Syn-anti conformational switching in an ethane-bridged Co(II)bisporphyrin induced by external stimuli: effects of inter-macrocyclic interactions, axial ligation and chemical and electrochemical oxidations.

PubMed

Dey, Soumyajit; Rath, Sankar Prasad

2014-02-07

The syn-anti conformational switching has been demonstrated in the ethane-bridged dicobalt(II)bisporphyrin which is present in the syn-form only. The addition of either perylene or axial ligands to Co(II)(bisporphyrin) completely transforms the syn form into the anti because of strong π-π interaction and axial coordination, respectively. The complex undergoes four 1e-oxidations in CH2Cl2 which are indicative of strong through space interactions between the two cofacial Co-porphyrins at 295 K. The first oxidation is a metal centered one and occurs at a potential much lower than that of the monomeric analog. However, the second oxidation, which is again metal centered, was at a significantly higher potential. The large difference between the first two oxidations, as observed here, is due to much stronger inter-porphyrin interactions. The step-wise oxidations have been performed both chemically and electro-chemically while the progress of the reactions was monitored by UV-visible and (1)H NMR spectroscopy. After 1e-oxidation, a very broad (1)H NMR signal results with increased difference between two meso resonances, which indicates that the two macrocycles are in the syn-form with lesser interplanar separation as also observed by DFT. However, 2e-oxidation results in the stabilization of the anti form. The addition of axial ligands to Co(II)(bisporphyrin) also completely transforms the syn form into the anti form. While additions of THF and I2/I(-) both result in the formation of five-coordinate complexes, Co(II) is oxidized to Co(III) in the case of the latter. However, additions of 1-methylimidazole, pyridine and pyrazine as axial ligands result in the formation of a six-coordinate complex in which Co(II) is spontaneously oxidized to Co(III) in air.

Continuous-flow oxidative cyanation of primary and secondary amines using singlet oxygen.

PubMed

Ushakov, Dmitry B; Gilmore, Kerry; Kopetzki, Daniel; McQuade, D Tyler; Seeberger, Peter H

2014-01-07

Primary and secondary amines can be rapidly and quantitatively oxidized to the corresponding imines by singlet oxygen. This reactive form of oxygen was produced using a variable-temperature continuous-flow LED-photoreactor with a catalytic amount of tetraphenylporphyrin as the sensitizer. α-Aminonitriles were obtained in good to excellent yields when trimethylsilyl cyanide served as an in situ imine trap. At 25°C, primary amines were found to undergo oxidative coupling prior to cyanide addition and yielded secondary α-aminonitriles. Primary α-aminonitriles were synthesized from the corresponding primary amines for the first time, by an oxidative Strecker reaction at -50 °C. This atom-economic and protecting-group-free pathway provides a route to racemic amino acids, which was exemplified by the synthesis of tert-leucine hydrochloride from neopentylamine. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The chemical foundations of nitroalkene fatty acid signaling through addition reactions with thiols.

PubMed

Turell, Lucía; Steglich, Martina; Alvarez, Beatriz

2018-03-22

Nitroalkene fatty acids can be formed in vivo and administered exogenously. They exert pleiotropic signaling actions with cytoprotective and antiinflammatory effects. The presence of the potent electron withdrawing nitro group confers electrophilicity to the adjacent β-carbon. Thiols (precisely, thiolates) are strong nucleophiles and can react with nitroalkene fatty acids through reversible Michael addition reactions. In addition, nitroalkene fatty acids can undergo several other processes including metabolic oxidation, reduction, esterification, nitric oxide release and partition into hydrophobic compartments. The signaling actions of nitroalkenes are mainly mediated by reactions with critical thiols in regulatory proteins. Thus, the thio-Michael addition reaction provides a framework for understanding the molecular basis of the biological effects of nitroalkene fatty acids at the crossroads of thiol signaling and electrophilic lipid signaling. In this review, we describe the reactions of nitroalkene fatty acids in biological contexts. We focus on the Michael addition-elimination reaction with thiols and its mechanism, and extrapolate kinetic and thermodynamic considerations to in vivo settings. Copyright © 2018 Elsevier Inc. All rights reserved.

Oxidative stress and dietary phytochemicals: Role in cancer chemoprevention and treatment.

PubMed

Chikara, Shireen; Nagaprashantha, Lokesh Dalasanur; Singhal, Jyotsana; Horne, David; Awasthi, Sanjay; Singhal, Sharad S

2018-01-28

Several epidemiological observations have shown an inverse relation between consumption of plant-based foods, rich in phytochemicals, and incidence of cancer. Phytochemicals, secondary plant metabolites, via their antioxidant property play a key role in cancer chemoprevention by suppressing oxidative stress-induced DNA damage. In addition, they modulate several oxidative stress-mediated signaling pathways through their anti-oxidant effects, and ultimately protect cells from undergoing molecular changes that trigger carcinogenesis. In several instances, however, the pro-oxidant property of these phytochemicals has been observed with respect to cancer treatment. Further, in vitro and in vivo studies show that several phytochemicals potentiate the efficacy of chemotherapeutic agents by exacerbating oxidative stress in cancer cells. Therefore, we reviewed multiple studies investigating the role of dietary phytochemicals such as, curcumin (turmeric), epigallocatechin gallate (EGCG; green tea), resveratrol (grapes), phenethyl isothiocyanate (PEITC), sulforaphane (cruciferous vegetables), hesperidin, quercetin and 2'-hydroxyflavanone (2HF; citrus fruits) in regulating oxidative stress and associated signaling pathways in the context of cancer chemoprevention and treatment. Copyright © 2017 Elsevier B.V. All rights reserved.

Cyclosporin A is unable to inhibit carboxyatractyloside-induced permeability transition in aged mitochondria.

PubMed

García, Noemí; Zazueta, Cecilia; Martínez-Abundis, Eduardo; Pavón, Natalia; Chávez, Edmundo

2009-04-01

We studied the effect of mitochondrial ageing on membrane permeability transition. The results obtained indicate that aged mitochondria are neither able to retain Ca2+ nor to maintain a high transmembrane electric gradient. In addition, aged mitochondria undergo a large amplitude swelling. These dysfunctions were circumvented by the addition of cyclosporin A. Furthermore, it is shown that ageing-induced permeability transition causes oxidative damage on the matrix enzyme aconitase. The observed damage in aged mitochondria requires Ca2+ addition; therefore, it was not seen when Sr2+ replaced Ca2+. Two important findings in this work were the fact that despite of the presence of cyclosporin A, carboxyatractyloside was still able to induce permeability transition, and that ageing induced mitochondrial DNA disruption and release of cytochrome c. It is likely that the membrane's increased permeability is due to the effect of fatty acids, since bovine serum albumin makes mitochondria able to retain Ca2+. However, the possibility that the damage might be the result of oxidative stress cannot be discarded.

Thiol oxidation and di-tyrosine formation in human plasma proteins induced by inflammatory concentrations of hypochlorous acid.

PubMed

Colombo, Graziano; Clerici, Marco; Altomare, Alessandra; Rusconi, Francesco; Giustarini, Daniela; Portinaro, Nicola; Garavaglia, Maria Lisa; Rossi, Ranieri; Dalle-Donne, Isabella; Milzani, Aldo

2017-01-30

In this study, we assessed the oxidative damage occurring in plasma proteins when human blood was exposed to inflammatory concentrations of hypochlorous acid (HOCl). We used specific thiol labelling and Western blot analyses to determine protein thiol oxidation, as well as analytical gel filtration HPLC coupled to fluorescence detection to explore formation of high molecular weight (HMW) protein aggregates. Thiol-containing proteins oxidized by HOCl were identified by redox proteomics. Mass spectrometry (MS) analysis was performed to elucidate the protein composition of HMW aggregates. α1-antitrypsin, transthyretin, and haptoglobin showed thiol oxidation at HOCl concentrations higher than those causing complete oxidation of albumin. At the highest HOCl concentrations, formation of carbonylated and di-tyrosine cross-linked HMW protein aggregates also occurred. MS analysis identified fibrinogen, complement C3 and apolipoprotein A-I as components of HMW protein aggregates. These results could be relevant for human diseases characterized by inflammatory conditions in which myeloperoxidase and HOCl are involved. In this study we evaluated the oxidative damage occurring on plasma proteins when reconstituted human blood was exposed to inflammatory concentrations of hypochlorous acid (HOCl). Pathophysiological concentrations of HOCl are able to induce different modifications on plasma proteins such as carbonylation, sulfhydryl oxidation and formation of high molecular weight (HMW) protein aggregates characterized by di-tyrosine fluorescence. There are two relevant aspects emerging from this paper. The first one consists on identifying low abundant proteins undergoing sulfhydryl oxidation by biotin-maleimide derivatization followed by MALDI-TOF mass spectrometry. This approach suggests three low-abundant proteins undergoing HOCl-induced oxidation: transthyretin, α1-antitrypsin, and haptoglobin. In addition, we analysed HMW protein aggregates forming after HOCl exposure. These aggregates are characterized by carbonylation, intra- and/or intermolecular di-tyrosine bridges. After their isolation from SDS-PAGE gel electrophoresis, using electrospray tandem mass spectrometry coupled to reversed-phase nanoscale capillary liquid chromatography, we identified some protein constituents of these HMW aggregates such as α, β, γ fibrinogen chains, apolipoprotein A-I and complement C3. In particular, our work highlights how fibrinogen is an important constituent of HOCl-induced HMW protein aggregates validating the mass spectrometry result with additional experiments. Further investigations are required in order to evaluate the possibility to use carbonylated and di-Tyr cross-linked HMW protein aggregates as (early) biomarkers for disease progression in inflammatory conditions in which myeloperoxidase and HOCl are involved. Copyright © 2016 Elsevier B.V. All rights reserved.

Light-driven, proton-controlled, catalytic aerobic C-H oxidation mediated by a Mn(III) porphyrinoid complex.

PubMed

Neu, Heather M; Jung, Jieun; Baglia, Regina A; Siegler, Maxime A; Ohkubo, Kei; Fukuzumi, Shunichi; Goldberg, David P

2015-04-15

The visible light-driven, catalytic aerobic oxidation of benzylic C-H bonds was mediated by a Mn(III) corrolazine complex. To achieve catalytic turnovers, a strict selective requirement for the addition of protons was established. The resting state of the catalyst was unambiguously characterized by X-ray diffraction as [Mn(III)(H2O)(TBP8Cz(H))](+), in which a single, remote site on the ligand is protonated. If two remote sites are protonated, however, reactivity with O2 is shut down. Spectroscopic methods revealed that the related Mn(V)(O) complex is also protonated at the same remote site at -60 °C, but undergoes valence tautomerization upon warming.

A pilot randomized crossover trial assessing the safety and short-term effects of pomegranate supplementation in hemodialysis patients.

PubMed

Rivara, Matthew B; Mehrotra, Rajnish; Linke, Lori; Ruzinski, John; Ikizler, T Alp; Himmelfarb, Jonathan

2015-01-01

Oxidative stress and systemic inflammation are highly prevalent in patients undergoing maintenance hemodialysis (MHD) and are linked to excess cardiovascular risk. This study examined whether short-term supplementation with pomegranate juice and extract is safe and well tolerated by MHD patients. The secondary aim was to assess the effect of pomegranate supplementation on oxidative stress, systemic inflammation, monocyte function, and blood pressure. Prospective, randomized, crossover, pilot clinical trial (NCT01562340). The study was conducted from March to October 2012 in outpatient dialysis facilities in the Seattle metropolitan area. Twenty-four patients undergoing MHD (men, 64%; mean age, 61 ± 14 years) were randomly assigned to receive pomegranate juice or extract during a 4-week intervention period. After a washout period, all patients received the alternative treatment during a second 4-week intervention period. Patients assigned to receive pomegranate juice received 100 mL of juice before each dialysis session. Patients assigned to receive pomegranate extract were given 1,050 mg of extract daily. The main outcome measures were safety and tolerability of pomegranate juice and extract. Additional secondary outcomes assessed included serum lipids, laboratory biomarkers of inflammation (C-reactive protein and interleukin 6) and oxidative stress (plasma F2 isoprostanes and isofurans), monocyte cytokine production, and predialysis blood pressure. Both pomegranate juice and extract were safe and well tolerated by study participants. Over the study period, neither treatment had a significant effect on lipid profiles, plasma C-reactive protein, interleukin 6, F2-isoprostane or isofuran concentrations, predialysis systolic or diastolic blood pressure nor changed the levels of monocyte cytokine production. Both pomegranate juice and extract are safe and well tolerated by patients undergoing MHD but do not influence markers of inflammation or oxidative stress nor affect predialysis blood pressure. Copyright © 2015 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.

Mass spectrometric characterization of human serum albumin dimer: A new potential biomarker in chronic liver diseases.

PubMed

Naldi, Marina; Baldassarre, Maurizio; Nati, Marina; Laggetta, Maristella; Giannone, Ferdinando Antonino; Domenicali, Marco; Bernardi, Mauro; Caraceni, Paolo; Bertucci, Carlo

2015-08-10

Human serum albumin (HSA) undergoes several structural alterations affecting its properties in pro-oxidant and pro-inflammatory environments, as it occurs during liver cirrhosis. These modifications include the formation of albumin dimers. Although HSA dimers were reported to be an oxidative stress biomarker, to date nothing is known about their role in liver cirrhosis and related complications. Additionally, no high sensitive analytical method was available for HSA dimers assessment in clinical settings. Thus the HSA dimeric form in human plasma was characterized by mass spectrometry using liquid chromatography tandem mass spectrometry (LC-ESI-Q-TOF) and matrix assisted laser desorption time of flight (MALDI-TOF) techniques. N-terminal and C-terminal truncated HSA, as well as the native HSA, undergo dimerization by binding another HSA molecule. This study demonstrated the presence of both homo- and hetero-dimeric forms of HSA. The dimerization site was proved to be at Cys-34, forming a disulphide bridge between two albumin molecules, as determined by LC-MS analysis after tryptic digestion. Interestingly, when plasma samples from cirrhotic subjects were analysed, the dimer/monomer ratio resulted significantly increased when compared to that of healthy subjects. These isoforms could represent promising biomarkers for liver disease. Additionally, this analytical approach leads to the relative quantification of the residual native HSA, with fully preserved structural integrity. Copyright © 2014 Elsevier B.V. All rights reserved.

Thermochemical and kinetic analyses on oxidation of isobutenyl radical and 2-hydroperoxymethyl-2-propenyl radical.

PubMed

Zheng, X L; Sun, H Y; Law, C K

2005-10-13

In recognition of the importance of the isobutene oxidation reaction in the preignition chemistry associated with engine knock, the thermochemistry, chemical reaction pathways, and reaction kinetics of the isobutenyl radical oxidation at low to intermediate temperature range were computationally studied, focusing on both the first and the second O2 addition to the isobutenyl radical. The geometries of reactants, important intermediates, transition states, and products in the isobutenyl radical oxidation system were optimized at the B3LYP/6-311G(d,p) and MP2(full)/6-31G(d) levels, and the thermochemical properties were determined on the basis of ab initio, density functional theory, and statistical mechanics. Enthalpies of formation for several important intermediates were calculated using isodesmic reactions at the DFT and the CBS-QB3 levels. The kinetic analysis of the first O2 addition to the isobutenyl radical was performed using enthalpies at the CBS-QB3 and G3(MP2) levels. The reaction forms a chemically activated isobutenyl peroxy adduct which can be stabilized, dissociate back to reactants, cyclize to cyclic peroxide-alkyl radicals, and isomerize to the 2-hydroperoxymethyl-2-propenyl radical that further undergoes another O2 addition. The reaction channels for isomerization and cyclization and further dissociation on this second O2 addition were analyzed using enthalpies at the DFT level with energy corrections based on similar reaction channels for the first O2 addition. The high-pressure limit rate constants for each reaction channel were determined as functions of temperature by the canonical transition state theory for further kinetic model development.

Short stack modeling of degradation in solid oxide fuel cells. Part II. Sensitivity and interaction analysis

NASA Astrophysics Data System (ADS)

Gazzarri, J. I.; Kesler, O.

In the first part of this two-paper series, we presented a numerical model of the impedance behaviour of a solid oxide fuel cell (SOFC) aimed at simulating the change in the impedance spectrum induced by contact degradation at the interconnect-electrode, and at the electrode-electrolyte interfaces. The purpose of that investigation was to develop a non-invasive diagnostic technique to identify degradation modes in situ. In the present paper, we appraise the predictive capabilities of the proposed method in terms of its robustness to uncertainties in the input parameters, many of which are very difficult to measure independently. We applied this technique to the degradation modes simulated in Part I, in addition to anode sulfur poisoning. Electrode delamination showed the highest robustness to input parameter variations, followed by interconnect oxidation and interconnect detachment. The most sensitive degradation mode was sulfur poisoning, due to strong parameter interactions. In addition, we simulate several simultaneous two-degradation-mode scenarios, assessing the method's capabilities and limitations for the prediction of electrochemical behaviour of SOFC's undergoing multiple simultaneous degradation modes.

Identification of Furan Metabolites Derived from Cysteine-cis-2-Butene-1,4-Dial-Lysine Crosslinks

PubMed Central

Lu, Ding; Peterson, Lisa A.

2010-01-01

Furan is a rodent hepatotoxicant and carcinogen. Since this compound is an important industrial intermediate and has been detected in heat-processed foods and smoke, humans are likely exposed to this toxic compound. Characterization of urinary metabolites of furan will lead to the development of biomarkers to assess human health risks associated with furan exposure. Previous studies indicate that furan is oxidized to a reactive α, β-unsaturated dialdehyde, cis-2-butene-1,4-dial (BDA), in a reaction catalyzed by cytochrome P450. Five previously characterized metabolites are derived from the reaction of BDA with cellular nucleophiles such as glutathione and protein. They include the mono-glutathione reaction product, N-[4-carboxy-4-(3-mercapto-1H-pyrrol-1-yl)-1-oxobutyl]-L-cysteinylglycine cyclic sulfide and its downstream metabolite, S-[1-(1,3-dicarboxypropyl)-1H-pyrrol-3-yl]methylthiol as well as R-2-acetylamino-6-(2,5-dihydro-2-oxo-1H-pyrrol-1-yl)-1-hexanoic acid and N-acetyl-S-[1-(5-acetylamino-5-carboxypentyl)-1H-pyrrol-3-yl]-L-cysteine and its sulfoxide. The last two compounds are downstream metabolites of a BDA-derived cysteine-lysine crosslink, S-[1-(5-amino-5-carboxypentyl)-1H-pyrrol-3-yl]-L-cysteine. In this report, we present the characterization of seven additional urinary furan metabolites, all of which are derived from this crosslink. The cysteinyl residue is subject to several biotransformation reactions, including N-acetylation and S-oxidation. Alternatively, it can undergo β-elimination followed by S-methylation to a methylthiol intermediate that is further oxidized to a sulfoxide. The lysine portion of the crosslink is either N-acetylated or undergoes an oxidative transamination reaction to generate an α-ketoacid metabolite that undergoes oxidative decarboxylation. Some of these metabolites are among the most abundant furan metabolites present in urine as judged by LC-MS/MS analysis, indicating that the oxidation of furan to BDA and BDA’s subsequent reaction with cellular cysteine and lysine residues may represent a significant in vivo pathway of furan biotransformation. Since they are derived from cellular BDA reaction products, these metabolites are markers of furan exposure and bioactivation and could be explored as potential biomarkers in human studies. PMID:20043645

Morphological and chemical changes of aerosolized E. coli treated with a dielectric barrier discharge

DOE PAGES

Romero-Mangado, Jaione; Nordlund, Dennis; Soberon, Felipe; ...

2016-02-12

This paper presents the morphological and chemical modification of the cell structure of aerosolized Escherichia coli treated with a dielectric barrier discharge (DBD). Exposure to DBD results in severe oxidation of the bacteria, leading to the formation of hydroxyl groups and carbonyl groups and a significant reduction in amine functionalities and phosphate groups. Near edge x-ray absorption fine structure(NEXAFS) measurements confirm the presence of additional oxide bonds upon DBD treatment, suggesting oxidation of the outer layer of the cell wall. Electron microscopy images show that the bacteria undergo physical distortion to varying degrees, resulting in deformation of the bacterial structure.more » The electromagnetic field around the DBD coil causes severe damage to the cell structure, possibly resulting in leakage of vital cellular materials. The oxidation and chemical modification of the bacterial components are evident from the Fourier transform infrared spectroscopy and NEXAFS results. The bacterial reculture experiments confirm inactivation of airborne E. coli upon treating with DBD.« less

Brain-derived neurotrophic factor (BDNF) and oxidative stress in heroin-dependent male patients undergoing methadone maintenance treatment.

PubMed

Tsai, Meng-Chang; Huang, Tiao-Lai

2017-03-01

Brain-derived neurotrophic factor (BDNF) and oxidative stress may play a role in patients with heroin dependence. The aim of this study was to investigate the serum levels and activities of BDNF and oxidative stress markers, such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), thiobarbituric acid reactive substances (TBARS), protein carbonyl content (PCC), and 8-hydroxy 2'-deoxyguanosine (8-OHdG), in heroin-dependent patients undergoing methadone maintenance treatment (MMT). 60 heroin-dependent male MMT patients and 30 healthy males were recruited for this study. The serum BDNF and oxidative stress markers of these subjects were measured with assay kits. Analyses of covariance (ANCOVAs) with age and body mass index adjustments indicated that the serum levels of BDNF in the MMT patients were significantly higher than those in the healthy controls (F=5.169; p=0.026). However, there were no significant differences between the heroin-dependent patients and the healthy controls in the serum levels or activities of oxidative stress markers (p>0.05). In conclusion, our results suggest that MMT increases BDNF levels in heroin-dependent patients, and that patients undergoing MMT might be in a balanced state of reduced oxidation. Copyright © 2017 Elsevier Ireland Ltd. All rights reserved.

Microbial mediated iron redox cycling in Fe (hydr)oxides for nitrite removal.

PubMed

Lu, Yongsheng; Xu, Lu; Shu, Weikang; Zhou, Jizhi; Chen, Xueping; Xu, Yunfeng; Qian, Guangren

2017-01-01

Nitrite, at an environmentally relevant concentration, was significantly reduced with iron (hydr)oxides mediated by Shewanella oneidensis MR-1. The average nitrite removal rates of 1.28±0.08 and 0.65±0.02(mgL -1 )h -1 were achieved with ferrihydrite and magnetite, respectively. The results showed that nitrite removal was able to undergo multiple redox cycles with iron (hydr)oxides mediated by Shewanella oneidensis MR-1. During the bioreduction of the following cycles, biogenic Fe(II) was subsequently chemically oxidized to Fe(III), which is associated with nitrite reduction. There was 11.18±1.26mgL -1 of NH 4 + -N generated in the process of redox cycling of ferrihydrite. Additionally, results obtained by using X-ray diffraction showed that ferrihydrite and magnetite remained mainly stable in the system. This study indicated that redox cycling of Fe in iron (hydr)oxides was a potential process associated with NO 2 - -N removal from solution, and reduced most nitrite abiotically to gaseous nitrogen species. Copyright © 2016 Elsevier Ltd. All rights reserved.

A peroxynitrite complex of copper: formation from a copper-nitrosyl complex, transformation to nitrite and exogenous phenol oxidative coupling or nitration.

PubMed

Park, Ga Young; Deepalatha, Subramanian; Puiu, Simona C; Lee, Dong-Heon; Mondal, Biplab; Narducci Sarjeant, Amy A; del Rio, Diego; Pau, Monita Y M; Solomon, Edward I; Karlin, Kenneth D

2009-11-01

Reaction of nitrogen monoxide with a copper(I) complex possessing a tridentate alkylamine ligand gives a Cu(I)-(*NO) adduct, which when exposed to dioxygen generates a peroxynitrite (O=NOO(-))-Cu(II) species. This undergoes thermal transformation to produce a copper(II) nitrito (NO(2) (-)) complex and 0.5 mol equiv O(2). In the presence of a substituted phenol, the peroxynitrite complex effects oxidative coupling, whereas addition of chloride ion to dissociate the peroxynitrite moiety instead leads to phenol ortho nitration. Discussions include the structures (including electronic description) of the copper-nitrosyl and copper-peroxynitrite complexes and the formation of the latter, based on density functional theory calculations and accompanying spectroscopic data.

Electrochemical oxidation of quinoline aqueous solution on β-PbO2 anode and the evolution of phytotoxicity on duckweed.

PubMed

Ma, Xiangjuan; Bian, Lixia; Ding, Jingfeng; Wu, Yaping; Xia, Huilong; Li, Jionghui

2017-04-01

Electrochemical oxidation of quinoline on a β-PbO 2 electrode modified with fluoride resin and the comprehensive toxicity of intermediates formed during oxidation on duckweed were investigated in detail. The results showed that quinoline was initially hydroxylated at the C-2 and C-8 positions by hydroxyl radicals (·OH) electro-generated on a β-PbO 2 anode, yielding 2(1H)-quinolinone and 8-hydroxyquinoline, then undergoing ring cleavage to form pyridine, nicotinic acid, pyridine-2-carboxaldehyde and acetophenone, which were ultimately converted to biodegradable organic acids. NO 3 - was the final form of quinoline-N. The growth of duckweed exposed to the oxidized quinoline solution was gradually inhibited with the decrease in pH and the formation of intermediates. However, the growth inhibition of duckweed could be eliminated beyond 120 min of oxidation, indicating the comprehensive toxicity of the quinoline solution reduced when the amount of quinoline removed was above 80%. Additionally, the adjustment of the pH to 7.5 and the addition of nutrients to the treated quinoline solution before culturing duckweed could obviously alleviate the inhibition on duckweed. Thus, partial electrochemical degradation of quinoline offers a cost-effective and clean alternative for pretreatment of wastewater containing nitrogen-heterocyclic compounds before biological treatment. The duckweed test presents a simple method for assessing the comprehensive toxicity of intermediates.

Atmospheric Oxidation Mechanism of Furfural Initiated by Hydroxyl Radicals.

PubMed

Zhao, Xiaocan; Wang, Liming

2017-05-04

Furfural is emitted into the atmosphere because of its potential applications as an intermediate to alkane fuels from biomass, industrial usages, and biomass burning. The kinetic and mechanistic information on the furfural chemistry is necessary to assess the fate of furfural in the atmosphere and its impact on the air quality. Here we studied the atmospheric oxidation mechanisms of furfural initiated by the OH radicals using quantum chemistry and kinetic calculations. The reaction of OH and furfural was initiated mainly by OH additions to C 2 and C 5 positions, forming R2 and R5 adducts, which could undergo rapid ring-breakage to form R2B and R5B, respectively. Our calculations showed that these intermediate radicals reacted rather slowly with O 2 under the atmospheric conditions because the additions of O 2 to these radicals are only slightly exothermic and highly reversible. Alternatively, these radicals would react directly with O 3 , NO 2 , HO 2 /RO 2 , etc. Namely, the atmospheric oxidation of furfural would unlikely result in ozone formation. Under typical atmospheric conditions, the main products in OH-initiated furfural oxidation include 2-oxo-3-pentene-1,5-dialdehyde, 5-hydroxy-2(5H)-furanone, 4-oxo-2- butenoic acid, and 2,5-furandione. These compounds will likely stay in the gas phase and are subject to further photo-oxidation.

Glucose Oxidase Induces Cellular Senescence in Immortal Renal Cells through ILK by Downregulating Klotho Gene Expression

PubMed Central

Troyano-Suárez, Nuria; del Nogal-Avila, María; Mora, Inés; Sosa, Patricia; López-Ongil, Susana; Rodriguez-Puyol, Diego; Olmos, Gemma; Ruíz-Torres, María Piedad

2015-01-01

Cellular senescence can be prematurely induced by oxidative stress involved in aging. In this work, we were searching for novel intermediaries in oxidative stress-induced senescence, focusing our interest on integrin-linked kinase (ILK), a scaffold protein at cell-extracellular matrix (ECM) adhesion sites, and on the Klotho gene. Cultured renal cells were treated with glucose oxidase (GOx) for long time periods. GOx induced senescence, increasing senescence associated β-galactosidase activity and the expression of p16. In parallel, GOx increased ILK protein expression and activity. Ectopic overexpression of ILK in cells increased p16 expression, even in the absence of GOx, whereas downregulation of ILK inhibited the increase in p16 due to oxidative stress. Additionally, GOx reduced Klotho gene expression and cells overexpressing Klotho protein did not undergo senescence after GOx addition. We demonstrated a direct link between ILK and Klotho since silencing ILK expression in cells and mice increases Klotho expression and reduces p53 and p16 expression in renal cortex. In conclusion, oxidative stress induces cellular senescence in kidney cells by increasing ILK protein expression and activity, which in turn reduces Klotho expression. We hereby present ILK as a novel downregulator of Klotho gene expression. PMID:26583057

Theoretical insight into reaction mechanisms of 2,4-dinitroanisole with hydroxyl radicals for advanced oxidation processes.

PubMed

Zhou, Yang; Liu, Xiaoqiang; Jiang, Weidong; Shu, Yuanjie

2018-01-24

The detailed degradation mechanism of an insensitive explosive, 2,4-dinitroanisole (DNAN), in advanced oxidation processes (AOPs) was investigated computationally at the M06-2X/6-311 + G(d,p)/SMD level of theory. Results obtained show that the addition-elimination reaction is the dominant mechanism. The phenol products formed can continue to be oxidized to benzoquinone radicals that are often detected by experiments and may be the initial reactants of ring-opening reactions. The H-abstraction reaction is an unavoidable competing mechanism; the intermediate generated can also undergo the process of addition-elimination reaction. The nitro departure reaction involves not only hydroxyl radical (•OH), but also other active substances (such as •H). More importantly, we found that AOP technology can easily degrade DNAN, similar to TNT and DNT. Thus, this method is worth trying in experiments. The conclusions of this work provide theoretical support for such experimental research. Graphical abstract Possible pathways of degradation by •OH radicals in advanced oxidation processes (AOPs) of the typical insensitive explosive 2,4-dinitroanisole (DNAN) were investigated by density functional theory (DFT) methods. Based on the Gibbs free energy barriers and intermediates, the dominant reaction mechanism was determined. The conclusions will be helpful in utilizing AOP technology to remove DNAN pollution.

Glucose Oxidase Induces Cellular Senescence in Immortal Renal Cells through ILK by Downregulating Klotho Gene Expression.

PubMed

Troyano-Suárez, Nuria; del Nogal-Avila, María; Mora, Inés; Sosa, Patricia; López-Ongil, Susana; Rodriguez-Puyol, Diego; Olmos, Gemma; Ruíz-Torres, María Piedad

2015-01-01

Cellular senescence can be prematurely induced by oxidative stress involved in aging. In this work, we were searching for novel intermediaries in oxidative stress-induced senescence, focusing our interest on integrin-linked kinase (ILK), a scaffold protein at cell-extracellular matrix (ECM) adhesion sites, and on the Klotho gene. Cultured renal cells were treated with glucose oxidase (GOx) for long time periods. GOx induced senescence, increasing senescence associated β-galactosidase activity and the expression of p16. In parallel, GOx increased ILK protein expression and activity. Ectopic overexpression of ILK in cells increased p16 expression, even in the absence of GOx, whereas downregulation of ILK inhibited the increase in p16 due to oxidative stress. Additionally, GOx reduced Klotho gene expression and cells overexpressing Klotho protein did not undergo senescence after GOx addition. We demonstrated a direct link between ILK and Klotho since silencing ILK expression in cells and mice increases Klotho expression and reduces p53 and p16 expression in renal cortex. In conclusion, oxidative stress induces cellular senescence in kidney cells by increasing ILK protein expression and activity, which in turn reduces Klotho expression. We hereby present ILK as a novel downregulator of Klotho gene expression.

In situ XANES and EXAFS Analysis of Redox Active Fe Center Ionic Liquids

DOE PAGES

Apblett, Christopher A.; Stewart, David M.; Fryer, Robert T.; ...

2015-10-23

We apply in situ X-Ray Absorption Near Edge Spectroscopy (XANES) and Extended X-Ray Absorption Fine Structure (EXAFS) techniques to a metal center ionic liquid undergoing oxidation and reduction in a three electrode spectroscopic cell. Furthermore, the determination of the extent of reduction under negative bias on the working electrode and the extent of oxidation are determined after pulse voltammetry to quiescence. While the ionic liquid undergoes full oxidation, it undergoes only partial reduction, likely due to transport issues on the timescale of the experiment. Nearest neighbor Fe-O distances in the fully oxidized state match well to expected values for similarlymore » coordinated solids, but reduction does not result in an extension of the Fe-O bond length, as would be expected from comparisons to the solid phase. Instead, little change in bond length is observed. Finally, we suggest that this may be due to a more complex interaction between the monodentate ligands of the metal center anion and the surrounding charge cloud, rather than straightforward electrostatics between the metal center and the nearest neighbor grouping.« less

Positive effect of combined exercise training in a model of metabolic syndrome and menopause: autonomic, inflammatory, and oxidative stress evaluations.

PubMed

Conti, Filipe Fernandes; Brito, Janaina de Oliveira; Bernardes, Nathalia; Dias, Danielle da Silva; Malfitano, Christiane; Morris, Mariana; Llesuy, Susana Francisca; Irigoyen, Maria-Cláudia; De Angelis, Kátia

2015-12-15

It is now well established that after menopause cardiometabolic disorders become more common. Recently, resistance exercise has been recommended as a complement to aerobic (combined training, CT) for the treatment of cardiometabolic diseases. The aim of this study was to evaluate the effects of CT in hypertensive ovariectomized rats undergoing fructose overload in blood pressure variability (BPV), inflammation, and oxidative stress parameters. Female rats were divided into the following groups (n = 8/group): sedentary normotensive Wistar rats (C), and sedentary (FHO) or trained (FHOT) ovariectomized spontaneously hypertensive rats undergoing and fructose overload. CT was performed on a treadmill and ladder adapted to rats in alternate days (8 wk; 40-60% maximal capacity). Arterial pressure (AP) was directly measured. Oxidative stress and inflammation were measured on cardiac and renal tissues. The association of risk factors (hypertension + ovariectomy + fructose) promoted increase in insulin resistance, mean AP (FHO: 174 ± 4 vs. C: 108 ± 1 mmHg), heart rate (FHO: 403 ± 12 vs. C: 352 ± 11 beats/min), BPV, cardiac inflammation (tumor necrosis factor-α-FHO: 65.8 ± 9.9 vs. C: 23.3 ± 4.3 pg/mg protein), and oxidative stress cardiac and renal tissues. However, CT was able to reduce mean AP (FHOT: 158 ± 4 mmHg), heart rate (FHOT: 303 ± 5 beats/min), insulin resistance, and sympathetic modulation. Moreover, the trained rats presented increased nitric oxide bioavailability, reduced tumor necrosis factor-α (FHOT: 33.1 ± 4.9 pg/mg protein), increased IL-10 in cardiac tissue and reduced lipoperoxidation, and increased antioxidant defenses in cardiac and renal tissues. In conclusion, the association of risk factors promoted an additional impairment in metabolic, cardiovascular, autonomic, inflammatory, and oxidative stress parameters and combined exercise training was able to attenuate these dysfunctions. Copyright © 2015 the American Physiological Society.

Serum oxidizability and antioxidant status in patients undergoing in vitro fertilization.

PubMed

Aurrekoetxea, Igor; Ruiz-Sanz, José Ignacio; del Agua, Ainhoa Ruiz; Navarro, Rosaura; Hernández, M Luisa; Matorras, Roberto; Prieto, Begoña; Ruiz-Larrea, M Begoña

2010-09-01

To evaluate the serum oxidizability and antioxidant status in women undergoing an in vitro fertilization (IVF) cycle and to assess the possible relationship of the oxidizability indexes with the pregnancy rate. Prospective, longitudinal study. Public university and public university hospital. Systematically recruited cohort of 125 women undergoing either IVF or intracytoplasmic sperm injection (ICSI). Serum samples were collected before the beginning of the use of gonadotropins (basal) and the day of human chorionic gonadotropin (hCG) administration (final) during an IVF cycle. The Cu2+-induced serum oxidation in terms of the oxidation rate in the lag (Vlag) and propagation (Vmax) phases and the time at which the oxidation rate is maximal (tmax), and measurements of serum total antioxidant activity (TAA), tocopherol, hydrophilic antioxidants, malondialdehyde, and nitric oxide. Albumin, urate, bilirubin, alpha-tocopherol and gamma-tocopherol, TAA, and tmax statistically significantly decreased after the IVF cycle. Conception cycles were associated with a serum more prone to oxidation compared with nonconception cycles. In multivariate logistic regression analysis, the difference (final-basal) of the oxidation index Vlag (OR 1.394) and the body mass index (OR 0.785) were independent predictors of pregnancy. Treatment with IVF induces the production of reactive oxygen species (ROS), which is reflected in a serum less protected against oxidation. The results also suggest a role for ROS in the occurrence of conception in IVF. Copyright (c) 2010 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.

Study of the Synchrotron Photoionization Oxidation of 2-Methylfuran Initiated by O(3P) under Low-Temperature Conditions at 550 and 650 K.

PubMed

Fathi, Yasmin; Meloni, Giovanni

2017-09-21

The O-( 3 P)-initiated oxidation of 2-methylfuran (2-MF) was investigated using vacuum-ultraviolet synchrotron radiation from the Advanced Light Source at Lawrence Berkeley National Laboratory. Reaction species were studied by multiplexed photoionization mass spectrometry at 550 and 650 K. The oxygen addition pathway is favored in this reaction, forming four triplet diradicals that undergo intersystem crossing into singlet epoxide species that lead to the formation of products at m/z 30 (formaldehyde), 42 (propene), 54 (1-butyne, 1,3-butadiene, and 2-butyne), and 70 (2-butenal, methyl vinyl ketone, and 3-butenal). Mass-to-charge ratios, photoionization spectra, and adiabatic ionization energies for each primary reaction species were obtained and used to characterize their identities. In addition, by means of electronic structure calculations, potential energy surface scans of the different species produced throughout the oxidation were examined to further validate the primary chemistry occurring. Branching fractions for the formation of the primary products were calculated at the two temperatures and contribute 81.0 ± 21.4% at 550 K and 92.1 ± 25.5% at 650 K.

Cooperative Metal+Ligand Oxidative Addition and Sigma-Bond Metathesis: A DFT Study

DOE PAGES

Lopez, Kent G.; Cundari, Thomas R.; Gary, J. Brannon

2018-01-17

A computational study of the experimentally proposed mechanism of alkyne diboration by a PDICo complex yielded two fundamental catalytic steps that undergo remarkable electronic changes, PDI = bis(imino)-pyridine. The reactions are envisaged via DFT (density functional theory) and MCSCF (multi-configuration self-consistent field) simulations as (i) a cooperative metal+ligand oxidative addition, and (ii) a sigma-bond metathesis induced ligand-to-metal charge transfer. Analysis of the bonding of pertinent intermediates/TSs also yielded important insight that may be illuminating with regards to the larger field of green catalysis that seeks to ennoble base metals through synergy with potentially redox non-innocent (RNI) ligands. For the presentmore » case, massive changes in electronic structure do not incur massive energetic penalties. Finally, in conjunction with previous research, one may postulate that structural and energetic “fluidity” among several electronic states of RNI-M 3d along the reaction coordinate is an essential signature of redox cooperativity and thus ennoblement.« less

Cooperative Metal+Ligand Oxidative Addition and Sigma-Bond Metathesis: A DFT Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lopez, Kent G.; Cundari, Thomas R.; Gary, J. Brannon

A computational study of the experimentally proposed mechanism of alkyne diboration by a PDICo complex yielded two fundamental catalytic steps that undergo remarkable electronic changes, PDI = bis(imino)-pyridine. The reactions are envisaged via DFT (density functional theory) and MCSCF (multi-configuration self-consistent field) simulations as (i) a cooperative metal+ligand oxidative addition, and (ii) a sigma-bond metathesis induced ligand-to-metal charge transfer. Analysis of the bonding of pertinent intermediates/TSs also yielded important insight that may be illuminating with regards to the larger field of green catalysis that seeks to ennoble base metals through synergy with potentially redox non-innocent (RNI) ligands. For the presentmore » case, massive changes in electronic structure do not incur massive energetic penalties. Finally, in conjunction with previous research, one may postulate that structural and energetic “fluidity” among several electronic states of RNI-M 3d along the reaction coordinate is an essential signature of redox cooperativity and thus ennoblement.« less

Helicobacter Catalase Devoid of Catalytic Activity Protects the Bacterium against Oxidative Stress*♦

PubMed Central

Benoit, Stéphane L.; Maier, Robert J.

2016-01-01

Catalase, a conserved and abundant enzyme found in all domains of life, dissipates the oxidant hydrogen peroxide (H2O2). The gastric pathogen Helicobacter pylori undergoes host-mediated oxidant stress exposure, and its catalase contains oxidizable methionine (Met) residues. We hypothesized catalase may play a large stress-combating role independent of its classical catalytic one, namely quenching harmful oxidants through its recyclable Met residues, resulting in oxidant protection to the bacterium. Two Helicobacter mutant strains (katAH56A and katAY339A) containing catalase without enzyme activity but that retain all Met residues were created. These strains were much more resistant to oxidants than a catalase-deletion mutant strain. The quenching ability of the altered versions was shown, whereby oxidant-stressed (HOCl-exposed) Helicobacter retained viability even upon extracellular addition of the inactive versions of catalase, in contrast to cells receiving HOCl alone. The importance of the methionine-mediated quenching to the pathogen residing in the oxidant-rich gastric mucus was studied. In contrast to a catalase-null strain, both site-change mutants proficiently colonized the murine gastric mucosa, suggesting that the amino acid composition-dependent oxidant-quenching role of catalase is more important than the well described H2O2-dissipating catalytic role. Over 100 years after the discovery of catalase, these findings reveal a new non-enzymatic protective mechanism of action for the ubiquitous enzyme. PMID:27605666

Gas-Phase Oxidation of Neutral Basic Residues in Polypeptide Cations by Periodate

NASA Astrophysics Data System (ADS)

Pilo, Alice L.; Bu, Jiexun; McLuckey, Scott A.

2016-12-01

The gas-phase oxidation of doubly protonated peptides containing neutral basic residues to various products, including [M + H + O]+, [M - H]+, and [M - H - NH3]+, is demonstrated here via ion/ion reactions with periodate. It was previously demonstrated that periodate anions are capable of oxidizing disulfide bonds and methionine, tryptophan, and S-alkyl cysteine residues. However, in the absence of these easily oxidized sites, we show here that systems containing neutral basic residues can undergo oxidation. Furthermore, we show that these neutral basic residues primarily undergo different types of oxidation (e.g., hydrogen abstraction) reactions than those observed previously (i.e., oxygen transfer to yield the [M + H + O]+ species) upon gas-phase ion/ion reactions with periodate anions. This chemistry is illustrated with a variety of systems, including a series of model peptides, a cell-penetrating peptide containing a large number of unprotonated basic sites, and ubiquitin, a roughly 8.6 kDa protein.

Photo-induced living radical polymerization of acrylates utilizing a discrete copper(II)-formate complex.

PubMed

Anastasaki, Athina; Nikolaou, Vasiliki; Brandford-Adams, Francesca; Nurumbetov, Gabit; Zhang, Qiang; Clarkson, Guy J; Fox, David J; Wilson, Paul; Kempe, Kristian; Haddleton, David M

2015-04-04

A photo-polymerization protocol, utilizing a pre-formed and well-characterized Cu(II) formate complex, [Cu(Me6-Tren)(O2CH)](ClO4), mediated by UV light is described. In the absence of additional reducing agents and/or photosensitizers, ppm concentrations of the oxidatively stable [Cu(Me6-Tren)(O2CH)](ClO4), furnish near-quantitative conversions within 2 h, yielding poly(acrylates) with low dispersities (∼1.10) and exceptional end-group fidelity, capable of undergoing in situ chain extension and block copolymerization.

Nucleophilic addition of Grignard reagents to 3-acylindoles: stereoselective synthesis of highly substituted indoline scaffolds.

PubMed

Wang, Lu; Shao, Yushang; Liu, Yuanhong

2012-08-03

3-Acylindoles undergo nucleophilic-type reactions with Grignard reagents to efficiently afford either cis- or trans-substituted indolines, depending on the different quenching procedures. The enolate intermediate could be trapped by aryl acyl chlorides to provide indolines bearing a quaternary carbon center with high stereoselectivity. In contrast, the use of benzyl bromide as an electrophile results in the fragmentation of the indole ring. The indoline products could be easily transformed into indoles through oxidation with DDQ in a one-pot manner.

The effect of brain death in rat steatotic and non-steatotic liver transplantation with previous ischemic preconditioning.

PubMed

Jiménez-Castro, Mónica B; Meroño, Noelia; Mendes-Braz, Mariana; Gracia-Sancho, Jordi; Martínez-Carreres, Laia; Cornide-Petronio, Maria Eugenia; Casillas-Ramirez, Araní; Rodés, Juan; Peralta, Carmen

2015-01-01

Most liver grafts undergoing transplantation derive from brain dead donors, which may also show hepatic steatosis, being both characteristic risk factors in liver transplantation. Ischemic preconditioning shows benefits when applied in non-brain dead clinical situations like hepatectomies, whereas it has been less promising in the transplantation from brain dead patients. This study examined how brain death affects preconditioned steatotic and non-steatotic liver grafts undergoing transplantation. Steatotic and non-steatotic grafts from non-brain dead and brain dead-donors were cold stored for 6h and then transplanted. After 2, 4, and 16 h of reperfusion, hepatic damage was analysed. In addition, two therapeutic strategies, ischemic preconditioning and/or acetylcholine pre-treatment, and their underlying mechanisms were characterized. Preconditioning benefits in non-brain dead donors were associated with nitric oxide and acetylcholine generation. In brain dead donors, preconditioning generated nitric oxide but did not promote acetylcholine upregulation, and this resulted in inflammation and damage. Acetylcholine treatment in brain dead donors, through PKC, increased antioxidants and reduced lipid peroxidation, nitrotyrosines and neutrophil accumulation, altogether protecting against damage. The combination of acetylcholine and preconditioning conferred stronger protection against damage, oxidative stress and neutrophil accumulation than acetylcholine treatment alone. These superior beneficial effects were due to a selective preconditioning-mediated generation of nitric oxide and regulation of PPAR and TLR4 pathways, which were not observed when acetylcholine was administered alone. Our findings propose the combination of acetylcholine+preconditioning as a feasible and highly protective strategy to reduce the adverse effects of brain death and to ultimately improve liver graft quality. Copyright © 2014 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.

Catalysis by cytochrome P-450 of an oxidative reaction in xenobiotic aldehyde metabolism: deformylation with olefin formation.

PubMed Central

Roberts, E S; Vaz, A D; Coon, M J

1991-01-01

As we have briefly described elsewhere, cytochrome P-450 catalyzes the oxidative deformylation of cyclohexane carboxaldehyde to yield cyclohexene and formic acid in a reaction believed to involve a peroxyhemiacetal-like adduct formed between the substrate and molecular oxygen-derived hydrogen peroxide. This reaction is a useful model for the demethylation reactions catalyzed by the steroidogenic P-450s, aromatase, and lanosterol demethylase. In the present study, the cytochrome P-450-catalyzed formation of olefinic products from a series of xenobiotic aldehydes has been demonstrated. Isobutyraldehyde and trimethylacetaldehyde, but not propionaldehyde, are converted to the predicted olefinic products, suggesting a requirement for branching at the alpha carbon. In addition, the four C5 aldehydes of similar hydrophobicity were compared for their ability to undergo the reaction. The straight-chain valeraldehyde gave no olefinic products with five different rabbit liver microsomal P-450 isozymes. However, increasing activity was seen with the other isomers in the order of isovaleraldehyde, 2-methylbutyraldehyde, and trimethylacetaldehyde, with all of the P-450 cytochromes. The catalytic rate with trimethylacetaldehyde is highest with antibiotic-inducible P-450 form 3A6, followed by phenobarbital-inducible form 2B4 and ethanol-inducible form 2E1. Citronellal, a beta-branched aldehyde that is found in many essential oils and is widely used as an odorant and a flavorant, was found to undergo the oxidative deformylation reaction to yield 2,6-dimethyl-1,5-heptadiene, but only with P-450 2B4. The oxidative cleavage reaction with olefin formation appears to be widespread, as judged by the variety of aldehydes that serve as substrates and of P-450 cytochromes that serve as catalysts. PMID:1924356

Hot corrosion of the B2 nickel aluminides

NASA Technical Reports Server (NTRS)

Ellis, David L.

1993-01-01

The hot corrosion behavior of the B2 nickel aluminides was studied to determine the inherent hot corrosion resistance of the beta nickel aluminides and to develop a mechanism for the hot corrosion of the beta nickel aluminides. The effects of the prior processing of the material, small additions of zirconium, stoichiometry of the materials, and preoxidation of the samples were also examined. Additions of 2, 5, and 15 w/o chromium were used to determine the effect of chromium on the hot corrosion of the beta nickel aluminides and the minimum amount of chromium necessary for good hot corrosion resistance. The results indicate that the beta nickel aluminides have inferior inherent hot corrosion resistance despite their excellent oxidation resistance. Prior processing and zirconium additions had no discernible effect on the hot corrosion resistance of the alloys. Preoxidation extended the incubation period of the alloys only a few hours and was not considered to be an effective means of stopping hot corrosion. Stoichiometry was a major factor in determining the hot corrosion resistance of the alloys with the higher aluminum alloys having a definitely superior hot corrosion resistance. The addition of chromium to the alloys stopped the hot corrosion attack in the alloys tested. From a variety of experimental results, a complex hot corrosion mechanism was proposed. During the early stages of the hot corrosion of these alloys the corrosion is dominated by a local sulphidation/oxidation form of attack. During the intermediate stages of the hot corrosion, the aluminum depletion at the surface leads to a change in the oxidation mechanism from a protective external alumina layer to a mixed nickel-aluminum spinel and nickel oxide that can occur both externally and internally. The material undergoes extensive cracking during the later portions of the hot corrosion.

Oxidative stress and mitochondrial damage in coronary artery bypass graft surgery: effects of antioxidant treatments.

PubMed

Milei, J; Ferreira, R; Grana, D R; Boveris, A

2001-01-01

We examined antioxidant actions in 73 patients undergoing coronary artery surgery by assessing mitochondrial damage and oxidative stress in ventricular biopsies obtained at preischemia and postreperfusion. Those patients who received antioxidant therapy benefited by less oxidative stress and mitochondrial damage.

Novel Biomarker of Oxidative Stress Is Associated With Risk of Death in Patients With Coronary Artery Disease.

PubMed

Patel, Riyaz S; Ghasemzadeh, Nima; Eapen, Danny J; Sher, Salman; Arshad, Shawn; Ko, Yi-an; Veledar, Emir; Samady, Habib; Zafari, A Maziar; Sperling, Laurence; Vaccarino, Viola; Jones, Dean P; Quyyumi, Arshed A

2016-01-26

Free radical scavengers have failed to improve patient outcomes, promoting the concept that clinically important oxidative stress may be mediated by alternative mechanisms. We sought to examine the association of emerging aminothiol markers of nonfree radical mediated oxidative stress with clinical outcomes. Plasma levels of reduced (cysteine and glutathione) and oxidized (cystine and glutathione disulphide) aminothiols were quantified by high performance liquid chromatography in 1411 patients undergoing coronary angiography (mean age 63 years, male 66%). All patients were followed for a mean of 4.7 ± 2.1 years for the primary outcome of all-cause death (n=247). Levels of cystine (oxidized) and glutathione (reduced) were associated with risk of death (P<0.001 both) before and after adjustment for covariates. High cystine and low glutathione levels (>+1 SD and <-1 SD, respectively) were associated with higher mortality (adjusted hazard ratio [HR], 1.63; 95% confidence interval [CI], 1.19-2.21; HR, 2.19; 95% CI, 1.50-3.19; respectively) compared with those outside these thresholds. Furthermore, the ratio of cystine/glutathione was also significantly associated with mortality (adjusted HR, 1.92; 95% CI, 1.39-2.64) and was independent of and additive to high-sensitivity C-reactive protein level. Similar associations were found for other outcomes of cardiovascular death and combined death and myocardial infarction. A high burden of oxidative stress, quantified by the plasma aminothiols, cystine, glutathione, and their ratio, is associated with mortality in patients with coronary artery disease, a finding that is independent of and additive to the inflammatory burden. Importantly, these data support the emerging role of nonfree radical biology in driving clinically important oxidative stress. © 2015 The Authors.

Oxidation of monohydric phenol substrates by tyrosinase. An oximetric study.

PubMed

Naish-Byfield, S; Riley, P A

1992-11-15

The purity of commercially available mushroom tyrosinase was investigated by non-denaturing PAGE. Most of the protein in the preparation migrated as a single band under these conditions. This band contained both tyrosinase and dopa oxidase activity. No other activity of either classification was found in the preparation. Oxygen consumption by tyrosinase during oxidation of the monohydric phenol substrates tyrosine and 4-hydroxyanisole (4HA) was monitored by oximetry in order to determine the stoichiometry of the reactions. For complete oxidation, the molar ratio of oxygen: 4HA was 1:1. Under identical conditions, oxidation of tyrosine required 1.5 mol of oxygen/mol of tyrosine. The additional oxygen uptake during tyrosine oxidation is due to the internal cyclization of dopaquinone to form cyclodopa, which undergoes a redox reaction with dopaquinone to form dopachrome and dopa, which is then oxidized by the enzyme, leading to an additional 0.5 mol of oxygen/mol of original substrate. Oxygen consumption for complete oxidation of 200 nmol of 4HA was constant over a range of concentrations of tyrosinase of 33-330 units/ml of substrate. The maximum rate of reaction was directly proportional to the concentration of tyrosinase, whereas the length of the lag phase decreased non-linearly with increasing tyrosinase concentration. Activation of the enzyme by exposure to citrate was not seen, nor was the lag phase abolished by exposure of the enzyme to low pH. Michaelis-Menten analysis of tyrosinase in which the lag phase is abolished by pre-exposure of the enzyme to a low concentration of dithiothreitol gave Km values for tyrosine and 4HA of 153 and 20 microM respectively.

The effects of Losartan on oxidative stress and inflammation in non-diabetic patients undergoing chronic hemodialysis.

PubMed

Kayabasi, H; Yilmaz, Z; Sit, D; Kadiroglu, A K; Yilmaz, E

2013-01-01

We aimed to evaluate the effects of Losartan, an angiotensin receptor blocker, on serum inflammatory markers, plasma thiol groups, and oxidative stres indexes among patients undergoing hemodialysis (HD) treatment. Fiftytwo end-stage renal disease (ESRD) patients undergoing chronic HD programme for at least 12 months, and thirty age and gender matched healthy volunteers were enrolled into this prospective clinical trial. Plasma levels of thiol groups (SH), total antioxidant capacitiy (TAC), and total oxidant status (TOS) were studied. Oxidative stress index (OSI) was calculated by TOS/TAC. Firstly results of patients were compared with healthy subjects and then patients were treated by Losartan 50-100 mg and followed up for three months. Among patients, SH Groups, TAC, TOS, and OSI were statistically higher than controls. Also the inflammatory markers were significantly higher in patients than controls and albumin was lower among patients. At the end of the 3 months among all patients the mean value of TAC was increased to 1.7±0.4 micromol Trolox Eqv./L. from 1.4±0.2, and SH groups to 0.33±0.02 mmol/L from 0.22±0.01, (p < 0.001) while TOS decreased to 7.2±1.1 micromol H(2)O(2) Eqv./L from 9.5±4.5, and OSI decreased to 5.0±0.8 from 7.1±3.2 (p < 0.001). Losartan was effective in controlling blood pressure, and decreasing OSI, a marker of elevated oxidative stress, and increasing plasma levels of SH groups, an antioxidant, in ESRD patients undergoing hemodialysis. So, it may not be only a hypotensive drug, but also improves OS, particularly in patients with ESRD.

Detection of Cysteine Redox States in Mitochondrial Proteins in Intact Mammalian Cells.

PubMed

Habich, Markus; Riemer, Jan

2017-01-01

Import, folding, and activity regulation of mitochondrial proteins are important for mitochondrial function. Cysteine residues play crucial roles in these processes as their thiol groups can undergo (reversible) oxidation reactions. For example, during import of many intermembrane space (IMS) proteins, cysteine oxidation drives protein folding and translocation over the outer membrane. Mature mitochondrial proteins can undergo changes in the redox state of specific cysteine residues, for example, as part of their enzymatic reaction cycle or as adaptations to changes of the local redox environment which might influence their activity. Here we describe methods to study changes in cysteine residue redox states in intact cells. These approaches allow to monitor oxidation-driven protein import as well as changes of cysteine redox states in mature proteins during oxidative stress or during the reaction cycle of thiol-dependent enzymes like oxidoreductases.

The 5-lipoxygenase inhibitor tepoxalin induces oxidative damage and altered PTEN status prior to apoptosis in canine osteosarcoma cell lines.

PubMed

Loftus, J P; Cavatorta, D; Bushey, J J; Levine, C B; Sevier, C S; Wakshlag, J J

2016-06-01

The 5-lipoxygenase (5-LOX) inhibitor tepoxalin has been shown to slow canine osteosarcoma (OSA) tumour xenografts growth, yet the mechanisms are poorly elucidated. Further examination of tepoxalin in canine OSA cell lines shows that tepoxalin treated cells undergo apoptosis through caspase-3 activation and annexin staining. Interestingly, apoptosis is superseded by an increase in reactive oxygen species (ROS), as measured by activation of dihydrorhodamine 123 and mitosox. This increase in ROS appears to be related to the 5-LOX inhibitor regardless of cellular 5-LOX status, and was not observed after treatment with the tepoxalin metabolite RWJ20142. Additionally, 5-LOX inhibition by tepoxalin appears to increase phosphatase and tensin (PTEN) homolog activity by preventing its alkylation or oxidation. PTEN modification or inhibition allows phosphoinositide-3 (PI3) kinase activity thereby heightening activation of protein kinase B (AKT) phosphorylation. Our data suggest that off target oxidation and LOX inhibition play roles in the apoptotic response. © 2014 John Wiley & Sons Ltd.

Direct observation of spatially heterogeneous single-layer graphene oxide reduction kinetics.

PubMed

McDonald, Matthew P; Eltom, Ahmed; Vietmeyer, Felix; Thapa, Janak; Morozov, Yurii V; Sokolov, Denis A; Hodak, Jose H; Vinodgopal, Kizhanipuram; Kamat, Prashant V; Kuno, Masaru

2013-01-01

Graphene oxide (GO) is an important precursor in the production of chemically derived graphene. During reduction, GO's electrical conductivity and band gap change gradually. Doping and chemical functionalization are also possible, illustrating GO's immense potential in creating functional devices through control of its local hybridization. Here we show that laser-induced photolysis controllably reduces individual single-layer GO sheets. The reaction can be followed in real time through sizable decreases in GO's photoluminescence efficiency along with spectral blueshifts. As-produced reduced graphene oxide (rGO) sheets undergo additional photolysis, characterized by dramatic emission enhancements and spectral redshifts. Both GO's reduction and subsequent conversion to photobrightened rGO are captured through movies of their photoluminescence kinetics. Rate maps illustrate sizable spatial and temporal heterogeneities in sp(2) domain growth and reveal how reduction "flows" across GO and rGO sheets. The observed heterogeneous reduction kinetics provides mechanistic insight into GO's conversion to chemically derived graphene and highlights opportunities for overcoming its dynamic, chemical disorder.

Effect of ultraviolet radiation in the photo-oxidation of High Density Polyethylene and Biodegradable Polyethylene films

NASA Astrophysics Data System (ADS)

Martínez-Romo, A.; González Mota, R.; Bernal, J. J. Soto; Frausto Reyes, C.; Rosales Candelas, I.

2015-01-01

One of the most widely used plastics in the world is the High density polyethylene (HDPE), it is a stable material due to its carbon-carbon bonds, causing their slow degradation; which is why we are looking for alternative ways to accelerate the degradation process of this polymer. An alternative is the addition of oxidized groups in its molecular structure, which results in the development of polymers susceptible to biodegradation (PE-BIO). In this paper, HDPE and PE-BIO films were exposed to UV-B radiation (320-280 nm) at different exposure times, 0-60 days. The effects of UV radiation in samples of HDPE and PE-BIO were characterized using infrared spectroscopy with attenuated total reflectance (ATR). The results show that the exposed materials undergo changes in their molecular structure, due to the infrared bands formed which corresponds to the photo-oxidation of HDPE and PE films when submitted to UV-B radiation.

Zirconia ceramics for excess weapons plutonium waste

NASA Astrophysics Data System (ADS)

Gong, W. L.; Lutze, W.; Ewing, R. C.

2000-01-01

We synthesized a zirconia (ZrO 2)-based single-phase ceramic containing simulated excess weapons plutonium waste. ZrO 2 has large solubility for other metallic oxides. More than 20 binary systems A xO y-ZrO 2 have been reported in the literature, including PuO 2, rare-earth oxides, and oxides of metals contained in weapons plutonium wastes. We show that significant amounts of gadolinium (neutron absorber) and yttrium (additional stabilizer of the cubic modification) can be dissolved in ZrO 2, together with plutonium (simulated by Ce 4+, U 4+ or Th 4+) and impurities (e.g., Ca, Mg, Fe, Si). Sol-gel and powder methods were applied to make homogeneous, single-phase zirconia solid solutions. Pu waste impurities were completely dissolved in the solid solutions. In contrast to other phases, e.g., zirconolite and pyrochlore, zirconia is extremely radiation resistant and does not undergo amorphization. Baddeleyite (ZrO 2) is suggested as the natural analogue to study long-term radiation resistance and chemical durability of zirconia-based waste forms.

Influence of metabolic inhibitors on mitochondrial permeability transition and glutathione status.

PubMed

Reed, D J; Savage, M K

1995-05-24

Treatment of isolated mitochondria with Ca2+ and inorganic phosphate (Pi) induces an inner membrane permeability that appears to be mediated through a cyclosporin A (CsA)-inhibitable Ca(2+)-dependent pore. Isolated mitochondria during inner membrane permeability undergo rapid efflux of matrix solutes such as glutathione as GSH and Ca2+, loss of coupled functions, and large amplitude swelling. Permeability transition without large amplitude swelling, a parameter often used to assess inner membrane permeability, has been observed. The addition of either oligomycin, antimycin, or sulfide to incubation buffer containing Ca2+ and Pi abolished large amplitude swelling of mitochondria. The GSH status during a Ca(2+)- and Pi-dependent mechanism of mitochondrial GSH release in isolated mitochondria was influenced significantly by metabolic inhibitors of the respiratory chain but did not prevent inner membrane permeability as demonstrated by the release of mitochondrial GSH and Ca2+. The release of GSH was inhibited by the addition of CsA, a potent inhibitor of permeability transition. Under these conditions we did not find GSSG; however, rapid oxidation of pyridine nucleotides and depletion of ATP and ADP with conversion to AMP occurred. The addition of CsA, prevented the oxidation of pyridine nucleotides and depletion of ATP and ADP. Since NADH and NADPH were extensively oxidized, protection against oxidative stress is reflected in maintenance of GSH and not observable lipid peroxidation. Evidence from transmission electron microscopy analysis, combined with the GSH release data, indicate that permeability transition can be observed in the absence of large amplitude swelling.

Dioxygenase-like reactivity of an isolable superoxo-nickel(II) complex.

PubMed

Company, Anna; Yao, Shenglai; Ray, Kallol; Driess, Matthias

2010-08-16

Although O(2) activation by metals such as iron and copper has been a matter of intensive research in the last decades, this type of chemistry for nickel systems is still in its infancy. Moreover, studies regarding the oxidizing ability of the resulting "Ni(n)-O(2)" species towards exogenous substrates are scarce. In this work, we report on the reactivity of an isolable and thermally stable mononuclear superoxo-nickel compound [Ni(II)(beta-diketiminato)(O(2))] (1) towards different types of organic substrates. In addition, we have been able to prove that the beta-diketiminato ligand can undergo partial intramolecular oxidation due to close proximity between the isopropyl groups of the beta-diketiminato-aryl and the superoxo subunits. Compound 1 performs hydrogen-atom abstraction from O-H and N-H groups and most importantly it shows an unprecedented dioxygenase-like reactivity in the oxidation of 2,4,6-tri-tert-butylphenol. The latter reaction most likely occurs through the mediation of a putative [Ni(III)-oxo] intermediate, affording an unprecedented oxidation product of the phenol that incorporates two oxygen atoms from a single O(2) subunit. Results presented herein provide evidence of the striking oxidizing ability of dioxygen-nickel species and further support the viability to use such systems as oxidation catalysts analogous to its heavy metal congener, palladium.

Theoretical perspectives on the mechanism and kinetics of the OH radical-initiated gas-phase oxidation of PCB126 in the atmosphere.

PubMed

Dang, Juan; Shi, Xiangli; Zhang, Qingzhu; Wang, Wenxing

2015-06-01

Polychlorinated biphenyls (PCBs) primarily exist in the gas phase in air and may undergo atmospheric oxidation degradations, particularly the oxidation reaction initiated by OH radicals. In this work, the mechanism of the OH radical-initiated atmospheric oxidation of the most toxic PCB congener 3,3',4,4',5-pentachlorobiphenyl (PCB126) was investigated by using quantum chemistry methods. The rate constants of the crucial elementary reactions were estimated by the Rice-Ramsperger-Kassel-Marcus (RRKM) theory. The oxidation products of the reaction of PCB126 with OH radicals include 3,3',4,4',5-pentachlorobiphenyl-ols, chlorophenols, 2,3,4,7,8-pentachlorodibenzofuran, 2,3,4,6,7-pentachlorodibenzofuran, dialdehydes, 3,3',4,4',5-pentachloro-5'-nitro-biphenyl, and 4,5-dichloro-2-nitrophenol. Particularly, the formation of polychlorinated dibenzofurans (PCDFs) from the atmospheric oxidation of PCBs is revealed for the first time. The overall rate constant of the OH addition reaction is 2.52×10(-13)cm(3)molecule(-1)s(-1) at 298K and 1atm. The atmospheric lifetime of PCB126 determined by OH radicals is about 47.08days which indicates that PCB126 can be transported long distances from local to global scales. Copyright © 2015 Elsevier B.V. All rights reserved.

Chemical Interactions of Hydraulic Fracturing Biocides with Natural Pyrite

NASA Astrophysics Data System (ADS)

Consolazio, Nizette A.

In conjunction with horizontal drilling, hydraulic fracturing or fracking has enabled the recovery of natural gas from low permeable shale formations. In addition to water, these fracking fluids employ proppants and up to 38 different chemical additives to improve the efficiency of the process. One important class of additives used in hydraulic fracturing is biocides. When applied appropriately, they limit the growth of harmful microorganisms within the well, saving energy producers 4.5 billion dollars each year. However, biocides or their harmful daughter products may return to the surface in produced water, which must then be appropriately stored, treated and disposed of. Little is known about the effect of mineral-fluid interactions on the fate of the biocides employed in hydraulic fracturing. In this study, we employed laboratory experiments to determine changes in the persistence and products of these biocides under controlled environments. While many minerals are present in shale formations, pyrite, FeS2(s) is particularly interesting because of its prevalence and reactivity. The FeII groups on the face of pyrite may be oxidized to form FeIII phases. Both of these surfaces have been shown to be reactive with organic compounds. Chlorinated compounds undergo redox reactions at the pyrite-fluid interface, and sulfur-containing compounds undergo exceptionally strong sorption to both pristine and oxidized pyrite. This mineral may significantly influence the degradation of biocides in the Marcellus Shale. Thus, the overall goal of this study was to understand the effect of pyrite on biocide reactivity in hydraulic fracturing, focusing on the influence of pyrite on specific functional groups. The first specific objective was to demonstrate the effect of pyrite and pyrite reaction products on the degradation of the bromine-containing biocide, DBNPA. On the addition of pyrite to DBNPA, degradation rates of the doubly brominated compound were found to increase significantly. DBNPA is proposed to undergo redox reactions with the pyrite surface, accepting two-electrons from pyrite, and thus becoming reduced. The primary product is the monobrominated analogue of DBNPA, 2-monobromo-3-nitrilopropionamide (or MBNPA). The surface area-normalized first-order initial degradation rate constant was found to be 5.1 L.m-2day-1. It was also determined that the dissolution and oxidation products of pyrite, Fe II, S2O32- and SO4 2- are unlikely to contribute to the reduction of the biocide. Taken together, the results illustrate that a surface reaction with pyrite has the ability to reduce the persistence of DBNPA, and as a consequence change the distribution of its reaction products. The second objective was to quantify the influence of water chemistry and interactions with pyrite on the degradation of the sulfur-containing biocide. Dazomet readily hydrolyzes in water due to the nucleophilic attack of hydroxide (OH-) anions. Thus the half-life of dazomet during the shut-in phase of hydraulic fracturing will decrease with increasing pH: 8.5 hours at pH 4.1 to 3.4 hours at pH 8.2.Dazomet degradation was rapidly accelerated upon exposure to the oxidized pyrite surface, reacting five times faster than hydrolysis in the absence of pyrite at a similar pH. The products measured were identical to those identified on hydrolysis (methyl isothiocyanate and formaldehyde) and no dissolved iron was detected in solutions. This suggests that the dithiocarbamate group in dazomet was able to chemisorb onto the oxidized pyrite surface, shifting the electron density of the molecule which resulted in accelerated hydrolysis of the biocide. The third objective explored the reactivity of various biocide functional groups due to the addition of pyrite. Several elimination mechanisms were identified, and tied to the reactivity of the specific functional group involved. The addition of pyrite led to accelerated degradation of dibromodicyanobutane. This is because the bromine (-Br) group is easily reduced. For methylene bis(thiocyanate), hydrolysis was a noteworthy elimination mechanism since the thiocyanate (-SCN) functionality is a good leaving group. Benzisothiazolinone and methyl isothiazolinone were stable at low pH due to the stabilizing donor-acceptor interactions between the organic biocides' carbonyl (-C=O) groups and salts in the solution. This body of work has illustrated that pristine pyrite can undergo redox reactions with brominated biocides used in hydraulic fracturing, reducing their persistence and altering the product distribution. This will change the efficacy and the risks associated with the use of these biocides in shales containing pyrite, particularly at lower pH where organic compounds are more stable to hydrolysis. However, at higher pH hydrolysis becomes more important, and additional studies will need to be conducted to investigate the pyrite contribution under these conditions. Conversely, the FeIII surface groups on oxidized pyrite can catalyze the hydrolysis of dazomet and may do so for other labile, sulfur-containing biocides as well. Overall, this research has shown that the physicochemical properties (such as the acid dissociation constant and the standard reduction potential) that govern the environmental reactivity of a molecule can be used to anticipate its reactivity in hydraulic fracturing.

Probing the structural dependency of photoinduced properties of colloidal quantum dots using metal-oxide photo-active substrates.

PubMed

Patty, Kira; Sadeghi, Seyed M; Campbell, Quinn; Hamilton, Nathan; West, Robert G; Mao, Chuanbin

2014-09-21

We used photoactive substrates consisting of about 1 nm coating of a metal oxide on glass substrates to investigate the impact of the structures of colloidal quantum dots on their photophysical and photochemical properties. We showed during irradiation these substrates can interact uniquely with such quantum dots, inducing distinct forms of photo-induced processes when they have different cores, shells, or ligands. In particular, our results showed that for certain types of core-shell quantum dot structures an ultrathin layer of a metal oxide can reduce suppression of quantum efficiency of the quantum dots happening when they undergo extensive photo-oxidation. This suggests the possibility of shrinking the sizes of quantum dots without significant enhancement of their non-radiative decay rates. We show that such quantum dots are not influenced significantly by Coulomb blockade or photoionization, while those without a shell can undergo a large amount of photo-induced fluorescence enhancement via such blockade when they are in touch with the metal oxide.

Probing the structural dependency of photoinduced properties of colloidal quantum dots using metal-oxide photo-active substrates

PubMed Central

Patty, Kira; Sadeghi, Seyed M.; Campbell, Quinn; Hamilton, Nathan; West, Robert G.; Mao, Chuanbin

2014-01-01

We used photoactive substrates consisting of about 1 nm coating of a metal oxide on glass substrates to investigate the impact of the structures of colloidal quantum dots on their photophysical and photochemical properties. We showed during irradiation these substrates can interact uniquely with such quantum dots, inducing distinct forms of photo-induced processes when they have different cores, shells, or ligands. In particular, our results showed that for certain types of core-shell quantum dot structures an ultrathin layer of a metal oxide can reduce suppression of quantum efficiency of the quantum dots happening when they undergo extensive photo-oxidation. This suggests the possibility of shrinking the sizes of quantum dots without significant enhancement of their non-radiative decay rates. We show that such quantum dots are not influenced significantly by Coulomb blockade or photoionization, while those without a shell can undergo a large amount of photo-induced fluorescence enhancement via such blockade when they are in touch with the metal oxide. PMID:25316953

Helicobacter Catalase Devoid of Catalytic Activity Protects the Bacterium against Oxidative Stress.

PubMed

Benoit, Stéphane L; Maier, Robert J

2016-11-04

Catalase, a conserved and abundant enzyme found in all domains of life, dissipates the oxidant hydrogen peroxide (H 2 O 2 ). The gastric pathogen Helicobacter pylori undergoes host-mediated oxidant stress exposure, and its catalase contains oxidizable methionine (Met) residues. We hypothesized catalase may play a large stress-combating role independent of its classical catalytic one, namely quenching harmful oxidants through its recyclable Met residues, resulting in oxidant protection to the bacterium. Two Helicobacter mutant strains ( katA H56A and katA Y339A ) containing catalase without enzyme activity but that retain all Met residues were created. These strains were much more resistant to oxidants than a catalase-deletion mutant strain. The quenching ability of the altered versions was shown, whereby oxidant-stressed (HOCl-exposed) Helicobacter retained viability even upon extracellular addition of the inactive versions of catalase, in contrast to cells receiving HOCl alone. The importance of the methionine-mediated quenching to the pathogen residing in the oxidant-rich gastric mucus was studied. In contrast to a catalase-null strain, both site-change mutants proficiently colonized the murine gastric mucosa, suggesting that the amino acid composition-dependent oxidant-quenching role of catalase is more important than the well described H 2 O 2 -dissipating catalytic role. Over 100 years after the discovery of catalase, these findings reveal a new non-enzymatic protective mechanism of action for the ubiquitous enzyme. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Nanosecond-Pulsed DBD Plasma-Generated Reactive Oxygen Species Trigger Immunogenic Cell Death in A549 Lung Carcinoma Cells through Intracellular Oxidative Stress

PubMed Central

Lin, Abraham; Truong, Billy; Patel, Sohil; Kaushik, Nagendra; Choi, Eun Ha; Fridman, Gregory; Fridman, Alexander; Miller, Vandana

2017-01-01

A novel application for non-thermal plasma is the induction of immunogenic cancer cell death for cancer immunotherapy. Cells undergoing immunogenic death emit danger signals which facilitate anti-tumor immune responses. Although pathways leading to immunogenic cell death are not fully understood; oxidative stress is considered to be part of the underlying mechanism. Here; we studied the interaction between dielectric barrier discharge plasma and cancer cells for oxidative stress-mediated immunogenic cell death. We assessed changes to the intracellular oxidative environment after plasma treatment and correlated it to emission of two danger signals: surface-exposed calreticulin and secreted adenosine triphosphate. Plasma-generated reactive oxygen and charged species were recognized as the major effectors of immunogenic cell death. Chemical attenuators of intracellular reactive oxygen species successfully abrogated oxidative stress following plasma treatment and modulated the emission of surface-exposed calreticulin. Secreted danger signals from cells undergoing immunogenic death enhanced the anti-tumor activity of macrophages. This study demonstrated that plasma triggers immunogenic cell death through oxidative stress pathways and highlights its potential development for cancer immunotherapy. PMID:28467380

Photo-oxidation of 6-thioguanine by UVA: the formation of addition products with low molecular weight thiol compounds.

PubMed

Ren, Xiaolin; Xu, Yao-Zhong; Karran, Peter

2010-01-01

The thiopurine, 6-thioguanine (6-TG) is present in the DNA of patients treated with the immunosuppressant and anticancer drugs azathioprine or mercaptopurine. The skin of these patients is selectively sensitive to UVA radiation-which comprises >90% of the UV light in incident sunlight-and they suffer high rates of skin cancer. UVA irradiation of DNA 6-TG produces DNA lesions that may contribute to the development of cancer. Antioxidants can protect 6-TG against UVA but 6-TG oxidation products may undergo further reactions. We characterize some of these reactions and show that addition products are formed between UVA-irradiated 6-TG and N-acetylcysteine and other low molecular weight thiol compounds including β-mercaptoethanol, cysteine and the cysteine-containing tripeptide glutathione (GSH). GSH is also adducted to 6-TG-containing oligodeoxynucleotides in an oxygen- and UVA-dependent nucleophilic displacement reaction that involves an intermediate oxidized 6-TG, guanine sulfonate (G(SO3) ). These photochemical reactions of 6-TG, particularly the formation of a covalent oligodeoxynucleotide-GSH complex, suggest that crosslinking of proteins or low molecular weight thiol compounds to DNA may be a previously unrecognized hazard in sunlight-exposed cells of thiopurine-treated patients. © 2010 The Authors. Journal Compilation. The American Society of Photobiology.

The effects of nitrous oxide on vascular endothelial growth factor (VEGF) and its soluble receptor 1 (VEGFR1) in patient undergoing urological surgery

PubMed Central

Hakimoglu, Yasemin; Can, Murat; Hakimoglu, Sedat; Gorkem Mungan, Ayca; Acikgoz, Sereften; Cikcikoglu Yildirim, Nuran; Aydin Mungan, Necmettin; Ozkocak Turan, Isil

2014-01-01

Objective: Anesthesia and surgical intervention, leads to the development of systemic inflammatory response. The severity of the inflammatory response depends on the pharmacological effects of anesthetic agents and duration of anesthesia. Objective of the study was to investigate the effect of nitrous oxide on VEGF and VEGFR1 levels in patients undergoing surgery. Methods: Forty-four patients undergoing elective urological surgery were included in the study. Anesthesia maintenance was provided with 1-2 MAC sevoflurane, O2 50%, N2O 50% in 4L/m transporter gase for group 1 (n=22) and 1-2 MAC sevoflurane, O2 50%, air 50% in 4L/m transporter gase for group 2 (n=22) Venous blood samples for the measurement of VEGF and VEGFR1 were taken before the induction of anaesthesia, 60 minutes of anesthesia induction, at the end of anaesthesia and 24 hours after operation. In statistical analysis Bonferroni test and analysis of variance at the repeated measures were used Results: In the postoperative period serum VEGF levels had decreased significantly in both group whereas VEGFR1 did not show a significant change. Conclusions: Nitrous oxide showed significant effect on angiogenic parameters. Further detailed studies are required to evaluate the effect of nitrous oxide. PMID:24639829

The effects of nitrous oxide on vascular endothelial growth factor (VEGF) and its soluble receptor 1 (VEGFR1) in patient undergoing urological surgery.

PubMed

Hakimoglu, Yasemin; Can, Murat; Hakimoglu, Sedat; Gorkem Mungan, Ayca; Acikgoz, Sereften; Cikcikoglu Yildirim, Nuran; Aydin Mungan, Necmettin; Ozkocak Turan, Isil

2014-01-01

Anesthesia and surgical intervention, leads to the development of systemic inflammatory response. The severity of the inflammatory response depends on the pharmacological effects of anesthetic agents and duration of anesthesia. OBJECTIVE of the study was to investigate the effect of nitrous oxide on VEGF and VEGFR1 levels in patients undergoing surgery. Forty-four patients undergoing elective urological surgery were included in the study. Anesthesia maintenance was provided with 1-2 MAC sevoflurane, O2 50%, N2O 50% in 4L/m transporter gase for group 1 (n=22) and 1-2 MAC sevoflurane, O2 50%, air 50% in 4L/m transporter gase for group 2 (n=22) Venous blood samples for the measurement of VEGF and VEGFR1 were taken before the induction of anaesthesia, 60 minutes of anesthesia induction, at the end of anaesthesia and 24 hours after operation. In statistical analysis Bonferroni test and analysis of variance at the repeated measures were used Results: In the postoperative period serum VEGF levels had decreased significantly in both group whereas VEGFR1 did not show a significant change. Nitrous oxide showed significant effect on angiogenic parameters. Further detailed studies are required to evaluate the effect of nitrous oxide.

Blood cardioplegia with N-acetylcysteine may reduce coronary endothelial activation and myocardial oxidative stress.

PubMed

Rodrigues, Alfredo J; Evora, Paulo R B; Bassetto, Solange; Alves, Lafaiete; Scorzoni Filho, Adilson; Origuela, Eliana A; Vicente, Walter V A

2009-01-01

The aim of this prospective study was to compare the efficacy of intermittent antegrade blood cardioplegia with or without n-acetylcysteine (NAC) in reducing myocardial oxidative stress and coronary endothelial activation. Twenty patients undergoing elective isolated coronary artery bypass graft surgery were randomly assigned to receive intermittent antegrade blood cardioplegia (32 degrees C-34 degrees C) with (NAC group) or without (control group) 300 mg of NAC. For these 2 groups we compared clinical outcome, hemodynamic evolution, systemic plasmatic levels of troponin I, and plasma concentrations of malondialdehyde (MDA) and soluble vascular adhesion molecule 1 (sVCAM-1) from coronary sinus blood samples. Patient demographic characteristics and operative and postoperative data findings in both groups were similar. There was no hospital mortality. Comparing the plasma levels of MDA 10 min after the aortic cross-clamping and of sVCAM-1 30 min after the aortic cross-clamping period with the levels obtained before the aortic clamping period, we observed increases of both markers, but the increase was significant only in the control group (P= .039 and P= .064 for MDA; P= .004 and P= .064 for sVCAM-1). In both groups there was a significant increase of the systemic serum levels of troponin I compared with the levels observed before cardiopulmonary bypass (P< .001), but the differences between the groups were not significant (P= .570). Our investigation showed that NAC as an additive to blood cardioplegia in patients undergoing on-pump coronary artery bypass graft surgery may reduce oxidative stress and the resultant coronary endothelial activation.

MFN1 deacetylation activates adaptive mitochondrial fusion and protects metabolically challenged mitochondria.

PubMed

Lee, Joo-Yong; Kapur, Meghan; Li, Ming; Choi, Moon-Chang; Choi, Sujin; Kim, Hak-June; Kim, Inhye; Lee, Eunji; Taylor, J Paul; Yao, Tso-Pang

2014-11-15

Fasting and glucose shortage activate a metabolic switch that shifts more energy production to mitochondria. This metabolic adaptation ensures energy supply, but also elevates the risk of mitochondrial oxidative damage. Here, we present evidence that metabolically challenged mitochondria undergo active fusion to suppress oxidative stress. In response to glucose starvation, mitofusin 1 (MFN1) becomes associated with the protein deacetylase HDAC6. This interaction leads to MFN1 deacetylation and activation, promoting mitochondrial fusion. Deficiency in HDAC6 or MFN1 prevents mitochondrial fusion induced by glucose deprivation. Unexpectedly, failure to undergo fusion does not acutely affect mitochondrial adaptive energy production; instead, it causes excessive production of mitochondrial reactive oxygen species and oxidative damage, a defect suppressed by an acetylation-resistant MFN1 mutant. In mice subjected to fasting, skeletal muscle mitochondria undergo dramatic fusion. Remarkably, fasting-induced mitochondrial fusion is abrogated in HDAC6-knockout mice, resulting in extensive mitochondrial degeneration. These findings show that adaptive mitochondrial fusion protects metabolically challenged mitochondria. © 2014. Published by The Company of Biologists Ltd.

Hydrolysis of the quinone methide of butylated hydroxytoluene in aqueous solutions.

PubMed

Willcockson, Maren Gulsrud; Toteva, Maria M; Stella, Valentino J

2013-10-01

Butylated hydroxytoluene or BHT is an antioxidant commonly used in pharmaceutical formulations. BHT upon oxidation forms a quinone methide (QM). QM is a highly reactive electrophilic species that can undergo nucleophilic addition. Here, the kinetic reactivity of QM with water at various apparent pH values in a 50% (v/v) water-acetonitrile solution at constant ionic strength of I = 0.5 (NaCl)4 , was studied. The hydrolysis of QM in the presence of added acid, base, sodium chloride, and phosphate buffer resulted in the formation of only one product--the corresponding 3,5-di-tert-butyl-4-hydroxybenzyl alcohol (BA). The rate of BA formation was catalyzed by the addition of acid and base, but not chloride and phosphate species. Nucleophilic excipients, used in the pharmaceutical formulation, or nucleophilic groups on active pharmaceutical ingredient molecule may form adducts with QM, the immediate oxidative product of BHT degradation, thus having implications for drug product impurity profiles. Because of these considerations, BHT should be used with caution in formulations containing drugs or excipients capable of acting as nucleophiles. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association.

Unexpected Catalytic Reactions of Silyl-protected Enoldiazoacetates With Nitrile Oxides That Form 5- Arylaminofuran-2(3H)-one-4-carboxylates

PubMed Central

Xu, Xinfang; Shabashov, Dmitry; Zavalij, Peter Y.; Doyle, Michael P.

2012-01-01

Silyl-protected enoldiazoacetates undergo dirhodium(II) catalyzed reactions with nitrile oxides to form acid-labile ketenimines via dipolar cycloaddition of nitrile oxides to a donor/acceptor cyclopropene and Lossen rearrangement of the dipolar adduct; acid catalysis converts the ketenimine to the furan product. PMID:22272728

The role of phospholipid oxidation products in inflammatory and autoimmune diseases: evidence from animal models and in humans.

PubMed

Leitinger, Norbert

2008-01-01

Since the discovery of oxidized phospholipids (OxPL) and their implication as modulators of inflammation in cardiovascular disease, roles for these lipid oxidation products have been suggested in many other disease settings. Lipid oxidation products accumulate in inflamed and oxidatively damaged tissue, where they are derived from oxidative modification of lipoproteins, but also from membranes of cells undergoing apoptosis. Thus, increased oxidative stress as well as decreased clearance of apoptotic cells has been implied to contribute to accumulation of OxPL in chronically inflamed tissues.A central role for OxPL in disease states associated with dyslipedemia, including atherosclerosis, diabetes and its complications, metabolic syndrome, and renal insufficiency, as well as general prothrombotic states, has been proposed. In addition, in organs which are constantly exposed to oxidative stress, including lung, skin, and eyes, increased levels of OxPL are suggested to contribute to inflammatory conditions. Moreover, accumulation of OxPL causes general immunmodulation and may lead to autoimmune diseases. Evidence is accumulating that OxPL play a role in lupus erythematosus, antiphospholipid syndrome, and rheumatoid arthritis. Last but not least, a role for OxPL in neurological disorders including multiple sclerosis (MS), Alzheimer's and Parkinson's disease has been suggested.This chapter will summarize recent findings obtained in animal models and from studies in humans that indicate that formation of OxPL represents a general mechanism that may play a major role in chronic inflammatory and autoimmune diseases.

EncM, a versatile enterocin biosynthetic enzyme involved in Favorskii oxidative rearrangement, aldol condensation, and heterocycle-forming reactions

PubMed Central

Xiang, Longkuan; Kalaitzis, John A.; Moore, Bradley S.

2004-01-01

The bacteriostatic natural product enterocin from the marine microbe “Streptomyces maritimus” has an unprecedented carbon skeleton that is derived from an aromatic polyketide biosynthetic pathway. Its caged tricyclic, nonaromatic core is derived from a linear poly-β-ketide precursor that formally undergoes a Favorskii-like oxidative rearrangement. In vivo characterization of the gene encM through mutagenesis and heterologous biosynthesis demonstrated that its protein product not only is solely responsible for the oxidative C—C rearrangement, but also facilitates two aldol condensations plus two heterocycle forming reactions. In total, at least five chiral centers and four rings are generated by this multifaceted flavoprotein. Heterologous expression of the enterocin biosynthesis genes encABCDLMN in Streptomyces lividans resulted in the formation of the rearranged metabolite desmethyl-5-deoxyenterocin and the shunt products wailupemycins D-G. Addition of the methyltransferase gene encK, which was previously proposed through mutagenesis to additionally assist EncM in the Favorskii rearrangement, shifted the production to the O-methyl derivative 5-deoxyenterocin. The O-methyltransferase EncK seems to be specific for the pyrone ring of enterocin, because bicyclic polyketides bearing pyrone rings are not methylated in vivo. Expression of encM with different combinations of homologous actinorhodin biosynthesis genes did not result in the production of oxidatively rearranged enterocin-actinorhodin hybrid compounds as anticipated, suggesting that wild-type EncM may be specific for its endogenous type II polyketide synthase or for benzoyl-primed polyketide precursors. PMID:15505225

Mass spectral analysis of N-oxides of Chemical Weapons Convention related aminoethanols under electrospray ionization conditions.

PubMed

Sridhar, L; Karthikraj, R; Murty, M R V S; Raju, N Prasada; Vairamani, M; Prabhakar, S

2011-02-28

N,N'-Dialkylaminoethanols are the hydrolyzed products or precursors of chemical warfare agents such as V-agents and nitrogen mustards, and they are prone to undergo oxidation in environmental matrices or during decontamination processes. Consequently, screening of the oxidized products of aminoethanols in aqueous samples is an important task in the verification of chemical weapons convention-related chemicals. Here we report the successful characterization of the N-oxides of N,N'-dialkylaminoethanols, alkyl diethanolamines, and triethanolamine using positive ion electrospray ionization mass spectrometry. The collision-induced dissociation (CID) spectra of the [M+H](+) and [M+Na](+) ions show diagnostic product ions that enable the unambiguous identification of the studied N-oxides, including those of isomeric compounds. The proposed fragmentation pathways are supported by high-resolution mass spectrometry data and product/precursor ion spectra. The CID spectra of [M+H](+) ions included [MH-CH(4)O(2)](+) as the key product ion, in addition to a distinctive alkene loss that allowed us to recognize the alkyl group attached to the nitrogen. The [M+Na](+) ions show characteristic product ions due to the loss of groups (R) attached to nitrogen either as a radical (R) or as a molecule [R+H or (R-H)] after hydrogen migration. Copyright © 2011 John Wiley & Sons, Ltd.

Wild Raspberry Subjected to Simulated Gastrointestinal Digestion Improves the Protective Capacity against Ethyl Carbamate-Induced Oxidative Damage in Caco-2 Cells

PubMed Central

Chen, Wei; Xu, Yang; Zhang, Lingxia; Li, Ya; Zheng, Xiaodong

2016-01-01

Ethyl carbamate (EC), a probable human carcinogen, occurs widely in many fermented foods. Previous studies indicated that EC-induced cytotoxicity was associated with oxidative stress. Wild raspberries are rich in polyphenolic compounds, which possess potent antioxidant activity. This study was conducted to investigate the protective effect of wild raspberry extracts produced before (RE) and after in vitro simulated gastrointestinal digestion (RD) on EC-induced oxidative damage in Caco-2 cells. Our primary data showed that ethyl carbamate could result in cytotoxicity and genotoxicity in Caco-2 cells and raspberry extract after digestion (RD) may be more effective than that before digestion (RE) in attenuating toxicity caused by ethyl carbamate. Further investigation by fluorescence microscope revealed that RD may significantly ameliorate EC-induced oxidative damage by scavenging the overproduction of intracellular reactive oxygen species (ROS), maintaining mitochondrial function and preventing glutathione (GSH) depletion. In addition, HPLC-ESI-MS results showed that the contents of identified polyphenolic compounds (esculin, kaempferol O-hexoside, and pelargonidin O-hexoside) were remarkably increased after digestion, which might be related to the better protective effect of RD. Overall, our results demonstrated that raspberry extract undergoing simulated gastrointestinal digestion may improve the protective effect against EC-induced oxidative damage in Caco-2 cells. PMID:26788245

An update on oxidative stress-mediated organ pathophysiology.

PubMed

Rashid, Kahkashan; Sinha, Krishnendu; Sil, Parames C

2013-12-01

Exposure to environmental pollutants and drugs can result in pathophysiological situations in the body. Research in this area is essential as the knowledge on cellular survival and death would help in designing effective therapeutic strategies that are needed for the maintenance of the normal physiological functions of the body. In this regard, naturally occurring bio-molecules can be considered as potential therapeutic targets as they are normally available in commonly consumed foodstuffs and are thought to have minimum side effects. This review article describes the detailed mechanisms of oxidative stress-mediated organ pathophysiology and the ultimate fate of the cells either to survive or to undergo necrotic or apoptotic death. The mechanisms underlying the beneficial role of a number of naturally occurring bioactive molecules in oxidative stress-mediated organ pathophysiology have also been included in the review. The review provides useful information about the recent progress in understanding the mechanism(s) of various types of organ pathophysiology, the complex cross-talk between these pathways, as well as their modulation in stressed conditions. Additionally, it suggests possible therapeutic applications of a number of naturally occurring bioactive molecules in conditions involving oxidative stress. Copyright © 2013 Elsevier Ltd. All rights reserved.

Immune-relevant thrombocytes of common carp undergo parasite-induced nitric oxide-mediated apoptosis.

PubMed

Fink, Inge R; Ribeiro, Carla M S; Forlenza, Maria; Taverne-Thiele, Anja; Rombout, Jan H W M; Savelkoul, Huub F J; Wiegertjes, Geert F

2015-06-01

Common carp thrombocytes account for 30-40% of peripheral blood leukocytes and are abundant in the healthy animals' spleen, the thrombopoietic organ. We show that, ex vivo, thrombocytes from healthy carp express a large number of immune-relevant genes, among which several cytokines and Toll-like receptors, clearly pointing at immune functions of carp thrombocytes. Few studies have described the role of fish thrombocytes during infection. Carp are natural host to two different but related protozoan parasites, Trypanoplasma borreli and Trypanosoma carassii, which reside in the blood and tissue fluids. We used the two parasites to undertake controlled studies on the role of fish thrombocytes during these infections. In vivo, but only during infection with T. borreli, thrombocytes were massively depleted from the blood and spleen leading to severe thrombocytopenia. Ex vivo, addition of nitric oxide induced a clear and rapid apoptosis of thrombocytes from healthy carp, supporting a role for nitric oxide-mediated control of immune-relevant thrombocytes during infection with T. borreli. The potential advantage for parasites to selectively deplete the host of thrombocytes via nitric oxide-induced apoptosis is discussed. Copyright © 2015 Elsevier Ltd. All rights reserved.

A Hexanuclear Iron(II) Layer with Two Square-Planar FeO4 Units Spanned by Tetrasiloxide Ligands: Mimicking of Minerals and Catalysts.

PubMed

Manicke, N; Hoof, S; Keck, M; Braun-Cula, B; Feist, M; Limberg, C

2017-07-17

A hexanuclear iron(II) siloxide complex has been prepared by reacting an incompletely condensed silsesquioxane first with NaOMe and then with Fe(OTf) 2 . In the process of product formation, the siloxane framework undergoes a transformation and it was shown that this happens already upon addition of base: Treatment of the ligand precursor with NaOMe leads to a completely condensed silsesquioxane cage with 12 Si atoms that is composed of 2 equiv of the tetrasiloxide ligands found in the product complex. Its iron centers form a two-dimensional array reminiscent of the situations found in minerals and two-dimensional oxide films caused by segregation of FeO x and silica. As the hexairon(II) assembly contains two high-spin square-planar FeO 4 units-suggested to represent the active sites in Fe-zeolites, which react with N 2 O to generate strongly oxidizing sites-it was treated with Me 3 NO. This led to the oxidation of two of the iron centers to the oxidation state +III and elimination of one iron ion, so that a pentanuclear, mixed valent iron siloxide was formed. All complexes were fully characterized.

Reversible Condensation of DNA using a Redox-Active Surfactant

PubMed Central

Hays, Melissa E.; Jewell, Christopher M.; Lynn, David M.; Abbott, Nicholas L.

2008-01-01

We report characterization of aqueous solutions of dilute Lambda phage DNA containing the redox-active surfactant (11-ferrocenylundecyl)trimethylammonium bromide (FTMA) as a function of the oxidation state of the FTMA. FTMA undergoes a reversible one-electron oxidation from a reduced state that forms micelles in aqueous solution to an oxidized state (containing the ferrocenium cation) that does not selfassociate in solution. This investigation sought to test the hypothesis that FTMA can be used to achieve reversible control over the conformation of DNA-surfactant complexes in solution. Whereas DNA adopts extended coil conformations in aqueous solutions, our measurements revealed that addition of reduced FTMA (2–5μM) to aqueous solutions of DNA (5 μM in nucleotide units) resulted in coexistence of extended coils and compact globules in solution. At higher concentrations of reduced FTMA (up to 30μM), the DNA was present as compact globules only. In contrast, oxidized FTMA had no measurable effect on the conformation of DNA, allowing DNA to maintain an extended coil state up to a concentration of 75μM oxidized FTMA. We further demonstrate that it is possible to chemically or electrochemically transform the oxidation state of FTMA in preformed complexes of FTMA and DNA, thus achieving in situ control over the conformations of the DNA in solution. These results provide guidance for the design of surfactant systems that permit active control of DNA-surfactant interactions. PMID:17428073

Switching Oxide Traps

NASA Technical Reports Server (NTRS)

Oldham, Timothy R.

2003-01-01

We consider radiation-induced charge trapping in SiO2 dielectric layers, primarily from the point of view of CMOS devices. However, SiO2 insulators are used in many other ways, and the same defects occur in other contexts. The key studies, which determined the nature of the oxide charge traps, were done primarily on gate oxides in CMOS devices, because that was the main radiation problem in CMOS at one time. There are two major reviews of radiation-induced oxide charge trapping already in the literature, which discuss the subject in far greater detail than is possible here. The first of these was by McLean et al. in 1989, and the second, ten years later, was intended as an update, because of additional, new work that had been reported. Basically, the picture that has emerged is that ionizing radiation creates electron-hole pairs in the oxide, and the electrons have much higher mobility than the holes. Therefore, the electrons are swept out of the oxide very rapidly by any field that is present, leaving behind any holes that escape the initial recombination process. These holes then undergo a polaron hopping transport toward the Si/SiO2 interface (under positive bias). Near the interface, some fraction of them fall into deep, relatively stable, long-lived hole traps. The nature and annealing behavior of these hole traps is the main focus of this paper.

Kinetic modeling of the oxidative degradation of additive free PE in bleach disinfected water

NASA Astrophysics Data System (ADS)

Mikdam, Aïcha; Colin, Xavier; Billon, Noëlle; Minard, Gaëlle

2016-05-01

The chemical interactions between PE and bleach were studied at 60°C in immersion in bleach solutions kept at a free chlorine concentration of 100 ppm and a pH of 5 or 7.2. It was found that the polymer undergoes a severe oxidation from the earliest weeks of exposure, in a superficial layer whose thickness (of about 50-70 µm) is almost independent of the pH value, although the superficial oxidation rate is faster in acidic than in neutral medium. Oxidation leads to the formation and accumulation of a large variety of carbonyl products (mostly ketones and carboxylic acids) and, after a few weeks, to a decrease in the average molar mass due to the large predominance of chain scissions over crosslinking. A scenario was elaborated for explaining such unexpected results. According to this scenario, the non-ionic molecules (Cl2 and ClOH) formed from the disinfectant in the water phase, would migrate deeply into PE and dissociate into highly reactive radicals (Cl• and HO•) in order to initiate a radical chain oxidation. A kinetic model was derived from this scenario for predicting the general trends of the oxidation kinetics and its dependence on environmental factors such as temperature, free chlorine concentration and pH. The validity of this model was successfully checked by comparing the numerical simulations with experimental data.

Nickel-catalyzed asymmetric α-arylation and heteroarylation of ketones with chloroarenes: effect of halide on selectivity, oxidation state, and room-temperature reactions.

PubMed

Ge, Shaozhong; Hartwig, John F

2011-10-19

We report the α-arylation of ketones with a range of aryl chlorides with enantioselectivities from 90 to 99% ee catalyzed by the combination of Ni(COD)(2) and (R)-BINAP and the coupling of ketones with a range of heteroaryl chlorides with enantioselectivities up to 99% ee catalyzed by Ni(COD)(2) and (R)-DIFLUORPHOS. The analogous reactions of bromoarenes occur with much lower enantioselectivities. Mechanistic studies showed that the difference in the rates of decomposition of the arylnickel(II) halide intermediates to {[(R)-BINAP]NiX}(2) likely accounts for the difference in the enantioselectivities of the reactions of bromoarenes and chloroarenes. This catalyst decomposition can be overcome by conducting the reactions with [(R)-BINAP]Ni(η(2)-NC-Ph) (4), which undergoes oxidative addition to haloarenes at room temperature.

Low and High Molecular Mass Dithienopyrrole-Naphthalene Bisimide Donor-Acceptor Compounds: Synthesis, Electrochemical and Spectroelectrochemical Behaviour.

PubMed

Rybakiewicz, Renata; Glowacki, Eric D; Skorka, Lukasz; Pluczyk, Sandra; Zassowski, Pawel; Apaydin, Dogukan Hazar; Lapkowski, Mieczyslaw; Zagorska, Malgorzata; Pron, Adam

2017-02-24

Two low molecular weight electroactive donor-acceptor-donor (DAD)-type molecules are reported, namely naphthalene bisimide (NBI) symmetrically core-functionalized with dithienopyrrole (NBI-(DTP) 2 ) and an asymmetric core-functionalized naphthalene bisimide with dithienopyrrole (DTP) substituent on one side and 2-ethylhexylamine on the other side (NBI-DTP-NHEtHex). Both compounds are characterized by low optical bandgaps (1.52 and 1.65 eV, respectively). NBI-(DTP) 2 undergoes oxidative electropolymerization giving the electroactive polymer of ambipolar character. Its two-step reversible reduction and oxidation is corroborated by complementary EPR and UV/Vis-NIR spectroelectrochemical investigations. The polymer turned out to be electrochemically active not only in aprotic solvents but also in aqueous electrolytes, showing a distinct photocathodic current attributed to proton reduction. Additionally, poly(NBI-(DTP) 2 ) was successfully tested as a photodiode material. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

OVERVIEW OF LEACHING CHEMISTRY AND TESTING RESEARCH IN ORD/EPA

EPA Science Inventory

Various anthropogenic activities generate hazardous solid wastes that are affluent in heavy metals and organics, which can cause significant damage to the environment and human health. Heavy metals can exist in multiple oxidation states, and can undergo oxidation or reduction whe...

Extracellular entrapment and degradation of single-walled carbon nanotubes

NASA Astrophysics Data System (ADS)

Farrera, Consol; Bhattacharya, Kunal; Lazzaretto, Beatrice; Andón, Fernando T.; Hultenby, Kjell; Kotchey, Gregg P.; Star, Alexander; Fadeel, Bengt

2014-05-01

Neutrophils extrude neutrophil extracellular traps (NETs) consisting of a network of chromatin decorated with antimicrobial proteins to enable non-phagocytic killing of microorganisms. Here, utilizing a model of ex vivo activated human neutrophils, we present evidence of entrapment and degradation of carboxylated single-walled carbon nanotubes (SWCNTs) in NETs. The degradation of SWCNTs was catalyzed by myeloperoxidase (MPO) present in purified NETs and the reaction was facilitated by the addition of H2O2 and NaBr. These results show that SWCNTs can undergo acellular, MPO-mediated biodegradation and imply that the immune system may deploy similar strategies to rid the body of offending microorganisms and engineered nanomaterials.Neutrophils extrude neutrophil extracellular traps (NETs) consisting of a network of chromatin decorated with antimicrobial proteins to enable non-phagocytic killing of microorganisms. Here, utilizing a model of ex vivo activated human neutrophils, we present evidence of entrapment and degradation of carboxylated single-walled carbon nanotubes (SWCNTs) in NETs. The degradation of SWCNTs was catalyzed by myeloperoxidase (MPO) present in purified NETs and the reaction was facilitated by the addition of H2O2 and NaBr. These results show that SWCNTs can undergo acellular, MPO-mediated biodegradation and imply that the immune system may deploy similar strategies to rid the body of offending microorganisms and engineered nanomaterials. Electronic supplementary information (ESI) available: Suppl. Fig. 1 - length distribution of SWCNTs; suppl. Fig. 2 - characterization of pristine vs. oxidized SWCNTs; suppl. Fig. 3 - endotoxin evaluation; suppl. Fig. 4 - NET characterization; suppl. Fig. 5 - UV-Vis/NIR analysis of biodegradation of oxidized SWCNTs; suppl. Fig. 6 - cytotoxicity of partially degraded SWCNTs. See DOI: 10.1039/c3nr06047k

Probing the structural dependency of photoinduced properties of colloidal quantum dots using metal-oxide photo-active substrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patty, Kira; Campbell, Quinn; Hamilton, Nathan

We used photoactive substrates consisting of about 1 nm coating of a metal oxide on glass substrates to investigate the impact of the structures of colloidal quantum dots on their photophysical and photochemical properties. We showed during irradiation these substrates can interact uniquely with such quantum dots, inducing distinct forms of photo-induced processes when they have different cores, shells, or ligands. In particular, our results showed that for certain types of core-shell quantum dot structures an ultrathin layer of a metal oxide can reduce suppression of quantum efficiency of the quantum dots happening when they undergo extensive photo-oxidation. This suggestsmore » the possibility of shrinking the sizes of quantum dots without significant enhancement of their non-radiative decay rates. We show that such quantum dots are not influenced significantly by Coulomb blockade or photoionization, while those without a shell can undergo a large amount of photo-induced fluorescence enhancement via such blockade when they are in touch with the metal oxide.« less

Unexpected catalytic reactions of silyl-protected enol diazoacetates with nitrile oxides that form 5-arylaminofuran-2(3H)-one-4-carboxylates.

PubMed

Xu, Xinfang; Shabashov, Dmitry; Zavalij, Peter Y; Doyle, Michael P

2012-02-03

Silyl-protected enol diazoacetates undergo dirhodium(II)-catalyzed reactions with nitrile oxides to form acid-labile ketenimines via dipolar cycloaddition of nitrile oxides to a donor/acceptor cyclopropene and Lossen rearrangement of the dipolar adduct; acid catalysis converts the ketenimine to the furan product. © 2012 American Chemical Society

Systemic inflammation and oxidative stress post-lung resection: Effect of pretreatment with N-acetylcysteine.

PubMed

Bastin, Anthony J; Davies, Nathan; Lim, Eric; Quinlan, Greg J; Griffiths, Mark J

2016-01-01

N-acetylcysteine has been used to treat a variety of lung diseases, where is it thought to have an antioxidant effect. In a randomized placebo-controlled double-blind study, the effect of N-acetylcysteine on systemic inflammation and oxidative damage was examined in patients undergoing lung resection, a human model of acute lung injury. Eligible adults were randomized to receive preoperative infusion of N-acetylcysteine (240 mg/kg over 12 h) or placebo. Plasma thiols, interleukin-6, 8-isoprostane, ischaemia-modified albumin, red blood cell glutathione and exhaled breath condensate pH were measured pre- and post-operatively as markers of local and systemic inflammation and oxidative stress. Patients undergoing lung resection and one-lung ventilation exhibited significant postoperative inflammation and oxidative damage. Postoperative plasma thiol concentration was significantly higher in the N-acetylcysteine-treated group. However, there was no significant difference in any of the measured biomarkers of inflammation or oxidative damage, or in clinical outcomes, between N-acetylcysteine and placebo groups. Preoperative administration of N-acetylcysteine did not attenuate postoperative systemic or pulmonary inflammation or oxidative damage after lung resection. NCT00655928 at ClinicalTrials.gov. © 2015 Asian Pacific Society of Respirology.

The Effect of Silane on the Microstructure, Corrosion, and Abrasion Resistances of the Anodic Films on Ti Alloy

NASA Astrophysics Data System (ADS)

Wang, Jinwei; Chen, Jiali

2016-04-01

Anodic oxide films on Ti-6Al-4V alloy are prepared using sodium hydroxide as the base electrolyte containing aminopropyl trimethoxysilane (APS) as an additive. Some APS undergo hydrolysis, adsorption, and chemical reaction with the TiO x to form Ti-O-Si bond as confirmed by ATR-FTIR and XPS spectra, and in turn their surface appearance and roughness are greatly changed with the addition of APS as observed by their SEM images. These amino anodic films possess much higher corrosive resistances since the formation of Ti-O-Si complex enhances the compactness of the anodic films and the existence of aminopropyl groups inside the pores provides additional blocking effects. Besides, their improvement in anti-abrasive capability is attributed to the toughening effect of the chemically bonded silanes and the lubrication functions from both the chemically bonded and physically absorbed silanes between the touched interfaces.

Vitamin E nanoemulsion activity on stored red blood cells.

PubMed

Silva, C A L; Azevedo Filho, C A; Pereira, G; Silva, D C N; Castro, M C A B; Almeida, A F; Lucena, S C A; Santos, B S; Barjas-Castro, M L; Fontes, A

2017-06-01

Stored red blood cells (RBCs) undergo numerous changes that have been termed RBC storage lesion, which can be related to oxidative damage. Vitamin E is an important antioxidant, acting on cell lipids. Thus, this study aimed to investigate vitamin E activity on stored RBCs. We prepared a vitamin E nanoemulsion that was added to RBC units and stored at 4 °C. Controls, without vitamin E, were kept under the same conditions. Reactive oxygen species (ROS) production was monitored for up to 35 days of storage. RBC elasticity was also evaluated using an optical tweezer system. Vitamin E-treated samples presented a significant decrease in ROS production. Additionally, the elastic constant for vitamin E-treated RBCs did not differ from the control. Vitamin E decreased the amount of ROS in stored RBCs. Because vitamin E acts on lipid oxidation, results suggest that protein oxidation should also be considered a key factor for erythrocyte elastic properties. Thus, further studies combining vitamin E with protein antioxidants deserve attention, aiming to better preserve overall stored RBC properties. © 2017 British Blood Transfusion Society.

Aqueous vanadium ion dynamics relevant to bioinorganic chemistry: A review.

PubMed

Kustin, Kenneth

2015-06-01

Aqueous solutions of the four highest vanadium oxidation states exhibit four diverse colors, which only hint at the diverse reactions that these ions can undergo. Cationic vanadium ions form complexes with ligands; anionic vanadium ions form complexes with ligands and self-react to form isopolyanions. All vanadium species undergo oxidation-reduction reactions. With a few exceptions, elucidation of the dynamics of these reactions awaited the development of fast reaction techniques before the kinetics of elementary ligation, condensation, reduction, and oxidation of the aqueous vanadium ions could be investigated. As the biological roles played by endogenous and therapeutic vanadium expand, it is appropriate to bring the results of the diverse kinetics studies under one umbrella. To achieve this goal this review presents a systematic examination of elementary aqueous vanadium ion dynamics. Copyright © 2014 Elsevier Inc. All rights reserved.

Protection from Oxidative Stress in Immunocytes of the Colonial Ascidian Botryllus schlosseri: Transcript Characterization and Expression Studies.

PubMed

Franchi, Nicola; Ballin, Francesca; Ballarin, Loriano

2017-02-01

Botryllus schlosseri is a cosmopolitan colonial ascidian that undergoes cyclical generation changes, or take-overs, during which adult zooids are resorbed and replaced by their buds. At take-over, adult tissues undergo diffuse apoptosis and effete cells are massively ingested by circulating phagocytes, with a consequent increase in oxygen consumption and in production of reactive oxygen species (ROS). The latter are responsible for the death of phagocytes involved in the clearance of apoptotic cells and corpses by phagocytosis-induced apoptosis. However, the majority of phagocytes and hemocytes do not die, even if they experience oxidative stress. This fact suggests the presence of detoxification mechanisms assuring their protection. To test this assumption, we searched for transcripts of genes involved in detoxification in the transcriptome of B. schlosseri. We identified and characterized transcripts for Cu/Zn superoxide dismutase (SOD), γ-glutamyl-cysteine ligase modulatory subunit (GCLM), glutathione synthase (GS), and two glutathione peroxidases (i.e., GPx3 and GPx5), all involved in protection from ROS. We also carried out a phylogenetic analysis of the putative amino acid sequences, confirming their similarity to their vertebrate counterparts, and studied the location of their mRNAs by in situ hybridization on hemocyte monolayers. We also analyzed gene transcription during the colonial blastogenetic cycle, which is the interval of time between one take-over and the next, by qRT-PCR. In addition, we investigated the effects of cadmium (Cd), an inducer of oxidative stress, on gene transcription. Our results indicated that i) antioxidant gene expression is modulated in the course of the blastogenetic cycle and upon exposure to Cd, and ii) hemocytes synthesize both enzymatic and nonenzymatic antioxidants, in line with the idea that they represent a major detoxification system for ascidians.

Aerobic exercise training promotes additional cardiac benefits better than resistance exercise training in postmenopausal rats with diabetes.

PubMed

Quinteiro, Hugo; Buzin, Morgana; Conti, Filipe Fernandes; Dias, Danielle da Silva; Figueroa, Diego; Llesuy, Susana; Irigoyen, Maria-Cláudia; Sanches, Iris Callado; De Angelis, Kátia

2015-05-01

The aim of this study was to evaluate the effects of aerobic exercise training or resistance exercise training on cardiac morphometric, functional, and oxidative stress parameters in rats with ovarian hormone deprivation and diabetes. Female Wistar rats (200-220 g) were divided into a sham-operated group (euglycemic sham-operated sedentary [ES]; n = 8) and three ovariectomized (bilateral removal of ovaries) and diabetic (streptozotocin 50 mg/kg IV) groups as follows: diabetic ovariectomized sedentary (DOS; n = 8), diabetic ovariectomized undergoing aerobic exercise training (DOTA; n = 8), and diabetic ovariectomized undergoing resistance exercise training (DOTR; n = 8). After 8 weeks of resistance (ladder) or aerobic (treadmill) exercise training, left ventricle function and morphometry were evaluated by echocardiography, whereas oxidative stress was evaluated at the left ventricle. The DOS group presented with increased left ventricle cavity in diastole and relative wall thickness (RWT), and these changes were attenuated in both DOTA and DOTR groups. Systolic and diastolic function was impaired in the DOS group compared with the ES group, and only the DOTA group was able to reverse this dysfunction. Lipoperoxidation and glutathione redox balance were improved in both trained groups compared with the DOS group. Glutathione peroxidase and superoxide dismutase were higher in the DOTA group than in the other studied groups. Correlations were observed between lipoperoxidation and left ventricle cavity in diastole (r = 0.55), between redox balance and RWT (r = 0.62), and between lipoperoxidation and RWT (r = -0.60). Aerobic exercise training and resistance exercise training promote attenuation of cardiac morphometric dysfunction associated with a reduction in oxidative stress in an experimental model of diabetes and menopause. However, only dynamic aerobic exercise training is able to attenuate systolic and diastolic dysfunction under this condition.

Nickel-catalyzed synthesis of diarylamines via oxidatively induced C-N bond formation at room temperature.

PubMed

Ilies, Laurean; Matsubara, Tatsuaki; Nakamura, Eiichi

2012-11-02

A nickel-catalyzed oxidative coupling of zinc amides with organomagnesium compounds selectively produces diarylamines under mild reaction conditions, with tolerance for chloride, bromide, hydroxyl, ester, and ketone groups. A diamine is bis-monoarylated. A bromoaniline undergoes N-arylation followed by Kumada-Tamao-Corriu coupling in one pot. The reaction may proceed via oxidatively induced reductive elimination of a nickel species.

Nondestructive evaluation of nuclear-grade graphite

NASA Astrophysics Data System (ADS)

Kunerth, D. C.; McJunkin, T. R.

2012-05-01

The material of choice for the core of the high-temperature gas-cooled reactors being developed by the U.S. Department of Energy's Next Generation Nuclear Plant Program is graphite. Graphite is a composite material whose properties are highly dependent on the base material and manufacturing methods. In addition to the material variations intrinsic to the manufacturing process, graphite will also undergo changes in material properties resulting from radiation damage and possible oxidation within the reactor. Idaho National Laboratory is presently evaluating the viability of conventional nondestructive evaluation techniques to characterize the material variations inherent to manufacturing and in-service degradation. Approaches of interest include x-ray radiography, eddy currents, and ultrasonics.

Bispectral analysis during deep sedation of pediatric oral surgery patients.

PubMed

Overly, Frank L; Wright, Robert O; Connor, Francis A; Jay, Gregory D; Linakis, James G

2005-02-01

Bispectral (BIS) analysis uses electroencephalogram information from a forehead electrode to calculate an index score (0 to 100; 0 = coma; 90 to 100 = awake). This index score correlates with the level of alertness in anesthetized patients. Classically, sedation has been monitored with clinical sedation scales such as the Observers Assessment of Alertness Sedation Scale (OAA/S), Modified Ramsey Scale, or a Visual Analog Scale (VAS). Our objective was to determine the correlation between clinical sedation scales and BIS index in pediatric patients undergoing sedation in an outpatient oral surgery setting. Prospective cohort study of patients aged 2 to 17 years undergoing sedation in an outpatient oral surgery office. Sedation was performed in the customary manner with the addition of BIS monitoring. Three clinical sedation scores (OAA/S: 5 to 1; 5 = awake, 1 = unresponsive; Modified Ramsey: 1 to 6; 1-2 = awake, 6 = unresponsive; VAS: 0 to 10; 0 = awake, 10 = unresponsive) were assigned every 5 minutes by an investigator blinded to the BIS index. Data were analyzed using a repeated measures linear regression model. Sixteen subjects undergoing oral surgery, ages 4.5 years to 17 years, were enrolled, mean age 12.6 years +/- 4.3 years (standard deviation). Patients received methohexital in addition to 1 or more of the following: nitrous oxide, fentanyl, or midazolam. The results of the longitudinal regression analysis showed a highly significant association between the sedation scales and the BIS index. The BIS monitor may be a useful adjunct in monitoring pediatric patients receiving sedation in the outpatient setting.

Substrate oxidation capacity in rodent skeletal muscle: effects of exposure to zero gravity

NASA Technical Reports Server (NTRS)

Baldwin, K. M.; Herrick, R. E.; McCue, S. A.

1993-01-01

A study was conducted, as part of the integrated National Aeronautics and Space Administration Space Life Sciences 1 mission flown in June of 1991, to ascertain the effects of 9 days of exposure to zero gravity on the capacity of rodent skeletal muscle fiber types to oxidize either [14C]pyruvate or [14C]palmitate under state 3 metabolic conditions, i.e., nonlimiting amounts of substrate and cofactors. In addition, activity levels of marker enzymes of the tricarboxylic acid cycle, malate shuttle, and beta-oxidation were measured. Results showed that significant differences in muscle weight occurred in both the predominantly slow vastus intermedius and predominantly fast vastus lateralis of flight vs. control groups (P < 0.05). Total protein content of the muscle samples was similar between groups. Both pyruvate oxidation capacity and the marker oxidative enzymes were not altered in the flight relative to control animals. However, the capacity to oxidize long-chain fatty acids was significantly reduced by 37% in both the high- and low-oxidative regions of the vastus muscle (P < 0.05). Although these findings of a selective reduction in fatty acid oxidation capacity in response to spaceflight are surprising, they are consistent with previous findings showing 1) an increased capacity to take up glucose and upregulate glucose transporter proteins and 2) a marked accumulation of triglycerides in the skeletal muscles of rats subjected to states of unloading. Thus, skeletal muscle of animals exposed to non-weight-bearing environments undergo subcellular transformations that may preferentially bias energy utilization to carbohydrates.

SPM oxidation and parallel writing on zirconium nitride thin films

NASA Astrophysics Data System (ADS)

Farkas, N.; Comer, J. R.; Zhang, G.; Evans, E. A.; Ramsier, R. D.; Dagata, J. A.

2005-07-01

Systematic investigation of the SPM oxidation process of sputter-deposited ZrN thin films is reported. During the intrinsic part of the oxidation, the density of the oxide increases until the total oxide thickness is approximately twice the feature height. Further oxide growth is sustainable as the system undergoes plastic flow followed by delamination from the ZrN-silicon interface keeping the oxide density constant. ZrN exhibits superdiffusive oxidation kinetics in these single tip SPM studies. We extend this work to the fabrication of parallel oxide patterns 70 nm in height covering areas in the square centimeter range. This simple, quick, and well-controlled parallel nanolithographic technique has great potential for biomedical template fabrication.

A COMPREHENSIVE APPROACH TO IDENTIFY AND QUANTIFY FUNDAMENTAL PARAMETERS THAT INFLUENCE METAL LEACHING CHEMISTRY IN LANDFILLS SYSTEMS (PRESENTATION)

EPA Science Inventory

Various anthropogenic activities generate hazardous solid wastes that are affluent in heavy metals, which can cause significant damage to the environment and human health. Heavy metals/metalloids can exist in multiple oxidation states, and can undergo oxidation or reduction when ...

A COMPREHENSIVE APPROACH TO IDENTIFY AND QUANTIFY FUNDAMENTAL PARAMETERS THAT INFLUENCE METAL LEACHING CHEMISTRY IN LANDFILLS SYSTEMS (ABSTRACT)

EPA Science Inventory

Various anthropogenic activities generate hazardous solid wastes that are affluent in heavy metals, which can cause significant damage to the environment and human health. Heavy metals/metalloids can exist in multiple oxidation states, and can undergo oxidation or reduction when ...

Development of Self-Healing Zirconium-Silicide Coatings for Improved Performance Zirconium-Alloy Fuel Cladding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sridharan, Kumar; Mariani, Robert; Bai, Xianming

Zirconium-alloy fuel claddings have been used successfully in Light Water Reactors (LWR) for over four decades. However, under high temperature accident conditions, zirconium-alloys fuel claddings exhibit profuse exothermic oxidation accompanied by release of hydrogen gas due to the reaction with water/steam. Additionally, the ZrO 2 layer can undergo monoclinic to tetragonal to cubic phase transformations at high temperatures which can induce stresses and cracking. These events were unfortunately borne out in the Fukushima-Daiichi accident in in Japan in 2011. In reaction to such accident, protective oxidation-resistant coatings for zirconium-alloy fuel claddings has been extensively investigated to enhance safety margins inmore » accidents as well as fuel performance under normal operation conditions. Such surface modification could also beneficially affect fuel rod heat transfer characteristics. Zirconium-silicide, a candidate coating material, is particularly attractive because zirconium-silicide coating is expected to bond strongly to zirconium-alloy substrate. Intermetallic compound phases of zirconium-silicide have high melting points and oxidation of zirconium silicide produces highly corrosion resistant glassy zircon (ZrSiO 4) and silica (SiO 2) which possessing self-healing qualities. Given the long-term goal of developing such coatings for use with nuclear reactor fuel cladding, this work describes results of oxidation and corrosion behavior of bulk zirconium-silicide and fabrication of zirconium-silicide coatings on zirconium-alloy test flats, tube configurations, and SiC test flats. In addition, boiling heat transfer of these modified surfaces (including ZrSi 2 coating) during clad quenching experiments is discussed in detail.« less

Free radicals in the regulation of damage and cell death - basic mechanisms and prevention.

PubMed

Silva, J P; Coutinho, O P

2010-06-01

Reactive oxygen (ROS) and nitrogen (RNS) species are known to accumulate intracellularly due to both exogenous and/or endogenous factors. In normal physiological conditions, these reactive species are maintained in an equilibrium state by the cells' antioxidant defence systems. In addition, they are recognised to play important roles in several physiological functions. However, when an imbalance in the equilibrium between oxidants and antioxidants occurs in favour of the former, we come to a situation defined as oxidative stress. ROS/RNS can cause damage to all biomolecules (namely proteins, lipids and DNA) and ultimately participate in the regulation of mechanisms leading to cell death, being implicated in the etiology of several pathologies (like neurodegenerative and cardiovascular diseases). To cope with oxidative stress, cells possess effective enzymatic (e.g. superoxide dismutase, catalase, glutathione peroxidase) and non-enzymatic (e.g. glutathione, thioredoxin, coenzyme Q) antioxidant systems. In addition, several compounds present in plants and vegetables (e.g. vitamins C and E, polyphenols) have been described to react with free radicals. However, some drawbacks associated to these natural compounds are in part responsible for the undergoing development of novel synthetic compounds capable of acting as antioxidants and protect cells against oxidative stress-induced cell death. Here, we review the basic mechanisms of ROS/RNS formation, as well as their interaction with biomolecules and regulation of cell death, in order to identify possible drug targets. We also report the importance of natural antioxidant systems and the ongoing research leading to the development of more powerful and effective antioxidant drugs.

Formation of reactive nitrogen oxides from urban grime photochemistry

NASA Astrophysics Data System (ADS)

Baergen, Alyson M.; Donaldson, D. James

2016-05-01

Impervious surfaces are ubiquitous in urban environments and constitute a substrate onto which atmospheric constituents can deposit and undergo photochemical and oxidative processing, giving rise to "urban grime" films. HNO3 and N2O5 are important sinks for NOx in the lower atmosphere and may be deposited onto these films, forming nitrate through surface hydrolysis. Although such deposition has been considered as a net loss of NOx from the atmosphere, there is increasing evidence that surface-associated nitrate undergoes further reaction. Here, we examine the gas phase products of the photochemistry of real, field-collected urban grime using incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS). Gas phase nitrogen oxides are emitted upon illumination of grime samples and their production increases with ambient relative humidity (RH) up to 35 % after which the production becomes independent of RH. These results are discussed in the context of water uptake onto and evaporation from grime films.

Zinc Supplementation Alters Plasma Aluminum and Selenium Status of Patients Undergoing Dialysis: A Pilot Study

PubMed Central

Guo, Chih-Hung; Chen, Pei-Chung; Hsu, Guoo-Shyng W.; Wang, Chia-Liang

2013-01-01

End stage renal disease patients undergoing long-term dialysis are at risk for abnormal concentrations of certain essential and non-essential trace metals and high oxidative stress. We evaluated the effects of zinc (Zn) supplementation on plasma aluminum (Al) and selenium (Se) concentrations and oxidative stress in chronic dialysis patients. Zn-deficient patients receiving continuous ambulatory peritoneal dialysis or hemodialysis were divided into two groups according to plasma Al concentrations (HA group, Al > 50 μg/L; and MA group, Al > 30 to ≤ 50 μg/L). All patients received daily oral Zn supplements for two months. Age- and gender-matched healthy individuals did not receive Zn supplement. Clinical variables were assessed before, at one month, and after the supplementation period. Compared with healthy subjects, patients had significantly lower baseline plasma Se concentrations and higher oxidative stress status. After two-month Zn treatment, these patients had higher plasma Zn and Se concentrations, reduced plasma Al concentrations and oxidative stress. Furthermore, increased plasma Zn concentrations were related to the concentrations of Al, Se, oxidative product malondialdehyde (MDA), and antioxidant enzyme superoxide dismutase activities. In conclusion, Zn supplementation ameliorates abnormally high plasma Al concentrations and oxidative stress and improves Se status in long-term dialysis patients. PMID:23609777

In vitro and in vivo acute response towards injectable thermosensitive chitosan/TEMPO-oxidized cellulose nanofiber hydrogel.

PubMed

Nguyen, Trang Ho Minh; Abueva, Celine; Ho, Hai Van; Lee, Sun-Young; Lee, Byong-Taek

2018-01-15

TEMPO-oxidized cellulose nanofiber (TOCNF) is a natural material with many promising properties, including biocompatibility and degradability. In this study, we integrated TOCNF at different concentrations (0.2, 0.4, 0.6, 0.8% w/v) with chitosan (CS) and created a thermosensitive injectable hydrogel intended for biomedical applications. These hydrogels can undergo sol-gel transition at body temperature through interactions between chitosan and β-glycerophosphate. The addition of TOCNF resulted in faster gelation time and increased porosity. These hydrogels with TOCNF showed improved biocompatibility both in vitro and in vivo compared to CS hydrogel. Both MC3T3-E1 pre-osteoblast cells and L929 fibroblast cells showed biocompatibility towards CS/TOCNF 0.4. After 7days of implantation, initial inflammatory response to CS/TOCNF 0.4 was found. Such response was significantly subsided within 14days. Cell infiltration within the hydrogel was also prominent, showing anti-inflammatory or wound healing (M2) macrophage at 14days after implantation. These results showed that the addition of TOCNF could significantly improve the biocompatibility of CS hydrogel as a biomaterial for biomedical application. Copyright © 2017 Elsevier Ltd. All rights reserved.

Metallophosphite-Catalyzed Asymmetric Acylation of α,β -Unsaturated Amides

PubMed Central

Nahm, Mary R.; Potnick, Justin R.; White, Peter S.; Johnson, Jeffrey S.

2007-01-01

The l-menthone-derived TADDOL phosphite 6b catalyzes highly enantioselective conjugate additions of acyl silanes to α,β-unsaturated amides. p-Methoxybenzoyl cyclohexyldimethylsilane adds to a variety of N,N-dimethyl acrylamide derivatives in the presence of the lithium salt of 6b. In many instances the α-silyl-γ-ketoamide product undergoes facile enantioenrichment (to 97–99% ee) upon recrystallization. Desilylation with HF·pyr affords the formal Stetter addition products. Baeyer–Villiger oxidation of the desilylated γ-ketoamides affords useful ester products. An X-ray diffraction study of 6b reveals that the isopropyl group of the menthone ketal influences the position of the syn-pseudoaxial phenyl group in the TADDOL structure. Through a crossover experiment, the silicon migration step in the reaction mechanism is shown to be strictly intramolecular. PMID:16492064

Electrochemical stability and corrosion resistance of Ti-Mo alloys for biomedical applications.

PubMed

Oliveira, N T C; Guastaldi, A C

2009-01-01

Electrochemical behavior of pure Ti and Ti-Mo alloys (6-20wt.% Mo) was investigated as a function of immersion time in electrolyte simulating physiological media. Open-circuit potential values indicated that all Ti-Mo alloys studied and pure Ti undergo spontaneous passivation due to spontaneously formed oxide film passivating the metallic surface, in the chloride-containing solution. It also indicated that the addition of Mo to pure Ti up to 15wt.% seems to improve the protection characteristics of its spontaneous oxides. Electrochemical impedance spectroscopy (EIS) studies showed high impedance values for all samples, increasing with immersion time, indicating an improvement in corrosion resistance of the spontaneous oxide film. The fit obtained suggests a single passive film present on the metals' surface, improving their resistance with immersion time, presenting the highest values to Ti-15Mo alloy. Potentiodynamic polarization showed a typical valve-metal behavior, with anodic formation of barrier-type oxide films, without pitting corrosion, even in chloride-containing solution. In all cases, the passive current values were quite small, and decrease after 360h of immersion. All these electrochemical results suggest that the Ti-15Mo alloy is a promising material for orthopedic devices, since electrochemical stability is directly associated with biocompatibility and is a necessary condition for applying a material as biomaterial.

The importance of intraoperative selenium blood levels on organ dysfunction in patients undergoing off-pump cardiac surgery: a randomised controlled trial.

PubMed

Stevanovic, Ana; Coburn, Mark; Menon, Ares; Rossaint, Rolf; Heyland, Daren; Schälte, Gereon; Werker, Thilo; Wonisch, Willibald; Kiehntopf, Michael; Goetzenich, Andreas; Rex, Steffen; Stoppe, Christian

2014-01-01

Cardiac surgery is accompanied by an increase of oxidative stress, a significantly reduced antioxidant (AOX) capacity, postoperative inflammation, all of which may promote the development of organ dysfunction and an increase in mortality. Selenium is an essential co-factor of various antioxidant enzymes. We hypothesized a less pronounced decrease of circulating selenium levels in patients undergoing off-pump coronary artery bypass (OPCAB) surgery due to less intraoperative oxidative stress. In this prospective randomised, interventional trial, 40 patients scheduled for elective coronary artery bypass grafting were randomly assigned to undergo either on-pump or OPCAB-surgery, if both techniques were feasible for the single patient. Clinical data, myocardial damage assessed by myocard specific creatine kinase isoenzyme (CK-MB), circulating whole blood levels of selenium, oxidative stress assessed by asymmetric dimethylarginine (ADMA) levels, antioxidant capacity determined by glutathionperoxidase (GPx) levels and perioperative inflammation represented by interleukin-6 (IL-6) levels were measured at predefined perioperative time points. At end of surgery, both groups showed a comparable decrease of circulating selenium concentrations. Likewise, levels of oxidative stress and IL-6 were comparable in both groups. Selenium levels correlated with antioxidant capacity (GPx: r = 0.720; p<0.001) and showed a negative correlation to myocardial damage (CK-MB: r =  -0.571, p<0.001). Low postoperative selenium levels had a high predictive value for the occurrence of any postoperative complication. OPCAB surgery is not associated with less oxidative stress and a better preservation of the circulating selenium pool than on-pump surgery. Low postoperative selenium levels are predictive for the development of complications. ClinicalTrials.gov NCT01409057.

Inference of the oxidative stress network in Anopheles stephensi upon Plasmodium infection.

PubMed

Shrinet, Jatin; Nandal, Umesh Kumar; Adak, Tridibes; Bhatnagar, Raj K; Sunil, Sujatha

2014-01-01

Ookinete invasion of Anopheles midgut is a critical step for malaria transmission; the parasite numbers drop drastically and practically reach a minimum during the parasite's whole life cycle. At this stage, the parasite as well as the vector undergoes immense oxidative stress. Thereafter, the vector undergoes oxidative stress at different time points as the parasite invades its tissues during the parasite development. The present study was undertaken to reconstruct the network of differentially expressed genes involved in oxidative stress in Anopheles stephensi during Plasmodium development and maturation in the midgut. Using high throughput next generation sequencing methods, we generated the transcriptome of the An. stephensi midgut during Plasmodium vinckei petteri oocyst invasion of the midgut epithelium. Further, we utilized large datasets available on public domain on Anopheles during Plasmodium ookinete invasion and Drosophila datasets and arrived upon clusters of genes that may play a role in oxidative stress. Finally, we used support vector machines for the functional prediction of the un-annotated genes of An. stephensi. Integrating the results from all the different data analyses, we identified a total of 516 genes that were involved in oxidative stress in An. stephensi during Plasmodium development. The significantly regulated genes were further extracted from this gene cluster and used to infer an oxidative stress network of An. stephensi. Using system biology approaches, we have been able to ascertain the role of several putative genes in An. stephensi with respect to oxidative stress. Further experimental validations of these genes are underway.

Interactions of Oxygen and Water Molecules with Pyrite Surface: A New Insight.

PubMed

Li, Yuqiong; Chen, Jianhua; Chen, Ye; Zhao, Cuihua; Zhang, Yibing; Ke, Baolin

2018-02-06

Pyrite is the most common sulfide in nature, and it is well-known for its roles in acid mine drainage, flotation separation of useful metal (Cu, Pb, Zn, and Mo) sulfide minerals, optoelectronic and photovoltaic application, pneumoconiosis, and even in the origin of life. However, the detailed oxidation behaviors of pyrite are still unclear and not well-understood. New oxidation pathways by O 2 on the pyrite (100) surface have been found in this work for the first time using density functional theory simulation; that is, besides Fe sites, S sites are also possible oxidation sites in the initial oxidation state of pyrite, where easier and stronger oxidation may occur. This is the first time to confirm the other researchers' conjecture on the direct oxidation of S sites, which explains the isotopic composition experiments that a minor amount of O 2 is permanently incorporated into SO 4 2- during pyrite oxidation (O in SO 4 2- is mainly derived from water). We constructed various H 2 O-O 2 coadsorption models on the pyrite surface by considering the adsorption sequence of H 2 O and O 2 . It is found that the H 2 O molecule undergoes step-wise dissociation in the presence of the O 2 molecule. Hydroxyl radical •OH is the reactive oxygen species during H 2 O dissociation. Cyclic voltammetric measurements confirm the presence of •OH. In addition, H 2 O 2 may also be formed on the surface in terms of H 2 O-then-O 2 sequence adsorption.

Reduction of graphene oxide by aniline with its concomitant oxidative polymerization.

PubMed

Xu, Li Qun; Liu, Yi Liang; Neoh, Koon-Gee; Kang, En-Tang; Fu, Guo Dong

2011-04-19

Graphene oxide (GO) nanosheets are readily reduced by aniline above room temperature in an aqueous acid medium, with the aniline simultaneously undergoing oxidative polymerization to produce the reduced graphene oxide-polyaniline nanofiber (RGO-PANi) composites. The resulting RGO-PANi composites and RGO (after dissolution of PANi) were characterized by XPS, XRD analysis, TGA, UV-visible absorption spectroscopy, and TEM. It was also found that the RGO-PANi composites exhibit good specific capacitance during galvanostatic charging-discharging when used as capacitor electrodes. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of interface reaction and diffusion on stress-oxidation coupling at high temperature

NASA Astrophysics Data System (ADS)

Yue, Mengkun; Dong, Xuelin; Fang, Xufei; Feng, Xue

2018-04-01

High-temperature structural materials undergo oxidation during the service, and stress would generate in the oxide film. Understanding the coupling effect between stress and oxidation contributes to the understanding of material degradation and failure during the oxidation process. Here, we propose a model to investigative the coupling effect of stress and oxidation at high temperature by considering the three-stage oxidation process, where both the interface reaction and the diffusion process are present. The governing equations including the oxidation kinetics and stress equilibrium for isothermal oxidation under stress-oxidation coupling effect have been derived. The theory is validated by comparing with the experimental results of SiO2 grown on Si substrate. Results show that the coupling of stress and oxidation influences the growth of the oxide film by affecting all three stages of the oxidation process.

Development of an accurate and high-throughput methodology for structural comprehension of chlorophylls derivatives. (I) Phytylated derivatives.

PubMed

Chen, Kewei; Ríos, José Julián; Pérez-Gálvez, Antonio; Roca, María

2015-08-07

Phytylated chlorophyll derivatives undergo specific oxidative reactions through the natural metabolism or during food processing or storage, and consequently pyro-, 13(2)-hydroxy-, 15(1)-hydroxy-lactone chlorophylls, and pheophytins (a and b) are originated. New analytical procedures have been developed here to reproduce controlled oxidation reactions that specifically, and in reasonable amounts, produce those natural target standards. At the same time and under the same conditions, 16 natural chlorophyll derivatives have been analyzed by APCI-HPLC-hrMS(2) and most of them by the first time. The combination of the high-resolution MS mode with powerful post-processing software has allowed the identification of new fragmentation patterns, characterizing specific product ions for some particular standards. In addition, new hypotheses and reaction mechanisms for the established MS(2)-based reactions have been proposed. As a general rule, the main product ions involve the phytyl and the propionic chains but the introduction of oxygenated functional groups at the isocyclic ring produces new and specific productions and at the same time inhibits some particular fragmentations. It is noteworthy that all b derivatives, except 15(1)-hydroxy-lactone compounds, undergo specific CO losses. We propose a new reaction mechanism based in the structural configuration of a and b chlorophyll derivatives that explain the exclusive CO fragmentation in all b series except for 15(1)-hydroxy-lactone b and all a series compounds. Copyright © 2015 Elsevier B.V. All rights reserved.

Nitrous Oxide Anesthesia and Plasma Homocysteine in Adolescents

PubMed Central

Nagele, Peter; Tallchief, Danielle; Blood, Jane; Sharma, Anshuman; Kharasch, Evan D.

2011-01-01

Background Nitrous oxide inactivates vitamin B12, inhibits methionine synthase and consequently increases plasma total homocysteine (tHcy). Prolonged exposure to nitrous oxide can lead to neuropathy, spinal cord degeneration and even death in children. We tested the hypothesis that nitrous oxide anesthesia causes a significant increase in plasma tHcy in children. Methods Twenty-seven children (age 10-18 years) undergoing elective major spine surgery were enrolled and serial plasma samples from 0 – 96 hours after induction were obtained. The anesthetic regimen, including the use of nitrous oxide, was at the discretion of the anesthesiologist. Plasma tHcy was measured using standard enzymatic assays. Results The median baseline plasma tHcy concentration was 5.1 μmol/L (3.9 – 8.0 μmol/L, interquartile range) and increased in all patients exposed to nitrous oxide (n=26) by an average of +9.4 μmol/L (geometric mean; 95% CI 7.1 – 12.5 μmol/L) or +228% (mean; 95% CI 178% - 279%). Plasma tHcy peaked between 6-8 hours after induction of anesthesia. One patient who did not receive nitrous oxide had no increase in plasma tHcy. Several patients experienced a several-fold increase in plasma tHcy (max. +567%). The increase in plasma tHcy was strongly correlated with the duration and average concentration of nitrous oxide anesthesia (r= 0.80; p<0.001). Conclusions Pediatric patients undergoing nitrous oxide anesthesia develop significantly increased plasma tHcy concentrations. The magnitude of this effect appears to be greater compared to adults; however, the clinical relevance is unknown. PMID:21680854

Biological and Environmental Transformations of Copper-Based Nanomaterials

PubMed Central

Wang, Zhongying; Von Dem Bussche, Annette; Kabadi, Pranita K.; Kane, Agnes B.; Hurt, Robert H.

2013-01-01

Copper-based nanoparticles are an important class of materials with applications as catalysts, conductive inks, and antimicrobial agents. Environmental and safety issues are particularly important for copper-based nanomaterials because of their potential large-scale use and their high redox activity and toxicity reported from in vitro studies. Elemental nanocopper oxidizes readily upon atmospheric exposure during storage and use, so copper oxides are highly relevant phases to consider in studies of environmental and health impacts. Here we show that copper oxide nanoparticles undergo profound chemical transformations under conditions relevant to living systems and the natural environment. Copper oxide nanoparticle (CuO-NP) dissolution occurs at lysosomal pH (4-5), but not at neutral pH in pure water. Despite the near-neutral pH of cell culture medium, CuO-NPs undergo significant dissolution in media over time scales relevant to toxicity testing due to ligand-assisted ion release, in which amino acid complexation is an important contributor. Electron paramagnetic resonance (EPR) spectroscopy shows that dissolved copper in association with CuO-NPs are the primary redox-active species. CuO-NPs also undergo sulfidation by a dissolution-reprecipitation mechanism, and the new sulfide surfaces act as catalysts for sulfide oxidation. Copper sulfide NPs are found to be much less cytotoxic than CuO NPs, which is consistent with the very low solubility of CuS. Despite this low solubility of CuS, EPR studies show that sulfidated CuO continues to generate some ROS activity due to the release of free copper by H2O2 oxidation during the Fenton-chemistry-based EPR assay. While sulfidation can serve as a natural detoxification process for nanosilver and other chalcophile metals, our results suggest that sulfidation may not fully and permanently detoxify copper in biological or environmental compartments that contain reactive oxygen species. PMID:24032665

High Activity of Au/K/TiO 2(110) for CO Oxidation: Alkali-Metal-Enhanced Dispersion of Au and Bonding of CO

DOE PAGES

Rodriguez, Jose A.; Grinter, David C.; Ramirez, Pedro J.; ...

2018-02-14

In this paper, images from scanning tunneling microscopy show high mobility for potassium (K) on an oxidized TiO 2(110) surface. At low coverages, the alkali metal occupies mainly terrace sites of the o-TiO 2(110) system. The results of X-ray photoelectron spectroscopy indicate that K is fully ionized. The electron transferred from K to the titania affects the reactivity of this oxide, favoring the dispersion of Au particles on the terraces of the o-TiO 2(110) surface. When small coverages of K and Au are present on the o-TiO 2(110) system, only a few K–Au pairs are formed and the alkali metalmore » affects Au chemisorption mainly through the oxide interactions. Addition of K to Au/o-TiO 2(110) enhances the reactivity of the system, opening new reaction paths for the adsorption and oxidation of carbon monoxide. CO can undergo disproportionation (2CO → C ads + CO 2,ads) on K/o-TiO 2(110) and Au/K/o-TiO 2(110) surfaces. The Au–KO x interface binds CO much better than plain Au–TiO 2, increasing the surface coverage of CO and facilitating its oxidation. Kinetic tests show that K promotes CO oxidation on Au/TiO 2. Finally, turnover frequencies of 2.1 and 10.8 molecules (Au site) -1 s –1 were calculated for oxidation of CO on Au/o-TiO 2(110) and Au/K/o-TiO 2(110) catalysts, respectively.« less

High Activity of Au/K/TiO 2(110) for CO Oxidation: Alkali-Metal-Enhanced Dispersion of Au and Bonding of CO

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rodriguez, Jose A.; Grinter, David C.; Ramirez, Pedro J.

In this paper, images from scanning tunneling microscopy show high mobility for potassium (K) on an oxidized TiO 2(110) surface. At low coverages, the alkali metal occupies mainly terrace sites of the o-TiO 2(110) system. The results of X-ray photoelectron spectroscopy indicate that K is fully ionized. The electron transferred from K to the titania affects the reactivity of this oxide, favoring the dispersion of Au particles on the terraces of the o-TiO 2(110) surface. When small coverages of K and Au are present on the o-TiO 2(110) system, only a few K–Au pairs are formed and the alkali metalmore » affects Au chemisorption mainly through the oxide interactions. Addition of K to Au/o-TiO 2(110) enhances the reactivity of the system, opening new reaction paths for the adsorption and oxidation of carbon monoxide. CO can undergo disproportionation (2CO → C ads + CO 2,ads) on K/o-TiO 2(110) and Au/K/o-TiO 2(110) surfaces. The Au–KO x interface binds CO much better than plain Au–TiO 2, increasing the surface coverage of CO and facilitating its oxidation. Kinetic tests show that K promotes CO oxidation on Au/TiO 2. Finally, turnover frequencies of 2.1 and 10.8 molecules (Au site) -1 s –1 were calculated for oxidation of CO on Au/o-TiO 2(110) and Au/K/o-TiO 2(110) catalysts, respectively.« less

Distribution of apparent activation energy counterparts during thermo - And thermo-oxidative degradation of Aronia melanocarpa (black chokeberry).

PubMed

Janković, Bojan; Marinović-Cincović, Milena; Janković, Marija

2017-09-01

Kinetics of degradation for Aronia melanocarpa fresh fruits in argon and air atmospheres were investigated. The investigation was based on probability distributions of apparent activation energy of counterparts (ε a ). Isoconversional analysis results indicated that the degradation process in an inert atmosphere was governed by decomposition reactions of esterified compounds. Also, based on same kinetics approach, it was assumed that in an air atmosphere, the primary compound in degradation pathways could be anthocyanins, which undergo rapid chemical reactions. A new model of reactivity demonstrated that, under inert atmospheres, expectation values for ε a occured at levels of statistical probability. These values corresponded to decomposition processes in which polyphenolic compounds might be involved. ε a values obeyed laws of binomial distribution. It was established that, for thermo-oxidative degradation, Poisson distribution represented a very successful approximation for ε a values where there was additional mechanistic complexity and the binomial distribution was no longer valid. Copyright © 2017 Elsevier Ltd. All rights reserved.

Experimental determination of self-heating and self-ignition risks associated with the dusts of agricultural materials commonly stored in silos.

PubMed

Ramírez, Alvaro; García-Torrent, Javier; Tascón, Alberto

2010-03-15

Agricultural products stored in silos, and their dusts, can undergo oxidation and self-heating, increasing the risk of self-ignition and therefore of fires and explosions. The aim of the present work was to determine the thermal susceptibility (as reflected by the Maciejasz index, the temperature of the emission of flammable volatile substances and the combined information provided by the apparent activation energy and the oxidation temperature) of icing sugar, bread-making flour, maize, wheat, barley, alfalfa, and soybean dusts, using experimental methods for the characterisation of different types of coal (no standardised procedure exists for characterising the thermal susceptibility of either coal or agricultural products). In addition, the thermal stability of wheat, i.e., the risk of self-ignition determined as a function of sample volume, ignition temperature and storage time, was determined using the methods outlined in standard EN 15188:2007. The advantages and drawbacks of the different methods used are discussed. (c) 2009 Elsevier B.V. All rights reserved.

Selective laser melting porous metallic implants with immobilized silver nanoparticles kill and prevent biofilm formation by methicillin-resistant Staphylococcus aureus.

PubMed

van Hengel, Ingmar A J; Riool, Martijn; Fratila-Apachitei, Lidy E; Witte-Bouma, Janneke; Farrell, Eric; Zadpoor, Amir A; Zaat, Sebastian A J; Apachitei, Iulian

2017-09-01

Implant-associated infection and limited longevity are two major challenges that orthopedic devices need to simultaneously address. Additively manufactured porous implants have recently shown tremendous promise in improving bone regeneration and osseointegration, but, as any conventional implant, are threatened by infection. In this study, we therefore used rational design and additive manufacturing in the form of selective laser melting (SLM) to fabricate porous titanium implants with interconnected pores, resulting in a 3.75 times larger surface area than corresponding solid implants. The SLM implants were biofunctionalized by embedding silver nanoparticles in an oxide surface layer grown using plasma electrolytic oxidation (PEO) in Ca/P-based electrolytes. The PEO layer of the SLM implants released silver ions for at least 28 days. X-ray diffraction analysis detected hydroxyapatite on the SLM PEO implants but not on the corresponding solid implants. In vitro and ex vivo assays showed strong antimicrobial activity of these novel SLM PEO silver-releasing implants, without any signs of cytotoxicity. The rationally designed SLM porous implants outperformed solid implants with similar dimensions undergoing the same biofunctionalization treatment. This included four times larger amount of released silver ions, two times larger zone of inhibition, and one additional order of magnitude of reduction in numbers of CFU in an ex vivo mouse infection model. Copyright © 2017 Elsevier Ltd. All rights reserved.

Development of a Near-Ir Cavity Enhanced Absorption Spectrometer for the Detection of Atmospheric Oxidation Products and Organoamines

NASA Astrophysics Data System (ADS)

Eddingsaas, Nathan C.; Jewell, Breanna; Thurnherr, Emily

2014-06-01

An estimated 10,000 to 100,000 different compounds have been measured in the atmosphere, each one undergoes many oxidation reactions that may or may not degrade air quality. To date, the fate of even some of the most abundant hydrocarbons in the atmosphere is poorly understood. One difficulty is the detection of atmospheric oxidation products that are very labile and decompose during analysis. To study labile species under atmospheric conditions, a highly sensitive, non-destructive technique is needed. Here we describe a near-IR incoherent broadband cavity enhanced absorption spectroscopy (IBBCEAS) setup that we are developing to meet this end. We have chosen to utilize the near-IR, where vibrational overtone absorptions are observed, due to the clean spectral windows and better spectral separation of absorption features. In one spectral window we can simultaneously and continuously monitor the composition of alcohols, hydroperoxides, and carboxylic acids in an air mass. In addition, we have used our CEAS setup to detect organoamines. The long effective path length of CEAS allows for low detection limits, even of the overtone absorption features, at ppb and ppt levels.

Interaction of ammonia with semiconducting oxide surfaces

NASA Astrophysics Data System (ADS)

Nigam, Sandeep; Sahoo, Suman Kalyan; Majumder, Chiranjib

2018-04-01

Using density functional theory (DFT) we have investigated the adsorption of NH3 molecule on the rutile SnO2(110) and mixed Sn0.5Ti0.5O2(110) surfaces. NH3 molecule gets absorbed on the 5-coordinated Sn atom (Sn5c) of the surface in tilted mode having an additional hydrogen bond with nearby surface bridged oxygen (Obr) atom. After adsorption, 3a1 molecular orbital of ammonia undergo significant dispersal as it donates its electron to surface atoms. The adsorption energy is found to be 1.4-1.6eV. Inclusion of Ti atoms in the SnO2 lattice leads to decrease in the adsorption energy value.

The hematological effects of nitrous oxide anesthesia in pediatric patients.

PubMed

Duma, Andreas; Cartmill, Christopher; Blood, Jane; Sharma, Anshuman; Kharasch, Evan D; Nagele, Peter

2015-06-01

Prolonged administration of nitrous oxide causes an increase in plasma homocysteine in children via vitamin B12 inactivation. However, it is unclear whether nitrous oxide doses used in clinical practice cause adverse hematological effects in pediatric patients. This retrospective study included 54 pediatric patients undergoing elective spinal surgery: 41 received nitrous oxide throughout anesthesia (maintenance group), 9 received nitrous oxide for induction and/or emergence (induction/emergence group), and 4 did not receive nitrous oxide (nitrous oxide-free group). Complete blood counts obtained before and up to 4 days after surgery were assessed for anemia, macrocytosis/microcytosis, anisocytosis, hyperchromatosis/hypochromatosis, thrombocytopenia, and leukopenia. The change (Δ) from preoperative to the highest postoperative value was calculated for mean corpuscular volume (MCV) and red cell distribution width (RDW). No pancytopenia was present in any patient after surgery. All patients had postoperative anemia, and none had macrocytosis. Postoperative MCV (mean [99% confidence interval]) peaked at 86 fL (85-88 fL), 85 fL (81-89 fL), and 88 fL (80-96 fL) and postoperative RDW at 13.2% (12.8-13.5%), 13.3% (12.7-13.8%), and 13.0% (11.4-14.6%) for the maintenance group, the induction/emergence group, and the nitrous oxide-free group. Two patients in the maintenance group (5%) developed anisocytosis (RDW >14.6%), but none in the induction/emergence group or in the nitrous oxide-free group (P = 0.43). Both ΔMCV (P = 0.52) and ΔRDW (P = 0.16) were similar across all groups. Nitrous oxide exposure for up to 8 hours is not associated with megaloblastic anemia in pediatric patients undergoing major spinal surgery.

The Hematological Effects of Nitrous Oxide Anesthesia in Pediatric Patients

PubMed Central

Duma, Andreas; Cartmill, Christopher; Blood, Jane; Sharma, Anshuman; Kharasch, Evan; Nagele, Peter

2016-01-01

Background Prolonged administration of nitrous oxide causes an increase in plasma homocysteine in children via vitamin B12 inactivation. However, it is unclear if nitrous oxide doses used in clinical practice cause adverse hematological effects in pediatric patients. Methods This retrospective study included 54 pediatric patients undergoing elective spinal surgery: 41 received nitrous oxide throughout anesthesia (maintenance group), 9 received nitrous oxide for induction and/or emergence (induction/emergence group), and 4 did not receive nitrous oxide (nitrous oxide-free group). Complete blood counts obtained before and up to 4 days after surgery were assessed for anemia, macro-/microcytosis, anisocytosis, hyper-/hypochromatosis, thrombocytopenia and leucopenia. The change (Δ) from preoperative to the highest postoperative value was calculated for mean corpuscular volume (MCV) and red cell distribution width (RDW). Results No pancytopenia was present in any patient after surgery. All patients had postoperative anemia; none had macrocytosis. Postoperative MCV (mean [99% CI]) peaked at 86 [85 to 88] fL, 85 [81 to 89] fL, and 88 [80 to 96] fL, and postoperative RDW at 13.2 [12.8 to 13.5] %, 13.3 [12.7 to 13.8] %, and 13.0 [11.4 to 14.6] % for the maintenance group, the induction/emergence group, and the nitrous oxide-free group. Two patients in the maintenance group (5 %) developed anisocytosis (RDW>14.6%), but none in the induction/emergence group or in the nitrous oxide-free group (P = 0.43). Both ΔMCV (P=0.52) and ΔRDW (P=0.16) were similar across all groups. Conclusions Nitrous oxide exposure for up to eight hours is not associated with megaloblastic anemia in pediatric patients undergoing major spinal surgery. PMID:25658315

Sequential anaerobic/aerobic biodegradation of chloroethenes--aspects of field application.

PubMed

Tiehm, Andreas; Schmidt, Kathrin R

2011-06-01

Because of a range of different industrial activities, sites contaminated with chloroethenes are a world-wide problem. Chloroethenes can be biodegraded by reductive dechlorination under anaerobic conditions as well as by oxidation under aerobic conditions. The tendency of chloroethenes to undergo reductive dechlorination decreases with a decreasing number of chlorine substituents, whereas with less chlorine substituents chloroethenes more easily undergo oxidative degradation. There is currently a growing interest in aerobic metabolic degradation of chloroethenes, which demonstrates advantages compared to cometabolic degradation pathways. Sequential anaerobic/aerobic biodegradation can overcome the disadvantages of reductive dechlorination and leads to complete mineralization of the chlorinated pollutants. This approach shows promise for site remediation in natural settings and in engineered systems. Copyright © 2011 Elsevier Ltd. All rights reserved.

Nazarov cyclization initiated by peracid oxidation: the total synthesis of (+/-)-rocaglamide.

PubMed

Malona, John A; Cariou, Kevin; Frontier, Alison J

2009-06-10

The total syntheses of aglafolin, rocagloic acid, and rocaglamide using Nazarov cyclization are described. Generation of the necessary oxyallyl cation intermediate was accomplished via peracid oxidation of an allenol ether to generate an unusual oxycarbenium ion species that undergoes cyclization. The synthesis is efficient, highly diastereoselective, and strategically distinct from previous syntheses of rocaglamide.

Reusable fast opening switch

DOEpatents

Van Devender, J.P.; Emin, D.

1983-12-21

A reusable fast opening switch for transferring energy, in the form of a high power pulse, from an electromagnetic storage device such as an inductor into a load. The switch is efficient, compact, fast and reusable. The switch comprises a ferromagnetic semiconductor which undergoes a fast transition between conductive and metallic states at a critical temperature and which undergoes the transition without a phase change in its crystal structure. A semiconductor such as europium rich europhous oxide, which undergoes a conductor to insulator transition when it is joule heated from its conductor state, can be used to form the switch.

Reusable fast opening switch

DOEpatents

Van Devender, John P.; Emin, David

1986-01-01

A reusable fast opening switch for transferring energy, in the form of a high power pulse, from an electromagnetic storage device such as an inductor into a load. The switch is efficient, compact, fast and reusable. The switch comprises a ferromagnetic semiconductor which undergoes a fast transition between conductive and insulating states at a critical temperature and which undergoes the transition without a phase change in its crystal structure. A semiconductor such as europium rich europhous oxide, which undergoes a conductor to insulator transition when it is joule heated from its conductor state, can be used to form the switch.

Reduction Rates for Higher Americium Oxidation States in Nitric Acid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grimes, Travis Shane; Mincher, Bruce Jay; Schmitt, Nicholas C

The stability of hexavalent americium was measured using multiple americium concentrations and nitric acid concentrations after contact with the strong oxidant sodium bismuthate. Contrary to our hypotheses Am(VI) was not reduced faster at higher americium concentrations, and the reduction was only zero-order at short time scales. Attempts to model the reduction kinetics using zero order kinetic models showed Am(VI) reduction in nitric acid is more complex than the autoreduction processes reported by others in perchloric acid. The classical zero-order reduction of Am(VI) was found here only for short times on the order of a few hours. We did show thatmore » the rate of Am(V) production was less than the rate of Am(VI) reduction, indicating that some Am(VI) undergoes two electron-reduction to Am(IV). We also monitored the Am(VI) reduction in contact with the organic diluent dodecane. A direct comparison of these results with those in the absence of the organic diluent showed the reduction rates for Am(VI) were not statistically different for both systems. Additional americium oxidations conducted in the presence of Ce(IV)/Ce(III) ions showed that Am(VI) is reduced without the typical growth of Am(V) observed in the systems sans Ce ion. This was an interesting result which suggests a potential new reduction/oxidation pathway for Am in the presence of Ce; however, these results were very preliminary, and will require additional experiments to understand the mechanism by which this occurs. Overall, these studies have shown that hexavalent americium is fundamentally stable enough in nitric acid to run a separations process. However, the complicated nature of the reduction pathways based on the system components is far from being rigorously understood.« less

Mechanical and spectroscopic properties of metal-containing polyimides

NASA Technical Reports Server (NTRS)

Taylor, L. T.; St.clair, A. K.

1983-01-01

The incorporation of specific metal ions into polyimides is described. Detailed studies have included various compounds of copper, lithium, and palladium as dopants. Addition of the metal during polymerization or after formation of the polyamic acid precedes the thermal imidization step. With many dianhydride-diamine-dopant combinations high quality variously colored films are produced. Many metal doped films exhibit (1) improved high temperature adhesive properties, (2) increased electrical conductivity, (3) excellent thermal stability, (4) improved acid/base resistance, (5) increased modulus in flexible films and (6) excellent high temperature tensile strength. X-ray photo-electron spectroscopic study of these films suggests that many of the additives undergo chemical modification during thermal imidization. Palladium dopants appear to be partially reduced to the metallic state, while lithium and copper dopants are probably converted to their oxides. Ion etching experiments with Auger electron spectroscopy monitoring are discussed.

Mechanical and spectroscopic properties of metal containing polyimides

NASA Technical Reports Server (NTRS)

Taylor, L. T.; St. Clair, A. K.

1984-01-01

The incorporation of specific metal ions into polyimides is described. Detailed studies have included various compounds of copper, lithium, and palladium as dopants. Addition of the metal during polymermzation or after formation of the polyamic acid precedes the thermal imidization step. With many dianhydride-diamine-dopant combinations high quality variously colored films are produced. Many metal doped films exhibit (1) improved high temperature adhesive properties, (2) increased electrical conductivity, (3) excellent thermal stability, (4) improved acid/base resistance, (5) increased modulus in flexible films and (6) excellent high temperature tensile strength. X-ray photo-electron spectroscopic study of these films suggests that many of the additives undergo chemical modification during thermal imidization. Palladium dopants appear to be partially reduced to the metallic state, while lithium and copper dopants are probably converted to their oxides. Ion etching experiments with Auger electron spectroscopy monitoring are discussed.

Solar photochemical oxidation of alcohols using catalytic hydroquinone and copper nanoparticles under oxygen: oxidative cleavage of lignin models.

PubMed

Mitchell, Lorna J; Moody, Christopher J

2014-11-21

Alcohols are converted into to their corresponding carbonyl compounds using catalytic amounts of 1,4-hydroquinone with a copper nanoparticle electron transfer mediator with oxygen as the terminal oxidant in acetone as solvent under visible light irradiation. These conditions employing biorenewable hydroquinone as reagent were developed from initial experiments using stoichiometric amounts of 1,4-benzoquinone as oxidant. A range of benzylic and aliphatic primary and secondary alcohols are oxidized, affording the corresponding aldehydes or ketones in moderate to excellent yields. The methodology is also applicable to the oxidative degradation of lignin model compounds that undergo C-C bond cleavage to give simple aromatic compounds.

Microdomain Formation, Oxidation, and Cation Ordering in LaCa 2Fe 3O 8+y

DOE PAGES

Price, Patrick M.; Browning, Nigel D.; Butt, Darryl P.

2015-03-23

The compound LaCa 2Fe 3O 8+y, also known as the Grenier phase, is known to undergo an order-disorder transformation (ODT) at high temperatures. Oxidation has been observed when the compound is cooled in air after the ODT. In this study, we have synthesized the Grenier compound in air using traditional solid state reactions and investigated the structure and composition before and after the ODT. Thermal analysis showed that the material undergoes an order-disorder transformation in both oxygen and argon atmospheres with dynamic, temperature dependent, oxidation upon cooling. Results from scanning transmission electron microscopy (STEM) suggest that the Grenier phase hasmore » preferential segregation of Ca and La on the two crystallographic A-sites before the ODT, but a random distribution above the ODT temperature. Furthermore, STEM images suggest the possibility that oxygen excess may exist in La-rich regions within microdomains rather than at microdomain boundaries.« less

Solute transport and the prediction of breakaway oxidation in gamma + beta Ni-Cr-Al alloys

NASA Technical Reports Server (NTRS)

Nesbitt, J. A.; Heckel, R. W.

1984-01-01

The Al transport and the condition leading to breakaway oxidation during the cyclic oxidation of gamma + beta NiCrAl alloys have been studied. The Al concentration/distance profiles were measured after various cyclic oxidation exposures at 1200 C. It was observed that cyclic oxidation results in a decreasing Al concentration at the oxide/metal interface, maintaining a constant flux of Al to the Al2O3 scale. It was also observed that breakaway oxidation occurs when the Al concentration at the oxide/metal interface approaches zero. A numerical model was developed to simulate the diffusional transport of Al and to predict breakaway oxidation in gamma + beta NiCrAl alloys undergoing cyclic oxidation. In a comparison of two alloys with similar oxide spalling characteristics, the numerical model was shown to predict correctly the onset of breakaway oxidation in the higher Al-content alloy.

Primary emissions and chemical oxidation of volatile organic compounds emitted from laboratory biomass burning sources during the 2016 FIREX FireLab campaign: measurements from a H3O+ chemical ionization mass spectrometer

NASA Astrophysics Data System (ADS)

Coggon, M. M.; Warneke, C.; Koss, A.; Sekimoto, K.; Yuan, B.; Lim, C. Y.; Hagan, D. H.; Kroll, J. H.; Cappa, C. D.; Gilman, J.; Lerner, B. M.; Jimenez, J. L.; Yokelson, R. J.; Roberts, J. M.; De Gouw, J. A.

2017-12-01

Non-methane organic gases (NMOG) emitted by biomass burning constitute a large source of reactive carbon in the atmosphere. Once emitted, these compounds may undergo series of reactions with the OH radical and nitrogen oxides to form secondary organic aerosol (SOA), ozone, or other health-impacting products. The complex emission profile and strong variability of biomass burning NMOG play an important, yet understudied, role in the variability of air quality outcomes such as SOA and ozone. In this study, we summarize measurements of biomass burning volatile organic compounds (VOCs) conducted using a H3O+ chemical ionization mass spectrometer (H3O+-CIMS) during the 2016 FIREX laboratory campaign in Missoula, MT. Specifically, we will present data demonstrating the chemical evolution of biomass burning VOCs artificially aged in a field-deployable photooxidation chamber and an oxidation flow reactor. More than 50 OH-oxidation experiments were conducted with biomass types representing a range of North American fuels. Across many fuel types, VOCs with high SOA and ozone formation potential, such as aromatics and furans, were observed to quickly react with the OH radical while oxidized species were generated. We compare the calculated OH reactivity of the primary emissions to the calculated OH reactivity used in many photochemical models and highlight areas requiring additional research in order to improve model/measurement comparisons.

Secondary organic aerosol formation from isoprene photooxidation

NASA Astrophysics Data System (ADS)

Kroll, J. H.; Ng, N. L.; Murphy, S. M.; Flagan, R. C.; Seinfeld, J. H.

2005-12-01

We report chamber studies of the formation of secondary organic aerosol (SOA) from the oxidation of isoprene (2-methyl-1,3-butadiene). Isoprene is the most abundant non-methane hydrocarbon emitted into the troposphere (source strength of ~500 Tg/year), so even small SOA yields may have a large impact on global SOA production. Reactions are carried out in Caltech's dual 28 m3 Teflon chambers, and aerosol growth is monitored by a differential mobility analyzer (DMA) and an Aerodyne time-of-flight aerosol mass spectrometer (AMS). Isoprene oxidation is initiated by the UV irradiation of isoprene in the presence of hydrogen peroxide, with NO added for high-NOx experiments. These conditions ensure that isoprene oxidation is initiated by reaction with the OH radical, with negligible interference from other oxidants (ozone, nitrate radicals, and O atoms). Aerosol growth is observed under both high-NOx and low-NOx conditions, at isoprene concentrations lower than measured in previous studies (down to 8 ppb). SOA yields are found to be in the range of 1-2%. Yields exhibit a complex dependence on NOx concentration, likely a result of changes in the chemistry of organic peroxy radicals. It is shown that condensable compounds are formed from further reactions of first-generation isoprene oxidation products; the rates and products of such gas-phase reactions are at present poorly understood. Additionally, measurements of SOA composition indicate that these products undergo reactions in the aerosol phase, leading to the formation of low-volatility oligomeric products.

A novel technique to determine cobalt exchangeability in soils using isotope dilution.

PubMed

Wendling, Laura A; Kirby, Jason K; McLaughlin, Michael J

2008-01-01

The environmental risk posed by Co contamination is largely a function of its oxidation state. Our objective was to assess the potential biological availability of Co and the reactions and fate of soluble Co(II) after addition to soils with varying physical and chemical characteristics. A potential risk in quantifying exchangeable Co in soils using isotope dilution techniques is the possible presence of two species of Co in soil solution and adsorbed on soil solid phases [Co(II) and Co(III)], coupled with the possibility that when an isotope of Co is added it may undergo a change in oxidation state during the measurement phase. In this study, we have utilized an isotope dilution technique with cation exchange and high-performance liquid chromatography-inductively coupled plasma-mass spectrometry to determine the isotopically exchangeable Co fraction in several soils with varying characteristics such as differing Al, Fe, and Mn oxide content; pH; and organic carbon content. The application of the cation exchange procedure adjusts measurements of isotopically exchangeable Co to correct for the presence of non-exchangeable 57Co not in equilibrium with the solution phase. Results indicated that oxidation of added 57Co(II) to 57Co(III) or precipitation of 57Co(II) may occur on the surfaces of some soils, particularly those with a high pH or substantial quantities of Mn oxide minerals. No detectable Co(III)(aq) was found in the aqueous extracts of the soils examined.

Effects of silymarin on biochemical and oxidative stress markers in end-stage renal disease patients undergoing peritoneal dialysis.

PubMed

Firuzi, Omidreza; Khajehrezaei, Soraya; Ezzatzadegan, Shahrokh; Nejati, Maryam; Jahanshahi, Keramat-Allah; Roozbeh, Jamshid

2016-10-01

Introduction End-stage renal disease (ESRD) patients especially those undergoing dialysis are vulnerable to several complications, in particular those related to oxidative stress. Silymarin is an herbal medicine commonly used as an antioxidant in different pathologies. Methods To evaluate the effect of silymarin on biochemical and oxidative stress markers, 50 ESRD patients undergoing peritoneal dialysis were randomly divided into two groups of silymarin (n = 28) and control (n = 22) and received silymarin (140 mg every 8 hours) or placebo for 2 months, respectively. Ferric reducing antioxidant power and total 8-iso-prostaglandin F 2α were measured in plasma, while catalase enzyme activity was measured in erythrocytes of both groups before and after treatment. Findings Ferric reducing antioxidant power values after treatment were significantly decreased in silymarin group compared to before treatment values (17.2 ± 2.9 and 15.9 ± 3.1 µM equivalent of quercetin/dL, respectively, P < 0.05). Conversely, catalase levels were increased 17.3% after silymarin consumption, while it was decreased 9.1% in control group. Further, hemoglobin (from 10.94 ± 2.17 to 11.54 ± 2.03 g/dL, P < 0.05) and albumin levels (from 3.48 ± 0.67 to 3.61 ± 0.53 g/dL, P < 0.05) were significantly increased after silymarin administration. Discussion It is concluded that silymarin could be regarded as a supplementary therapy for ESRD patients undergoing peritoneal dialysis in order to reduce complications. © 2016 International Society for Hemodialysis.

Heterogeneous Oxidation of Laboratory-generated Mixed Composition and Biomass Burning Particles

NASA Astrophysics Data System (ADS)

Lim, C. Y.; Sugrue, R. A.; Hagan, D. H.; Cappa, C. D.; Kroll, J. H.; Browne, E. C.

2016-12-01

Heterogeneous oxidation of organic aerosol (OA) can significantly transform the chemical and physical properties of particulate matter in the atmosphere, leading to changes to the chemical composition of OA and potential volatilization of organic compounds. It has become increasingly apparent that the heterogeneous oxidation kinetics of OA depend on the phase and morphology of the particles. However, most laboratory experiments to date have been performed on single-component, purely organic precursors, which may exhibit fundamentally different behavior than more complex particles in the atmosphere. Here we present laboratory studies of the heterogeneous oxidation of two more complex chemical systems: thin, organic coatings on inorganic seed particles and biomass burning OA. In the first system, squalane (C30H62), a model compound for reduced OA, is coated onto dry ammonium sulfate particles at various thicknesses (10-20 nm) and exposed to hydroxyl radical (OH) in a flow tube reactor. In the second, we use a semi-batch reactor to study the heterogeneous OH-initiated oxidation of biomass burning particles as a part of the 2016 FIREX campaign in Missoula, MT. The resulting changes in chemical composition are monitored with an Aerodyne High Resolution Time-of-flight Aerosol Mass Spectrometer (AMS) and a soot-particle AMS for the non-refractory and refractory systems, respectively. We show that the heterogeneous oxidation kinetics of these multicomponent particles are substantially different than that of the single-component particles. The oxidation of organic coatings is rapid, undergoing dramatic changes to carbon oxidation state and losing a significant amount of organic mass after relatively low OH exposures (equivalent to several days of atmospheric processing). In the case of biomass burning particles, the kinetics are complex, with different components (inferred by aerosol mass spectrometry) undergoing oxidation at different rates.

Manganese oxide helices, rings, strands, and films, and methods for their preparation

DOEpatents

Suib, Steven L.; Giraldo, Oscar; Marquez, Manuel; Brock, Stephanie

2003-01-07

Methods for the preparation of mixed-valence manganese oxide compositions with quaternary ammonium ions are described. The compositions self-assemble into helices, rings, and strands without any imposed concentration gradient. These helices, rings, and strands, as well as films having the same composition, undergo rapid ion exchange to replace the quaternary ammonium ions with various metal ions. And the metal-ion-containing manganese oxide compositions so formed can be heat treated to form semi-conducting materials with high surface areas.

Durable zinc oxide-containing sorbents for coal gas desulfurization

DOEpatents

Siriwardane, Ranjani V.

1996-01-01

Durable zinc-oxide containing sorbent pellets for removing hydrogen sulfide from a gas stream at an elevated temperature are made up to contain titania as a diluent, high-surface-area silica gel, and a binder. These materials are mixed, moistened, and formed into pellets, which are then dried and calcined. The resulting pellets undergo repeated cycles of sulfidation and regeneration without loss of reactivity and without mechanical degradation. Regeneration of the pellets is carried out by contacting the bed with an oxidizing gas mixture.

Simultaneous detection of low and high molecular weight carbonylated compounds derived from lipid peroxidation by electrospray ionization-tandem mass spectrometry.

PubMed

Milic, Ivana; Hoffmann, Ralf; Fedorova, Maria

2013-01-02

Reactive oxygen species (ROS) and other oxidative agents such as free radicals can oxidize polyunsaturated fatty acids (PUFA) as well as PUFA in lipids. The oxidation products can undergo consecutive reactions including oxidative cleavages to yield a chemically diverse group of products, such as lipid peroxidation products (LPP). Among them are aldehydes and ketones ("reactive carbonyls") that are strong electrophiles and thus can readily react with nucleophilic side chains of proteins, which can alter the protein structure, function, cellular distribution, and antigenicity. Here, we report a novel technique to specifically derivatize both low molecular and high molecular weight carbonylated LPP with 7-(diethylamino)coumarin-3-carbohydrazide (CHH) and analyze all compounds by electrospray ionization-mass spectrometry (ESI-MS) in positive ion mode. CHH-derivatized compounds were identified by specific neutral losses or fragment ions. The fragment ion spectra displayed additional signals that allowed unambiguous identification of the lipid, fatty acids, cleavage sites, and oxidative modifications. Oxidation of docosahexaenoic (DHA, 22:6), arachidonic (AA, 20:4), linoleic (LA, 18:2), and oleic acids (OA, 18:1) yielded 69 aliphatic carbonyls, whose structures were all deduced from the tandem mass spectra. When four phosphatidylcholine (PC) vesicles containing the aforementioned unsaturated fatty acids were oxidized, we were able to deduce the structures of 122 carbonylated compounds from the tandem mass spectra of a single shotgun analysis acquired within 15 min. The high sensitivity (LOD ∼ 1 nmol/L for 4-hydroxy-2-nonenal, HNE) and a linear range of more than 3 orders of magnitude (10 nmol/L to 10 μmol/L for HNE) will allow further studies on complex biological samples including plasma.

Light History Influences the Response of the Marine Cyanobacterium Synechococcus sp. WH7803 to Oxidative Stress1[W][OA

PubMed Central

Blot, Nicolas; Mella-Flores, Daniella; Six, Christophe; Le Corguillé, Gildas; Boutte, Christophe; Peyrat, Anne; Monnier, Annabelle; Ratin, Morgane; Gourvil, Priscillia; Campbell, Douglas A.; Garczarek, Laurence

2011-01-01

Marine Synechococcus undergo a wide range of environmental stressors, especially high and variable irradiance, which may induce oxidative stress through the generation of reactive oxygen species (ROS). While light and ROS could act synergistically on the impairment of photosynthesis, inducing photodamage and inhibiting photosystem II repair, acclimation to high irradiance is also thought to confer resistance to other stressors. To identify the respective roles of light and ROS in the photoinhibition process and detect a possible light-driven tolerance to oxidative stress, we compared the photophysiological and transcriptomic responses of Synechococcus sp. WH7803 acclimated to low light (LL) or high light (HL) to oxidative stress, induced by hydrogen peroxide (H2O2) or methylviologen. While photosynthetic activity was much more affected in HL than in LL cells, only HL cells were able to recover growth and photosynthesis after the addition of 25 μm H2O2. Depending upon light conditions and H2O2 concentration, the latter oxidizing agent induced photosystem II inactivation through both direct damage to the reaction centers and inhibition of its repair cycle. Although the global transcriptome response appeared similar in LL and HL cells, some processes were specifically induced in HL cells that seemingly helped them withstand oxidative stress, including enhancement of photoprotection and ROS detoxification, repair of ROS-driven damage, and regulation of redox state. Detection of putative LexA binding sites allowed the identification of the putative LexA regulon, which was down-regulated in HL compared with LL cells but up-regulated by oxidative stress under both growth irradiances. PMID:21670225

SULFATE PRODUCTION IN CLOUDS IN EASTERN CHINA: OBSERVATIONS FROM MT. TAI

NASA Astrophysics Data System (ADS)

Collett, J. L.; Shen, X.; Lee, T.; Wang, X.; Wang, W.; Wang, T.

2009-12-01

The fate of China’s sulfur dioxide emissions depends, in part, on the ability of regional clouds to support rapid aqueous oxidation of these emissions to sulfate. Sulfur dioxide oxidized in regional clouds is more likely to be removed by wet deposition while sulfur dioxide that undergoes slower gas phase oxidation is expected to survive longer in the atmosphere and exert a radiative forcing impact over a broader spatial scale. Two 2008 field campaigns conducted at Mt. Tai, an isolated peak on the NE China plain, provide insight into the importance of various aqueous phase sulfur oxidation pathways in the region. Single and two-stage cloudwater collectors were used to collect bulk and drop size-resolved samples of cloudwater. Collected cloudwater was analyzed for key species that influence in-cloud sulfate production, including pH, S(IV), H2O2, Fe and Mn. Other major cloud solutes, including inorganic ions, total organic carbon, formaldehyde, and organic acids were also analyzed, as were gas phase concentrations of SO2, O3, and H2O2. A wide range of cloud pH was observed, from below 3 to above 6. High concentrations of cloudwater sulfate were consistent with abundant sulfur dioxide emissions in the region. Despite its fast aqueous reaction with sulfur dioxide, high concentrations of residual hydrogen peroxide were measured in some clouds implying a substantial capacity for additional sulfate production. Ozone was found to be an important S(IV) oxidant in some periods when cloud pH was high. This presentation will examine the importance of different oxidants (H2O2, O3, and O2 catalyzed by trace metals) for sulfur oxidation and the overall capacity of regional clouds to support rapid aqueous phase sulfate production.

A Torquoselective Extrusion of Isoxazoline N-Oxides. Application to the Synthesis of Aryl Vinyl and Divinyl Ketones for Nazarov Cyclization

PubMed Central

Canterbury, Daniel P.; Herrick, Ildiko R.; Um, Joann; Houk, K. N.; Frontier, Alison J.

2009-01-01

A mild, convenient reaction sequence for the synthesis of Nazarov cyclization substrates is described. The [3+2] dipolar cycloaddition of a nitrone and an electron-deficient alkyne gives an isolable isoxazoline intermediate, which upon oxidation undergoes stereoselective extrusion of nitrosomethane to give aryl vinyl or divinyl ketones. PMID:20161228

Electrosynthesis of vanillin from isoeugenol using platinum electrode

NASA Astrophysics Data System (ADS)

Mubarok, H.; Hilyatudini; Saepudin, E.; Ivandini, T. A.

2017-04-01

Vanillin was synthesized from isoeugenol through electrochemical method in one compartment cell using platinum electrode. Cyclic voltammetry in 0.1 M TBAP in methanol and acetonitrile indicated the first oxidation potential at +0.21 and +0.16 V (vs. Ag/AgCl), respectively. Isoeugenolis was proposed to undergo the oxidation accompanied by oxidative cleavage of alkene bond into aldehyde. Accordingly, the synthesis of vanillin was conducted using chronoamperometry technique. The electrosynthesis result was analyzed by HPLC and GC/MS. The optimum condition of the oxidation potential, solvent ratio, time of electrolysis and amount of water was investigated.

Laboratory Studies on the Formation of Three C2H4O Isomers-Acetaldehyde (CH3CHO), Ethylene Oxide (c-C2H4O), and Vinyl Alcohol (CH2CHOH)-in Interstellar and Cometary Ices

NASA Astrophysics Data System (ADS)

Bennett, Chris J.; Osamura, Yoshihiro; Lebar, Matt D.; Kaiser, Ralf I.

2005-11-01

Laboratory experiments were conducted to unravel synthetic routes to form three C2H4O isomers-acetaldehyde (CH3CHO), ethylene oxide (c-C2H4O), and vinyl alcohol (CH2CHOH)-in extraterrestrial ices via electronic energy transfer processes initiated by electrons in the track of MeV ion trajectories. Here we present the results of electron irradiation on a 2:1 mixture of carbon dioxide (CO2) and ethylene (C2H4). Our studies suggest that suprathermal oxygen atoms can add to the carbon-carbon π bond of an ethylene molecule to form initially an oxirene diradical (addition to one carbon atom) and the cyclic ethylene oxide molecule (addition to two carbon atoms) at 10 K. The oxirene diradical can undergo a [1, 2]-H shift to the acetaldehyde molecule. Both the ethylene oxide and the acetaldehyde isomers can be stabilized in the surrounding ice matrix. To a minor amount, suprathermal oxygen atoms can insert into a carbon-hydrogen bond of the ethylene molecule, forming vinyl alcohol. Once these isomers have been synthesized inside the ice layers of the coated grains in cold molecular clouds, the newly formed molecules can sublime as the cloud reaches the hot molecular core stage. These laboratory investigations help to explain astronomical observations by Nummelin et al. and Ikeda et al. toward massive star-forming regions and hot cores, where observed fractional abundances of these isomers are higher than can be accounted for by gas-phase reactions alone. Similar synthetic routes could help explain the formation of acetaldehyde and ethylene oxide in comet C/1995 O1 (Hale-Bopp) and also suggest a presence of both isomers in Titan's atmosphere.

High catalytic activity of oriented 2.0.0 copper(I) oxide grown on graphene film

PubMed Central

Primo, Ana; Esteve-Adell, Ivan; Blandez, Juan F.; Dhakshinamoorthy, Amarajothi; Álvaro, Mercedes; Candu, Natalia; Coman, Simona M.; Parvulescu, Vasile I.; García, Hermenegildo

2015-01-01

Metal oxide nanoparticles supported on graphene exhibit high catalytic activity for oxidation, reduction and coupling reactions. Here we show that pyrolysis at 900 °C under inert atmosphere of copper(II) nitrate embedded in chitosan films affords 1.1.1 facet-oriented copper nanoplatelets supported on few-layered graphene. Oriented (1.1.1) copper nanoplatelets on graphene undergo spontaneous oxidation to render oriented (2.0.0) copper(I) oxide nanoplatelets on few-layered graphene. These films containing oriented copper(I) oxide exhibit as catalyst turnover numbers that can be three orders of magnitude higher for the Ullmann-type coupling, dehydrogenative coupling of dimethylphenylsilane with n-butanol and C–N cross-coupling than those of analogous unoriented graphene-supported copper(I) oxide nanoplatelets. PMID:26509224

Genetic Polymorphisms Associated with Hearing Threshold Shift in Subjects during First Encounter with Occupational Impulse Noise

PubMed Central

Grondin, Yohann; Bortoni, Magda E.; Sepulveda, Rosalinda; Ghelfi, Elisa; Bartos, Adam; Cotanche, Douglas; Clifford, Royce E.; Rogers, Rick A.

2015-01-01

Noise-induced hearing loss (NIHL) is the most significant occupational health issue worldwide. We conducted a genome-wide association study to identify single-nucleotide polymorphisms (SNPs) associated with hearing threshold shift in young males undergoing their first encounter with occupational impulse noise. We report a significant association of SNP rs7598759 (p < 5 x 10-7; p = 0.01 after permutation and correction; Odds Ratio = 12.75) in the gene coding for nucleolin, a multifunctional phosphoprotein involved in the control of senescence and protection against apoptosis. Interestingly, nucleolin has been shown to mediate the anti-apoptotic effect of HSP70, a protein found to prevent ototoxicity and whose polymorphisms have been associated with susceptibility to NIHL. Increase in nucleolin expression has also been associated with the prevention of apoptosis in cells undergoing oxidative stress, a well-known metabolic sequela of noise exposure. To assess the potential role of nucleolin in hearing loss, we tested down-regulation of nucleolin in cochlear sensory cells HEI-OC1 under oxidative stress conditions and report increased sensitivity to cisplatin, a chemotherapeutic drug with ototoxic side effects. Additional SNPs were found with suggestive association (p < 5 x 10-4), of which 7 SNPs were located in genes previously reported to be related to NIHL and 43 of them were observed in 36 other genes previously not reported to be associated with NIHL. Taken together, our GWAS data and in vitro studies reported herein suggest that nucleolin is a potential candidate associated with NIHL in this population. PMID:26121033

Capturing Labile Sulfenamide and Sulfinamide Serum Albumin Adducts of Carcinogenic Arylamines by Chemical Oxidation

PubMed Central

Peng, Lijuan; Turesky, Robert J.

2013-01-01

Aromatic amines and heterocyclic aromatic amines (HAAs) are a class of structurally related carcinogens that are formed during the combustion of tobacco or during the high temperature cooking of meats. These procarcinogens undergo metabolic activation by N-oxidation of the exocyclic amine group to produce N-hydroxylated metabolites, which are critical intermediates implicated in toxicity and DNA damage. The arylhydroxylamines and their oxidized arylnitroso derivatives can also react with cysteine (Cys) residues of glutathione or proteins to form, respectively, sulfenamide and sulfinamide adducts. However, sulfur-nitrogen linked adducted proteins are often difficult to detect because they are unstable and undergo hydrolysis during proteolytic digestion. Synthetic N-oxidized intermediates of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), a carcinogenic HAA produced in cooked meats, and 4-aminobiphenyl, a carcinogenic aromatic amine present in tobacco smoke were reacted with human serum albumin (SA) and formed labile sulfenamide or sulfinamide adducts at the Cys34 residue. Oxidation of the carcinogen-modified SA with m-chloroperoxybenzoic acid (m-CPBA) produced the arylsulfonamide adducts, which were stable to heat and the chemical reduction conditions employed to denature SA. The sulfonamide adducts of PhIP and 4-ABP were identified, by liquid chromatography/mass spectrometry, in proteolytic digests of denatured SA. Thus, selective oxidation of arylamine-modified SA produces stable arylsulfonamide-SA adducts, which may serve as biomarkers of these tobacco and dietary carcinogens. PMID:23240913

Modulation of oxidative damage by nitroxide free radicals.

PubMed

Dragutan, Ileana; Mehlhorn, Rolf J

2007-03-01

Piperidine nitroxides like 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) are persistent free radicals in non-acidic aqueous solutions and organic solvents that may have value as therapeutic agents in medicine. In biological environments, they undergo mostly reduction to stable hydroxylamines but can also undergo oxidation to reactive oxoammonium compounds. Reactions of the oxoammonium derivatives could have adverse consequences including chemical modification of vital macromolecules and deleterious effects on cell signaling. An examination of their reactivity in aqueous solution has shown that oxoammonium compounds can oxidize almost any organic as well as many inorganic molecules found in biological systems. Many of these reactions appear to be one-electron transfers that reduce the oxoammonium to the corresponding nitroxide species, in contrast to a prevalence of two-electron reductions of oxoammonium in organic solvents. Amino acids, alcohols, aldehydes, phospholipids, hydrogen peroxide, other nitroxides, hydroxylamines, phenols and certain transition metal ions and their complexes are among reductants of oxoammonium, causing conversion of this species to the paramagnetic nitroxide. On the other hand, thiols and oxoammonium yield products that cannot be detected by ESR even under conditions that would oxidize hydroxylamines to nitroxides. These products may include hindered secondary amines, sulfoxamides and sulfonamides. Thiol oxidation products other than disulfides cannot be restored to thiols by common enzymatic reduction pathways. Such products may also play a role in cell signaling events related to oxidative stress. Adverse consequences of the reactions of oxoammonium compounds may partially offset the putative beneficial effects of nitroxides in some therapeutic settings.

Real-Time Studies of Iron Oxalate-Mediated Oxidation of Glycolaldehyde as a Model for Photochemical Aging of Aqueous Tropospheric Aerosols.

PubMed

Thomas, Daniel A; Coggon, Matthew M; Lignell, Hanna; Schilling, Katherine A; Zhang, Xuan; Schwantes, Rebecca H; Flagan, Richard C; Seinfeld, John H; Beauchamp, J L

2016-11-15

The complexation of iron(III) with oxalic acid in aqueous solution yields a strongly absorbing chromophore that undergoes efficient photodissociation to give iron(II) and the carbon dioxide anion radical. Importantly, iron(III) oxalate complexes absorb near-UV radiation (λ > 350 nm), providing a potentially powerful source of oxidants in aqueous tropospheric chemistry. Although this photochemical system has been studied extensively, the mechanistic details associated with its role in the oxidation of dissolved organic matter within aqueous aerosol remain largely unknown. This study utilizes glycolaldehyde as a model organic species to examine the oxidation pathways and evolution of organic aerosol initiated by the photodissociation of aqueous iron(III) oxalate complexes. Hanging droplets (radius 1 mm) containing iron(III), oxalic acid, glycolaldehyde, and ammonium sulfate (pH ∼3) are exposed to irradiation at 365 nm and sampled at discrete time points utilizing field-induced droplet ionization mass spectrometry (FIDI-MS). Glycolaldehyde is found to undergo rapid oxidation to form glyoxal, glycolic acid, and glyoxylic acid, but the formation of high molecular weight oligomers is not observed. For comparison, particle-phase experiments conducted in a laboratory chamber explore the reactive uptake of gas-phase glycolaldehyde onto aqueous seed aerosol containing iron and oxalic acid. The presence of iron oxalate in seed aerosol is found to inhibit aerosol growth. These results suggest that photodissociation of iron(III) oxalate can lead to the formation of volatile oxidation products in tropospheric aqueous aerosols.

Nitric Oxide Decreases Acute Kidney Injury and Stage 3 Chronic Kidney Disease after Cardiac Surgery.

PubMed

Lei, Chong; Berra, Lorenzo; Rezoagli, Emanuele; Yu, Binglan; Dong, Hailong; Yu, Shiqiang; Hou, Lihong; Chen, Min; Chen, Wensheng; Wang, Hongbing; Zheng, Qijun; Shen, Jie; Jin, Zhenxiao; Chen, Tao; Zhao, Rong; Christie, Emily; Sabbisetti, Venkata S; Nordio, Francesco; Bonventre, Joseph V; Xiong, Lize; Zapol, Warren M

2018-06-22

No medical intervention has been identified that decreases acute kidney injury and improves renal outcome at 1-year after cardiac surgery. To determine whether administration of nitric oxide reduces the incidence of post-operative acute kidney injury and improves long-term kidney outcomes after multiple cardiac valve replacement requiring prolonged cardiopulmonary bypass. 244 Patients undergoing elective, multiple valve replacement surgery mostly due to rheumatic fever were randomized to receive either nitric oxide (treatment) or nitrogen (control). Nitric oxide and nitrogen were administered via the gas exchanger during cardiopulmonary bypass and by inhalation for 24h post-operatively. Primary outcome: Oxidation of ferrous plasma oxyhemoglobin to ferric methemoglobin was associated to a reduced post-operative acute kidney injury from 64% (control group) to 50% (nitric oxide) (RR, 95% CI; 0.78, 0.62-0.97;P=0.014). At 90-days, transition to stage 3 chronic kidney disease was reduced from 33% in the controls to 21% in the treatment group (RR, 95%CI; 0.64, 0.41 - 0.99;P=0.024); and at 1-year, from 31% to 18% (RR, 95% CI; 0.59, 0.36 - 0.96;P=0.017). Nitric oxide treatment reduced the overall major adverse kidney events at 30-days (RR, 95% CI; 0.40, 0.18 - 0.92;P=0.016, 90-days (RR, 95% CI; 0.40, 0.17 - 0.92;P=0.015 and 1-year (RR, 95% CI; 0.47, 0.20-1.10;P=0.041). In patients undergoing multiple valve replacement and prolonged cardiopulmonary bypass, administration of nitric oxide decreased the incidence of acute kidney injury, transition to stage 3 chronic kidney disease and major adverse kidney events at 30-days, 90-days, and 1-year. Clinical trial registered with ClinicalTrials.gov (NCT01802619).

Inflammatory response and extracorporeal circulation.

PubMed

Kraft, Florian; Schmidt, Christoph; Van Aken, Hugo; Zarbock, Alexander

2015-06-01

Patients undergoing cardiac surgery with extracorporeal circulation (EC) frequently develop a systemic inflammatory response syndrome. Surgical trauma, ischaemia-reperfusion injury, endotoxaemia and blood contact to nonendothelial circuit compounds promote the activation of coagulation pathways, complement factors and a cellular immune response. This review discusses the multiple pathways leading to endothelial cell activation, neutrophil recruitment and production of reactive oxygen species and nitric oxide. All these factors may induce cellular damage and subsequent organ injury. Multiple organ dysfunction after cardiac surgery with EC is associated with an increased morbidity and mortality. In addition to the pathogenesis of organ dysfunction after EC, this review deals with different therapeutic interventions aiming to alleviate the inflammatory response and consequently multiple organ dysfunction after cardiac surgery. Copyright © 2015 Elsevier Ltd. All rights reserved.

Dual C-H functionalization of N-aryl amines: synthesis of polycyclic amines via an oxidative Povarov approach.

PubMed

Min, Chang; Sanchawala, Abbas; Seidel, Daniel

2014-05-16

Iminium ions generated in situ via copper(I) bromide catalyzed oxidation of N-aryl amines readily undergo [4 + 2] cycloadditions with a range of dienophiles. This method involves the functionalization of both a C(sp(3))-H and a C(sp(2))-H bond and enables the rapid construction of polycyclic amines under relatively mild conditions.

A General Diastereoselective Catalytic Vinylogous Aldol Reaction Among Tetramic Acid-Derived Pyrroles

PubMed Central

2015-01-01

A catalytic diastereoselective aldol reaction has been developed for N1-arylated/C2-O-silylated/C3-methylated and brominated/C4-O-methylated pyrroles in its reactions with various aldehydes. Syn adducts emerge with regard to the vicinal nitrogen and oxygen heteroatom substituents. The N1-aryl residue undergoes oxidative cleavage, and the C3-bromine atom undergoes palladium-mediated coupling reactions, both without disturbing the newly created stereocenters. PMID:25119431

Propagation failures, breathing pulses, and backfiring in an excitable reaction-diffusion system.

PubMed

Manz, Niklas; Steinbock, Oliver

2006-09-01

We report results from experiments with a pseudo-one-dimensional Belousov-Zhabotinsky reaction that employs 1,4-cyclohexanedione as its organic substrate. This excitable system shows traveling oxidation pulses and pulse trains that can undergo complex sequences of propagation failures. Moreover, we present examples for (i) breathing pulses that undergo periodic changes in speed and size and (ii) backfiring pulses that near their back repeatedly generate new pulses propagating in opposite direction.

Chemical transformations during aging of zerovalent iron nanoparticles in the presence of common groundwater dissolved constituents.

PubMed

Reinsch, Brian C; Forsberg, Brady; Penn, R Lee; Kim, Christopher S; Lowry, Gregory V

2010-05-01

Nanoscale zerovalent iron (NZVI) that was aged in simulated groundwater was evaluated for alterations in composition and speciation over 6 months to understand the possible transformations NZVI could undergo in natural waters. NZVI was exposed to 10 mN of various common groundwater anions (Cl(-), NO(3)(-), SO(4)(2-), HPO(4)(2-), and HCO(3)(-)) or to dissolved oxygen (saturated, approximately 9 mg/L). Fresh and exposed NZVI samples, along with Fe-oxide model compounds, were then analyzed using synchrotron radiation X-ray absorption spectroscopy (XAS) to yield both relative oxidation state, using the X-ray absorption near edge structure (XANES), and quantitative speciation information regarding the types and proportions of mineral species present, from analysis of the extended X-ray absorption fine structure (EXAFS). Over 1 month of aging the dissolved anions inhibited the oxidation of the NZVI to varying degrees. Aging for 6 months, however, resulted in average oxidation states that were similar to each other regardless of the anion used, except for nitrate. Nitrate passivated the NZVI surface such that even after 6 months of aging the particles retained nearly the same mineral and Fe(0) content as fresh NZVI. Linear least-squares combination fitting (LCF) of the EXAFS spectra for 1 month-aged samples indicated that the oxidized particles remain predominantly a binary phase system containing Fe(0) and Fe(3)O(4), while the 6 month aged samples contained additional mineral phases such as vivianite (Fe(3)(PO(4))(2).8H(2)O) and iron sulfate species, possibly schwertmannite (Fe(3+)(16)O(16)(OH,SO(4))(12-13).10-12H(2)O). The presence of these additional mineral species was confirmed using synchrotron-based X-ray diffraction (XRD). NZVI exposed to water saturated with dissolved oxygen showed a rapid (<24 h) loss of Fe(0) and evolved both magnetite and maghemite (gamma-Fe(2)O(3)) within the oxide layer. These findings have implications toward the eventual fate, transport, and toxicity of NZVI used for groundwater remediation.

Impact of exposure to low concentrations of nitric oxide on protein profile in murine and human pancreatic islet cells

PubMed Central

Tapia-Limonchi, Rafael; Díaz, Irene; Cahuana, Gladys M; Bautista, Mario; Martín, Franz; Soria, Bernat; Tejedo, Juan R; Bedoya, Francisco J

2014-01-01

Homeostatic levels of nitric oxide (NO) protect efficiently against apoptotic death in both human and rodent pancreatic β cells, but the protein profile of this action remains to be determined. We have applied a 2 dimensional LC-MS-MALDI-TOF/TOF-based analysis to study the impact of protective NO in rat insulin-producing RINm5F cell line and in mouse and human pancreatic islets (HPI) exposed to serum deprivation condition. 24 proteins in RINm5F and 22 in HPI were identified to undergo changes in at least one experimental condition. These include stress response mitochondrial proteins (UQCRC2, VDAC1, ATP5C1, ATP5A1) in RINm5F cells and stress response endoplasmic reticulum proteins (HSPA5, PDIA6, VCP, GANAB) in HPI. In addition, metabolic and structural proteins, oxidoreductases and chaperones related with protein metabolism are also regulated by NO treatment. Network analysis of differentially expressed proteins shows their interaction in glucocorticoid receptor and NRF2-mediated oxidative stress response pathways and eNOS signaling. The results indicate that exposure to exogenous NO counteracts the impact of serum deprivation on pancreatic β cell proteome. Species differences in the proteins involved are apparent. PMID:25658244

Effect of intermediate layers on atomic layer deposition-aluminum oxide protected silver mirrors

NASA Astrophysics Data System (ADS)

Fryauf, David M.; Diaz Leon, Juan J.; Phillips, Andrew C.; Kobayashi, Nobuhiko P.

2017-07-01

This work investigates intermediate materials deposited between silver (Ag) thin-film mirrors and an aluminum oxide (AlOx) barrier overlayer and compares the effects on mirror durability to environmental stresses. Physical vapor deposition of various fluorides, oxides, and nitrides in combination with AlOx by atomic layer deposition (ALD) is used to develop several coating recipes. Ag-AlOx samples with different intermediate materials undergo aggressive high-temperature (80°C), high-humidity (80%) (HTHH) testing for 10 days. Reflectivity of mirror samples is measured before and after HTHH testing, and image processing techniques are used to analyze the specular surface of the samples after HTHH testing. Among the seven intermediate materials used in this work, TiN, MgAl2O4, NiO, and Al2O3 intermediate layers offer more robust protection against chemical corrosion and moisture when compared with samples with no intermediate layer. In addition, results show that the performance of the ALD-AlOx barrier overlayer depends significantly on the ALD-growth process temperature. Because higher durability is observed in samples with less transparent TiN and NiO layers, we propose a figure of merit based on post-HTHH testing reflectivity change and specular reflective mirror surface area remaining after HTHH testing to judge overall barrier performance.

Evidence for negative effects of elevated intra-abdominal pressure on pulmonary mechanics and oxidative stress.

PubMed

Davarcı, I; Karcıoğlu, M; Tuzcu, K; İnanoğlu, K; Yetim, T D; Motor, S; Ulutaş, K T; Yüksel, R

2015-01-01

To compare the effects of pneumoperitoneum on lung mechanics, end-tidal CO2 (ETCO2), arterial blood gases (ABG), and oxidative stress markers in blood and bronchoalveolar lavage fluid (BALF) during laparoscopic cholecystectomy (LC) by using lung-protective ventilation strategy. Forty-six patients undergoing LC and abdominal wall hernia (AWH) surgery were assigned into 2 groups. Measurements and blood samples were obtained before, during pneumoperitoneum, and at the end of surgery. BALF samples were obtained after anesthesia induction and at the end of surgery. Peak inspiratory pressure, ETCO2, and pCO2 values at the 30th minute were significantly increased, while there was a significant decrease in dynamic lung compliance, pH, and pO2 values in LC group. In BALF samples, total oxidant status (TOS), arylesterase, paraoxonase, and malondialdehyde levels were significantly increased; the glutathione peroxidase levels were significantly decreased in LC group. The serum levels of TOS and paraoxonase were significantly higher at the end of surgery in LC group. In addition, arylesterase level in the 30th minute was increased compared to baseline. Serum paraoxonase level at the end of surgery was significantly increased when compared to AWH group. Our study showed negative effects of pneumoperitoneum in both lung and systemic levels despite lung-protective ventilation strategy.

Modeling the Current and Future Roles of Particulate Organic Nitrates in the Southeastern United States.

PubMed

Pye, Havala O T; Luecken, Deborah J; Xu, Lu; Boyd, Christopher M; Ng, Nga L; Baker, Kirk R; Ayres, Benjamin R; Bash, Jesse O; Baumann, Karsten; Carter, William P L; Edgerton, Eric; Fry, Juliane L; Hutzell, William T; Schwede, Donna B; Shepson, Paul B

2015-12-15

Organic nitrates are an important aerosol constituent in locations where biogenic hydrocarbon emissions mix with anthropogenic NOx sources. While regional and global chemical transport models may include a representation of organic aerosol from monoterpene reactions with nitrate radicals (the primary source of particle-phase organic nitrates in the Southeast United States), secondary organic aerosol (SOA) models can underestimate yields. Furthermore, SOA parametrizations do not explicitly take into account organic nitrate compounds produced in the gas phase. In this work, we developed a coupled gas and aerosol system to describe the formation and subsequent aerosol-phase partitioning of organic nitrates from isoprene and monoterpenes with a focus on the Southeast United States. The concentrations of organic aerosol and gas-phase organic nitrates were improved when particulate organic nitrates were assumed to undergo rapid (τ = 3 h) pseudohydrolysis resulting in nitric acid and nonvolatile secondary organic aerosol. In addition, up to 60% of less oxidized-oxygenated organic aerosol (LO-OOA) could be accounted for via organic nitrate mediated chemistry during the Southern Oxidants and Aerosol Study (SOAS). A 25% reduction in nitrogen oxide (NO + NO2) emissions was predicted to cause a 9% reduction in organic aerosol for June 2013 SOAS conditions at Centreville, Alabama.

Synthesis of refractory materials

DOEpatents

Holt, Joseph B.

1984-01-01

Refractory metal nitrides are synthesized during a self-propagating combustion process utilizing a solid source of nitrogren. For this purpose, a metal azide is employed, preferably NaN.sub.3. The azide is combusted with Mg or Ca, and a metal oxide is selected from Groups III-A, IV-A, III-B, IV-B, or a rare earth metal oxide. The mixture of azide, Ca or Mg and metal oxide is heated to the mixture's ignition temperature. At that temperature the mixture is ignited and undergoes self-sustaining combustion until the starter materials are exhausted, producing the metal nitride.

Comment on "Active sites for CO2 hydrogenation to methanol on Cu/ZnO catalysts".

PubMed

Nakamura, Junji; Fujitani, Tadahiro; Kuld, Sebastian; Helveg, Stig; Chorkendorff, Ib; Sehested, Jens

2017-09-01

Kattel et al (Reports, 24 March 2017, p. 1296) report that a zinc on copper (Zn/Cu) surface undergoes oxidation to zinc oxide/copper (ZnO/Cu) during carbon dioxide (CO 2 ) hydrogenation to methanol and conclude that the Cu-ZnO interface is the active site for methanol synthesis. Similar experiments conducted two decades ago by Fujitani and Nakamura et al demonstrated that Zn is attached to formate rather than being fully oxidized. Copyright © 2017, American Association for the Advancement of Science.

Synthesis of refractory materials

DOEpatents

Holt, J.B.

1983-08-16

Refractory metal nitrides are synthesized during a self-propagating combustion process utilizing a solid source of nitrogen. For this purpose, a metal azide is employed, preferably NaN/sub 3/. The azide is combusted with Mg or Ca, and a metal oxide is selected from Groups III-A, IV-A, III-B, IV-B, or a rare earth metal oxide. The mixture of azide, Ca or Mg and metal oxide is heated to the mixture's ignition temperature. At that temperature the mixture is ignited and undergoes self-sustaining combustion until the starter materials are exhausted, producing the metal nitride.

Fundamental Reactive Characterization of Novel Nano-Scale Assembled Fuel/Oxidizers Using a New Mass-Spectrometry T-Jump Approach

DTIC Science & Technology

2014-03-01

Flame 2009, 156, (2), 322-333. 130 YEAR 4: The report has two sections 1. Ignition Initiation of Various Nanothermites 2. Alane as a dopant in...Lake ~ 236 Diiodine pentoxide (I2O5) Sigma-Aldrich < 50 Tin (IV) oxide (SnO2) Sigma-Aldrich < 50 Cobalt (II, III) oxide (Co3O4) Sigma-Aldrich < 50...and O2 (g)[53]. AgI (s) then undergoes melting at 831 K. Cobalt (II, III) oxide (Co3O4) decomposes around 1173 K into CoO (s) and O2 (g). The

Lindqvist Polyoxoniobate Ion-Assisted Electrodeposition of Cobalt and Nickel Water Oxidation Catalysts.

PubMed

Liu, YuPing; Guo, Si-Xuan; Ding, Liang; Ohlin, C André; Bond, Alan M; Zhang, Jie

2015-08-05

A method has been developed for the efficient electrodeposition of cobalt and nickel nanostructures with the assistance of the Lindqvist ion [Nb6O19](8-). Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Raman spectroscopy, inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma optical emission spectrometry, and a range of electrochemical techniques have been used to characterize the morphology, composition, catalytic water oxidation activity and stability of the films in alkaline solution. SEM images show that films consisting of nanoparticles with diameters of ca. 30 to 40 nm are formed after 40-50 potential cycles of deposition. Nb and Co/Ni are detected in the films by EDX. ICP-MS results show an elemental ratio of 1:1 for Co:Nb and 1:3 for Ni:Nb, respectively. Raman spectra reveal the presence of both [Nb6O19](8-) and Co(OH)2/Ni(OH)2. The films exhibit excellent stability and efficiency for electrocatalytic water oxidation in alkaline solution. Turnover frequencies of 12.9 and 13.2 s(-1) were determined by rotating ring disk electrode voltammetry at an overpotential of 480 mV for Co and Ni films, respectively. Fourier transformed large amplitude alternating current (FTAC) voltammetry reveals an additional underlying oxidation process for Co under catalytic turnover conditions, which indicates that a Co(IV) species is involved in the efficient catalytic water oxidation reactions. FTAC voltammetric data also suggest that the Ni films undergoes a clear phase transformation upon aging in aqueous 1 M NaOH and the electrogenerated higher oxidation state Ni from β-NiOOH is the more active form of the catalyst.

Changes in Adenosine Triphosphate and Nitric Oxide in the Urothelium of Patients with Benign Prostatic Hyperplasia and Detrusor Underactivity.

PubMed

Cho, Kang Jun; Koh, Jun Sung; Choi, Jinbong; Kim, Joon Chul

2017-12-01

We investigated changes in the levels of adenosine triphosphate and nitric oxide in the urothelium of men with detrusor underactivity and benign prostatic hyperplasia. We prospectively enrolled in study 30 men who planned to undergo surgical treatment for benign prostatic hyperplasia. The 15 patients with a bladder contractility index less than 100 were assigned to the detrusor underactivity group while the 15 with a bladder contractility index more than 100 were assigned to the no detrusor underactivity group. Bladder mucosal specimens were collected at surgical prostate resection, and adenosine triphosphate and endothelial nitric oxide synthase were analyzed in these specimens. The levels of adenosine triphosphate and endothelial nitric oxide synthase were compared between the 2 groups. The correlation of urodynamic parameters with adenosine triphosphate and endothelial nitric oxide synthase was assessed in all patients. Mean ± SEM endothelial nitric oxide synthase did not significantly differ between the detrusor underactivity and no underactivity groups (3.393 ± 0.969 vs 1.941 ± 0.377 IU/ml, p = 0.247). However, the mean level of adenosine triphosphate in the detrusor underactivity group was significantly lower than in the no detrusor underactivity group (1.289 ± 0.320 vs 9.262 ± 3.285 pmol, p = 0.011). In addition, in all patients adenosine triphosphate positively correlated with the bladder contractility index (r = 0.478, p = 0.018) and with detrusor pressure on maximal flow (r = 0.411, p = 0.046). Adenosine triphosphate was significantly decreased in the urothelium in men with detrusor underactivity and benign prostatic hyperplasia, reflecting the change in detrusor function. Copyright © 2017 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.

Modulation of the oxidative plasmatic state in gastroesophageal reflux disease with the addition of rich water molecular hydrogen: A new biological vision.

PubMed

Franceschelli, Sara; Gatta, Daniela Maria Pia; Pesce, Mirko; Ferrone, Alessio; Di Martino, Giuseppe; Di Nicola, Marta; De Lutiis, Maria Anna; Vitacolonna, Ester; Patruno, Antonia; Grilli, Alfredo; Felaco, Mario; Speranza, Lorenza

2018-05-01

Gastroesophageal reflux disease (GERD), a clinical condition characterized by reflux of gastroduodenal contents in the oesophagus, has proved to demonstrate a strong link between oxidative stress and the development of GERD. Proton pump inhibitors (PPIs) have been universally accepted as first-line therapy for management of GERD. The potential benefits of electrolysed reduced water (ERW), rich in molecular hydrogen, in improving symptoms and systemic oxidative stress associated with GERD was assessed. The study was performed on 84 GERD patients undergoing control treatment (PPI + tap water) or experimental treatment (PPI + ERW) for 3 months. These patients were subjected to the GERD-Health Related Quality of Life Questionnaire as well as derivatives reactive oxigen metabolites (d-ROMs) test, biological antioxidant potential (BAP) test, superoxide anion, nitric oxide and malondialdehyde assays, which were all performed as a proxy for the oxidative/nitrosative stress and the antioxidant potential status. Spearman's correlation coefficient was used to evaluate the correlation between scores and laboratory parameters. Overall results demonstrated that an optimal oxidative balance can be restored and GERD symptoms can be reduced rapidly via the integration of ERW in GERD patients. The relative variation of heartburn and regurgitation score was significantly correlated with laboratory parameters. Thus, in the selected patients, combination treatment with PPI and ERW improves the cellular redox state leading to the improvement of the quality of life as demonstrated by the correlation analysis between laboratory parameters and GERD symptoms. © 2018 The Authors. Journal of Cellular and Molecular Medicine published by John Wiley & Sons Ltd and Foundation for Cellular and Molecular Medicine.

New Insights on Non-Enzymatic Oxidation of Ganglioside GM1 Using Mass Spectrometry

NASA Astrophysics Data System (ADS)

Couto, Daniela; Melo, Tânia; Maciel, Elisabete; Campos, Ana; Alves, Eliana; Guedes, Sofia; Domingues, M. Rosário M.; Domingues, Pedro

2016-12-01

Gangliosides are acidic glycosphingolipids that are present in cell membranes and lipid raft domains, being particularly abundant in central nervous systems. They participate in modulating cell membrane properties, cell-cell recognition, cell regulation, and signaling. Disturbance in ganglioside metabolism has been correlated with the development of diseases, such as neurodegenerative diseases, and in inflammation. Both conditions are associated with an increased production of reactive oxidation species (ROS) that can induce changes in the structure of biomolecules, including lipids, leading to the loss or modification of their function. Oxidized phospholipids are usually involved in chronic diseases and inflammation. However, knowledge regarding oxidation of gangliosides is scarce. In order to evaluate the effect of ROS in gangliosides, an in vitro biomimetic model system was used to study the susceptibility of GM1 (Neu5Ac α2-3(Gal β1-3GalNAc β1-4)Gal β1-4Glc β1Cer) to undergo oxidative modifications. Oxidation of GM1 under Fenton reaction conditions was monitored using high resolution electrospray ionization-mass spectrometry (ESI-MS) and tandem mass spectrometry (ESI-MS/MS). Upon oxidation, GM1 underwent oxidative cleavages in the carbohydrate chain, leading to the formation of other gangliosides GM2 (GalNAcβ1-4Gal(Neu5Acα2-3)1-4Glcβ1Cer), GM3 (Neu5Acα2-3Galβ1-4Glcβ1Cer), asialo-GM1 (Gal β1-3GalNAc β1-4Gal β1-4Glc β1Cer), asialo-GM2 (GalNAc β1-4Gal β1-4Glc β1Cer), of the small glycolipids lactosylceramide (LacCer), glucosylceramide (GlcCer), and of ceramide (Cer). In addition, oxygenated GM1 and GM2 (as keto and hydroxy derivatives), glycans, oxidized glycans, and oxidized ceramides were also identified. Nonenzymatic oxidation of GM1 under oxidative stress contributes to the generation of other gangliosides that may participate in the imbalance of gangliosides metabolism in vivo, through uncontrolled enzymatic pathways and, consequently, play some role in neurodegenerative processes.

Degradation of Gate Oxide Integrity by Formation of Tiny Holes by Metal Contamination of Raw Wafer

NASA Astrophysics Data System (ADS)

Chen, Po-Ying

2008-12-01

Heavy metal atoms (such as Cu) spontaneously undergo a dissolution reaction when they come into contact with silicon. Most investigations in this extensively studied area begin with a clean, bare wafer and focus on metal contamination during the IC manufacturing stage. In this work, the effect of Fe and Cu contamination on raw wafers was elucidated. When two batches of raw wafers are scheduled, one uncontaminated and one with various degrees of contamination ranging from 0.1 to 10 ppb undergo the typical steps of the 90 nm LOGIC complementary metal-oxide-semiconductor (CMOS) semiconductor manufacturing process. The main contribution of this work is the discovery of a previously unidentified cause of gate oxide leakage: the formation of tiny holes by metal contamination during the wafer manufacturing stage. Because tiny holes are formed, a spontaneous reaction can occur even with at very low metal concentration (0.2 ppb), revealing that the wafer manufacturing stage is more vulnerable to metal contamination than the IC manufacturing stage and therefore requires stricter contamination control.

Carbon monoxide alleviates lipopolysaccharide-induced oxidative stress injury through suppressing the expression of Fis1 in NR8383 cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shi, Jia; Yu, Jian-bo, E-mail: yujianbo11@126.com; Liu, Wei

Acute respiratory distress syndrome (ARDS) is one of the most devastating complications of sepsis lacking of effective therapy. Mitochondrial dynamics undergoing continuous fusion and fission play a crucial role in mitochondrial structure and function. Fis1, as a small protein located on the outer membrane of mitochondria, has been thought to be an important protein mediated mitochondrial fission. During ARDS, alveolar macrophages suffer from increased oxidative stress and apoptosis, and also accompanied by disrupted mitochondrial dynamics. In addition, as one of the products of heme degradation catalyzed by heme oxygenase, carbon monoxide (CO) possesses powerful protective properties in vivo or inmore » vitro models, such as anti-inflammatory, antioxidant and anti-apoptosis function. However, there is little evidence that CO alleviates oxidative stress damage through altering mitochondrial fission in alveolar macrophages. In the present study, our results showed that CO increased cell vitality, improved mitochondrial SOD activity, reduced reactive oxygen species (ROS) production and inhibited cell apoptosis in NR8383 exposed to LPS. Meanwhile, CO decreased the expression of Fis1, increased mitochondrial membrane potential and sustained elongation of mitochondria in LPS-incubated NR8383. Overall, our study underscored a critical role of CO in suppressing the expression of Fis1 and alleviating LPS- induced oxidative stress damage in alveolar macrophages. - Highlights: • LPS exposure triggered cell injury in NR8383. • CO alleviated LPS-induced oxidative stress damage in alveolar macrophages. • CO inhibited Fis1 levels and improved mitochondrial function in LPS-induced NR8383.« less

The double-edged sword in pathogenic trypanosomatids: the pivotal role of mitochondria in oxidative stress and bioenergetics.

PubMed

Menna-Barreto, Rubem Figueiredo Sadok; de Castro, Solange Lisboa

2014-01-01

The pathogenic trypanosomatids Trypanosoma brucei, Trypanosoma cruzi, and Leishmania spp. are the causative agents of African trypanosomiasis, Chagas disease, and leishmaniasis, respectively. These diseases are considered to be neglected tropical illnesses that persist under conditions of poverty and are concentrated in impoverished populations in the developing world. Novel efficient and nontoxic drugs are urgently needed as substitutes for the currently limited chemotherapy. Trypanosomatids display a single mitochondrion with several peculiar features, such as the presence of different energetic and antioxidant enzymes and a specific arrangement of mitochondrial DNA (kinetoplast DNA). Due to mitochondrial differences between mammals and trypanosomatids, this organelle is an excellent candidate for drug intervention. Additionally, during trypanosomatids' life cycle, the shape and functional plasticity of their single mitochondrion undergo profound alterations, reflecting adaptation to different environments. In an uncoupling situation, the organelle produces high amounts of reactive oxygen species. However, these species role in parasite biology is still controversial, involving parasite death, cell signalling, or even proliferation. Novel perspectives on trypanosomatid-targeting chemotherapy could be developed based on better comprehension of mitochondrial oxidative regulation processes.

Influence of chain topology on polymer crystallization: poly(ethylene oxide) (PEO) rings vs. linear chains.

PubMed

Zardalidis, George; Mars, Julian; Allgaier, Jürgen; Mezger, Markus; Richter, Dieter; Floudas, George

2016-10-04

The absence of entanglements, the more compact structure and the faster diffusion in melts of cyclic poly(ethylene oxide) (PEO) chains have consequences on their crystallization behavior at the lamellar and spherulitic length scales. Rings with molecular weight below the entanglement molecular weight (M < M e ), attain the equilibrium configuration composed from twice-folded chains with a lamellar periodicity that is half of the corresponding linear chains. Rings with M > M e undergo distinct step-like conformational changes to a crystalline lamellar with the equilibrium configuration. Rings melt from this configuration in the absence of crystal thickening in sharp contrast to linear chains. In general, rings more easily attain their extended equilibrium configuration due to strained segments and the absence of entanglements. In addition, rings have a higher equilibrium melting temperature. At the level of the spherulitic superstructure, growth rates are much faster for rings reflecting the faster diffusion and more compact structure. With respect to the segmental dynamics in their semi-crystalline state, ring PEOs with a steepness index of ∼34 form some of the "strongest" glasses.

Nitric oxide released from JS-K induces cell death by mitotic catastrophe as part of necrosis in glioblastoma multiforme

PubMed Central

Günzle, Jessica; Osterberg, Nadja; Saavedra, Joseph E; Weyerbrock, Astrid

2016-01-01

The nitric oxide (NO) donor JS-K is specifically activated by glutathione S-transferases (GSTs) in GST-overexpressing cells. We have shown the induction of cell death in glioblastoma multiforme (GBM) cells at high JS-K doses but the mechanism remains unclear. The aim of this study was to determine whether NO-induced cell death is triggered by induction of apoptotic or necrotic pathways. For the first time, we demonstrate that NO induces cell death via mitotic catastrophe (MC) with non-apoptotic mechanisms in GBM cells. Moreover, the level of morphological changes indicating MC correlates with increased necrosis. Therefore, we conclude that MC is the main mechanism by which GBM cells undergo cell death after treatment with JS-K associated with necrosis rather than apoptosis. In addition, we show that PARP1 is not an exclusive marker for late apoptosis but is also involved in MC. Activating an alternative way of cell death can be useful for the multimodal cancer therapy of GBM known for its strong anti-apoptotic mechanisms and drug resistance. PMID:27584787

Nitric oxide released from JS-K induces cell death by mitotic catastrophe as part of necrosis in glioblastoma multiforme.

PubMed

Günzle, Jessica; Osterberg, Nadja; Saavedra, Joseph E; Weyerbrock, Astrid

2016-09-01

The nitric oxide (NO) donor JS-K is specifically activated by glutathione S-transferases (GSTs) in GST-overexpressing cells. We have shown the induction of cell death in glioblastoma multiforme (GBM) cells at high JS-K doses but the mechanism remains unclear. The aim of this study was to determine whether NO-induced cell death is triggered by induction of apoptotic or necrotic pathways. For the first time, we demonstrate that NO induces cell death via mitotic catastrophe (MC) with non-apoptotic mechanisms in GBM cells. Moreover, the level of morphological changes indicating MC correlates with increased necrosis. Therefore, we conclude that MC is the main mechanism by which GBM cells undergo cell death after treatment with JS-K associated with necrosis rather than apoptosis. In addition, we show that PARP1 is not an exclusive marker for late apoptosis but is also involved in MC. Activating an alternative way of cell death can be useful for the multimodal cancer therapy of GBM known for its strong anti-apoptotic mechanisms and drug resistance.

Spontaneous Tl(I)-to-Tl(III) oxidation in dynamic heterobimetallic Hg(II)/Tl(I) porphyrin complexes.

PubMed

Ndoyom, Victoria; Fusaro, Luca; Roisnel, Thierry; Le Gac, Stéphane; Boitrel, Bernard

2016-01-11

Strapped heterobimetallic Hg(II)/Tl(I) porphyrin complexes, with both metal ions bridged by the N-core in a dynamic way, undergo spontaneous Tl(I)-to-Tl(III) oxidation leading to a mono-Tl(III) complex and a mixed valence Tl(I)/Tl(III) bimetallic complex. It provides a new opportunity to tune metal ion translocations in bimetallic porphyrin systems.

Can Carbamates Undergo Radical Oxidation in the Soil Environment? A Case Study on Carbaryl and Carbofuran.

PubMed

Ćwieląg-Piasecka, Irmina; Witwicki, Maciej; Jerzykiewicz, Maria; Jezierska, Julia

2017-12-19

Radical oxidation of carbamate insecticides, namely carbaryl and carbofuran, was investigated with spectroscopic (electron paramagnetic resonance [EPR] and UV-vis) and theoretical (density functional theory [DFT] and ab initio orbital-optimized spin-component scaled MP2 [OO-SCS-MP2]) methods. The two carbamates were subjected to reaction with • OH, persistent DPPH • and galvinoxyl radical, as well as indigenous radicals of humic acids. The influence of fulvic acids on carbamate oxidation was also tested. The results obtained with EPR and UV-vis spectroscopy indicate that carbamates can undergo direct reactions with various radical species, oxidizing themselves into radicals in the process. Hence, they are prone to participate in the prolongation step of the radical chain reactions occurring in the soil environment. Theoretical calculations revealed that from the thermodynamic point of view hydrogen atom transfer is the preferred mechanism in the reactions of the two carbamates with the radicals. The activity of carbofuran was determined experimentally (using pseudo-first-order kinetics) and theoretically to be noticeably higher in comparison with carbaryl and comparable with gallic acid. The findings of this study suggest that the radicals present in soil can play an important role in natural remediation mechanisms of carbamates.

Kinetics and mechanism for the sonochemical degradation of a nonionic surfactant.

PubMed

Singla, Ritu; Grieser, Franz; Ashokkumar, Muthupandian

2009-03-26

The sonolytic degradation of the nonionic surfactant, octaethylene glycol monododecyl ether (C(12)E(8)), has been studied at various initial concentrations below and above its critical micelle concentration (CMC). It has been observed that the degradation rate increases with an increase in the initial concentration of the surfactant until the CMC is reached. Above the CMC an almost constant degradation rate is observed, suggesting that the surfactant in its monomer form is involved in the degradation process. The degradation process of C(12)E(8) involves two distinct primary processes occurring at the bubble/solution interface: (a) hydroxylation/oxidation of the surfactant and (b) pyrolytic fragmentation of the surfactant. The oxidative cleavage of ethylene oxide units provides evidence for OH radical attack. Hydroxylation of the ethoxy chain gives rise to various short-chain carboxyalkyl-polyethylene glycol intermediates. The polyethylene glycol chain formed, due to the scission of the C(12)E(8) molecule, undergoes rapid hydroxylation/oxidation to yield simple compounds that have the potential to undergo further degradation. The detection of multiple intermediates indicates that several processes affect the complete degradation pathways of the surfactant molecule. TOC analysis, however, indicates that the sonolytic mineralization of the surfactant is difficult to achieve at reasonable rates due to the relatively low surface activity of the degradation products formed during sonolysis.

Stereoselective Synthesis of Methylene Oxindoles via Palladium(II)-Catalyzed Intramolecular Cross-Coupling of Carbamoyl Chlorides.

PubMed

Le, Christine M; Sperger, Theresa; Fu, Rui; Hou, Xiao; Lim, Yong Hwan; Schoenebeck, Franziska; Lautens, Mark

2016-11-02

We report a highly robust, general and stereoselective method for the synthesis of 3-(chloromethylene)oxindoles from alkyne-tethered carbamoyl chlorides using PdCl 2 (PhCN) 2 as the catalyst. The transformation involves a stereo- and regioselective chloropalladation of an internal alkyne to generate a nucleophilic vinyl Pd II species, which then undergoes an intramolecular cross-coupling with a carbamoyl chloride. The reaction proceeds under mild conditions, is insensitive to the presence of moisture and air, and is readily scalable. The products obtained from this reaction are formed with >95:5 Z:E selectivity in nearly all cases and can be used to access biologically relevant oxindole cores. Through combined experimental and computational studies, we provide insight into stereo- and regioselectivity of the chloropalladation step, as well as the mechanism for the C-C bond forming process. Calculations provide support for a mechanism involving oxidative addition into the carbamoyl chloride bond to generate a high valent Pd IV species, which then undergoes facile C-C reductive elimination to form the final product. Overall, the transformation constitutes a formal Pd II -catalyzed intramolecular alkyne chlorocarbamoylation reaction.

Increased carboxyhemoglobin level during liver resection with inflow occlusion.

PubMed

Godai, Kohei; Hasegawa-Moriyama, Maiko; Kuniyoshi, Tamotsu; Matsunaga, Akira; Kanmura, Yuichi

2013-04-01

Controlling stress responses associated with ischemic changes due to bleeding and ischemia/reperfusion injury is essential for anesthetic management. Endogenous carboxyhemoglobin (COHb) is produced in the oxidative degradation of heme proteins by the stress-response enzyme heme oxygenase. Although the COHb level is elevated in critically ill patients, changes in endogenous COHb during anesthesia have not been well investigated. Therefore, we evaluated changes in endogenous COHb levels in patients undergoing liver resections with inflow occlusion. Levels of COHb were significantly increased after the Pringle maneuver. The inflow occlusion time in patients with increased COHb after the Pringle maneuver (∆COHb > 0.3 %) was significantly longer than in patients without increased COHb (∆COHb < 0.3 %) (P = 0.01). In addition, COHb changes were correlated with inflow occlusion time (P = 0.005, R(2) = 0.21). Neither total blood loss, transfusion volume of packed red blood cells, operation time, nor anesthetic time differed between patients with and without increased COHb. The results indicated that endogenous COHb levels were increased by inflow occlusion in patients undergoing liver resections, which suggests that changes in COHb may correlate with hepatic ischemia/reperfusion injury induced by inflow occlusion.

Graphene oxide-MnO2 nanocomposite for supercapacitor application

NASA Astrophysics Data System (ADS)

Muhammed Shafi, P.; Vishal, Jose K.; Chandra Bose, A.

2016-09-01

Increased depletion of fossil fuels along with global warming and climate change made the society to think about alternate green and sustainable energy sources and better energy storage devices. Extensive research has been performed on the development of solar cells, fuel cells, Lithium- ion battery and supercapacitors to combat the green house effect and its consequences, and to meet the increased energy crisis. Supercapacitors, also known as electrochemical capacitors are gained a great attention because of their pulse power supply, long cycle life (>100,000), simple principle and high dynamic of charge propagation. Its greater power density than lithium- ion battery and much larger energy density than conventional capacitors brought super capacitors to a promising energy storage device to meet the increased energy demands. Here we demonstrate supercapacitor electrode materials with graphene oxide (electric double layer capacitor) and α-MnO2 nanomaterial (pseudo-capacitor), as well as composite of these materials, which means that the bulk of the material undergoes a fast redox reaction to provide the capacitive response and they exhibit superior specific energies in addition to the carbon-based supercapacitors (double-layer capacitors). A simple soft chemical route is utilized to synthesize graphene oxide, α-MnO2 and graphene oxide-MnO2 composite. The phase and the structure of the synthesized materials are studied using X-ray diffractometry (XRD). The functional group and the presence of impurities are understood from Fourier transform infrared (FTIR) spectra. The capacitive properties of the graphene oxide, graphene oxide - MnO2 nanocomposite and α-MnO2 are tested with the help of cyclic voltammetry (CV) and galvanostatic charge - discharge techniques using 1 M Na2SO4 in aqueous solution as electrolyte. It was found that graphene oxide - MnO2 nanocomposite shows better electrochemical behaviour compared to individual graphene oxide and α-MnO2 nanomaterial.

Cellular glutathione levels in HL-60 cells during respiratory burst are not correlated with ultra-weak photon emission.

PubMed

Burgos, Rosilene Cristina Rossetto; Zhang, Wei; van Wijk, Eduard P A; Hankemeier, Thomas; Ramautar, Rawi; van der Greef, Jan

2017-10-01

Recently, ultra-weak photon emission (UPE) was developed as a novel tool for measuring oxidative metabolic processes, as its generation is related to reactive oxygen species (ROS). Both an imbalance in ROS or the uncontrolled production of ROS can lead to oxidative stress, which is commonly associated with many diseases. In addition to playing several biological functions, the thiol amino acid glutathione has an important antioxidant function in the body's defense against ROS. Specifically, glutathione is an important endogenous antioxidant that helps maintain oxidant levels. At the cellular level, glutathione is present in its reduced form (GSH) at relatively high concentrations (in the millimolar range) and in its oxidized form (GSSG) at low concentrations (in the micromolar range). Thus, the GSH/GSSG ratio is often used as an indicator of cellular redox state. Here, we used the HL-60 cell line as a model system in order to determine whether UPE is correlated with intracellular GSH and GSSG levels. HL-60 cells were differentiated into neutrophil-like cells and then stimulated to undergo respiratory burst. We then recorded UPE in real time for 9000 seconds and used capillary electrophoresis coupled to mass spectrometry to measure GSH and GSSG levels in cell extracts. We found that although respiratory burst significantly decreased the GSH/GSSG ratio, this change was not significantly correlated with the UPE profile. Copyright © 2017 Elsevier B.V. All rights reserved.

A novel accelerated oxidative stability screening method for pharmaceutical solids.

PubMed

Zhu, Donghua Alan; Zhang, Geoff G Z; George, Karen L S T; Zhou, Deliang

2011-08-01

Despite the fact that oxidation is the second most frequent degradation pathway for pharmaceuticals, means of evaluating the oxidative stability of pharmaceutical solids, especially effective stress testing, are still lacking. This paper describes a novel experimental method for peroxide-mediated oxidative stress testing on pharmaceutical solids. The method utilizes urea-hydrogen peroxide, a molecular complex that undergoes solid-state decomposition and releases hydrogen peroxide vapor at elevated temperatures (e.g., 30°C), as a source of peroxide. The experimental setting for this method is simple, convenient, and can be operated routinely in most laboratories. The fundamental parameter of the system, that is, hydrogen peroxide vapor pressure, was determined using a modified spectrophotometric method. The feasibility and utility of the proposed method in solid form selection have been demonstrated using various solid forms of ephedrine. No degradation was detected for ephedrine hydrochloride after exposure to the hydrogen peroxide vapor for 2 weeks, whereas both anhydrate and hemihydrate free base forms degraded rapidly under the test conditions. In addition, both the anhydrate and the hemihydrate free base degraded faster when exposed to hydrogen peroxide vapor at 30°C under dry condition than at 30°C/75% relative humidity (RH). A new degradation product was also observed under the drier condition. The proposed method provides more relevant screening conditions for solid dosage forms, and is useful in selecting optimal solid form(s), determining potential degradation products, and formulation screening during development. Copyright © 2011 Wiley-Liss, Inc.

The change in serum Thiol/Disulphide homeostasis after transrectal ultrasound guided prostate biopsy

PubMed Central

Tokgöz, Hüsnü; Taş, Selim; Giray, Özlem; Yalçınkaya, Soner; Tokgöz, Özlem; Koca, Cemile; Savaş, Murat; Erel, Özcan

2017-01-01

ABSTRACT Objectives The aim of this prospective clinical study was to investigate variations in a novel oxidative stress marker (thiol/disulphide homeostasis) in men who underwent transrectal ultrasound guided prostate biopsy (TRUSB). Materials and Methods A total of 22 men undergoing TRUSB of the prostate were enrolled in the study. Patients with abnormal digital rectal examination and/or total prostate specific antigen (PSA) over 4ng/mL underwent TRUSB with 12 cores. Serum samples were obtained before and just after the procedure to evaluate the possible changes in thiol/disulphide homeostasis. Mean age, total PSA and free PSA, prostate volume and histopathological data were also recorded. Results Mean age of the study population was 65.05±8.89 years. Significant decreases in native and total thiol levels were documented after the biopsy procedure. However, serum disulphide levels and disulphide/native thiol, disulphide/total thiol and native/total thiol ratios did not significantly change after TRUSB. No correlation was observed between oxidative parameters and total PSA and free PSA levels, prostate volume and histopathology of the prostate. However, mean patient age was significantly correlated with mean native and total thiol levels. Conclusion Significant decreases in serum native and total thiol levels related to the prostate biopsy procedure suggest that TRUSB causes acute oxidative stress in the human body. Since our trial is the first in the current literature to investigate these oxidative stress markers in urology practice, additional studies are warranted. PMID:28128906

HBOC vasoactivity: interplay between nitric oxide scavenging and capacity to generate bioactive nitric oxide species.

PubMed

Cabrales, Pedro; Friedman, Joel M

2013-06-10

Despite many advances in blood substitute research, the development of materials that are effective in maintaining blood volume and oxygen delivery remains a priority for emergency care and trauma. Clinical trials on hemoglobin (Hb)-based oxygen carriers (HBOCs) have not provided information on the mechanism of toxicity, although all commercial formulations have safety concerns. Specifically, it is important to reconcile the different hypotheses of Hb toxicity, such as nitric oxide (NO) depletion and oxidative reactions, to provide a coherent molecular basis for designing a safe HBOC. HBOCs with different sizes often exhibit differences in the degree of HBOC-induced vasoactivity. This has been attributed to differences in the degree of NO scavenging and in the extent of Hb extravasation. Additionally, it is appears that Hb can undergo reactions that compensate for NO scavenging by generating bioactive forms of NO. Engineering modifications to enhance bioactive NO production can result in diminished oxygen delivery by virtue of increased oxygen affinity. This strategy can prevent the HBOC from fulfilling the intended goal on preserving oxygenation; however, the NO production effects will increase perfusion and oxygen transport. Hb modifications influence NO scavenging and the capacity of certain HBOCs to compensate for NO scavenging through nitrite-mediated reactions that generate bioactive NO. Based on the current understanding of these NO-related factors, possible synthetic strategies are presented that address how HBOC formulations can be prepared that: (i) effectively deliver oxygen, (ii) maintain tissue perfusion, and (iii) limit/reverse underlying inflammation within the vasculature.

The change in serum Thiol/Disulphide homeostasis after transrectal ultrasound guided prostate biopsy.

PubMed

Tokgöz, Hüsnü; Taş, Selim; Giray, Özlem; Yalçınkaya, Soner; Tokgöz, Özlem; Koca, Cemile; Savaş, Murat; Erel, Özcan

2017-01-01

The aim of this prospective clinical study was to investigate variations in a novel oxidative stress marker (thiol/disulphide homeostasis) in men who underwent transrectal ultrasound guided prostate biopsy (TRUSB). A total of 22 men undergoing TRUSB of the prostate were enrolled in the study. Patients with abnormal digital rectal examination and/or total prostate specific antigen (PSA) over 4ng/mL underwent TRUSB with 12 cores. Serum samples were obtained before and just after the procedure to evaluate the possible changes in thiol/disulphide homeostasis. Mean age, total PSA and free PSA, prostate volume and histopathological data were also recorded. Mean age of the study population was 65.05±8.89 years. Significant decreases in native and total thiol levels were documented after the biopsy procedure. However, serum disulphide levels and disulphide/native thiol, disulphide/total thiol and native / total thiol ratios did not significantly change after TRUSB. No correlation was observed between oxidative parameters and total PSA and free PSA levels, prostate volume and histopathology of the prostate. However, mean patient age was significantly correlated with mean native and total thiol levels. Significant decreases in serum native and total thiol levels related to the prostate biopsy procedure suggest that TRUSB causes acute oxidative stress in the human body. Since our trial is the first in the current literature to investigate these oxidative stress markers in urology practice, additional studies are warranted. Copyright® by the International Brazilian Journal of Urology.

Sintering in Ceramics and Solid Oxide Fuel Cells

NASA Astrophysics Data System (ADS)

Hunt, Clay Dale

Nature's propensity to minimize energy, and the change in energy with respect to position, drives diffusion. Diffusion is a means by which mass transport resulting in the bonding of the particles of a powder compact can be achieved without melting. This phenomenon occurs in powdered materials near their melting temperature, and is referred to as "sintering". Because of the extreme melting temperature of some materials, sintering might be the only practical means of processing. The complexity and subtlety of sintering ceramics motivated the evaluation of empirical data and existing sintering models. This project examined polycrystalline cubic-zirconia sintering with and without transition-metal oxide additions that change sintering behavior. This study was undertaken to determine how sintering aids affect the driving force, and activation energy, the energy barrier that must be overcome in order for an atom or ion to diffuse, of the densification occurring during sintering. Examination of commercially-available cubic-zirconia powder sintering behavior was undertaken with dilatometry, which allows monitoring of the length change a material undergoes as it sinters, and with scanning electron microscopy, which facilitates the study of sintered-sample microstructure. MATLAB algorithms quantifying sintering results were developed. Results from this work include proposed definitions of a 26-year-old undefined function of density factor in a well-accepted mathematical model of sintering. These findings suggest activation energy is not changing with density, as is suggested by recent published results. The first numerical integration of the studied sintering model has been performed. With these tools, a measure of the activation energy of densification of cubic-zirconia with and without the addition of cobalt-oxide as a sintering aid has been performed. The resulting MATLAB algorithms can be used in future sintering studies. It is concluded that sintering enhancement achieved with cobalt-oxide addition comes from reduction in activation energy of densification of cubic-zirconia. Further, it is suggested that the activation energy of densification does not change with material density. This conclusion is supported by the sensitivity of the numerical integration of the aforementioned sintering model to changes in activation energy.

Dynamic of oxidative and nitrosative stress markers during the convalescent period of stroke patients undergoing rehabilitation.

PubMed

Manolescu, Bogdan Nicolae; Berteanu, M; Oprea, E; Chiriac, N; Dumitru, L; Vladoiu, S; Popa, O; Ianas, O

2011-07-01

Stroke patients have a redox imbalance, a consequence of both the cerebrovascular event and the associated pathological conditions. Our study was aimed to investigate the dynamic of some oxidative and nitrosative markers during the convalescent phase of postacute stroke patients undergoing rehabilitation. We assessed thiol, advanced oxidation protein product, protein carbonyl, 3-nitro-l-tyrosine, ceruloplasmin and oxidized LDL concentrations, as well as gamma-glutamyltranspeptidase (GGT) activity in 20 patients at the beginning of the hospitalization and at the discharge moment, respectively, and 24 apparently healthy controls. We found significantly increased values for GGT (P = 0.04), ceruloplasmin (P = 0.01) and protein carbonyl (P = 0.04) in stroke patients at the hospitalization moment when compared with healthy controls, while total thiols were significantly decreased (P = 0.002). Rehabilitation was associated with a significant decrease of protein carbonyl (P = 0.03) and oxidized LDL particle concentrations (P = 0.03), as well as GGT activity (P = 0.02). At the hospitalization moment, both GGT and ceruloplasmin were significantly negatively correlated with non-proteic thiols (r = -0.44, P = 0.049, and r = -0.53, P = 0.015, respectively) and significantly positively with protein carbonyls (r = +0.80, P < 0.001, and r = +0.69, P < 0.001, respectively) suggesting putative roles of GGT and ceruloplasmin in the redox imbalance. These results highlight the existence of a redox imbalance in postacute stroke patients, and the possible benefits of an antioxidant-based therapy for the recovery of these patients.

Characterization of oxidation end product of plasma albumin 'in vivo'.

PubMed

Musante, Luca; Bruschi, Maurizio; Candiano, Giovanni; Petretto, Andrea; Dimasi, Nazzareno; Del Boccio, Piero; Urbani, Andrea; Rialdi, Giovanni; Ghiggeri, Gian Marco

2006-10-20

Anti-oxidants are paradoxically much lower in plasma than inside cells even blood is comparably exposed to the oxidative stress. 'In vitro' models suggest a critical role of albumin as substitutive anti-oxidant in plasma but no proof for this role is available 'in vivo.' Herein, we demonstrate by LC/MS/MS that plasma albumin undergoes massive oxidation in primary nephrotic syndrome, involving stable sulphonation SO3- of the free SH of Cys 34 with +48Da increase in exact mass of the protein (ESI-MS) and formation of a fast moving isoform in the pH range between 5 and 7. Physical-chemical experiments with DSC and fluorescence spectra indicate a thermal stabilization of the structure upon oxidation. This is the first demonstration of massive oxidation of albumin 'in vivo' that reflects a functional role of the protein. Free radicals should be implicated in the pathogenesis of proteinuria in human FSGS.

Reactivity of nitrido complexes of ruthenium(VI), osmium(VI), and manganese(V) bearing Schiff base and simple anionic ligands.

PubMed

Man, Wai-Lun; Lam, William W Y; Lau, Tai-Chu

2014-02-18

Nitrido complexes (M≡N) may be key intermediates in chemical and biological nitrogen fixation and serve as useful reagents for nitrogenation of organic compounds. Osmium(VI) nitrido complexes bearing 2,2':6',2″-terpyridine (terpy), 2,2'-bipyridine (bpy), or hydrotris(1-pyrazolyl)borate anion (Tp) ligands are highly electrophilic: they can react with a variety of nucleophiles to generate novel osmium(IV)/(V) complexes. This Account describes our recent results studying the reactivity of nitridocomplexes of ruthenium(VI), osmium(VI), and manganese(V) that bear Schiff bases and other simple anionic ligands. We demonstrate that these nitrido complexes exhibit rich chemical reactivity. They react with various nucleophiles, activate C-H bonds, undergo N···N coupling, catalyze the oxidation of organic compounds, and show anticancer activities. Ruthenium(VI) nitrido complexes bearing Schiff base ligands, such as [Ru(VI)(N)(salchda)(CH3OH)](+) (salchda = N,N'-bis(salicylidene)o-cyclohexyldiamine dianion), are highly electrophilic. This complex reacts readily at ambient conditions with a variety of nucleophiles at rates that are much faster than similar reactions using Os(VI)≡N. This complex also carries out unique reactions, including the direct aziridination of alkenes, C-H bond activation of alkanes and C-N bond cleavage of anilines. The addition of ligands such as pyridine can enhance the reactivity of [Ru(VI)(N)(salchda)(CH3OH)](+). Therefore researchers can tune the reactivity of Ru≡N by adding a ligand L trans to nitride: L-Ru≡N. Moreover, the addition of various nucleophiles (Nu) to Ru(VI)≡N initially generate the ruthenium(IV) imido species Ru(IV)-N(Nu), a new class of hydrogen-atom transfer (HAT) reagents. Nucleophiles also readily add to coordinated Schiff base ligands in Os(VI)≡N and Ru(VI)≡N complexes. These additions are often stereospecific, suggesting that the nitrido ligand has a directing effect on the incoming nucleophile. M≡N is also a potential platform for the design of new oxidation catalysts. For example, [Os(VI)(N)Cl4](-) catalyzes the oxidation of alkanes by a variety of oxidants, and the addition of Lewis acids greatly accelerates these reactions. [Mn(V)(N)(CN)4]2(-) is another highly efficient oxidation catalyst, which facilitates the epoxidation of alkenes and the oxidation of alcohols to carbonyl compounds using H2O2. Finally, M≡N can potentially bind to and exert various effects on biomolecules. For example, a number of Os(VI)≡N complexes exhibit novel anticancer properties, which may be related to their ability to bind to DNA or other biomolecules.

Ni-Catalyzed Carbon-Carbon Bond-Forming Reductive Amination.

PubMed

Heinz, Christoph; Lutz, J Patrick; Simmons, Eric M; Miller, Michael M; Ewing, William R; Doyle, Abigail G

2018-02-14

This report describes a three-component, Ni-catalyzed reductive coupling that enables the convergent synthesis of tertiary benzhydryl amines, which are challenging to access by traditional reductive amination methodologies. The reaction makes use of iminium ions generated in situ from the condensation of secondary N-trimethylsilyl amines with benzaldehydes, and these species undergo reaction with several distinct classes of organic electrophiles. The synthetic value of this process is demonstrated by a single-step synthesis of antimigraine drug flunarizine (Sibelium) and high yielding derivatization of paroxetine (Paxil) and metoprolol (Lopressor). Mechanistic investigations support a sequential oxidative addition mechanism rather than a pathway proceeding via α-amino radical formation. Accordingly, application of catalytic conditions to an intramolecular reductive coupling is demonstrated for the synthesis of endo- and exocyclic benzhydryl amines.

Preparation of redox polymer cathodes for thin film rechargeable batteries

DOEpatents

Skotheim, T.A.; Lee, H.S.; Okamoto, Yoshiyuki.

1994-11-08

The present invention relates to the manufacture of thin film solid state electrochemical devices using composite cathodes comprising a redox polymer capable of undergoing oxidation and reduction, a polymer solid electrolyte and conducting carbon. The polymeric cathode material is formed as a composite of radiation crosslinked polymer electrolytes and radiation crosslinked redox polymers based on polysiloxane backbones with attached organosulfur side groups capable of forming sulfur-sulfur bonds during electrochemical oxidation.

Metal-free, flexible triboelectric generator based on MWCNT mesh film and PDMS layers

NASA Astrophysics Data System (ADS)

Hwang, Hayoung; Lee, Kang Yeol; Shin, Dongjoon; Shin, Jungho; Kim, Sangtae; Choi, Wonjoon

2018-06-01

We demonstrate a metal-free triboelectric energy harvester consisted of MWCNT mesh film and PDMS layer. Upon touch from a finger, the single electrode-mode energy harvester generates up to 27.0 W/m2 output power at 10 MΩ matched impedance. The device generates stable power upon touch by bare fingers or gloved fingers. Using copper counter electrode results in decreased power output, due to the weaker tendency in triboelectrification. The power output also scales with the pressure applied by the finger. The intertwined, condensed MWCNT network acts as a flexible yet effective current collector, with resistance across the device less than 10 Ω. This current collector possesses strong corrosion resistance and stability against potential oxidation, while its metal counterpart may undergo oxidation over extended exposure to air or frequent fracture upon straining. The flexible device form may be applied to various curved or irregular surfaces that undergo frequent human touches.

Mitochondrial fatty acid biosynthesis and muscle fiber plasticity in very long-chain acyl-CoA dehydrogenase-deficient mice.

PubMed

Tucci, Sara; Mingirulli, Nadja; Wehbe, Zeinab; Dumit, Verónica I; Kirschner, Janbernd; Spiekerkoetter, Ute

2018-01-01

The white skeletal muscle of very long-chain acyl-CoA-dehydrogenase-deficient (VLCAD -/- ) mice undergoes metabolic modification to compensate for defective β-oxidation in a progressive and time-dependent manner by upregulating glucose oxidation. This metabolic regulation seems to be accompanied by morphologic adaptation of muscle fibers toward the glycolytic fiber type II with the concomitant upregulation of mitochondrial fatty acid biosynthesis (mFASII) and lipoic acid biosynthesis. Dietary supplementation of VLCAD -/- mice with different medium-chain triglycerides over 1 year revealed that odd-chain species has no effect on muscle fiber switch, whereas even-chain species inhibit progressive metabolic adaptation. Our study shows that muscle may undergo adaptive mechanisms that are modulated by dietary supplementation. We describe for the first time a concomitant change of mFASII in this muscular adaptation process. © 2017 Federation of European Biochemical Societies.

Oxidation in the complementarity-determining regions differentially influences the properties of therapeutic antibodies

PubMed Central

Dashivets, Tetyana; Stracke, Jan; Dengl, Stefan; Knaupp, Alexander; Pollmann, Jan; Buchner, Johannes; Schlothauer, Tilman

2016-01-01

ABSTRACT Therapeutic antibodies can undergo a variety of chemical modification reactions in vitro. Depending on the site of modification, either antigen binding or Fc-mediated functions can be affected. Oxidation of tryptophan residues is one of the post-translational modifications leading to altered antibody functionality. In this study, we examined the structural and functional properties of a therapeutic antibody construct and 2 affinity matured variants thereof. Two of the 3 antibodies carry an oxidation-prone tryptophan residue in the complementarity-determining region of the VL domain. We demonstrate the differences in the stability and bioactivity of the 3 antibodies, and reveal differential degradation pathways for the antibodies susceptible to oxidation. PMID:27612038

Kinetics and thermodynamics of oxidation mediated reaction in L-cysteine and its methyl and ethyl esters in dimethyl sulfoxide-d6 by NMR spectroscopy

NASA Astrophysics Data System (ADS)

Dougherty, Ryan J.; Singh, Jaideep; Krishnan, V. V.

2017-03-01

L-Cysteine (L-Cys), L-Cysteine methyl ester (L-CysME) or L-Cysteine ethyl ester (L-CysEE), when dissolved in dimethyl sulfoxide, undergoes an oxidation process. This process is slow enough and leads to nuclear magnetic resonance (NMR) spectral changes that could be monitored in real time. The oxidation mediated transition is modeled as a pseudo-first order kinetics and the thermodynamic parameters are estimated using the Eyring's formulation. L-Cysteine and their esters are often used as biological models due to the remarkable thiol group that can be found in different oxidation states. This oxidation mediated transition is due to the combination of thiol oxidation to a disulfide followed by solvent-induced effects may be relevant in designing cysteine-based molecular models.

Electronic doping of transition metal oxide perovskites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cammarata, Antonio, E-mail: cammaant@fel.cvut.cz; Rondinelli, James M.

2016-05-23

CaFeO{sub 3} is a prototypical negative charge transfer oxide that undergoes electronic metal-insulator transition concomitant with a dilation and contraction of nearly rigid octahedra. Altering the charge neutrality of the bulk system destroys the electronic transition, while the structure is significantly modified at high charge content. Using density functional theory simulations, we predict an alternative avenue to modulate the structure and the electronic transition in CaFeO{sub 3}. Charge distribution can be modulated using strain-rotation coupling and thin film engineering strategies, proposing themselves as a promising avenue for fine tuning electronic features in transition metal-oxide perovskites.

A new and efficient synthetic method for 15N3-labeled cytosine nucleosides: Dimroth rearrangement of cytidine N3-oxides.

PubMed

Sako, Magoichi; Kawada, Hiroyoshi

2004-11-12

The treatment of (15)N(4)-labeled cytidine N(3)-oxide and (15)N(4)-labeled 2'-deoxycytidine N(3)-oxide, prepared from the appropriate unprotected uridines in three reaction steps, with benzyl bromide in the presence of excess lithium methoxide allowed the smooth occurrence of their Dimroth rearrangement even under mild conditions leading to the corresponding (15)N(3)-labeled uridine 4-O-benzyloximes which can easily undergo the reductive N-O bond cleavage to give the desirable (15)N(3)-labeled cytosine nucleosides in high total yields.

Nanoscale Phase Stability Reversal During the Nucleation and Growth of Titanium Oxide Minerals

NASA Astrophysics Data System (ADS)

Hummmer, D. R.; Heaney, P. J.; Kubicki, J. D.; Kent, P. R.; Post, J. E.

2008-12-01

Fine-grained titanium oxide minerals are important in soils, where they affect a variety of geochemical processes. They are also industrially important as catalysts, pigments, food additives, and dielectrics. Recent research has indicated an apparent reversal of thermodynamic stability between TiO2 phases at the nanoscale thought to be caused by an increased contribution of surface energy to the total free energy. Time-resolved X-ray diffraction (XRD) experiments in which titanium oxides crystallize from aqueous TiCl4 solutions confirm that anatase, a metastable phase, is always the first phase to nucleate under our range of initial conditions. Rutile peaks are observed only minutes after the first appearance of anatase, after which anatase abundance slowly decreases while rutile continues to form. Whole pattern refinement of diffraction data reveals that lattice constants of both phases increase throughout the crystallization process. In addition, transmission electron microscope (TEM) observations and kinetic modeling indicate that anatase does not undergo a solid-state transformation to the rutile structure as once thought. Instead, anatase appears to re-dissolve and then feed the growth of already nucleated rutile nanocrystals. Density functional theory (DFT) calculations were employed to model 1, 2, and 3 nm particles of both mineral phases. The total surface energies calculated from these models did yield lower values for anatase than for rutile by 8-13 kJ/mol depending on particle size, indicating that surface free energy is sufficient to account for stability reversal. However, these whole-particle surface energies were much higher than the sum of energies of each particle's constituent crystallographic surfaces. We attribute the excess energy to defects associated with the edges and corners of nanoparticles, which are not present on a 2-D periodic surface. This previously unreported edge and corner energy may play a dominant role in the stability reversal of nanocrystalline titanium oxides, as well as other mineral systems susceptible to reversals in phase stability at the nanoscale.

Exercise and chemotherapy-induced amenorrhea.

PubMed

Mathis, Katlynn M; Sturgeon, Kathleen M; Winkels, Renate M; Wiskemann, Joachim; Williams, Nancy I; Schmitz, Kathryn

2018-07-01

Chemotherapy-induced amenorrhea (CIA) is the temporary or permanent loss of menses experienced by premenopausal women undergoing chemotherapy treatment for cancer. Two possible mechanisms through which chemotherapy induces CIA have been identified: systemic endothelial dysfunction, resulting in decreased blood flow to the ovaries, and increased oxidative stress within the ovaries, both of which are proposed to lead to apoptosis of follicles. Endothelial dysfunction in ovarian arteries in women undergoing or who have undergone chemotherapy treatment is characterized by prothrombotic changes and thickening of the vascular wall. These changes result in occlusion of the blood vessels. Oxidative stress is increased and antioxidants decreased in the ovaries secondary to chemotherapy drugs, specifically cyclophosphamide. It is hypothesized that low to moderate intensity aerobic exercise during chemotherapy may prevent these changes and lessen the risk for developing CIA in premenopausal women. Low to moderate intensity aerobic exercise has been shown to improve endothelial function and blood flow in patients with cardiovascular disease-a disease state characterized by endothelial dysfunction and for which patients who have undergone chemotherapy are at increased risk. In mice, moderate intensity aerobic exercise has been shown to decrease the amount of oxidative stress within the ovaries, and in humans, chronic aerobic exercise has been shown to increase antioxidant production systemically. This hypothesis should be tested in both a mouse model, using sedentary and exercising mice treated with chemotherapy drugs that commonly result in CIA, as well as a human model to determine the effects of low to moderate intensity aerobic exercise on ovarian function in premenopausal women undergoing chemotherapy. Copyright © 2018 Elsevier Ltd. All rights reserved.

Stereoselective Borylative Ketone-Diene Coupling

PubMed Central

Cho, Hee Yeon; Yu, Zhiyong; Morken, James P.

2011-01-01

In the presence of catalytic Ni(cod)2 and P(t-Bu)3, ketones, dienes, and B2(pin)2 undergo a stereoselective multicomponent coupling reaction. Upon oxidation, the reaction furnishes 1,3-diols as the major reaction product. PMID:21905748

Linking Arsenic Metabolism and Toxic Effects

EPA Science Inventory

Although arsenic has been long recognized as a toxicant and a carcinogen, the molecular basis for few of its adverse effects are well understood. Like other metalloids, arsenic undergoes extensive metabolism involving oxidation state changes and formation of methyl-arsenic bonds ...

Synthesis of Graphite Oxide with Different Surface Oxygen Contents Assisted Microwave Radiation

PubMed Central

Ibarra-Hernández, Adriana

2018-01-01

Graphite oxide is synthesized via oxidation reaction using oxidant compounds that have lattice defects by the incorporation of unlike functional groups. Herein, we report the synthesis of the graphite oxide with diverse surface oxygen content through three (B, C, D) different modified versions of the Hummers method assisted microwave radiation compared with the conventional graphite oxide sample obtained by Hummers method (A). These methods allow not only the production of graphite oxide but also reduced graphene oxide, without undergoing chemical, thermal, or mechanical reduction steps. The values obtained of C/O ratio were ~2, 3.4, and ~8.5 for methodologies C, B, and D, respectively, indicating the presence of graphite oxide and reduced graphene oxide, according to X-ray photoelectron spectroscopy. Raman spectroscopy of method D shows the fewest structural defects compared to the other methodologies. The results obtained suggest that the permanganate ion produces reducing species during graphite oxidation. The generation of these species is attributed to a reversible reaction between the permanganate ion with π electrons, ions, and radicals produced after treatment with microwave radiation. PMID:29438280

Multiple transformation pathways of p-arsanilic acid to inorganic arsenic species in water during UV disinfection.

PubMed

Li, Suqi; Xu, Jing; Chen, Wei; Yu, Yingtan; Liu, Zizheng; Li, Jinjun; Wu, Feng

2016-09-01

p-Arsanilic acid (p-ASA) is widely used in China as livestock and poultry feed additive for promoting animal growth. The use of organoarsenics poses a potential threat to the environment because it is mostly excreted by animals in its original form and can be transformed by UV-Vis light excitation. This work examined the initial rate and efficiency of p-ASA phototransformation under UV-C disinfection lamp. Several factors influencing p-ASA phototransformation, namely, pH, initial concentration, temperature, as well as the presence of NaCl, NH4(+), and humic acid, were investigated. Quenching experiments and LC-MS were performed to investigate the mechanism of p-ASA phototransformation. Results show that p-ASA was decomposed to inorganic arsenic (including As(III) and As(V)) and aromatic products by UV-C light through direct photolysis and indirect oxidation. The oxidation efficency of p-ASA by direct photosis was about 32%, and those by HO and (1)O2 were 19% and 49%, respectively. Cleavage of the arsenic-benzene bond through direct photolysis, HO oxidation or (1)O2 oxidation results in simultaneous formation of inorganic As(III), As(IV), and As(V). Inorganic As(III) is oxidized to As(IV) and then to As(V) by (1)O2 or HO. As(IV) can undergo dismutation or simply react with oxygen to produce As(V) as well. Reactions of the organic moieties of p-ASA produce aniline, aminophenol and azobenzene derivatives as main products. The photoconvertible property of p-ASA implies that UV disinfection of wastewaters from poultry and swine farms containing p-ASA poses a potential threat to the ecosystem, especially agricultural environments. Copyright © 2016. Published by Elsevier B.V.

Human ER Oxidoreductin-1α (Ero1α) Undergoes Dual Regulation through Complementary Redox Interactions with Protein-Disulfide Isomerase.

PubMed

Kanemura, Shingo; Okumura, Masaki; Yutani, Katsuhide; Ramming, Thomas; Hikima, Takaaki; Appenzeller-Herzog, Christian; Akiyama, Shuji; Inaba, Kenji

2016-11-11

In the mammalian endoplasmic reticulum, oxidoreductin-1α (Ero1α) generates protein disulfide bonds and transfers them specifically to canonical protein-disulfide isomerase (PDI) to sustain oxidative protein folding. This oxidative process is coupled to the reduction of O 2 to H 2 O 2 on the bound flavin adenine dinucleotide cofactor. Because excessive thiol oxidation and H 2 O 2 generation cause cell death, Ero1α activity must be properly regulated. In addition to the four catalytic cysteines (Cys 94 , Cys 99 , Cys 104 , and Cys 131 ) that are located in the flexible active site region, the Cys 208 -Cys 241 pair located at the base of another flexible loop is necessary for Ero1α regulation, although the mechanistic basis is not fully understood. The present study revealed that the Cys 208 -Cys 241 disulfide was reduced by PDI and other PDI family members during PDI oxidation. Differential scanning calorimetry and small angle X-ray scattering showed that mutation of Cys 208 and Cys 241 did not grossly affect the thermal stability or overall shape of Ero1α, suggesting that redox regulation of this cysteine pair serves a functional role. Moreover, the flexible loop flanked by Cys 208 and Cys 241 provides a platform for functional interaction with PDI, which in turn enhances the oxidative activity of Ero1α through reduction of the Cys 208 -Cys 241 disulfide. We propose a mechanism of dual Ero1α regulation by dynamic redox interactions between PDI and the two Ero1α flexible loops that harbor the regulatory cysteines. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Microbial Fe biomineralization in mafic and ultramafic rocks

NASA Astrophysics Data System (ADS)

Templeton, A. S.; Mayhew, L.; McCollom, T.; Trainor, T.

2011-12-01

Fluid-filled microfractures within mafic and ultramafic rocks, such as basalt and peridotite, may be one of the most ubiquitous microbial habitats on the modern and ancient earth. In seafloor and subseafloor systems, one of the dominant energy sources is the oxidation of Fe by numerous potential oxidants under aerobic to anaerobic conditions. In particular, the oxidation of Fe may be directly catalyzed by microbial organisms, or result in the production of molecular hydrogen which can then fuel diverse lithotrophic metabolisms. However, it remains challenging to identify the dominant metabolic activities and unravel the microscale biogeochemical processes occuring within such rock-hosted systems. We are investigating the mechanisms of solid-state Fe-oxidation and biomineralization in basalt, olivine, pyroxenes and basalts, in the presence and absence of microbial organisms that can thrive across the full stability range of water. In this talk we will present synchrotron-based x-ray scattering and spectroscopic analyses of Fe speciation within secondary minerals formed during microbially-mediated vs. abiotic water-rock interactions. Determining the valence state and mineralogy of Fe-bearing phases is critical for determining the water-rock reaction pathways and identifying potential biominerals that may form; therefore, we will highlight new approaches for identifying key Fe transformations within complex geological media. In addition, many of our experimental studies involve the growth of lithotrophic biofilms on well-characterized mineral surfaces in order to determine the chemistry of the microbe-mineral interface during progressive electron-transfer reactions. By coupling x-ray spectroscopy, x-ray diffraction, and electron-microscopy measurements, we will also contrast the evolution of mineral surfaces that undergo microbially-mediated oxidative alteration against minerals surfaces that produce H2 to sustain anaerobic microbial communities.

2013 Early Career Achievement Award--Proteomics of muscle- and species-specificity in meat color stability.

PubMed

Suman, S P; Rentfrow, G; Nair, M N; Joseph, P

2014-03-01

Meat color is the most important quality trait influencing consumer purchase decisions. The interinfluential interactions between myoglobin and biomolecules govern color stability in meat. The advances in proteomics, such as high throughput analytical tools in mass spectrometry, 2-dimensional electrophoresis, and bioinformatics, offer themselves as robust techniques to characterize the proteome basis of muscle- and species-specific meat color phenomena. Differential abundance of chaperones and antioxidant proteins contributes to muscle-specific color stability in beef; the greater abundance of chaperones and antioxidant proteins in color-stable Longissimus lumborum than in color-labile Psoas major protects myoglobin and contributes to superior color stability of beef Longissimus steaks. Lipid oxidation-induced myoglobin oxidation is more critical to beef color than pork color due to the inherent differences in myoglobin chemistry; the number of nucleophilic histidine residues adducted by reactive aldehydes is greater in beef myoglobin than in pork myoglobin. Preferential adduction of secondary products of lipid oxidation to beef myoglobin accelerates metmyoglobin formation at a greater degree than in its pork counterpart. Mass spectrometric investigations revealed that although cherry-red carboxymyoglobin is more stable than oxymyoglobin, both redox forms undergo lipid oxidation-induced oxidation in model systems. The accuracy of mass spectrometry to detect the molecular mass of proteins has been applied to differentiate myoglobins from closely related meat animals, such as goats and sheep or emu and ostrich. In addition, this approach indicated that turkey myoglobin is 350 Da greater in molecular mass than beef myoglobin, and the unique biochemistry of turkey myoglobin could be responsible for its greater thermostability in model systems as well as the pink color defect observed in fully cooked uncured turkey products.

Ti-Catalyzed Multicomponent Oxidative Carboamination of Alkynes with Alkenes and Diazenes

PubMed Central

Davis-Gilbert, Zachary W.; Yao, Letitia J.; Tonks, Ian A.

2017-01-01

The inter- or intramolecular oxidative carboamination of alkynes catalyzed by [py2TiCl2NPh]2 is reported. These multicomponent reactions couple alkenes, alkynes and diazenes to form either α,β-unsaturated imines or α-(iminomethyl)cyclopropanes via a TiII/TiIV redox cycle. Each of these products is formed from a common azatitanacyclohexene intermediate that undergoes either β-H elimination or α,γ-coupling, wherein the selectivity is under substrate control. PMID:27790910

Electrolysis with diamond anodes: Eventually, there are refractory species!

PubMed

Mena, Ismael F; Cotillas, Salvador; Díaz, Elena; Sáez, Cristina; Rodríguez, Juan J; Cañizares, P; Mohedano, Ángel F; Rodrigo, Manuel A

2018-03-01

In this work, synthetic wastewater polluted with ionic liquid 1-butyl-3-methylimidazolium (Bmim) bis(trifluoromethanesulfonyl)imide (NTf 2 ) undergoes four electrolytic treatments with diamond anodes (bare electrolysis, electrolysis enhanced with peroxosulfate promoters, irradiated with UV light and with US) and results obtained were compared with those obtained with the application of Catalytic Wet Peroxide Oxidation (CWPO). Despite its complex heterocyclic structure, Bmim + cation is successfully depleted with the five technologies tested, being transformed into intermediates that eventually can be mineralized. Photoelectrolysis attained the lowest concentration of intermediates, while CWPO is the technology less efficient in their degradation. However, the most surprising result is that concentration of NTf 2 - anion does not change during the five advanced oxidation processes tested, pointing out its strong refractory character, being the first species that exhibits this character in wastewater undergoing electrolysis with diamond. This means that the hydroxyl and sulfate radicals mediated oxidation and the direct electrolysis are inefficient for breaking the C-S, C-F and S-N bounds of the NTf 2 - anion, which is a very interesting mechanistic information to understand the complex processes undergone in electrolysis with diamond. Copyright © 2017 Elsevier Ltd. All rights reserved.

Studies of Heterogenous Palladium and Related Catalysts for Aerobic Oxidation of Primary Alcohols

NASA Astrophysics Data System (ADS)

Ahmed, Maaz S.

Development of aerobic oxidation methods is of critical importance for the advancement of green chemistry, where the only byproduct produced is water. Recent work by our lab has produced an efficient Pd based heterogenous catalyst capable of preforming the aerobic oxidation of a wide spectrum of alcohols to either carboxylic acid or methyl ester. The well-defined catalyst PdBi 0.35Te0.23/C (PBT/C) catalyst has been shown to can perform the aerobic oxidation of alcohols to carboxylic acids in basic conditions. Additionally, we explored this catalyst for a wide range of alcohols and probed the nature of the selectivity of PBT/C for methyl esterification over other side products. Finally, means by which the catalyst operates with respect to oxidation states of the three components, Pd, Bi, and Te, was probed. Carboxylic acids are an important functional group due to their prevalence in various pharmaceutically active agents, agrochemicals, and commodity scale chemicals. The well-defined catalyst PBT/C catalyst was discovered to be effective for the oxidation of a wide spectrum of alcohols to carboxylic acid. The demonstrated substrate scope and functional group tolerance are the widest reported for an aerobic heterogeneous catalyst. Additionally, the catalyst has been implemented in a packed bed reactor with quantitative yield of benzoic acid maintained throughout a two-day run. Biomass derived 5-(hydroxymethyl)furfural (HMF) is also oxidized to 2,5-furandicarboxylic acid (FDCA) in high yield. Exploration of PBT/C for the oxidative methyl esterification was found to exhibit exquisite selectivity for the initial oxidation of primary alcohol instead of methanol, which is the bulk solvent. We explored this selectivity and conclude that it results from various substrate-surface interactions, which are not attainable by methanol. The primary alcohol can outcompete the methanol for binding on the catalyst surface through various interactions between the side chain of the alcohol solvent and the surface of the catalyst: (listed in order of strength) lone pair-surface (heterocyclic primary alcohols) > pi-surface (aryl primary alcohols) > van der Waals-surface (alkyl primary alcohols). These interactions were previously underappreciated in condensed phase heterogeneously catalyzed aerobic oxidations. Bi and Te serve as synergistic promoters that enhance both the rate and yield of the reactions relative to reactions employing Pd alone or Pd in combination with Bi or with Te as the sole promoter. We report X-ray absorption spectroscopic studies of the heterogenous catalyst. These methods show that the promoters undergo oxidation in preference to Pd, maintaining the Pd surface in the active metallic state and preventing inhibition by surface Pd-oxide formation. The data also suggest formation of a Pd-Te alloy phase that modifies the electronic properties of the Pd catalyst. Collectively, these results provide valuable insights into the synergistic benefits of multiple promoters in heterogeneous catalytic oxidation reactions.

Kinetics and mechanisms of the oxidation of iodide and bromide in aqueous solutions by a trans-dioxoruthenium(VI) complex.

PubMed

Lam, William W Y; Man, Wai-Lun; Wang, Yi-Ning; Lau, Tai-Chu

2008-08-04

The kinetics and mechanisms of the oxidation of I (-) and Br (-) by trans-[Ru (VI)(N 2O 2)(O) 2] (2+) have been investigated in aqueous solutions. The reactions have the following stoichiometry: trans-[Ru (VI)(N 2O 2)(O) 2] (2+) + 3X (-) + 2H (+) --> trans-[Ru (IV)(N 2O 2)(O)(OH 2)] (2+) + X 3 (-) (X = Br, I). In the oxidation of I (-) the I 3 (-)is produced in two distinct phases. The first phase produces 45% of I 3 (-) with the rate law d[I 3 (-)]/dt = ( k a + k b[H (+)])[Ru (VI)][I (-)]. The remaining I 3 (-) is produced in the second phase which is much slower, and it follows first-order kinetics but the rate constant is independent of [I (-)], [H (+)], and ionic strength. In the proposed mechanism the first phase involves formation of a charge-transfer complex between Ru (VI) and I (-), which then undergoes a parallel acid-catalyzed oxygen atom transfer to produce [Ru (IV)(N 2O 2)(O)(OHI)] (2+), and a one electron transfer to give [Ru (V)(N 2O 2)(O)(OH)] (2+) and I (*). [Ru (V)(N 2O 2)(O)(OH)] (2+) is a stronger oxidant than [Ru (VI)(N 2O 2)(O) 2] (2+) and will rapidly oxidize another I (-) to I (*). In the second phase the [Ru (IV)(N 2O 2)(O)(OHI)] (2+) undergoes rate-limiting aquation to produce HOI which reacts rapidly with I (-) to produce I 2. In the oxidation of Br (-) the rate law is -d[Ru (VI)]/d t = {( k a2 + k b2[H (+)]) + ( k a3 + k b3[H (+)]) [Br (-)]}[Ru (VI)][Br (-)]. At 298.0 K and I = 0.1 M, k a2 = (2.03 +/- 0.03) x 10 (-2) M (-1) s (-1), k b2 = (1.50 +/- 0.07) x 10 (-1) M (-2) s (-1), k a3 = (7.22 +/- 2.19) x 10 (-1) M (-2) s (-1) and k b3 = (4.85 +/- 0.04) x 10 (2) M (-3) s (-1). The proposed mechanism involves initial oxygen atom transfer from trans-[Ru (VI)(N 2O 2)(O) 2] (2+) to Br (-) to give trans-[Ru (IV)(N 2O 2)(O)(OBr)] (+), which then undergoes parallel aquation and oxidation of Br (-), and both reactions are acid-catalyzed.

Change of properties after oxidation of IG-11 graphite by air and CO 2 gas

NASA Astrophysics Data System (ADS)

Lim, Yun-Soo; Chi, Se-Hwan; Cho, Kwang-Yun

2008-02-01

Artificial graphite is typically manufactured by carbonization of a shaped body of a kneaded mixture using granular cokes as a filler and pitch as a binder. It undergoes a pitch impregnation process if necessary and finally applying graphitization heat treatment. The effect of thermal oxidation in air or a CO 2 atmosphere on IG-11 graphite samples is investigated in this study. The results show a localized oxidation process that progressively reveals the large coke particles with increasing level of overall weight loss in air. The surface of the graphite was peeled off and no change was found in the specific gravity after air oxidation. However, the specific gravity of graphite was continuously decreased by CO 2 oxidation. The decrease in the specific gravity by CO 2 oxidation was due to CO 2 gas that progressed from the surface to the interior. The pore shape after CO 2 oxidation differed from that under air oxidation.

A DFT Investigation of the Mechanism of Propene Ammoxidation over α-Bismuth Molybdate

DOE PAGES

Licht, Rachel B.; Bell, Alexis T.

2016-11-17

We investigated the mechanisms and energetics for the propene oxidation and ammoxidation occurring on the (010) surface of Bi 2 Mo 3 O 12 using density functional theory (DFT). An energetically feasible sequence of elementary steps for propene oxidation to acrolein, propene ammoxidation to acrylonitrile, and acrolein ammoxidation to acrylonitrile is proposed. Consistent with experimental findings, the rate-limiting step for both propene oxidation and ammoxidation is the initial hydrogen abstraction from the methyl group of propene, which is calculated to have an apparent activation energy of 27.3 kcal/mol. The allyl species produced in this reaction is stabilized as an allylmore » alkoxide, which can then undergo hydrogen abstraction to form acrolein or react with ammonia adsorbed on under-coordinated surface Bi 3+ cations to form allylamine. Dehydrogenation of allylamine is shown to produce acrylonitrile, whereas reaction with additional adsorbed ammonia leads to the formation of acetonitrile and hydrogen cyanide. The dehydrogenation of allyalkoxide species is found to have a significantly higher activation barrier than reaction with adsorbed ammonia, consistent with the observation that very little acrolein is produced when ammonia is present. Finally, we found that rapid reoxidation of the catalyst surface to release wate the driving force for all reactions involving the cleavage of C-H or N-H bonds, because practically all of these steps are endothermic. (Chemical Equation Presented).« less

Decrease of Total Antioxidative Capacity in Developed Low Cardiac Output Syndrome

PubMed Central

Kunt, Alper Sami; Andac, Mehmet Halit

2012-01-01

Background. It has been known that cardiac surgery induces an oxidative stress. The persistent oxidative stress during reperfusion may lead to depressed myocardial function resulting in low cardiac output syndrome (LCOS) necessitating inotropic or intra-aortic balloon counterpulsation support. Total antioxidant capacity (TAC) is a measurement of oxidative stress in tissues. The purpose of this study was to examine the TAC differences during coronary artery bypass graft (CABG) operation in patients who have developed LCOS and who have not. Material and Methods. Seventy-nine patients were enrolled in the study. Central venous blood samples were obtained immediately before surgery, during operation, and at the end of surgery to assess TAC. Clinical data regarding patient demographics and operative outcomes were prospectively collected and entered into our clinical database. Results. LCOS developed in 8 patients (10.12%). The TAC has decreased sharply in the LCOS patients compared with those who did not develop LCOS (P < 0.001) during operation. In addition, the receiver operating characteristic (ROC) area was 0.879. Conclusion. TAC has decreased during operation in a significant proportion of patients undergoing isolated CABG, and this is more prominent and serious and might be an independent variable in patients who have developed LCOS. This may be related to intraoperative misadventure or inadequate myocardial antioxidative protection. Routine measurement of the TAC during operation may provide information for assessment of the LCOS development. PMID:23251720

Stereoselective borylative ketone-diene coupling.

PubMed

Cho, Hee Yeon; Yu, Zhiyong; Morken, James P

2011-10-07

In the presence of catalytic Ni(cod)(2) and P(t-Bu)(3), ketones, dienes, and B(2)(pin)(2) undergo a stereoselective multicomponent coupling reaction. Upon oxidation, the reaction furnishes 1,3-diols as the major reaction product. © 2011 American Chemical Society

Fate of Zinc and Silver Engineered Nanoparticles in Sewerage Networks

EPA Science Inventory

Engineered zinc oxide (ZnO) and silver (Ag) nanoparticles (NPs) used in consumer products are largely released into the environment through the wastewater stream. Limited information is available regarding the transformations they undergo during their transit through sewerage sy...

The safety of addition of nitrous oxide to general anaesthesia in at-risk patients having major non-cardiac surgery (ENIGMA-II): a randomised, single-blind trial.

PubMed

Myles, Paul S; Leslie, Kate; Chan, Matthew T V; Forbes, Andrew; Peyton, Philip J; Paech, Michael J; Beattie, W Scott; Sessler, Daniel I; Devereaux, P J; Silbert, Brendan; Schricker, Thomas; Wallace, Sophie

2014-10-18

Nitrous oxide is commonly used in general anaesthesia but concerns exist that it might increase perioperative cardiovascular risk. We aimed to gather evidence to establish whether nitrous oxide affects perioperative cardiovascular risk. We did an international, randomised, assessor-blinded trial in patients aged at least 45 years with known or suspected coronary artery disease having major non-cardiac surgery. Patients were randomly assigned via automated telephone service, stratified by site, to receive a general anaesthetic with or without nitrous oxide. Attending anaesthetists were aware of patients' group assignments, but patients and assessors were not. The primary outcome measure was a composite of death and cardiovascular complications (non-fatal myocardial infarction, stroke, pulmonary embolism, or cardiac arrest) within 30 days of surgery. Our modified intention-to-treat population included all patients randomly assigned to groups and undergoing induction of general anaesthesia for surgery. This trial is registered at ClinicalTrials.gov, number NCT00430989. Of 10,102 eligible patients, we enrolled 7112 patients between May 30, 2008, and Sept 28, 2013. 3543 were assigned to receive nitrous oxide and 3569 were assigned not to receive nitrous oxide. 3483 patients receiving nitrous oxide and 3509 not receiving nitrous oxide were assessed for the primary outcome. The primary outcome occurred in 283 (8%) patients receiving nitrous oxide and in 296 (8%) patients not receiving nitrous oxide (relative risk 0·96, 95% CI 0·83–1·12; p=0·64). Surgical site infection occurred in 321 (9%) patients assigned to nitrous oxide, and in 311 (9%) patients in the no-nitrous oxide group (p=0·61), and severe nausea and vomiting occurred in 506 patients (15%) assigned to nitrous oxide and 378 patients (11%) not assigned to nitrous oxide (p<0·0001). Our findings support the safety profile of nitrous oxide use in major non-cardiac surgery. Nitrous oxide did not increase the risk of death and cardiovascular complications or surgical-site infection, the emetogenic effect of nitrous oxide can be controlled with antiemetic prophylaxis, and a desired effect of reduced volatile agent use was shown. Australian National Health and Medical Research Council; Australian and New Zealand College of Anaesthetists; Heart and Stroke Foundation of Quebec, Heart and Stroke Foundation of Ontario, Canada; General Research Fund of the Research Grant Council, Hong Kong Special Administrative Region, China.

Facile Rearrangement of 3-Oxoalkyl Radicals is Evident in Low-Temperature Gas-Phase Oxidation of Ketones

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scheer, Adam M.; Welz, Oliver; Sasaki, Darryl Y.

The pulsed photolytic chlorine-initiated oxidation of methyl-tert-butyl ketone (MTbuK), di-tert-butyl ketone (DTbuK), and a series of partially deuterated diethyl ketones (DEK) is studied in the gas phase at 8 Torr and 550–650 K. Products are monitored as a function of reaction time, mass, and photoionization energy using multiplexed photoionization mass spectrometry with tunable synchrotron ionizing radiation. The results establish that the primary 3-oxoalkyl radicals of those ketones, formed by abstraction of a hydrogen atom from the carbon atom in γ-position relative to the carbonyl oxygen, undergo a rapid rearrangement resulting in an effective 1,2-acyl group migration, similar to that inmore » a Dowd–Beckwith ring expansion. Without this rearrangement, peroxy radicals derived from MTbuK and DTbuK cannot undergo HO2 elimination to yield a closed-shell unsaturated hydrocarbon coproduct. However, not only are these coproducts observed, but they represent the dominant oxidation channels of these ketones under the conditions of this study. For MTbuK and DTbuK, the rearrangement yields a more stable tertiary radical, which provides the thermodynamic driving force for this reaction. Even in the absence of such a driving force in the oxidation of partially deuterated DEK, the 1,2-acyl group migration is observed. Quantum chemical (CBS-QB3) calculations show the barrier for gas-phase rearrangement to be on the order of 10 kcal mol–1. The MTbuK oxidation experiments also show several minor channels, including β-scission of the initial radicals and cyclic ether formation.« less

Oxidation of a critical methionine modulates DNA binding of the Drosophila melanogaster high mobility group protein, HMG-D.

PubMed

Dow, L K; Changela, A; Hefner, H E; Churchill, M E

1997-09-15

HMG-D is a major high mobility group chromosomal protein present during early embryogenesis in Drosophila melanogaster. During overexpression and purification of HMG-D from E. coli, a key DNA binding residue, methionine 13, undergoes oxidation to methionine sulfoxide. Oxidation of this critical residue decreases the affinity of HMG-D for DNA by three-fold, altering the structure of the HMG-D-DNA complex without affecting the structure of the free protein. This work shows that minor modification of DNA intercalating residues may be used to fine tune the DNA binding affinity of HMG domain proteins.

Microstructure, nickel suppression and mechanical characteristics of electropolished and photoelectrocatalytically oxidized biomedical nickel titanium shape memory alloy.

PubMed

Chu, C L; Guo, C; Sheng, X B; Dong, Y S; Lin, P H; Yeung, K W K; Chu, Paul K

2009-07-01

A new surface modification protocol encompassing an electropolishing pretreatment (EP) and subsequent photoelectrocatalytic oxidation (PEO) has been developed to improve the surface properties of biomedical nickel titanium (NiTi) shape memory alloy (SMA). Electropolishing is a good way to improve the resistance to localized breakdown of NiTi SMA whereas PEO offers the synergistic effects of advanced oxidation and electrochemical oxidation. Our results indicate that PEO leads to the formation of a sturdy titania film on the EP NiTi substrate. There is an Ni-free zone near the top surface and a graded interface between the titania layer and NiTi substrate, which bodes well for both biocompatibility and mechanical stability. In addition, Ni ion release from the NiTi substrate is suppressed, as confirmed by the 10-week immersion test. The modulus and hardness of the modified NiTi surface increase with larger indentation depths, finally reaching plateau values of about 69 and 3.1GPa, respectively, which are slightly higher than those of the NiTi substrate but much lower than those of a dense amorphous titania film. In comparison, after undergoing only EP, the mechanical properties of NiTi exhibit an inverse change with depth. The deformation mechanism is proposed and discussed. Our results indicate that surface modification by dual EP and PEO can notably suppress Ni ion release and improve the biocompatibility of NiTi SMA while the surface mechanical properties are not compromised, making the treated materials suitable for hard tissue replacements.

Randomized clinical trial on acute effects of i.v. iron sucrose during haemodialysis.

PubMed

Garcia-Fernandez, Nuria; Echeverria, Aitziber; Sanchez-Ibarrola, Alfonso; Páramo, José Antonio; Coma-Canella, Isabel

2010-03-01

Haemodialysis induces endothelial dysfunction by oxidation and inflammation. Intravenous iron administration during haemodialysis could worsen endothelial dysfunction. The aim of this study was to ascertain if iron produces endothelial dysfunction and the possible neutralizing effect of N-acetylcysteine when infused before iron. The oxidative and inflammatory effects of iron during haemodialysis were also assessed. Forty patients undergoing haemodialysis were studied in a randomized and cross-over design with and without N-acetylcysteine infused before iron sucrose (50 or 100 mg). Plasma Von Willebrand factor (vWF), soluble intercellular adhesion molecule-1 (sICAM-1) levels, malondialdehyde, total antioxidant capacity, CD11b/CD18 expression in monocytes, interleukin (IL)-8 in monocytes and plasma IL-8 were studied at baseline and during haemodialysis. Haemodialysis produced significant (P < 0.001) increase in plasma vWF, sICAM-1, malondialdehyde, IL-8 and CD11b/CD18 expression in monocytes, as well as decrease in total antioxidant capacity. Iron induced significant increase in plasma malondialdehyde and IL-8 in monocytes, but had no effect on total antioxidant capacity, CD11b/CD18 expression, plasma IL-8, vWF and sICAM-1. The addition of N-acetylcysteine to 50 mg of iron produced a significant (P = 0.040) decrease in malondialdehyde. Standard (100 mg) and low (50 mg) doses of iron during haemodialysis had no effects on endothelium. Iron only had minor effects on inflammation and produced an increase in oxidative stress, which was neutralized by N-acetylcysteine at low iron dose. Haemodialysis caused a significant increase in oxidative stress, inflammation and endothelial dysfunction markers.

Heat and mass transfer analysis for paraffin/nitrous oxide burning rate in hybrid propulsion

NASA Astrophysics Data System (ADS)

Ben-Basat (Sisi), Shani; Gany, Alon

2016-03-01

This research presents a physical-mathematical model for the combustion of liquefying fuels in hybrid combustors, accounting for blowing effect on the heat transfer. A particular attention is given to a paraffin/nitrous oxide hybrid system. The use of a paraffin fuel in hybrid propulsion has been considered because of its much higher regression rate enabling significantly higher thrust compared to that of common polymeric fuels. The model predicts the overall regression rate (melting rate) of the fuel and the different mechanisms involved, including evaporation, entrainment of droplets of molten material, and mass loss due to melt flow on the condensed fuel surface. Prediction of the thickness and velocity of the liquid (melt) layer formed at the surface during combustion was done as well. Applying the model for an oxidizer mass flux of 45 kg/(s m2) as an example representing experimental range, it was found that 21% of the molten liquid undergoes evaporation, 30% enters the gas flow by the entrainment mechanism, and 49% reaches the end of the combustion chamber as a flowing liquid layer. When increasing the oxidizer mass flux in the port, the effect of entrainment increases while that of the flowing liquid layer along the surface shows a relatively lower contribution. Yet, the latter is predicted to have a significant contribution to the overall mass loss. In practical applications it may cause reduced combustion efficiency and should be taken into account in the motor design, e.g., by reinforcing the paraffin fuel with different additives. The model predictions have been compared to experimental results revealing good agreement.

Myocardial oxidative metabolism and protein synthesis during mechanical circulatory support by extracorporeal membrane oxygenation.

PubMed

Priddy, Colleen M O'Kelly; Kajimoto, Masaki; Ledee, Dolena R; Bouchard, Bertrand; Isern, Nancy; Olson, Aaron K; Des Rosiers, Christine; Portman, Michael A

2013-02-01

Extracorporeal membrane oxygenation (ECMO) provides essential mechanical circulatory support necessary for survival in infants and children with acute cardiac decompensation. However, ECMO also causes metabolic disturbances, which contribute to total body wasting and protein loss. Cardiac stunning can also occur, which prevents ECMO weaning, and contributes to high mortality. The heart may specifically undergo metabolic impairments, which influence functional recovery. We tested the hypothesis that ECMO alters oxidative metabolism and protein synthesis. We focused on the amino acid leucine and integration with myocardial protein synthesis. We used a translational immature swine model in which we assessed in heart 1) the fractional contribution of leucine (FcLeucine) and pyruvate to mitochondrial acetyl-CoA formation by nuclear magnetic resonance and 2) global protein fractional synthesis (FSR) by gas chromatography-mass spectrometry. Immature mixed breed Yorkshire male piglets (n = 22) were divided into four groups based on loading status (8 h of normal circulation or ECMO) and intracoronary infusion [(13)C(6),(15)N]-L-leucine (3.7 mM) alone or with [2-(13)C]-pyruvate (7.4 mM). ECMO decreased pulse pressure and correspondingly lowered myocardial oxygen consumption (∼40%, n = 5), indicating decreased overall mitochondrial oxidative metabolism. However, FcLeucine was maintained and myocardial protein FSR was marginally increased. Pyruvate addition decreased tissue leucine enrichment, FcLeucine, and Fc for endogenous substrates as well as protein FSR. The heart under ECMO shows reduced oxidative metabolism of substrates, including amino acids, while maintaining 1) metabolic flexibility indicated by ability to respond to pyruvate and 2) a normal or increased capacity for global protein synthesis.

BRIEF COMMUNICATIONS: Q switching of a resonator by the metal-semiconductor phase transition

NASA Astrophysics Data System (ADS)

Bugaev, A. A.; Zakharchenya, Boris P.; Chudnovskiĭ, F. A.

1981-12-01

An experimental study was made of Q switching in a resonator by a mirror with a nonlinear reflection coefficient. This mirror was an interference reflecting structure containing a vanadium oxide film capable of undergoing a metal-semiconductor transition. The nonlinearity of the reflection coefficient was due to initiation of this phase transition by laser radiation. A determination was made of the parameters of a giant radiation pulse obtained using such a passive switch with a vanadium oxide film.

Oxidation of Peptides by Methyl(trifluoromethyl)dioxirane: the Protecting Group Matters

PubMed Central

Rella, Maria Rosaria; Williard, Paul G.

2011-01-01

Representative Boc protected and acetyl protected peptide methyl esters bearing alkyl side chains undergo effective oxidation using methyl(trifluoromethyl)dioxirane (1b) under mild conditions. We observe a protecting group dependency in the chemoselectivity displayed by the dioxirane 1b. N-hydroxylation occurs in the case of the Boc protected peptides, side chain hydroxylation takes place in the case of acetyl protected peptides. Both are attractive transformations since they yield derivatized peptides that serve as valuable synthons. PMID:17221970

Effect of doping with nickel ions on the structural state of a zinc oxide crystal

NASA Astrophysics Data System (ADS)

Dubinin, S. F.; Sokolov, V. I.; Parkhomenko, V. D.; Maksimov, V. I.; Gruzdev, N. B.

2009-10-01

The fine structure of a hexagonal zinc oxide crystal doped with nickel ions of the composition Zn1 - x Ni x O has been studied using neutron diffraction and magnetic measurements. It is established that even at very low doping levels ( x = 0.0004), the crystal undergoes local distortions in basal planes of the initial hexagonal lattice. The local distortions are assumed to be sources of the formation of ferromagnetism in compounds of this class.

NiAl Coatings Investigated for Use in Reusable Launch Vehicles

NASA Technical Reports Server (NTRS)

Raj, Sai V.; Ghosn, Louis J.; Barrett, Charles A.

2003-01-01

As part of its major investment in the area of advanced space transportation, NASA is developing new technologies for use in the second- and third-generation designs of reusable launch vehicles. Among the prototype rocket engines being considered for these launch vehicles are those designed to use liquid hydrogen as the fuel and liquid oxygen as the oxidizer. Advanced copper alloys, such as copper-chromium-niobium (Cu-8(at.%)Cr- 4(at.%)Nb, also referred to as GRCop-84), which was invented at the NASA Glenn Research Center, are being considered for use as liner materials in the combustion chambers and nozzle ramps of these engines. However, previous experience has shown that, in rocket engines using liquid hydrogen and liquid oxygen, copper alloys are subject to a process called blanching, where the material undergoes environmental attack under the action of the combustion gases. In addition, the copper alloy liners undergo thermomechanical fatigue, which often results in an initially square cooling channel deforming into a dog-house shape. Clearly, there is an urgent need to develop new coatings to protect copper liners from environmental attack inside rocket chambers and to lower the temperature of the liners to reduce the probability of deformation and failure by thermomechanical fatigue.

Multicomponent synthesis of 2-imidazolines.

PubMed

Bon, Robin S; van Vliet, Bart; Sprenkels, Nanda E; Schmitz, Rob F; de Kanter, Frans J J; Stevens, Christian V; Swart, Marcel; Bickelhaupt, F Matthias; Groen, Marinus B; Orru, Romano V A

2005-04-29

[reaction: see text] A multicomponent reaction (MCR) between amines, aldehydes, and isocyanides bearing an acidic alpha-proton gives easy access to a diverse range of highly substituted 2-imidazolines. The limitations of the methodology seem to be determined by the reactivity of the isocyanide and by the steric bulk on the in situ generated imine rather than by the presence of additional functional groups on the imine. Less reactive isocyanides, for example p-nitrobenzyl isocyanide 25a, react successfully with amines and aldehydes, using a catalytic amount of silver(I) acetate. Some of the resulting p-nitrophenyl-substituted 2-imidazolines undergo air oxidation to the corresponding imidazoles. Differences in reactivity of the employed isocyanides are explained with use of DFT calculations. Difficult reactions with ketones instead of aldehydes as the oxo-compound in this MCR are promoted by silver(I) acetate as well.

Formulation procedures, rationale, and preliminary IMP-H flight data for silicone paints with improved stability

NASA Technical Reports Server (NTRS)

Schutt, J. B.; Shai, C. M.

1973-01-01

Results are given of a class of silicone paints undergoing space qualification on IMP-H. In addition to ultraviolet irradiation, samples are presently reclining about 10 to the 16th power solar wind protons per year. Preliminary data, covering the time span of the first anniversary, give incremental solar absorptances of 0.03 for two white paints, and 0.01 for leafing aluminum and a green tinted white paint. Complementing these data are complete descriptions of techniques used in making these paints, stabilizing the zinc oxide pigment, and choosing a solvent. Outgassing characteristics of finished coatings are also included. An attempt toward unification of these various aspects of the aerospace paint problem is provided through documented photochemical reactions, and a generalized band representation of the problem and its solutions.

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

PubMed Central

Prentice, Boone M.

2013-01-01

Gas-phase ion/ion reactions are emerging as useful and flexible means for the manipulation and characterization of peptide and protein biopolymers. Acid/base-like chemical reactions (i.e., proton transfer reactions) and reduction/oxidation (redox) reactions (i.e., electron transfer reactions) represent relatively mature classes of gas-phase chemical reactions. Even so, especially in regards to redox chemistry, the widespread utility of these two types of chemistries is undergoing rapid growth and development. Additionally, a relatively new class of gas-phase ion/ion transformations is emerging which involves the selective formation of functional-group-specific covalent bonds. This feature details our current work and perspective on the developments and current capabilities of these three areas of ion/ion chemistry with an eye towards possible future directions of the field. PMID:23257901

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

PubMed

Prentice, Boone M; McLuckey, Scott A

2013-02-01

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

Effects of halogenated aromatics/aliphatics and nitrogen(N)-heterocyclic aromatics on estimating the persistence of future pharmaceutical compounds using a modified QSAR model.

PubMed

Lim, Seung Joo; Fox, Peter

2014-02-01

The effects of halogenated aromatics/aliphatics and nitrogen(N)-heterocyclic aromatics on estimating the persistence of future pharmaceutical compounds were investigated using a modified half life equation. The potential future pharmaceutical compounds investigated were approximately 2000 pharmaceutical drugs currently undergoing the United States Food and Drug Administration (US FDA) testing. EPI Suite (BIOWIN) model estimates the fates of compounds based on the biodegradability under aerobic conditions. While BIOWIN considered the biodegradability of a compound only, the half life equation used in this study was modified by biodegradability, sorption and cometabolic oxidation. It was possible that the potential future pharmaceutical compounds were more accurately estimated using the modified half life equation. The modified half life equation considered sorption and cometabolic oxidation of halogenated aromatic/aliphatics and nitrogen(N)-heterocyclic aromatics in the sub-surface, while EPI Suite (BIOWIN) did not. Halogenated aliphatics in chemicals were more persistent than halogenated aromatics in the sub-surface. In addition, in the sub-surface environment, the fates of organic chemicals were much more affected by halogenation in chemicals than by nitrogen(N)-heterocyclic aromatics. © 2013.

Computational Chemistry and Lubrication

NASA Technical Reports Server (NTRS)

Zehe, Michael J.

1998-01-01

Members of NASA Lewis Research Center's Tribology and Surface Science Branch are applying high-level computational chemistry techniques to the development of new lubrication systems for space applications and for future advanced aircraft engines. The next generation of gas turbine engines will require a liquid lubricant to function at temperatures in excess of 350 C in oxidizing environments. Conventional hydrocarbon-based lubricants are incapable of operating in these extreme environments, but a class of compounds known as the perfluoropolyether (PFAE) liquids (see the preceding illustration) shows promise for such applications. These commercially available products are already being used as lubricants in conditions where low vapor pressure and chemical stability are crucial, such as in satellite bearings and composite disk platters. At higher temperatures, however, these compounds undergo a decomposition process that is assisted (catalyzed) by metal and metal oxide bearing surfaces. This decomposition process severely limits the applicability of PFAE's at higher temperatures. A great deal of laboratory experimentation has revealed that the extent of fluid degradation depends on the chemical properties of the bearing surface materials. Lubrication engineers would like to understand the chemical breakdown mechanism to design a less vulnerable PFAE or to develop a chemical additive to block this degradation.

Tyrosinase-catalyzed oxidation of fluorophenols.

PubMed

Battaini, Giuseppe; Monzani, Enrico; Casella, Luigi; Lonardi, Emanuela; Tepper, Armand W J W; Canters, Gerard W; Bubacco, Luigi

2002-11-22

The activity of the type 3 copper enzyme tyrosinase toward 2-, 3-, and 4-fluorophenol was studied by kinetic methods and (1)H and (19)F NMR spectroscopy. Whereas 3- and 4-fluorophenol react with tyrosinase to give products that undergo a rapid polymerization process, 2-fluorophenol is not reactive and actually acts as a competitive inhibitor in the enzymatic oxidation of 3,4-dihydroxyphenylalanine (L-dopa). The tyrosinase-mediated polymerization of 3- and 4-fluorophenols has been studied in detail. It proceeds through a phenolic coupling pathway in which the common reactive fluoroquinone, produced stereospecifically by tyrosinase, eliminates an inorganic fluorine ion. The enzymatic reaction studied as a function of substrate concentration shows a prominent lag that is completely depleted in the presence of L-dopa. The kinetic parameters of the reactions can be correlated to the electronic and steric effects of the fluorine substituent position. Whereas the fluorine electron withdrawing effect appears to control the binding of the substrates (K(m) for 3- and 4-fluorophenols and K(I) for 2-fluorophenol), the k(cat) parameters do not follow the expected trend, indicating that in the transition state some additional steric effect rules the reactivity.

Nucleation, Growth, Annealing, and Coagulation of Refractory Oxides and Metals: Recent Experimental Progress and Applications to Astrophysical Systems

NASA Technical Reports Server (NTRS)

Nuth, J. A.; Rietmeijer, F. J. M.; Hallenbeck, S. L.; Withey, P. A.

1999-01-01

Starting with cooling, refractory vapors diluted in significant quantities of H and He there are four processes that most natural systems will undergo: nucleation, growth, annealing, and coagulation. Nucleation is the processes by which the first stable refractory nuclei form in the vapor. These are the seeds onto which the remaining vapors will condense during the growth stage. Solids of any composition will try to arrange themselves into the least energetic configuration, provided that there is sufficient energy available to support such processes as diffusion and the breaking of chemical bonds. There is a significant activation energy associated with the annealing process in refractory solids due to the relatively high energy of the chemical bonds in solids. The grains formed in most cosmochemical systems are extremely small and often tightly coupled to the gas. Because of their small physical cross sections coagulation may be a very slow process unless there is another driving force involved in addition to normal Brownian motion. In what follows we will briefly cover each of these four stages for refractory oxide and metal grains, although in inverse order.

The Escherichia coli thioredoxin homolog YbbN/Trxsc is a chaperone and a weak protein oxidoreductase.

PubMed

Caldas, Thérèse; Malki, Abderrahim; Kern, Renée; Abdallah, Jad; Richarme, Gilbert

2006-05-12

Escherichia coli contains two thioredoxins, Trx1 and Trx2, and a thioredoxin-like protein, YbbN, which presents a strong homology in its N-terminal part with thioredoxin 1 and 2. YbbN, however, does not possess the canonical Cys-x-x-Cys active site of thioredoxins, but instead a Ser-x-x-Cys site. In addition to Cys-38, located in the SxxC site, it contains a second cysteine, Cys-63, close to Cys-38 in the 3D model. Cys-38 and Cys-63 undergo an oxidoreduction process, suggesting that YbbN functions with two redox cysteines. Accordingly, YbbN catalyzes the oxidation of reduced RNase and the isomerization of scrambled RNase. Moreover, upon oxidation, its oligomeric state changes from dimers to tetramers and higher oligomers. YbbN also possesses chaperone properties, promoting protein folding after urea denaturation and forming complexes with unfolded proteins. This is the first biochemical characterization of a member of the YbbN class of bacterial thioredoxin-like proteins, and in vivo experiments will allow to determine the importance of its redox and chaperone properties in the cellular physiology.

Electroplating of aluminium microparticles with nickel to synthesise reactive core-shell structures for thermal joining applications

NASA Astrophysics Data System (ADS)

Schreiber, S.; Zaeh, M. F.

2018-06-01

Reactive particles represent a promising alternative for effectively joining components with freeform surfaces and different material properties. While the primary application of reactive systems is combustion synthesis for the production of high-performance alloys, the highly exothermic reaction can also be used to firmly bond thermosensitive joining partners. Core-shell structures are of special interest, since they function as separate microreactors. In this paper, a method to synthesise reactive nickel-aluminium core-shell structures via a two-step plating process is described. Based on an electroless process, the natural oxide layer of the aluminium particles is removed and substituted with a thin layer of nickel. Subsequently, the pre-treated particles are electroplated with nickel. The high reactivity of aluminium and the oxide layer play a significant role in adjusting the process parameters of the Watts bath. Additionally, the developed experimental set-up is introduced and the importance of process control is shown. In order to achieve reproducible results, the electroplating process was automated. Ignition tests with electromagnetic waves demonstrated that the particles undergo an exothermic reaction. Therefore, they can be used as a heat source in thermal joining applications.

Environmental Durability of Coated GRCop-84 Copper Alloys

NASA Technical Reports Server (NTRS)

Raj, Sai V.; Robinson, C.; Barrett, C.; Humphrey, D.

2005-01-01

An advanced Cu-8(at.%)Cr-4%Nb alloy developed at NASA's Glenn Research Center, and designated as GRCop-84, is currently being considered for use as liners in combustor chambers and nozzle ramps in NASA s future generations of reusable launch vehicles (RLVs). However, past experience has shown that unprotected copper alloys undergo an environmental attack called "blanching" in rocket engines using liquid hydrogen as fuel and liquid oxygen as the oxidizer. Potential for sulfidation attack of the liners in hydrocarbon-fueled engines is also of concern. As a result, protective overlay coatings alloys are being developed for GRCop-84. The oxidation behavior of several new coating alloys has been evaluated. GRCop-84 specimens were coated with several copper and nickel-based coatings, where the coatings were deposited by either vacuum plasma spraying or cold spraying techniques. Coated and uncoated specimens were thermally cycled in a furnace at different temperatures in order to evaluate the performance of the coatings. Additional studies were conducted in a high pressure burner rig using a hydrocarbon fuel and subjected to a high heat flux hydrogen-oxygen combustion flame in NASA s Quick Access Rocket Exhaust (QARE) rig. The performance of these coatings are discussed.

Clusterin protects H9c2 cardiomyocytes from oxidative stress-induced apoptosis via Akt/GSK-3β signaling pathway

PubMed Central

Jun, Hyoung-Oh; Kim, Dong-hun; Lee, Sae-Won; Lee, Hye Shin; Seo, Ji Hae; Kim, Jeong Hun; Kim, Jin Hyoung; Yu, Young Suk; Min, Bon Hong

2011-01-01

Clusterin is a secretory glycoprotein, which is highly up-regulated in a variety of normal and injury tissues undergoing apoptosis including infarct region of the myocardium. Here, we report that clusterin protects H9c2 cardiomyocytes from H2O2-induced apoptosis by triggering the activation of Akt and GSK-3β. Treatment with H2O2 induces apoptosis of H9c2 cells by promoting caspase cleavage and cytochrome c release from mitochondria. However, co-treatment with clusterin reverses the induction of apoptotic signaling by H2O2, thereby recovers cell viability. The protective effect of clusterin on H2O2-induced apoptosis is impaired by PI3K inhibitor LY294002, which effectively suppresses clusterin-induced activation of Akt and GSK-3β. In addition, the protective effect of clusterin is independednt on its receptor megalin, because inhibition of megalin has no effect on clusturin-mediated Akt/GSK-3β phosphoylation and H9c2 cell viability. Collectively, these results suggest that clusterin has a role protecting cardiomyocytes from oxidative stress and the Akt/GSK-3β signaling mediates anti-apoptotic effect of clusterin. PMID:21270507

Chemical evolution of atmospheric organic carbon over multiple generations of oxidation

NASA Astrophysics Data System (ADS)

Isaacman-VanWertz, Gabriel; Massoli, Paola; O'Brien, Rachel; Lim, Christopher; Franklin, Jonathan P.; Moss, Joshua A.; Hunter, James F.; Nowak, John B.; Canagaratna, Manjula R.; Misztal, Pawel K.; Arata, Caleb; Roscioli, Joseph R.; Herndon, Scott T.; Onasch, Timothy B.; Lambe, Andrew T.; Jayne, John T.; Su, Luping; Knopf, Daniel A.; Goldstein, Allen H.; Worsnop, Douglas R.; Kroll, Jesse H.

2018-02-01

The evolution of atmospheric organic carbon as it undergoes oxidation has a controlling influence on concentrations of key atmospheric species, including particulate matter, ozone and oxidants. However, full characterization of organic carbon over hours to days of atmospheric processing has been stymied by its extreme chemical complexity. Here we study the multigenerational oxidation of α-pinene in the laboratory, characterizing products with several state-of-the-art analytical techniques. Although quantification of some early generation products remains elusive, full carbon closure is achieved (within measurement uncertainty) by the end of the experiments. These results provide new insights into the effects of oxidation on organic carbon properties (volatility, oxidation state and reactivity) and the atmospheric lifecycle of organic carbon. Following an initial period characterized by functionalization reactions and particle growth, fragmentation reactions dominate, forming smaller species. After approximately one day of atmospheric aging, most carbon is sequestered in two long-lived reservoirs—volatile oxidized gases and low-volatility particulate matter.

Liquid-phase oxidation of cyclohexanone over cerium oxide catalyst

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shen, H.C.; Weng, H.S.

Catalytic oxidation of cyclohexanone in the liquid phase with glacial acetic acid as the solvent over cerium oxide was studied between 5 and 15 atm and 98 and 118 {degrees} C in a batch reactor. The products were adipic acid, glutaric acid, succinic acid, caprolactone, carbon oxides, etc. The reaction undergoes a short induction period prior to a rapid reaction regime. In both regimes, the reaction is independent of oxygen pressure when the system pressure is above 10 atm. The induction period is inversely proportional to both of the catalyst weight and cyclohexanone concentration.During the rapid reaction regime, the reactionmore » rate was found to be proportional to the 0.5 power of the catalyst weight and to the 1.5 power of the cyclohexanone concentration. Reaction mechanisms and rate expressions are proposed. The carbon oxides produced in this study were much lower than those previously reported. The cerium oxide catalyst is stable during the reaction.« less

CO oxidation on gold-supported iron oxides: New insights into strong oxide–metal interactions

DOE PAGES

Yu, Liang; Liu, Yun; Yang, Fan; ...

2015-07-14

Very active FeO x–Au catalysts for CO oxidation are obtained after depositing nanoparticles of FeO, Fe 3O 4, and Fe 2O 3 on a Au(111) substrate. Neither FeO nor Fe 2O 3 is stable under the reaction conditions. Under an environment of CO/O 2, they undergo oxidation (FeO) or reduction (Fe 2O 3) to yield nanoparticles of Fe 3O 4 that are not formed in a bulk phase. Using a combined experimental and theoretical approach, we show a strong oxide–metal interaction (SOMI) between Fe 3O 4 nanostructures and Au(111), which gives the oxide special properties, allows the formation of anmore » active phase, and provides a unique interface to facilitate a catalytic reaction. This work highlights the important role that the SOMI can play in enhancing the catalytic performance of the oxide component in metal–oxide catalysts.« less

Chemical evolution of atmospheric organic carbon over multiple generations of oxidation.

PubMed

Isaacman-VanWertz, Gabriel; Massoli, Paola; O'Brien, Rachel; Lim, Christopher; Franklin, Jonathan P; Moss, Joshua A; Hunter, James F; Nowak, John B; Canagaratna, Manjula R; Misztal, Pawel K; Arata, Caleb; Roscioli, Joseph R; Herndon, Scott T; Onasch, Timothy B; Lambe, Andrew T; Jayne, John T; Su, Luping; Knopf, Daniel A; Goldstein, Allen H; Worsnop, Douglas R; Kroll, Jesse H

2018-04-01

The evolution of atmospheric organic carbon as it undergoes oxidation has a controlling influence on concentrations of key atmospheric species, including particulate matter, ozone and oxidants. However, full characterization of organic carbon over hours to days of atmospheric processing has been stymied by its extreme chemical complexity. Here we study the multigenerational oxidation of α-pinene in the laboratory, characterizing products with several state-of-the-art analytical techniques. Although quantification of some early generation products remains elusive, full carbon closure is achieved (within measurement uncertainty) by the end of the experiments. These results provide new insights into the effects of oxidation on organic carbon properties (volatility, oxidation state and reactivity) and the atmospheric lifecycle of organic carbon. Following an initial period characterized by functionalization reactions and particle growth, fragmentation reactions dominate, forming smaller species. After approximately one day of atmospheric aging, most carbon is sequestered in two long-lived reservoirs-volatile oxidized gases and low-volatility particulate matter.

Metal/oxide interfacial effects on the selective oxidation of primary alcohols

PubMed Central

Zhao, Guofeng; Yang, Fan; Chen, Zongjia; Liu, Qingfei; Ji, Yongjun; Zhang, Yi; Niu, Zhiqiang; Mao, Junjie; Bao, Xinhe; Hu, Peijun; Li, Yadong

2017-01-01

A main obstacle in the rational development of heterogeneous catalysts is the difficulty in identifying active sites. Here we show metal/oxide interfacial sites are highly active for the oxidation of benzyl alcohol and other industrially important primary alcohols on a range of metals and oxides combinations. Scanning tunnelling microscopy together with density functional theory calculations on FeO/Pt(111) reveals that benzyl alcohol enriches preferentially at the oxygen-terminated FeO/Pt(111) interface and undergoes readily O–H and C–H dissociations with the aid of interfacial oxygen, which is also validated in the model study of Cu2O/Ag(111). We demonstrate that the interfacial effects are independent of metal or oxide sizes and the way by which the interfaces were constructed. It inspires us to inversely support nano-oxides on micro-metals to make the structure more stable against sintering while the number of active sites is not sacrificed. The catalyst lifetime, by taking the inverse design, is thereby significantly prolonged. PMID:28098146

Electrosynthesis of Biomimetic Manganese-Calcium Oxides for Water Oxidation Catalysis--Atomic Structure and Functionality.

PubMed

González-Flores, Diego; Zaharieva, Ivelina; Heidkamp, Jonathan; Chernev, Petko; Martínez-Moreno, Elías; Pasquini, Chiara; Mohammadi, Mohammad Reza; Klingan, Katharina; Gernet, Ulrich; Fischer, Anna; Dau, Holger

2016-02-19

Water-oxidizing calcium-manganese oxides, which mimic the inorganic core of the biological catalyst, were synthesized and structurally characterized by X-ray absorption spectroscopy at the manganese and calcium K edges. The amorphous, birnesite-type oxides are obtained through a simple protocol that involves electrodeposition followed by active-site creation through annealing at moderate temperatures. Calcium ions are inessential, but tune the electrocatalytic properties. For increasing calcium/manganese molar ratios, both Tafel slopes and exchange current densities decrease gradually, resulting in optimal catalytic performance at calcium/manganese molar ratios of close to 10 %. Tracking UV/Vis absorption changes during electrochemical operation suggests that inactive oxides reach their highest, all-Mn(IV) oxidation state at comparably low electrode potentials. The ability to undergo redox transitions and the presence of a minor fraction of Mn(III) ions at catalytic potentials is identified as a prerequisite for catalytic activity. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Characterization of un-hydrated and hydrated BioAggregate™ and MTA Angelus™.

PubMed

Camilleri, J; Sorrentino, F; Damidot, D

2015-04-01

BioAggregate™ is a novel material introduced for use as a root-end filling material. It is tricalcium silicate-based, free of aluminium and uses tantalum oxide as radiopacifier. BioAggregate contains additives to enhance the material performance. The purpose of this research was to characterize the un-hydrated and hydrated forms of BioAggregate using a combination of techniques, verify whether the additives if present affect the properties of the set material and compare these properties to those of MTA Angelus™. Un-hydrated and hydrated BioAggregate and MTA Angelus were assessed. Un-hydrated cement was tested for chemical composition, specific surface area, mineralogy and kinetics of hydration. The set material was investigated for mineralogy, microstructure and bioactivity. Scanning electron microscopy, X-ray energy dispersive spectroscopic analysis, X-ray fluorescence spectroscopy, X-ray diffraction and isothermal calorimetry were employed. The specific surface area was investigated using a gas adsorption method with nitrogen as the probe. BioAggregate was composed of tricalcium silicate, tantalum oxide, calcium phosphate and silicon dioxide and was free of aluminium. On hydration, the tricalcium silicate produced calcium silicate hydrate and calcium hydroxide. The former was deposited around the cement grains, while the latter reacted with the silicon dioxide to form additional calcium silicate hydrate. This resulted in reduction of calcium hydroxide in the aged cement. MTA Angelus reacted in a similar fashion; however, since it contained no additives, the calcium hydroxide was still present in the aged cement. Bioactivity was demonstrated by deposition of hydroxyapatite. BioAggregate exhibited a high specific surface area. Nevertheless, the reactivity determined by isothermal calorimetry appeared to be slow compared to MTA Angelus. The tantalum oxide as opposed to bismuth oxide was inert, and tantalum was not leached in solution. BioAggregate exhibited high calcium ion release early, which was maintained over the 28-day period as opposed to MTA Angelus, which demonstrated low early calcium ion release which increased as the material aged. The mineralogical composition of BioAggregate was different to MTA Angelus. As opposed to MTA Angelus, BioAggregate did not contain aluminium and contained additives such as calcium phosphate and silicon dioxide. As a consequence, BioAggregate reacted more slowly and formation of calcium hydroxide and leaching of calcium ions in solution were not evident as the material aged. The additives in BioAggregate modify the kinetics and the end products of hydration. Although newer generation tricalcium silicate-based materials contain similar constituents to MTA, they do not undergo the same setting reactions, and thus, their clinical performance will not be comparable to that of MTA.

Effect of biochar addition on short-term N2O and CO2 emissions during repeated drying and wetting of an anthropogenic alluvial soil.

PubMed

Yang, Fang; Lee, Xinqing; Theng, Benny K G; Wang, Bing; Cheng, Jianzhong; Wang, Qian

2017-06-01

Agricultural soils are an important source of greenhouse gases (GHG). Biochar application to such soils has the potential of mitigating global anthropogenic GHG emissions. Under irrigation, the topsoils in arid regions experience repeated drying and wetting during the crop growing season. Biochar incorporation into these soils would change the soil microbial environment and hence affect GHG emissions. Little information, however, is available regarding the effect of biochar addition on carbon dioxide (CO 2 ) and nitrous oxide (N 2 O) emissions from agricultural soils undergoing repeated drying and wetting. Here, we report the results of a 49-day aerobic incubation experiment, incorporating biochar into an anthropogenic alluvial soil in an arid region of Xinjiang Province, China, and measuring CO 2 and N 2 O emissions. Under both drying-wetting and constantly moist conditions, biochar amendment significantly increased cumulative CO 2 emission. At the same time, there was a significant reduction (up to ~20 %) in cumulative N 2 O emission, indicating that the addition of biochar to irrigated agricultural soils may effectively slow down global warming in arid regions of China.

Influence of oxygenation on chromium redox reactions with manganese sulfide (MnS(s)).

PubMed

Wadhawan, Amar R; Livi, Kenneth J; Stone, Alan T; Bouwer, Edward J

2015-03-17

Manganese sulfide (MnS(s)) minerals exist in sulfidic environments and can have unique reactive abilities because of sulfide, which is a known reductant, and Mn, the oxyhydroxides of which are known oxidants. This study elucidated the role of MnS(s) in controlling Cr speciation with implications on its fate and toxicity in the natural environment, specifically sulfidic sediments that undergo biogeochemical changes due to sediment resuspension during dredging, bioturbation, and flood events. In continuously mixed batch reaction experiments, aqueous CrVI reduction under anaerobic conditions occurred primarily on the surface of MnS(s) displaying a biphasic behavior- the initial rapid removal of CrVI from solution was followed by a slow decline due to surface passivation by reaction products, mainly sorbed or precipitated CrIII. The reaction progress increased with MnS(s) surface area loading but decreased on increasing CrVI concentration and pH, suggesting that surface site regeneration through product desorption was the rate-controlling mechanism. Below circum-neutral pH, higher solubility of MnS(s) resulted in additional CrVI reduction by reduced sulfur species in solution, whereas increased CrIII solubility lowered surface passivation allowing for more reactive sites to participate in the reaction. Aeration of MnS(s) at pH≥7 caused the formation of a heterogeneous MnIII(hydr)oxide that was composed of hausmanite and manganite. CrVI reoccurrence was observed on aeration of CrVI-spiked MnS(s) from the oxidation of product CrIII. The reoccurrence at pH≥7 was attributed to the oxidation of product CrIII by MnIII(hydr)oxide, whereas the reoccurrence at pH<7 was hypothesized from the oxidation of product CrIII by intermediate aqueous MnIII and/or sulfur species. Just as with Cr, MnS(s) may play an important role in speciation, fate, and transport of other environmental contaminants.

Dysregulated nitric oxide signaling as a candidate mechanism of fragile X syndrome and other neuropsychiatric disorders.

PubMed

Colvin, Steven M; Kwan, Kenneth Y

2014-01-01

A mechanistic understanding of the pathophysiology underpinning psychiatric disorders is essential for the development of targeted molecular therapies. For fragile X syndrome (FXS), recent mechanistic studies have been focused on the metabotropic glutamate receptor (mGluR) signaling pathway. This line of research has led to the discovery of promising candidate drugs currently undergoing various phases of clinical trial, and represents a model of how biological insights can inform therapeutic strategies in neurodevelopmental disorders. Although mGluR signaling is a key mechanism at which targeted treatments can be directed, it is likely to be one of many mechanisms contributing to FXS. A more complete understanding of the molecular and neural underpinnings of the disorder is expected to inform additional therapeutic strategies. Alterations in the assembly of neural circuits in the neocortex have been recently implicated in genetic studies of autism and schizophrenia, and may also contribute to FXS. In this review, we explore dysregulated nitric oxide signaling in the developing neocortex as a novel candidate mechanism of FXS. This possibility stems from our previous work demonstrating that neuronal nitric oxide synthase 1 (NOS1 or nNOS) is regulated by the FXS protein FMRP in the mid-fetal human neocortex. Remarkably, in the mid-late fetal and early postnatal neocortex of human FXS patients, NOS1 expression is severely diminished. Given the role of nitric oxide in diverse neural processes, including synaptic development and plasticity, the loss of NOS1 in FXS may contribute to the etiology of the disorder. Here, we outline the genetic and neurobiological data that implicate neocortical dysfunction in FXS, review the evidence supporting dysregulated nitric oxide signaling in the developing FXS neocortex and its contribution to the disorder, and discuss the implications for targeting nitric oxide signaling in the treatment of FXS and other psychiatric illnesses.

A Metagenomics-Based Metabolic Model of Nitrate-Dependent Anaerobic Oxidation of Methane by Methanoperedens-Like Archaea

PubMed Central

Arshad, Arslan; Speth, Daan R.; de Graaf, Rob M.; Op den Camp, Huub J. M.; Jetten, Mike S. M.; Welte, Cornelia U.

2015-01-01

Methane oxidation is an important process to mitigate the emission of the greenhouse gas methane and further exacerbating of climate forcing. Both aerobic and anaerobic microorganisms have been reported to catalyze methane oxidation with only a few possible electron acceptors. Recently, new microorganisms were identified that could couple the oxidation of methane to nitrate or nitrite reduction. Here we investigated such an enrichment culture at the (meta) genomic level to establish a metabolic model of nitrate-driven anaerobic oxidation of methane (nitrate-AOM). Nitrate-AOM is catalyzed by an archaeon closely related to (reverse) methanogens that belongs to the ANME-2d clade, tentatively named Methanoperedens nitroreducens. Methane may be activated by methyl-CoM reductase and subsequently undergo full oxidation to carbon dioxide via reverse methanogenesis. All enzymes of this pathway were present and expressed in the investigated culture. The genome of the archaeal enrichment culture encoded a variety of enzymes involved in an electron transport chain similar to those found in Methanosarcina species with additional features not previously found in methane-converting archaea. Nitrate reduction to nitrite seems to be located in the pseudoperiplasm and may be catalyzed by an unusual Nar-like protein complex. A small part of the resulting nitrite is reduced to ammonium which may be catalyzed by a Nrf-type nitrite reductase. One of the key questions is how electrons from cytoplasmically located reverse methanogenesis reach the nitrate reductase in the pseudoperiplasm. Electron transport in M. nitroreducens probably involves cofactor F420 in the cytoplasm, quinones in the cytoplasmic membrane and cytochrome c in the pseudoperiplasm. The membrane-bound electron transport chain includes F420H2 dehydrogenase and an unusual Rieske/cytochrome b complex. Based on genome and transcriptome studies a tentative model of how central energy metabolism of nitrate-AOM could work is presented and discussed. PMID:26733968

Methanobactin and the Link between Copper and Bacterial Methane Oxidation

PubMed Central

Semrau, Jeremy D.; Murrell, J. Colin; Gallagher, Warren H.; Dennison, Christopher; Vuilleumier, Stéphane

2016-01-01

SUMMARY Methanobactins (mbs) are low-molecular-mass (<1,200 Da) copper-binding peptides, or chalkophores, produced by many methane-oxidizing bacteria (methanotrophs). These molecules exhibit similarities to certain iron-binding siderophores but are expressed and secreted in response to copper limitation. Structurally, mbs are characterized by a pair of heterocyclic rings with associated thioamide groups that form the copper coordination site. One of the rings is always an oxazolone and the second ring an oxazolone, an imidazolone, or a pyrazinedione moiety. The mb molecule originates from a peptide precursor that undergoes a series of posttranslational modifications, including (i) ring formation, (ii) cleavage of a leader peptide sequence, and (iii) in some cases, addition of a sulfate group. Functionally, mbs represent the extracellular component of a copper acquisition system. Consistent with this role in copper acquisition, mbs have a high affinity for copper ions. Following binding, mbs rapidly reduce Cu2+ to Cu1+. In addition to binding copper, mbs will bind most transition metals and near-transition metals and protect the host methanotroph as well as other bacteria from toxic metals. Several other physiological functions have been assigned to mbs, based primarily on their redox and metal-binding properties. In this review, we examine the current state of knowledge of this novel type of metal-binding peptide. We also explore its potential applications, how mbs may alter the bioavailability of multiple metals, and the many roles mbs may play in the physiology of methanotrophs. PMID:26984926

Methylene Blue for Vasoplegia When on Cardiopulmonary Bypass During Double-Lung Transplantation.

PubMed

Carley, Michelle; Schaff, Jacob; Lai, Terrance; Poppers, Jeremy

2015-10-15

Vasoplegia syndrome, characterized by hypotension refractory to fluid resuscitation or high-dose vasopressors, low systemic vascular resistance, and normal-to-increased cardiac index, is associated with increased morbidity and mortality after cardiothoracic surgery. Methylene blue inhibits inducible nitric oxide synthase and guanylyl cyclase, and has been used to treat vasoplegia during cardiopulmonary bypass. However, because methylene blue is associated with increased pulmonary vascular resistance, its use in patients undergoing lung transplantion has been limited. Herein, we report the use of methylene blue to treat refractory vasoplegia during cardiopulmonary bypass in a patient undergoing double-lung transplantation.

Comparative evaluation of diffusion hypoxia and psychomotor skills with or without postsedation oxygenation following administration of nitrous oxide in children undergoing dental procedures: A clinical study.

PubMed

Khinda, Vineet Inder Singh; Bhuria, Parvesh; Khinda, Paramjit; Kallar, Shiminder; Brar, Gurlal Singh

2016-01-01

Diffusion hypoxia is the most serious potential complication associated with nitrous oxide. It occurs during the recovery period. Hence, administration of 100% oxygen is mandatory as suggested by many authors. The aim of this study is to evaluate the occurrence/nonoccurrence of diffusion hypoxia in two groups of patients undergoing routine dental treatment under nitrous oxide sedation when one group is subjected to 7 min of postsedation oxygenation and the second group of the patients is made to breathe room air for the similar period. A total of sixty patients within the age group of 7-10 years requiring invasive dental procedures were randomly divided into two groups of 30 each using chit method. In the control group, patients were administered 100% oxygen postsedation, whereas, in the study group, patients were made to breathe room air postsedation. Various parameters (pulse rate, respiratory rate, blood pressure, and oxygen saturation [SpO2]) were recorded pre- and post-operatively. Data were collected and then sent for statistical analysis. The mean postoperative SpO2 at measurement times 1, 3, 5, and 7 min in both the groups was higher than the mean preoperative SpO2. This increase was statistically significant. No significant difference was found between the Trieger test scores. This study proves that clinical occurrence of diffusion hypoxia is not possible while following the routine procedure of nitrous oxide sedation.

Fatigue and Oxidative Stress in Children Undergoing Leukemia Treatment.

PubMed

Rodgers, Cheryl; Sanborn, Chelse; Taylor, Olga; Gundy, Patricia; Pasvogel, Alice; Moore, Ida M Ki; Hockenberry, Marilyn J

2016-10-01

Fatigue is a frequent and distressing symptom in children undergoing leukemia treatment; however, little is known about factors influencing this symptom. Antioxidants such as glutathione can decrease symptom severity in adult oncology patients, but no study has evaluated antioxidants' effects on symptoms in pediatric oncology patients. This study describes fatigue patterns and associations of fatigue with antioxidants represented by reduced glutathione (GSH) and the reduced/oxidized glutathione (GSH/GSSG) ratio among children receiving leukemia treatment. A repeated measures design assessed fatigue and antioxidants among 38 children from two large U.S. cancer centers. Fatigue was assessed among school-age children and by parent proxy among young children. Antioxidants (GSH and GSH/GSSG ratio) were assessed from cerebrospinal fluid at four phases during leukemia treatment. Young children had a steady decline of fatigue from the end of induction treatment through the continuation phase of treatment, but no significant changes were noted among the school-age children. Mean antioxidant scores varied slightly over time; however, the GSH/GSSG ratios in these children were significantly lower than the normal ratio. Mean GSH/GSSG ratios significantly correlated to fatigue scores of the school-age children during early phases of treatment. Children with low mean GSH/GSSG ratios demonstrated oxidative stress. The low ratios noted early in therapy were significantly correlated with higher fatigue scores during induction and postinduction treatment phases. This finding suggests that increased oxidative stress during the more intensive phases of therapy may explain the experience of fatigue children report. © The Author(s) 2016.

Association Between Early Postoperative Acetaminophen Exposure and Acute Kidney Injury in Pediatric Patients Undergoing Cardiac Surgery.

PubMed

Van Driest, Sara L; Jooste, Edmund H; Shi, Yaping; Choi, Leena; Darghosian, Leon; Hill, Kevin D; Smith, Andrew H; Kannankeril, Prince J; Roden, Dan M; Ware, Lorraine B

2018-05-14

Acute kidney injury (AKI) is a common and serious complication for pediatric cardiac surgery patients associated with increased morbidity, mortality, and length of stay. Current strategies focus on risk reduction and early identification because there are no known preventive or therapeutic agents. Cardiac surgery and cardiopulmonary bypass lyse erythrocytes, releasing free hemoglobin and contributing to oxidative injury. Acetaminophen may prevent AKI by reducing the oxidation state of free hemoglobin. To test the hypothesis that early postoperative acetaminophen exposure is associated with reduced risk of AKI in pediatric patients undergoing cardiac surgery. In this retrospective cohort study, the setting was 2 tertiary referral children's hospitals. The primary and validation cohorts included children older than 28 days admitted for cardiac surgery between July 1, 2008, and June 1, 2016. Exclusion criteria were postoperative extracorporeal membrane oxygenation and inadequate serum creatinine measurements to determine AKI status. Acetaminophen exposure in the first 48 postoperative hours. Acute kidney injury based on Kidney Disease: Improving Global Outcomes serum creatinine criteria (increase by ≥0.3 mg/dL from baseline or at least 1.5-fold more than the baseline [to convert to micromoles per liter, multiply by 88.4]) in the first postoperative week. The primary cohort (n = 666) had a median age of 6.5 (interquartile range [IQR], 3.9-44.7) months, and 341 (51.2%) had AKI. In unadjusted analyses, those with AKI had lower median acetaminophen doses than those without AKI (47 [IQR, 16-88] vs 78 [IQR, 43-104] mg/kg, P < .001). In logistic regression analysis adjusting for age, cardiopulmonary bypass time, red blood cell distribution width, postoperative hypotension, nephrotoxin exposure, and Risk Adjustment for Congenital Heart Surgery score, acetaminophen exposure was protective against postoperative AKI (odds ratio, 0.86 [95% CI, 0.82-0.90] per each additional 10 mg/kg). Findings were replicated in the validation cohort (n = 333), who had a median age of 14.1 (IQR, 3.9-158.2) months, and 162 (48.6%) had AKI. Acetaminophen doses were 60 (95% CI, 40-87) mg/kg in those with AKI vs 70 (95% CI, 45-94) mg/kg in those without AKI (P = .03), with an adjusted odds ratio of 0.91 (95% CI, 0.84-0.99) for each additional 10 mg/kg. These results indicate that early postoperative acetaminophen exposure may be associated with a lower rate of AKI in pediatric patients who undergo cardiac surgery. Further analysis to validate these findings, potentially through a prospective, randomized trial, may establish acetaminophen as a preventive agent for AKI.

Randomized controlled study of the safety and efficacy of nitrous oxide-sedated endoscopic ultrasound-guided fine needle aspiration for digestive tract diseases.

PubMed

Wang, Cai-Xia; Wang, Jian; Chen, Yuan-Yuan; Wang, Jia-Ni; Yu, Xin; Yang, Feng; Sun, Si-Yu

2016-12-14

To evaluate the efficacy and safety of nitrous oxide-sedated endoscopic ultrasound-guided fine needle aspiration. Enrolled patients were divided randomly into an experimental group (inhalation of nitrous oxide) and a control group (inhalation of pure oxygen) and heart rate, blood oxygen saturation, blood pressure, electrocardiogram (ECG) changes, and the occurrence of complications were monitored and recorded. All patients and physicians completed satisfaction questionnaires about the examination and scored the process using a visual analog scale. There was no significant difference in heart rate, blood oxygen saturation, blood pressure, ECG changes, or complication rate between the two groups of patients ( P > 0.05). However, patient and physician satisfaction were both significantly higher in the nitrous oxide compared with the control group ( P < 0.05). Nitrous oxide-sedation is a safe and effective option for patients undergoing endoscopic ultrasound-guided fine needle aspiration.

Controlling the oxidation of bis-tridentate cobalt(ii) complexes having bis(2-pyridylalkyl)amines: ligand vs. metal oxidation.

PubMed

Anjana, S; Donring, S; Sanjib, P; Varghese, B; Murthy, Narasimha N

2017-08-22

Two bis-tridentate chelated cobalt(ii) complexes, which differ in the ligand structure by a methylene group, activate molecular oxygen (O 2 ), and give different oxidation products. The O 2 reaction of [Co II (pepma) 2 ] 2+ (1) with unsymmetrical 2-(2-pyridyl)-N-(2-pyridylmethyl)ethanamine (pepma) results in ligand oxidation, to the corresponding Co(ii) imine complex [Co II (pepmi) 2 ] 2+ (2). Contrastingly, the Co(ii) complex [Co II (bpma) 2 ] 2+ (3) of similar symmetrical bis(2-pyridylmethyl)amine (bpma), undergoes metal oxidation, yielding a cobalt(iii) complex, [Co III (bpma) 2 ] 2+ (4). The reversibility of the amine to imine conversion and the stability of the Co(ii) imine complex (2) are investigated. Furthermore, the solution dynamics of Co(ii) complexes are highlighted with the help of paramagnetic 1 H-NMR spectroscopy.

Mechanism study on mitochondrial fragmentation under oxidative stress caused by high-fluence low-power laser irradiation

NASA Astrophysics Data System (ADS)

Wu, Shengnan; Zhou, Feifan; Xing, Da

2012-03-01

Mitochondria are dynamic organelles that undergo continual fusion and fission to maintain their morphology and functions, but the mechanism involved is still not clear. Here, we investigated the effect of mitochondrial oxidative stress triggered by high-fluence low-power laser irradiation (HF-LPLI) on mitochondrial dynamics in human lung adenocarcinoma cells (ASTC-a-1). Upon HF-LPLI-triggered oxidative stress, mitochondria displayed a fragmented structure, which was abolished by exposure to dehydroascorbic acid (DHA), a reactive oxygen species scavenger, indicating that oxidative stress can induce mitochondrial fragmentation. Mitochondrial translocation of the profission protein dynamin-related protein 1 (Drp1) was observed following HF-LPLI, demonstrating apoptosis-related activation of Drp1. Notably, DHA pre-treatment prevented HF-LPLI-induced Drp1 activation. We conclude that mitochondrial oxidative stress through activation of Drp1 causes mitochondrial fragmentation.

Behavior of the Si/SiO2 interface observed by Fowler-Nordheim tunneling

NASA Technical Reports Server (NTRS)

Maserjian, J.; Zamani, N.

1982-01-01

Thin-oxide (40-50 A) metal oxide semiconductor (MOS) structures are shown to exhibit, before large levels of electron tunnel injection, the near-ideal behavior predicted for a uniform trapezoidal barrier with thick-oxide properties. The oscillatory field dependence caused by electron-wave interference at the Si/SiO2 interface suggests an abrupt, one-monolayer barrier transition (approximately 2.5 A) consistent with earlier work. After tunnel injection of 10 to the 17th - 5 x 10 to the 18th electrons/sq cm, the barrier undergoes appreciable degradation, leading to enhanced tunneling conductance. Reproducible behavior is observed among different samples. This effect is found to be consistent with the generation of positive states in the region of the oxide near the Si/SiO2 interface (less than 20 A), where the tunneling electrons emerge into the oxide conduction band.

Photolysis of natural B-triketonic herbicides in water

USDA-ARS?s Scientific Manuscript database

The fate of four natural triketones (leptospermone, isoleptospermone, grandiflorone and flavesone, pKa=4.0 to 4.5) in aqueous solution, in the dark and upon simulated solar light irradiation was investigated. In anionic form, triketones undergo oxidation in the dark, however, photolysis is much fast...

Using polyphenol derivatives to prevent muscle wasting.

PubMed

Francaux, Marc; Deldicque, Louise

2018-05-01

To highlight recent evidence for the ability of polyphenols and their derivatives to reduce muscle wasting in different pathological states. From January 2016 to August 2017, four articles dealt with the effects of polyphenols on muscle wasting, which were all carried out in mice. The four studies found that polyphenols reduced muscle mass loss associated with cancer cachexia, acute inflammation or sciatic nerve section. One study even showed that muscle mass was totally preserved when rutin was added to the diet of mice undergoing cancer cachexia. The beneficial effects of polyphenols on muscle wasting were mainly due to a reduction in the activation of the nuclear factor-kappa B pathway, a lower oxidative stress level and a better mitochondrial function. In addition, urolithin B was found to have a testosterone-like effect and to favorably regulate muscle protein balance. During the last 20 months, additional data have been collected about the beneficial effects of rutin, curcumin, quercetin, ellagitanins and urolithin B to limit the loss of muscle mass associated with several pathological states. However, currently, scientific evidence lacks for their use as nutraceuticals in human.

Attrition of precipitated iron Fischer-Tropsch catalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Datye, A.K.; Reardon, J.; Hanprasopwattana, A.

1996-12-31

Precipitated Iron catalysts used in slurry phase bubble column reactors are known to undergo attrition during use. The attrition reduces the lifetime of the catalyst as well as causing problems in separating the product liquids from the catalyst. In this study, the authors have investigated the underlying mechanisms that lead to attrition in precipitated iron catalysts. They have discovered that attrition takes place on two length scales. On the macro scale, attrition is caused by the break-up of the weak agglomerates that constitute this catalyst into individual crystallites. Addition of binders such as kaolin does not help significantly in strengtheningmore » the catalyst particles. In addition, there is a second process leading to nanoscale attrition that is caused by the break-up of individual iron oxide crystallites into nano particles of iron carbide as the catalyst is activated for reaction. Design of attrition resistant F-T catalysts must consider these two modes of catalyst attrition. Preliminary work in the laboratory directed at improving the attrition resistance of precipitated iron catalysts will also be described in this paper.« less

Short-term exercise worsens cardiac oxidative stress and fibrosis in 8-month-old db/db mice by depleting cardiac glutathione.

PubMed

Laher, Ismail; Beam, Julianne; Botta, Amy; Barendregt, Rebekah; Sulistyoningrum, Dian; Devlin, Angela; Rheault, Mark; Ghosh, Sanjoy

2013-01-01

Moderate exercise improves cardiac antioxidant status in young humans and animals with Type-2 diabetes (T2D). Given that both diabetes and advancing age synergistically decrease antioxidant expression in most tissues, it is unclear whether exercise can upregulate cardiac antioxidants in chronic animal models of T2D. To this end, 8-month-old T2D and normoglycemic mice were exercised for 3 weeks, and cardiac redox status was evaluated. As expected, moderate exercise increased cardiac antioxidants and attenuated oxidative damage in normoglycemic mice. In contrast, similar exercise protocol in 8-month-old db/db mice worsened cardiac oxidative damage, which was associated with a specific dysregulation of glutathione (GSH) homeostasis. Expression of enzymes for GSH biosynthesis [γ-glutamylcysteine synthase, glutathione reductase] as well as for GSH-mediated detoxification (glutathione peroxidase, glutathione-S-transferase) was lower, while toxic metabolites dependent on GSH for clearance (4-hydroxynonenal) were increased in exercised diabetic mice hearts. To validate GSH loss as an important factor for such aggravated damage, daily administration of GSH restored cardiac GSH levels in exercised diabetic mice. Such supplementation attenuated both oxidative damage and fibrotic changes in the myocardium. Expression of transforming growth factor beta (TGF-β) and its regulated genes which are responsible for such profibrotic changes were also attenuated with GSH supplementation. These novel findings in a long-term T2D animal model demonstrate that short-term exercise by itself can deplete cardiac GSH and aggravate cardiac oxidative stress. As GSH administration conferred protection in 8-month-old diabetic mice undergoing exercise, supplementation with GSH-enhancing agents may be beneficial in elderly diabetic patients undergoing exercise.

Phase equilibria in the iron oxide-cobalt oxide-phosphorus oxide system

NASA Technical Reports Server (NTRS)

De Guire, Mark R.; Prasanna, T. R. S.; Kalonji, Gretchen; O'Handley, Robert C.

1987-01-01

Two novel ternary compounds are noted in the present study of 1000 C solid-state equilibria in the Fe-Co-P-O system's Fe2O3-FePO4-Co3(Po4)2-CoO region: CoFe(PO4)O, which undergoes incongruent melting at 1130 C, and Co3Fe4(PO4)6, whose incongruent melting occurs at 1080 C. The liquidus behavior-related consequences of rapidly solidified cobalt ferrite formation from cobalt ferrite-phosphate melts are discussed with a view to spinel formation. It is suggested that quenching from within the spinel-plus-liquid region may furnish an alternative to quenching a homogeneous melt.

Modeling the Relationship Between Porosity and Permeability During Oxidation of Ablative Materials

NASA Technical Reports Server (NTRS)

Thornton, John M.; Panerai, Francesco; Ferguson, Joseph C.; Borner, Arnaud; Mansour, Nagi N.

2017-01-01

The ablative materials used in thermal protection systems (TPS) undergo oxidation during atmospheric entry which leads to an in-depth change in both permeability and porosity. These properties have a significant affect on heat transfer in a TPS during entry. X-ray micro-tomography has provided 3D images capturing the micro-structure of TPS materials. In this study, we use micro-tomography based simulations to create high-fidelity models relating permeability to porosity during oxidation of FiberForm, the carbon fiber preform of the Phenolic Impregnated Carbon Ablator (PICA) often used as a TPS material. The goal of this study is to inform full-scale models and reduce uncertainty in TPS modeling.

Electron microscopic, rock magnetic and paleomagnetic studies of mid-ocean ridge basalts

NASA Astrophysics Data System (ADS)

Wang, Daming

Mid-ocean ridge basalt (MORB) is the major source of marine magnetic anomalies which are the result of the earth's magnetic reversals recorded sequentially in progressively older oceanic crust, as embodied in the theory of sea-floor spreading. Titanomagnetite, the primary magnetic minerals in MORB, undergoes gradual low-temperature alteration to titanomaghemite after initial formation, presenting the paradoxical situation that apparently the original magnetic record stays well-preserved while carriers of this record undergo fundamental mineralogical transformations. An integrated electron microscopic, rock magnetic and paleomagnetic study of MORB has been carried out with the aim to understand the effects of low-temperaure alteration on magnetic properties of MORB. A component of this study documents the oxidation state of titanomagnetite in variably altered young (< 1 Ma) basalt. Titanomaghemites in discolored rims are, in a general sense, oxidized to a higher degree than those in the relatively unaltered gray interior. The titanomaghemite within the discolored rims appears to have oxidized relatively quickly. However, the alteration front of the discolored rims does not generally coincide with a pronounced jump in oxidation state, suggesting oxidation state of the Fe-Ti oxides and visible alteration in the discolored rims are not directly correlated. The natural remanent magnetization (NRM) of MORB shows comparatively higher intensity in early Tertiary and Cretaceous samples than in 10--30 Ma old samples. No compositional, petrological, rock-magnetic or paleomagnetic patterns are observed to account for the NRM variation trend. Geomagnetic field intensity is the only effect which can not be directly tested on the same samples, but shows a similar pattern as the measured NRM intensities. It is therefore concluded that the geomagnetic field strength was, on-average, significantly greater during the Cretaceous than during the Oligocene and Miocene. I proposed that the variability of oxidation state within a grain changes as a function of age: rapid oxidation giving rise to pronounced non-uniform oxidation within a grain during the first 10 to 20 m.y., whereupon oxidation of titanomagnetite gradually slows down due to equilibration with surrounding fluids. Meanwhile, oxidation gradients decrease gradually within a grain via diffusion. The change of oxidation state within a grain can greatly affect its internal stress, which in turn influences the magnetic stability. This stability, observed as coercivity or mean-destructive fields during alternating-field demagnetization, shows otherwise unexplained variations. These variations can only be explained by variability of oxidation degree within a given grain.

Metabolite screening of aromatic amine hair dyes using in vitro hepatic models.

PubMed

Skare, J A; Hewitt, N J; Doyle, E; Powrie, R; Elcombe, C

2009-11-01

Aromatic amines and heterocyclic amines are widely used ingredients in permanent hair dyes. However, little has been published on their potential for oxidation via hepatic cytochrome P450s. Therefore, the authors screened nine such compounds for their potential to undergo oxidative metabolism in human liver microsomes. Toluene-2,5-diamine (TDA), p-aminophenol, m-aminophenol, p-methylaminophenol, N,N'-bis(2-hydroxyethyl)-p-phenylenediamine, and 1-hydroxyethyl-4,5-diaminopyrazole showed no evidence of oxidative metabolism. Oxidized metabolites of 4-amino-2-hydroxytoluene (AHT), 2-methyl-5- hydroxyethylaminophenol (MHEAP), and phenyl methyl pyrazolone (PMP) were detected, but there was no evidence of beta-nicotinamide adenine dinucleotide phosphate (NADPH)-dependent covalent binding to microsomal protein, suggesting that these are not reactive metabolites. Metabolism of AHT, MHEAP, PMP, and TDA was further studied in human hepatocytes. All these compounds underwent conjugation, but no oxidative metabolites were found. The results suggest that none of the hair dye ingredients tested showed evidence of hepatic metabolism to potentially biologically reactive oxidized metabolites.

Iodinated contrast media can induce long-lasting oxidative stress in hemodialysis patients.

PubMed

Hwang, Seun Deuk; Kim, Yoon Ji; Lee, Sang Heun; Cho, Deok Kyu; Cho, Yun Hyeong; Moon, Sung Jin; Lee, Sang Choel; Yoon, Soo Young

2013-11-01

Due to their comorbidities, dialysis patients have many chances to undergo radiologic procedures using iodinated contrast media. We aimed to assess time-sequenced blood oxidative stress level after contrast exposure in hemodialysis (HD) patients compared to those in the non-dialysis population. We included 21 anuric HD patients [HD-coronary angiography (CAG) group] and 23 persons with normal renal function (nonHD-CAG group) scheduled for CAG, and assessed 4 oxidative stress markers [advanced oxidation protein products (AOPP); catalase; 8-hydroxydeoxyguanosine; and malondialdehyde] before and after CAG, and subsequently up to 28 days. In the nonHD-CAG group, only AOPP increased immediately after CAG and returned to baseline within one day. However, in the HD-CAG group, all four oxidative stress markers were significantly increased starting one day after CAG, and remained elevated longer than those in the nonHD-CAG group. Especially, AOPP level remained elevated for a month after contrast exposure. Our study showed that iodinated contrast media induces severe and prolonged oxidative stress in HD patients.

The HK2 Dependent "Warburg Effect" and Mitochondrial Oxidative Phosphorylation in Cancer: Targets for Effective Therapy with 3-Bromopyruvate.

PubMed

Lis, Paweł; Dyląg, Mariusz; Niedźwiecka, Katarzyna; Ko, Young H; Pedersen, Peter L; Goffeau, Andre; Ułaszewski, Stanisław

2016-12-15

This review summarizes the current state of knowledge about the metabolism of cancer cells, especially with respect to the "Warburg" and "Crabtree" effects. This work also summarizes two key discoveries, one of which relates to hexokinase-2 (HK2), a major player in both the "Warburg effect" and cancer cell immortalization. The second discovery relates to the finding that cancer cells, unlike normal cells, derive as much as 60% of their ATP from glycolysis via the "Warburg effect", and the remaining 40% is derived from mitochondrial oxidative phosphorylation. Also described are selected anticancer agents which generally act as strong energy blockers inside cancer cells. Among them, much attention has focused on 3-bromopyruvate (3BP). This small alkylating compound targets both the "Warburg effect", i.e., elevated glycolysis even in the presence oxygen, as well as mitochondrial oxidative phosphorylation in cancer cells. Normal cells remain unharmed. 3BP rapidly kills cancer cells growing in tissue culture, eradicates tumors in animals, and prevents metastasis. In addition, properly formulated 3BP shows promise also as an effective anti-liver cancer agent in humans and is effective also toward cancers known as "multiple myeloma". Finally, 3BP has been shown to significantly extend the life of a human patient for which no other options were available. Thus, it can be stated that 3BP is a very promising new anti-cancer agent in the process of undergoing clinical development.

Sensory effect of acetaldehyde on the perception of 3-mercaptohexan-1-ol and 3-isobutyl-2-methoxypyrazine: Role of acetaldehyde in sensory interactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Coetzee, C.; Brand, J.; Jacobson, Daniel A.

Background and Aims-Wine aroma is influenced by complex interactions between various wine constituents. This study investigated the sensory interactive effects of Sauvignon Blanc impact compounds, 3-mercaptohexan-1-ol and 3-isobutyl-2-methoxypyrazine, with acetaldehyde that typically forms during the oxidation of wine. Methods and Results-Spiked model wines were subjected to sensory descriptive analysis using a trained sensory panel. Additionally, the concentration of each compound varied from below aroma threshold values to high values as reported for wine. Depending on the concentration, acetaldehyde enhanced fruity attributes at a lower concentration, whereas suppression occurred at a higher concentration. Acetaldehyde effectively suppressed the green pepper aroma attributemore » at certain concentration values, whereas 3-mercaptohexan-1-ol suppressed oxidised green apple associated with acetaldehyde. Changes in attributes used for aroma description also occurred because of change in concentration. Conclusions-Complex sensory interactions may occur between Sauvignon Blanc impact compounds and one of the main oxidation-derived compounds, acetaldehyde. Acetaldehyde can enhance or suppress pleasant fruity characters depending on the concentration. Significance of the Study-This study showed the potential positive effect of acetaldehyde on white wine aroma when present at a low concentration. Formation of this compound during winemaking and ageing should, however, be controlled because of negative sensory interactions occurring at a higher concentration. In conclusion, this study may also contribute to the sensory characterisation of Sauvignon Blanc wine undergoing oxidation.« less

Sensory effect of acetaldehyde on the perception of 3-mercaptohexan-1-ol and 3-isobutyl-2-methoxypyrazine: Role of acetaldehyde in sensory interactions

DOE PAGES

Coetzee, C.; Brand, J.; Jacobson, Daniel A.; ...

2016-01-28

Background and Aims-Wine aroma is influenced by complex interactions between various wine constituents. This study investigated the sensory interactive effects of Sauvignon Blanc impact compounds, 3-mercaptohexan-1-ol and 3-isobutyl-2-methoxypyrazine, with acetaldehyde that typically forms during the oxidation of wine. Methods and Results-Spiked model wines were subjected to sensory descriptive analysis using a trained sensory panel. Additionally, the concentration of each compound varied from below aroma threshold values to high values as reported for wine. Depending on the concentration, acetaldehyde enhanced fruity attributes at a lower concentration, whereas suppression occurred at a higher concentration. Acetaldehyde effectively suppressed the green pepper aroma attributemore » at certain concentration values, whereas 3-mercaptohexan-1-ol suppressed oxidised green apple associated with acetaldehyde. Changes in attributes used for aroma description also occurred because of change in concentration. Conclusions-Complex sensory interactions may occur between Sauvignon Blanc impact compounds and one of the main oxidation-derived compounds, acetaldehyde. Acetaldehyde can enhance or suppress pleasant fruity characters depending on the concentration. Significance of the Study-This study showed the potential positive effect of acetaldehyde on white wine aroma when present at a low concentration. Formation of this compound during winemaking and ageing should, however, be controlled because of negative sensory interactions occurring at a higher concentration. In conclusion, this study may also contribute to the sensory characterisation of Sauvignon Blanc wine undergoing oxidation.« less

Mechanism of covalent modification of glyceraldehyde-3-phosphate dehydrogenase at its active site thiol by nitric oxide, peroxynitrite and related nitrosating agents.

PubMed

Mohr, S; Stamler, J S; Brüne, B

1994-07-18

Previous studies have suggested that glyceraldehyde-3-phosphate dehydrogenase (GAPDH) undergoes covalent modification of an active site thiol by a NO.-induced [32P]NAD(+)-dependent mechanism. However, the efficacy of GAPDH modification induced by various NO donors was found to be independent of spontaneous rates of NO. release. To further test the validity of this mechanism, we studied the effects of nitrosonium tertrafluoroborate (BF4NO), a strong NO+ donor. BF4NO potently induces GAPDH labeling by the radioactive nucleotide. In this case, the addition of thiol significantly attenuates enzyme modification by competing for the NO moiety in the formation of RS-NO. Peroxynitrite (ONOO-) also induces GAPDH modification in the presence of thiol, consistent with the notion that this species can transfer NO+ (or NO2+) through the intermediacy of RS-NO. However, the efficiency of this reaction is limited by ONOO- -induced oxidation of protein SH groups at the active site. ONOO- generation appears to account for the modification of GAPDH by SIN-1. Thus, S-nitrosylation of the active site thiol is a prequisite for subsequent post-translational modification with NAD+, and emphasizes the role of NO+ transfer in the initial step of this pathway. Our findings thus provide a uniform mechanism by which nitric oxide and related NO donors initiate non-enzymatic ADP-ribosylation (like) reactions. In biological systems, endogenous RS-NO are likely to support the NO group transfer to thiol-containing proteins.

Partially oxidised organic components in urban aerosol using GCXGC-TOF/MS

NASA Astrophysics Data System (ADS)

Hamilton, J. F.; Webb, P. J.; Lewis, A. C.; Hopkins, J. R.; Smith, S.; Davy, P.

2004-08-01

Partially oxidised organic compounds associated with PM2.5 aerosol collected in London, England, have been analysed using direct thermal desorption coupled to comprehensive gas chromatography-time of flight mass spectrometry (GCXGC-TOF/MS). Over 10000 individual organic components were isolated from around 10µg of aerosol material in a single procedure and with no sample pre-treatment. Chemical functionalities observed using this analytical technique ranged from alkanes to poly-oxygenated species. The chemical band structures commonly used in GCXGC for group type identifications overlap for this sample type, and have required mass spectrometry as an additional level of instrument dimensionality. An investigation of oxygenated volatile organic compounds (o-VOC) contained within urban aerosol has been performed and in a typical sample around 130 o-VOCs were identified based on retention behaviour and spectral match. In excess of 100 other oxygenated species were also observed but lack of mass spectral library or pure components prevents positive identification. Many of the carbonyl species observed could be mechanistically linked to gas phase aromatic hydrocarbon oxidation and there is good agreement in terms of speciation between the urban samples analysed here and those degradation products observed in smog chamber experiments of aromatic oxidation. The presence of partially oxidised species such as linear chain aldehydes and ketones and cyclic products such as furanones suggests that species generated early in the oxidative process may undergo gas to particle partitioning despite their relatively high volatility.

Partially oxidised organic components in urban aerosol using GCXGC-TOF/MS

NASA Astrophysics Data System (ADS)

Hamilton, J.; Webb, P.; Lewis, A.; Hopkins, J.; Smith, S.; Davy, P.

2004-03-01

Partially oxidised organic compounds associated with PM2.5 aerosol collected in London, England, have been analysed using direct thermal desorption coupled to comprehensive gas chromatography-time of flight mass spectrometry (GCXGC-OF/MS). Over 10 000 individual organic components were isolated from around 10 μg of aerosol material in a single procedure and with no sample pre-treatment. Chemical functionalities observed using this analytical technique ranged from alkanes to poly-oxygenated species. The chemical band structures commonly used in GCXGC for group type identifications overlap for this sample type, and have required mass spectrometry as an additional level of instrument dimensionality. An investigation of oxygenated volatile organic compounds (o-VOC) contained within urban aerosol has been performed and in a typical sample around 130 o-VOCs were identified based on retention behaviour and spectral match. In excess of 100 other oxygenated species were also observed but lack of mass spectral library or pure components prevents positive identification. Many of the carbonyl species observed could be mechanistically linked to gas phase aromatic hydrocarbon oxidation and there is good agreement in terms of speciation between the urban samples analysed here and those degradation products observed in smog chamber experiments of aromatic oxidation. The presence of partially oxidised species such as linear chain aldehydes and ketones and cyclic products such as furanones suggests that species generated relatively early in the oxidative process may undergo gas to particle partitioning despite their relatively high volatility.

Plant respirometer enables high resolution of oxygen consumption rates

NASA Technical Reports Server (NTRS)

Foster, D. L.

1966-01-01

Plant respirometer permits high resolution of relatively small changes in the rate of oxygen consumed by plant organisms undergoing oxidative metabolism in a nonphotosynthetic state. The two stage supply and monitoring system operates by a differential pressure transducer and provides a calibrated output by digital or analog signals.

Incorporation of flavonoid derivatives or pentagalloyl glucose into lignin enhances cell wall saccharification following mild alkaline or acidic pretreatments

USDA-ARS?s Scientific Manuscript database

Partial substitution of normal monolignols with phenolic precursors from other metabolic pathways may improve the susceptibility of lignified biomass to chemical pretreatment and enzymatic saccharification for biofuel production. Flavonoids and gallate esters readily undergo oxidative coupling react...

Solar chemistry of metal complexes

NASA Astrophysics Data System (ADS)

Gray, H. B.; Maverick, A. W.

1981-12-01

Electronic excited states of certain transition metal complexes undergo oxidation-reduction reactions that store chemical energy. Such reactions have been extensively explored for mononuclear complexes. Two classes of polynuclear species exhibit similar properties, and these complexes are now being studied as possible homogeneous sensitizer-catalysts for hydrogen production from aqueous solutions.

Nutrient uptake by marshes and seagrasses: Ecosystem functions and spatial variability in the provision of this ecosystem servoce

EPA Science Inventory

Nitrogen entering coastal wetlands undergoes several important transformations involving oxidation and reduction; some ends up in the atmosphere, while much of it remains in the sediments of healthy marshes and seagrass beds – the rest passes into receiving waters. Variability i...

A reversible fluorescent probe for real-time live-cell imaging and quantification of endogenous hydropolysulfides.

PubMed

Umezawa, Keitaro; Kamiya, Mako; Urano, Yasuteru

2018-05-23

The chemical biology of reactive sulfur species, including hydropolysulfides, has been a subject undergoing intense study in recent years, but further understanding of their 'intact' function in living cells has been limited due to a lack of appropriate analytical tools. In order to overcome this limitation, we developed a new type of fluorescent probe which reversibly and selectively reacts to hydropolysulfides. The probe enables live-cell visualization and quantification of endogenous hydropolysulfides without interference from intrinsic thiol species such as glutathione. Additionally, real-time reversible monitoring of oxidative-stress-induced fluctuation of intrinsic hydropolysulfides has been achieved with a temporal resolution in the order of seconds, a result which has not yet been realized using conventional methods. These results reveal the probe's versatility as a new fluorescence imaging tool to understand the function of intracellular hydropolysulfides. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Integrated amorphous silicon-aluminum long-range surface plasmon polariton (LR-SPP) waveguides

NASA Astrophysics Data System (ADS)

Sturlesi, Boaz; Grajower, Meir; Mazurski, Noa; Levy, Uriel

2018-03-01

We demonstrate the design, fabrication, and experimental characterization of a long range surface plasmon polariton waveguide that is compatible with complementary metal-oxide semiconductor backend technology. The structure consists of a thin aluminum strip embedded in amorphous silicon. This configuration offers a symmetric environment in which surface plasmon polariton modes undergo minimal loss. Furthermore, the plasmonic mode profile matches the modes of the dielectric (amorphous silicon) waveguide, thus allowing efficient coupling between silicon photonics and plasmonic platforms. The propagation length of the plasmonic waveguide was measured to be about 27 μm at the telecom wavelength around 1550 nm, in good agreement with numerical simulations. As such, the waveguide features both tight mode confinement and decent propagation length. On top of its photonic properties, placing a metal within the structure may also allow for additional functionalities such as photo-detection, thermo-optic tuning, and electro-optic control to be implemented.

Development of an analytical environmental TEM system and its application.

PubMed

Kishita, Keisuke; Sakai, Hisashi; Tanaka, Hiromochi; Saka, Hiroyasu; Kuroda, Kotaro; Sakamoto, Masayuki; Watabe, Akira; Kamino, Takeo

2009-12-01

Many automotive materials, such as catalysts and fuel cell materials, undergo significant changes in structure or properties when subjected to temperature change or the addition of a gas. For this reason, in the development of these materials, it is important to study the behavior of the material under controlled temperatures and gaseous atmospheres. Recently, a new environmental transmission electron microscope (TEM) has been developed for observation with a high resolution at high temperatures and under gaseous atmospheres, thus making it possible to analyze reaction processes in details. Also, the new TEM provides a high degree of reproducibility of observation conditions, thus making it possible to compare and validate observation of various specimens under a given set of conditions. Furthermore, easiness of gas condition and temperature control can provide a powerful tool for the studying of the mechanism of material change, such as oxidation and reduction reactions.

Myocardial Oxidative Metabolism and Protein Synthesis during Mechanical Circulatory Support by Extracorporeal Membrane Oxygenation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Priddy, MD, Colleen M.; Kajimoto, Masaki; Ledee, Dolena

2013-02-01

Extracorporeal membrane oxygenation (ECMO) provides mechanical circulatory support essential for survival in infants and children with acute cardiac decompensation. However, ECMO also causes metabolic disturbances, which contribute to total body wasting and protein loss. Cardiac stunning can also occur which prevents ECMO weaning, and contributes to high mortality. The heart may specifically undergo metabolic impairments, which influence functional recovery. We tested the hypothesis that ECMO alters oxidative. We focused on the amino acid leucine, and integration with myocardial protein synthesis. We used a translational immature swine model in which we assessed in heart (i) the fractional contribution of leucine (FcLeucine)more » and pyruvate (FCpyruvate) to mitochondrial acetyl-CoA formation by nuclear magnetic resonance and (ii) global protein fractional synthesis (FSR) by gas chromatography-mass spectrometry. Immature mixed breed Yorkshire male piglets (n = 22) were divided into four groups based on loading status (8 hours of normal circulation or ECMO) and intracoronary infusion [13C6,15N]-L-leucine (3.7 mM) alone or with [2-13C]-pyruvate (7.4 mM). ECMO decreased pulse pressure and correspondingly lowered myocardial oxygen consumption (~ 40%, n = 5), indicating decreased overall mitochondrial oxidative metabolism. However, FcLeucine was maintained and myocardial protein FSR was marginally increased. Pyruvate addition decreased tissue leucine enrichment, FcLeucine, and Fc for endogenous substrates as well as protein FSR. Conclusion: The heart under ECMO shows reduced oxidative metabolism of substrates, including amino acids, while maintaining (i) metabolic flexibility indicated by ability to respond to pyruvate, and (ii) a normal or increased capacity for global protein synthesis, suggesting an improved protein balance.« less

Impact and oxidation of single silver nanoparticles at electrode surfaces: one shot versus multiple events† †Electronic supplementary information (ESI) available: Summary of previous studies; Ag NP characterization: TEM and DLS; event duration histogram; maximum current histogram. See DOI: 10.1039/c6sc04483b Click here for additional data file.

PubMed Central

Kang, Minkyung; Bullions, Erin

2017-01-01

Single nanoparticle (NP) electrochemical impacts is a rapidly expanding field of fundamental electrochemistry, with applications from electrocatalysis to electroanalysis. These studies, which involve monitoring the electrochemical (usually current–time, I–t) response when a NP from solution impacts with a collector electrode, have the scope to provide considerable information on the properties of individual NPs. Taking the widely studied oxidative dissolution of individual silver nanoparticles (Ag NPs) as an important example, we present measurements with unprecedented noise (< 5 pA) and time resolution (time constant 100 μs) that are highly revealing of Ag NP dissolution dynamics. Whereas Ag NPs of diameter, d = 10 nm are mostly dissolved in a single event (on the timescale of the measurements), a wide variety of complex processes operate for NPs of larger diameter (d ≥ 20 nm). Detailed quantitative analysis of the I–t features, consumed charge, event duration and impact frequency leads to a major conclusion: Ag NPs undergo sequential partial stripping (oxidative dissolution) events, where a fraction of a NP is electrochemically oxidized, followed by the NP drifting away and back to the tunnelling region before the next partial stripping event. As a consequence, analysis of the charge consumed by single events (so-called “impact coulometry”) cannot be used as a general method to determine the size of colloidal NPs. However, a proper analysis of the I–t responses provides highly valuable information on the transient physicochemical interactions between NPs and polarized surfaces. PMID:28553474

HBOC Vasoactivity: Interplay Between Nitric Oxide Scavenging and Capacity to Generate Bioactive Nitric Oxide Species

PubMed Central

Friedman, Joel M.

2013-01-01

Abstract Significance: Despite many advances in blood substitute research, the development of materials that are effective in maintaining blood volume and oxygen delivery remains a priority for emergency care and trauma. Clinical trials on hemoglobin (Hb)-based oxygen carriers (HBOCs) have not provided information on the mechanism of toxicity, although all commercial formulations have safety concerns. Specifically, it is important to reconcile the different hypotheses of Hb toxicity, such as nitric oxide (NO) depletion and oxidative reactions, to provide a coherent molecular basis for designing a safe HBOC. Recent Advances: HBOCs with different sizes often exhibit differences in the degree of HBOC-induced vasoactivity. This has been attributed to differences in the degree of NO scavenging and in the extent of Hb extravasation. Additionally, it is appears that Hb can undergo reactions that compensate for NO scavenging by generating bioactive forms of NO. Critical Issues: Engineering modifications to enhance bioactive NO production can result in diminished oxygen delivery by virtue of increased oxygen affinity. This strategy can prevent the HBOC from fulfilling the intended goal on preserving oxygenation; however, the NO production effects will increase perfusion and oxygen transport. Future Directions: Hb modifications influence NO scavenging and the capacity of certain HBOCs to compensate for NO scavenging through nitrite-mediated reactions that generate bioactive NO. Based on the current understanding of these NO-related factors, possible synthetic strategies are presented that address how HBOC formulations can be prepared that: (i) effectively deliver oxygen, (ii) maintain tissue perfusion, and (iii) limit/reverse underlying inflammation within the vasculature. Antioxid. Redox Signal. 18, 2284–2297. PMID:23249305

Separating nano graphene oxide from the residual strong-acid filtrate of the modified Hummers method with alkaline solution

NASA Astrophysics Data System (ADS)

Hu, Xuebing; Yu, Yun; Wang, Yongqing; Zhou, Jianer; Song, Lixin

2015-02-01

In the modified Hummers method for preparing graphene oxide, the yellow slurry can be obtained. After filtering through a quantitative filter paper, the strong-acid filtrate containing the unprecipitated nano graphene oxide was gained. The corresponding filtrate was added gradually with an alkaline (NaOH or KOH) solution at room temperature. The unprecipitated nano graphene oxide could undergo fast aggregation when the pH value of the filtrate was about 1.7 and formed the stable floccules. X-ray diffraction analysis shows the dominant peak of the floccules is about 11°, which accords to the peak of graphene oxide. Spectra of X-ray photoelectron spectroscopy confirm the presence in the floccules of an abundance of oxygen functional groups and the purified graphene oxide floccules can be obtained. Atomic force microscopy measurement shows the graphene oxide floccules consists of sheet-like objects, mostly containing only a few layers (about 5 layers). Zeta potential analysis demonstrates the surface charge of the graphene oxide is pH-sensitive and its isoelectric point is ∼1.7. The flocculation mechanism of graphene oxide ascribes to the acid-base interaction with the surface functional groups of the carbon layers.

Heterogeneous oxidation of SO2 by O3-aged black carbon and its dithiothreitol oxidative potential.

PubMed

Xu, Weiwei; Li, Qian; Shang, Jing; Liu, Jia; Feng, Xiang; Zhu, Tong

2015-10-01

Ozone (O3) is an important atmospheric oxidant. Black carbon (BC) particles released into the atmosphere undergo an aging process via O3 oxidation. O3-aged BC particles may change their uptake ability toward trace reducing gases such as SO2 in the atmosphere, leading to different environmental and health effects. In this paper, the heterogeneous reaction process between O3-aged BC and SO2 was explored via in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Combined with ion chromatography (IC), DRIFTS was used to qualitatively and quantitatively analyze the sulfate product. The results showed that O3-aged BC had stronger SO2 oxidation ability than fresh BC, and the reactive species/sites generated on the surface had an important role in the oxidation of SO2. Relative humidity or 254nm UV (ultraviolet) light illumination enhanced the oxidation uptake of SO2 on O3-aged BC. The oxidation potentials of the BC particles were detected via dithiothreitol (DTT) assay. The DTT activity over BC was decreased in the process of SO2 reduction, with the consumption of oxidative active sites. Copyright © 2015. Published by Elsevier B.V.

Concentrations and behavior of oxygen and oxide ion in melts of composition CaO.MgO.xSiO2

NASA Technical Reports Server (NTRS)

Semkow, K. W.; Haskin, L. A.

1985-01-01

The behavior of oxygen and oxide ion in silicate melts was investigated through their electrochemical reactions at a platinum electrode. Values are given for the diffusion coefficient for molecular oxygen in diopside melt and the activation energy of diffusion. It is shown that molecular oxygen dissociates prior to undergoing reduction and that oxide ion reacts quickly with silicate polymers when it is produced. The concentration of oxide ion is kept low by a buffering effect of the silicate, the exact level being dependent on the silicate composition. Data on the kinetics of reaction of the dissociation of molecular oxygen and on the buffering reactions are provided. It is demonstrated that the data on oxygen in these silicate melts are consistent with those for solid buffers.

Effect of blowing agents on the oxidation resistance of carbon foams prepared from molten sucrose

NASA Astrophysics Data System (ADS)

Narasimman, R.; Prabhakaran, K.

2013-06-01

We have prepared low density carbon foams from molten sucrose using aluminium nitrate and boric acid blowing agents. A comparative study of the oxidation resistance of the carbon foams prepared using the two blowing agents are reported in the present paper. Oxidation of the carbon foams was evaluated under isothermal and non-isothermal conditions in air atmosphere using thermogravimetric analysis (TGA). We have observed that the alumina produced from the aluminium nitrate blowing agent acts as a catalyst whereas the boron produced from boric acid inhibits the oxidation of the carbon foams. The oxidation resistance of carbon foams increases with boron concentration. The oxidation onset temperature for the carbon foams prepared using boric acid blowing agent was nearly 60°C higher than that prepared using aluminium nitrate blowing agent. Carbon foams prepared using aluminium nitrate blowing agent undergoes complete oxidation at temperature less than 700°C. Whereas that prepared using boric acid blowing agent leave ˜ 50 wt.% residue at 900°C. Further evidence is provided by the kinetic analysis of the TGA using Coats-Redfern (CR) equation.

Redox status in a model of cancer stem cells.

PubMed

Zaccarin, Mattia; Bosello-Travain, Valentina; Di Paolo, Maria Luisa; Falda, Marco; Maiorino, Matilde; Miotto, Giovanni; Piccolo, Stefano; Roveri, Antonella; Ursini, Fulvio; Venerando, Rina; Toppo, Stefano

2017-03-01

Reversible oxidation of Cys residues is a crucial element of redox homeostasis and signaling. According to a popular concept in oxidative stress signaling, the oxidation of targets of signals can only take place following an overwhelming of the cellular antioxidant capacity. This concept, however, ignores the activation of feedback mechanisms possibly leading to a paradoxical effect. In a model of cancer stem cells (CSC), stably overexpressing the TAZ oncogene, we observed that the increased formation of oxidants is associated with a globally more reduced state of proteins. Redox proteomics revealed that several proteins, capable of undergoing reversible redox transitions, are indeed more reduced while just few are more oxidized. Among the proteins more oxidized, G6PDH emerges as both more expressed and activated by oxidation. This accounts for the observed more reduced state of the NADPH/NADP + couple. The dynamic redox flux generating this apparently paradoxical effect is rationalized in a computational system biology model highlighting the crucial role of G6PDH activity on the rate of redox transitions eventually leading to the reduction of reversible redox switches. Copyright © 2016 Elsevier Inc. All rights reserved.

Mechanistic Insights into the Catalytic Oxidation of Carboxylic Acids on Au/TiO 2: Partial Oxidation of Propionic and Butyric Acid to Gold Ketenylidene through Unsaturated Acids

DOE Office of Scientific and Technical Information (OSTI.GOV)

McEntee, Monica; Tang, Wenjie; Neurock, Matthew

Here, the partial oxidation of model C 2–C 4 (acetic, propionic, and butyric) carboxylic acids on Au/TiO 2 catalysts consisting of Au particles ~3 nm in size was investigated using transmission infrared spectroscopy and density functional theory. All three acids readily undergo oxidative dehydrogenation on Au/TiO 2. Propionic and butyric acid dehydrogenate at the C2–C3 positions, whereas acetic acid dehydrogenates at the C1–C2 position. The resulting acrylate and crotonate intermediates are subsequently oxidized to form β-keto acids that decarboxylate. All three acids form a gold ketenylidene intermediate, Au 2C=C=O, along the way to their full oxidation to form CO 2.more » Infrared measurements of Au 2C=C=O formation as a function of time provides a surface spectroscopic probe of the kinetics for the activation and oxidative dehydrogenation of the alkyl groups in the carboxylate intermediates that form.« less

Mechanistic Insights into the Catalytic Oxidation of Carboxylic Acids on Au/TiO 2: Partial Oxidation of Propionic and Butyric Acid to Gold Ketenylidene through Unsaturated Acids

DOE PAGES

McEntee, Monica; Tang, Wenjie; Neurock, Matthew; ...

2014-12-12

Here, the partial oxidation of model C 2–C 4 (acetic, propionic, and butyric) carboxylic acids on Au/TiO 2 catalysts consisting of Au particles ~3 nm in size was investigated using transmission infrared spectroscopy and density functional theory. All three acids readily undergo oxidative dehydrogenation on Au/TiO 2. Propionic and butyric acid dehydrogenate at the C2–C3 positions, whereas acetic acid dehydrogenates at the C1–C2 position. The resulting acrylate and crotonate intermediates are subsequently oxidized to form β-keto acids that decarboxylate. All three acids form a gold ketenylidene intermediate, Au 2C=C=O, along the way to their full oxidation to form CO 2.more » Infrared measurements of Au 2C=C=O formation as a function of time provides a surface spectroscopic probe of the kinetics for the activation and oxidative dehydrogenation of the alkyl groups in the carboxylate intermediates that form.« less

A Six-Coordinate Peroxynitrite Low-Spin Iron(III) Porphyrinate Complex—The Product of the Reaction of Nitrogen Monoxide (·NO (g)) with a Ferric-Superoxide Species

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, Savita K.; Schaefer, Andrew W.; Lim, Hyeongtaek

Peroxynitrite ( –OON=O, PN) is a reactive nitrogen species (RNS) which can effect deleterious nitrative or oxidative (bio)chemistry. It may derive from reaction of superoxide anion (O 2 •–) with nitric oxide (·NO) and has been suggested to form an as-yet unobserved bound heme-iron-PN intermediate in the catalytic cycle of nitric oxide dioxygenase (NOD) enzymes, which facilitate a ·NO homeostatic process, i.e., its oxidation to the nitrate anion. Here, a discrete six-coordinate low-spin porphyrinate-Fe III complex [(P Im)Fe III( –OON=O)] (P Im; a porphyrin moiety with a covalently tethered imidazole axial “base” donor ligand) has been identified and characterized bymore » various spectroscopies (UV–vis, NMR, EPR, XAS, resonance Raman) and DFT calculations, following its formation at –80 °C by addition of ·NO (g) to the heme-superoxo species, [(P Im)Fe III(O 2 •–)]. DFT calculations confirm that is a six-coordinate low-spin species with the PN ligand coordinated to iron via its terminal peroxidic anionic O atom with the overall geometry being in a cis-configuration. Complex thermally transforms to its isomeric low-spin nitrato form [(P Im)Fe III(NO 3 –)]. While previous (bio)chemical studies show that phenolic substrates undergo nitration in the presence of PN or PN-metal complexes, in the present system, addition of 2,4-di- tert-butylphenol ( 2,4DTBP) to complex does not lead to nitrated phenol; the nitrate complex still forms. Furthermore, DFT calculations reveal that the phenolic H atom approaches the terminal PN O atom (farthest from the metal center and ring core), effecting O–O cleavage, giving nitrogen dioxide (·NO 2) plus a ferryl compound [(P Im)Fe IV=O] (7); this rebounds to give [(P Im)Fe III(NO 3 –)].The generation and characterization of the long sought after ferriheme peroxynitrite complex has been accomplished.« less

A Six-Coordinate Peroxynitrite Low-Spin Iron(III) Porphyrinate Complex—The Product of the Reaction of Nitrogen Monoxide (·NO (g)) with a Ferric-Superoxide Species

DOE PAGES

Sharma, Savita K.; Schaefer, Andrew W.; Lim, Hyeongtaek; ...

2017-11-01

Peroxynitrite ( –OON=O, PN) is a reactive nitrogen species (RNS) which can effect deleterious nitrative or oxidative (bio)chemistry. It may derive from reaction of superoxide anion (O 2 •–) with nitric oxide (·NO) and has been suggested to form an as-yet unobserved bound heme-iron-PN intermediate in the catalytic cycle of nitric oxide dioxygenase (NOD) enzymes, which facilitate a ·NO homeostatic process, i.e., its oxidation to the nitrate anion. Here, a discrete six-coordinate low-spin porphyrinate-Fe III complex [(P Im)Fe III( –OON=O)] (P Im; a porphyrin moiety with a covalently tethered imidazole axial “base” donor ligand) has been identified and characterized bymore » various spectroscopies (UV–vis, NMR, EPR, XAS, resonance Raman) and DFT calculations, following its formation at –80 °C by addition of ·NO (g) to the heme-superoxo species, [(P Im)Fe III(O 2 •–)]. DFT calculations confirm that is a six-coordinate low-spin species with the PN ligand coordinated to iron via its terminal peroxidic anionic O atom with the overall geometry being in a cis-configuration. Complex thermally transforms to its isomeric low-spin nitrato form [(P Im)Fe III(NO 3 –)]. While previous (bio)chemical studies show that phenolic substrates undergo nitration in the presence of PN or PN-metal complexes, in the present system, addition of 2,4-di- tert-butylphenol ( 2,4DTBP) to complex does not lead to nitrated phenol; the nitrate complex still forms. Furthermore, DFT calculations reveal that the phenolic H atom approaches the terminal PN O atom (farthest from the metal center and ring core), effecting O–O cleavage, giving nitrogen dioxide (·NO 2) plus a ferryl compound [(P Im)Fe IV=O] (7); this rebounds to give [(P Im)Fe III(NO 3 –)].The generation and characterization of the long sought after ferriheme peroxynitrite complex has been accomplished.« less

Reactions of methyl groups on a non-reducible metal oxide: The reaction of iodomethane on stoichiometric α-Cr 2O 3(0001)

DOE PAGES

Dong, Yujung; Brooks, John D.; Chen, Tsung-Liang; ...

2015-06-10

The reaction of iodomethane on the nearly stoichiometric α-Cr 2O 3(0001) surface produces gas phase ethylene, methane, and surface iodine adatoms. The reaction is first initiated by the dissociation of iodomethane into surface methyl fragments, -CH 3, and iodine adatoms. Methyl fragments bound at surface Cr cation sites undergo a rate-limiting dehydrogenation reaction to methylene, =CH 2. The methylene intermediates formed from methyl dehydrogenation can then undergo coupling reactions to produce ethylene via two principle reaction pathways: (1) direct coupling of methylene and (2) methylene insertion into the methyl surface bond to form surface ethyl groups which undergo β-H eliminationmore » to produce ethylene. The liberated hydrogen also combines with methyl groups to form methane. Iodine adatoms from the dissociation of iodomethane deactivate the surface by simple site blocking of the surface Cr 3+ cations.« less

The cyclic oxidation resistance at 1200 C of beta-NiAl, FeAl, and CoAl alloys with selected third element additions

NASA Technical Reports Server (NTRS)

Barrett, C. A.; Titran, R. H.

1992-01-01

The intermetallic compounds Beta-NiAl, FeAl, and CoAl were tested in cyclic oxidation with selected third element alloy additions. Tests in static air for 200 1-hr cycles at 1200 C indicated by specific weight change/time data and x-ray diffraction analysis that the 5 at percent alloy additions did not significantly improve the oxidation resistance over the alumina forming baseline alloys without the additions. Many of the alloy additions were actually deleterious. Ta and Nb were the only alloy additions that actually altered the nature of the oxide(s) formed and still maintained the oxidation resistance of the protective alumina scale.

Iron cycling under oscillatory redox conditions: from observations to processes

NASA Astrophysics Data System (ADS)

Meile, C. D.; Chen, C.; Barcellos, D.; Wilmoth, J.; Thompson, A.

2017-12-01

Fe oxyhydroxides play a critical role in soils through their role as structural entities, their high sorption capacity, their role as terminal electron acceptors in the respiration of organic matter, as well as their potential to affect the reactivity of that organic matter. In soils that undergo repeated fluctuations in O2 concentrations, soil iron undergoes transformations between reduced and oxidized forms. The rate of Fe(II) oxidation can govern the nature of Fe(III) oxyhydroxides formed, and hence can affect rates of OC mineralization under suboxic conditions. But it remains unclear if this same behavior occurs in soils, where Fe(II) is mainly present as surface complexes. We documented the impact of such redox oscillations on iron cycling through targeted experiments, in which the magnitude and frequency of redox oscillations were varied systematically on soils from the Luquillo Critical Zone Observatory, Puerto Rico. Our observations demonstrated that higher O2 concentrations led to a faster Fe(II) oxidation and resulted in less crystalline Fe(III)-oxyhydroxides than lower O2 concentrations. We further studied the dynamics of iron phases by amending soil slurries with isotopically-labeled 57Fe(II) and developed a numerical model to quantify the individual processes. Our model showed a higher rate of Fe(III) reduction and increased sorption capacity following the oxidation of Fe(II) at high O2 levels than at low O2 levels, and revealed rapid Fe atom exchange between solution and solid phase. Concurrent measurements of CO2 in our oscillation experiments further illustrated the importance O2 fluctuations on coupled Fe-C dynamics.

Potato (Solanum tuberosum L.) tuber ageing induces changes in the proteome and antioxidants associated with the sprouting pattern.

PubMed

Delaplace, Pierre; Fauconnier, Marie-Laure; Sergeant, Kjell; Dierick, Jean-François; Oufir, Mouhssin; van der Wal, Froukje; America, Antoine H P; Renaut, Jenny; Hausman, Jean-François; du Jardin, Patrick

2009-01-01

During post-harvest storage, potato tubers age as they undergo an evolution of their physiological state influencing their sprouting pattern. In the present study, physiological and biochemical approaches were combined to provide new insights on potato (Solanum tuberosum L. cv. Désirée) tuber ageing. An increase in the physiological age index (PAI) value from 0.14 to 0.83 occurred during storage at 4 degrees C over 270 d. Using this reference frame, a proteomic approach was followed based on two-dimensional electrophoresis. In the experimental conditions of this study, a marked proteolysis of patatin occurred after the PAI reached a value of 0.6. In parallel, several glycolytic enzymes were up-regulated and cellular components influencing protein conformation and the response to stress were altered. The equilibrium between the 20S and 26S forms of the proteasome was modified, the 20S form that recycles oxidized proteins being up-regulated. Two proteins belonging to the cytoskeleton were also differentially expressed during ageing. As most of these changes are also observed in an oxidative stress context, an approach focused on antioxidant compounds and enzymes as well as oxidative damage on polyunsaturated fatty acids and proteins was conducted. All the changes observed during ageing seemed to allow the potato tubers to maintain their radical scavenging activity until the end of the storage period as no accumulation of oxidative damage was observed. These data are interpreted considering the impact of reactive oxygen species on the development and the behaviour of other plant systems undergoing ageing or senescence processes.

Perovskite Oxide Thin Film Growth, Characterization, and Stability

NASA Astrophysics Data System (ADS)

Izumi, Andrew

Studies into a class of materials known as complex oxides have evoked a great deal of interest due to their unique magnetic, ferroelectric, and superconducting properties. In particular, materials with the ABO3 perovskite structure have highly tunable properties because of the high stability of the structure, which allows for large scale doping and strain. This also allows for a large selection of A and B cations and valences, which can further modify the material's electronic structure. Additionally, deposition of these materials as thin films and superlattices through techniques such as pulsed laser deposition (PLD) results in novel properties due to the reduced dimensionality of the material. The novel properties of perovskite oxide heterostructures can be traced to a several sources, including chemical intermixing, strain and defect formation, and electronic reconstruction. The correlations between microstructure and physical properties must be investigated by examining the physical and electronic structure of perovskites in order to understand this class of materials. Some perovskites can undergo phase changes due to temperature, electrical fields, and magnetic fields. In this work we investigated Nd0.5Sr 0.5MnO3 (NSMO), which undergoes a first order magnetic and electronic transition at T=158K in bulk form. Above this temperature NSMO is a ferromagnetic metal, but transitions into an antiferromagnetic insulator as the temperature is decreased. This rapid transition has interesting potential in memory devices. However, when NSMO is deposited on (001)-oriented SrTiO 3 (STO) or (001)-oriented (LaAlO3)0.3-(Sr 2AlTaO6)0.7 (LSAT) substrates, this transition is lost. It has been reported in the literature that depositing NSMO on (110)-oriented STO allows for the transition to reemerge due to the partial epitaxial growth, where the NSMO film is strained along the [001] surface axis and partially relaxed along the [11¯0] surface axis. This allows the NSMO film enough freedom of movement to undergo a shear strain along the [11¯0] axes, allowing the NSMO film to switch phases. It was found that the desired magnetic and electrical properties were closely tied to the structural properties, which were highly sensitive to the precise growth conditions. These perovskite oxides can be further geometrically constrained by patterning, resulting in additional novel magnetic and electrical properties. One such method of patterning involves implanting Ar into a film to locally destabilize the ordered perovskite structure, therefore suppress the magnetic and electrical properties. However, to fully integrate this technique into devices which require multi-planar processes, the ability for a patterned perovskite film to withstand high temperature anneals is crucial in creating more advanced structures. The stability of Ar-implanted La0.7Sr0.3MnO 3 (LSMO) thin films was studied upon annealing at 400°C, 500°C, and 600°C. The LSMO retained its amorphous structure with little ferromagnetism after a 400°C anneal, but anneals at 500°C and 600°C resulted in partial recrystallization and a return of the ferromagnetic properties. This recrystallized film displayed semiconducting properties with a lower Curie temperature than the as deposited film. The deposition of an La 0.7Sr0.3FeO3 (LSFO) film onto an Ar implanted LSMO film at 400°C caused the LSMO film to almost fully recrystallize, suggesting that the deposition process also recrystallizes the Ar-implanted film. In conclusion, two perovskites films were explored in this thesis. NSMO films proved to be very sensitive to growth conditions, and Ar-implanted LSMO films quickly recrystallized past 400°C or a subsequent film deposition. These studies provide useful information on the structural and electronic transformations these films go through during heat treatment and strain engineering.

Lithium Assisted “Dissolution–Alloying” Synthesis of Nanoalloys from Individual Bulk Metals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barkholtz, Heather M.; Gallagher, James R.; Li, Tao

2016-04-12

We report new fundamental chemistry involved in the synthesis of bimetallic nanoalloys via dissolving the pure bulk transition metals in molten lithium. It is revealed at the atomic level that when two pure bulk transition metals such as Pd and Pt are placed in molten lithium (similar to 200 degrees C), they undergo a dissolution process in which the metal-metal bonds in pure bulk transition metals are completely ruptured, which results in the existence of individual Pd and Pt atoms surrounded by lithium atoms, as is evident by synchrotron X-ray adsorption techniques. Then, upon the conversion of metal lithium tomore » LiOH in humid air, the Pd and Pt atoms undergo an alloying process to aggregate into nanoalloys. This method was further expanded to include PdZn, which is notoriously difficult to prepare via traditional nanoalloy synthesis methods due to the easily oxidizable Zn component. The constantly reducing environment of metallic Li allowed for preparation of PdZn nanoalloys with minimal Zn oxidation via dissolution-alloying of individual bulk transition metals in molten lithium. Additionally, this lithium assisted "dissolution-alloying" method bypasses many complications intrinsic to conventional ion reduction-based nanoalloy synthesis including the necessity of ligated metal ions, the use of proper reducing agents and dispersing surfactants, and the presence of segregated phases due to different reduction potentials of the constituent metal ions.« less

Fragmentation and hydration of tektites and microtektites

USGS Publications Warehouse

Glass, B.P.; Muenow, D.W.; Bohor, B.F.; Meeker, G.P.

1997-01-01

An examination of data collected over the last 30 years indicates that the percent of glass fragments vs. whole splash forms in the Cenozoic microtektite strewn fields increases towards the source crater (or source region). We propose that this is due to thermal stress produced when tektites and larger microtektites fall into water near the source crater while still relatively hot (>1150 ??C). We also find evidence (low major oxide totals, frothing when melted) for hydration of most of the North American tektite fragments and microtektites found in marine sediments. High-temperature mass spectrometry indicates that these tektite fragments and microtektites contain up to 3.8 wt% H2O. The H2O-release behavior during the high-temperature mass-spectrometric analysis, plus high Cl abundances (???0.05 wt%), indicate that the North. American tektite fragments and microtektites were hydrated in the marine environment (i.e., the H2O was not trapped solely on quenching from a melt). The younger Ivory Coast and Australasian microtektites do not exhibit much evidence of hydration (at least not in excess of 0.5 wt% H2O); this suggests that the degree of hydration increases with age. In addition, we find that some glass spherules (with 65 wt% SiO2 can undergo simple hydration in the marine environment, while impact glasses (with <65 wt% SiO2) can also undergo palagonitization.

Lithium assisted “dissolution–alloying” synthesis of nanoalloys from individual bulk metals

DOE PAGES

Barkholtz, Heather M.; Gallagher, James R.; Li, Tao; ...

2016-03-27

Here, we report new fundamental chemistry involved in the synthesis of bimetallic nanoalloys via dissolving the pure bulk transition metals in molten lithium. It is revealed at the atomic level that when two pure bulk transition metals such as Pd and Pt are placed in molten lithium (~200°C), they undergo a dissolution process in which the metal-metal bonds in pure bulk transition metals are completely ruptured, resulting in the existence of individual Pd and Pt atoms surrounded by lithium atoms, as is evident by synchrotron Xray adsorption techniques. Then, upon the conversion of metal lithium to LiOH in humid air,more » the Pd and Pt atoms undergo an alloying process, to aggregate into nanoalloys. This method was further expanded to include PdZn, which is notoriously difficult to prepare via traditional nanoalloy synthesis methods due to the easily oxidizable Zn component. The constantly reducing environment of metallic Li allowed for preparation of PdZn nanoalloys with minimal Zn oxidation via dissolution-alloying of individual bulk transition metals in molten lithium. Additionally, this lithium assisted “dissolutionalloying” method bypasses many complications intrinsic to conventional ion reductionbased nanoalloy synthesis including the necessity of ligated metal ions, the use of proper reducing agents and dispersing surfactants, and the presence of segregated phases due to different reduction potentials of the constituent metal ions.« less

Type I allergic hypersensitivity reactions due to ethylene oxide sterilised leucocyte filters in patients with thalassaemia: report of four cases.

PubMed

Belen, Burcu; Polat, Meltem

2015-02-27

Ethylene oxide (EO) is a highly reactive gas used in sterilisation of heat sensitive medical devices, such as infusion sets, cannulae, intubation materials, ventriculoperitoneal shunts, dialysis catheters and stents. Allergic reactions due to EO have been reported in haemodialysis patients, patients undergoing extracorporeal photopheresis and donors of plasmapheresis. Clinical manifestations vary considerably and generally do not allow differentiation between IgE-mediated anaphylaxis and anaphylactoid reactions. We report four patients with thalassaemia who experienced anaphylaxis during transfusion due to ethylene oxide sterilised leucocyte filters. The aim of this report is to highlight the fact that frequently transfused patients can have allergic reactions due to EO particles left in leucocyte filters. 2015 BMJ Publishing Group Ltd.

Reactive nitrogen deposition to South East Asian rainforest

NASA Astrophysics Data System (ADS)

di Marco, Chiara F.; Phillips, Gavin J.; Thomas, Rick; Tang, Sim; Nemitz, Eiko; Sutton, Mark A.; Fowler, David; Lim, Sei F.

2010-05-01

The supply of reactive nitrogen (N) to global terrestrial ecosystems has doubled since the 1960s as a consequence of human activities, such as fertilizer application and production of nitrogen oxides by fossil-fuel burning. The deposition of atmospheric N species constitutes a major nutrient input to the biosphere. Tropical forests have been undergoing a radical land use change by increasing cultivation of sugar cane and oil palms and the remaining forests are increasingly affected by anthropogenic activities. Yet, quantifications of atmospheric nitrogen deposition to tropical forests, and nitrogen cycling under near-pristine and polluted conditions are rare. The OP3 project ("Oxidant and Particle Photochemical Processes above a Southeast Asian Tropical Rainforest") was conceived to study how emissions of reactive trace gases from a tropical rain forest mediate the regional scale production and processing of oxidants and particles, and to better understand the impact of these processes on local, regional and global scale atmospheric composition, chemistry and climate. As part of this study we have measured reactive, nitrogen containing trace gas (ammonia, nitric acid) and the associated aerosol components (ammonium, nitrate) at monthly time resolution using a simple filter / denuder for 16 months. These measurements were made at the Bukit Atur Global Atmospheric Watch tower near Danum Valley in the Malaysian state of Sabah, Borneo. In addition, the same compounds were measured at hourly time-resolution during an intensive measurement period, with a combination of a wet-chemistry system based on denuders and steam jet aerosol collectors and an aerosol mass spectrometer (HR-ToF-AMS), providing additional information on the temporal controls. During this period, concentrations and fluxes of NO, NO2 and N2O were also measured. The measurements are used for inferential dry deposition modelling and combined with wet deposition data from the South East Asian Acid Deposition Network to estimate the total annual atmospheric reactive nitrogen deposition to this tropical forest ecosystem and to quantify the relative contribution of the different chemical compounds.

Urinary phthalate and phthalate alternative metabolites and isoprostane among couples undergoing fertility treatment.

PubMed

Wu, Haotian; Olmsted, Alexandra; Cantonwine, David E; Shahsavari, Shahin; Rahil, Tayyab; Sites, Cynthia; Pilsner, J Richard

2017-02-01

Epidemiological data suggest associations between phthalate exposures to a variety of adverse reproductive outcomes including reduced sperm quality and reproductive success. While mechanisms of these associations are not fully elucidated, oxidative stress has been implicated as a potential mediator. We examined associations of urinary metabolites of phthalates and phthalate alternative plasticizers with oxidative stress among couples seeking fertility treatment. Seventeen urinary plasticizer metabolites and 15-F2t isoprostane, a biomarker of oxidative stress, were quantified in spot samples from 50 couples seeking fertility treatment who enrolled in the Sperm Environmental Epigenetics and Development Study during 2014-2015. In multivariable analyses, percent change in isoprostane was positively associated with interquartile range increases for the oxidative metabolites of di-2-ethylhexyl phthalate, [mono-2-ethyl-5-hydroxyhexyl phthalate (MEHHP; 20.0%, p=0.02), mono-2-ethyl-5-oxohexyl phthalate (MEOHP; 24.1%, p=0.01), and mono-2-ethyl-5-carboxypentyl phthalate (MECPP; 24.1%, p=0.004)], mono-isobutyl phthalate (MiBP; 17.8%, p=0.02), mono-hydroxyisobutyl phthalate (MHiBP; 27.5%, p=0.003), and cyclohexane-1,2-dicarboxylic acid mono-hydroxy-isononyl ester (MHINCH; 32.3%, p=0.002). Stratification of participants by sex revealed that isoprostane was positively associated with MHiBP (41.4%, p=0.01) and monocarboxy-isononyl phthalate (MCNP; 26.0%, p=0.02) among females and MEOHP (35.8%, p=0.03), MiBP (29.2%, p=0.01), MHiBP (34.7%, p=0.007) and MHINCH (49.0%, p=0.002) among males. Our results suggest that exposure to phthalates and phthalate replacements are associated with higher levels of oxidative stress in a sex-specific manner. Additional studies are needed to replicate our findings and to examine the potential health implications of the use of phthalates and alternative phthalates in consumer end products. Copyright © 2016 Elsevier Inc. All rights reserved.

Selective downregulation of mitochondrial electron transport chain activity and increased oxidative stress in human atrial fibrillation.

PubMed

Emelyanova, Larisa; Ashary, Zain; Cosic, Milanka; Negmadjanov, Ulugbek; Ross, Gracious; Rizvi, Farhan; Olet, Susan; Kress, David; Sra, Jasbir; Tajik, A Jamil; Holmuhamedov, Ekhson L; Shi, Yang; Jahangir, Arshad

2016-07-01

Mitochondria are critical for maintaining normal cardiac function, and a deficit in mitochondrial energetics can lead to the development of the substrate that promotes atrial fibrillation (AF) and its progression. However, the link between mitochondrial dysfunction and AF in humans is still not fully defined. The aim of this study was to elucidate differences in the functional activity of mitochondrial oxidative phosphorylation (OXPHOS) complexes and oxidative stress in right atrial tissue from patients without (non-AF) and with AF (AF) who were undergoing open-heart surgery and were not significantly different for age, sex, major comorbidities, and medications. The overall functional activity of the electron transport chain (ETC), NADH:O2 oxidoreductase activity, was reduced by 30% in atrial tissue from AF compared with non-AF patients. This was predominantly due to a selective reduction in complex I (0.06 ± 0.007 vs. 0.09 ± 0.006 nmol·min(-1)·citrate synthase activity(-1), P = 0.02) and II (0.11 ± 0.012 vs. 0.16 ± 0.012 nmol·min(-1)·citrate synthase activity(-1), P = 0.003) functional activity in AF patients. Conversely, complex V activity was significantly increased in AF patients (0.21 ± 0.027 vs. 0.12 ± 0.01 nmol·min(-1)·citrate synthase activity(-1), P = 0.005). In addition, AF patients exhibited a higher oxidative stress with increased production of mitochondrial superoxide (73 ± 17 vs. 11 ± 2 arbitrary units, P = 0.03) and 4-hydroxynonenal level (77.64 ± 30.2 vs. 9.83 ± 2.83 ng·mg(-1) protein, P = 0.048). Our findings suggest that AF is associated with selective downregulation of ETC activity and increased oxidative stress that can contribute to the progression of the substrate for AF. Copyright © 2016 the American Physiological Society.

Regulation of thrombosis and vascular function by protein methionine oxidation

PubMed Central

Gu, Sean X.; Stevens, Jeff W.

2015-01-01

Redox biology is fundamental to both normal cellular homeostasis and pathological states associated with excessive oxidative stress. Reactive oxygen species function not only as signaling molecules but also as redox regulators of protein function. In the vascular system, redox reactions help regulate key physiologic responses such as cell adhesion, vasoconstriction, platelet aggregation, angiogenesis, inflammatory gene expression, and apoptosis. During pathologic states, altered redox balance can cause vascular cell dysfunction and affect the equilibrium between procoagulant and anticoagulant systems, contributing to thrombotic vascular disease. This review focuses on the emerging role of a specific reversible redox reaction, protein methionine oxidation, in vascular disease and thrombosis. A growing number of cardiovascular and hemostatic proteins are recognized to undergo reversible methionine oxidation, in which methionine residues are posttranslationally oxidized to methionine sulfoxide. Protein methionine oxidation can be reversed by the action of stereospecific enzymes known as methionine sulfoxide reductases. Calcium/calmodulin-dependent protein kinase II is a prototypical methionine redox sensor that responds to changes in the intracellular redox state via reversible oxidation of tandem methionine residues in its regulatory domain. Several other proteins with oxidation-sensitive methionine residues, including apolipoprotein A-I, thrombomodulin, and von Willebrand factor, may contribute to vascular disease and thrombosis. PMID:25900980

Preparation of 152Gd targets from a small quantity of gadolinium oxide in a pyrochemical reaction

NASA Astrophysics Data System (ADS)

Lipski, A. R.

1995-02-01

A simple method utilizing small amounts (< 5 mg) of isotopically enriched material for the production of gadolinium targets is discussed. An electrostatically focused e-gun is used in the procedure in which 152Gd 2O 3 powder undergoes reduction-distillation and deposition onto an Fe foil.

A direct access to heterobimetallic complexes by roll-over cyclometallation.

PubMed

Schön, F; Leist, M; Neuba, A; Lang, J; Braun, C; Sun, Y; Niedner-Schatteburg, G; Bräse, S; Thiel, W R

2017-11-02

Complexes of the type [Cp*Ir(N,N')Cl] + (N,N' = 2-(2-dialkylaminopyrimidin-4-yl)pyrimidine) can undergo roll-over cyclometallation leading to a novel N,N'-donor site. Following this strategy heterobimetallic complexes including iridium(iii) and a Group X metal centre in the oxidation state +II were achieved.

Reduced graphene oxide and porphyrin. An interactive affair in 2-D.

PubMed

Wojcik, Aleksandra; Kamat, Prashant V

2010-11-23

Photoexcited cationic 5,10,15,20-tetrakis(1-methyl-4-pyridinio)porphyrin tetra(p-toluenesulfonate) (TMPyP) undergoes charge-transfer interaction with chemically reduced graphene oxide (RGO). Formation of the ground-state TMPyP-RGO complex in solution is marked by the red-shift of the porphyrin absorption band. This complexation was analyzed by Benesi-Hildebrand plot. Porphyrin fluorescence lifetime reduced from 5 to 1 ns upon complexation with RGO, indicating excited-state interaction between singlet excited porphyrin and RGO. Femtosecond transient absorption measurements carried out with TMPyP adsorbed on RGO film revealed fast decay of the singlet excited state, followed by the formation of a longer-living product with an absorption maximum around 515 nm indicating the formation of a porphyrin radical cation. The ability of TMPyP-RGO to undergo photoinduced charge separation was further confirmed from the photoelectrochemical measurements. TMPyP-RGO coated conducting glass electrodes are capable of generating photocurrent under visible excitation. These results are indicative of the electron transfer between photoexcited porphyrin and RGO. The role of graphene in accepting and shuttling electrons in light-harvesting assemblies is discussed.

Mechanisms of redox interactions of bilirubin with copper and the effects of penicillamine.

PubMed

Božić, Bojana; Korać, Jelena; Stanković, Dalibor M; Stanić, Marina; Popović-Bijelić, Ana; Bogdanović Pristov, Jelena; Spasojević, Ivan; Bajčetić, Milica

2017-12-25

Toxic effects of unconjugated bilirubin (BR) in neonatal hyperbilirubinemia have been related to redox and/or coordinate interactions with Cu 2+ . However, the development and mechanisms of such interactions at physiological pH have not been resolved. This study shows that BR reduces Cu 2+ to Cu 1+ in 1:1 stoichiometry. Apparently, BR undergoes degradation, i.e. BR and Cu 2+ do not form stable complexes. The binding of Cu 2+ to inorganic phosphates, liposomal phosphate groups, or to chelating drug penicillamine, impedes redox interactions with BR. Cu 1+ undergoes spontaneous oxidation by O 2 resulting in hydrogen peroxide accumulation and hydroxyl radical production. In relation to this, copper and BR induced synergistic oxidative/damaging effects on erythrocytes membrane, which were alleviated by penicillamine. The production of reactive oxygen species by BR and copper represents a plausible cause of BR toxic effects and cell damage in hyperbilirubinemia. Further examination of therapeutic potentials of copper chelators in the treatment of severe neonatal hyperbilirubinemia is needed. Copyright © 2017 Elsevier B.V. All rights reserved.

Palladium-Catalyzed Anti-Markovnikov Oxidation of Allylic Amides to Protected β-Amino Aldehydes.

PubMed

Dong, Jia Jia; Harvey, Emma C; Fañanás-Mastral, Martín; Browne, Wesley R; Feringa, Ben L

2014-12-10

A general method for the preparation of N-protected β-amino aldehydes from allylic amines or linear allylic alcohols is described. Here the Pd(II)-catalyzed oxidation of N-protected allylic amines with benzoquinone is achieved in tBuOH under ambient conditions with excellent selectivity toward the anti-Markovnikov aldehyde products and full retention of configuration at the allylic carbon. The method shows a wide substrate scope and is tolerant of a range of protecting groups. Furthermore, β-amino aldehydes can be obtained directly from protected allylic alcohols via palladium-catalyzed autotandem reactions, and the application of this method to the synthesis of β-peptide aldehydes is described. From a mechanistic perspective, we demonstrate that tBuOH acts as a nucleophile in the reaction and that the initially formed tert-butyl ether undergoes spontaneous loss of isobutene to yield the aldehyde product. Furthermore, tBuOH can be used stoichiometrically, thereby broadening the solvent scope of the reaction. Primary and secondary alcohols do not undergo elimination, allowing the isolation of acetals, which subsequently can be hydrolyzed to their corresponding aldehyde products.

Apoptotic signals induce specific degradation of ribosomal RNA in yeast

PubMed Central

Mroczek, Seweryn; Kufel, Joanna

2008-01-01

Organisms exposed to reactive oxygen species, generated endogenously during respiration or by environmental conditions, undergo oxidative stress. Stress response can either repair the damage or activate one of the programmed cell death (PCD) mechanisms, for example apoptosis, and finally end in cell death. One striking characteristic, which accompanies apoptosis in both vertebrates and yeast, is a fragmentation of cellular DNA and mammalian apoptosis is often associated with degradation of different RNAs. We show that in yeast exposed to stimuli known to induce apoptosis, such as hydrogen peroxide, acetic acid, hyperosmotic stress and ageing, two large subunit ribosomal RNAs, 25S and 5.8S, became extensively degraded with accumulation of specific intermediates that differ slightly depending on cell death conditions. This process is most likely endonucleolytic, is correlated with stress response, and depends on the mitochondrial respiratory status: rRNA is less susceptible to degradation in respiring cells with functional defence against oxidative stress. In addition, RNA fragmentation is independent of two yeast apoptotic factors, metacaspase Yca1 and apoptosis-inducing factor Aif1, but it relies on the apoptotic chromatin condensation induced by histone H2B modifications. These data describe a novel phenotype for certain stress- and ageing-related PCD pathways in yeast. PMID:18385160

In High-Light-Acclimated Coffee Plants the Metabolic Machinery Is Adjusted to Avoid Oxidative Stress Rather than to Benefit from Extra Light Enhancement in Photosynthetic Yield

PubMed Central

Martins, Samuel C. V.; Araújo, Wagner L.; Tohge, Takayuki; Fernie, Alisdair R.; DaMatta, Fábio M.

2014-01-01

Coffee (Coffea arabica L.) has been traditionally considered as shade-demanding, although it performs well without shade and even out-yields shaded coffee. Here we investigated how coffee plants adjust their metabolic machinery to varying light supply and whether these adjustments are supported by a reprogramming of the primary and secondary metabolism. We demonstrate that coffee plants are able to adjust its metabolic machinery to high light conditions through marked increases in its antioxidant capacity associated with enhanced consumption of reducing equivalents. Photorespiration and alternative pathways are suggested to be key players in reductant-consumption under high light conditions. We also demonstrate that both primary and secondary metabolism undergo extensive reprogramming under high light supply, including depression of the levels of intermediates of the tricarboxylic acid cycle that were accompanied by an up-regulation of a range of amino acids, sugars and sugar alcohols, polyamines and flavonoids such as kaempferol and quercetin derivatives. When taken together, the entire dataset is consistent with these metabolic alterations being primarily associated with oxidative stress avoidance rather than representing adjustments in order to facilitate the plants from utilizing the additional light to improve their photosynthetic performance. PMID:24733284

Pyrrolidine and Piperidine Formation Via Copper(II) Carboxylate Promoted Intramolecular Carboamination of Unactivated Olefins: Diastereoselectivity and Mechanism

PubMed Central

Sherman, Eric S.; Fuller, Peter H.; Kasi, Dhanalakshmi; Chemler, Sherry R.

2008-01-01

An expanded substrate scope and in depth analysis of the reaction mechanism of the copper(II) carboxylate promoted intramolecular carboamination of unactivated alkenes is described. This method provides access to N-functionalized pyrrolidines and piperidines. Both aromatic and aliphatic γ- and δ-alkenyl N-arylsulfonamides undergo the oxidative cyclization reaction efficiently. N-Benzoyl-2-allylaniline also underwent the oxidative cyclization. The terminal olefin substrates examined were more reactive than those with internal olefins, and the latter terminated in elimination rather than carbon-carbon bond formation. The efficiency of the reaction was enhanced by the use of more organic soluble copper(II) carboxylate salts, copper(II) neodecanoate in particular. The reaction times were reduced by the use of microwave heating. High levels of diastereoselectivity were observed in the synthesis of 2,5-disubstituted pyrrolidines, wherein the cis substitution pattern predominates. The mechanism of the reaction is discussed in the context of the observed reactivity and in comparison to analogous reactions promoted by other reagents and conditions. Our evidence supports a mechanism wherein the N-C bond is formed via intramolecular syn aminocupration and the C-C bond is formed via intramolecular addition of a primary carbon radical to an aromatic ring. PMID:17428100

Racial differences in ocular oxidative metabolism: implications for ocular disease.

PubMed

Siegfried, Carla J; Shui, Ying-Bo; Holekamp, Nancy M; Bai, Fang; Beebe, David C

2011-07-01

To compare the Po(2) distribution in different regions in the eyes of patients undergoing intraocular surgery. Before initiation of intraocular cataract and/or glaucoma surgery, an optical oxygen sensor was introduced into the anterior chamber via a peripheral corneal paracentesis. The tip of the flexible fiberoptic probe was positioned by the surgeon for 3 measurements in all patients: (1) near the central corneal endothelium, (2) in the mid-anterior chamber, and (3) in the anterior chamber angle. In patients scheduled to undergo cataract extraction, Po(2) was also measured (4) at the anterior lens surface and (5) in the posterior chamber just behind the iris. Oxygen measurements at the 5 locations were compared using a 2-tailed unpaired t test and multivariate regression. The Po(2) value was significantly higher in African American patients at all 5 locations compared with Caucasian patients. Adjusting for age increased the significance of this association. Adjusting for race revealed that age was associated with increased Po(2) beneath the central cornea. Racial differences in oxygen levels in the human eye reflect an important difference in oxidative metabolism in the cornea and lens and may reflect differences in systemic physiologic function. Increased oxygen or oxygen metabolites may increase oxidative stress, cell damage, intraocular pressure, and the risk of developing glaucoma. Oxygen use by the cornea decreases with age.

Two-electron oxidation of deoxyguanosine by a Ru(III) complex without involving oxygen molecules through disproportionation.

PubMed

Choi, Sunhee; Ryu, DaWeon; DellaRocca, Joseph G; Wolf, Matthew W; Bogart, Justin A

2011-07-18

Among the many mechanisms for the oxidation of guanine derivatives (G) assisted by transition metals, Ru(III) and Pt(IV) metal ions share basically the same principle. Both Ru(III)- and Pt(IV)-bound G have highly positively polarized C8-H's that are susceptible to deprotonation by OH(-), and both undergo two-electron redox reactions. The main difference is that, unlike Pt(IV), Ru(III) is thought to require O(2) to undergo such a reaction. In this study, however, we report that [Ru(III)(NH(3))(5)(dGuo)] (dGuo = deoxyguanosine) yields cyclic-5'-O-C8-dGuo (a two-electron G oxidized product, cyclic-dGuo) without O(2). In the presence of O(2), 8-oxo-dGuo and cyclic-dGuo were observed. Both [Ru(II)(NH(3))(5)(dGuo)] and cyclic-dGuo were produced from [Ru(III)(NH(3))(5)(dGuo)] accelerated by [OH(-)]. We propose that [Ru(III)(NH(3))(5)(dGuo)] disproportionates to [Ru(II)(NH(3))(5)(dGuo)] and [Ru(IV)(NH(3))(4)(NH(2)(-))(dGuo)], followed by a 5'-OH attack on C8 in [Ru(IV)(NH(3))(4)(NH(2)(-))(dGuo)] to initiate an intramolecular two-electron transfer from dGuo to Ru(IV), generating cyclic-dGuo and Ru(II) without involving O(2).

Randomized controlled study of the safety and efficacy of nitrous oxide-sedated endoscopic ultrasound-guided fine needle aspiration for digestive tract diseases

PubMed Central

Wang, Cai-Xia; Wang, Jian; Chen, Yuan-Yuan; Wang, Jia-Ni; Yu, Xin; Yang, Feng; Sun, Si-Yu

2016-01-01

AIM To evaluate the efficacy and safety of nitrous oxide-sedated endoscopic ultrasound-guided fine needle aspiration. METHODS Enrolled patients were divided randomly into an experimental group (inhalation of nitrous oxide) and a control group (inhalation of pure oxygen) and heart rate, blood oxygen saturation, blood pressure, electrocardiogram (ECG) changes, and the occurrence of complications were monitored and recorded. All patients and physicians completed satisfaction questionnaires about the examination and scored the process using a visual analog scale. RESULTS There was no significant difference in heart rate, blood oxygen saturation, blood pressure, ECG changes, or complication rate between the two groups of patients (P > 0.05). However, patient and physician satisfaction were both significantly higher in the nitrous oxide compared with the control group (P < 0.05). CONCLUSION Nitrous oxide-sedation is a safe and effective option for patients undergoing endoscopic ultrasound-guided fine needle aspiration. PMID:28028373

Oxidation promotes insertion of the CLIC1 chloride intracellular channel into the membrane.

PubMed

Goodchild, Sophia C; Howell, Michael W; Cordina, Nicole M; Littler, Dene R; Breit, Samuel N; Curmi, Paul M G; Brown, Louise Jennifer

2009-12-01

Members of the chloride intracellular channel (CLIC) family exist primarily as soluble proteins but can also auto-insert into cellular membranes to form ion channels. While little is known about the process of CLIC membrane insertion, a unique feature of mammalian CLIC1 is its ability to undergo a dramatic structural metamorphosis between a monomeric glutathione-S-transferase homolog and an all-helical dimer upon oxidation in solution. Whether this oxidation-induced metamorphosis facilitates CLIC1 membrane insertion is unclear. In this work, we have sought to characterise the role of oxidation in the process of CLIC1 membrane insertion. We examined how redox conditions modify the ability of CLIC1 to associate with and insert into the membrane using fluorescence quenching studies and a sucrose-loaded vesicle sedimentation assay to measure membrane binding. Our results suggest that oxidation of monomeric CLIC1, in the presence of membranes, promotes insertion into the bilayer more effectively than the oxidised CLIC1 dimer.

Gender and chronological age affect erythrocyte membrane oxidative indices in citrate phosphate dextrose adenine-formula 1 (CPDA-1) blood bank storage condition.

PubMed

Erman, Hayriye; Aksu, Uğur; Belce, Ahmet; Atukeren, Pınar; Uzun, Duygu; Cebe, Tamer; Kansu, Ahmet D; Gelişgen, Remisa; Uslu, Ezel; Aydın, Seval; Çakatay, Ufuk

2016-07-01

It is well known that in vitro storage lesions lead to membrane dysfunction and decreased number of functional erythrocytes. As erythrocytes get older, in storage media as well as in peripheral circulation, they undergo a variety of biochemical changes. In our study, the erythrocytes with different age groups in citrate phosphate dextrose adenine-formula 1 (CPDA-1) storage solution were used in order to investigate the possible effect of gender factor on oxidative damage. Oxidative damage biomarkers in erythrocyte membranes such as ferric reducing antioxidant power, pro-oxidant-antioxidant balance, protein-bound advance glycation end products, and sialic acid were analyzed. Current study reveals that change in membrane redox status during blood-bank storage condition also depends on both gender depended homeostatic factors and the presence of CPDA-1. During the storage period in CPDA-1, erythrocytes from the male donors are mostly affected by free radical-mediated oxidative stress but erythrocytes obtained from females are severely affected by glyoxidative stress.

21 CFR 73.2327 - Chromium oxide greens.

Code of Federal Regulations, 2010 CFR

2010-04-01

... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2327 Chromium oxide greens. (a) Identity and specifications. The color additive chromium oxide greens shall conform in identify and specifications to the requirements of § 73.1327 (a)(1) and (b). (b) Uses and restrictions. The color additive chromium oxide greens...

The effect of upper gastrointestinal system endoscopy process on serum oxidative stress levels.

PubMed

Turan, Mehmet Nuri; Aslan, Mehmet; Bolukbas, Filiz Fusun; Bolukbas, Cengiz; Selek, Sahbettin; Sabuncu, Tevfik

2016-12-01

Some authors have investigated the effects of oxidative stress in some process such as undergoing laparoscopic. However, the effect of upper gastrointestinal system endoscopy process on oxidative stress is unclear. We evaluated the short-term effect of upper gastrointestinal system endoscopy process on oxidative stress. Thirty patients who underwent endoscopy process and 20 healthy controls were enrolled in the prospective study. Serum total antioxidant capacity and total oxidant status measurements were measured before and after endoscopy process. The ratio percentage of total oxidant status to total antioxidant capacity was regarded as oxidative stress index. Before endoscopy process, serum total antioxidant capacity levels were higher, while serum total oxidant status levels and oxidative stress index values were lower in patients than controls, but this difference was not statistically significant (all, p > 0.05). After endoscopy process, serum total antioxidant capacity and total oxidant status levels were significantly higher in patients than before endoscopy process (both, p < 0.05). However, oxidative stress index values were slight higher in patients but this difference was not statistically significant (p > 0.05). We observed that serum TAC and TOS levels were increased in patients who underwent endoscopy process after endoscopy process. However, short-time upper gastrointestinal system endoscopy process did not cause an important change in the oxidative stress index. Further studies enrolling a larger number of patients are required to clarify the results obtained here.

Oxidative Stress Status and Placental Implications in Diabetic Rats Undergoing Swimming Exercise After Embryonic Implantation

PubMed Central

Damasceno, Débora Cristina; Sinzato, Yuri Karen; Ribeiro, Viviane Maria; Rudge, Marilza Vieira Cunha; Calderon, Iracema Mattos Paranhos

2015-01-01

The potential benefits and risks of physical exercise on fetal development during pregnancy remain unclear. The aim was to analyze maternal oxidative stress status and the placental morphometry to relate to intrauterine growth restriction (IUGR) from diabetic female rats submitted to swimming program after embryonic implantation. Pregnant Wistar rats were distributed into 4 groups (11 animals/group): control—nondiabetic sedentary rats, control exercised—nondiabetic exercised rats, diabetic—diabetic sedentary rats, and diabetic exercised—diabetic exercised rats. A swimming program was used as an exercise model. At the end of pregnancy, the maternal oxidative stress status, placental morphology, and fetal weight were analyzed. The swimming program was not efficient to reduce the hyperglycemia-induced oxidative stress. This fact impaired placental development, resulting in altered blood flow and energy reserves, which contributed to a deficient exchange of nutrients and oxygen for the fetal development, leading to IUGR. PMID:25361551

Oxidative stress and adipocyte biology: focus on the role of AGEs.

PubMed

Boyer, Florence; Vidot, Jennifer Baraka; Dubourg, Alexis Guerin; Rondeau, Philippe; Essop, M Faadiel; Bourdon, Emmanuel

2015-01-01

Diabetes is a major health problem that is usually associated with obesity, together with hyperglycemia and increased advanced glycation endproducts (AGEs) formation. Elevated AGEs elicit severe downstream consequences via their binding to receptors of AGEs (RAGE). This includes oxidative stress and oxidative modifications of biological compounds together with heightened inflammation. For example, albumin (major circulating protein) undergoes increased glycoxidation with diabetes and may represent an important biomarker for monitoring diabetic pathophysiology. Despite the central role of adipose tissue in many physiologic/pathologic processes, recognition of the effects of greater AGEs formation in this tissue is quite recent within the obesity/diabetes context. This review provides a brief background of AGEs formation and adipose tissue biology and thereafter discusses the impact of AGEs-adipocyte interactions in pathology progression. Novel data are included showing how AGEs (especially glycated albumin) may be involved in hyperglycemia-induced oxidative damage in adipocytes and its potential links to diabetes progression.

Biodegradation of halothane, enflurane and methoxyflurane.

PubMed

Sakai, T; Takaori, M

1978-08-01

The biodegradation of halothane, enflurane and methoxyflurane was studied in 22 patients undergoing abdominal surgery, by measuring the uptake and elimination of each agent and the fluoride excretion in urine. Six control patients were anaesthetized with nitrous oxide in oxygen together with neuromuscular blocking drugs, five patients with nitrous oxide in oxygen and 0.93% halothane, five with nitrous oxide in oxygen and 1.30% enflurane, and six with nitrous oxide in oxygen and 0.31% methoxyflurane. The ratio of the fluoride excretion in urine to the total amount of fluoride contained in the amount of each anaesthetic agent absorbed during anaesthesia was estimated to be 17.7% for halothane, 2.3% for enflurane and 46.3% for methoxyflurane. The serum fluoride concentration increased to a maximum of 15.8 +/- 3.8 mumol litre-1 (mean +/- SD) at 6 h after anaesthesia with methoxyflurane, while it did not exceed 8 mumol litre-1 with the other anaesthetic agents.

Tuning the Two-Dimensional Electron Liquid at Oxide Interfaces by Buffer-Layer-Engineered Redox Reactions.

PubMed

Chen, Yunzhong; Green, Robert J; Sutarto, Ronny; He, Feizhou; Linderoth, Søren; Sawatzky, George A; Pryds, Nini

2017-11-08

Polar discontinuities and redox reactions provide alternative paths to create two-dimensional electron liquids (2DELs) at oxide interfaces. Herein, we report high mobility 2DELs at interfaces involving SrTiO 3 (STO) achieved using polar La 7/8 Sr 1/8 MnO 3 (LSMO) buffer layers to manipulate both polarities and redox reactions from disordered overlayers grown at room temperature. Using resonant X-ray reflectometry experiments, we quantify redox reactions from oxide overlayers on STO as well as polarity induced electronic reconstruction at epitaxial LSMO/STO interfaces. The analysis reveals how these effects can be combined in a STO/LSMO/disordered film trilayer system to yield high mobility modulation doped 2DELs, where the buffer layer undergoes a partial transformation from perovskite to brownmillerite structure. This uncovered interplay between polar discontinuities and redox reactions via buffer layers provides a new approach for the design of functional oxide interfaces.

Long-term oxidization and phase transition of InN nanotextures

PubMed Central

2011-01-01

The long-term (6 months) oxidization of hcp-InN (wurtzite, InN-w) nanostructures (crystalline/amorphous) synthesized on Si [100] substrates is analyzed. The densely packed layers of InN-w nanostructures (5-40 nm) are shown to be oxidized by atmospheric oxygen via the formation of an intermediate amorphous In-Ox-Ny (indium oxynitride) phase to a final bi-phase hcp-InN/bcc-In2O3 nanotexture. High-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, electron energy loss spectroscopy and selected area electron diffraction are used to identify amorphous In-Ox-Ny oxynitride phase. When the oxidized area exceeds the critical size of 5 nm, the amorphous In-Ox-Ny phase eventually undergoes phase transition via a slow chemical reaction of atomic oxygen with the indium atoms, forming a single bcc In2O3 phase. PMID:21711908

[The modification of structural and functional properties of human hemoglobin induced by nitroglycerin under different oxygen regime conditions].

PubMed

Artyukhov, V G; Kalaeva, E A; Putintseva, O V; Polyubez'eva, A I

2016-03-01

Human oxyhemoglobin exhibits high resistance to nitroglycerin during incubation of the protein with this compound for 0.3-3 h. Prolonged exposure (24 h) leads to activation of methemoglobin production. In the presence of nitroglycerin hemoglobin molecules undergo rapid oxidation during deoxygenation with formation of methemoglobin as the terminal product of human oxyhemoglobin interaction with nitroglycerin. The scheme of interaction processes of oxyhemoglobin with nitroglycerin in different conditions of oxygen regime is proposed. Partially deliganded hemoglobin plays the leading role in the initiation of hemoglobin oxidation processes.

Total Synthesis of Plakilactones C, B and des-Hydroxyplakilactone B by the Oxidative Cleavage of Gracilioether Furanylidenes.

PubMed

Norris, Matthew D; Perkins, Michael V

2016-08-05

A chemoselective oxidative cleavage of synthetic gracilioether B, 11-epi-gracilioether C benzoate, and des-hydroxygracilioether C with pyridinium chlorochromate, which proceeds with loss of the furanyl acetate, has enabled total synthesis and stereochemical elucidation of the marine sponge metabolites (4R,6R)-plakilactone C, (4R,6R,9R)-plakilactone B, and (4R,6R)-des-hydroxyplakilactone B. des-Hydroxygracilioether C, the putative biosynthetic precursor to hippolachnin A, was also found to undergo a facile ene cyclization on treatment with SnCl4.

Mn1.4Co1.4Cu0.2O4 spinel protective coating on ferritic stainless steels for solid oxide fuel cell interconnect applications

NASA Astrophysics Data System (ADS)

Chen, Guoyi; Xin, Xianshuang; Luo, Ting; Liu, Leimin; Zhou, Yuchun; Yuan, Chun; Lin, Chucheng; Zhan, Zhongliang; Wang, Shaorong

2015-03-01

In an attempt to reduce the oxidation and Cr evaporation rates of solid oxide fuel cells (SOFCs), Mn1.4Co1.4Cu0.2O4 spinel coating is developed on the Crofer22 APU ferritic stainless steel substrate by a powder reduction technique. Doping of Cu into Mn-Co spinels improves electrical conductivity as well as thermal expansion match with the Crofer22 APU interconnect. Good adhesion between the coating and the alloy substrate is achieved by the reactive sintering process using the reduced powders. Long-term isothermal oxidation experiment and area specific resistance (ASR) measurement are investigated. The ASR is less than 4 mΩ cm2 even though the coated alloy undergoes oxidation at 800 °C for 530 h and four thermal cycles from 800 °C to room temperature. The Mn1.4Co1.4Cu0.2O4 spinel coatings demonstrate excellent anti-oxidation performance and long-term stability. It exhibits a promising prospect for the practical application of SOFC alloy interconnect.

Catalytic routes and oxidation mechanisms in photoreforming of polyols

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sanwald, Kai E.; Berto, Tobias F.; Eisenreich, Wolfgang

2016-12-01

Photocatalytic reforming of biomass-derived oxygenates leads to H 2 generation and evolution of CO 2 via parallel formation of organic intermediates through anodic oxidations on a Rh/TiO 2 photocatalyst. The reaction pathways and kinetics in the photoreforming of C 3–C 6 polyols were explored. Polyols are converted via direct and indirect hole transfer pathways resulting in (i) oxidative rupture of C–C bonds, (ii) oxidation to a-oxygen functionalized aldoses and ketoses (carbonyl group formation) and (iii) light-driven dehydration. Direct hole transfer to chemisorbed oxygenates on terminal Ti(IV)-OH groups, generating alkoxy-radicals that undergo ß-C–C-cleavage, is proposed for the oxidative C–C rupture. Carbonylmore » group formation and dehydration are attributed to indirect hole transfer at surface lattice oxygen sites [Ti_ _ _O_ _ _Ti] followed by the generation of carbon-centered radicals. Polyol chain length impacts the contribution of the oxidation mechanisms favoring the C–C bond cleavage (internal preferred over terminal) as the dominant pathway with higher polyol carbon number.« less

In situ evaluation of heavy metal-DNA interactions using an electrochemical DNA biosensor.

PubMed

Oliveira, S C B; Corduneanu, O; Oliveira-Brett, A M

2008-02-01

Heavy metal ions, lead, cadmium and nickel, are well known carcinogens with natural different origins and their direct mode of action is still not fully understood. A dsDNA-electrochemical biosensor, employing differential pulse voltammetry, was used for the in situ evaluation of Pb2+, Cd2+ and Ni2+ interaction with dsDNA. The results confirm that Pb2+, Cd2+ and Ni2+ bind to dsDNA, and that this interaction leads to different modifications in the dsDNA structure. These modifications were electrochemically recognized as changes in the oxidation peaks of guanosine and adenosine bases. Using homopolynucleotides of guanine and adenine it has been proved that the interaction between Pb2+ and DNA causes oxidative damage and preferentially takes place at adenine-containing segments, with the formation of 2,8-dihydroxyadenine, the oxidation product of adenine residues and a biomarker of DNA oxidative damage. The Pb2+ bound to dsDNA can still undergo oxidation. The interaction of Cd2+ and Ni2+ causes conformational changes, destabilizing the double helix, which can enable the action of other oxidative agents on DNA.

Water oxidation catalyzed by mononuclear ruthenium complexes with a 2,2'-bipyridine-6,6'-dicarboxylate (bda) ligand: how ligand environment influences the catalytic behavior.

PubMed

Staehle, Robert; Tong, Lianpeng; Wang, Lei; Duan, Lele; Fischer, Andreas; Ahlquist, Mårten S G; Sun, Licheng; Rau, Sven

2014-02-03

A new water oxidation catalyst [Ru(III)(bda)(mmi)(OH2)](CF3SO3) (2, H2bda = 2,2'-bipyridine-6,6'-dicarboxylic acid; mmi = 1,3-dimethylimidazolium-2-ylidene) containing an axial N-heterocyclic carbene ligand and one aqua ligand was synthesized and fully characterized. The kinetics of catalytic water oxidation by 2 were measured using stopped-flow technique, and key intermediates in the catalytic cycle were probed by density functional theory calculations. While analogous Ru-bda water oxidation catalysts [Ru(bda)L2] (L = pyridyl ligands) are supposed to catalyze water oxidation through a bimolecular coupling pathway, our study points out that 2, surprisingly, undergoes a single-site water nucleophilic attack (acid-base) pathway. The diversion of catalytic mechanisms is mainly ascribed to the different ligand environments, from nonaqua ligands to an aqua ligand. Findings in this work provide some critical proof for our previous hypothesis about how alternation of ancillary ligands of water oxidation catalysts influences their catalytic efficiency.

Effects of natural antioxidants on colour stability, lipid oxidation and metmyoglobin reducing activity in raw beef patties.

PubMed

Liu, Fang; Xu, Qian; Dai, Ruitong; Ni, Yuanying

2015-01-01

Minced meats undergo oxidative changes and develop rancidity more quickly than intact muscle since grinding exposes more of the muscle surface to air and microbial contamination. Due to concerns about toxicological safety of synthetic antioxidants, recent studies have put more focus on natural antioxidant compounds derived from food components. The effects of four natural antioxidants (vitamin E, carnosine, grape seed extract and tea catechins) on oxidative processes and metmyoglobin reducing activity in raw beef patties during refrigerated (4°C) storage were investigated and the results were compared with butylated hydroxyanisole treatment patties. The correlation of lipid oxidation, colour and metmyoglobin reducing activity of beef patties were also studied. Samples treated with carnosine had the highest redness values on the eighth day. Tea catechins, vitamin E and grape seed extract showed higher protective effect against lipid oxidation than carnosine. Metmyoglobin reducing activity increased greatly in all samples during the storage. Significant correlation between redness value and lipid oxidation was demonstrated, while a weak correlation between metmyoglobin reducing activity and any other parameters was shown.

Iodinated Contrast Media Can Induce Long-Lasting Oxidative Stress in Hemodialysis Patients

PubMed Central

Hwang, Seun Deuk; Kim, Yoon Ji; Lee, Sang Heun; Cho, Deok Kyu; Cho, Yun Hyeong; Moon, Sung Jin; Lee, Sang Choel

2013-01-01

Purpose Due to their comorbidities, dialysis patients have many chances to undergo radiologic procedures using iodinated contrast media. We aimed to assess time-sequenced blood oxidative stress level after contrast exposure in hemodialysis (HD) patients compared to those in the non-dialysis population. Materials and Methods We included 21 anuric HD patients [HD-coronary angiography (CAG) group] and 23 persons with normal renal function (nonHD-CAG group) scheduled for CAG, and assessed 4 oxidative stress markers [advanced oxidation protein products (AOPP); catalase; 8-hydroxydeoxyguanosine; and malondialdehyde] before and after CAG, and subsequently up to 28 days. Results In the nonHD-CAG group, only AOPP increased immediately after CAG and returned to baseline within one day. However, in the HD-CAG group, all four oxidative stress markers were significantly increased starting one day after CAG, and remained elevated longer than those in the nonHD-CAG group. Especially, AOPP level remained elevated for a month after contrast exposure. Conclusion Our study showed that iodinated contrast media induces severe and prolonged oxidative stress in HD patients. PMID:24142649

Exploring the synthesis and characterization of nanoenergetic materials from sol-gel chemistry

NASA Astrophysics Data System (ADS)

Walker, Jeremy D.

Nanoenergetic composite materials have been synthesized by a sol-gel chemical process where the addition of a weak base molecule induces the gelation of a hydrated metal salt solution. A proposed 'proton scavenging' mechanism, where a weak base molecule extracts a proton from the coordination sphere of the hydrated iron (III) complex in the gelation process to form iron (III) oxide/hydroxide, FeIIIxOyHz, has been confirmed for the weak base propylene oxide (PO), a 1,2 epoxide, as well as for the weak bases tetrahydrofuran (THF), a 1,4 epoxide, and pyridine, a heterocyclic nitrogen-containing compound. Gelation mechanisms for the formation of FeIIIxOyHz from THF and pyridine have been presented and confirmed through pH, XPS, and IR studies. THF follows a similar mechanism as PO, where the epoxide extracts a proton from the coordination sphere of the hydrated iron complex forming a protonated epoxide, which then undergoes irreversible ring-opening after reaction with a nucleophile in solution. Pyridine also extracts a proton from the hydrated metal complex, however, the stable six-membered molecule has low associated ring strain and does not endure ring-opening. Energetic properties for the Fe2O3/Al and RuO 2/Al sol-gel synthesized systems are also presented. Sol-gel chemistry synthesizes x-ray amorphous oxide matrices which contain substantial quantities of residual water and organic species. The iron (III) matrix, formed from the addition of a weak base epoxide molecule to a hydrated iron (III) nitrate solution, consists of stoichiometric Fe2O3, FeO(OH), and Fe(OH)3 and can only definitely be described as of Fe IIIxOyHz. XPS characterization of the metal oxide matrix synthesized from the addition of the weak base propylene oxide to a hydrated ruthenium (III) chloride solution corresponds to that of hydrous ruthenium (IV) oxide. Fe2O3/Al energetic systems were synthesized from the epoxides PO, trimethylene oxide (TMO) and 3,3 dimethyl oxetane (DMO). Energetic systems formed from each epoxide were each synthesized with different components, including: varying concentrations of nano-scale Al, micron Al, and carbon nanotubes. Surface area analysis of the synthesized matrices shows a direct correlation between the surface area of the iron (III) oxide matrix and the quantified exothermic heat of reaction of the energetic material due to the magnitude of the interfacial surface area contact between the iron (III) oxide matrix and the aluminum particles. The Fe2O3(PO)/Al systems possess the highest heat of reaction values due to the oxide surface area available for contact with the aluminum particles. Also, within systems, 1:1 Fe:nano Al samples possess the highest heat of reaction. Samples with nano-scale Al particles start reaction at 430°C, before the melting point of Al, whereas samples containing micron-Al do not react until ˜800°C, after the melting point of Al. The RuO2/Al energetic systems behave differently dependent on the atmosphere the sample is heated. Heating the RuO2/Al samples in an inert atmosphere results in the complete reduction of the ruthenium oxide matrix to Ru(0) before reaction with the aluminum particles. This results in the exothermic formation of RuxAly intermetallics, with the stoichiometry dependent on the initial Ru:Al concentration. However, heating the samples in an oxygen-rich atmosphere results in an exothermic reaction between RuO2 and Al. Post-reaction analysis of these samples reveals the sole existence of ruthenium (IV) oxide as the exothermic reaction vaporizes the aluminum particles.

Effect of Alloying Additions on Oxidation Behaviors of Ni-Fe Based Superalloy for Ultra-Supercritical Boiler Applications

NASA Astrophysics Data System (ADS)

Lu, Jintao; Yang, Zhen; Zhao, Xinbao; Yan, Jingbo; Gu, Y.

A new kind of Ni-Fe-based superalloy is designed recently for 750 °C-class A-USC boiler tube. The oxidation behavior of the designed alloys with various combinations of anti-oxidation additions, Cr, Al and Si, was investigated at 750 °C and 850 °C, respectively. The results indicated that the oxidation rate of tested alloys decreased with the increase of the sum of additions. Cr addition may drop the relative constant of parabolic rate greatly when temperature is raised. But the oxide scale, mainly consisted of NiCr spinel at 750 °C and NiCrMn spinel at 850 °C, was similar while the Cr content is in a range of 20-25 wt.% at tested temperatures. Al addition, however, showed the best effective to reduce the oxidation rates. Internal Al-rich oxide was observed at the scale/metal interface for alloys added with high content of Al and was increased with Al content increase. Very tiny difference between the oxide scales of the Si-added alloys was identified when Si content varies among 0.02-0.05 wt.%. Basing on these results, this presentation discussed the optimum combination of anti-oxidation additions as well as oxidation mechanisms in the designed Ni-Fe-base superalloy.

Oxidation of DJ-1 Induced by 6-Hydroxydopamine Decreasing Intracellular Glutathione

PubMed Central

Miyama, Akiko; Saito, Yoshiro; Yamanaka, Kazunori; Hayashi, Kojiro; Hamakubo, Takao; Noguchi, Noriko

2011-01-01

DJ-1, the causative gene of a familial form of Parkinson's disease (PD), has been reported to undergo preferential oxidation of the cysteine residue at position 106 (Cys-106) under oxidative stress; however, details of the molecular mechanisms are not well known. In the present study, mechanisms of DJ-1 oxidation induced by 6-hydroxydopamine (6-OHDA) were investigated by using SH-SY5Y cells. The treatment of these cells with 6-OHDA caused an obvious acidic spot sift of DJ-1 due to its oxidation. However, when catalase, which is an hydrogen peroxide (H2O2)-removing enzyme, was added during the treatment, it failed to prevent the oxidation induced by 6-OHDA, suggesting that electrophilic p-quinone formed from 6-OHDA, but not H2O2, was responsible for the DJ-1 oxidation. Benzoquinone, another electrophilic p-quinone, also induced DJ-1 oxidation. The intracellular glutathione (GSH) levels were significantly decreased by 6-OHDA, irrespective of the presence or absence of catalase. The inhibition of GSH synthesis by buthionine sulfoximine resulted in a decrease in GSH levels and enhancement of DJ-1 oxidation. The pretreatment of cells with N-acetyl-cysteine prevented the loss of intracellular GSH and subsequently DJ-1 oxidation induced by 6-OHDA. Collectively, these results suggest that electrophilic p-quinone formed from 6-OHDA induces DJ-1 oxidation by decreasing intracellular GSH. PMID:22132160

21 CFR 73.1991 - Zinc oxide.

Code of Federal Regulations, 2010 CFR

2010-04-01

... amounts consistent with good manufacturing practice. (d) Labeling. The color additive and any mixtues... ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1991 Zinc oxide. (a) Identity. (1) The color additive zinc...). It is principally composed of Zn. (2) Color additive mixtures for drug use made with zinc oxide may...

21 CFR 73.1327 - Chromium oxide greens.

Code of Federal Regulations, 2010 CFR

2010-04-01

... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1327 Chromium oxide greens. (a) Identity. (1) The color additive chromium oxide greens is principally chromic sesquioxide (Cr2O3). (2) Color additive... subpart as safe and suitable for use in color additive mixtures for coloring drugs. (b) Specifications...

Photodissociable dimer reduction products of 2-thiopyrimidine derivatives.

PubMed Central

Wrona, M; Giziewicz, J; Shugar, D

1975-01-01

Both 4,6-dimethyl-2-thipyrimidine and its 1-methyl derivative undergo polarographic reduction in aqueous medium, via a 1e/1H+ reduction to a free radical which rapidly dimerizes to products isolates and identified as 4,4'-bis-(4,6-dimethyl-3,4-dihydropyrimidin-2-thione) and the corresponding 1-methyl dimer. The dimers may be oxidized electrolytically to regenerate the parent monomers. Both dimers also undergo photodissociation to quantitatively regenerate the parent monomers, in high quantum yield, 0.23 and 0.35 M/Einstein. The correlation between electrochemical and photochemical reductions of 2-thiopyrimidines are discussed, as well as the significance of the dimer photodissociation reactions in relation to nucleic acid photochemistry. PMID:28516

Aromatic fluorine compounds. II. 1,2,4,5-Tetrafluorobenzene and related compounds

USGS Publications Warehouse

Finger, G.C.; Reed, F.H.; Burness, D.M.; Fort, D.M.; Blough, R.R.

1951-01-01

The synthesis and properties of 1,2,4,5-tetrafluorobenzene and a group of bromofluoro and chlorofluorobenzenes with a predominating 1,2,4,5-structure are described. Flash point and surface tension data for the fluorinated benzenes and the influence of chlorine substitution upon these values were studied. Under nitration conditions, 1,2,4,5-tetrafluorobenzene will not form a nitro derivative, but will undergo a preferential 1,4-fluorine displacement-oxidation mechanism to give 2,5-difluoro-1,4-benzoquinone. Diazotization reactions on 2-nitro-3,4,6-trifluoroaniline reveal that the nitro group or a fluorine atom in the 4- or 6-position may become labilized, under certain conditions, and undergo replacement.

Oxidation of silicon nitride sintered with rare-earth oxide additions

NASA Technical Reports Server (NTRS)

Mieskowski, D. M.; Sanders, W. A.

1985-01-01

The effects of rare-earth oxide additions on the oxidation of sintered Si3N4 were examined. Insignificant oxidation occurred at 700 and 1000 C, with no evidence of phase instability. At 1370 C, the oxidation rate was lowest for Y2O3 and increased for additions of La2O3, Sm2O3, and CeO2, in that order. Data obtained from X-ray diffraction, electron microprobe analysis, and scanning electron microscopy indicate that oxidation occurs via diffusion of cationic species from Si3N4 grain boundaries.

Examining mechanism of toxicity of copper oxide nanoparticles to Saccharomyces cerevisiae and Caenorhabditis elegans

NASA Astrophysics Data System (ADS)

Mashock, Michael J.

Copper oxide nanoparticles (CuO NPs) are an up and coming technology increasingly being used in industrial and consumer applications and thus may pose risk to humans and the environment. In the present study, the toxic effects of CuO NPs were studied with two model organisms Saccharomyces cerevisiae and Caenorhabditis elegans. The role of released Cu ions during dissolution of CuO NPs in growth media were studied with freshly suspended, aged NPs, and the released Cu 2+ fraction. Exposures to the different Cu treatments showed significant inhibition of S. cerevisiae cellular metabolic activity. Inhibition from the NPs was inversely proportional to size and was not fully explained by the released Cu ions. S. cerevisiae cultures grown under respiring conditions demonstrated greater metabolic sensitivity when exposed to CuO NPs compared to cultures undergoing fermentation. The cellular response to both CuO NPs and released Cu ions on gene expression was analyzed via microarray analysis after an acute exposure. It was observed that both copper exposures resulted in an increase in carbohydrate storage, a decrease in protein production, protein misfolding, increased membrane permeability, and cell cycle arrest. Cells exposed to NPs up-regulated genes related to oxidative phosphorylation but also may be inducing cell cycle arrest by a different mechanism than that observed with released Cu ions. The effect of CuO NPs on C. elegans was examined by using several toxicological endpoints. The CuO NPs displayed a more inhibitory effect, compared to copper sulfate, on nematode reproduction, feeding, and development. We investigated the effects of copper oxide nanoparticles and copper sulfate on neuronal health, a known tissue vulnerable to heavy metal toxicity. In transgenic C. eleganswith neurons expressing a green fluorescent protein reporter, neuronal degeneration was observed in up to 10% of the population after copper oxide nanoparticle exposure. Additionally, nematode mutant strains containing gene knockouts in the divalent-metal transporters smf-1 and smf-2 showed increased tolerance to copper exposure. These results lend credence to the hypothesis that some toxicological effects to eukaryotic organisms from copper oxide nanoparticle exposure may be due to properties specific to the nanoparticles and not solely from the released copper ions.

Oxidative stress and neurobehavioral problems in pediatric acute lymphoblastic leukemia patients undergoing chemotherapy.

PubMed

Stenzel, Stephanie L; Krull, Kevin R; Hockenberry, Marilyn; Jain, Neelam; Kaemingk, Kris; Miketova, Petra; Moore, Ida M

2010-03-01

Neurobehavioral problems after chemotherapy treatment for pediatric acute lymphoblastic leukemia (ALL) have been a recent focus of investigation. This study extended previous research that suggested oxidative stress as a potential mechanism for chemotherapy-induced central nervous system injury by examining early markers of oxidative stress in relation to subsequent neurobehavioral problems. Oxidized and unoxidized components of phosphatidylcholine (PC) were measured in the cerebrospinal fluid of 87 children with ALL at diagnosis, induction, and consolidation. Behavioral assessments were conducted postconsolidation and at the end of chemotherapy. Results revealed a significant association between physiologic reactivity (high vs. low PC changes from diagnosis) and behavioral outcomes (high vs. low pathology). Elevated oxidized PC fraction change was predictive of increased problems with aggression at the end of therapy as well as postconsolidation adaptability. Furthermore, symptoms of hyperactivity systematically changed over time in relation to both unoxidized PC and oxidized PC fraction reactivity. These findings suggest that symptoms of behavioral problems occur early in the course of chemotherapy and that increases in the cerebrospinal fluid PC markers of oxidative stress during induction and consolidation may help to predict certain future behavioral problems.

Beam-induced redox transformation of arsenic during As K-edge XAS measurements: availability of reducing or oxidizing agents and As speciation.

PubMed

Han, Young Soo; Jeong, Hoon Young; Hyun, Sung Pil; Hayes, Kim F; Chon, Chul Min

2018-05-01

During X-ray absorption spectroscopy (XAS) measurements of arsenic (As), beam-induced redox transformation is often observed. In this study, the As species immobilized by poorly crystallized mackinawite (FeS) was assessed for the susceptibility to beam-induced redox reactions as a function of sample properties including the redox state of FeS and the solid-phase As speciation. The beam-induced oxidation of reduced As species was found to be mediated by the atmospheric O 2 and the oxidation products of FeS [e.g. Fe(III) (oxyhydr)oxides and intermediate sulfurs]. Regardless of the redox state of FeS, both arsenic sulfide and surface-complexed As(III) readily underwent the photo-oxidation upon exposure to the atmospheric O 2 during XAS measurements. With strict O 2 exclusion, however, both As(0) and arsenic sulfide were less prone to the photo-oxidation by Fe(III) (oxyhydr)oxides than NaAsO 2 and/or surface-complexed As(III). In case of unaerated As(V)-reacted FeS samples, surface-complexed As(V) was photocatalytically reduced during XAS measurements, but arsenic sulfide did not undergo the photo-reduction.

A Reaction that Takes Place in Beakers but not in Conical Flasks

ERIC Educational Resources Information Center

White, Colin; Ophardt, Charles

2004-01-01

Inductors are substances that undergo a reaction and in so doing markedly accelerate or induce a simultaneous reaction. An experiment showing a reaction involving the oxidation of iodide to iodine by chromium (VI) found to be slow in the absence of acid, but which proceeded rapidly when iron (II) was induced is demonstrated.

Differential gene expression in Daphnia magna suggests distinct modes of action and bioavailability for ZnO nanoparticles and Zn ions

EPA Science Inventory

Zinc oxide nanoparticles (ZnO NPs) are being rapidly developed for use in consumer products, wastewater treatment and chemotherapy, providing several possible routes for ZnO NP exposure to humans and aquatic organisms. Recent studies have shown that ZnO NPs undergo rapid dissolut...

Impacts of halogen additions on mercury oxidation, in a slipstream selective catalyst reduction (SCR), reactor when burning sub-bituminous coal.

PubMed

Cao, Yan; Gao, Zhengyang; Zhu, Jiashun; Wang, Quanhai; Huang, Yaji; Chiu, Chengchung; Parker, Bruce; Chu, Paul; Pant, Wei-Ping

2008-01-01

This paper presents a comparison of impacts of halogen species on the elemental mercury (Hg(0)) oxidation in a real coal-derived flue gas atmosphere. It is reported there is a higher percentage of Hg(0) in the flue gas when burning sub-bituminous coal (herein Powder River Basin (PRB) coal) and lignite, even with the use of selective catalytic reduction (SCR). The higher Hg(0)concentration in the flue gas makes it difficult to use the wet-FGD process for the mercury emission control in coal-fired utility boilers. Investigation of enhanced Hg(0) oxidation by addition of hydrogen halogens (HF, HCl, HBr, and HI) was conducted in a slipstream reactor with and without SCR catalysts when burning PRB coal. Two commercial SCR catalysts were evaluated. SCR catalyst no. 1 showed higher efficiencies of both NO reduction and Hg(0) oxidation than those of SCR catalyst no. 2. NH3 addition seemed to inhibit the Hg(0) oxidation, which indicated competitive processes between NH3 reduction and Hg(0) oxidation on the surface of SCR catalysts. The hydrogen halogens, in the order of impact on Hg(0) oxidation, were HBr, HI, and HCl or HF. Addition of HBr at approximately 3 ppm could achieve 80% Hg(0) oxidation. Addition of HI at approximately 5 ppm could achieve 40% Hg(0) oxidation. In comparison to the empty reactor, 40% Hg(0) oxidation could be achieved when HCl addition was up to 300 ppm. The enhanced Hg(0) oxidation by addition of HBr and HI seemed not to be correlated to the catalytic effects by both evaluated SCR catalysts. The effectiveness of conversion of hydrogen halogens to halogen molecules or interhalogens seemed to be attributed to their impacts on Hg(0) oxidation.

Experimental and thermodynamic study of Co-Fe and Mn-Fe based mixed metal oxides for thermochemical energy storage application

NASA Astrophysics Data System (ADS)

André, Laurie; Abanades, Stéphane; Cassayre, Laurent

2017-06-01

Metal oxides are potential materials for thermochemical heat storage, and among them, cobalt oxide and manganese oxide are attracting attention. Furthermore, studies on mixed oxides are ongoing, as the synthesis of mixed oxides could be a way to answer the drawbacks of pure metal oxides, such as slow reaction kinetics, loss-in-capacity over cycles or sintering, selected for thermochemical heat storage application. The addition of iron oxide is under investigation and the obtained results are presented. This work proposes a comparison of thermodynamic modelling with experimental data in order to identify the impact of iron oxide addition to cobalt oxide and manganese oxide. Fe addition decreased the redox activity and energy storage capacity of Co3O4, whereas the cycling stability of Mn2O3 was significantly improved with added Fe amounts above 20 mol% while the energy storage capacity was unchanged. The thermodynamic modelling method to predict the behavior of the Mn-Fe-O and Co-Fe-O systems was validated, and the possibility to identify other mixed oxides becomes conceivable, by enabling the selection of transition metals additives for metal oxides destined for thermochemical energy storage applications.

Iridium complexes containing mesoionic C donors: selective C(sp3)-H versus C(sp2)-H bond activation, reactivity towards acids and bases, and catalytic oxidation of silanes and water.

PubMed

Petronilho, Ana; Woods, James A; Mueller-Bunz, Helge; Bernhard, Stefan; Albrecht, Martin

2014-11-24

Metalation of a C2-methylated pyridylimidazolium salt with [IrCp*Cl2]2 affords either an ylidic complex, resulting from C(sp(3))-H bond activation of the C2-bound CH3 group if the metalation is performed in the presence of a base, such as AgO2 or Na2CO3, or a mesoionic complex via cyclometalation and thermally induced heterocyclic C(sp(2))-H bond activation, if the reaction is performed in the absence of a base. Similar cyclometalation and complex formation via C(sp(2))-H bond activation is observed when the heterocyclic ligand precursor consists of the analogous pyridyltriazolium salt, that is, when the metal bonding at the C2 position is blocked by a nitrogen rather than a methyl substituent. Despite the strongly mesoionic character of both the imidazolylidene and the triazolylidene, the former reacts rapidly with D(+) and undergoes isotope exchange at the heterocyclic C5 position, whereas the triazolylidene ligand is stable and only undergoes H/D exchange under basic conditions, where the imidazolylidene is essentially unreactive. The high stability of the Ir-C bond in aqueous solution over a broad pH range was exploited in catalytic water oxidation and silane oxidation. The catalytic hydrosilylation of ketones proceeds with turnover frequencies as high as 6,000 h(-1) with both the imidazolylidene and the triazolylidene system, whereas water oxidation is enhanced by the stronger donor properties of the imidazol-4-ylidene ligands and is more than three times faster than with the triazolylidene analogue. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Potato (Solanum tuberosum L.) tuber ageing induces changes in the proteome and antioxidants associated with the sprouting pattern

PubMed Central

Delaplace, Pierre; Fauconnier, Marie-Laure; Sergeant, Kjell; Dierick, Jean-François; Oufir, Mouhssin; van der Wal, Froukje; America, Antoine H. P.; Renaut, Jenny; Hausman, Jean-François; du Jardin, Patrick

2009-01-01

During post-harvest storage, potato tubers age as they undergo an evolution of their physiological state influencing their sprouting pattern. In the present study, physiological and biochemical approaches were combined to provide new insights on potato (Solanum tuberosum L. cv. Désirée) tuber ageing. An increase in the physiological age index (PAI) value from 0.14 to 0.83 occurred during storage at 4 °C over 270 d. Using this reference frame, a proteomic approach was followed based on two-dimensional electrophoresis. In the experimental conditions of this study, a marked proteolysis of patatin occurred after the PAI reached a value of 0.6. In parallel, several glycolytic enzymes were up-regulated and cellular components influencing protein conformation and the response to stress were altered. The equilibrium between the 20S and 26S forms of the proteasome was modified, the 20S form that recycles oxidized proteins being up-regulated. Two proteins belonging to the cytoskeleton were also differentially expressed during ageing. As most of these changes are also observed in an oxidative stress context, an approach focused on antioxidant compounds and enzymes as well as oxidative damage on polyunsaturated fatty acids and proteins was conducted. All the changes observed during ageing seemed to allow the potato tubers to maintain their radical scavenging activity until the end of the storage period as no accumulation of oxidative damage was observed. These data are interpreted considering the impact of reactive oxygen species on the development and the behaviour of other plant systems undergoing ageing or senescence processes. PMID:19204031

Duration of senescent cell survival in vitro as a characteristic of organism longevity, an additional to the proliferative potential of fibroblasts.

PubMed

Yegorov, Yegor E; Zelenin, Alexander V

2003-04-24

More than 40 years have passed since the original publication by Hayflick and Moorhead led to the concept of the 'Hayflick limit' of the maximum number of divisions which somatic cells undergo in vitro. This concept is still regarded as a fundamental characteristic of species longevity. Here we want to emphasize another characteristic of somatic cells, namely, the duration of their survival in vitro in the non-dividing state after cessation of proliferation. This is suggested on the basis of results of recent experiments with so-called Japanese accelerated senescent mice. Results of these experiments reveal a good correlation between the longevity of the mice, the number of duplications of their fibroblasts in vitro, and the survival time of these cells in the non-dividing state. In routine culture conditions, cell survival time may be very long, as much as a few years. However, when the cells are grown under conditions of oxidative stress, cellular longevity is markedly shortened. This new test may serve as an additional marker of organismic longevity. The comparative value of both tests, the classical 'Hayflick limit' and the new test, is discussed.

A capillary zone electrophoresis method to detect conformers and dimers of antithrombin in therapeutic preparations.

PubMed

Marie, Anne-Lise; Tran, Nguyet Thuy; Saller, François; Abdou, Youmna Mohamed; Zeau, Pascal; Plantier, Jean-Luc; Urbain, Rémi; Borgel, Delphine; Taverna, Myriam

2016-07-01

Antithrombin (AT) is a human plasma glycoprotein that possesses anticoagulant and anti-inflammatory properties. However, the native (active) form of AT is unstable and undergoes conformational changes, leading to latent, cleaved, and heterodimeric forms. The presence of these alternative forms mostly inactive can highly impact the quality and therapeutic activity of pharmaceutical AT preparations. We developed a capillary zone electrophoresis method, based on a neutral polyethylene oxide-coated capillary and a buffer close to physiological conditions, enabling the separation of more than eight forms of AT. Several peaks were identified as native, latent, and heterodimeric forms. The CZE method was reproducible with intraday relative standard deviations less than 0.5 and 2% for migration times and peak areas, respectively. The method was applied to the comparison of AT preparations produced by five competitive pharmaceutical companies, and statistical tests were performed. Important differences in the proportion of each form were highlighted. In particular, one AT preparation was shown to contain a high quantity of heterodimer, and two preparations contained high quantities of latent form. In addition, one AT preparation exhibited additional forms, not yet identified. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High capacity lithium ion batteries composed of cobalt oxide nanoparticle anodes and Raman spectroscopic analysis of nanoparticle strain dynamics in batteries

NASA Astrophysics Data System (ADS)

Islam, Mohammad A.; Zuba, Mateusz; DeBiase, Vincent; Noviasky, Nicholas; Hawley, Christopher J.

2018-02-01

Cobalt nanoparticle thin films were electrophoretically deposited on copper current collectors and were annealed into thin films of hollow Co3O4 nanoparticles. These thin films were directly used as the anodes of lithium ion batteries (LIBs) without the addition of conducting carbons and bonding agents. LIBs thus fabricated show high gravimetric capacities and long cycle lives. For ≈1.0 μm thick Co3O4 nanoparticle films the gravimetric capacities of the batteries were more than 800 mAh g-1 at a current rate of C/15, which is about 90% of the theoretical maximum. Additionally, the batteries were able to undergo 200 charge/discharge cycles at a relatively fast rate of C/5 and maintain 50% of the initial capacity. In order to understand the electrochemistry of lithiation in the context of nanoparticles, Raman spectra were collected at different stages of the electrode cycles to determine the chemical and structural changes in the nanomaterials. Our results indicate that initially the electrode nanoparticles were under significant strain and as the battery underwent many cycles of charging/discharging the nanoparticles experienced progressive strain relaxation.

Effects of various additives on sintering of aluminum nitride

NASA Technical Reports Server (NTRS)

Komeya, K.; Inoue, H.; Tsuge, A.

1982-01-01

Effects of thirty additives on sintering A/N were investigated. The addition of alkali earth oxides and rare earth oxides gave fully densified aluminum nitride. This is due to the formation of nitrogen-containing aluminate liquid in the system aluminum nitride-alkali earth oxides or rare earth oxides. Microstructural studies of the sintered specimens with the above two types of additives suggested that the densification was due to the liquid phase sintering. Additions of silicon compounds resulted in poor densification by the formation of highly refractory compounds such as A/N polytypes.

Risk of iron overload is decreased in beating heart coronary artery surgery compared to conventional bypass.

PubMed

Mumby, S; Koh, T W; Pepper, J R; Gutteridge, J M

2001-11-29

Conventional cardiopulmonary bypass surgery (CCPB) increases the iron loading of plasma transferrin often to a state of plasma iron overload, with the presence of low molecular mass iron. Such iron is a potential risk factor for oxidative stress and microbial virulence. Here we assess 'off-pump' coronary artery surgery on the beating heart for changes in plasma iron chemistry. Seventeen patients undergoing cardiac surgery using the 'Octopus' myocardial wall stabilisation device were monitored at five time points for changes in plasma iron chemistry. This group was further divided into those (n=9) who had one- or two- (n=8) vessel grafts, and compared with eight patients undergoing conventional coronary artery surgery. Patients undergoing beating heart surgery had significantly lower levels of total plasma non-haem iron, and a decreased percentage saturation of their transferrin at all time points compared to conventional bypass patients. Plasma iron overload occurred in only one patient undergoing CCPB. Beating heart surgery appears to decrease red blood cell haemolysis, and tissue damage during the operative procedures and thereby significantly decreases the risk of plasma iron overload associated with conventional bypass.

Selectivity of protein oxidative damage during aging in Drosophila melanogaster.

PubMed Central

Das, N; Levine, R L; Orr, W C; Sohal, R S

2001-01-01

The purpose of the present study was to determine whether oxidation of various proteins during the aging process occurs selectively or randomly, and whether the same proteins are damaged in different species. Protein oxidative damage to the proteins, present in the matrix of mitochondria in the flight muscles of Drosophila melanogaster and manifested as carbonyl modifications, was detected immunochemically with anti-dinitrophenyl-group antibodies. Aconitase was found to be the only protein in the mitochondrial matrix that exhibited an age-associated increase in carbonylation. The accrual of oxidative damage was accompanied by an approx. 50% loss in aconitase activity. An increase in ambient temperature, which elevates the rate of metabolism and shortens the life span of flies, caused an elevation in the amount of aconitase carbonylation and an accelerated loss in its activity. Exposure to 100% ambient oxygen showed that aconitase was highly susceptible to undergo oxidative damage and loss of activity under oxidative stress. Administration of fluoroacetate, a competitive inhibitor of aconitase activity, resulted in a dose-dependent decrease in the life span of the flies. Results of the present study demonstrate that protein oxidative damage during aging is a selective phenomenon, and might constitute a mechanism by which oxidative stress causes age-associated losses in specific biochemical functions. PMID:11696009

Suppressing iron oxide nanoparticle toxicity by vascular targeted antioxidant polymer nanoparticles.

PubMed

Cochran, David B; Wattamwar, Paritosh P; Wydra, Robert; Hilt, J Zach; Anderson, Kimberly W; Eitel, Richard E; Dziubla, Thomas D

2013-12-01

The biomedical use of superparamagnetic iron oxide nanoparticles has been of continued interest in the literature and clinic. Their ability to be used as contrast agents for imaging and/or responsive agents for remote actuation makes them exciting materials for a wide range of clinical applications. Recently, however, concern has arisen regarding the potential health effects of these particles. Iron oxide toxicity has been demonstrated in in vivo and in vitro models, with oxidative stress being implicated as playing a key role in this pathology. One of the key cell types implicated in this injury is the vascular endothelial cells. Here, we report on the development of a targeted polymeric antioxidant, poly(trolox ester), nanoparticle that can suppress oxidative damage. As the polymer undergoes enzymatic hydrolysis, active trolox is locally released, providing a long term protection against pro-oxidant agents. In this work, poly(trolox) nanoparticles are targeted to platelet endothelial cell adhesion molecules (PECAM-1), which are able to bind to and internalize in endothelial cells and provide localized protection against the cytotoxicity caused by iron oxide nanoparticles. These results indicate the potential of using poly(trolox ester) as a means of mitigating iron oxide toxicity, potentially expanding the clinical use and relevance of these exciting systems. Copyright © 2013 Elsevier Ltd. All rights reserved.

Oxidation of primary amines to oximes with molecular oxygen using 1,1-diphenyl-2-picrylhydrazyl and WO3/Al2O3 as catalysts.

PubMed

Suzuki, Ken; Watanabe, Tomonari; Murahashi, Shun-Ichi

2013-03-15

The oxidative transformation of primary amines to their corresponding oximes proceeds with high efficiency under molecular oxygen diluted with molecular nitrogen (O2/N2 = 7/93 v/v, 5 MPa) in the presence of the catalysts 1,1-diphenyl-2-picrylhydrazyl (DPPH) and tungusten oxide/alumina (WO3/Al2O3). The method is environmentally benign, because the reaction requires only molecular oxygen as the terminal oxidant and gives water as a side product. Various alicyclic amines and aliphatic amines can be converted to their corresponding oximes in excellent yields. It is noteworthy that the oxidative transformation of primary amines proceeds chemoselectively in the presence of other functional groups. The key step of the present oxidation is a fast electron transfer from the primary amine to DPPH followed by proton transfer to give the α-aminoalkyl radical intermediate, which undergoes reaction with molecular oxygen and hydrogen abstraction to give α-aminoalkyl hydroperoxide. Subsequent reaction of the peroxide with WO3/Al2O3 gives oximes. The aerobic oxidation of secondary amines gives the corresponding nitrones. Aerobic oxidative transformation of cyclohexylamines to cyclohexanone oximes is important as a method for industrial production of ε-caprolactam, a raw material for Nylon 6.

Regulation of thrombosis and vascular function by protein methionine oxidation.

PubMed

Gu, Sean X; Stevens, Jeff W; Lentz, Steven R

2015-06-18

Redox biology is fundamental to both normal cellular homeostasis and pathological states associated with excessive oxidative stress. Reactive oxygen species function not only as signaling molecules but also as redox regulators of protein function. In the vascular system, redox reactions help regulate key physiologic responses such as cell adhesion, vasoconstriction, platelet aggregation, angiogenesis, inflammatory gene expression, and apoptosis. During pathologic states, altered redox balance can cause vascular cell dysfunction and affect the equilibrium between procoagulant and anticoagulant systems, contributing to thrombotic vascular disease. This review focuses on the emerging role of a specific reversible redox reaction, protein methionine oxidation, in vascular disease and thrombosis. A growing number of cardiovascular and hemostatic proteins are recognized to undergo reversible methionine oxidation, in which methionine residues are posttranslationally oxidized to methionine sulfoxide. Protein methionine oxidation can be reversed by the action of stereospecific enzymes known as methionine sulfoxide reductases. Calcium/calmodulin-dependent protein kinase II is a prototypical methionine redox sensor that responds to changes in the intracellular redox state via reversible oxidation of tandem methionine residues in its regulatory domain. Several other proteins with oxidation-sensitive methionine residues, including apolipoprotein A-I, thrombomodulin, and von Willebrand factor, may contribute to vascular disease and thrombosis. © 2015 by The American Society of Hematology.

Survey for reactive blends of asphalt and antistripping additives : final report.

DOT National Transportation Integrated Search

1983-01-01

When subjected to elevated temperatures, some blends of asphalts and antistripping additives undergo a reaction that causes the additive to be ineffective. The frequency ofoccurrence of reactive asphalt-additive blends used by the Virginia Department...

In situ/operando studies for the production of hydrogen through the water-gas shift on metal oxide catalysts.

PubMed

Rodriguez, José A; Hanson, Jonathan C; Stacchiola, Dario; Senanayake, Sanjaya D

2013-08-07

In this perspective article, we show how a series of in situ techniques {X-ray diffraction (XRD), pair-distribution-function analysis (PDF), X-ray absorption fine structure (XAFS), environmental transmission electron microscopy (ETEM), infrared spectroscopy (IR), ambient-pressure X-ray photoelectron spectroscopy (AP-XPS)} can be combined to perform detailed studies of the structural, electronic and chemical properties of metal oxide catalysts used for the production of hydrogen through the water-gas shift reaction (WGS, CO + H2O → H2 + CO2). Under reaction conditions most WGS catalysts undergo chemical transformations that drastically modify their composition with respect to that obtained during the synthesis process. Experiments of time-resolved in situ XRD, XAFS, and PDF indicate that the active phase of catalysts which combine Cu, Au or Pt with oxides such as ZnO, CeO2, TiO2, CeOx/TiO2 and Fe2O3 essentially involves nanoparticles of the reduced noble metals. The oxide support undergoes partial reduction and is not a simple spectator, facilitating the dissociation of water and in some cases modifying the chemical properties of the supported metal. Therefore, to optimize the performance of these catalysts one must take into consideration the properties of the metal and oxide phases. IR and AP-XPS have been used to study the reaction mechanism for the WGS on metal oxide catalysts. Data of IR spectroscopy indicate that formate species are not necessarily involved in the main reaction path for the water-gas shift on Cu-, Au- and Pt-based catalysts. Thus, a pure redox mechanism or associative mechanisms that involve either carbonate-like (CO3, HCO3) or carboxyl (HOCO) species should be considered. In the last two decades, there have been tremendous advances in our ability to study catalytic materials under reaction conditions and we are moving towards the major goal of fully understanding how the active sites for the production of hydrogen through the WGS actually work.

Bulk gold catalyzed oxidation reactions of amines and isocyanides and iron porphyrin catalyzed N-H and O-H bond insertion/cyclization reactions of diamines and aminoalcohols

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klobukowski, Erik

2011-01-01

This work involves two projects. The first project entails the study of bulk gold as a catalyst in oxidation reactions of isocyanides and amines. The main goal of this project was to study the activation and reactions of molecules at metal surfaces in order to assess how organometallic principles for homogeneous processes apply to heterogeneous catalysis. Since previous work had used oxygen as an oxidant in bulk gold catalyzed reactions, the generality of gold catalysis with other oxidants was examined. Amine N-oxides were chosen for study, due to their properties and use in the oxidation of carbonyl ligands in organometallicmore » complexes. When amine N-oxides were used as an oxidant in the reaction of isocyanides with amines, the system was able to produce ureas from a variety of isocyanides, amines, and amine N-oxides. In addition, the rate was found to generally increase as the amine N-oxide concentration increased, and decrease with increased concentrations of the amine. Mechanistic studies revealed that the reaction likely involves transfer of an oxygen atom from the amine N-oxide to the adsorbed isocyanide to generate an isocyanate intermediate. Subsequent nucleophilic attack by the amine yields the urea. This is in contrast to the bulk gold-catalyzed reaction mechanism of isocyanides with amines and oxygen. Formation of urea in this case was proposed to proceed through a diaminocarbene intermediate. Moreover, formation of the proposed isocyanate intermediate is consistent with the reactions of metal carbonyl ligands, which are isoelectronic to isocyanides. Nucleophilic attack at coordinated CO by amine N-oxides produces CO{sub 2} and is analogous to the production of an isocyanate in this gold system. When the bulk gold-catalyzed oxidative dehydrogenation of amines was examined with amine N-oxides, the same products were afforded as when O{sub 2} was used as the oxidant. When the two types of oxidants were directly compared using the same reaction system and conditions, it was found that the oxidative dehydrogenation of dibenzylamine to Nbenzylidenebenzylamine, with N-methylmorpholine N-oxide (NMMO), was nearly quantitative (96%) within 24 h. However, the reaction with oxygen was much slower, with only a 52% yield of imine product over the same time period. Moreover, the rate of reaction was found to be influenced by the nature of the amine N-oxide. For example, the use of the weakly basic pyridine N-oxide (PyNO) led to an imine yield of only 6% after 24 h. A comparison of amine N-oxide and O2 was also examined in the oxidation of PhCH{sub 2}OH to PhCHO catalyzed by bulk gold. In this reaction, a 52% yield of the aldehyde was achieved when NMMO was used, while only a 7% product yield was afforded when O{sub 2} was the oxidant after 48 h. The bulk gold-catalyzed oxidative dehydrogenation of cyclic amines generates amidines, which upon treatment with Aerosil and water were found to undergo hydrolysis to produce lactams. Moreover, 5-, 6-, and 7-membered lactams could be prepared through a one-pot reaction of cyclic amines by treatment with oxygen, water, bulk gold, and Aerosil. This method is much more atom economical than industrial processes, does not require corrosive acids, and does not generate undesired byproducts. Additionally, the gold and Aerosil catalysts can be readily separated from the reaction mixture. The second project involved studying iron(III) tetraphenylporphyrin chloride, Fe(TPP)Cl, as a homogeneous catalyst for the generation of carbenes from diazo reagents and their reaction with heteroatom compounds. Fe(TPP)Cl, efficiently catalyzed the insertion of carbenes derived from methyl 2-phenyldiazoacetates into O-H bonds of aliphatic and aromatic alcohols. Fe(TPP)Cl was also found to be an effective catalyst for tandem N-H and O-H insertion/cyclization reactions when 1,2-diamines and 1,2-alcoholamines were treated with diazo reagents. This approach provides a one-pot process for synthesizing piperazinones and morpholinones and related analogues such as quinoxalinones and benzoxazin-2-ones.« less

Oxidation of Ca-α-SiAlON Powders Prepared by Combustion Synthesis

PubMed Central

Li, Jinfu; Li, Zhongmin; Wang, Enhui; Wang, Zhanjun; Yin, Xiaowei; Zhang, Zuotai

2015-01-01

The oxidation of Ca-α-SiAlON synthesized by the combustion synthesis (CS) method with different additives was investigated in air atmosphere using thermogravimetric (TG) analysis in a temperature range from 1453 K to 1653 K. The experimental results indicated that oxidation was controlled by mixed chemical and diffusion steps. The oxidation products by XRD analysis were composed of SiO2 and CaAl2Si2O8 at low oxidation temperature, whereas the SiO2-Al2O3-CaO ternary glassy phase was formed at elevated temperature. The deviation of oxidation resistance from each sample may be due to the morphological difference brought about by different additive additions. This study reveals the effects of additives on the oxidation resistance of synthesized Ca-α-SiAlON powders. PMID:28793657

Insight into self-discharge of layered lithium-rich oxide cathode in carbonate-based electrolytes with and without additive

NASA Astrophysics Data System (ADS)

Li, Jianhui; Xing, Lidan; Zhang, Liping; Yu, Le; Fan, Weizhen; Xu, Mengqing; Li, Weishan

2016-08-01

Self-discharge behavior of layered lithium-rich oxide as cathode of lithium ion battery in a carbonated-based electrolyte is understood, and a simple boron-containing compound, trimethyl borate (TMB), is used as an electrolyte additive to suppress this self-discharge. It is found that layered lithium-rich oxide charged under 4.8 V in additive-free electrolyte suffers severe self-discharge and TMB is an effective electrolyte additive for self-discharge suppression. Physical characterizations from XRD, SEM, TEM, XPS and ICP-MS demonstrate that the crystal structure of the layered lithium-rich oxide collapses due to the chemical interaction between the charged oxide and electrolyte. When TMB is applied, the structural integrity of the oxide is maintained due to the protective cathode film generated from the preferential oxidation of TMB.

Serum Oxidant and Antioxidant Status Following an All-Out 21-km Run in Adolescent Runners Undergoing Professional Training—A One-Year Prospective Trial

PubMed Central

Tong, Tom K.; Kong, Zhaowei; Lin, Hua; Lippi, Giuseppe; Zhang, Haifeng; Nie, Jinlei

2013-01-01

This study investigated the 1-year longitudinal effect of professional training in adolescent runners on redox balance during intense endurance exercise. Changes in selected serum oxidant and antioxidant status in response to a 21-km running time trial in 10 runners (15.5 ± 1.3 years) undergoing professional training were evaluated twice in 12 months (pre- and post-evaluation). Venous blood samples were collected immediately before and 4-h following the 21-km run for analysis of serum concentrations of thiobarbituric acid-reactive substances (TBARS), xanthine oxidase (XO), catalase (CAT), reduced glutathione (GSH), superoxide dismutase (SOD), and total antioxidant capacity (T-AOC). In pre-evaluation trial, serum TBARS and SOD decreased after the 21-km run (p < 0.05) while XO, GSH, CAT and TAOC were unchanged. In post-evaluation trial, serum TBARS and SOD decreased, whereas XO and CAT increased post-exercise (p < 0.05). Furthermore, pre-exercise serum T-AOC, post-exercise serum XO, CAT, T-AOC (p < 0.05), and GSH (p = 0.057) appeared to be higher than the corresponding pre-evaluation values. The current findings suggest that a professional training regime in adolescent runners is not likely to jeopardize the development of their antioxidant defense. However, uncertainties in the maintenance of redox balance in runners facing increased exercise-induced oxidative stress as a consequence of training-induced enhancement of exercise capacity await further elucidation. PMID:23880864

Implementing supercritical water oxidation technology in a lunar base environmental control/life support system

NASA Technical Reports Server (NTRS)

Meyer Sedej, M.

1985-01-01

A supercritical water oxidation system (SCWOS) offers several advantages for a lunar base environmental control/life support system (ECLSS) compared to an ECLSS based on Space Station technology. In supercritically heated water (630 K, 250 atm) organic materials mix freely with oxygen and undergo complete combustion. Inorganic salts lose solubility and precipitate out. Implementation of SCWOS can make an ECLSS more efficient and reliable by elimination of several subsystems and by reduction in potential losses of life support consumables. More complete closure of the total system reduces resupply requirements from the earth, a crucial cost item in maintaining a lunar base.

Visualizing non-equilibrium lithiation of spinel oxide via in situ transmission electron microscopy

DOE PAGES

He, Kai; Zhang, Sen; Li, Jing; ...

2016-05-09

In this study, spinel transition metal oxides are an important class of materials that are being considered as electrodes for lithium-ion batteries, due to their low cost and high theoretical capacity. The lithiation of these compounds is known to undergo a two-step reaction, whereby intercalation and conversion occur in a sequential fashion. These two reactions are known to have distinct reaction dynamics, but it is unclear how the kinetics of these processes affect the overall electrochemical response. Here, we explore the lithiation of nanosized magnetite (F e3O 4) by employing a new strain-sensitive, bright-field scanning transmission electron microscopy approach.

Process for the manufacture of an attrition resistant sorbent used for gas desulfurization

DOEpatents

Venkataramani, Venkat S.; Ayala, Raul E.

2003-09-16

This process produces a sorbent for use in desulfurization of coal gas. A zinc titanate compound and a metal oxide are mixed by milling the compounds in an aqueous medium, the resulting mixture is dried and then calcined, crushed, sleved and formed into pellets for use in a moving-bed reactor. Metal oxides suitable for use as an additive in this process include: magnesium oxide, magnesium oxide plus molybdenum oxide, calcium oxide, yttrium oxide, hafnium oxide, zirconium oxide, cupric oxide, and tin oxide. The resulting sorbent has a percentage of the original zinc or titanium ions substituted for the oxide metal of the chosen additive.

Species Differences in the Oxidative Desulfurization of a Thiouracil-Based Irreversible Myeloperoxidase Inactivator by Flavin-Containing Monooxygenase Enzymes.

PubMed

Eng, Heather; Sharma, Raman; Wolford, Angela; Di, Li; Ruggeri, Roger B; Buckbinder, Leonard; Conn, Edward L; Dalvie, Deepak K; Kalgutkar, Amit S

2016-08-01

N1-Substituted-6-arylthiouracils, represented by compound 1 [6-(2,4-dimethoxyphenyl)-1-(2-hydroxyethyl)-2-thioxo-2,3-dihydropyrimidin-4(1H)-one], are a novel class of selective irreversible inhibitors of human myeloperoxidase. The present account is a summary of our in vitro studies on the facile oxidative desulfurization in compound 1 to a cyclic ether metabolite M1 [5-(2,4-dimethoxyphenyl)-2,3-dihydro-7H-oxazolo[3,2-a]pyrimidin-7-one] in NADPH-supplemented rats (t1/2 [half-life = mean ± S.D.] = 8.6 ± 0.4 minutes) and dog liver microsomes (t1/2 = 11.2 ± 0.4 minutes), but not in human liver microsomes (t1/2 > 120 minutes). The in vitro metabolic instability also manifested in moderate-to-high plasma clearances of the parent compound in rats and dogs with significant concentrations of M1 detected in circulation. Mild heat deactivation of liver microsomes or coincubation with the flavin-containing monooxygenase (FMO) inhibitor imipramine significantly diminished M1 formation. In contrast, oxidative metabolism of compound 1 to M1 was not inhibited by the pan cytochrome P450 inactivator 1-aminobenzotriazole. Incubations with recombinant FMO isoforms (FMO1, FMO3, and FMO5) revealed that FMO1 principally catalyzed the conversion of compound 1 to M1. FMO1 is not expressed in adult human liver, which rationalizes the species difference in oxidative desulfurization. Oxidation by FMO1 followed Michaelis-Menten kinetics with Michaelis-Menten constant, maximum rate of oxidative desulfurization, and intrinsic clearance values of 209 μM, 20.4 nmol/min/mg protein, and 82.7 μl/min/mg protein, respectively. Addition of excess glutathione essentially eliminated the conversion of compound 1 to M1 in NADPH-supplemented rat and dog liver microsomes, which suggests that the initial FMO1-mediated S-oxygenation of compound 1 yields a sulfenic acid intermediate capable of redox cycling to the parent compound in a glutathione-dependent fashion or undergoing further oxidation to a more electrophilic sulfinic acid species that is trapped intramolecularly by the pendant alcohol motif in compound 1. Copyright © 2016 by The American Society for Pharmacology and Experimental Therapeutics.

Cloud chemistry in eastern China: Observations from Mt. Tai

NASA Astrophysics Data System (ADS)

Collett, J. L.; Shen, X.; Lee, T.; Wang, X.; Li, Y.; Wang, W.; Wang, T.

2010-07-01

Until recently, studies of fog and cloud chemistry in China have been rare - even though the fate of China’s large sulfur dioxide emissions depends, in part, on the ability of regional clouds to support rapid aqueous oxidation to sulfate. Sulfur dioxide oxidized in regional clouds is more likely to be removed by wet deposition while sulfur dioxide that undergoes slower gas phase oxidation is expected to survive longer in the atmosphere and be transported over a much broader spatial scale. Two 2008 field campaigns conducted at Mt. Tai, an isolated peak on the NE China plain, provide insight into the chemical composition of regional clouds and the importance of various aqueous phase sulfur oxidation pathways. Single and two-stage Caltech Active Strand Cloudwater Collectors were used to collect bulk and drop size-resolved samples of cloudwater. Collected cloudwater was analyzed for key species that influence in-cloud sulfate production, including pH, S(IV), H2O2, Fe and Mn. Other major cloud solutes, including inorganic ions, total organic carbon (TOC), formaldehyde, and organic acids were also analyzed, as were gas phase concentrations of SO2, O3, and H2O2. A wide range of cloud pH was observed, from below 3 to above 6. High concentrations of cloudwater sulfate were consistent with abundant sulfur dioxide emissions in the region. Sampled clouds were also found to contain high concentrations of ammonium, nitrate, and organic carbon. Peak TOC concentrations reached approximately 200 ppmC, among the highest concentrations ever measured in cloudwater. Hydrogen peroxide was found to be the dominant aqueous phase S(IV) oxidant when cloud pH was less than approximately 5.4. Despite its fast reaction with sulfur dioxide in cloud droplets, high concentrations of residual hydrogen peroxide were measured in some clouds implying a substantial additional capacity for sulfate production. Ozone was found to be an important S(IV) oxidant when cloud pH was high. Oxidation of S(IV) by oxygen, catalyzed by Fe (III) and Mn(II) was generally the second or third fastest pathway for sulfate production. Differences between the pH and trace metal concentrations of small and large cloud droplets were observed, giving rise to aqueous phase sulfate production rates that were drop size-dependent for the ozone and metal-catalyzed pathways.

Hydroxylamine addition impact to Nitrosomonas europaea activity in the presence of monochloramine.

PubMed

Wahman, David G; Speitel, Gerald E

2015-01-01

In drinking water, monochloramine may promote ammonia–oxidizing bacteria (AOB) growth because of concurrent ammonia presence. AOB use (i) ammonia monooxygenase for biological ammonia oxidation to hydroxylamine and (ii) hydroxylamine oxidoreductase for biological hydroxylamine oxidation to nitrite. In addition, monochloramine and hydroxylamine abiotically react, providing AOB a potential benefit by removing the disinfectant (monochloramine) and releasing growth substrate (ammonia). Alternatively and because biological hydroxylamine oxidation supplies the electrons (reductant) required for biological ammonia oxidation, the monochloramine/hydroxylamine abiotic reaction represents a possible inactivation mechanism by consuming hydroxylamine and inhibiting reductant generation. To investigate the abiotic monochloramine and hydroxylamine reaction's impact on AOB activity, the current study used batch experiments with Nitrosomonas europaea (AOB pure culture), ammonia, monochloramine, and hydroxylamine addition. To decipher whether hydroxylamine addition benefitted N. europaea activity by (i) removing monochloramine and releasing free ammonia or (ii) providing an additional effect (possibly the aforementioned reductant source), a previously developed cometabolism model was coupled with an abiotic monochloramine and hydroxylamine model for data interpretation. N. europaea maintained ammonia oxidizing activity when hydroxylamine was added before complete ammonia oxidation cessation. The impact could not be accounted for by monochloramine removal and free ammonia release alone and was concentration dependent for both monochloramine and hydroxylamine. In addition, a preferential negative impact occurred for ammonia versus hydroxylamine oxidation. These results suggest an additional benefit of exogenous hydroxylamine addition beyond monochloramine removal and free ammonia release, possibly providing reductant generation.

Oxidative aging and secondary organic aerosol formation from simulated wildfire emissions

Treesearch

C. J. Hennigan; M. A. Miracolo; G. J. Engelhart; A. A. May; Cyle Wold; WeiMin Hao; T. Lee; A. P. Sullivan; J. B. Gilman; W. C. Kuster; J. A. de Gouw; J. L. Collett; S. M. Kreidenweis; A. L. Robinson

2010-01-01

Wildfires are a significant fraction of global biomass burning and a major source of trace gas and particle emissions in the atmosphere. Understanding the air quality and climate implications of wildfires is difficult since the emissions undergo complex transformations due to aging processes during transport away from the source. As part of the third Fire Lab at...

Synthesis of graphene oxide and reduced graphene oxide using volumetric method by a novel approach without NaNO2 or NaNO3

NASA Astrophysics Data System (ADS)

Gunda, Rajitha; Madireddy, Buchi Suresh; Dash, Raj Kishora

2018-02-01

In the present work, graphite was processed to graphene oxide (GO) using modified Hummer's method by volumetric titration approach, without attaining zero temperature and the addition of toxic chemicals (NaNO2/NaNO3). The complete oxidation of graphite to graphene oxide was obtained by controlled addition (volumetric titration) of KMnO4. The addition of higher KMnO4 resulted in partial oxidation and 2-3 mono-layers with less defects/disordered structure of reduced graphene oxide (RGO) sheets were achieved. Samples were analyzed by XRD, FT-IR, Raman analysis, and TEM analysis. X-ray diffraction displayed the oxidized peak of graphene oxide at 11.9° and reduced graphene oxide at 23.8°. The prolonged stability of the synthesized GO with lower mole ratios of oxidizing agent was confirmed from UV-visible spectroscopy. Based on the results, processed graphene oxide is found to be a candidate material for thermally stable capacitor application.

Biological and nonbiological modifications of carbamates

PubMed Central

Knaak, James B.

1971-01-01

Methylcarbamate insecticides undergo hydrolysis, oxidation, dealkylation, and conjugation in animals, plants, and insects to form similar or identical products. Carbaryl is hydroxylated in biological systems to form hydroxy, dihydro-dihydroxy, and N-hydroxymethyl carbaryl and is hydrolysed to form 1-naphthol. The products are conjugated, stored, or excreted. Carbofuran is hydroxylated at the 3 position and propoxur at the 5 position to form hydroxylated derivatives. N-hydroxymethyl derivatives of these two carbamates may also be formed. Hydrolysis appears to be the major metabolic pathway of carbofuran in the animal. Aldicarb is oxidized to its sulfoxide and then hydrolysed to the oxime sulfoxide in animals and plants. Plants hydrolyse the oxime sulfoxide to form the corresponding aldehyde, which is an intermediate in the formation of 2-methyl-2-(methyl-sulfinyl)propanol. Methomyl, which is structurally similar to aldicarb, is metabolized in plants to acetonitrile, carbon dioxide, and methylamine. Bux and Meobal undergo hydrolysis and hydroxylation to form N-hydroxy methylcarbamates, as well as hydroxybutylphenyl and hydroxymethylphenyl methylcarbamates. Zectran, which contains a dimethylamino group, is converted to the methylamino, amino, and methylformamido derivatives by insects and plants. In soil and water, methylcarbamate insecticides are hydrolysed to their respective phenols or oximes. PMID:4999481

Kinetic phase evolution of spinel cobalt oxide during lithiation

DOE PAGES

Li, Jing; He, Kai; Meng, Qingping; ...

2016-09-15

Spinel cobalt oxide has been proposed to undergo a multiple-step reaction during the electrochemical lithiation process. Understanding the kinetics of the lithiation process in this compound is crucial to optimize its performance and cyclability. In this work, we have utilized a low-angle annular dark-field scanning transmission electron microscopy method to visualize the dynamic reaction process in real time and study the reaction kinetics at different rates. We show that the particles undergo a two-step reaction at the single-particle level, which includes an initial intercalation reaction followed by a conversion reaction. At low rates, the conversion reaction starts after the intercalationmore » reaction has fully finished, consistent with the prediction of density functional theoretical calculations. At high rates, the intercalation reaction is overwhelmed by the subsequently nucleated conversion reaction, and the reaction speeds of both the intercalation and conversion reactions are increased. Phase-field simulations show the crucial role of surface diffusion rates of lithium ions in controlling this process. Furthermore, this work provides microscopic insights into the reaction dynamics in non-equilibrium conditions and highlights the effect of lithium diffusion rates on the overall reaction homogeneity as well as the performance.« less

Kinetic phase evolution of spinel cobalt oxide during lithiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Jing; He, Kai; Meng, Qingping

Spinel cobalt oxide has been proposed to undergo a multiple-step reaction during the electrochemical lithiation process. Understanding the kinetics of the lithiation process in this compound is crucial to optimize its performance and cyclability. In this work, we have utilized a low-angle annular dark-field scanning transmission electron microscopy method to visualize the dynamic reaction process in real time and study the reaction kinetics at different rates. We show that the particles undergo a two-step reaction at the single-particle level, which includes an initial intercalation reaction followed by a conversion reaction. At low rates, the conversion reaction starts after the intercalationmore » reaction has fully finished, consistent with the prediction of density functional theoretical calculations. At high rates, the intercalation reaction is overwhelmed by the subsequently nucleated conversion reaction, and the reaction speeds of both the intercalation and conversion reactions are increased. Phase-field simulations show the crucial role of surface diffusion rates of lithium ions in controlling this process. Furthermore, this work provides microscopic insights into the reaction dynamics in non-equilibrium conditions and highlights the effect of lithium diffusion rates on the overall reaction homogeneity as well as the performance.« less

Dipole-Oriented Molecular Solids Can Undergo a Phase Change and Still Maintain Electrical Polarization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cassidy, Andrew; Jørgensen, Mads R. V.; Rosu-Finsen, Alexander

2016-10-02

It has recently been demonstrated that nanoscale molecular films can spontaneously assemble to self-generate intrinsic electric fields that can exceed 10 8 V/m. These electric fields originate from polarization charges in the material that arise because the films self-assemble to orient molecular dipole moments. This has been called the spontelectric effect. Such growth of spontaneously polarized layers of molecular solids has implications for our understanding of how intermolecular interactions dictate the structure of molecular materials used in a range of applications, for example, molecular semiconductors, sensors, and catalysts. In this paper, we present the first in situ structural characterization ofmore » a representative spontelectric solid, nitrous oxide. Infrared spectroscopy, temperature-programmed desorption, and neutron reflectivity measurements demonstrate that polarized films of nitrous oxide undergo a structural phase transformation upon heating above 48 K. A mean-field model can be used to describe quantitatively the magnitude of the spontaneously generated field as a function of film-growth temperature, and this model also recreates the phase change. Finally, this reinforces the spontelectric model as a means of describing long-range dipole–dipole interactions and points to a new type of ordering in molecular thin films.« less

Ultrafast dynamics of the photo-excited hemes b and cn in the cytochrome b6f complex.

PubMed

Agarwal, Rachna; Chauvet, Adrien A P

2017-01-25

The dynamics of hemes b and c n within the cytochrome b 6 f complex are investigated by means of ultrafast broad-band transient absorption spectroscopy. On the one hand, the data reveal that, subsequent to visible light excitation, part of the b hemes undergoes pulse-limited photo-oxidation, with the liberated electron supposedly being transferred to one of the adjacent aromatic amino acids. Photo-oxidation is followed by charge recombination in about 8.2 ps. Subsequent to charge recombination, heme b is promoted to a vibrationally excited ground state that relaxes in about 4.6 ps. On the other hand, heme c n undergoes ultrafast ground state recovery in about 140 fs. Interestingly, the data also show that, in contrast to previous beliefs, Chl a is involved in the photochemistry of hemes. Indeed, subsequent to heme excitation, Chl a bleaches and recovers to its ground state in 90 fs and 650 fs, respectively. Chl a bleaching allegedly corresponds to the formation of a short lived Chl a anion. Beyond the previously suggested structural role, this study provides unique evidence that Chl a is directly involved in the photochemistry of the hemes.

Enhanced activity of gold-supported cobalt oxide for the electrochemical evolution of oxygen.

PubMed

Yeo, Boon Siang; Bell, Alexis T

2011-04-13

Scanning electron microscopy, linear sweep voltammetry, chronoamperometry, and in situ surface-enhanced Raman spectroscopy were used to investigate the electrochemical oxygen evolution reaction (OER) occurring on cobalt oxide films deposited on Au and other metal substrates. All experiments were carried out in 0.1 M KOH. A remarkable finding is that the turnover frequency for the OER exhibited by ∼0.4 ML of cobalt oxide deposited on Au is 40 times higher than that of bulk cobalt oxide. The activity of small amounts of cobalt oxide deposited on Pt, Pd, Cu, and Co decreased monotonically in the order Au > Pt > Pd > Cu > Co, paralleling the decreasing electronegativity of the substrate metal. Another notable finding is that the OER turnover frequency for ∼0.4 ML of cobalt oxide deposited on Au is nearly three times higher than that for bulk Ir. Raman spectroscopy revealed that the as-deposited cobalt oxide is present as Co(3)O(4) but undergoes progressive oxidation to CoO(OH) with increasing anodic potential. The higher OER activity of cobalt oxide deposited on Au is attributed to an increase in fraction of the Co sites present as Co(IV) cations, a state of cobalt believed to be essential for OER to occur. A hypothesis for how Co(IV) cations contribute to OER is proposed and discussed. © 2011 American Chemical Society

The mechanism of oxidation in chromophore maturation of wild-type green fluorescent protein: a theoretical study.

PubMed

Ma, Yingying; Sun, Qiao; Smith, Sean C

2017-05-24

Oxidation is viewed as the second and rate-limiting step in the chromophore maturation process of the wild-type green fluorescent protein (GFP) under aerobic conditions. Molecular oxygen is the necessary oxidant for GFP chromophore biosynthesis. In this study, density functional theory (DFT) calculations were employed to study the mechanism of oxidation. Our results indicate that the deprotonation of the Tyr66 α-carbon is probably the rate-limiting step in the oxidation step. Electron transfer from the enolate form of the five-membered heterocycle (EFMH) to molecular oxygen, generating the triplet radical complex [EFMH˙O 2 - ˙] T , is an important step. This complex undergoes intersystem crossing to form an open-shell singlet diradical complex before it forms the closed-shell singlet hydroperoxy adduct. The formation of the hydroperoxy adduct is a proton-coupled electron transfer process. The energy barrier of H 2 O 2 elimination is 16.5 kcal mol -1 . The oxidation product IFMHH 2 O 2 that we discovered is a hydroxylated cyclic imine structure, which is consistent with the crystal structure trapped in the colorless Y66L variant. The relative energy of the oxidation product is -48.7 kcal mol -1 , which is in accordance with the experimental observation that the thermodynamically unfavourable cyclized product is trapped by oxidation. The results herein support the cyclization-oxidation-dehydration mechanism for the chromophore maturation of GFP.

Critical temperature determination of detectable Cr diffusion enhancement by nanostructure through structural evolution analysis of the oxide films at 25-450 °C on 304 stainless steel

NASA Astrophysics Data System (ADS)

Gui, Y.; Meng, X. B.; Zheng, Z. J.; Gao, Y.

2017-10-01

The structural evolution of the oxide films at 25-450 °C on nanocrystalline (NC) and coarse crystalline (CC) 304 stainless steels (SS) was investigated. The structure of the oxide film on both NC and CC SSs was observed to undergo transient processes from a bi-layer to a single-layer and then back to a bi-layer when the temperature changed from the low range (25-150 °C) to the medium range (150-300 °C) and subsequently to the high range (300-450 °C), respectively. These formation mechanisms of the oxide films on SS were attributed to the different diffusion properties of Cr and Fe in the three temperature ranges. The thickness of the oxide films was similar between the NC and CC SSs below 300 °C due to their similar Crox/Feox concentration ratios in their oxide films at this temperature. Above 300 °C, Cr diffusion enhancement in the NC matrix led to a higher Crox/Feox ratio and better compactness of the oxide film, which resulted in a slower atomic diffusion rate in the oxide film and a thinner oxide film. Therefore, the temperature of 300 °C was concluded to be the critical temperature of the detectable Cr diffusion enhancement in the NC SS compared to the CC SS.

Antioxidative effects of sulfurous mineral water: protection against lipid and protein oxidation.

PubMed

Benedetti, S; Benvenuti, F; Nappi, G; Fortunati, N A; Marino, L; Aureli, T; De Luca, S; Pagliarani, S; Canestrari, F

2009-01-01

To investigate the antioxidative properties of sulfurous drinking water after a standard hydropinic treatment (500 ml day(-1) for 2 weeks). Forty apparently healthy adults, 18 men and 22 women, age 41-55 years old. The antioxidant profile and the oxidative condition were evaluated in healthy subjects supplemented for 2 weeks with (study group) or without (controls) sulfurous mineral water both before (T0) and after (T1) treatment. At T1, a significant decrease (P<0.05) in both lipid and protein oxidation products, namely malondialdehyde, carbonyls and AOPP, was found in plasma samples from subjects drinking sulfurous water with respect to controls. Concomitantly, a significant increment (P<0.05) of the total antioxidant capacity of plasma as well as of total plasmatic thiol levels was evidenced. Tocopherols, carotenoids and retinol remained almost unchanged before and after treatment in both groups. The improved body redox status in healthy volunteers undergoing a cycle of hydropinic therapy suggests major benefits from sulfurous water consumption in reducing biomolecule oxidation, possibly furnishing valid protection against oxidative damage commonly associated with aging and age-related degenerative diseases.

ortho-Methoxyphenols as Convenient Oxidative Bioconjugation Reagents with Application to Site-Selective Heterobifunctional Cross-Linkers.

PubMed

ElSohly, Adel M; MacDonald, James I; Hentzen, Nina B; Aanei, Ioana L; El Muslemany, Kareem M; Francis, Matthew B

2017-03-15

The synthesis of complex protein-based bioconjugates has been facilitated greatly by recent developments in chemoselective methods for biomolecular modification. The oxidative coupling of o-aminophenols or catechols with aniline functional groups is chemoselective, mild, and rapid; however, the oxidatively sensitive nature of the electron-rich aromatics and the paucity of commercial sources pose some obstacles to the general use of these reactive strategies. Herein, we identify o-methoxyphenols as air-stable, commercially available derivatives that undergo efficient oxidative couplings with anilines in the presence of periodate as oxidant. Mechanistic considerations informed the development of a preoxidation protocol that can greatly reduce the amount of periodate necessary for effective coupling. The stability and versatility of these reagents was demonstrated through the synthesis of complex protein-protein bioconjugates using a site-selective heterobifunctional cross-linker comprising both o-methoxyphenol and 2-pyridinecarboxaldehyde moieties. This compound was used to link epidermal growth factor to genome-free MS2 viral capsids, affording nanoscale delivery vectors that can target a variety of cancer cell types.

Alumina-supported sub-nanometer Pt 10 clusters: Amorphization and role of the support material in a highly active CO oxidation catalyst

DOE PAGES

Yin, Chunrong; Negreiros, Fabio R.; Barcaro, Giovanni; ...

2017-02-03

Catalytic CO oxidation is unveiled on size-selected Pt 10 clusters deposited on two very different ultrathin (≈0.5–0.7 nm thick) alumina films: (i) a highly ordered alumina obtained under ultra-high vacuum (UHV) by oxidation of the NiAl(110) surface and (ii) amorphous alumina obtained by atomic layer deposition (ALD) on a silicon chip that is a close model of real-world supports. Notably, when exposed to realistic reaction conditions, the Pt 10/UHV-alumina system undergoes a morphological transition in both the clusters and the substrate, and becomes closely akin to Pt 10/ALD-alumina, thus reconciling UHV-type surface-science and real-world experiments. The Pt 10 clusters, thoroughlymore » characterized via combined experimental techniques and theoretical analysis, exhibit among the highest CO oxidation activity per Pt atom reported for CO oxidation catalysts, due to the interplay of ultra-small size and support effects. Lastly, a coherent interdisciplinary picture then emerges for this catalytic system.« less

Apoprotein isolation and activation, and vibrational structure of the Helicobacter mustelae iron urease

PubMed Central

Carter, Eric L.; Proshlyakov, Denis A.; Hausinger, Robert P.

2011-01-01

The micro-aerophilic pathogen Helicobacter mustelae synthesizes an oxygen-labile, iron-containing urease (UreA2B2) in addition to its standard nickel-containing enzyme (UreAB). An apoprotein form of the iron urease was prepared from ureA2B2-expressing recombinant Escherichia coli cells that were grown in minimal medium. Temperature-dependent circular dichroism measurements of holoprotein and apoprotein demonstrate an enhancement of thermal stability associated with the UreA2B2 metallocenter. In parallel to the situation reported for nickel activation of the standard urease apoprotein, incubation of UreA2B2 apoprotein with ferrous ions and bicarbonate generated urease activity in a portion of the nascent active sites. In addition, ferrous ions were shown to be capable of reductively activating the oxidized metallocenter. Resonance Raman spectra of the inactive, aerobically-purified UreA2B2 holoprotein exhibit vibrations at 495 cm−1 and 784 cm−1, consistent with νs and νas modes of an Fe(III)-O-Fe(III) center; these modes undergo downshifts upon binding of urea and were unaffected by changes in pH. The low-frequency mode also exhibits an isotopic shift from 497 to 476 cm−1 upon 16O/18O bulk water isotope substitution. Expression of subunits of the conventional nickel-containing Klebsiella aerogenes urease in cells grown in rich medium without nickel resulted in iron incorporation into a portion of the protein. The inactive iron-loaded species exhibited a UV-visible spectrum similar to oxidized UreA2B2 and was capable of being reductively activated under anoxic conditions. Results from these studies more clearly define the formation and unique properties of the iron urease metallocenter. PMID:22196017

Investigation of some biologically relevant redox reactions using electrochemical mass spectrometry interfaced by desorption electrospray ionization.

PubMed

Lu, Mei; Wolff, Chloe; Cui, Weidong; Chen, Hao

2012-04-01

Recently we have shown that, as a versatile ionization technique, desorption electrospray ionization (DESI) can serve as a useful interface to combine electrochemistry (EC) with mass spectrometry (MS). In this study, the EC/DESI-MS method has been further applied to investigate some aqueous phase redox reactions of biological significance, including the reduction of peptide disulfide bonds and nitroaromatics as well as the oxidation of phenothiazines. It was found that knotted/enclosed disulfide bonds in the peptides apamin and endothelin could be electrochemically cleaved. Subsequent tandem MS analysis of the resulting reduced peptide ions using collision-induced dissociation (CID) and electron-capture dissociation (ECD) gave rise to extensive fragment ions, providing a fast protocol for sequencing peptides with complicated disulfide bond linkages. Flunitrazepam and clonazepam, a class of nitroaromatic drugs, are known to undergo reduction into amines which was proposed to involve nitroso and N-hydroxyl intermediates. Now in this study, these corresponding intermediate ions were successfully intercepted and their structures were confirmed by CID. This provides mass spectrometric evidence for the mechanism of the nitro to amine conversion process during nitroreduction, an important redox reaction involved in carcinogenesis. In addition, the well-known oxidation reaction of chlorpromazine was also examined. The putative transient one-electron transfer product, the chlorpromazine radical cation (m/z 318), was captured by MS, for the first time, and its structure was also verified by CID. In addition to these observations, some features of the DESI-interfaced electrochemical mass spectrometry were discussed, such as simple instrumentation and the lack of background signal. These results further demonstrate the feasibility of EC/DESI-MS for the study of the biology-relevant redox chemistry and would find applications in proteomics and drug development research.

Characterization of the reactive and dissociative behavior of transition metal oxide cluster ions in the gas phase.

PubMed

Maleknia, S; Brodbelt, J; Pope, K

1991-05-01

The reactive and dissociative behavior of molybdenum and tungsten oxide cluster ions has been studied in the gas phase using a triple quadrupole mass spectrometer. Cluster ions (MO3) n (-) were formed via a simple thermal desorption/electron capture negative ionization method, and their structures were characterized by collision-activated dissociation (CAD). Typically, the clusters fragment by losses of neutral (MO3) units. Reactions of the oxide cluster ions with ethylene oxide, cyclohexene oxide, ethylene sulfide cyclohexene sulfide, 2,3-butanedione, and 2,4-pentanedione were examined, and product ions were characterized by CAD. The clusters react with ethylene oxide by addition of ethylene oxide or net addition of oxygen, whereas the clusters react with ethylene sulfide via net addition of one or two sulfur atoms. Reactions of the clusters with the diones result in addition of one or two dione units, in some cases with dehydration.

Abiotic synthesis of fatty acids

NASA Technical Reports Server (NTRS)

Leach, W. W.; Nooner, D. W.; Oro, J.

1978-01-01

The formation of fatty acids by Fischer-Tropsch-type synthesis was investigated with ferric oxide, ammonium carbonate, potassium carbonate, powdered Pueblito de Allende carbonaceous chondrite, and filings from the Canyon Diablo meteorite used as catalysts. Products were separated and identified by gas chromatography and mass spectrometry. Iron oxide, Pueblito de Allende chondrite, and Canyon Diablo filings in an oxidized catalyst form yielded no fatty acids. Canyon Diablo filings heated overnight at 500 C while undergoing slow purging by deuterium produced fatty acids only when potassium carbonate was admixed; potassium carbonate alone also produced these compounds. The active catalytic combinations gave relatively high yields of aliphatic and aromatic hydrocarbons; substantial amounts of n-alkenes were almost invariably observed when fatty acids were produced; the latter were in the range C6 to C18, with maximum yield in C9 or 10.

Redox Proteomics Applied to the Thiol Secretome.

PubMed

Ghezzi, Pietro; Chan, Philippe

2017-03-01

Secreted proteins are important both as signaling molecules and potential biomarkers. Recent Advances: Protein can undergo different types of oxidation, both in physiological conditions or under oxidative stress. Several redox proteomics techniques have been successfully applied to the identification of glutathionylated proteins, an oxidative post-translational modification consisting in the formation of a mixed disulfide between a protein cysteine and glutathione. Redox proteomics has also been used to study other forms of protein oxidation. Because of the highest proportion of free cysteines in the cytosol, redox proteomics of protein thiols has focused, so far, on intracellular proteins. However, plasma proteins, such as transthyretin and albumin, have been described as glutathionylated or cysteinylated. The present review discusses the redox state of protein cysteines in relation to their cellular distribution. We describe the various approaches used to detect secreted glutathionylated proteins, the only thiol modification studied so far in secreted proteins, and the specific problems presented in the study of the secretome. This review focusses on glutathionylated proteins secreted under inflammatory conditions and that may act as soluble mediators (cytokines). Future studies on the redox secretome (including other forms of oxidation) might identify new soluble mediators and biomarkers of oxidative stress. Antioxid. Redox Signal. 26, 299-312.

Mechanical tearing of graphene on an oxidizing metal surface.

PubMed

George, Lijin; Gupta, Aparna; Shaina, P R; Das Gupta, Nandita; Jaiswal, Manu

2015-12-11

Graphene, the thinnest possible anticorrosion and gas-permeation barrier, is poised to transform the protective coatings industry for a variety of surface applications. In this work, we have studied the structural changes of graphene when the underlying copper surface undergoes oxidation upon heating. Single-layer graphene directly grown on a copper surface by chemical vapour deposition was annealed under ambient atmosphere conditions up to 400 °C. The onset temperature of the surface oxidation of copper is found to be higher for graphene-coated foils. Parallel arrays of graphene nanoripples are a ubiquitous feature of pristine graphene on copper, and we demonstrate that these form crucial sites for the onset of the oxidation of copper, particularly for ∼0.3-0.4 μm ripple widths. In these regions, the oxidation proceeds along the length of the nanoripples, resulting in the formation of parallel stripes of oxidized copper regions. We demonstrate from temperature-dependent Raman spectroscopy that the primary defect formation process in graphene involves boundary-type defects rather than vacancy or sp(3)-type defects. This observation is consistent with a mechanical tearing process that splits graphene into small polycrystalline domains. The size of these is estimated to be sub-50 nm.

Low-Dose Ionizing Radiation Exposure, Oxidative Stress and Epigenetic Programing of Health and Disease.

PubMed

Tharmalingam, Sujeenthar; Sreetharan, Shayenthiran; Kulesza, Adomas V; Boreham, Douglas R; Tai, T C

2017-10-01

Ionizing radiation exposure from medical diagnostic imaging has greatly increased over the last few decades. Approximately 80% of patients who undergo medical imaging are exposed to low-dose ionizing radiation (LDIR). Although there is widespread consensus regarding the harmful effects of high doses of radiation, the biological effects of low-linear energy transfer (LET) LDIR is not well understood. LDIR is known to promote oxidative stress, however, these levels may not be large enough to result in genomic mutations. There is emerging evidence that oxidative stress causes heritable modifications via epigenetic mechanisms (DNA methylation, histone modification, noncoding RNA regulation). These epigenetic modifications result in permanent cellular transformations without altering the underlying DNA nucleotide sequence. This review summarizes the major concepts in the field of epigenetics with a focus on the effects of low-LET LDIR (<100 mGy) and oxidative stress on epigenetic gene modification. In this review, we show evidence that suggests that LDIR-induced oxidative stress provides a mechanistic link between LDIR and epigenetic gene regulation. We also discuss the potential implication of LDIR exposure during pregnancy where intrauterine fetal development is highly susceptible to oxidative stress-induced epigenetic programing.

Second-Order Biomimicry: In Situ Oxidative Self-Processing Converts Copper(I)/Diamine Precursor into a Highly Active Aerobic Oxidation Catalyst.

PubMed

McCann, Scott D; Lumb, Jean-Philip; Arndtsen, Bruce A; Stahl, Shannon S

2017-04-26

A homogeneous Cu-based catalyst system consisting of [Cu(MeCN) 4 ]PF 6 , N , N '-di- tert -butylethylenediamine (DBED), and p -( N , N -dimethylamino)pyridine (DMAP) mediates efficient aerobic oxidation of alcohols. Mechanistic study of this reaction shows that the catalyst undergoes an in situ oxidative self-processing step, resulting in conversion of DBED into a nitroxyl that serves as an efficient cocatalyst for aerobic alcohol oxidation. Insights into this behavior are gained from kinetic studies, which reveal an induction period at the beginning of the reaction that correlates with the oxidative self-processing step, EPR spectroscopic analysis of the catalytic reaction mixture, which shows the buildup of the organic nitroxyl species during steady state turnover, and independent synthesis of oxygenated DBED derivatives, which are shown to serve as effective cocatalysts and eliminate the induction period in the reaction. The overall mechanism bears considerable resemblance to enzymatic reactivity. Most notable is the "oxygenase"-type self-processing step that mirrors generation of catalytic cofactors in enzymes via post-translational modification of amino acid side chains. This higher-order function within a synthetic catalyst system presents new opportunities for the discovery and development of biomimetic catalysts.

Exogenous acetaldehyde as a tool for modulating wine color and astringency during fermentation.

PubMed

Sheridan, Marlena K; Elias, Ryan J

2015-06-15

Wine tannins undergo modifications during fermentation and storage that can decrease their perceived astringency and increase color stability. Acetaldehyde acts as a bridging compound to form modified tannins and polymeric pigments that are less likely to form tannin-protein complexes than unmodified tannins. Red wines are often treated with oxygen in order to yield acetaldehyde, however this approach can lead to unintended consequences due to the generation of reactive oxygen species. The present study employs exogenous acetaldehyde at relatively low and high treatment concentrations during fermentation to encourage tannin modification without promoting potentially deleterious oxidation reactions. The high acetaldehyde treatment significantly increased polymeric pigments in the wine without increasing concentrations of free and sulfite-bound acetaldehyde. Protein-tannin precipitation was also significantly decreased with the addition of exogenous acetaldehyde. These results indicate a possible treatment of wines early in their production to increase color stability and lower astringency of finished wines. Copyright © 2015 Elsevier Ltd. All rights reserved.

Innovative strategy with potential to increase hemodialysis efficiency and safety

NASA Astrophysics Data System (ADS)

Chen, Hsiao-Chien; Lin, Hsiu-Chen; Chen, Hsi-Hsien; Mai, Fu-Der; Liu, Yu-Chuan; Lin, Chun-Mao; Chang, Chun-Chao; Tsai, Hui-Yen; Yang, Chih-Ping

2014-03-01

Uremic toxins are mainly represented by blood urine nitrogen (BUN) and creatinine (Crea) whose removal is critically important in hemodialysis (HD) for kidney disease. Patients undergoing HD have a complex illness, resulting from: inadequate removal of organic waste, dialysis-induced oxidative stress and membrane-induced inflammation. Here we report innovative breakthroughs for efficient and safe HD by using a plasmon-induced dialysate comprising Au nanoparticles (NPs)-treated (AuNT) water that is distinguishable from conventional deionized (DI) water. The diffusion coefficient of K3Fe(CN)6 in saline solution can be significantly increased from 2.76, to 4.62 × 10-6 cm s-1, by using AuNT water prepared under illumination by green light-emitting diodes (LED). In vitro HD experiments suggest that the treatment times for the removals of 70% BUN and Crea are reduced by 47 and 59%, respectively, using AuNT water instead of DI water in dialysate, while additionally suppressing NO release from lipopolysaccharide (LPS)-induced inflammatory cells.

From an Easily Accessible Pentacarbonylcobalt(I) Salt to Piano-Stool Cations [(arene)Co(CO)2 ].

PubMed

Meier, Stefan C; Holz, Albina; Schmidt, Alexei; Kratzert, Daniel; Himmel, Daniel; Krossing, Ingo

2017-10-17

The facile synthesis of a pentacarbonyl cobalt(I) salt without the need for a superacid as solvent is presented. This salt, [Co(CO) 5 ] + [Al(OR F ) 4 ] - {R F =C(CF 3 ) 3 }, readily accessible on a multigram scale, undergoes substitution reactions with arenes yielding the hitherto unknown class of two-legged cobalt piano-stool complexes [(arene)Co(CO) 2 ] + with four different arene ligands. Such a substitution chemistry would have been impossible in superacid solution, as the arenes used would have been oxidized and/or protonated. Thus, the general approach described herein may have a wide synthetic use. Additionally, the thermochemistry of the piano-stool complexes is shown to be not easy to describe computationally and most of the established DFT methods overestimate the reaction energies. Only CCSD(T) calculations close to the basis set limit gave energies fully agreeing with the experiment. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Contribution of Endogenous Bradykinin to Fibrinolysis, Inflammation, and Blood Product Transfusion Following Cardiac Surgery: A Randomized Clinical Trial

PubMed Central

Balaguer, JM; Yu, C; Byrne, JG; Ball, SK; Petracek, MR; Brown, NJ; Pretorius, M

2014-01-01

Bradykinin increases during cardiopulmonary bypass (CPB) and stimulates the release of nitric oxide, inflammatory cytokines, and tissue-type plasminogen activator (t-PA), acting through its B2 receptor. This study tested the hypothesis that endogenous bradykinin contributes to the fibrinolytic and inflammatory response to CPB and that bradykinin B2 receptor antagonism reduces fibrinolysis, inflammation, and subsequent transfusion requirements. Patients (N = 115) were prospectively randomized to placebo, ε-aminocaproic acid (EACA), or HOE 140, a bradykinin B2 receptor antagonist. Bradykinin B2 receptor antagonism decreased intraoperative fibrinolytic capacity as much as EACA, but only EACA decreased D-dimer formation and tended to decrease postoperative bleeding. Although EACA and HOE 140 decreased fibrinolysis and EACA attenuated blood loss, these treatments did not reduce the proportion of patients transfused. These data suggest that endogenous bradykinin contributes to t-PA generation in patients undergoing CPB, but that additional effects on plasmin generation contribute to decreased D-dimer concentrations during EACA treatment. PMID:23361105

The life of plant mitochondrial complex I.

PubMed

Braun, Hans-Peter; Binder, Stefan; Brennicke, Axel; Eubel, Holger; Fernie, Alisdair R; Finkemeier, Iris; Klodmann, Jennifer; König, Ann-Christine; Kühn, Kristina; Meyer, Etienne; Obata, Toshihiro; Schwarzländer, Markus; Takenaka, Mizuki; Zehrmann, Anja

2014-11-01

The mitochondrial NADH dehydrogenase complex (complex I) of the respiratory chain has several remarkable features in plants: (i) particularly many of its subunits are encoded by the mitochondrial genome, (ii) its mitochondrial transcripts undergo extensive maturation processes (e.g. RNA editing, trans-splicing), (iii) its assembly follows unique routes, (iv) it includes an additional functional domain which contains carbonic anhydrases and (v) it is, indirectly, involved in photosynthesis. Comprising about 50 distinct protein subunits, complex I of plants is very large. However, an even larger number of proteins are required to synthesize these subunits and assemble the enzyme complex. This review aims to follow the complete "life cycle" of plant complex I from various molecular perspectives. We provide arguments that complex I represents an ideal model system for studying the interplay of respiration and photosynthesis, the cooperation of mitochondria and the nucleus during organelle biogenesis and the evolution of the mitochondrial oxidative phosphorylation system. Copyright © 2014 Elsevier B.V. and Mitochondria Research Society. All rights reserved.

Identification of two frataxin isoforms in Zea mays: Structural and functional studies.

PubMed

Buchensky, Celeste; Sánchez, Manuel; Carrillo, Martin; Palacios, Oscar; Capdevila, Mercè; Domínguez-Vera, Jose M; Busi, Maria V; Atrian, Sílvia; Pagani, Maria A; Gomez-Casati, Diego F

2017-09-01

Frataxin is a ubiquitous protein that plays a role in Fe-S cluster biosynthesis and iron and heme metabolism, although its molecular functions are not entirely clear. In non-photosynthetic eukaryotes, frataxin is encoded by a single gene, and the protein localizes to mitochondria. Here we report the presence of two functional frataxin isoforms in Zea mays, ZmFH-1 and ZmFH-2. We confirmed our previous findings regarding plant frataxins: both proteins have dual localization in mitochondria and chloroplasts. Physiological, biochemical and biophysical studies show some differences in the expression pattern, protection against oxidants and in the aggregation state of both isoforms, suggesting that the two frataxin homologs would play similar but not identical roles in plant cell metabolism. In addition, two specific features of plant frataxins were evidenced: their ability to form dimers and their tendency to undergo conformational change under oxygen exposure. Copyright © 2017 Elsevier B.V. and Société Française de Biochimie et Biologie Moléculaire (SFBBM). All rights reserved.

Self-sensitization of tetracycline degradation with simulated solar light catalyzed by ZnO@montmorillonite

NASA Astrophysics Data System (ADS)

Zyoud, Ahed; Jondi, Waheed; AlDaqqah, Najat; Asaad, Sara; Qamhieh, Naser; Hajamohideen, AbdulRazack; Helal, Muath H. S.; Kwon, Hansang; Hilal, Hikmat S.

2017-12-01

Zinc oxide (ZnO) nano-particles were chemically deposited onto montmorillonite (MONT) clay particles. The composite ZnO@MONT was then characterized and used as a catalyst for photo-degradation of aqueous tetracycline. Unlike earlier studies, solar simulated light can be effectively used in this work. The composite shows high efficiency as adsorbent and as a photo-degradation catalyst. Both adsorbed and dissolved tetracycline molecules undergo mineralization under the photo-catalytic conditions, and up to 94% of the contaminant gross amount is completely mineralized. Other forms of ZnO particles, commercial ZnO and synthetic ZnO particles were examined in separate experiments. The ZnO@MONT is superior to both pristine counterparts. The ability of tetracycline to sensitize the supported ZnO particles, to solar simulated light, before being photo-degraded itself, is discussed here for the first time. In addition to enhanced catalytic activity of the ZnO@MONT, the composite can be efficiently recovered and reused with no significant loss of efficiency.

A multiantioxidant supplementation reduces damage from ischaemia reperfusion in patients after lower torso ischaemia. A randomised trial.

PubMed

Wijnen, M H W A; Roumen, R M H; Vader, H L; Goris, R J A

2002-06-01

open repair of intra-abdominal aortic aneurysm (AAA) is associated with lower torso ischaemia and reperfusion. to examine the effect of antioxidants on the activation and sequestration of white blood cells and muscle injury during AAA repair. forty-two patients undergoing elective infrarenal aneurysm repair, were randomised to either standard therapy (22 patients) or standard therapy with additional multiantioxidant supplementation (20 patients). Vitamin E and C, Allopurinol, N-acetylcysteine and mannitol was administered perioperatively. White blood cell count (WBC), serum creatine kinase, aspartateaminotransferase, lactate and lipofuscine were measured. WBC remained higher after reperfusion in the antioxidant group (p = 0.008). CK, ASAT and lipofuscine levels were significantly lower after reperfusion in the antioxidant group (p = 0.02, p = 0.018, p = 0.017). multi-antioxidant supplementation was associated with a reduction in serum CK and ASAT after AAA repair. This is likely due to a reduction in oxidative stress and a decreased leucocyte sequestration and activation. Copyright 2002 Elsevier Science Ltd.

What Predicts Patients’ Willingness to Undergo Online Treatment and Pay for Online Treatment? Results from a Web-Based Survey to Investigate the Changing Patient-Physician Relationship

PubMed Central

Bidmon, Sonja; Terlutter, Ralf

2016-01-01

Background Substantial research has focused on patients’ health information–seeking behavior on the Internet, but little is known about the variables that may predict patients’ willingness to undergo online treatment and willingness to pay additionally for online treatment. Objective This study analyzed sociodemographic variables, psychosocial variables, and variables of Internet usage to predict willingness to undergo online treatment and willingness to pay additionally for online treatment offered by the general practitioner (GP). Methods An online survey of 1006 randomly selected German patients was conducted. The sample was drawn from an e-panel maintained by GfK HealthCare. Missing values were imputed; 958 usable questionnaires were analyzed. Variables with multi-item measurement were factor analyzed. Willingness to undergo online treatment and willingness to pay additionally for online treatment offered by the GP were predicted using 2 multiple regression models. Results Exploratory factor analyses revealed that the disposition of patients’ personality to engage in information-searching behavior on the Internet was unidimensional. Exploratory factor analysis with the variables measuring the motives for Internet usage led to 2 separate factors: perceived usefulness (PU) of the Internet for health-related information searching and social motives for information searching on the Internet. Sociodemographic variables did not serve as significant predictors for willingness to undergo online treatment offered by the GP, whereas PU (B=.092, P=.08), willingness to communicate with the GP more often in the future (B=.495, P<.001), health-related information–seeking personality (B=.369, P<.001), actual use of online communication with the GP (B=.198, P<.001), and social motive (B=.178, P=.002) were significant predictors. Age, gender, satisfaction with the GP, social motive, and trust in the GP had no significant impact on the willingness to pay additionally for online treatment, but it was predicted by health-related information–seeking personality (B=.127, P=.07), PU (B=–.098, P=.09), willingness to undergo online treatment (B=.391, P<.001), actual use of online communication with the GP (B=.192, P=.001), highest education level (B=.178, P<.001), monthly household net income (B=.115, P=.01), and willingness to communicate with the GP online more often in the future (B=.076, P=.03). Conclusions Age, gender, and trust in the GP were not significant predictors for either willingness to undergo online treatment or to pay additionally for online treatment. Willingness to undergo online treatment was partly determined by the actual use of online communication with the GP, willingness to communicate online with the GP, health information–seeking personality, and social motivation for such behavior. Willingness to pay extra for online treatment was influenced by the monthly household net income category and education level. The results of this study are useful for online health care providers and physicians who are considering offering online treatments as a viable number of patients would appreciate the possibility of undergoing an online treatment offered by their GP. PMID:26846162

What Predicts Patients' Willingness to Undergo Online Treatment and Pay for Online Treatment? Results from a Web-Based Survey to Investigate the Changing Patient-Physician Relationship.

PubMed

Roettl, Johanna; Bidmon, Sonja; Terlutter, Ralf

2016-02-04

Substantial research has focused on patients' health information-seeking behavior on the Internet, but little is known about the variables that may predict patients' willingness to undergo online treatment and willingness to pay additionally for online treatment. This study analyzed sociodemographic variables, psychosocial variables, and variables of Internet usage to predict willingness to undergo online treatment and willingness to pay additionally for online treatment offered by the general practitioner (GP). An online survey of 1006 randomly selected German patients was conducted. The sample was drawn from an e-panel maintained by GfK HealthCare. Missing values were imputed; 958 usable questionnaires were analyzed. Variables with multi-item measurement were factor analyzed. Willingness to undergo online treatment and willingness to pay additionally for online treatment offered by the GP were predicted using 2 multiple regression models. Exploratory factor analyses revealed that the disposition of patients' personality to engage in information-searching behavior on the Internet was unidimensional. Exploratory factor analysis with the variables measuring the motives for Internet usage led to 2 separate factors: perceived usefulness (PU) of the Internet for health-related information searching and social motives for information searching on the Internet. Sociodemographic variables did not serve as significant predictors for willingness to undergo online treatment offered by the GP, whereas PU (B=.092, P=.08), willingness to communicate with the GP more often in the future (B=.495, P<.001), health-related information-seeking personality (B=.369, P<.001), actual use of online communication with the GP (B=.198, P<.001), and social motive (B=.178, P=.002) were significant predictors. Age, gender, satisfaction with the GP, social motive, and trust in the GP had no significant impact on the willingness to pay additionally for online treatment, but it was predicted by health-related information-seeking personality (B=.127, P=.07), PU (B=-.098, P=.09), willingness to undergo online treatment (B=.391, P<.001), actual use of online communication with the GP (B=.192, P=.001), highest education level (B=.178, P<.001), monthly household net income (B=.115, P=.01), and willingness to communicate with the GP online more often in the future (B=.076, P=.03). Age, gender, and trust in the GP were not significant predictors for either willingness to undergo online treatment or to pay additionally for online treatment. Willingness to undergo online treatment was partly determined by the actual use of online communication with the GP, willingness to communicate online with the GP, health information-seeking personality, and social motivation for such behavior. Willingness to pay extra for online treatment was influenced by the monthly household net income category and education level. The results of this study are useful for online health care providers and physicians who are considering offering online treatments as a viable number of patients would appreciate the possibility of undergoing an online treatment offered by their GP.

Effect of addition of butyl benzyl phthalate plasticizer and zinc oxide nanoparticles on mechanical properties of cellulose acetate butyrate/organoclay biocomposite

NASA Astrophysics Data System (ADS)

Putra, B. A. P.; Juwono, A. L.; Rochman, N. T.

2017-07-01

Plastics as packaging materials and coatings undergo increasing demands globally each year. This pose a serious problem to the environment due to its difficulty to degrade. One solution to addressing the problem of plastic wastes is the use of bioplastics. According to the European Organization Bioplastic, one of the biodegradable plastics is derivative of cellulose. To improve mechanical properties of bioplastic, biocomposites are made with the addition of certain additives and fillers. The aim of this study is to investigate the effect of butyl benzyl phthalate plasticizer (BBP) and ZnO nanoparticles addition on mechanical properties of cellulose acetate butyrate (CAB) / organoclay biocomposite. ZnO nanoparticles synthesized from commercial ZnO precursor by using sol-gel size reduction method. ZnO was dissolved in a solution of citric acid in the ratio 1:1 to 1:5 to form zinc citrate. Zinc citrate then decomposed by calcination at temperature of 600oC. ZnO nanoparticles with an average size of 44.4 nm is obtained at a ratio of 1: 2. The addition of ZnO nanoparticles and BBP plasticizer was varied to determine the effect on the mechanical properties of biocomposite. The addition of 10 - 15 %wt ZnO nanoparticles and 30 - 40 %wt BBP plasticizer was studied to determine the effect on the tensile strength, elongation, and modulus elasticity of the biocomposites. Biocomposite films were made by using solution casting method with acetone as solvent. The addition of plasticizer BBP and ZnO nanoparticles by 30% and 10% made biocomposite has a tensile strength of 2.223 MPa.

Oxidation of TaSi2-Containing ZrB2-SiC Ultra-High Temperature Materials

NASA Technical Reports Server (NTRS)

Opila, Elizabeth J.; Smith, Jim; Levine, Stanley R.; Lorincz, Jonathan; Reigel, Marissa

2010-01-01

Hot pressed coupons of composition ZrB2-20 v% SiC-5 v% TaSi2 and ZrB2-20 v% SiC-20 v% TaSi2 were oxidized in stagnant air at temperatures of 1627 and 1927C for one, five and ten 10-minute cycles. The oxidation reactions were characterized by weight change kinetics, x-ray diffraction, and SEM/EDS. Detailed WDS/microprobe quantitative analyses of the oxidation products were conducted for the ZrB2-20 v% SiC-20 v% TaSi2 sample oxidized for five 10-minute cycles at 1927C. Oxidation kinetics and product formation were compared to ZrB2-20 v% SiC with no TaSi2 additions. It was found that the 20 v% TaSi2 composition exhibited improved oxidation resistance relative to the material with no TaSi2 additions at 1627C. However, for exposures at 1927C less oxidation resistance and extensive liquid phase formation were observed compared to the material with no TaSi2 additions. Attempts to limit the liquid phase formation by reducing the TaSi2 content to 5 v% were unsuccessful. In addition, the enhanced oxidation resistance at 1627C due to 20 v% TaSi2 additions was not achieved at the 5 v% addition level. The observed oxidation product evolution is discussed in terms of thermodynamics and phase equilibria for the TaSi2-containing ZrB2-SiC material system. TaSi2-additions to ZrB2-SiC at any level are not recommended for ultra-high temperature (>1900C) applications due to excessive liquid phase formation.

High temperature behavior of B2-based ruthenium aluminide systems

NASA Astrophysics Data System (ADS)

Cao, Fang

Ru-modified NiAl-based bond coats have the potential to improve the durability of Superalloy-Thermal Barrier Coating systems (TBCs) for advanced gas turbine engines. A fundamental understanding of the high temperature mechanical behavior across the Ni-Al-Ru B2 phase field can provide direction for the development of these new bond coats for TBCs. The purpose of this study has been to describe the fundamental processes of creep deformation in single phase B2 Ru-Al-Ni ternary alloys which would form the basis for the bond coats. To accomplish this, five ternary alloys with compositions located within the B2 field across the NiAl-RuAl phase region were fabricated and investigated. Special emphasis was placed on characterizing creep deformation and describing the operative creep mechanisms in these alloys. At room temperature, brittle failure was observed in the Ni-rich alloys in compression, while improved strength and ductility were displayed in two Ru-rich ternary alloys at temperatures up to 700°C. Exceptional creep strength was observed in these alloys, as compared to other high melting temperature B2 intermetallics. A continuous increase of the melting temperature and creep resistance with the increasing of the Ru/Ni ratio in these alloys was observed. Post-creep dislocation analyses identified the presence of <100> and <110> edge dislocations in the Ni-rich alloys, while uniformly distributed jogged <100> screw dislocations predominated in the Ru-rich ternary alloys. A transition of the creep mechanism from viscous glide controlled to jogged screw motion in these Ru-Al-Ni ternary B2 alloys with increasing Ru/Ni ratio is demonstrated by the characteristics of the creep deformation process, stress change creep tests, post-creep dislocation analyses, and numerical modeling. Additionally, the knowledge of the cyclic oxidation behavior of ruthenium aluminide-based alloy is essential, as many high-temperature applications for which this intermetallic might be utilized undergo repeated severe thermal cycling. Thus the second portion of this thesis focuses on the characterization of the cyclic oxidation properties of RuAl-based alloys. The cyclic oxidation behavior of six RuAl-based alloys was studied in air over the temperature range of 1000°C to 1300°C. Oxidation kinetics have been shown to be influenced by microstructure as well as the addition of platinum.

Repurposing mitochondria from ATP production to ROS generation drives a pro-inflammatory phenotype in macrophages that depends on succinate oxidation by complex II

PubMed Central

Logan, A; Costa, A. S. H.; Varma, M.; Bryant, C. E.; Tourlomousis, P.; Däbritz, J. H. M.; Gottlieb, E.; Latorre, I.; Corr, S.C.; McManus, G.; Ryan, D.; Jacobs, H.T.; Szibor, M.; Xavier, R. J.; Braun, T.; Frezza, C.; Murphy, M. P.; O’Neill, L. A.

2018-01-01

Activated macrophages undergo metabolic reprogramming which drives their pro-inflammatory phenotype, but the mechanistic basis for this remains obscure. Here we demonstrate that upon lipopolysaccharide (LPS) stimulation macrophages shift from producing ATP by oxidative phosphorylation to glycolysis, while also increasing succinate levels. We show that increased mitochondrial oxidation of succinate via succinate dehydrogenase (SDH) and an elevation of mitochondrial membrane potential combine to drive mitochondrial ROS production. RNA sequencing reveals that this combination induces a pro-inflammatory gene expression profile, while an inhibitor of succinate oxidation, dimethyl malonate (DMM), promotes an anti-inflammatory outcome. Blocking ROS production with rotenone, by uncoupling mitochondria, or by expressing the alternative oxidase (AOX) inhibits this inflammatory phenotype, with AOX protecting mice from LPS lethality. The metabolic alterations that occur upon activation of macrophages therefore repurpose mitochondria from ATP synthesis to ROS production in order to promote a pro-inflammatory state. PMID:27667687

PML/RARA oxidation and arsenic binding initiate the antileukemia response of As2O3.

PubMed

Jeanne, Marion; Lallemand-Breitenbach, Valérie; Ferhi, Omar; Koken, Marcel; Le Bras, Morgane; Duffort, Stéphanie; Peres, Laurent; Berthier, Caroline; Soilihi, Hassane; Raught, Brian; de Thé, Hugues

2010-07-13

As(2)O(3) cures acute promyelocytic leukemia (APL) by initiating PML/RARA oncoprotein degradation, through sumoylation of its PML moiety. However, how As(2)O(3) initiates PML sumoylation has remained largely unexplained. As(2)O(3) binds vicinal cysteines and increases reactive oxygen species (ROS) production. We demonstrate that upon As(2)O(3) exposure, PML undergoes ROS-initiated intermolecular disulfide formation and binds arsenic directly. Disulfide-linked PML or PML/RARA multimers form nuclear matrix-associated nuclear bodies (NBs), become sumoylated and are degraded. Hematopoietic progenitors transformed by an As(2)O(3)-binding PML/RARA mutant exhibit defective As(2)O(3) response. Conversely, nonarsenical oxidants elicit PML/RARA multimerization, NB-association, degradation, and leukemia response in vivo, but do not affect PLZF/RARA-driven APLs. Thus, PML oxidation regulates NB-biogenesis, while oxidation-enforced PML/RARA multimerization and direct arsenic-binding cooperate to enforce APL's exquisite As(2)O(3) sensitivity. Copyright (c) 2010 Elsevier Inc. All rights reserved.

Enhanced Neuroprotective Effects of Coadministration of Tetrandrine with Glutathione in Preclinical Model of Parkinson's Disease

PubMed Central

Li, Xiang-Yun; Mei, Guang-Hai; Dong, Qiang; Zhang, Yu; Guo, Zhuang-Li; Su, Jing-Jing; Tang, Yu-Ping; Jin, Xue-Hong; Zhou, Hou-Guang; Huang, Yan-Yan

2015-01-01

Aim. In this study we examined the influence of tetrandrine (Tet) on the neuroprotective effects of glutathione (GSH) in the 6-hydroxydopamine- (6-OHDA-) lesioned rat model of Parkinson's disease (PD). Methods. Levels in the redox system, dopamine (DA) metabolism, dopaminergic neuronal survival, and apoptosis of the substantia nigra (SN) and striatum, as well as the rotational behavior of animals were examined after a 50-day administration of GSH + Tet (or GSH) and/or L-3,4-dihydroxyphenylalanine (L-dopa) to PD rats. Ethics Committee of Huashan Hospital, Fudan University approved the protocol (number SYXK2009-0082). Results. Administration of GSH or Tet alone did not show any significant effects on the factors evaluated in the PD rats. However, in the GSH + Tet group, we observed markedly decreased oxidative damage, inhibition of DA metabolism and enhanced DA synthesis, increased tyrosine hydroxylase- (TH-) immunopositive neuronal survival, and delayed apoptosis of dopaminergic neurons in the SN. Animal rotational behavior was improved in the GSH + Tet group. Additionally, coadministration of GSH + Tet appeared to offset the possible oxidative neurotoxicity induced by L-dopa. Conclusion. In this study, we demonstrated that tetrandrine allowed occurrence of the neuroprotective effect of glutathione probably due to inhibition of P-glycoprotein on 6-hydroxydopamine-lesioned rat models of Parkinson's disease, including rats undergoing long-term L-dopa treatment. PMID:26664824

Physiological and molecular implications of plant polyamine metabolism during biotic interactions

PubMed Central

Jiménez-Bremont, Juan F.; Marina, María; Guerrero-González, María de la Luz; Rossi, Franco R.; Sánchez-Rangel, Diana; Rodríguez-Kessler, Margarita; Ruiz, Oscar A.; Gárriz, Andrés

2014-01-01

During ontogeny, plants interact with a wide variety of microorganisms. The association with mutualistic microbes results in benefits for the plant. By contrast, pathogens may cause a remarkable impairment of plant growth and development. Both types of plant–microbe interactions provoke notable changes in the polyamine (PA) metabolism of the host and/or the microbe, being each interaction a complex and dynamic process. It has been well documented that the levels of free and conjugated PAs undergo profound changes in plant tissues during the interaction with microorganisms. In general, this is correlated with a precise and coordinated regulation of PA biosynthetic and catabolic enzymes. Interestingly, some evidence suggests that the relative importance of these metabolic pathways may depend on the nature of the microorganism, a concept that stems from the fact that these amines mediate the activation of plant defense mechanisms. This effect is mediated mostly through PA oxidation, even though part of the response is activated by non-oxidized PAs. In the last years, a great deal of effort has been devoted to profile plant gene expression following microorganism recognition. In addition, the phenotypes of transgenic and mutant plants in PA metabolism genes have been assessed. In this review, we integrate the current knowledge on this field and analyze the possible roles of these amines during the interaction of plants with microbes. PMID:24672533

Changes in the Conformational State of Hemoglobin in Hemodialysed Patients with Chronic Renal Failure

PubMed Central

Pieniazek, Anna; Gwozdzinski, Krzysztof

2015-01-01

The aim of this study was to evaluate the properties of internal components of erythrocytes in chronic renal failure (CRF) patients undergoing hemodialysis (HD) in comparison to control subjects. For investigation of conformational state of hemoglobin and nonheme proteins (NHP) the maleimide spin label (MSL) in electron paramagnetic resonance (EPR) was applied. The studies were performed using MSL in whole cells and hemolysate as well as proteins separated by ion exchange chromatography and checked by electrophoresis. Additionally the level of –SH groups in hemolysate and isolated internal proteins of CRF erythrocytes was determined using 4,4′-dithiodipyridine. All measurements were performed before and after hemodialysis. Oxidative stress accompanying CRF/hemodialysed patients caused a significant decrease in the mobility of internal components inside erythrocytes indicated by MSL (P < 0.02). The significant decrease in mobility of spin labeled HbA1c and HbA both before and after HD (P < 0.0002) as well as in nonheme proteins before hemodialysis (P < 0.05) versus control was indicated. Decrease in mobility of internal components of erythrocytes was accompanied by loss of thiols before and after hemodialysis versus control in NHP (P < 0.05), HbA1c (P < 0.0002), and HbA (P < 0.0005). These findings showed oxidative influence of hemodialysis on hemoglobins and internal nonheme proteins in erythrocytes of CRF patients. PMID:25866600

The Speciation of Silver Nanoparticles in Antimicrobial Fabric Before and After Exposure to a Hypochlorite/Detergent Solution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Impellitteri, Christopher A.; Tolaymat, Thabet M.; Scheckel, Kirk G.

2009-07-14

Because of their antibacterial properties, silver nanoparticles are often used in consumer products. To assess environmental and/or human health risks from these nanoparticles, there is a need to identify the chemical transformations that silver nanoparticles undergo in different environments. Thus an antimicrobial sock material containing Ag nanoparticles was examined by X-ray absorption spectroscopy to identify the speciation of Ag. The material was exposed to a hypochlorite/detergent solution and subjected to agitation. An elemental Ag nanopowder was also exposed to the hypochlorite/detergent solution or to a 1 mol L{sup -1} NaCl solution. Results showed that the sock material nanoparticles consisted ofmore » elemental Ag. After exposure to the hypochlorite/detergent solution, a significant portion (more than 50%) of the sock nanoparticles were converted, in situ, to AgCl. Results from exposures to elemental Ag nanopowder suggest that an oxidation step is necessary for the elemental Ag nanoparticles to transform into AgCl as there was no evidence of AgCl formation in the presence of chloride alone. As a result, if Ag ions leach from consumer products, any chloride present may quickly scavenge the ions. In addition, the efficacy of Ag, as an antimicrobial agent in fabrics, may be limited, or even negated, after washing in solutions containing oxidizers as AgCl is much less reactive than Ag ion.« less

Polyethylene Nanocomposites for the Next Generation of Ultralow-Transmission-Loss HVDC Cables: Insulation Containing Moisture-Resistant MgO Nanoparticles.

PubMed

Pourrahimi, Amir Masoud; Pallon, Love K H; Liu, Dongming; Hoang, Tuan Anh; Gubanski, Stanislaw; Hedenqvist, Mikael S; Olsson, Richard T; Gedde, Ulf W

2016-06-15

The use of MgO nanoparticles in polyethylene for cable insulation has attracted considerable interest, although in humid media the surface regions of the nanoparticles undergo a conversion to a hydroxide phase. A facile method to obtain MgO nanoparticles with a large surface area and remarkable inertness to humidity is presented. The method involves (a) low temperature (400 °C) thermal decomposition of Mg(OH)2, (b) a silicone oxide coating to conceal the nanoparticles and prevent interparticle sintering upon exposure to high temperatures, and (c) heat treatment at 1000 °C. The formation of the hydroxide phase on these silicone oxide-coated MgO nanoparticles after extended exposure to humid air was assessed by thermogravimetry, infrared spectroscopy, and X-ray diffraction. The nanoparticles showed essentially no sign of any hydroxide phase compared to particles prepared by the conventional single-step thermal decomposition of Mg(OH)2. The moisture-resistant MgO nanoparticles showed improved dispersion and interfacial adhesion in the LDPE matrix with smaller nanosized particle clusters compared with conventionally prepared MgO. The addition of 1 wt % moisture-resistant MgO nanoparticles was sufficient to decrease the conductivity of polyethylene 30 times. The reduction in conductivity is discussed in terms of defect concentration on the surface of the moisture-resistant MgO nanoparticles at the polymer/nanoparticle interface.

α-Tocopherol Is Ineffective in Preventing the Decomposition of Preformed Lipid Peroxides and May Promote the Accumulation of Toxic Aldehydes: A Potential Explanation for the Failure of Antioxidants to Affect Human Atherosclerosis

PubMed Central

Raghavamenon, Achuthan; Garelnabi, Mahdi; Babu, Sainath; Aldrich, Alex; Litvinov, Dmitry

2009-01-01

Abstract The decomposition of peroxidized lipids of low-density lipoprotein (LDL) has been suggested to be involved in atherosclerosis. In this study, an in vitro system with 13-hydroperoxylinoleic acid (13-HPODE) was used to determine the effects of antioxidants on its decomposition. Decomposition of 13-HPODE was not affected by α-tocopherol, several other antioxidants, or antioxidant enzymes. Moreover, the inclusion of α-tocopherol during the decomposition of 13-HPODE resulted in an accumulation of aldehydes. Further oxidation of aldehydes to carboxylic acids by a number of oxidases was prevented by α-tocopherol. Conversely, the formation of carboxylic acids may be conducive to plaque stabilization via immunomodulation, rapid degradation, and by calcium sequestration. Thus, the inhibition of formation of carboxylic acids could be a serious deleterious effect of antioxidant treatment. In contrast, α-keto acids, like pyruvic acid, promoted the conversion of 13-HPODE to 13-hydroxylinoleic acid (13-HODE) by readily undergoing decarboxylation into acetate. These observations suggest that agents that promote the reduction of lipid peroxides into lipid hydroxides could be far more effective in treating cardiovascular diseases as opposed α-tocopherol–like antioxidants that could affect additional steps in the oxidation cascade. Antioxid. Redox Signal. 11, 1237–1248. PMID:19186999

Mechanisms of Oxidative Stress Resistance in The Brain: Lessons Learned From Hypoxia Tolerant Extremophilic Vertebrates

PubMed Central

Garbarino, Valentina R.; Orr, Miranda E.; Rodriguez, Karl A.; Buffenstein, Rochelle

2016-01-01

The Oxidative Stress Theory of Aging has had tremendous impact in research involving aging and age-associated diseases including those that affect the nervous system. With over half a century of accrued data showing both strong support for and against this theory, there is a need to critically evaluate the data acquired from common biomedical research models, and to also diversify the species used in studies involving this proximate theory. One approach is to follow Orgel’s second axiom that “evolution is smarter than we are” and judiciously choose species that may have evolved to live with chronic or seasonal oxidative stressors. Vertebrates that have naturally evolved to live under extreme conditions (e.g., anoxia or hypoxia), as well as those that undergo daily or seasonal torpor encounter both decreased oxygen availability and subsequent reoxygenation, with concomitant increased oxidative stress. Due to its high metabolic activity, the brain may be particularly vulnerable to oxidative stress. Here, we focus on oxidative stress responses in the brains of certain mouse models as well as extremophilic vertebrates. Exploring the naturally evolved biological tools utilized to cope with seasonal or environmentally variable oxygen availability may yield key information pertinent for how to deal with oxidative stress and thereby mitigate its propagation of age-associated diseases. PMID:25841340

Solid oxide fuel cell with monolithic core

DOEpatents

McPheeters, Charles C.; Mrazek, Franklin C.

1988-01-01

A solid oxide fuel cell in which fuel and oxidant gases undergo an electrochemical reaction to produce an electrical output includes a monolithic core comprised of a corrugated conductive sheet disposed between upper and lower generally flat sheets. The corrugated sheet includes a plurality of spaced, parallel, elongated slots which form a series of closed, linear, first upper and second lower gas flow channels with the upper and lower sheets within which a fuel gas and an oxidant gas respectively flow. Facing ends of the fuel cell are generally V-shaped and provide for fuel and oxidant gas inlet and outlet flow, respectively, and include inlet and outlet gas flow channels which are continuous with the aforementioned upper fuel gas and lower oxidant gas flow channels. The upper and lower flat sheets and the intermediate corrugated sheet are preferably comprised of ceramic materials and are securely coupled together such as by assembly in the green state and sintering together during firing at high temperatures. A potential difference across the fuel cell, or across a stacked array of similar fuel cells, is generated when an oxidant gas such as air and a fuel such as hydrogen gas is directed through the fuel cell at high temperatures, e.g., between 700.degree. C. and 1100.degree. C.

Solid oxide fuel cell with monolithic core

DOEpatents

McPheeters, C.C.; Mrazek, F.C.

1988-08-02

A solid oxide fuel cell in which fuel and oxidant gases undergo an electrochemical reaction to produce an electrical output includes a monolithic core comprised of a corrugated conductive sheet disposed between upper and lower generally flat sheets. The corrugated sheet includes a plurality of spaced, parallel, elongated slots which form a series of closed, linear, first upper and second lower gas flow channels with the upper and lower sheets within which a fuel gas and an oxidant gas respectively flow. Facing ends of the fuel cell are generally V-shaped and provide for fuel and oxidant gas inlet and outlet flow, respectively, and include inlet and outlet gas flow channels which are continuous with the aforementioned upper fuel gas and lower oxidant gas flow channels. The upper and lower flat sheets and the intermediate corrugated sheet are preferably comprised of ceramic materials and are securely coupled together such as by assembly in the green state and sintering together during firing at high temperatures. A potential difference across the fuel cell, or across a stacked array of similar fuel cells, is generated when an oxidant gas such as air and a fuel such as hydrogen gas is directed through the fuel cell at high temperatures, e.g., between 700 C and 1,100 C. 8 figs.

Hemodynamic and oxidative mechanisms of tourniquet-induced muscle injury: near-infrared spectroscopy for the orthopedics setting

NASA Astrophysics Data System (ADS)

Shadgan, Babak; Reid, W. Darlene; Harris, R. Luke; Jafari, Siavash; Powers, Scott K.; O'Brien, Peter J.

2012-08-01

During orthopedic procedures, the tourniquets used to maintain bloodless surgical fields cause ischemia and then reperfusion (I/R), leading to oxidative muscle injury. Established methods exist neither for monitoring orthopedic I/R nor for predicting the extent of tourniquet-associated oxidative injury. To develop a predictive model for tourniquet-associated oxidative muscle injury, this study combined real-time near-infrared spectroscopy (NIRS) monitoring of I/R with Western blotting (WB) for oxidized proteins. We hypothesized strong correlations between NIRS-derived I/R indices and muscle protein oxidation. In 17 patients undergoing ankle fracture repair, a thigh tourniquet was inflated on the injured limb (300 mmHg). Using a continuous-wave (CW) NIRS setup, oxygenated (O2Hb), deoxygenated (HHb), and total (tHb) hemoglobin were monitored bilaterally (tourniquet versus control) in leg muscles. Leg muscle biopsies were collected unilaterally (tourniquet side) immediately after tourniquet inflation (pre) and before deflation (post). Average ischemia duration was 43.2±14.6 min. In post-compared to pre-biopsies, muscle protein oxidation (quantified using WB) increased 172.3%±145.7% (P<0.0005). Changes in O2Hb and tHb were negatively correlated with protein oxidation (respectively: P=0.040, R2=0.25 and P=0.003, R2=0.58). Reoxygenation rate was positively correlated with protein oxidation (P=0.041, R2=0.25). These data indicate that using CW NIRS, it is possible to predict orthopedic tourniquet-associated muscle oxidative injury noninvasively.

Flavonoids: hemisynthesis, reactivity, characterization and free radical scavenging activity.

PubMed

Es-Safi, Nour-Eddine; Ghidouche, Souhila; Ducrot, Paul Henri

2007-09-26

Phenolic compounds form one of the main classes of secondary metabolites. They display a large range of structures and they are responsible for the major organoleptic characteristics of plant-derived-foods and beverages, particularly color and taste properties and they also contribute to the nutritional qualities of fruits and vegetables. Phenolic compounds are also highly unstable compounds which undergo numerous enzymatic and chemical reactions during postharvest food storage and processing thus adding to the complexity of plant polyphenol composition. Among these compounds flavonoids constitute one of the most ubiquitous groups of all plant phenolics. Owing to their importance in food organoleptic properties and in human health, a better understanding of their structures, their reactivity and chemical properties in addition to the mechanisms generating them appears essential to predict and control food quality. The purpose of this work is an overview of our findings concerning the hemisynthesis, the reactivity and the enzymatic oxidation of some flavonoids and shed light on the mechanisms involved in some of these processes and the structures of the resulting products. The free radical scavenging activity of some of the synthesized compounds is also presented and a structure-activity relationship is discussed. The first part of this review concerns the synthesis and structural characterization of modified monomeric flavanols. The use of these compounds as precursor for the preparation of natural and modified dimeric procyanidin derivatives was then explored through different coupling reactions. The full characterization of the synthesized compounds was achieved by concerted use of NMR and ESI-MS techniques. The free radical scavenging activity of some of the synthesized compounds was investigated. The second part of this review concerns the enzymatic oxidation of several flavonols by Trametes versicolor laccase. Most of the major oxidation products have been isolated as pure compounds and their structures unambiguously established through spectroscopic methods. Correlation between the structure of the oxidation product and the substitution pattern of the starting materials allows mechanistic features of this transformation to be elucidated.

High pressure structural, elastic and vibrational properties of green energetic oxidizer ammonium dinitramide

NASA Astrophysics Data System (ADS)

Yedukondalu, N.; Ghule, Vikas D.; Vaitheeswaran, G.

2016-08-01

Ammonium DiNitramide (ADN) is one of the most promising green energetic oxidizers for future rocket propellant formulations. In the present work, we report a detailed theoretical study on structural, elastic, and vibrational properties of the emerging oxidizer under hydrostatic compression using various dispersion correction methods to capture weak intermolecular (van der Waals and hydrogen bonding) interactions. The calculated ground state lattice parameters, axial compressibilities, and equation of state are in good accord with the available experimental results. Strength of intermolecular interactions has been correlated using the calculated compressibility curves and elastic moduli. Apart from this, we also observe discontinuities in the structural parameters and elastic constants as a function of pressure. Pictorial representation and quantification of intermolecular interactions are described by the 3D Hirshfeld surfaces and 2D finger print maps. In addition, the computed infra-red (IR) spectra at ambient pressure reveal that ADN is found to have more hygroscopic nature over Ammonium Perchlorate (AP) due to the presence of strong hydrogen bonding. Pressure dependent IR spectra show blue- and red-shift of bending and stretching frequencies which leads to weakening and strengthening of the hydrogen bonding below and above 5 GPa, respectively. The abrupt changes in the calculated structural, mechanical, and IR spectra suggest that ADN might undergo a first order structural transformation to a high pressure phase around 5-6 GPa. From the predicted detonation properties, ADN is found to have high and low performance characteristics (DCJ = 8.09 km/s and PCJ = 25.54 GPa) when compared with ammonium based energetic oxidizers (DCJ = 6.50 km/s and PCJ = 17.64 GPa for AP, DCJ = 7.28 km/s and PCJ = 18.71 GPa for ammonium nitrate) and well-known secondary explosives for which DCJ = ˜8-10 km/s and PCJ = ˜30-50 GPa, respectively.

Kynurenine 3-monooxygenase from Pseudomonas fluorescens: substrate-like inhibitors both stimulate flavin reduction and stabilize the flavin-peroxo intermediate yet result in the production of hydrogen peroxide.

PubMed

Crozier-Reabe, Karen R; Phillips, Robert S; Moran, Graham R

2008-11-25

Kynurenine 3-monooxygenase (KMO) is a flavin-dependent hydroxylase that catalyzes the conversion of l-kynurenine (l-Kyn) to 3-hydroxykynurenine (3OHKyn) in the pathway for tryptophan catabolism. KMO inhibition has been widely suggested as an early treatment for stroke and other neurological disorders that involve ischemia. We have investigated the reductive and the oxidative half-reactions of a stable form of KMO from Pseudomonas fluorescens (KMO). The binding of l-Kyn by the enzyme is relatively slow and involves at least two reversible steps. The rate constant for reduction of the flavin cofactor by NADPH increases by a factor of approximately 2.5 x 10(3) when l-Kyn is bound. The rate of reduction of the KMO.l-Kyn complex is 160 s(-1), and the K(d) for the NADPH complex is 200 microM with charge-transfer absorption bands for the KMO(RED).l-Kyn.NADP(+) complex accumulating after reduction. The reduction potential of KMO is -188 mV and is unresponsive to the addition of l-Kyn or other inhibitory ligands. KMO inhibitors whose structures are reminiscent of l-Kyn such as m-nitrobenzoylalanine and benzoylalanine also stimulate reduction of flavin by NADPH and, in the presence of dioxygen, result in the stoichiometric liberation of hydrogen peroxide, diminishing the perceived therapeutic potential of inhibitors of this type. In the presence of the native substrate, the oxidative half-reaction exhibits triphasic absorbance data. A spectrum consistent with that of a peroxyflavin species accumulates and then decays to yield the oxidized enzyme. This species then undergoes minor spectral changes that, based on flavin difference spectra defined in the presence of 3OHKyn, can be correlated with product release. The oxidative half-reaction observed in the presence of saturating benzoylalanine or m-nitrobenzoylalanine also shows the accumulation of a peroxyflavin species that then decays to yield hydrogen peroxide without hydroxylation.

Identifying precursors and aqueous organic aerosol formation pathways during the SOAS campaign

NASA Astrophysics Data System (ADS)

Sareen, Neha; Carlton, Annmarie G.; Surratt, Jason D.; Gold, Avram; Lee, Ben; Lopez-Hilfiker, Felipe D.; Mohr, Claudia; Thornton, Joel A.; Zhang, Zhenfa; Lim, Yong B.; Turpin, Barbara J.

2016-11-01

Aqueous multiphase chemistry in the atmosphere can lead to rapid transformation of organic compounds, forming highly oxidized, low-volatility organic aerosol and, in some cases, light-absorbing (brown) carbon. Because liquid water is globally abundant, this chemistry could substantially impact climate, air quality, and health. Gas-phase precursors released from biogenic and anthropogenic sources are oxidized and fragmented, forming water-soluble gases that can undergo reactions in the aqueous phase (in clouds, fogs, and wet aerosols), leading to the formation of secondary organic aerosol (SOAAQ). Recent studies have highlighted the role of certain precursors like glyoxal, methylglyoxal, glycolaldehyde, acetic acid, acetone, and epoxides in the formation of SOAAQ. The goal of this work is to identify additional precursors and products that may be atmospherically important. In this study, ambient mixtures of water-soluble gases were scrubbed from the atmosphere into water at Brent, Alabama, during the 2013 Southern Oxidant and Aerosol Study (SOAS). Hydroxyl (OH⚫) radical oxidation experiments were conducted with the aqueous mixtures collected from SOAS to better understand the formation of SOA through gas-phase followed by aqueous-phase chemistry. Total aqueous-phase organic carbon concentrations for these mixtures ranged from 92 to 179 µM-C, relevant for cloud and fog waters. Aqueous OH-reactive compounds were primarily observed as odd ions in the positive ion mode by electrospray ionization mass spectrometry (ESI-MS). Ultra high-resolution Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) spectra and tandem MS (MS-MS) fragmentation of these ions were consistent with the presence of carbonyls and tetrols. Products were observed in the negative ion mode and included pyruvate and oxalate, which were confirmed by ion chromatography. Pyruvate and oxalate have been found in the particle phase in many locations (as salts and complexes). Thus, formation of pyruvate/oxalate suggests the potential for aqueous processing of these ambient mixtures to form SOAAQ.

Diffusion Barriers to Increase the Oxidative Life of Overlay Coatings

NASA Technical Reports Server (NTRS)

Nesbitt, James A.; Lei, Jih-Fen

1999-01-01

Currently, most blades and vanes in the hottest section of aero gas turbine engines require some type of coating for oxidation protection. Newly developed single crystal superalloys have the mechanical potential to operate at increasingly higher component temperatures. However, at these elevated temperatures, coating/substrate interdiffusion can shorten the protective life of the coating. Diffusion barriers between overlay coatings and substrates are being examined to extend the protective life of the coating. A previously- developed finite-difference diffusion model has been modified to predict the oxidative life enhancement due to use of a diffusion barrier. The original diffusion model, designated COSIM, simulates Al diffusion in the coating to the growing oxide scale as well as Al diffusion into the substrate. The COSIM model incorporates an oxide growth and spalling model to provide the rate of Al consumption during cyclic oxidation. Coating failure is predicted when the Al concentration at the coating surface drops to a defined critical level. The modified COSIM model predicts the oxidative life of an overlay coating when a diffusion barrier is present eliminating diffusion of Al from the coating into the substrate. Both the original and the modified diffusion models have been used to predict the effectiveness of a diffusion barrier in extending the protective life of a NiCrAl overlay coating undergoing cyclic oxidation at 1100 C.

Nitrous oxide has different effects on the EEG and somatosensory evoked potentials during isoflurane anaesthesia in patients.

PubMed

Porkkala, T; Jäntti, V; Kaukinen, S; Häkkinen, V

1997-04-01

Electroencephalogram (EEG) and somatosensory evoked potentials (SEPs) are altered by inhalation anaesthesia. Nitrous oxide is commonly used in combination with volatile anaesthetics. We have studied the effects of nitrous oxide on both EEG and SEPs simultaneously during isoflurane burst-suppression anaesthesia. Twelve ASA I-II patients undergoing abdominal or orthopaedic surgery were anaesthetized with isoflurane by mask. After intubation and relaxation the isoflurane concentration was increased to a level at which an EEG burst-suppression pattern occurred (mean isoflurane end-tidal concentration 1.9 (SD 0.2) %. With a stable isoflurane concentration, the patients received isoflurane-air-oxygen and isoflurane-nitrous oxide-oxygen (FiO2 0.4) in a randomized cross-over manner. EEG and SEPs were simultaneously recorded before, and after wash-out or wash-in periods for nitrous oxide. The proportion of EEG suppressions as well as SEP amplitudes for cortical N20 were calculated. The proportion of EEG suppressions decreased from 53.5% to 34% (P < 0.05) when air was replaced by nitrous oxide. At the same time, the cortical N20 amplitude was reduced by 69% (P < 0.01). The results suggest that during isoflurane anaesthesia, nitrous oxide has a different effect on EEG and cortical SEP at the same time. The effects of nitrous oxide may be mediated by cortical and subcortical generators.

Cardiolipin plays a role in KCN-induced necrosis.

PubMed

Tsesin, Natalia; Khalfin, Boris; Nathan, Ilana; Parola, Abraham H

2014-10-01

Cardiolipin (CL) is a unique anionic, dimeric phospholipid found almost exclusively in the inner mitochondrial membrane and is essential for the function of numerous enzymes that are involved in mitochondrial energy metabolism. While the role of cardiolipin in apoptosis is well established, its involvement in necrosis is enigmatic. In the present study, KCN-induced necrosis in U937 cells was used as an experimental model to assess the role of CL in necrosis. KCN addition to U937 cells induced reactive oxygen species (ROS) formation, while the antioxidants inhibited necrosis, indicating that ROS play a role in KCN-induced cell death. Further, CL oxidation was confirmed by the monomer green fluorescence of 10-N-nonyl acridine orange (NAO) and by TLC. Utilizing the red fluorescence of the dimeric NAO, redistribution of CL in mitochondrial membrane during necrosis was revealed. We also showed that the catalytic activity of purified adenosine triphosphate (ATP) synthase complex, known to be modulated by cardiolipin, decreased following KCN treatment. All these events occurred at an early phase of the necrotic process prior to rupture of the cell membrane. Furthermore, CL-deficient HeLa cells were found to be resistant to KCN-induced necrosis as compared with the wild type cells. We suggest that KCN, an effective reversible inhibitor of cytochrome oxidase and thereby of the respiratory chain leads to ROS increase, which in turn oxidizes CL (amongst other membrane phospholipids) and leads to mitochondrial membrane lipid reorganization and loss of CL symmetry. Finally, the resistance of CL-deficient cells to necrosis further supports the notion that CL, which undergoes oxidation during necrotic cell death, is an integral part of the milieu of events taking place in mitochondria leading to membrane disorganization and mitochondrial dysfunction. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Lactoperoxidase, an Antimicrobial Milk Protein, as a Potential Activator of Carcinogenic Heterocyclic Amines in Breast Cancer.

PubMed

Sheikh, Ishfaq Ahmad; Jiffri, Essam Hussain; Kamal, Mohammad Amjad; Ashraf, Ghulam Md; Beg, Mohd Amin

2017-11-01

Lactoperoxidase (LPO) is an antimicrobial protein secreted from mammary, salivary and other mucosal glands. It is an important member of heme peroxidase enzymes and the primary peroxidase enzyme present in breast tissues. In addition to the antimicrobial properties, LPO has been shown to be associated with breast cancer etiology. Heterocyclic amines, an important class of environmental and dietary carcinogens, have been increasingly associated with breast cancer etiology. Heterocyclic amines undergo activation in breast tissue as a result of oxidation by LPO. The current study includes three important heterocyclic amines, 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and 2-amino-1-methy-6-phenylimidazo[4,5-b]-pyridine (PhIP), that have carcinogenic activity. The structural binding characterization of IQ, MeIQx and PhIP with LPO was done using in silico approaches. Their binding pattern and interactions with LPO amino acid residues were analyzed. The three compounds bound in the distal heme cavity of LPO without replacing the important water molecule required for oxidation of substrate compounds. PhIP displayed lesser binding affinity for LPO in comparison to IQ and MeIQx. The binding mode of heterocyclic amines in distal heme cavity of LPO resembled to that of substrate binding pattern. The three heterocyclic amines are suggested to act as LPO substrate. The undisturbed water molecule present in distal heme cavity of the LPO is expected to facilitate the oxidation and activation of the three heterocyclic amines. These activated compounds may potentially bind with DNA in breast tissues forming DNA adducts and may subsequently lead to breast cancer initiation. Copyright© 2017, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.

Autoxidative and Cyclooxygenase-2 Catalyzed Transformation of the Dietary Chemopreventive Agent Curcumin*

PubMed Central

Griesser, Markus; Pistis, Valentina; Suzuki, Takashi; Tejera, Noemi; Pratt, Derek A.; Schneider, Claus

2011-01-01

The efficacy of the diphenol curcumin as a cancer chemopreventive agent is limited by its chemical and metabolic instability. Non-enzymatic degradation has been described to yield vanillin, ferulic acid, and feruloylmethane through cleavage of the heptadienone chain connecting the phenolic rings. Here we provide evidence for an alternative mechanism, resulting in autoxidative cyclization of the heptadienone moiety as a major pathway of degradation. Autoxidative transformation of curcumin was pH-dependent with the highest rate at pH 8 (2.2 μm/min) and associated with stoichiometric uptake of O2. Oxidation was also catalyzed by recombinant cyclooxygenase-2 (COX-2) (50 nm; 7.5 μm/min), and the rate was increased ≈10-fold by the addition of 300 μm H2O2. The COX-2 catalyzed transformation was inhibited by acetaminophen but not indomethacin, suggesting catalysis occurred by the peroxidase activity. We propose a mechanism of enzymatic or autoxidative hydrogen abstraction from a phenolic hydroxyl to give a quinone methide and a delocalized radical in the heptadienone chain that undergoes 5-exo cyclization and oxygenation. Hydration of the quinone methide (measured by the incorporation of O-18 from H218O) and rearrangement under loss of water gives the final dioxygenated bicyclopentadione product. When curcumin was added to RAW264.7 cells, the bicyclopentadione was increased 1.8-fold in cells activated by LPS; vanillin and other putative cleavage products were negligible. Oxidation to a reactive quinone methide is the mechanistic basis of many phenolic anti-cancer drugs. It is possible, therefore, that oxidative transformation of curcumin, a prominent but previously unrecognized reaction, contributes to its cancer chemopreventive activity. PMID:21071447

Nitroxides protect horseradish peroxidase from H2O2-induced inactivation and modulate its catalase-like activity.

PubMed

Samuni, Amram; Maimon, Eric; Goldstein, Sara

2017-08-01

Horseradish peroxidase (HRP) catalyzes H 2 O 2 dismutation while undergoing heme inactivation. The mechanism underlying this process has not been fully elucidated. The effects of nitroxides, which protect metmyoglobin and methemoglobin against H 2 O 2 -induced inactivation, have been investigated. HRP reaction with H 2 O 2 was studied by following H 2 O 2 depletion, O 2 evolution and heme spectral changes. Nitroxide concentration was followed by EPR spectroscopy, and its reactions with the oxidized heme species were studied using stopped-flow. Nitroxide protects HRP against H 2 O 2 -induced inactivation. The rate of H 2 O 2 dismutation in the presence of nitroxide obeys zero-order kinetics and increases as [nitroxide] increases. Nitroxide acts catalytically since its oxidized form is readily reduced to the nitroxide mainly by H 2 O 2 . The nitroxide efficacy follows the order 2,2,6,6-tetramethyl-piperidine-N-oxyl (TPO)>4-OH-TPO>3-carbamoyl proxyl>4-oxo-TPO, which correlates with the order of the rate constants of nitroxide reactions with compounds I, II, and III. Nitroxide catalytically protects HRP against inactivation induced by H 2 O 2 while modulating its catalase-like activity. The protective role of nitroxide at μM concentrations is attributed to its efficient oxidation by P940, which is the precursor of the inactivated form P670. Modeling the dismutation kinetics in the presence of nitroxide adequately fits the experimental data. In the absence of nitroxide the simulation fits the observed kinetics only if it does not include the formation of a Michaelis-Menten complex. Nitroxides catalytically protect heme proteins against inactivation induced by H 2 O 2 revealing an additional role played by nitroxide antioxidants in vivo. Copyright © 2017 Elsevier B.V. All rights reserved.

Carbon-Starvation Induces Cross-Resistance to Thermal, Acid, and Oxidative Stress in Serratia marcescens

PubMed Central

Pittman, Joseph R.; Kline, La’Kesha C.; Kenyon, William J.

2015-01-01

The broad host-range pathogen Serratia marcescens survives in diverse host and non-host environments, often enduring conditions in which the concentration of essential nutrients is growth-limiting. In such environments, carbon and energy source starvation (carbon-starvation) is one of the most common forms of stress encountered by S. marcescens. Related members of the family Enterobacteriaceae are known to undergo substantial changes in gene expression and physiology in response to the specific stress of carbon-starvation, enabling non-spore-forming cells to survive periods of prolonged starvation and exposure to other forms of stress (i.e., starvation-induced cross-resistance). To determine if carbon-starvation also results in elevated levels of cross-resistance in S. marcescens, both log-phase and carbon-starved cultures, depleted of glucose before the onset of high cell-density stationary-phase, were grown in minimal media at either 30 °C or 37 °C and were then challenged for resistance to high temperature (50 °C), low pH (pH 2.8), and oxidative stress (15 mM H2O2). In general, carbon-starved cells exhibited a higher level of resistance to thermal stress, acid stress, and oxidative stress compared to log-phase cells. The extent of carbon-starvation-induced cross-resistance was dependent on incubation temperature and on the particular strain of S. marcescens. In addition, strain- and temperature-dependent variations in long-term starvation survival were also observed. The enhanced stress-resistance of starved S. marcescens cells could be an important factor in their survival and persistence in many non-host environments and within certain host microenvironments where the availability of carbon sources is suboptimal for growth. PMID:27682115

Making Small-Scale Classroom Greenhouse Gas Flux Calculations Using a Handmade Gas Capture Hood

ERIC Educational Resources Information Center

Schouten, Peter W.; Sharma, Ashok; Burn, Stewart; Goodman, Nigel; Parisi, Alfio; Downs, Nathan; Lemckert, Charles

2013-01-01

The emissions of various types of greenhouse gases (GHGs) from natural and industrial sources are undergoing a great deal of scrutiny around the world. The three main GHGs that are of most concern are carbon dioxide (CO[subscript 2]), nitrous oxide (N[subscript 2]O) and methane (CH[subscript 4]). CO[subscript 2], N[subscript 2]O and CH[subscript…

C–H Functionalization of Cyclic Amines: Redox-Annulations with α,β-Unsaturated Carbonyl Compounds

PubMed Central

Kang, YoungKu; Richers, Matthew T.; Sawicki, Conrad H.; Seidel, Daniel

2015-01-01

Cyclic amines such as pyrrolidine and 1,2,3,4-tetrahydroisoquinoline undergo redox-annulations with α,β-unsaturated aldehydes and ketones. Carboxylic acid promoted generation of a conjugated azomethine ylide is followed by 6π-electrocylization, and, in some cases, tautomerization. The resulting ring-fused pyrrolines are readily oxidized to the corresponding pyrroles or reduced to pyrrolidines. PMID:26051897

Time-resolved XAFS spectroscopic studies of B-H and N-H oxidative addition to transition metal catalysts relevant to hydrogen storage

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bitterwolf, Thomas E.

2014-12-09

Successful catalytic dehydrogenation of aminoborane, H 3NBH 3, prompted questions as to the potential role of N-H oxidative addition in the mechanisms of these processes. N-H oxidative addition reactions are rare, and in all cases appear to involve initial dative bonding to the metal by the amine lone pairs followed by transfer of a proton to the basic metal. Aminoborane and its trimethylborane derivative block this mechanism and, in principle, should permit authentic N-H oxidative attrition to occur. Extensive experimental work failed to confirm this hypothesis. In all cases either B-H complexation or oxidative addition of solvent C-H bonds dominatemore » the chemistry.« less

21 CFR 73.2991 - Zinc oxide.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Zinc oxide. 73.2991 Section 73.2991 Food and Drugs... ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2991 Zinc oxide. (a) Identity and specifications. The color additive zinc oxide shall conform in identity and specifications to the requirements of § 73.1991...

Genome Scale Mutational Analysis of Geobacter sulfurreducens Reveals Distinct Molecular Mechanisms for Respiration and Sensing of Poised Electrodes versus Fe(III) Oxides.

PubMed

Chan, Chi Ho; Levar, Caleb E; Jiménez-Otero, Fernanda; Bond, Daniel R

2017-10-01

Geobacter sulfurreducens generates electrical current by coupling intracellular oxidation of organic acids to the reduction of proteins on the cell surface that are able to interface with electrodes. This ability is attributed to the bacterium's capacity to respire other extracellular electron acceptors that require contact, such as insoluble metal oxides. To directly investigate the genetic basis of electrode-based respiration, we constructed Geobacter sulfurreducens transposon-insertion sequencing (Tn-Seq) libraries for growth, with soluble fumarate or an electrode as the electron acceptor. Libraries with >33,000 unique insertions and an average of 9 insertions/kb allowed an assessment of each gene's fitness in a single experiment. Mutations in 1,214 different genomic features impaired growth with fumarate, and the significance of 270 genes unresolved by annotation due to the presence of one or more functional homologs was determined. Tn-Seq analysis of -0.1 V versus standard hydrogen electrode (SHE) electrode-grown cells identified mutations in a subset of genes encoding cytochromes, processing systems for proline-rich proteins, sensory networks, extracellular structures, polysaccharides, and metabolic enzymes that caused at least a 50% reduction in apparent growth rate. Scarless deletion mutants of select genes identified via Tn-Seq revealed a new putative porin-cytochrome conduit complex ( extABCD ) crucial for growth with electrodes, which was not required for Fe(III) oxide reduction. In addition, four mutants lacking components of a putative methyl-accepting chemotaxis-cyclic dinucleotide sensing network ( esnABCD ) were defective in electrode colonization but grew normally with Fe(III) oxides. These results suggest that G. sulfurreducens possesses distinct mechanisms for recognition, colonization, and reduction of electrodes compared to Fe(III) oxides. IMPORTANCE Since metal oxide electron acceptors are insoluble, one hypothesis is that cells sense and reduce metals using the same molecular mechanisms used to form biofilms on electrodes and produce electricity. However, by simultaneously comparing thousands of Geobacter sulfurreducens transposon mutants undergoing electrode-dependent respiration, we discovered new cytochromes and chemosensory proteins supporting growth with electrodes that are not required for metal respiration. This supports an emerging model where G. sulfurreducens recognizes surfaces and forms conductive biofilms using mechanisms distinct from those used for growth with metal oxides. These findings provide a possible explanation for studies that correlate electricity generation with syntrophic interspecies electron transfer by Geobacter and reveal many previously unrecognized targets for engineering this useful capability in other organisms. Copyright © 2017 Chan et al.

Secondary organic aerosol formation from isoprene photo-oxidation during cloud condensation-evaporation cycles (CUMULUS project)

NASA Astrophysics Data System (ADS)

Brégonzio-Rozier, Lola; Siekmann, Frank; Giorio, Chiara; Temime-Roussel, Brice; Pangui, Edouard; Morales, Sébastien; Gratien, Aline; Ravier, Sylvain; Monod, Anne; Doussin, Jean-Francois

2014-05-01

It is acknowledged that atmospheric photo-oxidation of Volatile Organic Compounds (VOC) leads to the formation of less volatile oxidized species. These compounds can undergo gas-to-particle conversion, leading to the formation of Secondary Organic Aerosols (SOA) in the atmosphere. Nevertheless, some of these oxidized species are water soluble and could also partition into cloud droplets. Higher molecular weight and less volatile compounds could be produced in the aqueous phase and remain in the particle phase after water evaporation (Ervens et al., 2011). The aim of the present work is to study SOA formation in the presence of cloud droplets during isoprene photo-oxidation. To this end, an original multiphase approach in a simulation chamber was set up in order to investigate the chemistry occurring in the gaseous, particulate and aqueous phases, and the exchange between these phases. Experiments were performed, within the CUMULUS project (CloUd MULtiphase chemistry of organic compoUndS in the troposphere), in the CESAM chamber (Wang et al., 2011). This chamber was designed to investigate multiphase processes under realistic actinic flux, and accurate control of both temperature and relative humidity. A specific protocol was set up to produce cloud events in the simulation chamber exhibiting a significant lifetime in the presence of light (10-12 minutes). By using this protocol, many clouds could be generated in a single experiment. In each experiment, around 800 ppb of isoprene was injected in the chamber together with HONO under dry conditions before irradiation. A Fourier Transform Infrared Spectrometer (FTIR), a Proton Transfer Reaction Mass Spectrometer (PTR-TOF-MS) and NOx and O3 analyzers were used to analyze gas-phase composition. Dried SOA size distributions and total concentrations were measured by a Scanning Mobility Particle Sizer (SMPS). An Aerodyne High Resolution Time-Of-Flight Aerosol Mass Spectrometer (HR-TOF-AMS) was also used to investigate aerosol composition. Cloud droplets size distributions were measured by a white light Optical Particle Counter (OPC). In all experiments, the dissolution of gaseous oxidation products into aqueous phase and SOA production have been observed during isoprene photo-oxidation in the presence of a cloud event. The overall results in additional SOA mass production and the dynamic of gaseous oxidation products and SOA mass concentrations will be presented. Ervens, B. et al. (2011). Atmospheric Chemistry and Physics 11(21): 11069-11102. Wang, J. et al. (2011). Atmospheric Measurement Techniques 4(11): 2465-2494.

Cat cracking technology with reduced discharge of harmful substances to the atmosphere

DOE Office of Scientific and Technical Information (OSTI.GOV)

Elshin, A.I.; Aliev, R.R.; Solyar, B.Z.

1995-11-01

The operation of cat crackers creates a number of ecological problems involving pollution of the atmosphere. In the regeneration of coked catalyst, up to 10 tonnes/day of sulfur oxides are discharged to the atmosphere, along with catalyst dust in amounts up to 2 tonnes/day and carbon monoxide up to 120 tonnes/day. With increasingly severe requirements for environmental protection, the problem of reducing harmful discharges to the atmosphere has become more acute, necessitating either preliminary hydrotreating of the feed or scrubber cleanup of the stack gas to remove sulfur oxides. The high cost of these processes has provided the impetus formore » proposing various types of bifunctional cracking catalysts and effective catalyst additives to bind sulfur oxides directly in the regenerator. Basic oxides (of aluminum, magnesium, calcium, etc.) react with sulfur oxides to form stable sulfates that are then reduced to hydrogen sulfide in the reactor, while re-forming the basic oxide. Binding sulfur oxides in the regenerator is favored by the presence of an oxidizing agent or by the introduction of a promoter for afterburning carbon monoxide to dioxide. Compositions consisting mainly of aluminum oxide ({>=}90% by weight) have been patented as catalyst additives for binding sulfur oxides; other compositions that have been patented consist of Group II metal oxides and other oxides that have oxidizing properties. The additives are introduced into the catalyst charge in amounts of 5-10% by weight. On the basis of research, an aluminium oxide additive, PS-17, has been developed for binding sulfur oxides in the course of cracking.« less

Oxide inclusions in laser additive manufactured stainless steel and their effects on impact toughness and stress corrosion cracking behavior

NASA Astrophysics Data System (ADS)

Lou, Xiaoyuan; Andresen, Peter L.; Rebak, Raul B.

2018-02-01

Intergranular and intragranular Si and Mn rich oxide inclusions are present in laser additive manufactured austenitic stainless steel. The uniform oxide dispersions in additive manufactured material promoted early initiation of microvoids and reduced its impact toughness relative to powder metallurgy (hot isostatic pressing) and wrought materials. For stress corrosion cracking in high temperature water, the silica inclusions along the grain boundaries preferentially dissolved and appeared to accelerate oxidation and caused extensive crack branching.

Monitoring the layer-by-layer self-assembly of graphene and graphene oxide by spectroscopic ellipsometry.

PubMed

Zhou, Kai-Ge; Chang, Meng-Jie; Wang, Hang-Xing; Xie, Yu-Long; Zhang, Hao-Li

2012-01-01

Thin films of graphene oxide, graphene and copper (II) phthalocyanine dye have been successfully fabricated by electrostatic layer-by-layer (LbL) assembly approach. We present the first variable angle spectroscopic ellipsometry (VASE) investigation on these graphene-dye hybrid thin films. The thickness evaluation suggested that our LbL assembly process produces highly uniform and reproducible thin films. We demonstrate that the refractive indices of the graphene-dye thin films undergo dramatic variation in the range close to the absorption of the dyes. This investigation provides new insight to the optical properties of graphene containing thin films and shall help to establish an appropriate optical model for graphene-based hybrid materials.

Visualizing the Cu/Cu2(O) Interface Transition in Nanoparticles with Environmental Scanning Transmission Electron Microscopy.

PubMed

LaGrow, Alec P; Ward, Michael R; Lloyd, David C; Gai, Pratibha L; Boyes, Edward D

2017-01-11

Understanding the oxidation and reduction mechanisms of catalytically active transition metal nanoparticles is important to improve their application in a variety of chemical processes. In nanocatalysis the nanoparticles can undergo oxidation or reduction in situ, and thus the redox species are not what are observed before and after reactions. We have used the novel environmental scanning transmission electron microscope (ESTEM) with 0.1 nm resolution in systematic studies of complex dynamic oxidation and reduction mechanisms of copper nanoparticles. The oxidation of copper has previously been reported to be dependent on its crystallography and its interaction with the substrate. By following the dynamic oxidation process in situ in real time with high-angle annular dark-field imaging in the ESTEM, we use conditions ideal to track the oxidation front as it progresses across a copper nanoparticle by following the changes in the atomic number (Z) contrast with time. The oxidation occurs via the nucleation of the oxide phase (Cu 2 O) from one area of the nanoparticle which then progresses unidirectionally across the particle, with the Cu-to-Cu 2 O interface having a relationship of Cu{111}//Cu 2 O{111}. The oxidation kinetics are related to the temperature and oxygen pressure. When the process is reversed in hydrogen, the reduction process is observed to be similar to the oxidation, with the same crystallographic relationship between the two phases. The dynamic observations provide unique insights into redox mechanisms which are important to understanding and controlling the oxidation and reduction of copper-based nanoparticles.

Some Properties of Beryllium Oxide and Beryllium Oxide - Columbium Ceramals

NASA Technical Reports Server (NTRS)

Robards, C F; Gangler, J J

1951-01-01

High-temperature tensile and thermal-shock investigations were conducted on beryllium oxide and beryllium oxide plus columbium metal additions. X-ray diffraction and metallographic results are given. The tensile strength of 6150 pounds per square inch for beryllium oxide at 1800 degrees F compared favorably with the zirconia bodies previously tested. Additions of 2, 5, 8, 10, 12, and 15 percent by weight of columbium metal failed to improve the shock resistance over that of pure beryllium oxide.

Noble metal superparticles and methods of preparation thereof

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Yugang; Hu, Yongxing

A method comprises heating an aqueous solution of colloidal silver particles. A soluble noble metal halide salt is added to the aqueous solution which undergoes a redox reaction on a surface of the silver particles to form noble metal/silver halide SPs, noble metal halide/silver halide SPs or noble metal oxide/silver halide SPs on the surface of the silver particles. The heat is maintained for a predetermined time to consume the silver particles and release the noble metal/silver halide SPs, the noble metal halide/silver halide SPs or the noble metal oxide/silver halide SPs into the aqueous solution. The aqueous solution ismore » cooled. The noble metal/silver halide SPs, the noble metal halide/silver halide SPs or noble metal oxide/silver halide SPs are separated from the aqueous solution. The method optionally includes adding a soluble halide salt to the aqueous solution.« less

Near-Infrared Free-Radical and Free-Radical-Promoted Cationic Photopolymerizations by In-Source Lighting Using Upconverting Glass.

PubMed

Kocaarslan, Azra; Tabanli, Sevcan; Eryurek, Gonul; Yagci, Yusuf

2017-11-13

A method is presented for the initiation of free-radical and free-radical-promoted cationic photopolymerizations by in-source lighting in the near-infrared (NIR) region using upconverting glass (UCG). This approach utilizes laser irradiation of UCG at 975 nm in the presence of fluorescein (FL) and pentamethyldiethylene triamine (PMDETA). FL excited by light emitted from the UCG undergoes electron-transfer reactions with PMDETA to form free radicals capable of initiating polymerization of methyl methacrylate. To execute the corresponding free-radical-promoted cationic polymerization of cyclohexene oxide, isobutyl vinyl ether, and N-vinyl carbazole, it was necessary to use FL, dimethyl aniline (DMA), and diphenyliodonium hexafluorophosphate as sensitizer, coinitiator, and oxidant, respectively. Iodonium ions promptly oxidize DMA radicals formed to the corresponding cations. Thus, cationic polymerization with efficiency comparable to the conventional irradiation source was achieved. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Neural crest development and craniofacial morphogenesis is coordinated by nitric oxide and histone acetylation

PubMed Central

Kong, Yawei; Grimaldi, Michael; Curtin, Eugene; Dougherty, Max; Kaufman, Charles; White, Richard M.; Zon, Leonard I.; Liao, Eric C.

2015-01-01

Cranial neural crest (CNC) cells are patterned and coalesce to facial prominences that undergo convergence and extension to generate the craniofacial form. We applied a chemical genetics approach to identify pathways that regulate craniofacial development during embryogenesis. Treatment with the nitric oxide synthase inhibitor TRIM abrogated first pharyngeal arch structures and induced ectopic ceratobranchial formation. TRIM promoted a progenitor CNC fate and inhibited chondrogenic differentiation, which were mediated through impaired nitric oxide (NO) production without appreciable effect on global protein S-nitrosylation. Instead, TRIM perturbed hox gene patterning and caused histone hypoacetylation. Rescue of TRIM phenotype was achieved with over-expression of histone acetyltransferase kat6a, inhibition of histone deacetylase, and complimentary NO. These studies demonstrate that NO signaling and histone acetylation are coordinated mechanisms that regulate CNC patterning, differentiation and convergence during craniofacial morphogenesis. PMID:24684905

One-Electron Oxidation of [M(P(t) Bu3 )2 ] (M=Pd, Pt): Isolation of Monomeric [Pd(P(t) Bu3 )2 ](+) and Redox-Promoted C-H Bond Cyclometalation.

PubMed

Troadec, Thibault; Tan, Sze-Yin; Wedge, Christopher J; Rourke, Jonathan P; Unwin, Patrick R; Chaplin, Adrian B

2016-03-07

Oxidation of zero-valent phosphine complexes [M(P(t) Bu3 )2 ] (M=Pd, Pt) has been investigated in 1,2-difluorobenzene solution using cyclic voltammetry and subsequently using the ferrocenium cation as a chemical redox agent. In the case of palladium, a mononuclear paramagnetic Pd(I) derivative was readily isolated from solution and fully characterized (EPR, X-ray crystallography). While in situ electrochemical measurements are consistent with initial one-electron oxidation, the heavier congener undergoes C-H bond cyclometalation and ultimately affords the 14 valence-electron Pt(II) complex [Pt(κ(2) PC -P(t) Bu2 CMe2 CH2 )(P(t) Bu3 )](+) with concomitant formation of [Pt(P(t) Bu3 )2 H](+) . © 2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

Revisiting the Corrosion of the Aluminum Current Collector in Lithium-Ion Batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, Tianyuan; Xu, Gui-Liang; Li, Yan

The corrosion of aluminum current collectors and the oxidation of solvents at a relatively high potential have been widely investigated with an aim to stabilize the electrochemical performance of lithium-ion batteries using such components. The corrosion behavior of aluminum current collectors was revisited using a home-build high-precision electrochemical measurement system, and the impact of electrolyte components and the surface protection layer on aluminum foil was systematically studied. The electrochemical results showed that the corrosion of aluminum foil was triggered by the electrochemical oxidation of solvent molecules, like ethylene carbonate, at a relative high potential. The organic radical cations generated frommore » the electrochemical oxidation are energetically unstable, and readily undergo a deprotonation reaction that generates protons and promote the dissolution of Al3+ from the aluminum foil. This new reaction mechanism can also shed light on the dissolution of transitional metal at high potentials.« less

Revisiting the Corrosion of the Aluminum Current Collector in Lithium-Ion Batteries

DOE PAGES

Ma, Tianyuan; Xu, Gui -Liang; Li, Yan; ...

2017-02-16

The corrosion of aluminum current collectors and the oxidation of solvents at a relatively high potential have been widely investigated with an aim to stabilize the electrochemical performance of lithium-ion batteries using such components. The corrosion behavior of aluminum current collectors was revisited using a home-build high-precision electrochemical measurement system, and the impact of electrolyte components and the surface protection layer on aluminum foil was systematically studied. The electrochemical results showed that the corrosion of aluminum foil was triggered by the electrochemical oxidation of solvent molecules, like ethylene carbonate, at a relative high potential. The organic radical cations generated frommore » the electrochemical oxidation are energetically unstable, and readily undergo a deprotonation reaction that generates protons and promote the dissolution of Al 3+ from the aluminum foil. Finally, this new reaction mechanism can also shed light on the dissolution of transitional metal at high potentials.« less

On the effect of Ti on the stability of amorphous indium zinc oxide used in thin film transistor applications

NASA Astrophysics Data System (ADS)

Lee, Sunghwan; Paine, David C.

2011-06-01

In2O3-based amorphous oxide channel materials are of increasing interest for thin film transisitor applications due, in part, to the remarkable stability of this class of materials amorphous structure and electronic properties. We report that this stability is degraded in the presence of Ti, which is widely used as a contact and/or adhesion layer. A cross-sectional transmission electron microscopy analysis, supported by glancing incident angle x-ray and selected area diffraction examination, shows that amorphous indium zinc oxide in contact with Ti undergoes crystallization to the bixbyite phase and reacts to form the rutile phase of TiO2 at a temperature of 200 °C. A basic thermodynamic analysis is presented and forms the basis of a model that describes both the crystallization and the resistivity decrease.

Revisiting the Corrosion of the Aluminum Current Collector in Lithium-Ion Batteries.

PubMed

Ma, Tianyuan; Xu, Gui-Liang; Li, Yan; Wang, Li; He, Xiangming; Zheng, Jianming; Liu, Jun; Engelhard, Mark H; Zapol, Peter; Curtiss, Larry A; Jorne, Jacob; Amine, Khalil; Chen, Zonghai

2017-03-02

The corrosion of aluminum current collectors and the oxidation of solvents at a relatively high potential have been widely investigated with an aim to stabilize the electrochemical performance of lithium-ion batteries using such components. The corrosion behavior of aluminum current collectors was revisited using a home-build high-precision electrochemical measurement system, and the impact of electrolyte components and the surface protection layer on aluminum foil was systematically studied. The electrochemical results showed that the corrosion of aluminum foil was triggered by the electrochemical oxidation of solvent molecules, like ethylene carbonate, at a relative high potential. The organic radical cations generated from the electrochemical oxidation are energetically unstable and readily undergo a deprotonation reaction that generates protons and promotes the dissolution of Al 3+ from the aluminum foil. This new reaction mechanism can also shed light on the dissolution of transitional metal at high potentials.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Menges, F.; Spieser, M.; Riel, H.

The thermal radiative near field transport between vanadium dioxide and silicon oxide at submicron distances is expected to exhibit a strong dependence on the state of vanadium dioxide which undergoes a metal-insulator transition near room temperature. We report the measurement of near field thermal transport between a heated silicon oxide micro-sphere and a vanadium dioxide thin film on a titanium oxide (rutile) substrate. The temperatures of the 15 nm vanadium dioxide thin film varied to be below and above the metal-insulator-transition, and the sphere temperatures were varied in a range between 100 and 200 °C. The measurements were performed using a vacuum-basedmore » scanning thermal microscope with a cantilevered resistive thermal sensor. We observe a thermal conductivity per unit area between the sphere and the film with a distance dependence following a power law trend and a conductance contrast larger than 2 for the two different phase states of the film.« less

Revisiting the Corrosion of the Aluminum Current Collector in Lithium-Ion Batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, Tianyuan; Xu, Gui -Liang; Li, Yan

The corrosion of aluminum current collectors and the oxidation of solvents at a relatively high potential have been widely investigated with an aim to stabilize the electrochemical performance of lithium-ion batteries using such components. The corrosion behavior of aluminum current collectors was revisited using a home-build high-precision electrochemical measurement system, and the impact of electrolyte components and the surface protection layer on aluminum foil was systematically studied. The electrochemical results showed that the corrosion of aluminum foil was triggered by the electrochemical oxidation of solvent molecules, like ethylene carbonate, at a relative high potential. The organic radical cations generated frommore » the electrochemical oxidation are energetically unstable, and readily undergo a deprotonation reaction that generates protons and promote the dissolution of Al 3+ from the aluminum foil. Finally, this new reaction mechanism can also shed light on the dissolution of transitional metal at high potentials.« less

Predicting storage-dependent damage to red blood cells using nitrite oxidation kinetics, peroxiredoxin-2 oxidation, and hemoglobin and free heme measurements.

PubMed

Oh, Joo-Yeun; Stapley, Ryan; Harper, Victoria; Marques, Marisa B; Patel, Rakesh P

2015-12-01

Storage-dependent damage to red blood cells (RBCs) varies significantly. Identifying RBC units that will undergo higher levels of hemolysis during storage may allow for more efficient inventory management decision-making. Oxidative-stress mediates storage-dependent damage to RBCs and will depend on the oxidant:antioxidant balance. We reasoned that this balance or redox tone will serve as a determinant of how a given RBC unit stores and that its assessment in "young" RBCs will predict storage-dependent hemolysis. RBCs were sampled from bags and segments stored for 7 to 42 days. Redox tone was assessed by nitrite oxidation kinetics and peroxiredoxin-2 (Prx-2) oxidation. In parallel, hemolysis was assessed by measuring cell-free hemoglobin (Hb) and free heme (hemin). Correlation analyses were performed to determine if Day 7 measurements predicted either the level of hemolysis at Day 35 or the increase in hemolysis during storage. Higher Day 7 Prx-2 oxidation was associated with higher Day 35 Prx-2 oxidation, suggesting that early assessment of this variable may identify RBCs that will incur the most oxidative damage during storage. RBCs that oxidized nitrite faster on Day 7 were associated with the greatest levels of storage-dependent hemolysis and increases in Prx-2 oxidation. An inverse relationship between storage-dependent changes in oxyhemoglobin and free heme was observed underscoring an unappreciated reciprocity between these molecular species. Moreover, free heme was higher in the bag compared to paired segments, with opposite trends observed for free Hb. Measurement of Prx-2 oxidation and nitrite oxidation kinetics early during RBC storage may predict storage-dependent damage to RBC including hemolysis-dependent formation of free Hb and heme. © 2015 AABB.

Syntheses, structures and redox properties of some complexes containing the Os(dppe)Cp* fragment, including [{Os(dppe)Cp*}2(mu-C triple bondCC triple bond C)].

PubMed

Bruce, Michael I; Costuas, Karine; Davin, Thomas; Halet, Jean-François; Kramarczuk, Kathy A; Low, Paul J; Nicholson, Brian K; Perkins, Gary J; Roberts, Rachel L; Skelton, Brian W; Smith, Mark E; White, Allan H

2007-12-14

The sequential conversion of [OsBr(cod)Cp*] (9) to [OsBr(dppe)Cp*] (10), [Os([=C=CH2)(dppe)Cp*]PF6 ([11]PF6), [Os(C triple bond CH)(dppe)Cp*] (12), [{Os(dppe)Cp*}2{mu-(=C=CH-CH=C=)}][PF6]2 ([13](PF6)2) and finally [{Os(dppe)Cp*}(2)(mu-C triple bond CC triple bond C)] (14) has been used to make the third member of the triad [{M(dppe)Cp*}2(mu-C triple bond CC triple bond C)] (M = Fe, Ru, Os). The molecular structures of []PF6, 12 and 14, together with those of the related osmium complexes [Os(NCMe)(dppe)Cp*]PF6 ([15]PF6) and [Os(C triple bond CPh)(dppe)Cp*] (16), have been determined by single-crystal X-ray diffraction studies. Comparison of the redox properties of 14 with those of its iron and ruthenium congeners shows that the first oxidation potential E1 varies as: Fe approximately Os < Ru. Whereas the Fe complex has been shown to undergo three sequential 1-electron oxidation processes within conventional electrochemical solvent windows, the Ru and Os compounds undergo no fewer than four sequential oxidation events giving rise to a five-membered series of redox related complexes [{M(dppe)Cp*}2(mu-C4)]n+ (n = 0, 1, 2, 3 and 4), the osmium derivatives being obtained at considerably lower potentials than the ruthenium analogues. These results are complimented by DFT and DT DFT calculations.

Effect of Alprazolam on Redox Status in Renal Transplantation Donors and Recipients.

PubMed

Güner Can, Meltem; Ilgaz Koçyiğit, Özgen; Aksu, Uğur; Özer, Ali; Toraman, Fevzi

2017-06-09

BACKGROUND Benzodiazepines are the most popular premedication drugs thought to act through the GABA/benzodiazepine receptor complex and alprazolam is one of the most potent benzodiazepines that have a quick onset. While there is a growing body of evidence supporting alprazolam in the amelioration of redox status in animals, no study has been performed concerning its antioxidant activity in humans. The purpose of this investigation was to determine the effect of alprazolam on redox status. MATERIAL AND METHODS This study was a four-group randomized controlled trial. Participants were recruited from Acibadem University Acibadem International Hospital and included a convenience sample of 82 donors and recipients undergoing renal transplantation. Patients were randomly divided into four groups. While donors and recipients in experimental groups (G1 and G3) were administered alprazolam 0.5 mg orally one hour before the operation, those in control groups (G2 and G4) were not. Serum advanced oxidative protein products, total thiol, free hemoglobin, ischemic modified albumin, and sialic acid levels at different time points were measured to evaluate the redox status. RESULTS All oxidative stress parameters were higher in the alprazolam premedication groups (G1, G3) at all time points than in the control groups (G2, G4). Basal values of oxidative parameters (at time point T1) in patients with CKD (G3, G4) were lower than in healthy donors (G1, G2). CONCLUSIONS Alprazolam premedication in donors and end-stage renal failure patients undergoing renal transplantation does not improve redox homeostasis but further experimental studies are needed.

Advanced Sensor Arrays and Packaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ryter, John Wesley; Romero, Christopher J.; Ramaiyan, Kannan

2016-08-11

Novel sensor packaging elements were designed, fabricated, and tested in order to facilitate the transition of electrochemical mixed-potential sensors toward commercialization. Of the two designs completed, the first is currently undergoing field trials, taking direct measurements within vehicle exhaust streams, while the second is undergoing preliminary laboratory testing. The sensors’ optimal operating conditions, sensitivity to hydrogen, and long-­term baseline stability were also investigated. The sensing capabilities of lanthanum chromite (La 0.8Sr 0.2CrO 3) and indium-­doped tin oxide (ITO) working electrodes were compared, and the ITO devices were selected for pre-­commercial field trials testing at a hydrogen fuel cell vehicle fuelingmore » station in California. Previous data from that fueling station were also analyzed, and the causes of anomalous baseline drift were identified.« less

Transformation of Cerium Oxide Nanoparticles from a Diesel Fuel Additive during Combustion in a Diesel Engine.

PubMed

Dale, James G; Cox, Steven S; Vance, Marina E; Marr, Linsey C; Hochella, Michael F

2017-02-21

Nanoscale cerium oxide is used as a diesel fuel additive to reduce particulate matter emissions and increase fuel economy, but its fate in the environment has not been established. Cerium oxide released as a result of the combustion of diesel fuel containing the additive Envirox, which utilizes suspended nanoscale cerium oxide to reduce particulate matter emissions and increase fuel economy, was captured from the exhaust stream of a diesel engine and was characterized using a combination of bulk analytical techniques and high resolution transmission electron microscopy. The combustion process induced significant changes in the size and morphology of the particles; ∼15 nm aggregates consisting of 5-7 nm faceted crystals in the fuel additive became 50-300 nm, near-spherical, single crystals in the exhaust. Electron diffraction identified the original cerium oxide particles as cerium(IV) oxide (CeO 2 , standard FCC structure) with no detectable quantities of Ce(III), whereas in the exhaust the ceria particles had additional electron diffraction reflections indicative of a CeO 2 superstructure containing ordered oxygen vacancies. The surfactant coating present on the cerium oxide particles in the additive was lost during combustion, but in roughly 30% of the observed particles in the exhaust, a new surface coating formed, approximately 2-5 nm thick. The results of this study suggest that pristine, laboratory-produced, nanoscale cerium oxide is not a good substitute for the cerium oxide released from fuel-borne catalyst applications and that future toxicity experiments and modeling will require the use/consideration of more realistic materials.

21 CFR 73.2991 - Zinc oxide.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 1 2013-04-01 2013-04-01 false Zinc oxide. 73.2991 Section 73.2991 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2991 Zinc oxide. (a) Identity and specifications. The color additive zinc oxide shall conform in...

21 CFR 73.2991 - Zinc oxide.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 1 2012-04-01 2012-04-01 false Zinc oxide. 73.2991 Section 73.2991 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2991 Zinc oxide. (a) Identity and specifications. The color additive zinc oxide shall conform in...

21 CFR 73.1991 - Zinc oxide.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 1 2014-04-01 2014-04-01 false Zinc oxide. 73.1991 Section 73.1991 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1991 Zinc oxide. (a) Identity. (1) The color additive zinc oxide is a white or yellow-white amorphous...

21 CFR 73.1991 - Zinc oxide.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 1 2013-04-01 2013-04-01 false Zinc oxide. 73.1991 Section 73.1991 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1991 Zinc oxide. (a) Identity. (1) The color additive zinc oxide is a white or yellow-white amorphous...

21 CFR 73.1991 - Zinc oxide.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 1 2012-04-01 2012-04-01 false Zinc oxide. 73.1991 Section 73.1991 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1991 Zinc oxide. (a) Identity. (1) The color additive zinc oxide is a white or yellow-white amorphous...

PREPARATION OF REFRACTORY OXIDE MICROSPHERE

DOEpatents

Haws, C.C. Jr.

1963-09-24

A method is described of preparing thorium oxide in the form of fused spherical particles about 1 to 2 microns in diameter. A combustible organic solution of thorium nitrate containing additive metal values is dispersed into a reflected, oxygen-fed flame at a temperature above the melting point of the resulting oxide. The metal additive is aluminum at a proportion such as to provide 1 to 10 weight per cent aluminum oxide in the product, silicon at the same proportion, or beryllium at a proportion of 12 to 25 weight per cent beryllium oxide in the product. A minor proportion of uranium values may also be provided in the solution. The metal additive lowers the oxide melting point and allows fusion and sphere formation in conventional equipment. The product particles are suitable for use in thorium oxide slurries for nuclear reactors. (AEC)

Effects of Graphene Oxide Addition on Mechanical and Thermal Properties of Evoh Films

NASA Astrophysics Data System (ADS)

González-Ruiz, Jesús; Yataco-Lazaro, Lourde; Virginio, Sueli; das Graças da Silva-Valenzuela, Maria; Moura, Esperidiana; Valenzuela-Díaz, Francisco

Currently, ethylene vinyl alcohol (EVOH) is one of the oxygen barrier materials most used for food packaging. The addition of graphene oxide nanosheets to the EVOH matrix is employed to improve their mechanic al and barrier properties. In this work, films of EVOH-based composites reinforced with graphene oxide were prepared by melt extrusion, using a twin screw extruder machine and blown extrusion process. The graphene oxide was prepared via chemical oxidation of natural graphite and then was exfoliated into nanosheets using the sonochemical method. The composite films samples were characterized using FTIR and DSC analysis. In addition, their mechanical properties were also determined.

Complement proteins bind to nanoparticle protein corona and undergo dynamic exchange in vivo

NASA Astrophysics Data System (ADS)

Chen, Fangfang; Wang, Guankui; Griffin, James I.; Brenneman, Barbara; Banda, Nirmal K.; Holers, V. Michael; Backos, Donald S.; Wu, Linping; Moghimi, Seyed Moein; Simberg, Dmitri

2017-05-01

When nanoparticles are intravenously injected into the body, complement proteins deposit on the surface of nanoparticles in a process called opsonization. These proteins prime the particle for removal by immune cells and may contribute toward infusion-related adverse effects such as allergic responses. The ways complement proteins assemble on nanoparticles have remained unclear. Here, we show that dextran-coated superparamagnetic iron oxide core-shell nanoworms incubated in human serum and plasma are rapidly opsonized with the third complement component (C3) via the alternative pathway. Serum and plasma proteins bound to the nanoworms are mostly intercalated into the nanoworm shell. We show that C3 covalently binds to these absorbed proteins rather than the dextran shell and the protein-bound C3 undergoes dynamic exchange in vitro. Surface-bound proteins accelerate the assembly of the complement components of the alternative pathway on the nanoworm surface. When nanoworms pre-coated with human plasma were injected into mice, C3 and other adsorbed proteins undergo rapid loss. Our results provide important insight into dynamics of protein adsorption and complement opsonization of nanomedicines.

Development of high strength ferritic steel for interconnect application in SOFCs

NASA Astrophysics Data System (ADS)

Froitzheim, J.; Meier, G. H.; Niewolak, L.; Ennis, P. J.; Hattendorf, H.; Singheiser, L.; Quadakkers, W. J.

High-Cr ferritic model steels containing various additions of the refractory elements Nb and/or W were studied with respect to oxidation behaviour (hot) tensile properties, creep behaviour and high-temperature electrical conductivity of the surface oxide scales. Whereas W additions of around 2 wt.% had hardly any effect on the oxidation rates at 800 and 900 °C, Nb additions of 1% led to a substantially enhanced growth rate of the protective surface oxide scale. It was found that this adverse effect can be alleviated by suitable Si additions. This is related to the incorporation of Si and Nb into Laves phase precipitates which also contribute to increased creep and hot tensile strength. The dispersion of Laves phase precipitates was greatly refined by combined additions of Nb and W. The high-temperature electrical conductivity of the surface oxide scales was similar to that of the Nb/W-free alloys. Thus the combined additions of Nb, W and Si resulted in an alloy with oxidation resistance, ASR contribution and thermal expansion comparable to the commercial alloy Crofer 22 APU, but with creep strength far greater than that of Crofer 22 APU.

[Effect of sodium and calcium ions on glutamate and glutamine oxidation by rat brain synaptosomes].

PubMed

Nilova, N S

1978-08-01

5 mM oxidative substrates and 0.15 mM Ca(2+) being used, different effects of Ca(2+) on the oxidation are possible, such as an additional inhibition of glutamine oxidation and an additional activation of glutamate oxidation. A decreased Na+-ion concentration in the medium inhibited synaptosomal respiration with glutamate as a substrate. With glutamine as a substrate oxygen consumption does not change.

Reactive Uptake of Dimethylamine by Ammonium Sulfate and Ammonium Sulfate-Sucrose Mixed Particles.

PubMed

Chu, Yangxi; Chan, Chak K

2017-01-12

Short-chain alkyl amines can undergo gas-to-particle partitioning via reactive uptake by ammonium salts, whose phases have been thought to largely influence the extent of amine uptake. Previous studies mainly focused on particles of single ammonium salt at either dry or wet conditions without any addition of organic compounds. Here we report the uptake of dimethylamine (DMA) by ammonium sulfate (AS) and AS-sucrose mixed particles at different relative humidities (RHs) using an electrodynamic balance coupled with in situ Raman spectroscopy. DMA is selected as a representative of short-chain alkyl amines, and sucrose is used as a surrogate of viscous and hydrophilic organics. Effective DMA uptake was observed for most cases, except for the water-limiting scenario at <5% RH and the formation of an ultraviscous sucrose coating at 10% RH and below. DMA uptake coefficients (γ) were estimated using the particle mass measurements during DMA uptake. Addition of sucrose can increase γ by absorbing water or inhibiting AS crystallization and decrease γ by elevating the particle viscosity and forming a coating layer. DMA uptake can be facilitated for crystalline AS or retarded for aqueous AS with hydrophilic viscous organics (e.g., secondary organic material formed via the oxidation of biogenic volatile organic compounds) present in aerosol particles.

NiXantphos: a deprotonatable ligand for room-temperature palladium-catalyzed cross-couplings of aryl chlorides.

PubMed

Zhang, Jiadi; Bellomo, Ana; Trongsiriwat, Nisalak; Jia, Tiezheng; Carroll, Patrick J; Dreher, Spencer D; Tudge, Matthew T; Yin, Haolin; Robinson, Jerome R; Schelter, Eric J; Walsh, Patrick J

2014-04-30

Although the past 15 years have witnessed the development of sterically bulky and electron-rich alkylphosphine ligands for palladium-catalyzed cross-couplings with aryl chlorides, examples of palladium catalysts based on either triarylphosphine or bidentate phosphine ligands for efficient room temperature cross-coupling reactions with unactivated aryl chlorides are rare. Herein we report a palladium catalyst based on NiXantphos, a deprotonatable chelating aryldiphosphine ligand, to oxidatively add unactivated aryl chlorides at room temperature. Surprisingly, comparison of an extensive array of ligands revealed that under the basic reaction conditions the resultant heterobimetallic Pd-NiXantphos catalyst system outperformed all the other mono- and bidentate ligands in a deprotonative cross-coupling process (DCCP) with aryl chlorides. The DCCP with aryl chlorides affords a variety of triarylmethane products, a class of compounds with various applications and interesting biological activity. Additionally, the DCCP exhibits remarkable chemoselectivity in the presence of aryl chloride substrates bearing heteroaryl groups and sensitive functional groups that are known to undergo 1,2-addition, aldol reaction, and O-, N-, enolate-α-, and C(sp(2))-H arylations. The advantages and importance of the Pd-NiXantphos catalyst system outlined herein make it a valuable contribution for applications in Pd-catalyzed arylation reactions with aryl chlorides.

NiXantphos: A Deprotonatable Ligand for Room-Temperature Palladium-Catalyzed Cross-Couplings of Aryl Chlorides

PubMed Central

2015-01-01

Although the past 15 years have witnessed the development of sterically bulky and electron-rich alkylphosphine ligands for palladium-catalyzed cross-couplings with aryl chlorides, examples of palladium catalysts based on either triarylphosphine or bidentate phosphine ligands for efficient room temperature cross-coupling reactions with unactivated aryl chlorides are rare. Herein we report a palladium catalyst based on NiXantphos, a deprotonatable chelating aryldiphosphine ligand, to oxidatively add unactivated aryl chlorides at room temperature. Surprisingly, comparison of an extensive array of ligands revealed that under the basic reaction conditions the resultant heterobimetallic Pd–NiXantphos catalyst system outperformed all the other mono- and bidentate ligands in a deprotonative cross-coupling process (DCCP) with aryl chlorides. The DCCP with aryl chlorides affords a variety of triarylmethane products, a class of compounds with various applications and interesting biological activity. Additionally, the DCCP exhibits remarkable chemoselectivity in the presence of aryl chloride substrates bearing heteroaryl groups and sensitive functional groups that are known to undergo 1,2-addition, aldol reaction, and O-, N-, enolate-α-, and C(sp2)–H arylations. The advantages and importance of the Pd–NiXantphos catalyst system outlined herein make it a valuable contribution for applications in Pd-catalyzed arylation reactions with aryl chlorides. PMID:24745758

Symmetrical N-acylsubstituted dihydrazones containing bithiophene core - Photophysical, electrochemical and thermal characterization

NASA Astrophysics Data System (ADS)

Jarczyk-Jedryka, Anna; Filapek, Michal; Malecki, Grzegorz; Kula, Slawomir; Janeczek, Henryk; Boharewicz, Bartosz; Iwan, Agnieszka; Schab-Balcerzak, Ewa

2016-04-01

Four symmetrical N-acylsubstituted dihydrazones containing bithiophene core were synthesized from condensation of 2,2‧-bithiophene-5,5‧-dicarboxyaldehyde with benzoic, isonicotinoyl, 2-thiophenic and 2-furoic hydrazide. The obtained compounds were characterized through the data from 1H nuclear magnetic resonance spectroscopy (NMR), infrared spectroscopy (IR), elemental analysis, UV-vis absorption spectroscopy, photoluminescence (PL), cyclic voltammetry (CV) and differential pulse voltammetry (DPV) measurements. Additionally, the electronic properties including orbital energies and resulting energy gaps were calculated by density functional theory (DFT). Their thermal behavior was investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). They were thermal sable up to 320 °C. The prepared N-acylsubstituted dihydrazones emitted light with λem in the range of 499-530 nm in solution, whereas, in solid state as blend with PMMA blue emission was observed. They undergo quasi-reversible and irreversible electrochemical reduction and oxidation processes, respectively. Additionally, the selected compounds were tested preliminary as component of active layer in organic photovoltaic cells. The highest value of power conversion efficiency, equal to 1.68% under simulated 100 mW/cm2 AM 1.5G irradiation was found for device with the architecture ITO/PEDOT:PSS/P3HT:PCBM:FBTH (1:2:2)/Al.

Insulin mimesis of vanadium derivatives. Oxidation of cysteine by V(V) oxo diperoxo complexes.

PubMed

Ballistreri, F P; Barbuzzi, E G; Tomaselli, G A; Toscano, R M

2000-05-30

Kinetics of the oxidation of cysteine to cystine by four V(V) oxo diperoxo complexes [VO(O2)2L] possessing insulin mimetic activity, where L = oxalate(oxa), picolinate (pic), bipyridil (bipy), phenanthroline(phen), were performed in water at 10 degrees C by the UV or stopped-flow technique. 51V NMR spectra indicate that oxa undergoes a total ligand dissociation differently from pic, bipy and phen which hold their ligands also in solution. The observed reactivity is deeply affected by the identity of the ligand. The process seems to require coordination of the cysteine to the metal, followed by oxidation within the coordination sphere. In this respect phen and bipy make the coordination of cysteine much easier than oxa and pic. It is suggested, also on the basis of some preliminary observations concerning the oxidation of C6H5CH2SH, that the oxidation process is triggered by an electron transfer step. The rate of this step would be higher for oxa and pic than for phen and bipy. The observation that the oxidative ability of these vanadium peroxo complexes is dependent upon the nature of the ligands might match the analogous finding that their insulin mimetic activity is also modulated by the ligand identities.

Insights into the Distinct Lithiation/Sodiation of Porous Cobalt Oxide by in Operando Synchrotron X-ray Techniques and Ab Initio Molecular Dynamics Simulations.

PubMed

Xu, Gui-Liang; Sheng, Tian; Chong, Lina; Ma, Tianyuan; Sun, Cheng-Jun; Zuo, Xiaobing; Liu, Di-Jia; Ren, Yang; Zhang, Xiaoyi; Liu, Yuzi; Heald, Steve M; Sun, Shi-Gang; Chen, Zonghai; Amine, Khalil

2017-02-08

Sodium-ion batteries (SIBs) have been considered as one of the promising power source candidates for the stationary storage industries owing to the much lower cost of sodium than lithium. It is well-known that the electrode materials largely determine the energy density of the battery systems. However, recent discoveries on the electrode materials showed that most of them present distinct lithium and sodium storage performance, which is not yet well understood. In this work, we performed a comparative understanding on the structural changes of porous cobalt oxide during its electrochemical lithiation and sodiation process by in operando synchrotron small angel X-ray scattering, X-ray diffraction, and X-ray absorption spectroscopy. It was found that compared to the lithiation process, the porous cobalt oxide undergoes less pore structure changes, oxidation state, and local structure changes as well as crystal structure evolution during its sodiation process, which is attributed to the intrinsic low sodiation activity of cobalt oxide as evidenced by ab initio molecular dynamics simulations. Moreover, it was indicated that the sodiation activity of metal sulfides is higher than that of metal oxides, indicating a better candidate for SIBs. Such understanding is crucial for future design and improvement of high-performance electrode materials for SIBs.

Performance and Reliability of Electrowetting-on-Dielectric (EWOD) Systems Based on Tantalum Oxide.

PubMed

Mibus, Marcel; Zangari, Giovanni

2017-12-06

The electrowetting-on-dielectric behavior of Cytop/Tantalum oxide (TaOx) bilayers is studied by measuring their response vs applied voltage and under prolonged periodic cycling, below and above the threshold voltage V T corresponding to the breakdown field for the oxide. TaOx exhibits symmetric solid state I-V characteristics, with electronic conduction dominated by Schottky, Poole-Frenkel emission; conduction is attributed to oxygen vacancies (6 × 10 16 cm -3 ), resulting in large currents at low bias. Electrolyte/Metal Oxide/Metal I-V characteristics show oxide degradation at (<5 V) cathodic bias; anodic bias in contrast results in stable characteristics until reaching the anodization voltage, where the oxide thickens, leading eventually to breakdown and oxygen production at the electrode. Electrowetting angle vs applied voltage undergoes three different stages: a parabolic variation of contact angle (CA) with applied voltage, CA saturation, and rebound of the CA to higher values due to degradation of the polymer layer. The contact angle remained stable for several hundred cycles if the applied voltage was less than V T ; degradation in contrast is fast when the voltage is above V T . Degradation of the electrowetting response with time is linked to charge accumulation in the polymer, which inhibits the rebound of the CA when voltage is being applied.

Endoplasmic Reticulum Stress and Oxidative Stress: A Vicious Nexus Implicated in Bowel Disease Pathophysiology

PubMed Central

Chong, Wai Chin; Shastri, Madhur D.; Eri, Rajaraman

2017-01-01

The endoplasmic reticulum (ER) is a complex protein folding and trafficking organelle. Alteration and discrepancy in the endoplasmic reticulum environment can affect the protein folding process and hence, can result in the production of misfolded proteins. The accumulation of misfolded proteins causes cellular damage and elicits endoplasmic reticulum stress. Under such stress conditions, cells exhibit reduced functional synthesis, and will undergo apoptosis if the stress is prolonged. To resolve the ER stress, cells trigger an intrinsic mechanism called an unfolded protein response (UPR). UPR is an adaptive signaling process that triggers multiple pathways through the endoplasmic reticulum transmembrane transducers, to reduce and remove misfolded proteins and improve the protein folding mechanism, in order to improve and maintain endoplasmic reticulum homeostasis. An increasing number of studies support the view that oxidative stress has a strong connection with ER stress. During the protein folding process, reactive oxygen species are produced as by-products, leading to impaired reduction-oxidation (redox) balance conferring oxidative stress. As the protein folding process is dependent on redox homeostasis, the oxidative stress can disrupt the protein folding mechanism and enhance the production of misfolded proteins, causing further ER stress. It is proposed that endoplasmic reticulum stress and oxidative stress together play significant roles in the pathophysiology of bowel diseases. PMID:28379196

Endoplasmic Reticulum Stress and Oxidative Stress: A Vicious Nexus Implicated in Bowel Disease Pathophysiology.

PubMed

Chong, Wai Chin; Shastri, Madhur D; Eri, Rajaraman

2017-04-05

The endoplasmic reticulum (ER) is a complex protein folding and trafficking organelle. Alteration and discrepancy in the endoplasmic reticulum environment can affect the protein folding process and hence, can result in the production of misfolded proteins. The accumulation of misfolded proteins causes cellular damage and elicits endoplasmic reticulum stress. Under such stress conditions, cells exhibit reduced functional synthesis, and will undergo apoptosis if the stress is prolonged. To resolve the ER stress, cells trigger an intrinsic mechanism called an unfolded protein response (UPR). UPR is an adaptive signaling process that triggers multiple pathways through the endoplasmic reticulum transmembrane transducers, to reduce and remove misfolded proteins and improve the protein folding mechanism, in order to improve and maintain endoplasmic reticulum homeostasis. An increasing number of studies support the view that oxidative stress has a strong connection with ER stress. During the protein folding process, reactive oxygen species are produced as by-products, leading to impaired reduction-oxidation (redox) balance conferring oxidative stress. As the protein folding process is dependent on redox homeostasis, the oxidative stress can disrupt the protein folding mechanism and enhance the production of misfolded proteins, causing further ER stress. It is proposed that endoplasmic reticulum stress and oxidative stress together play significant roles in the pathophysiology of bowel diseases.

Cinacalcet may improve oxidative DNA damage in maintenance hemodialysis patients: an observational study.

PubMed

Ari, Elif; Kaya, Yuksel; Demir, Halit; Asicioglu, Ebru; Eren, Zehra; Celik, Eray; Arikan, Hakki

2014-09-01

Oxidative stress is accepted as a non-classical cardiovascular risk factor in patients on maintenance hemodialysis (HD). The aim of this study was to evaluate the impact of cinacalcet on oxidative stress biomarkers, oxidative DNA damage (8-hydroxy-2'-deoxyguanosine/deoxyguanosine), endothelial function (FMD %) and carotid artery intima-media thickness (CIMT) in HD patients. Forty-two chronic HD patients with secondary hyperparathyroidism undergoing 60 mg/day cinacalcet treatment with a follow-up of 6 months and 38 age- and sex-matched healthy individuals were included in this prospective study. Plasma malondialdehyde (MDA) levels and 8-hydroxy-2'-deoxyguanosine/deoxyguanosine ratio (8-OHdG/dG) were determined as oxidative stress markers. Superoxide dismutase (SOD), paraoxonase (PON), catalase (CAT), carbonic anhydrase (CAN) and glutathione peroxidase (GPx) activities were measured as antioxidants. FMD % and CIMT were assessed by ultrasonography. MDA levels were decreased; SOD, PON, CAT, CAN and GPx activities were increased after 6 months of cinacalcet treatment in HD patients. Although CIMT remained stabile, there was a significant improvement in FMD % as well as a notable reduction trend in 8-OHdG/dG ratio after 6 months of treatment. Our data have demonstrated that cinacalcet improves oxidative stress, genomic damage, endothelial function and increases antioxidant protection in HD patients after 6 months of treatment.

Second-Order Biomimicry: In Situ Oxidative Self-Processing Converts Copper(I)/Diamine Precursor into a Highly Active Aerobic Oxidation Catalyst

PubMed Central

2017-01-01

A homogeneous Cu-based catalyst system consisting of [Cu(MeCN)4]PF6, N,N′-di-tert-butylethylenediamine (DBED), and p-(N,N-dimethylamino)pyridine (DMAP) mediates efficient aerobic oxidation of alcohols. Mechanistic study of this reaction shows that the catalyst undergoes an in situ oxidative self-processing step, resulting in conversion of DBED into a nitroxyl that serves as an efficient cocatalyst for aerobic alcohol oxidation. Insights into this behavior are gained from kinetic studies, which reveal an induction period at the beginning of the reaction that correlates with the oxidative self-processing step, EPR spectroscopic analysis of the catalytic reaction mixture, which shows the buildup of the organic nitroxyl species during steady state turnover, and independent synthesis of oxygenated DBED derivatives, which are shown to serve as effective cocatalysts and eliminate the induction period in the reaction. The overall mechanism bears considerable resemblance to enzymatic reactivity. Most notable is the “oxygenase”-type self-processing step that mirrors generation of catalytic cofactors in enzymes via post-translational modification of amino acid side chains. This higher-order function within a synthetic catalyst system presents new opportunities for the discovery and development of biomimetic catalysts. PMID:28470049

Stabilized tin-oxide-based oxidation/reduction catalysts

NASA Technical Reports Server (NTRS)

Watkins, Anthony Neal (Inventor); Oglesby, Donald M. (Inventor); Gulati, Suresh T. (Inventor); Summers, Jerry C. (Inventor); Schryer, David R. (Inventor); Davis, Patricia P. (Inventor); Leighty, Bradley D. (Inventor); Jordan, Jeffrey D. (Inventor); Schryer, Jacqueline L. (Inventor)

2008-01-01

The invention described herein involves a novel approach to the production of oxidation/reduction catalytic systems. The present invention serves to stabilize the tin oxide reducible metal-oxide coating by co-incorporating at least another metal-oxide species, such as zirconium. In one embodiment, a third metal-oxide species is incorporated, selected from the group consisting of cerium, lanthanum, hafnium, and ruthenium. The incorporation of the additional metal oxide components serves to stabilize the active tin-oxide layer in the catalytic process during high-temperature operation in a reducing environment (e.g., automobile exhaust). Moreover, the additional metal oxides are active components due to their oxygen-retention capabilities. Together, these features provide a mechanism to extend the range of operation of the tin-oxide-based catalyst system for automotive applications, while maintaining the existing advantages.

Structure-property relationships in NOx sensor materials composed of arrays of vanadium oxide nanoclusters

NASA Astrophysics Data System (ADS)

Putrevu, Naga Ravikanth; Darling, Seth B.; Segre, Carlo U.; Ganegoda, Hasitha; Khan, M. Ishaque

2017-12-01

The mixed-valent vanadium oxide based three-dimensional framework structure species [Cd3(H2O)12V16IVV2VO36(OH)6 (AO4)]·24H2O, (A = V,S) (Cd3(VO)o) represents a rare example of an interesting sensor material which exhibits NOx {NO + NO2} semiconducting gas sensor properties under ambient conditions. The electrical resistance of the sensor material Cd3(VO)o decreases in air. Combined characterization studies revealed that the building block, {V18O42(AO4)} cluster, of 3-D framework undergoes oxidation and remains intact for at least 2 months. The decrease in resistance is attributable to the reactivity of molecular oxygen towards vanadium which results in an increase in the oxidation state as well as the coordination number of vanadium center and decrease in band gap of Cd3(VO)o. Based on these results we propose that the changes in semiconducting properties of Cd3(VO)o under ambient conditions are due to the greater overlap between the O 2p and V 3d orbitals occurring during the oxidation.

Heme-assisted S-Nitrosation Desensitizes Ferric Soluble Guanylate Cyclase to Nitric Oxide*

PubMed Central

Fernhoff, Nathaniel B.; Derbyshire, Emily R.; Underbakke, Eric S.; Marletta, Michael A.

2012-01-01

Nitric oxide (NO) signaling regulates key processes in cardiovascular physiology, specifically vasodilation, platelet aggregation, and leukocyte rolling. Soluble guanylate cyclase (sGC), the mammalian NO sensor, transduces an NO signal into the classical second messenger cyclic GMP (cGMP). NO binds to the ferrous (Fe2+) oxidation state of the sGC heme cofactor and stimulates formation of cGMP several hundred-fold. Oxidation of the sGC heme to the ferric (Fe3+) state desensitizes the enzyme to NO. The heme-oxidized state of sGC has emerged as a potential therapeutic target in the treatment of cardiovascular disease. Here, we investigate the molecular mechanism of NO desensitization and find that sGC undergoes a reductive nitrosylation reaction that is coupled to the S-nitrosation of sGC cysteines. We further characterize the kinetics of NO desensitization and find that heme-assisted nitrosothiol formation of β1Cys-78 and β1Cys-122 causes the NO desensitization of ferric sGC. Finally, we provide evidence that the mechanism of reductive nitrosylation is gated by a conformational change of the protein. These results yield insights into the function and dysfunction of sGC in cardiovascular disease. PMID:23093402

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Gui -Liang; Sheng, Tian; Chong, Lina

Sodium-ion batteries (SIBs) have been considered as one of the promising power source candidates for the stationary storage industries owing to the much lower cost of sodium than lithium. It is well-known that the electrode materials largely determine the energy density of the battery systems. However, recent discoveries on the electrode materials showed that most of them present distinct lithium and sodium storage performance, which is not yet well understood. In this work, we performed a comparative understanding on the structural changes of porous cobalt oxide during its electrochemical lithiation and sodiation process by in operando synchrotron small angel X-raymore » scattering, X-ray diffraction, and X-ray absorption spectroscopy. It was found that compared to the lithiation process, the porous cobalt oxide undergoes less pore structure changes, oxidation state, and local structure changes as well as crystal structure evolution during its sodiation process, which is attributed to the intrinsic low sodiation activity of cobalt oxide as evidenced by ab initio molecular dynamics simulations. Moreover, it was indicated that the sodiation activity of metal sulfides is higher than that of metal oxides, indicating a better candidate for SIBs. Furthermore, such understanding is crucial for future design and improvement of high-performance electrode materials for SIBs.« less

Structural dependence of flavonoid interactions with Cu2+ ions: implications for their antioxidant properties.

PubMed Central

Brown, J E; Khodr, H; Hider, R C; Rice-Evans, C A

1998-01-01

The flavonoids constitute a large group of polyphenolic phytochemicals with antioxidant properties in vitro. The interactions of four structurally related flavonoids (quercetin, kaempferol, rutin and luteolin) with Cu2+ ions were investigated in terms of the extent to which they undergo complex formation through chelation or modification through oxidation, as well as in their structural dependence. The ortho 3',4'-dihydroxy substitution in the B ring is shown to be important for Cu2+-chelate formation, thereby influencing the antioxidant activity. The presence of a 3-hydroxy group in the flavonoid structure enhances the oxidation of quercetin and kaempferol, whereas luteolin and rutin, each lacking the 3-hydroxy group, do not oxidize as readily in the presence of Cu2+ ions. The results also demonstrate that the reactivities of the flavonoids in protecting low-density lipoprotein (LDL) against Cu2+ ion-induced oxidation are dependent on their structural properties in terms of the response of the particular flavonoid to Cu2+ ions, whether chelation or oxidation, their partitioning abilities between the aqueous compartment and the lipophilic environment within the LDL particle, and their hydrogen-donating antioxidant properties. PMID:9494082

Structure-property relationships in NO x sensor materials composed of arrays of vanadium oxide nanoclusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Putrevu, Naga Ravikanth; Darling, Seth B.; Segre, Carlo U.

The mixed-valent vanadium oxide based three-dimensional framework structure species [Cd 3(H 2O) 12V 16 IVV 2 VO 36(OH) 6(AO 4)]∙24H 2O, (A=V,S) (Cd 3(VO) o) represents a rare example of an interesting sensor material which exhibits NO x {NO+NO 2} semiconducting gas sensor properties under ambient conditions. The electrical resistance of the sensor material Cd 3(VO) o decreases in air. Combined characterization studies revealed that the building block, {V 18O 42(AO 4)} cluster, of 3-D framework undergoes oxidation and remains intact for at least 2 months. The decrease in resistance is attributable to the reactivity of molecular oxygen towards vanadiummore » which results in an increase in the oxidation state as well as the coordination number of vanadium center and decrease in band gap of Cd 3(VO) o. Based on these results we propose that the changes in semiconducting properties of Cd 3(VO) o under ambient conditions are due to the greater overlap between the O 2p and V 3d orbitals occurring during the oxidation.« less

Identification of hydrogen peroxide oxidation sites of alpha A- and alpha B-crystallins.

PubMed

Smith, J B; Jiang, X; Abraham, E C

1997-02-01

The alpha-crystallins are the most abundant structural proteins of the lens and, because of their chaperone activity, contribute to the solubility of the other crystallins. With aging, the lens crystallins undergo a variety of modifications which correlate with a loss of solubility and the development of cataract. A recent study demonstrating that alpha-crystallins exposed in vitro to FeCl3 and H2O2 exhibit decreased chaperone activity, implicates metal catalyzed oxidations of alpha-crystallins in this loss of solubility. The present study has determined that alpha-crystallins incubated with FeCl3 and H2O2 are modified by the nearly complete oxidation of all methionine residues to methionine sulfoxide, with no other detectable reaction products. The modifications were identified from the molecular weights of peptides formed by enzymatic digestion of the alpha-crystallins and located by tandem mass spectrometric analysis of the fragmentation pattern of the mass spectra of the fragments from peptides with oxidized methionine is loss of 64 Da, which corresponds to loss of CH3SOH from the methionine sulfoxide. These fragments are useful in identifying peptides that include oxidized methionine residues.

Reactivation of oxidized PTP1B and PTEN by Thioredoxin 1

PubMed Central

Schwertassek, Ulla; Haque, Aftabul; Krishnan, Navasona; Greiner, Romy; Weingarten, Lars; Dick, Tobias P.; Tonks, Nicholas K.

2014-01-01

The transient inactivation of protein phosphatases contributes to the efficiency and temporal control of kinase-dependent signal transduction. In particular, members of the protein tyrosine phosphatase family are known to undergo reversible oxidation of their active site cysteine. The thiol oxidation step requires activation of co-localized NADPH oxidases and is mediated by locally produced ROS, in particular H2O2. How oxidized phosphatases are returned to the reduced active state is less well studied. Both major thiol reductive systems, the thioredoxin and the glutathione systems, have been implicated in the reactivation of phosphatases. Here, we show that the protein tyrosine phosphatase PTP1B and the dual-specificity phosphatase PTEN are preferentially reactivated by the thioredoxin system. We show that inducible depletion of TRX1 slows down PTEN re-activation in intact living cells. Finally, using a mechanism-based trapping approach we demonstrate direct thiol disulfide exchange between the active sites of thioredoxin and either phosphatase. The application of thioredoxin trapping mutants represents a complementary approach to direct assays of PTP oxidation in elucidating the significance of redox regulation of PTP function in the control of cell signaling. PMID:24976139

"Outer-sphere to inner-sphere" redox cycling for ultrasensitive immunosensors.

PubMed

Akanda, Md Rajibul; Choe, Yu-Lim; Yang, Haesik

2012-01-17

This paper reports chemical-chemical (CC) and electrochemical-chemical-chemical (ECC) redox cycling, for use in ultrasensitive biosensor applications. A triple chemical amplification approach using an enzymatic reaction, CC redox cycling, and ECC redox cycling is applied toward electrochemical immunosensors of cardiac troponin I. An enzymatic reaction, in which alkaline phosphatase converts 4-aminophenyl phosphate to 4-aminophenol (AP), triggers CC redox cycling in the presence of an oxidant and a reductant, and electrochemical signals are measured with ECC redox cycling after an incubation period of time in an air-saturated solution. To obtain high, selective, and reproducible redox cycling without using redox enzymes, two redox reactions [the reaction between AP and the oxidant and the reaction between the oxidized form of AP (4-quinone imine, QI) and the reductant] should be fast, but an unwanted reaction between the oxidant and reductant should be very slow. Because species that undergo outer-sphere reactions (OSR-philic species) react slowly with species that undergo inner-sphere reactions (ISR-philic species), highly OSR-philic Ru(NH(3))(6)(3+) and highly ISR-philic tris(2-carboxyethyl)phosphine (TCEP) are chosen as the oxidant and reductant, respectively. The OSR- and ISR-philic QI/AP couple allows fast redox reactions with both the OSR-philic Ru(NH(3))(6)(3+) and the ISR-philic TCEP. Highly OSR-philic indium-tin oxide (ITO) electrodes minimize unwanted electrochemical reactions with highly ISR-philic species. Although the formal potential of the Ru(NH(3))(6)(3+)/Ru(NH(3))(6)(2+) couple is lower than that of the QI/AP couple, the endergonic reaction between Ru(NH(3))(6)(3+) and AP is driven by the highly exergonic reaction between TCEP and QI (via a coupled reaction mechanism). Overall, the "outer-sphere to inner-sphere" redox cycling in the order of highly OSR-philic ITO, highly OSR-philic Ru(NH(3))(6)(3+)/Ru(NH(3))(6)(2+) couple, OSR- and ISR-philic QI/AP couple, and highly ISR-philic TCEP allows high, selective, and reproducible signal amplification. The electrochemical data obtained by chronocoulometry permit a lower detection limits than those obtained by cyclic voltammetry. The detection limit of an immunosensor for troponin I in serum, calculated from the anodic charges in chronocoulometry, is ca. 10 fg/mL.

The effect of oxidation on the mechanical response and microstructure of porcine aortas.

PubMed

Stephen, Elizabeth A; Venkatasubramaniam, Arundhathi; Good, Theresa A; Topoleski, L D Timmie

2014-09-01

Reactive oxygen species (ROS), a product of many cellular functions, has been implicated in many age-related pathophysiological processes, including cardiovascular disease. The arterial proteins collagen and elastin may also undergo structural and functional changes due to damage caused by ROS. This study examined the effect of oxidation on the mechanical response of porcine aortas and aorta elastin and the associated changes in structural protein ultrastructure as a step in exploring the role of molecular changes in structural proteins with aging on elastic artery function. We examined the change in mechanical properties of aorta samples after various oxidation times as a first step in understanding how the oxidative environment associated with aging could impact mechanical properties of arterial structural proteins. We used confocal microscopy to visualize how the microstructure of isolated elastin changed with oxidation. We find that short term oxidation of elastin isolated from aortas leads to an increase in material stiffness, but also an increase in the fiber diameter, increase in void space in the matrix, and a decrease in the fiber orientation, possibly due to fiber cross-linking. The short term effects of oxidation on arterial collagen is more complex, with increase in material stiffness seen in the collagen region of the stress stretch curve at low extents of oxidation, but not at high levels of oxidation. These results may provide insight into the relationship between oxidative damage to tissue associated with aging and disease, structure of the arterial proteins elastin and collagen, and arterial mechanical properties and function. © 2013 Wiley Periodicals, Inc.

Aerospace Power Scholarly Research Program. Delivery Order 0011: Modeling Lithium-Ion Conducting Channel

DTIC Science & Technology

2005-12-01

Brinkmann, D. NMR, DSC, and conductivity study of a poly (ethylene oxide) complex electrolyte: PEO(LiClO4)x, Sol. St. Ionics 1986, 18-19, 295. (27...Electrochemical Characterizations of Dilithium Octacyanophthalocyanine Langmuir - Blodgett films, Langmuir 2002, 18, 2223. 20 ...phthalocyanine (Li2Pc) has been used in this development since it can undergo molecular self-assembly to form the ionic ally conducting channel. The

Decreased expression of adipose CD36 and FATP1 are associated with increased plasma nonesterified fatty acids during prolonged fasting in northern elephant seal pups (Mirounga angustirostris)

USDA-ARS?s Scientific Manuscript database

The northern elephant seal undergoes a 2-3 month post-weaning fast during which it depends primarily on the oxidation of fatty acids to meet its energetic demands. The concentration of plasma free fatty acids (FFA) increases and is associated with the development of insulin resistance in late-fasted...

Nitrations Conference Held at Menlo Park, California on 27-29 July 1983.

DTIC Science & Technology

1983-09-01

MECHANISM OF HOMOGENEOUS GAS-PHASE DECOMPOSITION OF NITROTOLUENES" D. F. McMillen, C. W. Larson, and D. M. Golden...NITROAROMATICS. THE MECHANISM OF HOMOGENEOUS GAS-PHASE DECOMPOSITION OF NITROTOLUENES" i 6:00 Wine Tasting 7:00 Banquet, International Dining Room THURSDAY, JULY...which undergo hydrolysis or oxidations in strong acid solutions can he easily nitrated. Aryl nitriles, which could not be dinitrated without

Plastic-bonded electrodes for nickel-cadmium accumulators. IV - Some specific problems of the positive active layer

NASA Astrophysics Data System (ADS)

Micka, K.; Mrha, J.; Klapste, B.

1980-06-01

The active layer of plastic-bonded nickel oxide electrodes undergoes expansion during discharging and contraction during charging; the latter however does not fully compensate for the expansion. These volume changes can be made reversible by the action of an external pressure. The electro-chemical behavior of the conductive components, carbon black and graphite, shows more or less severe corrosion during anodic current loading.

Effect of soybean lecithin on iron-catalyzed or chlorophyll-photosensitized oxidation of canola oil emulsion.

PubMed

Choe, Jeesu; Oh, Boyoung; Choe, Eunok

2014-11-01

The effect of soybean lecithin addition on the iron-catalyzed or chlorophyll-photosensitized oxidation of emulsions consisting of purified canola oil and water (1:1, w/w) was studied based on headspace oxygen consumption using gas chromatography and hydroperoxide production using the ferric thiocyanate method. Addition levels of iron sulfate, chlorophyll, and soybean lecithin were 5, 4, and 350 mg/kg, respectively. Phospholipids (PLs) during oxidation of the emulsions were monitored by high performance liquid chromatography. Addition of soybean lecithin to the emulsions significantly reduced and decelerated iron-catalyzed oil oxidation by lowering headspace oxygen consumption and hydroperoxide production. However, soybean lecithin had no significant antioxidant effect on chlorophyll-photosensitized oxidation of the emulsions. PLs in soybean lecithin added to the emulsions were degraded during both oxidation processes, although there was little change in PL composition. Among PLs in soybean lecithin, phosphatidylethanolamine and phosphatidylinositol were degraded the fastest in the iron-catalyzed and the chlorophyll-photosensitized oxidation, respectively. The results suggest that addition of soybean lecithin as an emulsifier can also improve the oxidative stability of oil in an emulsion. © 2014 Institute of Food Technologists®

Classic histamine H1 receptor antagonists: a critical review of their metabolic and pharmacokinetic fate from a bird's eye view.

PubMed

Sharma, A; Hamelin, B A

2003-04-01

The so-called "classic" histamine H(1) receptor antagonists are highly lipophilic compounds associated with significant biotransformation and tissue distribution. They are categorized according to their chemical structure into ethanolamines, alkylamines, ethylenediamines, piperazines, phenothiazines and piperidines, all of which have characteristic metabolic fates. The former four categories undergo primarily cytochrome P450-mediated oxidative N-desalkylations and deamination whereas the aromatic rings of the latter two undergo P450-mediated oxidative hydroxylation and/or epoxide formation. The common tertiary amino group is susceptible to oxidative metabolism by flavin containing monooxygenases forming N-oxides, and the alicyclic tertiary amines produce small amounts (up to 7%) of N-glucuronides in humans. Species, sex and racial differences in the metabolism and pharmacokinetics of antihistamines are known. Specific P450-isozymes implicated in the metabolism were identified in a few cases, such as CYP2D6 that contributes to the metabolism of promethazine, diphenhydramine and chlorpheniramine. Low circulating plasma concentrations of antihistamines are in part explained by significant first-pass effect and tissue distribution. Antihistaminic effects last up to 6 hours though some compounds exhibit a longer duration of action due to circulating active metabolites. Importantly, diphenhydramine inhibited CYP2D6 leading to a clinically significant drug-drug interaction with metoprolol. Other classic antihistamines were shown to be potent in vitro inhibitors of CYP2D6 and CYP3A4. The prescription-free access to most classic antihistamines can easily lead to their co-administration with other drugs metabolized by the same enzyme system thereby leading to drug accumulation and adverse effects. In depth knowledge of the metabolic pathways of classic antihistamines and the enzymes involved is crucial to prevent the high incidence of drug interactions in humans, which are predictable based on pre-clinical data but unexpected when such data is unavailable.