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Sample records for active oxygen complex

  1. Oxygen activation with transition metal complexes in aqueous solution

    SciTech Connect

    Bakac, Andreja

    2010-04-12

    Coordination to transition-metal complexes changes both the thermodynamics and kinetics of oxygen reduction. Some of the intermediates (superoxo, hydroperoxo, and oxo species) are close analogues of organic oxygen-centered radicals and peroxides (ROO{sm_bullet}, ROOH, and RO{sm_bullet}). Metal-based intermediates are typically less reactive, but more persistent, than organic radicals, which makes the two types of intermediates similarly effective in their reactions with various substrates. The self-exchange rate constant for hydrogen-atom transfer for the couples Cr{sub aq}OO{sup 2+}/Cr{sub aq}OOH{sup 2+} and L{sup 1}(H{sub 2}O)RhOO{sup 2+}/L{sup 1}(H{sub 2}O)RhOOH{sup 2+} was estimated to be 10{sup 1 {+-} 1} M{sup -1} s{sup -1}. The use of this value in the simplified Marcus equation for the Cr{sub aq}O{sup 2+}/Cr{sub aq}OOH{sup 2+} cross reaction provided an upper limit k{sub CrO,CrOH} {le} 10{sup (-2{+-}1)} M{sup -1} s{sup -1} for Cr{sub aq}O{sup 2+}/Cr{sub aq}OH{sup 2+} self-exchange. Even though superoxo complexes react very slowly in bimolecular self-reactions, extremely fast cross reactions with organic counterparts, i.e., acylperoxyl radicals, have been observed. Many of the intermediates generated by the interaction of O{sub 2} with reduced metal complexes can also be accessed by alternative routes, both thermal and photochemical.

  2. A ligand field chemistry of oxygen generation by the oxygen-evolving complex and synthetic active sites

    PubMed Central

    Betley, Theodore A; Surendranath, Yogesh; Childress, Montana V; Alliger, Glen E; Fu, Ross; Cummins, Christopher C; Nocera, Daniel G

    2007-01-01

    Oxygen–oxygen bond formation and O2 generation occur from the S4 state of the oxygen-evolving complex (OEC). Several mechanistic possibilities have been proposed for water oxidation, depending on the formal oxidation state of the Mn atoms. All fall under two general classifications: the AB mechanism in which nucleophilic oxygen (base, B) attacks electrophilic oxygen (acid, A) of the Mn4Ca cluster or the RC mechanism in which radical-like oxygen species couple within OEC. The critical intermediate in either mechanism involves a metal oxo, though the nature of this oxo for AB and RC mechanisms is disparate. In the case of the AB mechanism, assembly of an even-electron count, high-valent metal-oxo proximate to a hydroxide is needed whereas, in an RC mechanism, two odd-electron count, high-valent metal oxos are required. Thus the two mechanisms give rise to very different design criteria for functional models of the OEC active site. This discussion presents the electron counts and ligand geometries that support metal oxos for AB and RC O–O bond-forming reactions. The construction of architectures that bring two oxygen functionalities together under the purview of the AB and RC scenarios are described. PMID:17971328

  3. Developing mononuclear copper-active-oxygen complexes relevant to reactive intermediates of biological oxidation reactions.

    PubMed

    Itoh, Shinobu

    2015-07-21

    Active-oxygen species generated on a copper complex play vital roles in several biological and chemical oxidation reactions. Recent attention has been focused on the reactive intermediates generated at the mononuclear copper active sites of copper monooxygenases such as dopamine β-monooxygenase (DβM), tyramine β-monooxygenase (TβM), peptidylglycine-α-hydroxylating monooxygenase (PHM), and polysaccharide monooxygenases (PMO). In a simple model system, reaction of O2 and a reduced copper(I) complex affords a mononuclear copper(II)-superoxide complex or a copper(III)-peroxide complex, and subsequent H(•) or e(-)/H(+) transfer, which gives a copper(II)-hydroperoxide complex. A more reactive species such as a copper(II)-oxyl radical type species could be generated via O-O bond cleavage of the peroxide complex. However, little had been explored about the chemical properties and reactivity of the mononuclear copper-active-oxygen complexes due to the lack of appropriate model compounds. Thus, a great deal of effort has recently been made to develop efficient ligands that can stabilize such reactive active-oxygen complexes in synthetic modeling studies. In this Account, I describe our recent achievements of the development of a mononuclear copper(II)-(end-on)superoxide complex using a simple tridentate ligand consisting of an eight-membered cyclic diamine with a pyridylethyl donor group. The superoxide complex exhibits a similar structure (four-coordinate tetrahedral geometry) and reactivity (aliphatic hydroxylation) to those of a proposed reactive intermediate of copper monooxygenases. Systematic studies based on the crystal structures of copper(I) and copper(II) complexes of the related tridentate supporting ligands have indicated that the rigid eight-membered cyclic diamine framework is crucial for controlling the geometry and the redox potential, which are prerequisites for the generation of such a unique mononuclear copper(II)-(end-on)superoxide complex

  4. Oxygen activation and intramolecular C-H bond activation by an amidate-bridged diiron(II) complex.

    PubMed

    Jones, Matthew B; Hardcastle, Kenneth I; Hagen, Karl S; MacBeth, Cora E

    2011-07-18

    A diiron(II) complex containing two μ-1,3-(κN:κO)-amidate linkages has been synthesized using the 2,2',2''-tris(isobutyrylamido)triphenylamine (H(3)L(iPr)) ligand. The resulting diiron complex, 1, reacts with dioxygen (or iodosylbenzene) to effect intramolecular C-H bond activation at the methine position of the ligand isopropyl group. The ligand-activated product, 2, has been isolated and characterized by a variety of methods including X-ray crystallography. Electrospray ionization mass spectroscopy of 2 prepared from(18)O(2) was used to confirm that the oxygen atom incorporated into the ligand framework is derived from molecular oxygen. PMID:21667986

  5. Photocytotoxic activity of a nitrosyl phthalocyanine ruthenium complex--a system capable of producing nitric oxide and singlet oxygen.

    PubMed

    Carneiro, Zumira Aparecida; de Moraes, Juliana Cristina Biazzotto; Rodrigues, Fernando Postalli; de Lima, Renata Galvão; Curti, Carlos; da Rocha, Zênis Novaes; Paulo, Michele; Bendhack, Lusiane Maria; Tedesco, Antonio Claudio; Formiga, André Luiz Barboza; da Silva, Roberto Santana

    2011-08-01

    The synthesis, structural aspects, pharmacological assays, and in vitro photoinduced cytotoxic properties of [Ru(NO)(ONO)(pc)] (pc=phthalocyanine) are described. Its biological effect on the B16F10 cell line was studied in the presence and absence of visible light irradiation. At comparable irradiation levels, [Ru(NO)(ONO)(pc)] was more effective than [Ru(pc)] at inhibiting cell growth, suggesting that occurrence of nitric oxide release following singlet oxygen production upon light irradiation may be an important mechanism by which the nitrosyl ruthenium complex exhibits enhanced biological activity in cells. Following visible light activation, the [Ru(NO)(ONO)(pc)] complex displayed increased potency in B16F10 cells upon modifications to the photoinduced dose; indeed, enhanced potency was detected when the nitrosyl ruthenium complex was encapsulated in a drug delivery system. The liposome containing the [Ru(NO)(ONO)(pc)] complex was over 25% more active than the corresponding ruthenium complex in phosphate buffer solution. The activity of the complex was directly proportional to the ruthenium amount present inside the cell, as determined by inductively coupled plasma mass spectroscopy. Flow cytometry analysis revealed that the photocytotoxic activity was mainly due to apoptosis. Furthermore, the vasorelaxation induced by [Ru(NO)(ONO)(pc)], proposed as NO carrier, was studied in rat isolated aorta. The observed vasodilation was concentration-dependent. Taken together, the present findings demonstrate that the [Ru(NO)(ONO)(pc)] complex induces vascular relaxation and could be a potent anti-tumor agent. Nitric oxide release following singlet oxygen production upon visible light irradiation on a nitrosyl ruthenium complex produces two radicals and may elicit phototoxic responses that may find useful applications in photodynamic therapy. PMID:21726765

  6. Polydopamine-Coated Manganese Complex/Graphene Nanocomposite for Enhanced Electrocatalytic Activity Towards Oxygen Reduction

    PubMed Central

    Parnell, Charlette M.; Chhetri, Bijay; Brandt, Andrew; Watanabe, Fumiya; Nima, Zeid A.; Mudalige, Thilak K.; Biris, Alexandru S.; Ghosh, Anindya

    2016-01-01

    Platinum electrodes are commonly used electrocatalysts for oxygen reduction reactions (ORR) in fuel cells. However, this material is not economical due to its high cost and scarcity. We prepared an Mn(III) catalyst supported on graphene and further coated with polydopamine, resulting in superior ORR activity compared to the uncoated PDA structures. During ORR, a peak potential at 0.433 V was recorded, which is a significant shift compared to the uncoated material’s −0.303 V (both versus SHE). All the materials reduced oxygen in a wide pH range via a four-electron pathway. Rotating disk electrode and rotating ring disk electrode studies of the polydopamine-coated material revealed ORR occurring via 4.14 and 4.00 electrons, respectively. A rate constant of 6.33 × 106 mol−1s−1 was observed for the polydopamine-coated material–over 4.5 times greater than the uncoated nanocomposite and superior to those reported for similar carbon-supported metal catalysts. Simply integrating an inexpensive bioinspired polymer coating onto the Mn-graphene nanocomposite increased ORR performance significantly, with a peak potential shift of over +730 mV. This indicates that the material can reduce oxygen at a higher rate but with lower energy usage, revealing its excellent potential as an ORR electrocatalyst in fuel cells. PMID:27528439

  7. Polydopamine-Coated Manganese Complex/Graphene Nanocomposite for Enhanced Electrocatalytic Activity Towards Oxygen Reduction.

    PubMed

    Parnell, Charlette M; Chhetri, Bijay; Brandt, Andrew; Watanabe, Fumiya; Nima, Zeid A; Mudalige, Thilak K; Biris, Alexandru S; Ghosh, Anindya

    2016-01-01

    Platinum electrodes are commonly used electrocatalysts for oxygen reduction reactions (ORR) in fuel cells. However, this material is not economical due to its high cost and scarcity. We prepared an Mn(III) catalyst supported on graphene and further coated with polydopamine, resulting in superior ORR activity compared to the uncoated PDA structures. During ORR, a peak potential at 0.433 V was recorded, which is a significant shift compared to the uncoated material's -0.303 V (both versus SHE). All the materials reduced oxygen in a wide pH range via a four-electron pathway. Rotating disk electrode and rotating ring disk electrode studies of the polydopamine-coated material revealed ORR occurring via 4.14 and 4.00 electrons, respectively. A rate constant of 6.33 × 10(6) mol(-1)s(-1) was observed for the polydopamine-coated material-over 4.5 times greater than the uncoated nanocomposite and superior to those reported for similar carbon-supported metal catalysts. Simply integrating an inexpensive bioinspired polymer coating onto the Mn-graphene nanocomposite increased ORR performance significantly, with a peak potential shift of over +730 mV. This indicates that the material can reduce oxygen at a higher rate but with lower energy usage, revealing its excellent potential as an ORR electrocatalyst in fuel cells. PMID:27528439

  8. Order of Activity of Nitrogen, Iron Oxide, and FeNx Complexes towards Oxygen Reduction in Alkaline Medium.

    PubMed

    Zhu, Yansong; Zhang, Bingsen; Wang, Da-Wei; Su, Dang Sheng

    2015-12-01

    In alkaline medium, it seems that both metal-free and iron-containing carbon-based catalysts, such as nitrogen-doped nanocarbon materials, FeOx -doped carbon, and Fe/N/C catalysts, are active for the oxygen reduction reaction (ORR). However, the order of activity of these different active compositions has not been clearly determined. Herein, we synthesized nitrogen-doped carbon black (NCB), Fe3 O4 /CB, Fe3 O4 /NCB, and FeN4 /CB. Through the systematic study of the ORR catalytic activity of these four catalysts in alkaline solution, we confirmed the difference in the catalytic activity and catalytic mechanism for nitrogen, iron oxides, and Fe-N complexes, respectively. In metal-free NCB, nitrogen can improve the ORR catalytic activity with a four-electron pathway. Fe3 O4 /CB catalyst did not exhibit improved activity over that of NCB owing to the poor conductivity and spinel structure of Fe3 O4 . However, FeN4 coordination compounds as the active sites showed excellent ORR catalytic activity. PMID:26609795

  9. Cobalt(II) Ammine Complexes as Reversible Absorbers of Oxygen.

    ERIC Educational Resources Information Center

    Saito, Kazuo; Ogino, Kazuko

    1988-01-01

    Describes experiments designed to measure the oxygen content in the atmosphere and related areas in the high school laboratories. Considers the application of these activities to other programs. Includes a description of the binuclear complex and recommended procedures. (CW)

  10. Singlet Oxygen Generation by Cyclometalated Complexes and Applications†

    PubMed Central

    Ashen-Garry, David; Selke, Matthias

    2014-01-01

    While cyclometalated complexes have been extensively studied for optoelectronic applications, these compounds also represent a relatively new class of photosensitizers for the production of singlet oxygen. Thus far, singlet oxygen generation from cyclometalated Ir and Pt complexes has been studied in detail. In this review, photophysical data for singlet oxygen generation from these complexes is presented, and the mechanism of 1O2 generation is discussed, including evidence for singlet oxygen generation via an electron transfer mechanism for some of cyclometalated Ir complexes. The period from the first report of singlet oxygen generation by a cyclometalated Ir complex in 2002 through August 2013 is covered in this review. This new class of singlet oxygen photosensitizers may prove to be rather versatile due to the ease of substitution of ancillary ligands without loss of activity. Several cyclometalated complexes have been tethered to zeolites, polystyrene, or quantum dots. Applications for photooxygenation of organic molecules, including “traditional” singlet oxygen reactions (ene reaction, [4+2] and [2+2] cycloadditions) as well as oxidative coupling of amines are presented. Potential biomedical applications are also reviewed. PMID:24344628

  11. Evolution, atmospheric oxygen, and complex disease.

    PubMed

    Koch, Lauren Gerard; Britton, Steven L

    2007-08-20

    If evolution is an accurate statement of our biology, then disease must be tightly associated with its patterns. We considered selection for more optimal capacity for energy transfer as the most general pattern of evolution. From this, we propose that the etiology of complex disease is linked tightly to the evolutionary transition to cellular complexity that was afforded by the steep thermodynamic gradient of an oxygen atmosphere. In accord with this thesis, clinical studies reveal a strong statistical link between low aerobic capacity and all-cause mortality. In addition, large-scale unbiased network analyses demonstrate the pivotal role of oxygen metabolism in cellular function. The demonstration that multiple disease risks segregated during two-way artificial selection for low and high aerobic capacity in rats provides a remote test of these possible connections between evolution, oxygen metabolism, and complex disease. Even more broadly, an atmosphere with oxygen may be uniquely essential for development of complex life anywhere because oxygen is stable as a diatomic gas, is easily transported, and has a high electronegativity for participation in energy transfer via redox reactions. PMID:17473218

  12. Oxidorhenium(V) Complexes with Tetradentate Iminophenolate Ligands: Influence of Ligand Flexibility on the Coordination Motif and Oxygen-Atom-Transfer Activity.

    PubMed

    Zwettler, Niklas; Schachner, Jörg A; Belaj, Ferdinand; Mösch-Zanetti, Nadia C

    2016-06-20

    The synthesis of oxidorhenium(V) complexes 1-3 coordinated by tetradentate iminophenolate ligands H2L1-H2L3 bearing backbones of different rigidity (alkyl, cycloalkyl, and phenyl bridges) allows for the formation of distinct geometric isomers, including a symmetric trans-oxidochlorido coordination motif in complex 3. The complex employing a cycloalkyl-bridged ligand (2) of intermediate rigidity exhibits an interesting solvent- and temperature-dependent equilibrium between a symmetric (trans) isomer and an asymmetric (cis) isomer in solution. The occurrence of a symmetric isomer for 2 and 3 is confirmed by single-crystal X-ray diffraction analysis. Chlorido abstraction from 2 with AgOTf yields the corresponding cationic complex 2a, which does not exhibit an isomeric equilibrium in solution but adopts the isomeric form predominant for 2 in a given solvent. All complexes were, furthermore, employed in three benchmark oxygen-atom-transfer (OAT) reactions, namely, the reduction of perchlorate, the epoxidation of cyclooctene, and OAT from dimethyl sulfoxide (DMSO) to triphenylphosphane (PPh3), to assess the influence of the isomeric structure on the reactivity in these reactions. In perchlorate reduction, a clear structural influence was observed, where the trans arrangement in 3 led to the complete absence of activity. In the epoxidation reaction, all complexes led to comparable epoxide yields, albeit higher catalytic activity but lower overall stability of the catalysts with a trans arrangement was observed. In OAT from DMSO to PPh3, also a clear structural dependence was observed, where the trans complex 3 led to full phosphane conversion with an excess of oxidant, while the cis compound 1 was completely inactive. PMID:27251591

  13. Synergistic activities of a silver(I) glutamic acid complex and reactive oxygen species (ROS): a novel antimicrobial and chemotherapeutic agent.

    PubMed

    Batarseh, K I; Smith, M A

    2012-01-01

    The antimicrobial and chemotherapeutic activities of a silver(I) glutamic acid complex with the synergistic concomitant generation of reactive oxygen species (ROS) were investigated here. The ROS generation system employed was via Fenton chemistry. The antimicrobial and chemotherapeutic activities were investigated on Staphylococcus aureus ATCC 43300 and Escherichia coli bacteria, and Vero and MCF-7 tumor cell lines, respectively. Antimicrobial activities were conducted by determining minimum inhibitory concentration (MIC), while chemotherapeutic efficacies were done by serial dilution using standard techniques to determine the half maximal inhibitory concentration (IC50). The antimicrobial and chemotherapeutic results obtained were compared with positive control drugs gentamicin, oxacillin, penicillin, streptomycin and cisplatin, a ubiquitously used platinum-based antitumor drug, and with the silver(I) glutamic acid complex and hydrogen peroxide separately. Based on MIC and IC50 values, it was determined that this synergistic approach was very effective at extremely low concentrations, especially when compared with the other drugs evaluated here. This finding might be of great significance regarding metronomic dosing when this synergistic approach is clinically implemented. Since silver at low concentrations exhibits no toxic, mutagenic and carcinogenic activities, this might offer an alternative approach for the development of safer silver-based antimicrobial and chemotherapeutic drugs, thereby reducing or even eliminating the toxicity associated with current drugs. Accordingly, the present approach might be integrated into the systemic clinical treatment of infectious diseases and cancer. PMID:22680634

  14. Design of a highly efficient and wide pH electro-Fenton oxidation system with molecular oxygen activated by ferrous-tetrapolyphosphate complex.

    PubMed

    Wang, Li; Cao, Menghua; Ai, Zhihui; Zhang, Lizhi

    2015-03-01

    In this study, a novel electro-Fenton (EF) system was developed with iron wire, activated carbon fiber, and sodium tetrapolyphosphate (Na6TPP) as the anode, cathode, and electrolyte, respectively. This Na6TPP-EF system could efficiently degrade atrazine in a wide pH range of 4.0-10.2. The utilization of Na6TPP instead of Na2SO4 as the electrolyte enhanced the atrazine degradation rate by 130 times at an initial pH of 8.0. This dramatic enhancement was attributed to the formation of ferrous-tetrapolyphosphate (Fe(II)-TPP) complex from the electrochemical corrosion (ECC) and chemical corrosion (CC) of iron electrode in the presence of Na6TPP. The Fe(II)-TPP complex could provide an additional molecular oxygen activation pathway to produce more H2O2 and (•)OH via a series single-electron transfer processes, producing the Fe(III)-TPP complex. The cycle of Fe(II)/Fe(III) was easily realized through the electrochemical reduction (ECR) process on the cathode. More interestingly, we found that the presence of Na6TPP could prevent the iron electrode from excessive corrosion via phosphorization in the later stage of the Na6TPP-EF process, avoiding the generation of iron sludge. Gas chromatograph-mass spectrometry, liquid chromatography-mass spectrometry, and ion chromatography were used to investigate the degradation intermediates to propose a possible atrazine oxidation pathway in the Na6TPP-EF system. These interesting findings provide some new insight on the development of a low-cost and highly efficient EF system for wastewater treatment in a wide pH range. PMID:25631474

  15. In vitro effect of manganese chloride exposure on reactive oxygen species generation and respiratory chain complexes activities of mitochondria isolated from rat brain.

    PubMed

    Zhang, Surong; Fu, Juanling; Zhou, Zongcan

    2004-02-01

    Manganese (Mn) is known to induce mitochondrial dysfunction in excessive dose; however the mechanisms underlying its action are not elucidated clearly. To determine if Mn2+ can act directly on mitochondria or indirectly by producing reactive oxygen species (ROS), isolated mitochondria were exposed to different concentration of Mn2+ (5, 50, 500, 1000 microM). ROS generation, respiratory control ratio (RCR), mitochondrial membrane potential (MMP) and respiratory chain complexes activities were investigated. Dose-dependent inhibition of respiratory chain complexes and induction of ROS were observed; these changes were paralleled by decreasing of respiratory control ratio (RCR) both with succinate or glutamate + malate. Further investigation indicated that the membrane potential determined by Rhodamine123 release decreased after MnCl2 exposure at 1000 microM. In addition, effects of the antioxidants NAC (500 microM), GSH (500 microM) and Vitamin C (500 microM) were studied at 500 microM Mn2+. The results indicate that the effect of Mn2+ exposure on respiratory chain is not site-specific, and antioxidants can protect the mitochondria function by reducing the formation of free radicals. PMID:14630064

  16. Hexavalent chromium targets mitochondrial respiratory chain complex I to induce reactive oxygen species-dependent caspase-3 activation in L-02 hepatocytes.

    PubMed

    Xiao, Fang; Li, Yanhong; Dai, Lu; Deng, Yuanyuan; Zou, Yue; Li, Peng; Yang, Yuan; Zhong, Caigao

    2012-09-01

    Hexavalent chromium [Cr(VI)], which is used for various industrial applications, such as leather tanning and chroming, can cause a number of human diseases including inflammation and cancer. Cr(VI) exposure leads to severe damage to the liver, but the mechanisms involved in Cr(VI)-mediated toxicity in the liver are unclear. The present study provides evidence that Cr(VI) enhances reactive oxygen species (ROS) accumulation by inhibiting the mitochondrial respiratory chain complex (MRCC) I. Cr(VI) did not affect the expression levels of antioxidative proteins such as superoxide dismutase (SOD), catalase and thioredoxin (Trx), indicating that the antioxidative system was not involved in Cr(VI)-induced ROS accumulation. We found that ROS mediated caspase-3 activation partially depends on the downregulation of the heat shock protein (HSP) 70 and 90. In order to confirm our hypothesis that ROS plays a key role in Cr(VI)-mediated cytotoxicity, we used N-acetylcysteine (NAC) to inhibit the accumulation of ROS. NAC successfully blocked the inhibition of HSP70 and HSP90 as well as the activation of caspase-3, suggesting that ROS is essential in Cr(VI)-induced caspase-3 activation. By applying different MRCC substrates as electron donors, we also confirmed that Cr(VI) could accept the electrons leaked from MRCC I and the reduction occurs at MRCC I. In conclusion, the present study demonstrates that Cr(VI) induces ROS-dependent caspase-3 activation by inhibiting MRCC I activity, and MRCC I has been identified as a new target and a new mechanism for the apoptosis-inducing activity displayed by Cr(VI). PMID:22710416

  17. Free radicals and activated oxygen.

    PubMed

    Famaey, J P

    1982-01-01

    Superoxide anion (0(-2)), hydrogen peroxide (H2O2) and hydroxyl radical (OH.) are products of the biological reduction of 0(2). They are very reactive and poorly tolerated within living systems and enzymes that catalytically scavenge these products have been evolved as defense mechanisms. These include superoxide dismutases (SOD), catalase and peroxidases. Large amounts of O-2 are produced by different enzymatic and non enzymatic biological processes. Large amounts of activated oxygens are produced by phagocytosing cells such as macrophages and polymorphonuclear cells. This production is associated with the bactericidal actions of these cells but it also largely contributes to exacerbate and sustain the inflammation where these cells congregate. The arachidonic acid pathway triggered by the inflammatory stimuli is also a source for these oxidizing radicals. The production of activated oxygens has been associated with the normal aging process but also with various toxic reactions (e.g. the toxicity of the herbicide paraquat, of the ionizing radiations, of certain antibiotics such as streptonigrin, etc. . . .). O-2 induces the depolymerization of hyaluronic acid which lends viscosity and lubricating properties to synovial fluids. SOD possess antiinflammatory properties and a bovine SOD, orgotein, has now been largely investigated by intramuscular and intraarticular injections in the treatment of rheumatic diseases. Various antiinflammatory compounds (e.g. the salicylates) are able either to inhibit the production of these oxygen radicals or to scavenge them which seems of importance for their antiinflammatory properties. Singlet oxygen, another activated oxygen, might also play a role in the inflammatory process. PMID:6295769

  18. Increased generation of intracellular reactive oxygen species initiates selective cytotoxicity against the MCF-7 cell line resultant from redox active combination therapy using copper-thiosemicarbazone complexes.

    PubMed

    Akladios, Fady N; Andrew, Scott D; Parkinson, Christopher J

    2016-06-01

    The combination of cytotoxic copper-thiosemicarbazone complexes with phenoxazines results in an up to 50-fold enhancement in the cytotoxic potential of the thiosemicarbazone against the MCF-7 human breast adenocarcinoma cell line over the effect attributable to drug additivity-allowing minimization of the more toxic copper-thiosemicarbazone component of the therapy. The combination of a benzophenoxazine with all classes of copper complex examined in this study proved more effective than combinations of the copper complexes with related isoelectronic azines. The combination approach results in rapid elevation of intracellular reactive oxygen levels followed by apoptotic cell death. Normal fibroblasts representative of non-cancerous cells (MRC-5) did not display a similar elevation of reactive oxygen levels when exposed to similar drug levels. The minimization of the copper-thiosemicarbazone component of the therapy results in an enhanced safety profile against normal fibroblasts. PMID:26951232

  19. Active oxygen doctors the evidence

    NASA Astrophysics Data System (ADS)

    Castelló, Ana; Francès, Francesc; Corella, Dolores; Verdú, Fernando

    2009-02-01

    Investigation at the scene of a crime begins with the search for clues. In the case of bloodstains, the most frequently used reagents are luminol and reduced phenolphthalein (or phenolphthalin that is also known as the Kastle-Meyer colour test). The limitations of these reagents have been studied and are well known. Household cleaning products have evolved with the times, and new products with active oxygen are currently widely used, as they are considered to be highly efficient at removing all kinds of stains on a wide range of surfaces. In this study, we investigated the possible effects of these new cleaning products on latent bloodstains that may be left at a scene of a crime. To do so, various fabrics were stained with blood and then washed using cleaning agents containing active oxygen. The results of reduced phenolphthalein, luminol and human haemoglobin tests on the washed fabrics were negative. The conclusion is that these new products alter blood to such an extent that it can no longer be detected by currently accepted methods employed in criminal investigations. This inability to locate bloodstains means that highly important evidence (e.g. a DNA profile) may be lost. Consequently, it is important that investigators are aware of this problem so as to compensate for it.

  20. Oxygen Radical Scavenger Activity, EPR, NMR, Molecular Mechanics and Extended-Hückel Molecular Orbital Investigation of the Bis(Piroxicam)Copper(II) Complex.

    PubMed

    Cini, R; Pogni, R; Basosi, R; Donati, A; Rossi, C; Sabadini, L; Rollo, L; Lorenzini, S; Gelli, R; Marcolongo, R

    1995-01-01

    The oxygen radical scavenger activity (ORSA) of [Cu(II)(Pir)(2)] (HPir = Piroxicam = 4-hydroxy -2- methyl -N-2- pyridyl -2H- 1,2-benzothiazine -3- carboxamide 1,1-dioxide) was determined by chemiluminescence of samples obtained by mixing human neutrophils (from healthy subjects) and [Cu(II)(Pir)(2)(DMF)(2)] (DMF = N,N -dimethylformammide) in DMSO/GLY/PBS (2:1:2, v/v) solution (DMSO = dimethylsulfoxide, GLY = 1,2,3-propantriol, PBS = Dulbecco's buffer salt solution). The ratio of the residual radicals, for the HPir (1.02.10(-4)M) and [Cu(II)(Pir)(2)(DMF)(2)] (1.08.10(-5)M)/HPir (8.01.10-(-5)M) systems was higher than 12 (not stimulated) [excess of piroxicam was added (Cu/Pir molar ratio approximately 1:10) in order to have most of the metal complexed as bischelate]. In contrast, the ratio of residual radicals for the CuCl(2) (1.00.10(-5)M) and [Cu(II)(Pir)(2)(DMF)(2)] (1.08.10(-5)M)/Hpir (8.01.10(-5)M)system was 5. The [Cu(II)(Pir)(2)] compound is therefore a stronger radical scavenger than either HPir or CuCl(2). A molecular mechanics (MM) analysis of the gas phase structures of neutral HPir, its zwitterionic (HPir(+-)) and anionic (Pir(-)) forms, and some Cu(II)-piroxicam complexes based on X-ray structures allowed calculation of force constants. The most stable structure for HPir has a ZZZ conformation similar to that found in the Cu(II) (and Cd(II) complexes) in the solid state as well as in the gas phase. The structure is stabilized by a strong H bond which involves the N(amide)-H and O(enolic) groups. The MM simulation for the [Cu(II)(Pir)(2)(DMF)(2)] complex showed that two high repulsive intramolecular contacts exist between a pyridyl hydrogen atom of one Pir(-) molecule with the O donor of the other ligand. These interactions activate a transition toward a pseudo-tetrahedral geometry, in the case the apical ligands are removed. On refluxing a suspension of [Cu(II)(Pir)(2)(DMF)(2)] in acetone a brown microcystalline solid with the Cu(Pir)(2).0.5DMF

  1. Probing Oxygen Activation Sites in Two Flavoprotein Oxidases Using Chloride as an Oxygen Surrogate

    SciTech Connect

    Kommoju, Phaneeswara-Rao; Chen, Zhi-wei; Bruckner, Robert C.; Mathews, F. Scott; Jorns, Marilyn Schuman

    2011-08-16

    A single basic residue above the si-face of the flavin ring is the site of oxygen activation in glucose oxidase (GOX) (His516) and monomeric sarcosine oxidase (MSOX) (Lys265). Crystal structures of both flavoenzymes exhibit a small pocket at the oxygen activation site that might provide a preorganized binding site for superoxide anion, an obligatory intermediate in the two-electron reduction of oxygen. Chloride binds at these polar oxygen activation sites, as judged by solution and structural studies. First, chloride forms spectrally detectable complexes with GOX and MSOX. The protonated form of His516 is required for tight binding of chloride to oxidized GOX and for rapid reaction of reduced GOX with oxygen. Formation of a binary MSOX-chloride complex requires Lys265 and is not observed with Lys265Met. Binding of chloride to MSOX does not affect the binding of a sarcosine analogue (MTA, methylthioactetate) above the re-face of the flavin ring. Definitive evidence is provided by crystal structures determined for a binary MSOX-chloride complex and a ternary MSOX-chloride-MTA complex. Chloride binds in the small pocket at a position otherwise occupied by a water molecule and forms hydrogen bonds to four ligands that are arranged in approximate tetrahedral geometry: Lys265:NZ, Arg49:NH1, and two water molecules, one of which is hydrogen bonded to FAD:N5. The results show that chloride (i) acts as an oxygen surrogate, (ii) is an effective probe of polar oxygen activation sites, and (iii) provides a valuable complementary tool to the xenon gas method that is used to map nonpolar oxygen-binding cavities.

  2. Oxygen Activation by Co(II) and a Redox Non-Innocent Ligand: Spectroscopic Characterization of a Radical-Co(II)-Superoxide Complex with Divergent Catalytic Reactivity.

    PubMed

    Corcos, Amanda R; Villanueva, Omar; Walroth, Richard C; Sharma, Savita K; Bacsa, John; Lancaster, Kyle M; MacBeth, Cora E; Berry, John F

    2016-02-17

    Bimetallic (Et4N)2[Co2(L)2], (Et4N)2[1] (where (L)(3-) = (N(o-PhNC(O)(i)Pr)2)(3-)) reacts with 2 equiv of O2 to form the monometallic species (Et4N)[Co(L)O2], (Et4N)[3]. A crystallographically characterized analog (Et4N)2[Co(L)CN], (Et4N)2[2], gives insight into the structure of [3](1-). Magnetic measurements indicate [2](2-) to be an unusual high-spin Co(II)-cyano species (S = 3/2), while IR, EXAFS, and EPR spectroscopies indicate [3](1-) to be an end-on superoxide complex with an S = 1/2 ground state. By X-ray spectroscopy and calculations, [3](1-) features a high-spin Co(II) center; the net S = 1/2 spin state arises after the Co electrons couple to both the O2(•-) and the aminyl radical on redox non-innocent (L(•))(2-). Dianion [1](2-) shows both nucleophilic and electrophilic catalytic reactivity upon activation of O2 due to the presence of both a high-energy, filled O2(-) π* orbital and an empty low-lying O2(-) π* orbital in [3](1-). PMID:26799113

  3. An oxygen-sensitive luminescent Dy(iii) complex.

    PubMed

    Nakai, Hidetaka; Seo, Juncheol; Kitagawa, Kazuhiro; Goto, Takahiro; Matsumoto, Takahiro; Ogo, Seiji

    2016-06-21

    This paper presents the first dysprosium(iii) complex, [{((MeMe)ArO)3tacn}Dy(III)(THF)] (1(Dy)), that shows oxygen-sensitive luminescence. The synthesis, structure and oxygen-sensitive luminescence properties of 1(Dy) are reported (Φ = 0.050 and τ = 17.7 μs under N2, Φ = 0.011 and τ = 4.1 μs under O2 and KSV = 305 M(-1) in THF; KSV = 0.0077%(-1) in polystyrene film). The oxygen sensitive mechanism of 1(Dy) is discussed based on the photophysical properties of the corresponding gadolinium(iii) complex, [{((MeMe)ArO)3tacn}Gd(III)(THF)]. PMID:27191980

  4. Photosensitized generation of singlet oxygen by rhenium(I) complex

    NASA Astrophysics Data System (ADS)

    Burchinov, A. N.; Kiselev, V. M.; Penni, A. A.; Khistyaeva, V. V.

    2015-12-01

    The photosensitized generation of singlet oxygen in solutions of rhenium(I) complex fac-[Re(bipy)(CO)3NCCH3]+OTf-, where bipy=2,2'-bipyridine, in chloride methylene and carbon tetrachloride under continuous LED irradiation in the UV and visible ranges has been investigated.

  5. Controlling energy transfer in ytterbium complexes: oxygen dependent lanthanide luminescence and singlet oxygen formation.

    PubMed

    Watkis, Andrew; Hueting, Rebekka; Sørensen, Thomas Just; Tropiano, Manuel; Faulkner, Stephen

    2015-11-01

    Pyrene-appended ytterbium complexes have been prepared using Ugi reactions to vary the chromophore-lanthanide separation. Formation of the ytterbium(iii) excited state is sensitised via both the singlet and triplet excited states of the chromophore. Energy transfer from the latter is relatively slow, and gives rise to oxygen-dependent luminescence. PMID:26346499

  6. Catalytic Oxygen Evolution by a Bioinorganic Model of the Photosystem II Oxygen-Evolving Complex

    ERIC Educational Resources Information Center

    Howard, Derrick L.; Tinoco, Arthur D.; Brudvig, Gary W.; Vrettos, John S.; Allen, Bertha Connie

    2005-01-01

    Bioinorganic models of the manganese Mn4 cluster are important not only as aids in understanding the structure and function of the oxygen-evolving complex (OEC), but also in developing artificial water-oxidation catalysts. The mechanism of water oxidation by photosystem II (PSII) is thought to involve the formation of a high-valent terminal Mn-oxo…

  7. Biochar activated by oxygen plasma for supercapacitors

    NASA Astrophysics Data System (ADS)

    Gupta, Rakesh Kumar; Dubey, Mukul; Kharel, Parashu; Gu, Zhengrong; Fan, Qi Hua

    2015-01-01

    Biochar, also known as black carbon, is a byproduct of biomass pyrolysis. As a low-cost, environmental-friendly material, biochar has the potential to replace more expensive synthesized carbon nanomaterials (e.g. carbon nanotubes) for use in future supercapacitors. To achieve high capacitance, biochar requires proper activation. A conventional approach involves mixing biochar with a strong base and baking at a high temperature. However, this process is time consuming and energy inefficient (requiring temperatures >900 °C). This work demonstrates a low-temperature (<150 °C) plasma treatment that efficiently activates a yellow pine biochar. Particularly, the effects of oxygen plasma on the biochar microstructure and supercapacitor characteristics are studied. Significant enhancement of the capacitance is achieved: 171.4 F g-1 for a 5-min oxygen plasma activation, in comparison to 99.5 F g-1 for a conventional chemical activation and 60.4 F g-1 for untreated biochar. This enhancement of the charge storage capacity is attributed to the creation of a broad distribution in pore size and a larger surface area. The plasma activation mechanisms in terms of the evolution of the biochar surface and microstructure are further discussed.

  8. New ruthenium nitrosyl pincer complexes bearing an O2 ligand. Mono-oxygen transfer.

    PubMed

    Fogler, Eran; Efremenko, Irena; Gargir, Moti; Leitus, Gregory; Diskin-Posner, Yael; Ben-David, Yehoshoa; Martin, Jan M L; Milstein, David

    2015-03-01

    We report on Ru((II))(μ(2)-O2) nitrosyl pincer complexes that can return to their original Ru(0) state by reaction with mono-oxygen scavengers. Potential intermediates were calculated by density functional theory (DFT) and a mechanism is proposed, revealing a new type of metal-ligand cooperation consisting of activation of the O2 moiety by both the metal center and the NO ligand. Reaction of the Ru(0) nitrosyl complex 1 with O2 quantitatively yielded the crystallographically characterized Ru((II)) (μ(2)-O2) nitrosyl complex 2. Reaction of 2 with the mono-oxygen scavengers phosphines or CO gave the Ru(0) complex 1 and phosphine oxides, or the carbonyl complex 3 (1 trapped by CO) and CO2, respectively. Reaction of 2 with 1 equiv of phosphine at room temperature or -40 °C resulted in immediate formation of half an equivalent of 1 and 1 equiv of phosphine oxide, while half an equivalent of 2 remained unchanged. Overnight reaction at room temperature of 2 with excess CO (≥3 equiv) resulted in 3 and CO2 gas as the only products. Reaction of 1 with 1 equiv of mono-oxygen source (dioxirane) at -78 °C yielded the Ru((II))(μ(2)-O2) complex 2. Similarly, reaction of the Ru(0) dearomatized complex 4 with O2 led to the crystallographicaly characterized Ru((II))(μ(2)-O2) complex 5. Further reaction of 5 with mono-oxygen scavengers (phosphines or CO) led to the Ru(0) complex 4 and phosphine oxides or complex 6 (4 trapped by CO) and CO2. When instead only 1 equiv of 5 was reacted with 1 equiv of phosphine at room temperature, immediate formation of half an equivalent of 4 and 1 equiv of phosphine oxide took place, while half an equivalent of 5 remained unchanged. When 5 reacted with an excess of CO (≥3 equiv), complex 6 and CO2 gas were the only products obtained. DFT studies indicate a new mode of metal-ligand cooperation involving the nitrosyl ligand in the oxygen transfer process. PMID:25695626

  9. Complexes of self-interstitials with oxygen atoms in Ge

    SciTech Connect

    Khirunenko, L. I.; Pomozov, Yu. V.; Sosnin, M. G.; Abrosimov, N. V.; Riemann, H.

    2014-02-21

    Interactions of germanium self-interstitials with interstitial oxygen atoms in Ge subjected to irradiation at ∼80 K and subsequently to annealing have been studied. To distinguish the processes involving vacancies and self-interstitials the doping with tin was used. It was shown that absorption lines with maximum at 602, 674, 713 and 803 cm{sup −1} are self-interstitials-related. Two lines at 602 and 674, which develop upon annealing in the temperature range 180–240 K, belong to IO complexes, while the bands at 713 and 803 cm{sup −1}, which emerge after annealing at T>220 K, are associated with I{sub 2}O. It is argued that the annealing of IO occurs by two mechanisms: by dissociation and by diffusion.

  10. SAFETY ASPECTS OF OXYGEN AERATION ACTIVATED SLUDGE SYSTEMS

    EPA Science Inventory

    This project was carried out to assess the impact of the use of oxygen and oxygen-enriched air for aeration of activated sludge systems on the safety of municipal waste-water treatment plants and their personnel. The tasks included (1) determination of oxygen combustion hazards f...

  11. Henry's Law Activity of Oxygen in Molten Iron

    NASA Astrophysics Data System (ADS)

    Matousek, J. W.

    2015-09-01

    A model is proposed for the solubility of oxygen in molten iron in dilute solutions in which the oxygen exists in two states, free and associated. Only the free oxygen has thermodynamic activity in the sense of interaction with an electrochemical cell to produce the voltage described by the Nernst equation.

  12. BIOLOGICALLY ENHANCED OXYGEN TRANSFER IN THE ACTIVATED SLUDGE PROCESS (JOURNAL)

    EPA Science Inventory

    Biologically enhanced oxgyen transfer has been a hypothesis to explain observed oxygen transfer rates in activated sludge systems that were well above that predicted from aerator clean-water testing. The enhanced oxygen transfer rates were based on tests using BOD bottle oxygen ...

  13. Correlation between oxygen adsorption energy and electronic structure of transition metal macrocyclic complexes

    SciTech Connect

    Liu, Kexi; Lei, Yinkai; Wang, Guofeng

    2013-11-28

    Oxygen adsorption energy is directly relevant to the catalytic activity of electrocatalysts for oxygen reduction reaction (ORR). In this study, we established the correlation between the O{sub 2} adsorption energy and the electronic structure of transition metal macrocyclic complexes which exhibit activity for ORR. To this end, we have predicted the molecular and electronic structures of a series of transition metal macrocyclic complexes with planar N{sub 4} chelation, as well as the molecular and electronic structures for the O{sub 2} adsorption on these macrocyclic molecules, using the density functional theory calculation method. We found that the calculated adsorption energy of O{sub 2} on the transition metal macrocyclic complexes was linearly related to the average position (relative to the lowest unoccupied molecular orbital of the macrocyclic complexes) of the non-bonding d orbitals (d{sub z{sup 2}}, d{sub xy}, d{sub xz}, and d{sub yz}) which belong to the central transition metal atom. Importantly, our results suggest that varying the energy level of the non-bonding d orbitals through changing the central transition metal atom and/or peripheral ligand groups could be an effective way to tuning their O{sub 2} adsorption energy for enhancing the ORR activity of transition metal macrocyclic complex catalysts.

  14. In-Situ Formation of Cobalt-Phosphate Oxygen-Evolving Complex-Anchored Reduced Graphene Oxide Nanosheets for Oxygen Reduction Reaction

    PubMed Central

    Zhao, Zhi-Gang; Zhang, Jing; Yuan, Yinyin; Lv, Hong; Tian, Yuyu; Wu, Dan; Li, Qing-Wen

    2013-01-01

    Oxygen conversion process between O2 and H2O by means of electrochemistry or photochemistry has lately received a great deal of attention. Cobalt-phosphate (Co-Pi) catalyst is a new type of cost-effective artificial oxygen-evolving complex (OEC) with amorphous features during photosynthesis. However, can such Co-Pi OEC also act as oxygen reduction reaction (ORR) catalyst in electrochemical processes? The question remains unanswered. Here for the first time we demonstrate that Co-Pi OEC does be rather active for the ORR. Particularly, Co-Pi OEC anchoring on reduced graphite oxide (rGO) nanosheet is shown to possess dramatically improved electrocatalytic activities. Differing from the generally accepted role of rGO as an “electron reservoir”, we suggest that rGO serves as “peroxide cleaner” in enhancing the electrocatalytic behaviors. The present study may bridge the gap between photochemistry and electrochemistry towards oxygen conversion. PMID:23877331

  15. In-Situ Formation of Cobalt-Phosphate Oxygen-Evolving Complex-Anchored Reduced Graphene Oxide Nanosheets for Oxygen Reduction Reaction

    NASA Astrophysics Data System (ADS)

    Zhao, Zhi-Gang; Zhang, Jing; Yuan, Yinyin; Lv, Hong; Tian, Yuyu; Wu, Dan; Li, Qing-Wen

    2013-07-01

    Oxygen conversion process between O2 and H2O by means of electrochemistry or photochemistry has lately received a great deal of attention. Cobalt-phosphate (Co-Pi) catalyst is a new type of cost-effective artificial oxygen-evolving complex (OEC) with amorphous features during photosynthesis. However, can such Co-Pi OEC also act as oxygen reduction reaction (ORR) catalyst in electrochemical processes? The question remains unanswered. Here for the first time we demonstrate that Co-Pi OEC does be rather active for the ORR. Particularly, Co-Pi OEC anchoring on reduced graphite oxide (rGO) nanosheet is shown to possess dramatically improved electrocatalytic activities. Differing from the generally accepted role of rGO as an ``electron reservoir'', we suggest that rGO serves as ``peroxide cleaner'' in enhancing the electrocatalytic behaviors. The present study may bridge the gap between photochemistry and electrochemistry towards oxygen conversion.

  16. In-situ formation of cobalt-phosphate oxygen-evolving complex-anchored reduced graphene oxide nanosheets for oxygen reduction reaction.

    PubMed

    Zhao, Zhi-Gang; Zhang, Jing; Yuan, Yinyin; Lv, Hong; Tian, Yuyu; Wu, Dan; Li, Qing-Wen

    2013-01-01

    Oxygen conversion process between O₂ and H₂O by means of electrochemistry or photochemistry has lately received a great deal of attention. Cobalt-phosphate (Co-Pi) catalyst is a new type of cost-effective artificial oxygen-evolving complex (OEC) with amorphous features during photosynthesis. However, can such Co-Pi OEC also act as oxygen reduction reaction (ORR) catalyst in electrochemical processes? The question remains unanswered. Here for the first time we demonstrate that Co-Pi OEC does be rather active for the ORR. Particularly, Co-Pi OEC anchoring on reduced graphite oxide (rGO) nanosheet is shown to possess dramatically improved electrocatalytic activities. Differing from the generally accepted role of rGO as an "electron reservoir", we suggest that rGO serves as "peroxide cleaner" in enhancing the electrocatalytic behaviors. The present study may bridge the gap between photochemistry and electrochemistry towards oxygen conversion. PMID:23877331

  17. New dirhodium complex with activity towards colorectal cancer.

    PubMed

    Frade, Raquel F M; Candeias, Nuno R; Duarte, Catarina M M; André, Vânia; Duarte, M Teresa; Gois, Pedro M P; Afonso, Carlos A M

    2010-06-01

    A novel dirhodium complex (Rh(2)(L-PheAla)(2)(OAc)(2) is reported with strong activity towards human colon adenocarcinoma cells. Its effect was not accompanied by generation of reactive oxygen species (ROS) neither by activation of caspase-3. PMID:20434912

  18. Insight into the dynamics of lanthanide-DTPA complexes as revealed by oxygen-17 NMR.

    PubMed

    Fusaro, Luca; Mocci, Francesca; Muller, Robert N; Luhmer, Michel

    2012-08-01

    DTPA chelates of various diamagnetic and paramagnetic lanthanide(III) metal ions, as well as the chemically similar DTPA chelate of Y(3+), were studied in aqueous solution by variable temperature (17)O NMR with the aim of characterizing their internal dynamics. As a consequence of poor chemical shift dispersion and fast quadrupole relaxation, no dynamic exchange process could be detected for the diamagnetic complexes nor for the Sm-DTPA complex. In contrast, the spectra recorded for the Eu-DTPA complex show chemical exchange due to the well-known racemization process and, at high temperature, feature signal broadening that reveals a fluxional process involving the interchange of the coordinated and noncoordinated oxygen atoms of the carboxylate groups. The spectra recorded for the Pr-DTPA complex feature coalescence events due to such a fluxional process, which is ascribable to the rotation of the carboxylate groups. The activation free energy barriers determined experimentally are remarkably lower than the calculated activation barriers recently reported for the rotation of the carboxylate groups of various Ln-DOTA complexes. Furthermore, the smallest activation free energy measured for the Pr-DTPA complex, about 45 kJ mol(-1), is significantly lower than the activation free energy characterizing the racemization process. The fluxional behavior of the carboxylate groups is, however, not expected to significantly affect the residence time of the water molecule coordinated to the metal ion. PMID:22817329

  19. PARALLEL EVALUATION OF AIR- AND OXYGEN-ACTIVATED SLUDGE

    EPA Science Inventory

    To provide data on the relative merits of air and oxygen in the activated sludge process, two 1900-cu m/day (0.5-mgd) activated sludge pilot plant, one air and one oxygen system, were operated side-by-side at the Joint Water Pollution Control Plant, Carson, California. Both of th...

  20. Stereochemistry of lead(II) complexes with oxygen donor ligands.

    SciTech Connect

    Stavilla, Vitalie; Davidovich, Ruven L.; Whitmire, Kenton Herbert; Voit, Elena I.; Marinin, Dmitry V.

    2008-10-01

    This review discusses the coordination number (CN) and the coordination geometry of the first coordination sphere of Pb(II) atoms in crystal structures of 98 lead(II) complexes with O-donor ligands and the stereochemically active lone pair of electrons (LP, E) in the terms of the valence shell electron-pair repulsion (VSEPR) model. The CN of Pb(II) atoms of the first coordination sphere has values falling into the range (3 + E) to (6 + E). The following coordination polyhedra-{psi}-tetrahedron (I), {psi}-trigonal bipyramid (II), {psi}-octahedron (III), {psi}-pentagonal bipyramid with an axial (IV) or equatorial (V) vacant position are formed. For the investigated structures of the Pb(II) complexes, the formula of each compound, the overall CN of the Pb(II) atom considered as the sum of the CN in the first coordination sphere and the number of secondary bonds, the polyhedron shape, the Pb-O bond lengths, and O-Pb-O bond angles in the first coordination sphere, secondary bond lengths, references and REFCODEs are presented in the comprehensive Tables. The quantum chemical investigations performed using density functional theory (DFT) method have confirmed the stereochemical activity of the LP of Pb(II) atoms in the studied structures of lead(II) complexes with O-donor ligands.

  1. A biocompatible cobaltporphyrin-based complex micelle constructed via supramolecular assembly for oxygen transfer.

    PubMed

    Shen, Liangliang; Qu, Rui; Shi, Hejin; Huang, Fan; An, Yingli; Shi, Linqi

    2016-05-26

    Herein, a complex micelle as an oxygen nano-carrier is constructed through the hierarchical assembly of the diblock copolymer poly(ethylene glycol)-block-poly(l-lysine) (PEG-b-PLys), tetrakis(4-sulfonatophenyl)porphinato cobalt(ii) (Co(ii)TPPS), a heptapeptide (Cys-His-His-His-His-His-His) and heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin (TM-β-CD). Co(ii)TPPS was encapsulated into the cavities of TM-β-CDs driven by the host-guest interaction so that the irreversible formation of a μ-oxo-dimer of Co(ii)TPPS can be effectively prevented. The imidazole groups of the heptapeptide were selected as good axial ligands coordinating to the centric cobalt of Co(ii)TPPS, which subtly constituted the five-coordinated precursor serving as an active functional centre for oxygen binding. The sixth position of Co(ii)TPPS can bind oxygen. Furthermore, the host-guest inclusion (TM-β-CD/Co(ii)TPPS) was loaded into the hydrophobic core of the complex micelle and tightly fixed with PLys chains. The hydrophilic PEG blocks stretched in the aqueous solution constitute the shells which stabilize the structure of the complex micelle as well as impart the complex micelle sufficient blood circulation time. Moreover, the complex micelle exhibited excellent biocompatibility and cellular uptake. Therefore, the rationally designed amphiphilic structure can work as promising artificial O2 carriers in vivo. Potentially, the complex micelle can be expected to change the anaerobic microenvironment and find applications in the repair of the cells damaged by cellular hypoxia. PMID:27009911

  2. Enhanced optical oxygen sensing using a newly synthesized ruthenium complex together with oxygen carriers.

    PubMed

    Ertekin, Kadriye; Kocak, Suleyman; Sabih Ozer, M; Aycan, Sule; Cetinkaya, Bekir

    2003-11-12

    In this article, an emission based, simple and fast method is proposed for the determination of gaseous oxygen. A newly synthesized fluorophore, dichloro-{2,6-bis[1-(4-dimethylamino-phenylimino) ethyl]pyridine}ruthenium(II) has been used for oxygen sensing together with oxygen carrier perfluorochemicals (PFCs) in silicon matrix. It should be noted that the solubility of oxygen in fluorocarbons is about three to ten times large as that observed in the parent hydrocarbons or in water, respectively. Employed PFCs are chemically and biochemically inert, have high dissolution capacities for oxygen, and, once doped into sensing film, considerably enhance the response of sensing agent. PMID:18969220

  3. Theoretical study of the interaction between molecular oxygen and tetraaza macrocyclic manganese complexes.

    PubMed

    Costa, Alexandre; Silva, Adilson Luís Pereira; Viana, Rommel Bezerra; Tanaka, Auro Atsushi; Varela, Jaldyr de Jesus Gomes

    2016-09-01

    Theoretical chemistry calculations using the Density Functional Theory (DFT) were carried out to understand the interaction between oxygen (O2) and MnN4 type manganese-based complexes during the formation of MnN4-O2 adducts. In order to understand how this interaction is affected by different macrocyclic ligands, O2 was bonded to manganese-porphyrin (MnP), manganese-octamethylporphyrin (MnOMP), manganese-tetraaza[14]annulene (MnTAA), manganese-dibenzo [b,i] [1, 4, 8, 11]-tetraaza [14] annulene (MnDBTAA), manganese-2,3,9,10-tetramethyl-1,4,8,11-tetraazacyclotetradeca-1,3,8,10-tetraene ([(tim)Mn](2+)), and manganese-2,3,9,10-tetraphenyl-1,4,8,11-tetraazacyclotetradeca-1,3,8,10-tetraene ([(ph-tim)Mn](2+)). The binding and activation of the oxygen molecule was facilitated by an increasing trend in the O-O bond lengths and a decreasing one in the O-O vibrational frequency, with preference for the O2 side-on interaction among MnN4 macrocycles. The catalytic activities of the MnN4 complexes toward the O2 binding process increased in the following order: [(ph-tim)Mn](2+) < MnP < MnOMP < MnDBTAA < MnTAA < [(tim)Mn](2+). Therefore, it was concluded that the [(tim)Mn](2+)complex was the most active for the binding and activation of molecular oxygen. PMID:27553302

  4. Active site densities, oxygen activation and adsorbed reactive oxygen in alcohol activation on npAu catalysts.

    PubMed

    Wang, Lu-Cun; Friend, C M; Fushimi, Rebecca; Madix, Robert J

    2016-07-01

    The activation of molecular O2 as well as the reactivity of adsorbed oxygen species is of central importance in aerobic selective oxidation chemistry on Au-based catalysts. Herein, we address the issue of O2 activation on unsupported nanoporous gold (npAu) catalysts by applying a transient pressure technique, a temporal analysis of products (TAP) reactor, to measure the saturation coverage of atomic oxygen, its collisional dissociation probability, the activation barrier for O2 dissociation, and the facility with which adsorbed O species activate methanol, the initial step in the catalytic cycle of esterification. The results from these experiments indicate that molecular O2 dissociation is associated with surface silver, that the density of reactive sites is quite low, that adsorbed oxygen atoms do not spill over from the sites of activation onto the surrounding surface, and that methanol reacts quite facilely with the adsorbed oxygen atoms. In addition, the O species from O2 dissociation exhibits reactivity for the selective oxidation of methanol but not for CO. The TAP experiments also revealed that the surface of the npAu catalyst is saturated with adsorbed O under steady state reaction conditions, at least for the pulse reaction. PMID:27376884

  5. Oxygenation of ruthenium carbene complexes containing naphthothiophene or naphthofuran: spectroscopic and DFT studies.

    PubMed

    Tsai, Fu-Yuan; Lo, Ji-Xian; Hsu, Hsin-Tzu; Lin, Ying-Chih; Huang, Shou-Ling; Wang, Ju-Chun; Liu, Yi-Hong

    2013-11-01

    The aryl propargylic alcohol 1-[2-(thiophen-3-yl)phenyl]prop-2-yn-1-ol (1a) is readily prepared from 2-(thiophen-3-yl)benzaldehyde. In the presence of visible light, treatment of 1a with one-half mole equivalent of [Ru]Cl ([Ru]=Cp(dppe)Ru) (dppe=1,2-bis(diphenylphosphino)ethane) and NH4PF6 in O2 affords the naphtha[2,1-b]thiophene-4-carbaldehyde (4a) in high yields. The cyclization reaction of 1a proceeds through the formation of the carbene complex 2a that contains the naphtha[2,1-b]thiophene ring, which is isolated in a 1:1 stoichiometric reaction. The C-C bond formation between the inner carbon of the terminal triple bond and the heterocyclic ring is confirmed by structure determination of 2a using single-crystal X-ray diffraction analysis. Facile oxygenation of 2a by O2 yields the aldehyde product 4a accompanied by the formation of phosphine oxide of dppe. Oxygen is most likely activated by coordination to the ruthenium center when one PPh2 unit of the dppe ligand dissociates. This dissociated PPh2 unit then reacts with the coordinated oxygen nearby to generate half-oxidized dppe ligand and an unobserved oxo-carbene intermediate. Coupling of the oxo/carbene ligands followed by demetalation then yields 4a. Presumably the resulting complex with the half-oxidized dppe ligand continuously promotes cyclization/oxygenation of 1a to yield the second aldehyde molecule. In alcohol such as MeOH or EtOH, the oxygenation reaction affords a mixture of 4a and the corresponding esters 5a or 5a'. Four other aryl propargylic alcohols 1b-e, which contain thiophen-2-yl, isopropenyl, fur-3-yl, and fur-2-yl, respectively, on the aryl ring are also prepared. Analogous aldehydes 4b-e are similarly prepared from 1b-e, respectively. For oxygenations of 1b, 1d, and 1e in alcohol, mixtures of aldehyde 4, ester 5, and acetal 8 are obtained. The carbene complex 2b obtained from 1b was also characterized by single-crystal X-ray diffraction analysis. The UV/Vis spectra of 2a and 2b consist

  6. Reversible Oxygenation of α-Amino Acid–Cobalt(II) Complexes

    PubMed Central

    Zhang, Xincun; Yue, Fan; Li, Hui; Huang, Yan; Zhang, Yi; Wen, Hongmei; Wang, Jide

    2016-01-01

    We systematically investigated the reversibility, time lapse, and oxygenation-deoxygenation properties of 15 natural α-amino acid–Co(II) complexes through UV-vis spectrophotometer, polarographic oxygen electrode, and DFT calculations, respectively, to explore the relationship between the coordinating structure and reversible oxygenation of α-amino acid–Co(II) complexes. Results revealed that the α-amino acid structure plays a key role in the reversible oxygenation properties of these complexes. The specific configuration of the α-amino acid group affects the eg1 electron of Co(II) transfer to the π⁎ orbit of O2; this phenomenon also favors the reversible formation and dissociation of Co–O2 bond when O2 coordinates with Co(II) complexes. Therefore, the co-coordination of amino and carboxyl groups is a determinant of Co complexes to absorb O2 reversibly. The group adjacent to the α-amino acid unit evidently influences the dioxygen affinity and antioxidation ability of the complexes. The presence of amino (or imino) and hydroxy groups adjacent to the α-amino acid group increases the oxygenation-deoxygenation rate and the number of reversible cycles. Our findings demonstrate a new mechanism to develop reversible oxygenation complexes and to reveal the oxygenation of oxygen carriers. PMID:27022316

  7. Oxygen-independent induction of enzyme activities related to oxygen metabolism in yeast by copper.

    PubMed

    Galiazzo, F; Schiesser, A; Rotilio, G

    1988-04-14

    Aerobic growth of Saccharomyces cerevisiae in the presence of CuSO4 (between 0.1 and 1 mM) caused a generalized induction of major enzyme activities involved in 'housekeeping' routes of oxygen metabolism (cytochrome oxidase, glutathione peroxidases and catalase) which were comparable to or higher than that observed with Cu,Zn-superoxide dismutase. Fumarase and glutathione transferase, tested as controls for oxygen-unrelated activities, were found to decrease under the same conditions. In the absence of oxygen, copper addition to yeast resulted in significant increases of Cu,Zn-superoxide dismutase and glutathione peroxidases and a slight increase of cytochrome oxidase, with catalase remaining undetectable irrespective of whether or not copper was present. Other metal ions tested (Mn2+, Co2+) were unable to produce such effects. It is concluded that copper has a general inducing effect on enzymes related to metabolism of oxygen and oxygen derivatives, which is mediated neither by formation of O2-. and H2O2 nor by interaction with copper-specific apoproteins. These results point to a general role of copper as regulator of the expression of major enzyme activities involved in biological oxygen activation. PMID:2831994

  8. Rhenium complexes with visible-light-induced anticancer activity.

    PubMed

    Kastl, Anja; Dieckmann, Sandra; Wähler, Kathrin; Völker, Timo; Kastl, Lena; Merkel, Anna Lena; Vultur, Adina; Shannan, Batool; Harms, Klaus; Ocker, Matthias; Parak, Wolfgang J; Herlyn, Meenhard; Meggers, Eric

    2013-06-01

    Shedding light on the matter: Rhenium(I) indolato complexes with highly potent visible-light-triggered antiproliferative activity (complex 1: EC50 light=0.1 μM vs EC50 dark=100 μM) in 2D- and 3D-organized cancer cells are reported and can be traced back to an efficient generation of singlet oxygen, causing rapid morphological changes and an induction of apoptosis. PMID:23568508

  9. Functionalized active-nucleus complex sensor

    DOEpatents

    Pines, Alexander; Wemmer, David E.; Spence, Megan; Rubin, Seth

    2003-11-25

    A functionalized active-nucleus complex sensor that selectively associates with one or more target species, and a method for assaying and screening for one or a plurality of target species utilizing one or a plurality of functionalized active-nucleus complexes with at least two of the functionalized active-nucleus complexes having an attraction affinity to different corresponding target species. The functionalized active-nucleus complex has an active-nucleus and a targeting carrier. The method involves functionalizing an active-nucleus, for each functionalized active-nucleus complex, by incorporating the active-nucleus into a macromolucular or molecular complex that is capable of binding one of the target species and then bringing the macromolecular or molecular complexes into contact with the target species and detecting the occurrence of or change in a nuclear magnetic resonance signal from each of the active-nuclei in each of the functionalized active-nucleus complexes.

  10. Neuroprotection by Polynitrogen Manganese Complexes: Regulation of Reactive Oxygen Species-Related Pathways.

    PubMed

    Chen, Chunxia; Cao, Jing; Ma, Xiaoyan; Wang, Xiaobo; Chen, Qiuyun; Yan, Shihai; Zhao, Ningwei; Geng, Zhirong; Wang, Zhilin

    2016-01-01

    Cell death in the central nervous system causes neurologic diseases, in which reactive oxygen species (ROS) play a critical role by either inducing cellular oxidative stress or by increasing the cell tolerance against insult. Neurologic diseases may potentially be treated by regulating ROS levels in a certain range with small molecules. We studied preconditioning with two polynitrogen manganese complexes (1 and 2) to regulate intracellular ROS levels in the protection of both the differentiated rat pheochromocytoma cell line (PC12 cells) and neurons against H2O2-induced apoptosis. Pre-treatment with the two complexes attenuated the cell apoptosis caused by H2O2. And the ROS-related neuroprotective mechanisms were explored. Both complexes activate the hypoxia inducible factor-related pathways and increase the cell adaptation to oxidative stress. Pre-treatment with complex 1 eliminated intracellular ROS, which also activated antioxidase system, while short-term incubation of complex 2, generated low levels of ROS leading to cell survival. PMID:26857964

  11. Neuroprotection by Polynitrogen Manganese Complexes: Regulation of Reactive Oxygen Species-Related Pathways

    PubMed Central

    Chen, Chunxia; Cao, Jing; Ma, Xiaoyan; Wang, Xiaobo; Chen, Qiuyun; Yan, Shihai; Zhao, Ningwei; Geng, Zhirong; Wang, Zhilin

    2016-01-01

    Cell death in the central nervous system causes neurologic diseases, in which reactive oxygen species (ROS) play a critical role by either inducing cellular oxidative stress or by increasing the cell tolerance against insult. Neurologic diseases may potentially be treated by regulating ROS levels in a certain range with small molecules. We studied preconditioning with two polynitrogen manganese complexes (1 and 2) to regulate intracellular ROS levels in the protection of both the differentiated rat pheochromocytoma cell line (PC12 cells) and neurons against H2O2-induced apoptosis. Pre-treatment with the two complexes attenuated the cell apoptosis caused by H2O2. And the ROS-related neuroprotective mechanisms were explored. Both complexes activate the hypoxia inducible factor-related pathways and increase the cell adaptation to oxidative stress. Pre-treatment with complex 1 eliminated intracellular ROS, which also activated antioxidase system, while short-term incubation of complex 2, generated low levels of ROS leading to cell survival. PMID:26857964

  12. In Situ Studies of the Active Sites for the Water Gas Shift Reaction over Cu-CeO2 Catalysts: Complex Interaction Between Metallic Copper and Oxygen Vacancies of Ceria

    SciTech Connect

    Wang,X.; Rodriguez, J.; Hanson, J.; Gamarra, D.; Martinez-Arias, A.; Fernandez-Garcia, M.

    2006-01-01

    New information about the active sites for the water gas shift (WGS) reaction over Cu-CeO{sub 2} systems was obtained using in-situ, time-resolved X-ray diffraction (TR-XRD), X-ray absorption spectroscopy (TR-XAS, Cu K and Ce L3 edges), and infrared spectroscopy (DRIFTS). Cu-CeO{sub 2} nanoparticles prepared by a novel reversed microemulsion method (doped Ce1-xCuxO2 sample) and an impregnation method (impregnated CuO{sub x}/CeO{sub 2} sample) were studied. The results from all of the samples indicate that both metallic copper and oxygen vacancies in ceria were involved in the generation of active sites for the WGS reaction. Evidence was found for a synergistic Cu-O vacancy interaction. This interaction enhances the chemical activity of Cu, and the presence of Cu facilitates the formation of O vacancies in ceria under reaction conditions. Water dissociation occurred on the O vacancy sites or the Cu-O vacancy interface. No significant amounts of formate were formed on the catalysts during the WGS reaction. The presence of strongly bound carbonates is an important factor for the deactivation of the catalysts at high temperatures. This work identifies for the first time the active sites for the WGS reaction on Cu-CeO{sub 2} catalysts and illustrates the importance of in situ structural studies for heterogeneous catalytic reactions.

  13. An oxygen-17 dynamic NMR study of the Pr-DOTA complex.

    PubMed

    Fusaro, Luca; Luhmer, Michel

    2014-01-21

    The complex between (17)O-enriched DOTA (tetraazacyclododecanetetraacetic acid) and praseodymium(III) (Pr(3+)) was studied in aqueous solution by variable-temperature (17)O NMR at 14.1 T. pH effects as well as the influence of metal ions free in solution were investigated. At low temperature, the so-called TSAP and SAP conformations give rise to distinct signals for the oxygen atoms coordinated to the metal ion (O2); coalescence occurs between 20 and 30 °C. In contrast, a single signal was detected for the noncoordinated oxygen atoms (O1) in the entire investigated temperature range, i.e. between -3 and 135 °C. At high temperature, the spectra exhibit signal broadening that reveals the interchange of the O1 and O2 oxygen atoms of the carboxylate groups. The linewidths measured for O1 were deconvolved into contributions from quadrupole relaxation and chemical exchange, allowing the corresponding activation barriers to be determined. The present (17)O dynamic NMR study provides the first quantitative experimental data characterizing the interchange of the oxygen atoms in a DOTA chelate of a lanthanide metal ion. The activation entropy of this process is negligible and the activation enthalpy is found to range between 66 and 77 kJ mol(-1), depending on the pH and the presence of free Pr(3+) ions in solution. These data support the results of a previous computational study according to which the exchange mechanism involves the internal rotation of the carboxylate groups. PMID:24158053

  14. Neutralizing a Surface Charge on the FMN Subdomain Increases the Activity of Neuronal Nitric-oxide Synthase by Enhancing the Oxygen Reactivity of the Enzyme Heme-Nitric Oxide Complex*

    PubMed Central

    Haque, Mohammad Mahfuzul; Fadlalla, Mohammed; Wang, Zhi-Qiang; Ray, Sougata Sinha; Panda, Koustubh; Stuehr, Dennis J.

    2009-01-01

    Nitric-oxide synthases (NOSs) are calmodulin-dependent flavoheme enzymes that oxidize l-Arg to nitric oxide (NO) and l-citrulline. Their catalytic behaviors are complex and are determined by their rates of heme reduction (kr), ferric heme-NO dissociation (kd), and ferrous heme-NO oxidation (kox). We found that point mutation (E762N) of a conserved residue on the enzyme's FMN subdomain caused the NO synthesis activity to double compared with wild type nNOS. However, in the absence of l-Arg, NADPH oxidation rates suggested that electron flux through the heme was slower in E762N nNOS, and this correlated with the mutant having a 60% slower kr. During NO synthesis, little heme-NO complex accumulated in the mutant, compared with ∼50–70% of the wild-type nNOS accumulating as this complex. This suggested that the E762N nNOS is hyperactive because it minimizes buildup of an inactive ferrous heme-NO complex during NO synthesis. Indeed, we found that kox was 2 times faster in the E762N mutant than in wild-type nNOS. The mutational effect on kox was independent of calmodulin. Computer simulation and experimental measures both indicated that the slower kr and faster kox of E762N nNOS combine to lower its apparent Km,O2 for NO synthesis by at least 5-fold, which in turn increases its V/Km value and enables it to be hyperactive in steady-state NO synthesis. Our work underscores how sensitive nNOS activity is to changes in the kox and reveals a novel means for the FMN module or protein-protein interactions to alter nNOS activity. PMID:19473991

  15. Density functional theory studies of oxygen and carbonate binding to a dicopper patellamide complex.

    PubMed

    Latifi, Reza; Bagherzadeh, Mojtaba; Milne, Bruce F; Jaspars, Marcel; de Visser, Sam P

    2008-12-01

    In this work we present results of density functional theory (DFT) calculations on dicopper patellamides and their affinity for molecular oxygen and carbonate. Patellamides are cyclic octapeptides that are produced by a cyanobacterium, and may show promise as therapeutics. Thus, carbonate binding to a dicopper patellamide center gives a stable cyclic octapeptide with a twist of almost 90 degrees . The system exists in close-lying open-shell singlet and triplet spin states with two unpaired electrons in orthogonal sigma* orbitals on each metal center. Subsequently, we replaced carbonate with dioxygen and found a stable Cu2(mu-O)2 diamond shaped patellamide core. In this structure the original dioxygen bond is significantly weakened to essentially a single bond, which should enable the system to transfer these oxygen atoms to substrates. We predicted the IR and Raman spectra of the Cu2(mu-O)2 diamond shaped patellamide structure using density functional theory and found a considerable isotope effect on the O-O stretch vibration for 16O2 versus 18O2 bound structures. Our studies reveal that carbonate forms an extremely stable complex with dicopper patellamide, but that additional molecular oxygen to this system does not give a potential oxidant. Therefore, it is more likely that carbonate prepares the system for dioxygen binding by folding it into the correct configuration followed in the proposed catalytic cycle by a protonation event preceding dioxygen binding to enable the system to reorganize to form a stable Cu2(mu-O)2-patellamide cluster. Alternatively, carbonate may act as an inhibitor that blocks the catalytic activity of the system. It is anticipated that the Cu2(mu-O)2-patellamide structure is a potential active oxidant of the dicopper patellamide complex. PMID:18930320

  16. Bio-inspired multinuclear copper complexes covalently immobilized on reduced graphene oxide as efficient electrocatalysts for the oxygen reduction reaction.

    PubMed

    Xi, Yue-Ting; Wei, Ping-Jie; Wang, Ru-Chun; Liu, Jin-Gang

    2015-05-01

    Inspired by the multicopper active site of laccase, which efficiently catalyzes the oxygen reduction reaction (ORR), herein we report a novel bio-inspired ORR catalyst composed of a multinuclear copper complex that was immobilized on the surface of reduced graphene oxide (rGO) via the covalently grafted triazole-dipyridine (TADPy) dinucleating ligand. This rGO-TADPyCu catalyst exhibited high ORR activity and superior long-term stability compared to Pt/C in alkaline media. PMID:25825826

  17. Leukocytic oxygen activation and microbicidal oxidative toxins.

    PubMed

    Hurst, J K; Barrette, W C

    1989-01-01

    Following a brief introduction of cellular response to stimulation comprising leukocyte activation, three major areas are discussed: (1) the neutrophil oxidase; (2) myeloperoxidase (MPO)-dependent oxidative microbicidal reactions; and (3) MPO-independent oxidative reactions. Topics included in section (A) are current views on the activation mechanism, redox composition, structural and topographic organization of the oxidase, and its respiratory products. In section (B), emphasis is placed on recent research on cidal mechanisms of HOCl, including the oxidative biochemistry of active chlorine compounds, identification of sites of lesions in bacteria, and attendant metabolic consequences. In section (C), we review the (bio)chemistry of H2O2 and .OH microbicidal reactions, with particular attention being given to addressing the controversial issue of probe methods to identify .OH radical and critical assessment of the recent proposal that MPO-independent killing arises from site-specific metal-catalyzed Fenton-type chemistry. PMID:2548810

  18. Effect of ramping on oxygen precipitates and Cu-vacancy complex in Czochralski silicon

    NASA Astrophysics Data System (ADS)

    Xu, Jin; Lv, Yaochao; Guo, Weibin; Xie, Tingting

    2016-07-01

    The effect of ramping on oxygen precipitates and Cu-vacancy complex in Czochralski silicon has been investigated by means of Fourier transform infrared spectroscopy (FTIR) and photoluminescence (PL) measurements, respectively. It was found that ramping from low temperature could promote the formation of oxygen precipitates in copper-contaminated Czochralski silicon and the lower the start ramping temperature was, the more oxygen precipitates formed. Moreover, the amount of precipitated oxygen atoms increased with copper contamination temperature. Through the investigation of 0.97 eV PL line related with Cu-vacancy complex, it was revealed that a lower start ramping temperature led to a lower concentration of Cu-vacancy complex and the increase of the copper contamination temperature resulted in the decrease of concentration of Cu-vacancy complex.

  19. OXYGEN UTILIZATION IN ACTIVATED SLUDGE PLANTS: SIMULATION AND MODEL CALIBRATION

    EPA Science Inventory

    The objective of the research described in the report is to apply recent advances in activated sludge process modeling to the simulation of oxygen utilization rates in full scale activated sludge treatment plants. This is accomplished by calibrating the International Association ...

  20. Oxygen tension limits nitric oxide synthesis by activated macrophages.

    PubMed Central

    McCormick, C C; Li, W P; Calero, M

    2000-01-01

    Previous studies have established that constitutive calcium-dependent ('low-output') nitric oxide synthase (NOS) is regulated by oxygen tension. We have investigated the role of oxygen tension in the synthesis of NO by the 'high-output' calcium-independent NOS in activated macrophages. Hypoxia increased macrophage NOS gene expression in the presence of one additional activator, such as lipopolysaccharide or interferon-gamma, but not in the presence of both. Hypoxia markedly reduced the synthesis of NO by activated macrophages (as measured by accumulation of nitrite and citrulline), such that, at 1% oxygen tension, NO accumulation was reduced by 80-90%. The apparent K(m) for oxygen calculated from cells exposed to a range of oxygen tensions was found to be 10.8%, or 137 microM, O(2) This value is considerably higher than the oxygen tension in tissues, and is virtually identical to that reported recently for purified recombinant macrophage NOS. The decrease in NO synthesis did not appear to be due to diminished arginine or cofactor availability, since arginine transport and NO synthesis during recovery in normoxia were normal. Analysis of NO synthesis during hypoxia as a function of extracellular arginine indicated that an altered V(max), but not K(m)(Arg), accounted for the observed decrease in NO synthesis. We conclude that oxygen tension regulates the synthesis of NO in macrophages by a mechanism similar to that described previously for the calcium-dependent low-output NOS. Our data suggest that oxygen tension may be an important physiological regulator of macrophage NO synthesis in vivo. PMID:10970783

  1. Synergistic oxygen atom transfer by ruthenium complexes with non-redox metal ions.

    PubMed

    Lv, Zhanao; Zheng, Wenrui; Chen, Zhuqi; Tang, Zhiming; Mo, Wanling; Yin, Guochuan

    2016-07-28

    Non-redox metal ions can affect the reactivity of active redox metal ions in versatile biological and heterogeneous oxidation processes; however, the intrinsic roles of these non-redox ions still remain elusive. This work demonstrates the first example of the use of non-redox metal ions as Lewis acids to sharply improve the catalytic oxygen atom transfer efficiency of a ruthenium complex bearing the classic 2,2'-bipyridine ligand. In the absence of Lewis acid, the oxidation of ruthenium(ii) complex by PhI(OAc)2 generates the Ru(iv)[double bond, length as m-dash]O species, which is very sluggish for olefin epoxidation. When Ru(bpy)2Cl2 was tested as a catalyst alone, only 21.2% of cyclooctene was converted, and the yield of 1,2-epoxycyclooctane was only 6.7%. As evidenced by electronic absorption spectra and EPR studies, both the oxidation of Ru(ii) by PhI(OAc)2 and the reduction of Ru(iv)[double bond, length as m-dash]O by olefin are kinetically slow. However, adding non-redox metal ions such as Al(iii) can sharply improve the oxygen transfer efficiency of the catalyst to 100% conversion with 89.9% yield of epoxide under identical conditions. Through various spectroscopic characterizations, an adduct of Ru(iv)[double bond, length as m-dash]O with Al(iii), Ru(iv)[double bond, length as m-dash]O/Al(iii), was proposed to serve as the active species for epoxidation, which in turn generated a Ru(iii)-O-Ru(iii) dimer as the reduced form. In particular, both the oxygen transfer from Ru(iv)[double bond, length as m-dash]O/Al(iii) to olefin and the oxidation of Ru(iii)-O-Ru(iii) back to the active Ru(iv)[double bond, length as m-dash]O/Al(iii) species in the catalytic cycle can be remarkably accelerated by adding a non-redox metal, such as Al(iii). These results have important implications for the role played by non-redox metal ions in catalytic oxidation at redox metal centers as well as for the understanding of the redox mechanism of ruthenium catalysts in the oxygen atom

  2. A foundational methodology for determining system static complexity using notional lunar oxygen production processes

    NASA Astrophysics Data System (ADS)

    Long, Nicholas James

    This thesis serves to develop a preliminary foundational methodology for evaluating the static complexity of future lunar oxygen production systems when extensive information is not yet available about the various systems under consideration. Evaluating static complexity, as part of a overall system complexity analysis, is an important consideration in ultimately selecting a process to be used in a lunar base. When system complexity is higher, there is generally an overall increase in risk which could impact the safety of astronauts and the economic performance of the mission. To evaluate static complexity in lunar oxygen production, static complexity is simplified and defined into its essential components. First, three essential dimensions of static complexity are investigated, including interconnective complexity, strength of connections, and complexity in variety. Then a set of methods is developed upon which to separately evaluate each dimension. Q-connectivity analysis is proposed as a means to evaluate interconnective complexity and strength of connections. The law of requisite variety originating from cybernetic theory is suggested to interpret complexity in variety. Secondly, a means to aggregate the results of each analysis is proposed to create holistic measurement for static complexity using the Single Multi-Attribute Ranking Technique (SMART). Each method of static complexity analysis and the aggregation technique is demonstrated using notional data for four lunar oxygen production processes.

  3. Microfluidic Platform Generates Oxygen Landscapes for Localized Hypoxic Activation

    PubMed Central

    Rexius, Megan L.; Mauleon, Gerardo; Malik, Asrar B.; Rehman, Jalees; Eddington, David T.

    2014-01-01

    An open-well microfluidic platform generates an oxygen landscape using gas-perfused networks which diffuse across a membrane. The device enables real-time analysis of cellular and tissue responses to oxygen tension to define how cells adapt to heterogeneous oxygen conditions found in the physiological setting. We demonstrate that localized hypoxic activation of cells elicited specific metabolic and gene responses in human microvascular endothelial cells and bone marrow-derived mesenchymal stem cells. A robust demonstration of the compatibility of the device with standard laboratory techniques demonstrates the wide utility of the method. This platform is ideally suited to study real-time cell responses and cell-cell interactions within physiologically relevant oxygen landscapes. PMID:25315003

  4. Reactive Oxygen Species Mediated Activation of a Dormant Singlet Oxygen Photosensitizer: From Autocatalytic Singlet Oxygen Amplification to Chemicontrolled Photodynamic Therapy.

    PubMed

    Durantini, Andrés M; Greene, Lana E; Lincoln, Richard; Martínez, Sol R; Cosa, Gonzalo

    2016-02-01

    Here we show the design, preparation, and characterization of a dormant singlet oxygen ((1)O2) photosensitizer that is activated upon its reaction with reactive oxygen species (ROS), including (1)O2 itself, in what constitutes an autocatalytic process. The compound is based on a two segment photosensitizer-trap molecule where the photosensitizer segment consists of a Br-substituted boron-dipyrromethene (BODIPY) dye. The trap segment consists of the chromanol ring of α-tocopherol, the most potent naturally occurring lipid soluble antioxidant. Time-resolved absorption, fluorescence, and (1)O2 phosphorescence studies together with fluorescence and (1)O2 phosphorescence emission quantum yields collected on Br2B-PMHC and related bromo and iodo-substituted BODIPY dyes show that the trap segment provides a total of three layers of intramolecular suppression of (1)O2 production. Oxidation of the trap segment with ROS restores the sensitizing properties of the photosensitizer segment resulting in ∼40-fold enhancement in (1)O2 production. The juxtaposed antioxidant (chromanol) and prooxidant (Br-BODIPY) antagonistic chemical activities of the two-segment compound enable the autocatalytic, and in general ROS-mediated, activation of (1)O2 sensitization providing a chemical cue for the spatiotemporal control of (1)O2.The usefulness of this approach to selectively photoactivate the production of singlet oxygen in ROS stressed vs regular cells was successfully tested via the photodynamic inactivation of a ROS stressed Gram negative Escherichia coli strain. PMID:26789198

  5. Synthesis, characterization and biological relevance of some metal (II) complexes with oxygen, nitrogen and oxygen (ONO) donor Schiff base ligand derived from thiazole and 2-hydroxy-1-naphthaldehyde

    NASA Astrophysics Data System (ADS)

    Nagesh, G. Y.; Mruthyunjayaswamy, B. H. M.

    2015-04-01

    The novel Schiff base ligand 2-((2-hydroxynaphthalen-1-yl)methylene)-N-(4-phenylthiazol-2-yl)hydrazinecarboxamide (L) obtained by the condensation of N-(4-phenylthiazol-2-yl)hydrazinecarboxamide with 2-hydroxy-1-naphthaldehyde and its newly synthesized Cu(II), Co(II), Ni(II), Zn(II) and Cd(II) complexes have been characterized by microanalysis, molar conductance, IR, 1H NMR, ESI-mass, UV-Visible, TGA/DTA, ESR and powder X-ray diffraction data to explicate their structures. The IR results confirmed the tridentate binding of the ligand involving oxygen atom of amide carbonyl, azomethine nitrogen and naphthol oxygen. 1H NMR spectral data of the ligand (L) and its Zn(II) complex agreed well with the proposed structures. Thermogravimetric studies for Cu(II) and Ni(II) complexes indicated the presence of coordinated water molecules and the final product is the metal oxide. In order to appraise the effect of antimicrobial activity of metal ions upon chelation, the newly synthesized ligand and its metal complexes were screened for their antimicrobial activity by minimum inhibitory concentration (MIC) method. The DNA cleavage activities were studied using plasmid DNA pBR322 (Bangal re Genei, Bengaluru, Cat. No 105850) as a target molecule by agarose gel electrophoresis method. The brine shrimp bioassay was also carried out to study the in vitro cytotoxicity properties against Artemia salina. Furthermore, the antioxidant activity were determined in vitro by reduction of 1,1-diphenyl-2-picryl hydrazyl (DPPH). The ligand exhibited better in vitro-antioxidant activity than its metal complexes.

  6. Active and stable carbon nanotube/nanoparticle composite electrocatalyst for oxygen reduction

    PubMed Central

    Chung, Hoon T.; Won, Jong H.; Zelenay, Piotr

    2013-01-01

    Nanostructured carbon-based materials, such as nitrogen-doped carbon nanotube arrays, Co3O4/nitrogen-doped graphene hybrids and carbon nanotube–graphene complexes have shown respectable oxygen reduction reaction activity in alkaline media. Although certainly promising, the performance of these materials does not yet warrant implementation in the energy conversion/storage devices utilizing basic electrolytes, for example, alkaline fuel cells, metal-air batteries and certain electrolysers. Here we demonstrate a new type of nitrogen-doped carbon nanotube/nanoparticle composite oxygen reduction reaction electrocatalyst obtained from iron acetate as an iron precursor and from cyanamide as a nitrogen and carbon nanotube precursor in a simple, scalable and single-step method. The composite has the highest oxygen reduction reaction activity in alkaline media of any non-precious metal catalysts. When used at a sufficiently high loading, this catalyst also outperforms the most active platinum-based catalysts. PMID:23715281

  7. Characterization of Oxygen Bridged Manganese Model Complexes Using Multifrequency (17)O-Hyperfine EPR Spectroscopies and Density Functional Theory.

    PubMed

    Rapatskiy, Leonid; Ames, William M; Pérez-Navarro, Montserrat; Savitsky, Anton; Griese, Julia J; Weyhermüller, Thomas; Shafaat, Hannah S; Högbom, Martin; Neese, Frank; Pantazis, Dimitrios A; Cox, Nicholas

    2015-10-29

    Multifrequency pulsed EPR data are reported for a series of oxygen bridged (μ-oxo/μ-hydroxo) bimetallic manganese complexes where the oxygen is labeled with the magnetically active isotope (17)O (I = 5/2). Two synthetic complexes and two biological metallocofactors are examined: a planar bis-μ-oxo bridged complex and a bent, bis-μ-oxo-μ-carboxylato bridge complex; the dimanganese catalase, which catalyzes the dismutation of H2O2 to H2O and O2, and the recently identified manganese/iron cofactor of the R2lox protein, a homologue of the small subunit of the ribonuclotide reductase enzyme (class 1c). High field (W-band) hyperfine EPR spectroscopies are demonstrated to be ideal methods to characterize the (17)O magnetic interactions, allowing a magnetic fingerprint for the bridging oxygen ligand to be developed. It is shown that the μ-oxo bridge motif displays a small positive isotropic hyperfine coupling constant of about +5 to +7 MHz and an anisotropic/dipolar coupling of -9 MHz. In addition, protonation of the bridge is correlated with an increase of the hyperfine coupling constant. Broken symmetry density functional theory is evaluated as a predictive tool for estimating hyperfine coupling of bridging species. Experimental and theoretical results provide a framework for the characterization of the oxygen bridge in Mn metallocofactor systems, including the water oxidizing cofactor of photosystem II, allowing the substrate/solvent interface to be examined throughout its catalytic cycle. PMID:26225537

  8. Prolyl Hydroxylase PHD3 Activates Oxygen-dependent Protein Aggregation

    PubMed Central

    Rantanen, Krista; Pursiheimo, Juha; Högel, Heidi; Himanen, Virpi; Metzen, Eric

    2008-01-01

    The HIF prolyl hydroxylases (PHDs/EGLNs) are central regulators of the molecular responses to oxygen availability. One isoform, PHD3, is expressed in response to hypoxia and causes apoptosis in oxygenated conditions in neural cells. Here we show that PHD3 forms subcellular aggregates in an oxygen-dependent manner. The aggregation of PHD3 was seen under normoxia and was strongly reduced under hypoxia or by the inactivation of the PHD3 hydroxylase activity. The PHD3 aggregates were dependent on microtubular integrity and contained components of the 26S proteasome, chaperones, and ubiquitin, thus demonstrating features that are characteristic for aggresome-like structures. Forced expression of the active PHD3 induced the aggregation of proteasomal components and activated apoptosis under normoxia in HeLa cells. The apoptosis was seen in cells prone to PHD3 aggregation and the PHD3 aggregation preceded apoptosis. The data demonstrates the cellular oxygen sensor PHD3 as a regulator of protein aggregation in response to varying oxygen availability. PMID:18337469

  9. Excited states in the active media of oxygen - iodine lasers

    SciTech Connect

    Azyazov, V N

    2009-11-30

    A review of investigations of kinetic processes in active media oxygen - iodine lasers (OILs) performed in the last decade is presented. The mechanisms of pumping and quenching of electronically and vibrationally excited O{sub 2} and I{sub 2} molecules are considered, and dissociation mechanisms of I{sub 2} in the active medium of the OIL are analysed. The values of kinetic constants of processes proceeding in the active media of OILs are recommended. (review)

  10. Isolation of photosystem II-enriched membranes and the oxygen-evolving complex subunit proteins from higher plants.

    PubMed

    Yamamoto, Yasusi; Leng, Jing; Shen, Jian-Ren

    2011-01-01

    We describe methods to isolate highly active oxygen-evolving photosystem II (PSII) membranes and core complexes from higher plants, and to purify subunits of the oxygen-evolving complex (OEC). The membrane samples used as the material for various in vitro studies of PSII are prepared by solubilizing thylakoid membranes with the nonionic detergent Triton X-100, and the core complexes are prepared by further solubilization of the PSII membranes with n-dodecyl-β-D-maltoside (β-DDM). The OEC subunit proteins are dissociated from the PSII-enriched membranes by alkaline or salt treatment, and are then purified by ion-exchange chromatography using an automated high performance liquid chromatography system. PMID:20960116

  11. Intramolecular gamma-hydroxylations of nonactivated C-H bonds with copper complexes and molecular oxygen.

    PubMed

    Schönecker, Bruno; Zheldakova, Tatjana; Lange, Corinna; Günther, Wolfgang; Görls, Helmar; Bohl, Martin

    2004-11-19

    Copper(I) complexes incorporating the isomeric bidentate ligands IMPY (iminomethyl-2-pyridines) or AMPY (aminomethylene-2-pyridines) are quite unusual in their ability to bind and activate molecular oxygen. Using these complexes, hydroxylations of nonactivated CH, CH2, or CH3 groups in the gamma-position in relation to the imino-nitrogen atom, and with a specific orientation of one H atom with respect to the binuclear Cu-O species, can be achieved in synthetically useful yields. Through mechanistic studies employing conformationally well-defined molecules (for example, cyclic isoprenoids), coupled with solid-state X-ray structure analyses and force-field calculations, we postulate a seven-membered transition state for this reaction in which six atoms lie approximately in a plane. This plane is defined by the positions of the lone pairs on the nitrogen atoms, as well as the copper and the oxygen atoms. For a successful hydroxylation, one hydrogen atom should be located close to this plane. Prediction of the stereochemical course of these reactions is possible based on a simple geometrical criterion. The convenient introduction of IMPY and AMPY groups as auxiliaries into oxo and primary amino compounds and the simple hydrolysis after the hydroxylation procedure has allowed the synthesis of 3-hydroxy-1-oxo and 3-hydroxy-1-amino compounds. If desired, the 3-hydroxy-1-IMPY and -1-AMPY compounds can be reduced with NaBH4 to obtain 3-hydroxy-1-aminomethylpyridines. For a successful hydroxylation procedure, the method employed for the synthesis of the CuI complexes is very important. Starting either from CuI salts or from CuII salts with a subsequent reduction with benzoin/triethylamine may turn out to be the better way, depending on the ligand and the molecular structure. PMID:15521055

  12. Oxygen Reduction Mechanism of Monometallic Rhodium Hydride Complexes.

    PubMed

    Halbach, Robert L; Teets, Thomas S; Nocera, Daniel G

    2015-08-01

    The reduction of O2 to H2O mediated by a series of electronically varied rhodium hydride complexes of the form cis,trans-Rh(III)Cl2H(CNAd)(P(4-X-C6H4)3)2 (2) (CNAd = 1-adamantylisocyanide; X = F (2a), Cl (2b), Me (2c), OMe (2d)) was examined through synthetic and kinetic studies. Rhodium(III) hydride 2 reacts with O2 to afford H2O with concomitant generation of trans-Rh(III)Cl3(CNAd)(P(4-X-C6H4)3)2 (3). Kinetic studies of the reaction of the hydride complex 2 with O2 in the presence of HCl revealed a two-term rate law consistent with an HX reductive elimination (HXRE) mechanism, where O2 binds to a rhodium(I) metal center and generates an η(2)-peroxo complex intermediate, trans-Rh(III)Cl(CNAd)(η(2)-O2)(P(4-X-C6H4)3)2 (4), and a hydrogen-atom abstraction (HAA) mechanism, which entails the direct reaction of O2 with the hydride. Experimental data reveal that the rate of reduction of O2 to H2O is enhanced by electron-withdrawing phosphine ligands. Complex 4 was independently prepared by the addition of O2 to trans-Rh(I)Cl(CNAd)(P(4-X-C6H4)3)2 (1). The reactivity of 4 toward HCl reveals that such peroxo complexes are plausible intermediates in the reduction of O2 to H2O. These results show that the given series of electronically varied rhodium(III) hydride complexes facilitate the reduction of O2 to H2O according to a two-term rate law comprising HXRE and HAA pathways and that the relative rates of these two pathways, which can occur simultaneously and competitively, can be systematically modulated by variation of the electronic properties of the ancillary ligand set. PMID:26168057

  13. NADPH Oxidase- and Mitochondria-derived Reactive Oxygen Species in Proinflammatory Microglial Activation: A Bipartisan Affair?

    PubMed Central

    Bordt, Evan A.; Polster, Brian M.

    2014-01-01

    Microglia are the resident immune cells of the brain and play major roles in central nervous system development, maintenance, and disease. Brain insults cause microglia to proliferate, migrate, and transform into one or more activated states. Classical M1 activation triggers the production of proinflammatory factors such as tumor necrosis factor- α (TNF-α), interleukin-1β (IL-1β), nitric oxide (NO), and reactive oxygen species which, in excess, can exacerbate brain injury. The mechanisms underlying microglial activation are not fully understood, yet reactive oxygen species are increasingly implicated as mediators of microglial activation. In this review, we highlight studies linking reactive oxygen species, in particular hydrogen peroxide derived from NADPH oxidase-generated superoxide, to the classical activation of microglia. In addition, we critically evaluate controversial evidence suggesting a specific role for mitochondrial reactive oxygen species in the activation of the NLRP3 inflammasome, a multiprotein complex that mediates the production of IL-1β and IL-18. Finally, the limitations of common techniques used to implicate mitochondrial ROS in microglial and inflammasome activation, such as the use of the mitochondrially-targeted ROS indicator MitoSOX and the mitochondrially-targeted antioxidant MitoTEMPO, are also discussed. PMID:25091898

  14. Early oxygen-utilization and brain activity in preterm infants.

    PubMed

    Tataranno, Maria Luisa; Alderliesten, Thomas; de Vries, Linda S; Groenendaal, Floris; Toet, Mona C; Lemmers, Petra M A; Vosse van de, Renè E; van Bel, Frank; Benders, Manon J N L

    2015-01-01

    The combined monitoring of oxygen supply and delivery using Near-InfraRed spectroscopy (NIRS) and cerebral activity using amplitude-integrated EEG (aEEG) could yield new insights into brain metabolism and detect potentially vulnerable conditions soon after birth. The relationship between NIRS and quantitative aEEG/EEG parameters has not yet been investigated. Our aim was to study the association between oxygen utilization during the first 6 h after birth and simultaneously continuously monitored brain activity measured by aEEG/EEG. Forty-four hemodynamically stable babies with a GA < 28 weeks, with good quality NIRS and aEEG/EEG data available and who did not receive morphine were included in the study. aEEG and NIRS monitoring started at NICU admission. The relation between regional cerebral oxygen saturation (rScO2) and cerebral fractional tissue oxygen extraction (cFTOE), and quantitative measurements of brain activity such as number of spontaneous activity transients (SAT) per minute (SAT rate), the interval in seconds (i.e. time) between SATs (ISI) and the minimum amplitude of the EEG in μV (min aEEG) were evaluated. rScO2 was negatively associated with SAT rate (β=-3.45 [CI=-5.76- -1.15], p=0.004) and positively associated with ISI (β=1.45 [CI=0.44-2.45], p=0.006). cFTOE was positively associated with SAT rate (β=0.034 [CI=0.009-0.059], p=0.008) and negatively associated with ISI (β=-0.015 [CI=-0.026- -0.004], p=0.007). Oxygen delivery and utilization, as indicated by rScO2 and cFTOE, are directly related to functional brain activity, expressed by SAT rate and ISI during the first hours after birth, showing an increase in oxygen extraction in preterm infants with increased early electro-cerebral activity. NIRS monitored oxygenation may be a useful biomarker of brain vulnerability in high-risk infants. PMID:25965343

  15. Active impedance matching of complex structural systems

    NASA Technical Reports Server (NTRS)

    Macmartin, Douglas G.; Miller, David W.; Hall, Steven R.

    1991-01-01

    Viewgraphs on active impedance matching of complex structural systems are presented. Topics covered include: traveling wave model; dereverberated mobility model; computation of dereverberated mobility; control problem: optimal impedance matching; H2 optimal solution; statistical energy analysis (SEA) solution; experimental transfer functions; interferometer actuator and sensor locations; active strut configurations; power dual variables; dereverberation of complex structure; dereverberated transfer function; compensators; and relative power flow.

  16. Changes to coral health and metabolic activity under oxygen deprivation.

    PubMed

    Murphy, James W A; Richmond, Robert H

    2016-01-01

    On Hawaiian reefs, the fast-growing, invasive algae Gracilaria salicornia overgrows coral heads, restricting water flow and light, thereby smothering corals. Field data shows hypoxic conditions (dissolved oxygen (DO2) < 2 mg/L) occurring underneath algal mats at night, and concurrent bleaching and partial tissue loss of shaded corals. To analyze the impact of nighttime oxygen-deprivation on coral health, this study evaluated changes in coral metabolism through the exposure of corals to chronic hypoxic conditions and subsequent analyses of lactate, octopine, alanopine, and strombine dehydrogenase activities, critical enzymes employed through anaerobic respiration. Following treatments, lactate and octopine dehydrogenase activities were found to have no significant response in activities with treatment and time. However, corals subjected to chronic nighttime hypoxia were found to exhibit significant increases in alanopine dehydrogenase activity after three days of exposure and strombine dehydrogenase activity starting after one overnight exposure cycle. These findings provide new insights into coral metabolic shifts in extremely low-oxygen environments and point to ADH and SDH assays as tools for quantifying the impact of hypoxia on coral health. PMID:27114888

  17. Changes to coral health and metabolic activity under oxygen deprivation

    PubMed Central

    Richmond, Robert H.

    2016-01-01

    On Hawaiian reefs, the fast-growing, invasive algae Gracilaria salicornia overgrows coral heads, restricting water flow and light, thereby smothering corals. Field data shows hypoxic conditions (dissolved oxygen (DO2) < 2 mg/L) occurring underneath algal mats at night, and concurrent bleaching and partial tissue loss of shaded corals. To analyze the impact of nighttime oxygen-deprivation on coral health, this study evaluated changes in coral metabolism through the exposure of corals to chronic hypoxic conditions and subsequent analyses of lactate, octopine, alanopine, and strombine dehydrogenase activities, critical enzymes employed through anaerobic respiration. Following treatments, lactate and octopine dehydrogenase activities were found to have no significant response in activities with treatment and time. However, corals subjected to chronic nighttime hypoxia were found to exhibit significant increases in alanopine dehydrogenase activity after three days of exposure and strombine dehydrogenase activity starting after one overnight exposure cycle. These findings provide new insights into coral metabolic shifts in extremely low-oxygen environments and point to ADH and SDH assays as tools for quantifying the impact of hypoxia on coral health. PMID:27114888

  18. Activated oxygen alters cerebral microvascular responses in newborn pigs

    SciTech Connect

    Leffler, C.W.; Busiia, D.W.; Armstead, W.M.; Mirro, R.; Thelin, O. )

    1990-02-26

    In piglets, cerebral ischemia/reperfusion blocks prostanoid dependent cerebral vasodilation to hypercapnia (CO{sub 2}) and hypotension but not prostanoid independent dilation to isoproterenol (Isu) or constriction to norepinephrine (NE). Ischemia/reperfusion increases activated-O{sub 2} production by piglet brains. Using cranial windows in piglets, the authors investigated the hypothesis that activated oxygen can block prostanoid dependent cerebral vasodilator responses to CO{sub 2} and hypotension without altering responses to Isu and NE. Exposure to an activated oxygen generating system of xanthine oxidase, hypoxanthine, and Fe that made about 3 times the activated-O{sub 2} on the brain surface as ischemia/reperfusion caused reversible pial arteriolar dilation. After exposure, pial arteriolar dilation was reduced to CO{sub 2} and hypotension but not to Isu. NE constrictor responses were also unaltered. H{sub 2}O{sub 2} or H{sub 2}O{sub 2} + Fe caused constriction followed by reversible dilation. After exposure, pial arteriolar dilation in response to CO{sub 2} and hypotension was not altered. However, addition of xanthine oxidase and hypoxanthine with H{sub 2}O{sub 2} and Fe totally eliminated pial arteriolar dilator responses to CO{sub 2} and hypotension but did not decrease dilation caused by Isu or constriction caused by NE. The authors conclude that activated oxygen could produce the altered prostanoid dependent pial arteriolar responses observed following ischemia in piglets.

  19. A rhenium complex doped in a silica molecular sieve for molecular oxygen sensing: Construction and characterization.

    PubMed

    Yang, Xiaozhou; Li, Yanxiao

    2016-01-15

    This paper reported a diamine ligand and its Re(I) complex for potential application in oxygen sensing. The novelty of this diamine ligand localized at its increased conjugation chain which had a typical electron-withdrawing group of 1,3,4-oxadiazole. Electronic distribution of excited electrons and their lifetime were supposed to be increased, favoring oxygen sensing collision. This hypothesis was confirmed by single crystal analysis, theoretical calculation and photophysical measurement. It was found that this Re(I) complex had a long-lived emission peaking at 545 nm, favoring sensing application. By doping this complex into a silica matrix MCM-41, oxygen sensing performance and mechanism of the resulting composites were discussed in detail. Non-linear Stern-Volmer working curves were observed with maximum sensitivity of 5.54 and short response time of ~6 s. PMID:26478986

  20. A rhenium complex doped in a silica molecular sieve for molecular oxygen sensing: Construction and characterization

    NASA Astrophysics Data System (ADS)

    Yang, Xiaozhou; Li, Yanxiao

    2016-01-01

    This paper reported a diamine ligand and its Re(I) complex for potential application in oxygen sensing. The novelty of this diamine ligand localized at its increased conjugation chain which had a typical electron-withdrawing group of 1,3,4-oxadiazole. Electronic distribution of excited electrons and their lifetime were supposed to be increased, favoring oxygen sensing collision. This hypothesis was confirmed by single crystal analysis, theoretical calculation and photophysical measurement. It was found that this Re(I) complex had a long-lived emission peaking at 545 nm, favoring sensing application. By doping this complex into a silica matrix MCM-41, oxygen sensing performance and mechanism of the resulting composites were discussed in detail. Non-linear Stern-Volmer working curves were observed with maximum sensitivity of 5.54 and short response time of ~ 6 s.

  1. Antischistosomal Activity of Oxindolimine-Metal Complexes

    PubMed Central

    Dario, Bruno S.; Couto, Ricardo A. A.; Pinto, Pedro L. S.; da Costa Ferreira, Ana M.

    2015-01-01

    In recent years, a class of oxindole-copper and -zinc complex derivatives have been reported as compounds with efficient proapoptotic activity toward different tumor cells (e.g., neuroblastomas, melanomas, monocytes). Here we assessed the efficacy of synthesized oxindole-copper(II), -zinc(II), and -vanadyl (VO2+) complexes against adult Schistosoma mansoni worms. The copper(II) complexes (50% inhibitory concentrations of 30 to 45 μM) demonstrated greater antischistosomal properties than the analogous zinc and vanadyl complexes regarding lethality, reduction of motor activity, and oviposition. PMID:26239976

  2. Antischistosomal Activity of Oxindolimine-Metal Complexes.

    PubMed

    de Moraes, Josué; Dario, Bruno S; Couto, Ricardo A A; Pinto, Pedro L S; da Costa Ferreira, Ana M

    2015-10-01

    In recent years, a class of oxindole-copper and -zinc complex derivatives have been reported as compounds with efficient proapoptotic activity toward different tumor cells (e.g., neuroblastomas, melanomas, monocytes). Here we assessed the efficacy of synthesized oxindole-copper(II), -zinc(II), and -vanadyl (VO(2+)) complexes against adult Schistosoma mansoni worms. The copper(II) complexes (50% inhibitory concentrations of 30 to 45 μM) demonstrated greater antischistosomal properties than the analogous zinc and vanadyl complexes regarding lethality, reduction of motor activity, and oviposition. PMID:26239976

  3. Xanthohumol induces generation of reactive oxygen species and triggers apoptosis through inhibition of mitochondrial electron transfer chain complex I.

    PubMed

    Zhang, Bo; Chu, Wei; Wei, Peng; Liu, Ying; Wei, Taotao

    2015-12-01

    Xanthohumol is a prenylflavonoid extracted from hops (Humulus lupulus). It possesses anti-cancer and anti-inflammatory activities in vitro and in vivo, and offers therapeutic benefits for treatment of metabolic syndromes. However, the precise mechanisms underlying its pharmacological effects remain to be elucidated, together with its cellular target. Here, we provide evidence that xanthohumol directly interacts with the mitochondrial electron transfer chain complex I (NADH dehydrogenase), inhibits the oxidative phosphorylation, triggers the production of reactive oxygen species, and induces apoptosis. In addition, we show that as a result of the inhibition of the mitochondrial oxidative phosphorylation, xanthohumol exposure causes a rapid decrease of mitochondrial transmembrane potential. Furthermore, we showed that xanthohumol up-regulates the glycolytic capacity in cells, and thus compensates cellular ATP generation. Dissection of the multiple steps of aerobic respiration by extracellular flux assays revealed that xanthohumol specifically inhibits the activity of mitochondrial complex I, but had little effect on that of complex II, III and IV. Inhibition of complex I by xanthohumol caused the overproduction of reactive oxygen species, which are responsible for the induction of apoptosis in cancer cells. We also found that isoxanthohumol, the structural isomer of xanthohumol, is inactive to cells, suggesting that the reactive 2-hydroxyl group of xanthohumol is crucial for its targeting to the mitochondrial complex I. Together, the remodeling of cell metabolism revealed here has therapeutic potential for the use of xanthohumol. PMID:26453927

  4. Hypersensitivity to oxygen and shortened lifespan in a Drosophila mitochondrial complex II mutant.

    PubMed

    Walker, David W; Hájek, Petr; Muffat, Julien; Knoepfle, Dan; Cornelison, Stephanie; Attardi, Giuseppe; Benzer, Seymour

    2006-10-31

    Oxidative stress is implicated as a major cause of aging and age-related diseases, such as Parkinson's and Alzheimer's, as well as ischemia-reperfusion injury in stroke. The mitochondrial electron transport chain is the principal source of reactive oxygen species within cells. Despite considerable medical interest, the molecular mechanisms that regulate reactive oxygen species formation within the mitochondrion remain poorly understood. Here, we report the isolation and characterization of a Drosophila mutant with a defect in subunit b of succinate dehydrogenase (SDH; mitochondrial complex II). The sdhB mutant is hypersensitive to oxygen and displays hallmarks of a progeroid syndrome, including early-onset mortality and age-related behavioral decay. Pathological analysis of the flight muscle, which is amongst the most highly energetic tissues in the animal kingdom, reveals structural abnormalities in the mitochondria. Biochemical analysis shows that, in the mutant, there is a complex II-specific respiratory defect and impaired complex II-mediated electron transport, although the other respiratory complexes remain functionally intact. The complex II defect is associated with an increased level of mitochondrial hydrogen peroxide production, suggesting a possible mechanism for the observed sensitivity to elevated oxygen concentration and the decreased lifespan of the mutant fly. PMID:17056719

  5. Activation of molecular oxygen and the nature of the active oxygen species for CO oxidation on oxide supported Au catalysts.

    PubMed

    Widmann, D; Behm, R J

    2014-03-18

    Although highly dispersed Au catalysts with Au nanoparticles (NPs) of a few nanometers in diameter are well-known for their high catalytic activity for several oxidation and reduction reactions already at rather low temperatures for almost 30 years, central aspects of the reaction mechanism are still unresolved. While most studies focused on the active site, the active Au species, and the effect of the support material, the most crucial step during oxidation reactions, the activation of molecular oxygen and the nature of the resulting active oxygen species (Oact), received more attention just recently. This is topic of this Account, which focuses on the formation, location, and nature of the Oact species present on metal oxide supported Au catalysts under typical reaction conditions, at room temperature and above. It is mainly based on quantitative temporal analysis of products (TAP) reactor measurements, which different from most spectroscopic techniques are able to detect and quantify these species even at the extremely low concentrations present under realistic reaction conditions. Different types of pulse experiments were performed, during which the highly dispersed, realistic powder catalysts are exposed to very low amounts of reactants, CO and/or O2, in order to form and reactively remove Oact species and gain information on their formation, nature, and the active site for Oact formation. Our investigations have shown that the active oxygen species for CO oxidation on Au/TiO2 for reaction at 80 °C and higher is a highly stable atomic species, which at 80 °C is formed only at the perimeter of the Au-oxide interface and whose reactive removal by CO is activated, but not its formation. From these findings, it is concluded that surface lattice oxygen represents the Oact species for the CO oxidation. Accordingly, the CO oxidation proceeds via a Au-assisted Mars-van Krevelen mechanism, during which surface lattice oxygen close to the Au NPs is removed by reaction

  6. Removal of Biologically Active Organic Contaminants using Atomic Oxygen

    NASA Technical Reports Server (NTRS)

    Banks, Bruce A. (Inventor); Banks, Michael A. (Inventor); Banks, Eric B. (Inventor)

    2003-01-01

    Biomedical devices that are to come into contact with living tissue, such as prosthetic and other implants for the human body and the containers used to store and transport them, are together cleaned of non-living, but biologically active organic materials, including endotoxins such as lipopolysaccharides, and assembled into a hermetically sealed package without recontamination. This is achieved by cleaning both the device and package components together in an apparatus, which includes a hermetically sealed chamber, in which they are contacted with atomic oxygen which biocleans them, by oxidizing the biologically active organic materials. The apparatus also includes means for manipulating the device and container and hermetically sealing the cleaned device into the cleaned container to form the package. A calibrated witness coupon visually indicates whether or not the device and container have received enough exposure to the atomic oxygen to have removed the organic materials from their surfaces. Gamma radiation is then used to sterilize the device in the sealed container.

  7. Charge transfer induced activity of graphene for oxygen reduction

    NASA Astrophysics Data System (ADS)

    Shen, Anli; Xia, Weijun; Zhang, Lipeng; Dou, Shuo; Xia, Zhenhai; Wang, Shuangyin

    2016-05-01

    Tetracyanoethylene (TCNE), with its strong electron-accepting ability, was used to dope graphene as a metal-free electrocatalyst for the oxygen reduction reaction (ORR). The charge transfer process was observed from graphene to TCNE by x-ray photoelectron spectroscopy and Raman characterizations. Our density functional theory calculations found that the charge transfer behavior led to an enhancement of the electrocatalytic activity for the ORR.

  8. Effects of MCI-186 upon neutrophil-derived active oxygens.

    PubMed

    Sumitomo, K; Shishido, N; Aizawa, H; Hasebe, N; Kikuchi, K; Nakamura, M

    2007-01-01

    Reactions of 3-methyl-1-phenyl-2-pyrazoline-5-one (MCI-186) with hypochlorous acid and superoxide were analysed by spectrophotometry and mass spectrometry. The results were applied to the neutrophil system to evaluate the scavenging activity of neutrophil-derived active oxygen species by MCI-186. MCI-186 reacted rapidly with hypochlorous acid (1 x 10(6) M(-1)s(-1)) to form a chlorinated intermediate, followed by a slow conversion to a new spectrum. MCI-186 consumed 3 moles of hypochlorous acid and did not react with superoxide. The newly synthesized fluorescence probes, 2-[6-(4'-amino)-phenoxy-3H-xanthen-3-on-9-yl]benzoic acid (APF) and 2-[6-(4'-hydroxy)phenoxy-3H-anthen-3-on-9-yl]benzoic acid (HPF) successfully detected neutrophil-derived active oxygens (Setsukinai K, Urano Y, Kakinuma K, Majima HJ, Nagano T. Development of novel fluorescence probes that can reliably detect reactive oxygen species and distinguish specific species. J Biol Chem 2003; 278: 3170-3175). The rate constants for the reaction of hypochlorous acid with MCI-186 and fluorescence probes was in the order of MCI-186 > APF > HPF. Fluorescence due to the oxidation of APF and HPF was observed with the stimulated neutrophils. The result that the intensity from APF oxidation was higher than that from HPF oxidation is compatible with reports that APF selectively reacts with hypochlorous acid. Fluorescence due to oxidation of both APF and HPF decreased when the reactions were carried out in the presence of a fluorescence probe and MCI-186 in a dose-dependent manner. These results indicate that MCI-186 effectively scavenges neutrophil-derived hypochlorous acid and other active oxygens. PMID:17705989

  9. Excellently guarded materials against UV and oxygen in the surfactant molecular complex crystal matrix

    NASA Astrophysics Data System (ADS)

    Ichikawa, Haruyo; Iimura, Nahoko; Hirata, Hirotaka

    2000-07-01

    Crystalline surfactant molecular complexes (SCMs) generated between quaternary ammonium cationic surfactants such as CTAB and various additives disclose their excellent protective properties from UV light and oxygen to complex additive materials, which are occluded in the complex crystal matrix. The effects of UV and oxygen were followed by the absorption decay of additive chromophores in comparing that of naked additive specimens with that of those in the complexed state. From the decay profiles, the rate constants and the half-life times were estimated under the assumptions in which the photo and oxidation processes were dominated in accordance with the first-ordered reaction. The results afford us promising prospects in extending the shelf-life of every material, above all medicinal drug, with the consequence that these obtained values evidently demonstrate the remarkably suppressed rate and extremely elongated half-life times.

  10. Complex treatment of trophic affections with vascular patients using monochromatic red light and hyperbaric oxygenation

    NASA Astrophysics Data System (ADS)

    Babkina, Zinaida M.; Vasilyev, Mikhail V.; Zakharov, Vyacheslav P.; Nikolayev, Viktor V.; Babkin, Vasily I.; Samoday, Valery G.; Zon, Boris A.; Pakhomov, Gennady V.; Naskidashvili, Vasily I.; Kumin, Anatoly A.

    1996-11-01

    Monochromatic red light irradiation therapy of trophic skin affections with vascular patients permits to receive positive results with small wounds. A combination of monochromatic red light and hyperbaric oxygenation is most perspective when conducting a complex therapy of trophic wounds not more than 40 mm2 and allows to diminish time of treatment almost two times.

  11. Support nanostructure boosts oxygen transfer to catalytically active platinum nanoparticles.

    PubMed

    Vayssilov, Georgi N; Lykhach, Yaroslava; Migani, Annapaola; Staudt, Thorsten; Petrova, Galina P; Tsud, Nataliya; Skála, Tomáš; Bruix, Albert; Illas, Francesc; Prince, Kevin C; Matolín, Vladimír; Neyman, Konstantin M; Libuda, Jörg

    2011-04-01

    Interactions of metal particles with oxide supports can radically enhance the performance of supported catalysts. At the microscopic level, the details of such metal-oxide interactions usually remain obscure. This study identifies two types of oxidative metal-oxide interaction on well-defined models of technologically important Pt-ceria catalysts: (1) electron transfer from the Pt nanoparticle to the support, and (2) oxygen transfer from ceria to Pt. The electron transfer is favourable on ceria supports, irrespective of their morphology. Remarkably, the oxygen transfer is shown to require the presence of nanostructured ceria in close contact with Pt and, thus, is inherently a nanoscale effect. Our findings enable us to detail the formation mechanism of the catalytically indispensable Pt-O species on ceria and to elucidate the extraordinary structure-activity dependence of ceria-based catalysts in general. PMID:21423188

  12. Support nanostructure boosts oxygen transfer to catalytically active platinum nanoparticles

    NASA Astrophysics Data System (ADS)

    Vayssilov, Georgi N.; Lykhach, Yaroslava; Migani, Annapaola; Staudt, Thorsten; Petrova, Galina P.; Tsud, Nataliya; Skála, Tomáš; Bruix, Albert; Illas, Francesc; Prince, Kevin C.; MatolíN, VladimíR.; Neyman, Konstantin M.; Libuda, Jörg

    2011-04-01

    Interactions of metal particles with oxide supports can radically enhance the performance of supported catalysts. At the microscopic level, the details of such metal-oxide interactions usually remain obscure. This study identifies two types of oxidative metal-oxide interaction on well-defined models of technologically important Pt-ceria catalysts: (1) electron transfer from the Pt nanoparticle to the support, and (2) oxygen transfer from ceria to Pt. The electron transfer is favourable on ceria supports, irrespective of their morphology. Remarkably, the oxygen transfer is shown to require the presence of nanostructured ceria in close contact with Pt and, thus, is inherently a nanoscale effect. Our findings enable us to detail the formation mechanism of the catalytically indispensable Pt-O species on ceria and to elucidate the extraordinary structure-activity dependence of ceria-based catalysts in general.

  13. Diiridium Bimetallic Complexes Function as a Redox Switch To Directly Split Carbonate into Carbon Monoxide and Oxygen.

    PubMed

    Chen, Tsun-Ren; Wu, Fang-Siou; Lee, Hsiu-Pen; Chen, Kelvin H-C

    2016-03-23

    A pair of diiridium bimetallic complexes exhibit a special type of oxidation-reduction reaction that could directly split carbonate into carbon monoxide and molecular oxygen via a low-energy pathway needing no sacrificial reagent. One of the bimetallic complexes, Ir(III)(μ-Cl)2Ir(III), can catch carbonato group from carbonate and reduce it to CO. The second complex, the rare bimetallic complex Ir(IV)(μ-oxo)2Ir(IV), can react with chlorine to release O2 by the oxidation of oxygen ions with synergistic oxidative effect of iridium ions and chlorine atoms. The activation energy needed for the key reaction is quite low (∼20 kJ/mol), which is far less than the dissociation energy of the C═O bond in CO2 (∼750 kJ/mol). These diiridium bimetallic complexes could be applied as a redox switch to split carbonate or combined with well-known processes in the chemical industry to build up a catalytic system to directly split CO2 into CO and O2. PMID:26952250

  14. The NO-carbon reaction: the influence of potassium and CO on reactivity and populations of oxygen surface complexes

    SciTech Connect

    Diana Lopez; Joseph Calo

    2007-08-15

    Results on the effects of a metal catalyst and the role of CO as a reducing agent are reported for a resin char and a Wyodak coal char, as well as demineralized samples of the latter. The effect of an active metal catalyst, such as potassium in the current work, is to significantly increase the reactivity both by increasing the number of reaction sites via the catalyst dispersion and reducing the activation energy and by increasing CO{sub 2} production. The latter is a beneficial result because it means that less carbon is consumed per molecule of NO reduced. Additional CO in the gas phase 'catalyzes' NO reduction via the creation of more labile surface complexes and facilitation of desorption of other oxygen complexes. This effect decreases with an increasing temperature and disappears by about 1123 K. The activation energy of this reaction is comparable to that induced by the metal catalyst. 21 refs., 9 figs., 2 tabs.

  15. Evidence for the role of cyclic electron flow in photoprotection for oxygen-evolving complex.

    PubMed

    Huang, Wei; Yang, Ying-Jie; Hu, Hong; Zhang, Shi-Bao; Cao, Kun-Fang

    2016-05-01

    Cyclic electron flow (CEF) alleviates PSII photo-inhibition under high light by at least two different mechanisms: one is liked to thermal energy dissipation (qE) and the other one is independent of qE. However, the latter mechanism is unclear. Because the photodamage to PSII primarily occurred at the oxygen-evolving complex (OEC), and the stability of OEC is dependent on proton gradient across thylakoid membrane (ΔpH), we hypothesize that the CEF-dependent generation of ΔpH can alleviate photodamage to OEC. To test this hypothesis, we determined the effects of antimycin A (AA), methyl viologen (MV), chloramphenicol (CM), nigericin (Nig) on PSII activity and the stability of OEC for leaves of a light-demanding tropical tree species Erythrophleum guineense by the analysis of OKJIP chlorophyll a fluorescence transient. After high light treatment, the stronger decrease in Fv/Fm in the AA-, CM-, MV-, and Nig-treated samples was accompanied with larger photo damage of OEC. The AA-treated samples significantly showed lower CEF activity than the H2O-treated samples. Although the AA-treated leaves significantly showed stronger PSII photo-inhibition and photo-damage of OEC compared to the H2O-treated leaves, the value of non-photochemical quenching did not differ between them. Therefore, CEF activity was partly inhibited in the AA-treated samples, and the stronger PSII photo-inhibition in the AA-treated leaves was independent of qE. Taking together, we propose a hypothesis that CEF-dependent generation of ΔpH under high light plays an important role in photoprotection for the OEC activity. PMID:26968082

  16. On the determination of oxygen abundances in chromospherically active stars

    NASA Astrophysics Data System (ADS)

    Morel, T.; Micela, G.

    2004-08-01

    We discuss oxygen abundances derived from [O I] λ6300s and the O I triplet in stars spanning a wide range in chromospheric activity level, and show that these two indicators yield increasingly discrepant results with higher chromospheric/coronal activity measures. While the forbidden and permitted lines give fairly consistent results for solar-type disk dwarfs, spuriously high O I triplet abundances are observed in young Hyades and Pleiades stars, as well as in individual components of RS CVn binaries (up to 1.8 dex). The distinct behaviour of the [O I]-based abundances which consistently remain near-solar suggests that this phenomenon mostly results from large departures from LTE affecting the O I triplet at high activity level that are currently unaccounted for, but also possibly from a failure to adequately model the atmospheres of K-type stars. These results suggest that some caution should be exercised when interpreting oxygen abundances in active binaries or young open cluster stars. Based on observations collected at the European Southern Observatory, Chile (Proposals 64.L-0249 and 071.D-0260). Table \\ref{tab_data} is only available in electronic form at http://www.edpsciences.org

  17. Water-soluble phosphorescent ruthenium complex with a fluorescent coumarin unit for ratiometric sensing of oxygen levels in living cells.

    PubMed

    Hara, Daiki; Komatsu, Hirokazu; Son, Aoi; Nishimoto, Sei-Ichi; Tanabe, Kazuhito

    2015-04-15

    Dual emission was applied to a molecular probe for the ratiometric sensing of oxygen concentration in a living system. We prepared ruthenium complexes possessing a coumarin unit (Ru-Cou), in which the (3)MLCT phosphorescence of the ruthenium complex was efficiently quenched by molecular oxygen, whereas the coumarin unit emitted constant fluorescence independent of the oxygen concentration. The oxygen status could be determined precisely from the ratio of phosphorescence to fluorescence. We achieved the molecular imaging of cellular oxygen levels using Ru-Cou possessing an alkyl chain, which provided appropriate lipophilicity to increase cellular uptake. PMID:25848851

  18. Synthesis, Characterization, and Catalytic Oxygen Electroreduction Activities of Carbon-Supported PtW Nanoparticle Catalysts

    SciTech Connect

    Xiong, Liufeng; More, Karren Leslie; He, Ting

    2010-01-01

    Carbon-supported PtW (PtW/C) alloy nanoparticle catalysts with well-controlled particle size, dispersion, and composition uniformity, have been synthesized by wet chemical methods of decomposition of carbonyl cluster complexes, hydrolysis of metal salts, and chemical reactions within a reverse microemulsion. The synthesized PtW/C catalysts were characterized by X-ray diffraction, high-resolution transmission electron microscopy, and energy-dispersive spectroscopy. The catalytic oxygen electroreduction activities were measured by the hydrodynamic rotating disk electrode technique in an acidic electrolyte. The influence of the synthesis method on PtW particle size, size distribution, composition uniformity, and catalytic oxygen electroreduction activity, have been investigated. Among the synthesis methods studied, PtW/C catalysts prepared by the decomposition of carbonyl cluster complexes displayed the best platinum mass activity for oxygen reduction reaction under the current small scale production; a 3.4-fold catalytic enhancement was achieved in comparison to a benchmark Pt/C standard.

  19. Antiretroviral activity of thiosemicarbazone metal complexes.

    PubMed

    Pelosi, Giorgio; Bisceglie, Franco; Bignami, Fabio; Ronzi, Paola; Schiavone, Pasqualina; Re, Maria Carla; Casoli, Claudio; Pilotti, Elisabetta

    2010-12-23

    Thiosemicarbazones display a wide antimicrobial activity by targeting bacteria, fungi, and viruses. Here, we report our studies on the antiviral activity of two thiosemicarbazone metal complexes, [bis(citronellalthiosemicarbazonato)nickel(II)] and [aqua(pyridoxalthiosemicarbazonato)copper(II)] chloride monohydrate, against the retroviruses HIV-1 and HTLV-1/-2. Both compounds exhibit antiviral properties against HIV but not against HTLVs . In particular, the copper complex shows the most potent anti-HIV activity by acting at the post-entry steps of the viral cycle. PMID:21121632

  20. Why O2 is required by complex life on habitable planets and the concept of planetary "oxygenation time".

    PubMed

    Catling, David C; Glein, Christopher R; Zahnle, Kevin J; McKay, Christopher P

    2005-06-01

    Life is constructed from a limited toolkit: the Periodic Table. The reduction of oxygen provides the largest free energy release per electron transfer, except for the reduction of fluorine and chlorine. However, the bonding of O2 ensures that it is sufficiently stable to accumulate in a planetary atmosphere, whereas the more weakly bonded halogen gases are far too reactive ever to achieve significant abundance. Consequently, an atmosphere rich in O2 provides the largest feasible energy source. This universal uniqueness suggests that abundant O2 is necessary for the high-energy demands of complex life anywhere, i.e., for actively mobile organisms of approximately 10(-1)-10(0) m size scale with specialized, differentiated anatomy comparable to advanced metazoans. On Earth, aerobic metabolism provides about an order of magnitude more energy for a given intake of food than anaerobic metabolism. As a result, anaerobes do not grow beyond the complexity of uniseriate filaments of cells because of prohibitively low growth efficiencies in a food chain. The biomass cumulative number density, n, at a particular mass, m, scales as n (> m) proportional to m(-1) for aquatic aerobes, and we show that for anaerobes the predicted scaling is n proportional to m (-1.5), close to a growth-limited threshold. Even with aerobic metabolism, the partial pressure of atmospheric O2 (P(O2)) must exceed approximately 10(3) Pa to allow organisms that rely on O2 diffusion to evolve to a size approximately 10(3) m x P(O2) in the range approximately 10(3)-10(4) Pa is needed to exceed the threshold of approximately 10(2) m size for complex life with circulatory physiology. In terrestrial life, O(2) also facilitates hundreds of metabolic pathways, including those that make specialized structural molecules found only in animals. The time scale to reach P(O(2)) approximately 10(4) Pa, or "oxygenation time," was long on the Earth (approximately 3.9 billion years), within almost a factor of 2 of the Sun

  1. Device for measuring oxygen activity in liquid sodium

    DOEpatents

    Roy, P.; Young, R.S.

    1973-12-01

    A composite ceramic electrolyte in a configuration (such as a closed end tube or a plate) suitable to separate liquid sodium from a reference electrode with a high impedance voltmeter connected to measure EMF between the sodium and the reference electrode as a measure of oxygen activity in the sodium is described. The composite electrolyte consists of zirconiacalcia with a bonded layer of thoria-yttria. The device is used with a gaseous reference electrode on the zirconia-calcia side and liquid sodium on the thoria-yttria side of the electrolyte. (Official Gazette)

  2. Bioreductively Activated Reactive Oxygen Species (ROS) Generators as MRSA Inhibitors.

    PubMed

    Khodade, Vinayak S; Sharath Chandra, Mallojjala; Banerjee, Ankita; Lahiri, Surobhi; Pulipeta, Mallikarjuna; Rangarajan, Radha; Chakrapani, Harinath

    2014-07-10

    The number of cases of drug resistant Staphylococcus aureus infections is on the rise globally and new strategies to identify drug candidates with novel mechanisms of action are in urgent need. Here, we report the synthesis and evaluation of a series of benzo[b]phenanthridine-5,7,12(6H)-triones, which were designed based on redox-active natural products. We find that the in vitro inhibitory activity of 6-(prop-2-ynyl)benzo[b]phenanthridine-5,7,12(6H)-trione (1f) against methicillin-resistant Staphylococcus aureus (MRSA), including a panel of patient-derived strains, is comparable or better than vancomycin. We show that the lead compound generates reactive oxygen species (ROS) in the cell, contributing to its antibacterial activity. PMID:25050164

  3. A Synthetic Oxygen Atom Transfer Photocycle from a Diruthenium Oxyanion Complex.

    PubMed

    Corcos, Amanda R; Pap, József S; Yang, Tzuhsiung; Berry, John F

    2016-08-10

    Three new diruthenium oxyanion complexes have been prepared, crystallographically characterized, and screened for their potential to photochemically unmask a reactive Ru-Ru═O intermediate. The most promising candidate, Ru2(chp)4ONO2 (4, chp = 6-chloro-2-hydroxypyridinate), displays a set of signals centered around m/z = 733 amu in its MALDI-TOF mass spectrum, consistent with the formation of the [Ru2(chp)4O](+) ([6](+)) ion. These signals shift to 735 amu in 4*, which contains an (18)O-labeled nitrate. EPR spectroscopy and headspace GC-MS analysis indicate that NO2(•) is released upon photolysis of 4, also consistent with the formation of 6. Photolysis of 4 in CH2Cl2 at room temperature in the presence of excess PPh3 yields OPPh3 in 173% yield; control experiments implicate 6, NO2(•), and free NO3(-) as the active oxidants. Notably, Ru2(chp)4Cl (3) is recovered after photolysis. Since 3 is the direct precursor to 4, the results described herein constitute the first example of a synthetic cycle for oxygen atom transfer that makes use of light to generate a putative metal oxo intermediate. PMID:27406958

  4. TOR complex 2-Ypk1 signaling regulates actin polarization via reactive oxygen species.

    PubMed

    Niles, Brad J; Powers, Ted

    2014-12-01

    The evolutionarily conserved mTOR complex 2 (mTORC2) signaling pathway is an important regulator of actin cytoskeletal architecture and, as such, is a candidate target for preventing cancer cell motility and invasion. Remarkably, the precise mechanism(s) by which mTORC2 regulates the actin cytoskeleton have remained elusive. Here we show that in budding yeast, TORC2 and its downstream kinase Ypk1 regulate actin polarization by controlling reactive oxygen species (ROS) accumulation. Specifically, we find that TORC2-Ypk1 regulates actin polarization both by vacuole-related ROS, controlled by the phospholipid flippase kinase Fpk1 and sphingolipids, and by mitochondria-mediated ROS, controlled by the PKA subunit Tpk3. In addition, we find that the protein kinase C (Pkc1)/MAPK cascade, a well-established regulator of actin, acts downstream of Ypk1 to regulate ROS, in part by promoting degradation of the oxidative stress responsive repressor, cyclin C. Furthermore, we show that Ypk1 regulates Pkc1 activity through proper localization of Rom2 at the plasma membrane, which is also dependent on Fpk1 and sphingolipids. Together these findings demonstrate important links between TORC2/Ypk1 signaling, Fpk1, sphingolipids, Pkc1, and ROS as regulators of actin and suggest that ROS may play an important role in mTORC2-dependent dysregulation of the actin cytoskeleton in cancer cells. PMID:25253719

  5. Reactive oxygen species-activated nanomaterials as theranostic agents.

    PubMed

    Kim, Kye S; Lee, Dongwon; Song, Chul Gyu; Kang, Peter M

    2015-01-01

    Reactive oxygen species (ROS) are generated from the endogenous oxidative metabolism or from exogenous pro-oxidant exposure. Oxidative stress occurs when there is excessive production of ROS, outweighing the antioxidant defense mechanisms which may lead to disease states. Hydrogen peroxide (H2O2) is one of the most abundant and stable forms of ROS, implicated in inflammation, cellular dysfunction and apoptosis, which ultimately lead to tissue and organ damage. This review is an overview of the role of ROS in different diseases. We will also examine ROS-activated nanomaterials with emphasis on hydrogen peroxide, and their potential medical implications. Further development of the biocompatible, stimuli-activated agent responding to disease causing oxidative stress, may lead to a promising clinical use. PMID:26328770

  6. Reactive oxygen species-activated nanomaterials as theranostic agents

    PubMed Central

    Kim, Kye S; Lee, Dongwon; Song, Chul Gyu; Kang, Peter M

    2015-01-01

    Reactive oxygen species (ROS) are generated from the endogenous oxidative metabolism or from exogenous pro-oxidant exposure. Oxidative stress occurs when there is excessive production of ROS, outweighing the antioxidant defense mechanisms which may lead to disease states. Hydrogen peroxide (H2O2) is one of the most abundant and stable forms of ROS, implicated in inflammation, cellular dysfunction and apoptosis, which ultimately lead to tissue and organ damage. This review is an overview of the role of ROS in different diseases. We will also examine ROS-activated nanomaterials with emphasis on hydrogen peroxide, and their potential medical implications. Further development of the biocompatible, stimuli-activated agent responding to disease causing oxidative stress, may lead to a promising clinical use. PMID:26328770

  7. Collective dynamics of active filament complexes

    NASA Astrophysics Data System (ADS)

    Nogucci, Hironobu; Ishihara, Shuji

    2016-05-01

    Networks of biofilaments are essential for the formation of cellular structures that support various biological functions. For the most part, previous studies have investigated the collective dynamics of rodlike biofilaments; however, the shapes of the actual subcellular components are often more elaborate. In this study, we considered an active object composed of two active filaments, which represents the progression from rodlike biofilaments to complex-shaped biofilaments. Specifically, we numerically assessed the collective behaviors of these active objects in two dimensions and observed several types of dynamics, depending on the density and the angle of the two filaments as shape parameters of the object. Among the observed collective dynamics, a moving density band that we named a "moving smectic" is introduced here for the first time. By analyzing the trajectories of individual objects and the interactions among them, this study demonstrated how interactions among active biofilaments with complex shapes could produce collective dynamics in a nontrivial manner.

  8. The interrelationship between muscle oxygenation, muscle activation, and pulmonary oxygen uptake to incremental ramp exercise: influence of aerobic fitness.

    PubMed

    Boone, Jan; Barstow, Thomas J; Celie, Bert; Prieur, Fabrice; Bourgois, Jan

    2016-01-01

    We investigated whether muscle and ventilatory responses to incremental ramp exercise would be influenced by aerobic fitness status by means of a cross-sectional study with a large subject population. Sixty-four male students (age: 21.2 ± 3.2 years) with a heterogeneous peak oxygen uptake (51.9 ± 6.3 mL·min(-1)·kg(-1), range 39.7-66.2 mL·min(-1)·kg(-1)) performed an incremental ramp cycle test (20-35 W·min(-1)) to exhaustion. Breath-by-breath gas exchange was recorded, and muscle activation and oxygenation were measured with surface electromyography and near-infrared spectroscopy, respectively. The integrated electromyography (iEMG), mean power frequency (MPF), deoxygenated [hemoglobin and myoglobin] (deoxy[Hb+Mb]), and total[Hb+Mb] responses were set out as functions of work rate and fitted with a double linear function. The respiratory compensation point (RCP) was compared and correlated with the breakpoints (BPs) (as percentage of peak oxygen uptake) in muscle activation and oxygenation. The BP in total[Hb+Mb] (83.2% ± 3.0% peak oxygen uptake) preceded (P < 0.001) the BP in iEMG (86.7% ± 4.0% peak oxygen uptake) and MPF (86.3% ± 4.1% peak oxygen uptake), which in turn preceded (P < 0.01) the BP in deoxy[Hb+Mb] (88.2% ± 4.5% peak oxygen uptake) and RCP (87.4% ± 4.5% peak oxygen uptake). Furthermore, the peak oxygen uptake was significantly (P < 0.001) positively correlated to the BPs and RCP, indicating that the BPs in total[Hb+Mb] (r = 0.66; P < 0.001), deoxy[Hb+Mb] (r = 0.76; P < 0.001), iEMG (r = 0.61; P < 0.001), MPF (r = 0.63; P < 0.001), and RCP (r = 0.75; P < 0.001) occurred at a higher percentage of peak oxygen uptake in subjects with a higher peak oxygen uptake. In this study a close relationship between muscle oxygenation, activation, and pulmonary oxygen uptake was found, occurring in a cascade of events. In subjects with a higher aerobic fitness level this cascade occurred at a higher relative intensity. PMID:26701120

  9. Stress-Induced Nitrogen and Oxygen Segregation and Complexing Investigated by High Resolution Synchrotron FTIR: Preprint

    SciTech Connect

    Karoui, A.; Buonassisi, T.; Sahtout Karoui, F.; Rozgonyi, G. A.; Michael, M.; Weber, E. R.; Ciszek, T. F.

    2004-08-01

    Nitrogen doped Czochralski (N-CZ) and Float Zone (N-FZ) silicon were measured by high resolution synchrotron Fourier Transform IR spectroscopy (HR-FTIR). The chemical complexes were analyzed in specific regions with known extended defects, i.e., denuded or precipitated regions of annealed N-CZ Si wafers, in N-FZ Si with ring defects and on ''N-Skin'' region. The absorption lines were assigned to chemical complexes previously studied by first principles calculations. In annealed N-CZ Si wafers, a strong correlation was observed between the absorption line intensity depth variations and the defect distributions revealed by an Oxygen Precipitate Profiler (OPP), and oxygen and nitrogen SIMS profiles. Transformation of chemical complexes from one type to another was observed. A defect band, visible as an OPP peak at the denuded zone-bulk interface was found to be related to vacancy defect enhancement of oxygen precipitation via production of mobile N2. For the as grown N-FZ, the radial dependency of IR absorption line intensity is correlated to x-ray topography contrast.

  10. Activated carbon becomes active for oxygen reduction and hydrogen evolution reactions.

    PubMed

    Yan, Xuecheng; Jia, Yi; Odedairo, Taiwo; Zhao, Xiaojun; Jin, Zhao; Zhu, Zhonghua; Yao, Xiangdong

    2016-06-21

    We utilized a facile method for creating unique defects in the activated carbon (AC), which makes it highly active for the oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER). The ORR activity of the defective AC (D-AC) is comparable to the commercial Pt/C in alkaline medium, and the D-AC also exhibits excellent HER activity in acidic solution. PMID:27277286

  11. Linking Complexity with Cultural Historical Activity Theory

    ERIC Educational Resources Information Center

    McMurtry, Angus

    2006-01-01

    This paper explores the similarities and differences between complexity science's and cultural-historical activity theory's understandings of human learning. Notable similarities include their emphasis on the importance of social systems or collectives in understanding human knowledge and practices, as well as their characterization of systems'…

  12. An oxygen-insensitive Hif-3α isoform inhibits Wnt signaling by destabilizing the nuclear β-catenin complex

    PubMed Central

    Zhang, Peng; Bai, Yan; Lu, Ling; Li, Yun; Duan, Cunming

    2016-01-01

    Hypoxia-inducible factors (HIFs), while best known for their roles in the hypoxic response, have oxygen-independent roles in early development with poorly defined mechanisms. Here, we report a novel Hif-3α variant, Hif-3α2, in zebrafish. Hif-3α2 lacks the bHLH, PAS, PAC, and ODD domains, and is expressed in embryonic and adult tissues independently of oxygen availability. Hif-3α2 is a nuclear protein with significant hypoxia response element (HRE)-dependent transcriptional activity. Hif-3α2 overexpression not only decreases embryonic growth and developmental timing but also causes left-right asymmetry defects. Genetic deletion of Hif-3α2 by CRISPR/Cas9 genome editing increases, while Hif-3α2 overexpression decreases, Wnt/β-catenin signaling. This action is independent of its HRE-dependent transcriptional activity. Mechanistically, Hif-3α2 binds to β-catenin and destabilizes the nuclear β-catenin complex. This mechanism is distinct from GSK3β-mediated β-catenin degradation and is conserved in humans. These findings provide new insights into the oxygen-independent actions of HIFs and uncover a novel mechanism regulating Wnt/β-catenin signaling. DOI: http://dx.doi.org/10.7554/eLife.08996.001 PMID:26765566

  13. Phenol degradation in heterogeneous system generating singlet oxygen employing light activated electropolymerized phenothiazines

    NASA Astrophysics Data System (ADS)

    Piwowar, Katarzyna; Blacha-Grzechnik, Agata; Bernas, Paulina; Zak, Jerzy

    2015-12-01

    Five selected amine-derivatives of phenothiazine were electropolymerized on an ITO/glass substrate and then used in the daylight-activated process to produce in situ singlet oxygen which degrades phenol in a solution. The phenothiazines were immobilized in a simple electrochemical procedure in an acidic solution which led to the formation of an ultrathin transparent polymeric film. All films obtained on the ITO substrate including azure A (AA), azure C (AC), methylene blue (MB), toluidine blue (TBO), and thionine (Th) had a comparable surface coverage at the level of picomoles/cm2. The activity of these materials was then compared and presented in terms of an efficiency of the phenol degradation process in an aqueous solution by photogenerated singlet oxygen. That efficiency was determined by the UV-vis spectroscopy employing a phenol/4-aminoantipyrine complex. All the phenothiazine ultrathin polymeric films were capable of generating the singlet oxygen in the aqueous solution under daylight activation, which was used in the consecutive process of phenol degradation. The highest efficiency at a level of 51.4% and 45.4% was found for the AC/ITO and MB/ITO layers, respectively.

  14. Structure-Function of the Cytochrome b6f Complex of Oxygenic Photosynthesis

    SciTech Connect

    Cramer, W. A.; Yamashita, E.; Baniulis, D.; Whitelegge, J.; Hasan, S. S.

    2014-03-20

    Structure–function of the major integral membrane cytochrome b6f complex that functions in cyanobacteria, algae, and green plants to transfer electrons between the two reaction center complexes in the electron transport chain of oxygenic photosynthesis is discussed in the context of recently obtained crystal structures of the complex and soluble domains of cytochrome f and the Rieske iron–sulfur protein. The energy-transducing function of the complex, generation of the proton trans-membrane electrochemical potential gradient, centers on the oxidation/reduction pathways of the plastoquinol/plastoquinone (QH2/Q), the proton donor/acceptor within the complex. These redox reactions are carried out by five redox prosthetic groups embedded in each monomer, the high potential two iron–two sulfur cluster and the heme of cytochrome f on the electropositive side (p) of the complex, two noncovalently bound b-type hemes that cross the complex and the membrane, and a covalently bound c-type heme (cn) on the electronegative side (n). These five redox-active groups are organized in high- (cyt f/[2Fe–2S] and low-potential (hemes bp, bn, cn) electron transport pathways that oxidize and reduce the quinol and quinone on the p- and n-sides in a Q-cycle-type mechanism, while translocating as many as 2 H+ to the p-side aqueous side for every electron transferred through the high potential chain to the photosystem I reaction center. The presence of heme cn and the connection of the n-side of the membrane and b6f complex to the cyclic electron transport chain indicate that the Q cycle in the oxygenic photosynthetic electron transport chain differs from those connected to the bc1 complex in the mitochondrial respiratory chain and the chain in photosynthetic bacteria. Inferences from the structure and C2 symmetry of the complex for the pathway of QH2/Q transfer

  15. Adair-based hemoglobin equilibrium with oxygen, carbon dioxide and hydrogen ion activity.

    PubMed

    Mateják, Marek; Kulhánek, Tomáš; Matoušek, Stanislav

    2015-04-01

    As has been known for over a century, oxygen binding onto hemoglobin is influenced by the activity of hydrogen ions (H⁺), as well as the concentration of carbon dioxide (CO₂). As is also known, the binding of both CO₂and H⁺ on terminal valine-1 residues is competitive. One-parametric situations of these hemoglobin equilibria at specific levels of H⁺, O₂or CO₂are also well described. However, we think interpolating or extrapolating this knowledge into an 'empirical' function of three independent variables has not yet been completely satisfactory. We present a model that integrates three orthogonal views of hemoglobin oxygenation, titration, and carbamination at different temperatures. The model is based only on chemical principles, Adair's oxygenation steps and Van't Hoff equation of temperature dependences. Our model fits the measurements of the Haldane coefficient and CO₂hemoglobin saturation. It also fits the oxygen dissociation curve influenced by simultaneous changes in H⁺, CO₂and O₂, which makes it a strong candidate for integration into more complex models of blood acid-base with gas transport, where any combination of mentioned substances can appear. PMID:25594800

  16. Characterisation of the active/de-active transition of mitochondrial complex I☆

    PubMed Central

    Babot, Marion; Birch, Amanda; Labarbuta, Paola; Galkin, Alexander

    2014-01-01

    Oxidation of NADH in the mitochondrial matrix of aerobic cells is catalysed by mitochondrial complex I. The regulation of this mitochondrial enzyme is not completely understood. An interesting characteristic of complex I from some organisms is the ability to adopt two distinct states: the so-called catalytically active (A) and the de-active, dormant state (D). The A-form in situ can undergo de-activation when the activity of the respiratory chain is limited (i.e. in the absence of oxygen). The mechanisms and driving force behind the A/D transition of the enzyme are currently unknown, but several subunits are most likely involved in the conformational rearrangements: the accessory subunit 39 kDa (NDUFA9) and the mitochondrially encoded subunits, ND3 and ND1. These three subunits are located in the region of the quinone binding site. The A/D transition could represent an intrinsic mechanism which provides a fast response of the mitochondrial respiratory chain to oxygen deprivation. The physiological role of the accumulation of the D-form in anoxia is most probably to protect mitochondria from ROS generation due to the rapid burst of respiration following reoxygenation. The de-activation rate varies in different tissues and can be modulated by the temperature, the presence of free fatty acids and divalent cations, the NAD+/NADH ratio in the matrix, the presence of nitric oxide and oxygen availability. Cysteine-39 of the ND3 subunit, exposed in the D-form, is susceptible to covalent modification by nitrosothiols, ROS and RNS. The D-form in situ could react with natural effectors in mitochondria or with pharmacological agents. Therefore the modulation of the re-activation rate of complex I could be a way to ameliorate the ischaemia/reperfusion damage. This article is part of a Special Issue entitled: 18th European Bioenergetic Conference. Guest Editors: Manuela Pereira and Miguel Teixeira. PMID:24569053

  17. Oxygen Affects Gut Bacterial Colonization and Metabolic Activities in a Gnotobiotic Cockroach Model

    PubMed Central

    Tegtmeier, Dorothee; Thompson, Claire L.; Schauer, Christine

    2015-01-01

    The gut microbiota of termites and cockroaches represents complex metabolic networks of many diverse microbial populations. The distinct microenvironmental conditions within the gut and possible interactions among the microorganisms make it essential to investigate how far the metabolic properties of pure cultures reflect their activities in their natural environment. We established the cockroach Shelfordella lateralis as a gnotobiotic model and inoculated germfree nymphs with two bacterial strains isolated from the guts of conventional cockroaches. Fluorescence microscopy revealed that both strains specifically colonized the germfree hindgut. In diassociated cockroaches, the facultatively anaerobic strain EbSL (a new species of Enterobacteriaceae) always outnumbered the obligately anaerobic strain FuSL (a close relative of Fusobacterium varium), irrespective of the sequence of inoculation, which showed that precolonization by facultatively anaerobic bacteria does not necessarily favor colonization by obligate anaerobes. Comparison of the fermentation products of the cultures formed in vitro with those accumulated in situ indicated that the gut environment strongly affected the metabolic activities of both strains. The pure cultures formed the typical products of mixed-acid or butyrate fermentation, whereas the guts of gnotobiotic cockroaches accumulated mostly lactate and acetate. Similar shifts toward more-oxidized products were observed when the pure cultures were exposed to oxygen, which corroborated the strong effects of oxygen on the metabolic fluxes previously observed in termite guts. Oxygen microsensor profiles of the guts of germfree, gnotobiotic, and conventional cockroaches indicated that both gut tissue and microbiota contribute to oxygen consumption and suggest that the oxygen status influences the colonization success. PMID:26637604

  18. Oxygen Affects Gut Bacterial Colonization and Metabolic Activities in a Gnotobiotic Cockroach Model.

    PubMed

    Tegtmeier, Dorothee; Thompson, Claire L; Schauer, Christine; Brune, Andreas

    2016-02-01

    The gut microbiota of termites and cockroaches represents complex metabolic networks of many diverse microbial populations. The distinct microenvironmental conditions within the gut and possible interactions among the microorganisms make it essential to investigate how far the metabolic properties of pure cultures reflect their activities in their natural environment. We established the cockroach Shelfordella lateralis as a gnotobiotic model and inoculated germfree nymphs with two bacterial strains isolated from the guts of conventional cockroaches. Fluorescence microscopy revealed that both strains specifically colonized the germfree hindgut. In diassociated cockroaches, the facultatively anaerobic strain EbSL (a new species of Enterobacteriaceae) always outnumbered the obligately anaerobic strain FuSL (a close relative of Fusobacterium varium), irrespective of the sequence of inoculation, which showed that precolonization by facultatively anaerobic bacteria does not necessarily favor colonization by obligate anaerobes. Comparison of the fermentation products of the cultures formed in vitro with those accumulated in situ indicated that the gut environment strongly affected the metabolic activities of both strains. The pure cultures formed the typical products of mixed-acid or butyrate fermentation, whereas the guts of gnotobiotic cockroaches accumulated mostly lactate and acetate. Similar shifts toward more-oxidized products were observed when the pure cultures were exposed to oxygen, which corroborated the strong effects of oxygen on the metabolic fluxes previously observed in termite guts. Oxygen microsensor profiles of the guts of germfree, gnotobiotic, and conventional cockroaches indicated that both gut tissue and microbiota contribute to oxygen consumption and suggest that the oxygen status influences the colonization success. PMID:26637604

  19. Synthesis, characterization, photophysical and oxygen-sensing properties of a novel europium(III) complex

    NASA Astrophysics Data System (ADS)

    Feng, Nan; Xie, Jing; Zhang, Dawei

    2010-09-01

    In this paper, we report the synthesis, characterization, crystal structure, and photophysical properties of a novel Eu 3+ complex of Eu(DBM) 3IPD, where DBM = 1,3-diphenyl-propane-1,3-dione and IPD = 4-(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)-N,N-diphenylaniline. Its elementary application for oxygen-sensing application is also investigated by doping it into a silica matrix of MCM-41. Experimental data suggest that the 20 mg/g doped Eu(DBM) 3IPD/MCM-41 system exhibits a high sensitivity of 3.6 towards molecular oxygen with a good linear relationship of R2 = 0.9987. In addition, the 20 mg/g doped Eu(DBM) 3IPD/MCM-41 system owns a quick response of 8 s towards oxygen, along with its excellent atmosphere insensitivity and photobleaching resistance. All these results suggest that both Eu(DBM) 3IPD and Eu(DBM) 3IPD/MCM-41 systems are promising candidates for oxygen-sensing optical sensors.

  20. High-spin Mn-oxo complexes and their relevance to the oxygen-evolving complex within photosystem II.

    PubMed

    Gupta, Rupal; Taguchi, Taketo; Lassalle-Kaiser, Benedikt; Bominaar, Emile L; Yano, Junko; Hendrich, Michael P; Borovik, A S

    2015-04-28

    The structural and electronic properties of a series of manganese complexes with terminal oxido ligands are described. The complexes span three different oxidation states at the manganese center (III-V), have similar molecular structures, and contain intramolecular hydrogen-bonding networks surrounding the Mn-oxo unit. Structural studies using X-ray absorption methods indicated that each complex is mononuclear and that oxidation occurs at the manganese centers, which is also supported by electron paramagnetic resonance (EPR) studies. This gives a high-spin Mn(V)-oxo complex and not a Mn(IV)-oxy radical as the most oxidized species. In addition, the EPR findings demonstrated that the Fermi contact term could experimentally substantiate the oxidation states at the manganese centers and the covalency in the metal-ligand bonding. Oxygen-17-labeled samples were used to determine spin density within the Mn-oxo unit, with the greatest delocalization occurring within the Mn(V)-oxo species (0.45 spins on the oxido ligand). The experimental results coupled with density functional theory studies show a large amount of covalency within the Mn-oxo bonds. Finally, these results are examined within the context of possible mechanisms associated with photosynthetic water oxidation; specifically, the possible identity of the proposed high valent Mn-oxo species that is postulated to form during turnover is discussed. PMID:25852147

  1. Production and Characterization of Active Transparent PET Films for Oxygen Sensitive Foods Packaging

    NASA Astrophysics Data System (ADS)

    Rosaria Galdi, Maria; Incarnato, Loredana

    2010-06-01

    The aim of this work is to investigate possible solutions to realize active, transparent PET film suitable for packaging oxygen sensitive foods. At this purpose, monolayer active PET films at different oxygen scavenger concentrations and multilayer active ones were produced by cast extrusion laboratory scale equipments. To assess their activity and to verify the efficacy of such solutions, O2 absorption analyses were carried out in continuous by an innovative oxygen meter.

  2. Effect of trehalose on oxygen evolution and electron transfer in photosystem 2 complexes.

    PubMed

    Mamedov, M D; Petrova, I O; Yanykin, D V; Zaspa, A A; Semenov, A Yu

    2015-01-01

    The pigment-protein complex of photosystem 2 (PS 2) catalyzes the light-driven oxidation of water molecule and the reduction of plastoquinone. In this work, we studied the effect of the disaccharide trehalose, which is unique in its physicochemical properties, on isolated PS 2 complex. It was found that trehalose significantly stimulated the steady-state rate of oxygen evolution. The study of single flash-induced fluorescence decay kinetics demonstrated that trehalose did not affect the rate of QA(-) oxidation, although it led to an increase in the relative fractions of PS 2 reaction centers capable of QA(-) oxidation. Trehalose also prevented PS 2 complexes from being inactivated on prolonged storage. We propose that in the presence of trehalose, which affects the extent of hydration, the protein can preferentially exist in a more optimal conformation for effective functioning. PMID:25754040

  3. Successful Treatment of Lower Limb Complex Regional Pain Syndrome following Three Weeks of Hyperbaric Oxygen Therapy.

    PubMed

    Katznelson, Rita; Segal, Shira C; Clarke, Hance

    2016-01-01

    Hyperbaric oxygen therapy (HBOT) is a treatment that delivers 100% oxygen at increased atmospheric pressures. The efficacy of HBOT for treating pain has been described in various animal pain models and may have clinical efficacy in the treatment of human chronic pain syndromes. We present our experience with posttraumatic Complex Regional Pain Syndrome (CRPS) type 2 in a patient who underwent 15 sessions of HBOT. A 41-year-old male with one-year history of CRPS of left foot followed by left ankle fracture demonstrated less pain, decreased swelling, less allodynia, and improvement in skin color and range of motion of the lower limb after 3 weeks of HBOT. Patient was back to work for the first time in over a year. HBOT may be considered as a valuable therapeutic tool in the treatment of long-standing CRPS. PMID:27445607

  4. Low symmetry configurations of vacancy-oxygen complexes in irradiated silicon

    SciTech Connect

    Kusano, Y.; Saito, H.; Ohta, E.; Itoh, K. M.; Vlasenko, L. S.; Vlasenko, M. P.

    2015-12-28

    Two new electron paramagnetic resonance (EPR) spectra, labeled KU2 and KU3, emerge as a result of annealing of γ-ray irradiated silicon crystals in the temperature range 360–560 °C. The EPR intensities of KU2 and KU3 increase in the upper range of the annealing temperature where the EPR peaks of the vacancy-oxygen complex (A-center) diminish. The angular dependence study shows that the EPR spectra of KU2 and KU3 resemble that of SL1, the excited triplet (spin S = 1) state of A-centers, but with slightly different g and D-tensors representing lowering in symmetries. Microscopic lattice distortions caused by capturing of extra interstitial oxygen atoms by the A-centers are proposed to be the source of lowering of the symmetries associated with KU2 and KU3.

  5. Successful Treatment of Lower Limb Complex Regional Pain Syndrome following Three Weeks of Hyperbaric Oxygen Therapy

    PubMed Central

    Katznelson, Rita; Segal, Shira C.; Clarke, Hance

    2016-01-01

    Hyperbaric oxygen therapy (HBOT) is a treatment that delivers 100% oxygen at increased atmospheric pressures. The efficacy of HBOT for treating pain has been described in various animal pain models and may have clinical efficacy in the treatment of human chronic pain syndromes. We present our experience with posttraumatic Complex Regional Pain Syndrome (CRPS) type 2 in a patient who underwent 15 sessions of HBOT. A 41-year-old male with one-year history of CRPS of left foot followed by left ankle fracture demonstrated less pain, decreased swelling, less allodynia, and improvement in skin color and range of motion of the lower limb after 3 weeks of HBOT. Patient was back to work for the first time in over a year. HBOT may be considered as a valuable therapeutic tool in the treatment of long-standing CRPS. PMID:27445607

  6. Oxygen isotope fractionation in phosphates: the role of dissolved complex anions in isotope exchange.

    PubMed

    Zheng, Yong-Fei

    2016-01-01

    Oxygen isotope fractionation factors for phosphates were calculated by means of the increment method. The results suggest that Ag3PO4 and BiPO4 are enriched in (18)O relative to AgPO4, and the three phosphates are consistently depleted in (18)O relative to Ba3[PO4]2; fluorapatite and chlorapatite exhibit a similar behaviour of oxygen isotope fractionation with consistent enrichment of (18)O relative to hydroxyapatite. The valence, radii and coordination of metal cations play a quantitative role in dictating the (18)O/(16)O partitioning in these phosphates of different compositions. The calculated fractionation factors for the Ag3PO4-H2O system are in agreement with experimental determinations derived from enzyme-catalysed isotope exchange between dissolved inorganic phosphate and water at the longest reaction durations at low temperatures. This demonstrates that the precipitated Ag3PO4 has completely captured the oxygen isotope fractionation in the dissolved inorganic phosphate. The calculated fractionation factors for the F/Cl-apatite-water systems are in agreement with the enzyme-catalysed experimental fractionations for the dissolved phosphate-water system at the longest reaction durations but larger than fractionations derived from bacteria-facilitated exchange and inorganic precipitation experiments as well as natural observations. For the experimental calibrations of oxygen isotope fractionation involving the precipitation of dissolved phosphate species from aqueous solutions, the fractionation between precipitate and water is primarily dictated by the isotope equilibration between the dissolved complex anions and water prior to the precipitation. Therefore, the present results provide a quantitative means to interpret the temperature dependence of oxygen isotope fractionation in inorganic and biogenic phosphates. PMID:25587823

  7. Effect of surface area and chemisorbed oxygen on the SO2 adsorption capacity of activated char

    USGS Publications Warehouse

    Lizzio, A.A.; DeBarr, J.A.

    1996-01-01

    The objective of this study was to determine whether activated char produced from Illinois coal could be used effectively to remove sulfur dioxide from coal combustion flue gas. Chars were prepared from a high-volatile Illinois bituminous coal under a wide range of pyrolysis and activation conditions. A novel char preparation technique was developed to prepare chars with SO2 adsorption capacities significantly greater than that of a commercial activated carbon. In general, there was no correlation between SO2 adsorption capacity and surface area. Temperature-programmed desorption (TPD) was used to determine the nature and extent of carbon-oxygen (C-O) complexes formed on the char surface. TPD data revealed that SO2 adsorption was inversely proportional to the amount of C-O complex. The formation of a stable C-O complex during char preparation may have served only to occupy carbon sites that were otherwise reactive towards SO2 adsorption. A fleeting C(O) complex formed during SO2 adsorption is postulated to be the reaction intermediate necessary for conversion of SO2 to H2SO4. Copyright ?? 1996 Elsevier Science Ltd.

  8. Effect of oxygen on the microbial activities of thermophilic anaerobic biomass.

    PubMed

    Pedizzi, C; Regueiro, L; Rodriguez-Verde, I; Lema, J M; Carballa, M

    2016-07-01

    Low oxygen levels (μgO2L(-1)) in anaerobic reactors are quite common and no relevant consequences are expected. On the contrary, higher concentrations could affect the process. This work aimed to study the influence of oxygen (4.3 and 8.8mgO2L(-1), respectively) on the different microbial activities (hydrolytic, acidogenic and methanogenic) of thermophilic anaerobic biomass and on the methanogenic community structure. Batch tests in presence of oxygen were conducted using specific substrates for each biological activity and a blank (with minimum oxygen) was included. No effect of oxygen was observed on the hydrolytic and acidogenic activities. In contrast, the methane production rate decreased by 40% in all oxygenated batches and the development of active archaeal community was slower in presence of 8.8mgO2L(-1). However, despite this sensitivity of methanogens to oxygen at saturation levels, the inhibition was reversible. PMID:27020398

  9. Electrochemically fabricated polypyrrole-cobalt-oxygen coordination complex as high-performance lithium-storage materials.

    PubMed

    Guo, Bingkun; Kong, Qingyu; Zhu, Ying; Mao, Ya; Wang, Zhaoxiang; Wan, Meixiang; Chen, Liquan

    2011-12-23

    Current lithium-ion battery (LIB) technologies are all based on inorganic electrode materials, though organic materials have been used as electrodes for years. Disadvantages such as limited thermal stability and low specific capacity hinder their applications. On the other hand, the transition metal oxides that provide high lithium-storage capacity by way of electrochemical conversion reaction suffer from poor cycling stability. Here we report a novel high-performance, organic, lithium-storage material, a polypyrrole-cobalt-oxygen (PPy-Co-O) coordination complex, with high lithium-storage capacity and excellent cycling stability. Extended X-ray absorption fine structure and Raman spectroscopy and other physical and electrochemical characterizations demonstrate that this coordination complex can be electrochemically fabricated by cycling PPy-coated Co(3)O(4) between 0.0 V and 3.0 V versus Li(+)/Li. Density functional theory (DFT) calculations indicate that each cobalt atom coordinates with two nitrogen atoms within the PPy-Co coordination layer and the layers are connected with oxygen atoms between them. Coordination weakens the C-H bonds on PPy and makes the complex a novel lithium-storage material with high capacity and high cycling stability. PMID:22127820

  10. Tunable Phosphorescent NIR Oxygen Indicators Based on Mixed Benzo- and Naphthoporphyrin Complexes

    PubMed Central

    2010-01-01

    A series of π-extended phosphorescent palladium(II) and platinum(II) porphyrin complexes were synthesized, in which additional benzene rings are fused radially onto at least one of the four peripheral benzo groups. The photophysical properties of the metalloporphyrins palladium(II)-meso-tetra-(4-fluorophenyl)mononaphthotribenzoporphyrin (Pd1NF), cis-palladium(II)-meso-tetra-(4-fluorophenyl)dibenzodinaphthoporphyrin (Pd2NF), and palladium(II)-meso-tetra-(4-fluorophenyl)monobenzotrinaphthoporphyrin (Pd3NF) and the corresponding platinum(II) compounds (Pt1NF, cis-Pt2NF, Pt3NF) were investigated. The compounds under investigation absorb intensively in the near-infrared region (628−691 nm) and emit at room temperature at 815−882 nm. Phosphorescence quantum yields of the platinum(II) porphyrins range from 25 to 53% with luminescence decay times of 21 to 44 μs in deoxygenated toluene solutions at room temperature. The corresponding palladium(II) complexes exhibit quantum yields in the range of 7 to 18% with lifetimes of 106 to 206 μs. Density functional theory (DFT) calculations revealed nonplanar geometries for all complexes and corroborate the absorption characteristics. The subsequent π extension of the porphyrin system leads to near-infrared absorbing oxygen indicators with tailor-made luminescence properties as well as tunable oxygen sensitivity. PMID:20839844

  11. Molecular mimicry of substrate oxygen atoms by water molecules in the beta-amylase active site.

    PubMed

    Pujadas, G; Palau, J

    2001-08-01

    Soybean beta-amylase (EC 3.2.1.2) has been crystallized both free and complexed with a variety of ligands. Four water molecules in the free-enzyme catalytic cleft form a multihydrogen-bond network with eight strategic residues involved in enzyme-ligand hydrogen bonds. We show here that the positions of these four water molecules are coincident with the positions of four potential oxygen atoms of the ligands within the complex. Some of these waters are displaced from the active site when the ligands bind to the enzyme. How many are displaced depends on the shape of the ligand. This means that when one of the four positions is not occupied by a ligand oxygen atom, the corresponding water remains. We studied the functional/structural role of these four waters and conclude that their presence means that the conformation of the eight side chains is fixed in all situations (free or complexed enzyme) and preserved from unwanted or forbidden conformational changes that could hamper the catalytic mechanism. The water structure at the active pocket of beta-amylase is therefore essential for providing the ligand recognition process with plasticity. It does not affect the protein active-site geometry and preserves the overall hydrogen-bonding network, irrespective of which ligand is bound to the enzyme. We also investigated whether other enzymes showed a similar role for water. Finally, we discuss the potential use of these results for predicting whether water molecules can mimic ligand atoms in the active center. PMID:11468361

  12. Influence of oxygen-vacancy complex /A center/ on piezoresistance of n-type silicon.

    NASA Technical Reports Server (NTRS)

    Littlejohn, M. A.; Loggins, C. D., Jr.

    1972-01-01

    Changes in both magnitude and temperature dependence of the piezoresistance of electron-irradiated n-type silicon, induced by the latter's oxygen-vacancy complex (A center), are shown to be due to the fact that the presence of the A center causes the total conduction-band electron concentration to change with an applied stress. This change in electron concentration leads to an additional piezoresistance contribution that is expected to be important in certain many-valley semiconductors. This offers the possibility of tailoring the thermal variations of semiconductor mechanical sensors to more desirable values over limited temperature ranges.

  13. [Generation of Superoxide Radicals by Complex III in Heart Mitochondria and Antioxidant Effect of Dinitrosyl Iron Complexes at Different Partial Pressure of Oxygen].

    PubMed

    Dudylina, A L; Ivanova, M V; Shumaev, K B; Ruuge, E K

    2016-01-01

    The EPR spin-trapping technique and EPR-oximetry were used to study generation of superoxide radicals in heart mitochondria isolated from Wistar rats under conditions of variable oxygen concentration. Lithium phthalocyanine and TEMPONE-15N-D16 were chosen to determine oxygen content in a gas-permeable capillary tube containing mitochondria. TIRON was used as a spin trap. We investigated the influence of different oxygen concentrations in incubation mixture and demonstrated that heart mitochondria can generate superoxide in complex III at different partial pressure of oxygen as well as under the conditions of deep hypoxia (< 5% O2). Dinitrosyl iron complexes with glutathione (the pharmaceutical drug "Oxacom") exerted an antioxidant effect, regardless of the value of the partial pressure of oxygen, but the magnitude and kinetic characteristics of the effect depended on the concentration of the drug. PMID:27192832

  14. Energy conversion, redox catalysis and generation of reactive oxygen species by respiratory complex I.

    PubMed

    Hirst, Judy; Roessler, Maxie M

    2016-07-01

    Complex I (NADH:ubiquinone oxidoreductase) is critical for respiration in mammalian mitochondria. It oxidizes NADH produced by the Krebs' tricarboxylic acid cycle and β-oxidation of fatty acids, reduces ubiquinone, and transports protons to contribute to the proton-motive force across the inner membrane. Complex I is also a significant contributor to cellular oxidative stress. In complex I, NADH oxidation by a flavin mononucleotide, followed by intramolecular electron transfer along a chain of iron-sulfur clusters, delivers electrons and energy to bound ubiquinone. Either at cluster N2 (the terminal cluster in the chain) or upon the binding/reduction/dissociation of ubiquinone/ubiquinol, energy from the redox process is captured to initiate long-range energy transfer through the complex and drive proton translocation. This review focuses on current knowledge of how the redox reaction and proton transfer are coupled, with particular emphasis on the formation and role of semiquinone intermediates in both energy transduction and reactive oxygen species production. This article is part of a Special Issue entitled Respiratory complex I, edited by Volker Zickermann and Ulrich Brandt. PMID:26721206

  15. Hydrogen-oxygen driven Zero Emissions bus drives around KSC Visitor Complex

    NASA Technical Reports Server (NTRS)

    1999-01-01

    The Zero Emissions (ZE) transit bus passes a mock-up orbiter named Explorer on a trek through the KSC Visitor Complex. Provided by dbb fuel cell engines inc. of Vancouver, Canada, the ZE bus was brought to KSC as part of the Center's Alternative Fuel Initiatives Program. The bus uses a Proton Exchange Membrane fuel cell in which hydrogen and oxygen, from atmospheric air, react to produce electricity that powers an electric motor drive system. The by-product 'exhaust' from the fuel cell is water vapor, thus zero harmful emissions. A typical diesel-powered bus emits more than a ton of harmful pollutants from its exhaust every year. The ZE bus is being used on tour routes at the KSC Visitor Complex for two days to introduce the public to the concept.

  16. Hydrogen-oxygen driven Zero Emissions bus drives around KSC Visitor Complex

    NASA Technical Reports Server (NTRS)

    1999-01-01

    The Zero Emissions (ZE) transit bus tours the KSC Visitor Complex for a test ride. In the background are a mock-up orbiter named Explorer (left) and a stack of solid rocket boosters and external tank (right), typically used on Shuttle launches. Provided by dbb fuel cell engines inc. of Vancouver, Canada, the ZE bus was brought to KSC as part of the Center's Alternative Fuel Initiatives Program. The bus uses a Proton Exchange Membrane fuel cell in which hydrogen and oxygen, from atmospheric air, react to produce electricity that powers an electric motor drive system. The by-product 'exhaust' from the fuel cell is water vapor, thus zero harmful emissions. A typical diesel-powered bus emits more than a ton of harmful pollutants from its exhaust every year. The ZE bus is being used on tour routes at the KSC Visitor Complex for two days to introduce the public to the concept.

  17. Luminescent Nafion membranes dyed with ruthenium(II) complexes as sensing materials for dissolved oxygen

    SciTech Connect

    Garcia-Fresnadillo, D.; Orellana, G.; Marazuela, M.D.; Moreno-Bondi, M.C.

    1999-09-14

    The absorption spectroscopy, photophysics, and dioxygen quenching of [RuL{sub 3}]{sup 2+} luminescent probes, where L stands for 2,2{prime}-bipyridine, 1,10-phenanthroline, 5-octadecanamide-1,10-phenanthroline, and 4,7-diphenyl-1,10-phenanthroline (dip), electrostatically loaded onto Nafion ionomer membrane have been investigated in air and in organic solvents and water, with the aim of developing rugged materials for optical sensing of molecular oxygen. The significant differences in size and hydrophobicity of the Ru(II) dyes have been used to probe their location within the perfluorinated ionomer pore network, as well as to gain insight into the oxygen accessibility to its microcrystalline and interfacial domains. While the absorption maximums of the probes (444--458nm) remain relative unchanged, their emission wavelengths (578--622 nm) are extremely sensitive to the degree of Nafion swelling by the solvent. This feature has been characterized by measuring the density (1.19--2.04 g cm{sup {minus}3}) of the solvent-saturated ionomer and the mass and volume fractions of solvents (0.0--0.7) uptake by the original acidic Nafion and Li{sup +}-, Na{sup +}-, or K{sup +}-exchanged films. The excited-state lifetimes of the [RuL{sub 3}]{sup 2+} complexes (0.03--4.9{micro}s) reflect important variations of the microenvironment around the luminescent probes, which are rationalized in terms of their location and oxygen accessibility when loaded onto the polysulfonated material. Emission quenching rate constants of 1.7 {+-} 0.3 M{sup {minus}1}s{sup {minus}1} have been measured for the [Ru(dip){sub 3}]{sup 2+}-dyed films dipped in methanol; their oxygen sensitivity turns out to be independent of the Ru(II) loading and counterion of Nafion. Highly oxygen-sensitive luminescent membranes, suitable for continuous monitoring in organic solvents, water, or gas phase, have been prepared by immobilization of [Ru(dip){sub 3}]{sup 2+} indicator in 178-{micro}m thick Nafion, with response

  18. Oxygen reduction reaction activity on Pt{111} surface alloys.

    PubMed

    Attard, Gary A; Brew, Ashley; Ye, Jin-Yu; Morgan, David; Sun, Shi-Gang

    2014-07-21

    PtM overlayers (where M=Fe, Co or Ni) supported on Pt{111} are prepared via thermal annealing in either a nitrogen/water or hydrogen ambient of dilute aqueous droplets containing M(Z+) cations directly attached to the electrode. Two different PtM phases are detected depending on the nature of the post-annealing cooling environment. The first of these consists of small (<20 nm), closely packed microcrystals comprised of a central metallic core and a shell (several monolayers thick) of mixed metal oxides/hydroxides. The second type of PtM phase is prepared by cooling in a stream of hydrogen gas. Although this second phase also consists of numerous microcrystals covering the Pt{111} electrode surface, these are both flatter than before and moreover are entirely metallic in character. A positive shift in the onset of PtM oxide formation correlates with increased activity towards the oxygen reduction reaction (ORR), which we ascribe to the greater availability of platinum metallic sites under ORR conditions. PMID:24986646

  19. Photostable ester-substituted bis-cyclometalated cationic iridium(III) complexes for continuous monitoring of oxygen.

    PubMed

    Liu, Chun; Yu, Hongcui; Xing, Yang; Gao, Zhanming; Jin, Zilin

    2016-01-14

    Three bis-cyclometalated cationic Ir(iii) complexes , and with an ester substituent at the 4-position of the phenyl ring on the 2-phenylpyridine (ppy) have been synthesized and fully characterized. The emission maxima of ester-substituted Ir(iii) complexes show a notable blue-shift compared to the parent complex [Ir(ppy)2(phen)](+)PF6(-) (phen = 1,10-phenanthroline). The influence of an ester group on the photoelectric properties of the Ir(iii) complexes has been investigated systematically. The oxygen sensing films prepared from ethyl cellulose immobilized with Ir(iii) complexes exhibit excellent operational stability, high photostability and a quick response to oxygen. show extended luminescence lifetimes relative to , and display better sensitivity to changes in oxygen partial pressure. PMID:26630292

  20. Iron Complexation to Oxygen Rich Marine Natural Products: A Computational Study

    PubMed Central

    Manning, Thomas J.; Williams, Jimmy; Jarrard, Joey; Gorman, Teresa

    2010-01-01

    The natural products kahalalide F, halichondrin B, and discodermolide are relatively large structures that were originally harvested from marine organisms. They are oxygen rich structures that, to varying degrees, should have the ability to bind iron (II or III) by Fe-O and/or Fe-N bonds. In this semi empirical study, the binding of these natural products to iron (II) is studied and the aqueous stability factor (ASF) is used to determine which bonding configuration is most stable. The energy, the complex charge (+1), the average Fe-O (or Fe-N) bond distances and the dipole moments are used to calculate the ASF. The ASF provides insight to which complex will be the most stable and water soluble, important for a medicinal application. The ability of a molecule with a more than six oxygen and/or nitrogen atoms to bind iron (hexavalent, octahedral) by shifting which six atoms (O/N) are bound to the iron qualifies it as a polarity adaptive molecule. PMID:20161968

  1. Voltage-Dependent Regulation of Complex II Energized Mitochondrial Oxygen Flux.

    PubMed

    Bai, Fan; Fink, Brian D; Yu, Liping; Sivitz, William I

    2016-01-01

    Oxygen consumption by isolated mitochondria is generally measured during state 4 respiration (no ATP production) or state 3 (maximal ATP production at high ADP availability). However, mitochondria in vivo do not function at either extreme. Here we used ADP recycling methodology to assess muscle mitochondrial function over intermediate clamped ADP concentrations. In so doing, we uncovered a previously unrecognized biphasic respiratory pattern wherein O2 flux on the complex II substrate, succinate, initially increased and peaked over low clamped ADP concentrations then decreased markedly at higher clamped concentrations. Mechanistic studies revealed no evidence that the observed changes in O2 flux were due to altered opening or function of the mitochondrial permeability transition pore or to changes in reactive oxygen. Based on metabolite and functional metabolic data, we propose a multifactorial mechanism that consists of coordinate changes that follow from reduced membrane potential (as the ADP concentration in increased). These changes include altered directional electron flow, altered NADH/NAD+ redox cycling, metabolite exit, and OAA inhibition of succinate dehydrogenase. In summary, we report a previously unrecognized pattern for complex II energized O2 flux. Moreover, our findings suggest that the ADP recycling approach might be more widely adapted for mitochondrial studies. PMID:27153112

  2. Structural changes of the oxygen-evolving complex in photosystem II during the catalytic cycle.

    PubMed

    Glöckner, Carina; Kern, Jan; Broser, Matthias; Zouni, Athina; Yachandra, Vittal; Yano, Junko

    2013-08-01

    The oxygen-evolving complex (OEC) in the membrane-bound protein complex photosystem II (PSII) catalyzes the water oxidation reaction that takes place in oxygenic photosynthetic organisms. We investigated the structural changes of the Mn4CaO5 cluster in the OEC during the S state transitions using x-ray absorption spectroscopy (XAS). Overall structural changes of the Mn4CaO5 cluster, based on the manganese ligand and Mn-Mn distances obtained from this study, were incorporated into the geometry of the Mn4CaO5 cluster in the OEC obtained from a polarized XAS model and the 1.9-Å high resolution crystal structure. Additionally, we compared the S1 state XAS of the dimeric and monomeric form of PSII from Thermosynechococcus elongatus and spinach PSII. Although the basic structures of the OEC are the same for T. elongatus PSII and spinach PSII, minor electronic structural differences that affect the manganese K-edge XAS between T. elongatus PSII and spinach PSII are found and may originate from differences in the second sphere ligand atom geometry. PMID:23766513

  3. Voltage-Dependent Regulation of Complex II Energized Mitochondrial Oxygen Flux

    PubMed Central

    Bai, Fan; Fink, Brian D.; Yu, Liping; Sivitz, William I.

    2016-01-01

    Oxygen consumption by isolated mitochondria is generally measured during state 4 respiration (no ATP production) or state 3 (maximal ATP production at high ADP availability). However, mitochondria in vivo do not function at either extreme. Here we used ADP recycling methodology to assess muscle mitochondrial function over intermediate clamped ADP concentrations. In so doing, we uncovered a previously unrecognized biphasic respiratory pattern wherein O2 flux on the complex II substrate, succinate, initially increased and peaked over low clamped ADP concentrations then decreased markedly at higher clamped concentrations. Mechanistic studies revealed no evidence that the observed changes in O2 flux were due to altered opening or function of the mitochondrial permeability transition pore or to changes in reactive oxygen. Based on metabolite and functional metabolic data, we propose a multifactorial mechanism that consists of coordinate changes that follow from reduced membrane potential (as the ADP concentration in increased). These changes include altered directional electron flow, altered NADH/NAD+ redox cycling, metabolite exit, and OAA inhibition of succinate dehydrogenase. In summary, we report a previously unrecognized pattern for complex II energized O2 flux. Moreover, our findings suggest that the ADP recycling approach might be more widely adapted for mitochondrial studies. PMID:27153112

  4. Structural Changes of the Oxygen-evolving Complex in Photosystem II during the Catalytic Cycle*

    PubMed Central

    Glöckner, Carina; Kern, Jan; Broser, Matthias; Zouni, Athina; Yachandra, Vittal; Yano, Junko

    2013-01-01

    The oxygen-evolving complex (OEC) in the membrane-bound protein complex photosystem II (PSII) catalyzes the water oxidation reaction that takes place in oxygenic photosynthetic organisms. We investigated the structural changes of the Mn4CaO5 cluster in the OEC during the S state transitions using x-ray absorption spectroscopy (XAS). Overall structural changes of the Mn4CaO5 cluster, based on the manganese ligand and Mn-Mn distances obtained from this study, were incorporated into the geometry of the Mn4CaO5 cluster in the OEC obtained from a polarized XAS model and the 1.9-Å high resolution crystal structure. Additionally, we compared the S1 state XAS of the dimeric and monomeric form of PSII from Thermosynechococcus elongatus and spinach PSII. Although the basic structures of the OEC are the same for T. elongatus PSII and spinach PSII, minor electronic structural differences that affect the manganese K-edge XAS between T. elongatus PSII and spinach PSII are found and may originate from differences in the second sphere ligand atom geometry. PMID:23766513

  5. Complex networks in brain electrical activity

    NASA Astrophysics Data System (ADS)

    Ray, C.; Ruffini, G.; Marco-Pallarés, J.; Fuentemilla, L.; Grau, C.

    2007-08-01

    This letter reports a method to extract a functional network of the human brain from electroencephalogram measurements. A network analysis was performed on the resultant network and the statistics of the cluster coefficient, node degree, path length, and physical distance of the links, were studied. Even given the low electrode count of the experimental data the method was able to extract networks with network parameters that clearly depend on the type of stimulus presented to the subject. This type of analysis opens a door to studying the cerebral networks underlying brain electrical activity, and links the fields of complex networks and cognitive neuroscience.

  6. Sparfloxacin-metal complexes as antifungal agents - Their synthesis, characterization and antimicrobial activities

    NASA Astrophysics Data System (ADS)

    Sultana, Najma; Arayne, M. Saeed; Gul, Somia; Shamim, Sana

    2010-06-01

    Metal complexes with the third-generation quinolone antibacterial agent sparfloxacin (SPFX) or 5-amino-1-cyclopropyl-7-(cis-3,5-dimethyl-1-piperazinyl)-6,8,di-fluoro-1-4-dihydro-4-oxo-3-quinocarboxylic acid have been synthesized and characterized with physicochemical and spectroscopic techniques such as TLC, IR, NMR and elemental analyses. In these complexes, sparfloxacin acts as bidentate deprotonated ligands bound to the metal through the pyridone oxygen and one carboxylate oxygen. The antimicrobial activity of these complexes has been evaluated against four Gram-positive and seven Gram-negative bacteria. Antifungal activity against five different fungi has been evaluated and compared with reference drug sparfloxacin. Fe 2+-SPFX and Cd 2+-SPFX complexes showed remarkable potency as compared to the parent drug.

  7. Active matter transport on complex substrates

    NASA Astrophysics Data System (ADS)

    Olson Reichhardt, C. J.; Ray, D.; Reichhardt, C.

    2014-09-01

    Colloids interacting with complex landscapes created by optical means exhibit a remarkable variety of novel orderings and equilibrium states. It is also possible to study nonequilibrium properties for colloids driven over optical traps when there is an additional external electric field or some other form of external driving. Recently a new type of colloidal system has been realized in which the colloids are self-driven or self-motile and undergo a persistent random walk. Self motile particle systems fall into the broader class of self-driven systems called active matter. For the case of externally driven colloidal particles moving over random or periodic arrangements of traps, various types of pinning or jamming effects can arise. Far less is known about the mobility of active matter particles in the presence or random or periodic substrates. For example, it is not known whether increasing the activity of the particles would reduce the jamming effects caused by effective friction between particles. Here we show by varying the activity and the density of active particles that various types of motion can arise. In some cases, increasing the self-driving leads to a reduction in the net flow of particles through the system.

  8. Electrostatic effects on proton coupled electron transfer in oxomanganese complexes inspired by the oxygen-evolving complex of photosystem II.

    PubMed

    Amin, Muhamed; Vogt, Leslie; Vassiliev, Serguei; Rivalta, Ivan; Sultan, Mohammad M; Bruce, Doug; Brudvig, Gary W; Batista, Victor S; Gunner, M R

    2013-05-23

    The influence of electrostatic interactions on the free energy of proton coupled electron transfer in biomimetic oxomanganese complexes inspired by the oxygen-evolving complex (OEC) of photosystem II (PSII) are investigated. The reported study introduces an enhanced multiconformer continuum electrostatics (MCCE) model, parametrized at the density functional theory (DFT) level with a classical valence model for the oxomanganese core. The calculated pKa's and oxidation midpoint potentials (E(m)'s) match experimental values for eight complexes, indicating that purely electrostatic contributions account for most of the observed couplings between deprotonation and oxidation state transitions. We focus on pKa's of terminal water ligands in [Mn(II/III)(H2O)6](2+/3+) (1), [Mn(III)(P)(H2O)2](3-) (2, P = 5,10,15,20-tetrakis(2,6-dichloro-3-sulfonatophenyl)porphyrinato), [Mn2(IV,IV)(μ-O)2(terpy)2(H2O)2](4+) (3, terpy = 2,2':6',2″-terpyridine), and [Mn3(IV,IV,IV)(μ-O)4(phen)4(H2O)2](4+) (4, phen = 1,10-phenanthroline) and the pKa's of μ-oxo bridges and Mn E(m)'s in [Mn2(μ-O)2(bpy)4] (5, bpy = 2,2'-bipyridyl), [Mn2(μ-O)2(salpn)2] (6, salpn = N,N'-bis(salicylidene)-1,3-propanediamine), [Mn2(μ-O)2(3,5-di(Cl)-salpn)2] (7), and [Mn2(μ-O)2(3,5-di(NO2)-salpn)2] (8). The analysis of complexes 6-8 highlights the strong coupling between electron and proton transfers, with any Mn oxidation lowering the pKa of an oxo bridge by 10.5 ± 0.9 pH units. The model also accounts for changes in the E(m)'s by ligand substituents, such as found in complexes 6-8, due to the electron withdrawing Cl (7) and NO2 (8). The reported study provides the foundation for analysis of electrostatic effects in other oxomanganese complexes and metalloenzymes, where proton coupled electron transfer plays a fundamental role in redox-leveling mechanisms. PMID:23570540

  9. Activity-stability relationship in the surface electrochemistry of the oxygen evolution reaction.

    PubMed

    Chang, Seo Hyoung; Connell, Justin G; Danilovic, Nemanja; Subbaraman, Ram; Chang, Kee-Chul; Stamenkovic, Vojislav R; Markovic, Nenad M

    2014-01-01

    Understanding the functional links between the stability and reactivity of oxide materials during the oxygen evolution reaction (OER) is one key to enabling a vibrant hydrogen economy capable of competing with fossil fuel-based technologies. In this work, by focusing on the surface chemistry of monometallic Ru oxide in acidic and alkaline environments, we found that the kinetics of the OER are almost entirely controlled by the stability of the Ru surface atoms. The same activity-stability relationship was found for more complex, polycrystalline and single-crystalline SrRuO(3) thin films in alkaline solutions. We propose that the electrochemical transformation of either water (acidic solutions) or hydroxyl ions (alkaline solutions) to di-oxygen molecules takes place at defect sites that are inherently present on every electrode surface. During the OER, surface defects are also created by the corrosion of the Ru ions. The dissolution is triggered by the potential-dependent change in the valence state (n) of Ru: from stable but inactive Ru(4+) to unstable but active Ru(n>4+). We conclude that if the oxide is stable then it is completely inactive for the OER. A practical consequence is that the best materials for the OER should balance stability and activity in such a way that the dissolution rate of the oxide is neither too fast nor too slow. PMID:25490237

  10. Electrochemical activation of commercial polyacrylonitrile-based carbon fiber for the oxygen reduction reaction.

    PubMed

    Xu, Haibo; Xia, Guangsen; Liu, Haining; Xia, Shuwei; Lu, Yonghong

    2015-03-28

    Nitrogen (N)-doped carbon and its non-noble metal composite replacing platinum-based oxygen reduction reaction (ORR) electrocatalysts still have some fundamental problems that remain. Here the micron-sized commercial polyacrylonitrile-based carbon fiber (PAN-CF) electrode was modified using an electrochemical method, converting its inherent pyridinic-N into 2-pyridone (or 2-hydroxyl pyridine) functional group existing in three-dimensional active layers with remarkable ORR catalytic activity and stability. The carbon atom adjacent to the nitrogen and oxygen atoms is prone to act as an active site to efficiently catalyze a two-electron ORR process. However, after coordinating pyridone to the Cu(2+) ion, together with the electrochemical reaction, the chemical redox between Cu(+) and ORR intermediates synergistically tends towards a four-electron pathway in alkaline solution. In different medium, the complexation and dissociation can induce the charge transfer and reconstruction among proton, metal ion and pyridone functionalities, eventually leading to the changes of ORR performance. PMID:25712410

  11. Biological activity of ruthenium nitrosyl complexes.

    PubMed

    Tfouni, Elia; Truzzi, Daniela Ramos; Tavares, Aline; Gomes, Anderson Jesus; Figueiredo, Leonardo Elias; Franco, Douglas Wagner

    2012-01-01

    Nitric oxide plays an important role in various biological processes, such as neurotransmission, blood pressure control, immunological responses, and antioxidant action. The control of its local concentration, which is crucial for obtaining the desired effect, can be achieved with exogenous NO-carriers. Coordination compounds, in particular ruthenium(III) and (II) amines, are good NO-captors and -deliverers. The chemical and photochemical properties of several ruthenium amine complexes as NO-carriers in vitro and in vivo have been reviewed. These nitrosyl complexes can stimulate mice hippocampus slices, promote the lowering of blood pressure in several in vitro and in vivo models, and control Trypanosoma cruzi and Leishmania major infections, and they are also effective against tumor cells in different models of cancer. These complexes can be activated chemically or photochemically, and the observed biological effects can be attributed to the presence of NO in the compound. Their efficiencies are explained on the basis of the [Ru(II)NO(+)](3+)/[Ru(II)NO(0)](2+) reduction potential, the specific rate constant for NO liberation from the [RuNO](2+) moiety, and the quantum yield of NO release. PMID:22178685

  12. Growth enhancement and gene expression of Arabidopsis thaliana irradiated with active oxygen species

    NASA Astrophysics Data System (ADS)

    Watanabe, Satoshi; Ono, Reoto; Hayashi, Nobuya; Shiratani, Masaharu; Tashiro, Kosuke; Kuhara, Satoru; Inoue, Asami; Yasuda, Kaori; Hagiwara, Hiroko

    2016-07-01

    The characteristics of plant growth enhancement effect and the mechanism of the enhancement induced by plasma irradiation are investigated using various active species in plasma. Active oxygen species in oxygen plasma are effective for growth enhancement of plants. DNA microarray analysis of Arabidopsis thaliana indicates that the genes coding proteins that counter oxidative stresses by eliminating active oxygen species are expressed at significantly high levels. The size of plant cells increases owing to oxygen plasma irradiation. The increases in gene expression levels and cell size suggest that the increase in the expression level of the expansin protein is essential for plant growth enhancement phenomena.

  13. An oxygen reduction electrocatalyst based on carbon nanotube-graphene complexes.

    PubMed

    Li, Yanguang; Zhou, Wu; Wang, Hailiang; Xie, Liming; Liang, Yongye; Wei, Fei; Idrobo, Juan-Carlos; Pennycook, Stephen J; Dai, Hongjie

    2012-06-01

    Oxygen reduction reaction catalysts based on precious metals such as platinum or its alloys are routinely used in fuel cells because of their high activity. Carbon-supported materials containing metals such as iron or cobalt as well as nitrogen impurities have been proposed to increase scalability and reduce costs, but these alternatives usually suffer from low activity and/or gradual deactivation during use. Here, we show that few-walled carbon nanotubes, following outer wall exfoliation via oxidation and high-temperature reaction with ammonia, can act as an oxygen reduction reaction electrocatalyst in both acidic and alkaline solutions. Under a unique oxidation condition, the outer walls of the few-walled carbon nanotubes are partially unzipped, creating nanoscale sheets of graphene attached to the inner tubes. The graphene sheets contain extremely small amounts of irons originated from nanotube growth seeds, and nitrogen impurities, which facilitate the formation of catalytic sites and boost the activity of the catalyst, as revealed by atomic-scale microscopy and electron energy loss spectroscopy. Whereas the graphene sheets formed from the unzipped part of the outer wall of the nanotubes are responsible for the catalytic activity, the inner walls remain intact and retain their electrical conductivity, which facilitates charge transport during electrocatalysis. PMID:22635099

  14. The Kinetics of Dissociations of Aluminum - Oxygen Bonds in Aqueous Complexes - An NMR Study

    SciTech Connect

    Dr. William Casey

    2003-09-03

    OAK B262 The Kinetics of Dissociations of Aluminum--Oxygen Bonds in Aqueous Complexes--An NMR Study. In this project we determined rates and mechanisms of Al(III)-O bond rupture at mineral surfaces and in dissolved aluminum complexes. We then compared the experimental results to simulations in an attempt to predict rate coefficients. Most of the low-temperature reactions that are geochemically important involve a bonded atom or molecule that is replaced with another. We probe these reactions at the most fundamental level in order to establish a model to predict rates for the wide range of reactions that cannot be experimentally studied. The chemistry of small aluminum cluster (Figure) provides a window into the hydrolytic processes that control rates of mineral formation and the transformation of adsorbates into extended structures. The molecule shown below as an example exposes several types of oxygens to the bulk solution including seven structurally distinct sets of bridging hydroxyls. This molecule is a rich model for the aqueous interface of aluminum (hydr)oxide minerals, since it approaches colloidal dimensions in size, yet is a dissolved complex with +18 charge. We have conducted both {sup 17}O- {sup 27}Al- and {sup 19}F-NMR experiments to identify the reactive sites and to determine the rates of isotopic exchange between these sites and the bulk solution. The research was enormously successful and led to a series of papers that are being used as touchstones for assessing the accuracy of computer models of bond ruptures in water.

  15. Quantifying the Complexity of Flaring Active Regions

    NASA Astrophysics Data System (ADS)

    Stark, B.; Hagyard, M. J.

    1997-05-01

    While solar physicists have a better understanding of the importance magnetic fields play in the solar heating mechanism, it is still not possible to predict whether or when an active region will flare. In recent decades, qualitative studies of the changes in active region morphology have shown that there is generally an increase in the complexity of the spatial configuration of a solar active region leading up to a flare event. In this study, we quantify the spatial structure of the region using the Differential Box-Counting Method (DBC)of fractal analysis. We analyze data from NASA/Marshall Space Flight Center's vector magnetograph from two flaring active regions: AR 6089 from June 10, 1990, which produced one M1.7 flare, and AR 6659 from June 8, 9 and 10, 1991, this data set including one C5.7 and two M(6.4 and 3.2) flares. (AR 6659 produced several other flares). Several magnetic parameters are studied, including the transverse and longitudinal magnetic field components (Bt and Bl), the total field (Bmag), and the magnetic shear, which describes the non-potentiality of the field. Results are presented for the time series of magnetograms in relation to the timing of flare events.

  16. Quantifying the Complexity of Flaring Active Regions

    NASA Technical Reports Server (NTRS)

    Stark, B.; Hagyard, M. J.

    1997-01-01

    While solar physicists have a better understanding of the importance magnetic fields play in the solar heating mechanism, it is still not possible to predict whether or when an active region will flare. In recent decades, qualitative studies of the changes in active region morphology have shown that there is generally an increase in the complexity of the spatial configuration of a solar active region leading up to a flare event. In this study, we quantify the spatial structure of the region using the differential Box-Counting Method (DBC) of fractal analysis. We analyze data from NASA/Marshall Space Flight Centr's vector magnetograph from two flaring active regions: AR 6089 from June 10, 1990, which produced one M1.7 flare, and AR 6659 from June 8, 9 and 10, 1991, this data set including one C5.7 and two M(6.4 and 3.2) flare. (AR 6659 produced several other flares). Several magnetic parameters are studied, including the transverse and longitudinal magnetic field components (Bt and B1), the total field (Bmag), and the magnetic shear, which describes the non-potentiality of the field. Results are presented for the time series of magnetograms in relation to the timing of flare events.

  17. Calcium EXAFS establishes the Mn-Ca cluster in the oxygen-evolving complex of Photosystem II

    SciTech Connect

    Cinco, Roehl M.; McFarlane Holman, Karen L.; Robblee, John H.; Yano, Junko; Pizarro, Shelly A.; Bellacchio, Emanuele; Sauer, Kenneth; Yachandra, Vittal K.

    2002-08-02

    The proximity of Ca to the Mn cluster of the photosynthetic water-oxidation complex is demonstrated by X-ray absorption spectroscopy. We have collected EXAFS data at the Ca K-edge using active PS II membrane samples that contain approximately 2 Ca per 4 Mn. These samples are much less perturbed than previously investigated Sr-substituted samples, which were prepared subsequent to Ca depletion. The new Ca EXAFS clearly shows backscattering from Mn at 3.4 angstroms, a distance that agrees with that surmised from previously recorded Mn EXAFS. This result is also consistent with earlier related experiments at the Sr K-edge, using samples that contained functional Sr, that show Mn is {approx}; 3.5 angstroms distant from Sr. The totality of the evidence clearly advances the notion that the catalytic center of oxygen evolution is a Mn-Ca heteronuclear cluster.

  18. Supramolecular structural, thermal properties and biological activity of 3-(2-methoxyphenoxy)propane-1,2-diol metal complexes

    NASA Astrophysics Data System (ADS)

    Mahmoud, Walaa H.; Mahmoud, Nessma F.; Mohamed, Gehad G.; El-Bindary, Ashraf A.; El-Sonbati, Adel Z.

    2015-04-01

    New bi- and trivalent transition metal complexes of ligand 3-(2-methoxyphenoxy)propane-1,2-diol (GFS) were synthesized. The ligand and complexes were characterized via: melting point, UV/Visible, IR, 1H NMR, mass and diffused reflectance spectroscopy. The molecular structure of the investigated ligand (GFS) is optimized theoretically and the quantum chemical parameters are calculated. In addition, the complexes were characterized based on conductivity measurement, thermal analysis and biological activity. The infrared spectral study of GFS and its complexes, act as monobasic tridentate through the oxygen atom of hydroxyl group and two etheric oxygen atoms. Also, coordination to the unprotonated oxygen is evidenced from the disappearance of the OH signal in the 1H NMR spectra after complexation. The thermogravimetric analysis of the complexes shows metal oxide remaining as the final product. The compounds were tested against four bacterial species; two Gram positive bacteria (Bacillus subtilis and Staphylococcus aureus) and two Gram negative bacteria (Escherichia coli and Pseudomonas aeruginosa) as well as antifungal activity against (Candida albicans). The complexes showed significant activities against Gram positive bacteria than Gram negative bacteria. [Cd(GFS)Cl(H2O)2] complex showed remarkable antifungal activity. However, some complexes showed more chemotherapeutic efficiency than the parent GFS drug. The drug and complexes were also screened for their in vitro anticancer activity against the Breast cell line (MFC7) and the results obtained show that they exhibit a considerable anticancer activity.

  19. Oxygen isotope mapping of the Archean Sturgeon Lake caldera complex and VMS-related hydrothermal system, Northwestern Ontario, Canada

    NASA Astrophysics Data System (ADS)

    Holk, Gregory J.; Taylor, Bruce E.; Galley, Alan G.

    2008-08-01

    The hydrothermal and magmatic evolution of the Sturgeon Lake caldera complex is graphically documented by a regional-scale (525 km2) analysis of oxygen isotopes. Spatial variations in whole-rock oxygen isotope compositions provide a thermal map of the cumulative effects of multiple stages of hydrothermal metasomatism before, during, and after volcanogenic massive sulfide (VMS) mineralization. There is a progressive, upward increase in δ18O from less than 2‰ to greater than 15‰ through a 5-km-thick section above the Biedelman Bay subvolcanic intrusive complex. This isotopic trend makes it clear that at least the earlier phases of this intrusive complex were coeval with the overlying VMS-hosting cauldron succession and provided thermal energy to drive a convective hydrothermal circulation system. The sharp contrast in δ18O values between late stage phases of the Biedelman Bay intrusion and immediate hanging wall strata indicates that the main phase of VMS-related hydrothermal activity took place before late-stage resurgence in the cauldron-related magmatic activity. Mineralogical and isotopic evidence indicates the presence of both syn- and postmineralization hydrothermal activity defined by the presence of widespread semiconformable and more restricted discordant alteration zones that affect the pre- and syncauldron strata. The semiconformable alteration zones formed during early stages of hydrothermal circulation and are defined by widespread silicification and carbonatization in association with relatively high δ18O values. The discordant alteration assemblages, containing Al-silicate minerals with chloritoid and/or Fe-rich carbonate or chlorite, centered on synvolcanic faults represent restricted zones of both seawater inflow and hydrothermal fluid upflow. A rapid increase in δ18O values (˜7-9‰) over a short distance (<200 m) suggests marked cooling of hydrothermal fluid from ˜350°C to less than 130°C either just before or during discharge onto the

  20. Molecular dioxygen enters the active site of 12/15-lipoxygenase via dynamic oxygen access channels.

    PubMed

    Saam, Jan; Ivanov, Igor; Walther, Matthias; Holzhütter, Hermann-Georg; Kuhn, Hartmut

    2007-08-14

    Cells contain numerous enzymes that use molecular oxygen for their reactions. Often, their active sites are buried deeply inside the protein, which raises the question whether there are specific access channels guiding oxygen to the site of catalysis. Choosing 12/15-lipoxygenase as a typical example for such oxygen-dependent enzymes, we determined the oxygen distribution within the protein and defined potential routes for oxygen access. For this purpose, we have applied an integrated strategy of structural modeling, molecular dynamics simulations, site-directed mutagenesis, and kinetic measurements. First, we computed the 3D free-energy distribution for oxygen, which led to identification of four oxygen channels in the protein. All channels connect the protein surface with a region of high oxygen affinity at the active site. This region is localized opposite to the nonheme iron providing a structural explanation for the reaction specificity of this lipoxygenase isoform. The catalytically most relevant path can be obstructed by L367F exchange, which leads to a strongly increased Michaelis constant for oxygen. The blocking mechanism is explained in detail by reordering the hydrogen-bonding network of water molecules. Our results provide strong evidence that the main route for oxygen access to the active site of the enzyme follows a channel formed by transiently interconnected cavities whereby the opening and closure are governed by side chain dynamics. PMID:17675410

  1. Chemical Equilibrium Models for the S3 State of the Oxygen-Evolving Complex of Photosystem II.

    PubMed

    Isobe, Hiroshi; Shoji, Mitsuo; Shen, Jian-Ren; Yamaguchi, Kizashi

    2016-01-19

    We have performed hybrid density functional theory (DFT) calculations to investigate how chemical equilibria can be described in the S3 state of the oxygen-evolving complex in photosystem II. For a chosen 340-atom model, 1 stable and 11 metastable intermediates have been identified within the range of 13 kcal mol(-1) that differ in protonation, charge, spin, and conformational states. The results imply that reversible interconversion of these intermediates gives rise to dynamic equilibria that involve processes with relocations of protons and electrons residing in the Mn4CaO5 cluster, as well as bound water ligands, with concomitant large changes in the cluster geometry. Such proton tautomerism and redox isomerism are responsible for reversible activation/deactivation processes of substrate oxygen species, through which Mn-O and O-O bonds are transiently ruptured and formed. These results may allow for a tentative interpretation of kinetic data on substrate water exchange on the order of seconds at room temperature, as measured by time-resolved mass spectrometry. The reliability of the hybrid DFT method for the multielectron redox reaction in such an intricate system is also addressed. PMID:26717045

  2. A phosphorescent copper(I) complex: Synthesis, characterization, photophysical property, and oxygen-sensing behavior

    NASA Astrophysics Data System (ADS)

    Wen, Caihong; Tao, Guoquan; Xu, Xinhua; Feng, Xiaoqing; Luo, Rongcheng

    2011-09-01

    In this paper, we report the synthesis, crystal structure, photophysical properties, and electronic nature of a phosphorescent Cu(I) complex of [Cu(Phen-Np)(POP)]BF 4, where Phen-Np and POP stand for 2-(naphthalen-1-yl)-1H-imidazo[4,5-f][1,10]phenanthroline and bis(2-(diphenylphosphanyl)phenyl) ether, respectively. [Cu(Phen-Np)(POP)]BF 4 renders a yellow phosphorescence peaking at 545 nm, with a long excited state lifetime of 4.69 μs. Density functional calculation reveals that the emission comes from a triplet metal-to-ligand-charge-transfer excited state. We electrospun composite nanofibers of [Cu(Phen-Np)(POP)]BF 4 and polystyrene (PS), hoping to explore the possibility of using the composite nanofibers as an oxygen sensing material. The finally obtained samples with average diameter of ˜300 nm exhibit a maximum sensitivity of 7.2 towards molecular oxygen with short response time of 7 s due to the large surface-area-to-volume ratio of nanofibrous membranes. No photobleaching is detected in these samples.

  3. Synthesis, characterization and theoretical analysis on a oxygen-sensing phosphorescent copper(I) complex

    NASA Astrophysics Data System (ADS)

    Li, Zheng

    2011-10-01

    In this paper, we report the synthesis, crystal structure, photophysical properties, and electronic nature of a phosphorescent Cu(I) complex of [Cu(Phen-Ph)(PPh 3) 2]BF 4, where Phen-Ph and PPh 3 stand for 2-phenyl-1H-imidazo[4,5-f][1,10]phenanthroline and triphenylphosphine, respectively. [Cu(Phen-Ph)(PPh 3) 2]BF 4 renders a yellow phosphorescence peaking at 553 nm, with a long excited state lifetime of 13.2 μs under N 2 atmosphere. Density functional calculation reveals that the emission comes from a triplet metal-to-ligand-charge-transfer excited state. We electrospun composite nanofibers of [Cu(Phen-Ph)(PPh 3) 2]BF 4 and polystyrene (PS), hoping to explore the possibility of using the composite nanofibers as an oxygen sensing material. The finally obtained samples with average diameter of ˜400 nm exhibit a maximum sensitivity of 6.52 towards molecular oxygen with short response time of 15 s due to the large surface-area-to-volume ratio of nanofibrous membranes. No photobleaching is detected in these samples.

  4. Studies of reductive elimination reactions to form carbon-oxygen bonds from Pt(IV) complexes.

    PubMed

    Williams, B S; Goldberg, K I

    2001-03-21

    The platinum(IV) complexes fac-L(2)PtMe(3)(OR) (L(2) = bis(diphenylphosphino)ethane, o-bis(diphenylphosphino)benzene, R = carboxyl, aryl; L = PMe(3), R = aryl) undergo reductive elimination reactions to form carbon-oxygen bonds and/or carbon-carbon bonds. The carbon-oxygen reductive elimination reaction produces either methyl esters or methyl aryl ethers (anisoles) and L(2)PtMe(2), while the carbon-carbon reductive elimination reaction affords ethane and L(2)PtMe(OR). Choice of reaction conditions allows the selection of either type of coupling over the other. A detailed mechanistic study of the reductive elimination reactions supports dissociation of the OR(-) ligand as the initial step for the C-O bond formation reaction. This is followed by a nucleophilic attack of OR(-) upon a methyl group bound to the Pt(IV) cation to produce the products MeOR and L(2)PtMe(2). C-C reductive elimination proceeds from L(2)PtMe(3)(OR) by initial L (L = PMe(3)) or OR(-) (L(2) = dppe, dppbz) dissociation, followed by C-C coupling from the resulting five-coordinate intermediate. Our studies demonstrate that both C-C and C-O reductive elimination reactions from Pt(IV) are more facile in polar solvents, in the presence of Lewis acids, and for OR(-) groups that contain electron withdrawing substituents. PMID:11456927

  5. Kinetics and mechanisms of the oxidation of alcohols and hydroxylamines by hydrogen peroxide, catalyzed by methyltrioxorhenium, MTO, and the oxygen binding properties of cobalt Schiff base complexes

    SciTech Connect

    Zauche, Timothy

    1999-02-12

    Catalysis is a very interesting area of chemistry, which is currently developing at a rapid pace. A great deal of effort is being put forth by both industry and academia to make reactions faster and more productive. One method of accomplishing this is by the development of catalysts. Enzymes are an example of catalysts that are able to perform reactions on a very rapid time scale and also very specifically; a goal for every man-made catalyst. A kinetic study can also be carried out for a reaction to gain a better understanding of its mechanism and to determine what type of catalyst would assist the reaction. Kinetic studies can also help determine other factors, such as the shelf life of a chemical, or the optimum temperature for an industrial scale reaction. An area of catalysis being studied at this time is that of oxygenations. Life on this earth depends on the kinetic barriers for oxygen in its various forms. If it were not for these barriers, molecular oxygen, water, and the oxygenated materials in the land would be in a constant equilibrium. These same barriers must be overcome when performing oxygenation reactions on the laboratory or industrial scale. By performing kinetic studies and developing catalysts for these reactions, a large number of reactions can be made more economical, while making less unwanted byproducts. For this dissertation the activation by transition metal complexes of hydrogen peroxide or molecular oxygen coordination will be discussed.

  6. A mechanism of oxygen sensing in yeast. Multiple oxygen-responsive steps in the heme biosynthetic pathway affect Hap1 activity.

    PubMed

    Hon, Thomas; Dodd, Athena; Dirmeier, Reinhard; Gorman, Nadia; Sinclair, Peter R; Zhang, Li; Poyton, Robert O

    2003-12-12

    Heme plays central roles in oxygen sensing and utilization in many living organisms. In yeast, heme mediates the effect of oxygen on the expression of many genes involved in using or detoxifying oxygen. However, a direct link between intracellular heme level and oxygen concentration has not been vigorously established. In this report, we have examined the relationships among oxygen levels, heme levels, Hap1 activity, and HAP1 expression. We found that Hap1 activity is controlled in vivo by heme and not by its precursors and that heme activates Hap1 even in anoxic cells. We also found that Hap1 activity exhibits the same oxygen dose-response curves as Hap1-dependent aerobic genes and that these dose-response curves have a sharp break at approximately 1 microM O2. The results show that the intracellular signaling heme level, reflected as Hap1 activity, is closely correlated with oxygen concentration. Furthermore, we found that bypass of all heme synthetic steps but ferrochelatase by deuteroporphyrin IX does not circumvent the need for oxygen in Hap1 full activation by heme, suggesting that the last step of heme synthesis, catalyzed by ferrochelatase, is also subjected to oxygen control. Our results show that multiple heme synthetic steps can sense oxygen concentration and provide significant insights into the mechanism of oxygen sensing in yeast. PMID:14512429

  7. Asteroseismology of GD358 with complex core carbon and oxygen abundance profiles

    NASA Astrophysics Data System (ADS)

    Kim, Agnes; Provencal, Judith

    2015-08-01

    GD358 is the brightest (mv = 13.7) and best studied helium atmosphere white dwarf pulsator. We present an analysis based on over 1000 hours of observations spanning 2007-2014 as well as archival data going back to 1982. Each modern season of observations was obtained as part of multisite Whole Earth Telescope campaigns (WET). The WET allows continuous coverage of targets over the course of days to weeks. From the complete data set, we identify a total of 27 independent frequencies and fit 15 of them as m=0 modes in our asteroseismic analysis of GD358. As an upgrade to previous analyses of the star, we include complex carbon and oxygen core abundance profiles derived and parameterized from stellar evolution calculations.

  8. X-ray and vibrational spectroscopy of manganese complexes relevant to the oxygen-evolving complex of photosynthesis

    SciTech Connect

    Visser, Hendrik

    2001-05-16

    Manganese model complexes, relevant to the oxygen-evolving complex (OEC) in photosynthesis, were studied with Mn K-edge X-ray absorption near-edge spectroscopy (XANES), Mn Kb X-ray emission spectroscopy (XES), and vibrational spectroscopy. A more detailed understanding was obtained of the influence of nuclearity, overall structure, oxidation state, and ligand environment of the Mn atoms on the spectra from these methods. This refined understanding is necessary for improving the interpretation of spectra of the OEC. Mn XANES and Kb XES were used to study a di-(mu)-oxo and a mono-(mu)-oxo di-nuclear Mn compound in the (III,III), (III,IV), and (IV,IV) oxidation states. XANES spectra show energy shifts of 0.8 - 2.2 eV for 1-electron oxidation-state changes and 0.4 - 1.8 eV for ligand-environment changes. The shifts observed for Mn XES spectra were approximately 0.21 eV for oxidation state-changes and only approximately 0.04 eV for ligand-environment changes. This indicates that Mn Kb XES i s more sensitive to the oxidation state and less sensitive to the ligand environment of the Mn atoms than XANES. These complimentary methods provide information about the oxidation state and the ligand environment of Mn atoms in model compounds and biological systems. A versatile spectroelectrochemical apparatus was designed to aid the interpretation of IR spectra of Mn compounds in different oxidation states. The design, based on an attenuated total reflection device, permits the study of a wide spectral range: 16,700 (600 nm) - 225

  9. Oxygen Atom Exchange between H2O and Non-Heme Oxoiron(IV) Complexes: Ligand Dependence and Mechanism.

    PubMed

    Puri, Mayank; Company, Anna; Sabenya, Gerard; Costas, Miquel; Que, Lawrence

    2016-06-20

    Detailed studies of oxygen atom exchange (OAE) between H2(18)O and synthetic non-heme oxoiron(IV) complexes supported by tetradentate and pentadentate ligands provide evidence that they proceed by a common mechanism but within two different kinetic regimes, with OAE rates that span 2 orders of magnitude. The first kinetic regime involves initial reversible water association to the Fe(IV) complex, which is evidenced by OAE rates that are linearly dependent on [H2(18)O] and H2O/D2O KIEs of 1.6, while the second kinetic regime involves a subsequent rate determining proton-transfer step between the bound aqua and oxo ligands that is associated with saturation behavior with [H2(18)O] and much larger H2O/D2O KIEs of 5-6. [Fe(IV)(O)(TMC)(MeCN)](2+) (1) and [Fe(IV)(O)(MePy2TACN)](2+) (9) are examples of complexes that exhibit kinetic behavior in the first regime, while [Fe(IV)(O)(N4Py)](2+) (3), [Fe(IV)(O)(BnTPEN)](2+) (4), [Fe(IV)(O)(1Py-BnTPEN)](2+) (5), [Fe(IV)(O)(3Py-BnTPEN)](2+) (6), and [Fe(IV)(O)(Me2Py2TACN)](2+) (8) represent complexes that fall in the second kinetic regime. Interestingly, [Fe(IV)(O)(PyTACN)(MeCN)](2+) (7) exhibits a linear [H2(18)O] dependence below 0.6 M and saturation above 0.6 M. Analysis of the temperature dependence of the OAE rates shows that most of these complexes exhibit large and negative activation entropies, consistent with the proposed mechanism. One exception is complex 9, which has a near-zero activation entropy and is proposed to undergo ligand-arm dissociation during the RDS to accommodate H2(18)O binding. These results show that the observed OAE kinetic behavior is highly dependent on the nature of the supporting ligand and are of relevance to studies of non-heme oxoiron(IV) complexes in water or acetonitrile/water mixtures for applications in photocatalysis and water oxidation chemistry. PMID:27275633

  10. Combination therapy of normobaric oxygen with hypothermia or ethanol modulates pyruvate dehydrogenase complex in thromboembolic cerebral ischemia.

    PubMed

    Cai, Lipeng; Thibodeau, Alexa; Peng, Changya; Ji, Xunming; Rastogi, Radhika; Xin, Ruiqiang; Singh, Sunpreet; Geng, Xiaokun; Rafols, Jose A; Ding, Yuchuan

    2016-08-01

    Pyruvate dehydrogenase complex (PDH) is a brain mitochondrial matrix enzyme. PDH impairment after stroke is particularly devastating given PDH's critical role in the link between anaerobic and aerobic metabolism. This study evaluates the restoration of oxidative metabolism and energy regulation with a therapeutic combination of normobaric oxygen (NBO) plus either therapeutic hypothermia (TH) or ethanol. Sprague-Dawley rats were subjected to middle cerebral artery occlusion with an autologous embolus. One hour after occlusion, tissue-type plasminogen activator (t-PA) was administered alone or with NBO (60%), EtOH (1.0 g/kg), or TH (33°C), either singly or in combination. Neurological deficit score and infarct volume were assessed 24 hr after t-PA-induced reperfusion. PDH activity and reactive oxygen species (ROS) levels were measured 3 and 24 hr after t-PA. Western blotting was used to detect PDH and pyruvate dehydrogenase kinase (PDK) protein expression. After t-PA in ischemic rats, NBO combined with TH or EtOH most effectively decreased infarct volume and neurological deficit. The combined therapies produced greater increases in PDH activity and protein expression as well as greater decreases in PDK expression. Compared with the monotherapeutic approaches, the combined therapies provided the most significant declines in ROS generation. Reperfusion with t-PA followed by 60% NBO improves the efficacy of EtOH or TH in neuroprotection by ameliorating oxidative injury and improving PDH regulation. Comparable neuroprotective effects were found when treating with either EtOH or TH, suggesting a similar mechanism of neuroprotection and the possibility of substituting EtOH for TH in clinical settings. © 2016 Wiley Periodicals, Inc. PMID:27027410

  11. Cell death induced by direct laser activation of singlet oxygen at 1270 nm

    NASA Astrophysics Data System (ADS)

    Anquez, F.; El Yazidi Belkoura, I.; Suret, P.; Randoux, S.; Courtade, E.

    2013-02-01

    Singlet oxygen plays a major role in many chemical and biological photo-oxidation processes. It has a high chemical reactivity, which is commonly harnessed for therapeutic issues. Indeed, singlet oxygen is recognized as the major cytotoxic agent in photodynamic therapy. In this treatment of cancer, singlet oxygen is created, among other reactive species, by an indirect transfer of energy from light to molecular oxygen via excitation of a photosensitizer. In this paper, we show that the conventional singlet oxygen production scheme can be simplified. Production of singlet oxygen is achieved in living cells from photosensitizer-free 1270 nm laser excitation of the electronic ground state of molecular oxygen. The quantity of singlet oxygen produced in this way is sufficient to induce an oxidative stress leading to cell death. Other effects such as thermal stress are discriminated, and we conclude that cell death is only due to singlet oxygen creation. This new simplified scheme of singlet oxygen activation can be seen as a breakthrough for phototherapies of malignant diseases and/or as a non-invasive possibility to generate reactive oxygen species in a tightly controlled manner.

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

    PubMed Central

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

    2012-01-01

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

  13. Mitochondria are required for antigen-specific T cell activation through reactive oxygen species signaling

    PubMed Central

    Sena, Laura A.; Li, Sha; Jairaman, Amit; Prakriya, Murali; Ezponda, Teresa; Hildeman, David A.; Wang, Chyung-Ru; Schumacker, Paul T.; Licht, Jonathan D.; Perlman, Harris; Bryce, Paul J.; Chandel, Navdeep S.

    2013-01-01

    SUMMARY It is widely appreciated that T cells increase glycolytic flux during activation, however the role of mitochondrial flux is unclear. Here we have shown that mitochondrial metabolism, in the absence of glucose metabolism, was sufficient to support interleukin-2 (IL-2) induction. Furthermore, we used mice with reduced mitochondrial reactive oxygen species (mROS) production in T cells (T-Uqcrfs−/− mice) to show that mitochondria are required for T cell activation to produce mROS for activation of nuclear factor of activated T cells (NFAT) and subsequent IL-2 induction. These mice could not induce antigen-specific expansion of T cells in vivo, however Uqcrfs1−/− T cells retained the ability to proliferate in vivo under lymphopenic conditions. This suggests that Uqcrfs1−/− T cells were not lacking bioenergetically, but rather lacked specific ROS-dependent signaling events needed for antigen-specific expansion. Thus, mitochondrial metabolism is a critical component of T cell activation through production of complex III ROS. PMID:23415911

  14. Elaboration of copper-oxygen mediated C-H activation chemistry in consideration of future fuel and feedstock generation.

    PubMed

    Lee, Jung Yoon; Karlin, Kenneth D

    2015-04-01

    To contribute solutions to current energy concerns, improvements in the efficiency of dioxygen mediated C-H bond cleavage chemistry, for example, selective oxidation of methane to methanol, could minimize losses in natural gas usage or produce feedstocks for fuels. Oxidative C-H activation is also a component of polysaccharide degradation, potentially affording alternative biofuels from abundant biomass. Thus, an understanding of active-site chemistry in copper monooxygenases, those activating strong C-H bonds is briefly reviewed. Then, recent advances in the synthesis-generation and study of various copper-oxygen intermediates are highlighted. Of special interest are cupric-superoxide, Cu-hydroperoxo and Cu-oxy complexes. Such investigations can contribute to an enhanced future application of C-H oxidation or oxygenation processes using air, as concerning societal energy goals. PMID:25756327

  15. Elaboration of Copper-Oxygen Mediated C–H Activation Chemistry in Consideration of Future Fuel and Feedstock Generation

    PubMed Central

    Lee, Jung Yoon; Karlin, Kenneth D

    2015-01-01

    To contribute solutions for current energy concerns, improvements in the efficiency of C-H bond cleavage chemistry, e.g., selective oxidation of methane to methanol, could minimize losses in natural gas usage or produce feedstocks for fuels. Oxidative C-H activation is also a component of polysaccharide degradation, affording alternative biofuels from abundant biomass. Thus, an understanding of active-site chemistry in copper monooxygenases, those activating strong C-H bonds is briefly reviewed. Then, recent advances in the synthesis-generation and study of various copper-oxygen intermediates are highlighted. Of special interest are cupric-superoxide, Cu-hydroperoxo and Cu-oxy complexes. Such investigations can contribute to an enhanced future application of C-H oxidation or oxygenation processes using air, as concerning societal energy goals. PMID:25756327

  16. Ruthenium chalcogenonitrosyl and bridged nitrido complexes containing chelating sulfur and oxygen ligands.

    PubMed

    Ng, Ho-Yuen; Cheung, Wai-Man; Kwan Huang, Enrique; Wong, Kang-Long; Sung, Herman H-Y; Williams, Ian D; Leung, Wa-Hung

    2015-11-14

    Ruthenium thio- and seleno-nitrosyl complexes containing chelating sulfur and oxygen ligands have been synthesised and their de-chalcogenation reactions have been studied. The reaction of mer-[Ru(N)Cl3(AsPh3)2] with elemental sulfur and selenium in tetrahydrofuran at reflux afforded the chalcogenonitrosyl complexes mer-[Ru(NX)Cl3(AsPh3)2] [X = S (1), Se (2)]. Treatment of 1 with KN(R2PS)2 afforded trans-[Ru(NS)Cl{N(R2PS)2}2] [R = Ph (3), Pr(i) (4), Bu(t) (5)]. Alternatively, the thionitrosyl complex 5 was obtained from [Bu(n)4N][Ru(N)Cl4] and KN(Bu(t)2PS)2, presumably via sulfur atom transfer from [N(Bu(t)2PS)2](-) to the nitride. Reactions of 1 and 2 with NaLOEt (LOEt(-) = [Co(η(5)-C5H5){P(O)(LOEt)2}3](-)) gave [Ru(NX)LOEtCl2] (X = S (8), Se (9)). Treatment of [Bu(n)4N][Ru(N)Cl4] with KN(R2PS)2 produced Ru(IV)-Ru(IV)μ-nitrido complexes [Ru2(μ-N){N(R2PS)2}4Cl] [R = Ph (6), Pr(i) (7)]. Reactions of 3 and 9 with PPh3 afforded 6 and [Ru(NPPh3)LOEtCl2], respectively. The desulfurisation of 5 with [Ni(cod)2] (cod = 1,5-cyclooctadiene) gave the mixed valance Ru(III)-Ru(IV)μ-nitrido complex [Ru2(μ-N){N(Bu(t)2PS)2}4] (10) that was oxidised by [Cp2Fe](PF6) to give the Ru(IV)-Ru(IV) complex [Ru2(μ-N){N(Bu(t)2PS)2}4](PF6) ([10]PF6). The crystal structures of 1, 2, 3, 7, 9 and 10 have been determined. PMID:26442594

  17. Oxygen- and strontium-isotopic studies of the skye intrusive complex, northwest Scotland

    SciTech Connect

    Smith, B.M.

    1981-01-01

    This dissertation is comprised of three parts, each of which addresses some aspect of the meteoric-hydrothermal fluid/rock interaction which affected the rocks within and near the Skye intrusive complex. Part 1 was undertaken to determine the scale and magnitude of hydrothermal Sr contamination in the Coire Uaigneich Granophyre (CUG). Sr- and O-isotopic and electron microprobe results show that Sr was mobile in the low-/sup 18/O meteoric-hydrothermal fluids, that Sr-exchange between these fluids and the CUG was limited to thin (less than or equal to 1 cm) zones of bleached and albitized granophyre adjacent to fractures, and that the scale of O-exchange was much larger. Part 2 focuses on the stable isotopic and mineralogical compositions of the Beinn an Dubhaich Granite and its Durness Limestone host rocks. Part 3 is an attempt to discriminate between magmatic and subsolidus /sup 18/O depletions in porphyritic felsitic dikes from two widely separated regions of the intrusive complex. Eastern Red Hills felsites, collected approximately 9 km from the exposed margin of the Cuillins intrusion, probably crystallized from O-isotopically normal magmas. Empirical and experimental data on the kinetics of volume diffusion of oxygen in feldspar minerals and quartz (in the presence of H/sub 2/O) suggest that the /sup 18/O depletion in quartz and feldspar from the SPF may be attributed to very high-temperature (>600/sup 0/C) subsolidus exchange with circulating low-/sup 18/O fluids.

  18. Synthesis and reactions of U(III) complexes with tripodal nitrogen and oxygen donor ligands

    NASA Astrophysics Data System (ADS)

    McDonald, Robert; Sun, Yimin; Takats, Josef; Day, Victor W.; Eberspracher, Todd A.

    1994-10-01

    Reaction of UI3(THF)4 (where THF is tetrahydrofuran) with sodium or potassium hydrotris(3,5-dimethylpyrazolyl)borate ligand ((HBpz 3*)(-) in 1:1 and 1:2 ratios gives the corresponding U(HBpz 3*)I2(THF)2(1) and U(HBpz 3*)2I(2) complexes in excellent yields. Iodide abstraction from (2) with TlBPh4 results in the formation of the cationic complex (U(HBpz 3*)2(THF)) BPh4(3). The solid state structures of 1, 2 and 3 have been determined. Similar reactions with the anionic tripodal oxygen donor ligand ((eta (sub 5) - (5H5) Co(P(O)(OC2H5)2)3)(-) (L(sub OEt)) proceeded via oxidation of U(3+) to U(4+) and fragmentation of the ligand. The structures of some key compounds were established by X-ray crystallography. U(HBpz 3*)I2(THF)2 readily reacts with two equivalents of KH2Bpz (pz equivalent to pyrazolyl) to give U(HBpz3*)(H2Bpz2)2, but attempted substitution with other ligands led to mixtures or, in one case, displacement of the (HBpz 3*)(-) ligand.

  19. The confines of triple oxygen isotope exponents in elemental and complex mass-dependent processes

    NASA Astrophysics Data System (ADS)

    Bao, Huiming; Cao, Xiaobin; Hayles, Justin A.

    2015-12-01

    Small differences in triple isotope relationships, or Δ17O in the case of oxygen, have been increasingly used to study a range of problems including hydrological cycles, stratosphere-troposphere exchange, biogeochemical pathways and fluxes, and the Moon's origin in the geochemical and cosmochemical communities. A Δ17O value depends on the triple isotope exponent θ of involved reaction steps. However, the probabilistic distribution of the intrinsic and apparent θ values has not been examined for elemental processes and for processes that are out of equilibrium or bearing reservoir-transport complexities. A lack of knowledge on the confines of θ may hamper our understanding of the subtle differences among mass-dependent processes and may result in mischaracterization of a set of mass-dependent processes as being in violation of mass-dependent rules. Here we advocate a reductionist approach and explore θ confines starting from kinetic isotope effects (KIEs) within the framework of transition state theory (TST). The advantage of our KIE approach is that any elemental or composite, equilibrium or non-equilibrium process can be reduced to a set of KIEs with corresponding θKIE. We establish that the KIE between a reactant and a transition state (TS) is intrinsic. Given a range of KIEs known for Earth processes involving oxygen, we use a Monte Carlo calculation method and a range of oxygen-bonded molecular masses to obtain a distribution of θKIE values and subsequently that of θeq. Next, complexities are examined by looking into expected effects due to reaction progress, unbalanced fluxes, and reference frame. Finally, compounded reservoir-transport effects are examined using two simple processes - Rayleigh Distillation (RD) and Fractional Distillation (FD). Our results show that the apparent θ values between two species or two states of the same evolving species have much broader confines than the commonly used "canonical" confines of 0.51-0.53, particularly

  20. Method of Separating Oxygen From Spacecraft Cabin Air to Enable Extravehicular Activities

    NASA Technical Reports Server (NTRS)

    Graf, John C.

    2013-01-01

    Extravehicular activities (EVAs) require high-pressure, high-purity oxygen. Shuttle EVAs use oxygen that is stored and transported as a cryogenic fluid. EVAs on the International Space Station (ISS) presently use the Shuttle cryo O2, which is transported to the ISS using a transfer hose. The fluid is compressed to elevated pressures and stored as a high-pressure gas. With the retirement of the shuttle, NASA has been searching for ways to deliver oxygen to fill the highpressure oxygen tanks on the ISS. A method was developed using low-pressure oxygen generated onboard the ISS and released into ISS cabin air, filtering the oxygen from ISS cabin air using a pressure swing absorber to generate a low-pressure (high-purity) oxygen stream, compressing the oxygen with a mechanical compressor, and transferring the high-pressure, high-purity oxygen to ISS storage tanks. The pressure swing absorber (PSA) can be either a two-stage device, or a single-stage device, depending on the type of sorbent used. The key is to produce a stream with oxygen purity greater than 99.5 percent. The separator can be a PSA device, or a VPSA device (that uses both vacuum and pressure for the gas separation). The compressor is a multi-stage mechanical compressor. If the gas flow rates are on the order of 5 to 10 lb (.2.3 to 4.6 kg) per day, the compressor can be relatively small [3 16 16 in. (.8 41 41 cm)]. Any spacecraft system, or other remote location that has a supply of lowpressure oxygen, a method of separating oxygen from cabin air, and a method of compressing the enriched oxygen stream, has the possibility of having a regenerable supply of highpressure, high-purity oxygen that is compact, simple, and safe. If cabin air is modified so there is very little argon, the separator can be smaller, simpler, and use less power.

  1. The Effect of 30% Oxygen on Visuospatial Performance and Brain Activation: An Fmri Study

    ERIC Educational Resources Information Center

    Chung, S.C.; Tack, G.R.; Lee, B.; Eom, G.M.; Lee, S.Y.; Sohn, J.H.

    2004-01-01

    This study aimed to investigate the hypothesis that administration of the air with 30% oxygen compared with normal air (21% oxygen) enhances cognitive functioning through increased activation in the brain. A visuospatial task was presented while brain images were scanned by a 3 T fMRI system. The results showed that there was an improvement in…

  2. Catalytic Activity of Human Indoleamine 2,3-Dioxygenase (hIDO1) at Low Oxygen

    PubMed Central

    Kolawole, Ayodele O.; Hixon, Brian P.; Dameron, Laura S.; Chrisman, Ian M.; Smirnov, Valeriy V.

    2015-01-01

    A cytokine-inducible extrahepatic human indoleamine 2,3-dioxygenase (hIDO1) catalyzes the first step of the kynurenine pathway. Immunosuppressive activity of hIDO1 in tumor cells weakens host T-cell immunity, contributing to the progression of cancer. Here we report on enzyme kinetics and catalytic mechanism of hIDO1, studied at varied levels of dioxygen (O2) and L-tryptophan (L-Trp). Using a cytochrome b5-based activating system, we measured the initial rates of O2 decay with a Clark-type oxygen electrode at physiologically-relevant levels of both substrates. Kinetics was also studied in the presence of two substrate analogs: 1-methyl-L-tryptophan and norharmane. Quantitative analysis supports a steady-state rather than a rapid equilibrium kinetic mechanism, where the rates of individual pathways, leading to a ternary complex, are significantly different, and the overall rate of catalysis depends on contributions of both routes. One path, where O2 binds to ferrous hIDO1 first, is faster than the second route, which starts with the binding of L-Trp. However, L-Trp complexation with free ferrous hIDO1 is more rapid than that of O2. As the level of L-Trp increases, the slower route becomes a significant contributor to the overall rate, resulting in observed substrate inhibition. PMID:25712221

  3. Exceptional Oxygen Sensing Properties of New Blue Light-Excitable Highly Luminescent Europium(III) and Gadolinium(III) Complexes

    PubMed Central

    Borisov, Sergey M.; Fischer, Roland; Saf, Robert; Klimant, Ingo

    2016-01-01

    New europium(III) and gadolinium(III) complexes bearing 8-hydroxyphenalenone antenna combine efficient absorption in the blue part of the spectrum and strong emission in polymers at room temperature. The Eu(III) complexes show characteristic red luminescence whereas the Gd(III) dyes are strongly phosphorescent. The luminescence quantum yields are about 20% for the Eu(III) complexes and 50% for the Gd(III) dyes. In contrast to most state-of-the-art Eu(III) complexes the new dyes are quenched very efficiently by molecular oxygen. The luminescence decay times of the Gd(III) complexes exceed 1 ms which ensures exceptional sensitivity even in polymers of moderate oxygen permeability. These sensors are particularly suitable for trace oxygen sensing and may be good substitutes for Pd(II) porphyrins. The photophysical and sensing properties can be tuned by varying the nature of the fourth ligand. The narrow-band emission of the Eu(III) allows efficient elimination of the background light and autofluorescence and is also very attractive for use e.g. in multi-analyte sensors. The highly photostable indicators incorporated in nanoparticles are promising for imaging applications. Due to the straightforward preparation and low cost of starting materials the new dyes represent a promising alternative to the state-of-the-art oxygen indicators particularly for such applications as e.g. food packaging. PMID:27158252

  4. Atmospheric oxygen plasma activation of silicon (100) surfaces

    SciTech Connect

    Habib, Sara B.; Gonzalez, Eleazar II; Hicks, Robert F.

    2010-05-15

    Silicon (100) surfaces were converted to a hydrophilic state with a water contact angle of <5 deg. by treatment with a radio frequency, atmospheric pressure helium, and oxygen plasma. A 2 in. wide plasma beam, operating at 250 W, 1.0 l/min O{sub 2}, 30 l/min He, and a source-to-sample distance of 3{+-}0.1 mm, was scanned over the sample at 100{+-}2 mm/s. Plasma oxidation of HF-etched silicon caused the dispersive component of the surface energy to decrease from 55.1 to 25.8 dyn/cm, whereas the polar component of the surface energy increased from 0.3 to 42.1 dyn/cm. X-ray photoelectron spectroscopy revealed that the treatment generated a monolayer of covalently bonded oxygen on the Si(100) surface 0.15{+-}0.10 nm thick. The surface oxidation kinetics have been measured by monitoring the change in water contact angle with treatment time, and are consistent with a process that is limited by the mass transfer of ground-state oxygen atoms to the silicon surface.

  5. NOX4 in Mitochondria: Yeast Two-Hybrid-Based Interaction with Complex I Without Relevance for Basal Reactive Oxygen Species?

    PubMed Central

    Hirschhäuser, Christine; Bornbaum, Julia; Reis, Anna; Böhme, Sabrina; Kaludercic, Nina; Menabò, Roberta; Di Lisa, Fabio; Boengler, Kerstin; Shah, Ajay M.

    2015-01-01

    Abstract NADPH oxidases (NOXs) represent the only known dedicated source of reactive oxygen species (ROS) and thus a prime therapeutic target. Type 4 NOX is unique as it produces H2O2, is constitutively active, and has been suggested to localize to cardiac mitochondria, thus possibly linking mitochondrial and NOX-derived ROS formation. The aim of this study was to identify NOX4-binding proteins and examine the possible physiological localization of NOX4 to mitochondria and its impact on mitochondrial ROS formation. We here provide evidence that NOX4 can, in principle, enter protein–protein interactions with mitochondrial complex I NADH dehydrogenase subunits, 1 and 4L. However, under physiological conditions, NOX4 protein was neither detectable in the kidney nor in cardiomyocyte mitochondria. The NOX inhibitor, GKT136901, slightly reduced ROS formation in cardiomyocyte mitochondria, but this effect was observed in both wild-type and Nox4−/− mice. NOX4 may thus associate with mitochondrial complex I proteins, but in cardiac and renal mitochondria under basal conditions, expression is beyond our detection limits and does not contribute to ROS formation. Antioxid. Redox Signal. 23, 1106–1112. PMID:26237157

  6. Design of high pressure oxygen filter for extravehicular activity life support system, volume 1

    NASA Technical Reports Server (NTRS)

    Wilson, B. A.

    1977-01-01

    The experience of the National Aeronautics and Space Administration (NASA) with extravehicular activity life support emergency oxygen supply subsystems has shown a large number of problems associated with particulate contamination. These problems have resulted in failures of high pressure oxygen component sealing surfaces. A high pressure oxygen filter was designed which would (a) control the particulate contamination level in the oxygen system to a five-micron glass bead rating, ten-micron absolute condition (b) withstand the dynamic shock condition resulting from the sudden opening of 8000 psi oxygen system shutoff valve. Results of the following program tasks are reported: (1) contaminant source identification tests, (2) dynamic system tests, (3) high pressure oxygen filter concept evaluation, (4) design, (5) fabrication, (6) test, and (7) application demonstration.

  7. Ab-initio calculation study on the formation mechanism of boron-oxygen complexes in c-Si

    SciTech Connect

    Yu, Xuegong; Chen, Peng; Chen, Xianzi; Liu, Yong; Yang, Deren

    2015-07-15

    Boron-oxygen (B-O) complex in crystalline silicon (c-Si) solar cells is responsible for the light-induced efficiency degradation of solar cell. However, the formation mechanism of B-O complex is not clear yet. By Ab-initio calculation, it is found that the stagger-type oxygen dimer (O{sub 2i}{sup st}) should be the component of B-O complex, whose movement occurs through its structure reconfiguration at low temperature, instead of its long-distance diffusion. The O{sub 2i}{sup st} can form two stable “latent centers” with the B{sub s}, which are recombination-inactive. The latent centers can be evolved into the metastable recombination centers via their structure transformation in the presence of excess carriers. These results can well explain the formation behaviors of B-O complexes in c-Si.

  8. Reactive oxygen scavenging activity of matured whiskey and its active polyphenols.

    PubMed

    Koga, K; Taguchi, A; Koshimizu, S; Suwa, Y; Yamada, Y; Shirasaka, N; Yoshizumi, H

    2007-04-01

    The quality of whiskey is known to improve remarkably by its storage over many years. This process is commonly termed "maturing." In this process, polyphenols derived from lignin and tannin of the barrel have an important role in not only forming the matured flavor and taste but also contributing to the advance of clustering ethanol and water in whiskey. It is also likely that polyphenols generally possess reactive oxygen (RO) scavenging activity. The present study evaluated the RO scavenging activity (free-radical scavenging activity, H(2)O(2) reduction activity under peroxidase coculture, and H(2)O(2)scavenging activity) of 24 single malt whiskeys with a maturation age of 10 to 30 y produced in Japanese, Scotch (Islay), or Scotch (Speyside and Highland) regions. Single malt whiskey not only showed RO scavenging activity but there was also a positive correlation between this activity and the maturation age of whiskey exceeding the difference resulting from the manufacturing region. A nonvolatile fraction derived from the barrel was responsible for RO scavenging activity. In particular, the contents of ellagic and gallic acids and lyoniresinol, the main polyphenolic compounds in whiskey, increased with maturation age. For the free-radical scavenging activity per molecule, each compound was 1.68 to 3.14 times that of trolox (a water-soluble vitamin E). The activities of ellagic acid, gallic acid, and lyoniresinol in the whiskey (Yamazaki 18) were equivalent to that of 80.3, 31.2, and 11.1 ppm trolox, respectively. Accordingly, the total activity of these 3 compounds accounted for about 20% of the activity of the whiskey (630.7 ppm trolox). PMID:17995817

  9. Time-resolved luminescence imaging of intracellular oxygen levels based on long-lived phosphorescent iridium(III) complex.

    PubMed

    Liu, Shujuan; Zhang, Yangliu; Liang, Hua; Chen, Zejing; Liu, Ziyu; Zhao, Qiang

    2016-07-11

    Time-resolved luminescence imaging of intracellular oxygen levels has been demonstrated based on long-lived phosphorescent signal. A phosphorescent dinuclear iridium(III) complex Ir1 has been designed and synthesized, which exhibits excellent optical properties, such as high quantum yields, large Stokes shift, high photostability and long emission lifetime. The phosphorescent intensity and lifetime of complex are very sensitive to oxygen levels. Thus, the application of Ir1 for monitoring intracellular oxygen levels has been realized successfully. Especially, utilizing the advantageous long emission lifetime of Ir1, the background fluorescence interference could be eliminated effectively by using the photoluminescence lifetime imaging and time-gated luminescence imaging techniques, improving the signal-to-noise ratios in bioimaging. PMID:27410847

  10. Luminescent sensing of dissolved oxygen based on Ru(II) complex embedded in sol-gel matrix

    NASA Astrophysics Data System (ADS)

    Bi, Yubing; Tao, Wei; Hu, Yanli; Mao, Yimei; Zhao, Hui

    2015-11-01

    In biological cells and tissues environment, real-time monitoring and controlling dissolved oxygen (DO) provides critical information for studying cellular metabolism process, health status and pathological features. This paper developed an optical DO sensor based on fluorescence quenching principle, prepared tris(4,7-diphenyl-1,10- phenanthroline)ruthenium(II) dichloride complex sol-gel sensing film, and studied its sensing performance. The principle of this sensor is that dissolved oxygen has quenching effect towards the fluorescence emitted by ruthenium complex. So the fluorescence intensity is reduced due to the existence of DO. The measurement limit of DO was 10- 100%, the response time was 20s, and the resolution was 0.02. Compared to traditional dissolved oxygen electrode probe, this luminescent fiber had many advantages, such as smaller size, shorter response time and higher stability.

  11. A Method to Perform Direct Oxygen Analysis on Lunar Simulants and Other Complex Oxide Materials

    NASA Technical Reports Server (NTRS)

    Santiago-Maldonado, Edgardo

    2007-01-01

    An essential requirement for making space travel and long term missions more efficient and affordable to NASA includes finding innovative ways to supply oxygen for life support and propulsion. In this experiment, carrier gas hot extraction was investigated as a possible method for measuring the oxygen from samples of lunar soil simulants before and after oxygen extraction. The determination of oxygen using the R0600 Oxygen Determinator is usually limited to oxides with low oxygen concentrations, but after the manipulation of certain furnace operating parameters such as analysis time and ramp rate, the R0600 was used to determine the oxygen content of high concentration oxides such as Fe 2O3 , Al2O3 , and SiO2.

  12. Effects of carbohydrate on the internal oxygen concentration, oxygen uptake, and nitrogenase activity in detached pea nodules

    SciTech Connect

    Monroe, J.D. ); LaRue, T.A. )

    1989-10-01

    The interaction between carbon substrates and O{sub 2} and their effects on nitrogenase activity (C{sub 2}H{sub 2}) were examined in detached nodules of pea (Pisum sativum L. cv Sparkle). The internal O{sub 2} concentration was estimated from the fractional oxygenation of leghemoglobin measured by reflectance spectroscopy. Lowering the endogenous carbohydrate content of nodules by excising the shoots 16 hours before nodule harvest or by incubating detached nodules at 100 kPa O{sub 2} for 2 hours resulted in a 2- to 10-fold increase in internal O{sub 2}, and a decline in nitrogenase activity. Conversely, when detached nodules were supplied with 100 millimolar succinate, the internal O{sub 2} was lowered. Nitrogenase activity was stimulated by succinate but only at high external O{sub 2}. Oxygen uptake increased linearly with external O{sub 2} but was affected only slightly by the carbon treatments. The apparent diffusion resistance in the nodule cortex was similar in all of the treatments. Carbon substrates can thus affect nitrogenase activity indirectly by affecting the O{sub 2} concentration within detached nodules.

  13. Exploiting Complexity Information for Brain Activation Detection

    PubMed Central

    Zhang, Yan; Liang, Jiali; Lin, Qiang; Hu, Zhenghui

    2016-01-01

    We present a complexity-based approach for the analysis of fMRI time series, in which sample entropy (SampEn) is introduced as a quantification of the voxel complexity. Under this hypothesis the voxel complexity could be modulated in pertinent cognitive tasks, and it changes through experimental paradigms. We calculate the complexity of sequential fMRI data for each voxel in two distinct experimental paradigms and use a nonparametric statistical strategy, the Wilcoxon signed rank test, to evaluate the difference in complexity between them. The results are compared with the well known general linear model based Statistical Parametric Mapping package (SPM12), where a decided difference has been observed. This is because SampEn method detects brain complexity changes in two experiments of different conditions and the data-driven method SampEn evaluates just the complexity of specific sequential fMRI data. Also, the larger and smaller SampEn values correspond to different meanings, and the neutral-blank design produces higher predictability than threat-neutral. Complexity information can be considered as a complementary method to the existing fMRI analysis strategies, and it may help improving the understanding of human brain functions from a different perspective. PMID:27045838

  14. Exploiting Complexity Information for Brain Activation Detection.

    PubMed

    Zhang, Yan; Liang, Jiali; Lin, Qiang; Hu, Zhenghui

    2016-01-01

    We present a complexity-based approach for the analysis of fMRI time series, in which sample entropy (SampEn) is introduced as a quantification of the voxel complexity. Under this hypothesis the voxel complexity could be modulated in pertinent cognitive tasks, and it changes through experimental paradigms. We calculate the complexity of sequential fMRI data for each voxel in two distinct experimental paradigms and use a nonparametric statistical strategy, the Wilcoxon signed rank test, to evaluate the difference in complexity between them. The results are compared with the well known general linear model based Statistical Parametric Mapping package (SPM12), where a decided difference has been observed. This is because SampEn method detects brain complexity changes in two experiments of different conditions and the data-driven method SampEn evaluates just the complexity of specific sequential fMRI data. Also, the larger and smaller SampEn values correspond to different meanings, and the neutral-blank design produces higher predictability than threat-neutral. Complexity information can be considered as a complementary method to the existing fMRI analysis strategies, and it may help improving the understanding of human brain functions from a different perspective. PMID:27045838

  15. Study of oxygen scavenging PET-based films activated by water

    NASA Astrophysics Data System (ADS)

    Rossi, Gabriella; Scarfato, Paola; Incarnato, Loredana

    2016-05-01

    In this work an active barrier system consisting of a thin and transparent film based on polyethylene terephthalate (PET) was studied. Dynamic oxygen absorption measurements were performed at different values of relative humidity and temperature, pointing out that humidity is a key factor in activating the oxidation of the polymer sample. Moreover, the thermal and optical properties of the films were investigated and a good correlation was found between the crystallinity increase and the consequent transparency reduction occurring after the oxygen absorption.

  16. Oxygen requirements for formation and activity of the squalene expoxidase in Saccharomyces cerevisiae

    NASA Technical Reports Server (NTRS)

    Jahnke, L.; Klein, H. P.

    1983-01-01

    The effect of oxygen on squalene epoxidase activity in Saccharomyces cerevisiae was investigated. In cells grown in standing cultures, the epoxidase was localized mainly in the 'mitochondrial' fraction. Upon aeration, enzyme activity increased and the newly formed enzyme was associated with the 'microsomal' fraction. At 0.03 percent (vol/vol) oxygen, epoxidase levels doubled, whereas the ergosterol level was only slightly increased. Cycloheximide inhibited the increase in epoxidase under these conditions. An apparent K sub m for oxygen of 0.38 percent (vol/vol) was determined from a crude particulate preparation for the epoxidase.

  17. Ammonia Binding in the Second Coordination Sphere of the Oxygen-Evolving Complex of Photosystem II.

    PubMed

    Vinyard, David J; Askerka, Mikhail; Debus, Richard J; Batista, Victor S; Brudvig, Gary W

    2016-08-01

    Ammonia binds to two sites in the oxygen-evolving complex (OEC) of Photosystem II (PSII). The first is as a terminal ligand to Mn in the S2 state, and the second is at a site outside the OEC that is competitive with chloride. Binding of ammonia in this latter secondary site results in the S2 state S = (5)/2 spin isomer being favored over the S = (1)/2 spin isomer. Using electron paramagnetic resonance spectroscopy, we find that ammonia binds to the secondary site in wild-type Synechocystis sp. PCC 6803 PSII, but not in D2-K317A mutated PSII that does not bind chloride. By combining these results with quantum mechanics/molecular mechanics calculations, we propose that ammonia binds in the secondary site in competition with D1-D61 as a hydrogen bond acceptor to the OEC terminal water ligand, W1. Implications for the mechanism of ammonia binding via its primary site directly to Mn4 in the OEC are discussed. PMID:27433995

  18. Oxygen Sensing by Arterial Chemoreceptors Depends on Mitochondrial Complex I Signaling.

    PubMed

    Fernández-Agüera, M Carmen; Gao, Lin; González-Rodríguez, Patricia; Pintado, C Oscar; Arias-Mayenco, Ignacio; García-Flores, Paula; García-Pergañeda, Antonio; Pascual, Alberto; Ortega-Sáenz, Patricia; López-Barneo, José

    2015-11-01

    O2 sensing is essential for mammalian homeostasis. Peripheral chemoreceptors such as the carotid body (CB) contain cells with O2-sensitive K(+) channels, which are inhibited by hypoxia to trigger fast adaptive cardiorespiratory reflexes. How variations of O2 tension (PO2) are detected and the mechanisms whereby these changes are conveyed to membrane ion channels have remained elusive. We have studied acute O2 sensing in conditional knockout mice lacking mitochondrial complex I (MCI) genes. We inactivated Ndufs2, which encodes a protein that participates in ubiquinone binding. Ndufs2-null mice lose the hyperventilatory response to hypoxia, although they respond to hypercapnia. Ndufs2-deficient CB cells have normal functions and ATP content but are insensitive to changes in PO2. Our data suggest that chemoreceptor cells have a specialized succinate-dependent metabolism that induces an MCI state during hypoxia, characterized by the production of reactive oxygen species and accumulation of reduced pyridine nucleotides, which signal neighboring K(+) channels. PMID:26437605

  19. A green-emitting Cu complex for oxygen-sensing purpose: synthesis, characterization and photophysical features.

    PubMed

    Hui, Han; Wei, Li; Zhentao, Liu; Xiangen, Han

    2015-05-01

    In the present work, a green-emitting Cu(I) complex [Cu(BT-Et)(POP)]BF4 was synthesized and fully characterized, where BT-Et=4-(1-ethyl-1H-benzo[d]imidazol-2-yl)thiazole, POP=bis(2-(diphenylphosphanyl)phenyl) ether, respectively. An ethyl group was connected onto the diamine ligand to breach π-π attraction within solid [Cu(BT-Et)(POP)]BF4, favoring O2 molecule attack and sensitivity improvement. Its molecular identity was confirmed by single crystal analysis and theoretical calculation. [Cu(BT-Et)(POP)]BF4 emitted long-lived green emission peaking at 521nm upon photoexcitation which was vulnerable towards O2 molecule, making itself a potential oxygen sensing material. [Cu(BT-Et)(POP)]BF4 was then doped into a silica supporting matrix MCM-41. The resulting composite samples showed sensing behavior towards O2 molecule, with short response time of 10s and sensitivity of 5.56. PMID:25706596

  20. A green-emitting Cu complex for oxygen-sensing purpose: Synthesis, characterization and photophysical features

    NASA Astrophysics Data System (ADS)

    Hui, Han; Wei, Li; Zhentao, Liu; Xiangen, Han

    2015-05-01

    In the present work, a green-emitting Cu(I) complex [Cu(BT-Et)(POP)]BF4 was synthesized and fully characterized, where BT-Et = 4-(1-ethyl-1H-benzo[d]imidazol-2-yl)thiazole, POP = bis(2-(diphenylphosphanyl)phenyl) ether, respectively. An ethyl group was connected onto the diamine ligand to breach π-π attraction within solid [Cu(BT-Et)(POP)]BF4, favoring O2 molecule attack and sensitivity improvement. Its molecular identity was confirmed by single crystal analysis and theoretical calculation. [Cu(BT-Et)(POP)]BF4 emitted long-lived green emission peaking at 521 nm upon photoexcitation which was vulnerable towards O2 molecule, making itself a potential oxygen sensing material. [Cu(BT-Et)(POP)]BF4 was then doped into a silica supporting matrix MCM-41. The resulting composite samples showed sensing behavior towards O2 molecule, with short response time of 10 s and sensitivity of 5.56.

  1. The Complex Relationship of Extracorporeal Membrane Oxygenation and Acute Kidney Injury: Causation or Association?

    PubMed Central

    Kilburn, Daniel J.; Shekar, Kiran; Fraser, John F.

    2016-01-01

    Extracorporeal membrane oxygenation (ECMO) is a modified cardiopulmonary bypass (CPB) circuit capable of providing prolonged cardiorespiratory support. Recent advancement in ECMO technology has resulted in increased utilisation and clinical application. It can be used as a bridge-to-recovery, bridge-to-bridge, bridge-to-transplant, or bridge-to-decision. ECMO can restitute physiology in critically ill patients, which may minimise the risk of progressive multiorgan dysfunction. Alternatively, iatrogenic complications of ECMO clearly contribute to worse outcomes. These factors affect the risk : benefit ratio of ECMO which ultimately influence commencement/timing of ECMO. The complex interplay of pre-ECMO, ECMO, and post-ECMO pathophysiological processes are responsible for the substantial increased incidence of ECMO-associated acute kidney injury (EAKI). The development of EAKI significantly contributes to morbidity and mortality; however, there is a lack of evidence defining a potential benefit or causative link between ECMO and AKI. This area warrants investigation as further research will delineate the mechanisms involved and subsequent strategies to minimise the risk of EAKI. This review summarizes the current literature of ECMO and AKI, considers the possible benefits and risks of ECMO on renal function, outlines the related pathophysiology, highlights relevant investigative tools, and ultimately suggests an approach for future research into this under investigated area of critical care. PMID:27006941

  2. Redox-inactive metal ions promoted the catalytic reactivity of non-heme manganese complexes towards oxygen atom transfer.

    PubMed

    Choe, Cholho; Yang, Ling; Lv, Zhanao; Mo, Wanling; Chen, Zhuqi; Li, Guangxin; Yin, Guochuan

    2015-05-21

    Redox-inactive metal ions can modulate the reactivity of redox-active metal ions in a variety of biological and chemical oxidations. Many synthetic models have been developed to help address the elusive roles of these redox-inactive metal ions. Using a non-heme manganese(II) complex as the model, the influence of redox-inactive metal ions as a Lewis acid on its catalytic efficiency in oxygen atom transfer was investigated. In the absence of redox-inactive metal ions, the manganese(II) catalyst is very sluggish, for example, in cyclooctene epoxidation, providing only 9.9% conversion with 4.1% yield of epoxide. However, addition of 2 equiv. of Al(3+) to the manganese(II) catalyst sharply improves the epoxidation, providing up to 97.8% conversion with 91.4% yield of epoxide. EPR studies of the manganese(II) catalyst in the presence of an oxidant reveal a 16-line hyperfine structure centered at g = 2.0, clearly indicating the formation of a mixed valent di-μ-oxo-bridged diamond core, Mn(III)-(μ-O)2-Mn(IV). The presence of a Lewis acid like Al(3+) causes the dissociation of this diamond Mn(III)-(μ-O)2-Mn(IV) core to form monomeric manganese(iv) species which is responsible for improved epoxidation efficiency. This promotional effect has also been observed in other manganese complexes bearing various non-heme ligands. The findings presented here have provided a promising strategy to explore the catalytic reactivity of some di-μ-oxo-bridged complexes by adding non-redox metal ions to in situ dissociate those dimeric cores and may also provide clues to understand the mechanism of methane monooxygenase which has a similar diiron diamond core as the intermediate. PMID:25904197

  3. The role of beaded activated carbon's surface oxygen groups on irreversible adsorption of organic vapors.

    PubMed

    Jahandar Lashaki, Masoud; Atkinson, John D; Hashisho, Zaher; Phillips, John H; Anderson, James E; Nichols, Mark

    2016-11-01

    The objective of this study is to determine the contribution of surface oxygen groups to irreversible adsorption (aka heel formation) during cyclic adsorption/regeneration of organic vapors commonly found in industrial systems, including vehicle-painting operations. For this purpose, three chemically modified activated carbon samples, including two oxygen-deficient (hydrogen-treated and heat-treated) and one oxygen-rich sample (nitric acid-treated) were prepared. The samples were tested for 5 adsorption/regeneration cycles using a mixture of nine organic compounds. For the different samples, mass balance cumulative heel was 14 and 20% higher for oxygen functionalized and hydrogen-treated samples, respectively, relative to heat-treated sample. Thermal analysis results showed heel formation due to physisorption for the oxygen-deficient samples, and weakened physisorption combined with chemisorption for the oxygen-rich sample. Chemisorption was attributed to consumption of surface oxygen groups by adsorbed species, resulting in formation of high boiling point oxidation byproducts or bonding between the adsorbates and the surface groups. Pore size distributions indicated that different pore sizes contributed to heel formation - narrow micropores (<7Å) in the oxygen-deficient samples and midsize micropores (7-12Å) in the oxygen-rich sample. The results from this study help explain the heel formation mechanism and how it relates to chemically tailored adsorbent materials. PMID:27295065

  4. Assembly of Newly Imported Oxygen-Evolving Complex Subunits in Isolated Chloroplasts: Sites of Assembly and Mechanism of Binding.

    PubMed Central

    Hashimoto, A.; Ettinger, W. F.; Yamamoto, Y.; Theg, S. M.

    1997-01-01

    We have examined the assembly of the nuclear-encoded subunits of the oxygen-evolving complex (OEC) after their import into isolated intact chloroplasts. We showed that all three subunits examined (OE33, OE23, and OE17) partition between the thylakoid lumen and a site on the inner surface of the thylakoid membrane after import in a homologous system (e.g., pea or spinach subunits into pea or spinach chloroplasts, respectively). Although some interspecies protein import experiments resulted in OEC subunit binding, maize OE17 did not bind thylakoid membranes in chloroplasts isolated from peas. Newly imported OE33 and OE23 were washed from the membranes at the same concentrations of urea and NaCl as the native, indigenous proteins; this observation suggests that the former subunits are bound productively within the OEC. Inhibition of neither chloroplast protein synthesis nor light- or ATP-dependent energization of the thylakoid membrane significantly affected these assembly reactions, and we present evidence suggesting that incoming subunits actively displace those already bound to the thylakoid membrane. Transport of OE33 took place primarily in the stromal-exposed membranes and proceeded through a protease-sensitive, mature intermediate. Initial binding of OE33 to the thylakoid membrane occurred primarily in the stromal-exposed membranes, from where it migrated with measurable kinetics to the granal region. In contrast, OE23 assembly occurred in the granal membrane regions. This information is incorporated into a model of the stepwise assembly of oxygen-evolving photosystem II. PMID:12237359

  5. Singlet oxygen O2(a1Δg) formation via UV-excitation of isoprene-oxygen C5H8-O2 encounter complexes in gas phase

    NASA Astrophysics Data System (ADS)

    Pyryaeva, Alexandra P.; Goldort, Veniamin G.; Kochubei, Sergei A.; Baklanov, Alexey V.

    2014-08-01

    Photogeneration of singlet oxygen O2(a1Δg) resulted from photoexcitation at 248 and 266 nm of isoprene-oxygen mixtures at elevated oxygen pressure has been investigated. Pulse energy and oxygen pressure dependence of the singlet oxygen yield indicate one-quantum photoexcitation of the encounter complex isoprene-oxygen C5H8-O2 as a source of O2(a1Δg). Suggested mechanism of O2(a1Δg) photogeneration involves direct excitation of complex with simultaneous change of both partner spins like that observed in van der Waals complex C5H8-O2 [Vidma et al., J. Chem. Phys. 137 (2012) 054305]. Other supposed pathways involve collision-induced photogeneration of Herzberg III state O2(A'3Δg) or triplet isoprene as the intermediates.

  6. Carbon, hydrogen, and oxygen isotope studies of the regional metamorphic complex at Naxos, Greece

    USGS Publications Warehouse

    Rye, R.O.; Schuiling, R.D.; Rye, D.M.; Jansen, J.B.H.

    1976-01-01

    At Naxos, Greece, a migmatite dome is surrounded by schists and marbles of decreasing metamorphic grade. Sillimanite, kyanite, biotite, chlorite, and glaucophane zones are recognized at successively greater distances from the migmatite dome. Quartz-muscovite and quartz-biotite oxygen isotope and mineralogie temperatures range from 350 to 700??C. The metamorphic complex can be divided into multiple schist-rich (including migmatites) and marblerich zones. The ??18O values of silicate minerals in migmatite and schist units and quartz segregations in the schist-rich zones decrease with increase in metamorphic grades. The calculated ??18OH2O values of the metamorphic fluids in the schist-rich zones decrease from about 15??? in the lower grades to an average of about 8.5??? in the migmatite. The ??D values of OH-minerals (muscovite, biotite, chlorite, and glaucophane) in the schist-rich zones also decrease with increase in grade. The calculated ??DH2O values for the metamorphic fluid decrease from -5??? in the glaucophane zone to an average of about -70??? in the migmatite. The ??D values of water in fluid inclusions in quartz segregations in the higher grade rocks are consistent with this trend. The??18O values of silicate minerals and quartz segregations in marble-rich zones are usually very large and were controlled by exchange with the adjacent marbles. The ??D values of the OH minerals in some marble-rich zones may reflect the value of water contained in the rocks prior to metamorphism. Detailed data on 20 marble units show systematic variations of ??18O values which depend upon metamorphic grade. Below the 540??C isograd very steep ??18O gradients at the margins and large ??18O values in the interior of the marbles indicate that oxygen isotope exchange with the adjacent schist units was usually limited to the margins of the marbles with more exchange occurring in the stratigraphic bottom than in the top margins. Above the 540??C isograd lower ??18O values occur in

  7. Cytotoxic and Antitumor Activity of Sulforaphane: The Role of Reactive Oxygen Species

    PubMed Central

    Sestili, Piero; Fimognari, Carmela

    2015-01-01

    According to recent estimates, cancer continues to remain the second leading cause of death and is becoming the leading one in old age. Failure and high systemic toxicity of conventional cancer therapies have accelerated the identification and development of innovative preventive as well as therapeutic strategies to contrast cancer-associated morbidity and mortality. In recent years, increasing body of in vitro and in vivo studies has underscored the cancer preventive and therapeutic efficacy of the isothiocyanate sulforaphane. In this review article, we highlight that sulforaphane cytotoxicity derives from complex, concurring, and multiple mechanisms, among which the generation of reactive oxygen species has been identified as playing a central role in promoting apoptosis and autophagy of target cells. We also discuss the site and the mechanism of reactive oxygen species' formation by sulforaphane, the toxicological relevance of sulforaphane-formed reactive oxygen species, and the death pathways triggered by sulforaphane-derived reactive oxygen species. PMID:26185755

  8. Synthesis, characterization, and application of vanadium-salan complexes in oxygen transfer reactions.

    PubMed

    Adão, Pedro; Costa Pessoa, João; Henriques, Rui T; Kuznetsov, Maxim L; Avecilla, Fernando; Maurya, Mannar R; Kumar, Umesh; Correia, Isabel

    2009-04-20

    We report the synthesis and characterization of several chiral salen- and salan-type ligands and their vanadium complexes, which are derived from salicylaldehyde or salicylaldehyde derivatives and chiral diamines (1R,2R-diaminocyclohexane, 1S,2S-diaminocyclohexane, and 1S,2S-diphenylethylenediamine). The structures of H(2)sal(R,R-chan)(2+) x 2 Cl(-) x (CH(3))(2)CHOH x H(2)O (1c; H(2)sal(R,R-chan) = N,N'-salicyl-R,R-cyclohexanediaminium), Etvan(S,S-chen) (3c; Etvan(S,S-chen) = N,N'-3-ethoxy-salicylidene-S,S-cyclohexanediiminato), and naph(R,R-chen) (6c; naph(R,R-chen) = N,N'-naphthylidene-R,R-cyclohexanediiminato) were determined by single-crystal X-ray diffraction. The corresponding vanadium(IV) complexes and several other new complexes involving different salicylaldehyde-type precursors were prepared and characterized in the solid state and in solution by spectroscopic techniques: UV-vis, circular dichroism, electron paramagnetic resonance, and (51)V NMR, which provide information on the coordination geometry. The salan complexes oxidize in organic solvents to V(V) species, and this process was also studied using spectroscopic techniques. Single crystals suitable for X-ray diffraction were obtained for [{V(V)O[sal(S,S-dpan)]}(2)(mu-O)] x H(2)O x 2(CH(3))(2)CHOH (14c; sal(S,S-dpan) = N,N'-salicyl-S,S-diphenylethylenediaminato) and [{V(V)O[t-Busal(R,R-chan)]}(2)(mu-O)] x 2 (CH(3))(2)CHOH (15c), both containing an OV(V)(mu-O)V(V)O moiety (V(2)O(3)(4+) core) with tetradentate ligands and one mu-oxo bridge. Both structures are the first examples of dinuclear vanadium complexes involving the V(V)(2)O(3)(4+) core with tetradentate ligands, the configuration of the V(2)O(3) unit being twist-angular. The V-salen and V-salan complexes are tested as catalysts in the oxidation of styrene, cyclohexene, cumene, and methyl phenyl sulfide with H(2)O(2) and t-BuOOH as oxidants. Overall, the V-salan complexes show higher activity and normally better selectivity in alkene oxidation

  9. The effect of mayfly (Hexagenia spp.) burrowing activity on sediment oxygen demand in western Lake Erie

    USGS Publications Warehouse

    Edwards, William J.; Soster, Frederick M.; Matisoff, Gerald; Schloesser, Donald W.

    2009-01-01

    Previous studies support the hypothesis that large numbers of infaunal burrow-irrigating organisms in the western basin of Lake Erie may increase significantly the sediment oxygen demand, thus enhancing the rate of hypolimnetic oxygen depletion. We conducted laboratory experiments to quantify burrow oxygen dynamics and increased oxygen demand resulting from burrow irrigation using two different year classes of Hexagenia spp. nymphs from western Lake Erie during summer, 2006. Using oxygen microelectrodes and hot film anemometry, we simultaneously determined oxygen concentrations and burrow water flow velocities. Burrow oxygen depletion rates ranged from 21.7 mg/nymph/mo for 15 mm nymphs at 23 °C to 240.7 mg/nymph/mo for 23 mm nymphs at 13 °C. Sealed microcosm experiments demonstrated that mayflies increase the rate of oxygen depletion by 2-5 times that of controls, depending on size of nymph and water temperature, with colder waters having greater impact. At natural population densities, nymph pumping activity increased total sediment oxygen demand 0.3-2.5 times compared to sediments with no mayflies and accounted for 22-71% of the total sediment oxygen demand. Extrapolating laboratory results to the natural system suggest that Hexagenia spp. populations may exert a significant control on oxygen depletion during intermittent stratification. This finding may help explain some of the fluctuations in Hexagenia spp. population densities in western Lake Erie and suggests that mayflies, by causing their own population collapse irrespective of other environmental conditions, may need longer term averages when used as a bio-indicator of the success of pollution-abatement programs in western Lake Erie and possibly throughout the Great Lakes.

  10. Synthesis, characterization and anticancer activities of two lanthanide(III) complexes with a nicotinohydrazone ligand

    NASA Astrophysics Data System (ADS)

    Xu, Zhou-Qin; Mao, Xian-Jie; Jia, Lei; Xu, Jun; Zhu, Tao-Feng; Cai, Hong-Xin; Bie, Hong-Yan; Chen, Ru-Hua; Ma, Tie-liang

    2015-12-01

    Two isostructural acylhydrazone based complexes, namely [Ce(penh)2(H2O)4](NO3)3·4H2O (1) and [Sm(penh)2(NO3)2](NO3)·C2H5OH (2) (penh = 2-acetylpyridine nicotinohydrazone), have been obtained and characterized by physico-chemical and spectroscopic methods. The ten-coordinated lanthanide metal ion in each complex is surrounded by two independent tridentate neutral acylhydrazones with two ON2 donor sets. The other four coordination oxygen atoms are from four water molecules and two bidentate nitrate anions for complexes 1 and 2, respectively, thus giving distorted bicapped square antiprism geometry. Both complexes have excellent antitumor activity towards human pancreatic cancer (PATU8988), human colorectal cancer (lovo) and human gastric cancer(SGC7901) cell line. Furthermore, the cell apoptosis of complex 1 is detected by AnnexinV/PI flow cytometry.

  11. Oxygen-Evolving Porous Glass Plates Containing the Photosynthetic Photosystem II Pigment-Protein Complex.

    PubMed

    Noji, Tomoyasu; Kawakami, Keisuke; Shen, Jian-Ren; Dewa, Takehisa; Nango, Mamoru; Kamiya, Nobuo; Itoh, Shigeru; Jin, Tetsuro

    2016-08-01

    The development of artificial photosynthesis has focused on the efficient coupling of reaction at photoanode and cathode, wherein the production of hydrogen (or energy carriers) is coupled to the electrons derived from water-splitting reactions. The natural photosystem II (PSII) complex splits water efficiently using light energy. The PSII complex is a large pigment-protein complex (20 nm in diameter) containing a manganese cluster. A new photoanodic device was constructed incorporating stable PSII purified from a cyanobacterium Thermosynechococcus vulcanus through immobilization within 20 or 50 nm nanopores contained in porous glass plates (PGPs). PSII in the nanopores retained its native structure and high photoinduced water splitting activity. The photocatalytic rate (turnover frequency) of PSII in PGP was enhanced 11-fold compared to that in solution, yielding a rate of 50-300 mol e(-)/(mol PSII·s) with 2,6-dichloroindophenol (DCIP) as an electron acceptor. The PGP system realized high local concentrations of PSII and DCIP to enhance the collisional reactions in nanotubes with low disturbance of light penetration. The system allows direct visualization/determination of the reaction inside the nanotubes, which contributes to optimize the local reaction condition. The PSII/PGP device will substantively contribute to the construction of artificial photosynthesis using water as the ultimate electron source. PMID:27400072

  12. Piezospectroscopy of isolated lithium donors and lithium-oxygen donor complexes in silicon

    NASA Astrophysics Data System (ADS)

    Jagannath, C.; Ramdas, A. K.

    1981-05-01

    The effect of uniaxial stress on the excitation spectra of interstitial lithium donors (Li) and of lithium-oxygen donor complexes (Li-O) in silicon is studied under a high resolution. For a compressive force, F-->, along [001], each 1s-->np transition in Si(Li) splits into three components, the central component occurring at the zero-stress position even at 2 kbar, the highest stress used. The intensity of the high-energy component decreases dramatically while that of the low-energy component increases. At the highest stress only the central and the low-energy components survive and the position of the low-energy component reaches a constant value as the stress increases. Interstitial lithium donors have an anomalous, "inverted" ground state with the fivefold 1s(E+T2) state close to the effective-mass position, its site symmetry being Td; the totally symmetric 1s(A1) state lies 6Δc=1.76+/-0.04 meV above it. The inverted ground state, the small value of 6Δc, the stress dependence of the ground-state wave functions, and a shear-deformation-potential constant Ξu of 8.77 +/- 0.07 eV characterizing both the ground and the excited states account for its striking piezospectroscopic behavior. Our studies in Li-O donor centers show that they have a group-V-like ground state with 1s(A1) lying below 1s(E) and 1s(T2). One of the donor species has a symmetry lower than Td with a symmetry axis along <100>, showing the effects of orientational degeneracy in its piezospectroscopic behavior.

  13. Oxygen-evolving complex of photosystem II: correlating structure with spectroscopy.

    PubMed

    Pokhrel, Ravi; Brudvig, Gary W

    2014-06-28

    Water oxidation at the oxygen-evolving complex (OEC) of photosystem II (PSII) involves multiple redox states called Sn states (n = 0-4). The S1 → S2 redox transition of the OEC has been studied extensively using various forms of spectroscopy, including electron paramagnetic resonance (EPR) and Fourier transform infrared (FTIR) spectroscopy. In the S2 state, two isomers of the OEC are observed by EPR: a ST = 1/2 form and a ST = 5/2 form. DFT-based structural models of the OEC have been proposed for the two spin isomers in the S2 state, but the factors that determine the stability of one form or the other are not known. Using structural information on the OEC and its surroundings, in conjunction with spectroscopic information available on the S1 → S2 transition for a variety of site-directed mutations, Ca(2+) and Cl(-) substitutions, and small molecule inhibitors, we propose that the hydrogen-bonding network encompassing D1-D61 and the OEC-bound waters plays an important role in stabilizing one spin isomer over the other. In the presence of ammonia, PSII centers can be trapped in either the ST = 5/2 form after a 200 K illumination procedure or an ammonia-altered ST = 1/2 form upon annealing at 273 K. We propose a mechanism for ammonia binding to the OEC in the S2 state that takes into account the hydrogen-binding requirements for ammonia binding and the specificity for binding of ammonia but not methylamine. A discussion regarding the possibility of spin isomers of the OEC in the S1 state, analogous to the spin isomers of the S2 state, is also presented. PMID:24700294

  14. Inactivation of Pathogenic Bacteria on Seeds by Active Oxygen Species Generated in Low-Pressure Plasma

    NASA Astrophysics Data System (ADS)

    Ono, Reoto; Uchida, Shohei; Hayashi, Nobuya; Kosaka, Rina; Soeda, Yasutaka

    2015-09-01

    The inactivation of bacteria on seeds by active oxygen species generated by a low-pressure oxygen plasma is investigated. Species of active oxygen contributing to the inactivation of bacteria are attempted to be identified. Cylindrical stainless chamber with the internal volume of 17 L is used and RF antenna is set inside the chamber. The oxygen gas pressure is 20-100 Pa. RF power of 13.56 MHz is supplied to RF antenna and CCP is generated. After irradiation, bacteria are extracted from seeds and cultivated on nutrient agars. The number of colonies on these agars is counted after 48 h incubation. The number of bacteria on seeds decreases to less than 10-3 after plasma irradiation for 45 min comparing with that of control. The tendency of the reduction rate of bacteria on seeds has positive correlation with that of the light emission intensity of the singlet excited oxygen molecule as the oxygen gas pressure is varied. It is supposed that the singlet excited oxygen molecule would be one of the major factors for the inactivation of bacteria on seeds.

  15. Bond cleavage reactions in oxygen and nitrogen heterocycles by a rhodium phosphine complex

    SciTech Connect

    Jones, W.D.; Dong, L.; Myers, A.W. )

    1995-02-01

    The reactions of (C[sub 5]Me[sub 5])Rh(PMe[sub 3])PhH with furan, 2,5-dimethylfuran, 2,3-dihydrofuran, dibenzofuran, pyrrole, 1-methylpyrrole, 2,5-dimethylpyrrole, 1,2,5-trimethylpyrrole, carbazole, 9-methylcarbazole, pyrrolidine, pyridine, 3,5-lutidine, 2,4,6-collidine, pyrazole, 3-methylpyrazole, and piperidine have been investigated. While the oxygen heterocycles give only C-H activation, the nitrogen heterocycles yield C-H and N-H insertion products. The chloro derivative (C[sub 5]Me[sub 5])Rh(PMe[sub 3])[2-(1-methylpyrrole)]Cl was found to crystallize in the monoclinic space group C2/c with a = 13.753 (6) A, b = 9.665 (5) A, c = 30.14 (2) A, [beta] = 99.77 (5)-[degree], Z = 8, and V = 3949 (4.1) A[sup 3] while (C[sub 5]Me[sub 5])Rh(PMe[sub 5])[2-(3,5-lutidine)]Cl was found to crystallize in the monoclinic space group P2[sub 1]/c with a = 14.976 (8) A, b = 8.613 (5) A, c = 17.12 (2) A, [beta] = 101.90 (6)[degree], Z = 4, and V = 2160 (5.2) A[sup 3]. 30 refs., 2 figs., 3 tabs.

  16. Effect of oxygen transfer rate on the composition of the pectolytic enzyme complex of Aspergillus niger

    SciTech Connect

    Zetelaki-Horvath, K.; Vas, K.

    1981-01-01

    Optimal agitation and aeration conditions (assuring O/sub 2/ transfer rates (OTR) of 12-179 mmol/L-h) were determined for pectin lyase (PL) synthesis of an Aspergillus niger strain. Components of the pectolytic enzyme complex were also investigated in order to determine whether their O/sub 2/ demand is identical with or different from that of pectin lyase. Should the latter be the case, a possibility would be given to produce enzyme complexes of different agitation and aeration conditions. The mycelium yield of Aspergillus niger was maximum at an OTR of 100 mmol/L-h. The yields of the various pectolytic enzymes reached maximum at different OTRs. PL production was highest (0.555 mumol/min-mL) at an OTR of 60 mmol/L-h. Endopolygalacturonase (PG) production has a maximum at OTR 49 mmol/L-h, with a 2nd peak at 100-135 mmol O2/L-h. Pectin esterase (PE) synthesis showed a maximum at an OTR of 12-14 mmol/L-h, while both apple juice clarifying and macerating activities gave 2 maximum at 14 and 60 mmol/L-h due to the optima of PE and endo-PG. Macerating activity showed a high value at OTR optimal for PL production as well.

  17. XANES, EXAFS and Kbeta spectroscopic studies of the oxygen-evolving complex in Photosystem II

    SciTech Connect

    Robblee, John H.

    2000-12-01

    A key question for the understanding of photosynthetic water oxidation is whether the four oxidizing equivalents necessary to oxidize water to dioxygen are accumulated on the four Mn ions of the oxygen evolving complex (OEC), or whether some ligand-centered oxidations take place before the formation and release of dioxygen during the S{sub 3} {r_arrow} [S{sub 4}] {r_arrow} S{sub 0} transition. Progress in instrumentation and flash sample preparation allowed us to apply Mn K{beta} X-ray emission spectroscopy (Kb XES) to this problem for the first time. The K{beta} XES results, in combination with Mn X-ray absorption near-edge structure (XANES) and electron paramagnetic resonance (EPR) data obtained from the same set of samples, show that the S{sub 2} {r_arrow} S{sub 3} transition, in contrast to the S{sub 0} {r_arrow} S{sub 1} and S{sub 1} {r_arrow} S{sub 2} transitions, does not involve a Mn-centered oxidation. This is rationalized by manganese {mu}-oxo bridge radical formation during the S{sub 2} {r_arrow} S{sub 3} transition. Using extended X-ray absorption fine structure (EXAFS) spectroscopy, the local environment of the Mn atoms in the S{sub 0} state has been structurally characterized. These results show that the Mn-Mn distance in one of the di-{mu}-oxo-bridged Mn-Mn moieties increases from 2.7 {angstrom} in the S{sub 1} state to 2.85 {angstrom} in the S{sub 0} state. Furthermore, evidence is presented that shows three di-{mu}-oxo binuclear Mn{sub 2} clusters may be present in the OEC, which is contrary to the widely held theory that two such clusters are present in the OEC. The EPR properties of the S{sub 0} state have been investigated and a characteristic ''multiline'' signal in the S{sub 0} state has been discovered in the presence of methanol. This provides the first direct confirmation that the native S{sub 0} state is paramagnetic. In addition, this signal was simulated using parameters derived from three possible oxidation states of Mn in the S{sub 0

  18. Activity and Stability of Nanoscale Oxygen Reduction Catalysts

    SciTech Connect

    Shao-Horn, Yang

    2015-07-28

    Design of highly active and stable nanoscale catalysts for electro-oxidation of small organic molecules is of great importance to the development of efficient fuel cells. The amount and instability of Pt-based catalysts in the cathode limits the cost, efficiency and lifetime of proton exchange membrane fuel cells. We developed a microscopic understanding of the factors governing activity and stability in Pt and PtM alloys. Experimental efforts were focused on probing the size and shape dependence of ORR activity of Pt-based nanoparticles supported on carbon nanotubes. A microscopic understanding of the activity was achieved by correlating voltammetry and rotating ring disk electrodes to surface atomic and electronic structures, which were elucidated predominantly by high-resolution transmission electron microscopy (HRTEM), Scanning transmission electron microscopy energy dispersive X-ray Spectroscopy (STEM-EDS) and synchrotron X-ray absorption spectroscopy (XAS).

  19. SIMPLIFIED INJECTION OF OXYGEN GAS INTO AN ACTIVATED SLUDGE PROCESS

    EPA Science Inventory

    The Las Virgenes Municipal Water District conducted a pilot investigation of the Simplox process at their Tapia Water Reclamation Facility in Calabasas, California. The Simplox process, developed by the Cosmodyne Division of Cordon International, involves covering an activated sl...

  20. DESIGN PROCEDURES FOR DISSOLVED OXYGEN CONTROL OF ACTIVATED SLUDGE PROCESSES

    EPA Science Inventory

    This report presents design procedures and guidelines for the selection of aeration equipment and dissolved (DO) control systems for activated sludge treatment plants. Aeration methods, equipment and application techniques are examined and selection procedures offered. Various DO...

  1. Synthesis and antioxidant activities of transition metal complexes based 3-hydroxysalicylaldehyde-S-methylthiosemicarbazone

    NASA Astrophysics Data System (ADS)

    Bal-Demirci, Tülay; Şahin, Musa; Kondakçı, Esin; Özyürek, Mustafa; Ülküseven, Bahri; Apak, Reşat

    2015-03-01

    The nickel(II), iron(III), oxovanadium(IV) complexes of the 3-hydroxysalicylidene-S-methyl-thiosemicarbazone (L) were obtained from the 3-hydroxysalicyldehyde-S-methylthiosemicarbazone with the R1-substituted-salicylaldehyde (R1: H, 3-OH) in the presence of Ni(II), Fe(III), VO(IV) as template ion. The ligand and its complexes were characterized by elemental analysis, electronic, UV/Vis., 1H NMR, EPR and IR studies. The free ligand and its metal complexes have been tested for in vitro antioxidant capacity by reduction of copper(II) neocuproine (Cu(II)-Nc) using the CUPRAC method. The ligand exhibited more potent in vitro antioxidant capacity than its complexes. The obtained trolox equivalent antioxidant capacity (TEAC) value of the iron(III) complex (TEACCUPRAC = 3.27) was higher than those of other complexes. Furthermore, the antioxidant activity of the free ligand and its complexes were determined by in vitro methods measuring the scavenging activity of reactive oxygen species (ROS) including hydroxyl radical (radOH), superoxide anion radical (O2rad -), and hydrogen peroxide (H2O2), showing that especially the V(IV) and Fe(III) complexes had significant scavenging activity for ROS.

  2. Synthesis and antioxidant activities of transition metal complexes based 3-hydroxysalicylaldehyde-S-methylthiosemicarbazone.

    PubMed

    Bal-Demirci, Tülay; Şahin, Musa; Kondakçı, Esin; Özyürek, Mustafa; Ülküseven, Bahri; Apak, Reşat

    2015-03-01

    The nickel(II), iron(III), oxovanadium(IV) complexes of the 3-hydroxysalicylidene-S-methyl-thiosemicarbazone (L) were obtained from the 3-hydroxysalicyldehyde-S-methylthiosemicarbazone with the R1-substituted-salicylaldehyde (R1: H, 3-OH) in the presence of Ni(II), Fe(III), VO(IV) as template ion. The ligand and its complexes were characterized by elemental analysis, electronic, UV/Vis., (1)HNMR, EPR and IR studies. The free ligand and its metal complexes have been tested for in vitro antioxidant capacity by reduction of copper(II) neocuproine (Cu(II)-Nc) using the CUPRAC method. The ligand exhibited more potent in vitro antioxidant capacity than its complexes. The obtained trolox equivalent antioxidant capacity (TEAC) value of the iron(III) complex (TEACCUPRAC=3.27) was higher than those of other complexes. Furthermore, the antioxidant activity of the free ligand and its complexes were determined by in vitro methods measuring the scavenging activity of reactive oxygen species (ROS) including hydroxyl radical (OH), superoxide anion radical (O2(-)), and hydrogen peroxide (H2O2), showing that especially the V(IV) and Fe(III) complexes had significant scavenging activity for ROS. PMID:25467658

  3. The role of water and structure on the generation of reactive oxygen species in peptide/hypericin complexes.

    PubMed

    Souza, Márcia I; Silva, Emerson R; Jaques, Ygor M; Ferreira, Fabio F; Fileti, Eudes E; Alves, Wendel A

    2014-07-01

    Hybrid associates formed between peptide assemblies and fluorophores are attractive mainly because of their unique properties for biomedical applications. Recently, we demonstrated that the production of reactive oxygen species (ROS) by hypericin and their stability in excited states are enhanced upon conjugation with l,l-diphenylalanine microtubes (FF-MNTs). Although the detailed mechanisms responsible for improving the photophysical properties of ROS remain unclear, tentative hypotheses have suggested that the driving force is the growth of overall dipolar moments ascribed either to coupling between aligned H2O dipoles within the ordered structures or to the organization of hypericin molecules on peptide interfaces. To provide new insights on ROS activity in hypericin/FF-MNTs hybrids and further explore the role of water in this respect, we present results obtained from investigations on the behavior of these complexes organized into different crystalline arrangements. Specifically, we monitored and compared the photophysical performance of hypericin bound to FF-MNTs with peptides organized in both hexagonal (water-rich) and orthorhombic (water-free) symmetries. From a theoretical perspective, we present the results of new molecular dynamics simulations that highlight the distinct hypericin/peptide interaction at the interface of FF-MNTs for the different symmetries. As a conclusion, we propose that although water enhances photophysical properties, the organization induced by peptide structures and the availability of a hydrophobic environment surrounding the hypericin/peptide interface are paramount to optimizing ROS generation. The findings presented here provide useful basic research insights for designing peptide/fluorophore complexes with outstanding technological potential. PMID:24845629

  4. Titanium Dioxide-Grafted Copper Complexes: High-Performance Electrocatalysts for the Oxygen Reduction Reaction in Alkaline Media.

    PubMed

    Wang, Fei-Fei; Wei, Ping-Jie; Yu, Guo-Qiang; Liu, Jin-Gang

    2016-01-01

    The sluggish kinetics of the oxygen reduction reaction (ORR) at the cathodes of fuel cells significantly hampers fuel cell performance. Therefore, the development of high-performance, non-precious-metal catalysts as alternatives to noble metal Pt-based ORR electrocatalysts is highly desirable for the large-scale commercialization of fuel cells. TiO2 -grafted copper complexes deposited on multiwalled carbon nanotubes (CNTs) form stable and efficient electrocatalysts for the ORR. The optimized catalyst composite CNTs@TiO2 -ZA-[Cu(phen${{^{{\\rm NO}{_{2}}}}}$)(BTC)] shows surprisingly high selectivity for the 4 e(-) reduction of O2 to water (approximately 97 %) in alkaline solution with an onset potential of 0.988 V vs. RHE, and demonstrates superior stability and excellent tolerance for the methanol crossover effect in comparison to a commercial Pt/C catalyst. The copper complexes were grafted onto the surface of TiO2 through coordination of an imidazole-containing ligand, zoledronic acid (ZA), which binds to TiO2 through its bis-phosphoric acid anchoring group. Rational optimization of the copper catalyst's ORR performance was achieved by using an electron-deficient ligand, 5-nitro-1,10-phenanthroline (phen${{^{{\\rm NO}{_{2}}}}}$), and bridging benzene-1,3,5-tricarboxylate (BTC). This facile approach to the assembly of copper catalysts on TiO2 with rationally tuned ORR activity will have significant implications for the development of high-performance, non-precious-metal ORR catalysts. PMID:26602327

  5. Photosynthesis. Electronic structure of the oxygen-evolving complex in photosystem II prior to O-O bond formation.

    PubMed

    Cox, Nicholas; Retegan, Marius; Neese, Frank; Pantazis, Dimitrios A; Boussac, Alain; Lubitz, Wolfgang

    2014-08-15

    The photosynthetic protein complex photosystem II oxidizes water to molecular oxygen at an embedded tetramanganese-calcium cluster. Resolving the geometric and electronic structure of this cluster in its highest metastable catalytic state (designated S3) is a prerequisite for understanding the mechanism of O-O bond formation. Here, multifrequency, multidimensional magnetic resonance spectroscopy reveals that all four manganese ions of the catalyst are structurally and electronically similar immediately before the final oxygen evolution step; they all exhibit a 4+ formal oxidation state and octahedral local geometry. Only one structural model derived from quantum chemical modeling is consistent with all magnetic resonance data; its formation requires the binding of an additional water molecule. O-O bond formation would then proceed by the coupling of two proximal manganese-bound oxygens in the transition state of the cofactor. PMID:25124437

  6. Activity-induced tissue oxygenation changes in rat cerebellar cortex: interplay of postsynaptic activation and blood flow

    PubMed Central

    Offenhauser, Nikolas; Thomsen, Kirsten; Caesar, Kirsten; Lauritzen, Martin

    2005-01-01

    Functional neuroimaging relies on the robust coupling between neuronal activity, metabolism and cerebral blood flow (CBF), but the physiological basis of the neuroimaging signals is still poorly understood. We examined the mechanisms of activity-dependent changes in tissue oxygenation in relation to variations in CBF responses and postsynaptic activity in rat cerebellar cortex. To increase synaptic activity we stimulated the monosynaptic, glutamatergic climbing fibres that excite Purkinje cells via AMPA receptors. We used local field potentials to indicate synaptic activity, and recorded tissue oxygen partial pressure (Ptiss,O2) by polarographic microelectrodes, and CBF using laser-Doppler flowmetry. The disappearance rate of oxygen in the tissue increased linearly with synaptic activity. This indicated that, without a threshold, oxygen consumption increased as a linear function of synaptic activity. The reduction in Ptiss,O2 preceded the rise in CBF. The time integral (area) of the negative Ptiss,O2 response increased non-linearly showing saturation at high levels of synaptic activity, concomitant with a steep rise in CBF. This was accompanied by a positive change in Ptiss,O2. Neuronal nitric oxide synthase inhibition enhanced the initial negative Ptiss,O2 response (‘dip’), while attenuating the evoked CBF increase and positive Ptiss,O2 response equally. This indicates that increases in CBF counteract activity-induced reductions in Ptiss,O2, and suggests the presence of a tissue oxygen reserve. The changes in Ptiss,O2 and CBF were strongly attenuated by AMPA receptor blockade. Our findings suggest an inverse relationship between negative Ptiss,O2 and CBF responses, and provide direct in vivo evidence for a tight coupling between activity in postsynaptic AMPA receptors and cerebellar oxygen consumption. PMID:15774524

  7. Effects of hydrogen sulfide on the heme coordination structure and catalytic activity of the globin-coupled oxygen sensor AfGcHK.

    PubMed

    Fojtikova, Veronika; Bartosova, Martina; Man, Petr; Stranava, Martin; Shimizu, Toru; Martinkova, Marketa

    2016-08-01

    AfGcHK is a globin-coupled histidine kinase that is one component of a two-component signal transduction system. The catalytic activity of this heme-based oxygen sensor is due to its C-terminal kinase domain and is strongly stimulated by the binding of O2 or CO to the heme Fe(II) complex in the N-terminal oxygen sensing domain. Hydrogen sulfide (H2S) is an important gaseous signaling molecule and can serve as a heme axial ligand, but its interactions with heme-based oxygen sensors have not been studied as extensively as those of O2, CO, and NO. To address this knowledge gap, we investigated the effects of H2S binding on the heme coordination structure and catalytic activity of wild-type AfGcHK and mutants in which residues at the putative O2-binding site (Tyr45) or the heme distal side (Leu68) were substituted. Adding Na2S to the initial OH-bound 6-coordinate Fe(III) low-spin complexes transformed them into SH-bound 6-coordinate Fe(III) low-spin complexes. The Leu68 mutants also formed a small proportion of verdoheme under these conditions. Conversely, when the heme-based oxygen sensor EcDOS was treated with Na2S, the initially formed Fe(III)-SH heme complex was quickly converted into Fe(II) and Fe(II)-O2 complexes. Interestingly, the autophosphorylation activity of the heme Fe(III)-SH complex was not significantly different from the maximal enzyme activity of AfGcHK (containing the heme Fe(III)-OH complex), whereas in the case of EcDOS the changes in coordination caused by Na2S treatment led to remarkable increases in catalytic activity. PMID:27395436

  8. Oxygen control of breathing by an olfactory receptor activated by lactate

    PubMed Central

    Chang, Andy J.; Ortega, Fabian E.; Riegler, Johannes; Madison, Daniel V.; Krasnow, Mark A.

    2015-01-01

    Summary Animals have evolved homeostatic responses to changes in oxygen availability that act on different time scales. Although the hypoxia-inducible factor (HIF) transcriptional pathway that controls long term responses to low oxygen (hypoxia) has been established1, the pathway that mediates acute responses to hypoxia in mammals is not well understood. Here we show that the olfactory receptor Olfr78 is highly and selectively expressed in oxygen-sensitive glomus cells of the carotid body, a chemosensory organ at the carotid artery bifurcation that monitors blood oxygen and stimulates breathing within seconds when oxygen declines2. Olfr78 mutants fail to increase ventilation in hypoxia but respond normally to hypercapnia. Glomus cells are present in normal numbers and appear structurally intact, but hypoxia-induced carotid body activity is diminished. Lactate, a metabolite that rapidly accumulates in hypoxia and induces hyperventilation3–6, activates Olfr78 in heterologous expression experiments, induces calcium transients in glomus cells, and stimulates carotid sinus nerve activity through Olfr78. We propose that in addition to its role in olfaction, Olfr78 acts as a hypoxia sensor in the breathing circuit by sensing lactate produced when oxygen levels decline. PMID:26560302

  9. Aerobic composting of waste activated sludge: Kinetic analysis for microbiological reaction and oxygen consumption

    SciTech Connect

    Yamada, Y.; Kawase, Y. . E-mail: bckawase@mail.eng.toyo.ac.jp

    2006-07-01

    In order to examine the optimal design and operating parameters, kinetics for microbiological reaction and oxygen consumption in composting of waste activated sludge were quantitatively examined. A series of experiments was conducted to discuss the optimal operating parameters for aerobic composting of waste activated sludge obtained from Kawagoe City Wastewater Treatment Plant (Saitama, Japan) using 4 and 20 L laboratory scale bioreactors. Aeration rate, compositions of compost mixture and height of compost pile were investigated as main design and operating parameters. The optimal aerobic composting of waste activated sludge was found at the aeration rate of 2.0 L/min/kg (initial composting mixture dry weight). A compost pile up to 0.5 m could be operated effectively. A simple model for composting of waste activated sludge in a composting reactor was developed by assuming that a solid phase of compost mixture is well mixed and the kinetics for microbiological reaction is represented by a Monod-type equation. The model predictions could fit the experimental data for decomposition of waste activated sludge with an average deviation of 2.14%. Oxygen consumption during composting was also examined using a simplified model in which the oxygen consumption was represented by a Monod-type equation and the axial distribution of oxygen concentration in the composting pile was described by a plug-flow model. The predictions could satisfactorily simulate the experiment results for the average maximum oxygen consumption rate during aerobic composting with an average deviation of 7.4%.

  10. Local structural models of complex oxygen- and hydroxyl-rich GaP/InP(001) surfaces.

    PubMed

    Wood, Brandon C; Ogitsu, Tadashi; Schwegler, Eric

    2012-02-14

    We perform density-functional theory calculations on model surfaces to investigate the interplay between the morphology, electronic structure, and chemistry of oxygen- and hydroxyl-rich surfaces of InP(001) and GaP(001). Four dominant local oxygen topologies are identified based on the coordination environment: M-O-M and M-O-P bridges for the oxygen-decorated surface; and M-[OH]-M bridges and atop M-OH structures for the hydroxyl-decorated surface (M = In, Ga). Unique signatures in the electronic structure are linked to each of the bond topologies, defining a map to structural models that can be used to aid the interpretation of experimental probes of native oxide morphology. The M-O-M bridge can create a trap for hole carriers upon imposition of strain or chemical modification of the bonding environment of the M atoms, which may contribute to the observed photocorrosion of GaP/InP-based electrodes in photoelectrochemical cells. Our results suggest that a simplified model incorporating the dominant local bond topologies within an oxygen adlayer should reproduce the essential chemistry of complex oxygen-rich InP(001) or GaP(001) surfaces, representing a significant advantage from a modeling standpoint. PMID:22360213

  11. Oxygen Uptake by a Cobalt(II) Complex: An Undergraduate Experiment

    ERIC Educational Resources Information Center

    Appleton, Trevor G.

    1977-01-01

    An experimental procedure is described for studying oxygen uptake by a transition metal. This procedure is designed for use with undergraduates and may be used in organic or biochemistry laboratories. Diagrams of the apparatus are included. (MR)

  12. [Effect of substances which change the proton-motive force on activity of methane microbe oxygenation].

    PubMed

    Malashenko, Iu P; Sokolov, I G; Rokitko, P V; Romanovskaia, V A

    2006-01-01

    High extracellular concentration of K+ stimulated methane oxygenation with Methylomonas rubra 15 [Russian character: see text], Methylococcus thermophilus 111 [Russian character: see text] and Methylococcus capsulatus 494 at neutral value of pH. That was determined by K+ arrival to the cells at neutral medium pH that resulted in the increase of pH difference between the exterior and interior sides of the membrane (ApH) and, respectively, in the increase of the methane oxygenation rate. Thus, methane monooxygenation depends on the availability of ion gradients on a membrane. Ionophores valinomycin and monensin inhibited methane oxygenation by the cells of Methylomonas rubra 15 [Russian character: see text] that evidenced for the methane oxygenation dependence on the protone-motive force which could be formed as the result both of protons displacement with oxygenation of methane monooxygenation products and of the gradient of potassium and sodium ions. Protonophore FCCP suppressed completely methane oxygenation in Methylococcus capsulatus 494 and M. thermophilus 111 [Russian character: see text] at neutral pH, and took no effect at the alkaline values of pH. This suggests that FCCP dissipates the proton-motive force and does not inhibit methane monooxygenase activity. The results obtained indicate that the process of methane oxygenation should be combined with energy generation in a form of the transmembrane electric charge (delta psi) and proton gradient (deltapH). PMID:17243361

  13. Impairment of the mitochondrial respiratory chain activity in diethylnitrosamine-induced rat hepatomas: possible involvement of oxygen free radicals.

    PubMed

    Boitier, E; Merad-Boudia, M; Guguen-Guillouzo, C; Defer, N; Ceballos-Picot, I; Leroux, J P; Marsac, C

    1995-07-15

    Alterations in the energy metabolism of cancer cells have been reported for many years. However, the deleterious mechanisms involved in these deficiencies have not yet been clearly proved. The main goal of this study was to decipher the harmful mechanisms responsible for the respiratory chain deficiencies in the course of diethylnitrosamine (DENA)-induced rat hepatocarcinogenesis, where mitochondrial DNA abnormalities had been previously reported. The respiratory activity of freshly isolated hepatoma mitochondria, assessed by oxygen consumption experiments and enzymatic assays, presented a severe complex I deficiency 19 months after DENA treatment, and later on, in addition, a defective complex III activity. Since respiratory complex subunits are encoded by both nuclear and mitochondrial genes, we checked whether the respiratory chain defects were due to impaired synthesis processes. The specific immunodetection of complex I failed to show any alterations in the steady-state levels of both nuclear and mitochondrial encoded subunits in the hepatomas. Moreover, in vitro protein synthesis experiments carried out on freshly isolated hepatoma mitochondria did not bring to light any modifications in the synthesis of the mitochondrial subunits of the respiratory complexes, whatever the degree of tumor progression. Finally, Southern blot analysis of mitochondrial DNA did not show any major mitochondrial DNA rearrangements in DENA-induced hepatomas. Because the synthetic processes of respiratory complexes did not seem to be implicated in the respiratory chain impairment, these deficiencies could be partly ascribed to a direct toxic impact of highly reactive molecules on these complexes, thus impairing their function. The mitochondrial respiratory chain is an important generator of noxious, reactive oxygen free radicals such as superoxide and H2O2, which are normally catabolized by powerful antioxidant scavengers. Nineteen months after DENA treatment, a general collapse of

  14. In vitro activation of rat neutrophils and alveolar macrophages with IgA and IgG immune complexes. Implications for immune complex-induced lung injury.

    PubMed Central

    Warren, J. S.; Kunkel, S. L.; Johnson, K. J.; Ward, P. A.

    1987-01-01

    In the rat, both IgG and IgA immune complexes induce oxygen radical mediated lung injury that is partially complement-dependent. In vivo studies have suggested that the chief sources of oxygen radicals in IgG and IgA immune complex-induced lung injury are neutrophils and tissue macrophages, respectively. The current studies have been designed to provide additional insights into these two models of tissue injury. Preformed monoclonal IgG and IgA immune complexes stimulated dose-dependent O2-. and H2O2 production by alveolar macrophages. In contrast, neutrophils exhibited O2-. production and lysosomal enzyme secretion in response to IgG immune complexes, but not in response to IgA complexes. There is evidence that C5a significantly amplifies these responses. Purified human C5a enhanced the O2-. responses of neutrophils activated with IgG immune complexes and alveolar macrophages activated with either IgG or IgA immune complexes. Addition of C5a alone to neutrophils or alveolar macrophages had no direct stimulatory effect as measured by O2-. production. The observation that O2-. responses of immune complex-activated alveolar macrophages can be significantly enhanced by the presence of C5a and that C5a can also enhance O-2. responses of IgG immune complex-stimulated neutrophils suggests a potential amplification mechanism through which complement may participate in both IgG and IgA immune complex-induced lung injury. The present data corroborate in vivo studies which suggest that IgG immune complex lung injury is primarily neutrophil-mediated, whereas IgA complex lung injury is predominantly macrophage-mediated. PMID:2827492

  15. Tetranuclear vanadium complex, (VO)(4)(hpic)(4): a recyclable catalyst for oxidation of benzyl alcohols with molecular oxygen.

    PubMed

    Kodama, Shintaro; Ueta, Yukihiro; Yoshida, Jun; Nomoto, Akihiro; Yano, Shigenobu; Ueshima, Michio; Ogawa, Akiya

    2009-11-28

    Vanadium(iv) complexes bearing 3-hydroxypicolinic acid (H(2)hpic) as ligands, VO(Hhpic)(2) (1) and the cyclic tetramer (VO)(4)(hpic)(4) (2), have excellent catalytic ability for the oxidation of a variety of primary and secondary benzyl alcohols with molecular oxygen in acetonitrile or protic solvents such as ethanol and water, affording the corresponding aldehydes and ketones, respectively. Construction of multi-nuclear complexes by the selection of ligands attains higher turnover numbers and recycling of the catalyst. PMID:19885511

  16. Structural oxidation state studies of the manganese cluster in the oxygen evolving complex of photosystem II

    SciTech Connect

    Liang, W.

    1994-11-01

    X-ray absorption spectroscopy (XAS) was performed on Photosystem II (PSII)-enriched membranes prepared from spinach to explore: (1) the correlation between structure and magnetic spin state of the Mn cluster in the oxygen evolving complex (OEC) in the S{sub 2} state; and (2) the oxidation state changes of the Mn cluster in the flash-induced S-states. The structure of the Mn cluster in the S{sub 2} state with the g{approx}4 electron paramagnetic resonance (EPR) signal (S{sub 2}-g4 state) was compared with that in the S{sub 2} state with multiline signal (S{sub 2}-MLS state) and the S{sub 1} state. The S{sub 2}-g4 state has a higher XAS inflection point energy than that of the S{sub 1} state, indicating the oxidation of Mn in the advance from the S{sub 1} to the S{sub 2}-g4 state. Differences in the edge shape and in the extended X-ray absorption fine structure (EXAFS) show that the structure of the Mn cluster in the S{sub 2}-g4 state is different from that in the S{sub 2}-MLS or the S{sub 1} state. In the S{sub 2}-g4 state, the second shell of backscatterers from the Mn absorber contains two Mn-Mn distances of 2.73 {angstrom} and 2.85 {angstrom}. Very little distance disorder exists in the second shell of the S{sub 1} or S{sub 2}-MLS states. The third shell of the S{sub 2}-g4 state at about 3.3 {angstrom} also contains increased heterogeneity relative to that of the S{sub 2}-MLS or the S{sub 1} state. Various S-states were prepared at room-temperature by saturating, single-turnover flashes. The flash-dependent oscillation in the amplitude of the MLS was used to characterize the S-state composition and to construct {open_quotes}pure{close_quotes} S-state Mn K-edge spectra. The edge position shifts to higher energy by 1.8 eV upon the S{sub 1} {yields} S{sub 2} transition.

  17. Novel water-resistant UV-activated oxygen indicator for intelligent food packaging.

    PubMed

    Vu, Chau Hai Thai; Won, Keehoon

    2013-09-01

    For the first time, alginate polymer has been applied to prevent dyes from leaching out of colorimetric oxygen indicator films, which enable people to notice the presence of oxygen in the package in an economic and simple manner. The dye-based oxygen indicator film suffers from dye leaching upon contact with water. In this work, UV-activated visual oxygen indicator films were fabricated using thionine, glycerol, P25 TiO2, and zein as a redox dye, a sacrificial electron donor, UV-absorbing semiconducting photocatalyst, and an encapsulation polymer, respectively. When this zein-coated film was immersed in water for 24h, the dye leakage was as high as 80.80±0.45%. However, introduction of alginate (1.25%) as the coating polymer considerably diminished the dye leaching to only 5.80±0.06%. This is because the ion-binding ability of alginate could prevent the cation dye from leaching into water. This novel water-resistant UV-activated oxygen indicator was also successfully photo-bleached and regained colour fast in the presence of oxygen. PMID:23578614

  18. Evaluation of the Catalytic Activity and Cytotoxicity of Palladium Nanocubes. The Role of Oxygen

    PubMed Central

    Dahal, Eshan; Curtiss, Jessica; Subedi, Deepak; Chen, Gen; Houston, Jessica P.; Smirnov, Sergei

    2015-01-01

    Recently it has been reported that palladium nanocubes (PdNC) are capable of generating singlet oxygen without photo-excitation simply via chemisorption of molecular oxygen on its surface. Such a trait would make PdNC a highly versatile catalyst suitable in organic synthesis and a Reactive Oxygen Species (ROS) inducing cancer treatment reagent. Here we thoroughly investigated the catalytic activity of PdNC with respect to their ability to produce singlet oxygen and to oxidize 3,5,3′,5′-tetramethyl-benzidine (TMB), as well as, analyzed the cytotoxic properties of PdNC on HeLa cells. Our findings showed no evidence of singlet oxygen production by PdNC. The nanocubes’ activity is not necessarily linked to activation of oxygen. The oxidation of substrate on PdNC can be a first step followed by PdNC regeneration with oxygen or other oxidant. The catalytic activity of PdNC towards oxidation of TMB is very high and shows direct two-electrons oxidation when the surface of PdNC is clean and the ratio of TMB/PdNC is not very high. Sequential one electron oxidation is observed when the pristine quality of PdNC surface is compromised by serum or uncontrolled impurities and/or the ratio of TMB/PdNC is high. Clean PdNC in serum-free media efficiently induce apoptosis of HeLa cells. It is the primary route of cell death and is associated with hyperpolarization of mitochondria, contrary to a common mitochondrial depolarization initiated by ROS. Again, the effects are very sensitive to how well the pristine surface of PdNC is preserved, suggesting that PdNC can be used as an apoptosis inducing agent but only with appropriate drug delivery system. PMID:25886644

  19. Evaluation of the catalytic activity and cytotoxicity of palladium nanocubes: the role of oxygen.

    PubMed

    Dahal, Eshan; Curtiss, Jessica; Subedi, Deepak; Chen, Gen; Houston, Jessica P; Smirnov, Sergei

    2015-05-13

    Recently, it has been reported that palladium nanocubes (PdNC) are capable of generating singlet oxygen without photoexcitation simply via chemisorption of molecular oxygen on its surface. Such a trait would make PdNC a highly versatile catalyst suitable in organic synthesis and a Reactive Oxygen Species (ROS) inducing cancer treatment reagent. Here we thoroughly investigated the catalytic activity of PdNC with respect to their ability to produce singlet oxygen and to oxidize 3,3',5,5'-tetramethylbenzidine (TMB), and analyzed the cytotoxic properties of PdNC on HeLa cells. Our findings showed no evidence of singlet oxygen production by PdNC. The nanocubes' activity is not necessarily linked to activation of oxygen. The oxidation of substrate on PdNC can be a first step, followed by PdNC regeneration with oxygen or other oxidant. The catalytic activity of PdNC toward the oxidation of TMB is very high and shows direct two-electron oxidation when the surface of the PdNC is clean and the ratio of TMB/PdNC is not very high. Sequential one electron oxidation is observed when the pristine quality of PdNC surface is compromised by serum or uncontrolled impurities and/or the ratio of TMB/PdNC is high. Clean PdNC in serum-free media efficiently induce apoptosis of HeLa cells. It is the primary route of cell death and is associated with hyperpolarization of mitochondria, contrary to a common mitochondrial depolarization initiated by ROS. Again, the effects are very sensitive to how well the pristine surface of PdNC is preserved, suggesting that PdNC can be used as an apoptosis inducing agent, but only with appropriate drug delivery system. PMID:25886644

  20. Ligand Based Dual Fluorescence and Phosphorescence Emission from BODIPY Platinum Complexes and Its Application to Ratiometric Singlet Oxygen Detection.

    PubMed

    Geist, Fabian; Jackel, Andrej; Winter, Rainer F

    2015-11-16

    Four new 4,4-difluoro-4-bora-3a,4a-diaza-s-indacen-8-yl (BODIPY) platinum(II) complexes of the type cis-/trans-Pt(BODIPY)Br(PR3)2 (R = Et or Ph) were synthesized and characterized by NMR, electronic absorption, and luminescence spectroscopy. Three of the complexes were also studied by single crystal X-ray diffraction. The absorption profiles of the four complexes feature intense HOMO → LUMO π → π* transitions with molar extinction coefficients ε of ca. 50 000 M(-1)cm(-1) at around 475 nm and vibrational progressions that are characteristic of BODIPYs. Most remarkably, most complexes exhibit dual emissions through fluorescence at ca. 490 nm and phosphorescence at ca. 650 nm that originate from Pt-perturbed BODIPY-centered (1)ππ* or (3)ππ* states, respectively. Electronic absorption and luminescence spectroscopy data are in good agreement with our TD-DFT calculations. While the emission of the cis-complexes is dominated by fluorescence, their trans-isomers emit predominantly through phosphorescence with a phosphorescence quantum yield for trans-Pt(BODIPY)Br(PEt3)2 (trans-1) of 31.2%. trans-1 allows for ratiometric one-component oxygen sensing in fluid solution up to atmospheric concentration levels and exhibits a remarkably high Stern-Volmer constant for the quenching of the excited triplet state by oxygen of ca. 350 bar(-1) as determined by changes in phosphorescence intensity and lifetime. PMID:26540413

  1. Air-activated chemical warming devices: effects of oxygen and pressure.

    PubMed

    Raleigh, G; Rivard, R; Fabus, S

    2005-01-01

    Air-activated chemical warming devices use an exothermic chemical reaction of rapidly oxidizing iron to generate heat for therapeutic purposes. Placing these products in a hyperbaric oxygen environment greatly increases the supply of oxidant and thus increases the rate of reaction and maximum temperature. Testing for auto-ignition and maximum temperatures attained by ThermaCare Heat Wraps, Playtex Heat Therapy, and Heat Factory disposable warm packs under ambient conditions and under conditions similar to those encountered during hyperbaric oxygen treatments in monoplace and multiplace hyperbaric chambers (3 atm abs and > 95% oxygen) revealed a maximum temperature of 269 degrees F (132 degrees C) with no spontaneous ignition. The risk of thermal burn injury to adjacent skin may be increased significantly if these devices are used under conditions of hyperbaric oxygen. PMID:16509287

  2. Thermodynamic explanation of the universal correlation between oxygen evolution activity and corrosion of oxide catalysts

    PubMed Central

    Binninger, Tobias; Mohamed, Rhiyaad; Waltar, Kay; Fabbri, Emiliana; Levecque, Pieter; Kötz, Rüdiger; Schmidt, Thomas J.

    2015-01-01

    In recent years, the oxygen evolution reaction (OER) has attracted increased research interest due to its crucial role in electrochemical energy conversion devices for renewable energy applications. The vast majority of OER catalyst materials investigated are metal oxides of various compositions. The experimental results obtained on such materials strongly suggest the existence of a fundamental and universal correlation between the oxygen evolution activity and the corrosion of metal oxides. This corrosion manifests itself in structural changes and/or dissolution of the material. We prove from basic thermodynamic considerations that any metal oxide must become unstable under oxygen evolution conditions irrespective of the pH value. The reason is the thermodynamic instability of the oxygen anion in the metal oxide lattice. Our findings explain many of the experimentally observed corrosion phenomena on different metal oxide OER catalysts. PMID:26178185

  3. Thermodynamic explanation of the universal correlation between oxygen evolution activity and corrosion of oxide catalysts

    NASA Astrophysics Data System (ADS)

    Binninger, Tobias; Mohamed, Rhiyaad; Waltar, Kay; Fabbri, Emiliana; Levecque, Pieter; Kötz, Rüdiger; Schmidt, Thomas J.

    2015-07-01

    In recent years, the oxygen evolution reaction (OER) has attracted increased research interest due to its crucial role in electrochemical energy conversion devices for renewable energy applications. The vast majority of OER catalyst materials investigated are metal oxides of various compositions. The experimental results obtained on such materials strongly suggest the existence of a fundamental and universal correlation between the oxygen evolution activity and the corrosion of metal oxides. This corrosion manifests itself in structural changes and/or dissolution of the material. We prove from basic thermodynamic considerations that any metal oxide must become unstable under oxygen evolution conditions irrespective of the pH value. The reason is the thermodynamic instability of the oxygen anion in the metal oxide lattice. Our findings explain many of the experimentally observed corrosion phenomena on different metal oxide OER catalysts.

  4. Apogossypolone targets mitochondria and light enhances its anticancer activity by stimulating generation of singlet oxygen and reactive oxygen species

    PubMed Central

    Hu, Zhe-Yu; Wang, Jing; Cheng, Gang; Zhu, Xiao-Feng; Huang, Peng; Yang, Dajun; Zeng, Yi-Xin

    2011-01-01

    Apogossypolone (ApoG2), a novel derivative of gossypol, has been shown to be a potent inhibitor of antiapoptotic Bcl-2 family proteins and to have antitumor activity in multiple types of cancer cells. Recent reports suggest that gossypol stimulates the generation of cellular reactive oxygen species (ROS) in leukemia and colorectal carcinoma cells; however, gossypol-mediated cell death in leukemia cells was reported to be ROS-independent. This study was conducted to clarify the effect of ApoG2-induced ROS on mitochondria and cell viability, and to further evaluate its utility as a treatment for nasopharyngeal carcinoma (NPC). We tested the photocytotoxicity of ApoG2 to the poorly differentiated NPC cell line CNE-2 using the ROS-generating TL/10 illumination system. The rapid ApoG2-induced cell death was partially reversed by the antioxidant N-acetyl-L-cysteine (NAC), but the ApoG2-induced reduction of mitochondrial membrane potential (MMP) was not reversed by NAC. In the presence of TL/10 illumination, ApoG2 generated massive amounts of singlet oxygen and was more effective in inhibiting cell growth than in the absence of illumination. We also determined the influence of light on the anti-proliferative activity of ApoG2 using a CNE-2–xenograft mouse model. ApoG2 under TL/10 illumination healed tumor wounds and suppressed tumor growth more effectively than ApoG2 treatment alone. These results indicate that the ApoG2-induced CNE-2 cell death is partly ROS-dependent. ApoG2 may be used with photodynamic therapy (PDT) to treat NPC. PMID:21192843

  5. Antioxidative activity and growth regulation of Brassicaceae induced by oxygen radical irradiation

    NASA Astrophysics Data System (ADS)

    Hayashi, Nobuya; Ono, Reoto; Shiratani, Masaharu; Yonesu, Akira

    2015-06-01

    The growth regulation characteristics of plants are investigated when plant seeds are irradiated with atmospheric discharge plasma. Enhancement of the germination and lengths of the stem and root of plants are observed after seeding. The total length of the stem and root increases approximately 1.6 times after a cultivation period of 72 h. The growth regulation effect is found to be maintained for 80 h of cultivation after seeding. The growth regulation originates from the change in the antioxidative activity of plant cells induced by active oxygen species generated in the oxygen plasma, which leads to the production of growth factor in plants.

  6. REVIEW: Excited states in the active media of oxygen — iodine lasers

    NASA Astrophysics Data System (ADS)

    Azyazov, V. N.

    2009-11-01

    A review of investigations of kinetic processes in active media oxygen — iodine lasers (OILs) performed in the last decade is presented. The mechanisms of pumping and quenching of electronically and vibrationally excited O2 and I2 molecules are considered, and dissociation mechanisms of I2 in the active medium of the OIL are analysed. The values of kinetic constants of processes proceeding in the active media of OILs are recommended.

  7. DNA interaction, antioxidant activity, and bioactivity studies of two ruthenium(II) complexes

    NASA Astrophysics Data System (ADS)

    Han, Bing-Jie; Jiang, Guang-Bin; Yao, Jun-Hua; Li, Wei; Wang, Ji; Huang, Hong-Liang; Liu, Yun-Jun

    2015-01-01

    Two new ruthenium(II) polypyridyl complexes [Ru(dmb)2(dcdppz)](ClO4)2 (1) and [Ru(bpy)2(dcdppz)](ClO4)2 (2) were prepared and characterized. The crystal structure of the complex 2 was solved by single crystal X-ray diffraction. The complex crystallizes in the monoclinic system, space group P21/n with a = 12.9622(14) Å, b = 17.1619(19) Å, c = 22.7210(3) Å, β = 100.930(2)°, R = 0.0536, Rω = 0.1111. The DNA-binding constants for complexes 1 and 2 were determined to be 1.92 × 105 (s = 1.72) and 2.24 × 105 (s = 1.86) M-1, respectively. The DNA-binding behaviors showed that complexes 1 and 2 interact with DNA by intercalative mode. The antioxidant activities of the ligand and the complexes were performed. Ligand, dcdppz, has no cytotoxicity against the selected cell lines. Complex 1 shows higher cytotoxicity than complex 2, but lower than cisplatin toward selected cell lines. The apoptosis and cell cycle arrest were investigated, and the apoptotic mechanism of BEL-7402 cells was studied by reactive oxygen species (ROS), mitochondrial membrane potential and western blot analysis. Complex 1 induces apoptosis in BEL-7402 cells through ROS-mediated mitochondrial dysfunction pathway and by regulating the expression of Bcl-2 family proteins.

  8. The relationship between brain cortical activity and brain oxygenation in the prefrontal cortex during hypergravity exposure.

    PubMed

    Smith, Craig; Goswami, Nandu; Robinson, Ryan; von der Wiesche, Melanie; Schneider, Stefan

    2013-04-01

    Artificial gravity has been proposed as a method to counteract the physiological deconditioning of long-duration spaceflight; however, the effects of hypergravity on the central nervous system has had little study. The study aims to investigate whether there is a relationship between prefrontal cortex brain activity and prefrontal cortex oxygenation during exposure to hypergravity. Twelve healthy participants were selected to undergo hypergravity exposure aboard a short-arm human centrifuge. Participants were exposed to hypergravity in the +Gz axis, starting from 0.6 +Gz for women, and 0.8 +Gz for men, and gradually increasing by 0.1 +Gz until the participant showed signs of syncope. Brain cortical activity was measured using electroencephalography (EEG) and localized to the prefrontal cortex using standard low-resolution brain electromagnetic tomography (LORETA). Prefrontal cortex oxygenation was measured using near-infrared spectroscopy (NIRS). A significant increase in prefrontal cortex activity (P < 0.05) was observed during hypergravity exposure compared with baseline. Prefrontal cortex oxygenation was significantly decreased during hypergravity exposure, with a decrease in oxyhemoglobin levels (P < 0.05) compared with baseline and an increase in deoxyhemoglobin levels (P < 0.05) with increasing +Gz level. No significant correlation was found between prefrontal cortex activity and oxy-/deoxyhemoglobin. It is concluded that the increase in prefrontal cortex activity observed during hypergravity was most likely not the result of increased +Gz values resulting in a decreased oxygenation produced through hypergravity exposure. No significant relationship between prefrontal cortex activity and oxygenation measured by NIRS concludes that brain activity during exposure to hypergravity may be difficult to measure using NIRS. Instead, the increase in prefrontal cortex activity might be attributable to psychological stress, which could pose a problem for the use of a

  9. Changes in complex spike activity during classical conditioning.

    PubMed

    Rasmussen, Anders; Jirenhed, Dan-Anders; Wetmore, Daniel Z; Hesslow, Germund

    2014-01-01

    The cerebellar cortex is necessary for adaptively timed conditioned responses (CRs) in eyeblink conditioning. During conditioning, Purkinje cells acquire pause responses or "Purkinje cell CRs" to the conditioned stimuli (CS), resulting in disinhibition of the cerebellar nuclei (CN), allowing them to activate motor nuclei that control eyeblinks. This disinhibition also causes inhibition of the inferior olive (IO), via the nucleo-olivary pathway (N-O). Activation of the IO, which relays the unconditional stimulus (US) to the cortex, elicits characteristic complex spikes in Purkinje cells. Although Purkinje cell activity, as well as stimulation of the CN, is known to influence IO activity, much remains to be learned about the way that learned changes in simple spike firing affects the IO. In the present study, we analyzed changes in simple and complex spike firing, in extracellular Purkinje cell records, from the C3 zone, in decerebrate ferrets undergoing training in a conditioning paradigm. In agreement with the N-O feedback hypothesis, acquisition resulted in a gradual decrease in complex spike activity during the conditioned stimulus, with a delay that is consistent with the long N-O latency. Also supporting the feedback hypothesis, training with a short interstimulus interval (ISI), which does not lead to acquisition of a Purkinje cell CR, did not cause a suppression of complex spike activity. In contrast, observations that extinction did not lead to a recovery in complex spike activity and the irregular patterns of simple and complex spike activity after the conditioned stimulus are less conclusive. PMID:25140129

  10. XPC silencing in normal human keratinocytes triggers metabolic alterations through NOX-1 activation-mediated reactive oxygen species

    PubMed Central

    Rezvani, Hamid Reza; Rossignol, Rodrigue; Ali, Nsrein; Benard, Giovanni; Tang, Xiuwei; Yang, Hee Seung; Jouary, Thomas; de Verneuil, Hubert; Taïeb, Alain; Kim, Arianna L.; Mazurier, Frédéric

    2011-01-01

    Summary Cancer cells utilize complex mechanisms to remodel their bioenergetic properties. We exploited the intrinsic genomic stability of xeroderma pigmentosum C (XPC) to understand the interrelationships between genomic instability, reactive oxygen species (ROS) generation, and metabolic alterations during neoplastic transformation. We showed that knockdown of XPC (XPCKD) in normal human keratinocytes results in metabolism remodeling through NADPH oxidase-1 (NOX-1) activation, which in turn leads to increased ROS levels. While enforcing antioxidant defenses by overexpressing catalase, CuZnSOD, or MnSOD could not block the metabolism remodeling, impaired NOX-1 activation abrogates both alteration in ROS levels and modifications of energy metabolism. As NOX-1 activation is observed in human squamous cell carcinomas (SCCs), the blockade of NOX-1 could be a target for the prevention and the treatment of skin cancers. PMID:21167810

  11. Respiratory muscle activity and oxygenation during sleep in patients with muscle weakness.

    PubMed

    White, J E; Drinnan, M J; Smithson, A J; Griffiths, C J; Gibson, G J

    1995-05-01

    Patients with respiratory muscle weakness show nocturnal hypoventilation, with oxygen desaturation particularly during rapid eye movement (REM) sleep, but evidence in individuals with isolated bilateral diaphragmatic paresis (BDP) is conflicting. The effect of sleep on relative activity of the different respiratory muscles of such patients and, consequently, the precise mechanisms causing desaturation have not been clarified. We have studied eight patients, four with generalized muscle weakness and four with isolated BDP during nocturnal sleep with measurements including oxygen saturation and surface electromyographic (EMG) activity of various respiratory muscle groups. Nocturnal oxygenation correlated inversely with postural fall in vital capacity, an index of diaphragmatic strength. During REM sleep, hypopnoea and desaturation occurred particularly during periods of rapid eye movements (phasic REM sleep). In most subjects, such events were "central" in type and associated with marked suppression of intercostal muscle activity, but two subjects had recurrent desaturation due to "obstructive" hypopnoea and/or apnoea. Expiratory activity of the external oblique muscle was present whilst awake and during non-rapid eye movement (NREM) sleep in seven of the eight subjects in the semirecumbent posture. This probably represents an "accessory inspiratory" effect, which aids passive caudal diaphragmatic motion as the abdominal muscles relax at the onset of inspiration. Expiratory abdominal muscle activity was suppressed in phasic REM sleep, suggesting that loss of this "accessory inspiratory" effect may contribute to "central" hypopnoea. We conclude that, in patients with muscle weakness, nocturnal oxygenation correlates with diaphragmatic strength.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7656954

  12. New Active Optical Technique Developed for Measuring Low-Earth-Orbit Atomic Oxygen Erosion of Polymers

    NASA Technical Reports Server (NTRS)

    Banks, Bruce A.; deGroh, Kim K.; Demko, Rikako

    2003-01-01

    Polymers such as polyimide Kapton (DuPont) and Teflon FEP (DuPont, fluorinated ethylene propylene) are commonly used spacecraft materials because of desirable properties such as flexibility, low density, and in the case of FEP, a low solar absorptance and high thermal emittance. Polymers on the exterior of spacecraft in the low-Earth-orbit (LEO) environment are exposed to energetic atomic oxygen. Atomic oxygen reaction with polymers causes erosion, which is a threat to spacecraft performance and durability. It is, therefore, important to understand the atomic oxygen erosion yield E (the volume loss per incident oxygen atom) of polymers being considered in spacecraft design. The most common technique for determining E is a passive technique based on mass-loss measurements of samples exposed to LEO atomic oxygen during a space flight experiment. There are certain disadvantages to this technique. First, because it is passive, data are not obtained until after the flight is completed. Also, obtaining the preflight and postflight mass measurements is complicated by the fact that many polymers absorb water and, therefore, the mass change due to water absorption can affect the E data. This is particularly true for experiments that receive low atomic oxygen exposures or for samples that have a very low E. An active atomic oxygen erosion technique based on optical measurements has been developed that has certain advantages over the mass-loss technique. This in situ technique can simultaneously provide the erosion yield data on orbit and the atomic oxygen exposure fluence, which is needed for erosion yield determination. In the optical technique, either sunlight or artificial light can be used to measure the erosion of semitransparent or opaque polymers as a result of atomic oxygen attack. The technique is simple and adaptable to a rather wide range of polymers, providing that they have a sufficiently high optical absorption coefficient. If one covers a photodiode with a

  13. Carbon-Oxygen Bond Forming Mechanisms in Rhenium Oxo-Alkyl Complexes

    SciTech Connect

    Cheng, Mu-Jeng; Nielsen, Robert J.; Ahlquist, Marten; Goddard, William A.

    2010-04-07

    Three C-X bond formation mechanisms observed in the oxidation of (HBpz3)ReO(R)(OTf) [HBpz 3 = hydrotris(1-pyrazolyl)borate; R = Me, Et, and iPr; OTf = OSO2CF3] by dimethyl sulfoxide (DMSO) were investigated using quantum mechanics (M06//B3LYP DFT) combined with solvation (using the PBF Poisson-Boltzmann polarizable continuum solvent model). For R = Et we find the alkyl group is activated through α-hydrogen abstraction by external base OTf- with a free energy barrier of only 12.0 kcal/mol, leading to formation of acetaldehyde. Alternatively, ethyl migration across the M=O bond (leading to the formation of acetaldehyde and ethanol) poses a free energy barrier of 22.1 kcal/mol, and the previously proposed α-hydrogen transfer to oxo (a 2+2 forbidden reaction) poses a barrier of 44.9 kcal/mol. The rate-determining step to formation of the final product acetaldehyde is an oxygen atom transfer from DMSO to the ethylidene, with a free energy barrier of 15.3 kcal/mol. When R = iPr, the alkyl 1,2-migration pathway becomes the more favorable pathway (both kinetically and thermodynamically), with a free energy barrier (ΔG = 11.8 kcal/mol) lower than α-hydrogen abstraction by OTf- (ΔG = 13.5 kcal/mol). This suggests the feasibility of utilizing this type of migration to functionalize M-R to M-OR. We also considered the nucleophilic attack of water and ammonia on the Re-ethylidene α-carbon as a means of recovering two-electron-oxidized products from an alkane oxidation. Nucleophilic attack (with internal deprotonation of the nucleophile) is exothermic. However, the subsequent protonolysis of the Re-alkyl bond (to liberate an alcohol or amine) poses a barrier of 37.0 or 42.4 kcal/mol, respectively. Where comparisons are possible, calculated free energies agree very well with experimental measurements.

  14. Synthesis, DNA interactions and antibacterial PDT of Cu(II) complexes of phenanthroline based photosensitizers via singlet oxygen generation

    NASA Astrophysics Data System (ADS)

    Sudhamani, C. N.; Bhojya Naik, H. S.; Sangeetha Gowda, K. R.; Giridhar, M.; Girija, D.; Prashanth Kumar, P. N.

    2015-03-01

    Cu(II) complexes [Cu(mqt)(B)H2O]ClO4(1-3) of 2-thiol 4-methylquinoline and phenanthroline bases (B), viz 1,10-phenanthroline (phen in 1), Dipyrido[3,2-d:2‧,3‧-f]quinoxaline (dpq in 2) and Dipyrido[3,2-a:2‧,3‧-c]phenazine (dppz in 3) have been prepared and characterized by elemental analysis, IR, UV-Vis, magnetic moment values, EPR spectra and conductivity measurements. The spectral data reveal that all the complexes exhibit square-pyramidal geometry. The DNA-binding behaviors of the three complexes were investigated by absorption spectra, viscosity measurements and thermal denaturation studies. The DNA binding constants for complexes (1), (2) and (3) were determined to 2.2 × 103, 1.3 × 104 and 8.6 × 104 M-1 respectively. The experimental results suggest that these complexes interact with DNA through groove-binding mode. The photo induced cleavage studies shows that the complexes possess photonuclease property against pUC19 DNA under UV-Visible irradiation via a mechanistic pathway involving formation of singlet oxygen as the reactive species. Antimicrobial photodynamic therapy was studied using photodynamic antimicrobial chemotherapy (PACT) assay against Escherichiacoli and all complexes exhibited significant reduction in bacterial growth on photoirradiation.

  15. Synthesis, DNA interactions and antibacterial PDT of Cu(II) complexes of phenanthroline based photosensitizers via singlet oxygen generation.

    PubMed

    Sudhamani, C N; Bhojya Naik, H S; Sangeetha Gowda, K R; Giridhar, M; Girija, D; Prashanth Kumar, P N

    2015-03-01

    Cu(II) complexes [Cu(mqt)(B)H2O]ClO4(1-3) of 2-thiol 4-methylquinoline and phenanthroline bases (B), viz 1,10-phenanthroline (phen in 1), Dipyrido[3,2-d:2',3'-f]quinoxaline (dpq in 2) and Dipyrido[3,2-a:2',3'-c]phenazine (dppz in 3) have been prepared and characterized by elemental analysis, IR, UV-Vis, magnetic moment values, EPR spectra and conductivity measurements. The spectral data reveal that all the complexes exhibit square-pyramidal geometry. The DNA-binding behaviors of the three complexes were investigated by absorption spectra, viscosity measurements and thermal denaturation studies. The DNA binding constants for complexes (1), (2) and (3) were determined to 2.2×10(3), 1.3×10(4) and 8.6×10(4)M(-1) respectively. The experimental results suggest that these complexes interact with DNA through groove-binding mode. The photo induced cleavage studies shows that the complexes possess photonuclease property against pUC19 DNA under UV-Visible irradiation via a mechanistic pathway involving formation of singlet oxygen as the reactive species. Antimicrobial photodynamic therapy was studied using photodynamic antimicrobial chemotherapy (PACT) assay against Escherichiacoli and all complexes exhibited significant reduction in bacterial growth on photoirradiation. PMID:25544194

  16. Active medium gain study of electric-discharge oxygen-iodine laser

    NASA Astrophysics Data System (ADS)

    Kolobyanin, Yuriy; Adamenkov, Yuriy; Vyskubenko, Boris; Goryachev, Leonid; Ilyin, Sergey; Kalashnik, Anatoliy; Rakhimova, Tatiana; Rogozhnikov, Georgiy

    2007-05-01

    The paper reports on experimental studies of the active medium gain in supersonic electric-discharge oxygen-iodine laser (DOIL) based on traveling mw discharge. The measurements have included: absolute concentration, yield, and energy efficiency of production of SO in pure oxygen and oxygen-helium mixes at an oxygen partial pressure 3 to 15 Torr. For the gas flow to get rid of atomic oxygen, both heterogeneous mercury oxide coatings of the tube walls and homogeneous additives to the work mix, such as nitrogen oxide, have been used. The active medium of DOIL was formed using a nozzle array of the type of ejector sized as 10*50 mm2. The singlet oxygen-helium mix was supplied through three rows of sonic cylindrical nozzles, while the iodine-carrier gas mix - through two rows of supersonic conical nozzles with a half-opening angle of 10°(arc). The gas-phase iodine was produced in a quartz cell filled with iodine crystals. Room-temperature iodine vapors were picked up with a carrier gas (nitrogen or helium) and thus delivered into the nozzle array. The active medium was investigated by the high-resolution laser diode spectroscopy approach that used the laser type Vortex 6025 purchased from New Focus, Inc. The laser medium gain factor was determined by the intra-cavity approach having a sensitivity about 1*10 -6 cm -1. The static temperature of the medium was determined from the measurements of gain half-width. The gain of the active medium of electric-discharge OIL has been investigated. The DOIL in use was operating on a mix composed as O II:He=1:1 at a total pressure of 6 Torr and flowrate - about 1 mmol/s. With helium as an iodine carrier gas at a flowrate ~3 mmol/s, we have recorded a positive gain in the DOIL medium.

  17. Heterogenous Oxygen Isotopic Composition of a Complex Wark-Lovering Rim and the Margin of a Refractory Inclusion from Leoville

    NASA Technical Reports Server (NTRS)

    Simon, J. I.; Matzel, J. E. P.; Simon, S. B.; Weber, P. K.; Grossman, L.; Ross, D. K.; Hutcheon, I. D.

    2014-01-01

    Wark-Lovering (WL) rims [1] surrounding many refractory inclusions represent marker events in the early evolution of the Solar System in which many inclusions were exposed to changes in pressure [2], temperature [3], and isotopic reservoirs [4-7]. The effects of these events can be complex, not only producing mineralogical variability of WL rims [2], but also leading to mineralogical [8-10] and isotopic [7, 11, 12] changes within inclusion interiors. Extreme oxygen isotopic heterogeneity measured in CAIs has been explained by mixing between distinct oxygen gas reservoirs in the nebula [13]. Some WL rims contain relatively simple mineral layering and/or are isotopically homogeneous [14, 15]. As part of a larger effort to document and understand the modifications observed in some CAIs, an inclusion (L6) with a complex WL rim from Leoville, a member of the reduced CV3 subgroup was studied. Initial study of the textures and mineral chemistry was presented by [16]. Here we present NanoSIMS oxygen isotopic measurements to complement these petrologic observations.

  18. Anticancer activity assessment of two novel binuclear platinum (II) complexes.

    PubMed

    Shahsavani, Mohammad Bagher; Ahmadi, Shamseddin; Aseman, Marzieh Dadkhah; Nabavizadeh, S Masoud; Rashidi, Mehdi; Asadi, Zahra; Erfani, Nasrollah; Ghasemi, Atiyeh; Saboury, Ali Akbar; Niazi, Ali; Bahaoddini, Aminollah; Yousefi, Reza

    2016-08-01

    In the current study, two binuclear Pt (II) complexes, containing cis, cis-[Me2Pt (μ-NN) (μ-dppm) PtMe2] (1), and cis,cis-[Me2Pt(μ-NN)(μ dppm) Pt((CH2)4)] (2) in which NN=phthalazine and dppm=bis (diphenylphosphino) methane were evaluated for their anticancer activities and DNA/purine nucleotide binding properties. These Pt (II) complexes, with the non-classical structures, demonstrated a significant anticancer activity against Jurkat and MCF-7 cancer cell lines. The results of ethidium bromide/acridine orange staining and Caspase-III activity suggest that these complexes were capable to stimulate an apoptotic mechanism of cell death in the cancer cells. Using different biophysical techniques and docking simulation analysis, we indicated that these complexes were also capable to interact efficiently with DNA via a non-intercalative mechanism. According to our results, substitution of cyclopentane (in complex 2) with two methyl groups (in complex 1) results in significant improvement of the complex ability to interact with DNA and subsequently to induce the anticancer activity. Overall, these binuclear Pt (II) complexes are promising group of the non-classical potential anticancer agents which can be considered as molecular templates in designing of highly efficient platinum anticancer drugs. PMID:27289447

  19. Fabrication of Eu(III) complex doped nanofibrous membranes and their oxygen-sensing properties

    NASA Astrophysics Data System (ADS)

    Songzhu, Lin; Xiangting, Dong; Jinxian, Wang; Guixia, Liu; Wenshen, Yu; Ruokun, Jia

    2010-11-01

    In this paper, we report the synthesis, characterization, and photophysical properties of Eu(TTA) 3ECIP, where TTA = 2-thenoyltrifluoroacetonate, and ECIP = 1-ethyl-2-(N-ethyl-carbazole-yl-4-)imidazo[4,5-f]1,10-phenanthroline. Its elementary application for oxygen-sensing application is also investigated by doping it into a polymer matrix of polystyrene (PS). Experimental data suggest that the 2.5 wt% doped Eu(TTA) 3ECIP/PS nanofibrous membrane exhibits a high sensitivity of 3.4 towards oxygen with a good linear relationship of R2 = 0.9962. In addition, the 2.5 wt% doped Eu(TTA) 3ECIP/PS nanofibrous membrane owns a quick response of 8 s towards oxygen, along with its excellent atmosphere insensitivity and photobleaching resistance. All these results suggest that both Eu(TTA) 3ECIP and Eu(TTA) 3ECIP/PS system are promising candidates for oxygen-sensing optical sensors.

  20. Classifying organic materials by oxygen-to-carbon elemental ratio to predict the activation regime of Cloud Condensation Nuclei (CCN)

    NASA Astrophysics Data System (ADS)

    Kuwata, M.; Shao, W.; Lebouteiller, R.; Martin, S. T.

    2013-05-01

    The governing highly soluble, slightly soluble, or insoluble activation regime of organic compounds as cloud condensation nuclei (CCN) was examined as a function of oxygen-to-carbon elemental ratio (O : C). New data were collected for adipic, pimelic, suberic, azelaic, and pinonic acids. Secondary organic materials (SOMs) produced by α-pinene ozonolysis and isoprene photo-oxidation were also included in the analysis. The saturation concentrations C of the organic compounds in aqueous solutions served as the key parameter for delineating regimes of CCN activation, and the values of C were tightly correlated to the O : C ratios. The highly soluble, slightly soluble, and insoluble regimes of CCN activation were found to correspond to ranges of [O : C] > 0.6, 0.2 < [O : C] < 0.6, and [O : C] < 0.2, respectively. These classifications were evaluated against CCN activation data of isoprene-derived SOM (O : C = 0.69-0.72) and α-pinene-derived SOM (O : C = 0.38-0.48). Isoprene-derived SOM had highly soluble activation behavior, consistent with its high O : C ratio. For α-pinene-derived SOM, although CCN activation can be modeled as a highly soluble mechanism, this behavior was not predicted by the O : C ratio, for which a slightly soluble mechanism was anticipated. Complexity in chemical composition, resulting in continuous water uptake and the absence of a deliquescence transition that can thermodynamically limit CCN activation, might explain the difference in the behavior of α-pinene-derived SOM compared to that of pure organic compounds. The present results suggest that atmospheric particles dominated by hydrocarbon-like organic components do not activate (i.e., insoluble regime) whereas those dominated by oxygenated organic components activate (i.e., highly soluble regime) for typical atmospheric cloud life cycles.

  1. Classifying organic materials by oxygen-to-carbon elemental ratio to predict the activation regime of cloud condensation nuclei (CCN)

    NASA Astrophysics Data System (ADS)

    Kuwata, M.; Shao, W.; Lebouteiller, R.; Martin, S. T.

    2012-12-01

    The governing highly soluble, slightly soluble, or insoluble activation regime of organic compounds as cloud condensation nuclei (CCN) was examined as a function of oxygen-to-carbon elemental ratio (O : C). New data were collected for adipic, pimelic, suberic, azelaic and pinonic acids. Secondary organic materials (SOMs) produced by α-pinene ozonolysis and isoprene photo-oxidation were also included in the analysis. The saturation concentrations C of the organic compounds in aqueous solutions served as the key parameter for delineating regimes of CCN activation, and the values of C were tightly correlated to the O : C ratios. The highly soluble, slightly soluble, and insoluble regimes of CCN activation were found to correspond to ranges of [O : C] > 0.6, 0.2 < [O : C] < 0.6, and [O : C] < 0.2, respectively. These classifications were evaluated against CCN activation data of isoprene-derived SOM (O : C = 0.69-0.72) and α-pinene-derived SOM (O : C = 0.38-0.48). Isoprene-derived SOM had highly soluble activation behavior, consistent with its high O : C ratio. For α-pinene-derived SOM, although CCN activation can be modeled as a highly soluble mechanism, this behavior was not predicted by the O : C ratio, for which a slightly soluble mechanism was anticipated. Complexity in chemical composition, resulting in continuous water uptake and the absence of a deliquescence transition that can thermodynamically limit CCN activation, might explain the differences of α-pinene-derived SOM compared to the behavior of pure organic compounds. The present results suggest that atmospheric particles dominated by hydrocarbon-like organic components do not activate (i.e. insoluble regime) whereas those dominated by oxygenated organic components activate (i.e. highly soluble regime).

  2. Kinetics and mechanisms of the reactions of alkyl radicals with oxygen and with complexes of Co(III), Ru(III), and Ni(III)

    SciTech Connect

    Kelley, D.

    1990-10-08

    The kinetics of the reactions of C{sub 2}H{sub 5} radical with Co(NH{sub 3}){sub 5}X{sup 2+}, Ru(NH{sub 3}){sub 5}X{sup 2+}, and Co(dmgH){sub 2} (X) (Y) (X = Br, Cl, N{sub 3}, SCN; Y = H{sub 2}O, CH{sub 3}CN) complexes were studied using laser flash photolysis of ethylcobalt complexes. The kinetics were obtained by the kinetic probe method. Some relative rate constants were also determined by a competition method based on ethyl halide product ratios. The kinetics of colligation reactions of a series of alkyl radicals with {beta}-Ni(cyclam){sup 2+} were studied using flaser flash photolysis of alkylcobalt complexes. Again, the kinetics were obtained by employing the kinetic probe competition method. The kinetics of the unimolecular homolysis of a series of RNi(cyclam)H{sub 2}O{sup 2+} were studied. Activation parameters were obtained for the unimolecular homolysis of C{sub 2}H{sub 5}Ni(cyclam)H{sub 2}O{sup 2+}. Kinetic and thermodynamic data obtained from these reactions were compared with those for the {sigma}-bonded organometallic complexes. The kinetics of the unimolecular homolysis of a series of RNi(cyclam)H{sub 2}O{sup 2+} complexes were studied by monitoring the formation of the oxygen insertion product RO{sub 2}Ni(cyclam)H{sub 2}O{sup 2+}. The higher rate constants for the reactions of alkyl radicals with oxygen in solution, as compared with those measured in the gas phase, were discussed. 30 refs.

  3. FULL-SCALE DEMONSTRATION OF OPEN TANK OXYGEN ACTIVATED SLUDGE TREATMENT

    EPA Science Inventory

    This report presents an operating summary of a full-scale demonstration of the FMC open tank pure oxygen (FMC O2) activated sludge system, conducted at the facilities of the Metropolitan Denver Sewage Disposal District No. 1 (Metro) in Denver, Colorado. The system was operated ov...

  4. In vivo imaging of brain metabolism activity using a phosphorescent oxygen-sensitive probe

    PubMed Central

    Tsytsarev, Vassiliy; Arakawa, Hiroyuki; Borisov, Sergei; Pumbo, Elena; Erzurumlu, Reha S.; Papkovsky, Dmitri B.

    2013-01-01

    Several approaches have been adopted for real-time imaging of neural activity in vivo. We tested a new cell-penetrating phosphorescent oxygen-sensitive probe, NanO2-IR, to monitor temporal and spatial dynamics of oxygen metabolism in the neocortex following peripheral sensory stimulation. Probe solution was applied to the surface of anesthetized mouse brain; optical imaging was performed using a MiCAM-02 system. Trains of whisker stimuli were delivered and associated changes in phosphorescent signal were recorded in the contralateral somatosensory (“barrel”) cortex. Sensory stimulation led to changes in oxygenation of activated areas of the barrel cortex. The oxygen imaging results were compared to those produced by the voltage-sensitive dye RH-1691. While the signals emitted by the two probes differed in shape and amplitude, they both faithfully indicated specific whisker evoked cortical activity. Thus, NanO2-IR probe can be used as a tool in visualization and realtime analysis of sensory- evoked neural activity in vivo. PMID:23624034

  5. OXYGEN-ACTIVATED SLUDGE PLANT COMPLETES TWO YEARS OF SUCCESSFUL OPERATION

    EPA Science Inventory

    A detailed report of the conversion to and operational performance of an oxygen-activated sludge system at the Westgate wastewater treatment plant in Fairfax County, Virginia, is given in this report. It is presented in the form of a case history including the time span leading u...

  6. GAS PHASE SELECTIVE PHOTOXIDATION OF ALCOHOLS USING LIGHT-ACTIVATED TITANIUM DIOXIDE AND MOLECULAR OXYGEN

    EPA Science Inventory

    Gas Phase Selective Oxidation of Alcohols Using Light-Activated Titanium Dioxide and Molecular Oxygen

    Gas phase selective oxidations of various primary and secondary alcohols are studied in an indigenously built stainless steel up-flow photochemical reactor using ultravi...

  7. Electron Spin Resonance (ESR) detection of active oxygen species and organic phases in Martian soils

    NASA Technical Reports Server (NTRS)

    Tsay, Fun-Dow; Kim, Soon Sam; Liang, Ranty H.

    1989-01-01

    The presence of active oxygen species (O(-), O2(-), O3(-)) and other strong oxidants (Fe2O3 and Fe3O4) was invoked in interpretations of the Viking biological experiments and a model was also suggested for Martian surface chemistry. The non-biological interpretations of the biological results gain futher support as no organic compounds were detected in the Viking pyrolysis-gas chromatography mass spectrometer (GCSM) experiments at concentrations as low as 10 ppb. Electron spin resonance (ESR) measures the absorption of microwaves by a paramagnetic and/or ferromagnetic center in the presence of an external field. In many instances, ESR has the advantage of detailed submicroscopic identification of the transient species and/or unstable reaction intermediates in their environments. Since the higly active oxygen species (O(-), O2(-), O3(-), and R-O-O(-)) are all paramagnetic in nature, they can be readily detected in native form by the ESR method. Active oxygen species likely to occur in the Martian surface samples were detected by ESR in UV-irradiated samples containing MgO. A miniaturized ESR spectrometer system can be developed for the Mars Rover Sample Return Mission. The instrument can perform the following in situ Martian samples analyses: detection of active oxygen species; characterization of Martian surface chemistry and photooxidation processes; and searching for organic compounds in the form of free radicals preserved in subsoils, and detection of microfossils with Martian carbonate sediments.

  8. Multicopper models for the laccase active site: effect of nuclearity on electrocatalytic oxygen reduction.

    PubMed

    Tse, Edmund C M; Schilter, David; Gray, Danielle L; Rauchfuss, Thomas B; Gewirth, Andrew A

    2014-08-18

    Cu complexes of 2,2'-dipicolylamine (DPA) were prepared and tested as electrocatalysts for the oxygen reduction reaction (ORR). To study the effect of multinuclearity on the ORR, two Cu-DPA units were connected with a flexible linker, and a third metal-binding pocket was installed in the ligand framework. ORR onset potentials and the diffusion-limited current densities of di- and tricopper complexes of DPA derivatives were found to be comparable to those of the simpler Cu-DPA system. Electrochemical analyses, crystallographic data, and metal-substitution studies suggested that Cu complexes of DPA derivatives reacted with O2 via a binuclear intermolecular pathway but that the Cu center in the third binding site did not participate in the ORR process. This study highlights the viability of Cu-DPA complexes to mimic the T3-site of laccase, and serves as a guide for designing future laccase models. PMID:25072935

  9. Synthesis and characterisation of thiosemicarbazonato molybdenum(VI) complexes and their in vitro antitumor activity.

    PubMed

    Vrdoljak, Visnja; Dilović, Ivica; Rubcić, Mirta; Kraljević Pavelić, Sandra; Kralj, Marijeta; Matković-Calogović, Dubravka; Piantanida, Ivo; Novak, Predrag; Rozman, Andrea; Cindrić, Marina

    2010-01-01

    New dioxomolybdenum(VI) complexes were obtained by the reaction of [MoO2(acac)2] with thiosemicarbazone ligands derived from 3-thiosemicarbazide and 4-(diethylamino)salicylaldehyde (H2L1), 2-hydroxy-3-methoxybenzaldehyde (H2L2) or 2-hydroxy-1-naphthaldehyde (H2L3). In all complexes thiosemicarbazonato ligands are coordinated to molybdenum as tridentate ONS-donors. Octahedral coordination of each molybdenum atom is completed by methanol molecule (in 1a-3a) or by oxygen atom of Mo=O unit from the neighbouring molecule (in 1-3). All complexes were characterized by means of chemical analyses, IR spectroscopy, TG and NMR measurements. The molecular structures of the ligand H2L2 and complex [MoO2L2(CH3OH)].CH3OH (2a) have been determined by single crystal X-ray crystallography. The characterisation of thiosemicarbazonato molybdenum(VI) complexes (1-4) as well as of the 4-phenylthisemicarbazonato molybdenum(VI) complexes (5-8) in aqueous medium revealed that upon dissolving complexes in water, most likely to some extent dissociation took place, although experimental data didn't allow exact quantification of dissociation. The antiproliferative effects of studied molybdenum(VI) complexes (1-8) on the human cell lines were identical to the activity of their corresponding ligands. PMID:19815314

  10. Activation of Methanogenesis in Arid Biological Soil Crusts Despite the Presence of Oxygen

    PubMed Central

    Angel, Roey; Matthies, Diethart; Conrad, Ralf

    2011-01-01

    Methanogenesis is traditionally thought to occur only in highly reduced, anoxic environments. Wetland and rice field soils are well known sources for atmospheric methane, while aerated soils are considered sinks. Although methanogens have been detected in low numbers in some aerated, and even in desert soils, it remains unclear whether they are active under natural oxic conditions, such as in biological soil crusts (BSCs) of arid regions. To answer this question we carried out a factorial experiment using microcosms under simulated natural conditions. The BSC on top of an arid soil was incubated under moist conditions in all possible combinations of flooding and drainage, light and dark, air and nitrogen headspace. In the light, oxygen was produced by photosynthesis. Methane production was detected in all microcosms, but rates were much lower when oxygen was present. In addition, the δ13C of the methane differed between the oxic/oxygenic and anoxic microcosms. While under anoxic conditions methane was mainly produced from acetate, it was almost entirely produced from H2/CO2 under oxic/oxygenic conditions. Only two genera of methanogens were identified in the BSC-Methanosarcina and Methanocella; their abundance and activity in transcribing the mcrA gene (coding for methyl-CoM reductase) was higher under anoxic than oxic/oxygenic conditions, respectively. Both methanogens also actively transcribed the oxygen detoxifying gene catalase. Since methanotrophs were not detectable in the BSC, all the methane produced was released into the atmosphere. Our findings point to a formerly unknown participation of desert soils in the global methane cycle. PMID:21655270

  11. Activation energies for oxygen reduction on platinum alloys: theory and experiment.

    PubMed

    Anderson, Alfred B; Roques, Jérôme; Mukerjee, Sanjeev; Murthi, Vivek S; Markovic, Nenad M; Stamenkovic, Vojislav

    2005-01-27

    A combined theoretical and experimental analysis of the electrode potential dependencies of activation energies is presented for the first step in oxygen reduction over platinum and platinum alloy catalysts in both polycrystalline and carbon supported form. Tafel data for several of the catalysts are used to predict potential-dependent activation energies for oxygen reduction over the 0.6-0.9 V range in strong and weak acid. Comparisons with the theoretical curve show good agreement above 0.8 V, suggesting a fairly constant preexponential factor. Arrhenius determinations of activation energies over the 0.7-0.9 V range yield little trend for weak acid, possibly because of the larger uncertainties in the Arrhenius fits, but the strong acid results have smaller uncertainties and for them the measured activation energies trend up with potential. PMID:16851081

  12. Antifungal and Antioxidant Activities of Pyrrolidone Thiosemicarbazone Complexes

    PubMed Central

    Al-Amiery, Ahmed A.; Kadhum, Abdul Amir H.; Mohamad, Abu Bakar

    2012-01-01

    Metal complexes of (Z)-2-(pyrrolidin-2-ylidene)hydrazinecarbothioamide (L) with Cu(II), Co(II), and Ni(II) chlorides were tested against selected types of fungi and were found to have significant antifungal activities. The free-radical-scavenging ability of the metal complexes was determined by their interaction with the stable free radical 2,2′′-diphenyl-1-picrylhydrazyl, and all the compounds showed encouraging antioxidant activities. DFT calculations of the Cu complex were performed using molecular structures with optimized geometries. Molecular orbital calculations provide a detailed description of the orbitals, including spatial characteristics, nodal patterns, and the contributions of individual atoms. PMID:22400016

  13. In Situ Observation of Active Oxygen Species in Fe-Containing Ni-Based Oxygen Evolution Catalysts: The Effect of pH on Electrochemical Activity.

    PubMed

    Trześniewski, Bartek J; Diaz-Morales, Oscar; Vermaas, David A; Longo, Alessandro; Bras, Wim; Koper, Marc T M; Smith, Wilson A

    2015-12-01

    Ni-based oxygen evolution catalysts (OECs) are cost-effective and very active materials that can be potentially used for efficient solar-to-fuel conversion process toward sustainable energy generation. We present a systematic spectroelectrochemical characterization of two Fe-containing Ni-based OECs, namely nickel borate (Ni(Fe)-B(i)) and nickel oxyhydroxide (Ni(Fe)OOH). Our Raman and X-ray absorption spectroscopy results show that both OECs are chemically similar, and that the borate anions do not play an apparent role in the catalytic process at pH 13. Furthermore, we show spectroscopic evidence for the generation of negatively charged sites in both OECs (NiOO(-)), which can be described as adsorbed "active oxygen". Our data conclusively links the OER activity of the Ni-based OECs with the generation of those sites on the surface of the OECs. The OER activity of both OECs is strongly pH dependent, which can be attributed to a deprotonation process of the Ni-based OECs, leading to the formation of the negatively charged surface sites that act as OER precursors. This work emphasizes the relevance of the electrolyte effect to obtain catalytically active phases in Ni-based OECs, in addition to the key role of the Fe impurities. This effect should be carefully considered in the development of Ni-based compounds meant to catalyze the OER at moderate pHs. Complementarily, UV-vis spectroscopy measurements show strong darkening of those catalysts in the catalytically active state. This coloration effect is directly related to the oxidation of nickel and can be an important factor limiting the efficiency of solar-driven devices utilizing Ni-based OECs. PMID:26544169

  14. Unciaphenol, an Oxygenated Analogue of the Bergman Cyclization Product of Uncialamycin Exhibits Anti-HIV Activity.

    PubMed

    Williams, David E; Bottriell, Helen; Davies, Julian; Tietjen, Ian; Brockman, Mark A; Andersen, Raymond J

    2015-11-01

    Unciaphenol (2), an oxygenated analogue of the Bergman cyclization product of the enediyne uncialamycin (1), has been isolated along with 1 from cultures of the actinomycete Streptomyces uncialis. It is proposed that the C-22 OH substituent in 2 might arise from the attack of a nucleophilic oxygen species on the p-benzyne diradical intermediate IA in the Bergman cyclization of 1. 2 shows in vitro anti-HIV activity against viral strains that are resistant to clinically utilized anti-retroviral therapies. PMID:26465962

  15. Using activity theory to study cultural complexity in medical education.

    PubMed

    Frambach, Janneke M; Driessen, Erik W; van der Vleuten, Cees P M

    2014-06-01

    There is a growing need for research on culture, cultural differences and cultural effects of globalization in medical education, but these are complex phenomena to investigate. Socio-cultural activity theory seems a useful framework to study cultural complexity, because it matches current views on culture as a dynamic process situated in a social context, and has been valued in diverse fields for yielding rich understandings of complex issues and key factors involved. This paper explains how activity theory can be used in (cross-)cultural medical education research. We discuss activity theory's theoretical background and principles, and we show how these can be applied to the cultural research practice by discussing the steps involved in a cross-cultural study that we conducted, from formulating research questions to drawing conclusions. We describe how the activity system, the unit of analysis in activity theory, can serve as an organizing principle to grasp cultural complexity. We end with reflections on the theoretical and practical use of activity theory for cultural research and note that it is not a shortcut to capture cultural complexity: it is a challenge for researchers to determine the boundaries of their study and to analyze and interpret the dynamics of the activity system. PMID:24590549

  16. Highly oxygenated triterpenoids from the roots of Schisandra chinensis and their anti-inflammatory activities.

    PubMed

    Song, Qiu-Yan; Gao, Kun; Nan, Zhi-Biao

    2016-01-01

    A new highly oxygenated triterpenoid, schinchinenlactone D (1), and three known compounds (2-4) were isolated from the roots of Schisandra chinensis. Their structures were determined by combining the spectroscopic analysis with the theoretical computations. The anti-inflammatory activities of compounds 1-4 were evaluated, and compound 3 exhibits the most significant activity in the inhibition of NO production with an IC50 value of 10.6 μM. PMID:26313467

  17. Oxygen isotopic systematics of an open-system magma chamber:. An example from the Freetown Layered Complex of Sierra Leone

    NASA Astrophysics Data System (ADS)

    Chalokwu, Christopher I.; Ripley, Edward M.; Park, Young-Rok

    1999-03-01

    The Freetown Layered Complex of Sierra Leone is a 7-km thick, rift-related tholeiitic intrusion that formed ˜193 Ma ago during the opening of the middle Atlantic Ocean. The Complex was emplaced above Archean basement gneisses, granulites, and schists of the Kasila Group at pressures of 2.8 to 5.1 kbar. The δ 18O values of bulk cumulates (5.5-6.7), separated plagioclase (5.7-6.0), olivine (5.0-5.7), and clinopyroxene (5.1-5.8) spanning the entire stratigraphic section indicate that the Complex has preserved its primary magmatic oxygen isotopic composition. The δ 18O values of whole-rocks are uniform in Zone 1 (average = 5.74 ± 0.01) but vary widely in Zones 2 and 3 (average = 6.18 ± 0.52 and 5.71 ± 0.32, respectively). Variations in whole-rock δ 18O with stratigraphic height correlate well with plagioclase mode, with δ 18O values being highest in the strongly laminated anorthosites of Zones 2 and 3, and lowest in olivine gabbro from the cyclically layered subzone of Zone 3. The overall pattern of oxygen isotopic variation with stratigraphic height in the intrusion appears to the related to the accumulation of high-δ 18O, plagioclase-rich rocks that are overlain by low-δ 18O, olivine or pyroxene-rich rock types. Fractional crystallization in combination with mineral accumulation can explain the observed oxygen isotopic variations in the Complex. Oxygen isotopic thermometry yields equilibration temperatures of 1040 to 1290°C, which are similar to temperatures (1045 to 1381°C) estimated from the plagioclase-liquid thermometer applied to the Freetown bulk magma for each zone obtained by geochemical summation. The oxygen isotopic temperatures are highest where major influxes of new magmas have occurred, indicating negligible subsolidus resetting of mineral compositions. Contemporary diabase dikes intruding the Complex have whole-rock and plagioclase δ 18O values of 6.6 and 6.7, respectively, suggesting minimal interaction of the dikes with hydrothermal

  18. Oxovanadium(V) tetrathiacalix[4]arene complexes and their activity as oxidation catalysts.

    PubMed

    Hoppe, Elke; Limberg, Christian

    2007-01-01

    With the aim of modeling reactive moieties and relevant intermediates on the surfaces of vanadium oxide based catalysts during oxygenation/dehydrogenation of organic substrates, mono- and dinuclear vanadium oxo complexes of doubly deprotonated p-tert-butylated tetrathiacalix[4]arene (H4TC) have been synthesized and characterized: PPh4[(H2TC)VOCl(2)] (1) and (PPh4)2[{(H2TC)V(O)(mu-O)}2] (2). According to the NMR spectra of the dissolved complexes they both retain the structures adopted in the crystalline state, as revealed by single-crystal X-ray crystallography. Compounds 1 and 2 were tested as catalysts for the oxidation of alcohols with O(2) at 80 degrees C. Both 1 and 2 efficiently catalyze the oxidation of benzyl alcohol, crotyl alcohol, 1-phenyl-1-propanol, and fluorenol, and in most cases dinuclear complex 2 is more active than mononuclear complex 1. Moreover, the two thiacalixarene complexes 1 and 2 are in many instances more active than oxovanadium(V) complexes containing "classical" calixarene ligands tested previously. Complexes 1 and 2 also show significant activity in the oxidation of dihydroanthracene. Further investigations led to the conclusion that 1 acts as precatalyst that is converted to the active species PPh4[(TC)V==O] (3) at 80 degrees C by double intramolecular HCl elimination. For complex 2, the results of mechanistic investigations indicated that the oxidation chemistry takes place at the bridging oxo ligands and that the two vanadium centers cooperate during the process. The intermediate (PPh4)2[{H2TCV(O)}2(mu-OH)(mu-OC13H9)] (4) was isolated and characterized, also with respect to its reactivity, and the results afforded a mechanistic proposal for a reasonable catalytic cycle. The implications which these findings gathered in solution may have for oxidation mechanisms on the surfaces of V-based heterogeneous catalysts are discussed. PMID:17566134

  19. Combinatorial Development of Water Splitting Catalysts Based on the Oxygen Evolving Complex of Photosystem II

    SciTech Connect

    Woodbury, Neal

    2010-03-31

    The use of methods to create large arrays of potential catalysts for the reaction H2O ½ O2 + 2H+ on the anode of an electrolysis system were investigated. This reaction is half of the overall reaction involved in the splitting of water into hydrogen and oxygen gas. This method consisted of starting with an array of electrodes and developing patterned electrochemical approaches for creating a different, defined peptide at each position in the array. Methods were also developed for measuring the rate of reaction at each point in the array. In this way, the goal was to create and then tests many thousands of possible catalysts simultaneously. This type of approach should lead to an ability to optimize catalytic activity systematically, by iteratively designing and testing new libraries of catalysts. Optimization is important to decrease energy losses (over-potentials) associated with the water splitting reaction and thus for the generation of hydrogen. Most of the efforts in this grant period were focused on developing the chemistry and analytical methods required to create pattern peptide formation either using a photolithography approach or an electrochemical approach for dictating the positions of peptide bond formation. This involved testing a large number of different reactions and conditions. We have been able to find conditions that have allowed us to pattern peptide bond formation on both glass slides using photolithographic methods and on electrode arrays made by the company Combimatrix. Part of this effort involved generating novel approaches for performing mass spectroscopy directly from the patterned arrays. We have also been able to demonstrate the ability to measure current at each electrode due to electrolysis of water. This was performed with customized instrumentation created in collaboration with Combimatrix. In addition, several different molecular designs for peptides that bound metals (primarily Mn) were developed and synthesized and metal

  20. Tuning the activity of Pt(111) for oxygen electroreduction by subsurface alloying.

    PubMed

    Stephens, Ifan E L; Bondarenko, Alexander S; Perez-Alonso, Francisco J; Calle-Vallejo, Federico; Bech, Lone; Johansson, Tobias P; Jepsen, Anders K; Frydendal, Rasmus; Knudsen, Brian P; Rossmeisl, Jan; Chorkendorff, Ib

    2011-04-13

    To enable the development of low temperature fuel cells, significant improvements are required to the efficiency of the Pt electrocatalysts at the cathode, where oxygen reduction takes place. Herein, we study the effect of subsurface solute metals on the reactivity of Pt, using a Cu/Pt(111) near-surface alloy. Our investigations incorporate electrochemical measurements, ultrahigh vacuum experiments, and density functional theory. Changes to the OH binding energy, ΔE(OH), were monitored in situ and adjusted continuously through the subsurface Cu coverage. The incorporation of submonolayer quantities of Cu into Pt(111) resulted in an 8-fold improvement in oxygen reduction activity. The most optimal catalyst for oxygen reduction has an ΔE(OH) ≈ 0.1 eV weaker than that of pure Pt, validating earlier theoretical predictions. PMID:21417329

  1. Effects of oxygen concentration on the nitrifying activity of an aerobic hybrid granular sludge reactor.

    PubMed

    Filali, Ahlem; Bessiere, Yolaine; Sperandio, Mathieu

    2012-01-01

    The aim of the work was to quantify the influence of the simultaneous presence of flocs and granules in the nitrifying activity in a sequencing batch airlift reactor (SBAR). The nitrification rate and oxygen limitation of flocs, granules and hybrid sludge was investigated using respirometric assays at different dissolved oxygen concentrations. The spatial distribution of Ammonium Oxidizing Bacteria (AOB) and Nitrite Oxidizing Bacteria (NOB) was investigated using fluorescence in situ hybridization (FISH). Results showed that the nitrification rate was much less sensitive to oxygen limitation in systems containing a fraction of flocs than in pure granular sludge. Ammonium Oxidizing Bacteria (AOB) were found to be distributed in similar quantities in flocs and granules whereas the Nitrite Oxidizing Bacteria (NOB) were located preferentially in granules. This study showed that the presence of flocs with granules could increase the robustness of the process to transitory reductions of aeration. PMID:22233907

  2. Theoretical study of the multiline EPR signal from the S2 state of the oxygen evolving complex of photosystem II

    PubMed Central

    Bonvoisin, Jacques; Blondin, Geneviève; Girerd, Jean-Jacques; Zimmermann, Jean-Luc

    1992-01-01

    The Oxygen evolving complex of plant photosystem II is made of a manganese cluster that gives rise to a low temperature EPR multiline signal in the S2 oxidation state. The origin of this EPR signal has been addressed with respect to the question of the magnetic couplings between the electron and nuclear spins of the four possible Mn ions that make up this complex. Considering Mn(III) and Mn(IV) as the only possible oxidation states present in the S2 state, and no large anisotropy of the magnetic tensors, the breadths of the EPR spectra calculated for dimers and trimers with S = ½ have been compared with that of the biological site. It is concluded that neither a dinuclear nor a trinuclear complex made of Mn(III) and Mn(IV) can be responsible for the multiline signal; but that, by contrast, a tetranuclear Mn complex can be the origin of this signal. The general shape of the experimental spectrum, its particular hyperfine pattern, the positions of most of the hyperfine lines and their relative intensities can be fit by a tetramer model described by the following six fitting parameters: g ≈ 1.987, A1 ≈ 122.4 10-4 cm-1, A2 ≈ 87.2 10-4 cm-1, A3 ≈ 81.6 10-4 cm-1, A4 ≈ 19.1 10-4 cm-1 and δH = 24.5 G. A second model described by parameters very close to those given above except for A4 ≈ 77.5 10-4 cm-1 gives an equally good fit. However, no other set of parameters gives an EPR spectrum that reproduces the hyperfine pattern of the S2 multiline signal. This demonstrates that in the S2 state of the oxygen evolving complex, the four manganese ions are organized in a magnetic tetramer. PMID:19431827

  3. Anticancer Activity Studies of Ruthenium(II) Complex Toward Human Osteosarcoma HOS Cells.

    PubMed

    Zhu, Jian-Wei; Liu, Si-Hong; Zhang, Gui-Qiang; Xu, Hui-Hua; Wang, Yu-Xuan; Wu, Yong; Liu, Ya-Min; Wang, Yan; Liang, Jun-Bo; Guo, Qi-Feng

    2016-08-01

    A new Ru(II) complex [Ru(dmp)2(NMIP)](ClO4)2 (dmp = 2,9-dimethyl-1,10-phenanthroline, NMIP = 2'-(2″-nitro-3″,4″-methylenedioxyphenyl)imidazo[4',5'-f][1,10]-phenanthroline) was synthesized and characterized by elemental analysis, ESI-MS and (1)H NMR. The cytotoxic activity of the complex against MG-63, U2OS, HOS, and MC3T3-e1 cell lines was investigated by MTT method. The complex shows moderate cytotoxicity toward HOS (IC50 = 35.6 ± 2.6 µM) and MC3T3-e1 (IC50 = 41.6 ± 2.8 µM) cell lines. The morphological studies show that the complex can induce apoptosis in HOS cells and cause an increase of reactive oxygen species levels and a decrease in the mitochondrial membrane potential. The cell cycle distribution demonstrates that the complex inhibits the cell growth at S phase. Additionally, the antitumor activity in vivo reveals that the complex can induce a decrease in tumor weight. PMID:27007877

  4. {sup 35}Mn ESE-ENDOR of a mixed valence Mn(III)Mn(IV) complex: Comparison with the Mn cluster of the photosynthetic oxygen-evolving complex

    SciTech Connect

    Randall, D.W.; Sturgeon, B.E.; Ball, J.A.; Lorigan, G.A.; Chan, M.K.; Britt, R.D.; Klein, M.P. |; Armstrong, W.H.

    1995-11-29

    Analysis of {sup 55}Mn electron spin echo-electron nuclear double resonance (ESE-ENDOR) spectra obtained on a dinuclear mixed valence Mn(III)Mn(IV) complex [di-{mu}-oxotetrakis(2, 2`-bipyridine)dimanganese(III,IV)] (1) reveals the hyperfine and nuclear quadrupolar parameters for the spin I=5/2 {sup 55}Mn nucleus of both Mn(III) and Mn(IV) ions. The {sup 55}Mn ESE-ENDOR data obtained on the g = 2 Mn multiline EPR signal of the S{sub 2} state of the photosystem II oxygen-evolving complex demonstrate that this EPR signal cannot arise from a dinuclear Mn(III)-Mn(IV) center. The ENDOR spectra are consistent with a tetranuclear Mn cluster origin for the photosystem II multiline EPR signal. 75 refs., 7 figs., 2 tabs.

  5. Non-destructive measurement of carbonic anhydrase activity and the oxygen isotope composition of soil water

    NASA Astrophysics Data System (ADS)

    Jones, Sam; Sauze, Joana; Ogée, Jérôme; Wohl, Steven; Bosc, Alexandre; Wingate, Lisa

    2016-04-01

    Carbonic anhydrases are a group of metalloenzymes that catalyse the hydration of aqueous carbon dioxide (CO2). The expression of carbonic anhydrase by bacteria, archaea and eukarya has been linked to a variety of important biological processes including pH regulation, substrate supply and biomineralisation. As oxygen isotopes are exchanged between CO2 and water during hydration, the presence of carbonic anhydrase in plants and soil organisms also influences the oxygen isotope budget of atmospheric CO2. Leaf and soil water pools have distinct oxygen isotope compositions, owing to differences in pool sizes and evaporation rates, which are imparted on CO2during hydration. These differences in the isotopic signature of CO2 interacting with leaves and soil can be used to partition the contribution of photosynthesis and soil respiration to net terrestrial CO2 exchange. However, this relies on our knowledge of soil carbonic anhydrase activity and currently, the prevalence and function of these enzymes in soils is poorly understood. Isotopic approaches used to estimate soil carbonic anhydrase activity typically involve the inversion of models describing the oxygen isotope composition of CO2 fluxes to solve for the apparent, potentially catalysed, rate of oxygen exchange during hydration. This requires information about the composition of CO2 in isotopic equilibrium with soil water obtained from destructive, depth-resolved soil water sampling. This can represent a significant challenge in data collection given the considerable potential for spatial and temporal variability in the isotopic composition of soil water and limited a priori information with respect to the appropriate sampling resolution and depth. We investigated whether we could circumvent this requirement by constraining carbonic anhydrase activity and the composition of soil water in isotopic equilibrium with CO2 by solving simultaneously the mass balance for two soil CO2 steady states differing only in the

  6. Increased oxygen consumption following activation of brain: theoretical footnotes using spectroscopic data from barrel cortex.

    PubMed

    Mayhew, J; Johnston, D; Martindale, J; Jones, M; Berwick, J; Zheng, Y

    2001-06-01

    Optical imaging spectroscopy (OIS) and laser Doppler flowmetry (LDF) data sequences from anesthetized rats were used to determine the relationship between changes in oxy-and deoxygenated hemoglobin concentration and changes in blood volume and flow in the presence and absence of stimulation. The data from Jones et al. (accompanying paper) were used to explore the differences between two theoretical models of flow activation coupling. The essential difference between the two models is the extension of the model of Buxton and Frank by Hyder et al. (1998, J. Appl. Physiol. 85: 554--564) to incorporate change in capillary diffusivity coupled to flow. In both models activation-increased flow changes increase oxygen transport from the capillary; however, in Hyder et al.'s model the diffusivity of the capillary itself is increased. Hyder et al. proposed a parameter (Omega), a scaling "constant" linking increased blood flow and oxygen "diffusivity" in the capillary bed. Thus, in Buxton and Frank's theory, Omega = 0; i.e., there are no changes in diffusivity. In Hyder et al.'s theory, 0 < Omega < 1, and changes in diffusivity are assumed to be linearly related to flow changes. We elaborate the theoretical position of both models to show that, in principle, the different predictions from the two theories can be evaluated using optical imaging spectroscopy data. We find that both theoretical positions have limitations when applied to data from brief stimulation and when applied to data from mild hypercapnia. In summary, the analysis showed that although Hyder et al.'s proposal that diffusivity increased during activation did occur; it was shown to arise from an implementation of Buxton and Frank's theory under episodes of brief stimulation. The results also showed that the scaling parameter Omega is not a constant as the Hyder et al. model entails but in fact varies over the time course of the flow changes. Data from experiments in which mild hypercapnia was administered also

  7. Scavenging activity of "beta catechin" on reactive oxygen species generated by photosensitization of riboflavin.

    PubMed

    Kumari, M V; Yoneda, T; Hiramatsu, M

    1996-05-01

    "beta CATECHIN", a preparation containing green tea extract, ascorbic acid, sunflower seed extract, dunaliella carotene and natural vitamin E, has been designed as a model "universal antioxidant" that offers protection via its scavenging action on a wide range of free radicals, both water-soluble and fat-soluble. Reactive oxygen species like singlet oxygen, hydroxyl and superoxide radicals, are often generated in biological systems during photosensitized oxidation reactions. We report on the simultaneous effect of "beta CATECHIN" on active oxygen species generated during the photosensitized oxidation of riboflavin using 2,2,6,6-tetramethyl-4-piperidone (TMPD) as a "spin-trapping" agent. The intensities of the resulting stable nitroxide radical adduct, 2,2,6,6-tetramethyl-4-piperidone-1-oxyl (TEMPONE), were detected by electron spin resonance (ESR) spectroscopy. Results show simultaneous, nonspecific and complete scavenging action of reactive oxygen species generated in our in vitro model system by "beta CATECHIN". It is therefore suggested that "beta CATECHIN" could offer protection against free radical insult and in preventing cancer and other diseases that are mediated by reactive oxygen species. PMID:8739038

  8. Atrial natriuretic peptide regulates lipid mobilization and oxygen consumption in human adipocytes by activating AMPK

    SciTech Connect

    Souza, Sandra C.; Chau, Mary D.L.; Yang, Qing; Gauthier, Marie-Soleil; Clairmont, Kevin B.; Wu, Zhidan; Gromada, Jesper; Dole, William P.

    2011-07-08

    Highlights: {yields} Treatment of differentiated human adipocytes with atrial natriuretic peptide (ANP) increased lipolysis and oxygen consumption by activating AMP-activated protein kinase (AMPK). {yields} ANP stimulated lipid mobilization by selective activation of the alpha2 subunit of AMPK and increased energy utilization through activation of both the alpha1 and alpha2 subunits of AMPK. {yields} ANP enhanced adipocyte mitochondrial oxidative capacity as evidenced by induction of oxidative mitochondrial genes and increase in oxygen consumption. {yields} Exposure of human adipocytes to fatty acids and (TNF{alpha}) induced insulin resistance and decreased expression of mitochondrial genes which was restored to normal by ANP. -- Abstract: Atrial natriuretic peptide (ANP) has been shown to regulate lipid and carbohydrate metabolism providing a possible link between cardiovascular function and metabolism by mediating the switch from carbohydrate to lipid mobilization and oxidation. ANP exerts a potent lipolytic effect via cGMP-dependent protein kinase (cGK)-I mediated-stimulation of AMP-activated protein kinase (AMPK). Activation of the ANP/cGK signaling cascade also promotes muscle mitochondrial biogenesis and fat oxidation. Here we demonstrate that ANP regulates lipid metabolism and oxygen utilization in differentiated human adipocytes by activating the alpha2 subunit of AMPK. ANP treatment increased lipolysis by seven fold and oxygen consumption by two fold, both of which were attenuated by inhibition of AMPK activity. ANP-induced lipolysis was shown to be mediated by the alpha2 subunit of AMPK as introduction of dominant-negative alpha2 subunit of AMPK attenuated ANP effects on lipolysis. ANP-induced activation of AMPK enhanced mitochondrial oxidative capacity as evidenced by a two fold increase in oxygen consumption and induction of mitochondrial genes, including carnitine palmitoyltransferase 1A (CPT1a) by 1.4-fold, cytochrome C (CytC) by 1.3-fold, and

  9. Activation of gas-phase uranyl: from an oxo to a nitrido complex.

    PubMed

    Gong, Yu; Vallet, Valérie; Michelini, Maria del Carmen; Rios, Daniel; Gibson, John K

    2014-01-01

    The uranyl moiety, UO2(2+), is ubiquitous in the chemistry of uranium, the most prevalent actinide. Replacing the strong uranium-oxygen bonds in uranyl with other ligands is very challenging, having met with only limited success. We report here uranyl oxo bond activation in the gas phase to form a terminal nitrido complex, a previously elusive transformation. Collision induced dissociation of gas-phase UO2(NCO)Cl2(-) in an ion trap produced the nitrido oxo complex, NUOCl2(-), and CO2. NUOCl2(-) was computed by DFT to have Cs symmetry and a singlet ground state. The computed bond length and order indicate a triple U-N bond. Endothermic activation of UO2(NCO)Cl2(-) to produce NUOCl2(-) and neutral CO2 was computed to be thermodynamically more favorable than NCO ligand loss. Complete reaction pathways for the CO2 elimination process were computed at the DFT level. PMID:24354492

  10. [Light-induced production and consumption of oxygen by chloroplasts: activation and inhibition].

    PubMed

    Chan Van, N i; Nikandrov, V V; Brin, G P; Krasnovskii, A A

    1977-07-01

    Light-induced production and consumption of oxygen by pea chloroplasts are activated at certain concentrations of the solvents (diethyl ester, methyl alcohol, dimethylsulfoxide) and detergent Triton X-100. At higher concentrations of the compounds studied both reactions are inhibited. The uncouplers (methylamine and carbonyl cyanide-3-chlorophenylhydrazone) activate these processes. The agents studied have a similar effect on the processes of light-induced production and consumption of oxygen, which are limited by a common link bound to the phosphorylation site in photosystem I. The effects observed suggest that the inhibition may be due to inhibition of photosystem II, whereas the activation may be largely due to an action on photosystem I. PMID:907797

  11. LASERS: Efficient chemical oxygen — iodine laser with a high total pressure of the active medium

    NASA Astrophysics Data System (ADS)

    Zagidullin, M. V.; Nikolaev, V. D.; Svistun, M. I.; Khvatov, N. A.; Heiger, G. D.; Madden, T. J.

    2001-01-01

    A new concept of obtaining a high total pressure of the active medium of a chemical oxygen — iodine laser (OIL) is proposed and verified. The nozzle unit of the laser consists of the alternating vertical arrays of cylindrical nozzles to produce high-pressure nitrogen jets, plane slotted nozzles for the flow of O2(1Δ) oxygen, and vertical arrays of cylindrical nozzles to inject the N2 — I2 mixture between the first two streams. For a molar chlorine flow rate of 39.2 mmol s-1, the output power was 700 W and the chemical efficiency was 19.7 %. The combined use of the ejector nozzle unit proposed to obtain the active medium and a super-sonic diffuser allows a significant simplification of the ejection system for the exhaust active medium of the OIL.

  12. Catalytic activity trends of oxygen reduction reaction for nonaqueous Li-air batteries.

    PubMed

    Lu, Yi-Chun; Gasteiger, Hubert A; Shao-Horn, Yang

    2011-11-30

    We report the intrinsic oxygen reduction reaction (ORR) activity of polycrystalline palladium, platinum, ruthenium, gold, and glassy carbon surfaces in 0.1 M LiClO(4) 1,2-dimethoxyethane via rotating disk electrode measurements. The nonaqueous Li(+)-ORR activity of these surfaces primarily correlates to oxygen adsorption energy, forming a "volcano-type" trend. The activity trend found on the polycrystalline surfaces was in good agreement with the trend in the discharge voltage of Li-O(2) cells catalyzed by nanoparticle catalysts. Our findings provide insights into Li(+)-ORR mechanisms in nonaqueous media and design of efficient air electrodes for Li-air battery applications. PMID:22044022

  13. Trend in the Catalytic Activity of Transition Metals for the Oxygen Reduction Reaction by Lithium

    SciTech Connect

    Dathar, Gopi Krishna Phani; Shelton Jr, William Allison; Xu, Ye

    2012-01-01

    Periodic density functional theory (DFT) calculations indicate that the intrinsic activity of Au, Ag, Pt, Pd, Ir, and Ru for the oxygen reduction reaction by Li (Li-ORR) forms a volcano-like trend with respect to the adsorption energy of oxygen, with Pt and Pd being the most active. The trend is based on two mechanisms: the reduction of molecular O{sub 2} on Au and Ag and of atomic O on the remaining metals. Step edges are found to be more active for catalyzing the Li-ORR than close-packed surfaces. Our findings identify important considerations in the design of catalyst-promoted air cathodes for nonaqueous Li-air batteries.

  14. Improved oxygen reduction activity on Pt3Ni(111) via increased surface site availability.

    PubMed

    Stamenkovic, Vojislav R; Fowler, Ben; Mun, Bongjin Simon; Wang, Guofeng; Ross, Philip N; Lucas, Christopher A; Marković, Nenad M

    2007-01-26

    The slow rate of the oxygen reduction reaction (ORR) in the polymer electrolyte membrane fuel cell (PEMFC) is the main limitation for automotive applications. We demonstrated that the Pt3Ni(111) surface is 10-fold more active for the ORR than the corresponding Pt(111) surface and 90-fold more active than the current state-of-the-art Pt/C catalysts for PEMFC. The Pt3Ni(111) surface has an unusual electronic structure (d-band center position) and arrangement of surface atoms in the near-surface region. Under operating conditions relevant to fuel cells, its near-surface layer exhibits a highly structured compositional oscillation in the outermost and third layers, which are Pt-rich, and in the second atomic layer, which is Ni-rich. The weak interaction between the Pt surface atoms and nonreactive oxygenated species increases the number of active sites for O2 adsorption. PMID:17218494

  15. Antiparasitic activities of novel ruthenium/lapachol complexes.

    PubMed

    Barbosa, Marília I F; Corrêa, Rodrigo S; de Oliveira, Katia Mara; Rodrigues, Claudia; Ellena, Javier; Nascimento, Otaciro R; Rocha, Vinícius P C; Nonato, Fabiana R; Macedo, Taís S; Barbosa-Filho, José Maria; Soares, Milena B P; Batista, Alzir A

    2014-07-01

    The present study describes the synthesis, characterization, antileishmanial and antiplasmodial activities of novel diimine/(2,2'-bipyridine (bipy), 1,10-phenanthroline (phen), 4,4'-methylbipyridine (Me-bipy) and 4,4'-methoxybipyridine (MeO-bipy)/phosphine/ruthenium(II) complexes containing lapachol (Lap, 2-hydroxy-3-(3-33 methyl-2-buthenyl)-1,4-naphthoquinone) as bidentate ligand. The [Ru(Lap)(PPh3)2(bipy)]PF6 (1), [Ru(Lap)(PPh3)2(Me-bipy)]PF6 (2), [Ru(Lap)(PPh3)2(MeO-bipy)]PF6(3) and[Ru(Lap)(PPh3)2(phen)]PF6 (4) complexes, PPh3=triphenylphospine, were synthesized from the reactions of cis-[RuCl2(PPh3)2(X-bipy)] or cis-[RuCl2(PPh3)2(phen)], with lapachol. The [RuCl2(Lap)(dppb)] (5) [dppb=1,4-bis(diphenylphosphine)butane] was synthesized from the mer-[RuCl3(dppb)(H2O)] complex. The complexes were characterized by elemental analysis, molar conductivity, infrared and UV-vis spectroscopy, (31)P{(1)H} and (1)H NMR, and cyclic voltammetry. The Ru(III) complex, [RuCl2(Lap)(dppb)], was also characterized by the EPR technique. The structure of the complexes [Ru(Lap)(PPh3)2(bipy)]PF6 and [RuCl2(Lap)(dppb)] was elucidated by X-ray diffraction. The evaluation of the antiparasitic activities of the complexes against Leishmania amazonensis and Plasmodium falciparum demonstrated that lapachol-ruthenium complexes are more potent than the free lapachol. The [RuCl2(Lap)(dppb)] complex is the most potent and selective antiparasitic compound among the five new ruthenium complexes studied in this work, exhibiting an activity comparable to the reference drugs. PMID:24727183

  16. Tuning the catalytic activity of graphene nanosheets for oxygen reduction reaction via size and thickness reduction.

    PubMed

    Benson, John; Xu, Qian; Wang, Peng; Shen, Yuting; Sun, Litao; Wang, Tanyuan; Li, Meixian; Papakonstantinou, Pagona

    2014-11-26

    Currently, the fundamental factors that control the oxygen reduction reaction (ORR) activity of graphene itself, in particular, the dependence of the ORR activity on the number of exposed edge sites remain elusive, mainly due to limited synthesis routes of achieving small size graphene. In this work, the synthesis of low oxygen content (<2.5±0.2 at. %), few layer graphene nanosheets with lateral dimensions smaller than a few hundred nanometers were achieved using a combination of ionic liquid assisted grinding of high purity graphite coupled with sequential centrifugation. We show for the first time that the graphene nanosheets possessing a plethora of edges exhibited considerably higher electron transfer numbers compared to the thicker graphene nanoplatelets. This enhanced ORR activity was accomplished by successfully exploiting the plethora of edges of the nanosized graphene as well as the efficient electron communication between the active edge sites and the electrode substrate. The graphene nanosheets were characterized by an onset potential of -0.13 V vs Ag/AgCl and a current density of -3.85 mA/cm2 at -1 V, which represent the best ORR performance ever achieved from an undoped carbon based catalyst. This work demonstrates how low oxygen content nanosized graphene synthesized by a simple route can considerably impact the ORR catalytic activity and hence it is of significance in designing and optimizing advanced metal-free ORR electrocatalysts. PMID:25334050

  17. Mitochondrial impairment by PPAR agonists and statins identified via immunocaptured OXPHOS complex activities and respiration.

    PubMed

    Nadanaciva, Sashi; Dykens, James A; Bernal, Autumn; Capaldi, Roderick A; Will, Yvonne

    2007-09-15

    Mitochondrial impairment is increasingly implicated in the etiology of toxicity caused by some thiazolidinediones, fibrates, and statins. We examined the effects of members of these drug classes on respiration of isolated rat liver mitochondria using a phosphorescent oxygen sensitive probe and on the activity of individual oxidative phosphorylation (OXPHOS) complexes using a recently developed immunocapture technique. Of the six thiazolidinediones examined, ciglitazone, troglitazone, and darglitazone potently disrupted mitochondrial respiration. In accord with these data, ciglitazone and troglitazone were also potent inhibitors of Complexes II+III, IV, and V, while darglitazone predominantly inhibited Complex IV. Of the six statins evaluated, lovastatin, simvastatin, and cerivastatin impaired mitochondrial respiration the most, with simvastatin and lovastatin impairing multiple OXPHOS Complexes. Within the class of fibrates, gemfibrozil more potently impaired respiration than fenofibrate, clofibrate, or ciprofibrate. Gemfibrozil only modestly inhibited Complex I, fenofibrate inhibited Complexes I, II+III, and V, and clofibrate inhibited Complex V. Our findings with the two complementary methods indicate that (1) some members of each class impair mitochondrial respiration, whereas others have little or no effect, and (2) the rank order of mitochondrial impairment accords with clinical adverse events observed with these drugs. Since the statins are frequently co-prescribed with the fibrates or thiazolidinediones, various combinations of these three drug classes were also analyzed for their mitochondrial effects. In several cases, the combination additively uncoupled or inhibited respiration, suggesting that some combinations are more likely to yield clinically relevant drug-induced mitochondrial side effects than others. PMID:17658574

  18. A series of binuclear lanthanide(III) complexes: Crystallography, antimicrobial activity and thermochemistry properties studies

    NASA Astrophysics Data System (ADS)

    Zhang, Ying-Ying; Ren, Ning; Xu, Su-Ling; Zhang, Jian-Jun; Zhang, Da-Hai

    2015-02-01

    A series of novel lanthanide complexes with the general formula [Ln(3,4-DClBA)3phen]2 (Ln = Ho(1), Nd(2), Sm(3), Dy(4), Eu(5), Tb(6), Yb(7) and Er(8), 3,4-DClBA = 3,4-dichlorobenzoate, phen = 1,10-phenanthroline) were prepared at room temperature and characterized. The crystal structures of complexes 1-8 have been determined by single crystal X-ray diffraction. These complexes are isomorphous and lanthanide ions are all eight-coordinated to oxygen atoms and nitrogen atoms with distorted square-antiprism geometry. The thermal decomposition mechanism and TG-FTIR spectra of gaseous products of thermal decomposition processes for complexes 1-8 were acquired through TG/DSC-FTIR system. The heat capacities of complexes 1-8 were measured using DSC technology and fitted to a polynomial equation by the least-squares method. Complexes 3-6 display characteristic lanthanide emission bands in the visible region. Meanwhile, these complexes exhibit in good antimicrobial activity against Candida albicans, Escherichia coli, and Staphylococcus aureu.

  19. Mitochondrial impairment by PPAR agonists and statins identified via immunocaptured OXPHOS complex activities and respiration

    SciTech Connect

    Nadanaciva, Sashi; Dykens, James A.; Bernal, Autumn; Capaldi, Roderick A.; Will, Yvonne

    2007-09-15

    Mitochondrial impairment is increasingly implicated in the etiology of toxicity caused by some thiazolidinediones, fibrates, and statins. We examined the effects of members of these drug classes on respiration of isolated rat liver mitochondria using a phosphorescent oxygen sensitive probe and on the activity of individual oxidative phosphorylation (OXPHOS) complexes using a recently developed immunocapture technique. Of the six thiazolidinediones examined, ciglitazone, troglitazone, and darglitazone potently disrupted mitochondrial respiration. In accord with these data, ciglitazone and troglitazone were also potent inhibitors of Complexes II + III, IV, and V, while darglitazone predominantly inhibited Complex IV. Of the six statins evaluated, lovastatin, simvastatin, and cerivastatin impaired mitochondrial respiration the most, with simvastatin and lovastatin impairing multiple OXPHOS Complexes. Within the class of fibrates, gemfibrozil more potently impaired respiration than fenofibrate, clofibrate, or ciprofibrate. Gemfibrozil only modestly inhibited Complex I, fenofibrate inhibited Complexes I, II + III, and V, and clofibrate inhibited Complex V. Our findings with the two complementary methods indicate that (1) some members of each class impair mitochondrial respiration, whereas others have little or no effect, and (2) the rank order of mitochondrial impairment accords with clinical adverse events observed with these drugs. Since the statins are frequently co-prescribed with the fibrates or thiazolidinediones, various combinations of these three drug classes were also analyzed for their mitochondrial effects. In several cases, the combination additively uncoupled or inhibited respiration, suggesting that some combinations are more likely to yield clinically relevant drug-induced mitochondrial side effects than others.

  20. In vitro anticancer activities of Schiff base and its lanthanum complex

    NASA Astrophysics Data System (ADS)

    Neelima; Poonia, Kavita; Siddiqui, Sahabjada; Arshad, Md; Kumar, Dinesh

    2016-02-01

    Schiff base metal complexes are well-known to intercalate DNA. The La(III) complexes have been synthesized such that they hinder with the role of the topoisomerases, which control the topology of DNA during the cell-division cycle. Although several promising chemotherapeutics have been developed, on the basis of Schiff base metal complex DNA intercalating system they did not proceed past clinical trials due to their dose-limiting toxicity. Herein, we discuss an alternative compound, the La(III) complex, [La(L1)2Cl3]·7H2O based on a Schiff base ligand 2,3-dihydro-1H-indolo-[2,3-b]-phenazin-4(5H)-ylidene)benzothiazole-2-amine (L1), and report in vitro cell studies. Results of antitumor activity using cell viability assay, reactive oxygen species (ROS) generation and nuclear condensation in PC-3 (Human, prostate carcinoma) cells show that the metal complex is more potent than ligand. La(III) complexes have been synthesized by reaction of lanthanum(III) salt in 1:2 M ratio with ligands L1 and 3-(ethoxymethylene)-2,3-dihydro-1H-indolo[2,3-b]-phenazin-4(5H)-ylidene)benzathiazole-2-amine (L2) in methanol. The ligands and their La(III) complexes were characterized by molar conductance, magnetic susceptibility, elemental analyses, FT-IR, UV-Vis, 1H/13C NMR, thermogravimetric, XRD, and SEM analysis.

  1. Photoinduced nitric oxide and singlet oxygen release from ZnPC liposome vehicle associated with the nitrosyl ruthenium complex: synergistic effects in photodynamic therapy application.

    PubMed

    Maranho, Daniela Silva; de Lima, Renata Galvão; Primo, Fernando Lucas; da Silva, Roberto Santana; Tedesco, Antonio Claudio

    2009-01-01

    Under continuous photolysis at 675 nm, liposomal zinc phthalocyanine associated with nitrosyl ruthenium complex [Ru(NH.NHq)(tpy)NO](3+) showed the detection and quantification of nitric oxide (NO) and singlet oxygen ((1)O(2)) release. Photophysical and photochemical results demonstrated that the interaction between the nitrosyl ruthenium complex and the photosensitizer can enable an electron transfer process from the photosensitizer to the nitrosyl ruthenium complex which leads to NO release. Synergistic action of both photosensitizers and the nitrosyl ruthenium complex results in the production of reactive oxygen species and reactive nitrogen species, which is a potent oxidizing agent to many biological tissues, in particular neoplastic cells. PMID:19076310

  2. Highly enantioselective oxidative couplings of 2-naphthols catalyzed by chiral bimetallic oxovanadium complexes with either oxygen or air as oxidant.

    PubMed

    Guo, Qi-Xiang; Wu, Zhi-Jun; Luo, Zhi-Bin; Liu, Quan-Zhong; Ye, Jian-Liang; Luo, Shi-Wei; Cun, Lin-Feng; Gong, Liu-Zhu

    2007-11-14

    The chiral bimetallic oxovanadium complexes have been designed for the enantioselective oxidative coupling of 2-naphthols bearing various substituents at C6 and/or C7. The chirality transferring from the amino acid to the axis of the biphenyl in oxovanadium complexes 2 was found to occur with the use of UV and CD spectra and DFT calculation. The homo-coupling reaction with oxygen as the oxidant was promoted by 5 mol % of an oxovanadium complex derived from L-isoleucine and achiral biphenol to afford binaphthols in nearly quantitative yields with high enantioselectivities of up to 98% ee. An oxovanadium complex derived from L-isoleucine and H8-binaphthol is highly efficient at catalyzing the air-oxidized coupling of 2-naphthols with excellent enantioselectivities of up to 97% ee. 51V NMR study shows that the oxovanadium complexes have two vanadium(V) species. Kinetic studies, the cross-coupling reaction, and HRMS spectral studies on the reaction have been carried out and illustrate that two vanadium(V) species are both involved in catalysis and that the coupling reaction undergoes a radical-radical mechanism in an intramolecular manner. Quantum mechanical calculations rationalize the importance of the cooperative effects of the axial chirality matching S-amino acids on the stereocontrol of the oxidative coupling reaction. The application of the transformation in the preparation of chiral ligands and conjugated polymers confirms the importance of the current process in organic synthesis. PMID:17956093

  3. Rapid high-throughput assessment of aerobic bacteria in complex samples by fluorescence-based oxygen respirometry.

    PubMed

    O'Mahony, Fiach C; Papkovsky, Dmitri B

    2006-02-01

    A simple method has been developed for the analysis of aerobic bacteria in complex samples such as broth and food homogenates. It employs commercial phosphorescent oxygen-sensitive probes to monitor oxygen consumption of samples containing bacteria using standard microtiter plates and fluorescence plate readers. As bacteria grow in aqueous medium, at certain points they begin to deplete dissolved oxygen, which is seen as an increase in probe fluorescence above baseline signal. The time required to reach threshold signal is used to either enumerate bacteria based on a predetermined calibration or to assess the effects of various effectors on the growth of test bacteria by comparison with an untreated control. This method allows for the sensitive (down to a single cell), rapid (0.5 to 12 h) enumeration of aerobic bacteria without the need to conduct lengthy (48 to 72 h) and tedious colony counts on agar plates. It also allows for screening a wide range of chemical and environmental samples for their toxicity. These assays have been validated with different bacteria, including Escherichia coli, Micrococcus luteus, and Pseudomonas fluorescens, with the enumeration of total viable counts in broth and industrial food samples (packaged ham, chicken, and mince meat), and comparison with established agar plating and optical-density-at-600-nm assays has been given. PMID:16461677

  4. Strongly coupled Pd nanotetrahedron/tungsten oxide nanosheet hybrids with enhanced catalytic activity and stability as oxygen reduction electrocatalysts.

    PubMed

    Lu, Yizhong; Jiang, Yuanyuan; Gao, Xiaohui; Wang, Xiaodan; Chen, Wei

    2014-08-20

    The design and synthesis of highly active oxygen reduction reaction (ORR) catalysts with strong durability at low cost is extremely desirable but still remains a significant challenge. Here we develop an efficient strategy that utilizes organopalladium(I) complexes containing palladium-palladium bonds as precursors for the synthesis of strongly coupled Pd tetrahedron-tungsten oxide nanosheet hybrids (Pd/W18O49) to improve the electrocatalytic activity and stability of Pd nanocrystals. The hybrid materials are synthesized by direct nucleation, growth, and anchoring of Pd tetrahedral nanocrystals on the in situ-synthesized W18O49 nanosheets. Compared to supportless Pd nanocrystals and W18O49, their hybrids exhibited not only surprisingly high activity but also superior stability to Pt for the ORR in alkaline solutions. X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and electrochemical analyses indicated that the enhanced electrocatalytic activity and durability are associated with the increased number and improved catalytic activity of active sites, which is induced by the strong interaction between the Pd tetrahedrons and W18O49 nanosheet supports. The present study provides a novel strategy for synthesizing hybrid catalysts with strong chemical attachment and electrical coupling between nanocatalysts and supports. The strategy is expected to open up exciting opportunities for developing a novel class of metal-support hybrid nanoelectrocatalysts with improved ORR activity and durability for both fuel cells and metal-air batteries. PMID:25054583

  5. Oxygen deficient ZnO 1-x nanosheets with high visible light photocatalytic activity.

    PubMed

    Guo, Hong-Li; Zhu, Qing; Wu, Xi-Lin; Jiang, Yi-Fan; Xie, Xiao; Xu, An-Wu

    2015-04-28

    Zinc oxide is one of the most important wide-band-gap (3.2 eV) materials with versatile properties, however, it can not be excited by visible light. In this work, we have developed an exquisite and simple way to prepare oxygen-deficient ZnO 1-x nanosheets with a gray-colored appearance and excellent visible light photocatalytic activity. Detailed analysis based on UV-Vis absorption spectra, X-band electron paramagnetic resonance (EPR) spectra, and photoluminescence (PL) spectra confirms the existence of oxygen vacancies in ZnO 1-x. The incorporation of oxygen defects could effectively extend the light absorption of ZnO 1-x into the visible-light region due to the fact that the energy of the localized state is located in the forbidden gap. Thus, our obtained ZnO 1-x shows a higher photodegradation of methyl orange (MO) compared to defect-free ZnO under visible light illumination. Additionally, the high content of ˙OH radicals with a strong photo-oxidation capability over the ZnO 1-x nanosheets significantly contributes to the improvement in the photocatalytic performance. Our oxygen deficient ZnO 1-x sample shows a very high photocatalytic activity for the degradation of MO even after 5 cycles without any obvious decline. The results demonstrate that defect engineering is a powerful tool to enhance the optoelectronic and photocatalytic performances of nanomaterials. PMID:25812132

  6. Complexes trans-Pt(BODIPY)X(PEt3)2: excitation energy-dependent fluorescence and phosphorescence emissions, oxygen sensing and photocatalysis.

    PubMed

    Irmler, Peter; Winter, Rainer F

    2016-06-21

    We report on five new complexes with the general formula trans-Pt(BODIPY)X(PEt3)2 (), where the platinum(ii) ion is σ-bonded to a 4,4-difluoro-4-bora-3a,4a-diaza-s-indacen-8-yl (BODIPY) and an anionic ligand X(-) (X(-) = Cl(-), I(-), NO2(-), NCS(-), CH3(-)). All five complexes were characterized by multinuclear NMR, electronic absorption and luminescence spectroscopy and by X-ray diffraction analysis. Four of these complexes show efficient intersystem crossing (ISC) from an excited singlet state to a BODIPY-centred T1 state and exhibit dual fluorescence and phosphorescence emission from the BODIPY ligand. In , the fluorescence is almost completely quenched, whereas the phosphorescence quantum yield reaches a value of 40%. The rate of ISC and the ratio of phosphorescence to fluorescence emissions depend on the excitation wavelength (i.e. on which specific transition is excited). The performance of these complexes as one-component oxygen sensors and their photocatalytic activities were tested by Stern-Volmer quenching experiments and by monitoring the oxidation of 1,5-dihydroxynaphthalene with (1)O2 generated from the long-lived triplet state of the sensitizer by triplet-triplet annihilation with (3)O2. Exceptionally high (1)O2 generation quantum yields of up to near unity were obtained. PMID:27255789

  7. Photocytotoxic oxovanadium(IV) complexes showing light-induced DNA and protein cleavage activity.

    PubMed

    Sasmal, Pijus K; Saha, Sounik; Majumdar, Ritankar; Dighe, Rajan R; Chakravarty, Akhil R

    2010-02-01

    Oxovanadium(IV) complexes [VO(L)(B)]Cl(2) (1-3), where L is bis(2-benzimidazolylmethyl)amine and B is 1,10-phenanthroline (phen), dipyrido[3,2-d:2',3'-f]quinoxaline (dpq) or dipyrido[3,2-a:2',3'-c]phenazine (dppz), have been prepared, characterized, and their photo-induced DNA and protein cleavage activity studied. The photocytotoxicity of complex 3 has been studied using adenocarcinoma A549 cells. The phen complex 1, structurally characterized by single-crystal X-ray crystallography, shows the presence of a vanadyl group in six-coordinate VON(5) coordination geometry. The ligands L and phen display tridentate and bidentate N-donor chelating binding modes, respectively. The complexes exhibit a d-d band near 740 nm in 15% DMF-Tris-HCl buffer (pH 7.2). The phen and dpq complexes display an irreversible cathodic cyclic voltammetric response near -0.8 V in 20% DMF-Tris-HCl buffer having 0.1 M KCl as supporting electrolyte. The dppz complex 3 exhibits a quasi-reversible voltammogram near -0.6 V (vs SCE) that is assignable to the V(IV)-V(III) couple. The complexes bind to calf thymus DNA giving binding constant values in the range of 6.6 x 10(4)-2.9 x 10(5) M(-1). The binding site size, thermal melting and viscosity binding data suggest DNA surface and/or groove binding nature of the complexes. The complexes show poor "chemical nuclease" activity in dark in the presence of 3-mercaptopropionic acid or hydrogen peroxide. The dpq and dppz complexes are efficient photocleavers of plasmid DNA in UV-A light of 365 nm via a mechanistic pathway that involves formation of both singlet oxygen and hydroxyl radicals. The complexes show significant photocleavage of DNA in near-IR light (>750 nm) via hydroxyl radical pathway. Among the three complexes, the dppz complex 3 shows significant BSA and lysozyme protein cleavage activity in UV-A light of 365 nm via hydroxyl radical pathway. The dppz complex 3 also exhibits photocytotoxicity in non-small cell lung carcinoma/human lung

  8. Synthesis of Optically Active Polystyrene Catalyzed by Monophosphine Pd Complexes.

    PubMed

    Jouffroy, Matthieu; Armspach, Dominique; Matt, Dominique; Osakada, Kohtaro; Takeuchi, Daisuke

    2016-07-11

    Cationic Pd(II) monophosphine complexes derived from α- and β-cyclodextrins (CDs) promote the homopolymerization of styrene under carbon monoxide pressure. Although reversible CO coordination takes place under catalytic conditions according to (13) C NMR studies with (13) C-enriched CO, both complexes catalyze the formation of CO-free styrene polymers. These macromolecules display optical activity as a result of the presence of stereoregular sequences within the overall atactic polymer. PMID:27218801

  9. Hyperbaric oxygen preserves neurotrophic activity of carbon monoxide-exposed astrocytes.

    PubMed

    Jurič, Damijana M; Šuput, Dušan; Brvar, Miran

    2016-06-24

    In astrocytes, carbon monoxide (CO) poisoning causes oxidative stress and mitochondrial dysfunction accompanied by caspase and calpain activation. Impairment in astrocyte function can be time-dependently reduced by hyperbaric (3bar) oxygen (HBO). Due to the central role of astrocytes in maintaining neuronal function by offering neurotrophic support we investigated the hypothesis that HBO therapy may exert beneficial effect on acute CO poisoning-induced impairment in intrinsic neurotrophic activity. Exposure to 3000ppm CO in air followed by 24-72h of normoxia caused a progressive decline of gene expression, synthesis and secretion of nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) to different extent. 1h treatment with 100% oxygen disclosed a pressure- and time-dependent efficacy in preserving astrocytic neurotrophic support. The beneficial effect was most evident when the astrocytes were exposed to HBO 1-5h after exposure to CO. The results further support an active role of hyperbaric, not normobaric, oxygenation in reducing dysfunction of astrocytes after acute CO poisoning. By preserving endogenous neurotrophic activity HBO therapy might promote neuronal protection and thus prevent the occurrence of late neuropsychological sequelae. PMID:27113706

  10. Effect of KOH activation on the formation of oxygen structure in activated carbons synthesized from polymeric precursor.

    PubMed

    Park, Soo-Jin; Jung, Woo-Young

    2002-06-01

    In this work, the influence of KOH activation on the surface chemistry of activated carbons (ACs) synthesized from polystyrene-based cation exchangeable resin (PSI) has been investigated. The surface chemistry of ACs has been characterized by using Fourier transformed infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), pH measurement, and Boehm's titration method. As a result, PSI can be successfully converted into ACs with high porosities. The total oxygen content on the ACs studied increases with increasing the KOH-to-PSI ratio. FT-IR and XPS analyses show that the resulting carbons possess a number of oxygen surface functional groups, such as carbonyl, quinone, phenol, ether, and carboxylic acid groups. The highest oxygen content and acid value are observed at a KOH-to-PSI ratio of 4 (KPS-4). However, its pH and surface basicity are higher than those of a KOH-to-PSI ratio of 2 (KPS-2), indicating the formation of basic species, such as quinone and pyrone groups. Although the oxygen-containing groups with basic character exist in the resulting carbons, all the samples are still acidic in character. PMID:16290638

  11. Why are the 2-oxoacid dehydrogenase complexes so large? Generation of an active trimeric complex.

    PubMed

    Marrott, Nia L; Marshall, Jacqueline J T; Svergun, Dmitri I; Crennell, Susan J; Hough, David W; van den Elsen, Jean M H; Danson, Michael J

    2014-11-01

    The four-component polypeptides of the 2-oxoacid dehydrogenase complex from the thermophilic archaeon Thermoplasma acidophilum assemble to give an active multienzyme complex possessing activity with the branched-chain 2-oxoacids derived from leucine, isoleucine and valine, and with pyruvate. The dihydrolipoyl acyl-transferase (E2) core of the complex is composed of identical trimer-forming units that assemble into a novel 42-mer structure comprising octahedral and icosahedral geometric aspects. From our previously determined structure of this catalytic core, the inter-trimer interactions involve a tyrosine residue near the C-terminus secured in a hydrophobic pocket of an adjacent trimer like a ball-and-socket joint. In the present study, we have deleted the five C-terminal amino acids of the E2 polypeptide (IIYEI) and shown by equilibrium centrifugation that it now only assembles into a trimeric enzyme. This was confirmed by SAXS analysis, although this technique showed the presence of approximately 20% hexamers. The crystal structure of the trimeric truncated E2 core has been determined and shown to be virtually identical with the ones observed in the 42-mer, demonstrating that removal of the C-terminal anchor does not significantly affect the individual monomer or trimer structures. The truncated E2 is still able to bind both 2-oxoacid decarboxylase (E1) and dihydrolipoamide dehydrogenase (E3) components to give an active complex with catalytic activity similar to the native multienzyme complex. This is the first report of an active mini-complex for this enzyme, and raises the question of why all 2-oxoacid dehydrogenase complexes assemble into such large structures. PMID:25088564

  12. Lessons from isolable nickel(I) precursor complexes for small molecule activation.

    PubMed

    Yao, Shenglai; Driess, Matthias

    2012-02-21

    Small-molecule activation by transition metals is essential to numerous organic transformations, both biological and industrial. Creating useful metal-mediated activation systems often depends on stabilizing the metal with uncommon low oxidation states and low coordination numbers. This provides a redox-active metal center with vacant coordination sites well suited for interacting with small molecules. Monovalent nickel species, with their d(9) electronic configuration, are moderately strong one-electron reducing agents that are synthetically attractive if they can be isolated. They represent suitable reagents for closing the knowledge gap in nickel-mediated activation of small molecules. Recently, the first strikingly stable dinuclear β-diketiminate nickel(I) precursor complexes were synthesized, proving to be suitable promoters for small-molecule binding and activation. They have led to many unprecedented nickel complexes bearing activated small molecules in different reduction stages. In this Account, we describe selected achievements in the activation of nitrous oxide (N(2)O), O(2), the heavier chalcogens (S, Se, and Te), and white phosphorus (P(4)) through this β-diketiminatonickel(I) precursor species. We emphasize the reductive activation of O(2), owing to its promise in oxidation processes. The one-electron-reduced O(2) activation product, that is, the corresponding β-diketiminato-supported Ni-O(2) complex, is a genuine superoxonickel(II) complex, representing an important intermediate in the early stages of O(2) activation. It selectively acts as an oxygen-atom transfer agent, hydrogen-atom scavenger, or both towards exogenous organic substrates to yield oxidation products. The one-electron reduction of the superoxonickel(II) moiety was examined by using elemental potassium, β-diketiminatozinc(II) chloride, and β-diketiminatoiron(I) complexes, affording the first heterobimetallic complexes featuring a [NiO(2)M] subunit (M is K, Zn, or Fe). Through

  13. Circularly Polarized Luminescence in Enantiopure Europium and Terbium Complexes with Modular, All-Oxygen Donor Ligands

    PubMed Central

    Seitz, Michael; Do, King; Ingram, Andrew J.; Moore, Evan G.; Muller, Gilles; Raymond, Kenneth N.

    2009-01-01

    Abstract: Circulaly polarized luminescence from terbium(III) complexed and excited by chiral antenna ligands gives strong emission The modular synthesis of three new octadentate, enantiopure ligands are reported - one with the bidentate chelating unit 2-hydroxyisophthalamide (IAM) and two with 1-hydroxy-2-pyridinone (1,2-HOPO) units. A new design principle is introduced for the chiral, non-racemic hexamines which constitute the central backbones for the presented class of ligands. The terbium(III) complex of the IAM ligand, as well as the europium(III) complexes of the 1,2-HOPO ligands are synthesized and characterized by various techniques (NMR, UV, CD, luminescence spectroscopy). All species exhibit excellent stability and moderate to high luminescence efficiency (quantum yields ΦEu = 0.05–0.08 and ΦTb = 0.30–0.57) in aqueous solution at physiological pH. Special focus is put onto the properties of the complexes in regard to circularly polarized luminescence (CPL). The maximum luminescence dissymmetry factors (glum) in aqueous solution are high with |glum|max = 0.08 – 0.40. Together with the very favorable general properties (good stability, high quantum yields, long lifetimes), the presented lanthanide complexes can be considered as good candidates for analytical probes based on CPL in biologically relevant environments. PMID:19639983

  14. Reactive Oxygen Species Production by Potato Tuber Mitochondria Is Modulated by Mitochondrially Bound Hexokinase Activity1

    PubMed Central

    Camacho-Pereira, Juliana; Meyer, Laudiene Evangelista; Machado, Lilia Bender; Oliveira, Marcus Fernandes; Galina, Antonio

    2009-01-01

    Potato tuber (Solanum tuberosum) mitochondria (PTM) have a mitochondrially bound hexokinase (HK) activity that exhibits a pronounced sensitivity to ADP inhibition. Here we investigated the role of mitochondrial HK activity in PTM reactive oxygen species generation. Mitochondrial HK has a 10-fold higher affinity for glucose (Glc) than for fructose (KMGlc = 140 μm versus KMFrc = 1,375 μm). Activation of PTM respiration by succinate led to an increase in hydrogen peroxide (H2O2) release that was abrogated by mitochondrial HK activation. Mitochondrial HK activity caused a decrease in the mitochondrial membrane potential and an increase in oxygen consumption by PTM. Inhibition of Glc phosphorylation by mannoheptulose or GlcNAc induced a rapid increase in H2O2 release. The blockage of H2O2 release sustained by Glc was reverted by oligomycin and atractyloside, indicating that ADP recycles through the adenine nucleotide translocator and F0F1ATP synthase is operative during the mitochondrial HK reaction. Inhibition of mitochondrial HK activity by 60% to 70% caused an increase of 50% in the maximal rate of H2O2 release. Inhibition in H2O2 release by mitochondrial HK activity was comparable to, or even more potent, than that observed for StUCP (S. tuberosum uncoupling protein) activity. The inhibition of H2O2 release in PTM was two orders of magnitude more selective for the ADP produced from the mitochondrial HK reaction than for that derived from soluble yeast (Saccharomyces cerevisiae) HK. Modulation of H2O2 release and oxygen consumption by Glc and mitochondrial HK inhibitors in potato tuber slices shows that hexoses and mitochondrial HK may act as a potent preventive antioxidant mechanism in potato tubers. PMID:19109413

  15. Theoretical study on photooxidation mechanism of ruthenium complex [Ru(II)-(bpy)2 (TMBiimH2 )](2+) with molecular oxygen.

    PubMed

    Liu, Li-Hong; Wu, Dan; Xia, Shu-Hua; Cui, Ganglong

    2016-09-15

    Photoinduced reactions of ruthenium complexes with molecular oxygen have attracted a lot of experimental attention; however, the reaction mechanism remains elusive. In this work, we have used the density functional theory method to scrutinize the visible-light induced photooxidation mechanism of the ruthenium complex [Ru(II)-(bpy)2 (TMBiimH2 )](2+) (bpy: 2, 2-bipyridine and TMBiimH2 : 4, 5, 4, 5-tetramethyl-2, 2-biimidazole) initiated by the attack of molecular oxygen. The present computational results not only explain very well recent experiments, also provide new mechanistic insights. We found that: (1) the triplet energy transfer process between the triplet molecular oxygen and the metal-ligand charge transfer triplet state of the ruthenium complex, which leads to singlet molecular oxygen, is thermodynamically favorable; (2) the singlet oxygen addition process to the S0 ruthenium complex is facile in energy; (3) the chemical transformation from endoperoxide to epidioxetane intermediates can be either two- or one-step reaction (the latter is energetically favored). These findings contribute important mechanistic information to photooxidation reactions of ruthenium complexes with molecular oxygen. © 2016 Wiley Periodicals, Inc. PMID:27384925

  16. Highly branched platinum nanolance assemblies by polyallylamine functionalization as superior active, stable, and alcohol-tolerant oxygen reduction electrocatalysts

    NASA Astrophysics Data System (ADS)

    Fu, Gengtao; Jiang, Xian; Gong, Mingxing; Chen, Yu; Tang, Yawen; Lin, Jun; Lu, Tianhong

    2014-06-01

    The chemical functionalization of platinum (Pt) nanostructures is becoming a new trend in electrocatalysts designs. Meanwhile, highly branched Pt nanostructures are highly exciting electrocatalysts with high activity and stability owing to their specific physical and chemical properties. In this work, the polyallylamine (PAH) functionalized Pt nanolance assemblies (Pt NLAs) have been successfully synthesized by chemical reduction of PAH-PtII complex using formaldehyde (HCHO) in a two-phase water-complex system. The as-prepared Pt NLAs are highly branched and three-dimensionally (3D) interconnected nanostructures, which are composed of many long Pt nanolances in various directions. PAH functionalization improves the electrocatalytic activity of the Pt NLAs for an oxygen reduction reaction (ORR) because of high interface proton concentration on the Pt surface and excellent anti-oxidation ability of the Pt nanolances. Meanwhile, the PAH molecules bound on the Pt NLAs surface act as barrier networks to restrain accessibility of alcohol, exhibiting a high ORR selectivity. In addition, the PAH functionalized Pt NLAs show excellent durability for the ORR due to their particular 3D interconnected structure. The work demonstrates that the PAH functionalized Pt NLAs are indeed promising cathodic electrocatalysts for practical application in direct alcohol fuel cells.The chemical functionalization of platinum (Pt) nanostructures is becoming a new trend in electrocatalysts designs. Meanwhile, highly branched Pt nanostructures are highly exciting electrocatalysts with high activity and stability owing to their specific physical and chemical properties. In this work, the polyallylamine (PAH) functionalized Pt nanolance assemblies (Pt NLAs) have been successfully synthesized by chemical reduction of PAH-PtII complex using formaldehyde (HCHO) in a two-phase water-complex system. The as-prepared Pt NLAs are highly branched and three-dimensionally (3D) interconnected nanostructures

  17. Syntheses, characterization, biological activities and photophysical properties of lanthanides complexes with a tetradentate Schiff base ligand.

    PubMed

    Taha, Ziyad A; Ajlouni, Abdulaziz M; Al Momani, Waleed; Al-Ghzawi, Abeer A

    2011-10-15

    A tetradentate Schiff base ligand L (N,N'-bis(1-naphthaldimine)-o-phenylenediamine) was prepared from the condensation of 2-hydroxy-1-naphthaldehyde with o-phenylenediamine in a molar ratio of 2:1. New eight lanthanide metal complexes [LnL(NO(3))(2)(H(2)O)(x)](NO(3)) {Ln(III) = Nd, Dy, Sm, Pr, Gd, Tb, La and Er, x = 0 for Nd, Sm, 1 for La, Gd, Pr, Nd, Dy, and 2 for Tb} were prepared. The characterization and nature of bonding of these complexes were elucidated by elemental analysis, spectral analysis ((1)H NMR, FT-IR, UV-vis), molar conductivity measurements, luminescence spectra and thermogravimetric studies. Analytical and spectral data revealed that the ligand L coordinates to the central Ln(III) ions by its two imine nitrogen atoms and two phenolic oxygen atoms with 1:1 stoichiometry. Under the excitation with 329 nm at room temperature, Tb and Dy complexes exhibited characteristic luminescence of the central metal ions attributed to efficient energy transfer from the ligand to the metal center. Most of Ln(III) complexes found to exhibit antibacterial activities against a number of pathogenic bacteria. We found that the antioxident activity of Ln(III) complexes on DPPH(•) is concentration dependent and higher than that of the free ligand L. PMID:21764359

  18. Selective nitrogen doping in graphene: Enhanced catalytic activity for the oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Wang, Xianlong; Hou, Zhufeng; Ikeda, Takashi; Huang, Sheng-Feng; Terakura, Kiyoyuki; Boero, Mauro; Oshima, Masaharu; Kakimoto, Masa-Aki; Miyata, Seizo

    2011-12-01

    The structural and electronic properties of N-doped zigzag graphene ribbons with various ratios of dihydrogenated to monohydrogenated edge carbons are investigated within the density functional theory framework. We find that the stability of graphitic N next to the edge, which is claimed to play important roles in the catalytic activity in our previous work, will be enhanced with increasing the concentration of dihydrogenated carbons. Furthermore, the dihydrogenated edge carbons turn out to be easily converted into monohydrogenated ones in the presence of oxygen molecules at room temperature. Based on our results, we propose a possible way to enhance the oxygen reduction catalytic activity of N-doped graphene by controlling the degrees of hydrogenation of edge carbons. The characteristic features in the x-ray absorption and emission spectra for each specific N site considered here will also be given.

  19. Doped LaFeO3 as SOFC Catalysts: Control of Oxygen Mobility Oxidation Activity

    SciTech Connect

    N Lakshminarayanan; J Kuhn; S Rykov; J Millet; U Ozkan; T Rao; J Smedley; E Wang; E Muller; et al.

    2011-12-31

    The bulk structure and surface properties of Fe-based perovskite-type oxides with the formula La{sub 0.6}Sr{sub 0.4}Co{sub y}Fe{sub 1-y}O{sub 3-{delta}} for y = 0.1, 0.2, and 0.3 have been investigated. The properties were found to strongly depend upon Co content, temperature, and environment. The materials were selected due to their potential use as solid oxide fuel cell cathodes. The intermediate Co loading formed oxygen vacancies most easily and several other properties including oxidation activity and surface sites showed a similar non-linear trend. Trends are related to a possible transition in electronic structure. Activity for oxidation of methane, oxygen storage and chemical compatibility was shown to be superior to that of the La{sub 0.6}Sr{sub 0.4}MnO{sub 3}.

  20. Structural Characterization of Mutations at the Oxygen Activation Site in Monomeric Sarcosine Oxidase

    SciTech Connect

    Schuman Jorns, Marilyn; Chen, Zhi-wei; Mathews, F. Scott

    2010-04-30

    Oxygen reduction and sarcosine oxidation in monomeric sarcosine oxidase (MSOX) occur at separate sites above the si- and re-faces, respectively, of the flavin ring. Mutagenesis studies implicate Lys265 as the oxygen activation site. Substitution of Lys265 with a neutral (Met, Gln, or Ala) or basic (Arg) residue results in an {approx}10{sup 4}- or 250-fold decrease, respectively, in the reaction rate. The overall structure of MSOX and residue conformation in the sarcosine binding cavity are unaffected by replacement of Lys265 with Met or Arg. The side chain of Met265 exhibits the same configuration in each molecule of Lys265Met crystals and is nearly congruent with Lys265 in wild-type MSOX. The side chain of Arg265 is, however, dramatically shifted (4-5 {angstrom}) compared with Lys265, points in the opposite direction, and exhibits significant conformational variability between molecules of the same crystal. The major species in solutions of Lys265Arg is likely to contain a 'flipped-out' Arg265 and exhibit negligible oxygen activation, similar to Lys265Met. The 400-fold higher oxygen reactivity observed with Lys265Arg is attributed to a minor (<1%) 'flipped-in' Arg265 conformer whose oxygen reactivity is similar to that of wild-type MSOX. A structural water (WAT1), found above the si-face of the flavin ring in all previously determined MSOX structures, is part of an apparent proton relay system that extends from FAD N(5) to bulk solvent. WAT1 is strikingly absent in Lys265Met and Lys265Arg, a feature that may account for the apparent kinetic stabilization of a reductive half-reaction intermediate that is detectable with the mutants but not wild-type MSOX.

  1. Synthesis, structures and reactivity of ruthenium nitrosyl complexes containing Kläui's oxygen tripodal ligand.

    PubMed

    Ip, Ho-Fai; Yi, Xiao-Yi; Wong, Wai-Yeung; Williams, Ian D; Leung, Wa-Hung

    2011-11-01

    Ruthenium nitrosyl complexes containing the Kläui's oxgyen tripodal ligand L(OEt)(-) ([CpCo{P(O)(OEt)(2)}(3)](-) where Cp = η(5)-C(5)H(5)) were synthesized and their photolysis studied. The treatment of [Ru(N^N)(NO)Cl(3)] with [AgL(OEt)] and Ag(OTf) afforded [L(OEt)Ru(N^N)(NO)][OTf](2) where N^N = 4,4'-di-tert-butyl-2,2'-bipyridyl (dtbpy) (2·[OTf](2)), 2,2'-bipyridyl (bpy) (3·[OTf](2)), N,N,N'N'-tetramethylethylenediamine (4·[OTf](2)). Anion metathesis of 3·[OTf](2) with HPF(6) and HBF(4) gave 3·[PF(6)](2) and 3·[BF(4)](2), respectively. Similarly, the PF(6)(-) salt 4·[PF(6)](2) was prepared by the reaction of 4·[OTf](2) with HPF(6). The irradiation of [L(OEt)Ru(NO)Cl(2)] (1) with UV light in CH(2)Cl(2)-MeCN and tetrahydrofuran (thf)-H(2)O afforded [L(OEt)RuCl(2)(MeCN)] (5) and the chloro-bridged dimer [L(OEt)RuCl](2)(μ-Cl)(2) (6), respectively. The photolysis of complex [2][OTf](2) in MeCN gave [L(OEt)Ru(dtbpy)(MeCN)][OTf](2) (7). Refluxing complex 5 with RNH(2) in thf gave [L(OEt)RuCl(2)(NH(2)R)] (R = tBu (8), p-tol (9), Ph (10)). The oxidation of complex 6 with PhICl(2) gave [L(OEt)RuCl(3)] (11), whereas the reduction of complex 6 with Zn and NH(4)PF(6) in MeCN yielded [L(OEt)Ru(MeCN)(3)][PF(6)] (12). The reaction of 3·[BF(4)](2) with benzylamine afforded the μ-dinitrogen complex [{L(OEt)Ru(bpy)}(2)(μ-N(2))][BF(4)](2) (13) that was oxidized by [Cp(2)Fe]PF(6) to a mixed valence Ru(II,III) species. The formal potentials of the RuL(OEt) complexes have been determined by cyclic voltammetry. The structures of complexes 5,6,10,11 and 13 have been established by X-ray crystallography. PMID:21927766

  2. Active mixing of complex fluids at the microscale

    PubMed Central

    Ober, Thomas J.; Foresti, Daniele; Lewis, Jennifer A.

    2015-01-01

    Mixing of complex fluids at low Reynolds number is fundamental for a broad range of applications, including materials assembly, microfluidics, and biomedical devices. Of these materials, yield stress fluids (and gels) pose the most significant challenges, especially when they must be mixed in low volumes over short timescales. New scaling relationships between mixer dimensions and operating conditions are derived and experimentally verified to create a framework for designing active microfluidic mixers that can efficiently homogenize a wide range of complex fluids. Active mixing printheads are then designed and implemented for multimaterial 3D printing of viscoelastic inks with programmable control of local composition. PMID:26396254

  3. Complexation of oxygen ligands with dimeric rhodium(II) tetrakistrifluoroacetate in chloroform: 1H, 13C NMR and DFT studies

    NASA Astrophysics Data System (ADS)

    Głaszczka, Rafał; Jaźwiński, Jarosław

    2013-03-01

    The complexation of dimeric rhodium(II) tetrakistrifluoroacetylate with 25 ligands containing oxygen atoms: alcohols, ethers, ketones, aldehydes, carboxylic acids and esters in chloroform solution have been investigated by 1H and 13C NMR spectroscopy and Density Functional Theory (DFT) methods. Investigated ligands form 1:1 adducts in our experimental conditions, with stability constants in the order of several hundred mol-1. The exchange of ligands in solution is fast on the NMR spectroscopic timescale. The decrease of longitudinal relaxation times T1 in ligands in the presence of rhodium salt has been tested as the means of determination of the complexation site in ligands. The influence of complexation on chemical shifts in ligands was evaluated by a parameter complexation shift Δδ (Δδ = δadd - δlig). These parameters were positive (>0 ppm) and did not exceed 1 ppm for 1H NMR; and varied from ca. -5 to +15 ppm in the case of 13C NMR. The calculation by DFT methods using the B3LYP functional (structure optimization, electronic energy) and B3PW91 functional (shielding), and combinations of the (6-31G(2d), 6-311G++(2d,p), and LANL2DZ basis sets, followed by scaling procedures reproduced satisfactorily 1H and 13C chemical shifts and, with some limitations, allowed to estimate Δδ parameters.

  4. Heteronuclear Ir(III)-Ln(III) Luminescent Complexes: Small-Molecule Probes for Dual Modal Imaging and Oxygen Sensing.

    PubMed

    Jana, Atanu; Crowston, Bethany J; Shewring, Jonathan R; McKenzie, Luke K; Bryant, Helen E; Botchway, Stanley W; Ward, Andrew D; Amoroso, Angelo J; Baggaley, Elizabeth; Ward, Michael D

    2016-06-01

    Luminescent, mixed metal d-f complexes have the potential to be used for dual (magnetic resonance imaging (MRI) and luminescence) in vivo imaging. Here, we present dinuclear and trinuclear d-f complexes, comprising a rigid framework linking a luminescent Ir center to one (Ir·Ln) or two (Ir·Ln2) lanthanide metal centers (where Ln = Eu(III) and Gd(III), respectively). A range of physical, spectroscopic, and imaging-based properties including relaxivity arising from the Gd(III) units and the occurrence of Ir(III) → Eu(III) photoinduced energy-transfer are presented. The rigidity imposed by the ligand facilitates high relaxivities for the Gd(III) complexes, while the luminescence from the Ir(III) and Eu(III) centers provide luminescence imaging capabilities. Dinuclear (Ir·Ln) complexes performed best in cellular studies, exhibiting good solubility in aqueous solutions, low toxicity after 4 and 18 h, respectively, and punctate lysosomal staining. We also demonstrate the first example of oxygen sensing in fixed cells using the dyad Ir·Gd, via two-photon phosphorescence lifetime imaging (PLIM). PMID:27219675

  5. Gel-derived cation-π stacking films of carbon nanotube-graphene complexes as oxygen cathodes.

    PubMed

    Zhang, Tao; Matsuda, Hirofumi; Zhou, Haoshen

    2014-10-01

    A key challenge in processing carbon nanotubes and their composites for large-scale applications is aggregation. Cation-π stacking interactions have been discovered to disperse heavily entangled single-walled carbon nanotube (SWNT) bundles in ionic liquids (ILs). In this work, we found that a dispersible, silky single-layer graphene (SLG) can be readily gathered together to form a crosslinked gel after entrapping sufficient IL molecular via the likely noncovalent interaction. By incorporating the dispersed SWNTs into the gathered SLG gel synchronously, we prepared solid, finely crosslinked SWNTs-SLG films, assisted by an avenue of 2-step extraction to remove the IL completely. The gel-derived SWNTs-SLG complex film was applied as a support material of oxygen cathodes for Li-O2 batteries. It exhibited a remarkable improved cycleability in comparison to made of SWNTs and SLG alone due to the finely crosslinked feature. Decorated SWNTs and SLG can also form gel-derived complexes via the same process to construct support-catalyst complexes. A SWNTs-SLG film loaded with Ru nanoparticles exhibited not only catalytic effects, but also the ability to suppress the side reactions, and hence stabilized the whole Li-O2 battery. Our research introduces a gel-derived, high-dispersed processing of carbon nanotube-graphene complexes and demonstrates their favorable applications on Li-O2 batteries. PMID:25164151

  6. Highly branched PtCu bimetallic alloy nanodendrites with superior electrocatalytic activities for oxygen reduction reactions

    NASA Astrophysics Data System (ADS)

    Fu, Shaofang; Zhu, Chengzhou; Shi, Qiurong; Xia, Haibing; Du, Dan; Lin, Yuehe

    2016-02-01

    Morphology control is a promising strategy to improve the catalytic performance of Pt-based catalysts. In this work, we reported a facile synthesis of PtCu bimetallic alloy nanodendrites using Brij 58 as a template. The highly branched structures and porous features offer relatively large surface areas, which is beneficial to the enhancement of the catalytic activity for oxygen reduction reactions in fuel cells. In addition, the elimination of carbon supports showed an important effect on the stability of the catalysts. By tuning the ratio of Pt and Cu precursors, PtCu nanodendrites were almost four times more active on the basis of an equivalent Pt mass for oxygen reduction reactions than the commercial Pt/C catalyst.Morphology control is a promising strategy to improve the catalytic performance of Pt-based catalysts. In this work, we reported a facile synthesis of PtCu bimetallic alloy nanodendrites using Brij 58 as a template. The highly branched structures and porous features offer relatively large surface areas, which is beneficial to the enhancement of the catalytic activity for oxygen reduction reactions in fuel cells. In addition, the elimination of carbon supports showed an important effect on the stability of the catalysts. By tuning the ratio of Pt and Cu precursors, PtCu nanodendrites were almost four times more active on the basis of an equivalent Pt mass for oxygen reduction reactions than the commercial Pt/C catalyst. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr07682j

  7. A General Method for Multimetallic Platinum Alloy Nanowires as Highly Active and Stable Oxygen Reduction Catalysts.

    PubMed

    Bu, Lingzheng; Ding, Jiabao; Guo, Shaojun; Zhang, Xu; Su, Dong; Zhu, Xing; Yao, Jianlin; Guo, Jun; Lu, Gang; Huang, Xiaoqing

    2015-11-25

    An unconventional class of high-performance Pt alloy multimetallic nanowires (NWs) is produced by a general method. The obtained PtNi NWs exhibit amazingly specific and mass oxygen reduction reaction (ORR) activities with improvement factors of 51.1 and 34.6 over commercial Pt/C catalysts, respectively, and are also stable in ORR conditions, making them among the most efficient electrocatalysts for ORR. PMID:26459261

  8. Enhanced oxygen evolution activity of IrO2 and RuO2 (100) surfaces

    SciTech Connect

    Stoerzinger, Kelsey; Qiao, Liang; Biegalski, Michael D; Christen, Hans M; Shao-Horn, Yang

    2014-01-01

    The activities of the oxygen evolution reaction (OER) on IrO2 and RuO2 catalysts are among the highest known to date. However, the intrinsic OER activities of surfaces with defined crystallographic orientations are not well established experimentally. Here we report that the (100) surface of IrO2 and RuO2 is more active than the (110) surface that has been traditionally explored by density functional theory studies. The relation between the OER activity and density of coordinatively undersaturated metal sites exposed on each rutile crystallographic facet is discussed. The surface-orientation dependent activities can guide the design of high-surface-area catalysts with increased activity for electrolyzers, metal-air batteries, and photoelectrochemical water splitting applications.

  9. Quantifying the density and utilization of active sites in non-precious metal oxygen electroreduction catalysts.

    PubMed

    Sahraie, Nastaran Ranjbar; Kramm, Ulrike I; Steinberg, Julian; Zhang, Yuanjian; Thomas, Arne; Reier, Tobias; Paraknowitsch, Jens-Peter; Strasser, Peter

    2015-01-01

    Carbon materials doped with transition metal and nitrogen are highly active, non-precious metal catalysts for the electrochemical conversion of molecular oxygen in fuel cells, metal air batteries, and electrolytic processes. However, accurate measurement of their intrinsic turn-over frequency and active-site density based on metal centres in bulk and surface has remained difficult to date, which has hampered a more rational catalyst design. Here we report a successful quantification of bulk and surface-based active-site density and associated turn-over frequency values of mono- and bimetallic Fe/N-doped carbons using a combination of chemisorption, desorption and (57)Fe Mössbauer spectroscopy techniques. Our general approach yields an experimental descriptor for the intrinsic activity and the active-site utilization, aiding in the catalyst development process and enabling a previously unachieved level of understanding of reactivity trends owing to a deconvolution of site density and intrinsic activity. PMID:26486465

  10. Quantifying the density and utilization of active sites in non-precious metal oxygen electroreduction catalysts

    NASA Astrophysics Data System (ADS)

    Sahraie, Nastaran Ranjbar; Kramm, Ulrike I.; Steinberg, Julian; Zhang, Yuanjian; Thomas, Arne; Reier, Tobias; Paraknowitsch, Jens-Peter; Strasser, Peter

    2015-10-01

    Carbon materials doped with transition metal and nitrogen are highly active, non-precious metal catalysts for the electrochemical conversion of molecular oxygen in fuel cells, metal air batteries, and electrolytic processes. However, accurate measurement of their intrinsic turn-over frequency and active-site density based on metal centres in bulk and surface has remained difficult to date, which has hampered a more rational catalyst design. Here we report a successful quantification of bulk and surface-based active-site density and associated turn-over frequency values of mono- and bimetallic Fe/N-doped carbons using a combination of chemisorption, desorption and 57Fe Mössbauer spectroscopy techniques. Our general approach yields an experimental descriptor for the intrinsic activity and the active-site utilization, aiding in the catalyst development process and enabling a previously unachieved level of understanding of reactivity trends owing to a deconvolution of site density and intrinsic activity.

  11. Suppression of oxygen reduction reaction activity on Pt-based electrocatalysts from ionomer incorporation

    NASA Astrophysics Data System (ADS)

    Shinozaki, Kazuma; Morimoto, Yu; Pivovar, Bryan S.; Kocha, Shyam S.

    2016-09-01

    The impact of Nafion on the oxygen reduction reaction (ORR) activity is studied for Pt/C and Pt-alloy/C catalysts using thin-film rotating disk electrode (TF-RDE) methods in 0.1 M HClO4. Ultrathin uniform catalyst layers and standardized activity measurement protocols are employed to obtain accurate and reproducible ORR activity. Nafion lowers the ORR activity which plateaus with increasing loading on Pt catalysts. Pt particle size is found not to have significant influence on the extent of the SA decrease upon Nafion incorporation. Catalysts using high surface area carbon (HSC) support exhibit attenuated activity loss resulting from lower ionomer coverage on catalyst particles located within the deep pores. The impact of metallic composition on the activity loss due to Nafion incorporation is also discussed.

  12. Quantifying the density and utilization of active sites in non-precious metal oxygen electroreduction catalysts

    PubMed Central

    Sahraie, Nastaran Ranjbar; Kramm, Ulrike I.; Steinberg, Julian; Zhang, Yuanjian; Thomas, Arne; Reier, Tobias; Paraknowitsch, Jens-Peter; Strasser, Peter

    2015-01-01

    Carbon materials doped with transition metal and nitrogen are highly active, non-precious metal catalysts for the electrochemical conversion of molecular oxygen in fuel cells, metal air batteries, and electrolytic processes. However, accurate measurement of their intrinsic turn-over frequency and active-site density based on metal centres in bulk and surface has remained difficult to date, which has hampered a more rational catalyst design. Here we report a successful quantification of bulk and surface-based active-site density and associated turn-over frequency values of mono- and bimetallic Fe/N-doped carbons using a combination of chemisorption, desorption and 57Fe Mössbauer spectroscopy techniques. Our general approach yields an experimental descriptor for the intrinsic activity and the active-site utilization, aiding in the catalyst development process and enabling a previously unachieved level of understanding of reactivity trends owing to a deconvolution of site density and intrinsic activity. PMID:26486465

  13. Water-soluble ruthenium complexes bearing activity against protozoan parasites.

    PubMed

    Sarniguet, Cynthia; Toloza, Jeannette; Cipriani, Micaella; Lapier, Michel; Vieites, Marisol; Toledano-Magaña, Yanis; García-Ramos, Juan Carlos; Ruiz-Azuara, Lena; Moreno, Virtudes; Maya, Juan Diego; Azar, Claudio Olea; Gambino, Dinorah; Otero, Lucía

    2014-06-01

    Parasitic illnesses are major causes of human disease and misery worldwide. Among them, both amebiasis and Chagas disease, caused by the protozoan parasites, Entamoeba histolytica and Trypanosoma cruzi, are responsible for thousands of annual deaths. The lack of safe and effective chemotherapy and/or the appearance of current drug resistance make the development of novel pharmacological tools for their treatment relevant. In this sense, within the framework of the medicinal inorganic chemistry, metal-based drugs appear to be a good alternative to find a pharmacological answer to parasitic diseases. In this work, novel ruthenium complexes [RuCl2(HL)(HPTA)2]Cl2 with HL=bioactive 5-nitrofuryl containing thiosemicarbazones and PTA=1,3,5-triaza-7-phosphaadamantane have been synthesized and fully characterized. PTA was included as co-ligand in order to modulate complexes aqueous solubility. In fact, obtained complexes were water soluble. Their activity against T. cruzi and E. histolytica was evaluated in vitro. [RuCl2(HL4)(HPTA)2]Cl2 complex, with HL4=N-phenyl-5-nitrofuryl-thiosemicarbazone, was the most active compound against both parasites. In particular, it showed an excellent activity against E. histolytica (half maximal inhibitory concentration (IC50)=5.2 μM), even higher than that of the reference drug metronidazole. In addition, this complex turns out to be selective for E. histolytica (selectivity index (SI)>38). The potential mechanism of antiparasitic action of the obtained ruthenium complexes could involve oxidative stress for both parasites. Additionally, complexes could interact with DNA as second potential target by an intercalative-like mode. Obtained results could be considered a contribution in the search for metal compounds that could be active against multiple parasites. PMID:24740394

  14. Synthesis, crystal structure, DNA interaction and anticancer activity of tridentate copper(II) complexes.

    PubMed

    Li, Guan-Ying; Du, Ke-Jie; Wang, Jin-Quan; Liang, Jie-Wen; Kou, Jun-Feng; Hou, Xiao-Juan; Ji, Liang-Nian; Chao, Hui

    2013-02-01

    Three new tridentate copper(II) complexes [Cu(dthp)Cl(2)] (1) (dthp=2,6-di(thiazol-2-yl)pyridine), [Cu(dmtp)Cl(2)] (2) (dmtp=2,6-di(5-methyl-4H-1,2,4-triazol-3-yl)pyridine) and [Cu(dtp)Cl(2)] (3) (dtp=2,6-di(4H-1,2,4-triazol-3-yl)pyridine) have been synthesized and characterized. Crystal structure of complex 1 shows that the complex existed as distorted square pyramid with five co-ordination sites occupied by the tridentate ligand and the two chlorine anions. Ethidium bromide displacement assay, viscosity measurements, circular dichroism studies and cyclic voltammetric experiments suggested that these complexes bound to DNA via an intercalative mode. Three Cu(II) complexes were found to efficiently cleave DNA in the presence of sodium ascorbate, and singlet oxygen ((1)O(2)) and hydrogen peroxide were proved to contribute to the DNA cleavage process. They exhibited anticancer activity against HeLa, Hep-G2 and BEL-7402 cell lines. Nuclear chromatin cleavage has also been observed with AO/EB staining assay and the alkaline single-cell gel electrophoresis (comet assay). The results demonstrated that three Cu(II) complexes cause DNA damage that can induce the apoptosis of BEL-7402 cells. PMID:23186647

  15. CURRENT AND KINETIC HELICITY OF LONG-LIVED ACTIVITY COMPLEXES

    SciTech Connect

    Komm, Rudolf; Gosain, Sanjay

    2015-01-01

    We study long-lived activity complexes and their current helicity at the solar surface and their kinetic helicity below the surface. The current helicity has been determined from synoptic vector magnetograms from the NSO/SOLIS facility, and the kinetic helicity of subsurface flows has been determined with ring-diagram analysis applied to full-disk Dopplergrams from NSO/GONG and SDO/HMI. Current and kinetic helicity of activity complexes follow the hemispheric helicity rule with mainly positive values (78%; 78%, respectively, with a 95% confidence level of 31%) in the southern hemisphere and negative ones (80%; 93%, respectively, with a 95% confidence level of 22% and 14%, respectively) in the northern hemisphere. The locations with the dominant sign of kinetic helicity derived from Global Oscillation Network Group (GONG) and SDO/HMI data are more organized than those of the secondary sign even if they are not part of an activity complex, while locations with the secondary sign are more fragmented. This is the case for both hemispheres even for the northern one where it is not as obvious visually due to the large amount of magnetic activity present as compared to the southern hemisphere. The current helicity shows a similar behavior. The dominant sign of current helicity is the same as that of kinetic helicity for the majority of the activity complexes (83% with a 95% confidence level of 15%). During the 24 Carrington rotations analyzed here, there is at least one longitude in each hemisphere where activity complexes occur repeatedly throughout the epoch. These ''active'' longitudes are identifiable as locations of strong current and kinetic helicity of the same sign.

  16. Binuclear Rhodium(II) Complexes With Selective Antibacterial Activity.

    PubMed

    Bień, M; Lachowicz, T M; Rybka, A; Pruchnik, F P; Trynda, L

    1997-01-01

    Binuclear rhodium(II) complexes [Rh(2)Cl(2)(mu-OOCR)(2)(N-N)(2)] {R = H, Me; N-N = 2,2'-bipyridine (bpy), 1,10-phenanthroline (phen)} and [Rh(2)(mu-OOCR)(2)(N-N)(2)(H(2)O)(2)](RCOO)(2) (R = Me, Et;) have been synthesized and their structure and properties have been studied by electronic, IR and (1)H NMR spectroscopy. Antibacterial activity of these complexes against Escherichia coli and Staphylococcus aureus has been investigated. The most active antibacterial agents against E. coli were [Rh(2)Cl(2)(mu-OOCR)(2)(N-N)(2)] and [Rh(2)(mu-OOCR)(2)(N-N)(2)(H(2)O)(2)](RCOO)(2) {R = H and Me} which were considerably more active than the appropriate nitrogen ligands. The complexes show low activity against S. aureus. The activity of the complexes [Rh(2)(OOCR)(2)(N-N)(2)(H(2)O)(2)](OOCR)(2) against E. coli decreases in the series: R=H congruent withCH(3)>C(2)H(5)>C(3)H(7) congruent withC(4)H(9). The reverse order was found in the case of S. aureus. PMID:18475773

  17. Circularly Polarized Luminescence in Enantiopure Europium and Terbium Complexes with Modular, All-Oxygen Donor Ligands

    SciTech Connect

    Seitz, Michael; Do, King; Ingram, Andrew; Moore, Evan; Muller, Gilles; Raymond, Kenneth

    2009-06-04

    The modular syntheses of three new octadentate, enantiopure ligands are reported, one with the bidentate chelating unit 2-hydroxyisophthalamide (IAM) and two with bidentate 1-hydroxy-2-pyridinone (1,2-HOPO) units. A new design principle is introduced for the chiral, non-racemic hexamines which constitute the central backbones for the presented class of ligands. The terbium(III) complex of the IAM ligand, as well as the europium(III) complexes of the 1,2-HOPO ligands, are synthesized and characterized by various techniques (NMR, UV, CD, luminescence spectroscopy). All species exhibit excellent stability and moderate to high luminescence efficiency (quantum yields {phi}{sub Eu} = 0.05-0.08 and {phi}{sub Tb} = 0.30-0.57) in aqueous solution at physiological pH. Special focus is put onto the properties of the complexes in regard to circularly polarized luminescence (CPL). The maximum luminescence dissymmetry factors (glum) in aqueous solution are high with |glum|max = 0.08-0.40. Together with the very favorable general properties (good stability, high quantum yields, long lifetimes), the presented lanthanide complexes can be considered as good candidates for analytical probes based on CPL in biologically relevant environments.

  18. Hierarchically porous carbons with optimized nitrogen doping as highly active electrocatalysts for oxygen reduction

    NASA Astrophysics Data System (ADS)

    Liang, Hai-Wei; Zhuang, Xiaodong; Brüller, Sebastian; Feng, Xinliang; Müllen, Klaus

    2014-09-01

    Development of efficient, low-cost and stable electrocatalysts as the alternative to platinum for the oxygen reduction reaction is of significance for many important electrochemical devices, such as fuel cells, metal-air batteries and chlor-alkali electrolysers. Here we report a highly active nitrogen-doped, carbon-based, metal-free oxygen reduction reaction electrocatalyst, prepared by a hard-templating synthesis, for which nitrogen-enriched aromatic polymers and colloidal silica are used as precursor and template, respectively, followed by ammonia activation. Our protocol allows for the simultaneous optimization of both porous structures and surface functionalities of nitrogen-doped carbons. Accordingly, the prepared catalysts show the highest oxygen reduction reaction activity (half-wave potential of 0.85 V versus reversible hydrogen electrode with a low loading of 0.1 mg cm-2) in alkaline media among all reported metal-free catalysts. Significantly, when used for constructing the air electrode of zinc-air battery, our metal-free catalyst outperforms the state-of the-art platinum-based catalyst.

  19. Hierarchically porous carbons with optimized nitrogen doping as highly active electrocatalysts for oxygen reduction.

    PubMed

    Liang, Hai-Wei; Zhuang, Xiaodong; Brüller, Sebastian; Feng, Xinliang; Müllen, Klaus

    2014-01-01

    Development of efficient, low-cost and stable electrocatalysts as the alternative to platinum for the oxygen reduction reaction is of significance for many important electrochemical devices, such as fuel cells, metal-air batteries and chlor-alkali electrolysers. Here we report a highly active nitrogen-doped, carbon-based, metal-free oxygen reduction reaction electrocatalyst, prepared by a hard-templating synthesis, for which nitrogen-enriched aromatic polymers and colloidal silica are used as precursor and template, respectively, followed by ammonia activation. Our protocol allows for the simultaneous optimization of both porous structures and surface functionalities of nitrogen-doped carbons. Accordingly, the prepared catalysts show the highest oxygen reduction reaction activity (half-wave potential of 0.85 V versus reversible hydrogen electrode with a low loading of 0.1 mg cm(-2)) in alkaline media among all reported metal-free catalysts. Significantly, when used for constructing the air electrode of zinc-air battery, our metal-free catalyst outperforms the state-of the-art platinum-based catalyst. PMID:25229121

  20. Stable platinum nanoclusters on genomic DNA–graphene oxide with a high oxygen reduction reaction activity

    PubMed Central

    Tiwari, Jitendra N.; Nath, Krishna; Kumar, Susheel; Tiwari, Rajanish N.; Kemp, K. Christian; Le, Nhien H.; Youn, Duck Hyun; Lee, Jae Sung; Kim, Kwang S.

    2013-01-01

    Nanosize platinum clusters with small diameters of 2–4 nm are known to be excellent catalysts for the oxygen reduction reaction. The inherent catalytic activity of smaller platinum clusters has not yet been reported due to a lack of preparation methods to control their size (<2 nm). Here we report the synthesis of platinum clusters (diameter ≤1.4 nm) deposited on genomic double-stranded DNA–graphene oxide composites, and their high-performance electrocatalysis of the oxygen reduction reaction. The electrochemical behaviour, characterized by oxygen reduction reaction onset potential, half-wave potential, specific activity, mass activity, accelerated durability test (10,000 cycles) and cyclic voltammetry stability (10,000 cycles) is attributed to the strong interaction between the nanosize platinum clusters and the DNA–graphene oxide composite, which induces modulation in the electronic structure of the platinum clusters. Furthermore, we show that the platinum cluster/DNA–graphene oxide composite possesses notable environmental durability and stability, vital for high-performance fuel cells and batteries. PMID:23900456

  1. Oxygen activation in NO synthases: evidence for a direct role of the substrate.

    PubMed

    Brunel, Albane; Lang, Jérôme; Couture, Manon; Boucher, Jean-Luc; Dorlet, Pierre; Santolini, Jérôme

    2016-05-01

    Nitric oxide (NO) and the other reactive nitrogen species (RNOS) play crucial patho-physiological roles at the interface of oxidative stress and signalling processes. In mammals, the NO synthases (NOSs) are the source of these reactive nitrogen species, and so to understand the precise biological role of RNOS and NO requires elucidation of the molecular functioning of NOS. Oxygen activation, which is at the core of NOS catalysis, involves a sophisticated sequence of electron and proton transfers. While electron transfer in NOS has received much attention, the proton transfer processes has been scarcely investigated. Here, we report an original approach that combines fast-kinetic techniques coupled to resonance Raman spectroscopy with the use of synthetic analogues of NOS substrate. We characterise Fe(II)-O2 reaction intermediates in the presence of L-arginine (Arg), alkyl- and aryl-guanidines. The presence of new reaction intermediates, such as ferric haem-peroxide, that was formerly postulated, was tracked by analysing the oxygen activation reaction at different times and with different excitation wavelengths. Our results suggest that Arg is not a proton donor, but indirectly intervenes in oxygen activation mechanism by modulating the distal H-bond network and, in particular, by tuning the position and the role of the distal water molecule. This report supports a catalytic model with two proton transfers in step 1 (Arg hydroxylation) but only one proton transfer in step 2 (N(ω)-hydroxy-L-arginine oxidation). PMID:27419044

  2. Inhibitory activities of soluble and bound millet seed phenolics on free radicals and reactive oxygen species.

    PubMed

    Chandrasekara, Anoma; Shahidi, Fereidoon

    2011-01-12

    Oxidative stress, caused by reactive oxygen species (ROS), is responsible for modulating several pathological conditions and aging. Soluble and bound phenolic extracts of commonly consumed millets, namely, kodo, finger (Ravi), finger (local), foxtail, proso, little, and pearl, were investigated for their phenolic content and inhibition of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and ROS, namely, hydroxyl radical, peroxyl radical, hydrogen peroxide (H(2)O(2)), hypochlorous acid (HOCl), and singlet oxygen ((1)O(2)). Inhibition of DPPH and hydroxyl radicals was detrmined using electron paramagnetic resonance (EPR) spectroscopy. The peroxyl radical inhibitory activity was measured using the oxygen radical absorbance capacity (ORAC) assay. The scavenging of H(2)O(2), HOCl, and (1)O(2) was evaluated using colorimetric methods. The results were expressed as micromoles of ferulic acid equivalents (FAE) per gram of grain on a dry weight basis. In addition, major hydroxycinnamic acids were identified and quantified using high-performance liquid chromatography (HPLC) and HPLC-mass spectrometry (MS). All millet varieties displayed effective radical and ROS inhibition activities, which generally positively correlated with phenolic contents, except for hydroxyl radical. HPLC analysis revealed the presence of ferulic and p-coumaric acids as major hydroxycinnamic acids in phenolic extract and responsible for the observed effects. Bound extracts of millet contributed 38-99% to ROS scavenging, depending on the variety and the test system employed. Hence, bound phenolics must be included in the evaluation of the antioxidant activity of millets and other cereals. PMID:21133411

  3. Molecular Oxygen and Sulfur Reactivity of a Cyclotriveratrylene (CTV) Derived Trinuclear Copper(I) Complex

    PubMed Central

    Maiti, Debabrata; Woertink, Julia S.; Ghiladi, Reza A.; Solomon, Edward I.; Karlin, Kenneth D.

    2010-01-01

    Our continuing efforts into developing copper coordination chemistry relevant to dioxygen-processing copper proteins has led us to design and synthesize a cyclotriveratrylene (CTV)-based trinucleating ligand, CTV-TMPA, which employs tetradentate tris(2-pyridylmethyl)-amine chelates (TMPA) for their copper ion binding sites. Binding of three copper ions per CTV-TMPA unit was established by various chemical and spectroscopic methods such as UV-vis and resonance Raman (rR) spectroscopies. The following complexes were observed: A tricopper(I) complex [(CTV-TMPA)CuI3]3+ (1), a CO adduct [(CTV-TMPA)CuI3(CO)3]3+ (1-CO; ν(C=O) = 2094 cm−1), a triphenylphosphine adduct [(CTV-TMPA)CuI3(PPh3)3]3+ (1-PPh3), a tricopper(II) complex [(CTV-TMPA)CuII3]3+ (1-Ox) and its tris-monochloride or tris-monobromide adducts. Also, introduction of dioxygen to the −80 °C solutions of 1 leads to O2-adducts, the first example of a synthetic copper complex which can stabilize a mononuclear CuII-superoxo and dinuclear peroxo species simultaneously within one complex {[Cu] = 1.53 mM in THF: (μ-1,2-peroxo complex, λmax = 543 (ε 9650) nm): ν(O-O) = 825 ((Δ18O2) = −47) cm−1; ν(Cu-O) = 506 ((Δ18O2) = −26) cm−1: (superoxo complex, λmax = 427 (ε 3150) nm): ν(O-O) = 1129 ((Δ18O2) = −60) cm−1; ν(Cu-O) = 463 ((Δ18O2) =−27) cm−1}. Elemental sulfur reacts reversibly with 1 leading to a (proposed) hexanuclear species [{(CTV-TMPA)CuII3}2(μ-1,2-S22−)3]6+ (1-S) {λmax = 544 (ε 7270 nm }, possessing one dicopper(II)-disulfide structural type: {THF solvent) ν(S-S) = 489 ((Δ34S) = −10) cm−1; ν(Cu-S) = 506 ((Δ34S) = −5) cm−1}. Derivation of spectroscopic, structural and chemical conclusions were aided by the study of a close mononuclear analogue with one pyridyl group of the TMPA parent possessing a 6-CH2OCH3 substituent, this being part of the CTV-TMPA architecture. PMID:19663454

  4. A mathematical model relating cortical oxygenated and deoxygenated hemoglobin flows and volumes to neural activity

    NASA Astrophysics Data System (ADS)

    Cornelius, Nathan R.; Nishimura, Nozomi; Suh, Minah; Schwartz, Theodore H.; Doerschuk, Peter C.

    2015-08-01

    Objective. To describe a toolkit of components for mathematical models of the relationship between cortical neural activity and space-resolved and time-resolved flows and volumes of oxygenated and deoxygenated hemoglobin motivated by optical intrinsic signal imaging (OISI). Approach. Both blood flow and blood volume and both oxygenated and deoxygenated hemoglobin and their interconversion are accounted for. Flow and volume are described by including analogies to both resistive and capacitive electrical circuit elements. Oxygenated and deoxygenated hemoglobin and their interconversion are described by generalization of Kirchhoff's laws based on well-mixed compartments. Main results. Mathematical models built from this toolkit are able to reproduce experimental single-stimulus OISI results that are described in papers from other research groups and are able to describe the response to multiple-stimuli experiments as a sublinear superposition of responses to the individual stimuli. Significance. The same assembly of tools from the toolkit but with different parameter values is able to describe effects that are considered distinctive, such as the presence or absence of an initial decrease in oxygenated hemoglobin concentration, indicating that the differences might be due to unique parameter values in a subject rather than different fundamental mechanisms.

  5. Adsorption of cadmium ions on oxygen surface sites in activated carbon

    SciTech Connect

    Jia, Y.F.; Thomas, K.M.

    2000-02-08

    Various types of oxygen functional groups were introduced onto the surface of coconut shell derived activated carbon by oxidation using nitric acid. Fourier-transform infrared spectroscopy (FTIR), temperature-programmed desorption (TPD), and selective neutralization were used to characterize the surface oxygen functional groups. The oxidized carbons were also heat treated to provide a suite of carbons where the oxygen functional groups of various thermal stabilities were varied progressively. The adsorption of cadmium ions was enhanced dramatically by oxidation of the carbon. The ratio of released protons to adsorbed cadmium ions on oxidized carbon was approximately 2, indicating cation exchange was involved in the process of adsorption. Na{sup +} exchange studies with the oxidized carbon gave a similar ratio. After heat treatment of the oxidized carbons to remove oxygen functional groups, the ratio of H{sup +} released to Cd{sup 2+} adsorbed and the adsorption capacity decreased significantly. Both reversible and irreversible processes were involved in cadmium ion adsorption with reversible adsorption having higher enthalpy. The irreversible adsorption resulted from cation exchange with carboxylic acid groups, whereas the reversible adsorption probably involved physisorption of the partially hydrated cadmium ion.

  6. Microbial activities and phosphorus cycling: An application of oxygen isotope ratios in phosphate

    NASA Astrophysics Data System (ADS)

    Stout, Lisa M.; Joshi, Sunendra R.; Kana, Todd M.; Jaisi, Deb P.

    2014-08-01

    Microorganisms carry out biochemical transformations of nutrients that make up their cells. Therefore, understanding how these nutrients are transformed or cycled in natural environments requires knowledge of microbial activity. Commonly used indicators for microbial activity typically include determining microbial respiration by O2/CO2 measurements, cell counts, and measurement of enzyme activities. However, coupled studies on nutrient cycling and microbial activity are not given enough emphasis. Here we apply phosphate oxygen isotope ratios (δ18OP) as a tool for measurement of microbial activity and compare the rate of isotope exchange with methods of measuring microbial activities that are more commonly applied in environmental studies including respiration, dehydrogenase activity, alkaline phosphatase activity, and cell counts. Our results show that different bacteria may have different strategies for P uptake, storage and release, their respiration and consequently expression of DHA and APase activities, but in general the trend of their enzyme activities are comparable. Phosphate δ18OP values correlated well with these other parameters used to measure microbial activity with the strongest linear relationships between δ18OP and CO2 evolution (r = -0.99). Even though the rate of isotope exchange for each microorganism used in this study is different, the rate per unit CO2 respiration showed one general trend, where δ18OP values move towards equilibrium while CO2 is generated. While this suggests that P cycling among microorganisms used in this study can be generalized, further research is needed to determine whether the microorganism-specific isotope exchange trend may occur in natural environments. In summary, phosphate oxygen isotope measurements may offer an alternative for use as a tracer to measure microbial activity in soils, sediments, and many other natural environments.

  7. Comparison of Solar Active Region Complexity Andgeomagnetic Activity from 1996 TO 2014

    NASA Astrophysics Data System (ADS)

    Tanskanen, E. I.; Nikbakhsh, S.; Perez-Suarez, D.; Hackman, T.

    2015-12-01

    We have studied the influence of magnetic complexity of solar Active Regions (ARs)on geomagnetic activity from 1996 to 2014. Sunspots are visual indicators of ARswhere the solar magnetic field is disturbed. We have used International, American,Space Environment Service Center (SESC) and Space Weather Prediction Center(SWPC) sunspot numbers to examine ARs. Major manifestations of solar magneticactivity, such as flares and Coronal Mass Ejections (CMEs), are associated withARs. For this study we chose the Mount Wilson scheme. It classifies ARs in terms oftheir magnetic topology from the least complex (?) to the most complex one ( ?).Several cases have been found where the more complex structures produce strongerflares and CMEs than the less complex ones. We have a list of identified substormsavailable with different phases and their durations. This will be compared to ourmagnetic complexity data to analyse the effects of active region magnetic complexityto the magnetic activity on the vicinity of the Earth.

  8. In situ generated highly active copper oxide catalysts for the oxygen evolution reaction at low overpotential in alkaline solutions.

    PubMed

    Liu, Xiang; Cui, Shengsheng; Qian, Manman; Sun, Zijun; Du, Pingwu

    2016-04-25

    Developing efficient water oxidation catalysts made up of earth-abundant elements has attracted much attention as a step toward for future clean energy production. Herein we report a simple one-step method to generate a low cost copper oxide catalyst film in situ from a copper(ii) ethylenediamine complex. The resulting catalyst has excellent activity toward the oxygen evolution reaction in alkaline solutions. A catalytic current density of 1.0 mA cm(-2) and 10 mA cm(-2) for the catalyst film requires the overpotentials of only ∼370 mV and ∼475 mV in 1.0 M KOH, respectively. This catalytic performance shows that the new catalyst is one of the best Cu-based heterogeneous OER catalysts to date. PMID:27020763

  9. Targeted water soluble copper-tetrazolate complexes: interactions with biomolecules and catecholase like activities.

    PubMed

    Saha, Manideepa; Das, Mriganka; Nasani, Rajendar; Choudhuri, Indrani; Yousufuddin, Muhammed; Nayek, Hari Pada; Shaikh, Mobin M; Pathak, Biswarup; Mukhopadhyay, Suman

    2015-12-14

    Two new mononuclear water soluble copper(II) complexes, [Cu{(5-pyrazinyl)tetrazolate}2(1,10-phenanthroline)] 1 and [Cu{(5-pyrazinyl)tetrazolate}(1,10-phenanthroline)2](NO3)0.5(N3)0.5 2, have been synthesized using the metal mediated [2 + 3] cycloaddition reaction between copper bound azide and pyrazinecarbonitrile. The interactions of these copper tetrazolate complexes 1 and 2 with biomolecules like DNA and bovine serum albumin (BSA) are studied and the catecholase like catalytic activity of compound 2 is also explored. Structural determination reveals that both compounds 1 and 2 are octahedral in nature. Screening tests were conducted to quantify the binding ability of complexes (1 and 2) towards DNA and it was revealed that complex 2 has a stronger affinity to bind to CT-DNA. DFT studies indicated that a lower HOMO-LUMO energy gap between the DNA fragment and metal complexes might be the reason for this type of stronger interaction. DNA cleavage activity was explored by gel-electrophoresis and moderate to strong DNA cleavage properties were observed in the presence and absence of co-reagents. Inhibition of cleavage in the presence of sodium azide indicates the propagation of the activity through the production of singlet molecular oxygen. Furthermore enzyme kinetic studies reflect that complex 2 is also effective in mimicking catecholase like activities. An ESI-MS spectral study indicates the probable involvement of dimeric species [(phen)2Cu-(OH)2-Cu(phen)2](2+) in the catalytic cycle. PMID:26530012

  10. Efficient Management of Complex Striped Files in Active Storage

    SciTech Connect

    Piernas Canovas, Juan; Nieplocha, Jaroslaw

    2008-08-25

    Active Storage provides an opportunity for reducing the band- width requirements between the storage and compute elements of cur- rent supercomputing systems, and leveraging the processing power of the storage nodes used by some modern file systems. To achieve both objec- tives, Active Storage allows certain processing tasks to be performed directly on the storage nodes, near the data they manage. However, Active Storage must also support key requirements of scientific applications. In particular, Active Storage must be able to support striped files and files with complex formats (e.g., netCDF). In this paper, we describe how these important requirements can be addressed. The experimental results on a Lustre file system not only show that our proposal can re- duce the network traffic to near zero and scale the performance with the number of storage nodes, but also that it provides an efficient treatment of striped files and can manage files with complex data structures.

  11. Synthesis, characterization and biological activity of transition metal complexes with Schiff bases derived from 2-nitrobenzaldehyde with glycine and methionine

    NASA Astrophysics Data System (ADS)

    Singh, Bibhesh K.; Rajour, Hemant K.; Prakash, Anant

    Schiff bases derived from 2-nitrobenzaldehyde with amino acids (glycine, methionine) and their Co(II), Ni(II) and Cu(II) complexes have been synthesized and characterized by various physico-chemical techniques. From spectral studies, it has been concluded that the ligands acts as bidentate molecule, coordinates metal through azomethine nitrogen and carboxylate oxygen. Mass spectrum explains the successive degradation of the molecular species in solution and justifies ML2 complexes. X-ray powder diffraction helps to determine the cell parameters of the complexes. Molecular structure of the complexes has been optimized by MM2 calculations and suggests a square planar geometry. The ligands and their metal complexes have been tested in vitro against Streptococcus, Staph, Staphylococcus aureus and Escherchia coli bacteria in order to assess their antibacterial potential. The results indicate that the biological activity increases on complexation.

  12. Synthesis and characterization of chromium(III) Schiff base complexes: antimicrobial activity and its electrocatalytic sensing ability of catechol.

    PubMed

    Kumar, S Praveen; Suresh, R; Giribabu, K; Manigandan, R; Munusamy, S; Muthamizh, S; Narayanan, V

    2015-03-15

    A series of acyclic Schiff base chromium(III) complexes were synthesized with the aid of microwave irradiation method. The complexes were characterized on the basis of elemental analysis, spectral analysis such as UV-Visible, Fourier transform infrared (FT-IR), nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR) spectroscopies and electrospray ionization (ESI) mass spectrometry. Electrochemical analysis of the complexes indicates the presence of chromium ion in +3 oxidation state. Cr (III) ion is stabilized by the tetradentate Schiff base ligand through its nitrogen and phenolic oxygen. From the spectral studies it is understood that the synthesized chromium(III) complexes exhibits octahedral geometry. Antimicrobial activity of chromium complexes was investigated towards the Gram positive and Gram negative bacteria. In the present work, an attempt was made to fabricate a new kind of modified electrode based on chromium Schiff base complexes for the detection of catechol at nanomolar level. PMID:25576940

  13. Environmental layout complexity affects neural activity during navigation in humans.

    PubMed

    Slone, Edward; Burles, Ford; Iaria, Giuseppe

    2016-05-01

    Navigating large-scale surroundings is a fundamental ability. In humans, it is commonly assumed that navigational performance is affected by individual differences, such as age, sex, and cognitive strategies adopted for orientation. We recently showed that the layout of the environment itself also influences how well people are able to find their way within it, yet it remains unclear whether differences in environmental complexity are associated with changes in brain activity during navigation. We used functional magnetic resonance imaging to investigate how the brain responds to a change in environmental complexity by asking participants to perform a navigation task in two large-scale virtual environments that differed solely in interconnection density, a measure of complexity defined as the average number of directional choices at decision points. The results showed that navigation in the simpler, less interconnected environment was faster and more accurate relative to the complex environment, and such performance was associated with increased activity in a number of brain areas (i.e. precuneus, retrosplenial cortex, and hippocampus) known to be involved in mental imagery, navigation, and memory. These findings provide novel evidence that environmental complexity not only affects navigational behaviour, but also modulates activity in brain regions that are important for successful orientation and navigation. PMID:26990572

  14. Reactive oxygen species scavenging activity of Jixueteng evaluated by electron spin resonance (ESR) and photon emission.

    PubMed

    Toyama, Toshizo; Wada-Takahashi, Satoko; Takamichi, Maomi; Watanabe, Kiyoko; Yoshida, Ayaka; Yoshino, Fumihiko; Miyamoto, Chihiro; Maehata, Yojiro; Sugiyama, Shuta; Takahashi, Shun-Suke; Todoki, Kazuo; Lee, Masaichi-Chang-Il; Hamada, Nobushiro

    2014-12-01

    Jixueteng, the dried stem of Spatholobus suberectus Dunn (Leguminosae), is a traditional Chinese herbal medicine that is commonly classified as a herb that promotes blood circulation and can be used to treat blood stasis. The aim of this study was to examine the reactive oxygen species (ROS) scavenging activity of Jixueteng and other herbal medicines. The ROS scavenging activities of the water extracts of Jixueteng, Cnidium officinale and Salvia miltiorrhiza were examined using an electron spin resonance (ESR) technique and faint luminescence measurement. The ESR signal intensities of the superoxide anion (O2·) and hydroxyl radical (HO·) were reduced more by Jixueteng than the other herbal medicines we tested. High photon emission intensity to hydrogen peroxide (H202) and HO· was observed in Jixueteng using the XYZ chemiluminescence system that was used as faint luminescence measurement and analysis. The results of the present study revealed that the ROS scavenging activity of 8% Jixueteng was the strongest among the herbal medicines we tested. It has been reported that Jixueteng includes various polyphenols. In the ROS scavenging activity by Jixueteng, it is supposed that the antioxidant activity caused by these polyphenols would contribute greatly. In conclusion, a water extract component of Jixueteng had potent free radical scavenging activity and an antioxidative effect that inhibited the oxidative actions of O2·⁻, H2O2 and HO·. Therefore, Jixueteng represents a promising therapeutic drug for reactive oxygen-associated pathologies. PMID:25632478

  15. Photo biological activation of NSO donor mixed-ligand complexes: in vivo and preclinical perspectives.

    PubMed

    Selvaganapathy, Muthusamy; Pravin, Narayanaperumal; Pothiraj, Krishnan; Raman, Natarajan

    2014-09-01

    Pyrazolone incorporating N-acetylcysteine (NAC) mixed-ligand complexes are described as promising anti-inflammatory, anticonvulsant, SODs mimetic and cytotoxic compounds possibly due to its antioxidant profile. In this study, we have evaluated the pharmacologic activity, antioxidant and toxicological profiles of compounds (1-6). Among them, compounds 1 and 4 were haemobiocompatible than the others. Both complexes 1 and 4 display efficient photo-nuclease activity upon irradiation with UV-A light of 365 nm and red light of 647 nm as compared with others. Mechanistic studies reveal that the DNA cleavage oxidative pathway involves H2O2 and singlet oxygen as the reactive oxygen species. Interestingly, both compounds 1 and 4, show non-toxic effects in vitro to human normal lymphocyte cells, revealing that they are selective in killing only the cancer cells as expected for a better drug. In addition, considering the safety profile, these compounds are promising as preventive and/or therapeutic agents against oxidative damage. PMID:24995992

  16. Activation of the C-H bond by metal complexes

    NASA Astrophysics Data System (ADS)

    Shilov, Aleksandr E.; Shul'pin, Georgiy B.

    1990-09-01

    Reactions involving the cleavage of C-H bonds by metal complexes in saturated and aromatic hydrocarbons and also in other compounds are examined. Some of these processes occur with formation of a carbon-metal bond, whilst in others the interaction of the complexes with the hydrocarbon takes place without direct contact between the metal atom and the C-H bonds. Metal compounds are widely used as initiators of the liquid-phase oxidation of hydrocarbons at relatively low temperatures. There is a prospect of creating new technologies for the chemical processing of petroleum and gas hydrocarbons, whereby they can be converted into valuable products, for example, into alcohols, ketones, and carboxylic acids, on the basis of processes involving metal complexes. The study of the metal complex activation of the C-H bond also makes it possible to understand and model the metalloenzyme-catalysed hydrocarbon oxidation reactions in the living cell. The bibliography includes 340 references.

  17. C-H bond activation by f-block complexes.

    PubMed

    Arnold, Polly L; McMullon, Max W; Rieb, Julia; Kühn, Fritz E

    2015-01-01

    Most homogeneous catalysis relies on the design of metal complexes to trap and convert substrates or small molecules to value-added products. Organometallic lanthanide compounds first gave a tantalizing glimpse of their potential for catalytic C-H bond transformations with the selective cleavage of one C-H bond in methane by bis(permethylcyclopentadienyl)lanthanide methyl [(η(5) -C5 Me5 )2 Ln(CH3 )] complexes some 25 years ago. Since then, numerous metal complexes from across the periodic table have been shown to selectively activate hydrocarbon C-H bonds, but the challenges of closing catalytic cycles still remain; many f-block complexes show great potential in this important area of chemistry. PMID:25384554

  18. Synthesis, characterization and antioxidant activity copper-quercetin complex

    NASA Astrophysics Data System (ADS)

    Bukhari, S. Birjees; Memon, Shahabuddin; Mahroof-Tahir, M.; Bhanger, M. I.

    2009-01-01

    Quercetin (3,3',4',5,7-pentahydroxyflavone) one of the most abundant dietary flavonoids, has been investigated in the presence of Cu(II) in methanol. The spectroscopic studies (UV-vis, 1H NMR and IR) were useful to assess the relevant interaction of Quercetin with Cu(II) ions, the chelation sites and dependence of the complex structure from the metal/ligand ratio. A 1:2 (L:M) complex was indicated by Job's method of continuous variation, which was applied to ascertain the stoichiometric composition of the complex. The antioxidant activities of the compounds were evaluated by using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging method. The complexed flavonoid was much more effective free radical scavengers than the free flavonoids.

  19. Iodosylbenzene and iodylbenzene adducts of cerium(iv) complexes bearing chelating oxygen ligands.

    PubMed

    Au-Yeung, Ka-Chun; So, Yat-Ming; Wang, Guo-Cang; Sung, Herman H-Y; Williams, Ian D; Leung, Wa-Hung

    2016-04-01

    Reactions of [Ce(IV)(LOEt)2Cl2] (LOEt(-) = [Co(η(5)-C5H5){P(O)(OEt)2}3](-)) and [Ce(μ-O){N(Pr(i)2PO)2}4Cl2] with PhIO afford the λ3-iodane complexes [Ce(IV)(LOEt)2{OI(Cl)Ph}2] and [Ce{N(Pr(i)2PO)2}3{OI(Cl)Ph}], respectively, whereas that between [Ce(IV)(LOEt)2Cl2] and PhIO2 or excess PhIO yields the λ5-iodane adduct [Ce(IV)(LOEt)2{OI(O)ClPh}2]. The crystal structures of the Ce(IV)λ3- and λ5-iodane complexes have been determined and their oxo transfer reactivities have been investigated. PMID:26956671

  20. X-Ray spectroscopy of the photosynthetic oxygen-evolving complex

    PubMed Central

    Sauer, Kenneth; Yano, Junko; Yachandra, Vittal K.

    2008-01-01

    Water oxidation to dioxygen in photosynthesis is catalyzed by a Mn4Ca cluster with O bridging in Photosystem II (PS II) of plants, algae and cyanobacteria. A variety of spectroscopic methods have been applied to analyzing the participation of the complex. X-ray spectroscopy is particularly useful because it is element-specific, and because it can reveal important structural features of the complex with high accuracy and identify the participation of Mn in the redox chemistry. Following a brief history of the application of X-ray spectroscopy to PS II, an overview of newer results will be presented and a description of the present state of our knowledge based on this approach. PMID:19190720

  1. X-Ray Spectroscopy of the Photosynthetic Oxygen-Evolving Complex

    SciTech Connect

    Sauer, K.; Yano, J.; Yachandra, V.K.

    2009-05-27

    Water oxidation to dioxygen in photosynthesis is catalyzed by a Mn{sub 4}Ca cluster with O bridging in Photosystem II (PS II) of plants, algae and cyanobacteria. A variety of spectroscopic methods have been applied to analyzing the participation of the complex. X-ray spectroscopy is particularly useful because it is element-specific, and because it can reveal important structural features of the complex with high accuracy and identify the participation of Mn in the redox chemistry. Following a brief history of the application of X-ray spectroscopy to PS II, an overview of newer results will be presented and a description of the present state of our knowledge based on this approach.

  2. X-ray spectroscopy of the photosynthetic oxygen-evolving complex

    SciTech Connect

    Sauer, Ken; Yano, Junko; Yachandra, Vittal K

    2007-04-05

    Water oxidation to dioxygen in photosynthesis is catalyzed by a Mn4Ca cluster with O bridging in Photosystem II (PS II) of plants, algae and cyanobacteria. A variety of spectroscopic methods have been applied to analyzing the participation of the complex. X-ray spectroscopy is particularly useful because it is element-specific, and because it can reveal important structural features of the complex with high accuracy and identify the participation of Mn in the redox chemistry. Following a brief history of the application of X-ray spectroscopy to PS II, an overview of newer results will be presented and a description of the present state of our knowledge based on this approach.

  3. Multiple Noncovalent Bonding in Halogen Complexes with Oxygen Organics. I. Tertiary Amides.

    PubMed

    Suponitsky, Kyrill Yu; Burakov, N I; Kanibolotsky, Alexander L; Mikhailov, Vasilii A

    2016-06-23

    The present work describes the structure and binding of adducts of N,N'-diacetylpiperazine with halogens and interhalogens based on combination of different experimental methods and quantum chemical calculations. On the basis of conductometric and spectro-photometric experimental results, behavior of complexes in the acetonitrile solution was described. The iodine adduct with N,N'-diacetylpiperazine fully degrades into components. Adducts of interhalogens I-X (X = Cl or Br) with N,N'-diacetylpiperazine in acetonitrile partially dissociate to anionic [X-I-X](-) and cationic species. In the solid state, molecules are connected via C═O···I, C-H···I, and Cl···Cl attractive interactions. N,N'-diacetylpiperazine···dihalogen complex is stabilized by simultaneous C═O···I and C-H···I interactions. Such binding mode allows to explain the problems of the direct halogenation of acetyl-containing compounds with molecular halogens as reagents. We believe that the observed binding pattern can be used as prototypical for future design of halogeno complexes. PMID:27228362

  4. Cerium(III) Complex Modified Gold Electrode: An Efficient Electrocatalyst for the Oxygen Evolution Reaction.

    PubMed

    Garain, Samiran; Barman, Koushik; Sinha, Tridib Kumar; Jasimuddin, Sk; Haeberle, Jörg; Henkel, Karsten; Schmeisser, Dieter; Mandal, Dipankar

    2016-08-24

    Exploring efficient and inexpensive electrocatalysts for the oxidation of water is of great importance for various electrochemical energy storage and conversion technologies. In the present study, a new water-soluble [Ce(III)(DMF) (HSO4)3] complex was synthesized and characterized by UV-vis, photoluminescence, and high-resolution X-ray photoelectron spectroscopy techniques. Owing to classic 5d → 4f transitions, an intense photoluminescence in the UV region was observed from the water-soluble [Ce(III)(DMF) (HSO4)3] complex. A stacking electrode was designed where self-assembled l-cysteine monolayer modified gold was immobilized with the synthesized cerium complex and was characterized by scanning electron microscopy, electrochemical impedance spectroscopy, and cyclic voltammetry. The resulting electrode, i.e., [Ce(III)(DMF) (HSO4)3]-l-cysteine-Au stacks shows high electrocatalytic water oxidation behavior at an overpotential of η ≈ 0.34 V under neutral pH conditions. We also demonstrated a way where the overpotential is possible to decrease upon irradiation of UV light. PMID:27490440

  5. Local Activity Principle:. the Cause of Complexity and Symmetry Breaking

    NASA Astrophysics Data System (ADS)

    Mainzer, Klaus

    2013-01-01

    The principle of local activity is precisely the missing concept to explain the emergence of complex patterns in a homogeneous medium. Leon O. Chua discovered and defined this principle in the theory of nonlinear electronic circuits in a mathematically rigorous way. The local principle can be generalized and proven at least for the class of nonlinear reaction-diffusion systems in physics, chemistry, biology and brain research. Recently, it was realized by memristors for nanoelectronic device applications in technical brains. In general, the emergence of complex patterns and structures is explained by symmetry breaking in homogeneous media. The principle of local activity is the cause of symmetry breaking in homogeneous media. We argue that the principle of local activity is really fundamental in science and can even be identified in quantum cosmology as symmetry breaking of local gauge symmetries generating the complexity of matter and forces in our universe. Finally, we consider applications in economic, financial, and social systems with the emergence of equilibrium states, symmetry breaking at critical points of phase transitions and risky acting at the edge of chaos. In any case, the driving causes of symmetry breaking and the emergence of complexity are locally active elements, cells, units, or agents.

  6. Pt5Gd as a highly active and stable catalyst for oxygen electroreduction.

    PubMed

    Escudero-Escribano, María; Verdaguer-Casadevall, Arnau; Malacrida, Paolo; Grønbjerg, Ulrik; Knudsen, Brian P; Jepsen, Anders K; Rossmeisl, Jan; Stephens, Ifan E L; Chorkendorff, Ib

    2012-10-10

    The activity and stability of Pt(5)Gd for the oxygen reduction reaction (ORR) have been studied, using a combination of electrochemical measurements, angle-resolved X-ray photoelectron spectroscopy (AR-XPS), and density functional theory calculations. Sputter-cleaned, polycrystalline Pt(5)Gd shows a 5-fold increase in ORR activity, relative to pure Pt at 0.9 V, approaching the most active in the literature for catalysts prepared in this way. AR-XPS profiles after electrochemical measurements in 0.1 M HClO(4) show the formation of a thick Pt overlayer on the bulk Pt(5)Gd, and the enhanced ORR activity can be explained by means of compressive strain effects. Furthermore, these novel bimetallic electrocatalysts are highly stable, which, in combination with their enhanced activity, makes them very promising for the development of new cathode catalysts for fuel cells. PMID:22998588

  7. Evidence that reactive oxygen species do not mediate NF-κB activation

    PubMed Central

    Hayakawa, Makio; Miyashita, Hiroshi; Sakamoto, Isao; Kitagawa, Masatoshi; Tanaka, Hirofumi; Yasuda, Hideyo; Karin, Michael; Kikugawa, Kiyomi

    2003-01-01

    It has been postulated that reactive oxygen species (ROS) may act as second messengers leading to nuclear factor (NF)-κB activation. This hypothesis is mainly based on the findings that N-acetyl-l-cysteine (NAC) and pyrrolidine dithiocarbamate (PDTC), compounds recognized as potential antioxidants, can inhibit NF-κB activation in a wide variety of cell types. Here we reveal that both NAC and PDTC inhibit NF-κB activation independently of antioxidative function. NAC selectively blocks tumor necrosis factor (TNF)-induced signaling by lowering the affinity of receptor to TNF. PDTC inhibits the IκB–ubiquitin ligase activity in the cell-free system where extracellular stimuli-regulated ROS production does not occur. Furthermore, we present evidence that endogenous ROS produced through Rac/NADPH oxidase do not mediate NF-κB signaling, but instead lower the magnitude of its activation. PMID:12839997

  8. Coupling of total hemoglobin concentration, oxygenation, and neural activity in rat somatosensory cortex.

    PubMed

    Devor, Anna; Dunn, Andrew K; Andermann, Mark L; Ulbert, Istvan; Boas, David A; Dale, Anders M

    2003-07-17

    Recent advances in brain imaging techniques, including functional magnetic resonance imaging (fMRI), offer great promise for noninvasive mapping of brain function. However, the indirect nature of the imaging signals to the underlying neural activity limits the interpretation of the resulting maps. The present report represents the first systematic study with sufficient statistical power to quantitatively characterize the relationship between changes in blood oxygen content and the neural spiking and synaptic activity. Using two-dimensional optical measurements of hemodynamic signals, simultaneous recordings of neural activity, and an event-related stimulus paradigm, we demonstrate that (1) there is a strongly nonlinear relationship between electrophysiological measures of neuronal activity and the hemodynamic response, (2) the hemodynamic response continues to grow beyond the saturation of electrical activity, and (3) the initial increase in deoxyhemoglobin that precedes an increase in blood volume is counterbalanced by an equal initial decrease in oxyhemoglobin. PMID:12873390

  9. Redox Modulation of PTEN Phosphatase Activity by Hydrogen Peroxide and Bisperoxidovanadium Complexes.

    PubMed

    Lee, Chang-Uk; Hahne, Gernot; Hanske, Jonas; Bange, Tanja; Bier, David; Rademacher, Christoph; Hennig, Sven; Grossmann, Tom N

    2015-11-01

    PTEN is a dual-specificity protein tyrosine phosphatase. As one of the central tumor suppressors, a thorough regulation of its activity is essential for proper cellular homeostasis. The precise implications of PTEN inhibition by reactive oxygen species (e.g. H2 O2 ) and the subsequent structural consequences remain elusive. To study the effects of PTEN inhibition, bisperoxidovanadium (bpV) complexes serve as important tools with the potential for the treatment of nerve injury or cardiac ischemia. However, their mode of action is unknown, hampering further optimization and preventing therapeutic applications. Based on protein crystallography, mass spectrometry, and NMR spectroscopy, we elucidate the molecular basis of PTEN inhibition by H2O2 and bpV complexes. We show that both molecules inhibit PTEN via oxidative mechanisms resulting in the formation of the same intramolecular disulfide, therefore enabling the reactivation of PTEN under reductive conditions. PMID:26418532

  10. Redox Modulation of PTEN Phosphatase Activity by Hydrogen Peroxide and Bisperoxidovanadium Complexes

    PubMed Central

    Lee, Chang-Uk; Hahne, Gernot; Hanske, Jonas; Bange, Tanja; Bier, David; Rademacher, Christoph; Hennig, Sven; Grossmann, Tom N

    2015-01-01

    PTEN is a dual-specificity protein tyrosine phosphatase. As one of the central tumor suppressors, a thorough regulation of its activity is essential for proper cellular homeostasis. The precise implications of PTEN inhibition by reactive oxygen species (e.g. H2O2) and the subsequent structural consequences remain elusive. To study the effects of PTEN inhibition, bisperoxidovanadium (bpV) complexes serve as important tools with the potential for the treatment of nerve injury or cardiac ischemia. However, their mode of action is unknown, hampering further optimization and preventing therapeutic applications. Based on protein crystallography, mass spectrometry, and NMR spectroscopy, we elucidate the molecular basis of PTEN inhibition by H2O2 and bpV complexes. We show that both molecules inhibit PTEN via oxidative mechanisms resulting in the formation of the same intramolecular disulfide, therefore enabling the reactivation of PTEN under reductive conditions. PMID:26418532

  11. A Strategy to Promote the Electrocatalytic Activity of Spinels for Oxygen Reduction by Structure Reversal.

    PubMed

    Wu, Guangping; Wang, Jun; Ding, Wei; Nie, Yao; Li, Li; Qi, Xueqiang; Chen, Siguo; Wei, Zidong

    2016-01-22

    The electrocatalytic performance of a spinel for the oxygen reduction reaction (ORR) can be significantly promoted by reversing its crystalline structure from the normal to the inverse. As the spinel structure reversed, the activation and cleavage of O-O bonds are accelerated owing to a dissimilarity effect of the distinct metal atoms co-occupying octahedral sites. The Co(II)Fe(III)Co(III)O4 spinel with the Fe and Co co-occupying inverse structure exhibits an excellent ORR activity, which even exceeds that of the state-of-the-art commercial Pt/C by 42 mV in alkaline medium. PMID:26663768

  12. Structure-activity relationship in high-performance iron-based electrocatalysts for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Song, Ping; Wang, Ying; Pan, Jing; Xu, Weilin; Zhuang, Lin

    2015-12-01

    A sustainable Iron (Fe), Nitrogen (N) co-doped high performance Fe-Nx/C electrocatalyst for oxygen reduction reaction (ORR) is synthesized simply based on nitric acid oxidation of cheap carbon black. The obtained optimal nonprecious metal electrocatalyst shows high ORR performance in both alkaline and acidic conditions and possesses appreciable performance/price ratio due to its low cost. Furthermore, the structure-activity relationship of different active sites on Fe-Nx/C is revealed systematically: Fe-N4/2-C > Fe4-N-C > N-C >> Fe4-C ≥ C, from both experimental and theoretical points of view.

  13. Transcript levels of antioxidative genes and oxygen radical scavenging enzyme activities in chilled zucchini squash in response to superatmospheric oxygen

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The transcript levels of antioxidative genes including Mn-superoxide dismutase (Mn-SOD), Cu/Zn SOD, ascorbate peroxidise (APX), and catalase (CAT) do not vary significantly during storage at 5 °C with high oxygen treatment in freshly harvested zucchini squash (Cucurbita pepo L. cv. Elite). However, ...

  14. IMPACT OF BLEACHING STRESS ON THE FUNCTION OF THE OXYGEN EVOLVING COMPLEX OF ZOOXANTHELLAE FROM SCLERACTINIAN CORALS(1).

    PubMed

    Hill, Ross; Ralph, Peter J

    2008-04-01

    Global climate change is leading to the rise of ocean temperatures and is triggering mass coral bleaching events on reefs around the world. The expulsion of the symbiotic dinoflagellate algae is believed to occur as a result of damage to the photosynthetic apparatus of these symbionts, although the specific site of initial impact is yet to be conclusively resolved. Here, the sensitivity of the oxygen evolving complex (OEC) to bleaching stress was studied as well as its natural variation between seasons. The artificial electron donor, diphenyl carbazide (DPC), was added to cultured, freshly isolated and expelled (bleaching treatments only) zooxanthellae suspensions. Chl a fluorescence and oxygen production measurements showed that upon addition of DPC, no restoration of diminished photochemical efficiency occurred under control or bleaching conditions. This result was consistent between 12 h and 5 d bleaching treatments on Pocilloporadamicornis, indicating that the OEC is not the primary site of damage, and that zooxanthellae expulsion from the host is a nonselective process with respect to the functioning of the OEC. Further experiments measuring fast induction curves (FICs) revealed that in both summer and winter, the temperature when OEC function was lost occurred between 7°C and 14°C above the sea surface temperature. FIC and oxygen production measurements of P. damicornis during exposure to bleaching stress demonstrated that the thermotolerance of the OEC increased above the temperature of the bleaching treatment over a 4 h period. This finding indicates that the OEC has the capacity to acclimate between seasons and remains functional at temperatures well above bleaching thresholds. PMID:27041186

  15. Design Insights for Tuning the Electrocatalytic Activity of Perovskite Oxides for the Oxygen Evolution Reaction

    SciTech Connect

    Malkhandi, S; Trinh, P; Manohar, AK; Manivannan, A; Balasubramanian, M; Prakash, GKS; Narayanan, SR

    2015-04-16

    Rechargeable metal-air batteries and water electrolyzers based on aqueous alkaline electrolytes hold the potential to be sustainable solutions to address the challenge of storing large amounts of electrical energy generated from solar and wind resources. For these batteries and electrolyzers to be economically viable, it is essential to have efficient, durable, and inexpensive electrocatalysts for the oxygen evolution reaction. In this article, we describe new insights for predicting and tuning the activity of inexpensive transition metal oxides for designing efficient and inexpensive electrocatalysts. We have focused on understanding the factors determining the electrocatalytic activity for oxygen evolution in a strong alkaline medium. To this end, we have conducted a systematic investigation of nanophase calcium-doped lanthanum cobalt manganese oxide, an example of a mixed metal oxide that can be tuned for its electrocatalytic activity by varying the transition metal composition. Using X-ray absorption spectroscopy (XANES), X-ray photoelectron spectroscopy (XPS), electrochemical polarization experiments, and analysis of mechanisms, we have identified the key determinants of electrocatalytic activity. We have found that the Tafel slopes are determined by the oxidation states and the bond energy of the surface intermediates of Mn-OH and Co-OH bonds while the catalytic activity increased with the average d-electron occupancy of the sigma* orbital of the M-OH bond. We anticipate that such understanding will be very useful in predicting the behavior of other transition metal oxide catalysts.

  16. Khat (Catha edulis) generates reactive oxygen species and promotes hepatic cell apoptosis via MAPK activation.

    PubMed

    Abid, Morad Dirhem Naji; Chen, Juan; Xiang, Min; Zhou, Jie; Chen, Xiaoping; Gong, Feili

    2013-08-01

    A number of studies have suggested an association between khat (Catha edulis) chewing and acute liver lesions or chronic liver disease. However, little is known about the effects of khat on hepatic cells. In the current study, we investigated the mechanism behind khat-induced apoptosis in the L02 human hepatic cell line. We used cell growth inhibition assay, flow cytometry and Hoechst 33258 staining to measure hepatocyte apoptosis induced by khat. Western blot analysis was used to detect the expression levels of caspase-8 and -9, as well as those of Bax and Bcl-2. We also measured reactive oxygen species production. The results indicated that khat induced significant hepatocyte apoptosis in L02 cells. We found that khat activated caspase-8 and -9, upregulated Bax protein expression and downregulated Bcl-2 expression levels, which resulted in the coordination of apoptotic signals. Khat-induced hepatocyte apoptosis is primarily regulated through the sustained activation of the c-Jun NH2-terminal kinase (JNK) pathway and only partially via the extracellular signal-regulated kinase (ERK) cascade. Furthermore, the khat-induced reactive oxygen species (ROS) production and the activation of the ROS scavenger, N-acetyl-L-cysteine (NAC), attenuated the khat-induced activation of JNK and ERK. Our results demonstrate that khat triggers the generation of intracellular ROS and sequentially induces the sustainable activation of JNK, which in turn results in a decrease in cell viability and an increase in cell apoptosis. PMID:23708648

  17. Enhancing Electrocatalytic Oxygen Reduction on Nitrogen-Doped Graphene by Active Sites Implantation

    NASA Astrophysics Data System (ADS)

    Feng, Leiyu; Yang, Lanqin; Huang, Zujing; Luo, Jingyang; Li, Mu; Wang, Dongbo; Chen, Yinguang

    2013-11-01

    The shortage of nitrogen active sites and relatively low nitrogen content result in unsatisfying eletrocatalytic activity and durability of nitrogen-doped graphene (NG) for oxygen reduction reaction (ORR). Here we report a novel approach to substantially enhance electrocatalytic oxygen reduction on NG electrode by the implantation of nitrogen active sites with mesoporous graphitic carbon nitride (mpg-C3N4). Electrochemical characterization revealed that in neutral electrolyte the resulting NG (I-NG) exhibited super electrocatalytic activity (completely 100% of four-electron ORR pathway) and durability (nearly no activity change after 100000 potential cyclings). When I-NG was used as cathode catalyst in microbial fuel cells (MFCs), power density and its drop percentage were also much better than the NG and Pt/C ones, demonstrating that the current I-NG was a perfect alternative to Pt/C and offered a new potential for constructing high-performance and less expensive cathode which is crucial for large-scale application of MFC technology.

  18. Enhancing Electrocatalytic Oxygen Reduction on Nitrogen-Doped Graphene by Active Sites Implantation

    PubMed Central

    Feng, Leiyu; Yang, Lanqin; Huang, Zujing; Luo, Jingyang; Li, Mu; Wang, Dongbo; Chen, Yinguang

    2013-01-01

    The shortage of nitrogen active sites and relatively low nitrogen content result in unsatisfying eletrocatalytic activity and durability of nitrogen-doped graphene (NG) for oxygen reduction reaction (ORR). Here we report a novel approach to substantially enhance electrocatalytic oxygen reduction on NG electrode by the implantation of nitrogen active sites with mesoporous graphitic carbon nitride (mpg-C3N4). Electrochemical characterization revealed that in neutral electrolyte the resulting NG (I-NG) exhibited super electrocatalytic activity (completely 100% of four-electron ORR pathway) and durability (nearly no activity change after 100000 potential cyclings). When I-NG was used as cathode catalyst in microbial fuel cells (MFCs), power density and its drop percentage were also much better than the NG and Pt/C ones, demonstrating that the current I-NG was a perfect alternative to Pt/C and offered a new potential for constructing high-performance and less expensive cathode which is crucial for large-scale application of MFC technology. PMID:24264379

  19. Immersion freezing of ice nucleating active protein complexes

    NASA Astrophysics Data System (ADS)

    Hartmann, S.; Augustin, S.; Clauss, T.; Voigtländer, J.; Niedermeier, D.; Wex, H.; Stratmann, F.

    2012-08-01

    Biological particles, e.g. bacteria and their Ice Nucleating Active (INA) protein complexes, might play an important role for the ice formation in atmospheric mixed-phase clouds. Therefore, the immersion freezing behavior of INA protein complexes generated from a SnomaxTM solution/suspension was investigated as function of temperature in a range of -5 °C to -38 °C at the Leipzig Aerosol Cloud Interaction Simulator (LACIS). The immersion freezing of droplets containing small numbers of INA protein complexes occurs in a temperature range of -7 °C and -10 °C. The experiments performed in the lower temperature range, where all droplets freeze which contain at least one INA protein complex, are used to determine the average number of INA protein complexes present, assuming that the INA protein complexes are Poisson distributed over the droplet ensemble. Knowing the average number of INA protein complexes, the heterogeneous ice nucleation rate and rate coefficient of a single INA protein complex is determined by using the newly-developed CHESS model (stoCHastic model of idEntical poiSSon distributed ice nuclei). Therefore, we assume the ice nucleation process to be of stochastic nature, and a parameterization of the INA protein complex's nucleation rate. Analyzing the results of immersion freezing experiments from literature (SnomaxTM and Pseudomonas syringae bacteria), to results gained in this study, demonstrates that first, a similar temperature dependence of the heterogeneous ice nucleation rate for a single INA protein complex was found in all experiments, second, the shift of the ice fraction curves to higher temperatures can be explained consistently by a higher average number of INA protein complexes being present in the droplet ensemble, and finally the heterogeneous ice nucleation rate of one single INA protein complex might be also applicable for intact Pseudomonas syringae bacteria cells. The results obtained in this study allow a new perspective on the

  20. Reactive oxygen species in signalling the transcriptional activation of WIPK expression in tobacco.

    PubMed

    Xu, Juan; Yang, Kwang-Yeol; Yoo, Seung Jin; Liu, Yidong; Ren, Dongtao; Zhang, Shuqun

    2014-07-01

    Plant mitogen-activated protein kinases represented by tobacco WIPK (wounding-induced protein kinase) and its orthologs in other species are unique in their regulation at transcriptional level in response to stress and pathogen infection. We previously demonstrated that transcriptional activation of WIPK is essential for induced WIPK activity, and activation of salicylic acid-induced protein kinase (SIPK) by the constitutively active NtMEK2(DD) is sufficient to induce WIPK gene expression. Here, we report that the effect of SIPK on WIPK gene expression is mediated by reactive oxygen species (ROS). Using a combination of pharmacological and gain-of-function transgenic approaches, we studied the relationship among SIPK activation, WIPK gene activation in response to fungal cryptogein, light-dependent ROS generation in chloroplasts, and ROS generated via NADPH oxidase. In the conditional gain-of-function GVG-NtMEK2(DD) transgenic tobacco, induction of WIPK expression is dependent on the ROS generation in chloroplasts. Consistently, methyl viologen, an inducer of ROS generation in chloroplasts, highly activated WIPK expression. In addition to chloroplast-originated ROS, H(2)O(2) generated from the cell-surface NADPH oxidase could also activate WIPK gene expression, and inhibition of cryptogein-induced ROS generation also abolished WIPK gene activation. Our data demonstrate that WIPK gene activation is mediated by ROS, which provides a mechanism by which ROS influence cellular signalling processes in plant stress/defence response. PMID:24392654

  1. Tuning the surface oxygen concentration of {111} surrounded ceria nanocrystals for enhanced photocatalytic activities

    NASA Astrophysics Data System (ADS)

    Younis, Adnan; Chu, Dewei; Kaneti, Yusuf Valentino; Li, Sean

    2015-12-01

    For oxide semiconductors, the morphology, particle size and oxygen vacancies are usually considered as key influential parameters for photocatalytic degradation of organic pollutants/dyes. It is widely accepted that cation doping not only modifies their phase and microstructures but also introduces variations in oxygen vacancy concentration. Herein, we report the fabrication of sub-10 nm sized pure and indium doped CeO2 nanocrystals (NCs) via a facile, green hydrothermal method for the investigation of photocatalytic activities. X-ray diffraction and transmission electron microscopy were employed to examine the crystal phase and morphology of the as-prepared nanocrystals. Raman and X-ray photoelectron spectroscopy techniques were implemented to investigate the presence and variations in oxygen vacancy concentration in un-doped and indium doped CeO2 nanocrystals. The photocatalytic activity results revealed that 10 at% doping is the optimal indium doping level to demonstrate superior dye removal efficiency (~40%) over un-doped and doped CeO2 NCs. Moreover, the 10% In-doped CeO2 nanocrystals expressed excellent cycling stability and superior photocatalytic performance toward other dye pollutants. Finally, on the basis of our findings, a possible photocatalytic mechanism in which indium doping can generate more surface oxygen vacancies in the ceria lattice which delay the electron-hole recombination rates, thus increasing the lifetime of electron-hole separation for enhanced photocatalytic performances was proposed.For oxide semiconductors, the morphology, particle size and oxygen vacancies are usually considered as key influential parameters for photocatalytic degradation of organic pollutants/dyes. It is widely accepted that cation doping not only modifies their phase and microstructures but also introduces variations in oxygen vacancy concentration. Herein, we report the fabrication of sub-10 nm sized pure and indium doped CeO2 nanocrystals (NCs) via a facile

  2. Communication: CO oxidation by silver and gold cluster cations: Identification of different active oxygen species

    SciTech Connect

    Popolan, Denisia M.; Bernhardt, Thorsten M.

    2011-03-07

    The oxidation of carbon monoxide with nitrous oxide on mass-selected Au{sub 3}{sup +} and Ag{sub 3}{sup +} clusters has been investigated under multicollision conditions in an octopole ion trap experiment. The comparative study reveals that for both gold and silver cations carbon dioxide is formed on the clusters. However, whereas in the case of Au{sub 3}{sup +} the cluster itself acts as reactive species that facilitates the formation of CO{sub 2} from N{sub 2}O and CO, for silver the oxidized clusters Ag{sub 3}O{sub x}{sup +} (n= 1-3) are identified as active in the CO oxidation reaction. Thus, in the case of the silver cluster cations N{sub 2}O is dissociated and one oxygen atom is suggested to directly react with CO, whereas a second kind of oxygen strongly bound to silver is acting as a substrate for the reaction.

  3. High performance electrodes in vanadium redox flow batteries through oxygen-enriched thermal activation

    NASA Astrophysics Data System (ADS)

    Pezeshki, Alan M.; Clement, Jason T.; Veith, Gabriel M.; Zawodzinski, Thomas A.; Mench, Matthew M.

    2015-10-01

    The roundtrip electrochemical energy efficiency is improved from 63% to 76% at a current density of 200 mA cm-2 in an all-vanadium redox flow battery (VRFB) by utilizing modified carbon paper electrodes in the high-performance no-gap design. Heat treatment of the carbon paper electrodes in a 42% oxygen/58% nitrogen atmosphere increases the electrochemically wetted surface area from 0.24 to 51.22 m2 g-1, resulting in a 100-140 mV decrease in activation overpotential at operationally relevant current densities. An enriched oxygen environment decreases the amount of treatment time required to achieve high surface area. The increased efficiency and greater depth of discharge doubles the total usable energy stored in a fixed amount of electrolyte during operation at 200 mA cm-2.

  4. Effect of surface phosphorus functionalities of activated carbons containing oxygen and nitrogen on electrochemical capacitance

    PubMed Central

    Hulicova-Jurcakova, Denisa; Seredych, Mykola; Lu, Gao Qing; Kodiweera, N.K.A.C.; Stallworth, Phillip E.; Greenbaum, Steven; Bandosz, Teresa J.

    2009-01-01

    Micro/mesoporous activated carbons containing oxygen and phosphorus heteroatoms were modified by incorporation of nitrogen using melamine and urea precursors. The surface chemistry was analyzed by the means of elemental analysis, XPS, and 31P MAS NMR. The results indicate that upon the incorporation of nitrogen at high temperatures not only new species involving carbon/nitrogen/oxygen are formed but also the phosphorous environment is significantly altered. Both urea and melamine precursors have similar effects on formation of P–N and P–C bonds. These compounds, although present in small but measurable quantities seem to affect the performance of carbons in electrochemical capacitors. With an increase in the heterogeneity of phosphorus containing species and with a decrease in the content pyrophosphates the capacitance increases and the retention ratio of the capacitor is improved. PMID:20354586

  5. EFFECT OF MOLECULAR OXYGEN ON THE ACTIVATED CARBON ADSORPTION OF NATURAL ORGANIC MATTER IN OHIO RIVER WATER

    EPA Science Inventory

    Recently published data show that the adsorptive capacity of granular activated carbon for phenois increases significantly in the presence of molecular oxygen (Vidic, Suidan,Traegner and Nakhla, 1990). in this study, the effect of molecular oxygen on the adsorptive capacity of a...

  6. The crystal structure of an isopenicillin N synthase complex with an ethereal substrate analogue reveals water in the oxygen binding site.

    PubMed

    Clifton, Ian J; Ge, Wei; Adlington, Robert M; Baldwin, Jack E; Rutledge, Peter J

    2013-08-19

    Isopenicillin N synthase (IPNS) is a non-heme iron oxidase central to the biosynthesis of β-lactam antibiotics. IPNS converts the tripeptide δ-(L-α-aminoadipoyl)-L-cysteinyl-D-valine (ACV) to isopenicillin N while reducing molecular oxygen to water. The substrate analogue δ-(L-α-aminoadipoyl)-L-cysteinyl-O-methyl-D-threonine (ACmT) is not turned over by IPNS. Epimeric δ-(L-α-aminoadipoyl)-L-cysteinyl-O-methyl-D-allo-threonine (ACmaT) is converted to a bioactive penam product. ACmT and ACmaT differ from each other only in the stereochemistry at the β-carbon atom of their third residue. These substrates both contain a methyl ether in place of the isopropyl group of ACV. We report an X-ray crystal structure for the anaerobic IPNS:Fe(II):ACmT complex. This structure reveals an additional water molecule bound to the active site metal, held by hydrogen-bonding to the ether oxygen atom of the substrate analogue. PMID:23860486

  7. Study on a phosphorescent copper(I) complex and its oxygen-sensing performances upon polystyrene and MCM-41 matrixes

    NASA Astrophysics Data System (ADS)

    Xu, Xiao-yong; Xiao, Han-ning; Xu, Yi-ming; Zhang, Ming-jun

    In this paper, we synthesize a new ligand of 1-ethyl-2-(naphthalen-1-yl)-1H-imidazo[4,5-f][1,10]phenanthroline (Phen-Np-Et) and its corresponding Cu(I) complex of [Cu(Phen-Np-Et)(POP)]BF4, where POP is bis(2-(diphenylphosphanyl)phenyl) ether. The single-crystal structure, electronic nature and photophysical property of [Cu(Phen-Np-Et)(POP)]BF4 are discussed in detail. It is found that the yellow emission from [Cu(Phen-Np-Et)(POP)]BF4 owns a long excited state lifetime of 287 μs under pure N2 atmosphere. Theoretical calculation on [Cu(Phen-Np-Et)(POP)]+ suggests that the emission comes from a triplet metal-to-ligand-charge-transfer excited state. Then, [Cu(Phen-Np-Et)(POP)]BF4 are doped into two matrixes of polystyrene and MCM-41 to investigate the oxygen-sensing performance. Finally, sensitivity maxima of 9.6 and 3.6 are achieved by the composite nanofibers of [Cu(Phen-Np-Et)(POP)]BF4/polystyrene and the [Cu(Phen-Np-Et)(POP)]BF4/MCM-41, respectively. Both samples are highly sensitive toward molecular oxygen, owing to the large surface-area-to-volume ratios of nanofibrous membranes and MCM-41 matrix.

  8. Proton-Coupled Electron Transfer During the S-State Transitions of the Oxygen-Evolving Complex of Photosystem II.

    PubMed

    Amin, Muhamed; Vogt, Leslie; Szejgis, Witold; Vassiliev, Serguei; Brudvig, Gary W; Bruce, Doug; Gunner, M R

    2015-06-18

    The oxygen-evolving complex (OEC) of photosystem II (PSII) is a unique Mn4O5Ca cluster that catalyzes water oxidation via four photoactivated electron transfer steps. As the protein influence on the redox and protonation chemistry of the OEC remains an open question, we present a classical valence model of the OEC that allows the redox state of each Mn and the protonation state of bridging μ-oxos and terminal waters to remain in equilibrium with the PSII protein throughout the redox cycle. We find that the last bridging oxygen loses its proton during the transition from S0 to S1. Two possible S2 states are found depending on the OEC geometry: S2 has Mn4(IV) with a proton lost from a terminal water (W1) trapped by the nearby D1-D61 if O5 is closer to Mn4, or Mn1(IV), with partial deprotonation of D1-H337 and D1-E329 if O5 is closer to Mn1. In S3, the OEC is Mn4(IV) with W2 deprotonated. The estimated OEC Em's range from +0.7 to +1.3 V, enabling oxidation by P680(+), the primary electron donor in PSII. In chloride-depleted PSII, the proton release increases during the S1 to S2 transition, leaving the OEC unable to properly advance through the water-splitting cycle. PMID:25575266

  9. Contribution of transition metals in the reactive oxygen species activity of PM emissions from retrofitted heavy-duty vehicles

    NASA Astrophysics Data System (ADS)

    Verma, Vishal; Shafer, Martin M.; Schauer, James J.; Sioutas, Constantinos

    2010-12-01

    We assessed the contribution of water-soluble transition metals to the reactive oxygen species (ROS) activity of diesel exhaust particles (DEPs) from four heavy-duty vehicles in five retrofitted configurations (V-SCRT, Z-SCRT, DPX, hybrid, and school bus). A heavy-duty truck without any control device served as the baseline vehicle. Particles were collected from all vehicle-configurations on a chassis dynamometer under three driving conditions: cruise (80 km h -1), transient UDDS, and idle. A sensitive macrophage-based in vitro assay was used to determine the ROS activity of collected particles. The contribution of water-soluble transition metals in the measured activity was quantified by their removal using a Chelex ® complexation method. The study demonstrates that despite an increase in the intrinsic ROS activity (per mass basis) of exhaust PM with use of most control technologies, the overall ROS activity (expressed per km or per h) was substantially reduced for retrofitted configurations compared to the baseline vehicle. Chelex treatment of DEPs water extracts removed a substantial (≥70%) and fairly consistent fraction of the ROS activity, which ascertains the dominant role of water-soluble metals in PM-induced cellular oxidative stress. However, relatively lower removal of the activity in few vehicle-configurations (V-SCRT, DPX and school bus idle), despite a large aggregate metals removal, indicated that not all species were associated with the measured activity. A univariate regression analysis identified several transition metals (Fe, Cr, Co and Mn) as significantly correlated ( R > 0.60; p < 0.05) with the ROS activity. Multivariate linear regression model incorporating Fe, Cr and Co explained 90% of variability in ROS levels, with Fe accounting for the highest (84%) fraction of the variance.

  10. Similar Biological Activities of Two Isostructural Ruthenium and Osmium Complexes

    SciTech Connect

    Maksimoska,J.; Williams, D.; Atilla-Gokcumen, G.; Smalley, K.; Carroll, P.; Webster, R.; Filippakopoulos, P.; Knapp, S.; Herlyn, M.; Meggers, E.

    2008-01-01

    In this study, we probe and verify the concept of designing unreactive bioactive metal complexes, in which the metal possesses a purely structural function, by investigating the consequences of replacing ruthenium in a bioactive half-sandwich kinase inhibitor scaffold by its heavier congener osmium. The two isostructural complexes are compared with respect to their anticancer properties in 1205?Lu melanoma cells, activation of the Wnt signaling pathway, IC50 values against the protein kinases GSK-3? and Pim-1, and binding modes to the protein kinase Pim-1 by protein crystallography. It was found that the two congeners display almost indistinguishable biological activities, which can be explained by their nearly identical three-dimensional structures and their identical mode of action as protein kinase inhibitors. This is a unique example in which the replacement of a metal in an anticancer scaffold by its heavier homologue does not alter its biological activity.

  11. Superoxide scavenging activity of pirfenidone-iron complex

    SciTech Connect

    Mitani, Yoshihiro; Sato, Keizo Muramoto, Yosuke; Karakawa, Tomohiro; Kitamado, Masataka; Iwanaga, Tatsuya; Nabeshima, Tetsuji; Maruyama, Kumiko; Nakagawa, Kazuko; Ishida, Kazuhiko; Sasamoto, Kazumi

    2008-07-18

    Pirfenidone (PFD) is focused on a new anti-fibrotic drug, which can minimize lung fibrosis etc. We evaluated the superoxide (O{sub 2}{sup {center_dot}}{sup -}) scavenging activities of PFD and the PFD-iron complex by electron spin resonance (ESR) spectroscopy, luminol-dependent chemiluminescence assay, and cytochrome c reduction assay. Firstly, we confirmed that the PFD-iron complex was formed by mixing iron chloride with threefold molar PFD, and the complex was stable in distillated water and ethanol. Secondary, the PFD-iron complex reduced the amount of O{sub 2}{sup {center_dot}}{sup -} produced by xanthine oxidase/hypoxanthine without inhibiting the enzyme activity. Thirdly, it also reduced the amount of O{sub 2}{sup {center_dot}}{sup -} released from phorbor ester-stimulated human neutrophils. PFD alone showed few such effects. These results suggest the possibility that the O{sub 2}{sup {center_dot}}{sup -} scavenging effect of the PFD-iron complex contributes to the anti-fibrotic action of PFD used for treating idiopathic pulmonary fibrosis.

  12. Mobybdenum(VI)-oxygen complex containing citrage ligand: synthesis and characterization of K 6[Mo 2O 5(cit) 2]·5H 2O

    NASA Astrophysics Data System (ADS)

    Zhou, X.-H.; Xing, Y.-H.; Xu, J.-Q.; Li, D.-M.; Wang, R.-Z.; Liu, S.-Q.; Zeng, Q.-X.; Huang, X.-Y.

    1999-06-01

    The complex, K 6[Mo 2O 5(cit) 2]·5H 2O was obtained by crystallization from reaction of [Et 4N] 3[Mo 2FeS 8O 2 and potassium citrate (K 3cit) in methanol and water under an atmosphere of pure nitrogen at ambient temperature. The complex is triclinic, space group P1, a = 11.843(8) Å, b = 13.717(8) Å, c = 10.287(5) Å, α = 108.11(4) °, β = 99.42(5) (1) °, γ = 66.52(4) °, R = 0.034 for 4510 observed (I > 3 σ (I)) reflections. Single crystal structure analysis reveals that citrate ligand coordinated to molybdenum atom through two carboxylato oxygens and one deprotonated hydroxyl oxygen together with one bridging oxygen atom and two terminal oxygen atoms completes distorted coordination octahedron around each molybdenum atom. IR spectra are in agreement with the structure.

  13. Submaximal oxygen uptake kinetics, functional mobility, and physical activity in older adults with heart failure and reduced ejection fraction

    PubMed Central

    Hummel, Scott L; Herald, John; Alpert, Craig; Gretebeck, Kimberlee A; Champoux, Wendy S; Dengel, Donald R; Vaitkevicius, Peter V; Alexander, Neil B

    2016-01-01

    Background Submaximal oxygen uptake measures are more feasible and may better predict clinical cardiac outcomes than maximal tests in older adults with heart failure (HF). We examined relationships between maximal oxygen uptake, submaximal oxygen kinetics, functional mobility, and physical activity in older adults with HF and reduced ejection fraction. Methods Older adults with HF and reduced ejection fraction (n = 25, age 75 ± 7 years) were compared to 25 healthy age- and gender-matched controls. Assessments included a maximal treadmill test for peak oxygen uptake (VO2peak), oxygen uptake kinetics at onset of and on recovery from a submaximal treadmill test, functional mobility testing [Get Up and Go (GUG), Comfortable Gait Speed (CGS), Unipedal Stance (US)], and self-reported physical activity (PA). Results Compared to controls, HF had worse performance on GUG, CGS, and US, greater delays in submaximal oxygen uptake kinetics, and lower PA. In controls, VO2peak was more strongly associated with functional mobility and PA than submaximal oxygen uptake kinetics. In HF patients, submaximal oxygen uptake kinetics were similarly associated with GUG and CGS as VO2peak, but weakly associated with PA. Conclusions Based on their mobility performance, older HF patients with reduced ejection fraction are at risk for adverse functional outcomes. In this population, submaximal oxygen uptake measures may be equivalent to VO2 peak in predicting functional mobility, and in addition to being more feasible, may provide better insight into how aerobic function relates to mobility in older adults with HF. PMID:27594875

  14. Electron transfer characterization of iron and cobalt porphyrins and copper complexes, and of their metal-carbon and metal-oxygen bond energies

    SciTech Connect

    Qui, Aimin

    1992-12-31

    The electron-transfer and oxidation-reduction chemistry for the alkyl-iron and alkyl-cobalt porphyrins [(Por)M-R] and copper complexes has been investigated on the basis of cyclic voltammetric and controlled-potential-electrolysis measurements. Half-wave potentials for the oxidation and the reduction of (Por)M-R are directly influenced by the nature of the electron-donating or electron-withdrawing groups on the porphyrin ring and the structure of the alkyl groups. The redox potentials for a series of copper complexes are affected by the electron donating ability and the chelate effect of the ligands. Hydrolysis of the copper(II) cations (Cu{sup II}L{sub n}{sup 2+}) occurs in water. The reactivity of copper(I) complexes with dioxygen is directly related to the oxidation potential of the complexes in the solvent. The combination of Cu{sup I}(bpy)2{sup +} and tertiary-butyl hydroperoxide induces O{sub 2} activation to oxygenate methylenic carbon to ketones. Mechanistic schemes have been developed on the basis of electrochemical and spectrophotometric characteristics and reaction-product profiles for copper(II)-bis(bipyridine) [Cu{sup II}(bpy)2{sup 2+}]/base-induced activation of O{sub 2} to dehydrogenate primary alcohols to aldehydes. The free energies of bond formation (-{Delta}G{sub BF}) for the (Por)M-R and copper-ligand (oxygen or nitrogen) bonds have been determined from the redox potentials of the corresponding electrode reactions. The values of -{Delta}G{sub BF} are 14-35 kcal mol{sup {minus}1} for iron porphyrins and 20-38 kcal mol{sup {minus}1} for cobalt porphyrins which depend on the structures of the porphyrins and the alkyl groups. Apparent bond energies are 18-51 kcal mol{sup {minus}1} for the Cu{sup II}-L bonds are 46-78 kcal mol{sup {minus}1} for the Cu{sup I}-L bonds. The free energies of bond formation for the L{sub n}Cu{sup I}-OO bonds are 7-16 kcal mol{sup {minus}1}.

  15. Genome-wide activities of Polycomb complexes control pervasive transcription.

    PubMed

    Lee, Hun-Goo; Kahn, Tatyana G; Simcox, Amanda; Schwartz, Yuri B; Pirrotta, Vincenzo

    2015-08-01

    Polycomb group (PcG) complexes PRC1 and PRC2 are well known for silencing specific developmental genes. PRC2 is a methyltransferase targeting histone H3K27 and producing H3K27me3, essential for stable silencing. Less well known but quantitatively much more important is the genome-wide role of PRC2 that dimethylates ∼70% of total H3K27. We show that H3K27me2 occurs in inverse proportion to transcriptional activity in most non-PcG target genes and intergenic regions and is governed by opposing roaming activities of PRC2 and complexes containing the H3K27 demethylase UTX. Surprisingly, loss of H3K27me2 results in global transcriptional derepression proportionally greatest in silent or weakly transcribed intergenic and genic regions and accompanied by an increase of H3K27ac and H3K4me1. H3K27me2 therefore sets a threshold that prevents random, unscheduled transcription all over the genome and even limits the activity of highly transcribed genes. PRC1-type complexes also have global roles. Unexpectedly, we find a pervasive distribution of histone H2A ubiquitylated at lysine 118 (H2AK118ub) outside of canonical PcG target regions, dependent on the RING/Sce subunit of PRC1-type complexes. We show, however, that H2AK118ub does not mediate the global PRC2 activity or the global repression and is predominantly produced by a new complex involving L(3)73Ah, a homolog of mammalian PCGF3. PMID:25986499

  16. A simplified methodology to approach the complexity of foraminiferal calcite oxygen-isotope data - model comparison

    NASA Astrophysics Data System (ADS)

    Roche, Didier; Waelbroeck, Claire

    2016-04-01

    Since the pioneering work of Epstein (Epstein et al., 1953), numerous calcite isotopic records from the ocean have been used to attempt reconstructing paleoclimatic information. Additional to the well known complexity brought by the fact that foraminiferal calcite records both temperature and isotopic composition of the surrounding oceanic waters, an additional effect for surface - dwelling foraminifers is the fact that two different species do not have the same habitat and may thus record different signals. This is obvious when comparing paleoclimatic records where different species have been measured for the isotopic composition of the calcite. The difference in habitat produces a three dimensional spatial complexity (a foraminifera living in preferred climatic conditions at a specific location, but also at a specific depth, sometimes far from the surface) but also a temporal uncertainty (foraminifers generally live for only a few weeks and their growth season may be evolving through time with climate change). While the different species habitats potentially contain a wealth of information that could be used to better understand the sequences of climate change, this has seldom been used in modeling studies, most models deriving calcite isotopic signal from surface and annual mean conditions (e.g. Roche et al., 2014). In the present work, we propose a reduced complexity approach to compute the calcite for several planktonic foraminifers from climate model simulations under pre-industrial conditions. We base our approach on simple functions describing the temperature dependence of the different species growth rates (Lombard et al., 2009) and on probability of presence based on the physical variables computed in the climate model. We present a comparison to available sediment traps and core tops data as a validation of the methodology, focusing on the possibility for future applicability towards inversion of the signal measured in oceanic sediment cores. References

  17. Breakpoints in ventilation, cerebral and muscle oxygenation, and muscle activity during an incremental cycling exercise

    PubMed Central

    Racinais, Sebastien; Buchheit, Martin; Girard, Olivier

    2014-01-01

    The aim of this study was to locate the breakpoints of cerebral and muscle oxygenation and muscle electrical activity during a ramp exercise in reference to the first and second ventilatory thresholds. Twenty-five cyclists completed a maximal ramp test on an electromagnetically braked cycle-ergometer with a rate of increment of 25 W/min. Expired gazes (breath-by-breath), prefrontal cortex and vastus lateralis (VL) oxygenation [Near-infrared spectroscopy (NIRS)] together with electromyographic (EMG) Root Mean Square (RMS) activity for the VL, rectus femoris (RF), and biceps femoris (BF) muscles were continuously assessed. There was a non-linear increase in both cerebral deoxyhemoglobin (at 56 ± 13% of the exercise) and oxyhemoglobin (56 ± 8% of exercise) concomitantly to the first ventilatory threshold (57 ± 6% of exercise, p > 0.86, Cohen's d < 0.1). Cerebral deoxyhemoglobin further increased (87 ± 10% of exercise) while oxyhemoglobin reached a plateau/decreased (86 ± 8% of exercise) after the second ventilatory threshold (81 ± 6% of exercise, p < 0.05, d > 0.8). We identified one threshold only for muscle parameters with a non-linear decrease in muscle oxyhemoglobin (78 ± 9% of exercise), attenuation in muscle deoxyhemoglobin (80 ± 8% of exercise), and increase in EMG activity of VL (89 ± 5% of exercise), RF (82 ± 14% of exercise), and BF (85 ± 9% of exercise). The thresholds in BF and VL EMG activity occurred after the second ventilatory threshold (p < 0.05, d > 0.6). Our results suggest that the metabolic and ventilatory events characterizing this latter cardiopulmonary threshold may affect both cerebral and muscle oxygenation levels, and in turn, muscle recruitment responses. PMID:24782786

  18. Reconstructing ecosystem functions of the active microbial community of the Baltic Sea oxygen depleted sediments.

    PubMed

    Thureborn, Petter; Franzetti, Andrea; Lundin, Daniel; Sjöling, Sara

    2016-01-01

    Baltic Sea deep water and sediments hold one of the largest anthropogenically induced hypoxic areas in the world. High nutrient input and low water exchange result in eutrophication and oxygen depletion below the halocline. As a consequence at Landsort Deep, the deepest point of the Baltic Sea, anoxia in the sediments has been a persistent condition over the past decades. Given that microbial communities are drivers of essential ecosystem functions we investigated the microbial community metabolisms and functions of oxygen depleted Landsort Deep sediments by metatranscriptomics. Results show substantial expression of genes involved in protein metabolism demonstrating that the Landsort Deep sediment microbial community is active. Identified expressed gene suites of metabolic pathways with importance for carbon transformation including fermentation, dissimilatory sulphate reduction and methanogenesis were identified. The presence of transcripts for these metabolic processes suggests a potential for heterotrophic-autotrophic community synergism and indicates active mineralisation of the organic matter deposited at the sediment as a consequence of the eutrophication process. Furthermore, cyanobacteria, probably deposited from the water column, are transcriptionally active in the anoxic sediment at this depth. Results also reveal high abundance of transcripts encoding integron integrases. These results provide insight into the activity of the microbial community of the anoxic sediment at the deepest point of the Baltic Sea and its possible role in ecosystem functioning. PMID:26823996

  19. Involvement of Activated Oxygen in Nitrate-Induced Senescence of Pea Root Nodules.

    PubMed Central

    Escuredo, P. R.; Minchin, F. R.; Gogorcena, Y.; Iturbe-Ormaetxe, I.; Klucas, R. V.; Becana, M.

    1996-01-01

    The effect of short-term nitrate application (10 mM, 0-4 d) on nitrogenase (N2ase) activity, antioxidant defenses, and related parameters was investigated in pea (Pisum sativum L. cv Frilene) nodules. The response of nodules to nitrate comprised two stages. In the first stage (0-2 d), there were major decreases in N2ase activity and N2ase-linked respiration and concomitant increases in carbon cost of N2ase and oxygen diffusion resistance of nodules. There was no apparent oxidative damage, and the decline in N2ase activity was, to a certain extent, reversible. The second stage (>2 d) was typical of a senescent, essentially irreversible process. It was characterized by moderate increases in oxidized proteins and catalytic Fe and by major decreases in antioxidant enzymes and metabolites. The restriction in oxygen supply to bacteroids may explain the initial decline in N2ase activity. The decrease in antioxidant protection is not involved in this process and is not specifically caused by nitrate, since it also occurs with drought stress. However, comparison of nitrate- and drought-induced senescence shows an important difference: there is no lipid degradation or lipid peroxide accumulation with nitrate, indicating that lipid peroxidation is not necessarily involved in nodule senescence. PMID:12226252

  20. Reactive Oxygen Species in the Paraventricular Nucleus of the Hypothalamus Alter Sympathetic Activity During Metabolic Syndrome

    PubMed Central

    Cruz, Josiane C.; Flôr, Atalia F. L.; França-Silva, Maria S.; Balarini, Camille M.; Braga, Valdir A.

    2015-01-01

    The paraventricular nucleus of the hypothalamus (PVN) contains heterogeneous populations of neurons involved in autonomic and neuroendocrine regulation. The PVN plays an important role in the sympathoexcitatory response to increasing circulating levels of angiotensin II (Ang-II), which activates AT1 receptors in the circumventricular organs (OCVs), mainly in the subfornical organ (SFO). Circulating Ang-II induces a de novo synthesis of Ang-II in SFO neurons projecting to pre-autonomic PVN neurons. Activation of AT1 receptors induces intracellular increases in reactive oxygen species (ROS), leading to increases in sympathetic nerve activity (SNA). Chronic sympathetic nerve activation promotes a series of metabolic disorders that characterizes the metabolic syndrome (MetS): dyslipidemia, hyperinsulinemia, glucose intolerance, hyperleptinemia and elevated plasma hormone levels, such as noradrenaline, glucocorticoids, leptin, insulin, and Ang-II. This review will discuss the contribution of our laboratory and others regarding the sympathoexcitation caused by peripheral Ang-II-induced reactive oxygen species along the subfornical organ and paraventricular nucleus of the hypothalamus. We hypothesize that this mechanism could be involved in metabolic disorders underlying MetS. PMID:26779026

  1. Reconstructing ecosystem functions of the active microbial community of the Baltic Sea oxygen depleted sediments

    PubMed Central

    Franzetti, Andrea; Lundin, Daniel; Sjöling, Sara

    2016-01-01

    Baltic Sea deep water and sediments hold one of the largest anthropogenically induced hypoxic areas in the world. High nutrient input and low water exchange result in eutrophication and oxygen depletion below the halocline. As a consequence at Landsort Deep, the deepest point of the Baltic Sea, anoxia in the sediments has been a persistent condition over the past decades. Given that microbial communities are drivers of essential ecosystem functions we investigated the microbial community metabolisms and functions of oxygen depleted Landsort Deep sediments by metatranscriptomics. Results show substantial expression of genes involved in protein metabolism demonstrating that the Landsort Deep sediment microbial community is active. Identified expressed gene suites of metabolic pathways with importance for carbon transformation including fermentation, dissimilatory sulphate reduction and methanogenesis were identified. The presence of transcripts for these metabolic processes suggests a potential for heterotrophic-autotrophic community synergism and indicates active mineralisation of the organic matter deposited at the sediment as a consequence of the eutrophication process. Furthermore, cyanobacteria, probably deposited from the water column, are transcriptionally active in the anoxic sediment at this depth. Results also reveal high abundance of transcripts encoding integron integrases. These results provide insight into the activity of the microbial community of the anoxic sediment at the deepest point of the Baltic Sea and its possible role in ecosystem functioning. PMID:26823996

  2. Reversible amorphization and the catalytically active state of crystalline Co3O4 during oxygen evolution.

    PubMed

    Bergmann, Arno; Martinez-Moreno, Elias; Teschner, Detre; Chernev, Petko; Gliech, Manuel; de Araújo, Jorge Ferreira; Reier, Tobias; Dau, Holger; Strasser, Peter

    2015-01-01

    Water splitting catalysed by earth-abundant materials is pivotal for global-scale production of non-fossil fuels, yet our understanding of the active catalyst structure and reactivity is still insufficient. Here we report on the structurally reversible evolution of crystalline Co3O4 electrocatalysts during oxygen evolution reaction identified using advanced in situ X-ray techniques. At electrode potentials facilitating oxygen evolution, a sub-nanometre shell of the Co3O4 is transformed into an X-ray amorphous CoOx(OH)y which comprises di-μ-oxo-bridged Co(3+/4+) ions. Unlike irreversible amorphizations, here, the formation of the catalytically-active layer is reversed by re-crystallization upon return to non-catalytic electrode conditions. The Co3O4 material thus combines the stability advantages of a controlled, stable crystalline material with high catalytic activity, thanks to the structural flexibility of its active amorphous oxides. We propose that crystalline oxides may be tailored for generating reactive amorphous surface layers at catalytic potentials, just to return to their stable crystalline state under rest conditions. PMID:26456525

  3. Reversible amorphization and the catalytically active state of crystalline Co3O4 during oxygen evolution

    NASA Astrophysics Data System (ADS)

    Bergmann, Arno; Martinez-Moreno, Elias; Teschner, Detre; Chernev, Petko; Gliech, Manuel; de Araújo, Jorge Ferreira; Reier, Tobias; Dau, Holger; Strasser, Peter

    2015-10-01

    Water splitting catalysed by earth-abundant materials is pivotal for global-scale production of non-fossil fuels, yet our understanding of the active catalyst structure and reactivity is still insufficient. Here we report on the structurally reversible evolution of crystalline Co3O4 electrocatalysts during oxygen evolution reaction identified using advanced in situ X-ray techniques. At electrode potentials facilitating oxygen evolution, a sub-nanometre shell of the Co3O4 is transformed into an X-ray amorphous CoOx(OH)y which comprises di-μ-oxo-bridged Co3+/4+ ions. Unlike irreversible amorphizations, here, the formation of the catalytically-active layer is reversed by re-crystallization upon return to non-catalytic electrode conditions. The Co3O4 material thus combines the stability advantages of a controlled, stable crystalline material with high catalytic activity, thanks to the structural flexibility of its active amorphous oxides. We propose that crystalline oxides may be tailored for generating reactive amorphous surface layers at catalytic potentials, just to return to their stable crystalline state under rest conditions.

  4. Reversible amorphization and the catalytically active state of crystalline Co3O4 during oxygen evolution

    PubMed Central

    Bergmann, Arno; Martinez-Moreno, Elias; Teschner, Detre; Chernev, Petko; Gliech, Manuel; de Araújo, Jorge Ferreira; Reier, Tobias; Dau, Holger; Strasser, Peter

    2015-01-01

    Water splitting catalysed by earth-abundant materials is pivotal for global-scale production of non-fossil fuels, yet our understanding of the active catalyst structure and reactivity is still insufficient. Here we report on the structurally reversible evolution of crystalline Co3O4 electrocatalysts during oxygen evolution reaction identified using advanced in situ X-ray techniques. At electrode potentials facilitating oxygen evolution, a sub-nanometre shell of the Co3O4 is transformed into an X-ray amorphous CoOx(OH)y which comprises di-μ-oxo-bridged Co3+/4+ ions. Unlike irreversible amorphizations, here, the formation of the catalytically-active layer is reversed by re-crystallization upon return to non-catalytic electrode conditions. The Co3O4 material thus combines the stability advantages of a controlled, stable crystalline material with high catalytic activity, thanks to the structural flexibility of its active amorphous oxides. We propose that crystalline oxides may be tailored for generating reactive amorphous surface layers at catalytic potentials, just to return to their stable crystalline state under rest conditions. PMID:26456525

  5. Aligned carbon nanotube with electro-catalytic activity for oxygen reduction reaction

    DOEpatents

    Liu, Di-Jia; Yang, Junbing; Wang, Xiaoping

    2010-08-03

    A catalyst for an electro-chemical oxygen reduction reaction (ORR) of a bundle of longitudinally aligned carbon nanotubes having a catalytically active transition metal incorporated longitudinally in said nanotubes. A method of making an electro-chemical catalyst for an oxygen reduction reaction (ORR) having a bundle of longitudinally aligned carbon nanotubes with a catalytically active transition metal incorporated throughout the nanotubes, where a substrate is in a first reaction zone, and a combination selected from one or more of a hydrocarbon and an organometallic compound containing an catalytically active transition metal and a nitrogen containing compound and an inert gas and a reducing gas is introduced into the first reaction zone which is maintained at a first reaction temperature for a time sufficient to vaporize material therein. The vaporized material is then introduced to a second reaction zone maintained at a second reaction temperature for a time sufficient to grow longitudinally aligned carbon nanotubes over the substrate with a catalytically active transition metal incorporated throughout the nanotubes.

  6. High performance optical oxygen sensors based on iridium complexes exhibiting interchromophore energy shuttling.

    PubMed

    Medina-Rodríguez, Santiago; Denisov, Sergey A; Cudré, Yanouk; Male, Louise; Marín-Suárez, Marta; Fernández-Gutiérrez, Alberto; Fernández-Sánchez, Jorge F; Tron, Arnaud; Jonusauskas, Gediminas; McClenaghan, Nathan D; Baranoff, Etienne

    2016-05-10

    A doubly pyrene-grafted bis-cyclometallated iridium complex with engineered electronically excited states demonstrates reversible electronic energy transfer between adjacent chromophores giving rise to extremely long-lived red luminescence in solution (τ = 480 μs). Time-resolved spectroscopic studies afforded determination of pertinent photophysical parameters including rates of energy transfer and energy distribution between constituent chromophores in the equilibrated excited molecule (ca. 98% on the organic chromophores). Incorporation into a nanostructured metal-oxide matrix (AP200/19) gave highly sensitive O2 sensing films, as the detection sensitivity was 200-300% higher than with the commonly used PtTFPP and approaches the sensitivity of the best O2-sensing dyes reported to date. PMID:27094953

  7. Electrostatic Effects on Proton-Coupled Electron Transfer in Oxomanganese Complexes Inspired by the Oxygen-Evolving Complex of Photosystem II

    PubMed Central

    Amin, Muhamed; Vogt, Leslie; Vassiliev, Serguei; Rivalta, Ivan; Sultan, Mohammad M.; Bruce, Doug; Brudvig, Gary W.; Batista, Victor S.; Gunner, M. R.

    2013-01-01

    The influence of electrostatic interactions on the free energy of proton-coupled-electron-transfer (PCET) in biomimetic oxomanganese complexes inspired by the oxygen-evolving complex (OEC) of photosystem II (PSII), are investigated. The reported study introduces an enhanced Multi-Conformer Continuum Electrostatics (MCCE) model, parameterized at the density functional theory (DFT) level with a classical valence model for the oxomanganese core. The calculated pKas and oxidation midpoint potentials (Ems) match experimental values for eight complexes indicating that purely electrostatic contributions account for most of the observed couplings between deprotonation and oxidation state transitions. We focus on pKas of terminal water ligands in [Mn(II/III)(H2O)6]2+/3+ (1), [Mn(III)(P)(H2O)2]3- (2, P = 5,10,15,20- tetrakis (2,6-dichloro-3-sulfonatophenyl) porphyrinato), [Mn(IV,IV)2(μ-O)2(terpy)2(H2O)2]4+ (3, terpy = 2,2’:6’,2”-terpyridine) and [Mn3(IV,IV,IV)(μ-O)4(phen)4(H2O)2]4+ (4, phen = 1,10-phenanthroline) and the pKas of μ-oxo bridges and Mn Ems in [Mn2(μ-O)2(bpy)4]2+ (5, bpy = 2,2’-bipyridyl), [Mn2(μ-O)2(salpn)2] (6, salpn= N,N′-bis(salicylidene)-1,3-propanediamine), [Mn2(μ-O)2(3,5-di(Cl)-salpn)2] (7) and [Mn2(μ-O)2(3,5-di(NO2)-salpn)2] (8) which are most relevant to PCET mechanisms. The analysis of complexes 6-8 highlights the strong coupling between electron and proton transfers, with any Mn oxidation lowering the pKa of an oxo bridge by 10.5±0.9 pH units. The model also accounts for changes in the Ems due to ligand substituents, such as those in complexes 6-8, due to the electron withdrawing Cl (7) and NO2 (8). The reported study provides the foundation for analysis of electrostatic effects in other oxomanganese complexes and metalloenzymes, where PCET plays a fundamental role in redox-leveling mechanisms. PMID:23570540

  8. Single Crystal X- and Q-Band EPR Spectroscopy of a Binuclear Mn2(III,IV) Complex Relevant to the Oxygen-Evolving Complex of Photosystem II

    PubMed Central

    Yano, Junko; Sauer, Kenneth; Girerd, Jean-Jacques; Yachandra, Vittal K.

    2014-01-01

    The anisotropic g and hyperfine tensors of the Mn di-μ-oxo complex, [Mn2(III,IV)O2(phen)4](PF6)3·CH3CN, were derived by single-crystal EPR measurements at X- and Q-band frequencies. This is the first simulation of EPR parameters from single-crystal EPR spectra for multinuclear Mn complexes, which are of importance in several metalloenzymes; one of them is the oxygen-evolving complex in photosystem II (PS II). Single-crystal [Mn2(III,IV)O2(phen)4](PF6)3·CH3CN EPR spectra showed distinct resolved 55Mn hyperfine lines in all crystal orientations, unlike single-crystal EPR spectra of other Mn2(III,IV) di-μ-oxo bridged complexes. We measured the EPR spectra in the crystal ab- and bc-planes, and from these spectra we obtained the EPR spectra of the complex along the unique a-, b-, and c-axes of the crystal. The crystal orientation was determined by X-ray diffraction and single-crystal EXAFS (Extended X-ray Absorption Fine Structure) measurements. In this complex, the three crystallographic axes, a, b, and c, are parallel or nearly parallel to the principal molecular axes of Mn2(III,IV)O2(phen)4 as shown in the crystallographic data by Stebler et al. (Inorg. Chem. 1986, 25, 4743). This direct relation together with the resolved hyperfine lines significantly simplified the simulation of single-crystal spectra in the three principal directions due to the reduction of free parameters and, thus, allowed us to define the magnetic g and A tensors of the molecule with a high degree of reliability. These parameters were subsequently used to generate the solution EPR spectra at both X- and Q-bands with excellent agreement. The anisotropic g and hyperfine tensors determined by the simulation of the X- and Q-band single-crystal and solution EPR spectra are as follows: gx = 1.9887, gy = 1.9957, gz = 1.9775, and hyperfine coupling constants are AIIIx = |171| G, AIIIy = |176| G, AIIIz = |129| G, AIVx = |77| G, AIVy = |74| G, AIVz = |80| G. PMID:15198595

  9. Single crystal X- and Q-band EPR spectroscopy of a binuclear Mn(2)(III,IV) complex relevant to the oxygen-evolving complex of photosystem II.

    PubMed

    Yano, Junko; Sauer, Kenneth; Girerd, Jean-Jacques; Yachandra, Vittal K

    2004-06-23

    The anisotropic g and hyperfine tensors of the Mn di-micro-oxo complex, [Mn(2)(III,IV)O(2)(phen)(4)](PF(6))(3).CH(3)CN, were derived by single-crystal EPR measurements at X- and Q-band frequencies. This is the first simulation of EPR parameters from single-crystal EPR spectra for multinuclear Mn complexes, which are of importance in several metalloenzymes; one of them is the oxygen-evolving complex in photosystem II (PS II). Single-crystal [Mn(2)(III,IV)O(2)(phen)(4)](PF(6))(3).CH(3)CN EPR spectra showed distinct resolved (55)Mn hyperfine lines in all crystal orientations, unlike single-crystal EPR spectra of other Mn(2)(III,IV) di-micro-oxo bridged complexes. We measured the EPR spectra in the crystal ab- and bc-planes, and from these spectra we obtained the EPR spectra of the complex along the unique a-, b-, and c-axes of the crystal. The crystal orientation was determined by X-ray diffraction and single-crystal EXAFS (Extended X-ray Absorption Fine Structure) measurements. In this complex, the three crystallographic axes, a, b, and c, are parallel or nearly parallel to the principal molecular axes of Mn(2)(III,IV)O(2)(phen)(4) as shown in the crystallographic data by Stebler et al. (Inorg. Chem. 1986, 25, 4743). This direct relation together with the resolved hyperfine lines significantly simplified the simulation of single-crystal spectra in the three principal directions due to the reduction of free parameters and, thus, allowed us to define the magnetic g and A tensors of the molecule with a high degree of reliability. These parameters were subsequently used to generate the solution EPR spectra at both X- and Q-bands with excellent agreement. The anisotropic g and hyperfine tensors determined by the simulation of the X- and Q-band single-crystal and solution EPR spectra are as follows: g(x) = 1.9887, g(y) = 1.9957, g(z) = 1.9775, and hyperfine coupling constants are A(III)(x) = |171| G, A(III)(y) = |176| G, A(III)(z) = |129| G, A(IV)(x) = |77| G, A

  10. Cellular Metabolic Activity and the Oxygen and Hydrogen Stable Isotope Composition of Intracellular Water and Metabolites

    NASA Astrophysics Data System (ADS)

    Kreuzer-Martin, H. W.; Hegg, E. L.

    2008-12-01

    Intracellular water is an important pool of oxygen and hydrogen atoms for biosynthesis. Intracellular water is usually assumed to be isotopically identical to extracellular water, but an unexpected experimental result caused us to question this assumption. Heme O isolated from Escherichia coli cells grown in 95% H218O contained only a fraction of the theoretical value of labeled oxygen at a position where the O atom was known to be derived from water. In fact, fewer than half of the oxygen atoms were labeled. In an effort to explain this surprising result, we developed a method to determine the isotope ratios of intracellular water in cultured cells. The results of our experiments showed that during active growth, up to 70% of the oxygen atoms and 50% of the hydrogen atoms in the intracellular water of E. coli are generated during metabolism and can be isotopically distinct from extracellular water. The fraction of isotopically distinct atoms was substantially less in stationary phase and chilled cells, consistent with our hypothesis that less metabolically-generated water would be present in cells with lower metabolic activity. Our results were consistent with and explained the result of the heme O labeling experiment. Only about 40% of the O atoms on the heme O molecule were labeled because, presumably, only about 40% of the water inside the cells was 18O water that had diffused in from the culture medium. The rest of the intracellular water contained 16O atoms derived from either nutrients or atmospheric oxygen. To test whether we could also detect metabolically-derived hydrogen atoms in cellular constituents, we isolated fatty acids from log-phase and stationary phase E. coli and determined the H isotope ratios of individual fatty acids. The results of these experiments showed that environmental water contributed more H atoms to fatty acids isolated in stationary phase than to the same fatty acids isolated from log-phase cells. Stable isotope analyses of

  11. A Fractal Dimension Survey of Active Region Complexity

    NASA Technical Reports Server (NTRS)

    McAteer, R. T. James; Gallagher, Peter; Ireland, Jack

    2005-01-01

    A new approach to quantifying the magnetic complexity of active regions using a fractal dimension measure is presented. This fully-automated approach uses full disc MDI magnetograms of active regions from a large data set (2742 days of the SoHO mission; 9342 active regions) to compare the calculated fractal dimension to both Mount Wilson classification and flare rate. The main Mount Wilson classes exhibit no distinct fractal dimension distribution, suggesting a self-similar nature of all active regions. Solar flare productivity exhibits an increase in both the frequency and GOES X-ray magnitude of flares from regions with higher fractal dimensions. Specifically a lower threshold fractal dimension of 1.2 and 1.25 exists as a necessary, but not sufficient, requirement for an active region to produce M- and X-class flares respectively .

  12. Complex I-mediated reactive oxygen species generation: modulation by cytochrome c and NAD(P)+ oxidation-reduction state.

    PubMed Central

    Kushnareva, Yulia; Murphy, Anne N; Andreyev, Alexander

    2002-01-01

    Several lines of evidence indicate that mitochondrial reactive oxygen species (ROS) generation is the major source of oxidative stress in the cell. It has been shown that ROS production accompanies cytochrome c release in different apoptotic paradigms, but the site(s) of ROS production remain obscure. In the current study, we demonstrate that loss of cytochrome c by mitochondria oxidizing NAD(+)-linked substrates results in a dramatic increase of ROS production and respiratory inhibition. This increased ROS production can be mimicked by rotenone, a complex I inhibitor, as well as other chemical inhibitors of electron flow that act further downstream in the electron transport chain. The effects of cytochrome c depletion from mitoplasts on ROS production and respiration are reversible upon addition of exogenous cytochrome c. Thus in these models of mitochondrial injury, a primary site of ROS generation in both brain and heart mitochondria is proximal to the rotenone inhibitory site, rather than in complex III. ROS production at complex I is critically dependent upon a highly reduced state of the mitochondrial NAD(P)(+) pool and is achieved upon nearly complete inhibition of the respiratory chain. Redox clamp experiments using the acetoacetate/L-beta-hydroxybutyrate couple in the presence of a maximally inhibitory rotenone concentration suggest that the site is approx. 50 mV more electronegative than the NADH/NAD(+) couple. In the absence of inhibitors, this highly reduced state of mitochondria can be induced by reverse electron flow from succinate to NAD(+), accounting for profound ROS production in the presence of succinate. These results lead us to propose a model of thermodynamic control of mitochondrial ROS production which suggests that the ROS-generating site of complex I is the Fe-S centre N-1a. PMID:12180906

  13. Synthesis of tyrosine-involved corrole Cu(III), Mn(IV), and Mn(III) complexes as biomimetic models of oxygen evolving complex in photosystem II

    NASA Astrophysics Data System (ADS)

    Xia, M.; Gao, Y.

    2014-12-01

    Boc-protected tyrosine-attached corrole ligand on the " ortho" position compound 3, its corresponding copper (III) 4a, manganese (IV) 4b, and manganese (III) 4c complexes have been designed and synthesized based on the structures of active-centers of related biological systems. 1H NMR and electronic absorption spectra of these metal complexes are investigated. The crystal structure of 4a displays the relative position of TyrOH unit to the high valent metal center. Electrochemistry investigations display the possibilities of intramolecular electron or energy transfer between TyrOH group and metal corrole group.

  14. Geometric complexity identifies platelet activation in familial hypercholesterolemic patients.

    PubMed

    Bianciardi, Giorgio; Aglianò, Margherita; Volpi, Nila; Stefanutti, Claudia

    2015-06-01

    Familial hypercholesterolemia (FH), a genetic disease, is associated with a severe incidence of athero-thrombotic events, related, also, to platelet hyperreactivity. A plethora of methods have been proposed to identify those activated circulating platelets, none of these has proved really effective. We need efficient methods to identify the circulating platelet status in order to follow the patients after therapeutic procedures. We propose the use of computerized fractal analysis for an objective characterization of the complexity of circulating platelet shapes observed by means of transmission electron microscopy in order to characterize the in vivo hyperactivated platelets of familial hypercholesterolemic patients, distinguishing them from the in vivo resting platelets of healthy individuals. Platelet boundaries were extracted by means of automatically image analysis. Geometric complexity (fractal dimension, D) by box counting was automatically calculated. The platelet boundary observed by electron microscopy is fractal, the shape of the circulating platelets is more complex in FH (n = 6) than healthy subjects (n = 5, P < 0.01), with 100% correct classification in selected individuals. In vitro activated platelets from healthy subjects show an analogous increase of D. The observed high D in the platelet boundary in FH originates from the in vivo platelet activation. Computerized fractal analysis of platelet shape observed by transmission electron microscopy can provide accurate, quantitative data to study platelet activation in familial hypercholesterolemia and after administration of drugs or other therapeutic procedures. PMID:25877374

  15. The antimicrobial and antibiofilm activities of copper(II) complexes.

    PubMed

    Beeton, Michael L; Aldrich-Wright, Janice R; Bolhuis, Albert

    2014-11-01

    Biofilm-related bacterial infections pose a significant problem, as they are generally more tolerant to antibiotics and the immune system. Development of novel compounds with antibiofilm activity is therefore paramount. In this study we have analysed metal complexes of the general structure [M(IL)(AL)](2+) (where IL represents functionalised 1,10-phenanthrolines and AL represents 1S,2S- or 1R,2R-diaminocyclohexane) and [Cu(IL)3](2+). Antimicrobial activity was tested on a number of bacterial strains, showing that copper(II) compounds were active against both Gram-positive and Gram-negative bacteria, albeit that activity was generally higher for the former. The antibiofilm activity was then determined against a clinical isolate of meticillin-resistant Staphylococcus aureus (MRSA). Strikingly, the copper complexes tested showed significant activity against biofilms, and were better in the removal of biofilms than vancomycin, an antibiotic that is currently used in the treatment of MRSA infections. PMID:25124857

  16. Active control technique of fractional-order chaotic complex systems

    NASA Astrophysics Data System (ADS)

    Mahmoud, Gamal M.; Ahmed, Mansour E.; Abed-Elhameed, Tarek M.

    2016-06-01

    Several kinds of synchronization of fractional-order chaotic complex systems are challenging research topics of current interest since they appear in many applications in applied sciences. Our main goal in this paper is to introduce the definition of modified projective combination-combination synchronization (MPCCS) of some fractional-order chaotic complex systems. We show that our systems are chaotic by calculating their Lyapunov exponents. The fractional Lyapunov dimension of the chaotic solutions of these systems is computed. A scheme is introduced to calculate MPCCS of four different (or identical) chaotic complex systems using the active control technique. Special cases of this type, which are projective and anti C-C synchronization, are discussed. Some figures are plotted to show that MPCCS is achieved and its errors approach zero.

  17. Multiple redox-active chlorophylls in the secondary electron-transfer pathways of oxygen-evolving photosystem II.

    PubMed

    Tracewell, Cara A; Brudvig, Gary W

    2008-11-01

    Photosystem II (PS II) is unique among photosynthetic reaction centers in having secondary electron donors that compete with the primary electron donors for reduction of P680(+). We have characterized the photooxidation and dark decay of the redox-active accessory chlorophylls (Chl) and beta-carotenes (Car) in oxygen-evolving PS II core complexes by near-IR absorbance and EPR spectroscopies at cryogenic temperatures. In contrast to previous results for Mn-depleted PS II, multiple near-IR absorption bands are resolved in the light-minus-dark difference spectra of oxygen-evolving PS II core complexes including two fast-decaying bands at 793 and 814 nm and three slow-decaying bands at 810, 825, and 840 nm. We assign these bands to chlorophyll cation radicals (Chl(+)). The fast-decaying bands observed after illumination at 20 K could be generated again by reilluminating the sample. Quantization by EPR gives a yield of 0.85 radicals per PS II, and the yield of oxidized cytochrome b 559 by optical difference spectroscopy is 0.15 per PS II. Potential locations of Chl(+) and Car(+) species, and the pathways of secondary electron transfer based on the rates of their formation and decay, are discussed. This is the first evidence that Chls in the light-harvesting proteins CP43 and CP47 are oxidized by P680(+) and may have a role in Chl fluorescence quenching. We also suggest that a possible role for negatively charged lipids (phosphatidyldiacylglycerol and sulfoquinovosyldiacylglycerol identified in the PS II structure) could be to decrease the redox potential of specific Chl and Car cofactors. These results provide new insight into the alternate electron-donation pathways to P680(+). PMID:18850718

  18. Control of Lanthanide Coordination Environment: Synthesis, Structure, and Oxygen-Sensitive Luminescence Properties of an Eight-Coordinate Tb(III) Complex.

    PubMed

    Nakai, Hidetaka; Seo, Juncheol; Kitagawa, Kazuhiro; Goto, Takahiro; Nonaka, Kyoshiro; Matsumoto, Takahiro; Ogo, Seiji

    2016-07-01

    Coordination environment of the Tb(3+) ion in oxygen-sensitive luminescent complexes can be successfully controlled through the size of alkyl substituents on ligands {((RMe)ArOH)4cyclen} (R = tBu or Me; cyclen = 1,4,7,10-tetraazacyclododecane); a newly prepared eight-coordinate complex 1(tBu) shows higher oxygen sensitivity (KSV = 17 600) and lower luminescence quantum yield (Φ = 0.67 under N2) than those of the previously reported seven-coordinate analogues 1(Me) and [{((MeMe)ArO)3tacn}Tb(III)(THF)] (KSV = 12 600 and 8300, Φ = 0.91 and 0.91 under N2, respectively; tacn = 1,4,7-triazacyclononane; THF = tetrahydrofuran). The oxygen-sensitive mechanism is discussed on the basis of the photophysical properties of the corresponding Gd(III) complexes. PMID:27326826

  19. Effect of an Oxygen-Tolerant Bifurcating Butyryl Coenzyme A Dehydrogenase/Electron-Transferring Flavoprotein Complex from Clostridium difficile on Butyrate Production in Escherichia coli

    PubMed Central

    Aboulnaga, El-Hussiny; Pinkenburg, Olaf; Schiffels, Johannes; El-Refai, Ahmed; Buckel, Wolfgang

    2013-01-01

    The butyrogenic genes from Clostridium difficile DSM 1296T have been cloned and expressed in Escherichia coli. The enzymes acetyl-coenzyme A (CoA) C-acetyltransferase, 3-hydroxybutyryl-CoA dehydrogenase, crotonase, phosphate butyryltransferase, and butyrate kinase and the butyryl-CoA dehydrogenase complex composed of the dehydrogenase and two electron-transferring flavoprotein subunits were individually produced in E. coli and kinetically characterized in vitro. While most of these enzymes were measured using well-established test systems, novel methods to determine butyrate kinase and butyryl-CoA dehydrogenase activities with respect to physiological function were developed. Subsequently, the individual genes were combined to form a single plasmid-encoded operon in a plasmid vector, which was successfully used to confer butyrate-forming capability to the host. In vitro and in vivo studies demonstrated that C. difficile possesses a bifurcating butyryl-CoA dehydrogenase which catalyzes the NADH-dependent reduction of ferredoxin coupled to the reduction of crotonyl-CoA also by NADH. Since the reoxidation of ferredoxin by a membrane-bound ferredoxin:NAD+-oxidoreductase enables electron transport phosphorylation, additional ATP is formed. The butyryl-CoA dehydrogenase from C. difficile is oxygen stable and apparently uses oxygen as a co-oxidant of NADH in the presence of air. These properties suggest that this enzyme complex might be well suited to provide butyryl-CoA for solventogenesis in recombinant strains. The central role of bifurcating butyryl-CoA dehydrogenases and membrane-bound ferredoxin:NAD oxidoreductases (Rhodobacter nitrogen fixation [RNF]), which affect the energy yield of butyrate fermentation in the clostridial metabolism, is discussed. PMID:23772070

  20. Singlet molecular oxygen-quenching activity of carotenoids: relevance to protection of the skin from photoaging

    PubMed Central

    Terao, Junji; Minami, Yuko; Bando, Noriko

    2011-01-01

    Carotenoids are known to be potent quenchers of singlet molecular oxygen [O2 (1Δg)]. Solar light-induced photooxidative stress causes skin photoaging by accelerating the generation of reactive oxygen species via photodynamic actions in which O2 (1Δg) can be generated by energy transfer from excited sensitizers. Thus, dietary carotenoids seem to participate in the prevention of photooxidative stress by accumulating as antioxidants in the skin. An in vivo study using hairless mice clarified that a O2 (1Δg) oxygenation-specific peroxidation product of cholesterol, cholesterol 5α-hydroperoxide, accumulates in skin lipids due to ultraviolet-A exposure. Matrix metalloproteinase-9, a metalloproteinase family enzyme responsible for the formation of wrinkles and sagging, was enhanced in the skin of ultraviolet-A -irradiated hairless mice. The activation of metalloproteinase-9 and the accumulation of 5α-hydroperoxide, as well as formation of wrinkles and sagging, were lowered in mice fed a β-carotene diet. These results strongly suggest that dietary β-carotene prevents the expression of metalloproteinase-9 (at least in part), by inhibiting the photodynamic action involving the formation of 5α-hydroperoxide in the skin. Intake of β-Carotene therefore appears to be helpful in slowing down ultraviolet-A -induced photoaging in human skin by acting as a O2 (1Δg) quencher. PMID:21297913

  1. Investigation of a sterilization system using active oxygen species generated by ultraviolet irradiation.

    PubMed

    Yoshino, Kiyoshi; Matsumoto, Hiroyuki; Iwasaki, Tatsuyuki; Kinoshita, Shinobu; Noda, Kazutoshi; Oya, Kei; Iwamori, Satoru

    2015-01-01

    We have been investigating an advanced sterilization system that employs active oxygen species (AOS). We designed the sterilization equipment, including an evacuation system, which generates AOS from pure oxygen gas using ultraviolet irradiation, in order to study the conditions necessary for sterilization in the system's chamber. Using Geobachillus stearothermophilus spores (10(6) CFU) in a sterile bag as a biological indicator (BI) in the chamber of the AOS sterilization apparatus, we examined the viability of the BI as a function of exposure time, assessing the role of the decompression level in the sterilization performance. We found that the survival curves showed exponential reduction, and that the decompression level did not exert a significant influence on the survival curve. Subsequently, we investigated the sterilization effect as influenced by the spatial and environmental temperature variation throughout the chamber, and found that the sterilization effect varied with position, due to the varying environmental temperature in the respective areas. We confirmed that temperature is one of the most important factors influencing sterilization in the chamber, and estimated the temperature effect on the distribution of atomic oxygen concentration, using the quartz crystal microbalance (QCM) method with fluorocarbon thin film prepared by radio frequency sputtering. PMID:25817808

  2. In situ x-ray, electrochemical, and modeling investigation of the oxygen electrode activation.

    SciTech Connect

    Yildiz, B.; Chang, K.-C.; Meyers, D.; Carter, J. D.; You, H.

    2006-01-01

    Oxygen electrodes of solid oxide electrochemical cells have been shown to improve under strong cathodic and anodic polarization. Our study investigates the mechanism causing such improvement, using in situ x-ray and electrochemical characterization and electrochemical impedance modeling of the oxygen electrodes. Several porous and dense thin-film model electrodes of La{sub 0.8}Sr{sub 0.2}MnO{sub 3} (LSM) and La{sub 0.8}Sr{sub 0.2}MnO{sub 3} (LCM) on single crystal yttria-stabilized zirconia (YSZ) electrolytes have been analyzed in situ at the Advanced Photon Source (APS) using x-ray reflectivity and x-ray absorption near edge spectroscopy (XANES) at the Mn K-edge and La LII-edge. In situ x-ray reflectivity analysis show that no clear correlation between the polarization of the electrode and any further changes in the roughness of the LSM/YSZ interface exist. XANES measurements illustrate that the cathodic or anodic dc polarization at high temperature induces no detectable changes in Mn chemical state either in the bulk or at the surface of the LCM and LSM electrodes on YSZ, while the La chemical state changes reversibly at the electrode surface. This field-induced chemical change of La at the surface of electrodes is assumed to be a cause of the electrochemical activation through enhanced surface exchange of oxygen on the doped lanthanum manganite electrodes.

  3. Novel Organotin(IV) Schiff Base Complexes with Histidine Derivatives: Synthesis, Characterization, and Biological Activity

    PubMed Central

    Garza-Ortiz, Ariadna; Camacho-Camacho, Carlos; Sainz-Espuñes, Teresita; Rojas-Oviedo, Irma; Gutiérrez-Lucas, Luis Raúl; Gutierrez Carrillo, Atilano; Vera Ramirez, Marco A.

    2013-01-01

    Five novel tin Schiff base complexes with histidine analogues (derived from the condensation reaction between L-histidine and 3,5-di-tert-butyl-2-hydroxybenzaldehyde) have been synthesized and characterized. Characterization has been completed by IR and high-resolution mass spectroscopy, 1D and 2D solution NMR (1H, 13C  and 119Sn), as well as solid state 119Sn NMR. The spectroscopic evidence shows two types of structures: a trigonal bipyramidal stereochemistry with the tin atom coordinated to five donating atoms (two oxygen atoms, one nitrogen atom, and two carbon atoms belonging to the alkyl moieties), where one molecule of ligand is coordinated in a three dentate fashion. The second structure is spectroscopically described as a tetrahedral tin complex with four donating atoms (one oxygen atom coordinated to the metal and three carbon atoms belonging to the alkyl or aryl substituents), with one molecule of ligand attached. The antimicrobial activity of the tin compounds has been tested against the growth of bacteria in vitro to assess their bactericidal properties. While pentacoordinated compounds 1, 2, and 3 are described as moderate effective to noneffective drugs against both Gram-positive and Gram-negative bacteria, tetracoordinated tin(IV) compounds 4 and 5 are considered as moderate effective and most effective compounds, respectively, against the methicillin-resistant Staphylococcus aureus strains (Gram-positive). PMID:23864839

  4. Mononuclear copper (II) salicylate complexes with 1,2-dimethylimidazole and 2-methylimidazole: Synthesis, spectroscopic and crystal structure characterization and their superoxide scavenging activities

    NASA Astrophysics Data System (ADS)

    Abuhijleh, A. Latif

    2010-09-01

    The complexes cis-bis (1,2-dimethylimidazole) bis (salicylato) copper (II) ( 1) and tris (2-methylimidazole) (salicylato) copper (II) ( 2) have been prepared by the reaction of appropriate methylimidazole derivative with binuclear copper (II) aspirinate. Spectral and X-ray structural studies for complex 1 showed that the copper ion is coordinated in a cis arrangement to two imidazole nitrogen atoms and two carboxylate oxygen atoms from the salicylate mono-anion ligands. The second carboxylate oxygen atoms form weak axial interactions with the copper ion. Spectral, magnetic and analytical data for complex 2 showed that the copper ion is bonded to three 2-methylimidazole nitrogen atoms and one doubly deprotonated salicylate di-anion, which is chelated to Cu (II) ion through one of its carboxylate oxygen atoms and the deprotonated hydroxyl oxygen atom to form distorted square-pyramidal geometry having CuN 3O + O chromophore. The superoxide dismutase (SOD) mimetic activities (IC 50) of the complexes 1, 2 and the structurally known mixture complexes Cu (imidazole) n(salicylato) 2( 3) (where n = 2, 5 and 6) were determined using the xanthine-xanthine oxidase assay and compared with those reported for other copper (II) complexes with anti-inflammatory drugs. The results obtained indicated that complexes 1- 3 have high SOD-like activities, which may act as good mimics for native Cu, Zn-SOD enzyme.

  5. Phosphate oxygen isotopic evidence for a temperate and biologically active Archaean ocean.

    PubMed

    Blake, Ruth E; Chang, Sae Jung; Lepland, Aivo

    2010-04-15

    Oxygen and silicon isotope compositions of cherts and studies of protein evolution have been interpreted to reflect ocean temperatures of 55-85 degrees C during the early Palaeoarchaean era ( approximately 3.5 billion years ago). A recent study combining oxygen and hydrogen isotope compositions of cherts, however, makes a case for Archaean ocean temperatures being no greater than 40 degrees C (ref. 5). Ocean temperature can also be assessed using the oxygen isotope composition of phosphate. Recent studies show that (18)O:(16)O ratios of dissolved inorganic phosphate (delta(18)O(P)) reflect ambient seawater temperature as well as biological processing that dominates marine phosphorus cycling at low temperature. All forms of life require and concentrate phosphorus, and as a result of biological processing, modern marine phosphates have delta(18)O(P) values typically between 19-26 per thousand (VSMOW), highly evolved from presumed source values of approximately 6-8 per thousand that are characteristic of apatite in igneous rocks and meteorites. Here we report oxygen isotope compositions of phosphates in sediments from the 3.2-3.5-billion-year-old Barberton Greenstone Belt in South Africa. We find that delta(18)O(P) values range from 9.3 per thousand to 19.9 per thousand and include the highest values reported for Archaean rocks. The temperatures calculated from our highest delta(18)O(P) values and assuming equilibrium with sea water with delta(18)O = 0 per thousand (ref. 12) range from 26 degrees C to 35 degrees C. The higher delta(18)O(P) values are similar to those of modern marine phosphate and suggest a well-developed phosphorus cycle and evolved biologic activity on the Archaean Earth. PMID:20393560

  6. Redox-inactive metal ions modulate the reactivity and oxygen release of mononuclear non-haem iron(III)–peroxo complexes

    DOE PAGESBeta

    Bang, Suhee; Lee, Yong -Min; Hong, Seungwoo; Cho, Kyung -Bin; Nishida, Yusuke; Seo, Mi Sook; Sarangi, Ritimukta; Fukuzumi, Shunichi; Nam, Wonwoo

    2014-09-14

    Redox-inactive metal ions that function as Lewis acids play pivotal roles in modulating the reactivity of oxygen-containing metal complexes and metalloenzymes, such as the oxygen-evolving complex in photosystem II and its small-molecule mimics. Here we report the synthesis and characterization of non-haem iron(III)–peroxo complexes that bind redox-inactive metal ions, (TMC)FeIII–(μ,η2:η2-O2)–Mn+ (Mn+ = Sr2+, Ca2+, Zn2+, Lu3+, Y3+ and Sc3+; TMC, 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane). We demonstrate that the Ca2+ and Sr2+ complexes showed similar electrochemical properties and reactivities in one-electron oxidation or reduction reactions. However, the properties and reactivities of complexes formed with stronger Lewis acidities were found to be markedly different. Inmore » conclusion, complexes that contain Ca2+ or Sr2+ ions were oxidized by an electron acceptor to release O2, whereas the release of O2 did not occur for complexes that bind stronger Lewis acids. Furthermore, we discuss these results in the light of the functional role of the Ca2+ ion in the oxidation of water to dioxygen by the oxygen-evolving complex.« less

  7. Photo-induced oxidation of the uniquely liganded heme f in the cytochrome b6f complex of oxygenic photosynthesis.

    PubMed

    Chauvet, Adrien A P; Agarwal, Rachna; Haddad, André Al; van Mourik, Frank; Cramer, William A

    2016-05-14

    The ultrafast behavior of the ferrous heme f from the cytochrome b6f complex of oxygenic photosynthesis is revealed by means of transient absorption spectroscopy. Benefiting from the use of microfluidic technologies for handling the sample as well as from a complementary frame-by-frame analysis of the heme dynamics, the different relaxation mechanisms from vibrationally excited states are disentangled and monitored via the shifts of the heme α-absorption band. Under 520 nm laser excitation, about 85% of the heme f undergoes pulse-limited photo-oxidation (<100 fs), with the electron acceptor being most probably one of the adjacent aromatic amino acid residues. After charge recombination in 5.3 ps, the residual excess energy is dissipated in 3.6 ps. In a parallel pathway, the remaining 15% of the hemes directly relax from their excited state in 2.5 ps. In contrast to a vast variety of heme-proteins, including the homologous heme c1 from the cytochrome bc1 complex, there is no evidence that heme f photo-dissociates from its axial ligands. Due to its unique binding, with histidine and an unusual tyrosine as axial ligands, the heme f exemplifies a dependence of ultrafast dynamics on the structural environment. PMID:27108913

  8. Impact of Polymer Electrolyte Membrane Degradation Products on Oxygen Reduction Reaction Activity for Platinum Electrocatalysts

    SciTech Connect

    Christ, J. M.; Neyerlin, K. C.; Wang, H.; Richards, R.; Dinh, H. N.

    2014-10-30

    The impact of model membrane degradation compounds on the relevant electrochemical parameters for the oxygen reduction reaction (i.e. electrochemical surface area and catalytic activity), was studied for both polycrystalline Pt and carbon supported Pt electrocatalysts. Model compounds, representing previously published, experimentally determined polymer electrolyte membrane degradation products, were in the form of perfluorinated organic acids that contained combinations of carboxylic and/or sulfonic acid functionality. Perfluorinated carboxylic acids of carbon chain length C1 – C6 were found to have an impact on electrochemical surface area (ECA). The longest chain length acid also hindered the observed oxygen reduction reaction (ORR) performance, resulting in a 17% loss in kinetic current (determined at 0.9 V). Model compounds containing sulfonic acid functional groups alone did not show an effect on Pt ECA or ORR activity. Lastly, greater than a 44% loss in ORR activity at 0.9V was observed for diacid model compounds DA-Naf (perfluoro(2-methyl-3-oxa-5-sulfonic pentanoic) acid) and DA-3M (perfluoro(4-sulfonic butanoic) acid), which contained both sulfonic and carboxylic acid functionalities.

  9. Impact of Polymer Electrolyte Membrane Degradation Products on Oxygen Reduction Reaction Activity for Platinum Electrocatalysts

    DOE PAGESBeta

    Christ, J. M.; Neyerlin, K. C.; Wang, H.; Richards, R.; Dinh, H. N.

    2014-10-30

    The impact of model membrane degradation compounds on the relevant electrochemical parameters for the oxygen reduction reaction (i.e. electrochemical surface area and catalytic activity), was studied for both polycrystalline Pt and carbon supported Pt electrocatalysts. Model compounds, representing previously published, experimentally determined polymer electrolyte membrane degradation products, were in the form of perfluorinated organic acids that contained combinations of carboxylic and/or sulfonic acid functionality. Perfluorinated carboxylic acids of carbon chain length C1 – C6 were found to have an impact on electrochemical surface area (ECA). The longest chain length acid also hindered the observed oxygen reduction reaction (ORR) performance, resultingmore » in a 17% loss in kinetic current (determined at 0.9 V). Model compounds containing sulfonic acid functional groups alone did not show an effect on Pt ECA or ORR activity. Lastly, greater than a 44% loss in ORR activity at 0.9V was observed for diacid model compounds DA-Naf (perfluoro(2-methyl-3-oxa-5-sulfonic pentanoic) acid) and DA-3M (perfluoro(4-sulfonic butanoic) acid), which contained both sulfonic and carboxylic acid functionalities.« less

  10. Highly active oxygen reduction non-platinum group metal electrocatalyst without direct metal-nitrogen coordination

    NASA Astrophysics Data System (ADS)

    Strickland, Kara; Miner, Elise; Jia, Qingying; Tylus, Urszula; Ramaswamy, Nagappan; Liang, Wentao; Sougrati, Moulay-Tahar; Jaouen, Frédéric; Mukerjee, Sanjeev

    2015-06-01

    Replacement of noble metals in catalysts for cathodic oxygen reduction reaction with transition metals mostly create active sites based on a composite of nitrogen-coordinated transition metal in close concert with non-nitrogen-coordinated carbon-embedded metal atom clusters. Here we report a non-platinum group metal electrocatalyst with an active site devoid of any direct nitrogen coordination to iron that outperforms the benchmark platinum-based catalyst in alkaline media and is comparable to its best contemporaries in acidic media. In situ X-ray absorption spectroscopy in conjunction with ex situ microscopy clearly shows nitrided carbon fibres with embedded iron particles that are not directly involved in the oxygen reduction pathway. Instead, the reaction occurs primarily on the carbon-nitrogen structure in the outer skin of the nitrided carbon fibres. Implications include the potential of creating greater active site density and the potential elimination of any Fenton-type process involving exposed iron ions culminating in peroxide initiated free-radical formation.

  11. Antioxidant Activity of Oxygen Evolving Enhancer Protein 1 Purified from Capsosiphon fulvescens.

    PubMed

    Kim, Eun-Young; Choi, Youn Hee; Lee, Jung Im; Kim, In-Hye; Nam, Taek-Jeong

    2015-06-01

    This study was conducted to determine the antioxidant activity of a protein purified from Capsosiphon fulvescens. The purification steps included sodium acetate (pH 6) extraction and diethylaminoethyl-cellulose, reversed phase Shodex C4P-50 column chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis indicated that the molecular weight of the purified protein was 33 kDa. The N-terminus and partial peptide amino acid sequence of this protein was identical to the sequence of oxygen evolving enhancer (OEE) 1 protein. The antioxidant activity of the OEE 1 was determined in vitro using a scavenging test with 4 types of reactive oxygen species (ROS), including the 2,2-diphenyl-1-picrylhydrazyl radical, hydroxyl radical, superoxide anion, and hydrogen peroxide (H2 O2 ). OEE 1 had higher H2 O2 scavenging activity, which proved to be the result of enzymatic antioxidants rather than nonenzymatic antioxidants. In addition, OEE 1 showed less H2 O2 -mediated ROS formation in HepG2 cells. In conclusion, this study demonstrates that OEE 1 purified from C. fulvescens is an excellent antioxidant. PMID:25944160

  12. Highly active oxygen reduction non-platinum group metal electrocatalyst without direct metal–nitrogen coordination

    PubMed Central

    Strickland, Kara; Miner, Elise; Jia, Qingying; Tylus, Urszula; Ramaswamy, Nagappan; Liang, Wentao; Sougrati, Moulay-Tahar; Jaouen, Frédéric; Mukerjee, Sanjeev

    2015-01-01

    Replacement of noble metals in catalysts for cathodic oxygen reduction reaction with transition metals mostly create active sites based on a composite of nitrogen-coordinated transition metal in close concert with non-nitrogen-coordinated carbon-embedded metal atom clusters. Here we report a non-platinum group metal electrocatalyst with an active site devoid of any direct nitrogen coordination to iron that outperforms the benchmark platinum-based catalyst in alkaline media and is comparable to its best contemporaries in acidic media. In situ X-ray absorption spectroscopy in conjunction with ex situ microscopy clearly shows nitrided carbon fibres with embedded iron particles that are not directly involved in the oxygen reduction pathway. Instead, the reaction occurs primarily on the carbon–nitrogen structure in the outer skin of the nitrided carbon fibres. Implications include the potential of creating greater active site density and the potential elimination of any Fenton-type process involving exposed iron ions culminating in peroxide initiated free-radical formation. PMID:26059552

  13. Testing and Oxygen Assessment Results for a Next Generation Extravehicular Activity Portable Life Support System Fan

    NASA Technical Reports Server (NTRS)

    Paul, Heather L.; Jennings, Mallory A.; Rivera, Fatonia L.; Martin, Devin

    2011-01-01

    NASA is designing a next generation Extravehicular Activity (EVA) Portable Life Support System (PLSS) for use in future surface exploration endeavors. To meet the new requirements for ventilation flow at nominal and buddy modes, a fan has been developed and tested. This paper summarizes the results of the performance and life cycle testing efforts conducted at the NASA Johnson Space Center. Additionally, oxygen compatibility assessment results from an evaluation conducted at White Sands Test Facility (WSTF) are provided, and lessons learned and future recommendations are outlined.

  14. Evaluation of the persistence of micropollutants through pure-oxygen activated sludge nitrification and denitrification

    USGS Publications Warehouse

    Levine, A.D.; Meyer, M.T.; Kish, G.

    2006-01-01

    The persistence of pharmaceuticals, hormones, and household and industrial chemicals through a pure-oxygen activated sludge, nitrification, denitrification wastewater treatment facility was evaluated. Of the 125 micropollutants that were tested in this study, 55 compounds were detected in the untreated wastewater, and 27 compounds were detected in the disinfected effluent. The persistent compounds included surfactants, fire-retardant chemicals, pesticides, fragrance compounds, hormones, and one pharmaceutical. Physical-chemical properties of micropollutants that affected partitioning onto wastewater solids included vapor pressure and octanol-water partition coefficients.

  15. An ultrastable bimetallic carbide as platinum electrocatalyst support for highly active oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Yan, Zaoxue; Zhang, Mingmei; Xie, Jimin; Shen, Pei Kang

    2015-11-01

    Stable bimetallic carbide (Fe2MoC) with graphitized carbon (GC) as matrix has been synthesized through an ion-exchange method. The Pt nanoparticles are loaded on the GC-Fe2MoC composite to form Pt/GC-Fe2MoC electrocatalyst which shows much higher activity and stability than those of commercial Pt/C for oxygen reduction reaction in acidic media. The excellent performances of Pt/GC-Fe2MoC are mainly due to the inherent stability of GC-Fe2MoC and the promotion effect between Fe2MoC and Pt.

  16. Catalytic activity of metal oxides in hydrogen sulfide oxidation by oxygen and sulfur dioxide

    SciTech Connect

    Marshneva, V.I.; Mokrinskii, V.V.

    1989-02-01

    Separate investigations have been made of the catalytic activities of a wide range of oxides by groups I-VIII metals in the Claus reaction and oxidation of H/sub 2/S by oxygen. Only 9 of 21 oxides used in the Claus reaction exhibit stable activity. The remaining oxides are deactivated, mainly by absorbing H/sub 2/S and being converted into sulfides. There are similar tendencies in the changes of sulfur formation specific velocities in both processes in the series of stable oxides V/sub 2/O/sub 5/, TiO/sub 2/, Mn/sub 2/O/sub 3/, Al/sub 2/O/sub 3/, MgO, Cr/sub 2/O/sub 3/. Vanadium pentoxide is the most active catalyst in the total and partial oxidations of H/sub 2/S and the Claus reaction.

  17. Elucidating the activity of stepped Pt single crystals for oxygen reduction.

    PubMed

    Bandarenka, Aliaksandr S; Hansen, Heine A; Rossmeisl, Jan; Stephens, Ifan E L

    2014-07-21

    The unexpectedly high measured activity of Pt[n(111) × (111)] and Pt[n(111) × (100)] stepped single crystal surfaces towards the oxygen reduction reaction (ORR) is explained utilizing the hydroxyl binding energy as the activity descriptor. Using this descriptor (estimated using experimental data obtained by different groups), a well-defined Sabatier-type volcano is observed for the activities measured for the Pt[n(111) × (111)] and Pt[n(111) × (100)] stepped single crystals, in remarkable agreement with earlier theoretical studies. We propose that the observed destabilisation of *OH species at these surfaces is due to the decreased solvation of the adsorbed hydroxyl intermediates on adjacent terrace sites. PMID:24643715

  18. Reactive oxygen species production and antioxidant enzyme activity during epididymal sperm maturation in Corynorhinus mexicanus bats.

    PubMed

    Arenas-Ríos, Edith; Rosado García, Adolfo; Cortés-Barberena, Edith; Königsberg, Mina; Arteaga-Silva, Marcela; Rodríguez-Tobón, Ahiezer; Fuentes-Mascorro, Gisela; León-Galván, Miguel Angel

    2016-03-01

    Prolonged sperm storage in the epididymis of Corynorhinus mexicanus bats after testicular regression has been associated with epididymal sperm maturation in the caudal region, although the precise factors linked with this phenomenon are unknown. The aim of this work is to determine the role of reactive oxygen species (ROS) and changes in antioxidant enzymatic activity occurring in the spermatozoa and epididymal fluid over time, in sperm maturation and storage in the caput, corpus and cauda of the bat epididymis. Our data showed that an increment in ROS production coincided with an increase in superoxide dismutase (SOD) activity in epididymal fluid and with a decrease in glutathione peroxidase (GPX) activity in the spermatozoa in at different time points and epididymal regions. The increase in ROS production was not associated with oxidative damage measured by lipid peroxidation. The results of the current study suggest the existence of a shift in the redox balance, which might be associated with sperm maturation and storage. PMID:26952757

  19. Enhanced Surfactant Adsorption on Activated Carbon through Manipulation of Surface Oxygen Groups

    NASA Astrophysics Data System (ADS)

    Collins, John; Qu, Deyang; Foster, Michelle

    2012-02-01

    Passive energy storage is a necessary component for balancing the lifecycle budget with new forms of green energy. The work presented describes how surface oxygen groups (SOG) on granulated activated carbon have been manipulated using Nitric Acid in a controlled, stepwise fashion. The structure and surface functionality of the activated carbon samples were characterized using DRIFTS, Raman Spectroscopy and Porosimetry. Total surface area was found to increase proportionally with the removal of heteroatom material, exposing previously insulated active sites responsible for SOG attachment. Broad oxide peaks were deconvoluted and analyzed, allowing for absolute identification of evolving functionality at each oxidation stage. SOGs were maximized on the third oxidation cycle with the presence of conjugated aromatic, phenol, lactone, and carboxylic acid groups. FSN Zonyl nonionic was applied to all oxidized samples at various concentrations. Total adsorbed surfactant was quantified for each concentration / oxidation scheme using attenuated total reflection. The relative quantity and polarity of chemisorbed surfactant were qualitatively assessed for each equilibrium concentration.

  20. Palladium–platinum core-shell icosahedra with substantially enhanced activity and durability towards oxygen reduction

    SciTech Connect

    Wang, Xue; Choi, Sang-Il; Roling, Luke T.; Luo, Ming; Ma, Cheng; Zhang, Lei; Chi, Miaofang; Liu, Jingyue; Xie, Zhaoxiong; Herron, Jeffrey A.; Mavrikakis, Manos; Xia, Younan

    2015-07-02

    Conformal deposition of platinum as ultrathin shells on facet-controlled palladium nanocrystals offers a great opportunity to enhance the catalytic performance while reducing its loading. Here we report such a system based on palladium icosahedra. Owing to lateral confinement imposed by twin boundaries and thus vertical relaxation only, the platinum overlayers evolve into a corrugated structure under compressive strain. For the core-shell nanocrystals with an average of 2.7 platinum overlayers, their specific and platinum mass activities towards oxygen reduction are enhanced by eight- and sevenfold, respectively, relative to a commercial catalyst. Density functional theory calculations indicate that the enhancement can be attributed to the weakened binding of hydroxyl to the compressed platinum surface supported on palladium. After 10,000 testing cycles, the mass activity of the core-shell nanocrystals is still four times higher than the commercial catalyst. Ultimately, these results demonstrate an effective approach to the development of electrocatalysts with greatly enhanced activity and durability.

  1. Palladium-platinum core-shell icosahedra with substantially enhanced activity and durability towards oxygen reduction

    NASA Astrophysics Data System (ADS)

    Wang, Xue; Choi, Sang-Il; Roling, Luke T.; Luo, Ming; Ma, Cheng; Zhang, Lei; Chi, Miaofang; Liu, Jingyue; Xie, Zhaoxiong; Herron, Jeffrey A.; Mavrikakis, Manos; Xia, Younan

    2015-07-01

    Conformal deposition of platinum as ultrathin shells on facet-controlled palladium nanocrystals offers a great opportunity to enhance the catalytic performance while reducing its loading. Here we report such a system based on palladium icosahedra. Owing to lateral confinement imposed by twin boundaries and thus vertical relaxation only, the platinum overlayers evolve into a corrugated structure under compressive strain. For the core-shell nanocrystals with an average of 2.7 platinum overlayers, their specific and platinum mass activities towards oxygen reduction are enhanced by eight- and sevenfold, respectively, relative to a commercial catalyst. Density functional theory calculations indicate that the enhancement can be attributed to the weakened binding of hydroxyl to the compressed platinum surface supported on palladium. After 10,000 testing cycles, the mass activity of the core-shell nanocrystals is still four times higher than the commercial catalyst. These results demonstrate an effective approach to the development of electrocatalysts with greatly enhanced activity and durability.

  2. Active Oxygen Metabolites and Thromboxane in Phorbol Myristate Acetate Toxicity to the Isolated, Perfused Rat Lung.

    NASA Astrophysics Data System (ADS)

    Carpenter, Laurie Jean

    When administered intravenously or intratracheally to rats, rabbits and sheep, phorbol myristate acetate (PMA) produces changes in lung morphology and function are similar to those seen in humans with the adult respiratory distress syndrome (ARDS). Therefore, it is thought that information about the mechanism of ARDS development can be gained from experiments using PMA-treated animals. Currently, the mechanisms by which PMA causes pneumotoxicity are unknown. Results from other studies in rabbits and in isolated, perfused rabbit lungs suggest that PMA-induced lung injury is mediated by active oxygen species from neutrophils (PMN), whereas studies in sheep and rats suggest that PMN are not required for the toxic response. The role of PMN, active oxygen metabolites and thromboxane (TxA_2) in PMA-induced injury to isolated, perfused rat lungs (IPLs) was examined in this thesis. To determine whether PMN were required for PMA to produce toxicity to the IPL, lungs were perfused for 30 min with buffer containing various concentrations of PMA (in the presence or absence of PMN). When concentrations >=q57 ng/ml were added to medium devoid of added PMN, perfusion pressure and lung weight increased. When a concentration of PMA (14-28 ng/ml) that did not by itself cause lungs to accumulate fluid was added to the perfusion medium containing PMN (1 x 10 ^8), perfusion pressure increased, and lungs accumulated fluid. These results indicate that high concentrations of PMA produce lung injury which is independent of PMN, whereas injury induced by lower concentrations is PMN-dependent. To examine whether active oxygen species were involved in mediating lung injury induced by PMA and PMN, lungs were coperfused with the oxygen radical scavengers SOD and/or catalase. Coperfusion with either or both of these enzymes totally protected lungs against injury caused by PMN and PMA. These results suggest that active oxygen species (the hydroxyl radical in particular), mediate lung injury in

  3. Oxygenator Is the Main Responsible for Leukocyte Activation in Experimental Model of Extracorporeal Circulation: A Cautionary Tale

    PubMed Central

    Rungatscher, Alessio; Tessari, Maddalena; Stranieri, Chiara; Solani, Erika; Linardi, Daniele; Milani, Elisabetta; Montresor, Alessio; Merigo, Flavia; Salvetti, Beatrice; Menon, Tiziano

    2015-01-01

    In order to assess mechanisms underlying inflammatory activation during extracorporeal circulation (ECC), several small animal models of ECC have been proposed recently. The majority of them are based on home-made, nonstandardized, and hardly reproducible oxygenators. The present study has generated fundamental information on the role of oxygenator of ECC in activating inflammatory signaling pathways on leukocytes, leading to systemic inflammatory response, and organ dysfunction. The present results suggest that experimental animal models of ECC used in translational research on inflammatory response should be based on standardized, reproducible oxygenators with clinical characteristics. PMID:26063972

  4. Catalytic Activity of Platinum Monolayer on Iridium and Rhenium Alloy Nanoparticles for the Oxygen Reduction Reaction

    SciTech Connect

    Karan, Hiroko I.; Sasaki, Kotaro; Kuttiyiel, Kurian; Farberow, Carrie A.; Mavrikakis, Manos; Adzic, Radoslav R.

    2012-05-04

    A new type of electrocatalyst with a core–shell structure that consists of a platinum monolayer shell placed on an iridium–rhenium nanoparticle core or platinum and palladium bilayer shell deposited on that core has been prepared and tested for electrocatalytic activity for the oxygen reduction reaction. Carbon-supported iridium–rhenium alloy nanoparticles with several different molar ratios of Ir to Re were prepared by reducing metal chlorides dispersed on Vulcan carbon with hydrogen gas at 400 °C for 1 h. These catalysts showed specific electrocatalytic activity for oxygen reduction reaction comparable to that of platinum. The activities of PtML/PdML/Ir2Re1, PtML/Pd2layers/Ir2Re1, and PtML/Pd2layers/Ir7Re3 catalysts were, in fact, better than that of conventional platinum electrocatalysts, and their mass activities exceeded the 2015 DOE target. Our density functional theory calculations revealed that the molar ratio of Ir to Re affects the binding strength of adsorbed OH and, thereby, the O2 reduction activity of the catalysts. The maximum specific activity was found for an intermediate OH binding energy with the corresponding catalyst on the top of the volcano plot. The monolayer concept facilitates the use of much less platinum than in other approaches. Finally, the results with the PtML/PdML/Ir2Re electrocatalyst indicate that it is a promising alternative to conventional Pt electrocatalysts in low-temperature fuel cells.

  5. Geometric complexity is increased in in vitro activated platelets.

    PubMed

    Bianciardi, Giorgio

    2015-06-01

    This article investigates the use of computerized fractal analysis for objective characterization of the complexity of platelets in vitro stimulated by low level thrombin (0.02 U mL(-1) ), collected from healthy individuals and observed by means of transmission electron microscopy. Platelet boundaries were extracted by means of automatically image analysis. Local fractal dimension was evaluated by the box-counting technique (measure of geometric complexity of the platelet outline). The results showed that the platelet boundary is fractal when observed by transmission electron microscopy and that, after an in vitro platelet activation test, the shape of platelets present increased geometric complexity in comparison to the no stimulated platelets (P < 0.001), with 100% correct classification. Computerized fractal analysis of platelet shape by transmission electron microscopy can provide accurate, quantitative, data to study platelet activation. The results may play important roles in the evaluation of the platelets status in pathological conditions, like as atherosclerosis and diabetes mellitus, where in in vivo activated platelets have been described. PMID:25808036

  6. Distinct TFIID complexes mediate the effect of different transcriptional activators.

    PubMed Central

    Brou, C; Chaudhary, S; Davidson, I; Lutz, Y; Wu, J; Egly, J M; Tora, L; Chambon, P

    1993-01-01

    Multiple chromatographically separable complexes containing the TATA binding protein (TBP), which exhibit different functional properties, exist in HeLa cells. At least three distinct subpopulations of such complexes can be functionally defined as TFIID since they function with RNA polymerase II. Using a partially reconstituted HeLa cell in vitro transcription system and immunoprecipitation with a monoclonal antibody directed against TBP, we show that stimulation of transcription by the chimeric activators GAL-VP16, GAL-TEF-1 and GAL-ER(EF) requires the presence of factors which are tightly associated with these TFIID complexes. Moreover, the activity of GAL-TEF-1 appears to be mediated by at least two chromatographically distinct populations of TFIID. The factor(s) associated with one of these populations is also required for the activity of GAL-ER (EF) and GAL-VP16, while the factor(s) associated with the other population functions selectively with GAL-TEF-1. These two TFIID populations are composed of both common and unique TBP associated factors (TAFs). Images PMID:8440239

  7. Inhibition of histone deacetylase activity in reduced oxygen environment enhances the osteogenesis of mouse adipose-derived stromal cells.

    PubMed

    Xu, Yue; Hammerick, Kyle E; James, Aaron W; Carre, Antoine L; Leucht, Philipp; Giaccia, Amato J; Longaker, Michael T

    2009-12-01

    Recent studies suggest that oxygen tension has a great impact on the osteogenic differentiation capacity of mesenchymal cells derived from adipose tissue: reduced oxygen impedes osteogenesis. We have found that expansion of mouse adipose-derived stromal cells (mASCs) in reduced oxygen tension (10%) results in increased cell proliferation along with induction of histone deacetylase (HDAC) activity. In this study, we utilized two HDAC inhibitors (HDACi), sodium butyrate (NaB) and valproic acid (VPA), and studied their effects on mASCs expanded in various oxygen tensions (21%, 10%, and 1% O(2)). Significant growth inhibition was observed with NaB or VPA treatment in each oxygen tension. Osteogenesis was enhanced by treatment with NaB or VPA, particularly in reduced oxygen tensions (10% and 1% O(2)). Conversely, adipogenesis was decreased with treatments of NaB or VPA at all oxygen tensions. Finally, NaB- or VPA-treated, reduced oxygen tension-exposed (1% O(2)) ASCs were grafted into surgically created mouse tibial defects and resulted in significantly increased bone regeneration. In conclusion, HDACi significantly promote the osteogenic differentiation of mASCs exposed to reduced oxygen tension; HDACi may hold promise for future clinical applications of ASCs for skeletal regeneration. PMID:19505250

  8. Inhibition of Histone Deacetylase Activity in Reduced Oxygen Environment Enhances the Osteogenesis of Mouse Adipose-Derived Stromal Cells

    PubMed Central

    Xu, Yue; Hammerick, Kyle E.; James, Aaron W.; Carre, Antoine L.; Leucht, Philipp; Giaccia, Amato J.

    2009-01-01

    Recent studies suggest that oxygen tension has a great impact on the osteogenic differentiation capacity of mesenchymal cells derived from adipose tissue: reduced oxygen impedes osteogenesis. We have found that expansion of mouse adipose-derived stromal cells (mASCs) in reduced oxygen tension (10%) results in increased cell proliferation along with induction of histone deacetylase (HDAC) activity. In this study, we utilized two HDAC inhibitors (HDACi), sodium butyrate (NaB) and valproic acid (VPA), and studied their effects on mASCs expanded in various oxygen tensions (21%, 10%, and 1% O2). Significant growth inhibition was observed with NaB or VPA treatment in each oxygen tension. Osteogenesis was enhanced by treatment with NaB or VPA, particularly in reduced oxygen tensions (10% and 1% O2). Conversely, adipogenesis was decreased with treatments of NaB or VPA at all oxygen tensions. Finally, NaB- or VPA-treated, reduced oxygen tension–exposed (1% O2) ASCs were grafted into surgically created mouse tibial defects and resulted in significantly increased bone regeneration. In conclusion, HDACi significantly promote the osteogenic differentiation of mASCs exposed to reduced oxygen tension; HDACi may hold promise for future clinical applications of ASCs for skeletal regeneration. PMID:19505250

  9. Reactive oxygen species production in cardiac mitochondria after complex I inhibition: Modulation by substrate-dependent regulation of the NADH/NAD(+) ratio.

    PubMed

    Korge, Paavo; Calmettes, Guillaume; Weiss, James N

    2016-07-01

    Reactive oxygen species (ROS) production by isolated complex I is steeply dependent on the NADH/NAD(+) ratio. We used alamethicin-permeabilized mitochondria to study the substrate-dependence of matrix NADH and ROS production when complex I is inhibited by piericidin or rotenone. When complex I was inhibited in the presence of malate/glutamate, membrane permeabilization accelerated O2 consumption and ROS production due to a rapid increase in NADH generation that was not limited by matrix NAD(H) efflux. In the presence of inhibitor, both malate and glutamate were required to generate a high enough NADH/NAD(+) ratio to support ROS production through the coordinated activity of malate dehydrogenase (MDH) and aspartate aminotransferase (AST). With malate and glutamate present, the rate of ROS production was closely related to local NADH generation, whereas in the absence of substrates, ROS production was accelerated by increase in added [NADH]. With malate alone, oxaloacetate accumulation limited NADH production by MDH unless glutamate was also added to promote oxaloacetate removal via AST. α-ketoglutarate (KG) as well as AST inhibition also reversed NADH generation and inhibited ROS production. If malate and glutamate were provided before rather than after piericidin or rotenone, ROS generation was markedly reduced due to time-dependent efflux of CoA. CoA depletion decreased KG oxidation by α-ketoglutarate dehydrogenase (KGDH), such that the resulting increase in [KG] inhibited oxaloacetate removal by AST and NADH generation by MDH. These findings were largely obscured in intact mitochondria due to robust H2O2 scavenging and limited ability to control substrate concentrations in the matrix. We conclude that in mitochondria with inhibited complex I, malate/glutamate-stimulated ROS generation depends strongly on oxaloacetate removal and on the ability of KGDH to oxidize KG generated by AST. PMID:27068062

  10. An optimized molecular inclusion complex of diferuloylmethane: enhanced physical properties and biological activity

    PubMed Central

    Tan, Qunyou; Li, Yi; Wu, Jianyong; Mei, Hu; Zhao, Chunjing; Zhang, Jingqing

    2012-01-01

    Objective The purpose of this study was to explore and evaluate the enhanced physical properties and biological activity of a molecular inclusion complex (MICDH) comprising diferuloylmethane (DFM) and hydroxypropyl-β-cyclodextrin. Methods The preparation conditions of MICDH were optimized using an orthogonal experimental design. The solubility, in vitro release and model fitting, microscopic morphology, molecular structure simulation, anti-lung cancer activity, and action mechanism of MICDH were evaluated. Results The solubility of DFM was improved 4400-fold upon complexation with hydroxypropyl-β-cyclodextrin. The release rate of DFM was significantly higher from MICDH than from free DFM. MICDH exhibited higher antitumor activity against human lung adenocarcinoma A549 cells than free DFM. More cells were arrested in the S/G2 phase of the cell cycle or were induced to undergo apoptosis when treated with MICDH than when treated with free DFM. Furthermore, increased reactive oxygen species and intracellular calcium ion levels and decreased mitochondrial membrane potential were observed in cells treated with MICDH. Conclusion MICDH markedly improved the physical properties and antitumor activity of DFM. MICDH may prove to be a preferred alternative to free DFM as a formulation for DFM delivery in lung cancer treatment. PMID:23091376

  11. Differential inhibitory effects of methylmalonic acid on respiratory chain complex activities in rat tissues.

    PubMed

    Pettenuzzo, Leticia F; Ferreira, Gustavo da C; Schmidt, Anna Laura; Dutra-Filho, Carlos S; Wyse, Angela T S; Wajner, Moacir

    2006-02-01

    Methylmalonic acidemia is an inherited metabolic disorder biochemically characterized by tissue accumulation of methylmalonic acid (MMA) and clinically by progressive neurological deterioration and kidney failure, whose pathophysiology is so far poorly established. Previous studies have shown that MMA inhibits complex II of the respiratory chain in rat cerebral cortex, although no inhibition of complexes I-V was found in bovine heart. Therefore, in the present study we investigated the in vitro effect of 2.5mM MMA on the activity of complexes I-III, II, II-III and IV in striatum, hippocampus, heart, liver and kidney homogenates from young rats. We observed that MMA caused a significant inhibition of complex II activity in striatum and hippocampus (15-20%) at low concentrations of succinate in the medium, but not in the peripheral tissues. We also verified that the inhibitory property of MMA only occurred after exposing brain homogenates for at least 10 min with the acid, suggesting that this inhibition was mediated by indirect mechanisms. Simultaneous preincubation with the nitric oxide synthase inhibitor Nomega-nitro-L-arginine methyl ester (L-NAME) and catalase (CAT) plus superoxide dismutase (SOD) did not prevent MMA-induced inhibition of complex II, suggesting that common reactive oxygen (superoxide, hydrogen peroxide and hydroxyl radical) and nitric (nitric oxide) species were not involved in this effect. In addition, complex II-III (20-35%) was also inhibited by MMA in all tissues tested, and complex I-III only in the kidney (53%) and liver (38%). In contrast, complex IV activity was not changed by MMA in all tissues studied. These results indicate that MMA differentially affects the activity of the respiratory chain pending on the tissues studied, being striatum and hippocampus more vulnerable to its effect. In case our in vitro data are confirmed in vivo in tissues from methylmalonic acidemic patients, it is feasible that that the present findings may be

  12. Measuring the activities of higher organisms in activated sludge by means of mechanical shearing pretreatment and oxygen uptake rate.

    PubMed

    Hao, Xiaodi; Wang, Qilin; Cao, Yali; van Loosdrecht, Mark C M

    2010-07-01

    A pretreatment method was developed to assess the activities of higher organisms. The method is based on mechanical shearing to damage the large cells of the protozoan and metazoan community in activated sludge. The procedure was confirmed through experimentation to be effective in determining the activities of higher organisms by comparing oxygen uptake rates (OURs) before and after the higher organisms were eradicated. Shearing led to disintegration of flocs, which could be effectively reconstituted by centrifugation. The reconstitution of the sludge flocs was essential since otherwise the activity of the floc mass would be too high due to lack of diffusion limitation. Mechanical shearing had no influence on the morphology, quantity and specific activity of yeasts, and it was inferred that bacteria smaller than yeasts in size would also not be influenced by the applied shearing procedure. Moreover, the effect of filamentous organisms on the measured activities of higher organisms was experimentally demonstrated and analyzed, and determined to be so weak that it could be ignored. Based on these tests, five typical activated sludge processes were selected to measure the contribution of higher organisms to the original OUR. The measured activities of higher organisms ranged from 9.4 to 25.0% of the original OURs. PMID:20605188

  13. Maximal Oxygen Intake and Maximal Work Performance of Active College Women.

    ERIC Educational Resources Information Center

    Higgs, Susanne L.

    Maximal oxygen intake and associated physiological variables were measured during strenuous exercise on women subjects (N=20 physical education majors). Following assessment of maximal oxygen intake, all subjects underwent a performance test at the work level which had elicited their maximal oxygen intake. Mean maximal oxygen intake was 41.32…

  14. Linear free energy relationships for metal-ligand complexation: Bidentate binding to negatively-charged oxygen donor atoms

    NASA Astrophysics Data System (ADS)

    Carbonaro, Richard F.; Atalay, Yasemin B.; Di Toro, Dominic M.

    2011-05-01

    Stability constants for metal complexation to bidentate ligands containing negatively-charged oxygen donor atoms can be estimated from the following linear free energy relationship (LFER): log KML = χOO( αO log KHL,1 + αO log KHL,2) where KML is the metal-ligand stability constant for a 1:1 complex, KHL,1 and KHL,2 are the proton-ligand stability constants (the ligand p Ka values), and αO is the Irving-Rossotti slope. The parameter χOO is metal specific and has slightly different values for five and six membered chelate rings. LFERs are presented for 21 different metal ions and are accurate to within approximately 0.30 log units in predictions of log KML values. Ligands selected for use in LFER development include dicarboxylic acids, carboxyphenols, and ortho-diphenols. For ortho-hydroxybenzaldehydes, α-hydroxycarboxylic acids, and α-ketocarboxylic acids, a modification of the LFER where log KHL,2 is set equal to zero is required. The chemical interpretation of χOO is that it accounts for the extra stability afforded to metal complexes by the chelate effect. Cu-NOM binding constants calculated from the bidentate LFERs are similar in magnitude to those used in WHAM 6. This LFER can be used to make log KML predictions for small organic molecules. Since natural organic matter (NOM) contains many of the same functional groups (i.e. carboxylic acids, phenols, alcohols), the LFER log KML predictions shed light on the range of appropriate values for use in modeling metal partitioning in natural systems.

  15. Two-dimensional HYSCORE spectroscopy of superoxidized manganese catalase: a model for the oxygen-evolving complex of photosystem II.

    PubMed

    Coates, Christopher S; Milikisiyants, Sergey; Chatterjee, Ruchira; Whittaker, Mei M; Whittaker, James W; Lakshmi, K V

    2015-04-16

    The solar water-splitting protein complex, photosystem II (PSII), catalyzes one of the most energetically demanding reactions in Nature by using light energy to drive a catalyst capable of oxidizing water. The water oxidation reaction takes place at the tetra-nuclear manganese calcium-oxo (Mn4Ca-oxo) cluster at the heart of the oxygen-evolving complex (OEC) of PSII. Previous studies have determined the magnetic interactions between the paramagnetic Mn4Ca-oxo cluster and its environment in the S2 state of the OEC. The assignments for the electron-nuclear magnetic interactions that were observed in these studies were facilitated by the use of synthetic dimanganese di-μ-oxo complexes. However, there is an immense need to understand the effects of the protein environment on the coordination geometry of the Mn4Ca-oxo cluster in the OEC of PSII. In the present study, we use a proteinaceous model system to examine the protein ligands that are coordinated to the dimanganese catalytic center of manganese catalase from Lactobacillus plantarum. We utilize two-dimensional hyperfine sublevel correlation (2D HYSCORE) spectroscopy to detect the weak magnetic interactions of the paramagnetic dinuclear manganese catalytic center of superoxidized manganese catalase with the nitrogen and proton atoms of the surrounding protein environment. We obtain a complete set of hyperfine interaction parameters for the protons of a water molecule that is directly coordinated to the dinuclear manganese center. We also obtain a complete set of hyperfine and quadrupolar interaction parameters for two histidine ligands as well as a coordinated azide ligand, in azide-treated superoxidized manganese catalase. On the basis of the values of the hyperfine interaction parameters of the dimanganese model, manganese catalase, and those of the S2 state of the OEC of PSII, for the first time, we discuss the impact of a proteinaceous environment on the coordination geometry of multinuclear manganese clusters

  16. Non-hypoxic activation of the negative regulatory feedback loop of prolyl-hydroxylase oxygen sensors.

    PubMed

    Tug, Suzan; Delos Reyes, Buena; Fandrey, Joachim; Berchner-Pfannschmidt, Utta

    2009-07-10

    Hypoxia inducible factors (HIF) coordinate cellular responses towards hypoxia. HIFs are mainly regulated by a group of prolyl-hydroxylases (PHDs) that in the presence of oxygen, target the HIFalpha subunit for degradation. Herein, we studied the role of nitric oxide (NO) in regulating PHD activities under normoxic conditions. In the present study we show that different NO-donors initially inhibited endogenous PHD2 activity which led to accumulation of HIF-1alpha subsequently to enhance HIF-1 dependent increased PHD2 promoter activity. Consequently PHD2 abundance and activity were strongly induced which caused downregulation of HIF-1alpha. Interestingly, upregulation of endogenous PHD2 activity by NO was not found in cells that lack an intact pVHL dependent degradation pathway. Recovery of PHD activity required intact cells and was not observed in cell extracts or recombinant PHD2. In conclusion induction of endogenous PHD2 activity by NO is dependent on a feedback loop initiated despite normoxic conditions. PMID:19427832

  17. Mononuclear Ru(III) Schiff base complexes: Synthesis, spectral, redox, catalytic and biological activity studies

    NASA Astrophysics Data System (ADS)

    Priya, N. Padma; Arunachalam, S.; Manimaran, A.; Muthupriya, D.; Jayabalakrishnan, C.

    2009-04-01

    An octahedral ruthenium(III) Schiff base complexes of the type [RuX(EPh 3)(L)] (where, X = Cl/Br; E = As/P; L = dianion of the Schiff bases derived from acetoacetanilide with o-phenylenediamine and salicylaldehyde/ o-hydroxyacetophenone/ o-vanillin/2-hydroxy-1-naphthaldehyde) have been synthesized from the reactions of equimolar reactions of [RuX 3(EPh 3) 3] and Schiff bases in benzene. The new Ru(III) Schiff base complexes have been characterized by elemental analyses, FT-IR, electronic, 1H NMR and 13C NMR spectra, EPR spectral studies, powder X-ray diffraction (XRD) and electrochemical studies. The new complexes were found to be effective catalysts for aryl-aryl coupling and the oxidation of alcohols into their corresponding carbonyl compounds, respectively, using molecular oxygen atmosphere at ambient temperature. Further, the new Ru(III) Schiff base complexes were screened for their antibacterial activity against Pseudomonas aeruginosa, Vibrio cholera, Salomonella typhi and Staphylococcus aureaus.

  18. Oxygenation, EMG and position sense during computer mouse work. Impact of active versus passive pauses.

    PubMed

    Crenshaw, A G; Djupsjöbacka, M; Svedmark, A

    2006-05-01

    We investigated the effects of active versus passive pauses implemented during computer mouse work on muscle oxygenation and EMG of the forearm extensor carpi radialis muscle, and on wrist position sense. Fifteen healthy female subjects (age: 19-24 years) performed a 60-min mouse-operated computer task, divided into three 20 min periods, on two occasions separated by 3-6 days. On one occasion a passive pause (subjects resting) was implemented at the end of each 20-min period, and on another occasion an active pause (subjects performed a number of high intensity extensions of the forearm) was implemented. Also at the end of each 20-min period, test contractions were conducted and subjective ratings of fatigue and stress were obtained. Another parameter of interest was total haemoglobin calculated as the summation of oxy-and deoxy-haemoglobin, since it reflects blood volume changes. The most interesting findings were an overall increasing trend in total haemoglobin throughout the mouse work (P<0.001), and that this trend was greater for the active pause as compared to the passive pause (P<0.01). These data were accompanied by an overall increase in oxygen saturation (P<0.001), with a tendency, albeit not significant, toward a higher increase for the active pause (P=0.13). EMG amplitude and median frequency tended to decrease (P=0.08 and 0.05, respectively) during the mouse work but was not different between pause types. Borg ratings of forearm fatigue showed an overall increase during the activity (P<0.001), but the perceptions of stress did not change. Position sense did not change due to the mouse work for either pause type. While increasing trends were found for both pause types, the present study lends support to the hypothesis of an enhancement in oxygenation and blood volume for computer mouse work implemented with active pauses. However, a presumption of an association between this enhancement and attenuated fatigue during the mouse work was not supported

  19. Activities of topoisomerase I in its complex with SRSF1.

    PubMed

    Ishikawa, Takao; Krzysko, Krystiana A; Kowalska-Loth, Barbara; Skrajna, Aleksandra M; Czubaty, Alicja; Girstun, Agnieszka; Cieplak, Maja K; Lesyng, Bogdan; Staron, Krzysztof

    2012-02-28

    Human DNA topoisomerase I (topo I) catalyzes DNA relaxation and phosphorylates SRSF1. Whereas the structure of topo I complexed with DNA has been resolved, the structure of topo I in the complex with SRSF1 and structural determinants of topo I activities in this complex are not known. The main obstacle to resolving the structure is a contribution of unfolded domains of topo I and SRSF1 in formation of the complex. To overcome this difficulty, we employed a three-step strategy: identifying the interaction regions, modeling the complex, and validating the model with biochemical methods. The binding sites in both topo I and SRSF1 are localized in the structured regions as well as in the unfolded domains. One observes cooperation between the binding sites in topo I but not in SRSF1. Our results indicate two features of the unfolded RS domain of SRSF1 containing phosphorylated residues that are critical for the kinase activity of topo I: its spatial arrangement relative to topo I and the organization of its sequence. The efficiency of phosphorylation of SRSF1 depends on the length and flexibility of the spacer between the two RRM domains that uniquely determine an arrangement of the RS domain relative to topo I. The spacer also influences inhibition of DNA nicking, a prerequisite for DNA relaxation. To be phosphorylated, the RS domain has to include a short sequence recognized by topo I. A lack of this sequence in the mutants of SRSF1 or its spatial inaccessibility in SRSF9 makes them inadequate as topo I/kinase substrates. PMID:22320324

  20. Atomic Ordering Enhanced Electrocatalytic Activity of Nanoalloys for Oxygen Reduction Reaction

    SciTech Connect

    Loukrakpam, Rameshwori; Shan, Shiyao; Petkov, Valeri; Yang, Lefu; Luo, Jin; Zhong, Chuan-Jian

    2013-10-01

    For oxygen reduction reaction (ORR) over alloy electrocatalysts, the understanding of how the atomic arrangement of the metal species in the nanocatalysts is responsible for the catalytic enhancement is challenging for achieving better design and tailoring of nanoalloy catalysts. This paper reports results of an investigation of the atomic structures and the electrocatalytic activities of ternary and binary nanoalloys, aiming at revealing a fundamental insight into the unique atomic-scale structure-electrocatalytic activity relationship. PtIrCo catalyst and its binary counterparts (PtCo and PtIr) are chosen as a model system for this study. The effect of thermochemical treatment temperature on the atomic-scale structure of the catalysts was examined as a useful probe to the structure-activity correlation. The structural characterization of the binary and ternary nanoalloy catalysts was performed by combining surface sensitive techniques such as XPS and 3D atomic ordering sensitive techniques such as high-energy X-ray diffraction (HE-XRD) coupled to atomic pair distribution function (PDF) analysis (HE-XRD/PDFs) and computer simulations. The results show that the thermal treatment temperature tunes the nanoalloy’s atomic and chemical ordering in a different way depending on the chemical composition, leading to differences in the nanoalloy’s mass and specific activities. A unique structural tunability of the atomic ordering in a platinum-iridium-cobalt nanoalloy has been revealed for enhancing greatly the electrocatalytic activity toward oxygen reduction reaction, which has significant implication for rational design and nanoengineering of advanced catalysts for electrochemical energy conversion and storage.

  1. Biomass Oxidation: Formyl C-H Bond Activation by the Surface Lattice Oxygen of Regenerative CuO Nanoleaves.

    PubMed

    Amaniampong, Prince N; Trinh, Quang Thang; Wang, Bo; Borgna, Armando; Yang, Yanhui; Mushrif, Samir H

    2015-07-27

    An integrated experimental and computational investigation reveals that surface lattice oxygen of copper oxide (CuO) nanoleaves activates the formyl C-H bond in glucose and incorporates itself into the glucose molecule to oxidize it to gluconic acid. The reduced CuO catalyst regains its structure, morphology, and activity upon reoxidation. The activity of lattice oxygen is shown to be superior to that of the chemisorbed oxygen on the metal surface and the hydrogen abstraction ability of the catalyst is correlated with the adsorption energy. Based on the present investigation, it is suggested that surface lattice oxygen is critical for the oxidation of glucose to gluconic acid, without further breaking down the glucose molecule into smaller fragments, because of C-C cleavage. Using CuO nanoleaves as catalyst, an excellent yield of gluconic acid is also obtained for the direct oxidation of cellobiose and polymeric cellulose, as biomass substrates. PMID:26119659

  2. Metal-dithiocarbamate complexes: chemistry and biological activity.

    PubMed

    Hogarth, Graeme

    2012-10-01

    Dithiocarbamates are highly versatile mono-anionic chelating ligands which form stable complexes with all the transition elements and also the majority of main group, lanthanide and actinide elements. They are easily prepared from primary or secondary amines and depending upon the nature of the cation can show good solubility in water or organic solvents. They are related to the thiuram disulfides by a one-electron redox process (followed by dimerisation via sulfur-sulfur bond formation) which is easily carried out upon addition of iodide or ferric salts. Dithiocarbamates are lipophilic and generally bind to metals in a symmetrical chelate fashion but examples of other coordination modes are known, the monodentate and anisobidentate modes being most prevalent. They are planar sterically non-demanding ligands which can be electronically tuned by judicious choice of substituents. They stabilize metals in a wide range of oxidation states, this being attributed to the existence of soft dithiocarbamate and hard thioureide resonance forms, the latter formally resulting from delocalization of the nitrogen lone pair onto the sulfurs, and consequently their complexes tend to have a rich electrochemistry. Tetraethyl thiuramdisulfide (disulfiram or antabuse) has been used as a drug since the 1950s but it is only recently that dithiocarbamate complexes have been explored within the medicinal domain. Over the past two decades anti-cancer activity has been noted for gold and copper complexes, technetium and copper complexes have been used in PET-imaging, dithiocarbamates have been used to treat acute cadmium poisoning and copper complexes also have been investigated as SOD inhibitors. PMID:22931592

  3. Molecular hydrogen inhibits lipopolysaccharide-triggered NLRP3 inflammasome activation in macrophages by targeting the mitochondrial reactive oxygen species.

    PubMed

    Ren, Jian-Dong; Wu, Xiao-Bo; Jiang, Rui; Hao, Da-Peng; Liu, Yi

    2016-01-01

    The NLRP3 inflammasome, an intracellular multi-protein complex controlling the maturation of cytokine interleukin-1β, plays an important role in lipopolysaccharide (LPS)-induced inflammatory cascades. Recently, the production of mitochondrial reactive oxygen species (mtROS) in macrophages stimulated with LPS has been suggested to act as a trigger during the process of NLRP3 inflammasome activation that can be blocked by some mitochondria-targeted antioxidants. Known as a ROS scavenger, molecular hydrogen (H2) has been shown to possess therapeutic benefit on LPS-induced inflammatory damage in many animal experiments. Due to the unique molecular structure, H2 can easily target the mitochondria, suggesting that H2 is a potential antagonist of mtROS-dependent NLRP3 inflammasome activation. Here we have showed that, in mouse macrophages, H2 exhibited substantial inhibitory activity against LPS-initiated NLRP3 inflammasome activation by scavenging mtROS. Moreover, the elimination of mtROS by H2 resultantly inhibited mtROS-mediated NLRP3 deubiquitination, a non-transcriptional priming signal of NLRP3 in response to the stimulation of LPS. Additionally, the removal of mtROS by H2 reduced the generation of oxidized mitochondrial DNA and consequently decreased its binding to NLRP3, thereby inhibiting the NLRP3 inflammasome activation. Our findings have, for the first time, revealed the novel mechanism underlying the inhibitory effect of molecular hydrogen on LPS-caused NLRP3 inflammasome activation, highlighting the promising application of this new antioxidant in the treatment of LPS-associated inflammatory pathological damage. PMID:26488087

  4. Metal-Oxygen Bond Ionicity as an Efficient Descriptor for Doped NiOOH Photocatalytic Activity.

    PubMed

    Zaffran, Jeremie; Toroker, Maytal Caspary

    2016-06-01

    The computational design of solid catalysts has become a very "hot" field during the last decades, especially with the recent increase in computational tool performance. However, theoretical techniques are still very time demanding because they require the consideration of many adsorption configurations of the reaction intermediates on the surface. Herein, we propose to use the metal-oxygen (M-O) bond ionicity as a descriptor for the photocatalytic activity of one of the best catalysts for the oxygen evolution reaction (OER). Ionicity is a bulk property and thus carries the advantage of being easily obtainable from a simple Bader charge analysis by using density functional theory (DFT). We will show that this criterion can be used successfully to design efficient dopants for NiOOH material. This catalyst is known to exhibit interesting photoelectrochemical properties for OER if it is doped with specific transition metals. Finally, we demonstrate that other electronic properties that relate to bulk calculation, such as oxidation states and density of states, are not alone sufficient to explain the photocatalytic activity of the material. Thus, M-O bond ionicity attracts significant interest compared with other bulk observables obtained by using DFT computations. PMID:26945687

  5. Ordered mesoporous porphyrinic carbons with very high electrocatalytic activity for the oxygen reduction reaction

    PubMed Central

    Cheon, Jae Yeong; Kim, Taeyoung; Choi, YongMan; Jeong, Hu Young; Kim, Min Gyu; Sa, Young Jin; Kim, Jaesik; Lee, Zonghoon; Yang, Tae-Hyun; Kwon, Kyungjung; Terasaki, Osamu; Park, Gu-Gon; Adzic, Radoslav R.; Joo, Sang Hoon

    2013-01-01

    The high cost of the platinum-based cathode catalysts for the oxygen reduction reaction (ORR) has impeded the widespread application of polymer electrolyte fuel cells. We report on a new family of non-precious metal catalysts based on ordered mesoporous porphyrinic carbons (M-OMPC; M = Fe, Co, or FeCo) with high surface areas and tunable pore structures, which were prepared by nanocasting mesoporous silica templates with metalloporphyrin precursors. The FeCo-OMPC catalyst exhibited an excellent ORR activity in an acidic medium, higher than other non-precious metal catalysts. It showed higher kinetic current at 0.9 V than Pt/C catalysts, as well as superior long-term durability and MeOH-tolerance. Density functional theory calculations in combination with extended X-ray absorption fine structure analysis revealed a weakening of the interaction between oxygen atom and FeCo-OMPC compared to Pt/C. This effect and high surface area of FeCo-OMPC appear responsible for its significantly high ORR activity. PMID:24056308

  6. Ni- and Mn-Promoted Mesoporous Co3O4: A Stable Bifunctional Catalyst with Surface-Structure-Dependent Activity for Oxygen Reduction Reaction and Oxygen Evolution Reaction.

    PubMed

    Song, Wenqiao; Ren, Zheng; Chen, Sheng-Yu; Meng, Yongtao; Biswas, Sourav; Nandi, Partha; Elsen, Heather A; Gao, Pu-Xian; Suib, Steven L

    2016-08-17

    Efficient bifunctional catalysts for electrochemical oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are highly desirable due to their wide applications in fuel cells and rechargeable metal air batteries. However, the development of nonprecious metal catalysts with comparable activities to noble metals is still challenging. Here we report a one-step wet-chemical synthesis of Ni-/Mn-promoted mesoporous cobalt oxides through an inverse micelle process. Various characterization techniques including powder X-ray diffraction (PXRD), N2 sorption, transmission electron microscopy (TEM), and scanning electron microscopy (SEM) confirm the successful incorporation of Ni and Mn leading to the formation of Co-Ni(Mn)-O solid solutions with retained mesoporosity. Among these catalysts, cobalt oxide with 5% Ni doping demonstrates promising activities for both ORR and OER, with an overpotential of 399 mV for ORR (at -3 mA/cm(2)) and 381 mV (at 10 mA/cm(2)) for OER. Furthermore, it shows better durability than precious metals featuring little activity decay throughout 24 h continuous operation. Analyses of cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS), Raman, and O2-temperature-programmed desorption (O2-TPD) reveal that redox activity of Co(3+) to Co(4+) is crucial for OER performance, while the population of surface oxygen vacancies and surface area determine ORR activities. The comprehensive investigation of the intrinsic active sites for ORR and OER by correlating different physicochemical properties to the electrochemical activities is believed to provide important insight toward the rational design of high-performance electrocatalysts for ORR and OER reactions. PMID:27458646

  7. NQO1-induced activation of AMPK contributes to cancer cell death by oxygen-glucose deprivation

    PubMed Central

    Lee, Hyemi; Oh, Eun-Taex; Choi, Bo-Hwa; Park, Moon-Taek; Lee, Ja-Kyeong; Lee, Jae-Seon; Park, Heon Joo

    2015-01-01

    Oxygen and glucose deprivation (OGD) due to insufficient blood circulation can decrease cancer cell survival and proliferation in solid tumors. OGD increases the intracellular [AMP]/[ATP] ratio, thereby activating the AMPK. In this study, we have investigated the involvement of NQO1 in OGD-mediated AMPK activation and cancer cell death. We found that OGD activates AMPK in an NQO1-dependent manner, suppressing the mTOR/S6K/4E-BP1 pathway, which is known to control cell survival. Thus, the depletion of NQO1 prevents AMPK-induced cancer cell death in OGD. When we blocked OGD-induced Ca2+/CaMKII signaling, the NQO1-induced activation of AMPK was attenuated. In addition, when we blocked the RyR signaling, the accumulation of intracellular Ca2+ and subsequent activation of CaMKII/AMPK signaling was decreased in NQO1-expressing cells under OGD. Finally, siRNA-mediated knockdown of CD38 abrogated the OGD-induced activation of Ca2+/CaMKII/AMPK signaling. Taken together, we conclude that NQO1 plays a key role in the AMPK-induced cancer cell death in OGD through the CD38/cADPR/RyR/Ca2+/CaMKII signaling pathway. PMID:25586669

  8. Semi-synthesis of oxygenated dolabellane diterpenes with highly in vitro anti-HIV-1 activity.

    PubMed

    Pardo-Vargas, Alonso; Ramos, Freddy A; Cirne-Santos, Claudio Cesar; Stephens, Paulo Roberto; Paixão, Izabel Christina Palmer; Teixeira, Valeria Laneuville; Castellanos, Leonardo

    2014-09-15

    Research on dolabellane diterpenes of brown algae Dictyota spp. has shown that these diterpenoids have strong anti-HIV-1 activity, but there are not data about antiviral activity of dolabellane diterpenes isolated from octocorals, which are antipodes of those isolated from the brown algae. Dolabellanes 13-keto-1(R),11(S)-dolabella-3(E),7(E),12(18)-triene (1) and β-Araneosene (2) were isolated from the Caribbean octocoral Eunicea laciniata, and both showed low anti-HIV-1 activity and low toxicity. Since it was shown that oxygenated dolabellanes from algae have better anti-HIV-1 activity, in this work some derivatives of the main dolabellane of E. laciniata1 were obtained by epoxidation (3), epoxide opening (4), and allylic oxidation (5). The derivatives showed significant improvement in the anti-HIV-1potency (100-fold), being compounds 3 and 5 the most active ones. Their high antiviral activities, along with their low cytotoxicity, make them promissory antiviral compounds; and it is worth noting that the absolute configuration at the ring junction in the dolabellane skeleton does not seem to be determinant in the antiviral potency of these diterpeneoids. PMID:25176328

  9. Segregated Pt on Pd nanotubes for enhanced oxygen reduction activity in alkaline electrolyte.

    PubMed

    St John, Samuel; Atkinson, Robert W; Dyck, Ondrej; Sun, Cheng-Jun; Zawodzinski, Thomas A; Papandrew, Alexander B

    2015-12-01

    Nanoscaled Pt domains were integrated with Pd nanotubes via vapor deposition to yield a highly active electrocatalyst for the oxygen reduction reaction (ORR) in alkaline media. The surface-area-normalized ORR activity of these bi-metallic Pt-on-Pd nanotubes (PtPdNTs) was nearly 6× the corresponding carbon-supported Pt nanoparticle (Pt/C) activity at 0.9 V vs. RHE (1.5 vs. 0.24 mA cmmetal(-2), respectively). Furthermore, the high specific activity of the PtPdNTs was achieved without sacrificing mass-normalized activity, which is more than twice that of Pt/C (0.333 A mgPtPdNT(-1)vs. 0.141 A mgPt/C(-1)) and also greater than that of Pd/C (0.221 A mgPd/C(-1)). We attribute the enhancements in specific and mass activity to modifications of the segregated Pt electronic structure and to nanoscale porosity, respectively. PMID:26553367

  10. Enhanced electrocatalytic activity of nitrogen-doped olympicene/graphene hybrids for the oxygen reduction reaction.

    PubMed

    Hou, Xiuli; Zhang, Peng; Li, Shuang; Liu, Wei

    2016-08-17

    Developing inexpensive and non-precious metal electrocatalysts for the oxygen reduction reaction (ORR) is among the major goals in fuel cells. Herein, by using density-functional theory calculations, we show that N-doped olympicene/graphene hybrids exhibit unexpectedly high ORR catalytic activity-even comparable to that of the Pt(111) surface. Both graphitic-type and pyridine-type N-doped olympicene/graphene hybrids are highly active for the ORR and have good CO tolerance. The formation of the second H2O molecule is the rate-determining step for the ORR with the graphitic-type hybrid, whereas on the pyridine-type hybrid, it is the formation of OOH. Note that N-doped olympicene/graphene hybrid materials combine the high reactivity of olympicene and the high electrical conductivity of graphene, which allows them to be potentially used as low-cost and non-precious-metal ORR catalysts. PMID:27499058

  11. Enhanced oxygen reduction activity and solid oxide fuel cell performance with a nanoparticles-loaded cathode.

    PubMed

    Zhang, Xiaomin; Liu, Li; Zhao, Zhe; Tu, Baofeng; Ou, Dingrong; Cui, Daan; Wei, Xuming; Chen, Xiaobo; Cheng, Mojie

    2015-03-11

    Reluctant oxygen-reduction-reaction (ORR) activity has been a long-standing challenge limiting cell performance for solid oxide fuel cells (SOFCs) in both centralized and distributed power applications. We report here that this challenge has been tackled with coloading of (La,Sr)MnO3 (LSM) and Y2O3 stabilized zirconia (YSZ) nanoparticles within a porous YSZ framework. This design dramatically improves ORR activity, enhances fuel cell output (200-300% power improvement), and enables superior stability (no observed degradation within 500 h of operation) from 600 to 800 °C. The improved performance is attributed to the intimate contacts between nanoparticulate YSZ and LSM particles in the three-phase boundaries in the cathode. PMID:25686380

  12. Porous Dendritic Platinum Nanotubes with Extremely High Activity and Stability for Oxygen Reduction Reaction

    PubMed Central

    Zhang, Gaixia; Sun, Shuhui; Cai, Mei; Zhang, Yong; Li, Ruying; Sun, Xueliang

    2013-01-01

    Controlling the morphology of Pt nanostructures can provide opportunities to greatly increase their activity and stability. Porous dendritic Pt nanotubes were successfully synthesized by a facile, cost-effective aqueous solution method at room temperature in large scale. These unique structures are porous, hollow, hierarchical, and single crystalline, which not only gives them a large surface area with high catalyst utilization, but also improves mass transport and gas diffusion. These novel Pt structures exhibited significantly improved catalytic activity (4.4 fold) for oxygen reduction reaction (ORR) and greatly enhanced durability (6.1 fold) over that of the state-of-the-art commercial Pt/C catalyst. This work provides a promising approach to the design of highly efficient next-generation electrocatalysts. PMID:23524665

  13. Rationalizing the Hydrogen and Oxygen Evolution Reaction Activity of Two-Dimensional Hydrogenated Silicene and Germanene.

    PubMed

    Rupp, Caroline J; Chakraborty, Sudip; Anversa, Jonas; Baierle, Rogério J; Ahuja, Rajeev

    2016-01-20

    We have undertaken first-principles electronic structure calculations to show that the chemical functionalization of two-dimensional hydrogenated silicene (silicane) and germanene (germanane) can become a powerful tool to increase the photocatalytic water-splitting activity. Spin-polarized density functional theory within the GGA-PBE and HSE06 types of exchange correlation functionals has been used to obtain the structural, electronic, and optical properties of silicane and germanane functionalized with a series of nonmetals (N, P, and S), alkali metals (Li, Na, and K) and alkaline-earth metals (Mg and Ca). The surface-adsorbate interaction between the functionalized systems with H2 and O2 molecules that leads to envisaged hydrogen and oxygen evolution reaction activity has been determined. PMID:26704530

  14. Understanding Iron-based catalysts with efficient Oxygen reduction activity from first-principles calculations

    NASA Astrophysics Data System (ADS)

    Hafiz, Hasnain; Barbiellini, B.; Jia, Q.; Tylus, U.; Strickland, K.; Bansil, A.; Mukerjee, S.

    2015-03-01

    Catalysts based on Fe/N/C clusters can support the oxygen-reduction reaction (ORR) without the use of expensive metals such as platinum. These systems can also prevent some poisonous species to block the active sites from the reactant. We have performed spin-polarized calculations on various Fe/N/C fragments using the Vienna Ab initio Simulation Package (VASP) code. Some results are compared to similar calculations obtained with the Gaussian code. We investigate the partial density of states (PDOS) of the 3d orbitals near the Fermi level and calculate the binding energies of several ligands. Correlations of the binding energies with the 3d electronic PDOS's are used to propose electronic descriptors of the ORR associated with the 3d states of Fe. We also suggest a structural model for the most active site with a ferrous ion (Fe2+) in the high spin state or the so-called Doublet 3 (D3).

  15. Oxide Defect Engineering Enables to Couple Solar Energy into Oxygen Activation.

    PubMed

    Zhang, Ning; Li, Xiyu; Ye, Huacheng; Chen, Shuangming; Ju, Huanxin; Liu, Daobin; Lin, Yue; Ye, Wei; Wang, Chengming; Xu, Qian; Zhu, Junfa; Song, Li; Jiang, Jun; Xiong, Yujie

    2016-07-20

    Modern development of chemical manufacturing requires a substantial reduction in energy consumption and catalyst cost. Sunlight-driven chemical transformation by metal oxides holds great promise for this goal; however, it remains a grand challenge to efficiently couple solar energy into many catalytic reactions. Here we report that defect engineering on oxide catalyst can serve as a versatile approach to bridge light harvesting with surface reactions by ensuring species chemisorption. The chemisorption not only spatially enables the transfer of photoexcited electrons to reaction species, but also alters the form of active species to lower the photon energy requirement for reactions. In a proof of concept, oxygen molecules are activated into superoxide radicals on defect-rich tungsten oxide through visible-near-infrared illumination to trigger organic aerobic couplings of amines to corresponding imines. The excellent efficiency and durability for such a highly important process in chemical transformation can otherwise be virtually impossible to attain by counterpart materials. PMID:27351805

  16. Effect of glutaphen on generation of active oxygen species, photosynthetic electron transport, and the functional activity of photosystem 2 in Chlorella cells

    NASA Astrophysics Data System (ADS)

    Samovich, T. V.; Pshibytko, N. L.; Averina, N. G.

    2006-11-01

    Treatment of chlorella green algae (Chlorella sp.) for 2 h in the dark with the photodynamic herbicide glutaphen (GTP), consisting of 0.3 mM 1,10-phenanthroline and 0.6 mM glutamic acid, followed by illumination leads to efficient generation of active oxygen species (AOS). After 15 min of illumination, AOS accumulation reaches 200% compared with the level in cells of the control culture, then it decreases down to 130% and 115% after 1 day and 3 days of illumination. During the first few days after treatment, we observe inhibition of synthesis of a specific precursor of chlorophyll (Chl): 5-aminolevulinic acid molecules, and then we observe stimulation of the synthesis. The effect of GTP on the photosynthetic activity of chlorella does not depend on the AOS level but rather remains uniform, in contrast to its effect on the Chl biosynthesis system. GTP does not change the efficiency of light harvesting and charge separation at the reaction centers of photosystem (PS) 2, but significantly lowers the functional efficiency of the electron transport chain: the photochemical quenching constants for Chl a fluorescence and the effective quantum yield of photochemical reactions in photosystem 2 decrease. The major mechanism of action for GTP is probably displacement of the secondary quinone acceptor QB from its binding site on the D1 protein by the 1,10-phenanthroline, consequent inhibition of electron efflux from Q{A/-} and increase in the fraction of QB-nonreducing centers of PS 2. The active oxygen species generated in the cells have a photodegradative effect on the Chl biosynthesis system, in particular on its initial steps, and do not involve already formed pigment-protein complexes of PS 2.

  17. Synthesis and characterization of norfloxacin-transition metal complexes (group 11, IB): Spectroscopic, thermal, kinetic measurements and biological activity

    NASA Astrophysics Data System (ADS)

    Refat, Moamen S.

    2007-12-01

    The investigation of the new structures of Ag(I), Cu(II) and Au(III) complexes, [Ag 2(Nor) 2](NO 3) 2, [Cu(Nor) 2(H 2O) 2]SO 4·5H 2O and [Au(Nor) 2 (H 2O) 2]Cl 3 (where, Nor = norfloxacin) was done during the reaction of silver(I), copper(II) and gold(III) ions with norfloxacin drug ligand. Elemental analysis of CHN, infrared, electronic, 1H NMR and mass spectra, as well as thermo gravimetric analysis (TG and DTG) and conductivity measurements have been used to characterize the isolated complexes. The powder XRD studies confirm the amorphous nature of the complexes. The norfloxacin ligand is coordinated to Ag(I) and Au(III) ions as a neutral monodentate chelating through the N atom of piperidyl ring, but the copper(II) complex is coordinated through the carbonyl oxygen atom (quinolone group) and the oxygen atom of the carboxylic group. The norfloxacin and their metal complexes have been biologically tested, which resulted in norfloxacin complexes showing moderate activity against the gram positive and gram negative bacteria as well as against fungi.

  18. Conjugatable water-soluble Pt(II) and Pd(II) porphyrin complexes: novel nano- and molecular probes for optical oxygen tension measurement in tissue engineering.

    PubMed

    Giuntini, F; Chauhan, V M; Aylott, J W; Rosser, G A; Athanasiadis, A; Beeby, A; MacRobert, A J; Brown, R A; Boyle, R W

    2014-07-01

    Measurement of oxygen tension in compressed collagen sheets was performed using matrix-embedded optical oxygen sensors based on platinum(II) and palladium(II) porphyrins supported on polyacrylamide nanoparticles. Bespoke, fully water-soluble, mono-functionalised Pt(II) and Pd(II) porphyrin complexes designed for conjugation under mild conditions were obtained using microwave-assisted metallation. The new sensors display a linear response (1/τ vs. O2) to varying oxygen tension over a biologically relevant range (7.0 × 10(-4) to 2.7 × 10(-1) mM) in aqueous solutions; a behaviour that is maintained following conjugation to polyacrylamide nanoparticles, and following embedding of the nanosensors in compressed collagen sheets, paving the way to innovative approaches for real-time resolution of oxygen gradients throughout 3D matrices useful for tissue regeneration. PMID:24818569

  19. Osteogenic activity of vanadyl(IV)-ascorbate complex: evaluation of its mechanism of action.

    PubMed

    Cortizo, Ana M; Molinuevo, M Silvina; Barrio, Daniel A; Bruzzone, Liliana

    2006-01-01

    We have previously shown that different vanadium(IV) complexes regulate osteoblastic growth. Since vanadium compounds are accumulated in vivo in bone, they may affect bone turnover. The development of vanadium complexes with different ligands could be an alternative strategy of use in skeletal tissue engineering. In this study, we have investigated the osteogenic properties of a vanadyl(IV)-ascorbate (VOAsc) complex, as well as its possible mechanisms of action, on two osteoblastic cell lines in culture. VOAsc (2.5-25 microM) significantly stimulated osteoblastic proliferation (113-125% basal, p<0.01) in UMR106 cells, but not in the MC3T3E1 cell line. VOAsc (5-100 micrioM) dose-dependently stimulated type-I collagen production (107-156% basal) in osteoblasts. After 3 weeks of culture, 5-25 microM VOAsc increased the formation of nodules of mineralization in MC3T3E1 cells (7.7-20-fold control, p<0.001). VOAsc (50-100 microM) significantly stimulated apoptosis in both cell lines (170-230% basal, p<0.02-0.002), but did not affect reactive oxygen species production. The complex inhibited alkaline and neutral phosphatases from osteoblastic extracts with semi-maximal effect at 10 microM doses. VOAsc induced the activation and redistribution of P-ERK in a time- and dose-dependent manner. Inhibitors of the mitogen activated protein kinases (MAPK) pathway (PD98059 and UO126) partially blocked the VOAsc-enhanced osteoblastic proliferation and collagen production. In addition, wortmanin, a PI-3-K inhibitor and type-L channel blocker nifedipine also partially abrogated these effects of VOAsc on osteoblasts. Our in vitro results suggest that this vanadyl(IV)-ascorbate complex could be a useful pharmacological tool for bone tissue regeneration. PMID:16455285

  20. Oxidative DNA adducts after Cu(2+)-mediated activation of dihydroxy PCBs: role of reactive oxygen species.

    PubMed

    Spencer, Wendy A; Lehmler, Hans-Joachim; Robertson, Larry W; Gupta, Ramesh C

    2009-05-15

    Polychlorinated biphenyls (PCBs) are toxic industrial chemicals, complete carcinogens, and efficacious tumor promoters. However, the mechanism(s) of PCB-mediated carcinogenicity remains largely undefined. One likely pathway by which these agents may play a role in carcinogenesis is the generation of oxidative DNA damage by redox cycling of dihydroxylated PCB metabolites. We have now employed a new (32)P-postlabeling system to examine novel oxidative DNA lesions induced by Cu(2+)-mediated activation of PCB metabolites. (32)P postlabeling of DNA incubated with various PCB metabolites resulted in over a dozen novel polar oxidative DNA adducts that were chromatographically similar for all active agents. The most potent metabolites tested were the hydroquinones (hydroxyl groups arranged para to each other), yielding polar oxidative adduct levels ranging from 55 to 142 adducts/10(6) nucleotides. PCB catechols, or ortho-dihydroxy metabolites, were up to 40% less active than their corresponding hydroquinone congeners, whereas monohydroxylated and quinone metabolites did not produce detectable oxidative damage over that of vehicle. With the exception of 2,4,5-Cl-2',5'-dihydroxybiphenyl, this oxidative DNA damage seemed to be inversely related to chlorine content: no chlorine approximately mono->di->trichlorinated metabolites. Importantly, copper, but not iron, was essential for activation of the PCB metabolites to these polar oxidative DNA adducts, because in its absence or in the presence of the Cu(+)-specific scavenger bathocuproine, no adducts were detected. Intervention studies with known reactive oxygen species (ROS) modifiers suggested that H(2)O(2), singlet oxygen, hydroxyl radical, and superoxide may also be involved in this PCB-mediated oxidative DNA damage. These data indicate a mechanistic role for several ROS, in addition to copper, in PCB-induced DNA damage and provide further support for oxidative DNA damage in PCB-mediated carcinogenesis. PMID:19233261

  1. Some biologically active oxovanadium(IV) complexes of triazole derived Schiff bases: their synthesis, characterization and biological properties.

    PubMed

    Chohan, Zahid H; Sumrra, Sajjad H

    2010-10-01

    A series of biologically active oxovanadium(IV) complexes of triazole derived Schiff bases L(1)-L(5) have been synthesized and characterized by their physical, analytical, and spectral data. The synthesized ligands potentially act as bidentate, in which the oxygen of furfural and nitrogen of azomethine coordinate with the oxovanadium atom to give a stoichiometry of vanadyl complexes 1:2 (M:L) in a square-pyramidal geometry. In vitro antibacterial and antifungal activities on different species of pathogenic bacteria (E. coli, S. flexneri, P. aeruginosa, S. typhi, S. aureus, and B. subtilis) and fungi (T. longifusus, C. albicans, A. flavus, M. canis, F. solani, and C. glabrata) have been studied. All compounds showed moderate to significant antibacterial activity against one or more bacterial strains and good antifungal activity against most of the fungal strains. The brine shrimp bioassay was also carried out to check the cytotoxicity of coordinated and uncoordinated synthesized compounds. PMID:20429776

  2. Influence of oxygen limitation, absence of the cytochrome bc(1) complex and low pH on global gene expression in Gluconobacter oxydans 621H using DNA microarray technology.

    PubMed

    Hanke, Tanja; Richhardt, Janine; Polen, Tino; Sahm, Hermann; Bringer, Stephanie; Bott, Michael

    2012-02-10

    The genome-wide transcriptional responses of the strictly aerobic α-proteobacterium Gluconobacter oxydans 621H to oxygen limitation, to the absence of the cytochrome bc(1) complex, and to low pH were studied using DNA microarray analyses. Oxygen limitation caused expression changes of 486 genes, representing 20% of the chromosomal genes. Genes with an increased mRNA level included those for terminal oxidases, the cytochrome bc(1) complex, transhydrogenase, two alcohol dehydrogenases, heme biosynthesis, PTS proteins, proteins involved in cyclic diGMP synthesis and degradation, two sigma factors, flagella and chemotaxis proteins, several stress proteins, and a putative exporter protein. The downregulated genes comprised those for respiratory dehydrogenases, enzymes of central metabolism, PQQ biosynthesis, outer membrane receptors, Sec proteins, and proteins involved in transcription and translation. A ΔqrcABC mutant of G. oxydans showed a growth defect during cultivation on mannitol at pH 4 under oxygen saturation. Comparison of the transcriptomes of this mutant versus the wild type under these conditions revealed 51 differentially expressed genes. Interestingly, almost all of the 45 genes with increased expression in the ΔqrcABC mutant at pH 4 were also upregulated in the wild type grown at pH 6 under oxygen limitation. These results support an active role of the cytochrome bc(1) complex in G. oxydans respiration. The transcriptome comparison of G. oxydans wild type at pH 4 versus pH 6 in mannitol medium under oxygen-saturated conditions uncovered only 72 differentially expressed genes. The 35 upregulated genes included those for cytochrome bd oxidase, major polyol dehydrogenase, iron storage and oxidative stress proteins. Among the 37 downregulated genes were some encoding enzymes dealing with carbon dioxide, such as biotin carboxylase, biotin carboxyl carrier protein, and carboanhydrase. These results give first insights into global transcriptional responses of

  3. Integrin activation and focal complex formation in cardiac hypertrophy

    NASA Technical Reports Server (NTRS)

    Laser, M.; Willey, C. D.; Jiang, W.; Cooper, G. 4th; Menick, D. R.; Zile, M. R.; Kuppuswamy, D.

    2000-01-01

    Cardiac hypertrophy is characterized by both remodeling of the extracellular matrix (ECM) and hypertrophic growth of the cardiocytes. Here we show increased expression and cytoskeletal association of the ECM proteins fibronectin and vitronectin in pressure-overloaded feline myocardium. These changes are accompanied by cytoskeletal binding and phosphorylation of focal adhesion kinase (FAK) at Tyr-397 and Tyr-925, c-Src at Tyr-416, recruitment of the adapter proteins p130(Cas), Shc, and Nck, and activation of the extracellular-regulated kinases ERK1/2. A synthetic peptide containing the Arg-Gly-Asp (RGD) motif of fibronectin and vitronectin was used to stimulate adult feline cardiomyocytes cultured on laminin or within a type-I collagen matrix. Whereas cardiocytes under both conditions showed RGD-stimulated ERK1/2 activation, only collagen-embedded cells exhibited cytoskeletal assembly of FAK, c-Src, Nck, and Shc. In RGD-stimulated collagen-embedded cells, FAK was phosphorylated only at Tyr-397 and c-Src association occurred without Tyr-416 phosphorylation and p130(Cas) association. Therefore, c-Src activation is not required for its cytoskeletal binding but may be important for additional phosphorylation of FAK. Overall, our study suggests that multiple signaling pathways originate in pressure-overloaded heart following integrin engagement with ECM proteins, including focal complex formation and ERK1/2 activation, and many of these pathways can be activated in cardiomyocytes via RGD-stimulated integrin activation.

  4. Characterization and catechole oxidase activity of a family of copper complexes coordinated by tripodal pyrazole-based ligands.

    PubMed

    Marion, R; Zaarour, M; Qachachi, N A; Saleh, N M; Justaud, F; Floner, D; Lavastre, O; Geneste, F

    2011-11-01

    A family of tripodal pyrazole-based ligands has been synthesized by a condensation reaction between 1-hydroxypyrazoles and aminoalcohols. The diversity was introduced both on the substituents of the pyrazole ring and on the side chain. The corresponding copper(II) complexes have been prepared by reaction with CuCl(2) in tetrahydrofuran. They have been characterized by EPR, UV spectroscopy and cyclic voltammetry. The absence of the half-field splitting signals in EPR suggests that the complex exists in solution as mononuclear species. The influence of substituents and side chain of the tripodal ligand on the catecholase activity of the complexes was studied. The reaction rate depends on two factors. First, the presence of an oxygen atom in the third position of the side chain should be avoided to keep the effectiveness of the reaction. Second, the electronic and steric effects of substituents on the pyrazole ring strongly affect the catalytic activity of the complex. Thus, best results were obtained with complexes containing unsubstituted pyrazole based-ligands. Kinetic investigations with the best catalyst based on the Michaelis-Menten model show that the catalytic activity of the mononuclear complex is close to that of some dicopper complexes described in literature. PMID:21946439

  5. Synthesis, characterization and anticancer activity studies of ruthenium(II) polypyridyl complexes on A549 cells.

    PubMed

    Zeng, Chuan-Chuan; Jiang, Guang-Bin; Lai, Shang-Hai; Zhang, Cheng; Yin, Hui; Tang, Bing; Wan, Dan; Liu, Yun-Jun

    2016-08-01

    Four new ruthenium(II) polypyridyl complexes [Ru(N-N)2(bddp)](ClO4)21-4 (N-N=dmb: 4,4'-dimethyl-2,2'-bipyridine 1, bpy: 2,2'-bipyridine 2, phen: 1,10-phenanthroline 3 and dmp: 2,9-dimethyl-1,10-phenanthroline 4, bddp=benzilo[2,3-b]-1,4-diazabenzo[i]dipyrido[3,2-a:2',3'-c]phenazine) were synthesized and characterized by elemental analysis, ESI-MS and (1)H NMR. The cytotoxicity in vitro of the complexes against BEL-7402, HeLa, MG-63 and A549 cell lines was investigated by MTT method. The complexes show high cytotoxic activity toward the selected cell lines with an IC50 value ranging from 5.3±0.6 to 15.7±3.6μM. The apoptosis was studied with acridine orange (AO)/ethdium bromide (EB) and Hoechst 33258 staining methods. The cellular uptake was investigated with DAPI staining method. The reactive oxygen species (ROS) and mitochondrial membrane potential were performed under fluorescent microscope and flow cytometry. The complexes can induce an increase in the ROS levels and a decrease in the mitochondrial membrane potential. The comet assay was studied with fluorescent microscope. The percentage in apoptotic and necrotic cells and cell cycle arrest were assayed by flow cytometry. The effects of the complexes on the expression of caspases and Bcl-2 family proteins were studied by western blot analysis. The results show that the complexes induce apoptosis in A549 cells through an ROS-mediated mitochondrial dysfunction pathway, which was accompanied by regulating the expression of Bcl-2 family proteins. PMID:27288660

  6. Intensity of daily physical activity is associated with central hemodynamic and leg muscle oxygen availability in COPD.

    PubMed

    Louvaris, Zafeiris; Kortianou, Eleni A; Spetsioti, Stavroula; Vasilopoulou, Maroula; Nasis, Ioannis; Asimakos, Andreas; Zakynthinos, Spyros; Vogiatzis, Ioannis

    2013-09-01

    In chronic obstructive pulmonary disease (COPD), daily physical activity is reported to be adversely associated with the magnitude of exercise-induced dynamic hyperinflation and peripheral muscle weakness. There is limited evidence whether central hemodynamic, oxygen transport, and peripheral muscle oxygenation capacities also contribute to reduced daily physical activity. Nineteen patients with COPD (FEV1, 48 ± 14% predicted) underwent a treadmill walking test at a speed corresponding to the individual patient's mean walking intensity, captured by a triaxial accelerometer during a preceding 7-day period. During the indoor treadmill test, the individual patient mean walking intensity (range, 1.5 to 2.3 m/s2) was significantly correlated with changes from baseline in cardiac output recorded by impedance cardiography (range, 1.2 to 4.2 L/min; r = 0.73), systemic vascular conductance (range, 7.9 to 33.7 ml·min(-1)·mmHg(-1); r = 0.77), systemic oxygen delivery estimated from cardiac output and arterial pulse-oxymetry saturation (range, 0.15 to 0.99 L/min; r = 0.70), arterio-venous oxygen content difference calculated from oxygen uptake and cardiac output (range, 3.7 to 11.8 mlO2/100 ml; r = -0.73), and quadriceps muscle fractional oxygen saturation assessed by near-infrared spectrometry (range, -6 to 23%; r = 0.77). In addition, mean walking intensity significantly correlated with the quadriceps muscle force adjusted for body weight (range, 0.28 to 0.60; r = 0.74) and the ratio of minute ventilation over maximal voluntary ventilation (range, 38 to 89%, r = -0.58). In COPD, in addition to ventilatory limitations and peripheral muscle weakness, intensity of daily physical activity is associated with both central hemodynamic and peripheral muscle oxygenation capacities regulating the adequacy of matching peripheral muscle oxygen availability by systemic oxygen transport. PMID:23845982

  7. GT-CATS: Tracking Operator Activities in Complex Systems

    NASA Technical Reports Server (NTRS)

    Callantine, Todd J.; Mitchell, Christine M.; Palmer, Everett A.

    1999-01-01

    Human operators of complex dynamic systems can experience difficulti