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Sample records for activity complex-formation reactions

  1. G protein activation by G protein coupled receptors: ternary complex formation or catalyzed reaction?

    Science.gov (United States)

    Roberts, David J; Waelbroeck, Magali

    2004-09-01

    G protein coupled receptors catalyze the GDP/GTP exchange on G proteins, thereby activating them. The ternary complex model, designed to describe agonist binding in the absence of GTP, is often extended to G protein activation. This is logically unsatisfactory as the ternary complex does not accumulate when G proteins are activated by GTP. Extended models taking into account nucleotide binding exist, but fail to explain catalytic G protein activation. This review puts forward an enzymatic model of G protein activation and compares its predictions with the ternary complex model and with observed receptor phenomenon. This alternative model does not merely provide a new set of formulae but leads to a new philosophical outlook and more readily accommodates experimental observations. The ternary complex model implies that, HRG being responsible for efficient G protein activation, it should be as stable as possible. In contrast, the enzyme model suggests that although a limited stabilization of HRG facilitates GDP release, HRG should not be "too stable" as this might trap the G protein in an inactive state and actually hinder G protein activation. The two models also differ completely in the definition of the receptor "active state": the ternary complex model implies that the active state corresponds to a single active receptor conformation (HRG); in contrast, the catalytic model predicts that the active receptor state is mobile, switching smoothly through various conformations with high and low affinities for agonists (HR, HRG, HRGGDP, HRGGTP, etc.).

  2. Ionic liquid effects on Mizoroki-Heck reactions: more than just carbene complex formation.

    Science.gov (United States)

    Gyton, Matthew R; Cole, Marcus L; Harper, Jason B

    2011-08-28

    Reaction profiles for a Mizoroki-Heck reaction in either an ionic liquid or a molecular solvent with different palladium sources demonstrate that the rate enhancements observed in ionic liquids cannot be solely attributed to Pd-carbene complex formation.

  3. Rapid-reaction kinetic characterization of the pathway of streptokinase-plasmin catalytic complex formation.

    Science.gov (United States)

    Verhamme, Ingrid M; Bock, Paul E

    2008-09-19

    Binding of the fibrinolytic proteinase plasmin (Pm) to streptokinase (SK) in a tight stoichiometric complex transforms Pm into a potent proteolytic activator of plasminogen. SK binding to the catalytic domain of Pm, with a dissociation constant of 12 pm, is assisted by SK Lys(414) binding to a Pm kringle, which accounts for a 11-20-fold affinity decrease when Pm lysine binding sites are blocked by 6-aminohexanoic acid (6-AHA) or benzamidine. The pathway of SK.Pm catalytic complex formation was characterized by stopped-flow kinetics of SK and the Lys(414) deletion mutant (SKDeltaK414) binding to Pm labeled at the active site with 5-fluorescein ([5F]FFR-Pm) and the reverse reactions by competitive displacement of [5F]FFR-Pm with active site-blocked Pm. The rate constants for the biexponential fluorescence quenching caused by SK and SKDeltaK414 binding to [5F]FFR-Pm were saturable as a function of SK concentration, reporting encounter complex affinities of 62-110 nm in the absence of lysine analogs and 4900-6500 and 1430-2200 nm in the presence of 6-AHA and benzamidine, respectively. The encounter complex with SKDeltaK414 was approximately 10-fold weaker in the absence of lysine analogs but indistinguishable from that of native SK in the presence of 6-AHA and benzamidine. The studies delineate for the first time the sequence of molecular events in the formation of the SK.Pm catalytic complex and its regulation by kringle ligands. Analysis of the forward and reverse reactions supports a binding mechanism in which SK Lys(414) binding to a Pm kringle accompanies near-diffusion-limited encounter complex formation followed by two slower, tightening conformational changes.

  4. Integrin activation and focal complex formation in cardiac hypertrophy

    Science.gov (United States)

    Laser, M.; Willey, C. D.; Jiang, W.; Cooper, G. 4th; Menick, D. R.; Zile, M. R.; Kuppuswamy, D.

    2000-01-01

    Cardiac hypertrophy is characterized by both remodeling of the extracellular matrix (ECM) and hypertrophic growth of the cardiocytes. Here we show increased expression and cytoskeletal association of the ECM proteins fibronectin and vitronectin in pressure-overloaded feline myocardium. These changes are accompanied by cytoskeletal binding and phosphorylation of focal adhesion kinase (FAK) at Tyr-397 and Tyr-925, c-Src at Tyr-416, recruitment of the adapter proteins p130(Cas), Shc, and Nck, and activation of the extracellular-regulated kinases ERK1/2. A synthetic peptide containing the Arg-Gly-Asp (RGD) motif of fibronectin and vitronectin was used to stimulate adult feline cardiomyocytes cultured on laminin or within a type-I collagen matrix. Whereas cardiocytes under both conditions showed RGD-stimulated ERK1/2 activation, only collagen-embedded cells exhibited cytoskeletal assembly of FAK, c-Src, Nck, and Shc. In RGD-stimulated collagen-embedded cells, FAK was phosphorylated only at Tyr-397 and c-Src association occurred without Tyr-416 phosphorylation and p130(Cas) association. Therefore, c-Src activation is not required for its cytoskeletal binding but may be important for additional phosphorylation of FAK. Overall, our study suggests that multiple signaling pathways originate in pressure-overloaded heart following integrin engagement with ECM proteins, including focal complex formation and ERK1/2 activation, and many of these pathways can be activated in cardiomyocytes via RGD-stimulated integrin activation.

  5. Integrin activation and focal complex formation in cardiac hypertrophy

    Science.gov (United States)

    Laser, M.; Willey, C. D.; Jiang, W.; Cooper, G. 4th; Menick, D. R.; Zile, M. R.; Kuppuswamy, D.

    2000-01-01

    Cardiac hypertrophy is characterized by both remodeling of the extracellular matrix (ECM) and hypertrophic growth of the cardiocytes. Here we show increased expression and cytoskeletal association of the ECM proteins fibronectin and vitronectin in pressure-overloaded feline myocardium. These changes are accompanied by cytoskeletal binding and phosphorylation of focal adhesion kinase (FAK) at Tyr-397 and Tyr-925, c-Src at Tyr-416, recruitment of the adapter proteins p130(Cas), Shc, and Nck, and activation of the extracellular-regulated kinases ERK1/2. A synthetic peptide containing the Arg-Gly-Asp (RGD) motif of fibronectin and vitronectin was used to stimulate adult feline cardiomyocytes cultured on laminin or within a type-I collagen matrix. Whereas cardiocytes under both conditions showed RGD-stimulated ERK1/2 activation, only collagen-embedded cells exhibited cytoskeletal assembly of FAK, c-Src, Nck, and Shc. In RGD-stimulated collagen-embedded cells, FAK was phosphorylated only at Tyr-397 and c-Src association occurred without Tyr-416 phosphorylation and p130(Cas) association. Therefore, c-Src activation is not required for its cytoskeletal binding but may be important for additional phosphorylation of FAK. Overall, our study suggests that multiple signaling pathways originate in pressure-overloaded heart following integrin engagement with ECM proteins, including focal complex formation and ERK1/2 activation, and many of these pathways can be activated in cardiomyocytes via RGD-stimulated integrin activation.

  6. The Vtc proteins in vacuole fusion: coupling NSF activity to V(0) trans-complex formation

    DEFF Research Database (Denmark)

    Müller, Oliver; Bayer, Martin J; Peters, Christopher

    2002-01-01

    vacuole system has revealed two subsequent molecular events: trans-complex formation of V-ATPase proteolipid sectors (V(0)) and release of LMA1 from the membrane. We have now identified a hetero-oligomeric membrane integral complex of vacuolar transporter chaperone (Vtc) proteins integrating these events......, LMA1 release, but dispensible for all preceding steps, including V(0) trans-complex formation. This suggests that Vtc3p might act close to or at fusion pore opening. We propose that Vtc proteins may couple ATP-dependent NSF activity to a subset of V(0) sectors in order to activate them for V(0) trans...

  7. Mass-dependent and -independent fractionation of isotopes in Ni and Pb chelate complex formation reactions

    Energy Technology Data Exchange (ETDEWEB)

    Nomura, Masao; Kudo, Takashi; Adachi, Atsuhiko; Aida, Masao; Fujii, Yasuhiko [Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology, O-okayama Meguroku, Tokyo, 152-8550 (Japan)

    2013-11-13

    Mass independent fractionation (MIF) has been a very interesting topic in the field of inorganic isotope chemistry, in particular, geo- and cosmo- chemistry. In the present work, we studied the isotope fractionation of Ni(II) and Pb(II) ions in complex formation with chelating reagent EDTA. To obtain clear results on the mass dependence of the isotope fractionation, we have conducted long-distance ion exchange chromatography of Ni(II) and Pb(II), using chelate complex reagent EDTA. The results apparently show that the isotope fractionation in Ni complex formation system is governed by the mass dependent rule. On the other hand the isotope fractionation in the Pb complex system is governed by the mass independent rule or the nuclear volume effect.

  8. Mass-dependent and -independent fractionation of isotopes in Ni and Pb chelate complex formation reactions

    Science.gov (United States)

    Nomura, Masao; Kudo, Takashi; Adachi, Atsuhiko; Aida, Masao; Fujii, Yasuhiko

    2013-11-01

    Mass independent fractionation (MIF) has been a very interesting topic in the field of inorganic isotope chemistry, in particular, geo- and cosmo- chemistry. In the present work, we studied the isotope fractionation of Ni(II) and Pb(II) ions in complex formation with chelating reagent EDTA. To obtain clear results on the mass dependence of the isotope fractionation, we have conducted long-distance ion exchange chromatography of Ni(II) and Pb(II), using chelate complex reagent EDTA. The results apparently show that the isotope fractionation in Ni complex formation system is governed by the mass dependent rule. On the other hand the isotope fractionation in the Pb complex system is governed by the mass independent rule or the nuclear volume effect.

  9. Reaction of dimethyl ether with hydroxyl radicals: kinetic isotope effect and prereactive complex formation.

    Science.gov (United States)

    Bänsch, Cornelie; Kiecherer, Johannes; Szöri, Milan; Olzmann, Matthias

    2013-09-05

    The kinetic isotope effect of the reactions OH + CH3OCH3 (DME) and OH + CD3OCD3 (DME-d6) was experimentally and theoretically studied. Experiments were carried out in a slow-flow reactor at pressures between 5 and 21 bar (helium as bath gas) with production of OH by laser flash photolysis of HNO3 and time-resolved detection of OH by laser-induced fluorescence. The temperature dependences of the rate coefficients obtained can be described by the following modified Arrhenius expressions: k(OH+DME) = (4.5 ± 1.3) × 10(-16) (T/K)(1.48) exp(66.6 K/T) cm(3) s(-1) (T = 292-650 K, P = 5.9-20.9 bar) and k(OH+DME-d6) = (7.3 ± 2.2) × 10(-23) (T/K)(3.57) exp(759.8 K/T) cm(3) s(-1) (T = 387-554 K, P = 13.0-20.4 bar). A pressure dependence of the rate coefficients was not observed. The agreement of our experimental results for k(OH+DME) with values from other authors is very good, and from a fit to all available literature data, we derived the following modified Arrhenius expression, which reproduces the values obtained in the temperature range T = 230-1500 K at pressures between 30 mbar and 21 bar to better than within ±20%: k(OH+DME) = 8.45 × 10(-18) (T/K)(2.07) exp(262.2 K/T) cm(3) s(-1). For k(OH+DME-d6), to the best of our knowledge, this is the first experimental study. For the analysis of the reaction pathway and the kinetic isotope effect, potential energy diagrams were calculated by using three different quantum chemical methods: (I) CCSD(T)/cc-pV(T,Q)Z//MP2/6-311G(d,p), (II) CCSD(T)/cc-pV(T,Q)Z//CCSD/cc-pVDZ, and (III) CBS-QB3. In all three cases, the reaction is predicted to proceed via a prereaction OH-ether complex with subsequent intramolecular hydrogen abstraction and dissociation to give the methoxymethyl radical and water. Overall rate coefficients were calculated by assuming a thermal equilibrium between the reactants and the prereaction complex and by calculating the rate coefficients of the hydrogen abstraction step from canonical transition state theory

  10. Cerimetric determination of simvastatin in pharmaceuticals based on redox and complex formation reactions

    Energy Technology Data Exchange (ETDEWEB)

    Basavaiah, K.; Devi, O.Z [University of Mysore, Manasagangotri, Mysore (India). Dept. of Chemistry]. E-mail: basavaiahk@yahoo.co.in

    2008-07-01

    Two sensitive spectrophotometric methods are described for the determination of simvastatin (SMT) in bulk drug and in tablets. The methods are based on the oxidation of SMT by a measured excess of cerium (IV) in acid medium followed by determination of unreacted oxidant by two different reaction schemes. In one procedure (method A), the residual cerium (IV) is reacted with a fixed concentration of ferroin and the increase in absorbance is measured at 510 nm. The second approach (method B) involves the reduction of the unreacted cerium (IV) with a fixed quantity of iron (II), and the resulting iron (III) is complexed with thiocyanate and the absorbance measured at 470 nm. In both methods, the amount of cerium (IV) reacted corresponds to SMT concentration. The experimental conditions for both methods were optimized. In method A, the absorbance is found to increase linearly with SMT concentration (r = 0.9995) whereas in method B, the same decreased (r = -0.9943). The systems obey Beer's law for 0.6-7.5 and 0.5-5.0 {mu}g mL{sup -1} for method A and method B, respectively. The calculated molar absorptivity values are 2.7 X 104 and 1.06 X 105 Lmol{sup -1} cm{sup -1}, respectively; and the corresponding sandel sensitivity values are 0.0153 and 0.0039 {mu}g cm{sup -2}, respectively. The limit of detection (LOD) and quantification (LOQ) are reported for both methods. Intra-day and inter-day precision, and accuracy of the methods were established as per the current ICH guidelines. The methods were successfully applied to the determination of SMT in tablets and the results were statistically compared with those of the reference method by applying the Student's t-test and F-test. No interference was observed from the common excipients added to tablets. The accuracy and validity of the methods were further ascertained by performing recovery experiments via standard addition procedure. (author)

  11. Collectin-11/MASP complex formation triggers activation of the lectin complement pathway--the fifth lectin pathway initiation complex

    DEFF Research Database (Denmark)

    Ma, Ying Jie; Skjoedt, Mikkel-Ole; Garred, Peter

    2013-01-01

    complement pathway regulator MAP-1. Furthermore, we found that complex formation between recombinant collectin-11 and recombinant MASP-2 on Candida albicans leads to deposition of C4b. Native collectin-11 in serum mediated complement activation and deposition of C4b and C3b, and formation of the terminal...... complement complex on C. albicans. Moreover, spiking collectin-11-depleted serum, which did not mediate complement activation, with recombinant collectin-11 restored the complement activation capability. These results define collectin-11 as the fifth recognition molecule in the lectin complement pathway...

  12. Pressure dependent low temperature kinetics for CN + CH3CN: competition between chemical reaction and van der Waals complex formation.

    Science.gov (United States)

    Sleiman, Chantal; González, Sergio; Klippenstein, Stephen J; Talbi, Dahbia; El Dib, Gisèle; Canosa, André

    2016-06-01

    The gas phase reaction between the CN radical and acetonitrile CH3CN was investigated experimentally, at low temperatures, with the CRESU apparatus and a slow flow reactor to explore the temperature dependence of its rate coefficient from 354 K down to 23 K. Whereas a standard Arrhenius behavior was found at T > 200 K, indicating the presence of an activation barrier, a dramatic increase in the rate coefficient by a factor of 130 was observed when the temperature was decreased from 168 to 123 K. The reaction was found to be pressure independent at 297 K unlike the experiments carried out at 52 and 132 K. The work was complemented by ab initio transition state theory based master equation calculations using reaction pathways investigated with highly accurate thermochemical protocols. The role of collisional stabilization of a CNCH3CN van der Waals complex and of tunneling induced H atom abstractions were also considered. The experimental pressure dependence at 52 and 132 K is well reproduced by the theoretical calculations provided that an anharmonic state density is considered for the van der Waals complex CH3CNCN and its Lennard-Jones radius is adjusted. Furthermore, these calculations indicate that the experimental observations correspond to the fall-off regime and that tunneling remains small in the low-pressure regime. Hence, the studied reaction is essentially an association process at very low temperature. Implications for the chemistry of interstellar clouds and Titan are discussed.

  13. In vitro platelet activation, aggregation and platelet-granulocyte complex formation induced by surface modified single-walled carbon nanotubes.

    Science.gov (United States)

    Fent, János; Bihari, Péter; Vippola, Minnamari; Sarlin, Essi; Lakatos, Susan

    2015-08-01

    Surface modification of single-walled carbon nanotubes (SWCNTs) such as carboxylation, amidation, hydroxylation and pegylation is used to reduce the nanotube toxicity and render them more suitable for biomedical applications than their pristine counterparts. Toxicity can be manifested in platelet activation as it has been shown for SWCNTs. However, the effect of various surface modifications on the platelet activating potential of SWCNTs has not been tested yet. In vitro platelet activation (CD62P) as well as the platelet-granulocyte complex formation (CD15/CD41 double positivity) in human whole blood were measured by flow cytometry in the presence of 0.1mg/ml of pristine or various surface modified SWCNTs. The effect of various SWCNTs was tested by whole blood impedance aggregometry, too. All tested SWCNTs but the hydroxylated ones activate platelets and promote platelet-granulocyte complex formation in vitro. Carboxylated, pegylated and pristine SWCNTs induce whole blood aggregation as well. Although pegylation is preferred from biomedical point of view, among the samples tested by us pegylated SWCNTs induced far the most prominent activation and a well detectable aggregation of platelets in whole blood.

  14. Decay of Activity Complexes, Formation of Unipolar Magnetic Regions and Coronal Holes in their Causal Relation

    CERN Document Server

    Golubeva, Elena

    2016-01-01

    North-south asymmetry of sunspot activity resulted in an asynchronous reversal of the Sun's polar fields in the current cycle. The asymmetry is also observed in the formation of polar coronal holes. A stable coronal hole was first formed at the South Pole, despite the later polar-field reversal there. The aim of this study is to understand processes making this situation possible. Synoptic magnetic maps from the Global Oscillation Network Group and corresponding coronal-hole maps from the Extreme ultraviolet Imaging Telescope aboard the Solar and Heliospheric Observatory and the Atmospheric Imaging Assembly aboard the Solar Dynamics Observatory are analyzed here to study a causal relationship between the decay of activity complexes, evolution of large-scale magnetic fields, and formation of coronal holes. Ensembles of coronal holes associated with decaying active regions and activity complexes are presented. These ensembles take part in global rearrangements of the Sun's open magnetic flux. In particular, the...

  15. Decay of Activity Complexes, Formation of Unipolar Magnetic Regions, and Coronal Holes in Their Causal Relation

    Science.gov (United States)

    Golubeva, E. M.; Mordvinov, A. V.

    2016-12-01

    The peculiar development of solar activity in the current cycle resulted in an asynchronous reversal of the Sun's polar fields. The asymmetry is also observed in the formation of polar coronal holes. A stable coronal hole was first formed at the South Pole, despite the later polar-field reversal there. The aim of this study is to understand the processes making this situation possible. Synoptic magnetic maps from the Global Oscillation Network Group and corresponding coronal-hole maps from the Extreme ultraviolet Imaging Telescope onboard the Solar and Heliospheric Observatory and the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory are analyzed here to study the causal relationship between the decay of activity complexes, evolution of large-scale magnetic fields, and formation of coronal holes. Ensembles of coronal holes associated with decaying active regions and activity complexes are presented. These ensembles take part in global rearrangements of the Sun's open magnetic flux. In particular, the south polar coronal hole was formed from an ensemble of coronal holes that came into existence after the decay of multiple activity complexes observed during 2014.

  16. Studies on chalcone derivatives: Complex formation, thermal behavior, stability constant and antioxidant activity

    Science.gov (United States)

    El-Sayed, Yusif S.; Gaber, M.

    2015-02-01

    The chalcone 3-[4‧-dimethylaminophenyl]-1-(2-pyridyl) prop-2-en-1-one (DMAPP) and 3-(4‧-diethylaminophenyl)-1-(2-pyridinyl) prop-2-en-1-one abbreviated as DEAPP have been synthesized and characterized with IR, 1H NMR, 13C NMR spectroscopic techniques as described previously (El-Daly et al., 2008; Gaber et al., 2009; El-Sayed, 2013). By using UV visible spectroscopy method the mole fraction ratio for copper with DMAPP and DEAPP complexes were determined and it was found to be 1:1. The stability constants of this complex have been determined by Job's method. The stability constant (Kf) of copper with DMAPP and DEAPP complexes in universal buffer pH = 3.2 was determined to be 9.9 × 104 and 5.2 × 104 respectively. The effect of Cu(II) ion on the emission spectrum of the free chalcone is also assigned. Adherence to Beer's law and Ringbom optimum concentration ranges are determined. The thermal decomposition of the metal complexes is studied by TGA technique. The kinetic parameters like activation energy, pre-exponential factor and entropy of activation are estimated. The structure of complexes was energetically optimized through molecular mechanics applying MM+ force field coupled with molecular dynamics simulation. The bond lengths and bond angles have been calculated to confirm the geometry of the ligands and their Cu(II) complexes. The mode of interaction of the chalcone to copper nanoparticles was studied. The apparent association constants of the colloidal copper nanoparticles:chalcone complexes in solution were evaluated using the spectral method and compared with the formation constant of the Cu(II) chalcone complexes. Antioxidant activity of these chalcones was evaluated by using 1,1‧-diphenyl-2-picrylhydrazyl (DPPHrad) radicals scavenging method, which showed that the antioxidant activity of DMAPP has higher value than the DEAPP. Semi-empirical study results showed that DMAPP have higher dipole moment than DEAPP [1].

  17. Studies on chalcone derivatives: complex formation, thermal behavior, stability constant and antioxidant activity.

    Science.gov (United States)

    El-Sayed, Yusif S; Gaber, M

    2015-02-25

    The chalcone 3-[4'-dimethylaminophenyl]-1-(2-pyridyl) prop-2-en-1-one (DMAPP) and 3-(4'-diethylaminophenyl)-1-(2-pyridinyl) prop-2-en-1-one abbreviated as DEAPP have been synthesized and characterized with IR, (1)H NMR, (13)C NMR spectroscopic techniques as described previously (El-Daly et al., 2008; Gaber et al., 2009; El-Sayed, 2013). By using UV visible spectroscopy method the mole fraction ratio for copper with DMAPP and DEAPP complexes were determined and it was found to be 1:1. The stability constants of this complex have been determined by Job's method. The stability constant (Kf) of copper with DMAPP and DEAPP complexes in universal buffer pH=3.2 was determined to be 9.9×10(4) and 5.2×10(4) respectively. The effect of Cu(II) ion on the emission spectrum of the free chalcone is also assigned. Adherence to Beer's law and Ringbom optimum concentration ranges are determined. The thermal decomposition of the metal complexes is studied by TGA technique. The kinetic parameters like activation energy, pre-exponential factor and entropy of activation are estimated. The structure of complexes was energetically optimized through molecular mechanics applying MM(+) force field coupled with molecular dynamics simulation. The bond lengths and bond angles have been calculated to confirm the geometry of the ligands and their Cu(II) complexes. The mode of interaction of the chalcone to copper nanoparticles was studied. The apparent association constants of the colloidal copper nanoparticles:chalcone complexes in solution were evaluated using the spectral method and compared with the formation constant of the Cu(II) chalcone complexes. Antioxidant activity of these chalcones was evaluated by using 1,1'-diphenyl-2-picrylhydrazyl (DPPH) radicals scavenging method, which showed that the antioxidant activity of DMAPP has higher value than the DEAPP. Semi-empirical study results showed that DMAPP have higher dipole moment than DEAPP.

  18. The citric acid-Mn III,IVO 2(birnessite) reaction. Electron transfer, complex formation, and autocatalytic feedback

    Science.gov (United States)

    Wang, Yun; Stone, Alan T.

    2006-09-01

    Citrate released by plants, bacteria, and fungi into soils is subject to abiotic oxidation by MnO 2(birnessite), yielding 3-ketoglutarate, acetoacetate, and Mn II. Citrate loss and generation of products as a function of time all yield S-shaped curves, indicating autocatalysis. Increasing the citrate concentration decreases the induction period. The maximum rate ( rmax) along the reaction coordinate follows a Langmuir-Hinshelwood dependence on citrate concentration. Increases in pH decrease rmax and increase the induction time. Adding Mn II, Zn II, orthophosphate, or pyrophosphate at the onset of reaction decreases rmax. Mn II addition eliminates the induction period, while orthophosphate and pyrophosphate addition increase the induction period. These findings indicate that two parallel processes are responsible. The first, relatively slow process involves the oxidation of free citrate by surface-bound Mn III,IV, yielding Mn II and citrate oxidation products. The second process, which is subject to strong positive feedback, involves electron transfer from Mn II-citrate complexes to surface-bound Mn III,IV, generating Mn III-citrate and Mn II. Subsequent intramolecular electron transfer converts Mn III-citrate into Mn II and citrate oxidation products.

  19. VEGF-A/NRP1 stimulates GIPC1 and Syx complex formation to promote RhoA activation and proliferation in skin cancer cells

    Directory of Open Access Journals (Sweden)

    Ayumi Yoshida

    2015-09-01

    Full Text Available Neuropilin-1 (NRP1 has been identified as a VEGF-A receptor. DJM-1, a human skin cancer cell line, expresses endogenous VEGF-A and NRP1. In the present study, the RNA interference of VEGF-A or NRP1 suppressed DJM-1 cell proliferation. Furthermore, the overexpression of the NRP1 wild type restored shNRP1-treated DJM-1 cell proliferation, whereas NRP1 cytoplasmic deletion mutants did not. A co-immunoprecipitation analysis revealed that VEGF-A induced interactions between NRP1 and GIPC1, a scaffold protein, and complex formation between GIPC1 and Syx, a RhoGEF. The knockdown of GIPC1 or Syx reduced active RhoA and DJM-1 cell proliferation without affecting the MAPK or Akt pathway. C3 exoenzyme or Y27632 inhibited the VEGF-A-induced proliferation of DJM-1 cells. Conversely, the overexpression of the constitutively active form of RhoA restored the proliferation of siVEGF-A-treated DJM-1 cells. Furthermore, the inhibition of VEGF-A/NRP1 signaling upregulated p27, a CDK inhibitor. A cell-penetrating oligopeptide that targeted GIPC1/Syx complex formation inhibited the VEGF-A-induced activation of RhoA and suppressed DJM-1 cell proliferation. In conclusion, this new signaling pathway of VEGF-A/NRP1 induced cancer cell proliferation by forming a GIPC1/Syx complex that activated RhoA to degrade the p27 protein.

  20. Unusual Complex Formation and Chemical Reaction of Haloacetate Anion on the Exterior Surface of Cucurbit[6]uril in the Gas Phase

    Science.gov (United States)

    Choi, Tae Su; Ko, Jae Yoon; Heo, Sung Woo; Ko, Young Ho; Kim, Kimoon; Kim, Hugh I.

    2012-10-01

    Noncovalent interactions of cucurbit[6]uril (CB[6]) with haloacetate and halide anions are investigated in the gas phase using electrospray ionization ion mobility mass spectrometry. Strong noncovalent interactions of monoiodoacetate, monobromoacetate, monochloroacetate, dichloroacetate, and trichloroacetate on the exterior surface of CB[6] are observed in the negative mode electrospray ionization mass spectra. The strong binding energy of the complex allows intramolecular SN2 reaction of haloacetate, which yields externally bound CB[6]-halide complex, by collisional activation. Utilizing ion mobility technique, structures of exteriorly bound CB[6] complexes of haloacetate and halide anions are confirmed. Theoretically determined low energy structures using density functional theory (DFT) further support results from ion mobility studies. The DFT calculation reveals that the binding energy and conformation of haloacetate on the CB[6] surface affect the efficiency of the intramolecular SN2 reaction of haloacetate, which correlate well with the experimental observation.

  1. TGF-β induces p53/Smads complex formation in the PAI-1 promoter to activate transcription

    Science.gov (United States)

    Kawarada, Yuki; Inoue, Yasumichi; Kawasaki, Fumihiro; Fukuura, Keishi; Sato, Koichi; Tanaka, Takahito; Itoh, Yuka; Hayashi, Hidetoshi

    2016-01-01

    Transforming growth factor β (TGF-β) signaling facilitates tumor development during the advanced stages of tumorigenesis, but induces cell-cycle arrest for tumor suppression during the early stages. However, the mechanism of functional switching of TGF-β is still unknown, and it is unclear whether inhibition of TGF-β signaling results amelioration or exacerbation of cancers. Here we show that the tumor suppressor p53 cooperates with Smad proteins, which are TGF-β signal transducers, to selectively activate plasminogen activator inhibitor type-1 (PAI-1) transcription. p53 forms a complex with Smad2/3 in the PAI-1 promoter to recruit histone acetyltransferase CREB-binding protein (CBP) and enhance histone H3 acetylation, resulting in transcriptional activation of the PAI-1 gene. Importantly, p53 is required for TGF-β-induced cytostasis and PAI-1 is involved in the cytostatic activity of TGF-β in several cell lines. Our results suggest that p53 enhances TGF-β-induced cytostatic effects by activating PAI-1 transcription, and the functional switching of TGF-β is partially caused by p53 mutation or p53 inactivation during cancer progression. It is expected that these findings will contribute to optimization of TGF-β-targeting therapies for cancer. PMID:27759037

  2. Electrode kinetics and double layer structure IV. The Eu(II)/Eu(III) electrode reaction at the DME in 1 M KSCN; Influence of complex formation

    NARCIS (Netherlands)

    Kreuk, C.W. de; Sluyters-Rehbach, M.; Sluyters, J.H.

    1971-01-01

    A detailed study has been made of the kinetics of the Eu(III)/Eu(II) reaction at the DME in 1 M KSCN by means of impedance measurements. The data were analyzed according to the complex-plane method. Because of the considerable complexation of the europium ions in this medium, it appeared to be neces

  3. The prostaglandin receptor EP2 activates multiple signaling pathways and beta-arrestin1 complex formation during mouse skin papilloma development.

    Science.gov (United States)

    Chun, Kyung-Soo; Lao, Huei-Chen; Trempus, Carol S; Okada, Manabu; Langenbach, Robert

    2009-09-01

    Prostaglandin E(2) (PGE(2)) is elevated in many tumor types, but PGE(2)'s contributions to tumor growth are largely unknown. To investigate PGE(2)'s roles, the contributions of one of its receptors, EP2, were studied using the mouse skin initiation/promotion model. Initial studies indicated that protein kinase A (PKA), epidermal growth factor receptor (EGFR) and several effectors-cyclic adenosine 3',5'-monophosphate response element-binding protein (CREB), H-Ras, Src, protein kinase B (AKT) and extracellular signal-regulated kinase (ERK)1/2-were activated in 12-O-tetradecanoylphorbol-13-acetate (TPA)-promoted papillomas and that PKA and EGFR inhibition (H89 and AG1478, respectively) decreased papilloma formation. EP2's contributions to the activation of these pathways and papilloma development were determined by inhibiting endogenous TPA-induced PGE(2) production with indomethacin (Indo) and concomitantly treating with the EP2 agonist, CAY10399 (CAY). CAY treatment restored papilloma formation in TPA/Indo-treated mice and increased cyclic adenosine 3',5'-monophosphate and PKA activation as measured by p-CREB formation. CAY treatment also increased EGFR and Src activation and their inhibition by AG1478 and PP2 indicated that Src was upstream of EGFR. CAY also increased H-Ras, ERK1/2 and AKT activation, and AG1478 decreased their activation indicating EGFR being upstream. Supporting EP2's contribution, EP2-/- mice exhibited 65% fewer papillomas and reduced Src, EGFR, H-Ras, AKT and ERK1/2 activation. G protein-coupled receptor (GPCR) activation of EGFR has been reported to involve Src's activation via a GPCR-beta-arrestin-Src complex. Indeed, immunoprecipitation of beta-arrestin1 or p-Src indicated the presence of an EP2-beta-arrestin1-p-Src complex in papillomas. The data indicated that EP2 contributed to tumor formation via activation of PKA and EGFR and that EP2 formed a complex with beta-arrestin1 and Src that contributed to signaling and/or EP2 desensitization.

  4. The prostaglandin receptor EP2 activates multiple signaling pathways and β-arrestin1 complex formation during mouse skin papilloma development

    Science.gov (United States)

    Chun, Kyung-Soo; Lao, Huei-Chen; Trempus, Carol S.; Okada, Manabu; Langenbach, Robert

    2009-01-01

    Prostaglandin E2 (PGE2) is elevated in many tumor types, but PGE2's contributions to tumor growth are largely unknown. To investigate PGE2's roles, the contributions of one of its receptors, EP2, were studied using the mouse skin initiation/promotion model. Initial studies indicated that protein kinase A (PKA), epidermal growth factor receptor (EGFR) and several effectors—cyclic adenosine 3′,5′-monophosphate response element-binding protein (CREB), H-Ras, Src, protein kinase B (AKT) and extracellular signal-regulated kinase (ERK)1/2—were activated in 12-O-tetradecanoylphorbol-13-acetate (TPA)-promoted papillomas and that PKA and EGFR inhibition (H89 and AG1478, respectively) decreased papilloma formation. EP2's contributions to the activation of these pathways and papilloma development were determined by inhibiting endogenous TPA-induced PGE2 production with indomethacin (Indo) and concomitantly treating with the EP2 agonist, CAY10399 (CAY). CAY treatment restored papilloma formation in TPA/Indo-treated mice and increased cyclic adenosine 3′,5′-monophosphate and PKA activation as measured by p-CREB formation. CAY treatment also increased EGFR and Src activation and their inhibition by AG1478 and PP2 indicated that Src was upstream of EGFR. CAY also increased H-Ras, ERK1/2 and AKT activation, and AG1478 decreased their activation indicating EGFR being upstream. Supporting EP2's contribution, EP2−/− mice exhibited 65% fewer papillomas and reduced Src, EGFR, H-Ras, AKT and ERK1/2 activation. G protein-coupled receptor (GPCR) activation of EGFR has been reported to involve Src's activation via a GPCR–β-arrestin–Src complex. Indeed, immunoprecipitation of β-arrestin1 or p-Src indicated the presence of an EP2–β-arrestin1–p-Src complex in papillomas. The data indicated that EP2 contributed to tumor formation via activation of PKA and EGFR and that EP2 formed a complex with β-arrestin1 and Src that contributed to signaling and/or EP2

  5. Differences in complement activation between complement-resistant and complement-sensitive Moraxella (Branhamella) catarrhalis strains occur at the level of membrane attack complex formation.

    OpenAIRE

    Verduin, C.M.; Jansze, M.; Hol, C; Mollnes, T E; Verhoef, J; Van Dijk, H.

    1994-01-01

    The mechanism of resistance to human complement-mediated killing in Moraxella catarrhalis was studied by comparing different complement-sensitive and complement-resistant M. catarrhalis strains in a functional bystander hemolysis assay and an enzyme-linked immunosorbent assay (ELISA) for soluble terminal complement complexes. Complement-resistant stains appeared to activate complement to the same extent as, or even slightly better than, complement-sensitive strains. This indicates that comple...

  6. PIAS1 regulates CP2c localization and active promoter complex formation in erythroid cell-specific α-globin expression

    OpenAIRE

    Chul Kang, Ho; Hyung Chae, Ji; Jeon, Jinseon; Kim, Won; Hyun Ha, Dae; Ho Shin, June; Gil Kim, Chan; Geun Kim, Chul

    2010-01-01

    Data presented here extends our previous observations on α-globin transcriptional regulation by the CP2 and PIAS1 proteins. Using RNAi knockdown, we have now shown that CP2b, CP2c and PIAS1 are each necessary for synergistic activation of endogenous α-globin gene expression in differentiating MEL cells. In this system, truncated PIAS1 mutants lacking the ring finger domain recruited CP2c to the nucleus, as did wild-type PIAS1, demonstrating that this is a sumoylation-independent process. In v...

  7. Stereoregularity Drives Precipitation in Polyelectrolyte Complex Formation

    Science.gov (United States)

    Tirrell, Matthew; Perry, Sarah; Leon, Lorraine; Kade, Matthew; Priftis, Dimitris; Black, Katie; Hoffman, Kyle; Whitmer, Jonathan; Qin, Jian; de Pablo, Juan

    2014-03-01

    This study investigates the effect of stereoregularity on the formation of polypeptide-based complex formation and assembly into micelles, hydrogels and ordered phases. We demonstrate that fluid complex coacervate formation (rather than solid complex precipitation) between oppositely charged polypeptides requires at least one racemic partner in order to disrupt backbone hydrogen bonding networks and prevent the hydrophobic collapse of the polymers into compact, fibrillar secondary structures. Computer simulations bear this out and enable visualization of the molecular structure of the complexes. The ability to choose between conditions of fluid phase formation and solid phase formation is a useful tool in developing new self-assembled materials based on polyelectrolyte complex formation. Support from the Argonne National Laboratory Laboratory Research and Development Program (2011-217) is gratefully acknowledged.

  8. Dioxygen activation by a non-heme iron(II) complex: formation of an iron(IV)-oxo complex via C-H activation by a putative iron(III)-superoxo species.

    Science.gov (United States)

    Lee, Yong-Min; Hong, Seungwoo; Morimoto, Yuma; Shin, Woonsup; Fukuzumi, Shunichi; Nam, Wonwoo

    2010-08-11

    Iron(III)-superoxo intermediates are believed to play key roles in oxygenation reactions by non-heme iron enzymes. We now report that a non-heme iron(II) complex activates O(2) and generates its corresponding iron(IV)-oxo complex in the presence of substrates with weak C-H bonds (e.g., olefins and alkylaromatic compounds). We propose that a putative iron(III)-superoxo intermediate initiates the O(2)-activation chemistry by abstracting a H atom from the substrate, with subsequent generation of a high-valent iron(IV)-oxo intermediate from the resulting iron(III)-hydroperoxo species.

  9. Reaction time and psychophysiological activity.

    Science.gov (United States)

    Sersen, E A; Clausen, J; Lidsky, A

    1982-04-01

    Disjunctive reaction times (RT) involving two interstimulus intervals were obtained from 10 subjects during 4 sessions while recording heart period, skin conductance, and EEG. Multiple regression analysis indicated complex relationships between RT and skin conductance and heart period which varied with session level. The relationship of RT and skin conductance was predominantly linear but positive when level of skin conductance was low and negative when high. Heart period showed a predominantly curvilinear trend which also varied with level during the session. Fastest RTs tended to occur with long heart periods in short heart period sessions and vice versa. Fast RTs were also accompanied by relatively low EEG power before and after stimulation and by higher EEG frequency after the stimulus. The pattern of findings did not fully accord with the expectations of activation theory, and the proportion of RT variance accounted for was small. It is suggested that activation may vary to maintain a constant level of motor performance. Faster RT may occur under relaxed conditions and high arousal, and concentrated attentiveness may be an attempt to compensate for boredom or distraction.

  10. Single site mutations in the hetero-oligomeric Mrp antiporter from alkaliphilic Bacillus pseudofirmus OF4 that affect Na+/H+ antiport activity, sodium exclusion, individual Mrp protein levels, or Mrp complex formation.

    Science.gov (United States)

    Morino, Masato; Natsui, Shinsuke; Ono, Tomohiro; Swartz, Talia H; Krulwich, Terry A; Ito, Masahiro

    2010-10-01

    Mrp systems are widely distributed and structurally complex cation/proton antiporters. Antiport activity requires hetero-oligomeric complexes of all six or seven hydrophobic Mrp proteins (MrpA-MrpG). Here, a panel of site-directed mutants in conserved or proposed motif residues was made in the Mrp Na(+)(Li(+))/H(+) antiporter from an alkaliphilic Bacillus. The mutant operons were expressed in antiporter-deficient Escherichia coli KNabc and assessed for antiport properties, support of sodium resistance, membrane levels of each Mrp protein, and presence of monomeric and dimeric Mrp complexes. Antiport did not depend on a VFF motif or a conserved tyrosine pair, but a role for a conserved histidine in a potential quinone binding site of MrpA was supported. The importance of several acidic residues for antiport was confirmed, and the importance of additional residues was demonstrated (e.g. three lysine residues conserved across MrpA, MrpD, and membrane-bound respiratory Complex I subunits (NuoL/M/N)). The results extended indications that MrpE is required for normal membrane levels of other Mrp proteins and for complex formation. Moreover, mutations in several other Mrp proteins lead to greatly reduced membrane levels of MrpE. Thus, changes in either of the two Mrp modules, MrpA-MrpD and MrpE-MrpG, influence the other. Two mutants, MrpB-P37G and MrpC-Q70A, showed a normal phenotype but lacked the MrpA-MrpG monomeric complex while retaining the dimeric hetero-oligomeric complex. Finally, MrpG-P81A and MrpG-P81G mutants exhibited no antiport activity but supported sodium resistance and a low [Na(+)](in). Such mutants could be used to screen hypothesized but uncharacterized sodium efflux functions of Mrp apart from Na(+) (Li(+))/H(+) antiport.

  11. Pinacol Coupling Reactions Catalyzed by Active Zinc

    Institute of Scientific and Technical Information of China (English)

    Hui ZHAO; Wei DENG; Qing Xiang GUO

    2005-01-01

    Pinacol coupling reactions catalyzed by active zinc revealed high activity and extensive suitability. The efficiency of the reaction was improved apparently owing to decreasing reductive potential of zinc. In addition, the results indicated that the zinc activity has a direct relation to the coupling reactivity compared to untreated zinc or other general active zinc.

  12. Complex formation of p-carboxybenzeneboronic acid with fructose

    Energy Technology Data Exchange (ETDEWEB)

    Bulbul Islam, T.M.; Yoshino, K. [Shinshu Univ., Department of Chemistry, Matsumoto, Nagano (Japan)

    2000-10-01

    To increase the solubility of p-caboxybenzeneboronic acid (PCBA) in physiological pH 7.4, the complex formation of PCBA with fructose has been studied by {sup 11}B-NMR. PCBA formed complex with fructose and the complex increased the solubility of PCBA. The complex formation constant (log K) was obtained in pH 7.4 as 2.75 from the {sup 11}B-NMR spectra. Based on this result the complex formation ability of PCBA with fructose has been discussed. (author)

  13. Thermodynamics for complex formation between palladium(ii) and oxalate.

    Science.gov (United States)

    Pilný, Radomír; Lubal, Přemysl; Elding, Lars I

    2014-08-28

    Complex formation between [Pd(H2O)4](2+) and oxalate (ox = C2O4(2-)) has been studied spectrophoto-metrically in aqueous solution at variable temperature, ionic strength and pH. Thermodynamic parameters at 298.2 K and 1.00 mol dm(-3) HClO4 ionic medium for the complex formation [Pd(H2O)4](2+) + H2ox ⇄ [Pd(H2O)2(ox)] + 2H3O(+) with equilibrium constant K1,H (in mol dm(-3)) are log10K1,H = 3.38 ± 0.08, ΔH = -33 ± 3 kJ mol(-1), and ΔS = -48 ± 11 J K(-1) mol(-1), as determined from spectrophotometric equilibrium titrations at 15.0, 20.0, 25.0 and 31.0 °C. Thermodynamic overall stability constants β (in (mol dm(-3))(-n), n = 1,2) for [Pd(H2O)2(ox)] and [Pd(ox)2](2-) at zero ionic strength and 298.2 K, defined as the equilibrium constants for the reaction Pd(2+) + nox(2-) ⇄ [Pd(ox)n](2-2n) (water molecules omitted) are log10β = 9.04 ± 0.06 and log10β = 13.1 ± 0.3, respectively, calculated by use of Specific Ion Interaction Theory from spectrophotometric titrations with initial hydrogen ion concentrations of 1.00, 0.100 and 0.0100 mol dm(-3) and ionic strengths of 1.00, 2.00 or 3.00 mol dm(-3). The values derived together with literature data give estimated overall stability constants for Pd(ii) compounds such as [Pd(en)(ox)] and cis-[Pd(NH3)2Cl2], some of them analogs to Pt(ii) complexes used in cancer treatment. The palladium oxalato complexes are significantly more stable than palladium(ii) complexes with monodentate O-bonding ligands. A comparison between several different palladium complexes shows that different parameters contribute to the stability variations observed. These are discussed together with the so-called chelate effect.

  14. Complex Formation of Selected Radionuclides with Ligands Commonly Found in Ground Water: Low Molecular Organic Acids

    DEFF Research Database (Denmark)

    Jensen, Bror Skytte; Jensen, H.

    1985-01-01

    A general approach to the analysis of potentiometric data on complex formation between cations and polybasic amphoteric acids is described. The method is used for the characterisation of complex formation between Cs+, Sr2+, Co2+, La 3+, and Eu3+ with a α-hydroxy acids, tartaric acid and citric ac......, and with the α-amino acids, aspartic acid and L-cysteine. The cations have been chosen as typical components of reactor waste, and the acids because they are often found as products of microbial activity in pits or wherever organic material decays...

  15. Single Site Mutations in the Hetero-oligomeric Mrp Antiporter from Alkaliphilic Bacillus pseudofirmus OF4 That Affect Na+/H+ Antiport Activity, Sodium Exclusion, Individual Mrp Protein Levels, or Mrp Complex Formation*

    OpenAIRE

    Morino, Masato; Natsui, Shinsuke; Ono, Tomohiro; Swartz, Talia H.; Krulwich, Terry A.; Ito, Masahiro

    2010-01-01

    Mrp systems are widely distributed and structurally complex cation/proton antiporters. Antiport activity requires hetero-oligomeric complexes of all six or seven hydrophobic Mrp proteins (MrpA–MrpG). Here, a panel of site-directed mutants in conserved or proposed motif residues was made in the Mrp Na+(Li+)/H+ antiporter from an alkaliphilic Bacillus. The mutant operons were expressed in antiporter-deficient Escherichia coli KNabc and assessed for antiport properties, support of sodium resista...

  16. Liesegang patterns: Complex formation of precipitate in an electric field

    Indian Academy of Sciences (India)

    István Lagzi

    2005-02-01

    Formation of 1D Liesegang patterns was studied numerically in precipitation and reversible complex formation of precipitate scenarios in an electric field. The Ostwald’s supersaturation model reported by Büki, Kárpáti-Smidróczki and Zrínyi (BKZ model) was extended further. In the presence of an electric field the position of the first and the last bands () measured from the junction point of the outer and the inner electrolytes can be described by the function = 1 $_{}^{1/2}$ + 2 + 3 , where is the time elapsed until the nth band formation, 1, 2 and 3 are constants. The variation of the total number of bands with different electric field strengths () has a maximum. For higher one can observe a moving precipitation zone that becomes wider due to precipitation and reversible complex formation.

  17. Understanding Active Metal Reaction Kinetis with Cu-Mg Replacement Reaction

    Indian Academy of Sciences (India)

    Ilhami Ceyhun; Zafer Karagolge

    2017-02-01

    Metal substitution reactions are simple redox reactions. Thesereactions demonstrate the relative activity and the electrochemicalseries of metals. In particular, the purpose of thisstudy is to help students comprehend the displacement reactionamong, Mg metal and solutions containing Cu$^{+2}$, Ni$^{+2}$,Pb$^{+2}$, Cd$^{+2}$, Co$^{+2}$. This study is an important experiment towardsunderstanding reaction kinetics.

  18. Complexometric determination: Part I - EDTA and complex formation with the Cu2+ ion

    Directory of Open Access Journals (Sweden)

    Rajković Miloš B.

    2002-01-01

    Full Text Available Compounds forming very stable complexes - chelates, have a wide field of application in analytical chemistry. The most famous group of these compounds are complexons. Complexons represent organic polyaminocarbonic acids as for example ethylenediaminetetraacetic acid (EDTA and its salts. The EDTA molecule has six coordinative sites. It is a hexadentate ligands i.e. it has two binding nitrogen atoms and four oxygen atoms from carboxyl groups and it forms complexes with almost all metal ions. EDTA as a tetraprotonic acid, H4Y disociates through four steps, yielding the ions HsY-, H2Y2-, HY3- and Y4-. Which of the EDTA forms will be encountered in a solution, depends on the pH. Due to the poor solubility of EDTA in pure water, as well as in most organic solvents, the disodium salt of EDTA Na2H2Y-2H2O, under the commercial name complexon III, is utilized for analytical determinations. In water, EDTA forms soluble, stabile chelate complexes with all cations, at the molar ratio 1:1, regardless of the charge of the metal ion. In contrast to other equilibria, which are mainly defined by Le Chatellier's principle, equilibria related to metal-EDTA complex formation are also dependent on the influence of the secondary equilibria of EDTA complex formation. Complexing reactions, which are equilibrium reactions, are simultaneously influenced by the following factors: solution pH and the presence of complexing agents which may also form a stabile complex with metal ions. The secondary reaction influence may be viewed and monitored through conditional stability constants. In the first part of the paper, the reaction of the formation of the Cu2+-ion complex with EDTA is analyzed beginning from the main reaction through various influences of secondary reactions on the complex Cu2+-EDTA: pH effect, complexation effect and hydrolysis effect. The equations are given for conditional stability constants, which include equilibrium reactions under actual conditions.

  19. Enhancing Activity for the Oxygen Evolution Reaction

    DEFF Research Database (Denmark)

    Frydendal, Rasmus; Busch, Michael; Halck, Niels Bendtsen

    2014-01-01

    Electrochemical production of hydrogen, facilitated in electrolyzers, holds great promise for energy storage and solar fuel production. A bottleneck in the process is the catalysis of the oxygen evolution reaction, involving the transfer of four electrons. The challenge is that the binding energies...... of all reaction intermediates cannot be optimized individually. However, experimental investigations have shown that drastic improvements can be realized for manganese and cobalt-based oxides if gold is added to the surface or used as substrate. We propose an explanation for these enhancements based...... that the oxygen evolution reaction overpotential decreases by 100–300 mV for manganese oxides and 100 mV for cobalt oxides....

  20. Catalytic activity of carbons for methane decomposition reaction

    Energy Technology Data Exchange (ETDEWEB)

    Muradov, Nazim; Smith, Franklyn; T-Raissi, Ali [Florida Solar Energy Center, University of Central Florida, 1679 Clearlake Road, Cocoa, FL 32922 (United States)

    2005-05-15

    Catalytic decomposition of methane is an environmentally attractive approach to CO{sub 2}-free production of hydrogen. The objective of this work is to evaluate catalytic activity of a wide range of carbon materials for methane decomposition reaction and determine major factors governing their activity. It was demonstrated that the catalytic activity of carbon materials for methane decomposition is mostly determined by their structural and surface properties. Kinetics of methane decomposition reaction over disordered (amorphous) carbons such as carbon black and activated carbon were determined. The mechanism of carbon-catalyzed methane decomposition reaction and the nature of active sites on the carbon surface are discussed in this paper.

  1. Chemical reactions in solvents and melts

    CERN Document Server

    Charlot, G

    1969-01-01

    Chemical Reactions in Solvents and Melts discusses the use of organic and inorganic compounds as well as of melts as solvents. This book examines the applications in organic and inorganic chemistry as well as in electrochemistry. Organized into two parts encompassing 15 chapters, this book begins with an overview of the general properties and the different types of reactions, including acid-base reactions, complex formation reactions, and oxidation-reduction reactions. This text then describes the properties of inert and active solvents. Other chapters consider the proton transfer reactions in

  2. SPECTROPHOTOMETRIC STUDIES OF SANGUINARINE-Β-CYCLODEXTRIN COMPLEX FORMATION

    Directory of Open Access Journals (Sweden)

    Veaceslav Boldescu

    2008-06-01

    Full Text Available The main aim of this study was to investigate the influence of pH and the presence of hydrophilic polymer polyvinylpyrrolidone on the formation of sanguinarine-β-cyclodextrin (SANG-β-CD inclusion complex. Spectrophotometric studies of the SANG-β-CD systems in the presence and without 0.1 % PVP at the pH 5.0 did not show any evidence of the complex formation. However, the same systems showed several obvious evidences at the pH 8.0: the hyperchromic and the hypochromic effects and the presence of the isosbestic point in the region of 200 – 210 nm. The association constants calculated by three linear methods: Benesi-Hildebrand, Scott and Scatchard, were two times higher for the systems with addition of 0.1% PVP than for the systems without it.

  3. Complex formation between malate dehydrogenase and isocitrate dehydrogenase from Bacillus subtilis is regulated by tricarboxylic acid cycle metabolites.

    Science.gov (United States)

    Bartholomae, Maike; Meyer, Frederik M; Commichau, Fabian M; Burkovski, Andreas; Hillen, Wolfgang; Seidel, Gerald

    2014-02-01

    In Bacillus subtilis, recent in vivo studies revealed that particular enzymes of the tricarboxylic acid cycle form complexes that allow an efficient transfer of metabolites. Remarkably, a complex of the malate dehydrogenase (Mdh) (EC 1.1.1.37) with isocitrate dehydrogenase (Icd) (EC 1.1.1.42) was identified, although both enzymes do not catalyze subsequent reactions. In the present study, the interactions between these enzymes were characterized in vitro by surface plasmon resonance in the absence and presence of their substrates and cofactors. These analyses revealed a weak but specific interaction between Mdh and Icd, which was specifically stimulated by a mixture of substrates and cofactors of Icd: isocitrate, NADP(+) and Mg(2+). Wild-type Icd converted these substrates too fast, preventing any valid quantitative analysis of the interaction with Mdh. Therefore, binding of the IcdS104P mutant to Mdh was quantified because the mutation reduced the enzymatic activity by 174-fold but did not affect the stimulatory effect of substrates and cofactors on Icd-Mdh complex formation. The analysis of the unstimulated Mdh-IcdS104P interaction revealed kinetic constants of k(a) = 2.0 ± 0.2 × 10(2) m(-1) ·s(-1) and k(d) = 1.0 ± 0.1 × 10(-3) ·s(-1) and a K(D) value of 5.0 ± 0.1 μm. Addition of isocitrate, NADP(+) and Mg(2+) stimulated the affinity of IcdS104P to Mdh by 33-fold (K(D) = 0.15 ± 0.01 μm, k(a) = 1.7 ± 0.7 × 10(3) m(-1) ·s(-1), k(d) = 2.6 ± 0.6 × 10(-4) ·s(-1)). Analyses of the enzymatic activities of wild-type Icd and Mdh showed that Icd activity doubles in the presence of Mdh, whereas Mdh activity was slightly reduced by Icd. In summary, these data indicate substrate control of complex formation in the tricarboxylic acid cycle metabolon assembly and maintenance of the α-ketoglutarate supply for amino acid anabolism in vivo.

  4. Complex formation between human prostate-specific antigen and protease inhibitors in mouse plasma.

    Science.gov (United States)

    Hekim, Can; Riipi, Tero; Zhu, Lei; Laakkonen, Pirjo; Stenman, Ulf-Håkan; Koistinen, Hannu

    2010-04-01

    When secreted from the prostate, most of prostate-specific antigen (PSA) is free and enzymatically active. Upon reaching circulation, active PSA is inactivated by complex formation with protease inhibitors. To justify the use of mouse models for evaluation of the function of PSA and for studies on therapeutic modalities based on modulation of PSA activity, it is important to know whether PSA complexation is similar in mouse and man. To characterize the circulating forms of PSA in mouse, we used subcutaneous LNCaP and 22RV1 human prostate cancer cell xenograft tumor models. We also added PSA directly to mouse serum. Free and total PSA were measured by immunoassay, and PSA complexes were extracted by immunopurification followed by SDS-PAGE, in-gel trypsin digestion and identification of signature peptides by mass spectrometry. In mice bearing xenograft tumors, 68% of the immunoreactive PSA occurred in complex, and when added to mouse serum, over 70% of PSA forms complexes that comprises alpha(2)-macroglobulin and members of the alpha(1)-antitrypsin (AAT) family. In mouse plasma, PSA forms complexes similar to those in man, but the major immunoreactive complex contains AAT rather than alpha(1)-antichymotrypsin, which is the main complex forming serpin in man. The complex formation of PSA produced by xenograft tumor models in mice is similar to that of human prostate tumors with respect to the complexation of PSA. (c) 2009 Wiley-Liss, Inc.

  5. On the possibility of negative activation energies in bimolecular reactions

    Science.gov (United States)

    Jaffe, R. L.

    1978-01-01

    The temperature dependence of the rate constants for model reacting systems was studied to understand some recent experimental measurements which imply the existence of negative activation energies. A collision theory model and classical trajectory calculations are used to demonstrate that the reaction probability can vary inversely with collision energy for bimolecular reactions occurring on attractive potential energy surfaces. However, this is not a sufficient condition to ensure that the rate constant has a negative temperature dependence. On the basis of these calculations, it seems unlikely that a true bimolecular reaction between neutral molecules will have a negative activation energy.

  6. Complex formation between polyelectrolytes and oppositely charged oligoelectrolytes

    Science.gov (United States)

    Zhou, Jiajia; Barz, Matthias; Schmid, Friederike

    2016-04-01

    We study the complex formation between one long polyanion chain and many short oligocation chains by computer simulations. We employ a coarse-grained bead-spring model for the polyelectrolyte chains and model explicitly the small salt ions. We systematically vary the concentration and the length of the oligocation and examine how the oligocations affects the chain conformation, the static structure factor, the radial and axial distribution of various charged species, and the number of bound ions in the complex. At low oligocation concentration, the polyanion has an extended structure. Upon increasing the oligocation concentration, the polyanion chain collapses and forms a compact globule, but the complex still carries a net negative charge. Once the total charge of the oligocations is equal to that of the polyanion, the collapse stops and is replaced by a slow expansion. In this regime, the net charge on the complexes is positive or neutral, depending on the microion concentration in solution. The expansion can be explained by the reduction of the oligocation bridging. We find that the behavior and the structure of the complex are largely independent of the length of oligocations, and very similar to that observed when replacing the oligocations by multivalent salt cations, and conclude that the main driving force keeping the complex together is the release of monovalent counterions and coions. We speculate on the implications of this finding for the problem of controlled oligolyte release and oligolyte substitution.

  7. Direct activation of allylic alcohols in palladium catalyzed coupling reactions

    NARCIS (Netherlands)

    Gümrükçü, Y.

    2014-01-01

    The direct use of allylic alcohols in substitution reactions without pre-activation of the hydroxyl-group into a better leaving group or the use of additional stoichiometric in situ activators remains challenging due to the poor leaving group ability of the hydroxyl-group. Hence, it is important to

  8. Green synthesis of ZnO nanoparticles via complex formation by using Curcuma longa extract

    Science.gov (United States)

    Fatimah, Is; Yudha, Septian P.; Mutiara, Nur Afisa Lintang

    2016-02-01

    Synthesis of ZnO nanoparticles(NPs) were conducted via Zn(II) complex formation by using Curcuma longa extract as template. Curcuma longa extract has the ability to form zinc ions complex with curcumin as ligating agent. Study on synthesis was conducted by monitoring thermal degradation of the material. Successful formation of zinc oxide nanoparticles was confirmed by employing x-ray diffraction, surface area analysis and transmission electron microscopy(TEM) studies. From the XRD analysis it is denoted that ZnO in hexagonal wurtzite phase was formed and particle size was varied as varied temperature. The data are also confirmed by TEM analysis which shows the particle sie at the range 20-80nm. The NPs exhibited excelent photocatalytic activity for methylene blue degradation and also significant antibacterial activity for Eschericia coli. The activity in methylene blue degradation was also confirmed from fast chemical oxygen demand (COD) reduction.

  9. Green synthesis of ZnO nanoparticles via complex formation by using Curcuma longa extract

    Energy Technology Data Exchange (ETDEWEB)

    Fatimah, Is, E-mail: isfatimah@uii.ac.id; Yudha, Septian P.; Mutiara, Nur Afisa Lintang [Chemistry Department, Islamic University of Indonesia Kampus Terpadu UII, Jl. Kaliurang Km 14, Sleman, Yogyakarta (Indonesia)

    2016-02-08

    Synthesis of ZnO nanoparticles(NPs) were conducted via Zn(II) complex formation by using Curcuma longa extract as template. Curcuma longa extract has the ability to form zinc ions complex with curcumin as ligating agent. Study on synthesis was conducted by monitoring thermal degradation of the material. Successful formation of zinc oxide nanoparticles was confirmed by employing x-ray diffraction, surface area analysis and transmission electron microscopy(TEM) studies. From the XRD analysis it is denoted that ZnO in hexagonal wurtzite phase was formed and particle size was varied as varied temperature. The data are also confirmed by TEM analysis which shows the particle sie at the range 20-80nm. The NPs exhibited excelent photocatalytic activity for methylene blue degradation and also significant antibacterial activity for Eschericia coli. The activity in methylene blue degradation was also confirmed from fast chemical oxygen demand (COD) reduction.

  10. Changes in protein structure at the interface accompanying complex formation

    Directory of Open Access Journals (Sweden)

    Devlina Chakravarty

    2015-11-01

    Full Text Available Protein interactions are essential in all biological processes. The changes brought about in the structure when a free component forms a complex with another molecule need to be characterized for a proper understanding of molecular recognition as well as for the successful implementation of docking algorithms. Here, unbound (U and bound (B forms of protein structures from the Protein–Protein Interaction Affinity Database are compared in order to enumerate the changes that occur at the interface atoms/residues in terms of the solvent-accessible surface area (ASA, secondary structure, temperature factors (B factors and disorder-to-order transitions. It is found that the interface atoms optimize contacts with the atoms in the partner protein, which leads to an increase in their ASA in the bound interface in the majority (69% of the proteins when compared with the unbound interface, and this is independent of the root-mean-square deviation between the U and B forms. Changes in secondary structure during the transition indicate a likely extension of helices and strands at the expense of turns and coils. A reduction in flexibility during complex formation is reflected in the decrease in B factors of the interface residues on going from the U form to the B form. There is, however, no distinction in flexibility between the interface and the surface in the monomeric structure, thereby highlighting the potential problem of using B factors for the prediction of binding sites in the unbound form for docking another protein. 16% of the proteins have missing (disordered residues in the U form which are observed (ordered in the B form, mostly with an irregular conformation; the data set also shows differences in the composition of interface and non-interface residues in the disordered polypeptide segments as well as differences in their surface burial.

  11. Spectrophotometric Determination of 6-Propyl-2-Thiouracil in Pharmaceutical Formulations Based on Prussian Blue Complex Formation: An Undergraduate Instrumental Analysis Laboratory Experiment

    Science.gov (United States)

    Zakrzewski, Robert; Skowron, Monika; Ciesielski, Witold; Rembisz, Zaneta

    2016-01-01

    The laboratory experiment challenges students to determine 6-propyl-2-thiouracil (PTU) based on Prussian blue complex formation. Prussian blue is formed by ferricyanide and Fe(II) ions which are generated in situ from Fe(III) ions reduced by PTU. The absorbance of this product was measured at a wavelength of 840 nm, after a reaction time of 30…

  12. Theoretical Study on Catalyst Activation of Palladacycles in Heck Reaction

    Institute of Scientific and Technical Information of China (English)

    WANG Chen; FU Yao; LI Zhe; GUO Qing-Xiang

    2008-01-01

    A computational study with the B3PW91 density functional theory was carried out on the activation process of palladacycles as catalysts in the Heck reaction.Two possible pathways (i.e.anion reductive cleavage of the Pd-C bond,and olefin insertion into the Pd-C bond followed by β-H elimination)were taken into consideration.Computational results indicate that the palladacycles are activated via olefin insertion into the Pd-C bond followed by β-H elimination in the reaction conditions.

  13. Functional cooperation between FACT and MCM is coordinated with cell cycle and differential complex formation

    Directory of Open Access Journals (Sweden)

    Lin Chih-Li

    2010-02-01

    Full Text Available Abstract Background Functional cooperation between FACT and the MCM helicase complex constitutes an integral step during DNA replication initiation. However, mode of regulation that underlies the proper functional interaction of FACT and MCM is poorly understood. Methods & Results Here we present evidence indicating that such interaction is coordinated with cell cycle progression and differential complex formation. We first demonstrate the existence of two distinct FACT-MCM subassemblies, FACT-MCM2/4/6/7 and FACT-MCM2/3/4/5. Both complexes possess DNA unwinding activity and are subject to cell cycle-dependent enzymatic regulation. Interestingly, analysis of functional attributes further suggests that they act at distinct, and possibly sequential, steps during origin establishment and replication initiation. Moreover, we show that the phosphorylation profile of the FACT-associated MCM4 undergoes a cell cycle-dependent change, which is directly correlated with the catalytic activity of the FACT-MCM helicase complexes. Finally, at the quaternary structure level, physical interaction between FACT and MCM complexes is generally dependent on persistent cell cycle and further stabilized upon S phase entry. Cessation of mitotic cycle destabilizes the complex formation and likely leads to compromised coordination and activities. Conclusions Together, our results correlate FACT-MCM functionally and temporally with S phase and DNA replication. They further demonstrate that enzymatic activities intrinsically important for DNA replication are tightly controlled at various levels, thereby ensuring proper progression of, as well as exit from, the cell cycle and ultimately euploid gene balance.

  14. The Activity Reaction Core and Plasticity of Metabolic Networks.

    Directory of Open Access Journals (Sweden)

    2005-12-01

    Full Text Available Understanding the system-level adaptive changes taking place in an organism in response to variations in the environment is a key issue of contemporary biology. Current modeling approaches, such as constraint-based flux-balance analysis, have proved highly successful in analyzing the capabilities of cellular metabolism, including its capacity to predict deletion phenotypes, the ability to calculate the relative flux values of metabolic reactions, and the capability to identify properties of optimal growth states. Here, we use flux-balance analysis to thoroughly assess the activity of Escherichia coli, Helicobacter pylori, and Saccharomyces cerevisiae metabolism in 30,000 diverse simulated environments. We identify a set of metabolic reactions forming a connected metabolic core that carry non-zero fluxes under all growth conditions, and whose flux variations are highly correlated. Furthermore, we find that the enzymes catalyzing the core reactions display a considerably higher fraction of phenotypic essentiality and evolutionary conservation than those catalyzing noncore reactions. Cellular metabolism is characterized by a large number of species-specific conditionally active reactions organized around an evolutionary conserved, but always active, metabolic core. Finally, we find that most current antibiotics interfering with bacterial metabolism target the core enzymes, indicating that our findings may have important implications for antimicrobial drug-target discovery.

  15. Theoretical study about L-arginine complexes formation with thiotriazolin

    Directory of Open Access Journals (Sweden)

    L. I. Kucherenko

    2017-02-01

    Full Text Available Brain vascular diseases are one of the leading causes of morbidity, mortality and disability of population in the industrialized countries of the world. An important element of this problem’s solution is the creation of new highly effective and safe drugs, which would lead to mortality reduction, to increase in life expectancy and quality of life. Therefore it is interesting to create a new combined drug based on L-arginine and thiotriazolin. Purpose of the study: to consider the possible structure and energy characteristics of complexes formed by L-arginine, 3-methyl-1,2,4-triazolyl-5-thioacetate (MTTA and morpholine. Calculation method. The initial approximation to the complex geometry was obtained using molecular docking with the help of AutoDock Vina program. The obtained ternary complexes were pre-optimized by semi-empirical PM7 method with modeling the impact of the environment by COSMO method. The calculations were carried out using MOPAC2012 program. Then they were optimized by B97-D3/SVP + COSMO (Water dispersion-corrected DFT-D with geometrical spreading correction on insufficiency of gCP basis set. A more accurate calculation of the solvation energy was conducted by SMD. The calculations by density functional method were carried out using the ORCA 3.0.3 software. Energy complex formation in solution was calculated as the difference of the Gibbs free energy of the solvated complex and its individual components. Results. Quantum chemical calculations show, that thiotriazolin and L-arginine are able to form ternary complexes, where molecules are linked by multiple hydrogen bonds. The calculation data suggest, that studied complexes are thermodynamically unstable in solution. The energies of them are positive, but rather low despite charge gain of a number of intermolecular hydrogen bonds. Finding. Based on the results of the conducted quantum-chemical study of a three components system (MTTA, morpholine, and L-arginine it is possible

  16. Protease inhibitors activity in lepromatous leprosy and lepra reaction.

    Science.gov (United States)

    Yemul, V L; Sengupta, S R; Dhole, T N

    1983-01-01

    Serum alpha one antitrypsin levels were measured in 50 healthy age and sex matched controls with 45 lepromatous leprosy cases and 5 cases of lepra reaction. It was noted that the mean level in healthy controls was 281.00 mg%, while the mean levels in LL patients was 421.00 mg% and in LR 570.00 mg%. The elevation of Alpha one antitrypsin was statistically significant in LL patients. It is possible that the rise is a reaction to release of proteases and or higher complement activity, which are the results of a high bacillary loading to formation of immune complexes.

  17. HPV16E6-Dependent c-Fos Expression Contributes to AP-1 Complex Formation in SiHa Cells

    Directory of Open Access Journals (Sweden)

    Feixin Liang

    2011-01-01

    Full Text Available To date, the major role of HPV16E6 in cancer has been considered to be its ability to inhibit the p53 tumor-suppressor protein, thereby thwarting p53-mediated cytotoxic responses to cellular stress signals. Here, we show that HPV16E6-dependent c-fos oncogenic protein expression contributes to AP-1 complex formation under oxidative stress in SiHa cells (HPV16-positive squamous cell carcinoma of the cervix. In addition, we examined the role of HPV16E6 in TGF-α-induced c-fos expression and found that the c-fos protein expression induced by TGF-α is HPV16E6 dependent. Thus, our results provide the first evidence that HPV16E6 contributes to AP-1 complex formation after both ligand-dependent and independent EGFR activation, suggesting a new therapeutic approach to the treatment of HPV-associated tumors.

  18. Direct activation of allylic alcohols in palladium catalyzed coupling reactions

    OpenAIRE

    Gümrükçü, Y.

    2014-01-01

    The direct use of allylic alcohols in substitution reactions without pre-activation of the hydroxyl-group into a better leaving group or the use of additional stoichiometric in situ activators remains challenging due to the poor leaving group ability of the hydroxyl-group. Hence, it is important to develop new methods to activate (bio-mass derived) allyl-alcohols, which allow ‘green’ chemical processes for a broad substrate range. This may have a considerable impact on the methodology for fin...

  19. Radiation increases the cellular uptake of exosomes through CD29/CD81 complex formation

    Energy Technology Data Exchange (ETDEWEB)

    Hazawa, Masaharu; Tomiyama, Kenichi; Saotome-Nakamura, Ai; Obara, Chizuka; Yasuda, Takeshi; Gotoh, Takaya; Tanaka, Izumi; Yakumaru, Haruko; Ishihara, Hiroshi; Tajima, Katsushi, E-mail: tajima@nirs.go.jp

    2014-04-18

    Highlights: • Radiation increases cellular uptake of exosomes. • Radiation induces colocalization of CD29 and CD81. • Exosomes selectively bind the CD29/CD81 complex. • Radiation increases the cellular uptake of exosomes through CD29/CD81 complex formation. - Abstract: Exosomes mediate intercellular communication, and mesenchymal stem cells (MSC) or their secreted exosomes affect a number of pathophysiologic states. Clinical applications of MSC and exosomes are increasingly anticipated. Radiation therapy is the main therapeutic tool for a number of various conditions. The cellular uptake mechanisms of exosomes and the effects of radiation on exosome–cell interactions are crucial, but they are not well understood. Here we examined the basic mechanisms and effects of radiation on exosome uptake processes in MSC. Radiation increased the cellular uptake of exosomes. Radiation markedly enhanced the initial cellular attachment to exosomes and induced the colocalization of integrin CD29 and tetraspanin CD81 on the cell surface without affecting their expression levels. Exosomes dominantly bound to the CD29/CD81 complex. Knockdown of CD29 completely inhibited the radiation-induced uptake, and additional or single knockdown of CD81 inhibited basal uptake as well as the increase in radiation-induced uptake. We also examined possible exosome uptake processes affected by radiation. Radiation-induced changes did not involve dynamin2, reactive oxygen species, or their evoked p38 mitogen-activated protein kinase-dependent endocytic or pinocytic pathways. Radiation increased the cellular uptake of exosomes through CD29/CD81 complex formation. These findings provide essential basic insights for potential therapeutic applications of exosomes or MSC in combination with radiation.

  20. Melatonin activates the peroxidase-oxidase reaction and promotes oscillations.

    Science.gov (United States)

    Olsen, L F; Lunding, A; Lauritsen, F R; Allegra, M

    2001-06-22

    We have studied the peroxidase-oxidase reaction with NADH and O2 as substrates and melatonin as a cofactor in a semibatch reactor. We show for the first time that melatonin is an activator of the reaction catalyzed by enzymes from both plant and animal sources. Furthermore, melatonin promotes oscillatory dynamics in the pH range from 5 to 6. The frequency of the oscillations depends on the pH such that an increase in pH was accompanied by a decrease in frequency. Conversely, an increase in the flow rate of NADH or an increase in the average concentration of NADH resulted in an increase in oscillation frequency. Complex dynamics were not observed with melatonin as a cofactor. These results are discussed in relation to observations of oscillatory dynamics and the function of melatonin and peroxidase in activated neutrophils.

  1. From PII signaling to metabolite sensing: a novel 2-oxoglutarate sensor that details PII-NAGK complex formation.

    Directory of Open Access Journals (Sweden)

    Jan Lüddecke

    Full Text Available The widespread PII signal transduction proteins are known for integrating signals of nitrogen and energy supply and regulating cellular behavior by interacting with a multitude of target proteins. The PII protein of the cyanobacterium Synechococcus elongatus forms complexes with the controlling enzyme of arginine synthesis, N-acetyl-L-glutamate kinase (NAGK in a 2-oxoglutarate- and ATP/ADP-dependent manner. Fusing NAGK and PII proteins to either CFP or YFP yielded a FRET sensor that specifically responded to 2-oxoglutarate. The impact of the fluorescent tags on PII and NAGK was evaluated by enzyme assays, surface plasmon resonance spectroscopy and isothermal calorimetric experiments. The developed FRET sensor provides real-time data on PII - NAGK interaction and its modulation by the effector molecules ATP, ADP and 2-oxoglutarate in vitro. Additionally to its utility to monitor 2-oxoglutarate levels, the FRET assay provided novel insights into PII - NAGK complex formation: (i It revealed the formation of an encounter-complex between PII and NAGK, which holds the proteins in proximity even in the presence of inhibitors of complex formation; (ii It revealed that the PII T-loop residue Ser49 is neither essential for complex formation with NAGK nor for activation of the enzyme but necessary to form a stable complex and efficiently relieve NAGK from arginine inhibition; (iii It showed that arginine stabilizes the NAGK hexamer and stimulates PII - NAGK interaction.

  2. Self-activated, self-limiting reactions on Si surfaces

    DEFF Research Database (Denmark)

    Morgen, Per; Hvam, Jeanette; Bahari, Ali

    mechanism for the direct growth of ultrathin films (0-3 nm) of oxides and nitrides under ultrahigh vacuum conditions. Neutral oxygen and a microwave excited nitrogen plasma interact directly with Si surfaces kept at different temperatures during the reaction. The gas pressures are around 10-6 Torr......The direct thermally activated reactions of oxygen and ammonia with Si surfaces in furnaces have been used for a very long time in the semiconductor industry for the growth of thick oxides and nitride layers respectively. The oxidation mechanism was described in the Deal-Grove model as a diffusion......, and the temperatures vary from room temperature to 10000C.The growth is in these cases self-limiting, with the optimal oxide thickness around 0.7-0.8 nm, at 5000C, and up to a few nm for nitride. The self-limiting oxide case was recently predicted by Alex Demkov in a structural optimization to minimise the total...

  3. Localization and dynamics of amylose-lipophilic molecules inclusion complex formation in starch granules

    NARCIS (Netherlands)

    Manca, Marianna; Woortman, Albert J. J.; Mura, Andrea; Loos, Katja; Loi, Maria Antonietta

    2015-01-01

    Inclusion complex formation between lipophilic dye molecules and amylose polymers in starch granules is investigated using laser spectroscopy and microscopy. By combining confocal laser scanning microscopy (CLSM) with spatial resolved photoluminescence (PL) spectroscopy, we are able to discriminate

  4. Investigation of complex formation processes of hydroxypropylmethylcellulose and polymethacrylic acid in aqueous solutions

    Directory of Open Access Journals (Sweden)

    M. Katayeva

    2012-12-01

    Full Text Available The complex formation process of hydroxypropylcellulose (HPC with polymethacrylic acid (PMA have been studied using methods of turbidimetric and viscosimetric titration. Position of maximum depending on polymer concentration and molecular mass of polysaccharide have different values.

  5. Complete reaction mechanisms of mercury oxidation on halogenated activated carbon.

    Science.gov (United States)

    Rungnim, Chompoonut; Promarak, Vinich; Hannongbua, Supa; Kungwan, Nawee; Namuangruk, Supawadee

    2016-06-05

    The reaction mechanisms of mercury (Hg) adsorption and oxidation on halogenated activated carbon (AC) have been completely studied for the first time using density functional theory (DFT) method. Two different halogenated AC models, namely X-AC and X-AC-X (X=Cl, Br, I), were adopted. The results revealed that HgX is found to be stable-state on the AC edge since its further desorption from the AC as HgX, or further oxidation to HgX2, are energetically unfavorable. Remarkably, the halide type does not significantly affect the Hg adsorption energy but it strongly affects the activation energy barrier of HgX formation, which obviously increases in the order HgIBr-AC>Cl-AC. Thus, the study of the complete reaction mechanism is essential because the adsorption energy can not be used as a guideline for the rational material design in the halide impregnated AC systems. The activation energy is an important descriptor for the predictions of sorbent reactivity to the Hg oxidation process.

  6. Self-activated, self-limiting reactions on Si surfaces

    DEFF Research Database (Denmark)

    Morgen, Per; Hvam, Jeanette; Bahari, Ali

    The direct thermally activated reactions of oxygen and ammonia with Si surfaces in furnaces have been used for a very long time in the semiconductor industry for the growth of thick oxides and nitride layers respectively. The oxidation mechanism was described in the Deal-Grove model as a diffusion...... limited transport of oxygen to the oxide/silicon interface. For thin oxides the deal-Grove growth rate is initially constant, but for ultrathin oxides (a couple of nm thick) this is not true and the Deal-Grove model does not explain the mechanism. In a series of recent reports we have found a new...

  7. Characterization of Hydrogen Complex Formation in III-V Semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Williams, Michael D

    2006-09-28

    Atomic hydrogen has been found to react with some impurity species in semiconductors. Hydrogenation is a methodology for the introduction of atomic hydrogen into the semiconductor for the express purpose of forming complexes within the material. Efforts to develop hydrogenation as an isolation technique for AlGaAs and Si based devices failed to demonstrate its commercial viability. This was due in large measure to the low activation energies of the formed complexes. Recent studies of dopant passivation in long wavelength (0.98 - 1.55m) materials suggested that for the appropriate choice of dopants much higher activation energies can be obtained. This effort studied the formation of these complexes in InP, This material is extensively used in optoelectronics, i.e., lasers, modulators and detectors. The experimental techniques were general to the extent that the results can be applied to other areas such as sensor technology, photovoltaics and to other material systems. The activation energies for the complexes have been determined and are reported in the scientific literature. The hydrogenation process has been shown by us to have a profound effect on the electronic structure of the materials and was thoroughly investigated. The information obtained will be useful in assessing the long term reliability of device structures fabricated using this phenomenon and in determining new device functionalities.

  8. Microalloying of transition metal silicides by mechanical activation and field-activated reaction

    Energy Technology Data Exchange (ETDEWEB)

    Munir, Zuhair A. (Davis, CA); Woolman, Joseph N. (Davis, CA); Petrovic, John J. (Los Alamos, NM)

    2003-09-02

    Alloys of transition metal suicides that contain one or more alloying elements are fabricated by a two-stage process involving mechanical activation as the first stage and densification and field-activated reaction as the second stage. Mechanical activation, preferably performed by high-energy planetary milling, results in the incorporation of atoms of the alloying element(s) into the crystal lattice of the transition metal, while the densification and field-activated reaction, preferably performed by spark plasma sintering, result in the formation of the alloyed transition metal silicide. Among the many advantages of the process are its ability to accommodate materials that are incompatible in other alloying methods.

  9. Acceptors in II-IV Semiconductors - Incorporation and Complex Formation

    CERN Multimedia

    2002-01-01

    A strong effort is currently devoted to the investigation of defects and the electrical activation of dopant atoms in II-VI semiconductors. In particular, the knowledge about the behaviour of acceptors, prerequisite for the fabrication of p-type semiconductors, is rather limited. The perturbed $\\,{\\gamma\\gamma}$ -angular correlation technique (PAC) and the photoluminescence spectroscopy (PL) using the radioactive isotopes $^{77}\\!$Br and $^{111}\\!$Ag will be applied for investigating the behaviour of acceptor dopant atoms and their interactions with defects in II-VI semiconductors. The main topic will be the identification of the technical conditions for the incorporation of electrically active acceptors in the II-VI semiconductors ~ZnS, ZnSe, ZnTe, CdS, CdSe, and CdTe with particular emphasis on the compounds~ CdTe, ZnSe, and ZnTe. The investigations will be supplemented by first exploratory PL experiments with the group V acceptors $^{71}\\!$As and $^{121}\\!$Sb. With help of the probe $^{111}\\!$Ag, the pos...

  10. Consumer Activities and Reactions to Social Network Marketing

    Directory of Open Access Journals (Sweden)

    Bistra Vassileva

    2017-06-01

    Full Text Available The purpose of this paper is to understand consumer behavioural models with respect to their reactions to social network marketing. Theoretical background is focused on online and social network usage, motivations and behaviour. The research goal is to explore consumer reactions to the exposure of social network marketing based on the following criteria: level of brand engagement, word-of-mouth (WOM referral behaviour, and purchase intentions. Consumers are investigated based on their attitudes toward social network marketing and basic socio-demographic covariates using data from a sample size of 700 Bulgarian respondents (age group 21–54 years, Internet users, urban inhabitants. Factor and cluster analyses are applied. It is found that consumers are willing to receive information about brands and companies through social networks. They like to talk in social networks about these brands and companies and to share information as well (factor 2, brand engagement. Internet users are willing to share information received through social network advertising (factor 1, wom referral behaviour but they would not buy a certain brand as a result of brand communication activities in social networks (factor 3, purchase intention. Several practical implications regarding marketing activities through social networks are drawn.

  11. Dimeric interactions and complex formation using direct coevolutionary couplings.

    Science.gov (United States)

    dos Santos, Ricardo N; Morcos, Faruck; Jana, Biman; Andricopulo, Adriano D; Onuchic, José N

    2015-09-04

    We develop a procedure to characterize the association of protein structures into homodimers using coevolutionary couplings extracted from Direct Coupling Analysis (DCA) in combination with Structure Based Models (SBM). Identification of dimerization contacts using DCA is more challenging than intradomain contacts since direct couplings are mixed with monomeric contacts. Therefore a systematic way to extract dimerization signals has been elusive. We provide evidence that the prediction of homodimeric complexes is possible with high accuracy for all the cases we studied which have rich sequence information. For the most accurate conformations of the structurally diverse dimeric complexes studied the mean and interfacial RMSDs are 1.95Å and 1.44Å, respectively. This methodology is also able to identify distinct dimerization conformations as for the case of the family of response regulators, which dimerize upon activation. The identification of dimeric complexes can provide interesting molecular insights in the construction of large oligomeric complexes and be useful in the study of aggregation related diseases like Alzheimer's or Parkinson's.

  12. Antenatal glucocorticoids attenuate activation of the inflammatory reaction and clotting in preterm lambs

    NARCIS (Netherlands)

    Jaarsma, AS; Geven, WB; van Oeveren, W; Bambang-Oetomo, S

    2004-01-01

    Recently we have shown that activation of inflammatory reaction and clotting can be found immediately after delivery in preterm lambs ventilated for respiratory distress syndrome (RDS). To investigate whether antenatal glucocorticoids would attenuate postnatal activation of the inflammatory reaction

  13. Interactions between plutonism and detachments during metamorphic core complex formation, Serifos Island (Cyclades, Greece)

    Science.gov (United States)

    Rabillard, Aurélien; Arbaret, Laurent; Jolivet, Laurent; Le Breton, Nicole; Gumiaux, Charles; Augier, Romain; Grasemann, Bernhard

    2015-06-01

    In order to better understand the interactions between plutonic activity and strain localization during metamorphic core complex formation, the Miocene granodioritic pluton of Serifos (Cyclades, Greece) is studied. This pluton (11.6-9.5 Ma) intruded the Cycladic Blueschists during thinning of the Aegean domain along a system of low-angle normal faults belonging to the south dipping West Cycladic Detachment System (WCDS). Based on structural fieldwork, together with microstructural observations and anisotropy of magnetic susceptibility, we recognize a continuum of deformation from magmatic to brittle conditions within the magmatic body. This succession of deformation events is kinematically compatible with the development of the WCDS. The architecture of the pluton shows a marked asymmetry resulting from its interaction with the detachments. We propose a tectonic scenario for the emplacement of Serifos pluton and its subsequent cooling during the Aegean extension: (1) A first stage corresponds to the metamorphic core complex initiation and associated southwestward shearing along the Meghàlo Livadhi detachment. (2) In the second stage, the Serifos pluton has intruded the dome at shallow crustal level, piercing through the ductile/brittle Meghàlo Livadhi detachment. Southwest directed extensional deformation was contemporaneously transferred upward in the crust along the more localized Kàvos Kiklopas detachment. (3) The third stage was marked by synmagmatic extensional deformation and strain localization at the contact between the pluton and the host rocks resulting in nucleation of narrow shear zones, which (4) continued to develop after the pluton solidification.

  14. SOHLH2 is essential for synaptonemal complex formation during spermatogenesis in early postnatal mouse testes.

    Science.gov (United States)

    Park, Miree; Lee, Youngeun; Jang, Hoon; Lee, Ok-Hee; Park, Sung-Won; Kim, Jae-Hwan; Hong, Kwonho; Song, Hyuk; Park, Se-Pill; Park, Yun-Yong; Ko, Jung Jae; Choi, Youngsok

    2016-02-12

    Spermatogenesis- and oogenesis-specific helix-loop-helix transcription factor 2 (SOHLH2) is exclusively expressed in germ cells of the gonads. Previous studies show that SOHLH2 is critical for spermatogenesis in mouse. However, the regulatory mechanism of SOHLH2 during early spermatogenesis is poorly understood. In the present study, we analyzed the gene expression profile of the Sohlh2-deficient testis and examined the role of SOHLH2 during spermatogenesis. We found 513 genes increased in abundance, while 492 genes decreased in abundance in 14-day-old Sohlh2-deficient mouse testes compared to wildtype mice. Gene ontology analysis revealed that Sohlh2 disruption effects the relative abundance of various meiotic genes during early spermatogenesis, including Spo11, Dmc1, Msh4, Prdm9, Sycp1, Sycp2, Sycp3, Hormad1, and Hormad2. Western blot analysis and immunostaining showed that SYCP3, a component of synaptonemal complex, was significantly less abundant in Sohlh2-deficient spermatocytes. We observed a lack of synaptonemal complex formation during meiosis in Sohlh2-deficient spermatocytes. Furthermore, we found that SOHLH2 interacted with two E-boxes on the mouse Sycp1 promoter and Sycp1 promoter activity increased with ectopically expressed SOHLH2. Taken together, our data suggest that SOHLH2 is critical for the formation of synaptonemal complexes via its regulation of Sycp1 expression during mouse spermatogonial differentiation.

  15. Donor-Acceptor Properties of a Single-Molecule Altered by On-Surface Complex Formation.

    Science.gov (United States)

    Meier, Tobias; Pawlak, Rémy; Kawai, Shigeki; Geng, Yan; Liu, Xunshan; Decurtins, Silvio; Hapala, Prokop; Baratoff, Alexis; Liu, Shi-Xia; Jelínek, Pavel; Meyer, Ernst; Glatzel, Thilo

    2017-08-22

    Electron donor-acceptor molecules are of outstanding interest in molecular electronics and organic solar cells for their intramolecular charge transfer controlled via electrical or optical excitation. The preservation of their electronic character in the ground state upon adsorption on a surface is cardinal for their implementation in such single-molecule devices. Here, we investigate by atomic force microscopy and scanning tunneling microscopy a prototypical system consisting of a π-conjugated tetrathiafulvalene-fused dipyridophenazine molecule adsorbed on thin NaCl films on Cu(111). Depending on the adsorption site, the molecule is found either in a nearly undisturbed free state or in a bound state. In the latter case, the molecule adopts a specific adsorption site, leading to the formation of a chelate complex with a single Na(+) alkali cation pulled out from the insulating film. Although expected to be electronically decoupled, the charge distribution of the complex is drastically modified, leading to the loss of the intrinsic donor-acceptor character. The chelate complex formation is reversible with respect to lateral manipulations, enabling tunable donor-acceptor molecular switches activated by on-surface coordination.

  16. Audience reaction movie trailers and the Paranormal Activity franchise

    Directory of Open Access Journals (Sweden)

    Alexander Swanson

    2015-03-01

    Full Text Available This article addresses the concept and growing practice of audience reaction movie trailers, specifically for films in the horror genre. Popularized by the Paranormal Activity series of films, these trailers primarily utilize green night-vision video footage of a movie theater audience reacting to the film being advertised, yet also consist of webcam recordings of screaming fans, documentary-style B-roll footage of audiences filing into preview screenings with high levels of anticipation, and close-up shots of spectator facial expressions, accompanied by no footage whatsoever from the film being advertised. In analyzing these audience-centric promotional paratexts, my aim is to reveal them as attempting to sell and legitimize the experiential, communal, and social qualities of the theatrical movie viewing experience while at the same time calling for increased fan investment in both physical and online spaces. Through the analysis of audience reaction trailers, this article hopes to both join and engender conversations about horror fan participation, the nature of anticipatory texts as manipulative, and the current state of horror gimmickry in the form of the promotional paratext.

  17. Formylglycinamide Ribonucleotide Amidotransferase from Thermotoga maritima: Structural Insights into Complex Formation

    Energy Technology Data Exchange (ETDEWEB)

    Morar, Mariya; Hoskins, Aaron A.; Stubbe, JoAnne; Ealick, Steven E. (MIT); (Cornell)

    2008-10-02

    In the fourth step of the purine biosynthetic pathway, formyl glycinamide ribonucleotide (FGAR) amidotransferase, also known as PurL, catalyzes the conversion of FGAR, ATP, and glutamine to formyl glycinamidine ribonucleotide (FGAM), ADP, P{sub i}, and glutamate. Two forms of PurL have been characterized, large and small. Large PurL, present in most Gram-negative bacteria and eukaryotes, consists of a single polypeptide chain and contains three major domains: the N-terminal domain, the FGAM synthetase domain, and the glutaminase domain, with a putative ammonia channel located between the active sites of the latter two. Small PurL, present in Gram-positive bacteria and archaea, is structurally homologous to the FGAM synthetase domain of large PurL, and forms a complex with two additional gene products, PurQ and PurS. The structure of the PurS dimer is homologous with the N-terminal domain of large PurL, while PurQ, whose structure has not been reported, contains the glutaminase activity. In Bacillus subtilis, the formation of the PurLQS complex is dependent on glutamine and ADP and has been demonstrated by size-exclusion chromatography. In this work, a structure of the PurLQS complex from Thermotoga maritima is described revealing a 2:1:1 stoichiometry of PurS:Q:L, respectively. The conformational changes observed in TmPurL upon complex formation elucidate the mechanism of metabolite-mediated recruitment of PurQ and PurS. The flexibility of the PurS dimer is proposed to play a role in the activation of the complex and the formation of the ammonia channel. A potential path for the ammonia channel is identified.

  18. Quartz crystal microbalance with dissipation and microscale thermophoresis as tools for investigation of protein complex formation between thymidylate synthesis cycle enzymes.

    Science.gov (United States)

    Antosiewicz, Anna; Senkara, Elżbieta; Cieśla, Joanna

    2015-02-15

    Thymidylate synthase (TS) and dihydrofolate reductase (DHFR) play essential role in DNA synthesis, repair and cell division by catalyzing two subsequent reactions in thymidylate biosynthesis cycle. The lack of either enzyme leads to thymineless death of the cell, therefore inhibition of the enzyme activity is a common and successful tool in cancer chemotherapy and treatment of other diseases. However, the detailed mechanism of thymidylate synthesis cycle, especially the interactions between cycle enzymes and its role remain unknown. In this paper we are the first to show that human TS and DHFR enzymes form a strong complex which might be essential for DNA synthesis. Using two unique biosensor techniques, both highly sensitive to biomolecular interactions, namely quartz crystal microbalance with dissipation monitoring (QCM-D) and microscale thermophoresis (MST) we have been able to determine DHFR-TS binding kinetic parameters such as the Kd value being below 10 µM (both methods), k(on) = 0.46 × 10(4) M(-1) s(-1) and k(off) = 0.024 s(-1) (QCM-D). We also calculated Gibbs free energy as in the order of -30 kJ/mol and DHFR/TS molar ratio pointing to binding of 6 DHFR monomers per 1 TS dimer (both methods). Moreover, our data from MST analysis have pointed to positive binding cooperativity in TS-DHFR complex formation. The results obtained with both methods are comparable and complementary.

  19. Spectroscopic investigation on the inclusion complex formation between amisulpride and γ-cyclodextrin.

    Science.gov (United States)

    Negi, Jeetendra Singh; Singh, Shivpal

    2013-02-15

    The purpose of this research was to investigate inclusion complex formation between poorly soluble drug amisulpride (AMI) and γ-cyclodextrin (γ-CD). The solubility of AMI was enhanced by formation of inclusion complex of AMI with nano-hydrophobic cavity of γ-CD. The stoichiometry of inclusion complex was studied by continuous variation Job's plot method and found 1:1. The binding constant was found 1166.65 M(-1) by Benesi-Hildebrand plot. The molecular docking of AMI and γ-CD was done to investigate complexation. The inclusion complex formation was further confirmed by (1)H NMR and FT-IR, DSC and XRD analysis. The solubility of AMI was increased 3.74 times after inclusion complex formation with γ-CD.

  20. Activation Energy of Tantalum-Tungsten Oxide Thermite Reaction

    Energy Technology Data Exchange (ETDEWEB)

    Cervantes, O; Kuntz, J; Gash, A; Munir, Z

    2010-02-25

    The activation energy of a high melting temperature sol-gel (SG) derived tantalum-tungsten oxide thermite composite was determined using the Kissinger isoconversion method. The SG derived powder was consolidated using the High Pressure Spark Plasma Sintering (HPSPS) technique to 300 and 400 C to produce pellets with dimensions of 5 mm diameter by 1.5 mm height. A custom built ignition setup was developed to measure ignition temperatures at high heating rates (500-2000 C {center_dot} min{sup -1}). Such heating rates were required in order to ignite the thermite composite. Unlike the 400 C samples, results show that the samples consolidated to 300 C undergo an abrupt change in temperature response prior to ignition. This change in temperature response has been attributed to the crystallization of the amorphous WO{sub 3} in the SG derived Ta-WO{sub 3} thermite composite and not to a pre-ignition reaction between the constituents. Ignition temperatures for the Ta-WO{sub 3} thermite ranged from approximately 465-670 C. The activation energy of the SG derived Ta-WO{sup 3} thermite composite consolidated to 300 and 400 C were determined to be 37.787 {+-} 1.58 kJ {center_dot} mol{sup -1} and 57.381 {+-} 2.26 kJ {center_dot} mol{sup -1}, respectively.

  1. cAMP prevents TNF-induced apoptosis through inhibiting DISC complex formation in rat hepatocytes.

    Science.gov (United States)

    Bhattacharjee, Rajesh; Xiang, Wenpei; Wang, Yinna; Zhang, Xiaoying; Billiar, Timothy R

    2012-06-22

    Tumor necrosis factor α (TNF) is a pleiotropic proinflammatory cytokine that plays a role in immunity and the control of cell proliferation, cell differentiation, and apoptosis. The pleiotropic nature of TNF is due to the formation of different signaling complexes upon the binding of TNF to its receptor, TNF receptor type 1 (TNFR1). TNF induces apoptosis in various mammalian cells when the cells are co-treated with a transcription inhibitor like actinomycin D (ActD). When TNFR1 is activated, it recruits an adaptor protein, TNF receptor-associated protein with death domain (TRADD), through its cytoplasmic death effector domain (DED). TRADD, in turn, recruits other signaling proteins, including TNF receptor-associated protein 2 (TRAF2) and receptor-associated protein kinase (RIPK) 1, to form a complex. Subsequently, this complex combines with FADD and procaspase-8, converts into a death-inducing signaling complex (DISC) to induce apoptosis. Cyclic AMP (cAMP) is a second messenger that regulates various cellular processes such as cell proliferation, gene expression, and apoptosis. cAMP analogues are reported to act as anti-apoptotic agents in various cell types, including hepatocytes. We found that a cAMP analogue, dibutyryl cAMP (db-cAMP), inhibits TNF+ActD-induced apoptosis in rat hepatocytes. The protein kinase A (PKA) inhibitor KT-5720 reverses this inhibitory effect of cAMP on apoptosis. Cytoprotection by cAMP involves down-regulation of various apoptotic signal regulators like TRADD and FADD and inhibition of caspase-8 and caspase-3 cleavage. We also found that cAMP exerts its affect at the proximal level of TNF signaling by inhibiting the formation of the DISC complex upon the binding of TNF to TNFR1. In conclusion, our study shows that cAMP prevents TNF+ActD-induced apoptosis in rat hepatocytes by inhibiting DISC complex formation.

  2. Development of excretion stimulating techniques for radioactive materials via complex formation

    Energy Technology Data Exchange (ETDEWEB)

    Takaya, Haruo; Utsumi, Akira; Takatsu, Akiko [National Inst. of materials and Chemical Research, Tsukuba, Ibaraki (Japan)

    1999-02-01

    This research project aimed to establish a technique for rapid excretion of RI metals (Ni, Cd, Pb) incorporated into human body and here, development of removing agents which allow complex formation with metals was attempted. The reactivities of those agents with metals such as Ni, Cd were investigated. The gluco-formazan derivatives produced in the previous year; PF, PCF, PHF, PPF, PPCF and PPHF were investigated in the respect of reactivities with various metals. Those formazan derivatives were mixed with a metal ion (alkaline earth metals, lanthanoids, 1st transition metal) in buffered sodium-perchlorate solution to determine the chelating activity and the stability of metal chelation was estimated by spectrophotometric method. In formazan derivative with glucose, mannose or galactose, N atom of imino, azo and pyridyl groups, and O atoms of carboxyl and hydroxy groups possibly mediate the bonding with a metal ion. These chelate agents were little reactive for alkali metals, alkaline earth metals (Mg, Sr, Ba) or lanthanoid elements, but their affinities to Zn, Cd, Ni and Co were very high. It was demonstrated that either of the formazan derivatives was able to make chelate complex, suggesting that those are usable for excretion of RI metal ({sup 63}Ni and {sup 109}Cd). These gluco-formazan thus obtained were able to excrete these RI metals in the human body without affecting the metabolism of physiologically indispensable metals such as Ca, Mg, Fe etc. Furthermore, it seems necessary to make pharmacokinetic study on absorption, distribution, metabolism, excretion of the gluco-formazan derivatives. (M.N.)

  3. On the complex formation approach in modeling predator prey relations, mating, and sexual disease transmission

    Directory of Open Access Journals (Sweden)

    Horst R. Thieme

    2000-10-01

    Full Text Available Complex formation is used as a unified approach to derive representations and approximations of the functional response in predator prey relations, mating, and sexual disease transmission. Applications are given to the impact of a generalist predator on a prey population and the spread of a sexually transmitted disease in a multi-group heterosexual population.

  4. Complex formation and solubility of Pu(IV) with malonic and succinic acids

    Energy Technology Data Exchange (ETDEWEB)

    Sasaki, T.; Kobayashi, T.; Takagi, I.; Moriyama, H. [Kyoto Univ. (Japan). Dept. of Nuclear Engineering; Fujiwara, A. [Radioactive Waste Management Funding and Research Center, Tokyo (Japan); Kulyako, Y.M.; Perevalov, S.A.; Myasoedov, B.F. [Russian Academy of Sciences (RAS), Moscow (RU). V.I. Vernadsky Inst. of Geochemistry and Analytical Chemistry (GEOKHI)

    2009-07-01

    The complex formation constants of tetravalent plutonium ion with malonic and succinic acids in aqueous solution were determined by the solvent-extraction method. Also, by taking the known values of the solubility products, the hydrolysis constants and the formation constants, the experimental solubility data of plutonium in the presence of carboxylates were analyzed. (orig.)

  5. Comparative thermodynamic study on complex formation of native and hydroxypropylated cyclodextrins with benzoic acid

    Energy Technology Data Exchange (ETDEWEB)

    Terekhova, Irina V., E-mail: ivt@isc-ras.ru [Institute of Solution Chemistry of RAS, Ivanovo (Russian Federation)

    2011-11-10

    Highlights: Black-Right-Pointing-Pointer Comparative calorimetric study on complexation of benzoic acid by native and modified cyclodextrins was performed. Black-Right-Pointing-Pointer Van der Waals interactions are responsible for complex formation with {alpha}-cyclodextrins. Black-Right-Pointing-Pointer Complex formation of {beta}-cyclodextrins is governed by dehydration and hydrophobic interactions. Black-Right-Pointing-Pointer Binding of two benzoic acid molecules by {gamma}-cyclodextrins is driven by van der Waals interactions and solvent reorganization. Black-Right-Pointing-Pointer Hydroxypropyl groups favor binding of benzoic acid only with hydroxypropyl-{beta}-cyclodextrin. - Abstract: Complex formation of native and hydroxypropylated {alpha}-, {beta}- and {gamma}-cyclodextrins with benzoic acid in water was studied by means of calorimetry of solution at 298.15 K. The 1:1 complexes are formed with {alpha}- and {beta}-cyclodextrins, while 1:2 binding stoichiometry was observed for {gamma}-cyclodextrins. Thermodynamic parameters of complex formation of hydroxypropylated cyclodextrins were determined for the first time and analyzed. Comparison of binding affinity of native and modified cyclodextrins was carried out.

  6. Alkaline activated slag cements. Determination of reaction degree

    Directory of Open Access Journals (Sweden)

    Fernández-Jiménez, A.

    2001-03-01

    Full Text Available The aim of the present work was to evaluate the validity of non-calorimetric different methods, used in the determination of reaction degree of alkaline activated slag pastes. The methods used were: (a chemical separation by methanol-salicylic acid; (b determination of the weight loss mass between 100-600°C in TG curves, associated to chemically combined water; (c quantification of the -74 ppm signal in 29Si MAS-NMR spectra. The parameters considered in the process were: nature of the alkaline activator (Waterglass, Na2CO3 and NaOH, activator concentration (4% and 3% Na2O in mass with respect to the slag, curing temperature (25 and 45°C, slag specific surface (460 and 900 m2/kg and time of reaction (from 7 days to 18 months. The results obtained indicate that none of the three methods is definitive but complementary and they provide to follow the reactive evolution of the alkaline activated slag cements. The method based on the quantification of the -74 ppm signal in the 29Si MAS NMR is the most suitable method.

    El objetivo del presente trabajo fue evaluar la validez de diferentes métodos, no calorimétricos, utilizados en la determinación del grado de reacción de pastas de escoria activada alcalinamente. Los métodos utilizados fueron: (a método de separación química por disolución en metanol ácido-salicílico; (b determinación de las pérdidas de masa entre 100-600°C en las curvas de TG, pérdidas asociadas a la cantidad de agua químicamente combinada: (c cuantificación de la señal de -74 ppm de los espectros de 29Si RMN MAS. Las variables consideradas en el proceso fueron: naturaleza del activador alcalino (Waterglass, Na2CO3 y NaOH, concentración del activador (4% y 3% de Na2O en masa respecto a la escoria, temperatura de curado (25 y 45°C, superficie específica de la escoria (460 y 900 m2/kg y

  7. Synthesis, Reactions and Antimicrobial Activities of 8-Ethoxycoumarin Derivatives

    Directory of Open Access Journals (Sweden)

    Mostafa M. Khafagy

    2012-01-01

    Full Text Available Condensation of 3-acetyl-8-ethoxycoumarin (3 with thiosemicarbazide gave ethylidenehydrazinecarbothioamide 5, which was transformed into the thiazolidin-4-one derivatives 6,7. Interaction of 3 with DMF/POCl3 gave b-chloroacroline derivative 8. Treatment of 3 with malononitrile gave benzo[c]chromone and 2-aminobenzonitrile derivatives 9 and 10, respectively with respect to the reaction conditions. Condensation of 3-(2-bromoacetyl-8-ethoxycoumarin (4 with o-phenylenediamine gave 3-(quioxaline-2-yl-8-ethoxycoumarin hydrobromide (11, while 4 reacted with 2-aminopyridine to give chromenopyridopyrimidine derivative 12. Condensation of 4 with potassium thio-cyanate/methanol gave an unexpected derivative, 2H-chromeno-3-carboxy(methyl-carbonimidicthioanhydride 16, which upon treatment with (NH22·H2O gave 3-ethoxy-2-hydroxybenzaldehyde azine 19. Interaction of 4 with thiourea derivatives gave thiazole derivatives 20a–c. The structures of the newly synthesized compounds were confirmed by their spectra data. The newly synthesized compounds were also screened for their antimicrobial activity.

  8. Study of alpha one antitrypsin activity in lepra reaction.

    Science.gov (United States)

    Sengupta, S R; Dhole, T N; Jahagirdar, V L; Yemul, V L; Chawhan, R N

    1983-04-01

    In our earlier study (Yemul et, al, 1983) we have reported elevation of serum alpha one antitrypsin levels in patients of lepromatous leprosy and lepra reaction. In this study estimation of serum alpha one antitrypsin levels in fifty lepra reaction patients (8 of type 1 and 42 of type II) and fifty age and sex matched healthy controls is described. Alpha one antitrypsin levels were elevated in lepra reaction patients (type I--mean value of 332 mg% and S.D. +/- 118.8 and type II--mean value of 450 mg% and S.D. +/- 73.7) when compared with the healthy controls (mean value of 285 mg% and S.D. +/- 66.05). The increase in levels in type II lepra reaction patients was statistically significant. The results are discussed to correlate the increased levels of alpha one antitrypsin and the high bacterial load leading to the release of various proteases in type II lepra reaction.

  9. Measurement of the activation cross section for the (p,xn) reactions in niobium with potential applications as monitor reactions

    Energy Technology Data Exchange (ETDEWEB)

    Avila-Rodriguez, M.A. [Edmonton PET Centre, Cross Cancer Institute, Edmonton, AB, T6G 1Z2 (Canada)], E-mail: miguel.avila-rodriguez@utu.fi; Wilson, J.S. [Edmonton PET Centre, Cross Cancer Institute, Edmonton, AB, T6G 1Z2 (Canada); Schueller, M.J. [Brookhaven National Laboratory, Upton, NY 11973 (United States); McQuarrie, S.A. [Edmonton PET Centre, Cross Cancer Institute, Edmonton, AB, T6G 1Z2 (Canada)

    2008-08-15

    Excitation functions of the {sup 93}Nb(p,n){sup 93m}Mo, {sup 93}Nb(p,pn){sup 92m}Nb and {sup 93}Nb(p,{alpha}n){sup 89}Zr nuclear reactions were measured up to 17.4 MeV by the conventional activation method using the stacked-foil technique. Stacks were irradiated at different incident energies on the TR19/9 cyclotron at the Edmonton PET Centre. The potential of the measured excitation functions for use as monitor reactions was evaluated and tested by measuring activity ratios at a different facility. Single Nb foils were irradiated at incident energies in the range from 12 to 19 MeV on the TR19/9 cyclotron at Brookhaven National Laboratory. Results are compared with the published data and with theoretical values as determined by the nuclear reaction model code EMPIRE.

  10. Nickel-catalyzed sonogashira reactions of non-activated secondary alkyl bromides and iodides.

    Science.gov (United States)

    Yi, Jun; Lu, Xi; Sun, Yan-Yan; Xiao, Bin; Liu, Lei

    2013-11-18

    A nicked reaction: The title reaction of terminal alkynes with non-activated secondary alkyl iodides and bromides was accomplished for the first time. This reaction provides a new and practical approach for the synthesis of substituted alkynes (see scheme; cod=cyclo-1,5-octadiene). Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. cAMP prevents TNF-induced apoptosis through inhibiting DISC complex formation in rat hepatocytes

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacharjee, Rajesh [Department of Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA 15213 (United States); Xiang, Wenpei [Department of Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA 15213 (United States); Family Planning Research Institute, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, People' s Republic of China (China); Wang, Yinna [Vascular Medicine Institute, University of Pittsburgh School of Medicine, 10051-5A BST 3, 3501 Fifth Avenue, Pittsburgh, PA 15261 (United States); Zhang, Xiaoying [Department of Medicine/Endocrinology Division, University of Pittsburgh Medical Center, 200 Lothrop St., Pittsburgh, PA 15213 (United States); Billiar, Timothy R., E-mail: billiartr@upmc.edu [Department of Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA 15213 (United States)

    2012-06-22

    that cAMP exerts its affect at the proximal level of TNF signaling by inhibiting the formation of the DISC complex upon the binding of TNF to TNFR1. In conclusion, our study shows that cAMP prevents TNF + ActD-induced apoptosis in rat hepatocytes by inhibiting DISC complex formation.

  12. Designing ancillary ligands for heteroleptic/homoleptic zinc complex formation: synthesis, structures and application in ROP of lactides.

    Science.gov (United States)

    Jędrzkiewicz, D; Ejfler, J; Gulia, N; John, Ł; Szafert, S

    2015-08-14

    Synthesis and characterization of a series of new amino-phenol/naphthol ligands (L(1,2)-H) have been developed and their respective zinc complexes ( 1 and 2-Zn ) have been synthesized. The molecular structures of L(1)-H and 1, 2-Zn were explored in detail by NMR, single-crystal X-ray studies and DFT calculations, which confirmed the existence of complexes as stabile dimers both in a solution and in the solid state. All complexes mediate the ring-opening polymerization (ROP) of lactide highly efficiently, at room temperature, in a controlled fashion. The influence of the architecture of the ligand on the desired homo/heteroleptic complex formation, as well as the relationship between the initiator design and the catalytic activity have been investigated.

  13. Activated by Combined Magnrtic Field Gravitropic Reaction Reply on Nanodose of Biologicaly Active Compounds

    Science.gov (United States)

    Sheykina, Nadezhda; Bogatina, Nina

    The new science direction nanotechnologies initiated a big jump in the pharmacology and medicine. This leads to the big development of homeopathy. The most interest appeared while investigating of the reaction of biological object on the nano dose of iologically substances. The changing of concentration (in nmol/l) of biologically active material is also possible during weak energy action. For instance, weak combined magnetic field may change a little the concentration of ions that are oriented parallel to the external magnetic field and, by the analogy with said above, lead to the similar effects. Simple estimations give the value for the threshold to the magnetic field by two orders smaller than the geomagnetic field. By this investigation we wanted to understand whether the analogy in the action of nano dose of biologically active substances and weak combined magnetic field presents and whether the action of one of these factors may be replaced by other one. The effect of one of biologically active substances NPA (Naphtyl-Phtalame Acid) solution with the concentration 0.01 mol/l on the gravitropic reaction of cress roots was investigated. It was shown that its effect was the inhibition of cress roots gravitropic reaction. The same inhibition was achieved by the combined magnetic field action on the cress roots, germinated in water. The alternative component of the combined magnetic field coincided formally with the cyclotron frequency of NPA ions. So the analogy in the action of nano dose of biologically active substances and weak combined magnetic field was shown. The combined magnetic field using allows to decrease sufficiently the dose of biologically active substances. This fact can be of great importance in pharmacy and medicine.

  14. Peculiarities of litter invertebrates’ multispecies complexes formation on the Khortitsa island (Zaporizhzhya province

    Directory of Open Access Journals (Sweden)

    D. О. Fedorchenko

    2008-02-01

    Full Text Available Peculiarities of litter invertebrates’ complexes formation under conditions of the Khortitsa National Reserve (Zaporizhzhya province are studied. The dispersion of taxonomic groups of different levels (families and species in litter mesofauna is swayed by the inter- and intrasystem factors; the largest influence has the power of litter and its humidity. The rate of ecological factors’ influence at different taxonomic levels may diverge.

  15. The role of eIF-4C in protein synthesis initiation complex formation

    NARCIS (Netherlands)

    Goumans, H.; Thomas, A.; Verhoeven, H.; Voorma, H.O.; Benne, R.

    1980-01-01

    eIF-4C has a pronounced stimulatory effect on initiation complex formation with native 80-S ribosomes (80-Sn) as the only source of ribosomal subunits, but only a small effect when washed 40-S subunits are used. eIF-4C is accessary to eIF-3 in dissociating 80-Sn ribosomes. eIF-4C is present on 40-

  16. Curcumin complexation with cyclodextrins by the autoclave process: Method development and characterization of complex formation.

    Science.gov (United States)

    Hagbani, Turki Al; Nazzal, Sami

    2017-03-30

    One approach to enhance curcumin (CUR) aqueous solubility is to use cyclodextrins (CDs) to form inclusion complexes where CUR is encapsulated as a guest molecule within the internal cavity of the water-soluble CD. Several methods have been reported for the complexation of CUR with CDs. Limited information, however, is available on the use of the autoclave process (AU) in complex formation. The aims of this work were therefore to (1) investigate and evaluate the AU cycle as a complex formation method to enhance CUR solubility; (2) compare the efficacy of the AU process with the freeze-drying (FD) and evaporation (EV) processes in complex formation; and (3) confirm CUR stability by characterizing CUR:CD complexes by NMR, Raman spectroscopy, DSC, and XRD. Significant differences were found in the saturation solubility of CUR from its complexes with CD when prepared by the three complexation methods. The AU yielded a complex with expected chemical and physical fingerprints for a CUR:CD inclusion complex that maintained the chemical integrity and stability of CUR and provided the highest solubility of CUR in water. Physical and chemical characterizations of the AU complexes confirmed the encapsulated of CUR inside the CD cavity and the transformation of the crystalline CUR:CD inclusion complex to an amorphous form. It was concluded that the autoclave process with its short processing time could be used as an alternate and efficient methods for drug:CD complexation. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Roles of tumor necrosis factor alpha on sperm acrosin activity and acrosome reaction

    Institute of Scientific and Technical Information of China (English)

    Shu-LingBian; Guo-YiLiu; Hai-XiaWen; Shu-ZhenWang; JiangNi; WeiZhang; HuiSi

    2004-01-01

    Aim: To study the roles of tumor necrosis factor alpha (TNF-a)on the sperm acrosin activity and acrosome reaction. Methods:The sperm acrosin activity was tested by the method of BAEE/ADH Unity and the acrosome reaction by the Triple-stain technique. Results: TNF-a decreased the sperm acrosin activityand acrosome reaction (P<0.01, P<0.01, respectively);

  18. An Interactive Classroom Activity Demonstrating Reaction Mechanisms and Rate-Determining Steps

    Science.gov (United States)

    Jennings, Laura D.; Keller, Steven W.

    2005-01-01

    An interactive classroom activity that includes two-step reaction of unwrapping and eating chocolate candies is described which brings not only the reaction intermediate, but also the reactants and products into macroscopic view. The qualitative activation barriers of both steps can be adjusted independently.

  19. Reactions of 3-Formylchromone with Active Methylene and Methyl Compounds and Some Subsequent Reactions of the Resulting Condensation Products

    Directory of Open Access Journals (Sweden)

    M. Lácova

    2005-08-01

    Full Text Available This review presents a survey of the condensations of 3-formylchromone with various active methylene and methyl compounds, e.g. malonic or barbituric acid derivatives, five-membered heterocycles, etc. The utilisation of the condensation products for the synthesis of different heterocyclic systems, which is based on the ability of the γ-pyrone ring to be opened by the nucleophilic attack is also reviewed. Finally, the applications of microwave irradiation as an unconventional method of reaction activation in the synthesis of condensation products is described and the biological activity of some chromone derivatives is noted.

  20. Inhibition of PRL-2·CNNM3 Protein Complex Formation Decreases Breast Cancer Proliferation and Tumor Growth.

    Science.gov (United States)

    Kostantin, Elie; Hardy, Serge; Valinsky, William C; Kompatscher, Andreas; de Baaij, Jeroen H F; Zolotarov, Yevgen; Landry, Melissa; Uetani, Noriko; Martínez-Cruz, Luis Alfonso; Hoenderop, Joost G J; Shrier, Alvin; Tremblay, Michel L

    2016-05-13

    The oncogenic phosphatase of regenerating liver 2 (PRL-2) has been shown to regulate intracellular magnesium levels by forming a complex through an extended amino acid loop present in the Bateman module of the CNNM3 magnesium transporter. Here we identified highly conserved residues located on this amino acid loop critical for the binding with PRL-2. A single point mutation (D426A) of one of those critical amino acids was found to completely disrupt PRL-2·human Cyclin M 3 (CNNM3) complex formation. Whole-cell voltage clamping revealed that expression of CNNM3 influenced the surface current, whereas overexpression of the binding mutant had no effect, indicating that the binding of PRL-2 to CNNM3 is important for the activity of the complex. Interestingly, overexpression of the CNNM3 D426A-binding mutant in cancer cells decreased their ability to proliferate under magnesium-deprived situations and under anchorage-independent growth conditions, demonstrating a PRL-2·CNNM3 complex-dependent oncogenic advantage in a more stringent environment. We further confirmed the importance of this complex in vivo using an orthotopic xenograft breast cancer model. Finally, because molecular modeling showed that the Asp-426 side chain in CNNM3 buries into the catalytic cavity of PRL-2, we showed that a PRL inhibitor could abrogate complex formation, resulting in a decrease in proliferation of human breast cancer cells. In summary, we provide evidence that this fundamental regulatory aspect of PRL-2 in cancer cells could potentially lead to broadly applicable and innovative therapeutic avenues.

  1. A novel high throughput biochemical assay to evaluate the HuR protein-RNA complex formation.

    Directory of Open Access Journals (Sweden)

    Vito G D'Agostino

    Full Text Available The RNA binding protein HuR/ELAVL1 binds to AU-rich elements (AREs promoting the stabilization and translation of a number of mRNAs into the cytoplasm, dictating their fate. We applied the AlphaScreen technology using purified human HuR protein, expressed in a mammalian cell-based system, to characterize in vitro its binding performance towards a ssRNA probe whose sequence corresponds to the are present in TNFα 3' untranslated region. We optimized the method to titrate ligands and analyzed the kinetic in saturation binding and time course experiments, including competition assays. The method revealed to be a successful tool for determination of HuR binding kinetic parameters in the nanomolar range, with calculated Kd of 2.5±0.60 nM, k on of 2.76±0.56*10(6 M(-1 min(-1, and k off of 0.007±0.005 min(-1. We also tested the HuR-RNA complex formation by fluorescent probe-based RNA-EMSA. Moreover, in a 384-well plate format we obtained a Z-factor of 0.84 and an averaged coefficient of variation between controls of 8%, indicating that this biochemical assay fulfills criteria of robustness for a targeted screening approach. After a screening with 2000 small molecules and secondary verification with RNA-EMSA we identified mitoxantrone as an interfering compound with rHuR and TNFα probe complex formation. Notably, this tool has a large versatility and could be applied to other RNA Binding Proteins recognizing different RNA, DNA, or protein species. In addition, it opens new perspectives in the identification of small-molecule modulators of RNA binding proteins activity.

  2. Energetic Mechanism of Cytochrome c-Cytochrome c Oxidase Electron Transfer Complex Formation under Turnover Conditions Revealed by Mutational Effects and Docking Simulation.

    Science.gov (United States)

    Sato, Wataru; Hitaoka, Seiji; Inoue, Kaoru; Imai, Mizue; Saio, Tomohide; Uchida, Takeshi; Shinzawa-Itoh, Kyoko; Yoshikawa, Shinya; Yoshizawa, Kazunari; Ishimori, Koichiro

    2016-07-15

    Based on the mutational effects on the steady-state kinetics of the electron transfer reaction and our NMR analysis of the interaction site (Sakamoto, K., Kamiya, M., Imai, M., Shinzawa-Itoh, K., Uchida, T., Kawano, K., Yoshikawa, S., and Ishimori, K. (2011) Proc. Natl. Acad. Sci. U.S.A. 108, 12271-12276), we determined the structure of the electron transfer complex between cytochrome c (Cyt c) and cytochrome c oxidase (CcO) under turnover conditions and energetically characterized the interactions essential for complex formation. The complex structures predicted by the protein docking simulation were computationally selected and validated by the experimental kinetic data for mutant Cyt c in the electron transfer reaction to CcO. The interaction analysis using the selected Cyt c-CcO complex structure revealed the electrostatic and hydrophobic contributions of each amino acid residue to the free energy required for complex formation. Several charged residues showed large unfavorable (desolvation) electrostatic interactions that were almost cancelled out by large favorable (Columbic) electrostatic interactions but resulted in the destabilization of the complex. The residual destabilizing free energy is compensated by the van der Waals interactions mediated by hydrophobic amino acid residues to give the stabilized complex. Thus, hydrophobic interactions are the primary factors that promote complex formation between Cyt c and CcO under turnover conditions, whereas the change in the electrostatic destabilization free energy provides the variance of the binding free energy in the mutants. The distribution of favorable and unfavorable electrostatic interactions in the interaction site determines the orientation of the binding of Cyt c on CcO.

  3. Identification of general linear relationships between activation energies and enthalpy changes for dissociation reactions at surfaces.

    Science.gov (United States)

    Michaelides, Angelos; Liu, Z-P; Zhang, C J; Alavi, Ali; King, David A; Hu, P

    2003-04-02

    The activation energy to reaction is a key quantity that controls catalytic activity. Having used ab inito calculations to determine an extensive and broad ranging set of activation energies and enthalpy changes for surface-catalyzed reactions, we show that linear relationships exist between dissociation activation energies and enthalpy changes. Known in the literature as empirical Brønsted-Evans-Polanyi (BEP) relationships, we identify and discuss the physical origin of their presence in heterogeneous catalysis. The key implication is that merely from knowledge of adsorption energies the barriers to catalytic elementary reaction steps can be estimated.

  4. Effect of Ionic Liquids on Organic Reactions Based on Activity Coefficients at Infinite Dilution

    Institute of Scientific and Technical Information of China (English)

    马征; 董晓霞; 胡玉峰; 张柏松; 徐长英; 刘艳升

    2013-01-01

    It is important to know how ILs (ionic liquids) influence organic reaction. In this paper, activity coeffi-cients at infinite dilution of more than 80 organic compounds in ILs are collected and analyzed systematically. Through the study on typical organic reactions happened in ILs, such as Diels-Alder, esterification and Friedel-Crafts reaction, the ratio of activity coefficients at infinite dilution of products and reactants is employed to estimate different effects of different structural ILs on the rate and selectivity of reactions.

  5. The dual effects of Maillard reaction and enzymatic hydrolysis on the antioxidant activity of milk proteins.

    Science.gov (United States)

    Oh, N S; Lee, H A; Lee, J Y; Joung, J Y; Lee, K B; Kim, Y; Lee, K W; Kim, S H

    2013-08-01

    The objective of this study was to determine the enhanced effects on the biological characteristics and antioxidant activity of milk proteins by the combination of the Maillard reaction and enzymatic hydrolysis. Maillard reaction products were obtained from milk protein preparations, such as whey protein concentrates and sodium caseinate with lactose, by heating at 55°C for 7 d in sodium phosphate buffer (pH 7.4). The Maillard reaction products, along with untreated milk proteins as controls, were hydrolyzed for 0 to 3h with commercial proteases Alcalase, Neutrase, Protamex, and Flavorzyme (Novozymes, Bagsværd, Denmark). The antioxidant activity of hydrolyzed Maillard reaction products was determined by reaction with 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt, their 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity, and the ability to reduce ferric ions. Further characteristics were evaluated by the o-phthaldialdehyde method and sodium dodecyl sulfate-PAGE. The degree of hydrolysis gradually increased in a time-dependent manner, with the Alcalase-treated Maillard reaction products being the most highly hydrolyzed. Radical scavenging activities and reducing ability of hydrolyzed Maillard reaction products increased with increasing hydrolysis time. The combined products of enzymatic hydrolysis and Maillard reaction showed significantly greater antioxidant activity than did hydrolysates or Maillard reaction products alone. The hydrolyzed Maillard reaction products generated by Alcalase showed significantly higher antioxidant activity when compared with the other protease products and the antioxidant activity was higher for the whey protein concentrate groups than for the sodium caseinate groups. These findings indicate that Maillard reaction products, coupled with enzymatic hydrolysis, could act as potential antioxidants in the pharmaceutical, food, and dairy industries.

  6. Power Installations based on Activated Nuclear Reactions of Fission and Synthesis

    CERN Document Server

    Grigoriev, Yuriy

    2016-01-01

    The general scheme of power installations based on nuclear reactions of fission and synthesis activated by external sources is analyzed. The external activation makes possible to support nuclear reactions at temperatures and pressures lower than needed for chain reactions, so simplifies considerably practical realization of power installations. The possibility of operation on subcritical masses allows making installations compact and safe at emergency situations. Installations are suitable for transmutation of radioactive nuclides, what solves the problem of utilization of nuclear waste products. It is proposed and considered schemes of power installations based on nuclear reactions of fission and fusion, activated by external sources, different from ADS systems. Variants of activation of nuclear reactions of fission (U-235, 238, Pu-239) and fusion (Li-6,7, B-10,11) are considered.

  7. Fluorimetric determination of diosmin and hesperidin in combined dosage forms and in plasma through complex formation with terbium

    Directory of Open Access Journals (Sweden)

    Dalia Mohamed

    2013-06-01

    Full Text Available A sensitive and simple fluorimetric method was developed for the determination of diosmin and hesperidin. The proposed method involves the formation of ternary complex with Tb3+ in the presence of Tris buffer. The fluorescence quenching of Tb3+ at 549 and 494 nm (λex at 275 and 248 nm due to the complex formation was quantitatively measured for diosmin and hesperidin, respectively. The reaction conditions and the fluorescence spectral properties of the complexes have been investigated. Under the described conditions, the proposed method was applicable over the concentration range (4.93 × 10−6–1.81 × 10−5 mol and (3.28 × 10−6–1.64 × 10−5 mol with mean percentage recoveries 100.22 ± 0.89 and 99.13 ± 0.72 for diosmin and hesperidin, respectively. The proposed method was applied successfully for the determination of studied drugs in bulk powder, dosage forms and plasma samples. The results obtained by applying the described method were statistically analyzed and compared with those obtained by applying a reported method. The method was validated according to ICH recommendations.

  8. Layered metal laurates as active catalysts in the methyl/ethyl esterification reactions of lauric acid

    Energy Technology Data Exchange (ETDEWEB)

    Lisboa, Fabio da Silva; Cordeiro, Claudiney S.; Wypych, Fernando, E-mail: wypych@ufpr.br [Centro de Pesquisas em Quimica Aplicada (CEPESQ), Departamento de Quimica, Universidade Federal do Parana, Curitiba, PR (Brazil); Gardolinski, Jose Eduardo F. da Costa [Laboratorio de Analise de Minerais e Rochas (LAMIR), Departamento de Geologia, Universidade Federal do Parana, Curitiba, PR (Brazil)

    2012-07-01

    In this work we report the synthesis, characterization and investigation of the catalytic activity of layered copper(II), manganese(II), lanthanum(III) and nickel(II) laurates in the methyl and ethyl esterification reactions of lauric acid. In the methyl esterification, conversions between 80 and 90% were observed for all catalysts, while for the ethyl esterification only manganese laurate showed reasonable catalytic activity, with conversions close to 75%. Reuse of copper and lanthanum laurates in three cycles of reaction was also investigated and both catalysts preserved the structure and retained catalytic activity close to that observed for the first reaction cycle. (author)

  9. Formylation of N-arylpyrazole containing active amino group using Vilsmeier-Haack reaction

    Institute of Scientific and Technical Information of China (English)

    Yi Luo; Ping Zhong; Xiao Hong Zhang; Qiu Lian Lin; Ye Na Chen

    2008-01-01

    Two species of N-arylpyrazoles containing active amino group were synthesized.And formylations of N-arylpyazoles containing amino in different position of pyrazole rings using Vilsmeier-Haack reaction gave a series of useful pyrazole intermediates.The important features of this protocol were cheap materials,easy process,mild reaction conditions and good yield of products.

  10. Nanoreactors for simultaneous remote thermal activation and optical monitoring of chemical reactions.

    Science.gov (United States)

    Vázquez-Vázquez, Carmen; Vaz, Belén; Giannini, Vincenzo; Pérez-Lorenzo, Moisés; Alvarez-Puebla, Ramon A; Correa-Duarte, Miguel A

    2013-09-18

    We report herein the design of plasmonic hollow nanoreactors capable of concentrating light at the nanometer scale for the simultaneous performance and optical monitoring of thermally activated reactions. These reactors feature the encapsulation of plasmonic nanoparticles on the inner walls of a mesoporous silica capsule. A Diels-Alder cycloaddition reaction was carried out in the inner cavities of these nanoreactors to evidence their efficacy. Thus, it is demonstrated that reactions can be accomplished in a confined volume without alteration of the temperature of the bulk solvent while allowing real-time monitoring of the reaction progress.

  11. Cyanogenesis Inhibits Active Defense Reactions in Plants 1

    Science.gov (United States)

    Lieberei, Reinhard; Biehl, Böle; Giesemann, Anette; Junqueira, Nilton T. V.

    1989-01-01

    In the course of fungal attack on the cyanogenic rubber tree (Hevea brasiliensis Muell.-Arg.) HCN is liberated from infected tissue. The HCN interferes with plant host and fungal pathogen. It becomes inhibitory to active defense responses which are dependent on biosynthetic processes as far as a threshold concentration is transgressed. PMID:16666758

  12. On the activation energy of the formic acid oxidation reaction on platinum electrodes

    OpenAIRE

    Perales-Rondón, Juan V.; Herrero, Enrique; Feliu, Juan M

    2015-01-01

    A temperature dependent study on the formic acid oxidation reaction has been carried out in order to determine the activation energy of this reaction on different platinum single crystal electrodes, namely Pt(1 0 0), Pt(1 1 1), Pt(5 5 4) and Pt(5 4 4) surfaces. The chronoamperometric transients obtained with pulsed voltammetry have been analyzed to determine the current densities through the active intermediate and the CO formation rate. From the temperature dependency of those parameters, th...

  13. Generalization of the Activated Complex Theory of Reaction Rates. I. Quantum Mechanical Treatment

    Science.gov (United States)

    Marcus, R. A.

    1964-01-01

    In its usual form activated complex theory assumes a quasi-equilibrium between reactants and activated complex, a separable reaction coordinate, a Cartesian reaction coordinate, and an absence of interaction of rotation with internal motion in the complex. In the present paper a rate expression is derived without introducing the Cartesian assumption. The expression bears a formal resemblance to the usual one and reduces to it when the added assumptions of the latter are introduced.

  14. The Optimum Reaction Time, Activation Energy and Frequency Factor of Methyl Ricinoleate Nitration

    OpenAIRE

    Abdullah, Abdullah; Triyono, Triyono; Trisunaryanti, Wega; Haryadi, Winarto

    2013-01-01

    Determination of the optimum reaction time, activation energy (Ea) and frequency factor (A) of methyl ricinoleate nitration has been done. The nitration was conducted with the mole ratio of methyl ricinoleate to HNO3 of 1:15. The reaction was conducted at temperatures of 29 and 64 °C with a variation of reaction time for 10, 20, 30, 60, 90, 120, and 150 min. Determination of activation energy and frequency factor was performed in a temperature of 29, 33, 38, 44, 49, 57 and 64 °C. The results ...

  15. Aligned carbon nanotube with electro-catalytic activity for oxygen reduction reaction

    Science.gov (United States)

    Liu, Di-Jia; Yang, Junbing; Wang, Xiaoping

    2010-08-03

    A catalyst for an electro-chemical oxygen reduction reaction (ORR) of a bundle of longitudinally aligned carbon nanotubes having a catalytically active transition metal incorporated longitudinally in said nanotubes. A method of making an electro-chemical catalyst for an oxygen reduction reaction (ORR) having a bundle of longitudinally aligned carbon nanotubes with a catalytically active transition metal incorporated throughout the nanotubes, where a substrate is in a first reaction zone, and a combination selected from one or more of a hydrocarbon and an organometallic compound containing an catalytically active transition metal and a nitrogen containing compound and an inert gas and a reducing gas is introduced into the first reaction zone which is maintained at a first reaction temperature for a time sufficient to vaporize material therein. The vaporized material is then introduced to a second reaction zone maintained at a second reaction temperature for a time sufficient to grow longitudinally aligned carbon nanotubes over the substrate with a catalytically active transition metal incorporated throughout the nanotubes.

  16. Stability of furosemide polymorphs and the effects of complex formation with β-cyclodextrin and maltodextrin.

    Science.gov (United States)

    Garnero, Claudia; Chattah, Ana Karina; Longhi, Marcela

    2016-11-05

    The effect of the formation of supramolecular binary complexes with β-cyclodextrin and maltodextrin on the chemical and physical stability of the polymorphs I and II of furosemide was evaluated in solid state. The solid samples were placed under accelerated storage conditions and exposed to daylight into a stability chamber for a 6-month. Chemical stability was monitored by high performance liquid chromatography, while the physical stability was studied by solid state nuclear magnetic resonance, powder X-ray diffraction and scanning electron microscopy. Changes in the physical appearance of the samples were evaluated. The studies showed a significant stabilizing effect of β-cyclodextrin on furosemide form II. Our results suggest that the complex formation is a useful tool for improving the stability of furosemide polymorphs. These new complexes are promising candidates that can be used in the pharmaceutical industry for the preparation of alternative matrices that improve physicochemical properties.

  17. Substrate activation for O2 reactions by oxidized metal centers in biology.

    Science.gov (United States)

    Pau, Monita Y M; Lipscomb, John D; Solomon, Edward I

    2007-11-20

    The uncatalyzed reactions of O(2) (S = 1) with organic substrates (S = 0) are thermodynamically favorable but kinetically slow because they are spin-forbidden and the one-electron reduction potential of O(2) is unfavorable. In nature, many of these important O(2) reactions are catalyzed by metalloenzymes. In the case of mononuclear non-heme iron enzymes, either Fe(II) or Fe(III) can play the catalytic role in these spin-forbidden reactions. Whereas the ferrous enzymes activate O(2) directly for reaction, the ferric enzymes activate the substrate for O(2) attack. The enzyme-substrate complex of the ferric intradiol dioxygenases exhibits a low-energy catecholate to Fe(III) charge transfer transition that provides a mechanism by which both the Fe center and the catecholic substrate are activated for the reaction with O(2). In this Perspective, we evaluate how the coupling between this experimentally observed charge transfer and the change in geometry and ligand field of the oxidized metal center along the reaction coordinate can overcome the spin-forbidden nature of the O(2) reaction.

  18. Dynamics of nanoparticle-protein corona complex formation: analytical results from population balance equations.

    Directory of Open Access Journals (Sweden)

    Faryad Darabi Sahneh

    Full Text Available BACKGROUND: Nanoparticle-protein corona complex formation involves absorption of protein molecules onto nanoparticle surfaces in a physiological environment. Understanding the corona formation process is crucial in predicting nanoparticle behavior in biological systems, including applications of nanotoxicology and development of nano drug delivery platforms. METHOD: This paper extends the modeling work in to derive a mathematical model describing the dynamics of nanoparticle corona complex formation from population balance equations. We apply nonlinear dynamics techniques to derive analytical results for the composition of nanoparticle-protein corona complex, and validate our results through numerical simulations. RESULTS: The model presented in this paper exhibits two phases of corona complex dynamics. In the first phase, proteins rapidly bind to the free surface of nanoparticles, leading to a metastable composition. During the second phase, continuous association and dissociation of protein molecules with nanoparticles slowly changes the composition of the corona complex. Given sufficient time, composition of the corona complex reaches an equilibrium state of stable composition. We find analytical approximate formulae for metastable and stable compositions of corona complex. Our formulae are very well-structured to clearly identify important parameters determining corona composition. CONCLUSION: The dynamics of biocorona formation constitute vital aspect of interactions between nanoparticles and living organisms. Our results further understanding of these dynamics through quantitation of experimental conditions, modeling results for in vitro systems to better predict behavior for in vivo systems. One potential application would involve a single cell culture medium related to a complex protein medium, such as blood or tissue fluid.

  19. Can arsenic-phytochelatin complex formation be used as an indicator for toxicity in Helianthus annuus?

    Science.gov (United States)

    Raab, Andrea; Ferreira, Katia; Meharg, Andrew A; Feldmann, Jörg

    2007-01-01

    The formation of arsenic-phytochelatin (As-PC) complexes is thought to be part of the plant detoxification strategy for arsenic. This work examines (i) the arsenic (As) concentration-dependent formation of As-PC complex formation and (ii) redistribution and metabolism of As after arrested As uptake in Helianthus annuus. HPLC with parallel ICP-MS/ES-MS detection was used to identify and quantify the species present in plant extracts exposed to arsenate (As(V)) (between 0 and 66.7 micromol As l-1 for 24 h). At As concentrations below the EC50 value for root growth (22 micromol As l-1) As uptake is exponential, but it is reduced at concentrations above. Translocation between root and shoot seemed to be limited to the uptake phase of arsenic. No redistribution of As between root and shoot was observed after arresting As exposure. The formation of As-PC complexes was concentration-dependent. The amount and number of As-PC complexes increased exponentially with concentration up to 13.7 micromol As l-1. As(III)-PC3 and GS-As(III)-PC2 complexes were the dominant species in all samples. The ratio of PC-bound As to unbound As increased up to 1.3 micromol As l-1 and decreased at higher concentrations. Methylation of inorganic As was only a minor pathway in H. annuus with about 1% As methylated over a 32 d period. The concentration dependence of As-PC complex formation, amount of unbound reduced and oxidized PC2, and the relative uptake rate showed that As starts to influence the cellular metabolism of H. annuus negatively at As concentrations well below the EC50 value determined by more traditional means. Generally, As-PC complexes and PC-synthesis rate seem to be the more sensitive parameters to be studied when As toxicity values are to be estimated.

  20. Complement activation in leprosy: a retrospective study shows elevated circulating terminal complement complex in reactional leprosy.

    Science.gov (United States)

    Bahia El Idrissi, N; Hakobyan, S; Ramaglia, V; Geluk, A; Morgan, B Paul; Das, P Kumar; Baas, F

    2016-06-01

    Mycobacterium leprae infection gives rise to the immunologically and histopathologically classified spectrum of leprosy. At present, several tools for the stratification of patients are based on acquired immunity markers. However, the role of innate immunity, particularly the complement system, is largely unexplored. The present retrospective study was undertaken to explore whether the systemic levels of complement activation components and regulators can stratify leprosy patients, particularly in reference to the reactional state of the disease. Serum samples from two cohorts were analysed. The cohort from Bangladesh included multi-bacillary (MB) patients with (n = 12) or without (n = 46) reaction (R) at intake and endemic controls (n = 20). The cohort from Ethiopia included pauci-bacillary (PB) (n = 7) and MB (n = 23) patients without reaction and MB (n = 15) patients with reaction. The results showed that the activation products terminal complement complex (TCC) (P ≤ 0·01), C4d (P ≤ 0·05) and iC3b (P ≤ 0·05) were specifically elevated in Bangladeshi patients with reaction at intake compared to endemic controls. In addition, levels of the regulator clusterin (P ≤ 0·001 without R; P < 0·05 with R) were also elevated in MB patients, irrespective of a reaction. Similar analysis of the Ethiopian cohort confirmed that, irrespective of a reaction, serum TCC levels were increased significantly in patients with reactions compared to patients without reactions (P ≤ 0·05). Our findings suggests that serum TCC levels may prove to be a valuable tool in diagnosing patients at risk of developing reactions. © 2016 British Society for Immunology.

  1. Catalytic activation of carbohydrates as formaldehyde equivalents for Stetter reaction with enones.

    Science.gov (United States)

    Zhang, Junmin; Xing, Chong; Tiwari, Bhoopendra; Chi, Yonggui Robin

    2013-06-05

    We disclose the first catalytic activation of carbohydrates as formaldehyde equivalents to generate acyl anions as one-carbon nucleophilic units for a Stetter reaction. The activation involves N-heterocyclic carbene (NHC)-catalyzed C-C bond cleavage of carbohydrates via a retro-benzoin-type process to generate the acyl anion intermediates. This Stetter reaction constitutes the first success in generating formal formaldehyde-derived acyl anions as one-carbon nucleophiles for non-self-benzoin processes. The renewable nature of carbohydrates, accessible from biomass, further highlights the practical potential of this fundamentally interesting catalytic activation.

  2. Microwave activation of palladium nanoparticles for enhanced ethanol electrocatalytic oxidation reaction in alkaline medium

    CSIR Research Space (South Africa)

    Rohwer, MB

    2015-02-01

    Full Text Available in alkaline medium (in terms of high mass activity stability and fast reaction kinetics). The remarkable microwave-induced properties on the Pd catalyst promise to revolutionize the use of microwave for catalyst activation for enhanced heterogeneous catalysis...

  3. Direct Electrochemical Reaction of Horseradish Peroxidase Immobilized on the Surface of Active Carbon Powders

    Institute of Scientific and Technical Information of China (English)

    Dong Mei SUN; Chen Xin CAI; Wei XING; Tian Hong LU

    2004-01-01

    It is reported for the first time that horseradish peroxidase(HRP)immobilized on the active carbon can undergo a direct quasi-reversible electrochemical reaction. In addition,the immobilized HRP showed the stable bioelectrocatalytic activity for the reduction of H2O2.

  4. Solvent-Induced Reversal of Activities between Two Closely Related Heterogeneous Catalysts in the Aldol Reaction

    Energy Technology Data Exchange (ETDEWEB)

    Kandel, Kapil [Ames Laboratory; Althaus, Stacey M [Ames Laboratory; Peeraphatdit, Chorthip [Ames Laboratory; Kobayashi, Takeshi [Ames Laboratory; Trewyn, Brian G [Ames Laboratory; Pruski, Marek [Ames Laboratory; Slowing, Igor I [Ames Laboratory

    2013-01-11

    The relative rates of the aldol reaction catalyzed by supported primary and secondary amines can be inverted by 2 orders of magnitude, depending on the use of hexane or water as a solvent. Our analyses suggest that this dramatic shift in the catalytic behavior of the supported amines does not involve differences in reaction mechanism, but is caused by activation of imine to enamine equilibria and stabilization of iminium species. The effects of solvent polarity and acidity were found to be important to the performance of the catalytic reaction. This study highlights the critical role of solvent in multicomponent heterogeneous catalytic processes.

  5. Basophil activation test in the study of food and drug hypersensitivity reactions

    OpenAIRE

    Carrapatoso, I; Cadinha, S; Sanz, ML

    2005-01-01

    The increase in the prevalence of adverse reactions to foods and drugs represents a constant challenge to the development of new methods of diagnosis. A meta-analysis on published studies concerning the clinical usefulness of the Basophil activation test (BAT) in these reactions was performed. High sensibilities and specificities can be achieved if certain technical requirements are observed. BAT results have a positive and high significant correlations with other routine diagnostic ...

  6. Complex formation reactions of lanthanum(III), cerium(III), thorium(IV), dioxouranyl(IV) complexes with tricine.

    Science.gov (United States)

    Mohamed, Mahmoud M A

    2007-08-01

    Equilibrium studies for the heavy metal ions La(III), Ce(III), Th(IV) and UO2(IV) (M) complexes of the zwitterionic buffer tricine (L) in aqueous solution are investigated. Stoichiometry and stability constants for the different complexes formed as well as hydrolysis products of the metal cations are determined at 25 degrees C and ionic strength 0.1 M NaNO3. The stability of the formed complexes are discussed in terms of the nature of the heavy metal cation. The solid complexes are synthesized and characterized by means of elemental analysis, FTIR, and TG analysis. The general molecular formulae of the obtained complexes is suggested to be [M(L)2](NO3)n-2(H2O)x, where n = the charge of the metal cation, x = no. of water molecules.

  7. Analysis of the total activation cross section of all possible reactions producing the same radioactive nuclide for the%Analysis of the total activation cross section of all possible reactions producing the same radioactive nuclide for the

    Institute of Scientific and Technical Information of China (English)

    周丰群; 宋月丽; 拓飞; 孔祥忠

    2011-01-01

    Firstly, according to the regulation of growth and decay of radioactive nuclides produced in reactions, a formula used to calculate the total activation cross section of all possible reactions producing the same radioactive nuclide for the same element is

  8. Rate of pozzolanic reaction of two kinds of activated coal gangue

    Institute of Scientific and Technical Information of China (English)

    ZHOU Shuang-xi

    2009-01-01

    Two kinds of activated ways are used to prepare activated coal gangue fine powder,one is calcining coal gangue at 800 ℃ (gangue A),and the other is calcining coal gangue with a certain calcite at 800 ℃ (gangue B).The experiment shows that strengths of blended cement mortar with coal gangue B are higher than that of blended cement with coal gangue A.Hydration of cements with the two kinds of activated coal gangue is investigated through a differential thermal analysis.The weight loss due to Ca(OH)2 decomposition of hydration products by differential thermal anaiysis/thermo gravimetric (DTA/TG) can be used to quantify the pozzolanic reaction.A new method based on the composition of hydration cement is proposed to determine the degree of pozzolanic reaction.The results obtained suggest that the degree of pozzolanic reaction of gangue B is faster than that of gangue A.

  9. A reaction mode of carbene-catalysed aryl aldehyde activation and induced phenol OH functionalization

    Science.gov (United States)

    Chen, Xingkuan; Wang, Hongling; Doitomi, Kazuki; Ooi, Chong Yih; Zheng, Pengcheng; Liu, Wangsheng; Guo, Hao; Yang, Song; Song, Bao-An; Hirao, Hajime; Chi, Yonggui Robin

    2017-05-01

    The research in the field of asymmetric carbene organic catalysis has primarily focused on the activation of carbon atoms in non-aromatic scaffolds. Here we report a reaction mode of carbene catalysis that allows for aromatic aldehyde activation and remote oxygen atom functionalization. The addition of a carbene catalyst to the aldehyde moiety of 2-hydroxyl aryl aldehyde eventually enables dearomatization and remote OH activation. The catalytic process generates a type of carbene-derived intermediate with an oxygen atom as the reactive centre. Inexpensive achiral urea co-catalyst works cooperatively with the carbene catalyst, leading to consistent enhancement of the reaction enantioselectivity. Given the wide presence of aromatic moieties and heteroatoms in natural products and synthetic functional molecules, we expect our reaction mode to significantly expand the power of carbene catalysis in asymmetric chemical synthesis.

  10. Thermodynamics of the complex formation between Cu2+ and triglycine in water-ethanol solutions at 298 K

    Science.gov (United States)

    Pham Thi, L.; Usacheva, T. R.; Khrenova, T. M.; Sharnin, V. A.

    2017-07-01

    Thermodynamic functions Δr H, Δr G, and TΔr S of the complex formation between Cu2+ and triglycine in water-ethanol solutions are calculated on the basis of calorimetric data. It is found that raising the concentration of EtOH results in a monotonic increase in the exothermic effect of [CuHL]2+ complex formation due to the weakening of triglycine solvation with the mutual compensation of ion solvation contributions. The enthalpy of [CuL]+ complex formation has an exothermic maximum at 0.1-0.3 molar fractions of EtOH due to competition between the solvation contributions from ions and ligands.

  11. Toward an Automatic Determination of Enzymatic Reaction Mechanisms and Their Activation Free Energies.

    Science.gov (United States)

    Zinovjev, Kirill; Ruiz-Pernía, J Javier; Tuñón, Iñaki

    2013-08-13

    We present a combination of the string method and a path collective variable for the exploration of the free energy surface associated to a chemical reaction in condensed environments. The on-the-fly string method is employed to find the minimum free energy paths on a multidimensional free energy surface defined in terms of interatomic distances, which is a convenient selection to study bond forming/breaking processes. Once the paths have been determined, a reaction coordinate is defined as a measure of the advance of the system along these paths. This reaction coordinate can be then used to trace the reaction Potential of Mean Force from which the activation free energy can be obtained. This combination of methodologies has been here applied to the study, by means of Quantum Mechanics/Molecular Mechanics simulations, of the reaction catalyzed by guanidinoacetate methyltransferase. This enzyme catalyzes the methylation of guanidinoacetate by S-adenosyl-l-methionine, a reaction that involves a methyl transfer and a proton transfer and for which different reaction mechanisms have been proposed.

  12. Investigation of molecular interactions in the complex formation of tartaric acid derivatives with di(2-ethylhexyl) phosphoric acid

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The molecular interactions in the complex formation of two tartaric acid derivatives with di(2-ethylhexyl) phosphoric acid are investigated. The complex formation with a 1:1 stoichiometry between tartaric acid derivatives and D2EHPA can be obtained through UV-Vis titration, NMR chemical shifts and molecular dynamic simulations. Furthermore, the differences of the two complexes on the binding constants and strength of hydrogen bonds can also be determined. Such research will ideally provide insight into ways of regulating the complex forming properties of tartaric acid derivatives for composing or syn- thesizing new chiral resolving agents.

  13. Investigation of molecular interactions in the complex formation of tartaric acid derivatives with di(2-ethylhexyl) phosphoric acid

    Institute of Scientific and Technical Information of China (English)

    TAN Bin; ZHAI Zheng; LUO GuangSheng; WANG JiaDing

    2008-01-01

    The molecular interactions in the complex formation of two tartaric acid derivatives with di(2-ethylhexyl) phosphoric acid are investigated. The complex formation with a 1:1 stoichiometry between tartaric acid derivatives and D2EHPA can be obtained through UV-Vis titration, NMR chemical shifts and molecular dynamic simulations. Furthermore, the differences of the two complexes on the binding constants and strength of hydrogen bonds can also be determined. Such research will ideally provide insight into ways of regulating the complex forming properties of tartaric acid derivatives for composing or syn-thesizing new chiral resolving agents.

  14. Thermally activated reaction–diffusion-controlled chemical bulk reactions of gases and solids

    Directory of Open Access Journals (Sweden)

    S. Möller

    2015-01-01

    Full Text Available The chemical kinetics of the reaction of thin films with reactive gases is investigated. The removal of thin films using thermally activated solid–gas to gas reactions is a method to in-situ control deposition inventory in vacuum and plasma vessels. Significant scatter of experimental deposit removal rates at apparently similar conditions was observed in the past, highlighting the need for understanding the underlying processes. A model based on the presence of reactive gas in the films bulk and chemical kinetics is presented. The model describes the diffusion of reactive gas into the film and its chemical interaction with film constituents in the bulk using a stationary reaction–diffusion equation. This yields the reactive gas concentration and reaction rates. Diffusion and reaction rate limitations are depicted in parameter studies. Comparison with literature data on tokamak co-deposit removal results in good agreement of removal rates as a function of pressure, film thickness and temperature.

  15. Ranking the importance of nuclear reactions for activation and transmutation events

    CERN Document Server

    Arter, Wayne; Relton, Samuel D; Higham, Nicholas J

    2015-01-01

    Pathways-reduced analysis is one of the techniques used by the Fispact-II nuclear activation and transmutation software to study the sensitivity of the computed inventories to uncertainties in reaction cross-sections. Although deciding which pathways are most important is very helpful in for example determining which nuclear data would benefit from further refinement, pathways-reduced analysis need not necessarily define the most critical reaction, since one reaction may contribute to several different pathways. This work examines three different techniques for ranking reactions in their order of importance in determining the final inventory, viz. a pathways based metric (PBM), the direct method and one based on the Pearson correlation coefficient. Reasons why the PBM is to be preferred are presented.

  16. Activation Strain Analysis of SN2 Reactions at C, N, O, and F Centers.

    Science.gov (United States)

    Kubelka, Jan; Bickelhaupt, F Matthias

    2017-02-02

    Fundamental principles that determine chemical reactivity and reaction mechanisms are the very foundation of chemistry and many related fields of science. Bimolecular nucleophilic substitutions (SN2) are among the most common and therefore most important reaction types. In this report, we examine the trends in the SN2 reactions with respect to increasing electronegativity of the reaction center by comparing the well-studied backside SN2 Cl(-) + CH3Cl with similar Cl(-) substitutions on the isoelectronic series with the second period elements N, O, and F in place of C. Relativistic (ZORA) DFT calculations are used to construct the gas phase reaction potential energy surfaces (PES), and activation strain analysis, which allows decomposition of the PES into the geometrical strain and interaction energy, is employed to analyze the observed trends. We find that SN2@N and SN2@O have similar PES to the prototypical SN2@C, with the well-defined reaction complex (RC) local minima and a central barrier, but all stationary points are, respectively, increasingly stable in energy. The SN2@F, by contrast, exhibits only a single-well PES with no barrier. Using the activation strain model, we show that the trends are due to the interaction energy and originate mainly from the decreasing energy of the empty acceptor orbital (σ*A-Cl) on the reaction center A in the order of C, N, O, and F. The decreasing steric congestion around the central atom is also a likely contributor to this trend. Additional decomposition of the interaction energy using Kohn-Sham molecular orbital (KS-MO) theory provides further support for this explanation, as well as suggesting electrostatic energy as the primary reason for the distinct single-well PES profile for the FCl reaction.

  17. Protein complex formation and intranuclear dynamics of NAC1 in cancer cells.

    Science.gov (United States)

    Nakayama, Naomi; Kato, Hiroaki; Sakashita, Gyosuke; Nariai, Yuko; Nakayama, Kentaro; Kyo, Satoru; Urano, Takeshi

    2016-09-15

    Nucleus accumbens-associated protein 1 (NAC1) is a cancer-related transcription regulator protein that is also involved in the pluripotency and differentiation of embryonic stem cells. NAC1 is overexpressed in various carcinomas including ovarian, cervical, breast, and pancreatic carcinomas. NAC1 knock-down was previously shown to result in the apoptosis of ovarian cancer cell lines and to rescue their sensitivity to chemotherapy, suggesting that NAC1 may be a potential therapeutic target, but protein complex formation and the dynamics of intranuclear NAC1 in cancer cells remain poorly understood. In this study, analysis of HeLa cell lysates by fast protein liquid chromatography (FPLC) on a sizing column showed that the NAC1 peak corresponded to an apparent molecular mass of 300-500 kDa, which is larger than the estimated molecular mass (58 kDa) of the protein. Furthermore, live cell photobleaching analyses with green fluorescent protein (GFP)-fused NAC1 proteins revealed the intranuclear dynamics of NAC1. Collectively our results demonstrate that NAC1 forms a protein complex to function as a transcriptional regulator in cancer cells.

  18. Speciation of phytate ion in aqueous solution. Alkali metal complex formation in different ionic media.

    Science.gov (United States)

    De Stefano, Concetta; Milea, Demetrio; Pettignano, Alberto; Sammartano, Silvio

    2003-08-01

    The acid-base properties of phytic acid [ myo-inositol 1,2,3,4,5,6-hexakis(dihydrogen phosphate)] (H(12)Phy; Phy(12-)=phytate anion) were studied in aqueous solution by potentiometric measurements ([H+]-glass electrode) in lithium and potassium chloride aqueous media at different ionic strengths (0iodide (Et(4)NI; e.g., at I=0.5 mol L(-1), log K(3)(H)=11.7, 8.0, 9.1, and 9.1 in Et(4)NI, LiCl, NaCl and KCl, respectively; the protonation constants in Et(4)NI and NaCl were already reported), owing to the strong interactions occurring between the phytate and alkaline cations present in the background salt. We explained this in terms of complex formation between phytate and alkali metal ions. Experimental evidence allows us to consider the formation of 13 mixed proton-metal-ligand complexes, M(j)H(i)Phy((12-i-j)-), (M+ =Li+, Na+, K+), with jstability of alkali metal complexes follows the trend Li+ > or =Na+K+. Some measurements were also performed at constant ionic strength (I=0.5 mol L(-1)), using different mixtures of Et(4)NI and alkali metal chlorides, in order to confirm the formation of hypothesized and calculated metal-proton-ligand complex species and to obtain conditional protonation constants in these multi-component ionic media.

  19. Substrate-Na{sup +} complex formation: Coupling mechanism for {gamma}-aminobutyrate symporters

    Energy Technology Data Exchange (ETDEWEB)

    Pallo, Anna; Simon, Agnes [Department of Neurochemistry, Institute of Biomolecular Chemistry, Chemical Research Center, Hungarian Academy of Sciences (Hungary); Bencsura, Akos [Department of Theoretical Chemistry, Institute of Structural Chemistry, Chemical Research Center, Hungarian Academy of Sciences, Budapest (Hungary); Heja, Laszlo [Department of Neurochemistry, Institute of Biomolecular Chemistry, Chemical Research Center, Hungarian Academy of Sciences (Hungary); Kardos, Julianna, E-mail: jkardos@chemres.hu [Department of Neurochemistry, Institute of Biomolecular Chemistry, Chemical Research Center, Hungarian Academy of Sciences (Hungary)

    2009-07-24

    Crystal structures of transmembrane transport proteins belonging to the important families of neurotransmitter-sodium symporters reveal how they transport neurotransmitters across membranes. Substrate-induced structural conformations of gated neurotransmitter-sodium symporters have been in the focus of research, however, a key question concerning the mechanism of Na{sup +} ion coupling remained unanswered. Homology models of human glial transporter subtypes of the major inhibitory neurotransmitter {gamma}-aminobutyric acid were built. In accordance with selectivity data for subtype 2 vs. 3, docking and molecular dynamics calculations suggest similar orthosteric substrate (inhibitor) conformations and binding crevices but distinguishable allosteric Zn{sup 2+} ion binding motifs. Considering the occluded conformational states of glial human {gamma}-aminobutyric acid transporter subtypes, we found major semi-extended and minor ring-like conformations of zwitterionic {gamma}-aminobutyric acid in complex with Na{sup +} ion. The existence of the minor ring-like conformation of {gamma}-aminobutyric acid in complex with Na{sup +} ion may be attributed to the strengthening of the intramolecular H-bond by the electrostatic effect of Na{sup +} ion. Coupling substrate uptake into cells with the thermodynamically favorable Na{sup +} ion movement through substrate-Na{sup +} ion complex formation may be a mechanistic principle featuring transmembrane neurotransmitter-sodium symporter proteins.

  20. Ice Complex formation in arctic East Siberia during the MIS3 Interstadial

    Science.gov (United States)

    Wetterich, Sebastian; Tumskoy, Vladimir; Rudaya, Natalia; Andreev, Andrei A.; Opel, Thomas; Meyer, Hanno; Schirrmeister, Lutz; Hüls, Matthias

    2014-01-01

    A continuous 15 m long sequence of Ice Complex permafrost (Yedoma) exposed in a thermo-cirque at the southern coast of Bol'shoy Lyakhovsky Island (New Siberian Archipelago, Dmitry Laptev Strait) was studied to reconstruct past landscape and environmental dynamics. The sequence accumulated during the Marine Isotope Stage 3 (MIS3) Interstadial between >49 and 29 ka BP in an ice-wedge polygon. The frozen deposits were cryolithologically described and sampled on a vertical bluff between two ice wedges. According to sedimentological and geochronological data, the section is subdivided into three units which correlate with environmental conditions of the early, middle, and late MIS3 period. Palynological data support this stratification. The stable isotope signature of texture ice in the polygon structure reflects fractionation due to local freeze-thaw processes, while the signature of an approximately 5 m wide and more than 17 m high ice wedge fits very well into the regional stable-water isotope record. Regional climate dynamics during the MIS3 Interstadial and local landscape conditions of the polygonal patterned ground controlled the Ice Complex formation. The sequence presented here completes previously published MIS3 permafrost records in Northeast Siberia. Late Quaternary stadial-interstadial climate variability in arctic West Beringia is preserved at millennial resolution in the Ice Complex. A MIS3 climate optimum was revealed between 48 and 38 ka BP from the Ice Complex on Bol'shoy Lyakhovsky Island.

  1. EPR study of complex formation between copper (II) ions and sympathomimetic amines in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Preoteasa, E.A. [Inst. of Atomic Physics, IFIN, Bucharest (Romania); Duliu, O.G.; Grecu, V.V. [Bucharest, Univ. (Romania). Dept. of Atomic and Nuclear Physics

    1997-07-01

    The complex formation between sympathomimetic amines (SA): adrenaline (AD), noradrenaline (NA), dopamine (DA), ephedrine (ED) and p-tyramine (pTA), and Cu(II) ion in aqueous solution has been studied by X-band EPR at room temperature. Excepting pTA, all investigated SA yielded two types of complexes in different pH domains. All complexes consistent with a ligand fields having a distorted octahedral symmetry, i.e., hexacoordination of Cu(II). The covalence coefficient calculated from the isotropic g and A values has shown strong ionic sigma-type ligand bonds. A structural model with the Cu(II) ion bound by four catecholic O(hydroxy) atoms for the low pH complexes of AD, NA and DA is proposed. For the high pH complexes of the former compounds as well as for both Ed complexes, the authors suppose Cu(II) bound by two N (amino) and two O (hydroxy) atoms. The spectra are consistent to water binding on the longitudinal octahedron axis in all compounds excepting the high pH complex of Ed, where OH2- ions are bound. Possible implications for the SA-cell receptors interactions are discussed.

  2. Glycinin-gum arabic complex formation: Turbidity measurement and charge neutralization analysis.

    Science.gov (United States)

    Dong, Die; Hua, Yufei

    2016-11-01

    The interaction between glycinin and anionic polysaccharides has gained considerable attention recently because of its scientific impact on the stability of acid soymilk systems. In this study, the formation of glycinin/gum arabic complexes driven by electrostatic interactions was investigated. Turbidity titrations at different glycinin/gum arabic ratios were conducted and critical pH values (pHφ1) where insoluble complexes began forming were determined firstly. The corresponding pHφ1 values at glycinin/gum arabic ratios of 1:4, 1:2, 1:1, 2:1, 4:1 and 8:1 were 2.85, 3.25, 3.70, 4.40, 4.85 and 5.35, respectively. Afterwards, electromobilities for glycinin and gum arabic at the pH values between 4.1 and 2.6 were measured, and charge densities (ZN) for glycinin and gum arabic were calculated based on the soft particle analysis theory. Further analysis indicated that the product of glycinin/gum arabic ratio (ρ) and ZN ratio of glycinin/gum arabic was approximate 1 at any pHφ1 values. It was revealed that charge neutralization was achieved when glycinin/gum arabic insoluble complexes began forming. NaCl displayed multiple effects on glycinin/gum arabic complex formation according to turbidity and compositional analysis. The present study could provide basic guidance in acid soymilk designing. Copyright © 2016 Elsevier Ltd. All rights reserved.

  3. Thermodynamics of mixed-ligand complex formation of mercury (II) ethylenediaminetetraacetate with amino acids in solution

    Energy Technology Data Exchange (ETDEWEB)

    Pyreu, Dmitrii, E-mail: pyreu@mail.ru [Department of Inorganic and Analytic Chemistry, Ivanovo State University, Ermak 39, Ivanovo 153025 (Russian Federation); Kozlovskii, Eugenii [Department of Inorganic and Analytic Chemistry, Ivanovo State University, Ermak 39, Ivanovo 153025 (Russian Federation); Gruzdev, Matvei; Kumeev, Roman [Institute of Solution Chemistry, Ivanovo (Russian Federation)

    2012-11-20

    Highlights: Black-Right-Pointing-Pointer Stable mixed ligand complexes of HgEdta with amino acids at physiological pH value. Black-Right-Pointing-Pointer The thermodynamic and NMR data evident the ambidentate coordination mode of arginine. Black-Right-Pointing-Pointer Participation of the guanidinic group of Arg in coordination process. Black-Right-Pointing-Pointer Binuclear complexes (HgEdta){sub 2}L with the bridging function of amino acid. - Abstract: The mixed-ligand complex formation in the systems Hg{sup 2+} - Edta{sup 4-} - L{sup -}(L = Arg, Orn, Ser) has been studied by means of calorimetry, pH-potentiometry and NMR spectroscopy in aqueous solution at 298.15 K and the ionic strength of I = 0.5 (KNO{sub 3}). The thermodynamic parameters of formation of the HgEdtaL, HgEdtaHL and (HgEdta){sub 2}L complexes have been determined. The most probable coordination mode for the complexone and the amino acid in the mixed-ligand complexes was discussed.

  4. Complex formation during dissolution of metal oxides in molten alkali carbonates

    DEFF Research Database (Denmark)

    Li, Qingfeng; Borup, Flemming; Petrushina, Irina

    1999-01-01

    Dissolution of metal oxides in molten carbonates relates directly to the stability of materials for electrodes and construction of molten carbonate fuel cells. In the present work the solubilities of PbO, NiO, Fe2O3,and Bi2O3 in molten Li/K carbonates have been measured at 650 degrees C under...... carbon dioxide atmosphere. It is found that the solubilities of NiO and PbO decrease while those of Fe2O3 and Bi2O3 remain approximately constant as the lithium mole fraction increases from 0.43 to 0.62 in the melt. At a fixed composition of the melt, NiO and PbO display both acidic and basic dissolution...... as the partial pressure of carbon dioxide varies. By combination of solubility and electromotive force measurements, a model is constructed assuming the dissolution involves complex formation. The possible species for lead are proposed to be [Pb(CO3)(2)](-2) and/or [Pb(CO3)(3)](-4). A similar complex chemistry...

  5. The role of surface reactions on the active and selective catalyst design for bioethanol steam reforming

    Science.gov (United States)

    Benito, M.; Padilla, R.; Serrano-Lotina, A.; Rodríguez, L.; Brey, J. J.; Daza, L.

    In order to study the role of surface reactions involved in bioethanol steam reforming mechanism, a very active and selective catalyst for hydrogen production was analysed. The highest activity was obtained at 700 °C, temperature at which the catalyst achieved an ethanol conversion of 100% and a selectivity to hydrogen close to 70%. It also exhibited a very high hydrogen production efficiency, higher than 4.5 mol H 2 per mol of EtOH fed. The catalyst was operated at a steam to carbon ratio (S/C) of 4.8, at 700 °C and atmospheric pressure. No by-products, such as ethylene or acetaldehyde were observed. In order to consider a further application in an ethanol processor, a long-term stability test was performed under the conditions previously reported. After 750 h, the catalyst still exhibited a high stability and selectivity to hydrogen production. Based on the intermediate products detected by temperature programmed desorption and reaction (TPD and TPR) experiments, a reaction pathway was proposed. Firstly, the adsorbed ethanol is dehydrogenated to acetaldehyde producing hydrogen. Secondly, the adsorbed acetaldehyde is transformed into acetone via acetic acid formation. Finally, acetone is reformed to produce hydrogen and carbon dioxide, which were the final reaction products. The promotion of such reaction sequence is the key to develop an active, selective and stable catalyst, which is the technical barrier for hydrogen production by ethanol reforming.

  6. The role of surface reactions on the active and selective catalyst design for bioethanol steam reforming

    Energy Technology Data Exchange (ETDEWEB)

    Benito, M. [Instituto de Catalisis y Petroleoquimica (CSIC), C/Marie Curie 2, Campus Cantoblanco, 28049 Madrid (Spain); Ciemat, Av. Complutense 22, 28040 Madrid (Spain); Padilla, R.; Serrano-Lotina, A.; Rodriguez, L.; Daza, L. [Instituto de Catalisis y Petroleoquimica (CSIC), C/Marie Curie 2, Campus Cantoblanco, 28049 Madrid (Spain); Brey, J.J. [Hynergreen Technologies, Av. Buhaira 2, 41018 Sevilla (Spain)

    2009-07-01

    In order to study the role of surface reactions involved in bioethanol steam reforming mechanism, a very active and selective catalyst for hydrogen production was analysed. The highest activity was obtained at 700 C, temperature at which the catalyst achieved an ethanol conversion of 100% and a selectivity to hydrogen close to 70%. It also exhibited a very high hydrogen production efficiency, higher than 4.5 mol H{sub 2} per mol of EtOH fed. The catalyst was operated at a steam to carbon ratio (S/C) of 4.8, at 700 C and atmospheric pressure. No by-products, such as ethylene or acetaldehyde were observed. In order to consider a further application in an ethanol processor, a long-term stability test was performed under the conditions previously reported. After 750 h, the catalyst still exhibited a high stability and selectivity to hydrogen production. Based on the intermediate products detected by temperature programmed desorption and reaction (TPD and TPR) experiments, a reaction pathway was proposed. Firstly, the adsorbed ethanol is dehydrogenated to acetaldehyde producing hydrogen. Secondly, the adsorbed acetaldehyde is transformed into acetone via acetic acid formation. Finally, acetone is reformed to produce hydrogen and carbon dioxide, which were the final reaction products. The promotion of such reaction sequence is the key to develop an active, selective and stable catalyst, which is the technical barrier for hydrogen production by ethanol reforming. (author)

  7. Reaction invariant-based reduction of the activated sludge model ASM1 for batch applications

    DEFF Research Database (Denmark)

    Santa Cruz, Judith A.; Mussati, Sergio F.; Scenna, Nicolás J.

    2016-01-01

    that are unaffected by the reaction progress, i.e. so-called reaction invariants. The reaction invariant concept can be used to reduce the number of ordinary differential equations (ODEs) involved in batch bioreactor models. In this paper, a systematic methodology of model reduction based on this concept is applied...... to batch activated sludge processes described by the Activated Sludge Model No. 1 (ASM1) for carbon and nitrogen removal. The objective of the model reduction is to describe the exact dynamics of the states predicted by the original model with a lower number of ODEs. This leads to a reduction...... of the numerical complexity as nonlinear ODEs are replaced by linear algebraic relationships predicting the exact dynamics of the original model....

  8. Photocatalytic activity of layered perovskite-like oxides in practically valuable chemical reactions

    Science.gov (United States)

    Rodionov, I. A.; Zvereva, I. A.

    2016-03-01

    The photocatalytic properties of layered perovskite-like oxides corresponding to the Ruddlesen-Popper, Dion-Jacobson and Aurivillius phases are considered. Of the photocatalytic reactions, the focus is on the reactions of water splitting, hydrogen evolution from aqueous solutions of organic substances and degradation of model organic pollutants. Possibilities to conduct these reactions under UV and visible light in the presence of layered perovskite-like oxides and composite photocatalysts based on them are shown. The specific surface area, band gap energy, particle morphology, cation and anion doping and surface modification are considered as factors that affect the photocatalytic activity. Special attention is paid to the possibilities to enhance the photocatalytic activity by intercalation, ion exchange and exfoliation, which are inherent in this class of compounds. Conclusions are made about the prospects for the use of layered perovskite-like oxides in photocatalysis. The bibliography includes 253 references.

  9. Organocatalytic chemo- and regioselective oxyarylation of styrenes via a cascade reaction: remote activation of hydroxyl groups.

    Science.gov (United States)

    Zhang, Yu-Chen; Jiang, Fei; Wang, Shu-Liang; Shi, Feng; Tu, Shu-Jiang

    2014-07-01

    The first organocatalytic oxyarylation of styrenes has been established through a cascade of vinylogous Michael addition/alkoxyl transfer reactions of o- or p-hydroxylstyrenes with quinone imine ketals. The process leads to a highly chemo- and regioselective oxyarylation of styrenes and provides access to m-alkylated anilines in generally high yields and excellent diastereoselectivity (up to 99% yield, >95:5 dr). An investigation of the reaction pathway revealed that the existence and position of the hydroxyl group of styrene played crucial roles in the cascade reaction, suggesting that the two reactants were simultaneously activated by binaphthyl-derived phosphoric acid via hydrogen bonding interactions and long-distance conjugative effects. In addition, the activating group of the hydroxyl functionality in the products can be easily removed or transformed, demonstrating the applicability and utility of this strategy in styrene oxyarylation and in the synthesis of styrene-based compounds.

  10. Antibacterial Characteristics and Activity of Water-Soluble Chitosan Derivatives Prepared by the Maillard Reaction

    Directory of Open Access Journals (Sweden)

    Ying-Chien Chung

    2011-10-01

    Full Text Available The antibacterial activity of water-soluble chitosan derivatives prepared by Maillard reactions against Staphylococcus aureus, Listeria monocytogenes, Bacillus cereus, Escherichia coli, Shigella dysenteriae, and Salmonella typhimurium was examined. Relatively high antibacterial activity against various microorganisms was noted for the chitosan-glucosamine derivative as compared to the acid-soluble chitosan. In addition, it was found that the susceptibility of the test organisms to the water-soluble chitosan derivative was higher in deionized water than in saline solution. Metal ions were also found to reduce the antibacterial activity of the water-soluble chitosan derivative on S. aureus. The marked increase in glucose level, protein content and lactate dehydrogenase (LDH activity was observed in the cell supernatant of S. aureus exposed to the water-soluble chitosan derivative in deionized water. The results suggest that the water-soluble chitosan produced by Maillard reaction may be a promising commercial substitute for acid-soluble chitosan.

  11. Employing Magnetic Levitation to Monitor Reaction Kinetics and Measure Activation Energy

    Science.gov (United States)

    Benz, Lauren; Cesafsky, Karen E.; Le, Tran; Park, Aileen; Malicky, David

    2012-01-01

    This article describes a simple and inexpensive undergraduate-level kinetics experiment that uses magnetic levitation to monitor the progress and determine the activation energy of a condensation reaction on a polymeric solid support. The method employs a cuvette filled with a paramagnetic solution positioned between two strong magnets. The…

  12. Cerebral activation related to implicit sequence learning in a Double Serial Reaction Time task

    NARCIS (Netherlands)

    van der Graaf, FHCE; Maguire, RP; Leenders, KL; de Jong, BM

    2006-01-01

    Using functional magnetic resonance imaging (fMRI), we examined the distribution of cerebral activations related to implicitly learning a series of fixed stimulus-response combinations. In a novel - bimanual - variant of the Serial Reaction Time task (SRT), simultaneous finger movements of the two h

  13. Employing Magnetic Levitation to Monitor Reaction Kinetics and Measure Activation Energy

    Science.gov (United States)

    Benz, Lauren; Cesafsky, Karen E.; Le, Tran; Park, Aileen; Malicky, David

    2012-01-01

    This article describes a simple and inexpensive undergraduate-level kinetics experiment that uses magnetic levitation to monitor the progress and determine the activation energy of a condensation reaction on a polymeric solid support. The method employs a cuvette filled with a paramagnetic solution positioned between two strong magnets. The…

  14. Generalization of the Activated Complex Theory of Reaction Rates. II. Classical Mechanical Treatment

    Science.gov (United States)

    Marcus, R. A.

    1964-01-01

    In its usual classical form activated complex theory assumes a particular expression for the kinetic energy of the reacting system -- one associated with a rectilinear motion along the reaction coordinate. The derivation of the rate expression given in the present paper is based on the general kinetic energy expression.

  15. Adaptive and innate immune reactions regulating mast cell activation: from receptor-mediated signaling to responses

    DEFF Research Database (Denmark)

    Tkaczyk, Christine; Jensen, Bettina M; Iwaki, Shoko

    2006-01-01

    In this article, we have described studies that have demonstrated that mast cells can be activated as a consequence of adaptive and innate immune reactions and that these responses can be modified by ligands for other receptors expressed on the surface of mast cells. These various stimuli...

  16. Time-resolved FTIR studies provide activation free energy, activation enthalpy and activation entropy for GTPase reactions

    Science.gov (United States)

    Kötting, Carsten; Gerwert, Klaus

    2004-12-01

    GTPases, which catalyze the hydrolysis of GTP to GDP and P i, play a key role in the regulation of many biological processes. In this work, we quantify the activation parameters ΔG0∗,ΔH0∗andΔS0∗ for the hydrolysis reaction of GTP in water, in water with Mg 2+ ions and in Ras. Ras belongs to the superfamily of small GTPases (guanine nucleotide-binding proteins; GNBPs). Surprisingly, we find that in all cases, the activation energy consists mainly of enthalpic contributions. Additionally, the small entropic contributions in water and in Ras are similar, so that ΔΔ S* is close to 0. Thus the entropic contributions are only minor in GTPase catalysis and the enthalpic contributions from electrostatic interactions are key to the catalysis. The protein induced change in charge distribution of GTP can be monitored by time-resolved difference FTIR spectroscopy. For Ras the main effect due to protein binding is a charge shift towards the β-phosphate of GTP. This seems to have the main contribution to the catalytic mechanism. Because the G-domain of Ras is highly conserved in GNBPs, we propose that the finding here holds for all GNBPs.

  17. An Efficient Synthesis and Reactions of Novel Indol-ylpyridazinone Derivatives with Expected Biological Activity

    Directory of Open Access Journals (Sweden)

    Samar A. Abubshait

    2007-01-01

    Full Text Available Reaction of 4-anthracen-9-yl-4-oxo-but-2-enoic acid (1 with indole gave the corresponding butanoic acid 2. Cyclocondensation of 2 with hydrazine hydrate, phenyl hydrazine, semicarbazide and thiosemicarbazide gave the pyridazinone derivatives 3a-d. Reaction of 3a with POCl3 for 30 min gave the chloropyridazine derivative 4a, which was used to prepare the corresponding carbohydrate hydrazone derivatives 5a-d. Reaction of chloropyridazine 4a with some aliphatic or aromatic amines and anthranilic acid gave 6a-f and 7, respectively. When the reaction of the pyridazinone derivative 3a with POCl3 was carried out for 3 hr an unexpected product 4b was obtained. The structure of 4b was confirmed by its reaction with hydrazine hydrate to give hydrazopyridazine derivative 9, which reacted in turn with acetyl acetone to afford 10. Reaction of 4b with methylamine gave 11, which reacted with methyl iodide to give the trimethylammonium iodide derivative 12. The pyridazinone 3a also reacted with benzene- or 4-toluenesulphonyl chloride to give 13a-b and with aliphatic or aromatic aldehydes to give 14a-g. All proposed structures were supported by IR, 1H-NMR, 13C-NMR, and MS spectroscopic data. Some of the new products showed antibacterial activity.

  18. Prediction of insecticidal activity of Bacillus thuringiensis strains by polymerase chain reaction product profiles.

    OpenAIRE

    Carozzi, N B; Kramer, V C; Warren, G W; Evola, S; Koziel, M G

    1991-01-01

    A rapid analysis of Bacillus thuringiensis strains predictive of insecticidal activity was established by using polymerase chain reaction (PCR) technology. Primers specific to regions of high homology within genes encoding three major classes of B. thuringiensis crystal proteins were used to generate a PCR product profile characteristic of each insecticidal class. Predictions of insecticidal activity were made on the basis of the electrophoretic patterns of the PCR products. Included in the s...

  19. Platelet-neutrophil complex formation-a detailed in vitro analysis of murine and human blood samples.

    Science.gov (United States)

    Mauler, Maximilian; Seyfert, Julia; Haenel, David; Seeba, Hannah; Guenther, Janine; Stallmann, Daniela; Schoenichen, Claudia; Hilgendorf, Ingo; Bode, Christoph; Ahrens, Ingo; Duerschmied, Daniel

    2016-05-01

    Platelets form complexes with neutrophils during inflammatory processes. These aggregates migrate into affected tissues and also circulate within the organism. Several studies have evaluated platelet-neutrophil complexes as a marker of cardiovascular diseases in human and mouse. Although multiple publications have reported platelet-neutrophil complex counts, we noticed that different methods were used to analyze platelet-neutrophil complex formation, resulting in significant differences, even in baseline values. We established a protocol for platelet-neutrophil complex measurement with flow cytometry in murine and human whole blood samples. In vitro platelet-neutrophil complex formation was stimulated with ADP or PMA. We tested the effect of different sample preparation steps and cytometer settings on platelet-neutrophil complex detection and noticed false-positive counts with increasing acquisition speed. Platelet-neutrophil complex formation depends on platelet P-selectin expression, and antibody blocking of P-selectin consequently prevented ADP-induced platelet-neutrophil complex formation. These findings may help generating more comparable data among different research groups that examine platelet-neutrophil complexes as a marker for cardiovascular disease and novel therapeutic interventions.

  20. B-H bond activation using an electrophilic metal complex: insights into the reaction pathway.

    Science.gov (United States)

    Kumar, Rahul; Jagirdar, Balaji R

    2013-01-07

    A highly electrophilic ruthenium center in the [RuCl(dppe)(2)][OTf] complex brings about the activation of the B-H bond in ammonia borane (H(3)N·BH(3), AB) and dimethylamine borane (Me(2)HN·BH(3), DMAB). At room temperature, the reaction between [RuCl(dppe)(2)][OTf] and AB or DMAB results in trans-[RuH(η(2)-H(2))(dppe)(2)][OTf], trans-[RuCl(η(2)-H(2))(dppe)(2)][OTf], and trans-[RuH(Cl)(dppe)(2)], as noted in the NMR spectra. Mixing the ruthenium complex and AB or DMAB at low temperature (198/193 K) followed by NMR spectral measurements as the reaction mixture was warmed up to room temperature allowed the observation of various species formed enroute to the final products that were obtained at room temperature. On the basis of the variable-temperature multinuclear NMR spectroscopic studies of these two reactions, the mechanistic insights for B-H bond activation were obtained. In both cases, the reaction proceeds via an η(1)-B-H moiety bound to the metal center. The detailed mechanistic pathways of these two reactions as studied by NMR spectroscopy are described.

  1. Modeling and Fuzzy Logic Control of an Active Reaction Compensating Platform System

    Directory of Open Access Journals (Sweden)

    Y.J. Lin

    1995-01-01

    Full Text Available This article presents the application of the fuzzy logic (FL concept to the active control of a multiple degree of freedom reaction compensating platform system that is designed and used for isolating vibratory disturbances of space-based devices. The physical model used is a scaled down two-plate platform system. In this work, simulation is performed and presented. According to the desired performance specifications, a full range of investigation regarding the development of an FL stabilization controller for the system is conducted. Specifically, the study includes four stages: comprehensive dynamic modeling of the reaction compensating system; analysis of the dynamic responses of the platform system when it is subjected to various disturbances; design of an FL controller capable of filtering the vibratory disturbances transmitted to the bottom plate of the platform system; performance evaluation of the developed FL controller through computer simulations. To simplify the simulation work, the system model is linearized and the system component parameter variations are not considered. The performance of the FL controller is tested by exciting the system with an impulsive force applied at an arbitrarily chosen point on the top plate. It is shown that the proposed FL controller is robust in that the resultant active system is well stabilized when subjected to a random external disturbance. The comparative study of the performances of the FL controlled active reaction and passive reaction compensating systems also reveals that the FL controlled system achieves significant improvements in reducing vibratory accelerations over passive systems.

  2. Variability of single trial brain activation predicts fluctuations in reaction time.

    Science.gov (United States)

    Bender, Stephan; Banaschewski, Tobias; Roessner, Veit; Klein, Christoph; Rietschel, Marcella; Feige, Bernd; Brandeis, Daniel; Laucht, Manfred

    2015-03-01

    Brain activation stability is crucial to understanding attention lapses. EEG methods could provide excellent markers to assess neuronal response variability with respect to temporal (intertrial coherence) and spatial variability (topographic consistency) as well as variations in activation intensity (low frequency variability of single trial global field power). We calculated intertrial coherence, topographic consistency and low frequency amplitude variability during target P300 in a continuous performance test in 263 15-year-olds from a cohort with psychosocial and biological risk factors. Topographic consistency and low frequency amplitude variability predicted reaction time fluctuations (RTSD) in a linear model. Higher RTSD was only associated with higher psychosocial adversity in the presence of the homozygous 6R-10R dopamine transporter haplotype. We propose that topographic variability of single trial P300 reflects noise as well as variability in evoked cortical activation patterns. Dopaminergic neuromodulation interacted with environmental and biological risk factors to predict behavioural reaction time variability.

  3. Chemistry of phosphorus ylides 31: Reaction of azidocoumarin with active phosphonium ylides, synthesis and antitumour activities of chromenones

    Indian Academy of Sciences (India)

    Soher S Maigali; Mansoura A Abd-El-Maksoud; Fouad M Soliman

    2013-11-01

    The reaction of 4- azidochromen-2-one (1) with the nucleophilic phosphacumulene ylides 2, 8, and 12 afforded the new heterocyclic triazoles, triazepines, aziridine, pyrrolone containing a coumarin moiety. Cycloaddition reactions took place first to give triazoline 3 and 9. The triazolines rearranged to the triazepines 4, 10, and 13 accompanied by elimination of triphenylphosphine leading to the phosphorus-free triazepines 5, 11, and moreover, aziridine 6 was produced via nitrogen extrusion from the triazoline 3, followed by ring expansion to the pyrrolone 7. On the other hand, the reaction of the azidocoumarin 1 with the phosphallene yield 15 behaves differently and afforded the triazine 17 and azetone 18. The antitumour activity of compounds 3, 4, 6, and 11 was evaluated, in vitro, against (breast: MCF-7 and liver: HPEG2) human solid tumour cell lines. They showed values closed to that recorded by the reference drug doxorubicin.

  4. Search for reaction-in-flight neutrons using thulium activation at the National Ignition Facility

    Science.gov (United States)

    Grim, Gary; Rundberg, Robert; Tonchev, Anton; Fowler, Malcolm; Wilhelmy, Jerry; Archuleta, Tom; Bionta, Richard; Boswell, Mitzi; Gostic, Julie; Griego, Jeff; Knittel, Kenn; Klein, Andi; Moody, Ken; Shaughnessy, Dawn; Wilde, Carl; Yeamans, Charles

    2013-10-01

    We report on measurements of reaction-in-flight (RIF) neutrons at the National Ignition Facility. RIF neutrons are produced in cryogenically layered implision by up-scattered deuterium, or tritium ions that undergo subsequent fusion reactions. The rate of RIF neutron production is proportional to the fuel areal density (| | R) and ion-stopping length in the dense fuel assembly. Thus, RIF neutrons provide information on charge particle stopping in a strongly coupled plasma, where perturbative modeling breaks down. To measure RIF neutrons, a set of thulium activation foils was placed 50 cm from layered cryogenic implosions at the NIF. The reaction 169Tm(n,3n)167Tm has a neutron kinetic energy threshold of 14.96 MeV. We will present results from initial experiments performed during the spring of 2013. Prepared by LANL under Contract DE-AC-52-06-NA25396, TSPA, LA-UR-13-22085.

  5. Catalytic Activity of Dual Metal Cyanide Complex in Multi-component Coupling Reactions

    Institute of Scientific and Technical Information of China (English)

    Anaswara RAVINDRAN; Rajendra SRIVASTAVA

    2011-01-01

    Several dual metal cyanide catalysts were prepared from potassium ferrocyanide,metal chloride (where metal =Zn2+,Mn2+,Ni2+,Co2+ and Fe2+),t-butanol (complexing agent) and PEG-4000 (co-complexing agent).The catalysts were characterized by elemental analysis (CHN and X-ray fluorescence),X-ray diffraction,N2 adsorption-desorption,scanning electron microscopy,Fourier-transform infiared spectroscopy,and UV-Visible spectroscopy.The dual metal cyanide catalysts were used in several acid catalyzed multi-component coupling reactions for the synthesis of pharmaceutically important organic derivatives.In all these reactions,the Fe-Fe containing dual metal cyanide catalyst was the best catalyst.The catalysts can be recycled without loss in catalytic activity.The advantage of this method is the use of mild,efficient and reusable catalysts for various reactions,which makes them candidates for commercial use.

  6. Benchmarking of activation reaction distribution in an intermediate energy neutron field.

    Science.gov (United States)

    Ogawa, Tatsuhiko; Morev, Mikhail N; Hirota, Masahiro; Abe, Takuya; Koike, Yuya; Iwai, Satoshi; Iimoto, Takeshi; Kosako, Toshiso

    2011-07-01

    Neutron-induced reaction rate depth profiles inside concrete shield irradiated by intermediate energy neutron were calculated using a Monte-Carlo code and compared with an experiment. An irradiation field of intermediate neutron produced in the forward direction from a thick (stopping length) target bombarded by 400 MeV nucleon(-1) carbon ions was arranged at the heavy ion medical accelerator in Chiba. Ordinary concrete shield of 90 cm thickness was installed 50 cm downstream the iron target. Activation detectors of aluminum, gold and gold covered with cadmium were inserted at various depths. Irradiated samples were extracted after exposure and gamma-ray spectrometry was performed for each sample. Comparison of experimental and calculated shows good agreement for both low- and high-energy neutron-induced reaction except for (27)Al(n,X)(24)Na reaction at the surface.

  7. Effect of denitrifying bacteria on the electrochemical reaction of activated carbon fiber in electrochemical biofilm system

    Institute of Scientific and Technical Information of China (English)

    YING Diwen; JIA Jinping; ZHANG Lehua

    2007-01-01

    An electrochemical-activated denitrifying biofilm system consisting of activated carbon fiber electrodes immobilized with denitrifying bacteria film as cathode was studied.A revised model for an electrochemical-activated denitrifying biofilm was developed and validated by electrochemical analysis of cathodal polarization curves and nitrate consumption rate.The cathodal polarization curve and nitrate consumption rate were introduced to verify the rate of electrochemical reaction and the activity of denitrifying bacteria,respectively.It was shown that the denitrification process effectively strengthened the electrochemical reaction while the electron also intensified denitrification activity.Electron was transferred between electrochemical process and biological process not only by hydrogen molecule but also by new produced active hydrogen atom.Additionally,a parameter of apparent exchange current density was deprived from the cathodal polarization curve with high overpotential,and a new bio-effect current density was defined through statistical analysis,which was linearly dependent to the activity of denitrification bacteria.Activated carbon fiber (ACF) electrode was also found to be more suitable to the electrochemical denitrifying system compared with graphite and platinum.

  8. Experimental methods for quantifying the activity of platinum electrocatalysts for the oxygen reduction reaction.

    Science.gov (United States)

    Garsany, Yannick; Baturina, Olga A; Swider-Lyons, Karen E; Kocha, Shyam S

    2010-08-01

    A tutorial is provided for methods to accurately and reproducibly determine the activity of Pt-based electrocatalysts for the oxygen reduction reaction in proton exchange membrane fuel cells and other applications. The impact of various experimental parameters on electrocatalyst activity is demonstrated, and explicit experimental procedures and measurement protocols are given for comparison of electrocatalyst activity to fuel cell standards. (To listen to a podcast about this article, please go to the Analytical Chemistry multimedia page at pubs.acs.org/page/ancham/audio/index.html.).

  9. Effect of mechanical activation on TiC synthesis reaction in Al-Ti-C powder mixture

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    After milling in a high-energy ball miller for various times, the synthesis reaction process of the Al-Ti-C powder mixture were investigated by difference thermal analysis (DTA) and X-ray diffractometry (XRD). According to the patterns of reaction peaks on the DTA curves, the activation energy of each reaction was calculated. The experimental results of DTA show that the synthesis reaction of Al-Ti-C powder mixture can be enhanced after high-energy milling. The longer the milling time, the lower the reaction temperature. The synthesis reaction of TiC is transformed from Ti+C→TiC to Al3Ti+C→TiC+3Al with long period milling. Meanwhile, the activation energy of the reaction reduces with increasing milling time. The effect of milling time on reduced activation energy for low temperature region is more significant than that for high temperature region.

  10. Cold-induced precipitation of a monoclonal IgM: a negative activation enthalpy reaction.

    Science.gov (United States)

    Meliga, Stefano C; Farrugia, William; Ramsland, Paul A; Falconer, Robert J

    2013-01-17

    Cold-induced precipitation of a monoclonal IgM cryoglobulin isolated from a patient with Waldenström's macroglobulinemia was observed to have a negative activation enthalpy. The rate of the reaction increased, as the temperature decreased. Differential scanning calorimetry of the monoclonal IgM showed precipitation as an inverted peak during a downward temperature scan. The transition temperature was between 14 and 15 °C and was possibly concentration dependent. At temperatures below the transition the precipitation was best described by second-order kinetics. The difference in change in enthalpy between precipitation and disassociation suggests that cold-induced precipitation had a fast precipitation stage followed by a slower consolidation reaction. Negligible curvature of the Eyring plot suggested the precipitation reaction was dominated by van der Waal forces and hydrogen bonding. Conversely, during an upward temperature scan, disassociation was observed as a positive enthalpy peak. This reaction had two stages, a reaction undoing consolidation followed by heat-induced disassociation that had first-order kinetics.

  11. Force-activated reactivity switch in a bimolecular chemical reaction at the single molecule level

    Science.gov (United States)

    Szoszkiewicz, Robert; Garcia-Manyes, Sergi; Liang, Jian; Kuo, Tzu-Ling; Fernandez, Julio M.

    2010-03-01

    Mechanical force can deform the reacting molecules along a well-defined direction of the reaction coordinate. However, the effect of mechanical force on the free-energy surface that governs a chemical reaction is still largely unknown. The combination of protein engineering with single-molecule AFM force-clamp spectroscopy allows us to study the influence of mechanical force on the rate at which a protein disulfide bond is reduced by some reducing agents in a bimolecular substitution reaction (so-called SN2). We found that cleavage of a protein disulfide bond by hydroxide anions exhibits an abrupt reactivity ``switch'' at 500 pN, after which the accelerating effect of force on the rate of an SN2 chemical reaction greatly diminishes. We propose that an abrupt force-induced conformational change of the protein disulfide bond shifts its ground state, drastically changing its reactivity in SN2 chemical reactions. Our experiments directly demonstrate the action of a force-activated switch in the chemical reactivity of a single molecule. References: Sergi Garcia-Manyes, Jian Liang, Robert Szoszkiewicz, Tzu-Ling Kuo and Julio M. Fernandez, Nature Chemistry, 1, 236-242, 2009.

  12. Suppression of oxygen reduction reaction activity on Pt-based electrocatalysts from ionomer incorporation

    Energy Technology Data Exchange (ETDEWEB)

    Shinozaki, Kazuma; Morimoto, Yu; Pivovar, Bryan S.; Kocha, Shyam S.

    2016-09-01

    The impact of Nafion on the oxygen reduction reaction (ORR) activity is studied for Pt/C and Pt-alloy/C catalysts using thin-film rotating disk electrode (TF-RDE) methods in 0.1 M HClO4. Ultrathin uniform catalyst layers and standardized activity measurement protocols are employed to obtain accurate and reproducible ORR activity. Nafion lowers the ORR activity which plateaus with increasing loading on Pt catalysts. Pt particle size is found not to have significant influence on the extent of the SA decrease upon Nafion incorporation. Catalysts using high surface area carbon (HSC) support exhibit attenuated activity loss resulting from lower ionomer coverage on catalyst particles located within the deep pores. The impact of metallic composition on the activity loss due to Nafion incorporation is also discussed.

  13. Size-Dependent Electrocatalytic Activity of Free Gold Nanoparticles for the Glucose Oxidation Reaction.

    Science.gov (United States)

    Hebié, Seydou; Napporn, Teko W; Morais, Cláudia; Kokoh, K Boniface

    2016-05-18

    Understanding the fundamental relationship between the size and the structure of electrode materials is essential to design catalysts and enhance their activity. Therefore, spherical gold nanoparticles (GNSs) with a mean diameter from 4 to 15 nm were synthesized. UV/Vis spectroscopy, transmission electron microscopy, and under-potential deposition of lead (UPDPb ) were used to determine the morphology, size, and surface crystallographic structure of the GNSs. The UPDPb revealed that their crystallographic facets are affected by their size and the growth process. The catalytic properties of these GNSs toward glucose electrooxidation were studied by cyclic voltammetry, taking into account the scan rate and temperature effects. The results clearly show the size-dependent electrocatalytic activity for glucose oxidation reactions that are controlled by diffusion. Small GNSs with an average size of 4.2 nm exhibited high catalytic activity. This drastic increase in activity results from the high specific area and reactivity of the surface electrons induced by their small size. The reaction mechanism was investigated by in situ Fourier transform infrared reflectance spectroscopy. Gluconolactone and gluconate were identified as the intermediate and the final reaction product, respectively, of the glucose electrooxidation.

  14. Relationship between plasma membrane Ca2+-ATPase activity and acrosome reaction in guinea pig sperm

    Institute of Scientific and Technical Information of China (English)

    李明文; 陈大元

    1996-01-01

    The results obtained by biochemical measurement demonstrated for the first time that significant decrease of the plasma membrane Ca2+-ATPase activity occurred during capacitation and acrosome reaction of guinea pig sperm. Ethaorynic acid, one kind of Ca2+-ATPase antagonists, inhibited the plasma membrane Ca2+-ATPase activity, but calmodulin (50μg/mL) and trifluoperazine (200- 500μmol/L) did not, suggesting that calmodulin is not involved in ATP-driven Ca2+ efflux from sperm. However, calmodulin is involved in the control of Ca2+ influx. TFP, one kind of calmodulin antagonists, accelerated the acrosome reaction and Ca2+ uptake into sperm cells significantly. Ca2+-ATPase antagonists, quercetin, sodium orthovandate, furosemide and ethacrynic acid promoted the acrosome reaction, but inhibited Ca2+ uptake, which cannot be explained by their inhibitory effects on the plasma membrane Ca2+-ATPase activity. It is speculated that this phenomenon might be caused by simultaneous inhibitions of the activities of C

  15. Catalytic activity of copper (II) oxide prepared via ultrasound assisted Fenton-like reaction.

    Science.gov (United States)

    Angı, Arzu; Sanlı, Deniz; Erkey, Can; Birer, Özgür

    2014-03-01

    Copper (II) oxide nanoparticles were synthesized in an ultrasound assisted Fenton-like aqueous reaction between copper (II) cations and hydrogen peroxide. The reactions were initiated with the degradation of hydrogen peroxide by ultrasound induced cavitations at 0 °C or 5 °C and subsequent generation of the OH radical. The radical was converted into hydroxide anion in Fenton-like reactions and copper hydroxides were readily converted to oxides without the need of post annealing or aging of the samples. The products were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and Brunauer-Emmett-Teller (BET) surface area analysis. Catalytic activity of the nanoparticles for the hydrogen peroxide assisted degradation of polycyclic aromatic hydrocarbons in the dark was tested by UV-visible spectroscopy with methylene blue as the model compound. The rate of the reaction was first order, however the rate constants changed after the initial hour. Initial rate constants as high as 0.030 min(-1) were associated with the high values of surface area, i.e. 70 m(2)/g. Annealing of the products at 150 °C under vacuum resulted in the decrease of the catalytic activity, underlying the significance of the cavitation induced surface defects in the catalytic process.

  16. Nanoporous molybdenum carbide wires as an active electrocatalyst towards the oxygen reduction reaction.

    Science.gov (United States)

    Liao, Lei; Bian, Xiaojun; Xiao, Jingjing; Liu, Baohong; Scanlon, Micheál D; Girault, Hubert H

    2014-06-01

    A non-precious metal electrocatalyst has been developed for the oxygen reduction reaction based on nanoporous molybdenum carbide (nano-Mo2C) wires through a facile calcination of sub-nanometer periodic organic-inorganic hybrid nanowires. The highly dispersed Mo2C wires were composed of 10-15 nm nanocrystals with a mesopore size of 3.3 nm. The properties of nano-Mo2C wires were characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction and N2 adsorption/desorption porosimetry. The highly active surface area and enriched nanoporosity for nano-Mo2C wires are unique features that make them a high-performance electrocatalyst for oxygen reduction in an alkaline medium. The electrocatalysis and reaction kinetics results show that nano-Mo2C-based materials can be developed as new catalysts with high activity at low cost for electrochemical energy conversion applications.

  17. Biophysical assay for tethered signaling reactions reveals tether-controlled activity for the phosphatase SHP-1

    Science.gov (United States)

    Goyette, Jesse; Salas, Citlali Solis; Coker-Gordon, Nicola; Bridge, Marcus; Isaacson, Samuel A.; Allard, Jun; Dushek, Omer

    2017-01-01

    Tethered enzymatic reactions are ubiquitous in signaling networks but are poorly understood. A previously unreported mathematical analysis is established for tethered signaling reactions in surface plasmon resonance (SPR). Applying the method to the phosphatase SHP-1 interacting with a phosphorylated tether corresponding to an immune receptor cytoplasmic tail provides five biophysical/biochemical constants from a single SPR experiment: two binding rates, two catalytic rates, and a reach parameter. Tether binding increases the activity of SHP-1 by 900-fold through a binding-induced allosteric activation (20-fold) and a more significant increase in local substrate concentration (45-fold). The reach parameter indicates that this local substrate concentration is exquisitely sensitive to receptor clustering. We further show that truncation of the tether leads not only to a lower reach but also to lower binding and catalysis. This work establishes a new framework for studying tethered signaling processes and highlights the tether as a control parameter in clustered receptor signaling.

  18. The Reaction of Crotonic Anhydride with Scots and Corsican Pine: Investigation of Kinetic Profiles and Determination of Activation Energies

    OpenAIRE

    Özmen, Nilgül; ÇETİN, Nihat Sami

    2014-01-01

    The kinetics of the reaction of crotonic anhydride with Scots pine (Pinus sylvestris) and Corsican pine (Pinus nigra) using pyridine as catalyst/solvent was investigated and activation energies for the initial reaction determined. Activation energies were calculated from the Arrhenius equation using rate data obtained from time-course experiments repeated at several temperatures. In one method, reaction constants (k) were determined experimentally, while in the other method initial rates were...

  19. Implantable biodegradable sponges: effect of interpolymer complex formation of chitosan with gelatin on the release behavior of tramadol hydrochloride.

    Science.gov (United States)

    Foda, Nagwa H; El-laithy, Hanan M; Tadros, Mina I

    2007-01-01

    The effect of interpolymer complex formation between positively charged chitosan and negatively charged gelatin (Type B) on the release behavior of tramadol hydrochloride from biodegradable chitosan-gelatin sponges was studied. Mixed sponges were prepared by freeze-drying the cross-linked homogenous stable foams produced from chitosan and gelatin solutions where gelatin acts as a foam builder. Generation of stable foams was optimized where concentration, pH of gelatin solution, temperature, speed and duration of whipping process, and, chitosan-gelatin ratio drastically affect the properties and the stability of the produced foams. The prepared sponges were evaluated for their morphology, drug content, and microstructure using scanning electron microscopy, mechanical properties, uptake capacity, drug release profile, and their pharmacodynamic activity in terms of the analgesic effect after implantation in Wistar rats. It was revealed that whipping 7% (w/w) gelatin solution, of pH 5.5, for 15 min at 25 degrees C with a stirring speed of 1000 rpm was the optimum conditions for stable gelatin foam generation. Moreover, homogenous, uniform chitosan-gelatin foam with small air bubbles were produced by mixing 2.5% w/w chitosan solution with 7% w/w gelatin solution in 1:5 ratio. Indeed, polyionic complexation between chitosan and gelatin overcame the drawbacks of chitosan sponge mechanical properties where, pliable, soft, and compressible sponge with high fluid uptake capacity was produced at 25 degrees C and 65% relative humidity without any added plasticizer. Drug release studies showed a successful retardation of the incorporated drug where the t50% values of the dissolution profiles were 0.55, 3.03, and 4.73 hr for cross-linked gelatin, un-cross-linked chitosan-gelatin, and cross-linked chitosan-gelatin sponges, respectively. All the release experiments followed Higuchi's diffusion mechanism over 12 hr. The achieved drug prolongation was a result of a combined effect

  20. ASYMPTOTIC SOLUTION OF ACTIVATOR INHIBITOR SYSTEMS FOR NONLINEAR REACTION DIFFUSION EQUATIONS

    Institute of Scientific and Technical Information of China (English)

    Jiaqi MO; Wantao LIN

    2008-01-01

    A nonlinear reaction diffusion equations for activator inhibitor systems is considered. Under suitable conditions, firstly, the outer solution of the original problem is obtained, secondly, using the variables of multiple scales and the expanding theory of power series the formal asymptotic expansions of the solution are constructed, and finally, using the theory of differential inequalities the uniform validity and asymptotic behavior of the solution are studied.

  1. Quantum chemical study of Diels-Alder reactions catalyzed by Lewis acid activated oxazaborolidines.

    Science.gov (United States)

    Sakata, Ken; Fujimoto, Hiroshi

    2013-04-05

    The catalytic activity of Lewis acid activated oxazaborolidines in the Diels-Alder reaction between cyclopentadiene and methacrolein is investigated by using the DFT method. Oxazaborolidine is not able to coordinate to methacrolein in the absence of AlBr3 because the bonding stabilization is too small to cover the destabilization arising from the deformation of the two species. Accordingly, oxazaborolidine hardly catalyzes the cycloaddition by itself. The calculations show that the attachment of AlBr3 to the nitrogen atom of oxazaborolidine enhances the Lewis acidity of its boron center and enables it to coordinate to methacrolein. When the AlBr3-assisted oxazaborolidine is once coordinated, the catalytic activity originates mainly from the oxazaborolidine framework, and to a smaller extent from the attached AlBr3 part. The Lewis acid AlBr3 plays an additional role to facilitate the reaction by reducing the overlap repulsion between the diene and the dienophile. The attachment of AlBr3 to the oxygen atom, another Lewis basic site in oxazaborolidine, also gives a stable AlBr3-oxazaborolidine complex, but the reaction catalyzed by this complex is not preferred to that catalyzed by the complex in which AlBr3 is attached to the nitrogen atom. The electrophilicity of boron center in oxazaborolidine and those in the AlBr3-oxazaborolidine complexes are compared in terms of localized reactive orbitals.

  2. Nanoporous and highly active silicon carbide supported CeO₂-catalysts for the methane oxidation reaction.

    Science.gov (United States)

    Hoffmann, Claudia; Biemelt, Tim; Lohe, Martin R; Rümmeli, Mark H; Kaskel, Stefan

    2014-01-29

    CeOx @SiO2 nanoparticles are used for the first time for the generation of porous SiC materials with tailored pore diameter in the mesopore range containing encapsulated and catalytically active CeO2 nanoparticles. The nanocasting approach with a preceramic polymer and subsequent pyrolysis is performed at 1300 °C, selective leaching of the siliceous part results in CeOx /SiC catalysts with remarkable characteristics like monodisperse, spherical pores and specific surface areas of up to 438 m(2) ·g(-1) . Porous SiC materials are promising supports for high temperature applications. The catalysts show excellent activities in the oxidation of methane with onset temperatures of the reaction 270 K below the onset of the homogeneous reaction. The synthesis scheme using core-shell particles is suited to functionalize silicon carbide with a high degree of stabilization of the active nanoparticles against sintering in the core of the template even at pyrolysis temperatures of 1300 °C rendering the novel synthesis principle as an attractive approach for a wide range of catalytic reactions.

  3. Direct monitoring of the strand passage reaction of DNA topoisomerase II triggers checkpoint activation.

    Directory of Open Access Journals (Sweden)

    Katherine L Furniss

    Full Text Available By necessity, the ancient activity of type II topoisomerases co-evolved with the double-helical structure of DNA, at least in organisms with circular genomes. In humans, the strand passage reaction of DNA topoisomerase II (Topo II is the target of several major classes of cancer drugs which both poison Topo II and activate cell cycle checkpoint controls. It is important to know the cellular effects of molecules that target Topo II, but the mechanisms of checkpoint activation that respond to Topo II dysfunction are not well understood. Here, we provide evidence that a checkpoint mechanism monitors the strand passage reaction of Topo II. In contrast, cells do not become checkpoint arrested in the presence of the aberrant DNA topologies, such as hyper-catenation, that arise in the absence of Topo II activity. An overall reduction in Topo II activity (i.e. slow strand passage cycles does not activate the checkpoint, but specific defects in the T-segment transit step of the strand passage reaction do induce a cell cycle delay. Furthermore, the cell cycle delay depends on the divergent and catalytically inert C-terminal region of Topo II, indicating that transmission of a checkpoint signal may occur via the C-terminus. Other, well characterized, mitotic checkpoints detect DNA lesions or monitor unattached kinetochores; these defects arise via failures in a variety of cell processes. In contrast, we have described the first example of a distinct category of checkpoint mechanism that monitors the catalytic cycle of a single specific enzyme in order to determine when chromosome segregation can proceed faithfully.

  4. Energy-Related Small Molecule Activation Reactions: Oxygen Reduction and Hydrogen and Oxygen Evolution Reactions Catalyzed by Porphyrin- and Corrole-Based Systems.

    Science.gov (United States)

    Zhang, Wei; Lai, Wenzhen; Cao, Rui

    2017-02-22

    Globally increasing energy demands and environmental concerns related to the use of fossil fuels have stimulated extensive research to identify new energy systems and economies that are sustainable, clean, low cost, and environmentally benign. Hydrogen generation from solar-driven water splitting is a promising strategy to store solar energy in chemical bonds. The subsequent combustion of hydrogen in fuel cells produces electric energy, and the only exhaust is water. These two reactions compose an ideal process to provide clean and sustainable energy. In such a process, a hydrogen evolution reaction (HER), an oxygen evolution reaction (OER) during water splitting, and an oxygen reduction reaction (ORR) as a fuel cell cathodic reaction are key steps that affect the efficiency of the overall energy conversion. Catalysts play key roles in this process by improving the kinetics of these reactions. Porphyrin-based and corrole-based systems are versatile and can efficiently catalyze the ORR, OER, and HER. Because of the significance of energy-related small molecule activation, this review covers recent progress in hydrogen evolution, oxygen evolution, and oxygen reduction reactions catalyzed by porphyrins and corroles.

  5. Proline catalyzed α-aminoxylation reaction in the synthesis of biologically active compounds.

    Science.gov (United States)

    Kumar, Pradeep; Dwivedi, Namrata

    2013-02-19

    The search for new and efficient ways to synthesize optically pure compounds is an active area of research in organic synthesis. Asymmetric catalysis provides a practical, cost-effective, and efficient method to create a variety of complex natural products containing multiple stereocenters. In recent years, chemists have become more interested in using small organic molecules to catalyze organic reactions. As a result, organocatalysis has emerged both as a promising strategy and as an alternative to catalysis with expensive proteins or toxic metals. One of the most successful and widely studied secondary amine-based organocatalysts is proline. This small molecule can catalyze numerous reactions such as the aldol, Mannich, Michael addition, Robinson annulation, Diels-Alder, α-functionalization, α-amination, and α-aminoxylation reactions. Catalytic and enantioselective α-oxygenation of carbonyl compounds is an important reaction to access a variety of useful building blocks for bioactive molecules. Proline catalyzed α-aminoxylation using nitrosobenzene as oxygen source, followed by in situ reduction, gives enantiomerically pure 1,2-diol. This molecule can then undergo a variety of organic reactions. In addition, proline organocatalysis provides access to an assortment of biologically active natural products including mevinoline (a cholesterol lowering drug), tetrahydrolipstatin (an antiobesity drug), R(+)-α-lipoic acid, and bovidic acid. In this Account, we present an iterative organocatalytic approach to synthesize both syn- and anti-1,3-polyols, both enantio- and stereoselectively. This method is primarily based on proline-catalyzed sequential α-aminoxylation and Horner-Wadsworth-Emmons (HWE) olefination of aldehyde to give a γ-hydroxy ester. In addition, we briefly illustrate the broad application of our recently developed strategy for 1,3-polyols, which serve as valuable, enantiopure building blocks for polyketides and other structurally diverse and

  6. Complex formation between primycin and ergosterol: entropy-driven initiation of modification of the fungal plasma membrane structure.

    Science.gov (United States)

    Virág, Eszter; Pesti, Miklós; Kunsági-Máté, Sándor

    2012-04-01

    The interaction of the antibiotic primycin with the main fungal sterol, ergosterol, was investigated in vitro in order to monitor the effect of primycin on the fungal plasma membrane at the molecular level. The thermodynamic parameters of complex formation were determined by measuring Rayleigh scattering as a signal sensitive to particle size. The Benesi-Hildebrand method validated the 1 : 1 stoichiometry of the primycin-ergosterol complexes. A very low enthalpy change (ΔH=-1.14 kJ mol(-1)) was measured during the complex formation, which itself cannot be responsible for the molecular association. However, the entropy production (ΔS=29.78 J mol K(-1)) observed during the complex formation can describe the molecular interaction. This effect is probably due to the partial destruction of the solvation shell of the interacting species before the interlinking of the molecules. The results highlight the importance of ergosterol as concerns the mode of effect of primycin in the treatment of fungal infections. As the entropy has a determinant role in the ergosterol-primycin interaction, this interaction exhibits a very high temperature dependence, with the important consequence that the effect exerted by primycin on the cell membranes increases with rising temperature, and the effect is therefore pronounced in fevered bodies.

  7. Enzyme Stability and Activity in Non-Aqueous Reaction Systems: A Mini Review

    Directory of Open Access Journals (Sweden)

    Shihui Wang

    2016-02-01

    Full Text Available Enormous interest in biocatalysis in non-aqueous phase has recently been triggered due to the merits of good enantioselectivity, reverse thermodynamic equilibrium, and no water-dependent side reactions. It has been demonstrated that enzyme has high activity and stability in non-aqueous media, and the variation of enzyme activity is attributed to its conformational modifications. This review comprehensively addresses the stability and activity of the intact enzymes in various non-aqueous systems, such as organic solvents, ionic liquids, sub-/super-critical fluids and their combined mixtures. It has been revealed that critical factors such as Log P, functional groups and the molecular structures of the solvents define the microenvironment surrounding the enzyme molecule and affect enzyme tertiary and secondary structure, influencing enzyme catalytic properties. Therefore, it is of high importance for biocatalysis in non-aqueous media to elucidate the links between the microenvironment surrounding enzyme surface and its stability and activity. In fact, a better understanding of the correlation between different non-aqueous environments and enzyme structure, stability and activity can contribute to identifying the most suitable reaction medium for a given biotransformation.

  8. Study of Activation and Inhibition of Certain Metal Ions to Amylase Catalyzed Reaction by Microcalorimetry

    Institute of Scientific and Technical Information of China (English)

    张洪林; 于秀芳; 聂毅; 刘晓静; 张刚

    2003-01-01

    With or without activation or inhibition of metal ion, the power-time curves of amylase catalyzed reaction were determined by a 2277 thermal activity monitor (Sweden). The Michaelis constant ( K ), apparent Michaelis constant ( Km ), maximum velocity (vm) and apparent maximum velocity ( vam) of amylase catalyzed reaction were obtained using thermokinetic theory and reduced extent method. On the basis of data obtained, the following relationships between Km and concentration of metal ion (c) were established:for inhibitor of Ni2+ Km= 2.9648 × 10-3 - 1.3912 × 10-4c R = 0.9998 for inhibitor of Co2+ Km = 1.0227 × 10-3 + 8.2676 × 10-6c R = 0.9955 for activator of Ca2+ Km= 1.0630 × 10-7c2 - 1.8311 × 10-6c + 9.3058 × 10-6 R = 0.9999 for activator of Li+ Km= 5.6300 × 10-8c2 - 1.5329 × 10-6c + 1.2662 × 10-5 R =0.9999 The Km-c relationships show a strenuous inhibitory effect for Ni2+ and a strenuous active effect for Ca2+ .

  9. Control of Transcriptional Fidelity by Active Center Tuning as Derived from RNA Polymerase Endonuclease Reaction*

    Science.gov (United States)

    Sosunova, Ekaterina; Sosunov, Vasily; Epshtein, Vitaly; Nikiforov, Vadim; Mustaev, Arkady

    2013-01-01

    Precise transcription by cellular RNA polymerase requires the efficient removal of noncognate nucleotide residues that are occasionally incorporated. Mis-incorporation causes the transcription elongation complex to backtrack, releasing a single strand 3′-RNA segment bearing a noncognate residue, which is hydrolyzed by the active center that carries two Mg2+ ions. However, in most x-ray structures only one Mg2+ is present. This Mg2+ is tightly bound to the active center aspartates, creating an inactive stable state. The first residue of the single strand RNA segment in the backtracked transcription elongation complex strongly promotes transcript hydrolytic cleavage by establishing a network of interactions that force a shift of stably bound Mg2+ to release some of its aspartate coordination valences for binding to the second Mg2+ thus enabling catalysis. Such a rearrangement that we call active center tuning (ACT) occurs when all recognition contacts of the active center-bound RNA segment are established and verified by tolerance to stress. Transcription factor Gre builds on the ACT mechanism in the same reaction by increasing the retention of the second Mg2+ and by activating the attacking water, causing 3000–4000-fold reaction acceleration and strongly reinforcing proofreading. The unified mechanism for RNA synthesis and degradation by RNA polymerase predicts that ACT also executes NTP selection thereby contributing to high transcription fidelity. PMID:23283976

  10. Zn2+-stimulation of sperm capacitation and of the acrosome reaction is mediated by EGFR activation.

    Science.gov (United States)

    Michailov, Yulia; Ickowicz, Debbi; Breitbart, Haim

    2014-12-15

    Extracellular zinc regulates cell proliferation via the MAP1 kinase pathway in several cell types, and has been shown to act as a signaling molecule. The testis contains a relatively high concentration of Zn(2+), required in both the early and late stages of spermatogenesis. Despite the clinical significance of this ion, its role in mature sperm cells is poorly understood. In this study, we characterized the role of Zn(2+) in sperm capacitation and in the acrosome reaction. Western blot analysis revealed the presence of ZnR of the GPR39 type in sperm cells. We previously demonstrated the presence of active epidermal growth factor receptor (EGFR) in sperm, its possible transactivation by direct activation of G-protein coupled receptor (GPCR), and its involvement in sperm capacitation and in the acrosome reaction (AR). We show here that Zn(2+) activates the EGFR during sperm capacitation, which is mediated by activation of trans-membrane adenylyl cyclase (tmAC), protein kinase A (PKA), and the tyrosine kinase, Src. Moreover, the addition of Zn(2+) to capacitated sperm caused further stimulation of EGFR and phosphatydil-inositol-3-kinase (PI3K) phosphorylation, leading to the AR. The stimulation of the AR by Zn(2+) also occurred in the absence of Ca(2+) in the incubation medium, and required the tmAC, indicating that Zn(2+) activates a GPCR. The AR stimulated by Zn(2+) is mediated by GPR39 receptor, PKA, Src and the EGFR, as well as the EGFR down-stream effectors PI3K, phospholipase C (PLC) and protein kinase C (PKC). These data support a role for extracellular zinc, acting through the ZnR, in regulating multiple signaling pathways in sperm capacitation and the acrosome reaction.

  11. High Intrinsic Catalytic Activity of Two-Dimensional Boron Monolayers for Hydrogen Evolution Reaction

    CERN Document Server

    Shi, Li; Ouyang, Yixin; Wang, Jinlan

    2016-01-01

    Two-dimensional (2D) boron monolayers have been successfully synthesized on silver substrate very recently. Their potential application is thus of great significance. In this work, we explore the possibility of boron monolayers (BMs) as electrocatalysts for hydrogen evolution reaction (HER) by first-principle method. Our calculations show that the BMs are active catalysts for HER with nearly zero free energy of hydrogen adsorption, metallic conductivity and plenty of active sites in the basal plane. The effect of the substrate on the HER activity is further assessed. It is found that the substrate has a positive effect on the HER performance caused by the competitive effect of mismatch strain and charge transfer. The indepth understanding of the structure dependent HER activity is also provided.

  12. Autophosphorylation is crucial for CDK-activating kinase (Ee;CDKF;1) activity and complex formation in leafy spurge

    Science.gov (United States)

    Ee;CDKF;1 protein is involved in a phosphorylation cascade linked to early stages of cell cycle progression. Yeast two-hybrid screening performed using Ee;CDKF;1 as a bait indicated that one of the interacting proteins was Ee;CDKF;1. Protein-protein interaction of Ee;CDKF;1 was further confirmed by ...

  13. Assessment of the apparent activation energies for gas/solid reactions-carbonate decomposition

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The guidelines for assessing the apparent activation energies of gas/solid reactions have been proposed based on the ex-perimental results from literatures. In CO2 free inlet gas flow, CaCO3 decomposition between 950 and 1250 K with thin sample layercould be controlled by the interfacial chemical reaction with apparent activation energy E = (215+10) kJ/mol and E = (200±10)kJ/mol at T = 813 to 1020 K, respectively. With relatively thick sample layer between 793 and 1273 K, the CaCO3 decompositioncould be controlled by one or more steps involving self-cooling, nucleation, intrinsic diffusion and heat transfer of gases, and E couldvary between 147 andl90 kJ/mol. In CO2 containing inlet gas flow (5%-100% of CO2), E was determined to be varied from 949 to2897 kJ/mol. For SrCO3 and BaCO3 decompositions controlled by the interfacial chemical reaction, E was (213+15) kJ/mol (1000-1350 K) and (305+15) kJ/mol (1260-1400 K), respectively.

  14. Elucidation of inorganic reaction mechanisms in ionic liquids: the important role of solvent donor and acceptor properties.

    Science.gov (United States)

    Schmeisser, Matthias; van Eldik, Rudi

    2014-11-14

    In this article, we focus on the important role of solvent donor and acceptor properties of ionic liquids in the elucidation of inorganic reaction mechanisms. For this purpose, mechanistic and structural studies on typical inorganic reactions, performed in ionic liquids, have been conducted. The presented systems range from simple complex-formation and ligand-substitution reactions to the activation of small molecules by catalytically active complexes. The data obtained for the reactions in ionic liquids are compared with those for the same reactions carried out in conventional solvents, and are discussed with respect to the donor and acceptor properties of the applied ionic liquids. The intention of this perspective is to gain more insight into the role of ILs as solvents and their interaction with metal ions and complexes in solution.

  15. Origins of the Unfavorable Activation and Reaction Energies of 1-Azadiene Heterocycles Compared to 2-Azadiene Heterocycles in Diels-Alder Reactions.

    Science.gov (United States)

    Fell, Jason S; Martin, Blanton N; Houk, K N

    2017-02-17

    The reactivities of butadiene, cyclopentadiene, furan, thiophene, pyrrole, and their 1-aza- and 2-aza-derivatives in Diels-Alder reactions with ethylene and fumaronitrile were investigated with density functional theory (M06-2X/6-311G(d,p)). The activation free energies for the Diels-Alder reactions of cyclic 1-azadienes are 10-14 kcal mol(-1) higher than those of cyclic 2-azadienes, and the reaction free energies are 17-20 kcal mol(-1) more endergonic. The distortion/interaction model shows that the increased activation energies of cyclic 1-azadienes originate from increased transition state distortion energies and unfavorable interaction energies, arising from addition to the nitrogen terminus of the C═N bond.

  16. Measurement of the ^241Am(n,2n) Reaction Cross Section with the Activation Technique

    Science.gov (United States)

    Tonchev, A.; Crowell, A.; Fallin, B.; Howell, C.; Hutcheson, A.; Tornow, W.; Kelley, J.; Angell, C.; Karwowski, H.; Pedroni, R.; Becker, J.; Dashdorj, D.; Macri, R.; Wilhelmy, J.; Bond, E.; Fitzpatrick, J.; Slemmons, A.; Vieira, D.

    2006-10-01

    High-precision measurements of the ^241Am(n,2n)^240Am reaction have been performed with neutron energies from 8.8 to 14.0 MeV. The monoenergetic neutron beams were produced via the ^2H(d,n)^3He reaction using the 10 MV Tandem accelerator at TUNL. The radioactive targets consisted of 1mg highly-enriched ^241Am sandwiched between four different thin monitor foils. They were irradiated with a neutron flux of 3x10^7 n cm-2 s-1. After each irradiation the induced activity in the targets and monitors was measured off-line with 60% HPGe detectors. Our preliminary neutron induced cross sections will be compared with recent literature results and statistical model calculations using the GNASH and EMPIRE codes.

  17. Activation cross sections of proton induced nuclear reactions on palladium up to 80 MeV

    CERN Document Server

    Tárkányi, F; Takács, S; Csikai, J; Hermanne, A; Uddin, S; Baba, M

    2016-01-01

    Activation cross sections of proton induced nuclear reactions on palladium were measured up to 80 MeV by using the stacked foil irradiation technique and gamma ray spectrometry. The beam intensity, the incident energy and the energy degradation were controlled by a method based on flux constancy via normalization to the excitation functions of monitor reactions measured in parallel. Excitation functions for direct and cumulative cross-sections were measured for the production of ${}^{104m,104g,105}$${}^{g,106m,110m}$Ag, ${}^{100,101}$Pd, ${}^{99m,99g,100,}$${}^{101m}$${}^{,101g,102m,102g,105}$Rh and ${}^{103,}$${}^{97}$Ru radioisotopes. The cross section data were compared with the theoretical predictions of TENDL-2014 and -2015 libraries. For practical applications thick target yields were derived from the measured excitation functions. Application in the field of medical radionuclide production is shortly discussed.

  18. Tunable catalytic activity of solid solution metal-organic frameworks in one-pot multicomponent reactions.

    Science.gov (United States)

    Aguirre-Díaz, Lina María; Gándara, Felipe; Iglesias, Marta; Snejko, Natalia; Gutiérrez-Puebla, Enrique; Monge, M Ángeles

    2015-05-20

    The aim of this research is to establish how metal-organic frameworks (MOFs) composed of more than one metal in equivalent crystallographic sites (solid solution MOFs) exhibit catalytic activity, which is tunable by virtue of the metal ions ratio. New MOFs with general formula [InxGa1-x(O2C2H4)0.5(hfipbb)] were prepared by the combination of Ga and In. They are isostructural with their monometal counterparts, synthesized with Al, Ga, and In. Differences in their behavior as heterogeneous catalysts in the three-component, one pot Strecker reaction illustrate the potential of solid solution MOFs to provide the ability to address the various stages involved in the reaction mechanism.

  19. Metal diselenide nanoparticles as highly active and stable electrocatalysts for the hydrogen evolution reaction

    Science.gov (United States)

    Liang, Jia; Yang, Yingchao; Zhang, Jing; Wu, Jingjie; Dong, Pei; Yuan, Jiangtan; Zhang, Gengmin; Lou, Jun

    2015-09-01

    In this communication, nickel diselenide (NiSe2) nanoparticles are synthesized by a facile and low-cost hydrothermal method. The synthesis method can be extended to other metal diselenides as well. The electrode made of NiSe2 exhibits superior electrocatalytic activity in the hydrogen evolution reaction (HER). A low Tafel slope of 31.1 mV per decade is achieved for NiSe2, which is comparable to that of platinum (~30 mV per decade). Moreover, the catalytic activity of NiSe2 is very stable and no obvious degradation is found even after 1000 cyclic voltammetric sweeps.In this communication, nickel diselenide (NiSe2) nanoparticles are synthesized by a facile and low-cost hydrothermal method. The synthesis method can be extended to other metal diselenides as well. The electrode made of NiSe2 exhibits superior electrocatalytic activity in the hydrogen evolution reaction (HER). A low Tafel slope of 31.1 mV per decade is achieved for NiSe2, which is comparable to that of platinum (~30 mV per decade). Moreover, the catalytic activity of NiSe2 is very stable and no obvious degradation is found even after 1000 cyclic voltammetric sweeps. Electronic supplementary information (ESI) available: Experimental section, additional figures and tables. See DOI: 10.1039/c5nr03724g

  20. Catalytic activity of pyrite for coal liquefaction reaction; Tennen pyrite no shokubai seino ni kansuru kento

    Energy Technology Data Exchange (ETDEWEB)

    Hirano, K.; Kozu, M.; Okada, T.; Kobayashi, M. [Nippon Coal Oil Co. Ltd., Tokyo (Japan)

    1996-10-28

    Since natural pyrite is easy to obtain and cheap as coal liquefaction catalyst, it is to be used for the 150 t/d scale NEDOL process bituminous coal liquefaction pilot plant. NEDO and NCOL have investigated the improvement of catalytic activity of pulverized natural pyrite for enhancing performance and economy of the NEDOL process. In this study, coal liquefaction tests were conducted using natural pyrite catalyst pulverized by dry-type bowl mill under nitrogen atmosphere. Mechanism of catalytic reaction of the natural pyrite was discussed from relations between properties of the catalyst and liquefaction product. The natural pyrite provided an activity to transfer gaseous hydrogen into the liquefaction product. It was considered that pulverized pyrite promotes the hydrogenation reaction of asphaltene because pulverization increases its contact rate with reactant and the amount of active points on its surface. It was inferred that catalytic activity of pyrite is affected greatly by the chemical state of Fe and S on its surface. 3 refs., 4 figs., 1 tab.

  1. Impact of active phase chemical composition and dispersity on catalytic behavior in PROX reaction

    Science.gov (United States)

    Cherkezova-Zheleva, Z.; Paneva, D.; Todorova, S.; Kolev, H.; Shopska, M.; Yordanova, I.; Mitov, I.

    2014-04-01

    Iron and iron-platinum catalysts supported on activated carbon have been successfully synthesized by wet impregnation method and low-temperature treatment in inert atmosphere. The content of the supported phases corresponds to 10 wt % Fe and 0.5 wt % Pt. Four catalytic samples were synthesized: Sample A—activated carbon impregnated with Fe nitrate; Sample B—activated carbon impregnated with Pt salt; Sample C—activated carbon impregnated consequently with Fe and Pt salts; Sample D—activated carbon impregnated simultaneously with Fe and Pt salts. The as-prepared materials were characterized by Mössbauer spectroscopy, X-ray diffraction, infrared and X-ray photoelectron spectroscopy. The spectra show that the activated carbon support and the preparation procedure give rise to the synthesis of isolated metal Pt ions and ultradispersed Fe and Pt oxide species. Probably the presence of different functional groups of activated carbon gives rise to registered very high dispersion of loaded species on support. The catalytic tests were carried out in PROX reaction. A lower activity of bimetallic Pt-Fe samples was explained with the increase in surface oxygen species as a result of predomination of iron oxide on the support leading to the increase in selectivity to the H2 oxidation. Partial agglomeration of supported iron oxide phase was registered after catalytic tests.

  2. Moessbauer study of peroxynitrito complex formation with Fe{sup III}-chelates

    Energy Technology Data Exchange (ETDEWEB)

    Homonnay, Zoltan, E-mail: homonnay@ludens.elte.hu; Buszlai, Peter; Nador, Judit [Eoetvoes University, Institute of Chemistry (Hungary); Sharma, Virender K. [Florida Institute of Technology (United States); Kuzmann, Erno; Vertes, Attila [Eoetvoes University, Institute of Chemistry (Hungary)

    2012-03-15

    The reaction of the {mu}-oxo-diiron(III)-L complex (L = EDTA, ethylene diamine tetraacetate, HEDTA, hydroxyethyl ethylene diamine triacetate, and CyDTA, cyclohexane diamine tetraacetate) with peroxynitrite in alkaline solution was studied by Moessbauer spectroscopy using rapid-freezing technique. These complexes yield an (L)Fe{sup III}({eta}{sup 2}-O{sub 2}){sup 3-} complex ion when they react with hydrogen peroxide and the formation of the peroxide adduct results in a deep purple coloration of the solution. The same color appears when the reaction occurs with peroxinitrite. Although spectrophotometry indicated some difference between the molar extinction coefficients of the peroxo and the peroxinitrito adducts, the Moessbauer parameters proved to be the same within experimental error. It is concluded that the peroxynitrite ion decomposes when reacting with Fe{sup III}(L) and the peroxo adduct forms.

  3. Temperature dependence of bromine activation due to reaction with ozone in a proxy for organic aerosols

    Science.gov (United States)

    Edebeli, Jacinta; Ammann, Markus; Gilgen, Anina; Eichler, Anja; Schneebeli, Martin; Bartels-Rausch, Thorsten

    2016-04-01

    The discovery of boundary layer ozone depletion events in the Polar Regions [1] and in the mid-latitudes [2], two areas of very different temperature regimes, begs the question of temperature dependence of reactions responsible for these observations [3]. These ODEs have been attributed to ozone reacting with halides leading to reactive halogens (halogen activation) of which bromide is extensively studied, R1 - R3 [4, 5] (R1 is a multiphase reaction). O3 + Br-→ O2 + OBr- (R1) OBr- + H+ ↔ HOBr (R2) HOBr + H+ + Br-→ Br2 + H2O (R3) Despite extensive studies of ozone-bromide interactions, the temperature dependence of bromine activation is not clear [3]. This limits parameterization of the involved reactions and factors in atmospheric models [3, 6]. Viscosity changes in the matrix (such as organic aerosols) due to temperature have been shown to influence heterogeneous reaction rates and products beyond pure temperature effect [7]. With the application of coated wall flow-tubes, the aim of this study is therefore to investigate the temperature dependence of bromine activation by ozone interaction while attempting to characterize the contributions of the bulk and surface reactions to observed ozone uptake. Citric acid is used in this study as a hygroscopically characterized matrix whose viscosity changes with temperature and humidity. Here, we present reactive ozone uptake measured between 258 and 289 K. The data show high reproducibility. Comparison of measured uptake with modelled bulk uptake at different matrix compositions (and viscosities) indicate that bulk reactive uptake dominates, but there are other factors which still need further consideration in the model. References 1. Barrie, L.A., et al., Nature, 1988. 334: p. 138 - 141. 2. Hebestreit, K., et al., Science, 1999. 283: p. 55-57. 3. Simpson, W.R., et al., Atmospheric Chemistry and Physics, 2007. 7: p. 4375 - 4418. 4. Haag, R.W. and J. Hoigné, Environ Sci Technol, 1983. 17: p. 261-267. 5. Oum, K.W., et

  4. Ru complexes of Hoveyda-Grubbs type immobilized on lamellar zeolites: activity in olefin metathesis reactions.

    Science.gov (United States)

    Balcar, Hynek; Žilková, Naděžda; Kubů, Martin; Mazur, Michal; Bastl, Zdeněk; Čejka, Jiří

    2015-01-01

    Hoveyda-Grubbs type catalysts with cationic tags on NHC ligands were linker-free immobilized on the surface of lamellar zeolitic supports (MCM-22, MCM-56, MCM-36) and on mesoporous molecular sieves SBA-15. The activity of prepared hybrid catalysts was tested in olefin metathesis reactions: the activity in ring-closing metathesis of citronellene and N,N-diallyltrifluoroacetamide decreased in the order of support MCM-22 ≈ MCM-56 > SBA-15 > MCM-36; the hybrid catalyst based on SBA-15 was found the most active in self-metathesis of methyl oleate. All catalysts were reusable and exhibited low Ru leaching (<1% of Ru content). XPS analysis revealed that during immobilization ion exchange between Hoveyda-Grubbs type catalyst and zeolitic support occurred in the case of Cl(-) counter anion; in contrast, PF6 (-) counter anion underwent partial decomposition.

  5. Ru complexes of Hoveyda–Grubbs type immobilized on lamellar zeolites: activity in olefin metathesis reactions

    Science.gov (United States)

    Žilková, Naděžda; Kubů, Martin; Mazur, Michal; Bastl, Zdeněk; Čejka, Jiří

    2015-01-01

    Summary Hoveyda–Grubbs type catalysts with cationic tags on NHC ligands were linker-free immobilized on the surface of lamellar zeolitic supports (MCM-22, MCM-56, MCM-36) and on mesoporous molecular sieves SBA-15. The activity of prepared hybrid catalysts was tested in olefin metathesis reactions: the activity in ring-closing metathesis of citronellene and N,N-diallyltrifluoroacetamide decreased in the order of support MCM-22 ≈ MCM-56 > SBA-15 > MCM-36; the hybrid catalyst based on SBA-15 was found the most active in self-metathesis of methyl oleate. All catalysts were reusable and exhibited low Ru leaching (<1% of Ru content). XPS analysis revealed that during immobilization ion exchange between Hoveyda–Grubbs type catalyst and zeolitic support occurred in the case of Cl− counter anion; in contrast, PF6 − counter anion underwent partial decomposition. PMID:26664629

  6. Ru complexes of Hoveyda–Grubbs type immobilized on lamellar zeolites: activity in olefin metathesis reactions

    Directory of Open Access Journals (Sweden)

    Hynek Balcar

    2015-11-01

    Full Text Available Hoveyda–Grubbs type catalysts with cationic tags on NHC ligands were linker-free immobilized on the surface of lamellar zeolitic supports (MCM-22, MCM-56, MCM-36 and on mesoporous molecular sieves SBA-15. The activity of prepared hybrid catalysts was tested in olefin metathesis reactions: the activity in ring-closing metathesis of citronellene and N,N-diallyltrifluoroacetamide decreased in the order of support MCM-22 ≈ MCM-56 > SBA-15 > MCM-36; the hybrid catalyst based on SBA-15 was found the most active in self-metathesis of methyl oleate. All catalysts were reusable and exhibited low Ru leaching (− counter anion; in contrast, PF6− counter anion underwent partial decomposition.

  7. Study of activity and effectiveness factor of noble metal catalysts for water-gas shift reaction

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Sungkwang; Bae, Joongmyeon [Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 373-1, Guseong-Dong, Yuseong-Gu, Daejeon 305-701 (Korea); Kim, Kihyun [POSCO 1, Goedong-dong, Nam-gu, Pohang, Gyeongbuk 790-785 (Korea)

    2009-01-15

    Platinum on ceria-zirconia (CZO) catalysts for the water-gas shift (WGS) reaction were prepared with various platinum loadings. In addition, the activity of Pt/CZO catalysts was tested preliminarily at gas hourly space velocity (GHSV) of 5000 h{sup -1}. Activity tests were also conducted at GHSV of 200,000 h{sup -1} with limited conversions, and activation energies and pre-exponential factors for rate equations were obtained by fitting the data. The effectiveness factors were estimated on the basis of the intra-particle mass transfer. Moreover, with this estimation, an attempt was made to calculate the utilization of the Pt loading with an eggshell morphology. (author)

  8. Detection of specific polymerase chain reaction product by utilizing the 5'----3' exonuclease activity of Thermus aquaticus DNA polymerase.

    OpenAIRE

    1991-01-01

    The 5'----3' exonuclease activity of the thermostable enzyme Thermus aquaticus DNA polymerase may be employed in a polymerase chain reaction product detection system to generate a specific detectable signal concomitantly with amplification. An oligonucleotide probe, nonextendable at the 3' end, labeled at the 5' end, and designed to hybridize within the target sequence, is introduced into the polymerase chain reaction assay. Annealing of probe to one of the polymerase chain reaction product s...

  9. Acid activated montmorillonite as catalysts in methyl esterification reactions of lauric acid.

    Science.gov (United States)

    Zatta, Leandro; Ramos, Luiz Pereira; Wypych, Fernando

    2012-01-01

    The catalytic activity of acid activated montmorillonite in the esterification of free fatty acids (FFA) is reported. Standard Montmorillonite (MMT) type STx-1 provided by the Clay Mineral Society repository was activated using phosphoric, nitric and sulphuric acids under different conditions and the resulting materials were characterized and evaluated as catalysts in the methyl esterification of lauric acid. Blank reactions carried out in the absence of any added catalyst presented conversions of 32.64, 69.79 and 79.23%, for alcohol:lauric acid molar ratios of 60:1, 12:1 and 6:1, respectively. In the presence of the untreated clay and using molar ratios of 12:1 and 6:1 with 12% of catalyst, conversions of 70.92 and 82.30% were obtained, respectively. For the acid activated clays, conversions up to 93.08% of lauric acid to methyl laurate were obtained, much higher than those observed for the thermal conversion or using untreated montmorillonite. Relative good correlations were observed between the catalytic activity and the development of acid sites and textural properties of the resulting materials. Therefore, a simple acid activation was able to improve the catalytic activity and produce clay catalysts that are environmental friendly, cost effective, noncorrosive and reusable.

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

    Science.gov (United States)

    Itoh, Shinobu

    2015-07-21

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

  11. Synthesis of highly active and dual-functional electrocatalysts for methanol oxidation and oxygen reduction reactions

    Science.gov (United States)

    Zhao, Qi; Zhang, Geng; Xu, Guangran; Li, Yingjun; Liu, Baocang; Gong, Xia; Zheng, Dafang; Zhang, Jun; Wang, Qin

    2016-12-01

    The promising Pt-based ternary catalyst is crucial for polymer electrolyte membrane fuel cells (PEMFCs) due to improving catalytic activity and durability for both methanol oxidation reaction and oxygen reduction reaction. In this work, a facile strategy is used for the synthesis ternary RuMPt (M = Fe, Co, Ni, and Cu) nanodendrities catalysts. The ternary RuMPt alloys exhibit enhanced specific and mass activity, positive half-wave potential, and long-term stability, compared with binary Pt-based alloy and the commercial Pt/C catalyst, which is attributed to the high electron density and upshifting of the d-band center for Pt atoms, and synergistic catalytic effects among Pt, M, and Ru atoms by introducing a transition metal. Impressively, the ternary RuCoPt catalyst exhibits superior mass activity (801.59 mA mg-1) and positive half-wave potential (0.857 V vs. RHE) towards MOR and ORR, respectively. Thus, the RuMPt nanocomposite is a very promising material to be used as dual electrocatalyst in the application of PEMFCs.

  12. Boosting the Performance of the Nickel Anode in the Oxygen Evolution Reaction by Simple Electrochemical Activation

    KAUST Repository

    Shinagawa, Tatsuya

    2017-03-27

    The development of cost-effective and active water-splitting electrocatalysts that work at mild pH is an essential step towards the realization of sustainable energy and material circulation in our society. Its success requires a drastic improvement in the kinetics of the anodic half-reaction of the oxygen evolution reaction (OER), which determines the overall system efficiency to a large extent. A simple electrochemical protocol has been developed to activate Ni electrodes, by which a stable NiOOH phase was formed, which could weakly bind to alkali-metal cations. The electrochemically activated (ECA) Ni electrode reached a current of 10 mA at <1.40 V vs. the reversible hydrogen electrode (RHE) at practical operation temperatures (>75 °C) and a mild pH of ca. 10 with excellent stability (>24 h), greatly surpassing that of the state-of-the-art NiFeOx electrodes under analogous conditions. Water electrolysis was demonstrated with ECA-Ni and NiMo, which required an iR-free overall voltage of only 1.44 V to reach 10 mA cmgeo(-2) .

  13. Boosting the performance of the nickel anode in the oxygen evolution reaction by simple electrochemical activation

    Energy Technology Data Exchange (ETDEWEB)

    Shinagawa, Tatsuya; Ng, Marcus Tze-Kiat; Takanabe, Kazuhiro [King Abdullah Univ. of Science and Technology (KAUST), KAUST Catalysis Center (KCC) and Physical Sciences and Engineering Div. PSE, Thuwal (Saudi Arabia)

    2017-04-24

    The development of cost-effective and active water-splitting electrocatalysts that work at mild pH is an essential step towards the realization of sustainable energy and material circulation in our society. Its success requires a drastic improvement in the kinetics of the anodic half-reaction of the oxygen evolution reaction (OER), which determines the overall system efficiency to a large extent. A simple electrochemical protocol has been developed to activate Ni electrodes, by which a stable NiOOH phase was formed, which could weakly bind to alkali-metal cations. The electrochemically activated (ECA) Ni electrode reached a current of 10 mA at <1.40 V vs. the reversible hydrogen electrode (RHE) at practical operation temperatures (>75 C) and a mild pH of ca. 10 with excellent stability (>24 h), greatly surpassing that of the state-of-the-art NiFeO{sub x} electrodes under analogous conditions. Water electrolysis was demonstrated with ECA-Ni and NiMo, which required an iR-free overall voltage of only 1.44 V to reach 10 mA cm{sub geo}{sup -2}. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  14. In Situ Probing of the Active Site Geometry of Ultrathin Nanowires for the Oxygen Reduction Reaction.

    Science.gov (United States)

    Liu, Haiqing; An, Wei; Li, Yuanyuan; Frenkel, Anatoly I; Sasaki, Kotaro; Koenigsmann, Christopher; Su, Dong; Anderson, Rachel M; Crooks, Richard M; Adzic, Radoslav R; Liu, Ping; Wong, Stanislaus S

    2015-10-07

    To create truly effective electrocatalysts for the cathodic reaction governing proton exchange membrane fuel cells (PEMFC), namely the oxygen reduction reaction (ORR), necessitates an accurate and detailed structural understanding of these electrocatalysts, especially at the nanoscale, and to precisely correlate that structure with demonstrable performance enhancement. To address this key issue, we have combined and interwoven theoretical calculations with experimental, spectroscopic observations in order to acquire useful structural insights into the active site geometry with implications for designing optimized nanoscale electrocatalysts with rationally predicted properties. Specifically, we have probed ultrathin (∼2 nm) core-shell Pt∼Pd9Au nanowires, which have been previously shown to be excellent candidates for ORR in terms of both activity and long-term stability, from the complementary perspectives of both DFT calculations and X-ray absorption spectroscopy (XAS). The combination and correlation of data from both experimental and theoretical studies has revealed for the first time that the catalytically active structure of our ternary nanowires can actually be ascribed to a PtAu∼Pd configuration, comprising a PtAu binary shell and a pure inner Pd core. Moreover, we have plausibly attributed the resulting structure to a specific synthesis step, namely the Cu underpotential deposition (UPD) followed by galvanic replacement with Pt. Hence, the fundamental insights gained into the performance of our ultrathin nanowires from our demonstrated approach will likely guide future directed efforts aimed at broadly improving upon the durability and stability of nanoscale electrocatalysts in general.

  15. Heat and mass transfer in unsteady rotating fluid flow with binary chemical reaction and activation energy.

    Directory of Open Access Journals (Sweden)

    Faiz G Awad

    Full Text Available In this study, the Spectral Relaxation Method (SRM is used to solve the coupled highly nonlinear system of partial differential equations due to an unsteady flow over a stretching surface in an incompressible rotating viscous fluid in presence of binary chemical reaction and Arrhenius activation energy. The velocity, temperature and concentration distributions as well as the skin-friction, heat and mass transfer coefficients have been obtained and discussed for various physical parametric values. The numerical results obtained by (SRM are then presented graphically and discussed to highlight the physical implications of the simulations.

  16. Selective molecular recognition, C-H bond activation, and catalysis in nanoscale reaction vessels

    Energy Technology Data Exchange (ETDEWEB)

    Fiedler, Dorothea; Leung, Dennis H.; Raymond, Kenneth N.; Bergman, Robert G.

    2004-11-27

    Supramolecular chemistry represents a way to mimic enzyme reactivity by using specially designed container molecules. We have shown that a chiral self-assembled M{sub 4}L{sub 6} supramolecular tetrahedron can encapsulate a variety of cationic guests, with varying degrees of stereoselectivity. Reactive iridium guests can be encapsulated and the C-H bond activation of aldehydes occurs, with the host cavity controlling the ability of substrates to interact with the metal center based upon size and shape. In addition, the host container can act as a catalyst by itself. By restricting reaction space and preorganizing the substrates into reactive conformations, it accelerates the sigmatropic rearrangement of enammonium cations.

  17. Cross-section studies of relativistic deuteron reactions obtained by activation method

    CERN Document Server

    Wagner, V; Svoboda, O; Vrzalová, J; Majerle, M; Krása, A; Chudoba, P; Honusek, M; Kugler, A; Adam, J; Baldin, A; Furman, W; Kadykov, M; Khushvaktov, J; Sol-nyskhin, A; Tsoupko-Sitnikov, V; Závorka, L; Tyutyunnikov, S; Vladimirova, N

    2014-01-01

    The cross-sections of relativistic deuteron reactions on natural copper were studied in detail by means of activation method. The copper foils were irradiated during experiments with the big Quinta uranium target at Joint Institute for Nuclear Research (JINR) in Dubna, Russia. The deuteron beams with energies ranging from 1 GeV up to 8 GeV were produced by JINR Nuclotron. Residual nuclides were identified by the gamma spectrometry. Lack of such experimental cross-section values prevents the usage of copper foils from beam integral monitoring.

  18. An Investigation onγinduced activation reactions on human essential elements

    Institute of Scientific and Technical Information of China (English)

    吕翠娟; 马春旺; 刘一璞; 张文岗; 左嘉旭

    2015-01-01

    In radiotherapy, the energy of theγrays used could be larger than 10 MeV, which would potentially activate stable nucleus into a radioactive one. Theγinduced reactions on some of the human essential elements are studied to show the probability of changes of nuclei. The Talys 1.4 toolkit was adopted as the theoretical model for calculation. The reactions investigated include the (γ, n) and (γ, p) channels for the stable Na, Mg, Cl, K, Ca, and Fe isotopes, with the incident energy ofγranging from 1 to 30 MeV. It was found that the cross sections for the reactions are very low, and the maximum cross section is no larger than 100 mb. By considering the threshold energy of the channel, the half-life time of the residue nucleus, and the percentage of the element accounting for the weight and its importance in the body, it is suggested to track the radioactive nuclei 22Na, 41Ca, and 42,43K afterγtherapy. The results might be useful for medical diagnosis and disease treatment.

  19. Chemiluminescence assay of lipase activity using a synthetic substrate as proenhancer for luminol chemiluminescence reaction.

    Science.gov (United States)

    Ichibangase, Tomoko; Ohba, Yoshihito; Kishikawa, Naoya; Nakashima, Kenichiro; Kuroda, Naotaka

    2004-01-01

    A novel chemiluminescence (CL) assay method for lipase (triacylglycerol lipase, E.C.3.1.1.3) activity was developed by using the lauric acid ester of 2-(4-hydroxyphenyl)-4,5-diphenylimidazole (HDI) as a substrate. The method is based on the enhanced CL reaction of luminol-hydrogen peroxide-horseradish peroxidase (HRP) with HDI that is liberated from the substrate by enzymatic hydrolysis. To simplify the assay procedure, both the hydrolysis of the substrate and the enhanced CL reaction were performed in the same reaction mixture. Lipases from Candida cylindracea and porcine pancreas were successfully determined with the detection limits (blank signal + 3 SD) of 0.05 and 50.0 mU/tube, respectively. The method is simple and rapid, permitting the completion of single assay within 5 min. The reproducibilities obtained with replicate assays were relative standard deviations (RSDs) of 4.7% for within-day and 6.0% for between-day assays.

  20. Activation of organozinc reagents with t-Bu-P4 base for transition metal-free catalytic SN2' reaction.

    Science.gov (United States)

    Kobayashi, Koji; Ueno, Masahiro; Naka, Hiroshi; Kondo, Yoshinori

    2008-08-28

    The t-Bu-P4 base was found to be an excellent catalyst for activating organozinc reagents and was used to promote the S(N)2' reaction of alpha,beta-unsaturated esters bearing a gamma-chloride using various organozinc reagents: these reactions proceeded in high yields with excellent chemo-and regioselectivity.

  1. Impact of thermal processing and the Maillard reaction on the basophil activation of hazelnut allergic patients.

    Science.gov (United States)

    Cucu, Tatiana; De Meulenaer, Bruno; Bridts, Chris; Devreese, Bart; Ebo, Didier

    2012-05-01

    Food allergy, an abnormal immunological response due to sensitization to a food component, has become an important health problem, especially in industrialized countries. The aim of this study was to investigate the impact of thermal processing and glycation on the basophil activation by hazelnut proteins using a basophil activation test. Patients with systemic allergic reactions (SR; n=6) to hazelnut as well as patients with an isolated oral allergy syndrome (OAS; n=4) were investigated. Thermal processing of hazelnut proteins either in the presence or absence of wheat proteins did not result in major changes in the stimulatory activity of the basophils for patients with SR or OAS. For the patients with OAS, incubation of hazelnut proteins with glucose led to complete depletion of the stimulatory activity of the basophils. An increase in stimulatory activity of the basophils for two out of six patients with SR was observed. For the other four patients slight or complete abolition of the stimulatory activity was observed. These results indicate that some patients with SR to hazelnut are at risk when exposed to hazelnut proteins, even in processed foods.

  2. Assessment of released acrosin activity as a measurement of the sperm acrosome reaction

    Institute of Scientific and Technical Information of China (English)

    Rui-Zhi Liu; Wan-Li Na; Hong-Guo Zhang; Zhi-Yong Lin; Bai-Oong Xue; Zong-Oe Xu

    2008-01-01

    Aim: To develop a method for assessing sperm function by measuring released acrosin activity during the acrosome reaction (AR). Methods: Human semen samples were obtained from 24 healthy donors with proven fertility after 3-7 days of sexual abstinence. After collection, samples were liquefied for 30 min at room temperature. Standard semen parameters were evaluated according to World Health Organization (WHO) criteria. Calcium ionophore A23187 and progesterone (P4) were used to stimulate the sperm to undergo AR. After treatment, sperm were incubated with the supravital dye Hoechst33258, fixed in a glutaraldehyde-phosphate-buffered saline solution, and the acrosomal status was determined by fluorescence microscopy with fluorescein isothiocyanate-labeled Pisum sativum agglutinin (FITC-PSA). The percentage of sperm undergoing AR (AR%) was compared to sperm acrosin activities as assessed by spectrocolorimetry. The correlation between AR% and acrosin activity was determined by statistical analysis. Results: The AR% and released acrosin activity were both markedly increased with A23187 and P4 stimulation. Sperm motility and viability were significantly higher after stimulation with P4 versus stimula-tion with A23187 (P < 0.001). There was a significant positive correlation between released acrosin activity and AR% determined by FITC-PSA staining (r = 0.916, P < 0.001). Conclusion: Spectrocolorimetric measurement of released acrosin activity might serve as a reasonable alternative method to evaluate AR.

  3. Plasticity of Performance Curves Can Buffer Reaction Rates from Body Temperature Variation in Active Endotherms

    Directory of Open Access Journals (Sweden)

    Frank Seebacher

    2017-08-01

    Full Text Available Endotherms regulate their core body temperature by adjusting metabolic heat production and insulation. Endothermic body temperatures are therefore relatively stable compared to external temperatures. The thermal sensitivity of biochemical reaction rates is thought to have co-evolved with body temperature regulation so that optimal reaction rates occur at the regulated body temperature. However, recent data show that core body temperatures even of non-torpid endotherms fluctuate considerably. Additionally, peripheral temperatures can be considerably lower and more variable than core body temperatures. Here we discuss whether published data support the hypothesis that thermal performance curves of physiological reaction rates are plastic so that performance is maintained despite variable body temperatures within active (non-torpid endotherms, and we explore mechanisms that confer plasticity. There is evidence that thermal performance curves in tissues that experience thermal fluctuations can be plastic, although this question remains relatively unexplored for endotherms. Mechanisms that alter thermal responses locally at the tissue level include transient potential receptor ion channels (TRPV and TRPM and the AMP-activated protein kinase (AMPK both of which can influence metabolism and energy expenditure. Additionally, the thermal sensitivity of processes that cause post-transcriptional RNA degradation can promote the relative expression of cold-responsive genes. Endotherms can respond to environmental fluctuations similarly to ectotherms, and thermal plasticity complements core body temperature regulation to increase whole-organism performance. Thermal plasticity is ancestral to endothermic thermoregulation, but it has not lost its selective advantage so that modern endotherms are a physiological composite of ancestral ectothermic and derived endothermic traits.

  4. MOOC design analysis - Constructive alignment, interactions, task complexity, formative assessment & feedback

    NARCIS (Netherlands)

    Kasch, Julia; Van Rosmalen, Peter; Kalz, Marco

    2016-01-01

    Massive Open Online Courses (MOOCs) hold the potential of providing education at large scale. However, the challenge lies in the scalability of their educational design. It is unclear whether and to what extent MOOCs to provide active and complex learning activities, support and feedback to large nu

  5. Size-selective electrocatalytic activity of (Pt)n/MoS2for oxygen reduction reaction

    DEFF Research Database (Denmark)

    Bothra, Pallavi; Pandey, Mohnish; Pati, Swapan K.

    2016-01-01

    In the present work, we have investigated the electrocatalytic activity of the oxygen reduction reaction (ORR), O2 + 4H+ + 4e− → 2H2O, for (Pt)n clusters (n = 1, 2, 3, 5, 7, 10 and 12) adsorbed on semiconducting (2H) and metallic (1T) MoS2 monolayers using first principles density functional theory...... predicting (Pt)7/2H-MoS2 as the best ORR catalyst amongst the (Pt)n/MoS2 heterosystems with an overpotential value of 0.33 V has been established. Our finding proposes a new promising electrocatalyst towards better activity for ORR with very small amount of Pt loading....

  6. Enhanced Electrocatalytic Activity of Ethanol Oxidation Reaction on Palladium-Silver Nanoparticles via Removable Surface Ligands.

    Science.gov (United States)

    Zhang, Hucheng; Shang, Yingying; Zhao, Jing; Wang, Jianji

    2017-05-17

    This work developed a facile colloidal route to synthesize BH4(-)-capped PdxAgy nanoparticles (NPs) in water using the reducing ionic liquids of [Cnmim]BH4, and the resulting NPs were prone to form the nanocomposites with [amim](+)-modified reduced graphene (RG). The removal of the metal-free inorganic ions of BH4(-) can create the profoundly exposed interfaces on the PdxAgy NPs during the electrooxidation, and favor the ethanol oxidation reaction (EOR) in lowering energy barrier. The counterions of [Cnmim](+) can gather ethanol, OH(-) ions, and the reaction intermediates on catalysts, and synergistically interact with RG to facilitate the charge transfer in nanocomposites. The interface-modified RG nanosheets can effectively segregate the PdxAgy NPs from aggregation during the EOR. Along with the small size of 4.7 nm, the high alloying degree of 60.2%, the large electrochemical active surface area of 64.1 m(2) g(-1), and the great peak current density of 1501 mA cm(-2) mg(-1), Pd1Ag2@[C2mim]BH4-amimRG nanocomposite exhibits the low oxidation potentials, strong poison resistance, and stable catalytic activity for EOR in alkaline media, and hence can be employed as a promising anodic catalyst in ethanol fuel cells.

  7. Study of reactions of activated Mg-based powders in heated steam

    Science.gov (United States)

    Huang, Hai-tao; Zou, Mei-shuai; Guo, Xiao-yan; Yang, Rong-jie; Li, Yun-kai

    2014-01-01

    Activated Mg-based powders are prepared by high-energy milling and characterised with XRD, SEM, TG and BET techniques. This study focus on reactions of Mg-based powders with flowing steam that is heated at 500, 600, and 700 °C in a transparent pipe furnace. Morphologies and phases of solid reaction products are analysed by SEM, XRD, and residual metal content, and ignition delay times are measured. Experimental results show that all Mg-based powders oxidise at 500 °C and ignite at 600 °C. At 700 °C, all samples burn completely to form magnesium oxide (MgO) within 5 min. Residual metal contents and ignition delay times of all samples decrease with increasing temperature, and ignition delay times of activated Mg-based materials containing cobalto-cobaltic oxide (Co3O4) are only 22 s at 700 °C. Milled Mg powders are more reactive in heated steam than unmilled Mg powders, and the addition of Co3O4 further increases magnesium reactivity in heated steam.

  8. Effective synthesis of optically active trifluoromethyldiazirinyl homophenylalanine and aroylalanine derivatives with the Friedel-Crafts reaction in triflic acid.

    Science.gov (United States)

    Murashige, Ryo; Murai, Yuta; Hatanaka, Yasumaru; Hashimoto, Makoto

    2009-06-01

    The Friedel-Crafts reaction with 3-(3-methoxyphenyl)-3-(trifluoromethyl)-3H-diazirine and optically active N-TFA-Asp(Cl)-OMe in triflic acid afforded homophenylalanine derivatives without any loss of the optical purity.

  9. EFFECT OF FLUORINE AND CHLORINE IONS ON THE REACTION SINTERING OF MECHANICALLY ACTIVATED ZIRCON-ALUMINA MIXTURE

    Directory of Open Access Journals (Sweden)

    R. Zamani Foroshani

    2015-09-01

    Full Text Available The aim of this work was to study the effect of fluorine and chlorine ions on the formation of mullite during the reaction sintering of mechanically activated zircon-alumina powder mixture. The results showed that mechanical activation of zirconalumina powder mixture for 20 h led to grain refinement and partial amorphization. In the presence of fluorine and chlorine ions, complete formation of mullite in the mechanically activated sample occurred after 2 h of reaction sintering at 1300oC and 1400oC, respectively. In the sample lacking fluorine and chlorine ions, mullitization was not completed even after 2 h of reaction sintering at 1400oC. It was concluded that presence of fluorine and chlorine ions enhance the dissociation of zircon and formation of mullite during the reaction sintering of mechanically activated zircon-alumina mixture.

  10. SIMPL enhancement of tumor necrosis factor-α dependent p65-MED1 complex formation is required for mammalian hematopoietic stem and progenitor cell function.

    Directory of Open Access Journals (Sweden)

    Weina Zhao

    Full Text Available Significant insight into the signaling pathways leading to activation of the Rel transcription factor family, collectively termed NF-κB, has been gained. Less well understood is how subsets of NF-κB-dependent genes are regulated in a signal specific manner. The SIMPL protein (signaling molecule that interacts with mouse pelle-like kinase is required for full Tumor Necrosis Factor-α (TNFα induced NF-κB activity. We show that SIMPL is required for steady-state hematopoiesis and the expression of a subset of TNFα induced genes whose products regulate hematopoietic cell activity. To gain insight into the mechanism through which SIMPL modulates gene expression we focused on the Tnf gene, an immune response regulator required for steady-state hematopoiesis. In response to TNFα SIMPL localizes to the Tnf gene promoter where it modulates the initiation of Tnf gene transcription. SIMPL binding partners identified by mass spectrometry include proteins involved in transcription and the interaction between SIMPL and MED1 was characterized in more detail. In response to TNFα, SIMPL is found in p65-MED1 complexes where SIMPL enhances p65/MED1/SIMPL complex formation. Together our results indicate that SIMPL functions as a TNFα-dependent p65 co-activator by facilitating the recruitment of MED1 to p65 containing transcriptional complexes to control the expression of a subset of TNFα-induced genes.

  11. Activity diagrams for clinoptilolite: Susceptibility of this zeolite to further diagenetic reactions

    Energy Technology Data Exchange (ETDEWEB)

    Bowers, T.S.; Burns, R.G. [Massachusetts Institute of Technology, Cambridge (USA)

    1990-05-01

    Clinoptilolite is the predominant zeolite in diagenetically altered volcanic rocks at Yucca Mountain, Nevada, having formed by posteruptive reactions of ground water with vitric tuffs in the pyroclastic deposits. Compositional variations of clinoptilolites in the fractured and zeolitized tuffs not presently in contact with ground water and the vulnerability of zeolites to burial diagenesis raise questions about the long-term stability of clinoptilolite. Equilibrium activity diagrams were calculated for clinoptilolite solid solutions in the seven-component system Ca-Na-K-Mg-Fe-Al-Si plus H{sub 2}O, employing available thermodynamic data for related minerals, aqueous species, and water. Stability fields are portrayed graphically, assuming the presence of potassium feldspar, saponite, and hematite, and using ranges of activities for SiO{sub 2} and Al{sup 3+} defined by the saturation limits for several silica polymorphs, gibbsite, kaolinite, and pyrophyllite. The clinoptilolite stability field broadens with increasing atomic substitution of Ca for Na, and K for Ca, reaches a maximum for intermediate activities of dissolved Al, and decreases with increasing temperature. The thermodynamic calculations show that ground water of the sodium-bicarbonate type is approximately in equilibrium at 25C with calcite and several zeolites, including heulandite and calcic clinoptilolite. Mg-rich clinoptilolites are stabilized in ground water depleted in Ca{sup 2+}. The activity diagrams indicate that prolonged diagenetic reactions with ground water depleted in Al, enriched in Na or Ca, and heated by the thermal envelope surrounding buried nuclear waste may eliminate sorptive calcic clinoptilolites in fractured tuffs and underlying basal vitrophyre.

  12. Indirect determination of Li via 74Ge(n,γ)75mGe activation reaction induced by neutrons from 7Li(p,n)7Be reaction

    Science.gov (United States)

    Kumar, Sanjiv; Reddy, G. L. N.; Rao, Pritty; Verma, Rakesh; Ramana, J. V.; Vikramkumar, S.; Raju, V. S.

    2012-03-01

    An indirect method to determine Li by 74Ge(n,γ)75mGe activation reaction induced in a high purity Ge (detector) crystal by neutrons from the 7Li(p,n)7Be reaction in a typical particle-induced γ-ray emission (PIGE) spectroscopy experimental set-up is described. Performed with proton beams of energies in excess of 1.88 MeV, the threshold energy (Eth) of the 7Li(p,n)7Be reaction, the determination involves the activity measurement of 75mGe isotope that has a half-life of 47.7 s and decays with the emission of 139 keV γ-rays. Rapidity, selectivity and sensitivity down to ppm levels are the attractive features of the method. It is a suitable alternative to 7Li(p,p'γ)7Li reaction based PIGE technique in the analyses of matrices that contain light elements such as Be, B, F, Na and Al in significant proportions. Interferences can arise from elements, for example V and Ti, that have Eth ⩽ 1.88 MeV for (p,n) reaction. In the case of elements such as Cu, Mo which have with Eth > 1.88 MeV, the incident proton beam energy can be judiciously selected to avoid or minimize an interference. The method, under optimized irradiation conditions, does not entail a risk of neutron stimulated degradation of the performance of the detector. Besides analytical purposes, the measurement of the 75mGe activity can serve as a powerful tool to monitor even low (˜25 n/cm2 s) thermal neutron fluxes.

  13. Solution phase synthesis of halogenated graphene and the electrocatalytic activity for oxygen reduction reaction

    Institute of Scientific and Technical Information of China (English)

    Kuang-Hsu Wu; Da-Wei Wang; Qingcong Zeng; Yang Li; Ian R. Gentle

    2014-01-01

    Metal-free carbon electrocatalyts for the oxygen reduction reaction (ORR) are attractive for their high activity and economic advantages. However, the origin of the activity has never been clearly elucidated in a systematic manner. Halogen group elements are good candidates for elucidating the effect, although it has been a difficult task due to safety issues. In this report, we demonstrate the synthesis of Cl-, Br-and I-doped reduced graphene oxide through two solution phase syntheses. We have evaluated the effectiveness of doping and performed electrochemical measurements of the ORR activity on these halogenated graphene materials. Our results suggest that the high electroneg-ativity of the dopant is not the key factor for high ORR activity;both Br-and I-doped graphene pro-moted ORR more efficiently than Cl-doped graphene. Furthermore, an unexpected sulfur-doping in acidic conditions suggests that a high level of sulfide can degrade the ORR activity of the graphene material.

  14. Electrocatalytic activity of nitrogen doped carbon nanotubes with different morphologies for oxygen reduction reaction

    Energy Technology Data Exchange (ETDEWEB)

    Chen Zhu; Higgins, Drew [Department of Chemical Engineering, Waterloo Institute for Nanotechnology, Waterloo Institute for Sustainable Energy, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, N2L 3G1 (Canada); Chen Zhongwei, E-mail: zhwchen@uwaterloo.c [Department of Chemical Engineering, Waterloo Institute for Nanotechnology, Waterloo Institute for Sustainable Energy, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, N2L 3G1 (Canada)

    2010-06-30

    Nitrogen doped carbon nanotubes (NCNTs) were synthesized by a single step chemical vapor deposition technique using either ferrocene or iron(II) phthalocyanine as catalyst and pyridine as the carbon and nitrogen precursor. Variations in surface morphology and electrocatalytic activity for oxygen reduction reaction (ORR) were observed between the NCNTs synthesized using different catalysts. The structural and chemical characterizations were carried out using transmission electron microscopy (TEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The electrochemical activity of NCNTs was evaluated with rotating ring disc electrode (RRDE) voltammetry. Structural characterization suggested more defects formed on the NCNTs synthesized from ferrocene (Fc-NCNTs) which led to a rugged surface morphology compared to the NCNTs synthesized from iron(II) phthalocyanine (FePc-NCNTs). Based on the RRDE voltammetry study, Fc-NCNTs demonstrated much higher activity for ORR than FePc-NCNT. Evidences from the structural and chemical characterizations illustrate the potential impact of catalyst structure in shaping the surface structure of NCNTs and the positive effect of surface defects on ORR activity. These results showed that potential improvements on ORR activity of NCNTs could be achieved by tailoring the surface structure of NCNTs by using catalysts with different structures.

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

    Science.gov (United States)

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

    2014-11-26

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

  16. Spectrophotometric determination of nizatidine and ranitidine through charge transfer complex formation.

    Science.gov (United States)

    Walash, M; Sharaf-El Din, M; Metwalli, M E-S; RedaShabana, M

    2004-07-01

    Two Spectrophotometric procedures are presented for the determination of two commonly used H2-receptor antagonists, nizatidine (I) and ranitidine hydrochloride (II). The methods are based mainly on charge transfer complexation reaction of these drugs with either p-chloranilic acid (rho-CA) or 2, 3 dichloro-5, 6-dicyanoquinone (DDQ). The produced colored products are quantified spectrophotometrically at 515 and 467 nm in chloranilic acid and DDQ methods, respectively. The molar ratios for the reaction products and the optimum assay conditions were studied. The methods determine the cited drugs in concentration ranges of 20-200 and 20-160 microg/mL for nizatidine and ranges of 20-240 and 20-140 microg/mL for ranitidine with chloranilic acid and DDQ methods, respectively. A more detailed investigation of the complexes formed was made with respect to their composition, association constant, molar absorptivity and free energy change. The proposed procedures were successfully utilized in the determination of the drugs in pharmaceutical preparations. The standard addition method was applied by adding nizatidine and ranitidine to the previously analyzed tablets or capsules. The recovery of each drug was calculated by comparing the concentration obtained from the spiked mixtures with those of the pure drug. The results of analysis of commercial tablets and the recovery study (standard addition method) of the cited drugs suggested that there is no interference from any excipients, which are present in tablets or capsules. Statistical comparison of the results was performed with regard to accuracy and precision using student's t-test and F-ratio at 95% confidence level. There is no significant difference between the reported and proposed methods with regard to accuracy and precision.

  17. Superior long-term activity for a Pt-Re alloy compared to Pt in methanol oxidation reactions

    Science.gov (United States)

    Duke, Audrey S.; Xie, Kangmin; Monnier, John R.; Chen, Donna A.

    2017-03-01

    Pt-Re bimetallic catalysts have shown enhanced activity compared to pure Pt for reactions involving oxidation, but the origins of this improved activity are not fully understood. Methanol oxidation on a Pt-Re alloy surface and pure Pt foil was studied in a microreactor coupled to an ultrahigh vacuum chamber. For reaction at 60 °C, the Pt-Re alloy surface exhibits superior long-term activity over a 24 h reaction period compared to pure Pt. The initial activity of Pt is 10-15% higher than on Pt-Re; however, the Pt surface gradually loses activity after 10 h online, whereas the activity of Pt-Re does not diminish. Post-reaction XPS shows that more carbon accumulates on the Pt than on Pt-Re, and the improved long-term activity is attributed to a greater ability of Pt-Re to oxidize the carbonaceous intermediates that eventually poison active sites. Both Pt and Pt-Re surfaces have almost no activity for methanol oxidation until a minimum coverage of oxygen is achieved from O2 dissociation. A comparison with methanol oxidation studies on Pt and Pt-Re in a pressure regime that is 150 times lower than in this work demonstrates that more carbon and less oxygen accumulate on the surfaces during reaction at the lower pressures.

  18. Kinetics and activation thermodynamics of methane monooxygenase compound Q formation and reaction with substrates.

    Science.gov (United States)

    Brazeau, B J; Lipscomb, J D

    2000-11-07

    The transient kinetics of formation and decay of the reaction cycle intermediates of the Methylosinus trichosporium OB3b methane monooxygenase (MMO) catalytic cycle are studied as a function of temperature and substrate type and deuteration. Kinetic evidence is presented for the existence of three intermediates termed compounds O, P, and P forming after the addition of O(2) to diferrous MMO hydroxylase (H(r)) and before the formation of the reactive intermediate compound Q. The Arrhenius plots for these reactions are linear and independent of substrate concentration and type, showing that substrate does not participate directly in the oxygen activation phase of the catalytic cycle. Analysis of the transient kinetic data revealed only small changes relative to the weak optical spectrum of H(r) for any of these intermediates. In contrast, large changes in the 430 nm spectral region are associated with the formation of Q. The decay reaction of Q exhibits an apparent first-order concentration dependence for all substrates tested, and the observed rate constant depends on the substrate type. The kinetics of the decay reaction of Q yield a nonlinear Arrhenius plot when methane is the substrate, and the rates in both segments of the plot increase linearly with methane concentration. Together these observations suggest that at least two reactions with a methane concentration dependence, and perhaps two methane molecules, are involved in the decay process. When CD(4) is used as the substrate, a large isotope effect and a linear Arrhenius plot are observed. Analogous plots for all other MMO substrates tested (e.g., ethane) are linear, and no isotope effect for deuterated analogues is observed. This demonstrates that a step other than C-H bond breaking is rate limiting for alternative MMO substrates. A two step Q decay mechanism is proposed that provides an explanation for the lack of an isotope effect for alternative MMO substrates and the fact that rate of oxidation of

  19. Automatically activated shame reactions and perceived legitimacy of discrimination: A longitudinal study among people with mental illness.

    Science.gov (United States)

    Rüsch, Nicolas; Todd, Andrew R; Bodenhausen, Galen V; Olschewski, Manfred; Corrigan, Patrick W

    2010-03-01

    Perceived legitimacy of discrimination shapes reactions to mental illness stigma among stigmatized individuals. We assessed deliberately endorsed versus automatic shame-related reactions to mental illness as predictors of change in perceived legitimacy of discrimination over six months among 75 people with mental illness. Automatically activated shame-related associations with mental illness were measured using the Brief Implicit Association Test, deliberately endorsed beliefs via self-report. Controlling for depression and perceived stigma, stronger baseline automatic shame-related associations, but not deliberately endorsed beliefs, predicted higher perceived legitimacy of discrimination after six months. Automatically activated shame reactions may increase vulnerability to mental illness stigma.

  20. Kinetic studies on surface-mediated activation of bovine factor XII and prekallikrein. Effects of kaolin and high-Mr kininogen on the activation reactions.

    Science.gov (United States)

    Sugo, T; Kato, H; Iwanaga, S; Takada, K; Sakakibara, S

    1985-01-02

    The kaolin-mediated reciprocal activation of bovine factor XII and prekallikrein was divided into the following two reactions: the activation of factor XII by plasma kallikrein (reaction 1) and the activation of prekallikrein by factor XIIa (reaction 2). The effects of high-Mr kininogen and kaolin surface on the kinetics of these activation reactions were studied. High-Mr kininogen markedly enhanced the rate of reactions 1 and 2 in the presence of kaolin, and the enhancements were highly dependent on the concentrations of the protein cofactor and amount of kaolin surface. For the activation of factor XII by plasma kallikrein (reaction 1), high-Mr kininogen was required when a low concentration of factor XII and kaolin was used. The molar ratio of the protein cofactor to factor XII for optimal activation was found to be approximately 1:1. The apparent Km value and the kcat/Km value for plasma kallikrein on factor XII were calculated to be 4 nM and 5.2 X 10(7) s-1 X M-1, respectively. The activation of prekallikrein by factor XIIa, (reaction 2) proceeded even in the absence of high-Mr kininogen and kaolin. The addition of the protein cofactor and surface to the reaction mixture remarkably accelerated the reaction, and the apparent Km value for factor XIIa on prekallikrein was reduced from 1 microM to 40 nM. Moreover, the kcat/Km value was altered from 7.3 X 10(4) to 1.1 X 10(6) s-1 X M-1). These results suggest that high-Mr kininogen accelerates the surface-mediated activation of factor XII and prekallikrein by enhancing the susceptibility of factor XII to plasma kallikrein, on the one hand, and the affinity of factor XIIa for prekallikrein, on the other hand. Kaolin may play an important role in the concentration and organization of these components on the negatively charged surface.

  1. Mixed ligand complex formation of FeIII with boric acid and typical N-donor multidentate ligands

    Indian Academy of Sciences (India)

    G N Mukherjee; Ansuman Das

    2002-06-01

    Equilibrium study of the mixed ligand complex formation of FeIII with boric acid in the absence and in the presence of 2,2'-bipyridine, 1,10-phenanthroline, diethylenetriamine and triethylenetetramine (L) in different molar ratios provides evidence of formation of Fe(OH)2+, Fe(OH)$^{+}_{2}$, Fe(L)3+, Fe(H2BO4), Fe(OH)(H2BO4)-, Fe(OH)2(H2BO4)2-, Fe(L)(H2BO4) and Fe2(L)2(BO4)+ complexes. Fe(L)$^{3+}_{2}$, Fe(L)2(H2BO4) and Fe2(L)4(BO4)+ complexes are also indicated with 2,2'-bipyridine and 1,10-phenanthroline. Complex formation equilibria and stability constants of the complexes at 25 ± 0 × 1° C in aqueous solution at a fixed ionic strength, = 0.1 mol -3 (NaNO3) have been determined by potentiometric method.

  2. Directed surfaces structures and interfaces for enhanced electrocatalyst activity, selectivity, and stability for energy conversion reactions

    Energy Technology Data Exchange (ETDEWEB)

    Jaramillo, Thomas F. [Stanford Univ., CA (United States). Dept. of Chemical Engineering. Shriram Center

    2016-04-20

    In this project, we have employed a systematic approach to develop active, selective, and stable catalyst materials for important electrochemical reactions involving energy conversion. In particular, we have focused our attention on developing active catalyst materials for the hydrogen evolution reaction (HER), oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). HER: We have synthesized and investigated several highly active and acid stable non-precious metal HER catalysts, including: [Mo3S13]2- nanoclusters (Nature Chemistry, 2014) and molybdenum phosphosulfide (MoP|S) (Angewandte Chemie, 2014). We have also aimed to engineer these catalyst formulations in a membrane electrode assembly (MEA) for fundamental studies of water electrolysis at high current densities, approximately 1 A/cm2 (ChemSusChem, 2015). We furthermore investigated transition metal phosphide (TMP) catalysts for HER by a combined experimental–theoretical approach (Energy & Environmental Science, 2015). By synthesizing different TMPs and comparing experimentally determined HER activities with the hydrogen adsorption free energies, ΔGH, calculated by density functional theory, we showed that the TMPs follow a volcano relationship for the HER. Using our combined experimental–theoretical model, we predicted that the mixed metal TMP, Fe0.5Co0.5P, should have a near-optimal ΔGH. We synthesized several mixtures of Co and Fe phosphides alloys and confirmed that Fe0.5Co0.5P exhibits the highest HER activity of the investigated TMPs (Energy & Environmental Science, 2015). The understanding gained as to how to improve catalytic activity for the HER, particularly for non-precious metal materials, is important to DOE targets for sustainable H2 production. OER: We have developed a SrIrO3/IrOx catalyst for acidic conditions (submitted, 2016). The Sr

  3. A simplified method for detecting macroamylasemia by measuring serum amylase activity at different reaction temperatures.

    Science.gov (United States)

    Koda, T; Kuratsune, H; Kurahori, T

    1983-06-01

    Amylase activity in serum and urine, and isoamylase, were measured in 300 patients with abdominal pain to detect cases of macroamylasemia. Of these patients, 9 had hyperamylasemia and 2 were diagnosed as cases of macroamylasemia on the basis of their amylase/creatinine clearance ratio, the gel filtration pattern of their amylase on a dextran column, and results of immunological analysis. Amylase activity in macroamylasemia is reported to show an anomalous response to increase in reaction-temperature. In this report, measurements of the temperature-activity relationships of serum amylase confirmed that the ratio of serum amylase activity at 50 degrees C to that at 25 degrees C (AMY-50 degrees C/AMY-25 degrees C ratio) in patients with macroamylasemia was higher than that in normal subjects or patients with pancreatitis. Moreover, when macromolecular amylase in the sera of patients with macroamylasemia was separated from amylase of normal molecular weight by dextran gel chromatography, it showed a significantly higher AMY-50 degrees C/AMY-25 degrees C ratio than the latter. Measurement of this AMY-50 degrees C/AMY-25 degrees C ratio seems to be a convenient and useful method for differential diagnosis of hyperamylasemia.

  4. Colorimetric determination of sildenafil citrate (Viagra) through ion-associate complex formation.

    Science.gov (United States)

    Amin, Alaa S; Moustafa, Moustafa E; El-Dosoky, Reham

    2009-01-01

    A simple, quick, accurate, and sensitive colorimetric method is described for the determination of sildenafil citrate (SLD). The method is based on the reaction of SLD with Congo Red, Sudan II, and Gentian Violet in buffered aqueous solutions at pH 2.5, 6.5, and 11.0, respectively, to give highly colored soluble ion-associate complex species; the colored products are quantitated colorimetrically at 523, 554, and 569 nm, respectively. The various experimental conditions were optimized. The stoichiometric ratio was found to be 1:1 for all ion associates; the calculated logarithmic stability constants were 8.51, 7.79, and 5.58, respectively. Beer's law was obeyed over the concentration range of 0.2-7.0 microg/mL, whereas the Ringbom optimum concentration range was 0.4-6.5 microg/mL. Values for molar absorptivity, Sandell sensitivity, and detection and quantification limits were also calculated. The proposed method was successfully applied to the determination of SLD in Viagra tablets and in serum samples by using the technique of standard additions with mean accuracy values of 100.06 +/- 1.14, 99.87 +/- 0.70, and 99.86 +/- 0.97% for Viagra tablets and 99.88 +/- 0.60, 99.90 +/- 0.90, and 100.24 +/- 0.80% for serum samples, respectively.

  5. Evidence for the Active Phase of Heterogeneous Catalysts through In Situ Reaction Product Imaging and Multiscale Modeling

    Energy Technology Data Exchange (ETDEWEB)

    Matera, S.; Blomberg, S.; Hoffmann, M. J.; Zetterberg, J.; Gustafson, J.; Lundgren, E.; Reuter, K.

    2015-06-17

    We use multiscale modeling to analyze laser-induced fluorescence (LIF) measurements of the CO oxidation reaction over Pd(100) at near-ambient reaction conditions. Integrating density functional theory-based kinetic Monte Carlo simulations of the active catalyst into fluid-dynamical simulations of the mass transport inside the reactor chamber, we calculate the reaction product concentration directly above the catalyst surface. Comparing corresponding data calculated for different surface models against the measured LIF signals, we can discriminate the one that predominantly actuates the experimentally measured catalytic activity. For the probed CO oxidation reaction conditions, the experimental activity is due to pristine Pd(100) possibly coexisting with other (oxidic) domains on the surface.

  6. H2/D2 exchange reaction on mono-disperse Pt clusters: enhanced activity from minute O2 concentrations

    DEFF Research Database (Denmark)

    Riedel, Jakob Nordheim; Rötzer, Marian David; Jørgensen, Mikkel;

    2016-01-01

    The H2/D2 exchange reaction was studied on mono-disperse Pt8 clusters in a μ-reactor. The chemical activity was studied at temperatures varying from room temperature to 180 °C using mass spectrometry. It was found that minute amounts of O2 in the gas stream increased the chemical activity...... significantly. XPS and ISS before and after reaction suggest little or no sintering during reaction. A reaction pathway is suggested based on DFT. H2 desorption is identified as the rate-limiting step and O2 is confirmed as the source of the increased activity. The binding energy of platinum atoms in a SiO2...... supported Pt8 cluster is found to be comparable to the interatomic binding energies of bulk platinum, underlining the stability of the model system....

  7. Palladium- and copper-mediated N-aryl bond formation reactions for the synthesis of biological active compounds

    Directory of Open Access Journals (Sweden)

    Burkhard Koenig

    2011-01-01

    Full Text Available N-Arylated aliphatic and aromatic amines are important substituents in many biologically active compounds. In the last few years, transition-metal-mediated N-aryl bond formation has become a standard procedure for the introduction of amines into aromatic systems. While N-arylation of simple aromatic halides by simple amines works with many of the described methods in high yield, the reactions may require detailed optimization if applied to the synthesis of complex molecules with additional functional groups, such as natural products or drugs. We discuss and compare in this review the three main N-arylation methods in their application to the synthesis of biologically active compounds: Palladium-catalysed Buchwald–Hartwig-type reactions, copper-mediated Ullmann-type and Chan–Lam-type N-arylation reactions. The discussed examples show that palladium-catalysed reactions are favoured for large-scale applications and tolerate sterically demanding substituents on the coupling partners better than Chan–Lam reactions. Chan–Lam N-arylations are particularly mild and do not require additional ligands, which facilitates the work-up. However, reaction times can be very long. Ullmann- and Buchwald–Hartwig-type methods have been used in intramolecular reactions, giving access to complex ring structures. All three N-arylation methods have specific advantages and disadvantages that should be considered when selecting the reaction conditions for a desired C–N bond formation in the course of a total synthesis or drug synthesis.

  8. Screening of catalytic oxygen reduction reaction activity of metal-doped graphene by density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Xin, E-mail: chenxin830107@pku.edu.cn; Chen, Shuangjing; Wang, Jinyu

    2016-08-30

    Highlights: • The screened M-G structures are very thermodynamically stable, and the stability is even higher than that of the corresponding bulk metal surfaces. • The binding energies of ORR intermediates suggest that they are not linear dependence, which are different form the cases found on some metal-based catalysts. • The Au-, Co-, and Ag-G structures could be used as the ORR catalysts. - Abstract: Graphene doping is a promising direction for developing effective oxygen reduction reaction (ORR) catalysts. In this paper, we computationally investigated the ORR performance of 10 kinds of metal-doped graphene (M-G) catalysts, namely, Al-, Si-, Mn-, Fe-, Co-, Ni-, Pd-, Ag-, Pt-, and Au-G. The results shown that the binding energies of the metal atoms incorporated into the graphene vacancy are higher than their bulk cohesive energies, indicating the formed M-G catalysts are even more stable than the corresponding bulk metal surfaces, and thus avoid the metals dissolution in the reaction environment. We demonstrated that the linear relation among the binding energies of the ORR intermediates that found on metal-based materials does not hold for the M-G catalysts, therefore a single binding energy of intermediate alone is not sufficient to evaluate the ORR activity of an arbitrary catalyst. By analysis of the detailed ORR processes, we predicted that the Au-, Co-, and Ag-G materials can be used as the ORR catalysts.

  9. Temperature dependent halogen activation by N2O5 reactions on halide-doped ice surfaces

    Directory of Open Access Journals (Sweden)

    J. A. Thornton

    2012-02-01

    Full Text Available We examined the reaction of N2O5 on frozen halide salt solutions as a function of temperature and composition using a coated wall flow tube technique coupled to a chemical ionization mass spectrometer (CIMS. The molar yield of photo-labile halogen compounds was near unity for almost all conditions studied, with the observed reaction products being nitryl chloride (ClNO2 and/or molecular bromine (Br2. The relative yield of ClNO2 and Br2 depended on the ratio of bromide to chloride ions in the solutions used to form the ice. At a bromide to chloride ion molar ratio greater than 1/30 in the starting solution, Br2 was the dominant product otherwise ClNO2 was primarily produced on these near pH-neutral brines. We demonstrate that the competition between chlorine and bromine activation is a function of the ice/brine temperature presumably due to the preferential precipitation of NaCl hydrates from the brine below 250 K. Our results provide new experimental confirmation that the chemical environment of the brine layer changes with temperature and that these changes can directly affect multiphase chemistry. These findings have implications for modeling air-snow-ice interactions in polar regions and likely in polluted mid-latitude regions during winter as well.

  10. Temperature dependent halogen activation by N2O5 reactions on halide-doped ice surfaces

    Directory of Open Access Journals (Sweden)

    J. A. Thornton

    2012-06-01

    Full Text Available We examined the reaction of N2O5 on frozen halide salt solutions as a function of temperature and composition using a coated wall flow tube technique coupled to a chemical ionization mass spectrometer (CIMS. The molar yield of photo-labile halogen compounds was near unity for almost all conditions studied, with the observed reaction products being nitryl chloride (ClNO2 and/or molecular bromine (Br2. The relative yield of ClNO2 and Br2 depended on the ratio of bromide to chloride ions in the solutions used to form the ice. At a bromide to chloride ion molar ratio greater than 1/30 in the starting solution, Br2 was the dominant product otherwise ClNO2 was primarily produced on these near pH-neutral brines. We demonstrate that the competition between chlorine and bromine activation is a function of the ice/brine temperature presumably due to the preferential precipitation of NaCl hydrates from the brine below 250 K. Our results provide new experimental confirmation that the chemical environment of the brine layer changes with temperature and that these changes can directly affect multiphase chemistry. These findings have implications for modeling air-snow-ice interactions in polar regions and likely in polluted mid-latitude regions during winter as well.

  11. Microstructure and Interfacial Reactions During Active Metal Brazing of Stainless Steel to Titanium

    Science.gov (United States)

    Laik, A.; Shirzadi, A. A.; Tewari, R.; Kumar, Anish; Jayakumar, T.; Dey, G. K.

    2013-05-01

    Microstructural evolution and interfacial reactions during active metal vacuum brazing of Ti (grade-2) and stainless steel (SS 304L) using a Ag-based alloy containing Cu, Ti, and Al was investigated. A Ni-depleted solid solution layer and a discontinuous layer of (Ni,Fe)2TiAl intermetallic compound formed on the SS surface and adjacent to the SS-braze alloy interface, respectively. Three parallel contiguous layers of intermetallic compounds, CuTi, AgTi, and (Ag,Cu)Ti2, formed at the Ti-braze alloy interface. The diffusion path for the reaction at this interface was established. Transmission electron microscopy revealed formation of nanocrystals of Ag-Cu alloy of size ranging between 20 and 30 nm in the unreacted braze alloy layer. The interdiffusion zone of β-Ti(Ag,Cu) solid solution, formed on the Ti side of the joint, showed eutectoid decomposition to lamellar colonies of α-Ti and internally twinned (Cu,Ag)Ti2 intermetallic phase, with an orientation relationship between the two. Bend tests indicated that the failure in the joints occurred by formation and propagation of the crack mostly along the Ti-braze alloy interface, through the (Ag,Cu)Ti2 phase layer.

  12. SABER: a computational method for identifying active sites for new reactions.

    Science.gov (United States)

    Nosrati, Geoffrey R; Houk, K N

    2012-05-01

    A software suite, SABER (Selection of Active/Binding sites for Enzyme Redesign), has been developed for the analysis of atomic geometries in protein structures, using a geometric hashing algorithm (Barker and Thornton, Bioinformatics 2003;19:1644-1649). SABER is used to explore the Protein Data Bank (PDB) to locate proteins with a specific 3D arrangement of catalytic groups to identify active sites that might be redesigned to catalyze new reactions. As a proof-of-principle test, SABER was used to identify enzymes that have the same catalytic group arrangement present in o-succinyl benzoate synthase (OSBS). Among the highest-scoring scaffolds identified by the SABER search for enzymes with the same catalytic group arrangement as OSBS were L-Ala D/L-Glu epimerase (AEE) and muconate lactonizing enzyme II (MLE), both of which have been redesigned to become effective OSBS catalysts, demonstrated by experiments. Next, we used SABER to search for naturally existing active sites in the PDB with catalytic groups similar to those present in the designed Kemp elimination enzyme KE07. From over 2000 geometric matches to the KE07 active site, SABER identified 23 matches that corresponded to residues from known active sites. The best of these matches, with a 0.28 Å catalytic atom RMSD to KE07, was then redesigned to be compatible with the Kemp elimination using RosettaDesign. We also used SABER to search for potential Kemp eliminases using a theozyme predicted to provide a greater rate acceleration than the active site of KE07, and used Rosetta to create a design based on the proteins identified.

  13. Dynamics of activity free radical oxidation reactions in students with cerebral palsy results over the course of the educational process

    Directory of Open Access Journals (Sweden)

    Makarova E.V.

    2012-12-01

    Full Text Available The dynamics of changes activity of reactions is studied freely radical oxidize for students with the consequences of child's cerebral paralysis. 20 students took part in an experiment. Found that the course of study they have more active free radical oxidation reactions and decreases the activity of antiradical protection. Given the use of additional physical activity in aerobic training indicators intracellular antioxidant defense system increased, decreased content of reaction products of lipid peroxidation. However, increased rates of maximum oxygen consumption and increased tolerance of students with cerebral palsy to the consequences of physical activity. It is set that the pathological changes of metabolism for students ground the necessity of application of the differentiated physical loadings. The optimum forms of physical rehabilitation of the aerobic training is the dosed walking, medical swimming, dosed after distance, sometimes and by the corner of getting up pedestrian ascents. Loading is increased due to a volume, but not intensity of exercises.

  14. Engineering of carboligase activity reaction in Candida glabrata for acetoin production.

    Science.gov (United States)

    Li, Shubo; Xu, Nan; Liu, Liming; Chen, Jian

    2014-03-01

    Utilization of Candida glabrata overproducing pyruvate is a promising strategy for high-level acetoin production. Based on the known regulatory and metabolic information, acetaldehyde and thiamine were fed to identify the key nodes of carboligase activity reaction (CAR) pathway and provide a direction for engineering C. glabrata. Accordingly, alcohol dehydrogenase, acetaldehyde dehydrogenase, pyruvate decarboxylase, and butanediol dehydrogenase were selected to be manipulated for strengthening the CAR pathway. Following the rational metabolic engineering, the engineered strain exhibited increased acetoin biosynthesis (2.24 g/L). In addition, through in silico simulation and redox balance analysis, NADH was identified as the key factor restricting higher acetoin production. Correspondingly, after introduction of NADH oxidase, the final acetoin production was further increased to 7.33 g/L. By combining the rational metabolic engineering and cofactor engineering, the acetoin-producing C. glabrata was improved stepwise, opening a novel pathway for rational development of microorganisms for bioproduction.

  15. Activation cross sections of proton induced nuclear reactions on gold up to 65 MeV

    CERN Document Server

    Ditrói, F; Takács, S; Hermanne, A

    2016-01-01

    Activation cross sections of proton induced reactions on gold for production of $^{197m,197g,195m,195g, 193m,193g,192}$Hg, $^{196m,196g(cum),195g(cum),194,191(cum)}$Au, $^{191(cum)}$Pt and $^{192}$Ir were measured up to 65 MeV proton energy, some of them for the first time. The new data are in acceptably good agreement with the recently published earlier experimental data in the overlapping energy region. The experimental data are compared with the predictions of the TALYS 1.6 (results in TENDL-2015 on-line library) and EMPIRE 3.2 code.

  16. Measurements of cross-sections of the proton-induced activation reactions

    CERN Document Server

    Uddin, M S; Ditrói, F; Hagiwara, M; Tarkanyi, F

    2005-01-01

    Excitation functions for the /sup 89/Y(p, x)/sup 89,88,86/Zr, /sup 89 /Y(p, x)/sup 88,87,87m,86/Y, /sup 89/Y(p, x)/sup 85,83,82/Sr and /sup 89/Y(p, x)/sup 84,83/Rb reactions were measured by a stacked foil activation technique in the energy range 15-80 MeV. The production for the long lived products like /sup 88/Zr, and /sup 88/Y are significantly larger than that of /sup nat/Mo+p, /sup nat/Nb+p and /sup nat/Zr+p processes. The productions of the medical isotopes, /sup 85/Sr and /sup 83/Sr are also effective by Y+p process using 80 MeV beam. The model calculations using ALICE-IPPE code compiled in MENDL-2P have the general trend of the measured results.

  17. Palladium nanoparticle anchored polyphosphazene nanotubes: preparation and catalytic activity on aryl coupling reactions

    Indian Academy of Sciences (India)

    V Devi; A Ashok Kumar; S Sankar; K Dinakaran

    2015-06-01

    Highly accessible-supported palladium (Pd) nanoparticles anchored polyphosphazene (PPZ) nanotubes (NTs) having average diameter of 120 nm were synthesized rapidly at room temperature and homogeneously decorated with Pd nanoparticles. The resultant PPZ–Pd nanocomposites were morphologically and structurally characterized by means of transmission electron microscope equipped with energy-dispersive X-ray spectroscopy and X-ray diffraction analysis. Characterization results showed that the Pd nanoparticles with good dispersibility could be well anchored onto the surfaces of the PPZ NTs. The PPZ–Pd NTs show enhanced catalytic activity for the Suzuki coupling of aryl bromides with arylboronic acid. In addition, these PPZ–Pd NTs show excellent behaviour as reusable catalysts of the Suzuki and Heck coupling reactions.

  18. Singular characteristics and unique chemical bond activation mechanisms of photocatalytic reactions on plasmonic nanostructures

    Science.gov (United States)

    Christopher, Phillip; Xin, Hongliang; Marimuthu, Andiappan; Linic, Suljo

    2012-12-01

    The field of heterogeneous photocatalysis has almost exclusively focused on semiconductor photocatalysts. Herein, we show that plasmonic metallic nanostructures represent a new family of photocatalysts. We demonstrate that these photocatalysts exhibit fundamentally different behaviour compared with semiconductors. First, we show that photocatalytic reaction rates on excited plasmonic metallic nanostructures exhibit a super-linear power law dependence on light intensity (rate ∝intensityn, with n > 1), at significantly lower intensity than required for super-linear behaviour on extended metal surfaces. We also demonstrate that, in sharp contrast to semiconductor photocatalysts, photocatalytic quantum efficiencies on plasmonic metallic nanostructures increase with light intensity and operating temperature. These unique characteristics of plasmonic metallic nanostructures suggest that this new family of photocatalysts could prove useful for many heterogeneous catalytic processes that cannot be activated using conventional thermal processes on metals or photocatalytic processes on semiconductors.

  19. The Olefin Metathesis Reactions Combined with Organo-Iron Arene Activation Towards Dendrimers, and Polymers

    Science.gov (United States)

    Astruc, Didier; Martinez, Victor

    The subjects treated in the two lectures of the North Atlantic Treaty Organization (NATO) summer course are (1) the combination of arene activation and perfunctionalization using organo-iron chemistry with olefin metathesis incuding metathesis of dendritic polyolefin molecules; (2) the synthesis of metallodendritic benzylidene complexes that catalyse ring-opening metathesis polymerization (ROMP) under ambient conditions and the formation of dendritic stars; (3) the use of stoichiometric and catalytic electron-transfer processes with standard reservoirs of electrons (reductants) or electron holes (oxidants) iron complexes to achieve noteworthy metathesis reactions or synthesize compounds that are useful in metathesis. Only the two first topics are treated in this chapter, and interested readers can find references concerning the third aspect called in the introduction and subsequently cited in the reference list.

  20. The Differential Gibbs Free Energy of Activation and its Implications in the Transition-State of Enzymatic Reactions

    Science.gov (United States)

    Maggi, F.; Riley, W. J.

    2016-12-01

    We propose a mathematical framework to introduce the concept of differential free energy of activation in enzymatically catalyzed reactions, and apply it to N uptake by microalgae and bacteria. This framework extends the thermodynamic capabilities of the classical transition-state theory in and harmonizes the consolidated definitions of kinetic parameters with their thermodynamic and physical meaning. Here, the activation energy is assumed to be a necessary energetic level for equilibrium complexation between reactants and activated complex; however, an additional energy contribution is required for the equilibrium activated complex to release reaction products. We call this "differential free energy of activation"; it can be described by a Boltzmann distribution, and corresponds to a free energy level different from that of complexation. Whether this level is above or below the free energy of activation depends on the reaction, and defines energy domains that correspond to "superactivated", "activated", and "subactivated" complexes. The activated complex reaching one of those states will eventually release the products from an energy level different than that of activation. The concept of differential free energy of activation was tested on 57 independent experiments of NH­4+ and NO3- uptake by various microalgae and bacteria at temperatures ranging between 1 and 45oC. Results showed that the complexation equilibrium always favored the activated complex, but the differential energy of activation led to an apparent energy barrier consistent with observations. Temperature affected all energy levels within this framework but did not alter substantially these thermodynamic features. Overall the approach: (1) provides a thermodynamic and mathematical link between Michaelis-Menten and rate constants; (2) shows that both kinetic parameters can be described or approximated by Arrhenius' like equations; (3) describes the likelihood of formation of sub-, super-, and

  1. Surfactant induced complex formation and their effects on the interfacial properties of seawater.

    Science.gov (United States)

    Guzmán, Eduardo; Santini, Eva; Benedetti, Alessandro; Ravera, Francesca; Ferrari, Michele; Liggieri, Libero

    2014-11-01

    The effect of a cationic surfactant, hexadecyltrimethylammonium bromide (CTAB), on the interfacial properties of seawater has been studied by dynamic and equilibrium surface tension and by dilational rheology essays. Important modifications of the surface tension and dilational rheology response have been observed already at the very low CTAB concentrations, where the effects due to the high ionic strength are negligible. The comparison with the effects of CTAB in different seawater models, or in natural seawater fractions, points out the establishment of strong interactions between the surfactant molecules and the lipophilic fraction of organic material dispersed/dissolved in seawater, affecting the interfacial activity of the molecules. Considering the biochemical richness of seawater, these results can be explained assuming interaction mechanisms and adsorption schemes similar to those speculated for protein and other macromolecules in the presence of surfactants, which in fact show similar features. Thus already at the low concentrations the surfactant molecules form highly surface-active complexes with part of the organic fraction of seawater. At the larger surfactant concentrations these complexes compete for adsorption with an excess of free CTAB molecules which, according to the thermodynamic conditions, are most favoured to occupy the liquid interface. The results of this study underline the important role of the sea organic content in enhancing the surface-activity of surfactants, which is relevant for a deeper understand of the direct and indirect effects of these types of pollutants on the physico-chemical environment in the sea coastal areas and develop mitigation strategies.

  2. [High activity antiretroviral therapy change associated to adverse drug reactions in a specialized center in Venezuela].

    Science.gov (United States)

    Subiela, José D; Dapena, Elida

    2016-03-01

    Adverse drug reactions (ADRs) represent the first cause of change of the first-line highly active antiretroviral therapy (HAART) regimen, therefore, they constitute the main limiting factor in the long-term follow up of HIV patients in treatment. A retrospective study was carried out in a specialized center in Lara State, Venezuela, including 99 patients over 18 years of age who had change of first-line HAART regimen due to ADRs, between 2010 and 2013. The aims of this research were to describe the sociodemographic and clinical variables, frequency of ADRs related to change of HAART, duration of the first-line HAART regimen, to determine the drugs associated with ARVs and to identify the risk factors. The ADRs constituted 47.5% of all causes of change of first-line HAART regimen, the median duration was 1.08±0.28 years. The most frequent ADRs were anemia (34.3%), hypersensitivity reactions (20.2%) and gastrointestinal intolerance (13.1%). The most frequent ARV regimen type was the protease inhibitors-based regimen (59.6%), but zidovudine was the ARV most linked to ADRs (41.4%). The regression analysis showed increased risk of ADRs in singles and students in the univariate analysis and heterosexuals and homosexuals in multivariate analysis; and decreased risk in active workers. The present work shows the high prevalence of ADRs in the studied population and represents the first case-based study that describes the pharmacoepidemiology of a cohort of HIV-positive patients treated in Venezuela.

  3. Enhanced electrocatalytic activity of MoSx on TCNQ-treated electrode for hydrogen evolution reaction

    KAUST Repository

    Chang, Yunghuang

    2014-10-22

    Molybdenum sulfide has recently attracted much attention because of its low cost and excellent catalytical effects in the application of hydrogen evolution reaction (HER). To improve the HER efficiency, many researchers have extensively explored various avenues such as material modification, forming hybrid structures or modifying geometric morphology. In this work, we reported a significant enhancement in the electrocatalytic activity of the MoSx via growing on Tetracyanoquinodimethane (TCNQ) treated carbon cloth, where the MoSx was synthesized by thermolysis from the ammonium tetrathiomolybdate ((NH4)2MoS4) precursor at 170 °C. The pyridinic N- and graphitic N-like species on the surface of carbon cloth arising from the TCNQ treatment facilitate the formation of Mo5+ and S2 2- species in the MoSx, especially with S2 2- serving as an active site for HER. In addition, the smaller particle size of the MoSx grown on TCNQ-treated carbon cloth reveals a high ratio of edge sites relative to basal plane sites, indicating the richer effective reaction sites and superior electrocatalytic characteristics. Hence, we reported a high hydrogen evolution rate for MoSx on TCNQ-treated carbon cloth of 6408 mL g-1 cm-2 h-1 (286 mmol g-1 cm-2 h-1) at an overpotential of V = 0.2 V. This study provides the fundamental concepts useful in the design and preparation of transition metal dichalcogenide catalysts, beneficial in the development in clean energy.

  4. The association of pathergy reaction and active clinical presentations of Behçet’s disease

    Directory of Open Access Journals (Sweden)

    Shirin Assar

    2017-04-01

    Full Text Available Objectives : The pathergy skin test is a hypersensitivity reaction to a prick skin trauma caused by a pin or a needle, which is considered as a specific presentation in Behçet’s disease (BD and the precise mechanism of this test is not well elucidated. This study was designed to evaluate the association of pathergy reaction (PR with the active clinical manifestations of BD patients, to assess the clinical importance of PR. Materials and methods : This was a cohort study on 1675 BD patients who fulfilled the entry criteria based on the International Criteria for Behçet’s Disease (ICBD from 1975 to 2011. The patients were divided into two groups; the pathergy positive group included 841 patients (50.2% and the pathergy negative group 834 patients (49.8%. The active mucocutaneous and systemic disease manifestations were analyzed according to the presence of the PR. The odds ratio and 95% confidence interval (95% CI were calculated for each item. Results : In this study, 841 patients (50.2% had a positive pathergy test. Patient’s mean age and mean disease duration were similar in the two groups (pathergy positive and pathergy negative patients. There was no association between positive pathergy test and age of patients, or disease duration. The PR was associated with male gender (p = 0.013, oral aphthosis (p < 0.001, pseudofolliculitis (p < 0.001, anterior uveitis (p = 0.001 and posterior uveitis (p = 0.028. Conclusions : The presence of PR was associated with male gender, as well as some of mucocutaneous manifestations and uveitis in adult patients. There was no association with retinitis and vascular involvements. PR isn’t associated with the severity of the disease.

  5. DETECTION OF PHENOL DEGRADING BACTERIA AND PSEUDOMONAS PUTIDA IN ACTIVATED SLUDGE BY POLYMERASE CHAIN REACTION

    Directory of Open Access Journals (Sweden)

    H. Movahedyan ، H. Khorsandi ، R. Salehi ، M. Nikaeen

    2009-04-01

    Full Text Available Phenol is one of the organic pollutants in various industrial wastewaters especially petrochemical and oil refining. Biological treatment is one of the considerable choices for removing of phenol present in these wastewaters. Identification of effective microbial species is considered as one of the important priorities for production of the biomass in order to achieve desirable kinetic of biological reactions. Basic purpose of this research is identification of phenol-degrading Pseudomonas Putida in activated sludge by polymerase chain reaction (PCR that has high speed and specificity. In this research, 10 various colonies of phenol-degrading bacteria were isolated from municipal activated sludge and the rate of phenol removal and growth rate of these bacteria were assessed in different concentrations of phenol (200 – 900 mg/L. Confirmation of the largest subunit of multicomponent phenol hydroxylase (LmPH gene and gene coding the N fragment in Pseudomonas Putida-derived methyl phenol operon (DmpN gene through PCR were used for general identification of phenol-degrading bacteria and Pseudomonas Putida, respectively. Presence of a 600 bp (base pairs bond in all of isolated strains indicated that they contain phenol hydroxylase gene. 6 of 10 isolated bacteria were Pseudomonas Putida because they produced a 199 bp PCR product by DmpN primers. According to PCR results in this study, the best phenol-degrading bacteria that can utilize 500 – 600 mg/L phenol completely after 48 hours incubation, belong to Pseudomonas Putida strains. It is clear that use of isolated bacteria can lead to considerable decrease of treatment time as well as promotion of phenol removal rate.

  6. Reaction pathway and oxidation mechanisms of dibutyl phthalate by persulfate activated with zero-valent iron

    Energy Technology Data Exchange (ETDEWEB)

    Li, Huanxuan [School of Environment and Energy, South China University of Technology, Guangzhou 510006 (China); The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, China, Guangzhou 510640 (China); Wan, Jinquan, E-mail: ppjqwan@scut.edu.cn [School of Environment and Energy, South China University of Technology, Guangzhou 510006 (China); The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, China, Guangzhou 510640 (China); State Key Lab Pulp and Paper Engineering, South China University of Technology, Guangzhou 510640 (China); Ma, Yongwen [School of Environment and Energy, South China University of Technology, Guangzhou 510006 (China); The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, China, Guangzhou 510640 (China); State Key Lab Pulp and Paper Engineering, South China University of Technology, Guangzhou 510640 (China); Wang, Yan [School of Environment and Energy, South China University of Technology, Guangzhou 510006 (China); The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, China, Guangzhou 510640 (China)

    2016-08-15

    This study investigated reaction pathway and oxidation mechanisms of dibutyl phthalate (DBP) by persulfate (PS) activated with zero-valent iron (ZVI). The DBP degradation was studied at three pH values (acidic, neutral and basic) in the presence of different organic scavengers. Using a chemical probe method, both sulfate radical (SO{sub 4}·{sup −}) and hydroxyl radical (·OH) were found to be primary oxidants at pH 3.0 and pH 7.0, respectively while ·OH was the major specie to oxidize DBP at pH 11.0. A similar result was found in an experiment of Electron Spin Resonance spin-trapping where in addition to ·OH, superoxide radical (O{sub 2}·{sup −}) was detected at pH 11.0. The transformation of degradation products including dimethyl phthalate (DMP), diethyl phthalate (DEP), phthalic anhydride, and acetophenone exhibited diverse variation during the reaction processes. The phthalic anhydride concentration appeared to be maximum at all pHs. Another eleven intermediate products were also found at pH 3.0 by GC–MS and HPLC analysis, and their degradation mechanisms and pathways were proposed. It was suggested that dealkylation, hydroxylation, decarboxylation and hydrogen extraction were the dominant degradation mechanisms of DBP at pH 3.0. - Highlights: • Both SO{sub 4}{sup −}· and ·OH were found to be the major active species at pH 3.0 and pH 7.0. • ·OH and ·O2– were the primary oxidants pH 11.0. • The intermediate products were investigated as well as the degradation pathway. • Dealkylation, hydroxylation, decarboxylation, H-extraction were the major mechanisms.

  7. Temporal evolution of oscillatory activity predicts performance in a choice-reaction time reaching task.

    Science.gov (United States)

    Perfetti, Bernardo; Moisello, Clara; Landsness, Eric C; Kvint, Svetlana; Pruski, April; Onofrj, Marco; Tononi, Giulio; Ghilardi, M Felice

    2011-01-01

    In this study, we characterized the patterns and timing of cortical activation of visually guided movements in a task with critical temporal demands. In particular, we investigated the neural correlates of motor planning and on-line adjustments of reaching movements in a choice-reaction time task. High-density electroencephalography (EEG, 256 electrodes) was recorded in 13 subjects performing reaching movements. The topography of the movement-related spectral perturbation was established across five 250-ms temporal windows (from prestimulus to postmovement) and five frequency bands (from theta to beta). Nine regions of interest were then identified on the scalp, and their activity was correlated with specific behavioral outcomes reflecting motor planning and on-line adjustments. Phase coherence analysis was performed between selected sites. We found that motor planning and on-line adjustments share similar topography in a fronto-parietal network, involving mostly low frequency bands. In addition, activities in the high and low frequency ranges have differential function in the modulation of attention with the former reflecting the prestimulus, top-down processes needed to promote timely responses, and the latter the planning and control of sensory-motor processes.

  8. Oxygen Reduction Reaction Activity and Durability of Pt Catalysts Supported on Titanium Carbide

    Directory of Open Access Journals (Sweden)

    Morio Chiwata

    2015-06-01

    Full Text Available We have prepared Pt nanoparticles supported on titanium carbide (TiC (Pt/TiC as an alternative cathode catalyst with high durability at high potentials for polymer electrolyte fuel cells. The Pt/TiC catalysts with and without heat treatment were characterized by X-ray diffraction (XRD, X-ray photoelectron spectroscopy (XPS, and transmission electron microscopy (TEM. Hemispherical Pt nanocrystals were found to be dispersed uniformly on the TiC support after heat treatment at 600 °C in 1% H2/N2 (Pt/TiC-600 °C. The electrochemical properties (cyclic voltammetry, electrochemically active area (ECA, and oxygen reduction reaction (ORR activity of Pt/TiC-600 °C and a commercial Pt/carbon black (c-Pt/CB were evaluated by the rotating disk electrode (RDE technique in 0.1 M HClO4 solution at 25 °C. It was found that the kinetically controlled mass activity for the ORR on Pt/TiC-600 °C at 0.85 V (507 A g−1 was comparable to that of c-Pt/CB (527 A g−1. Moreover, the durability of Pt/TiC-600 °C examined by a standard potential step protocol (E = 0.9 V↔1.3 V vs. RHE, holding 30 s at each E was much higher than that for c-Pt/CB.

  9. Calcium-dependent protein kinases responsible for the phosphorylation of a bZIP transcription factor FD crucial for the florigen complex formation.

    Science.gov (United States)

    Kawamoto, Nozomi; Sasabe, Michiko; Endo, Motomu; Machida, Yasunori; Araki, Takashi

    2015-02-09

    Appropriate timing of flowering is critical for reproductive success and necessarily involves complex genetic regulatory networks. A mobile floral signal, called florigen, is a key molecule in this process, and flowering locus T (FT) protein is its major component in Arabidopsis. FT is produced in leaves, but promotes the floral transition in the shoot apex, where it forms a complex with a basic region/leucine-zipper (bZIP) transcription factor, FD. Formation of the florigen complex depends on the supposed phosphorylation of FD; hitherto, however, the responsible protein kinase(s) have not been identified. In this study, we prepared protein extracts from shoot apices of plants around the floral transition, and detected a protein kinase activity that phosphorylates a threonine residue at position 282 of FD (FD T282), which is a crucial residue for the complex formation with FT via 14-3-3. The kinase activity was calcium-dependent. Subsequent biochemical, cellular, and genetic analyses showed that three calcium-dependent protein kinases (CDPKs) efficiently phosphorylate FD T282. Two of them (CPK6 and CPK33) are expressed in shoot apical meristem and directly interact with FD, suggesting they have redundant functions. The loss of function of one CDPK (CPK33) resulted in a weak but significant late-flowering phenotype.

  10. Rabring7 Degrades c-Myc through Complex Formation with MM-1

    Science.gov (United States)

    Torii, Ayako; Tashiro, Erika; Miyazawa, Makoto; Ariga, Hiroyoshi; Iguchi-Ariga, Sanae M. M.

    2012-01-01

    We have reported that a novel c-Myc-binding protein, MM-1, repressed E-box-dependent transcription and transforming activities of c-Myc and that a mutation of A157R in MM-1, which is often observed in patients with leukemia or lymphoma, abrogated all of the repressive activities of MM-1 toward c-Myc, indicating that MM-1 is a novel tumor suppressor. MM-1 also binds to the ubiquitin-proteasome system, leading to degradation of c-Myc. In this study, we identified Rabring7, a Rab7-binding and RING finger-containing protein, as an MM-1-binding protein, and we found that Rabring7 mono-ubiquitinated MM-1 in the cytoplasm without degradation of MM-1. Rabring7 was also found to bind to c-Myc and to ubiquitinate c-Myc in a threonine 58-dependent manner. When c-Myc was co-transfected with MM-1 and Rabring7, c-Myc was degraded. Furthermore, it was found that c-Myc was stabilized in MM-1-knockdown cells even when Rabring7 was transfected and that Rabring7 was bound to and co-localized with MM-1 and c-Myc after MM-1 and Rabring7 had been translocated from the cytoplasm to the nucleus. These results suggest that Rabring7 stimulates c-Myc degradation via mono-ubiquitination of MM-1. PMID:22844532

  11. Rabring7 degrades c-Myc through complex formation with MM-1.

    Directory of Open Access Journals (Sweden)

    Rina Narita

    Full Text Available We have reported that a novel c-Myc-binding protein, MM-1, repressed E-box-dependent transcription and transforming activities of c-Myc and that a mutation of A157R in MM-1, which is often observed in patients with leukemia or lymphoma, abrogated all of the repressive activities of MM-1 toward c-Myc, indicating that MM-1 is a novel tumor suppressor. MM-1 also binds to the ubiquitin-proteasome system, leading to degradation of c-Myc. In this study, we identified Rabring7, a Rab7-binding and RING finger-containing protein, as an MM-1-binding protein, and we found that Rabring7 mono-ubiquitinated MM-1 in the cytoplasm without degradation of MM-1. Rabring7 was also found to bind to c-Myc and to ubiquitinate c-Myc in a threonine 58-dependent manner. When c-Myc was co-transfected with MM-1 and Rabring7, c-Myc was degraded. Furthermore, it was found that c-Myc was stabilized in MM-1-knockdown cells even when Rabring7 was transfected and that Rabring7 was bound to and co-localized with MM-1 and c-Myc after MM-1 and Rabring7 had been translocated from the cytoplasm to the nucleus. These results suggest that Rabring7 stimulates c-Myc degradation via mono-ubiquitination of MM-1.

  12. Automatic Activity and Reaction Time in Relation to Extraversion and Behavioral Impulsivity in Children and Adolescents.

    Science.gov (United States)

    Zahn, Theodore P.; And Others

    1994-01-01

    Forty-five children and adolescents had skin conductance recorded during a presentation of tones and a reaction time test and were assessed for extraversion. Found that extraversion was negatively correlated with skin conductance response magnitudes to all stimuli--somewhat more strongly for reaction-time stimuli--and with reaction time. (HTH)

  13. Synthesis and anti-inflammatory activity of 3-indolyl pyridine derivatives through one-pot multi component reaction

    Indian Academy of Sciences (India)

    Prakasam Thirumurugan; S Mahalaxmi; Paramasivan T Perumal

    2010-11-01

    A simple protocol for the efficient preparation of 2-(1-Indol-3-yl)-6-methoxy-4-arylpyridine-3,5-dicarbonitrile has been achieved through one-pot multi-component reaction under reflux condition. These compounds showed a good anti-inflammatory activity. Also a series of bis-Hantzsch dihydropyridine derivatives were synthesized and they exhibit analgesic activity.

  14. Activation of the inflammatory reaction within minutes after birth in ventilated preterm lambs with neonatal respiratory distress syndrome

    NARCIS (Netherlands)

    Jaarsma, AS; Geven, WB; van Oeveren, W; Oetomo, SB

    2004-01-01

    To study the activation of the inflammatory reaction within minutes after birth, we measured parameters of inflammation before and immediately after birth. To assess whether respiratory distress syndrome (RDS) or birth itself initiates activation, we compared preterm ventilated lambs with term nonve

  15. Activation of the inflammatory reaction within minutes after birth in ventilated preterm lambs with neonatal respiratory distress syndrome

    NARCIS (Netherlands)

    Jaarsma, AS; Geven, WB; van Oeveren, W; Oetomo, SB

    2004-01-01

    To study the activation of the inflammatory reaction within minutes after birth, we measured parameters of inflammation before and immediately after birth. To assess whether respiratory distress syndrome (RDS) or birth itself initiates activation, we compared preterm ventilated lambs with term

  16. Estimating youth locomotion ground reaction forces using an accelerometer-based activity monitor.

    Directory of Open Access Journals (Sweden)

    Jennifer M Neugebauer

    Full Text Available To address a variety of questions pertaining to the interactions between physical activity, musculoskeletal loading and musculoskeletal health/injury/adaptation, simple methods are needed to quantify, outside a laboratory setting, the forces acting on the human body during daily activities. The purpose of this study was to develop a statistically based model to estimate peak vertical ground reaction force (pVGRF during youth gait. 20 girls (10.9 ± 0.9 years and 15 boys (12.5 ± 0.6 years wore a Biotrainer AM over their right hip. Six walking and six running trials were completed after a standard warm-up. Average AM intensity (g and pVGRF (N during stance were determined. Repeated measures mixed effects regression models to estimate pVGRF from Biotrainer activity monitor acceleration in youth (girls 10-12, boys 12-14 years while walking and running were developed. Log transformed pVGRF had a statistically significant relationship with activity monitor acceleration, centered mass, sex (girl, type of locomotion (run, and locomotion type-acceleration interaction controlling for subject as a random effect. A generalized regression model without subject specific random effects was also developed. The average absolute differences between the actual and predicted pVGRF were 5.2% (1.6% standard deviation and 9% (4.2% standard deviation using the mixed and generalized models, respectively. The results of this study support the use of estimating pVGRF from hip acceleration using a mixed model regression equation.

  17. Reactions of Yttrium-Carbon Bonds with Active Hydrogen-Containing Molecules. A Useful Synthetic Method for Permethylyttrocene Derivatives

    NARCIS (Netherlands)

    Haan, Klaas H. den; Wielstra, Ytsen; Teuben, Jan H.

    1987-01-01

    Reactions of the permethylyttrocene compounds Cp*2YCH(SiMe3)2 (1) and Cp*2YMe·THF (2) with a variety of active hydrogen-containing substrates are reported. With HCl the known complexes (Cp*2YCl)2 and Cp*2YCl·THF are formed. Reaction with 2,4-pentadione gives Cp*2Y(acac) (3). Alcoholysis of 1 in Et2O

  18. Effect of pH and chemical mechanical planarization process conditions on the copper-benzotriazole complex formation

    Science.gov (United States)

    Cho, Byoung-Jun; Kim, Jin-Yong; Hamada, Satomi; Shima, Shohei; Park, Jin-Goo

    2016-06-01

    Benzotriazole (BTA) has been used to protect copper (Cu) from corrosion during Cu chemical mechanical planarization (CMP) processes. However, an undesirable Cu-BTA complex is deposited after Cu CMP processes and it should be completely removed at post-Cu CMP cleaning for next fabrication process. Therefore, it is very important to understand of Cu-BTA complex formation behavior for its applications such as Cu CMP and post-Cu CMP cleaning. The present study investigated the effect of pH and polisher conditions on the formation of Cu-BTA complex layers using electrochemical techniques (potentiodynamic polarization and electrochemical impedance spectroscopy) and the surface contact angle. The wettability was not a significant factor for the polishing interface, as no difference in the contact angles was observed for these processes. Both electrochemical techniques revealed that BTA had a unique advantage of long-term protection for Cu corrosion in an acidic condition (pH 3).

  19. Protons and Mg2+ cations as probes in investigating the role of GTP in initiation complex formation.

    Science.gov (United States)

    Beaudry, P; Begard, E; Douzou, P; Grunberg-Manago, M

    1978-12-01

    fMet-tRNAfMet binding to both 30-S subunits and to 70-S particles is dependent on both pH AND Mg2+ concentration: for fMet-tRNAfMet binding to 70-S particles, variations of pH and Mg2+ concentration are tightly interdependent. This behavior can be interpreted by the polyelectrolyte theory as a direct consequence of the fact that the binding occurs in a polyanionic micro-environment. The pH-dependent binding to 70-S particles clearly shows the involvement of two prototropic groups which appear to be those carrying out GTP hydrolysis, therefore directly linked to initiation complex formation; in the presence of a non-hydrolyzable analogue to GTP, guanosine 5'-[beta, gamma-imido]triphosphate, the binding of fMet-tRNAfMet shows much less interdependence between variation of pH and Mg2+ concentration.

  20. Expression of a kinase-dead form of CPK33 involved in florigen complex formation causes delayed flowering.

    Science.gov (United States)

    Kawamoto, Nozomi; Endo, Motomu; Araki, Takashi

    2015-01-01

    Regulation of flowering time is crucial for reproductive success of plants. FLOWERING LOCUS T (FT) protein is a central component of florigen and forms a ternary complex with 14-3-3 and FD, a basic leucine zipper transcription factor, in the shoot apex and promotes flowering. This complex formation requires phosphorylation of threonine residue at position 282 of FD. A calcium-dependent protein kinase CPK33 is responsible for the phosphorylation. However, possibly due to functional redundancy among calcium-dependent protein kinases, impact of the loss of CPK33 reported in the previous study was rather limited. Here, we report that expression of a kinase-dead form of CPK33 caused a clear delayed-flowering phenotype, supporting for an important role of CPK33 in florigen function through FD phosphorylation.

  1. Complex formation of CdSe/ZnS/TOPO nanocrystal vs. molecular chaperone in aqueous solution by hydrophobic interaction

    Energy Technology Data Exchange (ETDEWEB)

    Horiuchi, Hiromi [Department of Applied Physics, Tokyo University of Agriculture and Technology, Naka-cho 2-24-16, Kogane-i, Tokyo 184-8588 (Japan)]. E-mail: horihiro@cc.tuat.ac.jp; Iwami, Noriya [Department of Applied Physics, Tokyo University of Agriculture and Technology, Naka-cho 2-24-16, Kogane-i, Tokyo 184-8588 (Japan); Tachibana, Fumi [Department of Applied Physics, Tokyo University of Agriculture and Technology, Naka-cho 2-24-16, Kogane-i, Tokyo 184-8588 (Japan); Ohtaki, Akashi [Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, Naka-cho 2-24-16, Kogane-i, Tokyo 184-8588 (Japan); Iizuka, Ryo [Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, Naka-cho 2-24-16, Kogane-i, Tokyo 184-8588 (Japan); Zako, Tamotsu [Bioengineering Laboratory, RIKEN - Institute of Physical and Chemical Research, 2-1, Hirosawa, Wako, Saitama 351-0198 (Japan); Oda, Masaru [Department of Applied Physics, Tokyo University of Agriculture and Technology, Naka-cho 2-24-16, Kogane-i, Tokyo 184-8588 (Japan); Strategic Research Initiative for Future Nano-Science and Technology, Tokyo University of Agriculture and Technology, Naka-cho 2-24-16, Kogane-i, Tokyo 184-8588 (Japan); Yohda, Masafumi [Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, Naka-cho 2-24-16, Kogane-i, Tokyo 184-8588 (Japan); Strategic Research Initiative for Future Nano-Science and Technology, Tokyo University of Agriculture and Technology, Naka-cho 2-24-16, Kogane-i, Tokyo 184-8588 (Japan); Tani, Toshiro [Department of Applied Physics, Tokyo University of Agriculture and Technology, Naka-cho 2-24-16, Kogane-i, Tokyo 184-8588 (Japan); Strategic Research Initiative for Future Nano-Science and Technology, Tokyo University of Agriculture and Technology, Naka-cho 2-24-16, Kogane-i, Tokyo 184-8588 (Japan)

    2007-11-15

    Feasibilities to stabilize CdSe/ZnS/trioctylphosphineoxide (TOPO) nanocrystals (quantum dots, QDs) in aqueous solutions with prefoldin macromolecules in their bioactive states are reported. Prefoldin is a jellyfish-shaped hexameric co-chaperone of the group II chaperonins. As a protein folding intermediate is captured within its central cavity, so CdSe/ZnS/TOPO QDs would also be included within this cavity. It is also found the QDs can be much more dispersed in aqueous solutions and suspended for certain period of time by adding trace amount of t-butanol in the buffer prior to the mixing of the QDs mother solution. While biochemical procedures are evaluated with ordinary fluorescence measurements, possible complex formations are also evaluated with TIRFM single-molecule detection techniques.

  2. Near-infrared light controlled photocatalytic activity of carbon quantum dots for highly selective oxidation reaction.

    Science.gov (United States)

    Li, Haitao; Liu, Ruihua; Lian, Suoyuan; Liu, Yang; Huang, Hui; Kang, Zhenhui

    2013-04-21

    Selective oxidation of alcohols is a fundamental and significant transformation for the large-scale production of fine chemicals, UV and visible light driven photocatalytic systems for alcohol oxidation have been developed, however, the long wavelength near infrared (NIR) and infrared (IR) light have not yet fully utilized by the present photocatalytic systems. Herein, we reported carbon quantum dots (CQDs) can function as an effective near infrared (NIR) light driven photocatalyst for the selective oxidation of benzyl alcohol to benzaldehyde. Based on the NIR light driven photo-induced electron transfer property and its photocatalytic activity for H2O2 decomposition, this metal-free catalyst could realize the transformation from benzyl alcohol to benzaldehyde with high selectivity (100%) and conversion (92%) under NIR light irradiation. HO˙ is the main active oxygen specie in benzyl alcohol selective oxidative reaction confirmed by terephthalic acid photoluminescence probing assay (TA-PL), selecting toluene as the substrate. Such metal-free photocatalytic system also selectively converts other alcohol substrates to their corresponding aldehydes with high conversion, demonstrating a potential application of accessing traditional alcohol oxidation chemistry.

  3. Teaching reactions and stoichiometry: A comparison of guided inquiry and traditional laboratory activities

    Science.gov (United States)

    Meister Thomas, Lynn

    There is a major movement in science education towards the inclusion of science inquiry and process. Guided-inquiry instruction is expected to have a positive impact on students' concrete and conceptual knowledge along with their ability to engage in the practices of science. This study examined the impact of inquiry-based teaching on student achievement. The topics of reactions and stoichiometry were taught in two different periods of first-year secondary honors chemistry. Both classes received the same lectures and assignments for this curriculum and both classes performed the same laboratory activities. However, one class received traditional, step-by-step (often called "cookbook") laboratory instructions while the other class developed their own procedures and made decisions about data to complete the laboratory activities. Pre- and post-tests were given to each class, followed by a test of retention after ten weeks. The results of this study indicate that inquiry-based instruction has a positive impact on student achievement. A significant increase between pre- and post- test scores for the experimental group as opposed to the scores for the control group suggests that achievement was correlated with guided inquiry instruction methods. Additionally, a notable trend suggested that guided inquiry instruction has a positive effect on learning retention.

  4. Solvation mechanisms of nedocromil sodium from activation energy and reaction enthalpy measurements of dehydration and dealcoholation.

    Science.gov (United States)

    Richards, Alison C; McColm, Ian J; Harness, J Barrie

    2002-04-01

    Two independent athermal methods of analysis have been used to determine the activation energies associated with the dehydration of nedocromil sodium hydrates. For the highest temperature reaction, monohydrate to the anhydrate, the differences in the measured activation energies indicate a three-dimensional nucleation mechanism in the bulk of the crystal with subsequent three-dimensional anhydrate crystal growth. The number of critical nuclei varies inversely with heating rate. Measured enthalpy values for successive removal of water molecules at 31.7 +/- 1.0, 91.3 +/- 0.8, and 193 +/- 0.6 degrees C are the same, within experimental error, at 21.6 +/- 2.6 kJ (mol H(2)O)(-1), as determined from differential thermal analysis traces. This result implies that an earlier concept of "strong" and "weak" water binding is not relevant and temperatures at which H(2)O molecules are removed is related to nucleation effects and not bond energies. The low temperature shoulder on the 91.3 degrees C peak is identified as an effect arising from open pan analysis conditions. The appearance of "transient" peaks in the conditioning stage of nedocromil sodium trihydrate thermal analysis experiments have been investigated and an explanation based on the presence of alcoholates [(NS)(4) small middle dot 5CH(3)OH, (NS)(5) small middle dot 9C(2)H(5)OH, and (NS)(2) small middle dot C(3)H(7)OH] in the preparations is proposed.

  5. In vivo protein interactions and complex formation in the Pectobacterium atrosepticum subtype I-F CRISPR/Cas System.

    Directory of Open Access Journals (Sweden)

    Corinna Richter

    Full Text Available Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR and their associated proteins (Cas; CRISPR associated are a bacterial defense mechanism against extra-chromosomal elements. CRISPR/Cas systems are distinct from other known defense mechanisms insofar as they provide acquired and heritable immunity. Resistance is accomplished in multiple stages in which the Cas proteins provide the enzymatic machinery. Importantly, subtype-specific proteins have been shown to form complexes in combination with small RNAs, which enable sequence-specific targeting of foreign nucleic acids. We used Pectobacterium atrosepticum, a plant pathogen that causes soft-rot and blackleg disease in potato, to investigate protein-protein interactions and complex formation in the subtype I-F CRISPR/Cas system. The P. atrosepticum CRISPR/Cas system encodes six proteins: Cas1, Cas3, and the four subtype specific proteins Csy1, Csy2, Csy3 and Cas6f (Csy4. Using co-purification followed by mass spectrometry as well as directed co-immunoprecipitation we have demonstrated complex formation by the Csy1-3 and Cas6f proteins, and determined details about the architecture of that complex. Cas3 was also shown to co-purify all four subtype-specific proteins, consistent with its role in targeting. Furthermore, our results show that the subtype I-F Cas1 and Cas3 (a Cas2-Cas3 hybrid proteins interact, suggesting a protein complex for adaptation and a role for subtype I-F Cas3 proteins in both the adaptation and interference steps of the CRISPR/Cas mechanism.

  6. In vivo protein interactions and complex formation in the Pectobacterium atrosepticum subtype I-F CRISPR/Cas System.

    Science.gov (United States)

    Richter, Corinna; Gristwood, Tamzin; Clulow, James S; Fineran, Peter C

    2012-01-01

    Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) and their associated proteins (Cas; CRISPR associated) are a bacterial defense mechanism against extra-chromosomal elements. CRISPR/Cas systems are distinct from other known defense mechanisms insofar as they provide acquired and heritable immunity. Resistance is accomplished in multiple stages in which the Cas proteins provide the enzymatic machinery. Importantly, subtype-specific proteins have been shown to form complexes in combination with small RNAs, which enable sequence-specific targeting of foreign nucleic acids. We used Pectobacterium atrosepticum, a plant pathogen that causes soft-rot and blackleg disease in potato, to investigate protein-protein interactions and complex formation in the subtype I-F CRISPR/Cas system. The P. atrosepticum CRISPR/Cas system encodes six proteins: Cas1, Cas3, and the four subtype specific proteins Csy1, Csy2, Csy3 and Cas6f (Csy4). Using co-purification followed by mass spectrometry as well as directed co-immunoprecipitation we have demonstrated complex formation by the Csy1-3 and Cas6f proteins, and determined details about the architecture of that complex. Cas3 was also shown to co-purify all four subtype-specific proteins, consistent with its role in targeting. Furthermore, our results show that the subtype I-F Cas1 and Cas3 (a Cas2-Cas3 hybrid) proteins interact, suggesting a protein complex for adaptation and a role for subtype I-F Cas3 proteins in both the adaptation and interference steps of the CRISPR/Cas mechanism.

  7. THE PRINCIPLES OF POWER-RISE BUILDINGS COMPLEXES FORMATION USING WIND ENERGY

    Directory of Open Access Journals (Sweden)

    NEVGAMONNIY G. U.

    2015-11-01

    Full Text Available Raising of problem. The methodology of designing energy-efficient tower building should be based on systematic analysis of the building as a unified energy system. The prominent architect Norman Foster (Sir Norman Foster writes: "Architects cannot solve all the world's environmental problems, but we can design buildings that require only a fraction of current energy consumption, in addition, through proper urban planning we can affect traffic flows. The location and functionality of buildings, its structural flexibility and technological resources, orientation, shape and structure, heating and ventilation characteristics used in the construction materials - all these parameters affect the amount of energy required for the construction, operation and maintenance of the building, and as for transportation, moving to it and from it" [1]. Purpose. The purpose of the study is scientific justification principles of architectural formation decisions of the power-rise energy efficient complexes and developing methods of architectural design of PRBC using wind energy. To develop the science-based principles forming the architectural buildings with the use of alternative energy and determine the specific features of the architectural design of buildings. Conclusion. The principles of architectural forming in the use of wind power and identify possible trends for the development of buildings with integrated wind installations. Polyfunctional wind power plants are in special properties of certain material and structural elements of the building structure, improve aerodynamic performance of the outer shell and therefore wind energy devices. Thus, the power efficiency of energy active building depends on its space solutions.

  8. ParB Partition Proteins: Complex Formation and Spreading at Bacterial and Plasmid Centromeres

    Directory of Open Access Journals (Sweden)

    Barbara Funnell

    2016-08-01

    Full Text Available In bacteria, active partition systems contribute to the faithful segregation of both chromosomes and low-copy-number plasmids. Each system depends on a site-specific DNA binding protein to recognize and assemble a partition complex at a centromere-like site, commonly called parS. Many plasmid and all chromosomal centromere-binding proteins are dimeric helix-turn-helix DNA binding proteins, which are commonly named ParB. Although the overall sequence conservation among ParBs is not high, the proteins share similar domain and functional organization, and they assemble into similar higher-order complexes. In vivo, ParBs spread; that is, DNA binding extends away from the parS site into the surrounding nonspecific DNA, a feature that reflects higher-order complex assembly. ParBs bridge and pair DNA at parS and nonspecific DNA sites. ParB dimers interact with each other via flexible conformations of an N-terminal region. This review will focus on the properties of the HTH centromere-binding protein, in light of recent experimental evidence and models that are adding to our understanding of how these proteins assemble into large and dynamic partition complexes at and around their specific DNA sites.

  9. Dynamic Modelling Reveals 'Hotspots' on the Pathway to Enzyme-Substrate Complex Formation.

    Directory of Open Access Journals (Sweden)

    Shane E Gordon

    2016-03-01

    Full Text Available Dihydrodipicolinate synthase (DHDPS catalyzes the first committed step in the diaminopimelate pathway of bacteria, yielding amino acids required for cell wall and protein biosyntheses. The essentiality of the enzyme to bacteria, coupled with its absence in humans, validates DHDPS as an antibacterial drug target. Conventional drug design efforts have thus far been unsuccessful in identifying potent DHDPS inhibitors. Here, we make use of contemporary molecular dynamics simulation and Markov state models to explore the interactions between DHDPS from the human pathogen Staphylococcus aureus and its cognate substrate, pyruvate. Our simulations recover the crystallographic DHDPS-pyruvate complex without a priori knowledge of the final bound structure. The highly conserved residue Arg140 was found to have a pivotal role in coordinating the entry of pyruvate into the active site from bulk solvent, consistent with previous kinetic reports, indicating an indirect role for the residue in DHDPS catalysis. A metastable binding intermediate characterized by multiple points of intermolecular interaction between pyruvate and key DHDPS residue Arg140 was found to be a highly conserved feature of the binding trajectory when comparing alternative binding pathways. By means of umbrella sampling we show that these binding intermediates are thermodynamically metastable, consistent with both the available experimental data and the substrate binding model presented in this study. Our results provide insight into an important enzyme-substrate interaction in atomistic detail that offers the potential to be exploited for the discovery of more effective DHDPS inhibitors and, in a broader sense, dynamic protein-drug interactions.

  10. The Protein Kingdom Extended: Ordered and Intrinsically Disordered Proteins, Their Folding, Supramolecular Complex Formation, and Aggregation

    Science.gov (United States)

    Turoverov, Konstantin K.; Kuznetsova, Irina M.; Uversky, Vladimir N.

    2010-01-01

    The native state of a protein is usually associated with a compact globular conformation possessing a rigid and highly ordered structure. At the turn of the last century certain studies arose which concluded that many proteins cannot, in principle, form a rigid globular structure in an aqueous environment, but they are still able to fulfill their specific functions — i.e., they are native. The existence of the disordered regions allows these proteins to interact with their numerous binding partners. Such interactions are often accompanied by the formation of complexes that possess a more ordered structure than the original components. The functional diversity of these proteins, combined with the variability of signals related to the various intra-and intercellular processes handled by these proteins and their capability to produce multi-variant and multi-directional responses allow them to form a unique regulatory net in a cell. The abundance of disordered proteins inside the cell is precisely controlled at the synthesis and clearance levels as well as via interaction with specific binding partners and posttranslational modifications. Another recently recognized biologically active state of proteins is the functional amyloid. The formation of such functional amyloids is tightly controlled and therefore differs from the uncontrolled formation of pathogenic amyloids which are associated with the pathogenesis of several conformational diseases, the development of which is likely to be determined by the failures of the cellular regulatory systems rather than by the formation of the proteinaceous deposits and/or by the protofibril toxicity. PMID:20097220

  11. Investigation of vesicle-capsular plague antigen complex formation by elastic laser radiation scattering

    Science.gov (United States)

    Guseva, N. P.; Maximova, Irina S.; Romanov, Sergey V.; Shubochkin, L. P.; Tatarintsev, Sergey N.

    1991-05-01

    Recently a great deal of attention has been given to the investigation artificial lipid liposomes, due to their application as "containers" for directed transport of biologically active compounds into particular cells, organs and tissues for prophylaxis and therapy of infectious diseases. The use of traditional methods of liposome investigation, such as sedimentation, electrophoresis and chromatography is impeded by low liposome resistivity to different deformations. In conjunction with this, optical methods of laser light scattering are promising as they allow nondisturbing, precise and quick investigations. This paper describes the investigation of vesicle systems prepared from egg lecithin of Serva Corporation and their complexes with the capsular antigen of the plague microbe. The capsular antigen Fl was obtained from EV plague microbe grown at 37° C on Huttinger agar. Fl was isolated by gel-filtration on ASA-22 followed by freeze drying of the preparation. Angular dependences of polarized radiation scattering were measured for several liposome suspension samples in a saline solution before and after the interaction with the plague microbe capsular antigen. The aim of the investigation was to analyze the nature of mutual antigen arrangement in a liposome and to develop methods for measuring its inclusion percentage.

  12. Improving the electrocatalytic performance of carbon nanotubes for VO2+/VO2+ redox reaction by KOH activation

    Science.gov (United States)

    Dai, Lei; Jiang, Yingqiao; Meng, Wei; Zhou, Huizhu; Wang, Ling; He, Zhangxing

    2017-04-01

    In this paper, carbon nanotubes (CNTs) was activated by KOH treatment at high temperature and investigated as catalyst for VO2+/VO2+ redox reaction for vanadium redox flow battery (VRFB). X-ray photoelectron spectroscopy results suggest that the oxygen-containing groups can be introduced on CNTs by KOH activation. The mass transfer of vanadium ions can be accelerated by chemical etching by KOH activation and improved wettability due to the introduction of hydrophilic groups. The electrochemical properties of VO2+/VO2+ redox reaction can be enhanced by introduced oxygen-containing groups as active sites. The sample treated at 900 °C with KOH/CNTs mass ratio of 3:1 (CNTs-3) exhibits the highest electrocatalytic activity for VO2+/VO2+ redox reaction. The cell using CNTs-3 as positive catalyst demonstrates the smallest electrochemical polarization, the highest capacity and efficiency among the samples. Using KOH-activated CNTs-3 can increase the average energy efficiency of the cell by 4.4%. This work suggests that KOH-activated CNTs is a low-cost, efficient and promising catalyst for VO2+/VO2+ redox reaction for VRFB system.

  13. Shatter Complex Formation in the Twin Craters Lava Flow, Zuni-Bandera Field, New Mexico

    Science.gov (United States)

    von Meerscheidt, H. C.; Bleacher, J. E.; Brand, B. D.; deWet, A.; Samuels, R.; Hamilton, C.; Garry, W. B.; Bandfield, J. L.

    2013-12-01

    . Prominent ';a';a channels travel around the bluff, leaving a 'wake' of uncovered ground on the downstream side. We interpret this shatter area to have been a branching tube network within an active sheet. The limestone bluff acted as an obstacle that caused a backup of lava within the tubes, driving episodes of shattering. The mounds likely represent earlier solidified sections between active, possibly braided, tube branches, which remained as mounds within the shatter area after the adjacent crust subsided. When lava broke out from the pressurized sheet-like lobe, it formed the ';a';a channels. This section of the flow field is interpreted using inferences from shatter ring formation, but is perhaps better termed a shatter sheet or shatter complex. This study has implications for understanding lava flow dynamics at constriction points, as well as the evolution and morphology of shatter rings.

  14. The Synthesis and Electrocatalytic Activities of Molybdenum Sulfide for Hydrogen Evolution Reaction

    KAUST Repository

    Li, Zhengxing

    2014-07-01

    In the context of the future hydrogen economy, effective production of hydrogen (H2) from readily available and sustainable resources is of crucial importance. Hydrogen generation via water splitting by solar energy or electricity has attracted great attention in recent years. In comparison with photocatalytic water-splitting directly using solar light, which is ideal but the relevant technologies are not yet mature, electrolysis of water with catalyst is more practical at the current stage. The Pt-group noble metals are the most effective electrocatalysts for hydrogen evolution reaction (HER) from water, but their high costs limit their applications. Due to the earth-abundance and low price, MoS2 is expected to be a good alternative of the Pt-group metals for HER. Plenty of researches have been conducted for improving the HER activities of MoS2 by optimizing its synthesis method. However, it remains challenging to prepare MoS2 catalysts with high and controllable activity, and more investigations are still needed to better understand the structure-performance correlation in this system. In this thesis, we report a new strategy for fabricating MoS2 eletrocatalysts which gives rise to much improved HER performance and allows us to tune the electrocatalytic activity by varying the preparation conditions. Specifically, we sulfurized molybdenum oxide on the surface of a Ti foil electrode via a facile chemical vapor deposition (CVD) method, and directly used the electrode for HER testing. Depending on the CVD temperature, the MoO2-MoS2 nanocomposites show different HER activities. Under the optimal synthesis condition (400ºC), the resulting catalyst exhibited excellent HER activity: an onset potential (overpotential) of 0.095 V versus RHE and the Tafel slope of 40 mv/dec. Such a performance exceeds those of most reported MoS2 based HER electrocatalysts. We demonstrated that the CVD temperature has significant influence on the catalysts in crystallinity degree, particle

  15. Equilibrium and kinetic analysis of human interleukin-13 and IL-13 receptor alpha-2 complex formation.

    Science.gov (United States)

    Lacy, Eilyn R

    2012-03-01

    Interleukin 13 (IL-13) is a pleiotropic cytokine secreted by activated T cells. Both IL-13 and its polymorphic variant (IL-13-R110Q) have been shown to be associated with multiple diseases such as asthma and allergy. Two IL-13 receptors have been identified, IL-13R alpha-1 receptor (IL-13Rα1) and IL-13R alpha-2 receptor (IL-13Rα2). It has been well established that IL-13 binds to IL-13Rα1 alone with low nM affinity while binding to the IL-13Rα1/IL-4R receptor complex is significantly tighter (pM). The affinity between IL-13 and IL-13Rα2, however, remains elusive. Several values have been reported in the literature varying from 20 pM to 2.5 nM. The affinities previously reported were obtained using surface plasmon resonance (SPR) or Scatchard analysis of (125) I-IL-13 binding data. This report presents the results for the kinetics and equilibrium binding analysis studies performed using label-free kinetic exclusion assay (KEA) for the interaction of human IL-13 and IL-13Rα2. KEA equilibrium analysis showed that the affinities of IL-13Rα2 are 107 and 56 pM for IL-13 and its variant (IL-13-R110Q), respectively. KEA kinetic analysis showed that a tight and very stable complex is formed between IL-13Rα2 and IL-13, as shown by calculated dissociation rate constants slower than 5 × 10(-5) per second. Kinetic analysis also showed significant differences in the kinetic behavior of wild type (wt) versus IL-13-R110Q. IL-13-R110Q not only associates to IL-13Rα2 slower than wt human IL-13 (wt-IL-13), as previously reported, but IL-13-R110Q also dissociates slower than wt-IL-13. These results show that IL-13Rα2 is a high affinity receptor and provide a new perspective on kinetic behavior that could have significant implications in the understanding of the role of IL-13-R110Q in the disease state.

  16. Systems biology of lignin biosynthesis in Populus trichocarpa: heteromeric 4-coumaric acid:coenzyme A ligase protein complex formation, regulation, and numerical modeling.

    Science.gov (United States)

    Chen, Hsi-Chuan; Song, Jina; Wang, Jack P; Lin, Ying-Chung; Ducoste, Joel; Shuford, Christopher M; Liu, Jie; Li, Quanzi; Shi, Rui; Nepomuceno, Angelito; Isik, Fikret; Muddiman, David C; Williams, Cranos; Sederoff, Ronald R; Chiang, Vincent L

    2014-03-01

    As a step toward predictive modeling of flux through the pathway of monolignol biosynthesis in stem differentiating xylem of Populus trichocarpa, we discovered that the two 4-coumaric acid:CoA ligase (4CL) isoforms, 4CL3 and 4CL5, interact in vivo and in vitro to form a heterotetrameric protein complex. This conclusion is based on laser microdissection, coimmunoprecipitation, chemical cross-linking, bimolecular fluorescence complementation, and mass spectrometry. The tetramer is composed of three subunits of 4CL3 and one of 4CL5. 4CL5 appears to have a regulatory role. This protein-protein interaction affects the direction and rate of metabolic flux for monolignol biosynthesis in P. trichocarpa. A mathematical model was developed for the behavior of 4CL3 and 4CL5 individually and in mixtures that form the enzyme complex. The model incorporates effects of mixtures of multiple hydroxycinnamic acid substrates, competitive inhibition, uncompetitive inhibition, and self-inhibition, along with characteristic of the substrates, the enzyme isoforms, and the tetrameric complex. Kinetic analysis of different ratios of the enzyme isoforms shows both inhibition and activation components, which are explained by the mathematical model and provide insight into the regulation of metabolic flux for monolignol biosynthesis by protein complex formation.

  17. Studies of the Catalytic Activity and Deactivation of Calcined Layered Double Hydroxides in the Reaction of Ethanol with Propylene Oxide

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The reaction of ethanol with propylene oxide over calcined layered double hydroxides(CLDH) was investigated. The results show that CLDH has a good activity and a good selectivity, but the activity and the selectivity of CLDH decrease when CLDH reforms LDH- the so called "memory effect". The influence of the "memory effect" on the CLDH returning to LDH was studied by the hydration reaction. It is shown that the "memory effect" is not complete, and the decreases of the Mg/Al molar ratio of LDH and the crystallite size due to the increase of the hydration reaction time result in the drop of the activity and the selectivity.Keyworcds Ethanol, Propylene oxide, Calcined layered double hydroxide, "Memory effect", Hydration

  18. Cationic Pd(II)-catalyzed C–H activation/cross-coupling reactions at room temperature: synthetic and mechanistic studies

    Science.gov (United States)

    Nishikata, Takashi; Abela, Alexander R; Huang, Shenlin

    2016-01-01

    Summary Cationic palladium(II) complexes have been found to be highly reactive towards aromatic C–H activation of arylureas at room temperature. A commercially available catalyst [Pd(MeCN)4](BF4)2 or a nitrile-free cationic palladium(II) complex generated in situ from the reaction of Pd(OAc)2 and HBF4, effectively catalyzes C–H activation/cross-coupling reactions between aryl iodides, arylboronic acids and acrylates under milder conditions than those previously reported. The nature of the directing group was found to be critical for achieving room temperature conditions, with the urea moiety the most effective in promoting facile coupling reactions at an ortho C–H position. This methodology has been utilized in a streamlined and efficient synthesis of boscalid, an agent produced on the kiloton scale annually and used to control a range of plant pathogens in broadacre and horticultural crops. Mechanistic investigations led to a proposed catalytic cycle involving three steps: (1) C–H activation to generate a cationic palladacycle; (2) reaction of the cationic palladacycle with an aryl iodide, arylboronic acid or acrylate, and (3) regeneration of the active cationic palladium catalyst. The reaction between a cationic palladium(II) complex and arylurea allowed the formation and isolation of the corresponding palladacycle intermediate, characterized by X-ray analysis. Roles of various additives in the stepwise process have also been studied. PMID:27340491

  19. Cationic Pd(II-catalyzed C–H activation/cross-coupling reactions at room temperature: synthetic and mechanistic studies

    Directory of Open Access Journals (Sweden)

    Takashi Nishikata

    2016-05-01

    Full Text Available Cationic palladium(II complexes have been found to be highly reactive towards aromatic C–H activation of arylureas at room temperature. A commercially available catalyst [Pd(MeCN4](BF42 or a nitrile-free cationic palladium(II complex generated in situ from the reaction of Pd(OAc2 and HBF4, effectively catalyzes C–H activation/cross-coupling reactions between aryl iodides, arylboronic acids and acrylates under milder conditions than those previously reported. The nature of the directing group was found to be critical for achieving room temperature conditions, with the urea moiety the most effective in promoting facile coupling reactions at an ortho C–H position. This methodology has been utilized in a streamlined and efficient synthesis of boscalid, an agent produced on the kiloton scale annually and used to control a range of plant pathogens in broadacre and horticultural crops. Mechanistic investigations led to a proposed catalytic cycle involving three steps: (1 C–H activation to generate a cationic palladacycle; (2 reaction of the cationic palladacycle with an aryl iodide, arylboronic acid or acrylate, and (3 regeneration of the active cationic palladium catalyst. The reaction between a cationic palladium(II complex and arylurea allowed the formation and isolation of the corresponding palladacycle intermediate, characterized by X-ray analysis. Roles of various additives in the stepwise process have also been studied.

  20. Digallane with redox-active diimine ligand: dualism of electron-transfer reactions.

    Science.gov (United States)

    Fedushkin, Igor L; Skatova, Alexandra A; Dodonov, Vladimir A; Chudakova, Valentina A; Bazyakina, Natalia L; Piskunov, Alexander V; Demeshko, Serhiy V; Fukin, Georgy K

    2014-05-19

    The reactivity of digallane (dpp-Bian)Ga-Ga(dpp-Bian) (1), which consists of redox-active ligand 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (dpp-Bian), has been studied. The reaction of 1 with I2 proceeds via one-electron oxidation of each of two dpp-Bian ligands to a radical-anionic state and affords complex (dpp-Bian)IGa-GaI(dpp-Bian) (2). Dissolution of complex 2 in pyridine (Py) gives monomeric compound (dpp-Bian)GaI(Py) (3) as a result of a solvent-induced intramolecular electron transfer from the metal-metal bond to the dpp-Bian ligands. Treatment of compound 3 with B(C6F5)3 leads to removal of pyridine and restores compound 2. The reaction of compound 1 with 3,6-di-tert-butyl-ortho-benzoquinone (3,6-Q) proceeds with oxidation of all the redox-active centers in 1 (the Ga-Ga bond and two dpp-Bian dianions) and results in mononuclear catecholate (dpp-Bian)Ga(Cat) (4) (Cat = [3,6-Q](2-)). Treatment of 4 with AgBF4 gives a mixture of [(dpp-Bian)2Ag][BF4] (5) and (dpp-Bian)GaF(Cat) (6), which both consist of neutral dpp-Bian ligands. The reduction of benzylideneacetone (BA) with 1 generates the BA radical-anions, which dimerize, affording (dpp-Bian)Ga-(BA-BA)-Ga(dpp-Bian) (7). In this case the Ga-Ga bond remains unchanged. Within 10 min at 95 °C in solution compound 7 undergoes transformation to paramagnetic complex (dpp-Bian)Ga(BA-BA) (8) and metal-free compound C36H40N2 (9). The latter is a product of intramolecular addition of the C-H bond of one of the iPr groups to the C═N bond in dpp-Bian. Diamagnetic compounds 3, 5, 6, and 9 have been characterized by NMR spectroscopy, and paramagnetic complexes 2, 4, 7, and 8 by ESR spectroscopy. Molecular structures of 2-7 and 9 have been established by single-crystal X-ray analysis.

  1. Method for increasing -SiC yield on solid state reaction of coal fly ash and activated carbon powder

    Indian Academy of Sciences (India)

    Sulardjaka; Jamasri; M W Wildan; Kusnanto

    2011-07-01

    A novel process for increasing -SiC yield on solid state reaction of coal fly ash and micro powder activated carbon powder has been proposed. -SiC powder was synthesized at temperature 1300°C for 2 h under vacuum condition with 1 l/min argon flow. Cycling synthesis process has been developed for increasing -SiC yield on solid state reaction of coal fly ash and activated carbon powder. Synthesized products were analyzed by XRD with Cu-K radiation, FTIR spectrometer and SEM fitted with EDAX. The results show that the amount of relative -SiC is increased with the number of cycling synthesis.

  2. Activation energies as the validity criterion of a model for complex reactions that can be in oscillatory states

    Directory of Open Access Journals (Sweden)

    Anić S.

    2007-01-01

    Full Text Available Modeling of any complex reaction system is a difficult task. If the system under examination can be in various oscillatory dynamic states, the apparent activation energies corresponding to different pathways may be of crucial importance for this purpose. In that case the activation energies can be determined by means of the main characteristics of an oscillatory process such as pre-oscillatory period, duration of the oscillatory period, the period from the beginning of the process to the end of the last oscillation, number of oscillations and others. All is illustrated on the Bray-Liebhafsky oscillatory reaction.

  3. Intrinsic activation barriers and coadsorption effects for reactions on metal surfaces: unified formalism within the UBI-QEP approach

    Science.gov (United States)

    Sellers, Harrell; Shustorovich, Evgeny

    2002-04-01

    We present a unified formulation of the unity bond index-quadratic exponential potential method (UBI-QEP, formerly known as the BOC-MP method) of determining metal surface reaction energetics. We give a unified treatment of enthalpies and intrinsic activation barriers for dissociation and recombination reactions as particular cases of disproportionation reactions. We discuss numerous examples of elementary reactions, which form a database for various reaction mechanisms. We start with the zero coverage limit and then focus on coadsorption effects on reaction energetics on monometallic and bimetallic (alloy) surfaces. We consider first the full treatment and then develop the “uniform scaling” approximation, with guidelines (and examples) where it may be efficiently used. We provide tables of numerical values covering most of practically important cases of coadsorption effects on fcc(1 1 1) and fcc(1 0 0) surfaces, which allow one to easily estimate coverage effects on activation barriers by simple interpolation. We also clarify the nature of basic UBI-QEP parameters and correlation between local and global adsorbate coverage. These developments, illustrated by various examples, make applications of the UBI-QEP method much easier for practitioners, particularly those who have no UBI-model computer program and make calculations by hand.

  4. Acute effects of exercise and active video games on adults' reaction time and perceived exertion.

    Science.gov (United States)

    Guzmán, José F; López-García, Jesús

    2016-11-01

    The purpose of the present study was to examine the acute effects of resting, aerobic exercise practised alone, and aerobic exercise with active video games (AVG), on complex reaction time (CRT) and the post-exercise acute rate of perceived exertion (RPE) in young healthy adults. The experimental group was composed of 92 healthy young adults, 78 males and 13 females (age M = 21.9 ± 2.7 years) who completed two sessions, A and B. In session A, participants rode 30 min on an ergometer, while in session B they exercised for 30 min on an ergometer while playing an AVG on a Wii. The control group was composed of 30 young adults, 26 males and 4 females (age M = 21.4 ± 2.9 years) who rested for 30 min. In each session, a CRT task was performed before and after exercising or resting, and post-exercise global RPE was noted. Repeated measures general linear model (GLM) and Wilcoxon tests were performed. (1) Both aerobic exercise alone and aerobic exercise combined with AVG improved CRT, while resting did not; (2) aerobic exercise combined with AVG did not improve CRT more than aerobic exercise only; and (3) RPE was lower after aerobic exercise combined with AVG compared with aerobic exercise only. In young adults, exercise produces acute benefits on CRT, and practising exercise with AVG helps to decrease RPE.

  5. Reactivity Descriptors for the Activity of Molecular MN4 Catalysts for the Oxygen Reduction Reaction.

    Science.gov (United States)

    Zagal, José H; Koper, Marc T M

    2016-11-14

    Similarities are established between well-known reactivity descriptors of metal electrodes for their activity in the oxygen reduction reaction (ORR) and the reactivity of molecular catalysts, in particular macrocyclic MN4 metal complexes confined to electrode surfaces. We show that there is a correlation between the M(III) /M(II) redox potential of MN4 chelates and the M-O2 binding energies. Specifically, the binding energy of O2 (and other O species) follows the M(III) -OH/M(II) redox transition for MnN4 and FeN4 chelates. The ORR volcano plot for MN4 catalysts is similar to that for metal catalysts: catalysts on the weak binding side (mostly CoN4 chelates) yield mainly H2 O2 as the product, with an ORR onset potential independent of the pH value on the NHE scale (and therefore pH-dependent on the RHE scale); catalysts on the stronger binding side yield H2 O as the product with the expected pH-dependence on the NHE scale. The suggested descriptors also apply to heat-treated pyrolyzed MN4 catalysts. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Antioxidant Activity of Magnolol and Honokiol: Kinetic and Mechanistic Investigations of Their Reaction with Peroxyl Radicals.

    Science.gov (United States)

    Amorati, Riccardo; Zotova, Julija; Baschieri, Andrea; Valgimigli, Luca

    2015-11-06

    Magnolol and honokiol, the bioactive phytochemicals contained in Magnolia officinalis, are uncommon antioxidants bearing isomeric bisphenol cores substituted with allyl functions. We have elucidated the chemistry behind their antioxidant activity by experimental and computational methods. In the inhibited autoxidation of cumene and styrene at 303 K, magnolol trapped four peroxyl radicals, with a kinh of 6.1 × 10(4) M(-1) s(-1) in chlorobenzene and 6.0 × 10(3) M(-1) s(-1) in acetonitrile, and honokiol trapped two peroxyl radicals in chlorobenzene (kinh = 3.8 × 10(4) M(-1) s(-1)) and four peroxyl radicals in acetonitrile (kinh = 9.5 × 10(3) M(-1) s(-1)). Their different behavior arises from a combination of intramolecular hydrogen bonding among the reactive OH groups (in magnolol) and of the OH groups with the aromatic and allyl π-systems, as confirmed by FT-IR spectroscopy and DFT calculations. Comparison with structurally related 3,3',5,5'-tetramethylbiphenyl-4,4'-diol, 2-allylphenol, and 2-allylanisole allowed us to exclude that the antioxidant behavior of magnolol and honokiol is due to the allyl groups. The reaction of the allyl group with a peroxyl radical (C-H hydrogen abstraction) proceeds with rate constant of 1.1 M(-1) s(-1) at 303 K. Magnolol and honokiol radicals do not react with molecular oxygen and produce no superoxide radical under the typical settings of inhibited autoxidations.

  7. The DNA Binding Activity of p53 Displays Reaction-Diffusion Kinetics

    Science.gov (United States)

    Hinow, Peter; Rogers, Carl E.; Barbieri, Christopher E.; Pietenpol, Jennifer A.; Kenworthy, Anne K.; DiBenedetto, Emmanuele

    2006-01-01

    The tumor suppressor protein p53 plays a key role in maintaining the genomic stability of mammalian cells and preventing malignant transformation. In this study, we investigated the intracellular diffusion of a p53-GFP fusion protein using confocal fluorescence recovery after photobleaching. We show that the diffusion of p53-GFP within the nucleus is well described by a mathematical model for diffusion of particles that bind temporarily to a spatially homogeneous immobile structure with binding and release rates k1 and k2, respectively. The diffusion constant of p53-GFP was estimated to be Dp53-GFP = 15.4 μm2 s−1, significantly slower than that of GFP alone, DGFP = 41.6 μm2 s−1. The reaction rates of the binding and unbinding of p53-GFP were estimated as k1 = 0.3 s−1 and k2 = 0.4 s−1, respectively, values suggestive of nonspecific binding. Consistent with this finding, the diffusional mobilities of tumor-derived sequence-specific DNA binding mutants of p53 were indistinguishable from that of the wild-type protein. These data are consistent with a model in which, under steady-state conditions, p53 is latent and continuously scans DNA, requiring activation for sequence-specific DNA binding. PMID:16603489

  8. Study of activation cross-sections of deuteron induced reactions on rhodium up to 40 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Ditroi, F., E-mail: ditroi@atomki.hu [Institute of Nuclear Research of the Hungarian Academy of Sciences (ATOMKI), Debrecen (Hungary); Tarkanyi, F.; Takacs, S. [Institute of Nuclear Research of the Hungarian Academy of Sciences (ATOMKI), Debrecen (Hungary); Hermanne, A. [Cyclotron Laboratory, Vrije Universiteit Brussel (VUB), Brussels (Belgium); Yamazaki, H.; Baba, M.; Mohammadi, A. [Cyclotron Radioisotope Center (CYRIC) Tohoku University, Sendai (Japan); Ignatyuk, A.V. [Institute of Physics and Power Engineering (IPPE), Obninsk (Russian Federation)

    2011-09-15

    Highlights: {yields} Excitation function measurement of deuteron induced reactions on rhodium up to 40 MeV. {yields} Model code calculations with EMPIRE, ALICE and TALYS. {yields} Integral production yield calculation. {yields} Thin layer activation (TLA) with the produced isotopes. - Abstract: In the frame of a systematic study of the activation cross-sections of deuteron induced nuclear reactions, excitation functions of the {sup 103}Rh(d,x) {sup 100,101,103}Pd, {sup 100g,101m,101g,102m,102g}Rh and {sup 103g}Ru reactions were determined up to 40 MeV. Cross-sections were measured with the activation method using a stacked foil irradiation technique. Excitation functions of the contributing reactions were calculated using the ALICE-IPPE, EMPIRE-II and TALYS codes. From the measured cross-section data integral production yields were calculated and compared with experimental integral yield data reported in the literature. From the measured cross-sections and previous data, activation curves were deduced to support thin layer activation (TLA) on rhodium and Rh containing alloys.

  9. Supramolecular composite materials from cellulose, chitosan, and cyclodextrin: facile preparation and their selective inclusion complex formation with endocrine disruptors.

    Science.gov (United States)

    Duri, Simon; Tran, Chieu D

    2013-04-23

    We have successfully developed a simple one-step method of preparing high-performance supramolecular polysaccharide composites from cellulose (CEL), chitosan (CS), and (2,3,6-tri-O-acetyl)-α-, β-, and γ-cyclodextrin (α-, β-, and γ-TCD). In this method, [BMIm(+)Cl(-)], an ionic liquid (IL), was used as a solvent to dissolve and prepare the composites. Because a majority (>88%) of the IL used was recovered for reuse, the method is recyclable. XRD, FT-IR, NIR, and SEM were used to monitor the dissolution process and to confirm that the polysaccharides were regenerated without any chemical modifications. It was found that unique properties of each component including superior mechanical properties (from CEL), excellent adsorption for pollutants and toxins (from CS), and size/structure selectivity through inclusion complex formation (from TCDs) remain intact in the composites. Specifically, the results from kinetics and adsorption isotherms show that whereas CS-based composites can effectively adsorb the endocrine disruptors (polychlrophenols, bisphenol A), their adsorption is independent of the size and structure of the analytes. Conversely, the adsorption by γ-TCD-based composites exhibits a strong dependence on the size and structure of the analytes. For example, whereas all three TCD-based composites (i.e., α-, β-, and γ-TCD) can effectively adsorb 2-, 3-, and 4-chlorophenol, only the γ-TCD-based composite can adsorb analytes with bulky groups including 3,4-dichloro- and 2,4,5-trichlorophenol. Furthermore, the equilibrium sorption capacities for the analytes with bulky groups by the γ-TCD-based composite are much higher than those by CS-based composites. Together, these results indicate that the γ-TCD-based composite with its relatively larger cavity size can readily form inclusion complexes with analytes with bulky groups, and through inclusion complex formation, it can strongly adsorb many more analytes and has a size/structure selectivity compared to

  10. Thermodynamic study of complex formation between Kryptofix-5 and Sn2+ in several individual and binary non-aqueous solvents using a conductometric method

    Science.gov (United States)

    Khoshnood, Razieh Sanavi; Hatami, Elaheh

    2014-12-01

    The complex formation between 1,13-bis(8-quinolyl)-1,4,7,10,13-pentaoxatridecane (Kryptofix-5) and Sn2+ ions was studied in pure acetonitrile (AN), dimethylformamide (DMF), 1,4-dioxane (DOX), and methanol (MeOH) and in acetonitrile-1,4-dioxane (AN-DOX), acetonitrile-dichloromethane (AN-DCM), acetonitrile-methanol (AN-MeOH), and acetonitrile-dimethylformamide (AN-DMF) binary mixed solvent solutions at different temperatures using conductometric method. 1: 1 [ML] complex is formed between the metal cation and ligand in most solvent systems but in the cases of AN-MeOH (MeOH = 90 mol %) binary mixture and in pure MeOH a 2: 1 [M2L] complex was observed, that is the stoichiometry of complexes may be changed by the nature of the medium. The stability order of the (Kryptofix-5·Sn)2+ complex in the studied binary mixed solvent solutions at 25°C was found to be AN-DOX > AN-DCM > AN-MeOH > AN-DMF and in the case of pure solvents at 25°C the sequence was the following: AN > DMF > DOX. A non-linear behavior was observed for changes of log K f of (Kryptofix-5·Sn)2+ complex versus the composition of the binary mixed solvents, which was explained in terms of solvent-solvent intractions and also by the preferential solvation of the f species involved in the complexation reaction. The values of standard enthalpy changes (Δ Hc°) for complexation reactions were obtained from the slope of the Van't Hoff plots and the changes in standard entropy (Δ Sc°) were calculated from the relationship Δ Gc,298.15° = Δ Hc° - 298.15Δ Sc°. The results show that in most cases, the (Kryptofix-5·Sn)2+ complex is both enthalpy and entropy stabilized.

  11. Non-innocent additives in a palladium(II)-catalyzed C-H bond activation reaction: insights into multimetallic active catalysts.

    Science.gov (United States)

    Anand, Megha; Sunoj, Raghavan B; Schaefer, Henry F

    2014-04-16

    The role of a widely employed additive (AgOAc) in a palladium acetate-catalyzed ortho-C-H bond activation reaction has been examined using the M06 density functional theory. A new hetero-bimetallic Pd-(μ-OAc)3-Ag is identified as the most likely active species. This finding could have far-reaching implications with respect to the notion of the active species in palladium catalysis in the presence of other metal salt additives.

  12. A novel DNA deletion-ligation reaction catalyzed in vitro by a developmentally controlled activity from Tetrahymena cells.

    Science.gov (United States)

    Robinson, E K; Cohen, P D; Blackburn, E H

    1989-09-08

    Developmentally controlled genomic deletion-ligations occur during ciliate macronuclear differentiation. We have identified a novel activity in Tetrahymena cell-free extracts that efficiently catalyzes a specific set of intramolecular DNA deletion-ligation reactions. When synthetic DNA oligonucleotide substrates were used, all the deletion-ligation products resembled those formed in vivo in that they resulted from deletions between pairs of short direct repeats. The reaction is ATP-dependent, salt-sensitive, and strongly influenced by the oligonucleotide substrate sequence. The deletion-ligation activity has an apparent size of 200-500 kd, no nuclease-sensitive component, and is highly enriched in cells developing new macronuclei. The temperature inactivation profile of the activity parallels the temperature lethality profile specific for Tetrahymena cells developing new macronuclei. We suggest that this deletion-ligation activity carries out the genomic deletions in developing macronuclei in vivo.

  13. Computation of Accurate Activation Barriers for Methyl-Transfer Reactions of Sulfonium and Ammonium Salts in Aqueous Solution.

    Science.gov (United States)

    Gunaydin, Hakan; Acevedo, Orlando; Jorgensen, William L; Houk, K N

    2007-05-01

    The energetics of methyl-transfer reactions from dimethylammonium, tetramethylammonium, and trimethylsulfonium to dimethylamine were computed with density functional theory, MP2, CBS-QB3, and quantum mechanics/molecular mechanics (QM/MM) Monte Carlo methods. At the CBS-QB3 level, the gas-phase activation enthalpies are computed to be 9.9, 15.3, and 7.9 kcal/mol, respectively. MP2/6-31+G(d,p) activation enthalpies are in best agreement with the CBS-QB3 results. The effects of aqueous solvation on these reactions were studied with polarizable continuum model, generalized Born/surface area (GB/SA), and QM/MM Monte Carlo simulations utilizing free-energy perturbation theory in which the PDDG/PM3 semiempirical Hamiltonian for the QM and explicit TIP4P water molecules in the MM region were used. In the aqueous phase, all of these reactions proceed more slowly when compared to the gas phase, since the charged reactants are stabilized more than the transition structure geometries with delocalized positive charges. In order to obtain the aqueous-phase activation free energies, the gas-phase activation free energies were corrected with the solvation free energies obtained from single-point conductor-like polarizable continuum model and GB/SA calculations for the stationary points along the reaction coordinate.

  14. Promotional effect of phosphorus doping on the activity of the Fe-N/C catalyst for the oxygen reduction reaction

    DEFF Research Database (Denmark)

    Hu, Yang; Zhu, Jianbin; Lv, Qing

    2015-01-01

    Cost-effective, active and stable electrocatalysts for the oxygen reduction reaction (ORR) are highly desirable for the wide-spread adoption of technologies such as fuel cells and metal-air batteries. Among the already reported non-precious metal catalysts, carbon-supported transition metal-nitro...

  15. The Davis-Beirut Reaction: a novel entry into 2H-indazoles and indazolones. Recent biological activity of indazoles.

    Science.gov (United States)

    Haddadin, Makhluf J; Conrad, Wayne E; Kurth, Mark J

    2012-10-01

    A novel, easy method for the syntheses of richly diversified 2H-indazoles and indazolones, called the Davis-Beirut reaction, and other recent 2H-indazole synthetic routes are briefly reviewed. An update on the biological activity of indazoles is also surveyed.

  16. Polyhedral Palladium-Silver Alloy Nanocrystals as Highly Active and Stable Electrocatalysts for the Formic Acid Oxidation Reaction

    National Research Council Canada - National Science Library

    Fu, Geng-Tao; Liu, Chang; Zhang, Qi; Chen, Yu; Tang, Ya-Wen

    2015-01-01

    .... As a preliminary electrochemical application, the Pd-Ag alloy polyhedrons are applied in the formic acid oxidation reaction, which shows higher electrocatalytic activity and stability than commercially available Pd black due to the "synergistic effects" between Pd and Ag atoms.

  17. An In Vitro Model for Studying Neutrophil Activation During Cardiopulmonary Bypass by Using a Polymerase Chain Reaction Thermocycler

    NARCIS (Netherlands)

    Tang, Min; Zhao, Xiao-Gang; Gu, Y. John; Chen, Chang-Zhi

    2010-01-01

    The accurate temperature control of a polymerase chain reaction (PCR) thermocycler was exploited in developing an in vitro model to study neutrophil activation during cardiopulmonary bypass. Neutrophils from 12 volunteers underwent temperature changes in a PCR thermocycler (37 degrees C for 30 minut

  18. Synthesis and Biological Activity of Some 3,5-Diaryl-1-Benzothiazolopyrazoline Derivatives: Reaction of Chalcones with 2-Hyrazinobenzothiazoles

    Directory of Open Access Journals (Sweden)

    Vandana Sharma

    2009-01-01

    Full Text Available A series of 3,5-diaryl-1-benzothiazolopyrazoline derivatives were synthesized by the reaction of appropriately substituted chalcones and 2-hydrazinobenzothiazole in ethanol. The synthesized heterocycles have been characterized on the basis of their chemical properties and spectroscopic data. These compounds were tested for biological activity against a variety of test organisms.

  19. Synthesis and Biological Activity of Some 3, 5-Diarylisoxazoline Derivatives: Reaction of Substituted Chalcones with Hydroxylamine Hydrochloride

    Directory of Open Access Journals (Sweden)

    Vandana Sharma

    2010-01-01

    Full Text Available A series of 3-aryl-5-styrylisoxazoline/ 3,5-diarylisoxazoline derivatives were synthesized by the reaction of appropriately substituted chalcones and hydroxylamine hydrochloride in presence of alkali in ethanol. The synthesized heterocycles have been characterized on the basis of their chemical properties and spectroscopic data. These compounds were tested for biological activity against a variety of test organisms

  20. An In Vitro Model for Studying Neutrophil Activation During Cardiopulmonary Bypass by Using a Polymerase Chain Reaction Thermocycler

    NARCIS (Netherlands)

    Tang, Min; Zhao, Xiao-Gang; Gu, Y. John; Chen, Chang-Zhi

    The accurate temperature control of a polymerase chain reaction (PCR) thermocycler was exploited in developing an in vitro model to study neutrophil activation during cardiopulmonary bypass. Neutrophils from 12 volunteers underwent temperature changes in a PCR thermocycler (37 degrees C for 30

  1. Zeolite H-BEA catalysed multicomponent reaction: One-pot synthesis of amidoalkyl naphthols - Biologically active drug-like molecules

    Indian Academy of Sciences (India)

    Sunil R Mistry; Rikesh S Joshi; Kalpana C Maheria

    2011-07-01

    Zeolite has been used as an efficient and a novel heterogeneous catalyst for one-pot synthesis of biologically active drug-like molecules, amidoalkyl naphthols. This green route involves multicomponent reaction of 2-naphthol, aromatic aldehydes and amide in the presence of a catalytic amount of zeolite H-Beta (H-BEA) under solvent reflux as well as solvent-free conditions.

  2. Particle size dependence on oxygen reduction reaction activity of electrodeposited TaOx catalysts in acidic media

    KAUST Repository

    Seo, J.

    2013-11-13

    The size dependence of the oxygen reduction reaction activity was studied for TaOx nanoparticles electrodeposited on carbon black for application to polymer electrolyte fuel cells (PEFCs). Compared with a commercial Ta2O5 material, the ultrafine oxide nanoparticles exhibited a distinctively high onset potential different from that of the bulky oxide particles.

  3. Activation cross-sections of deuteron induced nuclear reactions on neodymium up to 50 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Tárkányi, F.; Takács, S. [Institute for Nuclear Research of the Hungarian Academy of Sciences (ATOMKI), Debrecen (Hungary); Ditrói, F., E-mail: ditroi@atomki.hu [Institute for Nuclear Research of the Hungarian Academy of Sciences (ATOMKI), Debrecen (Hungary); Hermanne, A. [Cyclotron Laboratory, Vrije Universiteit Brussel (VUB), Brussels (Belgium); Yamazaki, H.; Baba, M.; Mohammadi, A. [Cyclotron Radioisotope Center (CYRIC), Tohoku University, Sendai (Japan); Ignatyuk, A.V. [Institute of Physics and Power Engineering (IPPE), Obninsk (Russian Federation)

    2014-04-01

    Highlights: • Experimental excitation function of deuteron induced reactions on natural Nd. • Model code calculations with EMPIRE-D, ALICE-D and TALYS (TENDL-2012). • Physical yield calculation and comparison. • Discussion of medical and industrial applications. - Abstract: In the frame of a systematic study of activation cross sections of deuteron induced nuclear reactions on rare earths, the reactions on neodymium for production of therapeutic radionuclides were measured for the first time. The excitation functions of the {sup nat}Nd(d,x) {sup 151,150,149,148m,148g,146,144,143}Pm, {sup 149,147,139m}Nd, {sup 142}Pr and {sup 139g}Ce nuclear reactions were assessed by using the stacked foil activation technique and high resolution γ-spectrometry. The experimental excitation functions were compared to the theoretical predictions calculated with the modified model codes ALICE-IPPE-D and EMPIRE-II-D and with the data in the TENDL-2012 library based on latest version of the TALYS code. The application of the data in the field of medical isotope production and nuclear reaction theory is discussed.

  4. Thermodynamics of mixed-ligand complex formation of zinc nitrilotriacetate with amino acids and dipeptides in solution

    Energy Technology Data Exchange (ETDEWEB)

    Pyreu, Dmitrii, E-mail: pyreu@mail.ru [Department of Inorganic and Analytic Chemistry, Ivanovo State UniversityErmak 39, Ivanovo 153025 (Russian Federation); Gruzdev, Matvey; Kumeev, Roman [G.A. Krestov Institute of Solution Chemistry of the Russian Academy of Sciences, Ivanovo (Russian Federation); Gridchin, Sergei [Ivanovo State University of Chemistry and Technology, Ivanovo (Russian Federation)

    2014-10-20

    Highlights: • Stable mixed ligand complexes of ZnNta with amino acids and dipeptides. • Histamine-like coordination mode of His in the complex ZnNtaHis. • Glycine-like coordination of Lys and Orn in the complexes ZnNtaL and ZnNtaHL • NH{sub 2}, CO-coordination mode of GlyGly in the complex ZnNtaGG. • NH{sub 2}, N{sup −} or NH2, N{sup −}, COO-coordination modes of GlyGly in the complex ZnNtaGGH{sub −1}. - Abstract: The isothermal calorimetry, pH-potentiometric titration and {sup 1}H and {sup 13}C NMR methods has been used to study the mixed-ligand complex formation in the systems Zn{sup 2+}–Nta{sup 3–}–L{sup −} (L = His, Orn, Lys, GlyGly, AlaAla) in aqueous solution at 298.15 K and the ionic strength of I = 0.5 (KNO{sub 3}). The thermodynamic parameters of formation of the mixed complexes have been determined. The relationship between the probable coordination modes of the complexone and amino acid or dipeptide molecules in the mixed-ligand complex and the thermodynamic parameters has been discussed.

  5. Steady state and time-resolved fluorescence spectroscopy of quinine sulfate dication bound to sodium dodecylsulfate micelles: Fluorescent complex formation

    Energy Technology Data Exchange (ETDEWEB)

    Joshi, Sunita; Pant, Debi D., E-mail: ddpant@pilani.bits-pilani.ac.in

    2014-01-15

    Interaction of quinine sulfate dication (QSD) with anionic, sodium dodecylsulphate (SDS) surfactant has been studied at different premicellar, micellar and postmicellar concentrations in aqueous phase using steady state, time-resolved fluorescence and fluorescence anisotropy techniques. At premicellar concentrations of SDS, the decrease in absorbance, appearance of an extra fluorescence band at lower wavelengths and tri-exponential decay behavior of fluorescence, are attributed to complex formation between QSD molecules and surfactant monomers. At postmicellar concentrations the red shift in fluorescence spectrum, increase in quantum yield and increase in fluorescence lifetimes are attributed to incorporation of solute molecules to micelles. At lower concentrations of SDS, a large shift in fluorescence is observed on excitation at the red edge of absorption spectrum and this is explained in terms of distribution of ion pairs of different energies in the ground state and the observed fluorescence lifetime behavior corroborates with this model. The temporal fluorescence anisotropy decay of QSD in SDS micelles allowed determination of restriction on the motion of the fluorophore. All the different techniques used in this study reveal that the photophysics of QSD is very sensitive to the microenvironments of SDS micelles and QSD molecules reside at the water-micelle interface. -- Highlights: • Probe molecule is very sensitive to microenvironment of micelles. • Highly fluorescent ion-pair formation has been observed. • Modulated photophysics of probe molecule in micellar solutions has been observed. • Probe molecules strongly bind with micelles and reside at probe–micelle interface.

  6. Mixed-ligand complex formation equilibria of CuII with biguanide in presence of glycine as the auxiliary ligand

    Indian Academy of Sciences (India)

    Tannistha Roy Barman; G N Mukherjee

    2006-09-01

    Equilibrium study on the mixed ligand complex formation of CuII with biguanide(Bg) and glycine (HG), indicated the formation of the complexes: Cu(Bg)2+, Cu(Bg)$_{2}^{2+}$, Cu(Bg-H)(Bg)+, Cu(Bg-H)2, Cu(Bg)(OH)+, Cu(Bg-H)(OH); Cu(G)+, Cu(G)(OH), Cu(G)2; Cu(G)(Bg)+, Cu(G)(Bg-H); (G)Cu(Bg)Cu(G)2+, (G)Cu(Bg-H)Cu(G)+, and (G)Cu(Bg-2H)Cu(G). From the deprotonation constants of coordinated biguanide (Bg) in the complexes Cu(Bg)(OH)+, Cu(Bg-H)(Bg)+ and Cu(G)(Bg)+, the Lewis basicities of the coordinated ligand species (Bg-H)-, OH- and glycinate (G-) were found to be of the order: (Bg-H)- >> OH- > G-. Bridging (N1-N4, N2-N5) tetradentate mode of coordination by biguanide species Bg, (Bg-H)- and (Bg-2H)2- was indicated from the occurrence of biguanide-bridged dinuclear mixed ligand complexes (G)Cu(Bg)Cu(G)2+, (G)Cu(Bg-H)Cu(G)+, (G)Cu(Bg-2H)Cu(G) in the complexation equilibria.

  7. FRK inhibits migration and invasion of human glioma cells by promoting N-cadherin/β-catenin complex formation.

    Science.gov (United States)

    Shi, Qiong; Song, Xu; Wang, Jun; Gu, Jia; Zhang, Weijian; Hu, Jinxia; Zhou, Xiuping; Yu, Rutong

    2015-01-01

    Fyn-related kinase (FRK), a member of Src-related tyrosine kinases, is recently reported to function as a potent tumor suppressor in several cancer types. Our previous study has also shown that FRK over-expression inhibited the migration and invasion of glioma cells. However, the mechanism of FRK effect on glioma cell migration and invasion, a feature of human malignant gliomas, is still not clear. In this study, we found that FRK over-expression increased the protein level of N-cadherin, but not E-cadherin. Meanwhile, FRK over-expression promoted β-catenin translocation to the plasma membrane, where it formed complex with N-cadherin, while decreased β-catenin level in the nuclear fraction. In addition, down-regulation of N-cadherin by siRNA promoted the migration and invasion of glioma U251 and U87 cells and abolished the inhibitory effect of FRK on glioma cell migration and invasion. In summary, these results indicate that FRK inhibits migration and invasion of human glioma cells by promoting N-cadherin/β-catenin complex formation.

  8. Complex formation between the uncoupler carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP) and valinomycin in the presence of potassium.

    Science.gov (United States)

    O'Brien, T A; Nieva-Gomez, D; Gennis, R B

    1978-03-25

    Spectroscopic evidence is presented which indicates that the uncoupler carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP) and the peptide antibiotic valinomycin form a complex in the presence of potassium. Complex formation has been observed both in aqueous and nonaqueous media. Several techniques have been used to indicate the existence of a complex in aqueous solution. In the presence of valinomycin and K+, the absorption spectrum of FCCP is significantly perturbed, and there is also a large induced circular dichroism signal. In addition, the previously characterized complex which forms between valinomycin, K+, and the fluorescent probe 8-anilino-1-naphthalene-sulfonate (ANS) in aqueous solution is apparently disrupted by the addition of FCCP. The result is an effective quenching of the fluorescence due to the bound probe as it is displaced from the valinomycin.K+ by the uncoupler. In a nonpolar solvent, the absorption spectrum of FCCP is also perturbed by valinomycin in the presence of K+, again indicating the formation of a complex. These data point to the importance of considering the role of valinomycin.K+.uncoupler complex in interpreting physiological or ion transport data in which these substances have been used together.

  9. Transition metal catalyzed carbonylation reactions carbonylative activation of C-X bonds

    CERN Document Server

    Beller, Matthias

    2014-01-01

    This book provides students and researchers in organic synthesis with a detailed discussion of carbonylation from the basics through to applications. It discusses the past, present and future of carbonylation reactions.

  10. Activation energies of pericyclic reactions: performance of DFT, MP2, and CBS-QB3 methods for the prediction of activation barriers and reaction energetics of 1,3-dipolar cycloadditions, and revised activation enthalpies for a standard set of hydrocarbon pericyclic reactions.

    Science.gov (United States)

    Ess, Daniel H; Houk, K N

    2005-10-27

    Activation barriers and reaction energetics for the three main classes of 1,3-dipolar cycloadditions, including nine different reactions, were evaluated with the MPW1K and B3LYP density functional methods, MP2, and the multicomponent CBS-QB3 method. The CBS-QB3 values were used as standards for 1,3-dipolar cycloaddition activation barriers and reaction energetics, and the density functional theory (DFT) and MP2 methods were benchmarked against these values. The MPW1K/6-31G* method and basis set performs best for activation barriers, with a mean absolute deviation (MAD) value of 1.1 kcal/mol. The B3LYP/6-31G* method and basis set performs best for reaction enthalpies, with a MAD value of 2.4 kcal/mol, while the MPW1K method shows large errors for reaction energetics. The MP2 method gives the expected systematic underestimation of barriers. Concerted and nearly synchronous transition structures are predicted by all DFT and MP2 methods. Also reported are revised estimated 0 K experimental activation enthalpies for a standard set of hydrocarbon pericyclic reactions and updated comparisons to experiment for DFT, ab initio, and multicomponent methods. B3LYP and MPW1K methods with MAD values of 1.5 and 2.1 kcal/mol, respectively, fortuitously outperform the multicomponent CBS-QB3 method, which has a MAD value of 2.3. The MAD value of the O3LYP functional improves to 2.4 kcal/mol from the previously reported 3.0 kcal/mol.

  11. Microwave-Mediated Hetero Diels-Alder reaction: Synthesis of biologically active compounds

    OpenAIRE

    D’Aurizio, Antonio

    2009-01-01

    Heterocyclic compounds represent almost two-thirds of all the known organic compounds: they are widely distributed in nature and play a key role in a huge number of biologically important molecules including some of the most significant for human beings. A powerful tool for the synthesis of such compounds is the hetero Diels-Alder reaction (HDA), that involve a [4+2] cycloaddition reaction between heterodienes and suitable dienophiles. Among heterodienes to be used in such six-membered ...

  12. A Modified activation method for reaction total cross section and yield measurements at low astrophysically relevant energies

    Energy Technology Data Exchange (ETDEWEB)

    Artemov, S.V., E-mail: artemov@inp.uz [Institute of Nuclear Physics of Uzbekistan Academy of Sciences, Tashkent (Uzbekistan); Igamov, S.B.; Karakhodjaev, A.A.; Radyuk, G.A.; Tojiboyev, O.R.; Salikhbaev, U.S.; Ergashev, F.Kh.; Nam, I.V. [Institute of Nuclear Physics of Uzbekistan Academy of Sciences, Tashkent (Uzbekistan); Aliev, M.K.; Kholbaev, I.; Rumi, R.F.; Khalikov, R.I.; Eshkobilov, Sh.Kh.; Muminov, T.M. [Research Institute of Applied Physics, National University of Uzbekistan, Tashkent (Uzbekistan)

    2016-07-21

    The activation method is proposed for collection of the sufficient statistics during the investigation of the nuclear astrophysical reactions at low energies with the short-living residual nuclei formation. The main feature is a multiple cyclical irradiation of a target by an ion beam and measurement of the radioactivity decay curve. The method was tested by the yield measurement of the {sup 12}C(p,γ){sup 13}N reaction with detecting the annihilation γγ- coincidences from {sup 13}N(β{sup +}ν){sup 13}C decay at the two-arm scintillation spectrometer.

  13. Potassium-decorated active carbon supported Co-Mo-based catalyst for water-gas shift reaction

    Institute of Scientific and Technical Information of China (English)

    Yixin Lian; RuiFen Xiao; Weiping Fang; Yiquan Yang

    2011-01-01

    The effect of potassium-decoration was studied on the activity of water-gas shift(WGS)reaction over the Co-Mo-based catalysts supported on active carbon(AC),which was prepared by incipient wetness co-impregnation method.The decoration of potassium on active carbon in advance enhances the activities of the CoMo-K/AC catalysts for WGS reaction.Highest activity(about 92% conversion)was obtained at250 ℃ for the catalyst with an optimum K2O/AC weight ratio in the range from 0.12 to 0.15.The catalysts were characterized by TPR and EPR,and the results show that activated carbon decorated with potassium makes Co-Mo species highly dispersed,and thus easily reduced and sulfurized.XRD results show that an appropriate content of potassium-decoration on active carbon supports may favors the formation of highly dispersed Co9Ss-type structures which are situated on the edge or a site in contact with MoS2,K-Mo-O-S,Mo-S-K phase.Those active species are responsible for the high activity of CoMo-K/AC catalysts.

  14. Optimal control of a Cope rearrangement by coupling the reaction path to a dissipative bath or a second active mode

    Energy Technology Data Exchange (ETDEWEB)

    Chenel, A. [Laboratoire de Chimie Physique, UMR 8000 and CNRS, Université Paris-Sud, F-91405 Orsay (France); Meier, C. [Laboratoire Collisions, Agrégats, Réactivité, UMR 5589, IRSAMC, Université Paul Sabatier, F-31062 Toulouse (France); Dive, G. [Centre d’Ingéniérie des Protéines, Université de Liège, Sart Tilman, B6, B-4000 Liège (Belgium); Desouter-Lecomte, M. [Laboratoire de Chimie Physique, UMR 8000 and CNRS, Université Paris-Sud, F-91405 Orsay (France); Département de Chimie, Université de Liège, Bât B6c, Sart Tilman, B4000 Liège (Belgium)

    2015-01-14

    We compare the strategy found by the optimal control theory in a complex molecular system according to the active subspace coupled to the field. The model is the isomerization during a Cope rearrangement of Thiele’s ester that is the most stable dimer obtained by the dimerization of methyl-cyclopentadienenylcarboxylate. The crudest partitioning consists in retaining in the active space only the reaction coordinate, coupled to a dissipative bath of harmonic oscillators which are not coupled to the field. The control then fights against dissipation by accelerating the passage across the transition region which is very wide and flat in a Cope reaction. This mechanism has been observed in our previous simulations [Chenel et al., J. Phys. Chem. A 116, 11273 (2012)]. We compare here, the response of the control field when the reaction path is coupled to a second active mode. Constraints on the integrated intensity and on the maximum amplitude of the fields are imposed limiting the control landscape. Then, optimum field from one-dimensional simulation cannot provide a very high yield. Better guess fields based on the two-dimensional model allow the control to exploit different mechanisms providing a high control yield. By coupling the reaction surface to a bath, we confirm the link between the robustness of the field against dissipation and the time spent in the delocalized states above the transition barrier.

  15. Prevention of a systematic underestimation of antioxidant activity in competition assays. The impact of unspecific reactions of the reactive species.

    Science.gov (United States)

    Beljaars, Christiaan P; Balk, Jiska M; Bast, Aalt; Haenen, Guido R M M

    2010-02-12

    In antioxidant competition assays, an antioxidant (A) and a detector compound (D) compete for a reactive species (R). In the evaluation of these assays, it is tacitly assumed that all of R is captured by either D or A. Due to the - by definition - high reactivity of R, unspecific reactions of R are likely to occur and neglecting these reactions will result in a systematic underestimation of antioxidant activity. It was shown that in the standard hydroxyl radical scavenging assay this was indeed the case; the inaccurate mathematical evaluation resulted in an underestimation of antioxidant activity of 25% in this competition assay. The systematic underestimation of antioxidant activity can be prevented by using an adjusted Stern-Volmer equation that takes into account that only part of R is captured by D or A.

  16. Activation cross-sections of deuteron induced nuclear reactions on manganese up to 40 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Ditroi, F., E-mail: ditroi@atomki.hu [Institute of Nuclear Research of the Hungarian Academy of Sciences (ATOMKI), Debrecen (Hungary); Tarkanyi, F.; Takacs, S. [Institute of Nuclear Research of the Hungarian Academy of Sciences (ATOMKI), Debrecen (Hungary); Hermanne, A. [Cyclotron Laboratory, Vrije Universiteit Brussel (VUB), Brussels (Belgium); Yamazaki, H.; Baba, M.; Mohammadi, A. [Cyclotron and Radioisotope Center (CYRIC), Tohoku University, Sendai (Japan); Ignatyuk, A.V. [Institute of Physics and Power Engineering (IPPE), Obninsk (Russian Federation)

    2011-09-01

    In the frame of a systematic study on activation cross-sections of deuteron induced reactions experimental excitation functions on {sup 55}Mn were measured with the activation method using the stacked foil irradiation technique up to 40 MeV. By using high resolution {gamma}-ray spectrometry, cross-section data for the production of {sup 56,54,52}Mn and {sup 51}Cr were determined. Comparison with the earlier published data and with the results predicted by the ALICE-IPPE and EMPIRE-II theoretical codes - improved for more reliable calculations for d-induced reactions - and with data in the TENDL 2010 libraries are also included. Thick target yields were calculated from a fit to our experimental excitation curves and implications for practical applications in industrial (Thin Layer Activation) accelerator technology are discussed.

  17. Analysis of the total activation cross section of all possible reactions producing the same radioactive nuclide for the same element

    Institute of Scientific and Technical Information of China (English)

    ZHOU Feng-Qun; SONG Yue-Li; TUO Fei; KONG Xiang-Zhong

    2011-01-01

    Firstly,according to the regulation of growth and decay of radioactive nuclides produced in reactions,a formula used to calculate the total activation cross section of all possible reactions producing the same radioactive nuclide for the same element is deduced,and it is pointed out that the activation formula given in two references is incorrect.Then,as an example,the so-called total activation cross section in one of the two references is analyzed and the correct results of the cross sections of 182W(n,p)182(m+g)Ta,183W(n,p)183Ta and 206Pb(n,a)203Hg induced by neutrons around 14 MeV calculated with the data given in the literature,the nuclear parameters and some evaluated values are given.Finally,the correct results are compared with other values collected in the literature.

  18. Activation cross-sections of deuteron induced nuclear reactions on rhenium up to 40 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Ditrói, F., E-mail: ditroi@atomki.hu [Institute of Nuclear Research of the Hungarian Academy of Sciences (ATOMKI), Debrecen (Hungary); Tárkányi, F.; Takács, S. [Institute of Nuclear Research of the Hungarian Academy of Sciences (ATOMKI), Debrecen (Hungary); Hermanne, A. [Cyclotron Laboratory, Vrije Universiteit Brussel (VUB), Brussels (Belgium); Yamazaki, H.; Baba, M.; Mohammadi, A. [Cyclotron Radioisotope Center (CYRIC), Tohoku University, Sendai (Japan); Ignatyuk, A.V. [Institute of Physics and Power Engineering (IPPE), Obninsk (Russian Federation)

    2013-02-01

    Highlights: ► Excitation function measurement of deuteron induced reactions on rhenium up to 40 MeV. ► Model code calculations with EMPIRE-D, ALICE-D and TALYS (TENDL-2011). ► Integral production yield calculation. ► Thin layer activation (TLA) curves; {sup 185}Os and {sup 186}Re. -- Abstract: As a part of a thorough work of excitation functions on deuteron induced reactions, experimental cross-sections of {sup 185,183m,183g,182}Os and {sup 188,186,184m,184g,183}Re activation products on {sup nat}Re were measured up to 40 MeV for the first time with the activation method using a stacked foil irradiation technique and high resolution γ-spectrometry. Comparison with the former results of other laboratories and with the predictions of the ALICE-IPPE and EMPIRE-3 model codes, modified for improved calculations for deuteron reactions, and with data in the TENDL-2011 library are also presented. Thick target yields were given deduced from our experimental cross-sections and compared with the few literature values. For practical applications (thin layer activation) also activity versus depth distributions were calculated for selected isotopes.

  19. Active MnO{sub x} electrocatalysts prepared by atomic layer deposition for oxygen evolution and oxygen reduction reactions

    Energy Technology Data Exchange (ETDEWEB)

    Pickrahn, Katie L.; Park, Sang Wook; Gorlin, Yelena; Lee, Han-Bo-Ram; Jaramillo, Thomas F.; Bent, Stacey F. [Department of Chemical Engineering, Stanford University, Stanford, CA 94305-5025 (United States)

    2012-10-15

    The ability to deposit conformal catalytic thin films enables opportunities to achieve complex nanostructured designs for catalysis. Atomic layer deposition (ALD) is capable of creating conformal thin films over complex substrates. Here, ALD-MnO{sub x} on glassy carbon is investigated as a catalyst for the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR), two reactions that are of growing interest due to their many applications in alternative energy technologies. The films are characterized by X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy, ellipsometry, and cyclic voltammetry. The as-deposited films consist of Mn(II)O, which is shown to be a poor catalyst for the ORR, but highly active for the OER. By controllably annealing the samples, Mn{sub 2}O{sub 3} catalysts with good activity for both the ORR and OER are synthesized. Hypotheses are presented to explain the large difference in the activity between the MnO and Mn{sub 2}O{sub 3} catalysts for the ORR, but similar activity for the OER, including the effects of surface oxidation under experimental conditions. These catalysts synthesized though ALD compare favorably to the best MnO{sub x} catalysts in the literature, demonstrating a viable way to produce highly active, conformal thin films from earth-abundant materials for the ORR and the OER. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  20. Surface-Limited Synthesis of Pt Nanocluster Decorated Pd Hierarchical Structures with Enhanced Electrocatalytic Activity toward Oxygen Reduction Reaction.

    Science.gov (United States)

    Yang, Tao; Cao, Guojian; Huang, Qingli; Ma, Yanxia; Wan, Sheng; Zhao, Hong; Li, Na; Sun, Xia; Yin, Fujun

    2015-08-12

    Exploring superior catalysts with high catalytic activity and durability is of significant for the development of an electrochemical device involving the oxygen reduction reaction. This work describes the synthesis of Pt-on-Pd bimetallic heterogeneous nanostructures, and their high electrocatalytic activity toward the oxygen reduction reaction (ORR). Pt nanoclusters with a size of 1-2 nm were generated on Pd nanorods (NRs) through a modified Cu underpotential deposition (UPD) process free of potential control and a subsequent surface-limited redox reaction. The Pt nanocluster decorated Pd nanostructure with a ultralow Pt content of 1.5 wt % exhibited a mass activity of 105.3 mA mg(-1) (Pt-Pd) toward ORR, comparable to that of the commercial Pt/C catalyst but 4 times higher than that of carbon supported Pd NRs. More importantly, the carbon supported Pt-on-Pd catalyst displays relatively small losses of 16% in electrochemical surface area (ECSA) and 32% in mass activity after 10 000 potential sweeps, in contrast to respective losses of 46 and 64% for the commercial Pt/C catalyst counterpart. The results demonstrated that Pt decoration might be an efficient way to improve the electrocatalytic activity of Pd and in turn allow Pd to be a promising substitution for commercial Pt catalyst.

  1. Metal halide hydrates as lewis acid catalysts for the conjugated friedel-crafts reactions of indoles and activated olefins

    Energy Technology Data Exchange (ETDEWEB)

    Schwalm, Cristiane S.; Ceschi, Marco Antonio; Russowsky, Dennis, E-mail: dennis@iq.ufrgs.b [Universidade Federal do Rio Grande do Sul (IQ/UFRGS), Porto Alegre, RS (Brazil). Inst. de Quimica

    2011-07-01

    Metal halide hydrates such as SnCl{sub 2{center_dot}}2H{sub 2}O, MnCl{sub 2{center_dot}}4H{sub 2}O, SrCl{sub 2{center_dot}}6H{sub 2}O, CrCl{sub 2{center_dot}}6H{sub 2}O, CoCl{sub 2{center_dot}}6H{sub 2}O e CeCl{sub 3{center_dot}}7H{sub 2}O were investigated as mild Lewis acids catalysts for the conjugate Friedel-Crafts reaction between indoles and activated olefins. The reactions were carried out with aliphatic unsaturated ketones over a period of days at room temperature, while chalcones reacted only under reflux conditions. The reactions with nitrostyrene s were either performed in solvent or under solventless conditions. In all cases reasonable to good yields were obtained. (author)

  2. Adduct Formation, B-H Activation and Ring Expansion at Room Temperature from Reactions of HBcat with NHCs.

    Science.gov (United States)

    Würtemberger-Pietsch, Sabrina; Schneider, Heidi; Marder, Todd B; Radius, Udo

    2016-09-05

    We report the reactions of catecholborane (HBcat; 1) with unsaturated and saturated NHCs as well as CAAC(Me) . Mono-NHC adducts of the type HBcat⋅NHC (NHC=nPr2 Im, iPr2 Im, iPr2 Im(Me) , and Dipp2 Im) were obtained by stoichiometric reactions of HBcat with the unsaturated NHCs. The reaction of CAAC(Me) with HBcat yielded the B-H activated product CAAC(Me) (H)Bcat via insertion of the carbine-carbon atom into the B-H bond. The saturated NHC Dipp2 SIm reacted in a 2:2 ratio yielding an NHC ring-expanded product at room temperature forming a six-membered -B-C=N-C=C-N- ring via C-N bond cleavage and further migration of the hydrides from two HBcat molecules to the former carbene-carbon atom.

  3. Monocatenary, branched, double-headed, and bolaform surface active carbohydrate esters via photochemical thiol-ene/-yne reactions.

    Science.gov (United States)

    Boyère, Cédric; Broze, Guy; Blecker, Christophe; Jérôme, Christine; Debuigne, Antoine

    2013-10-18

    An original and versatile method for the synthesis of a range of novel mannose-based surfactants was developed via metal-free photo-induced thiol-ene/-yne 'click' reactions. This light-mediated hydrothiolation reaction involving a thiolated mannose was successfully applied to terminal and internal alkenes, dienes, and alkynes, leading to monocatenary, branched, double-headed, and bolaform amphiphilic carbohydrate esters, respectively. A surface activity study showed that these new compounds possess valuable properties and display specific behavior at the air-water interface. It also demonstrated the greater flexibility of the thioether moiety in the spacer of the surfactants produced via a thiol-ene reaction in comparison with the triazole heterocyclic rings in similar glucose-based surfactants synthesized elsewhere by the alkyne-azide 1,3-dipolar addition.

  4. On-demand electrochemical activation of the click reaction on self-assembled monolayers on gold presenting masked acetylene groups.

    Science.gov (United States)

    Choi, Inseong; Kim, Young-Kwan; Min, Dal-Hee; Lee, SangWook; Yeo, Woon-Seok

    2011-10-26

    We report on a new surface modification method for grafting a "dynamic" property for on-demand activation of the click reaction. Our approach utilizes the acetylene group masked with dicobalt hexacarbonyl, Co(2)(CO)(6), which is not reactive toward the click reaction. Electrochemical treatment reveals the acetylene group on the selected region, which is then used as a chemical handle for surface functionalization via the click reaction with an azide-containing molecule. Electrochemical and chemical conversions on the surface were verified by cyclic voltammetry, X-ray photoelectron spectroscopy, and fluorescence spectroscopy. We have demonstrated immobilization of an azide-modified RGD peptide and promotion of cell adhesion/migration to the region of electrochemical induction.

  5. Modeling of catalytically active metal complex species and intermediates in reactions of organic halides electroreduction.

    Science.gov (United States)

    Lytvynenko, Anton S; Kolotilov, Sergey V; Kiskin, Mikhail A; Eremenko, Igor L; Novotortsev, Vladimir M

    2015-02-28

    The results of quantum chemical modeling of organic and metal-containing intermediates that occur in electrocatalytic dehalogenation reactions of organic chlorides are presented. Modeling of processes that take place in successive steps of the electrochemical reduction of representative C1 and C2 chlorides - CHCl3 and Freon R113 (1,1,2-trifluoro-1,2,2-trichloroethane) - was carried out by density functional theory (DFT) and second-order Møller-Plesset perturbation theory (MP2). It was found that taking solvation into account using an implicit solvent model (conductor-like screening model, COSMO) or considering explicit solvent molecules gave similar results. In addition to modeling of simple non-catalytic dehalogenation, processes with a number of complexes and their reduced forms, some of which were catalytically active, were investigated by DFT. Complexes M(L1)2 (M = Fe, Co, Ni, Cu, Zn, L1H = Schiff base from 2-pyridinecarbaldehyde and the hydrazide of 4-pyridinecarboxylic acid), Ni(L2) (H2L2 is the Schiff base from salicylaldehyde and 1,2-ethylenediamine, known as salen) and Co(L3)2Cl2, representing a fragment of a redox-active coordination polymer [Co(L3)Cl2]n (L3 is the dithioamide of 1,3-benzenedicarboxylic acid), were considered. Gradual changes in electronic structure in a series of compounds M(L1)2 were observed, and correlations between [M(L1)2](0) spin-up and spin-down LUMO energies and the relative energies of the corresponding high-spin and low-spin reduced forms, as well as the shape of the orbitals, were proposed. These results can be helpful for determination of the nature of redox-processes in similar systems by DFT. No specific covalent interactions between [M(L1)2](-) and the R113 molecule (M = Fe, Co, Ni, Zn) were found, which indicates that M(L1)2 electrocatalysts act rather like electron transfer mediators via outer-shell electron transfer. A relaxed surface scan of the adducts {M(L1)2·R113}(-) (M = Ni or Co) versus the distance between the

  6. Influence of the overall charge and local charge density of pectin on the complex formation between pectin and beta-lactoglobulin

    NARCIS (Netherlands)

    Sperber, Bram L. H. M.; Schols, Henk A.; Stuart, Martien A. Cohen; Norde, Willem; Voragen, Alphons G. J.

    2009-01-01

    The complex formation between beta-lactoglobulin (beta-lg) and pectin is studied using pectins with different physicochemical characteristics. Pectin allows for the control of both the overall charge by degree of methyl-esterification as well as local charge density by the degree of blockiness. Vary

  7. Ternary complex formation between AmtB, GlnZ and the nitrogenase regulatory enzyme DraG reveals a novel facet of nitrogen regulation in bacteria.

    Science.gov (United States)

    Huergo, Luciano F; Merrick, Mike; Pedrosa, Fábio O; Chubatsu, Leda S; Araujo, Luíza M; Souza, Emanuel M

    2007-12-01

    Ammonium movement across biological membranes is facilitated by a class of ubiquitous channel proteins from the Amt/Rh family. Amt proteins have also been implicated in cellular responses to ammonium availability in many organisms. Ammonium sensing by Amt in bacteria is mediated by complex formation with cytosolic proteins of the P(II) family. In this study we have characterized in vitro complex formation between the AmtB and P(II) proteins (GlnB and GlnZ) from the diazotrophic plant-associative bacterium Azospirillum brasilense. AmtB-P(II) complex formation only occurred in the presence of adenine nucleotides and was sensitive to 2-oxoglutarate when Mg(2+) and ATP were present, but not when ATP was substituted by ADP. We have also shown in vitro complex formation between GlnZ and the nitrogenase regulatory enzyme DraG, which was stimulated by ADP. The stoichiometry of this complex was 1:1 (DraG monomer : GlnZ trimer). We have previously reported that in vivo high levels of extracellular ammonium cause DraG to be sequestered to the cell membrane in an AmtB and GlnZ-dependent manner. We now report the reconstitution of a ternary complex involving AmtB, GlnZ and DraG in vitro. Sequestration of a regulatory protein by the membrane-bound AmtB-P(II) complex defines a new regulatory role for Amt proteins in Prokaryotes.

  8. A biocompatible in vivo ligation reaction and its application for noninvasive bioluminescent imaging of protease activity in living mice.

    Science.gov (United States)

    Godinat, Aurélien; Park, Hyo Min; Miller, Stephen C; Cheng, Ke; Hanahan, Douglas; Sanman, Laura E; Bogyo, Matthew; Yu, Allen; Nikitin, Gennady F; Stahl, Andreas; Dubikovskaya, Elena A

    2013-05-17

    The discovery of biocompatible reactions had a tremendous impact on chemical biology, allowing the study of numerous biological processes directly in complex systems. However, despite the fact that multiple biocompatible reactions have been developed in the past decade, very few work well in living mice. Here we report that D-cysteine and 2-cyanobenzothiazoles can selectively react with each other in vivo to generate a luciferin substrate for firefly luciferase. The success of this "split luciferin" ligation reaction has important implications for both in vivo imaging and biocompatible labeling strategies. First, the production of a luciferin substrate can be visualized in a live mouse by bioluminescence imaging (BLI) and furthermore allows interrogation of targeted tissues using a "caged" luciferin approach. We therefore applied this reaction to the real-time noninvasive imaging of apoptosis associated with caspase 3/7. Caspase-dependent release of free D-cysteine from the caspase 3/7 peptide substrate Asp-Glu-Val-Asp-D-Cys (DEVD-(D-Cys)) allowed selective reaction with 6-amino-2-cyanobenzothiazole (NH(2)-CBT) in vivo to form 6-amino-D-luciferin with subsequent light emission from luciferase. Importantly, this strategy was found to be superior to the commercially available DEVD-aminoluciferin substrate for imaging of caspase 3/7 activity. Moreover, the split luciferin approach enables the modular construction of bioluminogenic sensors, where either or both reaction partners could be caged to report on multiple biological events. Lastly, the luciferin ligation reaction is 3 orders of magnitude faster than Staudinger ligation, suggesting further applications for both bioluminescence and specific molecular targeting in vivo.

  9. Measurement of reaction-in-flight neutrons using thulium activation at the National Ignition Facility

    Science.gov (United States)

    Grim, G. P.; Rundberg, R.; Fowler, M. M.; Hayes, A. C.; Jungman, G.; Boswell, M.; Klein, A.; Wilhelmy, J.; Tonchev, A.; Yeamans, C. B.

    2014-09-01

    We report on the first observation of tertiary reaction-in-flight (RIF) neutrons produced in compressed deuterium and tritium filled capsules using the National Ignition Facility at Lawrence Livermore National Laboratory, Livermore, CA. RIF neutrons are produced by third-order, out of equilibrium ("in-flight") fusion reactions, initiated by primary fusion products. The rate of RIF reactions is dependent upon the range of the elastically scattered fuel ions and therefore a diagnostic of Coulomb physics within the plasma. At plasma temperatures of ˜5 keV, the presence of neutrons with kinetic energies greater than 15 MeV is a unique signature for RIF neutron production. The reaction 169Tm(n,3n)167Tm has a threshold of 15.0 MeV, and a unique decay scheme making it a suitable diagnostic for observing RIF neutrons. RIF neutron production is quantified by the ratio of 167Tm/168Tm observed in a 169Tm foil, where the reaction 169Tm(n,2n)168Tm samples the primary neutron fluence. Averaged over 4 implosions1-4 at the NIF, the 167Tm/168Tm ratio is measured to be 1.5 +/- 0.3 x 10-5, leading to an average ratio of RIF to primary neutron ratio of 1.0 +/- 0.2 x 10-4. These ratios are consistent with the predictions for charged particle stopping in a quantum degenerate plasma.

  10. Supervisors' attitudes and skills for active listening with regard to working conditions and psychological stress reactions among subordinate workers.

    Science.gov (United States)

    Mineyama, Sachiko; Tsutsumi, Akizumi; Takao, Soshi; Nishiuchi, Kyoko; Kawakami, Norito

    2007-03-01

    We investigated whether supervisors' listening attitudes and skills were related to working conditions and psychological stress reactions among their subordinates. The subjects included 41 male supervisors and their immediate subordinates (n=203). The supervisors completed a short version of the Active Listening Attitude Scale (ALAS) consisting of two subscales: Listening Attitude and Listening Skill for Active Listening. The subordinates rated working conditions and their psychological stress reactions using selected scales of the Job Content Questionnaire and the Brief Job Stress Questionnaire. Those subordinates who worked under supervisors with a higher score of Listening Attitude and Listening Skill reported a more favorable psychological stress reaction than those who worked under supervisors with a lower score of Listening Attitude and Listening Skill. Those subordinates who worked under supervisors with a higher score of Listening Skill reported higher worksite support than those who worked under supervisors with a lower score of Listening Skill. Those subordinates who worked under supervisors with a higher score of Listening Attitude reported higher job control than those who worked under supervisors with a lower score of Listening Attitude. A supervisor's listening attitude and skill appeared to affect psychological stress reactions predominantly among male subordinates than among female subordinates. Psychological stress reactions were lower among younger subordinates who worked under supervisors with high listening skill, while no statistically difference was observed among older subordinates. These findings suggest that a supervisor's listening attitude and skill have an effect on working conditions and psychological stress reactions among subordinates and that the effects vary according to the subordinates' sex and age.

  11. The research of neurospecific proteins and lysosomal peptidehydrolases in frontal neocortex during forming conditioned reaction of active avoiding of rats

    Directory of Open Access Journals (Sweden)

    Vyatkin O. K.

    2009-04-01

    Full Text Available Dynamics of the activity of neuronal cell adhesion molecule (NCAM and lysosomal cysteine cathepsins B, L, H was researched in frontal neocortex of rat brain during forming a conditioned reaction of active avoiding. The quantitative estimation of NCAM content in the neocortex membrane fraction was carried on by ELISA in 3, 7, 14 and 21 days after starting animals’ training. The dynamics correlation between the NCAM content increasing and cysteine cathepsins activity was obtained, especially for aminopeptidase cathepsin H during the process of memory engram forming in frontal neocortex of rat brain.

  12. On the possibility of the reaction (CuMoO4 + C, using the apparent activation energy method

    Directory of Open Access Journals (Sweden)

    A. D. Mekhtiev

    2015-07-01

    Full Text Available This article discusses the calculation of the apparent activation energy (CuМоO4 + C on the DTA (Differential Thermal Analysis curve, to study and optimize the time-temperature synthesis mode, in particular, the activation energy. Activation energy allows us to investigate the elementary act of chemical interaction. Thus, we propose to use this method to calculate the interaction of Eact (CuМоO4 + C in the solid phase of hardening occurring during synthesis. These results allow us to trace how much energy is expended to start the reaction.

  13. EEG reactions of the human brain in the gradient magnetic field zone of the active geological fault (pilot study)

    Science.gov (United States)

    Pobachenko, S. V.; Shitov, A. V.; Grigorjev, P. E.; Sokolov, M. V.; Zubrilkin, A. I.; Vypiraylo, D. N.; Solovjev, A. V.

    2016-12-01

    This paper presents the results of experimental studies of the dynamics of the functional state of a person within the zone of an active geological fault characterized by abnormal spatial distribution of the magnetic- field vector values. It is shown that these geophysical modifications have a pronounced effect on the fluctuations of the electrical activity of the human brain. When the person gets into a zone with abnormal levels of gradient magnetic field in the absence of any subjective sensations, a nonspecific orientation activation reaction is observed, which is characterized by a significant increase in the levels of peak performance in key functional EEG frequency bands.

  14. An insight into the process and mechanism of a mechanically activated reaction for synthesizing AlH3 nano-composites.

    Science.gov (United States)

    Duan, Congwen; Hu, Lianxi; Sun, Yu; Zhou, Haiping; Yu, Huan

    2015-10-07

    The reaction pathway as well as the mechanism of the solid state reaction between MgH2 and AlCl3 has been a mystery so far. Based on SEM, TEM and NMR (Nuclear Magnetic Resonance) analyses, an amorphous intermediate (AlH6)n was preferentially formed and recrystallized as a γ phase at the final stage of the reaction. As a novel finding, this research provides a deep insight into the process and mechanism of this mechanically activated reaction.

  15. Surface complex formation between aliphatic nitrile molecules and transition metal atoms for thermally stable lithium-ion batteries.

    Science.gov (United States)

    Kim, Young-Soo; Lee, Hochun; Song, Hyun-Kon

    2014-06-11

    Non-flammability of electrolyte and tolerance of cells against thermal abuse should be guaranteed for widespread applications of lithium-ion batteries (LIBs). As a strategy to improve thermal stability of LIBs, here, we report on nitrile-based molecular coverage on surface of cathode active materials to block or suppress thermally accelerated side reactions between electrode and electrolyte. Two different series of aliphatic nitriles were introduced as an additive into a carbonate-based electrolyte: di-nitriles (CN-[CH2]n-CN with n = 2, 5, and 10) and mono-nitriles (CH3-[CH2]m-CN with m = 2, 5, and 10). On the basis of the strong interaction between the electronegativity of nitrile functional groups and the electropositivity of cobalt in LiCoO2 cathode, aliphatic mono- and di-nitrile molecules improved the thermal stability of lithium ion cells by efficiently protecting the surface of LiCoO2. Three factors, the surface coverage θ, the steric hindrance of aliphatic moiety within nitrile molecule, and the chain polarity, mainly affect thermal tolerance as well as cell performances at elevated temperature.

  16. Dissection of the radical reactions linked to fetal hemoglobin reveals enhanced pseudoperoxidase activity

    Directory of Open Access Journals (Sweden)

    Khuanpiroon eRatanasopa

    2015-02-01

    Full Text Available In the presence of excess hydrogen peroxide (H2O2, ferrous (Fe+2 human hemoglobin (Hb (α2β2 undergoes a rapid conversion to a higher oxidation ferryl state (Fe+4 which rapidly autoreduces back to the ferric form (Fe+3 as H2O2 is consumed in the reaction. In the presence of additional H2O2 the ferric state can form both ferryl Hb and an associated protein radical in a pseudoperoxidative cycle that results in the loss of radicals and heme degradation. We examined whether adult HbA exhibits a different pseudoenzymatic activity than fetal Hb (α2γ2 due to the switch of γ to β subunits. Rapid mixing of the ferric forms of both proteins with excess H2O2 resulted in biphasic kinetic time courses that can be assigned to γ/β and α respectively. Although there was a 1.5 fold increase in the fast reacting γ /β subunits the slower reacting phases (attributed to α subunits of both proteins were essentially the same. However, the rate constant for the auto-reduction of ferryl back to ferric for both proteins was found to be 76% higher for HbF than HbA and in the presence of the mild reducing agent, ascorbate there was a 3 -fold higher reduction rate in ferryl HbF as opposed to ferryl HbA. Using quantitative mass spectrometry in the presence of H2O2 we found oxidized γ/β Cys93, to be more abundantly present in HbA than HbF, whereas higher levels of nitrated β Tyr35 containing peptides were found in HbA samples treated with nitrite. The extraordinary stability of HbF reported here may explain the evolutionary advantage this protein may confer onto co-inherited hemoglobinopathies and can also be utilized in the engineering of oxidatively stable Hb-based oxygen carriers.

  17. Increased metabolic activity detected by FLIM in human breast cancer cells with desmoplastic reaction: a pilot study

    Science.gov (United States)

    Natal, Rodrigo de Andrade; Pelegati, Vitor B.; Bondarik, Caroline; Mendonça, Guilherme R.; Derchain, Sophie F.; Lima, Carmen P.; Cesar, Carlos L.; Sarian, Luís. O.; Vassallo, José

    2015-07-01

    Introduction: In breast cancer (BC), desmoplastic reaction, assembled primarily by fibroblasts, is associated with unfavorable prognosis, but the reason of this fact remains still unclear. In this context, nonlinear optics microscopy, including Fluorescence Lifetime Imaging Microscopy (FLIM), has provided advancement in cellular metabolism research. In this paper, our purpose is to differentiate BC cells metabolism with or without contact to desmoplastic reaction. Formalin fixed, paraffin embedded samples were used at different points of hematoxylin stained sections. Methodology: Sections from 14 patients with invasive ductal breast carcinoma were analyzed with FLIM methodology to NAD(P)H and FAD fluorescence lifetime on a Confocal Upright LSM780 NLO device (Carl Zeiss AG, Germany). Quantification of the fluorescence lifetime and fluorescence intensity was evaluated by SPC Image software (Becker &Hickl) and ImageJ (NIH), respectively. Optical redox ratio was calculated by dividing the FAD fluorescence intensity by NAD(P)H fluorescence intensity. Data value for FLIM measurements and fluorescence intensities were calculated using Wilcoxon test; p< 0.05 was considered significant. Results: BC cells in contact with desmoplastic reaction presented a significantly lower NAD(P)H and FAD fluorescence lifetime. Furthermore, optical redox ratio was also lower in these tumor cells. Conclusion: Our results suggest that contact of BC cells with desmoplastic reaction increase their metabolic activity, which might explain the adverse prognosis of cases associated with higher peritumoral desmoplastic reaction.

  18. Production of Medical Radioisotopes with High Specific Activity in Photonuclear Reactions with $\\gamma$ Beams of High Intensity and Large Brilliance

    CERN Document Server

    Habs, D

    2010-01-01

    We study the production of radioisotopes for nuclear medicine in $(\\gamma,x{\\rm n}+y{\\rm p})$ photonuclear reactions or ($\\gamma,\\gamma'$) photoexcitation reactions with high flux [($10^{13}-10^{15}$)$\\gamma$/s], small diameter $\\sim (100 \\, \\mu$m$)^2$ and small band width ($\\Delta E/E \\approx 10^{-3}-10^{-4}$) $\\gamma$ beams produced by Compton back-scattering of laser light from relativistic brilliant electron beams. We compare them to (ion,$x$n$ + y$p) reactions with (ion=p,d,$\\alpha$) from particle accelerators like cyclotrons and (n,$\\gamma$) or (n,f) reactions from nuclear reactors. For photonuclear reactions with a narrow $\\gamma$ beam the energy deposition in the target can be managed by using a stack of thin target foils or wires, hence avoiding direct stopping of the Compton and pair electrons (positrons). $(\\gamma,\\gamma')$ isomer production via specially selected $\\gamma$ cascades allows to produce high specific activity in multiple excitations, where no back-pumping of the isomer to the ground st...

  19. Intramolecular C-N bond activation and ring-expansion reactions of N-heterocyclic carbenes.

    Science.gov (United States)

    Hemberger, Patrick; Bodi, Andras; Berthel, Johannes H J; Radius, Udo

    2015-01-19

    Intramolecular ring-expansion reactions (RER) of the N-heterocyclic carbene 1,3-dimethylimidazolin-2-ylidene were observed upon vacuum ultraviolet (VUV) photoexcitation. Similarly to RERs reported in the solvent phase, for the reaction of NHCs with main-group-element hydrides, hydrogen transfer to the NHC carbon atom is the crucial initial step. In an ionization-mediated protonation, 1,3-dimethylimidazolin-2-ylidene forms an imidazolium ion, which is the rate-limiting step on the pathway to two six-membered ring products, namely, methylpyrimidinium and -pyrazinium ions. To unravel the reaction path, we have used imaging photoelectron photoion coincidence spectroscopy with VUV synchrotron radiation, as well as high-level composite method calculations. Similarities and differences between the mechanism in the gas phase and in the condensed phase are discussed.

  20. Remarkable fluorescence enhancement versus complex formation of cationic porphyrins on the surface of ZnO nanoparticles

    KAUST Repository

    Aly, Shawkat Mohammede

    2014-06-12

    Fluorescence enhancement of organic fluorophores shows tremendous potential to improve image contrast in fluorescence-based bioimaging. Here, we present an experimental study of the interaction of two cationic porphyrins, meso-tetrakis(1-methylpyridinium-4-yl)porphyrin chloride (TMPyP) and meso-tetrakis(4-N,N,N-trimethylanilinium)porphyrin chloride (TMAP), with cationic surfactant-stabilized zinc oxide nanoparticles (ZnO NPs) based on several steady-state and time-resolved techniques. We show the first experimental measurements demonstrating a clear transition from pronounced fluorescence enhancement to charge transfer (CT) complex formation by simply changing the nature and location of the positive charge of the meso substituent of the cationic porphyrins. For TMPyP, we observe a sixfold increase in the fluorescence intensity of TMPyP upon addition of ZnO NPs. Our experimental results indicate that the electrostatic binding of TMPyP with the surface of ZnO NPs increases the symmetry of the porphyrin macrocycle. This electronic communication hinders the rotational relaxation of the meso unit and/or decreases the intramolecular CT character between the cavity and the meso substituent of the porphyrin, resulting in the enhancement of the intensity of the fluorescence. For TMAP, on the other hand, the different type and nature of the positive charge resulting in the development of the CT band arise from the interaction with the surface of ZnO NPs. This observation is confirmed by the femtosecond transient absorption spectroscopy, which provides clear spectroscopic signatures of photoinduced electron transfer from TMAP to ZnO NPs. © 2014 American Chemical Society.

  1. Establishment of an in silico phospholipidosis prediction method using descriptors related to molecular interactions causing phospholipid-compound complex formation.

    Science.gov (United States)

    Haranosono, Yu; Nemoto, Shingo; Kurata, Masaaki; Sakaki, Hideyuki

    2016-04-01

    Although phospholipidosis (PLD) often affects drug development, there is no convenient in vitro or in vivo test system for PLD detection. In this study, we developed an in silico PLD prediction method based on the PLD-inducing mechanism. We focused on phospholipid (PL)-compound complex formation, which inhibits PL degradation by phospholipase. Thus, we used some molecular interactions, such as electrostatic interactions, hydrophobic interactions, and intermolecular forces, between PL and compounds as descriptors. First, we performed descriptor screening for intermolecular force and then developed a new in silico PLD prediction using descriptors related to molecular interactions. Based on the screening, we identified molecular refraction (MR) as a descriptor of intermolecular force. It is known that ClogP and most-basic pKa can be used for PLD prediction. Thereby, we developed an in silico prediction method using ClogP, most-basic pKa, and MR, which were related to hydrophobic interactions, electrostatic interactions, and intermolecular forces. In addition, a resampling method was used to determine the cut-off values for each descriptor. We obtained good results for 77 compounds as follows: sensitivity = 95.8%, specificity = 75.9%, and concordance = 88.3%. Although there is a concern regarding false-negative compounds for pKa calculations, this predictive ability will be adequate for PLD screening. In conclusion, the mechanism-based in silico PLD prediction method provided good prediction ability, and this method will be useful for evaluating the potential of drugs to cause PLD, particularly in the early stage of drug development, because this method only requires knowledge of the chemical structure.

  2. Inhibition of anaphylaxis-like reaction and mast cell activation by water extract from the fruiting body of Phellinus linteus.

    Science.gov (United States)

    Choi, Yun Ho; Yan, Guang Hai; Chai, Ok Hee; Lim, Jung Min; Sung, So Young; Zhang, Xin; Kim, Ji-Hyun; Choi, Su Hwan; Lee, Moo Sam; Han, Eui-Hyeog; Kim, Hyoung Tae; Song, Chang Ho

    2006-07-01

    Mast cell-mediated anaphylactic reaction is involved in many allergic diseases such as asthma and allergic rhinitis. Phellinus linteus has been used as a traditional herb medicine in oriental countries and is known to have anti-tumor, immunomodulatory, anti-inflammatory, and anti-allergic activities. However, roles of Phellinus linteus in the mast cell-mediated anaphylactic reactions have not fully been examined. In the present study, we have investigated the effects of water extract from the fruiting body of Phellinus linteus (WEPL) on mast cell-mediated anaphylaxis-like reactions. Oral administration of WEPL inhibited the compound 48/80-induced systemic anaphylaxis-like reaction and ear swelling response. WEPL also inhibited the anti-dinitrophenyl (DNP) IgE-mediated passive systemic and cutaneous anaphylaxis. WEPL had no cytotoxicity on rat peritoneal mast cells (RPMC). WEPL dose-dependently reduced histamine release from RPMC activated by compound 48/80 or anti-DNP IgE. Moreover, WEPL decreased the compound 48/80-induced calcium uptake into RPMC. Furthermore, WEPL increased the level of intracellular cAMP and significantly inhibited the compound 48/80-induced cAMP reduction in RPMC. These results suggest that WEPL may serve as an effective therapeutic agent for allergic diseases.

  3. An iridium-mediated C-H activation/CO2-carboxylation reaction of 1,1-bisdiphenylphosphinomethane.

    Science.gov (United States)

    Langer, Jens; Fabra, María José; García-Orduña, Pilar; Lahoz, Fernando J; Görls, Helmar; Oro, Luis A; Westerhausen, Matthias

    2010-09-07

    The reaction of 1,1-bisdiphenylphosphinomethane (dppm, 4 eq.) with [IrCl(coe)(2)](2) results in a solvent dependent equilibrium from which the complexes [IrCl(dppm)(dppm-H)(H)] (1) and [Ir(dppm)(2)]Cl (2) were isolated. When 2 is dissolved in methanol, [IrCl(dppm)(2)(H)][OCH(3)] (4) is formed as dominant species in solution. The C-H activation reaction which leads to 1 and 4 can be suppressed by adding an additional dppm ligand per iridium center resulting in the formation of [Ir(dppm)(3)]Cl (5). If the reaction of dppm with [IrX(coe)(2)](2) (X = Cl, I) is performed under an atmosphere of CO(2) the complexes [IrX(dppm)(H){(Ph(2)P)(2)C-COOH}] (6: X = Cl; 7: X = I) are formed by a CH activation/CO(2) carboxylation sequence. The reaction of 6 with NH(4)PF yields [IrCl(dppm)(2)(H)]PF(6).(10). Additionally the lithium compounds [Li(dme)(2)(dppm-H)] (3) and [Li(dme){(Ph(2)P)(2)CHCOO}](2) (8) were prepared for comparison. The molecular structures of the compounds 1, 3, 5, 7, 8 and of the related iridium complex [IrCl(dppm)(2)(H)]I (11) are reported.

  4. Surface Acidity as Descriptor of Catalytic Activity for Oxygen Evolution Reaction in Li-O2 Battery.

    Science.gov (United States)

    Zhu, Jinzhen; Wang, Fan; Wang, Beizhou; Wang, Youwei; Liu, Jianjun; Zhang, Wenqing; Wen, Zhaoyin

    2015-10-28

    Unraveling the descriptor of catalytic activity, which is related to physical properties of catalysts, is a major objective of catalysis research. In the present study, the first-principles calculations based on interfacial model were performed to study the oxygen evolution reaction mechanism of Li2O2 supported on active surfaces of transition-metal compounds (TMC: oxides, carbides, and nitrides). Our studies indicate that the O2 evolution and Li(+) desorption energies show linear and volcano relationships with surface acidity of catalysts, respectively. Therefore, the charging voltage and desorption energies of Li(+) and O2 over TMC could correlate with their corresponding surface acidity. It is found that certain materials with an appropriate surface acidity can achieve the high catalytic activity in reducing charging voltage and activation barrier of rate-determinant step. According to this correlation, CoO should have as active catalysis as Co3O4 in reducing charging overpotential, which is further confirmed by our comparative experimental studies. Co3O4, Mo2C, TiC, and TiN are predicted to have a relatively high catalytic activity, which is consistent with the previous experiments. The present study enables the rational design of catalysts with greater activity for charging reactions of Li-O2 battery.

  5. Asymmetric hydrogenation with highly active IndolPhos-Rh catalysts: kinetics and reaction mechanism

    NARCIS (Netherlands)

    Wassenaar, J.; Kuil, M.; Lutz, M.; Spek, A.L.; Reek, J.N.H.

    2010-01-01

    The mechanism of the IndolPhos-Rh-catalyzed asymmetric hydrogenation of prochiral olefins has been investigated by means of X-ray crystal structure determination, kinetic measurements, high-pressure NMR spectroscopy, and DFT calculations. The mechanistic study indicates that the reaction follows an

  6. The role of reaction pathways and support interactions in the development of high activity hydrotreating catalysts

    DEFF Research Database (Denmark)

    Topsøe, Henrik; Hinnemann, Berit; Nørskov, Jens Kehlet

    2005-01-01

    Scanning tunneling microscopy (STM) investigations have recently provided the first atom-resolved images of reaction intermediates in the key steps of the hydrogenation (HYD) and direct desulfurization (DDS) pathways in hydrodesulfurization over MoS(2) nanoclusters. Surprisingly, special brim sites...

  7. Catalytic activation of copper (II) salts on the reaction of peroxynitrite with propofol in alkaline medium.

    Science.gov (United States)

    Kohnen, Stephan; Halusiak, Emilie; Mouithys-Mickalad, Ange; Deby-Dupont, Ginette; Deby, Carol; Hans, Pol; Lamy, Maurice; Noels, Alfred F

    2005-06-01

    We report here on the role of copper (II) salts on the acceleration of peroxynitrite (ONOO-) decomposition and ONOO- reaction with the anaesthetic agent propofol (2,6-diisopropylphenol) in alkaline medium. We observed a strong acceleration of the ONOO- decomposition in alkaline medium in the presence of copper (I and II) salts. After 18 h of ONOO- reaction with propofol, we observed nitrosated, nitrated, and oxidized (quinone and diphenylquinone) derivatives of propofol, but in the presence of Cu(II) (20% molar vs ONOO-), the yields of quinone and nitrosopropofol strongly increased. We also observed that the temperature and the atmosphere influenced the effects of Cu(II) on ONOO- reactions with propofol: low temperatures promoted nitrosation and high temperatures promoted oxidation; O2 atmosphere increased the general reactivity and the yield of nitrated and oxidized products. We highlighted the influence of Cu(II) salts on the radical character of the reaction by direct EPR technique. The exact mechanism of the Cu(II) catalysis remains unexplained, but we suggest the formation of a copper complex with propofol or, more probably, the oxidation of ONOO- into ONOO. by copper ions promoting the formation of quinone and nitrosopropofol according to a previously reported mechanism [M. Cudic, C. Ducrocq, Transformations of 2,6-diisopropylphenol by NO-derived nitrogen oxides, particularly peroxynitrite, Nitric Oxide 4 (2000) 147-156].

  8. A Mechanistic Study of Direct Activation of Allylic Alcohols in Palladium Catalyzed Amination Reactions

    NARCIS (Netherlands)

    Gumrukcu, Y.; de Bruin, B.; Reek, J.N.H.

    2015-01-01

    We here report a computational approach on the mechanism of allylicamination reactions using allyl-alcohols and amines as the substrates and phosphoramidite palladium catalyst 1a, which operates in the presence of catalytic amount of 1,3-diethylurea as a co-catalyst. DFT calculations showed a cooper

  9. Solvent-free Reactions of Formylferrocene with Active Methylene Containing Compounds

    Institute of Scientific and Technical Information of China (English)

    BAI Yin-Juan; GAN Hai-Ying; LU Jun; SHI Zhen

    2003-01-01

    @@ Since ferrocene was synthesized, derivatives of ferrocene have attracted the attention of chemists, and recently solvent-free organic reaction has been an important new dimension in preparative organic chemistry. [1] Solventless synthesis without the use of supporting reagents which can avoid the risk of high pressure development and volatile toxic solvent employment is very amaizing and eco-friendly.

  10. New macrocycles with potent antituberculosis activity accessed by one-pot multicomponent reactions

    NARCIS (Netherlands)

    Kim, D.; Huang, Y.; Wang, K.; Doemling, A.

    Based on modeling studies, we hypothesized that tylosin derivatives without formyl group should rather adopt an erythromycin-like binding mode to the ribosome. Twenty four 16-membered macrocyclic compounds were accessed by multicomponent reactions (Gewald, Ugi) of tylosin and investigated for their

  11. A catalytically active membrane reactor for fast, exothemic, heterogeneously catalysed reactions

    NARCIS (Netherlands)

    Veldsink, J.W.; Damme, R.M.J. van; Versteeg, G.F.; Swaaij, W.P.M. van

    1992-01-01

    A membrane reactor with separated feed of reactants is demonstrated as a promising contactor type when dealing with heterogeneously catalysed, very fast and exothermic gas phase reactions. Due to the separation of reactants a good control of the system is obtained, because process variables can be v

  12. Asymmetric hydrogenation with highly active IndolPhos-Rh catalysts: kinetics and reaction mechanism

    NARCIS (Netherlands)

    Wassenaar, J.; Kuil, M.; Lutz, M.; Spek, A.L.; Reek, J.N.H.

    2010-01-01

    The mechanism of the Indol- Phos–Rh-catalyzed asymmetric hydrogenation of prochiral olefins has been investigated by means of X-ray crystal structure determination, kinetic measurements, high-pressure NMR spectroscopy, and DFT calculations. The mechanistic study indicates that the reaction follows a

  13. Asymmetric hydrogenation with highly active IndolPhos-Rh catalysts: kinetics and reaction mechanism

    NARCIS (Netherlands)

    Wassenaar, J.; Kuil, M.; Lutz, M.; Spek, A.L.; Reek, J.N.H.

    2010-01-01

    The mechanism of the IndolPhos-Rh-catalyzed asymmetric hydrogenation of prochiral olefins has been investigated by means of X-ray crystal structure determination, kinetic measurements, high-pressure NMR spectroscopy, and DFT calculations. The mechanistic study indicates that the reaction follows an

  14. New macrocycles with potent antituberculosis activity accessed by one-pot multicomponent reactions

    NARCIS (Netherlands)

    Kim, D.; Huang, Y.; Wang, K.; Doemling, A.

    2013-01-01

    Based on modeling studies, we hypothesized that tylosin derivatives without formyl group should rather adopt an erythromycin-like binding mode to the ribosome. Twenty four 16-membered macrocyclic compounds were accessed by multicomponent reactions (Gewald, Ugi) of tylosin and investigated for their

  15. Active sites in Cu-SSZ-13 deNOx catalyst under reaction conditions: a XAS/XES perspective

    Science.gov (United States)

    Lomachenko, Kirill A.; Borfecchia, Elisa; Bordiga, Silvia; Soldatov, Alexander V.; Beato, Pablo; Lamberti, Carlo

    2016-05-01

    Cu-SSZ-13 is a highly active catalyst for the NH3-assisted selective catalytic reduction (SCR) of the harmful nitrogen oxides (NOx, x=1, 2). Since the catalytically active sites for this reaction are mainly represented by isolated Cu ions incorporated into the zeolitic framework, element-selective studies of Cu local environment are crucial to fully understand the enhanced catalytic properties of this material. Herein, we highlight the recent advances in the characterization of the most abundant Cu-sites in Cu-SSZ-13 upon different reaction-relevant conditions made employing XAS and XES spectroscopies, complemented by computational analysis. A concise review of the most relevant literature is also presented.

  16. Synthesis, DNA binding and complex formation reactions of 3-amino-5,6-dimethyl-1,2,4-triazine with Pd(II) and some selected biorelevant ligands

    Science.gov (United States)

    Shoukry, Azza A.; Alghanmi, Reem M.

    2015-03-01

    With the purpose of studying the binding behavior of Pd(II) complexes with DNA as the main biological target, and their ability to penetrate reasonably into tumour cells and destroy their replication ability, Pd(ADT)Cl2 complex was synthesized and characterized, where ADT is 3-amino-5,6-dimethyl-1,2,4-triazine. Stoichiometry and stability constants of the complexes formed between various biologically relevant ligands (amino acids, amides, DNA constituents, and dicarboxylic acids) and [Pd(ADT)(H2O)2]2+ were investigated at 25 °C and at constant 0.1 mol dm-3 ionic strength. The concentration distribution diagrams of the various species formed are evaluated. Further investigation of the binding properties of the diaqua complex [Pd(ADT)(H2O)2]2+ with calf thymus DNA (CT-DNA) was investigated by UV-vis spectroscopy. The intrinsic binding constants (Kb) calculated from UV-vis absorption studies was calculated to be 2.00 × 103 mol dm-3. The calculated (Kb) value was found to be of lower magnitude than that of the classical intercalator EB (Ethidium bromide) (Kb = 1.23(±0.07) × 105 mol dm-3) suggesting an electrostatic and/or groove binding mode for the interaction with CT-DNA. Thermal denaturation has been systematically studied by spectrophotometric method and the calculated ΔTm was nearly 5 °C, supporting the electrostatic and/or groove binding mode for the interaction between the complex and CT-DNA

  17. Peripheral Blood Leukocytes and Serum Nested Polymerase Chain Reaction Are Complementary Methods for Monitoring Active Cytomegalovirus Infection in Transplant Patients

    Directory of Open Access Journals (Sweden)

    PD Andrade

    2013-01-01

    Full Text Available BACKGROUND: Human cytomegalovirus is an important cause of morbidity and mortality in immunocompromised patients. Qualitative polymerase chain reaction (PCR has proven to be a sensitive and effective technique in defining active cytomegalovirus infection, in addition to having low cost and being a useful test for situations in which there is no need for quantification. Real-time PCR has the advantage of quantification; however, the high cost of this methodology makes it impractical for routine use.

  18. Palladium-catalyzed C-H activation/intramolecular amination reaction: a new route to 3-aryl/alkylindazoles.

    Science.gov (United States)

    Inamoto, Kiyofumi; Saito, Tadataka; Katsuno, Mika; Sakamoto, Takao; Hiroya, Kou

    2007-07-19

    A method for the catalytic C-H activation of hydrazone compounds followed by intramolecular amination is described. It requires the use of a catalytic amount of Pd(OAc)2 in the presence of Cu(OAc)2 and AgOCOCF3, which efficiently effects the cyclization to afford variously substituted indazoles. The reactions proceed under relatively mild conditions and thus tolerate a variety of functional groups, including alkoxycarbonyl and cyano groups and halogen atoms.

  19. Conformational changes of active site of copper zinc superoxide dismutase can be detected sensitively by electron-transfer reaction

    Institute of Scientific and Technical Information of China (English)

    舒占永

    1996-01-01

    The electron-transfer (ET) reaction between Fe(CN)64- and copper zinc superoxide dismutase (CuZn-SOD) occurs at the active site of the enzyme. The ET parameters which are sensitive to the denaturation have been used to determine the conformational changes of the active site induced by guanidine hydrochloride and thermal denaturation. The decreases of ET rates for all the denatured enzyme samples reflect the collapse of the active cavity of enzyme in the unfolding processes. The interesting changes of ET amplitude for the enzyme denatured at different pH values suggest that electrostatic interaction plays an important role in the conformational changes of active site. From the results of the kinetic analyses, it is concluded that the conformational changes of the active site are parallel with the inactivation.

  20. Rate Constants and Activation Energies for Gas‐Phase Reactions of Three Cyclic Volatile Methyl Siloxanes with the Hydroxyl Radical

    Science.gov (United States)

    Safron, Andreas; Strandell, Michael; Kierkegaard, Amelie

    2015-01-01

    ABSTRACT Reaction with hydroxyl radicals (OH) is the major pathway for removal of cyclic volatile methyl siloxanes (cVMS) from air. We present new measurements of second‐order rate constants for reactions of the cVMS octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6) with OH determined at temperatures between 313 and 353 K. Our measurements were made using the method of relative rates with cyclohexane as a reference substance and were conducted in a 140‐mL gas‐phase reaction chamber with online mass spectrometry analysis. When extrapolated to 298 K, our measured reaction rate constants of D4 and D5 with the OH radical are 1.9 × 10−12 (95% confidence interval (CI): (1.7–2.2) × 10−12) and 2.6 × 10−12 (CI: (2.3–2.9) × 10−12) cm3 molecule−1 s−1, respectively, which are 1.9× and 1.7× faster than previous measurements. Our measured rate constant for D6 is 2.8 × 10−12 (CI: (2.5–3.2) × 10−12) cm3 molecule−1 s−1 and to our knowledge there are no comparable laboratory measurements in the literature. Reaction rates for D5 were 33% higher than for D4 (CI: 30–37%), whereas the rates for D6 were only 8% higher than for D5 (CI: 5–10%). The activation energies of the reactions of D4, D5, and D6 with OH were not statistically different and had a value of 4300 ± 2800 J/mol. PMID:27708500

  1. Rate Constants and Activation Energies for Gas-Phase Reactions of Three Cyclic Volatile Methyl Siloxanes with the Hydroxyl Radical.

    Science.gov (United States)

    Safron, Andreas; Strandell, Michael; Kierkegaard, Amelie; Macleod, Matthew

    2015-07-01

    Reaction with hydroxyl radicals (OH) is the major pathway for removal of cyclic volatile methyl siloxanes (cVMS) from air. We present new measurements of second-order rate constants for reactions of the cVMS octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6) with OH determined at temperatures between 313 and 353 K. Our measurements were made using the method of relative rates with cyclohexane as a reference substance and were conducted in a 140-mL gas-phase reaction chamber with online mass spectrometry analysis. When extrapolated to 298 K, our measured reaction rate constants of D4 and D5 with the OH radical are 1.9 × 10(-12) (95% confidence interval (CI): (1.7-2.2) × 10(-12)) and 2.6 × 10(-12) (CI: (2.3-2.9) × 10(-12)) cm(3) molecule(-1) s(-1), respectively, which are 1.9× and 1.7× faster than previous measurements. Our measured rate constant for D6 is 2.8 × 10(-12) (CI: (2.5-3.2) × 10(-12)) cm(3) molecule(-1) s(-1) and to our knowledge there are no comparable laboratory measurements in the literature. Reaction rates for D5 were 33% higher than for D4 (CI: 30-37%), whereas the rates for D6 were only 8% higher than for D5 (CI: 5-10%). The activation energies of the reactions of D4, D5, and D6 with OH were not statistically different and had a value of 4300 ± 2800 J/mol.

  2. Synthesis, characterization, and catalytic activity in Suzuki coupling and catalase-like reactions of new chitosan supported Pd catalyst.

    Science.gov (United States)

    Baran, Talat; Inanan, Tülden; Menteş, Ayfer

    2016-07-10

    The aim of this study is to analyze the synthesis of a new chitosan supported Pd catalyst and examination of its catalytic activity in: Pd catalyst was synthesized using chitosan as a biomaterial and characterized with FTIR, TG/DTG, XRD, (1)H NMR, (13)C NMR, SEM-EDAX, ICP-OES, Uv-vis spectroscopies, and magnetic moment, along with molar conductivity analysis. Biomaterial supported Pd catalyst indicated high activity and long life time as well as excellent turnover number (TON) and turnover frequency (TOF) values in Suzuki reaction. Biomaterial supported Pd catalyst catalyzed H2O2 decomposition reaction with considerable high activity using comparatively small loading catalyst (10mg). Redox potential of biomaterial supported Pd catalyst was still high without negligible loss (13% decrease) after 10 cycles in reusability tests. As a consequence, eco-friendly biomaterial supported Pd catalyst has superior properties such as high thermal stability, long life time, easy removal from reaction mixture and durability to air, moisture and high temperature.

  3. Kinetics and Quantitative Structure—Activity Relationship Study on the Degradation Reaction from Perfluorooctanoic Acid to Trifluoroacetic Acid

    Directory of Open Access Journals (Sweden)

    Chen Gong

    2014-08-01

    Full Text Available Investigation of the degradation kinetics of perfluorooctanoic acid (PFOA has been carried out to calculate rate constants of the main elementary reactions using the multichannel Rice-Ramsperger-Kassel-Marcus theory and canonical variational transition state theory with small-curvature tunneling correction over a temperature range of 200~500 K. The Arrhenius equations of rate constants of elementary reactions are fitted. The decarboxylation is role step in the degradation mechanism of PFOA. For the perfluorinated carboxylic acids from perfluorooctanoic acid to trifluoroacetic acid, the quantitative structure–activity relationship of the decarboxylation was analyzed with the genetic function approximation method and the structure–activity model was constructed. The main parameters governing rate constants of the decarboxylation reaction from the eight-carbon chain to the two-carbon chain were obtained. As the structure–activity model shows, the bond length and energy of C1–C2 (RC1–C2 and EC1–C2 are positively correlated to rate constants, while the volume (V, the energy difference between EHOMO and ELUMO (ΔE, and the net atomic charges on atom C2 (QC2 are negatively correlated.

  4. Kinetic Isotope Effects for Alkaline Phosphatase Reactions: Implications for the Role of Active Site Metal Ions in Catalysis

    Science.gov (United States)

    Zalatan, Jesse G.; Catrina, Irina; Mitchell, Rebecca; Grzyska, Piotr K.; O’Brien, Patrick J.; Herschlag, Daniel; Hengge, Alvan C.

    2011-01-01

    Enzyme-catalyzed phosphoryl transfer reactions have frequently been suggested to proceed through transition states that are altered from their solution counterparts, with the alterations presumably arising from interactions with active site functional groups. In particular, the phosphate monoester hydrolysis reaction catalyzed by Escherichia coli alkaline phosphatase (AP) has been the subject of intensive scrutiny. Recent linear free energy relationship (LFER) studies suggest that AP catalyzes phosphate monoester hydrolysis through a loose transition state, similar to that in solution. To gain further insight into the nature of the transition state and active site interactions, we have determined kinetic isotope effects (KIEs) for AP-catalyzed hydrolysis reactions with several phosphate monoester substrates. The LFER and KIE data together provide a consistent picture for the nature of the transition state for AP-catalyzed phosphate monoester hydrolysis and support previous models suggesting that the enzymatic transition state is similar to that in solution. Moreover, the KIE data provides unique information regarding specific interactions between the transition state and the active site Zn2+ ions. These results provide strong support for a model in which electrostatic interactions between the bimetallo Zn2+ site and a nonbridging phosphate ester oxygen atom make a significant contribution to the large rate enhancement observed for AP-catalyzed phosphate monoester hydrolysis. PMID:17630738

  5. Kinetic isotope effects for alkaline phosphatase reactions: implications for the role of active-site metal ions in catalysis.

    Science.gov (United States)

    Zalatan, Jesse G; Catrina, Irina; Mitchell, Rebecca; Grzyska, Piotr K; O'brien, Patrick J; Herschlag, Daniel; Hengge, Alvan C

    2007-08-08

    Enzyme-catalyzed phosphoryl transfer reactions have frequently been suggested to proceed through transition states that are altered from their solution counterparts, with the alterations presumably arising from interactions with active-site functional groups. In particular, the phosphate monoester hydrolysis reaction catalyzed by Escherichia coli alkaline phosphatase (AP) has been the subject of intensive scrutiny. Recent linear free energy relationship (LFER) studies suggest that AP catalyzes phosphate monoester hydrolysis through a loose transition state, similar to that in solution. To gain further insight into the nature of the transition state and active-site interactions, we have determined kinetic isotope effects (KIEs) for AP-catalyzed hydrolysis reactions with several phosphate monoester substrates. The LFER and KIE data together provide a consistent picture for the nature of the transition state for AP-catalyzed phosphate monoester hydrolysis and support previous models suggesting that the enzymatic transition state is similar to that in solution. Moreover, the KIE data provides unique information regarding specific interactions between the transition state and the active-site Zn2+ ions. These results provide strong support for a model in which electrostatic interactions between the bimetallo Zn2+ site and a nonbridging phosphate ester oxygen atom make a significant contribution to the large rate enhancement observed for AP-catalyzed phosphate monoester hydrolysis.

  6. Mechanism and Stereoselectivity in an Asymmetric N-Heterocyclic Carbene-Catalyzed Carbon-Carbon Bond Activation Reaction.

    Science.gov (United States)

    Pareek, Monika; Sunoj, Raghavan B

    2016-11-18

    The mechanism and origin of stereoinduction in a chiral N-heterocyclic carbene (NHC) catalyzed C-C bond activation of cyclobutenone has been established using B3LYP-D3 density functional theory computations. The activation of cyclobutenone as an NHC-bound vinyl enolate and subsequent reaction with the electrophilic sulfonyl imine leads to the lactam product. The most preferred stereocontrolling transition state exhibits a number of noncovalent interactions rendering additional stabilization. The computed enantio- and diastereoselectivities are in good agreement with the previous experimental observations.

  7. A convenient method for experimental determination of yields and isomeric ratios in photonuclear reactions measured by the activation technique

    Science.gov (United States)

    Kolev, D.; Dobreva, E.; Nenov, N.; Todorov, V.

    1995-02-01

    A generalized exact formula is derived for a determination of the experimental isomeric ratio in any incident particle activation. For the particular case, when the activity of the ground state results from the simultaneous decay of both states and can be conveniently measured, the appropriate modification of this formula is evaluated and applied to six photonuclear reactions induced by 43 MeV bremsstrahlung. The experimental isomeric yield ratios of (γ, 3n) 110m,gIn; (γ, p) (γ, pn), (γ, 2n2p) 117m,gIn; (γ, n) 164m,gHo and (γ, 3n) 162m,gHo are deduced.

  8. Activity and Stability of Rare Earth-Based Hydride Alloys as Catalysts of Hydrogen Absorption-Oxidation Reactions

    Institute of Scientific and Technical Information of China (English)

    Ying Taokai(应桃开); Gao Xueping(高学平); Hu Weikang(胡伟康); Noréus Dag

    2004-01-01

    Rare earth-based AB5-type hydrogen storage alloys as catalysts of hydrogen-diffusion electrodes for hydrogen absorption and oxidation reactions in alkaline fuel cells were investigated. It is demonstrated that the meta-hydride hydrogen-diffusion electrodes could be charged by hydrogen gas and electrochemically discharged at the same time to retain a stable oxidation potential for a long period. The catalytic activities and stability are almost comparable with a Pt catalyst on the active carbon. Further improvement of performances is expected via reduction of catalyst size into nanometers.

  9. Self-regulation effects in QB-active bacterial reaction centers

    Science.gov (United States)

    Goushcha, A. O.; Scott, G. W.; Holzwarth, A. R.; Kharkyanen, V. N.

    1999-10-01

    Dynamic self-organization effects in proteins under non-equilibrium conditions of photoinduced charge separation are discussed. Successive charge transfer turnover events induce cumulative structural rearrangements with long relaxation times. Perturbations by the modified macromolecular structure on the turnover rate result in an autocatalytic feedback mechanism and may lead to formation of new conformational states. Under such conditions, the efficiency of charge separation and transfer may change by several orders of magnitude, stabilizing the charge-separated state and facilitating charge flow through the molecule. Experimental results on bacterial photosynthetic reaction centers indicate that dynamic self-organization effects determine the function of these macromolecules, favoring stabilization of the charge-separated state over the non-functional recombination event. The protein-cofactor system of reaction centers may be described as a molecular machine that functions under non-equilibrium conditions of electron flow to promote a charge-separated state.

  10. Activation cross sections of proton induced nuclear reactions on ytterbium up to 70 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Tarkanyi, F. [Institute of Nuclear Research of the Hungarian Academy of Sciences (ATOMKI), 4026 Debrecen, Bem ter 18/c (Hungary); Hermanne, A. [Cyclotron Laboratory, Vrije Universiteit Brussel (VUB), 1090 Brussels (Belgium); Takacs, S.; Ditroi, F. [Institute of Nuclear Research of the Hungarian Academy of Sciences (ATOMKI), 4026 Debrecen, Bem ter 18/c (Hungary); Kiraly, B. [Institute of Nuclear Research of the Hungarian Academy of Sciences (ATOMKI), 4026 Debrecen, Bem ter 18/c (Hungary)], E-mail: kiralyb@atomki.hu; Yamazaki, H.; Baba, M.; Mohammadi, A. [Cyclotron and Radioisotope Center (CYRIC), Tohoku University, Sendai 980-8578 (Japan); Ignatyuk, A.V. [Institute of Physics and Power Engineering (IPPE), Obninsk 249020 (Russian Federation)

    2009-09-01

    Cross sections of proton induced nuclear reactions on ytterbium were measured up to 70 MeV by using the standard stacked foil irradiation technique and high-resolution gamma-ray spectroscopy. Experimental cross sections and derived integral yields are reported for the first time for the {sup nat}Yb(p,xn){sup 173,172mg,171mg,170,167}Lu, {sup nat}Yb(p,x){sup 175cum,166cum}Yb and {sup nat}Yb(p,x){sup 173ind,172ind,168,167cum,165cum}Tm reactions. No earlier experimental cross section data were found in the literature. The experimental data were compared to and analyzed with the results of the theoretical model code ALICE-IPPE. Production routes of medical radioisotope {sup 167}Tm are discussed.

  11. Highly active antiretroviral therapy induced adverse drug reactions in Indian human immunodeficiency virus positive patients (RETRACTED by plagiarism

    Directory of Open Access Journals (Sweden)

    Rajesh R

    2011-03-01

    Full Text Available THIS ARTICLE WAS RETRACTED AFTER A PLAGIARISM INVESTIGATIONObjective: To assess the incidence, severity pattern, causality, predictability and preventability of adverse drug reactions (ADRs and to identify risk factors for adverse drug reactions in highly active antiretroviral therapy.Methods: Enrolled patients were intensively monitored for ADRs to highly active antiretroviral therapy. Predictability was assessed based on history of previous exposure to the drug or literature incidence of ADRs. Preventability was assessed using Schumock and Thornton criteria and severity was assessed using modified Hartwig and Siegel scale. Multivariate logistic regressions were used to identify the risk factors for ADRs.Results: Monitoring of 130 retropositive patients by active pharmacovigilance identified 74 ADRs from 57 patients. Anemia and hepatotoxicity were the most commonly observed ADRs. The organ system commonly affected by ADR was red blood cell (21.4%.The ADRs were moderate in 77% of cases. Type A reactions (77% were more common. A total of 10.8% ADRs were definitely preventable. The incidence rate of ADRs (65.9% was highest with Zidovudine + Lamivudine + Nevirapine combination. A total of 84% interruptions to highly active antiretroviral therapy were due to toxicity. CD4 less than 200 cells/µl, female gender and tuberculosis were observed as risk factors for ADRs.Conclusion: Incidence of ADRs in intensively monitored patients was found to be 43.8%. Anemia in HIV patients is an influential risk factor for occurrence of ADRs. With the increasing access to antiretroviral in India, clinicians must focus on early detection and prevention of ADRs to highly active antiretroviral therapy.

  12. ACTIVATION REACTION ON THE ELECTROENCEPHALOGRAM IN SUBSTANCE DEPENDENT PATIENTS: LINKS TO ADDICTION STUDIES AND PSYCHOLOGICAL FACTORS AND CHANGES IN NEUROFEEDBACK TRAINING

    Directory of Open Access Journals (Sweden)

    M. e Melnikov

    2014-01-01

    Full Text Available Depth of activation reaction (α-activity suppression during the eyes-opening task is considered to be an important quantitative characteristic of α-band brainwaves. Activation reaction was assessed from O1 and O2 leads in 31 male substance dependent subjects. In 7 cases it was measured twice: before and after α- or β-brainwave biofeedback training. The correlations were found between grade of α suppression in eyes-opening task and attitude towards disease and treatment, personality maturity, and level of pathological personality traits. Activation reaction was significantly improved by α-training and non-significantly diminished after β-1-training.

  13. Psychosocial versus physiological stress - Meta-analyses on deactivations and activations of the neural correlates of stress reactions.

    Science.gov (United States)

    Kogler, Lydia; Müller, Veronika I; Chang, Amy; Eickhoff, Simon B; Fox, Peter T; Gur, Ruben C; Derntl, Birgit

    2015-10-01

    Stress is present in everyday life in various forms and situations. Two stressors frequently investigated are physiological and psychosocial stress. Besides similar subjective and hormonal responses, it has been suggested that they also share common neural substrates. The current study used activation-likelihood-estimation meta-analysis to test this assumption by integrating results of previous neuroimaging studies on stress processing. Reported results are cluster-level FWE corrected. The inferior frontal gyrus (IFG) and the anterior insula (AI) were the only regions that demonstrated overlapping activation for both stressors. Analysis of physiological stress showed consistent activation of cognitive and affective components of pain processing such as the insula, striatum, or the middle cingulate cortex. Contrarily, analysis across psychosocial stress revealed consistent activation of the right superior temporal gyrus and deactivation of the striatum. Notably, parts of the striatum appeared to be functionally specified: the dorsal striatum was activated in physiological stress, whereas the ventral striatum was deactivated in psychosocial stress. Additional functional connectivity and decoding analyses further characterized this functional heterogeneity and revealed higher associations of the dorsal striatum with motor regions and of the ventral striatum with reward processing. Based on our meta-analytic approach, activation of the IFG and the AI seems to indicate a global neural stress reaction. While physiological stress activates a motoric fight-or-flight reaction, during psychosocial stress attention is shifted towards emotion regulation and goal-directed behavior, and reward processing is reduced. Our results show the significance of differentiating physiological and psychosocial stress in neural engagement. Furthermore, the assessment of deactivations in addition to activations in stress research is highly recommended.

  14. Sol–gel synthesis of palladium nanoparticles supported on reduced graphene oxide: an active electrocatalyst for hydrogen evolution reaction

    Indian Academy of Sciences (India)

    Fereshteh Chekin

    2015-08-01

    In this work, the synthesis and characterization of palladium nanoparticle-reduced graphene oxide hybrid (Pd–rGO) material is reported. Techniques of X-ray diffraction, transmission electron microscope (TEM), energy-dispersive X-ray, FT-IR spectroscopy, thermogravimetric analysis and cyclic voltammetry were used to characterize the structure and properties of the Pd–rGO. Results demonstrate the effect of Pd on the reduced GO. The average particle size of the Pd nanoparticles supported on rGO obtained from TEM is about 12–18 nm. Moreover, glassy carbon electrode (GCE) modified with palladium nanoparticle–graphene oxide hybrid (Pd–rGO/GCE) was prepared by casting of the Pd–rGO solution on GCE. The electrochemical and catalytic activity of the Pd–rGO/GCE was studied in 0.1 M H2SO4 solution. The Pd–rGO/GCE electrode exhibited remarkable electrocatalytic activity for the hydrogen evolution reaction (HER). At potential more negative than −0.4 V vs. Ag|AgCl|KCl3M, the current is mainly due to hydrogen evolution reaction. Finally, the kinetic parameters of hydrogen evolution reaction are also discussed on the Pd–rGO/GCE.

  15. A linear energy relationship between activation energy and absolute hardness: a case study with the O(3P) atom-addition reactions to polyaromatic hydrocarbons.

    Science.gov (United States)

    Orrego, Juan F; Truong, Thanh N; Mondragón, Fanor

    2008-09-11

    A new linear relationship between absolute hardness and global activation energy of O-addition reaction to a series of aromatic hydrocarbons (benzene, naphthalene, phenanthrene, and pyrene) is presented. A total of seventeen O((3)P)-addition reactions were evaluated. Thermal rate constants were calculated for each elementary reaction and used to estimate the total rate constants. This information was employed to obtain the global activation energy. A new linear relationship is shown and is estimated that it can be used within the RC-TST framework to predict relative rate constants for any reaction within an O-addition to PAH class from just absolute hardness values.

  16. A Mechanistic Study of Direct Activation of Allylic Alcohols in Palladium Catalyzed Amination Reactions

    OpenAIRE

    Yasemin Gumrukcu; Bas de Bruin; Reek, Joost N. H.

    2015-01-01

    We here report a computational approach on the mechanism of allylicamination reactions using allyl-alcohols and amines as the substrates and phosphoramidite palladium catalyst 1a, which operates in the presence of catalytic amount of 1,3-diethylurea as a co-catalyst. DFT calculations showed a cooperative hydrogen-bonding array between the urea moiety and the hydroxyl group of the allyl alcohol, which strengthens the hydrogen bond between the O-H moiety of the coordinated allyl-alcohol and th...

  17. The Use of Gel Electrophoresis to Study the Reactions of Activated Amino Acids with Oligonucleotides

    Science.gov (United States)

    Zieboll, Gerhard; Orgel, Leslie E.

    1994-01-01

    We have used gel electrophoresis to study the primary covalent addition of amino acids to oligonu-cleotides or their analogs and the subsequent addition of further molecules of the amino acids to generate peptides covalently linked to the oligonucleotides. We have surveyed the reactions of a variety of amino acids with the phosphoramidates derived from oligonucleotide 5 inches phosphates and ethylenediamine. We find that arginine and amino acids can interact with oligonucleotidesl through stacking interactions react most efficiently. D- and L-amino acids give indistinguishable families of products.

  18. Bimolecular reactions of activated species: An analysis of problematic HC(O)C(O) chemistry

    Science.gov (United States)

    Shannon, Robin J.; Robertson, Struan H.; Blitz, Mark A.; Seakins, Paul W.

    2016-09-01

    Experimental studies have demonstrated the importance of non-thermal bimolecular association chemistry. Recently a fully reversible method for incorporating any number of such non-thermal reactions into a single master equation has been developed (Green and Robertson, 2014) [10]. Using this methodology experimental results for the system: (1) (CHO)2 + OH → HC(O)C(O) + H2O, (2) HC(O)C(O) → HCO + CO, (3) HC(O)C(O) + O2 → OH + CO + CO2, are modeled, reproducing the temperature and pressure dependence of the OH yield. An issue remains as to how to model energy partition into HC(O)C(O).

  19. Activation cross-sections of deuteron induced nuclear reactions on gold up to 40 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Tarkanyi, F. [Institute of Nuclear Research of the Hungarian Academy of Sciences (ATOMKI), Debrecen (Hungary); Ditroi, F., E-mail: ditroi@atomki.hu [Institute of Nuclear Research of the Hungarian Academy of Sciences (ATOMKI), Debrecen (Hungary); Hermanne, A. [Cyclotron Laboratory, Vrije Universiteit Brussel (VUB), Brussels (Belgium); Takacs, S.; Kiraly, B. [Institute of Nuclear Research of the Hungarian Academy of Sciences (ATOMKI), Debrecen (Hungary); Yamazaki, H.; Baba, M.; Mohammadi, A. [Cyclotron and Radioisotope Center (CYRIC), Tohoku University, Sendai (Japan); Ignatyuk, A.V. [Institute of Physics and Power Engineering (IPPE), Obninsk (Russian Federation)

    2011-06-15

    Cross-sections of deuteron induced nuclear reactions on gold were measured up to 40 MeV by using the standard stacked foil irradiation technique and high resolution gamma-ray spectroscopy. Experimental cross-sections and derived integral yields are reported for the {sup 197}Au(d,xn){sup 197m,197g,195m,195g}Hg and {sup 197}Au(d,x){sup 198g,196m,196g,195,194}Au nuclear reactions. The experimental data are analyzed and compared to literature and predictions of the ALICE-IPPE, EMPIRE and TALYS theoretical model codes. The application of the new cross-sections for accelerator technology, medical radioisotope production, thin layer activation and dose calculation is discussed.

  20. Study on the reaction activity of CuO/y-Al2O3 for dry flue gas desulfurization

    Institute of Scientific and Technical Information of China (English)

    WANG Yan; ZHANG Chao; ZHENG Ying; ZHENG Chu-guang

    2004-01-01

    The copper oxide bed regenerable adsorber process can efficiently remove sulfur dioxide (SO2) and sulfur trioxide (SO3) and reduce nitrogen oxides (NOx) from flue gas with no solid or liquid byproducts. This paper investigates the dry flue gas desulfurization activities of the CuO/γ-Al2O3 under different operation conditions finding that the dispersion degree of copper oxide can achieve a threshold value, which is 0.47mg/m2 carriers. The conclusion confirms that the sulfur capacity of desulfurizer is associated with flue gas' space velocity, reaction temperature, copper content and the structure of sorbent pellet, etc. And with the condition of the desulfurization reaction temperature 673 K, the space velocity 11 200 h-1 and the S/Cu mole ratio under 1, the sulfur removal efficiency can go upwards to 95%.

  1. Kinetic method for assaying the halogenating activity of myeloperoxidase based on reaction of celestine blue B with taurine halogenamines.

    Science.gov (United States)

    Sokolov, A V; Kostevich, V A; Kozlov, S O; Donskyi, I S; Vlasova, I I; Rudenko, A O; Zakharova, E T; Vasilyev, V B; Panasenko, O M

    2015-06-01

    Myeloperoxidase (MPO) is a challenging molecular target which, if put under control, may allow regulating the development of inflammatory reactions associated with oxidative/halogenative stress. In this paper, a new kinetic method for assaying the halogenating activity of MPO is described. The method is based on measuring the rate of iodide-catalyzed oxidation of celestine blue B (CB) by oxygen and taurine N-chloramine (bromamine). The latter is produced in a reaction of taurine with HOCl (HOBr). CB is not a substrate for the peroxidase activity of MPO and does not react with hydrogen peroxide and superoxide anion radical. Taurine N-chloramine (bromamine) reacts with CB in molar ratio of 1:2. Using the new method, we studied the dependence of MPO activity on concentration of substrates and inhibitors. The specificity of MPO inhibition by non-proteolyzed ceruloplasmin is characterized. The inhibition of taurine N-chloramine production by neutrophils and HL-60 cells in the presence of MPO-affecting substances is demonstrated. The new method allows determining the kinetic parameters of MPO halogenating activity and studying its inhibition by various substances, as well as screening for potential inhibitors of the enzyme.

  2. Enhancement in the Catalytic Activity of Pd/USY in the Heck Reaction Induced by H2 Bubbling

    Directory of Open Access Journals (Sweden)

    Miki Niwa

    2010-12-01

    Full Text Available Pd was loaded on ultra stable Y (USY zeolites prepared by steaming NH4-Y zeolite under different conditions. Heck reactions were carried out over the prepared Pd/USY. We found that H2 bubbling was effective in improving not only the catalytic activity of Pd/USY, but also that of other supported Pd catalysts and Pd(OAc2. Moreover, the catalytic activity of Pd/USY could be optimized by choosing appropriate steaming conditions for the preparation of the USY zeolites; Pd loaded on USY prepared at 873 K with 100% H2O gave the highest activity (TOF = 61,000 h−1, which was higher than that of Pd loaded on other kinds of supports. The prepared Pd/USY catalysts were applicable to the Heck reactions using various kinds of substrates including bromo- and chloro-substituted aromatic and heteroaromatic compounds. Characterization of the acid properties of the USY zeolites revealed that the strong acid site (OHstrong generated as a result of steaming had a profound effect on the catalytic activity of Pd.

  3. Oral drug delivery system based on interpolymer complex formation between poly(acrylic acid) and poly(vinyl pyrrolidone-co-vinyl acetate)

    CSIR Research Space (South Africa)

    Germishuizen, A

    2005-07-01

    Full Text Available system based on interpolymer complex formation between poly(acrylic acid) and poly(vinyl pyrrolidone-co-vinyl acetate) 13 July 2005 André Germishuizen Supporting the Manufacturing and Materials Industry in its quest for global competitiveness CSIR... approved polymers square4 Polyacids - crosslinked poly(acrylic acid) (PAA) - poly(methacrylic acid) (PMAA) - poly(vinyl acetate phthalate) (PVAP) - cellulose acetate phthalate (CAP) square4 Polybases - poly(vinyl pyrrolidone-co-vinyl acetate) (PVP...

  4. Lewis base activation of Lewis acids: catalytic, enantioselective vinylogous aldol addition reactions.

    Science.gov (United States)

    Denmark, Scott E; Heemstra, John R

    2007-07-20

    The generality of Lewis base catalyzed, Lewis acid mediated, enantioselective vinylogous aldol addition reactions has been investigated. The combination of silicon tetrachloride and chiral phosphoramides is a competent catalyst for highly selective additions of a variety of alpha,beta-unsaturated ketone-, 1,3-diketone-, and alpha,beta-unsaturated amide-derived dienolates to aldehydes. These reactions provided high levels of gamma-site selectivity for a variety of substitution patterns on the dienyl unit. Both ketone- and morpholine amide-derived dienol ethers afforded high enantio- and diastereoselectivity in the addition to conjugated aldehydes. Although alpha,beta-unsaturated ketone-derived dienolate did not react with aliphatic aldehydes, alpha,beta-unsaturated amide-derived dienolates underwent addition at reasonable rates affording high yields of vinylogous aldol product. The enantioselectivities achieved with the morpholine derived-dienolate in the addition to aliphatic aldehydes was the highest afforded to date with the silicon tetrachloride-chiral phosphoramide system. Furthermore, the ability to cleanly convert the morpholine amide to a methyl ketone was demonstrated.

  5. Active site diversification of P450cam with indole generates catalysts for benzylic oxidation reactions.

    Science.gov (United States)

    Kelly, Paul P; Eichler, Anja; Herter, Susanne; Kranz, David C; Turner, Nicholas J; Flitsch, Sabine L

    2015-01-01

    Cytochrome P450 monooxygenases are useful biocatalysts for C-H activation, and there is a need to expand the range of these enzymes beyond what is naturally available. A panel of 93 variants of active self-sufficient P450cam[Tyr96Phe]-RhFRed fusion enzymes with a broad diversity in active site amino acids was developed by screening a large mutant library of 16,500 clones using a simple, highly sensitive colony-based colorimetric screen against indole. These mutants showed distinct fingerprints of activity not only when screened in oxidations of substituted indoles but also for unrelated oxidations such as benzylic hydroxylations.

  6. Active site diversification of P450cam with indole generates catalysts for benzylic oxidation reactions

    Directory of Open Access Journals (Sweden)

    Paul P. Kelly

    2015-09-01

    Full Text Available Cytochrome P450 monooxygenases are useful biocatalysts for C–H activation, and there is a need to expand the range of these enzymes beyond what is naturally available. A panel of 93 variants of active self-sufficient P450cam[Tyr96Phe]-RhFRed fusion enzymes with a broad diversity in active site amino acids was developed by screening a large mutant library of 16,500 clones using a simple, highly sensitive colony-based colorimetric screen against indole. These mutants showed distinct fingerprints of activity not only when screened in oxidations of substituted indoles but also for unrelated oxidations such as benzylic hydroxylations.

  7. Changes in brain activation patterns according to cross-training effect in serial reaction time task An functional MRI study

    Institute of Scientific and Technical Information of China (English)

    Yong Hyun Kwon; Jung Won Kwon; Ji Won Park

    2013-01-01

    Cross-training is a phenomenon related to motor learning, where motor performance of the untrained limb shows improvement in strength and skill execution following unilateral training of the homologous contralateral limb. We used functional MRI to investigate whether motor performance of the untrained limb could be improved using a serial reaction time task according to motor sequential learning of the trained limb, and whether these skill acquisitions led to changes in brain activation patterns. We recruited 20 right-handed healthy subjects, who were randomly allocated into training and control groups. The training group was trained in performance of a serial reaction time task using their non-dominant left hand, 40 minutes per day, for 10 days, over a period of 2 weeks. The control group did not receive training. Measurements of response time and percentile of response accuracy were performed twice during pre- and post-training, while brain functional MRI was scanned during performance of the serial reaction time task using the untrained right hand. In the training group, prominent changes in response time and percentile of response accuracy were observed in both the untrained right hand and the trained left hand between pre- and post-training. The control group showed no significant changes in the untrained hand between pre- and post-training. In the training group, the activated volume of the cortical areas related to motor function (i.e., primary motor cortex, premotor area, posterior parietal cortex) showed a gradual decrease, and enhanced cerebellar activation of the vermis and the newly activated ipsilateral dentate nucleus were observed during performance of the serial reaction time task using the untrained right hand, accompanied by the cross-motor learning effect. However, no significant changes were observed in the control group. Our findings indicate that motor skills learned over the 2-week training using the trained limb were transferred to the

  8. Unprecedented Reaction Pathway of Sterically Crowded Calcium Complexes: Sequential C-N Bond Cleavage Reactions Induced by C-H Bond Activations.

    Science.gov (United States)

    Yang, Yang; Wang, Haobing; Ma, Haiyan

    2017-01-17

    Five bis(quinolylmethyl)-(1H-indolylmethyl)amine (BQIA) compounds, that is, {(quinol-8-yl-CH2 )2 NCH2 (3-Br-1H-indol-2-yl)} (L(1) H) and {[(8-R(3) -quinol-2-yl)CH2 ]2 NCH(R(2) )[3-R(1) -1H-indol-2-yl]} (L(2-5) H) (L(2) H: R(1) =Br, R(2) =H, R(3) =H; L(3) H: R(1) =Br, R(2) =H, R(3) =iPr; L(4) H: R(1) =H, R(2) =CH3 , R(3) =iPr; L(5) H: R(1) =H, R(2) =nBu, R(3) =iPr) were synthesized and used to prepare calcium complexes. The reactions of L(1-5) H with silylamido calcium precursors (Ca[N(SiMe2 R)2 ]2 (THF)2 , R=Me or H) at room temperature gave heteroleptic products (L(1, 2) )CaN(SiMe3 )2 (1, 2), (L(3, 4) )CaN(SiHMe2 )2 (3 a, 4 a) and homoleptic complexes (L(3, 5) )2 Ca (D3, D5). NMR and X-ray analyses proved that these calcium complexes were stabilized through Ca⋅⋅⋅C-Si, Ca⋅⋅⋅H-Si or Ca⋅⋅⋅H-C agostic interactions. Unexpectedly, calcium complexes ((L(3-5) )CaN(SiMe3 )2 ) bearing more sterically encumbered ligands of the same type were extremely unstable and underwent C-N bond cleavage processes as a consequence of intramolecular C-H bond activation, leading to the exclusive formation of (E)-1,2-bis(8-isopropylquinol-2-yl)ethane. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Recent advances in unveiling active sites in molybdenum sulfide-based electrocatalysts for the hydrogen evolution reaction

    Science.gov (United States)

    Seo, Bora; Joo, Sang Hoon

    2017-07-01

    Hydrogen has received significant attention as a promising future energy carrier due to its high energy density and environmentally friendly nature. In particular, the electrocatalytic generation of hydrogen fuel is highly desirable to replace current fossil fuel-dependent hydrogen production methods. However, to achieve widespread implementation of electrocatalytic hydrogen production technology, the development of highly active and durable electrocatalysts based on Earth-abundant elements is of prime importance. In this context, nanostructured molybdenum sulfides (MoS x ) have received a great deal of attention as promising alternatives to precious metal-based catalysts. In this focus review, we summarize recent efforts towards identification of the active sites in MoS x -based electrocatalysts for the hydrogen evolution reaction (HER). We also discuss recent synthetic strategies for the engineering of catalyst structures to achieve high active site densities. Finally, we suggest ongoing and future research challenges in the design of advanced MoS x -based HER electrocatalysts.

  10. Water-gas shift reaction on CuO-ZnO catalysts: I. Structure and catalytic activity

    Energy Technology Data Exchange (ETDEWEB)

    Kalchev, M.G.; Andreev, A.A. [Institute of Catalysis, Sofia (Bulgaria); Zotov, N.S. [Institute of Applied Mineralogy, Sofia (Bulgaria)

    1995-11-01

    The physicochemical properties of CuO-ZnO samples with different CuO contents were investgated by a complex of physical methods: DSC, XPS, EPR, TPR, and XRD. The samples containing {approximately}25 wt % CuO exhibited a maximum catalytic activity in the water-gas shift reaction. The catalytic activity was attributed to copper ions aggregated on the highly dispersed and defective CuO surface and to an anion-modified ZnO surface. Aggregates of copper ions, formed on metal species and probably modified with hydroxyl and carbonate groups, were shown to play a decisive role in the catalytic activity of the samples containing more than 15 wt % CuO.

  11. Antioxidant and antimicrobial activity of Maillard reaction products from xylan with chitosan/chitooligomer/glucosamine hydrochloride/taurine model systems.

    Science.gov (United States)

    Wu, Shuping; Hu, Jiao; Wei, Liuting; Du, Yumin; Shi, Xiaowen; Zhang, Lina

    2014-04-01

    The structure, UV absorbance, browning intensity, fluorescence changes, antioxidant activity and antimicrobial assessment of Maillard reaction products (MRPs) derived from xylan with chitosan, chitooligomer, glucosamine hydrochloride and taurine model systems were evaluated. The results revealed that all MRPs had similar infrared spectra and molecular structures. MRPs from different model systems on the UV absorbance at 294 nm after heated 90 min and browning intensity at 420 nm showed the similar law: xylan-taurine > xylan-glucosamine hydrochloride > xylan-chitooligomer > xylan-chitosan, and the order of DPPH scavenging activity of MRPs was as follows: xylan-chitosan > xylan-chitooligomer > xylan-glucosamine hydrochloride > xylan-taurine, which revealed that the properties of MRPs were closely related to molecular weight of model systems. Moreover, the highest radical scavenging activity of MRPs from xylan with chitosan/chitooligomer/glucosamine hydrochloride/taurine model systems was 65.9%, 63.7%, 46.4% and 42.5%, respectively.

  12. Mechanical bending induced catalytic activity enhancement of monolayer 1 T'-MoS2 for hydrogen evolution reaction

    Science.gov (United States)

    Shi, Wenwu; Wang, Zhiguo; Fu, Yong Qing

    2017-09-01

    In this paper, mechanisms behind enhancement of catalytic activity of MoS2 mono-layer (three atomic layers) for hydrogen evolution reaction (HER) by mechanically applying bending strain were investigated using density functional theory. Results showed that with the increase of bending strains, the Gibbs free energy for hydrogen adsorption on the MoS2 mono-layer was decreased from 0.18 to -0.04 eV and to 0.13 eV for the bend strains applied along the zigzag and armchair directions, respectively. The mechanism for the enhanced catalytic activity comes from the changes of density of electronic states near the Fermi energy level, which are induced by the changes of the Mo-S and Mo-Mo bonds upon bending. This report provides a new design methodology to improve the catalytic activity of catalysts based on two-dimensional transition metal dichalcogenides through a simple mechanical bending.

  13. Metallic Iron-Nickel Sulfide Ultrathin Nanosheets As a Highly Active Electrocatalyst for Hydrogen Evolution Reaction in Acidic Media.

    Science.gov (United States)

    Long, Xia; Li, Guixia; Wang, Zilong; Zhu, HouYu; Zhang, Teng; Xiao, Shuang; Guo, Wenyue; Yang, Shihe

    2015-09-23

    We report on the synthesis of iron-nickel sulfide (INS) ultrathin nanosheets by topotactic conversion from a hydroxide precursor. The INS nanosheets exhibit excellent activity and stability in strong acidic solutions as a hydrogen evolution reaction (HER) catalyst, lending an attractive alternative to the Pt catalyst. The metallic α-INS nanosheets show an even lower overpotential of 105 mV at 10 mA/cm(2) and a smaller Tafel slope of 40 mV/dec. With the help of DFT calculations, the high specific surface area, facile ion transport and charge transfer, abundant electrochemical active sites, suitable H(+) adsorption, and H2 formation kinetics and energetics are proposed to contribute to the high activity of the INS ultrathin nanosheets toward HER.

  14. Highly active and reusable catalyst from Fe-Mg-hydrotalcite anionic clay for Friedel-Crafts type benzylation reactions

    Indian Academy of Sciences (India)

    Vasant R Choudhary; Rani Jha; Pankaj A Choudhari

    2005-11-01

    Fe-Mg-hydrotalcite (Mg/Fe = 3) anionic clay with or without calcination (at 200-800°C) has been used for the benzylation of toluene and other aromatic compounds by benzyl chloride. Hydrotalcite before and after its calcination was characterized for surface area, crystalline phases and basicity. Both the hydrotalcite, particularly after its use in the benzylation reaction, and the catalyst derived from it by its calcination at 200-800°C show high catalytic activity for the benzylation of toluene and other aromatic compounds. The catalytically active species present in the catalyst in its most active form are the chlorides and oxides of iron on the catalyst surface.

  15. Pt monolayer shell on hollow Pd core electrocatalysts: Scale up synthesis, structure, and activity for the oxygen reduction reaction

    Directory of Open Access Journals (Sweden)

    Vukmirovic Miomir B.

    2013-01-01

    Full Text Available We report on synthesis, characterization and the oxygen reduction reaction (ORR kinetics of Pt monolayer shell on Pd(hollow, or Pd-Au(hollow core electrocatalysts. Comparison between the ORR catalytic activity of the electrocatalysts with hollow cores and those of Pt solid and Pt hollow nanoparticles has been obtained using the rotating disk electrode technique. Hollow nanoparticles were made using Ni or Cu nanoparticles as sacrificial templates. The Pt ORR specific and mass activities of the electrocatalysts with hollow cores were found considerably higher than those of the electrocatalysts with the solid cores. We attribute this enhanced Pt activity to the smooth surface morphology and hollow-induced lattice contraction, in addition to the mass-saving geometry of hollow particles.

  16. Kinetic study on Michael-type reactions of β-nitrostyrenes with cyclic secondary amines in acetonitrile: transition-state structures and reaction mechanism deduced from negative enthalpy of activation and analyses of LFERs.

    Science.gov (United States)

    Um, Ik-Hwan; Kang, Ji-Sun; Park, Jong-Yoon

    2013-06-07

    A kinetic study is reported for the Michael-type reactions of X-substituted β-nitrostyrenes (1a-j) with a series of cyclic secondary amines in MeCN. The plots of pseudo-first-order rate constant k(obsd) vs [amine] curve upward, indicating that the reactions proceed through catalyzed and uncatalyzed routes. The dissection of k(obsd) into Kk2 and Kk3 (i.e., the rate constants for the uncatalyzed and catalyzed routes, respectively) revealed that Kk3 is much larger than Kk2, implying that the reactions proceed mainly through the catalyzed route when [amine] > 0.01 M. Strikingly, the reactivity of β-nitrostyrene (1g) toward piperidine decreases as the reaction temperature increases. Consequently, a negative enthalpy of activation is obtained, indicating that the reaction proceeds through a relatively stable intermediate. The Brønsted-type plots for the reactions of 1g are linear with β(nuc) = 0.51 and 0.61, and the Hammett plots for the reactions of 1a-j are also linear with ρX = 0.84 and 2.10 for the uncatalyzed and catalyzed routes, respectively. The reactions are concluded to proceed through six-membered cyclic transition states for both the catalyzed and uncatalyzed routes. The effects of the substituent X on reactivity and factors influencing β(nuc) and ρX obtained in this study are discussed.

  17. Science Letters: Nitrogen doping of activated carbon loading Fe2O3 and activity in carbon-nitric oxide reaction

    Institute of Scientific and Technical Information of China (English)

    WAN Xian-kai; ZOU Xue-quan; SHI Hui-xiang; WANG Da-hui

    2007-01-01

    Nitrogen doping of activated carbon loading Fe2O3 was performed by annealing in ammonia, and the activity of the modified carbon for NO reduction was studied in the presence of oxygen. Results show that Fe2O3 enhances the amount of surface oxygen complexes and facilitates nitrogen incorporation in the carbon, especially in the form of pyridinic nitrogen. The modified carbon shows excellent activity for NO reduction in the low temperature regime (<500 ℃) because of the cooperative effect of Fe2O3 and the surface nitrogen species.

  18. Kinetic studies of overlapping pyrolysis reactions in industrial waste activated sludge.

    Science.gov (United States)

    Yang, Xiaoyi; Jiang, Zhenpeng

    2009-07-01

    A sludge pyrolytic kinetics model was established in this study. Two types of sewage sludge from different industrial wastewater treatment plant produced different DTG (Derivative Thermogravimetry) shapes with an overlapping pattern. The multi-heating rate method was conducted to evaluate the kinetics for obtaining reasonable pyrolysis mechanisms and DTG curves were divided into several peaks using the Lorentz fitting method based on the composition of the sludge and the desire for precision. The peaks formed corresponded to the pyrolysis reactions of volatile matter, microbe cells, proteins, inorganic substances and char respectively, which can be reasonably explained based on the results from the flue gas analyzer and the chemical analysis. Two types of sewage sludge were found to have similar pyrolysis mechanisms. Reasonable reasons were also given to explain the distortion and lag observed in the DTG curves and pyrolysis mechanism.

  19. A Mechanistic Study of Direct Activation of Allylic Alcohols in Palladium Catalyzed Amination Reactions

    Directory of Open Access Journals (Sweden)

    Yasemin Gumrukcu

    2015-03-01

    Full Text Available We here report a computational approach on the mechanism of allylicamination reactions using allyl-alcohols and amines as the substrates and phosphoramidite palladium catalyst 1a, which operates in the presence of catalytic amount of 1,3-diethylurea as a co-catalyst. DFT calculations showed a cooperative hydrogen-bonding array between the urea moiety and the hydroxyl group of the allyl alcohol, which strengthens the hydrogen bond between the O-H moiety of the coordinated allyl-alcohol and the carbonyl-moiety of the ligand. This hydrogen bond pattern facilitates the (rate-limiting C-O oxidative addition step and leads to lower energy isomers throughout the catalytic cycle, clarifying the role of the urea-moiety.

  20. Morphological transformation during activation and reaction of an iron Fischer-Tropsch catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Jackson, N.B.; Kohler, S.; Harrington, M. [Sandia National Lab., Albuquerque, NM (United States)] [and others

    1995-12-31

    The purpose of this project is to support the development of slurry-phase bubble column processes being studied at the La Porte Alternative Fuel Development Unit. This paper describes the aspects of Sandia`s recent work regarding the advancement and understanding of the iron catalyst used in the slurry phase process. A number of techniques were used to understand the chemical and physical effects of pretreatment and reaction on the attrition and carbon deposition characteristics of iron catalysts. Unless otherwise stated, the data discussed was derived form experiments carried out on the catalyst chosen for the summer 1994 Fischer-Tropsch run at LaPorte, UCI 1185-78-370, (an L 3950 type) that is 88% Fe{sub 2}O{sub 3}, 11% CuO, and 0.052%K{sub 2}O.

  1. Highly active and non-corrosive catalytic systems for the coupling reactions of ethylene oxide and CO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Shuyao; Jin, So Jeong; Kim, Young Jin; Lee, Je Seung; Kim, Hoon Sik [Dept. of Chemistry and Research Institute of Basic Sciences, Kyung Hee University, Seoul (Korea, Republic of); Hong, Jongki; Lee, Won Woong [College of Pharmacy, Kyung Hee University, Seoul (Korea, Republic of); Ryu, Jung Bok [R and D Center, Chuncheon (Korea, Republic of)

    2017-02-15

    Lithium halide-based molten salts (LiX-[BMIm]Br) synthesized from the reactions of lithium halides (LiX, X = Cl or Br) with 1-butyl-3-methylimidazolium bromide ([BMIm]Br), and their catalytic performances and corrosivities were tested for the coupling reactions of ethylene oxide with carbon dioxide to produce ethylene carbonate. The activity of a molten salt was influenced with the change of halide ion. At a fixed molar amount of LiX, the activity of LiX-[BMIm]Br increased with increasing molar ratio of LiX/[BMIm]Br up to 1–1.25, and then decreased thereafter. Fast atom bombardment mass spectral analysis of LiBr-[BMIm]Br, obtained by dissolving LiBr in [BMIm]Br in a 1:1 molar ratio, implies that [Li{sub a} X{sub a+1}]{sup −} are active species for the carboxylation of ethylene oxide with LiX-[BMIm]Br. The corrosion test toward carbon steel coupons demonstrates that all the Cl-containing molten salts are corrosive, whereas the salts without containing Cl{sup −} are non-corrosive under the carboxylation condition.

  2. Activation cross-sections of proton induced reactions on vanadium in the 37–65 MeV energy range

    Energy Technology Data Exchange (ETDEWEB)

    Ditrói, F., E-mail: ditroi@atomki.hu [Institute for Nuclear Research, Hungarian Academy of Sciences (ATOMKI), Debrecen (Hungary); Tárkányi, F.; Takács, S. [Institute for Nuclear Research, Hungarian Academy of Sciences (ATOMKI), Debrecen (Hungary); Hermanne, A. [Cyclotron Laboratory, Vrije Universiteit Brussel (VUB), Brussels (Belgium)

    2016-08-15

    Highlights: • Proton induced nuclear reactions on natural vanadium in the 35–65 MeV range. • Stacked foil irradiation technique. • Comparison of results with the EMPIRE and TENDL-2015 calculations. • Application of results in thin layer activation is demonstrated. - Abstract: Experimental excitation functions for proton induced reactions on natural vanadium in the 37–65 MeV energy range were measured with the activation method using a stacked foil irradiation technique. By using high resolution gamma spectrometry cross-section data for the production of {sup 51,48}Cr, {sup 48}V, {sup 48,47,46,44m,44g,43}Sc and {sup 43,42}K were determined. Comparisons with the earlier published data are presented and results predicted by different theoretical codes (EMPIRE and TALYS) are included. Thick target yields were calculated from a fit to our experimental excitation curves and compared with the earlier experimental yield data. Depth distribution curves to be used for thin layer activation (TLA) are also presented.

  3. Theoretical Study on Highly Active Bifunctional Metalloporphyrin Catalysts for the Coupling Reaction of Epoxides with Carbon Dioxide.

    Science.gov (United States)

    Hasegawa, Jun-Ya; Miyazaki, Ray; Maeda, Chihiro; Ema, Tadashi

    2016-10-01

    Highly active bifunctional metalloporphyrin catalysts were developed for the coupling reaction of epoxides with CO2 to produce cyclic carbonates. The bifunctional catalysts have both quaternary ammonium halide groups and a metal center. To elucidate the roles of these catalytic groups, DFT calculations were performed. Control reactions using tetrabutylammonium halide as a catalyst were also investigated for comparison. In the present article, the results of our computational studies are overviewed. The computational results are consistent with the experimental data and are useful for elucidating the structure-activity relationship. The key features responsible for the high catalytic activity of the bifunctional catalysts are as follows: 1) the cooperative action of the halide anion (nucleophile) and the metal center (Lewis acid); 2) the near-attack conformation, leading to the efficient opening of the epoxide ring in the rate-determining step; and 3) the conformational change of the quaternary ammonium cation to stabilize various anionic species generated during catalysis, in addition to the robustness (thermostability) of the catalysts.

  4. Effect of cerium on photosynthetic pigments and photochemical reaction activity in soybean seedling under ultraviolet-B radiation stress.

    Science.gov (United States)

    Liang, Chanjuan; Zhang, Guangsheng; Zhou, Qing

    2011-09-01

    Effects of cerium (Ce) on photosynthetic pigments and photochemical reaction activity in soybean (Glycine max L.) under ultraviolet-B (UV-B) radiation stress were studied under laboratory conditions. UV-B radiation caused the decrease in chlorophyll content, net photosynthetic rate, Hill reaction activity, photophosphorylation rate and Mg(2+)-ATPase activity. Ce (III) (20 mg L(-1)) could alleviate UV-B-induced inhibition to these photosynthetic parameters because values of these photosynthetic parameters in Ce (III) + UV-B treatment were obviously higher than those with UV-B treatment alone. Dynamic changes of the above photosynthetic parameters show that Ce (III) could slow down the decrease rate of these photosynthetic parameters during a 5-day UV-B radiation and quicken the restoration during recovery period. The final restoration degree of five parameters mentioned above in leaves exposed to low level of UV-B radiation (0.15 W m(2)) was higher than that exposed to high level (0.45 W m(2)). Correlating net photosynthetic rate with other four parameters, we found that the regulating mechanisms Ce (ΠΙ) on photosynthesis under various level of UV-B radiation were not the same. The protective effects of Ce (III) on photosynthesis in plants were influenced by the intensity of UV-B radiation.

  5. Chemical characteristics and enhanced hepatoprotective activities of Maillard reaction products derived from milk protein-sugar system.

    Science.gov (United States)

    Oh, Nam Su; Young Lee, Ji; Lee, Hyun Ah; Joung, Jae Yeon; Shin, Yong Kook; Kim, Sae Hun; Kim, Younghoon; Lee, Kwang Won

    2016-02-01

    The objective of this study was to investigate the characteristics, antioxidative properties, and hepatoprotective effects of Maillard reaction products (MRP) from milk protein reacted with sugars. The MRP were obtained from milk protein, whey protein concentrates and sodium caseinate, using 2 types of sugars, lactose and glucose, by heating the mixture at 55°C for 7d in a sodium phosphate buffer (pH 7.4). Changes in the chemical modification of the milk protein were monitored by measuring the protein-bound carbonyls and PAGE protein profiles. The results showed that the amount of protein-bound carbonyls increased after Maillard reaction (MR). In addition, sodium dodecyl sulfate-PAGE analysis indicated a formation of high-molecular weight complexes through MR. The modification sites induced by MR of milk protein were monitored by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis of tryptic-digested gel spots of MRP. As a result, modification and their localization in AA sequence of MRP was identified. Also, the MRP showed higher antioxidant activities than the intact milk protein, and they reduced intracellular reactive oxygen species production and inhibited the depletion of the reduced glutathione concentrations in the HepG2 cells. In particular, glucose-sodium caseinate MRP showed the highest biological activities among all MRP. Therefore, these results suggest that the MRP from milk protein reacting with sugars possess effective antioxidant activity and have a protective ability against oxidative damage.

  6. Identifying the active site in nitrogen-doped graphene for the VO2+/VO2(+) redox reaction.

    Science.gov (United States)

    Jin, Jutao; Fu, Xiaogang; Liu, Qiao; Liu, Yanru; Wei, Zhiyang; Niu, Kexing; Zhang, Junyan

    2013-06-25

    Nitrogen-doped graphene sheets (NGS), synthesized by annealing graphite oxide (GO) with urea at 700-1050 °C, were studied as positive electrodes in a vanadium redox flow battery. The NGS, in particular annealed at 900 °C, exhibited excellent catalytic performance in terms of electron transfer (ET) resistance (4.74 ± 0.51 and 7.27 ± 0.42 Ω for the anodic process and cathodic process, respectively) and reversibility (ΔE = 100 mV, Ipa/Ipc = 1.38 at a scan rate of 50 mV s(-1)). Detailed research confirms that not the nitrogen doping level but the nitrogen type in the graphene sheets determines the catalytic activity. Among four types of nitrogen species doped into the graphene lattice including pyridinic-N, pyrrolic-N, quaternary nitrogen, and oxidic-N, quaternary nitrogen is verified as a catalytic active center for the [VO](2+)/[VO2](+) couple reaction. A mechanism is proposed to explain the electrocatalytic performance of NGS for the [VO](2+)/[VO2](+) couple reaction. The possible formation of a N-V transitional bonding state, which facilitates the ET between the outer electrode and reactant ions, is a key step for its high catalytic activity.

  7. Lipopolysaccharide induces apoptosis of cytotrophoblasts by activating an innate immune reaction in vitro

    Institute of Scientific and Technical Information of China (English)

    LI Si-yang; SHANG Tao; LI Shu-juan; RUI Guang-hai; LI Qiu-ling

    2007-01-01

    Background Enhanced apoptosis of cytotrophoblasts in early pregnancy is associated with high risk of intrauterine growth retardation and preeclampsia, which are two common pregnant complications. Its etiological factors remain unclear. Cytotrophoblasts share some traits with innate immune cells and may show response to lipopolysaccharide. This study was conducted to demonstrate whether lipopolysaccharide has apoptosis-inducing effects on cytotrophoblast and the role of innate immune reaction in this process.Methods Cytotrophoblasts were isolated from early pregnant villous tissues and cultured with serum-free medium.Subsequently, cytotrophoblasts were treated with lipopolysaccharide at the concentrations of 0 (control), 25, 50, 100 and 200 ng/ml for 24 hours. Apoptosis of cytotrophoblasts was determined by light microscopy, Hoechst 33258 DNA staining with a fluorescent microscope, transmission electron microscope and annexin V-fluorescein isothiocyanate-conjugated /propidium iodide (PI) staining with flow cytometry. Then expression of caspase-3 was detected by Western blot. Confocal immunofluorescence technique was used to detect tumor necrosis factor α expression in cytotrophoblasts. The levels of tumor necrosis factor α in the culture medium were detected by enzyme-linked immunosorbent assay.Results Under light, fluorescence microscope and transmission electron microscope, characteristic alternations of apoptosis in cytotrophoblasts were observed after lipopolysaccharide treatment. Flow cytometry results showed that lipopolysaccharide significantly increased apoptosis indexes of cytotrophoblasts. Significant statistical differences were found in the above groups (P≤0.01). The mean relative densities of bands corresponding to caspase-3 were significantly increased in groups treated with lipopolysaccharide, as compared with the normal control (P<0.001). Tumor necrosis factor α expression was found to increase in cytotrophoblasts by confocal

  8. Surface chemistry of Au/TiO2: Thermally and photolytically activated reactions

    Science.gov (United States)

    Panayotov, Dimitar A.; Morris, John R.

    2016-03-01

    The fascinating particle size dependence to the physical, photophysical, and chemical properties of gold has motivated thousands of studies focused on exploring the ability of supported gold nanoparticles to catalyze chemical transformations. In particular, titanium dioxide-supported gold (Au/TiO2) nanoparticles may provide the right combination of electronic structure, structural dynamics, and stability to affect catalysis in important practical applications from environmental remediation to selective hydrogenation to carbon monoxide oxidation. Harnessing the full potential of Au/TiO2 will require a detailed atomic-scale understanding of the thermal and photolytic processes that accompany chemical conversion. This review describes some of the unique properties exhibited by particulate gold before delving into how those properties affect chemistry on titania supports. Particular attention is given first to thermally driven reactions on single crystal system. This review then addresses nanoparticulate samples in an effort begin to bridge the so-called materials gap. Building on the foundation provided by the large body of work in the field of thermal catalysis, the review describes new research into light-driven catalysis on Au/TiO2. Importantly, the reader should bear in mind throughout this review that thermal chemistry and thermal effects typically accompany photochemistry. Distinguishing between thermally-driven stages of a reaction and photo-induced steps remains a significant challenge, but one that experimentalists and theorists are beginning to decipher with new approaches. Finally, a summary of several state-of-the-art studies describes how they are illuminating new frontiers in the quest to exploit Au/TiO2 as an efficient catalyst and low-energy photocatalyst.

  9. Measurements of activation reaction rates in transverse shielding concrete exposed to the secondary particle field produced by intermediate energy heavy ions on an iron target

    Science.gov (United States)

    Ogawa, T.; Morev, M. N.; Iimoto, T.; Kosako, T.

    2012-01-01

    Reaction rate distributions were measured inside a 60-cm thick concrete pile placed at the lateral position of a thick (stopping length) iron target that was bombarded with heavy ions, 400 MeV/u C and 800 MeV/u Si. Foils of aluminum and gold, as well as gold, tungsten and manganese covered with cadmium were inserted at various locations in the concrete pile to serve as activation detectors. Features of reaction rate distribution, such as the shape of the reaction rate profile, contribution of the neutrons from intra-nuclear cascade and that from evaporation to the activation reactions are determined by the analysis of measured reaction rates. The measured reaction rates were compared with those calculated with radiation transport simulation codes, FLUKA and PHITS, to verify their capability to predict induced activity. The simulated reaction rates agree with the experimental results within a factor of three in general. However, systematic discrepancies between simulated reaction rates and measured reaction rates attributed to the neutron source terms are observed.

  10. Cerium carbide embedded in nitrogen-doped carbon as a highly active electrocatalyst for oxygen reduction reaction

    Science.gov (United States)

    Wang, Wei; Xue, Shouyuan; Li, Jinmei; Wang, Fengxia; Kang, Yumao; Lei, Ziqiang

    2017-08-01

    In this study, cerium carbide embedded in nitrogen-doped carbon (CeCx-NC) has been prepared by a facile pyrolysis of melamine formaldehyde resin containing rare-earth element. The as-prepared CeCx-NC catalyst shows high electrocatalytic activity towards oxygen reduction reaction (ORR) in alkaline electrolyte, with the half wave potential being almost equal to commercial Pt/C, nearly four electron transfer number, good toxicity tolerance durability and cycle stability. This rare-earth metal carbide opens a novel avenue for advanced electrocatalyst.

  11. All-oxide Raman-active traps for light and matter: probing redox homeostasis model reactions in aqueous environment.

    Science.gov (United States)

    Alessandri, Ivano; Depero, L E

    2014-04-09

    Core-shell colloidal crystals can act as very efficient traps for light and analytes. Here it is shown that Raman-active probes can be achieved using SiO2-TiO2 core-shell beads. These systems are successfully tested in monitoring of glutathione redox cycle at physiological concentration in aqueous environment, without need of any interfering enhancers. These materials represent a promising alternative to conventional, metal-based SERS probes for investigating chemical and biochemical reactions under real working conditions. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Synthesis and Some Reactions of 1-aryl-4-acetyl-5-methyl-1,2,3-triazole Derivatives with Anticonvulsant Activity.

    Science.gov (United States)

    Nassar, Ekhlass M; Abdelrazek, Fathy M; Ayyad, Rezk R; El-Farargy, Ahmed F

    2016-01-01

    The triazoles 3a-d underwent condensation reactions with 4-(piperidin-1-yl)-benzaldehyde to afford the chalcones 5a-d. Chalcone derivatives 5a-d were reacted with 2,3-diaminomaleonitrile, thiourea and hydrazine hydrate to afford the novel diazepine-dicarbonitrile derivatives 7a-d, the pyrimidine-2-thiol derivatives 9a-d and hydrazino-pyrimidines 10a-d respectively. Structures of the prepared compounds were elucidated by physical and spectral data like FT-IR, (1)H NMR, (13)C NMR, and mass spectroscopy. Some of the synthesized compounds were screened for their anticonvulsant activity and SAR.

  13. Highly active and stable Pt electrocatalysts promoted by antimony-doped SnO2 supports for oxygen reduction reactions

    DEFF Research Database (Denmark)

    Yin, Min; Xu, Junyuan; Li, Qingfeng

    2014-01-01

    supports composed of oxides and carbon and supported platinum catalysts were prepared. Using the pure oxide support, the Pt/ATO catalyst displayed superior specific activity and stability for the oxygen reduction reactions (ORRs). Low surface area of ATO caused poor dispersion of Pt particles compared......Alternative composite supports for platinum catalysts were synthesized from antimony doped tin dioxide (ATO) nanoparticles. In the range of the antimony content from 0 to 11mol%, the highest electrical conductivity of 1.1Scm-1 at 130°C was obtained for the 5mol% Sb ATO, from which composite...

  14. Measurement of activation reaction rate distributions in a lead assembly bombarded with 500-MeV protons

    CERN Document Server

    Takada, H; Sasa, T; Tsujimoto, K; Yasuda, H

    2000-01-01

    Reaction rate distributions of various activation detectors such as the /sup nat/Ni(n, x)/sup 58/Co, /sup 197/Au(n,2n)/sup 196/Au, and /sup 197/Au(n,4n)/sup 194/Au reactions were measured to study the production and the transport of spallation neutrons in a lead assembly bombarded with protons of 500 MeV. The measured data were analyzed with the nucleon-meson transport code NMTC/JAERI combined with the MCNP4A code using the nuclide production cross sections based on the JENDL Dosimetry File and those calculated with the ALICE-F code. It was found that the NMTC/JAERI-MCNP4A calculations agreed well with the experiments for the low-energy-threshold reaction of /sup nat/Ni(n, x)/sup 58/Co. With the increase of threshold energy, however, the calculation underestimated the experiments, especially above 20 MeV. The reason for the disagreement can be attributed to the underestimation of the neutron yield in the tens of mega-electron-volt regions by the NMTC/JAERI code. (32 refs).

  15. Biogenic synthesis of palladium nanoparticles using Pulicaria glutinosa extract and their catalytic activity towards the Suzuki coupling reaction.

    Science.gov (United States)

    Khan, Mujeeb; Khan, Merajuddin; Kuniyil, Mufsir; Adil, Syed Farooq; Al-Warthan, Abdulrahman; Alkhathlan, Hamad Z; Tremel, Wolfgang; Tahir, Muhammad Nawaz; Siddiqui, Mohammed Rafiq H

    2014-06-28

    Green synthesis of nanomaterials finds the edge over chemical methods due to its environmental compatibility. Herein, we report a facile and eco-friendly method for the synthesis of palladium (Pd) nanoparticles (NPs) using an aqueous solution of Pulicaria glutinosa, a plant widely found in a large region of Saudi Arabia, as a bioreductant. The as-prepared Pd NPs were characterized using ultraviolet-visible (UV-vis) spectroscopy, powder X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and Fourier transform-infrared spectroscopy (FT-IR). The hydroxyl groups of the plant extract (PE) molecules were found mainly responsible for the reduction and growth of Pd NPs. FT-IR analysis confirmed the dual role of the PE, both as a bioreductant as well as a capping ligand, which stabilizes the surface of Pd NPs. The crystalline nature of the Pd NPs was identified using XRD analysis which confirmed the formation of a face-centered cubic structure (JCPDS: 87-0641, space group: Fm3m (225)). Furthermore, the as-synthesized Pd NPs demonstrated excellent catalytic activity towards the Suzuki coupling reaction under aqueous and aerobic conditions. Kinetic studies of the catalytic reaction monitored using GC confirmed that the reaction completes in less than 5 minutes.

  16. Measurement of activation cross-sections for high-energy neutron-induced reactions of Bi and Pb

    Science.gov (United States)

    Zaman, Muhammad; Kim, Guinyun; Kim, Kwangsoo; Naik, Haladhara; Shahid, Muhammad; Lee, Manwoo

    2015-08-01

    The cross-sections for 209Bi(n, 4n)206Bi, 209Bi(n, 5n)205Bi, natPb(n, xn)204mPb, natPb(n, xn)203Pb, natPb(n, xn)202mPb,natPb(n, xn)201Pb, natPb(n, xn)200Pb, natPb(n, αxn)203Hg and natPb(n, p xn)202Tl reactions were determined at the Korean Institute of Radiological and Medical Sciences (KIRAMS), Korea in the neutron energy range of 15.2 to 37.2 MeV. The above cross-sections were obtained by using the activation and off-line γ-ray spectrometric technique. The quasi-monoenergetic neutron used for the above reactions are based on the 9Be(p, n) reaction. Simulations of the spectral flux from the Be target were done using the MCNPX program. The cross-sections were estimated with the TALYS 1.6 code using the default parameter. The data from the present work and literature were compared with the data from the EAF-2010 and the TENDL-2013 libraries, and calculated values of TALYS 1.6 code. It shows that appropriate level density model, the γ-ray strength function, and the spin cut-off parameter are needed to obtain a good agreement between experimental data and theoretical values from TALYS 1.6 code.

  17. Novel sesquiterpenes from Schisandra grandiflora: isolation, cytotoxic activity and synthesis of their triazole derivatives using "click" reaction.

    Science.gov (United States)

    Poornima, B; Siva, Bandi; Shankaraiah, G; Venkanna, A; Nayak, V Lakshma; Ramakrishna, Sistla; Venkat Rao, C; Babu, K Suresh

    2015-03-06

    Phytochemical investigation of hexane extract from the fruits of Schisandra grandiflora afforded three novel sesquiterpenes (1-3) along with the three known compounds (4-6). The structures of these isolates were determined by extensive analysis of spectroscopic data (1D, 2D NMR). Further, a series of triazole analogues of 3 and 4 were prepared using "Click" reaction protocol. The reaction scheme involving one-carbon homologation of 3 and 4 using the Bestmann-Ohira reagent followed by regioselective Huisgen 1,3-dipolar cycloaddition reaction of various azides leading to the formation of triazole analogues (20a-20k &21a-21c) which is being reported for the first time. All the triazole products were characterized using spectral data analysis. The anti-proliferative activity of the isolates and the synthetic analogues were studied against Hela (Cervical cancer), A549 (Lung cancer), DU-145 (Prostate cancer), MCF-7 (Breast cancer) and B-16 (Mouse melanoma) cancer cell lines. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

  18. Click reaction based synthesis, antimicrobial, and cytotoxic activities of new 1,2,3-triazoles.

    Science.gov (United States)

    El Sayed Aly, Mohamed Ramadan; Saad, Hosam Ali; Mohamed, Mosselhi Abdelnabi Mosselhi

    2015-07-15

    Three-motif pharmacophoric models 20a-e and 21-25 were prepared in good yields by CuAAC of two azido substrates 2 and 11 with seven terminal acetylenic derivatives including chalcones 17a-e, theophylline 18 and cholesterol 19. The structure of these compounds was elucidated by NMR, MS, IR spectroscopy and micro analyses. This series was screened as antimicrobial and cytotoxic agents in vitro. Most derivatives showed appreciable antibacterial activity, but they displayed weak cytotoxic, and antifungal activities. Notably, conjugate 25 (cream of the crop) was found to be more active than Ampicillin against Escherichia coli and Staphylococcus aureus and showed appreciable antifungal and cytotoxic activities as well.

  19. Oxidative photoredox-catalytic activation of aliphatic nucleophiles for C(sp(3))-C(sp(2)) cross-coupling reactions.

    Science.gov (United States)

    Jahn, Emanuela; Jahn, Ullrich

    2014-12-01

    In the light you will find the road (Led Zeppelin): Visible-light photoredox catalysis leads the way in overcoming the reactivity limitations of alkyl nucleophiles in cross-coupling reactions. Iridium-triggered oxidative photoredox activation of alkyltrifluoroborate or carboxylic acids affords alkyl radicals, which undergo nickel-catalyzed cross-coupling reactions.

  20. [Reaction of NO with metal oxides and urea supported on activated carbons at low temperature].

    Science.gov (United States)

    Cui, Hua-Fei; Li, Cai-Ting; Lu, Pei; Peng, Dun-Liang; Guo, Jing; Chen, Ling

    2010-11-01

    The catalysts were prepared by activated carbon fiber (ACF) loaded different contents of NiO and NiO-CeO2, Urea was loaded on the prepared catalysts as reductant. The experiments of selective catalytic reductions (SCR) of NO were carried out from 30 to 120 degrees C. The experiments of SEM, BET and XRD of the samples were also carried out selectively to study the catalysts properties, respectively. The experimental results showed that the loaded mass fraction of NiO could greatly affect the catalytic activity of the catalysts. 10% NiO catalyst activity and activity stability were both higher than that of the others, and it could yield about 50% removal efficiency of NO at 90 degrees C. With the loaded mass increasing, the catalytic activity was obviously decreased. And furthermore, the catalyst of 5% NiO-5% CeO2/ACF had the best catalytic activities on SCR NO and stability among the prepared NiO-CeO2/ACF catalysts, and its NO removal efficiency was over 55% at 110 degrees C. When the loaded mass increased, the similar phenomenon was observed, which was due to the decreasing of specific surface area of the catalysts. The metal oxides, loaded on ACF, were the catalytic centers in this study. Moreover, 5% CeO2-5% NiO/ACF had the highest catalytic activity than 10% CeO2/ACF and 10% NiO/ ACF. Therefore, there should be synergistic effect between CeO2 and NiO. Finally, the catalytic mechanism of SCR on NO at low temperature was discussed.

  1. Bimolecular recombination reactions: K-adiabatic and K-active forms of the bimolecular master equations and analytic solutions.

    Science.gov (United States)

    Ghaderi, Nima

    2016-03-28

    Expressions for a K-adiabatic master equation for a bimolecular recombination rate constant krec are derived for a bimolecular reaction forming a complex with a single well or complexes with multiple well, where K is the component of the total angular momentum along the axis of least moment of inertia of the recombination product. The K-active master equation is also considered. The exact analytic solutions, i.e., the K-adiabatic and K-active steady-state population distribution function of reactive complexes, g(EJK) and g(EJ), respectively, are derived for the K-adiabatic and K-active master equation cases using properties of inhomogeneous integral equations (Fredholm type). The solutions accommodate arbitrary intermolecular energy transfer models, e.g., the single exponential, double exponential, Gaussian, step-ladder, and near-singularity models. At the high pressure limit, the krec for both the K-adiabatic and K-active master equations reduce, respectively, to the K-adiabatic and K-active bimolecular Rice-Ramsperger-Kassel-Marcus theory (high pressure limit expressions). Ozone and its formation from O + O2 are known to exhibit an adiabatic K. The ratio of the K-adiabatic to the K-active recombination rate constants for ozone formation at the high pressure limit is calculated to be ∼0.9 at 300 K. Results on the temperature and pressure dependence of the recombination rate constants and populations of O3 will be presented elsewhere.

  2. Bimolecular recombination reactions: K-adiabatic and K-active forms of the bimolecular master equations and analytic solutions

    Science.gov (United States)

    Ghaderi, Nima

    2016-03-01

    Expressions for a K-adiabatic master equation for a bimolecular recombination rate constant krec are derived for a bimolecular reaction forming a complex with a single well or complexes with multiple well, where K is the component of the total angular momentum along the axis of least moment of inertia of the recombination product. The K-active master equation is also considered. The exact analytic solutions, i.e., the K-adiabatic and K-active steady-state population distribution function of reactive complexes, g(EJK) and g(EJ), respectively, are derived for the K-adiabatic and K-active master equation cases using properties of inhomogeneous integral equations (Fredholm type). The solutions accommodate arbitrary intermolecular energy transfer models, e.g., the single exponential, double exponential, Gaussian, step-ladder, and near-singularity models. At the high pressure limit, the krec for both the K-adiabatic and K-active master equations reduce, respectively, to the K-adiabatic and K-active bimolecular Rice-Ramsperger-Kassel-Marcus theory (high pressure limit expressions). Ozone and its formation from O + O2 are known to exhibit an adiabatic K. The ratio of the K-adiabatic to the K-active recombination rate constants for ozone formation at the high pressure limit is calculated to be ˜0.9 at 300 K. Results on the temperature and pressure dependence of the recombination rate constants and populations of O3 will be presented elsewhere.

  3. Achieving Remarkable Activity and Durability toward Oxygen Reduction Reaction Based on Ultrathin Rh-Doped Pt Nanowires.

    Science.gov (United States)

    Huang, Hongwen; Li, Kan; Chen, Zhao; Luo, Laihao; Gu, Yuqian; Zhang, Dongyan; Ma, Chao; Si, Rui; Yang, Jinlong; Peng, Zhenmeng; Zeng, Jie

    2017-06-21

    The research of active and sustainable electrocatalysts toward oxygen reduction reaction (ORR) is of great importance for industrial application of fuel cells. Here, we report a remarkable ORR catalyst with both excellent mass activity and durability based on sub 2 nm thick Rh-doped Pt nanowires, which combine the merits of high utilization efficiency of Pt atoms, anisotropic one-dimensional nanostructure, and doping of Rh atoms. Compared with commercial Pt/C catalyst, the Rh-doped Pt nanowires/C catalyst shows a 7.8 and 5.4-fold enhancement in mass activity and specific activity, respectively. The combination of extended X-ray absorption fine structure analysis and density functional theory calculations reveals that the compressive strain and ligand effect in Rh-doped Pt nanowires optimize the adsorption energy of hydroxyl and in turn enhance the specific activity. Moreover, even after 10000 cycles of accelerated durability test in O2 condition, the Rh-doped Pt nanowires/C catalyst exhibits a drop of 9.2% in mass activity, against a big decrease of 72.3% for commercial Pt/C. The improved durability can be rationalized by the increased vacancy formation energy of Pt atoms for Rh-doped Pt nanowires.

  4. Effect of Static Magnetic Field on α-Amylase Activity and Enzymatic Reaction

    Institute of Scientific and Technical Information of China (English)

    JIA Shaoyi; LIU Yong; WU Songhai; WANG Zhibin

    2009-01-01

    The effect of magnetic field on α-amylase was studied. Under the experimental conditions, α-amylase solution was treated by 0.15 T, 0.30 T and 0.45 T static magnetic fields for a known period of time, then the activ-ity, kinetic parameters, and the secondary conformation were investigated. The results showed that there was a con-siderable effect of the magnetic exposure on the α-amylase. The activity was increased by 27%, 34.1%, 37.8% compared with the control. It was also found that both kinetic parameters Km and Vm could be decreased due to the increasing magnetic field, Km decreased from 2.20×102 to 0.87×102, whereas Vm decreased from 2.0×103 g/min to 1.1×103g/min. At the same time, there were some irregular changes in α-amylase secondary conformation.

  5. Bifunctional enhancement of oxygen reduction reaction activity on Ag catalysts due to water activation on LaMnO3 supports in alkaline media.

    Science.gov (United States)

    Park, Shin-Ae; Lee, Eun-Kyung; Song, Hannah; Kim, Yong-Tae

    2015-08-27

    Ag is considered to be one of the best candidates for oxygen reduction reaction electrocatalysts in alkaline media for application in various electrochemical energy devices. In this study, we demonstrate that water activation is a key factor in enhancing the ORR activity in alkaline media, unlike in acid environments. Ag supported on LaMnO3 having a high oxophilicity showed a markedly higher ORR activity than that on carbon with inert surfaces. Through various electrochemical tests, it was revealed that the origin of the enhanced ORR activity of Ag/LaMnO3 is the bifunctional effect mainly due to the water activation at the interface between Ag and LaMnO3. Furthermore, the ligand effect due to the charge transfer from Mn to Ag leads to the enhancement of both oxygen activation on Ag and water activation on Mn sites, and hence, an improvement in the ORR activity of Ag/LaMnO3. On the other hand, the strain effect based on the fine structure variation in the lattice was negligible. We therefore suggest that the employment of a co-catalyst or support with highly oxophilic nature and the maximization of the interface between catalyst and support should be considered in the design of electrocatalysts for the ORR in alkaline media.

  6. Interesterification reaction activity, fatty acid composition and selectivity ratio of soybean oil

    Directory of Open Access Journals (Sweden)

    El-Shattory, Y.

    1998-12-01

    Full Text Available The interesterification reaction was carried out by adding oleic acid to soybean oil by ratio 1:2 w/w under different conditions of temperature, stirring and catalyst percentages. Assessment of the interesterification of oils was reported by determination of saponification value, iodine value and fatty acids composition. This study showed that linolenic acid which is responsible for flavour instability of soybean oil and consider as primary factor contributing to deterioration of this oil could be reduced to less than or equals 3%.

    Se han llevado a cabo reacciones de interesterificación mediante la adición de ácido oleico a aceite de soja en la relación 1:2 w/w bajo diferentes condiciones de temperatura, agitación y porcentaje de catalizador. La evaluación de la interesterificación de los aceites se realizó por determinación del índice de saponificación, el índice de iodo y la composición en ácidos grasos. Este estudio mostró que el ácido linolénico, que es responsable de la inestabilidad del flavor del aceite de soja y considerado como factor primario que contribuye a la deterioración de este aceite, podría ser reducido a cantidades menores o iguales al 3%.

  7. Adaptive reaction of boys’ sympathetic-adrenal system to physical activity in puberty.

    Directory of Open Access Journals (Sweden)

    Alekcei Anatolevich Zverev

    2016-04-01

    Full Text Available This paper deals with the study of adaptive reactions of the sympathetic-adrenal system of 11-16-year-old boys to graduated exercise at different pubertal stages. To evaluate the functional state of the cardiovascular system, the heart rate, systolic and cardiac output were determined. The state of the sympathetic-adrenal system was analyzed by the excretion level of catecholamines and DOPA. Cardiac output in response to graduated exercise in boys at pubertal stages 1-2 is substantially ensured by the increased heart rate, and at the other stages of puberty - mainly due to increase in stroke volume, which is estimated as a favorable response to exercise. In mechanisms of urgent adaptation to graduated exercise, the boys of third and fourth pubertal stages show an intensive functioning of the cardiovascular system and a reducing reserve capacity of the sympathetic-adrenal system. The adolescents of fifth pubertal stage show economical response to functional tests, a reduced reactivity of the components of the sympathetic-adrenal system on the background of a significant increase in the excretion of precursors.

  8. Reverse micelles: inert nano-reactors or physico-chemically active guides of the capped reactions.

    Science.gov (United States)

    Uskoković, Vuk; Drofenik, Miha

    2007-05-31

    Reverse micelles present self-assembled multi-molecular entities formed within specific compositional ranges of water-in-oil microemulsions. The structure of a reverse micelle is typically represented as nano-sized droplet of a polar liquid phase, capped by a monolayer of surfactant molecules, and uniformly distributed within a non-polar, oil phase. Although their role in serving as primitive membranes for encapsulation of primordial self-replicating chemical cycles that anticipated the very origins of life has been proposed, their first application for 'parent(hesis)ing' chemical reactions with an aim to produce 'templated' 2D arrays of nanoparticles dates back to only 25 years ago. Reverse micelles have since then been depicted as passive nano-reactors that via their shapes template the growing crystalline nuclei into narrowly dispersed or even perfectly uniform nano-sized particles. Despite this, numerous examples can be supported, where from deviations from the simple unilateral correlations between size and shape distribution of reverse micelles and the particles formed within may be reasonably implied. A rather richer, dynamical role of reverse micelles, with potential significance in the research and design of complex, self-assembly synthesis pathways, as well as possible adoption of their application as an aspect of biomimetic approach, is suggested herein.

  9. Effects of the isolated influence of means the training directed on activization neurogenic stimulus (drive reactions in recovery in modern pentathlon

    Directory of Open Access Journals (Sweden)

    Efremenko A.V.

    2009-12-01

    Full Text Available Activization conditions neurogenic stimulus (drive of reactions for stimulation of recovery processes after intense impellent activity are shown. Activation of activity of the cardio respiratory system is rotined in the conditions of the standard testing on the second day after implementation of the experimental restoration motive mode. The increase of stability of frequency of heart-throbs is marked in the conditions of the standard even loading. Presented foundation for the complex use of trainings restoration facilities of activation of physiological stimuli of reactions.

  10. Surface spectators and their role in relationships between activity and selectivity of the oxygen reduction reaction in acid environments.

    Energy Technology Data Exchange (ETDEWEB)

    Ciapina, Eduardo G.; Lopes, Pietro P.; Subbaraman, Ram; Ticianelli, Edson A.; Stamenkovic, Vojislav; Strmcnik, Dusan; Markovic, Nenad M.

    2015-11-01

    We use the rotating ring disk (RRDE) method to study activity-selectivity relationships for the oxygen reduction reaction (ORR) on Pt(111) modified by various surface coverages of adsorbed CNad (ΘCNad). The results demonstrate that small variations in ΘCNad have dramatic effect on the ORR activity and peroxide production, resulting in “volcano-like” dependence with an optimal surface coverage of ΘCNad = 0.3 ML. These relationships can be simply explained by balancing electronic and ensemble effects of co-adsorbed CNad and adsorbed spectator species from the supporting electrolytes, without the need for intermediate adsorption energy arguments. Although this study has focused on the Pt(111)-CNad/H2SO4 interface, the results and insight gained here are invaluable for controlling another dimension in the properties of electrochemical interfaces.

  11. A convenient method for experimental determination of yields and isomeric ratios in photonuclear reactions measured by the activation technique

    Energy Technology Data Exchange (ETDEWEB)

    Kolev, D. [Sofia Univ. (Bulgaria). Dept. of Physics; Dobreva, E. [Sofia Univ. (Bulgaria). Dept. of Physics; Nenov, N. [Sofia Univ. (Bulgaria). Dept. of Physics; Todorov, V. [A Higher Institute of Medicine, Sofia (Bulgaria)

    1995-03-15

    A generalized exact formula is derived for a determination of the experimental isomeric ratio in any incident particle activation. For the particular case, when the activity of the ground state results from the simultaneous decay of both states and can be conveniently measured, the appropriate modification of this formula is evaluated and applied to six photonuclear reactions induced by 43 MeV bremsstrahlung. The experimental isomeric yield ratios of ({gamma}, 3n) {sup 110m,g}In; ({gamma}, p) ({gamma}, pn), ({gamma}, 2n2p) {sup 117m,g}In; ({gamma}, n) {sup 164m,g}Ho and ({gamma}, 3n) {sup 162m,g}Ho are deduced. ((orig.)).

  12. Activation cross-sections of proton induced reactions on vanadium in the 37-65 MeV energy range

    CERN Document Server

    Ditrói, F; Takács, S; Hermanne, A

    2016-01-01

    Experimental excitation functions for proton induced reactions on natural vanadium in the 37-65 MeV energy range were measured with the activation method using a stacked foil irradiation technique. By using high resolution gamma spectrometry cross-section data for the production of $^{51,48}$Cr, $^{48}$V, $^{48,47,46,44m,44g,43}$Sc and $^{43,42}$K were determined. Comparisons with the earlier published data are presented and results predicted by different theoretical codes (EMPIRE and TALYS) are included. Thick target yields were calculated from a fit to our experimental excitation curves and compared with the earlier experimental yield data. Depth distribution curves to be used for thin layer activation (TLA) are also presented.

  13. Effects of some inhibitors of protein synthesis on the chloroplast fine structure, CO2 fixation and the Hill reaction activity

    Directory of Open Access Journals (Sweden)

    S. Więckowski

    2015-01-01

    Full Text Available A comparative study concerning the effects of chloramphenicol (100 μg ml-1, actidione (10 μg ml-1, 5-bromouracil (190 μg ml-1, actinomycin D (30 μg ml-1 and DL-ethionine (800 μg ml-1 on the chloroplast fine structure, 14CO2 incorporation and the Hill reaction activity was the subject of the experiments presented in this paper. The experiments were conducted on bean seedlings under the conditions when chlorophyll accumulation was inhibited only partially. The results obtained indicate that chloromphenicol is responsible for the reduction of the number of grana per section of plastid and for the formation of numerous vesicles in the stroma. In the presence of actidione, actinomycin D or DL-ethionine the lamellae are poorly differentiated into .stroma and granum regions and there occur disturbances in the typical orientation of lamellae within chloroplasts. Only in the presence of 5-bromouracil the development of chloroplast structure resemble that in control plants. A comparison of the results obtained with those published earlier (Więckowski et al., 1974; Ficek and Więckowski, 1974 shows that such processes as assimilatory pigment accumulation, the rate of CO2 fixation, the Hill reaction activity, and the development of lamellar system are suppressed in a different extent by the inhibitors used.

  14. Measurement method of activation cross-sections of reactions producing short-lived nuclei with 14 MeV neutrons

    CERN Document Server

    Kawade, K; Kasugai, Y; Shibata, M; Iida, T; Takahashi, A; Fukahori, T

    2003-01-01

    We describe a method for obtaining reliable activation cross-sections in the neutron energy range between 13.4 and 14.9 MeV for the reactions producing short-lived nuclei with half-lives between 0.5 and 30 min. We noted neutron irradiation fields and measured induced activities, including (1) the contribution of scattered low-energy neutrons, (2) the fluctuation of the neutron fluence rate during the irradiation, (3) the true coincidence sum effect, (4) the random coincidence sum effect, (5) the deviation in the measuring position due to finite sample thickness, (6) the self-absorption of the gamma-ray in the sample material and (7) the interference reactions producing the same radionuclides or the ones emitting the gamma-ray with the same energy of interest. The cross-sections can be obtained within a total error of 3.6%, when good counting statistics are achieved, including an error of 3.0% for the standard cross-section of sup 2 sup 7 Al (n, alpha) sup 2 sup 4 Na. We propose here simple methods for measuri...

  15. [Photodynamic reaction and oxidative stress - influence of the photodynamic effect on the activity antioxidant enzymes].

    Science.gov (United States)

    Romiszewska, Anna; Nowak-Stępniowska, Agata

    2014-01-01

    The interaction of light with a photosensitizer, accumulated in a tissue in the presence of oxygen, leads to formation of reactive oxygen species, mainly of singlet oxygen and free radicals. These factors react with biomolecules producing their oxidized states. Reactive oxygen species, such as singlet oxygen and free radicals are able to damage membranes, DNA, enzymes, structural peptides and other cellular structures leading to cell death. An antioxidant protection of cell is formed by enzymes belonging to the family of oxidoreductases: superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GR). Photodynamic therapy leads to the increased production of oxidizing toxic forms. It is important to analyze impact of PDT on the activity of antioxidant enzymes, such as SOD, CAT, GPx. The activity of antioxidant enzymes during the photodynamic effect is influenced by both the light energy dose and the concentration of photosensitizer. The presence only of the photosensitizer or only the light energy may also result in changes in the activity of these enzymes. The differences in changes in the activity of these enzymes depend on the type of used photosensitizer. A phenomenon of selective accumulation of photosensitizer in tumor tissues is used in the photodynamic method of tumor diagnosis and treatment.

  16. Raney copper catalysts for the water-gas shift reaction: I. Preparation, activity and stability

    CSIR Research Space (South Africa)

    Mellor, JR

    1997-12-23

    Full Text Available at the stated conditions compared favourably to the co-precipitated and industrial catalyst alternatives due to a similar active phase composition and high metallic copper surface areas. Raney copper catalyst deactivation in a poison-free environment...

  17. A Catalytically Active Membrane Reactor for Fast, Highly Exothermic, Heterogeneous Gas Reactions. A Pilot Plant Study

    NARCIS (Netherlands)

    Veldsink, Jan W.; Versteeg, Geert F.; Swaaij, Wim P.M. van

    1995-01-01

    Membrane reactors have been frequently studied because of their ability to combine chemical activity and separation properties into one device. Due to their thermal stability and mechanical strength, ceramic membranes are preferred over polymeric ones, but small transmembrane fluxes obstruct a wides

  18. Reactions to Humorous Sexual Stimuli as a Function of Sexual Activeness and Satisfaction.

    Science.gov (United States)

    Prerost, Frank J.

    1984-01-01

    Assessed male (N=60) and female (N=60) responses to pictorial humorous sexual material in relationship to degree of sexual expression and personal satisfaction with sexual behavior. Results showed persons with active and satisfying sexual expression enjoyed sexually explicit cartoons and showed less preference for aggressive themes. (LLL)

  19. Electrochemical Dealloying of PdCu3 Nanoparticles to Achieve Pt-like Activity for the Hydrogen Evolution Reaction.

    Science.gov (United States)

    Jana, Rajkumar; Bhim, Anupam; Bothra, Pallavi; Pati, Swapan K; Peter, Sebastian C

    2016-10-20

    Manipulating the d-band center of the metal surface and hence optimizing the free energy of hydrogen adsorption (ΔGH ) close to the optimal adsorption energy (ΔGH =0) for hydrogen evolution reaction (HER), is an efficient strategy to enhance the activity for HER. Herein, we report a oleylamine-mediated (acting as the solvent, stabilizer, and reducing agent) strategy to synthesize intermetallic PdCu3 nanoparticles (NPs) without using any external reducing agent. Upon electrochemical cycling, PdCu3 transforms into Pd-rich PdCu (ΔGH =0.05 eV), exhibiting remarkably enhanced activity (with a current density of 25 mA cm(-2) at ∼69 mV overpotential) as an alternative to Pt for HER. The first-principle calculation suggests that formation of low coordination number Pd active sites alters the d-band center and hence optimal adsorption of hydrogen, leading to enhanced activity. This finding may provide guidelines towards the design and development of Pt-free highly active and robust electrocatalysts. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Electro-activation of sweet defatted whey: Impact on the induced Maillard reaction products and bioactive peptides.

    Science.gov (United States)

    Kareb, Ourdia; Gomaa, Ahmed; Champagne, Claude P; Jean, Julie; Aïder, Mohammed

    2017-04-15

    Electro-activation was used to add value to sweet defatted whey. This study aimed to investigate and to characterize the bioactive compounds formed under different electro-activation conditions by molecular and proteomic approaches. The effects of electric current intensity (400, 500 or 600mA) and whey concentration (7, 14 or 21% (w/v)) as a function of the electro-activation time (0, 15, 30 or 45min) were evaluated. The targeted dependent variables were the formation of Maillard reaction products (MRPs), protein hydrolysates and glycated compounds. It was shown that the MRPs derived from electro-activated whey at a concentration of 14% had the highest potential of biological activity. SDS-PAGE analyses indicated the formation of hydrolysates and glycated compounds with different molecular weight distributions. FTIR indicated the predominance of intermediate MRPs, such as the Schiff base compounds. LC-MS/MS and proteomics analysis showed the production of multi-functional bioactive peptides due to the hydrolysis of whey proteins.

  1. High and low density PHA- (but not ConA-) activated T cells stimulate the autologous mixed lymphocyte reaction.

    Science.gov (United States)

    Brahmi, Z; Thomas, J E

    1985-01-01

    In this study, PHA- and ConA-activated cells (PAC and CAC) were used as stimulators in mixed lymphocyte reactions (MLR) using autologous (auto) and allogeneic (allo) peripheral mononuclear cells as responders. PAC, but not CAC, were stimulatory in allo- and auto-MLR, and this stimulation was not due to residual PHA. In PAC which have been activated for 96 h, auto-MLR was due to determinants present on low density T-cell blasts, while with PAC which had been stimulated for more than 192 h, the determinants seemed to be associated with high density T cells. Anti-T3 monoclonal antibodies and certain anti-DR suppressed auto- and allo-MLR mediated by PAC when present throughout the entire MLR assays. CAC suppressed PAC-mediated auto-MLR in a dose-dependent fashion. This inhibition was not DR-restricted and was reversed by the addition of exogenous IL-2. Our results indicate that: depending upon the length of activation, both low density and high density PHA-activated T cells exhibited strong stimulatory capacity in auto-MLR; ConA-activated T cells failed to stimulate auto- or allo-MLR and suppressed MLR mediated by PAC; this suppression was due to suppressor cells, not to suppressor factors, and was readily reversed by exogenous IL-2; pretreatment of CAC with anti-TAC did not reverse the inhibition.

  2. Comparisons between abiotic nitration and biotransformation reactions of phenolic micropollutants in activated sludge.

    Science.gov (United States)

    Jewell, Kevin S; Wick, Arne; Ternes, Thomas A

    2014-01-01

    The transformation of selected phenolic substances was investigated during biological wastewater treatment. A main emphasis was put on the relevance of abiotic processes leading to toxic nitrophenolic transformation products (TPs). Due to their environmental relevance, the antiseptic ortho-phenylphenol (OPP), the plastics additive bisphenol A (BPA) and the psychoactive drug dextrorphan have been studied. Batch experiments confirmed that nitro- and nitroso-phenolic TPs can be formed under acidic conditions when nitrite is present. HNO2, N2O3 and NO and NO2 radicals are likely involved in the abiotic process. It was found that the process was promoted by the freezing of water samples, since this can lead to an unexpected pH drop. However, under conditions present at wastewater treatment plants (neutral pH, low nitrite concentrations), the formation of appreciable concentrations is rather unlikely through this process, since HNO2 concentrations are extremely low and NO and NO2 radicals will also react with other wastewater constituents. Thus, the transformation of phenolic substances such as OPP and BPA is mainly caused by biotic transformation. In addition to hydroxylation as a common reaction under aerobic conditions, the formation of sulfate conjugates was detected with the original compounds as well as with nitrophenolic TPs. Therefore, even when nitro-phenolic substances are formed it is likely that they are further transformed to sulfate conjugates. In raw wastewater and WWTP effluent nitrated BPA and NO2-dextrorphan were not detected. Only nitro-OPP was found in the influent of a WWTP with 2.3 ng/L, but it was not identified in the WWTP effluents. The concentrations of dextrorphan increased slightly during WWTP passage, possibly due to the cleavage of the glucuronide-conjugate, its human metabolite form, or demethylation of the prodrug dextromethorphan.

  3. Application of the Triazolization Reaction to Afford Dihydroartemisinin Derivatives with Anti-HIV Activity

    Directory of Open Access Journals (Sweden)

    Sampad Jana

    2017-02-01

    Full Text Available Artemisinin and synthetic derivatives of dihydroartemisinin are known to possess various biological activities. Post-functionalization of dihydroartemisinin with triazole heterocycles has been proven to lead to enhanced therapeutic potential. By using our newly developed triazolization strategy, a library of unexplored fused and 1,5-disubstituted 1,2,3-triazole derivatives of dihydroartemisinin were synthesized in a single step. All these newly synthesized compounds were characterized and evaluated for their anti-HIV (Human Immunodeficiency Virus potential in MT-4 cells. Interestingly; three of the synthesized triazole derivatives of dihydroartemisinin showed activities with half maximal inhibitory concentration (IC50 values ranging from 1.34 to 2.65 µM.

  4. Highly active iridium/iridium-tin/tin oxide heterogeneous nanoparticles as alternative electrocatalysts for the ethanol oxidation reaction.

    Science.gov (United States)

    Du, Wenxin; Wang, Qi; Saxner, David; Deskins, N Aaron; Su, Dong; Krzanowski, James E; Frenkel, Anatoly I; Teng, Xiaowei

    2011-09-28

    Ethanol is a promising fuel for low-temperature direct fuel cell reactions due to its low toxicity, ease of storage and transportation, high-energy density, and availability from biomass. However, the implementation of ethanol fuel cell technology has been hindered by the lack of low-cost, highly active anode catalysts. In this paper, we have studied Iridium (Ir)-based binary catalysts as low-cost alternative electrocatalysts replacing platinum (Pt)-based catalysts for the direct ethanol fuel cell (DEFC) reaction. We report the synthesis of carbon supported Ir(71)Sn(29) catalysts with an average diameter of 2.7 ± 0.6 nm through a "surfactant-free" wet chemistry approach. The complementary characterization techniques, including aberration-corrected scanning transmission electron microscopy equipped with electron energy loss spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy, are used to identify the "real" heterogeneous structure of Ir(71)Sn(29)/C particles as Ir/Ir-Sn/SnO(2), which consists of an Ir-rich core and an Ir-Sn alloy shell with SnO(2) present on the surface. The Ir(71)Sn(29)/C heterogeneous catalyst exhibited high electrochemical activity toward the ethanol oxidation reaction compared to the commercial Pt/C (ETEK), PtRu/C (Johnson Matthey) as well as PtSn/C catalysts. Electrochemical measurements and density functional theory calculations demonstrate that the superior electro-activity is directly related to the high degree of Ir-Sn alloy formation as well as the existence of nonalloyed SnO(2) on surface. Our cross-disciplinary work, from novel "surfactant-free" synthesis of Ir-Sn catalysts, theoretical simulations, and catalytic measurements to the characterizations of "real" heterogeneous nanostructures, will not only highlight the intriguing structure-property correlations in nanosized catalysts but also have a transformative impact on the commercialization of DEFC technology by replacing Pt with low

  5. Kinetics and mechanism of the stepwise complex formation of Cu(II) with tren-centered tris-macrocycles.

    Science.gov (United States)

    Soibinet, Matthieu; Gusmeroli, Deborah; Siegfried, Liselotte; Kaden, Thomas A; Palivan, Cornelia; Schweiger, Arthur

    2005-06-21

    The stepwise complexation kinetics of Cu2+ with three tetratopic ligands L1, L2 and L3, tren-centred macrocycles with different bridges connecting the 14-membered macrocycles with the tren unit, have been measured by stopped-flow photodiode array techniques at 25 degrees C, I= 0.5 M (KNO3), and pH = 4.96. The reaction between the first Cu2+ and the ligand consists of several steps. In a rapid reaction Cu2+ first binds to the flexible and more reactive tren-unit. In this intermediate a translocation from the tren unit to the macrocyclic ring, which forms the thermodynamic more stable complex, takes place. This species can react further with a second Cu2+ to give a heterotopic dinuclear species with one Cu2+ bound by the tren-unit and the other coordinated by the macrocycle. A further translocation occurs to give the homoditopic species with two Cu2+ in the macrocycles. Finally a slow rearrangement of the dinuclear complex gives the final species. The rates of the translocation are dependent on the length and rigidity of the bridge, whereas the complexation rates with the tren unit are little affected by it. VIS spectra of the species obtained by fitting the kinetic results, EPR-spectra taken during the reaction, and ES mass spectra of the products confirm the proposed mechanism. The addition of a second, third and fourth equivalent of Cu2+ proceeds in an analogous way, but is complicated by the fact that we start and end with a mixture of species. These steps were evaluated in a qualitative way only.

  6. Activation cross sections of $\\alpha$-particle induced nuclear reactions on hafnium and deuteron induced nuclear reaction on tantalum: production of $^{178}$W/$^{178m}$Ta generator

    CERN Document Server

    Tárk'anyi, F; Ditrói, F; Hermanne, A; Ignatyuk, A V; Uddin, M S

    2014-01-01

    In the frame of a systematic study of charged particle production routes of medically relevant radionuclei, the excitation function for indirect production of $^{178m}$Ta through $^{nat}$Hf($\\alpha$,xn)$^{178}$W-$^{178m}$Ta nuclear reaction was measured for the first time up to 40 MeV. In parallel, the side reactions $^{nat}$Hf($\\alpha$,x)$^{179,177,176,175}$W, $^{183,182,178g,177,176,175}$Ta, $^{179m,177m,175}$Hf were also assessed. Stacked foil irradiation technique and $\\gamma$-ray spectrometry were used. New experimental cross section data for the $^{nat}$Ta(d,xn)$^{178}$W reaction are also reported up to 40 MeV. The measured excitation functions are compared with the results of the ALICE-IPPE, and EMPIRE nuclear reaction model codes and with the TALYS 1.4 based data in the TENDL-2013 library. The thick target yields were deduced and compared with yields of other charged particle ((p,4n), (d,5n) and ($^3$He,x)) production routes for $^{178}$W.

  7. Sulfato Complex Formation of V(V) and V(IV) in Pyrosulfate Melts Investigated by Potentiometry and Spectroscopic Methods

    DEFF Research Database (Denmark)

    Rasmussen, Søren Birk; Eriksen, Kim Michael; Fehrmann, Rasmus

    1999-01-01

    with the oxo sulfato vanadate equilibria VO(SO4)2,2- + SO4,2- = VO(SO4)3,4- for V(IV) and (VO)2O(SO4)4,4- + 2SO4,2- = 2VO2(SO4)2,3- + S2O7,2- for V(V), and 2VO2(SO4)2,3- + SO2 + SO4,2- 2VO(SO4)3,4- for the V(V)-V(IV) redox reaction in melts saturated with sulfate. Constants for these equilibria have also been...

  8. Modulating activity of M1 receptor to the reaction of ileal smooth muscle.

    Science.gov (United States)

    Glaza, Izabela; Szadujkis-Szadurski, Leszek; Szadujkis-Szadurski, Rafał; Gajdus, Marta; Olkowska, Joanna

    2011-08-03

    The subject of the study was determination of the effect of drugs on ileal smooth muscle contraction induced by activation of M(1) type muscarinic receptors. Drugs that have an effect on muscarinic receptors are divided to agonists, with close ties to the receptor and high internal activity and antagonists, with no internal activity. Conducted experiments tested interactions between a broad-spectrum agonist of muscarinic receptors, carbachol and a selective muscarinic receptor antagonist of M(1) type, pirenzepine. Testing was conducted on tissues isolated from rat's intestine. Male Wistar rats with weight between 220 g and 360 g were anesthetized by intraperitoneal injection of urethane (120 mg/kg). Concentration-effect curves were determined with the use of cumulated concentration method, in accordance with the van Rossum method (1963) in Kenakin modification (2006). The purpose of the study was determination of concentration-effect curves for carbachol. This curve was compared with the curve of receptor occupation depending on concentration of this drug. Based on concentration-effect curves, the average value of EC(50) was calculated for carbachol, amounting to 2.44×10(-6) [M/l]. The results confirmed that atropine is effective in stopping contractions caused by carbachol, meeting the conditions of competitive antagonists. Atropine caused the shift of curves for carbachol to the right. Pirenzepine, selectively blocking muscarinic receptors of M(1) type gave similar results. It was proved that in the preparation of gastric fundus smooth muscle, M(1) type receptors occur not only presynaptically, but also postsynaptically.

  9. Modulating activity of M1 receptor to the reaction of ileal smooth muscle

    Directory of Open Access Journals (Sweden)

    Izabela Glaza

    2011-08-01

    Full Text Available Background:The subject of the study was determination of the effect of drugs on ileal smooth muscle contraction induced by activation of M1 type muscarinic receptors. Drugs that have an effect on muscarinic receptors are divided to agonists, with close ties to the receptor and high internal activity and antagonists, with no internal activity. Conducted experiments tested interactions between a broad-spectrum agonist of muscarinic receptors, carbachol and a selective muscarinic receptor antagonist of M1 type, pirenzepine.Material/Methods:Testing was conducted on tissues isolated from rat’s intestine. Male Wistar rats with weight between 220 g and 360 g were anesthetized by intraperitoneal injection of urethane (120 mg/kg. Concentration-effect curves were determined with the use of cumulated concentration method, in accordance with the van Rossum method (1963 in Kenakin modification (2006.Results:The purpose of the study was determination of concentration-effect curves for carbachol. This curve was compared with the curve of receptor occupation depending on concentration of this drug. Based on concentration-effect curves, the average value of EC50 was calculated for carbachol, amounting to 2.44×10–6 [M/l].Conclusions:The results confirmed that atropine is effective in stopping contractions caused by carbachol, meeting the conditions of competitive antagonists. Atropine caused the shift of curves for carbachol to the right. Pirenzepine, selectively blocking muscarinic receptors of M1 type gave similar results. It was proved that in the preparation of gastric fundus smooth muscle, M1 type receptors occur not only presynaptically, but also postsynaptically.

  10. Active and Durable Hydrogen Evolution Reaction Catalyst Derived from Pd-Doped Metal-Organic Frameworks.

    Science.gov (United States)

    Chen, Jitang; Xia, Guoliang; Jiang, Peng; Yang, Yang; Li, Ren; Shi, Ruohong; Su, Jianwei; Chen, Qianwang

    2016-06-01

    The water electrolysis is of critical importance for sustainable hydrogen production. In this work, a highly efficient and stable PdCo alloy catalyst (PdCo@CN) was synthesized by direct annealing of Pd-doped metal-organic frameworks (MOFs) under N2 atmosphere. In 0.5 M H2SO4 solution, PdCo@CN displays remarkable electrocatalytic performance with overpotential of 80 mV, a Tafel slope of 31 mV dec(-1), and excellent stability of 10 000 cycles. Our studies reveal that noble metal doped MOFs are ideal precursors for preparing highly active alloy electrocatalysts with low content of noble metal.

  11. Spectrophotometric determination of benzydamine HCl, levamisole HCl and mebeverine HCl through ion-pair complex formation with methyl orange

    Science.gov (United States)

    El-Didamony, Akram M.

    2008-03-01

    A simple, rapid and sensitive spectrophotometric method has been proposed for the assay of benzydamine HCl (BENZ), levamisole HCl (LEV) and mebeverine HCl (MBV) in bulk and pharmaceutical formulations. The method based on the reaction of the selected drugs with methyl orange (MO) in buffered aqueous solution at pH 3.6. The formed yellow ion-pair complexes were extracted with dichloromethane and measured quantitatively with maximum absorption at 422 nm. The analytical parameters and their effects on the reported systems are investigated. The extracts are intensely colored and very stable at room temperature. The calibration graphs were linear over the concentration range of 2-10 μg ml -1 for BENZ, 6-24 μg ml -1 for LEV and 4-14 μg ml -1 for MBV. The stoichiometry of the reaction was found to be 1:1 in all cases and the conditional stability constant ( Kf) of the complexes have been calculated. The proposed method was successfully extended to pharmaceutical preparations-tablets. Excipients used as additive in commercial formulations did not interfere in the analysis. The proposed method can be recommended for quality control and routine analysis where time, cost effectiveness and high specificity of analytical technique are of great importance.

  12. Application of soft- and hard-modelling approaches to resolution of kinetics of electron donor-acceptor complex formation of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone with imipramine in different solutions

    Energy Technology Data Exchange (ETDEWEB)

    Hasani, Masoumeh [Faculty of Chemistry, Bu-Ali Sina University, Mahdieh, Hamedan, 65174 (Iran, Islamic Republic of)], E-mail: hasani@basu.ac.ir; Shariati-Rad, Masoud [Faculty of Chemistry, Bu-Ali Sina University, Mahdieh, Hamedan, 65174 (Iran, Islamic Republic of); Abdollahi, Hamid [Department of Chemistry, Institute for Advanced Studies in Basic Sciences, Zanjan (Iran, Islamic Republic of)

    2009-03-23

    Kinetics of electron donor-acceptor (EDA) complex formation of imipramine and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) was investigated spectrophotometrically in acetonitrile, 1,2-dichloroethane, and chloroform solutions using soft- and hard-modelling approaches. From the results of exploratory analysis of kinetic data and the spectral changes by soft-modelling approaches, evolving factor analysis (EFA) and orthogonal projection approach (OPA), a consecutive two-steps reaction with two intermediates was proposed for the process in acetonitrile and 1,2-dichloroethane media and one with a single intermediate in chloroform solution. Secondly, by applying, multivariate nonlinear least squares hard-modelling approach on the collected experimental kinetic data matrix, the nonlinear parameters (rate constants) as well as the linear parameters (spectral profiles) were obtained by fitting the collected experimental kinetic data matrix to the proposed model. Small values of standard deviation in the resulting parameters and sum of squares of the residuals (ssq) obtained showed the proper selection of the model. Furthermore, the values of lack of fit and percent of explained variance confirmed the correct identified models. Identification of the model with the aid of soft-modelling approaches followed by application of the hard-modelling approaches decreases significantly the rotational ambiguity associated with the obtained concentration and spectral profiles. Variations in the kinetic constants were in complete agreement with the model proposed and the solvent polarities.

  13. Acid-base behavior of cryptand 1, 4, 7, 10, 13, 16, 21, 24-octaaza-bicycio[8, 8, 8] hexacosan-3, 8, 12, 17, 20, 25-hexone and complex formation

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The bicyclic cryptand 1,4, 7, 10, 13, 16, 21, 24-octaaza-bigcyclo [8, 8, 8] hexacosan-3, 8, 12, 17, 20, 25-hexone (COBH) bearing diaminoethane groups along the eight-atom bridges was synthesized. The structure consists of discrete neutral macrobicyclic units; the two cycles share the two tertiary amine nitrogen atoms, which exhibit an endo-endo conformation. Three identical branches formed by 1, 2-diaminoethane link the two tertiary amine groups. The protonation reactions ofcryptand (COBH) and its complex formation with copper (Ⅱ) were investigated by potentiometry in water and in a DMSO/water (80: 20 in mass ratio) mixture as solvents. The cryptand acts as a bis-base through its two Nbridgehead and exhibits a strong cooperativity that favors the first protonation and makes the second one difficult (pK 5.0 ). An inward rotation of the amide groups to form hydrogen bonds accounts for this cooperativity. The interaction of COBH with copper (Ⅱ) leads to several binuclear complex proton contents.

  14. The role of chemokines and chemokine receptors in eosinophil activation during inflammatory allergic reactions

    Directory of Open Access Journals (Sweden)

    Oliveira S.H.P.

    2003-01-01

    Full Text Available Chemokines are important chemotactic cytokines that play a fundamental role in the trafficking of leukocytes to sites of inflammation. They are also potent cell-activating factors, inducing cytokine and histamine release and free radical production, a fact that makes them particularly important in the pathogenesis of allergic inflammation. The action of chemokines is regulated at the level of agonist production and processing as well as at the level of receptor expression and coupling. Therefore, an analysis of the ligands must necessarily consider receptors. Eosinophils are target cells involved in the allergic inflammatory response since they are able to release a wide variety of mediators including CC and CXC chemokines and express their receptors. These mediators could damage the airway epithelial cells and might be important to stimulate other cells inducing an amplification of the allergic response. This review focuses on recently emerging data pertaining to the importance of chemokines and chemokine receptors in promoting eosinophil activation and migration during the allergic inflammatory process. The analysis of the function of eosinophils and their chemokine receptors during allergic inflammation might be a good approach to understanding the determinants of asthma severity and to developing novel therapies.

  15. Metal nanoparticle/ionic liquid/cellulose: new catalytically active membrane materials for hydrogenation reactions.

    Science.gov (United States)

    Gelesky, Marcos A; Scheeren, Carla W; Foppa, Lucas; Pavan, Flavio A; Dias, Silvio L P; Dupont, Jairton

    2009-07-13

    Transition metal-containing membrane films of 10, 20, and 40 μm thickness were obtained by the combination of irregularly shaped nanoparticles with monomodal size distributions of 4.8 ± 1.1 nm (Rh(0)) and 3.0 ± 0.4 nm (Pt(0)) dispersed in the ionic liquid (IL) 1-n-butyl-3-methylimidazolium bis(trifluoromethane sulfonyl)imide (BMI·(NTf)(2)) with a syrup of cellulose acetate (CA) in acetone. The Rh(0) and Pt(0) metal concentration increased proportionally with increases in film thickness up to 20 μm, and then the material became metal saturated. The presence of small and stable Rh(0) or Pt(0) nanoparticles induced an augmentation in the CA/IL film surface areas. The augmentation of the IL content resulted in an increase of elasticity and decrease in tenacity and toughness, whereas the stress at break was not influenced. The introduction of IL probably causes an increase in the separation between the cellulose macromolecules that results in a higher flexibility, lower viscosity, and better formability of the cellulose material. The nanoparticle/IL/CA combinations exhibit an excellent synergistic effect that enhances the activity and durability of the catalyst for the hydrogenation of cyclohexene. The nanoparticle/IL/cellulose acetate film membranes display higher catalytic activity (up to 7353 h(-1) for the 20 μm film of CA/IL/Pt(0)) and stability than the nanoparticles dispersed only in the IL.

  16. A multi-scale model of the oxygen reduction reaction on highly active graphene nanosheets in alkaline conditions

    Science.gov (United States)

    Vazquez-Arenas, Jorge; Ramos-Sanchez, Guadalupe; Franco, Alejandro A.

    2016-10-01

    A multi-scale model based on a mean field approach, is proposed to describe the ORR mechanism on N-GN catalysts in alkaline media. The model implements activation energies calculated with Density Functional Theory (DFT) at the atomistic level, and scales up them into a continuum framework describing the cathode/electrolyte interface at the mesoscale level. The model also considers mass and momentum transports arising in the region next to the rotating electrode for all ionic species and O2; correction of potential drop and electrochemical double-layer capacitance. Most fitted parameters describing the kinetics of ORR elementary reactions are sensitive in the multi-scale model, which results from the incorporation of activation energies using the mean field method, unlike single-scale modelling Errors in the deviations from activation energies are found to be moderate, except for the elementary step (2) related to the formation of O2ads, which can be assigned to the inherent DFT limitations. The consumption of O2ads to form OOHads is determined as the rate-determining step as a result of its highest energy barrier (163.10 kJ mol-1) in the system, the largest error obtained for the deviation from activation energy (28.15%), and high sensitivity. This finding is confirmed with the calculated surface concentration and coverage of electroactive species.

  17. Pt skin coated hollow Ag-Pt bimetallic nanoparticles with high catalytic activity for oxygen reduction reaction

    Science.gov (United States)

    Fu, Tao; Huang, Jianxing; Lai, Shaobo; Zhang, Size; Fang, Jun; Zhao, Jinbao

    2017-10-01

    The catalytic activity and stability of electrocatalyst is critical for the commercialization of fuel cells, and recent reports reveal the great potential of the hollow structures with Pt skin coat for developing high-powered electrocatalysts due to their highly efficient utilization of the Pt atoms. Here, we provide a novel strategy to prepare the Pt skin coated hollow Ag-Pt structure (Ag-Pt@Pt) of ∼8 nm size at room temperature. As loaded on the graphene, the Ag-Pt@Pt exhibits a remarkable mass activity of 0.864 A/mgPt (at 0.9 V, vs. reversible hydrogen electrode (RHE)) towards oxygen reduction reaction (ORR), which is 5.30 times of the commercial Pt/C catalyst, and the Ag-Pt@Pt also shows a better stability during the ORR catalytic process. The mechanism of this significant enhancement can be attributed to the higher Pt utilization and the unique Pt on Ag-Pt surface structure, which is confirmed by the density functional theory (DFT) calculations and other characterization methods. In conclusion, this original work offers a low-cost and environment-friendly method to prepare a high active electrocatalyst with cheaper price, and this work also discloses the correlation between surface structures and ORR catalytic activity for the hollow structures with Pt skin coat, which can be instructive for designing novel advanced electrocatalysts for fuel cells.

  18. Carbon Supported Engineering NiCo2O4 Hybrid Nanofibers with Enhanced Electrocatalytic Activity for Oxygen Reduction Reaction

    Directory of Open Access Journals (Sweden)

    Diab Hassan

    2016-09-01

    Full Text Available The design of cheap and efficient oxygen reduction reaction (ORR electrocatalysts is of a significant importance in sustainable and renewable energy technologies. Therefore, ORR catalysts with superb electrocatalytic activity and durability are becoming a necessity but still remain challenging. Herein, we report C/NiCo2O4 nanocomposite fibers fabricated by a straightforward electrospinning technique followed by a simple sintering process as a promising ORR electrocatalyst in alkaline condition. The mixed-valence oxide can offer numerous accessible active sites. In addition, the as-obtained C/NiCo2O4 hybrid reveals significantly remarkable electrocatalytic performance with a highly positive onset potential of 0.65 V, which is only 50 mV lower than that of commercially available Pt/C catalysts. The analyses indicate that C/NiCo2O4 catalyst can catalyze O2-molecules via direct four electron pathway in a similar behavior as commercial Pt/C catalysts dose. Compared to single NiCo2O4 and carbon free NiCo2O4, the C/NiCo2O4 hybrid displays higher ORR current and more positive half-wave potential. The incorporated carbon matrices are beneficial for fast electron transfer and can significantly impose an outstanding contribution to the electrocatalytic activity. Results indicate that the synthetic strategy hold a potential as efficient route to fabricate highly active nanostructures for practical use in energy technologies.

  19. Exploring the catalytic activity of pristine T6[100] surface for oxygen reduction reaction: A first-principles study

    Science.gov (United States)

    Banerjee, Paramita; Chakrabarty, Soubhik; Thapa, Ranjit; Das, G. P.

    2017-10-01

    The electrocatalytic activity of T6[100] surface containing both sp3 (C1) and sp2 (C2) hybridized carbon atoms is explored using first-principles density functional theory based approach. The top layered C1 atom of the surface is found to be more active towards the oxygen reduction reaction (ORR), as compared to that of C2 atom. This is attributed to the presence of dangling σ bond in the corresponding C1 atom, leading to the high electron density near the Ferrmi level. Whereas, the π electron in the top layered C2 atom forms a weak out of plane network. As estimated from free energy profile, the overpotential is much lower when C1 is considered as the active site and the final step i.e desorption of final OH- ion is found to be the potential determining step. We have also reported the effect of Si dopant on the catalytic activity of T6[100] surface and explained the origin of high overpotential value in this case. Thus in this report, we propose a new metal-free catalyst i.e T6[100] surface, having both sp2 (maintains the high metallicity needed to reduce ohmic loss) and sp3 (helps in capturing the upcoming molecules) hybridized carbon atoms, as a potential candidate for ORR.

  20. Critical solvent thermodynamic effect on molecular recognition: The case of the complex formation of carboxylates and ammonium-squaramido based receptors

    Energy Technology Data Exchange (ETDEWEB)

    Piña, M. Nieves, E-mail: neus.pinya@uib.es; López, Kenia A.; Costa, Antoni; Morey, Jeroni, E-mail: jeroni.morey@uib.es

    2013-10-10

    Graphical abstract: - Highlights: • The enthalpy–entropy compensation in the complex is independent of the spacer used. • The enthalpy–entropy compensation is dependent on the microscopic nature of the binary mixture. • The enthalpy–entropy compensation is dependent on the proportion of the components of the binary mixture. - Abstract: An isothermal titration microcalorimetry (ITC) study on the supramolecular complex formation between carboxylates and ammonium-squaramido based receptors at different ethanol:water proportions is reported. The results obtained show that the formation enthalpy sign of a supramolecular complex in a water–ethanol binary mixture can be influenced by the proportion of the cosolvent. Moreover there is an enthalpy–entropy compensation process in the supramolecular complex formation; in poor water mixtures the process is endothermic, whilst in reach water mixtures the process is exothermic. This behavior is mostly due to the intrinsic nature of the mixture between water and ethanol, and particularly the process of solvation and desolvation of receptor, substrate and complex. When this study is repeated with binary mixtures of water–methanol and water–DMSO it is observed that the nature of the organic solvent affects the results. While the mixture water–methanol has a behavior similar to water–ethanol mixture, the water–DMSO mixture shows clear differences. In order to check this compensation process, △Cp values are calculated at two different proportions water–ethanol, and they are consistent with an enthalpy–entropy compensation process similar to that described by the inclusion process for certain hydrophilic cyclodextrines. The results obtained show that the enthalpy–entropy compensation detected in the supramolecular complex formation between carboxylates and ammonium-squaramido receptors is independent of the spacer used, and more dependent on the microscopic nature and proportion of the binary mixture.

  1. Oxo iron(IV) as an oxidative active intermediate of p-chlorophenol in the Fenton reaction: a DFT study.

    Science.gov (United States)

    Mignon, Pierre; Pera-Titus, Marc; Chermette, Henry

    2012-03-21

    Debate continues over which active species plays the role of oxidative agent during the Fenton reaction-the HO˙ radical or oxo iron [Fe(IV)O](2+). In this context, the present study investigates the oxidation of p-chlorophenol by [Fe(IV)O(H(2)O)(5)](2+) using DFT calculations, within gas-phase and micro-solvated models, in order to explore the possible role of oxo iron as a reactant. The results show that the chlorine atom substitution of p-chlorophenol by oxo iron is a highly stabilising step (ΔH = -83 kcal mol(-1)) with a free energy barrier of 5.8 kcal mol(-1) in the micro-solvated model. This illustrates the high oxidising power of the [Fe(IV)O(H(2)O)(5)](2+) complex. On the other hand, the breaking of the Fe-O bond, leading to the formation of hydroquinone, is observed to be the rate-determining step of the reaction. The rather large free energy barrier corresponding to this bond cleavage amounts to 10.2 and 9.3 kcal mol(-1) in the gas-phase and micro-solvated models, respectively. Elsewhere, the lifetime of the HO˙ radical has previously been shown to be extremely small. These facts, combined with observations of oxo iron under certain experimental conditions, suggest that oxo iron is a highly plausible oxidative species of the reaction. In addition, a trigonal bipyramidal iron complex, coordinated either by hydroxyl groups and/or by water molecules, has been found in all described mechanisms. This structure appears to be a stable intermediate; and to our knowledge, it has not been characterised by previous studies.

  2. Effect of reaction environments on the reactivity of PCB (2-chlorobiphenyl) over activated carbon impregnated with palladized iron

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Hyeok [Department of Civil Engineering, University of Texas at Arlington, 416 Yates Drive, Arlington, TX 76019-0308 (United States); Al-Abed, Souhail R., E-mail: al-abed.souhail@epa.gov [National Risk Management Research Laboratory, U.S. Environmental Protection Agency, 26 West Martin Luther King Drive, Cincinnati, OH 45268 (United States)

    2010-07-15

    Reactive activated carbon (RAC) impregnated with palladized iron nanoparticles has been developed to treat polychlorinated biphenyls (PCBs). In this study, we evaluated the effects of various reaction environments on the adsorption-mediated dechlorination of 2-chlorobiphenyl (2-ClBP) in the RAC system. The results were discussed in close connection to the implementation issue of the RAC system for the remediation of contaminated sites with PCBs. Adsorption event of 2-ClBP onto RAC limited the overall performance under condition with a 2-ClBP/RAC mass ratio of less than 1.0 x 10{sup -4} above which dechlorination of 2-ClBP adsorbed to RAC was the reaction rate-determining step. Acidic and basic conditions were harmful to 2-ClBP adsorption and iron stability while neutral pH showed the highest adsorption-promoted dechlorination of 2-ClBP and negligible metal leaching. Coexisting natural organic matter (NOM) slightly inhibited 2-ClBP adsorption onto RAC due to the partial partitioning of 2-ClBP into NOM in the liquid phase while the 2-ClBP absorbed into NOM, which also tended to adsorb onto RAC, was less available for the dechlorination reaction. Common anions slowed down 2-ClBP adsorption but adsorbed 2-ClBP was almost simultaneously dechlorinated. Some exceptions included strong inhibitory effect of carbonate species on 2-ClBP adsorption and severe detrimental effect of sulfite on 2-ClBP dechlorination. Results on treatment of 2-ClBP spiked to actual sediment supernatants implied site-specific reactivity of RAC.

  3. Synthesis of dual-doped non-precious metal electrocatalysts and their electrocatalytic activity for oxygen reduction reaction

    Institute of Scientific and Technical Information of China (English)

    Li Xu; Guoshun Pan; Xiaolu Liang; Guihai Luo; Chunli Zou; Gaopan Chen

    2014-01-01

    The pyrolyzed carbon supported ferrum polypyrrole (Fe-N/C) catalysts are synthesized with or without selected dopants, p-toluenesulfonic acid (TsOH), by a facile thermal annealing approach at desired temperature for optimizing their activity for the oxygen reduction reaction (ORR) in O2-saturated 0.1 mol/L KOH solution. The electrochemical techniques such as cyclic voltammetry (CV) and rotating disk electrode (RDE) are employed with the Koutecky-Levich theory to quantitatively obtain the ORR kinetic constants and the reaction mechanisms. It is found that catalysts doped with TsOH show significantly improved ORR activity relative to the TsOH-free one. The average electron transfer numbers for the catalyzed ORR are determined to be 3.899 and 3.098, respectively, for the catalysts with and without TsOH-doping. The heat-treatment is found to be a necessary step for catalyst activity improvement, and the catalyst pyrolyzed at 600◦C gives the best ORR activity. An onset potential and the potential at the current density of -1.5 mA/cm2 for TsOH-doped catalyst after pyrolysis are 30 mV and 170 mV, which are more positive than those without pyrolized. Furthermore, the catalyst doped with TsOH shows higher tolerance to methanol compared with commercial Pt/C catalyst in 0.1 mol/L KOH. To understand this TsOH doping and pyrolyzed effect, X-ray diffraction (XRD), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) are used to characterize these catalysts in terms of their structure and composition. XPS results indicate that the pyrrolic-N groups are the most active sites, a finding that is supported by the correspondence between changes in pyridinic-N content and ORR activity that occur with changing temperature. Sulfur species are also structurally bound to carbon in the forms of C-Sn-C, an additional beneficial factor for the ORR.

  4. Structure, activity, and stability of platinum alloys as catalysts for the oxygen reduction reaction

    DEFF Research Database (Denmark)

    Vej-Hansen, Ulrik Grønbjerg

    and dealloying due to kinetic barriers, despite the thermodynamic driving force for dissolution. This is followed by our results on trying to decouple the strain and ligand effects for platinum skin structures, and determining whether there is any correlation between adsorption energy and surface stability...... in these systems. We find that there is such a correlation for some adsorbates, indicating that there exists a limit for the stability of an overlayer for a given adsorption strength. Finally, we introduce our work on platinum alloy nanoparticles, and our attempt to isolate the features which result...... in the increased activity that has been seen experimentally. We show how the platinum-platinum distance at the surface is decreased for a variety of alloy phases in the core, with greater compression of the overlayer for core phases with lattice parameters which are either much smaller or much larger than pure...

  5. Activation of Trifluoromethylthio Moiety by Appending Iodonium Ylide under Copper Catalysis for Electrophilic Trifluoromethylation Reaction

    Institute of Scientific and Technical Information of China (English)

    Ibrayim Saidalimu; Shugo Suzuki; Etsuko Tokunaga; Norio Shibata

    2016-01-01

    A novel iodonium-ylide compound 2 that appends a trifluoromethylthio (SCF3) group is disclosed as a new,shelf-stable electrophilic trifluoromethylation reagent.Unlike known shelf-stable electrophilic trifluoromethylation reagents,2 has a stable SCF3 group which is activated by appending iodonium ylide under copper catalysis via sulfonium ylide to generate a cationic trifluoromethyl (CF3) species.Reagent 2 was found to be an efficient electrophilic trifluoromethylation reagent for a wide range of silyl enol ethers 3 under copper catalysis.Cyclic and acyclic a-trifluoromethyl ketones 4 were obtained by reagent 2 in moderate to good yields.On the other hand,a difluoromethylthio analogue 5 did not affect intermolecular transfer difluoromethylation to substrates.Instead,intramolecular 1,4-migration proceeded similar to the Stevens rearrangement to provide 6 in 21% yield,independent of the presence of nucleophiles 3.

  6. Ethanol oxidation reaction activity of highly dispersed Pt/SnO{sub 2} double nanoparticles on carbon black

    Energy Technology Data Exchange (ETDEWEB)

    Higuchi, Eiji; Miyata, Kazumasa; Takase, Tomonori; Inoue, Hiroshi [Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University, Sakai, Osaka 599-8531 (Japan)

    2011-02-15

    Highly dispersed Pt and SnO{sub 2} double nanoparticles containing different Pt/Sn ratios (denoted as Pt/SnO{sub 2}/CB) were prepared on carbon black (CB) by the modified Boennemann method. The average size of Pt and SnO{sub 2} nanoparticles was 3.1 {+-} 0.5 nm and 2.5 {+-} 0.3 nm, respectively, in Pt/SnO{sub 2}(3:1)/CB, 3.0 {+-} 0.5 nm and 2.6 {+-} 0.3 nm, respectively, in Pt/SnO{sub 2}(1:1)/CB, and 2.8 {+-} 0.5 nm and 2.5 {+-} 0.3 nm, respectively, in Pt/SnO{sub 2}(1:3)/CB. The Pt/SnO{sub 2}(3:1)/CB electrode showed the highest specific activity and lowest overpotential for ethanol oxidation reaction (EOR), and was superior to a Pt/CB electrode. Current density for EOR at 0.40 and 0.60 V vs. reversible hydrogen electrode for the Pt/SnO{sub 2}(3:1)/CB electrode decayed more slowly than that for the Pt/CB electrode because of a synergistic effect between Pt and SnO{sub 2} nanoparticles. The predominant reaction product was acetic acid, and its current efficiency was about 70%, while that for CO{sub 2} production was about 30%. (author)

  7. Establishment of activity indicator of TiO{sub 2} photocatalytic reaction-Hydroxyl radical trapping method

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Chen-Yu, E-mail: cychang@mdu.edu.tw [Department of Life Science, Ming-Dao University, 369 Wen-Hua Road, Peetow, Chang-Hua County 52345, Taiwan (China); Hsieh, Yung-Hsu [Department of Environmental Engineering, National Chung-Hsing University, 250 Kuo-Kuang Road, Taichung, Taiwan (China); Hsieh, Ling-Ling [Department of Radiological Technology, Central Taiwan University of Sciences and Technology, 11 Pu-Tze Lane, Pei-Tun District, Taichung, Taiwan (China); Yao, Kuo-Shan; Cheng, Ta-Chih [Department of Life Science, Ming-Dao University, 369 Wen-Hua Road, Peetow, Chang-Hua County 52345, Taiwan (China)

    2009-07-30

    In this study, a new, low cost and easy method, hydroxyl radical trapping method, was employed to investigate the photo-activity of UV/TiO{sub 2} photocatalytic reaction. The Taguchi method was utilized to optimize the preparation of titanium dioxide (TiO{sub 2}) thin-film reactor through the modified chemical vapor deposition (CVD) method. The optimal yield of hydroxyl radicals was then evaluated by calculating the conversion ratio of salicylic acid under the optimal conditions. In the experiments, salicylic acid was used as the free-radical scavenger and the formation of three different intermediates were examined to shed light on the trend and kinetics of reaction of hydroxyl radical with organic substance under different operation conditions. The results indicated that the yield of hydroxyl radicals increased with increasing irradiation intensity and dissolved oxygen level. The optimal experimental conditions obtained in this study were irradiation with intensity of 2.9 mW cm{sup -2} on salicylic acid at concentration of 250 mg L{sup -1} by both agitation and aeration processes (dissolved oxygen level = 8.2 mg O{sub 2} L{sup -1}) at pH 5. Such conditions could achieve the optimal hydroxyl radical yield of 5.1 x 10{sup -17} M.

  8. Study of 20O via the (d,p) reaction in inverse kinematics employing the active gas target detector ANASEN

    Science.gov (United States)

    Santiago-Gonzalez, D.; Wiedenhöver, I.; Baby, L. T.; Koshchiy, E.; Rogachev, G. V.; Blackmon, J. C.; Linhardt, L. E.

    2013-10-01

    The energetic location of the d3/2-orbital in neutron-rich nuclei is of particular interest as it determines the location of the drip-line in the oxygen isotopes. Its behavior has recently been described as a consequence of three-body forces. Manifestations of such forces are traced through the location of the d3/2 orbital, which closer to stability leads to highly excited states. In order to study the location and fragmentation of this orbital in 20O a beam of the short-lived 19O was produced at the RESOLUT radioactive beam facility of the Florida State University with an intensity of 1 ×105 pps, 65 % purity and 4.11 MeV/u. The chamber of the active gas target detector ANASEN was filled with molecular deuterium gas (D2) which yielded 20O via the 19O (d , p) reaction. The ejected protons were measured with large solid angle coverage and for beam energies between 2.9 and 3.7 MeV/u. Data from the 17O(d , p) 18O reaction was acquired to verify our experimental methods and analysis techniques. We will present the latest advances in the analysis of the 19O(d , p) 20O data and demonstrate the capabilities of ANASEN. Work supported by the National Science Foundation.

  9. Copper(I) complexes with trispyrazolylmethane ligands: synthesis, characterization, and catalytic activity in cross-coupling reactions.

    Science.gov (United States)

    Haldón, Estela; Álvarez, Eleuterio; Nicasio, M Carmen; Pérez, Pedro J

    2012-08-01

    Three novel Cu(I) complexes bearing tris(pyrazolyl)methane ligands, Tpm(x), have been prepared from reactions of equimolar amounts of CuI and the ligands Tpm, (HC(pz)(3)), Tpm*, (HC(3,5-Me(2)-pz)(3)), and Tpm(Ms), (HC(3-Ms-pz)(3)). X-ray diffraction studies have shown that the Tpm and Tpm(Ms) derivatives exhibit a 2:1 Cu:ligand ratio, whereas the Tpm* complex is a mononuclear species in nature. The latter has been employed as a precatalyst in the arylation of amides and aromatic thiols with good activity. The synthesis of a Tpm*Cu(I)-phthalimidate, a feasible intermediate in this catalytic process, has also been performed. Low temperature (1)H NMR studies in CDCl(3) have indicated that this complex exists in solution as a mixture of two, neutral and ionic forms. Conductivity measurements have reinforced this proposal, the ionic form predominating in a very polar solvent such as DMSO. The reaction of Tpm*Cu(I)-phthalimidate with iodobenzene afforded the expected C-N coupling product in 76% yield accounting for its role as an intermediate in this transformation.

  10. Transglutaminase activity changes during the hypersensitive reaction, a typical defense response of tobacco NN plants to TMV.

    Science.gov (United States)

    Del Duca, Stefano; Betti, Lucietta; Trebbi, Grazia; Serafini-Fracassini, Donatella; Torrigiani, Patrizia

    2007-10-01

    The occurrence of glutamyl polyamines (PAs) and changes in activity and levels of transglutaminase (TGase, EC 2.3.2.13), the enzyme responsible for their synthesis, are reported during the progression of the hypersensitive reaction (HR) of resistant NN tobacco plants (Nicotiana tabacum L. cv. Samsun) to tobacco mosaic virus (TMV). Mature leaves of tobacco were collected over 0-72 h after inoculation with TMV or phosphate buffer (mock). In vivo synthesis of polyamine glutamyl derivatives (glutamyl PAs), catalyzed by TGase activity, was evaluated after supplying labeled putrescine (Pu, a physiological substrate of TGase) to leaves. Results show that, starting from 24 h, mono-(gamma-glutamyl)-Pu and bis-(gamma-glutamyl)-Sd were recovered in TMV-inoculated samples but not in mock-inoculated ones; 2 days later, in the former, the amount of glutamyl derivatives further increased. An in vitro radiometric assay showed that, in TMV-inoculated leaves, TGase activity increased from 24 h onwards relative to mock controls. An immunoblot analysis with AtPng1p polyclonal antibody detected a 72-kDa protein whose amount increased at 72 h in TMV-inoculated leaves and in the lesion-enriched areas. A biotin-labeled cadaverine incorporation assay showed that TGase activity occurred in S1 (containing soluble proteins), S2 (proteins released by both cell walls and membranes) and S3 (membrane intrinsic proteins) fractions. In S3 fraction, where changes were the most relevant, TGase activity was enhanced in both mock-inoculated and TMV-inoculated samples, but the stimulation persisted only in the latter case. These data are discussed in the light of a possible role of TGase activity and glutamyl PAs in the defense against a viral plant pathogen.

  11. Study of inclusion complex formation between tropaeolin OO and beta-cyclodextrin by spectrophotometry and Infrared spectroscopy.

    Science.gov (United States)

    Wang, Huai You; Han, Juan; Feng, Xia Guang; Pang, Yan Ling

    2006-09-01

    The mechanism of the inclusion of tropaeolin OO (TPOO) and beta-cyclodextrin (beta-CD) has been studied by spectrophotometry. The inclusion depth of the guest molecule in the host molecule was demonstrated by infrared spectrometry. Effect of the pH, concentrations of beta-CD, solvents and ionic strength on the inclusion of TPOO and beta-CD were examined. The result showed that TPOO reacts with beta-CD to form a 1:1 host-guest complex with an apparent formation constant of 1.50 x 10(3) l mol(-1). The thermodynamic parameters of inclusion reaction, DeltaG degrees , DeltaH degrees and DeltaS degrees were obtained.

  12. Recombinant Escherichia coli GMP reductase: kinetic, catalytic and chemical mechanisms, and thermodynamics of enzyme-ligand binary complex formation.

    Science.gov (United States)

    Martinelli, Leonardo Krás Borges; Ducati, Rodrigo Gay; Rosado, Leonardo Astolfi; Breda, Ardala; Selbach, Bruna Pelegrim; Santos, Diógenes Santiago; Basso, Luiz Augusto

    2011-04-01

    Guanosine monophosphate (GMP) reductase catalyzes the reductive deamination of GMP to inosine monophosphate (IMP). GMP reductase plays an important role in the conversion of nucleoside and nucleotide derivatives of guanine to adenine nucleotides. In addition, as a member of the purine salvage pathway, it also participates in the reutilization of free intracellular bases. Here we present cloning, expression and purification of Escherichia coli guaC-encoded GMP reductase to determine its kinetic mechanism, as well as chemical and thermodynamic features of this reaction. Initial velocity studies and isothermal titration calorimetry demonstrated that GMP reductase follows an ordered bi-bi kinetic mechanism, in which GMP binds first to the enzyme followed by NADPH binding, and NADP(+) dissociates first followed by IMP release. The isothermal titration calorimetry also showed that GMP and IMP binding are thermodynamically favorable processes. The pH-rate profiles showed groups with apparent pK values of 6.6 and 9.6 involved in catalysis, and pK values of 7.1 and 8.6 important to GMP binding, and a pK value of 6.2 important for NADPH binding. Primary deuterium kinetic isotope effects demonstrated that hydride transfer contributes to the rate-limiting step, whereas solvent kinetic isotope effects arise from a single protonic site that plays a modest role in catalysis. Multiple isotope effects suggest that protonation and hydride transfer steps take place in the same transition state, lending support to a concerted mechanism. Pre-steady-state kinetic data suggest that product release does not contribute to the rate-limiting step of the reaction catalyzed by E. coli GMP reductase.

  13. Palladium(II) complexes with tris(2-carboxyethyl)phosphine, structure, reactions and cytostatic activity.

    Science.gov (United States)

    Pruchnik, Hanna; Lis, Tadeusz; Latocha, Małgorzata; Zielińska, Aleksandra; Pruchnik, Florian P

    2016-03-01

    Water soluble and air stable P(RCOOH)3 (R=C2H4) (TCEP) is an efficient reducing agent used in biochemistry to break S-S bond in peptides, proteins and other compounds containing S-S bonds. The similarity between the coordination chemistry of Pd(II) and Pt(II) led to the investigations of antitumor activity of palladium(II) compounds however the Pd(II) complexes with TCEP were not investigated. New palladium(II) complexes with (TCEP): trans-[PdCl2(TCEP)2] (1) and trans-[Pd2(μ-Cl)2Cl2(TCEP)2] (2) were fully characterized by (1)H, (13)C, (31)P NMR, IR and ESI-MS spectroscopic techniques. Complexes are stable in non-aqueous DMSO and DMF. In aqueous solutions Cl ligands are substituted by COO groups of phosphines. Complex 2, after crystallization from water gives polymeric compound with bridging phosphine ligand [PdCl{P(RCOO-κO-μ-O')(RCOOH)2-κP}] (3). Structures of trans-[PdCl2{P(RCOOD)3}2] (1a), trans-[Pd2(μ-Cl)2PdCl2{P(RCOOD)3}2] (2a), and [PdCl{P(RCOO-κO-μ-O')(RCOOD)2-κP}]n (3a) have been determined by X-ray crystallography. NMR and ESI-MS spectra reveal that [PdP2(RCOO-κO)2(RCOO)n(RCOOH)4-n](n)(-) complexes are formed in aqueous solution of 1. Geometry optimization in the gas phase at the B3LYP/3-21G** level indicated that complex 2 with butterfly structure is more stable than that with coplanar coordination. In aqueous solution of 2, the main products [Pd2{P(RCOO-κO-μ-O')(RCOO-κO)(RCOOH)}2] and [Pd{P(RCOO-κO)2(RCOOH)}(H2O)] exist in equilibrium which depends on temperature: content of mononuclear compound increases as the temperature is raised. Complexes 1 and 2 are active agents against melanoma and breast cancer cells.

  14. Constitutively activated barley ROPs modulate epidermal cell size, defense reactions and interactions with fungal leaf pathogens.

    Science.gov (United States)

    Pathuri, Indira Priyadarshini; Zellerhoff, Nina; Schaffrath, Ulrich; Hensel, Götz; Kumlehn, Jochen; Kogel, Karl-Heinz; Eichmann, Ruth; Hückelhoven, Ralph

    2008-12-01

    RHO-like monomeric G-proteins of plants (ROPs, also called RACs), are involved in plant development and interaction with the environment. The barley (Hordeum vulgare) ROP protein HvRACB has been shown to be required for entry of the biotrophic powdery mildew fungus Blumeria graminis f.sp. hordei (Bgh) into living host cells. To get a deeper insight into evolutionarily conserved functions of ROPs in cell polarity and pathogen responses, we stably expressed constitutively activated (CA) mutant variants of different barley ROPs (HvRACB, HvRAC1, HvRAC3) in barley. CA HvROPs induced epidermal cell expansion and/or abolished polarity in tip growing root hairs. All three CA HvROPs enhanced susceptibility of barley to penetration by Bgh whereas only CA HvRAC1 supported whole cell H(2)O(2) production in non-penetrated cells. Despite increasing penetration by Bgh, CA HvRAC1 promoted callose deposition at sites of fungal attack and resistance to penetration by Magnaporthe oryzae. The data show an involvement of ROPs in polar growth processes of the monocot barley and in responses to fungal pathogens with different life style.

  15. Reaction of physiological factors on the solar-geomagnetic activity (the physical mechanisms)

    Science.gov (United States)

    Avakyan, Sergey; Voronin, Nikolai; Dubarenko, Konstantin

    This presentation proposes and provides substantiation for a hypothesis concerning the mechanism by which solar and geomagnetic activity (mainly of solar flares and magnetic storms) affects the biosphere, including man. The hypothesis, including a physical mechanism introduced by the authors, is that high-lying (Rydberg) states of all gases of the earth’s upper atmosphere are excited by ionospheric energetic electrons. Rydberg atoms, molecules and ions of all atmospheric gases emit characteristic radio emission in the spectral range from decimeters to millimeters. This radiation can easily penetrate to low atmosphere and biosphere carrying complete information about power and duration of solar flare and geomagnetic storms to biosphere. The microwave radioemission have the resonances at the spectral range 109 ÷ 1012 Hz at the cells and membranes, DNA and RNA, molecules of haemoglobin, erythrocytes, and this fact can explain the extremely small threshold for influence of ionospheric radioemission at the monochromatic (characteristic) transitions on biological objects, including the viscosity of blood. The energy estimates of the flux intensity of microwave radiation of the ionosphere from Rydberg states are used to prove for the first time that the values of this flux agree with the experimental data. A method is proposed for distinguishing the contributions of microwave radiation and magnetic perturbation in the geo-biocorrelations, taking into account the effect that the magnetic-field variations are not in phase with the flux of corpuscles from the radiation belts in the ionosphere during the period of a geomagnetic storm. Quanta of microwave radiation are emitted from the heights of 90 - 360 km, i.e. in the basic ionosphere regions. Their energy by almost 10 orders of magnitude exceeds that of the quanta of low-frequency electromagnetic background of the ionosphere (with the frequencies lower than 100 Hz, which coincide with those of biorhythms). Thereby

  16. Engineering hybrid between nickel oxide and nickel cobaltate to achieve exceptionally high activity for oxygen reduction reaction

    Science.gov (United States)

    Cui, Zhentao; Wang, Shuguang; Zhang, Yihe; Cao, Minhua

    2014-12-01

    The porous NiO/NiCo2O4 nanotubes are prepared via a coaxial electrospinning technique followed by an annealing treatment. The resultant NiO/NiCo2O4 hybrid is developed as a highly efficient electrocatalyst, which exhibits significantly enhanced electrocatalytic activity, long-term operation stability, and tolerance to crossover effect compared to NiO nanofibers, NiCo2O4 nanofibers and commercial Pt(20%)/C for oxygen reduction reactions (ORR) in alkaline environment. The excellent electrocatalytic performance may be attributed to the unique microstructures of the porous NiO/NiCo2O4 nanotubes, such as heterogeneous hybrid structure, open porous tubular structure, and the well dispersity of the two components. Moreover, the promising and straightforward coaxial electrospinning proves itself to be an efficient pathway for the preparation of nanomaterials with tubular architectures and it can be used for large-scale production of catalysts in fuel cells.

  17. Polyhedral Palladium-Silver Alloy Nanocrystals as Highly Active and Stable Electrocatalysts for the Formic Acid Oxidation Reaction

    Science.gov (United States)

    Fu, Geng-Tao; Liu, Chang; Zhang, Qi; Chen, Yu; Tang, Ya-Wen

    2015-09-01

    Polyhedral noble-metal nanocrystals have received much attention and wide applications as electrical and optical devices as well as catalysts. In this work, a straightforward and effective hydrothermal route for the controllable synthesis of the high-quality Pd-Ag alloy polyhedrons with uniform size is presented. The morphology, composition and structure of the Pd-Ag alloy polyhedrons are fully characterized by the various physical techniques, demonstrating the Pd-Ag alloy polyhedrons are highly alloying. The formation/growth mechanisms of the Pd-Ag alloy polyhedrons are explored and discussed based on the experimental observations and discussions. As a preliminary electrochemical application, the Pd-Ag alloy polyhedrons are applied in the formic acid oxidation reaction, which shows higher electrocatalytic activity and stability than commercially available Pd black due to the “synergistic effects” between Pd and Ag atoms.

  18. Activity and Stability of RuOx Based Electrocatalysts for the Oxygen Evolution Reaction

    DEFF Research Database (Denmark)

    Paoli, Elisa Antares

    . By coupling Electrochemical Quartz Crystal Microbalance (EQCM) measurements with Inductively Coupled Plasma – Mass Spectrometry (ICP-MS) analyses of the electrolyte, we emphasize the importance of monitoring the mass loss. Finally, the thesis focuses on improving the stability of ruthenium dioxide under OER......The focus of this Ph.D. thesis is on the electrocatalytic oxygen evolution reaction (OER) in acidic media for Proton Exchange Membrane (PEM) Electrolyser applications. This technology is an attractive alternative for storage of renewable energy, such as from solar and wind power, in small scale...... and stable OER catalysts. To contain costs and precious metals supply, the mass activity should be maximized. However, in order to define the properties of a catalyst, knowing the distinction between geometric and electronic effects is fundamental. It is not trivial to determine the intrinsic catalytic...

  19. Potential of the polymerase chain reaction in the diagnosis of active Toxoplasma infection by detection of parasite in blood.

    Science.gov (United States)

    Guy, E C; Joynson, D H

    1995-07-01

    Blood samples from 54 patients presenting with acute toxoplasmic lymphadenopathy were tested for the presence of Toxoplasma gondii DNA using a nested polymerase chain reaction (PCR). PCR test results of a single blood sample obtained 2-23 weeks after onset of illness were positive for 19 (35%) of the 54 patients. Nine (53%) of 17 patients were positive by PCR when the initial blood sample was collected within the first 5 weeks of illness. In 7 of the 19 patients found positive, further blood samples were available, and subsequent clearance of T. gondii DNA from the blood was demonstrated. On the basis of positive findings among patients with acute toxoplasmosis and the absence of positive findings among 10 uninfected persons and 43 with past Toxoplasma infection, a positive PCR result appears to be a helpful indicator of active disease. However, since only 53% of patients with lymphadenopathy persisting < or = 5 weeks were positive, a negative PCR result does not exclude recent infection.

  20. Synthesis, characterization and photocatalytic activity of fluorine doped TiO2 nanoflakes synthesized using solid state reaction method.

    Science.gov (United States)

    Umadevi, M; Parimaladevi, R; Sangari, M

    2014-01-01

    Fluorine doped TiO2 were synthesized by solid state reaction method. Optical and structural properties of fluorine doped TiO2 were investigated by X-ray diffraction, Fourier transform infrared spectroscopy, UV-vis diffusion reflectance spectroscopy and scanning electron microscopic techniques. The prepared fluorine doped TiO2 was smaller in size with respect to pure TiO2 and it is tetragonal in crystalline structure. Nanoflakes like structure of pure and fluorine doped TiO2 was confirmed from SEM image. Fluorine doped TiO2 shows smaller band gap, high strain and dislocation density when compared to pure TiO2. It also has higher photocatalytic activity with respect to pure TiO2.