Reaction Kinetics of Hydrogen Atom Abstraction from C4-C6 Alkenes by the Hydrogen Atom and Methyl Radical.

PubMed

Wang, Quan-De; Liu, Zi-Wu

2018-06-14

Alkenes are important ingredients of realistic fuels and are also critical intermediates during the combustion of a series of other fuels including alkanes, cycloalkanes, and biofuels. To provide insights into the combustion behavior of alkenes, detailed quantum chemical studies for crucial reactions are desired. Hydrogen abstractions of alkenes play a very important role in determining the reactivity of fuel molecules. This work is motivated by previous experimental and modeling evidence that current literature rate coefficients for the abstraction reactions of alkenes are still in need of refinement and/or redetermination. In light of this, this work reports a theoretical and kinetic study of hydrogen atom abstraction reactions from C4-C6 alkenes by the hydrogen (H) atom and methyl (CH 3 ) radical. A series of C4-C6 alkene molecules with enough structural diversity are taken into consideration. Geometry and vibrational properties are determined at the B3LYP/6-31G(2df,p) level implemented in the Gaussian-4 (G4) composite method. The G4 level of theory is used to calculate the electronic single point energies for all species to determine the energy barriers. Conventional transition state theory with Eckart tunneling corrections is used to determine the high-pressure-limit rate constants for 47 elementary reaction rate coefficients. To faciliate their applications in kinetic modeling, the obtained rate constants are given in the Arrhenius expression and rate coefficients for typical reaction classes are recommended. The overall rate coefficients for the reaction of H atom and CH 3 radical with all the studied alkenes are also compared. Branching ratios of these reaction channels for certain alkenes have also been analyzed.

Hydrogen assisted growth of high quality epitaxial graphene on the C-face of 4H-SiC

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

Cai, Tuocheng; Jia, Zhenzhao; Yan, Baoming

2015-01-05

We demonstrate hydrogen assisted growth of high quality epitaxial graphene on the C-face of 4H-SiC. Compared with the conventional thermal decomposition technique, the size of the growth domain by this method is substantially increased and the thickness variation is reduced. Based on the morphology of epitaxial graphene, the role of hydrogen is revealed. It is found that hydrogen acts as a carbon etchant. It suppresses the defect formation and nucleation of graphene. It also improves the kinetics of carbon atoms via hydrocarbon species. These effects lead to increase of the domain size and the structure quality. The consequent capping effectmore » results in smooth surface morphology and suppression of multilayer growth. Our method provides a viable route to fine tune the growth kinetics of epitaxial graphene on SiC.« less

Facile Synthesis and Superior Catalytic Activity of Nano-TiN@N-C for Hydrogen Storage in NaAlH4.

PubMed

Zhang, Xin; Ren, Zhuanghe; Lu, Yunhao; Yao, Jianhua; Gao, Mingxia; Liu, Yongfeng; Pan, Hongge

2018-05-09

Herein, we synthesize successfully ultrafine TiN nanoparticles (<3 nm in size) embedded in N-doped carbon nanorods (nano-TiN@N-C) by a facile one-step calcination process. The prepared nano-TiN@N-C exhibits superior catalytic activity for hydrogen storage in NaAlH 4 . Adding 7 wt % nano-TiN@N-C induces more than 100 °C reduction in the onset dehydrogenation temperature of NaAlH 4 . Approximately 4.9 wt % H 2 is rapidly released from the 7 wt % nano-TiN@N-C-containing NaAlH 4 at 140 °C within 60 min, and the dehydrogenation product is completely hydrogenated at 100 °C within 15 min under 100 bar of hydrogen, exhibiting significantly improved desorption/absorption kinetics. No capacity loss is observed for the nano-TiN@N-C-containing sample within 25 de-/hydrogenation cycles because nano-TiN functions as an active catalyst instead of a precursor. A severe structural distortion with extended bond lengths and reduced bond strengths for Al-H bonding when the [AlH 4 ] - group adsorbs on the TiN cluster is demonstrated for the first time by density functional theory calculations, which well-explains the reduced de-/hydrogenation temperatures of the nano-TiN@N-C-containing NaAlH 4 . These findings provide new insights into designing and synthesizing high-performance catalysts for hydrogen storage in complex hydrides.

WxC-β-SiC Nanocomposite Catalysts Used in Aqueous Phase Hydrogenation of Furfural.

PubMed

Rogowski, Jacek; Andrzejczuk, Mariusz; Berlowska, Joanna; Binczarski, Michal; Kregiel, Dorota; Kubiak, Andrzej; Modelska, Magdalena; Szubiakiewicz, Elzbieta; Stanishevsky, Andrei; Tomaszewska, Jolanta; Witonska, Izabela Alina

2017-11-22

This study investigates the effects of the addition of tungsten on the structure, phase composition, textural properties and activities of β-SiC-based catalysts in the aqueous phase hydrogenation of furfural. Carbothermal reduction of SiO₂ in the presence of WO₃ at 1550 °C in argon resulted in the formation of W x C-β-SiC nanocomposite powders with significant variations in particle morphology and content of W x C-tipped β-SiC nano-whiskers, as revealed by TEM and SEM-EDS. The specific surface area (SSA) of the nanocomposite strongly depended on the amount of tungsten and had a notable impact on its catalytic properties for the production of furfuryl alcohol (FA) and tetrahydrofurfuryl alcohol (THFA). Nanocomposite W x C-β-SiC catalysts with 10 wt % W in the starting mixture had the highest SSA and the smallest W x C crystallites. Some 10 wt % W nanocomposite catalysts demonstrated up to 90% yield of THFA, in particular in the reduction of furfural derived from biomass, although the reproducible performance of such catalysts has yet to be achieved.

A polarizable dipole-dipole interaction model for evaluation of the interaction energies for N-H···O=C and C-H···O=C hydrogen-bonded complexes.

PubMed

Li, Shu-Shi; Huang, Cui-Ying; Hao, Jiao-Jiao; Wang, Chang-Sheng

2014-03-05

In this article, a polarizable dipole-dipole interaction model is established to estimate the equilibrium hydrogen bond distances and the interaction energies for hydrogen-bonded complexes containing peptide amides and nucleic acid bases. We regard the chemical bonds N-H, C=O, and C-H as bond dipoles. The magnitude of the bond dipole moment varies according to its environment. We apply this polarizable dipole-dipole interaction model to a series of hydrogen-bonded complexes containing the N-H···O=C and C-H···O=C hydrogen bonds, such as simple amide-amide dimers, base-base dimers, peptide-base dimers, and β-sheet models. We find that a simple two-term function, only containing the permanent dipole-dipole interactions and the van der Waals interactions, can produce the equilibrium hydrogen bond distances compared favorably with those produced by the MP2/6-31G(d) method, whereas the high-quality counterpoise-corrected (CP-corrected) MP2/aug-cc-pVTZ interaction energies for the hydrogen-bonded complexes can be well-reproduced by a four-term function which involves the permanent dipole-dipole interactions, the van der Waals interactions, the polarization contributions, and a corrected term. Based on the calculation results obtained from this polarizable dipole-dipole interaction model, the natures of the hydrogen bonding interactions in these hydrogen-bonded complexes are further discussed. Copyright © 2013 Wiley Periodicals, Inc.

Adsorption and dissociation of molecular hydrogen on orthorhombic β-Mo 2C and cubic δ-MoC (001) surfaces

DOE PAGES

Posada-Pérez, Sergio; Viñes, Francesc; Valero, Rosendo; ...

2016-10-03

Molybdenum carbides are increasingly used in heterogeneously catalyzed hydrogenation reactions, which imply the adsorption and dissociation of molecular hydrogen. In this paper, a systematic density functional theory based study, including or excluding dispersion terms, concerning the interaction and stability of H 2 with cubic δ-MoC(001) and orthorhombic β-Mo 2C(001) surfaces, is presented. In the latter case the two possible C or Mo terminations are considered. In addition, different situations for the H covered surfaces are examined. Computational results including dispersive forces predict an essentially spontaneous dissociation of H 2 on β-Mo 2C(001) independently of the surface termination, whereas on δ-MoC(001)more » molecular hydrogen dissociation implies a small but noticeable energy barrier. Furthermore, the ab initio thermodynamics formalism has been used to compare the stability of different H coverages. In conclusion, core level binding energies and vibrational frequencies are presented with the aim to assist the interpretation of yet unavailable data from X-ray photoelectron and infrared spectroscopies.« less

Ti3C2 MXene co-catalyst on metal sulfide photo-absorbers for enhanced visible-light photocatalytic hydrogen production

NASA Astrophysics Data System (ADS)

Ran, Jingrun; Gao, Guoping; Li, Fa-Tang; Ma, Tian-Yi; Du, Aijun; Qiao, Shi-Zhang

2017-01-01

Scalable and sustainable solar hydrogen production through photocatalytic water splitting requires highly active and stable earth-abundant co-catalysts to replace expensive and rare platinum. Here we employ density functional theory calculations to direct atomic-level exploration, design and fabrication of a MXene material, Ti3C2 nanoparticles, as a highly efficient co-catalyst. Ti3C2 nanoparticles are rationally integrated with cadmium sulfide via a hydrothermal strategy to induce a super high visible-light photocatalytic hydrogen production activity of 14,342 μmol h-1 g-1 and an apparent quantum efficiency of 40.1% at 420 nm. This high performance arises from the favourable Fermi level position, electrical conductivity and hydrogen evolution capacity of Ti3C2 nanoparticles. Furthermore, Ti3C2 nanoparticles also serve as an efficient co-catalyst on ZnS or ZnxCd1-xS. This work demonstrates the potential of earth-abundant MXene family materials to construct numerous high performance and low-cost photocatalysts/photoelectrodes.

DFT STUDY OF HYDROGEN STORAGE ON Li- AND Na-DOPED C59B HETEROFULLERENE

NASA Astrophysics Data System (ADS)

Zahedi, Ehsan; Mozaffari, Majid

2014-05-01

Effect of light alkali metal (Li and Na) decorated on the C59B heterofullerene for hydrogen storage is considered using DFT-MPW1PW91 method. Results show that Li and Na atoms strongly prefer to adsorb on top of five-member and six-member ring where a carbon atom is replaced by a boron atom. Significant charge transfer from the alkali metal to the C59B compensates for the electron deficiency of C59B and makes the latter aromatic in nature. Corrected binding energies of hydrogen molecule on the alkali-doped C59B using counterpoise method, structural properties and NBO analysis indicate that first hydrogen molecule is adsorbed physically and does not support minimal conditions of DOE requirement. Finally, positive values of binding energies for the adsorption of a second hydrogen molecule show that alkali doped C59B are capable of storing a maximum of one hydrogen molecule.

Hydrogenation and Deuteration of C{sub 2}H{sub 2} and C{sub 2}H{sub 4} on Cold Grains: A Clue to the Formation Mechanism of C{sub 2}H{sub 6} with Astronomical Interest

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

Kobayashi, Hitomi; Kawakita, Hideyo; Hidaka, Hiroshi

We quantitatively investigated the hydrogen addition reactions of acetylene (C{sub 2}H{sub 2}) and ethylene (C{sub 2}H{sub 4}) on amorphous solid water (ASW) at 10 and 20 K relevant to the formation of ethane (C{sub 2}H{sub 6}) on interstellar icy grains. We found that the ASW surface enhances the reaction rates for C{sub 2}H{sub 2} and C{sub 2}H{sub 4} by approximately a factor of 2 compared to those on the pure-solid C{sub 2}H{sub 2} and C{sub 2}H{sub 4} at 10 K, probably due to an increase in the sticking coefficient and adsorption energy of the H atoms on ASW. In contrastmore » to the previous proposal that the hydrogenation rate of C{sub 2}H{sub 4} is orders of magnitude larger than that of C{sub 2}H{sub 2}, the present results show that the difference in hydrogenation rates of C{sub 2}H{sub 2} and C{sub 2}H{sub 4} is only within a factor of 3 on both the surfaces of pure solids and ASW. In addition, we found the small kinetic isotope effect for hydrogenation/deuteration of C{sub 2}H{sub 2} and C{sub 2}H{sub 4} at 10 K, despite the requirement of quantum tunneling. At 20 K, the reaction rate of deuteration becomes even larger than that of hydrogenation. These unusual isotope effects might originate from a slightly larger number density of D atoms than H atoms on ASW at 20 K. The hydrogenation of C{sub 2}H{sub 2} is four times faster than CO hydrogenation and can produce C{sub 2}H{sub 6} efficiently through C{sub 2}H{sub 4} even in the environment of a dark molecular cloud.« less

Hierarchical Porous Li2Mg(NH)2@C Nanowires with Long Cycle Life Towards Stable Hydrogen Storage

PubMed Central

Xia, Guanglin; Tan, Yingbin; Li, Dan; Guo, Zaiping; Liu, Huakun; Liu, Zongwen; Yu, Xuebin

2014-01-01

The hierarchical porous Li2Mg(NH)2@C nanowires full of micropores, mesopores, and macropores are successfully fabricated via a single-nozzle electrospinning technique combined with in-situ reaction between the precursors, i.e., MgCl2 and LiN3, under physical restriction upon thermal annealing. The explosive decomposition of LiN3 well dispersed in the electrospun nanowires during carbothermal treatment induces a highly porous structure, which provides a favourable way for H2 delivering in and out of Li2Mg(NH)2 nanoparticles simultaneously realized by the space-confinement of the porous carbon coating. As a result, the thus-fabricated Li2Mg(NH)2@C nanowires present significantly enhanced thermodynamics and kinetics towards hydrogen storage performance, e.g., a complete cycle of H2 uptake and release with a capacity close to the theoretical value at a temperature as low as 105°C. This is, to the best of our knowledge, the lowest cycling temperature reported to date. More interestingly, induced by the nanosize effects and space-confinement function of porous carbon coating, a excellently stable regeneration without apparent degradation after 20 de-/re-hydrogenation cycles at a temperature as low as 130°C was achieved for the as-prepared Li2Mg(NH)2@C nanowires. PMID:25307874

Effects of Molybdenum Addition on Hydrogen Desorption of TiC Precipitation-Hardened Steel

NASA Astrophysics Data System (ADS)

Song, Eun Ju; Baek, Seung-Wook; Nahm, Seung Hoon; Suh, Dong-Woo

2018-05-01

The hydrogen-trap states in TiC and MoC that have coherent interfaces with ferrite were investigated using first-principles calculation. The trapping sites of TiC were the interfaces and interstitial sites of ferrite. On the other hand, the trapping sites of MoC were ferrite interstitial sites; the interface had a negative binding energy with H. Thermal desorption analysis confirms that the amounts of diffusible hydrogen were significantly reduced by addition of Mo in Ti-bearing steel.

Conformation-induced remote meta-C-H activation of amines

NASA Astrophysics Data System (ADS)

Tang, Ri-Yuan; Li, Gang; Yu, Jin-Quan

2014-03-01

Achieving site selectivity in carbon-hydrogen (C-H) functionalization reactions is a long-standing challenge in organic chemistry. The small differences in intrinsic reactivity of C-H bonds in any given organic molecule can lead to the activation of undesired C-H bonds by a non-selective catalyst. One solution to this problem is to distinguish C-H bonds on the basis of their location in the molecule relative to a specific functional group. In this context, the activation of C-H bonds five or six bonds away from a functional group by cyclometallation has been extensively studied. However, the directed activation of C-H bonds that are distal to (more than six bonds away) functional groups has remained challenging, especially when the target C-H bond is geometrically inaccessible to directed metallation owing to the ring strain encountered in cyclometallation. Here we report a recyclable template that directs the olefination and acetoxylation of distal meta-C-H bonds--as far as 11 bonds away--of anilines and benzylic amines. This template is able to direct the meta-selective C-H functionalization of bicyclic heterocycles via a highly strained, tricyclic-cyclophane-like palladated intermediate. X-ray and nuclear magnetic resonance studies reveal that the conformational biases induced by a single fluorine substitution in the template can be enhanced by using a ligand to switch from ortho- to meta-selectivity.

Conformation-induced remote meta-C-H activation of amines.

PubMed

Tang, Ri-Yuan; Li, Gang; Yu, Jin-Quan

2014-03-13

Achieving site selectivity in carbon-hydrogen (C-H) functionalization reactions is a long-standing challenge in organic chemistry. The small differences in intrinsic reactivity of C-H bonds in any given organic molecule can lead to the activation of undesired C-H bonds by a non-selective catalyst. One solution to this problem is to distinguish C-H bonds on the basis of their location in the molecule relative to a specific functional group. In this context, the activation of C-H bonds five or six bonds away from a functional group by cyclometallation has been extensively studied. However, the directed activation of C-H bonds that are distal to (more than six bonds away) functional groups has remained challenging, especially when the target C-H bond is geometrically inaccessible to directed metallation owing to the ring strain encountered in cyclometallation. Here we report a recyclable template that directs the olefination and acetoxylation of distal meta-C-H bonds--as far as 11 bonds away--of anilines and benzylic amines. This template is able to direct the meta-selective C-H functionalization of bicyclic heterocycles via a highly strained, tricyclic-cyclophane-like palladated intermediate. X-ray and nuclear magnetic resonance studies reveal that the conformational biases induced by a single fluorine substitution in the template can be enhanced by using a ligand to switch from ortho- to meta-selectivity.

Tetrahedral silsesquioxane-C2H2Ti complex for hydrogen storage

NASA Astrophysics Data System (ADS)

Konda, Ravinder; Tavhare, Priyanka; Ingale, Nilesh; Chaudhari, Ajay

2018-04-01

The interaction of molecular hydrogen with tetrahedral silsesquioxane (T4)-C2H2Ti complex has been studied using Density Functional Theory with M06-2X functional and MP2 method with 6-311++G** basis set. T4-C2H2Ti complex can absorb maximum five hydrogen molecules with the gravimetric hydrogen storage capacity of 3.4 wt %. Adsorption energy calculations show that H2 adsorption on T4-C2H2Ti complex is favorable at room temperature by both the methods. We have studied the effect of temperature and pressure on Gibbs free energy corrected adsorption energies. Molecular dynamics simulations for H2 adsorbed T4-C2H2Ti complex have also been performed at 300K and show that loosely bonded H2 molecule flies away within 1fs. Various interaction energies within the complex are studied. Stability of a complex is predicted by means of a gap between Highest Occupied Molecular Orbital (HUMO) and Lowest Unoccupied Molecular Orbital (LUMO). The H2 desorption temperature for T4-C2H2Ti complex is calculated with Van't Hoff equation and it is found to be 229K.

Thermally induced evolution of hydrogenated amorphous carbon

NASA Astrophysics Data System (ADS)

Mangolini, Filippo; Rose, Franck; Hilbert, James; Carpick, Robert W.

2013-10-01

The thermally induced structural evolution of hydrogenated amorphous carbon (a-C:H) films was investigated in situ by X-ray photoelectron spectroscopy for annealing temperatures up to 500 °C. A model for the conversion of sp3- to sp2-hybridized carbon in a-C:H vs. temperature and time was developed and applied to determine the ranges of activation energies for the thermally activated processes occurring. The energies are consistent with ordering and clustering of sp2 carbon, scission of sp3 carbon-hydrogen bonds and formation of sp2 carbon, and direct transformation of sp3- to sp2-hybridized carbon.

Chemical grafting of Co9S8 onto C60 for hydrogen spillover and storage.

PubMed

Han, Lu; Qin, Wei; Zhou, Jia; Jian, Jiahuang; Lu, Songtao; Wu, Xiaohong; Fan, Guohua; Gao, Peng; Liu, Boyu

2017-04-20

Metal modified C 60 is considered to be a potential hydrogen storage medium due to its high theoretical capacity. Research interest is growing in various hybrid inorganic compounds-C 60 . While the design and synthesis of a novel hybrid inorganic compound-C 60 is difficult to attain, it has been theorized that the atomic hydrogen could transfer from the inorganic compound to the adjacent C 60 surfaces via spillover and surface diffusion. Here, as a proof of concept experiment, we graft Co 9 S 8 onto C 60 via a facile high energy ball milling process. The Raman, XPS, XRD, TEM, HTEM and EELS measurements have been conducted to evaluate the composition and structure of the pizza-like hybrid material. In addition, the electrochemical measurements and calculated results demonstrate that the chemical "bridges" (C-S bonds) between these two materials enhance the binding strength and, hence, facilitate the hydriding reaction of C 60 during the hydrogen storage process. As a result, an increased hydrogen storage capacity of 4.03 wt% is achieved, along with a favorable cycling stability of ∼80% after 50 cycles. Excluding the direct hydrogen storage contribution from Co 9 S 8 in the hybrid paper, the hydrogen storage ability of C 60 was enhanced by 5.9× through the hydriding reaction caused by the Co 9 S 8 modifier. Based on these experimental measurements and theoretical calculations, the unique chemical structure reported here could potentially inspire other C 60 -based advanced hybrids.

Infrared Spectra of Protonated Quinoline (1-C_9H_7NH^{+}) in Solid Para-Hydrogen

NASA Astrophysics Data System (ADS)

Tseng, Chih-Yu; Lee, Yuan-Pern

2017-06-01

Large protonated polycyclic aromatic hydrocarbons (H^{+}PAH) and polycyclic aromatic nitrogen heterocycles (H^{+}PANH) have been proposed as possible carriers of unidentified infrared (UIR) emission bands from galactic objects. The nitrogen atom in H^{+}PANH is expected to induce a blue shift of the C=C stretching band near 6.2 μm so that their emission bands might agree with the UIR band better than those of H^{+}PAH. In this work, we report the IR spectrum of protonated quinoline and its neutral species measured upon electron bombardment during deposition of a mixture of quinoline and para-hydrogen at 3.2 K. New features were assigned to 1-C_9H_7NH^{+} and 1-C_9H_7NH, indicating that the protonation and hydrogenation occur at the N-atom site. The intensities of features of 1-C_9H_7NH^{+} diminished when the matrix was maintained in darkness for 10 h, whereas those of 1-C_9H_7NH increased. Spectral assignments were made according to comparison of experimental results with anharmonic vibrational wavenumbers and IR intensities calculated with the B3LYP/6-311++G(d,p) method. Although agreement between the observed spectrum of 1-C_9H_7NH^{+} and the UIR emission bands is unsatisfactory, presumably because of the small size of quinoline, we did observe C=C stretching bands at 1641.4, 1598.4, 1562.0 \\wn, blue-shifted from those at 1618.7, 1580.8, 1510.0 \\wn of the corresponding protonated PAH (C_{10}H_{9}^{+}), pointing to the direction of the UIR bands.

Ti3C2 MXene co-catalyst on metal sulfide photo-absorbers for enhanced visible-light photocatalytic hydrogen production

PubMed Central

Ran, Jingrun; Gao, Guoping; Li, Fa-Tang; Ma, Tian-Yi; Du, Aijun; Qiao, Shi-Zhang

2017-01-01

Scalable and sustainable solar hydrogen production through photocatalytic water splitting requires highly active and stable earth-abundant co-catalysts to replace expensive and rare platinum. Here we employ density functional theory calculations to direct atomic-level exploration, design and fabrication of a MXene material, Ti3C2 nanoparticles, as a highly efficient co-catalyst. Ti3C2 nanoparticles are rationally integrated with cadmium sulfide via a hydrothermal strategy to induce a super high visible-light photocatalytic hydrogen production activity of 14,342 μmol h−1 g−1 and an apparent quantum efficiency of 40.1% at 420 nm. This high performance arises from the favourable Fermi level position, electrical conductivity and hydrogen evolution capacity of Ti3C2 nanoparticles. Furthermore, Ti3C2 nanoparticles also serve as an efficient co-catalyst on ZnS or ZnxCd1−xS. This work demonstrates the potential of earth-abundant MXene family materials to construct numerous high performance and low-cost photocatalysts/photoelectrodes. PMID:28045015

AB INITIO calculation of the electromigration wind valence of interstitial hydrogen in f.c.c metals

NASA Astrophysics Data System (ADS)

van Ek, J.; Lodder, A.

1990-02-01

Calculated electromigration wind valences, obtained within a KKR-Green function description, are presented. It is shown that the electromigration wind valence of hydrogen along different migration paths in Cu, Ag and Pd can be calculated including charge transfer effects in the impurity cluster. A nice procedure for retrieving the scalar character of the wind valence in an f.c.c metal introduces an explanation for the isotope effect in the wind valence.

Is light-induced degradation of a-Si:H/c-Si interfaces reversible?

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

El Mhamdi, El Mahdi; Holovsky, Jakub; Demaurex, Bénédicte

2014-06-23

Thin hydrogenated amorphous silicon (a-Si:H) films deposited on crystalline silicon (c-Si) surfaces are sensitive probes for the bulk electronic properties of a-Si:H. Here, we use such samples during repeated low-temperature annealing and visible-light soaking to investigate the long-term stability of a-Si:H films. We observe that during annealing the electronic improvement of the interfaces follows stretched exponentials as long as hydrogen evolution in the films can be detected. Once such evolution is no longer observed, the electronic improvement occurs much faster. Based on these findings, we discuss how the reversibility of light-induced defects depends on (the lack of observable) hydrogen evolution.

Hydrogen molecules inside fullerene C70: quantum dynamics, energetics, maximum occupancy, and comparison with C60.

PubMed

Sebastianelli, Francesco; Xu, Minzhong; Bacić, Zlatko; Lawler, Ronald; Turro, Nicholas J

2010-07-21

Recent synthesis of the endohedral complexes of C(70) and its open-cage derivative with one and two H(2) molecules has opened the path for experimental and theoretical investigations of the unique dynamic, spectroscopic, and other properties of systems with multiple hydrogen molecules confined inside a nanoscale cavity. Here we report a rigorous theoretical study of the dynamics of the coupled translational and rotational motions of H(2) molecules in C(70) and C(60), which are highly quantum mechanical. Diffusion Monte Carlo (DMC) calculations were performed for up to three para-H(2) (p-H(2)) molecules encapsulated in C(70) and for one and two p-H(2) molecules inside C(60). These calculations provide a quantitative description of the ground-state properties, energetics, and the translation-rotation (T-R) zero-point energies (ZPEs) of the nanoconfined p-H(2) molecules and of the spatial distribution of two p-H(2) molecules in the cavity of C(70). The energy of the global minimum on the intermolecular potential energy surface (PES) is negative for one and two H(2) molecules in C(70) but has a high positive value when the third H(2) is added, implying that at most two H(2) molecules can be stabilized inside C(70). By the same criterion, in the case of C(60), only the endohedral complex with one H(2) molecule is energetically stable. Our results are consistent with the fact that recently both (H(2))(n)@C(70) (n = 1, 2) and H(2)@C(60) were prepared, but not (H(2))(3)@C(70) or (H(2))(2)@C(60). The ZPE of the coupled T-R motions, from the DMC calculations, grows rapidly with the number of caged p-H(2) molecules and is a significant fraction of the well depth of the intermolecular PES, 11% in the case of p-H(2)@C(70) and 52% for (p-H(2))(2)@C(70). Consequently, the T-R ZPE represents a major component of the energetics of the encapsulated H(2) molecules. The inclusion of the ZPE nearly doubles the energy by which (p-H(2))(3)@C(70) is destabilized and increases by 66% the

Hydrogen saline prevents selenite-induced cataract in rats

PubMed Central

Yang, Chun-xiao; Ding, Tian-bing

2013-01-01

Purpose The aim of this study was to investigate the potential antioxidative effect and mechanism for the protective effects of hydrogen saline on selenite-induced cataract in rats. Methods Sprague-Dawley rat pups were divided into the following groups: control (Group A), selenite induced (Group B), and selenite plus hydrogen saline treated (Group C). Rat pups in Groups B and C received a single subcutaneous injection of sodium selenite (25 μmol/kg bodyweight) on postnatal day 12. Group C also received an intraperitoneal injection of H2 saline (5 ml/kg bodyweight) daily from postnatal day 8 to postnatal day 17. The development of cataract was assessed weekly by slit-lamp examination for 2 weeks. After sacrifice, extricated lenses were analyzed for activities of superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, and glutathione S-transferase, levels of malondialdehyde, reduced glutathione (GSH), and total sulfhydryl contents. Results The magnitude of lens opacification in Group B was significantly higher than in Group A (p<0.05), while Group C had less opacification than Group B (p<0.05). Compared with Group B, the mean activities of the antioxidant enzymes superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, and glutathione S-transferase, levels of GSH, and total sulfhydryl contents were higher, whereas the level of malondialdehyde was lower following treatment with hydrogen saline(p<0.05). Conclusions This is an initial report showing that hydrogen saline can prevent selenite-induced cataract in rats. It acts via maintaining antioxidant enzymes and GSH, protecting the sulfhydryl group, and inhibiting lipid peroxidation. PMID:23922487

Structural consequences of hydrogen intercalation of epitaxial graphene on SiC(0001)

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

Emery, Jonathan D., E-mail: jdemery@anl.gov, E-mail: bedzyk@northwestern.edu; Johns, James E.; McBriarty, Martin E.

2014-10-20

The intercalation of various atomic species, such as hydrogen, to the interface between epitaxial graphene (EG) and its SiC substrate is known to significantly influence the electronic properties of the graphene overlayers. Here, we use high-resolution X-ray reflectivity to investigate the structural consequences of the hydrogen intercalation process used in the formation of quasi-free-standing (QFS) EG/SiC(0001). We confirm that the interfacial layer is converted to a layer structurally indistinguishable from that of the overlying graphene layers. This newly formed graphene layer becomes decoupled from the SiC substrate and, along with the other graphene layers within the film, is vertically displacedmore » by ∼2.1 Å. The number of total carbon layers is conserved during the process, and we observe no other structural changes such as interlayer intercalation or expansion of the graphene d-spacing. These results clarify the under-determined structure of hydrogen intercalated QFS-EG/SiC(0001) and provide a precise model to inform further fundamental and practical understanding of the system.« less

Catalytic Carbonyl Allylation, Propargylation and Vinylation from the Alcohol or Aldehyde Oxidation Level via C-C Bond Forming Hydrogenation and Transfer Hydrogenation: A Departure from Preformed Organometallic Reagents**

PubMed Central

Bower, John F.; Kim, In Su; Patman, Ryan L.; Krische, Michael J.

2009-01-01

Classical protocols for carbonyl allylation, propargylation and vinylation typically rely upon the use of preformed allyl metal, allenyl metal and vinyl metal reagents, respectively, mandating stoichiometric generation of metallic byproducts. Through transfer hydrogenative C-C coupling, carbonyl addition may be achieved from the aldehyde or alcohol oxidation level in the absence of stoichiometric organometallic reagents or metallic reductants. Here, we review transfer hydrogenative methods for carbonyl addition, which encompass the first cataltyic protocols enabling direct C–H functionalization of alcohols. PMID:19040235

Carbon-Hydrogen (C-H) Bond Activation at PdIV: A Frontier in C-H Functionalization Catalysis.

PubMed

Topczewski, Joseph J; Sanford, Melanie S

2015-01-01

The direct functionalization of carbon-hydrogen (C-H) bonds has emerged as a versatile strategy for the synthesis and derivatization of organic molecules. Among the methods for C-H bond activation, catalytic processes that utilize a Pd II /Pd IV redox cycle are increasingly common. The C-H activation step in most of these catalytic cycles is thought to occur at a Pd II centre. However, a number of recent reports have suggested the feasibility of C-H cleavage occurring at Pd IV complexes. Importantly, these latter processes often result in complementary reactivity and selectivity relative to analogous transformations at Pd II . This Mini Review highlights proposed examples of C-H activation at Pd IV centres. Applications of this transformation in catalysis as well as mechanistic details obtained from stoichiometric model studies are discussed. Furthermore, challenges and future perspectives for the field are reviewed.

[Hydrogen production and enzyme activity of acidophilic strain X-29 at different C/N ratio].

PubMed

Li, Qiu-bo; Xing, De-feng; Ren, Nan-qi; Zhao, Li-hua; Song, Ye-ying

2006-04-01

Some fermentative bacteria can produce hydrogen by utilizing carbohydrate and other kinds of organic compounds as substrates. Hydrogen production was also determined by both the limiting of growth and related enzyme activity in energy metabolism. Carbon and nitrogen are needed for the growth and metabolism of microorganisms. In addition, the carbon/nitrogen (C/N) ratio can influence the material metabolized and the energy produced. In order to improve the hydrogen production efficiency of the bacteria, we analyzed the effect of different C/N ratios on hydrogen production and the related enzyme activities in the acidophilic strain X-29 using batch test. The results indicate that the differences in the metabolism level and enzyme activity are obvious at different C/N ratios. Although the difference in liquid fermentative products produced per unit of biomass is not obvious, hydrogen production is enhanced at a specifically determined ratio. At a C/N ratio of 14 the accumulative hydrogen yield of strain X-29 reaches the maximum, 2210.9 mL/g. At different C/N ratios, the expression of hydrogenase activity vary; the activity of hydrogenase decrease quickly after reaching a maximum along with the fermentation process, but the time of expression is short. The activity of alcohol dehydrogenase (ADH) tend to stabilize after reaching a peak along with the fermentation process, the difference in expression activity is little, and the expression period is long at different C/N ratios. At a C/N ratio of 14 hydrogenase and ADH reach the maximum 2.88 micromol x (min x mg)(-1) and 33.2 micromol x (min x mg)(-1), respectively. It is shown that the C/N ratio has an important effect on enhancing hydrogen production and enzyme activity.

Testing of DLR C/C-SiC and C/C for HIFiRE 8 Scramjet Combustor

NASA Technical Reports Server (NTRS)

Glass, David E.; Capriotti, Diego P.; Reimer, Thomas; Kutemeyer, Marius; Smart, Michael K.

2014-01-01

Ceramic Matrix Composites (CMCs) have been proposed for use as lightweight hot structures in scramjet combustors. Previous studies have calculated significant weight savings by utilizing CMCs (active and passive) versus actively cooled metallic scramjet structures. Both a carbon/carbon (C/C) and a carbon/carbon-silicon carbide (C/C-SiC) material fabricated by DLR (Stuttgart, Germany) are being considered for use in a passively cooled combustor design for Hypersonic International Flight Research Experimentation (HIFiRE) 8, a joint Australia / Air Force Research Laboratory hypersonic flight program, expected to fly at Mach 7 for approximately 30 sec, at a dynamic pressure of 55 kilopascals. Flat panels of the DLR C/C and C/C-SiC materials were installed downstream of a hydrogen-fueled, dual-mode scramjet combustor and tested for several minutes at conditions simulating flight at Mach 5 and Mach 6. Gaseous hydrogen fuel was used to fuel the scramjet combustor. The test panels were instrumented with embedded Type K and Type S thermocouples. Zirconia felt insulation was used during some of the tests to reduce heat loss from the back surface and thus increase the heated surface temperature of the C/C-SiC panel approximately 177 C (350 F). The final C/C-SiC panel was tested for three cycles totaling over 135 sec at Mach 6 enthalpy. Slightly more erosion was observed on the C/C panel than the C/C-SiC panels, but both material systems demonstrated acceptable recession performance for the HIFiRE 8 flight.

A first principles analysis of the hydrogenation of C1C4 aldehydes and ketones over Ru(0001)

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

Sinha, Nishant K.; Neurock, Matthew

The structure and degree of substitution of C₁–C₄ oxygenate molecules can influence their chemisorption and reactivity on metal surfaces. Gradient-corrected periodic density functional theory calculations were carried out to analyze alkyl substituent effects on the hydrogenation of C₁–C₄ aldehydes and ketones to their corresponding alcohols. All of these aldehydes along with acetone were found to adsorb in a di-ση1η2(C,O) mode onto the Ru(0001) surface and result in rehybridization of the C=O bond. Steric hindrance from two alkyl substituents on the carbonyl backbone of methyl ethyl ketone (MEK), however, prevents it from binding di-ση1η2(C,O). It adsorbs instead atop a Ru atommore » in an g1(O) configuration through its oxygen atom. Hydrogenation of both aldehydes and ketones can occur through either a hydroxy or an alkoxy mechanism. The hydroxy route proceeds via the formation of the hydroxyalkyl intermediate R₁R₂C*OH by the addition of hydrogen to the oxygen of the carbonyl, whereas the alkoxy mechanism proceeds by the addition of hydrogen to the carbon end to form the alkoxy intermediate R₂CHO*). DFT calculations indicate that the activation barrier for the initial addition of hydrogen to the carbon to form the C–H bond in the alkoxy mechanism is independent of the substituent groups that are attached to the carbon center as these groups are oriented away from the surface in the transition state and thus have little influence on the activation energies. The activation barriers for the addition of hydrogen to the oxygen of the carbonyl to form the O–H bond in the hydroxy mechanism, however, was found to linearly correlate with the binding energy of the hydroxyalkyl intermediate that forms. This trend can be explained through the Brønsted–Evans–Polanyi relationship and the fact that both the hydroxyalkyl products and carbonyl reactants interact via their carbon centers and are correlated with one another. All of the carbonyls

The effect of hydrogen on B4C coatings fabrication in inductively coupled plasma torch

NASA Astrophysics Data System (ADS)

Guo, Q. J.; Zhao, P.; Li, L.; Zhou, Q. J.; Ni, G. H.; Meng, Y. D.

2018-02-01

Boron carbide (B4C) coatings are prepared by an RF inductively coupled plasma (ICP) torch with different amounts of hydrogen introduced into the sheath gas. The effects of the added hydrogen on the characteristics of the plasma are diagnosed by optical emission spectroscopy and high speed photography. The effects on the melting of B4C particles in the plasma are studied by scanning electron microscopy (SEM). The microstructure of the B4C coatings was determined with SEM imaging and x-ray diffraction analysis. The results show that adding hydrogen to the sheath gas leads to plasma contraction, which results in higher gas temperature of plasma. It also enhances B4C particles spheroidizing and improves the compactness of B4C coatings. Plasma processing does not change the main phase of boron carbide. The obtained results on B4C coatings on Cu substrates allows for improving the B4C coatings fabrication process.

Tribological properties of amorphous hydrogenated (a-C:H) and hydrogen-free tetrahedral (ta-C) diamond-like carbon coatings under jatropha biodegradable lubricating oil at different temperatures

NASA Astrophysics Data System (ADS)

Mobarak, H. M.; Masjuki, H. H.; Mohamad, E. Niza; Kalam, M. A.; Rashedul, H. K.; Rashed, M. M.; Habibullah, M.

2014-10-01

The application of diamond-like carbon (DLC) coatings on automotive components is emerging as a favorable strategy to address the recent challenges in the industry. DLC coatings can effectively lower the coefficient of friction (CoF) and wear rate of engine components, thereby improving their fuel efficiency and durability. The lubrication of ferrous materials can be enhanced by a large amount of unsaturated and polar components of oils. Therefore, the interaction between nonferrous coatings (e.g., DLC) and vegetable oil should be investigated. A ball-on-plate tribotester was used to run the experiments. Stainless steel plates coated with amorphous hydrogenated (a-C:H) DLC and hydrogen-free tetrahedral (ta-C) DLC that slide against 440C stainless steel ball were used to create a ball-on-plate tribotester. The wear track was investigated through scanning electron microscopy. Energy dispersive and X-ray photoelectron spectroscopies were used to analyze the tribofilm inside the wear track. Raman analysis was performed to investigate the structural changes in the coatings. At high temperatures, the CoF in both coatings decreased. The wear rate, however, increased in the a-C:H but decreased in the ta-C DLC-coated plates. The CoF and the wear rate (coated layer and counter surface) were primarily influenced by the graphitization of the coating. Tribochemical films, such as polyphosphate glass, were formed in ta-C and acted as protective layers. Therefore, the wear rate of the ta-C DLC was lower than that of the-C:H DLC.

A new method for investigating infrared spectra of protonated benzene (C6H7+) and cyclohexadienyl radical (c-C6H7) using para-hydrogen.

PubMed

Bahou, Mohammed; Wu, Yu-Jong; Lee, Yuan-Pern

2012-04-21

We use protonated benzene (C(6)H(7)(+)) and cyclohexadienyl radical (c-C(6)H(7)) to demonstrate a new method that has some advantages over other methods currently used. C(6)H(7)(+) and c-C(6)H(7) were produced on electron bombardment of a mixture of benzene (C(6)H(6)) and para-hydrogen during deposition onto a target at 3.2 K. Infrared (IR) absorption lines of C(6)H(7)(+) decreased in intensity when the matrix was irradiated at 365 nm or maintained in the dark for an extended period, whereas those of c-C(6)H(7) increased in intensity. Observed vibrational wavenumbers, relative IR intensities, and deuterium isotopic shifts agree with those predicted theoretically. This method, providing a wide spectral coverage with narrow lines and accurate relative IR intensities, can be applied to larger protonated polyaromatic hydrocarbons and their neutral species which are difficult to study with other methods.

Neutron diffraction reveals hydrogen bonds critical for cGMP-selective activation: Insights for cGMP-dependent protein kinase agonist design

DOE PAGES

Huang, Gilbert Y.; Gerlits, Oksana O.; Blakeley, Matthew P.; ...

2014-10-01

High selectivity of cyclic-nucleotide binding (CNB) domains for cAMP and cGMP are required for segregating signaling pathways; however, the mechanism of selectivity remains unclear. To investigate the mechanism of high selectivity in cGMP-dependent protein kinase (PKG), we determined a room-temperature joint X-ray/neutron (XN) structure of PKG Iβ CNB-B, a domain 200-fold selective for cGMP over cAMP, bound to cGMP (2.2 Å), and a low-temperature X-ray structure of CNB-B with cAMP (1.3 Å). Finally, the XN structure directly describes the hydrogen bonding interactions that modulate high selectivity for cGMP, while the structure with cAMP reveals that all these contacts are disrupted,more » explaining its low affinity for cAMP.« less

Hydrogen bonds determine the signal arrangement in 13C NMR spectra of nicotinate

NASA Astrophysics Data System (ADS)

Gamov, G. A.; Kuranova, N. N.; Pogonin, A. E.; Aleksandriiskii, V. V.; Sharnin, V. A.

2018-02-01

Present work reports on studies of sodium nicotinate solutions in water and aqueous ethanol by means of 1H, 13C, 15N NMR spectroscopy. The H(2) nucleus was observed to be the least shielded among pyridine ring protons whilst C(6) signal placed in the lowest field in relation to the other pyridine carbons. The hydrogen bonds formation between nicotinate and water molecules was shown to be probable reason of signal arrangement in 13C NMR spectra of nicotinate. The heteronitrogen of nicotinate is less prone to the hydrogen bonding with water molecules than that of nicotinamide. The data on the change in the Gibbs energy of the nicotinate transfer and the results of the 13C NMR experiment are compared.

C-H···O Hydrogen Bonding. The Prototypical Methane-Formaldehyde System: A Critical Assessment.

PubMed

Moore, Kevin B; Sadeghian, Keyarash; Sherrill, C David; Ochsenfeld, Christian; Schaefer, Henry F

2017-11-14

Distinguishing the functionality of C-H···O hydrogen bonds (HBs) remains challenging, because their properties are difficult to quantify reliably. Herein, we present a study of the model methane-formaldehyde complex (MFC). Six stationary points on the MFC potential energy surface (PES) were obtained at the CCSD(T)/ANO2 level. The CCSDT(Q)/CBS interaction energies of the conformers range from only -1.12 kcal mol -1 to -0.33 kcal mol -1 , denoting a very flat PES. Notably, only the lowest energy stationary point (MFC1) corresponds to a genuine minimum, whereas all other stationary points-including the previously studied ideal case of a e (C-H···O) = 180°-exhibit some degree of freedom that leads to MFC1. Despite the flat PES, we clearly see that the HB properties of MFC1 align with those of the prototypical water dimer O-H···O HB. Each HB property generally becomes less prominent in the higher-energy conformers. Only the MFC1 conformer prominently exhibits (1) elongated C-H donor bonds, (2) attractive C-H···O═C interactions, (3) n(O) → σ*(C-H) hyperconjugation, (4) critical points in the electron density from Bader's method and from the noncovalent interactions method, (5) positively charged donor hydrogen, and (6) downfield NMR chemical shifts and nonzero 2 J(C M -H M ···O F ) coupling constants. Based on this research, some issues merit further study. The flat PES hinders reliable determinations of the HB-induced shifts of the C-H stretches; a similarly difficult challenge is observed for the experiment. The role of charge transfer in HBs remains an intriguing open question, although our BLW and NBO computations suggest that it is relevant to the C-H···O HB geometries. These issues notwithstanding, the prominence of the HB properties in MFC1 serves as clear evidence that the MFC is predominantly bound by a C-H···O HB.

Hydrogen-enhanced-plasticity mediated decohesion for hydrogen-induced intergranular and ``quasi-cleavage'' fracture of lath martensitic steels

NASA Astrophysics Data System (ADS)

Nagao, Akihide; Dadfarnia, Mohsen; Somerday, Brian P.; Sofronis, Petros; Ritchie, Robert O.

2018-03-01

Hydrogen embrittlement of lath martenistic steels is characterized by intergranular and "quasi-cleavage" transgranular fracture. Recent transmission electron microscopy (TEM) analyses (Nagao et al., 2012a, 2014a, 2014b, 2014c) of samples lifted from beneath fracture surfaces through focused ion beam machining (FIB) revealed a failure mechanism that can be termed hydrogen-enhanced-plasticity mediated decohesion. Fracture occurs by the synergistic action of the hydrogen-enhanced localized plasticity and decohesion. In particular, intergranular cracking takes place by dislocation pile-ups impinging on prior austenite grain boundaries and "quasi-cleavage" is the case when dislocation pile-ups impinge on block boundaries. These high-angle boundaries, which have already weakened by the presence of hydrogen, debond by the pile-up stresses. The micromechanical model of Novak et al. (2010) is used to quantitatively describe and predict the hydrogen-induced failure of these steels. The model predictions verify that introduction of nanosized (Ti,Mo)C precipitates in the steel microstructure enhances the resistance to hydrogen embrittlement. The results are used to discuss microstructural designs that are less susceptible to hydrogen-induced failure in systems with fixed hydrogen content (closed systems).

Hydrogen trapping under the effect of W-C mixed layers

NASA Astrophysics Data System (ADS)

Liu, N.; Huang, J.; Sato, K.; Xu, Q.; Shi, L. Q.; Wang, Y. X.

2014-03-01

The retention of hydrogen (H) isotope in plasma-facing materials (PFMs) is an important issue for next step fusion device. We used density functional theory (DFT) to study the chemical bonds of H in tungsten-carbon (W-C) mixed layers of tungsten surface, aiming to explore the retention behaviour of H in PFMs. The solubility of C in W was first calculated for revealing the phase components in W-C mixed layers. It was found that C has low solubility in W, which prefers to be segregated on the W surface. Vacancies can enhance the solution of C in W. This makes C appear somewhat carbide feature. Thus, W-C mixed layers should contain multiple phase components. H retention strongly depends on the phase components in the W-C mixed layers. The solution of C will suppress the retention of H in W no matter whether neighbouring vacancies are present, or not. Hydrocarbon precursors, which were observed in desorption experiments, prefer to form by means of H binding to C atoms in C amorphous, or in precipitators in the W-C mixed layers, while not in tungsten carbide phase or in W bulk. Our investigation reasonably explains the experimental results.

SiC Sensors in Extreme Environments: Real-time Hydrogen Monitoring for Energy Plant Applications

NASA Astrophysics Data System (ADS)

Ghosh, Ruby

2008-03-01

Clean, efficient energy production, such as the gasification of coal (syngas), requires physical and chemical sensors for exhaust gas monitoring as well as real-time control of the combustion process. Wide-bandgap semiconducting materials systems can meet the sensing demands in these extreme environments consisting of chemically corrosive gases at high temperature and pressure. We have developed a SiC based micro-sensor for detection of hydrogen containing species with millisecond response at 600 C. The sensor is a Pt-SiO2-SiC device with a dense Pt catalytic sensing film, capable of withstanding months of continuous high temperature operation. The device was characterized in robust sensing module that is compatible with an industrial reactor. We report on the performance of the SiC sensor in a simulated syngas ambient at 370 C containing the common interferants CO2, CH4 and CO [1]. In addition we demonstrate that hours of exposure to >=1000 ppm H2S and 15% water vapor does not degrade the sensor performance. To elucidate the mechanisms responsible for the hydrogen response of the sensor we have modeled the hydrogen adsorptions kinetics at the internal Pt-SiO2 interface, using both the Tempkin and Langmuir isotherms. Under the conditions appropriate for energy plant applications, the response of our sensor is significantly larger than that obtained from ultra-high vacuum electrochemical sensor measurements at high temperatures. We will discuss the role of morphology, at the nano to micro scale, on the enhanced catalytic activity observed for our Pt sensing films in response to a heated hydrogen gas stream at atmospheric pressure. [1] R. Loloee, B. Chorpening, S. Beers & R. Ghosh, Hydrogen monitoring for power plant applications using SiC sensors, Sens. Actuators B:Chem. (2007), doi:10.1016/j.snb.2007.07.118

Adsorption, hydrogenation and dehydrogenation of C2H on a CoCu bimetallic layer

NASA Astrophysics Data System (ADS)

Wu, Donghai; Yuan, Jinyun; Yang, Baocheng; Chen, Houyang

2018-05-01

In this paper, adsorption, hydrogenation and dehydrogenation of C2H on a single atomic layer of bimetallic CoCu were investigated using first-principles calculations. The CoCu bimetallic layer is formed by Cu replacement of partial Co atoms on the top layer of a Co(111) surface. Our adsorption and reaction results showed those sites, which have stronger adsorption energy of C2H, possess higher reactivity. The bimetallic layer possesses higher reactivity than either of the pure monometallic layer. A mechanism of higher reactivity of the bimetallic layer is proposed and identified, i.e. in the bimetallic catalyst, the catalytic performance of one component is promoted by the second component, and in our work, the catalytic performance of Co atoms in the bimetallic layer are improved by introducing Cu atoms, lowing the activation barrier of the reaction of C2H. The bimetallic layer could tune adsorption and reaction of C2H by modulating the ratio of Co and Cu. Results of adsorption energies and adsorption configurations reveal that C2H prefers to be adsorbed in parallel on both the pure Co metallic and CoCu bimetallic layers, and Co atoms in subsurface which support the metallic or bimetallic layer have little effect on C2H adsorption. For hydrogenation reactions, the products greatly depend on the concentration and initial positions of hydrogen atoms, and the C2H hydrogenation forming acetylene is more favorable than forming vinylidene in both thermodynamics and kinetics. This study would provide fundamental guidance for hydrocarbon reactions on Co-based and/or Cu-based bimetallic surface chemistry and for development of new bimetallic catalysts.

Elimination of C-6-hydrogen during the formation of ecdysteroids from cholesterol in Locusta migratoria ovaries

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

Fujimoto, Y.; Hiramoto, M.; Kakinuma, K.

1989-03-01

Being administered to Locusta migratoria adult females, (6-{sup 3}H, 4-{sup 14}C)cholesterol was incorporated into ecdysone and 2-deoxyecdysone. The ratio of {sup 3}H/{sup 14}C of the two ecdysteroids isolated from newly laid eggs revealed that C-6-hydrogen of cholesterol was eliminated during the conversion to ecdysteroids in the ovaries of the insects. Thus, a hypothetical mechanism involving migration of the C-6-hydrogen to the C-5 position in the formation of A/B cis junction turned out to be less likely.

Vitamin C-linker-conjugated tripeptide AHK stimulates BMP-2-induced osteogenic differentiation of mouse myoblast C2C12 cells.

PubMed

Jung, Jung-Il; Park, Kyeong-Yong; Lee, Yura; Park, Mira; Kim, Jiyeon

Vitamin C-linker-conjugated Ala-His-Lys tripeptide (Vit C-AHK) is a derivative of Vitamin C-conjugated tripeptides, which were originally developed as a component of a product for collagen synthesis enhancement or human dermal fibroblast growth. Here, we investigated the effect of Vit C-AHK on bone morphogenetic protein (BMP)-2-induced osteoblast differentiation in a cell culture model. Vit C-AHK enhanced proliferation of C2C12 cells and induction of BMP-2-induced alkaline phosphatase, a typical marker of osteoblast differentiation. Vit C-AHK also stimulated the phosphorylation and translocation of Smad1/5/8 to the nucleus and phosphorylation of mitogen-activated protein kinases (MAPKs) including ERK1/2 and p38. In addition, Vit C-AHK enhanced the BMP-2-induced mRNA expression of osteoblast differentiation-related genes such as ALP, BMP-2, Osteocalcin, and Runx2. Our results suggest that Vit C-AHK exerts an enhancing effect on osteoblast proliferation and differentiation through activation of Smad1/5/8 and MAPK ERK1/2 and p38 signaling and without significant cytotoxicity. These results provide important data for the development of peptide-based bone-regenerative agents and treatment of bone-related disorders. Copyright © 2018 International Society of Differentiation. Published by Elsevier B.V. All rights reserved.

Magnetic Fe@g-C3N4: A Photoactive Catalyst for the Hydrogenation of Alkenes and Alkynes

EPA Science Inventory

A photoactive catalyst, Fe@g-C3N4, has been developed for the hydrogenation of alkenes and alkynes using hydrazine hydrate as a source of hydrogen. The magnetically separable Fe@g-C3N4 eliminates the use of high pressure hydrogenation and the reaction can be accomplished using vi...

Effects of vitamin C, vitamin E, and molecular hydrogen on the placental function in trophoblast cells.

PubMed

Guan, Zhong; Li, Huai-Fang; Guo, Li-Li; Yang, Xiang

2015-08-01

This study aimed to investigate the effects of three different antioxidants, namely vitamin C, vitamin E, and molecular hydrogen, on cytotrophoblasts in vitro. Two trophoblast cell lines, JAR and JEG-3, were exposed to different concentrations of vitamin C (0, 25, 50, 100, 500, 1,000, 5,000 μmol/L), vitamin E (0, 25, 50, 100, 500, 1,000, 5,000 μmol/L), and molecular hydrogen (0, 25, 50, 100, 500 μmol/L) for 48 h. The cell viability was detected using the MTS assay. The secretion of human chorionic gonadotropin (hCG) and the tumor necrosis factor-α (TNF-α) were assessed and the expression of TNF-α mRNA was observed by real-time RT-PCR. Cell viability was significantly suppressed by 500 μmol/L vitamins C and E (P < 0.05), but not by 500 μmol/L molecular hydrogen (P > 0.05). The expression of TNF-α was increased by 100 μmol/L vitamin C and 50 μmol/L vitamins E, separately or combined (P < 0.05), but not by molecular hydrogen (0-500 μmol/L), as validated by real-time RT-PCR. But the secretion of hCG was both inhibited by 50-500 μmol/L molecular hydrogen and high levels of vitamin C and E, separately or combined. High levels of antioxidant vitamins C and E may have significant detrimental effects on placental function, as reflected by decreased cell viability and secretion of hCG; and placental immunity, as reflected by increased production of TNF-a. Meanwhile hydrogen showed no such effects on cell proliferation and TNF-α expression, but it could affect the level of hCG, indicating hydrogen as a potential candidate of antioxidant in the management of preeclampsia (PE) should be further studied.

The H{sub 60}Si{sub 6}C{sub 54} heterofullerene as high-capacity hydrogen storage medium

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

Yong, Yongliang, E-mail: ylyong@haust.edu.cn; Department of Physics, Zhejiang University, Hangzhou 310027; Zhou, Qingxiao

2016-07-15

With the great success in Si atoms doped C{sub 60} fullerene and the well-established methods for synthesis of hydrogenated carbon fullerenes, this leads naturally to wonder whether Si-doped fullerenes are possible for special applications such as hydrogen storage. Here by using first-principles calculations, we design a novel high-capacity hydrogen storage material, H{sub 60}Si{sub 6}C{sub 54} heterofullerene, and confirm its geometric stability. It is found that the H{sub 60}Si{sub 6}C{sub 54} heterofullerene has a large HOMO-LUMO gap and a high symmetry, indicating it is high chemically stable. Further, our finite temperature simulations indicate that the H{sub 60}Si{sub 6}C{sub 54} heterofullerene ismore » thermally stable at 300 K. H{sub 2} molecules would enter into the cage from the Si-hexagon ring because of lower energy barrier. Through our calculation, a maximum of 21 H{sub 2} molecules can be stored inside the H{sub 60}Si{sub 6}C{sub 54} cage in molecular form, leading to a gravimetric density of 11.11 wt% for 21H{sub 2}@H{sub 60}Si{sub 6}C{sub 54} system, which suggests that the hydrogenated Si{sub 6}C{sub 54} heterofullerene could be suitable as a high-capacity hydrogen storage material.« less

The effect of the hydrogen fluoride chain on the aromaticity of C6H6 in the C6H6...(HF)1-4 complexes

NASA Astrophysics Data System (ADS)

Jouypazadeh, Hamidreza; Farrokhpour, Hossein; Solimannejad, Mohammad

2018-02-01

The effect of the hydrogen fluoride chain ((HF)n) on the aromaticity and π character of C-C bonds of C6H6 in the C6H6...(HF)n (n = 1-4) complexes were investigated using density functional theory employing RM05 functional. It was found that the binding energy between C6H6 and different (HF)n chains showed a maximum at n = 3 (C6H6...(HF)3). Also, the π-hydrogen interaction (πHI) and the bifurcated fluorine interaction (BFI) increased and decreased the π character of the C-C bond of C6H6, respectively. In addition, the change of aromaticity of the C6H6 due to the interaction with the HF chains was also studied using three different aspects such as aromatic fluctuation index (FLU), average two centre index (ATI) and proton nuclear magnetic resonance (HNMR) spectrum. The most change in the aromaticity happens when the C6H6 interacts with (HF)3 chain. The variation of aromaticity with the binding energy and the summation of two-body terms were investigated and very good linear correlations were observed.

Selective C70 encapsulation by a robust octameric nanospheroid held together by 48 cooperative hydrogen bonds

PubMed Central

Markiewicz, Grzegorz; Jenczak, Anna; Kołodziejski, Michał; Holstein, Julian J.; Stefankiewicz, Artur R

2017-01-01

Self-assembly of multiple building blocks via hydrogen bonds into well-defined nanoconstructs with selective binding function remains one of the foremost challenges in supramolecular chemistry. Here, we report the discovery of a enantiopure nanocapsule that is formed through the self-assembly of eight amino acid functionalised molecules in nonpolar solvents through 48 hydrogen bonds. The nanocapsule is remarkably robust, being stable at low and high temperatures, and in the presence of base, presumably due to the co-operative geometry of the hydrogen bonding motif. Thanks to small pore sizes, large internal cavity and sufficient dynamicity, the nanocapsule is able to recognize and encapsulate large aromatic guests such as fullerenes C60 and C70. The structural and electronic complementary between the host and C70 leads to its preferential and selective binding from a mixture of C60 and C70. PMID:28488697

Magnetic Fe@g??C3N4: A Photoactive Catalyst for the Hydrogenation of Alkenes and Alkynes

EPA Pesticide Factsheets

A photoactive catalyst, Fe@g-C3N4, has been developed for the hydrogenation of alkenes and alkynes using hydrazine hydrate as a source of hydrogen. The magnetically separable Fe@g-C3N4 eliminates the use of high pressure hydrogenation, and the reaction can be accomplished using visible light without the need for external sources of energy.This dataset is associated with the following publication:Baig, N., S. Verma, R. Varma , and M. Nadagouda. Magnetic Fe@g-C3N4: A Photoactive Catalyst for the Hydrogenation of Alkenes and Alkynes. ACS Sustainable Chemistry & Engineering. American Chemical Society, Washington, DC, USA, 4(3): 1661-1664, (2016).

Late-Transition-Metal-Modified β-Mo 2C Catalysts for Enhanced Hydrogenation during Guaiacol Deoxygenation

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

Baddour, Frederick G.; Witte, Vanessa A.; Nash, Connor P.

Molybdenum carbide has been identified as a promising bifunctional catalyst in the deoxygenation of a variety of pyrolysis vapor model compounds. Although high deoxygenation activity has been demonstrated, complementary hydrogenation activity has been limited, especially for lignin-derived, aromatic model compounds. The ability to control the relative site densities of acidic and hydrogenation functionalities represents a catalyst design challenge for these materials with the goal to improve hydrogenation activity under ex situ catalytic fast pyrolysis (CFP) conditions. Here in this paper, we demonstrate that the addition of Pt and Ni to Mo 2C resulted in an increase in the H*-site densitymore » with only a minor decrease in the acid-site density. In contrast, the addition of Pd did not significantly alter the H* or acid site densities. High conversions (>94%) and high selectivities to 0-oxygen products (>80%) were observed in guaiacol deoxygenation under ex situ CFP conditions (350 °C and 0.44 MPa H 2) for all catalysts. Pt addition resulted in the greatest deoxygenation, and site-time yields to hydrogenated products over the Pt/Mo 2C catalyst were increased to 0.048 s -1 compared to 0.015-0.019 s -1 for all other catalysts. The Pt/Mo 2C catalyst demonstrated the highest hydrogenation performance, but modification with Ni also significantly enhanced hydrogenation performance, representing a promising lower-cost alternative.« less

Late-Transition-Metal-Modified β-Mo 2C Catalysts for Enhanced Hydrogenation during Guaiacol Deoxygenation

DOE PAGES

Baddour, Frederick G.; Witte, Vanessa A.; Nash, Connor P.; ...

2017-10-26

Molybdenum carbide has been identified as a promising bifunctional catalyst in the deoxygenation of a variety of pyrolysis vapor model compounds. Although high deoxygenation activity has been demonstrated, complementary hydrogenation activity has been limited, especially for lignin-derived, aromatic model compounds. The ability to control the relative site densities of acidic and hydrogenation functionalities represents a catalyst design challenge for these materials with the goal to improve hydrogenation activity under ex situ catalytic fast pyrolysis (CFP) conditions. Here in this paper, we demonstrate that the addition of Pt and Ni to Mo 2C resulted in an increase in the H*-site densitymore » with only a minor decrease in the acid-site density. In contrast, the addition of Pd did not significantly alter the H* or acid site densities. High conversions (>94%) and high selectivities to 0-oxygen products (>80%) were observed in guaiacol deoxygenation under ex situ CFP conditions (350 °C and 0.44 MPa H 2) for all catalysts. Pt addition resulted in the greatest deoxygenation, and site-time yields to hydrogenated products over the Pt/Mo 2C catalyst were increased to 0.048 s -1 compared to 0.015-0.019 s -1 for all other catalysts. The Pt/Mo 2C catalyst demonstrated the highest hydrogenation performance, but modification with Ni also significantly enhanced hydrogenation performance, representing a promising lower-cost alternative.« less

Kelvin probe force microscopy studies of the charge effects upon adsorption of carbon nanotubes and C60 fullerenes on hydrogen-terminated diamond

NASA Astrophysics Data System (ADS)

Kölsch, S.; Fritz, F.; Fenner, M. A.; Kurch, S.; Wöhrl, N.; Mayne, A. J.; Dujardin, G.; Meyer, C.

2018-01-01

Hydrogen-terminated diamond is known for its unusually high surface conductivity that is ascribed to its negative electron affinity. In the presence of acceptor molecules, electrons are expected to transfer from the surface to the acceptor, resulting in p-type surface conductivity. Here, we present Kelvin probe force microscopy (KPFM) measurements on carbon nanotubes and C60 adsorbed onto a hydrogen-terminated diamond(001) surface. A clear reduction in the Kelvin signal is observed at the position of the carbon nanotubes and C60 molecules as compared with the bare, air-exposed surface. This result can be explained by the high positive electron affinity of carbon nanotubes and C60, resulting in electron transfer from the surface to the adsorbates. When an oxygen-terminated diamond(001) is used instead, no reduction in the Kelvin signal is obtained. While the presence of a charged adsorbate or a difference in work function could induce a change in the KPFM signal, a charge transfer effect of the hydrogen-terminated diamond surface, by the adsorption of the carbon nanotubes and the C60 fullerenes, is consistent with previous theoretical studies.

Protective effects of dietary selenium and vitamin C in barium-induced cardiotoxicity.

PubMed

Elwej, Awatef; Ghorbel, Imen; Chaabane, Mariem; Soudani, Nejla; Marrekchi, Rim; Jamoussi, Kamel; Mnif, Hela; Boudawara, Tahia; Zeghal, Najiba; Sefi, Mediha

2017-11-01

Several metals including barium (Ba) known as environmental pollutants provoke deleterious effects on human health. The present work pertains to the potential ability of selenium (Se) and/or vitamin C, used as nutritional supplements, to alleviate the toxic effects induced by barium chloride (BaCl 2 ) in the heart of adult rats. Animals were randomly divided into seven groups of six each: group 1, serving as negative controls, received distilled water; group 2 received in their drinking water BaCl 2 (67 ppm); group 3 received both Ba and Se (sodium selenite 0.5 mg kg -1 of diet); group 4 received both Ba and vitamin C (200 mg kg -1 bodyweight) via force feeding; group 5 received Ba, Se, and vitamin C; and groups 6 and 7, serving as positive controls, received either Se or vitamin C for 21 days. The exposure of rats to BaCl 2 caused cardiotoxicity as monitored by an increase in malondialdehyde, hydrogen peroxide, and advanced oxidation protein product levels, a decrease in Na + -K + adenosine triphosphatase (ATPase), Mg 2+ ATPase, and acetylcholinesterase activities and in antioxidant defense system (catalase, glutathione peroxidase, superoxide dismutase, glutathione, and nonprotein thiols). Plasma lactate dehydrogenase and creatine kinase activities, total cholesterol, triglyceride, and low-density lipoprotein-cholesterol levels increased, while high-density lipoprotein-cholesterol level decreased. Coadministration of Se and/or vitamin C restored the parameters indicated above to near control values. The histopathological findings confirmed the biochemical results. Se and vitamin C may be a promising therapeutic strategy for Ba-induced heart injury.

Ni-C-N Nanosheets as Catalyst for Hydrogen Evolution Reaction.

PubMed

Yin, Jie; Fan, Qiaohui; Li, Yuxuan; Cheng, Fangyi; Zhou, Panpan; Xi, Pinxian; Sun, Shouheng

2016-11-09

We report a facile nitrogenation/exfoliation process to prepare hybrid Ni-C-N nanosheets. These nanosheets are <2 nm thin, chemically stable, and metallically conductive. They serve as a robust catalyst for the hydrogen evolution reaction in 0.5 M H 2 SO 4 , or 1.0 M KOH or 1.0 M PBS (pH = 7). For example, they catalyze the hydrogen evolution reaction in 0.5 M H 2 SO 4 at an onset potential of 34.7 mV, an overpotential of 60.9 mV (at j = 10 mA cm -2 ) and with remarkable long-term stability (∼10% current drop after 70 h testing period). They are promising as a non-Pt catalyst for practical hydrogen evolution reaction.

Molecular hydrogen protects human lymphocyte AHH-1 cells against 12C6+ heavy ion radiation.

PubMed

Yang, Yanyong; Gao, Fu; Zhang, Hong; Hunag, Yijuan; Zhang, Pei; Liu, Cong; Li, Bailong; Cai, Jianming

2013-12-01

To investigate the potential protective role of molecular hydrogen (H(2)) against (12)C(6+) heavy ion radiation, which is a major hazard for space travel and has been also widely used in heavy ion radiotherapy. H(2) was dissolved in Roswell Park Memorial Institute (RPMI) 1640 medium under high pressure (0.4 Mpa) to a saturated level by using an apparatus produced by our department. A 2-[6-(4'-hydroxy) phenoxy-3H-xanthen-3-on-9-yl] benzoate (HPF) probe and a 2',7'-Dichlorodihydrofluorescein diacetate (H2DCFH-DA) fluorescent dye were used to measure the intracellular reactive oxygen species (ROS) level. Cell apoptosis were determined by double-staining with Annexin V-fluorescein isothiocyanate (Annexin V-FITC) and propidium iodide (PI) as well as a Hoechst 33342 staining method alternatively. Subsequently, cell cycle analysis was performed using a PI staining method and the expression of apoptotic protein was examined by Western blot. In this study, we demonstrated H(2) reduced ROS level in Human lymphocyte AHH-1 cells as well as in the radiolysis of water. Our data also showed H(2) attenuated (12)C(6+) radiation- induced cell apoptosis and also alleviated radiation-induced G2/M cell cycle arrest. Heavy ion radiation-induced Caspase 3 activation was also inhibited by H(2) treatment. In conclusion, these data showed that H(2) attenuated (12)C(6+) radiation-induced cell apoptosis through reducing the ROS level and modulating apoptotic molecules, thus indicating the potential of H(2) as a safe and effective radioprotectant.

Amide-Directed Photoredox Catalyzed C-C Bond Formation at Unactivated sp3 C-H Bonds

PubMed Central

Chu, John C. K.; Rovis, Tomislav

2017-01-01

Carbon-carbon (C-C) bond formation is paramount in the synthesis of biologically relevant molecules, modern synthetic materials and commodity chemicals such as fuels and lubricants. Traditionally, the presence of a functional group is required at the site of C-C bond formation. Strategies that allow C-C bond formation at inert carbon-hydrogen (C-H) bonds allow scientists to access molecules which would otherwise be inaccessible and to develop more efficient syntheses of complex molecules.1,2 Herein we report a method for the formation of C-C bonds by directed cleavage of traditionally non-reactive C-H bonds and their subsequent coupling with readily available alkenes. Our methodology allows for the selective C-C bond formation at single C-H bonds in molecules that contain a multitude of seemingly indifferentiable such bonds. Selectivity arises through a relayed photoredox catalyzed oxidation of an N-H bond. We anticipate our findings to serve as a starting point for functionalization at inert C-H bonds through a hydrogen atom transfer strategy. PMID:27732580

Liquid-Phase Catalytic Transfer Hydrogenation of Furfural over Homogeneous Lewis Acid-Ru/C Catalysts.

PubMed

Panagiotopoulou, Paraskevi; Martin, Nickolas; Vlachos, Dionisios G

2015-06-22

The catalytic performance of homogeneous Lewis acid catalysts and their interaction with Ru/C catalyst are studied in the catalytic transfer hydrogenation of furfural by using 2-propanol as a solvent and hydrogen donor. We find that Lewis acid catalysts hydrogenate the furfural to furfuryl alcohol, which is then etherified with 2-propanol. The catalytic activity is correlated with an empirical scale of Lewis acid strength and exhibits a volcano behavior. Lanthanides are the most active, with DyCl3 giving complete furfural conversion and a 97 % yield of furfuryl alcohol at 180 °C after 3 h. The combination of Lewis acid and Ru/C catalysts results in synergy for the stronger Lewis acid catalysts, with a significant increase in the furfural conversion and methyl furan yield. Optimum results are obtained by using Ru/C combined with VCl3 , AlCl3 , SnCl4 , YbCl3 , and RuCl3 . Our results indicate that the combination of Lewis acid/metal catalysts is a general strategy for performing tandem reactions in the upgrade of furans. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Long-term treatment of hydrogen-rich saline abates testicular oxidative stress induced by nicotine in mice.

PubMed

Li, Shu; Lu, DanDan; Zhang, Yaling; Zhang, Yi

2014-01-01

The present study was designed to test the hypothesis that long-term treatment with hydrogen-rich saline abated testicular oxidative stress induced by nicotine in mice. The effects of hydrogen-rich saline (6 ml/kg, i.p.), vitamin C (60 mg/kg, i.p.) and vitamin E (100 mg/kg, i.p.) on reproductive system and testicular oxidative levels in nicotine-treated (4.5 mg/kg, s.b.) mice were investigated. It was found that vitamin C and vitamin E attenuated serum oxidative level, but did not lower testicular oxidative levels in mice subjected to chronic nicotine treatment, and did not improve the male reproductive damage and apoptosis induced by nicotine. Different from normal antioxidants, vitamin C and vitamin E, hydrogen-rich saline abated oxidative stress in testis, and protected against nicotine-induced male reproductive damages. Our results first demonstrated that long-term treatment with hydrogen-rich saline attenuated testicular oxidative level and improved male reproductive function in nicotine-treated mice.

Mechanically induced c-fos expression is mediated by cAMP in MC3T3-E1 osteoblasts

NASA Technical Reports Server (NTRS)

Fitzgerald, J.; Hughes-Fulford, M.

1999-01-01

In serum-deprived MC3T3-E1 osteoblasts, mechanical stimulation caused by mild (287 x g) centrifugation induced a 10-fold increase in mRNA levels of the proto-oncogene, c-fos. Induction of c-fos was abolished by the cAMP-dependent protein kinase inhibitor H-89, suggesting that the transient c-fos mRNA increase is mediated by cAMP. Down-regulation of protein kinase C (PKC) activity by chronic TPA treatment failed to significantly reduce c-fos induction, suggesting that TPA-sensitive isoforms of PKC are not responsible for c-fos up-regulation. In addition, 287 x g centrifugation increased intracellular prostaglandin E2 (PGE2) levels 2.8-fold (P<0. 005). Since we have previously shown that prostaglandin E2 (PGE2) can induce c-fos expression via a cAMP-mediated mechanism, we asked whether the increase in c-fos mRNA was due to centrifugation-induced PGE2 release. Pretreatment with the cyclooxygenase inhibitors indomethacin and flurbiprofen did not hinder the early induction of c-fos by mechanical stimulation. We conclude that c-fos expression induced by mild mechanical loading is dependent primarily on cAMP, not PKC, and initial induction of c-fos is not necessarily dependent on the action of newly synthesized PGE2.

Enhanced Hydrogen Storage Properties and Reversibility of LiBH4 Confined in Two-Dimensional Ti3C2.

PubMed

Zang, Lei; Sun, Weiyi; Liu, Song; Huang, Yike; Yuan, Huatang; Tao, Zhanliang; Wang, Yijing

2018-05-30

LiBH 4 is of particular interest as one of the most promising materials for solid-state hydrogen storage. Herein, LiBH 4 is confined into a novel two-dimensional layered Ti 3 C 2 MXene through a facile impregnation method for the first time to improve its hydrogen storage performance. The initial desorption temperature of LiBH 4 is significantly reduced, and the de-/rehydrogenation kinetics are remarkably enhanced. It is found that the initial desorption temperature of LiBH 4 @2Ti 3 C 2 hybrid decreases to 172.6 °C and releases 9.6 wt % hydrogen at 380 °C within 1 h, whereas pristine LiBH 4 only releases 3.2 wt % hydrogen under identical conditions. More importantly, the dehydrogenated products can partially rehydrogenate at 300 °C and under 95 bar H 2 . The nanoconfined effect caused by unique layered structure of Ti 3 C 2 can hinder the particles growth and agglomeration of LiBH 4 . Meanwhile, Ti 3 C 2 could possess superior effect to destabilize LiBH 4 . The synergetic effect of destabilization and nanoconfinement contributes to the remarkably lowered desorption temperature and improved de-/rehydrogenation kinetics.

Macroporous Inverse Opal-like MoxC with Incorporated Mo Vacancies for Significantly Enhanced Hydrogen Evolution.

PubMed

Li, Feng; Zhao, Xianglong; Mahmood, Javeed; Okyay, Mahmut Sait; Jung, Sun-Min; Ahmad, Ishfaq; Kim, Seok-Jin; Han, Gao-Feng; Park, Noejung; Baek, Jong-Beom

2017-07-25

The hydrogen evolution reaction (HER) is one of the most important pathways for producing pure and clean hydrogen. Although platinum (Pt) is the most efficient HER electrocatalyst, its practical application is significantly hindered by high-cost and scarcity. In this work, an Mo x C with incorporated Mo vacancies and macroporous inverse opal-like (IOL) structure (Mo x C-IOL) was synthesized and studied as a low-cost efficient HER electrocatalyst. The macroporous IOL structure was controllably fabricated using a facile-hard template strategy. As a result of the combined benefits of the Mo vacancies and structural advantages, including appropriate hydrogen binding energy, large exposed surface, robust IOL structure and fast mass/charge transport, the synthesized Mo x C-IOL exhibited significantly enhanced HER electrocatalytic performance with good stability, with performance comparable or superior to Pt wire in both acidic and alkaline solutions.

Sargassum horneri methanol extract rescues C2C12 murine skeletal muscle cells from oxidative stress-induced cytotoxicity through Nrf2-mediated upregulation of heme oxygenase-1.

PubMed

Kang, Ji Sook; Choi, Il-Whan; Han, Min Ho; Hong, Su Hyun; Kim, Sung Ok; Kim, Gi-Young; Hwang, Hye Jin; Kim, Byung Woo; Choi, Byung Tae; Kim, Cheol Min; Choi, Yung Hyun

2015-02-05

Sargassum horneri, an edible marine brown alga, is typically distributed along the coastal seas of Korea and Japan. Although several studies have demonstrated the anti-oxidative activity of this alga, the regulatory mechanisms have not yet been defined. The aim of the present study was to examine the cytoprotective effects of S. horneri against oxidative stress-induced cell damage in C2C12 myoblasts. We demonstrated the anti-oxidative effects of a methanol extract of S. horneri (SHME) in a hydrogen peroxide (H2O2)-stimulated C2C12 myoblast model. Cytotoxicity was determined using the 3-(4,5-dimetylthiazol-2-yl)-2,5-diphenyl-tetrazolium assay and mode of cell death by cell cycle analysis. DNA damage was measured using a comet assay and expression of phospho-histone γH2A.X (p-γH2A.X). Levels of cellular oxidative stress as reactive oxygen species (ROS) accumulation were measured using 2',7'-dichlorofluorescein diacetate. The involvement of selected genes in the oxidative stress-mediated signaling pathway was explored using Western blot analysis. SHME attenuated H2O2-induced growth inhibition and exhibited scavenging activity against intracellular ROS that were induced by H2O2. The SHME also inhibited comet tail formation, p-γH2A.X expression, and the number of sub-G1 hypodiploid cells, suggesting that it prevents H2O2-induced cellular DNA damage and apoptotic cell death. Furthermore, the SHME significantly enhanced the expression of heme oxygenase-1 (HO-1) associated with induction of nuclear factor-erythroid 2 related factor 2 (Nrf2) in a time- and concentration-dependent manner. Moreover, the protective effect of the SHME on H2O2-induced C2C12 cell damage was significantly abolished by zinc protoporphyrin IX, a HO-1 competitive inhibitor, in C2C12 cells. These findings suggest that the SHME augments cellular antioxidant defense capacity through both intrinsic free radical scavenging activity and activation of the Nrf2/HO-1 pathway, protecting C2C12 cells from H2

Hydrogen storage property of alkali and alkaline-earth metal atoms decorated C24 fullerene: A DFT study

NASA Astrophysics Data System (ADS)

Zhang, Yafei; Cheng, Xinlu

2018-04-01

The hydrogen storage behavior of alkali and alkaline-earth metal (AM = Li, Na, K, Mg, Ca) atoms decorated C24 fullerene was investigated by using density functional theory (DFT) study. Our results indicate that the AM atoms prefer to adsorb atop the center of tetragon of C24 fullerene with the largest binding energy than other possible adsorption sites. Moreover, the hydrogen storage gravimetric density of 24H2/6Li/C24, 24H2/6Na/C24 and 36H2/6Ca/C24 configurations reaches up to 12.7 wt%, 10.1 wt% and 12 wt%, higher than the year 2020 target from the US department of energy (DOE). Also, the average adsorption energies of H2 molecules of the 24H2/6Li/C24, 24H2/6Na/C24 and 36H2/6Ca/C24 configurations are -0.198 eV/H2, -0.164 eV/H2 and -0.138 eV/H2, locate the desirable range under the physical adsorption at near ambient conditions. These findings will have important implications on designing new hydrogen storage materials in the future.

The role of grain boundaries in hydrogen diffusion in metals at 25 C

NASA Technical Reports Server (NTRS)

Danford, M. D.

1993-01-01

The effect of grain size on hydrogen diffusion at 25 C was examined for 4340 steel (body-centered cubic) and for Inconel 718 (face-centered cubic). It was found that the effect of grain size is important for body-centered cubic structures, but plays a much less important role in face centered cubic structures. Accurate measurements of hydrogen desorption coefficients during hydrogen desorption show that these are not greatly different for both types of structures.

Hydrogen peroxide-induced apoptosis in human gingival fibroblasts

PubMed Central

Gutiérrez-Venegas, Gloria; Guadarrama-Solís, Adriana; Muñoz-Seca, Carmen; Arreguín-Cano, Juan Antonio

2015-01-01

In the process of bleaching vital, discolored teeth, low concentrations of hydrogen peroxide (H2O2) are effective alternatives to heat-activated 30% H2O2. However, interest has been expressed in the assessment of pathological effects of long-term exposure to bleaching agents such as irritation and ulceration of the gingival or other soft tissues. The aim of the present study was to determine the effect of hydrogen peroxide on apoptosis in human gingival fibroblasts (HGF). Cytochrome c, Bcl-2, Bax, Bid and caspase-3 protein expression were detected by Western blotting. HGF cell apoptosis induced by H2O2 was both dose and time dependent. The addition of H2O2 resulted in the release of cytochrome c to the cytosol, and an increase of Caspase-3 cleavage. Data suggest that oxidative stress-induced apoptosis in HGF is intrinsic pathway involved the release of apoptotic signal from mitochondria. PMID:26884825

Quasi free-standing epitaxial graphene fabrication on 3C-SiC/Si(111)

NASA Astrophysics Data System (ADS)

Amjadipour, Mojtaba; Tadich, Anton; Boeckl, John J.; Lipton-Duffin, Josh; MacLeod, Jennifer; Iacopi, Francesca; Motta, Nunzio

2018-04-01

Growing graphene on SiC thin films on Si is a cheaper alternative to the growth on bulk SiC, and for this reason it has been recently intensively investigated. Here we study the effect of hydrogen intercalation on epitaxial graphene obtained by high temperature annealing on 3C-SiC/Si(111) in ultra-high vacuum. By using a combination of core-level photoelectron spectroscopy, low energy electron diffraction, and near-edge x-ray absorption fine structure (NEXAFS) we find that hydrogen saturates the Si atoms at the topmost layer of the substrate, leading to free-standing graphene on 3C-SiC/Si(111). The intercalated hydrogen fully desorbs after heating the sample at 850 °C and the buffer layer appears again, similar to what has been reported for bulk SiC. However, the NEXAFS analysis sheds new light on the effect of hydrogen intercalation, showing an improvement of graphene’s flatness after annealing in atomic H at 600 °C. These results provide new insight into free-standing graphene fabrication on SiC/Si thin films.

Reversible depression in the T{sub c} of thin Nb films due to enhanced hydrogen adsorption

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

Jisrawi, N.M.; Ruckman, M.W.; Thurston, T.R.

The effect of large hydrogen concentrations ({approx}30{percent} atomic), on the superconducting transition temperature T{sub c} of Nb films is discussed. The hydrogen is incorporated in solutionlike phases which occur at these concentrations because the ({alpha} to {beta}) hydride transition in these films is suppressed. X-ray-diffraction data show an asymmetric expansion of the [110] Nb interplanar spacing. This can be as high as a 6{endash}8thinsp{percent} expansion perpendicular to the plane of the film for the addition of {approximately}70{percent} hydrogen, with only a 1{endash}2thinsp{percent} change in the plane of the film. T{sub c} is depressed to a value near 50{percent} of thatmore » of the undoped film with about 30{percent} atomic hydrogen, and returns to its initial value when the hydrogen is removed. A discussion is given of how both disorder and changes in the electronic structure can affect T{sub c}. {copyright} {ital 1998} {ital The American Physical Society}« less

Highly Efficient visible-light-induced photoactivity of magnetically retrievable Fe3O4@SiO2@Bi2WO6@g-C3N4 hierarchical microspheres for the degradation of organic pollutant and production of hydrogen

NASA Astrophysics Data System (ADS)

Lu, Dingze; Wang, Hongmei; Shen, Qingqing; Kondamareddy, Kiran Kumar; Neena D

2017-07-01

The new multifunctional composite Fe3O4@SiO2@Bi2WO6@g-C3N4 (FSBG) hierarchical microspheres with Bi2WO6/g-C3N4 heterostructure as an outer shell and Fe3O4@SiO2 as a magnetic core have been synthesized and characterized for photocatalytic applications. An efficient and adoptable approach of synthesizing magnetic Bi2WO6/g-C3N4 hierarchical microspheres of grape-like morphology is realized. The as-synthesized structures exhibit highly efficient visible-light absorption and separation efficiency of photo-induced charge. The visible-light-induced photocatalytic activity of g-C3N4, Fe3O4@SiO2@Bi2WO6, and FSBG is evaluated by investigating the photodegradation of Rhodamine B (RhB) and hydrogen (H2) out of water. The comparative study reveals that the FSBG microspheres exhibit an optimum visible-light-induced photocatalytic activity in degrading Rhodamin B (RhB), which is 3.06 and 1.92 times to that of g-C3N4 and Fe3O4@SiO2@Bi2WO6 systems respectively and 3.89 and 2.31 times in the production of hydrogen (H2) out of water, respectively. The FSBG composite microspheres also exhibit good magnetic recoverability. An alternate mechanism for the enhanced visible-light photocatalytic activity is given in the present manuscript.

IGF-1 prevents simvastatin-induced myotoxicity in C2C12 myotubes.

PubMed

Bonifacio, Annalisa; Sanvee, Gerda M; Brecht, Karin; Kratschmar, Denise V; Odermatt, Alex; Bouitbir, Jamal; Krähenbühl, Stephan

2017-05-01

Statins are generally well tolerated, but treatment with these drugs may be associated with myopathy. The mechanisms of statin-associated myopathy are not completely understood. Statins inhibit AKT phosphorylation by an unclear mechanism, whereas insulin-like growth factor (IGF-1) activates the IGF-1/AKT signaling pathway and promotes muscle growth. The aims of the study were to investigate mechanisms of impaired AKT phosphorylation by simvastatin and to assess effects of IGF-1 on simvastatin-induced myotoxicity in C2C12 myotubes. C2C12 mouse myotubes were exposed to 10 μM simvastatin and/or 10 ng/mL IGF-1 for 18 h. Simvastatin inhibited the IGF-1/AKT signaling pathway, resulting in increased breakdown of myofibrillar proteins, impaired protein synthesis and increased apoptosis. Simvastatin inhibited AKT S473 phosphorylation, indicating reduced activity of mTORC2. In addition, simvastatin impaired stimulation of AKT T308 phosphorylation by IGF-1, indicating reduced activation of the IGF-1R/PI3K pathway by IGF-1. Nevertheless, simvastatin-induced myotoxicity could be at least partially prevented by IGF-1. The protective effects of IGF-1 were mediated by activation of the IGF-1R/AKT signaling cascade. Treatment with IGF-1 also suppressed muscle atrophy markers, restored protein synthesis and inhibited apoptosis. These results were confirmed by normalization of myotube morphology and protein content of C2C12 cells exposed to simvastatin and treated with IGF-1. In conclusion, impaired activity of AKT can be explained by reduced function of mTORC2 and of the IGF-1R/PI3K pathway. IGF-1 can prevent simvastatin-associated cytotoxicity and metabolic effects on C2C12 cells. The study gives insight into mechanisms of simvastatin-associated myotoxicity and provides potential targets for therapeutic intervention.

Hydrogen Permeation in Cold-Rolled High-Mn Twinning-Induced Plasticity Steels

NASA Astrophysics Data System (ADS)

Han, Do Kyeong; Hwang, A. In; Byeon, Woo Jun; Noh, Seung Jeong; Suh, Dong-Woo

2017-11-01

Hydrogen permeation is investigated in cold-rolled Fe-0.6C-18Mn-(1.5Al) alloys. The hydrogen mobility is lower in cold-rolled alloys compared with annealed alloys. Al-containing alloy shows less deceleration of hydrogen mobility compared with the Al-free alloy. This is attributed to the reduced formation of mechanical twins and dislocations. Mechanical twins trap hydrogen strongly but are vulnerable to crack initiation; suppression of these is thought to be a major favorable influence of Al on hydrogen-induced mechanical degradation.

Low Activation Joining of SiC/SiC Composites for Fusion Applications: Modeling Thermal and Irradiation-induced Swelling Effects on Integrity of Ti3SiC2/SiC Joint

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

Nguyen, Ba Nghiep; Henager, Charles H.; Kurtz, Richard J.

This work developed a continuum damage mechanics model that incorporates thermal expansion combined with irradiation-induced swelling effects to study the origin of cracking observed in recent irradiation experiments. Micromechanical modeling using an Eshelby-Mori-Tanaka approach was used to compute the thermoelastic properties of the Ti3SiC2/SiC joint needed for the model. In addition, a microstructural dual-phase Ti3SiC2/SiC model was developed to determine irradiation-induced swelling of the composite joint at a given temperature resulting from differential swelling of SiC and the Ti3SiC2 MAX phase. Three cases for the miniature torsion hourglass (THG) specimens containing a Ti3SiC2/SiC joint were analyzed corresponding to three irradiationmore » temperatures: 800oC, 500oC, and 400oC.« less

Cardiac c-Kit Biology Revealed by Inducible Transgenesis.

PubMed

Gude, Natalie A; Firouzi, Fareheh; Broughton, Kathleen M; Ilves, Kelli; Nguyen, Kristine P; Payne, Christina R; Sacchi, Veronica; Monsanto, Megan M; Casillas, Alexandria R; Khalafalla, Farid G; Wang, Bingyan J; Ebeid, David E; Alvarez, Roberto; Dembitsky, Walter P; Bailey, Barbara A; van Berlo, Jop; Sussman, Mark A

2018-06-22

Biological significance of c-Kit as a cardiac stem cell marker and role(s) of c-Kit+ cells in myocardial development or response to pathological injury remain unresolved because of varied and discrepant findings. Alternative experimental models are required to contextualize and reconcile discordant published observations of cardiac c-Kit myocardial biology and provide meaningful insights regarding clinical relevance of c-Kit signaling for translational cell therapy. The main objectives of this study are as follows: demonstrating c-Kit myocardial biology through combined studies of both human and murine cardiac cells; advancing understanding of c-Kit myocardial biology through creation and characterization of a novel, inducible transgenic c-Kit reporter mouse model that overcomes limitations inherent to knock-in reporter models; and providing perspective to reconcile disparate viewpoints on c-Kit biology in the myocardium. In vitro studies confirm a critical role for c-Kit signaling in both cardiomyocytes and cardiac stem cells. Activation of c-Kit receptor promotes cell survival and proliferation in stem cells and cardiomyocytes of either human or murine origin. For creation of the mouse model, the cloned mouse c-Kit promoter drives Histone2B-EGFP (enhanced green fluorescent protein; H2BEGFP) expression in a doxycycline-inducible transgenic reporter line. The combination of c-Kit transgenesis coupled to H2BEGFP readout provides sensitive, specific, inducible, and persistent tracking of c-Kit promoter activation. Tagging efficiency for EGFP+/c-Kit+ cells is similar between our transgenic versus a c-Kit knock-in mouse line, but frequency of c-Kit+ cells in cardiac tissue from the knock-in model is 55% lower than that from our transgenic line. The c-Kit transgenic reporter model reveals intimate association of c-Kit expression with adult myocardial biology. Both cardiac stem cells and a subpopulation of cardiomyocytes express c-Kit in uninjured adult heart

L-Theanine Protects H9C2 Cells from Hydrogen Peroxide-Induced Apoptosis by Enhancing Antioxidant Capability.

PubMed

Li, Chengjian; Yan, Qiongxian; Tang, Shaoxun; Xiao, Wenjun; Tan, Zhiliang

2018-04-09

BACKGROUND L-theanine is a non-protein amino acid in green tea, and its hepatoprotection and neuroprotection have been verified. However, whether L-theanine can prevent cardiomyocytes from apoptosis is unclear yet. This study evaluated the protective effects of L-theanine on H2O2-induced heart injury in vitro. MATERIAL AND METHODS The certified H9C2 cells were pretreated with L-theanine (0 mM, 4 mM, 8 mM, and 16 mM) for 24 h, followed by 160 µM H2O2 solution for 4 h. The cell viability and antioxidant indices were assayed. Quantitative evaluation of apoptosis was performed by flow cytometric analysis. Nuclear morphology of the cells was monitored by 4',6-diamidino-2-phenylindole staining. Expression of Caspase-3, poly ADP-ribose polymerase (PARP), c-Jun N-terminal kinase (JNK), and mitogen-activated protein kinase p38 was assayed by Western blot. RESULTS Compared to the H2O2 treatment, all doses of L-theanine treatments increased the cell viability, glutathione level, and the activities of glutathione peroxidase and superoxide dismutase (P<0.001). The contents of reactive oxygen species, nitric oxide, and oxidized glutathione were decreased by L-theanine treatments (P<0.001). Meanwhile, L-theanine treatments decreased the apoptosis ratio of H2O2-induced H9C2 cells (P<0.001). Pro-Caspase-3 expression was upregulated and cleavaged-PARP expression was inhibited by L-theanine (P<0.001). However, the phosphorylation of JNK and p38 was not affected by L-theanine treatments (P>0.05). CONCLUSIONS These data indicate that L-theanine pretreatment prevents H2O2-induced apoptosis in H9C2 cells, probably via antioxidant capacity improvement. Therefore, it might be a promising potential drug candidate for prophylaxis of ischemia/reperfusion-induced heart diseases.

Growth of boron doped hydrogenated nanocrystalline cubic silicon carbide (3C-SiC) films by Hot Wire-CVD

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

Pawbake, Amit; Tata Institute of Fundamental Research, Colaba, Mumbai 400 005; Mayabadi, Azam

Highlights: • Boron doped nc-3C-SiC films prepared by HW-CVD using SiH{sub 4}/CH{sub 4}/B{sub 2}H{sub 6}. • 3C-Si-C films have preferred orientation in (1 1 1) direction. • Introduction of boron into SiC matrix retard the crystallanity in the film structure. • Film large number of SiC nanocrystallites embedded in the a-Si matrix. • Band gap values, E{sub Tauc} and E{sub 04} (E{sub 04} > E{sub Tauc}) decreases with increase in B{sub 2}H{sub 6} flow rate. - Abstract: Boron doped nanocrystalline cubic silicon carbide (3C-SiC) films have been prepared by HW-CVD using silane (SiH{sub 4})/methane (CH{sub 4})/diborane (B{sub 2}H{sub 6}) gasmore » mixture. The influence of boron doping on structural, optical, morphological and electrical properties have been investigated. The formation of 3C-SiC films have been confirmed by low angle XRD, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Fourier transform infra-red (FTIR) spectroscopy and high resolution-transmission electron microscopy (HR-TEM) analysis whereas effective boron doping in nc-3C-SiC have been confirmed by conductivity, charge carrier activation energy, and Hall measurements. Raman spectroscopy and HR-TEM analysis revealed that introduction of boron into the SiC matrix retards the crystallanity in the film structure. The field emission scanning electron microscopy (FE-SEM) and non contact atomic force microscopy (NC-AFM) results signify that 3C-SiC film contain well resolved, large number of silicon carbide (SiC) nanocrystallites embedded in the a-Si matrix having rms surface roughness ∼1.64 nm. Hydrogen content in doped films are found smaller than that of un-doped films. Optical band gap values, E{sub Tauc} and E{sub 04} decreases with increase in B{sub 2}H{sub 6} flow rate.« less

Deciphering cGMP signatures and cGMP-dependent pathways in plant defence

PubMed Central

Meier, Stuart; Madeo, Laura; Ederli, Luisa; Donaldson, Lara; Gehring, Chris

2009-01-01

The second messenger, 3′,5′-cyclic monophosphate (cGMP), is a critical component of many different processes in plants while guanylyl cyclases that catalyse the formation of cGMP from GTP have remained somewhat elusive in higher plants. Consequently, two major aims are the discovery of novel GCs and the identification of cGMP mediated processes. Recently, we have reported temporal signatures of ozone (O3)-induced hydrogen peroxide (H2O2) and nitric oxide (NO) generation, their effect on cGMP generation, and consequent transcriptional changes of genes diagnostic for stress responses in tobacco. We demonstrated that O3 and NO induced early transcriptional activation of the scavenger encoding proteins, alternative oxidase (AOX1a), glutathione peroxidase (GPX) and the induction of ethylene production through aminocyclopropancarboxylic acid synthase (ACS2) are cGMP-independent. By contrast, the early response of the phenylalanine ammonia lyase gene (PALa) and the late response of the gene encoding the pathogenesis-related protein (PR1a) show critical dependence on cGMP. Here we show differential cGMP responses to virulent and avirulent Pseudomonas syringae strains and propose that host-pathogen recognition and/or down-stream processes are transduced by complex cGMP signatures. This is in accordance with the identification of a growing number of multi-domain molecules in Arabidopsis that are reported to contain putative functional GC catalytic centers. PMID:19794847

ENVIRONMENTAL TECHNOLOGY VERIFICATION REPORT: BIOQUELL, INC. CLARIS C HYDROGEN PEROXIDE GAS GENERATOR

EPA Science Inventory

The Environmental Technology Verification report discusses the technology and performance of the Clarus C Hydrogen Peroxide Gas Generator, a biological decontamination device manufactured by BIOQUELL, Inc. The unit was tested by evaluating its ability to decontaminate seven types...

A single Watson-Crick G x C base pair in water: aqueous hydrogen bonds in hydrophobic cavities.

PubMed

Sawada, Tomohisa; Fujita, Makoto

2010-05-26

Hydrogen bond (H-bond) formation in water has been a challenging task because water molecules are constant competitors. In biological systems, however, stable H-bonds are formed by shielding the H-bonding sites from the competing water molecules within hydrophobic pockets. Inspired by the nature's elaborated way, we found that even mononucleotides (G and C) can form the minimal G x C Watson-Crick pair in water by simply providing a synthetic cavity that efficiently shields the Watson-Crick H-bonding sites. The minimal Watson-Crick structure in water was elucidated by NMR study and firmly characterized by crystallographic analysis. The crystal structure also displays that, within the cavity, coencapsulated anions and solvents efficiently mediate the minimal G x C Watson-Crick pair formation. Furthermore, the competition experiments with the other nucleobases clearly revealed the evident selectivity for the G x C base pairing in water. These results show the fact that a H-bonded nucleobase pair was effectively induced and stabilized in the local environment of an artificial hydrophobic cavity.

Promising SiC support for Pd catalyst in selective hydrogenation of acetylene to ethylene

NASA Astrophysics Data System (ADS)

Guo, Zhanglong; Liu, Yuefeng; Liu, Yan; Chu, Wei

2018-06-01

In this study, SiC supported Pd nanoparticles were found to be an efficient catalyst in acetylene selective hydrogenation reaction. The ethylene selectivity can be about 20% higher than that on Pd/TiO2 catalyst at the same acetylene conversion at 90%. Moreover, Pd/SiC catalyst showed a stable catalytic life at 65 °C with 80% ethylene selectivity. With the detailed characterization using temperature-programmed reduction (H2-TPR), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), N2 adsorption/desorption analysis, CO-chemisorption and thermo-gravimetric analysis (TGA), it was found that SiC owns a lower surface area (22.9 m2/g) and a broad distribution of meso-/macro-porosity (from 5 to 65 nm), which enhanced the mass transfer during the chemical process at high reaction rate and decreased the residence time of ethylene on catalyst surface. Importantly, SiC support has the high thermal conductivity, which favored the rapid temperature homogenization through the catalyst bed and inhabited the over-hydrogenation of acetylene. The surface electronic density of Pd on Pd/SiC catalyst was higher than that on Pd/TiO2, which could promote desorption of ethylene from surface of the catalyst. TGA results confirmed a much less coke deposition on Pd/SiC catalyst.

Ultrafine Nanocrystalline CeO2@C-Containing NaAlH4 with Fast Kinetics and Good Reversibility for Hydrogen Storage.

PubMed

Zhang, Xin; Liu, Yongfeng; Wang, Ke; Li, You; Gao, Mingxia; Pan, Hongge

2015-12-21

A nanocrystalline CeO2@C-containing NaAlH4 composite is successfully synthesized in situ by hydrogenating a NaH-Al mixture doped with CeO2@C. Compared with NaAlH4 , the as-prepared CeO2@C-containing NaAlH4 composite, with a minor amount of excess Al, exhibits significantly improved hydrogen storage properties. The dehydrogenation onset temperature of the hydrogenated [NaH-Al-7 wt % CeO2@C]-0.04Al sample is 77 °C lower than that of the pristine sample because of a reduced kinetic barrier. More importantly, the dehydrogenated sample absorbs ∼4.7 wt % hydrogen within 35 min at 100°C and 10 MPa of hydrogen. Compositional and structural analyses reveal that CeO2 is converted to CeH2 during ball milling and that the newly formed CeH2 works with the excess of Al to synergistically improve the hydrogen storage properties of NaAlH4. Our findings will aid in the rational design of novel catalyst-doped complex hydride systems with low operating temperatures, fast kinetics, and long-term cyclability. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Exploring the activity of a novel Au/TiC(001) model catalyst towards CO and CO 2 hydrogenation

DOE PAGES

Asara, Gian Giacomo; Ricart, Josep M.; Rodriguez, Jose A.; ...

2015-02-02

Small metallic nanoparticles supported on transition metal carbides exhibit an unexpected high activity towards a series of chemical reactions. In particular, the Au/TiC system has proven to be an excellent catalyst for SO 2 decomposition, thiophene hydrodesulfurization, O 2 and H 2 dissociation and the water gas shift reaction. Recent studies have shown that Au/TiC is a very good catalyst for the reverse water–gas shift (CO 2 + H 2 → CO + H 2O) and CO 2 hydrogenation to methanol. The present work further expands the range of applicability of this novel type of systems by exploring the catalyticmore » activity of Au/TiC towards the hydrogenation of CO or CO 2 with periodic density functional theory (DFT) calculations on model systems. Hydrogen dissociates easily on Au/TiC but direct hydrogenation of CO to methanol is hindered by very high activation barriers implying that, on this model catalyst, methanol production from CO 2 involves the hydrogenation of a HOCO-like intermediate. Thus, when dealing with mixtures of syngas (CO/CO 2/H 2/H 2O), CO could be transformed into CO 2 through the water gas shift reaction with subsequent hydrogenation of CO 2 to methanol.« less

Apoptosis in differentiating C2C12 muscle cells selectively targets Bcl-2-deficient myotubes

PubMed Central

Schoneich, Christian; Dremina, Elena; Galeva, Nadezhda; Sharov, Victor

2014-01-01

Muscle cell apoptosis accompanies normal muscle development and regeneration, as well as degenerative diseases and aging. C2C12 murine myoblast cells represent a common model to study muscle differentiation. Though it was already shown that myogenic differentiation of C2C12 cells is accompanied by enhanced apoptosis in a fraction of cells, either the cell population sensitive to apoptosis or regulatory mechanisms for the apoptotic response are unclear so far. In the current study we characterize apoptotic phenotypes of different types of C2C12 cells at all stages of differentiation, and report here that myotubes of differentiated C2C12 cells with low levels of anti-apoptotic Bcl-2 expression are particularly vulnerable to apoptosis even though they are displaying low levels of pro-apoptotic proteins Bax, Bak and Bad. In contrast, reserve cells exhibit higher levels of Bcl-2 and high resistance to apoptosis. The transfection of proliferating myoblasts with Bcl-2 prior to differentiation did not protect against spontaneous apoptosis accompanying differentiation of C2C12 cell but led to Bcl-2 overexpression in myotubes and to significant protection from apoptotic cell loss caused by exposure to hydrogen peroxide. Overall, our data advocate for a Bcl-2-dependent mechanism of apoptosis in differentiated muscle cells. However, downstream processes for spontaneous and hydrogen peroxide induced apoptosis are not completely similar. Apoptosis in differentiating myoblasts and myotubes is regulated not through interaction of Bcl-2 with pro-apoptotic Bcl-2 family proteins such as Bax, Bak, and Bad. PMID:24129924

Legacy of human-induced C erosion and burial on soil-atmosphere C exchange.

PubMed

Van Oost, Kristof; Verstraeten, Gert; Doetterl, Sebastian; Notebaert, Bastiaan; Wiaux, François; Broothaerts, Nils; Six, Johan

2012-11-20

Carbon exchange associated with accelerated erosion following land cover change is an important component of the global C cycle. In current assessments, however, this component is not accounted for. Here, we integrate the effects of accelerated C erosion across point, hillslope, and catchment scale for the 780-km(2) Dijle River catchment over the period 4000 B.C. to A.D. 2000 to demonstrate that accelerated erosion results in a net C sink. We found this long-term C sink to be equivalent to 43% of the eroded C and to have offset 39% (17-66%) of the C emissions due to anthropogenic land cover change since the advent of agriculture. Nevertheless, the erosion-induced C sink strength is limited by a significant loss of buried C in terrestrial depositional stores, which lagged the burial. The time lag between burial and subsequent loss at this study site implies that the C buried in eroded terrestrial deposits during the agricultural expansion of the last 150 y cannot be assumed to be inert to further destabilization, and indeed might become a significant C source. Our analysis exemplifies that accounting for the non-steady-state C dynamics in geomorphic active systems is pertinent to understanding both past and future anthropogenic global change.

Legacy of human-induced C erosion and burial on soil–atmosphere C exchange

PubMed Central

Van Oost, Kristof; Verstraeten, Gert; Doetterl, Sebastian; Notebaert, Bastiaan; Wiaux, François; Broothaerts, Nils; Six, Johan

2012-01-01

Carbon exchange associated with accelerated erosion following land cover change is an important component of the global C cycle. In current assessments, however, this component is not accounted for. Here, we integrate the effects of accelerated C erosion across point, hillslope, and catchment scale for the 780-km2 Dijle River catchment over the period 4000 B.C. to A.D. 2000 to demonstrate that accelerated erosion results in a net C sink. We found this long-term C sink to be equivalent to 43% of the eroded C and to have offset 39% (17–66%) of the C emissions due to anthropogenic land cover change since the advent of agriculture. Nevertheless, the erosion-induced C sink strength is limited by a significant loss of buried C in terrestrial depositional stores, which lagged the burial. The time lag between burial and subsequent loss at this study site implies that the C buried in eroded terrestrial deposits during the agricultural expansion of the last 150 y cannot be assumed to be inert to further destabilization, and indeed might become a significant C source. Our analysis exemplifies that accounting for the non–steady-state C dynamics in geomorphic active systems is pertinent to understanding both past and future anthropogenic global change. PMID:23134723

Internal hydrogen-induced subcritical crack growth in austenitic stainless steels

NASA Astrophysics Data System (ADS)

Huang, J. H.; Altstetter, C. J.

1991-11-01

The effects of small amounts of dissolved hydrogen on crack propagation were determined for two austenitic stainless steel alloys, AISI 301 and 310S. In order to have a uniform distribution of hydrogen in the alloys, they were cathodically charged at high temperature in a molten salt electrolyte. Sustained load tests were performed on fatigue precracked specimens in air at 0 ‡C, 25 ‡C, and 50 ‡C with hydrogen contents up to 41 wt ppm. The electrical potential drop method with optical calibration was used to continuously monitor the crack position. Log crack velocity vs stress intensity curves had definite thresholds for subcritical crack growth (SCG), but stage II was not always clearly delineated. In the unstable austenitic steel, AISI 301, the threshold stress intensity decreased with increasing hydrogen content or increasing temperature, but beyond about 10 wt ppm, it became insensitive to hydrogen concentration. At higher concentrations, stage II became less distinct. In the stable stainless steel, subcritical crack growth was observed only for a specimen containing 41 wt ppm hydrogen. Fractographic features were correlated with stress intensity, hydrogen content, and temperature. The fracture mode changed with temperature and hydrogen content. For unstable austenitic steel, low temperature and high hydrogen content favored intergranular fracture while microvoid coalescence dominated at a low hydrogen content. The interpretation of these phenomena is based on the tendency for stress-induced phase transformation, the different hydrogen diffusivity and solubility in ferrite and austenite, and outgassing from the crack tip. After comparing the embrittlement due to internal hydrogen with that in external hydrogen, it is concluded that the critical hydrogen distribution for the onset of subcritical crack growth is reached at a location that is very near the crack tip.

Hierarchical Cu2O foam/g-C3N4 photocathode for photoelectrochemical hydrogen production

NASA Astrophysics Data System (ADS)

Ma, Xinzhou; Zhang, Jingtao; Wang, Biao; Li, Qiuguo; Chu, Sheng

2018-01-01

Solar photoelectrochemical (PEC) hydrogen production is a promising way for solving energy and environment problems. Earth-abundant Cu2O is a potential light absorber for PEC hydrogen production. In this article, hierarchical porous Cu2O foams are prepared by thermal oxidation of the electrochemically deposited Cu foams. PEC performances of the Cu2O foams are systematically studied and discussed. Benefiting from their higher light harvesting and more efficient charge separation, the Cu2O foams demonstrate significantly enhanced photocurrents and photostability compared to their film counterparts. Moreover, by integrating g-C3N4, hierarchical Cu2O foam/g-C3N4 composites are prepared with further improved photocurrent and photostability, appearing to be potential photocathodes for solar PEC hydrogen production. This study may provide a new and useful insight for the development of Cu2O-based photocathodes for PEC hydrogen production.

NAD(P)H-Independent Asymmetric C=C Bond Reduction Catalyzed by Ene Reductases by Using Artificial Co-substrates as the Hydrogen Donor

PubMed Central

Winkler, Christoph K; Clay, Dorina; Entner, Marcello; Plank, Markus; Faber, Kurt

2014-01-01

To develop a nicotinamide-independent single flavoenzyme system for the asymmetric bioreduction of C=C bonds, four types of hydrogen donor, encompassing more than 50 candidates, were investigated. Six highly potent, cheap, and commercially available co-substrates were identified that (under the optimized conditions) resulted in conversions and enantioselectivities comparable with, or even superior to, those obtained with traditional two-enzyme nicotinamide adenine dinucleotide phosphate (NAD(P)H)-recycling systems. PMID:24382795

Hydrogenation of fructose to 2,5-dimethyltetrahydrofuran using a sulfur poisoned Pt/C catalyst

USDA-ARS?s Scientific Manuscript database

In order to expand the number of biobased chemicals available, fructose has been hydrogenated to 2,5-dimethyltetrahydrofuran using a sulfided Pt/C catalyst. The reaction was carried out in a stirred reactor at 10.3 MPa H2 and 175°C which allowed a 10% fructose solution to be converted in about 2 h. ...

Interaction of Cu(+) with cytosine and formation of i-motif-like C-M(+)-C complexes: alkali versus coinage metals.

PubMed

Gao, Juehan; Berden, Giel; Rodgers, M T; Oomens, Jos

2016-03-14

The Watson-Crick structure of DNA is among the most well-known molecular structures of our time. However, alternative base-pairing motifs are also known to occur, often depending on base sequence, pH, or the presence of cations. Pairing of cytosine (C) bases induced by the sharing of a single proton (C-H(+)-C) may give rise to the so-called i-motif, which occurs primarily in expanded trinucleotide repeats and the telomeric region of DNA, particularly at low pH. At physiological pH, silver cations were recently found to stabilize C dimers in a C-Ag(+)-C structure analogous to the hemiprotonated C-dimer. Here we use infrared ion spectroscopy in combination with density functional theory calculations at the B3LYP/6-311G+(2df,2p) level to show that copper in the 1+ oxidation state induces an analogous formation of C-Cu(+)-C structures. In contrast to protons and these transition metal ions, alkali metal ions induce a different dimer structure, where each ligand coordinates the alkali metal ion in a bidentate fashion in which the N3 and O2 atoms of both cytosine ligands coordinate to the metal ion, sacrificing hydrogen-bonding interactions between the ligands for improved chelation of the metal cation.

Suppression of nanoindentation-induced phase transformation in crystalline silicon implanted with hydrogen

NASA Astrophysics Data System (ADS)

Jelenković, Emil V.; To, Suet

2017-09-01

In this paper the effect of hydrogen implantation in silicon on nanoindentation-induced phase transformation is investigated. Hydrogen ions were implanted in silicon through 300 nm thick oxide with double energy implantation (75 and 40 keV). For both energies implantation dose was 4 × 1016 cm-2. Some samples were thermally annealed at 400 °C. The micro-Raman spectroscopy was applied on nanoindentation imprints and the obtained results were related to the pop out/elbow appearances in nanoindentatioin unloading-displacement curves. The Raman spectroscopy revealed a suppression of Si-XII and Si-III phases and formation of a-Si in the indents of hydrogen implanted Si. The high-resolution x-ray diffraction measurements were taken to support the analysis of silicon phase formation during nanoindentation. Implantation induced strain, high hydrogen concentration, and platelets generation were found to be the factors that control suppression of c-Si phases Si-XII and Si-III, as well as a-Si phase enhancement during nanoindentation. [Figure not available: see fulltext.

Effects of vitamin C treatment on collar-induced intimal thickening

PubMed Central

Arun, Mehmet Zuhuri; Üstünes, Levent; Sevin, Gülnur; Özer, Erdener

2015-01-01

Vitamin C has efficient antioxidant properties and is involved in important physiological processes such as collagen synthesis. As such, vitamin C deficiency leads to serious complications, including vascular diseases. The aim of this study was to investigate the effects of vitamin C treatment on collar-induced intimal thickening. Rabbits were fed a normocholesterolemic diet and a non-occlusive silicon collar was placed around the left carotid artery for 3, 7, and 14 days. The rabbits were treated with or without vitamin C (150 mg/kg/day). Collar-induced intimal thickening became apparent at day 7. The effect of the collar on intimal thickening was more prominent at day 14. Vitamin C treatment significantly inhibited collar-induced intimal thickening at day 14. The placement of the collar around the carotid artery decreased maximum contractile responses against contractile agents (KCl, phenylephrine, 5-hydroxytryptamine). The effect of the collar on contractile responses was enhanced as days elapsed. Decreased contractile responses of collared carotid arteries normalized at day 14 in the vitamin C treatment group. Vitamin C treatment also restored sensitivity to phenylephrine. The collar also significantly decreased acetylcholine-induced relaxations at day 3 and day 7. Acetylcholine-induced relaxations normalized in collared-arteries in the placebo group at day 14. Vitamin C treatment significantly increased acetylcholine-induced relaxations of both normal and collared carotid arteries at day 14. MMP-9 expression increased in collared arteries at day 3 and day 7 but did not change at day 14. MMP-2 expression increased in collared arteries at day 14. However, vitamin C treatment reduced collar-stimulated expression of MMP-2 at day 14. These findings indicate that vitamin C may have potentially beneficial effects on the early stages of atherosclerosis. Furthermore these results, for the first time, may indicate that vitamin C can also normalize decreased contractile

Hydrogenation Reactions on Au/TiC(001): Effects of Au-C Interactions on the Dissociation of H-2

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

Rodriguez, J.A.; Florez, E.; Gomez, T.

2010-10-01

Density functional calculations carried out for realistic models evidence that Au particles supported on TiC(001) are very active towards H2 dissociation. The molecular mechanisms show that the support is not a mere spectator but plays a major role in the catalyzed reaction and acts as a reservoir of atomic H, making this system an excellent candidate as a catalyst for the hydrogenation of olefins and hydrodesulfurization reactions.

A RhxSy/C Catalyst for the Hydrogen Oxidation and Hydrogen Evolution Reactions in HBr

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

Masud, J; Nguyen, TV; Singh, N

Rhodium sulfide (Rh2S3) on carbon support was synthesized by refluxing rhodium chloride with ammonium thiosulfate. Thermal treatment of Rh2S3 at high temperatures (600 degrees C to 850 degrees C) in presence of argon resulted in the transformation of Rh2S3 into Rh3S4, Rh17S15 and Rh which were characterized by TGA/DTA, XRD, EDX, and deconvolved XPS analyses. The catalyst particle size distribution ranged from 3 to 12 nm. Cyclic voltammetry and rotating disk electrode measurements were used to evaluate the catalytic activity for hydrogen oxidation and evolution reactions in H2SO4 and HBr solutions. The thermally treated catalysts show high activity for themore » hydrogen reactions. The exchange current densities (i(o)) of the synthesized RhxSy catalysts in H-2-saturated 1M H2SO4 and 1M HBr for HER and HOR were 0.9 mA/cm(2) to 1.0 mA/cm(2) and 0.8 to 0.9 mA/cm(2), respectively. The lower i(o) values obtained in 1M HBr solution compared to in H2SO4 might be due to the adsorption of Br- on the active surface. Stable electrochemical active surface area (ECSA) of RhxSy catalyst was obtained for CV scan limits between 0 V and 0.65 V vs. RHE. Scans with upper voltage limit beyond 0.65 V led to decreased and unreproducible ECSA measurements. (C) The Author(s) 2015. Published by ECS. All rights reserved.« less

3D ordered porous MoxC (x = 1 or 2) for advanced hydrogen evolution and Li storage.

PubMed

Yu, Hong; Fan, Haosen; Wang, Jiong; Zheng, Yun; Dai, Zhengfei; Lu, Yizhong; Kong, Junhua; Wang, Xin; Kim, Young Jin; Yan, Qingyu; Lee, Jong-Min

2017-06-01

3D ordered porous structures of Mo x C are prepared with different Mo to C ratios and tested for two possible promising applications: hydrogen evolution reaction (HER) through water splitting and lithium ion batteries (LIBs). Mo 2 C and MoC with 3D periodic ordered structures are prepared with a similar process but different precursors. The 3D ordered porous MoC exhibits excellent cycling stability and rate performance as an anode material for LIBs. A discharge capacity of 450.9 mA h g -1 is maintained up to 3000 cycles at 10.0 A g -1 . The Mo 2 C with a similar ordered porous structure shows impressive electrocatalytic activity for the HER in neutral, alkaline and acidic pH solutions. In particular, Mo 2 C shows an onset potential of only 33 mV versus a reversible hydrogen electrode (RHE) and a Tafel slope of 42.5 mV dec -1 in a neutral aqueous solution (1.0 M phosphate buffer solution), which is approaching that of the commercial Pt/C catalyst.

H{sub 2}S induces vasoconstriction of rat cerebral arteries via cAMP/adenylyl cyclase pathway

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

Li, Sen; Ping, Na-na; Cao, Lei, E-mail: leicao@mail.xjtu.edu.cn

2015-12-15

Hydrogen sulfide (H{sub 2}S), traditionally known for its toxic effects, is now involved in regulating vascular tone. Here we investigated the vasoconstrictive effect of H{sub 2}S on cerebral artery and the underlying mechanism. Sodium hydrosulfide (NaHS), a donor of H{sub 2}S, concentration-dependently induced vasoconstriction on basilar artery, which was enhanced in the presence of isoprenaline, a β-adrenoceptor agonist or forskolin, an adenylyl cyclase activator. Administration of NaHS attenuated the vasorelaxant effects of isoprenaline or forskolin. Meanwhile, the NaHS-induced vasoconstriction was diminished in the presence of 8B-cAMP, an analog of cAMP, but was not affected by Bay K-8644, a selective L-typemore » Ca{sup 2+} channel agonist. These results could be explained by the revised effects of NaHS on isoprenaline-induced cAMP elevation and forskolin-stimulated adenylyl cyclase activity. Additionally, NaHS-induced vasoconstriction was enhanced by removing the endothelium or in the presence of L-NAME, an inhibitor of nitric oxide synthase. L-NAME only partially attenuated the effect of NaHS which was given together with forskolin on the pre-contracted artery. In conclusion, H{sub 2}S induces vasoconstriction of cerebral artery via, at least in part, cAMP/adenylyl cyclase pathway. - Highlights: • The vasoactivity effect of NaHS, a donor of H{sub 2}S, was studied on rat cerebral arteries. • H{sub 2}S induces a constriction, not a relaxant effect on basilar arteries. • The vasoconstrictive effect is invovled in inhibiting adenylyl cyclase to reduce cAMP levels. • The vasoconstriction is partially antagonized by NO, and does not necessarily act via NO pathway.« less

Nanodiamond for hydrogen storage: temperature-dependent hydrogenation and charge-induced dehydrogenation.

PubMed

Lai, Lin; Barnard, Amanda S

2012-02-21

Carbon-based hydrogen storage materials are one of hottest research topics in materials science. Although the majority of studies focus on highly porous loosely bound systems, these systems have various limitations including use at elevated temperature. Here we propose, based on computer simulations, that diamond nanoparticles may provide a new promising high temperature candidate with a moderate storage capacity, but good potential for recyclability. The hydrogenation of nanodiamonds is found to be easily achieved, in agreement with experiments, though we find the stability of hydrogenation is dependent on the morphology of nanodiamonds and surrounding environment. Hydrogenation is thermodynamically favourable even at high temperature in pure hydrogen, ammonia, and methane gas reservoirs, whereas water vapour can help to reduce the energy barrier for desorption. The greatest challenge in using this material is the breaking of the strong covalent C-H bonds, and we have identified that the spontaneous release of atomic hydrogen may be achieved through charging of hydrogenated nanodiamonds. If the degree of induced charge is properly controlled, the integrity of the host nanodiamond is maintained, which indicates that an efficient and recyclable approach for hydrogen release may be possible. This journal is © The Royal Society of Chemistry 2012

Downregulation of lipin-1 induces insulin resistance by increasing intracellular ceramide accumulation in C2C12 myotubes

PubMed Central

Huang, Shujuan; Huang, Suling; Wang, Xi; Zhang, Qingli; Liu, Jia; Leng, Ying

2017-01-01

Dysregulation of lipid metabolism in skeletal muscle is involved in the development of insulin resistance. Mutations in lipin-1, a key lipid metabolism regulator leads to significant systemic insulin resistance in fld mice. However, the function of lipin-1 on lipid metabolism and insulin sensitivity in skeletal muscle is still unclear. Herein we demonstrated that downregulation of lipin-1 in C2C12 myotubes by siRNA transfection suppressed insulin action, characterized by reduced insulin stimulated Akt phosphorylation and glucose uptake. Correspondingly, decreased lipin-1 expression was observed in palmitate-induced insulin resistance in C2C12 myotubes, suggested that lipin-1 might play a role in the etiology of insulin resistance in skeletal muscle. The insulin resistance induced by lipin-1 downregulation was related to the disturbance of lipid homeostasis. Lipin-1 silencing reduced intracellular DAG and TAG levels, but elevated ceramide accumulation in C2C12 myotubes. Moreover, the impaired insulin stimulated Akt phosphorylation and glucose uptake caused by lipin-1 silencing could be blocked by the pretreatment with SPT inhibitor myriocin, ceramide synthase inhibitor FB1, or PP2A inhibitor okadaic acid, suggested that the increased ceramide accumulation might be responsible for the development of insulin resistance induced by lipin-1 silencing in C2C12 myotubes. Meanwhile, decreased lipin-1 expression also impaired mitochondrial function in C2C12 myotubes. Therefore, our study suggests that lipin-1 plays an important role in lipid metabolism and downregulation of lipin-1 induces insulin resistance by increasing intracellular ceramide accumulation in C2C12 myotubes. These results offer a molecular insight into the role of lipin-1 in the development of insulin resistance in skeletal muscle. PMID:28123341

Downregulation of lipin-1 induces insulin resistance by increasing intracellular ceramide accumulation in C2C12 myotubes.

PubMed

Huang, Shujuan; Huang, Suling; Wang, Xi; Zhang, Qingli; Liu, Jia; Leng, Ying

2017-01-01

Dysregulation of lipid metabolism in skeletal muscle is involved in the development of insulin resistance. Mutations in lipin-1, a key lipid metabolism regulator leads to significant systemic insulin resistance in fld mice. However, the function of lipin-1 on lipid metabolism and insulin sensitivity in skeletal muscle is still unclear. Herein we demonstrated that downregulation of lipin-1 in C2C12 myotubes by siRNA transfection suppressed insulin action, characterized by reduced insulin stimulated Akt phosphorylation and glucose uptake. Correspondingly, decreased lipin-1 expression was observed in palmitate-induced insulin resistance in C2C12 myotubes, suggested that lipin-1 might play a role in the etiology of insulin resistance in skeletal muscle. The insulin resistance induced by lipin-1 downregulation was related to the disturbance of lipid homeostasis. Lipin-1 silencing reduced intracellular DAG and TAG levels, but elevated ceramide accumulation in C2C12 myotubes. Moreover, the impaired insulin stimulated Akt phosphorylation and glucose uptake caused by lipin-1 silencing could be blocked by the pretreatment with SPT inhibitor myriocin, ceramide synthase inhibitor FB1, or PP2A inhibitor okadaic acid, suggested that the increased ceramide accumulation might be responsible for the development of insulin resistance induced by lipin-1 silencing in C2C12 myotubes. Meanwhile, decreased lipin-1 expression also impaired mitochondrial function in C2C12 myotubes. Therefore, our study suggests that lipin-1 plays an important role in lipid metabolism and downregulation of lipin-1 induces insulin resistance by increasing intracellular ceramide accumulation in C2C12 myotubes. These results offer a molecular insight into the role of lipin-1 in the development of insulin resistance in skeletal muscle.

Hydrogenation of the Exocyclic Olefinic Bond at C-16/C-17 Position of ent-Kaurane Diterpene Glycosides of Stevia rebaudiana Using Various Catalysts

PubMed Central

Chaturvedula, Venkata Sai Prakash; Prakash, Indra

2013-01-01

Catalytic hydrogenation of the exocyclic double bond present between C16 and C17 carbons of the four ent-kaurane diterpene glycosides namely rebaudioside A, rebaudioside B, rebaudioside C, and rebaudioside D isolated from Stevia rebaudiana has been carried out using Pt/C, Pd(OH)2, Rh/C, Raney Ni, PtO2, and 5% Pd/BaCO3 to their corresponding dihydro derivatives with 17α and 17β methyl group isomers. Reactions were performed using the above-mentioned catalysts with the solvents methanol, water, and ethanol/water (8:2) under various conditions. Synthesis of reduced steviol glycosides was performed using straightforward chemistry and their structures were characterized on the basis of 1D and 2D NMR spectral data, including a comparison with reported spectral data. PMID:23896597

Reduction of hydrogen peroxide-induced erythrocyte damage by Carica papaya leaf extract.

PubMed

Okoko, Tebekeme; Ere, Diepreye

2012-06-01

To investigate the in vitro antioxidant potential of Carica papaya (C. papaya) leaf extract and its effect on hydrogen peroxide-induced erythrocyte damage assessed by haemolysis and lipid peroxidation. Hydroxyl radical scavenging activities, hydrogen ion scavenging activity, metal chelating activity, and the ferrous ion reducing ability were assessed as antioxidant indices. In the other experiment, human erythrocytes were treated with hydrogen peroxide to induce erythrocyte damage. The extract (at various concentrations) was subsequently incubated with the erythrocytes and later analysed for haemolysis and lipid peroxidation as indices for erythrocyte damage. Preliminary investigation of the extract showed that the leaf possessed significant antioxidant and free radical scavenging abilities using in vitro models in a concentration dependent manner (P<0.05). The extract also reduced hydrogen peroxide induced erythrocyte haemolysis and lipid peroxidation significantly when compared with ascorbic acid (P<0.05). The IC50 values were 7.33 mg/mL and 1.58 mg/mL for inhibition of haemolysis and lipid peroxidation, respectively. In all cases, ascorbic acid (the reference antioxidant) possessed higher activity than the extract. The findings show that C. papaya leaves possess significant bioactive potential which is attributed to the phytochemicals which act in synergy. Thus, the leaves can be exploited for pharmaceutical and nutritional purposes.

P7C3 Attenuates the Scopolamine-Induced Memory Impairments in C57BL/6J Mice.

PubMed

Jiang, Bo; Song, Lu; Huang, Chao; Zhang, Wei

2016-05-01

Memory impairment is the most common symptom in patients with Alzheimer's disease. The purpose of this study is to evaluate the memory enhancing effects of P7C3, a recently identified compound with robust proneurogenic and neuroprotective effects, on the cognitive impairment induced by scopolamine, a muscarinic acetylcholine receptor antagonist. Different behavior tests including the Y-maze, Morris water maze, and passive avoidance tests were performed to measure cognitive functions. Scopolamine significantly decreased the spontaneous alternation and step-through latency of C57BL/6J mice in Y-maze test and passive avoidance test, whereas increased the time of mice spent to find the hidden platform in Morris water maze test. Importantly, intraperitoneal administration of P7C3 effectively reversed those Scopolamine-induced cognitive impairments in C57BL/6J mice. Furthermore, P7C3 treatment significantly enhanced the level of brain-derived neurotrophic factor (BDNF) signaling pathway in the cortex and hippocampus, and the usage of selective BDNF signaling inhibitor fully blocked the anti-amnesic effects of P7C3. Therefore, these findings suggest that P7C3 could improve the scopolamine-induced learning and memory impairment possibly through activation of BDNF signaling pathway, thereby exhibiting a cognition-enhancing potential.

Carbon and Mo transformations during the synthesis of mesoporous Mo2C/carbon catalysts by carbothermal hydrogen reduction

NASA Astrophysics Data System (ADS)

Wang, Haiyan; Liu, Shida; Liu, Bing; Montes, Vicente; Hill, Josephine M.; Smith, Kevin J.

2018-02-01

The synthesis of mesoporous Mo2C/carbon catalysts by carbothermal hydrogen reduction is reported. Petroleum coke (petcoke) was activated with KOH at 800 °C to obtain high surface area microporous activated petcoke (APC; 2000 m2/g). The APC was wet impregnated with ammonium heptamolybdate (AHM: 10 wt% Mo), dried and reduced in H2 at temperatures from 400 to 800 °C, to yield Mo2C/APC catalysts. Increased reduction temperature increased the Mo2C yield and the mesoporous volume of the Mo2C/APC. At a reduction temperature of 750 °C the mesopore volume of the catalyst doubled compared to the APC support and accounted for 37% of the total pore volume. Maintaining the final CHR temperature for 90 min further increased the Mo2C yield and mesoporosity of the catalyst. The role of Mo2C in the catalytic hydrogenation of the APC and mesopore generation is demonstrated. The activity of the Mo2C/carbon catalysts in the hydrodeoxygenation of 4-methyl phenol increased with increased CHR temperature and catalyst mesoporosity.

Mitomycin C induces multidrug resistance in glaucoma surgery.

PubMed

Hueber, Arno; Esser, Johannes M; Kociok, Norbert; Welsandt, Gerhard; Lüke, Christoph; Roters, Sigrid; Esser, Peter J

2008-02-01

Despite the adjuvant use of mitomycin C during trabeculectomy, failures still occur. We investigated whether cultured human Tenon fibroblasts exposed to low-dose mitomycin C developed a multidrug resistance phenotype in vitro, and whether mitomycin C treatment during previous filtration surgery induces P-glycoprotein expression in vivo. Cultured human Tenon fibroblasts treated with low-dose 0.01 nM mitomycin C for 2 weeks were subsequently treated with 0.1 to 100 microM mitomycin C in the absence or presence of 4 microM verapamil, and allowed to recover for 24 hours. Low-dose mitomycin C-treated fibroblasts were analysed for P-glycoprotein expression using flow cytometry, immunoblotting, and RT-PCR for mdr-1 mRNA. In addition, fibroblasts were treated with low dose 0.1 nM 5-fluorouracil for 2 weeks and analysed for P-glycoprotein expression using flow cytometry. Expression of P-glycoprotein was analysed in surgically removed Tenon tissue (n = 30) using immunohistochemistry. Of the 30 patients, 20 had a previous trabeculectomy, of which nine had previous adjuvant therapy with mitomycin C during trabeculectomy. Partial resistance to mitomycin C after low-dose mitomycin C pre-treatment was significantly neutralised by the addition of verapamil. Low-dose mitomycin C up-regulated P-glycoprotein expression, but not mdr-1 mRNA expression. 5-Fluorouracil did not induce P-glycoprotein expression. P-glycoprotein expression was detected in all nine patients exposed to mitomycin C during previous trabeculectomies. Only six of 21 specimens from patients not previously exposed to mitomycin C showed faint P-glycoprotein expression. The induction of P-glycoprotein by mitomycin C could explain some failures that occur after repeated use of mitomycin C during trabeculectomy. The concomitant use of verapamil or the use of 5-fluorouracil alone could increase the success rate of repeat trabeculectomies.

Computational Study of Pincer Iridium Catalytic Systems: C-H, N-H, and C-C Bond Activation and C-C Coupling Reactions

NASA Astrophysics Data System (ADS)

Zhou, Tian

Computational chemistry has achieved vast progress in the last decades in the field, which was considered to be only experimental before. DFT (density functional theory) calculations have been proven to be able to be applied to large systems, while maintaining high accuracy. One of the most important achievements of DFT calculations is in exploring the mechanism of bond activation reactions catalyzed by organometallic complexes. In this dissertation, we discuss DFT studies of several catalytic systems explored in the lab of Professor Alan S. Goldman. Headlines in the work are: (1) (R4PCP)Ir alkane dehydrogenation catalysts are highly selective and different from ( R4POCOP)Ir catalysts, predicting different rate-/selectivity-determining steps; (2) The study of the mechanism for double C-H addition/cyclometalation of phenanthrene or biphenyl by (tBu4PCP)Ir(I) and ( iPr4PCP)Ir illustrates that neutral Ir(III) C-H addition products can undergo a very facile second C-H addition, particularly in the case of sterically less-crowded Ir(I) complexes; (3) (iPr4PCP)Ir pure solid phase catalyst is highly effective in producing high yields of alpha-olefin products, since the activation enthalpy for dehydrogenation is higher than that for isomerization via an allyl pathway; higher temperatures favor the dehydrogenation/isomerization ratio; (4) (PCP)Ir(H)2(N2H4) complex follows a hydrogen transfer mechanism to undergo both dehydrogenation to form N 2 and H2, as well as hydrogen transfer followed by N-N bond cleavage to form NH3, N2, and H2; (5) The key for the catalytic effect of solvent molecule in CO insertion reaction for RMn(CO)5 is hydrogen bond assisted interaction. The basicity of the solvent determines the strength of the hydrogen bond interaction during the catalytic path and determines the catalytic power of the solvent; and (6) Dehydrogenative coupling of unactivated C-H bonds (intermolecular vinyl-vinyl, intramolecular vinyl-benzyl) is catalyzed by precursors of the

IP{sub 3}-dependent intracellular Ca{sup 2+} release is required for cAMP-induced c-fos expression in hippocampal neurons

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

Zhang, Wenting; Tingare, Asmita; Ng, David Chi-Heng

2012-08-24

Highlights: Black-Right-Pointing-Pointer cAMP-induced c-fos expression in hippocampal neurons requires a submembraneous Ca{sup 2+} pool. Black-Right-Pointing-Pointer The submembraneous Ca{sup 2+} pool derives from intracellular ER stores. Black-Right-Pointing-Pointer Expression of IP{sub 3}-metabolizing enzymes inhibits cAMP-induced c-fos expression. Black-Right-Pointing-Pointer SRE-mediated and CRE-mediated gene expression is sensitive to IP{sub 3}-metabolizing enzymes. Black-Right-Pointing-Pointer Intracellular Ca{sup 2+} release is required for cAMP-induced nuclear translocation of TORC1. -- Abstract: Ca{sup 2+} and cAMP are widely used in concert by neurons to relay signals from the synapse to the nucleus, where synaptic activity modulates gene expression required for synaptic plasticity. Neurons utilize different transcriptional regulators to integrate informationmore » encoded in the spatiotemporal dynamics and magnitude of Ca{sup 2+} and cAMP signals, including some that are Ca{sup 2+}-responsive, some that are cAMP-responsive and some that detect coincident Ca{sup 2+} and cAMP signals. Because Ca{sup 2+} and cAMP can influence each other's amplitude and spatiotemporal characteristics, we investigated how cAMP acts to regulate gene expression when increases in intracellular Ca{sup 2+} are buffered. We show here that cAMP-mobilizing stimuli are unable to induce expression of the immediate early gene c-fos in hippocampal neurons in the presence of the intracellular Ca{sup 2+} buffer BAPTA-AM. Expression of enzymes that attenuate intracellular IP{sub 3} levels also inhibited cAMP-dependent c-fos induction. Synaptic activity induces c-fos transcription through two cis regulatory DNA elements - the CRE and the SRE. We show here that in response to cAMP both CRE-mediated and SRE-mediated induction of a luciferase reporter gene is attenuated by IP{sub 3} metabolizing enzymes. Furthermore, cAMP-induced nuclear translocation of the CREB coactivator TORC1 was

Synthesis of [1-.sup.13C]pyruvic acid], [2-.sup.13C]pyruvic acid], [3-.sup.13C]pyruvic acid] and combinations thereof

DOEpatents

Martinez, Rodolfo A. , Unkefer; Clifford J. , Alvarez; Marc, A [Santa Fe, NM

2012-06-12

The present invention is directed to the labeled compounds, ##STR00001## wherein C* is each either .sup.13C and .sup.12C where at least one C* is .sup.13C, each hydrogen of the methylene group is hydrogen or deuterium, the methyl group includes either zero or three deuterium atoms, Q is sulfide, sulfinyl, or sulfone, Z is an aryl group such as 1-naphthyl, substituted 1-naphthyl, 2-naphthyl, substituted 2-naphthyl, or a phenyl group ##STR00002## wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4 and R.sub.5 are each independently either hydrogen, a C.sub.1-C.sub.4 lower alkyl, a halogen, and an amino group such as NH.sub.2, NHR and NRR' where R and R' are each independently either a C.sub.1-C.sub.4 lower alkyl, a phenyl, and an alkoxy group, and the methyl group can include either zero or three deuterium atoms. The present invention is also directed to the labeled compounds ##STR00003##

Acetylene and Ethylene Adsorption on a β-Mo 2C(100) Surface: A Periodic DFT Study on the Role of C- and Mo-Terminations for Bonding and Hydrogenation Reactions

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

Jimenez-Orozco, Carlos; Florez, Elizabeth; Moreno, Andres

Mo 2C catalysts are widely used in hydrogenation reactions; however, the role of the C and Mo terminations in these catalysts is not clear. Understanding the binding of adsorbates is key for explaining the activity of Mo 2C. The adsorption of acetylene and ethylene, probe molecules representing alkynes and olefins, respectively, was studied in this paper on a β-Mo 2C(100) surface with C and Mo terminations using calculations based on periodic density functional theory. Moreover, the role of the C/Mo molar ratio was investigated to compare the catalytic potential of cubic (δ-MoC) and orthorhombic (β-Mo 2C) surfaces. The geometry andmore » electronic properties of the clean δ-MoC(001) and β-Mo 2C(100) surfaces have a strong influence on the binding of unsaturated hydrocarbons. The adsorption of ethylene is weaker than that of acetylene on the surfaces of the cubic and orthorhombic systems; adsorption of the hydrocarbons was stronger on β-Mo 2C(100) than on δ-MoC(001). The C termination in β-Mo 2C(100) actively participates in both acetylene and ethylene adsorption and is not merely a spectator. Finally, the results of this work suggest that the β-Mo 2C(100)-C surface could be the one responsible for the catalytic activity during the hydrogenation of unsaturated C≡C and C=C bonds, while the Mo-terminated surface could be poisoned or transformed by the strong adsorption of C and CH x fragments.« less

Acetylene and Ethylene Adsorption on a β-Mo 2C(100) Surface: A Periodic DFT Study on the Role of C- and Mo-Terminations for Bonding and Hydrogenation Reactions

DOE PAGES

Jimenez-Orozco, Carlos; Florez, Elizabeth; Moreno, Andres; ...

2017-08-18

Mo 2C catalysts are widely used in hydrogenation reactions; however, the role of the C and Mo terminations in these catalysts is not clear. Understanding the binding of adsorbates is key for explaining the activity of Mo 2C. The adsorption of acetylene and ethylene, probe molecules representing alkynes and olefins, respectively, was studied in this paper on a β-Mo 2C(100) surface with C and Mo terminations using calculations based on periodic density functional theory. Moreover, the role of the C/Mo molar ratio was investigated to compare the catalytic potential of cubic (δ-MoC) and orthorhombic (β-Mo 2C) surfaces. The geometry andmore » electronic properties of the clean δ-MoC(001) and β-Mo 2C(100) surfaces have a strong influence on the binding of unsaturated hydrocarbons. The adsorption of ethylene is weaker than that of acetylene on the surfaces of the cubic and orthorhombic systems; adsorption of the hydrocarbons was stronger on β-Mo 2C(100) than on δ-MoC(001). The C termination in β-Mo 2C(100) actively participates in both acetylene and ethylene adsorption and is not merely a spectator. Finally, the results of this work suggest that the β-Mo 2C(100)-C surface could be the one responsible for the catalytic activity during the hydrogenation of unsaturated C≡C and C=C bonds, while the Mo-terminated surface could be poisoned or transformed by the strong adsorption of C and CH x fragments.« less

Acetylene adsorption on δ-MoC(001), TiC(001) and ZrC(001) surfaces: A comprehensive periodic DFT study

DOE PAGES

Jimenez-Orozco, Carlos; Florez, Elizabeth; Moreno, Andres; ...

2016-12-06

A comprehensive study of acetylene adsorption on δ-MoC(001), TiC(001) and ZrC(001) surfaces was carried out by means of calculations based on periodic density functional theory, using the Perdew–Burke–Ernzerhof exchange–correlation functional. It was found that the bonding of acetylene was significantly affected by the electronic and structural properties of the carbide surfaces. The adsorbate interacted with metal and/or carbon sites of the carbide. The interaction of acetylene with the TiC(001) and ZrC(001) surfaces was strong (binding energies higher than $-$3.5 eV), while moderate acetylene adsorption energies were observed on δ-MoC(001) ($-$1.78 eV to –0.66 eV). Adsorption energies, charge density difference plotsmore » and Mulliken charges suggested that the binding of the hydrocarbon to the surface had both ionic and covalent contributions. According to the C–C bond lengths obtained, the adsorbed molecule was modified from acetylene-like into ethylene-like on the δ-MoC(001) surface (desired behavior for hydrogenation reactions) but into ethane-like on TiC(001) and ZrC(001). The obtained results suggest that the δ-MoC(001) surface is expected to have the best performance in selective hydrogenation reactions to convert alkynes into alkenes. Another advantage of δ-MoC(001) is that, after C 2H 2 adsorption, surface carbon sites remain available, which are necessary for H 2 dissociation. Furthermore, these sites were occupied when C 2H 2 was adsorbed on TiC(001) and ZrC(001), limiting their application in the hydrogenation of alkynes.« less

Gallic Acid Induces a Reactive Oxygen Species-Provoked c-Jun NH2-Terminal Kinase-Dependent Apoptosis in Lung Fibroblasts

PubMed Central

Chen, Chiu-Yuan; Chen, Kun-Chieh; Yang, Tsung-Ying; Liu, Hsiang-Chun; Hsu, Shih-Lan

2013-01-01

Idiopathic pulmonary fibrosis is a chronic lung disorder characterized by fibroblasts proliferation and extracellular matrix accumulation. Induction of fibroblast apoptosis therefore plays a crucial role in the resolution of this disease. Gallic acid (3,4,5-trihydroxybenzoic acid), a common botanic phenolic compound, has been reported to induce apoptosis in tumor cell lines and renal fibroblasts. The present study was undertaken to examine the role of mitogen-activated protein kinases (MAPKs) in lung fibroblasts apoptosis induced by gallic acid. We found that treatment with gallic acid resulted in activation of c-Jun NH2-terminal kinase (JNK), extracellular signal-regulated kinase (ERK), and protein kinase B (PKB, Akt), but not p38MAPK, in mouse lung fibroblasts. Inhibition of JNK using pharmacologic inhibitor (SP600125) and genetic knockdown (JNK specific siRNA) significantly inhibited p53 accumulation, reduced PUMA and Fas expression, and abolished apoptosis induced by gallic acid. Moreover, treatment with antioxidants (vitamin C, N-acetyl cysteine, and catalase) effectively diminished gallic acid-induced hydrogen peroxide production, JNK and p53 activation, and cell death. These observations imply that gallic acid-mediated hydrogen peroxide formation acts as an initiator of JNK signaling pathways, leading to p53 activation and apoptosis in mouse lung fibroblasts. PMID:23533505

Hydrogen bonded C-H···Y (Y = O, S, Hal) molecular complexes: A natural bond orbital analysis

NASA Astrophysics Data System (ADS)

Isaev, A. N.

2016-03-01

Hydrogen bonded C-H···Y complexes formed by H2O, H2S molecules, hydrogen halides, and halogen-ions with methane, halogen substituted methane as well as with the C2H2 and NCH molecules were studied at the MP2/aug-cc-pVDZ level. The structure of NBOs corresponding to lone pair of acceptor Y, n Y, and vacant anti-σ-bond C-H of proton donor was analyzed and estimates of second order perturbation energy E(2) characterizing donor-acceptor n Y → σ C-H * charge-transfer interaction were obtained. Computational results for complexes of methane and its halogen substituted derivatives show that for each set of analogous structures, the EnY→σ*C-H (2) energy tends to grow with an increase in the s-component percentage in the lone pair NBO of acceptor Y. Calculations for different C···Y distances show that the equilibrium geometries of complexes lie in the region where the E(2) energy is highest and it changes symbatically with the length of the covalent E-H bond when the R(C···Y) distance is varied. The performed analysis allows us to divide the hydrogen bonded complexes into two groups, depending on the pattern of overlapping for NBOs of the hydrogen bridge.

Modeling thermal and irradiation-induced swelling effects on the integrity of Ti3SiC2/SiC joints

NASA Astrophysics Data System (ADS)

Nguyen, Ba Nghiep; Henager, Charles H.; Kurtz, Richard J.

2017-11-01

Previously, results for CVD-SiC joined by a solid state displacement reaction to form a dual-phase SiC/MAX phase joint subsequently irradiated at 800 °C to 5 dpa indicated some cracking in the joint. This paper elucidates the cracking origin by developing a model that accounts for differential thermal expansion and irradiation-induced swelling between the substrate and joint materials by using a continuum damage mechanics approach with support from micromechanical modeling. Damage accumulation in joined specimens irradiated at four temperatures (300 °C, 400 °C, 500 °C and 800 °C) is analyzed. We assume the experimental irradiation dose is sufficient to cause saturation swelling in SiC. The analyses indicate that the SiC/MAX joint survives irradiation-induced swelling at all the irradiation temperatures considered. The joint experiences only minor damage when heated to and irradiated at 800 °C as well as cooling to room temperature. The prediction agrees with the experimental findings available for this case. However, the joint heated to 300 °C suffers severe damage during irradiation-induced swelling at this temperature, and additional damage after cooling to room temperature. Irradiation at 400 °C and subsequent cooling to room temperature produced similar damage to the irradiation 300 °C case, but to a lesser extent. The joint heated to 500 °C and irradiated at this temperature suffered only very minor damage, but further moderate damage occurred after cooling to room temperature.

Hydrogen Peroxide-Dependent Uptake of Iodine by Marine Flavobacteriaceae Bacterium Strain C-21▿

PubMed Central

Amachi, Seigo; Kimura, Koh; Muramatsu, Yasuyuki; Shinoyama, Hirofumi; Fujii, Takaaki

2007-01-01

The cells of the marine bacterium strain C-21, which is phylogenetically closely related to Arenibacter troitsensis, accumulate iodine in the presence of glucose and iodide (I−). In this study, the detailed mechanism of iodine uptake by C-21 was determined using a radioactive iodide tracer, 125I−. In addition to glucose, oxygen and calcium ions were also required for the uptake of iodine. The uptake was not inhibited or was only partially inhibited by various metabolic inhibitors, whereas reducing agents and catalase strongly inhibited the uptake. When exogenous glucose oxidase was added to the cell suspension, enhanced uptake of iodine was observed. The uptake occurred even in the absence of glucose and oxygen if hydrogen peroxide was added to the cell suspension. Significant activity of glucose oxidase was found in the crude extracts of C-21, and it was located mainly in the membrane fraction. These findings indicate that hydrogen peroxide produced by glucose oxidase plays a key role in the uptake of iodine. Furthermore, enzymatic oxidation of iodide strongly stimulated iodine uptake in the absence of glucose. Based on these results, the mechanism was considered to consist of oxidation of iodide to hypoiodous acid by hydrogen peroxide, followed by passive translocation of this uncharged iodine species across the cell membrane. Interestingly, such a mechanism of iodine uptake is similar to that observed in iodine-accumulating marine algae. PMID:17933915

Effect of hydrogen on the melting of the Fe-C system and the fate of the subducted carbon

NASA Astrophysics Data System (ADS)

Lai, X.; Chen, B.; Gao, J.; Zhu, F.

2017-12-01

The subducted oceanic crust carries significant amount of carbonates and organic carbons from the surface into the deep mantle. Through slab-mantle interactions, subducted carbons can react with metallic iron in the metal-saturated regions of the mantle and form various reduced species such as Fe carbides. The Fe-C system is found to have higher eutectic melting temperature than mantle geotherm and thus carbon by forming iron carbides may be "redox freezed" in the mantle (Rohrbach and Schmidt 2011). Hydrogen was found to be have significant effect on the melting of the Fe-light-elements systems such as the Fe-S system (Shibazaki et al., 2011). Here we report experimental results from both multi-anvil press and diamond anvil cell experiments on the melting behaviors of the Fe-C-H system. C14H12, a solid-state C-H organic compound was used as a C-H source to react with the metallic iron at high pressure and high temperature conditions. With excess C14H12, hydrogen in the FeHx alloy was totally replaced by carbon at 14.8-24.7 GPa. Conversely, with excess Fe, the existence of hydrogen is found to depress the melting temperature of the Fe-C system by at least 100 K. Hydrogen may facilitate the transport and cycling of subducted carbon in the deep mantle and contribute to formation of superdeep diamonds (Smith et al. 2016). Rohrbach, Arno, and Max W. Schmidt. "Redox freezing and melting in the Earth's deep mantle resulting from carbon-iron redox coupling." Nature 472.7342 (2011): 209. Shibazaki, Yuki, et al. "Effect of hydrogen on the melting temperature of FeS at high pressure: Implications for the core of Ganymede." Earth and Planetary Science Letters 301.1 (2011): 153-158. Smith, Evan M., et al. "Large gem diamonds from metallic liquid in Earth's deep mantle." Science 354.6318 (2016): 1403-1405.

Ejection of the Massive Hydrogen-rich Envelope Timed with the Collapse of the Stripped SN 2014C

PubMed Central

Margutti, Raffaella; Kamble, A.; Milisavljevic, D.; Zapartas, E.; de Mink, S. E.; Drout, M.; Chornock, R.; Risaliti, G.; Zauderer, B. A.; Bietenholz, M.; Cantiello, M.; Chakraborti, S.; Chomiuk, L.; Fong, W.; Grefenstette, B.; Guidorzi, C.; Kirshner, R.; Parrent, J. T.; Patnaude, D.; Soderberg, A. M.; Gehrels, N. C.; Harrison, F.

2017-01-01

We present multi-wavelength observations of SN 2014C during the first 500 days. These observations represent the first solid detection of a young extragalactic stripped-envelope SN out to high-energy X-rays ~40 keV. SN 2014C shows ordinary explosion parameters (Ek ~ 1.8 × 1051 erg and Mej ~ 1.7 M⊙). However, over an ~1 year timescale, SN 2014C evolved from an ordinary hydrogen-poor supernova into a strongly interacting, hydrogen-rich supernova, violating the traditional classification scheme of type-I versus type-II SNe. Signatures of the SN shock interaction with a dense medium are observed across the spectrum, from radio to hard X-rays, and revealed the presence of a massive shell of ~1 M⊙of hydrogen-rich material at ~6 × 1016 cm. The shell was ejected by the progenitor star in the decades to centuries before collapse. This result challenges current theories of massive star evolution, as it requires a physical mechanism responsible for the ejection of the deepest hydrogen layer of H-poor SN progenitors synchronized with the onset of stellar collapse. Theoretical investigations point at binary interactions and/or instabilities during the last nuclear burning stages as potential triggers of the highly time-dependent mass loss. We constrain these scenarios utilizing the sample of 183 SNe Ib/c with public radio observations. Our analysis identifies SN 2014C-like signatures in ~10% of SNe. This fraction is reasonably consistent with the expectation from the theory of recent envelope ejection due to binary evolution if the ejected material can survive in the close environment for 103–104 years. Alternatively, nuclear burning instabilities extending to core C-burning might play a critical role. PMID:28684881

Guanidine hydrochloride-induced alkali molten globule model of horse ferrocytochrome c.

PubMed

Jain, Rishu; Kaur, Sandeep; Kumar, Rajesh

2013-02-01

This article compares structural, kinetic and thermodynamic properties of previously unknown guanidine hydrochloride (GdnHCl)-induced alkali molten globule (MG) state of horse 'ferrocytochrome c' (ferrocyt c) with the known NaCl-induced alkali-MG state of ferrocyt c. It is well known that Cl(-) arising from GdnHCl refolds and stabilizes the acid-denatured protein to MG state. We demonstrate that the GdnH(+) arising from GdnHCl (≤0.2 M) also transforms the base-denatured CO-liganded ferrocyt c (carbonmonoxycyt c) to MG state by making the electrostatic interactions to the negative charges of the protein. Structural and molecular properties extracted from the basic spectroscopic (circular dichroism (CD), fluorescence, FTIR and NMR) experiments suggest that the GdnH(+)- and Na(+)-induced MG states of base-denatured carbonmonoxycyt c are molecular compact states containing native-like secondary structures and disordered tertiary structures. Kinetic experiments involving the measurement of the CO association to the alkaline ferrocyt c in the presence of different GdnHCl and NaCl concentrations indicate that the Na(+)-induced MG state is more constrained relative to that of GdnH(+)-induced MG state. Analyses of thermal (near UV-CD) denaturation curves of the base-denatured protein in the presence of different GdnHCl and NaCl concentration also indicate that the Na(+)-induced MG state is thermally more stable than the GdnH(+)-induced MG state.

Modeling thermal and irradiation-induced swelling effects on the integrity of Ti 3SiC 2/SiC joints

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

Nguyen, Ba Nghiep; Henager, Charles H.; Kurtz, Richard J.

Previously, results for CVD-SiC joined by a solid state displacement reaction to form a dual-phase SiC/MAX phase joint subsequently irradiated at 800 °C to 5 dpa indicated some cracking in the joint. Here, this paper elucidates the cracking origin by developing a model that accounts for differential thermal expansion and irradiation-induced swelling between the substrate and joint materials by using a continuum damage mechanics approach with support from micromechanical modeling. Damage accumulation in joined specimens irradiated at four temperatures (300 °C, 400 °C, 500 °C and 800 °C) is analyzed. We assume the experimental irradiation dose is sufficient to causemore » saturation swelling in SiC. The analyses indicate that the SiC/MAX joint survives irradiation-induced swelling at all the irradiation temperatures considered. The joint experiences only minor damage when heated to and irradiated at 800 °C as well as cooling to room temperature. The prediction agrees with the experimental findings available for this case. However, the joint heated to 300 °C suffers severe damage during irradiation-induced swelling at this temperature, and additional damage after cooling to room temperature. Irradiation at 400 °C and subsequent cooling to room temperature produced similar damage to the irradiation 300 °C case, but to a lesser extent. Finally, the joint heated to 500 °C and irradiated at this temperature suffered only very minor damage, but further moderate damage occurred after cooling to room temperature.« less

Modeling thermal and irradiation-induced swelling effects on the integrity of Ti 3SiC 2/SiC joints

DOE PAGES

Nguyen, Ba Nghiep; Henager, Charles H.; Kurtz, Richard J.

2017-09-08

Previously, results for CVD-SiC joined by a solid state displacement reaction to form a dual-phase SiC/MAX phase joint subsequently irradiated at 800 °C to 5 dpa indicated some cracking in the joint. Here, this paper elucidates the cracking origin by developing a model that accounts for differential thermal expansion and irradiation-induced swelling between the substrate and joint materials by using a continuum damage mechanics approach with support from micromechanical modeling. Damage accumulation in joined specimens irradiated at four temperatures (300 °C, 400 °C, 500 °C and 800 °C) is analyzed. We assume the experimental irradiation dose is sufficient to causemore » saturation swelling in SiC. The analyses indicate that the SiC/MAX joint survives irradiation-induced swelling at all the irradiation temperatures considered. The joint experiences only minor damage when heated to and irradiated at 800 °C as well as cooling to room temperature. The prediction agrees with the experimental findings available for this case. However, the joint heated to 300 °C suffers severe damage during irradiation-induced swelling at this temperature, and additional damage after cooling to room temperature. Irradiation at 400 °C and subsequent cooling to room temperature produced similar damage to the irradiation 300 °C case, but to a lesser extent. Finally, the joint heated to 500 °C and irradiated at this temperature suffered only very minor damage, but further moderate damage occurred after cooling to room temperature.« less

GATA-dependent regulation of TPO-induced c-mpl gene expression during megakaryopoiesis.

PubMed

Sunohara, Masataka; Morikawa, Shigeru; Fuse, Akira; Sato, Iwao

2014-01-01

Thrombopoietin (TPO) and its receptor, c-Mpl, play the crucial role during megakaryocytopoiesis. Previously, we have shown that the promoter activity of c-mpl induced by TPO is modulated by transcription through a PKC-dependent pathway and that GATA(-77) is involved as a positive regulatory element in TPO-induced c-mpl gene expression in the megakaryoblastic CMK cells. In this research, to examine participating possibility of GATA promoter element in TPO- induced c-mpl gene expression through a PKC-independent pathway, the promoter activity of site-directed mutagenesis and the effect of potein kinase C modulator were measured by a transient transfection assay system. Together with our previous results on the TPO-induced c-mpl promoter, this study indicates destruction of -77GATA in c-mpl promoter decreased the activity by 47.3% under existence of GF109203. These results suggest that GATA promoter element plays significant role in TPO-induced c-mpl gene expression through a PKC-independent pathway.

Photocatalytic Hydrogen-Evolution Cross-Couplings: Benzene C-H Amination and Hydroxylation.

PubMed

Zheng, Yi-Wen; Chen, Bin; Ye, Pan; Feng, Ke; Wang, Wenguang; Meng, Qing-Yuan; Wu, Li-Zhu; Tung, Chen-Ho

2016-08-17

We present a blueprint for aromatic C-H functionalization via a combination of photocatalysis and cobalt catalysis and describe the utility of this strategy for benzene amination and hydroxylation. Without any sacrificial oxidant, we could use the dual catalyst system to produce aniline directly from benzene and ammonia, and phenol from benzene and water, both with evolution of hydrogen gas under unusually mild conditions in excellent yields and selectivities.

Complement factor C5a induces atherosclerotic plaque disruptions

PubMed Central

Wezel, Anouk; de Vries, Margreet R; Lagraauw, H Maxime; Foks, Amanda C; Kuiper, Johan; Quax, Paul HA; Bot, Ilze

2014-01-01

Complement factor C5a and its receptor C5aR are expressed in vulnerable atherosclerotic plaques; however, a causal relation between C5a and plaque rupture has not been established yet. Accelerated atherosclerosis was induced by placing vein grafts in male apoE−/− mice. After 24 days, when advanced plaques had developed, C5a or PBS was applied locally at the lesion site in a pluronic gel. Three days later mice were killed to examine the acute effect of C5a on late stage atherosclerosis. A significant increase in C5aR in the plaque was detectable in mice treated with C5a. Lesion size and plaque morphology did not differ between treatment groups, but interestingly, local treatment with C5a resulted in a striking increase in the amount of plaque disruptions with concomitant intraplaque haemorrhage. To identify the potential underlying mechanisms, smooth muscle cells and endothelial cells were treated in vitro with C5a. Both cell types revealed a marked increase in apoptosis after stimulation with C5a, which may contribute to lesion instability in vivo. Indeed, apoptosis within the plaque was seen to be significantly increased after C5a treatment. We here demonstrate a causal role for C5a in atherosclerotic plaque disruptions, probably by inducing apoptosis. Therefore, intervention in complement factor C5a signalling may be a promising target in the prevention of acute atherosclerotic complications. PMID:25124749

Protective effects of quercetin and vitamin C against nicotine-induced toxicity in the blood of Wistar rats.

PubMed

Paunović, Milica G; Ognjanović, Branka I; Matić, Miloš M; Štajn, Andraš Š; Saičić, Zorica S

2016-12-01

Nicotine is a potential inducer of oxidative stress, through which it can damage numerous biological molecules. The aim of our study was to investigate the prooxidative effects of nicotine and protective (additive or synergistic) effects of quercetin and vitamin C in the blood of experimental animals, to determine whether the combination of these antioxidants might be beneficial for clinical purposes. Wistar albino rats were receiving intraperitoneal nicotine injection (0.75 mg kg-1 per day) or saline (control group) or nicotine plus quercetin (40 mg kg-1 per day) and vitamin C (100 mg kg-1 per day) for three consecutive days. On day 4, we determined their blood lipid profile, liver enzymes, oxidative stress parameters, and antioxidative system parameters. Compared to untreated control, nicotine significantly increased total cholesterol, LDLcholesterol, triglycerides, liver enzymes (alanine transaminase, aspartate transaminase, and lactate dehydrogenase) and oxidative stress parameters (superoxide anion, hydrogen peroxide, and lipid peroxide) and decreased HDL-cholesterol, glutathione, and superoxide dismutase/catalase activity. Quercetin + vitamin C reversed these values significantly compared to the nicotine alone group. Our results confirm that nicotine has significant prooxidative effects that may disrupt the redox balance and show that the quercetin + vitamin C combination supports antioxidant defence mechanisms with strong haematoprotective activity against nicotine-induced toxicity. In practical terms, this means that a diet rich in vitamin C and quercetin could prevent nicotine-induced toxicity and could also be useful in the supportive care of people exposed to nicotine.

Radotinib induces high cytotoxicity in c-KIT positive acute myeloid leukemia cells.

PubMed

Heo, Sook-Kyoung; Noh, Eui-Kyu; Kim, Jeong Yi; Jo, Jae-Cheol; Choi, Yunsuk; Koh, SuJin; Baek, Jin Ho; Min, Young Joo; Kim, Hawk

2017-06-05

Previously, we reported that radotinib, a BCR-ABL1 tyrosine kinase inhibitor, induced cytotoxicity in acute myeloid leukemia (AML) cells. However, the effects of radotinib in the subpopulation of c-KIT-positive AML cells were unclear. We observed that low-concentration radotinib had more potent cytotoxicity in c-KIT-positive cells than c-KIT-negative cells from AML patients. To address this issue, cell lines with high c-KIT expression, HEL92.1.7, and moderate c-KIT expression, H209, were selected. HEL92.1.7 cells were grouped into intermediate and high c-KIT expression populations. The cytotoxicity of radotinib against the HEL92.1.7 cell population with intermediate c-KIT expression was not different from that of the population with high c-KIT expression. When H209 cells were grouped into c-KIT expression-negative and c-KIT expression-positive populations, radotinib induced cytotoxicity in the c-KIT-positive population, but not the c-KIT-negative population. Thus, radotinib induces cytotoxicity in c-KIT-positive cells, regardless of the c-KIT expression intensity. Therefore, radotinib induces significant cytotoxicity in c-KIT-positive AML cells, suggesting that radotinib is a potential target agent for the treatment of c-KIT-positive malignancies including AML. Copyright © 2017 Elsevier B.V. All rights reserved.

Reduction of hydrogen peroxide-induced erythrocyte damage by Carica papaya leaf extract

PubMed Central

Okoko, Tebekeme; Ere, Diepreye

2012-01-01

Objective To investigate the in vitro antioxidant potential of Carica papaya (C. papaya) leaf extract and its effect on hydrogen peroxide-induced erythrocyte damage assessed by haemolysis and lipid peroxidation. Methods Hydroxyl radical scavenging activities, hydrogen ion scavenging activity, metal chelating activity, and the ferrous ion reducing ability were assessed as antioxidant indices. In the other experiment, human erythrocytes were treated with hydrogen peroxide to induce erythrocyte damage. The extract (at various concentrations) was subsequently incubated with the erythrocytes and later analysed for haemolysis and lipid peroxidation as indices for erythrocyte damage. Results Preliminary investigation of the extract showed that the leaf possessed significant antioxidant and free radical scavenging abilities using in vitro models in a concentration dependent manner (P<0.05). The extract also reduced hydrogen peroxide induced erythrocyte haemolysis and lipid peroxidation significantly when compared with ascorbic acid (P<0.05). The IC50 values were 7.33 mg/mL and 1.58 mg/mL for inhibition of haemolysis and lipid peroxidation, respectively. In all cases, ascorbic acid (the reference antioxidant) possessed higher activity than the extract. Conclusions The findings show that C. papaya leaves possess significant bioactive potential which is attributed to the phytochemicals which act in synergy. Thus, the leaves can be exploited for pharmaceutical and nutritional purposes. PMID:23569948

Synthesis of [1-.sup.13C]pyruvic acid], [2-.sup.13C]pyruvic acid], [3-.sup.13C]pyruvic acid] and combinations thereof

DOEpatents

Martinez, Rodolfo A [Santa Fe, NM; Unkefer, Clifford J [Los Alamos, NM; Alvarez, Marc A [Santa Fe, NM

2009-09-01

The present invention is directed to labeled compounds, of the formulae ##STR00001## wherein C* is each independently selected from the group consisting of .sup.13C and .sup.12C with the proviso that at least one C* is .sup.13C, each hydrogen of the methylene group can independently be either hydrogen or deuterium, the methyl group includes either zero or three deuterium atoms, Q is from the group of sulfide, sulfinyl, and sulfone, Z is an aryl group from the group of 1-naphthyl, substituted 1-naphthyl, 2-naphthyl, substituted 2-naphthyl, and phenyl groups with the structure ##STR00002## wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4 and R.sub.5 are each independently from the group of hydrogen, a C.sub.1-C.sub.4 lower alkyl, a halogen, and an amino group from the group of NH.sub.2, NHR and NRR' where R and R' are each independently from the group of a C.sub.1-C.sub.4 lower alkyl, a phenyl, and an alkoxy group, and the methyl group can include either zero or three deuterium atoms.

Determination of Hydrogen Diffusion Coefficients in Fused Silica From 23 to 250°C Using Raman Spectroscopy

NASA Astrophysics Data System (ADS)

Shang, L.; Chou, I.; Lu, W.; Burruss, R. C.

2008-12-01

The oxygen buffer technique is routinely used in experimental studies of redox sensitive geochemical reactions at elevated pressures (P) and temperatures (T). However, this technique is limited to T above about 400°C due to the low permeability of sample containers (Pt or Ag-Pd alloys) to hydrogen at lower T. Preliminary results of Chou et al. (Geochim. Cosmochim. Acta, 2008, doi:10.1016/j.gca.2008.07.030) indicate that the use of fused silica capillary (FSC) container may extend this technique to lower T. In this study, hydrogen diffusion coefficients (D) in FSC were determined from 23 to 250°C by measuring the loss of hydrogen from the FSC containers (0.3 mm OD, 0.1 mm ID, and ~10 mm long) with Raman spectroscopy using CO2 as an internal standard. First, CO2 was loaded cryogenically in a FSC capsule (Chou et al., ibid.). The capsule was then inserted in a protective ceramic tube, sealed in a gold capsule containing Fe powder and water, and heated at 300°C under 100 MPa of Ar external P in a cold-seal pressure vessel for several days allowing H2 to diffuse into the capsule. After quench, the Raman spectra were collected and the initial relative concentration of hydrogen in the silica capsule was derived from the peak height ratios between H2 (near 587 cm-1) and CO2 (near 1387 cm- 1). The sample capsule was then heated at a fixed T at one atmosphere to let H2 diffuse out of the capsule, and the changes of hydrogen concentration were monitored by Raman spectroscopy after quench. This process was repeated with different heating durations at 23 (room T), 50, 102, 157, 200, and 250°C. The values of D (in cm2s-1) in FSC were obtained by fitting the observed changes of hydrogen concentration to an equation based on Fick's second law. Our results can be represented by: Ln D (±0.14) = (-39810/RT) - 9.5491 (r2 = 0.9985) where R is the gas constant, and T in Kelvin. The slope corresponds to an activation energy of 39.81 kJ/mol. Our D values are about a half order of

A theoretical study of the hydrogen bonding between the vic-, cis- and trans-C 2H 2F 2 isomers and hydrogen fluoride

NASA Astrophysics Data System (ADS)

Rusu, Victor H.; da Silva, João Bosco P.; Ramos, Mozart N.

2009-04-01

MP2/6-31++G(d,p) and B3LYP/6-31++G(d,p) theoretical calculations have been employed to investigate the hydrogen bonding formation involving the vic-, cis- and trans-C 2H 2F 2 isomers and hydrogen fluoride. Our calculations have revealed for each isomer the preferential existence of two possible hydrogen-bonded complexes: a non-cyclic complex and a cyclic complex. For all the three isomers the binding energies for the non-cyclic and cyclic hydrogen complexes are essentially equal using both the MP2 and B3LYP calculations, being that the cyclic structure is slightly more stable. For instance, the binding energies including BSSE and ZPE corrections for the non-cyclic and cyclic structures of cis-C 2H 2F···HF are 8.7 and 9.0 kJ mol -1, respectively, using B3LYP calculations. The cyclic complex formation reduces the polarity, in contrast to what occurs with the non-cyclic complex. This result is more accentuated in vic-C 2H 2F 2···HF. In this latter, Δ μ(cyclic) is -3.07 D, whereas Δ μ(non-cyclic) is +1.92 D using B3LYP calculations. Their corresponding MP2 values are +0.44 D and -1.89 D, respectively. As expected, the complexation produces an H sbnd F stretching frequency downward shift, whereas its IR intensity is enhanced. On the other hand, the vibrational modes of the vic-, cis- and trans-C 2H 2F 2 isomers are little affected by complexation. The new vibrational modes due to hydrogen bonding formation show several interesting features, in particular the HF bending modes which are pure rotations in the free molecule.

Parathyroid hormone induces c-fos and c-jun messenger RNA in rat osteoblastic cells

NASA Technical Reports Server (NTRS)

Clohisy, J. C.; Scott, D. K.; Brakenhoff, K. D.; Quinn, C. O.; Partridge, N. C.

1992-01-01

PTH is a potent regulator of osteoblast gene expression, yet the nuclear events that mediate PTH action are poorly understood. We were interested in identifying immediate early genes which may regulate PTH-altered gene expression in the osteoblast. Therefore, we examined the effects of PTH on c-fos and c-jun gene expression in a rat osteoblastic cell line (UMR 106-01). Under control conditions, c-fos and c-jun mRNAs were present at low basal levels. After PTH treatment, c-fos mRNA abundance dramatically increased, with a maximal and transient response at 30 min. PTH also stimulated an increase in c-jun mRNA, but in a biphasic manner, with maximal levels at 30 min and 2 h. These responses were dose dependent, not altered by cotreatment with the protein synthesis inhibitor cycloheximide, and preceded PTH-induced expression of matrix metallo-proteinase-1 mRNA. Nuclear run-on assays demonstrated an increased rate of c-fos and c-jun transcription after PTH exposure. To determine the signal transduction pathways involved, second messenger analogs were tested for their ability to mimic the effects of PTH. 8-Bromo-cAMP and phorbol 12-myristate 13-acetate (PMA) caused increases in the abundance of c-fos and c-jun transcripts. Ionomycin had no effect on the expression of these genes. Pretreatment of the cells with PMA resulted in a decrease in basal c-jun expression, but did not alter the PTH-mediated increase in c-fos, c-jun, or matrix metalloproteinase-1 mRNAs.(ABSTRACT TRUNCATED AT 250 WORDS).

Stable hydrogen and carbon isotopic compositions of long-chain (C21-C33) n-alkanes and n-alkenes in insects

NASA Astrophysics Data System (ADS)

Chikaraishi, Yoshito; Kaneko, Masanori; Ohkouchi, Naohiko

2012-10-01

We report the molecular and stable isotopic (δD and δ13C) compositions of long-chain n-alkanes in common insects including the cabbage butterfly, swallowtail, wasp, hornet, grasshopper, and ladybug. Insect n-alkanes are potential candidates of the contamination of soil and sedimentary n-alkanes that are believed to be derived from vascular plant waxes. Long-chain n-alkanes (range C21-33; maximum C23-C29) are found to be abundant in the insects (31-781 μg/dry g), with a carbon preference index (CPI) of 5.1-31.5 and an average chain length (ACL) of 24.9-29.3. The isotopic compositions (mean ± 1σ, n = 33) of the n-alkanes are -195 ± 16‰ for hydrogen and -30.6 ± 2.4‰ for carbon. The insect n-alkanes are depleted in D by approximately 30-40‰ compared with wax n-alkanes from C3 (-155 ± 25‰) and C4 vascular plants (-167 ± 13‰), whereas their δ13C values fall between those of C3 (-36.2 ± 2.4‰) and C4 plants (-20.3 ± 2.4‰). Thus, the contribution of insect-derived n-alkanes to soil and sediment could potentially shift δD records of n-alkanes toward more negative values and potentially muddle the assumed original C3/C4 balance in the δ13C records of the soil and sedimentary n-alkanes. n-Alkenes are also found in three insects (swallowtail, wasp and hornet). They are more depleted in D relative to the same carbon numbered n-alkanes (δDn-alkene - δDn-alkane = -17 ± 16‰), but the δ13C values are almost identical to those of the n-alkanes (δ13Cn-alkene - δ13Cn-alkane = 0.1 ± 0.2‰). These results suggest that these n-alkenes are desaturated products of the same carbon numbered n-alkanes.

VEGF-independent angiogenic pathways induced by PDGF-C

PubMed Central

Kumar, Anil; Zhang, Fan; Lee, Chunsik; Li, Yang; Tang, Zhongshu; Arjunan, Pachiappan

2010-01-01

VEGF is believed to be a master regulator in both developmental and pathological angiogenesis. The role of PDGF-C in angiogenesis, however, is only at the beginning of being revealed. We and others have shown that PDGF-C is a critical player in pathological angiogenesis because of its pleiotropic effects on multiple cellular targets. The angiogenic pathways induced by PDGF-C are, to a large extent, VEGF-independent. These pathways may include, but not limited to, the direct effect of PDGF-C on vascular cells, the effect of PDGF-C on tissue stroma fibroblasts, and its effect on macrophages. Taken together, the pleiotropic, versatile and VEGF-independent angiogenic nature of PDGF-C has placed it among the most important target genes for antiangiogenic therapy. PMID:20871734

Modeling thermal and irradiation-induced swelling effects on the integrity of Ti 3 SiC 2 /SiC joints

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

Nguyen, Ba Nghiep; Henager, Charles H.; Kurtz, Richard J.

Previously, results for CVD-SiC joints created using solid state displacement reactions to form a dual-phase SiC/MAX phase irradiated at 800°C and 5 dpa indicated some extent of cracking in the joint and along the CVD-SiC/joint interface. This paper elucidates the origin of cracking by thermomechanical modeling combined with irradiation-induced swelling effects using a continuum damage approach with support of micromechanical modeling. Three irradiation temperatures (400°C, 500°C and 800°C) are considered assuming experimental irradiation doses in a range leading to saturation swelling in SiC. The analyses indicate that a SiC/MAX joint heated to 400°C fails during irradiation-induced swelling at this temperaturemore » while it experiences some damage after being heated to 500°C and irradiated at the same temperature. However, it fails during cooling from 500°C to room temperature. The joint experiences minor damage when heated to and irradiated at 800°C but does not fail after cooling. The prediction agrees with the experimental findings available for this case.« less

Hydrogen isotope fractionation between C-H-O species in magmatic fluids

NASA Astrophysics Data System (ADS)

Foustoukos, D. I.; Mysen, B. O.

2012-12-01

Constraining the hydrogen isotope fractionation between H-bearing volatiles (e.g. H2, CH4, hydrocarbons, H2O) as function of temperature and pressure helps to promote our understanding of the isotopic composition of evolved magmatic fluids and the overall mantle-cycling of water and reduced C-O-H volatiles. To describe the thermodynamics of the exchange reactions between the different H/D isotopologues of H2 and CH4 under supercritical water conditions, a novel experimental technique has been developed by combining vibrational Raman spectroscopy with hydrothermal diamond anvil cell designs (HDAC), which offers a method to monitor the in-situ evolution of H/D containing species. To this end, the equilibrium relationship between H2-D2-HD in supercritical fluid was investigated at temperatures ranging from 300 - 800 oC and pressures ~ 0.3 - 1.3 GPa [1]. Experimental results obtained in-situ and ex-situ show a significant deviation from the theoretical values of the equilibrium constant predicted for ideal-gas reference state, and with an apparent negative temperature effect triggered by the enthalpy contributions due to mixing in supercritical water. Here, we present a series of HDAC experiments conducted to evaluate the role of supercritical water on the isotopic equilibrium between H/D methane isotopologues at 600 - 800 oC and 409 - 1622 MPa. In detail, tetrakis-silane (Si5C12H36) was reacted with H2O-D2O aqueous solution in the presence of either Ni or Pt metal catalyst, resulting to the formation of deuterated methane species such as CH3D, CHD3, CH2D2 and CD4. Two distinctly different set of experiments ("gas phase"; "liquid phase") were performed by adjusting the silane/water proportions. By measuring the relative intensities of Raman vibrational modes of species, experimental results demonstrate distinctly different thermodynamic properties for the CH4-CH3D-CHD3-CH2D2 equilibrium in gas and liquid-water-bearing systems. In addition, the D/H molar ratio of

A novel IrNi@PdIr/C core-shell electrocatalyst with enhanced activity and durability for the hydrogen oxidation reaction in alkaline anion exchange membrane fuel cells.

PubMed

Qin, Bowen; Yu, Hongmei; Jia, Jia; Jun, Chi; Gao, Xueqiang; Yao, Dewei; Sun, Xinye; Song, Wei; Yi, Baolian; Shao, Zhigang

2018-03-08

Herein, a novel non-platinum core-shell catalyst, namely, IrNi@PdIr/C was prepared via a galvanic replacement reaction; it exhibits enhanced hydrogen oxidation activity and excellent stability under alkaline conditions. Electrochemical experiments demonstrated that the mass and specific activities at 50 mV of IrNi@PdIr/C are 2.1 and 2.2 times that of commercial Pt/C in 0.1 M KOH at 298 K, respectively. Moreover, accelerated degradation tests have shown that the electrochemically active surface area (ECSA) of IrNi@PdIr/C reduces by only 5.1%, which is almost 4 times less than that of commercial Pt/C and the mass activity at 50 mV of IrNi@PdIr/C after 2000 potential cycles is still 1.8 times higher than that of aged Pt/C. XRD and XPS analysis suggest that the enhanced HOR activity is attributed to the weakening of the hydrogen binding to the PdIr overlayers induced by the IrNi core. The better stability to potential cycling can be associated with the PdIr shell, which inhibits oxide formation. These results suggest that IrNi@PdIr/C is a promising non-platinum anode catalyst for alkaline anion exchange membrane fuel cells.

Hydrogen Treatment Protects against Cell Death and Senescence Induced by Oxidative Damage.

PubMed

Han, A Lum; Park, Seong-Hoon; Park, Mi Sung

2017-02-28

Hydrogen has potential for preventive and therapeutic applications as an antioxidant. However, micro- and macroparticles of hydrogen in water disappear easily over time. In order to eliminate reactive oxygen species (ROS) related with the aging process, we used functional water containing nanoparticle hydrogen. Nanoparticle hydrogen does not disappear easily and collapse under water after long periods of time. We used murine embryonic fibroblasts that were isolated from 12.5-day embryos of C57BL/6 mice. We investigated the ability of nanoparticle hydrogen in water to suppress hydroxyurea-induced ROS production, cytotoxicity, and the accumulation of β-galactosidase (an indicator of aging), and promote cell proliferation. The accumulation of β-galactosidase in the cytoplasm and the appearance of abnormal nuclei were inhibited by daily treatment of cells with hydrogen water. When the aging process was accelerated by hydroxyurea-induced oxidative stress, the effect of hydrogen water was even more remarkable. Thus, this study showed the antioxidant and anti-senescence effects of hydrogen water. Nanoparticle hydrogen water is potentially a potent anti-aging agent.

Vitamin C deficiency aggravates tumor necrosis factor α-induced insulin resistance.

PubMed

Qing, Zhou; Xiao-Hui, Wu; Xi-Mei, Wu; Chao-Chun, Zou

2018-06-15

Chronic low-grade inflammation plays a major role in the development of insulin resistance. The potential role and underlying mechanism of vitamin C, an antioxidant and anti-inflammatory agent, was investigated in tumor necrosis factor-α (TNF-α)-induced insulin resistance. Gulonolactone oxidase knockout (Gulo -/- ) mice genetically unable to synthesize vitamin C were used to induce insulin resistance by continuously pumping small doses of TNF-α for seven days, and human liver hepatocellular carcinoma cells (HepG2 cells) were used to induce insulin resistance by treatment with TNF-α. Vitamin C deficiency aggravated TNF-α-induced insulin resistance in Gulo -/- mice, resulting in worse glucose tolerance test (GTT) results, higher fasting plasma insulin level, and the inactivation of the protein kinase B (AKT)/glycogen synthase kinase-3β (GSK3β) pathway in the liver. Vitamin C deficiency also worsened liver lipid accumulation and inflammation in TNF-α-treated Gulo -/- mice. In HepG2 cells, vitamin C reversed the TNF-α-induced reduction of glucose uptake and glycogen synthesis, which were mediated by increasing GLUT2 levels and the activation of the insulin receptor substrate (IRS-1)/AKT/GSK3β pathway. Furthermore, vitamin C inhibited the TNF-α-induced activation of not only the mitogen-activated protein kinase (MAPKs), but also nuclear factor-kappa B (NF-κB) signaling. Taken together, vitamin C is essential for preventing and improving insulin resistance, and the supplementing with vitamin C may be an effective therapeutic intervention for metabolic disorders. Copyright © 2018 Elsevier B.V. All rights reserved.

C3d enhanced DNA vaccination induced humoral immune response to glycoprotein C of pseudorabies virus

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

Tong Tiezhu; Provincial Key Laboratory of Preventive Veterinary Medicine, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan 430070; Fan Huiying

2006-09-08

Murine C3d were utilized to enhance immunogenicity of pseudorabies virus (PrV) gC DNA vaccination. Three copies of C3d and four copies of CR2-binding domain M28{sub 4} were fused, respectively, to truncated gC gene encoding soluble glycoprotein C (sgC) in pcDNA3.1. BALB/c mice were, respectively, immunized with recombinant plasmids, blank vector, and inactivated vaccine. The antibody ELISA titer for sgC-C3d{sub 3} DNA was 49-fold more than that for sgC DNA, and the neutralizing antibody obtained 8-fold rise. Protection of mice from death after lethal PrV (316 LD{sub 5}) challenge was augmented from 25% to 100%. Furthermore, C3d fusion increased Th2-biased immunemore » response by inducing IL-4 production. The IL-4 level for sgC-C3d{sub 3} DNA immunization approached that for the inactivated vaccine. Compared to C3d, M28 enhanced sgC DNA immunogenicity to a lesser extent. In conclusion, we demonstrated that murine C3d fusion significantly enhanced gC DNA immunity by directing Th1-biased to a balanced and more effective Th1/Th2 response.« less

Phosphine-substrate recognition through the C-H...O hydrogen bond: application to the asymmetric Pauson-Khand reaction.

PubMed

Solà, Jordi; Riera, Antoni; Verdaguer, Xavier; Maestro, Miguel A

2005-10-05

A unique methine moiety attached to three heteroatoms (O, P, S) and contained in the PuPHOS and CamPHOS ligands serves as a strong hydrogen-bond donor. Nonclassical hydrogen bonding of this methine with an amido-carbonyl acceptor provides a completely diastereoselective ligand exchange process between an alkyne dicobalthexacarbonyl complex and a phosphine ligand. This weak contact has been studied by means of X-ray analysis, 1H NMR, and quantum mechanical calculations and revealed that the present interaction falls in the range of strong C-H...O=C bonds. The hydrogen-bond bias obtained in the ligand exchange process has been exploited in the asymmetric intermolecular Pauson-Khand reaction to yield the corresponding cyclization adducts in up to 94% ee.

Crystal structure of rivastigmine hydrogen tartrate Form I (Exelon®), C 14H 23N 2O 2(C 4H 5O 6)

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

Kaduk, James A.; Zhong, Kai; Gindhart, Amy M.

2016-03-08

The crystal structure of rivastigmine hydrogen tartrate has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional techniques. Rivastigmine hydrogen tartrate crystallizes in space groupP2 1(#4) witha= 17.538 34(5),b= 8.326 89(2),c= 7.261 11(2) Å,β= 98.7999(2)°,V= 1047.929(4) Å 3, andZ= 2. The un-ionized end of the hydrogen tartrate anions forms a very strong hydrogen bond with the ionized end of another anion to form a chain. The ammonium group of the rivastigmine cation forms a strong discrete hydrogen bond with the carbonyl oxygen atom of the un-ionized end of the tartrate anion. These hydrogen bondsmore » form a corrugated network in thebc-plane. Both hydroxyl groups of the tartrate anion form intramolecular O–H···O hydrogen bonds. Several C–H···O hydrogen bonds appear to contribute to the crystal energy. The powder pattern is included in the Powder Diffraction File ™as entry 00-064-1501.« less

Enhanced activity of Au-Fe/C anodic electrocatalyst for direct borohydride-hydrogen peroxide fuel cell

NASA Astrophysics Data System (ADS)

Yi, Lanhua; Wei, Wei; Zhao, Caixian; Tian, Li; Liu, Jing; Wang, Xianyou

2015-07-01

Carbon supported Au-Fe bimetallic nanocatalysts (Au-Fe/C) are facilely prepared via a modified NaBH4 reduction method in aqueous solution at room temperature, and used as the anode electrocatalyst of direct borohydride-hydrogen peroxide fuel cell (DBHFC). The physical and electrochemical properties of the Au-Fe/C electrocatalysts are characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), cyclic voltammetry (CV), rotating disc electrode (RDE) voltammetry, chronoamperometry (CA), chronopotentiometry (CP), and fuel cell test. The results show that Au-Fe/C catalysts display higher catalytic activity for the direct electrooxidation of BH4- than carbon supported pure Au nanocatalyst (Au/C), especially Au50Fe50/C catalyst presents the highest catalytic activity among all as-prepared catalysts. Besides, the single DBHFC with Au50Fe50/C anode and Au/C cathode obtains the maximum power density as high as 34.9 mW cm-2 at 25 °C.

Experimental and theoretical studies of novel hydrogen diffuson in fullerite C_60

NASA Astrophysics Data System (ADS)

Fitzgerald, Stephen; Hannachi, Rym; Sholl, David; Sieber, Kurt; Gerogiorgis, Dimitrios

2004-03-01

Given the present interest in hydrogen storage within novel forms of carbon we have investigated the behavior of molecular H2 within solid fullerite C_60. Although C_60 will never be a practical storage medium, it does offer an ideal system to study the interaction of hydrogen within a well-characterized curved graphitic matrix. Our results based on infrared spectroscopy and loading isotherms indicate that isolated interstitial H2 bind preferentially in the lattice octahedral sites and diffuse by hopping between octahedral and tetrahedral sites^1. Parallel replica dynamics and minimum energy path calculations reveal an unexpected diffusion mechanism involving H2 molecules hopping into an already occupied octahedral site^2. This creates a short-lived H2 dimer, with a lower activation barrier for hopping that greatly enhances the diffusion rates. These calculations have been confirmed by experimental isotherm measurements and simulations using a rigorously derived lattice model that show a greatly reduced outgassing life-time with increasing H2 concentrations. ^1 S. A. FitzGerald, S. Forth and M. Rinkoski, Phys. Rev. B, 65, 140302 (2002). ^2 B. P. Uberuaga, A. F. Voter, K. K. Sieber, and D. S. Sholl, Phys. Rev. Lett., 91, 105901 (2003).

Mitochondria related peptide MOTS-c suppresses ovariectomy-induced bone loss via AMPK activation

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

Ming, Wei, E-mail: weiming@xiyi.edu.cn; Department of Pharmacology, Xi’an Medical University, Xi’an 710021; Lu, Gan, E-mail: leonming99@163.com

Therapeutic targeting bone loss has been the focus of the study in osteoporosis. The present study is intended to evaluate whether MOTS-c, a novel mitochondria related 16 aa peptide, can protect mice from ovariectomy-induced osteoporosis. After ovary removal, the mice were injected with MOTS-c at a dose of 5 mg/kg once a day for 12 weeks. Our results showed that MOTS-c treatment significantly alleviated bone loss, as determined by micro-CT examination. Mechanistically, we found that the receptor activator of nuclear factor-κB ligand (RANKL) induced osteoclast differentiation was remarkably inhibited by MOTS-c. Moreover, MOTS-c increased phosphorylated AMPK levels, and compound C, anmore » AMPK inhibitor, could partially abrogate the effects of the MOTS-c on osteoclastogenesis. Thus, our findings provide evidence that MOTS-c may exert as an inhibitor of osteoporosis via AMPK dependent inhibition of osteoclastogenesis. -- Highlights: •MOTS-c decreases OVX-induced bone loss in vivo. •MOTS-c inhibits RANKL-induced osteoclast formation. •MOTS-c inhibits RANKL-induced osteoclast-specific gene expression. •MOTS-c represses osteoclast differentiation via the activation of AMPK.« less

Zinc induces exposure of hydrophobic sites in the C-terminal domain of gC1q-R/p33.

PubMed

Kumar, Rajeev; Peerschke, Ellinor I B; Ghebrehiwet, Berhane

2002-09-01

Endothelial cells and platelets are known to express gC1q-R on their surface. In addition to C1q, endothelial cell gC1q-R has been shown to bind high molecular weight kininogen (HK) and factor XII (FXII). However, unlike C1q, whose interaction with gC1q-R does not require divalent ions, the binding of HK to gC1q-R is absolutely dependent on the presence of zinc. However, the mechanism by which zinc modulates this interaction is not fully understood. To investigate the role of zinc, binding studies were done using the hydrophobic dye, bis-ANS. The fluorescence intensity of bis-ANS, greatly increases and the emission maximum is blue-shifted from 525 to 485nm upon binding to hydrophobic sites on proteins. In this report, we show that a blue-shift in emission maximum is also observed when bis-ANS binds to gC1q-R in the presence but not in the absence of zinc suggesting that zinc induces exposure of hydrophobic sites in the molecule. The binding of bis-ANS to gC1q-R is specific, dose-dependent, and reversible. In the presence of zinc, this binding is abrogated by monoclonal antibody 74.5.2 directed against gC1q-R residues 204-218. This segment of gC1q-R, which corresponds to the beta6 strand in the crystal structure, has been shown previously to be the binding site for HK. A similar trend in zinc-induced gC1q-R binding was also observed using the hydrophobic matrix octyl-Sepharose. Taken together, our data suggest that zinc can induce the exposure of hydrophobic sites in the C-terminal domain of gC1q-R involved in binding to HK/FXII.

Creatine kinase MM TaqI and methylenetetrahydrofolate reductase C677T and A1298C gene polymorphisms influence exercise-induced C-reactive protein levels.

PubMed

Miranda-Vilela, Ana Luisa; Akimoto, Arthur K; Lordelo, Graciana S; Pereira, Luiz C S; Grisolia, Cesar K; Klautau-Guimarães, Maria de Nazaré

2012-01-01

Physical training induces beneficial adaptations, but exhausting exercise increases reactive oxygen species, which can cause muscular injuries with consequent inflammatory processes, implying jeopardized performance and possibly overtraining. Acute strenuous exercise almost certainly exceeds the benefits of physical activity; it can compromise performance and may contribute to increased future risk of cardiovascular disease (CVD) in athletes. Polymorphisms in the muscle-type creatine kinase (CK-MM) gene may influence performance and adaptation to training, while many potentially significant genetic variants are reported as risk factors for CVD. Therefore, we investigated the influence of polymorphisms in CK-MM TaqI and NcoI, methylenetetrahydrofolate reductase (MTHFR C677T and A1298C) and C-reactive protein (CRP G1059C) genes on exercise-induced damage and inflammation markers. Blood samples were taken immediately after a race (of at least 4 km) that took place outdoors on flat tracks, and were submitted to genotyping and biochemical evaluation of aspartate aminotransferase (AST), CK, CRP and high-sensitivity CRP (hs-CRP). CK-MM TaqI polymorphism significantly influenced results of AST, CK and hs-CRP, and an association between MTHFR C677T and A1298C with CRP level was found, although these levels did not exceed reference values. Results indicate that these polymorphisms can indirectly influence performance, contribute to higher susceptibility to exercise-induced inflammation or protection against it, and perhaps affect future risks of CVD in athletes.

Creatine kinase MM TaqI and methylenetetrahydrofolate reductase C677T and A1298C gene polymorphisms influence exercise-induced C-reactive protein levels.

PubMed

Miranda-Vilela, Ana Luisa; Akimoto, Arthur K; Lordelo, Graciana S; Pereira, Luiz C S; Grisolia, Cesar K; Klautau-Guimarães, Maria de Nazaré

2012-03-01

Physical training induces beneficial adaptations, but exhausting exercise increases reactive oxygen species, which can cause muscular injuries with consequent inflammatory processes, implying jeopardized performance and possibly overtraining. Acute strenuous exercise almost certainly exceeds the benefits of physical activity; it can compromise performance and may contribute to increased future risk of cardiovascular disease (CVD) in athletes. Polymorphisms in the muscle-type creatine kinase (CK-MM) gene may influence performance and adaptation to training, while many potentially significant genetic variants are reported as risk factors for CVD. Therefore, we investigated the influence of polymorphisms in CK-MM TaqI and NcoI, methylenetetrahydrofolate reductase (MTHFR C677T and A1298C) and C-reactive protein (CRP G1059C) genes on exercise-induced damage and inflammation markers. Blood samples were taken immediately after a race (of at least 4 km) that took place outdoors on flat tracks, and were submitted to genotyping and biochemical evaluation of aspartate aminotransferase (AST), CK, CRP and high-sensitivity CRP (hs-CRP). CK-MM TaqI polymorphism significantly influenced results of AST, CK and hs-CRP, and an association between MTHFR C677T and A1298C with CRP level was found, although these levels did not exceed reference values. The results indicate that these polymorphisms can indirectly influence performance, contribute to higher susceptibility to exercise-induced inflammation or protection against it, and perhaps affect future risks of CVD in athletes.

The acute phase response of C3, C5, ceruloplasmin, and C-reactive protein induced by turpentine pleurisy in the rabbit.

PubMed Central

Giclas, P. C.; Manthei, U.; Strunk, R. C.

1985-01-01

Concentrations of five serum proteins, C3, C5, ceruloplasmin, C-reactive protein, and albumin, have been measured during the acute phase response in rabbits with turpentine-induced pleurisy. C-reactive protein concentrations in the circulation rose abruptly between 12 and 36 hours to a level greater than 50 times the pretreatment concentration, then returned to undetectable amounts by 96 hours. C3 and ceruloplasmin both showed some increase in concentration by 12 hours and reached their maximum concentrations of two to three times the baseline levels 48-72 hours after the turpentine treatment. Concentrations were still elevated at 120 hours, after which time they gradually returned to normal. C5 and albumin concentrations in the turpentine-treated rabbits did not differ from the baseline concentrations. The same five proteins were measured in the inflammatory exudate. C-reactive protein was not detectable at any of the time points. C3, C5, ceruloplasmin, and albumin were present in normal pleural fluid at roughly half their serum concentrations. The activities of C3, C5, and ceruloplasmin were low in the early exudate, but C3 and C5 activity rose relative to their concentrations in the later samples of pleural fluid. The specific activities of C3 and C5 were higher in the pleural fluid at 72 hours than in plasma, while that of ceruloplasmin remained less in the pleural fluid than in plasma throughout the experiment. The involvement of these proteins and their relation to the inflammatory response are discussed. Images Figure 6 PMID:2409807

Ejection of the Massive Hydrogen-rich Envelope Timed with the Collapse of the Stripped SN 2014C

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

Margutti, Raffaella; Kamble, A.; Milisavljevic, D.

2017-02-01

We present multi-wavelength observations of SN 2014C during the first 500 days. These observations represent the first solid detection of a young extragalactic stripped-envelope SN out to high-energy X-rays ∼40 keV. SN 2014C shows ordinary explosion parameters ( E {sub k} ∼ 1.8 × 10{sup 51} erg and M {sub ej} ∼ 1.7 M{sub ⊙}). However, over an ∼1 year timescale, SN 2014C evolved from an ordinary hydrogen-poor supernova into a strongly interacting, hydrogen-rich supernova, violating the traditional classification scheme of type-I versus type-II SNe. Signatures of the SN shock interaction with a dense medium are observed across the spectrum,more » from radio to hard X-rays, and revealed the presence of a massive shell of ∼1 M {sub ⊙} of hydrogen-rich material at ∼6 × 10{sup 16} cm. The shell was ejected by the progenitor star in the decades to centuries before collapse. This result challenges current theories of massive star evolution, as it requires a physical mechanism responsible for the ejection of the deepest hydrogen layer of H-poor SN progenitors synchronized with the onset of stellar collapse. Theoretical investigations point at binary interactions and/or instabilities during the last nuclear burning stages as potential triggers of the highly time-dependent mass loss. We constrain these scenarios utilizing the sample of 183 SNe Ib/c with public radio observations. Our analysis identifies SN 2014C-like signatures in ∼10% of SNe. This fraction is reasonably consistent with the expectation from the theory of recent envelope ejection due to binary evolution if the ejected material can survive in the close environment for 10{sup 3}–10{sup 4} years. Alternatively, nuclear burning instabilities extending to core C-burning might play a critical role.« less

Computational simulation of the effects of oxygen on the electronic states of hydrogenated 3C-porous SiC

PubMed Central

2012-01-01

A computational study of the dependence of the electronic band structure and density of states on the chemical surface passivation of cubic porous silicon carbide (pSiC) was performed using ab initio density functional theory and the supercell method. The effects of the porosity and the surface chemistry composition on the energetic stability of pSiC were also investigated. The porous structures were modeled by removing atoms in the [001] direction to produce two different surface chemistries: one fully composed of silicon atoms and one composed of only carbon atoms. The changes in the electronic states of the porous structures as a function of the oxygen (O) content at the surface were studied. Specifically, the oxygen content was increased by replacing pairs of hydrogen (H) atoms on the pore surface with O atoms attached to the surface via either a double bond (X = O) or a bridge bond (X-O-X, X = Si or C). The calculations show that for the fully H-passivated surfaces, the forbidden energy band is larger for the C-rich phase than for the Si-rich phase. For the partially oxygenated Si-rich surfaces, the band gap behavior depends on the O bond type. The energy gap increases as the number of O atoms increases in the supercell if the O atoms are bridge-bonded, whereas the band gap energy does not exhibit a clear trend if O is double-bonded to the surface. In all cases, the gradual oxygenation decreases the band gap of the C-rich surface due to the presence of trap-like states. PMID:22913486

Infrared and Raman spectroscopy and quantum chemistry calculation studies of C H⋯O hydrogen bondings and thermal behavior of biodegradable polyhydroxyalkanoate

NASA Astrophysics Data System (ADS)

Sato, Harumi; Dybal, Jiří; Murakami, Rumi; Noda, Isao; Ozaki, Yukihiro

2005-06-01

This review paper reports infrared (IR) and Raman spectroscopy and quantum chemistry calculation studies of C-H⋯O hydrogen bondings and thermal behavior of biodegradable polyhydroxyalkanoates. IR and Raman spectra were measured for poly(3-hydroxybutyrate) (PHB) and a new type of bacterial copolyester, poly(3-hydroxybutyrate- co-3-hydroxyhexanoate), P(HB- co-HHx) (HHx=12 mol%) over a temperature range of 20 °C to higher temperatures (PHB, 200 °C; HHx=12 mol%, 140 °C) to explore their structure and thermal behavior. One of bands due to the CH 3 asymmetric stretching modes appears near 3010 cm -1 in the IR and Raman spectra of PHB and P(HB- co-HHx) at 20 °C. These frequencies of IR and Raman CH 3 asymmetric stretching bands are much higher than usual. These anomalous frequencies of the CH 3 asymmetric stretching bands together with the X-ray crystallographic structure of PHB have suggested that there is an inter- or intra-molecular C-H⋯O hydrogen bond between the C dbnd6 O group in one helical structure and the CH 3 group in the other helical structure in PHB and P(HB- co-HHx). The quantum chemical calculation of model compounds of PHB also has suggested the existence of C-H⋯O hydrogen bonds in PHB and P(HB- co-HHx). It is very likely that a chain of C-H⋯O hydrogen bond pairs link two parallel helical structures in the crystalline parts. The temperature-dependent IR and Raman spectral variations have revealed that the crystallinity of P(HB- co-HHx) (HHx=12 mol%) decreases gradually from a fairly low temperature (about 60 °C), while the crystallinity of PHB remains almost unchanged until just below its melting temperature. It has also been found from the IR and Raman studies that for both PHB and P(HB- co-HHx) the weakening of the C-H⋯O hydrogen bonds starts from just above room temperature, but the deformation of helical structures occurs after the weakening of the C-H⋯O hydrogen bonds advances to some extent.

Reduced-HMGB1 suppresses poly(I:C)-induced inflammation in keratinocytes.

PubMed

Mori, Hideki; Murakami, Masamoto; Tsuda, Teruko; Kameda, Kenji; Utsunomiya, Ryo; Masuda, Kana; Shiraishi, Ken; Dai, Xiuju; Tohyama, Mikiko; Nakaoka, Hiroki; Sayama, Koji

2018-05-01

High mobility group box 1 (HMGB1) is a nuclear protein that stabilizes DNA and facilitates gene transcription. Additionally, cell stress or death induces the release of HMGB1 outside the cell membrane, where HMGB1 functions as an alarmin, causing an inflammatory response in combination with other cytokines, damage-associated molecular patterns (DAMPs), and pathogen-associated molecular patterns (PAMPs). To evaluate the effect of reduced-HMGB1 (previously termed chemoattractive-HMGB1) on polyinosine-polycytidylic acid [poly(I:C)]-induced inflammation in normal human keratinocytes (NHKs). We focused on downstream components of the poly(I:C)-Toll-like receptor 3 (TLR3), retinoic acid-inducible gene-I (RIG-I), and melanoma differentiation-associated protein 5 (MDA5) pathways, including IκBα, nuclear factor (NF)-κB p65, mitogen-activated protein kinase (MAPK), and interferon regulatory factor 3 (IRF3), and assessed whether these pathways are involved in the suppression of poly(I:C)-induced inflammation in NHKs by HMGB1. An immunoprecipitation was performed to know whether HMGB1 could bind to poly(I:C), and immunofluorescence staining and flow cytometric analysis were performed to check whether reduced-HMGB interferes with cellular uptake of poly(I:C) translocation (possibly by endocytosis). Application of exogenous HMGB1 before, but not after, exerted a suppressive effect on poly(I:C)-induced inflammation in NHKs. In addition, reduced-HMGB1, but not disulfide-HMGB1, exerted a suppressive effect on poly(I:C)-induced inflammation in NHKs, suggesting the importance of the redox status of exogenous HMGB1. Pre-treatment with reduced-HMGB1 inhibited the phosphorylation of IκBα, NF-κB p65, and IRF3 induced by poly(I:C) stimulation in NHKs; however, phosphorylation of p38, extracellular signal-regulated kinase (ERK), and c-Jun N-terminal kinase (JNK) was unaffected. Disulfide-HMGB1 formed a complex with poly(I:C), as did reduced- and oxidized-HMGB1, albeit to a lesser

Mitomycin C-induced apoptosis in cultured human Tenon's capsule fibroblasts.

PubMed

Kim, J W; Kim, S K; Song, I H; Kim, I T

1999-06-01

To investigate the mitomycin C-induced apoptotic cell death of fibroblasts, the primarily cultured human Tenon's capsule fibroblasts were exposed to a clinically used dosage of 0.4 mg/ml of mitomycin C for 5 minutes. TUNEL (TdT-mediated dUTP-biotin nick end labeling) assay and electron microscopic studies were performed to determine the extent of mitomycin C-induced apoptosis. A flow cytometric study was performed to quantify the apoptotic cell population over time. The TUNEL stains were positive and electron microscopy showed features of apoptotic cell death in some fibroblasts 3 and 5 days after treatment. Flow cytometric analysis using Annexin V-propidium iodide double staining detected apoptotic cells 3 days after treatment. These apoptotic cell populations increased at 4 days and were sustained for one week. This study revealed that the clinical effects of mitomycin C on fibroblasts may be mediated not only by antiproliferative but also apoptotic cell death to some degree. Therefore, the apoptotic cell death of fibroblasts induced by mitomycin C should be considered to properly understand the mechanism of wound healing after trabeculectomy with adjunctive mitomycin C.

Absence of PDGF-induced, PKC-independent c-fos expression in a chemically transformed C3H/10T1/2 cell clone.

PubMed

Vassbotn, F S; Skar, R; Holmsen, H; Lillehaug, J R

1992-09-01

The effect of platelet-derived growth factor (PDGF) on c-fos mRNA transcription was studied in the immortalized mouse embryo fibroblast C3H/10T1/2 Cl 8 (10T1/2) cells and the chemically transformed, tumorigenic subclone C3H/10T1/2 Cl 16 (Cl 16). In the 10T1/2 cells as well as the Cl 16 subclone, the dose-dependent PDGF stimulation of c-fos mRNA synthesis was similar in both logarithmically growing and confluent cultures. c-fos mRNA was induced severalfold by 12-O-tetradecanoylphorbol-13-acetate (TPA) in both 10T1/2 and Cl 16. Down-regulation of protein kinase C (PKC) activity by TPA pretreatment inhibited PDGF-stimulated c-fos mRNA expression in Cl 16 cells but did not affect this induction in the 10T1/2 cells. This inhibition was not a general phenomenon of 3-methylcholanthrene-mediated transformation of 10T1/2 cells since experiments with another transformed 10T1/2 cell clone, C3H/10T1/2 TPA 482, gave qualitatively the same results as the 10T1/2 cells. Receptor binding experiments showed that the nontransformed and transformed cells had a comparable number of PDGF receptors, 1.3 x 10(5) and 0.7 x 10(5) receptors per cell, respectively. Furthermore, cAMP-induced c-fos expression induced by forskolin is formerly shown to be independent of PKC down-regulation. In our experiments, forskolin induced c-fos expression in both clones. However, PKC down-regulation inhibited the forskolin-induced c-fos expression in Cl 16 cells. This apparently demonstrates cross talk between PKC and PKA in the c-fos induction pathway. The present results provide evidence for an impaired mechanism for activating c-fos expression through PKC-independent, PDGF-induced signal transduction in the chemically transformed Cl 16 fibroblasts compared to that in nontransformed 10T1/2 cells.

Sm@C2v(3)-C80: site-hopping motion of endohedral Sm atom and metal-induced effect on redox profile

NASA Astrophysics Data System (ADS)

Xu, Wei; Niu, Ben; Shi, Zujin; Lian, Yongfu; Feng, Lai

2012-10-01

A new metallofullerene Sm@C2v(3)-C80 was synthesized and characterized. X-Ray analysis showed that the endohedral Sm atom undergoes a hopping motion between several off-center sites, even at low temperature. In addition, a comparative electrochemical study between Sm@C2v(3)-C80 and Yb@C2v(3)-C80 revealed their different redox potentials, suggesting a metal-induced effect on their redox profiles.A new metallofullerene Sm@C2v(3)-C80 was synthesized and characterized. X-Ray analysis showed that the endohedral Sm atom undergoes a hopping motion between several off-center sites, even at low temperature. In addition, a comparative electrochemical study between Sm@C2v(3)-C80 and Yb@C2v(3)-C80 revealed their different redox potentials, suggesting a metal-induced effect on their redox profiles. CCDC reference number 894168. For crystallographic data in CIF or other electronic format see DOI: 10.1039/c2nr32193a

Desulfurization of Thiophene on Au/TiC(001): Au−C Interactions and Charge Polarization

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

Rodriguez, J.; Liu, P; Takahashi, Y

2009-01-01

Photoemission and first-principles DF calculations were used to study the interaction of thiophene with TiC(001) and Au/TiC(001) surfaces. The adsorption strength of thiophene on TiC(001) is weak, and the molecule desorbs at temperatures below 200 K. The molecule binds to Ti centers of TiC(001) through its sulfur atom with negligible structural perturbations. In spite of the very poor desulfurization performance of TiC(001) or Au(111), a Au/TiC(001) system displays a hydrodesulfurization activity higher than that of conventional Ni/MoS{sub x} catalysts. The Au?TiC(001) interactions induce a polarization of electron density around Au which substantially increases the chemical reactivity of this metal. Aumore » nanoparticles drastically increase the hydrodesulfurization activity of TiC(001) by enhancing the bonding energy of thiophene and by helping in the dissociation of H{sub 2} to produce the hydrogen necessary for the hydrogenolysis of C-S bonds and the removal of sulfur. H{sub 2} spontaneously dissociates on small two-dimensional clusters of gold in contact with TiC(001). On these systems, the adsorption energy of thiophene is 0.45-0.65 eV larger than that on TiC(001) or Au(111). Thiophene binds in a ?5 configuration with a large elongation ({approx}0.2 {angstrom}) of the C-S bonds.« less

Fluopsin C induces oncosis of human breast adenocarcinoma cells.

PubMed

Ma, Li-sha; Jiang, Chang-you; Cui, Min; Lu, Rong; Liu, Shan-shan; Zheng, Bei-bei; Li, Lin; Li, Xia

2013-08-01

Fluopsin C, an antibiotic isolated from Pseudomonas jinanesis, has shown antitumor effects on several cancer cell lines. In the current study, the oncotic cell death induced by fluopsin C was investigated in human breast adenocarcinoma cells in vitro. Human breast adenocarcinoma cell lines MCF-7 and MD-MBA-231 were used. The cytotoxicity was evaluated using MTT assay. Time-lapse microscopy and transmission electron microscopy were used to observe the morphological changes. Cell membrane integrity was assessed with propidium iodide (PI) uptake and lactate dehydrogenase (LDH) assay. Flow cytometry was used to measure reactive oxygen species (ROS) level and mitochondrial membrane potential (Δψm). A multimode microplate reader was used to analyze the intracellular ATP level. The changes in cytoskeletal system were investigated with Western blotting and immunostaining. Fluopsin C (0.5-8 μmol/L) reduced the cell viability in dose- and time-dependent manners. Its IC50 values in MCF-7 and MD-MBA-231 cells at 24 h were 0.9 and 1.03 μmol/L, respectively. Fluopsin C (2 μmol/L) induced oncosis in both the breast adenocarcinoma cells characterized by membrane blebbing and swelling, which was blocked by pretreatment with the pan-caspase inhibitor Z-VAD-fmk. In MCF-7 cells, fluopsin C caused PI uptake into the cells, significantly increased LDH release, induced cytoskeletal system degradation and ROS accumulation, decreased the intracellular ATP level and Δψm. Noticeably, fluopsin C exerted comparable cytotoxicity against the normal human hepatocytes (HL7702) and human mammary epithelial cells with the IC50 values at 24 h of 2.7 and 2.4 μmol/L, respectively. Oncotic cell death was involved in the anticancer effects of fluopsin C on human breast adenocarcinoma cells in vitro. The hepatoxicity of fluopsin C should not be ignored.

Inhibition of Rho Is Required for cAMP-induced Melanoma Cell Differentiation

PubMed Central

Buscà, Roser; Bertolotto, Corine; Abbe, Patricia; Englaro, Walter; Ishizaki, Toshimasa; Narumiya, Shuh; Boquet, Patrice; Ortonne, Jean-Paul; Ballotti, Robert

1998-01-01

Up-regulation of the cAMP pathway by forskolin or α-melanocyte stimulating hormone induces melanocyte and melanoma cell differentiation characterized by stimulation of melanin synthesis and dendrite development. Here we show that forskolin-induced dendricity is associated to a disassembly of actin stress fibers. Since Rho controls actin organization, we studied the role of this guanosine triphosphate (GTP)-binding protein in cAMP-induced dendrite formation. Clostridium botulinum C3 exotransferase, which inhibits Rho, mimicked the effect of forskolin in promoting dendricity and stress fiber disruption, while the Escherichia coli toxin cytotoxic necrotizing factor-1 (CNF-1), which activates Rho and the expression of a constitutively active Rho mutant, blocked forskolin-induced dendrite outgrowth. In addition, overexpression of a constitutively active form of the Rho target p160 Rho-kinase (P160ROCK) prevented the dendritogenic effects of cAMP. Our results suggest that inhibition of Rho and of its target p160ROCK are required events for cAMP-induced dendrite outgrowth in B16 cells. Furthermore, we present evidence that Rho is involved in the regulation of melanogenesis. Indeed, Rho inactivation enhanced the cAMP stimulation of tyrosinase gene transcription and protein expression, while Rho constitutive activation impaired these cAMP-induced effects. This reveals that, in addition to controlling dendricity, Rho also participates in the regulation of melanin synthesis by cAMP. PMID:9614180

Testing of DLR C/C-SiC for HIFiRE 8 Scramjet Combustor

NASA Technical Reports Server (NTRS)

Glass, David E.; Capriotti, Diego P.; Reimer, Thomas; Kutemeyer, Marius; Smart, Michael

2013-01-01

Ceramic Matrix Composites (CMCs) have been proposed for hot structures in scramjet combustors. Previous studies have calculated significant weight savings by utilizing CMCs (active and passive) versus actively cooled metallic scramjet structures. Both a C/C and a C/C-SiC material system fabricated by DLR (Stuttgart, Germany) are being considered for use in a passively cooled combustor design for HIFiRE 8, a joint Australia / AFRL hypersonic flight program, expected to fly at Mach 7 for approximately 30 sec, at a dynamic pressure of 55 kPa. Flat panels of the DLR C/C and the C/C-SiC were tested in the NASA Langley Direct Connect Rig (DCR) at Mach 5 and Mach 6 enthalpy for several minutes. Gaseous hydrogen fuel was used to fuel the scramjet combustor. The test panels were instrumented with embedded Type K and Type S thermocouples. Zirconia felt insulation was used in some of the tests to increase the surface temperature of the C/C-SiC panel for approximately 350degF. The final C/C-SiC panel was tested for 3 cycles totaling over 135 sec at Mach 6 enthalpy. Slightly more erosion was observed on the C/C panel than the C/C-SiC panels, but both material systems demonstrated acceptable recession performance for the HIFiRE 8 flight.

Ethanol inhibits thrombin-induced secretion by human platelets at a site distinct from phospholipase C or protein kinase C.

PubMed Central

Benistant, C; Rubin, R

1990-01-01

Ethanol is known to inhibit the activation of platelets in response to several physiological agonists, but the mechanism of this action is unclear. The addition of physiologically relevant concentrations of ethanol (25-150 mM) to suspensions of washed human platelets resulted in the inhibition of thrombin-induced secretion of 5-hydroxy[14C]tryptamine. Indomethacin was included in the incubation buffer to prevent feedback amplification by arachidonic acid metabolites. Ethanol had no effect on the activation of phospholipase C by thrombin, as determined by the formation of inositol phosphates and the mobilization of intracellular Ca2+. Moreover, ethanol did not interfere with the thrombin-induced formation of diacylglycerol or phosphatidic acid. Stimulation of platelets with phorbol ester (5-50 nM) resulted in 5-hydroxy[14C]tryptamine release comparable with those with threshold doses of thrombin. However, ethanol did not inhibit phorbol-ester-induced secretion. Ethanol also did not interfere with thrombin- or phorbol-ester-induced phosphorylation of myosin light chain (20 kDa) or a 47 kDa protein, a known substrate for protein kinase C. By electron microscopy, ethanol had no effect on thrombin-induced shape change and pseudopod formation, but prevented granule centralization and fusion. The results indicate that ethanol does not inhibit platelet secretion by interfering with the activation of phosphoinositide-specific phospholipase C or protein kinase C by thrombin. Rather, the data demonstrate an inhibition of a Ca2(+)-mediated event such as granule centralization. Images p495-a PMID:2117442

Rapid thermal annealing of Amorphous Hydrogenated Carbon (a-C:H) films

NASA Technical Reports Server (NTRS)

Alterovitz, Samuel A.; Pouch, John J.; Warner, Joseph D.

1987-01-01

Amorphous hydrogenated carbon (a-C:H) films were deposited on silicon and quartz substrates by a 30 kHz plasma discharge technique using methane. Rapid thermal processing of the films was accomplished in nitrogen gas using tungsten halogen light. The rapid thermal processing was done at several fixed temperatures (up to 600 C), as a function of time (up to 1800 sec). The films were characterized by optical absorption and by ellipsometry in the near UV and the visible. The bandgap, estimated from extrapolation of the linear part of a Tauc plot, decreases both with the annealing temperature and the annealing time, with the temperature dependence being the dominating factor. The density of states parameter increases up to 25 percent and the refractive index changes up to 20 percent with temperature increase. Possible explanations of the mechanisms involved in these processes are discussed.

Ortho and para hydrogen dimers on G/SiC(0001): combined STM and DFT study.

PubMed

Merino, P; Švec, M; Martínez, J I; Mutombo, P; Gonzalez, C; Martín-Gago, J A; de Andres, P L; Jelinek, P

2015-01-01

The hydrogen (H) dimer structures formed upon room-temperature H adsorption on single layer graphene (SLG) grown on SiC(0001) are addressed using a combined theoretical-experimental approach. Our study includes density functional theory (DFT) calculations for the full (6√3 × 6√3)R30° unit cell of the SLG/SiC(0001) substrate and atomically resolved scanning tunneling microscopy images determining simultaneously the graphene lattice and the internal structure of the H adsorbates. We show that H atoms normally group in chemisorbed coupled structures of different sizes and orientations. We make an atomic scale determination of the most stable experimental geometries, the small dimers and ellipsoid-shaped features, and we assign them to hydrogen adsorbed in para dimers and ortho dimers configuration, respectively, through comparison with the theory.

Solvation Thermodynamic Properties of Hydrogen Sulfide in [C4mim][PF6], [C4mim][BF4], and [C4mim][Cl] Ionic Liquids, Determined by Molecular Simulations.

PubMed

Sánchez-Badillo, Joel; Gallo, Marco; Alvarado, Sandra; Glossman-Mitnik, Daniel

2015-08-20

Removal of hydrogen sulfide (H2S) and acid gases from natural gas is accomplished by absorption processes using a solvent. The gas solubility in a liquid can be used to measure the degree of removal of the gas and is quantified by the Henry's constant, the free energy of solvation at infinite dilution, or the excess chemical potential. In this work, Henry's constants and thermodynamic properties of solvation of H2S were calculated in three ionic liquids: [C4mim][PF6], [C4mim][BF4], and [C4mim][Cl] ([C4mim], 1-butyl-3-methyl imidazolium). The first step in this work was the evaluation of the force fields for the gas and condensed phases in order to obtain accurate values for the excess chemical potential for H2S on each ionic liquid using free energy perturbation techniques. In the H2S-[C4mim][PF6] and H2S-[C4mim][BF4] systems, the results obtained by molecular simulation agree with the experimental values reported in the literature. However, the solvation free energy calculated for the H2S-[C4mim][Cl] system can be considered predictive because of the lack of experimental data at the simulated conditions. Based on these results, the best solvent for removing H2S is [C4mim][Cl] because it has the highest affinity for this species (lowest value of the Henry's constant). Also, solvation thermodynamic properties such as enthalpy and entropy were calculated in order to evaluate their contribution to the free energy of solvation.

Emodin attenuates TNF-α-induced apoptosis and autophagy in mouse C2C12 myoblasts though the phosphorylation of Akt.

PubMed

Chen, Dexiu; Liu, Junshan; Lu, Lu; Huang, Yanfeng; Wang, Yanjing; Wang, Mingqing; Liu, Yangyang; Xie, Dandan; Chen, Jiebing; Diao, Jianxin; Wei, Lianbo; Wang, Ming

2016-05-01

Emodin, a major component of Rheum palmatum, has been reported to significantly protect neural tissue against apoptosis and autophagy. However, the effects and underlying mechanisms of action of emodin in muscle atrophy are still poorly defined. In this study, we investigated the protective effects and the underlying mechanisms by which emodin acts on tumor necrosis factor alpha (TNF-α)-induced apoptosis and autophagy in mouse C2C12 myoblasts. Emodin, at various concentrations, decreased TNF-α-induced apoptosis in C2C12 myoblasts, which were analyzed by Hoechst 33342 staining and annexin V/PI analysis. Emodin also inhibited the collapse of the mitochondrial membrane potential and the generation of reactive oxygen species in TNF-α-stimulated C2C12 myoblasts. Consistent with these results, the expression of Bcl-2 was increased, whereas the expression of Bax, cleaved-caspase 3 and cleaved-PARP was decreased after emodin treatment. These data demonstrate that emodin attenuated apoptosis in TNF-α-stimulated C2C12 myoblasts through mitochondrial signaling pathways. In addition, emodin inhibited autophagy in TNF-α-stimulated C2C12 myoblasts by suppressing the expression of LC3-II, Beclin-1 and Atg7. Emodin also resulted in the upregulation of the phosphorylated forms of Akt. Taken together, these results suggest that emodin inhibited apoptosis and autophagy in TNF-α-induced C2C12 myoblasts, possibly through the activation of phosphorylated Akt. Our findings suggest that emodin could be a potential therapeutic agent in the treatment of muscle atrophy. Copyright © 2016 Elsevier B.V. All rights reserved.

Light-induced yellowing of selectively 13C-enriched dehydrogenation polymers (DHPs). Part 1, Side-chain 13C-enriched DHP ([alpha], [beta], and [gamma]-13C)

Treesearch

Jim Parkas; Magnus Paulsson; Terashima Noritsugu; Ulla Westermark; Sally Ralph

2004-01-01

Light-induced yellowing has been studied using side-chain ([alpha], [beta], and [gamma]) 13C-enriched DHP (dehydrogenation polymer) and quantitative solution state 13C NMR spectroscopy. The DHP was formed from 13C-enriched coniferin using an enzymatic system consisting of [beta]-glucosidase, glucose oxidase, and peroxidase in a pH 6 buffer solution. The DHP was applied...

Peroxidative permeabilization of liposomes induced by cytochrome c/cardiolipin complex.

PubMed

Firsov, Alexander M; Kotova, Elena A; Korepanova, Evgeniya A; Osipov, Anatoly N; Antonenko, Yuri N

2015-03-01

Interaction of cytochrome c with mitochondrial cardiolipin converting this electron transfer protein into peroxidase is accepted to play an essential role in apoptosis. Cytochrome c/cardiolipin peroxidase activity was found here to cause leakage of carboxyfluorescein, sulforhodamine B and 3-kDa (but not 10-kDa) fluorescent dextran from liposomes. A marked decrease in the amplitude of the autocorrelation function was detected with a fluorescence correlation spectroscopy setup upon incubation of dye-loaded cardiolipin-containing liposomes with cytochrome c and H2O2, thereby showing release of fluorescent markers from liposomes. The cytochrome c/H2O2-induced liposome leakage was suppressed upon increasing the ionic strength, in contrast to the leakage provoked by Fe/ascorbate, suggesting that the binding of cyt c to negatively-charged membranes was required for the permeabilization process. The cyt c/H2O2-induced liposome leakage was abolished by cyanide presumably competing with H2O2 for coordination with the central iron atom of the heme in cyt c. The cytochrome c/H2O2 permeabilization activity was substantially diminished by antioxidants (trolox, butylhydroxytoluene and quercetin) and was precluded if fully saturated tetramyristoyl-cardiolipin was substituted for bovine heart cardiolipin. These data favor the involvement of oxidized cardiolipin molecules in membrane permeabilization resulting from cytochrome c/cardiolipin peroxidase activity. In agreement with previous observations, high concentrations of cyt c induced liposome leakage in the absence of H2O2, however this process was not sensitive to antioxidants and cyanide suggesting direct membrane poration by the protein without the involvement of lipid peroxidation. Copyright © 2014 Elsevier B.V. All rights reserved.

Nitric oxide regulates stretch-induced proliferation in C2C12 myoblasts.

PubMed

Soltow, Quinlyn A; Lira, Vitor A; Betters, Jenna L; Long, Jodi H D; Sellman, Jeff E; Zeanah, Elizabeth H; Criswell, David S

2010-09-01

Mechanical stretch of skeletal muscle activates nitric oxide (NO) production and is an important stimulator of satellite cell proliferation. Further, cyclooxygenase (COX) activity has been shown to promote satellite cell proliferation in response to stretch. Since COX-2 expression in skeletal muscle can be regulated by NO we sought to determine if NO is required for stretch-induced myoblast proliferation and whether supplemental NO can counter the effects of COX-2 and NF-kappaB inhibitors. C2C12 myoblasts were cultured for 24 h, then switched to medium containing either the NOS inhibitor, L-NAME (200 microM), the COX-2 specific inhibitor NS-398 (100 microM), the NF-kappaB inhibiting antioxidant, PDTC (5 mM), the nitric oxide donor, DETA-NONOate (10-100 microM) or no supplement (control) for 24 h. Subgroups of each treatment were exposed to 1 h of 15% cyclic stretch (1 Hz), and were then allowed to proliferate for 24 h before fixing. Proliferation was measured by BrdU incorporation during the last hour before fixing, and DAPI stain. Stretch induced a twofold increase in nuclear number compared to control, and this effect was completely inhibited by L-NAME, NS-398 or PDTC (P < 0.05). Although DETA-NONOate (10 microM) did not affect basal proliferation, the NO-donor augmented the stretch-induced increase in proliferation and rescued stretch-induced proliferation in NS-398-treated cells, but not in PDTC-treated cells. In conclusion, NO, COX-2, and NF-kappaB are necessary for stretch-induced proliferation of myoblasts. Although COX-2 and NF-kappaB are both involved in basal proliferation, NO does not affect basal growth. Thus, NO requires the synergistic effect of stretch in order to induce muscle cell proliferation.

Fundamental study of hydrogen-attachment-induced peptide fragmentation occurring in the gas phase and during the matrix-assisted laser desorption/ionization process.

PubMed

Asakawa, Daiki; Takahashi, Hidenori; Iwamoto, Shinichi; Tanaka, Koichi

2018-05-09

Mass spectrometry with hydrogen-radical-mediated fragmentation techniques has been used for the sequencing of proteins/peptides. The two methods, matrix-assisted laser desorption/ionization in-source decay (MALDI-ISD) and hydrogen attachment/abstraction dissociation (HAD) are known as hydrogen-radical-mediated fragmentation techniques. MALDI-ISD occurs during laser induced desorption processes, whereas HAD utilizes the association of hydrogen with peptide ions in the gas phase. In this study, the general mechanisms of MALDI-ISD and HAD of peptides were investigated. We demonstrated the fragmentation of four model peptides and investigated the fragment formation pathways using density functional theory (DFT) calculations. The current experimental and computational joint study indicated that MALDI-ISD and HAD produce aminoketyl radical intermediates, which immediately undergo radical-induced cleavage at the N-Cα bond located on the C-terminal side of the radical site, leading to the c'/z˙ fragment pair. In the case of MALDI-ISD, the z˙ fragments undergo a subsequent reaction with the matrix to give z' and matrix adducts of the z fragments. In contrast, the c' and z˙ fragments react with hydrogen atoms during the HAD processes, and various fragment species, such as c˙, c', z˙ and z', were observed in the HAD-MS/MS mass spectra.

DsbA-L prevents obesity-induced inflammation and insulin resistance by suppressing the mtDNA release-activated cGAS-cGAMP-STING pathway

PubMed Central

Cervantes, Christopher; Liu, Juan; He, Sijia; Zhou, Haiyan; Zhang, Bilin; Cai, Huan; Yin, Dongqing; Hu, Derong; Li, Zhi; Chen, Hongzhi; Gao, Xiaoli; Wang, Fang; O’Connor, Jason C.; Xu, Yong; Liu, Meilian; Dong, Lily Q.

2017-01-01

Chronic inflammation in adipose tissue plays a key role in obesity-induced insulin resistance. However, the mechanisms underlying obesity-induced inflammation remain elusive. Here we show that obesity promotes mtDNA release into the cytosol, where it triggers inflammatory responses by activating the DNA-sensing cGAS-cGAMP-STING pathway. Fat-specific knockout of disulfide-bond A oxidoreductase-like protein (DsbA-L), a chaperone-like protein originally identified in the mitochondrial matrix, impaired mitochondrial function and promoted mtDNA release, leading to activation of the cGAS-cGAMP-STING pathway and inflammatory responses. Conversely, fat-specific overexpression of DsbA-L protected mice against high-fat diet-induced activation of the cGAS-cGAMP-STING pathway and inflammation. Taken together, we identify DsbA-L as a key molecule that maintains mitochondrial integrity. DsbA-L deficiency promotes inflammation and insulin resistance by activating the cGAS-cGAMP-STING pathway. Our study also reveals that, in addition to its well-characterized roles in innate immune surveillance, the cGAS-cGAMP-STING pathway plays an important role in mediating obesity-induced metabolic dysfunction. PMID:29087318

DsbA-L prevents obesity-induced inflammation and insulin resistance by suppressing the mtDNA release-activated cGAS-cGAMP-STING pathway.

PubMed

Bai, Juli; Cervantes, Christopher; Liu, Juan; He, Sijia; Zhou, Haiyan; Zhang, Bilin; Cai, Huan; Yin, Dongqing; Hu, Derong; Li, Zhi; Chen, Hongzhi; Gao, Xiaoli; Wang, Fang; O'Connor, Jason C; Xu, Yong; Liu, Meilian; Dong, Lily Q; Liu, Feng

2017-11-14

Chronic inflammation in adipose tissue plays a key role in obesity-induced insulin resistance. However, the mechanisms underlying obesity-induced inflammation remain elusive. Here we show that obesity promotes mtDNA release into the cytosol, where it triggers inflammatory responses by activating the DNA-sensing cGAS-cGAMP-STING pathway. Fat-specific knockout of disulfide-bond A oxidoreductase-like protein (DsbA-L), a chaperone-like protein originally identified in the mitochondrial matrix, impaired mitochondrial function and promoted mtDNA release, leading to activation of the cGAS-cGAMP-STING pathway and inflammatory responses. Conversely, fat-specific overexpression of DsbA-L protected mice against high-fat diet-induced activation of the cGAS-cGAMP-STING pathway and inflammation. Taken together, we identify DsbA-L as a key molecule that maintains mitochondrial integrity. DsbA-L deficiency promotes inflammation and insulin resistance by activating the cGAS-cGAMP-STING pathway. Our study also reveals that, in addition to its well-characterized roles in innate immune surveillance, the cGAS-cGAMP-STING pathway plays an important role in mediating obesity-induced metabolic dysfunction.

Low molecular weight guluronate prevents TNF-α-induced oxidative damage and mitochondrial dysfunction in C2C12 skeletal muscle cells.

PubMed

Dun, Yun-lou; Zhou, Xiao-lin; Guan, Hua-shi; Yu, Guang-li; Li, Chun-xia; Hu, Ting; Zhao, Xia; Cheng, Xiao-lei; He, Xiao-xi; Hao, Jie-jie

2015-09-01

Muscle wasting is associated with a variety of chronic or inflammatory disorders. Evidence suggests that inflammatory cytokines play a vital role in muscle inflammatory pathology and this may result in oxidative damage and mitochondrial dysfunction in skeletal muscle. In our study, we used microwave degradation to prepare a water-soluble low molecular weight guluronate (LMG) of 3000 Da from Fucus vesiculosus obtained from Canada, the Atlantic Ocean. We demonstrated the structural characteristics, using HPLC, FTIR and NMR of LMG and investigated its effects on oxidative damage and mitochondrial dysfunction in C2C12 skeletal muscle cells induced by tumor necrosis factor alpha (TNF-α), a cell inflammatory cytokine. The results indicated that LMG could alleviate mitochondrial reactive oxygen species (ROS) production, increase the activities of antioxidant enzymes (GSH and SOD), promote mitochondrial membrane potential (MMP) and upregulate the expression of mitochondrial respiratory chain protein in TNF-α-induced C2C12 cells. LMG supplement also increased the mitochondrial DNA copy number and mitochondrial biogenesis related genes in TNF-α-induced C2C12 cells. LMG may exert these protective effects through the nuclear factor kappa B (NF-κB) signaling pathway. These suggest that LMG is capable of protecting TNF-α-induced C2C12 cells against oxidative damage and mitochondrial dysfunction.

Conditions Inducing Excessive O-GlcNAcylation Inhibit BMP2-Induced Osteogenic Differentiation of C2C12 Cells.

PubMed

Gu, Hanna; Song, Mina; Boonanantanasarn, Kanitsak; Baek, Kyunghwa; Woo, Kyung Mi; Ryoo, Hyun-Mo; Baek, Jeong-Hwa

2018-01-09

Hyperglycemic conditions in diabetic patients can affect various cellular functions, including the modulation of osteogenic differentiation. However, the molecular mechanisms by which hyperglycemia affects osteogenic differentiation are yet to be clarified. This study aimed to investigate whether the aberrant increase in protein O -linked-β- N -acetylglucosamine glycosylation ( O -GlcNAcylation) contributes to the suppression of osteogenic differentiation due to hyperglycemia. To induce osteogenic differentiation, C2C12 cells were cultured in the presence of recombinant human bone morphogenetic protein 2 (BMP2). Excessive protein O -GlcNAcylation was induced by treating C2C12 cells with high glucose, glucosamine, or N -acetylglucosamine concentrations or by O -GlcNAc transferase (OGT) overexpression. The effect of O -GlcNAcylation on osteoblast differentiation was then confirmed by examining the expression levels of osteogenic marker gene mRNAs, activity of alkaline phosphatase, and transcriptional activity of Runx2, a critical transcription factor for osteoblast differentiation and bone formation. Cell treatment with high glucose, glucosamine or N -acetylglucosamine increased O -GlcNAcylation of Runx2 and the total levels of O -GlcNAcylated proteins, which led to a decrease in the transcriptional activity of Runx2, expression levels of osteogenic marker genes (Runx2, osterix, alkaline phosphatase, and type I collagen), and activity of alkaline phosphatase. These inhibitory effects were rescued by lowering protein O -GlcNAcylation levels by adding STO45849, an OGT inhibitor, or by overexpressing β- N -acetylglucosaminidase. Our findings suggest that excessive protein O -GlcNAcylation contributes to high glucose-suppressed osteogenic differentiation.

Tripeptidyl Peptidase II Is Required for c-MYC-Induced Centriole Overduplication and a Novel Therapeutic Target in c-MYC-Associated Neoplasms.

PubMed

Duensing, Stefan; Darr, Sebastian; Cuevas, Rolando; Melquiot, Nadja; Brickner, Anthony G; Duensing, Anette; Münger, Karl

2010-09-01

Centrosome aberrations are frequently detected in c-MYC-associated human malignancies. Here, we show that c-MYC-induced centrosome and centriole overduplication critically depend on the protease tripeptidyl peptidase II (TPPII). We found that TPPII localizes to centrosomes and that overexpression of TPPII, similar to c-MYC, can disrupt centriole duplication control and cause centriole multiplication, a process during which maternal centrioles nucleate the formation of more than a single daughter centriole. We report that inactivation of TPPII using chemical inhibitors or siRNA-mediated protein knockdown effectively reduced c-MYC-induced centriole overduplication. Remarkably, the potent and selective TPPII inhibitor butabindide not only potently suppressed centriole aberrations but also caused significant cell death and growth suppression in aggressive human Burkitt lymphoma cells with c-MYC overexpression. Taken together, these results highlight the role of TPPII in c-MYC-induced centriole overduplication and encourage further studies to explore TPPII as a novel antineoplastic drug target.

Tripeptidyl Peptidase II Is Required for c-MYC–Induced Centriole Overduplication and a Novel Therapeutic Target in c-MYC–Associated Neoplasms

PubMed Central

Duensing, Stefan; Darr, Sebastian; Cuevas, Rolando; Melquiot, Nadja; Brickner, Anthony G.; Duensing, Anette; Münger, Karl

2010-01-01

Centrosome aberrations are frequently detected in c-MYC–associated human malignancies. Here, we show that c-MYC–induced centrosome and centriole overduplication critically depend on the protease tripeptidyl peptidase II (TPPII). We found that TPPII localizes to centrosomes and that overexpression of TPPII, similar to c-MYC, can disrupt centriole duplication control and cause centriole multiplication, a process during which maternal centrioles nucleate the formation of more than a single daughter centriole. We report that inactivation of TPPII using chemical inhibitors or siRNA-mediated protein knockdown effectively reduced c-MYC–induced centriole overduplication. Remarkably, the potent and selective TPPII inhibitor butabindide not only potently suppressed centriole aberrations but also caused significant cell death and growth suppression in aggressive human Burkitt lymphoma cells with c-MYC overexpression. Taken together, these results highlight the role of TPPII in c-MYC–induced centriole overduplication and encourage further studies to explore TPPII as a novel antineoplastic drug target. PMID:21647238

Activation of c-Jun N-terminal kinase and apoptosis in endothelial cells mediated by endogenous generation of hydrogen peroxide

NASA Technical Reports Server (NTRS)

Ramachandran, Anup; Moellering, Douglas; Go, Young-Mi; Shiva, Sruti; Levonen, Anna-Liisa; Jo, Hanjoong; Patel, Rakesh P.; Parthasarathy, Sampath; Darley-Usmar, Victor M.

2002-01-01

Reactive oxygen species have been implicated in the activation of signal transduction pathways. However, extracellular addition of oxidants such as hydrogen peroxide (H2O2) often requires concentrations that cannot be readily achieved under physiological conditions to activate biological responses such as apoptosis. Explanations for this discrepancy have included increased metabolism of H2O2 in the extracellular environment and compartmentalization within the cell. We have addressed this issue experimentally by examining the induction of apoptosis of endothelial cells induced by exogenous addition of H2O2 and by a redox cycling agent, 2,3-dimethoxy-1,4-naphthoquinone, that generates H2O2 in cells. Here we show that low nanomolar steady-state concentrations (0.1-0.5 nmol x min(-1) x 10(6) cells) of H2O2 generated intracellularly activate c-Jun N terminal kinase and initiate apoptosis in endothelial cells. A comparison with bolus hydrogen peroxide suggests that the low rate of intracellular formation of this reactive oxygen species results in a similar profile of activation for both c-Jun N terminal kinase and the initiation of apoptosis. However, a detailed analysis reveals important differences in both the duration and profile for activation of these signaling pathways.

C/EBPα expression is downregulated in human nonmelanoma skin cancers and inactivation of C/EBPα confers susceptibility to UVB-induced skin squamous cell carcinomas.

PubMed

Thompson, Elizabeth A; Zhu, Songyun; Hall, Jonathan R; House, John S; Ranjan, Rakesh; Burr, Jeanne A; He, Yu-Ying; Owens, David M; Smart, Robert C

2011-06-01

Human epidermis is routinely subjected to DNA damage induced by UVB solar radiation. Cell culture studies have revealed an unexpected role for C/EBPα (CCAAT/enhancer-binding protein-α) in the DNA damage response network, where C/EBPα is induced following UVB DNA damage, regulates the G(1) checkpoint, and diminished or ablated expression of C/EBPα results in G(1) checkpoint failure. In the current study we observed that C/EBPα is induced in normal human epidermal keratinocytes and in the epidermis of human subjects exposed to UVB radiation. The analysis of human skin precancerous and cancerous lesions (47 cases) for C/EBPα expression was conducted. Actinic keratoses, a precancerous benign skin growth and precursor to squamous cell carcinoma (SCC), expressed levels of C/EBPα similar to normal epidermis. Strikingly, all invasive SCCs no longer expressed detectable levels of C/EBPα. To determine the significance of C/EBPα in UVB-induced skin cancer, SKH-1 mice lacking epidermal C/EBPα (CKOα) were exposed to UVB. CKOα mice were highly susceptible to UVB-induced SCCs and exhibited accelerated tumor progression. CKOα mice displayed keratinocyte cell cycle checkpoint failure in vivo in response to UVB that was characterized by abnormal entry of keratinocytes into S phase. Our results demonstrate that C/EBPα is silenced in human SCC and loss of C/EBPα confers susceptibility to UVB-induced skin SCCs involving defective cell cycle arrest in response to UVB.

C/EBPα Expression Is Downregulated in Human Nonmelanoma Skin Cancers and Inactivation of C/EBPα Confers Susceptibility to UVB-Induced Skin Squamous Cell Carcinomas

PubMed Central

Thompson, Elizabeth A.; Zhu, Songyun; Hall, Jonathan R.; House, John S.; Ranjan, Rakesh; Burr, Jeanne A.; He, Yu-Ying; Owens, David M.; Smart, Robert C.

2012-01-01

Human epidermis is routinely subjected to DNA damage induced by UVB solar radiation. Cell culture studies have revealed an unexpected role for C/EBPα (CCAAT/enhancer-binding protein-α) in the DNA damage response network, where C/EBPα is induced following UVB DNA damage, regulates the G1 checkpoint, and diminished or ablated expression of C/EBPα results in G1 checkpoint failure. In the current study we observed that C/EBPα is induced in normal human epidermal keratinocytes and in the epidermis of human subjects exposed to UVB radiation. The analysis of human skin precancerous and cancerous lesions (47 cases) for C/EBPα expression was conducted. Actinic keratoses, a precancerous benign skin growth and precursor to squamous cell carcinoma (SCC), expressed levels of C/EBPα similar to normal epidermis. Strikingly, all invasive SCCs no longer expressed detectable levels of C/EBPα. To determine the significance of C/EBPα in UVB-induced skin cancer, SKH-1 mice lacking epidermal C/EBPα (CKOα) were exposed to UVB. CKOα mice were highly susceptible to UVB-induced SCCs and exhibited accelerated tumor progression. CKOα mice displayed keratinocyte cell cycle checkpoint failure in vivo in response to UVB that was characterized by abnormal entry of keratinocytes into S phase. Our results demonstrate that C/EBPα is silenced in human SCC and loss of C/EBPα confers susceptibility to UVB-induced skin SCCs involving defective cell cycle arrest in response to UVB. PMID:21346772

The role of cPLA2 in Methylglyoxal-induced cell apoptosis of HUVECs

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

Yuan, Jie; Zhu, Chao; Hong, Yali

2017-05-15

Methylglyoxal (MGO), a highly reactive dicarbonyl compound, is mainly formed as a byproduct of glycolysis. Elevated MGO level is known to induce apoptosis of vascular endothelial cells, which is implicated with progression of atherosclerosis and diabetic complications. However, the underlying mechanisms have not been exhaustively investigated yet. Here, we further characterized the mechanisms how MGO induced apoptosis in human umbilical vein endothelial cells (HUVECs). Our data revealed that cytosolic phospholipase A2 (cPLA2) played an important role in MGO-induced cell apoptosis. It was found that MGO could increase both the activity and expression of cPLA2. Inhibition of cPLA2 by Pyrrophenone (PYR)more » or siRNA significantly attenuated the MGO-induced apoptosis. Additionally, MGO time-dependently decreased the phosphorylation of nuclear factor κB (NF-κB). Pretreatment of the cells with NF-κB inhibitor, BAY11-7082, further increased MGO-induced apoptosis of HUVECs, indicating that NF-κB played a survival role in this MGO-induced apoptosis. Furthermore, in the presence of si-cPLA2 or PYR, MGO no longer decreased NF-κB phosphorylation. Beyond that, the antioxidant N-acetyl cysteine (NAC) could reverse the changes of both cPLA2 and NF-κB caused by MGO. p38, the upstream of cPLA2, was also significantly phosphorylated by MGO. However, p38 inhibitor failed to reverse the apoptosis induced by MGO. This study gives an important insight into the downstream signaling mechanisms of MGO, cPLA2-NF-κB, in endothelial apoptosis. - Highlights: • cPLA2 participated in MGO-induced HUVECs apoptosis. • Inhibition of NF-κB was involved in MGO-cPLA2-mediated cell apoptosis. • Antioxidant NAC attenuated MGO-induced cPLA2 activation and cell apoptosis.« less

GUCY2C Signaling Opposes the Acute Radiation-Induced GI Syndrome.

PubMed

Li, Peng; Wuthrick, Evan; Rappaport, Jeff A; Kraft, Crystal; Lin, Jieru E; Marszalowicz, Glen; Snook, Adam E; Zhan, Tingting; Hyslop, Terry M; Waldman, Scott A

2017-09-15

High doses of ionizing radiation induce acute damage to epithelial cells of the gastrointestinal (GI) tract, mediating toxicities restricting the therapeutic efficacy of radiation in cancer and morbidity and mortality in nuclear disasters. No approved prophylaxis or therapy exists for these toxicities, in part reflecting an incomplete understanding of mechanisms contributing to the acute radiation-induced GI syndrome (RIGS). Guanylate cyclase C (GUCY2C) and its hormones guanylin and uroguanylin have recently emerged as one paracrine axis defending intestinal mucosal integrity against mutational, chemical, and inflammatory injury. Here, we reveal a role for the GUCY2C paracrine axis in compensatory mechanisms opposing RIGS. Eliminating GUCY2C signaling exacerbated RIGS, amplifying radiation-induced mortality, weight loss, mucosal bleeding, debilitation, and intestinal dysfunction. Durable expression of GUCY2C, guanylin, and uroguanylin mRNA and protein by intestinal epithelial cells was preserved following lethal irradiation inducing RIGS. Oral delivery of the heat-stable enterotoxin (ST), an exogenous GUCY2C ligand, opposed RIGS, a process requiring p53 activation mediated by dissociation from MDM2. In turn, p53 activation prevented cell death by selectively limiting mitotic catastrophe, but not apoptosis. These studies reveal a role for the GUCY2C paracrine hormone axis as a novel compensatory mechanism opposing RIGS, and they highlight the potential of oral GUCY2C agonists (Linzess; Trulance) to prevent and treat RIGS in cancer therapy and nuclear disasters. Cancer Res; 77(18); 5095-106. ©2017 AACR . ©2017 American Association for Cancer Research.

Bodipy-C60 triple hydrogen bonding assemblies as heavy atom-free triplet photosensitizers: preparation and study of the singlet/triplet energy transfer.

PubMed

Guo, Song; Xu, Liang; Xu, Kejing; Zhao, Jianzhang; Küçüköz, Betül; Karatay, Ahmet; Yaglioglu, Halime Gul; Hayvali, Mustafa; Elmali, Ayhan

2015-07-01

Supramolecular triplet photosensitizers based on hydrogen bonding-mediated molecular assemblies were prepared. Three thymine-containing visible light-harvesting Bodipy derivatives ( B-1 , B-2 and B-3 , which show absorption at 505 nm, 630 nm and 593 nm, respectively) were used as H-bonding modules, and 1,6-diaminopyridine-appended C 60 was used as the complementary hydrogen bonding module ( C-1 ), in which the C 60 part acts as a spin converter for triplet formation. Visible light-harvesting antennae with methylated thymine were prepared as references ( B-1-Me , B-2-Me and B-3-Me ), which are unable to form strong H-bonds with C-1 . Triple H-bonds are formed between each Bodipy antenna ( B-1 , B-2 and B-3 ) and the C 60 module ( C-1 ). The photophysical properties of the H-bonding assemblies and the reference non-hydrogen bond-forming mixtures were studied using steady state UV/vis absorption spectroscopy, fluorescence emission spectroscopy, electrochemical characterization, and nanosecond transient absorption spectroscopy. Singlet energy transfer from the Bodipy antenna to the C 60 module was confirmed by fluorescence quenching studies. The intersystem crossing of the latter produced the triplet excited state. The nanosecond transient absorption spectroscopy showed that the triplet state is either localized on the C 60 module (for assembly B-1·C-1 ), or on the styryl-Bodipy antenna (for assemblies B-2·C-1 and B-3·C-1 ). Intra-assembly forward-backward (ping-pong) singlet/triplet energy transfer was proposed. In contrast to the H-bonding assemblies, slow triplet energy transfer was observed for the non-hydrogen bonding mixtures. As a proof of concept, these supramolecular assemblies were used as triplet photosensitizers for triplet-triplet annihilation upconversion.

Reprint of "Stable hydrogen and carbon isotopic compositions of long-chain (C21-C33) n-alkanes and n-alkenes in insects"

NASA Astrophysics Data System (ADS)

Chikaraishi, Yoshito; Kaneko, Masanori; Ohkouchi, Naohiko

2013-06-01

We report the molecular and stable isotopic (δD and δ13C) compositions of long-chain n-alkanes in common insects including the cabbage butterfly, swallowtail, wasp, hornet, grasshopper, and ladybug. Insect n-alkanes are potential candidates of the contamination of soil and sedimentary n-alkanes that are believed to be derived from vascular plant waxes. Long-chain n-alkanes (range C21-33; maximum C23-C29) are found to be abundant in the insects (31-781 μg/dry g), with a carbon preference index (CPI) of 5.1-31.5 and an average chain length (ACL) of 24.9-29.3. The isotopic compositions (mean ± 1σ, n = 33) of the n-alkanes are -195 ± 16‰ for hydrogen and -30.6 ± 2.4‰ for carbon. The insect n-alkanes are depleted in D by approximately 30-40‰ compared with wax n-alkanes from C3 (-155 ± 25‰) and C4 vascular plants (-167 ± 13‰), whereas their δ13C values fall between those of C3 (-36.2 ± 2.4‰) and C4 plants (-20.3 ± 2.4‰). Thus, the contribution of insect-derived n-alkanes to soil and sediment could potentially shift δD records of n-alkanes toward more negative values and potentially muddle the assumed original C3/C4 balance in the δ13C records of the soil and sedimentary n-alkanes. n-Alkenes are also found in three insects (swallowtail, wasp and hornet). They are more depleted in D relative to the same carbon numbered n-alkanes (δDn-alkene - δDn-alkane = -17 ± 16‰), but the δ13C values are almost identical to those of the n-alkanes (δ13Cn-alkene - δ13Cn-alkane = 0.1 ± 0.2‰). These results suggest that these n-alkenes are desaturated products of the same carbon numbered n-alkanes.

Cellular FLICE-inhibitory Protein (cFLIP) Isoforms Block CD95- and TRAIL Death Receptor-induced Gene Induction Irrespective of Processing of Caspase-8 or cFLIP in the Death-inducing Signaling Complex*

PubMed Central

Kavuri, Shyam M.; Geserick, Peter; Berg, Daniela; Dimitrova, Diana Panayotova; Feoktistova, Maria; Siegmund, Daniela; Gollnick, Harald; Neumann, Manfred; Wajant, Harald; Leverkus, Martin

2011-01-01

Death receptors (DRs) induce apoptosis but also stimulate proinflammatory “non-apoptotic” signaling (e.g. NF-κB and mitogen-activated protein kinase (MAPK) activation) and inhibit distinct steps of DR-activated maturation of procaspase-8. To examine whether isoforms of cellular FLIP (cFLIP) or its cleavage products differentially regulate DR signaling, we established HaCaT cells expressing cFLIPS, cFLIPL, or mutants of cFLIPL (cFLIPD376N and cFLIPp43). cFLIP variants blocked TRAIL- and CD95L-induced apoptosis, but the cleavage pattern of caspase-8 in the death inducing signaling complex was different: cFLIPL induced processing of caspase-8 to the p43/41 fragments irrespective of cFLIP cleavage. cFLIPS or cFLIPp43 blocked procaspase-8 cleavage. Analyzing non-apoptotic signaling pathways, we found that TRAIL and CD95L activate JNK and p38 within 15 min. cFLIP variants and different caspase inhibitors blocked late death ligand-induced JNK or p38 MAPK activation suggesting that these responses are secondary to cell death. cFLIP isoforms/mutants also blocked death ligand-mediated gene induction of CXCL-8 (IL-8). Knockdown of caspase-8 fully suppressed apoptotic and non-apoptotic signaling. Knockdown of cFLIP isoforms in primary human keratinocytes enhanced CD95L- and TRAIL-induced NF-κB activation, and JNK and p38 activation, underscoring the regulatory role of cFLIP for these DR-mediated signals. Whereas the presence of caspase-8 is critical for apoptotic and non-apoptotic signaling, cFLIP isoforms are potent inhibitors of TRAIL- and CD95L-induced apoptosis, NF-κB activation, and the late JNK and p38 MAPK activation. cFLIP-mediated inhibition of CD95 and TRAIL DR could be of crucial importance during keratinocyte skin carcinogenesis and for the activation of innate and/or adaptive immune responses triggered by DR activation in the skin. PMID:21454681

1,25-DIHYDROXYVITAMIN D3 INDUCES MONOCYTIC DIFFERENTIATION OF HUMAN MYELOID LEUKEMIA CELLS BY REGULATING C/EBPβ EXPRESSION THROUGH MEF2C

PubMed Central

Zheng, Ruifang; Wang, Xuening; Studzinski, George P.

2015-01-01

Myogenic enhancer factor2 (Mef2) consists of a family of transcription factors involved in morphogenesis of skeletal, cardiac and smooth muscle cells. Among the four isoforms (Mef2A, 2B, 2C, and 2D), Mef2C was also found to play important roles in hematopoiesis. At myeloid progenitor level, Mef2C expression favors monocytic differentiation. Previous studies from our laboratory demonstrated that ERK5 was activated in 1,25-dihydroxyvitamin D3 (1,25D)-induced monocytic differentiation in AML cells and ERK5 activation was accompanied by increased Mef2C phosphorylation. We therefore examined the role of Mef2C in 1,25D-induced monocytic differentiation in AML cell lines (HL60, U937 and THP1) and found that knockdown of Mef2C with small interfering RNA (siRNA) significantly decreases the expression of the monocytic marker, CD14, without affecting the expression of the general myeloid marker, CD11b. CCAAT/Enhancer-binding protein (C/EBP) β, which can bind to CD14 promoter and increase its transcription, has been shown to be the downstream effector of 1,25D-induced monocytic differentiation in AML cells. When Mef2C was knocked down, expression of C/EBPβ was reduced at both mRNA and protein levels. The protein expression levels of cell cycle regulators, p27Kip1 and cyclin D1, were not affected by Mef2C knockdown, nor the monopoiesis related transcription factor, ATF2 (Activating Transcription Factor 2). Thus, we conclude that 1,25D-induced monocytic differentiation, and CD14 expression in particular, is mediated through activation of ERK5-Mef2C-C/EBPβ signaling pathway, and that Mef2C does not seem to modulate cell cycle progression. PMID:25448741

The unique functional role of the C-HS hydrogen bond in the substrate specificity and enzyme catalysis of type 1 methionine aminopeptidase.

PubMed

Reddi, Ravikumar; Singarapu, Kiran Kumar; Pal, Debnath; Addlagatta, Anthony

2016-07-19

It is intriguing how nature attains recognition specificity between molecular interfaces where there is no apparent scope for classical hydrogen bonding or polar interactions. Methionine aminopeptidase (MetAP) is one such enzyme where this fascinating conundrum is at play. In this study, we demonstrate that a unique C-HS hydrogen bond exists between the enzyme methionine aminopeptidase (MetAP) and its N-terminal-methionine polypeptide substrate, which allows specific interaction between apparent apolar interfaces, imposing a strict substrate recognition specificity and efficient catalysis, a feature replicated in Type I MetAPs across all kingdoms of life. We evidence this evolutionarily conserved C-HS hydrogen bond through enzyme assays on wild-type and mutant MetAP proteins from Mycobacterium tuberculosis that show a drastic difference in catalytic efficiency. The X-ray crystallographic structure of the methionine bound protein revealed a conserved water bridge and short contacts involving the Met side-chain, a feature also observed in MetAPs from other organisms. Thermal shift assays showed a remarkable 3.3 °C increase in melting temperature for methionine bound protein compared to its norleucine homolog, where C-HS interaction is absent. The presence of C-HS hydrogen bonding was also corroborated by nuclear magnetic resonance spectroscopy through a change in chemical shift. Computational chemistry studies revealed the unique role of the electrostatic environment in facilitating the C-HS interaction. The significance of this atypical hydrogen bond is underscored by the fact that the function of MetAP is essential for any living cell.

Vitamin C mitigates oxidative/nitrosative stress and inflammation in doxorubicin-induced cardiomyopathy.

PubMed

Akolkar, Gauri; da Silva Dias, Danielle; Ayyappan, Prathapan; Bagchi, Ashim K; Jassal, Davinder S; Salemi, Vera Maria Cury; Irigoyen, Maria Claudia; De Angelis, Katia; Singal, Pawan K

2017-10-01

Increase in oxidative/nitrosative stress is one of the mechanisms associated with the development of cardiotoxicity due to doxorubicin (Dox), a potent chemotherapy drug. Previously, we reported mitigation of Dox-induced oxidative/nitrosative stress and apoptosis by vitamin C (Vit C) in isolated cardiomyocytes. In the present in vivo study in rats, we investigated the effect of prophylactic treatment with Vit C on Dox-induced apoptosis, inflammation, oxidative/nitrosative stress, cardiac dysfunction, and Vit C transporter proteins. Dox (cumulative dose: 15 mg/kg) in rats reduced systolic and diastolic cardiac function and caused structural damage. These changes were associated with a myocardial increase in reactive oxygen species, reduction in antioxidant enzyme activities, increased expression of apoptotic proteins, and inflammation. Dox also caused an increase in the expression of proapoptotic proteins Bax, Bnip-3, Bak, and caspase-3. An increase in oxidative/nitrosative stress attributable to Dox was indicated by an increase in superoxide, protein carbonyl formation, lipid peroxidation, nitric oxide (NO), NO synthase (NOS) activity, protein nitrosylation, and inducible NOS protein expression. Dox increased the levels of cardiac proinflammatory cytokines TNF-α, IL-1β, and IL-6, whereas the expression of Vit C transporter proteins (sodium-ascorbate cotransporter 2 and glucose transporter 4) was reduced. Prophylactic and concurrent treatment with Vit C prevented all these changes and improved survival in the Vit C + Dox group. Vit C also improved Dox-mediated systolic and diastolic dysfunctions and structural damage. These results suggest a cardioprotective role of Vit C in Dox-induced cardiomyopathy by reducing oxidative/nitrosative stress, inflammation, and apoptosis, as well as improving Vit C transporter proteins. NEW & NOTEWORTHY This in vivo study provides novel data that vitamin C improves cardiac structure and function in doxorubicin-induced cardiomyopathy

C-fos mediates antipsychotic-induced neurotensin gene expression in the rodent striatum.

PubMed

Robertson, G S; Tetzlaff, W; Bedard, A; St-Jean, M; Wigle, N

1995-07-01

The ubiquitous inducibility of the immediate-early gene c-fos in the central nervous system has led to the search for downstream genes which are regulated by its product, Fos. Recent evidence suggests that c-fos induction by a single injection of the classical antipsychotic haloperidol may contribute to the subsequent increase in neurotensin gene expression in the rodent striatum. Consistent with this proposal, in the present study haloperidol-induced Fos-like immunoreactivity and neurotensin/neuromedin N messenger RNA were found to be expressed by the same population of striatal neurons. Moreover, inhibition of haloperidol-induced c-fos expression by intrastriatal injection of antisense phosphorothioate oligodeoxynucleotides complimentary either to bases 109-126 or 127-144 of c-fos attenuated the subsequent increase in neurotensin/neuromedin N messenger RNA. However, injection of a sense phosphorothioate oligodeoxynucleotide corresponding to bases 127-144 of c-fos did not reduce haloperidol-induced c-fos or neurotensin/neuromedin N expression. Furthermore, constitutive expression of Jun-like immunoreactivity in the striatum was not reduced by either the sense or antisense phosphorothioate oligodeoxynucleotides. Similarly, the sense and antisense phosphorothioate oligodeoxynucleotide failed to reduce proenkephalin messenger RNA, which is located in the same striatal neurons that express haloperidol-induced neurotensin/neuromedin N messenger RNA, which is located in the same striatal neurons that express haloperidol-induced neurotensin/neuromedin N messenger RNA. Lastly, haloperidol-induced increases in nerve growth factor I-A-, JunB- and FosB-like immunoreactivity and fosB messenger RNA were not decreased by intrastriatal injection of either the sense or antisense phosphorothioate oligodeoxynucleotides. These results indicate that the antisense phosphorothioate oligodeoxynucleotides attenuated haloperidol-induced neurotensin/neuromedin N expression by selectively

Vitamins C and E for asthma and exercise-induced bronchoconstriction.

PubMed

Wilkinson, Mark; Hart, Anna; Milan, Stephen J; Sugumar, Karnam

2014-06-17

The association between dietary antioxidants and asthma or exercise-induced bronchoconstriction (EIB) is not fully understood. Vitamin C and vitamin E are natural antioxidants that are predominantly present in fruits and vegetables; inadequate vitamin E intake is associated with airway inflammation. It has been postulated that the combination may be more beneficial than either single antioxidant for people with asthma and exercise-induced bronchoconstriction. To assess the effects of supplementation of vitamins C and E versus placebo (or no vitamin C and E supplementation) on exacerbations and health-related quality of life (HRQL) in adults and children with chronic asthma. To also examine the potential effects of vitamins C and E on exercise-induced bronchoconstriction in people with asthma and in people without a diagnosis of asthma who experience symptoms only on exercise. Trials were identified from the Cochrane Airways Review Group Specialised Register and from trial registry websites. Searches were conducted in September 2013. We included randomised controlled trials of adults and children with a diagnosis of asthma. We separately considered trials in which participants had received a diagnosis of exercise-induced bronchoconstriction (or exercise-induced asthma). Trials comparing vitamin C and E supplementation versus placebo were included. We included trials in which asthma management for treatment and control groups included similar background therapy. Short-term use of vitamins C and E at the time of exacerbation or for cold symptoms in people with asthma is outside the scope of this review. Two review authors independently screened the titles and abstracts of potential studies and subsequently screened full-text study reports for inclusion. We used standard methods as expected by The Cochrane Collaboration. It was not possible to aggregate the five included studies (214 participants). Four studies (206 participants) addressed the question of whether

Differences in cocaine-induced place preference persistence, locomotion and social behaviors between C57BL/6J and BALB/cJ mice

PubMed Central

WANG, Jian-Li; WANG, Bei; CHEN, Wen

2014-01-01

C57BL/6J and BALB/cJ mice display significant differences in sociability and response to drugs, but the phenotypic variability of their susceptibility to cocaine is still not well known. In this study, the differences between these two mice strains in the persistence of cocaine-induced conditioned place preference (CPP), as well as the locomotion and social behaviors after the 24-hour withdrawal from a four-day cocaine (20 mg/kg/day) administration were investigated. The results showed that the cocaine-induced CPP persisted over two weeks in C57BL/6J mice, while it diminished within one week among BALB/cJ mice. After 24-hours of cocaine withdrawal, high levels of locomotion as well as low levels of social interaction and aggressive behavior were found in C57BL/6J mice, but no significant changes were found in BALB/cJ mice, indicating that cocaine-induced CPP persistence, locomotion and social behavior are not consistent between these two strains, and that overall C57BL/6J mice are more susceptible to cocaine than BALB/cJ mice at the tested doses. PMID:25297083

Differences in cocaine-induced place preference persistence, locomotion and social behaviors between C57BL/6J and BALB/cJ mice.

PubMed

Wang, Jian-Li; Wang, Bei; Chen, Wen

2014-09-01

C57BL/6J and BALB/cJ mice display significant differences in sociability and response to drugs, but the phenotypic variability of their susceptibility to cocaine is still not well known. In this study, the differences between these two mice strains in the persistence of cocaine-induced conditioned place preference (CPP), as well as the locomotion and social behaviors after the 24-hour withdrawal from a four-day cocaine (20 mg/kg/day) administration were investigated. The results showed that the cocaine-induced CPP persisted over two weeks in C57BL/6J mice, while it diminished within one week among BALB/cJ mice. After 24-hours of cocaine withdrawal, high levels of locomotion as well as low levels of social interaction and aggressive behavior were found in C57BL/6J mice, but no significant changes were found in BALB/cJ mice, indicating that cocaine-induced CPP persistence, locomotion and social behavior are not consistent between these two strains, and that overall C57BL/6J mice are more susceptible to cocaine than BALB/cJ mice at the tested doses.

Novel indole-based inhibitors of IMPDH: introduction of hydrogen bond acceptors at indole C-3.

PubMed

Watterson, Scott H; Dhar, T G Murali; Ballentine, Shelley K; Shen, Zhongqi; Barrish, Joel C; Cheney, Daniel; Fleener, Catherine A; Rouleau, Katherine A; Townsend, Robert; Hollenbaugh, Diane L; Iwanowicz, Edwin J

2003-04-07

The development of a series of novel indole-based inhibitors of 5'-inosine monophosphate dehydrogenase (IMPDH) is described. Various hydrogen bond acceptors at C-3 of the indole were explored. The synthesis and the structure-activity relationships (SARs) derived from in vitro studies are outlined.

CYP2C9 polymorphism in non-steroidal anti-inflammatory drugs-induced gastropathy.

PubMed

Ma, Juan; Yang, Xiu Yan; Qiao, Liang; Liang, Liu Qin; Chen, Min Hu

2008-05-01

Non-steroidal anti-inflammatory drugs (NSAID) induce gastroduodenal mucosal injury and are metabolized by cytochrome P450 2C9 (CYP2C9). It is postulated that CYP2C9 genotype is associated with NSAID-induced gastropathy. This study aims to determine whether individuals with a CYP2C9 allele mutation are susceptible to NSAID-induced gastropathy. A total of 109 patients diagnosed as having rheumatic diseases and taking NSAID were appraised as having gastropathy by endoscopy, stool occult blood test and questionnaire two weeks after entering the study. Their peripheral blood was analyzed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). A total of 47.7% gastropathy (33% erosions, 14.7% ulcers, 2.75% ulcer bleeding) and 56% dyspeptic symptoms were presented. Only one CYP2C9*2 heterozygote (*1/*2) was found in the group with gastropathy and two variant alleles (CYP2C9*2 and CYP2C9* 3) could not be found in the group without gastropathy. There was no significant difference in both CYP2C9 genotype (0.96%vs 0%) and CYP2C9 variant allele frequency (1.92%vs 0%) between patients with and without gastropathy. These results confirm the high prevalence of NSAID-induced gastropathy but do not support the postulation that CYP2C9*2 and CYP2C9*3 contribute to the development of NSAID-induced gastropathy. This may be due to the low frequency of the two alleles in the population studied.

Inflammation-mediated skin tumorigenesis induced by epidermal c-Fos

PubMed Central

Briso, Eva M.; Guinea-Viniegra, Juan; Bakiri, Latifa; Rogon, Zbigniew; Petzelbauer, Peter; Eils, Roland; Wolf, Ronald; Rincón, Mercedes; Angel, Peter; Wagner, Erwin F.

2013-01-01

Skin squamous cell carcinomas (SCCs) are the second most prevalent skin cancers. Chronic skin inflammation has been associated with the development of SCCs, but the contribution of skin inflammation to SCC development remains largely unknown. In this study, we demonstrate that inducible expression of c-fos in the epidermis of adult mice is sufficient to promote inflammation-mediated epidermal hyperplasia, leading to the development of preneoplastic lesions. Interestingly, c-Fos transcriptionally controls mmp10 and s100a7a15 expression in keratinocytes, subsequently leading to CD4 T-cell recruitment to the skin, thereby promoting epidermal hyperplasia that is likely induced by CD4 T-cell-derived IL-22. Combining inducible c-fos expression in the epidermis with a single dose of the carcinogen 7,12-dimethylbenz(a)anthracene (DMBA) leads to the development of highly invasive SCCs, which are prevented by using the anti-inflammatory drug sulindac. Moreover, human SCCs display a correlation between c-FOS expression and elevated levels of MMP10 and S100A15 proteins as well as CD4 T-cell infiltration. Our studies demonstrate a bidirectional cross-talk between premalignant keratinocytes and infiltrating CD4 T cells in SCC development. Therefore, targeting inflammation along with the newly identified targets, such as MMP10 and S100A15, represents promising therapeutic strategies to treat SCCs. PMID:24029918

Tributyltin interacts with mitochondria and induces cytochrome c release.

PubMed Central

Nishikimi, A; Kira, Y; Kasahara, E; Sato, E F; Kanno, T; Utsumi, K; Inoue, M

2001-01-01

Although triorganotins are potent inducers of apoptosis in various cell types, the critical targets of these compounds and the mechanisms by which they lead to cell death remain to be elucidated. There are two major pathways by which apoptotic cell death occurs: one is triggered by a cytokine mediator and the other is by a mitochondrion-dependent mechanism. To elucidate the mechanism of triorganotin-induced apoptosis, we studied the effect of tributyltin on mitochondrial function. We found that moderately low doses of tributyltin decrease mitochondrial membrane potential and induce cytochrome c release by a mechanism inhibited by cyclosporine A and bongkrekic acid. Tributyltin-induced cytochrome c release is also prevented by dithiols such as dithiothreitol and 2,3-dimercaptopropanol but not by monothiols such as GSH, N-acetyl-L-cysteine, L-cysteine and 2-mercaptoethanol. Further studies with phenylarsine oxide agarose revealed that tributyltin interacts with the adenine nucleotide translocator, a functional constituent of the mitochondrial permeability transition pore, which is selectively inhibited by dithiothreitol. These results suggest that, at low doses, tributyltin interacts selectively with critical thiol residues in the adenine nucleotide translocator and opens the permeability transition pore, thereby decreasing membrane potential and releasing cytochrome c from mitochondria, a series of events consistent with established mechanistic models of apoptosis. PMID:11368793

C4 deficiency is a predisposing factor for Streptococcus pneumoniae-induced autoantibody production

PubMed Central

Yammani, Rama D.; Leyva, Marcela A.; Jennings, Ryan N.; Haas, Karen M.

2015-01-01

Reductions in C4 levels may predispose individuals to infection with encapsulated bacteria as well as autoimmunity. In this study, we examined the role C4 has in protection against Streptococcus pneumoniae-induced autoimmunity. Mild respiratory infection with serotype 19F pneumococci selectively induced systemic anti-dsDNA IgA production in naïve C4-/- mice, but not C3-/- or wild type mice. Systemic challenge with virulent serotype 3 pneumococci also induced anti-dsDNA IgA production in immune C4-/- mice. Remarkably, pneumococcal polysaccharide (PPS) vaccination alone induced C4-/- mice to produce increased anti-dsDNA IgA levels that were maintained in some mice for months. These effects were most pronounced in female C4-/- mice. Importantly, immunization-induced increases in anti-dsDNA IgA levels were strongly associated with increased IgA deposition in kidneys. Cross-reactivity between pneumococcal antigens and dsDNA played a partial role in the induction of anti-dsDNA IgA, but a major role for PPS-associated TLR2 agonists was also revealed. Administration of the TLR2/4 antagonist, OxPAPC, at the time of PPS immunization completely blocked the production of anti-dsDNA IgA in C4-/- mice without suppressing PPS-specific Ab production. The TLR2 agonist, Pam3Csk4, similarly induced anti-dsDNA IgA production in C4-/- mice, which OxPAPC also prevented. LPS, a TLR4 agonist, had no effect. Pam3Csk4, but not LPS, also induced dsDNA-specific IgA production by C4-/- splenic IgA+ B cells in vitro, indicating TLR2 agonists can stimulate autoAb production via B cell-intrinsic mechanisms. Collectively, our results show an important role for C4 in suppressing autoAb production elicited by cross-reactive antigens and TLR2 agonists associated with S. pneumoniae. PMID:25339671

The effect of intratympanic vitamin C administration on cisplatin-induced ototoxicity.

PubMed

Celebi, Saban; Gurdal, M Mustafa; Ozkul, M Haluk; Yasar, Husamettin; Balikci, H Huseyin

2013-03-01

The objective of this study is to investigate the effect of intratympanic injection of vitamin C on cisplatin-induced ototoxicity. The study included 24 albino adult female rats (48 ears). The study animals were divided into four groups each of which was composed of six animals including a control (intraperitoneal cisplatin), a cisplatin-saline (saline intratympanic + intraperitoneal cisplatin), a C vit (intratympanic vitamin C) and a cisplatin-C vit group (intraperitoneal cisplatin + intratympanic vitamin C). As two animals had died due to cisplatin-induced ototoxicity (one in the control and one in the cisplatin-saline group) they were excluded from the study. The experiment was terminated, performing distortion product otoacoustic emission (DPOAE) measurement prior to procedures and at the end of the experiment. The results of the statistical analysis were evaluated. In the cisplatin-C vit group, there were no significant decreases in DPOAE amplitudes at 2 kHz (p > 0.05). Although a decrease was observed in DPOAE amplitudes at 2.8, 4, 6, and 8 kHz frequencies, these amplitude reductions were significantly lower than the control group (p < 0.05). Intratympanic vit C infusion provided a protective effect against cisplatin-induced ototoxicity primarily at 2 kHz and at other frequencies (2.8, 4, 6, and 8 kHz), and it did not produce a toxic effect in the cochlea.

MnOx/C nanocomposite: An insight on high-performance supercapacitor and non-enzymatic hydrogen peroxide detection

NASA Astrophysics Data System (ADS)

Ahuja, Preety; Kumar Ujjain, Sanjeev; Kanojia, Rajni

2017-05-01

In this work, we have used microemulsion method for synthesis of MnOx/C nanocomposite and investigated its electrochemical properties via fabrication of supercapacitor and non-enzymatic hydrogen peroxide (H2O2) sensor. In-situ inclusion of conducting carbon in manganese oxide (MnOx/C) enhances the network conductivity facilitating the charge transfer process which is beneficial for supercapacitor and sensing applications. MnOx/C provides high energy and power density, 31.6 Wh kg-1 and 3.8 kW kg-1 respectively and short relaxation time ∼3 ms for fabricated cell (MnOx/C//MnOx/C) endowing excellent power delivery capacity. Furthermore, MnOx/C as sensor, exhibits excellent catalytic activity toward the oxidation of H2O2 and shows high sensitivity (0.37 mA mM-1 cm-2) with low detection limit (0.5 μM at an S/N of 3). Hence, this study provides new avenue for high performance supercapacitor and H2O2 detection.

KRAS G12C Drug Development: Discrimination between Switch II Pocket Configurations Using Hydrogen/Deuterium-Exchange Mass Spectrometry

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

Lu, Jia; Harrison, Rane A.; Li, Lianbo

KRAS G12C, the most common RAS mutation found in non-small-cell lung cancer, has been the subject of multiple recent covalent small-molecule inhibitor campaigns including efforts directed at the guanine nucleotide pocket and separate work focused on an inducible pocket adjacent to the switch motifs. Multiple conformations of switch II have been observed, suggesting that switch II pocket (SIIP) binders may be capable of engaging a range of KRAS conformations. Here we report the use of hydrogen/deuterium-exchange mass spectrometry (HDX MS) to discriminate between conformations of switch II induced by two chemical classes of SIIP binders. We investigated the structural basismore » for differences in HDX MS using X-ray crystallography and discovered a new SIIP configuration in response to binding of a quinazoline chemotype. These results have implications for structure-guided drug design targeting the RAS SIIP.« less

Experimental controls on D/H and 13C/12C ratios of kerogen, bitumen and oil during hydrous pyrolysis

USGS Publications Warehouse

Schimmelmann, A.; Boudou, J.-P.; Lewan, M.D.; Wintsch, R.P.

2001-01-01

Large isotopic transfers between water-derived hydrogen and organic hydrogen occurred during hydrous pyrolysis experiments of immature source rocks, in spite of only small changes in organic 13C/12C. Experiments at 330 ??C over 72 h using chips or powder containing kerogen types I and III identify the rock/water ratio as a main factor affecting ????D for water and organic hydrogen. Our data suggest that larger rock permeability and smaller rock grain size increase the H-isotopic transfer between water-derived hydrogen and thermally maturing organic matter. Increasing hydrostatic pressure may have a similar effect, but the evidence remains inconclusive. ?? 2001 Elsevier Science Ltd. All rights reserved.

Enhancement of Ti-containing hydrogenated carbon (Tisbnd C:H) films by high-power plasma-sputtering

NASA Astrophysics Data System (ADS)

Gwo, Jyh; Chu, Chun-Lin; Tsai, Ming-Jui; Lee, Shyong

2012-02-01

Ti-containing amorphous hydrogenated carbon (Tisbnd C:H) thin films were deposited on stainless steel SS304 substrates by high-power pulsed magnetron sputtering (HPPMS) in an atmosphere of mixed Ar and C2H2 gases using titanium metal as the cathodic material. The multilayer structure of the deposited film had a Tisbnd TiCsbnd DLC gradient to improve adhesion and reduce residual stress. This study investigates the effects of substrate bias and target-to-substrate distance on the mechanical properties of Tisbnd C:H films. Film properties, including composition, morphology, microstructure, mechanical, and tribology, were examined by glow discharge spectroscopy (GDS), scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, and a nanoindenter and a pin-on-disk tribometer. Experiments revealed impressive results.

Moisture-Induced Spallation and Interfacial Hydrogen Embrittlement of Alumina Scales

NASA Technical Reports Server (NTRS)

Smialek, James L.

2005-01-01

Thermal expansion mismatch stresses and interfacial sulfur activity are the major factors producing primary Al2O3 scale spallation on high temperature alloys. However, moisture-induced delayed spallation appears as a secondary, but often dramatic, illustration of an additional mechanistic detail. A historical review of delayed failure of alumina scales and TBC s on superalloys is presented herein. Similarities with metallic phenomena suggest that hydrogen embrittlement from ambient humidity, resulting from the reaction Al+3H2O=Al(OH)3+3H(+)+3e(-), is the operative mechanism. This proposal was tested by standard cathodic hydrogen charging in 1N H2SO4, applied to Rene N5 pre-oxidized at 1150 C for 1000 1-hr cycles, and monitored by weight change, induced current, and microstructure. Here cathodic polarization at -2.0 V abruptly stripped mature Al2O3 scales at the oxide-metal interface. Anodic polarization at +2.0 V, however, produced alloy dissolution. Finally, with no applied voltage, the electrolyte alone produced neither scale spallation nor alloy dissolution. These experiments thus highlight the detrimental effects of hydrogen charging on alumina scale adhesion. It is proposed that interfacial hydrogen embrittlement is produced by moist air and is the root cause of both moisture-induced, delayed scale spallation and desktop TBC failures.

Hydrogen incorporation induced the octahedral symmetry variation in VO2 films

NASA Astrophysics Data System (ADS)

Lee, Dooyong; Kim, Hyegyeong; Kim, Ji Woong; Lee, Ik Jae; Kim, Yooseok; Yun, Hyung-Joong; Lee, Jouhahn; Park, Sungkyun

2017-02-01

This study examined the microscopic aspects of macroscopic physical property variations of hydrogen annealed VO2 films, deposited on Al2O3(0001) substrates by RF magnetron sputtering. The temperature-dependent electrical resistivity showed that the as-grown film exhibited a metal-insulator-transition (MIT) at 55.20 °C and 49.26 °C during heating and cooling, respectively. On the other hand, no MIT was observed for the film annealed under a hydrogen environment. Spectroscopic measurements during the in-situ hydrogenation process showed that hydrogen annealing (∼0.3 mbar, up to 300 °C) promoted the V3+ state above 100 °C. Raman spectroscopy and X-ray diffraction confirmed that the as-grown film changed from a monoclinic to rutile structure during hydrogen annealing. In addition, the shift of the (020) diffraction peak position of the hydrogen-annealed film to a lower angle compare to that of the known rutile VO2 film was attributed to the expansion of the unit cell. In addition, local structure analysis showed that an increase in octahedral symmetry after hydrogen annealing is one of the main explanations for the metallic characteristics of the hydrogen-annealed film.

Hydrogen induced fracture characteristics of single crystal nickel-based superalloys

NASA Technical Reports Server (NTRS)

Chen, Po-Shou; Wilcox, Roy C.

1990-01-01

A stereoscopic method for use with x ray energy dispersive spectroscopy of rough surfaces was adapted and applied to the fracture surfaces single crystals of PWA 1480E to permit rapid orientation determinations of small cleavage planes. The method uses a mathematical treatment of stereo pair photomicrographs to measure the angle between the electron beam and the surface normal. One reference crystal orientation corresponding to the electron beam direction (crystal growth direction) is required to perform this trace analysis. The microstructure of PWA 1480E was characterized before fracture analysis was performed. The fracture behavior of single crystals of the PWA 1480E nickel-based superalloy was studied. The hydrogen-induced fracture behavior of single crystals of the PWA 1480E nickel-based superalloy was also studied. In order to understand the temperature dependence of hydrogen-induced embrittlement, notched single crystals with three different crystal growth orientations near zone axes (100), (110), and (111) were tensile tested at 871 C (1600 F) in both helium and hydrogen atmospheres at 34 MPa. Results and conclusions are given.

Vitamin C prevents memory impairment induced by waterpipe smoke: role of oxidative stress.

PubMed

Alqudah, Mohammad A Y; Alzoubi, Karem H; Ma'abrih, Ghida'a M; Khabour, Omar F

2018-05-22

Waterpipe tobacco smoking (WTS) was previously shown to be associated with memory deficits, which were related to oxidative stress. Vitamin C (VitC) has established antioxidant properties against memory deficits associated with several diseases and conditions. In this study, the potential protective effect of VitC on memory impairment induced by WTS exposure was evaluated in a rat model. VitC was administered to animals via oral gavage (100 mg/kg/day, 6 days a week for 4 weeks). At the same period, animals were exposed to WTS for one hour/day, 6 days a week for 4 weeks. Using radial arm water maze (RAWM), behavioral tests were conducted to evaluate the spatial learning and memory. In addition, hippocampal levels of oxidative stress biomarkers were analyzed. WTS exposure impaired both short- and long-term memory (p < .05). On the other hand, VitC protected memory impairment induced by WTS (p < .05). Moreover, VitC prevented the reduction in hippocampus ratio of GSH/GSSG (p < .05) induced by WTS. Furthermore, WTS reduced hippocampus activity of glutathione peroxidase (GPx) and catalase, which were also normalized by VitC treatment. However, thiobarbituric acid reactive substance (TBARS) levels were not changed by WTS and/or by VitC (p > .05). In conclusion, WTS resulted in inducing memory impairment, which was prevented by VitC administration. This could be related to preserving hippocampus antioxidant mechanisms by VitC during WTS exposure.

Carbon Displacement-Induced Single Carbon Atomic Chain Formation and its Effects on Sliding of SiC Fibers in SiC/graphene/SiC Composite

DOE PAGES

Wallace, Joseph B.; Chen, Di; Shao, Lin

2015-11-03

Understanding radiation effects on the mechanical properties of SiC composites is important to their application in advanced reactor designs. By means of molecular dynamics simulations, we found that due to strong interface bonding between the graphene layers and SiC, the sliding friction of SiC fibers is largely determined by the frictional behavior between graphene layers. Upon sliding, carbon displacements between graphene layers can act as seed atoms to induce the formation of single carbon atomic chains (SCACs) by pulling carbon atoms from the neighboring graphene planes. The formation, growth, and breaking of SCACs determine the frictional response to irradiation.

Angiotensin II down-regulates nephrin–Akt signaling and induces podocyte injury: roleof c-Abl

PubMed Central

Yang, Qian; Ma, Yiqiong; Liu, Yipeng; Liang, Wei; Chen, Xinghua; Ren, Zhilong; Wang, Huiming; Singhal, Pravin C.; Ding, Guohua

2016-01-01

Recent studies have shown that nephrin plays a vital role in angiotensin II (Ang II)–induced podocyte injury and thus contributes to the onset of proteinuria and the progression of renal diseases, but its specific mechanism remains unclear. c-Abl is an SH2/SH3 domain–containing nonreceptor tyrosine kinase that is involved in cell survival and regulation of the cytoskeleton. Phosphorylated nephrin is able to interact with molecules containing SH2/SH3 domains, suggesting that c-Abl may be a downstream molecule of nephrin signaling. Here we report that Ang II–infused rats developed proteinuria and podocyte damage accompanied by nephrin dephosphorylation and minimal interaction between nephrin and c-Abl. In vitro, Ang II induced podocyte injury and nephrin and Akt dephosphorylation, which occurred in tandem with minimal interaction between nephrin and c-Abl. Moreover, Ang II promoted c-Abl phosphorylation and interaction between c-Abl and SH2 domain–containing 5′-inositol phosphatase 2 (SHIP2). c-Abl small interfering RNA (siRNA) and STI571 (c-Abl inhibitor) provided protection against Ang II–induced podocyte injury, suppressed the Ang II-induced c-Abl–SHIP2 interaction and SHIP2 phosphorylation, and maintained a stable level of nephrin phosphorylation. These results indicate that c-Abl is a molecular chaperone of nephrin signaling and the SHIP2-Akt pathway and that the released c-Abl contributes to Ang II–induced podocyte injury. PMID:26510503

In-situ TEM on (de)hydrogenation of Pd at 0.5-4.5 bar hydrogen pressure and 20-400°C.

PubMed

Yokosawa, Tadahiro; Alan, Tuncay; Pandraud, Gregory; Dam, Bernard; Zandbergen, Henny

2012-01-01

We have developed a nanoreactor, sample holder and gas system for in-situ transmission electron microscopy (TEM) of hydrogen storage materials up to at least 4.5 bar. The MEMS-based nanoreactor has a microheater, two electron-transparent windows and a gas inlet and outlet. The holder contains various O-rings to have leak-tight connections with the nanoreactor. The system was tested with the (de)hydrogenation of Pd at pressures up to 4.5 bar. The Pd film consisted of islands being 15 nm thick and 50-500 nm wide. In electron diffraction mode we observed reproducibly a crystal lattice expansion and shrinkage owing to hydrogenation and dehydrogenation, respectively. In selected-area electron diffraction and bright/dark-field modes the (de)hydrogenation of individual Pd particles was followed. Some Pd islands are consistently hydrogenated faster than others. When thermally cycled, thermal hysteresis of about 10-16°C between hydrogen absorption and desorption was observed for hydrogen pressures of 0.5-4.5 bar. Experiments at 0.8 bar and 3.2 bar showed that the (de)hydrogenation temperature is not affected by the electron beam. This result shows that this is a fast method to investigate hydrogen storage materials with information at the nanometer scale. Copyright © 2011 Elsevier B.V. All rights reserved.

Engineering of hydrogenated two-dimensional h-BN/C superlattices as electrostatic substrates.

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

Liu, Zhun; Zhong, Xiaoliang; Yan, Hui

2016-01-14

Hybridized two-dimensional materials incorporating domains from the hexagonal boron nitride (h-BN) and graphene is an interesting branch of materials science due to their highly tunable electronic properties. In the present study, we investigate the hydrogenated two-dimensional (2D) h-BN/C superlattices (SLs) with zigzag edges using first-principles calculations. We found that the domain width, the phase ratio, and the vertical dipole orientation all have significant influence on the stability of SLs. The electronic reconstruction is associated with the lateral polar discontinuities at the zigzag edges and the vertically polarized (B2N2H4)(m) domains, which modifies the electronic structures and the spatial potential of themore » SLs significantly. Furthermore, we demonstrate that the hydrogenated 2D h-BN/C SLs can be applied in engineering the electronic structure of graphene: laterally-varying doping can be achieved by taking advantage of the spatial variation of the surface potential of the SLs. By applying an external vertical electric field on these novel bidirectional heterostructures, graphene doping levels and band offsets can be tuned to a wide range, such that the graphene doping profile can be switched from the bipolar (p-n junction) to unipolar (n(+)-n junction) mode. It is expected that such bidirectional heterostructures provide an effective approach for developing novel nanoscale electronic devices and improving our understanding of the fundamentals of low-dimensional materials.« less

Domain-specific c-Myc ubiquitylation controls c-Myc transcriptional and apoptotic activity

PubMed Central

Zhang, Qin; Spears, Erick; Boone, David N.; Li, Zhaoliang; Gregory, Mark A.; Hann, Stephen R.

2013-01-01

The oncogenic transcription factor c-Myc causes transformation and tumorigenesis, but it can also induce apoptotic cell death. Although tumor suppressors are necessary for c-Myc to induce apoptosis, the pathways and mechanisms are unclear. To further understand how c-Myc switches from an oncogenic protein to an apoptotic protein, we examined the mechanism of p53-independent c-Myc–induced apoptosis. We show that the tumor suppressor protein ARF mediates this switch by inhibiting ubiquitylation of the c-Myc transcriptional domain (TD). Whereas TD ubiquitylation is critical for c-Myc canonical transcriptional activity and transformation, inhibition of ubiquitylation leads to the induction of the noncanonical c-Myc target gene, Egr1, which is essential for efficient c-Myc–induced p53-independent apoptosis. ARF inhibits the interaction of c-Myc with the E3 ubiquitin ligase Skp2. Overexpression of Skp2, which occurs in many human tumors, inhibits the recruitment of ARF to the Egr1 promoter, leading to inhibition of c-Myc–induced apoptosis. Therapeutic strategies could be developed to activate this intrinsic apoptotic activity of c-Myc to inhibit tumorigenesis. PMID:23277542

Laser-induced transformation of supramolecular complexes: approach to controlled formation of hybrid multi-yolk-shell Au-Ag@a-C:H nanostructures

PubMed Central

Manshina, A. A.; Grachova, E. V.; Povolotskiy, A. V.; Povolotckaia, A. V.; Petrov, Y. V.; Koshevoy, I. O.; Makarova, A. A.; Vyalikh, D. V.; Tunik, S. P.

2015-01-01

In the present work an efficient approach of the controlled formation of hybrid Au–Ag–C nanostructures based on laser-induced transformation of organometallic supramolecular cluster compound is suggested. Herein the one-step process of the laser-induced synthesis of hybrid multi-yolk-shell Au-Ag@a-C:H nanoparticles which are bimetallic gold-silver subnanoclusters dispersed in nanospheres of amorphous hydrogenated a-C:H carbon is reported in details. It has been demonstrated that variation of the experimental parameters such as type of the organometallic precursor, solvent, deposition geometry and duration of laser irradiation allows directed control of nanoparticles’ dimension and morphology. The mechanism of Au-Ag@a-C:H nanoparticles formation is suggested: the photo-excitation of the precursor molecule through metal-to-ligand charge transfer followed by rupture of metallophilic bonds, transformation of the cluster core including red-ox intramolecular reaction and aggregation of heterometallic species that results in the hybrid metal/carbon nanoparticles with multi-yolk-shell architecture formation. It has been found that the nanoparticles obtained can be efficiently used for the Surface-Enhanced Raman Spectroscopy label-free detection of human serum albumin in low concentration solution. PMID:26153347

Hollow core-shell structured Ni-Sn@C nanoparticles: a novel electrocatalyst for the hydrogen evolution reaction.

PubMed

Lang, Leiming; Shi, Yi; Wang, Jiong; Wang, Feng-Bin; Xia, Xing-Hua

2015-05-06

Pt-free electrocatalysts with high activity and low cost are highly pursued for hydrogen production by electrochemically splitting water. Ni-based alloy catalysts are potential candidates for the hydrogen evolution reaction (HER) and have been studied extensively. Here, we synthesized novel hollow core-shell structure Ni-Sn@C nanoparticles (NPs) by sol-gel, chemical vapor deposition, and etching processes. The prepared electrocatalysts with porous hollow carbon layers have a high conductivity and large active area, which exhibit good electrocatalytic activity toward HER. The Tafel slope of ∼35 millivolts per decade measured in acidic solution for Ni-Sn@C NPs is the smallest one to date for the Ni-Sn alloy catalysts, and exceeds those of the most non-noble metal catalysts, indicating a possible Volmer-Heyrovsky reaction mechanism. The synthetic method can be extended to prepare other hollow core-shell structure electrocatalysts for low-temperature fuel cells.

Main factors causing intergranular and quasi-cleavage fractures at hydrogen-induced cracking in tempered martensitic steels

NASA Astrophysics Data System (ADS)

Kurokawa, Ami; Doshida, Tomoki; Hagihara, Yukito; Suzuki, Hiroshi; Takai, Kenichi

2018-05-01

Though intergranular (IG) and quasi-cleavage (QC) fractures have been widely recognized as typical fracture modes of the hydrogen-induced cracking in high-strength steels, the main factor has been unclarified yet. In the present study, the hydrogen content dependence on the main factor causing hydrogen-induced cracking has been examined through the fracture mode transition from QC to IG at the crack initiation site in the tempered martensitic steels. Two kinds of tempered martensitic steels were prepared to change the cohesive force due to the different precipitation states of Fe3C on the prior γ grain boundaries. A high amount of Si (H-Si) steel has a small amount of Fe3C on the prior austenite grain boundaries. Whereas, a low amount of Si (L-Si) steel has a large amount of Fe3C sheets on the grain boundaries. The fracture modes and initiations were observed using FE-SEM (Field Emission-Scanning Electron Microscope). The crack initiation sites of the H-Si steel were QC fracture at the notch tip under various hydrogen contents. While the crack initiation of the L-Si steel change from QC fracture at the notch tip to QC and IG fractures from approximately 10 µm ahead of the notch tip as increasing in hydrogen content. For L-Si steels, two possibilities are considered that the QC or IG fracture occurred firstly, or the QC and IG fractures occurred simultaneously. Furthermore, the principal stress and equivalent plastic strain distributions near the notch tip were calculated with FEM (Finite Element Method) analysis. The plastic strain was the maximum at the notch tip and the principle stress was the maximum at approximately 10 µm from the notch tip. The position of the initiation of QC and IG fracture observed using FE-SEM corresponds to the position of maximum strain and stress obtained with FEM, respectively. These findings indicate that the main factors causing hydrogen-induced cracking are different between QC and IG fractures.

Lemon grass (Cymbopogon citratus (D.C) Stapf) polyphenols protect human umbilical vein endothelial cell (HUVECs) from oxidative damage induced by high glucose, hydrogen peroxide and oxidised low-density lipoprotein.

PubMed

Campos, J; Schmeda-Hirschmann, G; Leiva, E; Guzmán, L; Orrego, R; Fernández, P; González, M; Radojkovic, C; Zuñiga, F A; Lamperti, L; Pastene, E; Aguayo, C

2014-05-15

The aromatic herb Cymbopogon citratus Stapf is widely used in tropical and subtropical countries in cooking, as a herbal tea, and in traditional medicine for hypertension and diabetes. Some of its properties have been associated with the in vitro antioxidant effect of polyphenols isolated from their aerial parts. However, little is known about C. citratus effects on endothelial cells oxidative injury. Using chromatographic procedures, a polyphenol-rich fraction was obtained from C. citratus (CCF) and their antioxidant properties were assessed by cooper-induced LDL oxidation assay. The main constituents of the active CCF, identified by high-performance liquid chromatography with diode-array detection and mass spectrometry (HPLC-DAD-MS), were chlorogenic acid, isoorientin and swertiajaponin. CCF 10 and 100 μg/ml diminishes reactive oxidative species (ROS) production in human umbilical vein endothelial cell (HUVECs), challenged with high D-glucose (60% inhibition), hydrogen peroxide (80% inhibition) or oxidised low-density lipoprotein (55% inhibition). CCF 10 or 100 μg/ml did not change nitric oxide (NO) production. However, CCF was able to inhibit vasoconstriction induced by the thromboxane A2 receptor agonist U46619, which suggest a NO-independent vasodilatador effect on blood vessels. Our results suggest that lemon grass antioxidant properties might prevent endothelial dysfunction associated to an oxidative imbalance promoted by different oxidative stimuli. Copyright © 2013 Elsevier Ltd. All rights reserved.

Pd/C Synthesized with Citric Acid: An Efficient Catalyst for Hydrogen Generation from Formic Acid/Sodium Formate

PubMed Central

Wang, Zhi-Li; Yan, Jun-Min; Wang, Hong-Li; Ping, Yun; Jiang, Qing

2012-01-01

A highly efficient hydrogen generation from formic acid/sodium formate aqueous solution catalyzed by in situ synthesized Pd/C with citric acid has been successfully achieved at room temperature. Interestingly, the presence of citric acid during the formation and growth of the Pd nanoparticles on carbon can drastically enhance the catalytic property of the resulted Pd/C, on which the conversion and turnover frequency for decomposition of formic acid/sodium formate system can reach the highest values ever reported of 85% within 160 min and 64 mol H2 mol−1 catalyst h−1, respectively, at room temperature. The present simple, low cost, but highly efficient CO-free hydrogen generation system at room temperature is believed to greatly promote the practical application of formic acid system on fuel cells. PMID:22953041

Creep-rupture behavior of candidate Stirling engine alloys after long-term aging at 760 deg C in low-pressure hydrogen

NASA Technical Reports Server (NTRS)

Titran, R. H.

1984-01-01

Nine candidate Stirling automotive engine alloys were aged at 760 C for 3500 hr in low pressure hydrogen or argon to determine the resulting effects on mechanical behavior. Candidate heater head tube alloys were CG-27, W545, 12RN72, INCONEL-718, and HS-188 while candidate cast cylinder-regenerator housing alloys were SA-F11, CRM-6D, XF-818, and HS-31. Aging per se is detrimental to the creep rupture and tensile strengths of the iron base alloys. The presence of hydrogen does not significantly contribute to strength degradation. Based percent highway driving cycle; CG-27 has adequate 3500 hr - 870 C creep rupture strength and SA-Fll, CRM-6D, and XF-818 have adequate 3500 hr - 775 C creep rupture strength.

The effects of forskolin and rolipram on cAMP, cGMP and free fatty acid levels in diet induced obesity.

PubMed

Doseyici, S; Mehmetoglu, I; Toker, A; Yerlikaya, F H; Erbay, E

2014-07-01

Obesity is a major health problem. We investigated the effects of forskolin and rolipram in the diet of animals in which obesity had been induced. We used 50 female albino Wistar rats that were assigned randomly into five groups as follows: group 1, control; group 2, high fat diet; group 3, high fat diet + forskolin; group 4, high fat diet + rolipram; and group 5, high fat diet + rolipram + forskolin. The rats were fed for 10 weeks and rolipram and forskolin were administered during last two weeks. The animals were sacrificed and blood samples were obtained. Serum cAMP, cGMP and free fatty acids (FFA) levels were measured using ELISA assays. We also measured weight gain during the 10 week period. cAMP and FFA levels of groups 3, 4 and 5 were significantly higher than those of groups 1 and 2. We found no significant differences in serum cGMP levels among the groups. The weight gain in groups 3, 4 and 5 was significantly less than for group 2. We also found that the weight gain in group 5 was significantly less than in groups 3 and 4. We found that both forskolin and rolipram stimulated lipolysis and inhibited body weight increase by increasing cAMP levels. Also, combination therapy using the two agents may be more effective in preventing diet induced obesity than either agent alone. We found also that these agents did not effect cellular cGMP levels in diet induced obesity.

Tuning a Schottky barrier of epitaxial graphene/4H-SiC (0001) by hydrogen intercalation

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

Dharmaraj, P.; Justin Jesuraj, P.; Jeganathan, K., E-mail: kjeganathan@yahoo.com

We report the electron transport properties of epitaxial graphene (EG) grown on 4H-SiC (0001) by low energy electron-beam irradiation. As-grown EG (AEG) on SiC interface exhibits rectifying current-voltage characteristics with a low Schottky barrier (SB) of 0.55 ± 0.05 eV and high reverse current leakage. The SB of AEG/SiC junction is extremely impeded by the Fermi level pinning (FLP) above the Dirac point due to charged states at the interface. Nevertheless, a gentle hydrogen intercalation at 900 °C enables the alleviation of both FLP and carrier scattering owing to the saturation of dangling bonds as evidenced by the enhancement of SB (0.75 ± 0.05 eV) and highmore » electron mobility well excess of 6000 cm{sup 2} V{sup −1} s{sup −1}.« less

Purine 3':5'-cyclic nucleotides with the nucleobase in a syn orientation: cAMP, cGMP and cIMP.

PubMed

Řlepokura, Katarzyna Anna

2016-06-01

Purine 3':5'-cyclic nucleotides are very well known for their role as the secondary messengers in hormone action and cellular signal transduction. Nonetheless, their solid-state conformational details still require investigation. Five crystals containing purine 3':5'-cyclic nucleotides have been obtained and structurally characterized, namely adenosine 3':5'-cyclic phosphate dihydrate, C10H12N5O6P·2H2O or cAMP·2H2O, (I), adenosine 3':5'-cyclic phosphate 0.3-hydrate, C10H12N5O6P·0.3H2O or cAMP·0.3H2O, (II), guanosine 3':5'-cyclic phosphate pentahydrate, C10H12N5O7P·5H2O or cGMP·5H2O, (III), sodium guanosine 3':5'-cyclic phosphate tetrahydrate, Na(+)·C10H11N5O7P(-)·4H2O or Na(cGMP)·4H2O, (IV), and sodium inosine 3':5'-cyclic phosphate tetrahydrate, Na(+)·C10H10N4O7P(-)·4H2O or Na(cIMP)·4H2O, (V). Most of the cyclic nucleotide zwitterions/anions [two from four cAMP present in total in (I) and (II), cGMP in (III), cGMP(-) in (IV) and cIMP(-) in (V)] are syn conformers about the N-glycosidic bond, and this nucleobase arrangement is accompanied by Crib-H...Npur hydrogen bonds (rib = ribose and pur = purine). The base orientation is tuned by the ribose pucker. An analysis of data obtained from the Cambridge Structural Database made in the context of syn-anti conformational preferences has revealed that among the syn conformers of various purine nucleotides, cyclic nucleotides and dinucleotides predominate significantly. The interactions stabilizing the syn conformation have been indicated. The inter-nucleotide contacts in (I)-(V) have been systematized in terms of the chemical groups involved. All five structures display three-dimensional hydrogen-bonded networks.

Reactivity of Transition Metals (Pd Pt Cu Ag Au) toward Molecular Hydrogen Dissociation: Extended Surfaces versus Particles Supported on TiC(001) or Small Is Not Always Better and Large Is Not Always Bad

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

Rodriguez J. A.; Gomez T.; Florez E.

2011-06-16

The reactivity of Pd{sub 4}, Pt{sub 4}, Cu{sub 4}, Ag{sub 4}, and Au{sub 4} clusters supported on TiC(001) toward molecular hydrogen dissociation has been studied by means of density functional based theory and periodic models and compared to that of the (111) and (001) surfaces. Pd{sub 4} and Pt{sub 4} interact rather strongly with the TiC(001) substrate, but the interaction of molecular hydrogen with the Pd{sub 4}/TiC and Pt{sub 4}/TiC systems is also very strong. As a consequence of the substantial admetal {leftrightarrow} carbide interactions, the adsorbed H{sub 2} molecule becomes more difficult to dissociate than on the corresponding extendedmore » (111) and (001) surfaces. Here, having a small supported particle does not lead to an enhanced chemical activity. On the contrary, for the Cu{sub 4}/TiC, Ag{sub 4}/TiC, and Au{sub 4}/TiC systems the combination of the small size of the particle and the polarization induced by the underlying carbide facilitates the dissociation of the hydrogen molecule with respect to the case of the extended surfaces. Here, the reduced size effectively enhances the activity of the supported particle. Thus, our results for the M(111), M(100), and M{sub 4}/TiC(001) systems show the complex interplay that can take place among the nature of the admetal, particle size effects, and support interactions.« less

Reactivity of Transition Metals (Pd, Pt, Cu, Ag, Au) toward Molecular Hydrogen Dissociation: Extended Surfaces versus Particles Supported on TiC(001) or Small Is Not Always Better and Large Is Not Always Bad

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

Rodriguez, J.A.; Gomez, T.; Florez, E.

2011-05-11

The reactivity of Pd{sub 4}, Pt{sub 4}, Cu{sub 4}, Ag{sub 4}, and Au{sub 4} clusters supported on TiC(001) toward molecular hydrogen dissociation has been studied by means of density functional based theory and periodic models and compared to that of the (111) and (001) surfaces. Pd{sub 4} and Pt{sub 4} interact rather strongly with the TiC(001) substrate, but the interaction of molecular hydrogen with the Pd{sub 4}/TiC and Pt{sub 4}/TiC systems is also very strong. As a consequence of the substantial admetal {leftrightarrow} carbide interactions, the adsorbed H{sub 2} molecule becomes more difficult to dissociate than on the corresponding extendedmore » (111) and (001) surfaces. Here, having a small supported particle does not lead to an enhanced chemical activity. On the contrary, for the Cu{sub 4}/TiC, Ag{sub 4}/TiC, and Au{sub 4}/TiC systems the combination of the small size of the particle and the polarization induced by the underlying carbide facilitates the dissociation of the hydrogen molecule with respect to the case of the extended surfaces. Here, the reduced size effectively enhances the activity of the supported particle. Thus, our results for the M(111), M(100), and M{sub 4}/TiC(001) systems show the complex interplay that can take place among the nature of the admetal, particle size effects, and support interactions.« less

Formation and infrared absorption of protonated naphthalenes (1-C10H9+ and 2-C10H9+) and their neutral counterparts in solid para-hydrogen.

PubMed

Bahou, Mohammed; Wu, Yu-Jong; Lee, Yuan-Pern

2013-02-14

Protonated naphthalene (C(10)H(9)(+)) and its neutral counterparts (hydronaphthyl radicals, C(10)H(9)) are important intermediates in the reactions of aromatic compounds and in understanding the unidentified infrared (IR) emissions from interstellar media. We report the IR spectra of 1-C(10)H(9)(+), 2-C(10)H(9)(+), 1-C(10)H(9), and 2-C(10)H(9) trapped in solid para-hydrogen (p-H(2)); the latter three are new. These species were produced upon electron bombardment of a mixture of naphthalene (C(10)H(8)) and p-H(2) during matrix deposition. The intensities of IR features of 1-C(10)H(9)(+) decreased after the matrix was maintained in darkness for 19 h, whereas those of 1-C(10)H(9) and 2-C(10)H(9) increased. Irradiation of this matrix sample with light at 365 nm diminished lines of 1-C(10)H(9)(+) and 2-C(10)H(9) and enhanced lines of 1-C(10)H(9) and 2-C(10)H(9)(+); the latter species was unstable and converted to 1-C(10)H(9)(+) in less than 30 min and 2-C(10)H(9) was converted to 1-C(10)H(9) at 365 nm. Observed wavenumbers and relative intensities of these species agree satisfactorily with the anharmonic vibrational wavenumbers and IR intensities predicted with the B3PW91/6-311++G(2d,2p) method. Compared with spectra recorded previously with IR photodissociation of Ar-tagged C(10)H(9)(+) or IR multiphoton dissociation of C(10)H(9)(+), our method has the advantages of producing high-resolution IR spectra with a wide spectral coverage, true IR intensity and excellent ratio of signal to noise; both protonated species and their neutral counterparts are produced with little interference from other fragments. With these advantages, the IR spectra of 1-C(10)H(9)(+), 2-C(10)H(9)(+), 1-C(10)H(9), and 2-C(10)H(9) are here clearly characterized.

Compound C induces protective autophagy in human cholangiocarcinoma cells via Akt/mTOR-independent pathway.

PubMed

Zhao, Xiaofang; Luo, Guosong; Cheng, Ying; Yu, Wenjing; Chen, Run; Xiao, Bin; Xiang, Yuancai; Feng, Chunhong; Fu, Wenguang; Duan, Chunyan; Yao, Fuli; Xia, Xianming; Tao, Qinghua; Wei, Mei; Dai, Rongyang

2018-07-01

Compound C, a well-known inhibitor of AMP-activated protein kinase (AMPK), has been reported to exert antitumor activities in some types of cells. Whether compound C can exert antitumor effects in human cholangiocarcinoma (CCA) remains unknown. Here, we demonstrated that compound C is a potent inducer of cell death and autophagy in human CCA cells. Autophagy inhibitors increased the cytotoxicity of compound C towards human CCA cells, as confirmed by increased LDH release, and PARP cleavage. It is notable that compound C treatment increased phosphorylated Akt, sustained high levels of phosphorylated p70S6K, and decreased mTOR regulated p-ULK1 (ser757). Based on the data that blocking PI3K/Akt or mTOR had no apparent influence on autophagic response, we suggest that compound C induces autophagy independent of Akt/mTOR signaling in human CCA cells. Further study demonstrated that compound C inhibited the phosphorylation of JNK and its target c-Jun. Blocking JNK by SP600125 or siRNA suppressed autophagy induction upon compound C treatment. Moreover, compound C induced p38 MAPK activation, and its inhibition promoted autophagy induction via JNK activation. In addition, compound C induced p53 expression, and its inhibition attenuated compound C-induced autophagic response. Thus, compound C triggers autophagy, at least in part, via the JNK and p53 pathways in human CCA cells. In conclusion, suppresses autophagy could increase compound C sensitivity in human CCA. © 2018 Wiley Periodicals, Inc.

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

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

Bhattacharjee, Rajesh; Xiang, Wenpei; Family Planning Research Institute, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, People's Republic of China

2012-06-22

Highlights: Black-Right-Pointing-Pointer cAMP blocks cell death induced by TNF and actinomycin D in cultured hepatocytes. Black-Right-Pointing-Pointer cAMP blocks NF-{kappa}B activation induced by TNF and actinomycin D. Black-Right-Pointing-Pointer cAMP blocks DISC formation following TNF and actinomycin D exposure. Black-Right-Pointing-Pointer cAMP blocks TNF signaling at a proximal step. -- Abstract: Tumor necrosis factor {alpha} (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 1more » (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

Carvedilol inhibits cADPR- and IP3-induced Ca2+ release.

PubMed

Morgan, Anthony J; Bampali, Konstantina; Ruas, Margarida; Factor, Cailley; Back, Thomas G; Chen, S R Wayne; Galione, Antony

2016-06-01

Spontaneous Ca 2+ waves, also termed store-overload-induced Ca 2+ release (SOICR), in cardiac cells can trigger ventricular arrhythmias especially in failing hearts. SOICR occurs when RyRs are activated by an increase in sarcoplasmic reticulum (SR) luminal Ca 2+ . Carvedilol is one of the most effective drugs for preventing arrhythmias in patients with heart failure. Furthermore, carvedilol analogues with minimal β-blocking activity also block SOICR showing that SOICR-inhibiting activity is distinct from that for β-block. We show here that carvedilol is a potent inhibitor of cADPR-induced Ca 2+ release in sea urchin egg homogenate. In addition, the carvedilol analog VK-II-86 with minimal β-blocking activity also suppresses cADPR-induced Ca 2+ release. Carvedilol appeared to be a non-competitive antagonist of cADPR and could also suppress Ca 2+ release by caffeine. These results are consistent with cADPR releasing Ca 2+ in sea urchin eggs by sensitizing RyRs to Ca 2+ involving a luminal Ca 2+ activation mechanism. In addition to action on the RyR, we also observed inhibition of inositol 1,4,5-trisphosphate (IP 3 )-induced Ca 2+ release by carvedilol suggesting a common mechanism between these evolutionarily related and conserved Ca 2+ release channels.

Persistent induction of c-fos and c-jun expression by asbestos

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

Heintz, N.H.; Mossman, B.T.; Janssen, Y.M.

To investigate the mechanisms of asbestos-induced carcinogenesis, expression of c-fos and c-jun protooncogenes was examined in rat pleural mesothelial cells and hamster tracheal epithelial cells after exposure to crocidolite or chrysotile asbestos. In contrast to phorbol 12-myristate 13-acetate, which induces rapid and transient increases in c-fos and c-jun mRNA, asbestos causes 2- to 5-fold increases in c-fos and c-jun mRNA that persist for at least 24 hr in mesothelial cells. The induction of c-fos and c-jun mRNA by asbestos in mesothelial cells is dose-dependent and is most pronounced with crocidolite, the type of asbestos most pathogenic in the causation ofmore » pleural mesothelioma. Induction of c-jun gene expression by asbestos occurs in tracheal epithelial cells but is not accompanied by a corresponding induction of c-fos gene expression. In both cell types, asbestos induces increases in protein factors that bind specifically to the DNA sites that mediate gene expression by the AP-1 family of transcription factors. The persistent induction of AP-1 transcription factors by asbestos suggests a model of asbestos-induced carcinogenesis involving chronic stimulation of cell proliferation through activation of the early response gene pathway that includes c-jun and/or c-fos. 30 refs., 5 figs.« less

Vitamin C and common cold-induced asthma: a systematic review and statistical analysis.

PubMed

Hemilä, Harri

2013-11-26

Asthma exacerbations are often induced by the common cold, which, in turn, can be alleviated by vitamin C. To investigate whether vitamin C administration influences common cold-induced asthma. Systematic review and statistical analysis of the identified trials. Medline, Scopus and Cochrane Central were searched for studies that give information on the effects of vitamin C on common cold-induced asthma. All clinically relevant outcomes related to asthma were included in this review. The estimates of vitamin C effect and their confidence intervals [CI] were calculated for the included studies. Three studies that were relevant for examining the role of vitamin C on common cold-induced asthma were identified. The three studies had a total of 79 participants. Two studies were randomized double-blind placebo-controlled trials. A study in Nigeria on asthmatics whose asthma attacks were precipitated by respiratory infections found that 1 g/day vitamin C decreased the occurrence of asthma attacks by 78% (95% CI: 19% to 94%). A cross-over study in former East-Germany on patients who had infection-related asthma found that 5 g/day vitamin C decreased the proportion of participants who had bronchial hypersensitivity to histamine by 52 percentage points (95% CI: 25 to 71). The third study did not use a placebo. Administration of a single dose of 1 gram of vitamin C to Italian non-asthmatic common cold patients increased the provocative concentration of histamine (PC20) 3.2-fold (95% CI: 2.0 to 5.1), but the vitamin C effect was significantly less when the same participants did not suffer from the common cold. The three reviewed studies differed substantially in their methods, settings and outcomes. Each of them found benefits from the administration of vitamin C; either against asthma attacks or against bronchial hypersensitivity, the latter of which is a characteristic of asthma. Given the evidence suggesting that vitamin C alleviates common cold symptoms and the findings

Vitamin C and common cold-induced asthma: a systematic review and statistical analysis

PubMed Central

2013-01-01

Background Asthma exacerbations are often induced by the common cold, which, in turn, can be alleviated by vitamin C. Objective To investigate whether vitamin C administration influences common cold-induced asthma. Methods Systematic review and statistical analysis of the identified trials. Medline, Scopus and Cochrane Central were searched for studies that give information on the effects of vitamin C on common cold-induced asthma. All clinically relevant outcomes related to asthma were included in this review. The estimates of vitamin C effect and their confidence intervals [CI] were calculated for the included studies. Results Three studies that were relevant for examining the role of vitamin C on common cold-induced asthma were identified. The three studies had a total of 79 participants. Two studies were randomized double-blind placebo-controlled trials. A study in Nigeria on asthmatics whose asthma attacks were precipitated by respiratory infections found that 1 g/day vitamin C decreased the occurrence of asthma attacks by 78% (95% CI: 19% to 94%). A cross-over study in former East-Germany on patients who had infection-related asthma found that 5 g/day vitamin C decreased the proportion of participants who had bronchial hypersensitivity to histamine by 52 percentage points (95% CI: 25 to 71). The third study did not use a placebo. Administration of a single dose of 1 gram of vitamin C to Italian non-asthmatic common cold patients increased the provocative concentration of histamine (PC20) 3.2-fold (95% CI: 2.0 to 5.1), but the vitamin C effect was significantly less when the same participants did not suffer from the common cold. Conclusions The three reviewed studies differed substantially in their methods, settings and outcomes. Each of them found benefits from the administration of vitamin C; either against asthma attacks or against bronchial hypersensitivity, the latter of which is a characteristic of asthma. Given the evidence suggesting that vitamin C

A Rh xS y/C Catalyst for the Hydrogen Oxidation and Hydrogen Evolution Reactions in HBr

DOE PAGES

Masud, Jahangir; Nguyena, Trung V.; Singh, Nirala; ...

2015-02-01

Rhodium sulfide (Rh 2S 3) on carbon support was synthesized by refluxing rhodium chloride with ammonium thiosulfate. Thermal treatment of Rh 2S 3 at high temperatures (600°C to 850°C) in presence of argon resulted in the transformation of Rh 2S 3 into Rh 3S 4, Rh 17S 15 and Rh which were characterized by TGA/DTA, XRD, EDX, and deconvolved XPS analyses. The catalyst particle size distribution ranged from 3 to 12 nm. Cyclic voltammetry and rotating disk electrode measurements were used to evaluate the catalytic activity for hydrogen oxidation and evolution reactions in H 2SO 4 and HBr solutions. Themore » thermally treated catalysts show high activity for the hydrogen reactions. The exchange current densities (i o) of the synthesized Rh xS y catalysts in H 2-saturated 1M H 2SO 4 and 1M HBr for HER and HOR were 0.9 mA/cm 2 to 1.0 mA/cm 2 and 0.8 to 0.9 mA/cm 2, respectively. The lower i o values obtained in 1M HBr solution compared to in H 2SO 4 might be due to the adsorption of Br - on the active surface. Stable electrochemical active surface area (ECSA) of Rh xS y catalyst was obtained for CV scan limits between 0 V and 0.65 V vs. RHE. Scans with upper voltage limit beyond 0.65 V led to decreased and unreproducible ECSA measurements.« less

The effect of Fe-Rh alloying on CO hydrogenation to C 2+ oxygenates

DOE PAGES

Palomino, Robert; Magee, Joseph W.; Llorca, Jordi; ...

2015-05-20

A combination of reactivity and structural studies using X-ray diffraction (XRD), pair distribution function (PDF), and transmission electron microscopy (TEM) was used to identify the active phases of Fe-modified Rh/TiO 2 catalysts for the synthesis of ethanol and other C 2+ oxygenates from CO hydrogenation. XRD and TEM confirm the existence of Fe–Rh alloys for catalyst with 1–7 wt% Fe and ~2 wt% Rh. Rietveld refinements show that FeRh alloy content increases with Fe loading up to ~4 wt%, beyond which segregation to metallic Fe becomes favored over alloy formation. Catalysts that contain Fe metal after reduction exhibit some carburizationmore » as evidenced by the formation of small amounts of Fe 3C during CO hydrogenation. Analysis of the total Fe content of the catalysts also suggests the presence of FeO x also increased under reaction conditions. Reactivity studies show that enhancement of ethanol selectivity with Fe loading is accompanied by a significant drop in CO conversion. Comparison of the XRD phase analyses with selectivity suggests that higher ethanol selectivity is correlated with the presence of Fe–Rh alloy phases. As a result, the interface between Fe and Rh serves to enhance the selectivity of ethanol, but suppresses the activity of the catalyst which is attributed to the blocking or modifying of Rh active sites.« less

Development of High Temperature SiC Based Hydrogen/Hydrocarbon Sensors with Bond Pads for Packaging

NASA Technical Reports Server (NTRS)

Xu, Jennifer C.; Hunter, Gary W.; Chen, Liangyu; Biagi-Labiosa, Azlin M.; Ward, Benjamin J.; Lukco, Dorothy; Gonzalez, Jose M., III; Lampard, Peter S.; Artale, Michael A.; Hampton, Christopher L.

2011-01-01

This paper describes efforts towards the transition of existing high temperature hydrogen and hydrocarbon Schottky diode sensor elements to packaged sensor structures that can be integrated into a testing system. Sensor modifications and the technical challenges involved are discussed. Testing of the sensors at 500 C or above is also presented along with plans for future development.

Implication of transcriptional repression in compound C-induced apoptosis in cancer cells

PubMed Central

Dai, R Y; Zhao, X F; Li, J J; Chen, R; Luo, Z L; Yu, L X; Chen, S K; Zhang, C Y; Duan, C Y; Liu, Y P; Feng, C H; Xia, X M; Li, H; Fu, J; Wang, H Y

2013-01-01

Compound C, a well-known inhibitor of AMP-activated protein kinase (AMPK), has been reported to induce apoptosis in some types of cells. However, the underlying mechanisms remain largely unclear. Using a DNA microarray analysis, we found that the expression of many genes was downregulated upon treatment with compound C. Importantly, compound C caused transcriptional repression with the induction of p53, a well-known marker of transcriptional stress response, in several cancer cell lines. Compound C did not induce the phosphorylation of p53 but dramatically increased the protein level of p53 similar to some other transcriptional inhibitors, including 5,6-dichloro-1-β-D-ribobenzimidazole (DRB). Consistent with previous reports, we found that compound C initiated apoptotic death of cancer cells in an AMPK-independent manner. Similar to DRB and actinomycin D (ActD), two classic transcription inhibitors, compound C not only resulted in the loss of Bcl-2 and Bcl-xl protein but also induced the phosphorylation of eukaryotic initiation factor-alpha (eIF2α) on Ser51. Hence, the phosphorylation of eIF2α might be a novel marker of transcriptional inhibition. It is noteworthy that compound C-mediated apoptosis of cancer cells is correlated with decreased expression of Bcl-2 and Bcl-xl and the phosphorylation of eIF2α on Ser51. Remarkably, compound C exhibits potent anticancer activities in vivo. Taken together, our data suggest that compound C may be an attractive candidate for anticancer drug development. PMID:24157877

Hydrogen-Rich Water Ameliorates Total Body Irradiation-Induced Hematopoietic Stem Cell Injury by Reducing Hydroxyl Radical

PubMed Central

Xue, Xiaolei; Han, Xiaodan; Li, Yuan; Lu, Lu; Li, Deguan

2017-01-01

We examined whether consumption of hydrogen-rich water (HW) could ameliorate hematopoietic stem cell (HSC) injury in mice with total body irradiation (TBI). The results indicated that HW alleviated TBI-induced HSC injury with respect to cell number alteration and to the self-renewal and differentiation of HSCs. HW specifically decreased hydroxyl radical (∙OH) levels in the c-kit+ cells of 4 Gy irradiated mice. Proliferative bone marrow cells (BMCs) increased and apoptotic c-kit+ cells decreased in irradiated mice uptaken with HW. In addition, the mean fluorescence intensity (MFI) of γ-H2AX and percentage of 8-oxoguanine positive cells significantly decreased in HW-treated c-kit+ cells, indicating that HW can alleviate TBI-induced DNA damage and oxidative DNA damage in c-kit+ cells. Finally, the cell cycle (P21), cell apoptosis (BCL-XL and BAK), and oxidative stress (NRF2, HO-1, NQO1, SOD, and GPX1) proteins were significantly altered by HW in irradiated mouse c-kit+ cells. Collectively, the present results suggest that HW protects against TBI-induced HSC injury. PMID:28243358

Hydrogen-Rich Water Ameliorates Total Body Irradiation-Induced Hematopoietic Stem Cell Injury by Reducing Hydroxyl Radical.

PubMed

Zhang, Junling; Xue, Xiaolei; Han, Xiaodan; Li, Yuan; Lu, Lu; Li, Deguan; Fan, Saijun

2017-01-01

We examined whether consumption of hydrogen-rich water (HW) could ameliorate hematopoietic stem cell (HSC) injury in mice with total body irradiation (TBI). The results indicated that HW alleviated TBI-induced HSC injury with respect to cell number alteration and to the self-renewal and differentiation of HSCs. HW specifically decreased hydroxyl radical ( ∙ OH) levels in the c-kit + cells of 4 Gy irradiated mice. Proliferative bone marrow cells (BMCs) increased and apoptotic c-kit + cells decreased in irradiated mice uptaken with HW. In addition, the mean fluorescence intensity (MFI) of γ -H2AX and percentage of 8-oxoguanine positive cells significantly decreased in HW-treated c-kit + cells, indicating that HW can alleviate TBI-induced DNA damage and oxidative DNA damage in c-kit + cells. Finally, the cell cycle (P21), cell apoptosis (BCL-XL and BAK), and oxidative stress (NRF2, HO-1, NQO1, SOD, and GPX1) proteins were significantly altered by HW in irradiated mouse c-kit + cells. Collectively, the present results suggest that HW protects against TBI-induced HSC injury.

Radiation-induced segregation at grain boundaries in AL-6XN stainless steels irradiated by hydrogen ions

NASA Astrophysics Data System (ADS)

Long, Yunxiang; Zheng, Zhongcheng; Guo, Liping; Zhang, Weiping; Shen, Zhenyu; Tang, Rui

2018-04-01

The effect of high concentration of hydrogen on the segregation of radiation-induced segregation (RIS) in AL-6XN stainless steels has been investigated by transmission electron microscopy (TEM) with energy-dispersive X-ray spectroscopy. Specimens were irradiated with 100 keV H2+ ions from 1 dpa to 5 dpa at 380 °C to investigated the dose dependence of grain boundary RIS. A specimen was irradiated to 5 dpa at 290 °C to study the effect of irradiation temperature. The trends of Cr depletion and Ni enrichment with irradiation dose is similar to that of other austenitic steels reported in the literatures, but the higher concentration of hydrogen made the RIS profile wider. An abnormal phenomenon that the degree of RIS increased with decreasing irradiation temperature was found, indicating that with the retention of hydrogen in the steels, temperature dependence of RIS is dominated by the quantity of retained hydrogen, rather than by thermal segregation processes.

c-Jun and Hypoxia-Inducible Factor 1 Functionally Cooperate in Hypoxia-Induced Gene Transcription

PubMed Central

Alfranca, Arántzazu; Gutiérrez, M. Dolores; Vara, Alicia; Aragonés, Julián; Vidal, Felipe; Landázuri, Manuel O.

2002-01-01

Under low-oxygen conditions, cells develop an adaptive program that leads to the induction of several genes, which are transcriptionally regulated by hypoxia-inducible factor 1 (HIF-1). On the other hand, there are other factors which modulate the HIF-1-mediated induction of some genes by binding to cis-acting motifs present in their promoters. Here, we show that c-Jun functionally cooperates with HIF-1 transcriptional activity in different cell types. Interestingly, a dominant-negative mutant of c-Jun which lacks its transactivation domain partially inhibits HIF-1-mediated transcription. This cooperative effect is not due to an increase in the nuclear amount of the HIF-1α subunit, nor does it require direct binding of c-Jun to DNA. c-Jun and HIF-1α are able to associate in vivo but not in vitro, suggesting that this interaction involves the participation of additional proteins and/or a posttranslational modification of these factors. In this context, hypoxia induces phosphorylation of c-Jun at Ser63 in endothelial cells. This process is involved in its cooperative effect, since specific blockade of the JNK pathway and mutation of c-Jun at Ser63 and Ser73 impair its functional cooperation with HIF-1. The functional interplay between c-Jun and HIF-1 provides a novel insight into the regulation of some genes, such as the one for VEGF, which is a key regulator of tumor angiogenesis. PMID:11739718

Short-chain C6 ceramide sensitizes AT406-induced anti-pancreatic cancer cell activity

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

Zhao, Xiaoguang; Sun, Baoyou; Zhang, Jingjing

Our previous study has shown that AT406, a first-in-class small molecular antagonist of IAPs (inhibitor of apoptosis proteins), inhibits pancreatic cancer cell proliferation in vitro and in vivo. The aim of this research is to increase AT406's sensitivity by adding short-chain C6 ceramide. We show that co-treatment of C6 ceramide dramatically potentiated AT406-induced caspase/apoptosis activation and cytotoxicity in established (Panc-1 and Mia-PaCa-2 lines) and primary human pancreatic cancer cells. Reversely, caspase inhibitors largely attenuated C6 ceramide plus AT406-induced above cancer cell death. Molecularly, C6 ceramide downregulated Bcl-2 to increase AT406's sensitivity in pancreatic cancer cells. Intriguingly, C6 ceramide-mediated AT406 sensitization was nullifiedmore » with Bcl-2 shRNA knockdown or pretreatment of the Bcl-2 inhibitor ABT-737. In vivo, liposomal C6 ceramide plus AT406 co-administration dramatically inhibited Panc-1 xenograft tumor growth in severe combined immunodeficient (SCID) mice. The combined anti-tumor activity was significantly more potent than either single treatment. Expressions of IAPs (cIAP1/XIAP) and Bcl-2 were downregulated in Panc-1 xenografts with the co-administration. Together, we demonstrate that C6 ceramide sensitizes AT406-mediated anti-pancreatic cancer cell activity possibly via downregulating Bcl-2. - Highlights: • C6 ceramide dramatically potentiates AT406-induced pancreatic cancer cell death. • C6 ceramide facilitates AT406-induced pancreatic cancer cell apoptosis. • C6 ceramide downregulates Bcl-2 to increase AT406's sensitivity in pancreatic cancer cells. • Liposomal C6 ceramide enhances AT406-induced anti-pancreatic cancer activity in vivo.« less

Metal-organic cooperative catalysis in C-H and C-C bond activation and its concurrent recovery.

PubMed

Park, Young Jun; Park, Jung-Woo; Jun, Chul-Ho

2008-02-01

components using a hydrogen-bonded self-assembled system as a catalyst support. This catalyst-recovery system provides a homogeneous phase at high temperature during the reaction and a heterogeneous phase at room temperature after the reaction. The product could be separated conveniently from the self-assembly support system by decanting the upper layer. The immobilized catalysts of both 2-aminopyridine and rhodium metal species sustained high catalytic activity for up to the eight catalytic reactions. In conclusion, the successful incorporation of an organocatalytic cycle into a transition metal catalyzed reaction led us to find MOCC for C-H and C-C bond activation. In addition, the hydrogen-bonded self-assembled support has been developed for an efficient and effective recovery system of homogeneous catalysts and could be successful in immobilizing both metal and organic catalysts.

Correction of both spontaneous and DEB-induced chromosome instability in Fanconi anemia FA-C cells by FACC cDNA

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

Stavropoulos, D.J.; Tomkins, D.J.; Allingham-Hawkins, D.J.

1994-09-01

Cells from all four Fanconi anemia complementation groups show hypersensitivity to cell-killing by mitomycin C (MMC), diepoxybutane (DEB) and other DNA cross-linking agents, and increased spontaneous and DEB-induced chromosome aberrations (CA). The extent of these phenotypes varies between lymphoblastoid cell lines from different complementation groups. Our data showed that the difference in MMC hypersensitivity and DEB-CA was not always coupled. While 230N (FA-B) had higher DEB-induced CA/cell than 536N (FA-C) (7.42 vs. 4.46 respectively), that latter was much more sensitive to cell-killing by MMC (dose at 10% survival, D{sub 10}: 5.2 vs. 1.2 ng/ml respectively). Strathdes et al. (1992) clonedmore » a cDNA Fanconi anemia complementation group C (FACC) which complemented the hypersensitivity to MMC and DEB cell-killing of FA-C cells (536N) but not cells from the other three complementation groups. The present study was initiated to determine whether chromosome instability in 536N is also complemented by the FACC (FAC3) cDNA. The pREP4-FAC3 vector was transfected into 536N and transfectants selected with hygromycin B. The DEB D{sub 10} of 536N (1.0 {mu}M) was corrected to the control level (16.2 {mu}M for 3TO) by FACC (15.1 {mu}M for 536N-FACC), as previously demonstrated. Chromosome instability (cab, cse, ctb, cte) was determined without and with 0.1 {mu}g/ml DEB treatment. Spontaneous CA of 536N (0.30 aberrations/cell) was corrected to the control level (0.04 for 3TO) by FACC (0.06 for 536N-FACC). Similarly, the DEB-induced CA was corrected (2.74 for 536N vs. 0.06 and 0.02 for 3TO and 536N-FACC respectively). Thus, at least for FA complementation group C, hypersensitivity to cell-killing and chromosome instability are not dissociated and are most likely caused by the same gene defect.« less

Ion collision-induced chemistry in pure and mixed loosely bound clusters of coronene and C60 molecules.

PubMed

Domaracka, Alicja; Delaunay, Rudy; Mika, Arkadiusz; Gatchell, Michael; Zettergren, Henning; Cederquist, Henrik; Rousseau, Patrick; Huber, Bernd A

2018-05-23

Ionization, fragmentation and molecular growth have been studied in collisions of 22.5 keV He2+- or 3 keV Ar+-projectiles with pure loosely bound clusters of coronene (C24H12) molecules or with loosely bound mixed C60-C24H12 clusters by using mass spectrometry. The heavier and slower Ar+ projectiles induce prompt knockout-fragmentation - C- and/or H-losses - from individual molecules and highly efficient secondary molecular growth reactions before the clusters disintegrate on picosecond timescales. The lighter and faster He2+ projectiles have a higher charge and the main reactions are then ionization by ions that are not penetrating the clusters. This leads mostly to cluster fragmentation without molecular growth. However, here penetrating collisions may also lead to molecular growth but to a much smaller extent than with 3 keV Ar+. Here we present fragmentation and molecular growth mass distributions with 1 mass unit resolution, which reveals that the same numbers of C- and H-atoms often participate in the formation and breaking of covalent bonds inside the clusters. We find that masses close to those with integer numbers of intact coronene molecules, or with integer numbers of both intact coronene and C60 molecules, are formed where often one or several H-atoms are missing or have been added on. We also find that super-hydrogenated coronene is formed inside the clusters.

Direct Aldehyde C-H Arylation and Alkylation via the Combination of Nickel, Hydrogen Atom Transfer, and Photoredox Catalysis.

PubMed

Zhang, Xiaheng; MacMillan, David W C

2017-08-23

A mechanism that enables direct aldehyde C-H functionalization has been achieved via the synergistic merger of photoredox, nickel, and hydrogen atom transfer catalysis. This mild, operationally simple protocol transforms a wide variety of commercially available aldehydes, along with aryl or alkyl bromides, into the corresponding ketones in excellent yield. This C-H abstraction coupling technology has been successfully applied to the expedient synthesis of the medicinal agent haloperidol.

Vitamin C Protects Chondrocytes against Monosodium Iodoacetate-Induced Osteoarthritis by Multiple Pathways.

PubMed

Chiu, Pu-Rong; Hu, Yu-Chen; Huang, Tzu-Ching; Hsieh, Bau-Shan; Yeh, Jou-Pei; Cheng, Hsiao-Ling; Huang, Li-Wen; Chang, Kee-Lung

2016-12-27

Osteoarthritis (OA) is the most prevalent joint disease. Dietary intake of vitamin C relates to a reduction in cartilage loss and OA. This study examined the efficacy of vitamin C to prevent OA with the in vitro chondrosarcoma cell line (SW1353) and the in vivo monosodium iodoacetate (MIA)-induced OA rat. Results demonstrated that, in SW1353 cells, treatment with 5 μM MIA inhibited cell growth and increased oxidative stress, apoptosis, and proteoglycan loss. In addition, the expression levels of the pro-inflammatory cytokines IL-6, IL-17A, and TNF-α and matrix metalloproteinases (MMPs) MMP-1, MMP-3, and MMP-13 were increased. All of these MIA-induced changes could be prevented with treatment of 100 μM vitamin C. In an animal model, intra-articular injection of MIA-induced cartilage degradation resembled the pathological changes of OA, and treatment of vitamin C could lessen these changes. Unexpectedly, vitamin C's effects did not strengthen with the increasing dosage, while the 100 mg/kg dosage was more efficient than the 200 or 300 mg/kg dosages. Vitamin C possessed multiple capacities for prevention of OA progress, including a decrease in apoptosis and in the expression of pro-inflammatory cytokines and MMPs in addition to the well-known antioxidation.

Nickel sulfide/graphitic carbon nitride/strontium titanate (NiS/g-C3N4/SrTiO3) composites with significantly enhanced photocatalytic hydrogen production activity.

PubMed

Luo, Xiu-Li; He, Gang-Ling; Fang, Yue-Ping; Xu, Yue-Hua

2018-05-15

NiS/g-C 3 N 4 /SrTiO 3 (NS/CN/STO) composites were prepared using a facile hydrothermal method. The synergistic effect of g-C 3 N 4 /SrTiO 3 (CN/STO) heterojunction and NiS cocatalyst enhanced the photocatalytic hydrogen evolution activity of NS/CN/STO. A hydrogen production rate of 1722.7 μmol h -1  g -1 was obtained when the 2%NiS/20%g-C 3 N 4 /SrTiO 3 (2NS/20CN/STO) was used for the photocatalytic hydrogen evolution in the presence of methanol used as a sacrificial agent under UV-vis light irradiation; the photocatalytic hydrogen production rate of 2NS/20CN/STO is 32.8, 8.9 and 4.2 times the value of that obtained with pure g-C 3 N 4 , SrTiO 3 and 20%g-C 3 N 4 /SrTiO 3 (20CN/STO), respectively. Moreover, in photoelectrochemical investigations when compared with 20CN/STO, SrTiO 3 and g-C 3 N 4 , 2NS/20CN/STO exhibited significant photocurrent enhancement. The heterojunction and cocatalyst in NS/CN/STO improved the charge separation efficiency and the lifetime of the charge carriers, leading to the enhanced generation of electrons for photocatalytic hydrogen production. Copyright © 2018 Elsevier Inc. All rights reserved.

Linear ketenimines. Variable structures of C,C-dicyanoketenimines and C,C-bis-sulfonylketenimines.

PubMed

Finnerty, Justin; Mitschke, Ullrich; Wentrup, Curt

2002-02-22

C,C-dicyanoketenimines 10a-c were generated by flash vacuum thermolysis of ketene N,S-acetals 9a-c or by thermal or photochemical decomposition of alpha-azido-beta-cyanocinnamonitrile 11. In the latter reaction, 3,3-dicyano-2-phenyl-1-azirine 12 is also formed. IR spectroscopy of the keteniminines isolated in Ar matrixes or as neat films, NMR spectroscopy of 10c, and theoretical calculations (B3LYP/6-31G) demonstrate that these ketenimines have variable geometry, being essentially linear along the CCN-R framework in polar media (neat films and solution), but in the gas phase or Ar matrix they are bent, as is usual for ketenimines. Experiments and calculations agree that a single CN substituent as in 13 is not enough to enforce linearity, and sulfonyl groups are less effective that cyano groups in causing linearity. C,C-bis(methylsulfonyl)ketenimines 4-5 and a C-cyano-C-(methylsulfonyl)ketenimine 15 are not linear. The compound p-O2NC6H4N=C=C(COOMe)2 previously reported in the literature is probably somewhat linearized along the CCNR moiety. A computational survey (B3LYP/6-31G) of the inversion barrier at nitrogen indicates that electronegative C-substituents dramatically lower the barrier; this is also true of N-acyl substituents. Increasing polarity causes lower barriers. Although N-alkylbis(methylsulfonyl)ketenimines are not calculated to be linear, the barriers are so low that crystal lattice forces can induce planarity in N-methylbis(methylsulfonyl)ketenimine 3.

Protective effects of C-phycocyanin on alcohol-induced acute liver injury in mice

NASA Astrophysics Data System (ADS)

Xia, Dong; Liu, Bing; Luan, Xiying; Sun, Junyan; Liu, Nana; Qin, Song; Du, Zhenning

2016-03-01

Excessive alcohol consumption leads to liver disease. Extensive evidence suggests that C-phycocyanin (C-PC), a chromophore phycocyanobilin derived from Spirulina platensis, exerts protective effects against chemical-induced organ damage. In this study, we investigated whether C-PC could protect against ethanol-induced acute liver injury. Serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), triglyceride (TG), total cholesterol (CHOL), low-density lipoprotein (LDL), liver homogenate malondialdehyde (MDA), superoxide dismutase (SOD) content were measured, and pathological examination of liver sections were examined. C-PC showed obvious inhibitory effects on serum ALT, AST, TG, CHOL, LDL and MDA, and SOD content significantly increased in the liver. The structure of hepatic lobules was clear, liver sinus returned to normal, and liver cell cords were arranged in neat rows. Cloudiness, swelling, inflammatory cell infiltration and spotty necrosis of liver cells were significantly reduced. Therefore, C-PC can significantly protect against ethanol-induced acute liver injury.

c-mip impairs podocyte proximal signaling and induces heavy proteinuria

PubMed Central

Zhang, Shao-Yu; Kamal, Maud; Dahan, Karine; Pawlak, André; Ory, Virginie; Desvaux, Dominique; Audard, Vincent; Candelier, Marina; Mohamed, Fatima Ben; Matignon, Marie; Christov, Christo; Decrouy, Xavier; Bernard, Veronique; Mangiapan, Gilles; Lang, Philippe; Guellaën, Georges; Ronco, Pierre; Sahali, Djillali

2010-01-01

Idiopathic nephrotic syndrome comprises several podocyte diseases of unknown origin, affecting the glomerular podocyte, which plays a key role in controlling the permeability of the kidney filter to proteins. It is characterized by the daily loss of more than 3 g of protein in urine, with no inflammatory lesions or cell infiltration. Nephrotic syndrome may be associated with serious complications, including sodium retention, hyperlipidemia, infectious diseases and thromboembolic events. The molecular mechanisms underlying non genetic nephrotic syndromes are unknown. We report here that the abundance of c-mip (c-maf inducing protein) increases in the podocytes of patients with acquired idiopathic nephrotic syndromes, including minimal change nephrotic syndrome (MCNS), a subset of focal and segmental glomerulosclerosis (FSGS) and membranous nephropathy (MN), in which the podocyte is the main target of injury. Transgenic mice overproducing c-mip in podocytes developed proteinuria without morphological alterations, inflammatory lesions or cell infiltration. We found that c-mip turned off podocyte signaling by preventing the interaction of nephrin with the tyrosine kinase Fyn, thereby decreasing nephrin phosphorylation in vitro and in vivo. Moreover, c-mip inhibited interactions between Fyn and N-WASP and between Nck and nephrin, potentially accounting for cytoskeletal disorganization and the effacement of foot processes. The intravenous injection of a small interfering RNA (siRNA) targeting c-mip prevented lipopolysaccharide-induced proteinuria in mice. These results provide new insights into the molecular mechanism of acquired podocyte diseases. PMID:20484117

Influence of N-H...O and C-H...O hydrogen bonds on the 17O NMR tensors in crystalline uracil: computational study.

PubMed

Ida, Ramsey; De Clerk, Maurice; Wu, Gang

2006-01-26

We report a computational study for the 17O NMR tensors (electric field gradient and chemical shielding tensors) in crystalline uracil. We found that N-H...O and C-H...O hydrogen bonds around the uracil molecule in the crystal lattice have quite different influences on the 17O NMR tensors for the two C=O groups. The computed 17O NMR tensors on O4, which is involved in two strong N-H...O hydrogen bonds, show remarkable sensitivity toward the choice of cluster model, whereas the 17O NMR tensors on O2, which is involved in two weak C-H...O hydrogen bonds, show much smaller improvement when the cluster model includes the C-H...O hydrogen bonds. Our results demonstrate that it is important to have accurate hydrogen atom positions in the molecular models used for 17O NMR tensor calculations. In the absence of low-temperature neutron diffraction data, an effective way to generate reliable hydrogen atom positions in the molecular cluster model is to employ partial geometry optimization for hydrogen atom positions using a cluster model that includes all neighboring hydrogen-bonded molecules. Using an optimized seven-molecule model (a total of 84 atoms), we were able to reproduce the experimental 17O NMR tensors to a reasonably good degree of accuracy. However, we also found that the accuracy for the calculated 17O NMR tensors at O2 is not as good as that found for the corresponding tensors at O4. In particular, at the B3LYP/6-311++G(d,p) level of theory, the individual 17O chemical shielding tensor components differ by less than 10 and 30 ppm from the experimental values for O4 and O2, respectively. For the 17O quadrupole coupling constant, the calculated values differ by 0.30 and 0.87 MHz from the experimental values for O4 and O2, respectively.

Hydrogen-Induced Cold Cracking in High-Frequency Induction Welded Steel Tubes

NASA Astrophysics Data System (ADS)

Banerjee, Kumkum

2016-04-01

Detailed investigation was carried out on 0.4C steel tubes used for the telescopic front fork of two-wheelers to establish the root cause for the occurrence of transverse cracks at the weld heat-affected zone of the tubes. Fractographic and microstructural observations provide evidences of delayed hydrogen-induced cracking. The beneficial microstructure for avoiding the transverse cracks was found to be the bainitic-martensitic, while martensitic structure was noted to be deleterious.

DISTINCT FUNCTIONS OF JNK AND C-JUN IN OXIDANT-INDUCED HEPATOCYTE DEATH

PubMed Central

Amir, Muhammad; Liu, Kun; Zhao, Enpeng; Czaja, Mark J.

2013-01-01

Overactivation of c-Jun N-terminal kinase (JNK)/c-Jun signaling is a central mechanism of hepatocyte injury and death including that from oxidative stress. However, the functions of JNK and c-Jun are still unclear, and this pathway also inhibits hepatocyte death. Previous studies of menadione-induced oxidant stress demonstrated that toxicity resulted from sustained JNK/c-Jun activation as death was blocked by the c-Jun dominant negative TAM67. To further delineate the function of JNK/c-Jun signaling in hepatocyte injury from oxidant stress, the effects of direct JNK inhibition on menadione-induced death were examined. In contrast to the inhibitory effect of TAM67, pharmacological JNK inhibition by SP600125 sensitized the rat hepatocyte cell line RALA255-10G to death from menadione. SP600125 similarly sensitized mouse primary hepatocytes to menadione toxicity. Death from SP600125/menadione was c-Jun dependent as it was blocked by TAM67, but independent of c-Jun phosphorylation. Death occurred by apoptosis and necrosis and activation of the mitochondrial death pathway. Short hairpin RNA knockdowns of total JNK or JNK2 sensitized to death from menadione, whereas a jnk1 knockdown was protective. Jnk2 null mouse primary hepatocytes were also sensitized to menadione death. JNK inhibition magnified decreases in cellular ATP content and β-oxidation induced by menadione. This effect mediated cell death as chemical inhibition of β-oxidation also sensitized cells to death from menadione, and supplementation with the β-oxidation substrate oleate blocked death. Components of the JNK/c-Jun signaling pathway have opposing functions in hepatocyte oxidant stress with JNK2 mediating resistance to cell death and c-Jun promoting death. PMID:22644775

PtNi Alloy Cocatalyst Modification of Eosin Y-Sensitized g-C3N4/GO Hybrid for Efficient Visible-Light Photocatalytic Hydrogen Evolution

NASA Astrophysics Data System (ADS)

Wang, Peng; Zong, Lanlan; Guan, Zhongjie; Li, Qiuye; Yang, Jianjun

2018-02-01

An economic and effective Pt-based alloy cocatalyst has attracted considerable attention due to their excellent catalytic activity and reducing Pt usage. In this study, PtNi alloy cocatalyst was successfully decorated on the g-C3N4/GO hybrid photocatalyst via a facile chemical reduction method. The Eosin Y-sensitized g-C3N4/PtNi/GO-0.5% composite photocatalyst yields about 1.54 and 1178 times higher hydrogen evolution rate than the Eosin Y-sensitized g-C3N4/Pt/GO-0.5% and g-C3N4/Ni/GO-0.5% samples, respectively. Mechanism of enhanced performance for the g-C3N4/PtNi/GO composite was also investigated by different characterization, such as photoluminescence, transient photocurrent response, and TEM. These results indicated that enhanced charge separation efficiency and more reactive sites are responsible for the improved hydrogen evolution performance due to the positive synergetic effect between Pt and Ni. This study suggests that PtNi alloy can be used as an economic and effective cocatalyst for hydrogen evolution reaction. [Figure not available: see fulltext.

3-Methyl-7-(2-thienyl)pyrido[2,3-d]pyrimidine-2,4(1H,3H)-dione: pi-stacked bilayers built from N-H...O, C-H...O and C-H...pi hydrogen bonds.

PubMed

Trilleras, Jorge; Quiroga, Jairo; Cobo, Justo; Glidewell, Christopher

2009-06-01

In the title compound, C(12)H(9)N(3)O(2)S, the thienyl substituent is disordered over two sets of sites with occupancies of 0.749 (3) and 0.251 (3). A combination of N-H...O, C-H...O and C-H...pi hydrogen bonds links the molecules into bilayers and these bilayers are themselves linked into a continuous structure by pi-pi stacking interactions.

Drug-induced Sweet's syndrome secondary to hepatitis C antiviral therapy.

PubMed

Gheorghe, Liana; Cotruta, Bogdan; Trifu, Viorel; Cotruta, Cristina; Becheanu, Gabriel; Gheorghe, Cristian

2008-09-01

Pegylated interferon-alpha in combination with ribavirin currently represents the therapeutic standard for the hepatitis C virus infection. Interferon based therapy may be responsible for many cutaneous side effects. We report a case of drug-induced Sweet's syndrome secondary to hepatitis C antiviral therapy. To our knowledge, this is the first reported case of Sweet's syndrome in association with pegylated interferon-alpha therapy.

Glutathione Depletion Induced by c-Myc Downregulation Triggers Apoptosis on Treatment with Alkylating Agents1

PubMed Central

Biroccio, Annamaria; Benassi, Barbara; Fiorentino, Francesco; Zupi, Gabriella

2004-01-01

Abstract Here we investigate the mechanism(s) involved in the c-Myc-dependent drug response of melanoma cells. By using three M14-derived c-Myc low-expressing clones, we demonstrate that alkylating agents, cisplatin and melphalan, trigger apoptosis in the c-Myc antisense transfectants, but not in the parental line. On the contrary, topoisomerase inhibitors, adriamycin and camptothecin, induce apoptosis to the same extent regardless of c-Myc expression. Because we previously demonstrated that c-Myc downregulation decreases glutathione (GSH) content, we evaluated the role of GSH in the apoptosis induced by the different drugs. In control cells treated with one of the alkylating agents or the others, GSH depletion achieved by l-buthionine-sulfoximine preincubation opens the apoptotic pathway. The apoptosis proceeded through early Bax relocalization, cytochrome c release, and concomitant caspase-9 activation, whereas reactive oxygen species production and alteration of mitochondria membrane potential were late events. That GSH was determining in the c-Myc-dependent drug-induced apoptosis was demonstrated by altering the intracellular GSH content of the c-Myc low-expressing cells up to the level of controls. Indeed, GSH ethyl ester-mediated increase of GSH abrogated apoptosis induced by cisplatin and melphalan by inhibition of Bax/cytochrome c redistribution. The relationship among c-Myc, GSH content, and the response to alkylating agent has been also evaluated in the M14 Myc overexpressing clones as well as in the melanoma JR8 c-Myc antisense transfectants. All together, these results demonstrate that GSH plays a key role in governing c-Myc-dependent drug-induced apoptosis. PMID:15153331

Intestinal Enteroids Model Guanylate Cyclase C-Dependent Secretion Induced by Heat-Stable Enterotoxins.

PubMed

Pattison, Amanda M; Blomain, Erik S; Merlino, Dante J; Wang, Fang; Crissey, Mary Ann S; Kraft, Crystal L; Rappaport, Jeff A; Snook, Adam E; Lynch, John P; Waldman, Scott A

2016-10-01

Enterotoxigenic Escherichia coli (ETEC) causes ∼20% of the acute infectious diarrhea (AID) episodes worldwide, often by producing heat-stable enterotoxins (STs), which are peptides structurally homologous to paracrine hormones of the intestinal guanylate cyclase C (GUCY2C) receptor. While molecular mechanisms mediating ST-induced intestinal secretion have been defined, advancements in therapeutics have been hampered for decades by the paucity of disease models that integrate molecular and functional endpoints amenable to high-throughput screening. Here, we reveal that mouse and human intestinal enteroids in three-dimensional ex vivo cultures express the components of the GUCY2C secretory signaling axis. ST and its structural analog, linaclotide, an FDA-approved oral secretagog, induced fluid accumulation quantified simultaneously in scores of enteroid lumens, recapitulating ETEC-induced intestinal secretion. Enteroid secretion depended on canonical molecular signaling events responsible for ETEC-induced diarrhea, including cyclic GMP (cGMP) produced by GUCY2C, activation of cGMP-dependent protein kinase (PKG), and opening of the cystic fibrosis transmembrane conductance regulator (CFTR). Importantly, pharmacological inhibition of CFTR abrogated enteroid fluid secretion, providing proof of concept for the utility of this model to screen antidiarrheal agents. Intestinal enteroids offer a unique model, integrating the GUCY2C signaling axis and luminal fluid secretion, to explore the pathophysiology of, and develop platforms for, high-throughput drug screening to identify novel compounds to prevent and treat ETEC diarrheal disease. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

Effects of interleukin-7/interleukin-7 receptor on RANKL-mediated osteoclast differentiation and ovariectomy-induced bone loss by regulating c-Fos/c-Jun pathway.

PubMed

Zhao, Ji-Jun; Wu, Zhao-Feng; Yu, Ying-Hao; Wang, Ling; Cheng, Li

2018-09-01

To explore the effects of IL-7/IL-7R on the RANKL-mediated osteoclast differentiation in vitro and OVX-induced bone loss in vivo. BMMs and RAW264.7 were transfected with IL-7, IL-7R siRNA, c-Fos siRNA, and c-jun siRNA and later stimulated by RANKL. TRAP and toluidine blue staining were used to observe osteoclast formation and bone resorption, respectively. HE and TRAP staining were used to detect trabecular bone microstructure and osteoclasts of mice, respectively. qRT-PCR and Western blot analysis were used to examine expression. IL-7 unregulated the expression of CTSK, NFATc1, MMP9, and the phosphorylation of p38 and Akt by activating the c-Fos/c-Jun pathway, which increased osteoclast numbers and bone resorption in RANKL-stimulated macrophages. While IL-7R siRNA and c-Fos siRNA decreased the expression, as well as and the phosphorylation of p38 and Akt.IL-7 decreased the BMD and OPG expression in OVX-induced mice and increased the TRAP positive cells, the mRNA expression of c-fos, c-jun, and RANKL, which was contradictory to IL-7R siRNA, and c-Fos siRNA. Furthermore, IL-7R siRNA and c-Fos siRNA caused thicker trabeculae, increased trabecular number, and decreased osteolysis in OVX mice. IL-7/IL-7R can promote RANKL-mediated osteoclast formation and bone resorption by activating the c-Fos/c-Jun pathway, as well as inducing bone loss in OVX mice. © 2018 Wiley Periodicals, Inc.

Efficacy of vitamin C against liver and kidney damage induced by paraquat toxicity.

PubMed

Awadalla, Eatemad A

2012-07-01

Paraquat has been demonstrated to be a highly toxic compound for humans and animals and many cases of acute poisoning and death have been reported over the past few decades. The current experiment aimed to examine if vitamin C (ascorbic acid) alleviates the morphological changes induced by paraquat (PQ) administration in the liver and kidney of male albino rats. Male adult rats received paraquat (PQ) (1.5 mg/kg body weight) daily for three weeks. Vitamin C (VC) at a dose of 20 mg/kg body weight was given concomitantly with PQ to rats. Animals were divided into three groups in this experiment (control, PQ and PQ+VC). The morphopathological manifestations were investigated in tissues from liver and kidney. As expected, PQ administration induced marked changes in the morphological structure of the liver and kidney in PQ demonstrated animals. Importantly, vitamin C administration restored PQ-induced changes in the studied organs. Vitamin C administration attenuated the morphological damages induced by PQ in the liver and kidney of experimental animals. Our results suggest an antitoxic effect of vitamin C against paraquat. Copyright © 2010 Elsevier GmbH. All rights reserved.

Endotoxin-induced shock in the rat. A role for C5a.

PubMed Central

Smedegård, G.; Cui, L. X.; Hugli, T. E.

1989-01-01

Administration of endotoxin from gram-negative bacteria to rats results in systemic hypotension, an increased hematocrit, and decreased numbers of circulating leukocytes (polymorphonuclear), monocytes, and platelets. These potentially lethal physiologic changes may be partially attributed to complement activation and generation of anaphylatoxins by the endotoxin (LPS). We demonstrated an elevation in the plasma levels of both C3a and C5a in LPS-treated rats. Injection of 5 micrograms C5ades Arg (rat) into rats produced effects similar to those induced by LPS, including decreased mean arterial pressure (systemic hypotension) and decreased numbers of circulating polymorphonuclear leukocytes, monocytes, and platelets. Unlike the response to LPS, C5a did not increase the hematocrit, indicating little effect on vascular permeability at the doses used. When LPS-treated animals were pretreated with F(ab')2 fragments of rabbit anti-rat C5a, no changes were measured in the circulating cell counts compared with LPS alone; however a significant improvement in the mean arterial pressure and a decrease in hematocrit was observed. We conclude that LPS-induced (septic) shock in the rat may result, in part, from the effects of complement activation and particularly from the generation of C5a. The influence of C5a on the LPS effect in the rat appears to enhance both the hypotensive (mean arterial pressure) and vascular permeability (hematocrit) responses. These results appear to support and confirm earlier observations that anti-human C5a increased survival in a septic-shock monkey model by eliminating circulating C5a and presumably thereby reducing the effects of endotoxin on blood pressure. Our results demonstrate that C5a plays a significant role in the hemodynamic changes associated with endotoxin-induced shock. Neutralization of C5a with specific antibodies may reduce the hypotensive response to endotoxin sufficiently to prevent lethal septic shock both in animals and in man

Deactivation of Ceria Supported Palladium through C–C Scission during Transfer Hydrogenation of Phenol with Alcohols

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

Nelson, Nicholas C.; Manzano, J. Sebastián; Slowing, Igor I.

The stability of palladium supported on ceria (Pd/CeO 2) was studied during liquid flow transfer hydrogenation using primary and secondary alcohols as hydrogen donors. For primary alcohols, the ceria support was reduced to cerium hydroxy carbonate within 14 h and was a contributing factor toward catalyst deactivation. For secondary alcohols, cerium hydroxy carbonate was not observed during the same time period and the catalyst was stable upon prolonged reaction. Regeneration through oxidation/reduction does not restore initial activity likely due to irreversible catalyst restructuring. Lastly, a deactivation mechanism involving C–C scission of acyl and carboxylate intermediates is proposed.

Deactivation of Ceria Supported Palladium through C–C Scission during Transfer Hydrogenation of Phenol with Alcohols

DOE PAGES

Nelson, Nicholas C.; Manzano, J. Sebastián; Slowing, Igor I.

2016-11-21

The stability of palladium supported on ceria (Pd/CeO 2) was studied during liquid flow transfer hydrogenation using primary and secondary alcohols as hydrogen donors. For primary alcohols, the ceria support was reduced to cerium hydroxy carbonate within 14 h and was a contributing factor toward catalyst deactivation. For secondary alcohols, cerium hydroxy carbonate was not observed during the same time period and the catalyst was stable upon prolonged reaction. Regeneration through oxidation/reduction does not restore initial activity likely due to irreversible catalyst restructuring. Lastly, a deactivation mechanism involving C–C scission of acyl and carboxylate intermediates is proposed.

Up-regulation of microglial cathepsin C expression and activity in lipopolysaccharide-induced neuroinflammation.

PubMed

Fan, Kai; Wu, Xuefei; Fan, Bin; Li, Ning; Lin, Yongzhong; Yao, Yiwen; Ma, Jianmei

2012-05-20

Cathepsin C (Cat C) functions as a central coordinator for activation of many serine proteases in inflammatory cells. It has been recognized that Cat C is responsible for neutrophil recruitment and production of chemokines and cytokines in many inflammatory diseases. However, Cat C expression and its functional role in the brain under normal conditions or in neuroinflammatory processes remain unclear. Our previous study showed that Cat C promoted the progress of brain demyelination in cuprizone-treated mice. The present study further investigated the Cat C expression and activity in lipopolysaccharide (LPS)-induced neuroinflammation in vivo and in vitro. C57BL/6 J mice were intraperitoneally injected with either 0.9% saline or lipopolysaccharide (LPS, 5 mg/kg). Immunohistochemistry (IHC) and in situ hybridization (ISH) were used to analyze microglial activation, TNF-α, IL-1β, IL-6, iNOS mRNAs expressions and cellular localization of Cat C in the brain. Nitrite assay was used to examine microglial activation in vitro; RT-PCR and ELISA were used to determine the expression and release of Cat C. Cat C activity was analyzed by cellular Cat C assay kit. Data were evaluated for statistical significance with paired t test. Cat C was predominantly expressed in hippocampal CA2 neurons in C57BL/6 J mice under normal conditions. Six hours after LPS injection, Cat C expression was detected in cerebral cortical neurons; whereas, twenty-four hours later, Cat C expression was captured in activated microglial cells throughout the entire brain. The duration of induced Cat C expression in neurons and in microglial cells was ten days and three days, respectively. In vitro, LPS, IL-1β and IL-6 treatments increased microglial Cat C expression in a dose-dependent manner and upregulated Cat C secretion and its activity. Taken together, these data indicate that LPS and proinflammatory cytokines IL-1β, IL-6 induce the expression, release and upregulate enzymatic activity of Cat C in

Up-regulation of microglial cathepsin C expression and activity in lipopolysaccharide-induced neuroinflammation

PubMed Central

2012-01-01

Background Cathepsin C (Cat C) functions as a central coordinator for activation of many serine proteases in inflammatory cells. It has been recognized that Cat C is responsible for neutrophil recruitment and production of chemokines and cytokines in many inflammatory diseases. However, Cat C expression and its functional role in the brain under normal conditions or in neuroinflammatory processes remain unclear. Our previous study showed that Cat C promoted the progress of brain demyelination in cuprizone-treated mice. The present study further investigated the Cat C expression and activity in lipopolysaccharide (LPS)-induced neuroinflammation in vivo and in vitro. Methods C57BL/6 J mice were intraperitoneally injected with either 0.9% saline or lipopolysaccharide (LPS, 5 mg/kg). Immunohistochemistry (IHC) and in situ hybridization (ISH) were used to analyze microglial activation, TNF-α, IL-1β, IL-6, iNOS mRNAs expressions and cellular localization of Cat C in the brain. Nitrite assay was used to examine microglial activation in vitro; RT-PCR and ELISA were used to determine the expression and release of Cat C. Cat C activity was analyzed by cellular Cat C assay kit. Data were evaluated for statistical significance with paired t test. Results Cat C was predominantly expressed in hippocampal CA2 neurons in C57BL/6 J mice under normal conditions. Six hours after LPS injection, Cat C expression was detected in cerebral cortical neurons; whereas, twenty-four hours later, Cat C expression was captured in activated microglial cells throughout the entire brain. The duration of induced Cat C expression in neurons and in microglial cells was ten days and three days, respectively. In vitro, LPS, IL-1β and IL-6 treatments increased microglial Cat C expression in a dose-dependent manner and upregulated Cat C secretion and its activity. Conclusions Taken together, these data indicate that LPS and proinflammatory cytokines IL-1β, IL-6 induce the expression, release and

Cardiolipin-Specific Peroxidase Reactions of Cytochrome c in Mitochondria During Irradiation-Induced Apoptosis

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

Belikova, Natalia A.; Jiang Jianfei; Tyurina, Yulia Y.

2007-09-01

Purpose: To determine whether cytochrome c (cyt c) content and associated cardiolipin oxidation can be determinants of cell sensitivity to irradiation-induced apoptosis. Methods and Materials: The small interfering RNA (siRNA) approach was used to engineer HeLa cells with lowered contents of cyt c (14%, HeLa 1.2 cells). Cells were treated by {gamma}-irradiation (in doses of 5-40 Gy). Lipid oxidation was characterized by electrospray ionization mass spectrometry analysis and fluorescence high-performance liquid chromatography-based Amplex Red assay. Release of a proapoptotic factor (cyt c, Smac/DIABLO) was detected by Western blotting. Apoptosis was revealed by caspase-3/7 activation and phosphatidylserine externalization. Results: Irradiation causedmore » selective accumulation of hydroperoxides in cardiolipin (CL) but not in other phospholipids. HeLa 1.2 cells responded by a lower irradiation-induced accumulation of CL oxidation products than parental HeLa cells. Proportionally decreased release of a proapoptotic factor, Smac/DIABLO, was detected in cyt c-deficient cells after irradiation. Caspase-3/7 activation and phosphatidylserine externalization were proportional to the cyt c content in cells. Conclusions: Cytochrome c is an important catalyst of CL peroxidation, critical to the execution of the apoptotic program. This new role of cyt c in irradiation-induced apoptosis is essential for the development of new radioprotectors and radiosensitizers.« less

Hydrogen defects in α-Al2O3 and water weakening of sapphire and alumina ceramics between 600°C and 1000°C: II. Mechanical properties

USGS Publications Warehouse

Castaing, J.; Kronenberg, A.K.; Kirby, S.H.; Mitchell, T.E.

2000-01-01

Hydrogen impurities in alumina have been introduced by hydrothermal annealing (see part I). In this paper, we report on reductions in the flow strength of α-Al2O3 single crystals and polycrystals associated with hydrogen incorporation. Prior to deformation, α-Al2O3 single crystal and ceramic specimens were annealed in the presence of supercritical water at 850° or 900°C, under 1500 MPa pressure. Sapphire and alumina ceramics were plastically deformed between 600° and 1000°C under 1500 MPa pressure, by the addition of a uniaxial stress. Flow stresses are reduced by a factor of two, due to the presence of water, for sapphire and large grain (30–50 μm) polycrystals, as a result of enhanced dislocation mobility. Flow stresses of fine-grained (3–5 μm) polycrystals are reduced by water by a factor of six. This large reduction in strength is attributed to a change in mechanism from dislocation glide under dry conditions to grain boundary sliding under hydrothermal conditions.

Radiation-induced chromosomal instability in BALB/c and C57BL/6 mice: the difference is as clear as black and white

NASA Technical Reports Server (NTRS)

Ponnaiya, B.; Cornforth, M. N.; Ullrich, R. L.

1997-01-01

Genomic instability has been proposed to be the earliest step in radiation-induced tumorigenesis. It follows from this hypothesis that individuals highly susceptible to induction of tumors by radiation should exhibit enhanced radiation-induced instability. BALB/c white mice are considerably more sensitive to radiation-induced mammary cancer than C57BL/6 black mice. In this study, primary mammary epithelial cell cultures from these two strains were examined for the "delayed" appearance of chromosomal aberrations after exposure to 137Cs gamma radiation, as a measure of radiation-induced genomic instability. As expected, actively dividing cultures from both strains showed a rapid decline of initial asymmetrical aberrations with time postirradiation. However, after 16 population doublings, cells from BALB/c mice exhibited a marked increase in the frequency of chromatid-type breaks and gaps which remained elevated throughout the time course of the experiment (28 doublings). No such effect was observed for the cells of C57BL/6 mice; after the rapid clearance of initial aberrations, the frequency of chromatid-type aberrations in the irradiated population remained at or near those of nonirradiated controls. These results demonstrate a correlation between the latent expression of chromosomal damage in vitro and susceptibility for mammary tumors, and provide further support for the central role of radiation-induced instability in the process of tumorigenesis.

Reactions between atomic chlorine and pyridine in solid para-hydrogen: infrared spectrum of the 1-chloropyridinyl (C5H5N-Cl) radical.

PubMed

Das, Prasanta; Bahou, Mohammed; Lee, Yuan-Pern

2013-02-07

With infrared absorption spectra we investigated the reaction between Cl atom and pyridine (C(5)H(5)N) in a para-hydrogen (p-H(2)) matrix. Pyridine and Cl(2) were co-deposited with p-H(2) at 3.2 K; a planar C(5)H(5)N-Cl(2) complex was identified from the observed infrared spectrum of the Cl(2)/C(5)H(5)N/p-H(2) matrix. Upon irradiation at 365 nm to generate Cl atom in situ and annealing at 5.1 K for 3 min to induce secondary reaction, the 1-chloropyridinyl radical (C(5)H(5)N-Cl) was identified as the major product of the reaction Cl + C(5)H(5)N in solid p-H(2); absorption lines at 3075.9, 1449.7, 1200.6, 1148.8, 1069.3, 1017.4, 742.9, and 688.7 cm(-1) were observed. The assignments are based on comparison of observed vibrational wavenumbers and relative IR intensities with those predicted using the B3PW91/6-311++G(2d, 2p) method. The observation of the preferential addition of Cl to the N-site of pyridine to form C(5)H(5)N-Cl radical but not 2-, 3-, or 4-chloropyridine (ClC(5)H(5)N) radicals is consistent with the reported theoretical prediction that formation of the former proceeds via a barrierless path.

Lipoic Acid Exerts Antioxidant and Anti-inflammatory Effects in Response to Heat Shock in C2C12 Myotubes.

PubMed

Lee, Cheng-Tse; Chang, Li-Ching; Wu, Pei-Fung

2016-06-01

This study explored that lipoic acid treatment for 24 h significantly upregulated and promoted heat shock-induced catalase expression and downregulated GPx1 messenger RNA (mRNA) expression, indicating that lipoic acid exhibits antioxidant activity in the decomposition of hydrogen peroxide by upregulating catalase expression. Moreover, lipoic acid treatment for 3 h increased and promoted heat shock-induced interleukin (IL)-6 mRNA and protein levels and that for 24 h downregulated IL-6 mRNA expression, suggesting a dual effect of lipoic acid on IL-6 regulation. Lipoic acid alone failed to increase or reduce tumor necrosis factor (TNF)-α mRNA and protein levels, whereas heat shock alone downregulated TNF-α mRNA and protein expression. These data suggest that lipoic acid does not have a proinflammatory role and that heat shock acts as an anti-inflammatory agent by downregulating TNF-α expression in C2C12 myotubes. Moreover, lipoic acid or heat shock alone upregulated the IL-6 receptor (IL-6R-α) and glycoprotein 130 (gp130) mRNA expression followed by IL-6 expression; these data indicate that the regulation of lipoic acid or heat shock is mediated by IL-6R signaling, thus suggesting that C2C12 myotubes possesses a mechanism for regulating IL-6R and gp130 expression following lipoic acid treatment or heat shock.

An exploration of the antioxidant effects of garlic saponins in mouse-derived C2C12 myoblasts.

PubMed

Kang, Ji Sook; Kim, Sung Ok; Kim, Gi-Young; Hwang, Hye Jin; Kim, Byung Woo; Chang, Young-Chae; Kim, Wun-Jae; Kim, Cheol Min; Yoo, Young Hyun; Choi, Yung Hyun

2016-01-01

In this study, we aimed to confirm the protective effects of garlic saponins against oxidative stress-induced cellular damage and to further elucidate the underlying mechanisms in mouse-derived C2C12 myoblasts. Relative cell viability was determined by 3-(4.5-dimethylthiazol-2-yl)-2.5 diphenyltetrazolium bromide assay. Comet assay was used to measure DNA damage and oxidative stress was determined using 2',7'-dichlorofluorescein diacetate to measure intracellular reactive oxygen species (ROS) generation. Western blot analysis and small interfering RNA (siRNA)-based knockdown were used in order to investigate the possible molecular mechanisms. Our results revealed that garlic saponins prevented hydrogen peroxide (H2O2)-induced growth inhibition and exhibited scavenging activity against intracellular ROS. We also observed that garlic saponins prevented H2O2-induced comet tail formation and decreased the phosphorylation levels of γH2AX expression, suggesting that they can prevent H2O2-induced DNA damage. In addition, garlic saponins increased the levels of heme oxygenase-1 (HO-1), a potent antioxidant enzyme associated with the induction and phosphorylation of nuclear factor erythroid 2-related factor 2 (Nrf2) and the translocation of Nrf2 from the cytosol into the nucleus. However, the protective effects of garlic saponins on H2O2-induced ROS generation and growth inhibition were significantly reduced by zinc protoporphyrin Ⅸ, an HO-1 competitive inhibitor. In addition, the potential of garlic saponins to mediate HO-1 induction and protect against H2O2‑mediated growth inhibition was adversely affected by transient transfection with Nrf2-specific siRNA. Garlic saponins activated extracellular signal‑regulated kinase (ERK) signaling, whereas a specific ERK inhibitor was able to inhibit HO-1 upregulation, as well as Nrf2 induction and phosphorylation. Taken together, the findings of our study suggest that garlic saponins activate the Nrf2/HO-1 pathway by enabling

The role of ventral striatal cAMP signaling in stress-induced behaviors

PubMed Central

Plattner, Florian; Hayashi, Kanehiro; Hernandez, Adan; Benavides, David R.; Tassin, Tara C.; Tan, Chunfeng; Day, Jonathan; Fina, Maggy W.; Yuen, Eunice Y.; Yan, Zhen; Goldberg, Matthew S.; Nairn, Angus C.; Greengard, Paul; Nestler, Eric J.; Taussig, Ronald; Nishi, Akinori; Houslay, Miles D.; Bibb, James A.

2015-01-01

The cAMP/PKA signaling cascade is a ubiquitous pathway acting downstream of multiple neuromodulators. We found that the phosphorylation of phosphodiesterase-4 (PDE4) by cyclin-dependent protein kinase 5 (Cdk5) facilitates cAMP degradation and homeostasis of cAMP/PKA signaling. In mice, loss of Cdk5 throughout the forebrain elevated cAMP levels and increased PKA activity in striatal neurons, and altered behavioral responses to acute or chronic stressors. Ventral striatum- or D1 dopamine receptor-specific conditional knockout of Cdk5, or ventral striatum infusion of a small interfering peptide that selectively targets the regulation of PDE4 by Cdk5, all produced analogical effects on stress-induced behavioral responses. Together, our results demonstrate that altering cAMP signaling in medium spiny neurons of the ventral striatum can effectively modulate stress-induced behavioral states. We propose that targeting the Cdk5 regulation of PDE4 could be a new therapeutic approach for clinical conditions associated with stress, such as depression. PMID:26192746

Hybrid phage displaying SLAQVKYTSASSI induces protection against Candida albicans challenge in BALB/c mice.

PubMed

Wang, Yicun; Su, Quanping; Dong, Shuai; Shi, Hongxi; Gao, Xiang; Wang, Li

2014-01-01

The polymorphic fungus Candida albicans (C. albicans) can live as an aggressive pathogen and cause many diseases in hosts, for which no effective vaccine exists. The secreted aspartyl proteinase 2 (Sap2) plays a protective role in systemically infected BALB/c mice. Protective cellular immune responses can be preferentially induced when antigens are displayed on small particles. Therefore, the emphasis is placed on developing new phage vaccine to inhibit C. albicans infection. In this study, the ability of the hybrid phage displaying the epitope SLAQVKYTSASSI and recombinant protein of Sap2 (rSap2) for inducing immune protective responses against C. albicans infection was evaluated by lymphoproliferative assay, to gather cytokine and antibody measurements in BALB/c mice. Our results showed that, strong cellular and humoral immune responses were induced in a mouse model immunized with hybrid phage or rSap2. Furthermore, the protection against lethal challenge with C. albicans was observed in mice vaccinated hybrid phage without adjuvant. These findings demonstrate that the hybrid phage displaying the epitope SLAQVKYTSASSI might be a potential vaccine against C. albicans infections.

C-phycocyanin modulates selenite-induced cataractogenesis in rats.

PubMed

Kumari, Rasiah Pratheepa; Sivakumar, Jeyarajan; Thankappan, Bency; Anbarasu, Kumarasamy

2013-01-01

The present investigation is aimed to evaluate the anticataractogenic potential of C-phycocyanin (C-PC), extracted and purified from Spirulina platensis. Enucleated rat lenses were maintained in vitro in Dulbecco's modified Eagle medium (DMEM). Group I contained DMEM, Group II and Group III contained 100 μM of sodium selenite, Group III was subdivided into three viz IIIa, IIIb, IIIc supplemented with 100, 150, 200 μg of C-PC respectively. In the in vivo study, on tenth day post partum: Group I rat pups received an intraperitoneal injection of saline, Group II, IIIa, IIIb, and IIIc rat pups received a subcutaneous injection of sodium selenite (19 μmol/kg bodyweight) Group IIIa, IIIb, IIIc also received an intraperitoneal injection of 100, 150, 200 mg/kg body weight of C-PC, respectively, from postpartum days 9-14. On termination of the experiment, the lenses from both in vitro and in vivo studies were subjected to morphological examination and subsequently processed to estimate the activities of antioxidant enzymes namely superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, levels of reduced glutathione and lipid peroxidation products. Sodium selenite-exposed, C-PC-treated rat lenses (Group IIIc), showed significant restoration of antioxidant enzyme activity (p < 0.05) when compared to their counterpart Group II. Group IIIc conserved the levels of GSH and lipid peroxidation products at near to normal levels as compared with Group II. Results conclude the possible role of C-PC in modulating the antioxidant enzyme status, thereby retarding sodium selenite-induced cataract incidence both in vitro and in vivo.

Irradiation-induced β to α SiC transformation at low temperature

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

Parish, Chad M.; Koyanagi, Takaaki; Kondo, Sosuke

Here, we observed that β-SiC, neutron irradiated to 9 dpa (displacements per atom) at ≈1440 °C, began transforming to α-SiC, with radiation-induced Frank dislocation loops serving as the apparent nucleation sites. 1440 °C is a far lower temperature than usual β → α phase transformations in SiC. SiC is considered for applications in advanced nuclear systems, as well as for electronic or spintronic applications requiring ion irradiation processing. β-SiC, preferred for nuclear applications, is metastable and undergoes a phase transformation at high temperatures (typically 2000 °C and above). Nuclear reactor concepts are not expected to reach the very high temperaturesmore » for thermal transformation. However, our results indicate incipient β → α phase transformation, in the form of small (~5–10 nm) pockets of α-SiC forming in the β matrix. In service transformation could degrade structural stability and fuel integrity for SiC-based materials operated in this regime. However, engineering this transformation deliberately using ion irradiation could enable new electronic applications.« less

Irradiation-induced β to α SiC transformation at low temperature

DOE PAGES

Parish, Chad M.; Koyanagi, Takaaki; Kondo, Sosuke; ...

2017-04-26

Here, we observed that β-SiC, neutron irradiated to 9 dpa (displacements per atom) at ≈1440 °C, began transforming to α-SiC, with radiation-induced Frank dislocation loops serving as the apparent nucleation sites. 1440 °C is a far lower temperature than usual β → α phase transformations in SiC. SiC is considered for applications in advanced nuclear systems, as well as for electronic or spintronic applications requiring ion irradiation processing. β-SiC, preferred for nuclear applications, is metastable and undergoes a phase transformation at high temperatures (typically 2000 °C and above). Nuclear reactor concepts are not expected to reach the very high temperaturesmore » for thermal transformation. However, our results indicate incipient β → α phase transformation, in the form of small (~5–10 nm) pockets of α-SiC forming in the β matrix. In service transformation could degrade structural stability and fuel integrity for SiC-based materials operated in this regime. However, engineering this transformation deliberately using ion irradiation could enable new electronic applications.« less

CoMoS2/rGO/C3N4 ternary heterojunctions catalysts with high photocatalytic activity and stability for hydrogen evolution under visible light irradiation

NASA Astrophysics Data System (ADS)

Xu, Xuejun; Si, Zhichun; Liu, Liping; Wang, Zehao; Chen, Ze; Ran, Rui; He, Yonghong; Weng, Duan

2018-03-01

Noble metal free MoS2/g-C3N4 catalyst has attracted intense attentions for visible light photocatalytic hydrogen evolution as a result of its earth abundance, low cost and unique heterojunctions stacked with two dimensional sheets. However, the low charge separation efficiency resulted from the poor conductivity of g-C3N4 and MoS2, and lack of abundant active sites from coordinative unsaturated atoms in MoS2, restricts the photocatalytic hydrogen evolution activity and stability enhancement of MoS2/C3N4 composite catalysts. Herein, CoMoS2/rGO/g-C3N4 catalysts with ternary heterojunctions are prepared by facile solvothermal method, which exhibit high visible light photocatalytic activity and stability for hydrogen evolution. The optimal hydrogen evolution rate of CoMoS2/rGO/g-C3N4 catalysts is 684 μmol g-1 h-1 when the content of CoMoS2 is 2% and the content of rGO is 0.5%. The stability of CoMoS2/rGO/C3N4 catalysts just decrease about 3% after 4 cycling runs for 16 h. The good catalytic performances of catalysts are attributed to the synergistic effect among the g-C3N4 nanosheets, rGO nanosheets and CoMoS2 nanosheets. The high conductivity of rGO nanosheets enhances the electron-hole separation and charge transfer, and Co doping increases the active sites for hydrogen evolution due to the increase of unsaturated atoms in CoMoS2 nanosheets.

Complement component C5a mediates hemorrhage-induced intestinal damage

PubMed Central

Fleming, Sherry D.; Phillips, Lauren M.; Lambris, John D.; Tsokos, George C.

2008-01-01

Background Complement has been implicated in the pathogenesis of intestinal damage and inflammation in multiple animal models. Although the exact mechanism is unknown, inhibition of complement prevents hemodynamic alterations in hemorrhage. Materials/Methods C57Bl/6, complement 5 deficient (C5−/−) and sufficient (C5+/+) mice were subjected to 25% blood loss. In some cases, C57Bl/6 mice were treated with C5a receptor antagonist (C5aRa) post-hemorrhage. Intestinal injury, leukotriene B4, and myeloperoxidase production were assessed for each treatment group of mice. Results Mice subjected to significant blood loss without major trauma develop intestinal inflammation and tissue damage within two hours. We report here that complement 5 (C5) deficient mice are protected from intestinal tissue damage when subjected to hemorrhage (Injury score = 0.36 compared to wildtype hemorrhaged animal injury score = 2.89; p<0.05). We present evidence that C5a represents the effector molecule because C57Bl/6 mice treated with a C5a receptor antagonist displayed limited intestinal injury (Injury score = 0.88), leukotriene B4 (13.16 pg/mg tissue) and myeloperoxidase (115.6 pg/mg tissue) production compared to hemorrhaged C57Bl/6 mice (p<0.05). Conclusion Complement activation is important in the development of hemorrhage-induced tissue injury and C5a generation is critical for tissue inflammation and damage. Thus, therapeutics targeting C5a may be useful therapeutics for hemorrhage-associated injury. PMID:18639891

Disruption of a hydrogen bond network in human versus spider monkey cytochrome c affects heme crevice stability.

PubMed

Goldes, Matthew E; Jeakins-Cooley, Margaret E; McClelland, Levi J; Mou, Tung-Chung; Bowler, Bruce E

2016-05-01

The hypothesis that the recent rapid evolution of primate cytochromes c, which primarily involves residues in the least stable Ω-loop (Ω-loop C, residues 40-57), stabilizes the heme crevice of cytochrome c relative to other mammals, is tested. To accomplish this goal, we have compared the properties of human and spider monkey cytochrome c and a set of four variants produced in the process of converting human cytochrome c into spider monkey cytochrome c. The global stability of all variants has been measured by guanidine hydrochloride denaturation. The stability of the heme crevice has been assessed with the alkaline conformational transition. Structural insight into the effects of the five amino acid substitutions needed to convert human cytochrome c into spider monkey cytochrome c is provided by a 1.15Å resolution structure of spider monkey cytochrome c. The global stability for all variants is near 9.0kcal/mol at 25°C and pH7, which is higher than that observed for other mammalian cytochromes c. The heme crevice stability is more sensitive to the substitutions required to produce spider monkey cytochrome c with decreases of up to 0.5 units in the apparent pKa of the alkaline conformational transition relative to human cytochrome c. The structure of spider monkey cytochrome c indicates that the Y46F substitution destabilizes the heme crevice by disrupting an extensive hydrogen bond network that connects three surface loops including Ω-loop D (residues 70-85), which contains the Met80 heme ligand. Copyright © 2015 Elsevier Inc. All rights reserved.

Effects of Hydrogen-Rich Saline on Hepatectomy-Induced Postoperative Cognitive Dysfunction in Old Mice.

PubMed

Tian, Yue; Guo, Shanbin; Zhang, Yan; Xu, Ying; Zhao, Ping; Zhao, Xiaochun

2017-05-01

This study aims to investigate the protective effects and underlying mechanisms of hydrogen-rich saline on the cognitive functions of elder mice with partial hepatectomy-induced postoperative cognitive dysfunction (POCD). Ninety-six old male Kunming mice were randomly divided into 4 groups (n = 24 each): control group (group C), hydrogen-rich saline group (group H), POCD group (group P), and POCD + hydrogen-rich saline group (group PH). Cognitive function was subsequently assessed using Morris water-maze (MWM) test. TNF-α and IL-1β levels were measured by enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry, along with NF-κB activity determined by ELISA. The morphology of hippocampal tissues were further observed by HE staining. Learning and memory abilities of mice were significantly impaired at day 10 and day 14 post-surgery, as partial hepatectomy significantly prolonged the escape latency, decreased time at the original platform quadrant and frequency of crossing in group P when compared to group C (p < 0.05). The surgery also increased the contents of TNF-α, IL-1β, and NF-κB activity at all time points after surgery (p < 0.05). The introduction of hydrogen-rich saline (group PH) partially rescued spatial memory and learning as it shortened escape latency and increased time and crossing frequency of original platform compared to group P (p < 0.05). Moreover, such treatment also decreased TNF-α and IL-1β levels and NF-κB activity (p < 0.05). In addition, cell necrosis in the hippocampus induced by hepatectomy was also rescued by hydrogen-rich saline. Hydrogen-rich saline can alleviate POCD via inhibiting NF-κB activity in the hippocampus and reducing inflammatory response.

Promoter motifs required for c-mpl gene expression induced by thrombopoietin in CMK cells.

PubMed

Sunohara, Masataka; Sato, Iwao; Morikawa, Shigeru

2017-11-30

Thrombopoietin (TPO) and its receptor, c-Mpl, are the central regulators of megakaryocyte development and platelet production and are also crucial to regulate megakaryocytopoiesis. TPO remarkably elevated c-mpl promoter activity, while the protein kinase C (PKC) inhibitors, GF109203, H7 and Calphostin C, clearly reduced the steady level of its promoter activity.  In the present study, motifs crucial for c-mpl promoter activity induced by TPO treatment have been analyzed using a human megakaryoblastic cell line, CMK. Destruction of the -107Sp1 and the -57Sp1 sites in the c-mpl promoter enhancer region resulted in decrease of the promoter activity by 53.1% and 64.4%, respectively, and destruction of -69Ets and -28Ets elements dramatically decreased the promoter activity by 96.4% and 87.8%, respectively, while mutation of -77GATA moderately reduced the activity by 31.4%. The result was in agreement with our previous report that showed the crucial motifs in the c-mpl promoter for the promoter activity induced by PMA-treatment. This indicates that TPO-induced activation of the c-mpl promoter activity is fully modulated by transcription through a PKC-dependent pathway and the two Sp1 and two Ets motifs are crucial for the activation of the c-mpl promoter activity rather than a GATA motif in the c-mpl promoter of CMK cells.

Bone-induced c-kit expression in prostate cancer: a driver of intraosseous tumor growth

PubMed Central

Mainetti, Leandro E.; Zhe, Xiaoning; Diedrich, Jonathan; Saliganan, Allen D.; Cho, Won Jin; Cher, Michael L.; Heath, Elisabeth; Fridman, Rafael; Kim, Hyeong-Reh Choi; Bonfil, R. Daniel

2014-01-01

Loss of BRCA2 function stimulates prostate cancer (PCa) cell invasion and is associated with more aggressive and metastatic tumors in PCa patients. Concurrently, the receptor tyrosine kinase c-kit is highly expressed in skeletal metastases of PCa patients and induced in PCa cells placed into the bone microenvironment in experimental models. However, the precise requirement of c-kit for intraosseous growth of PCa and its relation to BRCA2 expression remain unexplored. Here, we show that c-kit expression promotes migration and invasion of PCa cells. Alongside, we found that c-kit expression in PCa cells parallels BRCA2 downregulation. Gene rescue experiments with human BRCA2 transgene in c-kit-transfected PCa cells resulted in reduction of c-kit protein expression and migration and invasion, suggesting a functional significance of BRCA2 downregulation by c-kit. The inverse association between c-kit and BRCA2 gene expressions in PCa cells was confirmed using laser capture microdissection in experimental intraosseous tumors and bone metastases of PCa patients. Inhibition of bone-induced c-kit expression in PCa cells transduced with lentiviral short hairpin RNA reduced intraosseous tumor incidence and growth. Overall, our results provide evidence of a novel pathway that links bone-induced c-kit expression in PCa cells to BRCA2 downregulation and supports bone metastasis. PMID:24798488

A New Protein Phosphatase 2C (FsPP2C1) Induced by Abscisic Acid Is Specifically Expressed in Dormant Beechnut Seeds1

PubMed Central

Lorenzo, Oscar; Rodríguez, Dolores; Nicolás, Gregorio; Rodríguez, Pedro L.; Nicolás, Carlos

2001-01-01

An abscisic acid (ABA)-induced cDNA fragment encoding a putative protein phosphatase 2C (PP2C) was obtained by means of differential reverse transcriptase-polymerase chain reaction approach. The full-length clone was isolated from a cDNA library constructed using mRNA from ABA-treated beechnut (Fagus sylvatica) seeds. This clone presents all the features of plant type PP2C and exhibits homology to members of this family such as AthPP2CA (61%), ABI1 (48%), or ABI2 (47%), therefore it was named FsPP2C1. The expression of FsPP2C1 is detected in dormant seeds and increases after ABA treatment, when seeds are maintained dormant, but it decreases and tends to disappear when dormancy is being released by stratification or under gibberellic acid treatment. Moreover, drought stress seems to have no effect on FsPP2C1 transcript accumulation. The FsPP2C1 transcript expression is tissue specific and was found to accumulate in ABA-treated seeds rather than in other ABA-treated vegetative tissues examined. These results suggest that the corresponding protein could be related to ABA-induced seed dormancy. By expressing FsPP2C1 in Escherichia coli as a histidine tag fusion protein, we have obtained direct biochemical evidence supporting Mg2+-dependent phosphatase activity of this protein. PMID:11299374

Infrared spectra of the 1-pyridinium (C5H5NH+) cation and pyridinyl (C5H5NH and 4-C5H6N) radicals isolated in solid para-hydrogen.

PubMed

Golec, Barbara; Das, Prasanta; Bahou, Mohammed; Lee, Yuan-Pern

2013-12-19

Protonated pyridine and its neutral counterparts (C5H6N) are important intermediates in organic and biological reactions and in the atmosphere. We have recorded the IR absorption spectra of the 1-pyridinium (C5H5NH(+)) cation, 1-pyridinyl (C5H5NH), and 4-pyridinyl (4-C5H6N) produced on electron bombardment during matrix deposition of a mixture of pyridine (C5H5N) and p-H2 at 3.2 K; all spectra were previously unreported. The IR features of C5H5NH(+) diminished in intensity after the matrix was maintained in darkness for 15 h, whereas those of C5H5NH and 4-C5H6N radicals increased. Irradiation of this matrix with light at 365 nm diminished lines of C5H5NH(+) and C5H5NH but enhanced lines of 4-C5H6N slightly, whereas irradiation at 405 nm diminished lines of 4-C5H6N significantly. Observed wavenumbers and relative intensities of these species agree satisfactorily with the anharmonic vibrational wavenumbers and IR intensities predicted with the B3LYP/6-31++G(d,p) method. Assignments of C5H5NH and 4-C5H6N radicals were further supported by the observation of similar spectra when a Cl2/C5H5N/p-H2 matrix was irradiated first at 365 nm and then with IR light to generate H atoms to induce the H + C5H5N reaction.

Hepatitis C virus core protein induces hepatic steatosis via Sirt1-dependent pathway.

PubMed

Zhang, Chuanhai; Wang, Jingjing; Zhang, Hanlin; Liu, Shunai; Lee, Hyuek Jong; Jin, Wanzhu; Cheng, Jun

2018-05-01

Hepatic steatosis is a common feature of patients with chronic hepatitis C. Previous reports have shown that the overexpression of hepatitis C virus core-encoding sequences (hepatitis C virus genotypes 3a and 1b) significantly induces intracellular triglyceride accumulation. However, the underlying mechanism has not yet been revealed. To investigate whether Sirt1 is involved in hepatitis C virus-mediated hepatic steatosis, the overexpression of hepatitis C virus core 1b protein and Sirt1 and the knockdown of Sirt1 in HepG2 cells were performed. To confirm the results of the cellular experiment liver-specific Sirt1 KO mice with lentivirus-mediated hepatitis C virus core 1b overexpression were studied. Our results show that hepatitis C virus core 1b protein overexpression led to the accumulation of triglycerides in HepG2 cells. Notably the expression of PPARγ2 was dramatically increased at both the mRNA and protein levels by hepatitis C virus core 1b overexpression. The protein expression of Sirt1 is an upstream regulator of PPARγ2 and was also significantly increased after core 1b overexpression. In addition, the overexpression or knockdown of Sirt1 expression alone was sufficient to modulate p300-mediated PPARγ2 deacetylation. In vivo studies showed that hepatitis C virus core protein 1b-induced hepatic steatosis was attenuated in liver-specific Sirt1 KO mice by downregulation of PPARγ2 expression. Sirt1 mediates hepatitis C virus core protein 1b-induced hepatic steatosis by regulation of PPARγ2 expression. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

DR-induced escape of O and C from early Mars

NASA Astrophysics Data System (ADS)

Zhao, Jinjin; Tian, Feng; Ni, Yufang; Huang, Xiaomeng

2017-03-01

Energetic particles produced in Dissociative recombination (DR) reactions could escape planets with low gravity, such as Mars, if they could overcome collisions with the surrounding background gases. In this work, a 3-D Monte Carlo model is developed to study these photochemical escape processes on early Mars. Although the DR reaction rates of O2+, CO2+, and CO+ increase monotonically with solar soft X-ray and extreme ultraviolet (XUV) flux, the peak of the calculated DR-induced escape rates of O is near 3 × XUV, and the DR-induced escape rates of C increase with XUV until 10 × XUV. The non-monotonic behavior can be explained by the increased column densities of background species in high XUV conditions, which can deflect energetic particles through collisions more efficiently. At 20 × XUV, CO+ DR is the main source of escaping O and C, and the escape of secondary particles could contribute to 30∼40% and 10% of the total escape of O and C respectively. The time-integrated DR-induced escape of O and C is equivalent to 1 m of H2O and 20 mbar of CO2 escaping early Mars since 4.5 billion years ago. The accumulated CO2 loss is much lower than what's needed to explain the carbon isotopic ratios on Mars and much lower than the total CO2 needed to warm up early Mars. If more vigorous escape mechanisms were absent on early Mars, substantial inventories of volatiles have not been detected yet.

Intranasal Administration of poly(I:C) and LPS in BALB/c Mice Induces Airway Hyperresponsiveness and Inflammation via Different Pathways

PubMed Central

Starkhammar, Magnus; Kumlien Georén, Susanna; Swedin, Linda; Dahlén, Sven-Erik; Adner, Mikael; Cardell, Lars Olaf

2012-01-01

Background Bacterial and viral infections are known to promote airway hyperresponsiveness (AHR) in asthmatic patients. The mechanism behind this reaction is poorly understood, but pattern recognizing Toll-like receptors (TLRs) have recently been suggested to play a role. Materials and Methods To explore the relation between infection-induced airway inflammation and the development of AHR, poly(I:C) activating TLR3 and LPS triggering TLR4, were chosen to represent viral and bacterial induced interactions, respectively. Female BALB/c or MyD88-deficient C57BL/6 mice were treated intranasally with either poly(I:C), LPS or PBS (vehicle for the control group), once a day, during 4 consecutive days. Results When methacholine challenge was performed on day 5, BALB/c mice responded with an increase in airway resistance. The maximal resistance was higher in the poly(I:C) and LPS treated groups than among the controls, indicating development of AHR in response to repeated TLR activation. The proportion of lymphocytes in broncheoalveolar lavage fluid (BALF) increased after poly(I:C) treatment whereas LPS enhanced the amount of neutrophils. A similar cellular pattern was seen in lung tissue. Analysis of 21 inflammatory mediators in BALF revealed that the TLR response was receptor-specific. MyD88-deficient C57BL/6 mice responded to poly (I:C) with an influx of lymphocytes, whereas LPS caused no inflammation. Conclusion In vivo activation of TLR3 and TLR4 in BALB/c mice both caused AHR in conjunction with a local inflammatory reaction. The AHR appeared to be identical regardless of which TLR that was activated, whereas the inflammation exhibited a receptor specific profile in terms of both recruited cells and inflammatory mediators. The inflammatory response caused by LPS appeared to be dependent on MyD88 pathway. Altogether the presented data indicate that the development of AHR and the induction of local inflammation might be the result of two parallel events, rather than one

Aripiprazole inhibits polyI:C-induced microglial activation possibly via TRPM7.

PubMed

Sato-Kasai, Mina; Kato, Takahiro A; Ohgidani, Masahiro; Mizoguchi, Yoshito; Sagata, Noriaki; Inamine, Shogo; Horikawa, Hideki; Hayakawa, Kohei; Shimokawa, Norihiro; Kyuragi, Sota; Seki, Yoshihiro; Monji, Akira; Kanba, Shigenobu

2016-12-01

Viral infections during fetal and adolescent periods, as well as during the course of schizophrenia itself have been linked to the onset and/or relapse of a psychosis. We previously reported that the unique antipsychotic aripiprazole, a partial D2 agonist, inhibits the release of tumor necrosis factor (TNF)-α from interferon-γ-activated rodent microglial cells. Polyinosinic-polycytidylic acid (polyI:C) has recently been used as a standard model of viral infections, and recent in vitro studies have shown that microglia are activated by polyI:C. Aripiprazole has been reported to ameliorate behavioral abnormalities in polyI:C-induced mice. To clarify the anti-inflammatory properties of aripiprazole, we investigated the effects of aripiprazole on polyI:C-induced microglial activation in a cellular model of murine microglial cells and possible surrogate cells for human microglia. PolyI:C treatment of murine microglial cells activated the production of TNF-α and enhanced the p38 mitogen-activated protein kinase (MAPK) pathway, whereas aripiprazole inhibited these responses. In addition, polyI:C treatment of possible surrogate cells for human microglia markedly increased TNF-α mRNA expression in cells from three healthy volunteers. Aripiprazole inhibited this increase in cells from two individuals. PolyI:C consistently increased intracellular Ca 2+ concentration ([Ca 2+ ] i ) in murine microglial cells by influx of extracellular Ca 2+ . We demonstrated that transient receptor potential in melastatin 7 (TRPM7) channels contributed to this polyI:C-induced increase in [Ca 2+ ] i . Taken together, these data suggest that aripiprazole may be therapeutic for schizophrenia by reducing microglial inflammatory reactions, and TRPM7 may be a novel therapeutic target for schizophrenia. Further studies are needed to validate these findings. Copyright © 2016 Elsevier B.V. All rights reserved.

Measurement and Analysis of Atomic Hydrogen and Diatomic Molecular AlO, C2, CN, and TiO Spectra Following Laser-induced Optical Breakdown

PubMed Central

Parigger, Christian G.; Woods, Alexander C.; Witte, Michael J.; Swafford, Lauren D.; Surmick, David M.

2014-01-01

In this work, we present time-resolved measurements of atomic and diatomic spectra following laser-induced optical breakdown. A typical LIBS arrangement is used. Here we operate a Nd:YAG laser at a frequency of 10 Hz at the fundamental wavelength of 1,064 nm. The 14 nsec pulses with anenergy of 190 mJ/pulse are focused to a 50 µm spot size to generate a plasma from optical breakdown or laser ablation in air. The microplasma is imaged onto the entrance slit of a 0.6 m spectrometer, and spectra are recorded using an 1,800 grooves/mm grating an intensified linear diode array and optical multichannel analyzer (OMA) or an ICCD. Of interest are Stark-broadened atomic lines of the hydrogen Balmer series to infer electron density. We also elaborate on temperature measurements from diatomic emission spectra of aluminum monoxide (AlO), carbon (C2), cyanogen (CN), and titanium monoxide (TiO). The experimental procedures include wavelength and sensitivity calibrations. Analysis of the recorded molecular spectra is accomplished by the fitting of data with tabulated line strengths. Furthermore, Monte-Carlo type simulations are performed to estimate the error margins. Time-resolved measurements are essential for the transient plasma commonly encountered in LIBS. PMID:24561875

Measurement and analysis of atomic hydrogen and diatomic molecular AlO, C2, CN, and TiO spectra following laser-induced optical breakdown.

PubMed

Parigger, Christian G; Woods, Alexander C; Witte, Michael J; Swafford, Lauren D; Surmick, David M

2014-02-14

In this work, we present time-resolved measurements of atomic and diatomic spectra following laser-induced optical breakdown. A typical LIBS arrangement is used. Here we operate a Nd:YAG laser at a frequency of 10 Hz at the fundamental wavelength of 1,064 nm. The 14 nsec pulses with anenergy of 190 mJ/pulse are focused to a 50 µm spot size to generate a plasma from optical breakdown or laser ablation in air. The microplasma is imaged onto the entrance slit of a 0.6 m spectrometer, and spectra are recorded using an 1,800 grooves/mm grating an intensified linear diode array and optical multichannel analyzer (OMA) or an ICCD. Of interest are Stark-broadened atomic lines of the hydrogen Balmer series to infer electron density. We also elaborate on temperature measurements from diatomic emission spectra of aluminum monoxide (AlO), carbon (C2), cyanogen (CN), and titanium monoxide (TiO). The experimental procedures include wavelength and sensitivity calibrations. Analysis of the recorded molecular spectra is accomplished by the fitting of data with tabulated line strengths. Furthermore, Monte-Carlo type simulations are performed to estimate the error margins. Time-resolved measurements are essential for the transient plasma commonly encountered in LIBS.

c-Myc-induced apoptosis in fibroblasts is inhibited by specific cytokines.

PubMed Central

Harrington, E A; Bennett, M R; Fanidi, A; Evan, G I

1994-01-01

We have investigated the mechanism by which deregulated expression of c-Myc induces death by apoptosis in serum-deprived fibroblasts. We demonstrate that Myc-induced apoptosis in low serum is inhibited by a restricted group of cytokines, principally the insulin-like growth factors and PDGF. Cytokine-mediated protection from apoptosis is not linked to the cytokines' abilities to promote growth. Protection from apoptosis is evident in the post-commitment (mitogen-independent) S/G2/M phases of the cell cycle and also in cells that are profoundly blocked in cell cycle progression by drugs. Moreover, IGF-I inhibition of apoptosis occurs in the absence of protein synthesis, and so does not require immediate early gene expression. We conclude that c-Myc-induced apoptosis does not result from a conflict of growth signals but appears to be a normal physiological aspect of c-Myc function whose execution is regulated by the availability of survival factors. We discuss the possible implications of these findings for models of mammalian cell growth in vivo. Images PMID:8045259

Using 13C labeled glucose to determine soil microbial and physical controls of new C incorporation under drying-rewetting cycles and conservation agricultural management

NASA Astrophysics Data System (ADS)

Li, L.; Schaeffer, S. M.

2017-12-01

Drying-rewetting cycles can induce carbon (C) depletion in soil, while conservation agricultural management aims at soil C sequestration. Understanding the combined effect of drying-rewetting cycles and conservation management is critical for sustaining agricultural soil under climate change. Soil organic C can be stored in a relatively rapidly cycling active pool, or a more slowly cycling passive pool. We conducted a 24-days mesocosm incubation using an agricultural soil from western Tennessee under 35-years of conservation management. Different lengths of drought period before rewetting of 0, 3, 6, and 24 days were applied on the mesocosms. To trace the fate of newly added C, 13C labeled glucose was added to the mesocosms at the beginning of the incubation. After 24 days, dissolvable organic C, microbial biomass C, accumulative microbial respiration, and extracellular enzyme activity were analyzed to evaluate the active C pool; hydrogen peroxide oxidation and aggregate size fractionation were used to examine the passive C pool. The highest cumulative microbial respiration was found in the 6-days treatment combining a N-fixing cover crop with no-tillage, and the lowest in the 24-day treatment with a wheat cover crop combined with conventional-tillage (1000.0±20.5 and 106.8±17.5 µg C-CO2 g-1 dry soil, respectively). The 6-days treatment induced 0.5-4.3 times higher cumulative C-CO2 emission than the 3-days treatment. The proportion of macroaggregates in bulk soil varied between 97.2% and 76.7%, and it was negatively correlated with drying-rewetting frequency. The proportion of microaggregates in bulk soil varied between 21.9% and 2.1%, and it was positively correlated with drying-rewetting frequency. 13C recovery rate in bulk soil varied between 11-53%. The vetch-cover-crop-with-no-tillage treatment facilitated 13C accumulation the most. Our results show that the N fixing cover crops combined with no-tillage treatment induced the highest C accumulation in bulk

High glucose inhibits the aspirin-induced activation of the nitric oxide/cGMP/cGMP-dependent protein kinase pathway and does not affect the aspirin-induced inhibition of thromboxane synthesis in human platelets.

PubMed

Russo, Isabella; Viretto, Michela; Barale, Cristina; Mattiello, Luigi; Doronzo, Gabriella; Pagliarino, Andrea; Cavalot, Franco; Trovati, Mariella; Anfossi, Giovanni

2012-11-01

Since hyperglycemia is involved in the "aspirin resistance" occurring in diabetes, we aimed at evaluating whether high glucose interferes with the aspirin-induced inhibition of thromboxane synthesis and/or activation of the nitric oxide (NO)/cGMP/cGMP-dependent protein kinase (PKG) pathway in platelets. For this purpose, in platelets from 60 healthy volunteers incubated for 60 min with 5-25 mmol/L d-glucose or iso-osmolar mannitol, we evaluated the influence of a 30-min incubation with lysine acetylsalicylate (L-ASA; 1-300 μmol/L) on 1) platelet function under shear stress; 2) aggregation induced by sodium arachidonate or ADP; 3) agonist-induced thromboxane production; and 4) NO production, cGMP synthesis, and PKG-induced vasodilator-stimulated phosphoprotein phosphorylation. Experiments were repeated in the presence of the antioxidant agent amifostine. We observed that platelet exposure to 25 mmol/L d-glucose, but not to iso-osmolar mannitol, 1) reduced the ability of L-ASA to inhibit platelet responses to agonists; 2) did not modify the L-ASA-induced inhibition of thromboxane synthesis; and 3) prevented the L-ASA-induced activation of the NO/cGMP/PKG pathway. Preincubation with amifostine reversed the high-glucose effects. Thus, high glucose acutely reduces the antiaggregating effect of aspirin, does not modify the aspirin-induced inhibition of thromboxane synthesis, and inhibits the aspirin-induced activation of the NO/cGMP/PKG pathway. These results identify a mechanism by which high glucose interferes with the aspirin action.

EFFECTS OF NUCLEAR INDUCED BREAKUP ON THE FUSION OF 6Li+12C AND 6He+12C SYSTEMS AROUND BARRIER ENERGIES

NASA Astrophysics Data System (ADS)

Duhan, Sukhvinder S.; Singh, Manjeet; Kharab, Rajesh

2012-06-01

We have studied the effects of nuclear induced breakup channel coupling on the fusion cross-section for 6Li+12C and 6He+12C systems in the near barrier energy regime using the dynamic polarization potential (DPP) approach. It has been found that there is enhancement in the fusion cross-section with respect to standard one-dimensional barrier penetration model in the below barrier energy regime while at energies above the barrier there is suppression of fusion cross-section with respect to simple barrier penetration model is observed. The agreement between data and predictions for 6Li+12C system improves significantly as a result of the inclusion of nuclear induced DPP.

Autoimmune severe hypertriglyceridemia induced by anti-apolipoprotein C-II antibody.

PubMed

Yamamoto, Hiroyasu; Tanaka, Minoru; Yoshiga, Satomi; Funahashi, Tohru; Shimomura, Iichiro; Kihara, Shinji

2014-05-01

Among type V hyperlipoproteinemias, only one-fourth of the patients have genetic defects in lipoprotein lipase (LPL) or in its associated molecules; the exact mechanism in other patients is usually unknown. The aim of the study was to report a case of severe hypertriglyceridemia induced by anti-apolipoprotein (apo) C-II autoantibody and to clarify its pathogenesis. A 29-year-old Japanese woman presented with severe persistent hypertriglyceridemia since the age of 20 years. The past history was negative for acute pancreatitis, eruptive xanthomas, or lipemia retinalis. LPL mass and activities were normal. Plasma apo C-II levels were extremely low, but no mutation was observed in APOC2. Apo C-II protein was detected in the serum by immunoprecipitation and Western blotting. Large amounts of IgG and IgM were incorporated with apo C-II protein coimmunoprecipitated by anti-apo C-II antibody. IgG, but not IgM, purified from the serum prevented interaction of apo C-II with lipid substrate and diminished LPL hydrolysis activity. We identified anti-apo C-II antibody in a myeloma-unrelated severe hypertriglyceridemic patient. In vitro analysis confirmed that the autoantibody disrupted the interaction between apo C-II and lipid substrate, suggesting the etiological role of anti-apo C-II antibody in severe hypertriglyceridemia in this patient.

Dok5 is involved in the signaling pathway of neurotrophin-3 against TrkC-induced apoptosis.

PubMed

Pan, Yanfang; Zhang, Jing; Liu, Wei; Shu, Pengcheng; Yin, Bin; Yuan, Jiangang; Qiang, Boqin; Peng, Xiaozhong

2013-10-11

TrkC is a dependence receptor and many reports have shown that neurotrophin-3 promotes cell survival by inhibiting TrkC-induced apoptosis in many cell lines. However, the identity of the adaptor protein involved in the NT-3/TrkC signaling pathway regulating cell death and survival remains unclear. The downstream of tyrosine kinase/docking protein (Dok) adaptor protein 5 is one substrate of the TrkC receptor. Because NT-3 and its receptor, TrkC, are strongly expressed by sensory neurons, we measured the expression of Dok5 and TrkC in the developing mouse spinal cord and dorsal root ganglia (DRG). We found that the number of cells positive for both Dok5 and TrkC decreases with DRG development. Immunoprecipitation and immunofluorescence staining showed that Dok5 interacted with TrkC and partially colocalized with TrkC in DRG neurons. In HEK293T cells, TrkC triggered apoptosis, but NT-3 prevented TrkC-induced apoptosis. Interestingly, siRNA knockdown of Dok5 expression partially prevented the protection of NT-3 against TrkC-induced apoptosis by regulating the activity of caspase-3. Taken together, we concluded that Dok5 is necessary for NT-3 signaling to block TrkC-induced apoptosis. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Spatially resolved, substrate-induced rectification in C 60 bilayers on copper

DOE PAGES

Smerdon, J. A.; Darancet, P.; Guest, J. R.

2017-02-22

Here, we demonstrate rectification ratios ( RR) of ≳1000 at biases of 1.3 V in bilayers of C 60 deposited on copper. Using scanning tunneling spectroscopy and first-principles calculations, we show that the strong coupling between C 60 and the Cu(111) surface leads to the metallization of the bottom C 60 layer, while the molecular orbitals of the top C60 are essentially unaffected. Due to this substrate-induced symmetry breaking and to a tunneling transport mechanism, the system behaves as a hole-blocking layer, with a spatial dependence of the onset voltage on intra-layer coordination. Together with previous observations of strong electron-blockingmore » character of pentacene/C 60 bilayers on Cu(111), this work further demonstrates the potential of strongly hybridized, C 60-coated electrodes to harness the electrical functionality of molecular components.« less

6-Shogaol enhances renal carcinoma Caki cells to TRAIL-induced apoptosis through reactive oxygen species-mediated cytochrome c release and down-regulation of c-FLIP(L) expression.

PubMed

Han, Min Ae; Woo, Seon Min; Min, Kyoung-jin; Kim, Shin; Park, Jong-Wook; Kim, Dong Eun; Kim, Sang Hyun; Choi, Yung Hyun; Kwon, Taeg Kyu

2015-02-25

6-Shogaol, a potent bioactive compound in ginger (Zingiber officinale Roscoe), has been reported for anti-inflammatory and anti-cancer activity. In this study, we investigated the effect of 6-shogaol to enhance tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis. The combined treatment with 6-shogaol and TRAIL markedly induces apoptosis in various cancer cells (renal carcinoma Caki cells, breast carcinoma MDA-MB-231 cells and glioma U118MG cells), but not in normal mesangial cells and normal mouse kidney cells. 6-Shogaol reduced the mitochondrial membrane potential (MMP) and released cytochrome c from mitochondria to cytosol via Bax activation. Furthermore, we found that 6-shogaol induced down-regulation of c-FLIP(L) expression at the post-translational levels and the overexpression of c-FLIP(L) markedly inhibited 6-shogaol plus TRAIL-induced apoptosis. Moreover, 6-shogaol increased reactive oxygen species (ROS) production in Caki cells. Pretreatment with ROS scavengers attenuated 6-shogaol plus TRAIL-induced apoptosis through inhibition of MMP reduction and down-regulation of c-FLIP(L) expression. In addition, 6-gingerol, another phenolic alkanone isolated from ginger, did not enhance TRAIL-induced apoptosis and down-regulate c-FLIP(L) expression. Taken together, our results demonstrated that 6-shogaol enhances TRAIL-mediated apoptosis in renal carcinoma Caki cells via ROS-mediated cytochrome c release and down-regulation of c-FLIP(L) expression. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Manganese-induced Neurotoxicity: From C. elegans to Humans

PubMed Central

Chen, Pan; Chakraborty, Sudipta; Peres, Tanara V.; Bowman, Aaron B.; Aschner, Michael

2014-01-01

Manganese (Mn) is one of the most abundant metals on the earth. It is required for normal cellular activities, but overexposure leads to toxicity. Neurons are more susceptible to Mn-induced toxicity than other cells, and accumulation of Mn in the brain results in Manganism that presents with Parkinson's disease (PD)-like symptoms. In the last decade, a number of Mn transporters have been identified, which improves our understanding of Mn transport in and out of cells. However, the mechanism of Mn-induced neurotoxicity is only partially uncovered, with further research needed to explore the whole picture of Mn-induced toxicity. In this review, we will address recent progress in Mn-induced neurotoxicity from C. elegans to humans, and explore future directions that will help understand the mechanisms of its neurotoxicity. PMID:25893090

(001) 3C SiC/Ni contact interface: In situ XPS observation of annealing induced Ni2Si formation and the resulting barrier height changes

NASA Astrophysics Data System (ADS)

Tengeler, Sven; Kaiser, Bernhard; Chaussende, Didier; Jaegermann, Wolfram

2017-04-01

The electronic states of the (001) 3C SiC/Ni interface prior and post annealing are investigated via an in situ XPS interface experiment, allowing direct observation of the induced band bending and the transformation from Schottky to ohmic behaviour for the first time. A single domain (001) 3C SiC sample was prepared via wet chemical etching. Nickel was deposited on the sample in multiple in situ deposition steps via RF sputtering, allowing observation of the 3C SiC/Ni interface formation. Over the course of the experiments, an upward band bending of 0.35 eV was observed, along with defect induced Fermi level pinning. This indicates a Schottky type contact behaviour with a barrier height of 0.41 eV. The subsequent annealing at 850 °C for 5 min resulted in the formation of a Ni2Si layer and a reversal of the band bending to 0.06 eV downward. Thus explaining the ohmic contact behaviour frequently reported for annealed n-type 3C SiC/Ni contacts.

Upper limits to the reaction rate coefficients of C(n)(-) and C(n)H(-) (n = 2, 4, 6) with molecular hydrogen.

PubMed

Endres, Eric S; Lakhmanskaya, Olga; Hauser, Daniel; Huber, Stefan E; Best, Thorsten; Kumar, Sunil S; Probst, Michael; Wester, Roland

2014-08-21

In the interstellar medium (ISM) ion–molecule reactions play a key role in forming complex molecules. Since 2006, after the radioastronomical discovery of the first of by now six interstellar anions, interest has grown in understanding the formation and destruction pathways of negative ions in the ISM. Experiments have focused on reactions and photodetachment of the identified negatively charged ions. Hints were found that the reactions of CnH(–) with H2 may proceed with a low (<10(–13) cm(3) s(–1)), but finite rate [Eichelberger, B.; et al. Astrophys. J. 2007, 667, 1283]. Because of the high abundance of molecular hydrogen in the ISM, a precise knowledge of the reaction rate is needed for a better understanding of the low-temperature chemistry in the ISM. A suitable tool to analyze rare reactions is the 22-pole radiofrequency ion trap. Here, we report on reaction rates for Cn(–) and CnH(–) (n = 2, 4, 6) with buffer gas temperatures of H2 at 12 and 300 K. Our experiments show the absence of these reactions with an upper limit to the rate coefficients between 4 × 10(–16) and 5 × 10(–15) cm(3) s(–1), except for the case of C2(–), which does react with a finite rate with H2 at low temperatures. For the cases of C2H(–) and C4H(–), the experimental results were confirmed with quantum chemical calculations. In addition, the possible influence of a residual reactivity on the abundance of C4H(–) and C6H(–) in the ISM were estimated on the basis of a gas-phase chemical model based on the KIDA database. We found that the simulated ion abundances are already unaffected if reaction rate coefficients with H2 were below 10(–14) cm(3) s(–1).

Simultaneous Study of Mechanical Stretch-Induced Cell Proliferation and Apoptosis on C2C12 Myoblasts.

PubMed

Feng, Yu; Tian, Xiang-Yang; Sun, Peng; Cheng, Ze-Peng; Shi, Reng-Fei

2018-06-27

Mechanical stretch may cause myoblasts to either proliferate or undergo apoptosis. Identifying the molecular events that switch the fate of a stretched cell from proliferation to apoptosis is practically important in the field of regenerative medicine. A recent study on vascular smooth muscle cells illustrated that identification of these events may be achieved by addressing the stretch-induced opposite cellular outcomes simultaneously within a single investigation. To define conditions or a model in which both proliferation and apoptosis can be studied at the same time, we exposed in vitro cultured C2C12 myoblasts to a cyclic mechanical stretch regimen of 15% elongation at a stretching frequency of 1 Hz for 0, 2, 4, 6, or 8 h every day, consecutively, for 3 days. Both proliferation and apoptosis were observed. Moreover, as the duration of the stretch was prolonged, cell proliferation increased until it peaked at the optimal stretching duration. Afterwards, apoptosis gradually prevailed. Therefore, we established a model in which stretch-induced cell proliferation and apoptosis can be studied simultaneously. © 2018 S. Karger AG, Basel.

Photo-induced oxidant-free oxidative C-H/N-H cross-coupling between arenes and azoles

NASA Astrophysics Data System (ADS)

Niu, Linbin; Yi, Hong; Wang, Shengchun; Liu, Tianyi; Liu, Jiamei; Lei, Aiwen

2017-02-01

Direct cross-coupling between simple arenes and heterocyclic amines under mild conditions is undoubtedly important for C-N bonds construction. Selective C(sp2)-H amination is more valuable. Herein we show a selective C(sp2)-H amination of arenes (alkyl-substituted benzenes, biphenyl and anisole derivatives) accompanied by hydrogen evolution by using heterocyclic azoles as nitrogen sources. The reaction is selective for C(sp2)-H bonds, providing a mild route to N-arylazoles. The KIE (kinetic isotope effect) experiment reveals the cleavage of C-H bond is not involved in the rate-determining step. Kinetic studies indicate the first-order behaviour with respect to the arene component. It is interesting that this system works without the need for any sacrificial oxidant and is highly selective for C(sp2)-H activation, whereas C(sp3)-H bonds are unaffected. This study may have significant implications for the functionalization of methylarenes which are sensitive to oxidative conditions.

Highly selective hydrogenation of furfural to furfuryl alcohol over Pt nanoparticles supported on g-C3N4 nanosheets catalysts in water.

PubMed

Chen, Xiufang; Zhang, Ligang; Zhang, Bo; Guo, Xingcui; Mu, Xindong

2016-06-22

Graphitic carbon nitride nanosheets were investigated for developing effective Pt catalyst supports for selective hydrogenation of furfural to furfuryl alcohol in water. The nanosheets with an average thickness of about 3 nm were synthesized by a simple and green method through thermal oxidation etching of bulk g-C3N4 in air. Combined with the unique feature of nitrogen richness and locally conjugated structure, the g-C3N4 nanosheets with a high surface area of 142 m(2) g(-1) were demonstrated to be an excellent supports for loading small-size Pt nanoparticles. Superior furfural hydrogenation activity in water with complete conversion of furfural and high selectivity of furfuryl alcohol (>99%) was observed for g-C3N4 nanosheets supported Pt catalysts. The large specific surface area, uniform dispersion of Pt nanoparticles and the stronger furfural adsorption ability of nanosheets contributed to the considerable catalytic performance. The reusability tests showed that the novel Pt catalyst could maintain high activity and stability in the furfural hydrogenation reaction.

Highly selective hydrogenation of furfural to furfuryl alcohol over Pt nanoparticles supported on g-C3N4 nanosheets catalysts in water

NASA Astrophysics Data System (ADS)

Chen, Xiufang; Zhang, Ligang; Zhang, Bo; Guo, Xingcui; Mu, Xindong

2016-06-01

Graphitic carbon nitride nanosheets were investigated for developing effective Pt catalyst supports for selective hydrogenation of furfural to furfuryl alcohol in water. The nanosheets with an average thickness of about 3 nm were synthesized by a simple and green method through thermal oxidation etching of bulk g-C3N4 in air. Combined with the unique feature of nitrogen richness and locally conjugated structure, the g-C3N4 nanosheets with a high surface area of 142 m2 g-1 were demonstrated to be an excellent supports for loading small-size Pt nanoparticles. Superior furfural hydrogenation activity in water with complete conversion of furfural and high selectivity of furfuryl alcohol (>99%) was observed for g-C3N4 nanosheets supported Pt catalysts. The large specific surface area, uniform dispersion of Pt nanoparticles and the stronger furfural adsorption ability of nanosheets contributed to the considerable catalytic performance. The reusability tests showed that the novel Pt catalyst could maintain high activity and stability in the furfural hydrogenation reaction.

Highly selective hydrogenation of furfural to furfuryl alcohol over Pt nanoparticles supported on g-C3N4 nanosheets catalysts in water

PubMed Central

Chen, Xiufang; Zhang, Ligang; Zhang, Bo; Guo, Xingcui; Mu, Xindong

2016-01-01

Graphitic carbon nitride nanosheets were investigated for developing effective Pt catalyst supports for selective hydrogenation of furfural to furfuryl alcohol in water. The nanosheets with an average thickness of about 3 nm were synthesized by a simple and green method through thermal oxidation etching of bulk g-C3N4 in air. Combined with the unique feature of nitrogen richness and locally conjugated structure, the g-C3N4 nanosheets with a high surface area of 142 m2 g−1 were demonstrated to be an excellent supports for loading small-size Pt nanoparticles. Superior furfural hydrogenation activity in water with complete conversion of furfural and high selectivity of furfuryl alcohol (>99%) was observed for g-C3N4 nanosheets supported Pt catalysts. The large specific surface area, uniform dispersion of Pt nanoparticles and the stronger furfural adsorption ability of nanosheets contributed to the considerable catalytic performance. The reusability tests showed that the novel Pt catalyst could maintain high activity and stability in the furfural hydrogenation reaction. PMID:27328834

Pharmacogenetics of ribavirin-induced anemia in hepatitis C.

PubMed

Ampuero, Javier; Romero-Gómez, Manuel

2016-09-01

Pharmacogenetics assesses inherited genetic differences in drug metabolic pathways and its role in medicine is growing. Ribavirin (RBV) and peginterferon were the standard of care therapy in hepatitis C virus infection during 15 years, with the addition of first-generation protease inhibitors at the beginning of 2010s. New direct-acting agents are the new standard of care, but RBV remains important in some scenarios. The main adverse effect of RBV is anemia, which requires dose reduction and even stopping treatment in some patients. Pharmacogenetics has identified ITPA and SLC28/29 genes to be closely related to RBV-induced anemia. The routine evaluation of these genes could help to identify those patients at risk of developing anemia during the hepatitis C virus treatment.

Jet-induced star formation in 3C 285 and Minkowski's Object

NASA Astrophysics Data System (ADS)

Salomé, Q.; Salomé, P.; Combes, F.

2015-02-01

How efficiently star formation proceeds in galaxies is still an open question. Recent studies suggest that active galactic nucleus (AGN) can regulate the gas accretion and thus slow down star formation (negative feedback). However, evidence of AGN positive feedback has also been observed in a few radio galaxies (e.g. Centaurus A, Minkowski's Object, 3C 285, and the higher redshift 4C 41.17). Here we present CO observations of 3C 285 and Minkowski's Object, which are examples of jet-induced star formation. A spot (named 3C 285/09.6 in the present paper) aligned with the 3C 285 radio jet at a projected distance of ~70 kpc from the galaxy centre shows star formation that is detected in optical emission. Minkowski's Object is located along the jet of NGC 541 and also shows star formation. Knowing the distribution of molecular gas along the jets is a way to study the physical processes at play in the AGN interaction with the intergalactic medium. We observed CO lines in 3C 285, NGC 541, 3C 285/09.6, and Minkowski's Object with the IRAM 30 m telescope. In the central galaxies, the spectra present a double-horn profile, typical of a rotation pattern, from which we are able to estimate the molecular gas density profile of the galaxy. The molecular gas appears to be in a compact reservoir, which could be evidence of an early phase of the gas accretion after a recent merger event in 3C 285. No kinematic signature of a molecular outflow is detected by the 30 m telescope. Interestingly, 3C 285/09.6 and Minkowski's Object are not detected in CO. The cold gas mass upper limits are consistent with a star formation induced by the compression of dense ambient material by the jet. The depletion time scales in 3C 285/09.6 and Minkowski's Object are of the order of and even shorter than what is found in 3C 285, NGC 541, and local spiral galaxies (109 yr). The upper limit of the molecular gas surface density in 3C 285/09.6 at least follows a Schmidt-Kennicutt law if the emitting region

Protective effect of C-peptide on experimentally induced diabetic nephropathy and the possible link between C-peptide and nitric oxide.

PubMed

Elbassuoni, Eman A; Aziz, Neven M; El-Tahawy, Nashwa F

2018-06-01

Diabetic nephropathy one of the major microvascular diabetic complications. Besides hyperglycemia, other factors contribute to the development of diabetic complications as the proinsulin connecting peptide, C-peptide. We described the role of C-peptide replacement therapy on experimentally induced diabetic nephropathy, and its potential mechanisms of action by studying the role of nitric oxide (NO) as a mediator of C-peptide effects by in vivo modulating its production by N G -nitro-l-arginine methyl ester (L-NAME). Renal injury markers measured were serum urea, creatinine, tumor necrosis factor alpha, and angiotensin II, and malondialdehyde, total antioxidant, Bcl-2, and NO in renal tissue. In conclusion, diabetic induction resulted in islet degenerations and decreased insulin secretion with its metabolic consequences and subsequent renal complications. C-Peptide deficiencies in diabetes might have contributed to the metabolic and renal error, since C-peptide treatment to the diabetic rats completely corrected these errors. The beneficial effects of C-peptide are partially antagonized by L-NAME coadministration, indicating that NO partially mediates C-peptide effects.

Doxorubicin-induced nitrosative stress is mitigated by vitamin C via the modulation of nitric oxide synthases.

PubMed

Akolkar, Gauri; Bagchi, Ashim K; Ayyappan, Prathapan; Jassal, Davinder S; Singal, Pawan K

2017-04-01

An increase in oxidative stress is suggested to be the main cause in Doxorubicin (Dox)-induced cardiotoxicity. However, there is now evidence that activation of inducible nitric oxide synthase (iNOS) and nitrosative stress are also involved. The role of vitamin C (Vit C) in the regulation of nitric oxide synthase (NOS) and reduction of nitrosative stress in Dox-induced cardiotoxicity is unknown. The present study investigated the effects of Vit C in the mitigation of Dox-induced changes in the levels of nitric oxide (NO), NOS activity, protein expression of NOS isoforms, and nitrosative stress as well as cytokines TNF-α and IL-10 in isolated cardiomyocytes. Cardiomyocytes isolated from adult Sprague-Dawley rats were segregated into four groups: 1 ) control, 2 ) Vit C (25 µM), 3 ) Dox (10 µM), and 4 ) Vit C + Dox. Dox caused a significant increase in the generation of superoxide radical (O 2 ·- ), peroxynitrite, and NO, and these effects of Dox were blunted by Vit C. Dox increased the expression of iNOS and altered protein expression as well as activation of endothelial NOS (eNOS). These changes were prevented by Vit C. Dox induced an increase in the ratio of monomeric/dimeric eNOS, promoting the production of O 2 ·- , which was prevented by Vit C by increasing the stability of the dimeric form of eNOS. Vit C protected against the Dox-induced increase in TNFα as well as a reduction in IL-10. These results suggest that Vit C provides cardioprotection by reducing oxidative/nitrosative stress and inflammation via a modulation of Dox-induced increase in the NO levels and NOS activity. Copyright © 2017 the American Physiological Society.

Auxin-induced nitric oxide, cGMP and gibberellins were involved in the gravitropism

NASA Astrophysics Data System (ADS)

Cai, Weiming; Hu, Liwei; Hu, Xiangyang; Cui, Dayong; Cai, Weiming

Gravitropism is the asymmetric growth or curvature of plant organs in response to gravistimulation. There is a complex signal transduction cascade which involved in the differential growth of plants in response to changes in the gravity vector. The role of auxin in gravitropism has been demonstrated by many experiments, but little is known regarding the molecular details of such effects. In our studies before, mediation of the gravitropic bending of soybean roots and rice leaf sheath bases by nitric oxide, cGMP and gibberellins, are induced by auxin. The asymmetrical distribution of nitric oxide, cGMP and gibberellins resulted from the asymmetrical synthesis of them in bending sites. In soybean roots, inhibitions of NO and cGMP synthesis reduced differential NO and cGMP accumulation respectively, which both of these effects can lead to the reduction of gravitropic bending. Gibberellin-induced OsXET, OsEXPA4 and OsRWC3 were also found involved in the gravitropic bending. These data indicated that auxin-induced nitric oxide, cGMP and gibberellins were involved in the gravitropism. More experiments need to prove the more detailed mechanism of them.

Activation of tyrosine kinase c-Abl contributes to α-synuclein–induced neurodegeneration

PubMed Central

Lee, Su Hyun; Kim, Donghoon; Karuppagounder, Senthilkumar S.; Kumar, Manoj; Mao, Xiaobo; Shin, Joo Ho; Lee, Yunjong; Pletnikova, Olga; Troncoso, Juan C.; Dawson, Valina L.; Dawson, Ted M.; Ko, Han Seok

2016-01-01

Aggregation of α-synuclein contributes to the formation of Lewy bodies and neurites, the pathologic hallmarks of Parkinson disease (PD) and α-synucleinopathies. Although a number of human mutations have been identified in familial PD, the mechanisms that promote α-synuclein accumulation and toxicity are poorly understood. Here, we report that hyperactivity of the nonreceptor tyrosine kinase c-Abl critically regulates α-synuclein–induced neuropathology. In mice expressing a human α-synucleinopathy–associated mutation (hA53Tα-syn mice), deletion of the gene encoding c-Abl reduced α-synuclein aggregation, neuropathology, and neurobehavioral deficits. Conversely, overexpression of constitutively active c-Abl in hA53Tα-syn mice accelerated α-synuclein aggregation, neuropathology, and neurobehavioral deficits. Moreover, c-Abl activation led to an age-dependent increase in phosphotyrosine 39 α-synuclein. In human postmortem samples, there was an accumulation of phosphotyrosine 39 α-synuclein in brain tissues and Lewy bodies of PD patients compared with age-matched controls. Furthermore, in vitro studies show that c-Abl phosphorylation of α-synuclein at tyrosine 39 enhances α-synuclein aggregation. Taken together, this work establishes a critical role for c-Abl in α-synuclein–induced neurodegeneration and demonstrates that selective inhibition of c-Abl may be neuroprotective. This study further indicates that phosphotyrosine 39 α-synuclein is a potential disease indicator for PD and related α-synucleinopathies. PMID:27348587

Characterization of keratinocyte differentiation induced by ascorbic acid: protein kinase C involvement and vitamin C homeostasis.

PubMed

Savini, Isabella; Catani, Maria Valeria; Rossi, Antonello; Duranti, Guglielmo; Melino, Gerry; Avigliano, Luciana

2002-02-01

Epidermal keratinocytes undergo differentiation in response to several stimuli to form the cornified envelope, a structure that contributes to the barrier function of skin. Although differentiation has been extensively analyzed, the precise role of vitamin C during this process is still not defined. Ascorbic acid, besides acting as a radical scavenger, has been shown to promote mesenchymal differentiation. In this study, we found that keratinocytes grown in ascorbate-supplemented medium developed a differentiated phenotype, as demonstrated by enhanced expression of marker genes and increase in cornified envelope content. The pro-differentiating effects of ascorbate were mediated by the protein-kinase-C-dependent induction of activating protein 1 DNA binding activity; indeed, down-modulation of protein kinase C activity abolished differentiation triggered by ascorbic acid. Although vitamin C appeared to regulate the same signaling pathway modulated by calcium, a classical in vitro inducer of epidermal differentiation, nonetheless terminally differentiated keratinocytes exhibited different ascorbate homeostasis and cellular antioxidant status. Indeed, we found that, unlike calcium, differentiation promoted by ascorbate was accompanied by (i) an enhanced ascorbate transport, due to overexpression of specific transporters, (ii) a great efficiency of dehydroascorbate uptake, and (iii) an increase in glutathione content with respect to proliferating cells. Ascorbic acid may be useful to promote epidermal differentiation, avoiding depletion of hydrophilic antioxidant stores.

Mitomycin-C induces the apoptosis of human Tenon's capsule fibroblast by activation of c-Jun N-terminal kinase 1 and caspase-3 protease.

PubMed

Seong, Gong Je; Park, Channy; Kim, Chan Yoon; Hong, Young Jae; So, Hong-Seob; Kim, Sang-Duck; Park, Raekil

2005-10-01

To investigate whether mitochondrial dysfunction and mitogen-activated protein kinase family proteins are implicated in apoptotic signaling of human Tenon's capsule fibroblasts (HTCFs) by mitomycin-C. Apoptosis was determined by Hoechst nuclei staining, agarose gel electrophoresis, and flow cytometry in HTCFs treated with 0.4 mg/mL mitomycin-C for 5 minutes. Enzymatic digestion of florigenic biosubstrate assessed the catalytic activity of caspase proteases, including caspase-3, caspase-8, and caspase-9. Phosphotransferase activity of c-Jun N-terminal kinase (JNK) 1 was measured by in vitro immune complex kinase assay using c-Jun(1-79) protein as a substrate. Mitochondrial membrane potential transition (MPT) was measured by flow cytometric analysis of JC-1 staining. Mitomycin-C (0.4 mg/mL) induced the apoptosis of HTCFs, which was characterized as nucleic acid and genomic DNA fragmentation, chromatin condensation, and sub-G(0)/G(1) fraction of cell cycle increase. The catalytic activity of caspase-3 and caspase-9 was significantly increased and was accompanied by cytosolic release of cytochrome c and MPT in response to mitomycin-C. Treatment with mitomycin-C resulted in the increased expression of Fas, FasL, Bad, and phosphorylated p53 and a decreased level of phosphorylated AKT. Treatment with mitomycin-C also increased the phosphotransferase activity and tyrosine phosphorylation of JNK1, whose inhibitor significantly suppressed the cytotoxicity of mitomycin-C. Mitomycin-C induced the apoptosis of HTCFs through the activation of intrinsic and extrinsic caspase cascades with mitochondrial dysfunction. It also activated Fas-mediated apoptotic signaling of fibroblasts. Furthermore, the activation of JNK1 played a major role in the cytotoxicity of mitomycin-C.

Acetyl-l-carnitine partially prevents benzene-induced hematotoxicity and oxidative stress in C3H/He mice.

PubMed

Sun, Rongli; Zhang, Juan; Wei, Haiyan; Meng, Xing; Ding, Qin; Sun, Fengxia; Cao, Meng; Yin, Lihong; Pu, Yuepu

2017-04-01

Benzene is an environmental pollutant and occupational toxicant which induces hematotoxicity. Our previous metabonomics study suggested that acetyl-l-carnitine (ALCAR) decreased in the mouse plasma and bone marrow (BM) cells due to benzene exposure. In the present study, the topic on whether ALCAR influences hematotoxicity caused by benzene exposure was explored. Thirty-two male C3H/He mice were divided into four groups: control group (C: vehicle, oil), benzene group (150mg/kg body weight (b.w.) benzene), benzene+A1 group (150mg/kg b.w. benzene+100mg/kg b.w. ALCAR), and benzene+A2 group (150mg/kg b.w. benzene+200mg/kg b.w. ALCAR). Benzene was injected subcutaneously, and ALCAR was orally administrated via gavage once daily for 4 weeks consecutively. After the experimental period, the blood routine, BM cell number and frequency of hematopoietic stem/progenitor cell (HS/PC) were assessed. The mitochondrial membrane potential and ATP level were determined to evaluate the mitochondrial function. Reactive oxygen species (ROS), hydrogen peroxide (H 2 O 2 ) and malondialdehyde (MDA) levels were also examined, and the comet assay was performed to measure oxidative stress. Results showed that ALCAR intervention can partially reduce the benzene-induced damage on BM and HS/PCs and can simultaneously alleviate the DNA damage by reducing benzene-induced H 2 O 2, ROS, and MDA. Copyright © 2017 Elsevier B.V. All rights reserved.

One-pot synthesis of K-doped g-C3N4 nanosheets with enhanced photocatalytic hydrogen production under visible-light irradiation

NASA Astrophysics Data System (ADS)

Wang, Yanyun; Zhao, Shuo; Zhang, Yiwei; Fang, Jiasheng; Zhou, Yuming; Yuan, Shenhao; Zhang, Chao; Chen, Wenxia

2018-05-01

Graphite carbon nitride (g-C3N4), as a promising low cost, visible light driven conjugated polymer semiconductor photocatalyst, has attracted wide attentions from researchers. However, low light absorption efficiency and inadequate charge separation limit the potential applications of g-C3N4. This paper exhibits K-doped g-C3N4 prepared by a facile thermal polymerization with KBr as the K source. The experiments of photocatalytic hydrogen evolution demonstrate that KBr content strongly affects the activity of the catalyst. XRD, FT-IR, XPS, SEM, TEM, UV-vis diffuse reflectance spectra, photoluminescence (PL) characterization methods are used to study the effects of potassium on the catalyst performance. The results find that K-modified g-C3N4 has a narrower band gap and enhanced light harvesting properties. Moreover, the photocatalytic hydrogen evolution rate (HER) of the optimized K-doped g-C3N4 nanosheets (10 wt % KBr) reaches 1337.2 μmol g-1h-1, which is about 5.6 times in comparison with that of pure g-C3N4 (239.8 μmol g-1h-1). The doping of the potassium may increase the π-conjugated systems and accelerate the electron transport rate, then improve the photocatalytic properties. Based on the results of the analysis, a possible mechanism is proposed.

Vitamin K3 and vitamin C alone or in combination induced apoptosis in leukemia cells by a similar oxidative stress signalling mechanism.

PubMed

Bonilla-Porras, Angelica R; Jimenez-Del-Rio, Marlene; Velez-Pardo, Carlos

2011-06-10

Secondary therapy-related acute lymphoblastic leukemia might emerge following chemotherapy and/or radiotherapy for primary malignancies. Therefore, other alternatives should be pursued to treat leukemia. It is shown that vitamin K3- or vitamin C- induced apoptosis in leukemia cells by oxidative stress mechanism involving superoxide anion radical and hydrogen peroxide generation, activation of NF-κB, p53, c-Jun, protease caspase-3 activation and mitochondria depolarization leading to nuclei fragmentation. Cell death was more prominent when Jurkat and K562 cells are exposed to VC and VK3 in a ratio 1000:1 (10 mM: 10 μM) or 100:1 (300 μM: 3 μM), respectively. We provide for the first time in vitro evidence supporting a causative role for oxidative stress in VK3- and VC-induced apoptosis in Jurkat and K562 cells in a domino-like mechanism. Altogether these data suggest that VK3 and VC should be useful in the treatment of leukemia.

Identification of the receptors for somatostatin (SST) and cortistatin (CST) in chickens and investigation of the roles of cSST28, cSST14, and cCST14 in inhibiting cGHRH1-27NH2-induced growth hormone secretion in cultured chicken pituitary cells.

PubMed

Meng, Fengyan; Huang, Guian; Gao, Shunyu; Li, Juan; Yan, Zhenxin; Wang, Yajun

2014-03-25

Somatostatin receptors (SSTRs) are proposed to mediate the actions of somatostatin (SST) and its related peptide, cortistatin (CST), in vertebrates. However, the identity, functionality, and tissue expression of these receptors remain largely unknown in most non-mammalian vertebrates including birds. In this study, five SSTRs (named cSSTR1, cSSTR2, cSSTR3, cSSTR4, cSSTR5) were cloned from chicken brain by RT-PCR. Using a pGL3-CRE-luciferase reporter system, we demonstrated that activation of each cSSTR expressed in CHO cells by cSST28, cSST14 and cCST14 treatment could inhibit forskolin-induced luciferase activity of CHO cells, indicating the functional coupling of all cSSTRs to Gi protein(s). Interestingly, cSSTR1-4 expressed in CHO cells could be activated by cSST28, cSST14 and cCST14 with high potencies, suggesting that they may function as the receptors common for these peptides. In contrast, cSSTR5 could be potently activated by cSST28 only, indicating that it is a cSST28-specific receptor. Using RT-PCR, wide expression of cSSTRs was detected in chicken tissues including pituitary. In accordance with their expression in pituitary, cSST28, cSST14, and cCST14 were demonstrated to inhibit basal and novel cGHRH1-27NH2-induced GH secretion in cultured chicken pituitary cells dose-dependently (0-10nM) by Western blot analysis, suggesting the involvement of cSSTR(s) common for these peptides in mediating their inhibitory actions. Collectively, our study establishes a molecular basis to elucidate the roles of SST/CST in birds and provide insights into the roles of SST/CST in vertebrates, such as their conserved actions on pituitary. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Improving the photocatalytic hydrogen production of Ag/g-C3N4 nanocomposites by dye-sensitization under visible light irradiation

NASA Astrophysics Data System (ADS)

Qin, Jiayi; Huo, Jingpei; Zhang, Piyong; Zeng, Jian; Wang, Tingting; Zeng, Heping

2016-01-01

process for H2 production, the diagram for the rate of hydrogen generation vs. the amount of fluorescein, the figure for the photocatalytic hydrogen production testing system, tables of contrast experiments for photocatalytic hydrogen generation and elemental composition of the CN in all the samples. See DOI: 10.1039/c5nr06346a

Diene Hydroacylation from the Alcohol or Aldehyde Oxidation Level via Ruthenium Catalyzed C-C Bond Forming Transfer Hydrogenation: Synthesis of β,γ-Unsaturated Ketones

PubMed Central

Shibahara, Fumitoshi; Bower, John F.; Krische, Michael J.

2011-01-01

Under the conditions of ruthenium catalyzed transfer hydrogenation, isoprene couples to benzylic and aliphatic alcohols 1a–1g to deliver β,γ-unsaturated ketones 3a–3g in good to excellent isolated yields. Under identical conditions, aldehydes 2a–2g couple to isoprene to provide an identical set of β,γ-unsaturated ketones 3a–3g in good to excellent isolated yields. As demonstrated by the coupling of butadiene, myrcene and 1,2-dimethylbutadiene to representative alcohols 1b, 1c and 1e, diverse acyclic dienes participate in transfer hydrogenative coupling to form β,γ-unsaturated ketones. In all cases, complete branch-regioselectivity is observed and, with the exception of adduct 3j, isomerization to the conjugated enone is not detected. Thus, formal intermolecular diene hydroacylation is achieved from the alcohol or aldehyde oxidation level. In earlier studies employing a related ruthenium catalyst, acyclic dienes were coupled to carbonyl partners from the alcohol or aldehyde oxidation level to furnish branched homoallylic alcohols. Thus, under transfer hydrogenative coupling conditions, all oxidations levels of substrate (alcohol or aldehyde) and product (homoallyl alcohol or β,γ-unsaturated ketone) are accessible. PMID:18841895

BPN, a marine-derived PTP1B inhibitor, activates insulin signaling and improves insulin resistance in C2C12 myotubes.

PubMed

Xu, Qi; Luo, Jiao; Wu, Ning; Zhang, Renshuai; Shi, Dayong

2018-01-01

Insulin resistance is a key feature of type 2 diabetes mellitus (T2DM) and is characterized by defects in insulin signaling. Protein tyrosine phosphatase 1B (PTP1B) is a major negative regulator of insulin signaling cascade and has attracted intensive investigation in recent T2DM therapy study. BPN, a marine-derived bromophenol compound, was isolated from the red alga Rhodomela confervoides. This study investigated the effects of BPN on the insulin signaling pathway in insulin-resistant C2C12 myotubes by inhibiting PTP1B. Molecular docking study and analysis of small- molecule interaction with PTP1B all showed BPN inhibited PTP1B activity via binding to the catalytic site through hydrogen bonds. We then found that BPN permeated into C2C12 myotubes, on the one hand, activated insulin signaling in an insulin-independent manner in C2C12 cells; on the other hand, ameliorated palmitate-induced insulin resistance through augmenting insulin sensitivity. Moreover, our studies also showed that PTP1B inhibition by BPN increased glucose uptake in normal and insulin-resistant C2C12 myotubes through glucose transporter 4 (GLUT4) translocation. Taken together, BPN activates insulin signaling and alleviates insulin resistance and represents a potential candidate for further development as an antidiabetic agent. Copyright © 2017 Elsevier B.V. All rights reserved.

C1 CHEMISTRY FOR THE PRODUCTION OF ULTRA-CLEAN LIQUID TRANSPORTATION FUELS AND HYDROGEN

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

Gerald P. Huffman

2004-03-31

Faculty and students from five universities--the University of Kentucky, University of Pittsburgh, University of Utah, West Virginia University, and Auburn University--are collaborating in a research program to develop C1 chemistry processes to produce ultra-clean liquid transportation fuels and hydrogen, the zero-emissions transportation fuel of the future. The feedstocks contain one carbon atom per molecular unit. They include synthesis gas (syngas), a mixture of carbon monoxide and hydrogen produced by coal gasification or reforming of natural gas, methane, methanol, carbon dioxide, and carbon monoxide. An important objective is to develop C1 technology for the production of liquid transportation fuel and hydrogenmore » from domestically plentiful resources such as coal, coalbed methane, and natural gas. An Industrial Advisory Board with representatives from Chevron-Texaco, Eastman Chemical, Conoco-Phillips, the Air Force Research Laboratory, the U.S. Army National Automotive Center (Tank & Automotive Command--TACOM), and Tier Associates provides guidance on the practicality of the research. The current report presents results obtained in this research program during the six months of the subject contract from October 1, 2002 through March 31, 2003. The results are presented in thirteen detailed reports on research projects headed by various faculty members at each of the five CFFS Universities. Additionally, an Executive Summary has been prepared that summarizes the principal results of all of these projects during the six-month reporting period.« less

Efficient hydrogen isotopologues separation through a tunable potential barrier: The case of a C2N membrane.

PubMed

Qu, Yuanyuan; Li, Feng; Zhao, Mingwen

2017-05-03

Isotopes separation through quantum sieving effect of membranes is quite promising for industrial applications. For the light hydrogen isotopologues (eg. H 2 , D 2 ), the confinement of potential wells in porous membranes to isotopologues was commonly regarded to be crucial for highly efficient separation ability. Here, we demonstrate from first-principles that a potential barrier is also favorable for efficient hydrogen isotopologues separation. Taking an already-synthesized two-dimensional carbon nitride (C 2 N-h2D) as an example, we predict that the competition between quantum tunneling and zero-point-energy (ZPE) effects regulated by the tensile strain leads to high selectivity and permeance. Both kinetic quantum sieving and equilibrium quantum sieving effects are considered. The quantum effects revealed in this work offer a prospective strategy for highly efficient hydrogen isotopologues separation.

Tyrosine Kinase Inhibitors Induce Down-Regulation of c-Kit by Targeting the ATP Pocket

PubMed Central

Descarpentries, Clotilde; Frisan, Emilie; Adam, Kevin; Verdier, Frederique; Floquet, Célia; Dubreuil, Patrice; Lacombe, Catherine; Fontenay, Michaela; Mayeux, Patrick; Kosmider, Olivier

2013-01-01

The stem cell factor receptor (SCF) c-Kit plays a pivotal role in regulating cell proliferation and survival in many cell types. In particular, c-Kit is required for early amplification of erythroid progenitors, while it must disappear from cell surface for the cell entering the final steps of maturation in an erythropoietin-dependent manner. We initially observed that imatinib (IM), an inhibitor targeting the tyrosine kinase activity of c-Kit concomitantly down-regulated the expression of c-Kit and accelerated the Epo-driven differentiation of erythroblasts in the absence of SCF. We investigated the mechanism by which IM or related masitinib (MA) induce c-Kit down-regulation in the human UT-7/Epo cell line. We found that the down-regulation of c-Kit in the presence of IM or MA was inhibited by a pre-incubation with methyl-β-cyclodextrin suggesting that c-Kit was internalized in the absence of ligand. By contrast to SCF, the internalization induced by TKI was independent of the E3 ubiquitin ligase c-Cbl. Furthermore, c-Kit was degraded through lysosomal, but not proteasomal pathway. In pulse-chase experiments, IM did not modulate c-Kit synthesis or maturation. Analysis of phosphotyrosine peptides in UT-7/Epo cells treated or not with IM show that IM did not modify overall tyrosine phosphorylation in these cells. Furthermore, we showed that a T670I mutation preventing the full access of IM to the ATP binding pocket, did not allow the internalization process in the presence of IM. Altogether these data show that TKI-induced internalization of c-Kit is linked to a modification of the integrity of ATP binding pocket. PMID:23637779

YC-1 potentiates cAMP-induced CREB activation and nitric oxide production in alveolar macrophages.

PubMed

Hwang, Tsong-Long; Tang, Ming-Chi; Kuo, Liang-Mou; Chang, Wen-De; Chung, Pei-Jen; Chang, Ya-Wen; Fang, Yao-Ching

2012-04-15

Alveolar macrophages play significant roles in the pathogenesis of several inflammatory lung diseases. Increases in exhaled nitric oxide (NO) are well documented to reflect disease severity in the airway. In this study, we investigated the effect of 3-(5'-hydroxymethyl-2'-furyl)-1-benzyl indazole (YC-1), a known activator of soluble guanylyl cyclase, on prostaglandin (PG)E₁ (a stable PGE₂ analogue) and forskolin (a adenylate cyclase activator) induced NO production and inducible NO synthase (iNOS) expression in rat alveolar macrophages (NR8383). YC-1 did not directly cause NO production or iNOS expression, but drastically potentiated PGE₁- or forskolin-induced NO production and iNOS expression in NR8383 alveolar macrophages. Combination treatment with YC-1 and PGE₁ significantly increased phosphorylation of the cAMP response element-binding protein (CREB), but not nuclear factor (NF)-κB activation. The combined effect on NO production, iNOS expression, and CREB phosphorylation was reversed by a protein kinase (PK)A inhibitor (H89), suggesting that the potentiating functions were mediated through a cAMP/PKA signaling pathway. Consistent with this, cAMP analogues, but not the cGMP analogue, caused NO release, iNOS expression, and CREB activation. YC-1 treatment induced an increase in PGE₁-induced cAMP formation, which occurred through the inhibition of cAMP-specific phosphodiesterase (PDE) activity. Furthermore, the combination of rolipram (an inhibitor of PDE4), but not milronone (an inhibitor of PDE3), and PGE₁ also triggered NO production and iNOS expression. In summary, YC-1 potentiates PGE₁-induced NO production and iNOS expression in alveolar macrophages through inhibition of cAMP PDE activity and activation of the cAMP/PKA/CREB signaling pathway. Copyright © 2012 Elsevier Inc. All rights reserved.

Calcium Channels, Rho-Kinase, Protein Kinase-C, and Phospholipase-C Pathways Mediate Mercury Chloride-Induced Myometrial Contractions in Rats.

PubMed

Koli, Swati; Prakash, Atul; Choudhury, Soumen; Mandil, Rajesh; Garg, Satish K

2018-05-21

Adverse effects of mercury on female reproduction are reported; however, its effect on myogenic activity of uterus and mechanism thereof is obscure. Present study was undertaken to unravel the mechanistic pathways of mercuric chloride (HgCl 2 )-induced myometrial contraction in rats. Isometric tension in myometrial strips of rats following in vitro exposure to HgCl 2 was recorded using data acquisition system-based physiograph. HgCl 2 produced concentration-dependent (10 nM-100 μM) uterotonic effect which was significantly (p < 0.05) reduced in Ca 2+ -free solution and inhibited in the presence of nifedipine (1 μM), a L-type Ca 2+ channel blocker, thus suggesting the importance of extracellular Ca 2+ and its entry through L-type calcium channels in HgCl 2 -induced myometrial contractions in rats. Cumulative concentration-response curve of HgCl 2 was significantly (p < 0.05) shifted towards right in the presence of Y-27632 (10 μM), a Rho-kinase inhibitor, suggesting the involvement of Ca 2+ -sensitization pathway in mediating HgCl 2 -induced myometrial contraction. HgCl 2 -induced myometrial contraction was also significantly (p < 0.05) inhibited in the presence of methoctramine or para-fluoro-hexahydro-siladifenidol, a selective M 2 and M 3 receptor antagonists, respectively, which evidently suggest that mercury also interacts with M 2 and M 3 muscarinic receptors to produce myometrial contractions. U-73122 and GF-109203X, the respective inhibitors of PLC and PKC-dependent pathways, downstream to the receptor activation, also significantly (p < 0.05) attenuated the uterotonic effect of HgCl 2 on rat uterus. Taken together, present study evidently reveals that HgCl 2 interacts with muscarinic receptors and activates calcium signaling cascades involving calcium channels, Rho-kinase, protein kinase-C, and phospholipase-C pathways to exert uterotonic effect in rats. Graphical Abstract Graphical abstract depicting the mechanism of mercury-induced

Essential role of the cAMP-cAMP response-element binding protein pathway in opiate-induced homeostatic adaptations of locus coeruleus neurons.

PubMed

Cao, Jun-Li; Vialou, Vincent F; Lobo, Mary Kay; Robison, Alfred J; Neve, Rachael L; Cooper, Donald C; Nestler, Eric J; Han, Ming-Hu

2010-09-28

Excessive inhibition of brain neurons in primary or slice cultures can induce homeostatic intrinsic plasticity, but the functional role and underlying molecular mechanisms of such plasticity are poorly understood. Here, we developed an ex vivo locus coeruleus (LC) slice culture system and successfully recapitulated the opiate-induced homeostatic adaptation in electrical activity of LC neurons seen in vivo. We investigated the mechanisms underlying this adaptation in LC slice cultures by use of viral-mediated gene transfer and genetic mutant mice. We found that short-term morphine treatment of slice cultures almost completely abolished the firing of LC neurons, whereas chronic morphine treatment increased LC neuronal excitability as revealed during withdrawal. This increased excitability was mediated by direct activation of opioid receptors and up-regulation of the cAMP pathway and accompanied by increased cAMP response-element binding protein (CREB) activity. Overexpression of a dominant negative CREB mutant blocked the increase in LC excitability induced by morphine- or cAMP-pathway activation. Knockdown of CREB in slice cultures from floxed CREB mice similarly decreased LC excitability. Furthermore, the ability of morphine or CREB overexpression to up-regulate LC firing was blocked by knockout of the CREB target adenylyl cyclase 8. Together, these findings provide direct evidence that prolonged exposure to morphine induces homeostatic plasticity intrinsic to LC neurons, involving up-regulation of the cAMP-CREB signaling pathway, which then enhances LC neuronal excitability.

Electronic absorption spectra of hydrogenated protonated naphthalene and proflavine

NASA Astrophysics Data System (ADS)

Bonaca, A.; Bilalbegović, G.

2011-09-01

We study hydrogenated cations of two polycyclic hydrocarbon molecules as models of hydrogenated organic species that form in the interstellar medium. Optical spectra of the hydrogenated naphthalene cation Hn-C10H+8 for n= 1, 2 and 10, as well as the astrobiologically interesting hydrogenated proflavine cation Hn-C13H11N+3 for n= 1 and 14, are calculated. The pseudopotential time-dependent density functional theory is used. It is found that the fully hydrogenated proflavine cation H14-C13H11N+3 shows a broad spectrum in which the positions of individual lines are almost lost. The positions, shapes and intensities of lines change in hydronaphthalene and hydroproflavine cations, showing that hydrogen additions induce substantially different optical spectra in comparison with base polycyclic hydrocarbon cations. One calculated line in the visible spectrum of H10-C10H+8 and one in the visible spectrum of H-C13H11N+3 are close to the measured diffuse interstellar bands. We also present the positions of near-ultraviolet lines.

Total Leishmania antigens with Poly(I:C) induce Th1 protective response.

PubMed

Sanchez, M V; Eliçabe, R J; Di Genaro, M S; Germanó, M J; Gea, S; García Bustos, M F; Salomón, M C; Scodeller, E A; Cargnelutti, D E

2017-11-01

Our proposal was to develop a vaccine based on total Leishmania antigens (TLA) adjuvanted with polyinosinic-polycytidylic acid [Poly(I:C)] able to induce a Th1 response which can provide protection against Leishmania infection. Mice were vaccinated with two doses of TLA-Poly(I:C) administered by subcutaneous route at 3-week interval. Humoral and cellular immune responses induced by the immunization were measured. The protective efficacy of the vaccine was evaluated by challenging mice with infective promastigotes of Leishmania (Leishmania) amazonensis into the footpad. Mice vaccinated with TLA-Poly(I:C) showed a high anti-Leishmania IgG titre, as well as increased IgG1 and IgG2a subclass titres compared with mice vaccinated with the TLA alone. The high IgG2a indicated a Th1 bias response induced by the TLA-Poly(I:C) immunization. Accordingly, the cellular immune response elicited by the formulation was characterized by an increased production of IFN-γ and no significant production of IL-4. The TLA-Poly(I:C) immunization elicited good protection, which was associated with decreased footpad swelling, a lower parasite load and a reduced histopathological alteration in the footpad. Our findings demonstrate a promising vaccine against cutaneous leishmaniasis that is relatively economic and easy to develop and which should be taken into account for preventing leishmaniasis in developing countries. © 2017 John Wiley & Sons Ltd.

Detection of interstellar ethylene oxide (c-C2H4O).

PubMed

Dickens, J E; Irvine, W M; Ohishi, M; Ikeda, M; Ishikawa, S; Nummelin, A; Hjalmarson, A

1997-11-10

We report the identification of 10 transitions that support the detection of the small cyclic molecule ethylene oxide (c-C2H4O) in Sgr B2N. Although one of these transitions is severely blended, so that an accurate intensity and line width could not be determined, and two other lines are only marginally detected, we have done Gaussian fits to the remaining seven lines and have performed a rotation diagram analysis. Our results indicate a rotation temperature T(rot) = 18 K and a molecular column density N(c-C2H4O) = 3.3 x 10(14) cm-2, corresponding to a fractional abundance relative to molecular hydrogen of order 6 x 10(-11). This is a factor of more than 200 higher than the abundance for this molecule suggested by the "new standard" chemistry model of Lee, Bettens, & Herbst. This result suggests that grain chemistry might play an effective role in the production of c-C2H4O. No transitions of this molecule were detected in either Sgr B2M or Sgr B2NW.

Hydrogen-Induced Plastic Deformation in ZnO

NASA Astrophysics Data System (ADS)

Lukáč, F.; Čížek, J.; Vlček, M.; Procházka, I.; Anwand, W.; Brauer, G.; Traeger, F.; Rogalla, D.; Becker, H.-W.

In the present work hydrothermally grown ZnO single crystals covered with Pd over-layer were electrochemically loaded with hydrogen and the influence of hydrogen on ZnO micro structure was investigated by positron annihilation spectroscopy (PAS). Nuclear reaction analysis (NRA) was employed for determination of depth profile of hydrogen concentration in the sample. NRA measurements confirmed that a substantial amount of hydrogen was introduced into ZnO by electrochemical charging. The bulk hydrogen concentration in ZnO determined by NRA agrees well with the concentration estimated from the transported charge using the Faraday's law. Moreover, a subsurface region with enhanced hydrogen concentration was found in the loaded crystals. Slow positron implantation spectroscopy (SPIS) investigations of hydrogen-loaded crystal revealed enhanced concentration of defects in the subsurface region. This testifies hydrogen-induced plastic deformation of the loaded crystal. Absorbed hydrogen causes a significant lattice expansion. At low hydrogen concentrations this expansion is accommodated by elastic straining, but at higher concentrations hydrogen-induced stress exceeds the yield stress in ZnO and plastic deformation of the loaded crystal takes place. Enhanced hydrogen concentration detected in the subsurface region by NRA is, therefore, due to excess hydrogen trapped at open volume defects introduced by plastic deformation. Moreover, it was found that hydrogen-induced plastic deformation in the subsurface layer leads to typical surface modification: formation of hexagonal shape pyramids on the surface due to hydrogen-induced slip in the [0001] direction.

Role of promoter element in c-mpl gene expression induced by TPO.

PubMed

Sunohara, Masataka; Morikawa, Shigeru; Fuse, Akira; Sato, Iwao

2013-01-01

Thrombopoietin (TPO) and its receptor, c-Mpl, play the crucial role for the development of megakaryocyte and considered to regulate megakaryocytopoiesis. Previously we reported that TPO increased the c-mpl promoter activity determined by a transient expression system using a vector containing the luciferase gene as a reporter and the expression of the c-mpl gene is modulated by transcription through a protein kinase C (PKC)-dependent pathway in the megakaryoblastic cells. In this research, to elucidate the required elements in c-mpl promoter, the promoter activity of the deletion constructs and site-directed mutagenesis were measured by a transient transfection assay system. Destruction of -77GATA in c-mpl promoter decreased the activity by 22.8%. Our study elucidated that -77GATA involved in TPO-induced c-mpl gene expression in a human megakaryoblastic cell line, CMK.

Noble-metal-free g-C3N4/Ni(dmgH)2 composite for efficient photocatalytic hydrogen evolution under visible light irradiation

NASA Astrophysics Data System (ADS)

Cao, Shao-Wen; Yuan, Yu-Peng; Barber, James; Loo, Say Chye Joachim; Xue, Can

2014-11-01

We report an economic photocatalytic H2 generation system consisting of earth-abundant elements only by coupling graphitic carbon nitride (g-C3N4) with Ni(dmgH)2 sub-microwires that serve as effective co-catalysts for H2 evolution. This composite photocatalyst exhibits efficient hydrogen evolution under visible-light irradiation in the presence of triethanolamine as electron donor. The optimal coupling of 3.5 wt% Ni(dmgH)2 to g-C3N4 (5 mg composite) allows for a steady H2 generation rate of 1.18 μmol/h with excellent stability. This study demonstrates that the combination of polymeric g-C3N4 semiconductor and small proportion of transition-metal-based co-catalyst could serve as a stable, earth-abundant and low-cost system for solar-to-hydrogen conversion.

C1 inhibitor-mediated myocardial protection from chronic intermittent hypoxia-induced injury

PubMed Central

Fu, Jinrong; Guo, Furong; Chen, Cheng; Yu, Xiaoman; Hu, Ke; Li, Mingjiang

2016-01-01

The optimal treatment for chronic intermittent hypoxia (CIH)-induced cardiovascular injuries has yet to be determined. The aim of the current study was to explore the potential protective effect and mechanism of a C1 inhibitor in CIH in the myocardium. The present study used a rat model of CIH in which complement regulatory protein, known as C1 inhibitor (C1INH), was administered to the rats in the intervention groups. Cardiomyocyte apoptosis was detected by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling. The expression of proteins associated with the apoptotic pathway, such as B-cell lymphoma 2 (Bcl-2), Bax and caspase-3 were detected by western blot analysis. The expression of complement C3 protein and RNA were also analyzed. C1INH was observed to improve the cardiac function in rats with CIH. Myocardial myeloperoxidase activity, a marker of neutrophil infiltration, was significantly decreased in the C1INH intervention group compared with the CIH control group, and cardiomyocyte apoptosis was significantly attenuated (P<0.05). Western blotting and reverse transcription-polymerase chain reaction analysis indicated that the protein expression levels of Bcl-2 were decreased and those of Bax were increased in the CIH group compared with the normal control group, but the protein expression levels of Bcl-2 were increased and those of Bax were decreased in the C1INH intervention group, as compared with the CIH group. Furthermore, the CIH-induced expression and synthesis of complement C3 in the myocardium were also reduced in the C1INH intervention group. C1INH, in addition to inhibiting complement activation and inflammation, preserved cardiac function in CIH-mediated myocardial cell injury through an anti-apoptotic mechanism. PMID:27698713