Valentine, Joan Selverstone; Zhu, Haining

    1998-05-20

    In this review we have focused much of our discussion on the mechanistic details of how the native enzymes function and how mechanistic developments/insights with synthetic small molecule complexes possessing SOD activity have influenced our understanding of the electron transfer processes involved with the natural enzymes. A few overriding themes have emerged. Clearly, the SOD enzymes operate at near diffusion controlled rates and to achieve such catalytic turnover activity, several important physical principles must be operative. Such fast electron transfer processes requires a role for protons; i.e., proton-coupled electron transfer (''H-atom transfer'') solves the dilemma of charge separation developing in the transition state for the electron transfer step. Additionally, outer-sphere electron transfer is likely a most important pathway for manganese and iron dismutases. This situation arises because the ligand exchange rates on these two ions in water never exceed {approx}10{sup +7} s{sup -1}; consequently, 10{sup +9} catalytic rates require more subtle mechanistic insights. In contrast, copper complexes can achieve diffusion controlled (>10{sup +9}) exchange rates in water; thus inner-sphere electron transfer processes are more likely to be operative in the Cu/Zn enzymes. Recent studies have continued to expand our understanding of the mechanism of action of this most important class of redox active enzymes, the superoxide dismutases, which have been critical in the successful adaptation of life on this planet to an oxygen-based metabolism. The design of SOD mimic drugs, synthetic models compounds that incorporate this superoxide dismutase catalytic activity and are capable of functioning in vivo, offers clear potential benefits in the control of diseases, ranging from the control of neurodegenerative conditions, such as Parkinson's or Alzheimer's disease, to cancer.

  4. Simultaneous Determination of Trace Amount of Chlorite,Chlorate and Common Inorganic Anions in Running Water with kOH Isocratic Elution by Ion Chromatographic Method%KOH等度淋洗IC法同时测定自来水中微量ClO2-、ClO3-及常规阴离子

    Institute of Scientific and Technical Information of China (English)

    陈东; 罗倚坪

    2014-01-01

    The method to determine a trace of chlorite, chlorate and common inorganic anions in running water with KOH isocratic elution by ion chromatography was investigated. The conditions of method was that the concentration of KOH is 20. 5 mmol/L, the flow rate is 1. 0 mL/min, and the injection volume is 50 μL. The results showed that the concentration of F-,Cl-,NO3 -, SO4 2-,ClO2 -,ClO3 - in water was determined completely only in 12 minutes. The correlation coefficients of calibration curve was 0. 997 0-0. 999 9,while the detection limits was between 0. 05-7. 00 μg/L. The relative standard deviation( RSD) and the recoveries were between 0. 61%-3. 82%and 97. 6%-101. 7%, respectively. The method was sensitive, accurate and rapid, which was favorable to simultaneous quantification of chlorite, chlorate and common inorganic anions in drinking water.%建立了KOH等度淋洗离子色谱法同时测定自来水中微量亚氯酸盐、氯酸盐及氟化物、氯化物、硝酸盐、硫酸盐的分析方法。该方法以20.5 mmol/L KOH为淋洗液,流速1.0 mL/min,进样量50μL。结果表明,6种阴离子可在12分钟内检测完毕,各离子的线性相关系数为0.9970~0.9999;检出限为0.05~7.00μg/L;精密度为0.61%~3.82%;回收率为97.6%~101.7%,能够满足饮用水中这些指标的定量需要,是一种灵敏、准确、快速的理想方法。

  5. Hypochlorite and superoxide radicals can act synergistically to induce fragmentation of hyaluronan and chondroitin sulphates

    DEFF Research Database (Denmark)

    Rees, Martin D; Hawkins, Clare Louise; Davies, Michael Jonathan

    2004-01-01

    chelators and the metal ion-binding protein BSA, consistent with chloramide decomposition and polymer fragmentation occurring via O2*--dependent one-electron reduction, possibly catalysed by trace metal ions. Polymer fragmentation induced by O2*- [generated by the superoxide thermal source 1, di-(4...

  6. Dehydroepiandrosterone inhibits the spontaneous release of superoxide radical by alveolar macrophages in vitro in asbestosis

    Energy Technology Data Exchange (ETDEWEB)

    Rom, W.N.; Harkin, T. (New York Univ. Medical Center, New York (United States))

    1991-08-01

    Asbestosis is characterized by an alveolar macrophage alveolitis with injury and fibrosis of the lower respiratory tract. Alveolar macrophages recovered by bronchoalveolar lavage spontaneously release exaggerated amounts of oxidants including superoxide anion and hydrogen peroxide that may mediate alveolar epithelial cell injury. Dehydroepiandrosterone (DHEA) is a normally occurring adrenal androgen that inhibits glucose-6-phosphate dehydrogenase, the initial enzyme in the pentose phosphate shunt necessary for NADPH generation and superoxide anion formation. In this regard, the authors hypothesized that DHEA may reduce asbestos-induced oxidant release. DHEA added in vitro to alveolar macrophages lavaged from 11 nonsmoking asbestos workers significantly reduced superoxide anion release. DHEA is an antioxidant and potential anticarcinogenic agent that may have a therapeutic role in reducing the increased oxidant burden in asbestos-induced alveolitis of the lower respiratory tract.

  7. Synergy of metal and nonmetal dopants for visible-light photocatalysis: a case-study of Sn and N co-doped TiO2.

    Science.gov (United States)

    Zhuang, Huaqiang; Zhang, Yingguang; Chu, Zhenwei; Long, Jinlin; An, Xiaohan; Zhang, Hongwen; Lin, Huaxiang; Zhang, Zizhong; Wang, Xuxu

    2016-04-14

    This paper mainly focuses on the synergistic effect of Sn and N dopants to enhance the photocatalytic performance of anatase TiO2 under visible light or simulated solar light irradiation. The Sn and N co-doped TiO2 (SNT-x) photocatalysts were successfully prepared by the facile sol-gel method and the post-nitridation route in the temperature range of 400-550 °C. All the as-prepared samples were characterized in detail by X-ray diffraction, UV-vis diffuse reflectance spectroscopy, transmission electron microscopy, X-ray photoelectron and electron spin resonance spectroscopy and photoelectrochemical measurements. The characterization results reveal that the co-incorporation of Sn and N atoms remarkably modifies the electronic structure of TiO2, which gives rise to a prominent separation of photogenerated charge carriers and more efficient interfacial charge-transfer reactions in a photocatalytic process. The enhanced photocatalytic activity is attributed to the intensified active oxygen species including hydroxyl radicals (˙OH) and superoxide anion radicals (O2˙(-)) for degradation of organic pollutants. And the result of photocatalytic hydrogen production further confirms the existence of the synergistic effect in the SNT-x samples, because they exhibit higher photocatalytic activity than the sum of N/TiO2 and Sn/TiO2. This work provides a paradigm to consolidate the understanding of the synergistic effect of metal and non-metal co-doped TiO2 in domains of photocatalysis and photoelectrochemistry.

  8. Theoretical Limiting Potentials in Mg/O2 Batteries

    DEFF Research Database (Denmark)

    Smith, Jeffrey G.; Naruse, Junichi; Hiramatsu, Hidehiko

    2016-01-01

    A rechargeable battery based on a multivalent Mg/O2 couple is an attractive chemistry due to its high theoretical energy density and potential for low cost. Nevertheless, metal-air batteries based on alkaline earth anodes have received limited attention and generally exhibit modest performance....... In addition, many fundamental aspects of this system remain poorly understood, such as the reaction mechanisms associated with discharge and charging. The present study aims to close this knowledge gap and thereby accelerate the development of Mg/O2 batteries by employing first-principles calculations...... by the presence of large thermodynamic overvoltages. In contrast, MgO2-based cells are predicted to be much more efficient: superoxide-terminated facets on MgO2 crystallites enable low overvoltages and round-trip efficiencies approaching 90%. These data suggest that the performance of Mg/O2 batteries can...

  9. Dark production of extracellular superoxide by the coral Porites astreoides and representative symbionts

    Directory of Open Access Journals (Sweden)

    Tong Zhang

    2016-11-01

    Full Text Available The reactive oxygen species (ROS superoxide has been implicated in both beneficial and detrimental processes in coral biology, ranging from pathogenic disease resistance to coral bleaching. Despite the critical role of ROS in coral health, there is a distinct lack of ROS measurements and thus an incomplete understanding of underpinning ROS sources and production mechanisms within coral systems. Here, we quantified in situ extracellular superoxide concentrations at the surfaces of aquaria-hosted Porites astreoides during a diel cycle. High concentrations of superoxide (~10’s of nM were present at coral surfaces, and these levels did not change significantly as a function of time of day. These results indicate that the coral holobiont produces extracellular superoxide in the dark, independent of photosynthesis. As a short-lived anion at physiological pH, superoxide has a limited ability to cross intact biological membranes. Further, removing surface mucus layers from the P. astreoides colonies did not impact external superoxide concentrations. We therefore attribute external superoxide derived from the coral holobiont under these conditions to the activity of the coral host epithelium, rather than mucus-derived epibionts or internal sources such as endosymbionts (e.g., Symbiodinium. However, endosymbionts likely contribute to internal ROS levels via extracellular superoxide production. Indeed, common coral symbionts, including multiple strains of Symbiodinium (clades A to D and the bacterium Endozoicomonas montiporae LMG 24815, produced extracellular superoxide in the dark and at low light levels. Further, representative P. astreoides symbionts, Symbiodinium CCMP2456 (clade A and E. montiporae, produced similar concentrations of superoxide alone and in combination with each other, in the dark and low light, and regardless of time of day. Overall, these results indicate that healthy, non-stressed P. astreoides and representative symbionts produce

  10. Synthesis of decacationic [60]fullerene decaiodides giving photoinduced production of superoxide radicals and effective PDT-mediation on antimicrobial photoinactivation.

    Science.gov (United States)

    Wang, Min; Maragani, Satyanarayana; Huang, Liyi; Jeon, Seaho; Canteenwala, Taizoon; Hamblin, Michael R; Chiang, Long Y

    2013-05-01

    We report a novel class of highly water-soluble decacationic methano[60]fullerene decaiodides C60[>M(C3N6(+)C3)2]-(I(-))10 [1-(I(-))10] capable of co-producing singlet oxygen (Type-II) and highly reactive hydroxyl radicals, formed from superoxide radicals in Type-I photosensitizing reactions, upon illumination at both UVA and white light wavelengths. The O2(-)·-production efficiency of 1-(I(-))10 was confirmed by using an O2(-)·-reactive bis(2,4-dinitrobenzenesulfonyl)tetrafluorofluorescein probe and correlated to the photoinduced electron-transfer event going from iodide anions to (3)C60*[>M(C3N6(+)C3)2] leading to C60(-)·[>M(C3N6(+)C3)2]. Incorporation of a defined number (ten) of quaternary ammonium cationic charges per C60 in 1 was aimed to enhance its ability to target pathogenic Gram-positive and Gram-negative bacterial cells. We used the well-characterized malonato[60]fullerene diester monoadduct C60[>M(t-Bu)2] as the starting fullerene derivative to provide a better synthetic route to C60[>M(C3N6(+)C3)2] via transesterification reaction under trifluoroacetic acid catalyzed conditions. These compounds may be used as effective photosensitizers and nano-PDT drugs for photoinactivation of pathogens.

  11. Superoxide production and expression of NAD(P)H oxidases by transformed and primary human colonic epithelial cells

    DEFF Research Database (Denmark)

    Perner, A; Andresen, L; Pedersen, G

    2003-01-01

    Superoxide (O(2)(-)) generation through the activity of reduced nicotinamide dinucleotide (NADH) or reduced nicotinamide dinucleotide phosphate (NADPH) oxidases has been demonstrated in a variety of cell types, but not in human colonic epithelial cells.......Superoxide (O(2)(-)) generation through the activity of reduced nicotinamide dinucleotide (NADH) or reduced nicotinamide dinucleotide phosphate (NADPH) oxidases has been demonstrated in a variety of cell types, but not in human colonic epithelial cells....

  12. Production of superoxide/hydrogen peroxide by the mitochondrial 2-oxoadipate dehydrogenase complex.

    Science.gov (United States)

    Goncalves, Renata L S; Bunik, Victoria I; Brand, Martin D

    2016-02-01

    In humans, mutations in dehydrogenase E1 and transketolase domain containing 1 (DHTKD1) are associated with neurological abnormalities and accumulation of 2-oxoadipate, 2-aminoadipate, and reactive oxygen species. The protein encoded by DHTKD1 has sequence and structural similarities to 2-oxoglutarate dehydrogenase, and the 2-oxoglutarate dehydrogenase complex can produce superoxide/H2O2 at high rates. The DHTKD1 enzyme is hypothesized to catalyze the oxidative decarboxylation of 2-oxoadipate, a shared intermediate of the degradative pathways for tryptophan, lysine and hydroxylysine. Here, we show that rat skeletal muscle mitochondria can produce superoxide/H2O2 at high rates when given 2-oxoadipate. We identify the putative mitochondrial 2-oxoadipate dehydrogenase complex as one of the sources and characterize the conditions that favor its superoxide/H2O2 production. Rates increased at higher NAD(P)H/NAD(P)(+) ratios and were higher at each NAD(P)H/NAD(P)(+) ratio when 2-oxoadipate was present, showing that superoxide/H2O2 was produced during the forward reaction from 2-oxoadipate, but not in the reverse reaction from NADH in the absence of 2-oxoadipate. The maximum capacity of the 2-oxoadipate dehydrogenase complex for production of superoxide/H2O2 is comparable to that of site IF of complex I, and seven, four and almost two-fold lower than the capacities of the 2-oxoglutarate, pyruvate and branched-chain 2-oxoacid dehydrogenase complexes, respectively. Regulation by ADP and ATP of H2O2 production driven by 2-oxoadipate was very different from that driven by 2-oxoglutarate, suggesting that site AF of the 2-oxoadipate dehydrogenase complex is a new source of superoxide/H2O2 associated with the NADH isopotential pool in mitochondria.

  13. Superoxide and its metabolism during germination and axis growth of Vigna radiata (L.) Wilczek seeds.

    Science.gov (United States)

    Singh, Khangembam Lenin; Chaudhuri, Abira; Kar, Rup Kumar

    2014-01-01

    Involvement of reactive oxygen species in regulation of plant growth and development is recently being demonstrated with various results depending on the experimental system and plant species. Role of superoxide and its metabolism in germination and axis growth was investigated in case of Vigna radiata seeds, a non-endospermous leguminous species having epigeal germination, by studying the effect of different reactive oxygen species (ROS) inhibitors, distribution of O2(•)- and H2O2 and ROS enzyme profile in axes. Germination percentage and axis growth were determined under treatment with ROS inhibitors and scavengers. Localization of O2(•)- and H2O2 was done using nitroblue tetrazolium (NBT) and 3,3',5,5'-tetramethyl benzidine dihydrochloride hydrate (TMB), respectively. Apoplastic level of O2(•)- was monitored by spectrophotometric analysis of bathing medium of axes. Profiles of NADPH oxidase and superoxide dismutase (SOD) were studied by in-gel assay. Germination was retarded by treatments affecting ROS level except H2O2 scavengers, while axis growth was retarded by all. Superoxide synthesis inhibitor and scavenger prevented H2O2 accumulation in axes in later phase as revealed from TMB staining. Activity of Cu/Zn SOD1 was initially high and declined thereafter. Superoxide being produced in apoplast possibly by NADPH oxidase activity is further metabolized to (•)OH via H2O2. Germination process depends possibly on (•)OH production in the axes. Post-germinative axis growth requires O2(•)- while the differentiating zone of axis (radicle) requires H2O2 for cell wall stiffening.

  14. The conduction bands of MgO, MgS and HfO2

    NARCIS (Netherlands)

    Boer, P.K. de; Groot, R.A. de

    1998-01-01

    Electronic structure calculations for MgO, MgS and HfO2 are reported. It is shown that the conduction bands of MgO and MgS have predominantly anion character, contrary to the common picture of the conduction band being derived from cation states. In transition metal oxides, unoccupied anion states a

  15. Assessment of the roles of reactive oxygen species in the UV and visible light photocatalytic degradation of cyanotoxins and water taste and odor compounds using C-TiO2.

    Science.gov (United States)

    Fotiou, Theodora; Triantis, Theodoros M; Kaloudis, Triantafyllos; O'Shea, Kevin E; Dionysiou, Dionysios D; Hiskia, Anastasia

    2016-03-01

    Visible light (VIS) photocatalysis has large potential as a sustainable water treatment process, however the reaction pathways and degradation processes of organic pollutants are not yet clearly defined. The presence of cyanobacteria cause water quality problems since several genera can produce potent cyanotoxins, harmful to human health. In addition, cyanobacteria produce taste and odor compounds, which pose serious aesthetic problems in drinking water. Although photocatalytic degradation of cyanotoxins and taste and odor compounds have been reported under UV-A light in the presence of TiO2, limited studies have been reported on their degradation pathways by VIS photocatalysis of these problematic compounds. The main objectives of this work were to study the VIS photocatalytic degradation process, define the reactive oxygen species (ROS) involved and elucidate the reaction mechanisms. We report carbon doped TiO2 (C-TiO2) under VIS leads to the slow degradation of cyanotoxins, microcystin-LR (MC-LR) and cylindrospermopsin (CYN), while taste and odor compounds, geosmin and 2-methylisoborneol, were not appreciably degraded. Further studies were carried-out employing several specific radical scavengers (potassium bromide, isopropyl alcohol, sodium azide, superoxide dismutase and catalase) and probes (coumarin) to assess the role of different ROS (hydroxyl radical OH, singlet oxygen (1)O2, superoxide radical anion [Formula: see text] ) in the degradation processes. Reaction pathways of MC-LR and CYN were defined through identification and monitoring of intermediates using liquid chromatography tandem mass spectrometry (LC-MS/MS) for VIS in comparison with UV-A photocatalytic treatment. The effects of scavengers and probes on the degradation process under VIS, as well as the differences in product distributions under VIS and UV-A, suggested that the main species in VIS photocatalysis is [Formula: see text] , with OH and (1)O2 playing minor roles in the degradation

  16. L-arginine regulates neuronal nitric oxide synthase production of superoxide and hydrogen peroxide.

    Science.gov (United States)

    Tsai, Pei; Weaver, John; Cao, Guan Liang; Pou, Sovitj; Roman, Linda J; Starkov, Anatoly A; Rosen, Gerald M

    2005-03-15

    Tetrahydrobiopterin (H(4)B) in the absence of L-arginine has been shown to be an important factor in promoting the direct formation of hydrogen peroxide (H(2)O(2)) at the expense of superoxide (O(2)(*-)) by neuronal nitric oxide synthase (NOS1) [Rosen GM, Tsai P, Weaver J, Porasuphatana S, Roman LJ, Starkov AA, et al. Role of tetrahydrobiopterin in the regulation of neuronal nitric-oxide synthase-generated superoxide. J Biol Chem 2002;277:40275-80]. Based on these findings, it is hypothesized that L-arginine also shifts the equilibrium between O(2)(*-) and H(2)O(2). Experiments were designed to test this theory. As the concentration of L-arginine and N(omega)-hydroxyl-L-arginine increases, the rate of NADPH consumption for H(4)B-bound NOS1 decreased resulting in lower rates of both O(2)(*-) and H(2)O(2) generation, while increasing the rate of nitric oxide (*NO) production. At saturating concentrations of L-arginine or N(omega)-hydroxyl-L-arginine (50microM), NOS1 still produced O(2)(*-) and H(2)O(2). Both L-arginine and N(omega)-hydroxyl-L-arginine have greater impact on the rate of generation of O(2)(*-) than on H(2)O(2).

  17. Placental NAD(P)H oxidase mediated superoxide generation in early pregnancy.

    NARCIS (Netherlands)

    Raijmakers, M.; Burton, G.J.; Jauniaux, E.; Seed, P.T.; Peters, W.H.M.; Steegers, E.A.P.; Poston, L.

    2006-01-01

    Early placental development is characterised by rapid cell differentiation and migration, matrix remodelling and angiogenesis. The enzyme NAD(P)H oxidase is a major source of superoxide anions implicated in signalling pathways regulating these processes in other systems. It is also thought to be

  18. 超氧化物歧化酶与血管成形术后再狭窄%Superoxide Dismutase and Restenosis after Angioplasty

    Institute of Scientific and Technical Information of China (English)

    吴龙

    2013-01-01

    Angioplasty is the effective treatment in cardiovascular diseases, but the high rate of restenosis after angioplasty has deeply affected its clinical application. In the recent years, the redox hypothesis of restenosis has been more and more recognized. Oxidative stress is the state of imbalance in redox, leading to the increased generation of reactive oxygen species, such as superoxide anion( O-2 ·) A large number of studies have shown that O-2 · is elevated in the developing neointimal after angioplasty and plays an essential role in neointimal vascular smooth muscle cells proliferation. Superoxide dismutase( SOD ) is the only antioxidase which can dismutate O-2 · to hydrogen peroxide. The intensive study of the relationship between SOD and restenosis will potentially provide a new idea in the recognition and prevention of restenosis.%血管成形术是广泛运用于心血管病的有效手段,但术后血管再狭窄的高发生率严重影响其临床疗效.近年来,再狭窄的氧化应激学说越来越受到重视.氧化应激是指氧化还原状态的失衡,导致活性氧簇的产生增多,如超氧阴离子(O-2·).大量研究表明,O-2 ·在血管再狭窄新生内膜形成过程中异常增多,对再狭窄过程中血管平滑肌细胞的增殖起到重要作用.超氧化物歧化酶(SOD)是唯一能将O-2 ·催化成相对稳定的过氧化氢的抗氧化酶,深入研究SOD与再狭窄之间的关系,将对认识和防治再狭窄提供新的思路.

  19. Bacteriocuprein superoxide dismutases in pseudomonads

    Energy Technology Data Exchange (ETDEWEB)

    Steinman, H.M.

    1985-06-01

    Two new instances of the rare bacteriocuprein form of superoxide dismutase have been discovered in Pseudomonas diminuta and P. maltophilia. Each species contains a manganese superoxide dismutase as well. Eight other strains of Pseudomonas and Xanthomonas spp. lacked bacteriocupreins and contained either a manganese or an iron superoxide dismutase. Native molecular weights and isoelectric points were determined for all these bacterial dismutases. A monospecific polyclonal antibody was prepared against the bacteriocuprein from Photobacterium leiognathi; it was not cross-reactive with the bacteriocuprein from either Pseudomonas strain. Bacteriocupreins have previously been identified in only two procaryotes, P. leiognathi and Caulobacter crescentus. The discovery of the Pseudomonas bacteriocupreins reveals a broader distribution, raising the possibility that bacteriocupreins are a continuous line of descent among procryotes and not isolated evolutionary occurrences, as previous data suggested.

  20. Endogenous antioxidant defense induction by melon superoxide dismutase reduces cardiac hypertrophy in spontaneously hypertensive rats.

    Science.gov (United States)

    Carillon, Julie; Rugale, Caroline; Rouanet, Jean-Max; Cristol, Jean-Paul; Lacan, Dominique; Jover, Bernard

    2014-08-01

    We assessed the influence of SODB, a melon superoxide dismutase (SOD), on left ventricular (LV) hypertrophy in SHR. SODB (4 or 40U SOD) was given orally for 4 or 28 days to SHR. For each treatment period, LV weight index (LVWI) and cardiomyocytes size were measured. SOD, glutathione peroxidase (GPx) and catalase expressions, and LV production and presence of superoxide anion were determined. Pro-inflammatory markers were also measured. SODB reduced LVWI and cardiomyocytes size after 4 or 28 days. Cardiac SOD and GPx increased by 30-40% with SODB. The presence but not production of superoxide anion was significantly reduced by SODB. No effect of SODB was detected on inflammatory status in any group. The beneficial effect of SODB on cardiac hypertrophy seems to be related to the stimulation of endogenous antioxidant defense, suggesting that SODB may be of interest as a dietary supplementation during conventional antihypertensive therapy.

  1. Comparative study of diethyl phthalate degradation by UV/H2O2 and UV/TiO2: kinetics, mechanism, and effects of operational parameters.

    Science.gov (United States)

    Song, Chengjie; Wang, Liping; Ren, Jie; Lv, Bo; Sun, Zhonghao; Yan, Jing; Li, Xinying; Liu, Jingjing

    2016-02-01

    The photodegradation of diethyl phthalate (DEP) by UV/H2O2 and UV/TiO2 is studied. The DEP degradation kinetics and multiple crucial factors effecting the clearance of DEP are investigated, including initial DEP concentration ([DEP]0), initial pH values (pH0), UV light intensity, anions (Cl(-), NO(3-), SO4 (2-), HCO3 (-), and CO3 (2-)), cations (Mg(2+), Ca(2+), Mn(2+), and Fe(3+)), and humic acid (HA). Total organic carbon (TOC) removal is tested by two treatments. And, cytotoxicity evolution of DEP degradation intermediates is detected. The relationship between molar ratio ([H2O2]/[DEP] or [TiO2]/[DEP]) and degradation kinetic constant (K) is also studied. And, the cytotoxicity tests of DEP and its degradation intermediates in UV/H2O2 and UV/TiO2 treatments are researched. The DEP removal efficiency of UV/H2O2 treatment is higher than UV/TiO2 treatment. The DEP degradation fitted a pseudo-first-order kinetic pattern under experimental conditions. The K linearly related with molar ratio in UV/H2O2 treatment while nature exponential relationship is observed in the case of UV/TiO2. However, K fitted corresponding trends better in H2O2 treatment than in TiO2 treatment. The Cl(-) is in favor of the DEP degradation in UV/H2O2 treatment; in contrast, it is disadvantageous to the DEP degradation in UV/TiO2 treatment. Other anions are all disadvantageous to the DEP degradation in two treatments. Fe(3+) promotes the degradation rates significantly. And, all other cations in question inhibit the degradation of DEP. HA hinders DEP degradation in two treatments. The intermediates of DEP degradation in UV/TiO2 treatment are less toxic to biological cell than that in UV/H2O2 treatment.

  2. Ubisemiquinone is the electron donor for superoxide formation by complex III of heart mitochondria.

    Science.gov (United States)

    Turrens, J F; Alexandre, A; Lehninger, A L

    1985-03-01

    Much evidence indicates that superoxide is generated from O2 in a cyanide-sensitive reaction involving a reduced component of complex III of the mitochondrial respiratory chain, particularly when antimycin A is present. Although it is generally believed that ubisemiquinone is the electron donor to O2, little experimental evidence supporting this view has been reported. Experiments with succinate as electron donor in the presence of antimycin A in intact rat heart mitochondria, which contain much superoxide dismutase but little catalase, showed that myxothiazol, which inhibits reduction of the Rieske iron-sulfur center, prevented formation of hydrogen peroxide, determined spectrophotometrically as the H2O2-peroxidase complex. Similarly, depletion of the mitochondria of their cytochrome c also inhibited formation of H2O2, which was restored by addition of cytochrome c. These observations indicate that factors preventing the formation of ubisemiquinone also prevent H2O2 formation. They also exclude ubiquinol, which remains reduced under these conditions, as the reductant of O2. Since cytochrome b also remains fully reduced when myxothiazol is added to succinate- and antimycin A-supplemented mitochondria, reduced cytochrome b may also be excluded as the reductant of O2. These observations, which are consistent with the Q-cycle reactions, by exclusion of other possibilities leave ubisemiquinone as the only reduced electron carrier in complex III capable of reducing O2 to O2-.

  3. Photocatalytic activity of magnetically anatase TiO2 with high crystallinity and stability for dyes degradation: Insights into the dual roles of SiO2 interlayer between TiO2 and CoFe2O4

    Science.gov (United States)

    Yang, Zewei; Shi, Yingying; Wang, Bing

    2017-03-01

    A novel magnetically separable photocatalyst comprising hollow TiO2-SiO2-CoFe2O4 (TSC) was prepared. In the TSC photocatalyst, an SiO2 interlayer between CoFe2O4 core and TiO2 shell is used to both weaken adverse influence of the magnetic core on photocatalysis and increase the temperature of the transition from anatase to rutile phase TiO2, thus increasing the anatase TiO2 crystallinity. Such an interlayer promotes photocatalytic activity by changing the competition between the injecting process and reacting process of the photogenerated carriers. The photocatalytic activity of TSC was determined for degradation of dye molecules in water under either UV or visible light. The photocatalytic reaction of cationic dyes was governed by rad OH radicals, while O2rad - was the main active species in the initial photoreaction of anionic dyes.

  4. Economical synthesis of potassium superoxide

    Science.gov (United States)

    Bell, A. T.; Sadhukhan, P.

    1979-01-01

    High-frequency discharge in oxygen can be used to prepare superoxides of alkali and alkaline-earth metals. Since no direct-current discharge at the electrodes is present, no sputtering can contaminate the product, hence a high conversion efficiency.

  5. Redox state and O2*- production in neutrophils of Crohn's disease patients.

    Science.gov (United States)

    Biagioni, Chiara; Favilli, Fabio; Catarzi, Serena; Marcucci, Tommaso; Fazi, Marilena; Tonelli, Francesco; Vincenzini, Maria T; Iantomasi, Teresa

    2006-02-01

    The aim of this in vitro study was to evaluate the intracellular redox state and respiratory burst (RB) in neutrophils of patients with Crohn's disease (CD). The intracellular redox state and RB in neutrophils was assessed by the superoxide anion (O2*-) production induced in these cells after stimulation by various factors related to the molecular mechanisms that, if altered, may be responsible for an abnormal immune response. This can, in part, cause the onset of inflammation and tissue damage seen in CD. This study demonstrated a decreased glutathione/glutathione disulfide (GSH/GSSG) ratio index of an increased oxidative state in CD patient neutrophils. Moreover, our findings showed a decrease in tumor necrosis factor (TNF-alpha)- or phorbol 12-myristate 13-acetate (PMA)-induced O2*- production in CD patient neutrophils adherent to fibronectin as compared with controls. A decreased adhesion was also demonstrated. For this reason, the involvement of altered mechanisms of protein kinase C (PKC) and beta-integrin activation in CD patient neutrophils is suggested. These data also showed that the harmful effects of TNF-alpha cannot be caused by excessive reactive oxygen species (ROS) production induced by neutrophils. Decreased cell viability after a prolonged time of adhesion (20 hrs) was also measured in CD patient neutrophils. The findings of this study demonstrate, for the first time, that granulocyte-macrophage colony-stimulating factor (GM-CSF), a compound recently used in CD therapy, is able to activate the RB for a prolonged time both in control and CD patient neutrophils. Increased viability of CD patient neutrophils caused by GM-CSF stimulation was also observed. In conclusion, our results indicate that decreased O2*- production and adhesion, caused, in part, by an anomalous response to TNF-alpha, together with low GSH level and low cell viability, may be responsible for the defective neutrophil function found in CD patients. This can contribute to the

  6. An in vivo study on the photo-enhanced toxicities of S-doped TiO2 nanoparticles to zebrafish embryos (Danio rerio) in terms of malformation, mortality, rheotaxis dysfunction, and DNA damage.

    Science.gov (United States)

    He, Xiaojia; Aker, Winfred G; Hwang, Huey-Min

    2014-08-01

    The role of light on the acute toxicities of S-doped and Sigma TiO2 nanoparticles in zebrafish was studied. Metrics included mortality for both, and rheotaxis dysfunction and DNA damage for S-doped only. It was found that the acute toxicity of S-TiO2 nanoparticles was enhanced by simulated sunlight (SSL) irradiation (96-h LC50 of 116.56 ppm) and exceeded that of Sigma TiO2, which was essentially non-toxic. Behavioral disorder, in terms of rheotaxis, was significantly increased by treatment with S-TiO2 nanoparticles under SSL irradiation. In order to further understand its toxicity mechanism, we investigated hair cells in neuromasts of the posterior lateral line (PLL) using DASPEI staining. Significant hair cell damage was observed in the treated larvae. The Comet assay was employed to investigate the DNA damage, which might be responsible for the loss of hair cells. Production of the superoxide anion ([Formula: see text]), a major ROS generated by TiO2 nanoparticles, was assayed and used to postulate causative factors to account for these damages. Oxidative effects were most severe in the liver, heart, intestine, pancreatic duct, and pancreatic islet - results consistent with our earlier findings in the investigation of embryonic malformation. TEM micrographs, used to further investigate the fate of S-TiO2 nanoparticles at the cellular level, suggested receptor-mediated autophagy and vacuolization. Our findings validate the benefit of using the transparent zebrafish embryo as an in vivo model for evaluating photo-induced nanotoxicity. These results highlight the importance of conducting a systematic risk assessment in connection with the use of doped TiO2 nanoparticles in aquatic ecosystems.

  7. Novel mechanisms for superoxide-scavenging activity of human manganese superoxide dismutase determined by the K68 key acetylation site.

    Science.gov (United States)

    Lu, Jiaqi; Cheng, Kuoyuan; Zhang, Bo; Xu, Huan; Cao, Yuanzhao; Guo, Fei; Feng, Xudong; Xia, Qing

    2015-08-01

    Superoxide is the primary reactive oxygen species generated in the mitochondria. Manganese superoxide dismutase (SOD2) is the major enzymatic superoxide scavenger present in the mitochondrial matrix and one of the most crucial reactive oxygen species-scavenging enzymes in the cell. SOD2 is activated by sirtuin 3 (SIRT3) through NAD(+)-dependent deacetylation. However, the exact acetylation sites of SOD2 are ambiguous and the mechanisms underlying the deacetylation-mediated SOD2 activation largely remain unknown. We are the first to characterize SOD2 mutants of the acetylation sites by investigating the relative enzymatic activity, structures, and electrostatic potential of SOD2 in this study. These SOD2 mutations affected the superoxide-scavenging activity in vitro and in HEK293T cells. The lysine 68 (K68) site is the most important acetylation site contributing to SOD2 activation and plays a role in cell survival after paraquat treatment. The molecular basis underlying the regulation of SOD2 activity by K68 was investigated in detail. Molecular dynamics simulations revealed that K68 mutations induced a conformational shift of residues located in the active center of SOD2 and altered the charge distribution on the SOD2 surface. Thus, the entry of the superoxide anion into the coordinated core of SOD2 was inhibited. Our results provide a novel mechanistic insight, whereby SOD2 acetylation affects the structure and charge distribution of SOD2, its tetramerization, and p53-SOD2 interactions of SOD2 in the mitochondria, which may play a role in nuclear-mitochondrial communication during aging.

  8. Anion exchange membrane

    Science.gov (United States)

    Verkade, John G; Wadhwa, Kuldeep; Kong, Xueqian; Schmidt-Rohr, Klaus

    2013-05-07

    An anion exchange membrane and fuel cell incorporating the anion exchange membrane are detailed in which proazaphosphatrane and azaphosphatrane cations are covalently bonded to a sulfonated fluoropolymer support along with anionic counterions. A positive charge is dispersed in the aforementioned cations which are buried in the support to reduce the cation-anion interactions and increase the mobility of hydroxide ions, for example, across the membrane. The anion exchange membrane has the ability to operate at high temperatures and in highly alkaline environments with high conductivity and low resistance.

  9. Evidence for production of oxidizing radicals by the particulate O-2-forming system from human neutrophils.

    Science.gov (United States)

    Tauber, A I; Gabig, T G; Babior, B M

    1979-04-01

    The particulate O-2-forming system from human neutrophils was found to oxidize methional and 2-keto-4-methylthiobutyric acid (KMB) to ethylene, indicating the formation by this system of strongly oxidizing radicals. Conforming this interpretation was the observation that ethylene production was inhibited by the radical scavengers benzoate, ethanol, and mannitol. Ethylene production was also sharply reduced by superoxide dismutase, implicatin O-2 as a precursor of oxidizing radicals. In our system catalase only partially inhibited ethylene generation from either methional or KMB, suggesting that oxidizing radicals are generated at least in part by the reacton of O-2 with compounds other than H2O2. We propose that in neutrophils oxidizing radicals are formed in a reaction between O-2 and a peroxide according to the following equation: O-2 + ROOH leads to RO . + OH- + O2, in which ROOH may be hydrogen peroxide, an alkyl peroxide, or an acyl peroxide (i.e., a peroxy acid).

  10. Effect of Bothrops alternatus snake venom on macrophage phagocytosis and superoxide production: participation of protein kinase C

    Directory of Open Access Journals (Sweden)

    SS Setubal

    2011-01-01

    Full Text Available Envenomations caused by different species of Bothrops snakes result in severe local tissue damage, hemorrhage, pain, myonecrosis, and inflammation with a significant leukocyte accumulation at the bite site. However, the activation state of leukocytes is still unclear. According to clinical cases and experimental work, the local effects observed in envenenomation by Bothrops alternatus are mainly the appearance of edema, hemorrhage, and necrosis. In this study we investigated the ability of Bothrops alternatus crude venom to induce macrophage activation. At 6 to 100 ¼g/mL, BaV is not toxic to thioglycollate-elicited macrophages; at 3 and 6 ¼g/mL, it did not interfere in macrophage adhesion or detachment. Moreover, at concentrations of 1.5, 3, and 6 ¼g/mL the venom induced an increase in phagocytosis via complement receptor one hour after incubation. Pharmacological treatment of thioglycollate-elicited macrophages with staurosporine, a protein kinase (PKC inhibitor, abolished phagocytosis, suggesting that PKC may be involved in the increase of serum-opsonized zymosan phagocytosis induced by BaV. Moreover, BaV also induced the production of anion superoxide (O2_ by thioglycollate-elicited macrophages. This BaV stimulated superoxide production was abolished after treating the cells with staurosporine, indicating that PKC is an important signaling pathway for the production of this radical. Based on these results, we suggest that phagocytosis and reactive oxygen species are involved in the pathogenesis of local tissue damage characteristic of Bothrops spp. envenomations.

  11. AMPK dysregulation promotes diabetes-related reduction of superoxide and mitochondrial function.

    Science.gov (United States)

    Dugan, Laura L; You, Young-Hyun; Ali, Sameh S; Diamond-Stanic, Maggie; Miyamoto, Satoshi; DeCleves, Anne-Emilie; Andreyev, Aleksander; Quach, Tammy; Ly, San; Shekhtman, Grigory; Nguyen, William; Chepetan, Andre; Le, Thuy P; Wang, Lin; Xu, Ming; Paik, Kacie P; Fogo, Agnes; Viollet, Benoit; Murphy, Anne; Brosius, Frank; Naviaux, Robert K; Sharma, Kumar

    2013-11-01

    Diabetic microvascular complications have been considered to be mediated by a glucose-driven increase in mitochondrial superoxide anion production. Here, we report that superoxide production was reduced in the kidneys of a steptozotocin-induced mouse model of type 1 diabetes, as assessed by in vivo real-time transcutaneous fluorescence, confocal microscopy, and electron paramagnetic resonance analysis. Reduction of mitochondrial biogenesis and phosphorylation of pyruvate dehydrogenase (PDH) were observed in kidneys from diabetic mice. These observations were consistent with an overall reduction of mitochondrial glucose oxidation. Activity of AMPK, the major energy-sensing enzyme, was reduced in kidneys from both diabetic mice and humans. Mitochondrial biogenesis, PDH activity, and mitochondrial complex activity were rescued by treatment with the AMPK activator 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside (AICAR). AICAR treatment induced superoxide production and was linked with glomerular matrix and albuminuria reduction in the diabetic kidney. Furthermore, diabetic heterozygous superoxide dismutase 2 (Sod2(+/-)) mice had no evidence of increased renal disease, and Ampka2(-/-) mice had increased albuminuria that was not reduced with AICAR treatment. Reduction of mitochondrial superoxide production with rotenone was sufficient to reduce AMPK phosphorylation in mouse kidneys. Taken together, these results demonstrate that diabetic kidneys have reduced superoxide and mitochondrial biogenesis and activation of AMPK enhances superoxide production and mitochondrial function while reducing disease activity.

  12. Anions in Cometary Comae

    Science.gov (United States)

    Charnley, Steven B.

    2011-01-01

    The presence of negative ions (anions) in cometary comae is known from Giotto mass spectrometry of IP/Halley. The anions 0-, OH-, C-, CH- and CN- have been detected, as well as unidentified anions with masses 22-65 and 85-110 amu (Chaizy et al. 1991). Organic molecular anions are known to have a significant impact on the charge balance of interstellar clouds and circumstellar envelopes and have been shown to act as catalysts for the gas-phase synthesis of larger hydrocarbon molecules in the ISM, but their importance in cometary comae has not yet been explored. We present details of the first attempt to model the chemistry of anions in cometary comae. Based on the combined chemical and hydro dynamical model of Rodgers & Charnley (2002), we investigate the role of large carbon-chain anions in cometary coma chemistry. We calculate the effects of these anions on coma thermodynamics, charge balance and examine their impact on molecule formation.

  13. Copper complexes of 1,10-phenanthroline and related compounds as superoxide dismutase mimetics.

    Science.gov (United States)

    Bijloo, G J; van der Goot, H; Bast, A; Timmerman, H

    1990-11-01

    In a preliminary study we tested CuSO4.5H2O, (Cu(II]2[3,5-diisopropylsalicylate]4.2H2O and a number of copper complexes of substituted 1,10-phenanthrolines for superoxide anion dismutase activity. It appeared that this activity depends on the ligands involved and might be governed by the redox potential of the Cu(I) complex/Cu(II) complex couple. The strong superoxide anion dismutase activity of Cu(II)[DMP]2 complex can be expected considering its high redox potential. Rather surprisingly is the superoxide anion dismutase activity of the Cu(I)[DMP]2 complex since it involves oxidation to Cu(II)[DMP]2 complex. From regression analysis it was established that steric and field effects of the substituents of the investigated phenanthrolines play an important role in SOD activity and therefore it is concluded that complex formation is important for the superoxide dismutase-like activity.

  14. Species-specific control of external superoxide levels by the coral holobiont during a natural bleaching event

    Science.gov (United States)

    Diaz, Julia M.; Hansel, Colleen M.; Apprill, Amy; Brighi, Caterina; Zhang, Tong; Weber, Laura; McNally, Sean; Xun, Liping

    2016-12-01

    The reactive oxygen species superoxide (O2.-) is both beneficial and detrimental to life. Within corals, superoxide may contribute to pathogen resistance but also bleaching, the loss of essential algal symbionts. Yet, the role of superoxide in coral health and physiology is not completely understood owing to a lack of direct in situ observations. By conducting field measurements of superoxide produced by corals during a bleaching event, we show substantial species-specific variation in external superoxide levels, which reflect the balance of production and degradation processes. Extracellular superoxide concentrations are independent of light, algal symbiont abundance and bleaching status, but depend on coral species and bacterial community composition. Furthermore, coral-derived superoxide concentrations ranged from levels below bulk seawater up to ~120 nM, some of the highest superoxide concentrations observed in marine systems. Overall, these results unveil the ability of corals and/or their microbiomes to regulate superoxide in their immediate surroundings, which suggests species-specific roles of superoxide in coral health and physiology.

  15. Nitric oxide and superoxide transport in a cross section of the rat outer medulla. I. Effects of low medullary oxygen tension

    National Research Council Canada - National Science Library

    Edwards, Aurélie; Layton, Anita T

    2010-01-01

    ...) on the distribution of nitric oxide (NO), superoxide (O(2)(-)) and total peroxynitrite (ONOO), we developed a mathematical model that simulates the transport of those species in a cross section of the rat OM...

  16. Diosgenin inhibits superoxide generation in FMLP-activated mouse neutrophils via multiple pathways.

    Science.gov (United States)

    Lin, Y; Jia, R; Liu, Y; Gao, Y; Zeng, X; Kou, J; Yu, B

    2014-12-01

    Diosgenin possesses anti-inflammatory and anticancer properties. Activated neutrophils produce high concentrations of the superoxide anion which is involved in the pathophysiology of inflammation-related diseases and cancer. In the present study, the inhibitory effect and possible mechanisms of diosgenin on superoxide generation were investigated in mouse bone marrow neutrophils. Diosgenin potently and concentration-dependently inhibited the extracellular and intracellular superoxide anion generation in Formyl-Met-Leu-Phe (FMLP)- activated neutrophils, with IC50 values of 0.50 ± 0.08 μM and 0.66 ± 0.13 μM, respectively. Such inhibition was not mediated by scavenging the superoxide anion or by a cytotoxic effect. Diosgenin inhibited the phosphorylation of p47phox and membrane translocation of p47phox and p67phox, and thus blocking the assembly of nicotinamide adenine dinucleotide phosphate oxidase. Moreover, cellular cyclic adenosine monophosphate (cAMP) levels and protein kinase A (PKA) expression were also effectively increased by diosgenin. It attenuated FMLP-induced increase of phosphorylation of cytosolic phospholipase A (cPLA2), p21-activated kinase (PAK), Akt, p38 mitogen-activated protein kinase (p38MAPK), extracellular signal-regulated kinase (ERK1/2), and c-Jun N-terminal kinase (JNK). Our data indicate that diosgenin exhibits inhibitory effects on superoxide anion production through the blockade of cAMP, PKA, cPLA2, PAK, Akt and MAPKs signaling pathways. The results may explain the clinical implications of diosgenin in the treatment of inflammation-related disorders.

  17. Superoxide dismutase prevents development of adenocarcinoma in a rat model of Barrett's esophagus

    Institute of Scientific and Technical Information of China (English)

    Elena Piazuelo; Carmelo Cebrián; Alfredo Escartín; Pilar Jiménez; Fernando Soteras; Javier Ortego; Angel Lanas

    2005-01-01

    AIM: To test whether antioxidant treatment could prevent the progression of Barrett's esophagus to adenocarcinoma.METHODS: In a rat model of gastroduodenoesophageal reflux by esophagojejunal anastomosis with gastric preservation, groups of 6-10 rats were randomized to receive treatment with superoxide dismutase (SOD) or vehicle and followed up for 4 mo. Rat's esophagus was assessed by histological analysis, superoxide anion and peroxinitrite generation, SOD levels and DNA oxidative damage.RESULTS: All rats undergoing esophagojejunostomy developed extensive esophageal mucosal ulceration and inflammation by mo 4. The process was associated with a progressive presence of intestinal metaplasia beyondthe anastomotic area (9% 1st mo and 50% 4th mo) (94% at the anastomotic level) and adenocarcinoma(11% 1st mo and 60% 4th mo). These changes were associated with superoxide anion and peroxinitrite mucosal generation, an early and significant increase of DNA oxidative damage and a significant decrease in SOD levels (P<0.05). Exogenous administration of SOD decreased mucosal superoxide levels, increased mucosal SOD levels and reduced the risk of developing intestinal metaplasia beyond the anastomotic area (odds ratio = 0.326; 95%CI: 0.108-0.981; P = 0.046),and esophageal adenocarcinoma (odds ratio = 0.243;95%CI: 0.073-0.804; P = 0.021).CONCLUSION: Superoxide dismutase prevents the progression of esophagitis to Barrett's esophagus and adenocarcinoma in this rat model of gastrointestinal reflux, supporting a role of antioxidants in the chemoprevention of esophageal adenocarcinoma.

  18. Synthesis, Structural Diversity and Mimic Superoxide Dismutase of Mn(II) Complexes Derived from N, O-donor Schiff bases.

    Science.gov (United States)

    Qin, Jie; Yin, Qiang; Zhao, Shan-Shan; Wang, Jun-Zheng; Qian, Shao-Song

    2016-01-01

    Two new potentially tetradentate Schiff base ligands N'-(pyridin-2-ylmethylene)nicotinohydrazide (L1), and N'-(pyridin-2-ylmethylene)isonicotinohydrazide (L(2)) were synthesized. Reactions of hydrazone ligands L(1) and L(2) with Mn(NO(3))(2) afford two mononuclear Mn(II) complexes, [Mn(L(1))(NO(3))(H(2)O)(2)]•(NO(3)) (1) and [Mn(L(2))(2)(NO(3))(H(2)O)]•(NO(3)) (2). For complexes 1 and 2, L(1) and L(2) act as pincer-like tridentate or bidentate ligands, respectively. The Mn(II) ions in the two compounds are both in heptacoordinated environment, while the two molecules display diverse solid-state supramolecular structures because of the different orientation of Npyridine and hydrogen bonding patterns of nitrate anions. Complex 1 features 2D supramolecular sheet, while complex 2 is double-chain supramolecular structure. Both of the two complexes exhibit moderate superoxide dismutase (SOD) mimetic activity.

  19. Photocatalytic self-cleaning cotton fabrics with platinum (IV) chloride modified TiO2 and N-TiO2 coatings

    Science.gov (United States)

    Long, Mingce; Zheng, Longhui; Tan, Beihui; Shu, Heping

    2016-11-01

    To enable photocatalytic self-cleaning cotton fabrics working under visible light irradiation, platinum (IV) chloride modified TiO2 (Pt-TiO2) and N-TiO2 (Pt-N-TiO2) nanosols are synthesized through a low temperature precipitation-peptization method. According to the characterizations of XRD, DRS and TEM, all nanoparticles are anatase nanocrystallites in the sizes of less than 10 nm, while N-TiO2 nanoparticles have better crystallization and smaller sizes. However, the cotton fabrics functionalized with Pt-TiO2 display significantly enhanced photocatalytic activity for methyl orange degradation and coffee stain removal under both solar simulator and visible light irradiation, while the performance of that coatings of Pt-N-TiO2 is poor. Further XRF and XPS results indicate that surface species on N-TiO2 block the adsorption of PtCl62- anions, whereas these anions strongly attach on the surface of TiO2 nanoparticles, and accordingly enable functionalized cotton fabrics efficient visible light driven activities based on a mechanism of charge transfer from ligand to metal (CTLM) excitation.

  20. Rebamipide attenuates nonsteroidal anti-inflammatory drugs (NSAID) induced lipid peroxidation by the manganese superoxide dismutase (MnSOD) overexpression in gastrointestinal epithelial cells.

    Science.gov (United States)

    Nagano, Y; Matsui, H; Shimokawa, O; Hirayama, A; Tamura, M; Nakamura, Y; Kaneko, T; Rai, K; Indo, H P; Majima, H J; Hyodo, I

    2012-04-01

    Nonsteroidal anti-inflammatory drugs (NSAIDs) often cause gastrointestinal complications such as gastric ulcers and erosions. Recent studies on the pathogenesis have revealed that NSAIDs induce lipid peroxidation in gastric epithelial cells by generating superoxide anion in mitochondria, independently with cyclooxygenase-inhibition and the subsequent prostaglandin deficiency. Although not clearly elucidated, the impairment of mitochondrial oxidative phosphorylation, or uncoupling, by NSAIDs is associated with the generation of superoxide anion. Physiologically, superoxide is immediately transformed into hydrogen peroxide and diatomic oxygen with manganese superoxide dismutase (MnSOD). Rebamipide is an antiulcer agent that showed protective effects against NSAID-induced lipid peroxidation in gastrointestinal tracts. We hypothesized that rebamipide may attenuate lipid peroxidation by increasing the expression of MnSOD protein in mitochondria and decreasing the leakage of superoxide anion in NSAID-treated gastric and small intestinal epithelial cells. Firstly, to examine rebamipide increases the expression of MnSOD proteins in mitochondria of gastrointestinal epithelial cells, we underwent Western blotting analysis against anti-MnSOD antibody in gastric RGM1 cells and small intestinal IEC6 cells. Secondly, to examine whether the pretreatment of rebamipide decreases NSAID-induced mitochondrial impairment and lipid peroxidation, we treated these cells with NSAIDs with or without rebamipide pretreatment, and examined with specific fluorescent indicators. Finally, to examine whether pretreatment of rebamipide attenuates NSAID-induced superoxide anion leakage from mitochondria, we examined the mitochondria from indomethacin-treated RGM1 cells with electron spin resonance (ESR) spectroscopy using a specific spin-trapping reagent, CYPMPO. Rebamipide increased the expression of MnSOD protein, and attenuated NSAID-induced mitochondrial impairment and lipid peroxidation in RGM1

  1. Superoxide-responsive gene expression in Arabidopsis thaliana and Zea mays.

    Science.gov (United States)

    Xu, Junhuan; Tran, Thu; Padilla Marcia, Carmen S; Braun, David M; Goggin, Fiona L

    2017-08-01

    Superoxide (O2(-)) and other reactive oxygen species (ROS) are generated in response to numerous biotic and abiotic stresses. Different ROS have been reported to elicit different transcriptional responses in plants, and so ROS-responsive marker genes and promoter::reporter gene fusions have been proposed as indirect means of detecting ROS and discriminating among different species. However, further information about the specificity of transcriptional responses to O2(-) is needed in order to assess potential markers for this critical stress-responsive signaling molecule. Using qRT-PCR, the expression of 12 genes previously reported to be upregulated by O2(-) was measured in Arabidopsis thaliana plants exposed to elicitors of common stress-responsive ROS: methyl viologen (an inducer of O2(-)), rose bengal (an inducer of singlet oxygen, (1)ΔO2), and exogenous hydrogen peroxide (H2O2). Surprisingly, Zinc-Finger Protein 12 (AtZAT12), which had previously been used as a reporter for H2O2, responded more strongly to O2(-) than to H2O2; moreover, the expression of an AtZAT12 promoter-reporter fusion (AtZAT12::Luc) was enhanced by diethyldithiocarbamate, which inhibits dismutation of O2(-) to H2O2. These results suggest that AtZAT12 is transcriptionally upregulated in response to O2(-), and that AtZAT12::Luc may be a useful biosensor for detecting O2(-) generation in vivo. In addition, transcripts encoding uncoupling proteins (AtUCPs) showed selectivity for O2(-) in Arabidopsis, and an AtUCP homolog upregulated by methyl viologen was also identified in maize (Zea mays L.), indicating that there are O2(-)-responsive members of this family in monocots. These results expand our limited knowledge of ROS-responsive gene expression in monocots, as well as O2(-)-selective responses in dicots. Copyright © 2017 The Authors. Published by Elsevier Masson SAS.. All rights reserved.

  2. Type II skeletal myofibers possess unique properties that potentiate mitochondrial H(2)O(2) generation.

    Science.gov (United States)

    Anderson, Ethan J; Neufer, P Darrell

    2006-03-01

    Mitochondrial dysfunction is implicated in a number of skeletal muscle pathologies, most notably aging-induced atrophy and loss of type II myofibers. Although oxygen-derived free radicals are thought to be a primary cause of mitochondrial dysfunction, the underlying factors governing mitochondrial superoxide production in different skeletal myofiber types is unknown. Using a novel in situ approach to measure H(2)O(2) production (indicator of superoxide formation) in permeabilized rat skeletal muscle fiber bundles, we found that mitochondrial free radical leak (H(2)O(2) produced/O(2) consumed) is two- to threefold higher (P < 0.05) in white (WG, primarily type IIB fibers) than in red (RG, type IIA) gastrocnemius or soleus (type I) myofibers during basal respiration supported by complex I (pyruvate + malate) or complex II (succinate) substrates. In the presence of respiratory inhibitors, maximal rates of superoxide produced at both complex I and complex III are markedly higher in RG and WG than in soleus muscle despite approximately 50% less mitochondrial content in WG myofibers. Duplicate experiments conducted with +/-exogenous superoxide dismutase revealed striking differences in the topology and/or dismutation of superoxide in WG vs. soleus and RG muscle. When normalized for mitochondrial content, overall H(2)O(2) scavenging capacity is lower in RG and WG fibers, whereas glutathione peroxidase activity, which is largely responsible for H(2)O(2) removal in mitochondria, is similar in all three muscle types. These findings suggest that type II myofibers, particularly type IIB, possess unique properties that potentiate mitochondrial superoxide production and/or release, providing a potential mechanism for the heterogeneous development of mitochondrial dysfunction in skeletal muscle.

  3. A new formula to calculate activity of superoxide dismutase in indirect assays.

    Science.gov (United States)

    Zhang, Chen; Bruins, Marieke E; Yang, Zhi-Qiang; Liu, Shu-Tao; Rao, Ping-Fan

    2016-06-15

    To calculate superoxide dismutase (SOD) activity rapidly and accurately by indirect SOD assays, a formula based on the ratio of the catalytic speed of SOD to the reaction speed of the indicator with superoxide anion was deduced. The accuracy of this formula was compared with the conventional formula based on inhibition in five indirect SOD assays. The new formula was validated in nearly the entire SOD activity range, whereas the conventional formula was validated only during inhibition of 40-60%. This formula might also be used for the assays of other enzymes.

  4. The Superoxide Reductase from the Early Diverging Eukaryote Giardia Intestinalis

    Energy Technology Data Exchange (ETDEWEB)

    Cabelli, D.E.; Testa, F.; Mastronicola, D.; Bordi, E.; Pucillo, L.P.; Sarti, P.; Saraiva, L.M.; Giuffre, A.; Teixeira, M.

    2011-10-15

    Unlike superoxide dismutases (SODs), superoxidereductases (SORs) eliminate superoxide anion (O{sub 2}{sup {sm_bullet}-}) not through its dismutation, but via reduction to hydrogen peroxide (H{sub 2}O{sub 2}) in the presence of an electron donor. The microaerobic protist Giardia intestinalis, responsible for a common intestinal disease in humans, though lacking SOD and other canonical reactive oxygen species-detoxifying systems, is among the very few eukaryotes encoding a SOR yet identified. In this study, the recombinant SOR from Giardia (SOR{sub Gi}) was purified and characterized by pulse radiolysis and stopped-flow spectrophotometry. The protein, isolated in the reduced state, after oxidation by superoxide or hexachloroiridate(IV), yields a resting species (T{sub final}) with Fe{sup 3+} ligated to glutamate or hydroxide depending on pH (apparent pK{sub a} = 8.7). Although showing negligible SOD activity, reduced SOR{sub Gi} reacts with O{sub 2}{sup {sm_bullet}-} with a pH-independent second-order rate constant k{sub 1} = 1.0 x 10{sup 9} M{sup -1} s{sup -1} and yields the ferric-(hydro)peroxo intermediate T{sub 1}; this in turn rapidly decays to the T{sub final} state with pH-dependent rates, without populating other detectable intermediates. Immunoblotting assays show that SOR{sub Gi} is expressed in the disease-causing trophozoite of Giardia. We propose that the superoxide-scavenging activity of SOR in Giardia may promote the survival of this air-sensitive parasite in the fairly aerobic proximal human small intestine during infection.

  5. Identification of iron(III) peroxo species in the active site of the superoxide reductase SOR from Desulfoarculus baarsii

    CERN Document Server

    Mathé, Christelle; Horner, Olivier; Lombard, Murielle; Latour, Jean-Marc; Fontecave, Marc; Nivière, Vincent

    2015-01-01

    The active site of superoxide reductase SOR consists of an Fe2+ center in an unusual [His4 Cys1] square-pyramidal geometry. It specifically reduces superoxide to produce H2O2. Here, we have reacted the SOR from Desulfoarculus baarsii directly with H2O2. We have found that its active site can transiently stabilize an Fe3+-peroxo species that we have spectroscopically characterized by resonance Raman. The mutation of the strictly conserved Glu47 into alanine results in a stabilization of this Fe3+-peroxo species, when compared to the wild-type form. These data support the hypothesis that the reaction of SOR proceeds through such a Fe3+-peroxo intermediate. This also suggests that Glu47 might serve to help H2O2 release during the reaction with superoxide.

  6. Relative reactivity of dihydropyridine derivatives to electrogenerated superoxide ion in DMSO solutions: a voltammetric approach.

    Science.gov (United States)

    Oriz, María Eugenia; Núñez-Vergara, Luis Joaquin; Squella, Juan Arturo

    2003-02-01

    To evaluate the reaction of a large series of pharmacologically significant 1,4-dihydropyridine (1,4-DHP) compounds with superoxide (O2.-) in dimethylsulfoxide using differential pulse voltammetry and controlled potential electrolysis. Differential pulse voltammetry was used to track the consumption of O2.-, and controlled potential electrolysis was used to electrogenerate O2.-. With the addition of 1,4-DHP, the oxidation peak current of O2.- decreased concentration dependently, suggesting that 1,4-DHP reacts with O2.-, that is, 1,4-DHP scavenges O2.- in dimethylsulfoxide. very easy and direct voltammetric procedure to study the relative reactivity of different 1,4-DHP with O2.- is proposed. Using the proposed method we have found that all commercial 1,4-DHP reacts with O2.-. The following order of rates was obtained: felodipine > or = vitamin E > isradipine > nimodipine > furnidipine > nitrendipine > nisoldipine > nifedipine. Furthermore, it was demonstrated that the hydrogen at the N-position of 1,4-DHP compounds could be released as a proton in the presence of O2.-, thus the electrogenerated O2.- worked as a proton acceptor to 1,4-DHP.

  7. Macroporous mesh of nanoporous gold in electrochemical monitoring of superoxide release from skeletal muscle cells.

    Science.gov (United States)

    Banan Sadeghian, Ramin; Han, Jiuhui; Ostrovidov, Serge; Salehi, Sahar; Bahraminejad, Behzad; Ahadian, Samad; Chen, Mingwei; Khademhosseini, Ali

    2017-02-15

    Real-time monitoring of metabolically relevant biochemicals released in minuscule amounts is of utmost diagnostic importance. Superoxide anion as a primary member of reactive oxygen species, has physiological and pathological effects that depend on its concentration and release rate. Here we present fabrication and successfully testing of a highly sensitive electrochemical biosensor featuring a three-dimensional macroporous mesh of nanoporous gold tailored to measure the dynamics of extracellular superoxide concentration. Wide and accessible surface of the mesh combined with high porosity of the thin nanoporous gold coating enables capturing the analyte in pico- to nano-molar ranges. The mesh is functionalized with cytochrome-c (cyt-c) and incorporated as a working electrode to measure the release rate of drug-induced superoxides from C2C12 cells through a porous membrane. The device displays a considerably improved superoxide sensitivity of 7.29nAnM(-)(1)cm(-)(2) and a low level of detection of 70pM. Such sensitivity is orders of magnitude higher than any similar enzyme-based electrochemical superoxide sensor and is attributed to the facile diffusion of the analyte through the well-spread nanofeatured gold skin. Superoxide generation rates captured from monolayer myoblast cultures containing about 4×10(4) cells, varied from 1.0 to 9.0nMmin(-)(1) in a quasi-linear fashion as a function of drug concentration. This work provides a platform for the development of highly sensitive molecular electrochemical biosensors.

  8. Over-expressed copper/zinc superoxide dismutase localizes to mitochondria in neurons inhibiting the angiotensin II-mediated increase in mitochondrial superoxide.

    Science.gov (United States)

    Li, Shumin; Case, Adam J; Yang, Rui-Fang; Schultz, Harold D; Zimmerman, Matthew C

    2013-01-01

    Angiotensin II (AngII) is the main effector peptide of the renin-angiotensin system (RAS), and contributes to the pathogenesis of cardiovascular disease by exerting its effects on an array of different cell types, including central neurons. AngII intra-neuronal signaling is mediated, at least in part, by reactive oxygen species, particularly superoxide (O2 (•-)). Recently, it has been discovered that mitochondria are a major subcellular source of AngII-induced O2 (•-). We have previously reported that over-expression of manganese superoxide dismutase (MnSOD), a mitochondrial matrix-localized O2 (•-) scavenging enzyme, inhibits AngII intra-neuronal signaling. Interestingly, over-expression of copper/zinc superoxide dismutase (CuZnSOD), which is believed to be primarily localized to the cytoplasm, similarly inhibits AngII intra-neuronal signaling and provides protection against AngII-mediated neurogenic hypertension. Herein, we tested the hypothesis that CuZnSOD over-expression in central neurons localizes to mitochondria and inhibits AngII intra-neuronal signaling by scavenging mitochondrial O2 (•-). Using a neuronal cell culture model (CATH.a neurons), we demonstrate that both endogenous and adenovirus-mediated over-expressed CuZnSOD (AdCuZnSOD) are present in mitochondria. Furthermore, we show that over-expression of CuZnSOD attenuates the AngII-mediated increase in mitochondrial O2 (•-) levels and the AngII-induced inhibition of neuronal potassium current. Taken together, these data clearly show that over-expressed CuZnSOD in neurons localizes in mitochondria, scavenges AngII-induced mitochondrial O2 (•-), and inhibits AngII intra-neuronal signaling.

  9. Over-expressed copper/zinc superoxide dismutase localizes to mitochondria in neurons inhibiting the angiotensin II-mediated increase in mitochondrial superoxide

    Directory of Open Access Journals (Sweden)

    Shumin Li

    2014-01-01

    Full Text Available Angiotensin II (AngII is the main effector peptide of the renin–angiotensin system (RAS, and contributes to the pathogenesis of cardiovascular disease by exerting its effects on an array of different cell types, including central neurons. AngII intra-neuronal signaling is mediated, at least in part, by reactive oxygen species, particularly superoxide (O2·−. Recently, it has been discovered that mitochondria are a major subcellular source of AngII-induced O2·−. We have previously reported that over-expression of manganese superoxide dismutase (MnSOD, a mitochondrial matrix-localized O2·− scavenging enzyme, inhibits AngII intra-neuronal signaling. Interestingly, over-expression of copper/zinc superoxide dismutase (CuZnSOD, which is believed to be primarily localized to the cytoplasm, similarly inhibits AngII intra-neuronal signaling and provides protection against AngII-mediated neurogenic hypertension. Herein, we tested the hypothesis that CuZnSOD over-expression in central neurons localizes to mitochondria and inhibits AngII intra-neuronal signaling by scavenging mitochondrial O2·−. Using a neuronal cell culture model (CATH.a neurons, we demonstrate that both endogenous and adenovirus-mediated over-expressed CuZnSOD (AdCuZnSOD are present in mitochondria. Furthermore, we show that over-expression of CuZnSOD attenuates the AngII-mediated increase in mitochondrial O2·− levels and the AngII-induced inhibition of neuronal potassium current. Taken together, these data clearly show that over-expressed CuZnSOD in neurons localizes in mitochondria, scavenges AngII-induced mitochondrial O2·−, and inhibits AngII intra-neuronal signaling.

  10. Superoxide reductase from Desulfoarculus baarsii: reaction mechanism and role of glutamate 47 and lysine 48 in catalysis

    CERN Document Server

    Lombard, M; Touati, D; Fontecave, M; Nivière, V

    2015-01-01

    Superoxide reductase (SOR) is a small metalloenzyme that catalyzes reduction of O(2)(*)(-) to H(2)O(2) and thus provides an antioxidant mechanism against superoxide radicals. Its active site contains an unusual mononuclear ferrous center, which is very efficient during electron transfer to O(2)(*)(-) [Lombard, M., Fontecave, M., Touati, D., and Nivi{\\`e}re, V. (2000) J. Biol. Chem. 275, 115-121]. The reaction of the enzyme from Desulfoarculus baarsii with superoxide was studied by pulse radiolysis methods. The first step is an extremely fast bimolecular reaction of superoxide reductase with superoxide, with a rate constant of (1.1 +/- 0.3) x 10(9) M(-1) s(-1). A first intermediate is formed which is converted to a second one at a much slower rate constant of 500 +/- 50 s(-1). Decay of the second intermediate occurs with a rate constant of 25 +/- 5 s(-1). These intermediates are suggested to be iron-superoxide and iron-peroxide species. Furthermore, the role of glutamate 47 and lysine 48, which are the closest...

  11. Iron-responsive regulation of the Helicobacter pylori iron-cofactored superoxide dismutase SodB is mediated by Fur.

    NARCIS (Netherlands)

    F.D.J. Ernst (Florian); G. Homuth (Georg); J. Stoof (Jeroen); U. Mader; B. Waidner (Barbara); E.J. Kuipers (Ernst); M. Kist (Manfred); J.G. Kusters (Johannes); S. Bereswill (Stefan); A.H.M. van Vliet (Arnoud)

    2005-01-01

    textabstractMaintaining iron homeostasis is a necessity for all living organisms, as free iron augments the generation of reactive oxygen species like superoxide anions, at the risk of subsequent lethal cellular damage. The iron-responsive regulator Fur controls iron metabolism in many bacteria, inc

  12. Synthesis and anion recognition of neutral receptors based on multiamide calix[4]arene

    Institute of Scientific and Technical Information of China (English)

    LIU; Shunying; WANG; Fajun; WEI; Lanhua; XIAO; Wang; MENG

    2004-01-01

    Two multiamide calix[4]arenes (5, 6) were synthesized and characterized by IR, 1H NMR, MS and elemental analysis. The binding properties of receptors with some anions (p-O2NPhOPO2-3, p-O2NPhO-, H2PO-4, Ac-, Cl-, Br- and I-) were studied by UV-Vis spectra. The results indicate that the tetraamide calix[4]arenes (5, 6) have a good selectivity to the anions containing aromatic ring (p-O2NPhOPO32 , p-O2NPhO-). The 1 : 1 complexes between host and guest were formed through multiple hydrogen bonding and π-π interactions. The hosts 5 and 6also show a definite binding ability for the anions (H2 PO-4, Ac-, Cl-) that have no ultraviolet absorption, which provides a simple method of spectrum detection for these anions.

  13. Superoxide dismutase versus ferricytochrome C: determining rate constants for the spin trapping of superoxide by cyclic nitrones.

    Science.gov (United States)

    Weaver, John; Tsai, Pei; Pou, Sovitj; Rosen, Gerald M

    2004-11-26

    Given that spin trapping/electron paramagnetic resonance (EPR) spectroscopy has become the primary technique to identify important biologically generated free radicals, such as superoxide (O(2)(*-)), in vitro and in vivo models, evaluation of the efficiency of specific spin traps to identify this free radical is paramount. Recently, a family of ester-containing nitrones has been prepared, which appears to have distinct advantages for spin trapping O(2)(*-) compared to the well-studied spin traps 5,5-dimethyl-1-pyrroline N-oxide 1 and 5-(diethoxyphosphoryl)-5-methyl-1-pyrroline N-oxide 2. An important determinant in the selection of a spin trap is the rate constant (k(app)) for its reaction with O(2)(*-), and several different methods have been employed in estimating this k(app). In this paper, the two most frequently used scavengers of O(2)(*-), ferricytochrome c and Cu/Zn-SOD, were evaluated as competitive inhibitors for spin trapping this free radical. Data presented herein demonstrate that SOD is the preferred compound when determining the k(app) for the reaction of O(2)(*-) with spin traps. Using this model, the k(app) for the reaction of nitrone 1, 5-tert-butoxycarbonyl-5-methyl-1-pyrroline N-oxide 3, and 5-methoxycarbonyl-5-methyl-1-pyrroline N-oxide 4 with O(2)(*)(-) was estimated to be 24.6 +/- 3.1, 73.0 +/- 12, and 89.4 +/- 1.0 M(-1) s(-1) at pH 7.0, respectively. Several other comparative studies between known spin traps were also undertaken.

  14. Weak C-H$\\cdots$F-C interactions in carboxylate anion binding: Synthesis, spectroscopic and X-ray structural studies of [Co(phen)2CO3]2 (C7H3O2FCl)Cl$\\cdots$11H2O and [Co(phen)2CO3](C7H3NO4Cl)$\\cdot$6H2O

    Indian Academy of Sciences (India)

    A Singh; R P Sharma; T Aree; P Venugopalan

    2010-09-01

    Two new complex salts containing 2,5-substituted benzoate ions, [Co(phen)2CO3]2 (C7H3O2FCl)Cl$\\cdot$11H2O (1) and [Co(phen)2CO3](C7H3NO4Cl)$\\cdot$6H2O (2) (where phen = 1,10-phenanthroline, C7H3O2FCl = 2-chloro-5-fluorobenzoate (cfbz) and C7H3NO4Cl = 2-chloro-5-nitrobenzoate(cnbz)) were synthesized by reacting carbonatobis(1,10-phenanthroline)cobalt(III) chloride with appropriate salts in aqueous medium. A detailed packing analysis has been undertaken to delineate the role of second sphere C-H$\\cdots$F and C-H$\\cdots$O interactions amid other heteroatom interactions. The complex salts have been characterized by elemental analyses, spectroscopic studies (IR, UV/Visible, multinuclear NMR), conductance and solubility product measurements. Single crystal X-ray structure determination revealed ionic structures of both the complex salts having discrete ions along with lattice water molecules. Crystal lattice is stabilized by a variety of hydrogen bonding interactions, i.e. O-H$\\cdots$O, C-H$\\cdots$O and C-H$\\cdots$F involving second sphere coordination besides - interaction. Furthermore, packing analyses reveal that C-H…F interactions can manifest even in the presence of a large number of heteroatom interactions.

  15. Universality in Nonaqueous Alkali Oxygen Reduction on Metal Surfaces: Implications for Li−O2 and Na−O2 Batteries

    DEFF Research Database (Denmark)

    Krishnamurthy, Dilip; Hansen, Heine Anton; Viswanathan, Venkatasubramanian

    2016-01-01

    Nonaqueous metal−oxygen batteries, particularly lithium−oxygen and sodium−oxygen, have emerged as possible high energy density alternatives to Li-ion batteries that could address the limited driving range issues faced by electric vehicles. Many fundamental questions remain unanswered, including...... the origin of the differences in the discharge product formed, i.e., Li2O2 versus Li2O in Li−O2 batteries and NaO2 versus Na2O2 in Na−O2 batteries. In this Letter, we analyze the role of the electrode (electrocatalyst) in determining the selectivity of the discharge product through a tuning of the nucleation...... in Li−O2 batteries. Our analysis suggests that Au(100), Ag(111), and Au(111) are capable of nucleating Li2O2 with very low overpotentials. We also show that the free energy of adsorbed NaO2* is a descriptor determining the nucleation rate for sodium superoxide, NaO2, the primary discharge product in Na...

  16. Free tyrosine and tyrosine-rich peptide-dependent superoxide generation catalyzed by a copper-binding, threonine-rich neurotoxic peptide derived from prion protein

    Directory of Open Access Journals (Sweden)

    Ken Yokawa, Tomoko Kagenishi, Kaishi Goto, Tomonori Kawano

    2009-01-01

    Full Text Available Previously, generation of superoxide anion (O2•- catalyzed by Cu-binding peptides derived from human prion protein (model sequence for helical Cu-binding motif VNITKQHTVTTTT was most active in the presence of catecholamines and related aromatic monoamines such as phenylethylamine and tyramine, has been reported [Kawano, T., Int J Biol Sci 2007; 3: 57-63]. The peptide sequence (corresponding to helix 2 tested here is known as threonine-rich neurotoxic peptide. In the present article, the redox behaviors of aromatic monoamines, 20 amino acids and prion-derived tyrosine-rich peptide sequences were compared as putative targets of the oxidative reactions mediated with the threonine-rich prion-peptide. For detection of O2•-, an O2•--specific chemiluminescence probe, Cypridina luciferin analog was used. We found that an aromatic amino acid, tyrosine (structurally similar to tyramine behaves as one of the best substrates for the O2•- generating reaction (conversion from hydrogen peroxide catalyzed by Cu-bound prion helical peptide. Data suggested that phenolic moiety is required to be an active substrate while the presence of neither carboxyl group nor amino group was necessarily required. In addition to the action of free tyrosine, effect of two tyrosine-rich peptide sequences YYR and DYEDRYYRENMHR found in human prion corresponding to the tyrosine-rich region was tested as putative substrates for the threonine-rich neurotoxic peptide. YYR motif (found twice in the Y-rich region showed 2- to 3-fold higher activity compared to free tyrosine. Comparison of Y-rich sequence consisted of 13 amino acids and its Y-to-F substitution mutant sequence revealed that the tyrosine-residues on Y-rich peptide derived from prion may contribute to the higher production of O2•-. These data suggest that the tyrosine residues on prion molecules could be additional targets of the prion-mediated reactions through intra- or inter-molecular interactions. Lastly

  17. Free tyrosine and tyrosine-rich peptide-dependent superoxide generation catalyzed by a copper-binding, threonine-rich neurotoxic peptide derived from prion protein.

    Science.gov (United States)

    Yokawa, Ken; Kagenishi, Tomoko; Goto, Kaishi; Kawano, Tomonori

    2009-01-01

    Previously, generation of superoxide anion (O(2)(*-)) catalyzed by Cu-binding peptides derived from human prion protein (model sequence for helical Cu-binding motif VNITKQHTVTTTT was most active) in the presence of catecholamines and related aromatic monoamines such as phenylethylamine and tyramine, has been reported [Kawano, T., Int J Biol Sci 2007; 3: 57-63]. The peptide sequence (corresponding to helix 2) tested here is known as threonine-rich neurotoxic peptide. In the present article, the redox behaviors of aromatic monoamines, 20 amino acids and prion-derived tyrosine-rich peptide sequences were compared as putative targets of the oxidative reactions mediated with the threonine-rich prion-peptide. For detection of O(2)(*-), an O(2)(*-)-specific chemiluminescence probe, Cypridina luciferin analog was used. We found that an aromatic amino acid, tyrosine (structurally similar to tyramine) behaves as one of the best substrates for the O(2)(*-) generating reaction (conversion from hydrogen peroxide) catalyzed by Cu-bound prion helical peptide. Data suggested that phenolic moiety is required to be an active substrate while the presence of neither carboxyl group nor amino group was necessarily required. In addition to the action of free tyrosine, effect of two tyrosine-rich peptide sequences YYR and DYEDRYYRENMHR found in human prion corresponding to the tyrosine-rich region was tested as putative substrates for the threonine-rich neurotoxic peptide. YYR motif (found twice in the Y-rich region) showed 2- to 3-fold higher activity compared to free tyrosine. Comparison of Y-rich sequence consisted of 13 amino acids and its Y-to-F substitution mutant sequence revealed that the tyrosine-residues on Y-rich peptide derived from prion may contribute to the higher production of O(2)(*-). These data suggest that the tyrosine residues on prion molecules could be additional targets of the prion-mediated reactions through intra- or inter-molecular interactions. Lastly, possible

  18. Evidence that the reactivity of the martian soil is due to superoxide ions

    Science.gov (United States)

    Yen, A. S.; Kim, S. S.; Hecht, M. H.; Frant, M. S.; Murray, B.

    2000-01-01

    The Viking Landers were unable to detect evidence of life on Mars but, instead, found a chemically reactive soil capable of decomposing organic molecules. This reactivity was attributed to the presence of one or more as-yet-unidentified inorganic superoxides or peroxides in the martian soil. Using electron paramagnetic resonance spectroscopy, we show that superoxide radical ions (O2-) form directly on Mars-analog mineral surfaces exposed to ultraviolet radiation under a simulated martian atmosphere. These oxygen radicals can explain the reactive nature of the soil and the apparent absence of organic material at the martian surface.

  19. Poly[aqua-μ-bromido-(μ2-5-methylpyrazine-2-carboxylato-κ4N1,O2:O2,O2′lead(II

    Directory of Open Access Journals (Sweden)

    Pan Yang

    2012-09-01

    Full Text Available In the title coordination polymer, [PbBr(C6H5N2O2(H2O]n, the PbII atom is coordinated by one pyrazine N atom, two bridging Br atoms, a water molecule and three carboxylate O atoms. Bridging by the two anions generates a layer structure parallel to (001; the layers are linked by O—H...N and O—H...Br hydrogen bonds, forming a three-dimensional network. The lone pair is stereochemically active, resulting in a Ψ-dodecahedral coordination environment for PbII.

  20. Probing Mechanisms for Inverse Correlation between Rate Performance and Capacity in K-O2 Batteries.

    Science.gov (United States)

    Xiao, Neng; Ren, Xiaodi; He, Mingfu; McCulloch, William D; Wu, Yiying

    2017-02-08

    Owing to the formation of potassium superoxide (K(+) + O2 + e(-) = KO2), K-O2 batteries exhibit superior round-trip efficiency and considerable energy density in the absence of any electrocatalysts. For further improving the practical performance of K-O2 batteries, it is important to carry out a systematic study on parameters that control rate performance and capacity to comprehensively understand the limiting factors in superoxide-based metal-oxygen batteries. Herein, we investigate the influence of current density and oxygen diffusion on the nucleation, growth, and distribution of potassium superoxide (KO2) during the discharge process. It is observed that higher current results in smaller average sizes of KO2 crystals but a larger surface coverage on the carbon fiber electrode. As KO2 grows and covers the cathode surface, the discharge will eventually end due to depletion of the oxygen-approachable electrode surface. Additionally, higher current also induces a greater gradient of oxygen concentration in the porous carbon electrode, resulting in less efficient loading of the discharge product. These two factors explain the observed inverse correlation between current and capacity of K-O2 batteries. Lastly, we demonstrate a reduced graphene oxide-based K-O2 battery with a large specific capacity (up to 8400 mAh/gcarbon at a discharge rate of 1000 mA/gcarbon) and a long cycle life (over 200 cycles).

  1. HIV-1-infected monocytes and monocyte-derived macrophages are impaired in their ability to produce superoxide radicals.

    Science.gov (United States)

    Howell, A L; Groveman, D S; Wallace, P K; Fanger, M W

    1997-01-01

    Monocytes and monocyte-derived macrophages play a key role in immune defense against pathogenic organisms. Superoxide anion production is a key mechanism by which phagocytes kill pathogens. We sought to determine whether human immunodeficiency virus-infected monocytes and monocyte-derived macrophages are compromised in their ability to produce the superoxide anion following stimulation with phorbol myristate acetate (PMA) or after cross-linking the type I Fc receptor for IgG (Fc gamma RI). Fc gamma RI was cross-linked by the binding of monoclonal antibody 197, which reacts with an epitope of Fc gamma RI via its Fc region. Monocytes and monocyte-derived macrophages obtained from seronegative donors were infected in vitro with human immunodeficiency virus-1JR-FL and used in effector assays that measured superoxide anion production by the reduction of nitroblue tetrazolium. Reduced nitroblue tetrazolium was measured spectrophotometrically and by microscopy in which the percentage of cells containing intracellular deposits of the dye was assessed. By spectrophotometric measurement, we found that human immunodeficiency virus-infected monocytes and monocyte-derived macrophages produced less superoxide anion following either phorbol myristate acetate stimulation or Fc gamma RI cross-linking than uninfected cells from the same donor. Using microscopy we saw no difference in the percentage of infected and uninfected macrophages containing intracellular deposits of nitroblue tetrazolium suggesting that human immunodeficiency virus-infected macrophages produce less superoxide anion on a per cell basis than uninfected macrophages. Activation of human immunodeficiency virus-infected monocytes with interferon-gamma for 72 h prior to stimulation with phorbol myristate acetate or monoclonal antibody 197 increased their ability to reduce nitroblue tetrazolium. These findings suggest that impairment in the production of reactive oxygen intermediates may, in some cases, contribute to

  2. [Generation of superoxide radicals by the mitochondrial respiratory chain of isolated cardiomyocytes].

    Science.gov (United States)

    Kashkarov, K P; Vasil'eva, E V; Ruuge, E K

    1994-06-01

    Generation of superoxide radicals by the mitochondrial respiratory chain of cardiomyocites isolated from rat heart and treated with saponin was studied. The rate of O2- production was measured by electron paramagnetic resonance (EPR) spectroscopy using hydroxylamine TEMPONE-H as spin trap. A device has been constructed which provided permanent stirring of cardiomyocyte samples directly in the cavity and prevented cell aggregation. When substrates and antimycin A and/or rotenone are added, the radical production rate increased and reached its maximum in the presence of the both inhibitors. Superoxide dismutase as well as KCN suppressed the radical production, thus being suggestive of the generation of superoxide radicals in the bc1 complex, while the mechanism of O2- production is the same as was suggested for isolated mitochondria. The ratio between rates of O2- generation by isolated cardiomyocytes under various experimental conditions is in a good accord with corresponding parameter of isolated mitochondria. However, in the case of cardiomyocytes the absolute values of the O2- production rate are approximately twice as high as those in isolated mitochondria, presumably due to the partial damage of the mitochondrial respiratory chain during the isolation procedure.

  3. The changes of serum nitric oxide,angiotensin Ⅱ and superoxide anion in renal artery hypertension rat%肾动脉性高血压大鼠血清一氧化氮、血管紧张素Ⅱ和超氧阴离子水平的变化

    Institute of Scientific and Technical Information of China (English)

    马向红; 杨万松; 黄体钢; 周丽娟; 倪燕平; 樊振旺

    2004-01-01

    目的探讨一氧化氮、血管紧张素Ⅱ和超氧阴离子(O2-)在高血压发病机制中的作用.方法将体重256~285g雄性Wistar大鼠随机分成5组,每组l0只,实验前测量血压、心率.对照组进行假手术及常规饮食喂养,单纯结扎组:不完全结扎一侧肾动脉及常规饮食喂养,结扎+Losartan组:不完全结扎一侧肾动脉并在水中加入Losartan20mg·kg-1·d-1,结扎+精氨酸(L-Arg)组:不完全结扎一侧肾动脉并在水中加入L-Arg 2 g·kg-1·d-1,结扎+L-Arg+Losartan组:不完全结扎一侧肾动脉并在水中加入L-Arg 2 g·kg-1·d-1和Losartan 20 mg·kg-1·d-1,结扎后1周测量血压、心率并取血测血管紧张素Ⅱ(AngⅡ),环岛苷磷酸(cGMP),一氧化氮(NO),一氧化氮合成酶(NOS),O2-,超氧化物歧化酶(SOD)浓度.结果单纯结扎组收缩压较结扎前明显升高(P<0.05),而结扎+Losartan组收缩压较单纯结扎组明显减低(P<0.05),结扎+L-Arg组血压较对照组增加,但较单纯结扎组降低,较结扎+Losafran组高(P<0.05),结扎+L-Arg+Losartan组血压较对照组增加,但低于单纯结扎组和结扎+L-Arg组(P<0.05).实验前、后各组心率无变化(P>0.05).单纯结扎组AngⅡ较对照组明显升高(P<0.05),而结扎+Losartan组升高更加明显(P<0.01).各组之间cGMP水平无显著差异(P>0.05),单纯结扎组NO、NOS水平明显降低(P<0.05),结扎+Losartan组NO、NOS水平较单纯结扎组无显著差异(P>0.05),结扎+L-Arg组NOS水平较单纯结扎组升高,结扎+L-Arg+Losartan组NO、NOS水平较单纯结扎组升高(P<0.05).单纯结扎组和结扎+L-Arg组O2-水平较对照组明显升高(P<0.05),结扎+Losartan组O2-水平较单纯结扎组降低(P<0.05),单纯结扎组SOD水平明显下降(P<0.05),结扎+L-Arg组和结扎+L-Arg+Losartan组SOD水平较单纯结扎组升高(P<0.05).结论O2-、AngⅡ和NO平衡失调在高血压发病机制中具有重要作用,L-Arg和Losartan具有保护作用.

  4. Effect of Y2(CO3)3 and Surfactants on Electrorheological Performance of SiO2 Particle Materials

    Institute of Scientific and Technical Information of China (English)

    许明远; 马淑珍; 李淑新; 李俊然; 张少华; 魏宸官; 高松

    2004-01-01

    The SiO2 particle material has weak electrorheological (ER) activity. The ER performance of the SiO2 particles can be ameliorated after adsorbing Y2(CO3)3. In this paper, the effect of Y2(CO3)3 and different surfactants on the ER performance of the SiO2 particle materials is investigated. The results show that anionic or cationic surfactants maybe enhance the ER activity of SiO2 material, and nonionic surfactants cannot when surfactants are added during the process of the SiO2 particle preparation, only the anionic surfactant, AES, can enhance markedly the ER performance of the material. The surface area, pore volume and pore diameter of the particles were measured. The effect of Y2(CO3)3 and the surfactants on the microstructure of SiO2 materials and the relationship between ER effect and the microstructure are described.

  5. Dihydronium tetrachromate(VI, (H3O2Cr4O13

    Directory of Open Access Journals (Sweden)

    Vladislav Kulikov

    2013-02-01

    Full Text Available The crystal structure of (H3O2Cr4O13 is isotypic with K2Cr4O13. The finite tetrachromate anion in the title structure consists of four vertex-sharing CrO4 tetrahedra and exhibits a typical zigzag arrangement. The crystal packing is stabilized by hydrogen bonds between these anions and hydronium cations. The two different hydronium cations are surrounded by nine O atoms of tetrachromate anions, with O...O distances ranging between 2.866 (8 and 3.282 (7 Å.

  6. Enhanced sensitivity of Cypridina luciferin analog (CLA) chemiluminescence for the detection of O2- with non ionic detergents

    NARCIS (Netherlands)

    Osman, A.M.; Laane, C.; Hilhorst, R.

    2000-01-01

    Superoxide anion-triggered chemiluminescence of Cypridina luciferin analogue (CLA), 2-methyl-6-phenyl-3,7-dohydroimidazo[1,2-]pyrazin-3-one, is enhanced by non-ionic detergents such as Tween 20, Triton X-100 and Tween 80. At the concentration of 0.6øv/v) the largest increase (2.7-fold) of CLA light

  7. Myocardial capillary permeability after regional ischemia and reperfusion in the in vivo canine heart. Effect of superoxide dismutase

    DEFF Research Database (Denmark)

    Svendsen, Jesper Hastrup; Bjerrum, P J; Haunsø, S

    1991-01-01

    This study assesses the effect of the superoxide anion scavenger superoxide dismutase on myocardial capillary permeability-surface area (PS) products for small hydrophilic molecules after ischemia and reperfusion. Open-chest dogs underwent a 20-minute occlusion of the left anterior descending...... the start of reperfusion. In 13 dogs, no scavenger treatment was given (nonprotected control group), whereas eight dogs were treated systemically with 15,000 units/kg superoxide dismutase during 1 hour, starting 20 minutes before ischemia. In the control group, three dogs developed reperfusion ventricular...... fibrillation in contrast to none in the superoxide dismutase group. Before ischemia, plasma flow rate, myocardial capillary extraction fraction, and PS values were similar in the two groups. Five minutes after the start of reperfusion, plasma flow rate increased significantly (p less than 0.01) in both groups...

  8. Activation of Mitochondrial Uncoupling Protein 4 and ATP-Sensitive Potassium Channel Cumulatively Decreases Superoxide Production in Insect Mitochondria.

    Science.gov (United States)

    Slocińska, Malgorzata; Rosinski, Grzegorz; Jarmuszkiewicz, Wieslawa

    2016-01-01

    It has been evidenced that mitochondrial uncoupling protein 4 (UCP4) and ATP-regulated potassium channel (mKATP channel) of insect Gromphadorhina coqereliana mitochondria decrease superoxide anion production. We elucidated whether the two energy-dissipating systems work together on a modulation of superoxide level in cockroach mitochondria. Our data show that the simultaneous activation of UCP4 by palmitic acid and mKATP channel by pinacidil revealed a cumulative effect on weakening mitochondrial superoxide formation. The inhibition of UCP4 by GTP (and/or ATP) and mKATP channel by ATP elevated superoxide production. These results suggest a functional cooperation of both energy-dissipating systems in protection against oxidative stress in insects.

  9. A superoxide dismutase of metacestodes of Taenia taeniaeformis.

    Science.gov (United States)

    Leid, R W; Suquet, C M

    1986-03-01

    Superoxide dismutase was purified from Taenia taeniaeformis metacestodes by sequential ion exchange chromatography on quaternary-amino-ethyl-cellulose, gel filtration chromatography on ACA 44 and ion exchange chromatography on DEAE-cellulose, followed by chromatofocusing on polybuffer exchanger 94. This isolation procedure resulted in the detection of a single protein-staining band on alkaline gels, coincident with enzyme activity. We have, however, detected what appear to be two peaks of enzyme activity within this single protein-staining band. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis using gradient slab gels and analysis under reducing conditions, resulted in the detection of only one protein at an apparent Mr of 16,600, while analysis under non-reducing conditions, gave a single protein of an apparent Mr of 64,000. The isoelectric point of the purified protein is 6.6. Boiling for 3 min completely destroyed the enzyme, whereas incubation for 2 h at 37 degrees C resulted in the loss of 56% of the enzymic activity. Incubation with 10 mM KCN resulted in 83% inhibition of the enzyme. We have detected up to 168 U ml-1 of enzyme activity in the cyst fluid surrounding the parasite in situ. This is the first instance in which any parasite superoxide dismutase has been purified to apparent homogeneity. Parasite-mediated enzymic destruction of superoxide anion can not only protect against oxygen toxicity as a result of normal parasite respiratory processes but also may serve as yet another mechanism used by tissue-dwelling parasites to evade host immunologic attack.

  10. Excellent photocatalytic degradation activities of ordered mesoporous anatase TiO2-SiO2 nanocomposites to various organic contaminants.

    Science.gov (United States)

    Dong, Weiyang; Sun, Yaojun; Ma, Qingwei; Zhu, Li; Hua, Weiming; Lu, Xinchun; Zhuang, Guoshun; Zhang, Shicheng; Guo, Zhigang; Zhao, Dongyuan

    2012-08-30

    Ordered 2-D hexagonal mesoporous TiO(2)-SiO(2) nanocomposites consisted of anatase TiO(2) nanocrystals and amorphous SiO(2) nanoparticles, with large mesochannels and high specific surface areas, have been extensively and detailedly evaluated using various cationic dyes (methylene blue, safranin O, crystal violet, brilliant green, basic fuchsin and rhodamine-6G), anionic dyes (acid fuchsin, orange II, reactive brilliant red X3B and acid red 1) and microcystin-LR. We use mesoporous 80TiO(2)-20SiO(2)-900 for the degradation of cationic dyes and MC-LR, due to the dominant adsorption of SiOH groups and synergistic role of coupled adsorption and photocatalytic oxidation. For anionic dyes, due to the adsorption results predominantly from TiOH groups, our strategy realizes the enhanced photocatalytic oxidation by strong surface acids and larger available specific surface area. Based on this, we prepared 90TiO(2)-10SiO(2)-700 to degrade them. The results show that our samples exhibit excellent degradation activities to all the contaminants, which are much higher than that of P25 photocatalyst. The dyes are not only decolorized promptly but degraded readily as well. It is strongly indicated that our mesoporous nanocomposites are considerably stable and reusable. These results demonstrate that our mesoporous TiO(2)-SiO(2) nanocomposites present extensive and promising application in the fast and highly efficient degradation of various organic pollutants. Copyright © 2012 Elsevier B.V. All rights reserved.

  11. Reversible activation of the neutrophil superoxide generating system by hexachlorocyclohexane: correlation with effects on a subcellular superoxide-generating fraction.

    Science.gov (United States)

    English, D; Schell, M; Siakotos, A; Gabig, T G

    1986-07-01

    gamma-Hexachlorocyclohexane was found to exert profound effects on the phosphatidylinositol cycle, cytosolic calcium level, and the respiratory burst of human neutrophils. Exposure of neutrophils prelabelled with 32P to 4 X 10(-4) M gamma-hexachlorocyclohexane almost tripled radioactivity in phosphatidic acid and correspondingly decreased radioactivity in phosphatidylinositol 4,5 bisphosphate. Under similar conditions, gamma-hexachlorocyclohexane evoked the generation of superoxide at a rate of over 11 nmol/min/10(6) cells and more than doubled cytosolic-free calcium concentration as monitored by Quin-2 fluorescence. Because intermediates of the phosphatidylinositol cycle, via increases in available calcium levels or activated protein kinase C, are considered potential second messengers for activation of the NADPH-dependent O-2-generating system, we compared neutrophil responses to gamma-hexachlorocyclohexane with responses to phorbol myristate acetate, an activator of protein kinase C with well known effects on neutrophils. Like phorbol myristate acetate, gamma-hexachlorocyclohexane induced neutrophil degranulation but was not an effective chemotactic stimulus. The ability of gamma-hexachlorocyclohexane to induce a pattern of oxidative activation in neutrophil cytoplasts similar to that in intact cells indicated that concurrent degranulation was not required for sustained O-2 generation in response to this agent. When neutrophils or neutrophil cytoplasts exposed to gamma-hexachlorocyclohexane were centrifuged and resuspended in stimulus-free medium, O-2 generation ceased entirely but could be reinitiated by addition of the same stimulus. This finding was in contrast to the continued O-2 production by phorbol myristate acetate-stimulated neutrophils similarly washed and resuspended in stimulus-free medium. Unlike subcellular fractions of phorbol myristate acetate-stimulated neutrophils, corresponding fractions prepared from gamma

  12. Superoxide dismutases in chronic gastritis.

    Science.gov (United States)

    Švagelj, Dražen; Terzić, Velimir; Dovhanj, Jasna; Švagelj, Marija; Cvrković, Mirta; Švagelj, Ivan

    2016-04-01

    Human gastric diseases have shown significant changes in the activity and expression of superoxide dismutase (SOD) isoforms. The aim of this study was to detect Mn-SOD activity and expression in the tissue of gastric mucosa, primarily in chronic gastritis (immunohistochemical Helicobacter pylori-negative gastritis, without other pathohistological changes) and to evaluate their possible connection with pathohistological diagnosis. We examined 51 consecutive outpatients undergoing endoscopy for upper gastrointestinal symptoms. Patients were classified based on their histopathological examinations and divided into three groups: 51 patients (archive samples between 2004-2009) with chronic immunohistochemical Helicobacter pylori-negative gastritis (mononuclear cells infiltration were graded as absent, moderate, severe) divided into three groups. Severity of gastritis was graded according to the updated Sydney system. Gastric tissue samples were used to determine the expression of Mn-SOD with anti-Mn-SOD Ab immunohistochemically. The Mn-SOD expression was more frequently present in specimens with severe and moderate inflammation of gastric mucosa than in those with normal mucosa. In patients with normal histological finding, positive immunoreactivity of Mn-SOD was not found. Our results determine the changes in Mn-SOD expression occurring in the normal gastric mucosa that had undergone changes in the intensity of chronic inflammatory infiltrates in the lamina propria. © 2016 APMIS. Published by John Wiley & Sons Ltd.

  13. [Involvement of carbonate/bicarbonate ions in the superoxide-generating reaction of adrenaline autoxidation].

    Science.gov (United States)

    Sirota, T V

    2015-01-01

    An important role of carbonate/bicarbonate ions has been recognized in the superoxide generating reaction of adrenaline autooxidation in an alkaline buffer (a model of quinoid adrenaline oxidation in the body). It is suggested that these ions are directly involved not only in formation of superoxide anion radical (О(2)(-)) but also other radicals derived from the carbonate/bicarbonate buffer. Using various buffers it was shown that the rate of accumulation of adrenochrome, the end product of adrenaline oxidation, and the rate of О(2)(-)· formation depend on concentration of carbonate/bicarbonate ions in the buffer and that these ions significantly accelerate adrenaline autooxidation thus demonstrating prooxidant properties. The detectable amount of diformazan, the product of nitro blue tetrazolium (NBT) reduction, was significantly higher than the amount of adrenochrome formed; taking into consideration the literature data on О(2)(-)· detection by NBT it is suggested that adrenaline autooxidation is accompanied by one-electron reduction not only of oxygen dissolved in the buffer and responsible for superoxide formation but possible carbon dioxide also dissolved in the buffer as well as carbonate/bicarbonate buffer components leading to formation of corresponding radicals. The plots of the dependence of the inhibition of adrenochrome and diformazan formation on the superoxide dismutase concentration have shown that not only superoxide radicals are formed during adrenaline autooxidation. Since carbonate/bicarbonate ions are known to be universally present in the living nature, their involvement in free radical processes proceeding in the organism is discussed.

  14. Preparation of hollow TiO2 nanoparticles through TiO2 deposition on polystyrene latex particles and characterizations of their structure and photocatalytic activity

    Science.gov (United States)

    2012-01-01

    In a mixed solvent of water and ethanol, polystyrene/titanium dioxide (PSt/TiO2) composite particles of core-shell structure were prepared by hydrolysis of tetrabutyl titanate in the presence of cationic PSt particles or anionic PSt particles surface-treated using γ-aminopropyl triethoxysilane. Hollow TiO2 particles were obtained through calcination of the PSt/TiO2 core-shell particles to burn off the PSt core or through dissolution of the core by tetrahydrofuran (THF). An alternative process constituted of preheating the PSt/TiO2 particles at 200°C to allow partial crystallization followed by calcination or PSt dissolution by THF. The outcome TiO2 particles thus prepared were examined by TEM, and hollow TiO2 particles were observed. The crystalline phase structure and phase transformation were characterized, which revealed that preheating before the removal of the PSt core was useful to achieve the desired hollow TiO2 particles, and the calcination process was beneficial to the formation of anatase and rutile structures. The tests of TiO2 particles as catalyst in the photodegradation of Rhodamine B demonstrated that a much higher catalytic activity was observed with the TiO2 hollow particles prepared through calcination combined with preheating. PMID:23176612

  15. Angiotensin II stimulates superoxide production by nitric oxide synthase in thick ascending limbs.

    Science.gov (United States)

    Gonzalez-Vicente, Agustin; Saikumar, Jagannath H; Massey, Katherine J; Hong, Nancy J; Dominici, Fernando P; Carretero, Oscar A; Garvin, Jeffrey L

    2016-02-01

    Angiotensin II (Ang II) causes nitric oxide synthase (NOS) to become a source of superoxide (O2 (-)) via a protein kinase C (PKC)-dependent process in endothelial cells. Ang II stimulates both NO and O2 (-) production in thick ascending limbs. We hypothesized that Ang II causes O2 (-) production by NOS in thick ascending limbs via a PKC-dependent mechanism. NO production was measured in isolated rat thick ascending limbs using DAF-FM, whereas O2 (-) was measured in thick ascending limb suspensions using the lucigenin assay. Consistent stimulation of NO was observed with 1 nmol/L Ang II (P thick ascending limbs via a PKC- and NADPH oxidase-dependent process; and (2) the effect of Ang II is not due to limited substrate.

  16. Mitochondrial complex II-derived superoxide is the primary source of mercury toxicity in barley root tip.

    Science.gov (United States)

    Tamás, Ladislav; Zelinová, Veronika

    2017-02-01

    Enhanced superoxide generation and significant inhibition of succinate dehydrogenase (SDH) activity followed by a strong reduction of root growth were detected in barley seedlings exposed to a 5μM Hg concentration for 30min, which increased further in an Hg dose-dependent manner. While at a 25μM Hg concentration no cell death was detectable, a 50μM Hg treatment triggered cell death in the root meristematic zone, which was markedly intensified after the treatment of roots with 100μM Hg and was detectable in the whole root tips. Generation of superoxide and H2O2 was a very rapid response of root tips occurring even after 5min of exposure to Hg. Application of an NADPH oxidase inhibitor or the inhibition of electron flow in mitochondria by the inhibition of complex I did not influence the Hg-induced H2O2 production. Treatment of roots with thenoyltrifluoroacetone, a non-competitive inhibitor of SDH, markedly reduced root growth and induced both superoxide and H2O2 production in a dose dependent manner. Similar to results obtained in intact roots, Hg strongly inhibited SDH activity in the crude mitochondrial fraction and caused a considerable increase of superoxide production, which was markedly reduced by the competitive inhibitors of SDH. These results indicate that the mitochondrial complex II-derived superoxide is the primary source of Hg toxicity in the barley root tip.

  17. Effect of Mn cluster on the formation of superoxide radicals in photoinhibition of photosystem Ⅱ

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    To further realize the action of superoxide radicals (O-2) in photoinhibition of photosystem Ⅱ (PS Ⅱ),we employed 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as a spin trap, associated with EPR spectroscopy, to study the effect of illumination time on O-*2 formation during high light photoinhibition in PS Ⅱ membranes and Mn-depleted PS Ⅱ membranes. Results indicated that the removal of Mn cluster from PSⅡmembranes has a strong influence on the dynamnics of superoxide formation.The relative mechanism was also discussed.These novel findings may further promote the studies of the structure and function of PSⅡand the mechanism of photoinhibition.

  18. Superoxide-dependent hydroxylation by myeloperoxidase.

    Science.gov (United States)

    Kettle, A J; Winterbourn, C C

    1994-06-24

    When stimulated, neutrophils undergo a respiratory burst converting oxygen to superoxide. Although superoxide is critical for microbial killing by phagocytic cells, the precise role it plays has yet to be established. It has been proposed to optimize their production of hypochlorous acid and to be required for the generation of hydroxyl radicals. Superoxide is also involved in the hydroxylation of salicylate by neutrophils. However, the mechanism of this reaction is unknown. We found that neutrophils stimulated with opsonized zymosan hydroxylated salicylate to produce mainly 2,5-dihydroxybenzoate. Its formation was dependent on superoxide and a heme protein but was independent of hydrogen peroxide and hydroxyl radicals. Production of 2,5-dihydroxybenzoate was enhanced by methionine, which scavenges hypochlorous acid. Neutrophils from an individual with myeloperoxidase deficiency hydroxylated salicylate at only 13% of the level of control cells. Purified human myeloperoxidase and xanthine oxidase plus hypoxanthine hydroxylated salicylate to produce 2,5-dihydroxybenzoate. As with neutrophils, the reaction required superoxide but not hydrogen peroxide and was unaffected by hydroxyl radical scavengers. Thus, myeloperoxidase catalyzes superoxide-dependent hydroxylation. This newly recognized reaction may be relevant to the in vivo functions of superoxide and myeloperoxidase.

  19. Highly efficient conversion of superoxide to oxygen using hydrophilic carbon clusters.

    Science.gov (United States)

    Samuel, Errol L G; Marcano, Daniela C; Berka, Vladimir; Bitner, Brittany R; Wu, Gang; Potter, Austin; Fabian, Roderic H; Pautler, Robia G; Kent, Thomas A; Tsai, Ah-Lim; Tour, James M

    2015-02-24

    Many diseases are associated with oxidative stress, which occurs when the production of reactive oxygen species (ROS) overwhelms the scavenging ability of an organism. Here, we evaluated the carbon nanoparticle antioxidant properties of poly(ethylene glycolated) hydrophilic carbon clusters (PEG-HCCs) by electron paramagnetic resonance (EPR) spectroscopy, oxygen electrode, and spectrophotometric assays. These carbon nanoparticles have 1 equivalent of stable radical and showed superoxide (O2 (•-)) dismutase-like properties yet were inert to nitric oxide (NO(•)) as well as peroxynitrite (ONOO(-)). Thus, PEG-HCCs can act as selective antioxidants that do not require regeneration by enzymes. Our steady-state kinetic assay using KO2 and direct freeze-trap EPR to follow its decay removed the rate-limiting substrate provision, thus enabling determination of the remarkable intrinsic turnover numbers of O2 (•-) to O2 by PEG-HCCs at >20,000 s(-1). The major products of this catalytic turnover are O2 and H2O2, making the PEG-HCCs a biomimetic superoxide dismutase.

  20. Anion-π catalysis.

    Science.gov (United States)

    Zhao, Yingjie; Beuchat, César; Domoto, Yuya; Gajewy, Jadwiga; Wilson, Adam; Mareda, Jiri; Sakai, Naomi; Matile, Stefan

    2014-02-05

    The introduction of new noncovalent interactions to build functional systems is of fundamental importance. We here report experimental and theoretical evidence that anion-π interactions can contribute to catalysis. The Kemp elimination is used as a classical tool to discover conceptually innovative catalysts for reactions with anionic transition states. For anion-π catalysis, a carboxylate base and a solubilizer are covalently attached to the π-acidic surface of naphthalenediimides. On these π-acidic surfaces, transition-state stabilizations up to ΔΔGTS = 31.8 ± 0.4 kJ mol(-1) are found. This value corresponds to a transition-state recognition of KTS = 2.7 ± 0.5 μM and a catalytic proficiency of 3.8 × 10(5) M(-1). Significantly increasing transition-state stabilization with increasing π-acidity of the catalyst, observed for two separate series, demonstrates the existence of "anion-π catalysis." In sharp contrast, increasing π-acidity of the best naphthalenediimide catalysts does not influence the more than 12 000-times weaker substrate recognition (KM = 34.5 ± 1.6 μM). Together with the disappearance of Michaelis-Menten kinetics on the expanded π-surfaces of perylenediimides, this finding supports that contributions from π-π interactions are not very important for anion-π catalysis. The linker between the π-acidic surface and the carboxylate base strongly influences activity. Insufficient length and flexibility cause incompatibility with saturation kinetics. Moreover, preorganizing linkers do not improve catalysis much, suggesting that the ideal positioning of the carboxylate base on the π-acidic surface is achieved by intramolecular anion-π interactions rather than by an optimized structure of the linker. Computational simulations are in excellent agreement with experimental results. They confirm, inter alia, that the stabilization of the anionic transition states (but not the neutral ground states) increases with the π-acidity of the

  1. The role of macrocyclic ligands in the peroxo/superoxo nature of Ni-O2 biomimetic complexes.

    Science.gov (United States)

    Zapata-Rivera, Jhon; Caballol, Rosa; Calzado, Carmen J

    2012-06-15

    The impact of the macrocyclic ligand on the electronic structure of two LNi-O2 biomimetic adducts, [Ni(12-TMC)O2](+) (12-TMC = 1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane) and [Ni(14-TMC)O2](+) (14-TMC = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane), has been inspected by means of difference-dedicated configuration interaction calculations and a valence bond reading of the wavefunction. The system containing the 12-membered macrocyclic ligand has been experimentally described as a side-on nickel(III)-peroxo complex, whereas the 14-membered one has been characterized as an end-on nickel(II)-superoxide. Our results put in evidence the relationship between the steric effect of the macrocyclic ligand, the O2 coordination mode and the charge transfer extent between the Ni center and the O2 molecule. The 12-membered macrocyclic ligand favors a side-on coordination, a most efficient overlap between Ni 3d and O2 π* orbitals and, consequently, a larger charge transfer from LNi fragment to O2 molecule. The analysis of the ground-state electronic structure shows an enhancement of the peroxide nature of the Ni-O2 interaction for [Ni(12-TMC)O2](+), although a dominant superoxide character is found for both systems.

  2. Vibrational spectroscopy of microhydrated conjugate base anions.

    Science.gov (United States)

    Asmis, Knut R; Neumark, Daniel M

    2012-01-17

    -water hydrogen bonding is observed. When there are more than three hydrating water molecules (n > 3), the formation of a particularly stable four-membered water ring is observed for hydrated nitrate and bicarbonate clusters. This ring binds in either a side-on (bicarbonate) or top-on (nitrate) fashion. In the case of bicarbonate, additional water molecules then add to this water ring rather than directly to the anion, indicating a preference for surface hydration. In contrast, doubly charged sulfate dianions are internally hydrated and characterized by the closing of the first hydration shell at n = 12. The situation is different for the (-)O(2)C(CH(2))(6)CO(2-) (suberate) dianion, which adapts to the hydration network by changing from a linear to a folded structure at n > 15. This change is driven by the formation of additional solute-solvent hydrogen bonds.

  3. TiO2 Nanosols Applied Directly on Textiles Using Different Purification Treatments

    Directory of Open Access Journals (Sweden)

    Simona Ortelli

    2015-11-01

    Full Text Available Self-cleaning applications using TiO2 coatings on various supporting media have been attracting increasing interest in recent years. This work discusses the issue of self-cleaning textile production on an industrial scale. A method for producing self-cleaning textiles starting from a commercial colloidal nanosuspension (nanosol of TiO2 is described. Three different treatments were developed for purifying and neutralizing the commercial TiO2 nanosol: washing by ultrafiltration; purifying with an anion exchange resin; and neutralizing in an aqueous solution of ammonium bicarbonate. The different purified TiO2 nanosols were characterized in terms of particle size distribution (using dynamic light scattering, electrical conductivity, and ζ potential (using electrophoretic light scattering. The TiO2-coated textiles’ functional properties were judged on their photodegradation of rhodamine B (RhB, used as a stain model. The photocatalytic performance of the differently treated TiO2-coated textiles was compared, revealing the advantages of purification with an anion exchange resin. The study demonstrated the feasibility of applying commercial TiO2 nanosol directly on textile surfaces, overcoming problems of existing methods that limit the industrial scalability of the process.

  4. Synthesis and Crystal Structure of a Two-dimensional Zinc(Ⅱ) Coordination Polymer:[Zn2(DTB)(DMF)4(H2O)2]n (DTM= 1,4-Dinitro-2,3,5,6-tetracarboxylatebenzene Tetravalent Anion; DMF = Dimethylformamide)

    Institute of Scientific and Technical Information of China (English)

    石敬民; 尹海亮; 吴长举

    2004-01-01

    A two-dimensional coordination polymer [Zn2(DTB)(DMF)4(H2O)2]n has been synthesized by 1,4-dinitro-2,3,5,6-tetracarboxylatebenzenic acid and hydrate zinc perchlorate in the solutions of DMF and H2O. The crystal belongs to the triclinic system, space group P with a = 8.887(6), b = 9.225(6), c = 9.828(7)(°A), α = 85.249(11), β = 74.863(11), γ= 86.510(13)°, V = 774.4(9), Z = 1, C22H32N6O18Zn2, Mr = 799.28, Dc = 1.714 g/cm3, F(000) = 410 and μ= 1.639 mm-1. The structure was refined to R = 0.0539 and wR = 0.1161 for 1584 observed reflections (I > 2б(I)). In the complex there exist two kinds of coordination environments for the zinc(Ⅱ) ions and a two-dimensional sheet is formed via the coordination of carboxylates and zinc(Ⅱ) ions.

  5. Differential production of superoxide by neuronal mitochondria

    Directory of Open Access Journals (Sweden)

    Levin Leonard A

    2008-01-01

    Full Text Available Abstract Background Mitochondrial DNA (mtDNA mutations, which are present in all mitochondria-containing cells, paradoxically cause tissue-specific disease. For example, Leber's hereditary optic neuropathy (LHON results from one of three point mutations mtDNA coding for complex I components, but is only manifested in retinal ganglion cells (RGCs, a central neuron contained within the retina. Given that RGCs use superoxide for intracellular signaling after axotomy, and that LHON mutations increase superoxide levels in non-RGC transmitochondrial cybrids, we hypothesized that RGCs regulate superoxide levels differently than other neuronal cells. To study this, we compared superoxide production and mitochondrial electron transport chain (METC components in isolated RGC mitochondria to mitochondria isolated from cerebral cortex and neuroblastoma SK-N-AS cells. Results In the presence of the complex I substrate glutamate/malate or the complex II substrate succinate, the rate of superoxide production in RGC-5 cells was significantly lower than cerebral or neuroblastoma cells. Cerebral but not RGC-5 or neuroblastoma cells increased superoxide production in response to the complex I inhibitor rotenone, while neuroblastoma but not cerebral or RGC-5 cells dramatically decreased superoxide production in response to the complex III inhibitor antimycin A. Immunoblotting and real-time quantitative PCR of METC components demonstrated different patterns of expression among the three different sources of neuronal mitochondria. Conclusion RGC-5 mitochondria produce superoxide at significantly lower rates than cerebral and neuroblastoma mitochondria, most likely as a result of differential expression of complex I components. Diversity in METC component expression and function could explain tissue specificity in diseases associated with inherited mtDNA abnormalities.

  6. Structural characterization of nanosized CeO(2)-SiO(2), CeO(2)-TiO(2), and CeO(2)-ZrO(2) catalysts by XRD, Raman, and HREM techniques.

    Science.gov (United States)

    Reddy, Benjaram M; Khan, Ataullah; Lakshmanan, Pandian; Aouine, Mimoun; Loridant, Stéphane; Volta, Jean-Claude

    2005-03-03

    Structural characteristics of nanosized ceria-silica, ceria-titania, and ceria-zirconia mixed oxide catalysts have been investigated using X-ray diffraction (XRD), Raman spectroscopy, BET surface area, thermogravimetry, and high-resolution transmission electron microscopy (HREM). The effect of support oxides on the crystal modification of ceria cubic lattice was mainly focused. The investigated oxides were obtained by soft chemical routes with ultrahighly dilute solutions and were subjected to thermal treatments from 773 to 1073 K. The XRD results suggest that the CeO(2)-SiO(2) sample primarily consists of nanocrystalline CeO(2) on the amorphous SiO(2) surface. Both crystalline CeO(2) and TiO(2) anatase phases were noted in the case of CeO(2)-TiO(2) sample. Formation of cubic Ce(0.75)Zr(0.25)O(2) and Ce(0.6)Zr(0.4)O(2) (at 1073 K) were observed in the case of the CeO(2)-ZrO(2) sample. Raman measurements disclose the fluorite structure of ceria and the presence of oxygen vacancies/Ce(3+). The HREM results reveal well-dispersed CeO(2) nanocrystals over the amorphous SiO(2) matrix in the cases of CeO(2)-SiO(2), isolated CeO(2), and TiO(2) (anatase) nanocrystals, some overlapping regions in the case of CeO(2)-TiO(2), and nanosized CeO(2) and Ce-Zr oxides in the case of CeO(2)-ZrO(2) sample. The exact structural features of these crystals as determined by digital diffraction analysis of HREM experimental images reveal that the CeO(2) is mainly in cubic fluorite geometry. The oxygen storage capacity (OSC) as determined by thermogravimetry reveals that the OSC of the mixed oxide systems is more than that of pure CeO(2) and is system dependent.

  7. Metabolic stability of superoxide adducts derived from newly developed cyclic nitrone spin traps.

    Science.gov (United States)

    Bézière, Nicolas; Hardy, Micael; Poulhès, Florent; Karoui, Hakim; Tordo, Paul; Ouari, Olivier; Frapart, Yves-Michel; Rockenbauer, Antal; Boucher, Jean-Luc; Mansuy, Daniel; Peyrot, Fabienne

    2014-02-01

    Reactive oxygen species are by-products of aerobic metabolism involved in the onset and evolution of various pathological conditions. Among them, the superoxide radical is of special interest as the origin of several damaging species such as H2O2, hydroxyl radical, or peroxynitrite (ONOO(-)). Spin trapping coupled with ESR is a method of choice to characterize these species in chemical and biological systems and the metabolic stability of the spin adducts derived from reaction of superoxide and hydroxyl radicals with nitrones is the main limit to the in vivo application of the method. Recently, new cyclic nitrones bearing a triphenylphosphonium or permethylated β-cyclodextrin moiety have been synthesized and their spin adducts demonstrated increased stability in buffer. In this article, we studied the stability of the superoxide adducts of four new cyclic nitrones in the presence of liver subcellular fractions and biologically relevant reductants using an original setup combining a stopped-flow device and an ESR spectrometer. The kinetics of disappearance of the spin adducts were analyzed using an appropriate simulation program. Our results highlight the interest of the new spin trapping agents CD-DEPMPO and CD-DIPPMPO for specific detection of superoxide with high stability of the superoxide adducts in the presence of liver microsomes.

  8. Electrochemistry of surface wired cytochrome c and bioelectrocatalytic sensing of superoxide

    Indian Academy of Sciences (India)

    Susmita Behera; Ramendra Sundar Dey; Manas Kumar Rana; C Retna Raj

    2013-03-01

    Electrochemistry of cytochrome c (Cyt-c) wired on an electrode modified with the self-assemblies of 4,4'-dithio-dibutyric acid (DTB) and 2-pyrazineethane thiol (PET) by covalent and electrostatic binding and the amperometric sensing of superoxide (O$^{−}_{2}$) are described. Cyt-c wired on the mixed self-assembly of DTB and PET displays well-defined voltammetric response at 0.025V with a peak-to-peak separation ( ) of 5mV. Pyrazine unit in the mixed self-assembly promotes the electron transfer in the redox reaction of surface wired Cyt-c. Cyt-c wired on the mixed self-assembly has been used for the amperometric sensing of superoxide. The enzymatically generated superoxide has been successfully detected using the Cyt-c wired electrode. High sensitivity and fast response for superoxide have been achieved. Uric acid does not interfere in the amperometric measurement of superoxide. The interference due to H2O2 has been eliminated by using enzyme catalase.

  9. Serine 1179 Phosphorylation of Endothelial Nitric Oxide Synthase Increases Superoxide Generation and Alters Cofactor Regulation.

    Science.gov (United States)

    Peng, Hu; Zhuang, Yugang; Harbeck, Mark C; He, Donghong; Xie, Lishi; Chen, Weiguo

    2015-01-01

    Endothelial nitric oxide synthase (eNOS) is responsible for maintaining systemic blood pressure, vascular remodeling and angiogenesis. In addition to producing NO, eNOS can also generate superoxide (O2-.) in the absence of the cofactor tetrahydrobiopterin (BH4). Previous studies have shown that bovine eNOS serine 1179 (Serine 1177/human) phosphorylation critically modulates NO synthesis. However, the effect of serine 1179 phosphorylation on eNOS superoxide generation is unknown. Here, we used the phosphomimetic form of eNOS (S1179D) to determine the effect of S1179 phosphorylation on superoxide generating activity, and its sensitivity to regulation by BH4, Ca2+, and calmodulin (CAM). S1179D eNOS exhibited significantly increased superoxide generating activity and NADPH consumption compared to wild-type eNOS (WT eNOS). The superoxide generating activities of S1179D eNOS and WT eNOS did not differ significantly in their sensitivity to regulation by either Ca2+ or CaM. The sensitivity of the superoxide generating activity of S1179D eNOS to inhibition by BH4 was significantly reduced compared to WT eNOS. In eNOS-overexpressing 293 cells, BH4 depletion with 10mM DAHP for 48 hours followed by 50ng/ml VEGF for 30 min to phosphorylate eNOS S1179 increased ROS accumulation compared to DAHP-only treated cells. Meanwhile, MTT assay indicated that overexpression of eNOS in HEK293 cells decreased cellular viability compared to control cells at BH4 depletion condition (Psuperoxide generation: S1179 phosphorylation increases superoxide production while decreasing sensitivity to the inhibitory effect of BH4 on this activity.

  10. Superoxide dismutase overexpression protects against glucocorticoid-induced depressive-like behavioral phenotypes in mice.

    Science.gov (United States)

    Uchihara, Yuki; Tanaka, Ken-ichiro; Asano, Teita; Tamura, Fumiya; Mizushima, Tohru

    2016-01-22

    In the stress response, activation of the hypothalamic-pituitary-adrenal axis, and particularly the release of glucocorticoids, plays a critical role. However, dysregulation of this system and sustained high plasma levels of glucocorticoids can result in depression. Recent studies have suggested the involvement of reactive oxygen species (ROS), such as superoxide anion, in depression. However, direct evidence for a role of ROS in the pathogenesis of this disorder is lacking. In this study, using transgenic mice expressing human Cu/Zn-superoxide dismutase (SOD1), an enzyme that catalyzes the dismutation of superoxide anions, we examined the effect of SOD1 overexpression on depressive-like behavioral phenotypes in mice. Depressive-like behaviors were induced by daily subcutaneous administration of the glucocorticoid corticosterone for 4 weeks, and was monitored with the social interaction test, the sucrose preference test and the forced swim test. These tests revealed that transgenic mice overexpressing SOD1 are more resistant to glucocorticoid-induced depressive-like behavioral disorders than wild-type animals. Furthermore, compared with wild-type mice, transgenic mice showed a reduction in the number of 8-hydroxy-2'-deoxyguanosine (a marker of oxidative stress)-positive cells in the hippocampal CA3 region following corticosterone administration. These results suggest that overexpression of SOD1 protects mice against glucocorticoid-induced depressive-like behaviors by decreasing cellular ROS levels.

  11. [Reliability of electron-transport membranes and the role of oxygen anion-radicals in aging: stochastic modulation of the genetic program].

    Science.gov (United States)

    Kol'tover, V K

    2010-01-01

    All biomolecular constructions and nanorecators are designed to perform preset functions. All of them operate with limited reliability, namely, for each and every device or bionanoreactor normal operation alternates with accidental malfunctions (failures). Timely preventive maintenance replacement (prophylaxis) of functional elements in cells and tissues, the so-called turnover, is the main line of assuring high system reliability of organism as a whole. There is a finite number of special groups of genes (reliability assuring structures, RAS) that perform supervisory functions over the preventive maintenance. In a hierarchic pluricellular organism, RAS are genetic regulatory networks of a special group of cells, like hypothalamic neurons in the suprachiasmatic nucleus of mammals. Of the primary importance is limited reliability of mitochondrial nanoreactors, since the random malfunctions of electron transport chains produce reactive anion-radicals of oxygen (superoxide radical, O2*(-)). With time, O2*(-) radicals initiate accumulation of irreparable damages in RAS. When these damages accumulate up to preset threshold level, a fatal decrease in reliability of RAS occurs. Thus, aging is the stochastic consequence of programmed deficiency in reliability of biomolecular constructions and nanoreactors including the genetically preset limit of the system reliability. This reliability approach provides the realistic explanation of the data on prolongation of life of experimental animals with antioxidants as well as the explanation of similar "hormetic" effects of ionizing radiation in low doses.

  12. On the use of L-012, a luminol-based chemiluminescent probe, for detecting superoxide and identifying inhibitors of NADPH oxidase: a reevaluation.

    Science.gov (United States)

    Zielonka, Jacek; Lambeth, J David; Kalyanaraman, Balaraman

    2013-12-01

    L-012, a luminol-based chemiluminescent (CL) probe, is widely used in vitro and in vivo to detect NADPH oxidase (Nox)-derived superoxide (O2(*-)) and identify Nox inhibitors. Yet understanding of the free radical chemistry of the L-012 probe is still lacking. We report that peroxidase and H2O2 induce superoxide dismutase (SOD)-sensitive, L-012-derived CL in the presence of oxygen. O2(*-) alone does not react with L-012 to emit luminescence. Self-generated O2(*-) during oxidation of L-012 and luminol analogs artifactually induce CL inhibitable by SOD. These aspects make assays based on luminol analogs less than ideal for specific detection and identification of O2(*-) and NOX inhibitors.

  13. Extracellular superoxide production, viability and redox poise in response to desiccation in recalcitrant Castanea sativa seeds.

    Science.gov (United States)

    Roach, Thomas; Beckett, Richard P; Minibayeva, Farida V; Colville, Louise; Whitaker, Claire; Chen, Hongying; Bailly, Christophe; Kranner, Ilse

    2010-01-01

    Reactive oxygen species (ROS) are implicated in seed death following dehydration in desiccation-intolerant 'recalcitrant' seeds. However, it is unknown if and how ROS are produced in the apoplast and if they play a role in stress signalling during desiccation. We studied intracellular damage and extracellular superoxide (O(2)(.-)) production upon desiccation in Castanea sativa seeds, mechanisms of O(2)(.-) production and the effect of exogenously supplied ROS. A transient increase in extracellular O(2)(.-) production by the embryonic axes preceded significant desiccation-induced viability loss. Thereafter, progressively more oxidizing intracellular conditions, as indicated by a significant shift in glutathione half-cell reduction potential, accompanied cell and axis death, coinciding with the disruption of nuclear membranes. Most hydrogen peroxide (H(2)O(2))-dependent O(2)(.-) production was found in a cell wall fraction that contained extracellular peroxidases (ECPOX) with molecular masses of approximately 50 kDa. Cinnamic acid was identified as a potential reductant required for ECPOX-mediated O(2)(.-) production. H(2)O(2), applied exogenously to mimic the transient ROS burst at the onset of desiccation, counteracted viability loss of sub-lethally desiccation-stressed seeds and of excised embryonic axes grown in tissue culture. Hence, extracellular ROS produced by embryonic axes appear to be important signalling components involved in wound response, regeneration and growth.

  14. Potentiometric anion selective sensors

    NARCIS (Netherlands)

    Antonisse, Martijn M.G.; Reinhoudt, David N.

    1999-01-01

    In comparison with selective receptors (and sensors) for cationic species, work on the selective complexation and detection of anions is of more recent date. There are three important components for a sensor, a transducer element, a membrane material that separates the transducer element and the aqu

  15. Hydrophilic property of SiO2-TiO2 overlayer films and TiO2/SiO2 mixing films

    Institute of Scientific and Technical Information of China (English)

    关凯书; 徐宏; 吕宝君

    2004-01-01

    The photo-induced hydrophilicity of SiO2 overlayer on TiO2 films prepared by sol-gel method was investigated by means of soak angle measurement, XPS, UV-VIS and FTIR spectra. The results show that, compared with the TiO2 film without SiO2 overlayer, when the TiO2 film is thoroughly covered by SiO2 overlayer, the hydrophilicity and the sustained effect are enhanced. It is found that the significant growth of the OH group occurs in the surface of SiO2 overlayer. The different mechanism of enhanced hydrophilicity between SiO2 overlayer on TiO2 films and TiO2/SiO2 mixing films was analyzed. The result suggests that the photo-generated electrons created in the interface between TiO2 and SiO2 tend to reduce the Ti(Ⅳ) cation to the Ti(Ⅲ) state, and the photogenerated holes transmit through the SiO2 layer to uppermost surface efficiently. Once the holes go up to the surface, they tend to make the surface hydrophilic. The stable hydrophilicity of SiO2 overlayer which adsorbs more stable OH groups, enhances the sustained effect, i.e. the super-hydrophilic state can be maintained for a long time in dark place.

  16. Decomposition of 3,5-dinitrobenzamide in aqueous solution during UV/H2O2 and UV/TiO2 oxidation processes.

    Science.gov (United States)

    Yan, Yingjie; Liao, Qi-Nan; Ji, Feng; Wang, Wei; Yuan, Shoujun; Hu, Zhen-Hu

    2017-02-01

    3,5-Dinitrobenzamide has been widely used as a feed additive to control coccidiosis in poultry, and part of the added 3,5-dinitrobenzamide is excreted into wastewater and surface water. The removal of 3,5-dinitrobenzamide from wastewater and surface water has not been reported in previous studies. Highly reactive hydroxyl radicals from UV/hydrogen peroxide (H2O2) and UV/titanium dioxide (TiO2) advanced oxidation processes (AOPs) can decompose organic contaminants efficiently. In this study, the decomposition of 3,5-dinitrobenzamide in aqueous solution during UV/H2O2 and UV/TiO2 oxidation processes was investigated. The decomposition of 3,5-dinitrobenzamide fits well with a fluence-based pseudo-first-order kinetics model. The decomposition in both two oxidation processes was affected by solution pH, and was inhibited under alkaline conditions. Inorganic anions such as NO3(-), Cl(-), SO4(2-), HCO3(-), and CO3(2-) inhibited the degradation of 3,5-dinitrobenzamide during the UV/H2O2 and UV/TiO2 oxidation processes. After complete decomposition in both oxidation processes, approximately 50% of 3,5-dinitrobenzamide was decomposed into organic intermediates, and the rest was mineralized to CO2, H2O, and other inorganic anions. Ions such as NH4(+), NO3(-), and NO2(-) were released into aqueous solution during the degradation. The primary decomposition products of 3,5-dinitrobenzamide were identified using time-of-flight mass spectrometry (LCMS-IT-TOF). Based on these products and ions release, a possible decomposition pathway of 3,5-dinitrobenzamide in both UV/H2O2 and UV/TiO2 processes was proposed.

  17. Redox enzyme-mimicking activities of CeO2 nanostructures: Intrinsic influence of exposed facets

    Science.gov (United States)

    Yang, Yushi; Mao, Zhou; Huang, Wenjie; Liu, Lihua; Li, Junli; Li, Jialiang; Wu, Qingzhi

    2016-10-01

    CeO2 nanoparticles (NPs) have been well demonstrated as an antioxidant in protecting against oxidative stress-induced cellular damages and a potential therapeutic agent for various diseases thanks to their redox enzyme-mimicking activities. The Ce3+/Ce4+ ratio and oxygen vacancies on the surface have been considered as the major originations responsible for the redox enzyme-mimicking activities of CeO2 NPs. Herein, CeO2 nanostructures (nanocubes and nanorods) exposed different facets were synthesized via a facile hydrothermal method. The characterizations by X-ray photoelectron spectroscopy, Raman spectroscopy, and UV-Vis spectroscopy show that the Ce3+/Ce4+ ratio and oxygen vacancy content on the surfaces of as-synthesized CeO2 nanostructures are nearly at the same levels. Meanwhile, the enzymatic activity measurements indicate that the redox enzyme-mimicking activities of as-synthesized CeO2 nanostructures are greatly dependent on their exposed facets. CeO2 nanocubes with exposed {100} facets exhibit a higher peroxidase but lower superoxide dismutase activity than those of the CeO2 nanorods with exposed {110} facets. Our results provide new insights into the redox enzyme-mimicking activities of CeO2 nanostructures, as well as the design and synthesis of inorganic nanomaterials-based artificial enzymes.

  18. Hydropropidine: a novel, cell-impermeant fluorogenic probe for detecting extracellular superoxide.

    Science.gov (United States)

    Michalski, Radoslaw; Zielonka, Jacek; Hardy, Micael; Joseph, Joy; Kalyanaraman, Balaraman

    2013-01-01

    Here we report the synthesis and characterization of a membrane-impermeant fluorogenic probe, hydropropidine (HPr(+)), the reduction product of propidium iodide, for detecting extracellular superoxide (O(2)(•-)). HPr(+) is a positively charged water-soluble analog of hydroethidine (HE), a fluorogenic probe commonly used for monitoring intracellular O(2)(•-). We hypothesized that the presence of a highly localized positive charge on the nitrogen atom would impede cellular uptake of HPr(+) and allow for exclusive detection of extracellular O(2)(•-). Our results indicate that O(2)(•-) reacts with HPr(+) (k=1.2×10(4) M(-1) s(-1)) to form exclusively 2-hydroxypropidium (2-OH-Pr(2+)) in cell-free and cell-based systems. This reaction is analogous to the reaction between HE and O(2)(•-) (Zhao et al., Free Radic. Biol. Med.34:1359-1368; 2003). During the course of this investigation, we also reassessed the rate constants for the reactions of O(2)(•-) with HE and its mitochondria targeted analog (Mito-HE or MitoSOX Red) and addressed the discrepancies between the present values and those reported previously by us. Our results indicate that the rate constant between O(2)(•-) and HPr(+) is slightly higher than that of HE and O(2)(•-) and is closer to that of Mito-HE and O(2)(•-). Similar to HE, HPr(+) undergoes oxidation in the presence of various oxidants (peroxynitrite-derived radicals, Fenton's reagent, and ferricytochrome c) forming the corresponding propidium dication (Pr(2+)) and the dimeric products (e.g., Pr(2+)-Pr(2+)). In contrast to HE, there was very little intracellular uptake of HPr(+). We conclude that HPr(+) is a useful probe for detecting O(2)(•-) and other one-electron oxidizing species in an extracellular milieu. Copyright © 2012. Published by Elsevier Inc.

  19. Hyperglycemic switch from mitochondrial nitric oxide to superoxide production in endothelial cells.

    Science.gov (United States)

    Brodsky, Sergey V; Gao, Shujuan; Li, Hong; Goligorsky, Michael S

    2002-11-01

    The accumulated ultrastructural and biochemical evidence is highly suggestive of the existence of mitochondrial nitric oxide (NO) synthase (mtNOS), where local production of NO regulates the electron transport along the respiratory chain. Here, the functional competence of mtNOS in situ in a living cell was examined using an intravital fluorescent NO indicator, 4,5-diaminofluorescein, employing a new procedure for loading it into the mitochondria to demonstrate local NO generation in undisrupted endothelial cells and in isolated mitochondria as well as in human embryonic kidney cells stably expressing endothelial NOS. With the use of this approach, we showed that endothelial cells incubated in the presence of high concentration of D-glucose (but not L-glucose) are characterized by the reduced NO synthetic function of mitochondria despite the unaltered abundance of the enzyme. In parallel, mitochondrial generation of superoxide was augmented in endothelial cells incubated in the presence of a high concentration of D-glucose. Both the NO generation and superoxide production in hyperglycemic environment could be restored to control levels by treating cells with a cell-permeable superoxide dismutase mimetic. In addition, enhanced mitochondrial superoxide production could be suppressed with an inhibitor of NOS in stimulated endothelial cells. In conclusion, the data 1) provide direct evidence of mitochondrial NO production in endothelial cells, 2) demonstrate its suppression and enhanced superoxide generation in hyperglycemic environment, and 3) provide evidence that "uncoupled" mtNOS represents an important source of superoxide anions in endothelial cells incubated in high glucose-containing medium.

  20. AgACTiO2 nanoparticles with microbiocide properties under visible light

    Science.gov (United States)

    Caro, Carlos; Gámez, Francisco; Jesús Sayagues, Maria; Polvillo, Rocio; Royo, Jose Luis

    2015-05-01

    A new nanostructure based on TiO2, activated carbon and silver nanoparticles is synthesized in this work. The optical and morphological characterization of the nanoparticles is performed with well-established physicochemical-techniques. The photocatalytic properties of TiO2 are improved with activated carbon and extended to visible radiation with a silver nanoparticles doping. The synergy of the three materials to enhance biocide activity is successfully demonstrated in vitro in cultures of bacteria and algae and in aquatic controlled environments. This activity is supposed to be due to the augmentation in the superoxide and hydroxyl radicals in the presence of activated charcoal.

  1. The use of superoxide mixtures as air-revitalization chemicals in hyperbaric, self-contained, closed-circuit breathing apparatus

    Science.gov (United States)

    Wood, P. C.; Wydeven, T.

    1985-01-01

    In portable breathing apparatus applications at 1 atm, potassium superoxide (KO2) has exhibited low-utilization efficiency of the available oxygen (O2) and diminished carbon dioxide-(CO2) scrubbing capacity caused by the formation of a fused, hydrated-hydroxide/carbonate product coating on the superoxide granules. In earlier work, it was discovered that granules fabricated from an intimate mixture of KO2 and calcium superoxide, Ca(O2)2, did not exhibit formation of a fused product coating and the utilization efficiency with respect to both O2 release and CO2 absorption was superior to KO2 granules when both types of granules were reacted with humidified CO2 under identified conditions. In the work described here, single pellets of KO2, KO2/Ca(O2), mixtures and commercially available KO2 tables and granules were reacted with a flow of humidified CO2 in helium at 1- and 10-atm total pressure and at an initial temperature of 40 C. In the 1-atm flow tests, the reaction rates and utilization efficiency of the KO2/Ca(O2)2 pellets were markedly superior to the KO2 pellets, tablets, and granules when the samples were reacted under identical conditions. However, at 10 atm, the rates of O2 release and CO2 absorption, as well as the utilization efficiencies of all the superoxide samples, were one-third to one-eighth of the values observed at 1 atm. The decrease in reaction performance at 10 atm compared to that at 1 atm has been attributed principally to the lower bulk diffusivity of the CO2 and H2O reactants in helium at the higher pressure and secondarily to the moderation of the reaction temperature caused by the higher heat capacity of the 10-atm helium.

  2. An improved superoxide-generating nanodevice for oxidative stress studies in cultured cells

    Directory of Open Access Journals (Sweden)

    Minoru Tamura

    2015-06-01

    Full Text Available The effects of reactive oxygen species on cells have attracted great attention from both physiological and pathological aspects. Superoxide (O2− is the primary reactive oxygen species formed in animals. We previously developed an O2−-generating nanodevice consisting of NADPH oxidase 2 (Nox2 and modulated activating factors. However, the device was subsequently found to be unstable in a standard culture medium. Here we improved the device in stability by cross-linking. This new nanodevice, Device II, had a half-life of 3 h at 37 °C in the medium. Device II induced cell death in 80% of HEK293 cells after 24 h of incubation. Superoxide dismutase alone did not diminish the effect of the device, but eliminated the effect when used together with catalase, confirming that the cell death was caused by H2O2 derived from O2−. Flow cytometric analyses revealed that Device II induced caspase-3 activation in HEK293 cells, suggesting that the cell death proceeded largely through apoptosis.

  3. High-Content Imaging Assays for Identifying Compounds that Generate Superoxide and Impair Mitochondrial Membrane Potential in Adherent Eukaryotic Cells.

    Science.gov (United States)

    Billis, Puja; Will, Yvonne; Nadanaciva, Sashi

    2014-02-19

    Reactive oxygen species (ROS) are constantly produced in cells as a result of aerobic metabolism. When there is an excessive production of ROS and the cell's antioxidant defenses are overwhelmed, oxidative stress occurs. The superoxide anion is a type of ROS that is produced primarily in mitochondria but is also generated in other regions of the cell including peroxisomes, endoplasmic reticulum, plasma membrane, and cytosol. Here, a high-content imaging assay using the dye dihydroethidium is described for identifying compounds that generate superoxide in eukaryotic cells. A high-content imaging assay using the fluorescent dye tetramethylrhodamine methyl ester is also described to identify compounds that impair mitochondrial membrane potential in eukaryotic cells. The purpose of performing both assays is to identify compounds that (1) generate superoxide at lower concentrations than they impair mitochondrial membrane potential, (2) impair mitochondrial membrane potential at lower concentrations than they generate superoxide, (3) generate superoxide and impair mitochondrial function at similar concentrations, and (4) do not generate superoxide or impair mitochondrial membrane potential during the duration of the assays.

  4. Effect of Korea red ginseng on cerebral blood flow and superoxide production

    Institute of Scientific and Technical Information of China (English)

    Cuk Seong KIM; Jin Bong PARK; Kwang-Jin KIM; Seok Jong CHANG; Sung-Woo RYOO; Byeong Hwa JEON

    2002-01-01

    AIM: To investigate the effects of Korea red ginseng (KRG) on the cerebral perfusion rate in the rats and the generation of superoxide anion in the endothelial cells. METHODS: The cerebral perfusion rate was measured using laser-doppler flowmetry before and after the administration of crude saponin (CS) and saponin-free fraction (SFF) of KRG in the anesthetized rats. The superoxide generation was measured by the method based on lucigeninenhanced chemiluminescence in the cultured endothelial cells. RESULTS: The relative cerebral perfusion rate (rCBF) was significantly increased by the intraperitoneal injection of CS (100 mg/kg) in the rats, but SFF had no effect on the rCBF. Chronic treatment with CS for 7 d significantly inhibited the decrease of forebrain cerebral blood flow induced by clamping both carotid arteries in the rats. Furthermore, CS (0.1 g/L) significantly suppressed NADPH-induced superoxide generation in the human umbilical vein endothelial cells (P<0.01).CONCLUSION: The present study demonstrated that crude saponin fraction of KRG enhanced cerebral blood flow in rats. Furthermore, crude saponin fraction of KRG abrogated the NADPH-driven superoxide generation in endothelial cells.

  5. Alleviation of drought stress by mycorrhizas is related to increased root H2O2 efflux in trifoliate orange

    Science.gov (United States)

    Huang, Yong-Ming; Zou, Ying-Ning; Wu, Qiang-Sheng

    2017-01-01

    The Non-invasive Micro-test Technique (NMT) is used to measure dynamic changes of specific ions/molecules non-invasively, but information about hydrogen peroxide (H2O2) fluxes in different classes of roots by mycorrhiza is scarce in terms of NMT. Effects of Funneliformis mosseae on plant growth, H2O2, superoxide radical (O2·−), malondialdehyde (MDA) concentrations, and H2O2 fluxes in the taproot (TR) and lateral roots (LRs) of trifoliate orange seedlings under well-watered (WW) and drought stress (DS) conditions were studied. DS strongly inhibited mycorrhizal colonization in the TR and LRs, whereas mycorrhizal inoculation significantly promoted plant growth and biomass production. H2O2, O2·−, and MDA concentrations in leaves and roots were dramatically lower in mycorrhizal seedlings than in non-mycorrhizal seedlings under DS. Compared with non-mycorrhizal seedlings, mycorrhizal seedlings had relatively higher net root H2O2 effluxes in the TR and LRs especially under WW, as well as significantly higher total root H2O2 effluxes in the TR and LRs under WW and DS. Total root H2O2 effluxes were significantly positively correlated with root colonization but negatively with root H2O2 and MDA concentrations. It suggested that mycorrhizas induces more H2O2 effluxes of the TR and LRs, thus, alleviating oxidative damage of DS in the host plant. PMID:28176859

  6. Degradability of Treated Ethion Insecticide by TiO2 Photocatalysis.

    Science.gov (United States)

    Hassarangsee, Siriporn; Uthaibutra, Jamnong; Nomura, Nakao; Whangchai, Kanda

    2015-01-01

    Ethion, an insecticide, is widely used with fruit and vegetable crops. This research studied the reduction and oxidative degradation of standard ethion by TiO2 photocatalysis. A standard ethion solution (1 mg L(-1)) was treated with different concentrations of TiO2 powder (5, 10, 20, 40 and 60 mg mL(-1)) for 0, 15, 30, 45 and 60 min. The amount of ethion residue was detected by gas chromatography with flame photometric detection (GC-FPD) and the concentration of anions produced as major degradation products was determined by Ion Chromatography (IC). The TiO2 photocatalysis efficiently reduced ethion concentrations, with the highest degradation rate occurring within the first 15 min of reaction. The reaction produced sulphate and phosphate anions. The TiO2photocatalysis reduced 1 mg L(-1) ethion to 0.18 mg L(-1) when treated with 60 mg mL(-1) TiO2 powder for 60 min. The lethal concentration (LC50) of standard ethion was also estimated and compared to the treated ethion. All treatments, especially 60 mg mL(-1) TiO2 powder, markedly detoxified ethion, as tested with brine shrimp (Artemia salina L.), with an LC50 value of 765.8 mg mL(-1), compared to the control of 1.01 mg mL(-1).

  7. Photocatalytic decomposition of gaseous formaldehyde using TiO2, SiO2−TiO2 and Pt−TiO2

    OpenAIRE

    Byung-Yong Lee; Sung-Wook Kim; Sung-Chul Lee; Hyun-Ho Lee; Suk-Jin Choung

    2003-01-01

    In this study, in order to improve the photocatalytic decomposition activities of formaldehyde, TiO2 catalyst modified with SiO2 substitution and metal (Pt, Cu and Fe) impregnation, were tested. In case of TiO2 substituted by SiO2, the optimal catalytic activity was found at the mole ration of 2 : 8. Among the metal impregnated TiO2, the Pt impregnated TiO2 showed the best activity even better than that of P-25 which is widely used in commercial application. However, Cu and Fe impregnated TiO...

  8. Characterization and improved solar light activity of vanadium doped TiO2/diatomite hybrid catalysts.

    Science.gov (United States)

    Wang, Bin; Zhang, Guangxin; Leng, Xue; Sun, Zhiming; Zheng, Shuilin

    2015-03-21

    V-doped TiO2/diatomite composite photocatalysts with different vanadium concentrations were synthesized by a modified sol-gel method. The diatomite was responsible for the well dispersion of TiO2 nanoparticles on the matrix and consequently inhibited the agglomeration. V-TiO2/diatomite hybrids showed red shift in TiO2 absorption edge with enhanced absorption intensity. Most importantly, the dopant energy levels were formed in the TiO2 bandgap due to V(4+) ions substituted to Ti(4+) sites. The 0.5% V-TiO2/diatomite photocatalyst displayed narrower bandgap (2.95 eV) compared to undoped sample (3.13 eV) and other doped samples (3.05 eV) with higher doping concentration. The photocatalytic activities of V doped TiO2/diatomite samples for the degradation of Rhodamine B under stimulated solar light illumination were significantly improved compared with the undoped sample. In our case, V(4+) ions incorporated in TiO2 lattice were responsible for increased visible-light absorption and electron transfer to oxygen molecules adsorbed on the surface of TiO2 to produce superoxide radicals ˙O2(-), while V(5+) species presented on the surface of TiO2 particles in the form of V2O5 contributed to e(-)-h(+) separation. In addition, due to the combination of diatomite as support, this hybrid photocatalyst could be separated from solution quickly by natural settlement and exhibited good reusability.

  9. Simulated-sunlight-activated photocatalysis of Methylene Blue using cerium-doped SiO2/TiO2 nanostructured fibers

    Institute of Scientific and Technical Information of China (English)

    Yu Liu; Hongbing Yu; Zhenning Lv; Sihui Zhan; Jiangyao Yang; Xinhong Peng; Yixuan Ren; Xiaoyan Wu

    2012-01-01

    Cerium-doped SiO2/TiO2 nanostructured fibers were fabricated by electrospinning technology.The prepared fibers were characterized by thermogravimetric analysis (TGA),scanning electron microscopy (SEM),X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR).Using the fibers as catalysts,photocatalytic degradation of Methylene Blue (MB) aqueous solution was carried out under simulated sunlight.The 0.2% Ce doping proved to be the optimal concentration for the doping of TiO2/SiO2,compared to other Ce-doped molar concentrations.The 0.2% Ce-doped SiO2/TiO2 fibers exhibited higher photocatalytic activity than industrial Degussa P25 and the samples doped with only Ce or SiO2.The reasons for improving the photocatalytic activity were also discussed.Several operational parameters were studied,which showed that the photocatalytic efficiency of MB was influenced by parameters such as the initial dye concentration,the initial pH,inorganic anions,and so on.In addition,the influences of an electron acceptor and a radical scavenger suggested that OH was the dominant photooxidant during the photocatalytic process.The reuse evaluation of the fibers indicated that their photocatalytic activity had good stability.

  10. Process for the preparation of calcium superoxide

    Science.gov (United States)

    Ballou, E. V.; Wood, P. C.; Wydeven, T. J.; Spitze, L. A. (Inventor)

    1978-01-01

    Calcium superoxide is prepared in high yields by spreading a quantity of calcium peroxide diperoxyhydrate on the surface of a container, positioning said container in a vacuum chamber on a support structure through which a coolant fluid can be circulated, partially evacuating said vacuum chamber, allowing the temperature of the diperoxyhydrate to reach the range of about 0 to about 40 C; maintaining the temperature selected for a period of time sufficient to complete the disproproriation of the diperoxyhydrate to calcium superoxide, calcium hydroxide, oxygen, and water; constantly and systematically removing the water as it is formed by sweeping the reacting material with a current of dry inert gas and/or by condensation of said water on a cold surface; backfilling the chamber with a dry inert gas; and finally, recovering the calcium superoxide produced.

  11. Differentiating between apparent and actual rates of H2O2 metabolism by isolated rat muscle mitochondria to test a simple model of mitochondria as regulators of H2O2 concentration

    Directory of Open Access Journals (Sweden)

    Jason R. Treberg

    2015-08-01

    Full Text Available Mitochondria are often regarded as a major source of reactive oxygen species (ROS in animal cells, with H2O2 being the predominant ROS released from mitochondria; however, it has been recently demonstrated that energized brain mitochondria may act as stabilizers of H2O2 concentration (Starkov et al. [1] based on the balance between production and the consumption of H2O2, the later of which is a function of [H2O2] and follows first order kinetics. Here we test the hypothesis that isolated skeletal muscle mitochondria, from the rat, are able to modulate [H2O2] based upon the interaction between the production of ROS, as superoxide/H2O2, and the H2O2 decomposition capacity. The compartmentalization of detection systems for H2O2 and the intramitochondrial metabolism of H2O2 leads to spacial separation between these two components of the assay system. This results in an underestimation of rates when relying solely on extramitochondrial H2O2 detection. We find that differentiating between these apparent rates found when using extramitochondrial H2O2 detection and the actual rates of metabolism is important to determining the rate constant for H2O2 consumption by mitochondria in kinetic experiments. Using the high rate of ROS production by mitochondria respiring on succinate, we demonstrate that net H2O2 metabolism by mitochondria can approach a stable steady-state of extramitochondrial [H2O2]. Importantly, the rate constant determined by extrapolation of kinetic experiments is similar to the rate constant determined as the [H2O2] approaches a steady state.

  12. Engineering the TiO2 -graphene interface to enhance photocatalytic H2 production.

    Science.gov (United States)

    Liu, Lichen; Liu, Zhe; Liu, Annai; Gu, Xianrui; Ge, Chengyan; Gao, Fei; Dong, Lin

    2014-02-01

    In this work, TiO2 -graphene nanocomposites are synthesized with tunable TiO2 crystal facets ({100}, {101}, and {001} facets) through an anion-assisted method. These three TiO2 -graphene nanocomposites have similar particle sizes and surface areas; the only difference between them is the crystal facet exposed in TiO2 nanocrystals. UV/Vis spectra show that band structures of TiO2 nanocrystals and TiO2 -graphene nanocomposites are dependent on the crystal facets. Time-resolved photoluminescence spectra suggest that the charge-transfer rate between {100} facets and graphene is approximately 1.4 times of that between {001} facets and graphene. Photoelectrochemical measurements also confirm that the charge-separation efficiency between TiO2 and graphene is greatly dependent on the crystal facets. X-ray photoelectron spectroscopy reveals that Ti-C bonds are formed between {100} facets and graphene, while {101} facets and {001} facets are connected with graphene mainly through Ti-O-C bonds. With Ti-C bonds between TiO2 and graphene, TiO2 -100-G shows the fastest charge-transfer rate, leading to higher activity in photocatalytic H2 production from methanol solution. TiO2 -101-G with more reductive electrons and medium interfacial charge-transfer rate also shows good H2 evolution rate. As a result of its disadvantageous electronic structure and interfacial connections, TiO2 -001-G shows the lowest H2 evolution rate. These results suggest that engineering the structures of the TiO2 -graphene interface can be an effective strategy to achieve excellent photocatalytic performances.

  13. Effect of alcohol exposure on hepatic superoxide generation and hepcidin expression

    Institute of Scientific and Technical Information of China (English)

    Duygu; Dee; Harrison-Findik; Sizhao; Lu; Emily; M; Zmijewski; Jocelyn; Jones; Matthew; C; Zimmerman

    2013-01-01

    AIM: To understand the role of mitochondrial-produced superoxide(O 2 ?) in the regulation of iron-regulatory hormone, hepcidin by alcohol in the liver. METHODS: For alcohol experiments, manganese superoxide dismutase knockout mice heterozygous for Sod2 gene expression(Sod2 +/) and age-matched littermate control mice(LMC), expressing Sod2 gene on both alleles, were exposed to either 10%(w/v) ethanol in the drinking water or plain water(control) for 7 d. Total cellular O 2 ? levels in hepatocytes isolated from the livers of mice were measured by electron paramagnetic resonance spectroscopy. The mitochondrial-targeted, O 2 ?-sensitive fluorogenic probe, MitoSOX Red and flow cytometry were utilized to measure O 2 ? in mitochondria. Gene and protein expression were determined by Taqman Real-time quantitative PCR and Western blotting, respectively. RESULTS: Sod2 +/- mice expressed 40% less MnSOD protein(SOD2) in hepatocytes compared to LMC mice. The deletion of Sod2 allele did not alter the basal expression level of hepcidin in the liver. 10% ethanol exposure for 1 wk inhibited hepatic hepcidin mRNA expression three-fold both in Sod2 +/ and LMC mice. O 2 ? levels in hepatocytes of untreated Sod2 +/ mice were three-fold higher than in untreated LMC mice, as observed by electron paramagnetic resonance spectroscopy. O 2 ? levels in mitochondria of Sod2 +/ mice were four-fold higher than in mitochondria of untreated LMC mice, as measured by MitoSOX Red fluorescence and flow cytometry. Alcohol induced a two-fold higher increase in O 2 ? levels in hepatocytes of LMC mice than in Sod2 +/ mice compared to respective untreated counterparts. In contrast, 1 wk alcohol exposure did not alter mitochondrial O 2 ? levels in both Sod2 +/- and control mice. CONCLUSION: Mitochondrial O2 ? is not involved in the inhibition of liver hepcidin transcription and thereby regulation of iron metabolism by alcohol. These findings also suggest that short-term alcohol consumption significantly

  14. UV/TiO2 photocatalytic degradation of xanthene dyes.

    Science.gov (United States)

    Pereira, Luciana; Pereira, Raquel; Oliveira, Catarina S; Apostol, Laura; Gavrilescu, Mariana; Pons, Marie-Noëlle; Zahraa, Orfan; Alves, Maria Madalena

    2013-01-01

    UV/titanium dioxide (TiO(2)) degradation of two xanthene dyes, erythrosine B (Ery) and eosin Y (Eos), was studied in a photocatalytic reactor. Photocatalysis was able to degrade 98% of Ery and 73% of Eos and led to 65% of chemical oxygen demand removal. Experiments in buffered solutions at different initial pH values reveal the pH dependence of the process, with better results obtained under acidic conditions due to the electrostatic attraction caused by the opposite charges of TiO(2) (positive) and of anionic dyes (negative). Batch activity tests under methanogenic conditions showed the high toxicity exerted by the dyes even at low concentrations (~85% with initial concentration of 0.3 mmol L(-1)), but the end products of photocatalytic treatment were much less toxic toward methanogenic bacteria, as detoxification of 85 ± 5% for Eos and 64 ± 7% for Ery were obtained. In contrast, the dyes had no inhibitory effect on the biogenic-carbon biodegradation activity of aerobic biomass, obtained by respirometry. The results demonstrate that photocatalysis combining UV/TiO(2) as a pretreatment followed by an anaerobic biological process may be promising for the treatment of wastewaters produced by many industries.

  15. A new method that investigates superoxide versus respiration in vitro using bioluminescence and Sepharose-bound adenosine derivatives

    Energy Technology Data Exchange (ETDEWEB)

    Lippman, R.D.

    1982-06-01

    In vitro reactions between superoxide and phosphate derivatives of adenosine yielded quantitative amounts of stable ozonide-products. ADP-ozonide was formed in an optimized in vitro synthesis from ADP + O-(2) and affected by inhibitors and uncouplers in a similar manner to in vivo, oxidative-phosphorylation results. ADP-ozonide was further reacted with phosphoric acid to form ATP. Superoxide and ADP-ozonide may be important carrier-intermediates between respiration's electron-transport chain and nodule ATP formation in vivo.

  16. Partial oxidation of methanol catalyzed with Au/TiO2, Au/ZrO2 and Au/ZrO2-TiO2 catalysts

    Science.gov (United States)

    Hernández-Ramírez, E.; Wang, J. A.; Chen, L. F.; Valenzuela, M. A.; Dalai, A. K.

    2017-03-01

    Mesoporous TiO2, ZrO2 and ZrO2-TiO2 mixed oxides were synthesized by the sol-gel method and the Au/TiO2, Au/ZrO2 and Au/ZrO2-TiO2 catalysts were prepared by deposition-precipitation method using urea solution as a precipitating agent. These materials were characterized by UV-vis spectroscopy, X-ray diffraction (XRD), N2 adsorption-desorption isotherms, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and in situ FTIR-pyridine (FTIR-Py) adsorption. XRD patterns of the samples confirmed the formation of ZrTiO4 phase in the ZrO2-TiO2 mixed oxides. TEM micrographs showed that nanosized gold particles on the catalyst had an average diameter smaller than 5 nm. Metallic gold (Au0) and oxidized Au species (Aunδ+) on the surface of the catalysts were evidenced by UV-vis and XPS characterization. In the partial oxidation of methanol (POM) reaction, among the six catalysts, the high metallic Au0/Au+ ratio and low surface acidity in the Au/ZrO2 catalysts are chiefly responsible for the highest hydrogen production rate in the whole temperature range between 210 and 300 °C. Methanol decomposition as secondary reaction was favored on TiO2-based catalysts at higher temperature, producing a large amount of CO. Formation of ZrO2-TiO2 solid solution resulted in generation of both Brønsted and Lewis acid sites; as a result, dehydrogenation and oxidative dehydrogenation of methanol was allowed over Au/ZrO2-TiO2 catalysts.

  17. Neural stem cells genetically modified to overexpress cu/zn-superoxide dismutase enhance amelioration of ischemic stroke in mice.

    Science.gov (United States)

    Sakata, Hiroyuki; Niizuma, Kuniyasu; Wakai, Takuma; Narasimhan, Purnima; Maier, Carolina M; Chan, Pak H

    2012-09-01

    The harsh host brain microenvironment caused by production of reactive oxygen species after ischemic reperfusion injury offers a significant challenge to survival of transplanted neural stem cells (NSCs) after ischemic stroke. Copper/zinc-superoxide dismutase (SOD1) is a specific antioxidant enzyme that counteracts superoxide anions. We have investigated whether genetic manipulation to overexpress SOD1 enhances survival of grafted stem cells and accelerates amelioration of ischemic stroke. NSCs genetically modified to overexpress or downexpress SOD1 were administered intracerebrally 2 days after transient middle cerebral artery occlusion. Histological and behavioral tests were examined from Days 0 to 28 after stroke. Overexpression of SOD1 suppressed production of superoxide anions after ischemic reperfusion injury and reduced NSC death after transplantation. In contrast, downexpression of SOD1 promoted superoxide generation and increased oxidative stress-mediated NSC death. Transplantation of SOD1-overexpressing NSCs enhanced angiogenesis in the ischemic border zone through upregulation of vascular endothelial growth factor. Moreover, grafted SOD1-overexpressing NSCs reduced infarct size and improved behavioral performance compared with NSCs that were not genetically modified. Our findings reveal a strong involvement of SOD1 expression in NSC survival after ischemic reperfusion injury. We propose that conferring antioxidant properties on NSCs by genetic manipulation of SOD1 is a potential approach for enhancing the effectiveness of cell transplantation therapy in ischemic stroke.

  18. Microsomal superoxide anion production and NADPH-oxidation in a series of 22 aziridinylbenzoquinones

    NARCIS (Netherlands)

    Prins, Bram; Koster, Andries Sj.; Verboom, Willem; Reinhoudt, David N.

    1989-01-01

    Several 2,5-bis(1-aziridinyl)-1,4-benzoquinones (BABQs) can be activated to alkylating species by reduction of the quinone moiety. On the other hand, cytotoxicity of these compounds can be induced by redox cycling. A series of BABQs and their methylated analogues (BMABQs) with different substituents

  19. Effect of beta2-adrenergic agonists on eosinophil adhesion, superoxide anion generation, and degranulation

    Directory of Open Access Journals (Sweden)

    Toru Noguchi

    2015-09-01

    Conclusions: These findings suggest that formoterol, but not salbutamol, suppresses eosinophil functions enhanced by IL-5, LTD4, or IP-10. As these factors are involved in the development of asthma exacerbation, our results strongly support the hypothesis that administration of formoterol is a novel strategy for treating asthma exacerbation.

  20. Study on Properties of Composite Oxides TiO2/SiO2

    Institute of Scientific and Technical Information of China (English)

    ZHOUYasong; JIANGGuowei

    2002-01-01

    The nanometer particles of TiO2 and TiO2/SiO2 oxides were prepared by sol-gel and supercritical fluid drying method.The properties of TiO2 and TiO2/SiO2 were characterized by means of BET(Brunner-Emmett-Teller method), TEM(transmission electron microscopy), SEM(Scanning electron microscopy), XRD(X-ray differaction) and FTIR(Fourier transform-infrared) techniques.The effects of different preparation route,prehydrolysis and non-prehydrolysis,on the properties of TiO2/SiO2 oxide were also examined.Experimental results show that the termal stability of pure TiO2 is improved greatly when it is mixed with SiO2 in nanometer level.The composite TiO2/SiO2 oxides form Ti-O-Si chemical bonds,which creates new Broensted acidity stes.The acidity character is related to TiO2/SiO2 chemical composition and preparation methods.The acidity of TiO2/SiO2 oxides by prehydrolysis is greater than that of by non-prehydrolysis.Ti atom is rich on the surface of TiO2/SiO2.

  1. Differential effects of superoxide and hydrogen peroxide on myogenic signaling, membrane potential, and contractions of mouse renal afferent arterioles.

    Science.gov (United States)

    Li, Lingli; Lai, En Yin; Wellstein, Anton; Welch, William J; Wilcox, Christopher S

    2016-06-01

    Myogenic contraction is the principal component of renal autoregulation that protects the kidney from hypertensive barotrauma. Contractions are initiated by a rise in perfusion pressure that signals a reduction in membrane potential (Em) of vascular smooth muscle cells to activate voltage-operated Ca(2+) channels. Since ROS have variable effects on myogenic tone, we investigated the hypothesis that superoxide (O2 (·-)) and H2O2 differentially impact myogenic contractions. The myogenic contractions of mouse isolated and perfused single afferent arterioles were assessed from changes in luminal diameter with increasing perfusion pressure (40-80 mmHg). O2 (·-), H2O2, and Em were assessed by fluorescence microscopy during incubation with paraquat to increase O2 (·-) or with H2O2 Paraquat enhanced O2 (·-) generation and myogenic contractions (-42 ± 4% vs. -19 ± 4%, P contractions (-10 ± 1% vs. -19 ± 2%, P contractions with paraquat without preventing the reduction in Em Myogenic contractions were independent of the endothelium and largely independent of nitric oxide. We conclude that O2 (·-) and H2O2 activate different signaling pathways in vascular smooth muscle cells linked to discreet membrane channels with opposite effects on Em and voltage-operated Ca(2+) channels and therefore have opposite effects on myogenic contractions.

  2. Effects of synthesis methods on catalytic activities of CoOx-TiO2 for low-temperature NH3-SCR of NO.

    Science.gov (United States)

    Zhu, Li; Zeng, Yiqing; Zhang, Shule; Deng, Jinli; Zhong, Qin

    2017-04-01

    A series of cobalt doped TiO2 (Co-TiO2) and CoOx loaded TiO2 (Co/TiO2) catalysts prepared by sol-gel and impregnation methods respectively were investigated on selective catalytic reduction with NH3 (NH3-SCR) of NO. It was found that Co-TiO2 catalyst showed more preferable catalytic activity at low temperature range. From characterization results of XRD, TEM, Raman and FT-IR, Co species were proved to be doped into TiO2 lattice by replaced Ti atoms. After being characterized and analyzed by NH3-TPD, PL, XPS, EPR and DRIFTS, it was found that the better NH3-SCR activities of Co-TiO2 catalysts, compared with Co/TiO2 catalyst, were ascribed to the formation of more oxygen vacancies which further promoted the production of more superoxide ions (O2(-)). The superoxide ions were crucial for the formation of low temperature SCR reaction intermediates (NO3(-)) by reacting with adsorbed NO molecule. Therefore, these aspects were responsible for the higher low temperature NH3-SCR activity of Co-TiO2 catalysts.

  3. Tetrapotassium cis-dioxido-trans-bis(sulfato-kappa O)sulfato(kappa O-2,O ')molybdate(VI)

    DEFF Research Database (Denmark)

    Schäffer, Susan Jeanne Cline; Berg, Rolf W.

    2008-01-01

    The title compound, K-4[(MoO2)-O-VI(SO4)(3)], was precipitated from a melt of molybdenum(VI) oxide and potassium sulfate in potassium disulfate. The compound contains monomeric [(MoO2)-O-VI(SO4)(3)](4-) anions, with the Mo-VI atom, both oxide ligands, and the S atom and both ligating O atoms...

  4. Manganese superoxide dismutase and breast cancer recurrence

    DEFF Research Database (Denmark)

    Cronin-Fenton, Deirdre P; Christensen, Mariann; Lash, Timothy L

    2014-01-01

    BACKGROUND: Manganese superoxide dismutase (MnSOD) inhibits oxidative damage and cancer therapy effectiveness. A polymorphism in its encoding gene (SOD2: Val16Ala rs4880) may confer poorer breast cancer survival, but data are inconsistent. We examined the association of SOD2 genotype and breast...

  5. Calorimetric Study of Thermal Denaturation of Superoxide Dismutase

    Institute of Scientific and Technical Information of China (English)

    王邦宁; 谈夫

    1994-01-01

    The thermal denaturation of superoxide dismutase (SOD) from bovine erythrocytes was studied at various pH values of different buffers and at various concentrations of solutions of two neutral salts by differential scanning calorimetry. The experiments performed indicate that the PIPES is a buffer non-coordinating with the SOD, and that the binding of the anions studied influences more or less the thermal denaturation of SOD, but the effect on the oxidation form of SOD is more apparent. A new conformer of SOD with lower thermostability was discovered by the experiments performed in different buffers at certain pH values higher than the isoelectric point of SOD, or at higher concentrations of neutral salt solutions. The new conformer may be converted irreversibly into the usual conformer with high thermostability during heating. Based on the thermodynamic parameters obtained in distilled water and by thermodynamic analysis using the Ooi’s model, it is revealed that the large enthalpy △Hdc contributed by

  6. Enhanced Oxidative Stress and Physiological Damage in Daphnia magna by Copper in the Presence of Nano-TiO2

    Directory of Open Access Journals (Sweden)

    W. H. Fan

    2012-01-01

    Full Text Available This study examines the potential hazard of an individual nanomaterial on the Cu biotoxicity to aquatic organisms. Daphnia magna in the absence or presence of nano-TiO2 was exposed to Cu. Maintaining nano-TiO2 at a safe concentration cannot eliminate its potential hazard. The biomarkers superoxide dismutase, catalase, and Na+/K+-ATPase in D. magna were measured. Cu in the presence of nano-TiO2 induced higher levels of oxidative stress and physiological damage because of the sorption of Cu. Nano-TiO2 also caused Na+/K+-ATPase inhibition possibly by impeding the Na+/K+ transfer channel. The correlations among the biomarkers, mortality, and accumulation further showed that the overloading reactive oxygen species generation caused by nano-TiO2 contributed to deeper oxidative stress and physiological regulation, thereby causing greater toxic injury.

  7. Determination of common anions in oxalate by ion chromatography coupled with UV photolysis pretreatment

    Institute of Scientific and Technical Information of China (English)

    Sheng Lin Cao; Ming Li Ye; Wei De Lv; Guang Wen Pan; Ting Ting Zhang; Zhong Yang Hu; Li Na Liang; Yan Zhu

    2012-01-01

    A new and simple method was developed to determine anions in oxalate of analytical reagent grade.After UV photolysis with optimal 1% H2O2 in 10,000 mg/L oxalate in the fabricated photoreactor,sample was directly injected into IC system.Satisfactory linearity,detections limits,good repeatability and spiked recovery were obtained.The method was successfully applied to determine anions in two commercial oxalate samples.

  8. Resonant spectra of quadrupolar anions

    CERN Document Server

    Fossez, K; Nazarewicz, W; Michel, N; Garrett, W R; Płoszajczak, M

    2016-01-01

    In quadrupole-bound anions, an extra electron is attached at a sufficiently large quadrupole moment of a neutral molecule, which is lacking a permanent dipole moment. The nature of the bound states and low-lying resonances of such anions is of interest for understanding the threshold behavior of open quantum systems in general. In this work, we investigate the properties of quadrupolar anions as extreme halo systems, the formation of rotational bands, and the transition from a subcritical to supercritical electric quadrupole moment. We solve the electron-plus-molecule problem using a non-adiabatic coupled-channel formalism by employing the Berggren ensemble, which explicitly contains bound states, narrow resonances, and the scattering continuum. We demonstrate that binding energies and radii of quadrupolar anions strictly follow the scaling laws for two-body halo systems. Contrary to the case of dipolar anions, ground-state band of quadrupolar anions smoothly extend into the continuum, and many rotational ban...

  9. Production of superoxide from photosystem II-light harvesting complex II supercomplex in STN8 kinase knock-out rice mutants under photoinhibitory illumination.

    Science.gov (United States)

    Poudyal, Roshan Sharma; Nath, Krishna; Zulfugarov, Ismayil S; Lee, Choon-Hwan

    2016-09-01

    When phosphorylation of Photosystem (PS) II core proteins is blocked in STN8 knock-out mutants of rice (Oryza sativa) under photoinhibitory illumination, the mobilization of PSII supercomplex is prevented. We have previously proposed that more superoxide (O2(-)) is produced from PSII in the mutant (Nath et al., 2013, Plant J. 76, 675-686). Here, we clarify the type and site for the generation of reactive oxygen species (ROS). Using both histochemical and fluorescence probes, we observed that, compared with wild-type (WT) leaves, levels of ROS, including O2(-) and hydrogen peroxide (H2O2), were increased when leaves from mutant plants were illuminated with excess light. However, singlet oxygen production was not enhanced under such conditions. When superoxide dismutase was inhibited, O2(-) production was increased, indicating that it is the initial event prior to H2O2 production. In thylakoids isolated from WT leaves, kinase was active in the presence of ATP, and spectrophotometric analysis of nitrobluetetrazolium absorbance for O2(-) confirmed that PSII-driven superoxide production was greater in the mutant thylakoids than in the WT. This contrast in levels of PSII-driven superoxide production between the mutants and the WT plants was confirmed by conducting protein oxidation assays of PSII particles from osstn8 leaves under strong illumination. Those assays also demonstrated that PSII-LHCII supercomplex proteins were oxidized more in the mutant, thereby implying that PSII particles incur greater damage even though D1 degradation during PSII-supercomplex mobilization is partially blocked in the mutant. These results suggest that O2(-) is the major form of ROS produced in the mutant, and that the damaged PSII in the supercomplex is the primary source of O2(-).

  10. Interaction of electron leak and proton leak in respiratory chain of mitochondria——Proton leak induced by superoxide from an electron leak pathway of univalent reduction of oxygen

    Institute of Scientific and Technical Information of China (English)

    刘树森; 焦选茂; 王孝铭; 张力

    1996-01-01

    By incubating the isolated rat myocardial mitochondria with xanthine-xanthine oxidase, anexogenous superoxide (O2) generating system, and by ischemia-reperfusion procedure of isolated rat heart as an endogenous O2 generating system, it was found that both sources of O2 showed the same injurious effects on mitochondrial function resulting in (i) increasing proton leak rate, lowering proton pumping activity and Ht/2e ratio of respiratory chain, and (ii) decreasing transmembrane potential of energized mitochondria] inner membrane by succinate oxidation. The injurious effects of O2 on these mitochondrial bioenergitical parameters mentioned above exhibited a dosage- or reaction time-dependent mode. (X has no effects on the electron transfer activity and transmembrane potential of nonenergized mitochondria. Being a superoxide scavenger, 3, 4-dihydroxylphenyl lactate showed obvious protection effects against damage of both exogenous superoxide sources from xanthine-xanthine oxidase system and endogenous Or sou

  11. Adsorption of O2, SO2, and SO3 on nickel oxide. Mechanism for sulfate formation

    Science.gov (United States)

    Mehandru, S. P.; Anderson, A. B.

    1985-01-01

    Calculations based on the atom superposition and electron delocalization molecular orbital (ASED-MO) technique suggest that O2 will adsorb perferentially end-on at an angle 45 deg from normal on a nickel cation site on the (100) surface of NiO. SO2 adsorption is also stronger on the nickel site; SO2 bonds through the sulfur atom is a plane perpendicular to the surface. Adsorption energies for SO3 on the nickel and oxygen sites are comparable in the perferred orientation in which the SO3 plane is parallel to the surface. On activation, SO3 adsorbed to an O2(-) site forms a trigonal pyramidal SO4 species which yields, with a low barrier, a tetrahedral sulfate anion. Subsequently the anion reorients on the surface. Possibilities for alternative mechanisms which require the formation of Ni3(+) or O2(-) are discussed. NiSO4 thus formed leads to the corrosion of Ni at high temperatures in the SO2+O2/SO3 The SO2+O2/SO3 atmosphere, as discussed in the experimental literature.

  12. Species and Organ Diversity in the Effects of Hydrogen Peroxide on Superoxide Dismutase Activity In Vitro

    Institute of Scientific and Technical Information of China (English)

    Hong-Yan Cheng; Song-Quan Song

    2006-01-01

    Superoxide dismutase (SOD) is ubiquitous in aerobic organisms and constitutes the first link in the enzyme scavenging system of reactive oxygen species. In the present study, species and organ diversity of SOD activity in a solution and in an in-gel assay system, as well as the effects of hydrogen peroxide (H2O2) on SOD activity, were investigated. In a solution assay system, SOD activity of jackfruit root, shoot, leaves, axes, and cotyledons, of maize embryos and endosperms, of mung bean leaves and seeds, of sacred lotus axes and cotyledons, and of rice and wheat leaves was increased by 1-15 mmol/L H2O2. However, SOD activity in rice root and seeds, maize roots and leaves, mung bean roots and shoots, and wheat seeds was decreased by 1-15 mmol/L H2O2. The SOD activity of wheat root and soybean roots, leaves, axes, and cotyledons was increased by 1-4 mmol/L H2O2, but was decreased by concentrations of H2O2 >4 mmol/L. The SOD activity of soybean shoots was not affected by 1-15 mmol/L H2O2. The SOD activity in crude mitochondria of jackfruit,maize, and upas seeds, as well as in purified mitochondria of jackfruit, was also increased by 1-15 mmol/L H2O2. In the in-gel assay system, the SOD in jackfruit cotyledons was comprised of Mn-SOD, Cu/Zn-SOD, and Fe-SOD, the crude mitochondria of jackfruit seeds and maizes embryo was comprised of Mn-SOD and Cu/Zn-SOD, and the crude mitochondria of maize seeds was comprised of Mn-SOD only. In the present study,H2O2 markedly inhibited Cu/Zn-SOD and Fe-SOD activity.

  13. pH dependent catalytic activities of platinum nanoparticles with respect to the decomposition of hydrogen peroxide and scavenging of superoxide and singlet oxygen

    Science.gov (United States)

    Liu, Yi; Wu, Haohao; Li, Meng; Yin, Jun-Jie; Nie, Zhihong

    2014-09-01

    Recently, platinum (Pt) nanoparticles (NPs) have received increasing attention in the field of catalysis and medicine due to their excellent catalytic activity. To rationally design Pt NPs for these applications, it is crucial to understand the mechanisms underlying their catalytic and biological activities. This article describes a systematic study on the Pt NP-catalyzed decomposition of hydrogen peroxide (H2O2) and scavenging of superoxide (O2&z.rad;-) and singlet oxygen (1O2) over a physiologically relevant pH range of 1.12-10.96. We demonstrated that the catalytic activities of Pt NPs can be modulated by the pH value of the environment. Our results suggest that Pt NPs possess peroxidase-like activity of decomposing H2O2 into &z.rad;OH under acidic conditions, but catalase-like activity of producing H2O and O2 under neutral and alkaline conditions. In addition, Pt NPs exhibit significant superoxide dismutase-like activity of scavenging O2&z.rad;- under neutral conditions, but not under acidic conditions. The 1O2 scavenging ability of Pt NPs increases with the increase in the pH of the environment. The study will provide useful guidance for designing Pt NPs with desired catalytic and biological properties.Recently, platinum (Pt) nanoparticles (NPs) have received increasing attention in the field of catalysis and medicine due to their excellent catalytic activity. To rationally design Pt NPs for these applications, it is crucial to understand the mechanisms underlying their catalytic and biological activities. This article describes a systematic study on the Pt NP-catalyzed decomposition of hydrogen peroxide (H2O2) and scavenging of superoxide (O2&z.rad;-) and singlet oxygen (1O2) over a physiologically relevant pH range of 1.12-10.96. We demonstrated that the catalytic activities of Pt NPs can be modulated by the pH value of the environment. Our results suggest that Pt NPs possess peroxidase-like activity of decomposing H2O2 into &z.rad;OH under acidic conditions

  14. The preparation of calcium superoxide in a flowing gas stream and fluidized bed

    Science.gov (United States)

    Wood, P. C.; Ballou, E. V.; Spitze, L. A.; Wydeven, T.

    1980-01-01

    Superoxides can be used as sources of chemically stored oxygen in emergency breathing apparatus. The work reported here describes the use of a low-pressure nitrogen gas sweep through the reactant bed, for temperature control and water vapor removal. For a given set of gas temperature, bed thickness, and reaction time values, the highest purity calcium superoxide, Ca(O2)2, was obtained at the highest space velocity of the nitrogen gas sweep. The purity of the product was further increased by flow conditions that resulted in the fluidization of the reactant bed. However, scale-up of the low-pressure fluidized bed process was limited to the formation of agglomerates of reactant particles, which hindered thermal control by the flowing gas stream. A radiofrequency flow discharge inside the reaction chamber prevented agglomeration, presumably by dissipation of the static charges on the fluidized particles.

  15. Evaluation of dyes adsorption properties of TiO2-alginate biohybrid material

    Science.gov (United States)

    Barrón Zambrano, J. A.; Sánchez Morales, G.; Ávila Ortega, A.; Muñoz Rodríguez, D.; Carrera Figueiras, C.

    2013-06-01

    In this study a TiO2-alginate biohybrid material was obtained by the sol gel method and its adsorption properties were compared to those of its precursors using eosin B (anionic) as model dye. The results showed that the TiO2 and biohybrid have a greater affinity for eosine B than alginate. The maximum adsorption capacity for the eosin B was obtained at pH = 10. Kinetic studies showed that the biohybrid has greater rate and adsorption capacity than its precursors. Kinetic data were fitted to a pseudo-second order kinetic model. The experimental isotherms were fitted to the Langmuir model.

  16. Characterization of RuO2+SnO2/Ti anodes with high SnO2-concentrations

    Institute of Scientific and Technical Information of China (English)

    王欣; 唐电; 周敬恩

    2004-01-01

    Two SnO2 + RuO2/Ti anodes with high SnO2-concentrations were prepared by painting, sintering and annealing through a sol-gel technique. The microstructure, morphology and grain size of coatings and the electrochemical properties of the anodes were investigated by XRD, DTA, SEM, TEM and CV. It is demonstrated that the anodic coatings consist of solid solution (Sn, X)O2 (X represents Ru or Ti) phases. The average grain size of the coatings is about less than 30 nm. When the annealing temperature increases from 450 ℃ to 600 ℃, the solid solutions decompose. The crystal of the coating is equiaxial. The morphology of TiO2 + SnO2/Ti coatings is a mixture of mud-flat cracking with a kind of agglomerated structure.

  17. Serine 1179 Phosphorylation of Endothelial Nitric Oxide Synthase Increases Superoxide Generation and Alters Cofactor Regulation.

    Directory of Open Access Journals (Sweden)

    Hu Peng

    Full Text Available Endothelial nitric oxide synthase (eNOS is responsible for maintaining systemic blood pressure, vascular remodeling and angiogenesis. In addition to producing NO, eNOS can also generate superoxide (O2-. in the absence of the cofactor tetrahydrobiopterin (BH4. Previous studies have shown that bovine eNOS serine 1179 (Serine 1177/human phosphorylation critically modulates NO synthesis. However, the effect of serine 1179 phosphorylation on eNOS superoxide generation is unknown. Here, we used the phosphomimetic form of eNOS (S1179D to determine the effect of S1179 phosphorylation on superoxide generating activity, and its sensitivity to regulation by BH4, Ca2+, and calmodulin (CAM. S1179D eNOS exhibited significantly increased superoxide generating activity and NADPH consumption compared to wild-type eNOS (WT eNOS. The superoxide generating activities of S1179D eNOS and WT eNOS did not differ significantly in their sensitivity to regulation by either Ca2+ or CaM. The sensitivity of the superoxide generating activity of S1179D eNOS to inhibition by BH4 was significantly reduced compared to WT eNOS. In eNOS-overexpressing 293 cells, BH4 depletion with 10mM DAHP for 48 hours followed by 50ng/ml VEGF for 30 min to phosphorylate eNOS S1179 increased ROS accumulation compared to DAHP-only treated cells. Meanwhile, MTT assay indicated that overexpression of eNOS in HEK293 cells decreased cellular viability compared to control cells at BH4 depletion condition (P<0.01. VEGF-mediated Serine 1179 phosphorylation further decreased the cellular viability in eNOS-overexpressing 293 cells (P<0.01. Our data demonstrate that eNOS serine 1179 phosphorylation, in addition to enhancing NO production, also profoundly affects superoxide generation: S1179 phosphorylation increases superoxide production while decreasing sensitivity to the inhibitory effect of BH4 on this activity.

  18. The role of a cytosolic superoxide dismutase in barley-pathogen interactions

    KAUST Repository

    Lightfoot, Damien J.

    2016-03-19

    Reactive oxygen species (ROS), including superoxide (O2-HO2) and hydrogen peroxide (H2O2), are differentially produced during resistance responses to biotrophic pathogens and during susceptible responses to necrotrophic and hemi-biotrophic pathogens. Superoxide dismutase (SOD) is responsible for the catalysis of the dismutation of O2-HO2 to H2O2, regulating the redox status of plant cells. Increased SOD activity has been correlated previously with resistance in barley to the hemi-biotrophic pathogen Pyrenophora teres f. teres (Ptt, the causal agent of the net form of net blotch disease), but the role of individual isoforms of SOD has not been studied. A cytosolic CuZnSOD, HvCSD1, was isolated from barley and characterized as being expressed in tissue from different developmental stages. HvCSD1 was up-regulated during the interaction with Ptt and to a greater extent during the resistance response. Net blotch disease symptoms and fungal growth were not as pronounced in transgenic HvCSD1 knockdown lines in a susceptible background (cv. Golden Promise), when compared with wild-type plants, suggesting that cytosolic O2-HO2 contributes to the signalling required to induce a defence response to Ptt. There was no effect of HvCSD1 knockdown on infection by the hemi-biotrophic rice blast pathogen Magnaporthe oryzae or the biotrophic powdery mildew pathogen Blumeria graminis f. sp. hordei, but HvCSD1 also played a role in the regulation of lesion development by methyl viologen. Together, these results suggest that HvCSD1 could be important in the maintenance of the cytosolic redox status and in the differential regulation of responses to pathogens with different lifestyles.

  19. Composite Electrode SnO2/TiO2 for Dye-Sensitized Solar Cells

    Institute of Scientific and Technical Information of China (English)

    Jiang Bin XIA; Fu You LI; Shu Ming YANG; Chun Hui HUANG

    2004-01-01

    Composite nanoporous electrode SnO2/TiO2 was fabricated for the dye sensitized solar cell (DSSC) with N3 (Cis-Ru). After introducing of TiO2, the open-circuit photovoltage (Voc) was higher than that of the pure SnO2 electrode, while short-circuit photocurrent (Isc) was varied with the ratio of the TiO2. Appropriate content of the TiO2 can be beneficial to the efficiency of the solar cell, and it gives negative impact on the composite electrode when the content of TiO2 is higher.

  20. α-PbO2-type high-pressure polymorph of GeO2

    Science.gov (United States)

    Prakapenka, Vitali B.; Dubrovinsky, Leonid S.; Shen, Guoyin; Rivers, Mark L.; Sutton, Stephen R.; Dmitriev, V.; Weber, H.-P.; Le Bihan, T.

    2003-04-01

    We have studied the high pressure polymorphism of GeO2 at pressures up to 60 GPa and temperatures to ˜1800 K in a laser-heated diamond anvil cell. We have synthesized an α-PbO2-type (space group Pbcn) phase of GeO2 and demonstrated that it is the stable post-CaCl2-type (space group Pnnm) polymorph at pressures above 44 GPa. The α-PbO2-structured GeO2, with a bulk modulus of 256(5) GPa, is denser than CaCl2 type by 1.6% at 60 GPa. Our study shows that group-IV element dioxides (SiO2, GeO2, SnO2, and PbO2) have a common sequence of high-pressure structural transformations: rutile-type⇒CaCl2-type⇒α-PbO2-type.

  1. Mitochondrial respiratory chain and thioredoxin reductase regulate intermembrane Cu,Zn-superoxide dismutase activity: implications for mitochondrial energy metabolism and apoptosis.

    Science.gov (United States)

    Iñarrea, Pedro; Moini, Hadi; Han, Derick; Rettori, Daniel; Aguiló, Ignacio; Alava, Maria Angeles; Iturralde, María; Cadenas, Enrique

    2007-07-01

    IMS (intermembrane space) SOD1 (Cu/Zn-superoxide dismutase) is inactive in isolated intact rat liver mitochondria and is activated following oxidative modification of its critical thiol groups. The present study aimed to identify biochemical pathways implicated in the regulation of IMS SOD1 activity and to assess the impact of its functional state on key mitochondrial events. Exogenous H2O2 (5 microM) activated SOD1 in intact mitochondria. However, neither H2O2 alone nor H2O2 in the presence of mitochondrial peroxiredoxin III activated SOD1, which was purified from mitochondria and subsequently reduced by dithiothreitol to an inactive state. The reduced enzyme was activated following incubation with the superoxide generating system, xanthine and xanthine oxidase. In intact mitochondria, the extent and duration of SOD1 activation was inversely correlated with mitochondrial superoxide production. The presence of TxrR-1 (thioredoxin reductase-1) was demonstrated in the mitochondrial IMS by Western blotting. Inhibitors of TxrR-1, CDNB (1-chloro-2,4-dinitrobenzene) or auranofin, prolonged the duration of H2O2-induced SOD1 activity in intact mitochondria. TxrR-1 inactivated SOD1 purified from mitochondria in an active oxidized state. Activation of IMS SOD1 by exogenous H2O2 delayed CaCl2-induced loss of transmembrane potential, decreased cytochrome c release and markedly prevented superoxide-induced loss of aconitase activity in intact mitochondria respiring at state-3. These findings suggest that H2O2, superoxide and TxrR-1 regulate IMS SOD1 activity reversibly, and that the active enzyme is implicated in protecting vital mitochondrial functions.

  2. Preparation and Properties of SiO2 Supported Nitrogen-Doped Visible-Light Response TiO2-xNy/SiO2 Photocatalysts%SiO2负载氮掺杂TiO2可见光响应光催化剂的制备及性能

    Institute of Scientific and Technical Information of China (English)

    陈孝云; 陆东芳; 张淑惠; 黄碧珠

    2012-01-01

    Nitrogen-doped TiO2 photocatalysts supported on SiO2 (TSN) with Visible-light response were prepared by a hydrolysis-precipitation method. The photocatalytic activity of the title catalyst was investigated using the photocatalytic degradation of phenol as a model reaction. The separability of TSN was determined by gravity sedimentation. The catalyst was characterized by XPS, FTIR, UV-Vis DRS, XRD, TEM and N2 adsorption isotherm. The results show that the anion N is incorporated into TiO2 lattice and substitutes part of 0. TSN with suitable N-doping exhibits high activity under ultraviolet light, artificial visible light and solar irradiation. TSN exhibits better decantability and less deactivation. Doping of N can form a new bond of Ti-O-N resulting in a new band gap above the valence band of TiO2 to extend the adsorption edge to 450~500 nm. Also, SiO2 is beneficial to the higher dispersion and larger surface area of TSN.%以四氯化钛为钛源,尿素为氮源,采用液相水解-沉淀法制得SiO2负载N掺杂TiO2可见光响应TiO2-xNy/SiO2光催化剂(TSN).以苯酚为模型物,考察了TSN在可见光区、紫外光区及太阳光下的光催化活性,以及催化剂的使用寿命、分离性能.采用XPS 、FTIR 、UV-Vis DRS、XRD、TEM和低温氮物理吸附等对催化剂的结构进行表征.结果表明,N以阴离子形式进入TiO2体相并置换晶格中的O,适量N掺杂的TSN在紫外光区、可见光区及太阳光下均表现出较高的活性.SiO2与TiO2界面间有Ti-O-Si键形成,结合牢固.N掺杂在TiO2表面生成Ti-O-N键,形成新的能级结构,使催化剂的吸收红移至450~500 nm,诱发TiO2可见光催化活性.SiO2负载可减小TiO2颗粒平均尺寸,增加催化剂比表面积;同时SiO2负载还可改善催化剂的分离性能,提高催化剂使用寿命.

  3. Pretreatment with H2O2 Alleviates Aluminum-induced Oxidative Stress in Wheat Seedlings

    Institute of Scientific and Technical Information of China (English)

    Fang Jie Xu; Chong Wei Jin; Wen Jing Liu; Yong Song Zhang; Xian Yong Lin

    2011-01-01

    Hydrogen peroxide(H2O2)is a key reactive oxygen species(ROS)in signal transduction pathways Ieading to activation of plant defenses against biotic and abiotic stresses.In this study,we investigated the effects of H2O2 pretreatment on aluminum (Al)induced antioxidant responses in root tips of two wheat(Triticum aestivum L.)genotypes,Yangmai-5(Al-sensitive)and Jian-864(Al-tolerant).Al increased and root elongation inhibition in Yangmai-5 than in Jian-864.However,H2O2 pretreatment alleviated Alinduced deleterious effects in both genotypes.Under Al stress,H2O2 pretreatment increased the activities of superoxide dismutase,catalase,peroxidase,ascorbate peroxidase and monodehydroascorbate reductase,glutathione reductase and giutathione peroxidase as well as the levels of ascorbate and glutathione more significantly in Yangmai-5 than in Jian-864.Furthermore,H2O2 pretreatment also increased the total antioxidant capacity evaluated as the 2,2-diphenyl-1-picrylhydrazyl-radical scavenging activity and the ferric reducing/antioxidant power more significantly in Yangmai-5 than in Jian-864.Therefore,we conclude that H2O2 pretreatment improves wheat Al acclimation during subsequent Al exposure by enhancing the antioxidant defense capacity,which prevents ROS accumulation,and that the enhancement is greater in the Al-sensitive genotype than in the Al-tolerant genotype.

  4. Durability of Ag-TiO2 Photocatalysts Assessed for the Degradation of Dichloroacetic Acid

    Directory of Open Access Journals (Sweden)

    Víctor M. Menéndez-Flores

    2008-01-01

    Full Text Available The stability of Ag-TiO2 photocatalysts was examined for the photocatalytic degradation of dichloroacetic acid (DCA as a function of the recycling times. The photocatalytic activity was investigated by measuring the rate of H+ ions released during the photodegradation of DCA and confirmed by measuring the total organic carbon removal. The photodegradation reactions were studied at pH 3 and pH 10 for a series of Ag-TiO2 photocatalysts as different with Ag loadings . All the Ag-TiO2 and bare TiO2 photocatalysts showed a decrease in photocatalytic activity on recycling for the DCA photodegradation reaction. The decrease in activity can be attributed to poisoning of active sites by Cl− anions formed during the photocatalytic DCA degradation. The photocatalytic activity was, however, easily recovered by a simple washing technique. The reversibility of the poisoning is taken as evidence to support the idea that the recycling of Ag-P25 TiO2 photocatalysts does not have a permanent negative effect on their photocatalytic performance for the degradation of DCA. The choice of the preparation procedure for the Ag-TiO2 photocatalysts is shown to be of significant importance for the observed changes in the photocatalytic activity of the Ag-TiO2 particles.

  5. Synthesis of Water-Based Dispersions of Polymer/TiO2 Hybrid Nanospheres

    Directory of Open Access Journals (Sweden)

    Lu Jin

    2015-08-01

    Full Text Available We develop a strategy for preparing water-based dispersions of polymer/TiO2 nanospheres that can be used to form composite materials applicable in various fields. The formed hybrid nanospheres are monodisperse and possess a hierarchical structure. It starts with the primary TiO2 nanoparticles of about 5 nm, which first assemble to nanoclusters of about 30 nm and then are integrated into monomer droplets. After emulsion polymerization, one obtains the water-based dispersions of polymer/TiO2 nanospheres. To achieve universal size, it is necessary to have treatments with intense turbulent shear generated in a microchannel device at different stages. In addition, a procedure combining synergistic actions of steric and anionic surfactants has been designed to warrant the colloidal stability of the process. Since the formed polymer/TiO2 nanospheres are stable aqueous dispersions, they can be easily mixed with TiO2-free polymeric nanoparticle dispersions to form new dispersions, where TiO2-containing nanospheres are homogeneously distributed in the dispersions at the nanoscale, thus leading to various applications. As an example, the proposed strategy has been applied to generate polystyrene/TiO2 nanospheres of about 100 nm in diameter.

  6. Melting behavior of (Th,U)O2 and (Th,Pu)O2 mixed oxides

    Science.gov (United States)

    Ghosh, P. S.; Kuganathan, N.; Galvin, C. O. T.; Arya, A.; Dey, G. K.; Dutta, B. K.; Grimes, R. W.

    2016-10-01

    The melting behaviors of pure ThO2, UO2 and PuO2 as well as (Th,U)O2 and (Th,Pu)O2 mixed oxides (MOX) have been studied using molecular dynamics (MD) simulations. The MD calculated melting temperatures (MT) of ThO2, UO2 and PuO2 using two-phase simulations, lie between 3650-3675 K, 3050-3075 K and 2800-2825 K, respectively, which match well with experiments. Variation of enthalpy increments and density with temperature, for solid and liquid phases of ThO2, PuO2 as well as the ThO2 rich part of (Th,U)O2 and (Th,Pu)O2 MOX are also reported. The MD calculated MT of (Th,U)O2 and (Th,Pu)O2 MOX show good agreement with the ideal solidus line in the high thoria section of the phase diagram, and evidence for a minima is identified around 5 atom% of ThO2 in the phase diagram of (Th,Pu)O2 MOX.

  7. Unique Characteristics of Recombinant Hybrid Manganese Superoxide Dismutase from Staphylococcus equorum and S. saprophyticus.

    Science.gov (United States)

    Retnoningrum, Debbie S; Rahayu, Anis Puji; Mulyanti, Dina; Dita, Astrid; Valerius, Oliver; Ismaya, Wangsa T

    2016-04-01

    A recombinant hybrid of manganese dependent-superoxide dismutase of Staphylococcus equorum and S. saprophyticus has successfully been overexpressed in Escherichia coli BL21(DE3), purified, and characterized. The recombinant enzyme suffered from degradation and aggregation upon storage at -20 °C, but not at room temperature nor in cold. Chromatographic analysis in a size exclusion column suggested the occurrence of dimeric form, which has been reported to contribute in maintaining the stability of the enzyme. Effect of monovalent (Na(+), K(+)), divalent (Ca(2+), Mg(2+)), multivalent (Mn(2+/4+), Zn(2+/4+)) cations and anions (Cl(-), SO4 (2-)) to the enzyme stability or dimeric state depended on type of cation or anion, its concentration, and pH. However, tremendous effect was observed with 50 mM ZnSO4, in which thermostability of both the dimer and monomer was increased. Similar situation was not observed with MnSO4, and its presence was detrimental at 200 mM. Finally, chelating agent appeared to destabilize the dimer around neutral pH and dissociate it at basic pH. The monomer remained stable upon addition of ethylene diamine tetraacetic acid. Here we reported unique characteristics and stability of manganese dependent-superoxide dismutase from S. equorum/saprophyticus.

  8. Lithium ion conductive behavior of TiO2 nanotube/ionic liquid matrices

    OpenAIRE

    2014-01-01

    A series of TiO_2 nanotube (TNT)/ionic liquid matrices were prepared, and their lithium ion conductive properties were studied. SEM images implied that ionic liquid was dispersed on the whole surface of TNT. Addition of TNT to ionic liquid (1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide (BMImTFSA)) resulted in significant increase of ionic conductivity. Furthermore, lithium transference number was also largely enhanced due to the interaction of anion with TNT. Vogel-Fulcher-Tam...

  9. Substitution of arginine for lysine 134 alters electrostatic parameters of the active site in shark Cu,Zn superoxide dismutase.

    Science.gov (United States)

    Calabrese, L; Polticelli, F; O'Neill, P; Galtieri, A; Barra, D; Schininà, E; Bossa, F

    1989-06-19

    The complete amino acid sequence was determined for the Cu,Zn superoxide dismutase from the shark Prionace glauca. The active site region shows the substitution of an Arg for Lys at position 134, which is important for electrostatic facilitation of the diffusion of O2- to the catalytically active copper. This change may be related to observed alterations of electrostatic parameters of the enzyme (pK of the pH dependence of the enzyme activity, rate of inactivation by H2O2), although it preserves a high efficiency of dismutation at neutral pH.

  10. Diurnal O2 and carbohydrate levels in wheat kernels during embryony.

    Science.gov (United States)

    Carman, John G; Bishop, Deborah L

    2004-09-01

    In vitro zygotic and somatic embryogenesis procedures for wheat have been improved by simulating in ovulo nutritional, hormonal and dissolved oxygen (dO2) conditions. However, diurnal fluctuations in these conditions during early embryony are not well characterized. In this study, dO2 and water-soluble carbohydrate Levels in wheat kernels were determined after 8 h of light and 8 h of dark at approximately 6, 12 and 18 day post anthesis (DPA). Clark style O2 microelectrodes, having a tip diameter of approximately 115 microm, were inserted into intact kernels immediately distil to the developing embryo, and dO2 levels were recorded at 50 microm intervals into the center of kernels. High-performance anion exchange chromatography with pulsed amperometric detection was used to quantify carbohydrate levels in endosperm sap. dO2 levels in the chlorophyllous layer of the pericarp reached 190 mmoLm(-3) during the day, which probably represents, because of photosynthesis, a supersaturated O2 condition relative to the external environment (21% O2). At the embryo surface, dO2 levels at 6 DPA ranged from 135 to 170 mmolm(-3). At 12 and 18 DPA, dO2 levels at the embryo axis ranged from 100 to 150mmolm(-3). At all three stages, dO2 levels in the center of the endosperm were below 13 mmolm(-3). Extreme fluctuations in carbohydrate levels were observed diurnally during rapid seed fill (12DPA). Levels of sucrose and short-chain fructans were much higher during the day than during the night. In contrast, fructose, glucose, and myo-inositol levels were much higher during the night than during the day. By 18DPA (hard dough stage), carbohydrate levels tended to be similar during the day and night. These dynamic fluctuations may assist in regulating embryony in ovulo, and their simulation might improve the development of somatic and zygotic embryos in vitro.

  11. Role of extracellular superoxide dismutase in hypertension.

    Science.gov (United States)

    Gongora, Maria Carolina; Qin, Zhenyu; Laude, Karine; Kim, Ha Won; McCann, Louise; Folz, J Rodney; Dikalov, Sergey; Fukai, Tohru; Harrison, David G

    2006-09-01

    We previously found that angiotensin II-induced hypertension increases vascular extracellular superoxide dismutase (ecSOD), and proposed that this is a compensatory mechanism that blunts the hypertensive response and preserves endothelium-dependent vasodilatation. To test this hypothesis, we studied ecSOD-deficient mice. ecSOD(-/-) and C57Blk/6 mice had similar blood pressure at baseline; however, the hypertension caused by angiotensin II was greater in ecSOD(-/-) compared with wild-type mice (168 versus 147 mm Hg, respectively; P<0.01). In keeping with this, angiotensin II increased superoxide and reduced endothelium-dependent vasodilatation in small mesenteric arterioles to a greater extent in ecSOD(-/-) than in wild-type mice. In contrast to these findings in resistance vessels, angiotensin II paradoxically improved endothelium-dependent vasodilatation, reduced intracellular and extracellular superoxide, and increased NO production in aortas of ecSOD(-/-) mice. Whereas aortic expression of endothelial NO synthase, Cu/ZnSOD, and MnSOD were not altered in ecSOD(-/-) mice, the activity of Cu/ZnSOD was increased by 80% after angiotensin II infusion. This was associated with a concomitant increase in expression of the copper chaperone for Cu/ZnSOD in the aorta but not in the mesenteric arteries. Moreover, the angiotensin II-induced increase in aortic reduced nicotinamide-adenine dinucleotide phosphate oxidase activity was diminished in ecSOD(-/-) mice as compared with controls. Thus, during angiotensin II infusion, ecSOD reduces hypertension, minimizes vascular superoxide production, and preserves endothelial function in resistance arterioles. We also identified novel compensatory mechanisms involving upregulation of copper chaperone for Cu/ZnSOD, increased Cu/ZnSOD activity, and decreased reduced nicotinamide-adenine dinucleotide phosphate oxidase activity in larger vessels. These compensatory mechanisms preserve large vessel function when ecSOD is absent in

  12. Anionic surface binders

    Directory of Open Access Journals (Sweden)

    Aljaž-Rožič Mateja

    2004-01-01

    Full Text Available The MELAMIN Chemical Factory in Kočevje manufactures synthetic resins and binders for the paper industry. Binders based on AKD (alkyl ketene dimer are produced which are used for binding paper and cardboard in the range of neutral and partially basic pH. Cationic and, lately, anionic binders are mostly used for the bulk binding of paper and board. The possibility of using AKD binders on paper or board surfaces is presented. In this case partially cationic AKD binders may be applied. When optical whiteners are used, the application of AKD binders is recommended. In the case of paper it is possible to substitute acrylate binders by AKD binders. The best results are obtained when the paper is first partly treated in bulk and subsequently surface treated.

  13. Purification of O2-sensitive metalloproteins.

    Science.gov (United States)

    Echavarri-Erasun, Carlos; Arragain, Simon; Rubio, Luis M

    2014-01-01

    The most dependable factor to perform successful biochemical experiments in an O2-free environment is the experience required to set up an efficient laboratory, to properly manipulate samples, to anticipate potential O2-related problems, and to maintain the complex laboratory setup operative. There is a long list of O2-related issues that may ruin your experiments. We provide here a guide to minimize these risks.

  14. Local structure and electronic properties of BaTaO2N with perovskite-type structure

    NARCIS (Netherlands)

    Fang, C.M.; Wijs, G.A. de; Orhan, E.; With, G. de; de Groot, R.A.; Hintzen, H.T.; Marchand, R.

    2003-01-01

    First-principles calculation based on density-functional theory in the pseudo-potential approach have been performed for the total energy and crystal structure of BaTaO2N. The calculations indicate a random occupation of the anionic positions by O and N in a cubic structure, in agreement with neutro

  15. Selective adsorption of manganese onto cobalt for optimized Mn/Co/TiO2 Fischer-Tropsch catalysts

    NARCIS (Netherlands)

    Feltes, T.E.; Espinosa-Alonso, L.; de Smit, E.; D'Souza, L.; Meyer, R.J.; Weckhuysen, B.M.; Regalbuto, J.R.

    2013-01-01

    The Strong Electrostatic Adsorption (SEA) method was applied to the rational design of a promoted Co catalyst for Fischer–Tropsch (FT) synthesis. A series of Mn/Co/TiO2 catalysts were prepared by selective deposition of the [MnO4] anion onto the supported Co3O4 phase. Qualitative ICP-OES and XPS mea

  16. The preparation of calcium superoxide at subambient temperatures and pressures. [oxygen source for breathing apparatus

    Science.gov (United States)

    Ballou, E. V.; Wood, P. C.; Spitze, L. A.; Wydeven, T.; Stein, R.

    1977-01-01

    The effects of disproportionations at lower temperatures and also of a range of reaction chamber pressures on the preparation of calcium superoxide, Ca(O2)2, from calcium peroxide diperoxyhydrate were studied. About 60% purity of product was obtained by a disproportionation procedure. The significance of features of this procedure for a prospective scale-up of the mass prepared in a single experiment is considered. The optimum pressure for product purity was determined, and the use of a molecular sieve desiccant is described.

  17. Resonant spectra of quadrupolar anions

    Science.gov (United States)

    Fossez, K.; Mao, Xingze; Nazarewicz, W.; Michel, N.; Garrett, W. R.; Płoszajczak, M.

    2016-09-01

    In quadrupole-bound anions, an extra electron is attached at a sufficiently large quadrupole moment of a neutral molecule, which is lacking a permanent dipole moment. The nature of the bound states and low-lying resonances of such anions is of interest for understanding the threshold behavior of open quantum systems in general. In this work, we investigate the properties of quadrupolar anions as halo systems, the formation of rotational bands, and the transition from a subcritical to supercritical electric quadrupole moment. We solve the electron-plus-rotor problem using a nonadiabatic coupled-channel formalism by employing the Berggren ensemble, which explicitly contains bound states, narrow resonances, and the scattering continuum. The rotor is treated as a linear triad of point charges with zero monopole and dipole moments and nonzero quadrupole moment. We demonstrate that binding energies and radii of quadrupolar anions strictly follow the scaling laws for two-body halo systems. Contrary to the case of dipolar anions, ground-state band of quadrupolar anions smoothly extend into the continuum, and many rotational bands could be identified above the detachment threshold. We study the evolution of a bound state of an anion as it dives into the continuum at a critical quadrupole moment and we show that the associated critical exponent is α =2 . Everything considered, quadrupolar anions represent a perfect laboratory for the studies of marginally bound open quantum systems.

  18. Rutin inhibits proliferation, attenuates superoxide production and decreases adhesion and migration of human cancerous cells.

    Science.gov (United States)

    Ben Sghaier, Mohamed; Pagano, Alessandra; Mousslim, Mohamed; Ammari, Youssef; Kovacic, Hervé; Luis, José

    2016-12-01

    Lung and colorectal cancer are the principal causes of death in the world. Rutin, an active flavonoid compound, is known for possessing a wide range of biological activities. In this study, we examined the effect of rutin on the viability, superoxide anion production, adhesion and migration of human lung (A549) and colon (HT29 and Caco-2) cancer cell lines. In order to control the harmlessness of the tested concentrations of rutin, the viability of cancer cell lines was assessed using a 3-(4,5-dimethylthiazol- 2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay. ROS generation was measured by lucigenin chemiluminescence detecting superoxide ions. To investigate the effect of rutin on the behavior of human lung and colon cancer cell lines, we performed adhesion assays, using various purified extracellular matrix (ECM) proteins. Finally, in vitro cell migration assays were explored using modified Boyden chambers. The viability of cancerous cells was inhibited by rutin. It also significantly attenuated the superoxide production in HT29 cells. In addition, rutin affected adhesion and migration of A549 and HT29 cell. These findings indicate that rutin, a natural molecule, might have potential as anticancer agent against lung and colorectal carcinogenesis.

  19. Lower Superoxide Dismutase 2 (SOD2) Protein Content in Mononuclear Cells Is Associated with Better Survival in Patients with Hemodialysis Therapy

    Science.gov (United States)

    Shen, Jianlin

    2016-01-01

    Mitochondrial superoxide dismutase 2 (SOD2) converts superoxide anions to hydrogen peroxide and oxygen. Human data on SOD2 protein content in chronic kidney disease (CKD) are sparse and mortality data are lacking. We investigated SOD2 protein content in monocytes from patients with hemodialysis therapy (n = 81), CKD stage 1–5 (n = 120), and healthy controls (n = 13) using in-cell Western assays. SOD2 protein decreased from CKD stage 1 until stage 4 whereas it increased again in stage 5 with and without hemodialysis. SOD2 gene expression, analyzed by quantitative real-time PCR, was not significantly different between the groups. Elevating cellular superoxide production reduced SOD2 protein content. This effect was abolished by the superoxide dismutase mimetic Tempol. Using gelelectrophoresis and Western blot we did not detect nitrotyrosine modifications of SOD2 in CKD. Finally, in patients with CKD stage 5 with hemodialysis therapy higher than median SOD2 protein content was associated with higher all-cause mortality. In conclusion, SOD2 protein content declined in CKD until stage 4 while SOD2 gene expression did not. Increased cellular superoxide anion production might affect SOD2 protein content. In advanced CKD (stage 5) SOD2 protein content increased again, but higher than median SOD2 protein content in these patients did not confer a survival benefit. PMID:27630759

  20. Lower Superoxide Dismutase 2 (SOD2 Protein Content in Mononuclear Cells Is Associated with Better Survival in Patients with Hemodialysis Therapy

    Directory of Open Access Journals (Sweden)

    Katharina Krueger

    2016-01-01

    Full Text Available Mitochondrial superoxide dismutase 2 (SOD2 converts superoxide anions to hydrogen peroxide and oxygen. Human data on SOD2 protein content in chronic kidney disease (CKD are sparse and mortality data are lacking. We investigated SOD2 protein content in monocytes from patients with hemodialysis therapy (n=81, CKD stage 1–5 (n=120, and healthy controls (n=13 using in-cell Western assays. SOD2 protein decreased from CKD stage 1 until stage 4 whereas it increased again in stage 5 with and without hemodialysis. SOD2 gene expression, analyzed by quantitative real-time PCR, was not significantly different between the groups. Elevating cellular superoxide production reduced SOD2 protein content. This effect was abolished by the superoxide dismutase mimetic Tempol. Using gelelectrophoresis and Western blot we did not detect nitrotyrosine modifications of SOD2 in CKD. Finally, in patients with CKD stage 5 with hemodialysis therapy higher than median SOD2 protein content was associated with higher all-cause mortality. In conclusion, SOD2 protein content declined in CKD until stage 4 while SOD2 gene expression did not. Increased cellular superoxide anion production might affect SOD2 protein content. In advanced CKD (stage 5 SOD2 protein content increased again, but higher than median SOD2 protein content in these patients did not confer a survival benefit.

  1. Lower Superoxide Dismutase 2 (SOD2) Protein Content in Mononuclear Cells Is Associated with Better Survival in Patients with Hemodialysis Therapy.

    Science.gov (United States)

    Krueger, Katharina; Shen, Jianlin; Maier, Alexandra; Tepel, Martin; Scholze, Alexandra

    2016-01-01

    Mitochondrial superoxide dismutase 2 (SOD2) converts superoxide anions to hydrogen peroxide and oxygen. Human data on SOD2 protein content in chronic kidney disease (CKD) are sparse and mortality data are lacking. We investigated SOD2 protein content in monocytes from patients with hemodialysis therapy (n = 81), CKD stage 1-5 (n = 120), and healthy controls (n = 13) using in-cell Western assays. SOD2 protein decreased from CKD stage 1 until stage 4 whereas it increased again in stage 5 with and without hemodialysis. SOD2 gene expression, analyzed by quantitative real-time PCR, was not significantly different between the groups. Elevating cellular superoxide production reduced SOD2 protein content. This effect was abolished by the superoxide dismutase mimetic Tempol. Using gelelectrophoresis and Western blot we did not detect nitrotyrosine modifications of SOD2 in CKD. Finally, in patients with CKD stage 5 with hemodialysis therapy higher than median SOD2 protein content was associated with higher all-cause mortality. In conclusion, SOD2 protein content declined in CKD until stage 4 while SOD2 gene expression did not. Increased cellular superoxide anion production might affect SOD2 protein content. In advanced CKD (stage 5) SOD2 protein content increased again, but higher than median SOD2 protein content in these patients did not confer a survival benefit.

  2. Pyruvate anions neutralize peritoneal dialysate cytotoxicity.

    Science.gov (United States)

    Mahiout, A; Brunkhorst, R

    1995-01-01

    A new peritoneal dialysate containing pyruvate anions was developed in order to avoid cytotoxic effect of conventional lactate-based dialysate. The dialysate has a final pH of 5.4 to 5.6 and is composed of 1.36-3.86% glucose-monohydrate; 132 mmol/l sodium; 1.75 mmol/l calcium; 0.75 mmol/l magnesium; 102 mmol/l chloride and 35 mmol/l pyruvate. For cytotoxicity testing peritoneal macrophages, and mesothelial cells (MC) were exposed to conventional lactate dialysate, and pyruvate dialysate. We investigated the O2- generation and cytokine synthesis after endotoxin stimulation in peritoneal macrophages and the proliferation of mesothelial cells of cultured human MC. After exposure to lactate dialysate O2- generation and cytokine synthesis in peritoneal macrophages and proliferation of mesothelial cells were inhibited when compared to solution containing pyruvate and the control solution. After preincubation with 3.86% glucose containing solutions, all negative effects became even more pronounced in the lactate group whereas after pre-exposure to pyruvate containing solution the toxic effects were absent. These results suggest that the acute toxic effects of commercially available peritoneal dialysates can be avoided by the use of sodium pyruvate instead of sodium lactate.

  3. Catalytic combustion of toluene on Pd/CeO2-TiO2 catalysts.

    Science.gov (United States)

    Chen, Yu-Wen; Lee, Der-Shing

    2013-03-01

    Pd/TiO2 and Pd/CeO2 were reported to be very active to destruct toluene. Combination of TiO2 and CeO2 is an interesting candidate to achieve a catalyst with higher activity. In this study, a series of Pd/CeO2-TiO2 catalysts with various Pd loadings were prepared. CeO2-TiO2 was prepared by impregnation of aqueous solution of cerium nitrate into TiO2 support. It was then calcined at 400 degrees C. Pd was loaded by incipient-wetness impregnation method. The Pd loadings in all samples were fixed at 0.5 wt.%. The catalysts were characterized by powder X-ray diffraction, transmission electron microscopy, high resolution transmission electron microscopy, temperature-programmed reduction of hydrogen, and X-ray photoelectron spectroscopy. The catalysts were tested for total oxidation of toluene. The feed concentration of toluene was 8.564 g/m3 (2085 ppm), with GHSV = 10,000 h(-1). Pd particle sizes were 3-5 nm and well-dispersed on the support. CeO2 on TiO2 was easier to reduce than the bulk CeO2, therefore it could enhance the activity of VOC destruction. Pd/CeO2-TiO2 was more active than Pd/CeO2 and Pd/TiO2. Pd/CeO2-TiO2 with Ce/Ti ratio of 2/8 was very active for toluene destruction, due to its lower oxygen reduction temperature of ceria and higher concentration of Pd(0).

  4. The Characteristics and Regulatory Mechanisms of Superoxide Generation from eNOS Reductase Domain.

    Directory of Open Access Journals (Sweden)

    Hu Peng

    Full Text Available In addition to superoxide (O2.- generation from nitric oxide synthase (NOS oxygenase domain, a new O2.- generation site has been identified in the reductase domain of inducible NOS (iNOS and neuronal NOS (nNOS. Cysteine S-glutathionylation in eNOS reductase domain also induces O2.- generation from eNOS reductase domain. However, the characteristics and regulatory mechanism of the O2.- generation from NOS reductase domain remain unclear. We cloned and purified the wild type bovine eNOS (WT eNOS, a mutant of Serine 1179 replaced with aspartic acid eNOS (S1179D eNOS, which mimics the negative charge caused by phosphorylationand truncated eNOS reductase domain (eNOS RD. Both WT eNOS and S1179D eNOS generated significant amount of O2.- in the absence of BH4 and L-arginine. The capacity of O2.- generation from S1179D eNOS was significantly higher than that of WT eNOS (1.74:1. O2.- generation from both WT eNOS and S1179D eNOS were not completely inhibited by 100nM tetrahydrobiopterin(BH4. This BH4 un-inhibited O2.- generation from eNOS was blocked by 10mM flavoprotein inhibitor, diphenyleneiodonium (DPI. Purified eNOS reductase domain protein confirmed that this BH4 un-inhibited O2.- generation originates at the FMN or FAD/NADPH binding site of eNOS reductase domain. DEPMPO-OOH adduct EPR signals and NADPH consumptions analyses showed that O2.- generation from eNOS reductase domain was regulated by Serine 1179 phosphorylation and DPI, but not by L-arginine, BH4 or calmodulin (CaM. In addition to the heme center of eNOS oxygenase domain, we confirmed another O2.- generation site in the eNOS reductase domain and characterized its regulatory properties.

  5. Reducing Dietary Cation-Anion Difference on Acid-Base Balance, Plasma Minerals Level and Anti-Oxidative Stress of Female Goats

    Institute of Scientific and Technical Information of China (English)

    WU Wen-xuan; YANG Yi; ZHANG Ji-kun; LI Sheng-li

    2013-01-01

    Reducing dietary cation-anion difference (DCAD) has been proved an effective way to prevent milk fever in dairy cows. Based on the similar physiological gastro-intestinal tract anatomy and metabolic process between female goats and dairy cows, this study was conducted to evaluate the effects of varying DCAD on fluid acid-base status, plasma minerals concentration and anti-oxidative stress capacity of female goats. Urinary pH, plasma Ca, P and Mg;and anti-oxidative stress indices of total superoxide dismutase (T-SOD), hydrogen peroxide (H2O2), glutathione peroxidase (GSH-Px) and malondialdehyde (MDA) were determined to evaluate the effect. Forty-eight Guizhou black female goats ((15±1.9) mon of old, (22.3±3.75) kg of BW) were randomly allocated to 4 blocks of 12 goats each and were fed 1 of 4 diets differed in DCAD level (calculated as Na+K-Cl-S, mEq kg-1 DM). Levels of DCAD were preliminarily designed to be control (+150 mEq kg-1 DM, CON), high DCAD (+300 mEq kg-1 DM, HD), low DCAD (0 mEq kg-1 DM, LD) and negative DCAD (-150 mEq kg-1 DM, ND), respectively. A commercial anionic salts (Animate) and sodium bicarbonate (NaHCO3) were supplemented to reduce and increase DCAD level, respectively. There was no difference in dry matter intake for 4 groups of goats. Urine pH was aggressively decreased (P0.05) plasma Mg level. There was no significant (P>0.05) difference in plasma GSH-Px activity and H2O2, but anionic salts supplementation in LD and ND significantly increased (P<0.05) plasma T-SOD activity and tended to reduce MDA (P<0.1) over HD and CON. Results from this study indicated that reducing DCAD could decrease urine pH and increase plasma Ca concentration of female goats. Additionally, reducing DCAD was helpful to enhance anti-oxidative stress capability of female goats.

  6. Molecular mass spectrometric identification of superoxide dismutase in the liver of mice Mus musculus and Mus spretus using a metallomics analytical approach.

    Science.gov (United States)

    González-Fernández, M; García-Barrera, T; Gómez-Ariza, J L

    2011-11-01

    This paper reports the identification and quantification of superoxide dismutase in the liver of Mus musculus and Mus spretus mice using a metallomics analytical approach. The approach consisted of using orthogonal chromatographic systems coupled to ICP-MS and UV detectors. Size-exclusion fractionation of the cytosolic extracts was followed by anion-exchange chromatographic separation of Cu- and Zn-containing species. After purification then tryptic digestion, Cu- and Zn-containing superoxide dismutase was identified by nESI-QqTOF. The MS-MS spectra of doubly charged peptides, with the Mascot searching engine, were used to obtain the sequence of the protein.

  7. Seven-coordinate anion complex with a tren-based urea: binding discrepancy of hydrogen sulfate in solid and solution states.

    Science.gov (United States)

    Pramanik, Avijit; Thompson, Bethtrice; Hayes, Trina; Tucker, Kimberly; Powell, Douglas R; Bonnesen, Peter V; Ellis, Erick D; Lee, Ken S; Yu, Hongtao; Hossain, Md Alamgir

    2011-06-21

    Structural characterization of a hydrogen sulfate complex with a tren-based urea suggests that the anion is coordinated with six NH···O bonds (d(N···O) = 2.857 (3) to 3.092 (3) Å) and one OH···O bond (d(O···O) = 2.57 (2) Å) from three receptors; however, in solution the anion is bound within the pseudo-cavity of one receptor.

  8. Seven-coordinate anion complex with a tren-based urea: Binding discrepancy of hydrogen sulfate in solid and solution states

    Energy Technology Data Exchange (ETDEWEB)

    Pramanik, Avijit [Jackson State University; Thompson, Bethtrice [Jackson State University; Hayes, Trina [Jackson State University; Tucker, Kimberly [Jackson State University; Powell, Douglas R. [University of Oklahoma, Norman; Bonnesen, Peter V [ORNL; Ellis, Erick D [Jackson State University; Lee, Ken S. [Jackson State University; Yu, Hongtau [Jackson State University; Hossain, Md. Alamgir [Jackson State University

    2011-01-01

    Structural characterization of a hydrogen sulfate complex with a tren-based urea suggests that the anion is coordinated with sixNH Obonds (dN O = 2.857 (3) to 3.092 (3)A ) and one OH O bond (dO O = 2.57 (2) A ) from three receptors; however, in solution the anion is bound within the pseudocavity of one receptor.

  9. Preparation and photocatalytic activity of Cu2+-doped TiO2/SiO2

    Institute of Scientific and Technical Information of China (English)

    Ru-fen Chen; Cui-xuan Zhang; Juan Deng; Guo-qiang Song

    2009-01-01

    Cu2+-doped nanostructured TiO2-coated SiO2. (TiO2./SiO2) particles were prepared by the layer-by-layer assembly technique and their photocatalytic property was studied. TiO2 colloids were synthesized by the sol-gel method using TiOSO4 as a precursor. The experimental results showed that TiO2 nanopowders on the surface of SiO2 particles were well distributed and compact. The amount of TiO2 increased with the increase in coating layers. The shell structure appeared to be composed of anatase titania nanocrystals at 550℃. The 2-layer coated TiO2 particles on the surface showed a higher degradation rate compared with all the dif-ferent-layer samples. The photocatalytic activity of Cu2+-doped TiO2/SiO2 was higher than that of undoped TiO2/SiO2. The optimum dopant content was about 0.10wt%.

  10. Photoelectrochemical Properties of CuS-GeO2-TiO2 Composite Coating Electrode

    Science.gov (United States)

    Wen, Xinyu; Zhang, Huawei

    2016-01-01

    The ITO (indium tin oxide) conductive glass-matrix CuS-GeO2-TiO2 composite coating was generated via EPD (electrophoretic deposition) and followed by a sintering treatment at 450°C for 40 minutes. Characterizations of the CuS-GeO2-TiO2 composite coating were taken by SEM (scanning electron microscope), XRD (X-ray diffraction), EDX (energy dispersive X-ray), UV-Vis DRS (ultraviolet-visible diffuse reflection spectrum), and FT-IR (Fourier transform infrared spectroscopy). Results showed that CuS and GeO2 had dispersed in this CuS-GeO2-TiO2 composite coating (mass percentages for CuS and GeO2 were 1.23% and 2.79%, respectively). The electrochemical studies (cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and Tafel polarization) of this CuS-GeO2-TiO2 composite coating electrode were performed in pH = 9.51 Na2CO3-NaHCO3 buffer solution containing 0.50 mol/L CH3OH under the conditions of visible light, ultraviolet light (λ = 365 nm), and dark (without light irradiation as control), respectively. Electrochemical studies indicated that this CuS-GeO2-TiO2 composite coating electrode had better photoelectrocatalytic activity than the pure TiO2 electrode in the electrocatalysis of methanol under visible light. PMID:27055277

  11. Visible-light-Mediated TiO2 photocatalysis of fluoroquinolone antibacterial agents.

    Science.gov (United States)

    Paul, Tias; Miller, Penney L; Strathmann, Timothy J

    2007-07-01

    This study reports on the photocatalytic transformation of fluoroquinolone antibacterial agents (ciprofloxacin, enrofloxacin, norfloxacin, and flumequine) in aqueous titanium dioxide (TiO2) suspensions irradiated with ultraviolet (UV; lambda > 324 nm) or visible light (lambda > 400, > 420, or > 450 nm). Visible-light-mediated fluoroquinolone degradation is unexpected from direct photolysis or established TiO2 band gap photoexcitation mechanisms, which both require UV light. Visible-light-mediated photocatalysis requires an appropriate conduction band electron acceptor (e.g., O2, BrO3-), but is not dependent upon hydroxyl radical, superoxide, or other reactive oxygen species generated upon TiO2 band gap excitation. The process slows considerably when fluoroquinolone adsorption is inhibited. Whereas fluoroquinolone decomposition in UV-irradiated TiO2 suspensions is accompanied by mineralization, no changes in dissolved organic carbon occur during visible-light-photocatalyzed degradation. Results are consistent with a proposed charge-transfer mechanism initiated by photoexcitation of surface-complexed fluoroquinolone molecules. Complexation to the TiO2 surface causes a red shift in the fluoroquinolone absorption spectrum (via ligand-to-metal charge transfer), enabling photoexcitation by visible light. Fluoroquinolone oxidation then occurs by electron transfer into the TiO2 conduction band, which delivers the electron to an adsorbed electron acceptor. The lack of organic carbon mineralization indicates formation of stable organic byproducts that are resistant to further degradation by visible light. In UV-irradiated TiO2 suspensions, the charge-transfer mechanism acts in parallel with the semiconductor band gap photoexcitation mechanism.

  12. Photoactivity and hydrophilic property of SiO2 and SnO2 co-doped TiO2 nano-composite thin films

    Directory of Open Access Journals (Sweden)

    Lek Sikong

    2010-08-01

    Full Text Available SiO2 and SnO2 co-doped TiO2 nano-composite thin films were prepared by sol-gel method. The effects of film thicknessand amount of SiO2 and SnO2 co-doping into TiO2 nano-composite films on phase presence, crystallite size, photocatalyticreaction and hydrophilicity were investigated. Thickness of 3-coating layers (238 nm seems to provide the highest photocatalyticactivity. The crystallinity of anatase phases, crystallite sizes and photocatalytic reactions of SiO2 and SnO2 co-dopedTiO2 films decrease with an increase in SiO2 content. It was found that more amount of SiO2 addition seems to inhibit graingrowth and the formation of anatase phase; especially when it was synthesized at temperature less than 600°C. The photocatalyticreaction seems to decrease with an increase in SiO2 doping when the concentrations of SnO2 in the composite films are fixed. It was apparent that 1SiO2/1SnO2/TiO2 composite film exhibits the highest photoactivity. Suitable amounts of SiO2and SnO2 doping into the TiO2 composite films tend to enhance the hydrophilic property of the films. It was also apparentthat the 3SiO2/3SnO2/TiO2, 5SiO2/5SnO2/TiO2 and 10SiO2/3SnO2/TiO2 composite films exhibit super hydrophilic characteristicsunder UV irradiation for 30 min.

  13. Photoactive TiO2 Films Formation by Drain Coating for Endosulfan Degradation

    Directory of Open Access Journals (Sweden)

    Natalia Tapia-Orozco

    2013-01-01

    Full Text Available Heterogeneous photocatalysis is an advanced oxidation process in which a photoactive catalyst, such as TiO2, is attached to a support to produce free radical species known as reactive oxygen species (ROS that can be used to break down toxic organic compounds. In this study, the draining time, annealing temperature, and draining/annealing cycles for TiO2 films grown by the drain coating method were evaluated using a 23 factorial experimental design to determine the photoactivity of the films via endosulfan degradation. The TiO2 films prepared with a large number of draining/annealing cycles at high temperatures enhanced (P>0.05 endosulfan degradation and superoxide radical generation after 30 minutes of illumination with UV light. We demonstrated a negative correlation (R2=0.69; P>0.01 between endosulfan degradation and superoxide radical generation. The endosulfan degradation rates were the highest at 30 minutes with the F6 film. In addition, films prepared using conditions F1, F4, and F8 underwent an adsorption/desorption process. The kinetic reaction constants, Kapp (min−1, were 0.0101, 0.0080, 0.0055, 0.0048, and 0.0035 for F6, F2, F5, F3, and F1, respectively. The endosulfan metabolites alcohol, ether, and lactone were detected and quantified at varying levels in all photocatalytic assays.

  14. Protective effect of pomegranate seed oil against H2O2 -induced oxidative stress in cardiomyocytes

    Science.gov (United States)

    Bihamta, Mehdi; Hosseini, Azar; Ghorbani, Ahmad; Boroushaki, Mohammad Taher

    2017-01-01

    Objective: It has been well documented that oxidative stress is involved in the pathogenesis of cardiac diseases. Previous studies have shown that pomegranate seed oil (PSO) has antioxidant properties. This study was designed to investigate probable protective effects of PSO against hydrogen peroxide (H2O2)-induced damage in H9c2 cardiomyocytes. Materials and Methods: The cells were pretreated 24 hr with PSO 1 hr before exposure to 200 µM H2O2. Cell viability was evaluated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium (MTT) assay. The level of reactive oxygen species (ROS) and lipid peroxidation were measured by fluorimetric methods. Results: H2O2 significantly decreased cell viability which was accompanied by an increase in ROS production and lipid peroxidation and a decline in superoxide dismutase activity. Pretreatment with PSO increased viability of cardiomyocytes and decrease the elevated ROS production and lipid peroxidation. Also, PSO was able to restore superoxide dismutase activity. Conclusion: PSO has protective effect against oxidative stress-induced damage in cardiomyocytes and can be considered as a natural cardioprotective agent to prevent cardiovascular diseases. PMID:28265546

  15. Protective effect of pomegranate seed oil against H2O2 -induced oxidative stress in cardiomyocytes

    Directory of Open Access Journals (Sweden)

    Mehdi Bihamta

    2017-01-01

    Full Text Available Objective: It has been well documented that oxidative stress is involved in the pathogenesis of cardiac diseases. Previous studies have shown that pomegranate seed oil (PSO has antioxidant properties. This study was designed to investigate probable protective effects of PSO against hydrogen peroxide (H2O2-induced damage in H9c2 cardiomyocytes.Materials and Methods: The cells were pretreated 24 hr with PSO 1 hr before exposure to 200 µM H2O2. Cell viability was evaluated using 3-(4,5-dimethylthiazol-2-yl-2,5-diphenyl tetrazolium (MTT assay. The level of reactive oxygen species (ROS and lipid peroxidation were measured by fluorimetric methods.Results: H2O2 significantly decreased cell viability which was accompanied by an increase in ROS production and lipid peroxidation and a decline in superoxide dismutase activity. Pretreatment with PSO increased viability of cardiomyocytes and decrease the elevated ROS production and lipid peroxidation. Also, PSO was able to restore superoxide dismutase activity.Conclusion: PSO has protective effect against oxidative stress-induced damage in cardiomyocytes and can be considered as a natural cardioprotective agent to prevent cardiovascular diseases.

  16. Electrocatalysis of Oxygen Evolution Reaction on Ti/SnO2+ RuO2+ MnO2/MnO2 Electrode in Sulfuric Acid Solution

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The Ti-Supported MnO2 electrode was modified by introducing SnO2 +RuO2 +MnO2 as an intermediate layer into the Ti/MnO2 interface. The anodic polarization curves were measured at various temperatures ranging from 30 to 80 ℃ and the activation energy for the oxygen evolution reaction was evaluated. The experimental activation energy increased linearly with increasing the overpotential. The activation energy at the equilibrium potential was linearly correlated with the difference between the crystal field stabilization energies of Mn4+ at initial state and Mn4+ at transition state. The electrocatalysis characteristics of the anode were discussed by means of themechanism of the substitution reaction of the ligand(SN 1 and SN2) and molecular orbital theory.The results show that the anode has better electrocatalystic characteristics.

  17. Extracellular but not cytosolic superoxide dismutase protects against oxidant-mediated endothelial dysfunction

    Directory of Open Access Journals (Sweden)

    Erin L. Foresman

    2013-01-01

    Full Text Available Superoxide (O2•− contributes to the development of cardiovascular disease. Generation of O2•− occurs in both the intracellular and extracellular compartments. We hypothesized that the gene transfer of cytosolic superoxide dismutase (SOD1 or extracellular SOD (SOD3 to blood vessels would differentially protect against O2•−-mediated endothelial-dependent dysfunction. Aortic ring segments from New Zealand rabbits were incubated with adenovirus (Ad containing the gene for Escherichia coli β-galactosidase, SOD1, or SOD3. Activity assays confirmed functional overexpression of both SOD3 and SOD1 isoforms in aorta 24 h following gene transfer. Histochemical staining for β-galactosidase showed gene transfer occurred in the endothelium and adventitia. Next, vessels were prepared for measurement of isometric tension in Kreb's buffer containing xanthine. After precontraction with phenylephrine, xanthine oxidase impaired relaxation to the endothelium-dependent dilator acetylcholine (ACh, max relaxation 33±4% with XO vs. 64±3% without XO, p<0.05, whereas relaxation to the endothelium-independent dilator sodium nitroprusside was unaffected. In the presence of XO, maximal relaxation to ACh was improved in vessels incubated with AdSOD3 (55±2%, p<0.05 vs. control but not AdSOD1 (34±4%. We conclude that adenoviral-mediated gene transfer of SOD3, but not SOD1, protects the aorta from xanthine/XO-mediated endothelial dysfunction. These data provide important insight into the location and enzymatic source of O2•− production in vascular disease.

  18. Adsorption of O2, SO2, and SO3, on nickel oxide - Mechanism for sulfate formation

    Science.gov (United States)

    Mehandru, S. P.; Anderson, A. B.

    1986-01-01

    Calculations based on the atom superposition and electron delocalization molecular orbital technique suggest that O2 will adsorb preferentially end-on at an angle 45 deg from normal on a nickel cation site on the (100) surface of NiO. SO2 adsorption is also stronger on the nickel site; SO2 bonds through the sulfur atom in a plane perpendicular to the surface. Adsorption energies for SO3 on the nickel and oxygen sites are comparable in the preferred orientation in which the SO3 plane is parallel to the surface. The calculations suggest that the strength of adsorption varies as O2 greater than SO2 greater than SO3. On activation, SO3 adsorbed to an O(2-) site forms a trigonal pyramidal SO4 species which yields, with a low barrier, a tetrahedral sulfate anion. Subsequently the anion reorients on the surface. Alternative mechanisms which require the formation of Ni(3+) or O(-) are discussed. NiSO4 thus formed may play a passivating role for the corrosion of Ni at low temperatures in the SO2 + O2 + SO3 atmospheres and an active role at high temperatures, as discussed in the experimental literature.

  19. Synthesis and characterization of a monomeric mutant Cu/Zn superoxide dismutase with partially reconstituted enzymic activity.

    Science.gov (United States)

    Banci, L; Bertini, I; Chiu, C Y; Mullenbach, G T; Viezzoli, M S

    1995-12-15

    A monomeric analog of human Cu/Zn superoxide dismutase (F50E/G51E SOD), previously characterized and found to have reduced enzymic activity, was here further modified by replacing Glu133 with Gln. This substitution does not dramatically affect the coordination geometry at the active site, but enhances enzymic activity, and also increases the affinity for anions at the active site. This behavior parallels earlier published results in which this point mutation was made in the dimeric wild-type enzyme. The analog described here has afforded for the first time a monomeric superoxide dismutase with substantial activity. This point mutation does not significantly influence the protein structure but interactions with anions, including superoxide, are altered with respect to the monomeric form. The present monomeric Glu133Gln mutant has partially restored enzymic activity. The diminished activity of the monomeric analogs is discussed in the light of possible minor structural changes and some of their characteristics are compared with those of naturally occurring mutants associated with various neurological diseases.

  20. Sandwich structure of Pd doped nanostructure TiO2 film as O2 sensor.

    Science.gov (United States)

    Wang, Hairong; Sun, Quantao; Chen, Lei; Zhao, Yulong

    2013-09-01

    In this paper, we investigated the sensing properties of sandwich structure of TiO2/Pd/TiO2 thin films at various operating temperatures and oxygen partial pressures. The nanostructure TiO2 thin films were prepared by the sol-gel method. Various thickness of Pd buried layer was deposited by magnetron sputtering of a pure Pd target. The films were characterized using X-ray diffraction analysis and SEM. It was found that TiO2/Pd/TiO2 thin films have the p-type behavior while the pure TiO2 thin film is n-type semiconductor materials. We found that the structure of TiO2/Pd/TiO2 thin films with 10 s sputtering Pd layer has a better stability at 240 °C.

  1. Synthesis and characterization of TiO2 and Ag/TiO2 nanostructure

    Science.gov (United States)

    Gahlot, Swati; Thakur, Amit Kumar; Kulshrestha, Vaibhav; Shahi, V. K.

    2013-02-01

    Single phase anatase TiO2 nanoparticles were prepared using Titanium tertachloride (TiCl4) as precursor through an inexpensive method. Well dispersed nanocomposites of silver at TiO2 were synthesized successfully by photochemical route. Both TiO2 and Ag/TiO2 were characterized using X-Ray Diffraction (XRD) and transmission electron microscopy (TEM). The particle size of TiO2 is found to be ˜ 11 nm and ˜ 22 nm for Ag/TiO2, by XRD and confirmed by TEM. TEM micrographs also show the single phase crystal of TiO2 and confirm the deposition of silver among TiO2.

  2. SnO2/TiO2 bilayer thin films exhibiting superhydrophilic properties

    Science.gov (United States)

    Talinungsang, Nibedita Paul; Purkayastha, Debarun Dhar

    2017-05-01

    Nanostructured thin films of TiO2, SnO2, and SnO2/TiO2 have been deposited by sol-gel method. The films are characterized by X-ray diffraction, wettability and optical properties. In the present work, we have achieved a way of converting hydrophilic to super-hydrophilic state by incorporating TiO2 buffer layer in between substrate and SnO2 film, which has its utility in anti-fogging surfaces. The decrease in contact angle of water over SnO2/TiO2 bilayer is attributed to the increase in roughness of the film as well as surface energy of the substrate.

  3. Stable compositions and geometrical structures of titanium oxide cluster cations and anions studied by ion mobility mass spectrometry

    Science.gov (United States)

    Ohshimo, Keijiro; Norimasa, Naoya; Moriyama, Ryoichi; Misaizu, Fuminori

    2016-05-01

    Geometrical structures of titanium oxide cluster cations and anions have been investigated by ion mobility mass spectrometry and quantum chemical calculations based on density functional theory. Stable cluster compositions with respect to collision induced dissociation were also determined by changing ion injection energy to an ion drift cell for mobility measurements. The TinO2n-1+ cations and TinO2n- anions were predominantly observed at high injection energies, in addition to TinO2n+ for cations and TinO2n+1- for anions. Collision cross sections of TinO2n+ and TinO2n+1- for n = 1-7, determined by ion mobility mass spectrometry, were compared with those obtained theoretically as orientation-averaged cross sections for the optimized structures by quantum chemical calculations. All of the geometrical structures thus assigned have three-dimensional structures, which are in marked contrast with other oxides of late transition metals. One-oxygen atom dissociation processes from TinO2n+ and TinO2n+1- by collisions were also explained by analysis of spin density distributions.

  4. Effect of rutile phase on V2O5 supported over TiO2 mixed phase for the selective catalytic reduction of NO with NH3

    Science.gov (United States)

    Zhang, Shule; Zhong, Qin; Wang, Yining

    2014-09-01

    A series of V2O5/TiO2 catalysts with different ratios of TiO2 rutile phase was prepared. Focusing on the effect of TiO2 rutile phase on V2O5/TiO2 catalyst for the selective catalytic reduction (SCR) of NO with NH3, the NO conversion for the different catalysts was investigated. The experimental results showed that a small amount of TiO2 rutile phase could improve the NO conversion significantly below 270 °C. Analysis by XRD, NH3-TPD, UV-vis, EPR and DFT calculation showed that the rutile phase of TiO2 supporter decreased the band gap, especially, the conduction band level. It improved the formation of reduced V species and superoxide ions that were important to the low-temperature SCR reaction.

  5. High-reflectivity HfO2/SiO2 ultraviolet mirrors.

    Science.gov (United States)

    Torchio, Philippe; Gatto, Alexandre; Alvisi, Marco; Albrand, Gérard; Kaiser, Norbert; Amra, Claude

    2002-06-01

    High-reflectivity dense multilayer coatings were produced for the ultraviolet spectral region. Thin-film single layers and UV mirrors were deposited by ion plating and plasma ion-assisted deposition high-energetic technologies. Optical characterizations of HfO2 and SiO2 single layers are made. The optical constants obtained for these two materials are presented. HfO2 and SiO2 mirrors with a reflectance of approximately 99% near 250 nm are reported.

  6. Phosphazene-promoted anionic polymerization

    KAUST Repository

    Zhao, Junpeng

    2014-01-01

    In the recent surge of metal-free polymerization techniques, phosphazene bases have shown their remarkable potential as organic promoters/catalysts for the anionic polymerization of various types of monomers. By complexation with the counterion (e.g. proton or lithium cation), phosphazene base significantly improve the nucleophilicity of the initiator/chain-end resulting in rapid and usually controlled anionic/quasi-anionic polymerization. In this review, we will introduce the general mechanism, i.e. in situ activation (of initiating sites) and polymerization, and summarize the applications of such a mechanism on macromolecular engineering toward functionalized polymers, block copolymers and complex macromolecular architectures.

  7. Photoetching of Immobilized TiO2-ENR50-PVC Composite for Improved Photocatalytic Activity

    Directory of Open Access Journals (Sweden)

    M. A. Nawi

    2012-01-01

    Full Text Available Commercially acquired TiO2 photocatalyst (99% anatase powder was mixed with epoxidized natural rubber-50 (ENR50/polyvinyl chloride (PVC blend by ultrasonication and immobilized onto glass plates as TiO2-ENR50-PVC composite via a dip-coating method. Photoetching of the immobilized TiO2-ENR50-PVC composite was investigated under the irradiation of a 45 W compact fluorescent lamp and characterized by chemical oxygen demand (COD analysis, scanning electron microscopy-energy dispersive X-ray (SEM-EDX spectrometry, thermogravimetry analysis (TGA, and fourier transform infrared (FTIR spectroscopy. The BET surface area of the photoetched TiO2 composite was observed to be larger than the original TiO2 powder due to the systematic removal of ENR50 while PVC was retained within the composite. It also exhibited better photocatalytic efficiency than the TiO2 powder in a slurry mode and was highly reproducible and reusable. More than 98% of MB removal was consistently achieved for 10 repeated runs of the photo-etched photocatalyst system. About 93% of the 20 mg L−1 MB was mineralized over a period of 480 min. The presence of SO42−, NO3−, and Cl− anions was detected in the mineralized solution where the solution pH was reduced from 7 to 4.

  8. Doped-TiO2 Photocatalysts and Synthesis Methods to Prepare TiO2 Films

    Institute of Scientific and Technical Information of China (English)

    Ying CUI; Hao DU; Lishi WEN

    2008-01-01

    TiO2 is a promising photocatalyst. However, the low photocatalytic efficiency calls for the modification of TiO2. Metal- and nonmetal-doping of TiO2 have been proved to be effective ways to enhance photocatalytic properties. This review provides a deep insight into the understanding of the metal- and nonmetal-doped TiO2 photocatalysts. This article begins with the introduction of the crystal structures of TiO2 and applications of TiO2 materials. We then reviewed the doped-TiO2 system in two categories: (1) metal-doped TiO2photocatalysts system, and (2) nonmetal-doped TiO2 photocatalysts system. Both experimental results and theoretical analyses are elaborated in this section. In the following part, for the advantages of TiO2 thin films over particles, various preparation methods to obtain TiO2 thin films are briefly discussed. Finally, this review ends with a concise conclusion and outlook of new trends in the development of TiO2-based photocatalysts.

  9. Hazards of TiO2 and amorphous SiO2 nanoparticles

    NARCIS (Netherlands)

    Reijnders, L.; Kahn, H.A.; Arif, I.A.

    2012-01-01

    TiO2 and amorphous SiO2 nanoparticles have been described as ‘safe’, ‘non-toxic’ and ‘environment friendly’ in scientific literature. However, though toxicity data are far from complete, there is evidence that these nanoparticles are hazardous. TiO2 nanoparticles have been found hazardous to humans

  10. Enhanced photocatalytic performances of CeO2/TiO2 nanobelt heterostructures.

    Science.gov (United States)

    Tian, Jian; Sang, Yuanhua; Zhao, Zhenhuan; Zhou, Weijia; Wang, Dongzhou; Kang, Xueliang; Liu, Hong; Wang, Jiyang; Chen, Shaowei; Cai, Huaqiang; Huang, Hui

    2013-11-25

    CeO2 /TiO2 nanobelt heterostructures are synthesized via a cost-effective hydrothermal method. The as-prepared nanocomposites consist of CeO2 nanoparticles assembled on the rough surface of TiO2 nanobelts. In comparison with P25 TiO2 colloids, surface-coarsened TiO2 nanobelts, and CeO2 nanoparticles, the CeO2 /TiO2 nanobelt heterostructures exhibit a markedly enhanced photocatalytic activity in the degradation of organic pollutants such as methyl orange (MO) under either UV or visible light irradiation. The enhanced photocatalytic performance is attributed to a novel capture-photodegradation-release mechanism. During the photocatalytic process, MO molecules are captured by CeO2 nanoparticles, degraded by photogenerated free radicals, and then released to the solution. With its high degradation efficiency, broad active light wavelength, and good stability, the CeO2 /TiO2 nanobelt heterostructures represent a new effective photocatalyst that is low-cost, recyclable, and will have wide application in photodegradation of various organic pollutants. The new capture-photodegradation-release mechanism for improved photocatalysis properties is of importance in the rational design and synthesis of new photocatalysts.

  11. Hazards of TiO2 and amorphous SiO2 nanoparticles

    NARCIS (Netherlands)

    Reijnders, L.; Kahn, H.A.; Arif, I.A.

    2012-01-01

    TiO2 and amorphous SiO2 nanoparticles have been described as ‘safe’, ‘non-toxic’ and ‘environment friendly’ in scientific literature. However, though toxicity data are far from complete, there is evidence that these nanoparticles are hazardous. TiO2 nanoparticles have been found hazardous to humans

  12. TiO2 ve ZrO2/TiO2 Kompozit Mikrokürecik Sentezi ve Metilen Mavisinin Degradasyonunda Fotokatalitik Aktiviteleri

    OpenAIRE

    Vaizoğulları, Ali İmran; Balcı, Ahmet; Uğurlu, Mehmet; KARAOĞLU, Muhammet Hamdi

    2016-01-01

    TiO2 and ZrO2/TiO2 composite microsphere particles were synthesized using the sol‐gel method. Photoactivity of TiO2 and ZrO2/TiO2 were compared.  Particles were characterized using X‐ray diffraction (XRD), infrared spectroscopy (FTIR), scanning electron microscopy (SEM) of X‐ray (EDAX), and transmission electron microscopy (TEM). The study revealed that TiO2 particles were microspheres.    The decorating of ZrO2 particles on TiO2 surface was successfully carried out that was pr...

  13. Synthesis of TiO2 and ZrO2/TiO2 Composite Microspheres and Their Photo‐Catalytic Degradation of Methylene Blue

    OpenAIRE

    Vaizoğulları, Ali İmran; Balcı, Ahmet; UĞURLU, Mehmet; Karaoğlu, Muhammet Hamdi

    2016-01-01

    TiO2 and ZrO2/TiO2 composite microsphere particles were synthesized using the sol‐gel method. Photoactivity of TiO2 and ZrO2/TiO2 were compared.  Particles were characterized using X‐ray diffraction (XRD), infrared spectroscopy (FTIR), scanning electron microscopy (SEM) of X‐ray (EDAX), and transmission electron microscopy (TEM). The study revealed that TiO2 particles were microspheres.    The decorating of ZrO2 particles on TiO2 surface was successfully carried out that was pr...

  14. Photocatalytic Degradation of Caffeine with Synthetized Catalyst ZrO2-TiO2%复合光催化剂ZrO2-TiO2催化降解咖啡因的试验研究

    Institute of Scientific and Technical Information of China (English)

    蔡磊; 韩旭; 邓慧萍

    2013-01-01

    The composite photocatalyst ZrO2-TiO2 was successfully synthesized using the sol-gel impregnation method. The photocatalytic degradation kinetics of caffeine with synthetized ZrO2-TiO2 was investigated under different initial concentration,photocatalyst dose,inorganic anions. The results indicated that degradation rate was quicker when the initial concentration was lower,and the optimal photocatalyst dose at highest efficiency was 0.5 g/L . Four inorganic anions,including CO32-,SO42-,Cl-,PO43-,inhibited the photocatalytic degradation of caffeine, and their inhibition effects followed the order of CO32->PO43->SO42->Cl-.%采用溶液凝胶浸渍法制备了复合光催化剂ZrO2-TiO2,研究了不同咖啡因初始浓度、复合光催化剂投加量、无机阴离子条件下对光催化降解咖啡因动力学过程的影响.结果表明,咖啡因初始浓度越低,降解速率越快,复合催化剂的最佳投加量为0.5 g/L .投加CO32-、SO42-、Cl-、PO43-四种无机阴离子的钠盐后,光催化反应的速率都受到了抑制,其抑制作用顺序为CO32->PO43->SO42->Cl-.

  15. Using Distonic Radical Ions to Probe the Chemistry of Key Combustion Intermediates: The Case of the Benzoxyl Radical Anion

    Science.gov (United States)

    Li, Cong; Lam, Adrian K. Y.; Khairallah, George N.; White, Jonathan M.; O'Hair, Richard A. J.; da Silva, Gabriel

    2013-04-01

    The benzoxyl radical is a key intermediate in the combustion of toluene and other aromatic hydrocarbons, yet relatively little experimental work has been performed on this species. Here, a combination of electrospray ionization (ESI), multistage mass spectrometry experiments, and density functional theory (DFT) calculations are used to examine the formation and fragmentation of a benzoxyl (benzyloxyl) distonic radical anion. Excited 4-carboxylatobenzoxyl radical anions were produced via two methods: (1) collision induced dissociation (CID) of the nitrate ester 4-(nitrooxymethyl)benzoate, -O2CC6H4CH2ONO2, and (2) reaction of ozone with the 4-carboxylatobenzyl radical anion, -O2CC6H4CH2 •. In neither case was the stabilized -O2CC6H4CH2O• radical anion intermediate detected. Instead, dissociation products at m/ z 121 and 149 were observed. These products are attributed to benzaldehyde (O2 -CC6H4CHO) and benzene (-O2CC6H5) products from respective loss of H and HCO radicals in the vibrationally excited benzoxyl intermediate. In no experiments was a product at m/ z 120 (i.e., -O2CC6H4 •) detected, corresponding to absence of the commonly assumed phenyl radical + CH2=O channel. The results reported suggest that distonic ions are useful surrogates for reactive intermediates formed in combustion chemistry.

  16. SiO2 and TiO2 nanoparticles synergistically trigger macrophage inflammatory responses.

    Science.gov (United States)

    Tsugita, Misato; Morimoto, Nobuyuki; Nakayama, Masafumi

    2017-04-11

    Silicon dioxide (SiO2) nanoparticles (NPs) and titanium dioxide (TiO2) NPs are the most widely used inorganic nanomaterials. Although the individual toxicities of SiO2 and TiO2 NPs have been extensively studied, the combined toxicity of these NPs is much less understood. In this study, we observed unexpected and drastic activation of the caspase-1 inflammasome and production of IL-1β in mouse bone marrow-derived macrophages stimulated simultaneously with SiO2 and TiO2 NPs at concentrations at which these NPs individually do not cause macrophage activation. Consistent with this, marked lung inflammation was observed in mice treated intratracheally with both SiO2 and TiO2 NPs. In macrophages, SiO2 NPs localized in lysosomes and TiO2 NPs did not; while only TiO2 NPs produced ROS, suggesting that these NPs induce distinct cellular damage leading to caspase-1 inflammasome activation. Intriguingly, dynamic light scattering measurements revealed that, although individual SiO2 and TiO2 NPs immediately aggregated to be micrometer size, the mixture of these NPs formed a stable and relatively monodisperse complex with a size of ~250 nm in the presence of divalent cations. Taken together, these results suggest that SiO2 and TiO2 NPs synergistically induce macrophage inflammatory responses and subsequent lung inflammation. Thus, we propose that it is important to assess the synergistic toxicity of various combinations of nanomaterials.

  17. Pentaarylfullerenes as noncoordinating cyclopentadienyl anions

    NARCIS (Netherlands)

    Bouwkamp, Marco W.; Meetsma, Auke

    2009-01-01

    The first example of an early-transition-metal complex involving a pentaarylfullerene was prepared. Instead of half-sandwich complexes, solvent separated ion pairs were obtained in which the pentaarylfullerene moiety acts as noncoordinating cyclopentadienyl anion.

  18. The detailed crystal and electronic structures of the cotunnite-type ZrO2

    Science.gov (United States)

    Zhang, Yan; Duan, Li; Ji, Vincent

    2016-07-01

    The detailed crystal and orbital-decomposed electronic structures of cotunnite-type ZrO2 have been investigated by using the first-principles projector augmented wave (PAW) potential within the generalized gradient approximation as well as taking into account on-site Coulomb repulsive interaction (GGA+U). The optimized structure shows that the OI and OII anions are surrounded by an arbitrary tetrahedron of four Zr cations and an arbitrary pentahedron of five Zr cations, respectively, in turn, the Zr cation is surrounded by an arbitrary tetrakaidecahedron formed by nine oxygen ligands. Although one more Zr cation is coordinated to OII, the larger bond lengths between OII and its adjacent five Zr cations (dOII-Zr) than those between OI and its adjacent four Zr cations (dOI-Zr) makes density of states (DOS) of s and three p (px , py and pz) states of the OII anion driving down in lower energy region and driving up in higher energy region. No crystal-field splitting is observed between three p (px , py and pz) states of anions OI and OII (between three p (px , py and pz) states and five d (dxy , dyz , dxz , dz2 and dx2-y2) states of cation Zr) is resulted from the arrangements of the surrounding cations (anions) do not have any symmetry. The additional covalent character upon Zr-O ionic bonds is attributed to the hybridization of itinerant Zr(5s) and less filled Zr(4d) states to the separated O(2s) and O(2p) states.

  19. Subsarcolemmal and interfibrillar mitochondria display distinct superoxide production profiles.

    Science.gov (United States)

    Crochemore, C; Mekki, M; Corbière, C; Karoui, A; Noël, R; Vendeville, C; Vaugeois, J-M; Monteil, C

    2015-03-01

    Cardiac subsarcolemmal mitochondria (SSM) and interfibrillar mitochondria (IFM) subpopulations display distinct biochemical, morphological, and functional characteristics. Moreover, they appear to be differently influenced during cardiac pathologies or toxic injuries. Although mitochondrial reactive oxygen species seem to play a critical role in cardiac function and diseases, limited information exists about the superoxide production characteristics of these mitochondrial subpopulations. In this work, using direct measurement of superoxide by electron paramagnetic resonance, we showed that differences in superoxide production profiles were present between cardiac IFM and SSM, in terms of intensity and major sites of superoxide generation. In SSM incubated with glutamate plus malate as substrates, the total observed superoxide levels were significantly higher than those observed with IFM, with an important contribution of the NADH-oxidizing site of complex I (site If) and the quinol-oxidizing site of complex III (site IIIQ0). In both IFM and SSM, succinate leads to similar rates of total superoxide levels with a substantial role for contribution of reverse electron transfer. Finally, using two spin probes with different membrane permeabilities, our data on complex III showed direct intra- and extra-mitochondrial superoxide release whereas complex I- and II-dependent superoxide were exclusively released inside the mitochondria, confirming previous studies. Feasibility of this approach to measure intra- and extra-mitochondrial superoxide levels and to characterize distinct superoxide production profiles of cardiac IFM and SSM has been demonstrated.

  20. Localization and distribution of superoxide dismutase-1 in the neural tube morphogenesis of chick embryo.

    Science.gov (United States)

    Dhage, Prajakta A; Kamble, Lekha K; Bhargava, Shobha Y

    2017-02-01

    Superoxide dismutase 1 (SOD- 1) is an antioxidant enzyme that regulates the levels of Reactive oxygen species (ROS) by catalyzing the conversion of superoxide radical into hydrogen peroxide (H2O2) and oxygen. ROS are known to play a significant role in various cellular processes, via redox modification of a variety of molecules that participate in signaling pathways involved in this processes. As the levels of ROS in cells are controlled by the levels of antioxidant enzymes, thus SOD-1 may be indirectly involved in regulating different cellular processes by maintaining the required levels of H2O2. Therefore, in the present study we have investigated the possible involvement of SOD- 1 in the neurulation during the development of chick embryo. During gastrulation, SOD- 1 immunoreactivity was observed throughout the ectoderm and cauda mesoderm areas, however, its presence during neurulation was restricted to certain areas of neural tube particularly in the dorsal neural tube where neural tube closure takes place. Assaying enzyme activity revealed a significant increase in the SOD activity during neurulation. Further, inhibition of SOD- 1 by Diethyldithiocarbamate (DDC) induced abnormalities in the development of the neural tube. SOD- 1 inhibition specifically affected the closure of neural tube in the anterior region. Thus, here we report the presence of SOD- 1 mainly in the ectoderm and tissues of ectodermal origin during gastrulation to neurulation which suggests that it may be involved in the regulating the cellular processes during neural tube morphogenesis.

  1. Cellular detection of 50 Hz magnetic fields and weak blue light: effects on superoxide levels and genotoxicity.

    Science.gov (United States)

    Höytö, Anne; Herrala, Mikko; Luukkonen, Jukka; Juutilainen, Jukka; Naarala, Jonne

    2017-06-01

    We tested the hypothesis that the effects of 50 Hz magnetic fields (MFs) on superoxide levels and genotoxicity depend on the presence of blue light. Human SH-SY5Y neuroblastoma cells were exposed to a 50 Hz, 100 μT MF with or without non-phototoxic level of blue light for 24 h. We also studied whether these treatments alter responses to menadione, an agent that induces mitochondrial superoxide (O2(• -)) production and DNA damage. Micronuclei, proliferation, viability, cytosolic and mitochondrial O2(• -) levels were assessed. MF (without blue light) increased cytosolic O2(• -) production and blue light suppressed this effect. Mitochondrial O2(• -) production was reduced by both MF and blue light, but these effects were not additive. Micronucleus frequency was not affected by blue light or MF alone, but blue light (significantly when combined with MF) enhanced menadione-induced micronuclei. The original simple hypothesis (blue light is needed for MF effects) was not supported, but interaction of MF and blue light was nevertheless observed. The results are consistent with MF effects on light-independent radical reactions.

  2. Nanocrystalline TiO2/SnO2 heterostructures for gas sensing.

    Science.gov (United States)

    Lyson-Sypien, Barbara; Kusior, Anna; Rekas, Mieczylaw; Zukrowski, Jan; Gajewska, Marta; Michalow-Mauke, Katarzyna; Graule, Thomas; Radecka, Marta; Zakrzewska, Katarzyna

    2017-01-01

    The aim of this research is to study the role of nanocrystalline TiO2/SnO2 n-n heterojunctions for hydrogen sensing. Nanopowders of pure SnO2, 90 mol % SnO2/10 mol % TiO2, 10 mol % SnO2/90 mol % TiO2 and pure TiO2 have been obtained using flame spray synthesis (FSS). The samples have been characterized by BET, XRD, SEM, HR-TEM, Mössbauer effect and impedance spectroscopy. Gas-sensing experiments have been performed for H2 concentrations of 1-3000 ppm at 200-400 °C. The nanomaterials are well-crystallized, anatase TiO2, rutile TiO2 and cassiterite SnO2 polymorphic forms are present depending on the chemical composition of the powders. The crystallite sizes from XRD peak analysis are within the range of 3-27 nm. Tin exhibits only the oxidation state 4+. The H2 detection threshold for the studied TiO2/SnO2 heterostructures is lower than 1 ppm especially in the case of SnO2-rich samples. The recovery time of SnO2-based heterostructures, despite their large responses over the whole measuring range, is much longer than that of TiO2-rich samples at higher H2 flows. TiO2/SnO2 heterostructures can be intentionally modified for the improved H2 detection within both the small (1-50 ppm) and the large (50-3000 ppm) concentration range. The temperature Tmax at which the semiconducting behavior begins to prevail upon water desorption/oxygen adsorption depends on the TiO2/SnO2 composition. The electrical resistance of sensing materials exhibits a power-law dependence on the H2 partial pressure. This allows us to draw a conclusion about the first step in the gas sensing mechanism related to the adsorption of oxygen ions at the surface of nanomaterials.

  3. Nanocrystalline TiO2/SnO2 heterostructures for gas sensing

    Science.gov (United States)

    Kusior, Anna; Rekas, Mieczylaw; Zukrowski, Jan; Gajewska, Marta; Michalow-Mauke, Katarzyna; Graule, Thomas; Radecka, Marta; Zakrzewska, Katarzyna

    2017-01-01

    The aim of this research is to study the role of nanocrystalline TiO2/SnO2 n–n heterojunctions for hydrogen sensing. Nanopowders of pure SnO2, 90 mol % SnO2/10 mol % TiO2, 10 mol % SnO2/90 mol % TiO2 and pure TiO2 have been obtained using flame spray synthesis (FSS). The samples have been characterized by BET, XRD, SEM, HR-TEM, Mössbauer effect and impedance spectroscopy. Gas-sensing experiments have been performed for H2 concentrations of 1–3000 ppm at 200–400 °C. The nanomaterials are well-crystallized, anatase TiO2, rutile TiO2 and cassiterite SnO2 polymorphic forms are present depending on the chemical composition of the powders. The crystallite sizes from XRD peak analysis are within the range of 3–27 nm. Tin exhibits only the oxidation state 4+. The H2 detection threshold for the studied TiO2/SnO2 heterostructures is lower than 1 ppm especially in the case of SnO2-rich samples. The recovery time of SnO2-based heterostructures, despite their large responses over the whole measuring range, is much longer than that of TiO2-rich samples at higher H2 flows. TiO2/SnO2 heterostructures can be intentionally modified for the improved H2 detection within both the small (1–50 ppm) and the large (50–3000 ppm) concentration range. The temperature T max at which the semiconducting behavior begins to prevail upon water desorption/oxygen adsorption depends on the TiO2/SnO2 composition. The electrical resistance of sensing materials exhibits a power-law dependence on the H2 partial pressure. This allows us to draw a conclusion about the first step in the gas sensing mechanism related to the adsorption of oxygen ions at the surface of nanomaterials. PMID:28144570

  4. Oxidation of silicon surface with atomic oxygen radical anions

    Institute of Scientific and Technical Information of China (English)

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