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1

Iron-catalyzed tandem oxidative coupling and annulation: an efficient approach to construct polysubstituted benzofurans.  

PubMed

The combination of FeCl(3) x 6 H(2)O and di-tert-butyl peroxide offers a novel and efficient method for the construction of polysubstituted benzofurans 3 from the reaction of simple phenols 1 and beta-keto esters 2, which are expected to give coumarins in the well-known Pechmann condensation. A variety of phenols reacted with beta-keto esters to provide a range of benzofuran products in moderate to excellent yields. The regio-specific annulation was proven by the X-ray molecular structure of the product 3k. Hydrate of FeCl(3) is essential for an achievement of the present transformation. The kinetic isotopic effect (KIE) experiments were carried out by competition experiments and displayed a k(H)/k(D) = 1.0 +/- 0.1. The kinetic isotopic effect indicated that aromatic C-H bond cleavage is not involved in the rate-determining steps of the present transformation. Moreover, the results clearly demonstrate that the dichotomous catalytic behavior of the iron catalyst, which is transition-metal catalyst in the oxidative coupling step and Lewis acid in the condensation step. The possible intermediate 5 was synthesized and converted into the desired benzofuran 3a under the reaction conditions. A tentative mechanism of the formation of benzofurans 3 was proposed. PMID:19899754

Guo, Xingwei; Yu, Rong; Li, Haijun; Li, Zhiping

2009-12-01

2

Accelerator mass spectrometry with a coupled tandem-linac system  

SciTech Connect

A coupled system provides higher energies, which allows one to extend AMS to hitherto untouched mass regions. Another important argument is that the complexity, although bothersome for the operation, increases the selectivity of detecting a particular isotope. The higher-energy argument holds for any heavy-ion accelerator which is capable of delivering higher energy than a tandem. The present use of tandem-linac combinations for AMS, rather than cyclotrons, linacs or combinations of these machines, has mainly to do with the fact that this technique was almost exclusively developed around tandem accelerators. Therefore the tandem-linac combination is a natural extension to higher energies. The use of negative ions has some particular advantages in suppressing background from unwanted elements that do not form stable negative ions (e.g., N, Mg, Ar). On the other hand, this limits the detection of isotopes to elements which do form negative ions. For particular problems it may therefore be advantageous to use a positive-ion machine. What really matters most for choosing one or the other machine is to what extent the entire accelerator system can be operated in a truly quantiative way from the ion source to the detection system. 20 references, 4 figures.

Kutschera, W.

1984-01-01

3

Perovskite catalysts for oxidative coupling  

DOEpatents

Perovskites of the structure A[sub 2]B[sub 2]C[sub 3]O[sub 10] are useful as catalysts for the oxidative coupling of lower alkane to heavier hydrocarbons. A is alkali metal; B is lanthanide or lanthanum, cerium, neodymium, samarium, praseodymium, gadolinium or dysprosium; and C is titanium.

Campbell, K.D.

1991-06-25

4

Separation of intermediates of iron-catalyzed dopamine oxidation reactions using reversed-phase ion-pairing chromatography coupled in tandem with UV-visible and ESI-MS detections.  

PubMed

Reversed-phase ion-pairing chromatography (RP-IPC) is coupled on-line with electrospray ionization-mass spectrometry (ESI-MS) through an interface comprising a four-way switch valve and an anion exchange column. Regeneration of the anion exchange column can be accomplished on-line by switching the four-way switch valve to interconnect the column to a regeneration solution. Positioning the anion exchange column between the RP-IPC and ESI-MS instruments allows the ion-pairing reagent (IPR) sodium octane sulfonate to be removed. The IPC-ESI-MS method enabled us to separate and detect four intermediates of the Fe(III)-catalyzed dopamine oxidation. In particular, 6-hydroxydopamine, which is short-lived and highly neurotoxic, was detected and quantified. Together with the separation of other intermediates, gaining insight into the mechanism and kinetics of the Fe(III)-catalyzed dopamine oxidation becomes possible. PMID:23217306

Zhang, Lin; Yagnik, Gargey; Jiang, Dianlu; Shi, Shuyun; Chang, Peter; Zhou, Feimeng

2012-10-29

5

The coming of age of liquid chromatography coupled to tandem mass spectrometry in the endocrinology laboratory  

Microsoft Academic Search

Liquid chromatography coupled to tandem mass spectrometry (LC–MS\\/MS) has been rapidly incorporated in the routine of the endocrinology laboratory. Most endocrinologists are aware of the benefits afforded by this technique and tandem mass spectrometers are clearly no longer a mere research method but an important tool widely used for diagnosis. In the last 15 years, LC–MS\\/MS has replaced techniques such

Valdemir Melechco Carvalho

6

Verapamil quantification in human plasma by liquid chromatography coupled to tandem mass spectrometry  

Microsoft Academic Search

An analytical method based on liquid chromatography with positive ion electrospray ionization (ESI) coupled to tandem mass spectrometry detection (LC–MS\\/MS) was developed for the determination of Verapamil in human plasma using Metoprolol as the internal standard. The analyte and internal standard were extracted from the plasma samples by liquid–liquid extraction and chromatographed on a C8 analytical column. The mobile phase

Ney Carter do C. Borges; Gustavo D. Mendes; Rafael E. Barrientos-Astigarraga; Paulo Galvinas; Celso H. Oliveira; Gilberto De Nucci

2005-01-01

7

Coupled operation of the Oak Ridge isochronous cyclotron and the 25 MV tandem  

SciTech Connect

Coupled operation of the 25 MV tandem and the Oak Ridge Isochronous Cyclotron (ORIC) was achieved on January 27, 1981. A beam of 38 MeV /sup 16/O/sup 2 +/ was injected into ORIC, stripped to 8/sup +/ and accelerated to 324 MeV. Shortly afterwards, the energy was increased to the maximum design value of 25 MeV/amu (400 MeV). A spectrum taken of the scattering of this beam from a thin /sup 208/Pb target in the broad range spectrograh exhibited a resolution of 115 keV (FWHM). Performance of the system was in close agreement with that predicted from calculations.

Lord, R.S.; Ball, J.B.; Beckers, R.M.; Cleary, T.P.; Hudson, E.D.; Ludemann, C.A.; Martin, J.A.; Milner, W.T.; Mosko, S.W.; Ziegler, N.F.

1981-01-01

8

Nitric oxide and excitation–contraction coupling  

Microsoft Academic Search

Excitation–contraction (EC) coupling is driven by an ion-channel-mediated calcium cycle that produces myofilament contraction and relaxation. Even though nitric oxide synthases (NOS) were definitively described within the heart a decade ago, the role that nitric oxide (NO) plays in cardiac regulation remains highly controversial. There is a growing consensus, however, that NO modulates the activity of several key calcium channels

Joshua M Hare

2003-01-01

9

Oxidative coupling of methane on silver catalysts  

Microsoft Academic Search

Bulk silver catalysts were found to be active for the oxidative coupling of methane to ethane and ethylene if operated under oxygen-limited conditions at atmospheric pressure and at temperatures above 1020 K. The addition of small amounts of sodium phosphate as promoter increases markedly the C2 selectivity (to values above 90%) and yield (>10%) by efficient suppression of reaction steps

X. Bao; M. Muhler; R. Schlögl; G. Ertl

1995-01-01

10

Oxidative coupling of methane over natural manganese oxide  

Microsoft Academic Search

Oxydehydrogenative coupling of methane to higher hydrocarbons has been achieved with high selectivity towards C2 products over natural mineral manganese oxides. Oxide treatments under hydrocarbon atmosphere show that the reduction of manganese ions Mn(IV), Mn(III) to Mn(II) is mainly responsible for the catalyst deactivation. The tests using CH4 + CD4 equimolecular mixtures and the analysis of the (HD)C2 products by

L. M. Ioffe; T. Lopez; Y. G. Borodko; R. Gomez

1995-01-01

11

Characterization of four Phyllanthus species using liquid chromatography coupled to tandem mass spectrometry.  

PubMed

This paper reports a comparison of four Phyllanthus species (P. amarus, P. stipulatus, P. niruri and P. tenellus), commonly known as stone breaker, by the characterization of the chemical profile of their aqueous extracts. Such characterization was carried out using liquid chromatography coupled to ion trap tandem mass spectrometry (LC-IT-MS(n)) under reversed-phase gradient elution mode. The results of MS/MS and MS(3) on-line experiments, using the electrospray ionization source in the positive and negative mode, are extensively discussed. Furthermore, quercetin-3-O-?-d-glucuronopyranoside was isolated in multimilligram scale from the aqueous extract of P. stipulatus and characterized by mass spectrometry and NMR. Although it is an unusual flavonol in natural products, LC-IT-MS(n) experiments showed it to be present also in P. amarus. PMID:23611623

Sprenger, Ricardo da Fontoura; Cass, Quezia Bezerra

2013-04-03

12

Affinity chromatographic selection of carbonylated proteins followed by identification of oxidation sites using tandem mass spectrometry.  

PubMed

It has been shown that oxidatively modified forms of proteins accumulate during oxidative stress, aging, and in some age-related diseases. One of the unique features of a wide variety of routes by which proteins are oxidized is the generation of carbonyl groups. This paper reports a method for the isolation of oxidized proteins, which involves (1) biotinylation of oxidized proteins with biotin hydrazide and (2) affinity enrichment using monomeric avidin affinity chromatography columns. The selectivity of the method was validated by adding in vitro oxidized biotinylated BSA to a yeast lysate and showing that the predominant protein recovered was BSA. This method was applied to the question of whether large doses of 2-nitropropane produce oxidized proteins. A study of rat liver homogenates showed that animals dosed with 2-nitropropane produced 17 times more oxidized protein than controls in 6 h. Tryptic digestion of these oxidized proteins followed by reversed-phase chromatography and tandem mass spectrometry led to the identification of 14 peptides and their parent proteins. Nine of the 14 identified peptides were found to carry 1 or 2 oxidation sites and 5 of the 9 peptides were biotinylated. The significance of this affinity method is that it allows the isolation of oxidized proteins from the rest of the proteome and facilitates their identification. In some cases, it is even possible to identify the site of oxidation. PMID:15828771

Mirzaei, Hamid; Regnier, Fred

2005-04-15

13

Operational experience for coupled operation of the Holifield tandem electrostatic accelerator and isochronous cyclotron  

SciTech Connect

Coupled operation of the 25 MV tandem accelerator and the Oak Ridge Isochronous Cyclotron of the Holifield Heavy Ion Research Facility began in January 1981. Since that time the use of the cyclotron in this mode has become routine. Thirty-six different ion species in the range from /sup 9/Be to /sup 150/Nd have been accelerated; 106 separate beam setups have been provided. Since the beginning of coupled operation, significant improvement of cyclotron systems, and setup and operating techniques, have been made. The graphite electrostatic deflector septum formerly used for high-current light ion beams has been replaced by a thin molybdenum septum. Extraction system positioning mechanisms have been refined and recalibrated and more precise and reliable position readouts have been provided. The computer-based control system has been improved. The frequency range of the rf system has been increased to eliminate an energy dead-band. Cyclotron setup calculations have been improved and standardized methods have been developed to consistently achieve well-centered orbits, correct beam extraction system positions, and electrostatic and magnetic strengths. A totally new beam bunching system has been installed. The improvements in the phase-lock system of the beam buncher have been especially effective. A large number of obsolete and unreliable power supplies have been replaced. Beam extraction efficiency has been increased from approx.50% to approx.70%. Accuracy of obtaining the desired energy without fine tuning is now approx.1% compared to 2 to 3% in early coupled operation. Beam setup time (tuning) has been reduced by approx.20%. Unscheduled maintenance has been reduced by a factor of two.

Martin, J.A.; Dowling, D.T.; Haynes, D.L.; Hudson, E.D.; Jones, C.M.; Juras, R.C.; Lane, S.S.; Ludemann, C.A.; Meigs, M.J.; Milner, W.T.

1986-10-01

14

Oxidative coupling of methane over sodium promoted praseodymium oxide  

SciTech Connect

Unpromoted and alkali-promoted lanthanide oxides were evaluated in the oxidative coupling of methane to higher hydrocarbons. Methane conversion was carried out catalytically and in a redox mode by cycling methane and air independently over the lanthanide oxides. The sodium-promoted nonstoichiometric oxide, 4% Na on Pr{sub 6}O{sub 11}, was most active and selective, giving in the redox mode 21% methane conversion and 76% C{sub 2}{sup +} selectivity at 800 C and 1.4. WHSV (weight hourly space velocity, g CH{sub 4}/g cat. hr). At comparable conversion catalytic methane conversion had a C{sub 2}{sup +} selectivity of 64%. This selectivity deficit with respect to redox is attributed to an additional destructive route of the methyl radical, namely the reaction with molecular oxygen to yield a methylperoxy intermediate. Process variable studies support a mechanism whereby methane is activated at the metal oxide surface to form a methyl radical and in the gas phase C{sub 2}{sup +} hydrocarbon building occurs.

Gaffney, A.M.; Jones, C.A.; Leonard, J.J.; Sofranko, J.A. (ARCO Chemical Company, Newton Square, PA (USA))

1988-12-01

15

Magnoelastic coupling in magnetic oxide nanoparticles  

NASA Astrophysics Data System (ADS)

Phonons are exquisitely sensitive to finite length scale effects in a wide variety of materials. To investigate confinement in combination with strong magnetoelastic interactions, we measured the infrared vibrational properties of MnO and CoFe2O4 nanoparticles and their parent compounds. For MnO, a charge and bonding analysis reveals that Born effective charge, local effective charge, total polarizability, and the force constant are overall lower in the nanoparticles compared to the bulk. We find that the spin-lattice coupling drops from ˜7 cm-1 in the single crystal to <1 cm-1 in the nanoparticles. For CoFe2O4, the spectroscopic response is sensitive to the size-induced crossover to the superparamagnetic state, which occurs between 7 and 10 nm, and a spin-phonon coupling analysis supports the core-shell model. Moreover, it provides an estimate of the thickness of the magnetically disordered shell, increasing from 0.4 nm in the 14 nm particles to 0.8 nm in the 5 nm particles, demonstrating that the associated local lattice distortions take place on the length scale of the unit cell. These findings are important for understanding finite length scale effects in magnetic oxides and other more complex functional oxides.

Sun, Qi; Baker, Sheila; Birkel, Christina; Seshadri, Ram; Tremel, Wolfgang; Christianson, Andrew; Musfeldt, Janice

2012-02-01

16

Determination of the glucocorticoids prednisone, prednisolone, dexamethasone, and cortisol in human serum using liquid chromatography coupled to tandem mass spectrometry  

Microsoft Academic Search

Glucocorticoids are an important component of immunosuppressive therapy for solid organ transplantation. A method to quantitate prednisone, prednisolone, dexamethasone and cortisol in human serum has been developed. Analysis is performed utilizing reversed-phase liquid chromatography coupled to tandem mass spectrometry. The method was validated to a lower limit of quantitation of 5.4ng\\/ml for prednisone and cortisol, and 10.7ng\\/ml for dexamethasone and

Valerie A Frerichs; Kathleen M Tornatore

2004-01-01

17

Enantiomeric analysis of drugs of abuse in wastewater by chiral liquid chromatography coupled with tandem mass spectrometry  

Microsoft Academic Search

The manuscript concerns the development and validation of a method for enantiomeric analysis of structurally related amphetamines (amphetamine, methamphetamine, 4-methylenedioxymethamphetamine (MDMA), 3,4-methylenedioxyamphetamine (MDA) and 3,4-methylenedioxy-N-ethylamphetamine (MDEA)), ephedrines (ephedrine, pseudoephedrine and norephedrine) and venlafaxine in wastewater by means of chiral chromatography coupled with tandem mass spectrometry. Solid-phase extraction on Oasis HLB sorbent used for sample clean-up and concentration of analytes resulted

Barbara Kasprzyk-Hordern; Vishnu V. R. Kondakal; David R. Baker

2010-01-01

18

Methane Coupling over Magnesium Oxide: How Doping Can Work.  

PubMed

Electronic doping of magnesium oxide catalysts has an effect on the oxidative coupling of methane. Highly active sites can be created by co-modification of MgO with iron and gold in ppm quantities. PMID:24106011

Schwach, Pierre; Willinger, Marc Georg; Trunschke, Annette; Schlögl, Robert

2013-09-17

19

Tandem metal-oxide affinity chromatography for enhanced depth of phosphoproteome analysis.  

PubMed

In eukaryotic cells many diverse cellular functions are regulated by reversible protein phosphorylation. In recent years, phosphoproteomics has become a powerful tool to study protein phosphorylation because it allows unbiased localization, and site-specific quantification, of in vivo phosphorylation of hundreds of proteins in a single experiment. A common strategy to identify phosphoproteins and their phosphorylation sites from complex biological samples is the enrichment of phosphopeptides from digested cellular lysates followed by mass spectrometry. However, despite the high sensitivity of modern mass spectrometers the large dynamic range of protein abundance and the transient nature of protein phosphorylation remained major pitfalls in MS-based phosphoproteomics. Tandem metal-oxide affinity chromatography (MOAC) represents a robust and highly selective approach for the identification and site-specific quantification of low abundant phosphoproteins that is based on the successive enrichment of phosphoproteins and -peptides. This strategy combines protein extraction under denaturing conditions, phosphoprotein enrichment using Al(OH)3-based MOAC, tryptic digestion of enriched phosphoproteins followed by TiO2-based MOAC of phosphopeptides. Thus, tandem MOAC effectively targets the phosphate moiety of phosphoproteins and phosphopeptides and, thus, allows probing of the phosphoproteome to unprecedented depth. PMID:24136551

Beckers, Gerold J M; Hoehenwarter, Wolfgang; Röhrig, Horst; Conrath, Uwe; Weckwerth, Wolfram

2014-01-01

20

In muro feruloylation and oxidative coupling in monocots  

PubMed Central

Recently we have suggested that (glucurono)arabinoxylans [(G)AX] feruloylation and oxidative coupling occur both intra-protoplasmically and, extra-protoplasmically, in the plant cell wall. In this work we illustrate a model of two possible mechanisms of polysaccharide feruloylation and oxidative coupling in plants. Moreover, we take into consideration the possible role of in muro feruloylation as a rapid defense mechanism against potential plant pathogen and parasite infections.

Piro, Gabriella; Dalessandro, Giuseppe

2009-01-01

21

Energy coupling in Mn 2+ oxidation by a marine bacterium  

Microsoft Academic Search

ATP synthesis couple to Mn2+ oxidation was demonstrated with partially or wholly everted membrane vesicles from marine bacterial strain SSW22. The extent of ATP synthesis in these experiments was greater in earlier experiments. Chemiosmosis is the most probable mechanism for energy coupling because 2,4-dinitrophenol at appropriate concentrations stimulated Mn2+ oxidation by intact cells, membrane vesicles or extracts of strains SSW22,

Henry L. Ehrlich; John C. Salerno

1990-01-01

22

High ethylene to ethane processes for oxidative coupling  

DOEpatents

Oxidative coupling of lower alkane to higher hydrocarbon is conducted using catalyst comprising barium and/or strontium component and a metal oxide combustion promoter in the presence of vapor phase halogen component. High ethylene to ethane mole ratios in the product can be obtained over extended operating periods.

Chafin, Richard B. (Hurricane, WV); Warren, Barbara K. (Charleston, WV)

1991-01-01

23

Towards the total synthesis of neurotrophically active tashironins: rapid construction of the tetracyclic core through a tandem oxidative dearomatization–IMDA reaction–RCM protocol  

Microsoft Academic Search

An exceptionally short (three step) strategy involving tandem oxidative dearomatization, intramolecular Diels–Alder (IMDA) reaction and RCM has been devised to generate the complete carbon framework present in tashironin-type sesquiterpenoid natural products.

Goverdhan Mehta; Pulakesh Maity

2007-01-01

24

Validation of antibiotics in catfish by on-line solid phase extraction coupled to liquid chromatography tandem mass spectrometry.  

PubMed

For the first time automated on-line solid phase extraction coupled to liquid chromatography tandem mass spectrometry was developed for the simultaneous determination of 13 antibiotics (sulfonamides and tetracyclines) in catfish. The method proposed was validated according to Commission Decision 2002/657/EC, showing good linearity between 2 and 350 ?g kg(-1), high recovery (80-99%) and reproducibility (13-20%) values, lower detection limits than 0.1 ?g kg(-1), and quantification limits under 2.4 ?g kg(-1) (between 39 and 84 times lower than the MRL fixed by the EU). Moreover, the proposed method was also used to determine sulfonamides and tetracyclines in 16 out of 107 samples, all previously analysed by microbiological screening that gave positive results. Five out of 13 antibiotics were found, having tetracycline the higher occurrence (10 samples); in all cases the concentrations were lower than the MRL established. PMID:23107742

Hurtado de Mendoza, Jorge; Maggi, Luana; Bonetto, Liliana; Rodríguez Carmena, Beatriz; Lezana, Alicia; Mocholí, Francisco A; Carmona, Manuel

2012-03-03

25

Upgrading light hydrocarbons via tandem catalysis: a dual homogeneous Ta/Ir system for alkane/alkene coupling.  

PubMed

Light alkanes and alkenes are abundant but are underutilized as energy carriers because of their high volatility and low energy density. A tandem catalytic approach for the coupling of alkanes and alkenes has been developed in order to upgrade these light hydrocarbons into heavier fuel molecules. This process involves alkane dehydrogenation by a pincer-ligated iridium complex and alkene dimerization by a Cp*TaCl2(alkene) catalyst. These two homogeneous catalysts operate with up to 60/30 cooperative turnovers (Ir/Ta) in the dimerization of 1-hexene/n-heptane, giving C13/C14 products in 40% yield. This dual system can also effect the catalytic dimerization of n-heptane (neohexene as the H2 acceptor) with cooperative turnover numbers of 22/3 (Ir/Ta). PMID:23799786

Leitch, David C; Lam, Yan Choi; Labinger, Jay A; Bercaw, John E

2013-07-02

26

Wide spectral bandwidth electro-absorption modulator using coupled micro-cavity with asymmetric tandem quantum well.  

PubMed

For reliable three dimensional (3D) imaging system, it is necessary for the optical shutter to have a wide spectral bandwidth operation and enhanced modulation depth. We propose an electro-absorption modulator (EAM) based on coupled Fabry-Perot cavities with micro-cavity (CCMC) which uses asymmetric tandem quantum wells (ATQWs) to obtain improved spectral bandwidth and enhanced modulation depth. Several modulator designs are investigated to obtain improved modulation performance such as wider spectral bandwidth and enhanced modulation depth. It was found that among all the studied modulator geometries, CCMC structure with ATQWs provides the widest spectral bandwidth of 9.6nm and high modulation depth in excess of 50% at -24V, which is good agreement with theoretical calculations. These results suggest that EAM has excellent potential as optical shutter for 3D imaging application. PMID:23038593

Na, Byung Hoon; Ju, Gun Wu; Choi, Hee Ju; Cho, Yong Chul; Park, Yong Hwa; Park, Chang Young; Lee, Yong Tak

2012-08-13

27

Determination of the glucocorticoids prednisone, prednisolone, dexamethasone, and cortisol in human serum using liquid chromatography coupled to tandem mass spectrometry.  

PubMed

Glucocorticoids are an important component of immunosuppressive therapy for solid organ transplantation. A method to quantitate prednisone, prednisolone, dexamethasone and cortisol in human serum has been developed. Analysis is performed utilizing reversed-phase liquid chromatography coupled to tandem mass spectrometry. The method was validated to a lower limit of quantitation of 5.4 ng/ml for prednisone and cortisol, and 10.7 ng/ml for dexamethasone and prednisolone, with error below 7% at the lower limits. The between-day relative standard deviations ranged 2.9-7.1%. Comparison of cortisol analysis to an established method using clinical samples yielded differences below 15% for 26 of 28 determinations. PMID:15018795

Frerichs, Valerie A; Tornatore, Kathleen M

2004-04-01

28

Analysis of omeprazole, midazolam and hydroxy-metabolites in plasma using liquid chromatography coupled to tandem mass spectrometry.  

PubMed

A method has been developed and validated for the quantitation of midazolam, alphahydroxy-midazolam, omeprazole, and hydroxyomeprazole from one 250 microL sample of human plasma using high performance liquid chromatography coupled to tandem mass spectrometry. The method was validated for a daily working range of 0.400-100 ng/mL, with limits of detection between 2 and 15 pg/mL. The inter-assay variation was less than 15% for all analytes at four control concentrations and the samples were stable for three freeze-thaw cycles under the analysis conditions and 24 h in the post-preparative analysis matrix. This method was used to analyze samples in support of clinical studies probing the activity of the cytochrome P-450 enzyme system. PMID:16027049

Frerichs, Valerie A; Zaranek, Colleen; Haas, Curtis E

2005-09-25

29

Online monitoring oxidative products and metabolites of nicotine by free radicals generation with Fenton reaction in tandem mass spectrometry.  

PubMed

In general, over 70% absorbed nicotine is metabolized to cotinine and trans-3'-hydroxycotinine by cytochrome oxidase P450, and nicotine is also a major addictive and the psychoactive component in cigarettes. As a xenobiotic metabolism, hydrophobic compounds are usually converted into more hydrophilic products through enzyme systems such as cytochrome oxidase P450, sulfotransferases, and UDP-glucuronosyltransferases to deliver drug metabolites out of the cell during the drug metabolic process. In this study, an electrodeless electrochemical oxidation (EEO) reaction via Fenton reaction by producing free radical to react with nicotine to immediately monitor the oxidative products and metabolic derivatives of nicotine by tandem mass spectrometer (MS) is done. Fenton reaction generates free radicals via ferrous ion (Fe(2+)) and hydrogen peroxide (H2O2) to oxidize DNA and to degrade proteins in cells. In the EEO method, the oxidative products of nicotine including cotinine, cotinine-N-oxide, trans-3'-hydroxycotinine, nornicotine, norcotinine, 4-oxo-4-(3-pyridyl)-butanoic acid, 4-hydroxy-4-(3-pyridyl)-butanoic acid, and nicotine-N'-oxide were detected by tandem mass spectrometer to simulate the changes of nicotine and its derivatives in a time-dependent manner. PMID:23983622

Liang, Shih-Shin; Shiue, Yow-Ling; Kuo, Chao-Jen; Guo, Su-Er; Liao, Wei-Ting; Tsai, Eing-Mei

2013-07-25

30

Online Monitoring Oxidative Products and Metabolites of Nicotine by Free Radicals Generation with Fenton Reaction in Tandem Mass Spectrometry  

PubMed Central

In general, over 70% absorbed nicotine is metabolized to cotinine and trans-3?-hydroxycotinine by cytochrome oxidase P450, and nicotine is also a major addictive and the psychoactive component in cigarettes. As a xenobiotic metabolism, hydrophobic compounds are usually converted into more hydrophilic products through enzyme systems such as cytochrome oxidase P450, sulfotransferases, and UDP-glucuronosyltransferases to deliver drug metabolites out of the cell during the drug metabolic process. In this study, an electrodeless electrochemical oxidation (EEO) reaction via Fenton reaction by producing free radical to react with nicotine to immediately monitor the oxidative products and metabolic derivatives of nicotine by tandem mass spectrometer (MS) is done. Fenton reaction generates free radicals via ferrous ion (Fe2+) and hydrogen peroxide (H2O2) to oxidize DNA and to degrade proteins in cells. In the EEO method, the oxidative products of nicotine including cotinine, cotinine-N-oxide, trans-3?-hydroxycotinine, nornicotine, norcotinine, 4-oxo-4-(3-pyridyl)-butanoic acid, 4-hydroxy-4-(3-pyridyl)-butanoic acid, and nicotine-N?-oxide were detected by tandem mass spectrometer to simulate the changes of nicotine and its derivatives in a time-dependent manner.

Liang, Shih-Shin; Shiue, Yow-Ling; Kuo, Chao-Jen; Liao, Wei-Ting; Tsai, Eing-Mei

2013-01-01

31

Multiresidue Determination of Sulfonamides, Macrolides, Trimethoprim, and Chloramphenicol in Sewage Sludge and Sediment Using Ultrasonic Extraction Coupled with Solid Phase Extraction and Liquid Chromatography-Tandem Mass Spectrometry  

Microsoft Academic Search

A sensitive and feasible method was developed for the simultaneous determination of 10 trace antibiotic residues including sulfonamides, macrolides, trimethoprim, and chloramphenicol in sewage sludge and sediment. The method involved ultrasonic extraction followed by solid phase extraction cleanup and liquid chromatography-tandem mass spectrometry coupled with electrospray ionization in positive mode. The antibiotics were identified and determined by internal standard method

Cai-Ming TANG; Qiu-Xin HUANG; Yi-Yi YU; Xian-Zhi PENG

2009-01-01

32

Rapid residue analysis of fluoroquinolones in raw bovine milk by online solid phase extraction followed by liquid chromatography coupled to tandem mass spectrometry  

Microsoft Academic Search

Online solid phase extraction followed by liquid chromatography coupled to tandem mass spectrometry was used for the determination of 15 fluoroquinolones and one quinolone antibiotic in raw bovine and skimmed commercial milk. Milk samples were partially deproteinized and defatted by 15min centrifugation and then subjected to online solid phase extraction. Chromatographic separation was achieved in less than 15min. Identification and

Lina Kantiani; Marinella Farré; Damià Barceló

33

Synthesis of differentially substituted hexaethynylbenzenes based on tandem Sonogashira and Negishi cross-coupling reactions.  

PubMed

[reaction: see text] Synthesis of polyethynyl-substituted aromatic compounds was achieved efficiently by the use of the Negishi cross-coupling reaction, and this method, coupled with the Sonogashira reaction, was applied to the synthesis of differentially substituted hexaethynylbenzenes from chloroiodobenzenes. PMID:11463331

Sonoda, M; Inaba, A; Itahashi, K; Tobe, Y

2001-07-26

34

Tandem genomic arrangement of a G protein ( Gna15) and G protein-coupled receptor ( s1p 4 \\/ lp C1 \\/ Edg6) gene  

Microsoft Academic Search

A genomic analysis of the s1p4\\/lpC1\\/Edg6 mouse sphingosine-1-phosphate (S1P) G protein-coupled receptor gene revealed it to be located on central chromosome 10 and to consist of two exons with an intronless coding region. Surprisingly, we found the gene encoding the promiscuously coupling G?15 protein (Gna15) located in tandem just upstream, an arrangement conserved in the human genome (on chromosome 19p13.3).

James J. A Contos; Xiaoqin Ye; Valerie P Sah; Jerold Chun

2002-01-01

35

Redox couples of inducible nitric oxide synthase.  

PubMed

We report direct electrochemistry of the iNOS heme domain in a DDAB film on the surface of a basal plane graphite electrode. Cyclic voltammetry reveals FeIII/II and FeII/I couples at -191 and -1049 mV (vs Ag/AgCl). Imidazole and carbon monoxide in solution shift the FeIII/II potential by +20 and +62 mV, while the addition of dioxygen results in large catalytic waves at the onset of FeIII reduction. Voltammetry at higher scan rates (with pH variations) reveals that the FeIII/II cathodic peak can be resolved into two components, which are attributable to FeIII/II couples of five- and six-coordinate hemes. Digital simulation of our experimental data implicates water dissociation from the heme as a gating mechanism for ET in iNOS. PMID:16089428

Udit, Andrew K; Belliston-Bittner, Wendy; Glazer, Edith C; Nguyen, Yen Hoang Le; Gillan, James M; Hill, Michael G; Marletta, Michael A; Goodin, David B; Gray, Harry B

2005-08-17

36

Redox Couples of Inducible Nitric Oxide Synthase  

PubMed Central

We report direct electrochemistry of the iNOS heme domain in a DDAB film on the surface of a basal plane graphite electrode. Cyclic voltammetry reveals FeIII/II and FeII/I couples at ?191 and ?1049 mV (vs. Ag/AgCl). Added ligands imidazole and carbon monoxide shift the FeIII/II potential by +20 and +62 mV, while the addition of dioxygen results in large catalytic waves at the onset of FeIII reduction. Voltammetry at higher scan rates reveals that the FeIII/II cathodic peak can be resolved into two components, which are attributable to FeIII/II couples of 5- and 6-coordinate hemes. Digital simulation of our experimental data implicates water dissociation from the heme as a gating mechanism for ET in iNOS.

Udit, Andrew K.; Belliston-Bittner, Wendy; Glazer, Edith C.; Le Nguyen, Yen Hoang; Gillan, James M.; Hill, Michael G.; Marletta, Michael A.; Goodin, David B.; Gray, Harry B.

2008-01-01

37

Oxidative coupling of methane II. Composite catalysts of basic materials  

Microsoft Academic Search

Composite catalysts consisting of Li, Na, and K carbonates, hydroxides, oxides, and sulfates supported on CaO and in some instances on α-AlâOâ, MgO, and CaSOâ have been tested for the oxidative coupling of methane to C{sub n} hydrocarbons (n ⥠2). Normalized reaction conditions were generally T = 740°C, P°{sub CHâ} = 0.67 bar, P°{sub Oâ} = 0.074 bar, and

J. A. S. P. Carreiro; M. Baerns

1989-01-01

38

Functional-group-tolerant catalytic migratory oxidative coupling of nitrones.  

PubMed

A copper-catalyzed migratory oxidative-coupling reaction between nitrones and various ethers/amines exhibited high functional-group tolerance. Even in aqueous media, the reaction proceeded efficiently. For practical use of this catalysis, a unique sequential Huisgen cycloaddition was demonstrated. Mechanistic investigations revealed that the reaction proceeded through oxidative catalytic activation of ethers/amines to afford iminium/oxonium intermediates by concurrent dual one-electron abstractions by copper(II) and oxyl radicals. PMID:22763980

Hashizume, Shogo; Oisaki, Kounosuke; Kanai, Motomu

2012-07-04

39

Quantification of tizanidine in human plasma by liquid chromatography coupled to tandem mass spectrometry.  

PubMed

A simple, sensitive and rapid high-performance liquid chromatography/positive ion electrospray tandem mass spectrometry (MS/MS) method was developed and validated for the assay of tizanidine in human plasma. Following liquid-liquid extraction, the analytes were separated using an isocratic mobile phase on a reversed-phase column and analyzed by MS/MS in the selected reaction monitoring mode. The assay exhibited a linear dynamic range of 50-5000 pg/mL for tizanidine in human plasma. The lower limit of quantification was 50 pg/mL with a relative standard deviation of less than 13%. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. A run time of 2.5 min for each sample made it possible to analyze more than 300 human plasma samples per day. The validated method has been successfully used to analyze human plasma samples for application in pharmacokinetic, bioavailability or bioequivalence studies. PMID:16810637

Nirogi, Ramakrishna V S; Kandikere, Vishwottam N; Shukla, Manoj; Mudigonda, Koteshwara; Maurya, Santosh

2006-01-01

40

Quantification of metaxalone in human plasma by liquid chromatography coupled to tandem mass spectrometry.  

PubMed

A simple, rapid, sensitive, and selective liquid chromatography-tandem mass spectrometry (MS) method was developed and validated for the quantification of metaxalone, a skeletal muscle relaxant, in human plasma using galantamine as internal standard (IS). Following liquid-liquid extraction, the analytes were separated using an isocratic mobile phase on a reverse phase C18 column and analyzed by MS in the multiple reaction monitoring mode using the respective [M+H]+ ions, m/z 222/161 for metaxalone and m/z 288/213 for the IS. The assay exhibited a linear dynamic range of 50-5000 microg/L for metaxalone in human plasma. The lower limit of quantification was 50 microg/L with a relative standard deviation of less than 10%. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. A run time of 2.5 min for each sample made it possible to analyze more than 400 human plasma samples per day. The validated method has been successfully used to analyze human plasma samples for application in pharmacokinetic, bioavailability, or bioequivalence studies. PMID:16803662

Nirogi, Ramakrishna V S; Kandikere, Vishwottam N; Shukla, Manoj; Mudigonda, Koteshwara; Shrivastava, Wishu; Datla, Praveen V

2006-05-01

41

Quantification of granisetron in human plasma by liquid chromatography coupled to electrospray tandem mass spectrometry.  

PubMed

A simple, sensitive and rapid high-performance liquid chromatography/electrospray ionization tandem mass spectrometry method was developed and validated for the assay of granisetron in human plasma. Following liquid-liquid extraction, the analytes were separated using an isocratic mobile phase on a reversed-phase C18 column and analyzed by MS in the multiple reaction monitoring mode using the respective [M+H]+ ions, m/z 313/138 for granisetron and m/z 409/228 for the IS. The assay exhibited a linear dynamic range of 0.1-20 ng/mL for granisetron in human plasma. The lower limit of quantification was 100 pg/mL with a relative standard deviation of less than 5%. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. A run time of 2.0 min for each sample made it possible to analyze more than 400 human plasma samples per day. The validated method has been successfully used to analyze human plasma samples for application in pharmacokinetic, bioavailability or bioequivalence studies. PMID:16389637

Nirogi, Ramakrishna V S; Kandikere, Vishwottam N; Shukla, Manoj; Mudigonda, Koteshwara; Maurya, Santosh; Boosi, Ravikumar

2006-09-01

42

Screening and characterization of natural antioxidants in four Glycyrrhiza species by liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry.  

PubMed

Licorice, derived from the dried roots and rhizomes of several species of genus Glycyrrhiza L. (Leguminosae family), has been traditionally used in herbal medicine for over 4000 years. In recent years, the interest in antioxidative constituents in licorice has greatly increased. In this work, a new method based on 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) spiking test combined with HPLC coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (Q-TOF MS/MS) analysis was developed to screen and identify the antioxidants in licorice. The results of the method validation indicated that the developed method was reliable and repeatable. Compared with DPPH on-line method, the HPLC-Q-TOF MS/MS method combined with DPPH spiking test offered much higher sensitivity and resolution. Using this method, 35 radical scavengers were screened from four Glycyrrhiza species (G. inflata, G. glabra, G. pallidiflora and G. uralensis), and 21 of them were unambiguously or tentatively identified by HPLC-Q-TOF MS/MS. Among the 21 identified flavonoids, 10 compounds had been reported to possess antioxidative activities in the previous studies, and the radical scavenging activities of the other 11 compounds were reported for the first time. The effects of six purified flavonoids on DPPH radical and lipid peroxidation were evaluated for validation of the developed method. The results indicated that HPLC-Q-TOF MS/MS coupled with DPPH treatment is an efficient and powerful method to discover the potential antioxidative compounds from the complex natural product mixtures. In this study, the identified components with free radical scavenging activity, would help to explain the therapeutic benefit of licorice in the treatment of human disease associated with oxidative stress. PMID:21968349

Li, Yan-Jing; Chen, Jun; Li, Ying; Li, Qin; Zheng, Yun-Feng; Fu, Yu; Li, Ping

2011-09-16

43

Tandem aldehyde-alkyne-amine coupling/cycloisomerization: A new synthesis of coumarins  

PubMed Central

Summary Cu-catalyzed A3 coupling of ethoxyacetylene, pyrrolidine and salicylaldehydes led to a concomitant cycloisomerization followed by hydrolysis of the resultant vinyl ether to afford coumarins in a cascade process. The reaction proceeded through exclusive 6-endo-dig cyclization and is compatible with halo and keto groups giving coumarins in good to moderate yields.

Thirupathi, Nuligonda; Haribabu, Madala

2013-01-01

44

Simultaneous analysis of 28 urinary VOC metabolites using ultra high performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry (UPLC-ESI/MSMS).  

PubMed

Volatile organic compounds (VOCs) are ubiquitous in the environment, originating from many different natural and anthropogenic sources, including tobacco smoke. Long-term exposure to certain VOCs may increase the risk for cancer, birth defects, and neurocognitive impairment. Therefore, VOC exposure is an area of significant public health concern. Urinary VOC metabolites are useful biomarkers for assessing VOC exposure because of non-invasiveness of sampling and longer physiological half-lives of urinary metabolites compared with VOCs in blood and breath. We developed a method using reversed-phase ultra high performance liquid chromatography (UPLC) coupled with electrospray ionization tandem mass spectrometry (ESI/MSMS) to simultaneously quantify 28 urinary VOC metabolites as biomarkers of exposure. We describe a method that monitors metabolites of acrolein, acrylamide, acrylonitrile, benzene, 1-bromopropane, 1,3-butadiene, carbon-disulfide, crotonaldehyde, cyanide, N,N-dimethylformamide, ethylbenzene, ethylene oxide, propylene oxide, styrene, tetrachloroethylene, toluene, trichloroethylene, vinyl chloride and xylene. The method is accurate (mean accuracy for spiked matrix ranged from 84 to 104%), sensitive (limit of detection ranged from 0.5 to 20 ng mL(-1)) and precise (the relative standard deviations ranged from 2.5 to 11%). We applied this method to urine samples collected from 1203 non-smokers and 347 smokers and demonstrated that smokers have significantly elevated levels of tobacco-related biomarkers compared to non-smokers. We found significant (p<0.0001) correlations between serum cotinine and most of the tobacco-related biomarkers measured. These findings confirm that this method can effectively quantify urinary VOC metabolites in a population exposed to volatile organics. PMID:23062436

Alwis, K Udeni; Blount, Benjamin C; Britt, April S; Patel, Dhrusti; Ashley, David L

2012-04-21

45

Synthesis of ?-extended porphyrins via intramolecular oxidative coupling.  

PubMed

Porphyrins fused with other aromatic units at the meso- and ?-positions have recently emerged as a hot topic of research. Their synthesis typically starts with preparation of precursors via either Suzuki coupling of a meso-bromoporphyrin or mixed-aldehyde condensation, and is followed by oxidative aromatic coupling, often using high-valent metal reagents (DDQ/Sc(OTf)(3) and Fe(III) salts are among the most popular). In recent years, porphyrins were oxidatively coupled not only with well-known aromatic hydrocarbons such as naphthalene and pyrene, but also with more complex heterocyclic fragments, including indole, phenanthro[1,10,9,8-cdefg]carbazole and BODIPY. A subtle relationship exists between the output of intramolecular oxidative coupling and the nature of the second aromatic moiety, cation in the porphyrin cavity, oxidant, and type of remaining meso-substituent. The extension of the porphyrin chromophore leads to significant change in linear and non-linear optical properties. Very strong bathochromic shifts of absorption (?(max) reaching 1.5-2 microns in some cases) and increases in two-photon absorption cross-sections are typical for these functional dyes. PMID:22649792

Lewtak, Jan P; Gryko, Daniel T

2012-10-18

46

Solar hydrogen production by tandem cell system composed of metal oxide semiconductor film photoelectrode and dye-sensitized solar cell  

NASA Astrophysics Data System (ADS)

Photocatalytic and photoelectrochemical approaches to solar hydrogen production in our group were introduced. In photocatalytic water splitting system using NiOx/ TiO2 powder photocatalyst with concentrated Na2CO3 aqueous solution, solar energy conversion efficiency to H2 and O2 production (STH efficiency) was 0.016%. In addition, STH efficiency of visible light responding photocatalyst, NiOx/ promoted In0.9Ni0.1TaO4, was estimated at 0.03%. In photoelectrochemical system using an oxide semiconductor film phptoelectrode, STH efficiencies of meosporous TiO2 (Anatase) , mesoporous visible light responding S-doped TiO2 (Anatase) and WO3 film were 0.32-0.44% at applied potential of 0.35 V vs NHE, 0.14% at 0.55 V and 0.44% at 0.9 V, respectively. Finally, solar hydrogen production by tandem cell system composed of an oxide semiconductor photoelectrode, a Pt wire counter electrode and a dye-sensitized solar cell (DSC) was investigated. As photoelectrodes, meosporous TiO2 (Anatase), mesoporous S-doped TiO2 (Anatase), WO3, BiVO4 and Fe2O3 film were tested. STH efficiency of tandem cell system composed of a WO3 film photoelectrode, and a two-series-connected DSC (Voc = 1.4 V) was 2.5-2.8%. In conclusion, it is speculated that more than 5% STH efficiency will be obtained by tandem cell system composed of an oxide semiconductor photoelectrode and a two-series-connected DSC in near future. This suggests a cost-effective and practical application of this system for solar hydrogen production.

Arakawa, H.; Shiraishi, C.; Tatemoto, M.; Kishida, H.; Usui, D.; Suma, A.; Takamisawa, A.; Yamaguchi, T.

2007-10-01

47

A novel solution for hydroxylated PAHs removal by oxidative coupling reaction using Mn oxide  

Microsoft Academic Search

In this study, removals of 1-naphthol by oxidative-coupling reaction using birnessite, one of the natural Mn oxides present in soil, was investigated in various experimental conditions (reaction time, Mn oxide loadings, pH). The removal efficiency of 1-naphthol by birnessite was high in all the experimental conditions, and UV-visible and mass spectrometric analyses on the supernatant after reaction confirmed that the

Ki-Hoon Kang; Dong-Min Lim; Hyun-Sang Shin

2008-01-01

48

[Determination of 215 pesticide residues in ginger using liquid chromatography coupled with electrospray ionization tandem mass spectrometry].  

PubMed

A multiresidue analytical method was developed for the determination of 215 pesticides in ginger using liquid chromatography coupled with electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). The pesticide residues were extracted from ginger by acetonitrile containing 1% (v/v) acetic acid, cleaned-up by a Sep-Pak Vac cartridge, eluted with acetonitrile-toluene (3:1, v/v). The eluate was concentrated to about 0.5 mL with a rotary evaporator, dried with nitrogen at room temperature. The sample was redissolved in an acetonitrile-water mixture (3:2, v/v), then analyzed using LC-MS/MS in multiple reaction monitoring (MRM) mode via positive electrospray ionization. The recovery test was conducted at spiked level of limit of quantification (LOQ). The validation results were as follows: the overall recoveries were from 68.1% to 132.6% of which 94.4% of the recoveries were from 70% to 120%, with the relative standard deviations of 0.4%-25.0%. The limits of detection (S/N = 3) and the limits of quantification (S/N = 10) were 0.01-70.45 microg/L and 0.04-234.84 microg/L, respectively. The results demonstrated that this method is simple and with acceptable sensitivity and accuracy to meet the requirements of the multiple pesticide residue analysis. This method is applicable to determine 215 pesticide residues in ginger. PMID:20873579

Cao, Jing; Pang, Guofang; Wang, Minglin; Fan, Chunlin

2010-06-01

49

Rapid isolation of new furostanol saponins from fenugreek seeds based on ultra-performance liquid chromatography coupled with a hybrid quadrupole time-of-flight tandem mass spectrometry.  

PubMed

An ultra-performance liquid chromatography coupled with a hybrid quadrupole time-of-flight tandem mass spectrometry method was established to rapidly identify and guide the isolation of target saponins from fenugreek seeds. Based on the online screening performance, totally forty-six furostanol saponins were detected and elucidated. Among them, twenty compounds were predicted to be new. To rapidly obtain new furostanol saponins from these seeds, a further phytochemical study was carried out under the guidance of the ultra-performance liquid chromatography coupled with a hybrid quadrupole time-of-flight tandem mass spectrometry. Finally, six new furostanol saponins, named as trigoneosides XIV (1), XV (2), XVI (3), XVIIa (4), XVIIb (5), and XIV (6), together with one known furostanol saponin, parvifloside (7), were rapidly obtained, and their definitive structures were determined by NMR and chemical evidence. PMID:22740265

Pang, Xu; Kang, Liping; Yu, Heshui; Zhao, Yang; Xiong, Chengqi; Zhang, Jie; Shan, Junjie; Ma, Baiping

2012-06-01

50

Evaluation of Multidimensional Chromatography Coupled with Tandem Mass Spectrometry (LC\\/LC?MS\\/MS) for Large-Scale Protein Analysis:  The Yeast Proteome  

Microsoft Academic Search

Highly complex protein mixtures can be directly analyzed after proteolysis by liquid chromatography coupled with tandem mass spectrometry (LC-MS\\/MS). In this paper, we have utilized the combination of strong cation exchange (SCX) and reversed-phase (RP) chromatography to achieve two-dimensional separation prior to MS\\/MS. One milligram of whole yeast protein was proteolyzed and separated by SCX chromatography (2.1 mm i.d.) with

Junmin Peng; Joshua E. Elias; Carson C. Thoreen; Larry J. Licklider; Steven P. Gygi

2003-01-01

51

Application of hollow fibre liquid phase microextraction for the multiresidue determination of pesticides in alcoholic beverages by ultra-high pressure liquid chromatography coupled to tandem mass spectrometry  

Microsoft Academic Search

An alternative method has been developed to determine more than 50 pesticides in alcoholic beverages using hollow fibre liquid phase microextraction (HF-LPME) followed by ultra-high pressure liquid chromatography coupled to tandem mass spectrometry (UHPLC–MS\\/MS), without any further clean-up step. Pesticides were extracted from the sample to the organic solvent immobilized in the fibre and they were desorbed in methanol prior

P. Plaza Bolaños; R. Romero-González; A. Garrido Frenich; J. L. Martínez Vidal

2008-01-01

52

Headspace solid phase microextraction in-situ supercritical fluid extraction coupled to gas chromatography–tandem mass spectrometry for simultaneous determination of perfluorocarboxylic acids in sediments  

Microsoft Academic Search

Headspace solid phase microextraction (HS-SPME) in-situ supercritical fluid extraction (SFE) was investigated for the determination of trace amounts of perfluorocarboxylic acids (PFCAs) in sediments. Quantitation was performed by using gas chromatography coupled to negative chemical ionization–tandem mass spectrometry (GC–NCI–MS\\/MS). The optimum conditions of HS-SPME following SFE were obtained using 500?L n-butanol as a derivatization reagent in supercritical carbon dioxide with

Wen-Lin Liu; Bao-Huey Hwang; Zu-Guang Li; Jen-Fon Jen; Maw-Rong Lee

2011-01-01

53

Identification of components in Zhi-Zi-Da-Huang decoction by HPLC coupled with electrospray ionization tandem mass spectrometry, photodiode array and fluorescence detectors  

Microsoft Academic Search

High-performance liquid chromatography (HPLC) coupled with electrospray ionization (ESI) tandem mass spectrometry (MS) in positive and negative ion mode and photodiode array (PDA) and fluorescence detectors (FD) was applied to simultaneously characterise thirty active components in Zhi-Zi-Da-Huang decoction (ZZDHD). The analysis was preformed on a Lichrospher C18 column (4.6mm×250mm, 5?m) using a binary eluent (0.1% aqueous acetic acid (A) and

Hang Wang; Fang Feng

2009-01-01

54

High-Throughput Screening of Drugs of Abuse in Urine by Supported Liquid–Liquid Extraction and UHPLC Coupled to Tandem MS  

Microsoft Academic Search

A qualitative method, involving supported liquid–liquid extraction (SLE) and ultra high pressure liquid chromatography coupled\\u000a to tandem mass spectrometry (UHPLC-MS–MS), was developed for the rapid tentative identification of various drugs of abuse\\u000a in urine. In this study, 28 drugs and metabolites were covered by the screening procedure. Before analysis, urine samples\\u000a were extracted by SLE and good extraction recoveries were

Aubert Maquille; Davy Guillarme; Serge Rudaz; Jean-Luc Veuthey

2009-01-01

55

Quantitative multi-residue determination of ?-agonists in bovine urine using on-line immunoaffinity extraction-coupled column packed capillary liquid chromatography-tandem mass spectrometry  

Microsoft Academic Search

This report demonstrates the potential of on-line immunoaffinity extraction and coupled column packed capillary liquid chromatography-ion spray tandem mass spectrometry for multi-residue determination of five ?-agonists, clenbuterol, mabuterol, mapenterol, methylclenbuterol, and tolubuterol, in bovine urine using an automated column switching system. Trace enrichment and preliminary sample cleanup was performed on-line using bovine urine diluted with phosphate-buffered saline. The column switching

Jenny Cai; Jack Henion

1997-01-01

56

Combined application of high resolution and tandem mass spectrometers to characterize methionine oxidation in a parathyroid hormone formulation.  

PubMed

Identification and monitoring of degradation products is a critical aspect of drug product stability programs. This process can present unique challenges when working with complex biopharmaceutical formulations that do not readily lend themselves to straightforward HPLC analysis. The therapeutic 34 amino acid parathyroid hormone fragment (PTH1-34) contains methionine (Met) residues at positions 8 and 18. Oxidation of these Met residues results in reduced biological activity and thus efficacy of the potential drug product. Here, we present an effective approach for the identification of PTH1-34 oxidation products in a drug product formulation in which the stability indicating method used non-MS compatible HPLC conditions to separate excipients, drug substance and degradation products. High resolution and tandem mass spectrometers were used in conjunction with cyanogen bromide (CNBr) mediated digestion to accurately identify the oxidation products observed in an alternative MS compatible HPLC method used for drug substance analysis. All anticipated CNBr digested peptide fragments, including both oxidized and nonoxidized peptide fragments, were positively identified using TOF MS without the need for additional enzymatic digestion. Once identified, the oxidation products generated were injected onto the original non-MS compatible HPLC drug product stability indicating method and the respective retention times were confirmed. This allowed the oxidative stability of different formulations to be effectively monitored during the solid state stability program and during variant selection. PMID:19711445

Pan, Changkang; Valente, Joseph J; LoBrutto, Rosario; Pickett, Jennifer S; Motto, Michael

2010-03-01

57

Proteomic analysis of the organ of corti using nanoscale liquid chromatography coupled with tandem mass spectrometry.  

PubMed

The organ of Corti (OC) in the cochlea plays an essential role in auditory signal transduction in the inner ear. For its minute size and trace amount of proteins, the identification of the molecules in pathophysiologic processes in the bone-encapsulated OC requires both delicate separation and a highly sensitive analytical tool. Previously, we reported the development of a high resolution metal-free nanoscale liquid chromatography system for highly sensitive phosphoproteomic analysis. Here this system was coupled with a LTQ-Orbitrap XL mass spectrometer to investigate the OC proteome from normal hearing FVB/N male mice. A total of 628 proteins were identified from six replicates of single LC-MS/MS analysis, with a false discovery rate of 1% using the decoy database approach by the OMSSA search engine. This is currently the largest proteome dataset for the OC. A total of 11 proteins, including cochlin, myosin VI, and myosin IX, were identified that when defective are associated with hearing impairment or loss. This study demonstrated the effectiveness of our nanoLC-MS/MS platform for sensitive identification of hearing loss-associated proteins from minute amount of tissue samples. PMID:22942697

Peng, Hong; Liu, Miao; Pecka, Jason; Beisel, Kirk W; Ding, Shi-Jian

2012-07-02

58

Assay of zofenopril and its active metabolite zofenoprilat by liquid chromatography coupled with tandem mass spectrometry.  

PubMed

Zofenopril is a pro-drug designed to undergo metabolic hydrolysis yielding the active free sulfhydryl compound zofenoprilat, which is an angiotensin converting enzyme (ACE) inhibitor, endowed also with a marked cardioprotective activity. A simple, highly sensitive specific LC-MS-MS method was developed for the determination of zofenopril and zofenoprilat in human plasma. In order to prevent oxidative degradation of zofenoprilat and its internal standard, their free sulfhydryl groups were protected by treatment with N-ethylmaleimide (NEM), which produced the succinimide derivatives. The compounds and their corresponding fluorine derivatives, used as internal standards, were extracted from plasma with toluene. The reconstituted dried extracts were chromatographed and then monitored by a triple-stage-quadrupole instrument operating in the negative ion spray ionization mode. The method was validated over the concentration range of 1-300 ng/ml for zofenopril and 2-600 ng/ml for zofenoprilat. Inter- and intra-assay precision and accuracy of both zofenopril and zofenoprilat were better than 10%. The limit of quantitation was 1 ng/ml with zofenopril and 2 ng/ml with zofenoprilat. Extraction recovery proved to be on average 84.8% with zofenopril and 70.1% with zofenoprilat. Similar recoveries were shown by the above two internal standards. The method was applied to measure plasma concentrations of zofenopril and zofenoprilat in 18 healthy volunteers treated orally with zofenopril calcium salt at the dose of 60 mg. PMID:11145066

Dal Bo, L; Mazzucchelli, P; Marzo, A

2000-12-01

59

Identification of ginkgolic acid (15:1) metabolites in rats following oral administration by high-performance liquid chromatography coupled to tandem mass spectrometry.  

PubMed

1. In this article, metabolites of ginkgolic acid (GA) (15:1) in rats plasma, bile, urine and faeces after oral administration have been investigated for the first time by high-performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS) with the aid of on-line hydrogen/deuterium (H/D) exchange technique and ?-glucuronidase hydrolysis experiments. 2. After oral administration of GA (15:1, M0) to rats at a dose of 10 mg/kg, it was found that metabolites M1-M5 together with parent compound (M0) existed in rat plasma; parent compound (M0) and metabolites M2-M5 were observed in rat bile, and parent compound (M0) with metabolites M1 and M2 were discovered in rat faeces, and there was no parent compound and metabolite detectable in rat urine. 3. Two oxidative metabolites of GA (15:1, M0) were identified as 2-hydroxy-6-(pentadec-8-enyl-10-hydroxy) benzoic acid (M1) and 2-hydroxy-6-(pentadec-8-enyl-11-hydroxy-13-carbonyl) benzoic acid (M2), respectively. Metabolites M3, M4 and M5 were identified as the mono-glucuronic acid conjugates of parent compound (M0), M1 and M2, respectively. 4. The results indicated that M1 and M2 with parent compound (M0) were mainly eliminated in faeces and three glucuronide metabolites (M3, M4 and M5) excreted in bile as the predominant forms after oral administration of GA (15:1) to rats. PMID:23205533

Xia, Hongjun; Liu, Zhenhua; Hu, Haihong; Zhou, Hui; Zeng, Su

2012-12-04

60

Investigation of beta-oxidation intermediates in normal and MCAD-deficient human fibroblasts using tandem mass spectrometry.  

PubMed

Mitochondrial fatty acid beta-oxidation was studied by incubating stable isotope-labeled fatty acid probes with human fibroblasts in the presence of L-carnitine. The acylcarnitine intermediates produced were analyzed by tandem mass spectrometry. Oxidation by normal fibroblasts produced specific acylcarnitine intermediates corresponding to acyl-CoA dehydrogenase substrates mainly of 10 or less carbons. These probes demonstrated that the pathway, involving all beta-oxidative steps, could be examined. Oxidation of the same precursors by cells with medium chain acyl-CoA dehydrogenase (EC 1.3.99.2) (MCAD) deficiency, which is caused by different DNA mutations, produced acylcarnitine profiles which appear to be specific to this enzyme defect, regardless of the DNA mutation. Increased amounts of octanoyl-, decanoyl-, or decenoylcarnitine were detected. The ratios of octanoylcarnitine to decanoyl- or decenoylcarnitine appear specific for MCAD deficiency. Even though the concentration of labeled decenoylcarnitine (C10:1) was elevated in incubations of MCAD-deficient cells with labeled linoleate or with a fatty acid mixture which included palmitate, oleate, and linoleate, the predominant intermediate was octanoylcarnitines. These results suggest that MCAD-deficient cells readily convert decanoyl-CoA into octanoyl-CoA. This in vitro system could be utilized to study fatty acid oxidation disorders and to study the origins of metabolic intermediates associated with them. PMID:7551818

Nada, M A; Chace, D H; Sprecher, H; Roe, C R

1995-02-01

61

Determination of fungicides in wine by mixed-mode solid phase extraction and liquid chromatography coupled to tandem mass spectrometry.  

PubMed

A novel procedure for the determination of nine selected fungicides (metalaxyl-M, azoxystrobin, myclobutanil, flusilazole, penconazole, tebuconazole, propiconazole, diniconazole and difenoconazole) in wine samples is presented. Sample enrichment and purification is simultaneously performed using mixed-mode, anion exchange and reversed-phase, OASIS MAX solid-phase extraction (SPE) cartridges. Analytes were determined by liquid chromatography coupled to tandem mass spectrometry using atmospheric pressure electrospray ionization (LC-ESI-MS/MS). Parameters affecting the chromatographic determination and the extraction-purification processes were thoroughly investigated. Under optimized conditions, 10 mL of wine were firstly diluted 1:1 with ultrapure water and then passed through the mixed-mode SPE cartridge at a flow of ca. 5 mLmin(-1). After a washing step with 5 mL of an aqueous NH(4)OH solution (5%, w:v), analytes were recovered with just 1 mL of methanol and injected in the LC-MS/MS system without any additional purification. The selective extraction process avoided significant changes in the ionization efficiency for red and white wine extracts in comparison with pure standards in methanol. Performance of the method was good in terms of precision (RSDs<11%) and accuracy (absolute recoveries>72%, determined against pure standards in methanol) reporting method LOQs in the range of 0.01-0.79 ngmL(-1) for target compounds, which are far below the EU maxima residue levels (MRLs) for fungicides in vinification grapes and wine. Several commercial wines from different geographic areas in Spain were analyzed. In most samples, metalaxyl-M and azoxystrobin were found at concentrations up to several ngmL(-1). PMID:20971470

Carpinteiro, I; Ramil, M; Rodríguez, I; Cela, R

2010-10-07

62

A new high-throughput analysis for drug metabolism profiling using liquid chromatography coupled with tandem mass spectrometry.  

PubMed

We developed 3 liquid chromatography (LC) methods coupled to tandem mass spectrometry for comprehensive high-throughput profiling of drug metabolism, employing different columns with gradient systems of aqueous 10 mmol/L ammonium acetate and acetonitrile. The methods were established using testosterone (TST), imipramine (IMP), acetaminophen (APAP) and salbutamol (SBM), which have markedly different values of partition coefficient, P. Method I, using an octadecylized silica (ODS) column (ACQUITY UPLC BEH C18) with a steep gradient, was suitable for analyzing TST and its metabolites, and IMP and its metabolites. These substrates could not be analyzed by Method II, using another ODS column (Atlantis dC18), or Method III, using an Atlantis HILIC silica column. APAP and its metabolites could be analyzed simultaneously by Method II, but not Method I or III. SBM and its metabolites could be detected simultaneously only by Method III. The developed analytical methods were further evaluated with a panel of 18 additional drugs. Based on the retention times and peak shapes, we propose general criteria, in terms of calculated LogP (cLogP) value, for method selection. Broadly speaking, drugs with high cLogP, those with intermediate cLogP and those with low cLogP were best analyzed by Methods I, II and III, respectively, although drugs with borderline values of cLogP could be evaluated by both the relevant methods. The injection cycle for each method was within 10 min, including up to 3 min conditioning time. These methods are expected be useful in high-throughput screening assays to examine biotransformations of candidate drugs. PMID:23471703

Kusumoto, K; Nagao, T; Ogihara, T

2013-03-07

63

Rapid and sensitive hormonal profiling of complex plant samples by liquid chromatography coupled to electrospray ionization tandem mass spectrometry  

PubMed Central

Background Plant hormones play a pivotal role in several physiological processes during a plant's life cycle, from germination to senescence, and the determination of endogenous concentrations of hormones is essential to elucidate the role of a particular hormone in any physiological process. Availability of a sensitive and rapid method to quantify multiple classes of hormones simultaneously will greatly facilitate the investigation of signaling networks in controlling specific developmental pathways and physiological responses. Due to the presence of hormones at very low concentrations in plant tissues (10-9 M to 10-6 M) and their different chemistries, the development of a high-throughput and comprehensive method for the determination of hormones is challenging. Results The present work reports a rapid, specific and sensitive method using ultrahigh-performance liquid chromatography coupled to electrospray ionization tandem spectrometry (UPLC/ESI-MS/MS) to analyze quantitatively the major hormones found in plant tissues within six minutes, including auxins, cytokinins, gibberellins, abscisic acid, 1-amino-cyclopropane-1-carboxyic acid (the ethylene precursor), jasmonic acid and salicylic acid. Sample preparation, extraction procedures and UPLC-MS/MS conditions were optimized for the determination of all plant hormones and are summarized in a schematic extraction diagram for the analysis of small amounts of plant material without time-consuming additional steps such as purification, sample drying or re-suspension. Conclusions This new method is applicable to the analysis of dynamic changes in endogenous concentrations of hormones to study plant developmental processes or plant responses to biotic and abiotic stresses in complex tissues. An example is shown in which a hormone profiling is obtained from leaves of plants exposed to salt stress in the aromatic plant, Rosmarinus officinalis.

2011-01-01

64

Quantitative assay for six potential breast cancer biomarker peptides in human serum by liquid chromatography coupled to tandem mass spectrometry.  

PubMed

An assay to quantify several possible breast cancer peptide biomarkers in human serum has been developed and validated, using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). The peptides include bradykinin, Hyp(3)-bradykinin, des-Arg(9)-bradykinin and fragments of fibrinogen alpha-chain (Fib-alpha([605-629])), inter-alpha-trypsin inhibitor heavy chain 4 (ITIH(4[666-687])) and complement component 4a (C4a([1337-1350])). Ile(13)-ITIH(4[666-687]), d20-C4a([1337-1350]) and Sar-D-Phe(8)-des-Arg(9)-bradykinin were used as internal standards. Bovine plasma, with 2 mM captopril and 2 mM D-L-mercaptoethanol-3-guanidino-ethylthiopropanoic acid (MEGETPA) to prevent rapid degradation of the bradykinins, was used as analyte-free matrix. Recoveries for solid-phase extraction (SPE) on mixed-mode weak cation exchange sorbents were between 62 and 90%. Multiple reaction monitoring (MRM) on a triple quadrupole mass spectrometer equipped with a heated electrospray source (H-ESI), operating in the positive ion-mode, was used for detection. The assay was fully validated and stabilities of the peptides were extensively explored. Bradykinin (10-500 ng/ml), Hyp(3)-bradykinin (4-200 ng/ml), des-Arg(9)-bradykinin (2-100 ng/ml), Fib-alpha([605-629]) (120-3000 ng/ml), ITIH(4[666-687]) (0.4-10 ng/ml) and C4a([1337-1350]) (1-25 ng/ml) were simultaneously quantified with deviations from the nominal concentrations below 22% and intra- and inter-assay precisions below 15 and 20%, respectively, for all peptides at all concentrations. The method has been successfully applied to several serum samples from breast cancer patients and matched controls. PMID:20116351

van den Broek, Irene; Sparidans, Rolf W; Schellens, Jan H M; Beijnen, Jos H

2010-01-18

65

Identification of isoflavonoids in several kudzu samples by high-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry.  

PubMed

Pueraria lobata is a rich source of isoflavonoids. The detection and identification of isoflavonoid components from Pueraria radix (RP), callus and cell cultures, is very important for the safest and most effective use of kudzu as a medicinal plant, and for the studies on quantitative analysis and secondary metabolism of isoflavonoids in vitro cultures. Liquid chromatography is coupled with negative and positive electrospray ionization (ESI) tandem mass spectrometry (MS-MS), and photodiode array detection is used to characterize and detect isoflavonoids in root, callus, and cell samples of P. lobata. Characteristic product ions of aglycones, O-glucosides, and C-glucosides were obtained from the full-scan ESI-MS chromatography of the major peaks and the MS-MS spectra of the protonated ions. Five major components of puerarin, daidzin-6"-O-acetylester, genistin-6"-O-malonylester, biochanin A-7-O-glucoside-6"-O-malonylester, and daidzein are detected and identified from the methanolic extract of P. lobata callus cultures. The major isoflavonoid components of P. lobata cell suspension cultures are identified as puerarin, daidzin, daidzin-6"-O-acetylester, genistin-6"-O-malonylester, biochanin A-7-O-glucoside-6"-O-malonylester, genistein-8-C-glucoside-6"-O-malonylester, and daidzein, on the basis of ESI-MS and MS-MS spectra analysis. Likewise, puerarin, daidzin, genistein-6"-O-malonylester, 3'-methoxypuerarin, and daidzein are detected and identified from RP. Of those isoflavonoid components detected, daidzin-6"-O-acetylester is a new isoflavonoid glucoside and is for the first time detected from P. lobata cultures in vitro. PMID:16620495

Fang, Congbing; Wan, Xiaochun; Tan, Huarong; Jiang, Changjun

2006-02-01

66

OXIDATIVE COUPLING OF METHANE USING INORGANIC MEMBRANE REACTORS  

SciTech Connect

The objective of this research is to study the oxidative coupling of methane in catalytic inorganic membrane reactors. A specific target is to achieve conversion of methane to C{sub 2} hydrocarbons at very high selectivity and higher yields than in conventional non-porous, co-feed, fixed bed reactors by controlling the oxygen supply through the membrane. A membrane reactor has the advantage of precisely controlling the rate of delivery of oxygen to the catalyst. This facility permits balancing the rate of oxidation and reduction of the catalyst. In addition, membrane reactors minimize the concentration of gas phase oxygen thus reducing non selective gas phase reactions, which are believed to be a main route for the formation of CO{sub x} products. Such gas phase reactions are a cause of decreased selectivity in the oxidative coupling of methane in conventional flow reactors. Membrane reactors could also produce higher product yields by providing better distribution of the reactant gases over the catalyst than the conventional plug flow reactors. Membrane reactor technology also offers the potential for modifying the membranes both to improve catalytic properties as well as to regulate the rate of the permeation/diffusion of reactants through the membrane to minimize by-product generation. Other benefits also exist with membrane reactors, such as the mitigation of thermal hot-spots for highly exothermic reactions such as the oxidative coupling of methane. The application of catalytically active inorganic membranes has potential for drastically increasing the yield of reactions which are currently limited by either thermodynamic equilibria, product inhibition, or kinetic selectivity.

Dr. Y.H. Ma; Dr. W.R. Moser; Dr. A.G. Dixon; Dr. A.M. Ramachandra; Dr. Y. Lu; C. Binkerd

1998-04-01

67

Atomic Scale Interface Coupling Effects in Epitaxial Oxides  

NASA Astrophysics Data System (ADS)

The fabrication of well controlled heterointerfaces is the cornerstone for much of modern microelectronics. High quality interfaces of novel materials, particularly of the correlated transition metal oxides, enable the creation of structures with rich and surprising phenomena. In this thesis, we present two epitaxial interfaces in which atomic scale details control the properties of the structure. (1) MBE grown BaO/Si is a prototype for the epitaxial oxide/silicon interface, which is of interest for future generations of MOSFET devices. Using a combination of synchrotron X-ray diffraction, TEM, RHEED and first principles calculations, we identify a sub-Angstrom rumpling reconstruction at the interface which elucidates how the sharp transition from a diamond covalent lattice to ionic rocksalt occurs. (2) La1- xSrxMnO 3 is a CMR oxide. By manipulation of its composition, strain, thickness and carrier distribution we are able to achieve a large resonant coupling between the oxygen octahedra rotation of a SrTiO3 substrate and a La1-xSrxMnO 3 film. The divergence of the rotation amplitude at the structural transition of the SrTiO3 leads to pronounced changes in the transport and magnetic properties of the film. We describe the mechanical coupling using a quantitative atomic model and explain it as the result of the role of octahedra orientation in La1-xSr xMnO3.

Segal, Yaron

68

Modeling of the catalytic oxidative coupling of methane  

SciTech Connect

Catalytic reaction equations describing processes typical of oxidative coupling catalysts were incorporated into a gas-phase, chemical kinetics model. Modeling is used to predict limits in C{sub 2} yield, describe product trends as a function of gas-phase and generalized catalyst behavior and use these results as a guide to catalyst design. The catalytic reaction set included methane activation, hydrocarbon activation and/or product oxidation. A combined hydrodynamic, chemical kinetics and transport model (HCT) utilizing 140 gas-phase reaction equations plus the catalytic set was employed. The model predicts that a highly selective and active catalyst would be capable of yielding adequate C{sub 2} hydrocarbons to justify production. However, a highly selective catalyst with activity characteristic of current oxidative coupling catalysts is predicted to yield no more than 35% C{sub 2} hydrocarbons. Any non- selective catalytic reactions lead to unacceptably low yields of C{sub 2} hydrocarbons. A significant finding of this work is the determination of a ``window`` of catalyst activity where both thermally-induced and catalytic reactions affect the products. For lower catalyst activities, gas-phase processes determine the outcome; for higher catalyst activities, the selectivity of the catalyst determines the product distribution.

Hair, L.M.; Pitz, W.J.; Droege, M.W.; Westbrook, C.K.

1992-04-01

69

Modeling of the catalytic oxidative coupling of methane  

SciTech Connect

Catalytic reaction equations describing processes typical of oxidative coupling catalysts were incorporated into a gas-phase, chemical kinetics model. Modeling is used to predict limits in C{sub 2} yield, describe product trends as a function of gas-phase and generalized catalyst behavior and use these results as a guide to catalyst design. The catalytic reaction set included methane activation, hydrocarbon activation and/or product oxidation. A combined hydrodynamic, chemical kinetics and transport model (HCT) utilizing 140 gas-phase reaction equations plus the catalytic set was employed. The model predicts that a highly selective and active catalyst would be capable of yielding adequate C{sub 2} hydrocarbons to justify production. However, a highly selective catalyst with activity characteristic of current oxidative coupling catalysts is predicted to yield no more than 35% C{sub 2} hydrocarbons. Any non- selective catalytic reactions lead to unacceptably low yields of C{sub 2} hydrocarbons. A significant finding of this work is the determination of a window'' of catalyst activity where both thermally-induced and catalytic reactions affect the products. For lower catalyst activities, gas-phase processes determine the outcome; for higher catalyst activities, the selectivity of the catalyst determines the product distribution.

Hair, L.M.; Pitz, W.J.; Droege, M.W.; Westbrook, C.K.

1992-04-01

70

Association of a Variable Number of Tandem Repeats in the Endothelial Constitutive Nitric Oxide Synthase Gene With Essential Hypertension in Japanese  

Microsoft Academic Search

An impaired synthesis of nitric oxide (NO) by the vascular endothelium has been implicated in the pathogenesis of essential hypertension (EH). The possible association between a variable number of tandem repeats (VNTR) polymorphism in intron 4 of the endothelial constitutive NO synthase (ecNOS) gene and EH in Japanese subjects was investigated. A total of 123 individuals with EH and 120

Jiro Uwabo; Masayoshi Soma; Tomohiro Nakayama; Katsuo Kanmatsuse

1998-01-01

71

Dissipation and residues of clethodim and its oxidation metabolites in a rape-field ecosystem using QuEChERS and liquid chromatography/tandem mass spectrometry.  

PubMed

A rapid, sensitive and selective method using Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) procedure for simultaneous determination of clethodim and its oxidation metabolites (clethodim sulfoxide and clethodim sulphone) in soil, rape plant and rape seed was developed using high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS). The limits of detection (LODs) of the proposed method ranged from 0.002mg/kg to 0.01mg/kg, and average recoveries were 78.7-104.2%. The trial results showed that clethodim dissipated so rapidly that few clethodim residues were detectable. Clethodim sulfoxide dissipated quickly in rape plant and soil with half-lives of 4.3 and 4.0days, respectively. Clethodim sulphone showed a tendency of rapid increase initially followed by a decrease in rape plant but could not be detected in soil. The terminal residues of clethodim in rape seedsat harvest time were below the maximum residue limit (MRL, 0.5mg/kg). PMID:24054227

You, Xiangwei; Liang, Lin; Liu, Fengmao

2013-07-26

72

Noncollinear coupling of iron layers through native iron oxide spacers  

SciTech Connect

We have found a magnetic superstructure in multilayers that consist of iron and its native oxide. Employing nuclear resonant scattering of synchrotron radiation from {sup 57}Fe probe layers, this manifests as 1/2-order Bragg peaks in the reflectivity curve. From the field dependence of their intensity, we deduce the existence of two magnetic sublattices that are canted by an angle of almost 90 deg. and rotate as one unit in low fields. For higher fields, the two sets of moments gradually align collinear to the external field. This behavior can be explained by a coupling of two adjacent Fe layers that is mediated by an antiferromagnetic order in the oxide spacer between them.

Diederich, Thomas; Couet, Sebastien; Roehlsberger, Ralf [Hamburger Synchrotronstrahlungslabor (HASYLAB), Deutsches Elektronen-Synchrotron (DESY), Notkestrasse 85, 22603 Hamburg (Germany)

2007-08-01

73

Structural characterization of minor metabolites and pharmacokinetics of ganoderic acid C2 in rat plasma by HPLC coupled with electrospray ionization tandem mass spectrometry.  

PubMed

The metabolites and pharmacokinetics of ganoderic acid C2 (GAC2), a bioactive triterpenoid in Ganoderma lucidum in rat plasma were investigated by high-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS). Totally, ten minor phase I metabolites of GAC2 were characterized after oral administration of GAC2, on the basis of their mass fragmentation pathways or direct comparison with authentic compounds by high-performance liquid chromatography coupled with diode array detection and electrospray ion trap tandem mass spectrometry (HPLC-DAD-ESI-MS(n)), and liquid chromatography coupled with electrospray ionization hybrid ion trap and time-of-flight mass spectrometry (LC-ESI-IT-TOF/MS) methods. Moreover, a rapid and specific method for quantification of GAC2 in rat plasma after oral administration was developed by using a liquid-liquid extraction procedure and HPLC-ESI-MS/MS analysis. It is the first time to report the metabolites and pharmacokinetics of GAC2. PMID:23312386

Guo, Xiao-Yu; Liu, Dan; Ye, Min; Han, Jian; Deng, Sa; Ma, Xiao-Chi; Zhao, YanYan; Zhang, Baojing; Shen, Xuan; Che, Qing-Ming

2012-11-23

74

Human G-protein-coupled inwardly rectifying potassium channel (GIRK1) gene (KCNJ3): Localization to chromosome 2 and identification of a simple tandem repeat polymorphism  

SciTech Connect

The gene encoding the human G-protein-coupled inwardly rectifying potassium channel designated GIRK1 (gene symbol, KCNJ3) was mapped to chromosome 2 by analyzing its segregation in a panel of human-hamster somatic cell hybrids. This assignment was confirmed by fluorescence in situ hybridization to metaphase chromosomes, and the gene was further localized to band 2q24.1. A highly informative simple tandem repeat DNA polymorphism of the form (CA)[sub n] was identified and used to localize KCNJ3 within the genetic map of the long arm of chromosome 2. 8 refs., 1 fig., 2 tabs.

Stoffel, M.; Powell, K.L.; Espinosa, R. III; Philipson, L.H.; Le Beau, M.M.; Bell, G.I. (Univ. of Chicago, IL (United States))

1994-05-01

75

Coupled polaronic and ion transport in nanocrystalline metal oxide electrodes  

NASA Astrophysics Data System (ADS)

We report new computational methods and fundamental understanding in the dynamics of coupled charge and ion transport in nanoscale metal oxides. The methods attack the multi-scale problem of simulating the collective diffusivities of ions and charge compensating e-/h+ carriers in single crystal particles, across particle-particle grain boundaries, and through networks of grains for select systems. Methods include embedded quantum mechanical clusters at the DFT and MP2 levels of theory for atomic-scale polaronic and ion transport kinetics, classical DFT-based free energy calculations for grain-scale conductivity in the framework of the Poisson-Nernst-Planck formalism, and phase field simulation of charged particle diffusivity for conductivity at the grain network scale. This combination of approaches is one of a kind in terms of its multi-scale range, scaling, and computational efficiency. We are presently focused on coupled electron and Li+ ion transport in polymorphs of TiO2, and also in mixed valence spinel oxides, for electrode conductivity optimization and improving energy storage materials performance for Li+ batteries.

Rosso, Kevin

2012-02-01

76

Azobisisobutyronitrile initiated aerobic oxidative transformation of amines: coupling of primary amines and cyanation of tertiary amines.  

PubMed

In the presence of a catalytic amount of radical initiator AIBN, primary amines are oxidatively coupled to imines and tertiary amines are cyanated to ?-aminonitriles. These "metal-free" aerobic oxidative coupling reactions may find applications in a wide range of "green" oxidation chemistry. PMID:23106189

Liu, Lianghui; Wang, Zikuan; Fu, Xuefeng; Yan, Chun-Hua

2012-10-29

77

Promotion by tetrachloromethane of the oxidative coupling of methane on silica-supported alkaline earth oxides  

SciTech Connect

The introduction of a small quantity of tetrachloromethane (TEM) into the feed stream has been shown to remarkably enhance the oxidative coupling of methane over alkaline earth oxides supported on silica. That this enhancement, in terms of both selectivity and yield to C{sub 2} hydrocarbons, occurs over a wide range of catalyst loading, feed composition, reaction temperature, and contact time has been illustrated using BaO/SiO{sub 2} as the catalyst. It has been demonstrated that over this catalyst, the coupling and nonselective oxidation processes occur predominantly independently of each other. The high ratio of C{sub 2}H{sub 4}/C{sub 2}H{sub 6} observed in the products is accounted for by the rapid homogeneous oxidative dehydrogenation of C{sub 2}H{sub 6}, a process which is evidently further enhanced by the presence of TCM. It is suggested that TCM promotes the coupling reaction by facilitating the hydrogen abstraction step from methane. Continuous cofeeding of the additive is required to maintain high selectivity and yield of C{sub 2} hydrocarbons in the products.

Ahmed, S.; Moffat, J.B. (Univ. of Waterloo, Ontario (Canada))

1990-02-01

78

Sulfide oxidation coupled to ATP synthesis in chicken liver mitochondria.  

PubMed

Chicken liver mitochondria consumed O2 at an accelerated rate when supplied with low concentrations of hydrogen sulfide. Maximum respiration occurred in 10 microM sulfide, and continued more slowly up to concentrations as high as 60 microM. Sulfide oxidation was coupled to adenosine triphosphate (ATP) synthesis, as shown by firefly luciferase luminescence and by measurement of the mitochondrial membrane electrochemical gradient. Synthesis of ATP required low, steady-state concentrations of sulfide (< 5 microM), which were maintained by use of a syringe pump. The ratio of consumed O2 to sulfide changed at low sulfide and O2 concentrations, indicating alternative metabolic reactions and products. In low concentrations of sulfide, presumably most similar to physiological, the O2/sulfide ratio was 0.75. This is the first report of sulfide oxidation linked to ATP synthesis in any organism not specifically adapted to a sulfide-rich environment. We suggest that this may be a widespread mitochondrial trait, and that it is consistent with the hypothesis that mitochondria originated from sulfide-oxidizing symbionts. PMID:11337256

Yong, R; Searcy, D G

2001-05-01

79

Quantitative Analysis of amino acid oxidation markers by tandem mass spectrometry  

PubMed Central

Oxidative stress plays a central role in the pathogenesis of diverse chronic inflammatory disorders including diabetic complications, cardiovascular disease, aging, neurodegenerative disease, autoimmune disorders and pulmonary fibrosis. Protein misfolding can lead to chronic endoplasmic reticulum (ER) stress which can exacerbate oxidative stress. This can trigger apoptotic cascades resulting in chronic inflammatory disorders. Despite intense interest in origins and magnitude of oxidative stress, ability to quantify oxidants has been limited because they are short-lived. We have developed quantitative mass spectrometry (MS) based analytical strategies to analyze stable end-products of protein oxidation. These molecules provide quantitative and mechanistic assessment of degree of oxidative stress in cell cultures, tissues and biofluids of animal models of disease and human samples. Our studies support the hypothesis that unique reactive intermediates generated in localized microenvironments of vulnerable tissues promote end-organ damage. The ability to quantify these changes and assess response to therapies will be pivotal in understanding disease mechanisms and monitoring efficacy of therapy.

Vivekanandan-Giri, Anuradha; Byun, Jaeman; Pennathur, Subramaniam

2011-01-01

80

Oxidative DNA damage induced by copper and hydrogen peroxide promotes CGfiTT tandem mutations at methylated CpG dinucleotides in nucleotide excision repair- deficient cells  

Microsoft Academic Search

Oxidative DNA damage may play an important role in human disease including cancer. Previously, mutational spectra have been determined using sys- tems that include transition metal ions and hydro- gen peroxide (H2O2). GfiT transversions and CfiT transitions were the most common mutations observed including some CCfiTT tandem muta- tions. CfiT transition mutations at methylated CpG dinucleotides are the most common

Dong-Hyun Lee; Timothy R. O'Connor; Gerd P. Pfeifer

81

On-line measurement of oxidative degradation kinetics for trace gasoline contaminants in aqueous solutions and natural water by membrane introduction tandem mass spectrometry  

Microsoft Academic Search

Membrane introduction mass spectrometry (MIMS) was used to directly monitor the loss of trace gasoline contaminants (benzene, toluene, 2-methylthiophene and methylcyclohexane) in nanomolar (ppb) aqueous solutions under a variety of UV-induced advanced oxidation processes (AOP). The decay kinetics of these contaminants were followed simultaneously in “real-time” via tandem mass spectrometric techniques by re-circulating the reaction mixture in a closed loop

Janet H. L. Nelson; Duane A. Friesen; Chris G. Gill; Erik T. Krogh

2010-01-01

82

Quantitation of five nevirapine oxidative metabolites in human plasma using liquid chromatography–tandem mass spectrometry  

Microsoft Academic Search

A multiple-reaction-monitoring LC\\/MS\\/MS method for the analysis of nevirapine oxidative metabolites, 2-hydroxynevirapine, 3-hydroxynevirapine, 8-hydroxynevirapine, 12-hydroxynevirapine, and 4-carboxynevirapine, in human plasma was developed and validated. The metabolites were isolated from 50?L heparinized plasma by enzymatic hydrolysis of the glucuronide conjugates to the free metabolite followed by protein precipitation with acetonitrile. Peaks were quantitated at 3.03min for the 4-carboxynevirapine metabolite, at 3.72,

Lois S. Rowland; Thomas R. MacGregor; Scot J. Campbell; Rand Jenkins; Amy B. Pearsall; Jennifer P. Morris

2007-01-01

83

Quantitative mapping of oxidation-sensitive cysteine residues in SERCA in vivo and in vitro by HPLC-electrospray-tandem MS: selective protein oxidation during biological aging.  

PubMed

The selective reversible S-glutathiolation of specific SERCA (sarcoplasmic/endoplasmic-reticulum Ca2+-ATPase) cysteine residues represents a novel physiologic pathway of NO (nitric oxide)-dependent arterial smooth muscle relaxation [Adachi, Weisbrod, Pimentel, Ying, Sharov, Schöneich and Cohen (2004) Nat. Med. 10, 1200-1207]. This mechanism may be impaired through the irreversible oxidation of functionally important cysteine residues as a consequence of oxidative stress and aging. To establish whether in vivo aging and in vitro oxidation by peroxynitrite result in the loss of such functionally important cysteine residues of SERCA, we have developed and optimized a quantitative method to monitor the oxidation state of the individual SERCA cysteine residues using a maleimide-based fluorescence dye, TG1 (ThioGlo 1), as a label for cysteine residues that have not been altered by oxidation and are not involved in disulphide bridges. A high efficiency for TG1 labelling of such residues and the chemical structure of cysteine-TG1 adducts were validated by MS analysis of model peptides, model proteins and rat skeletal muscle SERCA1. Tryptic peptides containing 18 out of a total of 24 cysteine residues were identified by HPLC-ESI (electrospray ionization)-MS/MS (tandem MS). Two cysteine residues, at positions 344 and 349, were detected in the form of an internal disulphide bridge, and another 16 were found to be labelled with TG1. Using HPLC-ESI-MS, we quantitatively mapped peroxynitrite oxidation of eight cysteine residues (positions 364, 417, 420, 498, 525, 674, 675 and 938), some of which are involved in the control of SERCA activity. Biological aging resulted in the partial modification of cysteine residues 377, 498, 525, 561, 614, 636, 674, 675, 774 and 938. Neither peroxynitrite exposure nor biological aging affected the apparent SERCA1 ATP affinity. Our data show an age-dependent loss of cysteine residues (approx. 2.8 mol of cysteine/mol of SERCA1), which may be partially responsible for the age-dependent decrease in the specific Ca2+-ATPase activity (by 40%). PMID:16307534

Sharov, Victor S; Dremina, Elena S; Galeva, Nadezhda A; Williams, Todd D; Schöneich, Christian

2006-03-15

84

Rapid residue analysis of four triazolopyrimidine herbicides in soil, water, and wheat by ultra-performance liquid chromatography coupled to tandem mass spectrometry.  

PubMed

A sensitive and effective method for simultaneous determination of triazolopyrimidine sulfonamide herbicide residues in soil, water, and wheat was developed using ultra-performance liquid chromatography coupled with tandem mass spectrometry. The four herbicides (pyroxsulam, flumetsulam, metosulam, and diclosulam) were cleaned up with an off-line C18 SPE cartridge and detected by tandem mass spectrometry using an electrospray ionization source in positive mode (ESI+). The determination of the target compounds was achieved in <2.0 min. The limits of detection were below 1 ?g kg(-1), while the limits of quantification did not exceed 3 ?g kg(-1) in different matrices. Quantitation was determined from calibration curves of standards containing 0.05-100 ?g L(-1) with r(2)?>?0.997. Recovery studies were conducted at three spiked levels (0.2, 1, and 5 ?g kg(-1) for water; 5, 10, and 100 ?g kg(-1) for soil and wheat). The overall average recoveries for this method in water, soil, wheat plants, and seeds at three levels ranged from 75.4% to 106.0%, with relative standard deviations in the range of 2.1-12.5% (n = 5) for all analytes. PMID:21221546

Liu, Xingang; Xu, Jun; Li, Yuanbo; Dong, Fengshou; Li, Jing; Song, Wenchen; Zheng, Yongquan

2011-01-08

85

Highly(>=98%) Stereo- and Regioselective Trisubstituted Alkene Synthesis of Wide Applicability via 1-Halo-1-alkyne Hydroboration-Tandem Negishi-Suzuki Coupling or Organoborate Migratory Insertion Protocol  

PubMed Central

(Z)-1-Halo-1-alkenylboranes (7), preparable in 82–90% yields as ?98% isomerically pure compounds via hydroboration of 1-halo-1-alkynes, have been converted to a wide range of trisubstituted alkenes via three different routes in the tail-to-head (T-to-H) direction, i.e., (i) Palladium-catalyzed Negishi-Suzuki tandem alkenylation, (ii) treatment of 7 with organolithium or Grignard reagents to generate ?-bromo-1-alkenylboronate complexes (10) that can undergo migratory insertion of a carbon group (R2) to form (E)-alkenylboranes (11) with inversion of alkene configuration (?98% inversion), followed by fluoride-promoted Suzuki alkenylation, and (iii) Negishi coupling to generate (Z)-alkenylboranes (8) in ?98% retention of configuration, followed by treatment with organolithium or Grignard reagents to produce trisubstituted alkenes with reversed stereo configurations. The synthetic utility of the present methodology has been demonstrated in the highly selective synthesis of side chain (4) of scyphostatin in 28% yield over nine steps in the longest linear sequence from allyl alcohol. Thus, this new tandem protocol has been emerged as the most widely applicable and highly selective route to trisubstituted alkenes including those that are otherwise difficult to prepare.

Xu, Shiqing; Lee, Ching-Tien; Rao, Honghua

2013-01-01

86

Direct Amidation from Alcohols and Amines through a Tandem Oxidation Process Catalyzed by Heterogeneous-Polymer-Incarcerated Gold Nanoparticles under Aerobic Conditions.  

PubMed

We describe herein a highly elegant and suitable synthesis of amide products from alcohols and amines through a tandem oxidation process that uses molecular oxygen as a terminal oxidant. Carbon-black-stabilized polymer-incarcerated gold (PICB-Au) or gold/cobalt (PICB-Au/Co) nanoparticles were employed as an efficient heterogeneous catalyst depending on alcohol reactivity and generated only water as the major co-product of the reaction. A wide scope of substrate applicability was shown with 42 examples. The catalysts could be recovered and reused without loss of activity by using a simple operation. PMID:24166844

Soulé, Jean-François; Miyamura, Hiroyuki; Kobayashi, Sh?

2013-09-12

87

Liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) determination of phase II metabolites of the mycotoxin zearalenone in the model plant Arabidopsis thaliana.  

PubMed

The biotransformation products of zearalenone, a Fusarium mycotoxin, were elucidated using the model plant Arabidopsis thaliana. After treatment of plant seedlings with 50 microM zearalenone, both the liquid media and the plant extracts were analysed by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). An array of 17 different metabolites, most prominently glucosides, malonylglucosides, di-hexose- and hexose-pentose disaccharides of zearalenone, and alpha- and beta-zearalenol, were detected in the samples. Time courses for the different zearalenone metabolites were recorded and they give a closer insight into the metabolism kinetics. A scheme proposing the zearalenone metabolism in A. thaliana is given. The aspect of food safety regarding the (potential) occurrence of masked mycotoxins in agricultural commodities is discussed. PMID:17071522

Berthiller, F; Werner, U; Sulyok, M; Krska, R; Hauser, M-T; Schuhmacher, R

2006-11-01

88

Identification and quantitation of cocaine, benzoylecgonine, and cocaethylene in blood, serum, and plasma using ultra-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS).  

PubMed

Cocaine is a widely abused stimulant. Numerous methods exist for the identification of the drug, or more commonly, one of its metabolites in urine. Urine testing is useful for most cases, but it is necessary to use other matrices in forensic situations and when subjects are anuric. We describe a novel method for the analysis of cocaine, benzoylecgonine, and cocaethylene in blood, serum, and plasma utilizing ultra-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS). Sample preparation has been minimized to a simple deproteinization step in which each specimen is mixed with an acetonitrile-internal standard mixture. The method has excellent precision across the linear range of 25-2,000 ng/mL for each analyte. With a run-time of 4 min, this method provides a significant improvement over traditional GC/MS methods. PMID:20077068

Kriger, Scott; Gunn, Josh; Terrell, Andrea R

2010-01-01

89

Liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) determination of phase II metabolites of the mycotoxin zearalenone in the model plant Arabidopsis thaliana  

PubMed Central

The biotransformation products of zearalenone, a Fusarium mycotoxin, were elucidated using the model plant Arabidopsis thaliana. After treatment of plant seedlings with 50 ?M zearalenone, both the liquid media and the plant extracts were analysed by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). An array of 17 different metabolites, most prominently glucosides, malonylglucosides, di-hexose- and hexose–pentose disaccharides of zearalenone, and ?- and ?-zearalenol, were detected in the samples. Time courses for the different zearalenone metabolites were recorded and they give a closer insight into the metabolism kinetics. A scheme proposing the zearalenone metabolism in A. thaliana is given. The aspect of food safety regarding the (potential) occurrence of masked mycotoxins in agricultural commodities is discussed.

BERTHILLER, F.; WERNER, U.; SULYOK, M.; KRSKA, R.; HAUSER, M.-T.; SCHUHMACHER, R.

2010-01-01

90

Direct lactonization of alkenols via osmium tetroxide-mediated oxidative cleavage.  

PubMed

[reaction: see text] A highly efficient, mild, and simple protocol is presented for the tandem OsO(4)-mediated oxidative cleavage/oxidative lactonization of alkenols to lactones. The protocol couples the OsO(4)-catalyzed oxidative cleavage of olefins with Oxone as the co-oxidant with the direct oxidation of aldehydes in alcoholic solvents to their corresponding esters. PMID:12916988

Schomaker, Jennifer M; Travis, Benjamin R; Borhan, Babak

2003-08-21

91

Magnetoelectric Coupling Effects in Multiferroic Complex Oxide Composite Structures  

NASA Astrophysics Data System (ADS)

A central goal of electronics based on correlated materials or `Mottronics' is the ability to switch between distinct collective states with a control voltage. Small changes in structure and charge density near a transition can tip the balance between competing phases, leading to dramatic changes in electronic and magnetic properties. In this work, we demonstrate that an electric field induced two-step ferroelastic switching pathway in (011) oriented 0.71Pb(Mg1/3Nb2/3)O3-0.29PbTiO3 (PMN-PT) substrates can be used to tune the Verwey metal-insulator transition in epitaxial Fe3O4 films in a stable and reversible manner. We also observe robust non-volatile resistance switching in Fe3O4 up to room temperature, driven by ferroelastic strain. These results provides a framework for realizing non-volatile and reversible tuning of order parameters coupled to lattice-strain in epitaxial oxide heterostructures over a broad range of temperatures, with potential device applications.

Liu, Ming; Hoffman, Jason; Wang, Jing; Zhang, Jinxing; Nelson-Cheeseman, Brittany; Bhattacharya, Anand

2013-05-01

92

[Oxidative efficiency of the system of electrolysis coupled ozonation].  

PubMed

The oxidation system of electrolysis coupled ozonation (electrolysis-ozonation) was used to degrade 4-chlorophenol (4-CP), and its mechanism was discussed on the basis of kinetic analysis. The experimental results indicated the electrolysis-ozonation system had a significant synergistic effect during degradation of 4-CP. For example, the electrolysis-ozonation had the 4-CP removal rate of 92.7% and the COD removal rate of 64.9% in 900 s, respectively; while electrolysis alone plus ozonation alone only had the 4-CP removal rate of 69.7% and the COD removal rate of 30.1% under the same conditions. The results of H2O2 concentration analysis and photocurrent test showed that the synergistic mechanism of electrolysis-ozonation included two factors: (1) production of *03- at the cathode; (2) H2O2 generation resulting from reduction of dissolved oxygen. The above two factors led to generation of *OH in system effectively. PMID:21072927

Zhou, Qi; Zhang, Rong; Wang, Xun-Hua; Tong, Shao-Ping; Ma, Chun-An

2010-09-01

93

Treatment of pharmaceutical effluent by ultrasound coupled with dual oxidant system  

Microsoft Academic Search

In this study, sonolysis (US), a dual oxidant system (DOX), and ultrasound coupled with a dual oxidant system (US\\/DOX) were employed to degrade real pharmaceutical effluent. In a DOX system, two effective oxidizing agents such as hydrogen peroxide and activated persulphate were used simultaneously. In this work, for the first time, an easily available waste material, iron swarf, was used

Senthilnathan Nachiappan; Karuppan Muthukumar

2012-01-01

94

Simultaneous determination of zolazepam and tiletamine in dog plasma by liquid chromatography coupled to a tandem mass spectrometry.  

PubMed

A mixture of tiletamine, a dissociative anesthetic, and zolazepam, a minor tranquilizer, has been widely used as an anesthetic or an immobilizing agent in a variety of animal species. However, interestingly, their pharmacokinetic behaviors have been published only in polar bears and pigs. In this study, we introduce a sensitive liquid chromatography/tandem mass spectrometry (LC/MS/MS) method for determining the two drugs in dog plasma. After simple protein precipitation with acetonitrile including midazolam (internal standard), the analytes were chromatographed on a reversed-phase column with a mobile phase of 10?m m ammonium acetate aqueous solution and acetonitrile (1:4, v/v). The accuracy and precision of the assay were in accordance with FDA regulations for the validation of bioanalytical methods. This method was used to measure the concentrations of zolazepam and tiletamine in plasma after a single intramuscular 10?mg dose of each in beagle dogs. PMID:22259017

Noh, Kyeumhan; Kim, Kil-Soo; Ahn, Byoungki; Archimbault, Pillippe; Oh, Tae-Ho; Kang, Wonku

2012-01-18

95

Iron\\/copper promoted oxidative homo-coupling reaction of terminal alkynes using air as the oxidant  

Microsoft Academic Search

An inexpensive catalytic system, which used a readily available Fe(acac)3 and trace quantity of Cu(acac)2 as the co-catalyst and air as the oxidant for the homo-coupling of terminal alkynes, has been developed. The catalytic system could also apply to the cross-coupling reaction of two different terminal alkynes.

Xu Meng; Chuanbin Li; Baochun Han; Tiansheng Wang; Baohua Chen

2010-01-01

96

Quantitation of parent drug and its unstable metabolites by in situ coulometric oxidation and liquid chromatography-tandem mass spectrometry.  

PubMed

Recent FDA and ICH guidances on safety testing of drug metabolites have challenged the way we traditionally think about quantitative bioanalytical methods. Such assays, in general, require a reference standard for each analyte to construct calibration curves and prepare quality control samples. However, early in the drug development process, metabolite standards may not be readily available, and if they are inherently unstable, they are difficult to synthesize or purify. In this paper, we describe a novel in-line method for producing and then quantifying a very unstable metabolite which is based upon the in situ postcolumn coulometric oxidation of the parent drug. Lacking any metabolite standards, the feasibility of simultaneously quantifying a development drug (compound A) and its unstable hydroxylated metabolites (metabolite B) was investigated. Reference standards for these ostensibly major human metabolites could not be reliably obtained due to rapid degradation upon purification and/or subsequent storage. Following high-performance liquid chromatography (HPLC) separation, parent drug and its [(13)C(3)-(15)N] isotopically labeled internal standard were quantitatively converted to equal amounts of a diastereomeric pair of hydroxylated metabolites using a postcolumn coulometric electrochemical cell before reaching the mass spectrometer. The concentration of the injected parent (which is equal to the total concentration of the in-line generated metabolites since the conversion to metabolite is quantitative) and the tandem mass spectrometry (MS/MS) signals of the electrochemically generated metabolites were used to construct a calibration curve for quantifying both the parent drug and its hydroxylated metabolites. Plasma extracts from humans dosed with compound A contained chromatographically distinct liquid chromatography-mass spectrometry (LC-MS) signals (m/z 538) for in vivo formed hydroxylated metabolites and the electrochemically oxidized parent drug which had been converted in-line into its chemically identical twin. Both peaks in this study sample could be quantified using a single calibration curve obtained under the same coulometric conditions using known amounts of the parent drug. Although no attempt was made to fully validate a bioanalytical method, the practicality of this in situ quantification approach was further confirmed by the preliminary bioanalytical analysis of a selection of plasma samples collected following oral administration (50 mg) of compound A in a clinical study. PMID:21105697

Tong, Wei; Chowdhury, Swapan K; Su, Ai-Duen; Alton, Kevin B

2010-11-24

97

Phosphine Oxides as Stabilizing Ligands for the Palladium-Catalyzed Cross-Coupling of Potassium Aryldimethylsilanolates  

PubMed Central

The palladium-catalyzed cross-coupling reaction of potassium (4-methoxyphenyl)dimethylsilanolate (K+1?) with aryl bromides has been demonstrated using triphenylphosphine oxide as a stabilizing ligand. Unsymmetrical biaryls can be prepared from a variety of aryl bromides in good yield with short reaction times. Qualitative kinetics studies compared effects of different phosphine oxides on the rate of cross-coupling and established the beneficial effect of these ligands in the reaction of electron-rich arylsilanolates. The improved yield and reproducibility of the cross-coupling of several bromides was demonstrated by direct comparison of reactions performed with and without triphenylphosphine oxide under non-rigorous exclusion of oxygen.

Denmark, Scott E.; Smith, Russell C.; Tymonko, Steven A.

2012-01-01

98

Methyl Radicals in Oxidative Coupling of Methane Directly Confirmed by Synchrotron VUV Photoionization Mass Spectroscopy  

NASA Astrophysics Data System (ADS)

Gas-phase methyl radicals have been long proposed as the key intermediate in catalytic oxidative coupling of methane, but the direct experimental evidence still lacks. Here, employing synchrotron VUV photoionization mass spectroscopy, we have directly observed the formation of gas-phase methyl radicals during oxidative coupling of methane catalyzed by Li/MgO catalysts. The concentration of gas-phase methyl radicals correlates well with the yield of ethylene and ethane products. These results lead to an enhanced fundamental understanding of oxidative coupling of methane that will facilitate the exploration of new catalysts with improved performance.

Luo, Liangfeng; Tang, Xiaofeng; Wang, Wendong; Wang, Yu; Sun, Shaobo; Qi, Fei; Huang, Weixin

2013-04-01

99

Electro-mechanical coupling of semiconductor film grown on stainless steel by oxidation  

NASA Astrophysics Data System (ADS)

Electro-mechanical coupling phenomenon in oxidation film on stainless steel has been discovered by using current-sensing atomic force microscopy, along with the I-V curves measurements. The oxidation films exhibit either ohmic, n-type, or p-type semiconductor properties, according to the obtained I-V curves. This technique allows characterizing oxidation films with high spatial resolution. Semiconductor properties of oxidation films must be considered as additional stress corrosion cracking mechanisms.

Lin, M. C.; Wang, G.; Guo, L. Q.; Qiao, L. J.; Volinsky, Alex A.

2013-09-01

100

Proton-coupled electron-transfer oxidation of phenols by hexachloroiridate(IV).  

PubMed

One-electron oxidation of phenol, 2,4,6-trimethylphenol, and 2,6-dimethylphenol by [IrCl(6)](2-) in aqueous solution has a simple pH dependence, indicating slow bimolecular oxidation of ArOH and faster oxidation of ArO(-). H/D kinetic isotope effects as large as 3.5 for oxidation of ArOH support concerted proton-coupled electron transfer with water as the proton acceptor. PMID:19006385

Song, Na; Stanbury, David M

2008-12-15

101

Coupling of anodic and cathodic reactions for phenol electro-oxidation using three-dimensional electrodes  

Microsoft Academic Search

We studied the electrochemical oxidation of phenol by the coupling of anodic and cathodic reactions. The experiments were done in an electrochemical filter press cell equipped with an Sb-doped SnO2-coated titanium foam and a RVC cathode. The oxidation occurs by a direct oxidation on the anodic side, while on the cathodic side oxidation occurs via an electro-Fenton mechanism. We studied

E Fockedey; A Van Lierde

2002-01-01

102

Characterization of grape seed procyanidins by comprehensive two-dimensional hydrophilic interaction × reversed phase liquid chromatography coupled to diode array detection and tandem mass spectrometry.  

PubMed

In this work, the development and optimization of a new methodology to analyze grape seed procyanidins based on the application of two-dimensional comprehensive LC is presented. This two-dimensional method involves the use of a microbore column containing a diol stationary phase in the first dimension coupled to either a C18 partially porous short column or a C18 monolithic column in the second dimension. The orthogonal hydrophilic interaction × reversed phase liquid chromatography (HILIC×RP-LC) system is interfaced through a ten-port two-position switching valve. The optimized HILIC×RP-LC separation followed by diode array and tandem mass spectrometry detection (HILIC×RP-LC-DAD-MS/MS) made possible the direct analysis of a complex grape seed extract and allowed the tentative identification of 43 flavan-3-ols, including monomers and procyanidin oligomers till a polymerization degree of 7 units with different galloylation degrees. To the best of our knowledge, this is the first time that this powerful analytical technique is employed to characterize complex procyanidin samples. This work successfully demonstrates the great capabilities of the HILIC×RP-LC-DAD-MS/MS coupling for the direct analysis of very complex natural samples like grape seeds. PMID:23224621

Montero, Lidia; Herrero, Miguel; Prodanov, Marin; Ibáñez, Elena; Cifuentes, Alejandro

2012-12-08

103

Coupled biotic-abiotic Mn(II) oxidation pathway mediates the formation and structural evolution of biogenic Mn oxides  

NASA Astrophysics Data System (ADS)

Manganese (Mn) oxides are among the strongest oxidants and sorbents in the environment, impacting the transport and speciation of metals, cycling of carbon, and flow of electrons within soils and sediments. The oxidation of Mn(II) to Mn(III/IV) oxides has been primarily attributed to biological processes, due in part to the faster rates of bacterial Mn(II) oxidation compared to observed mineral-induced and other abiotic rates. Here we explore the reactivity of biogenic Mn oxides formed by a common marine bacterium ( Roseobacter sp. AzwK-3b), which has been previously shown to oxidize Mn(II) via the production of extracellular superoxide. Oxidation of Mn(II) by superoxide results in the formation of highly reactive colloidal birnessite with hexagonal symmetry. The colloidal oxides induce the rapid oxidation of Mn(II), with dramatically accelerated rates in the presence of organics, presumably due to mineral surface-catalyzed organic radical generation. Mn(II) oxidation by the colloids is further accelerated in presence of both organics and light, implicating reactive oxygen species in aiding abiotic oxidation. Indeed, the enhancement of Mn(II) oxidation is negated when the colloids are reacted with Mn(II) in the presence of superoxide dismutase, an enzyme that scavenges the reactive oxygen species (ROS) superoxide. The reactivity of the colloidal phase is short-lived due to the rapid evolution of the birnessite from hexagonal to pseudo-orthogonal symmetry. The secondary particulate triclinic birnessite phase exhibits a distinct lack of Mn(II) oxidation and subsequent Mn oxide formation. Thus, the evolution of initial reactive hexagonal birnessite to non-reactive triclinic birnessite imposes the need for continuous production of new colloidal hexagonal particles for Mn(II) oxidation to be sustained, illustrating an intimate dependency of enzymatic and mineral-based reactions in Mn(II) oxidation. Further, the coupled enzymatic and mineral-induced pathways are linked such that enzymatic formation of Mn oxide is requisite for the mineral-induced pathway to occur. Here, we show that Mn(II) oxidation involves a complex network of abiotic and biotic processes, including enzymatically produced superoxide, mineral catalysis, organic reactions with mineral surfaces, and likely photo-production of ROS. The complexity of coupled reactions involved in Mn(II) oxidation here highlights the need for further investigations of microbially-mediated Mn oxide formation, including identifying the role of Mn oxide surfaces, organics, reactive oxygen species, and light in Mn(II) oxidation and Mn oxide phase evolution.

Learman, D. R.; Wankel, S. D.; Webb, S. M.; Martinez, N.; Madden, A. S.; Hansel, C. M.

2011-10-01

104

[Determination of 7 nipagin ester preservatives in leather by ultra performance liquid chromatography-tandem mass spectrometry coupled with gel permeation chromatographic clean-up].  

PubMed

A novel method has been developed for the rapid separation and determination of 7 nipagin ester preservatives in leather by ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) coupled with gel permeation chromatographic (GPC) clean-up. Nipagin ester preservatives in leather were extracted by ultrasonic extraction with methanol. The extract was dried by a rotavapor and purified by GPC, then redissolved in the solvent of methanol-water (1 : 1, v/v). The chromatographic analysis was performed on an Acquity UPLC BEH C18 column (50 mm x 2.1 mm, 1.7 microm) with a gradient elution of methanol and water as the mobile phases. The analytes were detected by electrospray ionization (ESI) tandem mass spectrometry with multiple reaction monitoring (MRM) in negative ion mode. Good linearity (r > 0.99) was observed between 0.1 and 1.0 mg/L for all the analytes. The recoveries and relative standard deviations (RSDs) were checked by spiking samples with the 7 nipagin ester preservatives at the three levels of 0.5, 1.0 and 3.0 mg/kg. The average recoveries of the 7 nipagin ester preservatives were from (79.44 +/- 5.67)% to (98.07 +/- 9.50)%. The precision values expressed as RSD ranged from 4.24% to 14.00% (n = 6). The limits of detection were 4 -12 microg/kg and the limits of quantification were 13.2 - 39.6 microg/kg for the analytes. The method is simple, rapid, sensitive and accurate, and suitable for the quantitative determination and confirmation of 7 nipagin ester preservatives in leather. PMID:22032160

Wu, Gang; Zhao, Shanhong; Wu, Jianjian; Dong, Suozhuai; Guo, Fanglong; Wang, Lijun; Ye, Qingfu

2011-06-01

105

Quantification of fexofenadine in human plasma by liquid chromatography coupled to electrospray tandem mass spectrometry using mosapride as internal standard.  

PubMed

A rapid high-performance liquid chromatography/positive ion electrospray tandem mass spectrometry method was developed and validated for the quantification of fexofenadine in human plasma using mosapride as internal standard. Following solid-phase extraction, the analytes were separated using an isocratic mobile phase on a reverse-phase column and analyzed by MS/MS in the multiple reaction monitoring mode using the respective [M+H]+ ions, m/z 502/466 for fexofenadine and m/z 422/198 for the IS. The method exhibited a linear dynamic range of 1-500 ng/mL for fexofenadine in human plasma. The lower limit of quantification was 1 ng/mL with a relative standard deviation of less than 5% for fexofenadine. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. The total chromatographic run time of 2 min for each sample made it possible to analyze more than 400 human plasma samples per day. The validated method has been successfully used to analyze human plasma samples for application in pharmacokinetic, bioavailability or bioequivalence studies. PMID:17221908

Nirogi, Ramakrishna V S; Kandikere, Vishwottam N; Shukla, Manoj; Mudigonda, Koteshwara; Maurya, Santosh; Komarneni, Prashanth

2007-02-01

106

Simultaneous determination of clozapine and its N-desmethyl and N-oxide metabolites in plasma by liquid chromatography\\/electrospray tandem mass spectrometry and its application to plasma level monitoring in schizophrenic patients  

Microsoft Academic Search

A liquid chromatography tandem mass spectrometry (LC-MS-MS) assay method for the simultaneous determination of clozapine and its N-desmethyl (norclozapine) and N-oxide metabolites in human plasma is described. The compounds were extracted from plasma by a single step liquid-liquid extraction procedure and analyzed using a high performance liquid chromatography electrospray tandem mass spectrometer system. The compounds were eluted isocratically on a

M Aravagiri; S. R Marder

2001-01-01

107

Oxidative coupling of methane over oxide-supported sodium-manganese catalysts  

SciTech Connect

The oxidative coupling of methane over Mn/Na{sub 2}WO{sub 4}/SiO{sub 2}, Mn/Na{sub 2}WO{sub 4}/MgO, and NaMnO{sub 4}/MgO catalysts was studied using both a cofeed flow system and a pulse reactor. At 800{degrees}C and 1 atm, and using a CH{sub 4}/O{sub 2} ratio of ca. 8/1, a methane conversion of 20% was achieved at a C{sub 2+} selectivity of {ge}80%, with no diluent in the reagents. The similar catalytic behaviors of the three catalysts suggest that a common active site, consisting of an Na-O-Mn species, may be involved. Results from a pulse reaction sequence (an O{sub 2} pulse followed by a series of pure CH{sub 4} pulses) indicate that the active species are not stable under reaction conditions unless gas phase O{sub 2} is present, and that bulk lattice oxygen does not participate in the methane coupling reaction when carried out in the cofeed mode. There is a linear relationship between the specific activity for CH{sub 4} conversion and the concentration of surface Mn, which is believed to be responsible for the activation of O{sub 2}. The resulting form of oxygen then abstracts a hydrogen atom from CH{sub 4}. Sodium is essential for preventing the complete oxidation of CH{sub 4}, perhaps by isolating the Mn ions. The tungstate ions appear to impart stability to the catalysts. 39 refs., 11 figs., 5 tabs.

Wang, Dingjun; Rosynek, M.P.; Lunsford, J.H. [Texas A & M Univ., College Station, TX (United States)

1995-09-01

108

Microstructural study of a nitroxide-mediated poly(ethylene oxide)\\/polystyrene block copolymer (PEO- b PS) by electrospray tandem mass spectrometry  

Microsoft Academic Search

Electrospray ionization tandem mass spectrometry has been used to characterize the microstructure of a nitroxide-mediated\\u000a poly(ethylene oxide)\\/polystyrene block copolymer, called SG1-capped PEO-b-PS. The main dissociation route of co-oligomers adducted with lithium or silver cation was observed to proceed via the homolytic\\u000a cleavage of a C-ON bond, aimed at undergoing reversible homolysis during nitroxide mediated polymerization. This cleavage\\u000a results in the

Marion Girod; Trang N. T. Phan; Laurence Charles

2008-01-01

109

Rapid quantification of nebivolol in human plasma by liquid chromatography coupled with electrospray ionization tandem mass spectrometry.  

PubMed

A simple, sensitive and rapid liquid chromatographic/electrospray ionization tandem mass spectrometric method was developed and validated for the quantitation of nebivolol in human plasma. The method involved a simple single-step liquid-liquid extraction with diethyl ether/dichloromethane (70/30). The analyte was chromatographed on Waters symmetry C18 reversed-phase chromatographic column by isocratic elution with water:acetonitrile:formic acid (30:70:0.03, v/v) and analyzed by mass spectrometry in the multiple reaction monitoring mode. The precursor to product ion transitions of m/z 406.4-151.5 and m/z 409.1-228.1 were used to measure the analyte and the internal standard (I.S.), respectively. The chromatographic runtime was 2 min and the weighted (1/x2) calibration curves were linear over the range 50-10,000 pg/mL. The method was validated in terms of accuracy, precision, absolute recovery, freeze-thaw stability, bench-top stability and re-injection reproducibility. The limit of detection and lower limit of quantification in human plasma were 10 and 50 pg/mL, respectively. The within- and between-batch accuracy and precision were found to be well within acceptable limits (<10%). The analyte was stable after three freeze-thaw cycles (deviation <10%). The average absolute recoveries of nebivolol and tamsulosin, used as an internal standard, from spiked plasma samples were 73.4+/-3.7 and 72.1+/-2.0%, respectively. The assay method described here was applied to study the pharmacokinetics of nebivolol. PMID:16006083

Ramakrishna, N V S; Vishwottam, K N; Koteshwara, M; Manoj, S; Santosh, M; Varma, D P

2005-07-11

110

Membrane assisted solvent extraction coupled with liquid chromatography tandem mass spectrometry applied to the analysis of alkylphenols in water samples.  

PubMed

This work describes the development and validation of a novel, simple, sensitive and environmental friendly analytical method for the determination of alkylphenols in different types of water samples. The methodology was based on a membrane assisted solvent extraction of only 15 mL of water sample with 500 ?L of hexane in combination with liquid chromatography-electrospray ionization tandem mass spectrometry in negative mode (LC-ESI-MS/MS). Acquisition was performed in the multiple reaction monitoring (MRM) mode recording two transitions for the identification of the target compounds. Quantitation is based on the use of deuterated labelled standards as surrogate standards. The figures of merit were satisfactory in all cases: absolute recoveries were close to 50% for most investigated compounds and relative recoveries varied between 81 and 108%. Repeatability and intermediate precision were <20% for all compounds. Uncertainty assessment of measurement was estimated on the basis of an in-house validation according to EURACHEM/CITAC guide. Quantitation limits of the method (MQL) were lower than 0.04 ?g L(-1) in all cases, which allow the achievement of the limits established by the Directive 2008/105/EC for surface and seawater samples and by the new proposal COM (2011) 876 final. The feasibility of the proposed method was demonstrated analyzing seawater, surface water and drinking water samples from different areas of A Coruña (Northwest of Spain). The analyses evidenced the presence of nonylphenol in seawater (MQL-0.13 ?g L(-1)) and surface water samples (0.12-0.19 ?g L(-1)). The highest concentration was observed in drinking water (0.25 ?g L(-1)). PMID:23394746

Salgueiro-González, N; Turnes-Carou, I; Muniategui-Lorenzo, S; López-Mahía, P; Prada-Rodríguez, D

2013-01-23

111

Rapid quantification of miglustat in human plasma and cerebrospinal fluid by liquid chromatography coupled with tandem mass spectrometry.  

PubMed

Miglustat (OGT 918) is an iminosugar recently introduced in therapeutic as potential alternative therapy in disorders found in several diseases such as Tay-Sachs, Gaucher or Niemann-Pick diseases. A highly sensitive liquid-chromatography-electrospray tandem mass spectrometry (LC-MS/MS) assay was developed for the quantification of miglustat in human plasma and cerebrospinal fluid (CSF). The sample preparation consists in a simple protein precipitation with a mixture of acetonitrile/methanol (75/25) which yields 100% recovery. The isocratic separation utilizes an Atlantis Hilic (3 microm, 150 mm x 2.1 mm) column, with a mobile phase of acetonitrile/water/ammonium acetate buffer (75/10/15, v/v/v) delivered at 230 microl/min. Selected reaction monitoring (SRM) mode was used with the transitions m/z 220-->158 for the miglustat and m/z 208-->m/z 146 for the miglitol (internal standard). Good linearity was observed in a range from 125 to 2500 ng/ml and from 50 to 1000 ng/ml, for plasma and CSF, respectively. The within-run precision of the assay was less than 6%, and the between-run run precision was less than 6.5%, for six replicates at each of three concentrations and evaluated on three separated days for both plasma and CSF mediums. Assay accuracy was in the range of 98-106.5%. Stability of miglustat was reported under a variety of storage conditions. The miglustat concentrations in two children are presented to demonstrate the clinical interest of this new method. PMID:19095507

Guitton, Jérôme; Coste, Sylvie; Guffon-Fouilhoux, Nathalie; Cohen, Sabine; Manchon, Monique; Guillaumont, Marc

2008-12-03

112

Enzymatic modification of kraft lignin through oxidative coupling with water-soluble phenols  

Microsoft Academic Search

The aromatic polymer lignin can be modified through promotion of oxidative coupling between phenolic groups on lignin and various phenols. The reaction is initiated by an oxidation of both components, e.g., by using the oxidoreductases laccase or peroxidase. Coupling between phenolic monomers and lignin has previously been studied by the use of radio-labeled phenols. In this study, incorporation of water-soluble

M. Lund; A. J. Ragauskas

2001-01-01

113

Quantification of anthelmintic drug residues in milk and muscle tissues by liquid chromatography coupled to Orbitrap and liquid chromatography coupled to tandem mass spectrometry  

Microsoft Academic Search

A simple method for the determination of some anthelmintic drugs and phenylbutazone residues in milk and muscle was developed. Following a fast and easy extraction and evaporation procedure, the extract was injected into an ultra performance liquid chromatography system coupled to a single stage Orbitrap detector. The high mass resolution of 50,000 full width at half maximum and corresponding narrow

A. Kaufmann; P. Butcher; K. Maden; S. Walker; M. Widmer

2011-01-01

114

Calcium-centred phosphine oxide reactivity: P-C metathesis, reduction and P-P coupling.  

PubMed

Reactions of triphenylphosphine oxide and diphenylphosphine oxide with calcium alkyls and amides in the presence of PhSiH(3) occur to give P-C bond cleavage, P(V) to P(III) reduction and P-P coupling. PMID:20379562

Hill, Michael S; Mahon, Mary F; Robinson, Thomas P

2010-01-28

115

Cr(III) oxidation coupled with Mn(II) bacterial oxidation in the environment  

Microsoft Academic Search

Purpose  Cr(III) oxidation to Cr(VI) significantly increases Cr mobility and toxicity and thus its environmental risks. Manganese (Mn)\\u000a oxides may serve as the potential oxidants of Cr(III) in environment. Natural Mn oxides in the environment are believed to\\u000a be derived from bacterial oxidation. The objective of this study was to examine the Cr(III) oxidation capacity of biogenic\\u000a Mn oxide and the

Ji-Zheng He; You-Ting Meng; Yuan-Ming Zheng; Li-Mei Zhang

2010-01-01

116

High-throughput peptide identification from protein digests using data-dependent multiplexed tandem FTICR mass spectrometry coupled with capillary liquid chromatography.  

PubMed

Tandem mass spectrometry (MS/MS) plays an important role in the unambiguous identification and structural elucidation of biomolecules. In contrast to conventional MS/MS approaches for protein identification where an individual polypeptide is sequentially selected and dissociated, a multiplexed-MS/MS approach increases throughput by selecting several peptides for simultaneous dissociation using either infrared multiphoton dissociation (IRMPD) or multiple frequency sustained off-resonance irradiation (SORI) collisionally induced dissociation (CID). The high mass measurement accuracy and resolution of FTICR combined with knowledge of peptide dissociation pathways allows the fragments arising from several different parent ions to be assigned. Herein we report the application of multiplexed-MS/MS coupled with on-line separations for the identification of peptides present in complex mixtures (i.e., whole cell lysate digests). Software was developed to enable "on-the-fly" data-dependent peak selection of a subset of polypeptides from each FTICR MS acquisition. In the subsequent MS/MS acquisitions, several coeluting peptides were fragmented simultaneously using either IRMPD or SORI-CID techniques. The utility of this approach has been demonstrated using a bovine serum albumin tryptic digest separated by capillary LC where multiple peptides were readily identified in single MS/MS acquisitions. We also present initial results from multiplexed-MS/MS analysis of a D. radiodurans whole cell digest to illustrate the utility of this approach for high-throughput analysis of a bacterial proteome. PMID:11476231

Li, L; Masselon, C D; Anderson, G A; Pasa-Toli?, L; Lee, S W; Shen, Y; Zhao, R; Lipton, M S; Conrads, T P; Toli?, N; Smith, R D

2001-07-15

117

Rapid determination of estrogens in milk samples based on magnetite nanoparticles/polypyrrole magnetic solid-phase extraction coupled with liquid chromatography-tandem mass spectrometry.  

PubMed

In this study, a nanocomposite of polypyrrole-coated magnetite nanoparticles (denoted as MNPs/PPy) was prepared and employed as magnetic solid-phase extraction (MSPE) sorbent for extraction of estrogens from milk samples. Because the polypyrrole coating possessed a highly ?-conjugated structure and hydrophobicity, MNPs/PPy showed excellent performance for the estrogen extraction. Estrogens could be captured directly by MNPs/PPy from milk samples without protein precipitation. Moreover, the extraction could be carried out within 3 min. Thus, a rapid, simple, and effective method for the analysis of estrogens in milk samples was established by coupling MNPs/PPy-based MSPE with liquid chromatography-tandem mass spectrometry (LC-MS/MS). The limits of detections for estrogens investigated were in the range of 5.1-66.7 ng/L. The recoveries of estrogens (concentration range of 0.5-20 ng/mL) from milk samples were in the range of 83.4-108.5%, with relative standard deviations ranging between 4.2 and 15.4%. PMID:21749040

Gao, Qiang; Luo, Dan; Bai, Mei; Chen, Zong-Wei; Feng, Yu-Qi

2011-07-21

118

Carbamazepine in municipal wastewater and wastewater sludge: ultrafast quantification by laser diode thermal desorption-atmospheric pressure chemical ionization coupled with tandem mass spectrometry.  

PubMed

In this study, the distribution of the anti-epileptic drug carbamazepine (CBZ) in wastewater (WW) and aqueous and solid phases of wastewater sludge (WWS) was carried out. A rapid and reliable method enabling high-throughput sample analysis for quicker data generation, detection, and monitoring of CBZ in WW and WWS was developed and validated. The ultrafast method (15s per sample) is based on the laser diode thermal desorption-atmospheric pressure chemical ionization (LDTD-APCI) coupled to tandem mass spectrometry (MS/MS). The optimization of instrumental parameters and method application for environmental analysis are presented. The performance of the novel method was evaluated by estimation of extraction recovery, linearity, precision and detection limit. The method detection limits was 12 ng L(-1) in WW and 3.4 ng g(-1) in WWS. The intra- and inter-day precisions were 8% and 11% in WW and 6% and 9% in WWS, respectively. Furthermore, three extraction methods, ultrasonic extraction (USE), microwave-assisted extraction (MAE) and accelerated solvent extraction (ASE) with three different solvent condition such as methanol, acetone and acetonitrile:ethyle acetate (5:1, v/v) were compared on the basis of procedural blank and method recovery. Overall, ASE showed the best extraction efficiency with methanol as compared to USE and MAE. Furthermore, the quantification of CBZ in WW and WWS samples showed the presence of contaminant in all stages of the treatment plant. PMID:22967548

Mohapatra, D P; Brar, S K; Tyagi, R D; Picard, P; Surampalli, R Y

2012-05-29

119

Determination of phenolic compounds in rose hip (Rosa canina) using liquid chromatography coupled to electrospray ionisation tandem mass spectrometry and diode-array detection.  

PubMed

Liquid chromatography coupled with negative and positive electrospray ionisation (ESI) tandem mass spectrometry (MS/MS) and diode-array detection (DAD) was used for determination of phenols in rose hip (Rosa canina) extract. ESI mass spectra of the chromatographically separated phenols gave the molecular weight of the compounds through prominent [M - H](-) ions for most of the compounds and M(+) ions for the anthocyanins. Collision induced dissociation (CID) of the [M - H](-) (or M(+)) precursor ions yielded product ions which determined the molecular weight of the aglycones. In-source fragmentation followed by CID of the resulting deprotonated aglycone ([A - H](-)) provided product ions for the identification of the unconjugated phenols. The identification was based on comparison with product ion spectra of commercial standards. UV-diode-array spectra were used for identity confirmation. This combined approach allowed the identification in rose hip extract of an anthocyanin, i.e. cyanidin-3-O-glucoside, several glycosides of quercetin and glycosides of taxifolin and eriodictyol. Phloridzin was identified, and several conjugates of methyl gallate were also found, one of which was tentatively identified as methyl gallate-rutinoside. Catechin and quercetin were found as the aglycones in the extract. PMID:11921243

Hvattum, Erlend

2002-01-01

120

A method for multiple mycotoxin analysis in wines by solid phase extraction and multifunctional cartridge purification, and ultra-high-performance liquid chromatography coupled to tandem mass spectrometry.  

PubMed

An analytical method using two solid phase extractions and ultra-high-performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS) was developed for the identification and quantification of 14 mycotoxins (patulin, deoxynivalenol, aflatoxins B(1), B(2), G(1), G(2), M(1), T-2 toxin, HT-2 toxin, zearalenone, fumonisins B(1), B(2), B(3), and ochratoxin A) in domestic and imported wines. Mycotoxins were purified with an Oasis HLB cartridge, followed by a MultiSep(TM) #229 Ochra. As a result, sufficient removal of the pigments and highly polar matrices from the red wines was achieved. UHPLC conditions were optimized, and 14 mycotoxins were separated in a total of 13 min. Determinations performed using this method produced high correlation coefficients for the 14 mycotoxins (R > 0.990) and recovery rates ranging from 76 to 105% with good repeatability (relative standard deviation RSD < 12%). Twenty-seven samples of domestic and imported wines were analyzed using this method. Although ochratoxin A (OTA) and fumonisins (FMs) were detected in several samples, the FM levels were less than limits of quantification (LOQs) (1 ?g/L), and even the largest of the OTA levels was below the EU regulatory level (2 ?g/L). These results suggest that the health risk posed to consumers from the wines available in Japan is relatively low. PMID:22822458

Tamura, Masayoshi; Takahashi, Ayumi; Uyama, Atsuo; Mochizuki, Naoki

2012-06-15

121

Simultaneous determination of five estrogens and four androgens in water samples by online solid-phase extraction coupled with high-performance liquid chromatography-tandem mass spectrometry.  

PubMed

A novel method for simultaneous determination of five estrogens and four androgens by online solid-phase extraction (SPE) coupled with high-performance liquid chromatography-tandem mass spectrometry (HPLC-ESI-MS/MS) in water samples was developed. An aliquot of 50 mL water sample after filtration was injected directly into autosampler and the analytes were preconcentrated on a NG1 online SPE column. After cleanup step the analytes were eluted in back flush mode and then separated on a liquid chromatography column. The experimental parameters, such as sample loading flow rate, cleanup condition and elution time, were optimized in detail. Estrogens and androgens were detected in negative and positive mode, respectively. High ionization efficiency of all the analytes was achieved by adding of 1‰ ammonia in the mobile phase. The recoveries ranged from 31.8% to 119.0% and the inter-day RSDs ranged from 2.7% to 19.6%. The limits of detections (LODs) were between 0.1 and 2.5 ng/L. The proposed method was successfully applied to the analysis of three types of water samples, including river water, influent and effluent water from a wastewater treatment plant (WWTP). The recoveries of androgens were not that good and a further study is being planned to improve the sensitivity for them. The proposed method is simple, sensitive and suitable for simultaneous analysis and monitoring of estrogens and androgens in water samples. PMID:23398990

Guo, Feng; Liu, Qian; Qu, Guang-bo; Song, Shan-jun; Sun, Jian-teng; Shi, Jian-bo; Jiang, Gui-bin

2013-01-23

122

Application of hollow fibre liquid phase microextraction for the multiresidue determination of pesticides in alcoholic beverages by ultra-high pressure liquid chromatography coupled to tandem mass spectrometry.  

PubMed

An alternative method has been developed to determine more than 50 pesticides in alcoholic beverages using hollow fibre liquid phase microextraction (HF-LPME) followed by ultra-high pressure liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS), without any further clean-up step. Pesticides were extracted from the sample to the organic solvent immobilized in the fibre and they were desorbed in methanol prior to chromatographic analysis. Experimental parameters related to microextraction such as type of organic solvent, extraction time and agitation rate have been optimized. The extraction method has been validated for several types of alcoholic beverages such as wine and beer, and no matrix effect was observed. The technique requires minimal sample handling and solvent consumption. Using optimum conditions, low detection limits (0.01-5.61microgL(-1)) and good linearity (R(2)>0.95) were obtained. Repeatability and interday precision ranged from 3.0 to 16.8% and from 5.9 to 21.2%, respectively. Finally the optimized method was applied to real samples and carbaryl, triadimenol, spyroxamine, epoxiconazole, triflumizol and fenazaquin were detected in some of the analyzed samples. The obtained results indicated that the new method can be successfully applied for extraction and determination of pesticides in alcoholic beverages, increasing sample throughput. PMID:18762301

Bolaños, P Plaza; Romero-González, R; Frenich, A Garrido; Vidal, J L Martínez

2008-08-20

123

[Determination of ten pesticides of pyrazoles and pyrroles in tea by accelerated solvent extraction coupled with gas chromatography-tandem mass spectrometry].  

PubMed

An effective method was developed and applied to determine the residues of ten pesticides of pyrazoles and pyrroles in tea by accelerated solvent extraction coupled with gas chromatography-tandem mass spectrometry (ASE-GC-MS/MS). The samples were extracted with ethyl acetate-hexane (1:1, v/v) for 5 min at 1.03 x 10(7) Pa and 100 degree C for one cycle. Then, they were purified by Envi-Carb/PSA column, and eluted by ethyl acetate-hexane (1:1, v/v). The analytes were determined by GC-MS/MS and quantified by external standard method. The limits of quantification were 0.003 mg/kg for fenpyroximate, 0.001 mg/kg for fipronil-sulfide, 0.002 mg/kg for fipronil, 0.005 mg/kg for fipronil-sulfone, 0.002 mg/kg for chlorfenapyr, 0.006 mg/kg for flusilazole, 0.001 mg/kg for difenzoquat, 0.001 mg/kg for pyraflufen-ethyl, 0.000 3 mg/kg for tebufenpyrad and 0.005 mg/kg for tolfenpyrad. The results show that the proposed method is sensitive and accurate for the determination of the ten pesticide residues. PMID:23785993

Xu, Dunming; Lu, Shengyu; Chen, Dajie; Lan, Jinchang; Zhang, Zhigang; Yang, Fang; Zhou, Yu

2013-03-01

124

[Rapid analysis of eight lipophilic pesticide residues in vegetables by dispersive liquid-liquid microextraction coupled with gas chromatography-tandem mass spectrometry].  

PubMed

A novel method for rapid determination of eight lipophilic pesticides in vegetables was developed using dispersive liquid-liquid micro-extraction (DLLME) coupled with gas chromatography-tandem mass spectrometry (GC-MS/MS). The analyte in the vegetable was extracted with water-acetone (5 : 1, v/v) solution. Then, the extract was transferred into a centrifugal tube with 25 mg primary secondary amine (PSA), 50 mg C18 and 25 mg graphitized carbon black powder. The important parameters that affected the extraction efficiency were studied, such as the extraction and dispersed solvents, and the extraction time. The results showed that a good extraction efficiency was obtained, with acetone used as the dispersed solvent and 50.0 microL chlorobenzene used as the extraction solvent. Under the optimum conditions, the enrichment factors ranged from 526 to 878. The linearity ranges of the eight targeted compounds were 0.005 - 10 mg/kg, and the limits of detection (signal/noise = 3) were 0.001 - 0.02 mg/kg, with the correlation coefficients varying from 0.992 1 to 0.998 9. The recoveries of the pesticides ranged from 60.1% to 82.5% with the relative standard deviations between 1.2% and 9.6%. The method has been used to analyze the eight lipophilic pesticide residues in vegetable samples with satisfactory results. PMID:23256389

Zhou, Min; Li, Wei; Du, Xiaoting; Xia, Zhongxing; Chen, Meichun

2012-08-01

125

Hydrophilic interaction ultra-performance liquid chromatography coupled with triple-quadrupole tandem mass spectrometry for highly rapid and sensitive analysis of underivatized amino acids in functional foods.  

PubMed

This work presented a new analytical methodology based on hydrophilic interaction ultra-performance liquid chromatography coupled with triple-quadrupole tandem mass spectrometry in multiple-reaction monitoring mode for analysis of 24 underivatized free amino acids (FAAs) in functional foods. The proposed method was first reported and validated by assessing the matrix effects, linearity, limit of detections and limit of quantifications, precision, repeatability, stability and recovery of all target compounds, and it was used to determine the nutritional substances of FAAs in ginkgo seeds and further elucidate the nutritional value of this functional food. The result showed that ginkgo seed turned out to be a good source of FAAs with high levels of several essential FAAs and to have a good nutritional value. Furthermore, the principal component analysis was performed to classify the ginkgo seed samples on the basis of 24 FAAs. As a result, the samples could be mainly clustered into three groups, which were similar to areas classification. Overall, the presented method would be useful for the investigation of amino acids in edible plants and agricultural products. PMID:23361945

Zhou, Guisheng; Pang, Hanqing; Tang, Yuping; Yao, Xin; Mo, Xuan; Zhu, Shaoqing; Guo, Sheng; Qian, Dawei; Qian, Yefei; Su, Shulan; Zhang, Li; Jin, Chun; Qin, Yong; Duan, Jin-ao

2013-01-30

126

Content determination of the major constituents of Yinchenzhufu decoction via ultra high-performance liquid chromatography coupled with electrospray ionisation tandem mass spectrometry.  

PubMed

In this study, we developed a method using ultra high-performance liquid chromatography coupled with electrospray ionisation tandem mass spectrometry for determining the contents of chlorogenic acid, atractylenolide I, atractylenolide III, benzoylaconine, benzoylmesaconine, benzoylhypaconine, glycyrrhizic acid, glycyrrhetic acid, liquiritigenin, and cinnamic acid in Yinchenzhufu decoction, a classic traditional Chinese medicine prescription. Separation was performed on a C18 column (4.6mm i.d.×250mm, 5?m) and achieved with good linearity (r(2)>0.9984) within 35min. Gradient elution was applied using a mobile phase of 0.05% acetic acid/acetonitrile. The analytes were quantified on an LCQ ion trap mass spectrometer in electrospray ionisation full-scan mode. Variations in the intra- and inter-day precision of all analytes were below 4.57%, and the accuracy was evaluated by a recovery test within the range of 97.88-102.25%. The method successfully quantified the 10 compounds in five sample batches of Yinchenzhufu decoction, and the results show that the method is accurate, sensitive, and reliable. PMID:23411001

Wang, Qian; Shi, Rong; Ma, Yue-Ming; Jiang, Peng; Zhong, Jie; Cui, Hong-Yan; Liu, Ping; Liu, Cheng-Hai

2013-01-21

127

[Determination of deoxynivalenol in grain and its products by solid-phase extraction coupled with high performance liquid chromatography-tandem mass spectrometry].  

PubMed

A method was established for the determination of deoxynivalenol (vomitoxin) in grain and its products based on solid-phase extraction coupled with high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The sample was firstly extracted by acetonitrile-water (84:16, v/v). The extract was then cleaned-up by an HLB solid phase extraction cartridge. The separation was carried out on a Phenomenex Kinetex C18 column (100 mm x4. 6 mm, 2.6 microm) with a gradient elution using 0.3% per hundred ammonia solution-acetonitrile as mobile phases. The analysis of deoxynivalenol was performed under electrospray negative ionization mode. The limit of detection (LOD, S/N= 3) and the limit of quantification (LOQ, S/N = 10) were 20 microg/kg and 50 microg/kg, respectively. A good linearity (r > 0.99) was achieved for the target compound over the range of 20-1000 pg/L. The recoveries at the three spiked levels (50, 100, 500 microg/kg) in the blank matrices such as flour, barley, soybean, rice, cornmeal, cassava and wheat, were varied from 75.6% to 111.0% with the relative standard deviations no more than 13. 0%. The method is accurate, efficient, sensitive and practical. The cost of pretreatment is obviously reduced by replacing immunoaffinity columns and Mycosep columns with HLB columns which have the same purification effect. PMID:23451526

Huang, Juan; Chen, Guosong; Zhang, Xiaoyan; Shen, Chongyu; Lü, Chen; Wu, Bin; Liu, Yan; Chen, Huilan; Ding, Tao

2012-11-01

128

Quality evaluation of cortex moutan by high performance liquid chromatography coupled with diode array detector and electrospary ionization tandem mass spectrometry.  

PubMed

An high performance liquid chromatography (HPLC) coupled with diode array detector (DAD) and electrospray ionization tandem mass spectrometry (ESI/MS(n)) method was developed for quality evaluation of Cortex Moutan through identification of common constituents based on chromatographic fingerprints and determination of key pharmacological compounds. The representative chromatographic fingerprints of Cortex Moutan were obtained by analyzing 10 batches of samples under the optimized HPLC conditions and the results showed that the chromatographic profiles of the analyzed samples were very similar. Total of nineteen common peaks were detected and seventeen of them were identified rapidly by their characteristic UV profile and the information of molecular structure provided by ESI/MS(n) experiments. Simultaneously, five key pharmacological compounds, namely gallic acid, oxypaeoniflorin, paeoniflorin, benzoylpaeoniflorin and paeonol, were determined by the validated HPLC-DAD method. The linear calibration curves were acquired with correlation coefficients higher than 0.999. The precisions of intra-day and inter-day were not exceeding 3.1%, and the recoveries of five analytes were from 92.86 to 99.35%. This developed method that combined the chromatographic fingerprints and quantification assay ensured the phytoequivalence and pharmacological effects of Cortex Moutan and was successfully applied to the quality control of Cortex Moutan. PMID:16946533

He, Qing; Ge, Zhi-Wei; Song, Yue; Cheng, Yi-Yu

2006-09-01

129

A comparison of the environmental impact of pesticide multiresidues and their occurrence in river waters surveyed by liquid chromatography coupled in tandem with UV diode array detection and mass spectrometry  

Microsoft Academic Search

Twenty-two pesticides and metabolites selected on the basis of a regional priority list, were surveyed in surface river waters by high performance liquid chromatography coupled in tandem with UV diode array detection and mass spectrometry, after an off-line pre-concentration step. Pesticide concentrations ranged between 0.07 and 4.8 ?g\\/l according to the compound and sampling period. Analytical results were linked to

S Irace-Guigand; J. J Aaron; P Scribe; D Barcelo

2004-01-01

130

Synthesis of trisubstituted alkenes via direct oxidative arene-alkene coupling.  

PubMed

The use of an inorganic oxidant with an acetic acid/acetonitrile solvent combination has been identified as optimal for direct arene/1,2-disubstituted alkene oxidative couplings, providing an efficient route to trisubstituted alkenes. The acetonitrile cosolvent dramatically accelerates the rate of reaction, and an insoluble inorganic oxidant limits unwanted oxidation of substrates. The scope of this procedure is illustrated with arenes and alkenes containing electron-donating and -withdrawing substituents resulting in a general synthetic strategy to trisubstituted alkenes. In situ ESI-MS analysis of the reaction components has identified the key Pd intermediates in the Fujiwara-Moritani catalytic cycle. PMID:23841693

Jones, Roderick C; Ga??zowski, Micha?; O'Shea, Donal F

2013-07-25

131

Non-invasive assessment of oxidatively damaged DNA: liquid chromatography-tandem mass spectrometry analysis of urinary 8-oxo-7,8-dihydro-2'-deoxyguanosine.  

PubMed

The ability to non-invasively assess DNA oxidation and its repair, has significant utility in large-scale, population-based studies. Such studies could include the assessments of: the efficacy of antioxidant intervention strategies, pathological roles of DNA oxidation in various disease states and population or interindividual differences in antioxidant defence and DNA repair. The most popular method, to non-invasively assess oxidative insult to the genome is by the analysis of urine for 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), using chromatographic techniques or immunoassay procedures. The provenance of extracellular 8-oxodG remains a subject for debate. However, previous studies have shown that factors, such as diet and cell death, do not appear to contribute to extracellular 8-oxodG, leaving processes, such as the repair of DNA and/or the 2'-deoxyribonucleotide pool, as the sole source of endogenous 8-oxodG. The method in this chapter describes a non-invasive approach for assessing oxidative stress, via the efficient extraction of urinary 8-oxodG using a validated solid-phase extraction procedure. Subsequent analysis by liquid chromatography-tandem mass spectrometry provides the advantages of sensitivity, internal standardisation, and robust peak identification, and is widely considered to be the "gold standard". PMID:21057935

Mistry, Vilas; Teichert, Friederike; Sandhu, Jatinderpal K; Singh, Rajinder; Evans, Mark D; Farmer, Peter B; Cooke, Marcus S

2011-01-01

132

Phosphine Oxides as Stabilizing Ligands for the Palladium-Catalyzed Cross-Coupling of Potassium Aryldimethylsilanolates.  

PubMed

The palladium-catalyzed cross-coupling reaction of potassium (4-methoxyphenyl)dimethylsilanolate (K(+)1(-)) with aryl bromides has been demonstrated using triphenylphosphine oxide as a stabilizing ligand. Unsymmetrical biaryls can be prepared from a variety of aryl bromides in good yield with short reaction times. Qualitative kinetics studies compared effects of different phosphine oxides on the rate of cross-coupling and established the beneficial effect of these ligands in the reaction of electron-rich arylsilanolates. The improved yield and reproducibility of the cross-coupling of several bromides was demonstrated by direct comparison of reactions performed with and without triphenylphosphine oxide under non-rigorous exclusion of oxygen. PMID:23162169

Denmark, Scott E; Smith, Russell C; Tymonko, Steven A

2007-06-25

133

Synthesis of the carbon framework of scholarisine A by intramolecular oxidative coupling.  

PubMed

Scholarisine A, isolated from the leaves of Alstonia scholaris, is a monoterpene indole alkaloid with an unprecedented cage-like structure. In this paper, preparation of the distinctive cage-like core skeleton of scholarisine A is described. The key feature of this synthetic strategy is an intramolecular oxidative coupling reaction at the late stage to construct a 10-oxa-tricyclo[5.3.1.0(3,?8)]undecan-9-one structure fused with indolenine. Intramolecular oxidative coupling by using N-iodosuccinimide gave the carbon framework of scholarisine A in moderate yield, which is the first example of intramolecular oxidative-coupling reaction between non-activated enolate and indole. This study lays the foundation for continued investigations towards the total synthesis of scholarisine A. PMID:23400955

Watanabe, Tsugunori; Kato, Nobuki; Umezawa, Naoki; Higuchi, Tsunehiko

2013-02-11

134

Steady-state and transient catalytic oxidation and coupling of methane  

SciTech Connect

This project addresses the conversion of methane from natural gas into ethane, ethylene and higher hydrocarbons. Our research explores the mechanistic and practical implications of carrying out the methane oxidative coupling reaction in reactor designs other than conventional packed-beds with co-fed reactants. These alternate reactor designs are needed to prevent the full oxidation of methane, which limits C{sub 2}, yields in methane oxidative coupling reactions. The research strategy focuses on preventing contact between the 0{sub 2} reactant required for favorable overall thermodynamics and the C{sub 2+} products of methane coupling. The behavior of various reactor designs are simulated using detailed kinetic transport models. These simulations have suggested that the best way to prevent high C0{sub 2} yields is to separate the oxygen and hydrocarbon streams altogether. As a result, the project has focused on the experimental demonstration of proton transport membrane reactors for the selective conversion of methane into higher hydrocarbons.

Iglesia, E.; Perry, D.L.; Heinemann, H.

1995-06-01

135

Quantification of carvedilol in human plasma by high-performance liquid chromatography coupled to electrospray tandem mass spectrometry: application to bioequivalence study.  

PubMed

A rapid, sensitive and specific method to quantify carvedilol in human plasma using metoprolol as the internal standard (IS) is described. The analyte and the IS were extracted from plasma by liquid-liquid extraction using a diethyl-ether solvent. After removed and dried the organic phase, the extracts were reconstituted with a fixed volume of acetonitrile-water (50/50; v/v). The extracts were analyzed by a high performance liquid chromatography coupled to electrospray tandem mass spectrometry (HPLC-MS/MS). Chromatography was performed isocratically on Alltech Prevail C18 5 microm analytical column, (150 mm x 4.6 mm i.d.). The method had a chromatographic run time of 3.5 min and a linear calibration curve over the range 0.1-200 ng ml(-1) (r2>0.997992). The limit of quantification was 0.1 ng ml(-1). This HPLC-MS/MS procedure was used to assess the bioequivalence of two carvedilol 25 mg tablet formulations (carvedilol test formulation from Laboratórios Biosintética Ltda and Coreg from Roche Químicos e Farmacêuticos S.A standard reference formulation). A single 25 mg dose of each formulation was administered to healthy volunteers. The study was conducted using an open, randomized, two-period crossover design with a 2-week wash-out interval. Since the 90% CI for C(max) and AUCs ratios were all inside the 80-125% interval proposed by the US Food and Drug Administration Agency, it was concluded that carvedilol formulation elaborated by Laboratórios Biosintética Ltda is bioequivalent to Coreg formulation for both the rate and the extent of absorption. PMID:16005691

do Carmo Borges, Ney Carter; Mendes, Gustavo Duarte; de Oliveira Silva, Diogo; Marcondes Rezende, Vinicius; Barrientos-Astigarraga, Rafael Eliseo; De Nucci, Gilberto

2005-08-01

136

Screening of drugs in equine plasma using automated on-line solid-phase extraction coupled with liquid chromatography-tandem mass spectrometry.  

PubMed

A rapid liquid chromatography-tandem mass spectrometry (LC-MS-MS) method was developed for the simultaneous screening of 19 drugs of different classes in equine plasma using automated on-line solid-phase extraction (SPE) coupled with a triple quadrupole mass spectrometer. Plasma samples were first protein precipitated using acetonitrile. After centrifugation, the supernatant was directly injected into the on-line SPE system and analysed by a triple quadrupole LC-MS-MS in positive electrospray ionisation (+ESI) mode with selected reaction monitoring (SRM) scan function. On-line extraction and chromatographic separation of the targeted drugs were performed using respectively a polymeric extraction column (2 cm L x 2.1mm ID, 25 microm particle size) and a reversed-phase C18 LC column (3 cm L x 2.1mm ID, 3 microm particle size) with gradient elution to provide fast analysis time. The overall instrument turnaround time was 9.5 min, inclusive of post-run and equilibration time. Plasma samples fortified with 19 targeted drugs including narcotic analgesics, local anaesthetics, antipsychotics, bronchodilators, mucolytics, corticosteroids, sedative and tranquillisers at sub-parts per billion (ppb) to low parts per trillion (ppt) levels could be consistently detected. No significant matrix interference was observed at the expected retention times of the targeted ion transitions. Over 70% of the drugs studied gave detection limits at or below 100 pg/mL, with some detection limits reaching down to 19 pg/mL. The method had been validated for extraction recovery, precision and sensitivity, and a blockage study had also been carried out. This method is used regularly in the authors' laboratory to screen for the presence of targeted drugs in pre-race plasma samples from racehorses. PMID:20122690

Kwok, W H; Leung, David K K; Leung, Gary N W; Wan, Terence S M; Wong, Colton H F; Wong, Jenny K Y

2010-01-18

137

Detection of seven pesticides in cucumbers using hollow fibre-based liquid-phase microextraction and ultra-high pressure liquid chromatography coupled to tandem mass spectrometry.  

PubMed

A liquid-phase microextraction (LPME) methodology based on the use of porous polyvinylidene fluoride (PVDF) hollow fibres was developed for extracting seven pesticides from cucumbers. The seven pesticides include propoxur, carbofuran, atrazine, cyanatryn, metolachlor, prometryn and tebuconazole. The PVDF hollow fibre provides higher extraction efficiency due to its higher porosity and better solvent compatibility. A new desorption methodology was developed since some pesticides were absorbed by the wall pore of the PVDF. Ultra-high pressure liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS) was used for pesticide analysis. In order to obtain high recoveries and enrichment factors of the analytes, several parameters such as method of sealing, acceptor phase (organic solvents), stirring speed, extraction time, salting out effect, desorption mode and time were optimized. A fast, simple method for closing fibre ends was practiced by using mechanical crimping. Pesticides were extracted from the sample to the organic solvent and then desorbed in a mixture of methanol:water (1:1 v/v) prior to chromatographic analysis. Limits of detection (LOD) for the multi-reaction-monitoring (MRM) mode of the method varies from 0.01 to 0.31 ?g/kg with optimized sample preparation. Calibration curves are linear with R² ? 0.991. Enrichment factor of the hollow fibre LPME ranges from 100 to 147. Matrix effect has been considered and is in the range of 76-122%. The relative recoveries from cucumber samples are between 63% and 119% with the relative standard deviation (RSD, n=6) lower than 20%. PMID:22682952

Wang, Jianfeng; Du, Zhenxia; Yu, Wenlian; Qu, Shuping

2012-05-15

138

Quantification of cyproheptadine in human plasma by high-performance liquid chromatography coupled to electrospray tandem mass spectrometry in a bioequivalence study.  

PubMed

A rapid, sensitive and specific method to quantify cyproheptadine in human plasma using amitriptyline as the internal standard (IS) is described. The analyte and the IS were extracted from plasma by liquid-liquid extraction using a diethyl-ether/dichloromethane (70/30; v/v) solvent. After removing and drying the organic phase, the extracts were reconstituted with a fixed volume of acetonitrile/water (50/50 v/v)+0.1% of acetic acid. The extracts were analyzed by high performance liquid chromatography coupled to electrospray tandem mass spectrometry (LC-MS/MS). Chromatography was performed isocratically using an Alltech Prevail C18 5 µm analytical column, (150 mm?x?4.6 mm I.D.). The method had a chromatographic run time of 4 min and a linear calibration curve ranging from 0.05 to 10 ng/mL (r2?>?0.99). The limit of quantification was 0.05 ng/mL. This HPLC/MS/MS procedure was used to assess the bioequivalence of cyproheptadine in two cyproheptadine?+?cobamamide (4 mg?+?1 mg) tablet formulations (Cobactin® [cyproheptadine?+?cobamamide] test formulation supplied from Zambon Laboratórios Farmacêuticos Ltda. and Cobavital® from Solvay Farma (standard reference formulation)). A single 4 mg?+?1 mg [cyproheptadine?+?cobamamide] dose of each formulation was administered to healthy volunteers. The study was conducted using an open, randomized, two-period crossover design with a 1-week washout interval. Since the 90% CI for Cmax and AUCs ratios were all within the 80-125% bioequivalence limit proposed by the US Food and Drug Administration, it was concluded that the cyproheptadine test formulation (Cobactin®) is bioequivalent to the Cobavital® formulation for both the rate and the extent of absorption of cyproheptadine. PMID:21432861

Mendes, Gustavo Duarte; Arruda, André; Chen, Lu Shi; de Almeida Magalhães, José Cássio; Alkharfy, Khalid M; De Nucci, Gilberto

2011-03-23

139

Oxidative Phosphorylation coupled with Aerobic and Anaerobic Respiration in a Bacterial Cell-free System  

Microsoft Academic Search

IT has been presumed that in anaerobic respiration, such as nitrate1 or sulphate2 respiration, formation of some high-energy phosphate is coupled with the process in a similar way to oxidative phosphorylation in aerobic respiration. We have reported3 that, in the whole cell system of Pseudomonas denitrificans, radioactive inorganic phosphate (32Pi) is incorporated into labile organic phosphates coupled with the denitrification

Tomoko Ohnishi; Takeshi Mori

1962-01-01

140

Treatment of pharmaceutical effluent by ultrasound coupled with dual oxidant system.  

PubMed

In this study, sonolysis (US), a dual oxidant system (DOX), and ultrasound coupled with a dual oxidant system (US/DOX) were employed to degrade real pharmaceutical effluent. In a DOX system, two effective oxidizing agents such as hydrogen peroxide and activated persulphate were used simultaneously. In this work, for the first time, an easily available waste material, iron swarf, was used as an activator for persulphate oxidation. Iron swarf coupled with an ultrasound system showed better activation. High iron dosage, acidic pH and high temperature favoured degradation with both DOX and US/DOX. Sequential addition of iron swarf produced better results compared to single-step addition. The activation energy was found to be 47.25 and 23.47 kJ/mol for DOX and US/DOX, respectively. The biodegradability index of the effluent was enhanced from 0.13 to 0.81 after treatment with US/DOX. PMID:23530332

Nachiappan, Senthilnathan; Muthukumar, Karuppan

141

MEASUREMENT OF PYRETHROID RESIDUES IN ENVIRONMENTAL AND FOOD SAMPLES BY ENHANCED SOLVENT EXTRACTION/SUPERCRITICAL FLUID EXTRACTION COUPLED WITH GAS CHROMATOGRAPHY-TANDEM MASS SPECTROMETRY  

EPA Science Inventory

The abstract summarizes pyrethorid methods development research. It provides a summary of sample preparation and analytical techniques such as supercritical fluid extraction, enhance solvent extraction, gas chromatography and tandem mass spectrometry....

142

Oxidative Coupling of Enolates, Enol Silanes and Enamines: Methods and Natural Product Synthesis  

PubMed Central

The oxidative coupling of enolates, enol silanes, and enamines provides a direct method for the construction of useful 1,4-dicarbonyl synthons. Despite being first reported in 1935, with subsequent important advances beginning in the 1970’s, the development of this powerful reaction into a reliable methodology was somewhat limited. In recent years, there have been a number of reports from several research groups demonstrating advances in several neglected areas of oxidative coupling. This microreview summarizes these new advances in methodology and provides an overview of recent natural product syntheses that showcase the power of these transformations.

Guo, Fenghai; Clift, Michael D.

2013-01-01

143

Iron-Catalyzed Oxidative Cross-Coupling of Phenols and Alkenes.  

PubMed

A novel bioinspired iron-catalyzed oxidative cross-coupling reaction between phenols and conjugated alkenes was developed. This method enables the direct coupling of phenols with styrene, ?-alkyl- and ?-arylstyrenes, ?-alkyl styrenes, and stilbenes, thereby providing a new strategy for the preparation of the pharmacologically important 2,3-dihydrobenzofuran motif. In addition, this study revealed that under a different set of conditions an oxidative/addition dearomatization reaction of 1,1'-bi-2-naphthol (BINOL) with styrene can take place. PMID:23758172

Kshirsagar, Umesh A; Regev, Clil; Parnes, Regev; Pappo, Doron

2013-06-11

144

Cr(III) Oxidation Coupled With Microbially-Mediated Mn(II) Oxidation  

SciTech Connect

Cr(VI) can be reduced to less toxic and mobile Cr(III) species through abiotic and biological processes. Reductive immobilization of Cr(VI) has been widely explored as a cost effective technology for site remediation; Mn oxides are regarded as primary oxidants for Cr(III) oxidation in the environment; and Generation of Mn oxides from Mn(II) in natural environments is believed to be biologically catalyzed.

Youxian Wu; Baolin Deng

2006-04-05

145

A novel two-phase oxidative coupling of 2-naphthols suspended in aqueous Fe 3+ solutions  

Microsoft Academic Search

The oxidative coupling of 2-naphthols suspended in aqueous Fe3+ solutions gives corresponding 1,1? -bi-2-naphthols in the yields of 91–95%. This reaction can be also effectively applied to the large-scale synthesis of 1,1? -bi-2-naphthol. It was suggested that the oxidation occurred at the surface of the crystalline 2-naphthols via a solid-liquid process.

Teruo Matsuura

1996-01-01

146

Coupling Pd-Catalyzed Alcohol Oxidation to Olefin Functionalization: Hydrohalogenation/Hydroalkoxylation of Styrenes  

PubMed Central

A hydrochlorination reaction of styrenes catalyzed by PdII in combination with CuII was developed, which was followed by an in situ conversion of electron-rich products to an ether in the presence of an alcohol. Mechanistic experiments indicate that olefin functionalization is coupled to an alcohol oxidation, wherein a Pd hydride formed in the ?-hydride elimination step of the alcohol oxidation was incorporated into the product.

Podhajsky, Susanne M.; Sigman, Matthew S.

2009-01-01

147

Biphasic oxidation of arenes with oxygen catalysed by Pd(II)—heteropoly acid system: oxidative coupling versus hydroxylation  

Microsoft Academic Search

Liquid-phase oxidation of benzene or toluene with oxygen (100–140°C, 5–10atm, in AcOH–H2O) catalysed by the Pd(OAc)2–H5[PMo10V2O40] redox system leads mainly to oxidative coupling (biphenyl and terphenyl or bitolyl) and ring hydroxylation (phenol or cresol). The reaction has been carried out homogeneously (at [H2O] <15vol.% in the solvent) and in biphasic conditions including an arene phase and an AcOH–H2O catalyst phase

H. A. Burton; I. V. Kozhevnikov

2002-01-01

148

Reduced Coupling of Oxidative Phosphorylation In Vivo Precedes Electron Transport Chain Defects Due to Mild Oxidative Stress in Mice  

PubMed Central

Oxidative stress and mitochondrial function are at the core of many degenerative conditions. However, the interaction between oxidative stress and in vivo mitochondrial function is unclear. We used both pharmacological (2 week paraquat (PQ) treatment of wild type mice) and transgenic (mice lacking Cu, Zn-superoxide dismutase (SOD1?/?)) models to test the effect of oxidative stress on in vivo mitochondrial function in skeletal muscle. Magnetic resonance and optical spectroscopy were used to measure mitochondrial ATP and oxygen fluxes and cell energetic state. In both models of oxidative stress, coupling of oxidative phosphorylation was significantly lower (lower P/O) at rest in vivo in skeletal muscle and was dose-dependent in the PQ model. Despite this reduction in efficiency, in vivo mitochondrial phosphorylation capacity (ATPmax) was maintained in both models, and ex vivo mitochondrial respiration in permeabilized muscle fibers was unchanged following PQ treatment. In association with the reduced P/O, PQ treatment led to a dose-dependent reduction in PCr/ATP ratio and increased phosphorylation of AMPK. These results indicate that oxidative stress uncouples oxidative phosphorylation in vivo and results in energetic stress in the absence of defects in the mitochondrial electron transport chain.

Siegel, Michael P.; Kruse, Shane E.; Knowels, Gary; Salmon, Adam; Beyer, Richard; Xie, Hui; Van Remmen, Holly; Smith, Steven R.; Marcinek, David J.

2011-01-01

149

Biocompatible, functional spheres based on oxidative coupling assembly of green tea polyphenols.  

PubMed

Green luminescent, monodisperse, smooth, porous and hollow spheres were simply prepared by Cu(2+) and temperature mediated oxidative coupling assembly of green tea polyphenols in water. These polymeric tea polyphenol spheres are GSH responsive, acid resistant but alkali-responsive, ideally used as platform for controlled delivery of functional guests. PMID:23470166

Chen, Zhenhua; Wang, Caihong; Chen, Junze; Li, Xudong

2013-03-11

150

Production of N2 through Anaerobic Ammonium Oxidation Coupled to Nitrate Reduction in Marine Sediments  

Microsoft Academic Search

In the global nitrogen cycle, bacterial denitrification is recognized as the only quantitatively important process that converts fixed nitrogen to atmospheric nitrogen gas, N2, thereby influencing many aspects of ecosystem function and global biogeochemistry. However, we have found that a process novel to the marine nitrogen cycle, anaerobic oxidation of ammonium coupled to nitrate reduction, contributes substantially to N2 production

Bo Thamdrup; Tage Dalsgaard

2002-01-01

151

Total Synthesis of (±)-Decinine via an Oxidative Biaryl Coupling with Defined Axial Chirality.  

PubMed

The total synthesis of (±)-decinine has been achieved. The key steps in the synthesis involved the formation of lasubine II via a gold catalyzed annulation of 1-(but-3-yn-1-yl)piperidine and the formation of the 12-membered ring of decinine (1) with complementary atropselectivity via a VOF(3)-mediated oxidative biaryl coupling reaction. PMID:22746388

Shan, Zhen-Hua; Liu, Ji; Xu, Ling-Min; Tang, Ye-Feng; Chen, Jia-Hua; Yang, Zhen

2012-06-29

152

Palladium-catalyzed synthesis of 2-aminobenzoxazinones by aerobic oxidative coupling of anthranilic acids and isocyanides.  

PubMed

Isocyanides have emerged as valuable C1 building blocks in palladium catalysis. Their potential has, however, mainly been exploited for the synthesis of amidines and amidine-containing heterocycles. To illustrate the broader applicability of isocyanides, we have recently developed a novel oxidative coupling of diamines and isocyanides furnishing valuable guanidine-containing heterocycles. We here report the extension of this protocol to the coupling of anthranilic acids and isocyanides leading to medicinally relevant 2-aminobenzoxazinones. This is a particularly challenging substrate class for this reaction due to the possibility of undesired decarboxylative pathways and the susceptibility of the products to nucleophilic attack. Therefore, this work underlines the generality and broad potential of the oxidative coupling of bisnucleophiles and isocyanides, facilitating the further implementation of this chemistry in library design. PMID:24063265

Vlaar, Tjøstil; Orru, Romano V A; Maes, Bert U W; Ruijter, Eelco

2013-10-08

153

Dinuclear chiral vanadium catalysts for oxidative coupling of 2-naphthols via a dual activation mechanism.  

PubMed

This review describes our recent efforts in the development of chiral dinuclear vanadium complexes that work as dual activation catalysts for the oxidative coupling of 2-naphthols. The dinuclear vanadium(iv) complex (R(a),S,S)- was prepared by complexation of VOSO(4) with the Schiff base derived from (R)-3,3'-diformyl-2,2'-dihydroxy-1,1'-binaphthyl () and (S)-tert-leucine. Since the dinuclear vanadium(iv) complex was found to be readily oxidized to afford a corresponding vanadium(v) species during preparation in air, a new synthetic procedure using VOCl(3) has been applied towards dinuclear vanadium(v) complexes (R(a),S,S)- and (R(a),S,S)-. To the best of our knowledge, (R(a),S,S)-, and show considerably higher catalytic activity than previously reported vanadium complexes for the oxidative coupling of 2-naphthols. PMID:18802502

Takizawa, Shinobu; Katayama, Tomomi; Sasai, Hiroaki

2008-07-17

154

Copper-mediated oxidative direct C-C (hetero)aromatic cross-coupling.  

PubMed

Some new types of copper-mediated intermolecular oxidative direct C-C (hetero)aromatic cross-couplings are described. A combination of the simple CuCl(2) salt and molecular oxygen allows 1,3-azoles to couple with terminal alkynes directly to form the corresponding heteroarylacetylenes. This direct version of Sonogashira-type coupling can be applied to the reaction with polyfluoroarenes. A copper acetate complex enables direct biaryl coupling between 2-arylazines and 1,3-azoles even in the absence of any palladium catalysts. Moreover, the Cu-based protocol can be extended to the coupling with indoles and pyrroles, in which a catalytic variant is also possible by using an ideal co-oxidant, atmospheric oxygen. On the other hand, a copper-promoted annulative direct coupling of o-alkynylphenols and -anilines with 1,3-azoles can provide a unique dehydrogenative approach to C3-azolylbenzoheteroles from nonhalogenated and nonmetalated starting materials. In addition, a related N-azolylindole synthesis from similar substrates is also disclosed. PMID:22991692

Hirano, Koji; Miura, Masahiro

2012-11-11

155

Nitrogen loss from soil through anaerobic ammonium oxidation coupled to iron reduction  

NASA Astrophysics Data System (ADS)

The oxidation of ammonium is a key step in the nitrogen cycle, regulating the production of nitrate, nitrous oxide and dinitrogen. In marine and freshwater ecosystems, anaerobic ammonium oxidation coupled to nitrite reduction, termed anammox, accounts for up to 67% of dinitrogen production. Dinitrogen production through anaerobic ammonium oxidation has not been observed in terrestrial ecosystems, but the anaerobic oxidation of ammonium to nitrite has been observed in wetland soils under iron-reducing conditions. Here, we incubate tropical upland soil slurries with isotopically labelled ammonium and iron(III) to assess the potential for anaerobic ammonium oxidation coupled to iron(III) reduction, otherwise known as Feammox, in these soils. We show that Feammox can produce dinitrogen, nitrite or nitrate in tropical upland soils. Direct dinitrogen production was the dominant Feammox pathway, short-circuiting the nitrogen cycle and resulting in ecosystem nitrogen losses. Rates were comparable to aerobic nitrification and to denitrification, the latter being the only other process known to produce dinitrogen in terrestrial ecosystems. We suggest that Feammox could fuel nitrogen losses in ecosystems rich in poorly crystalline iron minerals, with low or fluctuating redox conditions.

Yang, Wendy H.; Weber, Karrie A.; Silver, Whendee L.

2012-08-01

156

Tandem Mass Spectrometry in Physiology  

NSDL National Science Digital Library

Tandem mass spectrometry coupled to liquid chromatography (LC-MS/MS) allows identification of proteins in a complex mixture without need for protein purification ("shotgun" proteomics). Recent progress in LC-MS/MS-based quantification, phosphoproteomic analysis, and targeted LC-MS/MS using multiple reaction monitoring (MRM) has made LC-MS/MS a powerful tool for the study of cell physiology.

2007-12-01

157

Initial operation of ORIC with tandem injection  

SciTech Connect

Coupled operation of the 25 MV tandem and ORIC was achieved on January 27, 1981. The initial beam was 324 MeV /sup 16/O/sup 8 +/ followed shortly by oxygen at 400 MeV-the maximum design energy. Following additional installation and testing of the tandem, coupled operation for a nuclear physics experiment began in August. Performance of the system was in close agreement with that predicted from calculations.

Ludemann, C.A.; Ball, J.B.; Beckers, R.M.; Cleary, T.P.; Hudson, E.D.; Lord, R.S.; Martin, J.A.; Milner, W.T.; Mosko, S.W.; Ziegler, N.F.

1981-01-01

158

Multi-residue analysis of steroids at sub-ng\\/L levels in surface and ground-waters using liquid chromatography coupled to tandem mass spectrometry  

Microsoft Academic Search

Most analytical methodologies currently available for the determination of steroids in water only identify a few representative compounds (mainly estrogens). In this context, a multi-residue methodology based on liquid chromatography–tandem mass spectrometry was developed for the determination of 26 steroids including natural and synthetic estrogens, progestagens and androgens. The method described involves limited sample preparation as it includes a filtration

Emmanuelle Vulliet; Laure Wiest; Robert Baudot; Marie-Florence Grenier-Loustalot

2008-01-01

159

Increased levels of hydrogen peroxide and nitric oxide in male partners of infertile couples.  

PubMed

We investigated the prevalence of oxidative stress in male partners of infertile couples displaying different inflammation patterns in their genital tract and/or oligospermia. The levels of acknowledged oxidative stress markers (8-isoprostanes [8-EPI], diene conjugates, reactive oxygen species-total antioxidant capacity [ROS-TAC] score) were elevated in both leukocytospermic men and subjects whose inflammation was limited only to expressed prostatic secretion and/or post-massage urine. Oligospermic men with severe inflammation were different from oligospermic men who had no inflammation at all - the former had elevated 8-EPI, diene conjugates and ROS-TAC score when compared to the latter indicating that inflammation has substantially more significant impact on oxidative stress markers than oligospermia status. At the same time nitric oxide (NO) and hydrogen peroxide (H2 O2 ) levels were significantly increased not only in the men with severe inflammation but also in men with borderline inflammation in their genital tact and in men having non-inflammatory oligospermia. NO, H2 O2 and 8-EPI were negatively correlated with per cent of normal sperms, and NO and H2 O2 showed negative correlation also with sperm count. We can conclude that in men presenting with couple infertility the acknowledged oxidative stress markers are substantially associated with markers of inflammation in genital tract while NO and H2 O2 display high levels also in patients with mild inflammation and non-inflammatory oligospermia. PMID:24106058

Kullisaar, T; Türk, S; Kilk, K; Ausmees, K; Punab, M; Mändar, R

2013-09-17

160

Bending localization of nitrous oxide under anharmonicity and Fermi coupling: the dynamical potential approach  

NASA Astrophysics Data System (ADS)

This paper studies the vibrational nonlinear dynamics of nitrous oxide with Fermi coupling between the symmetric stretching and bending coordinates by classical dynamical potential approach. This is a global approach in the sense that the overall dynamics is evidenced by the classical nonlinear variables such as the fixed points and the focus are on a set of levels instead of individual ones. The dynamics of nitrous oxide is demonstrated to be not so much dependent on the excitation energy. Moreover, the localized bending mode is shown to be ubiquitous in all the energy range studied.

Zhang, Chi; Fang, Chao; Wu, Guo-Zhen

2010-11-01

161

On-line measurement of oxidative degradation kinetics for trace gasoline contaminants in aqueous solutions and natural water by membrane introduction tandem mass spectrometry.  

PubMed

Membrane introduction mass spectrometry (MIMS) was used to directly monitor the loss of trace gasoline contaminants (benzene, toluene, 2-methylthiophene and methylcyclohexane) in nanomolar (ppb) aqueous solutions under a variety of UV-induced advanced oxidation processes (AOP). The decay kinetics of these contaminants were followed simultaneously in "real-time" via tandem mass spectrometric techniques by re-circulating the reaction mixture in a closed loop over a semi-permeable membrane interface. The photocatalyzed degradations were observed to follow pseudo-first-order kinetics with rate constants ranging from 0.006 to 0.2 min?¹ depending on the reaction conditions. We report rate enhancements for several UV-based advanced oxidative processes using physiosorbed titanium dioxide (TiO?/UV, TiO?/UV/O?, TiO?/UV/H?O?) and compare these to the direct photolysis of H?O? under otherwise identical conditions. The relative degradation rates of 4 trace contaminants are reported for reactions carried out in the same solution. The degradation kinetics were also monitored directly in a natural surface water spiked with the same contaminant suite. The observed decay kinetics in the presence of TiO? in air-saturated natural water were similar to those carried out in deionized water. However, when the photo-oxidation was enhanced by the addition of H?O?, the degradation was markedly slower in natural water relative to deionized water due to competition for photons by dissolved organic matter. This work further demonstrates the use of MIMS as a sensitive on-line measurement technique for "in-situ" reaction monitoring of organic contaminants at environmentally relevant concentrations in complex solutions and reactive media. PMID:20924917

Nelson, Janet H L; Friesen, Duane A; Gill, Chris G; Krogh, Erik T

2010-11-01

162

Mismatched wear couple zirconium oxide and aluminum oxide in total hip arthroplasty  

Microsoft Academic Search

A patient complained about a squeaking noise in his total hip arthroplasty. Clinical evaluation revealed good function, and there were no signs of loosening on the radiograph. Physiotherapy did not alter this phenomenon, and ultimately a revision was performed 42 months after the first surgery. The analysis of the retrievals revealed that a zirconium oxide ceramic head had been paired

Michael Morlock; Roman Nassutt; Rolf Janssen; Gerd Willmann; Matthias Honl

2001-01-01

163

Plasma assisted oxidation of perovskites for forming high temperature superconductors using inductively coupled discharges  

Microsoft Academic Search

This patent describes a method for plasma assisted oxidation of a perovskite material. It comprises placing the perovskite material in a toroidally shaped inductively coupled plasma reactor; operating the plasma reactor; operating the plasma reactor with an alternating current power supply at a frequency below 5 MHz; operating the plasma reactor with a power density between 0.1 and 10 W\\/cm³;

M. Borden; K. Daniell; M. Magida; C. Zarowin

1992-01-01

164

Efforts to improve coupled in situ chemical oxidation with bioremediation: a review of optimization strategies  

Microsoft Academic Search

Purpose  In order to provide highly effective yet relatively inexpensive strategies for the remediation of recalcitrant organic contaminants,\\u000a research has focused on in situ treatment technologies. Recent investigation has shown that coupling two common treatments—in\\u000a situ chemical oxidation (ISCO) and in situ bioremediation—is not only feasible but in many cases provides more efficient and\\u000a extensive cleanup of contaminated subsurfaces. However, the

Nora B. Sutton; J. Tim C. Grotenhuis; Alette A. M. Langenhoff; Huub H. M. Rijnaarts

2011-01-01

165

A Critical Assessment of Li\\/MgO-Based Catalysts for the Oxidative Coupling of Methane  

Microsoft Academic Search

Li\\/MgO is one of the most frequently investigated catalysts for the oxidative coupling of methane. Besides catalytic testing, it is also a suitable system to perform surface science experiments and quantum chemical calculations, which is not possible for many other active catalysts. However, the real structure of Li\\/MgO, the nature of the active center and the structure - activity relationship

Sebastian Arndt; Guillaume Laugel; Sergey Levchenko; Raimund Horn; Manfred Baerns; Matthias Scheffler; Robert Schlögl; Reinhard Schomäcker

2011-01-01

166

Proton translocation coupled to formate oxidation in anaerobically grown fermenting Escherichia coli  

Microsoft Academic Search

Proton translocation, coupled to formate oxidation and hydrogen evolution, was studied in anaerobically grown fermenting Escherichia coli JW136 carrying hydrogenase 1 (hya) and hydrogenase 2 (hyb) double deletions. Rapid acidification of the medium by EDTA-treated anaerobic suspension of the whole cells or its alkalization by inverted membranes was observed in response to application of formate. The formate-dependent proton translocation and

Marta Hakobyan; Harutjun Sargsyan; Karine Bagramyan

2005-01-01

167

CuCl-mediated intramolecular oxidative coupling of aryl- and alkenyltrimethylstannane functions  

PubMed

[reaction: see text] The syntheses of bis-trimethylstannanes 8, 10, 12-14, 16, 18, 21, and 22 are described. Treatment of these substances with approximately 5 equiv of CuCl in DMF at rt for 30-60 min effects, in each case, oxidative coupling between the two sp2 carbon centers bearing the Me3Sn function to produce good-to-excellent yields of tricyclic products 23-31, respectively. PMID:10814356

Piers; Yee; Gladstone

2000-02-24

168

An in situ XRD investigation of singly and doubly promoted manganese oxide methane coupling catalysts  

Microsoft Academic Search

In situ X-ray diffraction (XRD) and concurrent measurements of catalytic performance have been used to characterize the solid phases present during various stages in the history of working methane coupling catalytic systems. Three such systems were studied: unpromoted, K-promoted, and KCl-promoted manganese oxide. In each case the effect of pulses of CHClâ on the activity, selectivity, and catalyst structure was

G. D. Moggridge; T. Rayment; R. M. Lambert

1992-01-01

169

Coupled effects of temperature gradient and oxidation on thermal stress in thermal barrier coating system  

Microsoft Academic Search

The thermal stress fields in thermal barrier coating (TBC) system are studied in the present paper. The thermal stress fields are induced by the non-linear coupled effect of temperature gradient, oxidation, thermal fatigue, creep, morphology of TBC system as well as cooling rate. TBC system is assumed to be partially stabilized ZrO2 by 8 wt.% Y2O3 (PSZ) or mullite over

Y. C. Zhou; T. Hashida

2001-01-01

170

Facile synthesis of dibranched conjugated dienes via palladium-catalyzed oxidative coupling of N-tosylhydrazones.  

PubMed

A facile and highly regioselective Pd-catalyzed oxidative coupling of N-tosylhydrazones providing efficient access to 2,3-disubstituted-1,3-butadienes has been developed. This process features readily available starting materials and mild reaction conditions. Further transformations of the obtained dibranched 1,3-dienes, through Diels-Alder reactions and indene synthesis, are also demonstrated, which reveal their great potential for synthetic utility. PMID:23991430

Jiang, Huanfeng; He, Li; Li, Xianwei; Chen, Huoji; Wu, Wanqing; Fu, Wei

2013-08-29

171

Study of kinetic desorption rate constant in fish muscle and agarose gel model using solid phase microextraction coupled with liquid chromatography with tandem mass spectrometry.  

PubMed

This study aims to use solid phase microextraction (SPME), a simple tool to investigate diffusion rate (time) constant of selected pharmaceuticals in gel and fish muscle by comparing desorption rate of diffusion of the drugs in both agarose gel prepared with phosphate-buffered saline (PBS; pH 7.4) and fish muscle. The gel concentration (agarose gel model) that could be used to simulate tissue matrix (fish muscle) for free diffusion of drugs under in vitro and in vivo conditions was determined to model mass transfer phenomena between fibre polymer coating and environmental matrix such that partition coefficients and desorption time constant (diffusion coefficient) can be determined. SPME procedure involves preloading the extraction phase (fibre) with the standards from spiked PBS for 1h via direct extraction. Subsequently, the preloaded fibre is introduced to the sample such fish or agarose gel for specified time ranging from 0.5 to 60 h. Then, fibre is removed at specified time and desorbed in 100 ?L of desorption solution (acetonitrile: water 1:1) for 90 min under agitation speed of 1000 rpm. The samples extract were immediately injected to the instrument and analysed using liquid chromatography coupled with tandem mass spectrometry (LC/MS/MS). The limit of detection of the method in gel and fish muscle was 0.01-0.07 ng mL(-1) and 0.07-0.34 ng g(-1), respectively, while the limit quantification was 0.10-0.20 ng mL(-1) in gel samples and 0.40-0.97 ng g(-1) in fish sample. The reproducibility of the method was good (5-15% RSD). The results suggest that kinetics of desorption of the compounds in fish tissue and different viscosity of gel can be determined using desorption time constant. In this study, desorption time constant which is directly related to desorption rate (diffusion kinetics) of selected drugs from the fibre to the gel matrix is faster as the viscosity of the gel matrix reduces from 2% (w/v) to 0.8% (w/v). As the concentration of gel reduces, viscosity of the gel will be reduced therefore allowing faster diffusion which invariably affect desorption time constant. Also, desorption time constant of model drugs in the fish muscle and 0.8-0.9% (w/v) gel model are similar based on free diffusion of studied compounds. In addition, in vitro and in vivo desorption time constant comparison shows that desorption time constant in an in vivo system (live fish muscle) is generally higher than an in vitro system (dead fish muscle) except for sertraline and nordiazepam. This study demonstrates SPME as a simple investigative tool to understand kinetics of desorption in an in vivo system with a goal to measure desorption rate of pharmaceuticals in fish. PMID:22884200

Togunde, Oluranti Paul; Oakes, Ken; Servos, Mark; Pawliszyn, Janusz

2011-12-24

172

Comprehensive experimental and numerical optimization of surface morphology of transparent conductive oxide films for tandem thin film photovoltaic cells  

Microsoft Academic Search

Typical thin-film photovoltaic cells incorporate a textured transparent conductive oxide to efficiently harvest solar energy. What should be the ideally desired morphology of this textured surface for best cell performance - is highly debated but remains an unsolved mystery. We present a comprehensive methodology to 1) accurately model, 2) extract macroscopically sufficient statistical finger-prints and 3) predict best desired values

Mukul Agrawal; Michel Frei; Yashraj Bhatnagar; Tobias Repmann; Karin Witting; J. Schroeder; Chris Eberspacher

2010-01-01

173

Analysis of phenolic compounds by high-performance liquid chromatography coupled to electrospray ionization tandem mass spectrometry in senescent and water-stressed tobacco  

Microsoft Academic Search

Evaluation of a significant part of the phenylpropanoid pathway metabolites is facilitated by the fast high-performance liquid chromatography with electrospray ionization tandem mass spectrometry (LC–MS\\/MS) analytical method. The technology described was applied in tobacco plants (Nicotiana tabacum L. cv. Wisconsin) to identify 20 phenolic compounds and to detect differences in phenylpropanoid profiles in two types of experiments. In the first

Laura Torras-Claveria; Olga Jáuregui; Carles Codina; Antonio F. Tiburcio; Jaume Bastida; Francesc Viladomat

174

Quantitation of entacapone glucuronide in rat plasma by on-line coupled restricted access media column and liquid chromatography–tandem mass spectrometry  

Microsoft Academic Search

A column-switching liquid chromatography–electrospray ionization-tandem mass spectrometric (LC–ESI-MS–MS) method was developed for the direct analysis of entacapone glucuronide in plasma. The plasma samples (5 ?l) were injected onto a C18-alkyl-diol silica (ADS) column and the matrix compounds were washed to waste with a mixture of 20 mM ammonium acetate solution at pH 4.0–acetonitrile (97:3). The retained analyte fraction containing (E)-

Helena Keski-Hynnilä; Knut Raanaa; Markus Forsberg; Pekka Männistö; Jyrki Taskinen; Risto Kostiainen

2001-01-01

175

Photoinitiated Coupling of Unmodified Monosaccharides to Iron Oxide Nanoparticles for Sensing Proteins and Bacteria  

PubMed Central

We report a versatile approach for the immobilization of unmodified monosaccharides onto iron oxide nanoparticles. Covalent coupling of the carbohydrate onto iron oxide nanoparticle surfaces was accomplished by the CH insertion reaction of photochemically activated phosphate-functionalized perfluorophenylazides (PFPAs), and the resulting glyconanoparticles were characterized by IR, TGA, and TEM. The surface-bound d-mannose showed the recognition ability towards Concanavalin A and Escherichia coli strain ORN178 that possesses mannose-specific receptor sites. Owing to the simplicity and versatility of the technique, together with the magnetic property of iron oxide nanoparticles, the methodology developed in this study serves as a general approach for the preparation of magnetic glyconanoparticles to be used in clinical diagnosis, sensing, and de-contamination.

Liu, Li-Hong; Dietsch, Herve; Schurtenberger, Peter; Yan, Mingdi

2009-01-01

176

Sulfide Oxidation Coupled to Arsenate Reduction by a Diverse Microbial Community in a Soda Lake†  

PubMed Central

We characterized the arsenate-reducing, sulfide-oxidizing population of Mono Lake, California, by analyzing the distribution and diversity of rrnA, cbbL, and dissimilatory arsenate reductase (arrA) genes in environmental DNA, arsenate-plus sulfide-amended lake water, mixed cultures, and isolates. The arsenate-reducing community was diverse. An organism represented by an rrnA sequence previously retrieved from Mono Lake and affiliated with the Desulfobulbaceae (Deltaproteobacteria) appears to be an important member of the arsenate-reducing, sulfide-oxidizing community. Sulfide oxidation coupled with arsenate reduction appears to proceed via a two-electron transfer, resulting in the production of arsenite and an intermediate S compound that is subsequently disproportionated. A realgar-like As/S mineral was formed in some experiments.

Hollibaugh, James T.; Budinoff, Charles; Hollibaugh, Ryan A.; Ransom, Briana; Bano, Nasreen

2006-01-01

177

Quantification of DNA damage products resulting from deamination, oxidation and reaction with products of lipid peroxidation by liquid chromatography isotope dilution tandem mass spectrometry  

PubMed Central

The analysis of damage products as biomarkers of inflammation has been hampered by a poor understanding of the chemical biology of inflammation, the lack of sensitive analytical methods, and a focus on single chemicals as surrogates for inflammation. To overcome these problems, we developed a general and sensitive liquid chromatographic tandem mass spectrometry (LC/MS-MS) method to quantify, in a single DNA sample, the nucleoside forms of seven DNA lesions reflecting the range of chemistries associated with inflammation: 2?-deoxyuridine, 2?-deoxyxanthosine, and 2?-deoxyinosine from nitrosative deamination; 8-oxo-2?-deoxyguanosine from oxidation; and 1,N2-etheno-2?-deoxyguanosine, 1,N6-etheno-2?-deoxyadenosine, and 3,N4-etheno-2?-deoxycytidine arising from reaction of DNA with lipid peroxidation products. Using DNA purified from cells or tissues under conditions that minimize artifacts, individual nucleosides are purified by HPLC and quantified by isotope-dilution, electrospray ionization LC/MS-MS. The method can be applied to other DNA damage products and requires 4-6 days to complete depending upon the number of samples.

Taghizadeh, Koli; McFaline, Jose L.; Pang, Bo; Sullivan, Matthew; Dong, Min; Plummer, Elaine; Dedon, Peter C.

2009-01-01

178

Oxidative cascade reactions yielding polyhydroxy-theaflavins and theacitrins in the formation of black tea thearubigins: evidence by tandem LC-MS.  

PubMed

LC-MS(n) and direct infusion-MS(n) have been applied for the first time to the characterisation of crude thearubigins isolated from black tea. The data generated have been used to test two hypotheses of thearubigin structure: (i) that a significant fraction of the thearubigins consist of polyhydroxylated derivatives of the better-known catechin dimers (theaflavins, theaflavin mono- and di-gallates, theacitrins) in redox equilibrium with their associated quinones; and (ii) that a significant fraction of the thearubigins consist of dicarboxylic acids generated by oxidative cleavage of aromatic diols. The data were consistent with the polyhydroxylation hypothesis and did not support the dicarboxylic acid hypothesis. Evidence is presented for the presence in crude thearubigins of at least 29 hydroxylated theaflavins (with between one and six oxygen insertions), at least 12 theaflavin mono-gallates (with between one and six oxygen insertions), at least nine theaflavin di-gallates (with between one and four oxygen insertions), and at least ten theacitrin mono-gallates (with between one and four oxygen insertions). Evidence is also presented for at least ten mono- or di-quinone forms of the parent compounds and hydroxylated derivatives in each of these homologous series. A general method for the analysis of complex mixtures by tandem LC-MS is furthermore introduced and established. PMID:21776470

Kuhnert, Nikolai; Clifford, Michael N; Müller, Anja

2010-10-14

179

Measurement of tissue acyl-CoAs using flow-injection tandem mass spectrometry: acyl-CoA profiles in short-chain fatty acid oxidation defects  

PubMed Central

The primary accumulating metabolites in fatty acid oxidation defects are intramitochondrial acyl-CoAs. Typically, secondary metabolites such as acylcarnitines, acylglycines and dicarboxylic acids are measured to study these disorders. Methods have not been adapted for tissue acyl-CoA measurement in defects with primarily acyl-CoA accumulation. Our objective was to develop a method to measure fatty acyl-CoA species that are present in tissues of mice with fatty acid oxidation defects using flow-injection tandem mass spectrometry. Following the addition of internal standards of [13C2] acetyl-CoA, [13C8] octanoyl-CoA, and [C17] heptadecanoic CoA, acyl-CoA’s are extracted from tissue samples and are injected directly into the mass spectrometer. Data is acquired using a 506.9 neutral loss scan and multiple reaction-monitoring (MRM). This method can identify all long, medium and short-chain acyl-CoA species in wild type mouse liver including predicted 3-hydroxyacyl-CoA species. We validated the method using liver of the short-chain-acyl-CoA dehydrogenase (SCAD) knock-out mice. As expected, there is a significant increase in [C4] butyryl-CoA species in the SCAD ?/? mouse liver compared to wild type. We then tested the assay in liver from the short-chain 3-hydroxyacyl-CoA dehydrogenase (SCHAD) deficient mice to determine the profile of acyl-CoA accumulation in this less predictable model. There was more modest accumulation of medium chain species including 3-hydroxyacyl-CoA’s consistent with the known chain-length specificity of the SCHAD enzyme.

Palladino, Andrew A.; Chen, Jie; Kallish, Staci; Stanley, Charles A.; Bennett, Michael J.

2013-01-01

180

Tandem betatron  

DOEpatents

Two betatrons are provided in tandem for alternately accelerating an electron beam to avoid the single flux swing limitation of conventional betatrons and to accelerate the electron beam to high energies. The electron beam is accelerated in a first betatron during a period of increasing magnetic flux. The electron beam is extracted from the first betatron as a peak magnetic flux is reached and then injected into a second betatron at a time of minimum magnetic flux in the second betatron. The cycle may be repeated until the desired electron beam energy is obtained. In one embodiment, the second betatron is axially offset from the first betatron to provide for electron beam injection directly at the axial location of the beam orbit in the second betatron.

Keinigs, R.K.

1991-01-01

181

Tandem betatron  

DOEpatents

Two betatrons are provided in tandem for alternately accelerating an electron beam to avoid the single flux swing limitation of conventional betatrons and to accelerate the electron beam to high energies. The electron beam is accelerated in a first betatron during a period of increasing magnetic flux. The electron beam is extracted from the first betatron as a peak magnetic flux is reached and then injected into a second betatron at a time of minimum magnetic flux in the second betatron. The cycle may be repeated until the desired electron beam energy is obtained. In one embodiment, the second betatron is axially offset from the first betatron to provide for electron beam injection directly at the axial location of the beam orbit in the second betatron.

Keinigs, R.K.

1991-12-31

182

Anaerobic oxidation of methane coupled to nitrate reduction in a novel archaeal lineage.  

PubMed

Anaerobic oxidation of methane (AOM) is critical for controlling the flux of methane from anoxic environments. AOM coupled to iron, manganese and sulphate reduction have been demonstrated in consortia containing anaerobic methanotrophic (ANME) archaea. More recently it has been shown that the bacterium Candidatus 'Methylomirabilis oxyfera' can couple AOM to nitrite reduction through an intra-aerobic methane oxidation pathway. Bioreactors capable of AOM coupled to denitrification have resulted in the enrichment of 'M. oxyfera' and a novel ANME lineage, ANME-2d. However, as 'M. oxyfera' can independently couple AOM to denitrification, the role of ANME-2d in the process is unresolved. Here, a bioreactor fed with nitrate, ammonium and methane was dominated by a single ANME-2d population performing nitrate-driven AOM. Metagenomic, single-cell genomic and metatranscriptomic analyses combined with bioreactor performance and (13)C- and (15)N-labelling experiments show that ANME-2d is capable of independent AOM through reverse methanogenesis using nitrate as the terminal electron acceptor. Comparative analyses reveal that the genes for nitrate reduction were transferred laterally from a bacterial donor, suggesting selection for this novel process within ANME-2d. Nitrite produced by ANME-2d is reduced to dinitrogen gas through a syntrophic relationship with an anaerobic ammonium-oxidizing bacterium, effectively outcompeting 'M. oxyfera' in the system. We propose the name Candidatus 'Methanoperedens nitroreducens' for the ANME-2d population and the family Candidatus 'Methanoperedenaceae' for the ANME-2d lineage. We predict that 'M. nitroreducens' and other members of the 'Methanoperedenaceae' have an important role in linking the global carbon and nitrogen cycles in anoxic environments. PMID:23892779

Haroon, Mohamed F; Hu, Shihu; Shi, Ying; Imelfort, Michael; Keller, Jurg; Hugenholtz, Philip; Yuan, Zhiguo; Tyson, Gene W

2013-07-28

183

Regiocontrolled aerobic oxidative coupling of indoles and benzene using Pd catalysts with 4,5-diazafluorene ligands  

PubMed Central

Palladium-catalyzed aerobic oxidative cross-couplings of indoles and benzene have been achieved by using 4,5-diazafluorene derivatives as ancillary ligands. Proper choice of the neutral and anionic ligands enables control over the reaction regioselectivity.

Campbell, Alison N.; Meyer, Eric B.

2011-01-01

184

Interchain coupled chain dynamics of poly(ethylene oxide) in blends with poly(methyl methacrylate): Coupling model analysis  

NASA Astrophysics Data System (ADS)

Quasielastic neutron scattering and molecular dynamics simulation data from poly(ethylene oxide) (PEO)/poly(methyl methacrylate) (PMMA) blends found that for short times the self-dynamics of PEO chain follows the Rouse model, but at longer times past tc = 1-2 ns it becomes slower and departs from the Rouse model in dependences on time, momentum transfer, and temperature. To explain the anomalies, others had proposed the random Rouse model (RRM) in which each monomer has different mobility taken from a broad log-normal distribution. Despite the success of the RRM, Diddens et al. [Eur. Phys. Lett. 95, 56003 (2011)] extracted the distribution of friction coefficients from the MD simulations of a PEO/PMMA blend and found that the distribution is much narrower than expected from the RRM. We propose a simpler alternative explanation of the data by utilizing alone the observed crossover of PEO chain dynamics at tc. The present problem is just a special case of a general property of relaxation in interacting systems, which is the crossover from independent relaxation to coupled many-body relaxation at some tc determined by the interaction potential and intermolecular coupling/constraints. The generality is brought out vividly by pointing out that the crossover also had been observed by neutron scattering from entangled chains relaxation in monodisperse homopolymers, and from the segmental ?-relaxation of PEO in blends with PMMA. The properties of all the relaxation processes in connection with the crossover are similar, despite the length scales of the relaxation in these systems are widely different.

Ngai, K. L.; Wang, Li-Min

2011-11-01

185

Identification of Novel in vivo MAP Kinase Substrates in Arabidopsis thaliana Through Use of Tandem Metal Oxide Affinity Chromatography*  

PubMed Central

Mitogen-activated protein kinase (MPK) cascades are important for eukaryotic signal transduction. They convert extracellular stimuli (e.g. some hormones, growth factors, cytokines, microbe- or damage-associated molecular patterns) into intracellular responses while at the same time amplifying the transmitting signal. By doing so, they ensure proper performance, and eventually survival, of a given organism, for example in times of stress. MPK cascades function via reversible phosphorylation of cascade components MEKKs, MEKs, and MPKs. In plants the identity of most MPK substrates remained elusive until now. Here, we provide a robust and powerful approach to identify and quantify, with high selectivity, site-specific phosphorylation of MPK substrate candidates in the model plant Arabidopsis thaliana. Our approach represents a two-step chromatography combining phosphoprotein enrichment using Al(OH)3-based metal oxide affinity chromatography, tryptic digest of enriched phosphoproteins, and TiO2-based metal oxide affinity chromatography to enrich phosphopeptides from complex protein samples. When applied to transgenic conditional gain-of-function Arabidopsis plants supporting in planta activation of MPKs, the approach allows direct measurement and quantification ex vivo of site-specific phosphorylation of several reported and many yet unknown putative MPK substrates in just a single experiment.

Hoehenwarter, Wolfgang; Thomas, Martin; Nukarinen, Ella; Egelhofer, Volker; Rohrig, Horst; Weckwerth, Wolfram; Conrath, Uwe; Beckers, Gerold J. M.

2013-01-01

186

Denitrification coupled to pyrite oxidation and changes in groundwater quality in a shallow sandy aquifer  

NASA Astrophysics Data System (ADS)

This study focuses on denitrification in a sandy aquifer using geochemical analyses of both sediment and groundwater, combined with groundwater age dating ( 3H/ 3He). The study sites are located underneath cultivated fields and an adjacent forested area at Oostrum, The Netherlands. Shallow groundwater in the region has high nitrate concentrations (up to 8 mM) due to intense fertilizer application. Nitrate removal from the groundwater below cultivated fields correlates with sulfate production, and the release of dissolved Fe 2+ and pyrite-associated trace metals (e.g. As, Ni, Co and Zn). These results, and the presence of pyrite in the sediment matrix within the nitrate removal zone, indicate that denitrification coupled to pyrite oxidation is a major process in the aquifer. Significant nitrate loss coupled to sulfate production is further confirmed by comparing historical estimates of regional sulfate and nitrate loadings to age-dated groundwater sulfate and nitrate concentrations, for the period 1950-2000. However, the observed increases in sulfate concentration are about 50% lower than would be expected from complete oxidation of pyrite to sulfate, possibly due to the accumulation of intermediate oxidation state sulfur compounds, such as elemental sulfur. Pollutant concentrations (NO 3, Cl, As, Co and Ni) measured in the groundwater beneath the agricultural areas in 1996 and 2006 show systematic decreases most likely due to declining fertilizer use.

Zhang, Yan-Chun; Slomp, Caroline P.; Broers, Hans Peter; Passier, Hilde F.; Cappellen, Philippe Van

2009-11-01

187

Enzymatic processing of fumiquinazoline F: a tandem oxidative-acylation strategy for the generation of multicyclic scaffolds in fungal indole alkaloid biosynthesis.  

PubMed

Aspergillus fumigatus Af293 is a known producer of quinazoline natural products, including the antitumor fumiquinazolines, of which the simplest member is fumiquinazoline F (FQF) with a 6-6-6 tricyclic core derived from anthranilic acid, tryptophan, and alanine. FQF is the proposed biological precursor to fumiquinazoline A (FQA) in which the pendant indole side chain has been modified via oxidative coupling of an additional molecule of alanine, yielding a fused 6-5-5 imidazoindolone. We recently identified fungal anthranilate-activating nonribosomal peptide synthetase (NRPS) domains through bioinformatics approaches. One domain previously identified is part of the trimodular NRPS Af12080, which we predict is responsible for FQF formation. We now show that two adjacent A. fumigatus ORFs, a monomodular NRPS Af12050 and a flavoprotein Af12060, are necessary and sufficient to convert FQF to FQA. Af12060 oxidizes the 2',3'-double bond of the indole side chain of FQF, and the three-domain NRPS Af12050 activates l-Ala as the adenylate, installs it as the pantetheinyl thioester on its carrier protein domain, and acylates the oxidized indole for subsequent intramolecular cyclization to create the 6-5-5 imidazolindolone of FQA. This work provides experimental validation of the fumiquinazoline biosynthetic cluster of A. fumigatus Af293 and describes an oxidative annulation biosynthetic strategy likely shared among several classes of polycyclic fungal alkaloids. PMID:20804163

Ames, Brian D; Liu, Xinyu; Walsh, Christopher T

2010-09-08

188

Synthesis of novel bis(perfluorophenyl azides) coupling agents: Evaluation of their performance by crosslinking of poly(ethylene oxide)  

Microsoft Academic Search

Novel bis(perfluorophenyl azides) coupling agents, containing spacer arms from ethylene or ethylene glycol subunits, were successfully synthesized. Nitrenes photogenerated from these novel bis(PFPA) coupling agents were applied successfully to the cross-linking of poly(ethylene oxide) (PEO10,000) in either aqueous medium or at the solid state, thus, we demonstrated the potential of these bis(PFPA) molecules as promising coupling agents in surface engineering.

Hakim Mehenni; Osman M. Bakr

2011-01-01

189

N?Benzyl DABCO Tribromide–Promoted Oxidative Coupling of Benzyl Cyanides: A Convenient Procedure for the Synthesis of ?, ???Dicyanostilbenes  

Microsoft Academic Search

A convenient and efficient procedure was developed for preparing ?,???icyanostilbenes through the oxidative coupling reaction of benzyl cyanide derivatives using N?benzyl DABCO tribromide as the oxidative bromination reagent in the presence of K2CO3 as a base.

Firouz Matloubi Moghaddam; Dordaneh Zargarani; Hassan Zali Boeini

2008-01-01

190

Oxidative coupling of methane in a mixed-conducting perovskite membrane reactor  

Microsoft Academic Search

Ionic-electronic mixed-conducting perovskite-type oxide La0.6Sr0.4Co0.8Fe0.2O3 was applied as a dense membrane for oxygen supply in a reactor for methane coupling. The oxygen permeation properties were studied in the pO2-range of 10?3?1 bar at 1073–1273 K, using helium as a sweeping gas at the permeate side of the membrane. The oxygen semi-permeability has a value close to 1 mmol m?2 s?1

J. E. ten Elshof; H. J. M. Bouwmeester; H. Verweij

1995-01-01

191

Transformation of trace organic compounds in drinking water by enzymatic oxidative coupling  

SciTech Connect

Enzymatic methods have shown promise for removing aromatic compounds from (high-strength) industrial wastewater. The removal of these compounds was studied at low levels that might be encountered in surface waters which receive some industrial discharge. The results indicate that enzymatic oxidative coupling using horseradish peroxidase and hydrogen perioxide may be useful in eliminating some aromatics that are not well-removed in biological or physical water treatment, but the nature of the byproducts must be determined to assure that the products are not more undesirable than the initial compounds. 21 references, 4 figures, 2 tables.

Maloney, S.W.; Manem, J.; Mallevialle, J.; Fiessinger, F.

1986-03-01

192

Catalytic oxidation of CO by N2O conducted via the neutral oxide cluster couple VO2/VO3.  

PubMed

Neutral vanadium and cobalt oxide clusters are generated at the same time employing a V-Co mixed target. Experimental results indicate that the reaction VO2 + N2O ? VO3 + N2 occurs in a fast flow reactor. This interpretation is further supported for a gas mixture of CO and N2O in the flow cell: regeneration of VO2 is observed for this case via the reaction VO3 + CO ? VO2 + CO2. A full catalytic cycle for the reaction N2O + CO ? N2 + CO2 is thus complete at room temperature enabled by the VO2/VO3 cluster couple. DFT calculations demonstrate that the entire catalytic process is overall barrierless and reproduce the experimental results quite well. PMID:23685848

Wang, Zhe-Chen; Yin, Shi; Bernstein, Elliot R

2013-05-17

193

Comprehensive separation and analysis of alkaloids from Stephania yunnanensis by counter-current chromatography coupled with liquid chromatography tandem mass spectrometry analysis.  

PubMed

The polar compounds such as alkaloid compounds are important bioactive components in traditional Chinese medicines. In present study, a comprehensive method for separation and analysis of polar compounds from the polar fraction of traditional Chinese medicine Stephania yunnanensis was established. Both the major components and minor components were analyzed by counter-current chromatography combined with liquid chromatography tandem mass spectrometry (LC-MS(n)). From 50 mg polar fraction of crude extract, 15.2mg corydine and 4.8 mg stepharine with purities over 90% were successfully separated via a polar solvent system n-butanol: methanol: water (4:1:5, v/v) with 10 mM NaOH as an additive in the lower phase, in one step operation. Their structures were further identified by 1H NMR and FTICR-MS. Besides, three minor components were identified by HPLC-MS(n) based on the fragmentation behavior of the purified compounds. PMID:22041142

Dai, Xiaojing; Hu, Ruilin; Sun, Cuirong; Pan, Yuanjiang

2011-10-14

194

Quantitative determination of plant phenolics in Urtica dioica extracts by high-performance liquid chromatography coupled with tandem mass spectrometric detection.  

PubMed

A method for quantification of 45 plant phenolics (including benzoic acids, cinnamic acids, flavonoid aglycones, C- and O-glycosides, coumarins, and lignans) in plant extracts was developed, based on reversed phase HPLC separation of extract components, followed by tandem mass spectrometric detection. The phenolic profile of 80% MeOH extracts of the stinging nettle (Urtica dioica L.) herb, root, stem, leaf and inflorescence was obtained by using this method. Twenty-one of the investigated compounds were present at levels above the reliable quantification limit, with 5-O-caffeoylquinic acid, rutin and isoquercitrin as the most abundant. The inflorescence extracts were by far the richest in phenolics, with the investigated compounds amounting 2.5-5.1% by weight. As opposed to this, the root extracts were poor in phenolics, with only several acids and derivatives being present in significant amounts. The results obtained by the developed method represent the most detailed U. dioica chemical profile so far. PMID:24054211

Or?i?, Dejan; Franciškovi?, Marina; Bekvalac, Kristina; Svir?ev, Emilija; Beara, Ivana; Lesjak, Marija; Mimica-Duki?, Neda

2013-07-27

195

Enzymatic modification of kraft lignin through oxidative coupling with water-soluble phenols.  

PubMed

The aromatic polymer lignin can be modified through promotion of oxidative coupling between phenolic groups on lignin and various phenols. The reaction is initiated by an oxidation of both components, e.g., by using the oxidoreductases laccase or peroxidase. Coupling between phenolic monomers and lignin has previously been studied by the use of radio-labeled phenols. In this study, incorporation of water-soluble phenols into kraft lignin, using laccase as catalyst, was investigated. Several phenols with carboxylic or sulfonic acid groups were used as markers for the incorporation. The modified lignin was isolated and the amount of phenol incorporated was characterized by means of titration, quantitative 1H-NMR, and quantitative 31P-NMR after modification with 2-chloro-4,4,5,5-tetramethyl-1,2,3-dioxaphospholane. Only a few of the phenols studied were found to be incorporated into lignin. When the phenol guaiacol sulfonate was incorporated into kraft lignin, the lignin became water-soluble at pH 2.4 and a low ionic strength due to the introduction of sulfonic acid groups. The content of sulfonic acid groups in the product was 0.5-0.6 mmol/g lignin. A lower amount of 4-hydroxyphenylacetic acid was incorporated under similar conditions. PMID:11525617

Lund, M; Ragauskas, A J

2001-06-01

196

Coupling membrane separation and photocatalytic oxidation processes for the degradation of pharmaceutical pollutants.  

PubMed

The coupling of membrane separation and photocatalytic oxidation has been studied for the removal of pharmaceutical pollutants. The retention properties of two different membranes (nanofiltration and reverse osmosis) were assessed. Comparable selectivity on the separation of pharmaceuticals were observed for both membranes, obtaining a permeate stream with concentrations of each pharmaceutical below 0.5 mg L(-)(1) and a rejected flux highly concentrated (in the range of 16-25 mg L(-)(1) and 18-32 mg L(-)(1) of each pharmaceutical for NF-90 and BW-30 membranes, respectively), when an initial stream of six pharmaceuticals was feeding to the membrane system (10 mg L(-)(1) of each pharmaceutical). The abatement of concentrated pharmaceuticals of the rejected stream was evaluated by means of heterogeneous photocatalytic oxidation using TiO2 and Fe2O3/SBA-15 in presence of hydrogen peroxide as photo-Fenton system. Both photocatalytic treatments showed remarkable removals of pharmaceutical compounds, achieving values between 80 and 100%. The nicotine was the most refractory pollutant of all the studied pharmaceuticals. Photo-Fenton treatment seems to be more effective than TiO2 photocatalysis, as high mineralization degree and increased nicotine removal were attested. This work can be considered an interesting approach of coupling membrane separation and heterogeneous photocatalytic technologies for the successful abatement of pharmaceutical compounds in effluents of wastewater treatment plants. PMID:23863375

Martínez, F; López-Muñoz, M J; Aguado, J; Melero, J A; Arsuaga, J; Sotto, A; Molina, R; Segura, Y; Pariente, M I; Revilla, A; Cerro, L; Carenas, G

2013-07-03

197

Abcb11 deficiency induces cholestasis coupled to impaired ?-fatty acid oxidation in mice.  

PubMed

The bile salt export pump (BSEP) is an ATP-binding cassette transporter that serves as the primary system for removing bile salts from the liver. In humans, deficiency of BSEP, which is encoded by the ABCB11 gene, causes severe progressive cholestatic liver disease from early infancy. In previous studies of Abcb11 deficiency in mice generated on a mixed genetic background, the animals did not recapitulate the human disease. We reasoned that ABCB11 deficiency may cause unique changes in hepatic metabolism that are predictive of liver injury. To test this possibility, we first determined that Abcb11 knock-out (KO) C57BL/6J mice recapitulate human deficiency. Before the onset of cholestasis, Abcb11 KO mice have altered hepatic lipid metabolism coupled with reduced expression of genes important in mitochondrial fatty acid oxidation. This was associated with increased serum free-fatty acids, reduced total white adipose, and marked impairment of long-chain fatty acid ?-oxidation. Importantly, metabolomic analysis confirmed that Abcb11 KO mice have impaired mitochondrial fatty acid ?-oxidation with the elevated fatty acid metabolites phenylpropionylglycine and phenylacetylglycine. These metabolic changes precede cholestasis but may be of relevance to cholestatic disease progression because altered fatty acid metabolism can enhance reactive oxygen species that might exacerbate cholestatic liver damage. PMID:22619174

Zhang, Yuanyuan; Li, Fei; Patterson, Andrew D; Wang, Yao; Krausz, Kristopher W; Neale, Geoffrey; Thomas, Sarah; Nachagari, Deepa; Vogel, Peter; Vore, Mary; Gonzalez, Frank J; Schuetz, John D

2012-05-22

198

Abcb11 Deficiency Induces Cholestasis Coupled to Impaired ?-Fatty Acid Oxidation in Mice*  

PubMed Central

The bile salt export pump (BSEP) is an ATP-binding cassette transporter that serves as the primary system for removing bile salts from the liver. In humans, deficiency of BSEP, which is encoded by the ABCB11 gene, causes severe progressive cholestatic liver disease from early infancy. In previous studies of Abcb11 deficiency in mice generated on a mixed genetic background, the animals did not recapitulate the human disease. We reasoned that ABCB11 deficiency may cause unique changes in hepatic metabolism that are predictive of liver injury. To test this possibility, we first determined that Abcb11 knock-out (KO) C57BL/6J mice recapitulate human deficiency. Before the onset of cholestasis, Abcb11 KO mice have altered hepatic lipid metabolism coupled with reduced expression of genes important in mitochondrial fatty acid oxidation. This was associated with increased serum free-fatty acids, reduced total white adipose, and marked impairment of long-chain fatty acid ?-oxidation. Importantly, metabolomic analysis confirmed that Abcb11 KO mice have impaired mitochondrial fatty acid ?-oxidation with the elevated fatty acid metabolites phenylpropionylglycine and phenylacetylglycine. These metabolic changes precede cholestasis but may be of relevance to cholestatic disease progression because altered fatty acid metabolism can enhance reactive oxygen species that might exacerbate cholestatic liver damage.

Zhang, Yuanyuan; Li, Fei; Patterson, Andrew D.; Wang, Yao; Krausz, Kristopher W.; Neale, Geoffrey; Thomas, Sarah; Nachagari, Deepa; Vogel, Peter; Vore, Mary; Gonzalez, Frank J.; Schuetz, John D.

2012-01-01

199

Effects of nanoparticle and porous metal oxide supports on the activity of palladium catalysts in the oxidative coupling of 4-methylpyridine  

Microsoft Academic Search

The oxidative coupling of 4-methylpyridine to 4,4?-dimethyl-2,2?-bipyridine over palladium oxide is a simple, environmentally friendly, one-step process to produce bipyridines, which are commonly used with transition metal ions to form complexes with interesting properties. However, the reaction is slow and the palladium catalyst deactivates during reaction, which means that catalyst improvements are needed for large-scale production of more economically viable

Luke M. Neal; Daniel Hernandez; Helena E. Hagelin-Weaver

2009-01-01

200

Rapid analysis of multiclass antibiotic residues and some of their metabolites in hospital, urban wastewater and river water by ultra-high-performance liquid chromatography coupled to quadrupole-linear ion trap tandem mass spectrometry.  

PubMed

The present work describes the development of a fast and robust analytical method for the determination of 53 antibiotic residues, covering various chemical groups and some of their metabolites, in environmental matrices that are considered important sources of antibiotic pollution, namely hospital and urban wastewaters, as well as in river waters. The method is based on automated off-line solid phase extraction (SPE) followed by ultra-high-performance liquid chromatography coupled to quadrupole linear ion trap tandem mass spectrometry (UHPLC-QqLIT). For unequivocal identification and confirmation, and in order to fulfill EU guidelines, two selected reaction monitoring (SRM) transitions per compound are monitored (the most intense one is used for quantification and the second one for confirmation). Quantification of target antibiotics is performed by the internal standard approach, using one isotopically labeled compound for each chemical group, in order to correct matrix effects. The main advantages of the method are automation and speed-up of sample preparation, by the reduction of extraction volumes for all matrices, the fast separation of a wide spectrum of antibiotics by using ultra-high-performance liquid chromatography, its sensitivity (limits of detection in the low ng/L range) and selectivity (due to the use of tandem mass spectrometry) The inclusion of ?-lactam antibiotics (penicillins and cephalosporins), which are compounds difficult to analyze in multi-residue methods due to their instability in water matrices, and some antibiotics metabolites are other important benefits of the method developed. As part of the validation procedure, the method developed was applied to the analysis of antibiotics residues in hospital, urban influent and effluent wastewaters as well as in river water samples. PMID:23347979

Gros, Meritxell; Rodríguez-Mozaz, Sara; Barceló, Damià

2013-01-10

201

Weathering of the Rio Blanco Quartz Diorite, Luquillo Mountains, Puerto Rico: Coupling Oxidation, Dissolution, And Fracturing  

SciTech Connect

In the mountainous Rio Icacos watershed in northeastern Puerto Rico, quartz diorite bedrock weathers spheroidally, producing a 0.2-2 m thick zone of partially weathered rock layers ({approx}2.5 cm thickness each) called rindlets, which form concentric layers around corestones. Spheroidal fracturing has been modeled to occur when a weathering reaction with a positive {Delta}V of reaction builds up elastic strain energy. The rates of spheroidal fracturing and saprolite formation are therefore controlled by the rate of the weathering reaction. Chemical, petrographic, and spectroscopic evidence demonstrates that biotite oxidation is the most likely fracture-inducing reaction. This reaction occurs with an expansion in d (0 0 1) from 10.0 to 10.5 {angstrom}, forming 'altered biotite'. Progressive biotite oxidation across the rindlet zone was inferred from thin sections and gradients in K and Fe(II). Using the gradient in Fe(II) and constraints based on cosmogenic age dates, we calculated a biotite oxidation reaction rate of 8.2 x 10{sup -14} mol biotite m{sup -2} s{sup -1}. Biotite oxidation was documented within the bedrock corestone by synchrotron X-ray microprobe fluorescence imaging and XANES. X-ray microprobe images of Fe(II) and Fe(III) at 2 {micro}m resolution revealed that oxidized zones within individual biotite crystals are the first evidence of alteration of the otherwise unaltered corestone. Fluids entering along fractures lead to the dissolution of plagioclase within the rindlet zone. Within 7 cm surrounding the rindlet-saprolite interface, hornblende dissolves to completion at a rate of 6.3 x 10{sup -13} mol hornblende m{sup -2} s{sup -1}: the fastest reported rate of hornblende weathering in the field. This rate is consistent with laboratory-derived hornblende dissolution rates. By revealing the coupling of these mineral weathering reactions to fracturing and porosity formation we are able to describe the process by which the quartz diorite bedrock disaggregates and forms saprolite. In the corestone, biotite oxidation induces spheroidal fracturing, facilitating the influx of fluids that react with other minerals, dissolving plagioclase and chlorite, creating additional porosity, and eventually dissolving hornblende and precipitating secondary minerals. The thickness of the resultant saprolite is maintained at steady state by a positive feedback between the denudation rate and the weathering advance rate driven by the concentration of pore water O{sub 2} at the bedrock-saprolite interface.

Buss, H.L.; Sak, P.B.; Webb, S.M.; Brantley, S.L.

2009-05-12

202

Automated determination of phenolic compounds in wine, berry, and grape samples using 96-blade solid phase microextraction system coupled with liquid chromatography-tandem mass spectrometry.  

PubMed

An automated 96-thin-film solid phase microextraction system was optimized for high throughput analysis of phenolic compounds in wine, berry, and grape samples. Liquid chromatography and tandem mass spectrometry methods were optimized and applied for separation and detection of compounds. Evaluation of five different stationary phases showed that polystyrene-divinylbenzene-polyacrylonitrile (PS-DVB-PAN) is the optimum extraction phase for the extraction of phenolic compounds under study. The thin-film PS-DVB-PAN SPME coating provided almost exhaustive extraction recovery for all phenolics compounds under study, except for naringenin with 80% recovery. Extraction efficiency, inter- and intra-day reproducibility, sensitivity, linearity, limit of detection and quantitation, and matrix effect were evaluated. Intra-day and inter-day reproducibility were in the respective range of 4-8 and 7-13% relative standard deviation (RSD) for all eight phenolic compounds. Limits of detection and quantitation of the proposed SPME-LC-MS/MS system for the analysis of analytes under study were found in the range of 0.2-3 and 0.5-10 ng/mL, respectively. Standard addition calibration was applied for the quantitative determination of unknown phenolic compounds from wine, berry, and grape samples. The assessment of matrix effect showed significant reduction of ion suppression/enhancement using SPME method in comparison with that of solvent extraction technique. PMID:23332787

Mirnaghi, Fatemeh S; Mousavi, Fatemeh; Rocha, Sílvia M; Pawliszyn, Janusz

2013-01-01

203

Fast profiling of chemical constituents in Yiqing Capsule by ultra-performance liquid chromatography coupled to electrospray ionization tandem mass spectrometry.  

PubMed

An ultra-performance liquid chromatography/electrospray ionization tandem mass spectrometry (UPLC-ESI-MS(n)) has been developed for structural characterization and identification of multi-constituents in Yiqing Capsule, a well-known combined herbal remedy prepared from the extract mixtures of Rhizoma Coptidis, Radix et Rhizoma Rhei and Radix Scutellariae. The UPLC analysis was performed on an Agilent ZorBax SB-C(18) column (4.6 mm×50 mm, 1.8 ?m) and gradient elution of 0.1% formic acid solution and acetonitrile in 16 min. Based on their retention times and mass spectra in comparison with the data from standards or references, a total of 29 compounds including 3 phenolic acids and 4 anthraquinones from Radix et Rhizoma Rhei, 8 alkaloids from Rhizoma Coptidis and 14 flavonoids from Radix Scutellariae were unambiguously identified or tentatively characterized in the complex system. The MS data and fragmentation information of two isomers of feruloylquinic acid were first reported in Radix et Rhizoma Rhei and in Yiqing Capsules. This study is expected to be accepted as an effective and reliable pattern for comprehensive and systematic characterization of this commonly used Chinese herbal preparation. PMID:22125294

Zheng, Guo-Dong; Li, Kai; Li, Yue-shan; Liu, E-Hu

2011-11-28

204

Quantitative analysis of D-24851, a novel anticancer agent, in human plasma and urine by liquid chromatography coupled with tandem mass spectrometry.  

PubMed

The development of a liquid chromatography/tandem mass spectrometric assay for the quantitative analysis of the novel tubulin inhibitor D-24851 in human plasma and urine is described. D-24851 and the deuterated internal standard were extracted from 250 microL of plasma or urine using hexane/ether (1:1, v/v). Subsequently, 10-microL aliquots of reconstituted extracts were injected onto an Inertsil ODS analytical column (50 x 2.0 mm i.d., 5 microm particle size). An eluent consisting of methanol/5 mM ammonium acetate, 0.004% formic acid in water (80:20, v/v) was pumped at a flow rate of 0.2 mL/min. An API 365 triple quadrupole mass spectrometer was used in the multiple reaction monitoring mode for sensitive detection. For human plasma a dynamic range of 1-1000 ng/mL was validated, and for human urine a range of 0.25-50 ng/mL. Validation was performed according to the most recent FDA guidelines and all results were within requirements. The assay has been successfully applied to support a phase I clinical trial with orally administered D-24851. PMID:15216507

Stokvis, Ellen; Nan-Offeringa, Lianda G A H; Ouwehand, Mariët; Tibben, Matthijs M; Rosing, Hilde; Schnaars, Yvonne; Grigat, Martina; Romeis, Peter; Schellens, Jan H M; Beijnen, Jos H

2004-01-01

205

Analysis of phenolic compounds by high-performance liquid chromatography coupled to electrospray ionization tandem mass spectrometry in senescent and water-stressed tobacco.  

PubMed

Evaluation of a significant part of the phenylpropanoid pathway metabolites is facilitated by the fast high-performance liquid chromatography with electrospray ionization tandem mass spectrometry (LC-MS/MS) analytical method. The technology described was applied in tobacco plants (Nicotiana tabacum L. cv. Wisconsin) to identify 20 phenolic compounds and to detect differences in phenylpropanoid profiles in two types of experiments. In the first one, senescent and non-senescent parts of flowering plants were compared, while in the second, watered plants were compared with water-stressed young plants. The 20 identified phenolic compounds were: seven hydroxycinnamoylquinic acids, seven hydroxycinnamic acid glucosides, one salicylic acid glucoside, two conjugated flavonols with disaccharides, and three hydroxycinnamic acid amides (HCAA) of putrescine. In general, the levels of phenylpropanoid compounds increased under water stress or senescent conditions, with the exception of HCAA, which decreased in senescent samples, and 4-O-p-coumaroylquinic acid and trihydroxycinamic acid-O-glucoside, which did not change in both experiments. The main product in all the samples was 5-O-caffeoylquinic acid (neochlorogenic acid). Another compound, kaempferol-7-O-neohesperidoside, was tentatively identified for the first time in tobacco plants. This method, which can be applied in other plant species, allows a simple and efficient comparative study of metabolite profile variations (qualitative and quantitative) in response to different physiological and/or environmental plant situations. PMID:22118617

Torras-Claveria, Laura; Jáuregui, Olga; Codina, Carles; Tiburcio, Antonio F; Bastida, Jaume; Viladomat, Francesc

2011-03-01

206

Development and validation of amisulpride in human plasma by HPLC coupled with tandem mass spectrometry and its application to a pharmacokinetic study.  

PubMed

In this study, authors developed a simple, sensitive and specific liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for quantification of Amisulpride in human plasma using Amisulpride-d(5) as an internal standard (IS). Chromatographic separation was performed on Zorbax Bonus-RP C18, 4.6 × 75 mm, 3.5 ?m column with an isocratic mobile phase composed of 0.2% formic acid:methanol (35:65 v/v), at a flow-rate of 0.5 mL/min. Amisulpride, Amisulpride-d(5) was detected at m/z 370.1?242.1 and 375.1?242.1. The drug and the IS were extracted by a liquid-liquid extraction method. The method was validated over a linear concentration range of 2.0-2500.0 ng/mL for Amisulpride with a correlation coefficient of (r(2)) ? 0.9982. This method demonstrated intra- and inter-day precision within 0.9 to 1.7 and 1.5 to 2.8 % and intra- and inter-day accuracy within 98.3 to 101.5 and 96.0 to 101.0 % for Amisulpride. Amisulpride was found to be stable at 3 freeze-thaw cycles, bench top and auto sampler stability studies. The developed method was successfully applied to a pharmacokinetic study. PMID:21886905

Mogili, Ramakotaiah; Kanala, Kanchanamala; Challa, Balasekhara Reddy; Chandu, Babu Rao; Bannoth, Chandrasekhar Kottapalli

2011-07-25

207

Development and Validation of Amisulpride in Human Plasma by HPLC Coupled with Tandem Mass Spectrometry and its Application to a Pharmacokinetic Study  

PubMed Central

In this study, authors developed a simple, sensitive and specific liquid chromatography–tandem mass spectrometry (LC–MS/MS) method for quantification of Amisulpride in human plasma using Amisulpride-d5 as an internal standard (IS). Chromatographic separation was performed on Zorbax Bonus-RP C18, 4.6 × 75 mm, 3.5 ?m column with an isocratic mobile phase composed of 0.2% formic acid:methanol (35:65 v/v), at a flow-rate of 0.5 mL/min. Amisulpride, Amisulpride-d5 was detected at m/z 370.1?242.1 and 375.1?242.1. The drug and the IS were extracted by a liquid-liquid extraction method. The method was validated over a linear concentration range of 2.0–2500.0 ng/mL for Amisulpride with a correlation coefficient of (r2) ? 0.9982. This method demonstrated intra- and inter-day precision within 0.9 to 1.7 and 1.5 to 2.8 % and intra- and inter-day accuracy within 98.3 to 101.5 and 96.0 to 101.0 % for Amisulpride. Amisulpride was found to be stable at 3 freeze–thaw cycles, bench top and auto sampler stability studies. The developed method was successfully applied to a pharmacokinetic study.

Mogili, Ramakotaiah; Kanala, Kanchanamala; Challa, Balasekhara Reddy; Chandu, Babu Rao; Bannoth, Chandrasekhar Kottapalli

2011-01-01

208

[Determination of seven pesticide residues in bamboo shoots by high performance liquid chromatography-tandem mass spectrometry coupled with solid-phase extraction].  

PubMed

A simple and efficient method based on solid-phase extraction (SPE) and high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was developed for the determination of butylene fipronil, chlorpyrifos, chlorantraniliprole, fipronil, imidacloprid, indoxacarb and phoxim residues in bamboo shoots. The sample was extracted with acetonitrile and purified by a primary secondary amine (PSA) solid-phase extraction cartridge. The detection of targets was performed by HPLC-MS/MS with multiple reaction monitoring (MRM) mode. All the seven pesticides were completely separated in 15 min with an excellent linear relationship. The limits of detection and the limits of quantification for the seven pesticides were 0.02-0.5 microg/kg and 0.08-1.5 microg/kg, respectively. The recoveries of the seven pesticides spiked in a bamboo shoot sample at the levels of 4, 8, 32 microg/kg were in the range from 76.0% to 102.6% (the RSD < or = 11.0%, n = 3). The method was successfully applied to the real bamboo shoot samples. The method has high accuracy and sensitivity, and is simple and quick. It can meet the requirement of the simultaneous determination of the seven pesticides in bamboo shoots. PMID:23697174

Ding, Ming; Zhong, Donglian; Tang, Fubin; Fang, Wei

2013-02-01

209

A validated assay for the simultaneous quantification of six tyrosine kinase inhibitors and two active metabolites in human serum using liquid chromatography coupled with tandem mass spectrometry.  

PubMed

A sensitive, sophisticated and practical bioanalytical assay for the simultaneous determination of six tyrosine kinase inhibitors (imatinib, sunitinib, nilotinib, dasatinib, pazopanib, regorafenib) and two active metabolites (N-desmethyl imatinib and N-desethyl sunitinib) was developed and validated. For the quantitative assay, a mixture of three stable isotopes as internal standards was added to human serum, standards and controls. Thereafter, samples were pre-treated using protein precipitation with methanol. The supernatant was diluted with water and injected into an ultra pressure liquid chromatographic system with an Acquity TQ tandem mass spectrometry detector. The compounds were separated on an Acquity BEH C18 analytical column (100mm×2.1mm ID, 1.7?m particle size) and eluted with a linear gradient system. The ions were detected in the multiple reaction monitoring mode. The lower limit of quantification and the linearity of all compounds generously met with the concentrations that are to be expected in clinical practice. The developed bioanalytical assay can be used for guiding TKI therapy in daily clinical practice as well as for investigator-initiated research. PMID:24013127

van Erp, Nielka P; de Wit, Djoeke; Guchelaar, Henk-Jan; Gelderblom, Hans; Hessing, Trees J; Hartigh, Jan den

2013-08-17

210

Flavonoid profiling in three citrus varieties native to the Republic of Korea using liquid chromatography coupled with tandem mass spectrometry: contribution to overall antioxidant activity.  

PubMed

A mixture of flavonoid components was isolated from the fruit peel of three varieties of citrus native to Republic of Korea, Citrus leiocarpa Hort. ex Tanaka (CLHT), Citrus aurantium L. (CAL) and Citrus erythrosa Hort. (CEH), via 70% methanol extraction followed by ethyl acetate elution over a silica gel cartridge. The flavonoid components of the mixture were analyzed via high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) in positive-ion mode and a comparison of the reported data. Among 17 characterized components, two flavanones, four flavones and two coumarin derivatives in the fruit peel of the three varieties were identified for the first time. The individual characterized components were quantified via HPLC-UV. The flavanones dominated in CAL, whereas the flavones prevailed in CLHT and CEH. The antioxidant activity of the flavonoid mixture of the fruit peel was determined via DPPH•, ABTS•? and reducing power assays. The antioxidant activity of CEH and CAL was greater than that of CLHT. PMID:21830229

Kim, Hae Gyeong; Kim, Gon-Sup; Park, Semin; Lee, Jung Han; Seo, On Nuri; Lee, Soo Jung; Kim, Jae Hoon; Shim, Jae-Han; Abd El-Aty, A M; Jin, Jong Sung; Shin, Sung Chul

2011-08-09

211

Stir bar sorptive extraction coupled to liquid chromatography-tandem mass spectrometry for the determination of pesticides in water samples: Method validation and measurement uncertainty.  

PubMed

Stir bar sorptive extraction followed by liquid desorption and high performance liquid chromatography with tandem mass spectrometry (SBSE-LD-LC-MSMS) has been developed for the determination of 15 pesticides or selected metabolites from different families (herbicides, insecticides, fungicides) in surface water samples. The optimization of parameters that could influence SBSE-LD efficiency was carried out by means of experimental design. Optimized conditions were established as follows concerning extraction time, stirring speed, aqueous medium characteristics (ionic strength and polarity) and back desorption solvent and time, respectively: 3h (800rpm), addition of 10% of sodium chloride, no addition of methanol as organic modifier, and 15min ultrasonic desorption in equivolume mixtures of acetonitrile-methanol. A specific and thorough cleanup procedure was developed and applied to each stir bar to avoid possible carry-over between consecutive extractions with the same stir bar. Pesticide quantification in water was achieved thanks to matrix matched calibration. Mean recoveries ranged from 93 to 101% (RSD <17%, n=30). Validated limits of quantification in matrix were between 0.02 and 1µgL(-1), depending on the compound. A specific experimental design was conducted to evaluate the measurement uncertainty, which was comprised between 13 and 51%, whatever the pesticide and the concentration level. The applicability of the SBSE-LD-LCMSMS method was evaluated by analyzing surface water samples and by comparing with conventional solid phase extraction-LC-MSMS procedure. PMID:24148364

Margoum, Christelle; Guillemain, Céline; Yang, Xi; Coquery, Marina

2013-05-02

212

Rhodium(III)-catalyzed direct oxidative cross coupling at the C5 position of chromones with alkenes.  

PubMed

An atom-economical, Rh(III)-catalyzed, direct oxidative cross-coupling at the C5 position of chromones and flavones with a broad range of alkenes was developed. The products were formed in a highly regioselective manner in good to excellent yields. The developed method was applied in the cross-coupling of natural products for the synthesis of hybrid molecules. PMID:23190176

Samanta, Rajarshi; Narayan, Rishikesh; Antonchick, Andrey P

2012-11-28

213

Facile Cu(I)-catalyzed oxidative coupling of anilines to azo compounds and hydrazines with diaziridinone under mild conditions.  

PubMed

A mild and highly efficient Cu(I)-catalyzed oxidative coupling of anilines is described. Various primary and secondary anilines can be efficiently coupled under mild conditions to the corresponding azo compounds and hydrazines in high yields. This method provides a direct and practical access to these compounds and is also amenable to gram scale with no special precautions to exclude air or moisture. PMID:23545123

Zhu, Yingguang; Shi, Yian

2013-04-01

214

Planar Multielectrode Array Coupled Complementary Metal Oxide Semiconductor Image Sensor for In vitro Electrophysiology  

NASA Astrophysics Data System (ADS)

A multielectrode array coupled complementary metal oxide semiconductor (CMOS) image sensor (MARC sensor) was developed for an in vitro electrophysiology experiment. The sensor chip was fabricated by a standard CMOS process, and has a 64 microelectrode array and a 180× 180 photodiode pixel array. The size of an on-chip microelectrode is 60× 60 ?m2 and the pixel size is 7.5× 7.5 ?m2. In addition, Pt black was fabricated on microelectrodes to obtain stimulation electrodes. The imaging function was demonstrated by the anatomical observation of a mouse hippocampal slice, and the electrical recording function was also demonstrated by monitoring the extracellular field potentials of the brain slice using on-chip microelectrodes. The MARC sensor is compatible with existing in vitro multichannel recording systems. This is the first report supporting our concept that microelectrode arrays and large-sized optical systems can be integrated onto single large-scale integration (LSI) architecture.

Nakajima, Arata; Noda, Toshihiko; Sasagawa, Kiyotaka; Tokuda, Takashi; Ishikawa, Yasuyuki; Shiosaka, Sadao; Ohta, Jun

2011-04-01

215

Nitrate reduction coupled with pyrite oxidation in the surface sediments of a sulfide-rich ecosystem  

NASA Astrophysics Data System (ADS)

studies of denitrification have focused on organic carbon as an electron donor, but reduced sulfur can also support denitrification. Few studies have reported nitrate (NO3-) reduction coupled with pyrite oxidation and its stoichiometry in surface sediments, especially without experimental pyrite addition. In this study, we evaluated NO3- reduction coupled with sulfur oxidation by long-term incubation of surface sediments from a sulfide-rich ecosystem in Akita Prefecture, Japan. The surface sediments were sampled from a mud pool and a riverbed. Fresh sediments and water were incubated under anoxic conditions (and one oxic condition) at 20°C. NO3- addition increased the SO42- concentration and decreased the NO3- concentration. SO42- production (?SO42-) was strongly and linearly correlated with NO3- consumption (?NO3-) during the incubation period (R2 = 0.983, P < 0.01, and n = 8), and the slope of the regression (?NO3-/?SO42-) and the stoichiometry indicated sulfur-driven NO3- reduction by indigenous autotrophic denitrifying bacteria. Framboidal pyrite and marcasite (both FeS2) were present in the sediments and functioned as the electron donors for autotrophic denitrification. Both ?NO3- and ?SO42- were higher in the riverbed sediment than in the mud pool sediment, likely because of the higher amount of easily oxidizable S (pyrite) in the riverbed sediment. Consistently low ammonium (NH4+) concentrations indicated that NO3- reduction by dissimilatory NO3- reduction to NH4+ was small but could not be disregarded. Our results demonstrate that sulfide-rich ecosystems with easily oxidizable metal-bound sulfides such as FeS2 near the ground surface may act as denitrification hot spots.

Hayakawa, Atsushi; Hatakeyama, Mizuho; Asano, Ryoki; Ishikawa, Yuichi; Hidaka, Shin

2013-06-01

216

Specialized Transducing Phage lambda Carrying the Genes for Coupling Factor of Oxidative Phosphorylation of Escherichia coli: Increased Synthesis of Coupling Factor on Induction of Prophage lambda asn  

Microsoft Academic Search

Studies were made of the synthesis of the coupling factor complex (F1-F0) of oxidative phosphorylation after prophage induction of a set of Escherichia coli strains lysogenic for defective transducing phage lambda asn, lambda uncA, or lambda bglC. The transducing phages had been isolated from a strain of E. coli carrying prophage lambda cI857 S7 within the bglB gene located near

Hiroshi Kanazawa; Toru Miki; Fumie Tamura; Takashi Yura; Masamitsu Futai

1979-01-01

217

Domain coupling and resistance in perpendicularly magnetized metal-oxide bilayers  

NASA Astrophysics Data System (ADS)

Two of the interesting problems in magnetic heterostructures are the exchange coupling in multilayers and the stabilization of domains with magnetization perpendicular to the film plane. In this work, these two phenomena are combined and the stabilization of a perpendicular domain structure in an ultra thin (<10nm) metallic layer, grown on a magnetic oxide (Yttrium Iron Garnet, YIG) layer with perpendicular anisotropy, by interlayer exchange coupling was studied. Further, this bilayer was used to study the physics of interlayer coupling and the associated magnetoresistance including the contribution of domain walls to spin-dependent scattering. YIG thin films, deposited on a gadolinium gallium garnet (GGG) substrate using magnetron sputtering, were post-annealed to crystallize the film. The crystallization of the YIG film was optimized by X-ray diffraction, its perpendicular magnetization confirmed by two different magnetometry measurements, and the characteristic stripe domains imaged by magnetic force microscopy (MFM). Next, Fe films of various thicknesses were deposited on the YIG film. Under optimal growth conditions, and up to a critical thickness, the domain structure of Fe was found to be exchange coupled to that of YIG and showed the characteristic stripe domains structure. However, MFM imaging of such FM/YIG bilayers is not conclusive because of the possible effects of the stray magnetic fields from the substrate (YIG). To independently resolve the domain structure of the FM and YIG layers, clement specific X-ray photoemission electron microscopy (XPEEM) with magnetic circular dichroism (MCD) contrast, was performed at the Advanced Light Source. The XPEEM images revealed that the Co (FM) layer was coupled perpendicularly to the YIG layer up to a Co thickness of 5nm, but as the Co layer thickness was increased, domains of both the Co layer and the surface of the YIG film started to show an in-plane domain structure. Preliminary micromagnetic simulations showed that the volume exchange stiffness term at the interface plays a dominant role, when compared with the bilinear and biquadratic coupling contributions, in determining the interlayer coupling. Finally, the magnetoresistance (MR) of such FM/YIG bilayers, by lithographically patterning the FM layer on a YIG underlayer, was measured to both study the changes in the domain structure as a function of applied field and the contribution of the domain wall to the resistance. Since the YIG layer is insulating, such transport measurement would be dominated by the FM (Co) layer. MR measurement in longitudinal (field parallel to current direction) and transverse (field perpendicular to current direction) geometries revealed anisotropic MR (AMR) characteristics. However, the anomaly in the data when measured in the perpendicular mode (field perpendicular to the sample surface) was shown to be due to the Hall effect and domain coupling between FM and YIG layer. Detailed analysis of the perpendicular measurement showed sensitivity to the initial domain structure of the Co/YIG bilayer and this was interpreted in terms of the domain wall resistance contribution to the total MR.

Chun, Yoonsoo

218

Detection of 22 antiepileptic drugs by ultra-performance liquid chromatography coupled with tandem mass spectrometry applicable to routine therapeutic drug monitoring.  

PubMed

The purpose of this study was to develop an ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method of 22 antiepileptics for routine therapeutic monitoring. The antiepileptics used in the analyses were carbamazepine, carbamazepine-10,11-epoxide, clobazam, N-desmethylclobazam, clonazepam, diazepam, N-desmethyldiazepam, ethosuximide, felbamate, gabapentin, lamotrigine, levetiracetam, N-desmethylmesuximide, nitrazepam, phenobarbital, phenytoin, primidone, tiagabine, topiramate, valproic acid, vigabatrin and zonisamide. After protein precipitation of 50??L plasma with methanol, the supernatant was diluted with water or was evaporated to dryness and reconstituted with mobile phase in the case of benzodiazepines. Separation was achieved on an Acquity UPLC BEH C?? column with a gradient mobile phase of 10?mm ammonium acetate containing 0.1% formic acid and methanol at a flow rate of 0.4?mL/min. An Acquity TQD instrument in multiple reaction monitoring mode with ion mode switching was used for detection. All antiepileptics were detected and quantified within 10?min, with no endogenous interference. All the calibration curves showed good linearity in the therapeutic range (r² ?

Shibata, Mai; Hashi, Sachiyo; Nakanishi, Haruka; Masuda, Satohiro; Katsura, Toshiya; Yano, Ikuko

2012-03-01

219

Simultaneous determination of phoxim and its photo-transformation metabolite residues in eggs using liquid chromatography coupled with electrospray ionization tandem mass spectrometry.  

PubMed

The principal objective of this study was to develop an appropriate, sensitive, and selective method for the simultaneous quantitative determination of phoxim and its photo-transformation product, O,O-diethyl alpha-cyanobenzylideneamino-thiophosphonate (DCTP) in both chicken and quail eggs. Eggs (1 g) were blended with anhydrous magnesium sulfate (1 g) for sample pretreatment and extracted with acetonitrile. The extracts were then further purified with SPE silica gel tubes deactivated with trimethylamine. Residues were analyzed via a reversed phase-liquid chromatography-tandem mass spectrometry (RP-LC-MS/MS) in positive-ion electrospray ionization (ESI) mode. Tebufenozide was utilized as an internal standard for the quantification of phoxim and its metabolite residues. The identification and quantification of analytes were based on ion transitions monitored by multiple reaction monitoring (MRM). LC-MS/MS analysis was performed from 0.02 to 1 mg kg(-1) and correlation coefficients (r(2)) ranging from 0.998 to 0.999 were obtained for both analytes in blank egg extracts. The relative standard deviations (RSDs) of intra- and inter-day variations ranged from 2.1% to 6.7% and from 2.8% to 6.4% for phoxim and DCTP in chicken and quail eggs. At all levels of fortification (0.02, 0.05, and 0.125 mg kg(-1)), the recoveries fell within a range of 81.3% to 93.6% for phoxim and 83.3% to 90.1% for DCTP. The matrix effect was <2%, due to the partial dilution of the sample. Decision limits (CCalpha) and detection capabilities (CCbeta) were in the range of 0.0005-0.0044 and 0.0054-0.0224 mg kg(-1), respectively. The method was evaluated further by analyzing real samples purchased from markets. All chicken and quail egg samples were free from residues of the target compounds. PMID:20638501

Lee, Jung Han; Park, Semin; Jeong, Won Young; Park, Hyung Jin; Kim, Hae Gyeong; Lee, Soo-Jung; Shim, Jae-Han; Kim, Soo Taek; Abd El-Aty, A M; Im, Moo Hyeog; Choi, Ok Ja; Shin, Sung Chul

2010-06-23

220

Simultaneous determination of ten biogenic amines in a thymopolypeptides injection using ultra-performance liquid chromatography coupled with electrospray ionization tandem quadrupole mass spectrometry.  

PubMed

A selective and sensitive ultra-performance liquid chromatography-electrospray ionization tandem mass spectrometry (UPLC-MS) method was developed for the simultaneous determination of ten biogenic amines (tryptamine, 2-phenylethylamine, putrescine, cadaverine, histamine, tyramine, spermidine, adrenaline, dopamine and spermine) in a thymopolypeptides injection from the Chinese market for the first time. Biogenic amines (BAs) were pre-column derivatised by dansyl chloride after direct sample dilution. Dansylated amines were separated on an ACQUITY UPLC BEH Shield RP18 column (2.1mm×150mm I.D., 1.7?m) using a gradient elution. Quantification was done by monitoring fragment ions of each derivative under the MS mode of multiple reaction monitoring (MRM). A satisfactory result of method validation was obtained. The linearity ranged from 0.32 to 1182.9?g/L and the correlation coefficients (r) for all amines were above 0.99. The LOD ranged from 0.08?g/L for 2-phenylethylamine and tyramine to 8.00?g/L for adrenaline; the LOQ ranged from 0.32?g/L for 2-phenylethylamine to 12.12?g/L for dopamine. The recovery ranged from 75.8 to 110.3% after spiking standard solutions of BAs to a sample at three levels. The intra and inter-day precision RSD were 0.78-8.85% and 1.39-9.93% respectively. Eighty-four injections were analyzed by this method. Nine biogenic amines were found in them except adrenaline. Moreover, the relationship between the result of test for depressor substances and the content of BAs was statistically analyzed. PMID:23644498

Li, Yong; Yang, Huaxin; Liao, Haiming; Fan, Huihong; Liang, Chenggang; Deng, Lijuan; Jin, Shaohong

2013-03-30

221

Enantioselective determination of 3-n-butylphthalide (NBP) in human plasma by liquid chromatography on a teicoplanin-based chiral column coupled with tandem mass spectrometry.  

PubMed

A novel and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated to determine the exposure of 3-n-butylphthalide (NBP) enantiomers in human plasma. The NBP enantiomers were extracted from human plasma using methyl tert-butyl ether. The baseline separation of R-(+)-NBP and S-(-)-NBP was achieved within 11.0min using a teicoplanin-based Astec Chirobiotic T column (250mm×4.6mm i.d., 5?m) under isocratic conditions at a flow rate of 0.6mL/min. The selection of the chiral stationary phase and the effect of the mobile phase composition on the resolution of the enantiomers were discussed. The selectivity, linearity, precision, accuracy, matrix effect, recovery, and stability were evaluated under optimized conditions. The LC-MS/MS method using 200?L of human plasma was linear over the concentration range of 5.00-400ng/mL for each enantiomer. The lower limit of quantification (LLOQ) for both enantiomers was 5.00ng/mL. The intra- and inter-assay precision values of the replicated quality control samples were within 8.0% for each enantiomer. The mean accuracy values for the quality control samples were within ±6.1% of the nominal values for R-(+)-NBP and S-(-)-NBP. No chiral inversion was observed during sample storage, preparation, and analysis. The method proved suitable for enantioselective pharmacokinetic studies of NBP after an oral administration of a therapeutic dose of racemic NBP. PMID:24103433

Diao, Xingxing; Ma, Zhiyu; Lei, Peng; Zhong, Dafang; Zhang, Yifan; Chen, Xiaoyan

2013-09-17

222

Quantitative analysis of ES-285, an investigational marine anticancer drug, in human, mouse, rat, and dog plasma using coupled liquid chromatography and tandem mass spectrometry.  

PubMed

A method was developed for the quantitative analysis of the novel anticancer agent ES-285 (spisulosine; free base) in human, mouse, rat, and dog plasma using high-performance liquid chromatography/electrospray ionization tandem mass spectrometry in order to support pre-clinical and clinical studies with the drug. Sample preparation was carried out by protein precipitation with acetonitrile, containing isotopically labeled (d(3)) ES-285 as internal standard. Aliquots of 10 micro l of the supernatant were injected directly on to an Inertsil ODS-3 column (50 x 2.0 mm i.d., 5 micro m). Elution was carried out using methanol-10 mM ammonium formate (pH 4) in water (80 : 20, v/v) pumped at a flow-rate of 0.2 ml min(-1) with a run time of 8 min. Multiple reaction monitoring chromatograms obtained on an API365 triple-quadrupole mass spectrometer were used for quantification. The lower limit of quantitation (LLOQ) was 10 ng ml(-1) in human, mouse, rat, and dog plasma and the linear dynamic range extended to 500 ng ml(-1). A full validation of the method was performed in human plasma, and partial validations were performed in mouse, rat and dog plasma. Accuracies and precisions were <20% at the LLOQ concentration and <15% for all other concentrations in all matrices. ES-285 was stable during all steps of the assay. Thus far this method has been used successfully to analyze over 500 samples in pre-clinical trials, and will be implemented in the planned clinical phase I studies. PMID:12794877

Stokvis, E; Nan-Offeringa, L; Rosing, H; López-Lázaro, L; Aceña, J L; Miranda, E; Lyubimov, A; Levine, B S; D'Aleo, C; Schellens, J H M; Beijnen, J H

2003-05-01

223

Determination of Phenolic Acids and Flavonoids in Taraxacum formosanum Kitam by Liquid Chromatography-Tandem Mass Spectrometry Coupled with a Post-Column Derivatization Technique.  

PubMed

A liquid chromatography-tandem mass spectrometry method (LC-MS/MS) was developed for the determination of phenolic acids and flavonoids in a medicinal Chinese herb Taraxacum formosanum Kitam. Initially, both phenolic acids and flavonoids were extracted with 50% ethanol in a water-bath at 60 °C for 3 h and eventually separated into acidic fraction and neutral fraction by using a C(18) cartridge. A total of 29 compounds were separated within 68 min by employing a Gemini C(18) column and a gradient solvent system of 0.1% formic acid and acetonitrile at a flow rate of 1.0 mL/min. Based on the retention behavior as well as absorption and mass spectra, 19 phenolic acids and 10 flavonoids were identified and quantified in T. formosanum, with the former ranging from 14.1 ?g/g to 10,870.4 ?g/g, and the latter from 9.9 ?g/g to 325.8 ?g/g. For further identification of flavonoids, a post-column derivatization method involving shift reagents such as sodium acetate or aluminum chloride was used and the absorption spectral characteristics without or with shift reagents were compared. An internal standard syringic acid was used for quantitation of phenolic acids, whereas (±) naringenin was found suitable for quantitation of flavonoids. The developed LC-MS/MS method showed high reproducibility, as evident from the relative standard deviation (RSD) values for intra-day and inter-day variability being 1.0-6.8% and 2.0-7.7% for phenolic acids and 3.7-7.4% and 1.5-8.1% for flavonoids, respectively, and thus may be applied for simultaneous determination of phenolic acids and flavonoids in Chinese herb and nutraceuticals. PMID:22312251

Chen, Hung-Ju; Inbaraj, Baskaran Stephen; Chen, Bing-Huei

2011-12-27

224

Concerning the dependence of the selectivity of the formation of ethane and ethylene on the degree of methane conversion during its oxidative coupling  

SciTech Connect

The dependence of the maximum selectivity and the limiting yield of C{sub 2} hydrocarbons on the degree of methane conversion during its gas-phase oxidative coupling were calculated by means of kinetic simulation. The correlation between the results of the calculations and the rersults obtained in the experimental studies dealing with catalytic oxidative coupling of methane is discussed.

Vedeneev, V.I.; Arutyunov, V.S.; Basevich, V.Ya.

1995-03-01

225

Multi-residue determination of the sorption of illicit drugs and pharmaceuticals to wastewater suspended particulate matter using pressurised liquid extraction, solid phase extraction and liquid chromatography coupled with tandem mass spectrometry.  

PubMed

Presented is the first comprehensive study of drugs of abuse on suspended particulate matter (SPM) in wastewater. Analysis of SPM is crucial to prevent the under-reporting of the levels of analyte that may be present in wastewater. Analytical methods to date analyse the aqueous part of wastewater samples only, removing SPM through the use of filtration or centrifugation. The development of an analytical method to determine 60 compounds on SPM using a combination of pressurised liquid extraction, solid phase extraction and liquid chromatography coupled with tandem mass spectrometry (PLE-SPE-LC-MS/MS) is reported. The range of compounds monitored included stimulants, opioid and morphine derivatives, benzodiazepines, antidepressants, dissociative anaesthetics, drug precursors, and their metabolites. The method was successfully validated (parameters studied: linearity and range, recovery, accuracy, reproducibility, repeatability, matrix effects, and limits of detection and quantification). The developed methodology was applied to SPM samples collected at three wastewater treatment plants in the UK. The average proportion of analyte on SPM as opposed to in the aqueous phase was <5% for several compounds including cocaine, benzoylecgonine, MDMA, and ketamine; whereas the proportion was >10% with regard to methadone, EDDP, EMDP, BZP, fentanyl, nortramadol, norpropoxyphene, sildenafil and all antidepressants (dosulepin, amitriptyline, nortriptyline, fluoxetine and norfluoxetine). Consequently, the lack of SPM analysis in wastewater sampling protocol could lead to the under-reporting of the measured concentration of some compounds. PMID:21968348

Baker, David R; Kasprzyk-Hordern, Barbara

2011-09-08

226

Development of a multi-mycotoxin analysis in beer-based drinks by a modified QuEChERS method and ultra-high-performance liquid chromatography coupled with tandem mass spectrometry.  

PubMed

An analytical method was developed for the identification and quantification of 15 mycotoxins (patulin, nivalenol, deoxynivalenol, aflatoxin B(1), B(2), G(1), G(2), M(1), T-2 toxin, HT-2 toxin, zearalenone, fumonisin B(1), B(2), B(3), and ochratoxin A) in beer-based drinks (beer, low-malt beer, new genre, and nonalcoholic) by a modified QuEChERS method and an ultra-high-performance liquid chromatography coupled with tandem mass spectrometry (UHPLC/MS/MS). Mycotoxins were extracted from samples using acetonitrile with sodium chloride, anhydrous magnesium sulfate, and sodium citrate, and were then purified with a solid phase extraction (SPE) cartridge including C18. The UHPLC conditions were also examined to establish its optimal conditions for separation. Fifteen mycotoxins were separated in a total of 6.5 min, and were quantified in the optimal mobile phase conditions. Determinations performed using this method produced high correlation coefficients of 15 mycotoxins (R>0.99) and recovery rates ranging from 70.3 to 110.7% with good repeatability (relative standard deviation RSD<14.6%). Further, 24 commercial beer-based drinks in Japan were analyzed using this method, and nivalenol, deoxynivalenol, and fumonisins were detected in several samples, but always under the limit of quantification (<5 ng/mL). These results suggest that the health risk to consumers from beer-based drinks in Japan is relatively low. PMID:21666361

Tamura, Masayoshi; Uyama, Atsuo; Mochizuki, Naoki

2011-01-01

227

Analysis and detection of the chemical constituents of Radix Polygalae and their metabolites in rats after oral administration by ultra high-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry.  

PubMed

Radix Polygalae (RP), the dried root of Polygala tenuifolia Willd., is a well-known traditional Chinese medicine to mediate sedative, antipsychotic, cognitive improving, neuroprotective, and anti-inflammatory therapeutic effects on the central nervous system. In this work, ultra high-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UHPLC/ESI-Q-TOF-MS/MS) was established for the separation and characterization of the chemical constituents in Radix Polygalae and their metabolites in rat plasma and urine after oral administration. Samples were separated on an Agilent Zorbax Eclipse Plus-C18 column (100mm×2.1mm, 1.8?m) with 0.1% formic acid aqueous solution and acetonitrile as the mobile phase under gradient conditions. Overall, 50 compounds were characterized from the RP, 9 of which are to our knowledge reported for the first time. In vivo, 10 components and 2 metabolites were observed in rat plasma, and 27 components and 7 metabolites were detected in rat urine. The results from this work improve our understanding on the chemical constituents of RP and their metabolic profiling. PMID:23860503

Ling, Yun; Li, Zhixiong; Chen, Mingcang; Sun, Zhaolin; Fan, Mingsong; Huang, Chenggang

2013-06-26

228

Insights into proton-coupled electron transfer mechanisms of electrocatalytic H2 oxidation and production  

PubMed Central

The design of molecular electrocatalysts for H2 oxidation and production is important for the development of alternative renewable energy sources that are abundant, inexpensive, and environmentally benign. Recently, nickel-based molecular electrocatalysts with pendant amines that act as proton relays for the nickel center were shown to effectively catalyze H2 oxidation and production. We developed a quantum mechanical approach for studying proton-coupled electron transfer processes in these types of molecular electrocatalysts. This theoretical approach is applied to a nickel-based catalyst in which phosphorous atoms are directly bonded to the nickel center, and nitrogen atoms of the ligand rings act as proton relays. The catalytic step of interest involves electron transfer between the nickel complex and the electrode as well as intramolecular proton transfer between the nickel and nitrogen atoms. This process can occur sequentially, with either the electron or proton transferring first, or concertedly, with the electron and proton transferring simultaneously without a stable intermediate. The electrochemical rate constants are calculated as functions of overpotential for the concerted electron-proton transfer reaction and the two electron transfer reactions in the sequential mechanisms. Our calculations illustrate that the concerted electron-proton transfer standard rate constant will increase as the equilibrium distance between the nickel and nitrogen atoms decreases and as the pendant amines become more flexible to facilitate the contraction of this distance with a lower energy penalty. This approach identifies the favored mechanisms under various experimental conditions and provides insight into the impact of substituents on the nitrogen and phosphorous atoms.

Horvath, Samantha; Fernandez, Laura E.; Soudackov, Alexander V.; Hammes-Schiffer, Sharon

2012-01-01

229

Insights into proton-coupled electron transfer mechanisms of electrocatalytic H2 oxidation and production  

SciTech Connect

The design of molecular electrocatalysts for H2 oxidation and production is important for the development of alternative renewable energy sources that are abundant, inexpensive, and environmentally benign. Recently nickel-based molecular electrocatalysts with pendant amines that act as proton relays for the nickel center were shown to effectively catalyze H2 oxidation and production. We developed a quantum mechanical approach for studying proton-coupled electron transfer processes in these types of molecular electrocatalysts. This theoretical approach is applied to a nickel-based catalyst in which phosphorous atoms are directly bonded to the nickel center and nitrogen atoms of the ligand rings act as proton relays. The cataly c step of interest involves electron transfer between the nickel complex and the electrode as well as intramolecular proton transfer between the nickel and nitrogen atoms. This process can occur sequentially, with either the electron or proton transferring first, or concertedly, with the electron and proton transferring simultaneously without a stable intermediate. The heterogeneous rate constants are calculated as functions of overpotential for the concerted electron-proton transfer reaction and the two electron transfer reactions in the sequential mechanisms. Our calculations illustrate that the concerted electron-proton transfer standard rate constant will increase as the equilibrium distance between the nickel and nitrogen atoms decreases and as the nitrogen atoms become more mobile to facilitate the contraction of this distance. This approach assists in the identification of the favored mechanisms under various experimental conditions and provides insight into the qualitative impact of substituents on the nitrogen and phosphorous atoms. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under FWP 56073.

Horvath, Samantha; Fernandez, Laura; Soudackov, Alexander V.; Hammes-Schiffer, Sharon

2012-09-25

230

Insights into proton-coupled electron transfer mechanisms of electrocatalytic H2 oxidation and production.  

PubMed

The design of molecular electrocatalysts for H(2) oxidation and production is important for the development of alternative renewable energy sources that are abundant, inexpensive, and environmentally benign. Recently, nickel-based molecular electrocatalysts with pendant amines that act as proton relays for the nickel center were shown to effectively catalyze H(2) oxidation and production. We developed a quantum mechanical approach for studying proton-coupled electron transfer processes in these types of molecular electrocatalysts. This theoretical approach is applied to a nickel-based catalyst in which phosphorous atoms are directly bonded to the nickel center, and nitrogen atoms of the ligand rings act as proton relays. The catalytic step of interest involves electron transfer between the nickel complex and the electrode as well as intramolecular proton transfer between the nickel and nitrogen atoms. This process can occur sequentially, with either the electron or proton transferring first, or concertedly, with the electron and proton transferring simultaneously without a stable intermediate. The electrochemical rate constants are calculated as functions of overpotential for the concerted electron-proton transfer reaction and the two electron transfer reactions in the sequential mechanisms. Our calculations illustrate that the concerted electron-proton transfer standard rate constant will increase as the equilibrium distance between the nickel and nitrogen atoms decreases and as the pendant amines become more flexible to facilitate the contraction of this distance with a lower energy penalty. This approach identifies the favored mechanisms under various experimental conditions and provides insight into the impact of substituents on the nitrogen and phosphorous atoms. PMID:22529352

Horvath, Samantha; Fernandez, Laura E; Soudackov, Alexander V; Hammes-Schiffer, Sharon

2012-04-23

231

Aqueous normal phase liquid chromatography coupled with tandem time-of-flight quadrupole mass spectrometry for determination of zanamivir in human serum  

PubMed Central

An aqueous normal phase (ANP) liquid chromatography coupled with a hybrid quadrupole time-of-flight mass spectrometry (ANP-LC-micrOTOFQ) method was used for the determination of zanamivir in human serum. Zanamivir was extracted with methanol from protein-precipitated human serum samples and further purified with SCX solid-phase extraction cartridges. Scherzo SM-C18, Agilent Zorbax SB-Aq, Cogent Diamond Hydride, Cogent Bidentate and Luna HILIC columns were compared and optimized for the retention and separation of zanamivir and he Luna HILIC and Diamond Hydride columns exhibited the best retention of zanamivir. The former provided a shorter retention time, a sharper peak and relatively high sensitivity, whereas the latter exhibited a longer retention time and less matrix interference. The analytical range of the calibration curve was between 5 and 1000 ng/mL.

Ge, Jing; Liu, Fengmao; Holmes, Eric H.; Ostrander, Gary K.; Li, Qing X.

2012-01-01

232

Computer simulation of spatial coupling in chemical oscillations of CO oxidation on two Pd(110) single crystals  

NASA Astrophysics Data System (ADS)

Gas-phase coupling between two Pd(110) single crystals in a UHV CO oxidation reaction in a continuous stirred tank reactor (CSTR) has been simulated by solving gas-phase mass balance equations with kinetic rate equations. This work was motivated by the experimental results which show that the frequency of partial pressure change in carbon monoxide is the same as the frequency of the work function change in the oscillation region and that the coupling between the two crystals occurred entirely via CO partial pressure. The computer simulation described here gives qualitative agreement with the experimental results. The change in the oscillatory region originating from the coupling of chemical oscillators which are slightly different to each other is successfully demonstrated by this model. The coupling of two oscillators having a simple periodic oscillation to produce mixed-mode oscillation was also successfully simulated.

Park, I. J.; Woo, S. I.

1993-09-01

233

Factors affecting the magnetic coupling in Sr2V3O9 type oxides: As for V substitution in the VO4 tetrahedra and nature of the cation.  

PubMed

A density functional theory study of the magnetic couplings in Sr2V3O9 type magnetic oxides suggests that whereas the intrachain coupling is always weakly ferromagnetic, the interchain coupling may be antiferromagnetic or even weakly ferromagnetic depending on the nature of the central tetrahedral atom (As/V) cations, and, to a lesser extent, structural details. PMID:24091906

Rodríguez-Fortea, Antonio; Llunell, Miquel; Alemany, Pere; Canadell, Enric

2013-10-22

234

Palladium(II)-catalyzed oxidative C-H/C-H coupling and eliminative S(N)(H) reactions in direct functionalization of imidazole oxides with indoles.  

PubMed

Two novel synthetic approaches to realize the direct C(sp(2))-H bond functionalization in cyclic nitrones are reported. Palladium(II)-catalyzed oxidative C-C coupling of 2,2-dialkyl-4-phenyl-2H-imidazole 1-oxides with indoles was shown to result in the formation of 5-indolyl-3-yl derivatives, while nucleophilic substitution of hydrogen (S(N)(H)) at C(5) of the same imidazole system was found to afford the corresponding deoxygenated compounds. PMID:22998018

Varaksin, Mikhail V; Utepova, Irina A; Chupakhin, Oleg N; Charushin, Valery N

2012-10-01

235

Polyoxometalate as co-catalyst of tetrabutylammonium bromide in polyethylene glycol (PEG) for coupling reaction of CO 2 and propylene oxide or ethylene oxide  

Microsoft Academic Search

The coupling reaction of CO2 and propylene oxide or ethylene oxide to produce corresponding cyclic carbonate in the presence of a catalytic system composed of n-Bu4NBr, ?2-(n-Bu4N)9P2W17O61(Co2+·Br) (abbreviated as P2W17Co) and PEG (MW 400) has been investigated. The experimental results indicated that the synthesis of propylene carbonate (PC) or ethylene carbonate (EC) achieved with over 98% yield and 100% selectivity

Dewu Sun; Hongju Zhai

2007-01-01

236

Kraft Lignin Chain Extension Chemistry via Propargylation, Oxidative Coupling, and Claisen Rearrangement.  

PubMed

Despite its aromatic and polymeric nature, the heterogeneous, stochastic, and reactive characteristics of softwood kraft lignin seriously limit its potential for thermoplastic applications. Our continuing efforts toward creating thermoplastic lignin polymers are now focused at exploring propargylation derivatization chemistry and its potential as a versatile novel route for the eventual utilization of technical lignins with a significant amount of molecular control. To do this, we initially report the systematic propargylation of softwood kraft lignin. The synthesized derivatives were extensively characterized with thermal methods (DSC, TGA), (1)H, (13)C, and quantitative (31)P NMR and IR spectroscopies. Further on, we explore the versatile nature of the lignin pendant propargyl groups by demonstrating two distinct chain extension chemistries; the solution-based, copper-mediated, oxidative coupling and the thermally induced, solid-state, Claissen rearrangement polymerization chemistries. Overall, we show that it is possible to modulate the reactivity of softwood kraft lignin via a combination of methylation and chain extension providing a rational means for the creation of higher molecular weight polymers with the potential for thermoplastic materials and carbon fibers with the desired control of structure-property relations. PMID:23962343

Sen, Sanghamitra; Sadeghifar, Hasan; Argyropoulos, Dimitris S

2013-09-12

237

Rapid colorimetric determination of reduced and oxidized glutathione using an end point coupled enzymatic assay.  

PubMed

A simple and rapid colorimetric coupled enzymatic assay for the determination of glutathione is described. The proposed method is based on the specific reaction catalyzed by ?-glutamyltransferase, which transfers the ?-glutamyl moiety from glutahione to an acceptor, with the formation of the ?-glutamyl derivative of the acceptor and cysteinylglycine. The latter dipeptide is a substrate of leucyl aminopeptidase, which hydrolyzes cysteinylglycine to glycine and cysteine that can be easily measured spectrophotometrically. The proposed method was used to measure the content of glutathione in acid extracts of bovine lens, to follow the NADPH-dependent reduction of glutathione disulfide (GSSG) to reduced glutathione (GSH) catalyzed by the enzyme glutathione reductase and to determine the glutathione content in human astrocytoma ADF cells subjected to oxidative stress. The results obtained showed that the method can be suitably used for the determination of GSH and GSSG in different biological samples and to monitor tissue or cell redox status under different conditions. It is also applicable for following reactions involving GSH and/or GSSG. PMID:23203508

Cappiello, Mario; Peroni, Eleonora; Lepore, Ambra; Moschini, Roberta; Del Corso, Antonella; Balestri, Francesco; Mura, Umberto

2012-11-27

238

Biological oxidation of Fe(II) in reduced nontronite coupled with nitrate reduction by Pseudogulbenkiania sp. Strain 2002  

NASA Astrophysics Data System (ADS)

The importance of microbial nitrate-dependent Fe(II) oxidation to iron biogeochemistry is well recognized. Past research has focused on oxidation of aqueous Fe2+ and structural Fe(II) in oxides, carbonates, and phosphate, but the importance of structural Fe(II) in phyllosilicates in this reaction is only recently studied. However, the effect of clay mineralogy on the rate and the mechanism of the reaction, and subsequent mineralogical end products are still poorly known. The objective of this research was to study the coupled process of microbial oxidation of Fe(II) in clay mineral nontronite (NAu-2), and nitrate reduction by Pseudogulbenkiania species strain 2002, and to determine mineralogical changes associated with this process. Bio-oxidation experiments were conducted using Fe(II) in microbially reduced nontronite as electron donor and nitrate as electron acceptor in bicarbonate-buffered medium under both growth and nongrowth conditions to investigate cell growth on this process. The extents of Fe(II) oxidation and nitrate reduction were measured by wet chemical methods. X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), and 57Fe-Mössbauer spectroscopy were used to observe mineralogical changes associated with Fe(III) reduction and Fe(II) oxidation in NAu-2. The bio-oxidation extent under growth and nongrowth conditions reached 67% and 57%, respectively. Over the same time period, nitrate was completely reduced under both conditions to nitrogen gas (N2), via an intermediate product nitrite. Abiotic oxidation by nitrite partly accelerated Fe(II) oxidation rate under the growth condition. The oxidized Fe(III) largely remained in the nontronite structure, but secondary minerals such as vivianite, ferrihydrite, and magnetite formed depending on specific experimental conditions. The results of this study highlight the importance of iron-bearing clay minerals in the global nitrogen cycle with potential applications in nitrate removal in natural environments.

Zhao, Linduo; Dong, Hailiang; Kukkadapu, Ravi; Agrawal, Abinash; Liu, Deng; Zhang, Jing; Edelmann, Richard E.

2013-10-01

239

Cofactor-apoprotein hydrogen bonding in oxidized and fully reduced flavodoxin monitored by trans-hydrogen-bond scalar couplings.  

PubMed

Hydrogen bonding plays a key role in the tight binding of the FMN cofactor and the regulation of its redox properties in flavodoxins. Hydrogen bonding interactions can be directly observed in solution by multidimensional heteronuclear NMR spectroscopy through the scalar couplings between donor and acceptor nuclei. Here we report on the detection of intermolecular trans-hydrogen-bond couplings ((h)J) between the flavin ring system and the backbone of Desulfovibrio vulgaris flavodoxin in the oxidized and the two-electron reduced states. For this purpose, experiments are adapted from pulse sequences previously applied to determining (h)J coupling constants in nucleic acid-base pairs and proteins. The resulting (h2)J(N,N), (h4)J(N,N), (h3)J(C,N), and (h1)J(H,N) couplings involve the (15)N(1), (13)C(2), and (15)N(3) nuclei of the pyrimidine moiety of FMN, whereas no such interactions are detectable for (13)C(4) and (15)N(5). Several long-range (15)N-(15)N, (13)C-(15)N, and (1)H-(15)N J-coupling constants within the flavin are obtained as "by-products". The magnitudes of both (h)J and regular J couplings are found to be dependent on the redox state. In general, good correlations between (h)J coupling constants and donor-group (1)H chemical shifts and also crystallographic donor-acceptor distances are observed. PMID:15515086

Löhr, Frank; Yalloway, Gary N; Mayhew, Stephen G; Rüterjans, Heinz

2004-11-01

240

A dual-cathode electro-Fenton oxidation coupled with anodic oxidation system used for 4-nitrophenol degradation  

Microsoft Academic Search

The degradation of 4-nitrophenol was investigated using a novel electrochemical oxidation system, in which the anodic oxidation at Ti\\/SnO2–Sb2O5–IrO2 electrode and the electro-Fenton oxidation with two cathodes were involved. In this system, gas diffusion electrode (GDE) was used to generate H2O2 by O2 reduction and graphite electrode was employed for the reduction of Fe3+ regenerating Fe2+. When the potential values

Y. Y. Chu; Y. Qian; W. J. Wang; X. L. Deng

241

Interchain coupled chain dynamics of poly(ethylene oxide) in blends with poly(methyl methacrylate): Coupling model analysis  

Microsoft Academic Search

Quasielastic neutron scattering and molecular dynamics simulation data from poly(ethylene oxide) (PEO)?poly(methyl methacrylate) (PMMA) blends found that for short times the self-dynamics of PEO chain follows the Rouse model, but at longer times past tc = 1–2 ns it becomes slower and departs from the Rouse model in dependences on time, momentum transfer, and temperature. To explain the anomalies, others

K. L. Ngai; Li-Min Wang

2011-01-01

242

Characterization of procyanidin B2 oxidation products in an apple juice model solution and confirmation of their presence in apple juice by high-performance liquid chromatography coupled to electrospray ion trap mass spectrometry.  

PubMed

Procyanidins (i.e. condensed tannins) are polyphenols commonly found in fruits. During juice and cider making, apple polyphenol oxidase catalyzes the oxidation of caffeoylquinic acid (CQA) into its corresponding o-quinone which further reacts with procyanidins and other polyphenols, leading to the formation of numerous oxidation products. However, the structure and the reaction pathways of these neoformed phenolic compounds are still largely unknown. Experiments were carried out on a model system to gain insights into the chemical processes occurring during the initial steps of fruit processing. Procyanidin B2 was oxidized by caffeoylquinic acid o-quinone (CQAoq) in an apple juice model solution. The reaction products were monitored using high performance liquid chromatography (HPLC) coupled to ultraviolet (UV)-visible and electrospray tandem mass spectrometry (ESI-MS/MS) in the negative mode. Oxidative conversion of procyanidin B2 ([M-H](-) at m/z 577) into procyanidin A2 at m/z 575 was unambiguously confirmed. In addition, several classes of products were characterized by their deprotonated molecules ([M-H](-)) and their MS/MS fragmentation patterns: hetero-dimers (m/z 929) and homo-dimers (m/z 1153 and 705) resulting from dimerization involving procyanidin and CQA molecules; intramolecular addition products at m/z 575, 573, 927, 1151 and 703. Interestingly, no extensive polymerization was observed. Analysis of a cider apple juice enabled comparison with the results obtained on a biosynthetic model solution. However, procyanidin A2 did not accumulate but seemed to be an intermediate in the formation of an end-product at m/z 573 for which two structural hypotheses are given. These structural modifications of native polyphenols as a consequence of oxidation probably have an impact on the organoleptic and nutritional properties of apple juices and other apple-derived foods. PMID:22124992

Poupard, Pascal; Sanoner, Philippe; Baron, Alain; Renard, Catherine M G C; Guyot, Sylvain

2011-11-01

243

Tandem hydrofoil system  

Microsoft Academic Search

A tandem hydrofoil system enables an improvement in the lift-drag ratio of a high-speed ship. The conditions for favorable application of this type of foil structure are determined. The data on hydrofoil boats using a tandem system are presented. The problem of the stability of the vertical plane motion of a hydrofoil with bow and stern foils is considered. The

Konstantin I. Matveev; Ivan Ivanovich Matveev

2001-01-01

244

Interfacial refractive index sensing using visible-excited intrinsic zinc oxide photoluminescence coupled to whispering gallery modes  

NASA Astrophysics Data System (ADS)

Whispering gallery modes (WGMs) excited by the intrinsic photoluminescence (PL) in zinc oxide microspherical resonators are investigated in this work. The microspheres were synthesized via a one-pot hydrothermal technique. A polymer was applied after the synthesis to fill remaining pores in the oxide particle. Defect-related ZnO PL was excited in the visible, coupling to WGMs. The observed WGMs red-shift with increasing refractive index of the surrounding medium with a sensitivity of 90-100 nm/refractive index unit. The spherical microresonators may be used to investigate binding to and structure at the particle/solution interface.

Moirangthem, Rakesh Singh; Erbe, Andreas

2013-07-01

245

Effect of oxidation of the ultrathin Fe electrode material on the strength of magnetoelectric coupling in composite multiferroics  

Microsoft Academic Search

We present an ab initio study of the effect of iron oxidation on magnetoelectric coupling which appears at the ferromagnet\\/ferroelectric interface, such as Fe2\\/ATiO3(001) (A=Ba,Pb) . The oxygen coverage, c , ranging between one half and two adsorbed O per each Fe atom was simulated within a slab geometry. Since the change in magnetization induced by electric polarization reversal remains

M. Fechner; S. Ostanin; I. Mertig

2009-01-01

246

Ionic liquid-derived imidazolium metal halides for the coupling reaction of ethylene oxide and CO 2  

Microsoft Academic Search

A series of ionic liquid-derived imidazolium metal halide complexes, (1-R-3- methylimidazolium)bMXaYb (M = Zn, Fe, Mn, In; R = CH3, C2H5, n-C4H9, CH2C6H5; X, Y = Cl, Br; a, b = 2, 3) were prepared by reacting metal halide, MXa with an equivalent of (1-R- 3-methylimidazolium)Y and their activities were tested for the coupling reactions of ethylene oxide and CO2

O-Sung Kwon; Jelliarko Palgunadi; Hyunjoo Lee; Jin Yong Bae; Byoung Sung Ahn; Hoon Sik Kim; Sang-Hoon Lee

2004-01-01

247

Tapered aluminum-doped vertical zinc oxide nanorod arrays as light coupling layer for solar energy applications  

Microsoft Academic Search

Tapered aluminum-doped vertical zinc oxide nanorod arrays have been prepared by using simple electrodeposition at 75°C from an aqueous solution of zinc nitrate and aluminum nitrate. Two substrates were used, i.e., copper indium gallium (di)selenide solar cells and a solar thermal absorber. The resulting nanorod arrays were of high optical quality, indicting their applicability as a light coupling layer via

Jie Chen; Hong Ye; Lorenz Aé; Yang Tang; David Kieven; Thorsten Rissom; Julia Neuendorf; Martha Ch. Lux-Steiner

2011-01-01

248

A dual-cathode electro-Fenton oxidation coupled with anodic oxidation system used for 4-nitrophenol degradation.  

PubMed

The degradation of 4-nitrophenol was investigated using a novel electrochemical oxidation system, in which the anodic oxidation at Ti/SnO(2)-Sb(2)O(5)-IrO(2) electrode and the electro-Fenton oxidation with two cathodes were involved. In this system, gas diffusion electrode (GDE) was used to generate H(2)O(2) by O(2) reduction and graphite electrode was employed for the reduction of Fe(3+) regenerating Fe(2+). When the potential values of GDE and graphite cathode were controlled at -0.80 and -0.10 V/SCE respectively, the optimum Fe(2+) concentration for 4-nitrophenol degradation was about 0.10mM, much lower than the concentration of 0.25 mM obtained in the single-cathode system. Due to the combination of electro-Fenton oxidation and anodic oxidation, an effective degradation and a high mineralization current efficiency (MCE) were achieved. After 600 min treatment, 74.5% of the original TOC was removed by the dual-cathode oxidation system. Moreover, it was confirmed that 57.0% of the original nitrogen could be removed in gaseous form from the simulated wastewater. These results indicate that this electrochemical oxidation process might provide an alternative for the degradation of organic pollutants. PMID:22104767

Chu, Y Y; Qian, Y; Wang, W J; Deng, X L

2011-11-02

249

Quantification of endogenous brassinosteroids in plant by on-line two-dimensional microscale solid phase extraction-on column derivatization coupled with high performance liquid chromatography-tandem mass spectrometry.  

PubMed

An on-line two-dimensional microscale solid phase extraction (2D?SPE)-on column derivatization (OCD)-high performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS) method was developed for quantification of brassinosteroids (BRs) in plant tissues. Five BRs with widest distribution in plant species and high bioactivity (24-epibrassinolide, 24-epicastasterone, 6-deoxo-24-epicastasterone, teasterone and typhastero) were selected as target analytes. 2D?SPE column packed sequentially with phenyl boronic acid silica sorbent (the first dimension) and C18 silica sorbent (the second dimension) was used to selectively extract and enrich BRs by 110-146 times. OCD was carried out on the second dimension of 2D?SPE column with m-aminophenylboronic acid (m-APBA) as a derivatization reagent, enhancing the sensitivity of MS/MS to BRs by 13-8437 times. It was also found that pre-trap of derivatization reagent on the C18 section of 2D?SPE column could increase reaction efficiency by 3-10 times. The whole process time of the on-line system was less than 30min. The detection limits of the method for five BRs were between 1.4 and 6.6pg with RSDs less than 10%. Endogeneous BRs in tomato leaves were analyzed by using this method. Owing to the high selectivity of this on-line 2D?SPE system, BRs in plant extracts could be quantified using matrix-free standard calibration method with relative recoveries in the range of 80-124%. PMID:23702098

Wu, Qian; Wu, Dapeng; Shen, Zheng; Duan, Chunfeng; Guan, Yafeng

2013-04-22

250

Scope and Mechanistic Study of the Coupling Reaction of ?, ?-Unsaturated Carbonyl Compounds with Alkenes: Uncovering Electronic Effects on Alkene Insertion vs Oxidative Coupling Pathways  

PubMed Central

The cationic ruthenium-hydride complex [(C6H6)(PCy3)(CO)RuH]+BF4? (1) was found to be a highly effective catalyst for the intermolecular conjugate addition of simple alkenes to ?,?-unsaturated carbonyl compounds to give (Z)-selective tetrasubstituted olefin products. The analogous coupling reaction of cinnamides with electron-deficient olefins led to the oxidative coupling of two olefinic C–H bonds in forming (E)-selective diene products. The intramolecular version of the coupling reaction efficiently produced indene and bicyclic fulvene derivatives. The empirical rate law for the coupling reaction of ethyl cinnamate with propene was determined as: rate = k[1]1[propene]0[cinnamate]?1. A negligible deuterium kinetic isotope effect (kH/kD = 1.1±0.1) was measured from both (E)-C6H5CH=C(CH3)CONHCH3 and (E)-C6H5CD=C(CH3)CONHCH3 with styrene. In contrast, a significant normal isotope effect (kH/kD = 1.7±0.1) was observed from the reaction of (E)-C6H5CH=C(CH3)CONHCH3 with styrene and styrene-d10. A pronounced carbon isotope effect was measured from the coupling reaction of (E)-C6H5CH=CHCO2Et with propene (13C(recovered)/13C(virgin) at C? = 1.019(6)), while a negligible carbon isotope effect (13C(recovered)/13C(virgin) at C? = 0.999(4)) was obtained from the reaction of (E)-C6H5CH=C(CH3)CONHCH3 with styrene. Hammett plots from the correlation of para-substituted p-X-C6H4CH=CHCO2Et (X = OCH3, CH3, H, F, Cl, CO2Me, CF3) with propene and from the treatment of (E)-C6H5CH=CHCO2Et with a series of para-substituted styrenes p-Y-C6H4CH=CH2 (Y = OCH3, CH3, H, F, Cl, CF3) gave the positive slopes for both cases (? = +1.1±0.1 and +1.5±0.1, respectively). Eyring analysis of the coupling reaction led to the thermodynamic parameters, ? H‡ = 20±2 kcal mol?1 and S‡ = ?42±5 e.u. Two separate mechanistic pathways for the coupling reaction have been proposed on the basis of these kinetic and spectroscopic studies.

Kwon, Ki-Hyeok; Lee, Do W.; Yi, Chae S.

2011-01-01

251

Controlled surface modification of Ti-40Nb implant alloy by electrochemically assisted inductively coupled RF plasma oxidation.  

PubMed

Low temperature metal oxidation induced by plasma in the absence of liquid electrolytes can be useful for the surface preparation of orthopedic devices since residues from these may be harmful and need to be removed before implantation. In this study the oxidation of Ti-40Nb for biomedical application was achieved by employing an inductively coupled radio frequency oxygen plasma. The correlation between the growth mode of the surface oxide and the electric conductivity ratio of the plasma and the oxide phase were studied by varying the sample temperature, oxygen gas pressure and additional bias potential. The plasma treated samples were characterised by confocal laser microscopy, SEM, EBSD, XPS, TEM and ToF-SIMS. The surface energy was determined by contact angle measurements using the Owens-Wendt-Rabel-Kaelble method. Well adhering oxide layers consisting of TiO2 and Nb2O5 with thicknesses between 50 and 150nm were obtained. Surface roughness values and microstructure indicate that the growth mode of the oxide can be well controlled by the sample temperature and oxygen gas pressure. At temperatures above 450°C a migration of Ti ions towards the surface controls the growth process. A bias potential higher than +50V causes rough and defective surfaces with high surface energies. PMID:23891813

Göttlicher, Markus; Rohnke, Marcus; Helth, Arne; Leichtweiß, Thomas; Gemming, Thomas; Gebert, Annett; Eckert, Jürgen; Janek, Jürgen

2013-07-25

252

Quantification of ethylenediamine-N,N'-bis(hydroxysulfophenylacetic) acid regioisomers and structural characterisation of its related polycondensation products by porous graphitic carbon high-performance liquid chromatography coupled to electrospray tandem mass spectrometry.  

PubMed

Among the commercial ethylenediamine-N,N'-bis(2-hydroxy)phenylacetic acid/iron(III) derivatives, ethylenediamine-N,N'-bis(2-hydroxy-5-sulphophenylacetic) acid/iron(III) (EDDHSA/Fe) represents one of the promising chelates for the treatment of chlorotic plants. Industrial synthesis of EDDHSA/Fe leads to relevant amounts of o,o-EDDHSA condensation products (o,o-EDDHSAcps) and other secondary products that might have important relevance from the agronomic point of view. However, their chemical structures have remained unknown to date. Analysis of iron complexes by ion-pair reversed-phase chromatography, coupled with electrospray tandem mass spectrometry revealed the presence of the meso-o,o-EDDHSA/Fe, rac-o,o-EDDHSA/Fe, o,p-EDDHSA/Fe regioisomers, the hydroxyl derivative of o,o-EDDHSA/Fe, and the three main EDDHSA condensation products chelating the iron(III) (EDDHSAcps/nFe). However, the chromatographic peaks of EDDHSAcps/Fe are not well resolved due to the large numbers of stereoisomers and the poor efficiency of the ion-pair reversed-phase separation method. An alternative chromatographic method is based on porous graphitic carbon (PGC) separation after pre-column decomplexation of the chelates with trifluoracetic acid, which was developed to allow detection of EDDHSA stereo/regioisomers, EDDHSAcps, and low-molecular-weight by-products. This extensive PGC-HPLC-ESI-MS/MS investigation provides quantitative determination of meso-o,o-EDDHSA, rac-o,o-EDDHSA and o,p-EDDHSA, in addition to characterisation of EDDHSAcps and the low-molecular-weight by-products. PGC separation coupled to a triple quadrupole ESI-MS detector allowed characterisation of free ligands using collision-induced dissociation experiments in positive and negative ionisation mode, providing comparative evaluation of EDDHSAcps in three commercial samples. For detection, the PGC-HPLC-ESI-MS/MS is the best method according to the limit of quantification and limit of detection (picomolar and sub-picomolar detection, respectively) for determination of meso-EDDHSA and rac-o,o-EDDHSA. Synthesis, purification and quantification of o,o-EDDHSA and o,p-EDDHSA by (1)H-nuclear magnetic resonance are also reported. PMID:24028933

Biasone, Alessandro; Cianci, Giusto; Di Tommaso, Donata; Piaggesi, Alberto; D'Alessandro, Nicola

2013-09-05

253

Cation effects in the oxidative coupling of methane on silica-supported binary alkali and alkaline earths  

SciTech Connect

The oxidative coupling of methane has been investigated with a series of silica-supported binary oxide catalysts containing alkali or alkaline earths or combinations of the former and latter. The conversion of methane and the stability of the silica-supported binary alkali metal oxides were found to increase with decreasing cation mobility, while the selectivities and conversions observed with the binary alkaline earths increase with cation size. The selectivities and conversions of binary alkali/alkaline earths appear to depend upon the size of the alkali and alkaline earth cations, respectively. With small quantities of TCM (CCl[sub 4]) added continuously to the feedstream, catalysts containing small alkali and large alkaline earth cations produced the largest selectivities and conversions. 23 refs., 14 figs., 2 tabs.

Voyatzis, R.; Moffat, J.B. (Univ. of Waterloo, Ontario (Canada))

1993-07-01

254

Remobilization of Cr(VI) from Cr(OH)3(s) coupled with heterogeneous Mn(II) oxidation  

NASA Astrophysics Data System (ADS)

Chromium(VI) is known to be the 2nd most common inorganic contaminant due to the wide range of applications of chromium in the industry. The most effective way to remove toxic Cr(VI) under natural conditions as well as in the engineered systems is to reduce it to less toxic Cr(III) using various reductants. Under circumneutral pH conditions, Cr(III) readily precipitates as sparingly soluble Cr(OH)3(s). This solid phase is generally considered as one of the most desirable remediation product of soil and groundwater contaminated by Cr(VI) because it is less toxic and less mobile form of chromium. In addition, this solid is usually believed to be relatively inert to natural oxidants such as dissolved oxygen and Mn oxides. The oxidation of Cr(III) by dissolved oxygen is known to be kinetically sluggish. Previous studies showed that dissolved Cr(III) could easily be oxidized by Mn oxides under acidic conditions but the oxidation became ineffective under neutral or higher pH conditions as a result of Cr(OH)3(s) precipitation. This study examines the potential remobilization of Cr(VI) from this solid by oxidation coupled with heterogeneous oxidation of Mn(II) by dissolved oxygen. 1.0 g/L Cr(OH)3(s) was reacted with 50 ?M Mn(II) in 50 mM NaNO3 at pH 7 to 9 in the presence or absence of dissolved oxygen. The pH was maintained with 10 or 50 mM buffers (MOPS for pH 7 and 8; CHES for pH 9). For the anaerobic conditions, the solutions were purged with N2 in sealed serum bottles. In the absence of dissolved oxygen, the oxidation of Cr(OH)3(s) did not occur either with or without dissolved Mn(II). When the solutions were open to atmosphere, by contrast, the oxidation of the solid did occur both in the presence and absence of Mn(II) when the pH was higher or at 8.0. The amounts of Cr(VI) released increased with increasing pH and were higher in the presence than the absence of Mn(II). At pH 9, Cr(VI) concentration rapidly increased for the first 130 hr and reached up to 300 ppb in the presence of Mn(II). The results of this study show that Cr(OH)3(s) can be oxidized by the product of heterogeneous Mn(II) oxidation and thereby would possibly become a source of toxic Cr(VI).

Lee, G.; Namgung, S.; Um, W.

2011-12-01

255

Aerobic Oxidative Coupling of o-Xylene: Discovery of 2-Fluoropyridine as a Ligand to Support Selective Pd-Catalyzed C-H Functionalization  

PubMed Central

An improved method for direct oxidative coupling of o-xylene could provide streamlined access to an important monomer used in polyimide resins. The use of 2-fluoropyridine as a ligand has been found to enable unprecedented levels of chemo- and regioselectivity in this Pd-catalyzed aerobic oxidative coupling reaction. Preliminary insights have been obtained into the origin of the effectiveness of 2-fluoropyridine as a ligand.

Izawa, Yusuke

2011-01-01

256

Development of a Merged Conjugate Addition/Oxidative Coupling Sequence. Application to the Enantioselective Total Synthesis of Metacycloprodigiosin and Prodigiosin R1  

PubMed Central

A merged conjugate addition/oxidative coupling sequence that represents an efficient strategy for preparing structurally diverse pyrroles has been developed. Success of the method hinged upon the controlled oxidative coupling of unsymmetrical silyl bis-enol ether intermediates, formed by the 1,4-addition of a Grignard reagent with subsequent enolate trapping by a (chloro)silylenol ether. The process was applied to the first enantioselective syntheses of the biologically active pyrrolophane natural products, metacycloprodigiosin and prodigiosin R1.

Clift, Michael D.; Thomson, Regan J.

2009-01-01

257

Determination of lanthanides in rock samples by inductively coupled plasma mass spectrometry using thorium as oxide and hydroxide correction standard  

NASA Astrophysics Data System (ADS)

Determination of lanthanides by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) using modified mathematical correction method has been studied. Normally, the ICP-MS analysis of middle and heavier lanthanides becomes difficult by severe spectroscopic overlap of M +, MO + or MOH + ions from lighter lanthanides and Ba. A correction method based on a single element oxide yield measurement, is a simple approach to correct for the above spectroscopic overlaps. But the uncertainty in the oxide and hydroxide yields measurement of lanthanides and barium over a long period of time can lead to inaccurate results even under fixed plasma conditions. To correct this, thorium was adopted as an oxide and hydroxide correction standard. Using a ratio of lanthanide oxide yield to thorium oxide yield, the lanthanide correction factors (LCF) were established and incorporated in the mathematical correction scheme. The same factors were also established for hydroxide correction. The proposed modified correction scheme was applied to the determination of lanthanides by ICP-MS from the USGS Standard Rock samples AGV-1 and G-2. The results are in good agreement with the reported values. The method also proved to be useful in isotopic ratio measurement of lanthanides having severe isobaric overlaps.

Raut, Narendra M.; Huang, Li-Shing; Aggarwal, Suresh K.; Lin, King-Chuen

2003-05-01

258

Liquid chromatography-tandem mass spectrometry of phosphatidylserine advanced glycated end products.  

PubMed

Phosphatidylserine (PS) is an aminophospholipid that is prone to glycation. In oxidative conditions, glycated PS may lead to the formation of Amadori compounds and advanced glycated end products (AGEs), which are known to accumulate in diabetic patients. Nevertheless, there have been no studies that identified products from the oxidative reaction of glycated PS. In this study, glycated 1-palmitoyl-2-oleoyl-PS was synthesized and further oxidized by Fenton reagent. The AGES formed were structurally characterized by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) in negative mode. The oxidation products from glycated PS that we have found include products arising from the oxidation of the fatty acyl chains (hydroperoxides, hydroxides and keto derivatives), and arising from oxidative cleavage of serine polar head and lyso-glycated PS. Oxidation in C6 of glucose lead to the formation of glucuronyl-PS. In addition, new products arising from oxidative cleavage of glucose moiety (between C1C2, C2C3 and C3C4 bonds) were identified as PS-AGES. The current findings add substantially to the best of our knowledge of PS glycoxidation products, opening new perspectives for the detection of these products in complex biological matrices. PMID:23769760

Maciel, Elisabete; da Silva, Raquel Nunes; Simões, Cláudia; Melo, Tânia; Ferreira, Rita; Domingues, Pedro; Domingues, M Rosário M

2013-06-14

259

Coupling of Dimethylsulfide Oxidation to Biomass Production by a Marine Flavobacterium?  

PubMed Central

Dimethylsulfide (DMS) is an important climatically active gas. In the sea, DMS is produced primarily by microbial metabolism of the compatible solute dimethylsulfoniopropionate. Laboratory growth of Bacteroidetes with DMS resulted in its oxidation to dimethyl sulfoxide but only in the presence of glucose. We hypothesized that electrons liberated from sulfur oxidation were used to augment biomass production.

Green, David H.; Shenoy, Damodar M.; Hart, Mark C.; Hatton, Angela D.

2011-01-01

260

Advanced oxidation processes coupled with electrocoagulation for the exhaustive abatement of Cr-EDTA  

Microsoft Academic Search

Using Cr-EDTA as a model system, a two-step method has been investigated for the abatement of persistent chromium complexes in water. The treatment consists of an oxidative decomposition of the organic ligands by means of ozonization or electrochemical oxidation at a boron doped diamond (BDD) electrode, followed by removal of the metal via electrochemical coagulation. In the designed synthetic waste,

Christian Durante; Marco Cuscov; Abdirisak Ahmed Isse; Giancarlo Sandonà; Armando Gennaro

2011-01-01

261

The Efficacy of Oxidative Coupling for Promoting In-Situ Immobilization of Hydroxylated Aromatics in Contaminated Soil and Sediments Systems - Final Report  

SciTech Connect

The study clearly shows that the structure and composition of the organic matter of soils and sediments are essential considerations for the selection of materials for engineered applications of oxidative coupling processes. A rate model was developed to facilitate quantitative evaluation and mechanistic interpretation of these fairly complex coupling processes.

Weber Jr., W. J.

2000-10-01

262

Rapid synthesis of an electron-deficient t-BuPHOX ligand: cross-coupling of aryl bromides with secondary phosphine oxides  

PubMed Central

Herein an efficient and direct copper-catalyzed coupling of oxazoline-containing aryl bromides with electron-deficient secondary phosphine oxides is reported. The resulting tertiary phosphine oxides can be reduced to prepare a range of PHOX ligands. The presented strategy is a useful alternative to known methods for constructing PHOX derivatives.

McDougal, Nolan T.; Streuff, Jan; Mukherjee, Herschel; Virgil, Scott C.; Stoltz, Brian M.

2010-01-01

263

Double quantum dot with tunable coupling in an enhancement-mode silicon metal-oxide semiconductor device with lateral geometry  

NASA Astrophysics Data System (ADS)

We present transport measurements of a tunable silicon metal- oxide-semiconductor double quantum dot device with lateral geometry. Experimentally extracted gate-to-dot capacitances show that the device is largely symmetric under the gate voltages applied. Intriguingly, these gate voltages themselves are not symmetric. Comparison with numerical simulations indicates that the applied gate voltages serve to offset an intrinsic asymmetry in the physical device. We also show a transition from a large single dot to two well isolated coupled dots, where the central gate of the device is used to controllably tune the interdot coupling. This work was supported by the LDRD program at Sandia National Laboratories, a multi-program laboratory operated by Sandia Corporation, a wholly owned subsidiary Lockheed-Martin Company, for the U. S. DOE NNSA under Contract No. DE-AC04-94AL85000

Tracy, L. A.; Young, R. W.; Ten Eyck, G. A.; Eng, K.; Childs, K. D.; Wendt, J. R.; Grubbs, R. K.; Stevens, J.; Lilly, M. P.; Carroll, M. S.; Nordberg, E. P.; Borras Pinilla, C.; Stalford, H. L.; Eriksson, M. A.

2011-03-01

264

Ultrathin limit of exchange bias coupling at oxide multiferroic/ferromagnetic interfaces.  

PubMed

Exchange bias coupling at the multiferroic- ferromagnetic interface in BiFeO3 /La0.7 Sr0.3 MnO3 heterostructures exhibits a critical thickness for ultrathin BiFeO3 layers of 5 unit cells (2 nm). Linear dichroism measurements demonstrate the dependence on the BiFeO3 layer thickness with a strong reduction for ultrathin layers, indicating diminished antiferromagnetic ordering that prevents interfacial exchange bias coupling. PMID:23847010

Huijben, M; Yu, P; Martin, L W; Molegraaf, H J A; Chu, Y-H; Holcomb, M B; Balke, N; Rijnders, G; Ramesh, R

2013-07-12

265

Synthesis of tylocrebrine and related phenanthroindolizidines by VOF3-mediated oxidative aryl-alkene coupling.  

PubMed

A highly convergent strategy to prepare phenanthroindolizidines is reported involving three consecutive C-C coupling reactions. This sequence features a novel VOF(3)-mediated aryl-alkene coupling in the final step, which enables regioselective preparation of C5-substituted phenanthroindolizidines for the first time. This strategy has been applied to the synthesis of eight natural and unnatural members in this class to investigate the scope of this chemistry and to explore structure-activity relationships. PMID:21142214

Niphakis, Micah J; Georg, Gunda I

2010-12-14

266

Pd(II)-catalyzed cross-coupling of sp3 C-H Bonds with sp2 and sp3 boronic acids using air as the oxidant.  

PubMed

O-Methyl hydroxamic acids, readily available from carboxylic acids, are found to be extremely reactive for beta-C-H activation by Pd(OAc)2. This reactivity is exploited to develop the first example of cross-coupling sp3 C-H bonds with sp3 boronic acids. Air was shown to be a suitable stoichiometric oxidant for the catalytic oxidative coupling reaction. A biologically active natural product is readily converted to its novel analogues through this coupling reaction. PMID:18479089

Wang, Dong-Hui; Wasa, Masayuki; Giri, Ramesh; Yu, Jin-Quan

2008-05-14

267

Oxide Etch Behavior in an Inductively Coupled C4F8 Discharge Characterized by Diode Laser Spectroscopy.  

NASA Astrophysics Data System (ADS)

This study reports on oxide and photoresist etch characteristics in an inductively coupled GEC Reference Cell as a function of reactor source power, bias power and pressure using C4F8. Diode laser absorption spectroscopy (DLAS) has shown that C4F8 is largely dissociated to form C2F4, CF2 and CF in the discharge. Over an oxide surface, CF2 and CF are consumed in the oxide etch process, but only when the bias power is sufficient to keep the oxide surface clean through energetic ion bombardment. For C4F8, this transition occurs at 60 eV (75 W bias power) in the GEC Cell. At higher bias powers (125 W) where oxide etching is fast ( 600 nm/min.), CF2 appears to be the key radical for the etch process since 50 percent (2.7-3.0 mTorr in a 15 mTorr C4F8 discharge) is consumed. These values were obtained by comparing the CF2 concentrations over non-reactive wafer surfaces versus blanket oxide wafer surfaces undergoing etching. CF is shown to display a similar trend, but its concentration is an order of magnitude less than CF2, and consequently cannot account on a mass basis for the amount of reactants necessary to balance the amount of etch products. Over a PR surface, neither CF2 nor CF concentrations vary as a function of PR etch rate. Consequently, they do not appear to be involved in the PR etch mechanism. However, PR etching is also critically dependent on bias power. PR films etch presumably due to energetic ion bombardment that degrades the PR film, making it liable to attack by fluorine.

Anderson, Harold; Barela, Marcus; Courtin, Geoff; Waters, Karla

2001-10-01

268

Novel Mode of Microbial Energy Metabolism: Organic Carbon Oxidation Coupled to Dissimilatory Reduction of Iron or Manganese  

PubMed Central

A dissimilatory Fe(III)- and Mn(IV)-reducing microorganism was isolated from freshwater sediments of the Potomac River, Maryland. The isolate, designated GS-15, grew in defined anaerobic medium with acetate as the sole electron donor and Fe(III), Mn(IV), or nitrate as the sole electron acceptor. GS-15 oxidized acetate to carbon dioxide with the concomitant reduction of amorphic Fe(III) oxide to magnetite (Fe3O4). When Fe(III) citrate replaced amorphic Fe(III) oxide as the electron acceptor, GS-15 grew faster and reduced all of the added Fe(III) to Fe(II). GS-15 reduced a natural amorphic Fe(III) oxide but did not significantly reduce highly crystalline Fe(III) forms. Fe(III) was reduced optimally at pH 6.7 to 7 and at 30 to 35°C. Ethanol, butyrate, and propionate could also serve as electron donors for Fe(III) reduction. A variety of other organic compounds and hydrogen could not. MnO2 was completely reduced to Mn(II), which precipitated as rhodochrosite (MnCO3). Nitrate was reduced to ammonia. Oxygen could not serve as an electron acceptor, and it inhibited growth with the other electron acceptors. This is the first demonstration that microorganisms can completely oxidize organic compounds with Fe(III) or Mn(IV) as the sole electron acceptor and that oxidation of organic matter coupled to dissimilatory Fe(III) or Mn(IV) reduction can yield energy for microbial growth. GS-15 provides a model for how enzymatically catalyzed reactions can be quantitatively significant mechanisms for the reduction of iron and manganese in anaerobic environments. Images

Lovley, Derek R.; Phillips, Elizabeth J. P.

1988-01-01

269

Novel mode of microbial energy metabolism: organic carbon oxidation coupled to dissimilatory reduction of iron or manganese.  

PubMed

A dissimilatory Fe(III)- and Mn(IV)-reducing microorganism was isolated from freshwater sediments of the Potomac River, Maryland. The isolate, designated GS-15, grew in defined anaerobic medium with acetate as the sole electron donor and Fe(III), Mn(IV), or nitrate as the sole electron acceptor. GS-15 oxidized acetate to carbon dioxide with the concomitant reduction of amorphic Fe(III) oxide to magnetite (Fe(3)O(4)). When Fe(III) citrate replaced amorphic Fe(III) oxide as the electron acceptor, GS-15 grew faster and reduced all of the added Fe(III) to Fe(II). GS-15 reduced a natural amorphic Fe(III) oxide but did not significantly reduce highly crystalline Fe(III) forms. Fe(III) was reduced optimally at pH 6.7 to 7 and at 30 to 35 degrees C. Ethanol, butyrate, and propionate could also serve as electron donors for Fe(III) reduction. A variety of other organic compounds and hydrogen could not. MnO(2) was completely reduced to Mn(II), which precipitated as rhodochrosite (MnCO(3)). Nitrate was reduced to ammonia. Oxygen could not serve as an electron acceptor, and it inhibited growth with the other electron acceptors. This is the first demonstration that microorganisms can completely oxidize organic compounds with Fe(III) or Mn(IV) as the sole electron acceptor and that oxidation of organic matter coupled to dissimilatory Fe(III) or Mn(IV) reduction can yield energy for microbial growth. GS-15 provides a model for how enzymatically catalyzed reactions can be quantitatively significant mechanisms for the reduction of iron and manganese in anaerobic environments. PMID:16347658

Lovley, D R; Phillips, E J

1988-06-01

270

Decarboxylative coupling of heptanoic acid. Manganese, cerium and zirconium oxides as catalysts  

Microsoft Academic Search

A series of catalysts containing 20wt.% of Mn, Ce and Zr oxides deposited on Al2O3, SiO2 and TiO2 has been studied in ketonisation of heptanoic acid. The most pronounced effect of alumina support on catalysts activity has been noted. Manganese oxide catalysts have shown the highest activity. The dependence of the concentration of MnO2 active phase on catalyst activity has

M Gli?ski; J Kije?ski

2000-01-01

271

Direct oxidative coupling of arenes with olefins by Rh-catalyzed C-H activation in air: observation of a strong cooperation of the acid.  

PubMed

A [{RhCl(cod)}(2)]/CCl(3) COOH system was developed for the oxidative coupling of non-chelate-assisted arenes with olefins in the presence of catalytic amounts of Cu(OAc)(2) ?H(2) O as a co-oxidant and oxygen as the terminal oxidant. The acid was an indispensable component in this system and played a very important role in the coupling reaction. This catalytic system was applied to the direct oxidative coupling of a series of arenes and olefins and the corresponding products were afforded in high yields with special chemo- and regioselectivity. This reaction provides an atom-efficient route to vinylarenes, which are widely used in various fine chemicals. PMID:22764062

Zheng, Lu; Wang, Jianhui

2012-07-04

272

Coupling of mitochondrial fatty acid uptake to oxidative flux in the intact heart.  

PubMed Central

The coordination of long chain fatty acid (LCFA) transport across the mitochondrial membrane (V(PAL)) with subsequent oxidation rate through beta-oxidation and the tricarboxylic acid (TCA) cycle (V(tca)) has been difficult to characterize in the intact heart. Kinetic analysis of dynamic (13)C-NMR distinguished these flux rates in isolated rabbit hearts. Hearts were perfused in a 9.4 T magnet with either 0.5 mM [2,4,6,8,10,12,14,16-(13)C(8)] palmitate (n = 4), or 0.5 mM (13)C-labeled palmitate plus 0.08 mM unlabeled butyrate (n = 4). Butyrate is a short chain fatty acid (SCFA) that bypasses the LCFA transporters of mitochondria. In hearts oxidizing palmitate alone, the ratio of V(TCA) to V(PAL) was 8:1. This is consistent with one molecule of palmitate yielding eight molecules of acetyl-CoA for the subsequent oxidation through the TCA cycle. Addition of butyrate elevated this ratio; V(TCA)/V(PAL) = 12:1 due to an SCFA-induced increase in V(TCA) of 43% (p < 0.05). However, SCFA oxidation did not significantly reduce palmitate transport into the mitochondria: V(PAL) = 1.0 +/- 0.2 micromol/min/g dw with palmitate alone versus 0.9 +/- 0.1 with palmitate plus butyrate. Thus, the products of beta-oxidation are preferentially channeled to the TCA cycle, away from mitochondrial efflux via carnitine acetyltransferase.

O'Donnell, J Michael; Alpert, Nathaniel M; White, Lawrence T; Lewandowski, E Douglas

2002-01-01

273

Tandem Brownian Queues.  

National Technical Information Service (NTIS)

We analyze a two-node tandem queue with Brownian input. We first derive an explicit expression for the joint distribution function of the workloads of the first and second queue, which also allows us to calculate their exact large-buffer asymptotics. The ...

M. R. H. Mandjes P. M. D. Lieshout

2006-01-01

274

Tandem mirror fusion research  

SciTech Connect

The tandem mirror program has evolved considerably in the last decade. Of significance is the viable reactor concept embodied in the MARS design. An aggressive experimental program, culminating in the operation of MFTF-B in late 1986, will provide a firm basis for refining the MARS design as necessary for constructing a reactor prototype in the 1990s.

Baldwin, D.E.

1983-12-02

275

Tandem resonator reflectance modulator  

Microsoft Academic Search

A wide band optical modulator is grown on a substrate as tandem Fabry-Perot resonators including three mirrors spaced by two cavities. The absorption of one cavity is changed relative to the absorption of the other cavity by an applied electric field, to cause a change in total reflected light, as light reflecting from the outer mirrors is in phase and

I. J. Fritz; J. R. Wendt

1994-01-01

276

Electro-oxidative polymerization and spectroscopic characterization of novel amide polymers using diphenylamine coupling  

SciTech Connect

The authors have electropolymerized 1,1{prime}-bis[[p-phenylamino(phenyl)]amido-]ferrocene from CH{sub 3}CN, tetrahydrofuran (THF), and CH{sub 2}Cl{sub 2} to form an alternating main chain polymer of diphenylbenzidine and ferrocene. As a comparison, the authors have electropolymerized 1,4 bis[[p-phenylamino(phenyl)]amido-]benzene which lacks the electrochemical response of the ferrocene group. In nonaqueous solvents, the diphenylbenzidine group shows two reversible le{sup {minus}} oxidations. The second le{sup {minus}} oxidation of the diphenylbenzidine overlaps with the le{sup {minus}} oxidation of the ferrocene group at 0.88 V vs. Ag/AgCl in CH{sub 2}Cl{sub 2}. The electrochemistry of the polymer film in aqueous acid shows two le{sup {minus}} waves consistent with oxidation of the diphenylbenzidine group to the cation and then the dication. The spectroelectrochemistry of both polymer films show broad, low-energy, near-IR bands in aprotic solvents such as CH{sub 2}Cl{sub 2}, THF, and CH{sub 3}CN and aqueous solutions with pH < 3. The authors assign these bands to intermolecular {pi} stacking of the protonated diphenylbenzidinium cations. The electrochemistry of both materials is chemically reversible and forms the basis for electrochromic and redox applications.

Wang, L.; Wang, Q.Q.; Cammarata, V. [Auburn Univ., AL (United States). Dept. of Chemistry

1998-08-01

277

Limestone Corrosion by Neutrophilic Sulfur-Oxidizing Bacteria: A Coupled Microbe-Mineral System  

Microsoft Academic Search

Subsurface karst aquifers receiving sulfidic water can host complex chemolithotrophic microbial communities that are capable of dissolving limestone, forming new karstic habitat. Neutrophilic sulfur-oxidizing bacteria use reduced sulfur compounds as energy rich substrate, potentially producing sulfuric acid as a geochemically reactive byproduct. The physicochemical relationship between a biofilm forming on a limestone surface and the extent of microbial influence on

Elspeth S. Steinhauer; Christopher R. Omelon; Philip C. Bennett

2010-01-01

278

The placebo effect and relaxation response: neural processes and their coupling to constitutive nitric oxide  

Microsoft Academic Search

The placebo effect appears to be a real phenomenon as is the scientifically demonstrated and examined relaxation response. Given this, we attempt to understand how these phenomena work in light of our current understanding of central and peripheral nervous system mechanisms. Central to our hypothesis is the significance of norepinephrine, nitric oxide and opioid signaling both in the central and

George B Stefano; Gregory L Fricchione; Brian T Slingsby; Herbert Benson

2001-01-01

279

Design of a visible light driven photo-electrochemical/electro-Fenton coupling oxidation system for wastewater treatment.  

PubMed

In this study, we report on a photo-electrochemical/electro-Fenton oxidation (PEC/EF) system by coupling visible light driven photo-electrochemical oxidation (PEC) and electro-Fenton oxidation (EF) in an undivided cell. Bi2WO6 nanoplates deposited on FTO glass (Bi2WO6/FTO) and Fe@Fe2O3 core-shell nanowires supported on activated carbon fiber (Fe@Fe2O3/ACF) were used as the anode and the cathode in the PEC/EF system, respectively. This novel PEC/EF system showed much higher activity than the single PEC and EF systems on degradation of rhodamine B in aqueous solution at natural pH. Moreover, the degradation and the instantaneous current efficiencies of the PEC/EF system were increased by 154% and 26% in comparison with the sum of those of single PEC and EF systems, respectively. These significant enhancements could be attributed to the synergetic effect from better separation of photo-generated carriers in the photo-anode and the transfer of photo-electrons to the oxygen diffusion cathode to generate more electro-generated H2O2 and hydroxyl radicals on the Fenton cathode. The better separation of photo-generated carriers contribute more to the overall degradation enhancement than the photo-electrons generated H2O2 and the subsequent Fenton reaction on the cathode during the PEC/EF process. PMID:23017238

Ding, Xing; Ai, Zhihui; Zhang, Lizhi

2012-09-10

280

Advanced oxidation processes coupled with electrocoagulation for the exhaustive abatement of Cr-EDTA.  

PubMed

Using Cr-EDTA as a model system, a two-step method has been investigated for the abatement of persistent chromium complexes in water. The treatment consists of an oxidative decomposition of the organic ligands by means of ozonization or electrochemical oxidation at a boron doped diamond (BDD) electrode, followed by removal of the metal via electrochemical coagulation. In the designed synthetic waste, EDTA has been used both as a chelating agent and as a mimic of the organic content of a typical wastewater provided by a purification leather plant. A crucial point evaluated is the influence of the oxidative pretreatment on the chemical modification of the synthetic waste and hence on the electrocoagulation efficacy. Because of the great stability of Cr complexes, such as Cr-EDTA, the classical coagulation methods, based on ligand exchange between Cr(III) and Fe(II) or Fe(III), are ineffective toward Cr abatement in the presence of organic substances. On the contrary, when advanced oxidation processes (AOPs), such as ozonization or electrooxidation at a BDD anode are applied in series with electrocoagulation (EC), complete abatement of the recalcitrant Cr fraction can be achieved. ECs have been carried out by using Fe sacrificial anodes, with alternating polarization and complete Cr abatement (over 99%) has been obtained with modest charge consumption. It has been found that Cr(III) is first oxidized to Cr(VI) in the AOP preceding EC. Then, during EC, Cr(VI) is mainly reduced back to Cr(III) by electrogenerated Fe(II). Thus, Cr is mainly eliminated as Cr(III). However, a small fraction of Cr(VI) goes with the precipitate as confirmed by XPS analysis of the sludge. PMID:21255817

Durante, Christian; Cuscov, Marco; Isse, Abdirisak Ahmed; Sandonà, Giancarlo; Gennaro, Armando

2010-12-28

281

Spin-Flop Coupling and Exchange Bias in Embedded Complex Oxide Micromagnets  

NASA Astrophysics Data System (ADS)

The magnetic domains of embedded micromagnets with 2?m×2?m dimensions defined in epitaxial La0.7Sr0.3MnO3 (LSMO) thin films and LaFeO3/LSMO bilayers were investigated using soft x-ray magnetic microscopy. Square micromagnets aligned with their edges parallel to the easy axes of LSMO provide an ideal experimental geometry for probing the influence of interface exchange coupling on the magnetic domain patterns. The observation of unique domain patterns not reported for ferromagnetic metal microstructures, namely divergent antiferromagnetic vortex domains and “Z”-type domains, suggests the simultaneous presence of spin-flop coupling and local exchange bias in this system.

Takamura, Yayoi; Folven, Erik; Shu, Jonathan B. R.; Lukes, Karl R.; Li, Binzhi; Scholl, Andreas; Young, Anthony T.; Retterer, Scott T.; Tybell, Thomas; Grepstad, Jostein K.

2013-09-01

282

Carbohydrate oxidation coupled to Fe(III) reduction, a novel form of anaerobic metabolism  

Microsoft Academic Search

An isolate, designated GC-29, that could incompletely oxidize glucose to acetate and carbon dioxide with Fe(III) serving as the electron acceptor was recovered from freshwater sediments of the Potomac River, Maryland. This metabolism yielded energy to support cell growth. Strain GC-29 is a facultatively anaerobic, Gram-negative motile rod which, in addition to glucose, also used sucrose, lactate, pyruvate, yeast extract,

John D. Coates; Terry Councell; Debra J. Ellis; Derek R. Lovley

1998-01-01

283

Nitric Oxide Formation in a Premixed Flame With High-Level Plasma Energy Coupling  

Microsoft Academic Search

This paper presents quantitative planar laser-induced fluorescence (PLIF) imaging of nitric oxide (NO) in a transient-arc direct-current plasmatron igniter using premixed air\\/fuel mixtures. Quantitative measurements of NO are reported as a function of gas flow rate (20-50 standard cubic feet per hour), plasma power (100-900 mA, 150-750 W), and equivalence ratio (0.7-1.3). Images were corrected for temperature effects by using

Xing Rao; Igor B. Matveev; Tonghun Lee

2009-01-01

284

Treatment of coking wastewater by coupling electrochemical oxidation and flocculation technology  

Microsoft Academic Search

The coking wastewater drainage will bring severe water environmental pollution, so reuse of post-treatment coking wastewater as make-up water for circulating cooling system is an important way. Electrochemical oxidation combined flocculation technology was proposed for treating coking wastewater. The effects of the electrolytic voltage, current density, electrode distance, pH value, electrolytic time, concentration of electrolyte and the dosage of flocculent

Lei Zhang; Gaifeng Xue; Shangchao Liu; Nan Zhang; Aimin Duan; Lina Wang; Gang Liu

2011-01-01

285

Peroxidase-mediated oxidative coupling of 1-naphthol: Characterization of polymerization products  

Microsoft Academic Search

The oxidative polymerization of 1-naphthol was investigated in the presence of horseradish peroxidase (HRP). Naphthol polymerization products (NPP) were characterized for their relative polarity using octanol–water partitioning experiments and reverse-phase high pressure liquid chromatography, for structure using size exclusion chromatography and liquid chromatography–mass spectrometry (LC\\/MS), and for ecotoxicity using inhibition of bacterial bioluminescence. Peroxidase addition resulted in the production of

Fangxiang Xu; David E. Koch; In Chul Kong; Robert P. Hunter; Alok Bhandari

2005-01-01

286

Interactions and coupling between emissions of methane and nitrous oxide from animal husbandry  

Microsoft Academic Search

The gases methane (CH4) and nitrous oxide (N2O) contribute to global warming, while N2O also affects the ozone layer. Sources of greenhouse gas emissions in animal husbandry include animals, animal houses (indoor\\u000a storage of animal excreta), outdoor storage, manure and slurry treatment (e.g., composting, anaerobic treatment), land application\\u000a and chemical fertilisers. Although in many countries emphasis is put on reduction

G. J. Monteny; C. M. Groenestein; M. A. Hilhorst

2001-01-01

287

Lactate oxidation coupled to iron or electrode reduction by Geobacter sulfurreducens PCA.  

PubMed

Geobacter sulfurreducens PCA completely oxidized lactate and reduced iron or an electrode, producing pyruvate and acetate intermediates. Compared to the current produced by Shewanella oneidensis MR-1, G. sulfurreducens PCA produced 10-times-higher current levels in lactate-fed microbial electrolysis cells. The kinetic and comparative analyses reported here suggest a prominent role of G. sulfurreducens strains in metal- and electrode-reducing communities supplied with lactate. PMID:22003020

Call, Douglas F; Logan, Bruce E

2011-10-14

288

Lactate Oxidation Coupled to Iron or Electrode Reduction by Geobacter sulfurreducens PCA?  

PubMed Central

Geobacter sulfurreducens PCA completely oxidized lactate and reduced iron or an electrode, producing pyruvate and acetate intermediates. Compared to the current produced by Shewanella oneidensis MR-1, G. sulfurreducens PCA produced 10-times-higher current levels in lactate-fed microbial electrolysis cells. The kinetic and comparative analyses reported here suggest a prominent role of G. sulfurreducens strains in metal- and electrode-reducing communities supplied with lactate.

Call, Douglas F.; Logan, Bruce E.

2011-01-01

289

CuO/ZnO coupled oxide films obtained by the electrodeposition technique and their photocatalytic activity in phenol degradation under solar irradiation.  

PubMed

CuO/ZnO coupled oxide films were electrodeposited onto an aluminum substrate and tested as photocatalysts in degradation of phenol molecules in aqueous solution under sunlight. The obtained films were characterized by X-ray diffraction, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The results showed that the photocatalytic activity of films was significant, especially to coupled oxide film with a CuO/ZnO ratio equal to 0.697, which presented about 70% degradation of the aromatic molecules and 42% of total organic carbon (TOC) removal at 300 min under solar irradiation. Therefore, this work highlights the potential application of CuO/ZnO coupled oxide films obtained by electrodeposition onto aluminum substrate in the field of photocatalysis. PMID:24037153

Paz, Diego S; Foletto, Edson L; Bertuol, Daniel A; Jahn, Sérgio L; Collazzo, Gabriela C; da Silva, Syllos S; Chiavone-Filho, Osvaldo; Nascimento, Claudio A O do

2013-01-01

290

Inactivation of Bacillus anthracis spores by single-walled carbon nanotubes coupled with oxidizing antimicrobial chemicals.  

PubMed

In this study, we investigated the sporicidal effects of single-walled carbon nanotubes (SWCNTs) and SWCNTs combined with oxidizing antimicrobial chemicals, H?O? and NaOCl, on B. anthracis spores. The results indicated that treatment with SWCNTs alone exhibited little sporicidal effect on B. anthracis spores, while treatment with H?O? or NaOCl alone showed moderate sporicidal effect. The combination treatment with SWCNTs (100 ?g/mL) and H?O? (1.5%) or NaOCl (0.25%) exhibited much stronger sporicidal effect on the spores, compared to treatment with H?O? or NaOCl alone at the same concentrations, doubling the log reduction of viable spore number (?3.3 log vs ?1.6 log). Such enhanced sporicidal efficiency was due to the synergistic effect contributed by the two individual antimicrobial mechanisms of SWCNTs and the oxidizing antimicrobial chemicals. The ordered sequential treatment with SWCNTs and H?O? or NaOCl revealed that SWCNTs played the key role in making the spores more permeable/susceptible to chemicals. This study demonstrated the potential of combination treatment with SWCNTs and oxidizing antimicrobial agents in developing highly effective sporicidal agents/methods. PMID:23167544

Lilly, Marquita; Dong, Xiuli; McCoy, Eric; Yang, Liju

2012-11-30

291

The quantitative analysis of heroin, methadone and their metabolites and the simultaneous detection of cocaine, acetylcodeine and their metabolites in human plasma by high-performance liquid chromatography coupled with tandem mass spectrometry  

Microsoft Academic Search

For a pharmacokinetic–pharmacodynamic study in opioid tolerant patients, who were treated with heroin in combination with methadone, a liquid chromatographic assay with tandem mass spectrometry detection (LC–MS\\/MS) was developed for the simultaneous determination of heroin, methadone, heroin metabolites 6-monoacetylmorphine, morphine, and morphine-6 and 3-glucuronide and methadone metabolite EMDP. To detect any abuse of substances besides the prescribed opioids the assay

Elisabeth J. Rook; Michel J. X. Hillebrand; Hilde Rosing; Jan M. van Ree; Jos H. Beijnen

2005-01-01

292

Solar-to-Chemical Energy Conversion with Photoelectrochemical Tandem Cells.  

PubMed

Efficiently and inexpensively converting solar energy into chemical fuels is an important goal towards a sustainable energy economy. An integrated tandem cell approach could reasonably convert over 20% of the sun's energy directly into chemical fuels like H2 via water splitting. Many different systems have been investigated using various combinations of photovoltaic cells and photoelectrodes, but in order to be economically competitive with the production of H2 from fossil fuels, a practical water splitting tandem cell must optimize cost, longevity and performance. In this short review, the practical aspects of solar fuel production are considered from the perspective of a semiconductor-based tandem cell and the latest advances with a very promising technology - metal oxide photoelectrochemical tandem cells - are presented. PMID:23574955

Sivula, Kevin

2013-01-01

293

Production date determination of uranium-oxide materials by inductively coupled plasma mass spectrometry.  

PubMed

The paper describes analytical methods developed for the production date determination of uranium-based nuclear materials by the measurement of 230Th/234U isotope ratio. An improved sample preparation method for the destructive analysis involving extraction chromatographic separation with TEVA resin was applied prior to the measurement by isotope dilution inductively coupled plasma sector field mass spectrometry (ICP-SFMS). The results obtained were compared with the direct, quasi-non-destructive measurement using laser ablation ICP-SFMS technique for age determination. The advantages and limitations of both methods are discussed. PMID:17765059

Varga, Zsolt; Surányi, Gergely

2007-08-03

294

Fast and smooth etching of indium tin oxides in BCl{sub 3}/Cl{sub 2} inductively coupled plasmas  

SciTech Connect

The etching characteristics of evaporation-deposited indium tin oxide (ITO) films in BCl{sub 3}/Cl{sub 2} inductively coupled plasmas have been studied. High etch rates >200 nm/min were obtained at large BCl{sub 3}/Cl{sub 2} gas flow ratios and high rf chuck powers, suggesting that the etching process is limited by sputter desorption of InCl{sub x} and SnCl{sub x} compounds. The addition of a small amount of CF{sub 4}, which acts as reducing agent, increased the etch rate by 30% and resulted in very smooth etched surfaces. It has also been found that the material crystallinity has a pronounced influence on ITO etch rate. ITO films annealed at 500 deg. C exhibited the maximum etch resistance.

Andagana, H. B.; Cao, X. A. [Department of Computer Science and Electrical Engineering, West Virginia University, Morgantown, West Virginia 26506 (United States)

2010-03-15

295

Poly(ethylene oxide) : succinonitrile—a polymeric matrix for fast-ion conducting redox-couple solid electrolytes  

NASA Astrophysics Data System (ADS)

A blend of poly(ethylene oxide), PEO, and succinonitrile, SN, was investigated for the first time for applying it as a polymeric matrix of low-cost and thermally stable fast-ion conducting redox-couple solid polymer electrolytes. The PEO-SN blend in equal weight fraction showed room temperature ionic conductivity of 1 × 10-8 S cm-1 with nearly two orders of magnitude higher than that of PEO due to reduced crystallinity. The blend resulted in a solid electrolyte with improved ionic conductivity of ~7 × 10-4 S cm-1 at 25 °C. The blend and its electrolyte showed thermal stability up to 100 °C, which is essential for outdoor application of dye-sensitized solar cells.

Gupta, Ravindra Kumar; Kim, Hyun-Min; Rhee, Hee-Woo

2011-05-01

296

Doped Mott insulators in (111) bilayers of perovskite transition-metal oxides with a strong spin-orbit coupling.  

PubMed

The electronic properties of Mott insulators realized in (111) bilayers of perovskite transition-metal oxides are studied. The low-energy effective Hamiltonians for such Mott insulators are derived in the presence of a strong spin-orbit coupling. These models are characterized by the antiferromagnetic Heisenberg interaction and the anisotropic interaction whose form depends on the d orbital occupancy. From exact diagonalization analyses on finite clusters, the ground state phase diagrams are derived, including a Kitaev spin liquid phase in a narrow parameter regime for t(2g) systems. Slave-boson mean-field analyses indicate the possibility of novel superconducting states induced by carrier doping into the Mott-insulating parent systems, suggesting the present model systems as unique playgrounds for studying correlation-induced novel phenomena. Possible experimental realizations are also discussed. PMID:23432283

Okamoto, Satoshi

2013-02-06

297

Surface modification of organic polymers with bioactive titanium oxide without the aid of a silane-coupling agent.  

PubMed

Polyethylene (PE), polyethylene terephthalate (PET), ethylene-vinyl alcohol copolymer (EVOH), and poly(epsilon-caprolactam) (Nylon 6) were successfully modified with a thin crystalline titanium oxide layer on their surfaces by a simple dipping into a titanium alkoxide solution and a subsequent soak in hot HCl solution, without the aid of a silane-coupling agent. The surface modified polymers formed a bone-like apatite layer in a simulated body fluid (SBF) within a period of 2 days. PE, PET, and Nylon 6 formed an apatite layer faster and had a higher adhesive strength to the apatite. Three-dimensional fabrics with open spaces in various sizes containing such surface modified polymer fibers are expected to be useful as bone substitutes, since they may be able to form apatite on their constituent fibers in the living body, and thus, integrate with living bone. PMID:17277978

Balas, F; Kokubo, T; Kawashita, M; Nakamura, T

2007-02-03

298

Doped Mott Insulators in (111) Bilayers of Perovskite Transition-Metal Oxides with a Strong Spin-Orbit Coupling  

SciTech Connect

The electronic properties of Mott insulators realized in (111) bilayers of perovskite transition-metal oxides are studied. The low-energy effective Hamiltonians for such Mott insulators are derived in the presence of a strong spin-orbit coupling. These models are characterized by the antiferromagnetic Heisenberg interaction and the anisotropic interaction whose form depends on the $d$ orbital occupancy. From exact diagonalization analyses on finite clusters, the ground state phase diagrams are derived, including a Kitaev spin liquid phase in a narrow parameter regime for $t_{2g}$ systems. Slave-boson mean-field analyses indicate the possibility of novel superconducting states induced by carrier doping into the Mott-insulating parent systems, suggesting the present model systems as unique playgrounds for studying correlation-induced novel phenomena. Possible experimental realizations are also discussed.

Okamoto, Satoshi [ORNL

2013-01-01

299

Singlet oxygen in the coupled photochemical and biochemical oxidation of dissolved organic matter.  

PubMed

Dissolved organic matter (DOM) is a significant (>700 Pg) global C pool. Transport of terrestrial DOM to the inland waters and coastal zones represents the largest flux of reduced C from land to water (215 Tg yr(-1)) (Meybeck, M. Am. J. Sci. 1983, 282, 401-450). Oxidation of DOM by interdependent photochemical and biochemical processes largely controls the fate of DOM entering surface waters. Reactive oxygen species (ROS) have been hypothesized to play a significant role in the photooxidation of DOM, because they may oxidize the fraction of DOM that is inaccessible to direct photochemical degradation by sunlight. We followed the effects of photochemically produced singlet oxygen ((1)O(2)) on DOM by mass spectrometry with (18)O-labeled oxygen, to understand how (1)O(2)-mediated transformations of DOM may lead to altered DOM bioavailability. The photochemical oxygen uptake by DOM attributed to (1)O(2) increased with DOM concentration, yet it remained a minority contributor to photochemical oxygen uptake even at very high DOM concentrations. When DOM samples were exposed to (1)O(2)-generating conditions (Rose Bengal and visible light), increases were observed in DOM constituents with higher oxygen content and release of H(2)O(2) was detected. Differential effects of H(2)O(2) and (1)O(2)-treated DOM showed that (1)O(2)-treated DOM led to slower bacterial growth rates relative to unmodified DOM. Results of this study suggested that the net effect of the reactions between singlet oxygen and DOM may be production of partially oxidized substrates with correspondingly lower potential biological energy yield. PMID:20408544

Cory, Rose M; McNeill, Kristopher; Cotner, James P; Amado, Andre; Purcell, Jeremiah M; Marshall, Alan G

2010-05-15

300

Phenol coupling initiated by one-electron oxidation of tyrosine units in peptides and histone.  

PubMed

Phenoxyl radicals generated pulse radiolytically by the reaction of N.3 with Gly-Tyr decay biomolecularly (2k = 4.7 X 10(8)M-1 s-1) with efficient formation of 2,2'-dimers, which enolize rapidly (k = 2.7 X 10(4) s-1) to produce the 2,2'-biphenolic product. The build-up of the characteristic 2,2'-biphenol fluorescence (400 nm) and absorption also indicated a delayed (k = 80 s-1) process, probably involving the phenoxyl <-> phenoxy-quinol equilibrium. About 60 per cent of the Gly-Tyr phenoxyls were found to dimerize to the 2,2'-biphenol, and a similarly efficient 2,2'-coupling seems to occur with other tyrosyls, such as Lys-Tyr-Lys and histone. gamma-Radiolysis was applied to estimate relative yields of formation of 2,2'-biphenols under various conditions. Dimerization is almost completely inhibited by cysteine or oxygen, consistent with phenoxyl 'repair' by cysteine or O-.2; disproportionation of O-.2 with SOD prevents repair. The phenol 2,2'-coupling is less efficient for .OH- and inefficient for e-aq-initiation. PMID:6603438

Prütz, W A; Butler, J; Land, E J

1983-08-01

301

Advanced oxidation of aromatic VOCs using a pilot system with electron beam-catalyst coupling  

NASA Astrophysics Data System (ADS)

The decomposition of volatile organic compounds (VOCs) using a pilot system of electron beam (EB)-catalyst coupling was investigated. Two aromatic VOCs, toluene (1800 ppmC) and o-xylene (1500 ppmC), were irradiated with a dose range of 0-10 kGy at room temperature. The removal efficiencies for toluene and o-xylene were 92.4% and 94.5%, respectively, under a 10 kGy absorbed dose condition, which were higher than the results of 45.7% and 52.3% when EB-only was used, respectively. The CO2 selectivity approached 100% for both toluene and o-xylene using the EB-catalyst coupling system, while the concentrations of O3 formed were 0.02 ppm (toluene) and 0.003 ppm (o-xylene) at 10 kGy. The aerosol concentration was also measured as 43.2 ?g/m3 (toluene) and 53.4 ?g/m3 (o-xylene) at 10 kGy absorbed dose.

Kim, Ki-Joon; Kim, Junghwan; Son, Youn-Suk; Chung, Sang-Gwi; Kim, Jo-Chun

2012-05-01

302

Coupling of exothermic and endothermic reactions in oxidative conversion of natural gas into ethylene\\/olefins over diluted SrO\\/LaâOâ\\/SA5205 catalyst  

Microsoft Academic Search

In the oxidative conversion of natural gas to ethylene\\/lower olefins over SrO (17.3 wt.%)\\/LaâOâ (17.9 wt.%)\\/SA5205 catalyst diluted with inert solid particles (inerts\\/catalyst(w\\/w) = 2.0) in the presence of limited Oâ, the exothermic oxidative conversion reactions of natural gas are coupled with the endothermic C{sub 2+} hydrocarbon thermal cracking reactions for avoiding hot spot formation and eliminating heat removal problems.

Vasant R. Choudhary; Shafeek A. R. Mulla

1997-01-01

303

Tandem resonator reflectance modulator  

SciTech Connect

A wide band optical modulator is grown on a substrate as tandem Fabry-Perot resonators including three mirrors spaced by two cavities. The absorption of one cavity is changed relative to the absorption of the other cavity by an applied electric field, to cause a change in total reflected light, as light reflecting from the outer mirrors is in phase and light reflecting from the inner mirror is out of phase with light from the outer mirrors. 8 figs.

Fritz, I.J.; Wendt, J.R.

1994-09-06

304

Korean red ginseng inhibits arginase and contributes to endotheliumdependent vasorelaxation through endothelial nitric oxide synthase coupling  

PubMed Central

Korean red ginseng water extract (KG-WE) has known beneficial effects on the cardiovascular system via inducting nitric oxide (NO) production in endothelium. Endothelial arginase inhibits the activity of endothelial nitric oxide synthase (eNOS) by substrate depletion, thereby reducing NO bioavailability and contributing to vascular diseases including hypertension, aging, and atherosclerosis. In the present study, we demonstrate that KG-WE inhibits arginase activity and negatively regulates NO production and reactive oxygen species generation in endothelium. This is associated with increased dimerization of eNOS without affecting the protein expression levels of either arginase or eNOS. In a vascular tension assay, when aortas isolated from wild type mice were incubated with KG-WE, NO-dependent enhanced vasorelaxation was observed. Furthermore, KG-WE administered via by drinking water to atherogenic model mice being fed high cholesterol diet improved impaired vascular function. Taken together, these results suggest that KG-WE may exert vasoprotective effects through augmentation of NO signaling by inhibiting arginase. Therefore, KG-WE may be useful in the treatment of vascular diseases derived from endothelial dysfunction, such as atherosclerosis.

Shin, Woosung; Yoon, Jeongyeon; Oh, Goo Taeg; Ryoo, Sungwoo

2013-01-01

305

Bodipy derivatives as organic triplet photosensitizers for aerobic photoorganocatalytic oxidative coupling of amines and photooxidation of dihydroxylnaphthalenes.  

PubMed

We used iodo-Bodipy derivatives that show strong absorption of visible light and long-lived triplet excited states as organic catalysts for photoredox catalytic organic reactions. Conventionally most of the photocatalysts are based on the off-the-shelf compounds, usually showing weak absorption in the visible region and short triplet excited state lifetimes. Herein, the organic catalysts are used for two photocatalyzed reactions mediated by singlet oxygen ((1)O2), that is, the aerobic oxidative coupling of amines and the photooxidation of dihydroxylnaphthalenes, which is coupled to the subsequent addition of amines to the naphthoquinones, via C-H functionalization of 1,4-naphthoquinone, to produce N-aryl-2-amino-1,4-naphthoquinones (one-pot reaction), which are anticancer and antibiotic reagents. The photoreactions were substantially accelerated with these new iodo-Bodipy organic photocatalysts compared to that catalyzed with the conventional Ru(II)/Ir(III) complexes, which show weak absorption in the visible region and short-lived triplet excited states. Our results will inspire the design and application of new organic triplet photosensitizers that show strong absorption of visible light and long-lived triplet excited state and the application of these catalysts in photoredox catalytic organic reactions. PMID:23668289

Huang, Ling; Zhao, Jianzhang; Guo, Song; Zhang, Caishun; Ma, Jie

2013-05-23

306

Monomolecular layers and thin films of silane coupling agents by vapor-phase adsorption on oxidized aluminum  

SciTech Connect

Thin films of tetraethoxysilane [TEOS], (3-bromopropyl)trimethoxysilane [BPS], trimethoxyvinylsilane [VS], and 3-(trimethoxysilyl) propyl methacrylate [TPM] on oxidized aluminum surfaces have been investigated by reflection-absorption FTIR spectroscopy, ellipsometry, contact angle, and quartz crystal microbalance (QCM) measurements. Gravimetric measurements with the QCM can reveal quantitative aspects of adsorption and film formation, even for films as thin as monolayers. Adsorption of these silane coupling agents from solution typically produces multilayer films. Vapor-phase adsorption of TEOS and TPM at room temperature results in monomolecular layers. The coupling agents VS and BPS require additional heating after the vapor-phase adsorption to initiate the hydrolysis and condensation reactions necessary for the surface attachment, which produces one to three layers. For vapor adsorbed films a packing density of 4-7 molecules/nm{sup 2} was found. The data strongly suggest that the organic moieties in several of these films have a preferential orientation on the surface; they can be viewed as two-dimensional, oligomeric siloxane networks with oriented organic chains. Subsequent heating of TPM films results in structural rearrangements; heating of TEOS results in complete condensation to SiO{sub 2} films. 43 refs., 6 figs., 4 tabs.

Kurth, D.G.; Bein, T. [Purdue Univ., West Lafayette, IN (United States)

1992-08-06

307

Silver nanoparticle exposure attenuates the viability of rat cerebellum granule cells through apoptosis coupled to oxidative stress.  

PubMed

The impact of silver nanoparticles (AgNPs) on the central nervous system is a topic with mounting interest and concern and the facts remain elusive. In the current study, the neurotoxicity of commercial AgNPs to rat cerebellum granule cells (CGCs) and the corresponding molecular mechanism are closely investigated. It is demonstrated that AgNPs induce significant cellular toxicity to CGCs in a dose-dependent manner without damaging the cell membrane. Flow cytometry analysis with the Annexin V/propidium iodide (PI) staining indicates that the apoptotic proportion of CGCs upon treatment with AgNPs is greatly increased compared to the negative control. Moreover, the activity of caspase-3 is largely elevated in AgNP-treated cells compared to the negative control. AgNPs are demonstrated to induce oxidative stress, reflected by the massive generation of reactive oxygen species (ROS), the depletion of antioxidant glutathione (GSH), and the increase of intracellular calcium. Histological examination suggests that AgNPs provoke destruction of the cerebellum granular layer in rats with concomitant activation of caspase-3, in parallel to the neurotoxicity of AgNPs observed in vitro. Taken together, it is demonstrated for the first time that AgNPs substantially impair the survival of primary neuronal cells through apoptosis coupled to oxidative stress, depending on the caspase activation-mediated signaling. PMID:23427069

Yin, Nuoya; Liu, Qian; Liu, Jiyan; He, Bin; Cui, Lin; Li, Zhuona; Yun, Zhaojun; Qu, Guangbo; Liu, Sijin; Zhou, Qunfang; Jiang, Guibin

2013-02-20

308

A critical test of the "tunneling and coupled motion" concept in enzymatic alcohol oxidation.  

PubMed

The physical mechanism of C-H bond activation by enzymes is the subject of intense study, and we have tested the predictions of two competing models for C-H activation in the context of alcohol dehydrogenase. The kinetic isotope effects (KIEs) in this enzyme have previously suggested a model of quantum mechanical tunneling and coupled motion of primary (1°) and secondary (2°) hydrogens. Here we measure the 2° H/T KIEs with both H and D at the 1° position and find that the 2° KIE is significantly deflated with D-transfer, consistent with the predictions of recent Marcus-like models of H-transfer. The results suggest that the fast dynamics of H-tunneling result in a 1° isotope effect on the structure of the tunneling ready state: the trajectory of D-transfer goes through a shorter donor-acceptor distance than that of H-transfer. PMID:24020836

Roston, Daniel; Kohen, Amnon

2013-09-10

309

Synfuels from fusion: producing hydrogen with the Tandem Mirror Reactor and thermochemical cycles  

SciTech Connect

This volume contains the following sections: (1) the Tandem Mirror fusion driver, (2) the Cauldron blanket module, (3) the flowing microsphere, (4) coupling the reactor to the process, (5) the thermochemical cycles, and (6) chemical reactors and process units. (MOW)

Werner, R.W.; Ribe, F.L.

1981-01-21

310

Biocompatible magnetofluorescent probes: luminescent silicon quantum dots coupled with superparamagnetic iron(III) oxide.  

PubMed

Luminescent silicon quantum dots (SiQDs) are gaining momentum in bioimaging applications, based on their unique combination of optical properties and biocompatibility. Here, we report the development of a multimodal probe that combines the optical properties of silicon quantum dots with the superparamagnetic properties of iron oxide nanoparticles to create biocompatible magnetofluorescent nanoprobes. Multiple nanoparticles of each type are coencapsulated within the hydrophobic core of biocompatible phospholipid-polyethyleneglycol (DSPE-PEG) micelles. The size distribution and composition of the magnetofluorescent nanoprobes were characterized by transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS). Enhanced cellular uptake of these probes in the presence of a magnetic field was demonstrated in vitro. Their luminescence stability in a prostate cancer tumor model microenvironment was demonstrated in vivo. This paves the way for multimodal silicon quantum-dot-based nanoplatforms for a variety of imaging and delivery applications. PMID:20738120

Erogbogbo, Folarin; Yong, Ken-Tye; Hu, Rui; Law, Wing-Cheung; Ding, Hong; Chang, Ching-Wen; Prasad, Paras N; Swihart, Mark T

2010-09-28

311

Manifold, bus support and coupling arrangement for solid oxide fuel cells  

NASA Astrophysics Data System (ADS)

Individual, tubular solid oxide fuel cells (SOFCs) are assembled into bundles called a module within a housing, with a plurality of modules arranged end-to-end in a linear, stacked configuration called a string. A common set of piping comprised of a suitable high temperature resistant material: (1) provides fuel and air to each module housing, (2) serves as electrically conducting buses, and (3) provides structural support for a string of SOFC modules. Ceramic collars are used to connect fuel and air inlet piping to each of the electrodes in an SOFC module and provide: (1) electrical insulation for the current carrying bus bars and gas manifolds, (2) damping for the fuel and air inlet piping, and (3) proper spacing between the fuel and air inlet piping to prevent contact between these tubes and possible damage to the SOFC.

Parry, Gareth W.

1988-04-01

312

Reduction of bromate to bromide coupled to acetate oxidation by anaerobic mixed microbial cultures.  

PubMed

Bromate, a weakly mutagenic oxidizing agent, exists in surface waters. The biodegradation of bromate was investigated by assessing the ability of mixed cultures of micro-organisms for utilization of bromate as electron acceptor and acetate as electron donor. Reduction of bromate was only observed at relatively low concentrations (<3.0 mM) in the absence of molecular oxygen. Under these conditions bromate was reduced stoichiometrically to bromide. Unadapted sludge from an activated sludge treatment plant and a digester reduced bromate without lag period at a constant rate. Using an enrichment culture adapted to bromate, it was demonstrated that bromate was a terminal electron acceptor for anaerobic growth. Approximately 50% of the acetate was utilized for growth with bromate by the enrichment culture. A doubling of 20 h was estimated from a logarithmic growth curve. Other electron acceptors, like perchlorate, chlorate and nitrate, were not reduced or at negligible rates by bromate-utilizing microorganisms. PMID:15607164

van Ginkel, C G; van Haperen, A M; van der Togt, B

2005-01-01

313

Cu-catalyzed cross-dehydrogenative coupling: A versatile strategy for C-C bond formations via the oxidative activation of sp3 C-H bonds  

PubMed Central

Cu-catalyzed cross-dehydrogenative coupling (CDC) methodologies were developed based on the oxidative activation of sp3 C–H bonds adjacent to a nitrogen atom. Various sp, sp2, and sp3 C–H bonds of pronucleophiles were used in the Cu-catalyzed CDC reactions. Based on these results, the mechanisms of the CDC reactions also are discussed.

Li, Zhiping; Bohle, D. Scott; Li, Chao-Jun

2006-01-01

314

A novel inductively coupled plasma\\/selected-ion flow tube mass spectrometer for the study of reactions of atomic and atomic oxide ions  

Microsoft Academic Search

A novel inductively coupled plasma\\/selected-ion flow tube (ICP\\/SIFT) mass spectrometer has been constructed for the study of the kinetics and product distributions of reactions of atomic and atomic oxide ions with neutral molecules. The ICP essentially provides a universal source for atomic ions. The operation of the instrument is demonstrated with prototype reactivity and kinetic measurements.

Gregory K. Koyanagi; Vitali V. Lavrov; Vladimir Baranov; Dmitry Bandura; Scott Tanner; James W. McLaren; Diethard K. Bohme

2000-01-01

315

Carbohydrate oxidation coupled to Fe(III) reduction, a novel form of anaerobic metabolism.  

PubMed

An isolate, designated GC-29, that could incompletely oxidize glucose to acetate and carbon dioxide with Fe(III) serving as the electron acceptor was recovered from freshwater sediments of the Potomac River, Maryland. This metabolism yielded energy to support cell growth. Strain GC-29 is a facultatively anaerobic, gram-negative motile rod which, in addition to glucose, also used sucrose, lactate, pyruvate, yeast extract, casamino acids or H2 as alternative electron donors for Fe(III) reduction. Stain GC-29 could reduce NO3(-), Mn(IV), U(VI), fumarate, malate, S2O3(2-), and colloidal S0 as well as the humics analog, 2,6-anthraquinone disulfonate. Analysis of the almost complete 16S rRNA sequence indicated that strain GC-29 belongs in the Shewanella genus in the epsilon subdivision of the Proteobacteria. The name Shewanella saccharophilia is proposed. Shewanella saccharophilia differs from previously described fermentative microorganisms that metabolize glucose with the reduction of Fe(III) because it transfers significantly more electron equivalents to Fe(III); acetate and carbon dioxide are the only products of glucose metabolism; energy is conserved from Fe(III) reduction; and glucose is not metabolized in the absence of Fe(III). The metabolism of organisms like S. saccharophilia may account for the fact that glucose is metabolized primarily to acetate and carbon dioxide in a variety of sediments in which Fe(III) reduction is the terminal electron accepting process. PMID:16887653

Coates, J D; Councell, T; Ellis, D J; Lovley, D R

1998-12-01

316

Archaeoglobus fulgidus couples CO oxidation to sulfate reduction and acetogenesis with transient formate accumulation.  

PubMed

The genome sequence of Archaeoglobus fulgidus VC16 encodes three CO dehydrogenase genes. Here we explore the capacity of A. fulgidus to use CO as growth substrate. Archaeoglobus fulgidus VC16 was successfully adapted to growth medium that contained sulfate and CO. In the presence of CO and sulfate the culture OD(660) increased to 0.41 and sulfide, carbon dioxide, acetate and formate were formed. Accumulation of formate was transient. Similar results, except that no sulfide was formed, were obtained when sulfate was omitted. Hydrogen was never detected. Under the conditions tested, the observed concentrations of acetate (18 mM) and formate (8.2 mM) were highest in cultures without sulfate. Proton NMR spectroscopy indicated that CO2, and not CO, is the precursor of formate and the methyl group of acetate. Methylviologen-dependent formate dehydrogenase activity (1.4 micromol formate oxidized min(-1) mg(-1)) was detected in cell-free extracts and expected to have a role in formate reuptake. It is speculated that formate formation proceeds through hydrolysis of formyl-methanofuran or formyl-tetrahydromethanopterin. This study demonstrates that A. fulgidus can grow chemolithoautotrophically with CO as acetogen, and is not strictly dependent on the presence of sulfate, thiosulfate or other sulfur compounds as electron acceptor. PMID:17564616

Henstra, Anne M; Dijkema, Cor; Stams, Alfons J M

2007-07-01

317

Immobilization of strontium during iron biomineralization coupled to dissimilatory hydrous ferric oxide reduction  

SciTech Connect

Abstract: The potential for incorporation of strontium (Sr) into biogenic Fe(II)-bearing minerals formed during microbial reduction of synthetic hydrous ferric oxide (HFO) was investigated in circumneutral bicarbonate-buffered medium containing SrCl2 at concentrations of 10 muM, 100 muM, or 1.0 mM. CaCl2 (10 mM) was added to some experiments to simulate a Ca-rich groundwater. In Ca-free systems, 89 to 100% of total Sr was captured in solid-phase compounds formed during reduction of 30 to 40 mmol Fe(III) L-1 over a 1-month period. A smaller fraction of total Sr (25 to 34%) was incorporated into the solid phase in cultures amended with 10 mM CaCl2. X-ray diffraction identified siderite and ferroan ankerite as major end products of HFO reduction in Ca-free and Ca-amended cultures, respectively. Scanning electron microscopy-energy dispersive x-ray spectroscopy revealed the presence of Sr associated with carbonate phases. Selective extraction of HFO reduction end products indicated that 46 to 100% of the solid-phase Sr was associated with carbonates. The sequestration of Sr into carbonate phases in the Ca-free systems occurred systematically according to a heterogeneous (Doerner-Hoskins) partition coefficient (DD-H) of 1.81+/-0.15. This DD-H value was 2 to 10 times higher than values determined for incorporation of Sr (10 muM) into FeCO3(S) precipitated abiotically at rates comparable to or greater than rates observed during HFO reduction, and fivefold higher than theoretical partition coefficients for equilibrium Fe(Sr)CO3 solid solution formation. Surface complexation and entrapment of Sr by rapidly growing siderite crystals (and possibly other biogenic Fe(II) solids) provides an explanation for the intensive scavenging of Sr in the Ca-free systems. The results of abiotic siderite precipitation experiments in the presence and absence of excess Ca indicate that substitution of Ca for Sr at foreign element incorporation sites (mass action effect) on growing FeCO3(S) surfaces can account for the inhibition of Sr incorporation into the siderite component of ankerite formed in the Ca-amended HFO reduction experiments. Likewise, substitution of Fe(II) for Sr may explain the absence of major Sr partitioning into the calcite component of ankerite. The findings indicate that under appropriate conditions, sequestration of metals in siderite produced during bacterial Fe(III) oxide reduction may provide a mechanism for retarding the migration of Sr and other divalent metal contaminants in anaerobic, carbonate-rich sedimentary environments. Copyright (C) 2002 Elsevier Science Ltd.

Roden, Eric E.; Leonardo, Michael R.; Ferris, F. G.

2002-08-15

318

A Pivotal Role for Tryptophan 447 in Enzymatic Coupling of Human Endothelial Nitric Oxide Synthase (eNOS)  

PubMed Central

Tetrahydrobiopterin (BH4) is a required cofactor for the synthesis of NO by NOS. Bioavailability of BH4 is a critical factor in regulating the balance between NO and superoxide production by endothelial NOS (eNOS coupling). Crystal structures of the mouse inducible NOS oxygenase domain reveal a homologous BH4-binding site located in the dimer interface and a conserved tryptophan residue that engages in hydrogen bonding or aromatic stacking interactions with the BH4 ring. The role of this residue in eNOS coupling remains unexplored. We overexpressed human eNOS W447A and W447F mutants in novel cell lines with tetracycline-regulated expression of human GTP cyclohydrolase I, the rate-limiting enzyme in BH4 synthesis, to determine the importance of BH4 and Trp-447 in eNOS uncoupling. NO production was abolished in eNOS-W447A cells and diminished in cells expressing W447F, despite high BH4 levels. eNOS-derived superoxide production was significantly elevated in W447A and W447F versus wild-type eNOS, and this was sufficient to oxidize BH4 to 7,8-dihydrobiopterin. In uncoupled, BH4-deficient cells, the deleterious effects of W447A mutation were greatly exacerbated, resulting in further attenuation of NO and greatly increased superoxide production. eNOS dimerization was attenuated in W447A eNOS cells and further reduced in BH4-deficient cells, as demonstrated using a novel split Renilla luciferase biosensor. Reduction of cellular BH4 levels resulted in a switch from an eNOS dimer to an eNOS monomer. These data reveal a key role for Trp-447 in determining NO versus superoxide production by eNOS, by effects on BH4-dependent catalysis, and by modulating eNOS dimer formation.

Benson, Matthew A.; Batchelor, Helen; Chuaiphichai, Surawee; Bailey, Jade; Zhu, Hanneng; Stuehr, Dennis J.; Bhattacharya, Shoumo; Channon, Keith M.; Crabtree, Mark J.

2013-01-01

319

Nuclear angiotensin-(1-7) receptor is functionally coupled to the formation of nitric oxide.  

PubMed

The kidney is an important target for the actions of the renin-angiotensin system (RAS) and this tissue contains a complete local RAS that expresses the bioactive peptides angiotensin II (ANG II) and Ang-(1-7). We find both angiotensin type 1 (AT(1)R) and type 2 (AT(2)R) receptors expressed on renal nuclei that stimulate reactive oxygen species and nitric oxide (NO), respectively. Since Ang-(1-7) also exhibits actions within the kidney and the Ang-(1-7)/Mas receptor protein contains a nuclear localization sequence, we determined the expression of Ang-(1-7) receptors in nuclei isolated from the kidneys of young adult sheep. Binding studies with (125)I-[Sar(1)Thr(8)]-ANG II revealed sites sensitive to the Ang-(1-7) antagonist [d-Ala(7)]-Ang-(1-7) (DALA, A779), as well as to AT(2) and AT(1) antagonists. Incubation of Ang-(1-7) [10(-15) to 10(-9) M] with isolated cortical nuclei elicited a dose-dependent increase in the fluorescence of the NO indicator [4-amino-5-methylamino-2',7']-difluorofluorescein diacetate. The NO response to Ang-(1-7) was abolished by the NO inhibitor N-nitro-l-arginine methyl ester and DALA, but not the AT(1) antagonist losartan or the AT(2) blocker PD123319. Immunofluorescent studies utilizing the Ang-(1-7)/Mas receptor antibody revealed immunolabeling of the proximal tubules but not staining within the glomerulus in cortical sections of the sheep kidney. In the nuclear fraction of isolated proximal tubules, immunoblots revealed the precursor angiotensinogen and renin, as well as functional activity for ACE, ACE2, and neprilysin. We conclude that renal nuclei express Ang-(1-7)/Mas receptors that are functionally linked to NO formation. The marked sensitivity of the intracellular NO response to Ang-(1-7) implicates a functional role of the Ang-(1-7) axis within the nucleus. Moreover, evidence for the precursor and enzymatic components of the RAS within the nuclear compartment of the proximal tubules provides a potential pathway for the intracellular generation of Ang-(1-7). PMID:20810609

Gwathmey, Tanya M; Westwood, Brian M; Pirro, Nancy T; Tang, Lijun; Rose, James C; Diz, Debra I; Chappell, Mark C

2010-09-01

320

Tandems as injectors for synchrotrons  

SciTech Connect

This is a review on the use of Tandem electrostatic accelerators for injection and filling of synchrotrons to accelerate intense beams of heavy-ions to relativistic energies. The paper emphasizes the need of operating the Tandems in pulsed mode for this application. It has been experimentally demonstrated that at the present this type of accelerators still provides the most reliable and best performance.

Ruggiero, A.G.

1992-08-01

321

Tandems as injectors for synchrotrons  

SciTech Connect

This is a review on the use of Tandem electrostatic accelerators for injection and filling of synchrotrons to accelerate intense beams of heavy-ions to relativistic energies. The paper emphasizes the need of operating the Tandems in pulsed mode for this application. It has been experimentally demonstrated that at the present this type of accelerators still provides the most reliable and best performance.

Ruggiero, A.G.

1992-01-01

322

Oxidative coupling of tyrosine and ferulic acid residues: Intra- and extra-protoplasmic occurrence, predominance of trimers and larger products, and possible role in inter-polymeric cross-linking  

Microsoft Academic Search

I discuss the range of oxidative phenolic coupling products formed from the tyrosine residues of cell wall glycoproteins and from the feruloyl residues of wall polysaccharides possibly by the action of peroxidases and\\/or laccases. In the cases of both tyrosine- and ferulate-coupling, the coupling products are not confined to dimers but include trimers and probably higher oligomers, which are sometimes

Stephen C. Fry

2004-01-01

323

Reversed-phase chiral liquid chromatography on polysaccharide-based stationary phase coupled with tandem mass spectrometry for simultaneous determination of four stereoisomers of MK-0974 in human plasma  

Microsoft Academic Search

MK-0974 (1a), N-[(3R,6S)-6-(2,3-difluorophenyl)-2-oxo-1-(2,2,2-trifuoroethyl)azepan-3-yl]-4-(2-oxo-2,3-dihydro-1H-imidazo-[4,5-B] pyridine-1-yl)piperidine-1-carboxamide, is a novel calcitonin gene-related peptide (CGRP) receptor antagonist with two chiral centers. Direct separation of its four stereoisomers (1a–d) was achieved using a cellulose chiral stationary phase, a Chiralcel OJ-RH column (150mm×4.6mm), under reversed-phase condition, following the extraction of 0.2mL plasma on Oasis ?Elution HLB 96-well solid-phase-extraction (SPE) plate. The tandem mass spectrometric detection was

Yang Xu; Donald G. Musson

2008-01-01

324

Magnetization States of All-Oxide Spin Valves Controlled by Charge-orbital Ordering of Coupled Ferromagnets  

NASA Astrophysics Data System (ADS)

Charge-orbital ordering is commonly present in complex transition metal oxides and offers interesting opportunities for novel electronic devices. In this work, we demonstrate for the first time that the magnetization states of the spin valve can be directly manipulated by charge-orbital ordering. We investigate the interlayer exchange coupling (IEC) between two epitaxial magnetite layers separated by a nonmagnetic epitaxial MgO dielectric. We find that the state of the charge-orbital ordering in magnetite defines the strength, and even the sign of the IEC. First-principles calculations further show that the charge-orbital ordering modifies the spin polarized electronic states at the Fe3O4/MgO interfaces and results in a sufficiently large phase shift of wave function which are responsible for the observed IEC sign change across Verwey temperature. Our findings may open new interesting avenues for the electric field control of the magnetization states of spin valves via charge-orbital ordering driven IEC sign change.

Wu, Han-Chun; Mryasov, Oleg N.; Abid, Mohamed; Radican, Kevin; Shvets, Igor V.

2013-05-01

325

Magnetization states of all-oxide spin valves controlled by charge-orbital ordering of coupled ferromagnets.  

PubMed

Charge-orbital ordering is commonly present in complex transition metal oxides and offers interesting opportunities for novel electronic devices. In this work, we demonstrate for the first time that the magnetization states of the spin valve can be directly manipulated by charge-orbital ordering. We investigate the interlayer exchange coupling (IEC) between two epitaxial magnetite layers separated by a nonmagnetic epitaxial MgO dielectric. We find that the state of the charge-orbital ordering in magnetite defines the strength, and even the sign of the IEC. First-principles calculations further show that the charge-orbital ordering modifies the spin polarized electronic states at the Fe(3)O(4)/MgO interfaces and results in a sufficiently large phase shift of wave function which are responsible for the observed IEC sign change across Verwey temperature. Our findings may open new interesting avenues for the electric field control of the magnetization states of spin valves via charge-orbital ordering driven IEC sign change. PMID:23665858

Wu, Han-Chun; Mryasov, Oleg N; Abid, Mohamed; Radican, Kevin; Shvets, Igor V

2013-01-01

326

Synthesis of (arylimido)vanadium complexes and their application for oxidative coupling reactions of silyl enol ether derivatives.  

PubMed

(Arylimido)vanadium(v) complexes, V(NAr)(OEt)Cl(2) [Ar = C(6)H(5), p-BrC(6)H(4), p-(MeO)C(6)H(4)] or V(NAr)Cl(3) [Ar = o-BrC(6)H(4), o-(MeO)C(6)H(4)] were synthesized by the reaction of VO(OEt)Cl(2) or VOCl(3), respectively, with the corresponding aryl isocyanates. X-Ray crystal structure determination for V(NAr)(OEt)Cl(2) (Ar = C(6)H(5) and p-BrC(6)H(4)) elucidates the alkoxido-bridged dimeric building blocks [V(NAr)(OEt)Cl(2)](2), wherein the substituent on the benzene ring was found to affect the character of the imido nitrogen. The (51)V NMR spectroscopic measurements indicated that the electronic state of the vanadium metal centre depends on the ligands connecting to the vanadium and the substituents on the benzene ring. The selective oxidative cross-coupling reaction of silyl ketene acetal with silyl enol ether was achieved using V(Np-BrC(6)H(4))Cl(3) or V(No-BrC(6)H(4))Cl(3). PMID:20859592

Nishina, Masafumi; Moriuchi, Toshiyuki; Hirao, Toshikazu

2010-09-22

327

X-ray absorption spectroscopy studies of spin-orbit coupling in 5d transition metal oxides.  

PubMed

In order to examine the effects of strong valence band spin-orbit coupling (SOC) in 5d transition metal oxides (TMOs), we have investigated the L(2) and L(3) edge white-line intensities of the x-ray absorption spectra of several 5d TMOs. The white-line intensities at both edges are found to decrease monotonously with increasing 5d electron occupancy, while their ratio showed anomalous behavior for late 5d TMOs (IrO(2), PtO(2), and Au(2)O(3)), deviating significantly from the theoretical value of 2 expected for the case of weak SOC. This observation serves as a clear experimental indication of strong SOC effects in 5d TMOs. We also discussed how the 5d TMOs can have charge transfer effects different from their counterpart 5d elemental metals by making comparative studies. Our works demonstrate the importance of j quantum states due to strong SOC in the 5d system. PMID:22227572

Cho, Deok-Yong; Park, Junghwan; Yu, Jaejun; Park, Je-Geun

2012-01-06

328

Platinum(II)-mediated dehydrosulfurization and oxidative carbon-carbon coupling in the gas-phase decomposition of thioethers  

NASA Astrophysics Data System (ADS)

The ion/molecule reaction (IMR) of "roll-over" cyclometalated [Pt(bipy-H)]+ (1) (bipy = 2,2'-bipyridine) with dimethyl sulfide (2) leads to the loss of ethene in the main reaction channel (55%); this corresponds to a formal dehydrosulfurization accompanied by the dehydrogenative ("oxidative") C-C coupling of the two methyl groups in dimethyl sulfide to form ethene. In order to obtain deeper insight into this rare reaction, the IMRs of 1 with several symmetric, asymmetric as well as cyclic thioethers and some thiols are probed. Common to many substrates is the formal transfer of H2S from the organic sulfur compound to the [Pt(bipy-H)]+ core accompanied by the expulsion of one or more alkene units. In contrast to the behavior of [Pt(bipy-H)]+ (1), bare Pt+, diatomic PtH+, and also the complex [Pt(phpy-H)]+ (phpy = 2-phenyl pyridine) are not able to bring about dehydrosulfurization. It is accordingly suggested that the (bipy-H)-ligand does not only affect the electronic structure of the platinum(II) core but, moreover, plays an active role as an acceptor in the initial hydrogen transfer from the thioether ligand to the LPt+ core (L = heterocyclic ligand).

Butschke, Burkhard; Schlangen, Maria; Schröder, Detlef; Schwarz, Helmut

2009-06-01

329

Structure of cytochrome a3-Cua3 couple in cytochrome c oxidase as revealed by nitric oxide binding studies.  

PubMed

The addition of NO to oxidized cytochrome c oxidase (ferrocytochrome c:oxygen oxidoreductase, EC 1.9.3.1) causes the appearance of a high-spin heme electron paramagnetic resonance (EPR) signal due to cytochrome a3. This suggests that NO coordinates to Cu+2a3 and breaks the antiferromagnetic couple by forming a cytochrome a+33-Cu+2a3-NO complex. The intensity of the high-spin cytochrome a3 signal depends on the method of preparation of the enzyme and maximally accounts for 58% of one heme. The effect of N-3 on the cytochrome a+33-Cu+2a3-NO complex is to reduce cytochrome a3 to the ferrous state, and this is followed by formation of a new complex that exhibits EPR signals characteristic of a triplet species. On the basis of optical and EPR results, a NO bridge between cytochrome a+23 and Cu+2a3 is proposed--i.e., cytochrome a+23-NO-Cu+2a3. The half-field transition observed at g = 4.34 in the EPR spectrum of this triplet species exhibits resolved copper hyperfine splittings with [A+2] = 0.020 cm-1, indicating that the Cu+2a3 in the cytochrome a+23-NO-Cu+2a3 complex is similar to a type 2 copper site. PMID:226967

Stevens, T H; Brudvig, G W; Bocian, D F; Chan, S I

1979-07-01

330

A novel use of oxidative coupling reactions for determination of some statins (cholesterol-lowering drugs) in pharmaceutical formulations  

NASA Astrophysics Data System (ADS)

New, accurate and reliable spectrophotometric methods for the assay of three statin drugs, atorvastatin calcium (AVS), fluvastatin sodium (FVS) and pravastatin sodium (PVS) in pure form and pharmaceutical formulations have been described. All methods involve the oxidative coupling reaction of AVS, FVS and PVS with 3-methyl-2-benzothiazolinone hydrazone hydrochloride monohydrate (MBTH) in the presence of Ce(IV) in an acidic medium to form colored products with ?max at 566, 615 and 664 nm, respectively. Beer's law was obeyed in the ranges of 2.0-20.0, 4.9-35.4 and 7.0-30.0 ?g mL -1 for AVS-MBTH, FVS-MBTH and PVS-MBTH, respectively. Molar absorptivities for the above three methods were found to be 3.24 × 10 4, 1.05 × 10 4 and 0.68 × 10 4 L mol -1 cm -1, respectively. Statistical treatment of the experimental results indicates that the methods are precise and accurate. The proposed methods have been applied to the determination of the components in commercial forms with no interference from the excipients. A comparative study between the suggested procedures and the official methods for these compounds in the commercial forms showed no significant difference between the two methods.

Ashour, Safwan; Bahbouh, Mahmoud; Khateeb, Mouhammed

2011-03-01

331

A novel use of oxidative coupling reactions for determination of some statins (cholesterol-lowering drugs) in pharmaceutical formulations.  

PubMed

New, accurate and reliable spectrophotometric methods for the assay of three statin drugs, atorvastatin calcium (AVS), fluvastatin sodium (FVS) and pravastatin sodium (PVS) in pure form and pharmaceutical formulations have been described. All methods involve the oxidative coupling reaction of AVS, FVS and PVS with 3-methyl-2-benzothiazolinone hydrazone hydrochloride monohydrate (MBTH) in the presence of Ce(IV) in an acidic medium to form colored products with ?(max) at 566, 615 and 664 nm, respectively. Beer's law was obeyed in the ranges of 2.0-20.0, 4.9-35.4 and 7.0-30.0 ?g mL(-1) for AVS-MBTH, FVS-MBTH and PVS-MBTH, respectively. Molar absorptivities for the above three methods were found to be 3.24×10(4), 1.05×10(4) and 0.68×10(4) L mol(-1) cm(-1), respectively. Statistical treatment of the experimental results indicates that the methods are precise and accurate. The proposed methods have been applied to the determination of the components in commercial forms with no interference from the excipients. A comparative study between the suggested procedures and the official methods for these compounds in the commercial forms showed no significant difference between the two methods. PMID:21237703

Ashour, Safwan; Bahbouh, Mahmoud; Khateeb, Mouhammed

2010-08-20

332

Multiplex Ultra-Performance Liquid Chromatography-Tandem Mass Spectrometry Method for Simultaneous Quantification in Human Plasma of Fluconazole, Itraconazole, Hydroxyitraconazole, Posaconazole, Voriconazole, Voriconazole-N-Oxide, Anidulafungin, and Caspofungin? †  

PubMed Central

Therapeutic drug monitoring (TDM) may contribute to optimizing the efficacy and safety of antifungal therapy because of the large variability in drug pharmacokinetics. Rapid, sensitive, and selective laboratory methods are needed for efficient TDM. Quantification of several antifungals in a single analytical run may best fulfill these requirements. We therefore developed a multiplex ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method requiring 100 ?l of plasma for simultaneous quantification within 7 min of fluconazole, itraconazole, hydroxyitraconazole, posaconazole, voriconazole, voriconazole-N-oxide, caspofungin, and anidulafungin. Protein precipitation with acetonitrile was used in a single extraction procedure for eight analytes. After reverse-phase chromatographic separation, antifungals were quantified by electrospray ionization-triple-quadrupole mass spectrometry by selected reaction monitoring detection using the positive mode. Deuterated isotopic compounds of azole antifungals were used as internal standards. The method was validated based on FDA recommendations, including assessment of extraction yields, matrix effect variability (<9.2%), and analytical recovery (80.1 to 107%). The method is sensitive (lower limits of azole quantification, 0.01 to 0.1 ?g/ml; those of echinocandin quantification, 0.06 to 0.1 ?g/ml), accurate (intra- and interassay biases of ?9.9 to +5% and ?4.0 to +8.8%, respectively), and precise (intra- and interassay coefficients of variation of 1.2 to 11.1% and 1.2 to 8.9%, respectively) over clinical concentration ranges (upper limits of quantification, 5 to 50 ?g/ml). Thus, we developed a simple, rapid, and robust multiplex UPLC-MS/MS assay for simultaneous quantification of plasma concentrations of six antifungals and two metabolites. This offers, by optimized and cost-effective lab resource utilization, an efficient tool for daily routine TDM aimed at maximizing the real-time efficacy and safety of different recommended single-drug antifungal regimens and combination salvage therapies, as well as a tool for clinical research.

Decosterd, Laurent Arthur; Rochat, Bertrand; Pesse, Benoit; Mercier, Thomas; Tissot, Frederic; Widmer, Nicolas; Bille, Jacques; Calandra, Thierry; Zanolari, Boris; Marchetti, Oscar

2010-01-01

333

Photocatalytic degradation of toluene over doped and coupled (Ti,M)O 2 (M = Sn or Zr) nanocrystalline oxides: Influence of the heteroatom distribution on deactivation  

Microsoft Academic Search

In this work, we have studied the photocatalytic oxidation (PCO) of toluene over Sn- and Zr-doped TiO2, and coupled TiO2\\/SnO2 and TiO2\\/ZrO2 catalysts. The TiO2 sample doped with Sn (8% of metal ions) is composed by the anatase and rutile phases of TiO2, while the Zr-doped sample (same dopant content) contains only the anatase phase. The coupled photocatalysts are formed,

Fernando Fresno; María D. Hernández-Alonso; David Tudela; Juan M. Coronado; Javier Soria

2008-01-01

334

Magnetic order and interfacial coupling in oxide thin films and heterostructures probed with soft x-ray dichroism  

SciTech Connect

The combination of novel magnetic properties induced by reduced dimensionality and strong magnetic interactions across interfaces leads to intriguing new properties in magnetic hetero- and nanostructures not observed in the constituent materials in bulk form. It is the careful optimization of the characteristics of the individual layers as well as the magnetic coupling across the interface that allows us to control the magnetic properties and tailor them for devices, e.g., in information storage and processing technology. Soft x-ray magnetic spectroscopies can make unique contributions to improving our understanding of complex magnetic nanostructures since these techniques provide elemental, valence- and site-symmetry specific information with high sensitivity and tunable probing depth. X-ray magnetic circular dichroism (XMCD) is sensitive to (unidirectional) ferromagnetic order, while x-ray magnetic linear dichroism (XMLD) can also detect (uniaxial) antiferromagnetic order. A crystalline electric field with cubic symmetry induces only a weak angular dependence in XMCD spectra [1] but can cause a very pronounced anisotropy in XMLD spectra [2]. Furthermore, non-magnetic sites with a distorted local cubic symmetry can give rise to an x-ray linear dichroism (XLD). In this presentation, we discuss how to distinguish between the individual contributions to soft x-ray dichroism spectra in order to extract the wealth of information about magnetic thin films, interfaces and hetero- and nanostructures contained in the data [3, 4, 5] We determined the magnetic structure of La{sub 0.7}Sr{sub 0.3}MnO{sub 3} (LSMO)/La{sub 0.7}Sr{sub 0.3}FeO{sub 3} (LSFO) superlattices with 6 unit cell thick sublayers using soft x-ray magnetic dichroism [5]. Circular dichroism was employed to study the characteristics of the ferromagnetic LSMO layer indicating a reduced magnetic ordering temperature of 200 K compared to the bulk value of 360 K. Linear dichroism is used to analyze the antiferromagnetic order in the LSFO layers which persists up to the bulk Neel temperature near 400 K. Our experiments clearly show that when the magnetization of the LSMO layer is aligned with a magnetic field, a torque is created on the Fe moments in the LSFO layer through exchange coupling at the interface realigning the Fe moments as well. Through comparison with theoretical calculations we are able to show that independent of the LSMO magnetization direction in the sample surface plane, the Fe moments are always oriented perpendicular to the Mn moments. This perpendicular alignment is due to the frustrated exchange coupling at the interface and the weak anisotropy in the thin LSFO layer. Revisiting previous XMLD studies of the Co/NiO(001) interface taking the impact of the crystal electric field on the XMLD into account for the first time, we show that NiO(001) exhibits a crystallographic and magnetic domain structure near the surface that is identical to that of the bulk. Upon Co deposition perpendicular coupling of Co and Ni moments is observed [2, 3] that persists even in the presence of uncompensated interface moments. We also measured the asphericity and the energy splitting of the 4f states in EuO thin films [4] - a material with fascinating properties and of technological importance for spintronics applications - using XMLD. Our measurements, which are confirmed by multiplet calculations, show that there is significant 4f anisotropy. This suggests that pinning of the f states by the local environment becomes feasible and can be tuned by external conditions, chemical doping, and strain for use in device applications. Moreover, we will discuss the impact of epitaxial strain on the magnetic properties and XMLD spectra of complex oxide thin films.

Arenholz, Elke; van der Laan, G.

2009-02-01

335

Assessing the kinetics of high temperature oxidation of Inconel 617 in a dedicated HTR impure helium facility coupling thermogravimetry and gas phase chromatography  

NASA Astrophysics Data System (ADS)

A new facility coupling thermogravimetric analysis (TGA) with gas phase chromatography (GPC) has been developed. This facility is dedicated for studying high temperature oxidation of Inconel 617 in impure helium environment containing H2O, H2 and CO at very low partial pressures (in the Pa range), which is representative of the high temperature reactor (HTR) concept developed within the Generation IV Forum. Simultaneous acquisition of mass gain and gas composition has allowed the influence of carbon monoxide and water vapour on the kinetics of oxidation to be studied. GPC measurements of gas consumption have allowed the plotting of individual mass gain curves for oxidation by H2O and CO. During isothermal exposure at 1123 K for 20 h, the oxidation was mainly due to water vapour with a minor contribution of carbon monoxide during the first hours. The contribution of water vapour to the oxidation kinetics was extracted. It was shown to obey a complete parabolic law and to be limited by an interfacial reaction during the first few hours of oxidation and to be controlled by a mixed interfacial and diffusion process, diffusion becoming the rate-determining step for long term oxidation. There was very good agreement between GPC measurements and the experimental TGA results.

Chapovaloff, J.; Rouillard, F.; Combrade, P.; Pijolat, M.; Wolski, K.

2013-10-01

336

A kinetic model of the dissolution of copper(II) oxide in EDTA solutions considering the coupling of metal and oxide ion transfer  

Microsoft Academic Search

The dissolution of metal oxides in solutions is related to the durability of protective oxide films on metals and the removal of corrosion scales on steels, and is important in corrosion science and corrosion protection engineering. In the study here, copper(II) oxide was sintered in a disk shape to maintain a constant surface area throughout dissolution, and the concentration of

Hiroki Tamura; Naotsugu Ito; Masahiko Kitano; Shinichi Takasaki

2001-01-01

337

Covalently linked tandem lesions in DNA.  

PubMed

Reactive oxygen species (ROS) generate a type of DNA damage called tandem lesions, two adjacent nucleotides both modified. A subcategory of tandem lesions consists of adjacent nucleotides linked by a covalent bond. Covalently linked tandem lesions generate highly characteristic liquid chromotography-tandem mass spectrometry (LC-MS/MS) elution profiles. We have used this property to comprehensively survey X-irradiated DNA for covalently linked tandem lesions. A total of 15 tandem lesions were detected in DNA irradiated in deoxygenated aqueous solution, five tandem lesions were detected in DNA that was irradiated in oxygenated solution. PMID:23106212

Patrzyc, Helen B; Dawidzik, Jean B; Budzinski, Edwin E; Freund, Harold G; Wilton, John H; Box, Harold C

2012-10-29

338

Use of oxidation and reduction vapor generation for lowering the detection limits of iodine in biological samples by inductively coupled plasma atomic emission spectrometry  

Microsoft Academic Search

Procedures of microwave oxygen combustion and microwave acid digestion of biological samples were optimized for the subsequent\\u000a determination of iodine. A new method was proposed for the generation of vapor iodine from periodate ions using hydrogen peroxide\\u000a as a reductant. Procedures were developed for determining iodine in biological samples by inductively coupled plasma atomic\\u000a emission spectrometry (ICP-AES) using oxidation and

E. A. Vtorushina; A. I. Saprykin; G. Knapp

2009-01-01

339

Optimization of process parameters and catalyst compositions in carbon dioxide oxidative coupling of methane over CaO–MnO\\/CeO 2 catalyst using response surface methodology  

Microsoft Academic Search

The optimization of process parameters and catalyst compositions for the CO2 oxidative coupling of methane (CO2-OCM) reaction over CaO–MnO\\/CeO2 catalyst was developed using Response Surface Methodology (RSM). The relationship between the responses, i.e. CH4 conversion, C2 hydrocarbons selectivity or yield, with four independent variables, i.e. CO2\\/CH4 ratio, reactor temperature, wt.% CaO and wt.% MnO in the catalyst, were presented as

Istadi; Nor Aishah Saidina Amin

2006-01-01

340

A Miniature Micro-Machined Millimeter-Wave Bandpass Filter By Complementary MetalOxideSemiconductor Compatible Inductively-Coupled-Plasma Deep-Trench Technology  

Microsoft Academic Search

In this paper, we demonstrate that miniature millimeter-wave band-pass filter can be obtained by replacing the traditional coplanar waveguide structures with the miniature lumped-spiral inductors and metal-insulator-metal (MIM) capacitors. To study the silicon substrate effects on the performances of the miniature spiral inductor and band-pass filter, complementary metal-oxide-semiconductor (CMOS)-process-compatible backside inductively-coupled-plasma (ICP) deep-trench technology was used to selectively remove the

Jin-Fa Chang; Yo-Sheng Lin; Chi-Chen Chen; Chang-Zhi Chen; Tao Wang; Shey-Shi Lu

2008-01-01

341

Enhanced catalytic activity of zeolite encapsulated Fe(III)-Schiff-base complexes for oxidative coupling of 2-napthol.  

PubMed

Iron(III) Schiff-base complexes of general formula [Fe(L)(2)Cl]·2H(2)O, where L = N,?-bis(salicylidene)ethylenediamine and N,N?-disalicylidene-1,2-phenylenediamine have been encapsulated within various alkali exchanged zeolites viz. LiY, NaY, and KY by flexible ligand method. The encapsulated complexes are characterized by EDX, scanning electron microscopy (SEM), powder X-ray diffraction (XRD), FT-IR, UV-vis, diffuse reflectance spectroscopy (DRS), electron spin resonance spectroscopy (ESR) and cyclic voltammetry studies. The diffuse reflectance UV-vis spectra of encapsulated complexes show a dramatic red shift of the charge transfer band with increasing electropositivity of the exchangeable cations. The electrochemical analysis predicts the shifting of the reduction potential toward negative values with increasing size of the alkali exchanged cations. The zeolite encapsulated Schiff-base complexes of iron are found to be catalytically active toward the oxidative coupling of 2-napthol. Metal complexes incorporated in potassium exchanged zeolite-Y are found to be more effective for catalytic conversion of 2-naphthol to binaphthol and induces higher selectivity toward the R-conformation. The catalytic conversion of 2-napthol to BINOL is found to depend on the reduction potential of the catalyst, with a more negative reduction potential being better for the catalytic conversion. Density functional calculation is being carried out on both the neat Fe-Salen and Fe-Salophen complexes and those encapsulated in NaY zeolite to investigate change in structural parameters, energies of the HOMO and LUMO, and global hardness and softness. Fukui functions, as local descriptors, are used to analyze the hard-hard interaction at a particular site of the complexes. PMID:22256783

Bania, Kusum K; Bharali, Dipsikha; Viswanathan, B; Deka, Ramesh C

2012-01-18

342

Simultaneous determination of aflatoxin B(1) and ochratoxin A in licorice roots and fritillary bulbs by solid-phase extraction coupled with high-performance liquid chromatography-tandem mass spectrometry.  

PubMed

An effective method was developed for screening licorice roots and fritillary bulbs for contamination by aflatoxin B(1) and ochratoxin A using high-performance liquid chromatography connected to tandem mass spectrometry (HPLC-MS/MS). The samples were pre-concentrated and purified using solid-phase extraction, which provided satisfactory results. The separation was performed on a Waters Xbridge(TM) C18 column with a linear gradient of acetonitrile - water containing 5mM ammonium acetate. The MS spectrum was acquired in positive mode with both single quadrupole (Q1) and multiple reaction monitoring (MRM). The optimised method offered a good linear correlation (r(2)>0.9967), excellent precision (RSD<2.83%) and acceptable recovery (from 92.78 to 105.37%). The limits of detection (LOD) and the limits of quantification (LOQ) were less than 0.024 ?g/kg and 0.095 ?g/kg, respectively. The validated method was successfully applied to the rapid screening for AFB(1) and OTA in licorice roots and fritillary bulbs. PMID:23411213

Wang, Lizhi; Wang, Zhen; Gao, Weiwei; Chen, Juan; Yang, Meihua; Kuang, Ying; Huang, Linfang; Chen, Shilin

2012-11-24

343

Fully-automated on-line solid phase extraction coupled to high-performance liquid chromatography-tandem mass spectrometric analysis at sub-ng/L levels of selected estrogens in surface water and wastewater.  

PubMed

A fully-automated on-line solid phase extraction liquid chromatographic/electrospray ionization tandem mass spectrometric method for the analysis of estrone (E1), 17-?-estradiol (?-E2), 17-?-ethinylestradiol (EE2), 17-?-estradiol (?-E2) and estriol (E3) in surface water and wastewater was developed. The method showed a very good linearity from 250 ng/L down to compound specific quantification limits, which were included between 0.25 and 2.00 ng/L. These limits were obtained with 2.5 mL aliquots of injected sample and the total analysis time per sample was slightly less than 10 min. Under these conditions, detection limits were 0.15 ng/L for E1, 0.31 ng/L for ?-E2, 0.52 ng/L for EE2, 0.59 ng/L for ?-E2 and 0.95 ng/L for E3. The method reliability was tested on different kinds of real samples spiked with the estrogens, obtaining recoveries approximately included between 71 and 95%. The application to samples collected in rivers, lakes and wastewater treatment plants evidenced the presence of the investigated compounds at sub-ng/L or low ng/L concentration levels. PMID:23433884

Ciofi, L; Fibbi, D; Chiuminatto, U; Coppini, E; Checchini, L; Del Bubba, M

2013-01-28

344

Development and optimisation of an on-line solid phase extraction coupled to ultra-high-performance liquid chromatography-tandem mass spectrometry methodology for the simultaneous determination of endocrine disrupting compounds in wastewater samples.  

PubMed

A process using a fully automated on-line solid-phase extraction system combined with ultra-high-performance liquid chromatography and tandem mass spectrometry detection (SPE-UHPLC-MS/MS) has been developed and applied to the determination of 27 endocrine disrupting compounds (EDCs) in sewage samples. This technology allows separation and detection of all substances in a single chromatographic run that requires less than 4 min. In order to obtain a more sensitive method for the quantification of these compounds in sewage samples, an on-line solid-phase extraction step with Oasis HLB columns was performed prior to chromatographic determination. The complete analysis of each sample by this process requires only 9 min, provides satisfactory recoveries (72-110%) and limits of detection on the order of a few nanograms per liter (0.3-2.1 ng L(-1)), demonstrating their potential for analyses of environmental samples. Thus, this methodology has been applied to samples collected from two wastewater treatment plants (WWTPs) located in Las Palmas de Gran Canaria (Canary Islands, Spain). One of these plants utilised conventional activated sludge treatment (CAS), while the other employed biomembrane reactor treatment (MBR). PMID:22342207

Vega-Morales, T; Sosa-Ferrera, Z; Santana-Rodríguez, J J

2012-02-02

345

Transition-metal-free oxidative coupling reactions for the formation of C-C and C-N bonds mediated by TEMPO and its derivatives.  

PubMed

The application of nitroxides for the development of new synthetic methods and their implementation in polymer chemistry, material science and beyond is one of the major research topics in our laboratory in the institute of organic chemistry at the WWU Münster. This short review focuses on our recent progress towards nitroxide-based transition-metal-free oxidative coupling reactions. The demand for organic surrogates for transition metals in such transformations is in our eyes unquestionable, since environmental and economic issues have become progressively more important in recent years. For this purpose, the 2,2,6,6-tetramethylpiperidine-N-oxyl radical (TEMPO) is shown to be a highly efficient oxidant for the homo- and cross-coupling of Grignard reagents. This powerful C-C bond forming strategy allows the generation of conjugated polymers from bifunctional Grignard reagents. Moreover, cross-coupling of alkynyl Grignard compounds and nitrones can be accomplished under aerobic atmosphere with catalytic amounts of TEMPO. It is also shown that TEMPO-derived N-oxoammonium salts can act as suitable oxidants for formation of C-N bonds between non-preactivated benzoxazoles and secondary amines under metal-free conditions. PMID:22871285

Murarka, Sandip; Wertz, Sebastian; Studer, Armido

2012-01-01

346

Unexpected weak magnetic exchange coupling between haem and non-haem iron in the catalytic site of nitric oxide reductase (NorBC) from Paracoccus denitrificans1.  

PubMed

Bacterial NOR (nitric oxide reductase) is a major source of the powerful greenhouse gas N2O. NorBC from Paracoccus denitrificans is a heterodimeric multi-haem transmembrane complex. The active site, in NorB, comprises high-spin haem b3 in close proximity with non-haem iron, FeB. In oxidized NorBC, the active site is EPR-silent owing to exchange coupling between FeIII haem b3 and FeBIII (both S=5/2). On the basis of resonance Raman studies [Moënne-Loccoz, Richter, Huang, Wasser, Ghiladi, Karlin and de Vries (2000) J. Am. Chem. Soc. 122, 9344-9345], it has been assumed that the coupling is mediated by an oxo-bridge and subsequent studies have been interpreted on the basis of this model. In the present study we report a VFVT (variable-field variable-temperature) MCD (magnetic circular dichroism) study that determines an isotropic value of J=-1.7 cm-1 for the coupling. This is two orders of magnitude smaller than that encountered for oxo-bridged diferric systems, thus ruling out this configuration. Instead, it is proposed that weak coupling is mediated by a conserved glutamate residue. PMID:23421449

Van Wonderen, Jessica H; Oganesyan, Vasily S; Watmough, Nicholas J; Richardson, David J; Thomson, Andrew J; Cheesman, Myles R

2013-05-01

347

Fundamental studies of the mechanism of catalytic reactions with catalysts effective in the gasification of carbon solids and the oxidative coupling of methane  

SciTech Connect

Work will continue on the oxidative coupling reaction of methane over ternary oxide catalysts to produce C{sub 2}, C{sub 3} and C{sub 4} hydrocarbons and particularly olefins with high selectivity. The work which has shown that close to 100% selectivity can be obtained has received wide attention and has resulted in collaborative efforts with industry (CRADA) towards the development of a commercial process. An immediate purpose of additional work is to increase the conversion without diminishing the extremely high selectivity of the reaction and also to permit operation at higher space velocity to reduce equipment size. The mechanism of this reaction is not understood and much additional work is needed to explain the role of carbon formation and of water as intermediates in the reaction and to investigate whether carbon oxides are intermediates. It has been found that oxides other than calcium-nickel-potassium oxides can be useful catalysts for this reaction in the presence of steam and at relatively low temperatures and long contact times. Better definition of the class of binary metal oxides is required and better catalyst characterization is needed to ensure reproducibility of catalyst preparation and operational results. Pretreatment of the catalyst should be shortened and higher space velocities must be obtained. Close collaboration with Orion ACT is required to advance the project toward the pilot plant stage. In the area of coal and char catalytic steam gasification, the large volume of data obtained at atmospheric pressure will be extended to operations at higher pressures.

Heinemann, H.; Somorjai, G.A.; Perry, D.L.

1992-03-01

348

Effects of metallic, semiconducting, and insulating substrates on the coupling involving radiative polaritons in thin oxide films.  

PubMed

Through simulations, this work explores the effects of conducting, semiconducting, and insulating substrates on the absorption of infrared radiation by radiative polaritons in oxide layers with thicknesses that range from 30 nm to 9 ?m. Using atomic layer deposition, oxide layers can be formed in the nanometer scale. Our results suggest that the chemistry and conductivity of the substrate determine the amount of absorption by radiative polaritons in oxide layers thinner than the skin depth. The effects of the chemistry and conductivity of the substrate are especially effective for oxide films thinner than about 250 nm, which we label as the substrate sensitive thickness of the oxide film. PMID:22449283

Vincent-Johnson, Anita J; Vasquez, Kyle A; Scarel, Giovanna; Hammonds, James S; Francoeur, Mathieu

2012-02-01

349

The efficacy of oxidative coupling for promoting in-situ immobilization of hydroxylated aromatics in contaminated soil and sediment systems. 1998 annual progress report  

SciTech Connect

'Hydroxylated aromatic compounds (HAC''s) and their precursors are common contaminants of surface and subsurface systems at DOE facilities. The environmental fate and transport of such compounds, particularly in subsurface systems, is generally dominated by their sorption and desorption by soils and sediments. Certain secondary chemical reactions, most specifically abiotic and/or enzymatic oxidative coupling, may be significant in controlling the sorption and subsequent desorption of such hydroxylated aromatics by soils and sediments. The principal objectives of this study are to investigate: (1) the role of abiotic/enzymatic coupling reactions on the immobilization of HAC''s; (2) the effects of environmental factors on such immobilization; and (3) preliminary engineering approaches utilizing enhanced abiotic/enzymatic coupling reactions to immobilize hydroxylated aromatics in-situ. Information gathered from the study will be useful in quantifying the behavior of this class of organic compounds in various subsurface contamination scenarios relevant to DOE facilities, and in specifying strategies for the selection and design of remediation technologies. Over the first two years of this three-year project, the authors have developed a significantly improved understanding of the mechanisms of hydroxylated aromatic compound sorption and immobilization by natural soils and sediments. Immobilization in this context is attributed to oxidative coupling of the hydroxylated aromatics subsequent to their sorption to a soil or sediment, and is quantified in terms of the amount of a sorbed target compound retained by a sorbent after a series of sequential water and solvent extractions. The presence of oxygen, metal oxides, and organic matter, all of which can potentially catalyze/facilitate the abiotic oxidative coupling of HAC''s, were investigated during these first two years. Three different HAC''s: phenol, trichlorophenol and o-cresol were included in the experimental program. Inorganic soil matrices were represented by a glacial wash sand (Wurtsmith sand) having very low organic content. Because the chemical nature of soil organic matter may potentially affect the extent of coupling or immobilization, sorbents having different organic matter compositions are being investigated. Two of the three studied to date are near-surface soils, characterized by geologically younger organic material (Fox Forest soil and Fox Grassland soil). The third sorbent is an older and diagenetically altered soil (Lachine Shale). Sorbent preparation, characterization and experimental protocol development were completed in the first year of the study while the second year of the project has focused primarily on experiments with natural systems, as planned. Preliminary work with engineered systems has been initiated earlier than scheduled in order to integrate and relate all aspects of the study.'

Weber, W.J. [Univ. of Michigan, Ann Arbor, MI (US); Bhandari, A. [Kansas State Univ., Manhattan, KS (US)

1998-06-01

350

Simple and sensitive assay for quantification of oseltamivir and its active metabolite oseltamivir carboxylate in human plasma using high-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry: improved applicability to pharmacokinetic study.  

PubMed

Although liquid chromatography/electrospray ionization tandem mass spectrometry-based assays have been reported for the measurement of the antiviral oseltamivir (OS) in human samples, these assays either involve complicated sample pretreatment or lack sensitivity. Here we introduce a straightforward approach to improve the assay performance for OS and its metabolite oseltamivir carboxylate (OSC) in human plasma. A very low concentration of mobile phase modifier can improve the ionization efficiency of both analytes, thus enabling a high sensitivity without any matrix effect. The fast LC gradient further increases the sensitivity by narrowing the peak width (6-9s) and eluting the analytes at higher organic content. The increased ionization efficiency and minimized matrix effects enabled us to introduce a one-step protein precipitation for sample clean-up without compromising the sensitivity. The lower limit of quantification was 0.34 ng/mL for both analytes, which was at least 3 times more sensitive than published assays that involve complicated sample pretreatment. The assay involves measurement of analytes and their stable-isotope internal standards in small-volume (30-?L) plasma. Sodium fluoride was utilized to prevent the hydrolysis of OS during and after sampling. The calibration curve was linear over the range of 0.34-1000 ng/mL. Accuracy was 95-110% and the precision was 2.2-11.0%. This method was applied successfully to the human pharmacokinetic study of OS, and can estimate the relevant pharmacokinetic parameters of OS with more accuracy. The approach utilized in the optimization of assay performance can be extended to the measurement of other drugs in biomatrices. PMID:23000242

Hu, Zhe-Yi; Laizure, S Casey; Meibohm, Bernd; Herring, Vanessa L; Parker, Robert B

2012-09-05

351

Separation, identification and rapid determination of liensine, isoliensinine and neferine from embryo of the seed of Nelumbo nucifera Gaertn. by liquid chromatography coupled to diode array detector and tandem mass spectrometry.  

PubMed

An application of mass spectrometric methods has been developed to characterize, prepare and quantitatively analyze three bisbenzylisoquinoline alkaloids (liensinine, isoliensinine and neferine) from embryo of the seed of Nelumbo nucifera Gaertn. Initially, an analytical method based on liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) with positive ionization mode using a MonoChrom C18 column (4.6 mm x 250 mm i.d. 10 microm) has been developed to characterize liensinine, isoliensinine and neferine, and then scaled up to purify them on a 21.4 mm x 250 mm preparative column. The structures of liensinine, isoliensinine and neferine were elucidated by NMR. Finally, a LC-MS/MS determination method, successfully applied to separation within 3 min, was developed for high throughput simultaneous measurement of liensinine, isoliensinine, and neferine in the extract samples. Multiple reaction monitoring (MRM) was used to monitor the transition of the protonated molecules m/z 611, 611, 625 [M+H]+ to the product ions m/z 206, 192, 206 for analysis of liensinine, isoliensinine and neferine. The LC-MS/MS system was linear in the concentration range of 0.0247-6.02 microg/ml with correlation coefficients of r2>0.992. The quantitative method was validated, with an S/N=3 detection limit of 0.15 ng for liensinine, 0.19 ng for isoliensinine and 0.1 2ng for neferine. The mass fractions of liensinine, isoliensinine, and neferine in the crude extract and the phenolic alkaloid sample of embryo of the seed of N. nucifera Gaertn. were 16.5+/-1.1 and 228.6+/-11.9 for liensinine (mg/g), 45.7+/-1.8 and 640.7+/-15.2 for isoliensinine (mg/g), 59.7+/-6.4 and 58.8+/-9.8 for neferine (mg/g). PMID:16846715

Chen, Yi; Fan, Guorong; Wu, Huiling; Wu, Yutian; Mitchell, Annabel

2006-07-18

352

Tandem Terminal Ion Source  

SciTech Connect

OAK-B135 Tandem Terminal Ion Source. The terminal ion source (TIS) was used in several experiments during this reporting period, all for the {sup 7}Be({gamma}){sup 8}B experiment. Most of the runs used {sup 1}H{sup +} at terminal voltages from 0.3 MV to 1.5 MV. One of the runs used {sup 2}H{sup +} at terminal voltage of 1.4 MV. The other run used {sup 4}He{sup +} at a terminal voltage of 1.37 MV. The list of experiments run with the TIS to date is given in table 1 below. The tank was opened four times for unscheduled source repairs. On one occasion the tank was opened to replace the einzel lens power supply which had failed. The 10 kV unit was replaced with a 15 kV unit. The second time the tank was opened to repair the extractor supply which was damaged by a tank spark. On the next occasion the tank was opened to replace a source canal which had sputtered away. Finally, the tank was opened to replace the discharge bottle which had been coated with aluminum sputtered from the exit canal.

None

2000-10-23

353

Separation and characterization of phenolic compounds in argan fruit pulp using liquid chromatography–negative electrospray ionization tandem mass spectroscopy  

Microsoft Academic Search

Liquid chromatography (LC) coupled to negative electrospray ionization (ESI) tandem mass spectrometry (MS\\/MS) was used for the sensitive identification of phenolic compounds in argan fruit pulp. Sixteen compounds were identified, mainly flavonoid glycosides and flavonoid aglycons.

Zoubida Charrouf; Miloudi Hilali; Olga Jauregui; Mohamed Soufiaoui; Dominique Guillaume

2007-01-01

354

Pulsating Tandem Microbubble for Localized and Directional Single Cell Membrane Poration  

PubMed Central

The interaction of laser-generated tandem microbubble (maximum diameter about 50 ?m) with single (rat mammary carcinoma) cells is investigated in a 25-?m liquid layer. Anti-phase and coupled oscillation of the tandem microbubble leads to the formation of alternating, directional microjets (with max. microstreaming velocity of 10 m/s) and vortices (max. vorticity of 350,000 s?1) in opposite directions. Localized and directional membrane poration (200 nm to 2 ?m in pore size) can be produced by the tandem microbubble in an orientation and proximity dependent manner, which is absence from a single oscillating microbubble of comparable size and at the same stand-off distance.

Sankin, G.N.; Yuan, F.; Zhong, P.

2013-01-01

355

Pulsating Tandem Microbubble for Localized and Directional Single-Cell Membrane Poration  

NASA Astrophysics Data System (ADS)

The interaction of laser-generated tandem microbubble (maximum diameter of about 50?m) with single (rat mammary carcinoma) cells is investigated in a 25-?m liquid layer. Antiphase and coupled oscillation of the tandem microbubble leads to the formation of alternating, directional microjets (with max microstreaming velocity of 10m/s) and vortices (max vorticity of 350000s-1) in opposite directions. Localized and directional membrane poration (200 nm to 2?m in pore size) can be produced by the tandem microbubble in an orientation and proximity-dependent manner, which is absent from a single oscillating microbubble of comparable size and at the same stand-off distance.

Sankin, G. N.; Yuan, F.; Zhong, P.

2010-08-01

356

Proteomic LC–MS systems using nanoscale liquid chromatography with tandem mass spectrometry  

Microsoft Academic Search

Current nano-scale liquid chromatography–tandem mass spectrometry (nanoLC–MS\\/MS) approaches in proteome research are reviewed from an analytical perspective. For comprehensive analysis of cellular proteins, analytical methods with higher resolution, sensitivity, and wider dynamic range are required. Miniaturized LC coupled with tandem mass spectrometry is currently one of the most versatile techniques. In this review, the current status of nanoLC–MS\\/MS systems as

Yasushi Ishihama

2005-01-01

357

Analysis of oxidation byproducts of dyfonate in various oxidant systems using high performance liquid chromatography coupled with quadrupole ion trap mass spectrometry  

Microsoft Academic Search

Dyfonate is a dithiophosphonate pesticide used to control lepidopterous insects in corn, potatoes, and peanuts. It may be transferred to the surface water and underground water system and can be degraded by free chlorine and other oxidants, which are used by water treatment plants during the disinfection process, to produce oxidation byproducts. These byproducts may be more toxic than their

Tongwen Wang; Evelyn Chamberlain; Honglan Shi; Craig D. Adams; Yinfa Ma

2010-01-01

358

Simultaneous quantification of atomoxetine as well as its primary oxidative and O-glucuronide metabolites in human plasma and urine using liquid chromatography tandem mass spectrometry (LC\\/MS\\/MS)  

Microsoft Academic Search

A sensitive and selective liquid chromatography tandem mass spectrometry (LC\\/MS\\/MS) method for the determination of atomoxetine and its metabolites (4-hydroxyatomoxetine, N-des-methylatomoxetine, and 4-hydroxyatomoxetine-O-glucuronide) has been developed for human plasma and urine. Using stable-labeled internal standards, the method proved to be accurate and precise for the analytes in all species, resulting in inter-batch accuracy (percent relative error, %RE) within 100±13% and

John H. Mullen; Richard L. Shugert; George D. Ponsler; Qimin Li; Bhaskar Sundaram; Heather L. Coales; Joseph E. Yakupkovic; Richard M. LeLacheur; William J. Wheeler; Frank J. Belas; John-Michael Sauer

2005-01-01

359

Automatic Quality Assessment of Peptide Tandem Mass Spectra  

Microsoft Academic Search

Motivation: A powerful proteomics methodology couples high-performance liquid chromatography (HPLC) with tandem mass spectrometry and database-search software, such as SEQUEST. Such a set-up, however, produces a large num- ber of spectra, many of which are of too poor quality to be useful. Hence a filter that eliminates poor spectra before the database search can significantly improve throughput and robustness. Moreover,

Marshall W. Bern; David Goldberg; W. Hayes Mcdonald; John R. Yates III

2004-01-01

360

Fast simultaneous quantitative analysis of FTY720 and its metabolite FTY720-P in human blood by on-line solid phase extraction coupled with liquid chromatography-tandem mass spectrometry.  

PubMed

Fingolimod (Gilenya; FTY720), has been recently approved for the treatment of multiple sclerosis in Europe and in the USA. In the present study, we have developed and validated a rapid and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to simultaneously quantify FTY720 and FTY720-P in human blood. The sample preparation involves the sample dilution with a solution made of dimethylhexylamine (DMHA), ortho-phosphoric acid and methanol prior to the on-line solid phase extraction (SPE) on a C(18) cartridge. The samples were then eluted on a C(18) column with a gradient elution of DMHA solution and acetonitrile and analyzed by LC-MS/MS using electrospay ionization in positive mode. The analysis time between 2 samples was 7.5 min. Standard curves were linear over the ranges of 0.0800 ng/mL (LLOQ) to 16.0 ng/mL for FTY720 and 0.100 ng/mL (LLOQ) to 20.0 ng/mL for FTY720-P with correlation coefficient (r(2)) greater than 0.997. The method selectivities for FTY720 and FTY720-P were demonstrated in six different batches of human blood. Intra-run and inter-run precision and accuracy within ± 20% (at the LLOQ) and ± 15% (other levels) were achieved during a 3-run validation for quality control samples (QCs). In addition, stability data obtained during freeze-thaw (3 cycles), at room temperature (24h), and in an auto-sampler were determined and reported. The method robustness was demonstrated by the consistent data obtained by reanalyzing human blood samples for several clinical studies. In addition comparative data for FTY720 and FTY720-P were obtained between our current method and those of two available separate LC-MS/MS assays. The results of the present work demonstrated that our bioanalytical LC-MS/MS method is rapid, sensitive, specific and reliable for the simultaneous quantitative analysis of FTY720 and FTY720-P in human blood. PMID:22018890

Emotte, Corinne; Deglave, Fany; Heudi, Olivier; Picard, Franck; Kretz, Olivier

2011-09-24

361

Liquid Chromatography with Post-Column Reagent Addition of Ammonia in Methanol Coupled to Negative Ion Electrospray Ionization Tandem Mass Spectrometry for Determination of Phenoxyacid Herbicides and their Degradation Products in Surface Water  

PubMed Central

A new liquid chromatography (LC)-negative ion electrospray ionization (ESI?)–tandem mass spectrometry (MS/MS) method with post-column addition of ammonia in methanol has been developed for the analysis of acid herbicides: 2,4-dichlorophenoxy acetic acid, 4-chloro-o-tolyloxyacetic acid, 2-(2-methyl-4-chlorophenoxy)butyric acid, mecoprop, dichlorprop, 4-(2,4-dichlorophenoxy) butyric acid, 2,4,5-trichlorophenoxy propionic acid, dicamba and bromoxynil, along with their degradation products: 4-chloro-2-methylphenol, 2,4-dichlorophenol, 2,4,5-trichlorophenol and 3,5-dibromo-4-hydroxybenzoic acid. The samples were extracted from the surface water matrix using solid-phase extraction (SPE) with a polymeric sorbent and analyzed with LC ESI? with selected reaction monitoring (SRM) using a three-point confirmation approach. Chromatography was performed on a Zorbax Eclipse XDB-C18 (50 × 4.6 mm i.d., 1.8 ?m) with a gradient elution using water-methanol with 2 mM ammonium acetate mobile phase at a flow rate of 0.15 mL/min. Ammonia in methanol (0.8 M) was added post-column at a flow rate of 0.05 mL/min to enhance ionization of the degradation products in the MS source. One SRM transition was used for quantitative analysis while the second SRM along with the ratio of SRM1/SRM2 within the relative standard deviation determined by standards for each individual pesticide and retention time match were used for confirmation. The standard deviation of ratio of SRM1/SRM2 obtained from standards run on the day of analysis for different phenoxyacid herbicides ranged from 3.9 to 18.5%. Limits of detection (LOD) were between 1 and 15 ng L?1 and method detection limits (MDL) with strict criteria requiring <25% deviation of peak area from best-fit line for both SRM1 and SRM2 ranged from 5 to 10 ng L?1 for acid ingredients (except dicamba at 30 ng L?1) and from 2 to 30 ng L?1 for degradation products. The SPE-LC-ESI? MS/MS method permitted low nanogram-per-liter determination of pesticides and degradation products for surface water samples.

Raina, Renata; Etter, Michele L.

2010-01-01

362

R&D issues in scale-up and manufacturing of amorphous silicon tandem modules  

SciTech Connect

R & D on amorphous silicon based tandem junction devices has improved the throughtput, the material utilization, and the performance of devices on commercial tin oxide coated glass. The tandem junction technology has been scaled-up to produce 8.6&hthinsp;Ft{sup 2} monolithically integrated modules in manufacturing at the TF1 plant. Optimization of performance and stability of these modules is ongoing. {copyright} {ital 1999 American Institute of Physics.}

Arya, R.R.; Carlson, D.E.; Chen, L.F.; Ganguly, G.; He, M.; Lin, G.; Middya, R.; Wood, G.; Newton, J.; Bennett, M.; Jackson, F.; Willing, F. [Solarex, a Business Unit of Amoco/Enron Solar, 826 Newtown-Yardley Road, Newtown, Pennsylvania 18940 (United States)

1999-03-01

363

Iodine-catalyzed tandem synthesis of terminal acetals and glycol mono esters from olefins.  

PubMed

A new metal-free protocol is described for the synthesis of terminal acetals by tandem oxidative rearrangement of olefins using oxone as an oxidant in the presence of iodine. Moreover, a one-pot procedure for the preparation of glycol mono esters from olefins is also presented for the first time using the same reagent system. PMID:23340691

Kumar, Macharla Arun; Swamy, Peraka; Naresh, Mameda; Reddy, Marri Mahender; Rohitha, Chozhiyath Nappunni; Prabhakar, Sripadi; Sarma, Akella Venkata Subrahmanya; Kumar, Joseph Richard Prem; Narender, Nama

2013-02-28

364

CHARACTERIZATION OF DOXYLAMINE AND PYRILAMINE METABOLITES VIA THERMOSPRAY/MASS SPECTROMETRY AND TANDEM MASS SPECTROMETRY  

EPA Science Inventory

Analysis of doxylamine N-oxide and pyrilamine N-oxide as synthetic standards and biologically derived metabolites by thermospray mass spectrometry (TSP/MS) provided (M + H)+ ions for each metabolite. TSP/tandem mass spectrometry (TSP/MS/MS) of the (M + H)+ ions provided fragment ...

365

Microstability of the TMX Tandem Mirror Experiments.  

National Technical Information Service (NTIS)

In the tandem mirror device, an efficient source of warm ions, the central cell, is available for stabilization of ion loss-cone instabilities. These instabilities previously limited ion confinement in single-cell mirror experiments. In the simple tandem ...

T. A. Casper L. V. Berzins

1987-01-01

366

Simulation and optimization of ammonia removal at low temperature for a double channel oxidation ditch based on fully coupled activated sludge model (FCASM): a full-scale study.  

PubMed

An optimal operating condition for ammonia removal at low temperature, based on fully coupled activated sludge model (FCASM), was determined in a full-scale oxidation ditch process wastewater treatment plant (WWTP). The FCASM-based mechanisms model was calibrated and validated with the data measured on site. Several important kinetic parameters of the modified model were tested through respirometry experiment. Validated model was used to evaluate the relationship between ammonia removal and operating parameters, such as temperature (T), dissolved oxygen (DO), solid retention time (SRT) and hydraulic retention time of oxidation ditch (HRT). The simulated results showed that low temperature have a negative effect on the ammonia removal. Through orthogonal simulation tests of the last three factors and combination with the analysis of variance, the optimal operating mode acquired of DO, SRT, HRT for the WWTP at low temperature were 3.5 mg L(-1), 15 d and 14 h, respectively. PMID:23831896

Yang, Min; Sun, Peide; Wang, Ruyi; Han, Jingyi; Wang, Jianqiao; Song, Yingqi; Cai, Jing; Tang, Xiudi

2013-06-15

367

Copper(ii) chloride mediated (aza)oxindole synthesis by oxidative coupling of Csp(2)-H and Csp(3)-H centers: substrate scope and DFT study.  

PubMed

A CuCl2 mediated direct intramolecular oxidative coupling of Csp(2)-H and Csp(3)-H centers gives access to 3,3-disubstituted oxindoles containing aromatic, heteroaromatic and alkyl substituents as well as a heteroatom at the quaternary center in good to excellent yields. The reaction is carried out in the presence of NaOtBu and CuCl2 in DMF at 110 °C. The key step of this reaction is the formation of an amidyl radical by one electron oxidation of amide enolate followed by an intramolecular radical cyclization reaction (homolytic aromatic substitution reaction). A detailed DFT study shows that the cyclization of the amidyl radical is the rate-limiting step in the oxindole synthesis, whereas the second single electron transfer (SET) becomes the rate-determining step in the aza-oxindole formation. Computational data are in agreement with the experimentally observed relative reactivity and regioselectivity. PMID:23989389

Dey, Chandan; Larionov, Evgeny; Kündig, E Peter

2013-08-29

368

Detection of some stable species during the oxidation of methane by coupling a jet-stirred reactor (JSR) to cw-CRDS  

NASA Astrophysics Data System (ADS)

We present the coupling of a jet-stirred reactor to detection by cw-CRDS in the near infrared and first results obtained during the oxidation of methane. The mixture is rapidly expanded from the jet-stirred reactor into a 80 cm-long cw-CRDS cell maintained at a the pressure around 1.33 kPa, thus freezing the reaction and decreasing pressure broadening of the absorption lines. Some stable species (CH4, H2O and CH2O) have been quantified through their well structured spectra around 1506 nm, while H2O2 and HO2 radicals could not be detected.

Bahrini, Chiheb; Herbinet, Olivier; Glaude, Pierre-Alexandre; Schoemaecker, Coralie; Fittschen, Christa; Battin-Leclerc, Frédérique

2012-05-01

369

Detection of some stable species during the oxidation of methane by coupling a jet-stirred reactor (JSR) to cw-CRDS.  

PubMed

We present the coupling of a jet-stirred reactor to detection by cw-CRDS in the near infrared and first results obtained during the oxidation of methane. The mixture is rapidly expanded from the jet-stirred reactor into a 80 cm-long cw-CRDS cell maintained at a the pressure around 1.33 kPa, thus freezing the reaction and decreasing pressure broadening of the absorption lines. Some stable species (CH4, H2O and CH2O) have been quantified through their well structured spectra around 1506 nm, while H2O2 and HO2 radicals could not be detected. PMID:23710075

Bahrini, Chiheb; Herbinet, Olivier; Glaude, Pierre-Alexandre; Schoemaecker, Coralie; Fittschen, Christa; Battin-Leclerc, Frédérique

2012-05-01

370

Optical excitations and coupling constants in FeO42- and CrO44- complexes in oxides: Density functional study  

NASA Astrophysics Data System (ADS)

The experimental crystal field (CF) and charge transfer (CT) spectra due to Fe6+-doped K2XO4 (X=S, Se, Cr) and Cr4+ in oxides have been investigated by density functional (DF) calculations on FeO42- and CrO44- complexes at different values of the metal-ligand distance, R. To this aim the coupling constants, A? and A?, with the A1 and the Jahn-Teller E modes have also been calculated. The present results explain reasonably the transition energies and coupling constants observed for Fe6+ and Cr4+ in oxides and account for the following experimental features: (i) The different nature of the first CF and CT excitations observed on passing from Fe6+ to Cr4+ in oxides. (ii) Why for Fe6+ in oxides the dominant coupling is with the E mode for the CF states while with the A1 mode for CT states. (iii) Why on going from Cr4+ to Fe6+ in oxides the coupling constant A? of CT states decreases while the opposite is found for CF ones. The role played by the covalency on these questions is explained on simple grounds, stressing that it drastically decreases the A? value for CT states. This fact together with the value ??=820 cm-1 accounts for the low value of the Huang-Rhys factor S?=2.5 in the assigned 1t1?-->4t2? CT excitation of K2SeO4:Fe6+. As a salient feature the R dependence of 10Dq (which determines A? for the 3T2 CF state) is found to be greatly sensitive to the small admixture (~0.5%) of 2s(O) orbitals in the antibonding 2e level. The electronic relaxation decreases the energy of the first CT transition of FeO42- by 19 000 cm-1, the charge distribution being however the same as that of the ground state. The important role played by the trigonal distortion for reducing the Jahn-Teller effect in the first excited state of Cr4+ in oxides is analyzed through a phenomenological model. Though no further neighbors of the host lattice are included, the calculated equilibrium distances for FeO42- and CrO44- are only 3% and 8% higher than experimental values found for Cr4+ to Fe6+ in oxides. Moreover the calculated value of the ?? frequency at the right equilibrium distance essentially coincides with experimental findings indicating that force constants between oxygen and further neighbors likely play a minor role. In comparison with recent ab initio plus configuration interaction results on FeO42- the DF scheme offers a simpler description of ground and CT states.

Wissing, K.; Barriuso, M. T.; Aramburu, J. A.; Moreno, M.

1999-12-01

371

Tandem motors increase well bore penetration rate  

SciTech Connect

Running a positive displacement downhole motor with tandem power sections and the proper bit significantly increases the rate of penetration and reduces stalling problems. The use of positive displacement mud motors (PDMs) with two power sections has improved penetration rates on a number of drilling applications in western Canada. The majority of all the tandem motor runs to date have been successful. Results of these tandem runs show that tandem motors should be considered in any situation where a single motor is run. This paper reviews the performance of tandem motors at several case sites. It describes the design, rate of penetration, bit selection, mud systems, and use in horizontal wells.

Matthews, S. [Halliburton Drilling Systems, Calgary, Alberta (Canada); McCosh, R. [CenAlta Well Services Inc., Calgary, Alberta (Canada)

1996-02-26

372

Persulfate oxidation for in situ remediation of TCE. I. Activated by ferrous ion with and without a persulfate-thiosulfate redox couple.  

PubMed

The objective of the laboratory study is to examine the conditions under which transition metal ions (e.g., ferrous ion, Fe2+) could activate the persulfate anion (S2O8(2)-) to produce a powerful oxidant known as the sulfate free radical (SO4-*) with a standard redox potential of 2.6 V. The SO4-* is capable of destroying groundwater contaminants in situ such as trichloroethylene (TCE). Experiments using Fe2+ as an activator under various molar ratios of S2O8(2)-/Fe2+/TCE in an aqueous system indicated that partial TCE degradation occurred almost instantaneously and then the reaction stalled. Either destruction of SO4-* in the presence of excess Fe2+ or the rapid conversion of all Fe2+ to Fe3+ limited the ultimate oxidizing capability of the system. Sequential addition of Fe2+ in small increments resulted in an increased TCE removal efficiency. Therefore, it appeared that Fe2+ played an important role in generating SO4-*. An observation of oxidation-reduction potential (ORP) variations revealed that the addition of sodium thiosulfate (Na2S2O3) to the ferrous ion activated persulfate system could significantly decrease the strong oxidizing conditions. It was hypothesized that the thiosulfate induced reducing conditions might convert Fe3+ to a lower valence state of Fe2+, making the Fe2+ available to activate persulfate decomposition. The sequential addition of thiosulfate (S2O3(2)-), after the initial stalling of ferrous ion activated persulfate oxidation of TCE, resulted in an improvement in TCE removal. The ferrous ion activated persulfate-thiosulfate redox couple resulted in fairly complete TCE degradation in aqueous systems in a short time frame. In soil slurry systems, TCE degradation was slower in comparison to aqueous systems. PMID:15081762

Liang, Chenju; Bruell, Clifford J; Marley, Michael C; Sperry, Kenneth L

2004-06-01

373

Simulation of uranium transport with variable temperature and oxidation potential: The computer program THCC (Thermo-Hydro-Chemical Coupling)  

SciTech Connect

A simulator of reactive chemical transport has been constructed with the capabilities of treating variable temperatures and variable oxidation potentials within a single simulation. Homogeneous and heterogeneous chemical reactions are simulated at temperature-dependent equilibrium, and changes of oxidation states of multivalent elements can be simulated during transport. Chemical mass action relations for formation of complexes in the fluid phase are included explicitly within the partial differential equations of transport, and a special algorithm greatly simplifies treatment of reversible precipitation of solid phases. This approach allows direct solution of the complete set of governing equations for concentrations of all aqueous species and solids affected simultaneously by chemical and physical processes. Results of example simulations of transport, along a temperature gradient, of uranium solution species under conditions of varying pH and oxidation potential and with reversible precipitation of uraninite and coffinite are presented. The examples illustrate how inclusion of variable temperature and oxidation potential in numerical simulators can enhance understanding of the chemical mechanisms affecting migration of multivalent waste elements.

Carnahan, C.L.

1986-12-01

374

Evidence for syntrophic acetate oxidation coupled to hydrogenotrophic methanogenesis in the high-temperature petroleum reservoir of Yabase oil field (Japan).  

PubMed

The methanogenic communities and pathways in a high-temperature petroleum reservoir were investigated through incubations of the production water and crude oil, combined with radiotracer experiments and molecular biological analyses. The incubations were conducted without any substrate amendment and under high-temperature and pressurized conditions that mimicked the in situ environment (55°C, 5 MPa). Changes in methane and acetate concentrations during the incubations indicated stoichiometric production of methane from acetate. Rates of hydrogenotrophic methanogenesis measured using [(14)C]-bicarbonate were 42-68 times those of acetoclastic methanogenesis measured using [2-(14) C]-acetate, implying the dominance of methane production by syntrophic acetate oxidation coupled to hydrogenotrophic methanogenesis in the environment. 16S rRNA gene sequence analyses of the incubated production water showed bacterial communities dominated by the genus Thermacetogenium, known as a thermophilic syntrophic acetate-oxidizing bacterium, and archaeal communities dominated by thermophilic hydrogenotrophic methanogens belonging to the genus Methanothermobacter. Furthermore, group-specific real-time PCR assays revealed that 16S rRNA gene copy numbers of the hydrogenotrophic methanogens affiliated with the order Methanobacteriales were almost identical to those of archaeal 16S rRNA genes. This study demonstrates that syntrophic acetate oxidation is the main methanogenic pathway in a high-temperature petroleum reservoir. PMID:20860731

Mayumi, Daisuke; Mochimaru, Hanako; Yoshioka, Hideyoshi; Sakata, Susumu; Maeda, Haruo; Miyagawa, Yoshihiro; Ikarashi, Masayuki; Takeuchi, Mio; Kamagata, Yoichi

2010-09-23

375

Novel biosensor for detecting hemoglobin and its oxidation state based on nonreciprocity in a coupled waveguide system  

NASA Astrophysics Data System (ADS)

We study the reflection of a tightly focused Gaussian beam off a near symmetric resonant tunneling structure comprising two identical coupled waveguides. The coupled waveguides are loaded on each side by a spacer layer and a high index prism. Reflection of a Gaussian beam from such a resonant structure is associated with beam distortion and even beam splitting. We start with the distortion of the beam profile for a symmetric structure as a function of various parameters of the system. The broken spatial symmetry is introduced through the reference channel on one side and the sample channel on the other side as spacer layers. We monitor the dip in the beam profile when the two channels are filled with the sample and the reference liquid. We show that presence and absence of hemoglobin and its oxygenation states can be quantified by looking at the beam profile dip. Our results may find applications in high resolution sensing.

Dutta-Gupta, Shourya; Martin, Olivier J. F.; Dutta Gupta, S.

2012-02-01

376

Tandem motors reduce well costs  

SciTech Connect

The new generation of tandem mud motors that recently appeared on the drilling scene is significantly affecting drilling efficiency worldwide. These motors provide drillers with increased horsepower at the bit, higher torque, and faster rates of penetration (ROP). With advanced engineering and more durable materials, motor life is being extended, thereby increasing the time between bit trips and reducing drilling costs. This article reviews the performance, design, and operation of these motors.

Hooper, M.; Daigle, C. [Halliburton Energy Services, Houston, TX (United States); Crowe, R. [Halliburton Energy Services, Aberdeen (United Kingdom)

1995-10-01

377

Degradation of X-3B dye by immobilized TiO 2 photocatalysis coupling anodic oxidation on BDD electrode  

Microsoft Academic Search

Photocatalysis on nano-sized TiO2 and electrocatalysis on boron-doped diamond (BDD) electrode, all belonged to advanced oxidation processes (AOPs) in the field of wastewater treatment, were united into one batch reactor in our experiments. Reactive brilliant red X-3B dye was used as model compound to study the combinatory effect between photocatalysis and electrocatalysis. The titania sol, deposited on glass substrate, prepared

Chunyong Zhang; Linjuan Gu; Yihua Lin; Yongxiang Wang; Degang Fu; Zhongze Gu

2009-01-01

378

Characterization of ultrathin metal-oxide-semiconductor structures using coupled current and capacitance-voltage models based on quantum calculation  

Microsoft Academic Search

We have developed a capacitance-voltage (C-V) and a current-voltage (I-V) quasistatic quantum model of ultrathin metal-oxide-semiconductor (MOS) structures based on the self-consistent solution of the Schrödinger and Poisson equations. The direct tunneling current takes into account the carrier distribution in energy subbands and uses the notions of corrected tunnel transparency and of impact frequency at the injecting electrode. These models

O. Simonetti; T. Maurel; M. Jourdain

2002-01-01

379

Magnetic coupling parameters at an oxide-oxide interface from first principles: Fe2O3-FeTiO3  

NASA Astrophysics Data System (ADS)

Charge mismatch at the interface between canted antiferromagnetic hematite (?-Fe2O3) and antiferromagnetic ilmenite (FeTiO3) is accommodated by the formation of mixed Fe2+ and Fe3+ contact layers, leading to uncompensated magnetic moments in the system. To derive the magnetic exchange interaction parameters of the end members and interface, we map total-energy differences of collinear spin arrangements obtained from density-functional theory calculations to a Heisenberg Hamiltonian using the least-squares method. Parameters for the end members, hematite (Jm3+,3+) and ilmenite (Jm2+,2+) are in good agreement with the values obtained from inelastic neutron-scattering data. The magnetic interaction parameters between Fe2+ and Fe3+ (Jm2+,3+) in the contact layer show a strong antiferromagnetic coupling to the adjacent hematite layers and thus explain the ferrimagnetism in the system.

Nabi, Hasan Sadat; Harrison, Richard J.; Pentcheva, Rossitza

2010-06-01

380

Origin of the front-back-gate coupling in partially depleted and fully depleted silicon-on-insulator metal-oxide-semiconductor field-effect transistors with accumulated back gate  

Microsoft Academic Search

It is shown that in thin-gate partially depleted silicon-on-insulator metal-oxide-semiconductor field-effect transistors (PD SOI MOSFETs) unexpected front-back-gate coupling effects occur when the back gate is operated in accumulation. This is particularly true for front-gate biases (VGF) beyond the threshold for electron valence-band tunneling to occur, inducing the so-called linear kink effect (LKE). As a consequence of this coupling, both the

N. Lukyanchikova; N. Garbar; A. Smolanka; M. Lokshin; E. Simoen; C. Claeys

2005-01-01

381

Application of modified direct denitration to support the ORNL coupled-end-to-end demonstration in production of mixed oxides suitable for pellet fabrication  

SciTech Connect

The current and future development of the Modified Direct Denitration (MDD) process is in support of Oak Ridge National Laboratory's (ORNL) Coupled End-to-End (CETE) research, development, and demonstration (R and D) of proposed advanced fuel reprocessing and fuel fabrication processes. This work will involve the co-conversion of the U/Pu/Np product streams from the UREX+3 separation flow sheet utilizing the existing MDD glove-box setup and the in-cell co-conversion of the U/Pu/Np/Am/Cm product streams from the UREX+1a flow sheet. Characterization equipment is being procured and installed. Oxide powder studies are being done on calcination/reduction variables, as well as pressing and sintering of pellets to permit metallographic examinations. (authors)

Walker, E.A.; Vedder, R.J.; Felker, L.K.; Marschman, S.C. [Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831 (United States)

2007-07-01

382

Results of Research on Tandem and Tip-Attached Tandem Propellers.  

National Technical Information Service (NTIS)

An investigation was made into the potential benefits of tandem propellers and tip-attached tandem propellers. Design calculations using lifting line and lifting surface theory were used, and model propellers were tested in open water. Two sets were teste...

J. B. Hadler P. C. Pien

1985-01-01

383

Gigantic ferroelectric polarization and magnetoelectric coupling in a ferrimagnetic oxide CaBaCo4O7  

NASA Astrophysics Data System (ADS)

From both fundamental and applications points of view, improper ferroelectrics that exhibiting a strong coupling between polarization and magnetic structure are challenging the scientific community. Several multiferroics belonging to that category have been reported; however, they exhibit rather small values of electric polarization combined with low magnetic ordering temperatures. Only the CuO (tenorite), the ordered perovskites LBaCuFeO5 and the Z-type hexaferrites display magnetic ordering temperatures near room temperature, but they all suffer from polarization much smaller than that of proper ferroelectrics. Here, we report a ferrimagnetic cobaltite, CaBaCo4O7, crystallizing in a polar space group, which enters an improper ferroelectric phase below TC= 64 K. Single crystals of CaBaCo4O7 demonstrate the highest polarization value reported among improper ferroelectrics to date, reaching 10 mC/m^2 at TC and approaching 16 mC/m^2 at 8 K. Moreover a large magnetoelectric coupling coefficient is also evidenced near TC. This result points to routes for exploring new multiferroics among ferrimagnetic phases.

Mitchell, John; Caignert, Vincent; Maignan, Antoine; Singh, Kiran; Simon, Charles; Raveau, Bernard; Pralong, Valerie; Chapon, Laurent

2013-03-01

384

Biomimetic oxidative treatment of spruce wood studied by pyrolysis–molecular beam mass spectrometry coupled with multivariate analysis and 13 C-labeled tetramethylammonium hydroxide thermochemolysis: implications for fungal degradation of wood  

Microsoft Academic Search

In this work, pyrolysis–molecular beam mass spectrometry analysis coupled with principal components analysis and 13C-labeled tetramethylammonium hydroxide thermochemolysis were used to study lignin oxidation, depolymerization, and demethylation\\u000a of spruce wood treated by biomimetic oxidative systems. Neat Fenton and chelator-mediated Fenton reaction (CMFR) systems as\\u000a well as cellulosic enzyme treatments were used to mimic the nonenzymatic process involved in wood brown-rot

Valdeir Arantes; Yuhui Qian; Stephen S. Kelley; Adriane M. F. Milagres; Timothy R. Filley; Jody Jellison; Barry Goodell

2009-01-01

385

Lisinopril quantification in human plasma by liquid chromatography–electrospray tandem mass spectrometry  

Microsoft Academic Search

An analytical method based on liquid chromatography with positive ion electrospray ionization (ESI) coupled to tandem mass spectrometry detection was developed for the determination of Lisinopril in human plasma using Enalaprilat as internal standard. The analyte and internal standard were extracted from the plasma samples by solid-phase extraction using Waters HLB Oasis® SPE cartridges and chromatographed on a C8 analytical

Ana A. F Padua; Rafael E Barrientos-Astigarraga; Vinicius M Rezende; Gustavo D Mendes; Gilberto De Nucci

2004-01-01

386

Tandem triad systems based on FRET for two-photon induced release of glutamate.  

PubMed

Tandem systems allowing enhanced two-photon (2P) absorption in a wavelength range permitting coupling of the primary excitation by energy transfer to an intramolecular cage known to have fragmentation properties suited to photolysis in neuroscience is demonstrated to lead to a 10-fold improvement in the 2P photolysis cross-section at experimentally compatible wavelengths. PMID:24108351

Picard, Sébastien; Cueto-Diaz, Eduardo Jose; Genin, Emilie; Clermont, Guillaume; Acher, Francine; Ogden, David; Blanchard-Desce, Mireille

2013-10-24

387

Chiral liquid chromatography-tandem mass spectrometric methods for stereoisomeric pharmaceutical determinations  

Microsoft Academic Search

The characterization of the drug metabolism and pharmacokinetic (DMPK) profiles of stereoisomers is a fundamental aspect of the drug discovery and development processes. Therefore, chiral drug bioassays are very important to pharmaceutical and biomedical researchers. The recent developments in chiral liquid chromatography coupled to atmospheric pressure ionization tandem mass spectrometry (LC-API-MS\\/MS) for the analysis of pharmaceuticals are reviewed. Various ionization

Jiwen Chen; Walter A. Korfmacher; Yunsheng Hsieh

2005-01-01

388

Thermal stability of TiAlN/TiAlON/Si{sub 3}N{sub 4} tandem absorbers prepared by reactive direct current magnetron sputtering  

SciTech Connect

Spectrally selective TiAlN/TiAlON/Si{sub 3}N{sub 4} tandem absorber was deposited on copper, stainless steel, and Nimonic substrates using a reactive direct current magnetron sputtering system. The absorptance and the emittance of the tandem absorbers were characterized using solar spectrum reflectometer and emissometer. The surface morphology of the tandem absorbers was studied using atomic force microscopy. The compositions and the thicknesses of the individual component layers have been optimized in such a way to achieve high absorptance (0.958) and low emittance (0.07 at 82 deg. C). In order to study the thermal stability of the tandem absorbers, they were subjected to heat treatment (in air and vacuum) at different temperatures and durations. The structural changes as a result of heating of the tandem absorbers were studied using micro-Raman spectroscopy. The tandem absorbers deposited on copper substrates exhibited high solar selectivity in the order of 9-10 even after heat treatment in air up to 600 deg. C for 2 h. These tandem absorbers also exhibited very high thermal stability (525 deg. C) in air for longer durations (50 h). The onset of oxidation for the tandem stack deposited on silicon substrates was 900 deg. C, indicating a very high oxidation resistance. The results of the present study indicate the importance of TiAlN/TiAlON/Si{sub 3}N{sub 4} tandem absorber for high temperature solar selective applications.

Barshilia, Harish C.; Selvakumar, N.; Rajam, K. S. [Surface Engineering Division, National Aerospace Laboratories, Post Bag No. 1779, Bangalore 560 017 (India)

2007-03-15

389

Isolation and Characterization of Desulfovibrio dechloracetivorans sp. nov., a Marine Dechlorinating Bacterium Growing by Coupling the Oxidation of Acetate to the Reductive Dechlorination of 2-Chlorophenol  

PubMed Central

Strain SF3, a gram-negative, anaerobic, motile, short curved rod that grows by coupling the reductive dechlorination of 2-chlorophenol (2-CP) to the oxidation of acetate, was isolated from San Francisco Bay sediment. Strain SF3 grew at concentrations of NaCl ranging from 0.16 to 2.5%, but concentrations of KCl above 0.32% inhibited growth. The isolate used acetate, fumarate, lactate, propionate, pyruvate, alanine, and ethanol as electron donors for growth coupled to reductive dechlorination. Among the halogenated aromatic compounds tested, only the ortho position of chlorophenols was reductively dechlorinated, and additional chlorines at other positions blocked ortho dechlorination. Sulfate, sulfite, thiosulfate, and nitrate were also used as electron acceptors for growth. The optimal temperature for growth was 30°C, and no growth or dechlorination activity was observed at 37°C. Growth by reductive dechlorination was revealed by a growth yield of about 1 g of protein per mol of 2-CP dechlorinated, and about 2.7 g of protein per mole of 2,6-dichlorophenol dechlorinated. The physiological features and 16S ribosomal DNA sequence suggest that the organism is a novel species of the genus Desulfovibrio and which we have designated Desulfovibrio dechloracetivorans. The unusual physiological feature of this strain is that it uses acetate as an electron donor and carbon source for growth with 2-CP but not with sulfate.

Sun, Baolin; Cole, James R.; Sanford, Robert A.; Tiedje, James M.

2000-01-01

390

Detecting long tandem duplications in genomic sequences  

PubMed Central

Background Detecting duplication segments within completely sequenced genomes provides valuable information to address genome evolution and in particular the important question of the emergence of novel functions. The usual approach to gene duplication detection, based on all-pairs protein gene comparisons, provides only a restricted view of duplication. Results In this paper, we introduce ReD Tandem, a software using a flow based chaining algorithm targeted at detecting tandem duplication arrays of moderate to longer length regions, with possibly locally weak similarities, directly at the DNA level. On the A. thaliana genome, using a reference set of tandem duplicated genes built using TAIR,a we show that ReD Tandem is able to predict a large fraction of recently duplicated genes (dS?tandem duplications involving non coding elements such as pseudo-genes or RNA genes. Conclusions ReD Tandem allows to identify large tandem duplications without any annotation, leading to agnostic identification of tandem duplications. This approach nicely complements the usual protein gene based which ignores duplications involving non coding regions. It is however inherently restricted to relatively recent duplications. By recovering otherwise ignored events, ReD Tandem gives a more comprehensive view of existing evolutionary processes and may also allow to improve existing annotations.

2012-01-01

391

FORUM: Bioinspired Heme, Heme/non-heme Diiron, Heme/copper and Inorganic NOx Chemistry: ?NO(g) Oxidation, Peroxynitrite-Metal Chemistry and ?NO(g) Reductive Coupling  

PubMed Central

The focus of this Forum review highlights work from our own laboratories and those of others in the area of biochemical and biologically inspired inorganic chemistry dealing with nitric oxide (nitrogen monoxide, ·NO(g)) and its biological roles and reactions. The latter focus is on (i) oxidation of ·NO(g) to nitrate by nitric oxide dioxygenases (NOD’s), and (ii) reductive coupling of two molecules of ·NO(g) to give N2O(g). In the former case, NOD’s are described and the highlighting of possible peroxynitrite-heme intermediates and consequences of this are given by discussion of recent works with myoglobin and a synthetic heme model system for NOD action. Summaries of recent copper complex chemistries with ·NO(g) and O2(g) leading to peroxynitrite species are given. The coverage of biological reductive coupling of ·NO(g) deals with bacterial nitric oxide reductases (NOR’s) with heme/non-heme diiron active sites, and on heme/Cu oxidases such as cytochrome c oxidase which can mediate the same chemistry. Recent designed protein and synthetic model compound (heme/non-heme diiron or heme/copper) as functional mimics are discussed in some detail. We also highlight examples from the chemical literature, not necessarily involving biologically relevant metal ions, which describe the oxidation of ·NO(g) to nitrate (or nitrite) and possible peroxynitrite intermediates, or reductive coupling of ·NO(g) to give nitrous oxide.

Schopfer, Mark P.; Wang, Jun; Karlin, Kenneth D.

2010-01-01

392

Emerging catalytic applications of transition metal oxide nanomaterials under microwave and conventional heating  

NASA Astrophysics Data System (ADS)

Heterogeneous transition metal oxide catalysts have advantages over homogeneous catalysts, such as easy separations and efficient recycling and minimization of metal traces in the products. Transition metal oxide nanomaterials with different properties such as shapes and particle size were synthesized by hydrothermal, solvothermal, solvent-free and by energy efficient microwave heating methods and characterized using X-Ray and microscopic techniques. The synthesized catalysts were tested for tandem reactions to form quinoxalines, oxidations of hydrocarbons to form alcohols, aldehydes and ketones, epoxidation, epoxide ring opening, and N-aryl coupling reactions. The kinetics and energy consumption associated with these reactions were compared for both microwave and conventionally heated reactions. Further, Synchrotron radiation-based time-resolved XRD experiments under a wide variety of temperature and pressure conditions were conducted to study the reactions under working conditions. EXAFS and XANES data collections were performed to determine inter-atomic distances and oxidation states of the catalysts.

Sithambaram, Shanthakumar

393

Plasticizing effect of K+ ions and succinonitrile on electrical conductivity of [poly(ethylene oxide)-succinonitrile]/KI-I2 redox-couple solid polymer electrolyte.  

PubMed

The plasticizing effect of the K(+) ions and succinonitrile on the electrical conductivity of a new redox-couple solid polymer electrolyte system, (1 - x)[0.5poly(ethylene oxide):0.5succinonitrile]:x[0.9KI:0.1I2] with x = 0-0.2 in weight fraction, is reported. An increase of x resulted in an increase of the electrical conductivity (?25°C) of the electrolyte. The electrolyte with x = 0.15 exhibited the highest ?25°C value, ~7 × 10(-4) S cm(-1), and is referred to as the optimum conducting composition (OCC). In addition to an increase of the mobile ion concentration with increasing x, X-ray diffractometry, Fourier-transform infrared spectroscopy, polarized optical microscopy, UV-vis spectroscopy, and differential scanning calorimetry studies revealed a decrease of poly(ethylene oxide) crystallinity/an increase of ionic mobility, indicating the plasticizing effect of the K(+) ions. Plasticizing and molecular diffusing properties of the succinonitrile further helped to improve the electrical conductivity of the electrolyte. PMID:23701293

Gupta, Ravindra Kumar; Rhee, Hee-Woo

2013-06-07

394

Isolation and characterization of a leech neuropeptide in rat brains: coupling to nitric oxide release in leech, rat and human tissues.  

PubMed

The osmoregulator peptide (leech osmoregulatory factor, LORF; IPEPYVWD) was first found in the leech central nervous system (CNS). Given the fact that certain peptides can be found in mammals and invertebrates, e.g., opioid, we examined rat brains to determine if LORF was present. This peptide was found and isolated by successive reversed-phase HPLC purification steps and characterized by electrospray mass spectrometry measurement. It was sequenced by Edman degradation and quantified in different tissues by ELISA. Our results demonstrate the presence of LORF in the hypothalamus, thalamus, and striatum (6 pmol/mg of protein extract) and in other brain areas at lower levels. This octapeptide is also present in the rat duodenum and liver (10 to 14 pmol/mg) and at lower levels in heart, lung, pancreas and caudal spinal cord (< 5 pmol/mg). The testes, adrenals and kidneys have the lowest levels of all the tissues examined (ca. 0.5 pmol/mg of protein). Furthermore, we also demonstrate that LORF is coupled to nitric oxide (NO) release in leech CNS, rat hypothalamus and human saphenous vein in a manner which is inhibited by a nitric oxide synthase inhibitor as well as an antibody directed toward LORF. The study demonstrates that LORF, and its function in relation to NO release, has been conserved over more than 400 million years of evolution. PMID:9645973

Salzet, M; Salzet, B; Sáutière, P; Lésage, J; Beauvillain, J C; Bilfinger, T V; Rialas, C; Bjenning, C; Stefano, G B

1998-03-30

395

Photochemical Tyrosine Oxidation with a Hydrogen-Bonded Proton Acceptor by Bidirectional Proton-Coupled Electron Transfer  

PubMed Central

Amino acid radical generation and transport are fundamentally important to numerous essential biological processes to which small molecule models lend valuable mechanistic insights. Pyridyl-amino acid-methyl esters are appended to a rhenium(I) tricarbonyl 1,10-phenanthroline core to yield rhenium–amino acid complexes with tyrosine ([Re]–Y–OH) and phenylalanine ([Re]–F). The emission from the [Re] center is more significantly quenched for [Re]–Y–OH upon addition of base. Time-resolved studies establish that excited-state quenching occurs by a combination of static and dynamic mechanisms. The degree of quenching depends on the strength of the base, consistent with a proton-coupled electron transfer (PCET) quenching mechanism. Comparative studies of [Re]–Y–OH and [Re]–F enable a detailed mechanistic analysis of a bidirectional PCET process.

Pizano, Arturo A.; Yang, Jay L.

2012-01-01

396

14 CFR 23.302 - Canard or tandem wing configurations.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 false Canard or tandem wing configurations. 23.302 Section...General § 23.302 Canard or tandem wing configurations. The forward structure of a canard or tandem wing configuration must:...

2010-01-01

397

14 CFR 23.302 - Canard or tandem wing configurations.  

Code of Federal Regulations, 2010 CFR

...2009-01-01 false Canard or tandem wing configurations. 23.302 Section...General § 23.302 Canard or tandem wing configurations. The forward structure of a canard or tandem wing configuration must:...

2009-01-01

398

14 CFR 23.302 - Canard or tandem wing configurations.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 false Canard or tandem wing configurations. 23.302 Section...General § 23.302 Canard or tandem wing configurations. The forward structure of a canard or tandem wing configuration must:...

2013-01-01

399

Nogo-A couples with Apg-1 through interaction and co-ordinate expression under hypoxic and oxidative stress.  

PubMed

Nogo-A is the largest isoform of the Nogo/RTN4 (reticulon 4) proteins and has been characterized as a major myelin-associated inhibitor of regenerative nerve growth in the adult CNS (central nervous system). Apart from the myelin sheath, Nogo-A is expressed at high levels in principal neurons of the CNS. The specificity of Nogo-A resides in its central domain, NiG. We identified Apg-1, a member of the stress-induced Hsp110 (heat-shock protein of 110 kDa) family, as a novel interactor of NiG/Nogo-A. The interaction is selective because Apg-1 interacts with Nogo-A/RTN4-A, but not with RTN1-A, the closest paralogue of Nogo-A. Conversely, Nogo-A binds to Apg-1, but not to Apg-2 or Hsp105, two other members of the Hsp110 family. We characterized the Nogo-A-Apg-1 interaction by affinity precipitation, co-immunoprecipitation and proximity ligation assay, using primary hippocampal neurons derived from Nogo-deficient mice. Under conditions of hypoxic and oxidative stress we found that Nogo-A and Apg-1 were tightly co-regulated in hippocampal neurons. Although both proteins were up-regulated under hypoxic conditions, their expression levels were reduced upon the addition of hydrogen peroxide. Taken together, we suggest that Nogo-A is closely involved in the neuronal response to hypoxic and oxidative stress, an observation that may be of relevance not only in stroke-induced ischaemia, but also in neuroblastoma formation. PMID:23909438

Kern, Florian; Stanika, Ruslan I; Sarg, Bettina; Offterdinger, Martin; Hess, Daniel; Obermair, Gerald J; Lindner, Herbert; Bandtlow, Christine E; Hengst, Ludger; Schweigreiter, Rüdiger

2013-10-15

400

Nogo-A couples with Apg-1 through interaction and co-ordinate expression under hypoxic and oxidative stress  

PubMed Central

Nogo-A is the largest isoform of the Nogo/RTN4 (reticulon 4) proteins and has been characterized as a major myelin-associated inhibitor of regenerative nerve growth in the adult CNS (central nervous system). Apart from the myelin sheath, Nogo-A is expressed at high levels in principal neurons of the CNS. The specificity of Nogo-A resides in its central domain, NiG. We identified Apg-1, a member of the stress-induced Hsp110 (heat-shock protein of 110 kDa) family, as a novel interactor of NiG/Nogo-A. The interaction is selective because Apg-1 interacts with Nogo-A/RTN4-A, but not with RTN1-A, the closest paralogue of Nogo-A. Conversely, Nogo-A binds to Apg-1, but not to Apg-2 or Hsp105, two other members of the Hsp110 family. We characterized the Nogo-A–Apg-1 interaction by affinity precipitation, co-immunoprecipitation and proximity ligation assay, using primary hippocampal neurons derived from Nogo-deficient mice. Under conditions of hypoxic and oxidative stress we found that Nogo-A and Apg-1 were tightly co-regulated in hippocampal neurons. Although both proteins were up-regulated under hypoxic conditions, their expression levels were reduced upon the addition of hydrogen peroxide. Taken together, we suggest that Nogo-A is closely involved in the neuronal response to hypoxic and oxidative stress, an observation that may be of relevance not only in stroke-induced ischaemia, but also in neuroblastoma formation.

Kern, Florian; Stanika, Ruslan I.; Sarg, Bettina; Offterdinger, Martin; Hess, Daniel; Obermair, Gerald J.; Lindner, Herbert; Bandtlow, Christine E.; Hengst, Ludger; Schweigreiter, Rudiger

2013-01-01

401

Efficient Tandem Polymer Solar Cells Fabricated by All-Solution Processing  

Microsoft Academic Search

Tandem solar cells, in which two solar cells with different absorption characteristics are linked to use a wider range of the solar spectrum, were fabricated with each layer processed from solution with the use of bulk heterojunction materials comprising semiconducting polymers and fullerene derivatives. A transparent titanium oxide (TiOx) layer separates and connects the front cell and the back cell.

Jin Young Kim; Kwanghee Lee; Nelson E. Coates; Daniel Moses; Thuc-Quyen Nguyen; Mark Dante; Alan J. Heeger

2007-01-01

402

Improved monolithic tandem solar cell  

DOEpatents

A single-crystal, monolithic, tandem, photovoltaic solar cell is described which includes (a) an InP substrate having upper and lower surfaces, (b) a first photoactive subcell on the upper surf ace of the InP substrate, (c) a second photoactive subcell on the first subcell; and (d) an optically transparent prismatic cover layer over the second subcell. The first photoactive subcell is GaInAsP of defined composition. The second subcell is InP. The two subcells are lattice matched.

Wanlass, M.W.

1991-04-23

403

Identification of acteoside and its major metabolites in rat urine by ultra-performance liquid chromatography combined with electrospray ionization quadrupole time-of-flight tandem mass spectrometry.  

PubMed

In this study, metabolites in the urine samples of rats orally administered with acteoside, a phenylethanoid glycoside compound, were detected and identified using ultra-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UPLC/ESI-QTOF-MS) combined with an automated MS(E) technique. Up to 35 metabolites (19 metabolites of the parent drug and 16 metabolites of the degradation products) were observed, including processes of oxidization, glucuronidation, sulfation, and methyl conjugation. According to the metabolic pathways, acteoside mainly functioned as a prodrug and underwent hydrolysis before being absorbed into the blood. The degradation products, especially caffeic acid and hydroxytyrosol, were involved in further metabolism which was responsible for the low oral bioavailability but obvious pharmacological activities of acteoside. In summary, this work provided valuable information on acteoside metabolism through the rapid and reliable UPLC/ESI-QTOF-MS technique, which could be widely used for the investigation of natural product metabolites. PMID:24141042

Qi, Meng; Xiong, Aizhen; Li, Pengfei; Yang, Qiming; Yang, Li; Wang, Zhengtao

2013-09-29

404

Reductive immobilization of U(VI) in Fe(III) oxide-reducing subsurface sediments: Analysis of coupled microbial-geochemical processes in experimental reactive transport systems  

SciTech Connect

Although the fundamental microbiological and geochemical processes underlying the potential use of dissimilatory metal-reducing bacteria (DMRB) to create subsurface redox barriers for immobilization of uranium and other redox-sensitive metal/radionuclide contaminants are well-understood (Lovley et al., 1991; Gorby and Lovley, 1992; Lovley and Phillips, 1992; Lovley, 1995; Fredrickson et al., 2000; Wielinga et al., 2000; Wielinga et al., 2001), several fundamental scientific questions need to be addressed in order to understand and predict how such treatment procedures would function under in situ conditions in the subsurface. These questions revolve around the dynamic interactions between hydrologic flux and the coupled microbial-geochemical processes which are likely to occur within a redox barrier treatment zone. A brief summary of such questions includes the following: (1) What are the kinetic limitations to the efficiency of microbial U(VI) scavenging in subsurface sediments? (2) Is U(VI) sorbed to Fe(III) oxide and other solid-phase surfaces subject to enzymatic reduction? If so, what are the relative kinetics of aqueous vs. sorbed U(VI) reduction? (3) What are the relative kinetics of direct, enzymatic U(VI) reduction vs. abiotic reduction of U(VI) by surface-bound biogenic Fe(II)? (4) Can coupled Fe(III) oxide/U(VI) reduction be sustained long-term in subsurface environments? What are the kinetic relationships between Fe(III) oxide reduction, DMRB growth, and U(VI) reduction in advectively open sedimentary systems? The overall objective of our research is to address the questions listed above through laboratory-based batch and reactive transport experiments with natural Fe(III) oxide-bearing subsurface materials and a representative pure culture DMRB. A unique feature of our research is that we are using levels of total uranium (ca. 10{sup -6} to 10{sup -4} mol per dm{sup 3} bulk volume) and aqueous/solid-phase ratios ({le} ca. 10{sup -3} mol U per kg sediment) which are much closer to those present in contaminated subsurface environments compared to levels employed in previous experimental studies of microbial U(VI) reduction. The goal is to develop a more realistic picture of the dynamics of U(VI) reduction and its interaction with Fe(III) oxide reduction in subsurface sedimentary environments. In doing so, our studies will provide benchmark information on process dynamics that will be useful for scaling up (e.g. through the use of field-scale reactive transport models) to in situ treatment scenarios. In addition, the experimental methodologies and modeling strategies developed for the project may applicable to the evaluation of in situ remediation technologies for other redox-sensitive metal-radionuclide contaminants such as Cr(VI) and Tc(VII). Numerical simulations are being developed hand-in-hand with the experimental work to aid in the interpretation of the observed dynamics of U(VI) behavior, and to contribute to the development of a predictive framework for assessing in situ metal-radionuclide remediation strategies driven by the activity of DMRB.

Roden, Eric E.; Barnett, Mark O.

2004-07-08

405

Preserved coupling of oxidative phosphorylation but decreased mitochondrial respiratory capacity in IL-1beta-treated human peritoneal mesothelial cells.  

PubMed

The peritoneal mesothelium acts as a regulator of serosal responses to injury, infection, and neoplastic diseases. After inflammation of the serosal surfaces, proinflammatory cytokines induce an "activated" mesothelial cell phenotype, the mitochondrial aspect of which has not previously been studied. After incubation of cultured human peritoneal mesothelial cells with interleukin (IL)-1beta for 48 h, respiratory activity of suspended cells was analyzed by high-resolution respirometry. Citrate synthase (CS) and lactate dehydrogenase (LDH) activities were determined by spectrophotometry. Treatment with IL-1beta resulted in a significant decline of respiratory capacity (p < 0.05). Respiratory control ratios (i.e., uncoupled respiration at optimum carbonyl cyanide p-trifluoromethoxyphenylhydrazone concentration divided by oligomycin inhibited respiration measured in unpermeabilized cells) remained as high as 11, indicating well-coupled mitochondria and functional integrity of the inner mitochondrial membrane. Whereas respiratory capacities of the cells declined in proportion with decreased CS activity (p < 0.05), LDH activity increased (p < 0.05). Taken together, these results indicate that IL-1beta exposure of peritoneal mesothelial cells does not lead to irreversible defects or inhibition of specific components of the respiratory chain, but is associated with a decrease of mitochondrial content of the cells that is correlated with an increase in LDH (and thus glycolytic) capacity. PMID:16456220

Stadlmann, Sylvia; Renner, Kathrin; Pollheimer, Juergen; Moser, Patrizia Lucia; Zeimet, Alain Gustave; Offner, Felix Albert; Gnaiger, Erich

2006-01-01

406

Experimental constraints on Fe isotope fractionation during magnetite and Fe carbonate formation coupled to dissimilatory hydrous ferric oxide reduction  

NASA Astrophysics Data System (ADS)

Iron isotope fractionation between aqueous Fe(II) and biogenic magnetite and Fe carbonates produced during reduction of hydrous ferric oxide (HFO) by Shewanella putrefaciens, Shewanella algae, and Geobacter sulfurreducens in laboratory experiments is a function of Fe(III) reduction rates and pathways by which biogenic minerals are formed. High Fe(III) reduction rates produced 56Fe/ 54Fe ratios for Fe(II) aq that are 2-3‰ lower than the HFO substrate, reflecting a kinetic isotope fractionation that was associated with rapid sorption of Fe(II) to HFO. In long-term experiments at low Fe(III) reduction rates, the Fe(II) aq-magnetite fractionation is -1.3‰, and this is interpreted to be the equilibrium fractionation factor at 22°C in the biologic reduction systems studied here. In experiments where Fe carbonate was the major ferrous product of HFO reduction, the estimated equilibrium Fe(II) aq-Fe carbonate fractionations were ca. 0.0‰ for siderite (FeCO 3) and ca. +0.9‰ for Ca-substituted siderite (Ca 0.15Fe 0.85CO 3) at 22°C. Formation of precursor phases such as amorphous nonmagnetic, noncarbonate Fe(II) solids are important in the pathways to formation of biogenic magnetite or siderite, particularly at high Fe(III) reduction rates, and these solids may have 56Fe/ 54Fe ratios that are up to 1‰ lower than Fe(II) aq. Under low Fe(III) reduction rates, where equilibrium is likely to be attained, it appears that both sorbed Fe(II) and amorphous Fe(II)(s) components have isotopic compositions that are similar to those of Fe(II) aq. The relative order of ? 56Fe values for these biogenic minerals and aqueous Fe(II) is: magnetite > siderite ? Fe(II) aq > Ca-bearing Fe carbonate, and this is similar to that observed for minerals from natural samples such as Banded Iron Formations (BIFs). Where magnetite from BIFs has ? 56Fe >0‰, the calculated ? 56Fe value for aqueous Fe(II) suggests a source from midocean ridge (MOR) hydrothermal fluids. In contrast, magnetite from BIFs that has ? 56Fe ?0‰ apparently requires formation from aqueous Fe(II) that had very low ? 56Fe values. Based on this experimental study, formation of low-? 56Fe Fe(II) aq in nonsulfidic systems seems most likely to have been produced by dissimilatory reduction of ferric oxides by Fe(III)-reducing bacteria.

Johnson, Clark M.; Roden, Eric E.; Welch, Susan A.; Beard, Brian L.

2005-02-01

407

Metabolism of sanguinarine in human and in rat: Characterization of oxidative metabolites produced by human CYP1A1 and CYP1A2 and rat liver microsomes using liquid chromatography–tandem mass spectrometry  

Microsoft Academic Search

The quaternary benzo[c]phenanthridine alkaloid, sanguinarine (SA), has been detected in the mustard oil contaminated with Argemone mexicana, which produced severe human intoxications during epidemic dropsy in India. Today, SA metabolism in human and in rat has not yet been fully elucidated. The goal of this study is to investigate the oxidative metabolites of SA formed during incubations with rat liver

Alain Deroussent; Micheline Ré; Henri Hoellinger; Thierry Cresteil

2010-01-01

408

Locomotion by Tandem and Parallel Wings  

Microsoft Academic Search

A two-dimensional analysis was carried out on the locomotion by tandem and parallel wings in relation to the free flight of dragonflies and beetles, remarking the mutual interference between fore and hind wings. The results obtained are summarized as follows: In the case of tandem wings, (1)High thrust and propulsive efficiency can be achieved when the forewing oscillates with a

Yoshimichi Tanida

2003-01-01

409

Survey of plant short tandem DNA repeats  

Microsoft Academic Search

Length variations in simple sequence tandem repeats are being given increased attention in plant genetics. Some short tandem repeats (STRs) from a few plant species, mainly those at the dinucleotide level, have been demonstrated to show polymorphisms and Mendelian inheritance. In the study reported here a search for all of the possible STRs ranging from mononucleotide up to tetranucleotide repeats

Z. Wang; J. L. Weber; G. Zhong; S. D. Tanksley

1994-01-01

410

Finding approximate tandem repeats in genomic sequences  

Microsoft Academic Search

An efficient algorithm is presented for detecting approximate tandem repeats in genomic sequences. The algorithm is based on a flexible statistical model which allows a wide range of definitions of approximate tandem repeats. The ideas and methods underlying the algorithm are described and examined and its effectiveness on genomic data is demonstrated.

Ydo Wexler; Zohar Yakhini; Yechezkel Kashi; Dan Geiger

2004-01-01

411

Inductively coupled plasma torch efficiency at atmospheric pressure for organo-chlorine liquid waste removal: chloroform destruction in oxidative conditions.  

PubMed

The performance of a plasma reactor for the degradation of chlorinated hydrocarbon waste is reported. Chloroform was used as a target for a recently patented destruction process based using an inductive plasma torch. Liquid waste was directly injected axially into the argon plasma with a supplied power of ~4kW in the presence of oxygen as oxidant and carrier gas. Decomposition was performed at CHCl(3) feed rates up to 400 g h(-1) with different oxygen/waste molar ratios, chloroform destruction was obtained with at least 99% efficiency and the energy efficiency reached 100 g kWh(-1). The conversion end products were identified and assayed by online FTIR spectroscopy (CO(2), HCl and H(2)O) and redox titration (Cl(2)). Considering phosgene as representative of toxic compounds, only very small quantities of toxics were released (<1 g h(-1)) even with high waste feed rates. The experimental results were very close to the equilibrium composition predicted by thermodynamic calculations. At the bottom of the reactor, the chlorinated acids were successfully trapped in a scrubber and transformed into mineral salts, hence, only CO(2) and H(2)O have been found in the final off-gases composition. PMID:23246953

Kamgang-Youbi, Georges; Poizot, Karine; Lemont, Florent

2012-11-19

412

Allantoin in human urine quantified by ultra-performance liquid chromatography–tandem mass spectrometry  

Microsoft Academic Search

Uric acid is a potent antioxidant and scavenger of singlet oxygen and other radicals in humans. Allantoin, the predominant product of free radical-induced oxidation of uric acid, is efficiently excreted in the urine and has potential as a biomarker of oxidative stress. We developed a rapid and specific assay for urinary allantoin using ultra-performance liquid chromatography–tandem mass spectrometry suitable for

Adviye A. Tolun; Haoyue Zhang; Dora Il’yasova; Judit Sztáray; Sarah P. Young; David S. Millington

2010-01-01

413

Coupled modeling of gas hydrate formation and anaerobic methane oxidation in near-surface sediments at Hydrate Ridge  

NASA Astrophysics Data System (ADS)

A comprehensive one-dimensional transport-reaction model (C. CANDI) was modified to investigate the formation of near-surface methane gas hydrates through ascending methane-bearing fluids at the sea floor of the southern summit of Hydrate Ridge, Cascadia Margin. A considerable salinity increase was observed 120 cm below the sediment-surface. A hydrate layer was almost unaffected from sampling and the adjacent sediment visually dry and fragmented. The piece of hydrate was removed immediately from the sediment before dissociation could commence. Samples separated in that way showed chloride concentrations up to 800 mM, a salt-enrichment of about 1.5 times the seawater salinity. Corresponding ? 18O and ? D profiles indicate that chloride anomalies certainly originated from hydrate formation. The enhanced diagenetic model C.CANDI was applied to pore water chloride and sulfate profiles using steady state as well as non-steady state approaches to simulate the response of gas hydrate formation to varying fluid-flow rates and time. Upward fluid flow rates of 20 cm/yr, as determined by the model, are sufficient to account for the pore water sulfate profiles that arise from methane oxidation. The potential maximum concentration of dissolved methane in interstitial water in the presence of gas hydrate is given by thermodynamic considerations. The general trend of the measured chloride concentrations can be described by a source function for hydrate that produces significant quantities of gas hydrate at 120 cm sediment depth, the lower model boundary. Integrated hydrate formation rates of 102-103 mol m-2 h-1 were determined by the non-steady state modeling approach. These rates are about 10 times smaller than values reported from hydrate formation from water solution in the laboratory and several orders of magnitude larger than values calculated for Blake Ridge sediments (ODP 997).

Haeckel, M.; Rickert, D.; Suess, E.

2001-12-01

414

Evaluation Methods for Corrosion Damage of Components in Cooling Systems of Nuclear Power Plants by Coupling Analysis of Corrosion and Flow Dynamics (IV) Comparison of Wall Thinning Rates Calculated with the Coupled Model of Static Electrochemical Analysis and Dynamic Double Oxide Layer Analysis and Their Values Measured at a PWR Plant  

Microsoft Academic Search

In order to confirm applicability and accuracy of FAC evaluation methods based on the coupled FAC model of static electrochemical analysis and dynamic oxide layer growth analysis, wall thinning rates calculated with the proposed methods were compared with those measured for the secondary piping of a PWR plant. Distributions of flow velocity and temperature along the whole system were calculated

Shunsuke UCHIDA; Masanori NAITOH; Yasushi UEHARA; Hidetoshi OKADA; Taku OHIRA; Hideki TAKIGUCHI; Wataru SUGINO; Seiichi KOSHIZUKA

2010-01-01

415

Growth characteristics of micro-plasma oxidation ceramic coatings on Ti alloy by inductively coupled plasma-atomic emission spectrometer technique  

NASA Astrophysics Data System (ADS)

The aim of this work was to study the growth characteristics of micro-plasma oxidation ceramic coatings on Ti 6Al 4V alloy. Compound ceramic coatings were prepared on Ti 6Al 4V alloy by pulsed micro-plasma oxidation (MPO) in NaAlO2 solution. The phase composition and surface morphology of the coating were investigated by X-ray diffractometry and scanning electron microscopy. The solution of Ti from the substrate and the content of Al in the electrolyte were studied by inductively coupled plasma-atomic emission spectrometer (ICP-AES) technique. Ti from the substrate dissolved and came into the coating and the electrolyte during MPO process. The content of Ti in the electrolyte under the pulsed bi-polar mode was more than that of the pulsed single-polar mode. The phase composition and structure of the coating was attributable to the space steric hindrance of Al congregated on the electrode surface due to the effect of the electric field and the electrolyte characters. For the pulsed single-polar mode, the coating was mainly composed of a large amount of ?-Al2O3 and a small amount of ?-Al2O3. And the coating was mainly structured by Al from the electrolyte. However, the coating was composed of a large amount of Al2TiO5 and a little ?-Al2O3 and rutile TiO2 for the pulsed bi-polar mode. And the coating was structured both by Ti from the substrate and Al from the electrolyte.

Yao, Zhongping; Jiang, Zhaohua; Wang, Fuping; Xue, Wei

2007-02-01

416

Effect of ion-irradiation induced defects on the nanocluster Si/Er{sup 3+} coupling in Er-doped silicon-rich silicon oxide  

SciTech Connect

The effect of ion-irradiation induced defects on the nanocluster Si/Er{sup 3+} coupling in Er-doped silicon-rich silicon oxide (SRSO) thin film is investigated. Er-doped SRSO, which consists of silicon nanoclusters (nc-Si) in a SiO{sub 2} matrix, was fabricated using electron-cyclotron resonance plasma enhanced chemical vapor deposition using SiH{sub 4} and O{sub 2} with concurrent sputtering of Er followed by a high temperature annealing. Defects were introduced into the film via irradiation with 3 MeV Si ions and subsequently removed by high temperature annealings. The authors find that ion irradiation reduces Er{sup 3+} luminescence from SRSO films, even when the excitation cross section and luminescence efficiency of Er{sup 3+} ions are completely restored. On the other hand, ion irradiation increases the intrinsic nc-Si luminescence and has little effect on the Er{sup 3+} luminescence from a similarly prepared, Er-doped SiO{sub 2} film, indicating that the presence of irradiation induced defects in the initial amorphous film can reduce the number of Er{sup 3+} ions available for nc-Si mediated luminescence by as much as a factor of 3.

Seo, Se-Young; Jeong, Hoon; Shin, Jung H.; Choi, Han Woo; Woo, Hyung Joo; Kim, Joon Kon [Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), 373-1, Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Ion Beam Application Group, Korean Institute of Geoscience and Mineral Resources, Daejeon 305-350 (Korea, Republic of)

2007-07-09

417

Cisapride a green analytical reagent for rapid and sensitive determination of bromate in drinking water, bread and flour additives by oxidative coupling spectrophotometric methods  

NASA Astrophysics Data System (ADS)

Green analytical methods using Cisapride (CPE) as green analytical reagent was investigated in this work. Rapid, simple, and sensitive spectrophotometric methods for the determination of bromate in water sample, bread and flour additives were developed. The proposed methods based on the oxidative coupling between phenoxazine and Cisapride in the presence of bromate to form red colored product with max at 520 nm. Phenoxazine and Cisapride and its reaction products were found to be environmentally friendly under the optimum experimental condition. The method obeys beers law in concentration range 0.11-4.00 g ml-1 and molar absorptivity 1.41 × 104 L mol-1 cm-1. All variables have been optimized and the presented reaction sequences were applied to the analysis of bromate in water, bread and flour additive samples. The performance of these method was evaluated in terms of Student's t-test and variance ratio F-test to find out the significance of proposed methods over the reference method. The combination of pharmaceutical drugs reagents with low concentration create some unique green chemical analyses.

Al Okab, Riyad Ahmed

2013-02-01

418

Determination of hexanal as an oxidative marker in vegetable oils using an automated dynamic headspace sampler coupled to a gas chromatograph/mass spectrometer.  

PubMed

An automated dynamic headspace sampler coupled to a gas chromatograph/mass spectrometer was evaluated as an oxidative marker to determine hexanal content in vegetable oils. For the effective analysis, a cooled injection system (CIS) was used to focus and to introduce the hexanal desorbed from the Tenax TA. The temperature of the CIS was maintained at -60 °C for 12 min before desorbing the hexanal. Hexanal was separated on a capillary column (DB-5, 0.25 mm × 60 m, 0.25 µm in film thickness) from 50 to 230 °C, followed by mass spectrometer-selected ion monitoring analysis at m/z 56. The instrumental response to hexanal was highly linear from 10 ng mL(-1) to 1 µg mL(-1) (r(2) = 0.9999). The relative standard deviation (RSD) of intra- and inter-day repeatability was acceptable, with values of less than 3.88 and 4.25%, respectively. The LOD and LOQ of hexanal were determined by gas chromatograph/mass spectrometer-selected ion monitoring to be 3.3 and 9.8 ng mL(-1), respectively. The acid value, peroxide value and fatty acid composition revealed a good correlation with the hexanal concentration. PMID:21908914

Ha, Jaeho; Seo, Dong-Won; Chen, Xi; Hwang, Jin-Bong; Shim, You-Shin

2011-01-01

419

Oak Ridge 25-MV tandem accelerator  

SciTech Connect

A brief description is presented of the scope and status of the heavy ion accelerator facility, and status of the project is discussed. Initial operation of the 25 MV tandem accelerator from National Electrostatics Corporation is covered. (GHT)

Jones, C.M.

1981-01-01