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Sample records for effect hydrogen binding

  1. Effective Binding of Methane Using a Weak Hydrogen Bond.

    PubMed

    Henley, Alice; Bound, Michelle; Besley, Elena

    2016-05-26

    The weak hydrogen bond is an important type of noncovalent interaction, which has been shown to contribute to stability and conformation of proteins and large biochemical membranes, stereoselectivity, crystal packing, and effective gas storage in porous materials. In this work, we systematically explore the interaction of methane with a series of functionalized organic molecules specifically selected to exhibit a weak hydrogen bond with methane molecules. To enhance the strength of hydrogen bond interactions, the functional groups include electron-enriched sites to allow sufficient polarization of the C-H bond of methane. The binding between nine functionalized benzene molecules and methane has been studied using the second order Møller-Plesset perturbation theory to reveal that benzenesulfonic acid (C6H5-SO3H) and phenylphosphonic acid (C6H5-PO3H2) have the greatest potential for efficient methane capture through hydrogen bonding interactions. Both acids exhibit efficient binding potential with up to three methane molecules. For additional insight, the atomic charge distribution associated with each binding site is presented. PMID:27148999

  2. Effects of co-operative ligand binding on protein amide NH hydrogen exchange.

    PubMed

    Polshakov, Vladimir I; Birdsall, Berry; Feeney, James

    2006-03-01

    Amide protection factors have been determined from NMR measurements of hydrogen/deuterium amide NH exchange rates measured on assigned signals from Lactobacillus casei apo-DHFR and its binary and ternary complexes with trimethoprim (TMP), folinic acid and coenzymes (NADPH/NADP(+)). The substantial sizes of the residue-specific DeltaH and TDeltaS values for the opening/closing events in NH exchange for most of the measurable residues in apo-DHFR indicate that sub-global or global rather than local exchange mechanisms are usually involved. The amide groups of residues in helices and sheets are those most protected in apo-DHFR and its complexes, and the protection factors are generally related to the tightness of ligand binding. The effects of ligand binding that lead to changes in amide protection are not localised to specific binding sites but are spread throughout the structure via a network of intramolecular interactions. Although the increase in protein stability in the DHFR.TMP.NADPH complex involves increased ordering in the protein structure (requiring TDeltaS energy) this is recovered, to a large extent, by the stronger binding (enthalpic DeltaH) interactions made possible by the reduced motion in the protein. The ligand-induced protection effects in the ternary complexes DHFR.TMP.NADPH (large positive binding co-operativity) and DHFR.folinic acid.NADPH (large negative binding co-operativity) mirror the co-operative effects seen in the ligand binding. For the DHFR.TMP.NADPH complex, the ligand-induced protection factors result in DeltaDeltaG(o) values for many residues being larger than the DeltaDeltaG(o) values in the corresponding binary complexes. In contrast, for DHFR.folinic acid.NADPH, the DeltaDeltaG(o) values are generally smaller than many of those in the corresponding binary complexes. The results indicate that changes in protein conformational flexibility on formation of the ligand complex play an important role in determining the co-operativity in

  3. Hydrogen Effect against Hydrogen Embrittlement

    NASA Astrophysics Data System (ADS)

    Murakami, Yukitaka; Kanezaki, Toshihiko; Mine, Yoji

    2010-10-01

    The well-known term “hydrogen embrittlement” (HE) expresses undesirable effects due to hydrogen such as loss of ductility, decreased fracture toughness, and degradation of fatigue properties of metals. However, this article shows, surprisingly, that hydrogen can have an effect against HE. A dramatic phenomenon was found in which charging a supersaturated level of hydrogen into specimens of austenitic stainless steels of types 304 and 316L drastically improved the fatigue crack growth resistance, rather than accelerating fatigue crack growth rates. Although this mysterious phenomenon has not previously been observed in the history of HE research, its mechanism can be understood as an interaction between hydrogen and dislocations. Hydrogen can play two roles in terms of dislocation mobility: pinning (or dragging) and enhancement of mobility. Competition between these two roles determines whether the resulting phenomenon is damaging or, unexpectedly, desirable. This finding will, not only be the crucial key factor to elucidate the mechanism of HE, but also be a trigger to review all existing theories on HE in which hydrogen is regarded as a dangerous culprit.

  4. Ligand selectivity of soluble guanylyl cyclase: effect of the hydrogen-bonding tyrosine in the distal heme pocket on binding of oxygen, nitric oxide, and carbon monoxide.

    PubMed

    Martin, Emil; Berka, Vladimir; Bogatenkova, Elena; Murad, Ferid; Tsai, Ah-Lim

    2006-09-22

    Although soluble guanylyl cyclase (sGC) functions in an environment in which O(2), NO, and CO are potential ligands for its heme moiety, the enzyme displays a high affinity for only its physiological ligand, NO, but has a limited affinity for CO and no affinity for O(2). Recent studies of a truncated version of the sGC beta(1)-subunit containing the heme-binding domain (Boon, E. M., Huang, S H., and Marletta, M. A. (2005) Nat. Chem. Biol., 1, 53-59) showed that introduction of the hydrogen-bonding tyrosine into the distal heme pocket changes the ligand specificity of the heme moiety and results in an oxygen-binding sGC. The hypothesis that the absence of hydrogen-bonding residues in the distal heme pocket is sufficient to provide oxygen discrimination by sGC was put forward. We tested this hypothesis in a context of a complete sGC heterodimer containing both the intact alpha(1)- and beta(1)-subunits. We found that the I145Y substitution in the full-length beta-subunit of the sGC heterodimer did not produce an oxygen-binding enzyme. However, this substitution impeded the association of NO and destabilized the NO.heme complex. The tyrosine in the distal heme pocket also impeded both the binding and dissociation of the CO ligand. We propose that the mechanism of oxygen exclusion by sGC not only involves the lack of hydrogen bonding in the distal heme pocket, but also depends on structural elements from other domains of sGC. PMID:16864588

  5. Tight-binding model for hydrogen-silicon interactions

    SciTech Connect

    Min, B.J.; Lee, Y.H.; Wang, C.Z.; Chan, C.T.; Ho, K.M. Department of Physics and Astronomy, Ames Laboratory, Iowa State University, Ames, Iowa 50011 )

    1992-03-15

    We have developed an empirical tight-binding model for use in molecular-dynamics simulations to study hydrogen-silicon systems. The hydrogen-silicon interaction is constructed to reproduce the electronic energy levels and vibration frequencies of silane (SiH{sub 4}). Further use of the model in the studies of disilane (Si{sub 2}H{sub 6}) and of hydrogen on the Si(111) surface also yields results in good agreement with first-principles calculations and experiments.

  6. Kinetic study of the effects of calcium ions on cationic artichoke (Cynara scolymus L.) peroxidase: calcium binding, steady-state kinetics and reactions with hydrogen peroxide.

    PubMed

    Hiner, Alexander N P; Sidrach, Lara; Chazarra, Soledad; Varón, Ramón; Tudela, José; García-Cánovas, Francisco; Rodríguez-López, José Neptuno

    2004-01-01

    The apparent catalytic constant (k(cat)) of artichoke (Cynara scolymus L.) peroxidase (AKPC) with 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) increased 130-fold in the presence of calcium ions (Ca2+) but the affinity (K(m)) of the enzyme for ABTS was 500 times lower than for Ca2+-free AKPC. AKPC is known to exhibit an equilibrium between 6-aquo hexa-coordinate and penta-coordinate forms of the haem iron that is modulated by Ca2+ and affects compound I formation. Measurements of the Ca2+ dissociation constant (K(D)) were complicated by the water-association/dissociation equilibrium yielding a global value more than 1000 times too high. The value for the Ca2+ binding step alone has now been determined to be K(D) approximately 10 nM. AKPC-Ca2+ was more resistant to inactivation by hydrogen peroxide (H(2)O(2)) and exhibited increased catalase activity. An analysis of the complex H(2)O(2) concentration dependent kinetics of Ca2+-free AKPC is presented. PMID:15556277

  7. Application of Henry's Law for Binding Energies of Adsorbed Hydrogen

    NASA Astrophysics Data System (ADS)

    Gillespie, Andrew; Dohnke, Elmar; Stalla, David; Sweany, Mark; Pfeifer, Peter

    2015-03-01

    The method of isosteres is the simplest method used to calculate the differential enthalpy of adsorption. However, it is incredibly sensitive to the choice of model and respective fitting parameters. For a set of isotherms measured on a specific sample, most models converge upon a similar value at high coverage, but are inconsistent in the low pressure regime. In this talk, we investigate the application of various models for localized and mobile adsorption at low pressures in order to obtain binding energy of hydrogen to the adsorbent surface. Henry's Law analysis of the Langmuir Model of adsorption yield binding energies in excellent agreement with those obtained from the Clausius Clapeyron relation. Work supported by DOE-EERE, Award No. DE-FG36-08GO18142.

  8. Correlating hydrogen oxidation and evolution activity on platinum at different pH with measured hydrogen binding energy

    SciTech Connect

    Sheng, WC; Zhuang, ZB; Gao, MR; Zheng, J; Chen, JGG; Yan, YS

    2015-01-08

    The hydrogen oxidation/evolution reactions are two of the most fundamental reactions in distributed renewable electrochemical energy conversion and storage systems. The identification of the reaction descriptor is therefore of critical importance for the rational catalyst design and development. Here we report the correlation between hydrogen oxidation/evolution activity and experimentally measured hydrogen binding energy for polycrystalline platinum examined in several buffer solutions in a wide range of electrolyte pH from 0 to 13. The hydrogen oxidation/evolution activity obtained using the rotating disk electrode method is found to decrease with the pH, while the hydrogen binding energy, obtained from cyclic voltammograms, linearly increases with the pH. Correlating the hydrogen oxidation/evolution activity to the hydrogen binding energy renders a monotonic decreasing hydrogen oxidation/evolution activity with the hydrogen binding energy, strongly supporting the hypothesis that hydrogen binding energy is the sole reaction descriptor for the hydrogen oxidation/evolution activity on monometallic platinum.

  9. Correlating hydrogen oxidation and evolution activity on platinum at different pH with measured hydrogen binding energy

    NASA Astrophysics Data System (ADS)

    Sheng, Wenchao; Zhuang, Zhongbin; Gao, Minrui; Zheng, Jie; Chen, Jingguang G.; Yan, Yushan

    2015-01-01

    The hydrogen oxidation/evolution reactions are two of the most fundamental reactions in distributed renewable electrochemical energy conversion and storage systems. The identification of the reaction descriptor is therefore of critical importance for the rational catalyst design and development. Here we report the correlation between hydrogen oxidation/evolution activity and experimentally measured hydrogen binding energy for polycrystalline platinum examined in several buffer solutions in a wide range of electrolyte pH from 0 to 13. The hydrogen oxidation/evolution activity obtained using the rotating disk electrode method is found to decrease with the pH, while the hydrogen binding energy, obtained from cyclic voltammograms, linearly increases with the pH. Correlating the hydrogen oxidation/evolution activity to the hydrogen binding energy renders a monotonic decreasing hydrogen oxidation/evolution activity with the hydrogen binding energy, strongly supporting the hypothesis that hydrogen binding energy is the sole reaction descriptor for the hydrogen oxidation/evolution activity on monometallic platinum.

  10. Correlating hydrogen oxidation and evolution activity on platinum at different pH with measured hydrogen binding energy.

    PubMed

    Sheng, Wenchao; Zhuang, Zhongbin; Gao, Minrui; Zheng, Jie; Chen, Jingguang G; Yan, Yushan

    2015-01-01

    The hydrogen oxidation/evolution reactions are two of the most fundamental reactions in distributed renewable electrochemical energy conversion and storage systems. The identification of the reaction descriptor is therefore of critical importance for the rational catalyst design and development. Here we report the correlation between hydrogen oxidation/evolution activity and experimentally measured hydrogen binding energy for polycrystalline platinum examined in several buffer solutions in a wide range of electrolyte pH from 0 to 13. The hydrogen oxidation/evolution activity obtained using the rotating disk electrode method is found to decrease with the pH, while the hydrogen binding energy, obtained from cyclic voltammograms, linearly increases with the pH. Correlating the hydrogen oxidation/evolution activity to the hydrogen binding energy renders a monotonic decreasing hydrogen oxidation/evolution activity with the hydrogen binding energy, strongly supporting the hypothesis that hydrogen binding energy is the sole reaction descriptor for the hydrogen oxidation/evolution activity on monometallic platinum. PMID:25569511

  11. Synergistic effects in hydrogen-helium bubbles.

    PubMed

    Hayward, Erin; Deo, Chaitanya

    2012-07-01

    The detrimental effects of hydrogen and helium on structural materials undergoing irradiation are well documented, if not well understood. There is experimental evidence to suggest that a synergistic effect between the two elements exists, which results in increased damage when both are present. This situation is expected in the next generation of fusion and fission reactors, so a fundamental understanding of these synergistic interactions is needed to predict materials performance. We perform atomistic simulations of hydrogen and helium bubbles in body-centered cubic iron to determine the mechanism behind this effect. We first develop an interatomic potential suitable for describing the interactions between hydrogen and helium. Through analysis of the energetics and structure of these bubbles, we explain the observed synergy as a consequence of bubble growth through helium induced loop punching, aided by the presence of hydrogen, instead of as a direct interaction between hydrogen and helium. The hydrogen benefits from an increased area of free surface on which to bind. PMID:22691382

  12. Effects of hydrogen on metals

    NASA Technical Reports Server (NTRS)

    Cataldo, C. E.

    1969-01-01

    Several rules to guide choice of materials, and methods of welding, electroplating, and heat treatment will provide a method for minimizing failures in storage tanks and related hardware. Failures are caused by high-pressure hydrogen effects, the formation of hydrides in titanium, and hydrogen absorption through various metals processing techniques.

  13. Unveiling Residual Molecular Binding in Triply Charged Hydrogen Bromide

    SciTech Connect

    Penent, F.; Lablanquie, P.; Palaudoux, J.; Gamblin, G.; Carniato, S.; Andric, L.; Hikosaka, Y.; Ito, K.

    2011-03-11

    We present an experimental and theoretical study of triply charged hydrogen bromide ions formed by photoionization of the inner 3d shell of Br. The experimental results, obtained by detecting the 3d photoelectron in coincidence with the two subsequent Auger electrons, are analyzed using calculated potential energy curves of HBr{sup 3+}. The competition between the short-range chemical binding potential and the Coulomb repulsion in the dissociative process is shown. Two different mechanisms are observed for double Auger decay: one, a direct process with simultaneous ejection of two Auger electrons to final HBr{sup 3+} ionic states and the other, a cascade process involving double Auger decay characterized by the autoionization of Br*{sup +} ion subsequent to the HBr{sup 2+} fragmentation.

  14. Optimizing the Binding Energy of Hydrogen on Nanostructured Carbon Materials through Structure Control and Chemical Doping

    SciTech Connect

    Jie Liu

    2011-02-01

    The DOE Hydrogen Sorption Center of Excellence (HSCoE) was formed in 2005 to develop materials for hydrogen storage systems to be used in light-duty vehicles. The HSCoE and two related centers of excellence were created as follow-on activities to the DOE Office of Energy Efficiency and Renewable Energy’s (EERE’s) Hydrogen Storage Grand Challenge Solicitation issued in FY 2003. The Hydrogen Sorption Center of Excellence (HSCoE) focuses on developing high-capacity sorbents with the goal to operate at temperatures and pressures approaching ambient and be efficiently and quickly charged in the tank with minimal energy requirements and penalties to the hydrogen fuel infrastructure. The work was directed at overcoming barriers to achieving DOE system goals and identifying pathways to meet the hydrogen storage system targets. To ensure that the development activities were performed as efficiently as possible, the HSCoE formed complementary, focused development clusters based on the following four sorption-based hydrogen storage mechanisms: 1. Physisorption on high specific surface area and nominally single element materials 2. Enhanced H2 binding in Substituted/heterogeneous materials 3. Strong and/or multiple H2 binding from coordinated but electronically unsatruated metal centers 4. Weak Chemisorption/Spillover. As a member of the team, our group at Duke studied the synthesis of various carbon-based materials, including carbon nanotubes and microporous carbon materials with controlled porosity. We worked closely with other team members to study the effect of pore size on the binding energy of hydrogen to the carbon –based materials. Our initial project focus was on the synthesis and purification of small diameter, single-walled carbon nanotubes (SWNTs) with well-controlled diameters for the study of their hydrogen storage properties as a function of diameters. We developed a chemical vapor deposition method that synthesized gram quantities of carbon nanotubes with

  15. Localizing Carbohydrate Binding Sites in Proteins Using Hydrogen/Deuterium Exchange Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Zhang, Jingjing; Kitova, Elena N.; Li, Jun; Eugenio, Luiz; Ng, Kenneth; Klassen, John S.

    2016-01-01

    The application of hydrogen/deuterium exchange mass spectrometry (HDX-MS) to localize ligand binding sites in carbohydrate-binding proteins is described. Proteins from three bacterial toxins, the B subunit homopentamers of Cholera toxin and Shiga toxin type 1 and a fragment of Clostridium difficile toxin A, and their interactions with native carbohydrate receptors, GM1 pentasaccharides (β-Gal-(1→3)-β-GalNAc-(1→4)[α-Neu5Ac-(2→3)]-β-Gal-(1→4)-Glc), Pk trisaccharide (α-Gal-(1→4)-β-Gal-(1→4)-Glc) and CD-grease (α-Gal-(1→3)-β-Gal-(1→4)-β-GlcNAcO(CH2)8CO2CH3), respectively, served as model systems for this study. Comparison of the differences in deuterium uptake for peptic peptides produced in the absence and presence of ligand revealed regions of the proteins that are protected against deuterium exchange upon ligand binding. Notably, protected regions generally coincide with the carbohydrate binding sites identified by X-ray crystallography. However, ligand binding can also result in increased deuterium exchange in other parts of the protein, presumably through allosteric effects. Overall, the results of this study suggest that HDX-MS can serve as a useful tool for localizing the ligand binding sites in carbohydrate-binding proteins. However, a detailed interpretation of the changes in deuterium exchange upon ligand binding can be challenging because of the presence of ligand-induced changes in protein structure and dynamics.

  16. Analytic variational calculation of the ground-state binding energy of hydrogen in intermediate and intense magnetic fields

    NASA Technical Reports Server (NTRS)

    Wilson, L. W.

    1974-01-01

    The present work investigates analytically the effect of an intermediate or intense magnetic field, such as probably exist in white dwarfs and near pulsars, on the binding energy of the hydrogen ground state. A wave-function 'prescription' is given for an analytic variational calculation of the binding energy. The calculation still gives a smooth transition between intermediate and intense fields. An explicit calculation of the ground-state binding energy as B goes to infinity is provided for the Yafet et al. (1956) trial function.

  17. The Origins of Femtomolar Protein–Ligand Binding: Hydrogen Bond Cooperativity and Desolvation Energetics in the Biotin–(Strept)Avidin Binding Site

    PubMed Central

    DeChancie, Jason; Houk, K.N.

    2008-01-01

    The unusually strong reversible binding of biotin by avidin and streptavidin has been investigated by density functional and MP2 ab initio quantum mechanical methods. The solvation of biotin by water has also been studied through QM/MM/MC calculations. The ureido moiety of biotin in the bound state hydrogen bonds to five residues, three to the carbonyl oxygen and one for each –NH group. These five hydrogen bonds act cooperatively, leading to stabilization that is larger than the sum of individual hydrogen-bonding energies. The charged aspartate is the key residue that provides the driving force for cooperativity in the hydrogen-bonding network for both avidin and streptavidin by greatly polarizing the urea of biotin. If the residue is removed, the network is disrupted, and the attenuation of the energetic contributions from the neighboring residues results in significant reduction of cooperative interactions. Aspartate is directly hydrogen-bonded with biotin in streptavidin and is one residue removed in avidin. The hydrogen-bonding groups in streptavidin are computed to give larger cooperative hydrogen-bonding effects than avidin. However, the net gain in electrostatic binding energy is predicted to favor the avidin-bicyclic urea complex due to the relatively large penalty for desolvation of the streptavidin binding site (specifically expulsion of bound water molecules). QM/MM/MC calculations involving biotin and the ureido moiety in aqueous solution, featuring PDDG/PM3, show that water interactions with the bicyclic urea are much weaker than (strept)avidin interactions due to relatively low polarization of the urea group in water. PMID:17417839

  18. Dissection of the binding of hydrogen peroxide to trypsin using spectroscopic methods and molecular modeling.

    PubMed

    Song, Wei; Yu, Zehua; Hu, Xinxin; Liu, Rutao

    2015-02-25

    Studies on the effects of environmental pollutants to protein in vitro has become a global attention. Hydrogen peroxide (H2O2) is used as an effective food preservative and bleacher in industrial production. The toxicity of H2O2 to trypsin was investigated by multiple spectroscopic techniques and the molecular docking method at the molecular level. The intrinsic fluorescence of trypsin was proved to be quenched in a static process based on the results of fluorescence lifetime experiment. Hydrogen bonds interaction and van der Waals forces were the main force to generate the trypsin-H2O2 complex on account of the negative ΔH(0) and ΔS(0). The binding of H2O2 changed the conformational structures and internal microenvironment of trypsin illustrated by UV-vis absorption, fluorescence, synchronous fluorescence, three-dimensional (3D) fluorescence and circular dichroism (CD) results. However, the binding site was far away from the active site of trypsin and the trypsin activity was only slightly affected by H2O2, which was further explained by molecular docking investigations. PMID:25228036

  19. Dissection of the binding of hydrogen peroxide to trypsin using spectroscopic methods and molecular modeling

    NASA Astrophysics Data System (ADS)

    Song, Wei; Yu, Zehua; Hu, Xinxin; Liu, Rutao

    2015-02-01

    Studies on the effects of environmental pollutants to protein in vitro has become a global attention. Hydrogen peroxide (H2O2) is used as an effective food preservative and bleacher in industrial production. The toxicity of H2O2 to trypsin was investigated by multiple spectroscopic techniques and the molecular docking method at the molecular level. The intrinsic fluorescence of trypsin was proved to be quenched in a static process based on the results of fluorescence lifetime experiment. Hydrogen bonds interaction and van der Waals forces were the main force to generate the trypsin-H2O2 complex on account of the negative ΔH0 and ΔS0. The binding of H2O2 changed the conformational structures and internal microenvironment of trypsin illustrated by UV-vis absorption, fluorescence, synchronous fluorescence, three-dimensional (3D) fluorescence and circular dichroism (CD) results. However, the binding site was far away from the active site of trypsin and the trypsin activity was only slightly affected by H2O2, which was further explained by molecular docking investigations.

  20. Regulation of protein-ligand binding affinity by hydrogen bond pairing.

    PubMed

    Chen, Deliang; Oezguen, Numan; Urvil, Petri; Ferguson, Colin; Dann, Sara M; Savidge, Tor C

    2016-03-01

    Hydrogen (H)-bonds potentiate diverse cellular functions by facilitating molecular interactions. The mechanism and the extent to which H-bonds regulate molecular interactions are a largely unresolved problem in biology because the H-bonding process continuously competes with bulk water. This interference may significantly alter our understanding of molecular function, for example, in the elucidation of the origin of enzymatic catalytic power. We advance this concept by showing that H-bonds regulate molecular interactions via a hitherto unappreciated donor-acceptor pairing mechanism that minimizes competition with water. On the basis of theoretical and experimental correlations between H-bond pairings and their effects on ligand binding affinity, we demonstrate that H-bonds enhance receptor-ligand interactions when both the donor and acceptor have either significantly stronger or significantly weaker H-bonding capabilities than the hydrogen and oxygen atoms in water. By contrast, mixed strong-weak H-bond pairings decrease ligand binding affinity due to interference with bulk water, offering mechanistic insight into why indiscriminate strengthening of receptor-ligand H-bonds correlates poorly with experimental binding affinity. Further support for the H-bond pairing principle is provided by the discovery and optimization of lead compounds targeting dietary melamine and Clostridium difficile toxins, which are not realized by traditional drug design methods. Synergistic H-bond pairings have therefore evolved in the natural design of high-affinity binding and provide a new conceptual framework to evaluate the H-bonding process in biological systems. Our findings may also guide wider applications of competing H-bond pairings in lead compound design and in determining the origin of enzymatic catalytic power. PMID:27051863

  1. Regulation of protein-ligand binding affinity by hydrogen bond pairing

    PubMed Central

    Chen, Deliang; Oezguen, Numan; Urvil, Petri; Ferguson, Colin; Dann, Sara M.; Savidge, Tor C.

    2016-01-01

    Hydrogen (H)-bonds potentiate diverse cellular functions by facilitating molecular interactions. The mechanism and the extent to which H-bonds regulate molecular interactions are a largely unresolved problem in biology because the H-bonding process continuously competes with bulk water. This interference may significantly alter our understanding of molecular function, for example, in the elucidation of the origin of enzymatic catalytic power. We advance this concept by showing that H-bonds regulate molecular interactions via a hitherto unappreciated donor-acceptor pairing mechanism that minimizes competition with water. On the basis of theoretical and experimental correlations between H-bond pairings and their effects on ligand binding affinity, we demonstrate that H-bonds enhance receptor-ligand interactions when both the donor and acceptor have either significantly stronger or significantly weaker H-bonding capabilities than the hydrogen and oxygen atoms in water. By contrast, mixed strong-weak H-bond pairings decrease ligand binding affinity due to interference with bulk water, offering mechanistic insight into why indiscriminate strengthening of receptor-ligand H-bonds correlates poorly with experimental binding affinity. Further support for the H-bond pairing principle is provided by the discovery and optimization of lead compounds targeting dietary melamine and Clostridium difficile toxins, which are not realized by traditional drug design methods. Synergistic H-bond pairings have therefore evolved in the natural design of high-affinity binding and provide a new conceptual framework to evaluate the H-bonding process in biological systems. Our findings may also guide wider applications of competing H-bond pairings in lead compound design and in determining the origin of enzymatic catalytic power. PMID:27051863

  2. A diminished role for hydrogen bonds in antifreeze protein binding to ice.

    PubMed

    Chao, H; Houston, M E; Hodges, R S; Kay, C M; Sykes, B D; Loewen, M C; Davies, P L; Sönnichsen, F D

    1997-12-01

    The most abundant isoform (HPLC-6) of type I antifreeze protein (AFP1) in winter flounder is a 37-amino-acid-long, alanine-rich, alpha-helical peptide, containing four Thr spaced 11 amino acids apart. It is generally assumed that HPLC-6 binds ice through a hydrogen-bonding match between the Thr and neighboring Asx residues to oxygens atoms on the {2021} plane of the ice lattice. The result is a lowering of the nonequilibrium freezing point below the melting point (thermal hysteresis). HPLC-6, and two variants in which the central two Thr were replaced with either Ser or Val, were synthesized. The Ser variant was virtually inactive, while only a minor loss of activity was observed in the Val variant. CD, ultracentrifugation, and NMR studies indicated no significant structural changes or aggregation of the variants compared to HPLC-6. These results call into question the role of hydrogen bonds and suggest a much more significant role for entropic effects and van der Waals interactions in binding AFP to ice. PMID:9398184

  3. Boron nanoparticles with high hydrogen loading: mechanism for B-H binding and potential for improved combustibility and specific impulse.

    PubMed

    Perez, Jesus Paulo L; McMahon, Brandon W; Yu, Jiang; Schneider, Stefan; Boatz, Jerry A; Hawkins, Tom W; McCrary, Parker D; Flores, Luis A; Rogers, Robin D; Anderson, Scott L

    2014-06-11

    Ball milling of boron in an H2 atmosphere was found to result in hydrogen uptake of up to 5% by weight (36 mol %). The nature of the hydrogen binding to boron was probed by a combination of ab initio theory, IR spectroscopy, thermogravimetric analysis, and mass spectral measurements of gases evolved during sample heating. The dominant binding mode is found to be H atoms bound to B atoms in the surface layer of the particles, and the high hydrogen loading results from production of very high surface area, indicating that gaseous H2 is an effective agent promoting size reduction in milling. Hydrogen incorporated in the samples was found to be stable for at least a month under ambient conditions. Desorption is observed beginning at ∼60 °C and continuing as the temperature is increased, with broad desorption features peaking at ∼250 and ∼450 °C, and ending at ∼800 °C. Unprotected hydrogenated boron nanoparticles were found to be reactive with O2 producing a hydrated boron oxide surface layer that decomposed readily at 100 °C leading to desorption of H2O. Hydrogenated boron nanoparticles were found to promote a higher flame height in the hypergolic ignition of ionic liquids upon contact with nitric acid. PMID:24806745

  4. Spectroscopic investigations into the binding of hydrogen sulfide to synthetic picket-fence porphyrins.

    PubMed

    Hartle, Matthew D; Prell, James S; Pluth, Michael D

    2016-03-21

    The reversible binding of hydrogen sulfide (H2S) to hemeprotein sites has been attributed to several factors, likely working in concert, including the protected binding pocket environment, proximal hydrogen bond interactions, and iron ligation environment. To investigate the importance of a sterically-constrained, protected environment on sulfide reactivity with heme centers, we report here the reactivity of H2S and HS(-) with the picket-fence porphyrin system. Our results indicate that the picket-fence porphyrin does not bind H2S in the ferric or ferrous state. By contrast, reaction of the ferric scaffold with HS(-) results in reduction to the ferrous species, followed by ligation of one equivalent of HS(-), as evidenced by UV-vis, NMR spectroscopy and mass spectrometry studies. Measurement of the HS(-) binding affinities in the picket-fence or tetraphenyl porphyrin systems revealed identical binding. Taken together, these results suggest that the protected, sterically-constrained binding pocket alone is not the primary contributor for stabilization of ferric H2S/HS(-) species in model systems, but that other interactions, such as hydrogen bonding, must play a critical role in facilitation of reversible interactions in ferric hemes. PMID:26869340

  5. Accurate hydrogen bond energies within the density functional tight binding method.

    PubMed

    Domínguez, A; Niehaus, T A; Frauenheim, T

    2015-04-01

    The density-functional-based tight-binding (DFTB) approach has been recently extended by incorporating one-center exchange-like terms in the expansion of the multicenter integrals. This goes beyond the Mulliken approximation and leads to a scheme which treats in a self-consistent way the fluctuations of the whole dual density matrix and not only its diagonal elements (Mulliken charges). To date, only the performance of this new formalism to reproduce excited-state properties has been assessed (Domínguez et al. J. Chem. Theory Comput., 2013, 9, 4901-4914). Here we study the effect of our corrections on the computation of hydrogen bond energies for water clusters and water-containing systems. The limitations of traditional DFTB to reproduce hydrogen bonds has been acknowledged often. We compare our results for a set of 22 small water clusters and water-containing systems as well as for five water hexadecamers to those obtained with the DFTB3 method. Additionally, we combine our extension with a third-order energy expansion in the charge fluctuations. Our results show that the new formalisms significantly improve upon original DFTB. PMID:25763597

  6. Serum albumin forms a lactoferrin-like soluble iron-binding complex in presence of hydrogen carbonate ions.

    PubMed

    Ueno, Hiroshi M; Urazono, Hiroshi; Kobayashi, Toshiya

    2014-02-15

    The iron-lactoferrin complex is a common food ingredient because of its iron-solubilizing capability in the presence of hydrogen carbonate ions. However, it is unclear whether the formation of a stable iron-binding complex is limited to lactoferrin. In this study, we investigated the effects of bovine serum albumin (BSA) on iron solubility and iron-catalyzed lipid oxidation in the presence of hydrogen carbonate ions. BSA could solubilize >100-fold molar equivalents of iron at neutral pH, exceeding the specific metal-binding property of BSA. This iron-solubilizing capability of BSA was impaired by thermally denaturing BSA at ≥ 70 °C for 10 min at pH 8.5. The resulting iron-BSA complex inhibited iron-catalyzed oxidation of soybean oil in a water-in-oil emulsion measured using the Rancimat test. Our study is the first to show that BSA, like lactoferrin, forms a soluble iron-binding complex in the presence of hydrogen carbonate ions. PMID:24128453

  7. Predictive binding geometry of ligands to DNA minor groove: isohelicity and hydrogen-bonding pattern.

    PubMed

    Stockert, Juan C

    2014-01-01

    The interaction of drugs and dyes with nucleic acids, particularly when binding to DNA minor groove occurs, has increasing importance in biomedical sciences. This is due to the resulting biological activity and to the possibility of recognizing AT and GC base pairs. In such cases, DNA binding can be predicted if appropriate helical and hydrogen-bonding parameters are deduced from DNA models, and a simplified geometrical rule in the form of a stencil is then applied on computer-drawn molecules of interest. Relevant structure parameter values for minor groove binders are the length (4.6 < L < 5.4 Å) and angle (152 < σ < 156.5°) between three consecutive units, measured at the level of hydrogen donor or acceptor groups. Application of the stencil shows that predictive methods can aid in the design of new compounds, by checking the possible binding of isohelical sequence-specific ligands along the DNA minor groove. PMID:24162975

  8. Characterization of hydrogen binding to tungsten and beryllium surfaces using low energy ion beam analysis

    NASA Astrophysics Data System (ADS)

    Kolasinski, Robert; Whaley, Josh

    2015-11-01

    In this study, we use low energy ion beam analysis to determine how hydrogen interacts with tungsten and beryllium surfaces. The goal of this work is to provide insight into processes that contribute to recycling from plasma-facing surfaces in magnetic fusion devices. Here we have applied low energy ion scattering (LEIS) to enable detection of adsorbed hydrogen at sub-monolayer resolution and to provide isotopic sensitivity. We probe the surfaces of interest with He + and Ne + at energies less than 5 keV to determine the structure and composition of the first few atomic layers. This approach enables us to examine how hydrogen surface concentrations evolve in real time, providing insight into adsorption kinetics. In addition, we have developed a means of determining the hydrogen binding configuration at different temperatures by exploiting mechanisms of ion channeling along surfaces. Using these methods, we have been able to identify hydrogen binding configurations for the W(100) +H, W(110) +H, and Be(0001) +H adsorption systems. We also report on our efforts to more accurately and efficiently model atomic collisions during scattering, key steps needed to extract structural information from LEIS signals. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. DOE's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  9. Physicochemical and in vitro binding properties of barley β-glucan treated with hydrogen peroxide.

    PubMed

    Lee, Sang Hoon; Jang, Gwi Yeong; Kim, Min Young; Hwang, In Guk; Kim, Hyun Young; Woo, Koan Sik; Lee, Mi Ja; Kim, Tae Jip; Lee, Junsoo; Jeong, Heon Sang

    2016-02-01

    This study investigated the changes in content, purity, physical properties, and in vitro binding properties of barley β-glucan by oxidation treatment. Barleys (Hordeum vulgare) were oxidized, using different concentrations of hydrogen peroxide (0.2-1.0% H2O2). The total and soluble β-glucan contents ranged from 8.41% and 4.81% in the control to 9.48% and 6.45% in the 0.6% H2O2 treatment. With increasing H2O2 concentration, the purity of β-glucan increased from 35% to 70%, whereas molecular weight (MW), viscosity, and water-binding capacities decreased to 2.0 × 10(4)Da, 3.9 cP, and 4.45 g water/g β-glucan, respectively. Oil binding capacities ranged from 8.29 g of oil/g in non-oxidized β-glucan to 9.42 g of oil/g in β-glucan oxidized with 0.6% H2O2. The MW, viscosity, and binding capacities of waxy barley β-glucan were higher than those of non-waxy barley β-glucan. Oxidation by hydrogen peroxide improved the physical properties and in vitro binding capacity of barley β-glucan. PMID:26304404

  10. Correlating the hydrogen evolution reaction activity in alkaline electrolytes with the hydrogen binding energy on monometallic surfaces

    SciTech Connect

    Sheng, WC; Myint, M; Chen, JGG; Yan, YS

    2013-05-01

    The slow reaction kinetics of the hydrogen evolution and oxidation reactions (HER/HOR) on platinum in alkaline electrolytes hinders the development of alkaline electrolysers, solar hydrogen cells and alkaline fuel cells. A fundamental understanding of the exchange current density of the HER/HOR in alkaline media is critical for the search and design of highly active electrocatalysts. By studying the HER on a series of monometallic surfaces, we demonstrate that the HER exchange current density in alkaline solutions can be correlated with the calculated hydrogen binding energy (HBE) on the metal surfaces via a volcano type of relationship. The HER activity varies by several orders of magnitude from Pt at the peak of the plot to W and Au located on the bottom of each side of the plot, similar to the observation in acids. Such a correlation suggests that the HBE can be used as a descriptor for identifying electrocatalysts for HER/HOR in alkaline media, and that the HER exchange current density can be tuned by modifying the surface chemical properties.

  11. Effective hydrogen storage: a strategic chemistry challenge.

    PubMed

    David, William I F

    2011-01-01

    This paper gives an overview of the current status and future potential of hydrogen storage from a chemistry perspective and is based on the concluding presentation of the Faraday Discussion 151--Hydrogen Storage Materials. The safe, effective and economical storage of hydrogen is one of the main scientific and technological challenges in the move towards a low-carbon economy. One key sector is transportation where future vehicles will most likely be developed around a balance of battery-electric and hydrogen fuel-cell electric technologies. Although there has been a very significant research effort in solid-state hydrogen storage, high-pressure gas storage combined with conventional metal hydrides is still seen as the current intermediate-term candidate for car manufacturers. Significant issues have arisen in the search for improved solid-state hydrogen storage materials; for example, facile reversibility has been a major challenge for many recently studied complex hydrides while physisorption in porous structures is still restricted to cryogenic temperatures. However, many systems fulfil the majority of necessary criteria for improved hydrogen storage--indeed, the discovery of reversibility in multicomponent hydride systems along with recent chemistry breakthroughs in off-board and solvent-assisted regeneration suggest that the goal of both improved on-board reversible and off-board regenerated hydrogen storage systems can be achieved. PMID:22455082

  12. Theoretical investigation of the binding of a positron to vibrational excited states of hydrogen cyanide molecule

    NASA Astrophysics Data System (ADS)

    Kita, Yukiumi; Tachikawa, Masanori

    2014-05-01

    We theoretically analyzed positron affinities (PA) of hydrogen cyanide (HCN) molecule at vibrational excited states to elucidate the effect of molecular vibrations on the binding of a positron to the molecule. Using the configuration interaction method in the multi-component molecular orbital theory and anharmonic vibrational state analysis with the variational Monte Carlo technique, we found that the vibrational excitations of the CN and CH stretching modes enhance the PA value compared to that of the vibrational ground state, whereas the excitation of bending mode deenhances it. The largest PA enhancement is found at the excited states of the CH stretching mode; the PA values are 43.02 (1) and 46.34 (2) meV for the fundamental tone and overtone states, respectively. With the linear regression analysis, we confirmed that the PA variation of HCN molecule at each vibrational state arises from the variation of permanent dipole moment and dipole-polarizability due to each vibrational excitation. Contribution to the Topical Issue "Electron and Positron Induced Processes", edited by Michael Brunger, Radu Campeanu, Masamitsu Hoshino, Oddur Ingólfsson, Paulo Limão-Vieira, Nigel Mason, Yasuyuki Nagashima and Hajime Tanuma.

  13. Communication: Towards the binding energy and vibrational red shift of the simplest organic hydrogen bond: Harmonic constraints for methanol dimer

    SciTech Connect

    Heger, Matthias; Suhm, Martin A.; Mata, Ricardo A.

    2014-09-14

    The discrepancy between experimental and harmonically predicted shifts of the OH stretching fundamental of methanol upon hydrogen bonding to a second methanol unit is too large to be blamed mostly on diagonal and off-diagonal anharmonicity corrections. It is shown that a decisive contribution comes from post-MP2 electron correlation effects, which appear not to be captured by any of the popular density functionals. We also identify that the major deficiency is in the description of the donor OH bond. Together with estimates for the electronic and harmonically zero-point corrected dimer binding energies, this work provides essential constraints for a quantitative description of this simple hydrogen bond. The spectroscopic dissociation energy is predicted to be larger than 18 kJ/mol and the harmonic OH-stretching fundamental shifts by about −121 cm{sup −1} upon dimerization, somewhat more than in the anharmonic experiment (−111 cm{sup −1})

  14. Effects of Hydrogen on Tantalum Nitride Resistors

    NASA Technical Reports Server (NTRS)

    Weiler, James

    2000-01-01

    In this paper we report on observations of degradation of thin film Tantalum Nitride chip resistors in a hermetically sealed hybrid. The observations have been attributed to the reaction of residual Palladium with desorbed Hydrogen on the surface of the resistor film. Hydrogen gas has been observed to desorb from various sources within the sealed hybrid as a result of temperature elevation. The hydrogen gas has been reported to undergo a reaction with elements such as Platinum and Palladium causing device degradation in Gallium Arsenide Field Effect Transistors. The experimental procedures and data relating to this observation along with a discussion of available risk mitigation techniques will be presented.

  15. Effect of a high intensity laser beam on impurity binding energy in a nanocone

    NASA Astrophysics Data System (ADS)

    Paredes, H.; Beltrán Ríos, C. L.; Gutíerrez, W.

    2016-02-01

    This paper presents theoretical results of a study that analyzed the effect of a high- frequency laser in the ground state binding energy of a hydrogenic donnor impurity. For these results, the trigonometric sweep method and framework of the effective mass approximation is applied. The results showed that the binding energy changes depending on the laser intensity and the impurity position across of the nanocone axis. The results agree with previous results obtained in similar systems.

  16. Universal dependence of hydrogen oxidation and evolution reaction activity of platinum-group metals on pH and hydrogen binding energy.

    PubMed

    Zheng, Jie; Sheng, Wenchao; Zhuang, Zhongbin; Xu, Bingjun; Yan, Yushan

    2016-03-01

    Understanding how pH affects the activity of hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) is key to developing active, stable, and affordable HOR/HER catalysts for hydroxide exchange membrane fuel cells and electrolyzers. A common linear correlation between hydrogen binding energy (HBE) and pH is observed for four supported platinum-group metal catalysts (Pt/C, Ir/C, Pd/C, and Rh/C) over a broad pH range (0 to 13), suggesting that the pH dependence of HBE is metal-independent. A universal correlation between exchange current density and HBE is also observed on the four metals, indicating that they may share the same elementary steps and rate-determining steps and that the HBE is the dominant descriptor for HOR/HER activities. The onset potential of CO stripping on the four metals decreases with pH, indicating a stronger OH adsorption, which provides evidence against the promoting effect of adsorbed OH on HOR/HER. PMID:27034988

  17. Universal dependence of hydrogen oxidation and evolution reaction activity of platinum-group metals on pH and hydrogen binding energy

    PubMed Central

    Zheng, Jie; Sheng, Wenchao; Zhuang, Zhongbin; Xu, Bingjun; Yan, Yushan

    2016-01-01

    Understanding how pH affects the activity of hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) is key to developing active, stable, and affordable HOR/HER catalysts for hydroxide exchange membrane fuel cells and electrolyzers. A common linear correlation between hydrogen binding energy (HBE) and pH is observed for four supported platinum-group metal catalysts (Pt/C, Ir/C, Pd/C, and Rh/C) over a broad pH range (0 to 13), suggesting that the pH dependence of HBE is metal-independent. A universal correlation between exchange current density and HBE is also observed on the four metals, indicating that they may share the same elementary steps and rate-determining steps and that the HBE is the dominant descriptor for HOR/HER activities. The onset potential of CO stripping on the four metals decreases with pH, indicating a stronger OH adsorption, which provides evidence against the promoting effect of adsorbed OH on HOR/HER. PMID:27034988

  18. Removal of glycosaminoglycans from bovine granulosa cells contributes to increased binding of hydrogen-3 heparin

    SciTech Connect

    Ax, R.L.; Stodd, C.M.; Boehm, S.K.; Bellin, M.E.

    1986-02-01

    Granulosa cells from small or large bovine follicles were pretreated with enzymes that hydrolyze various glycosaminoglycans, and binding of (/sup 3/H)-heparin to the granulosa was measured. Binding of (/sup 3/H) heparin increased significantly after enzymatic pretreatments with chondroitinase ABC and fungal hyaluronidase, and similar results were obtained with granulosa from small and large follicles. No changes in binding of (/sup 3/H) heparin were detected after hydrolyses with chondroitinase AC and heparinase in either follicle size. Heparitinase, which hydrolyzes heparan sulfate, led to a significant 50% increase in binding of (/sup 3/H) heparin to granulosa from large follicles but was without effect in small follicles. These results suggest that the lower binding of (/sup 3/H) heparin, which has been reported with follicular enlargement, may be due to heparan sulfate occupying or obstructing binding sites for heparin on granulosa from large follicles.

  19. Significant Quantum Effects in Hydrogen Activation

    SciTech Connect

    Kyriakou, Georgios; Davidson, Erlend R.; Peng, Guowen; Roling, Luke T.; Singh, Suyash; Boucher, Matthew B.; Marcinkowski, Matthew D.; Mavrikakis, Manos; Michaelides, Angelos; Sykes, E. Charles H.

    2014-03-31

    Dissociation of molecular hydrogen is an important step in a wide variety of chemical, biological, and physical processes. Due to the light mass of hydrogen, it is recognized that quantum effects are often important to its reactivity. However, understanding how quantum effects impact the reactivity of hydrogen is still in its infancy. Here, we examine this issue using a well-defined Pd/Cu(111) alloy that allows the activation of hydrogen and deuterium molecules to be examined at individual Pd atom surface sites over a wide range of temperatures. Experiments comparing the uptake of hydrogen and deuterium as a function of temperature reveal completely different behavior of the two species. The rate of hydrogen activation increases at lower sample temperature, whereas deuterium activation slows as the temperature is lowered. Density functional theory simulations in which quantum nuclear effects are accounted for reveal that tunneling through the dissociation barrier is prevalent for H2 up to 190 K and for D2 up to 140 K. Kinetic Monte Carlo simulations indicate that the effective barrier to H2 dissociation is so low that hydrogen uptake on the surface is limited merely by thermodynamics, whereas the D2 dissociation process is controlled by kinetics. These data illustrate the complexity and inherent quantum nature of this ubiquitous and seemingly simple chemical process. Examining these effects in other systems with a similar range of approaches may uncover temperature regimes where quantum effects can be harnessed, yielding greater control of bond-breaking processes at surfaces and uncovering useful chemistries such as selective bond activation or isotope separation.

  20. Significant Quantum Effects in Hydrogen Activation

    PubMed Central

    2014-01-01

    Dissociation of molecular hydrogen is an important step in a wide variety of chemical, biological, and physical processes. Due to the light mass of hydrogen, it is recognized that quantum effects are often important to its reactivity. However, understanding how quantum effects impact the reactivity of hydrogen is still in its infancy. Here, we examine this issue using a well-defined Pd/Cu(111) alloy that allows the activation of hydrogen and deuterium molecules to be examined at individual Pd atom surface sites over a wide range of temperatures. Experiments comparing the uptake of hydrogen and deuterium as a function of temperature reveal completely different behavior of the two species. The rate of hydrogen activation increases at lower sample temperature, whereas deuterium activation slows as the temperature is lowered. Density functional theory simulations in which quantum nuclear effects are accounted for reveal that tunneling through the dissociation barrier is prevalent for H2 up to ∼190 K and for D2 up to ∼140 K. Kinetic Monte Carlo simulations indicate that the effective barrier to H2 dissociation is so low that hydrogen uptake on the surface is limited merely by thermodynamics, whereas the D2 dissociation process is controlled by kinetics. These data illustrate the complexity and inherent quantum nature of this ubiquitous and seemingly simple chemical process. Examining these effects in other systems with a similar range of approaches may uncover temperature regimes where quantum effects can be harnessed, yielding greater control of bond-breaking processes at surfaces and uncovering useful chemistries such as selective bond activation or isotope separation. PMID:24684530

  1. Anion Binding in Metal-Organic Frameworks Functionalized with Urea Hydrogen-Bonding Groups

    SciTech Connect

    Custelcean, Radu; Moyer, Bruce A; Bryantsev, Vyacheslav S.; Hay, Benjamin P.

    2006-01-01

    A series of metal-organic frameworks (MOFs) functionalized with urea hydrogen-bonding groups has been synthesized and structurally analyzed by single-crystal X-ray diffraction to evaluate the efficacy of anion coordination by urea within the structural constraints of the MOFs. We found that urea-based functionalities may be used for anion binding within metal-organic frameworks when the tendency for urea{hor_ellipsis}urea self-association is decreased by strengthening the intramolecular CH{hor_ellipsis}O hydrogen bonding of N-phenyl substituents to the carbonyl oxygen atom. Theoretical calculations indicate that N,N'-bis(m-pyridyl)urea (BPU) and N,N'-bis(m-cyanophenyl)urea (BCPU) should have enhanced hydrogen-bonding donor abilities toward anions and decreased tendencies to self-associate into hydrogen-bonded tapes compared to other disubstituted ureas. Accordingly, BPU and BCPU were incorporated in MOFs as linkers through coordination of various Zn, Cu, and Ag transition metal salts, including Zn(ClO{sub 4}){sub 2}, ZnSO{sub 4}, Cu(NO{sub 3}){sub 2}, Cu(CF{sub 3}SO{sub 3}){sub 2}, AgNO{sub 3}, and AgSO{sub 3}CH{sub 3}. Structural analysis by single-crystal X-ray diffraction showed that these linkers are versatile anion binders, capable of chelate hydrogen bonding to all of the oxoanions explored. Anion coordination by the urea functionalities was found to successfully compete with urea self-association in all cases except for that of charge-diffuse perchlorate.

  2. Large-scale molecular dynamics simulation: Effect of polarization on thrombin-ligand binding energy.

    PubMed

    Duan, Li L; Feng, Guo Q; Zhang, Qing G

    2016-01-01

    Molecular dynamics (MD) simulations lasting 500 ns were performed in explicit water to investigate the effect of polarization on the binding of ligands to human α-thrombin based on the standard nonpolarizable AMBER force field and the quantum-derived polarized protein-specific charge (PPC). The PPC includes the electronic polarization effect of the thrombin-ligand complex, which is absent in the standard force field. A detailed analysis and comparison of the results of the MD simulation with experimental data provided strong evidence that intra-protein, protein-ligand hydrogen bonds and the root-mean-square deviation of backbone atoms were significantly stabilized through electronic polarization. Specifically, two critical hydrogen bonds between thrombin and the ligand were broken at approximately 190 ns when AMBER force field was used and the number of intra-protein backbone hydrogen bonds was higher under PPC than under AMBER. The thrombin-ligand binding energy was computed using the molecular mechanics Poisson-Boltzmann surface area (MM/PBSA) method, and the results were consistent with the experimental value obtained using PPC. Because hydrogen bonds were unstable, it was failed to predict the binding affinity under the AMBER force field. Furthermore, the results of the present study revealed that differences in the binding free energy between AMBER and PPC almost comes from the electrostatic interaction. Thus, this study provides evidence that protein polarization is critical to accurately describe protein-ligand binding. PMID:27507430

  3. Large-scale molecular dynamics simulation: Effect of polarization on thrombin-ligand binding energy

    PubMed Central

    Duan, Li L.; Feng, Guo Q.; Zhang, Qing G.

    2016-01-01

    Molecular dynamics (MD) simulations lasting 500 ns were performed in explicit water to investigate the effect of polarization on the binding of ligands to human α-thrombin based on the standard nonpolarizable AMBER force field and the quantum-derived polarized protein-specific charge (PPC). The PPC includes the electronic polarization effect of the thrombin-ligand complex, which is absent in the standard force field. A detailed analysis and comparison of the results of the MD simulation with experimental data provided strong evidence that intra-protein, protein-ligand hydrogen bonds and the root-mean-square deviation of backbone atoms were significantly stabilized through electronic polarization. Specifically, two critical hydrogen bonds between thrombin and the ligand were broken at approximately 190 ns when AMBER force field was used and the number of intra-protein backbone hydrogen bonds was higher under PPC than under AMBER. The thrombin-ligand binding energy was computed using the molecular mechanics Poisson-Boltzmann surface area (MM/PBSA) method, and the results were consistent with the experimental value obtained using PPC. Because hydrogen bonds were unstable, it was failed to predict the binding affinity under the AMBER force field. Furthermore, the results of the present study revealed that differences in the binding free energy between AMBER and PPC almost comes from the electrostatic interaction. Thus, this study provides evidence that protein polarization is critical to accurately describe protein-ligand binding. PMID:27507430

  4. Effect of hydrogen on surface of niobium

    SciTech Connect

    Gadgil, V.J.; Keim, E.G.

    1998-12-31

    Niobium single crystals are used as substrate material for constructing superconducting quantum interference device of SQUID. The use of niobium is prompted by the fact that it is a low {Tc} metallic superconductor. In order to fabricate the device the surface of the crystal has to be polished flat. This is achieved by combination of mechanical polishing and electrochemical polishing. It has been reported that during electrochemical polishing hydrogen can enter the material forming Niobium hydrides. These can result in surface roughening of a magnitude greater than the thickness of the films subsequently deposited. This leads to failure of the films. The problem can be solved by annealing the material at 300 C to remove any hydrogen that might be present. However it is phenomenologically interesting to study the effect of electrochemical hydrogen charging on the surface of Niobium.

  5. An antibody binding site on cytochrome c defined by hydrogen exchange and two-dimensional NMR

    SciTech Connect

    Paterson, Y.; Englander, S.W.; Roder, H. )

    1990-08-17

    The interaction of a protein antigen, horse cytochrome c (cyt c), with a monoclonal antibody has been studied by hydrogen-deuterium (H-D) exchange labeling and two-dimensional nuclear magnetic resonance (2D NMR) methods. The H-exchange rate of residues in three discontiguous regions of the cyt c polypeptide backbone was slowed by factors up to 340-fold in the antibody-antigen complex compared with free cyt c. The protected residues, 36 to 38, 59, 60, 64 to 67, 100, and 101, and their hydrogen-bond acceptors, are brought together in the three-dimensional structure to form a contiguous, largely exposed protein surface with an area of about 750 square angstroms. The interaction site determined in this way is consistent with prior epitope mapping studies and includes several residues that were not previously identified. The hydrogen exchange labeling approach can be used to map binding sites on small proteins in antibody-antigen complexes and may be applicable to protein-protein and protein-ligand interactions in general.

  6. Investigation of Laser Peening Effects on Hydrogen Charged Stainless Steels

    SciTech Connect

    Zaleski, Tania M.

    2008-10-30

    Hydrogen-rich environments such as fuel cell reactors can exhibit damage caused by hydrogen permeation in the form of corrosion cracking by lowering tensile strength and decreasing material ductility. Coatings and liners have been investigated, but there were few shot-peening or laser peening studies referenced in the literature with respect to preventing hydrogen embrittlement. The surface compressive residual stress induced by laser peening had shown success in preventing stress corrosion cracking (SCC) for stainless steels in power plants. The question arose if the residual stresses induced by laser peening could delay the effects of hydrogen in a material. This study investigated the effect of laser peening on hydrogen penetration into metal alloys. Three areas were studied: laser peening, hydrogenation, and hydrogen detection. This study demonstrated that laser peening does not reduce the hydrogen permeation into a stainless steel surface nor does it prevent hydrogen embrittlement. The effect of laser peening to reduce hydrogen-assisted fatigue was unclear.

  7. Effects of contamination on radioligand binding parameters.

    PubMed

    Lazareno, S; Birdsall, N J

    2000-02-01

    Radioligand binding studies are used to provide quantitative estimates of parameters such as the receptor density of a tissue and the affinity values of labelled and unlabelled ligands. The presence of an unlabelled competing contaminant, which might be present because of actual contamination, inadequate radioligand purification or the breakdown of the radioligand to an active species, has surprising effects on these estimates: the apparent affinity of the radioligand is increased but the Ki values of unlabelled ligands are unaffected. The most striking and sensitive effects are on radioligand association kinetics, which become independent of radioligand concentration at high radioligand concentrations. PMID:10664609

  8. Insight into hydrogenation of graphene: Effect of hydrogen plasma chemistry

    SciTech Connect

    Felten, A.; Nittler, L.; Pireaux, J.-J.; McManus, D.; Rice, C.; Casiraghi, C.

    2014-11-03

    Plasma hydrogenation of graphene has been proposed as a tool to modify the properties of graphene. However, hydrogen plasma is a complex system and controlled hydrogenation of graphene suffers from a lack of understanding of the plasma chemistry. Here, we correlate the modifications induced on monolayer graphene studied by Raman spectroscopy with the hydrogen ions energy distributions obtained by mass spectrometry. We measure the energy distribution of H{sup +}, H{sub 2}{sup +}, and H{sub 3}{sup +} ions for different plasma conditions showing that their energy strongly depends on the sample position, pressure, and plasma power and can reach values as high as 45 eV. Based on these measurements, we speculate that under specific plasma parameters, protons should possess enough energy to penetrate the graphene sheet. Therefore, a graphene membrane could become, under certain conditions, transparent to both protons and electrons.

  9. Hydrogen Bound Complexes with Tropolone: Binding Motifs, Barrier Heights, and the Search for Bifurcating Systems

    NASA Astrophysics Data System (ADS)

    Nemchick, Deacon; Chew, Kathryn; Vaccaro, Patrick

    2014-06-01

    The potentially frustrated transfer of a proton between the hydroxylic (proton-donating) and ketonic (proton-accepting) oxygen atom centers in tropolone (TrOH) long has served as a model system for the study of coherent (symmetrical) proton-transfer events. A litany of hydrogen-bound complexes [TrOH \\cdot Xn] can be formed in situ by docking amphoteric ligands onto the TrOH substrate under supersonic free-jet expansion conditions. Binary (n = 1) and higher order (n = 2, 3, ldots) complexes formed with formic acid, hydrogen fluoride, acetic acid and propiolic acid (X = FA, HF, AA, and PA) have been synthesized and interrogated using a variety of spectroscopic probes built upon the intense ˜{A1}B2-˜{X1}{A}1 (π *←π) near-ultraviolet absorption system of bare tropolone, thereby providing vibronically resolved information through combined use of laser-induced fluorescence (LIF), dispersed fluorescence (DF), fluorescence hole-burning (FHB), and stimulated emission pumping (SEP) methods. Experimental results reveal the propensity for binary complexes to adopt a higher-energy external binding motif (ligand attached to the seven membered aromatic ring) over the energetically preferred internal form (ligand bound to the O-H\\cdotsO reaction center), where the latter cleft-bound species can undergo unique symmetric (coherent) double proton-transfer reactions. These findings will be discussed in light of supporting quantum-chemical calculations.

  10. New hydrogen-bond potentials for use in determining energetically favorable binding sites on molecules of known structure.

    PubMed

    Boobbyer, D N; Goodford, P J; McWhinnie, P M; Wade, R C

    1989-05-01

    An empirical energy function designed to calculate the interaction energy of a chemical probe group, such as a carbonyl oxygen or an amine nitrogen atom, with a target molecule has been developed. This function is used to determine the sites where ligands, such as drugs, may bind to a chosen target molecule which may be a protein, a nucleic acid, a polysaccharide, or a small organic molecule. The energy function is composed of a Lennard-Jones, an electrostatic and a hydrogen-bonding term. The latter is dependent on the length and orientation of the hydrogen bond and also on the chemical nature of the hydrogen-bonding atoms. These terms have been formulated by fitting to experimental observations of hydrogen bonds in crystal structures. In the calculations, thermal motion of the hydrogen-bonding hydrogen atoms and lone-pair electrons may be taken into account. For example, in a alcoholic hydroxyl group, the hydrogen may rotate around the C-O bond at the observed tetrahedral angle. In a histidine residue, a hydrogen atom may be bonded to either of the two imidazole nitrogens and movement of this hydrogen will cause a redistribution of charge which is dependent on the nature of the probe group and the surrounding environment. The shape of some of the energy functions is demonstrated on molecules of pharmacological interest. PMID:2709375

  11. Lipin 2 binds phosphatidic acid by the electrostatic hydrogen bond switch mechanism independent of phosphorylation.

    PubMed

    Eaton, James M; Takkellapati, Sankeerth; Lawrence, Robert T; McQueeney, Kelley E; Boroda, Salome; Mullins, Garrett R; Sherwood, Samantha G; Finck, Brian N; Villén, Judit; Harris, Thurl E

    2014-06-27

    Lipin 2 is a phosphatidic acid phosphatase (PAP) responsible for the penultimate step of triglyceride synthesis and dephosphorylation of phosphatidic acid (PA) to generate diacylglycerol. The lipin family of PA phosphatases is composed of lipins 1-3, which are members of the conserved haloacid dehalogenase superfamily. Although genetic alteration of LPIN2 in humans is known to cause Majeed syndrome, little is known about the biochemical regulation of its PAP activity. Here, in an attempt to gain a better general understanding of the biochemical nature of lipin 2, we have performed kinetic and phosphorylation analyses. We provide evidence that lipin 2, like lipin 1, binds PA via the electrostatic hydrogen bond switch mechanism but has a lower rate of catalysis. Like lipin 1, lipin 2 is highly phosphorylated, and we identified 15 phosphosites. However, unlike lipin 1, the phosphorylation of lipin 2 is not induced by insulin signaling nor is it sensitive to inhibition of the mammalian target of rapamycin. Importantly, phosphorylation of lipin 2 does not negatively regulate either membrane binding or PAP activity. This suggests that lipin 2 functions as a constitutively active PA phosphatase in stark contrast to the high degree of phosphorylation-mediated regulation of lipin 1. This knowledge of lipin 2 regulation is important for a deeper understanding of how the lipin family functions with respect to lipid synthesis and, more generally, as an example of how the membrane environment around PA can influence its effector proteins. PMID:24811178

  12. Lipin 2 Binds Phosphatidic Acid by the Electrostatic Hydrogen Bond Switch Mechanism Independent of Phosphorylation*

    PubMed Central

    Eaton, James M.; Takkellapati, Sankeerth; Lawrence, Robert T.; McQueeney, Kelley E.; Boroda, Salome; Mullins, Garrett R.; Sherwood, Samantha G.; Finck, Brian N.; Villén, Judit; Harris, Thurl E.

    2014-01-01

    Lipin 2 is a phosphatidic acid phosphatase (PAP) responsible for the penultimate step of triglyceride synthesis and dephosphorylation of phosphatidic acid (PA) to generate diacylglycerol. The lipin family of PA phosphatases is composed of lipins 1–3, which are members of the conserved haloacid dehalogenase superfamily. Although genetic alteration of LPIN2 in humans is known to cause Majeed syndrome, little is known about the biochemical regulation of its PAP activity. Here, in an attempt to gain a better general understanding of the biochemical nature of lipin 2, we have performed kinetic and phosphorylation analyses. We provide evidence that lipin 2, like lipin 1, binds PA via the electrostatic hydrogen bond switch mechanism but has a lower rate of catalysis. Like lipin 1, lipin 2 is highly phosphorylated, and we identified 15 phosphosites. However, unlike lipin 1, the phosphorylation of lipin 2 is not induced by insulin signaling nor is it sensitive to inhibition of the mammalian target of rapamycin. Importantly, phosphorylation of lipin 2 does not negatively regulate either membrane binding or PAP activity. This suggests that lipin 2 functions as a constitutively active PA phosphatase in stark contrast to the high degree of phosphorylation-mediated regulation of lipin 1. This knowledge of lipin 2 regulation is important for a deeper understanding of how the lipin family functions with respect to lipid synthesis and, more generally, as an example of how the membrane environment around PA can influence its effector proteins. PMID:24811178

  13. Competitive Halide Binding by Halogen Versus Hydrogen Bonding: Bis-triazole Pyridinium.

    PubMed

    Nepal, Binod; Scheiner, Steve

    2015-09-14

    The binding of F(-) , Cl(-) , Br(-) , and I(-) anions by bis-triazole-pyridine (BTP) was examined by quantum chemical calculations. There is one H atom on each of the two triazole rings that chelate the halide via H bonds. These H atoms were replaced by halogens Cl, Br, and I, thus substituting H bonds by halogen bonds. I substitution strongly enhances the binding; Br has a smaller effect, and Cl weakens the interaction. The strength of the interaction is sensitive to the overall charge on the BTP, rising as the binding agent becomes singly and then doubly positively charged. The strongest preference of a halide for halogenated as compared to unsubstituted BTP, as much as several orders of magnitude, is observed for I(-) . Both unsubstituted and I-substituted BTP could be used to selectively extract F(-) from a mixture of halides. PMID:26234647

  14. Hydrogen cyanide health effects. Final report

    SciTech Connect

    Carson, B.L.; Baker, L.H.; Herndon, B.L.; Ellis, H.V. III; Horn, E.M.

    1981-09-01

    Health effects literature primarily related to inhalation exposures to hydrogen cyanide was collected, evaluated, tabulated and summarized. Approximately 170 documents were collected from computerized and manual literature searches covering the period 1899-1981. Pharmacologists and an M.D. epidemiologist rated the documents according to their applicability to the study and their methodology. The approximately 20 documents considered useful for deriving a range of concern for human exposure to hydrogen cyanide from automotive emissions were tabulated. The 25 pages of tables detail the results of acute and repeated dose testing of mice, rats, guinea pigs, rabbits, cats, monkeys, dogs, goats, donkeys and humans as well as human occupational studies. Most of the documents evaluated are described in an annotated bibliography.

  15. Isotope effects of hydrogen and atom tunnelling

    NASA Astrophysics Data System (ADS)

    Buchachenko, A. L.; Pliss, E. M.

    2016-06-01

    The abnormally high mass-dependent isotope effects in liquid-phase hydrogen (deuterium) atom transfer reactions, which are customarily regarded as quantum effects, are actually the products of two classical effects, namely, kinetic and thermodynamic ones. The former is determined by the rate constants for atom transfer and the latter is caused by nonbonded (or noncovalent) isotope effects in the solvation of protiated and deuterated reacting molecules. This product can mimic the large isotope effects that are usually attributed to tunnelling. In enzymatic reactions, tunnelling is of particular interest; its existence characterizes an enzyme as a rigid molecular machine in which the residence time of reactants on the reaction coordinate exceeds the waiting time for the tunnelling event. The magnitude of isotope effect becomes a characteristic parameter of the internal dynamics of the enzyme catalytic site. The bibliography includes 61 references.

  16. Effects Of Aging On Embrittlement By Hydrogen

    NASA Technical Reports Server (NTRS)

    Lassila, D. H.; Birnbaum, H. K.

    1989-01-01

    Report discusses study of grain-boundary fracture of hydrogen-charged nickel under conditions in which hydrogen is immobile. Thermally-charged nickel specimens aged at several temperatures for various periods of time to allow hydrogen to diffuse. Specimens then quenched and tested in liquid nitrogen (at temperature of 77 K) so distribution of hydrogen produced by aging maintained.

  17. Radiative transfer effects in primordial hydrogen recombination

    SciTech Connect

    Ali-Haiemoud, Yacine; Hirata, Christopher M.; Grin, Daniel

    2010-12-15

    The calculation of a highly accurate cosmological recombination history has been the object of particular attention recently, as it constitutes the major theoretical uncertainty when predicting the angular power spectrum of cosmic microwave background anisotropies. Lyman transitions, in particular the Lyman-{alpha} line, have long been recognized as one of the bottlenecks of recombination, due to their very low escape probabilities. The Sobolev approximation does not describe radiative transfer in the vicinity of Lyman lines to a sufficient degree of accuracy, and several corrections have already been computed in other works. In this paper, we compute the impact of some radiative transfer effects that were previously ignored, or for which previous treatments were incomplete. First, the effect of Thomson scattering in the vicinity of the Lyman-{alpha} line is evaluated, using a full redistribution kernel incorporated into a radiative transfer code. The effect of feedback of distortions generated by the optically thick deuterium Lyman-{alpha} line blueward of the hydrogen line is investigated with an analytic approximation. It is shown that both effects are negligible during cosmological hydrogen recombination. Second, the importance of high-lying, nonoverlapping Lyman transitions is assessed. It is shown that escape from lines above Ly{gamma} and frequency diffusion in Ly{beta} and higher lines can be neglected without loss of accuracy. Third, a formalism generalizing the Sobolev approximation is developed to account for the overlap of the high-lying Lyman lines, which is shown to lead to negligible changes to the recombination history. Finally, the possibility of a cosmological hydrogen recombination maser is investigated. It is shown that there is no such maser in the purely radiative treatment presented here.

  18. Hydride-induced amplification of performance and binding enthalpies in chromium hydrazide gels for Kubas-type hydrogen storage.

    PubMed

    Hamaed, Ahmad; Hoang, Tuan K A; Moula, Golam; Aroca, Ricardo; Trudeau, Michel L; Antonelli, David M

    2011-10-01

    Hydrogen is the ideal fuel because it contains the most energy per gram of any chemical substance and forms water as the only byproduct of consumption. However, storage still remains a formidable challenge because of the thermodynamic and kinetic issues encountered when binding hydrogen to a carrier. In this study, we demonstrate how the principal binding sites in a new class of hydrogen storage materials based on the Kubas interaction can be tuned by variation of the coordination sphere about the metal to dramatically increase the binding enthalpies and performance, while also avoiding the shortcomings of hydrides and physisorpion materials, which have dominated most research to date. This was accomplished through hydrogenation of chromium alkyl hydrazide gels, synthesized from bis(trimethylsilylmethyl) chromium and hydrazine, to form materials with low-coordinate Cr hydride centers as the principal H(2) binding sites, thus exploiting the fact that metal hydrides form stronger Kubas interactions than the corresponding metal alkyls. This led to up to a 6-fold increase in storage capacity at room temperature. The material with the highest capacity has an excess reversible storage of 3.23 wt % at 298 K and 170 bar without saturation, corresponding to 40.8 kg H(2)/m(3), comparable to the 2015 DOE system goal for volumetric density (40 kg/m(3)) at a safe operating pressure. These materials possess linear isotherms and enthalpies that rise on coverage, retain up to 100% of their adsorption capacities on warming from 77 to 298 K, and have no kinetic barrier to adsorption or desorption. In a practical system, these materials would use pressure instead of temperature as a toggle and can thus be used in compressed gas tanks, currently employed in the majority of hydrogen test vehicles, to dramatically increase the amount of hydrogen stored, and therefore range of any vehicle. PMID:21863869

  19. Effect of hydrogenation on interaction force among carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Fallah, Ahmadreza; Nakayama, Yoshikazu

    2013-04-01

    Hydrogenation of carbon nanotubes (CNTs) was achieved with flowing hydrogen gas and heating CNTs up to 800 °C. Electron microcopy images show the etching effect of the hydrogen as well as the appearance of defects after hydrogenation. Infrared spectroscopy confirmed the presence of CHx groups on the sidewalls of the functionalized CNTs. Raman spectra of the pristine and hydrogenated samples revealed a transition from graphitic to a disordered and defected structure by increasing the hydrogenation time. We measured the interaction force among CNTs in the pristine and hydrogenated samples. Results showed that the interaction force is reduced sharply upon hydrogenation. After examination of the relation between different experimentally obtained results and the interaction force trend, we discuss how hydrogenation affects the interaction force among CNTs by increasing roughness and formation of repulsive dipoles on the CNT surface.

  20. Binding energy of the ground and first few excited states of hydrogenic donor impurity in a rectangular GaAs quantum dot in the presence of electric field

    NASA Astrophysics Data System (ADS)

    Wang, Sheng; Kang, Yun; Li, Xian-Li

    2014-12-01

    Within the quasi-one-dimensional effective potential model and effective mass approximation, we calculate the ground and the first 9 excited-state binding energies of a hydrogenic donor impurity in a rectangular quantum dot (RQD) in the presence of electric field. The analytical form of the quasi-one-dimensional effective potential replacing the three-dimensional Coulomb potential in our model is derived by Fourier transforms. We discuss detailedly dependence of the binding energies on the impurity positions and electric fields. For the ground-state binding energy, our results qualitatively agree with that of Mendoza et al. (2005) in which they only calculated the ground-state binding energies in cubic quantum dots by variational method. However, for first 9 excited-state binding energies, such dependence has complex manner since there are two or three peaks in the electronic probability density distribution curves. The strengths and positions of these peaks in RQD affect the interaction potential between electron and impurity, which appears to be the critical control on the binding energies of impurity. The applied electric field pushes the positions of these peaks downwards, and the strengths of peaks located at the upper half of RQD increase while the strengths of lower peaks firstly decrease, then increase with increasing electric field. The high peak strength can lead to increase of the binding energy while the large distance between the position of peak and impurity center results in reduce of the energy, which is an interesting competition. This competition is more obvious for excited-state binding energies of off-central impurity.

  1. Label-Free, In-Solution Screening of Peptide Libraries for Binding to Protein Targets Using Hydrogen Exchange Mass Spectrometry.

    PubMed

    Maaty, Walid S; Weis, David D

    2016-02-01

    There is considerable interest in the discovery of peptide ligands that bind to protein targets. Discovery of such ligands is usually approached by screening large peptide libraries. However, the individual peptides must be tethered to a tag that preserves their individual identities (e.g., phage display or one-bead one-compound). To overcome this limitation, we have developed a method for screening libraries of label-free peptides for binding to a protein target in solution as a single batch. The screening is based on decreased amide hydrogen exchange by peptides that bind to the target. Hydrogen exchange is measured by mass spectrometry. We demonstrate the approach using a peptide library derived from the Escherichia coli proteome that contained 6664 identifiable features. The library was spiked separately with a peptide spanning the calmodulin binding domain of endothelial nitric oxide synthase (eNOS, 494-513) and a peptide spanning the N-terminal 20 residues of bovine ribonuclease A (S peptide). Human calmodulin and bovine ribonuclease S (RNase S) were screened against the library. Using a novel data analysis workflow, we identified the eNOS peptide as the only calmodulin binding peptide and S peptide as the only ribonuclease S binding peptide in the library. PMID:26741284

  2. Effects of hydrogen surface processes on hydrogen retention in plasma facing components

    NASA Astrophysics Data System (ADS)

    Guterl, Jerome; Smirnov, Roman; Krasheninnikov, Sergei

    2014-10-01

    Hydrogen retention and recycling on metallic plasma-facing components (PFCs) are among the key-issues for future fusion devices due to both safety and operational reasons. For tungsten, which has been chosen as divertor material in ITER, parameters of hydrogen desorption from Wsurfaces, experimentally measured for fusion-related conditions, show a large discrepancy. Indeed, various complex phenomena may affect hydrogen desorption (e.g atomic islands, roughness, surface reconstruction, impurities, ect). In this work, we investigate effects of hydrogen desorption from W surfaces on hydrogen retention in W material. Two regimes of hydrogen surface desorption (readsorption-limited and recombination-limited) can be identified and may affect the kinetic order of desorption. Within these desorption regimes, it is shown that release of hydrogen from W material in fusion-related conditions may be surface-limited at low temperature and diffusion-limited at high temperature. Analyses of hydrogen release regimes for thermodesorption experiments and plasma operations in fusion reactors show that surface processes may strongly affect retention and release of hydrogen from W material. In this context, effects of W surface coverage with oxygen on hydrogen desorption are discussed since high concentrations of oxygen on PFCs surfaces are expected in future fusion devices. This work is performed under the auspices of USDOE Grant No. DE-FG02-04ER54739 and the PSI Science Center Grant DE-SC0001999 at UCSD.

  3. Effects of high pressure hydrogen on metals

    NASA Technical Reports Server (NTRS)

    Chandler, W. T.; Walter, R. J.

    1970-01-01

    Hydrogen environment embrittlement causes failure of hydrogen storage vessels at and below design pressures of 5000 to 6000 psi. Investigation of thirty-five alloys determines their susceptibility to such embrittlement.

  4. Analysis of hydrogen adsorption and surface binding configuration on tungsten using direct recoil spectrometry

    SciTech Connect

    Kolasinski, R. D.; Hammond, K. D.; Whaley, J. A.; Buchenauer, D. A.; Wirth, B. D.

    2014-12-03

    In our work, we apply low energy ion beam analysis to examine directly how the adsorbed hydrogen concentration and binding configuration on W(1 0 0) depend on temperature. We exposed the tungsten surface to fluxes of both atomic and molecular H and D. We then probed the H isotopes adsorbed along different crystal directions using 1–2 keV Ne+ ions. At saturation coverage, H occupies two-fold bridge sites on W(1 0 0) at 25 °C. Moreover, the H coverage dramatically changes the behavior of channeled ions, as does reconstruction of the surface W atoms. For the exposure conditions examined here, we find that surface sites remain populated with H until the surface temperature reaches 200 °C. Then, we observe H rapidly desorbing until only a residual concentration remains at 450 °C. Development of an efficient atomistic model that accurately reproduces the experimental ion energy spectra and azimuthal variation of recoiled H is underway.

  5. Analysis of hydrogen adsorption and surface binding configuration on tungsten using direct recoil spectrometry

    DOE PAGESBeta

    Kolasinski, R. D.; Hammond, K. D.; Whaley, J. A.; Buchenauer, D. A.; Wirth, B. D.

    2014-12-03

    In our work, we apply low energy ion beam analysis to examine directly how the adsorbed hydrogen concentration and binding configuration on W(1 0 0) depend on temperature. We exposed the tungsten surface to fluxes of both atomic and molecular H and D. We then probed the H isotopes adsorbed along different crystal directions using 1–2 keV Ne+ ions. At saturation coverage, H occupies two-fold bridge sites on W(1 0 0) at 25 °C. Moreover, the H coverage dramatically changes the behavior of channeled ions, as does reconstruction of the surface W atoms. For the exposure conditions examined here, wemore » find that surface sites remain populated with H until the surface temperature reaches 200 °C. Then, we observe H rapidly desorbing until only a residual concentration remains at 450 °C. Development of an efficient atomistic model that accurately reproduces the experimental ion energy spectra and azimuthal variation of recoiled H is underway.« less

  6. Trap effect of vacancy on hydrogen diffusivity in bcc-Fe

    NASA Astrophysics Data System (ADS)

    Zhu, Deqiong; Oda, Takuji

    2016-02-01

    Evaluation of tritium effective diffusivity in structural materials with defects is essential to appropriately estimate the accumulation and leakage of tritium in fusion reactors. In the present work, we focus on the trap effect of vacancy on the diffusivity of hydrogen in bcc-Fe. The hydrogen effective diffusivities in different bcc-Fe systems with varied hydrogen/vacancy ratios (H/V ratios) are evaluated by using molecular statics (MS) and molecular dynamics (MD) simulations, and are compared with that in the system without vacancy. The hydrogen effective diffusivity is obviously decreased due to the vacancy trap effect. The trap effect is more profound in small H/V-ratio systems due to the dependence of V-H binding energy on the number of trapped H atoms. The trapped H atoms hardly contribute to hydrogen diffusivity because of the difficulty in detrapping and small mobility of V-H complex. This fact results in a good correlation between the effective diffusivity of hydrogen and the fraction of H atoms solute in the bulk without being trapped by vacancy.

  7. Lattice strain effects in graphane and partially-hydrogenated graphene sheets

    SciTech Connect

    Morris, James R; Averill, Frank; He, Dr. Haiyan; Pan, Dr. Bicai; Cooper, Valentino R; Peng, L.

    2010-01-01

    This paper presents a brief review of recent developments in the studies of fully hydrogenated graphene sheets, also known as graphane, and related initial results on partially hydrogenated structures. For the fully hydrogenated case, some important discrepancies, specifically whether or not the graphene sheet expands or contracts upon hydrogenation, exist between published first-principles calculations, and between calculations and experiment. The lattice change has important effects on partially hydrogenated structures. In addition, calculations of the interfacial energy must carefully account for the strain energy in neighboring regions: For sufficiently large regions between interfaces, defects at the interface which relieve the strain may be energetically preferable. Our preliminary first-principles calculations of ribbon structures, with interfaces between graphane and graphene regions, indicate that the interfaces do indeed have substantial misfit strains. Similarly, our tight-binding simulations show that at ambient temperatures, segments of graphene sheets may spontaneously combine with atomic hydrogen to form regions of graphane. Here, small amounts of chemisorbed hydrogen distort the graphene layer, due to the lattice misfit, and may induce the adsorption of more hydrogen atoms.

  8. Hydrogen-tritium exchange survey of allosteric effects in hemoglobin

    SciTech Connect

    Englander, J.J.; Englander, S.W.

    1987-04-07

    The oxy and deoxy forms of hemoglobin display major differences in H-exchange behavior. Hydrogen-tritium exchange experiments on hemoglobin were performed in the low-resolution mode to observe the dependence of these differences on pH (Bohr effect), organic phosphates, and salt. Unlike a prior report, increasing pH was found to decrease the oxy-deoxy difference monotonically, in general accordance with the alkaline Bohr effect. A prior report that the H-exchange difference between oxy- and deoxyhemoglobin vanishes at pH 9, and thus appears to reflect the Bohr effect alone, was found to be due to the borate buffer used, which at high pH tends to abolish the oxy-deoxy difference in a limited region of the H-exchange curve. Effects on hemoglobin H exchange due to organic phosphates parallel the differential binding of these agents (inositol hexaphosphate more than diphosphoglycerate, deoxy more than oxy, at low pH more than at high pH). Added salt slows H exchange of deoxyhemoglobin and has no effect on the oxy form. These results display the sensitivity of simple H-exchange measurements for finding and characterizing effects on structure and dynamics that may occur anywhere in the protein and help to define conditions for higher resolution approaches that can localize the changes observed.

  9. Elucidation of Nonadditive Effects in Protein-Ligand Binding Energies: Thrombin as a Case Study.

    PubMed

    Calabrò, Gaetano; Woods, Christopher J; Powlesland, Francis; Mey, Antonia S J S; Mulholland, Adrian J; Michel, Julien

    2016-06-23

    Accurate predictions of free energies of binding of ligands to proteins are challenging partly because of the nonadditivity of protein-ligand interactions; i.e., the free energy of binding is the sum of numerous enthalpic and entropic contributions that cannot be separated into functional group contributions. In principle, molecular simulations methodologies that compute free energies of binding do capture nonadditivity of protein-ligand interactions, but efficient protocols are necessary to compute well-converged free energies of binding that clearly resolve nonadditive effects. To this end, an efficient GPU-accelerated implementation of alchemical free energy calculations has been developed and applied to two congeneric series of ligands of the enzyme thrombin. The results show that accurate binding affinities are computed across the two congeneric series and positive coupling between nonpolar R(1) substituents and a X = NH3(+) substituent is reproduced, albeit with a weaker trend than experimentally observed. By contrast, a docking methodology completely fails to capture nonadditive effects. Further analysis shows that the nonadditive effects are partly due to variations in the strength of a hydrogen-bond between the X = NH3(+) ligands family and thrombin residue Gly216. However, other partially compensating interactions occur across the entire binding site, and no single interaction dictates the magnitude of the nonadditive effects for all the analyzed protein-ligand complexes. PMID:27248478

  10. Effects of Internal and External Hydrogen on Inconel 718

    NASA Technical Reports Server (NTRS)

    Walter, R. J.; Frandsen, J. D.

    1999-01-01

    Internal hydrogen embrittlement (IHE) and hydrogen environment embrittlement (HEE) tensile and bend crack growth tests were performed on Inconel 718. For the IHE tests, the specimens were precharged to approximately 90 ppm hydrogen by exposure to 34.5 MPa H2 at 650 C. The HEE tests were performed in 34.5 MPa H2. Parameters evaluated were test temperature, strain rate for smooth and notch specimen geometries. The strain rate effect was very significant at ambient temperature for both IHE and HEE and decreased with increasing temperatures. For IHE, the strain rate effect was neglible at 260'C, and for HEE the strain rate effect was neglible at 400 C. At low temperatures, IHE was more severe than HEE, and at high temperatures HEE was more severe than IHE with a cross over temperature about 350 C. At 350 C, the equilibrium hydrogen concentration in Inconel 718 is about 50% lower than the hydrogen content of the precharged IHE specimens. Dislocation hydrogen sweeping of surface absorbed hydrogen was the likely transport mechanism for increasing the hydrogen concentration in the HEE tests sufficiently to produce the same degree of embrittlement as that of the more highly hydrogen charged IHE specimens. The main IHE fracture characteristic was formation of large, brittle flat facets, which decreased with increasing test temperature. The IHE fracture matrix surrounding the large facets ranged between brittle fine faceted to microvoid ductility depending upon strain rate, specimen geometry as well as temperature. The HEE fractures were characteristically fine featured, transgranular and brittle with a significant portion forming a "saw tooth" crystallographic pattern. Both IHE and HEE fractures were predominantly along the {1 1 1) slip and twin boundaries. With respect to embrittlement mechanism, it was postulated that dislocation hydrogen sweeping and hydrogen enhanced localized plasticity were active in HEE and IHE for concentrating hydrogen along (1 1 1) slip and twin

  11. Negligible Isotopic Effect on Dissociation of Hydrogen Bonds.

    PubMed

    Ge, Chuanqi; Shen, Yuneng; Deng, Gang-Hua; Tian, Yuhuan; Yu, Dongqi; Yang, Xueming; Yuan, Kaijun; Zheng, Junrong

    2016-03-31

    Isotopic effects on the formation and dissociation kinetics of hydrogen bonds are studied in real time with ultrafast chemical exchange spectroscopy. The dissociation time of hydrogen bond between phenol-OH and p-xylene (or mesitylene) is found to be identical to that between phenol-OD and p-xylene (or mesitylene) in the same solvents. The experimental results demonstrate that the isotope substitution (D for H) has negligible effects on the hydrogen bond kinetics. DFT calculations show that the isotope substitution does not significantly change the frequencies of vibrational modes that may be along the hydrogen bond formation and dissociation coordinate. The zero point energy differences of these modes between hydrogen bonds with OH and OD are too small to affect the activation energy of the hydrogen bond dissociation in a detectible way at room temperature. PMID:26967376

  12. Hydrogen in vanadium: Site occupancy and isotope effects

    NASA Astrophysics Data System (ADS)

    Xin, Xiao; Johansson, Robert; Wolff, Max; Hjörvarsson, Björgvin

    2016-04-01

    We discuss the influence of site occupancy on the absorption of the hydrogen isotopes H and D in thin V(001) layers. By growing V(001) under biaxial compressive strain in Fe/V(001) superlattices, the hydrogen (H as well as D) is forced to reside exclusively in octahedral (Oz) sites, even at the lowest concentrations. A weakening of the isotope effects is observed when hydrogen resides in octahedral as compared to tetrahedral sites.

  13. Effect of water on hydrogen permeability

    NASA Technical Reports Server (NTRS)

    Hulligan, David; Tomazic, William A.

    1987-01-01

    Doping of hydrogen with CO and CO2 was developed to reduce hydrogen permeation in Stirling engines by forming a low permeability oxide coating on the inner surface of the heater head tubes. Although doping worked well, under certain circumstances the protective oxide could be chemically reduced by the hydrogen in the engine. Some oxygen is required in the hydrogen to prevent reduction. Eventually, all the oxygen in the hydrogen gas - whatever its source - shows up as water. This is the result of hydrogen reducing the CO, CO2, or the protective inner surface oxides. This water can condense in the engine system under the right conditions. If the concentration of water vapor is reduced to a low enough level, the hydrogen can chemically reduce the oxide coating, resulting in an increase in permeability. This work was done to define the minimum water content required to avoid this reduction in the oxide coating. The results of this testing show that a minimum of approximately 750 ppm water is required to prevent an increase in permeability of CG-27, a high temperature metal alloy selected for Stirling engine heater tubes.

  14. Effects of heparin on insulin binding and biological activity

    SciTech Connect

    Kriauciunas, K.M.; Grigorescu, F.; Kahn, C.R.

    1987-02-01

    The effect of heparin, a polyanionic glycosaminoglycan known to alter the function of many proteins, on insulin binding and bioactivity was studied. Cultured human lymphocytes (IM-9) were incubated with varying concentrations of heparin, then extensively washed, and /sup 125/I-labeled insulin binding was measured. Heparin at concentrations used clinically for anticoagulation (1-50 U/ml) inhibited binding in a dose-dependent manner; 50% inhibition of binding occurred with 5-10 U/ml. Scatchard analysis indicated that the decrease in binding was due to a decrease in both the affinity and the apparent number of available insulin receptors. The effect occurred within 10 min at 22 degrees C and persisted even after the cells were extensively washed. Inhibition of insulin binding also occurred when cells were preincubated with heparinized plasma or heparinized serum but not when cells were incubated with normal serum or plasma from blood anticoagulated with EDTA. By contrast, other polyanions and polycations, e.g., poly-L-glutamic acid, poly-L-lysine, succinylated poly-L-lysine, and histone, did not inhibit binding. Heparin also inhibited insulin binding in Epstein-Barr (EB) virus-transformed lymphocytes but had no effect on insulin binding to isolated adipocytes, human erythrocytes, or intact hepatoma cells. When isolated adipocytes were incubated with heparin, there was a dose-dependent inhibition of insulin-stimulated glucose oxidation and, to a lesser extent, of basal glucose oxidation. Although heparin has no effect on insulin binding to intact hepatoma cells, heparin inhibited both insulin binding and insulin-stimulated autophosphorylation in receptors solubilized from these cells.

  15. Production and Physiological Effects of Hydrogen Sulfide

    PubMed Central

    2014-01-01

    Abstract Significance: Hydrogen sulfide (H2S) has been recognized as a physiological mediator with a variety of functions. It regulates synaptic transmission, vascular tone, inflammation, transcription, and angiogenesis; protects cells from oxidative stress and ischemia-reperfusion injury; and promotes healing of ulcers. Recent Advances: In addition to cystathionine β-synthase and cystathionine γ-lyase, 3-mercaptopyruvate sulfurtransferase along with cysteine aminotransferase was recently demonstrated to produce H2S. Even in bacteria, H2S produced by these enzymes functions as a defense against antibiotics, suggesting that the cytoprotective effect of H2S is a universal defense mechanism in organisms from bacteria to mammals. Critical Issues: The functional form of H2S—undissociated H2S gas, dissociated HS ion, or some other form of sulfur—has not been identified. Future Directions: The regulation of H2S production by three enzymes may lead to the identification of the physiological signals that are required to release H2S. The identification of the physiological functions of other forms of sulfur may also help understand the biological significance of H2S. Antioxid. Redox Signal. 20, 783–793. PMID:23581969

  16. Effect of dietary turmeric on breath hydrogen.

    PubMed

    Shimouchi, Akito; Nose, Kazutoshi; Takaoka, Motoko; Hayashi, Hiroko; Kondo, Takaharu

    2009-08-01

    Turmeric is widely used in Indian cuisine. The main constituents of turmeric are curcumin and its analogues, which are well-known antioxidant compounds. In the present study, we hypothesized that turmeric in curry might increase bowel motility and activate hydrogen-producing bacterial flora in the colon, thereby increasing the concentration of breath hydrogen. Eight healthy subjects fasted for 12 h and ingested curry and rice with or without turmeric (turmeric knockout curry). Breath-hydrogen concentrations were analyzed every 15 min for 6 h by gas chromatography with a semiconductor detector. Curry with turmeric significantly increased the area under the curve of breath hydrogen and shortened small-bowel transit time, compared with curry not containing turmeric. These results suggested that dietary turmeric activated bowel motility and carbohydrate colonic fermentation. PMID:19034660

  17. Intense laser field and conduction band-edge nonparabolicity effects on hydrogenic impurity states of InGaN QW

    NASA Astrophysics Data System (ADS)

    El Ghazi, Haddou

    2015-09-01

    In this paper, hydrogenic impurity ground-state binding energy in unstrained wurtzite (In, Ga)N symmetric quantum well is investigated. The heterostructure is considered under the action of an intense laser field (ILF) incorporating an additional internal probe as well as the conduction band-edge nonparabolicity effect (CBENP). The variational approach is used within the framework of single band effective-mass approximation with two-parametric 1S-hydrogenic trial wavefunction. The competition effect between internal and external perturbations is also shown. Our results reveal that the binding energy is the largest for the well width around the effective Bohr radius and is strongly influenced by both parameters. Moreover, the principle effect of ILF (CBENP) is to reduce (enhance) the binding energy. It is found that the lift of the conduction band-edge can be easily eliminated by adjusting the ILF-parameter.

  18. Ionic Hydrogen Bonds and Lipid Packing Defects Determine the Binding Orientation and Insertion Depth of RecA on Multicomponent Lipid Bilayers.

    PubMed

    Zhang, Leili; Rajendram, Manohary; Weibel, Douglas B; Yethiraj, Arun; Cui, Qiang

    2016-08-25

    We describe a computational and experimental approach for probing the binding properties of the RecA protein at the surface of anionic membranes. Fluorescence measurements indicate that RecA behaves differently when bound to phosphatidylglycerol (PG)- and cardiolipin (CL)-containing liposomes. We use a multistage computational protocol that integrates an implicit membrane/solvent model, the highly mobile mimetic membrane model, and the full atomistic membrane model to study how different anionic lipids perturb RecA binding to the membrane. With anionic lipids studied here, the binding interface involves three key regions: the N-terminal helix, the DNA binding loop L2, and the M-M7 region. The nature of binding involves both electrostatic interactions between cationic protein residues and lipid polar/charged groups and insertion of hydrophobic residues. The L2 loop contributes more to membrane insertion than the N-terminal helix. More subtle aspects of RecA-membrane interaction are influenced by specific properties of anionic lipids. Ionic hydrogen bonds between the carboxylate group in phosphatidylserine and several lysine residues in the C-terminal region of RecA stabilize the parallel (∥) binding orientation, which is not locally stable on PG- and CL-containing membranes despite similarity in the overall charge density. Lipid packing defects, which are more prevalent in the presence of conical lipids, are observed to enhance the insertion depth of hydrophobic motifs. The computational finding that RecA binds in a similar orientation to PG- and CL-containing membranes is consistent with the fact that PG alone is sufficient to induce RecA polar localization, although CL might be more effective because of its tighter binding to RecA. The different fluorescence behaviors of RecA upon binding to PG- and CL-containing liposomes is likely due to the different structures and flexibility of the C-terminal region of RecA when it binds to different anionic phospholipids

  19. Conformational changes of the glucocorticoid receptor ligand binding domain induced by ligand and cofactor binding, and the location of cofactor binding sites determined by hydrogen/deuterium exchange mass spectrometry

    PubMed Central

    Frego, Lee; Davidson, Walter

    2006-01-01

    HXMS (hydrogen/deuterium exchange mass spectrometry) of the glucocorticoid receptor ligand-binding domain (GR LBD) complexed with the agonist dexamethasone and the antagonist RU-486 is described. Variations in the rates of exchange were observed in regions consistent with the published crystal structures of GR LBD complexed with RU-486 when compared with the GR dexamethasone complex. We also report the HXMS results for agonist-bound GR LBD with the coactivator transcriptional intermediary factor 2 (TIF2) and anatagonist-bound GR LBD with nuclear receptor corepressor (NCoR). Alterations in exchange rates observed for agonist-bound GR LBD with TIF2 present were consistent with the published crystal structural contacts for the complex. Alterations in exchange rates observed for antagonist-bound GR LBD with NCoR were a subset of those observed with TIF2 binding, suggesting a common or overlapping binding site for coactivator and corepressor. PMID:16600964

  20. Effect of dipole polarizability on positron binding by strongly polar molecules

    NASA Astrophysics Data System (ADS)

    Gribakin, G. F.; Swann, A. R.

    2015-11-01

    A model for positron binding to polar molecules is considered by combining the dipole potential outside the molecule with a strongly repulsive core of a given radius. Using existing experimental data on binding energies leads to unphysically small core radii for all of the molecules studied. This suggests that electron-positron correlations neglected in the simple model play a large role in determining the binding energy. We account for these by including the polarization potential via perturbation theory and non-perturbatively. The perturbative model makes reliable predictions of binding energies for a range of polar organic molecules and hydrogen cyanide. The model also agrees with the linear dependence of the binding energies on the polarizability inferred from the experimental data (Danielson et al 2009 J. Phys. B: At. Mol. Opt. Phys. 42 235203). The effective core radii, however, remain unphysically small for most molecules. Treating molecular polarization non-perturbatively leads to physically meaningful core radii for all of the molecules studied and enables even more accurate predictions of binding energies to be made for nearly all of the molecules considered.

  1. Mass analyzed threshold ionization of phenolṡCO: Intermolecular binding energies of a hydrogen-bonded complex

    NASA Astrophysics Data System (ADS)

    Haines, Stephen R.; Dessent, Caroline E. H.; Müller-Dethlefs, Klaus

    1999-08-01

    [PhenolṡCO]+ was studied using a combination of two-color resonant zero kinetic energy (ZEKE) spectroscopy and mass analyzed threshold ionization (MATI) spectroscopy to investigate the interaction of the CO ligand with a hydrogen-bonding cation. Vibrational progressions were observed in three intermolecular modes, the in-plane bend (42 cm-1), stretch (130 cm-1), and in-plane wag (160 cm-1), and are consistent with a planar hydrogen-bonded structure where the CO bonds through the carbon atom to the phenol OH group. Dissociation energies for the S0, S1, and D0 states were determined as 659±20, 849±20, and 2425±10 cm-1, respectively. The cationic and neutral dissociation energies of the phenolṡCO complex are considerably stronger than those of phenolṡN2, demonstrating the extent to which the larger quadrupole of CO affects the strength of binding.

  2. Crystal structures of α-dioxygenase from Oryza sativa: insights into substrate binding and activation by hydrogen peroxide.

    PubMed

    Zhu, Guangyu; Koszelak-Rosenblum, Mary; Malkowski, Michael G

    2013-10-01

    α-Dioxygenases (α-DOX) are heme-containing enzymes found predominantly in plants and fungi, where they generate oxylipins in response to pathogen attack. α-DOX oxygenate a variety of 14-20 carbon fatty acids containing up to three unsaturated bonds through stereoselective removal of the pro-R hydrogen from the α-carbon by a tyrosyl radical generated via the oxidation of the heme moiety by hydrogen peroxide (H2 O2 ). We determined the X-ray crystal structures of wild type α-DOX from Oryza sativa, the wild type enzyme in complex with H2 O2 , and the catalytically inactive Y379F mutant in complex with the fatty acid palmitic acid (PA). PA binds within the active site cleft of α-DOX such that the carboxylate forms ionic interactions with His-311 and Arg-559. Thr-316 aids in the positioning of carbon-2 for hydrogen abstraction. Twenty-five of the twenty eight contacts made between PA and residues lining the active site occur within the carboxylate and first eight carbons, indicating that interactions within this region of the substrate are responsible for governing selectivity. Comparison of the wild type and H2 O2 structures provides insight into enzyme activation. The binding of H2 O2 at the distal face of the heme displaces residues His-157, Asp-158, and Trp-159 ≈ 2.5 Å from their positions in the wild type structure. As a result, the Oδ2 atom of Asp-158 interacts with the Ca atom in the calcium binding loop, the side chains of Trp-159 and Trp-213 reorient, and the guanidinium group of Arg-559 is repositioned near Tyr-379, poised to interact with the carboxylate group of the substrate. PMID:23934749

  3. Bactericidal effect of hydrogen peroxide on spacecraft isolates

    NASA Technical Reports Server (NTRS)

    Wardle, M. D.; Renninger, G. M.

    1975-01-01

    Results are presented for an experimental study designed to assess the effect of hydrogen peroxide on both sporeforming and nonsporeforming spacecraft isolates as an initial step in determining its suitability for microbiological decontamination of certain United States spacecraft. Survivor data were obtained for eight bacterial isolates (six sporeformers and two nonsporeformers) recovered before launch Mariner 9 and exposed to concentrations of 3, 10, and 15% hydrogen peroxide. The effects of various concentrations of hydrogen peroxide on the spores are presented in tabular form, along with the percentage of survival of nonsporeformers exposed to hydrogen peroxide. No viable vegetative cells were recovered after a 10-min exposure time to any of the three concentration of hydrogen peroxide.

  4. Effects of Hydrogen on Tantalum Nitride Resistors

    NASA Technical Reports Server (NTRS)

    Weiler, James

    1999-01-01

    This document is a presentation about the investigation of drift reported in static frequency output from the analog circuit of a Multichannel Microwave Integrated circuit hybrid microelectronic filter module for space flight application. Electron Dispersion X-Ray Detector )EDAX) Analysis of the 35k ohm thin film Tantalum Nitride Chip resistors identified Palladium in the film. A catalytic reaction of Palladium and hydrogen produces mono atomic hydrogen. When the filter module cavities were filled with a 4 % hydrogen 96 % Nitrogen gas mixture at 25C and monitored the electrical performance for 24 hours. Some channels drifted in a similar pattern as the channel being investigated. Palladium was found on the resistors. The corrective actions taken are reviewed, which resulted in a stable circuit.

  5. Ab initio Design of Ca-Decorated Organic Frameworks for High Capacity Molecular Hydrogen Storage with Enhanced Binding

    SciTech Connect

    Sun, Y. Y.; Lee, K.; Kim, Y. H.; Zhang, S. B.

    2009-01-01

    Ab initio calculations show that Ca can decorate organic linkers of metal-organic framework, MOF-5, with a binding energy of 1.25 eV. The Ca-decorated MOF-5 can store molecular hydrogen (H{sub 2}) in both high gravimetric (4.6 wt %) and high volumetric (36 g/l) capacities. Even higher capacities (5.7 wt % and 45 g/l) can be obtained in a rationally designed covalent organic framework system, COF-{alpha}, with decorated Ca. Both density functional theory and second-order Moller-Plesset perturbation calculations show that the H{sub 2} binding in these systems is significantly stronger than the van der Waals interactions, which is required for H{sub 2} storage at near ambient conditions.

  6. Hydrogen bonding motifs of protein side chains: descriptions of binding of arginine and amide groups.

    PubMed Central

    Shimoni, L.; Glusker, J. P.

    1995-01-01

    The modes of hydrogen bonding of arginine, asparagine, and glutamine side chains and of urea have been examined in small-molecule crystal structures in the Cambridge Structural Database and in crystal structures of protein-nucleic acid and protein-protein complexes. Analysis of the hydrogen bonding patterns of each by graph-set theory shows three patterns of rings (R) with one or two hydrogen bond acceptors and two donors and with eight, nine, or six atoms in the ring, designated R2(2)(8), R2(2)(9), and R1(2)(6). These three patterns are found for arginine-like groups and for urea, whereas only the first two patterns R2(2)(8) and R2(2)(9) are found for asparagine- and glutamine-like groups. In each case, the entire system is planar within 0.7 A or less. On the other hand, in macromolecular crystal structures, the hydrogen bonding patterns in protein-nucleic acid complexes between the nucleic acid base and the protein are all R2(2)(9), whereas hydrogen bonding between Watson-Crick-like pairs of nucleic acid bases is R2(2)(8). These two hydrogen bonding arrangements [R2(2)(9)] and R2(2)(8)] are predetermined by the nature of the groups available for hydrogen bonding. The third motif identified, R1(2)(6), involves hydrogen bonds that are less linear than in the other two motifs and is found in proteins. PMID:7773178

  7. Binding of endotoxin to macrophages: distinct effects of serum constituents.

    PubMed

    Tahri-Jouti, M A; Chaby, R

    1991-07-01

    The respective roles of serum lipoproteins, and of the complement component C3, in the binding of endotoxin (LPS) to macrophages were analyzed by an in vitro assay using [3H]LPS. The addition of an anti-C3 serum in the medium induced an apparent abolishment of the specific binding of LPS to mouse macrophages, but this effect appeared to be due to an actual increase of nonspecific binding. Isolated complexes of LPS with lipoproteins of high density (HDL3) and of very high density (VHDL) did not bind to macrophages. Furthermore, addition of HDL3 and VHDL in the incubation medium inhibited the specific binding of LPS to macrophages. These results suggest that C3 reduces nonspecific interactions between LPS and macrophages whereas associations between LPS and HDL3 or VHDL inhibit specific LPS-macrophage interactions. PMID:1937584

  8. H274Y's Effect on Oseltamivir Resistance: What Happens Before the Drug Enters the Binding Site.

    PubMed

    Yusuf, Muhammad; Mohamed, Nornisah; Mohamad, Suriyati; Janezic, Dusanka; Damodaran, K V; Wahab, Habibah A

    2016-01-25

    Increased reports of oseltamivir (OTV)-resistant strains of the influenza virus, such as the H274Y mutation on its neuraminidase (NA), have created some cause for concern. Many studies have been conducted in the attempt to uncover the mechanism of OTV resistance in H274Y NA. However, most of the reported studies on H274Y focused only on the drug-bound system, so the direct effects of the mutation on NA itself prior to drug binding still remain unclear. Therefore, molecular dynamics simulations of NA in apo form, followed by principal component analysis and interaction energy calculations, were performed to investigate the structural changes of the NA binding site as a result of the H274Y mutation. It was observed that the disruption of the NA binding site due to the H274Y mutation was initiated by the repulsive effect of Y274 on the 250-loop, which in turn altered the hydrogen-bonding network around residue 274. The rotated W295 side chain caused the upward movement of the 340-loop. Consequently, sliding box docking results suggested that the binding pathway of OTV was compromised because of the disruption of this binding site. This study also highlighted the importance of the functional group at C6 of the sialic acid mimicry. It is hoped that these results will improve the understanding of OTV resistance and shed some light on the design of a novel anti-influenza drug. PMID:26703840

  9. Effect of green laser irradiation on hydrogen production

    NASA Astrophysics Data System (ADS)

    Bidin, Noriah; Razak, Siti Noraiza A.; Radiana Azni, Siti; Nguroho, Waskito; Mohsin, Ali Kamel; Abdullah, Mundzir; Krishnan, Ganesan; Bakhtiar, Hazri

    2014-06-01

    The effect of green laser irradiation on hydrogen production via water electrolysis was investigated. Diode pumped solid-state laser operating in second harmonic generation was employed as a source of irradiation. The hydrogen production system was also irradiated by a conventional light, a halogen source, for comparison. The best catalyst was identified by mixing distilled water with two types of salt: NaCl and Na2SO4. Optimization of hydrogen production from water electrolysis was realized by using NaCl and green laser irradiation. The power of green laser irradiation and the concentration of NaCl in water contribute to hydrogen production. The hydrogen yield also depends on the distance and direction of the green beam to the electrode.

  10. Effect of process variables on photosynthetic algal hydrogen production.

    PubMed

    Hahn, John J; Ghirardi, Maria L; Jacoby, William A

    2004-01-01

    Chlamydomonas reinhardtii is a green alga that can use the sun's energy to split water into O(2) and H(2). This is accomplished by means of a two-phase cycle, an aerobic growth phase followed by an anaerobic hydrogen production phase. The effects of process variables on hydrogen production are examined here. These variables include cell concentration, light intensity, and reactor design parameters that affect light transport and mixing. An optimum cell concentration and light intensity are identified, and two reactor designs are compared. The maximum hydrogen production observed in this study was 0.29 mL of hydrogen per milliliter of suspension. This was measured at atmospheric pressure during a 96 h production cycle. This corresponds to an average hydrogen production rate of 0.12 mmol/mL.h. PMID:15176910

  11. NMR study of the phosphoryl binding loop in purine nucleotide proteins: Evidence for strong hydrogen binding in human N-ras p21

    SciTech Connect

    Redfield, A.G.; Papastavros, M.Z. )

    1990-04-10

    The structure of the phosphoryl binding region of human N-ras p21 was probed by using heteronuclear proton-observed NMR methods. Normal protein and a Gly-12 {yields} Asp-12 mutant protein were prepared with two amino acids labeled with {sup 15}N at their amide positions: valine and glycine, aspartic acid and glycine, and lysine and glycine. The authors completed the identification of amide {sup 15}NH resonances from Gly-12 and Asp-12 to the end of the phosphoryl binding domain consensus sequence (Lys-16) in protein complexed with GDP and have made tentative amide identifications from Val-9 to Ser-17. The methods used, together with initial identifications of the Gly-12 and -13 amide resonances, were described previously. The amide resonances of both Gly-13 and Lys-16 are shifted downfield below 10.4 ppm in both the normal and mutant proteins. These downfield shifts are presumed to be due to strong hydrogen bonds with the {beta}-phosphate of GDP.

  12. Binding of Fatty Acid Amide Amphiphiles to Bovine Serum Albumin: Role of Amide Hydrogen Bonding.

    PubMed

    Ghosh, Subhajit; Dey, Joykrishna

    2015-06-25

    The study of protein-surfactant interactions is important because of the widespread use of surfactants in industry, medicine, and pharmaceutical fields. Sodium N-lauroylsarcosinate (SL-Sar) is a widely used surfactant in cosmetics, shampoos. In this paper, we studied the interactions of bovine serum albumin (BSA) with SL-Sar and sodium N-lauroylglycinate (SL-Gly) by use of a number of techniques, including fluorescence and circular dichroism spectroscopy and isothermal titration calorimetry. The binding strength of SL-Sar is stronger than that of structurally similar SL-Gly, which differs only by the absence of a methyl group in the amide nitrogen atom. Also, these two surfactants exhibit different binding patterns with the BSA protein. The role of the amide bond and hence the surfactant headgroup in the binding mechanism is discussed in this paper. It was observed that while SL-Sar destabilized, SL-Gly stabilized the protein structure, even at concentrations less than the critical micelle concentration (cmc) value. The thermodynamics of surfactant binding to BSA was studied by use of ITC. From the ITC results, it is concluded that three molecules of SL-Sar in contrast to only one molecule of SL-Gly bind to BSA in one set of binding sites at room temperature. However, on increasing temperature four molecules of SL-Gly bind to the BSA through H-bonding and van der Waals interactions, due to loosening of the BSA structure. In contrast, with SL-Sar the binding process is enthalpy driven, and very little structural change of BSA was observed at higher temperature. PMID:26023820

  13. Effects of hydrogen atoms on surface conductivity of diamond film

    SciTech Connect

    Liu, Fengbin Cui, Yan; Qu, Min; Di, Jiejian

    2015-04-15

    To investigate the effects of surface chemisorbed hydrogen atoms and hydrogen atoms in the subsurface region of diamond on surface conductivity, models of hydrogen atoms chemisorbed on diamond with (100) orientation and various concentrations of hydrogen atoms in the subsurface layer of the diamond were built. By using the first-principles method based on density functional theory, the equilibrium geometries and densities of states of the models were studied. The results showed that the surface chemisorbed hydrogen alone could not induce high surface conductivity. In addition, isolated hydrogen atoms in the subsurface layer of the diamond prefer to exist at the bond centre site of the C-C bond. However, such a structure would induce deep localized states, which could not improve the surface conductivity. When the hydrogen concentration increases, the C-H-C-H structure and C-3H{sub bc}-C structure in the subsurface region are more stable than other configurations. The former is not beneficial to the increase of the surface conductivity. However, the latter would induce strong surface states near the Fermi level, which would give rise to high surface conductivity. Thus, a high concentration of subsurface hydrogen atoms in diamond would make significant contributions to surface conductivity.

  14. Proton form factor effects in hydrogenic atoms

    SciTech Connect

    Daza, F. Garcia; Kelkar, N. G.; Nowakowski, M.

    2011-10-21

    The proton structure corrections to the hyperfine splittings in electronic and muonic hydrogen are evaluated using the Breit potential with electromagnetic form factors. In contrast to other methods, the Breit equation with q{sup 2} dependent form factors is just an extension of the standard Breit equation which gives the hyperfine splitting Hamiltonian. Precise QED corrections are comparable to the structure corrections which therefore need to be evaluated ab initio.

  15. Effects of Hydrogen on GRCop-84

    NASA Technical Reports Server (NTRS)

    Ellis, David L.; Hastings, Keith

    2006-01-01

    This report is a section of the final report on the GRCop-84 task of the Constellation Program and incorporates the results obtained between October 2000 and September 2005 when the program ended. GRCop-84 contains approximately 5.5 wt% Nb. Nb can react with H and embrittle easily. Previous work had indicated the thermodynamic possibility that Cr 2 Nb could react with H and form niobium hydrides in the presence of high pressure H such as seen in the Space Shuttle Main Engine. In this study, samples were charged with H and then tested in both high pressure H and He environments to determine if measurable differences existed which indicate that hydrogen embrittlement occurs in GRCop-84. Tensile, notched tensile, stress rupture and low cycle fatigue properties were surveyed. High pressure H environment stress rupture testing resulted in a lower reduction in area than a high pressure He environment, and the LCF lives at high strain ranges fall below the lower 95 percent confidence interval for the baseline data, but in general no significant differences were noted either between H and He environment tests or between hydrogen charged materials and the baseline, uncharged extruded GRCop-84 data sets. There was also no discernable evidence of the formation of hydrides or changes in fracture morphology indicating hydrogen embrittlement occurred.

  16. Effect of Detergents on Galactoside Binding by Melibiose Permeases.

    PubMed

    Amin, Anowarul; Hariharan, Parameswaran; Chae, Pil Seok; Guan, Lan

    2015-09-29

    The effect of various detergents on the stability and function of the melibiose permeases of Escherichia coli (MelBEc) and Salmonella typhimurium (MelBSt) was studied. In n-dodecyl-β-d-maltoside (DDM) or n-undecyl-β-d-maltoside (UDM), WT MelBSt binds melibiose with an affinity similar to that in the membrane. However, with WT MelBEc or MelBSt mutants (Arg141 → Cys, Arg295 → Cys, or Arg363 → Cys), galactoside binding is not detected in these detergents, but binding to the phosphotransferase protein IIA(Glc) is maintained. In the amphiphiles lauryl maltose neopentyl glycol (MNG-3) or glyco-diosgenin (GDN), galactoside binding with all of the MelB proteins is observed, with slightly reduced affinities. MelBSt is more thermostable than MelBEc, and the thermostability of either MelB is largely increased in MNG-3 or GDN. Therefore, the functional defect with DDM or UDM likely results from the relative instability of the sensitive MelB proteins, and stability, as well as galactoside binding, is retained in MNG-3 or GDN. Furthermore, isothermal titration calorimetry of melibiose binding with MelBSt shows that the favorable entropic contribution to the binding free energy is decreased in MNG-3, indicating that the conformational dynamics of MelB is restricted in this detergent. PMID:26352464

  17. Effect of detergents on galactoside binding by melibiose permeases

    PubMed Central

    Amin, Anowarul; Hariharan, Parameswaran; Chae, Pil Seok; Guan, Lan

    2015-01-01

    The effect of various detergents on the stability and function of melibiose permeases of Escherichia coli (MelBEc) or Salmonella typhimurium (MelBSt) were studied. In n-dodecyl-β-d-maltoside (DDM) or n-undecyl-β-d-maltoside (UDM), WT MelBSt binds melibiose with an affinity similar to that in the membrane. However, with WT MelBEc or MelBSt mutants (Arg141→Cys, Arg295→Cys or Arg363→Cys), galactoside binding is not detected in these detergents, but binding to the phosphotransferase protein IIAGlc is maintained. In the amphiphiles lauryl maltose neopentyl glycol (MNG-3) or glyco-diosgenin (GDN), galactoside binding with all the MelB proteins is observed, with slightly reduced affinities. MelBSt is more thermostable than MelBEc, and the thermostability of either MelB is largely increased in MNG-3 or GDN. Therefore, the functional defect with DDM or UDM likely results from relative instability of the sensitive MelB proteins, and stability, as well as galactoside binding, is retained in MNG-3 or GDN. Furthermore, isothermal titration calorimetry of melibiose binding with MelBSt shows that the favorable entropic contribution to the binding free energy is decreased in MNG-3, indicating that the conformational dynamics of MelB is restricted in this detergent. PMID:26352464

  18. The Binding And Release of Oxygen And Hydrogen Peroxide are Directed 1 By a Hydrophobic Tunnel in Cholesterol Oxidase

    SciTech Connect

    Chen, L.; Lyubimov, A.Y.; Brammer, L.; Vrielink, A.; Sampson, N.S.

    2009-05-12

    The usage by enzymes of specific binding pathways for gaseous substrates or products is debated. The crystal structure of the redox enzyme cholesterol oxidase, determined at sub-angstrom resolution, revealed a hydrophobic tunnel that may serve as a binding pathway for oxygen and hydrogen peroxide. This tunnel is formed by a cascade of conformational rearrangements and connects the active site with the exterior surface of the protein. To elucidate the relationship between this tunnel and gas binding and release, three mutant enzymes were constructed to block the tunnel or its putative gate. Mutation of the proposed gating residue Asn485 to Asp or tunnel residue Phe359 or Gly347 to Trp or Asn reduces the catalytic efficiency of oxidation. The K mO 2 increases from 300 +/- 35 microM for the wild-type enzyme to 617 +/- 15 microM for the F359W mutant. The k cat for the F359W mutant-catalyzed reaction decreases 13-fold relative to that of the wild-type-catalyzed reaction. The N485D and G347N mutants could not be saturated with oxygen. Transfer of hydride from the sterol to the flavin prosthetic group is no longer rate-limiting for these tunnel mutants. The steady-state kinetics of both wild-type and tunnel mutant enzymes are consistent with formation of a ternary complex of steroid and oxygen during catalysis. Furthermore, kinetic cooperativity with respect to molecular oxygen is observed with the tunnel mutants, but not with the wild-type enzyme. A rate-limiting conformational change for binding and release of oxygen and hydrogen peroxide, respectively, is consistent with the cooperative kinetics. In the atomic-resolution structure of F359W, the indole ring of the tryptophan completely fills the tunnel and is observed in only a single conformation. The size of the indole is proposed to limit conformational rearrangement of residue 359 that leads to tunnel opening in the wild-type enzyme. Overall, these results substantiate the functional importance of the tunnel for

  19. Auroral zone effects on hydrogen geocorona structure and variability

    NASA Technical Reports Server (NTRS)

    Moore, T. E.; Biddle, A. P.; Waite, J. H., Jr.; Killeen, T. L.

    1985-01-01

    The effect of diurnal and magnetospheric modulations on the structure of the hydrogen geocorona is analyzed on the basis of recent observations. Particular attention is given to the enhancement of neutral escape by plasma effects, including the recently observed phenomenon of low-altitude ion acceleration. It is found that, while significant fluxes of neutral H should be produced by transverse ion acceleration in the auroral zone, the process is probably insufficient to account for the observed polar depletion of hydrogen atoms. Analysis of recent exospheric temperature measurements from the Dynamics Explorer-2 satellite suggest that neutral heating in and near the high latitude cusp may be the major contributor to depleted atomic hydrogen densities at high latitudes. Altitude profiles of the production rates for escaping neutral hydrogen atoms during periods of maximum, minimum, and typical solar activity are provided.

  20. Effects of glycation on meloxicam binding to human serum albumin

    NASA Astrophysics Data System (ADS)

    Trynda-Lemiesz, Lilianna; Wiglusz, Katarzyna

    2011-05-01

    The current study reports a binding of meloxicam a pharmacologically important new generation, non-steroidal anti-inflammatory drug to glycated form of the human serum albumin (HSA). The interaction of the meloxicam with nonglycated and glycated albumin has been studied at pH 7.4 in 0.05 M sodium phosphate buffer with 0.1 M NaCl, using fluorescence quenching technique and circular dichroism spectroscopy. Results of the present study have shown that the meloxicam could bind both forms of albumin glycated and nonglycated at a site, which was close to the tryptophan residues. Similarly, how for native albumin glycated form has had one high affinity site for the drug with association constants of the order of 10 5 M -1. The glycation process of the HSA significantly has affected the impact of the meloxicam on the binding of other ligands such as warfarin and bilirubin. The affinity of the glycated albumin for bilirubin as for native albumin has been reduced by meloxicam but observed effect was weaker by half (about 20%) compared with nonglycated albumin. In contrast to the native albumin meloxicam binding to glycated form of the protein only slightly affected the binding of warfarin. It seemed possible that the effects on warfarin binding might be entirely attributable to the Lys 199 modification which was in site I.

  1. The effects of hydrogen embrittlement of titanium

    NASA Technical Reports Server (NTRS)

    Taylor, Delbert J.

    1989-01-01

    Titanium alloys, by virtue of their attractive strength to density ratio, fatigue, fracture toughness and corrosion resistance are now commonly used in various aerospace and marine applications. The cost, once very expensive, has been reduced, making titanium even more of a competitive material today. Titanium and titanium alloys have a great affinity to several elements. Hydrogen, even in small amounts, can cause embrittlement, which in turn causes a reduction in strength and ductility. The reduction of strength and ductility is the subject of this investigation.

  2. Probing the C-H⋅⋅⋅π weak hydrogen bond in anesthetic binding: the sevoflurane-benzene cluster.

    PubMed

    Seifert, Nathan A; Zaleski, Daniel P; Pérez, Cristóbal; Neill, Justin L; Pate, Brooks H; Vallejo-López, Montserrat; Lesarri, Alberto; Cocinero, Emilio J; Castaño, Fernando; Kleiner, Isabelle

    2014-03-17

    Cooperativity between weak hydrogen bonds can be revealed in molecular clusters isolated in the gas phase. Here we examine the structure, internal dynamics, and origin of the weak intermolecular forces between sevoflurane and a benzene molecule, using multi-isotopic broadband rotational spectra. This heterodimer is held together by a primary C-H⋅⋅⋅π hydrogen bond, assisted by multiple weak C-H⋅⋅⋅F interactions. The multiple nonbonding forces hinder the internal rotation of benzene around the isopropyl C-H bond in sevoflurane, producing detectable quantum tunneling effects in the rotational spectrum. PMID:24520035

  3. Hydrogen Bonding and Binding of Polybasic Residues with Negatively Charged Mixed Lipid Monolayers

    SciTech Connect

    Lorenz, C.; Feraudo, J.; Travesset, A.

    2008-01-23

    Phosphoinositides, phosphorylated products of phosphatidylinositol, are a family of phospholipids present in tiny amounts (1% or less) in the cytosolic surface of cell membranes, yet they play an astonishingly rich regulatory role, particularly in signaling processes. In this letter, we use molecular dynamics simulations on a model system of mixed lipid monolayers to investigate the interaction of phosphatidylinositol 4,5-bisphosphate (PIP{sub 2}), the most common of the phosphoinositides, with a polybasic peptide consisting of 13 lysines. Our results show that the polybasic peptide sequesters three PIP{sub 2} molecules, forming a complex stabilized by the formation of multiple hydrogen bonds between PIP{sub 2} and the Lys residues. We also show that the polybasic peptide does not sequester other charged phospholipids such as phosphatidylserine because of the inability to form long-lived stable hydrogen bonds.

  4. Hydrogen effects on material behavior; Proceedings of the 4th International Conference on the Effect of Hydrogen on the Behavior of Materials, Moran, WY, Sept. 12-15, 1989

    SciTech Connect

    Moody, N.R.; Thompson, A.W.

    1990-01-01

    The present conference discusses hydrogen permeation, trapping, and transport in metals, hydrogen-induced phase transformations, hydrogen embrittlement studies on stainless steels, hydrogen effects on advanced materials, hydrogen-associated fracture processes, crack growth susceptibility, and hydrogen-resistant engineering alloys and applications. Attention is given to the behavior of hydrogen in evaporated metal films, hydrogen diffusivity in alpha-beta Zr alloys, acoustic emissions from steels containing hydrogen, synergistic effects of He and H isotopes in FCC metals, hydrogen transport by dislocations in Al alloys, the effect of hydrogen precipitation in an Al-{sup 9}Mg alloy, hydrogen effects on Ti oxidation in water vapor, hydrogen effects on the behavior of duplex stainless steels, hydrogen embrittlement of superalloys, hydrogen embrittlement of TiAl alloys, hydrogen-enhanced decohesion in Fe-Si single crystals, cathodic hydrogen embrittlement of a duplex stainless steel, and hydrogen embrittlement in lean uranium alloys.

  5. Effects of exercise on insulin binding to human muscle.

    PubMed

    Bonen, A; Tan, M H; Clune, P; Kirby, R L

    1985-04-01

    A procedure was developed to measure insulin binding to human skeletal muscle obtained via the percutaneous muscle biopsy technique. With this method the effects of exercise on insulin binding were investigated. Subjects (n = 9) exercised for 60 min on a bicycle ergometer at intensities ranging from 20-86% maximum O2 consumption (VO2max). Blood samples were obtained before, during, and after exercise and analyzed for glucose and insulin. Muscle samples (250 mg) for the vastus lateralis were obtained 30 min before exercise, at the end of exercise, and 60 min after exercise. Two subjects rested during the experimental period. There was no linear relationship between exercise intensities and the changes in insulin binding to human muscle. At rest (n = 2) and at exercise intensities below 60% VO2max (n = 5) no change in insulin binding occurred (P greater than 0.05). However, when exercise occurred at greater than or equal to 69% VO2max (n = 4), a pronounced decrement in insulin binding (30-50%) was observed (P less than 0.05). This persisted for 60 min after exercise. These results indicate that insulin binding in human muscle is not altered by 60 min of exercise at less than or equal to 60% VO2max but that a marked decrement occurs when exercise is greater than or equal to 69% VO2max. PMID:3885753

  6. Light irradiance and spectral distribution effects on cyanobacterial hydrogen production

    NASA Astrophysics Data System (ADS)

    Fatihah Salleh, Siti; Kamaruddin, Azlina; Hekarl Uzir, Mohamad; Rahman Mohamed, Abdul; Halim Shamsuddin, Abdul

    2016-03-01

    Light is an essential energy source for photosynthetic cyanobacteria. Changes in both light irradiance and spectral distribution will affect their photosynthetic productivity. Compared to the light irradiance, little investigations have been carried out on the effect of light spectra towards cyanobacterial hydrogen production. Hence, this work aims to investigate the effects of both light quantity and quality on biohydrogen productivity of heterocystous cyanobacterium, A.variabilis. Under white light condition, the highest hydrogen production rate of 31 µmol H2 mg chl a -1 h-1 was achieved at 70 µE m-2 s-1. When the experiment was repeated at the same light irradiance but different light spectra of blue, red and green, the accumulations of hydrogen were significantly lower than the white light except for blue light. As the light irradiance was increased to 350 µE m-2 s-1, the accumulated hydrogen under the blue light doubled that of the white light. Besides that, an unusual prolongation of the hydrogen production up to 120 h was observed. The results obtained suggest that blue light could be the most desirable light spectrum for cyanobacterial hydrogen production.

  7. Hydrogen peroxide excretion by oral streptococci and effect of lactoperoxidase-thiocyanate-hydrogen peroxide.

    PubMed Central

    Carlsson, J; Iwami, Y; Yamada, T

    1983-01-01

    Approved type strains of Streptococcus sanguis, S. mitis, S. mutans, and S. salivarius were grown under aerobic and anaerobic conditions. The rate of hydrogen peroxide excretion, oxygen uptake, and acid production from glucose by washed-cell suspensions of these strains were studied, and the levels of enzymes in cell-free extracts which reduced oxygen, hydrogen peroxide, or hypothiocyanite (OSCN-) in the presence of NADH or NADPH were assayed. The effects of lactoperoxidase-thiocyanate-hydrogen peroxide on the rate of acid production and oxygen uptake by intact cells, the activity of glycolytic enzymes in cell-free extracts, and the levels of intracellular glycolytic intermediates were also studied. All strains consumed oxygen in the presence of glucose. S. sanguis, S. mitis, and anaerobically grown S. mutans excreted hydrogen peroxide. There was higher NADH oxidase and NADH peroxidase activity in aerobically grown cells than in anaerobically grown cells. NADPH oxidase activity was low in all species. Acid production, oxygen uptake, and, consequently, hydrogen peroxide excretion were inhibited in all the strains by lactoperoxidase-thiocyanate-hydrogen peroxide. S. sanguis and S. mitis had a higher capacity than S. mutans and S. salivarius to recover from this inhibition. Higher activity in the former strains of an NADH-OSCN oxidoreductase, which converted OSCN- into thiocyanate, explained this difference. The change in levels of intracellular glycolytic intermediates after inhibition of glycolysis by OSCN- and the actual activity of glycolytic enzymes in cell-free extracts in the presence of OSCN- indicated that the primary target of OSCN- in the glycolytic pathway was glyceraldehyde 3-phosphate dehydrogenase. PMID:6832837

  8. The effect of local substrate motion on quantum hydrogen transfer in soybean lipoxygenase-1 modeled with QTES-DFTB dynamics

    NASA Astrophysics Data System (ADS)

    Mazzuca, James W.; Garashchuk, Sophya; Jakowski, Jacek

    2014-10-01

    The motion of local substrate nuclei is incorporated into the quantum hydrogen transfer reaction which occurs in the active site of soybean lipoxygenase-1, modeled within a quantum trajectory (QT) framework. Interactions within the active site are obtained from on-the-fly electronic structure (ES) calculations at the density-functional tight-binding (DFTB) level. By selectively constraining substrate nuclei, changes in the rate constants and kinetic isotope effect are computed over a 100 K temperature range. Substrate motion, occurring on the time-scale of the hydrogen transfer, enhances both the rate constants and isotope effect, but does not change trends captured in a constrained substrate environment.

  9. Hydrogenic donor impurity in parallel-triangular quantum wires: Hydrostatic pressure and applied electric field effects

    NASA Astrophysics Data System (ADS)

    Restrepo, R. L.; Giraldo, E.; Miranda, G. L.; Ospina, W.; Duque, C. A.

    2009-12-01

    The combined effects of the hydrostatic pressure and in-growth direction applied electric field on the binding energy of hydrogenic shallow-donor impurity states in parallel-coupled-GaAs- Ga1-xAlxAs-quantum-well wires are calculated using a variational procedure within the effective-mass and parabolic-band approximations. Results are obtained for several dimensions of the structure, shallow-donor impurity positions, hydrostatic pressure, and applied electric field. Our results suggest that external inputs such us hydrostatic pressure and in-growth direction electric field are two useful tools in order to modify the binding energy of a donor impurity in parallel-coupled-quantum-well wires.

  10. Large-scale first principles and tight-binding density functional theory calculations on hydrogen-passivated silicon nanorods

    NASA Astrophysics Data System (ADS)

    Zonias, Nicholas; Lagoudakis, Pavlos; Skylaris, Chris-Kriton

    2010-01-01

    We present a computational study by density functional theory (DFT) of entire silicon nanorods with up to 1648 atoms without any periodicity or symmetry imposed. The nanorods have been selected to have varying aspect ratios and levels of surface passivation with hydrogen. The structures of the nanorods have been optimized using a density functional tight-binding approach, while energies and electronic properties have been computed using linear-scaling DFT with plane-wave accuracy with the ONETEP (Skylaris et al 2005 J. Chem. Phys. 122 084119) program. The aspect ratio and surface passivation (1 × 1 and 2 × 1 reconstructions) along with the size of the nanorods which leads to quantum confinement along all three dimensions, significantly affect their electronic properties. The structures of the nanorods also show interesting behaviour as, depending on their characteristics, they can in certain areas retain the structure of bulk silicon while in other parts significantly deviate from it.

  11. Discriminatory effects in the optical binding of chiral nanoparticles

    NASA Astrophysics Data System (ADS)

    Forbes, Kayn A.; Bradshaw, David S.; Andrews, David L.

    2015-08-01

    The laser-induced intermolecular force that exists between two or more particles subjected to a moderately intense laser beam is termed `optical binding'. Completely distinct from the single-particle forces that give rise to optical trapping, the phenomenon of optical binding is a manifestation of the coupling between optically induced dipole moments in neutral particles. In conjunction with optical trapping, the optomechanical forces in optical binding afford means for the manipulation and fabrication of optically bound matter. The Casimir-Polder potential that is intrinsic to all matter can be overridden by the optical binding force in cases where the laser beam is of sufficient intensity. Chiral discrimination can arise when the laser input has a circular polarization, if the particles are themselves chiral. Then, it emerges that the interaction between particles with a particular handedness is responsive to the left- or right-handedness of the light. The present analysis, which expands upon previous studies of chiral discrimination in optical binding, identifies a novel mechanism that others have previously overlooked, signifying that the discriminatory effect is much more prominent than originally thought. The new theory leads to results for freely-tumbling chiral particles subjected to circularly polarized light. Rigorous conditions are established for the energy shifts to be non-zero and display discriminatory effects with respect to the handedness of the incident beam. Detailed calculations indicate that the energy shift is larger than those previously reported by three orders of magnitude.

  12. Effect of desipramine on dopamine receptor binding in vivo

    SciTech Connect

    Suhara, Tetsuya Jikei Univ., Tokyo ); Inoue, Osamu; Kobayasi, Kaoru )

    1990-01-01

    Effect of desipramine on the in vivo binding of {sup 3}H-SCH23390 and {sup 3}H-N-methylspiperone ({sup 3}H-NMSP) in mouse striatum was studied. The ratio of radioactivity in the striatum to that in the cerebellum at 15 min after i.v. injection of {sup 3}H-SCH23390 or 45 min after injection of {sup 3}H-NMSP were used as indices of dopamine D1 or D2 receptor binding in vivo, respectively. In vivo binding of D1 and D2 receptors was decreased in a dose-dependent manner by acute treatment with desipramine (DMI). A saturation experiment suggested that the DMI-induced reduction in the binding was mainly due to the decrease in the affinity of both receptors. No direct interactions between the dopamine receptors and DMI were observed in vitro by the addition of 1 mM of DMI into striatal homogenate. Other antidepressants such as imipramine, clomipramine, maprotiline and mianserin also decreased the binding of dopamine D1 and D2 receptors. The results indicated an important role of dopamine receptors in the pharmacological effect of antidepressants.

  13. Inner reorganization limiting electron transfer controlled hydrogen bonding: intra- vs. intermolecular effects.

    PubMed

    Martínez-González, Eduardo; Frontana, Carlos

    2014-05-01

    In this work, experimental evidence of the influence of the electron transfer kinetics during electron transfer controlled hydrogen bonding between anion radicals of metronidazole and ornidazole, derivatives of 5-nitro-imidazole, and 1,3-diethylurea as the hydrogen bond donor, is presented. Analysis of the variations of voltammetric EpIcvs. log KB[DH], where KB is the binding constant, allowed us to determine the values of the binding constant and also the electron transfer rate k, confirmed by experiments obtained at different scan rates. Electronic structure calculations at the BHandHLYP/6-311++G(2d,2p) level for metronidazole, including the solvent effect by the Cramer/Truhlar model, suggested that the minimum energy conformer is stabilized by intramolecular hydrogen bonding. In this structure, the inner reorganization energy, λi,j, contributes significantly (0.5 eV) to the total reorganization energy of electron transfer, thus leading to a diminishment of the experimental k. PMID:24653999

  14. Water's hydrogen bonds in the hydrophobic effect: a simple model.

    PubMed

    Xu, Huafeng; Dill, Ken A

    2005-12-15

    We propose a simple analytical model to account for water's hydrogen bonds in the hydrophobic effect. It is based on computing a mean-field partition function for a water molecule in the first solvation shell around a solute molecule. The model treats the orientational restrictions from hydrogen bonding, and utilizes quantities that can be obtained from bulk water simulations. We illustrate the principles in a 2-dimensional Mercedes-Benz-like model. Our model gives good predictions for the heat capacity of hydrophobic solvation, reproduces the solvation energies and entropies at different temperatures with only one fitting parameter, and accounts for the solute size dependence of the hydrophobic effect. Our model supports the view that water's hydrogen bonding propensity determines the temperature dependence of the hydrophobic effect. It explains the puzzling experimental observation that dissolving a nonpolar solute in hot water has positive entropy. PMID:16375338

  15. Poisoning effect on solubility of hydrogen isotopes in getter materials

    NASA Astrophysics Data System (ADS)

    Yamanaka, Shinsuke; Sato, Yuichi; Ogawa, Hidenori; Shirasu, Yoshirou; Miyake, Masanobu

    1991-03-01

    Hydrogen and deuterium solubilities in Ti-C and Zr-N alloys with various compositions have been measured at pressures below 100 Pa. All of the solubility data were found to follow Sieverts' law. The presence of carbon in Ti increased the solubilities of hydrogen isotopes and reduced the enthalpies of solution. The solubility increased and the enthalpy of solution decreased with addition of nitrogen into Zr. The hydrogen solubility in Ti-C and Zr-N alloys was larger than the deuterium solubility. Partial thermodynamic functions of hydrogen and deuterium in Ti-C and Zr-N alloys were obtained by a dilute solution model and compared with those in Ti-(O, N) and Zr-O alloys. The isotope effect of hydrogen and deuterium solubilities in the Ti-(O, N, C) and Zr-(O, N) alloys was discussed, and the tritium solubility in Ti-C and Zr-N alloys was evaluated from hydrogen and deuterium data.

  16. Epitope-distal effects accompany the binding of two distinct antibodies to hepatitis B virus capsids.

    PubMed

    Bereszczak, Jessica Z; Rose, Rebecca J; van Duijn, Esther; Watts, Norman R; Wingfield, Paul T; Steven, Alasdair C; Heck, Albert J R

    2013-05-01

    Infection of humans by hepatitis B virus (HBV) induces the copious production of antibodies directed against the capsid protein (Cp). A large variety of anticapsid antibodies have been identified that differ in their epitopes. These data, and the status of the capsid as a major clinical antigen, motivate studies to achieve a more detailed understanding of their interactions. In this study, we focused on the Fab fragments of two monoclonal antibodies, E1 and 3120. E1 has been shown to bind to the side of outward-protruding spikes whereas 3120 binds to the "floor" region of the capsid, between spikes. We used hydrogen-deuterium exchange coupled to mass spectrometry (HDX-MS) to investigate the effects on HBV capsids of binding these antibodies. Conventionally, capsids loaded with saturating amounts of Fabs would be too massive to be readily amenable to HDX-MS. However, by focusing on the Cp protein, we were able to acquire deuterium uptake profiles covering the entire 149-residue sequence and reveal, in localized detail, changes in H/D exchange rates accompanying antibody binding. We find increased protection of the known E1 and 3120 epitopes on the capsid upon binding and show that regions distant from the epitopes are also affected. In particular, the α2a helix (residues 24-34) and the mobile C-terminus (residues 141-149) become substantially less solvent-exposed. Our data indicate that even at substoichiometric antibody binding an overall increase in the rigidity of the capsid is elicited, as well as a general dampening of its breathing motions. PMID:23597076

  17. Relativistic corrections for screening effects on the energies of hydrogen-like atoms embedded in plasmas

    SciTech Connect

    Poszwa, A.; Bahar, M. K.

    2015-01-15

    The influence of relativistic and plasma screening effects on energies of hydrogen-like atoms embedded in plasmas has been studied. The Dirac equation with a more general exponential cosine screened potential has been solved numerically and perturbatively, by employing the direct perturbation theory. Properties of spectra corresponding to bound states and to different sets of the potential parameters have been studied both in nonrelativistic and relativistic approximations. Binding energies, fine-structure splittings, and relativistic energy shifts have been determined as functions of parameters of the potential. The results have been compared with the ones known from the literature.

  18. The effect of electron induced hydrogenation of graphene on its electrical transport properties

    SciTech Connect

    Woo, Sung Oh; Teizer, Winfried

    2013-07-22

    We report a deterioration of the electrical transport properties of a graphene field effect transistor due to energetic electron irradiation on a stack of Poly Methyl Methacrylate (PMMA) on graphene (PMMA/graphene bilayer). Prior to electron irradiation, we observed that the PMMA layer on graphene does not deteriorate the carrier transport of graphene but improves its electrical properties instead. As a result of the electron irradiation on the PMMA/graphene bilayer, the Raman “D” band appears after removal of PMMA. We argue that the degradation of the transport behavior originates from the binding of hydrogen generated during the PMMA backbone secession process.

  19. Neutron crystallographic studies reveal hydrogen bond and water-mediated interactions between a carbohydrate-binding module and its bound carbohydrate ligand.

    PubMed

    Fisher, S Zoë; von Schantz, Laura; Håkansson, Maria; Logan, Derek T; Ohlin, Mats

    2015-10-27

    Carbohydrate-binding modules (CBMs) are key components of many carbohydrate-modifying enzymes. CBMs affect the activity of these enzymes by modulating bonding and catalysis. To further characterize and study CBM-ligand binding interactions, neutron crystallographic studies of an engineered family 4-type CBM in complex with a branched xyloglucan ligand were conducted. The first neutron crystal structure of a CBM-ligand complex reported here shows numerous atomic details of hydrogen bonding and water-mediated interactions and reveals the charged state of key binding cleft amino acid side chains. PMID:26451738

  20. Observation of Binding and Rotation of Methane and Hydrogen within a Functional Metal–Organic Framework

    PubMed Central

    2016-01-01

    The key requirement for a portable store of natural gas is to maximize the amount of gas within the smallest possible space. The packing of methane (CH4) in a given storage medium at the highest possible density is, therefore, a highly desirable but challenging target. We report a microporous hydroxyl-decorated material, MFM-300(In) (MFM = Manchester Framework Material, replacing the NOTT designation), which displays a high volumetric uptake of 202 v/v at 298 K and 35 bar for CH4 and 488 v/v at 77 K and 20 bar for H2. Direct observation and quantification of the location, binding, and rotational modes of adsorbed CH4 and H2 molecules within this host have been achieved, using neutron diffraction and inelastic neutron scattering experiments, coupled with density functional theory (DFT) modeling. These complementary techniques reveal a very efficient packing of H2 and CH4 molecules within MFM-300(In), reminiscent of the condensed gas in pure component crystalline solids. We also report here, for the first time, the experimental observation of a direct binding interaction between adsorbed CH4 molecules and the hydroxyl groups within the pore of a material. This is different from the arrangement found in CH4/water clathrates, the CH4 store of nature. PMID:27410670

  1. Observation of Binding and Rotation of Methane and Hydrogen within a Functional Metal-Organic Framework.

    PubMed

    Savage, Mathew; da Silva, Ivan; Johnson, Mark; Carter, Joseph H; Newby, Ruth; Suyetin, Mikhail; Besley, Elena; Manuel, Pascal; Rudić, Svemir; Fitch, Andrew N; Murray, Claire; David, William I F; Yang, Sihai; Schröder, Martin

    2016-07-27

    The key requirement for a portable store of natural gas is to maximize the amount of gas within the smallest possible space. The packing of methane (CH4) in a given storage medium at the highest possible density is, therefore, a highly desirable but challenging target. We report a microporous hydroxyl-decorated material, MFM-300(In) (MFM = Manchester Framework Material, replacing the NOTT designation), which displays a high volumetric uptake of 202 v/v at 298 K and 35 bar for CH4 and 488 v/v at 77 K and 20 bar for H2. Direct observation and quantification of the location, binding, and rotational modes of adsorbed CH4 and H2 molecules within this host have been achieved, using neutron diffraction and inelastic neutron scattering experiments, coupled with density functional theory (DFT) modeling. These complementary techniques reveal a very efficient packing of H2 and CH4 molecules within MFM-300(In), reminiscent of the condensed gas in pure component crystalline solids. We also report here, for the first time, the experimental observation of a direct binding interaction between adsorbed CH4 molecules and the hydroxyl groups within the pore of a material. This is different from the arrangement found in CH4/water clathrates, the CH4 store of nature. PMID:27410670

  2. Hydrogen Effect on Nanomechanical Properties of the Nitrided Steel

    NASA Astrophysics Data System (ADS)

    Barnoush, Afrooz; Asgari, Masoud; Johnsen, Roy; Hoel, Rune

    2013-02-01

    In situ electrochemical nanoindentation is used to examine the effect of electrochemically charged hydrogen on mechanical properties of the nitride layer on low-alloy 2.25Cr-1Mo martensitic structural steel. By application of this method, we were able to trace the changes in the mechanical properties due to the absorption of atomic hydrogen to different depths within the compound and diffusion layers. The results clearly show that the hydrogen charging of the nitriding layer can soften the layer and reduce the hardness within both the compound and the diffusion layers. The effect is completely reversible and by removal of the hydrogen, the hardness recovers to its original value. The reduction in hardness of the nitride layer does not correlate to the nitrogen concentration, but it seems to be influenced by the microstructure and residual stress within the compound and diffusion layers. Findings show that nitriding can be a promising way to control the hydrogen embrittlement of the tempered martensitic steels.

  3. HYDROGEN EFFECTS ON LASER ENGINEERED NET SHAPE (LENS) REPAIRED WELDMENTS

    SciTech Connect

    Korinko, P; Thad Adams, T

    2006-10-06

    New methods of repairing mis-machined components are always of interest. In this study, an innovative method using Laser Engineered Net Shape{trademark} (LENS{reg_sign}) forming was used to repair intentionally mis-machined test articles. The components were repaired and subsequently hydrogen charged and burst tested. The LENS repair did not have an adverse effect on the solid state weld process that was used to repair the components. Hydrogen charged samples failed in a similar manner to the uncharged samples. Overall, the prospects for LENS repairing similar products are favorable and further work is encouraged.

  4. Analysis of nuclear quantum effects on hydrogen bonding.

    PubMed

    Swalina, Chet; Wang, Qian; Chakraborty, Arindam; Hammes-Schiffer, Sharon

    2007-03-22

    The impact of nuclear quantum effects on hydrogen bonding is investigated for a series of hydrogen fluoride (HF)n clusters and a partially solvated fluoride anion, F-(H2O). The nuclear quantum effects are included using the path integral formalism in conjunction with the Car-Parrinello molecular dynamics (PICPMD) method and using the second-order vibrational perturbation theory (VPT2) approach. For the HF clusters, a directional change in the impact of nuclear quantum effects on the hydrogen-bonding strength is observed as the clusters evolve toward the condensed phase. Specifically, the inclusion of nuclear quantum effects increases the F-F distances for the (HF)n=2-4 clusters and decreases the F-F distances for the (HF)n>4 clusters. This directional change occurs because the enhanced electrostatic interactions between the HF monomers become more dominant than the zero point energy effects of librational modes as the size of the HF clusters increases. For the F-(H2O) system, the inclusion of nuclear quantum effects decreases the F-O distance and strengthens the hydrogen bonding interaction between the fluoride anion and the water molecule because of enhanced electrostatic interactions. The vibrationally averaged 19F shielding constant for F-(H2O) is significantly lower than the value for the equilibrium geometry, indicating that the electronic density on the fluorine decreases as a result of the quantum delocalization of the shared hydrogen. Deuteration of this system leads to an increase in the vibrationally averaged F-O distance and nuclear magnetic shielding constant because of the smaller degree of quantum delocalization for deuterium. PMID:17388289

  5. Hydrogen effects on the age hardening behavior of 2024 aluminum

    NASA Technical Reports Server (NTRS)

    Wagner, J. A.; Louthan, M. R., Jr.; Sisson, R. D., Jr.

    1986-01-01

    It has been found that the fatigue crack growth rate in aluminum alloys increases significantly in the presence of moisture. This phenomenon along with a moisture effect observed in another context has been attributed to 'embrittlement' of the aluminum by absorbed hydrogen generated by the reaction of moisture with freshly exposed aluminum. A description is given of a number of age hardening experiments involving 2024 aluminum. These experiments show that a mechanism related to the segregation of absorbed hydrogen to the coherent theta-double-prime interfaces may account for the observed reduction in fatigue life. It is pointed out that this segregation promotes a loss of coherency in the hydrogen rich region at a fatigue crack tip. Subsequently, the loss of coherency causes local softening and reduces fatigue life.

  6. Effects of nucleoside analog incorporation on DNA binding to the DNA binding domain of the GATA-1 erythroid transcription factor.

    PubMed

    Foti, M; Omichinski, J G; Stahl, S; Maloney, D; West, J; Schweitzer, B I

    1999-02-01

    We investigate here the effects of the incorporation of the nucleoside analogs araC (1-beta-D-arabinofuranosylcytosine) and ganciclovir (9-[(1,3-dihydroxy-2-propoxy)methyl] guanine) into the DNA binding recognition sequence for the GATA-1 erythroid transcription factor. A 10-fold decrease in binding affinity was observed for the ganciclovir-substituted DNA complex in comparison to an unmodified DNA of the same sequence composition. AraC substitution did not result in any changes in binding affinity. 1H-15N HSQC and NOESY NMR experiments revealed a number of chemical shift changes in both DNA and protein in the ganciclovir-modified DNA-protein complex when compared to the unmodified DNA-protein complex. These changes in chemical shift and binding affinity suggest a change in the binding mode of the complex when ganciclovir is incorporated into the GATA DNA binding site. PMID:10037146

  7. Benchmark binding energies of ammonium and alkyl-ammonium ions interacting with water. Are ammonium-water hydrogen bonds strong?

    NASA Astrophysics Data System (ADS)

    Vallet, Valérie; Masella, Michel

    2015-01-01

    Alkyl-ammonium ion/water interactions are investigated using high level quantum computations, yielding thermodynamics data in good agreement with gas-phase experiments. Alkylation and hydration lead to weaken the NHsbnd O hydrogen bonds. Upon complete hydration by four water molecules, their main features are close to those of the OHsbnd O bond in the isolated water dimer. Energy decomposition analyses indicate that hydration of alkyl-ammonium ions are mainly due to electrostatic/polarization effects, as for hard monoatomic cations, but with a larger effect of dispersion.

  8. Thermodynamics of silicon nitridation - Effect of hydrogen

    NASA Technical Reports Server (NTRS)

    Shaw, N. J.; Zeleznik, F. J.

    1982-01-01

    Equilibrium compositions for the nitridization of Si were calculated to detect the effectiveness of H2 in removal of the oxide film and in increasing the concentration of SiO and reducing the proportions of O2. Gibbs free energy for the formation of SiN2O was computed above 1685 K, and at lower temperatures. The thermodynamic properties of SiN2O2 were then considered from 1000-3000 K, taking into account the known thermodynamic data for 39 molecular combinations of the Si, Ni, and O. The gases formed were assumed ideal mixtures with pure phase condensed species. The mole fractions were obtained for a system of SiO2 with each Si particle covered with a thin layer of SiO2 before nitridation, and a system in which the nitriding atmosphere had access to the Si. The presence of H2 was determined to enhance the removal of NiO2 in the first system, decrease the partial pressure of O2, increase the partial pressures of SiO, Si, H2O, NH3, and SiH4, while its effects were negligible in the Si system.

  9. Probing the binding sites and the effect of berbamine on the structure of bovine serum albumin

    NASA Astrophysics Data System (ADS)

    Cheng, Xiao-Xia; Lui, Yi; Zhou, Bo; Xiao, Xiao-He; Liu, Yi

    2009-06-01

    Berbamine, a naturally occurring isoquinoline alkaloid extracted from Berberis sp., is the active constituent of some Chinese herbal medicines and exhibits a variety of pharmacological activities. The effects of berbamine on the structure of bovine serum albumin (BSA) were investigated by circular dichroism, fluorescence and absorption spectroscopy under physiological conditions. Berbamine caused a static quenching of the intrinsic fluorescence of BSA, and the quenching data were analyzed by application of the Stern-Volmer equation. There was a single primary berbamine-binding site on BSA with a binding constant of 2.577 × 10 4 L mol -1 at 298 K. The thermodynamic parameters, enthalpy change (Δ H0) and entropy change (Δ S0) for the reaction were -76.5 kJ mol -1 and -173.4 J mol -1 K -1 according to the van't Hoff equation. The results showed that the hydrogen bond and van der Waals interaction were the predominant forces in the binding process. Competitive experiments revealed a displacement of warfarin by berbamine, indicating that the binding site was located at Drug sites I. The distance r between the donor (BSA) and the acceptor (berbamine) was obtained according to the Förster non-radiation energy transfer theory. The results of three-dimensional fluorescence spectra, UV-vis absorption difference spectra and circular dichroism of BSA in the presence of berbamine showed that the conformation of BSA was changed. The results provide a quantitative understanding of the effect of berbamine on the structure of bovine serum albumin, providing a useful guideline for further drug design.

  10. Sulfamate proton solvent exchange in heparin oligosaccharides: evidence for a persistent hydrogen bond in the antithrombin-binding pentasaccharide Arixtra.

    PubMed

    Langeslay, Derek J; Young, Robert P; Beni, Szabolcs; Beecher, Consuelo N; Mueller, Leonard J; Larive, Cynthia K

    2012-09-01

    Sulfamate groups (NHSO(3)(-)) are important structural elements in the glycosaminoglycans (GAGs) heparin and heparan sulfate (HS). In this work, proton nuclear magnetic resonance (NMR) line-shape analysis is used to explore the solvent exchange properties of the sulfamate NH groups within heparin-related mono-, di-, tetra- and pentasaccharides as a function of pH and temperature. The results of these experiments identified a persistent hydrogen bond within the Arixtra (fondaparinux sodium) pentasaccharide between the internal glucosamine sulfamate NH and the adjacent 3-O-sulfo group. This discovery provides new insights into the solution structure of the Arixtra pentasaccharide and suggests that 3-O-sulfation of the heparin N-sulfoglucosamine (GlcNS) residues pre-organize the secondary structure in a way that facilitates binding to antithrombin-III. NMR studies of the GlcNS NH groups can provide important information about heparin structure complementary to that available from NMR spectral analysis of the carbon-bound protons. PMID:22593556

  11. Effects of N-acetylimidazole on oxytocin binding in bovine mammary tissue

    SciTech Connect

    Zhao, X.; Gorewit, R.C.; Currie, W.B. )

    1990-01-01

    The effects of N-acetylimidazole on specific binding of oxytocin to microsomal fractions of bovine mammary gland were studied. N-acetylimidazole suppressed oxytocin binding, with time and concentration dependence. Decreased oxytocin binding activity appeared to be due to decreased affinity of the hormone for its receptor. Acetylation of oxytocin, rather than of oxytocin receptors, seemed to be responsible for the decreased binding.

  12. Origin of reverse annealing effect in hydrogen-implanted silicon

    SciTech Connect

    Di, Zengfeng; Nastasi, Michael A; Wang, Yongqiang

    2009-01-01

    In contradiction to conventional damage annealing, thermally annealed H-implanted Si exhibits an increase in damage or reverse annealing behavior, whose mechanism has remained elusive. On the basis of quantitative high resolution transmission electron microscopy combined with channeling Rutherford backscattering analysis, we conclusively elucidate that the reverse annealing effect is due to the nucleation and growth of hydrogen-induce platelets. Platelets are responsible for an increase in the height and width the channeling damage peak following increased isochronal anneals.

  13. Origin of reverse annealing effect in hydrogen-implanted silicon

    SciTech Connect

    Di, Z. F.; Wang, Y. Q.; Nastasi, M.; Theodore, N. David

    2010-04-12

    In contradiction to conventional damage annealing, thermally annealed H-implanted Si exhibits an increase in damage or reverse annealing behavior, whose mechanism has remained elusive. In this work, we conclusively elucidate that the reverse annealing effect is due to the nucleation and growth of hydrogen-induced platelets. Platelets are responsible for an increase in the height and width of the channeling damage peak following increased isochronal anneals.

  14. Evidence for separate substrate binding sites for hydrogen peroxide and cumene hydroperoxide (CHP) in the oxidation of ethanol by catalase

    SciTech Connect

    DeMaster, E.G.; Nagasawa,ss H.T.

    1986-03-01

    The oxidation of ethanol by purified bovine liver catalase (Sigma, C-40) can be supported by H/sub 2/O/sub 2/ or by CHP. The time course of the H/sub 2/O/sub 2/ supported reaction (using glucose/glucose oxidase as the H/sub 2/O/sub 2/ source) was linear for at least one hr, whereas the rate of acetaldehyde formation in the CHP (4.2 mM) supported reaction decreased with time. When catalase was exposed o CHP for 5 min before the addition of ethanol, the rate of CHP supported ethanol oxidation was reduced by more than 90% compared to incubations where the addition of ethanol preceded that of CHP. In the CHP inhibited state, the peroxidative activity of catalase was not restored by further addition of CHP or ethanol; however, addition of fresh catalase yielded its expected activity. Significantly, the CHP inhibited enzyme was equally effective as the untreated enzyme in catalyzing (a) the oxidation of ethanol in the presence H/sub 2/O/sub 2/ supported peroxidative activity as well as catalytic activity by CHP inhibited catalase points to separate binding sites for H/sub 2/O/sub 2/ and CHP in this reaction. Alternatively, CHP may bind adjacent to a common peroxide active site, thereby sterically impeding the binding of CHP - but not of H/sub 2/O/sub 2/ - to this active site.

  15. Effect of fullerenol surface chemistry on nanoparticle binding-induced protein misfolding

    NASA Astrophysics Data System (ADS)

    Radic, Slaven; Nedumpully-Govindan, Praveen; Chen, Ran; Salonen, Emppu; Brown, Jared M.; Ke, Pu Chun; Ding, Feng

    2014-06-01

    Fullerene and its derivatives with different surface chemistry have great potential in biomedical applications. Accordingly, it is important to delineate the impact of these carbon-based nanoparticles on protein structure, dynamics, and subsequently function. Here, we focused on the effect of hydroxylation -- a common strategy for solubilizing and functionalizing fullerene -- on protein-nanoparticle interactions using a model protein, ubiquitin. We applied a set of complementary computational modeling methods, including docking and molecular dynamics simulations with both explicit and implicit solvent, to illustrate the impact of hydroxylated fullerenes on the structure and dynamics of ubiquitin. We found that all derivatives bound to the model protein. Specifically, the more hydrophilic nanoparticles with a higher number of hydroxyl groups bound to the surface of the protein via hydrogen bonds, which stabilized the protein without inducing large conformational changes in the protein structure. In contrast, fullerene derivatives with a smaller number of hydroxyl groups buried their hydrophobic surface inside the protein, thereby causing protein denaturation. Overall, our results revealed a distinct role of surface chemistry on nanoparticle-protein binding and binding-induced protein misfolding.Fullerene and its derivatives with different surface chemistry have great potential in biomedical applications. Accordingly, it is important to delineate the impact of these carbon-based nanoparticles on protein structure, dynamics, and subsequently function. Here, we focused on the effect of hydroxylation -- a common strategy for solubilizing and functionalizing fullerene -- on protein-nanoparticle interactions using a model protein, ubiquitin. We applied a set of complementary computational modeling methods, including docking and molecular dynamics simulations with both explicit and implicit solvent, to illustrate the impact of hydroxylated fullerenes on the structure and

  16. Effect of hydrogen bonding and complexation with metal ions on the fluorescence of luotonin A.

    PubMed

    Miskolczy, Zsombor; Biczók, László

    2013-05-01

    Fluorescence characteristics of a biologically active natural alkaloid, luotonin A (LuA), were studied by steady-state and time-resolved spectroscopic methods. The rate constant of the radiationless deactivation from the singlet-excited state diminished by more than one order of magnitude when the solvent polarity was changed from toluene to water. Dual emission was found in polyfluorinated alcohols of large hydrogen bond donating ability due to photoinitiated proton displacement along the hydrogen bond. In CH2Cl2, LuA produced both 1 : 1 and 1 : 2 hydrogen-bonded complexes with hexafluoro-2-propanol (HFIP) in the ground state. Photoexcitation of the 1 : 2 complex led to protonated LuA, whose fluorescence appeared at a long wavelength. LuA served as a bidentate ligand forming 1 : 1 complexes with metal ions in acetonitrile. The stability of the complexes diminished in the series of Cd(2+) > Zn(2+) > Ag(+), and upon competitive binding of water to the metal cations. The effect of chelate formation on the fluorescent properties was revealed. PMID:23487318

  17. Effects of hydrogen atom spin exchange collisions on atomic hydrogen maser oscillation frequency

    NASA Technical Reports Server (NTRS)

    Crampton, S. B.

    1979-01-01

    Frequency shifts due to collisions between hydrogen atoms in an atomic hydrogen maser frequency standard are studied. Investigations of frequency shifts proportional to the spin exchange frequency shift cross section and those proportional to the duration of exchange collisions are discussed. The feasibility of operating a hydrogen frequency standard at liquid helium temperatures is examined.

  18. Critical Research for Cost-Effective Photoelectrochemical Production of Hydrogen

    SciTech Connect

    Xu, Liwei; Deng, Xunming; Abken, Anka; Cao, Xinmin; Du, Wenhui; Vijh, Aarohi; Ingler, William; Chen, Changyong; Fan, Qihua; Collins, Robert; Compaan, Alvin; Yan, Yanfa; Giolando, Dean; Turner, John

    2014-10-29

    The objective of this project is to develop critical technologies required for cost-effective production of hydrogen from sunlight and water using a-Si triple junction solar cell based photo-electrodes. In this project, Midwest Optoelectronics, LLC (MWOE) and its collaborating organizations utilize triple junction a-Si thin film solar cells as the core element to fabricate photoelectrochemical (PEC) cells. Triple junction a-Si/a-SiGe/a-SiGe solar cell is an ideal material for making cost-effective PEC system which uses sun light to split water and generate hydrogen. It has the following key features: 1) It has an open circuit voltage (Voc ) of ~ 2.3V and has an operating voltage around 1.6V. This is ideal for water splitting. There is no need to add a bias voltage or to inter-connect more than one solar cell. 2) It is made by depositing a-Si/a-SiGe/aSi-Ge thin films on a conducting stainless steel substrate which can serve as an electrode. When we immerse the triple junction solar cells in an electrolyte and illuminate it under sunlight, the voltage is large enough to split the water, generating oxygen at the Si solar cell side (for SS/n-i-p/sunlight structure) and hydrogen at the back, which is stainless steel side. There is no need to use a counter electrode or to make any wire connection. 3) It is being produced in large rolls of 3ft wide and up to 5000 ft long stainless steel web in a 25MW roll-to-roll production machine. Therefore it can be produced at a very low cost. After several years of research with many different kinds of material, we have developed promising transparent, conducting and corrosion resistant (TCCR) coating material; we carried out extensive research on oxygen and hydrogen generation catalysts, developed methods to make PEC electrode from production-grade a-Si solar cells; we have designed and tested various PEC module cases and carried out extensive outdoor testing; we were able to obtain a solar to hydrogen conversion efficiency (STH

  19. Hydrogenated amorphous silicon formation by flux control and hydrogen effects on the growth mechanism

    NASA Astrophysics Data System (ADS)

    Toyoda, H.; Sugai, H.; Kato, K.; Yoshida, A.; Okuda, T.

    1986-06-01

    The composition of particle flux to deposit hydrogenated amorphous silicon films in a glow discharge is controlled by a combined electrostatic-magnetic deflection technique. As a result, the films are formed firstly without hydrogen ion flux, secondly by neutral flux only, and thirdly by all species fluxes. Comparison of these films reveals the significant role of hydrogen in the surface reactions. Hydrogen breaks the Si-Si bond, decreases the sticking probability of the Si atom, and replaces the SiH bond by a SiH2 bond to increase the hydrogen content of the films.

  20. Inhibitory heterotrimeric GTP-binding proteins inhibit hydrogen peroxide-induced apoptosis by up-regulation of Bcl-2 via NF-{kappa}B in H1299 human lung cancer cells

    SciTech Connect

    Seo, Mi Ran; Nam, Hyo-Jung; Kim, So-Young; Juhnn, Yong-Sung

    2009-04-03

    Inhibitory heterotrimeric GTP-binding proteins (Gi proteins) mediate a variety of signaling pathways by coupling receptors and effectors to regulate cellular proliferation, differentiation, and apoptosis. However, the role of Gi proteins in the modulation of hydrogen peroxide-induced apoptosis is not clearly understood. Thus, we investigated the effect of Gi proteins on hydrogen peroxide-induced apoptosis and the underlying mechanisms in H1299 human lung cancer cells. The stable expression of constitutively active alpha subunits of Gi1 (G{alpha}i1QL), Gi2, or Gi3 inhibited hydrogen peroxide-induced apoptosis. The expression of G{alpha}i1QL up-regulated Bcl-2 expression, and the knockdown of Bcl-2 with siRNA abolished the anti-apoptotic effect of G{alpha}i1QL. G{alpha}i1 induced the transcription of Bcl-2 by activation of NF-{kappa}B, which resulted from an increase in NF-{kappa}B p50 protein. We conclude that G{alpha}i1 inhibits hydrogen peroxide-induced apoptosis of H1299 lung cancer cells by up-regulating the transcription of Bcl-2 through a p50-mediated NF-{kappa}B activation.

  1. Fully quantum mechanical calculation of the diffusivity of hydrogen in iron using the tight-binding approximation and path integral theory

    NASA Astrophysics Data System (ADS)

    Katzarov, Ivaylo H.; Pashov, Dimitar L.; Paxton, Anthony T.

    2013-08-01

    We present calculations of free energy barriers and diffusivities as functions of temperature for the diffusion of hydrogen in α-Fe. This is a fully quantum mechanical approach since the total energy landscape is computed using a self-consistent, transferable tight binding model for interstitial impurities in magnetic iron. Also the hydrogen nucleus is treated quantum mechanically and we compare here two approaches in the literature both based in the Feynman path integral formulation of statistical mechanics. We find that the quantum transition state theory which admits greater freedom for the proton to explore phase space gives result in better agreement with experiment than the alternative which is based on fixed centroid calculations of the free energy barrier. This will have an impact on future modeling and the simulation of hydrogen trapping and diffusion.

  2. Hydrogen Peroxide as an Effective Disinfectant for Pasteurella multocida

    PubMed Central

    Jung, In-Soo; Kim, Hyun-Jung; Jung, Won-Yong

    2014-01-01

    Pasteurella multocida (P. multocida) infections vary widely, from local infections resulting from animal bites and scratches to general infections. As of yet, no vaccine against P. multocida has been developed, and the most effective way to prevent pathogenic transmission is to clean the host environment using disinfectants. In this study, we identified which disinfectants most effectively inhibited environmental isolates of P. multocida. Three readily available disinfectants were compared: 3% hydrogen peroxide (HP), 70% isopropyl alcohol, and synthetic phenol. In suspension tests and zone inhibition tests, 3% HP was the most promising disinfectant against P. multocida. PMID:24954350

  3. High performance hydrogen-terminated diamond field effect transistors

    NASA Astrophysics Data System (ADS)

    Russell, Stephen A. O.

    Diamond provides extreme properties which make it suitable as a new substrate material for high performance electronics. It has the potential to provide both high frequency and high power performance while operating in extreme environments such as elevated temperature or exposed to corrosive chemicals or radiation. Research to date has shown the potential of diamond for this purpose with hydrogen-terminated diamond surface channel transistors already showing promise in terms of high frequency operation. The inherent instability of using atmospheric molecules to induce a p-type doping at this hydrogen-terminated diamond surface has so far limited power performance and robustness of operation. This work reports upon the scaling of surface channel hydrogen-terminated transistors with FET gate lengths of 250 nm and 120 nm showing performance comparable to other devices published to date. The gate length was then scaled for the first time to sub-100 nm dimensions with a 50 nm gate length FET fabricated giving record high-frequency performance with a fT of 53 GHz. An adapted fabrication procedure was developed for this project with special attention paid to the volatility of the particles upon the diamond surface. Equivalent RF circuit models were extracted for each gate length and analysed in detail. Work was then undertaken to investigate a more stable alternative to the atmospheric induced doping effect with alternative electron accepting materials being deposited upon the hydrogen-terminated diamond surface. The as yet untested organic material F16CuPc was deposited on to hydrogen-terminated diamond and demonstrated its ability to encapsulate and preserve the atmospheric induced sub-surface conductivity at room temperature. For the first time an inorganic material was also investigated as a potential encapsulation for the hydrogen-terminated diamond surface, MoO3 was chosen due to its high electron affinity and like F16CuPc also showed the ability to preserve and

  4. Binding profiles and cytokine-inducing effects of fish rhamnose-binding lectins on Burkitt's lymphoma Raji cells.

    PubMed

    Hosono, Masahiro; Sugawara, Shigeki; Matsuda, Atsushi; Tatsuta, Takeo; Koide, Yasuhiro; Hasan, Imtiaj; Hasan, Imtiaji; Ozeki, Yasuhiro; Nitta, Kazuo

    2014-10-01

    Rhamnose-binding lectin (RBL) is one of the animal lectin categories which take part in the innate immune responses of fish. Osmerus lanceolatus lectin (OLL) from shishamo smelt eggs is an RBL composed of two tandem-repeated domains, both of which are considered to be a carbohydrate-recognition domain. SAL, catfish (Silurus asotus) egg RBL composed of three domains, binds to Burkitt's lymphoma Raji cells through globotriaosylceramide (Gb3) carbohydrate chain and to reduce cell size and growth by altering membrane composition without causing cell death. In this experiment, we tried to compare the binding effects of these two RBLs on Raji cells. Flow cytometric and fluorescence microscopic analyses revealed that OLL also directly bound to and shrunk Raji cells with ten times less reactivity than SAL but reduced cell growth with decreasing cell viability. Anti-Gb3 antibody completely blocked the binding of SAL to Raji cells but not that of OLL. In addition, the direct bindings of OLL and SAL to Raji cells were comparably inhibited by melibiose, but lactose was more effective inhibitor for the binding of OLL than that of SAL. These results suggest that OLL has slightly different cell-binding property compared with SAL and binds not only to Gb3 but also to the other carbohydrate receptor-bearing β-galactoside chains. The quantitative RT-PCR analysis revealed that SAL induced the expression of TNF-α but not of IFN-γ, IL-1β, and IL-10. Thus, SAL-induced cytostatic effect on Raji cells might be partially caused by TNF-α-mediated signaling pathway. PMID:24861899

  5. Effect of ethanol on hydrogen peroxide-induced AMPK phosphorylation

    PubMed Central

    Liangpunsakul, Suthat; Wou, Sung-Eun; Zeng, Yan; Ross, Ruth A.; Jayaram, Hiremagalur N.; Crabb, David W.

    2008-01-01

    AMP-activated protein kinase (AMPK) responds to oxidative stress. Previous work has shown that ethanol treatment of cultured hepatoma cells and of mice inhibited the activity of AMPK and reduced the amount of AMPK protein. Ethanol generates oxidative stress in the liver. Since AMPK is activated by reactive oxygen species, it seems paradoxical that ethanol would inhibit AMPK in the hepatoma cells. In an attempt to understand the mechanism whereby ethanol inhibits AMPK, we studied the effect of ethanol on AMPK activation by exogenous hydrogen peroxide. The effects of ethanol, hydrogen peroxide, and inhibitors of protein phosphatase 2A (PP2A) [either okadaic acid or PP2A small interference RNA (siRNA)] on AMPK phosphorylation and activity were examined in rat hepatoma cells (H4IIEC3) and HeLa cells. In H4IIEC3 cells, hydrogen peroxide (H2O2, 1 mM) transiently increased the level of phospho-AMPK to 1.5-fold over control (P < 0.05). Similar findings were observed in HeLa cells, which do not express the upstream AMPK kinase, LKB1. H2O2 markedly increased the phosphorylation of LKB1 in H4IIEC3 cells. Ethanol significantly inhibited the phosphorylation of PKC-ζ, LKB1, and AMPK caused by exposure to H2O2. This inhibitory effect of ethanol required its metabolism. More importantly, the inhibitory effects of ethanol on H2O2-induced AMPK phosphorylation were attenuated by the presence of the PP2A inhibitor, okadaic acid, or PP2A siRNA. The inhibitory effect of ethanol on AMPK phosphorylation is exerted through the inhibition of PKC-ζ and LKB1 phosphorylation and the activation of PP2A. PMID:18832448

  6. Effect on influenza hemagglutinin protein binding with neutralizing antibody using terahertz spectroscopy technology

    NASA Astrophysics Data System (ADS)

    Sun, Yiwen; Zhong, Junlan; Zuo, Jian; Zhang, Cunlin

    2014-11-01

    Terahertz spectroscopy is sensitive to probe several aspects of biological systems. We have reported the terahertz dielectric spectrum is able to identify the type of the charges in the hydrogen-bonded antibodies' networks in our previous work. Recently we demonstrate a highly sensitive THz-TDS method to monitor binding interaction of influenza hemagglutinin (HA) against its target antibody F10. The terahertz dielectric properties of HA was strongly affected by the presence of a specific antibody. Protein solution concentration or even molecular binding interaction can also affect the terahertz signal. This enables us to detect the specificity and sensitivity of antibody-antigen binding under THz radiation.

  7. Warm Pressurant Gas Effects on the Liquid Hydrogen Bubble Point

    NASA Technical Reports Server (NTRS)

    Hartwig, Jason W.; McQuillen, John B.; Chato, David J.

    2013-01-01

    This paper presents experimental results for the liquid hydrogen bubble point tests using warm pressurant gases conducted at the Cryogenic Components Cell 7 facility at the NASA Glenn Research Center in Cleveland, Ohio. The purpose of the test series was to determine the effect of elevating the temperature of the pressurant gas on the performance of a liquid acquisition device. Three fine mesh screen samples (325 x 2300, 450 x 2750, 510 x 3600) were tested in liquid hydrogen using cold and warm noncondensible (gaseous helium) and condensable (gaseous hydrogen) pressurization schemes. Gases were conditioned from 0 to 90 K above the liquid temperature. Results clearly indicate a degradation in bubble point pressure using warm gas, with a greater reduction in performance using condensable over noncondensible pressurization. Degradation in the bubble point pressure is inversely proportional to screen porosity, as the coarsest mesh demonstrated the highest degradation. Results here have implication on both pressurization and LAD system design for all future cryogenic propulsion systems. A detailed review of historical heated gas tests is also presented for comparison to current results.

  8. Effect of temperature on layer separation by plasma hydrogenation

    SciTech Connect

    Di, Z. F.; Wang, Y. Q.; Nastasi, M.; Rossi, F.; Shao, L.; Thompson, P. E.

    2008-12-22

    We have studied hydrogen diffusion in plasma hydrogenated Si/SiGe/Si heterostructure at different temperatures. At low temperature, intrinsic point defects in the molecular beam epitaxy grown Si capping layer are found to compete with the buried strain SiGe layer for hydrogen trapping. The interaction of hydrogen with point defects affects the hydrogen long-range diffusion, and restricts the amount of hydrogen available for trapping by the SiGe layer. However, hydrogen trapping by the capping layer is attenuated with increasing hydrogenation temperature allowing more hydrogen to be trapped in the strain SiGe layer with subsequent surface blister formation. A potential temperature window for plasma hydrogenation induced layer separation is identified based on the combined considerations of trap-limited diffusion at low temperature and outdiffusion of H{sub 2} molecule together with the dissociation of Si-H bonds inside of H platelet at high temperature.

  9. Effect of temperature on layer separation by plasma-hydrogenation

    SciTech Connect

    Di, Zengfeng; Michael, Nastasi A; Wang, Yongqiang

    2008-01-01

    We have studied hydrogen diffusion in plasma hydrogenated Si/SiGe/Si heterostructure at different temperatures. At low temperature, intrinsic point defects in the molecular beam epitaxy grown Si capping layer are found to compete with the buried strain SiGe layer for hydrogen trapping. The interaction of hydrogen with point defects affects the hydrogen long-range diffusion, and restricts the amount of hydrogen available for trapping by the SiGe layer. However, hydrogen trapping by the capping layer is attenuated with increasing hydrogenation temperature allowing more hydrogen to be trapped in the strain SiGe layer with subsequent surface blister formation. A potential temperature window for plasma hydrogenation induced layer separation is identified based on the combined considerations of trap-limited diffusion at low temperature and outdiffusion of H{sub 2} molecule together with the dissociation of Si-H bonds inside of H platelet at high temperature.

  10. Feasibility and induced effects of subsurface porous media hydrogen storage

    NASA Astrophysics Data System (ADS)

    Tilmann Pfeiffer, Wolf; Li, Dedong; Wang, Bo; Bauer, Sebastian

    2015-04-01

    Fluctuations in energy production from renewable sources like wind or solar power can lead to shortages in energy supply which can be mitigated using energy storage concepts. Underground storage of hydrogen in porous sandstone formations could be a storage option for large amounts of energy over long storage cycles. However, this use of the subsurface requires an analysis of possible interactions with other uses of the subsurface such as geothermal energy storage or groundwater abstraction. This study aims at quantifying the feasibility of porous media hydrogen storage to provide stored energy on a timescale of several days to weeks as well as possible impacts on the subsurface. The hypothetical storage site is based on an anticlinal structure located in Schleswig-Holstein, northern Germany. The storage is injected and extracted using five wells completed in a partially eroded, heterogeneous sandstone layer in the top of the structure at a depth of about 500 m. The storage formation was parameterized based on a local facies model with intrinsic permeabilities of 250-2500 mD and porosities of 35-40%. Storage initialization and subsequent storage cycles, each consisting of a hydrogen injection and extraction, were numerically simulated. The simulation results indicate the general feasibility of this hydrogen storage concept. The simulated sandstone formation is able to provide an average of around 1480 t of hydrogen per week (1830 TJ) which is about 5% of the total weekly energy production or about 10% of the weekly energy consumption of Schleswig-Holstein with the hydrogen production rate being the limiting factor of the overall performance. Induced hydraulic effects are a result of the induced overpressure within the storage formation. Propagation of the pressure signal does not strongly depend on the formation heterogeneity and thus shows approximately radial characteristics with one bar pressure change in distances of about 5 km from the injection wells. Thermal

  11. HYDROGEN EFFECTS ON STRAIN-INDUCED MARTENSITE FORMATION IN TYPE 304L STAINLESS STEEL

    SciTech Connect

    Morgan, M; Ps Lam, P

    2008-12-11

    Unstable austenitic stainless steels undergo a strain-induced martensite transformation. The effect of hydrogen on this transformation is not well understood. Some researchers believe that hydrogen makes the transformation to martensite more difficult because hydrogen is an austenite stabilizer. Others believe that hydrogen has little or no effect at all on the transformation and claim that the transformation is simply a function of strain and temperature. Still other researchers believe that hydrogen should increase the ability of the metal to transform due to hydrogen-enhanced dislocation mobility and slip planarity. While the role of hydrogen on the martensite transformation is still debated, it has been experimentally verified that this transformation does occur in hydrogen-charged materials. What is the effect of strain-induced martensite on hydrogen embrittlement? Martensite near crack-tips or other highly strained regions could provide much higher hydrogen diffusivity and allow for quicker hydrogen concentration. Martensite may be more intrinsically brittle than austenite and has been shown to be severely embrittled by hydrogen. However, it does not appear to be a necessary condition for embrittlement since Type 21-6-9 stainless steel is more stable than Type 304L stainless steel but susceptible to hydrogen embrittlement. In this study, the effect of hydrogen on strain-induced martensite formation in Type 304L stainless steel was investigated by monitoring the formation of martensite during tensile tests of as-received and hydrogen-charged samples and metallographically examining specimens from interrupted tensile tests after increasing levels of strain. The effect of hydrogen on the fracture mechanisms was also studied by examining the fracture features of as-received and hydrogen-charged specimens and relating them to the stress-strain behavior.

  12. Substituent Effects on the Binding of Halides by Neutral and Dicationic Bis(triazolium) Receptors.

    PubMed

    Nepal, Binod; Scheiner, Steve

    2015-12-31

    The effects of substituent and overall charge upon the binding of a halide anion by a bis(triazolium) receptor are studied by M06-2X DFT calculations, with the aug-cc-pVDZ basis set. Comparison is also made between a receptor that engages in H-bonds, with a halogen-bonding species. Fluoride is clearly most strongly bound, followed by Cl(-), Br(-), and I(-) in that order. The dicationic receptor engages in stronger complexes, but not by a very wide margin compared to its neutral counterpart. The binding is enhanced as the substituent on the two triazolium rings becomes progressively more electron-withdrawing. Halogen-substituted receptors, whether neutral or cationic, display a greater sensitivity to substituent than do their H-bonding counterparts. Both Coulombic and charge transfer factors obey the latter trends but do not correctly reproduce the stronger halogen vs hydrogen bonding. Both H-bonds and halogen bonds are nearly linear within the complexes, due in part to bond rotations within the receptor that bring the two triazole rings closer to coplanarity with the central benzene ring. PMID:26645536

  13. Effect of fullerenol surface chemistry on nanoparticle binding-induced protein misfolding.

    PubMed

    Radic, Slaven; Nedumpully-Govindan, Praveen; Chen, Ran; Salonen, Emppu; Brown, Jared M; Ke, Pu Chun; Ding, Feng

    2014-07-21

    Fullerene and its derivatives with different surface chemistry have great potential in biomedical applications. Accordingly, it is important to delineate the impact of these carbon-based nanoparticles on protein structure, dynamics, and subsequently function. Here, we focused on the effect of hydroxylation - a common strategy for solubilizing and functionalizing fullerene - on protein-nanoparticle interactions using a model protein, ubiquitin. We applied a set of complementary computational modeling methods, including docking and molecular dynamics simulations with both explicit and implicit solvent, to illustrate the impact of hydroxylated fullerenes on the structure and dynamics of ubiquitin. We found that all derivatives bound to the model protein. Specifically, the more hydrophilic nanoparticles with a higher number of hydroxyl groups bound to the surface of the protein via hydrogen bonds, which stabilized the protein without inducing large conformational changes in the protein structure. In contrast, fullerene derivatives with a smaller number of hydroxyl groups buried their hydrophobic surface inside the protein, thereby causing protein denaturation. Overall, our results revealed a distinct role of surface chemistry on nanoparticle-protein binding and binding-induced protein misfolding. PMID:24934397

  14. Effect of quantum nuclear motion on hydrogen bonding

    SciTech Connect

    McKenzie, Ross H. Bekker, Christiaan; Athokpam, Bijyalaxmi; Ramesh, Sai G.

    2014-05-07

    This work considers how the properties of hydrogen bonded complexes, X–H⋯Y, are modified by the quantum motion of the shared proton. Using a simple two-diabatic state model Hamiltonian, the analysis of the symmetric case, where the donor (X) and acceptor (Y) have the same proton affinity, is carried out. For quantitative comparisons, a parametrization specific to the O–H⋯O complexes is used. The vibrational energy levels of the one-dimensional ground state adiabatic potential of the model are used to make quantitative comparisons with a vast body of condensed phase data, spanning a donor-acceptor separation (R) range of about 2.4 − 3.0 Å, i.e., from strong to weak hydrogen bonds. The position of the proton (which determines the X–H bond length) and its longitudinal vibrational frequency, along with the isotope effects in both are described quantitatively. An analysis of the secondary geometric isotope effect, using a simple extension of the two-state model, yields an improved agreement of the predicted variation with R of frequency isotope effects. The role of bending modes is also considered: their quantum effects compete with those of the stretching mode for weak to moderate H-bond strengths. In spite of the economy in the parametrization of the model used, it offers key insights into the defining features of H-bonds, and semi-quantitatively captures several trends.

  15. Effect of ECM Stiffness on Integrin-Ligand Binding Strength

    NASA Astrophysics Data System (ADS)

    Thomas, Gawain; Wen, Qi

    2014-03-01

    Many studies have shown that cells respond to the stiffness of their extracellular matrix (ECM). However, the mechanism of this stiffness sensing is not fully understood. We believe that cells probe stiffness by applying intracellular force to the ECM via the integrin-mediated adhesions. The linkage of integrins to the cytoskeleton has been modeled as a slip clutch, which has been shown to affect focal adhesion formation and hence force transmission in a stiffness dependent manner. In contrast, the bonds between integrins and ECM have been characterized as ``catch bonds.'' It is unclear how ECM viscoelasticity affects these catch bonds. We report, for the first time, the effects of ECM stiffness on the binding strength of integrins to ECM ligands by measuring the rupture force of individual integrin-ligand bonds of cells on collagen-coated polyacrylamide gels. Results show that the integrin-collagen bonds of 3T3 fibroblasts are nearly four times stronger on a stiff (30 kPa) gel than on a soft (3 kPa) gel. The stronger integrin bonds on stiffer substrates can promote focal adhesion formation. This suggests that the substrate stiffness regulates the cell-ECM adhesions not only by affecting the cytoskeleton-integrin links but also by modulating the binding of integrins to the ECM.

  16. Investigating binding particles distribution effects on polymer translocation through nanopore

    NASA Astrophysics Data System (ADS)

    Haji Abdolvahab, Rouhollah

    2016-03-01

    Chaperone driven polymer translocation is an important model for biopolymer's translocation in vivo. Binding proteins spatial distribution is a significant factor in calculating the translocation time of the polymer in this type of translocation. Here using a dynamical Monte Carlo simulation we compare the results of the usual uniform distribution with the exponential distribution of different rates for a stiff polymer. Our simulation results show that just by changing the chaperones spatial distribution the translocation time of the biopolymer will change by as large as an order. It can change the translocation regime of the polymer completely from a diffusive to a ballistic one. Although generally increasing the exponential rate and the background concentration will increase the translocation velocity, it is not always true and one should consider both the sequence and the background concentration. We show that the results depend on the sequence and changing the distribution rates for increasing the translocation velocity will change the whole Probability Density Function (PDF) of the polymer translocation time accordance to its sequence. The translocation time sequence dependency will change in the extreme cases e.g. in the high exponential rate. Investigating the binding protein size, λ, also shows the importance of the so called parking lot effect in distribution dependency of the translocation velocity. Although there is not any important dependency for λ = 1, translocation time depends clearly on the chaperone spatial distribution for the case of λ ≥ 2.

  17. Effect of aeration of sediment on cadmium binding

    SciTech Connect

    Zhuang, Y.; Allen, H.E.; Fu, G. . Dept. of Civil Engineering)

    1994-05-01

    Acid-volatile sulfide (AVS) has been shown to be the dominant phase reacting with metals in anoxic sediments. The AVS in sediment decreases upon resuspension due to storm and dredging, and in winter when the rate of aeration processes exceeds that of the formation of sulfide. The authors conducted a series of lab aeration experiments in batch reactors to investigate the effects of aeration of sediment on the sulfide content of sediment and on the partitioning of cadmium, a model toxic metal, to the sediment. Aeration of sediment results in rapid decrease of the AVS. The authors studied the sediment characteristics for aeration periods of approximately a month. During this time, the concentrations of dissolved metals increased by 200 to 400% or more, relative to the concentrations present at the beginning of the test. The concentration of metal associated with AVS and with pyrite decreased. During the aeration, there are increases in the concentrations of hydrous iron and manganese oxides, and these materials become increasingly more important in the binding of cadmium. Following the aeration, > 50% of the cadmium was associated with the extractable iron and manganese components of the sediment. Overall, the binding capacity of the sediments for cadmium decreased after aeration.

  18. Pharmacological effects and binding studies of new methylxanthine thioderivatives.

    PubMed

    Ragazzi, E; Froldi, G; Santi Soncin, E; Borea, P A; Fassina, G

    1989-01-01

    The effects of two methylxanthine derivatives, 6-thiocaffeine (TC) and 6-thiotheophylline (TT), were investigated in different in vitro and in vivo conditions. On guinea-pig isolated trachea, both TC and TT showed a relaxant effect (EC50 50 microM and 60 microM, respectively), more potent than theophylline (300 microM). In guinea-pig isolated atria TC (30-50 microM) was able to antagonize R-PIA (a stable agonist on adenosine receptors) negative effect in not a clearly competitive way. Higher concentration (100 microM) began to reverse that inhibitory effect. In vitro Ki of TC and TT for A1 and A2 adenosine receptors was intermediate in comparison to caffeine and theophylline. On the contrary, the two thioderivatives showed a higher affinity for [3H]-nitrendipine binding sites, in comparison to the original methylxanthines. All these data suggest a complex mechanism of action, probably at the level of adenosine extracellular receptors and L-type Ca2+ channels. In vivo experiments in mice provided evidence for a lack of CNS stimulant effects, but a loss of motor coordination was observed. Both thioderivatives showed a reduced acute toxicity. These data can be useful for the development of drugs for the therapy of asthma with reduced side effects. PMID:2560547

  19. Inhibitory Effect of Bridged Nucleosides on Thermus aquaticus DNA Polymerase and Insight into the Binding Interactions

    PubMed Central

    Kim, Sung-Kun; Castro, Aaron; Kim, Edward S.; Dinkel, Austin P.; Liu, Xiaoyun; Castro, Miguel

    2016-01-01

    Modified nucleosides have the potential to inhibit DNA polymerases for the treatment of viral infections and cancer. With the hope of developing potent drug candidates by the modification of the 2’,4’-position of the ribose with the inclusion of a bridge, efforts were focused on the inhibition of Taq DNA polymerase using quantitative real time PCR, and the results revealed the significant inhibitory effects of 2’,4’-bridged thymidine nucleoside on the polymerase. Study on the mode of inhibition revealed the competitive mechanism with which the 2’,4’-bridged thymidine operates. With a Ki value of 9.7 ± 1.1 μM, the 2’,4’-bridged thymidine proved to be a very promising inhibitor. Additionally, docking analysis showed that all the nucleosides including 2’,4’-bridged thymidine were able to dock in the active site, indicating that the substrate analogs reflect a structural complementarity to the enzyme active site. The analysis also provided evidence that Asp610 was a key binding site for 2’,4’-bridged thymidine. Molecular dynamics (MD) simulations were performed to further understand the conformational variations of the binding. The root-mean-square deviation (RMSD) values for the peptide backbone of the enzyme and the nitrogenous base of the inhibitor stabilized within 0.8 and 0.2 ns, respectively. Furthermore, the MD analysis indicates substantial conformational change in the ligand (inhibitor) as the nitrogenous base rotated anticlockwise with respect to the sugar moiety, complemented by the formation of several new hydrogen bonds where Arg587 served as a pivot axis for binding formation. In conclusion, the active site inhibition of Taq DNA polymerase by 2’,4’-bridged thymidine suggests the potential of bridged nucleosides as drug candidates. PMID:26820310

  20. Energetics of hydrogen storage in organolithium nanostructures

    SciTech Connect

    Namilae, Sirish; Fuentes-Cabrera, Miguel A; Radhakrishnan, Balasubramaniam; Gorti, Sarma B; Nicholson, Don M

    2007-01-01

    Ab-initio calculations based on the second order Moller-Plesset perturbation theory (MP2) were used to investigate the interaction of molecular hydrogen with alkyl lithium organometallic compounds. It is found that lithium in organolithium structures attracts two hydrogen molecules with a binding energy of about 0.14 eV. The calculations also show that organolithium compounds bind strongly with graphitic nanostructures. Therefore, these carbon based nanostructures functionalized with organolithium compounds can be effectively used for storage of molecular hydrogen. Energetics and mechanisms for achieving high weight percent hydrogen storage in organolithium based nanostructures are discussed.

  1. A 3-fold-symmetric ligand based on 2-hydroxypyridine: regulation of ligand binding by hydrogen bonding.

    PubMed

    Moore, Cameron M; Quist, David A; Kampf, Jeff W; Szymczak, Nathaniel K

    2014-04-01

    A tripodal ligand based on 2-hydroxypyridine is presented. Cu-Cl adducts of H3thpa with Cu(I) and Cu(II) provide complexes featuring highly directed, intramolecular hydrogen-bonding interactions. An upper limit for the hydrogen-bonding free energy to Cu(I)-Cl was estimated at ∼18 kcal/mol. PMID:24654846

  2. β-sheet-like hydrogen bonds interlock the helical turns of a photoswitchable foldamer to enhance the binding and release of chloride.

    PubMed

    Lee, Semin; Hua, Yuran; Flood, Amar H

    2014-09-01

    Inspired by halorhodopsin's use of photoisomerization to regulate chloride, aryltriazole-based foldamers have been created to "catch and release" chloride ions upon light irradiation of end-appended azobenzenes. The proposed mode of stabilization exploits a β-sheet-like hydrogen-bonding array to cooperatively interlock the ends of a foldamer together with its helical core. We find that the hydrogen-bonding array has a greater influence on stabilizing the helix than the π-stacked seam under the conditions examined (50:50 MeCN/THF). Thus, we show how it is possible to enhance the difference between Cl(-) binding and release using light-dependent control over the foldamer's degree of helix stabilization. Making and breaking three π-π contacts with light caused an 8-fold change in chloride affinity (40 300 M(-1) ⇄ 5000 M(-1)), five π-π contacts produced a 17-fold change (126 000 M(-1) ⇄ 7400 M(-1)), and strategically located hydrogen-bonding units enabled a greater 84-fold differential (970 000 M(-1) ⇄ 11 600 M(-1)). The improved performances were attributed to stepwise increases in the preorganization of the binding pocket that catches chloride while leaving the cis states with just one π-π contact relatively unchanged. PMID:25157797

  3. The effect of strain on the trapping of hydrogen at grain-boundary carbides in Ni-Cr-Fe alloys

    NASA Astrophysics Data System (ADS)

    Symons, D. M.; Young, G. A.; Scully, J. R.

    2001-02-01

    The present work quantifies the role of plastic deformation on the hydrogen-trapping behavior within the material and at the carbides. Isothermal desorption spectroscopy and thermal desorption spectroscopy (TDS) were performed on unstrained and strained alloy 600 (Ni-15Cr-8Fe) and alloy 690 (Ni-30Cr-8Fe), in order to quantify the effect of strain on the trapping energy. The results show that the M23C8 carbides in alloy 690 were stronger traps than the M7C3 carbides in alloy 600. It was further shown that cold work tended to increase the binding energy of hydrogen to the trap sites associated with grain-boundary carbides, although this effect was small.

  4. Biomolecular interaction study of hydralazine with bovine serum albumin and effect of β-cyclodextrin on binding by fluorescence, 3D, synchronous, CD, and Raman spectroscopic methods.

    PubMed

    Bolattin, Mallavva B; Nandibewoor, Sharanappa T; Chimatadar, Shivamurti A

    2016-07-01

    Spectrofluoremetric technique was employed to study the binding behavior of hydralazine with bovine serum albumin (BSA) at different temperatures. Binding study of bovine serum albumin with hydralazine has been studied by ultraviolet-visible spectroscopy, fluorescence spectroscopy and confirmed by three-dimensional, synchronous, circular dichroism, and Raman spectroscopic methods. Effect of β-cyclodextrin on binding was studied. The experimental results showed a static quenching mechanism in the interaction of hydralazine with bovine serum albumin. The binding constant and the number of binding sites are calculated according to Stern-Volmer equation. The thermodynamic parameters ∆H(o) , ∆G(o) , ∆S(o) at different temperatures were calculated. These indicated that the hydrogen bonding and weak van der Waals forces played an important role in the interaction. Based on the Förster's theory of non-radiation energy transfer, the binding average distance, r, between the donor (BSA) and acceptor (hydralazine) was evaluated and found to be 3.95 nm. Spectral results showed that the binding of hydralazine to BSA induced conformational changes in BSA. The effect of common ions on the binding of hydralazine to BSA was also examined. Copyright © 2016 John Wiley & Sons, Ltd. PMID:26785703

  5. Matrix effects on hydrogen-bonded complexes trapped in low-temperature matrices

    NASA Astrophysics Data System (ADS)

    Barnes, Austin J.; Mielke, Zofia

    2012-09-01

    There are several different possible matrix effects on hydrogen-bonded complexes trapped in low-temperature matrices: hydrogen-bonded complexes may be stabilised (compared with the gas phase) as a result of being trapped in a low-temperature matrix; metastable hydrogen-bonded complexes may be trapped in matrices; the matrix may influence the extent of proton transfer in a hydrogen-bonded complex; the matrix may influence the structure of a hydrogen-bonded complex. Each of these possible effects is examined in turn using selected examples from the literature as well as our own work.

  6. Microwave effect on camphor binding to rat olfactory epithelium

    SciTech Connect

    Philippova, T.M.; Novoselov, V.I.; Bystrova, M.F.; Alekseev, S.I.

    1988-01-01

    Microwave radiation decreased specific camphor binding to a membrane fraction of rat epithelium but not to a Triton X-100 extract of this fraction. Inhibition of the ligand binding did not depend on the modulation frequency of the microwave field in the region 1-100 Hz and was not a linear function of specific absorption rate (SAR). The decreased ligand binding was due to a shedding or release of the specific camphor-binding protein from the membrane into solution. It is highly probable that several other membrane proteins may be shed into solution during microwave exposure.

  7. Dual Effects of Adp and Adenylylimidodiphosphate on Cftr Channel Kinetics Show Binding to Two Different Nucleotide Binding Sites

    PubMed Central

    Weinreich, Frank; Riordan, John R.; Nagel, Georg

    1999-01-01

    The CFTR chloride channel is regulated by phosphorylation by protein kinases, especially PKA, and by nucleotides interacting with the two nucleotide binding domains, NBD-A and NBD-B. Giant excised inside-out membrane patches from Xenopus oocytes expressing human epithelial cystic fibrosis transmembrane conductance regulator (CFTR) were tested for their chloride conductance in response to the application of PKA and nucleotides. Rapid changes in the concentration of ATP, its nonhydrolyzable analogue adenylylimidodiphosphate (AMP-PNP), its photolabile derivative ATP-P3-[1-(2-nitrophenyl)ethyl]ester, or ADP led to changes in chloride conductance with characteristic time constants, which reflected interaction of CFTR with these nucleotides. The conductance changes of strongly phosphorylated channels were slower than those of partially phosphorylated CFTR. AMP-PNP decelerated relaxations of conductance increase and decay, whereas ATP-P3-[1-(2-nitrophenyl)ethyl]ester only decelerated the conductance increase upon ATP addition. ADP decelerated the conductance increase upon ATP addition and accelerated the conductance decay upon ATP withdrawal. The results present the first direct evidence that AMP-PNP binds to two sites on the CFTR. The effects of ADP also suggest two different binding sites because of the two different modes of inhibition observed: it competes with ATP for binding (to NBD-A) on the closed channel, but it also binds to channels opened by ATP, which might either reflect binding to NBD-A (i.e., product inhibition in the hydrolysis cycle) or allosteric binding to NBD-B, which accelerates the hydrolysis cycle at NBD-A. PMID:10398692

  8. Dual effects of ADP and adenylylimidodiphosphate on CFTR channel kinetics show binding to two different nucleotide binding sites.

    PubMed

    Weinreich, F; Riordan, J R; Nagel, G

    1999-07-01

    The CFTR chloride channel is regulated by phosphorylation by protein kinases, especially PKA, and by nucleotides interacting with the two nucleotide binding domains, NBD-A and NBD-B. Giant excised inside-out membrane patches from Xenopus oocytes expressing human epithelial cystic fibrosis transmembrane conductance regulator (CFTR) were tested for their chloride conductance in response to the application of PKA and nucleotides. Rapid changes in the concentration of ATP, its nonhydrolyzable analogue adenylylimidodiphosphate (AMP-PNP), its photolabile derivative ATP-P3-[1-(2-nitrophenyl)ethyl]ester, or ADP led to changes in chloride conductance with characteristic time constants, which reflected interaction of CFTR with these nucleotides. The conductance changes of strongly phosphorylated channels were slower than those of partially phosphorylated CFTR. AMP-PNP decelerated relaxations of conductance increase and decay, whereas ATP-P3-[1-(2-nitrophenyl)ethyl]ester only decelerated the conductance increase upon ATP addition. ADP decelerated the conductance increase upon ATP addition and accelerated the conductance decay upon ATP withdrawal. The results present the first direct evidence that AMP-PNP binds to two sites on the CFTR. The effects of ADP also suggest two different binding sites because of the two different modes of inhibition observed: it competes with ATP for binding (to NBD-A) on the closed channel, but it also binds to channels opened by ATP, which might either reflect binding to NBD-A (i.e., product inhibition in the hydrolysis cycle) or allosteric binding to NBD-B, which accelerates the hydrolysis cycle at NBD-A. PMID:10398692

  9. Effect of shot peening on hydrogen embrittlement of high strength steel

    NASA Astrophysics Data System (ADS)

    Li, Xin-feng; Zhang, Jin; Ma, Ming-ming; Song, Xiao-long

    2016-06-01

    The effect of shot peening (SP) on hydrogen embrittlement of high strength steel was investigated by electrochemical hydrogen charging, slow strain rate tensile tests, and hydrogen permeation tests. Microstructure observation, microhardness, and X-ray diffraction residual stress studies were also conducted on the steel. The results show that the shot peening specimens exhibit a higher resistance to hydrogen embrittlement in comparison with the no shot peening (NSP) specimens under the same hydrogen-charging current density. In addition, SP treatment sharply decreases the apparent hydrogen diffusivity and increases the subsurface hydrogen concentration. These findings are attributed to the changes in microstructure and compressive residual stress in the surface layer by SP. Scanning electron microscope fractographs reveal that the fracture surface of the NSP specimen exhibits the intergranular and quasi-cleavage mixed fracture modes, whereas the SP specimen shows only the quasi-cleavage fractures under the same hydrogen charging conditions, implying that the SP treatment delays the onset of intergranular fracture.

  10. Effect of the Hydrogen Bond on Photochemical Synthesis of Silver Nanoparticles.

    PubMed

    Zhao, Feng-jiao; Liu, Lei; Yang, Yang; Zhang, Rui-ling; Ren, Guang-hua; Xu, Da-li; Zhou, Pan-wang; Han, Ke-li

    2015-12-17

    The effect of a hydrogen bond on the photochemical synthesis of silver nanoparticles has been investigated via experimental and theoretical methods. In a benzophenone system, the photochemical synthesis process includes two steps, which are that hydrogen abstraction reaction and the following reduction reaction. We found that for the first step, an intermolecular hydrogen bond enhances the proton transfer. The efficiency of hydrogen abstraction increases with the hydrogen bond strength. For the second step, the hydrogen-bonded ketyl radical complex shows higher reducibility than the ketyl radical. The inductively coupled plasma-optical emission spectroscopy (ICP-OES) measurement exhibits a 2.49 times higher yield of silver nanoparticles in the hydrogen bond ketyl radical complex system than that for the ketyl radical system. Theoretical calculations show that the hydrogen bond accelerates electron transfer from the ketyl radical to the silver ion by raising the SOMO energy of the ketyl radical; thus, the SOMO-LUMO interaction is more favorable. PMID:26562362

  11. Nuclear Bound States of Molecular Hydrogen Physisorbed on Graphene: An Effective Two-Dimensional Model.

    PubMed

    de Lara-Castells, María Pilar; Mitrushchenkov, Alexander O

    2015-11-01

    The interaction potential of molecular hydrogen physisorbed on a graphene sheet is evaluated using the ab initio-based periodic dlDF+Das scheme and its accuracy is assessed by comparing the nuclear bound-state energies supported by the H2(D2/HD)/graphite potentials with the experimental energies. The periodic dlDF+Das treatment uses DFT-based symmetry-adapted perturbation theory on surface cluster models to extract the dispersion contribution to the interaction whereas periodic dispersionless density functional (dlDF) calculations are performed to determine the dispersion-free counterpart. It is shown that the H2/graphene interaction is effectively two-dimensional (2D), with the distance from the molecule center-of-mass to the surface plane and the angle between the diatomic axis and the surface normal as the relevant degrees of freedom. The global potential minimum is found at the orthogonal orientation of the molecule with respect to the surface plane, with an equilibrium distance of 3.17 Å and a binding energy of -51.9 meV. The comparison of the binding energies shows an important improvement of our approach over the vdW-corrected DFT schemes when we are dealing with the very weak H2/surface interaction. Next, the 2D nuclear bound-state energies are calculated numerically. As a cross-validation of the interaction potential, the bound states are also determined for molecular hydrogen on the graphite surface (represented as an assembly of graphene sheets). With the largest absolute deviation being 1.7 meV, the theoretical and experimental energy levels compare very favorably. PMID:26479965

  12. Strong Ionic Hydrogen Bonding Causes a Spectral Isotope Effect in Photoactive Yellow Protein

    PubMed Central

    Kaledhonkar, Sandip; Hara, Miwa; Stalcup, T. Page; Xie, Aihua; Hoff, Wouter D.

    2013-01-01

    Standard hydrogen bonds are of great importance for protein structure and function. Ionic hydrogen bonds often are significantly stronger than standard hydrogen bonds and exhibit unique properties, but their role in proteins is not well understood. We report that hydrogen/deuterium exchange causes a redshift in the visible absorbance spectrum of photoactive yellow protein (PYP). We expand the range of interpretable isotope effects by assigning this spectral isotope effect (SIE) to a functionally important hydrogen bond at the active site of PYP. The inverted sign and extent of this SIE is explained by the ionic nature and strength of this hydrogen bond. These results show the relevance of ionic hydrogen bonding for protein active sites, and reveal that the inverted SIE is a novel, to our knowledge, tool to probe ionic hydrogen bonds. Our results support a classification of hydrogen bonds that distinguishes the properties of ionic hydrogen bonds from those of both standard and low barrier hydrogen bonds, and show how this classification helps resolve a recent debate regarding active site hydrogen bonding in PYP. PMID:24314088

  13. Relativistic effects on information measures for hydrogen-like atoms

    NASA Astrophysics Data System (ADS)

    Katriel, Jacob; Sen, K. D.

    2010-01-01

    Position and momentum information measures are evaluated for the ground state of the relativistic hydrogen-like atoms. Consequences of the fact that the radial momentum operator is not self-adjoint are explicitly studied, exhibiting fundamental shortcomings of the conventional uncertainty measures in terms of the radial position and momentum variances. The Shannon and Rényi entropies, the Fisher information measure, as well as several related information measures, are considered as viable alternatives. Detailed results on the onset of relativistic effects for low nuclear charges, and on the extreme relativistic limit, are presented. The relativistic position density decays exponentially at large r, but is singular at the origin. Correspondingly, the momentum density decays as an inverse power of p. Both features yield divergent Rényi entropies away from a finite vicinity of the Shannon entropy. While the position space information measures can be evaluated analytically for both the nonrelativistic and the relativistic hydrogen atom, this is not the case for the relativistic momentum space. Some of the results allow interesting insight into the significance of recently evaluated Dirac-Fock vs. Hartree-Fock complexity measures for many-electron neutral atoms.

  14. Nanometer-Size Effect on Hydrogen Sites in Palladium Lattice.

    PubMed

    Akiba, Hiroshi; Kofu, Maiko; Kobayashi, Hirokazu; Kitagawa, Hiroshi; Ikeda, Kazutaka; Otomo, Toshiya; Yamamuro, Osamu

    2016-08-17

    Nanometer-sized materials attract much attention because their physical and chemical properties are substantially different from those of bulk materials owing to their size and surface effects. In this work, neutron powder diffraction experiments on the nanoparticles of palladium hydride, which is the most popular metal hydride, have been performed at 300, 150, and 44 K to investigate the positions of the hydrogen atoms in the face-centered cubic (fcc) lattice of palladium. We used high-quality PdD0.363 nanocrystals with a diameter of 8.0 ± 0.9 nm. The Rietveld analysis revealed that 30% of D atoms are located at the tetrahedral (T) sites and 70% at the octahedral (O) sites. In contrast, only the O sites are occupied in bulk palladium hydride and in most fcc metal hydrides. The temperature dependence of the T-site occupancy suggested that the T-sites are occupied only in a limited part, probably in the subsurface region, of the nanoparticles. This is the first study to determine the hydrogen sites in metal nanoparticles. PMID:27462875

  15. Isotope Effects in Collisional VT Relaxation of Molecular Hydrogen

    NASA Technical Reports Server (NTRS)

    Bieniek, R. J.

    2006-01-01

    A simple exponential-potential model of molecular collisions leads to a two-parameter analytic expression for rates of collisionally induced vibrational-translation (VT) energy exchange that has been shown to be accurate over variations of orders of magnitude as a function of temperature in a variety of systems. This includes excellent agreement with reported experimental and theoretical results for the fundamental self-relaxation rate of molecular hydrogen H2(v = 1) + H2 yields H2(v = 0) + H2. The analytic rate successfully follows the five-orders-of-magnitude change in experimental values for the temperature range 50-2000 K. This approach is now applied to isotope effects in the vibrational relaxation rates of excited HD and D2 in collision with H2: HD(v = 1)+H2 yields HD(v = 0)+H2 and D2(v = 1)+H2 yields D2(v = 0)+H2. The simplicity of the analytic expression for the thermal rate lends itself to convenient application in modeling the evolving vibrational populations of molecular hydrogen in shocked astrophysical environments.

  16. Performance of the MM/GBSA scoring using a binding site hydrogen bond network-based frame selection: the protein kinase case.

    PubMed

    Adasme-Carreño, Francisco; Muñoz-Gutierrez, Camila; Caballero, Julio; Alzate-Morales, Jans H

    2014-07-21

    A conformational selection method, based on hydrogen bond (Hbond) network analysis, has been designed in order to rationalize the configurations sampled using molecular dynamics (MD), which are commonly used in the estimation of the relative binding free energy of ligands to macromolecules through the MM/GBSA or MM/PBSA method. This approach makes use of protein-ligand complexes obtained from X-ray crystallographic data, as well as from molecular docking calculations. The combination of several computational approaches, like long MD simulations on protein-ligand complexes, Hbond network-based selection by scripting techniques and finally MM/GBSA, provides better statistical correlations against experimental binding data than previous similar reported studies. This approach has been successfully applied in the ranking of several protein kinase inhibitors (CDK2, Aurora A and p38), which present both diverse and related chemical structures. PMID:24901037

  17. Ultrafast effective multilevel atom method for primordial hydrogen recombination

    SciTech Connect

    Ali-Haiemoud, Yacine; Hirata, Christopher M.

    2010-09-15

    Cosmological hydrogen recombination has recently been the subject of renewed attention because of its importance for predicting the power spectrum of cosmic microwave background anisotropies. It has become clear that it is necessary to account for a large number n > or approx. 100 of energy shells of the hydrogen atom, separately following the angular momentum substates in order to obtain sufficiently accurate recombination histories. However, the multilevel atom codes that follow the populations of all these levels are computationally expensive, limiting recent analyses to only a few points in parameter space. In this paper, we present a new method for solving the multilevel atom recombination problem, which splits the problem into a computationally expensive atomic physics component that is independent of the cosmology and an ultrafast cosmological evolution component. The atomic physics component follows the network of bound-bound and bound-free transitions among excited states and computes the resulting effective transition rates for the small set of 'interface' states radiatively connected to the ground state. The cosmological evolution component only follows the populations of the interface states. By pretabulating the effective rates, we can reduce the recurring cost of multilevel atom calculations by more than 5 orders of magnitude. The resulting code is fast enough for inclusion in Markov chain Monte Carlo parameter estimation algorithms. It does not yet include the radiative transfer or high-n two-photon processes considered in some recent papers. Further work on analytic treatments for these effects will be required in order to produce a recombination code usable for Planck data analysis.

  18. Ultrafast effective multilevel atom method for primordial hydrogen recombination

    NASA Astrophysics Data System (ADS)

    Ali-Haïmoud, Yacine; Hirata, Christopher M.

    2010-09-01

    Cosmological hydrogen recombination has recently been the subject of renewed attention because of its importance for predicting the power spectrum of cosmic microwave background anisotropies. It has become clear that it is necessary to account for a large number n≳100 of energy shells of the hydrogen atom, separately following the angular momentum substates in order to obtain sufficiently accurate recombination histories. However, the multilevel atom codes that follow the populations of all these levels are computationally expensive, limiting recent analyses to only a few points in parameter space. In this paper, we present a new method for solving the multilevel atom recombination problem, which splits the problem into a computationally expensive atomic physics component that is independent of the cosmology and an ultrafast cosmological evolution component. The atomic physics component follows the network of bound-bound and bound-free transitions among excited states and computes the resulting effective transition rates for the small set of “interface” states radiatively connected to the ground state. The cosmological evolution component only follows the populations of the interface states. By pretabulating the effective rates, we can reduce the recurring cost of multilevel atom calculations by more than 5 orders of magnitude. The resulting code is fast enough for inclusion in Markov chain Monte Carlo parameter estimation algorithms. It does not yet include the radiative transfer or high-n two-photon processes considered in some recent papers. Further work on analytic treatments for these effects will be required in order to produce a recombination code usable for Planck data analysis.

  19. Intentional binding effect in children: insights from a new paradigm.

    PubMed

    Cavazzana, Annachiara; Begliomini, Chiara; Bisiacchi, Patrizia S

    2014-01-01

    Intentional binding (IB) refers to the temporal attraction between a voluntary action and its sensory consequence. Since its discovery in 2002, it has been considered to be a valid implicit measure of sense of agency (SoA), since it only occurs in the context of voluntary actions. The vast majority of studies considering IB have recruited young adults as participants, while neglecting possible age-related differences. The aim of the present work is to study the development of IB in 10-year-old children. In place of Libet's classical clock method, we decided to implement a new and more suitable paradigm in order to study IB, since children could have some difficulties in dealing with reading clocks. A stream of unpredictable letters was therefore used: participants had to remember which letter was on the screen when they made a voluntary action, heard a sound, or felt their right index finger moved down passively. In Experiment I, a group of young adults was tested in order to replicate the IB effect with this new paradigm. In Experiment II, the same paradigm was then administered to children in order to investigate whether such an effect has already emerged at this age. The data from Experiment I showed the presence of the IB effect in adults. However, Experiment II demonstrated a clear reduction of IB. The comparison of the two groups revealed that the young adult group differed from the children, showing a significantly stronger linkage between actions and their consequences. The results indicate a developmental trend in the IB effect. This finding is discussed in light of the maturation process of the frontal cortical network. PMID:25202256

  20. Intentional binding effect in children: insights from a new paradigm

    PubMed Central

    Cavazzana, Annachiara; Begliomini, Chiara; Bisiacchi, Patrizia S.

    2014-01-01

    Intentional binding (IB) refers to the temporal attraction between a voluntary action and its sensory consequence. Since its discovery in 2002, it has been considered to be a valid implicit measure of sense of agency (SoA), since it only occurs in the context of voluntary actions. The vast majority of studies considering IB have recruited young adults as participants, while neglecting possible age-related differences. The aim of the present work is to study the development of IB in 10-year-old children. In place of Libet’s classical clock method, we decided to implement a new and more suitable paradigm in order to study IB, since children could have some difficulties in dealing with reading clocks. A stream of unpredictable letters was therefore used: participants had to remember which letter was on the screen when they made a voluntary action, heard a sound, or felt their right index finger moved down passively. In Experiment I, a group of young adults was tested in order to replicate the IB effect with this new paradigm. In Experiment II, the same paradigm was then administered to children in order to investigate whether such an effect has already emerged at this age. The data from Experiment I showed the presence of the IB effect in adults. However, Experiment II demonstrated a clear reduction of IB. The comparison of the two groups revealed that the young adult group differed from the children, showing a significantly stronger linkage between actions and their consequences. The results indicate a developmental trend in the IB effect. This finding is discussed in light of the maturation process of the frontal cortical network. PMID:25202256

  1. Hydrogen Sulfide Up-Regulates the Expression of ATP-Binding Cassette Transporter A1 via Promoting Nuclear Translocation of PPARα

    PubMed Central

    Li, Dong; Xiong, Qinghui; Peng, Jin; Hu, Bin; Li, Wanzhen; Zhu, Yizhun; Shen, Xiaoyan

    2016-01-01

    ATP binding cassette transporter A1 (ABCA1) plays a key role in atherogenesis. Hydrogen sulfide (H2S), a gasotransmitter, has been reported to play an anti-atherosclerotic role. However, the underlying mechanisms are largely unknown. In this study we examined whether and how H2S regulates ABCA1 expression. The effect of H2S on ABCA1 expression and lipid metabolism were assessed in vitro by cultured human hepatoma cell line HepG2, and in vivo by ApoE−/− mice with a high-cholesterol diet. NaHS (an exogenous H2S donor) treatment significantly increased the expression of ABCA1, ApoA1, and ApoA2 and ameliorated intracellular lipid accumulation in HepG2 cells. Depletion of the endogenous H2S generator cystathionine γ-lyase (CSE) by small RNA interference (siRNA) significantly decreased the expression of ABCA1 and resulted in the accumulation of lipids in HepG2 cells. In vivo NaHS treatment significantly reduced the serum levels of total cholesterol (TC), triglycerides (TG), and low-density lipoproteins (LDL), diminished atherosclerotic plaque size, and increased hepatic ABCA1 expression in fat-fed ApoE−/− mice. Further study revealed that NaHS upregulated ABCA1 expression by promoting peroxisome proliferator-activated receptor α (PPARα) nuclear translocation. H2S up-regulates the expression of ABCA1 by promoting the nuclear translocation of PPARα, providing a fundamental mechanism for the anti-atherogenic activity of H2S. H2S may be a promising potential drug candidate for the treatment of atherosclerosis. PMID:27136542

  2. Hydrogen Sulfide Up-Regulates the Expression of ATP-Binding Cassette Transporter A1 via Promoting Nuclear Translocation of PPARα.

    PubMed

    Li, Dong; Xiong, Qinghui; Peng, Jin; Hu, Bin; Li, Wanzhen; Zhu, Yizhun; Shen, Xiaoyan

    2016-01-01

    ATP binding cassette transporter A1 (ABCA1) plays a key role in atherogenesis. Hydrogen sulfide (H₂S), a gasotransmitter, has been reported to play an anti-atherosclerotic role. However, the underlying mechanisms are largely unknown. In this study we examined whether and how H₂S regulates ABCA1 expression. The effect of H₂S on ABCA1 expression and lipid metabolism were assessed in vitro by cultured human hepatoma cell line HepG2, and in vivo by ApoE(-/-) mice with a high-cholesterol diet. NaHS (an exogenous H₂S donor) treatment significantly increased the expression of ABCA1, ApoA1, and ApoA2 and ameliorated intracellular lipid accumulation in HepG2 cells. Depletion of the endogenous H₂S generator cystathionine γ-lyase (CSE) by small RNA interference (siRNA) significantly decreased the expression of ABCA1 and resulted in the accumulation of lipids in HepG2 cells. In vivo NaHS treatment significantly reduced the serum levels of total cholesterol (TC), triglycerides (TG), and low-density lipoproteins (LDL), diminished atherosclerotic plaque size, and increased hepatic ABCA1 expression in fat-fed ApoE(-/-) mice. Further study revealed that NaHS upregulated ABCA1 expression by promoting peroxisome proliferator-activated receptor α (PPARα) nuclear translocation. H₂S up-regulates the expression of ABCA1 by promoting the nuclear translocation of PPARα, providing a fundamental mechanism for the anti-atherogenic activity of H₂S. H₂S may be a promising potential drug candidate for the treatment of atherosclerosis. PMID:27136542

  3. Predicting Allosteric Effects from Orthosteric Binding in Hsp90-Ligand Interactions: Implications for Fragment-Based Drug Design

    PubMed Central

    Larsson, Andreas; Nordlund, Paer; Jansson, Anna; Anand, Ganesh S.

    2016-01-01

    A key question in mapping dynamics of protein-ligand interactions is to distinguish changes at binding sites from those associated with long range conformational changes upon binding at distal sites. This assumes a greater challenge when considering the interactions of low affinity ligands (dissociation constants, KD, in the μM range or lower). Amide hydrogen deuterium Exchange mass spectrometry (HDXMS) is a robust method that can provide both structural insights and dynamics information on both high affinity and transient protein-ligand interactions. In this study, an application of HDXMS for probing the dynamics of low affinity ligands to proteins is described using the N-terminal ATPase domain of Hsp90. Comparison of Hsp90 dynamics between high affinity natural inhibitors (KD ~ nM) and fragment compounds reveal that HDXMS is highly sensitive in mapping the interactions of both high and low affinity ligands. HDXMS reports on changes that reflect both orthosteric effects and allosteric changes accompanying binding. Orthosteric sites can be identified by overlaying HDXMS onto structural information of protein-ligand complexes. Regions distal to orthosteric sites indicate long range conformational changes with implications for allostery. HDXMS, thus finds powerful utility as a high throughput method for compound library screening to identify binding sites and describe allostery with important implications for fragment-based ligand discovery (FBLD). PMID:27253209

  4. Effect of hydrogen on the mechanical properties of titanium and its alloys

    NASA Technical Reports Server (NTRS)

    Beck, F. H.

    1975-01-01

    Occluded hydrogen resulting from cathodic charging of commercially pure titanium and titanium alloys, Ti-8Al-1Mo-1V and Ti-6Al-4V, was shown to cause embrittlement of the alloys. Embrittlement was a function of the interstitial hydrogen content rather than the amount of precipitated titanium hydride. The effects of hydrogen concentration on the critical strain for plastic instability along pure shear directions was determined for alloys Ti-8Al-1Mo-1V and Ti-5Al-2.5Sn. Hydrogen, in concentrations below that necessary for spontaneous hydride precipitation, increased the strain necessary for instability formation or instability failure. The strain rate sensitivity also increased with increasing hydrogen concentration. The effect of hydrogen on slip and twinning was determined for titanium single crystals. The critical resolved shear stress for prism slip was increased and the critical resolved shear stress for twinning was decreased with increasing hydrogen concentration.

  5. Autoradiographic analysis of tritiated imipramine binding in the human brain post mortem: effects of suicide

    SciTech Connect

    Gross-Isseroff, R.; Israeli, M.; Biegon, A.

    1989-03-01

    In vitro quantitative autoradiography of high-affinity tritiated imipramine binding sites was performed on brains of 12 suicide victims and 12 matched controls. Region-specific differences in imipramine binding were found between the two groups. Thus, the pyramidal and molecular layers of the cornu ammoni hippocampal fields and the hilus of the dentate gyrus exhibited 80%, 60%, and 90% increases in binding in the suicide group, respectively. The postcentral cortical gyrus, insular cortex, and claustrum had 45%, 28%, and 75% decreases in binding in the suicide group, respectively. No difference in imipramine binding was observed in prefrontal cortical regions, in the basal ganglia, and in mesencephalic nuclei. No sex and postmortem delay effects on imipramine binding were found. Imipramine binding was positively correlated with age, the effect of age being most pronounced in portions of the basal ganglia and temporal cortex.

  6. Kinetics of hydrogen peroxide decomposition by catalase: hydroxylic solvent effects.

    PubMed

    Raducan, Adina; Cantemir, Anca Ruxandra; Puiu, Mihaela; Oancea, Dumitru

    2012-11-01

    The effect of water-alcohol (methanol, ethanol, propan-1-ol, propan-2-ol, ethane-1,2-diol and propane-1,2,3-triol) binary mixtures on the kinetics of hydrogen peroxide decomposition in the presence of bovine liver catalase is investigated. In all solvents, the activity of catalase is smaller than in water. The results are discussed on the basis of a simple kinetic model. The kinetic constants for product formation through enzyme-substrate complex decomposition and for inactivation of catalase are estimated. The organic solvents are characterized by several physical properties: dielectric constant (D), hydrophobicity (log P), concentration of hydroxyl groups ([OH]), polarizability (α), Kamlet-Taft parameter (β) and Kosower parameter (Z). The relationships between the initial rate, kinetic constants and medium properties are analyzed by linear and multiple linear regression. PMID:22565543

  7. Isotope Effect in Tunneling Ionization of Neutral Hydrogen Molecules.

    PubMed

    Wang, X; Xu, H; Atia-Tul-Noor, A; Hu, B T; Kielpinski, D; Sang, R T; Litvinyuk, I V

    2016-08-19

    It has been recently predicted theoretically that due to nuclear motion light and heavy hydrogen molecules exposed to strong electric field should exhibit substantially different tunneling ionization rates [O. I. Tolstikhin, H. J. Worner, and T. Morishita, Phys. Rev. A 87, 041401(R) (2013)]. We studied that isotope effect experimentally by measuring relative ionization yields for each species in a mixed H_{2}/D_{2} gas jet interacting with intense femtosecond laser pulses. In a reaction microscope apparatus, we detected ionic fragments from all contributing channels (single ionization, dissociation, and sequential double ionization) and determined the ratio of total single ionization yields for H_{2} and D_{2}. The measured ratio agrees quantitatively with the prediction of the generalized weak-field asymptotic theory in an apparent failure of the frozen-nuclei approximation. PMID:27588855

  8. Hydrogen environment effects on beryllium and titanium aluminides

    NASA Technical Reports Server (NTRS)

    Fritzemeier, L. G.; Jacinto, M. A.

    1990-01-01

    The NASP program has intensively studied the hydrogen-environment embrittlement (HEE) susceptibility of Be, alpha(2)-Ti3Al, and gamma-TiAl. Tensile tests are being conducted on candidate aerospace structure and propulsion candidate materials from each of the three groups, at temperatures in the -130 to +204 C range, in both 0.1 MPa and 13.8 MPa He and H2 environments, using SEM and TEM to discern the details of environmental effects. It has been established that while alpha(2) Ti3Al is HEE-susceptible even in the room-temperature and 13.8 MPa environment, neither Be nor gamma-TiAl are susceptible, even at the highest temperature tested.

  9. LiBr passivation effect of porous nanocrystalline hydrogenated silicon

    NASA Astrophysics Data System (ADS)

    Amor, Sana Ben; Haddadi, Ikbel; Seif, El Whibi; Daik, Ridha; Bousbih, Rabaa; Dimassi, Wissem; Ezzaouia, Hatem

    2015-12-01

    Nanocrystalline hydrogenated silicon (nc-Si:H) films were deposited on a p-type silicon substrate by plasma enhanced chemical vapor deposition (PECVD), using SiH4 and H2 as reactive gases. Porous (nc-Si:H) layers were afterward obtained and immersed in a lithium bromide (LiBr) aqueous solution in order to enhance their optical and electrical properties for a potential solar cells application. A decrease in the reflectivity to about 9% for Li/porous nc-Si:H layer deposited at 75 sccm against an increase in the minority carrier lifetime were obtained. We correlate these results to the change in crystalline characteristics and chemical composition of the layers in order to understand the effect of LiBr coating on nc-Si:H Through optical and electrical characterization we have demonstrated the possibility of using such LiBr treatment to improve the properties of porous nc-Si:H.

  10. Isotope Effect in Tunneling Ionization of Neutral Hydrogen Molecules

    NASA Astrophysics Data System (ADS)

    Wang, X.; Xu, H.; Atia-Tul-Noor, A.; Hu, B. T.; Kielpinski, D.; Sang, R. T.; Litvinyuk, I. V.

    2016-08-01

    It has been recently predicted theoretically that due to nuclear motion light and heavy hydrogen molecules exposed to strong electric field should exhibit substantially different tunneling ionization rates [O. I. Tolstikhin, H. J. Worner, and T. Morishita, Phys. Rev. A 87, 041401(R) (2013)]. We studied that isotope effect experimentally by measuring relative ionization yields for each species in a mixed H2/D2 gas jet interacting with intense femtosecond laser pulses. In a reaction microscope apparatus, we detected ionic fragments from all contributing channels (single ionization, dissociation, and sequential double ionization) and determined the ratio of total single ionization yields for H2 and D2 . The measured ratio agrees quantitatively with the prediction of the generalized weak-field asymptotic theory in an apparent failure of the frozen-nuclei approximation.

  11. Analysis of Copper-Binding Proteins in Rice Radicles Exposed to Excess Copper and Hydrogen Peroxide Stress

    PubMed Central

    Zhang, Hongxiao; Xia, Yan; Chen, Chen; Zhuang, Kai; Song, Yufeng; Shen, Zhenguo

    2016-01-01

    Copper (Cu) is an essential micronutrient for plants, but excess Cu can inactivate and disturb the protein function due to unavoidable binding to proteins at the cellular level. As a redox-active metal, Cu toxicity is mediated by the formation of reactive oxygen species (ROS). Cu-binding structural motifs may alleviate Cu-induced damage by decreasing free Cu2+ activity in cytoplasm or scavenging ROS. The identification of Cu-binding proteins involved in the response of plants to Cu or ROS toxicity may increase our understanding the mechanisms of metal toxicity and tolerance in plants. This study investigated change of Cu-binding proteins in radicles of germinating rice seeds under excess Cu and oxidative stress using immobilized Cu2+ affinity chromatography, two-dimensional electrophoresis, and mass spectra analysis. Quantitative image analysis revealed that 26 protein spots showed more than a 1.5-fold difference in abundances under Cu or H2O2 treatment compared to the control. The identified Cu-binding proteins were involved in anti-oxidative defense, stress response and detoxification, protein synthesis, protein modification, and metabolism regulation. The present results revealed that 17 out of 24 identified Cu-binding proteins have a similar response to low concentration Cu (20 μM Cu) and H2O2 stress, and 5 out of 24 were increased under low and high concentration Cu (100 μM Cu) but unaffected under H2O2 stress, which hint Cu ions can regulate Cu-binding proteins accumulation by H2O2 or no H2O2 pathway to cope with excess Cu in cell. The change pattern of these Cu-binding proteins and their function analysis warrant to further study the roles of Cu ions in these Cu-binding proteins of plant cells. PMID:27582750

  12. Analysis of Copper-Binding Proteins in Rice Radicles Exposed to Excess Copper and Hydrogen Peroxide Stress.

    PubMed

    Zhang, Hongxiao; Xia, Yan; Chen, Chen; Zhuang, Kai; Song, Yufeng; Shen, Zhenguo

    2016-01-01

    Copper (Cu) is an essential micronutrient for plants, but excess Cu can inactivate and disturb the protein function due to unavoidable binding to proteins at the cellular level. As a redox-active metal, Cu toxicity is mediated by the formation of reactive oxygen species (ROS). Cu-binding structural motifs may alleviate Cu-induced damage by decreasing free Cu(2+) activity in cytoplasm or scavenging ROS. The identification of Cu-binding proteins involved in the response of plants to Cu or ROS toxicity may increase our understanding the mechanisms of metal toxicity and tolerance in plants. This study investigated change of Cu-binding proteins in radicles of germinating rice seeds under excess Cu and oxidative stress using immobilized Cu(2+) affinity chromatography, two-dimensional electrophoresis, and mass spectra analysis. Quantitative image analysis revealed that 26 protein spots showed more than a 1.5-fold difference in abundances under Cu or H2O2 treatment compared to the control. The identified Cu-binding proteins were involved in anti-oxidative defense, stress response and detoxification, protein synthesis, protein modification, and metabolism regulation. The present results revealed that 17 out of 24 identified Cu-binding proteins have a similar response to low concentration Cu (20 μM Cu) and H2O2 stress, and 5 out of 24 were increased under low and high concentration Cu (100 μM Cu) but unaffected under H2O2 stress, which hint Cu ions can regulate Cu-binding proteins accumulation by H2O2 or no H2O2 pathway to cope with excess Cu in cell. The change pattern of these Cu-binding proteins and their function analysis warrant to further study the roles of Cu ions in these Cu-binding proteins of plant cells. PMID:27582750

  13. A Binding Site on IL-17A for Inhibitory Macrocycles Revealed by Hydrogen/Deuterium Exchange Mass Spectrometry.

    PubMed

    Espada, Alfonso; Broughton, Howard; Jones, Spencer; Chalmers, Michael J; Dodge, Jeffrey A

    2016-03-10

    Computational assessment of the IL-17A structure identified two distinct binding pockets, the β-hairpin pocket and the α-helix pocket. The β-hairpin pocket was hypothesized to be the site of binding for peptide macrocycles. Support for this hypothesis was obtained using HDX-MS which revealed protection to exchange only within the β-hairpin pocket. This data represents the first direct structural evidence of a small molecule binding site on IL-17A that functions to disrupt the interaction with its receptor. PMID:26854023

  14. Hydrogen effects in duplex stainless steel welded joints - electrochemical studies

    NASA Astrophysics Data System (ADS)

    Michalska, J.; Łabanowski, J.; Ćwiek, J.

    2012-05-01

    In this work results on the influence of hydrogen on passivity and corrosion resistance of 2205 duplex stainless steel (DSS) welded joints are described. The results were discussed by taking into account three different areas on the welded joint: weld metal (WM), heat-affected zone (HAZ) and parent metal. The corrosion resistance was qualified with the polarization curves registered in a synthetic sea water. The conclusion is that, hydrogen may seriously deteriorate the passive film stability and corrosion resistance to pitting of 2205 DSS welded joints. The presence of hydrogen in passive films increases corrosion current density and decreases the potential of the film breakdown. It was also found that degree of susceptibility to hydrogen degradation was dependent on the hydrogen charging conditions. WM region has been revealed as the most sensitive to hydrogen action.

  15. Computational Investigation of Glycosylation Effects on a Family 1 Carbohydrate-binding Module*

    PubMed Central

    Taylor, Courtney B.; Talib, M. Faiz; McCabe, Clare; Bu, Lintao; Adney, William S.; Himmel, Michael E.; Crowley, Michael F.; Beckham, Gregg T.

    2012-01-01

    Carbohydrate-binding modules (CBMs) are ubiquitous components of glycoside hydrolases, which degrade polysaccharides in nature. CBMs target specific polysaccharides, and CBM binding affinity to cellulose is known to be proportional to cellulase activity, such that increasing binding affinity is an important component of performance improvement. To ascertain the impact of protein and glycan engineering on CBM binding, we use molecular simulation to quantify cellulose binding of a natively glycosylated Family 1 CBM. To validate our approach, we first examine aromatic-carbohydrate interactions on binding, and our predictions are consistent with previous experiments, showing that a tyrosine to tryptophan mutation yields a 2-fold improvement in binding affinity. We then demonstrate that enhanced binding of 3–6-fold over a nonglycosylated CBM is achieved by the addition of a single, native mannose or a mannose dimer, respectively, which has not been considered previously. Furthermore, we show that the addition of a single, artificial glycan on the anterior of the CBM, with the native, posterior glycans also present, can have a dramatic impact on binding affinity in our model, increasing it up to 140-fold relative to the nonglycosylated CBM. These results suggest new directions in protein engineering, in that modifying glycosylation patterns via heterologous expression, manipulation of culture conditions, or introduction of artificial glycosylation sites, can alter CBM binding affinity to carbohydrates and may thus be a general strategy to enhance cellulase performance. Our results also suggest that CBM binding studies should consider the effects of glycosylation on binding and function. PMID:22147693

  16. Computational Investigation of Glycosylation Effects on a Family 1 Carbohydrate-Binding Module

    SciTech Connect

    Taylor, C. B.; Talib, M. F.; McCabe, C.; Bu, L.; Adney, W. S.; Himmel, M. E.; Crowley, M. F.; Beckham, G. T.

    2012-01-27

    Carbohydrate-binding modules (CBMs) are ubiquitous components of glycoside hydrolases, which degrade polysaccharides in nature. CBMs target specific polysaccharides, and CBM binding affinity to cellulose is known to be proportional to cellulase activity, such that increasing binding affinity is an important component of performance improvement. To ascertain the impact of protein and glycan engineering on CBM binding, we use molecular simulation to quantify cellulose binding of a natively glycosylated Family 1 CBM. To validate our approach, we first examine aromatic-carbohydrate interactions on binding, and our predictions are consistent with previous experiments, showing that a tyrosine to tryptophan mutation yields a 2-fold improvement in binding affinity. We then demonstrate that enhanced binding of 3-6-fold over a nonglycosylated CBM is achieved by the addition of a single, native mannose or a mannose dimer, respectively, which has not been considered previously. Furthermore, we show that the addition of a single, artificial glycan on the anterior of the CBM, with the native, posterior glycans also present, can have a dramatic impact on binding affinity in our model, increasing it up to 140-fold relative to the nonglycosylated CBM. These results suggest new directions in protein engineering, in that modifying glycosylation patterns via heterologous expression, manipulation of culture conditions, or introduction of artificial glycosylation sites, can alter CBM binding affinity to carbohydrates and may thus be a general strategy to enhance cellulase performance. Our results also suggest that CBM binding studies should consider the effects of glycosylation on binding and function.

  17. Sperm in poor quality semen from bulls during heat stress have a lower affinity for binding hydrogen-3 heparin

    SciTech Connect

    Ax, R.L.; Gilbert, G.R.; Shook, G.E.

    1987-01-01

    Binding assays with (/sup 3/H) heparin were performed using spermatozoa collected prior to, during, and following summer heat stress to dairy bulls. Ejaculates collected in August 1983 after a period of ambient temperatures exceeding 29.4/sup 0/C exhibited a high frequency of abnormal sperm, and motility was reduced in some samples. Sperm in samples collected during heat stress possessed dissociation constants for binding (/sup 3/H) heparin ranging from 134.5 to 163.2 nmol. In contrast, sperm in semen collected prior to and after heat stress had significantly lower dissociation constants (higher affinity) for (/sup 3/H)heparin, 12.9 to 56.4 nmol. The number of binding sites for (/sup 3/H) heparin on sperm did not change among collection periods. It was concluded that the binding affinity for (/sup 3/H) heparin may reflect membrane integrity of bull sperm.

  18. Effect of total binding capacity of thyroxine binding globulin on the free thyroxine index

    SciTech Connect

    Cuaron, A.

    1986-06-01

    In search of a definite source of misleading free thyroxine index (FT/sub 4/I), the relationship between in vitro thyroid testing results and thyroxine-binding globulin (TBG) capacities were reexamined in sera from a population with a relatively high prevalence of serum TBG alterations. Sera from 21 subjects with different total thyroxine-binding globulin capacities (TTBG), were loaded with graded amounts of thyroxine (T/sub 4/) and assayed for T/sub 4/, T/sub 3/ uptake (T/sub 3/U), TTBG, and free T/sub 4/ concentration (FT/sub 4/I). Serum T/sub 4/, T/sub 3/U, and the calculated FT/sub 4/ index (FT/sub 4/I) were able to separate efficiently the samples according to their FT/sub 4/, but their respective normal ranges varied with TTBG. Interpretation of the results of the in vitro tests, in the light of TTBG, greatly improved their operating characteristics in the study of 141 patients with a high prevalence of TBG alterations. The misleading FT/sub 4/I is not the outcome of reduced intrinsic sensitivities of the in vitro tests, but a consequence of a shift of their normal ranges caused by a change of TTBG. By estimating TTBG from the values of T/sub 4/ and T/sub 3/U, this problem is easily solved without adding cost.

  19. Effective hydrogen generator testing for on-site small engine

    NASA Astrophysics Data System (ADS)

    Chaiwongsa, Praitoon; Pornsuwancharoen, Nithiroth; Yupapin, Preecha P.

    2009-07-01

    We propose a new concept of hydrogen generator testing for on-site small engine. In general, there is a trade-off between simpler vehicle design and infrastructure issues, for instance, liquid fuels such as gasoline and methanol for small engine use. In this article we compare the hydrogen gases combination the gasoline between normal systems (gasoline only) for small engine. The advantage of the hydrogen combines gasoline for small engine saving the gasoline 25%. Furthermore, the new concept of hydrogen combination for diesel engine, bio-diesel engine, liquid petroleum gas (LPG), natural gas vehicle (NGV), which is discussed in details.

  20. Effect of hydrogen-switchable mirrors on the Casimir force.

    PubMed

    Iannuzzi, Davide; Lisanti, Mariangela; Capasso, Federico

    2004-03-23

    We present systematic measurements of the Casimir force between a gold-coated plate and a sphere coated with a hydrogen-switchable mirror. Hydrogen-switchable mirrors are shiny metals that can become transparent upon hydrogenation. Despite such a dramatic change of the optical properties of the sphere, we did not observe any significant decrease of the Casimir force after filling the experimental apparatus with hydrogen. This counterintuitive result can be explained by the Lifshitz theory that describes the Casimir attraction between metallic and dielectric materials. PMID:15024111

  1. Effect of hydrogen-switchable mirrors on the Casimir force

    PubMed Central

    Iannuzzi, Davide; Lisanti, Mariangela; Capasso, Federico

    2004-01-01

    We present systematic measurements of the Casimir force between a gold-coated plate and a sphere coated with a hydrogen-switchable mirror. Hydrogen-switchable mirrors are shiny metals that can become transparent upon hydrogenation. Despite such a dramatic change of the optical properties of the sphere, we did not observe any significant decrease of the Casimir force after filling the experimental apparatus with hydrogen. This counterintuitive result can be explained by the Lifshitz theory that describes the Casimir attraction between metallic and dielectric materials. PMID:15024111

  2. Binding isotope effects as a tool for distinguishing hydrophobic and hydrophilic binding sites of HIV-1 RT.

    PubMed

    Krzemińska, Agnieszka; Paneth, Piotr; Moliner, Vicent; Świderek, Katarzyna

    2015-01-22

    The current treatment for HIV-1 infected patients consists of a cocktail of inhibitors, in an attempt to improve the potency of the drugs by adding the possible effects of each supplied compound. In this contribution, nine different inhibitors of HIV-1 RT, one of the three key proteins responsible for the virus replication, have been selected to develop and test a computational protocol that allows getting a deep insight into the inhibitors' binding mechanism. The interaction between the inhibitors and the protein have been quantified by computing binding free energies through FEP calculations, while a more detailed characterization of the kind of inhibitor-protein interactions is based on frequency analysis of the ligands in the initial and final state, i.e. in solution and binding the protein. QM/MM calculation of heavy atoms ((13)C, (15)N, and (18)O) binding isotope effects (BIE) have been used to identify the binding sites of the different inhibitors. Specific interactions between the isotopically labeled atoms of the inhibitors and polar residues and magnesium cations on the hydrophilic pocket of the protein are responsible for the frequencies shifting that can be detected when comparing the IR spectra of the compounds in solution and in the protein. On the contrary, it seems that changes in vdW interactions from solution to the final state when the ligand is interacting with residues of the hydrophobic cavity, does not influence frequency modes and then no BIE are observed. Our results suggest that a proper computational protocol can be a valuable tool which in turn can be used to increase the efficiency of anti AIDS drugs. PMID:25132465

  3. HYDROGEN EFFECTS ON THE FRACTURE TOUGHNESS PROPERTIES OF FORGED STAINLESS STEELS

    SciTech Connect

    Morgan, M

    2008-03-28

    The effect of hydrogen on the fracture toughness properties of Types 304L, 316L and 21-6-9 forged stainless steels was investigated. Fracture toughness samples were fabricated from forward-extruded forgings. Samples were uniformly saturated with hydrogen after exposure to hydrogen gas at 34 MPa or 69 and 623 K prior to testing. The fracture toughness properties were characterized by measuring the J-R behavior at ambient temperature in air. The results show that the hydrogen-charged steels have fracture toughness values that were about 50-60% of the values measured for the unexposed steels. The reduction in fracture toughness was accompanied by a change in fracture appearance. Both uncharged and hydrogen-charged samples failed by microvoid nucleation and coalescence, but the fracture surfaces of the hydrogen-charged steels had smaller microvoids. Type 316L stainless steel had the highest fracture toughness properties and the greatest resistance to hydrogen degradation.

  4. Analytical chemical kinetic investigation of the effects of oxygen, hydrogen, and hydroxyl radicals on hydrogen-air combustion

    NASA Technical Reports Server (NTRS)

    Carson, G. T., Jr.

    1974-01-01

    Quantitative values were computed which show the effects of the presence of small amounts of oxygen, hydrogen, and hydroxyl radicals on the finite-rate chemical kinetics of premixed hydrogen-air mixtures undergoing isobaric autoignition and combustion. The free radicals were considered to be initially present in hydrogen-air mixtures at equivalence ratios of 0.2, 0.6, 1.0, and 1.2. Initial mixture temperatures were 1100 K, 1200 K, and 1500 K, and pressures were 0.5, 1.0, 2.0, and 4.0 atm. Of the radicals investigated, atomic oxygen was found to be the most effective for reducing induction time, defined as the time to 5 percent of the total combustion temperature rise. The reaction time, the time between 5 percent and 95 percent of the temperature rise, is not decreased by the presence of free radicals in the initial hydrogen-air mixture. Fuel additives which yield free radicals might be used to effect a compact supersonic combustor design for efficient operation in an otherwise reaction-limited combustion regime.

  5. Effect of hydrogen on superelasticity of the titanium nickelide-based alloy

    NASA Astrophysics Data System (ADS)

    Lotkov, Aleksandr; Baturin, Anatolii; Grishkov, Victor; Rodionov, Ivan; Kudiyarov, Victor; Lider, Andrei

    2015-10-01

    The hydrogen effect on the inelastic properties and plastic strain development after electrolythical hydrogenation in physiological solution was investigated. This effect virtually results in a failure under torsion of Ti49.1Ni50.9 (atom per cent) alloy specimens with coarse-grained (CG) and submicrocrystalline (SMC) structures. It is shown that hydrogen embrittlement (HE) phenomenon occurs irrespective of the grain size in the studied specimens at approximately equal strain values. However, compared to the specimens with CG structure, those with SMC structure accumulate two to three times more hydrogen for the same hydrogenation time. It is found that hydrogen has a much smaller effect on the inelastic properties of specimens with SMC structure as compared to those with CG structure.

  6. Effect of hydrogen on superelasticity of the titanium nickelide-based alloy

    SciTech Connect

    Lotkov, Aleksandr; Baturin, Anatolii; Grishkov, Victor Rodionov, Ivan; Kudiyarov, Victor Lider, Andrei

    2015-10-27

    The hydrogen effect on the inelastic properties and plastic strain development after electrolythical hydrogenation in physiological solution was investigated. This effect virtually results in a failure under torsion of Ti{sub 49.1}Ni{sub 50.9} (atom per cent) alloy specimens with coarse-grained (CG) and submicrocrystalline (SMC) structures. It is shown that hydrogen embrittlement (HE) phenomenon occurs irrespective of the grain size in the studied specimens at approximately equal strain values. However, compared to the specimens with CG structure, those with SMC structure accumulate two to three times more hydrogen for the same hydrogenation time. It is found that hydrogen has a much smaller effect on the inelastic properties of specimens with SMC structure as compared to those with CG structure.

  7. Plasma electron temperature and the entropy effect on hydrogen production

    NASA Astrophysics Data System (ADS)

    Chakartnarodom, Parinya

    The thesis is that the interaction between the microwave induced electric field and a conductive material will produce plasma with high effective temperature such that it is thermodynamically and kinetically possible to produce small molecules from large molecules. The high effective temperature increases the potency of the entropy term such that small molecules are produced from large molecules even though the enthalpy for the process is positive. This hypothesis will be tested in several reactions for which the entropy change is positive. The plasma enhanced chemical reactions examined here may also be important in the practical application of alternative fuel production. The specific reactions of interest to this thesis are: (1) H 2O→H2 + 1/2 O2; DeltaGo ( kJ) = 247.5--0.056T, (2) 1/2 N2 + H2O→ H2 + NO; DeltaGo (kJ) = 338.45--0.069T, (3) C + H2O →Fe H2 + CO; Delta Go(kJ) = 135.8--0.143 T, (4) C6H 10O5 → 5H2 + C + 5CO; DeltaGo( kJ) = 711.3--2.48T. Experiments are carried out to examine the chemical species present within the plasma by the optical emission spectrometer (OES) and in the resultant gas outflow by the flue gas analyzer as a function of incoming gas composition and composition of the solid materials at the point of plasma initiation. The chemical and plasma reactions observed experimentally will be compared to thermodynamic calculations as a method to test the hypothesis. In addition, hydrogen production from water and from water and nitrogen at elevated effective temperature produces products, which recombine with negative free energy change at lower temperatures. Based on our initial results, it is also necessary to hypothesize that spatiotemporal plasma discharges can produce molecular hydrogen and an associated oxidant at an elevated effective temperature such that the mixture is 'quenched' to a lower temperature where said mixture is kinetically stabilized against spontaneous recombination. In all experiments, the results from OES show

  8. Hydrogen permeation through metals

    SciTech Connect

    Huhn, D.K.

    1985-01-01

    The permeation of hydrogen through metals was studied both theoretically and experimentally. Gas phase permeation experiments with nickel, iron, and iron-titanium alloys were done at low temperatures, 270 to 343 K, and high temperatures, 751 to 384 K, with hydrogen pressures ranging from 10/sup 3/ to 10/sup 5/ Pa. Experiments at low temperatures used an electrochemical cell to detect the permeating hydrogen, deuterium, or hydrogen-deuterium flux. At high temperatures a vacuum system equipped with a mass spectrometer measured the permeating hydrogen flux. The permeability and diffusivity of hydrogen through nickel membranes, 10/sup -4/ to 10/sup -5/ m in thickness, was measured in the temperature range of 580 to 270 K. The experimental results did not exhibit postulated surface effects; however, trapping of hydrogen was observed with a trap density of 2.5 x 10/sup 23/ sites/m/sup 3/ and a binding energy of 33 kJ/mole. The permeability of hydrogen through iron-titanium alloys increased with titanium concentration with a maximum increase of approximately 10% for a Fe-3.04 wt% Ti alloy compared to pure iron. High temperature diffusivity measurements showed a small decrease in diffusivity with titanium concentration; therefore, the solubility increased.

  9. Isotopic effect and amorphization of deuterated hydrogen hydrate under high pressure

    NASA Astrophysics Data System (ADS)

    Machida, Shin-Ichi; Hirai, Hisako; Kawamura, Taro; Yamamoto, Yoshitaka; Yagi, Takehiko

    2011-04-01

    High-pressure experiments of a mixture of H2 and D2O were performed using a diamond-anvil cell in the pressure range of 0.5-77.0 GPa under room temperature. Raman measurements revealed that an exchange of the hydrogen atoms occurred between fluid hydrogen and liquid water before the formation of deuterated hydrogen hydrate, and that a high-pressure structure of hydrogen hydrate, a filled ice Ic structure, formed at the same pressure as H2-H2O system hydrate. Additionally, the Raman spectra of the vibron for the D2, HD and H2 molecules revealed that the guest hydrogen molecules were partly extracted from the filled ice Ic structure above 20 GPa. The extraction of hydrogen molecules occurred depending on the atomic weight of the guest hydrogen molecules, and the heavier molecules were selectively released from the filled ice Ic structure. This isotopic effect in the extraction of hydrogen molecules showed differences in the stability of hydrogen hydrate depending on the species of guest molecules between D2, HD, and H2. Above 65 GPa, the filled ice Ic structure of hydrogen hydrate transformed to an amorphous phase. Formation of the amorphous phase showed the high-pressure limitation of hydrogen hydrate as a crystal structure and a new mechanism for the dissociation of gas hydrates under high pressure and room temperature.

  10. Effect of γ-ray irradiation on the sorption of hydrogen by nanoporous carbon materials

    NASA Astrophysics Data System (ADS)

    Dolbin, A. V.; Manzhelii, V. G.; Esel'son, V. B.; Gavrilko, V. G.; Vinnikov, N. A.; Basnukaeva, R. M.; Khlistyuck, M. V.; Maletskii, V. P.; Nikolaev, V. G.; Kudriachenko, E. V.; Uvarova, I. Yu.; Tripachko, N. A.; Koda, V. Yu.

    2015-04-01

    The effects of radiation exposure in a hydrogen atmosphere on hydrogen sorption by a synthetic porous carbon nanosorbent, SCN (spherical carbonite saturated). The exposure was created by γ-rays from cobalt-60 (photon energy 1.2 MeV, irradiation dose 4.8 × 107 rad) in a normal hydrogen atmosphere at a pressure of 1 atm and a temperature of 300 K. The processes of hydrogen sorption-desorption by SCN samples before and after irradiation were studied in a temperature interval of 15-1173 K. It was found that the irradiation of SCN in a hydrogen atmosphere significantly increased the amount hydrogen sorbed in the sample. We conducted a comparison with the results of earlier studies investigating the influence of irradiation on the sorption of hydrogen by single-walled carbon nanotubes. The amount of physically sorbed hydrogen in the synthetic SCN sorbent that was irradiated in the hydrogen atmosphere, is four times greater than the amount of hydrogen that was physically sorbed by the single-walled carbon nanotubes that were irradiated under similar conditions. At a temperature below 25 K, the hydrogen diffusion in the SCN was almost temperature independent for the porous subsystem with the highest diffusion coefficients, which is typical for cases when the tunnel diffusion mechanism dominates the thermodynamic mechanism.

  11. 40 CFR 72.32 - Permit application shield and binding effect of permit application.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 16 2010-07-01 2010-07-01 false Permit application shield and binding effect of permit application. 72.32 Section 72.32 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) PERMITS REGULATION Acid Rain Permit Applications § 72.32 Permit application shield and binding effect...

  12. Binding energy effects in cascade evolution and sputtering

    SciTech Connect

    Robinson, M.T.

    1995-06-01

    The MARLOWE model was extended to include a binding energy dependent on the local crystalline order, so that atoms are bound less strongly to their lattice sites near surfaces or associated damage. Sputtering and cascade evolution were studied on the examples of self-ion irradiations of Cu and Au monocrystals. In cascades, the mean binding energy is reduced {approximately}8% in Cu with little dependence on the initial recoil energy; in Au, it is reduced {approximately}9% at 1 keV and {approximately}15% at 100 keV. In sputtering, the mean binding energy is reduced {approximately}8% in Cu and {approximately}15% in Au with little energy dependence; the yields are increased about half as much. Most sites from which sputtered atoms originate are isolated in both metals. Small clusters of such sites occur in Cu, but there are some large clusters in Au, especially in [111] targets. There are always more large clusters with damage-dependent binding than with a constant binding energy, but only a few clusters are compact enough to be regarded as pits.

  13. Hydrogen quantum effects in hydride LaNi5H7

    PubMed Central

    Kaneko, Tomoaki; Tezuka, Akinori; Ogawa, Hiroshi; Ikeshoji, Tamio

    2011-01-01

    Energy eigenvalues and wave functions of hydrogen atoms in hydride LaNi5H7 are calculated. First-principles electronic structure calculations are employed to obtain the three-dimensional potential energy structure of each hydrogen site. These quantum effects are not negligibly small in evaluation of enthalpy of formation, an important property of hydrogen storage. Including the temperature effect from hydrogen gas, experimental values are well reproduced. The excitation probability of inelastic neutron scattering is also calculated using the wave functions obtained. PMID:22065890

  14. Thermodynamic effects of replacements of Pro residues in helix interiors of maltose-binding protein.

    PubMed

    Prajapati, R S; Lingaraju, G M; Bacchawat, Kiran; Surolia, Avadhesha; Varadarajan, Raghavan

    2003-12-01

    Introduction of Pro residues into helix interiors results in protein destabilization. It is currently unclear if the converse substitution (i.e., replacement of Pro residues that naturally occur in helix interiors would be stabilizing). Maltose-binding protein is a large 370-amino acid protein that contains 21 Pro residues. Of these, three nonconserved residues (P48, P133, and P159) occur at helix interiors. Each of the residues was replaced with Ala and Ser. Stabilities were characterized by differential scanning calorimetry (DSC) as a function of pH and by isothermal urea denaturation studies as a function of temperature. The P48S and P48A mutants were found to be marginally more stable than the wild-type protein. In the pH range of 5-9, there is an average increase in T(m) values of P48A and P48S of 0.4 degrees C and 0.2 degrees C, respectively, relative to the wild-type protein. The other mutants are less stable than the wild type. Analysis of the effects of such Pro substitutions in MBP and in three other proteins studied to date suggests that substitutions are more likely to be stabilizing if the carbonyl group i-3 or i-4 to the mutation site is not hydrogen bonded in the wild-type protein. PMID:14635128

  15. Quantifying the Lunar Hydrogen Cycle: A Fast, Effective, and Economical CubeSat Approach

    NASA Astrophysics Data System (ADS)

    Collier, M.; Adams, M. L.; Barabash, S.; Calhoun, P. C.; Clark, P. E.; Farrell, W. M.; Folta, D. C.; Halekas, J.; Haque, S. E.; Hurley, D. M.; Keidar, M.; Keller, J. W.; Killen, R. M.; Kletzing, C.; MacDowall, R. J.; Malphrus, B. K.; McNeil, R. R.; Vondrak, R. R.; Wieser, M.

    2015-10-01

    The Moon breathes hydrogen: solar wind protons and micro-meteoroids deliver hydrogen to the lunar surface at local rates that depend on surface composition, local topography, and the presence of structures such as magnetic anomalies. Because the lunar surface is generally saturated with hydrogen, the implanted hydrogen escapes the surface and forms the hydrogen exosphere through a variety of processes including sputtering, recoil, and diffusion - giving the surface an effective hydrogen "albedo." These processes can lead to hydrogen deposition into cold traps and the formation of OH, and possibly water, through chemical alteration of oxygen-bearing minerals. Exospheric hydrogen is reclaimed by the solar wind as picked-up photoions and chargeexchange products. The exact pathway for each of these processes remains unknown, especially at regional scales, and quantifying each of these processes in this "lunar hydrogen cycle" as a function of solar zenith angle and plasma and space environment will lead to a unified understanding of the plasma, exospheric, and geologic Moon. CubeSats provide a fast, effective, and economical approach to quantifying the currently unknown parameters in the lunar hydrogen cycle.

  16. Design and Development of New Carbon-Based Sorbent Systems for an Effective Containment of Hydrogen

    SciTech Connect

    Alan C. Cooper

    2012-05-03

    This is a summary for work performed under cooperative agreement DE FC36 04GO14006 (Design and Development of New Carbon-based Sorbent Systems for an Effective Containment of Hydrogen). The project was directed to discover new solid and liquid materials that use reversible catalytic hydrogenation as the mechanism for hydrogen capture and storage. After a short period of investigation of solid materials, the inherent advantages of storing and transporting hydrogen using liquid-phase materials focused our attention exclusively on organic liquid hydrogen carriers (liquid carriers). While liquid carriers such as decalin and methylcyclohexane were known in the literature, these carriers suffer from practical disadvantages such as the need for very high temperatures to release hydrogen from the carriers and difficult separation of the carriers from the hydrogen. In this project, we were successful in using the prediction of reaction thermodynamics to discover liquid carriers that operate at temperatures up to 150 C lower than the previously known carriers. The means for modifying the thermodynamics of liquid carriers involved the use of certain molecular structures and incorporation of elements other than carbon into the carrier structure. The temperature decrease due to the more favorable reaction thermodynamics results in less energy input to release hydrogen from the carriers. For the first time, the catalytic reaction required to release hydrogen from the carriers could be conducted with the carrier remaining in the liquid phase. This has the beneficial effect of providing a simple means to separate the hydrogen from the carrier.

  17. Sensory and Cognitive Effects of Acute Exposure to Hydrogen Sulfide

    PubMed Central

    Fiedler, Nancy; Kipen, Howard; Ohman-Strickland, Pamela; Zhang, Junfeng; Weisel, Clifford; Laumbach, Robert; Kelly-McNeil, Kathie; Olejeme, Kelechi; Lioy, Paul

    2008-01-01

    Background Some epidemiologic studies have reported compromised cognitive and sensory performance among individuals exposed to low concentrations of hydrogen sulfide (H2S). Objectives We hypothesized a dose–response increase in symptom severity and reduction in sensory and cognitive performance in response to controlled H2S exposures. Methods In separate exposure sessions administered in random order over three consecutive weeks, 74 healthy subjects [35 females, 39 males; mean age (± SD) = 24.7 ± 4.2; mean years of education = 16.5 ± 2.4], were exposed to 0.05, 0.5, and 5 ppm H2S. During each exposure session, subjects completed ratings and tests before H2S exposure (baseline) and during the final hour of the 2-hr exposure period. Results Dose–response reduction in air quality and increases in ratings of odor intensity, irritation, and unpleasantness were observed. Total symptom severity was not significantly elevated across any exposure condition, but anxiety symptoms were significantly greater in the 5-ppm than in the 0.05-ppm condition. No dose–response effect was observed for sensory or cognitive measures. Verbal learning was compromised during each exposure condition. Conclusions Although some symptoms increased with exposure, the magnitude of these changes was relatively minor. Increased anxiety was significantly related to ratings of irritation due to odor. Whether the effect on verbal learning represents a threshold effect of H2S or an effect due to fatigue across exposure requires further investigation. These acute effects in a healthy sample cannot be directly generalized to communities where individuals have other health conditions and concomitant exposures. PMID:18197303

  18. The effect of hydrogen peroxide on polishing removal rate in CMP with various abrasives

    NASA Astrophysics Data System (ADS)

    Manivannan, R.; Ramanathan, S.

    2009-01-01

    The effect of hydrogen peroxide in chemical mechanical planarization slurries for shallow trench isolation was investigated. The various abrasives used in this study were ceria, silica, alumina, zirconia, titania, silicon carbide, and silicon nitride. Hydrogen peroxide suppresses the polishing of silicon dioxide and silicon nitride surfaces by ceria abrasives. The polishing performances of other abrasives were either unaffected or enhanced slightly with the addition of hydrogen peroxide. The ceria abrasives were treated with hydrogen peroxide, and the polishing of the work surfaces with the treated abrasive shows that the inhibiting action of hydrogen peroxide is reversible. It was found that the effect of hydrogen peroxide as an additive is a strong function of the nature of the abrasive particle.

  19. Lysozyme binding ability toward psychoactive stimulant drugs: Modulatory effect of colloidal metal nanoparticles.

    PubMed

    Sonu, Vikash K; Islam, Mullah Muhaiminul; Rohman, Mostofa Ataur; Mitra, Sivaprasad

    2016-10-01

    The interaction and binding behavior of the well-known psychoactive stimulant drugs theophylline (THP) and theobromine (THB) with lysozyme (LYS) was monitored by in-vitro fluorescence titration and molecular docking calculations under physiological condition. The quenching of protein fluorescence on addition of the drugs is due to the formation of protein-drug complex in the ground state in both the cases. However, the binding interaction is almost three orders of magnitude stronger in THP, which involves mostly hydrogen bonding interaction in comparison with THB where hydrophobic binding plays the predominant role. The mechanism of fluorescence quenching (static type) remains same also in presence of gold and silver nanoparticles (NPs); however, the binding capacity of LYS with the drugs changes drastically in comparison with that in aqueous buffer medium. While the binding affinity of LYS to THB increases ca. 100 times in presence of both the NPs, it is seen to decrease drastically (by almost 1000 fold) for THP. This significant modulation in binding behavior indicates that the drug transportation capacity of LYS can be controlled significantly with the formation protein-NP noncovalent assembly system as an efficient delivery channel. PMID:27419646

  20. Solvent Effects in the Hydrogenation of 2-Butanone

    SciTech Connect

    Akpa, B. S.; DAgostino, C.; Gladden, L. F.; Hindle, K.; Manyar, H.; McGregor, J.; Li, Ruoyu; Neurock, Matthew; Sinha, N.; Stitt, E. H.; Weber, D.; Zeitler, J. A.; Rooney, D. W.

    2012-03-27

    In liquid-phase reaction systems, the role of the solvent is often limited to the simple requirement of dissolving and/or diluting substrates. However, the correct choice, either pure or mixed, can significantly influence both reaction rate and selectivity. For multi-phase heterogeneously catalysed reactions observed variations may be due to changes in mass transfer rates, reaction mechanism, reaction kinetics, adsorption properties and combinations thereof. The liquid-phase hydrogenation of 2-butanone to 2- butanol over a Ru/SiO2 catalyst, for example, shows such complex rate behaviour when varying water/isopropyl alcohol (IPA) solvent ratios. In this paper, we outline a strategy which combines measured rate data with physical property measurements and molecular simulation in order to gain a more fundamental understanding of mixed solvent effects for this heterogeneously catalysed reaction. By combining these techniques, the observed complex behaviour of rate against water fraction is shown to be a combination of both mass transfer and chemical effects.

  1. Effect of thermal nonequilibrium on reactions in hydrogen combustion

    NASA Astrophysics Data System (ADS)

    Voelkel, S.; Raman, V.; Varghese, P. L.

    2016-03-01

    The presence of shocks in scramjet internal flows introduces nonequilibrium of internal energy modes of the molecules. Here, the effect of vibrational nonequilibrium on key reactions of hydrogen-air combustion is studied. A quasi-classical trajectory (QCT) approach is used to derive reaction probability for nonequilibrium conditions using ab initio-derived potential energy surfaces. The reaction rates under nonequilibrium are studied using a two-temperature description, where the vibrational modes are assumed to be distributed according to a Boltzmann distribution at a characteristic vibrational temperature, in addition to a translational temperature describing the translational and rotational population distribution. At scramjet-relevant conditions, it is found that the nonequilibrium reaction rate depends not only on the level of vibrational excitation, but also on the reactants involved. Conventional two-temperature models for reaction rates, often derived using empirical means, were found to be inaccurate under these conditions, and modified parameters are proposed based on the QCT calculations. It is also found that models that include details of the reaction process through dissociation energy, for instance, provide a better description of nonequilibrium effects.

  2. Effects of the Hydroxyl Group on Phenyl Based Ligand/ERRγ Protein Binding

    PubMed Central

    2015-01-01

    Bisphenol-A (4,4′-dihydroxy-2,2-diphenylpropane, BPA, or BPA-A) and its derivatives, when exposed to humans, may affect functions of multiple organs by specific binding to the human estrogen-related receptor γ (ERRγ). We carried out atomistic molecular dynamics (MD) simulations of three ligand compounds including BPA-A, 4-α-cumylphenol (BPA-C), and 2,2-diphenylpropane (BPA-D) binding to the ligand binding domain (LBD) of a human ERRγ to study the structures and energies associated with the binding. We used the implicit Molecular Mechanics/Poisson–Boltzmann Surface Area (MM/PBSA) method to estimate the free energies of binding for the phenyl based compound/ERRγ systems. The addition of hydroxyl groups to the aromatic ring had only a minor effect on binding structures and a significant effect on ligand/protein binding energy in an aqueous solution. Free binding energies of BPA-D to the ERRγ were found to be considerably less than those of BPA-A and BPA-C to the ERRγ. These results are well correlated with those from experiments where no binding affinities were determined in the BPA-D/ERRγ complex. No conformational change was observed for the helix 12 (H-12) of ERRγ upon binding of these compounds preserving an active transcriptional conformation state. PMID:25098505

  3. Binding of hydrocarbons and other extremely weak ligands to transition metal complexes that coordinate hydrogen: Investigation of cis-interactions and delocalized bonding involving sigma bonds

    SciTech Connect

    Kubas, G.J.; Eckert, J.; Luo, X.L.

    1997-07-01

    This is the final report of a three-year Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). At the forefront of chemistry are efforts to catalytically transform the inert C-H bonds in alkanes to more useful products using metal compounds. The goal is to observe binding and cleavage of alkane C-H bonds on metals or to use related silane Si-H bonding as models, analogous to the discovery of hydrogen (H{sub 2}) binding to metals. Studies of these unique sigma complexes (M{hor_ellipsis}H-Y; Y{double_bond}H, Si, C) will aid in developing new catalysts or technologies relevant to DOE interest, e.g., new methods for tritium isotope separation. Several transition metals (Mo, W, Mn, and Pt) were found to reversibly bind and cleave H{sub 2}, silanes, and halocarbons. The first metal-SiH{sub 4} complexes, thus serving as a model for methane reactions. A second goal is to study the dynamics and energetics of H-Y bonds on metals by neutron scattering, and evidence for interactions between bound H-Y and nearby H atoms on metal complexes has been found.

  4. Binding of the Respiratory Chain Inhibitor Antimycin to theMitochondrial bc1 Complex: A New Crystal Structure Reveals an AlteredIntramolecular Hydrogen-Bonding Pattern

    SciTech Connect

    Huang, Li-shar; Cobessi, David; Tung, Eric Y.; Berry, Edward A.

    2005-05-10

    Antimycin A (antimycin), one of the first known and most potent inhibitors of the mitochondrial respiratory chain, binds to the quinone reduction site of the cytochrome bc1 complex.Structure-activity-relationship studies have shown that the N-formylamino-salicyl-amide group is responsible for most of the binding specificity, and suggested that a low pKa for the phenolic OH group and an intramolecular H-bond between that OH and the carbonyl O of the salicylamide linkage are important. Two previous X-ray structures of antimycin bound to vertebrate bc1 complex gave conflicting results. A new structure reported here of the bovine mitochondrial bc1 complex at 2.28Angstrom resolution with antimycin bound, allows us for the first time to reliably describe the binding of antimycin and shows that the intramolecular hydrogen bond described in solution and in the small-molecule structure is replaced by one involving the NH rather than carbonyl O of the amide linkage, with rotation of the amide group relative to the aromatic ring. The phenolic OH and formylamino N form H-bonds with conserved Asp228 of cyt b, and the formylamino O H-bonds via a water molecule to Lys227. A strong density the right size and shape for a diatomic molecule is found between the other side of the dilactone ring and the alpha-A helix.

  5. Stress corrosion cracking of zirconium cladding tubes: IV. Effect of hydrogen saturation

    NASA Astrophysics Data System (ADS)

    Rozhnov, A. B.; Nikulin, S. A.; Khanzhin, V. G.; Belov, V. A.

    2011-04-01

    The effect of hydrogen saturation on the stress corrosion cracking (SCC) resistance of zirconium cladding tubes in an iodine-containing medium is studied. Comparative SCC tests are performed for tubes produced from E110 and E635 alloys with various hydrogen contents (up to 400 ppm). Hydrogen is shown to decrease the SCC resistance of the tubes predominantly because of the activation of pitting formation processes.

  6. The effect of ammonia upon the electrocatalysis of hydrogen oxidation and oxygen reduction on polycrystalline platinum

    NASA Astrophysics Data System (ADS)

    Verdaguer-Casadevall, Arnau; Hernandez-Fernandez, Patricia; Stephens, Ifan E. L.; Chorkendorff, Ib; Dahl, Søren

    2012-12-01

    The influence of ammonium ions on the catalysis of hydrogen oxidation and oxygen reduction is studied by means of rotating ring-disk electrode experiments on polycrystalline platinum in perchloric acid. While ammonium does not affect the hydrogen oxidation reaction, the oxygen reduction reaction is severely poisoned. Poisoning at the cathode explains the majority of the losses observed in polymer electrolyte membrane fuel cells contaminated with ammonia. Voltammetry in deaerated solution suggest that the poisoning can be attributed to either ammonium oxidation or increased binding to OH species.

  7. Effects of nitrogen on hydrogen retention in tungsten: First-principles calculations

    NASA Astrophysics Data System (ADS)

    Wang, Sheng; Kong, Xiang-Shan; Wu, Xuebang; Fang, Q. F.; Chen, Jun-Ling; Luo, G.-N.; Liu, C. S.

    2015-04-01

    While the use of nitrogen seeding to reduce the edge plasma temperature has been successfully applied in many tokamak experiments, questions remain as to effects of the nitrogen-enriched layer on hydrogen retention in tungsten. In this paper, we investigate the influence of nitrogen on hydrogen dissolution and diffusion behavior in tungsten using the first-principles. The nitrogen has little effect on the dissolution of hydrogen in the interstitial site but significantly impedes the accumulation of hydrogen in the vacancy, leading to the decrease of hydrogen retention in nitrogen-enriched layer. Meanwhile, both the interstitial nitrogen and the vacancy-nitrogen complex can significantly reduce the hydrogen effective diffusivity. This suggests that the nitrogen-enriched layer forming on the tungsten surface can act as a diffusion barrier for the re-emission of implanted hydrogen, enhancing hydrogen diffusion into the bulk, and consequently, increasing of hydrogen retention in bulk. These results provide a sound explanation for the recent experimental results.

  8. Inhibitory effect of midkine-binding peptide on tumor proliferation and migration

    PubMed Central

    Huang, Hui-Lian; Shen, Jian-Fen; Min, Li-Shan; Ping, Jin-Liang; Lu, Yong-Liang; Dai, Li-Cheng

    2015-01-01

    Background: To investigate the inhibitory effect of midkine-binding peptides on human umbilical vein endothelial cells (HUVECs) proliferation and angiogenesis of xenograft tumor. Methods: The midkine-binding peptides were panned by Ph.D.-7™ Phage Display Peptide Library Kit, and the specific binding activities of positive clones to target protein were examined by phage ELISA. The effect of midkine-binding peptides on proliferation of HUVECs was confirmed by MTT test. The xenograft tumor model was formed in BALB/c mice with the murine hepatocarcinoma cells H22 (H22). Microvessel density (MVD) was analyzed by immunohistochemistry of factor VIII staining. Results: Midkine-binding peptides have the inhibitory effects on tumor angiogenesis, a proliferation assay using human umbilical vein endothelial cells (HUVECs) indicated that particular midkine-binding peptides significantly inhibited the proliferation of the HUVECs. Midkine-binding peptides were also observed to efficiently suppress angiogenesis induced by murine hepatocarcinoma H22 cells in BALB/c nude mice. Conclusion: The midkine-binding peptides can inhibit solid tumor growth by retarding the formation of new blood vessels. The results indicate that midkine-binding peptides may represent potent anti-angiogenesis agents in vivo. PMID:26191241

  9. Hydrogen-induced effects on the CVD growth of high-quality graphene structures.

    PubMed

    Zhang, Xianfeng; Ning, Jing; Li, Xianglong; Wang, Bin; Hao, Long; Liang, Minghui; Jin, Meihua; Zhi, Linjie

    2013-09-21

    In this work, the hydrogen-induced effects on the CVD growth of high-quality graphene have been systematically studied by regulating the growth parameters mainly related to hydrogen. Experimental results demonstrate that under a high hydrogen flow rate, the competitive etching effect during the growth process is more prominent and even shows macroscopic selectivity. Based on these understandings, the hexagonal graphene domains with diverse edge modalities are controllably synthesized on a large scale by elaborately managing the competitive etching effect of hydrogen that existed during the formation of graphene. This study not only contributes to the understanding of the mechanism of CVD growth, especially the effects of hydrogen used in the system, but also provides a facile method to synthesize high-quality graphene structures with trimmed edge morphologies. PMID:23715011

  10. Anion A– • HX Clusters with Reduced Electron Binding Energies: Proton vs Hydrogen Atom Relocation Upon Electron Detachment

    SciTech Connect

    Wang, Xue B.; Kass, Steven R.

    2014-12-10

    Clustering an anion with one or more neutral molecules is a stabilizing process that enhances the oxidation potential of the complex relative to the free ion. Several hydrogen bond clusters (i.e., A— • HX, where A— = H2PO4— and CF3CO2— and HX = MeOH, PhOH, and Me2NOH or Et2NOH) are examined by photoelectron spectroscopy and M06-2X and CCSD(T) computations. Remarkably, these species are experimentally found to have adiabatic detachment energies that are smaller than those for the free ion and reductions of 0.47 to 1.87 eV are predicted computationally. Hydrogen atom and proton transfers upon vertical photodetachment are two limiting extremes on the neutral surface in a continuum of mechanistic pathways that account for these results, and the whole gamut of possibilities are predicted to occur.

  11. Protective Effects of Hydrogen Gas on Experimental Acute Pancreatitis

    PubMed Central

    Zhou, Hao-xin; Han, Bing; Hou, Li-Min; An, Ting-Ting; Jia, Guang; Cheng, Zhuo-Xin; Ma, Yong; Zhou, Yi-Nan; Kong, Rui; Wang, Shuang-Jia; Wang, Yong-Wei; Sun, Xue-Jun; Pan, Shang-Ha; Sun, Bei

    2016-01-01

    Acute pancreatitis (AP) is an inflammatory disease mediated by damage to acinar cells and pancreatic inflammation. In patients with AP, subsequent systemic inflammatory responses and multiple organs dysfunction commonly occur. Interactions between cytokines and oxidative stress greatly contribute to the amplification of uncontrolled inflammatory responses. Molecular hydrogen (H2) is a potent free radical scavenger that not only ameliorates oxidative stress but also lowers cytokine levels. The aim of the present study was to investigate the protective effects of H2 gas on AP both in vitro and in vivo. For the in vitro assessment, AR42J cells were treated with cerulein and then incubated in H2-rich or normal medium for 24 h, and for the in vivo experiment, AP was induced through a retrograde infusion of 5% sodium taurocholate into the pancreatobiliary duct (0.1 mL/100 g body weight). Wistar rats were treated with inhaled air or 2% H2 gas and sacrificed 12 h following the induction of pancreatitis. Specimens were collected and processed to measure the amylase and lipase activity levels; the myeloperoxidase activity and production levels; the cytokine mRNA expression levels; the 8-hydroxydeoxyguanosine, malondialdehyde, and glutathione levels; and the cell survival rate. Histological examinations and immunohistochemical analyses were then conducted. The results revealed significant reductions in inflammation and oxidative stress both in vitro and in vivo. Furthermore, the beneficial effects of H2 gas were associated with reductions in AR42J cell and pancreatic tissue damage. In conclusion, our results suggest that H2 gas is capable of ameliorating damage to the pancreas and AR42J cells and that H2 exerts protective effects both in vitro and in vivo on subjects with AP. Thus, the results obtained indicate that this gas may represent a novel therapy agent in the management of AP. PMID:27115738

  12. Quantum effects in a simple ring with hydrogen bonds.

    PubMed

    Kariev, Alisher M; Green, Michael E

    2015-05-14

    Complexes containing multiple arginines are common in proteins. The arginines are typically salt-bridged or hydrogen-bonded, so that their charges do not repel. Here we present a quantum calculation of a ring in which the components of a salt bridge composed of a guanidinium, the arginine side chain, and a carboxylic acid are separated by water molecules. When one water molecule is displaced from the ring, atomic charges of the other water molecule, as well as other properties, are significantly affected. The exchange and correlation energy differences between optimized and displaced rings are larger than thermal energy at room temperature, and larger than the sum of other energy differences. This suggests that calculations on proteins and other systems where such a ring may occur must take quantum effects into account; charges on certain atoms shift as substituents are added to the system: another water molecule, an -OH, or -CN bonded to either moiety. Also, charge shifts accompany proton shifts from the acid to guanidinium to ionize the salt bridge. The consequences of moving one water out of the ring give evidence for electron delocalization. Bond order and atomic charges are determined using natural bond orbital calculations. The geometry of the complex changes with ionization as well as the -OH and -CN additions but not in a simple manner. These results help in understanding the role of groups of arginines in salt-bridged clusters in proteins. PMID:25906287

  13. Anharmonic effects in atomic hydrogen: Superconductivity and lattice dynamical stability

    NASA Astrophysics Data System (ADS)

    Borinaga, Miguel; Errea, Ion; Calandra, Matteo; Mauri, Francesco; Bergara, Aitor

    2016-05-01

    We present first-principles calculations of metallic atomic hydrogen in the 400-600 GPa pressure range in a tetragonal structure with space group I 41/a m d , which is predicted to be its first atomic phase. Our calculations show a band structure close to the free-electron-like limit due to the high electronic kinetic energy induced by pressure. Bands are properly described even in the independent electron approximation fully neglecting the electron-electron interaction. Linear-response harmonic calculations show a dynamically stable phonon spectrum with marked Kohn anomalies. Even if the electron-electron interaction has a minor role in the electronic bands, the inclusion of electronic exchange and correlation in the density response is essential to obtain a dynamically stable structure. Anharmonic effects, which are calculated within the stochastic self-consistent harmonic approximation, harden high-energy optical modes and soften transverse acoustic modes up to a 20% in energy. Despite a large impact of anharmonicity has been predicted in several high-pressure hydrides, here the superconducting critical temperature is barely affected by anharmonicity, as it is lowered from its harmonic 318 K value only to 300 K at 500 GPa. We attribute the small impact of anharmonicity on superconductivity to the absence of softened optical modes and the fairly uniform distribution of the electron-phonon coupling among the vibrational modes.

  14. Parameterization of an effective potential for protein–ligand binding from host–guest affinity data

    PubMed Central

    Wickstrom, Lauren; Deng, Nanjie; He, Peng; Mentes, Ahmet; Nguyen, Crystal; Gilson, Michael K.; Kurtzman, Tom; Gallicchio, Emilio; Levy, Ronald M.

    2015-01-01

    Force field accuracy is still one of the “stalemates” in biomolecular modeling. Model systems with high quality experimental data are valuable instruments for the validation and improvement of effective potentials. With respect to protein–ligand binding, organic host–guest complexes have long served as models for both experimental and computational studies because of the abundance of binding affinity data available for such systems. Binding affinity data collected for cyclodextrin (CD) inclusion complexes, a popular model for molecular recognition, is potentially a more reliable resource for tuning energy parameters than hydration free energy measurements. Convergence of binding free energy calculations on CD host–guest systems can also be obtained rapidly, thus offering the opportunity to assess the robustness of these parameters. In this work, we demonstrate how implicit solvent parameters can be developed using binding affinity experimental data and the binding energy distribution analysis method (BEDAM) and validated using the Grid Inhomogeneous Solvation Theory analysis. These new solvation parameters were used to study protein–ligand binding in two drug targets against the HIV-1 virus and improved the agreement between the calculated and the experimental binding affinities. This work illustrates how benchmark sets of high quality experimental binding affinity data and physics-based binding free energy models can be used to evaluate and optimize force fields for protein–ligand systems. PMID:26256816

  15. In vitro effects of cytosolic inhibitor and opiates on the binding of [3H]oestradiol to nuclear type II binding sites of rat uterus and hypothalamus.

    PubMed

    Garai, J; Vértes, M; Kovács, S

    1989-03-01

    The effect of cytosolic ultrafiltrates prepared from intact rat uteri, brain hemispheres and hypothalami and of some opiate analogues on oestradiol binding to nuclear type II sites in rat uterus and hypothalamus was studied. Opiate binding in nuclear fraction of rat uteri was also evaluated. Both uterine and hypothalamic low affinity nuclear oestradiol binding was inhibited by filtrate from uteri, while only hypothalamic nuclear binding was decreased in presence of hypothalamic filtrate. Filtrate from brain was ineffective on nuclear oestradiol binding of the studied tissues. Concentration dependent inhibition of uterine nuclear oestradiol binding could be demonstrated by some opiate analogues in vitro. Specific low affinity nuclear binding of opiate antagonist naloxone and agonist dihydromorphine was observed in rat uteri which could be inhibited by uterine filtrate and oestradiol but not by hypothalamic filtrate or other steroids. Present findings support the probable intracellular interplay of opiates and oestradiol action and suggest that cytosolic inhibitor factor might be involved. PMID:2704239

  16. Effects of microstructure banding on hydrogen assisted fatigue crack growth in X65 pipeline steels

    SciTech Connect

    Ronevich, Joseph A.; Somerday, Brian P.; San Marchi, Chris W.

    2015-09-10

    Banded ferrite-pearlite X65 pipeline steel was tested in high pressure hydrogen gas to evaluate the effects of oriented pearlite on hydrogen assisted fatigue crack growth. Test specimens were oriented in the steel pipe such that cracks propagated either parallel or perpendicular to the banded pearlite. The ferrite-pearlite microstructure exhibited orientation dependent behavior in which fatigue crack growth rates were significantly lower for cracks oriented perpendicular to the banded pearlite compared to cracks oriented parallel to the bands. Thus the reduction of hydrogen assisted fatigue crack growth across the banded pearlite is attributed to a combination of crack-tip branching and impeded hydrogen diffusion across the banded pearlite.

  17. The effect of hydrogen on wear resistance of a titanium alloy in corrosive medium

    SciTech Connect

    Jiang, Xiaoxia; Li, Shishuo; Duan, Chengtian; Li, Ming )

    1990-08-01

    The effect of hydrogen on wear resistance of Ti-6Al-4V has been investigated in IN H{sub 2}SO{sub 4} at different polarized potentials. The morphology of debris and wear scars was observed in SEM and metallography. The contents of hydrogen in both wear debris and subsurface of specimen were determined by the gas chromatographic method and SIMS, respectively. The experiment shows that the wear losses may be partially controlled by cathode protection, but wear increases from over-protection. The unusual wear losses may be explained by hydrogen embrittlement of the Ti alloy because of hydrogen evolution on the specimen surface. 5 refs.

  18. Nuclear quantum effects of hydrogen bonds probed by tip-enhanced inelastic electron tunneling.

    PubMed

    Guo, Jing; Lü, Jing-Tao; Feng, Yexin; Chen, Ji; Peng, Jinbo; Lin, Zeren; Meng, Xiangzhi; Wang, Zhichang; Li, Xin-Zheng; Wang, En-Ge; Jiang, Ying

    2016-04-15

    We report the quantitative assessment of nuclear quantum effects on the strength of a single hydrogen bond formed at a water-salt interface, using tip-enhanced inelastic electron tunneling spectroscopy based on a scanning tunneling microscope. The inelastic scattering cross section was resonantly enhanced by "gating" the frontier orbitals of water via a chlorine-terminated tip, so the hydrogen-bonding strength can be determined with high accuracy from the red shift in the oxygen-hydrogen stretching frequency of water. Isotopic substitution experiments combined with quantum simulations reveal that the anharmonic quantum fluctuations of hydrogen nuclei weaken the weak hydrogen bonds and strengthen the relatively strong ones. However, this trend can be completely reversed when a hydrogen bond is strongly coupled to the polar atomic sites of the surface. PMID:27081066

  19. Effects of hydrogen isotopes in the irradiation damage of CLAM steel

    NASA Astrophysics Data System (ADS)

    Zhao, M. Z.; Liu, P. P.; Zhu, Y. M.; Wan, F. R.; He, Z. B.; Zhan, Q.

    2015-11-01

    The isotope effect of hydrogen in irradiation damage plays an important role in the development of reduced activation Ferritic/Martensitic steels in nuclear reactors. The evolutions of microstructures and mechanical properties of China low active martensitic (CLAM) steel subjected to hydrogen and deuterium ions irradiation are studied comparatively. Under the same irradiation conditions, larger size and smaller density of dislocation loops are generated by deuterium ion than by hydrogen ion. Irradiation hardening occurs under the ion irradiation and the hardening induced by hydrogen ion is higher than by deuterium ion. Moreover, the coarsening of M23C6 precipitates is observed, which can be explained by the solute drag mechanisms. It turns out that the coarsening induced by deuterium ion irradiation is more distinct than by hydrogen ion irradiation. No distinct variations for the compositions of M23C6 precipitates are found by a large number of statistical data after hydrogen isotopes irradiation.

  20. Synergetic effects in novel hydrogenated F-doped TiO2 photocatalysts

    NASA Astrophysics Data System (ADS)

    Samsudin, Emy Marlina; Abd Hamid, Sharifah Bee; Juan, Joon Ching; Basirun, Wan Jefrey; Centi, Gabriele

    2016-05-01

    The synergistic effect between fluorine and hydrogen in hydrogenated F-doped TiO2 photocatalysts is evaluated for the photocatalytic degradation of atrazine. The interaction between fluorine and hydrogen species in hydrogenated F-doped TiO2 overcomes the limitations of individual F-doped TiO2 and hydrogenated TiO2 photocatalyst properties. Hydrogenated F-doped TiO2 is photo-active under UV, visible and infrared light illumination with efficient electrons and holes separations. The optimized concentration of surface vacancies and Ti3+ centers coupled with enhanced surface hydrophilicity facilitates the production of surface-bound and free hydroxyl radicals. The surface of the catalyst contains dbnd Tisbnd F, dbnd Tisbnd OH, dbnd Tisbnd Ovacancy and dbnd Tisbnd H bonds as evidenced by XPS, Raman, FTIR and HR-TEM analysis. This combination also triggers the formation of new Ti3+ occupied states under the conduction band of hydrogenated F-doped TiO2. Moreover, the change in the pore structure from cylindrical to slits and larger surface area facilitates surface charge interactions. The thermal stability is also enhanced and a single anatase phase is obtained. The size of the particles of hydrogenated F-doped TiO2 is also uniform with defined and homogeneous crystal structure. This synergetic effect between fluorine and hydrogen opens up new alternatives in improving the properties of TiO2 and its photocatalytic activity.

  1. Effects of Hydrogen Cyanamide Application Rates and Timing on Fruit and Foliage of 'Climax' Rabbiteye Blueberry

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A field study was conducted to evaluate the effects of flower bud pruning or utilizing differing rates of hydrogen cyanamide, on development of vegetative and floral buds, as well as on leaf area, vegetative coverage, fruit damage and development, and yield. In this study, hydrogen cyanamide applica...

  2. Binding and photocleavage of a neutral nickel(II) bis(hydrogen pyridine-2,6-dicarboxylato) complex to DNA

    NASA Astrophysics Data System (ADS)

    Wang, Qingxiang; Li, Wenqi; Liu, Aifeng; Zhang, Bin; Gao, Feng; Li, Shunxing; Liao, Xiaolei

    2011-01-01

    A neutral nickel(II) bis(pyridine-2,6-dicarboxylato) complex, [Ni(Hdipic -) 2] (Hdipic - = monohydricsalt of pyridine-2,6-dicarboxylic acid) was synthesized and its interaction with DNA were comprehensively investigated by electronic absorption spectroscopy, viscosity, fluorescence, melting temperature and gel electrophoresis measurements in this paper. Spectrophotometric titration suggested that the nickel(II) complex could intercalatively bind to DNA via the planar dipicolinic acid moiety with a moderate binding strength of 1.6 × 10 4 M -1, and these results were further proved by the systematic studies of viscosity, ethidium bromide (EB) displacement and melting temperature experiments. Moreover, agarose gel electrophoresis assays showed that [Ni(Hdipic -) 2] had obvious photocleavage property for the supercoiled plasmid pBR322 DNA under 302 nm irradiation for 30 min, which allow us to postulate the studied complex as a proper candidate for photocleavage reagent.

  3. Quantum effects and anharmonicity in the H2-Li(+)-benzene complex: a model for hydrogen storage materials.

    PubMed

    Kolmann, Stephen J; D'Arcy, Jordan H; Jordan, Meredith J T

    2013-12-21

    Quantum and anharmonic effects are investigated in H2-Li(+)-benzene, a model for hydrogen adsorption in metal-organic frameworks and carbon-based materials. Three- and 8-dimensional quantum diffusion Monte Carlo (QDMC) and rigid-body diffusion Monte Carlo (RBDMC) simulations are performed on potential energy surfaces interpolated from electronic structure calculations at the M05-2X/6-31+G(d,p) and M05-2X/6-311+G(2df,p) levels of theory using a three-dimensional spline or a modified Shepard interpolation. These calculations investigate the intermolecular interactions in this system, with three- and 8-dimensional 0 K H2 binding enthalpy estimates, ΔH(bind) (0 K), being 16.5 kJ mol(-1) and 12.4 kJ mol(-1), respectively: 0.1 and 0.6 kJ mol(-1) higher than harmonic values. Zero-point energy effects are 35% of the value of ΔH(bind) (0 K) at M05-2X/6-311+G(2df,p) and cannot be neglected; uncorrected electronic binding energies overestimate ΔHbind (0 K) by at least 6 kJ mol(-1). Harmonic intermolecular binding enthalpies can be corrected by treating the H2 "helicopter" and "ferris wheel" rotations as free and hindered rotations, respectively. These simple corrections yield results within 2% of the 8-dimensional anharmonic calculations. Nuclear ground state probability density histograms obtained from the QDMC and RBDMC simulations indicate the H2 molecule is delocalized above the Li(+)-benzene system at 0 K. PMID:24359365

  4. MP2 Study of Physisorption of Molecular Hydrogen onto Defective Nanotubes: Cooperative Effect in Stone-Wales Defects.

    PubMed

    Lugo, G; Cuesta, I G; Sánchez Marín, J; Sánchez de Merás, A

    2016-07-14

    We use large-scale MP2 calculations to investigate the physisorption of molecular hydrogen on (9,0) defective carbon nanotubes (CNTs) of C72H18. These large (supra)molecular systems are typically studied using conventional DFT methods, which do not describe well the van der Waals interactions responsible for this process. Here we use CCSD(T)-calibrated MP2 calculations to estimate binding energies by considering four defective structures (hydrogenated divacancy, octagon-pentagon, and two Stone-Wales defects). The largest physisorption energies for the nondefective CNT are for configurations in which H2 points toward the center of one ring. The computed interaction energies for defect-free CNT are in the range 5.7 to 5.9 kJ/mol, in good agreement with the experimental value of 5.98 kJ/mol. The defects introduced in the (9,0)-CNT increase the surface area of the nanotube, such that the largest surface in found in the 55-77 Stone-Wales defective CNT that furthermore is the most aromatic. Only that defect enlarges the physisorption binding energy, which can become >25% larger. Moreover, a cooperative effect in the adsorption of H2 not appearing in the regular structure is found. PMID:27045203

  5. Effects of spermine binding on Taxol-stabilized microtubules

    NASA Astrophysics Data System (ADS)

    Cheng, Shengfeng; Regmi, Chola

    Previous studies have shown that polyamines such as spermine present in cells at physiological concentrations can facilitate the polymerization of tubulins into microtubules (MTs). A recent experiment demonstrates that in the presence of high-concentration spermine, Taxol-stabilized MTs undergo a shape transformation into inverted tubulin tubules (ITTs), the outside surface of which corresponds to the inside surface of a regular MT. However, the molecular mechanism underlying the shape transformation of MTs into ITTs is unclear. We perform all atom molecular dynamics simulations on Taxol-stabilized MT sheets containing two protofilaments surrounded by spermine ions. The spermine concentration is varied from 0 to 25mM to match the range probed experimentally. We identify important spermine binding regions on the MT surface and the influence of the spermine binding on the structure and dynamics of MTs. In contrast to Taxol, our results show that spermine binding seems to decrease the flexibility of tubulin proteins, resulting in weaker tubulin-tubulin contacts and promoting the bending of protofilaments into curved protofilaments, inverted rings, and eventually inverted tubules.

  6. Using neutrons and X-rays to study the effect of temperature on the short hydrogen bond in potassium hydrogen phthalate

    NASA Astrophysics Data System (ADS)

    Harte, Suzanne M.; Parkin, Andrew; Goeta, Andrés; Wilson, Chick C.

    2005-05-01

    Potassium hydrogen phthalate has been investigated at several temperatures by both neutron and X-ray single crystal diffraction methods. Previous studies have shown that medium-to-strong hydrogen bonds will frequently undergo changes in the behaviour of the hydrogen atom as temperature is increased. Observed effects include proton migration and disorder over two positions. No evidence for either effect is observed for the short hydrogen bond in potassium hydrogen phthalate between 30 and 300 K, in either the X-ray or neutron data. In addition to demonstrating the robust nature of the geometry of this interaction with respect to temperature, the study has shown once again that X-ray diffraction coupled with simple Fourier imaging methods can reliably screen such hydrogen bonds.

  7. Effect of species, life stage, and water temperature on the toxicity of hydrogen peroxide to fish

    USGS Publications Warehouse

    Rach, J.J.; Schreier, T.M.; Howe, G.E.; Redman, S.D.

    1997-01-01

    Hydrogen peroxide is a drug of low regulatory priority status that is effective in treating fish and fish eggs infected by fungi. However, only limited information is available to guide fish culturists in administering hydrogen peroxide to diseased fish. Laboratory tests were conducted to determine (1) the sensitivity of brown trout Salmo trutta, lake trout Salvelinus namaycush, fathead minnow Pimephales promelas, walleye Stizostedion vitreum, channel catfish Ictalurus punctatus, and bluegill Lepomis, machrochirus to hydrogen peroxide treatments; (2) the sensitivity of various life stages of rainbow trout Oncorhynchus mykiss to hydrogen peroxide treatments; and (3) the effect of water temperature on the acute toxicity of hydrogen peroxide to three fish species. Fish were exposed to hydrogen peroxide concentrations ranging from 100 to 5,000 mu L/L (ppm) for 15-min or 45-min treatments every other day for four consecutive treatments to determine the sensitivity of various species and life stages of fish. Except for walleye, most species of fish tested (less than or equal to 2 g) tolerated hydrogen peroxide of 1,000 mu L/L or greater. Walleyes were sensitive to hydrogen peroxide concentrations as low as 100 mu L/L. A correlation was found between the toxicity of hydrogen peroxide and the life stages of rainbow trout; larger fish were more sensitive. Generally, the toxicity of hydrogen peroxide increased for all species as water temperature increased. The results of these experiments demonstrate that it is important to consider the effects of species, life stage, and water temperature when conducting hydrogen peroxide treatments.

  8. MutaBind estimates and interprets the effects of sequence variants on protein-protein interactions.

    PubMed

    Li, Minghui; Simonetti, Franco L; Goncearenco, Alexander; Panchenko, Anna R

    2016-07-01

    Proteins engage in highly selective interactions with their macromolecular partners. Sequence variants that alter protein binding affinity may cause significant perturbations or complete abolishment of function, potentially leading to diseases. There exists a persistent need to develop a mechanistic understanding of impacts of variants on proteins. To address this need we introduce a new computational method MutaBind to evaluate the effects of sequence variants and disease mutations on protein interactions and calculate the quantitative changes in binding affinity. The MutaBind method uses molecular mechanics force fields, statistical potentials and fast side-chain optimization algorithms. The MutaBind server maps mutations on a structural protein complex, calculates the associated changes in binding affinity, determines the deleterious effect of a mutation, estimates the confidence of this prediction and produces a mutant structural model for download. MutaBind can be applied to a large number of problems, including determination of potential driver mutations in cancer and other diseases, elucidation of the effects of sequence variants on protein fitness in evolution and protein design. MutaBind is available at http://www.ncbi.nlm.nih.gov/projects/mutabind/. PMID:27150810

  9. Hydrogen Effects in Prestrained Transformation Induced Plasticity Steel

    NASA Astrophysics Data System (ADS)

    Ronevich, J. A.; De Cooman, B. C.; Speer, J. G.; De Moor, E.; Matlock, D. K.

    2012-07-01

    Thermal desorption analysis (TDA) was performed on laboratory heat-treated transformation induced plasticity (TRIP) steel with 14.5 pct retained austenite (RA), ultimate tensile strength (UTS) of 880 MPa, and elongation to failure of 33 pct. Samples were tensile prestrained 5 pct at 253 K (-20 °C), 296 K (23 °C), and 375 K (102 °C) to generate different amounts of deformation-induced martensite, 10.5, 5.5, and 0.5 pct, respectively, prior to cathodically charging to a hydrogen content of 1 to 2 ppm. TDA was performed on charged samples to determine the location and strength of hydrogen trapping sites. TDA results suggest that dislocations were the main trapping sites in prestrained TRIP steel. The TDA peak intensity increased with prestrain, suggesting that the quantity of hydrogen trap sites increased with deformation. Tensile tests were performed on the four hydrogen-charged TRIP steel conditions. As confirmed with transmission electron microscope images, samples with more homogeneous dislocation distributions ( i.e., prestrained at 375 K (102 °C)) exhibited greater resistance to hydrogen embrittlement than samples that included a high dislocation density adjacent to the formations of strain-induced martensite ( i.e., samples prestrained at 253 K (-20 °C) and 296 K (23 °C)).

  10. Strength of plasma coating and effect of a plasma coating on hydrogen entry

    NASA Astrophysics Data System (ADS)

    Nishiguchi, Hiroshi; Ohshima, Tamiko; Kawasaki, Hiroharu; Fukuda, Takayuki

    2016-01-01

    The strength of a plasma coating and the effect of the plasma coating on hydrogen entry were investigated to establish a method that provides a base material with highly resistant to hydrogen entry and embrittlement. Aluminum alloy A6061, which is highly resistant to hydrogen gas atmosphere, was employed as the coating material (300 W, 17 h, ∼40 µm thickness). Two types of specimen prepared by the hydrogen-charging method were adopted: the coated and uncoated specimens were (1) immersed in 20 mass % ammonium thiocyanate aqueous solution at 313 K for 48 h, or (2) exposed to hydrogen gas atmosphere at 100 MPa and 270 °C for 200 h. Hydrogen content measurements revealed that the A6061 plasma coating is highly resistant to hydrogen entry in corrosive environments. The coating reduced hydrogen entry by ∼50% during exposure to hydrogen gas atmosphere at 100 MPa and 270 °C. Moreover, the plasma coating method was found to be applicable in the elastic deformation region of the base material.

  11. The effect of hydrostatic pressure on the binding energy and diamagnetic susceptibility of a laser dressed donor impurity in a GaAs/GaAlAs nanowire superlattice

    NASA Astrophysics Data System (ADS)

    Safarpour, Gh.; Jamasb, A.; Dialameh, M.; Yazdanpanahi, S.

    2014-12-01

    In this paper the effects of hydrostatic pressure and laser radiation on the binding energy and diamagnetic susceptibility of an off-center hydrogenic donor impurity in a nanowire superlattice (NWSL) are studied. The energy eigenvalues and corresponding wave functions of ground and first excited states are numerically computed using finite difference method for a NWSL with circular cross-section which involved an array of spherical quantum dots (QDs). The numerical results show that oscillatory behaviors appear in binding energies and diamagnetic susceptibilities of ground and first excited states as impurity shifts away from center of QDs. Maximum values of ground state binding energy (first excited state binding energy) occur when impurity is located at the center of QDs (at the center of barriers). Additionally, binding energies of ground and first excited states shift towards higher (lower) energies as pressure (laser radiation) increases. An opposite behavior is observed for absolute value of diamagnetic susceptibility as pressure or laser radiation increases. Also, as the QDs' volume increases the binding energies (I) decrease or (II) increase, reach maximum values and then decrease; which strongly depend on the position of impurity.

  12. Effective hydrogen generation and resource circulation based on sulfur cycle system

    NASA Astrophysics Data System (ADS)

    Takahashi, Hideyuki; Mabuchi, Takashi; Hayashi, Tsugumi; Yokoyama, Shun; Tohji, Kazuyuki

    2013-12-01

    For the effective hydrogen generation from H2S, it should be compatible that the increscent of the photocatalytic (or electrochemical) activities and the development of effective utilization method of by-products (poly sulfide ion). In this study, "system integration" to construct the sulfur cycle system, which is compatible with the increscent of the hydrogen and or electron energy generation ratio and resource circulation, is investigated. Photocatalytic hydrogen generation rate can be enhanced by using stratified photocatalysts. Photo excited electron can be transpired to electrode to convert the electron energy to hydrogen energy. Poly sulfide ion as the by-products can be transferred into elemental sulfur and/or industrial materials such as rubber. Moreover, elemental sulfur can be transferred into H2S which is the original materials for hydrogen generation. By using this "system integration", the sulfur cycle system for the new energy generation can be constructed.

  13. Effective hydrogen generation and resource circulation based on sulfur cycle system

    SciTech Connect

    Takahashi, Hideyuki; Mabuchi, Takashi; Hayashi, Tsugumi; Yokoyama, Shun; Tohji, Kazuyuki

    2013-12-10

    For the effective hydrogen generation from H{sub 2}S, it should be compatible that the increscent of the photocatalytic (or electrochemical) activities and the development of effective utilization method of by-products (poly sulfide ion). In this study, “system integration” to construct the sulfur cycle system, which is compatible with the increscent of the hydrogen and or electron energy generation ratio and resource circulation, is investigated. Photocatalytic hydrogen generation rate can be enhanced by using stratified photocatalysts. Photo excited electron can be transpired to electrode to convert the electron energy to hydrogen energy. Poly sulfide ion as the by-products can be transferred into elemental sulfur and/or industrial materials such as rubber. Moreover, elemental sulfur can be transferred into H{sub 2}S which is the original materials for hydrogen generation. By using this “system integration”, the sulfur cycle system for the new energy generation can be constructed.

  14. Effect of the Hydrogen Bond in Photoinduced Water Dissociation: A Double-Edged Sword.

    PubMed

    Yang, Wenshao; Wei, Dong; Jin, Xianchi; Xu, Chenbiao; Geng, Zhenhua; Guo, Qing; Ma, Zhibo; Dai, Dongxu; Fan, Hongjun; Yang, Xueming

    2016-02-18

    Photoinduced water dissociation on rutile-TiO2 was investigated using various methods. Experimental results reveal that the water dissociation occurs via transferring an H atom to a bridge bonded oxygen site and ejecting an OH radical to the gas phase during irradiation. The reaction is strongly suppressed as the water coverage increases. Further scanning tunneling microscopy study demonstrates that hydrogen bonds between water molecules have a dramatic effect on the reaction. Interestingly, a single hydrogen bond in water dimer enhances the water dissociation reaction, while one-dimensional hydrogen bonds in water chains inhibit the reaction. Density functional theory calculations indicate that the effect of hydrogen bonds on the OH dissociation energy is likely the origin of this remarkable behavior. The results suggest that avoiding a strong hydrogen bond network between water molecules is crucial for water splitting. PMID:26810945

  15. Effects of Temperature on the p53-DNA Binding Interactions and Their Dynamical Behavior: Comparing the Wild Type to the R248Q Mutant

    PubMed Central

    Barakat, Khaled; Issack, Bilkiss B.; Stepanova, Maria; Tuszynski, Jack

    2011-01-01

    Background The protein p53 plays an active role in the regulation of cell cycle. In about half of human cancers, the protein is inactivated by mutations located primarily in its DNA-binding domain. Interestingly, a number of these mutations possess temperature-induced DNA-binding characteristics. A striking example is the mutation of Arg248 into glutamine or tryptophan. These mutants are defective for binding to DNA at 310 K although they have been shown to bind specifically to several p53 response elements at sub-physiological temperatures (298–306 K). Methodology/Principal Findings This important experimental finding motivated us to examine the effects of temperature on the structure and configuration of R248Q mutant and compare it to the wild type protein. Our aim is to determine how and where structural changes of mutant variants take place due to temperature changes. To answer these questions, we compared the mutant to the wild-type proteins from two different aspects. First, we investigated the systems at the atomistic level through their DNA-binding affinity, hydrogen bond networks and spatial distribution of water molecules. Next, we assessed changes in their long-lived conformational motions at the coarse-grained level through the collective dynamics of their side-chain and backbone atoms separately. Conclusions The experimentally observed effect of temperature on the DNA-binding properties of p53 is reproduced. Analysis of atomistic and coarse-grained data reveal that changes in binding are determined by a few key residues and provide a rationale for the mutant-loss of binding at physiological temperatures. The findings can potentially enable a rescue strategy for the mutant structure. PMID:22110706

  16. Hydrogen peroxide-mediated oxidative stress disrupts calcium binding on calmodulin: More evidence for oxidative stress in vitiligo

    SciTech Connect

    Schallreuter, K.U. . E-mail: k.schallreuter@bradford.ac.uk; Gibbons, N.C.J.; Zothner, C.; Abou Elloof, M.M.; Wood, J.M.

    2007-08-17

    Patients with acute vitiligo have low epidermal catalase expression/activities and accumulate 10{sup -3} M H{sub 2}O{sub 2}. One consequence of this severe oxidative stress is an altered calcium homeostasis in epidermal keratinocytes and melanocytes. Here, we show decreased epidermal calmodulin expression in acute vitiligo. Since 10{sup -3}M H{sub 2}O{sub 2} oxidises methionine and tryptophan residues in proteins, we examined calcium binding to calmodulin in the presence and absence of H{sub 2}O{sub 2} utilising {sup 45}calcium. The results showed that all four calcium atoms exchanged per molecule of calmodulin. Since oxidised calmodulin looses its ability to activate calcium ATPase, enzyme activities were followed in full skin biopsies from lesional skin of patients with acute vitiligo (n = 6) and healthy controls (n = 6). The results yielded a 4-fold decrease of ATPase activities in the patients. Computer simulation of native and oxidised calmodulin confirmed the loss of all four calcium ions from their specific EF-hand domains. Taken together H{sub 2}O{sub 2}-mediated oxidation affects calcium binding in calmodulin leading to perturbed calcium homeostasis and perturbed L-phenylalanine-uptake in the epidermis of acute vitiligo.

  17. The Effect of Atmospheric Hydrogen on the Albedo and Surface Temperature of Mars

    NASA Astrophysics Data System (ADS)

    Wallack, Nicole Lisa; Kaltenegger, Lisa; Ramirez, Ramses

    2016-01-01

    The presence of hydrogen in planetary atmospheres has been shown to have the potential to dramatically effect the temperatures of planets. The collision-induced absorption (CIA) of hydrogen with carbon dioxide or nitrogen has been shown to have a substantial effect on the atmospheric temperature and albedo of a planet, possibly to the point at which life could exist on a planet where without such CIA the planet would be too cold. Using a single-column radiative-convective climate model, we investigated the effect of the presence of hydrogen on planetary temperatures and albedos across different amounts of hydrogen and across host stars of different temperatures using present-day Mars-like planets. We found that the addition of hydrogen in a planet's atmosphere increased the surface temperature of the planet. This effect was stronger for the planets orbiting hotter stars. The water vapor profiles showed that this was the case due to the presence of more water vapor in the atmospheres of planets orbiting hotter stars across all percentages of hydrogen. The water vapor concentrations also varied more with the addition of more hydrogen for the planets orbiting hotter stars.

  18. Effects of hydrogen-rich water on depressive-like behavior in mice

    PubMed Central

    Zhang, Yi; Su, Wen-Jun; Chen, Ying; Wu, Teng-Yun; Gong, Hong; Shen, Xiao-Liang; Wang, Yun-Xia; Sun, Xue-Jun; Jiang, Chun-Lei

    2016-01-01

    Emerging evidence suggests that neuroinflammation and oxidative stress may be major contributors to major depressive disorder (MDD). Patients or animal models of depression show significant increase of proinflammatory cytokine interleukin-1β (IL-1β) and oxidative stress biomarkers in the periphery or central nervous system (CNS). Recent studies show that hydrogen selectively reduces cytotoxic oxygen radicals, and hydrogen-rich saline potentially suppresses the production of several proinflammatory mediators. Since current depression medications are accompanied by a wide spectrum of side effects, novel preventative or therapeutic measures with fewer side effects might have a promising future. We investigated the effects of drinking hydrogen-rich water on the depressive-like behavior in mice and its underlying mechanisms. Our study show that hydrogen-rich water treatment prevents chronic unpredictable mild stress (CUMS) induced depressive-like behavior. CUMS induced elevation in IL-1β protein levels in the hippocampus, and the cortex was significantly attenuated after 4 weeks of feeding the mice hydrogen-rich water. Over-expression of caspase-1 (the IL-1β converting enzyme) and excessive reactive oxygen species (ROS) production in the hippocampus and prefrontal cortex (PFC) was successfully suppressed by hydrogen-rich water treatment. Our data suggest that the beneficial effects of hydrogen-rich water on depressive-like behavior may be mediated by suppression of the inflammasome activation resulting in attenuated protein IL-1β and ROS production. PMID:27026206

  19. Effects of hydrogen-rich water on depressive-like behavior in mice.

    PubMed

    Zhang, Yi; Su, Wen-Jun; Chen, Ying; Wu, Teng-Yun; Gong, Hong; Shen, Xiao-Liang; Wang, Yun-Xia; Sun, Xue-Jun; Jiang, Chun-Lei

    2016-01-01

    Emerging evidence suggests that neuroinflammation and oxidative stress may be major contributors to major depressive disorder (MDD). Patients or animal models of depression show significant increase of proinflammatory cytokine interleukin-1β (IL-1β) and oxidative stress biomarkers in the periphery or central nervous system (CNS). Recent studies show that hydrogen selectively reduces cytotoxic oxygen radicals, and hydrogen-rich saline potentially suppresses the production of several proinflammatory mediators. Since current depression medications are accompanied by a wide spectrum of side effects, novel preventative or therapeutic measures with fewer side effects might have a promising future. We investigated the effects of drinking hydrogen-rich water on the depressive-like behavior in mice and its underlying mechanisms. Our study show that hydrogen-rich water treatment prevents chronic unpredictable mild stress (CUMS) induced depressive-like behavior. CUMS induced elevation in IL-1β protein levels in the hippocampus, and the cortex was significantly attenuated after 4 weeks of feeding the mice hydrogen-rich water. Over-expression of caspase-1 (the IL-1β converting enzyme) and excessive reactive oxygen species (ROS) production in the hippocampus and prefrontal cortex (PFC) was successfully suppressed by hydrogen-rich water treatment. Our data suggest that the beneficial effects of hydrogen-rich water on depressive-like behavior may be mediated by suppression of the inflammasome activation resulting in attenuated protein IL-1β and ROS production. PMID:27026206

  20. On quantum effects on the surface of solid hydrogen

    SciTech Connect

    Marchenko, V. I.

    2013-10-15

    The low-frequency spectrum of hypothetical superfluidity on the free surface of a quantum crystal of hydrogen is determined. In the quantum-rough state of the surface, crystallization waves with a quadratic spectrum should propagate. In the atomically smooth state, the spectrum is linear. Crystallization waves propagating along elementary steps are also considered.

  1. Effect of water on hydrogen permeability. [Stirling engines

    NASA Technical Reports Server (NTRS)

    Hulligan, D. D.; Tomazic, W. A.

    1984-01-01

    Doping of hydrogen with CO or CO2 was developed to reduce hydrogen permeation in Stirling engines by forming low permeability oxide coatings in the heater tubes. An end product of this process is water - which can condense in the cold parts of the engine system. If the water vapor is reduced to a low enough level, the hydrogen can reduce the oxide coating resulting in increased permeability. The equilibrium level of water (oxygen bearing gas) required to avoid reduction of the oxide coating was investigated. Results at 720 C and 13.8 MPa have shown that: (1) pure hydrogen will reduce the coating; (2) 500 ppm CO (500 ppm water equivalent) does not prevent the reduction; and (3) 500 ppm CO2 (1000 ppm water) appears to be close to the equilibrium level. Further tests are planned to define the equilibrium level more precisely and to extend the data to 820 C and 3.4, 6.9, and 13.8 MPa.

  2. The effect of hydrogen on the parameters of plastic deformation localization in low carbon steel

    SciTech Connect

    Lunev, Aleksey G. E-mail: nadjozhkin@ispms.tsc.ru; Nadezhkin, Mikhail V. E-mail: nadjozhkin@ispms.tsc.ru; Shlyakhova, Galina V.; Barannikova, Svetlana A.; Zuev, Lev B.

    2014-11-14

    In the present study, the effect of interstitial hydrogen atoms on the mechanical properties and plastic strain localization patterns in tensile tested polycrystals of low-carbon steel Fe-0.07%C has been studied using double exposure speckle photography technique. The main parameters of plastic flow localization at various stages of deformation hardening have been determined in polycrystals of steel electrolytically saturated with hydrogen in a three-electrode electrochemical cell at a controlled constant cathode potential. Also, the effect of hydrogen on changing of microstructure by using optical microscopy has been demonstrated.

  3. Divergent effects of oxidatively induced modification to the C8 of 2'-deoxyadenosine on transcription factor binding: 8,5'(S)-cyclo-2'-deoxyadenosine inhibits the binding of multiple sequence specific transcription factors, while 8-oxo-2'-deoxyadenosine increases binding of CREB and NF-kappa B to DNA.

    PubMed

    Abraham, Jessy; Brooks, Philip J

    2011-05-01

    DNA is exposed to endogenous and environmental factors that can form stable lesions. If not repaired, these lesions can lead to transcription/replication blocking or mutagenic bypass. Our previous work has focused on 8,5'-cyclopurine 2'-deoxyribonucleosides, a unique class of oxidatively induced DNA lesions that are specifically repaired by the NER pathway (see Brooks PJ [2008]: DNA Repair 7:1168-1179). Here we used EMSA to monitor the ability of sequence-specific transcription factors, HSF1, CREB, and NF-kappaB and "architectural" transcription factor, HMGA, to bind to their target sequences when 8, 5'(S)-cyclo-2'-deoxyadenosine (cyclo-dAdo) is present within their recognition sequences. For comparison, we also tested the effect of 8-oxo-7,8-dihydro-2'-deoxyadenosine (8-oxo-dAdo) in the same recognition sequences. The presence of a cyclo-dAdo lesion in the target sequence essentially eliminated the binding activity of HSF1, CREB, and NF-kappa B whereas HMGA retained some of its binding activity. In contrast, 8-oxo-dAdo had no obvious effect on the binding activity of HSF1 and HMGA in comparison to lesion-free DNA. Notably, though, CREB and NFκB binding increased when an 8-oxo-dAdo lesion was present in their target sequence. Competition EMSA showed about 2-3-fold increased affinity of both proteins for the 8-oxo-dAdo containing target sequence compared to lesion-free DNA. Molecular modeling of the lesions in the NF-kappaB sequence indicated that 8-oxo-dAdo may form an additional hydrogen bond with the protein, thereby strengthening the binding of NF-kappa B to its DNA target. The cyclo-dAdo lesion, in contrast, distorted the DNA structure, providing an explanation for the inhibition of NF-kappaB binding. PMID:20872830

  4. Effects of Cavities at the Nicotinamide Binding Site of Liver Alcohol Dehydrogenase on Structure, Dynamics and Catalysis

    PubMed Central

    2015-01-01

    A role for protein dynamics in enzymatic catalysis of hydrogen transfer has received substantial scientific support, but the connections between protein structure and catalysis remain to be established. Valine residues 203 and 207 are at the binding site for the nicotinamide ring of the coenzyme in liver alcohol dehydrogenase and have been suggested to facilitate catalysis with “protein-promoting vibrations” (PPV). We find that the V207A substitution has small effects on steady-state kinetic constants and the rate of hydrogen transfer; the introduced cavity is empty and is tolerated with minimal effects on structure (determined at 1.2 Å for the complex with NAD+ and 2,3,4,5,6-pentafluorobenzyl alcohol). Thus, no evidence is found to support a role for Val-207 in the dynamics of catalysis. The protein structures and ligand geometries (including donor–acceptor distances) in the V203A enzyme complexed with NAD+ and 2,3,4,5,6-pentafluorobenzyl alcohol or 2,2,2-trifluoroethanol (determined at 1.1 Å) are very similar to those for the wild-type enzyme, except that the introduced cavity accommodates a new water molecule that contacts the nicotinamide ring. The structures of the V203A enzyme complexes suggest, in contrast to previous studies, that the diminished tunneling and decreased rate of hydride transfer (16-fold, relative to that of the wild-type enzyme) are not due to differences in ground-state ligand geometries. The V203A substitution may alter the PPV and the reorganization energy for hydrogen transfer, but the protein scaffold and equilibrium thermal motions within the Michaelis complex may be more significant for enzyme catalysis. PMID:24437493

  5. Effects of vitamin B-6 nutrition on benzodiazepine (BDZ) receptor binding in the developing rat brain

    SciTech Connect

    Borek, J.P.; Guilarte, T.R. )

    1990-02-26

    A dietary deficiency of vitamin B-6 promotes seizure activity in neonatal animals and human infants. Previous studied have shown that neonatal vitamin B-6 deprivation results in reduced levels of brain gamma-aminobutyric acid (GABA) and increased binding at the GABA site of the GABA/BDZ receptor complex. Since the GABA and BDZ receptors are allosterically linked, this study was undertaken to determine if vitamin B-6 deprivation had an effect on BDZ receptor binding. Benzodiazepine receptor binding isotherms using {sup 3}H-flunitrazepam as ligand were performed in the presence and absence of 10 {mu}M GABA. The results indicate a significant increase in the binding affinity (Kd) in the presence of GABA in cerebellar membranes from deficient rat pups at 14 days of age with no effect on receptor number (Bmax). By 28 days of age, the increase in Kd was no longer present. No change in Kd or Bmax was observed in cortical tissue from deficient animals at 14 or 28 days of age. Preliminary studies of GABA-enhancement of {sup 3}H-flunitrazepam binding indicate that vitamin B-6 deficiency also induces alterations in the ability of GABA to enhance BZD receptor binding. In summary, these results indicate that the effects of vitamin B-6 deprivation on BDZ receptor binding are region specific and age related.

  6. Effective hydrodynamic hydrogen escape from an early Earth atmosphere inferred from high-accuracy numerical simulation

    NASA Astrophysics Data System (ADS)

    Kuramoto, Kiyoshi; Umemoto, Takafumi; Ishiwatari, Masaki

    2013-08-01

    Hydrodynamic escape of hydrogen driven by solar extreme ultraviolet (EUV) radiation heating is numerically simulated by using the constrained interpolation profile scheme, a high-accuracy scheme for solving the one-dimensional advection equation. For a wide range of hydrogen number densities at the lower boundary and solar EUV fluxes, more than half of EUV heating energy is converted to mechanical energy of the escaping hydrogen. Less energy is lost by downward thermal conduction even giving low temperature for the atmospheric base. This result differs from a previous numerical simulation study that yielded much lower escape rates by employing another scheme in which relatively strong numerical diffusion is implemented. Because the solar EUV heating effectively induces hydrogen escape, the hydrogen mixing ratio was likely to have remained lower than 1 vol% in the anoxic Earth atmosphere during the Archean era.

  7. Hydrogen effects in dilute III-N-V alloys: From defect engineering to nanostructuring

    SciTech Connect

    Pettinari, G.; Felici, M.; Capizzi, M.; Polimeni, A.; Trotta, R.

    2014-01-07

    The variation of the band gap energy of III-N-V semiconductors induced by hydrogen incorporation is the most striking effect that H produces in these materials. A special emphasis is given here to the combination of N-activity passivation by hydrogen with H diffusion kinetics in dilute nitrides. Secondary ion mass spectrometry shows an extremely steep (smaller than 5 nm/decade) forefront of the H diffusion profile in Ga(AsN) under appropriate hydrogenation conditions. This discovery prompts the opportunity for an in-plane nanostructuring of hydrogen incorporation and, hence, for a modulation of the material band gap energy at the nanoscale. The properties of quantum dots fabricated by a lithographically defined hydrogenation are presented, showing the zero-dimensional character of these novel nanostructures. Applicative prospects of this nanofabrication method are finally outlined.

  8. Isotope effects on desorption kinetics of hydrogen isotopes implanted into stainless steel by glow discharge

    SciTech Connect

    Matsuyama, M.; Kondo, M.; Noda, N.; Tanaka, M.; Nishimura, K.

    2015-03-15

    In a fusion device the control of fuel particles implies to know the desorption rate of hydrogen isotopes by the plasma-facing materials. In this paper desorption kinetics of hydrogen isotopes implanted into type 316L stainless steel by glow discharge have been studied by experiment and numerical calculation. The temperature of a maximum desorption rate depends on glow discharge time and heating rate. Desorption spectra observed under various experimental conditions have been successfully reproduced by numerical simulations that are based on a diffusion-limited process. It is suggested, therefore, that desorption rate of a hydrogen isotope implanted into the stainless steel is limited by a diffusion process of hydrogen isotope atoms in bulk. Furthermore, small isotope effects were observed for the diffusion process of hydrogen isotope atoms. (authors)

  9. Nanoscale microstructure effects on hydrogen behavior in rapidly solidified aluminum alloys

    SciTech Connect

    Tashlykova-Bushkevich, Iya I.

    2015-12-31

    The present work summarizes recent progress in the investigation of nanoscale microstructure effects on hydrogen behavior in rapidly solidified aluminum alloys foils produced at exceptionally high cooling rates. We focus here on the potential of modification of hydrogen desorption kinetics in respect to weak and strong trapping sites that could serve as hydrogen sinks in Al materials. It is shown that it is important to elucidate the surface microstructure of the Al alloy foils at the submicrometer scale because rapidly solidified microstructural features affect hydrogen trapping at nanostructured defects. We discuss the profound influence of solute atoms on hydrogen−lattice defect interactions in the alloys. with emphasis on role of vacancies in hydrogen evolution; both rapidly solidified pure Al and conventionally processed aluminum samples are considered.

  10. Hydrogenation-induced edge magnetization in armchair MoS2 nanoribbon and electric field effects

    NASA Astrophysics Data System (ADS)

    Ouyang, Fangping; Yang, Zhixiong; Ni, Xiang; Wu, Nannan; Chen, Yu; Xiong, Xiang

    2014-02-01

    We performed density functional theory study on the electronic and magnetic properties of armchair MoS2 nanoribbons (AMoS2NR) with different edge hydrogenation. Although bare and fully passivated AMoS2NRs are nonmagnetic semiconductors, it was found that hydrogenation in certain patterns can induce localized ferromagnetic edge state in AMoS2NRs and make AMoS2NRs become antiferromagnetic semiconductors or ferromagnetic semiconductors. Electric field effects on the bandgap and magnetic moment of AMoS2NRs were investigated. Partial edge hydrogenation can change a small-sized AMoS2NR from semiconductor to metal or semimetal under a moderate transverse electric field. Since the rate of edge hydrogenation can be controlled experimentally via the temperature, pressure and concentration of H2, our results suggest edge hydrogenation is a useful method to engineer the band structure of AMoS2NRs.

  11. Double binding energy differences: Mean-field or pairing effect?

    NASA Astrophysics Data System (ADS)

    Qi, Chong

    2012-10-01

    In this Letter we present a systematic analysis on the average interaction between the last protons and neutrons in atomic nuclei, which can be extracted from the double differences of nuclear binding energies. The empirical average proton-neutron interaction Vpn thus derived from experimental data can be described in a very simple form as the interplay of the nuclear mean field and the pairing interaction. It is found that the smooth behavior as well as the local fluctuations of the Vpn in even-even nuclei with N ≠ Z are dominated by the contribution from the proton-neutron monopole interactions. A strong additional contribution from the isoscalar monopole interaction and isovector proton-neutron pairing interaction is seen in the Vpn for even-even N = Z nuclei and for the adjacent odd-A nuclei with one neutron or proton being subtracted.

  12. Effect of carbon nanofibre structure on the binding of antibodies

    NASA Astrophysics Data System (ADS)

    Naguib, Nevin N.; Mueller, Yvonne M.; Bojczuk, Paul M.; Pía Rossi, María; Katsikis, Peter D.; Gogotsi, Yury

    2005-04-01

    Potential biomedical applications for carbon nanofibres include, but are not limited to, biosensors and drug delivery vehicles. For such applications, it is essential to know how carbon nanotubes interact with antibodies and proteins. We report on the successful adsorption of monoclonal CD3 antibodies on two types of carbon nanofibre produced by the same method and having the same average size and shape, but differing in surface structure and chemistry due to dissimilar post-treatments. Binding of proteins to nanofibres is enhanced by poly (L-lysine) (PLL) and improves with increasing disorder and hydrophilicity of the nanofibres' surface. Oxidized and disordered surfaces of pyrolytically stripped nanofibres show improved wetting and attachment of PLL and proteins compared to hydrophobic and well-ordered surfaces of heat-treated nanofibres. These results show that the surface of carbon nanofibres can be tailored for their use in biomedical applications.

  13. Effects of ligand binding upon flexibility of proteins.

    PubMed

    Erman, Burak

    2015-05-01

    Binding of a ligand on a protein changes the flexibility of certain parts of the protein, which directly affects its function. These changes are not the same at each point, some parts become more flexible and some others become stiffer. Here, an equation is derived that gives the stiffness map for proteins. The model is based on correlations of fluctuations of pairs of points in proteins, which may be evaluated at different levels of refinement, ranging from all atom molecular dynamics to general elastic network models, including the simplest case of isotropic Gaussian Network Model. The latter is used, as an example, to evaluate the changes of stiffness upon dimerization of ACK1. PMID:25737428

  14. Quantum Physics Inspired Optical Effects in Tight-Binding Lattices

    NASA Astrophysics Data System (ADS)

    Thompson, Clinton; Vemuri, Gautam

    We theoretically investigated the propagation of light inside an array of single-mode evanescently coupled waveguides that can be described by the tight-binding Hamiltonian. We show that directed photonic transport can be achieved with phase-displaced inputs. In addition, the form of a parity-symmetric waveguide-dependent coupling constant can tune the dynamics of the photon's wavepacket. Lastly, we examine the statistical aspects of the output light for different input fields when disorder is present in the waveguide array. We find that the light will undergo Anderson localization independent of the type of field and that the intensity fluctuations of the output light will increase with disorder at the initial waveguide.

  15. Effect of surface modification, microstructure, and trapping on hydrogen diffusion coefficients in high strength alloys

    NASA Astrophysics Data System (ADS)

    Jebaraj Johnley Muthuraj, Josiah

    Cathodic protection is widely used for corrosion prevention. However, this process generates hydrogen at the protected metal surface, and diffusion of hydrogen through the metal may cause hydrogen embrittlement or hydrogen induced stress corrosion cracking. Thus the choice of a metal for use as fasteners depends upon its hydrogen uptake, permeation, diffusivity and trapping. The diffusivity of hydrogen through four high strength alloys (AISI 4340, alloy 718, alloy 686, and alloy 59) was analyzed by an electrochemical method developed by Devanathan and Stachurski. The effect of plasma nitriding and microstructure on hydrogen permeation through AISI 4340 was studied on six different specimens: as-received (AR) AISI 4340, nitrided samples with and without compound layer, samples quenched and tempered (Q&T) at 320° and 520°C, and nitrided samples Q&T 520°C. Studies on various nitrided specimens demonstrate that both the gamma'-Fe 4N rich compound surface layer and the deeper N diffusion layer that forms during plasma nitriding reduce the effective hydrogen diffusion coefficient, although the gamma'-Fe4N rich compound layer has a larger effect. Multiple permeation transients yield evidence for the presence of only reversible trap sites in as-received, Q&T 320 and 520 AISI 4340 specimens, and the presence of both reversible and irreversible trap sites in nitrided specimens. Moreover, the changes in microstructure during the quenching and tempering process result in a significant decrease in the diffusion coefficient of hydrogen compared to as-received specimens. In addition, density functional theory-based molecular dynamics simulations yield hydrogen diffusion coefficients through gamma'- Fe4N one order of magnitude lower than through α-Fe, which supports the experimental measurements of hydrogen permeation. The effect of microstructure and trapping was also studied in cold rolled, solutionized, and precipitation hardened Inconel 718 foils. The effective hydrogen

  16. Combination moisture and hydrogen getter

    DOEpatents

    Harrah, L.A.; Mead, K.E.; Smith, H.M.

    1983-09-20

    A combination moisture and hydrogen getter comprises (a) a moisture getter comprising a readily oxidizable metal; and (b) a hydrogen getter comprising (1) a solid acetylenic compound and (2) a hydrogenation catalyst. A method of scavenging moisture from a closed container uses the combination moisture and hydrogen getter to irreversibly chemically reduce the moisture and chemically bind the resultant hydrogen.

  17. Combination moisture and hydrogen getter

    DOEpatents

    Not Available

    1982-04-29

    A combination moisture and hydrogen getter comprises (a) a moisture getter comprising a readily oxidizable metal; and (b) a hydrogen getter comprising (i) a solid acetylenic compound and (ii) a hydrogenation catalyst. A method of scavenging moisture from a closed container uses the combination moisture and hydrogen getter to irreversibly chemically reduce the moisture and chemically bind the reusltant hydrogen.

  18. Combination moisture and hydrogen getter

    DOEpatents

    Harrah, Larry A.; Mead, Keith E.; Smith, Henry M.

    1983-01-01

    A combination moisture and hydrogen getter comprises (a) a moisture getter comprising a readily oxidizable metal; and (b) a hydrogen getter comprising (i) a solid acetylenic compound and (ii) a hydrogenation catalyst. A method of scavenging moisture from a closed container uses the combination moisture and hydrogen getter to irreversibly chemically reduce the moisture and chemically bind the resultant hydrogen.

  19. Identification of procollagen promoter DNA-binding proteins: effects of dexamethasone

    SciTech Connect

    Sweeney, C.; Cutroneo, K.R.

    1987-05-01

    Glucocorticoids selectively decrease procollagen synthesis by decreasing procollagen mRNA transcription. Dexamethasone coordinately decreased total cellular type I and type III procollagen mRNAs in mouse embryonic skin fibroblasts. Since sequence specific DNA-binding proteins are known to modulate eukaryotic gene expression the authors identified in mouse fibroblasts nuclear proteins which bind to types I and III procollagen promoter DNAs. Nuclear proteins were electrophoresed, blotted onto nitrocellulose and probed with /sup 32/P-end-labeled type I and type III procollagen promoter DNAs in the presence of equimolar amounts of /sup 32/P-end-labeled vector DNA. Differences in total DNA binding were noted by the densitometric scans of the nuclear proteins. Dexamethasone treatment enhanced total DNA binding. Increasing the NaCl concentration decreased the number of promoter DNA-binding proteins without altering the relative specificity for the promoter DNAs. Promoter DNA binding to nuclear proteins was also inhibited by increasing concentrations of E. coli DNA. The number of DNA-binding proteins was greater for type III procollagen promoter DNA. The effect of dexamethasone treatment on promoter DNA binding to nuclear proteins was determined.

  20. The Effect of Hydrogen on the Bonding and Dissociation of Carbon Monoxide on AN IRON(100) Surface

    NASA Astrophysics Data System (ADS)

    Nassir, Mohamed Husain

    1993-01-01

    Adsorption and coadsorption of CO and H _2 on Fe(100) was studied using the following six methods: Temperature programmed desorption (TPD), x -ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), high resolution electron energy loss spectroscopy (HREELS), single reflection Fourier transform infrared spectroscopy (FTIR) and low-energy electron diffraction (LEED). The binding and dissociation of CO on a clean and hydrogen presaturated Fe(100) surface were investigated to provide better understanding of the first step in the Fischer-Tropsch synthesis, an important industrial catalytic reaction for converting CO and hydrogen to hydrocarbon. CO adsorbs molecularly on the clean surface in three states alpha_1, alpha_2 and alpha_3 . At temperatures above 350 K but below 440 K, CO is bound to the surface only in the highly perturbed alpha_3 state (pi -bonded geometry). The CO alpha_3 molecules are believed to occupy the 4-fold hollow sites. When the surface temperature is raised above 440 K, a fraction of the alpha_3 desorbs and the remainder dissociates. The dissociation fragments replace the CO alpha_3 molecules in the 4-fold hollow sites. These fragments recombine at higher temperatures and appear as beta CO. The bonding and dissociation of CO in the alpha_3 received more attention because it is believed that this state is a precursor to dissociation. A model describing the partitioning between desorption and dissociation is proposed in which the dissociation fragments displace the strongly bound CO in the beta -bonded state. The stoichiometry of this reaction at saturation requires that only half the original CO adsorbed in the beta-bonded CO state can dissociate. Presaturating the surface with hydrogen affects the bonding and dissociation of CO on the iron surface. One effect is to weaken CO-Fe bonds which results in a very weakly bound state (alpha^' _1). In addition to the alpha ^'_1 state, presaturating the surface with hydrogen

  1. Effect of hydrogen on the {beta} transus temperature of TC21 alloy

    SciTech Connect

    Zhu, T.K. Li, M.Q.

    2011-09-15

    Effect of hydrogen on the {beta} transus temperature of TC21 alloy was investigated by metallographic technique and dilatometry. It is found that the {beta} transus temperature is closely related to the hydrogen content. For the hydrogenated TC21 alloy, the starting and finishing temperatures of {alpha} {yields} {beta} phase transition decrease with the increasing of hydrogen content before the hydride precipitates. And the finishing temperature of {alpha} {yields} {beta} phase transition increases as the hydrogen content increases after the hydride precipitates. Furthermore, corresponding inherent mechanisms of the above-mentioned phenomena have been presented according to atomic diffusivity, interface migration and the precipitation of hydride. - Research Highlights: {yields} The {beta} transus temperature of TC21 alloy is closely related to hydrogen content. {yields} The mechanism for effect of hydrogen on the {beta} transus temperature is presented. {yields} Precipitation of hydride has a significant influence on the {beta} transus temperature. {yields} The {alpha}/{beta} interface migration has an important effect on the {beta} transus temperature. {yields} The improvement of atom diffusivity affects the {beta} transus temperature highly.

  2. Quantitative effects of antihydrophobic agents on binding constants and solubilities in water.

    PubMed Central

    Breslow, R; Halfon, S

    1992-01-01

    The effects of urea and of guanidinium chloride on binding constants in water for 6-(4-tert-butylanilino)-naphthalene-2-sulfonate and of bis(p-tert-butylphenyl) phosphate binding to beta-cyclodextrin and to N,N'-bis(6-beta-cyclo-dextrinyl)imidazolium ion have been determined. Their effects on the water solubility of p-tert-butylbenzyl alcohol and p-methylbenzyl alcohol have also been examined. Quantitative correlations show that the effects of these additives, which diminish hydrophobic effects, are similar for release of a tert-butylphenyl group from a cyclodextrin cavity into water or for solubilizing such a group from a second phase. The effects of these agents on the binding constants for double-ended substrates binding to the bis(cyclodextrin) host are much larger than for a simple substrate binding to monomeric cyclodextrin, consistent with additivity of free-energy perturbations. Ethanol also decreases binding in these systems, and increases solubilities, but the quantitative correlations are less straightforward. Images PMID:1495980

  3. Quasiparticle energies and excitonic effects in dense solid hydrogen near metallization

    NASA Astrophysics Data System (ADS)

    Dvorak, Marc; Chen, Xiao-Jia; Wu, Zhigang

    2014-07-01

    We investigate the crucial metallization pressure of the Cmca-12 phase of solid hydrogen (H) using many-body perturbation theory within the GW approximation. We consider the effects of self-consistency, plasmon-pole models, and the vertex correction on the quasiparticle band gap (Eg). Our calculations show that self-consistency leads to an increase in Eg by 0.33 eV over the one-shot G0W0 approach. Because of error cancellation between the effects of self-consistency and the vertex correction, the simplest G0W0 method underestimates Eg by only 0.16 eV compared with the prediction of the more accurate GWΓ approach. Employing the plasmon-pole models underestimates Eg by 0.1-0.2 eV compared to the full-frequency numerical integration results. We thus predict a metallization pressure around 280 GPa, instead of 260 GPa predicted previously. Furthermore, we compute the optical absorption including the electron-hole interaction by solving the Bethe-Salpeter equation (BSE). The resulting absorption spectra demonstrate substantial redshifts and enhancement of absorption peaks compared to the calculated spectra neglecting excitonic effects. We find that the exciton binding energy decreases with increasing pressure from 66 meV at 100 GPa to 12 meV at 200 GPa due to the enhanced electronic screening as solid H approaches metallization. Because optical measurements are so important in identifying the structure of solid H, our BSE results should improve agreement between theory and experiment.

  4. Hydrogen storage in carbon nanotubes.

    PubMed

    Hirscher, M; Becher, M

    2003-01-01

    The article gives a comprehensive overview of hydrogen storage in carbon nanostructures, including experimental results and theoretical calculations. Soon after the discovery of carbon nanotubes in 1991, different research groups succeeded in filling carbon nanotubes with some elements, and, therefore, the question arose of filling carbon nanotubes with hydrogen by possibly using new effects such as nano-capillarity. Subsequently, very promising experiments claiming high hydrogen storage capacities in different carbon nanostructures initiated enormous research activity. Hydrogen storage capacities have been reported that exceed the benchmark for automotive application of 6.5 wt% set by the U.S. Department of Energy. However, the experimental data obtained with different methods for various carbon nanostructures show an extreme scatter. Classical calculations based on physisorption of hydrogen molecules could not explain the high storage capacities measured at ambient temperature, and, assuming chemisorption of hydrogen atoms, hydrogen release requires temperatures too high for technical applications. Up to now, only a few calculations and experiments indicate the possibility of an intermediate binding energy. Recently, serious doubt has arisen in relation to several key experiments, causing considerable controversy. Furthermore, high hydrogen storage capacities measured for carbon nanofibers did not survive cross-checking in different laboratories. Therefore, in light of today's knowledge, it is becoming less likely that at moderate pressures around room temperature carbon nanostructures can store the amount of hydrogen required for automotive applications. PMID:12908227

  5. Effect of Hydrogen Plasma on Model Corrosion Layers of Bronze

    NASA Astrophysics Data System (ADS)

    Fojtíková, P.; Sázavská, V.; Mika, F.; Krčma, F.

    2016-05-01

    Our work is about plasmachemical reduction of model corrosion layers. The model corrosion layers were produced on bronze samples with size of 10 × 10 × 5 mm3, containing Cu and Sn. Concentrated hydrochloric acid was used as a corrosive environment. The application of reduction process in low-pressure low-temperature hydrogen plasma followed. A quartz cylindrical reactor with two outer copper electrodes was used. Plasma discharge was generated in pure hydrogen by a RF generator. Each corroded sample was treated in different conditions (supplied power and a continual or pulsed regime with a variable duty cycle mode). Process monitoring was ensured by optical emission spectroscopy. After treatment, samples were analyzed by SEM and EDX.

  6. Degenerate perturbative treatment of the hydrogenic Zeeman effect

    SciTech Connect

    Chen, A.C.

    1983-07-01

    Degenerate perturbation theory is applied to study the first 14 energy levels of the hydrogen atom in a uniform magnetic field up to the second order. The twofold degeneracy of all the levels among them in terms of the oscillator or parabolic states is completely removed. The results obtained with the use of the Pade approximant are compared with those found in the literature. Level crossings are discussed.

  7. Substituent effects on hydrogen bonding of aromatic amide-carboxylate.

    PubMed

    Sen, Ibrahim; Kara, Hulya; Azizoglu, Akın

    2016-10-01

    N-(p-benzoyl)-anthranilic acid (BAA) derivatives have been synthesized with different substituents (X: Br, Cl, OCH3, CH3), and their crystal structures have been analyzed in order to understand the variations in their molecular geometries with respect to the substituents by using (1)H NMR, (13)C NMR, IR and X-ray single-crystal diffraction. The carboxylic acid group forms classic OH⋯O hydrogen bonded dimers in a centrosymmetric R2(2)(8) ring motifs for BAA-Br and BAA-Cl. However, no carboxylic acid group forms classic OH⋯O hydrogen bonded dimers in BAA-OCH3 and BAA-CH3. The asymmetric unit consists of two crystallographically independent molecules in BAA-OCH3. DFT computations show that the interaction energies between monomer and dimer are in the range of 0.5-3.8kcal/mol with the B3LYP/6-31+G*, B3LYP/6-31++G*, B3LYP/6-31++G**, and B3LYP/AUG-cc-pVDZ levels of theory. The presence of different hydrogen bond patterns is also governed by the substrate. For monomeric compounds studied herein, theoretical calculations lead to two low-energy conformers; trans (a) and cis (b). Former one is more stable than latter by about 4kcal/mol. PMID:27239947

  8. Effects of Hydrogen Implantation into GaN

    SciTech Connect

    Abernathy, C.R.; Han, J.; Pearton, S.J.; Shul, R.J.; Song, C.Y.; Stavola, M.; Weinstein, M.G.; Wilson, R.G.; Zavada, J.M.

    1998-12-24

    Proton implantation in GaN is found to reduce the free carrier density through two mechanisms - first, by creating electron and hole traps at around Ec-0.8eV and Ev+0.9eV that lead to compensation in both n- and p-type material, and second, by leading to formation of (AH)O complexes, where A is any acceptor (Mg, Ca, Zn, Be, Cd). The former mechanism is usefid in creating high resistivity regions for device isolation, whereas the latter produces unintentional acceptor passivation that is detrimental to device performance. The strong affinity of hydrogen for acceptors leads to markedly different redistribution behavior for implanted in n- and p-GaN due to the chemical reaction to form neutral complexes in the latter. The acceptors may be reactivated by simple annealing at 2600{degrees}C, or by electron injection at 25-150{degrees}C that produces debonding of the (AH) centers. Implanted hydrogen is also strongly attracted to regions of strain in heterostructure samples during annealing, leading to pile-up at epi-epi and epi-substrate interfaces. II? spectroscopy shows that implanted hydrogen also decorates VG, defects in undoped and n-GaN.

  9. Hydrogen environment embrittlement.

    NASA Technical Reports Server (NTRS)

    Gray, H. R.

    1972-01-01

    Hydrogen embrittlement is classified into three types: internal reversible hydrogen embrittlement, hydrogen reaction embrittlement, and hydrogen environment embrittlement. Characteristics of and materials embrittled by these types of hydrogen embrittlement are discussed. Hydrogen environment embrittlement is reviewed in detail. Factors involved in standardizing test methods for detecting the occurrence of and evaluating the severity of hydrogen environment embrittlement are considered. The effects of test technique, hydrogen pressure, purity, strain rate, stress concentration factor, and test temperature are discussed.

  10. Effects of hydrogen on pitting susceptibility of type 310 stainless steel

    SciTech Connect

    Yang, Q.; Qiao, L.J.; Luo, J.L.; Chiovelli, S.

    1998-08-01

    Type 310 (UNS S31000) stainless steel (SS) membranes were precharged with hydrogen at various current densities. Effects of hydrogen on pitting susceptibility were investigated by carrying out the ASTM G 48 standard ferric chloride (FeCl{sub 3}) tests. Changes in pit density, pit size distribution, average pit diameter (D{sub a}), and apparent pit area percentage (A{sub p}) with hydrogen charging current density and immersion time (t) were measured statistically. Hydrogen in type 310 SS significantly promoted pit initiation and pit growth. D{sub a} and A{sub p} increased linearly with the logarithm of t (i.e., D{sub a} [or A{sub p}] = {alpha} ln t + {beta}). The value of the coefficient {alpha} increased with increases in charging current density. The interaction between hydrogen and defects, both in the surface film and the metal, were used to explain the deleterious effects of hydrogen on pitting corrosion. It was considered that hydrogen promoted pitting corrosion mainly through the formation of positive charge regions around defects in the surface film.

  11. Effects of Co and Al Contents on Cryogenic Mechanical Properties and Hydrogen Embrittlement for Austenitic Alloys

    SciTech Connect

    Li, X.Y.; Ma, L.M.; Li, Y.Y.

    2004-06-28

    The effects of Co and Al content on ambient and cryogenic mechanical properties, microstructure and hydrogen embrittlement of a high strength precipitate-strengthened austenitic alloy (Fe-Ni-Cr-Mo system) had been investigated with temperature range from 293K to 77 K. Hydrogen embrittlement tests were conducted using the method of high pressure thermal hydrogen charging. It was found that increasing Co content can cause increasing in ambient and cryogenic ductility, but has less effect on ultimate tensile strength. When Co content is 9.8%, obvious decrease was found in cryogenic yield strength. Increasing Al content can result in decreasing ambient and cryogenic ductility and severe hydrogen embrittlement, but slight increase in cryogenic yield strength. Increasing Co content, reducing Al content, and decreasing test temperature tend to decrease the hydrogen embrittlement tendency for the alloys. This work showed that the alloy with composition of Fe-31%Ni-15%Cr-5%Co-4.5%Mo-2.4%Ti-0.3%Al-0.3%Nb-0.2%V has the superior cryogenic mechanical properties and lower hydrogen embrittlement tendency, is a good high strength cryogenic hydrogen-resistant material.

  12. The effect of saturation of ACE binding sites on the pharmacokinetics of enalaprilat in man.

    PubMed Central

    Wade, J R; Meredith, P A; Hughes, D M; Elliott, H L

    1992-01-01

    1. Eight healthy male volunteers received oral enalapril, 10 mg, in the presence and absence of pretreatment with captopril, 50 mg, twice daily for 5 days. 2. Enalaprilat pharmacokinetics were characterised after both doses of enalapril to investigate the effect of saturating ACE binding sites by pretreatment with captopril. 3. The pharmacokinetics of enalaprilat were best described by a one compartment model with zero order input incorporating saturable binding to plasma and tissue ACE. 4. Values of AUC (0.72 h) for enalaprilat were 419 +/- 97 and 450 +/- 87 ng ml-1 h in the presence and absence of captopril, respectively. The difference was not statistically significant nor were there any other differences in model parameters. 5. Induction of ACE by captopril resulting in an increase in the number of ACE binding sites, may have obscured any effect of captopril on the occupancy of ACE binding sites by enalapril. PMID:1312853

  13. Effects of sodium on cell surface and intracellular TH-naloxone binding sites

    SciTech Connect

    Pollack, A.E.; Wooten, G.F.

    1987-07-27

    The binding of the opiate antagonist TH-naloxone was examined in rat whole brain homogenates and in crude subcellular fractions of these homogenates (nuclear, synaptosomal, and mitochondrial fractions) using buffers that approximated intra- (low sodium concentration) and extracellular (high sodium concentration) fluids. Saturation studies showed a two-fold decrease in the dissociation constant (Kd) in all subcellular fractions examined in extracellular buffer compared to intracellular buffer. In contrast, there was no significant effect of the buffers on the Bmax. Thus, TH-naloxone did not distinguish between binding sites present on cell surface and intracellular tissues in these two buffers. These results show that the sodium effect of opiate antagonist binding is probably not a function of altered selection of intra- and extracellular binding sites. 17 references, 2 tables.

  14. Identification of tail binding effect of kinesin-1 using an elastic network model.

    PubMed

    Kim, Jae In; Chang, Hyun Joon; Na, Sungsoo

    2015-10-01

    Kinesin is a motor protein that delivers cargo inside a cell. Kinesin has many different families, but they perform basically same function and have same motions. The walking motion of kinesin enables the cargo delivery inside the cell. Autoinhibition of kinesin is important because it explains how function of kinesin inside a cell is stopped. Former researches showed that tail binding is related to autoinhibition of kinesin. In this work, we performed normal mode analysis with elastic network model using different conformation of kinesin to determine the effect of tail binding by considering four models such as functional form, autoinhibited form, autoinhibited form without tail, and autoinhibited form with carbon structure. Our calculation of the thermal fluctuation and cross-correlation shows the change of tail-binding region in structural motion. Also strain energy of kinesin showed that elimination of tail binding effect leads the structure to have energetically similar behavior with the functional form. PMID:25676575

  15. Cellular retinol-binding protein and retinoic acid-binding protein in rat testes: effect of retinol depletion.

    PubMed

    Ong, D E; Tsai, C H; Chytil, F

    1976-02-01

    Testes of rats contain two cellular binding proteins of interest in vitamin A metabolism. One protein binds retinoic acid with high specificity; the other binds retinol with high specificity. When the cellular retinol-binding protein was partially purified from rat testes, it exhibited fluorescence excitation and emission spectra similar to that of all-trans-retinol in hexane. Exposure of this preparation to UV light destroyed this fluorescence but spectra identical to the original were obtained after addition of retinol. Hexane extracts of the binding protein had fluorescence spectra identical to all-trans-retinol, suggesting that this compound is bound to the protein in vivo. Extracts of testes from retinol depleted rats were submitted to gel filtration but failed to show a retinol-like fluorescence at the elution position of retinol binding protein. This fluorescence was observed in the preparations from pair fed control animals. However, after addition of all-trans-retinol to the extracts from the depleted rats, fluorescence at that elution position was observed. This indicates that in testes of retinol depleted rats the cellular retinol binding protein is present but without bound retinol, in contrast to the non-depleted rats where 30-43% of the binding protein had bound retinol. The amounts of cellular retinol binding protein and retinoic acid binding protein in testes, as determined by sucrose gradient centrifugation, were found to be similar for retinol depleted and pair fed control rats. PMID:942996

  16. Aluminium competitive effect on rare earth elements binding to humic acid

    NASA Astrophysics Data System (ADS)

    Marsac, Rémi; Davranche, Mélanie; Gruau, Gérard; Dia, Aline; Bouhnik-Le Coz, Martine

    2012-07-01

    Competitive mechanisms between rare earth elements (REE) and aluminium for humic acid (HA) binding were investigated by combining laboratory experiments and modeling to evaluate the effect of Al on REE-HA complexation. Results indicates that Al3+ competes more efficiently with heavy REE (HREE) than with light REE (LREE) in acidic (pH = 3) and low REE/HA concentration ratio conditions providing evidence for the Al high affinity for the few HA multidentate sites. Under higher pH - 5 to 6 - and high REE/HA conditions, Al is more competitive for LREE suggesting that Al is bound to HA carboxylic rather than phenolic sites. PHREEQC/Model VI Al-HA binding parameters were optimized to simulate precisely both Al binding to HA and Al competitive effect on REE binding to HA. REE-HA binding pattern is satisfactorily simulated for the whole experimental conditions by the ΔLK1A optimization (i.e. ΔLK1A controls the distribution width of log K around log KMA). The present study provides fundamental knowledge on Al binding mechanisms to HA. Aluminium competitive effect on other cations binding to HA depends clearly on its affinity for carboxylic, phenolic or chelate ligands, which is pH dependent. Under circumneutral pH such as in natural waters, Al should lead to LREE-depleted patterns since Al is expected to be bound to weak HA carboxylic groups. As deduced from the behavior of Al species, other potential competitor cations are expected to have their own competitive effect on REE-HA binding. Therefore, in order to reliably understand and model REE-HA patterns in natural waters, a precise knowledge of the exact behavior of the different REE competitor cations is required. Finally, this study highlights the ability of the REE to be used as a “speciation probe” to precisely describe cation interactions with HA as here evidenced for Al.

  17. Effects of temperature and ethanol on agonist and antagonist binding to rat heart muscarinic receptors in the absence and presence of GTP.

    PubMed Central

    Waelbroeck, M; Robberecht, P; Chatelain, P; De Neef, P; Christophe, J

    1985-01-01

    The effect of temperature on the binding of four agonists and three antagonists to rat heart muscarinic receptors was studied in the absence and presence of GTP. The binding of agonists to two states (or classes) of receptors, in the absence of GTP, led to enthalpy and entropy changes that decreased sharply above 25 degrees C, suggesting that agonists induced 'isomerization' reactions (large conformational changes and/or receptor-effector association). Both temperature increase and ethanol decreased hydrophobic interactions, thereby hindering binding and/or agonist-induced 'isomerization' reactions. Addition of GTP to the incubation medium also appeared to reverse (or prevent) 'isomerization' reactions. For agonist binding to the low-affinity state, in the presence of GTP, and for antagonist binding, the thermodynamic parameters observed could be readily explained by simple receptor-ligand associations; large entropy increases and small enthalpy increases, provoked by hydrophobic and ionic interactions, were partly neutralized by entropy and enthalpy decreases, due to hydrogen bonds and van der Waals interactions. The muscarinic antagonists used (atropine, n-methylscopolamine and dexetimide), being more hydrophobic molecules than the agonists tested (carbamylcholine, oxotremorine and pilocarpine), induced larger entropy changes or more negative enthalpy changes. PMID:4062907

  18. Effects of temperature and ethanol on agonist and antagonist binding to rat heart muscarinic receptors in the absence and presence of GTP.

    PubMed

    Waelbroeck, M; Robberecht, P; Chatelain, P; De Neef, P; Christophe, J

    1985-10-15

    The effect of temperature on the binding of four agonists and three antagonists to rat heart muscarinic receptors was studied in the absence and presence of GTP. The binding of agonists to two states (or classes) of receptors, in the absence of GTP, led to enthalpy and entropy changes that decreased sharply above 25 degrees C, suggesting that agonists induced 'isomerization' reactions (large conformational changes and/or receptor-effector association). Both temperature increase and ethanol decreased hydrophobic interactions, thereby hindering binding and/or agonist-induced 'isomerization' reactions. Addition of GTP to the incubation medium also appeared to reverse (or prevent) 'isomerization' reactions. For agonist binding to the low-affinity state, in the presence of GTP, and for antagonist binding, the thermodynamic parameters observed could be readily explained by simple receptor-ligand associations; large entropy increases and small enthalpy increases, provoked by hydrophobic and ionic interactions, were partly neutralized by entropy and enthalpy decreases, due to hydrogen bonds and van der Waals interactions. The muscarinic antagonists used (atropine, n-methylscopolamine and dexetimide), being more hydrophobic molecules than the agonists tested (carbamylcholine, oxotremorine and pilocarpine), induced larger entropy changes or more negative enthalpy changes. PMID:4062907

  19. Effect of hydrogen on degradation mechanism of zirconium: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Chakraborty, Poulami; Moitra, Amitava; Saha-Dasgupta, Tanusri

    2015-11-01

    Using large scale molecular dynamics simulation, we investigate the deleterious effect of hydrogen in Zr. We consider both dilute and concentrated limit of H. In the dilute and concentrated H limits, we study the effect of 1-5 atomic percentage of hydrogen, and that of ε-ZrH2 precipitate having 5-10 nm diameters, respectively. From the stress-strain curves and micro-structure analysis at different strain values, we characterize the deformation behavior and correlate our result with previously reported mechanisms. We show hydrogen atoms in dilute limit help in dislocation multiplication, following the hydrogen-enhanced localized plasticity mechanism. In the concentrated limit, on the other hand, dislocations and cracks nucleate from precipitate-matrix interface, indicating the decohesion mechanism as primary method for Zr degradation. These findings are corroborated with a nucleation and growth model as expressed in Kolmogorov-Johnson-Mehl-Avrami equation.

  20. The effect of hydrogen on the multiaxial stress-strain behavior of titanium tubing

    SciTech Connect

    Lentz, C.W.; Hecker, S.S.; Koss, D.A.; Stout, M.G.

    1983-12-01

    The influence of internal hydrogen on the multiaxial stress-strain behavior of commercially pure titanium has been studied. Thin-walled specimens containing either 20 or 1070 ppm hydrogen were tested at constant stress ratios in combined tension and internal pressure. Hydrogen lowers the yield strength but has no significant effect on strain hardening behavior at strains epsilon greater than or equal to 0.02. Thus, hydrogen embrittlement under plain strain or equibiaxial loading is not a consequence of changes of flow behavior. The yielding behavior is described well by Hill's quadratic yield criterion. As measured mechanically and pole figure analysis, the plastic anisotropy changes with deformation in a manner which depends on stress state. A strain dependent, texture-induced strengthening effect in equibiaxial tension an enhanced strain hardening rate.

  1. An atomistic study of the effects of stress and hydrogen on a dislocation lock in nickel

    SciTech Connect

    Hoagland, R.G.; Baskes, M.I.

    1998-03-19

    Even though austenitic alloys are commonly used in a hydrogen environment, hydrogen-induced fracture of these alloys has been reported. Most recently it has been shown that the failure of these alloys in hydrogen is initiated by void formation at slip band intersections. It is the object of this work to investigate the atomistic mechanisms that occur at these slip band intersections in the presence of hydrogen. Specifically it has been suggested that dislocation-dislocation interactions may play a large role in the initiation of voids or cracks. Hirth has summarized the various forms of dislocation interactions, traditionally called Lomer-Cottrell Locks (LCLs), that can occur. Baskes et al. have investigated the effects of stress on a LCL using an Embedded Atom Method (EAM) model for nickel developed previously by Angelo et al. The EAM is a well-established semi-empirical method of atomistic calculation that has been successfully used for over a decade to calculate the energetics and structure of defects in transition metals. The work by Angelo et al. established that the trapping of hydrogen to single dislocations had a maximum energy of ca. 0.1 eV while the trapping to a LCL was significantly greater, {approximately}0.33 eV, thus the authors expect that a LCL could be important in explaining the fracture behavior of a fcc material in a hydrogen environment. Baskes et al. found that under uniaxial stress a LCL in the absence of hydrogen underwent a number of transitions, but it did not dissociate or form a crack nucleus. In this work the authors extend the previous work to include the effects of hydrogen. Specifically they will simulate the experiments of Moody et al. for the case of room temperature exposure of Inconel to 190 atm of hydrogen.

  2. Modulatory effects of unsaturated fatty acids on the binding of glucocorticoids to rat liver glucocorticoid receptors.

    PubMed

    Vallette, G; Vanet, A; Sumida, C; Nunez, E A

    1991-09-01

    Binding of the synthetic glucocorticoid dexamethasone to the rat liver cytosol glucocorticoid receptor was inhibited by physiological concentrations of nonesterified fatty acids as a function of increasing dose, degree of unsaturation, and chain length of the fatty acid. Polyunsaturated fatty acids were the most potent inhibitors. Scatchard analysis and Line-weaver-Burk plots of the binding data revealed that both the association constants and number of binding sites decreased and that polyunsaturated fatty acids inhibition was of a mixed non-competitive type. The dissociation rate constant of [3H]dexamethasone from glucocorticoid receptors was increased by up to 10 times in the presence of docosahexaenoic acid, whereas a competitive inhibitor like the glucocorticoid antagonist RU 38486 had no effect. Moreover, sucrose density gradient analysis showed that docosahexaenoic acid inhibited the binding of [3H] dexamethasone to both the 8.8S and 4S forms. The results strongly suggest that unsaturated fatty acids are interacting at a site on the receptor different from the hormone binding site and the heat shock protein and that by binding to a second site unsaturated fatty acids greatly change the conformation of the hormone binding site to reduce its affinity for the hormone, either partially or completely depending on the concentration and the class of the fatty acid. PMID:1874175

  3. DNA Interactions Probed by Hydrogen-Deuterium Exchange (HDX) Fourier Transform Ion Cyclotron Resonance Mass Spectrometry Confirm External Binding Sites on the Minichromosomal Maintenance (MCM) Helicase.

    PubMed

    Graham, Brian W; Tao, Yeqing; Dodge, Katie L; Thaxton, Carly T; Olaso, Danae; Young, Nicolas L; Marshall, Alan G; Trakselis, Michael A

    2016-06-10

    The archaeal minichromosomal maintenance (MCM) helicase from Sulfolobus solfataricus (SsoMCM) is a model for understanding structural and mechanistic aspects of DNA unwinding. Although interactions of the encircled DNA strand within the central channel provide an accepted mode for translocation, interactions with the excluded strand on the exterior surface have mostly been ignored with regard to DNA unwinding. We have previously proposed an extension of the traditional steric exclusion model of unwinding to also include significant contributions with the excluded strand during unwinding, termed steric exclusion and wrapping (SEW). The SEW model hypothesizes that the displaced single strand tracks along paths on the exterior surface of hexameric helicases to protect single-stranded DNA (ssDNA) and stabilize the complex in a forward unwinding mode. Using hydrogen/deuterium exchange monitored by Fourier transform ion cyclotron resonance MS, we have probed the binding sites for ssDNA, using multiple substrates targeting both the encircled and excluded strand interactions. In each experiment, we have obtained >98.7% sequence coverage of SsoMCM from >650 peptides (5-30 residues in length) and are able to identify interacting residues on both the interior and exterior of SsoMCM. Based on identified contacts, positively charged residues within the external waist region were mutated and shown to generally lower DNA unwinding without negatively affecting the ATP hydrolysis. The combined data globally identify binding sites for ssDNA during SsoMCM unwinding as well as validating the importance of the SEW model for hexameric helicase unwinding. PMID:27044751

  4. Stark effect of hydrogenic impurities in a quantum box

    NASA Astrophysics Data System (ADS)

    del Castillo-Mussot, Marcelo; Vazquez, Gerardo J.; Mendoza, Carlos I.; Spector, Harold N.

    2004-03-01

    We extend the model of a cubic quantum box proposed by Ribeiro and Latge to carry out a variational calculation of the bindingenergy of impurities in such a structure as function of anelectric field.The binding energy of the impurities increases with the electric field. In addition, the electric field splits the energy of impurities on the faces of the box which are equivalent in the absence of the electric field.

  5. Prooxidative effect of copper--metallothionein in the acute cytotoxicity of hydrogen peroxide in Ehrlich ascites tumour cells.

    PubMed

    Suntres, Zacharias E; Lui, Edmund M K

    2006-01-16

    This study was concerned with the role of copper (Cu) and Cu-metallothionein (Cu-MT) in oxidative stress. Hydrogen peroxide (H(2)O(2))-induced oxidative injury was examined in Ehrlich ascites tumour cells isolated from host mice pretreated with 0, 1 or 2mg of CuSO(4) (ip) 24h earlier. Control Ehrlich cells contained low levels of Cu and Cu treatment produced dose-related increases in cellular Cu and Cu-MT levels and corresponding increases in sensitivity to oxidative toxicity of H(2)O(2) (LC(50), cell blebbing, lipid peroxidation, GSH depletion, and increase in intracellular free [Ca(2+)](i)). Hydrogen peroxide treatment also resulted in the oxidation of MT thiolates, reduction in the binding of Cu to MT resulting in translocation of Cu to other subcellular sites. d-penicillamine, a Cu-chelating agent, obliterated the sensitization effect of Cu-pretreatment and reduced the redistribution of MT-bound Cu, suggesting the participation of Cu ions derived from MT in promoting oxidant stress. Additional experiments with desferoxamine and mannitol have revealed the involvement of a Cu-dependent Fenton reaction in the mediation of the prooxidative effect of Cu-MT. These data suggest that cells with high levels of Cu-MT may be particularly susceptible to oxidative stress. PMID:16221516

  6. Effects of a Transition to a Hydrogen Economy on Employment in the United States

    SciTech Connect

    Tolley, George S.; Jones, Donald W. Mintz, Marianne M.; Smith, Barton A.; Carlson, Eric; Unnasch, Stefan; Lawrence, Michael; Chmelynski, Harry

    2008-07-01

    The U.S. Department of Energy report, Effects of a Transition to a Hydrogen Economy on Employment in the United States Report to Congress, estimates the effects on employment of a U.S. economy transformation to hydrogen between 2020 and 2050. The report includes study results on employment impacts from hydrogen market expansion in the transportation, stationary, and portable power sectors and highlights possible skill and education needs. This study is in response to Section 1820 of the Energy Policy Act of 2005 (Public Law 109-58) (EPACT). Section 1820, “Overall Employment in a Hydrogen Economy,” requires the Secretary of Energy to carry out a study of the effects of a transition to a hydrogen economy on several employment [types] in the United States. As required by Section 1820, the present report considers: • Replacement effects of new goods and services • International competition • Workforce training requirements • Multiple possible fuel cycles, including usage of raw materials • Rates of market penetration of technologies • Regional variations based on geography • Specific recommendations of the study Both the Administration’s National Energy Policy and the Department’s Strategic Plan call for reducing U.S. reliance on imported oil and reducing greenhouse gas emissions. The National Energy Policy also acknowledges the need to increase energy supplies and use more energy-efficient technologies and practices. President Bush proposed in his January 2003 State of the Union Address to advance research on hydrogen so that it has the potential to play a major role in America’s future energy system. Consistent with these aims, EPACT 2005 authorizes a research, development, and demonstration program for hydrogen and fuel cell technology. Projected results for the national employment impacts, projections of the job creation and job replacement underlying the total employment changes, training implications, regional employment impacts and the

  7. A Preorganized Hydrogen Bond Network and Its Effect on Anion Stability

    SciTech Connect

    Samet, Masoud; Wang, Xue B.; Kass, Steven R.

    2014-08-07

    Rigid tricyclic locked in all axial 1,3,5-cyclohexanetriol derivatives with 0–3 trifluoromethyl groups were synthesized and photoelectron spectra of their conjugate bases and chloride anion clusters are reported along with density functional computations. The resulting vertical and adiabatic detachment energies provide measures of the anion stabilization due to the hydrogen bond network and inductive effects. The latter mechanism is found to be transmitted through space via hydrogen bonds

  8. Isotope effects in dense solid hydrogen - Phase transition in deuterium at 190 + or - 20 GPa

    NASA Technical Reports Server (NTRS)

    Hemley, R. J.; Mao, H. K.

    1989-01-01

    Raman measurements of solid normal deuterium compressed in a diamond-anvil cell indicate that the material undergoes a structural phase transformation at 190 + or - 20 GPa and 77 K. Spectroscopically, the transition appears analogous to that observed in hydrogen at 145 + or - 5 GPa. The large isotope effect on the transition pressure suggests there is a significant vibrational contribution to the relative stability of the solid phases of hydrogen at very high densities.

  9. Disconfirming (Double Bind) Effects of Incongruent Multi-Channel Messages.

    ERIC Educational Resources Information Center

    Rummel, Lynda; And Others

    In an experiment designed to explore the immediate disconfirming effects of strong and mild incongruent messages and the impact of certain contextual constraints on disconfirming effects, 192 male undergraduates evaluated videotaped examples of strong and mild sarcasm and joking and the complementary congruent forms of straightforward positive and…

  10. Hydrogen effects on materials for CNG/H2 blends.

    SciTech Connect

    Farese, David; Keller, Jay O.; Somerday, Brian P.

    2010-09-01

    No concerns for Hydrogen-Enriched Compressed Natural gas (HCNG) in steel storage tanks if material strength is < 950 MPa. Recommend evaluating H{sub 2}-assisted fatigue cracking in higher strength steels at H{sub 2} partial pressure in blend. Limited fatigue testing on higher strength steel cylinders in H{sub 2} shows promising results. Impurities in Compressed Natural Gas (CNG) (e.g., CO) may provide extrinsic mechanism for mitigating H{sub 2}-assisted fatigue cracking in steel tanks.

  11. HYDROGEN EFFECTS ON FRACTURE TOUGHNESS OF TYPE 316L STAINLESS STEEL FROM 175 K TO 425 K

    SciTech Connect

    Morgan, M; Glenn Chapman, G

    2009-05-04

    The effects of hydrogen on the fracture-toughness properties of Type 316L stainless steel from 175 K to 425 K were measured. Fracture-toughness samples were fabricated from Type 316L stainless steel forgings and hydrogen-charged with hydrogen at 34 MPa and 623 K for two weeks prior to testing. The effect of hydrogen on the J-Integral vs. crack extension behavior was measured at various temperatures by fracturing non-charged and hydrogen-charged samples in an environmental chamber. Hydrogen-charged steels had lower toughness values than non-charged ones, but still retained good toughness properties. The fracture-toughness values of hydrogen-charged samples tested near ambient temperature were about 70% of non-charged values. For hydrogen-charged samples tested at 225 K and 425 K, the fracture-toughness values were 50% of the non-charged values. In all cases, fracture occurred by microvoid nucleation and coalescence, although the hydrogen-charged samples had smaller and more closely spaced microvoids. The results suggest that hydrogen effects on toughness are greater at 225 K than they are at ambient temperature because of strain-induced martensite formation. At 425 K, the hydrogen effects on toughness are greater than they are at ambient temperature because of the higher mobility of hydrogen.

  12. Ab-initio study of pressure effects and hydrogen impurity in HgO

    NASA Astrophysics Data System (ADS)

    Choi, Minseok; Park, Chul-Hong

    2016-06-01

    Through ab-initio pseudopotential calculations, we investigated the deformation potential of HgO semiconductors and the structural stabilities of various crystal structures under pressure. We also investigated the microscopic structure of the hydrogen (H) impurity in HgO. Especially the state of hydrogen atoms captured by an acceptor-like Hg-vacancy (V Hg ) is focused on. The location of H is found to be very different from the original Hg-site, forming a strong H-O bond. The capture two H atoms by V Hg is found to be energetically favorable: the binding energy for one H and the second H are 1.01 eV and 0.07 eV, respectively.

  13. Phosphorylation in protein-protein binding: effect on stability and function

    PubMed Central

    Nishi, Hafumi; Hashimoto, Kosuke; Panchenko, Anna R.

    2011-01-01

    Summary Post-translational modifications offer a dynamic way to regulate protein activity, subcellular localization and stability. Here we estimate the effect of phosphorylation on protein binding and function for different types of complexes from human proteome. We find that phosphorylation sites have a tendency to be located on binding interfaces in heterooligomeric and weak transient homooligomeric complexes. The analysis of molecular mechanisms of phosphorylation shows that phosphorylation may modulate the strength of interactions directly on interfaces and binding hotspots have a tendency to be phosphorylated in heterooligomers. Although majority of phosphosites do not show significant estimated stability differences upon attaching the phosphate groups, for about one third of all complexes it causes relatively large changes in binding energy. We discuss the cases where phosphorylation mediates the complex formation and regulates the function. We show that phosphorylation sites are not only more likely to be evolutionary conserved than surface residues but even more so than other interfacial residues. PMID:22153503

  14. NADP(+) binding effects tryptophan accessibility, folding and stability of recombinant B. malayi G6PD.

    PubMed

    Verma, Anita; Chandra, Sharat; Suthar, Manish Kumar; Doharey, Pawan Kumar; Siddiqi, Mohammad Imran; Saxena, Jitendra Kumar

    2016-04-01

    Brugia malayi Glucose 6-phosphate dehydrogenase apoenzyme (BmG6PD) was expressed and purified by affinity chromatography to study the differences in kinetic properties of enzyme and the effect of the cofactor NADP(+) binding on enzyme stability. The presence of cofactor NADP(+) influenced the tertiary structure of enzyme due to significant differences in the tryptophan microenvironment. However, NADP(+) binding have no effect on secondary structure of the enzyme. Quenching with acrylamide indicated that two or more tryptophan residues became accessible upon cofactor binding. Unfolding and cross linking study of BmG6PD showed that NADP(+) stabilized the protein in presence of high concentration of urea/GdmCl. A homology model of BmG6PD constructed using human G6PD (PDB id: 2BH9) as a template indicated 34% α-helix, 19% β-sheet and 47% random coil conformations in the predicted model of the enzyme. In the predicted model binding of NADP(+) to BmG6PD was less tight with the structural sites (-10.96kJ/mol binding score) as compared with the coenzyme site (-15.47kJ/mol binding score). PMID:26763177

  15. Effect of Thiol-Binding Reagents on the Metabolism of Thiosulfate and Tetrathionate by Thiobacillus neapolitanus

    PubMed Central

    Trudinger, P. A.

    1965-01-01

    Trudinger, P. A. (Division of Plant Industry, Canberra, Australia). Effect of thiol-binding reagents on the metabolism of thiosulfate and tetrathionate by Thiobacillus neapolitanus. J. Bacteriol. 89:617–625. 1965.—Iodoacetamide, N-ethyl maleimide (NEM), p-chloromercuribenzoate (CMB), Mercurochrome, and HgCl2 inhibited the oxidation of thiosulfate to sulfate by Thiobacillus neapolitanus; tetrathionate accumulated under these conditions. High concentrations of the thiol-binding reagents lowered the rate of oxidation of thiosulfate to tetrathionate; inhibition by CMB was reversed by high concentrations of thiosulfate. Relatively low concentrations of the thiol-binding reagents completely inhibited the oxidation and anaerobic metabolism of tetrathionate. Similar reagents had no effect on a soluble thiosulfate-oxidizing enzyme. Inhibition by thiol-binding reagents was overcome by washing the bacteria with Na2S or thioethanol after their exposure to the inhibitors. Under some conditions, the addition of thiosulfate or tetrathionate to bacterial suspensions before the addition of the thiol-binding reagents prevented the inhibition of thiosulfate and tetrathionate metabolism by these reagents. Thiosulfate catalyzed a rapid chemical breakdown of NEM and reacted with iodoacetamide. A complex between thiosulfate and mercuribenzoate was demonstrated. Three types of thiol group appear to be associated with the metabolism of thiosulfate and tetrathionate; one of these types may be located at the bacterial cell membrane. The results are consistent with the hypothesis that thiols (or disulfide groups) are binding sites for the substrates. PMID:14273636

  16. Effects of Varying the Three-Body Molecular Hydrogen

    SciTech Connect

    Turk, Matthew J.; Clark, Paul; Glover, S.C.O.; Greif, T.H.; Abel, Tom; Klessen, Ralf; Bromm, Volker; /Texas U., Astron. Dept.

    2011-03-03

    The transformation of atomic hydrogen to molecular hydrogen through three-body reactions is a crucial stage in the collapse of primordial, metal-free halos, where the first generation of stars (Population III stars) in the Universe are formed. However, in the published literature, the rate coefficient for this reaction is uncertain by nearly an order of magnitude. We report on the results of both adaptive mesh refinement (AMR) and smoothed particle hydrodynamics (SPH) simulations of the collapse of metal-free halos as a function of the value of this rate coefficient. For each simulation method, we have simulated a single halo three times, using three different values of the rate coefficient. We find that while variation between halo realizations may be greater than that caused by the three-body rate coefficient being used, both the accretion physics onto Population III protostars as well as the long-term stability of the disk and any potential fragmentation may depend strongly on this rate coefficient.

  17. Differential effects of exercise on brain opioid receptor binding and activation in rats.

    PubMed

    Arida, Ricardo Mario; Gomes da Silva, Sérgio; de Almeida, Alexandre Aparecido; Cavalheiro, Esper Abrão; Zavala-Tecuapetla, Cecilia; Brand, Serge; Rocha, Luisa

    2015-01-01

    Physical exercise stimulates the release of endogenous opioid peptides supposed to be responsible for changes in mood, anxiety, and performance. Exercise alters sensitivity to these effects that modify the efficacy at the opioid receptor. Although there is evidence that relates exercise to neuropeptide expression in the brain, the effects of exercise on opioid receptor binding and signal transduction mechanisms downstream of these receptors have not been explored. Here, we characterized the binding and G protein activation of mu opioid receptor, kappa opioid receptor or delta opioid receptor in several brain regions following acute (7 days) and chronic (30 days) exercise. As regards short- (acute) or long-term effects (chronic) of exercise, overall, higher opioid receptor binding was observed in acute-exercise animals and the opposite was found in the chronic-exercise animals. The binding of [(35) S]GTPγS under basal conditions (absence of agonists) was elevated in sensorimotor cortex and hippocampus, an effect more evident after chronic exercise. Divergence of findings was observed for mu opioid receptor, kappa opioid receptor, and delta opioid receptor receptor activation in our study. Our results support existing evidence of opioid receptor binding and G protein activation occurring differentially in brain regions in response to diverse exercise stimuli. We characterized the binding and G protein activation of mu, kappa, and delta opioid receptors in several brain regions following acute (7 days) and chronic (30 days) exercise. Higher opioid receptor binding was observed in the acute exercise animal group and opposite findings in the chronic exercise group. Higher G protein activation under basal conditions was noted in rats submitted to chronic exercise, as visible in the depicted pseudo-color autoradiograms. PMID:25330347

  18. Milk matrix effects on antibody binding analyzed by enzyme-linked immunosorbent assay and biolayer interferometry.

    PubMed

    Brandon, David L; Adams, Lisa M

    2015-04-01

    Biolayer interferometry (BLI) was employed to study the impact of the milk matrix on the binding of ricin to asialofetuin (ASF) and to antibodies. This optical sensing platform used ligands immobilized covalently or via biotin-streptavidin linkage, and the results were compared to those obtained by enzyme-linked immunosorbent assay (ELISA). In sandwich ELISA, the binding of ricin to ASF was dramatically decreased when galactose was present during the analyte or detection antibody binding step. Low concentrations of milk (1%, v/v) produced a similar reduction in ricin binding to ASF but not to a high-affinity monoclonal antibody (mAb), increasing the dissociation rate of ASF-ricin complexes up to 100-fold. The effect of milk on the binding of ricin to ASF was ascribable to dialyzable factors, and milk sugar can account for these effects. The use of high-affinity mAbs in ELISA effectively limits the milk matrix effect on ricin analysis. PMID:25822824

  19. MODELING THE EFFECTS OF FLEXIBILITY ON THE BINDING OF ENVIRONMENTAL ESTROGENS TO THE ESTROGEN RECEPTOR

    EPA Science Inventory

    Modeling the effects of flexibility on the binding of environmental estrogens to the estrogen receptor
    There are many reports of environmental endocrine disruption in the literature, yet it has been difficult to identify the specific chemicals responsible for these effects. ...

  20. Gas-phase hydrogen permeation through alpha-titanium - Surface film and dimensional effects

    NASA Technical Reports Server (NTRS)

    Shah, K. K.; Johnson, D. L.

    1982-01-01

    The process of hydrogen transport through alpha-Ti involves simultaneous diffusion and phase boundary reactions at both surfaces, with the relative effect on each surface depending on the extent of surface contamination as well as the physical dimensions of the titanium membrane used. It is shown by the present study that hydrogen permeation in commercially pure alpha-Ti increases exponentially with temperature and is dependent on the first power of the input pressure, whether the surface is as-polished, preoxidized or prenitrided. Permeation decreases in the case of the as-polished condition if nitride or oxide films are formed at the surface in contact with source hydrogen, while increasing slightly for the same condition if such films are formed at the hydrogen exit surface.

  1. Effects of microstructure banding on hydrogen assisted fatigue crack growth in X65 pipeline steels

    DOE PAGESBeta

    Ronevich, Joseph A.; Somerday, Brian P.; San Marchi, Chris W.

    2015-09-10

    Banded ferrite-pearlite X65 pipeline steel was tested in high pressure hydrogen gas to evaluate the effects of oriented pearlite on hydrogen assisted fatigue crack growth. Test specimens were oriented in the steel pipe such that cracks propagated either parallel or perpendicular to the banded pearlite. The ferrite-pearlite microstructure exhibited orientation dependent behavior in which fatigue crack growth rates were significantly lower for cracks oriented perpendicular to the banded pearlite compared to cracks oriented parallel to the bands. Thus the reduction of hydrogen assisted fatigue crack growth across the banded pearlite is attributed to a combination of crack-tip branching and impededmore » hydrogen diffusion across the banded pearlite.« less

  2. The effect of tensile stress on hydrogen diffusion in metal alloys

    NASA Technical Reports Server (NTRS)

    Danford, M. D.

    1992-01-01

    The effect of tensile stress on hydrogen diffusion has been determined for Type 303 stainless steel, A286 CRES, and Waspaloy and IN100 nickel-base alloys. It was found that hydrogen diffusion coefficients are not significantly affected by stress, while the hydrogen permeabilities are greatly affected in Type 303 stainless steel and A286 CRES (iron-based alloys), but are affected little in Waspaloy (nickel-base) and not affected in all in IN100 (nickel base). These observations might be taken as an indication that hydrogen permeabilities are affected by stress in iron-based alloys, but only slightly affected in nickel-based alloys. However, it is too early to make such a generalization based on the study of only these four alloys.

  3. Bimetallic ruthenium-copper nanoparticles embedded in mesoporous carbon as an effective hydrogenation catalyst.

    PubMed

    Liu, Jiajia; Zhang, Li Li; Zhang, Jiatao; Liu, Tao; Zhao, X S

    2013-11-21

    Bimetallic ruthenium-copper nanoparticles embedded in the pore walls of mesoporous carbon were prepared via a template route and evaluated in terms of catalytic properties in D-glucose hydrogenation. The existence of bimetallic entities was supported by Ru L3-edge and Cu K-edge X-ray absorption results. The hydrogen spillover effect of the bimetallic catalyst on the hydrogenation reaction was evidenced by the results of both hydrogen and carbon monoxide chemisorptions. The bimetallic catalyst displayed a higher catalytic activity than the single-metal catalysts prepared using the same approach, namely ruthenium or copper nanoparticles embedded in the pore walls of mesoporous carbon. This improvement was due to the changes in the geometric and electronic structures of the bimetallic catalyst because of the presence of the second metal. PMID:24072134

  4. Effect of argon addition on plasma parameters and dust charging in hydrogen plasma

    SciTech Connect

    Kakati, B. Kausik, S. S.; Saikia, B. K.; Bandyopadhyay, M.; Saxena, Y. C.

    2014-10-28

    Experimental results on effect of adding argon gas to hydrogen plasma in a multi-cusp dusty plasma device are reported. Addition of argon modifies plasma density, electron temperature, degree of hydrogen dissociation, dust current as well as dust charge. From the dust charging profile, it is observed that the dust current and dust charge decrease significantly up to 40% addition of argon flow rate in hydrogen plasma. But beyond 40% of argon flow rate, the changes in dust current and dust charge are insignificant. Results show that the addition of argon to hydrogen plasma in a dusty plasma device can be used as a tool to control the dust charging in a low pressure dusty plasma.

  5. Tunable Anderson Localization in Hydrogenated Graphene Based on the Electric Field Effect: First-Principles Study

    NASA Astrophysics Data System (ADS)

    Kang, Joongoo; Wei, Su-Huai

    2014-03-01

    We present a mechanism for reversible switching of the Anderson localization (AL) of electrons in hydrogenated graphene through modulation of the H coverage on graphene by external electric fields. The main idea is to exploit the unique acid-base chemistry (i.e., proton transfer reaction) between NH3 gas and hydrogenated graphene, which can be controlled by applying perpendicular electric fields. The proposed field-induced control of disorder in hydrogenated graphene not only has scientific merits in a systematic study of AL of electrons in grapheme but can also lead to new insight into the development of a new type of transistor based on reversible on/off switching of AL. Furthermore, the reversible and effective tuning of the H coverage on graphene should be useful for tailoring material properties of weakly hydrogenated graphene. This work was funded by the NREL LDRD program (DE-AC36-08GO28308).

  6. Alpha-amylase starch binding domains: cooperative effects of binding to starch granules of multiple tandemly arranged domains.

    PubMed

    Guillén, D; Santiago, M; Linares, L; Pérez, R; Morlon, J; Ruiz, B; Sánchez, S; Rodríguez-Sanoja, R

    2007-06-01

    The Lactobacillus amylovorus alpha-amylase starch binding domain (SBD) is a functional domain responsible for binding to insoluble starch. Structurally, this domain is dissimilar from other reported SBDs because it is composed of five identical tandem modules of 91 amino acids each. To understand adsorption phenomena specific to this SBD, the importance of their modular arrangement in relationship to binding ability was investigated. Peptides corresponding to one, two, three, four, or five modules were expressed as His-tagged proteins. Protein binding assays showed an increased capacity of adsorption as a function of the number of modules, suggesting that each unit of the SBD may act in an additive or synergic way to optimize binding to raw starch. PMID:17468268

  7. Hydrogen Storage Properties of Rigid Three-Dimensional Hofmann Clathrate Derivatives: The Effects of Pore Size

    SciTech Connect

    Culp, J.T.; Natesakhawat, Sittichai; Smith, M.R.; Bittner, E.; Matranga, C.S.; Bockrath, B.

    2008-05-01

    The effects of pore size on the hydrogen storage properties of a series of pillared layered solids based on the M(L)[M'(CN)4] structural motif, where M ) Co or Ni, L ) pyrazine (pyz), 4,4'-bipyridine (bpy), or 4,4'-dipyridylacetylene (dpac), and M' ) Ni, Pd, or Pt, has been investigated. The compounds all possess slitlike pores with constant in-plane dimensions and similar organic functionality. The pore heights vary as a function of L and provide a means for a systematic investigation of the effects of pore dimension on hydrogen storage properties in porous materials. Hydrogen isotherms were measured at 77 and 87 K up to a pressure of 1 atm. The pyz pillared materials with the smallest pore dimensions store hydrogen at a pore density similar to that of liquid hydrogen. The adsorbed hydrogen density drops by a factor of 2 as the relative pore size is tripled in the dpac material. The decreased storage efficiency diminishes the expected gravimetric gain in capacity for the larger pore materials. The heats of adsorption were found to range from 6 to 8 kJ/mol in the series and weakly correlate with pore size.

  8. Effect of the intramolecular hydrogen bond on the spectral and optical properties in chitosan oligosaccharide

    NASA Astrophysics Data System (ADS)

    Li, Xin; Yang, Mengshi; Shi, Xiao; Chu, Xiuxiang; Chen, Liang; Wu, Qiang; Wang, Yueyue

    2015-05-01

    The geometric structures, hydrogen bond types, IR spectra and nonlinear optical properties of chitosan oligosaccharide (degree of polymerization 2-5) are studied by density-functional theory (DFT) at B3LYP/6-31+G(d) level. We have analyzed the statistics of relationship between IR spectra and bond lengths, and angles of amino, hydroxyl. The results show that: (1) the active groups C3-OH, C6-OH and -NH2 can form intramolecular hydrogen bond in chitosan oligosaccharide; (2) the IR spectra of three active groups have size effect in growth process, however, its IR intensity increases significantly and IR frequencies are red shifted obviously when the active hydroxyl form hydrogen bonds, because the bond length of active hydroxyl becomes longer; (3) the effect of hydrogen bond on intensity and frequency of the three vibration mode of amino is the main factor and complication. The paper also provides the nonlinear optical properties of chitosan oligosaccharide. The reason why hydrogen bond can make an appreciable difference to IR spectra, and the nonlinear optical properties of chitosan oligosaccharide are discussed. This research has important significance in the characterization of chitosan oligosaccharide, the properties of chitosan material and hydrogen bond by infrared spectroscopy.

  9. Effect of cashew nut shell liquid on metabolic hydrogen flow on bovine rumen fermentation.

    PubMed

    Mitsumori, Makoto; Enishi, Osamu; Shinkai, Takumi; Higuchi, Koji; Kobayashi, Yosuke; Takenaka, Akio; Nagashima, Kyo; Mochizuki, Masami; Kobayashi, Yasuo

    2014-03-01

    Effect of cashew nut shell liquid (CNSL), a methane inhibitor, on bovine rumen fermentation was investigated through analysis of the metabolic hydrogen flow estimated from concentrations of short-chain fatty acids (SCFA) and methane. Three cows were fed a concentrate and hay diet without or with a CNSL-containing pellet. Two trials were conducted using CNSL pellets blended with only silica (trial 1) or with several other ingredients (trial 2). Methane production was measured in a respiration chamber system, and energy balance and nutrient digestibility were monitored. The estimated flow of metabolic hydrogen demonstrated that a part of metabolic hydrogen was used for hydrogen gas production, and a large amount of it flowed into production of methane and SCFA in both trial 1 and 2, when CNSL was administered to the bovine rumen. The results obtained by regression analyses showed that the effect of CNSL supply on methane reduction was coupled with a significant (P < 0.01) decrease of acetate and a significant (P < 0.01) increase of propionate and hydrogen gas. These findings reveal that CNSL is able to reduce methane and acetate production, and to increase hydrogen gas and propionate production in vivo. PMID:24128067

  10. Hydrogen bonding and vapor pressure isotope effect of deuterioisomeric methanethiols

    SciTech Connect

    Wolff, H.; Szydlowski, J.; Dill-Staffenberger, L.

    1981-04-16

    Wilson parameters, activity coefficients, association constants, and other thermodynamic functions which are derived from isothermal vapor pressure measurements between 223 and 293 K for binary mixtures of CH/sub 3/SH, CH/sub 3/SD, CS/sub 3/SH, and CD/sub 3/SD with n-hexane show the weakness of the hydrogen and the deuterium bonds of methanethiol. As far as these functions depend on the association model used for the calculation, the relation of their values to those obtained for the corresponding amines and alcohols under the same conditions attests the weak methanethiol association. While for the more strongly associated methylamines and methanols a greater energy of the deuterium bond compared to the hydrogen bond has clearly been observed, the differences between the thermodynamic functions of the systems with the SH compounds and of those with the SD compounds are insignificant. This observation as well as the fact that the vapor pressure ratios P-(CH/sub 3/SD)/P(CH/sub 3/SH) are only slightly greater than unity, that the ratios P(CD/sub 3/SD)/P(CH/sub 3/SH) are even greater than P(CD/sub 3/SH)/P(CH/sub 3/SH), and that the changes of these ratios with temperature and dilution are small in comparison to the strong increase of the corresponding quotients of the methylamines and the methanols are the consequence of the weak methanethiol association. P(CH/sub 3/SD)/P(CH/sub 3/SH), P(CD/sub 3/SH)/P(CH/sub 3/SH), and P(CD/sub 3/SD)/P(CH/sub 3/SH) are represented by equations of the type ln P/sub D/ P/sub H/ = -A/T/sup 2/ + B/T where A and B are nearly additive. The low values of A and B for CH/sub 3/SD/CH/sub 3/SH in comparison to the high values for CH/sub 3/ND/sub 2//CH/sub 3/NH/sub 2/ and CH/sub 3/OD/CH/sub 3/OH reflect the weakness of the methanethiol hydrogen bonds. The constants can be related to the thermochemical and the spectroscopic data reported in the literature.

  11. Bimetallic ruthenium-copper nanoparticles embedded in mesoporous carbon as an effective hydrogenation catalyst

    NASA Astrophysics Data System (ADS)

    Liu, Jiajia; Zhang, Li Li; Zhang, Jiatao; Liu, Tao; Zhao, X. S.

    2013-10-01

    Bimetallic ruthenium-copper nanoparticles embedded in the pore walls of mesoporous carbon were prepared via a template route and evaluated in terms of catalytic properties in d-glucose hydrogenation. The existence of bimetallic entities was supported by Ru L3-edge and Cu K-edge X-ray absorption results. The hydrogen spillover effect of the bimetallic catalyst on the hydrogenation reaction was evidenced by the results of both hydrogen and carbon monoxide chemisorptions. The bimetallic catalyst displayed a higher catalytic activity than the single-metal catalysts prepared using the same approach, namely ruthenium or copper nanoparticles embedded in the pore walls of mesoporous carbon. This improvement was due to the changes in the geometric and electronic structures of the bimetallic catalyst because of the presence of the second metal.Bimetallic ruthenium-copper nanoparticles embedded in the pore walls of mesoporous carbon were prepared via a template route and evaluated in terms of catalytic properties in d-glucose hydrogenation. The existence of bimetallic entities was supported by Ru L3-edge and Cu K-edge X-ray absorption results. The hydrogen spillover effect of the bimetallic catalyst on the hydrogenation reaction was evidenced by the results of both hydrogen and carbon monoxide chemisorptions. The bimetallic catalyst displayed a higher catalytic activity than the single-metal catalysts prepared using the same approach, namely ruthenium or copper nanoparticles embedded in the pore walls of mesoporous carbon. This improvement was due to the changes in the geometric and electronic structures of the bimetallic catalyst because of the presence of the second metal. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr03813k

  12. Quantitative and qualitative effects of N10-methylfolate on high-affinity folate binding in human leukocytes.

    PubMed

    Holm, J; Hansen, S I; Lyngbye, J

    1984-01-01

    N10-methylfolate acted as a potent competitive inhibitor of high-affinity [3H] folate binding in human leukocytes, while methotrexate had no effect. Furthermore, folate binding changed into a non-cooperative type in the presence of N10-methylfolate. Hence, in qualitative and quantitative respects, the substrate specificity characteristics of leukocyte folate binding resemble those of other high-affinity folate binding systems. PMID:6500843

  13. [The effect of cocaine on binding of tricyclic antidepressives in the synaptic plasma membranes in the brain].

    PubMed

    Bures, P; Krulík, R; Fisar, Z; Fuksová, K

    1993-10-01

    Effect of cocaine on binding of 3H-imipramine, 3H-desmethylimipramine, 3H-didesmethylimipramine and 3H-amitriptyline to brain synaptic plasma membranes (SPM) was studied. Binding of methylated tricyclic antidepressants was more affected. Cocaine inhibits 3H-imipramine binding at concentrations higher than 10(-5) mol/l. Binding stimulated by phosphatidylserine was affected more significantly. PMID:8269521

  14. Effective tight-binding model for transition metal dichalcogenides

    NASA Astrophysics Data System (ADS)

    Ho, Yen-Hung; Cazalilla, Miguel; Ochoa, Hector

    For transition metal dichalcogenides, various band models have been developed to describe the novel subband features. In this work, we propose a new effective minimum-band model by preforming a canonical transformation on the full-band Hamiltonian. We found that, depending on the form of transformation, both the Γ- and K-valley electrons can be well captured, including the frequency and band effective mass. And, for the full-band parameters used, starting from Wannier function basis set leads to a better result than from Slater-Koster basis set. A close inspection of the transformation projection also enables us to extract the modification on the site energy, as well as the orbital hopping between several nearest neighboring atoms. Instead of pure empirical fitting, our effective models preserve rich orbital physics inside, which is shown to be versatile in studying a variety of fundamental physical properties. Ministry of Science and Technology of Taiwan (NSC 102-2112-M-007-024-MY5).

  15. Antitumor effect of synergistic contribution of nitrite and hydrogen peroxide in the plasma activated medium

    NASA Astrophysics Data System (ADS)

    Kurake, Naoyuki; Tanaka, Hiromasa; Ishikawa, Kenji; Nakamura, Kae; Kajiyama, Hiroaki; Kikkawa, Fumiaki; Kondo, Takashi; Mizuno, Masaaki; Takeda, Keigo; Kondo, Hiroki; Sekine, Makoto; Hori, Masaru

    2015-09-01

    Non-equilibrium atmospheric pressure plasmas (NEAPP) have been attracted attention in the noble application of cancer therapy. Although good effects of the Plasma-Activated-Medium (PAM) such as the selective antitumor effect and killing effect for the anticancer agent resistant cells were reported, a mechanism of this effect has not been still clarified yet. In this study, we have investigated a contribution of the reactive nitrogen and oxygen species (RNOS) generated in PAM such as hydrogen peroxide and nitrite. Those species generated in the PAM quantitatively measured by light absorbance of commercial regent. Moreover, viable cell count after cell culture with those RNOS intentionally added medium or PAM were also measured by MTS assay. Our NEAPP source generated hydrogen peroxide and nitrite with the generation ratio of 0.35 μM/s and 9.8 μM/s. In those RNOS, hydrogen peroxide has respective antitumor effect. On the other hands, nitrite has no antitumor effect singly. But, synergistically enhance the antitumor effect of hydrogen peroxide. Moreover, this effect of those RNOS also contribute for the selectively cancer killing effect of PAM.

  16. Fundamental Kinetics of Supercritical Coal Liquefaction: Effect of Catalysts and Hydrogen-Donor Solvents

    SciTech Connect

    McCoy, Ben J; Madras, Girodhar; Smith, J M; Kodera, Yoichi

    1997-04-16

    This is the quarterly report on our recent progress toward the overall objective to understand the supercritical fluid extraction of hydrocarbons from coal. Our strategy is to simulate coal as a high molecular-weight polymeric material by studying the degradation of polymers under various conditions. The hypothesis we are testing is that degradation of such macromolecules is applicable to the decomposition (depolymerization) of the coal network. Polymer degradation and coal liquefaction are influenced strongly by the solvent in the reaction. This motivated our investigation of the effect of hydrogen donor solvents on polymer degradation. In particular, we obtained new experimental data to show how a hydrogen donor, 6-hydroxy tetralin, influences the degradation rate of polystyrene. We also developed a detailed radical mechanism for hydrogen donation based on the Rice-Herzfeld chain reaction concept with the elementary steps of initiation, depropagation, hydrogen abstraction, and termination. Expressions for the degradation rate parameters were obtained by applying continuous distribution kinetics to the MWD of the reacting polymer. The theory explains the different influences of the hydrogen donor solvent on the degradation rate coefficients for different polymers. Though developed for the degradation of polymers, the mechanism and the theory are potentially applicable for chain scission and addition reactions among distributions of paraffins, olefins, and radicals of all chain lengths. The concepts can, in principle, be extended to examine the effect of hydrogen donors on coal liquefaction and on the complex mixture of liquefaction compounds. Based on this work, a research paper titled "Effect of Hydrogen Donors on Polymer Degradation", has been submitted for publication. Our research paper entitled, "Molecular weight effect on the dynamics of polystyrene degradation", has been accepted for publication by the journal, Industrial and Engineering Chemistry Research.

  17. Effect of oxidative DNA damage in promoter elements on transcription factor binding.

    PubMed Central

    Ghosh, R; Mitchell, D L

    1999-01-01

    Reactive oxygen species produced by endogenous metabolic activity and exposure to a multitude of exogenous agents impact cells in a variety of ways. The DNA base damage 8-oxodeoxyguanosine (8-oxodG) is a prominent indicator of oxidative stress and has been well-characterized as a premutagenic lesion in mammalian cells and putative initiator of the carcinogenic process. Commensurate with the recent interest in epigenetic pathways of cancer causation we investigated how 8-oxodG alters the interaction between cis elements located on gene promoters and sequence-specific DNA binding proteins associated with these promoters. Consensus binding sequences for the transcription factors AP-1, NF-kappaB and Sp1 were modified site-specifically at guanine residues and electrophoretic mobility shift assays were performed to assess DNA-protein interactions. Our results indicate that whereas a single 8-oxodG was sufficient to inhibit transcription factor binding to AP-1 and Sp1 sequences it had no effect on binding to NF-kappaB, regardless of its position. We conclude from these data that minor alterations in base composition at a crucial position within some, but not all, promoter elements have the ability to disrupt transcription factor binding. The lack of inhibition by damaged NF-kappaB sequences suggests that DNA-protein contact sites may not be as determinative for stable p50 binding to this promoter as other, as yet undefined, structural parameters. PMID:10454620

  18. Mapping the Effect of Gly Mutations in Collagen on α2β1 Integrin Binding*

    PubMed Central

    Yigit, Sezin; Yu, Hongtao; An, Bo; Hamaia, Samir; Farndale, Richard W.; Kaplan, David L.; Lin, Yu-Shan; Brodsky, Barbara

    2016-01-01

    The replacement of one Gly in the essential repeating tripeptide sequence of the type I collagen triple helix results in the dominant hereditary bone disorder osteogenesis imperfecta. The mechanism leading to pathology likely involves misfolding and autophagy, although it has been hypothesized that some mutations interfere with known collagen interactions. Here, the effect of Gly replacements within and nearby the integrin binding GFPGER sequence was investigated using a recombinant bacterial collagen system. When a six-triplet human type I collagen sequence containing GFPGER was introduced into a bacterial collagen-like protein, this chimeric protein bound to integrin. Constructs with Gly to Ser substitutions within and nearby the inserted human sequence still formed a trypsin-resistant triple helix, suggesting a small local conformational perturbation. Gly to Ser mutations within the two Gly residues in the essential GFPGER sequence prevented integrin binding and cell attachment as predicted from molecular dynamics studies of the complex. Replacement of Gly residues C-terminal to GFPGER did not affect integrin binding. In contrast, Gly replacements N-terminal to the GFPGER sequence, up to four triplets away, decreased integrin binding and cell adhesion. This pattern suggests either an involvement of the triplets N-terminal to GFPGER in initial binding or a propagation of the perturbation of the triple helix C-terminal to a mutation site. The asymmetry in biological consequences relative to the mutation site may relate to the observed pattern of osteogenesis imperfecta mutations near the integrin binding site. PMID:27432884

  19. Lead and calcium binding to fulvic acids: Salt effect and competition

    SciTech Connect

    Pinheiro, J.P.; Mota, A.M.; Benedetti, M.F.

    1999-10-01

    Knowledge of the speciation of Pb in natural aquatic systems is important if the authors want to understand the bioavailability and mobility of Pb in polluted and natural environments. The results given in this paper were obtained under conditions as close as possible to natural conditions. These new data show that Pb strongly binds to fulvic acids. The authors also show that the competitive effect of Pb on Ca binding to the same fulvic acid is smaller than the salt effect on Ca binding to fulvic acids as pH varies from 4 to 8. All the data were analyzed with the NICCA-Donnan model developed to describe metal ion binding to natural organic matter. The model predictions of competitive and salt effects are excellent. Comparison of their results with previously published data suggests that metal ion binding strength is similar for fulvic acids from different origins. Thus, all data sets could be interpreted within the framework of a unified modeling approach.

  20. Effect of protein aggregates on characterization of FcRn binding of Fc-fusion therapeutics.

    PubMed

    Bajardi-Taccioli, Adriana; Blum, Andrew; Xu, Chongfeng; Sosic, Zoran; Bergelson, Svetlana; Feschenko, Marina

    2015-10-01

    Recycling of antibodies and Fc containing therapeutic proteins by the neonatal Fc receptor (FcRn) is known to prolong their persistence in the bloodstream. Fusion of Fc fragment of IgG1 to other proteins is one of the strategies to improve their pharmacokinetic properties. Accurate measurement of Fc-FcRn binding provides information about the strength of this interaction, which in most cases correlates with serum half-life of the protein. It can also offer insight into functional integrity of Fc region. We investigated FcRn binding activity of a large set of Fc-fusion samples after thermal stress by the method based on AlphaScreen technology. An unexpected significant increase in FcR binding was found to correlate with formation of aggregates in these samples. Monomer purified from a thermally-stressed sample had normal FcRn binding, confirming that its Fc portion was intact. Experiments with aggregates spiked into a sample with low initial aggregation level, demonstrated strong correlation between the level of aggregates and FcRn binding. This correlation varied significantly in different methods. By introducing modifications to the assay format we were able to minimize the effects of aggregated species on FcRn binding, which should prevent masking functional changes of Fc-fusion protein. Biolayer interferometry (BLI) was used as an alternative method to measure FcRn binding. Both optimized AlphaScreen- and BLI-based assays were sensitive to structural changes in Fc portion of the molecule, such as oxidation of methionines 252 and 428, and therefore suitable for characterization of FcRn binding. PMID:26254986

  1. Statistical Thermodynamics for Actin-Myosin Binding: The Crucial Importance of Hydration Effects.

    PubMed

    Oshima, Hiraku; Hayashi, Tomohiko; Kinoshita, Masahiro

    2016-06-01

    Actomyosin is an important molecular motor, and the binding of actin and myosin is an essential research target in biophysics. Nevertheless, the physical factors driving or opposing the binding are still unclear. Here, we investigate the role of water in actin-myosin binding using the most reliable statistical-mechanical method currently available for assessing biomolecules immersed in water. This method is characterized as follows: water is treated not as a dielectric continuum but as an ensemble of molecules; the polyatomic structures of proteins are taken into consideration; and the binding free energy is decomposed into physically insightful entropic and energetic components by accounting for the hydration effect to its full extent. We find that the actin-myosin binding brings large gains of electrostatic and Lennard-Jones attractive interactions. However, these gains are accompanied by even larger losses of actin-water and myosin-water electrostatic and LJ attractive interactions. Although roughly half of the energy increase due to the losses is cancelled out by the energy decrease arising from structural reorganization of the water released upon binding, the remaining energy increase is still larger than the energy decrease brought by the gains mentioned above. Hence, the net change in system energy is positive, which opposes binding. Importantly, the binding is driven by a large gain of configurational entropy of water, which surpasses the positive change in system energy and the conformational entropy loss occurring for actin and myosin. The principal physical origin of the large water-entropy gain is as follows: the actin-myosin interface is closely packed with the achievement of high shape complementarity on the atomic level, leading to a large increase in the total volume available to the translational displacement of water molecules in the system and a resultant reduction of water crowding (i.e., entropic correlations among water molecules). PMID

  2. A molecular dynamics study of nuclear quantum effect on the diffusion of hydrogen in condensed phase

    NASA Astrophysics Data System (ADS)

    Nagashima, Hiroki; Tsuda, Shin-ichi; Tsuboi, Nobuyuki; Koshi, Mitsuo; Hayashie, A. Koichi; Tokumasu, Takashi

    2014-10-01

    In this paper, the quantum effect of hydrogen molecule on its diffusivity is analyzed using Molecular Dynamics (MD) method. The path integral centroid MD (CMD) method is applied for the reproduction method of time evolution of the molecules. The diffusion coefficient of liquid hydrogen is calculated using the Green-Kubo method. The simulation is performed at wide temperature region and the temperature dependence of the quantum effect of hydrogen molecule is addressed. The calculation results are compared with those of classical MD results. As a result, it is confirmed that the diffusivity of hydrogen molecule is changed depending on temperature by the quantum effect. It is clarified that this result can be explained that the dominant factor by quantum effect on the diffusivity of hydrogen changes from the swollening the potential to the shallowing the potential well around 30 K. Moreover, it is found that this tendency is related to the temperature dependency of the ratio of the quantum kinetic energy and classical kinetic energy.

  3. A molecular dynamics study of nuclear quantum effect on the diffusion of hydrogen in condensed phase

    SciTech Connect

    Nagashima, Hiroki; Tokumasu, Takashi; Tsuda, Shin-ichi; Tsuboi, Nobuyuki; Koshi, Mitsuo; Hayashie, A. Koichi

    2014-10-06

    In this paper, the quantum effect of hydrogen molecule on its diffusivity is analyzed using Molecular Dynamics (MD) method. The path integral centroid MD (CMD) method is applied for the reproduction method of time evolution of the molecules. The diffusion coefficient of liquid hydrogen is calculated using the Green-Kubo method. The simulation is performed at wide temperature region and the temperature dependence of the quantum effect of hydrogen molecule is addressed. The calculation results are compared with those of classical MD results. As a result, it is confirmed that the diffusivity of hydrogen molecule is changed depending on temperature by the quantum effect. It is clarified that this result can be explained that the dominant factor by quantum effect on the diffusivity of hydrogen changes from the swollening the potential to the shallowing the potential well around 30 K. Moreover, it is found that this tendency is related to the temperature dependency of the ratio of the quantum kinetic energy and classical kinetic energy.

  4. Quantum effects and anharmonicity in the H2-Li+-benzene complex: A model for hydrogen storage materials

    NASA Astrophysics Data System (ADS)

    Kolmann, Stephen J.; D'Arcy, Jordan H.; Jordan, Meredith J. T.

    2013-12-01

    Quantum and anharmonic effects are investigated in H2-Li+-benzene, a model for hydrogen adsorption in metal-organic frameworks and carbon-based materials. Three- and 8-dimensional quantum diffusion Monte Carlo (QDMC) and rigid-body diffusion Monte Carlo (RBDMC) simulations are performed on potential energy surfaces interpolated from electronic structure calculations at the M05-2X/6-31+G(d,p) and M05-2X/6-311+G(2df,p) levels of theory using a three-dimensional spline or a modified Shepard interpolation. These calculations investigate the intermolecular interactions in this system, with three- and 8-dimensional 0 K H2 binding enthalpy estimates, ΔHbind (0 K), being 16.5 kJ mol-1 and 12.4 kJ mol-1, respectively: 0.1 and 0.6 kJ mol-1 higher than harmonic values. Zero-point energy effects are 35% of the value of ΔHbind (0 K) at M05-2X/6-311+G(2df,p) and cannot be neglected; uncorrected electronic binding energies overestimate ΔHbind (0 K) by at least 6 kJ mol-1. Harmonic intermolecular binding enthalpies can be corrected by treating the H2 "helicopter" and "ferris wheel" rotations as free and hindered rotations, respectively. These simple corrections yield results within 2% of the 8-dimensional anharmonic calculations. Nuclear ground state probability density histograms obtained from the QDMC and RBDMC simulations indicate the H2 molecule is delocalized above the Li+-benzene system at 0 K.

  5. Hydrogen environment embrittlement

    NASA Technical Reports Server (NTRS)

    Gray, H. R.

    1972-01-01

    Hydrogen embrittlement is classified into three types: internal reversible hydrogen embrittlement, hydrogen reaction embrittlement, and hydrogen environment embrittlement. Characteristics of and materials embrittled by these types of hydrogen embrittlement are discussed. Hydrogen environment embrittlement is reviewed in detail. Factors involved in standardizing test methods for detecting the occurrence of and evaluating the severity of hydrogen environment embrittlement are considered. The effect of test technique, hydrogen pressure, purity, strain rate, stress concentration factor, and test temperature are discussed. Additional research is required to determine whether hydrogen environment embrittlement and internal reversible hydrogen embrittlement are similar or distinct types of embrittlement.

  6. Effects of Water Models on Binding Affinity: Evidence from All-Atom Simulation of Binding of Tamiflu to A/H5N1 Neuraminidase

    PubMed Central

    Nguyen, Trang Truc; Viet, Man Hoang

    2014-01-01

    The influence of water models SPC, SPC/E, TIP3P, and TIP4P on ligand binding affinity is examined by calculating the binding free energy ΔGbind of oseltamivir carboxylate (Tamiflu) to the wild type of glycoprotein neuraminidase from the pandemic A/H5N1 virus. ΔGbind is estimated by the Molecular Mechanic-Poisson Boltzmann Surface Area method and all-atom simulations with different combinations of these aqueous models and four force fields AMBER99SB, CHARMM27, GROMOS96 43a1, and OPLS-AA/L. It is shown that there is no correlation between the binding free energy and the water density in the binding pocket in CHARMM. However, for three remaining force fields ΔGbind decays with increase of water density. SPC/E provides the lowest binding free energy for any force field, while the water effect is the most pronounced in CHARMM. In agreement with the popular GROMACS recommendation, the binding score obtained by combinations of AMBER-TIP3P, OPLS-TIP4P, and GROMOS-SPC is the most relevant to the experiments. For wild-type neuraminidase we have found that SPC is more suitable for CHARMM than TIP3P recommended by GROMACS for studying ligand binding. However, our study for three of its mutants reveals that TIP3P is presumably the best choice for CHARMM. PMID:24672329

  7. Effect of Li Adsorption on the Electronic and Hydrogen Storage Properties of Acenes: A Dispersion-Corrected TAO-DFT Study

    PubMed Central

    Seenithurai, Sonai; Chai, Jeng-Da

    2016-01-01

    Due to the presence of strong static correlation effects and noncovalent interactions, accurate prediction of the electronic and hydrogen storage properties of Li-adsorbed acenes with n linearly fused benzene rings (n = 3–8) has been very challenging for conventional electronic structure methods. To meet the challenge, we study these properties using our recently developed thermally-assisted-occupation density functional theory (TAO-DFT) with dispersion corrections. In contrast to pure acenes, the binding energies of H2 molecules on Li-adsorbed acenes are in the ideal binding energy range (about 20 to 40 kJ/mol per H2). Besides, the H2 gravimetric storage capacities of Li-adsorbed acenes are in the range of 9.9 to 10.7 wt%, satisfying the United States Department of Energy (USDOE) ultimate target of 7.5 wt%. On the basis of our results, Li-adsorbed acenes can be high-capacity hydrogen storage materials for reversible hydrogen uptake and release at ambient conditions. PMID:27609626

  8. Effect of Li Adsorption on the Electronic and Hydrogen Storage Properties of Acenes: A Dispersion-Corrected TAO-DFT Study.

    PubMed

    Seenithurai, Sonai; Chai, Jeng-Da

    2016-01-01

    Due to the presence of strong static correlation effects and noncovalent interactions, accurate prediction of the electronic and hydrogen storage properties of Li-adsorbed acenes with n linearly fused benzene rings (n = 3-8) has been very challenging for conventional electronic structure methods. To meet the challenge, we study these properties using our recently developed thermally-assisted-occupation density functional theory (TAO-DFT) with dispersion corrections. In contrast to pure acenes, the binding energies of H2 molecules on Li-adsorbed acenes are in the ideal binding energy range (about 20 to 40 kJ/mol per H2). Besides, the H2 gravimetric storage capacities of Li-adsorbed acenes are in the range of 9.9 to 10.7 wt%, satisfying the United States Department of Energy (USDOE) ultimate target of 7.5 wt%. On the basis of our results, Li-adsorbed acenes can be high-capacity hydrogen storage materials for reversible hydrogen uptake and release at ambient conditions. PMID:27609626

  9. Hybrid simulations of the effects of interstellar pickup hydrogen on the solar wind termination shock

    NASA Technical Reports Server (NTRS)

    Liewer, P. C.; Goldstein, B. E.; Omidi, N.

    1993-01-01

    Hybrid (kinetic ions/fluid electrons) plasma simulations are used to study the effects of a population of energetic interstellar pickup hydrogen ions on the solar wind termination shock. The pickup hydrogen is treated as a second ion species in the simulations, and thus the effects of the pick-ups on the shock, as well as the effects of the shock on the pickups, are treated in a fully self-consistent manner. For quasi-perpendicular shocks with 10-20 percent pickup hydrogen the pickup ions manifest themselves in a small foot ahead of the shock ramp caused by pickup ion reflection. For oblique shocks with smaller angles between the field and the shock normal, a large fraction of the pickup ions are reflected and move back upstream where they excite large amplitude magnetosonic waves which steepen into shocklets. These backstreaming pickup ions may provide advance warning of a spacecraft encounter with the termination shock.

  10. Uncoupling of gamma-aminobutyric acid B receptors from GTP-binding proteins by N-ethylmaleimide: effect of N-ethylmaleimide on purified GTP-binding proteins

    SciTech Connect

    Asano, T.; Ogasawara, N.

    1986-03-01

    Treatment of membranes from bovine cerebral cortex with N-ethylmaleimide (NEM) resulted in inhibition of gamma-aminobutyric acid (GABA) binding to GABAB receptors. The binding curve for increasing concentrations of agonist was shifted to the right by NEM treatment. Guanine nucleotide had little effect on the binding of GABA to NEM-treated membranes. The addition of purified GTP-binding proteins, which were the substrates of islet-activating protein (IAP), pertussis toxin, to the NEM-treated membranes caused a shift of the binding curve to the left, suggesting modification of GTP-binding proteins rather than receptors by NEM. The effect of NEM on two purified GTP-binding proteins, Gi (composed of three subunits with molecular weight of alpha, 41,000; beta, 35,000; gamma, 10,000) and Go (alpha, 39,000; beta, 35,000; gamma, 10,000) was studied. NEM did not significantly change guanosine 5'-(3-O-thio)triphosphate (GTP gamma S) binding and GTPase activity of these two proteins. NEM-treated Gi and Go were not ADP-ribosylated by IAP and did not increase GABA binding to NEM-treated membranes. When alpha and beta gamma subunits were treated with NEM and then mixed with nontreated alpha and beta gamma to form Gi or Go, respectively, both oligomers with NEM-treated alpha-subunits lost their abilities to be IAP substrates and to couple to receptors. Results indicate that NEM uncoupled GTP-binding proteins from receptors by modifying alpha-subunits of GTP-binding proteins, and the site seemed to be on or near the site of ADP-ribosylation by IAP. When alpha and beta gamma subunits were treated with NEM and then mixed to form Gi or Go, GTP gamma S binding in the absence of Mg2+ and GTPase activity were changed, although they were not affected when oligomers were treated with NEM. Results suggest the existence of another sulfhydryl group which is protected from NEM by the association of subunits.

  11. Effects of hydrogen atmosphere on pulsed-DC sputtered nanocrystalline Si:H films

    SciTech Connect

    Cherng, J.S.; Chang, S.H.; Hong, S.H.

    2012-10-15

    Highlights: ► Nanocrystalline silicon films were made by pulsed-DC magnetron sputtering. ► A threshold hydrogen concentration was required. ► High defect density due to ion bombardment and oxygen contamination caused low conductivity. -- Abstract: Hydrogenated nanocrystalline silicon (nc-Si:H) films were prepared by a pulsed-DC magnetron sputtering method under an atmosphere of hydrogen/argon mixture. The effects of hydrogen concentration on the structural and electrical properties of the films were systematically investigated using grazing incidence X-ray diffraction (GIXRD), Raman spectroscopy, and conductivity measurement. A threshold hydrogen concentration of about 70% was found necessary before any crystallinity was detectable. The deposition rate decreased monotonically with increasing hydrogen concentration, while the conductivity varied with crystallite size. The abnormally low conductivity level of these nc-Si:H films was due to the extraordinarily high defect density, which was attributed both to the enhanced ion bombardment from the pulsed-DC plasma and to the oxygen contamination from the target.

  12. Inhibitory effects of furan derivatives and phenolic compounds on dark hydrogen fermentation.

    PubMed

    Lin, Richen; Cheng, Jun; Ding, Lingkan; Song, Wenlu; Zhou, Junhu; Cen, Kefa

    2015-11-01

    The inhibitory effects of furan derivatives [i.e. furfural and 5-hydroxymethylfurfural (5-HMF)] and phenolic compounds (i.e. vanillin and syringaldehyde) on dark hydrogen fermentation from glucose were comparatively evaluated. Phenolic compounds exhibited stronger inhibition on hydrogen production and glucose consumption than furan derivatives under the same 15mM concentration. Furan derivatives were completely degraded after 72h fermentation, while over 55% of phenolic compounds remained unconverted after 108h fermentation. The inhibition coefficients of vanillin (14.05) and syringaldehyde (11.21) were higher than those of 5-HMF (4.35) and furfural (0.64). Vanillin exhibited the maximum decrease of hydrogen yield (17%). The consumed reducing power by inhibitors reduction from R-CHO to RCH2OH was a possible reason contributed to the decreased hydrogen yield. Vanillin exhibited the maximum delay of peak times of hydrogen production rate and glucose consumption. Soluble metabolites and carbon conversion efficiency decreased with inhibitors addition, which were consistent with hydrogen production. PMID:26247976

  13. Effect of hydrogen on dynamic charge transport in amorphous oxide thin film transistors.

    PubMed

    Kim, Taeho; Nam, Yunyong; Hur, Ji-Hyun; Park, Sang-Hee Ko; Jeon, Sanghun

    2016-08-12

    Hydrogen in zinc oxide based semiconductors functions as a donor or a defect de-activator depending on its concentration, greatly affecting the device characteristics of oxide thin-film transistors (TFTs). Thus, controlling the hydrogen concentration in oxide semiconductors is very important for achieving high mobility and minimizing device instability. In this study, we investigated the charge transport dynamics of the amorphous semiconductor InGaZnO at various hydrogen concentrations as a function of the deposition temperature of the gate insulator. To examine the nature of dynamic charge trapping, we employed short-pulse current-voltage and transient current-time measurements. Among various examined oxide devices, that with a high hydrogen concentration exhibits the best performance characteristics, such as high saturation mobility (10.9 cm(2) v(-1) s(-1)), low subthreshold slope (0.12 V/dec), and negligible hysteresis, which stem from low defect densities and negligible transient charge trapping. Our finding indicates that hydrogen atoms effectively passivate the defects in subgap states of the bulk semiconductor, minimizing the mobility degradation and threshold voltage instability. This study indicates that hydrogen plays a useful role in TFTs by improving the device performance and stability. PMID:27363543

  14. Effect of hydrogen on dynamic charge transport in amorphous oxide thin film transistors

    NASA Astrophysics Data System (ADS)

    Kim, Taeho; Nam, Yunyong; Hur, Ji-Hyun; Park, Sang-Hee Ko; Jeon, Sanghun

    2016-08-01

    Hydrogen in zinc oxide based semiconductors functions as a donor or a defect de-activator depending on its concentration, greatly affecting the device characteristics of oxide thin-film transistors (TFTs). Thus, controlling the hydrogen concentration in oxide semiconductors is very important for achieving high mobility and minimizing device instability. In this study, we investigated the charge transport dynamics of the amorphous semiconductor InGaZnO at various hydrogen concentrations as a function of the deposition temperature of the gate insulator. To examine the nature of dynamic charge trapping, we employed short-pulse current‑voltage and transient current‑time measurements. Among various examined oxide devices, that with a high hydrogen concentration exhibits the best performance characteristics, such as high saturation mobility (10.9 cm2 v‑1 s‑1), low subthreshold slope (0.12 V/dec), and negligible hysteresis, which stem from low defect densities and negligible transient charge trapping. Our finding indicates that hydrogen atoms effectively passivate the defects in subgap states of the bulk semiconductor, minimizing the mobility degradation and threshold voltage instability. This study indicates that hydrogen plays a useful role in TFTs by improving the device performance and stability.

  15. Copper contamination effects on hydrogen-air combustion under SCRAMJET (supersonic combustion ramjet) testing conditions

    SciTech Connect

    Chang, S.L.; Lottes, S.A.; Berry, G.F.

    1990-01-01

    Two forms of copper catalytic reactions (homogeneous and heterogeneous) in hydrogen flames were found in a literature survey. Hydrogen atoms in flames recombine into hydrogen molecules through catalytic reactions, and these reactions which affect the timing of the combustion process. Simulations of hydrogen flames with copper contamination were conducted by using a modified general chemical kinetics program (GCKP). Results show that reaction times of hydrogen flames are shortened by copper catalytic reactions, but ignition times are relatively insensitive to the reactions. The reduction of reaction time depends on the copper concentration, copper phase, particle size (if copper is in the condensed phase), and initial temperature and pressure. The higher the copper concentration of the smaller the particle, the larger the reduction in reaction time. For a supersonic hydrogen flame (Mach number = 4.4) contaminated with 200 ppm of gaseous copper species, the calculated reaction times are reduced by about 9%. Similar reductions in reaction time are also computed for heterogeneous copper contamination. Under scramjet testing conditions, the change of combustion timing appears to be tolerable (less than 5%) if the Mach number is lower than 3 or the copper contamination is less than 100 ppm. The higher rate the Mach number, the longer the reaction time and the larger the copper catalytic effects. 7 tabs., 8 figs., 34 refs.

  16. Fundamental studies on kinetic isotope effect (KIE) of hydrogen isotope fractionation in natural gas systems

    NASA Astrophysics Data System (ADS)

    Ni, Yunyan; Ma, Qisheng; Ellis, Geoffrey S.; Dai, Jinxing; Katz, Barry; Zhang, Shuichang; Tang, Yongchun

    2011-05-01

    Based on quantum chemistry calculations for normal octane homolytic cracking, a kinetic hydrogen isotope fractionation model for methane, ethane, and propane formation is proposed. The activation energy differences between D-substitute and non-substituted methane, ethane, and propane are 318.6, 281.7, and 280.2 cal/mol, respectively. In order to determine the effect of the entropy contribution for hydrogen isotopic substitution, a transition state for ethane bond rupture was determined based on density function theory (DFT) calculations. The kinetic isotope effect (KIE) associated with bond rupture in D and H substituted ethane results in a frequency factor ratio of 1.07. Based on the proposed mathematical model of hydrogen isotope fractionation, one can potentially quantify natural gas thermal maturity from measured hydrogen isotope values. Calculated gas maturity values determined by the proposed mathematical model using δD values in ethane from several basins in the world are in close agreement with similar predictions based on the δ 13C composition of ethane. However, gas maturity values calculated from field data of methane and propane using both hydrogen and carbon kinetic isotopic models do not agree as closely. It is possible that δD values in methane may be affected by microbial mixing and that propane values might be more susceptible to hydrogen exchange with water or to analytical errors. Although the model used in this study is quite preliminary, the results demonstrate that kinetic isotope fractionation effects in hydrogen may be useful in quantitative models of natural gas generation, and that δD values in ethane might be more suitable for modeling than comparable values in methane and propane.

  17. Fundamental studies on kinetic isotope effect (KIE) of hydrogen isotope fractionation in natural gas systems

    USGS Publications Warehouse

    Ni, Y.; Ma, Q.; Ellis, G.S.; Dai, J.; Katz, B.; Zhang, S.; Tang, Y.

    2011-01-01

    Based on quantum chemistry calculations for normal octane homolytic cracking, a kinetic hydrogen isotope fractionation model for methane, ethane, and propane formation is proposed. The activation energy differences between D-substitute and non-substituted methane, ethane, and propane are 318.6, 281.7, and 280.2cal/mol, respectively. In order to determine the effect of the entropy contribution for hydrogen isotopic substitution, a transition state for ethane bond rupture was determined based on density function theory (DFT) calculations. The kinetic isotope effect (KIE) associated with bond rupture in D and H substituted ethane results in a frequency factor ratio of 1.07. Based on the proposed mathematical model of hydrogen isotope fractionation, one can potentially quantify natural gas thermal maturity from measured hydrogen isotope values. Calculated gas maturity values determined by the proposed mathematical model using ??D values in ethane from several basins in the world are in close agreement with similar predictions based on the ??13C composition of ethane. However, gas maturity values calculated from field data of methane and propane using both hydrogen and carbon kinetic isotopic models do not agree as closely. It is possible that ??D values in methane may be affected by microbial mixing and that propane values might be more susceptible to hydrogen exchange with water or to analytical errors. Although the model used in this study is quite preliminary, the results demonstrate that kinetic isotope fractionation effects in hydrogen may be useful in quantitative models of natural gas generation, and that ??D values in ethane might be more suitable for modeling than comparable values in methane and propane. ?? 2011 Elsevier Ltd.

  18. Effects of deposition temperature on the effectiveness of hydrogen doping in Ga-doped ZnO thin films

    SciTech Connect

    Kim, Dong-Ho; Lee, Sung-Hun; Lee, Gun-Hwan; Kim, Hyun-Bum; Kim, Kwang Ho; Lee, Yoon-Gyu; Yu, Tae-Hwan

    2010-07-15

    Gallium-doped zinc oxide thin films were prepared on glass substrates by dc magnetron sputtering under various hydrogen contents in sputtering ambient. The carrier concentration of the films deposited at low-temperatures (80 and 160 deg. C) was increased due to the incorporation of hydrogen atoms, acting as shallow donors. A low resistivity of 4.0x10{sup -4} {Omega} cm was obtained for the film grown at 160 deg. C with H{sub 2} 10%, which has a carrier concentration of 8.2x10{sup 20}/cm{sup 3}. The beneficial effect of hydrogen doping was not observed for the films deposited at 270 deg. C. Both carrier concentration and mobility were decreased by the addition of hydrogen gas in the sputtering ambient. Variations in the electrical transport properties upon vacuum annealing showed that the difference is attributed to the thermal stability of interstitial hydrogen atoms in the films. The hydrogen incorporation was found to induce the lattice expansion and the free carrier absorption in near infrared range. The investigation of the structural and optical properties of the films upon annealing also revealed that the incorporated hydrogen atoms are unstable at high temperature, which is consistent with the results obtained in the electrical properties.

  19. Effect of pre-strain on susceptibility of Indian Reduced Activation Ferritic Martensitic Steel to hydrogen embrittlement

    NASA Astrophysics Data System (ADS)

    Sonak, Sagar; Tiwari, Abhishek; Jain, Uttam; Keskar, Nachiket; Kumar, Sanjay; Singh, Ram N.; Dey, Gautam K.

    2015-10-01

    The role of pre-strain on hydrogen embrittlement susceptibility of Indian Reduced Activation Ferritic Martensitic Steel was investigated using constant nominal strain-rate tension test. The samples were pre-strained to different levels of plastic strain and their mechanical behavior and mode of fracture under the influence of hydrogen was studied. The effect of plastic pre-strain in the range of 0.5-2% on the ductility of the samples was prominent. Compared to samples without any pre-straining, effect of hydrogen was more pronounced on pre-strained samples. Prior deformation reduced the material ductility under the influence of hydrogen. Up to 35% reduction in the total strain was observed under the influence of hydrogen in pre-strained samples. Hydrogen charging resulted in increased occurrence of brittle zones on the fracture surface. Hydrogen Enhanced Decohesion (HEDE) was found to be the dominant mechanism of fracture.

  20. Protein-protein recognition: an experimental and computational study of the R89K mutation in Raf and its effect on Ras binding.

    PubMed Central

    Zeng, J.; Fridman, M.; Maruta, H.; Treutlein, H. R.; Simonson, T.

    1999-01-01

    Binding of the protein Raf to the active form of Ras promotes activation of the MAP kinase signaling pathway, triggering cell growth and differentiation. Raf/Arg89 in the center of the binding interface plays an important role determining Ras-Raf binding affinity. We have investigated experimentally and computationally the Raf-R89K mutation, which abolishes signaling in vivo. The binding to [gamma-35S]GTP-Ras of a fusion protein between the Raf-binding domain (RBD) of Raf and GST was reduced at least 175-fold by the mutation, corresponding to a standard binding free energy decrease of at least 3.0 kcal/mol. To compute this free energy and obtain insights into the microscopic interactions favoring binding, we performed alchemical simulations of the RBD, both complexed to Ras and free in solution, in which residue 89 is gradually mutated from Arg into Lys. The simulations give a standard binding free energy decrease of 2.9+/-1.9 kcal/mol, in agreement with experiment. The use of numerous runs with three different force fields allows insights into the sources of uncertainty in the free energy and its components. The binding decreases partly because of a 7 kcal/mol higher cost to desolvate Lys upon binding, compared to Arg, due to better solvent interactions with the more concentrated Lys charge in the unbound state. This effect is expected to be general, contributing to the lower propensity of Lys to participate in protein-protein interfaces. Large contributions to the free energy change also arise from electrostatic interactions with groups up to 8 A away, namely residues 37-41 in the conserved effector domain of Ras (including 4 kcal/mol from Ser39 which loses a bifurcated hydrogen bond to Arg89), the conserved Lys84 and Lys87 of Raf, and 2-3 specific water molecules. This analysis will provide insights into the large experimental database of Ras-Raf mutations. PMID:10210183

  1. Effects of hydrogen-rich water on aging periodontal tissues in rats.

    PubMed

    Tomofuji, Takaaki; Kawabata, Yuya; Kasuyama, Kenta; Endo, Yasumasa; Yoneda, Toshiki; Yamane, Mayu; Azuma, Tetsuji; Ekuni, Daisuke; Morita, Manabu

    2014-01-01

    Oxidative damage is involved in age-related inflammatory reactions. The anti-oxidative effects of hydrogen-rich water suppress oxidative damage, which may aid in inhibiting age-related inflammatory reactions. We investigated the effects of drinking hydrogen-rich water on aging periodontal tissues in healthy rats. Four-month-old male Fischer 344 rats (n = 12) were divided into two groups: the experimental group (hydrogen-rich water treatment) and the control group (distilled water treatment). The rats consumed hydrogen-rich water or distilled water until 16 months of age. The experimental group exhibited lower periodontal oxidative damage at 16 months of age than the control group. Although protein expression of interleukin-1β did not differ, gene expression of Nod-like receptor protein 3 inflammasomes was activated in periodontal tissues from the experimental group as compared with the control group. Drinking hydrogen-rich water is proposed to have anti-aging effects on periodontal oxidative damage, but not on inflammatory reactions in healthy rats. PMID:24985521

  2. Differential effect of glucocorticoid receptor antagonists on glucocorticoid receptor nuclear translocation and DNA binding

    PubMed Central

    Spiga, Francesca; Knight, David M; Droste, Susanne K; Conway-Campbell, Becky; Kershaw, Yvonne; MacSweeney, Cliona P; Thomson, Fiona J; Craighead, Mark; Peeters, Bernard WMM; Lightman, Stafford L

    2016-01-01

    The effects of RU486 and S-P, a more selective glucocorticoid receptor antagonist from Schering-Plough, were investigated on glucocorticoid receptor nuclear translocation and DNA binding. In the in vitro study, AtT20 cells were treated with vehicle or with RU486, S-P or corticosterone (3–300 nM) or co-treated with vehicle or glucocorticoid receptor antagonists (3–300 nM) and 30 nM corticosterone. Both glucocorticoid receptor antagonists induced glucocorticoid receptor nuclear translocation but only RU486 induced DNA binding. RU486 potentiated the effect of corticosterone on glucocorticoid receptor nuclear translocation and DNA binding, S-P inhibited corticosterone-induced glucocorticoid receptor nuclear translocation, but not glucocorticoid receptor-DNA binding. In the in vivo study, adrenalectomized rats were treated with vehicle, RU486 (20 mg/kg) and S-P (50 mg/kg) alone or in combination with corticosterone (3 mg/kg). RU486 induced glucocorticoid receptor nuclear translocation in the pituitary, hippocampus and prefrontal cortex and glucocorticoid receptor-DNA binding in the hippocampus, whereas no effect of S-P on glucocorticoid receptor nuclear translocation or DNA binding was observed in any of the areas analysed. These findings reveal differential effects of RU486 and S-P on areas involved in regulation of hypothalamic–pituitary–adrenal axis activity in vivo and they are important in light of the potential use of this class of compounds in the treatment of disorders associated with hyperactivity of the hypothalamic–pituitary–adrenal axis. PMID:20093322

  3. The effect of diffusion on the binding of membrane-bound receptors to coated pits.

    PubMed Central

    Keizer, J; Ramirez, J; Peacock-López, E

    1985-01-01

    We have formulated a kinetic model for the primary steps that occur at the cell membrane during receptor-mediated endocytosis. This model includes the diffusion of receptor molecules, the binding of receptors to coated pits, the loss of coated pits by invagination, and random reinsertion of receptors and coated pits. Using the mechanistic statistical theory of nonequilibrium thermodynamics, we employ this mechanism to calculate the two-dimensional radial distribution of receptors around coated pits at steady state. From this we obtain an equation that describes the effect of receptor diffusion on the rate of binding to coated pits. Our equation does not assume that ligand binding is instantaneous and can be used to assess the effect of diffusion on the binding rate. Using experimental data for low density lipoprotein receptors on fibroblast cells, we conclude that the effect of diffusion on the binding of these receptors to coated pits is no more than 84% diffusion controlled. This corresponds to a dissociation rate constant for receptors on coated pits (k-) that is much less than the rate constant for invagination of the pits (lambda = 3.3 X 10(-3)/s) and a correlation length for the radial distribution function of six times the radius of a coated pit. Although the existing experimental data are compatible with any value of k-, we obtain a lower bound for the value of the binding constant (k+) of 2.3 X 10(-2)(micron)2/s. Comparison of the predicted radial distributions with experiment should provide a clear indication of the effect of diffusion on k+. PMID:2858230

  4. Lomofungin and dilomofungin: inhibitors of MBNL1-CUG RNA binding with distinct cellular effects.

    PubMed

    Hoskins, Jason W; Ofori, Leslie O; Chen, Catherine Z; Kumar, Amit; Sobczak, Krzysztof; Nakamori, Masayuki; Southall, Noel; Patnaik, Samarjit; Marugan, Juan J; Zheng, Wei; Austin, Christopher P; Disney, Matthew D; Miller, Benjamin L; Thornton, Charles A

    2014-06-01

    Myotonic dystrophy type 1 (DM1) is a dominantly inherited neuromuscular disorder resulting from expression of RNA containing an expanded CUG repeat (CUG(exp)). The pathogenic RNA is retained in nuclear foci. Poly-(CUG) binding proteins in the Muscleblind-like (MBNL) family are sequestered in foci, causing misregulated alternative splicing of specific pre-mRNAs. Inhibitors of MBNL1-CUG(exp) binding have been shown to restore splicing regulation and correct phenotypes in DM1 models. We therefore conducted a high-throughput screen to identify novel inhibitors of MBNL1-(CUG)12 binding. The most active compound was lomofungin, a natural antimicrobial agent. We found that lomofungin undergoes spontaneous dimerization in DMSO, producing dilomofungin, whose inhibition of MBNL1-(CUG)12 binding was 17-fold more potent than lomofungin itself. However, while dilomofungin displayed the desired binding characteristics in vitro, when applied to cells it produced a large increase of CUG(exp) RNA in nuclear foci, owing to reduced turnover of the CUG(exp) transcript. By comparison, the monomer did not induce CUG(exp) accumulation in cells and was more effective at rescuing a CUG(exp)-induced splicing defect. These results support the feasibility of high-throughput screens to identify compounds targeting toxic RNA, but also demonstrate that ligands for repetitive sequences may have unexpected effects on RNA decay. PMID:24799433

  5. Lomofungin and dilomofungin: inhibitors of MBNL1-CUG RNA binding with distinct cellular effects

    PubMed Central

    Hoskins, Jason W.; Ofori, Leslie O.; Chen, Catherine Z.; Kumar, Amit; Sobczak, Krzysztof; Nakamori, Masayuki; Southall, Noel; Patnaik, Samarjit; Marugan, Juan J.; Zheng, Wei; Austin, Christopher P.; Disney, Matthew D.; Miller, Benjamin L.; Thornton, Charles A.

    2014-01-01

    Myotonic dystrophy type 1 (DM1) is a dominantly inherited neuromuscular disorder resulting from expression of RNA containing an expanded CUG repeat (CUGexp). The pathogenic RNA is retained in nuclear foci. Poly-(CUG) binding proteins in the Muscleblind-like (MBNL) family are sequestered in foci, causing misregulated alternative splicing of specific pre-mRNAs. Inhibitors of MBNL1-CUGexp binding have been shown to restore splicing regulation and correct phenotypes in DM1 models. We therefore conducted a high-throughput screen to identify novel inhibitors of MBNL1-(CUG)12 binding. The most active compound was lomofungin, a natural antimicrobial agent. We found that lomofungin undergoes spontaneous dimerization in DMSO, producing dilomofungin, whose inhibition of MBNL1–(CUG)12 binding was 17-fold more potent than lomofungin itself. However, while dilomofungin displayed the desired binding characteristics in vitro, when applied to cells it produced a large increase of CUGexp RNA in nuclear foci, owing to reduced turnover of the CUGexp transcript. By comparison, the monomer did not induce CUGexp accumulation in cells and was more effective at rescuing a CUGexp-induced splicing defect. These results support the feasibility of high-throughput screens to identify compounds targeting toxic RNA, but also demonstrate that ligands for repetitive sequences may have unexpected effects on RNA decay. PMID:24799433

  6. Optimizing the affinity and specificity of ligand binding with the inclusion of solvation effect.

    PubMed

    Yan, Zhiqiang; Wang, Jin

    2015-09-01

    Solvation effect is an important factor for protein-ligand binding in aqueous water. Previous scoring function of protein-ligand interactions rarely incorporates the solvation model into the quantification of protein-ligand interactions, mainly due to the immense computational cost, especially in the structure-based virtual screening, and nontransferable application of independently optimized atomic solvation parameters. In order to overcome these barriers, we effectively combine knowledge-based atom-pair potentials and the atomic solvation energy of charge-independent implicit solvent model in the optimization of binding affinity and specificity. The resulting scoring functions with optimized atomic solvation parameters is named as specificity and affinity with solvation effect (SPA-SE). The performance of SPA-SE is evaluated and compared to 20 other scoring functions, as well as SPA. The comparative results show that SPA-SE outperforms all other scoring functions in binding affinity prediction and "native" pose identification. Our optimization validates that solvation effect is an important regulator to the stability and specificity of protein-ligand binding. The development strategy of SPA-SE sets an example for other scoring function to account for the solvation effect in biomolecular recognitions. PMID:26111900

  7. Structures of apo IRF-3 and IRF-7 DNA binding domains: effect of loop L1 on DNA binding

    SciTech Connect

    De Ioannes, Pablo; Escalante, Carlos R.; Aggarwal, Aneel K.

    2013-11-20

    Interferon regulatory factors IRF-3 and IRF-7 are transcription factors essential in the activation of interferon-{beta} (IFN-{beta}) gene in response to viral infections. Although, both proteins recognize the same consensus IRF binding site AANNGAAA, they have distinct DNA binding preferences for sites in vivo. The X-ray structures of IRF-3 and IRF-7 DNA binding domains (DBDs) bound to IFN-{beta} promoter elements revealed flexibility in the loops (L1-L3) and the residues that make contacts with the target sequence. To characterize the conformational changes that occur on DNA binding and how they differ between IRF family members, we have solved the X-ray structures of IRF-3 and IRF-7 DBDs in the absence of DNA. We found that loop L1, carrying the conserved histidine that interacts with the DNA minor groove, is disordered in apo IRF-3 but is ordered in apo IRF-7. This is reflected in differences in DNA binding affinities when the conserved histidine in loop L1 is mutated to alanine in the two proteins. The stability of loop L1 in IRF-7 derives from a unique combination of hydrophobic residues that pack against the protein core. Together, our data show that differences in flexibility of loop L1 are an important determinant of differential IRF-DNA binding.

  8. The effect of intermolecular hydrogen bonding on the planarity of amides.

    PubMed

    Platts, James A; Maarof, Hasmerya; Harris, Kenneth D M; Lim, Gin Keat; Willock, David J

    2012-09-14

    Ab initio and density functional theory (DFT) calculations on some model systems are presented to assess the extent to which intermolecular hydrogen bonding can affect the planarity of amide groups. Formamide and urea are examined as archetypes of planar and non-planar amides, respectively. DFT optimisations suggest that appropriately disposed hydrogen-bond donor or acceptor molecules can induce non-planarity in formamide, with OCNH dihedral angles deviating by up to ca. 20° from planarity. Ab initio energy calculations demonstrate that the energy required to deform an amide molecule from the preferred geometry of the isolated molecule is more than compensated by the stabilisation due to hydrogen bonding. Similarly, the NH(2) group in urea can be made effectively planar by the presence of appropriately positioned hydrogen-bond acceptors, whereas hydrogen-bond donors increase the non-planarity of the NH(2) group. Small clusters (a dimer, two trimers and a pentamer) extracted from the crystal structure of urea indicate that the crystal field acts to force planarity of the urea molecule; however, the interaction with nearest neighbours alone is insufficient to induce the molecule to become completely planar, and longer-range effects are required. Finally, the potential for intermolecular hydrogen bonding to induce non-planarity in a model of a peptide is explored. Inter alia, the insights obtained in the present work on the extent to which the geometry of amide groups may be deformed under the influence of intermolecular hydrogen bonding provide structural guidelines that can assist the interpretation of the geometries of such groups in structure determination from powder X-ray diffraction data. PMID:22847473

  9. Quantum Calculations on Hydrogen Bonds in Certain Water Clusters Show Cooperative Effects

    SciTech Connect

    Znamenskiy, Vasiliy S.; Green, Michael E.

    2007-01-09

    Water molecules in clefts and small clusters are in a significantly different environment than those in bulk water. We have carried out ab initio calculations that demonstrate this in a series of clusters, showing that cooperative effects must be taken into account in the treatment of hydrogen bonds and water clusters in such bounded systems. Hydrogen bonds between water molecules in simulations are treated most frequently by using point-charge water potentials, such as TIP3P or SPC, sometimes with a polarizable extension. These produce excellent results in bulk water, for which they are calibrated. Clefts are different from bulk; it is necessary to look at smaller systems and investigate the effect of limited numbers of neighbors. We start with a study of isolated clusters of water with varying numbers of neighbors of a hydrogen-bonded pair of water molecules. The cluster as a whole is in a vacuum. The clusters are defined so as to provide the possible arrangements of nearest neighbors of a central hydrogen-bonded pair of water molecules. We then scan the length and angles of the central hydrogen bond of the clusters, using density functional theory, for each possible arrangement of donor and acceptor hydrogen bonds on the central hydrogen-bonding pair; the potential of interaction of two water molecules varies with the number of donor and acceptor neighbors. This also involves changes in charge on the water molecules as a function of bond length and changes in energy and length as a function of the number of neighboring donor and acceptor molecules. The energy varies by approximately 6 kBT near room temperature from the highest to the lowest energy when bond length alone is varied, enough to seriously affect simulations.

  10. Quantum Calculations on Hydrogen Bonds in Certain Water Clusters Show Cooperative Effects.

    SciTech Connect

    Znamenskiy, Vasiliy S.; Green, Michael E.

    2006-12-08

    The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. Water molecules in clefts and small clusters are in a significantly different environment than those in bulk water. We have carried out ab initio calculations that demonstrate this in a series of clusters, showing that cooperative effects must be taken into account in the treatment of hydrogen bonds and water clusters in such bounded systems. Hydrogen bonds between water molecules in simulations are treated most frequently by using point-charge water potentials, such as TIP3P or SPC, sometimes with a polarizable extension. These produce excellent results in bulk water, for which they are calibrated. Clefts are different from bulk; it is necessary to look at smaller systems and investigate the effect of limited numbers of neighbors. We start with a study of isolated clusters of water with varying numbers of neighbors of a hydrogen-bonded pair of water molecules. The cluster as a whole is in a vacuum. The clusters are defined so as to provide the possible arrangements of nearest neighbors of a central hydrogen-bonded pair of water molecules. We then scan the length and angles of the central hydrogen bond of the clusters, using density functional theory, for each possible arrangement of donor and acceptor hydrogen bonds on the central hydrogen-bonding pair; the potential of interaction of two water molecules varies with the number of donor and acceptor neighbors. This also involves changes in charge on the water molecules as a function of bond length and changes in energy and length as a function of the number of neighboring donor and acceptor molecules. The energy varies by approximately 6 kBT near room temperature from the highest to the lowest energy when bond length alone is

  11. Hydrogen isotope effect on storage behavior of U2Ti and UZr2.3

    NASA Astrophysics Data System (ADS)

    Jat, Ram Avtar; Sawant, S. G.; Rajan, M. B.; Dhanuskar, J. R.; Kaity, Santu; Parida, S. C.

    2013-11-01

    U2Ti and UZr2.3 alloys were prepared by arc melting method, vacuum annealed and characterized by XRD, SEM and EDX methods. Hydrogen isotope effect on the storage behavior of these alloys were studied by measuring the hydrogen/deuterium desorption pressure-composition-temperature (PCT) profiles in the temperature range of 573-678 K using a Sievert's type volumetric apparatus. It was observed that, in the temperature and pressure range of investigation, all the isotherms show a single desorption plateau. The PCT data reveals that both U2Ti and UZr2.3 alloys had normal isotope effects on hydrogen/deuterium desorption at all experimental temperatures. Thermodynamic parameters for dehydrogenation and dedeuteration reactions of the corresponding hydrides and deuterides of the above alloys were deduced from the PCT data.

  12. Numerical analysis of the influence of scale effects and microstructure on hydrogen diffusion in polycrystalline aggregates

    SciTech Connect

    Legrand, Esaie; Bouhattate, Jamaa; Feaugas, Xavier; Touzain, S.; Garmestani, Hamid; Khaleel, Mohammad A.; Li, Dongsheng

    2013-04-01

    Predicting resistance to environmental degradation, especially hydrogen embrittlement (HE) has become a major concern for life assessment and risk analysis of structural materials. The microstructure of the materials plays a significant role in HE. Despite the large documentation about the subject, the contribution of hydrogen diffusion on this process stays unclear. In this work, we analyze the effects of the microstructure on hydrogen diffusion, especially the influence of grain boundaries considered as high diffusivity paths and possible sites of damage occurrence. Electrochemical permeation was simulated using finite elements method (FEM). Scale effects between the RVE (Representative Volume Element) and the size of the membrane are discussed. Domains of applicability for standard homogenization methods, especially Hashin Shtrikman model are studied using results from microstructural based FEM. Domains of invariance of diffusion behavior and concentration profiles for grain shapes and the size of the membrane are also analyzed. Thus, the difficulty to extract diffusion properties by permeation test for heterogeneous microstructures is highlighted and discussed.

  13. Effect of superalkali substituents on the strengths and properties of hydrogen and halogen bonds.

    PubMed

    Tian, Wenkai; Huang, Xin; Li, Qingzhong; Li, Wenzuo; Cheng, Jianbo; Gong, Baoan

    2013-03-01

    Quantum chemical calculations have been performed for the complexes Li(3)OCCX-Y (X = Cl, Br, H; Y = NH(3), H(2)O, H(2)S) and Li(3)OCN-X'Y' (X'Y' = ClF, BrCl, BrF, HF) to study the role of superalkalis in hydrogen and halogen bonds. The results show that the presence of an Li(3)O cluster in a Lewis acid weakens its acidity, while its presence in a Lewis base enhances its basicity. Furthermore, the latter effect is more prominent than the former one, and the presence of an Na(3)O cluster causes an even greater effect than Li(3)O. The strengths of hydrogen and halogen bonds were analyzed using molecular electrostatic potentials. The contributions of superalkalis to the strength of hydrogen and halogen bonds were elucidated by analyzing differences in electron density. PMID:23179773

  14. The Effect of Hydrogen Annealing on the Impurity Content of Alumina-Forming Alloys

    NASA Technical Reports Server (NTRS)

    Smialek, James L.

    2000-01-01

    Previously, the effect of hydrogen annealing on increasing the adhesion of Al2O3 scales had been related to the effective desulfurization that occurred during this process. The simultaneous reduction of other impurities has now been re-examined for up to 20 impurity elements in the case of five different alloys (NiCrAl, FeCrAl, PWA 1480, Rene'142, and Rene'N5). Hydrogen annealing produced measurable reductions in elemental concentration for B, C, Na, Mg, P, K, Sr, or Sn in varying degrees for at least one and up to three of these alloys. No single element was reduced by hydrogen annealing for all the alloys except sulfur. In many cases spalling occurred at low levels of these other impurities, while in other cases the scales were adherent at high levels of the impurities. No impurity besides sulfur was strongly correlated with adhesion.

  15. Effect of dehydrogenation/hydrogenation on the linear and nonlinear optical properties of Li@porphyrins.

    PubMed

    Wu, Heng-Qing; Sun, Shi-Ling; Zhong, Rong-Lin; Xu, Hong-Liang; Su, Zhong-Min

    2012-11-01

    In the present work, Li@porphyrins and their derivatives were designed in order to explore the effect of dehydrogenation/hydrogenation on linear and nonlinear optical properties. Their stable structures were obtained by the M06-2X method. Moreover, the M06-2X method showed that dehydrogenation/hydrogenation has greatly influences polarizabilities (α₀ values) and hyperpolarizabilities (β(tot) and γ(tot) values): α₀ values ranged from 331 to 389 au, β(tot) values from 0 to 2465 au, and γ(tot) values from -21.2 × 10⁴ to 21.4 × 10⁴ au. This new knowledge of the effect of dehydrogenation/hydrogenation on nonlinear optical properties may prove beneficial to the design and development of high-performance porphyrin materials. PMID:22722697

  16. Perturbed wavefunctions of the excited states of hydrogen atom in Stark effect

    SciTech Connect

    Sapra, G.K.; Bhasin, V.S.; Kothari, L.S. . Dept. of Physics Astrophysics)

    1994-03-15

    The authors extend the procedure originally suggested by Dalgarno and Lewis in studying the second-order Stark effect for the ground-state hydrogen atom to the excited states. They solve the perturbation equations for the excited states of hydrogen atom placed in an external electric field to obtain expressions for the perturbed wavefunctions. Here the emphasis is on studying in detail the nature of the perturbed wavefunction rather than energy shifts as investigated in most of the attempts made so far. The effect of the electric field on these wavefunctions is analyzed and the values of the electric polarizability of the hydrogen atom in the excited states obtained in this way are compared with the earlier work.

  17. Effect of oxide films on hydrogen permeability of candidate Stirling engine heater head tube alloys

    NASA Technical Reports Server (NTRS)

    Schuon, S. R.; Misencik, J. A.

    1981-01-01

    The effect of oxide films developed in situ from CO/CO2 doped hydrogen on high pressure hydrogen permeability at 820 C was studied on N-155, A-286, IN 800, 19-9DL, Nitronic 40, HS-188, and IN 718 tubing in a Stirling materials simulator. The hydrogen permeability decreased with increasing dopant levels of CO or CO2 and corresponding decreases in oxide porosity. Minor reactive alloying elements strongly influenced permeability. At high levels of CO or CO2, a liquid oxide formed on alloys with greater than 50 percent Fe. This caused increased permeability. The oxides formed on the inside tube walls were analyzed and their effective permeabilities were calculated.

  18. Improving the binding efficiency of quartz crystal microbalance biosensors by applying the electrothermal effect

    PubMed Central

    Huang, Yao-Hung; Chang, Jeng-Shian; Chao, Sheng D.; Wu, Kuang-Chong; Huang, Long-Sun

    2014-01-01

    A quartz crystal microbalance (QCM) serving as a biosensor to detect the target biomolecules (analytes) often suffers from the time consuming process, especially in the case of diffusion-limited reaction. In this experimental work, we modify the reaction chamber of a conventional QCM by integrating into the multi-microelectrodes to produce electrothermal vortex flow which can efficiently drive the analytes moving toward the sensor surface, where the analytes were captured by the immobilized ligands. The microelectrodes are placed on the top surface of the chamber opposite to the sensor, which is located on the bottom of the chamber. Besides, the height of reaction chamber is reduced to assure that the suspended analytes in the fluid can be effectively drived to the sensor surface by induced electrothermal vortex flow, and also the sample costs are saved. A series of frequency shift measurements associated with the adding mass due to the specific binding of the analytes in the fluid flow and the immobilized ligands on the QCM sensor surface are performed with or without applying electrothermal effect (ETE). The experimental results show that electrothermal vortex flow does effectively accelerate the specific binding and make the frequency shift measurement more sensible. In addition, the images of the binding surfaces of the sensors with or without applying electrothermal effect are taken through the scanning electron microscopy. By comparing the images, it also clearly indicates that ETE does raise the specific binding of the analytes and ligands and efficiently improves the performance of the QCM sensor. PMID:25538808

  19. Effect of d-amino acids on IgE binding to peanut allergens

    Technology Transfer Automated Retrieval System (TEKTRAN)

    D-amino acids are formed when L-amino acids are exposed to heat. The objective was to determine the existence of D-amino acids in roasted peanut and their effect on IgE binding. Raw and roasted peanut protein extracts were hydrolyzed in 6 N HCL under vacuum. The hydrolysates were then analyzed for D...

  20. Effect of Cropping Pattern and Crop Residue on Herbicide Binding to Soil

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The binding of herbicides to soil is dependent on many factors, including soil texture, organic matter, and pH. In 2007 we were conducting an experiment to determine the effect of cropping patterns on atrazine efficacy and fate, and found that there was a significant relationship between cropping p...

  1. Effects of Fasting on IGF-Binding Proteins, Glucose, and Cortisol in Channel Catfish (Ictalurus punctatus)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The effects of fasting on IGF-binding proteins, glucose, and cortisol in channel catfish were examined. Fed fish (controls) were compared to 14-, 30-, and 45-day fasted fish and 45-day fasted fish refed for 15 additional days. Body length and body weight changes, condition factor(CF), hepatosomati...

  2. In situ analysis of cisplatin binding to DNA: the effects of physiological ionic conditions.

    PubMed

    Park, Jin-Sung; Kim, Sook Ho; Lee, Nam-Kyung; Lee, Kyoung J; Hong, Seok-Cheol

    2012-03-01

    Platinum-based anti-cancer drugs form a major family of cancer chemotherapeutic agents. Cisplatin, the first member of the family, remains a potent anti-cancer drug and exhibits its clinical effect by inducing local DNA kinks and subsequently interfering with DNA metabolism. Although its mechanism is reasonably well understood, effects of intracellular ions on cisplatin activity are left to be elucidated because cisplatin binding to DNA, thus its drug efficacy, is modified by various ions. One such issue is the effect of carbonate ions: cisplatin binding to DNA is suppressed under physiological carbonate conditions. Here, we examined the role of common cellular ions (carbonate and chloride) by measuring cisplatin binding in relevant physiological buffers via a DNA micromanipulation technique. Using two orthogonal single-molecule methods, we succeeded in detecting hidden monofunctional adducts (kink-free, presumably clinically inactive form) and clearly showed that the major effect of carbonates was to form such adducts and to prevent them from converting to bifunctional adducts (kinked, clinically active). The chloride-rich environment also led to the formation of monofunctional adducts. Our approach is widely applicable to the study of the transient behaviours of various drugs and proteins that bind to DNA in different modes depending on various physical and chemical factors such as tension, torsion, ligands, and ions. PMID:22286168

  3. Dopamine transporter binding in social anxiety disorder: the effect of treatment with escitalopram.

    PubMed

    Warwick, J M; Carey, P D; Cassimjee, N; Lochner, C; Hemmings, S; Moolman-Smook, H; Beetge, E; Dupont, P; Stein, D J

    2012-06-01

    Social anxiety disorder (SAD) is characterised by fear of social or performance situations where the individual is exposed to unfamiliar people or to possible scrutiny by others. The literature on dopamine ligands and dopamine genotypes in SAD is however inconsistent. In this study we measured the effects of SSRI pharmacotherapy on dopamine transporter (DAT) binding in patients with SAD, also addressing variability in DAT genotype. Adult subjects meeting DSM-IV criteria for generalised SAD were studied before and after 12 weeks of pharmacotherapy with the selective serotonin reuptake inhibitor (SSRI) escitalopram. DAT single photon emission computed tomography (SPECT) using (123)I-FP-CIT was performed at baseline, and repeated at 12 weeks. Striatal DAT binding was analysed for changes following therapy, and for correlations with clinical efficacy, in the whole group as well as for a subgroup with the A10/A10 DAT genotype. The study included 14 subjects (9 male, 5 female) with a mean (SD) age of 41 (±13) years. The subjects' Liebowitz Social Anxiety Scale (LSAS) score was significantly decreased following pharmacotherapy. In the combined group the left caudate and left putamen showed clusters of increased DAT binding after therapy. The left caudate changes were also observed in the subgroup of 9 A10/A10 homozygotes. However no correlation was found between improved symptoms and DAT binding. The changes found in DAT binding in the caudate and putamen may be due to serotonergic activation of dopamine function by SSRI therapy. This is consistent with previous work indicating decreased DAT binding in SAD, and increased DAT binding after SSRI administration. PMID:22350963

  4. Magnetocaloric properties of distilled gadolinium: Effects of structural inhomogeneity and hydrogen impurity

    SciTech Connect

    Burkhanov, G. S.; Kolchugina, N. B.; Chzhan, V. B.; Chistyakov, O. D.; Tereshina, E. A.; Tereshina, I. S.; Politova, G. A.; Badurski, D.; Drulis, H.; Paukov, M.; Havela, L.

    2014-06-16

    High-purity Gd prepared by distillation is a structurally inhomogeneous system consisting of needle-shaped crystals of cross section 0.5–2.5 μm with near-c-axis orientation embedded in a matrix of nanosized (30–100 nm) grains. By measuring the magnetocaloric effect (MCE) directly, we find that the MCE values differ markedly for the plate-shaped samples cut out of a distillate along and perpendicular to the crystals. The effect of small controlled amounts of impurity (hydrogen) on the properties of distilled Gd is further studied. We observe opposite trends in the MCE response to hydrogen charging with respect to the crystal's orientation within the samples and discuss mechanisms interrelating the unique structural morphology with the impurity behavior. As an overall assessment, the Curie temperatures of α-GdH{sub x} solid solutions increase from 291 K up to 294 K when increasing hydrogen concentration x from 0 to 0.15. Hydrogenation is found to broaden the ferromagnetic-to-paramagnetic phase transition. Hydrogen-containing specimens demonstrate reversibility of MCE at these temperatures.

  5. HYDROGEN EFFECTS ON THE BURST PROPERTIES OF TYPE 304L STAINLESS STEEL FLAWED VESSELS

    SciTech Connect

    Morgan, M; Monica Hall, M; Ps Lam, P; Dean Thompson, D

    2008-03-27

    The effect of hydrogen on the burst properties Type 304L stainless steel vessels was investigated. The purpose of the study was to compare the burst properties of hydrogen-exposed stainless steel vessels burst with different media: water, helium gas, or deuterium gas. A second purpose of the tests was to provide data for the development of a predictive finite-element model. The burst tests were conducted on hydrogen-exposed and unexposed axially-flawed cylindrical vessels. The results indicate that samples burst pneumatically had lower volume ductility than those tested hydraulically. Deuterium gas tests had slightly lower ductility than helium gas tests. Burst pressures were not affected by burst media. Hydrogen-charged samples had lower volume ductility and slightly higher burst pressures than uncharged samples. Samples burst with deuterium gas fractured by quasi-cleavage near the inside wall. The results of the tests were used to improve a previously developed predictive finite-element model. The results show that predicting burst behavior requires as a material input the effect of hydrogen on the plastic strain to fracture from tensile tests. The burst test model shows that a reduction in the plastic strain to fracture of the material will result in lower volume ductility without a reduction in burst pressure which is in agreement with the burst results.

  6. Protective Effects of Hydrogen-Rich Saline on Rats with Smoke Inhalation Injury

    PubMed Central

    Chen, Xing; Liu, Qi; Wang, Dawei; Feng, Shihai; Zhao, Yongjian; Shi, Yun; Liu, Qun

    2015-01-01

    Objective. To explore the protective effects of hydrogen-rich saline on rats with smoke inhalation injury. Methods. 36 healthy male Sprague-Dawley rats were randomly divided into 3 groups (n = 12 per group): sham group (S), inhalation injury plus normal saline treatment group (I+NS), and inhalation injury plus hydrogen-rich saline treatment group (I+HS). 30 min after injury, normal saline and hydrogen-rich saline were injected intraperitoneally (5 mL/kg) in I+NS group and I+HS group, respectively. All rats were euthanized and blood and organ specimens were collected for determination 24 h after inhalation injury. Results. Tumor necrosis factor-alpha (TNF-α) levels, malondialdehyde (MDA) concentrations, nuclear factor kappa B (NF-κB) p65 expression, and apoptosis index (AI) in I+HS group were significantly decreased (P < 0.05), while superoxide dismutase (SOD) activities were increased compared with those in I+NS group; and a marked improvement in alveolar structure was also found after hydrogen-rich saline treatment. Conclusions. Hydrogen-rich saline treatment exerts protective effects in acute lung injury induced by inhalation injury, at least in part through the activation of anti-inflammatory and antioxidant pathways and inhibition of apoptosis. PMID:26090070

  7. The effect of a tin barrier layer on the permeability of hydrogen through mild steel and ferritic stainless steel

    SciTech Connect

    Bowker, J.; Piercy, G.R.

    1984-11-01

    Experiments were performed to measure the effectiveness of a commercially electroplated tin layer as a barrier to hydrogen, and to see how this altered when the tin layer was converted to FeSn. The authors measured the permeability of hydrogen through AISI 410 ferritic stainless steel and determined the effectiveness of tin as a surface barrier on it. The measured values for the permeability of hydrogen in iron and ferritic stainless steel are shown.

  8. Survey of phosphorylation near drug binding sites in the Protein Data Bank (PDB) and their effects.

    PubMed

    Smith, Kyle P; Gifford, Kathleen M; Waitzman, Joshua S; Rice, Sarah E

    2015-01-01

    While it is currently estimated that 40 to 50% of eukaryotic proteins are phosphorylated, little is known about the frequency and local effects of phosphorylation near pharmaceutical inhibitor binding sites. In this study, we investigated how frequently phosphorylation may affect the binding of drug inhibitors to target proteins. We examined the 453 non-redundant structures of soluble mammalian drug target proteins bound to inhibitors currently available in the Protein Data Bank (PDB). We cross-referenced these structures with phosphorylation data available from the PhosphoSitePlus database. Three hundred twenty-two of 453 (71%) of drug targets have evidence of phosphorylation that has been validated by multiple methods or labs. For 132 of 453 (29%) of those, the phosphorylation site is within 12 Å of the small molecule-binding site, where it would likely alter small molecule binding affinity. We propose a framework for distinguishing between drug-phosphorylation site interactions that are likely to alter the efficacy of drugs versus those that are not. In addition we highlight examples of well-established drug targets, such as estrogen receptor alpha, for which phosphorylation may affect drug affinity and clinical efficacy. Our data suggest that phosphorylation may affect drug binding and efficacy for a significant fraction of drug target proteins. PMID:24833420

  9. Survey of phosphorylation near drug binding sites in the Protein Data Bank (PDB) and their effects

    PubMed Central

    Smith, Kyle P.; Gifford, Kathleen M.; Waitzman, Joshua S.; Rice, Sarah E.

    2014-01-01

    While it is currently estimated that 40–50% of eukaryotic proteins are phosphorylated, little is known about the frequency and local effects of phosphorylation near pharmaceutical inhibitor binding sites. In this study, we investigated how frequently phosphorylation may affect the binding of drug inhibitors to target proteins. We examined the 453 non-redundant structures of soluble mammalian drug target proteins bound to inhibitors currently available in the Protein Data Bank (PDB). We cross-referenced these structures with phosphorylation data available from the PhosphoSitePlus database. 322/453 (71%) of drug targets have evidence of phosphorylation that has been validated by multiple methods or labs. For 132/453 (29%) of those, the phosphorylation site is within 12Å of the small molecule-binding site, where it would likely alter small molecule binding affinity. We propose a framework for distinguishing between drug-phosphorylation site interactions that are likely to alter the efficacy of drugs vs. those that are not. In addition we highlight examples of well-established drug targets, such as estrogen receptor alpha, for which phosphorylation may affect drug affinity and clinical efficacy. Our data suggest that phosphorylation may affect drug binding and efficacy for a significant fraction of drug target proteins. PMID:24833420

  10. Beyond the detergent effect: a binding site for sodium dodecyl sulfate (SDS) in mammalian apoferritin

    SciTech Connect

    Liu, Renyu Bu, Weiming; Xi, Jin; Mortazavi, Shirin R.; Cheung-Lau, Jasmina C.; Dmochowski, Ivan J.; Loll, Patrick J.

    2012-05-01

    Using X-ray crystallography and isothermal titration calorimetry, we show that sodium dodecyl sulfate (SDS) binds specifically to a pre-formed internal cavity in horse-spleen apoferritin. Although sodium dodecyl sulfate (SDS) is widely used as an anionic detergent, it can also exert specific pharmacological effects that are independent of the surfactant properties of the molecule. However, structural details of how proteins recognize SDS are scarce. Here, it is demonstrated that SDS binds specifically to a naturally occurring four-helix bundle protein: horse apoferritin. The X-ray crystal structure of the apoferritin–SDS complex was determined at a resolution of 1.9 Å and revealed that the SDS binds in an internal cavity that has previously been shown to recognize various general anesthetics. A dissociation constant of 24 ± 9 µM at 293 K was determined by isothermal titration calorimetry. SDS binds in this cavity by bending its alkyl tail into a horseshoe shape; the charged SDS head group lies in the opening of the cavity at the protein surface. This crystal structure provides insights into the protein–SDS interactions that give rise to binding and may prove useful in the design of novel SDS-like ligands for some proteins.

  11. Effects of oxymorphazone in frogs: long lasting antinociception in vivo, and apparently irreversible binding in vitro

    SciTech Connect

    Benyhe, S.; Hoffman, G.; Varga, E.; Hosztafi, S.; Toth, G.; Borsodi, A.; Wollemann, M.

    1989-01-01

    Oxymorphazone was found to be a relatively weak antinociceptive drug in intact frog (Rana esculenta) when acetic acid was used as pain stimulus. Frogs remained analgesic for at least 48 hrs following oxymorphazone administration. The ligand increased the latency of wiping reflex in spinal frogs too. There effects were blocked by naloxone. In equilibrium binding studies (/sup 3/H)oxymorphazone had high affinity to the opioid receptors of frog brain and spinal cord as well. Kinetic experiments show that only 25% of the bound (/sup 3/H)oxymorphazone is readily dissociable. Preincubation of the membranes with labeled oxymorphazone results in a washing resistant inhibition of the opioid binding sites. At least 70% of the (/sup 3/H)oxymorphazone specific binding is apparently irreversible after reaction at 5 nM ligand concentration, and this can be enhanced by a higher concentration of tritiated ligand.

  12. H/D isotope effect on structures, binding energies, and basis set superposition errors in F-(H2O)n (n = 1-3) clusters

    NASA Astrophysics Data System (ADS)

    Udagawa, Taro; Ishimoto, Takayoshi; Tachikawa, Masanori

    2014-09-01

    The H/D isotope effects on structures, binding energies, and basis set superposition errors (BSSEs) of hydrated fluoride anion clusters, F-(H2O)n (n = 1-3), are theoretically analyzed by using the MP2 level of multi-component molecular orbital (MC_MO-MP2) method, in which quantum nature of proton/deuteron and electron-electron correlation are directly taken account. Our results clearly show that the additional water molecule to F-(H2O)n-1 cluster forms stronger water-water hydrogen bond than that in simple water cluster, whereas the additional F--water hydrogen bond formation in F-(H2O)n cluster weakens the original F--water hydrogen bonds in F-(H2O)n-1 cluster. The BSSEs estimated in the MC_MO-MP2 calculations are slightly larger than those in the conventional MP2 calculations, due to the H/D geometrical isotope effect on the intermolecular distances. Consequently, the order of stability in several F-(H2O)3 cluster isomers cannot be adequately evaluated without BSSE corrections in our MC_MO-MP2 calculations, rather than the conventional MP2 ones.

  13. Super-saturated hydrogen effects on radiation damages in tungsten under the high-flux divertor plasma irradiation

    NASA Astrophysics Data System (ADS)

    Kato, D.; Iwakiri, H.; Watanabe, Y.; Morishita, K.; Muroga, T.

    2015-08-01

    Tungsten is a prime candidate as the divertor material of the ITER and DEMO reactors, which would be exposed to unprecedentedly high-flux plasmas as well as neutrons. For a better characterization of radiation damages in the tungsten under the divertor condition, we examine influences of super-saturated hydrogen on vacancies in the tungsten. The present calculations based on density functional theory (DFT) reveal unusual phenomena predicted at a super-saturated hydrogen concentration: (1) strongly enhanced vacancy concentration with the super-saturated hydrogen concentration is predicted by a thermodynamics model assuming multiple-hydrogen trapping, i.e. hydrogen clusters formation, in the vacancies; and (2) DFT molecular dynamics revealed that hydrogen clusters can prevent a vacancy from recombining with the neighboring crowdion-type self-interstitial-atom. This suggests that neutron damage effects will be increased in the presence of the hydrogen clusters.

  14. Structural and thermodynamic effects of ANS binding to human interleukin-1 receptor antagonist

    PubMed Central

    Latypov, Ramil F.; Liu, Dingjiang; Gunasekaran, Kannan; Harvey, Timothy S.; Razinkov, Vladimir I.; Raibekas, Andrei A.

    2008-01-01

    Although 8-anilinonaphthalene-1-sulfonic acid (ANS) is frequently used in protein folding studies, the structural and thermodynamic effects of its binding to proteins are not well understood. Using high-resolution two-dimensional NMR and human interleukin-1 receptor antagonist (IL-1ra) as a model protein, we obtained detailed information on ANS–protein interactions in the absence and presence of urea. The effects of ambient to elevated temperatures on the affinity and specificity of ANS binding were assessed from experiments performed at 25°C and 37°C. Overall, the affinity of ANS was lower at 37°C compared to 25°C, but no significant change in the site specificity of binding was observed from the chemical shift perturbation data. The same site-specific binding was evident in the presence of 5.2 M urea, well within the unfolding transition region, and resulted in selective stabilization of the folded state. Based on the two-state denaturation mechanism, ANS-dependent changes in the protein stability were estimated from relative intensities of two amide resonances specific to the folded and unfolded states of IL-1ra. No evidence was found for any ANS-induced partially denatured or aggregated forms of IL-1ra throughout the experimental conditions, consistent with a cooperative and reversible denaturation process. The NMR results support earlier observations on the tendency of ANS to interact with solvent-exposed positively charged sites on proteins. Under denaturing conditions, ANS binding appears to be selective to structured states rather than unfolded conformations. Interestingly, the binding occurs within a previously identified aggregation-critical region in IL-1ra, thus providing an insight into ligand-dependent protein aggregation. PMID:18305195

  15. Metal loading effect on rare earth element binding to humic acid: Experimental and modelling evidence

    NASA Astrophysics Data System (ADS)

    Marsac, Rémi; Davranche, Mélanie; Gruau, Gérard; Dia, Aline

    2010-03-01

    The effect of metal loading on the binding of rare earth elements (REE) to humic acid (HA) was studied by combining ultrafiltration and Inductively Coupled Plasma Mass Spectrometry techniques. REE-HA complexation experiments were performed at pH 3 for REE/C molar ratios ranging from ca 4 × 10 -4 to 2.7 × 10 -2. Results show that the relative amount of REE bound to HA strongly increases with decreasing REE/C. A middle-REE (MREE) downward concavity is shown by patterns at high metal loading, whereas patterns at low metal loading display a regular increase from La to Lu. Humic Ion Model VI modelling are close to the experimental data variations, provided that (i) the ΔLK 2 parameter (i.e. the Model VI parameter taken into account the presence of strong but low density binding sites) is allowed to increase regularly from La to Lu (from 1.1 to 2.1) and (ii) the published log KMA values (i.e. the REE-HA binding constants specific to Model VI) are slightly modified, in particular with respect to heavy REE. Modelling approach provided evidence that logKdREE patterns with varying REE/C likely arises because REE binding to HA occurs through two types of binding sites in different density: (i) a few strong sites that preferentially complex the heavy REE and thus control the logKdREE atterns at low REE/C; (ii) a larger amount of weaker binding sites that preferentially complex the middle-REE and thus control the logKdREE pattern at high REE/C. Hence, metal loading exerts a major effect on HA-mediated REE binding, which could explain the diversity of published conditional constants for REE binding with HA. A literature survey suggests that the few strong sites activated at low REE/C could be multidentate carboxylic sites, or perhaps N-, or P-functional groups. Finally, an examination of the literature field data proposed that the described loading effect could account for much of the variation in REE patterns observed in natural organic-rich waters (DOC > 5 mg L -1 and 4

  16. Excellent catalytic effects of highly crumpled graphene nanosheets on hydrogenation/dehydrogenation of magnesium hydride.

    PubMed

    Liu, Guang; Wang, Yijing; Xu, Changchang; Qiu, Fangyuan; An, Cuihua; Li, Li; Jiao, Lifang; Yuan, Huatang

    2013-02-01

    Highly crumpled graphene nanosheets (GNS) with a BET surface area as high as 1159 m(2) g(-1) was fabricated by a thermal exfoliation method. A systematic investigation was performed on the hydrogen sorption properties of MgH(2)-5 wt% GNS nanocomposites acquired by ball-milling. It was found that the as-synthesized GNS exhibited a superior catalytic effect on hydrogenation/dehydrogenation of MgH(2). Differential Scanning Calorimetry (DSC) and isothermal hydrogenation/dehydrogenation measurements indicated that both hydrogen sorption capacity and dehydrogenation/hydrogenation kinetics of the composites improved with increasing milling time. The composites MgH(2)-GNS milled for 20 h can absorb 6.6 wt% H(2) within 1 min at 300 °C and 6.3 wt% within 40 min at 200 °C, even at 150 °C, it can also absorb 6.0 wt% H(2) within 180 min. It was also demonstrated that MgH(2)-GNS-20 h could release 6.1 wt% H(2) at 300 °C within 40 min. In addition, microstructure measurements based on XRD, SEM, TEM as well as Raman spectra revealed that the grain size of thus-prepared MgH(2)-GNS nanocomposites decreased with increasing milling time, moreover, the graphene layers were broken into smaller graphene nanosheets in a disordered and irregular manner during milling. It was confirmed that these smaller graphene nanosheets on the composite surface, providing more edge sites and hydrogen diffusion channels, prevented the nanograins from sintering and agglomerating, thus, leading to promotion of the hydrogenation/dehydrogenation kinetics of MgH(2). PMID:23254449

  17. Effect of pressure and hydrogen flow in nucleation density and morphology of graphene bidimensional crystals

    NASA Astrophysics Data System (ADS)

    Chaitoglou, S.; Bertran, E.

    2016-07-01

    In this paper we present new results concerning the growth of graphene by low pressure chemical vapor deposition on polycrystalline copper foils and using methane as carbon precursor. We have studied the role of hydrogen and pressure in graphene growth on substrates of polycrystalline copper foil and we have examined how they affect the nucleation density and the size of graphene bidimensional crystals. For that, small ranges of pressure (between 10 and 30 Pa) and hydrogen flow (between 10 and 20 sccm) were explored. In addition, the antagonism between two of the main effects of hydrogen was studied. Hydrogen promotes the growth but, at the same time, applies an intense dry etching during the growth process of graphene. The challenge of the present study is to find the equilibrium between these two effects so that, the growth of highly ordered crystals on copper becomes possible. The results reveal that the total pressure during the growth process of graphene affects the size as well as the nucleation density of the graphene bidimensional crystals on polycrystalline copper. Besides, the hydrogen flow affects the morphology and quality of the graphene layer. An important parameter for a correct interpretation of the results is the change of the partial pressure ratio, < {P}{{{H}}2}> /< {P}{{{C}{{H}}}4}> , during the growth process under a constant flow of H2 and CH4. Dendritic graphene crystals with lobe lengths around 30 μm along with a nucleation density of 25 nuclei/10 000 μm2 were obtained in the studied technological conditions, which corroborates that a low nucleation of graphene is required to obtain large graphene islands and a low number of crystal boundaries. Raman spectroscopy and scanning electron microscopy evidenced the effects of hydrogen on the characteristics of growth and morphology of the graphene dendritic bidimensional crystals.

  18. CFTR gating II: Effects of nucleotide binding on the stability of open states.

    PubMed

    Bompadre, Silvia G; Cho, Jeong Han; Wang, Xiaohui; Zou, Xiaoqin; Sohma, Yoshiro; Li, Min; Hwang, Tzyh-Chang

    2005-04-01

    Previously, we demonstrated that ADP inhibits cystic fibrosis transmembrane conductance regulator (CFTR) opening by competing with ATP for a binding site presumably in the COOH-terminal nucleotide binding domain (NBD2). We also found that the open time of the channel is shortened in the presence of ADP. To further study this effect of ADP on the open state, we have used two CFTR mutants (D1370N and E1371S); both have longer open times because of impaired ATP hydrolysis at NBD2. Single-channel kinetic analysis of DeltaR/D1370N-CFTR shows unequivocally that the open time of this mutant channel is decreased by ADP. DeltaR/E1371S-CFTR channels can be locked open by millimolar ATP with a time constant of approximately 100 s, estimated from current relaxation upon nucleotide removal. ADP induces a shorter locked-open state, suggesting that binding of ADP at a second site decreases the locked-open time. To test the functional consequence of the occupancy of this second nucleotide binding site, we changed the [ATP] and performed similar relaxation analysis for E1371S-CFTR channels. Two locked-open time constants can be discerned and the relative distribution of each component is altered by changing [ATP] so that increasing [ATP] shifts the relative distribution to the longer locked-open state. Single-channel kinetic analysis for DeltaR/E1371S-CFTR confirms an [ATP]-dependent shift of the distribution of two locked-open time constants. These results support the idea that occupancy of a second ATP binding site stabilizes the locked-open state. This binding site likely resides in the NH2-terminal nucleotide binding domain (NBD1) because introducing the K464A mutation, which decreases ATP binding affinity at NBD1, into E1371S-CFTR shortens the relaxation time constant. These results suggest that the binding energy of nucleotide at NBD1 contributes to the overall energetics of the open channel conformation. PMID:15767296

  19. Seasonal Effects of a Late Application of Hydrogen Cyanamide on 'Climax' Rabbiteye Blueberry

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A field study was conducted to evaluate the effects of hydrogen cyanamide (H2CN2) on flower and leaf buds, foliage, and fruit of 'Climax' rabbiteye blueberry (Vaccinium ashei, Reade), a cultivar exhibiting erratic spring foliation following mild winters. Stems of 'Climax' in several stages of flower...

  20. HYDROGEN OXIDATION IN SOILS AS A POSSIBLE TOXIC-EFFECTS INDICATOR

    EPA Science Inventory

    Efficient soil bioassays are needed in a screening array to determine the toxicities of industrial products and wastes. Hydrogen consumption is a common soil microbiological process that we evaluated as a possible soil indicator of toxic effects. Elemental tritium was used as a t...

  1. Quantum effects and anharmonicity in the H{sub 2}-Li{sup +}-benzene complex: A model for hydrogen storage materials

    SciTech Connect

    Kolmann, Stephen J.; D'Arcy, Jordan H.; Jordan, Meredith J. T.

    2013-12-21

    Quantum and anharmonic effects are investigated in H{sub 2}-Li{sup +}-benzene, a model for hydrogen adsorption in metal-organic frameworks and carbon-based materials. Three- and 8-dimensional quantum diffusion Monte Carlo (QDMC) and rigid-body diffusion Monte Carlo (RBDMC) simulations are performed on potential energy surfaces interpolated from electronic structure calculations at the M05-2X/6-31+G(d,p) and M05-2X/6-311+G(2df,p) levels of theory using a three-dimensional spline or a modified Shepard interpolation. These calculations investigate the intermolecular interactions in this system, with three- and 8-dimensional 0 K H{sub 2} binding enthalpy estimates, ΔH{sub bind} (0 K), being 16.5 kJ mol{sup −1} and 12.4 kJ mol{sup −1}, respectively: 0.1 and 0.6 kJ mol{sup −1} higher than harmonic values. Zero-point energy effects are 35% of the value of ΔH{sub bind} (0 K) at M05-2X/6-311+G(2df,p) and cannot be neglected; uncorrected electronic binding energies overestimate ΔH{sub bind} (0 K) by at least 6 kJ mol{sup −1}. Harmonic intermolecular binding enthalpies can be corrected by treating the H{sub 2} “helicopter” and “ferris wheel” rotations as free and hindered rotations, respectively. These simple corrections yield results within 2% of the 8-dimensional anharmonic calculations. Nuclear ground state probability density histograms obtained from the QDMC and RBDMC simulations indicate the H{sub 2} molecule is delocalized above the Li{sup +}-benzene system at 0 K.

  2. Effect of hydrogen on plastic strain localization and fracture of steels

    NASA Astrophysics Data System (ADS)

    Nadjozhkin, M. V.; Lunev, A. G.; Li, Yu V.; Barannikova, S. A.

    2016-02-01

    The effect of interstitial hydrogen atoms on the mechanical properties and plastic strain localization patterns in tensile tested specimens of low-carbon steels have been studied using a double exposure speckle photography technique. It is found that the mechanical properties of low-carbon steels are affected adversely by hydrogen embrittlement. The deformation diagrams were examined for the deformed samples of low-carbon steels. These are found to show all the plastic flow stages: the linear, parabolic and pre-failure stages would occur for the respective values of the exponent n from the Ludwik-Holomon equation.

  3. Inactivation of aflatoxin B1 by using the synergistic effect of hydrogen peroxide and gamma radiation.

    PubMed Central

    Patel, U D; Govindarajan, P; Dave, P J

    1989-01-01

    Inactivation of aflatoxin B1 was studied by using gamma radiation and hydrogen peroxide. A 100-krad dose of gamma radiation was sufficient to inactivate 50 micrograms of aflatoxin B1 in the presence of 5% hydrogen peroxide, and 400 krad was required for total degradation of 100 micrograms of aflatoxin in the same system. Degradation of aflatoxin B1 was confirmed by high-pressure liquid chromatographic and thin-layer chromatographic analysis. Ames microsomal mutagenicity test showed loss of aflatoxin activity. This method of detoxification also reduces the toxin levels effectively in artificially contaminated groundnuts. Images PMID:2497710

  4. Effective interface state effects in hydrogenated amorphous-crystalline silicon heterostructures using ultraviolet laser photocarrier radiometry

    SciTech Connect

    Melnikov, A.; Mandelis, A.; Halliop, B.; Kherani, N. P.

    2013-12-28

    Ultraviolet photocarrier radiometry (UV-PCR) was used for the characterization of thin-film (nanolayer) intrinsic hydrogenated amorphous silicon (i-a-Si:H) on c-Si. The small absorption depth (approximately 10 nm at 355 nm laser excitation) leads to strong influence of the nanolayer parameters on the propagation and recombination of the photocarrier density wave (CDW) within the layer and the substrate. A theoretical PCR model including the presence of effective interface carrier traps was developed and used to evaluate the transport parameters of the substrate c-Si as well as those of the i-a-Si:H nanolayer. Unlike conventional optoelectronic characterization methods such as photoconductance, photovoltage, and photoluminescence, UV-PCR can be applied to more complete quantitative characterization of a-Si:H/c-Si heterojunction solar cells, including transport properties and defect structures. The quantitative results elucidate the strong effect of a front-surface passivating nanolayer on the transport properties of the entire structure as the result of effective a-Si:H/c-Si interface trap neutralization through occupation. A further dramatic improvement of those properties with the addition of a back-surface passivating nanolayer is observed and interpreted as the result of the interaction of the increased excess bulk CDW with, and more complete occupation and neutralization of, effective front interface traps.

  5. The effect of hydrogen embrittlement on the localized plastic deformation of aluminum alloy

    SciTech Connect

    Bochkareva, Anna Lunev, Aleksey; Barannikova, Svetlana; Gorbatenko, Vadim; Shlyakhova, Galina; Zuev, Lev

    2015-10-27

    The effect of hydrogen embrittlement on the localized plastic deformation of aluminum alloy D1 was investigated. The studies were performed for the test samples of aluminum alloy subjected to electrolytic hydrogenation. It is found that the mechanical properties and localized plastic deformation parameters of aluminum alloy are affected adversely by hydrogen embrittlement. The hydrogenated counterpart of alloy has a lower degree of ductility relative to the original alloy; however, the plastic flow behavior of material remains virtually unaffected. Using scanning electron and atomic force microscopy methods, the changes in the fracture surface were investigated. The deformation diagrams were examined for the deformed samples of aluminum alloy. These are found to show all the plastic flow stages: the linear, parabolic and pre-failure stages would occur for the respective values of the exponent n from the Ludwik-Holomon equation. Using digital speckle image technique, the local strain patterns were being registered for the original alloy D1 and the counterpart subjected to electrolytic hydrogenation for 100 h.

  6. GASEOUS HYDROGEN EFFECTS ON THE MECHANICAL PROPERTIES OF CARBON AND LOW ALLOY STEELS (U)

    SciTech Connect

    Lam, P

    2006-06-08

    This report is a compendium of sets of mechanical properties of carbon and low alloy steels following the short-term effects of hydrogen exposure. The property sets include the following: Yield Strength; Ultimate Tensile Strength; Uniform Elongation; Reduction of Area; Threshold Cracking, K{sub H} or K{sub th}; Fracture Toughness (K{sub IC}, J{sub IC}, and/or J-R Curve); and Fatigue Crack Growth (da/dN). These properties are drawn from literature sources under a variety of test methods and conditions. However, the collection of literature data is by no means complete, but the diversity of data and dependency of results in test method is sufficient to warrant a design and implementation of a thorough test program. The program would be needed to enable a defensible demonstration of structural integrity of a pressurized hydrogen system. It is essential that the environmental variables be well-defined (e.g., the applicable hydrogen gas pressure range and the test strain rate) and the specimen preparation be realistically consistent (such as the techniques to charge hydrogen and to maintain the hydrogen concentration in the specimens).

  7. The effect of hydrogen embrittlement on the localized plastic deformation of aluminum alloy

    NASA Astrophysics Data System (ADS)

    Bochkareva, Anna; Lunev, Aleksey; Barannikova, Svetlana; Gorbatenko, Vadim; Shlyakhova, Galina; Zuev, Lev

    2015-10-01

    The effect of hydrogen embrittlement on the localized plastic deformation of aluminum alloy D1 was investigated. The studies were performed for the test samples of aluminum alloy subjected to electrolytic hydrogenation. It is found that the mechanical properties and localized plastic deformation parameters of aluminum alloy are affected adversely by hydrogen embrittlement. The hydrogenated counterpart of alloy has a lower degree of ductility relative to the original alloy; however, the plastic flow behavior of material remains virtually unaffected. Using scanning electron and atomic force microscopy methods, the changes in the fracture surface were investigated. The deformation diagrams were examined for the deformed samples of aluminum alloy. These are found to show all the plastic flow stages: the linear, parabolic and pre-failure stages would occur for the respective values of the exponent n from the Ludwik-Holomon equation. Using digital speckle image technique, the local strain patterns were being registered for the original alloy D1 and the counterpart subjected to electrolytic hydrogenation for 100 h.

  8. Substrate and Transition State Binding in Alkaline Phosphatase Analyzed by Computation of Oxygen Isotope Effects.

    PubMed

    Roston, Daniel; Cui, Qiang

    2016-09-14

    Enzymes are powerful catalysts, and a thorough understanding of the sources of their catalytic power will facilitate many medical and industrial applications. Here we have studied the catalytic mechanism of alkaline phosphatase (AP), which is one of the most catalytically proficient enzymes known. We have used quantum mechanics calculations and hybrid quantum mechanics/molecular mechanics (QM/MM) simulations to model a variety of isotope effects relevant to the reaction of AP. We have calculated equilibrium isotope effects (EIEs), binding isotope effects (BIEs), and kinetic isotope effects (KIEs) for a range of phosphate mono- and diester substrates. The results agree well with experimental values, but the model for the reaction's transition state (TS) differs from the original interpretation of those experiments. Our model indicates that isotope effects on binding make important contributions to measured KIEs on V/K, which complicated interpretation of the measured values. Our results provide a detailed interpretation of the measured isotope effects and make predictions that can test the proposed model. The model indicates that the substrate is deformed in the ground state (GS) of the reaction and partially resembles the TS. The highly preorganized active site preferentially binds conformations that resemble the TS and not the GS, which induces the substrate to adapt to the enzyme, rather than the other way around-as with classic "induced fit" models. The preferential stabilization of the TS over the GS is what lowers the barrier to the chemical step. PMID:27541005

  9. Acetate production from lactose by Clostridium thermolacticum and hydrogen-scavenging microorganisms in continuous culture--effect of hydrogen partial pressure.

    PubMed

    Collet, Christophe; Gaudard, Olivier; Péringer, Paul; Schwitzguébel, Jean-Paul

    2005-08-22

    The effect of the addition of hydrogen-consuming microorganisms on the metabolism of Clostridium thermolacticum was studied. By growing this bacterium in continuous culture at 58 degrees C, on 29 mmol lactose l(-1) (10 gl(-1)) in the feed, with the H2-consuming microorganisms Methanothermobacter thermoautotrophicus and Moorella thermoautotrophica, the volumetric productivity of acetate was increased up to 3.9 mmol l(-1)h(-1) at a dilution rate of 0.058 h(-1). This was about three times higher than the maximal acetate volumetric productivity quantified when C. thermolacticum was cultivated alone. In the consortium, C. thermolacticum was the only species able to metabolize lactose; it produced not only acetate, but also hydrogen, carbon dioxide and lactate. The other species of the consortium were growing on these by-products. Meth. thermoautotrophicus played an important role as a very efficient hydrogen scavenger and decreased the hydrogen partial pressure drastically: hydrogen was converted to methane. Moor. thermoautotrophica converted lactate as well as hydrogen and carbon dioxide into acetate. As a consequence, lactose was efficiently consumed and the only organic product in the liquid phase was acetate. PMID:15992956

  10. Effect of Pd coating on hydrogen permeation of Ni-barium cerate mixed conductor.

    SciTech Connect

    Zhang, G.; Dorris, S.; Balachandran, U.; Liu, M.; Energy Technology; Georgia Inst. of Tech.

    2002-03-01

    Successful development of hydrogen separation membranes based on mixed ionic and electronic conductors will improve the economy of hydrogen production. For a gas separation process, interfacial polarization plays an increasingly important role as the ceramic membrane is made thinner to reduce the bulk resistance. In this paper, we report the effect of surface modification on surface properties of a composite membrane consisting of nickel and yttrium-doped barium cerate (Ni-BCY). The application of a Pd thin film on the surface of a Ni-BCY composite membrane significantly reduces the interfacial polarization resistance at temperatures from 500 to 900 C. The composition, morphology, and microstructure of the modified membrane surface dramatically influence the catalytic properties for hydrogen separation.

  11. Effect of Cadmium Plating Thickness on the Charpy Impact Energy of Hydrogen-Charged 4340 Steel

    NASA Astrophysics Data System (ADS)

    Es-Said, O. S.; Alcisto, J.; Guerra, J.; Jones, E.; Dominguez, A.; Hahn, M.; Ula, N.; Zeng, L.; Ramsey, B.; Mulazimoglu, H.; Li, Yong-Jun; Miller, M.; Alrashid, J.; Papakyriakou, M.; Kalnaus, S.; Lee, E. W.; Frazier, W. E.

    2016-07-01

    Hydrogen was intentionally introduced into ultra-high strength steel by cadmium plating. The purpose was to examine the effect of cadmium plate thickness and hence hydrogen on the impact energy of the steel. The AISI 4340 steel was austenitized at 1000 °C for 1 h, water quenched, and tempered at temperatures between 257 and 593 °C in order to achieve a range of targeted strength levels. The specimens were cadmium plated with 0.00508 mm (0.2 mils), 0.00762 mm (0.3 mils), and 0.0127 mm (0.5 mils). Results demonstrated that the uncharged specimens exhibited higher impact energy values when compared to the plated specimens at all tempering temperatures. The cadmium-plated specimens had very low Charpy impact values irrespective of their ultimate tensile strength values. The model of hydrogen transport by mobile dislocations to the fracture site appears to provide the most suitable explanation of the results.

  12. Carrier-envelope phase effects in few-cycle ionisation of atomic hydrogen

    NASA Astrophysics Data System (ADS)

    Kielpinski, David; Wallace, W. C.; Pullen, M. G.; Ghafur, O.; Laban, D. E.; Palmer, A. J.; Hanne, G. F.; Grum-Grzhimailo, A. N.; Bartschat, K.; Ivanov, I. A.; Kheifets, A. S.; Tong, X.-M.; Quiney, H. M.; Litvinyuk, I. V.; Sang, R. T.

    2012-06-01

    The control of strong-field photoionization with laser carrier-envelope phase (CEP) is the key enabling technique for attosecond science. Currently, quantitatively accurate ab initio simulations of this process can only be carried out for atomic hydrogen. We have observed CEP effects in the above-threshold ionisation of atomic hydrogen for the first time. The modulation due to CEP is mapped over a wide range of laser intensity and electron energy. The data is compared with ab initio simulations for the time dependent Schr"odinger equation carried out using three separate methodologies, as well as a semi-ab initio simulation method. We find reasonable agreement between experiment and all simulations over the entire sampled parameter space. Our results point the way toward accurate calibration of absolute laser CEP by means of the uniquely calculable hydrogen system.

  13. Effects of a transition to a hydrogen economy on employment in the United States Report to Congress

    SciTech Connect

    None, None

    2008-07-01

    DOE's Effects of a Transition to a Hydrogen Economy on Employment in the United States Report to Congress estimates the employment effects of a transformation of the U.S. economy to the use of hydrogen in the 2020 to 2050 timeframe. This report fulfills requirements of section 1820 of the Energy Policy Act of 2005.

  14. Solubility of hydrogen in metals and its effect of pore-formation and embrittlement. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Shahani, H. R.

    1984-01-01

    The effect of alloying elements on hydrogen solubility were determined by evaluating solubility equations and interaction coefficients. The solubility of dry hydrogen at one atmosphere was investigated in liquid aluminum, Al-Ti, Al-Si, Al-Fe, liquid gold, Au-Cu, and Au-Pd. The design of rapid heating and high pressure casting furnaces used in meta foam experiments is discussed as well as the mechanism of precipitation of pores in melts, and the effect of hydrogen on the shrinkage porosity of Al-Cu and Al-Si alloys. Hydrogen embrittlement in iron base alloys is also examined.

  15. Effect of BET Missense Mutations on Bromodomain Function, Inhibitor Binding and Stability

    PubMed Central

    Lori, Laura; Pasquo, Alessandra; Lori, Clorinda; Petrosino, Maria; Chiaraluce, Roberta; Tallant, Cynthia; Knapp, Stefan; Consalvi, Valerio

    2016-01-01

    Lysine acetylation is an important epigenetic mark regulating gene transcription and chromatin structure. Acetylated lysine residues are specifically recognized by bromodomains, small protein interaction modules that read these modification in a sequence and acetylation dependent way regulating the recruitment of transcriptional regulators and chromatin remodelling enzymes to acetylated sites in chromatin. Recent studies revealed that bromodomains are highly druggable protein interaction domains resulting in the development of a large number of bromodomain inhibitors. BET bromodomain inhibitors received a lot of attention in the oncology field resulting in the rapid translation of early BET bromodomain inhibitors into clinical studies. Here we investigated the effects of mutations present as polymorphism or found in cancer on BET bromodomain function and stability and the influence of these mutants on inhibitor binding. We found that most BET missense mutations localize to peripheral residues in the two terminal helices. Crystal structures showed that the three dimensional structure is not compromised by these mutations but mutations located in close proximity to the acetyl-lysine binding site modulate acetyl-lysine and inhibitor binding. Most mutations affect significantly protein stability and tertiary structure in solution, suggesting new interactions and an alternative network of protein-protein interconnection as a consequence of single amino acid substitution. To our knowledge this is the first report studying the effect of mutations on bromodomain function and inhibitor binding. PMID:27403962

  16. The neural correlates of age effects on verbal-spatial binding in working memory.

    PubMed

    Meier, Timothy B; Nair, Veena A; Meyerand, Mary E; Birn, Rasmus M; Prabhakaran, Vivek

    2014-06-01

    In this study, we investigated the neural correlates of age-related differences in the binding of verbal and spatial information utilizing event-related working memory tasks. Twenty-one right handed younger adults and twenty-one right handed older adults performed two versions of a dual task of verbal and spatial working memory. In the unbound dual task version letters and locations were presented simultaneously in separate locations, while in the bound dual task version each letter was paired with a specific location. In order to identify binding-specific differences, mixed-effects ANOVAs were run with the interaction of age and task as the effect of interest. Although older adults performed worse in the bound task than younger adults, there was no significant interaction between task and age on working memory performance. However, interactions of age and task were observed in brain activity analyses. Older adults did not display the greater unbound than bound task activity that younger adults did at the encoding phase in bilateral inferior parietal lobule, right putamen, and globus pallidus as well as at the maintenance phase in the cerebellum. We conclude that the binding of letters and locations in working memory is not as efficient in older adults as it is in younger adults, possibly due to the decline of cognitive control processes that are specific to working memory binding. PMID:24631396

  17. Effects of bromocriptine on (/sup 3/H)estradiol binding in cytosol of anterior pituitary

    SciTech Connect

    De Nicola, A.F.; Weisenberg, L.S.; Arakelian, M.C.; Libertun, C.

    1981-07-01

    The hypothalamus may control hormone receptors in the anterior pituitary either by a direct trophic effect or indirectly by regulation of serum pituitary hormone levels. Rats whose medial basal hypothalamus had been destroyed in order to suppress neural control of the gland showed a reduction in (/sup 3/H)estradiol binding in the anterior pituitary and high serum PRL levels; both changes were reversed by treatment of the lesioned rats with daily injections of bromocriptine, a dopamine agonist. In nonlesioned animals, the same treatment did not modify significantly those parameters. In another hyperprolactinemic model (rats with anterior pituitaries transplanted under the kidney capsule), (/sup 3/H)estradiol binding by the in situ pituitaries of the host rats was similar to that in the nongrafted controls. These results suggest that changes due to median eminence lesion are reversible and that bromocriptine is able to act as a substitutive therapy which restores binding of estradiol in glands whose receptors have been decreased by the effect of the lesion. High PRL levels due to pituitary transplant do not account for the observed changes in the pituitary estradiol binding.

  18. Calcium ion binding properties and the effect of phosphorylation on the intrinsically disordered Starmaker protein.

    PubMed

    Wojtas, Magdalena; Hołubowicz, Rafał; Poznar, Monika; Maciejewska, Marta; Ożyhar, Andrzej; Dobryszycki, Piotr

    2015-10-27

    Starmaker (Stm) is an intrinsically disordered protein (IDP) involved in otolith biomineralization in Danio rerio. Stm controls calcium carbonate crystal formation in vivo and in vitro. Phosphorylation of Stm affects its biomineralization properties. This study examined the effects of calcium ions and phosphorylation on the structure of Stm. We have shown that CK2 kinase phosphorylates 25 or 26 residues in Stm. Furthermore, we have demonstrated that Stm's affinity for calcium binding is dependent on its phosphorylation state. Phosphorylated Stm (StmP) has an estimated 30 ± 1 calcium binding sites per protein molecule with a dissociation constant (KD) of 61 ± 4 μM, while the unphosphorylated protein has 28 ± 3 sites and a KD of 210 ± 22 μM. Calcium ion binding induces a compaction of the Stm molecule, causing a significant decrease in its hydrodynamic radius and the formation of a secondary structure. The screening effect of Na(+) ions on calcium binding was also observed. Analysis of the hydrodynamic properties of Stm and StmP showed that Stm and StmP molecules adopt the structure of native coil-like proteins. PMID:26445027

  19. Effect of BET Missense Mutations on Bromodomain Function, Inhibitor Binding and Stability.

    PubMed

    Lori, Laura; Pasquo, Alessandra; Lori, Clorinda; Petrosino, Maria; Chiaraluce, Roberta; Tallant, Cynthia; Knapp, Stefan; Consalvi, Valerio

    2016-01-01

    Lysine acetylation is an important epigenetic mark regulating gene transcription and chromatin structure. Acetylated lysine residues are specifically recognized by bromodomains, small protein interaction modules that read these modification in a sequence and acetylation dependent way regulating the recruitment of transcriptional regulators and chromatin remodelling enzymes to acetylated sites in chromatin. Recent studies revealed that bromodomains are highly druggable protein interaction domains resulting in the development of a large number of bromodomain inhibitors. BET bromodomain inhibitors received a lot of attention in the oncology field resulting in the rapid translation of early BET bromodomain inhibitors into clinical studies. Here we investigated the effects of mutations present as polymorphism or found in cancer on BET bromodomain function and stability and the influence of these mutants on inhibitor binding. We found that most BET missense mutations localize to peripheral residues in the two terminal helices. Crystal structures showed that the three dimensional structure is not compromised by these mutations but mutations located in close proximity to the acetyl-lysine binding site modulate acetyl-lysine and inhibitor binding. Most mutations affect significantly protein stability and tertiary structure in solution, suggesting new interactions and an alternative network of protein-protein interconnection as a consequence of single amino acid substitution. To our knowledge this is the first report studying the effect of mutations on bromodomain function and inhibitor binding. PMID:27403962

  20. Effects of Plasma Hydrogenation on Trapping Properties of Dislocations in Heteroepitaxial InP/GaAs

    NASA Technical Reports Server (NTRS)

    Ringel, S. A.; Chatterjee, B.

    1994-01-01

    In previous work, we have demonstrated the effectiveness of a post-growth hydrogen plasma treatment for passivating the electrical activity of dislocations in metalorganic chemical vapor deposition (MOCVD) grown InP on GaAs substrates by a more than two order of magnitude reduction in deep level concentration and an improvement in reverse bias leakage current by a factor of approx. 20. These results make plasma hydrogenation an extremely promising technique for achieving high efficiency large area and light weight heteroepitaxial InP solar cells for space applications. In this work we investigate the carrier trapping process by dislocations in heteroepitaxial InP/GaAs and the role of hydrogen passivation on this process. It is shown that the charge trapping kinetics of dislocations after hydrogen passivation are significantly altered, approaching point defect-like behavior consistent with a transformation from a high concentration of dislocation-related defect bands within the InP bandgap to a low concentration of individual deep levels after hydrogen passivation. It is further shown that the "apparent" activation energies of dislocation related deep levels, before and after passivation, reduce by approx. 70 meV as DLTS fill pulse times are increased from 1 usec. to 1 msec. A model is proposed which explains these effects based on a reduction of Coulombic interaction between individual core sites along the dislocation cores by hydrogen incorporation. Knowledge of the trapping properties in these specific structures is important to develop optimum, low loss heteroepitaxial InP cells.

  1. Sensing (un)binding events via surface plasmons: effects of resonator geometry

    NASA Astrophysics Data System (ADS)

    Antosiewicz, Tomasz J.; Claudio, Virginia; Käll, Mikael

    2016-04-01

    The resonance conditions of localized surface plasmon resonances (LSPRs) can be perturbed in any number ways making plasmon nanoresonators viable tools in detection of e.g. phase changes, pH, gasses, and single molecules. Precise measurement via LSPR of molecular concentrations hinge on the ability to confidently count the number of molecules attached to a metal resonator and ideally to track binding and unbinding events in real-time. These two requirements make it necessary to rigorously quantify relations between the number of bound molecules and response of plasmonic sensors. This endeavor is hindered on the one hand by a spatially varying response of a given plasmonic nanosensor. On the other hand movement of molecules is determined by stochastic effects (Brownian motion) as well as deterministic flow, if present, in microfluidic channels. The combination of molecular dynamics and the electromagnetic response of the LSPR yield an uncertainty which is little understood and whose effect is often disregarded in quantitative sensing experiments. Using a combination of electromagnetic finite-difference time-domain (FDTD) calculations of the plasmon resonance peak shift of various metal nanosensors (disk, cone, rod, dimer) and stochastic diffusion-reaction simulations of biomolecular interactions on a sensor surface we clarify the interplay between position dependent binding probability and inhomogeneous sensitivity distribution. We show, how the statistical characteristics of the total signal upon molecular binding are determined. The proposed methodology is, in general, applicable to any sensor and any transduction mechanism, although the specifics of implementation will vary depending on circumstances. In this work we focus on elucidating how the interplay between electromagnetic and stochastic effects impacts the feasibility of employing particular shapes of plasmonic sensors for real-time monitoring of individual binding reactions or sensing low concentrations

  2. Effect of detergent binding on cytochrome P450 2B4 structure as analyzed by X-ray crystallography and deuterium-exchange mass spectrometry.

    PubMed

    Shah, Manish B; Jang, Hyun-Hee; Wilderman, P Ross; Lee, David; Li, Sheng; Zhang, Qinghai; Stout, C David; Halpert, James R

    2016-09-01

    Multiple crystal structures of CYP2B4 have demonstrated the binding of the detergent 5-cyclohexyl-1-pentyl-β-D-maltoside (CYMAL-5) in a peripheral pocket located adjacent to the active site. To explore the consequences of detergent binding, X-ray crystal structures of the peripheral pocket mutant CYP2B4 F202W were solved in the presence of hexaethylene glycol monooctyl ether (C8E6) and CYMAL-5. The structure in the presence of CYMAL-5 illustrated a closed conformation indistinguishable from the previously solved wild-type. In contrast, the F202W structure in the presence of C8E6 revealed a detergent molecule that coordinated the heme-iron and extended to the protein surface through the substrate access channel 2f. Despite the overall structural similarity of these detergent complexes, remarkable differences were observed in the A, A', and H helices, the F-G cassette, the C-D and β4 loop region. Hydrogen-deuterium exchange mass spectrometry (DXMS) was employed to probe these differences and to test the effect of detergents in solution. The presence of either detergent increased the H/D exchange rate across the plastic regions, and the results obtained by DXMS in solution were consistent in general with the relevant structural snapshots. The study provides insight into effect of detergent binding and the interpretation of associated conformational dynamics of CYP2B4. PMID:27280734

  3. Effects of Low Temperature on Hydrogen-Assisted Crack Growth in Forged 304L Austenitic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Jackson, Heather; San Marchi, Chris; Balch, Dorian; Somerday, Brian; Michael, Joseph

    2016-08-01

    The objective of this study was to evaluate effects of low temperature on hydrogen-assisted crack propagation in forged 304L austenitic stainless steel. Fracture initiation toughness and crack-growth resistance curves were measured using fracture mechanics specimens that were thermally precharged with 140 wppm hydrogen and tested at 293 K or 223 K (20 °C or -50 °C). Fracture initiation toughness for hydrogen-precharged forgings decreased by at least 50 to 80 pct relative to non-charged forgings. With hydrogen, low-temperature fracture initiation toughness decreased by 35 to 50 pct relative to room-temperature toughness. Crack growth without hydrogen at both temperatures was microstructure-independent and indistinguishable from blunting, while with hydrogen microcracks formed by growth and coalescence of microvoids. Initiation of microvoids in the presence of hydrogen occurred where localized deformation bands intersected grain boundaries and other deformation bands. Low temperature additionally promoted fracture initiation at annealing twin boundaries in the presence of hydrogen, which competed with deformation band intersections and grain boundaries as sites of microvoid formation and fracture initiation. A common ingredient for fracture initiation was stress concentration that arose from the intersection of deformation bands with these microstructural obstacles. The localized deformation responsible for producing stress concentrations at obstacles was intensified by low temperature and hydrogen. Crack orientation and forging strength were found to have a minor effect on fracture initiation toughness of hydrogen-supersaturated 304L forgings.

  4. Effects of Low Temperature on Hydrogen-Assisted Crack Growth in Forged 304L Austenitic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Jackson, Heather; San Marchi, Chris; Balch, Dorian; Somerday, Brian; Michael, Joseph

    2016-06-01

    The objective of this study was to evaluate effects of low temperature on hydrogen-assisted crack propagation in forged 304L austenitic stainless steel. Fracture initiation toughness and crack-growth resistance curves were measured using fracture mechanics specimens that were thermally precharged with 140 wppm hydrogen and tested at 293 K or 223 K (20 °C or -50 °C). Fracture initiation toughness for hydrogen-precharged forgings decreased by at least 50 to 80 pct relative to non-charged forgings. With hydrogen, low-temperature fracture initiation toughness decreased by 35 to 50 pct relative to room-temperature toughness. Crack growth without hydrogen at both temperatures was microstructure-independent and indistinguishable from blunting, while with hydrogen microcracks formed by growth and coalescence of microvoids. Initiation of microvoids in the presence of hydrogen occurred where localized deformation bands intersected grain boundaries and other deformation bands. Low temperature additionally promoted fracture initiation at annealing twin boundaries in the presence of hydrogen, which competed with deformation band intersections and grain boundaries as sites of microvoid formation and fracture initiation. A common ingredient for fracture initiation was stress concentration that arose from the intersection of deformation bands with these microstructural obstacles. The localized deformation responsible for producing stress concentrations at obstacles was intensified by low temperature and hydrogen. Crack orientation and forging strength were found to have a minor effect on fracture initiation toughness of hydrogen-supersaturated 304L forgings.

  5. Effects of laser radiation field on energies of hydrogen atom in plasmas

    NASA Astrophysics Data System (ADS)

    Bahar, M. K.

    2015-09-01

    In this study, for the first time, the Schrödinger equation with more general exponential cosine screened Coulomb (MGECSC) potential is solved numerically in the presence of laser radiation field within the Ehlotzky approximation using the asymptotic iteration method. The MGECSC potential includes four different potential forms in consideration of different sets of the parameters in the potential. By applying laser field, the total interaction potential of hydrogen atom embedded in plasmas converts to double well-type potential. The plasma screening effects under the influence of laser field as well as confinement effects of laser field on hydrogen atom in Debye and quantum plasmas are investigated by solving the Schrödinger equation with the laser-dressed MGECSC potential. It is resulted that since applying a monochromatic laser field on hydrogen atom embedded in a Debye and quantum plasma causes to shift in the profile of the total interaction potential, the confinement effects of laser field on hydrogen atom in plasmas modeled by the MGECSC potential change localizations of energy states.

  6. Effect of hydrogen on the multiaxial stress-strain behavior of titanium tubing

    SciTech Connect

    Lentz, C.W.; Koss, D.A.; Stout, M.G.

    1983-12-01

    The influence of internal hydrogen on the multiaxial stress-strain behavior of commercially pure titanium has been studied. Thin-walled tubing specimens containing either 20 or 1070 ppm hydrogen have been tested at constant stress ratios in combined tension and internal pressure. The addition of hydrogen lowers the yield strength for all loading paths but has no significant effect on the strain hardening behavior at strains greater than or equal to 0.02. Thus, the hydrogen embrittlement of titanium under plain strain or equibiaxial loading is not a consequence of changes of flow behavior. The yielding behavior of this anisotropic material is described well by Hill's (1950) quadratic yield criterion. As measured mechanically and by pole figure analysis, the plastic anisotropy changes with deformation in a manner which depends on stress state. Hill's criterion and the associated flow rule do not describe the multiaxial flow behavior well because of their inability to account for changes of texture which depend on multiaxial stress path. Hence a strain dependent, texture-induced strengthening effect in equibiaxial tension is observed, this effect having the form of an enhanced strain-hardening rate. 21 references.

  7. The influence of surface effects on the hydrogen absorption investigated on the V H model system

    NASA Astrophysics Data System (ADS)

    Müller, K.-H.; Paulus, H.; Kiss, G.

    2001-07-01

    The system V-O-H has been chosen as a model system to investigate surface effects on hydrogen absorption in metals. By means of XPS, SIMS, and thermal desorption mass spectrometry (TDMS) methods, the influence of oxygen segregated from the bulk as well as adsorbed from the gas phase has been pointed out. Segregated oxygen obstructs the hydrogen absorption, whereas non-stoichiometric and stoichiometric oxides have a preventing effect already with coverages in the range of monolayers. Ion bombardment in connection with sputter-cleaning or SNMS and SIMS analyses produces additional absorption sites in the surface near region for hydrogen. These can be populated by hydrogen from the gas phase during H 2 exposure or diffusing from the bulk, if the sample was H 2 loaded before. Beside elements like vanadium, there exist alloys (e.g. TiFe, LaNi 5, TiMn 2), which are particularly suitable for practical storage purposes. It is important for the further development of such alloys but also for a better understanding of absorption kinetics to investigate the influence of surface effects also on these alloys.

  8. Effects of laser radiation field on energies of hydrogen atom in plasmas

    SciTech Connect

    Bahar, M. K.

    2015-09-15

    In this study, for the first time, the Schrödinger equation with more general exponential cosine screened Coulomb (MGECSC) potential is solved numerically in the presence of laser radiation field within the Ehlotzky approximation using the asymptotic iteration method. The MGECSC potential includes four different potential forms in consideration of different sets of the parameters in the potential. By applying laser field, the total interaction potential of hydrogen atom embedded in plasmas converts to double well-type potential. The plasma screening effects under the influence of laser field as well as confinement effects of laser field on hydrogen atom in Debye and quantum plasmas are investigated by solving the Schrödinger equation with the laser-dressed MGECSC potential. It is resulted that since applying a monochromatic laser field on hydrogen atom embedded in a Debye and quantum plasma causes to shift in the profile of the total interaction potential, the confinement effects of laser field on hydrogen atom in plasmas modeled by the MGECSC potential change localizations of energy states.

  9. Protective Effect of Hydrogen Gas Therapy After Germinal Matrix Hemorrhage in Neonatal Rats

    PubMed Central

    Lekic, Tim; Manaenko, Anatol; Rolland, William; Fathali, Nancy; Peterson, Mathew; Tang, Jiping

    2013-01-01

    Background Germinal matrix hemorrhage (GMH) is a neurological disease of very low birth weight premature infants leading to post-hemorrhagic hydrocephalus, cerebral palsy, and mental retardation. Hydrogen (H2) is a potent antioxidant shown to selectively reverse cytotoxic oxygen-radical injury in the brain. This study investigated the therapeutic effect of hydrogen gas after neonatal GMH injury. Methods Neonatal rats underwent stereotaxic infusion of clostridial collagenase into the right germinal matrix brain region. Cognitive function was assessed at 3 weeks, and then sensorimotor function, cerebral, cardiac and splenic growths were measured 1 week thereafter. Results Hydrogen gas inhalation markedly suppressed mental retardation and cerebral palsy outcomes in rats at the juvenile developmental stage. The administration of H2 gas, early after neonatal GMH, also normalized the brain atrophy, splenomegaly and cardiac hypertrophy 1 month after injury. Conclusion This study supports the role of cytotoxic oxygen-radical injury in early neonatal GMH. Hydrogen gas inhalation is an effective strategy to help protect the infant brain from the post-hemorrhagic consequences of brain atrophy, mental retardation and cerebral palsy. Further studies are necessary to determine the mechanistic basis of these protective effects. PMID:21725762

  10. Deformation and fracture of aluminum-lithium alloys: The effect of dissolved hydrogen

    NASA Technical Reports Server (NTRS)

    Rivet, F. C.; Swanson, R. E.

    1990-01-01

    The effects of dissolved hydrogen on the mechanical properties of 2090 and 2219 alloys are studied. The work done during this semi-annual period consists of the hydrogen charging study and some preliminary mechanical tests. Prior to SIMS analysis, several potentiostatic and galvanostatic experiments were performed for various times (going from 10 minutes to several hours) in the cathodic zone, and for the two aqueous solutions: 0.04N of HCl and 0.1N NaOH both combined with a small amount of As2O3. A study of the surface damage was conducted in parallel with the charging experiments. Those tests were performed to choose the best charging conditions without surface damage. Disk rupture tests and tensile tests are part of the study designed to investigate the effect of temperature, surface roughness, strain rate, and environment on the fracture behavior. The importance of the roughness and environment were shown using the disk rupture test as well as the importance of the strain rate under hydrogen environment. The tensile tests, without hydrogen effects, have not shown significant differences between low and room temperature.

  11. Review on the effects of hydrogen at extreme pressures and temperatures on the mechanical behavior of polymers.

    SciTech Connect

    Hecht, Ethan S.

    2013-03-01

    The effects of hydrogen on the mechanics (e.g. strength, ductility, and fatigue resistance) of polymer materials are outlined in this report. There are a small number of studies reported in the literature on this topic, and even fewer at the extreme temperatures to which hydrogen service materials will be exposed. Several studies found little evidence that hydrogen affects the static tensile properties, long term creep, or ductile fracture of high density polyethylene or polyamide. However, there has been a report that a recoverable drop in the modulus of high density polyethylene is observable under high hydrogen pressure. A research need exists on the mechanical effects of hydrogen on the wide range of polymers used or considered for use in the hydrogen economy, due to the lack of data in the literature.

  12. Growth hormone (GH) binding and effects of GH analogs in transgenic mice

    SciTech Connect

    Bartke, A.; Steger, R.W.; Turyn, D.

    1994-12-31

    Overexpression of human (h) or bovine (b) growth hormone (GH) in transgenic mice is associated with marked (2- to 12-fold) and significant increase in hepatic binding of GH and prolactin (PRL). This is due to an increase in the number of GH and PRL receptors (GHR, PRLR) per mg of microsomal protein without changes in binding affinity. Comparison of results obtained in transgenic animals expressing bGH with a mouse metallothionein (MT) or a rat phosphoenolpyruvate carboxykinase (PEPCK) promoter suggests that effects of bGH on hepatic GHR and PRLR do not require GH overexpression during fetal life and, within the dose range tested, the effects on PRLR are not dose dependent. The increase in hepatic GHR was accompanied by significant increases in plasma GH-binding protein (GHBP) and in mean residence time of injected GH. Thus life-long elevation of peripheral GH levels alters the availability of both free GH and GHR. Site-directed in vitro mutagenesis was used to produce hGH and bGH analogs mutated within one of the sites involved in binding to GHR and PRLR. Mutating hGH to produce amino acid identity with bGH at Position 11, 18 (within Helix 1), 57, or 60 (within the loop between Helix 1 and 2) did not affect binding to GHR in vitro, or somatotropic activity in transgenic mice in vivo but reduced lactogenic activity in Nb{sub 2} cells by 22%-45%. Mutations of bGH designed to produce amino acid identity with hGH at one to four of the corresponding positions in the bGH molecule did not interfere with binding to GHR or somatotropic activity in vivo, and failed to produce significant binding to PRLR but resulted in alterations in the effects on the hypothalamic and anterior pituitary function in transgenic mice. Apparently region(s) outside the domains examined are essential for lactogenic activity of hGH, and different portions of the GH molecule are responsible for its diverse actions in vivo. 35 refs.

  13. Shape and Composition Effects on Photocatalytic Hydrogen Production for Pt-Pd Alloy Cocatalysts.

    PubMed

    Luo, Muhua; Lu, Pan; Yao, Weifeng; Huang, Cunping; Xu, Qunjie; Wu, Qiang; Kuwahara, Yasutaka; Yamashita, Hiromi

    2016-08-17

    The shape and composition effects of platinum-palladium (Pt-Pd) alloy nanoparticle cocatalysts on visible-light photocatalytic hydrogen evolution from an aqueous ammonium sulphite solution have been reported and discussed. The activity of Pt-Pd nanoparticles loaded Pt-Pd/CdS photocatalysts are affected based on both the Pt-Pd alloy nanoparticles' shape and their compositions. In this research, two shapes of Pt-Pd nanoparticles have been studied. One is Pt-Pd nanocubes enclosed by {100} crystal planes and the other is nano-octahedra covered with {111} crystal facets. Results show that the photocatalytic turnover frequency (TOF), defined as moles of hydrogen produced per surface mole of Pt-Pd metal atom per second, for Pt-Pd nanocubes/CdS (Pt-Pd NCs/CdS) photocatalyst can be 3.4 times more effective than Pt-Pd nano-octahedra/CdS (Pt-Pd NOTa/CdS) nanocomposite photocatalyst. Along with the shape effect, the atomic ratio of Pt to Pd can also impact the efficiency of Pt-Pd/CdS photocatalysts. When the Pt to Pd atomic ratio changes from 1:0 to about 2:1, the rate of hydrogen production increases from 900 μmol/h for Pt NCs/CdS catalyst to 1837 μmol/h for Pt-Pd (2:1) NCs/CdS photocatalyst-a 104% rate increase. This result suggests that the 33 mol % of more expensive Pt can be replaced with less costly Pd, resulting in a more than 100% hydrogen production rate increase. The finding of this research will lead to the research and development of highly effective catalysts for photocatalytic hydrogen production using solar photonic energy. PMID:27439590

  14. Collective vibrational effects in hydrogen bonded liquid amides and proteins studied by isotopic substitution

    NASA Astrophysics Data System (ADS)

    Nielsen, O. F.; Johansson, C.; Christensen, D. H.; Hvidt, S.; Flink, J.; Høime Hansen, S.; Poulsen, F.

    2000-09-01

    Raman spectroscopy is used to study the fast dynamics of simple liquid amides and proteins. Raman spectra in the visible region of liquid amides are obtained with a triple additive scanning monochromator, whereas FT-Raman technique is used in the near-IR region in order to avoid fluorescence from impurities in the proteins. Raman spectra are shown in the amide-I region of HCONHCH 3 ( N-methylformamide with all isotopes in their natural abundance), H 13CONHCH 3, HC 18ONHCH 3, human growth hormone, frog tropomyosin and chymotrypsin inhibitor 2 including C-13 and N-15 enriched samples of the latter. Resonance energy transfer (RET) between amide molecules gives rise to a non-coincidence effect of the anisotropic and the isotropic components of the amide-I band. This effect influences the band position in mixtures of liquid amide isotopomers. A further spectral feature caused by collective vibrational modes in the hydrogen bonded liquid amides is named coalescence of bands in mixtures of isotopomers (CBMI). The result of this effect is that only one band is found in mixtures of isotopomers where bands at different frequencies are observed for each of the isotopomers. A similar effect may account for the observation of protein amide-I bands with frequencies dependent only on the secondary structure of the protein and not on the amino acid residues. RET and CBMI are due to a collectivity of vibrational modes in different amide molecules. This collectivity may be related to a cooperativity of hydrogen bonds. A low-frequency band around 100 cm -1 is observed in hydrogen bonded liquid amides and proteins. Isotopic substitution shows that the mode corresponding to this band involves displacements of atoms in hydrogen bonds. This mode may drive a breaking of the hydrogen bond.

  15. Stability of surface and subsurface hydrogen on and in Au/Ni near-surface alloys

    NASA Astrophysics Data System (ADS)

    Celik, Fuat E.; Mavrikakis, Manos

    2015-10-01

    Periodic, self-consistent DFT-GGA (PW91) calculations were used to study the interaction of hydrogen atoms with the (111) surfaces of substitutional near-surface alloys (NSAs) of Au and Ni with different surface layer compositions and different arrangements of Au atoms in the surface layer. The effect of hydrogen adsorption on the surface and in the first and second subsurface layers of the NSAs was studied. Increasing the Au content in the surface layer weakens hydrogen binding on the surface, but strengthens subsurface binding, suggesting that the distribution of surface and subsurface hydrogen will be different than that on pure Ni(111). While the metal composition of the surface layer has an effect on the binding energy of hydrogen on NSA surfaces, the local composition of the binding site has a stronger effect. For example, fcc hollow sites consisting of three Ni atoms bind H nearly as strongly as on Ni(111), and fcc sites consisting of three Au atoms bind H nearly as weakly as on Au(111). Sites with one or two Au atoms show intermediate binding energies. The preference of hydrogen for three-fold Ni hollow sites alters the relative stabilities of different surface metal atom arrangements, and may provide a driving force for adsorbate-induced surface rearrangement.

  16. Stability of Surface and Subsurface Hydrogen on and in Au/Ni Near-Surface Alloys

    SciTech Connect

    Celik, Fuat E.; Mavrikakis, Manos

    2015-10-01

    Periodic, self-consistent DFT-GGA (PW91) calculations were used to study the interaction of hydrogen atoms with the (111) surfaces of substitutional near-surface alloys (NSAs) of Au and Ni with different surface layer compositions and different arrangements of Au atoms in the surface layer. The effect of hydrogen adsorption on the surface and in the first and second subsurface layers of the NSAs was studied. Increasing the Au content in the surface layer weakens hydrogen binding on the surface, but strengthens subsurface binding, suggesting that the distribution of surface and subsurface hydrogen will be different than that on pure Ni(111). While the metal composition of the surface layer has an effect on the binding energy of hydrogen on NSA surfaces, the local composition of the binding site has a stronger effect. For example, fcc hollow sites consisting of three Ni atoms bind H nearly as strongly as on Ni(111), and fcc sites consisting of three Au atoms bind H nearly as weakly as on Au(111). Sites with one or two Au atoms show intermediate binding energies. The preference of hydrogen for three-fold Ni hollow sites alters the relative stabilities of different surface metal atom arrangements, and may provide a driving force for adsorbate-induced surface rearrangement.

  17. Effect of corticosteroid binding proteins on the steroidogenic activity of bovine adrenocortical cell suspensions.

    PubMed

    Basset, M; Rostaing-Metz, B; Chambaz, E M

    1982-07-01

    The possible role of steroid binding proteins in the hormonal secretion process of a steroidogenic tissue was examined using bovine adrenocortical cell suspensions, either under basal conditions or in the presence of half-maximally active concentration (1 x 10(-9) M) of synthetic adrenocorticotropic hormone (ACTH). Three types of plasma cortisol binding proteins were used, namely bovine serum albumine (BSA), purified transcortin (CBG) and purified anticortisol immunoglobulins (IgG). When added to the incubation medium, CBG (at 1 x 10(-10) to 2 x 10(-9) M cortisol binding sites) and anticortisol IgG (at 4.8 x 10(-10) to 3 x 10(-9) M cortisol binding sites) did not influence either the basal nor the ACTH-stimulated net cortisol production of the cell preparations. Whereas crystallized and delipidated BSA showed also no effect, crude commercial BSA preparation (Cohn fraction V) exhibited an ACTH-like cofactor effect which resulted in a marked increase in the net cortisol production by stimulated cells. These observations might be explained by the presence in crude BSA of lipoprotein-cholesterol complexes, possibly acting as an extracellular source of cholesterol available for corticosteroidogenesis. It may be concluded that specific high affinity cortisol binding systems present outside adrenocortical steroidogenic cells do not influence their secretory activity under short term in vitro condition. In addition, it can be stressed that use of ill defined protein preparations (e.g. crude BSA) may lead to artifactual observations in the study of the differentiated functions of isolated steroidogenic cells. PMID:6287106

  18. Binding Selectivity of Abaloparatide for PTH-Type-1-Receptor Conformations and Effects on Downstream Signaling.

    PubMed

    Hattersley, Gary; Dean, Thomas; Corbin, Braden A; Bahar, Hila; Gardella, Thomas J

    2016-01-01

    The PTH receptor type 1 (PTHR1) mediates the actions of two endogenous polypeptide ligands, PTH and PTHrP, and thereby plays key roles in bone biology. Based on its capacity to stimulate bone formation, the peptide fragment PTH (1-34) is currently in use as therapy for osteoporosis. Abaloparatide (ABL) is a novel synthetic analog of human PTHrP (1-34) that holds promise as a new osteoporosis therapy, as studies in animals suggest that it can stimulate bone formation with less of the accompanying bone resorption and hypercalcemic effects that can occur with PTH (1-34). Recent studies in vitro suggest that certain PTH or PTHrP ligand analogs can distinguish between two high-affinity PTHR1 conformations, R(0) and RG, and that efficient binding to R(0) results in prolonged signaling responses in cells and prolonged calcemic responses in animals, whereas selective binding to RG results in more transient responses. As intermittent PTH ligand action is known to favor the bone-formation response, whereas continuous ligand action favors the net bone-resorption/calcemic response, we hypothesized that ABL binds more selectively to the RG vs the R(0) PTHR1 conformation than does PTH (1-34), and thus induces more transient signaling responses in cells. We show that ABL indeed binds with greater selectivity to the RG conformation than does PTH (1-34), and as a result of this RG bias, ABL mediates more transient cAMP responses in PTHR1-expressing cells. The findings provide a plausible mechanism (ie, transient signaling via RG-selective binding) that can help account for the favorable anabolic effects that ABL has on bone. PMID:26562265

  19. Effects of conformational ordering on protein/polyelectrolyte electrostatic complexation: ionic binding and chain stiffening.

    PubMed

    Cao, Yiping; Fang, Yapeng; Nishinari, Katsuyoshi; Phillips, Glyn O

    2016-01-01

    Coupling of electrostatic complexation with conformational transition is rather general in protein/polyelectrolyte interaction and has important implications in many biological processes and practical applications. This work studied the electrostatic complexation between κ-carrageenan (κ-car) and type B gelatin, and analyzed the effects of the conformational ordering of κ-car induced upon cooling in the presence of potassium chloride (KCl) or tetramethylammonium iodide (Me4NI). Experimental results showed that the effects of conformational ordering on protein/polyelectrolyte electrostatic complexation can be decomposed into ionic binding and chain stiffening. At the initial stage of conformational ordering, electrostatic complexation can be either suppressed or enhanced due to the ionic bindings of K(+) and I(-) ions, which significantly alter the charge density of κ-car or occupy the binding sites of gelatin. Beyond a certain stage of conformational ordering, i.e., helix content θ > 0.30, the effect of chain stiffening, accompanied with a rapid increase in helix length ζ, becomes dominant and tends to dissociate the electrostatic complexation. The effect of chain stiffening can be theoretically interpreted in terms of double helix association. PMID:27030165

  20. Effects of conformational ordering on protein/polyelectrolyte electrostatic complexation: ionic binding and chain stiffening

    NASA Astrophysics Data System (ADS)

    Cao, Yiping; Fang, Yapeng; Nishinari, Katsuyoshi; Phillips, Glyn O.

    2016-03-01

    Coupling of electrostatic complexation with conformational transition is rather general in protein/polyelectrolyte interaction and has important implications in many biological processes and practical applications. This work studied the electrostatic complexation between κ-carrageenan (κ-car) and type B gelatin, and analyzed the effects of the conformational ordering of κ-car induced upon cooling in the presence of potassium chloride (KCl) or tetramethylammonium iodide (Me4NI). Experimental results showed that the effects of conformational ordering on protein/polyelectrolyte electrostatic complexation can be decomposed into ionic binding and chain stiffening. At the initial stage of conformational ordering, electrostatic complexation can be either suppressed or enhanced due to the ionic bindings of K+ and I‑ ions, which significantly alter the charge density of κ-car or occupy the binding sites of gelatin. Beyond a certain stage of conformational ordering, i.e., helix content θ > 0.30, the effect of chain stiffening, accompanied with a rapid increase in helix length ζ, becomes dominant and tends to dissociate the electrostatic complexation. The effect of chain stiffening can be theoretically interpreted in terms of double helix association.

  1. Effects of conformational ordering on protein/polyelectrolyte electrostatic complexation: ionic binding and chain stiffening

    PubMed Central

    Cao, Yiping; Fang, Yapeng; Nishinari, Katsuyoshi; Phillips, Glyn O.

    2016-01-01

    Coupling of electrostatic complexation with conformational transition is rather general in protein/polyelectrolyte interaction and has important implications in many biological processes and practical applications. This work studied the electrostatic complexation between κ-carrageenan (κ-car) and type B gelatin, and analyzed the effects of the conformational ordering of κ-car induced upon cooling in the presence of potassium chloride (KCl) or tetramethylammonium iodide (Me4NI). Experimental results showed that the effects of conformational ordering on protein/polyelectrolyte electrostatic complexation can be decomposed into ionic binding and chain stiffening. At the initial stage of conformational ordering, electrostatic complexation can be either suppressed or enhanced due to the ionic bindings of K+ and I− ions, which significantly alter the charge density of κ-car or occupy the binding sites of gelatin. Beyond a certain stage of conformational ordering, i.e., helix content θ > 0.30, the effect of chain stiffening, accompanied with a rapid increase in helix length ζ, becomes dominant and tends to dissociate the electrostatic complexation. The effect of chain stiffening can be theoretically interpreted in terms of double helix association. PMID:27030165

  2. Effect of temperature and temperature shock on the stability of continuous cellulosic-hydrogen fermentation.

    PubMed

    Gadow, Samir I; Jiang, Hongyu; Watanabe, Ryoya; Li, Yu-You

    2013-08-01

    Three continuous stirred tank reactors (CSTR) were operated under mesophilic (37 ± 1°C), thermophilic (55 ± 1°C) and hyper-thermophilic (80 ± 1°C) temperatures for 164 days to investigate the effect of temperature and temperature shock on the cellulosic-dark hydrogen fermentation by mixed microflora. During steady state condition, the sudden decreases in the fermentation temperature occurred twice in each condition for 24h. The results show that the 55 ± 1 and 80 ± 1°C presented stable hydrogen yields of 12.28 and 9.72 mmol/g cellulose, respectively. However, the 37 ± 1°C presented low hydrogen yield of 3.56 mmol/g cellulose and methane yield of 5.4 mmol/g cellulose. The reactor performance under 55 ± 1 or 80 ± 1°C appeared to be more resilient to the sudden decreases in the fermentation temperature than 37 ± 1°C. The experimental analysis results indicated that the changing in soluble by-products could explain the effect of temperature and temperature shock, and the thermophilic temperature is expected having a better economic performance for cellulosic-hydrogen fermentation. PMID:23747441

  3. Effect of low-energy hydrogen ion implantation on dendritic web silicon solar cells

    NASA Technical Reports Server (NTRS)

    Rohatgi, A.; Meier, D. L.; Rai-Choudhury, P.; Fonash, S. J.; Singh, R.

    1986-01-01

    The effect of a low-energy (0.4 keV), short-time (2-min), heavy-dose (10 to the 18th/sq cm) hydrogen ion implant on dendritic web silicon solar cells and material was investigated. Such an implant was observed to improve the cell open-circuit voltage and short-circuit current appreciably for a number of cells. In spite of the low implant energy, measurements of internal quantum efficiency indicate that it is the base of the cell, rather than the emitter, which benefits from the hydrogen implant. This is supported by the observation that the measured minority-carrier diffusion length in the base did not change when the emitter was removed. In some cases, a threefold increase of the base diffusion length was observed after implantation. The effects of the hydrogen implantation were not changed by a thermal stress test at 250 C for 111 h in nitrogen. It is speculated that hydrogen enters the bulk by traveling along dislocations, as proposed recently for edge-defined film-fed growth silicon ribbon.

  4. Effect of silane/hydrogen ratio on microcrystalline silicon thin films by remote inductively coupled plasma

    NASA Astrophysics Data System (ADS)

    Guo, Y. N.; Wei, D. Y.; Xiao, S. Q.; Huang, S. Y.; Zhou, H. P.; Xu, S.

    2013-05-01

    Hydrogenated microcrystalline silicon (μc-Si:H) thin films were prepared by remote low frequency inductively coupled plasma (ICP) chemical vapor deposition system, and the effect of silane/hydrogen ratio on the microstructure and electrical properties of μc-Si:H films was systematically investigated. As silane/hydrogen ratio increases, the crystalline volume fraction Fc decreases and the ratio of the intensity of (220) peak to that of (111) peak drops as silane flow rate is increased. The FTIR result indicates that the μc-Si:H films prepared by remote ICP have a high optical response with a low hydrogen content, which is in favor of reducing light-induced degradation effect. Furthermore, the processing window of the phase transition region for remote ICP is much wider than that for typical ICP. The photosensitivity of μc-Si:H films can exceed 100 at the transition region and this ensures the possibility of the fabrication of microcrystalline silicon thin film solar cells with a open-circuit voltage of about 700 mV.

  5. Synergistic Effects of Alloying and Thiolate Modification in Furfural Hydrogenation over Cu-Based Catalysts.

    PubMed

    Pang, Simon H; Love, Nicole E; Medlin, J Will

    2014-12-01

    Control of bimetallic surface composition and surface modification with self-assembled monolayers (SAMs) represent two methods for modifying catalyst activity and selectivity. However, possible synergistic effects of employing these strategies in concert have not been previously explored. We investigated the effects of modifying Cu/Al2O3 catalysts by alloying with Ni and modifying with octadecanethiol (C18) SAMs, using furfural hydrogenation as a probe reaction. Incorporation of small amounts of Ni (Cu4Ni) improved catalytic activity while slightly reducing hydrogenation selectivity. Further incorporation of Ni resulted in high rates for decarbonylation and ring-opening. Modification of the Cu4Ni catalyst with C18-SAMs resulted in improvement in both the activity and hydrogenation selectivity. X-ray photoelectron spectroscopy experiments on bimetallic thin films and density functional theory calculations revealed that the C18-SAM kinetically stabilized Cu at the surface under hydrogenation conditions. These results indicate that thiolate monolayers can be used to control surface bimetallic composition to improve catalytic performance. PMID:26278941

  6. Effect of carbon on hydrogen desorption and absorption of mechanically milled MgH 2

    NASA Astrophysics Data System (ADS)

    Shang, C. X.; Guo, Z. X.

    The use of MgH 2, instead of pure Mg, in the mechanical synthesis of Mg-based hydrogen storage materials offers added benefit to powder size refinement and reduced oxygen contamination. Alloying additions can further improve the sorption kinetics at a relatively low temperature. This paper examines the effect of graphitic carbon on the desorption and absorption of MgH 2. Graphite powder of different concentrations were mechanically milled with MgH 2 particles. The milled powder was characterised by XRD, SEM and simultaneous TG and DSC techniques. The results show that graphite poses little influence on the desorption properties of MgH 2. However, it does benefit the absorption process, leading to rapid hydrogen uptake in the re-hydrogenated sample. After dehydrogenation, 5 wt.% of hydrogen was re-absorbed within 30 min at 250 °C for the ( MgH 2+10 G) mixture prior-milled for 8 h, while only 0.8 wt.% for the pure MgH 2 milled for 8 h, the effect may be attributed to the interaction between crystalline graphite with H 2 disassociation close to the MgH 2 or Mg surface. Moreover, graphite can also inhibit the formation of a new oxide layer on the surface of Mg particles.

  7. Effects of carbohydrate, protein and lipid content of organic waste on hydrogen production and fermentation products.

    PubMed

    Alibardi, Luca; Cossu, Raffaello

    2016-01-01

    Organic waste from municipalities, food waste and agro-industrial residues are ideal feedstocks for use in biological conversion processes in biorefinery chains, representing biodegradable materials containing a series of substances belonging to the three main groups of the organic matter: carbohydrates, proteins and lipids. Biological hydrogen production by dark fermentation may assume a central role in the biorefinery concept, representing an up-front treatment for organic waste capable of hydrolysing complex organics and producing biohydrogen. This research study was aimed at evaluating the effects of carbohydrate, protein and lipid content of organic waste on hydrogen yields, volatile fatty acid production and carbon-fate. Biogas and hydrogen productions were linearly correlated to carbohydrate content of substrates while proteins and lipids failed to produce significant contributions. Chemical composition also produced effects on the final products of dark fermentation. Acetic and butyric acids were the main fermentation products, with their ratio proving to correlate with carbohydrate and protein content. The results obtained in this research study enhance the understanding of data variability on hydrogen yields from organic waste. Detailed information on waste composition and chemical characterisation are essential to clearly identify the potential performances of the dark fermentation process. PMID:26254676

  8. Effect of ultrasonic pre-treatment of thermomechanical pulp on hydrogen peroxide bleaching

    NASA Astrophysics Data System (ADS)

    Loranger, E.; Charles, A.; Daneault, C.

    2012-12-01

    Ultrasound pre-treatments of softwood TMP had been carried to evaluate its impact on the efficiency of hydrogen peroxide bleaching. The trials were performed after a factorial design of experiment using frequency, power and time as variables. The experiments were conducted in an ultrasonic bath and then bleached with hydrogen peroxide. Measurements such as brightness, L*A*B* color system coordinate, residual hydrogen peroxide and metal content were evaluated on bleached pulp. The results indicate that the effect of ultrasonic treatment on brightness was dependent on the ultrasound frequency used; the brightness increased slightly at 68 kHz and decreased at 40 and 170 kHz. These results were correlated to the ultrasound effect on the generation of transition metals (copper, iron and manganese) which are responsible for catalytic decomposition of hydrogen peroxide. The influence of metal interference was minimized by using a chelating agent such as diethylene triamine pentaacetic acid (DTPA). With the results obtained in this study we have identified a set of option conditions, e.g. 1000 W, 40 kHz, 1.5 % consistency and 0.2% addition of DTPA prior to the bleaching stage (after ultrasonic pre-treatment) who improve brightness by 2.5 %ISO.

  9. Start Up of Biohydrogen Production System and Effect of Metal Ions on Hydrogen Production

    NASA Astrophysics Data System (ADS)

    Jiao, An-ying; Li, Yong-feng; Yue, Li-ran; Yang, Chuan-ping

    2010-11-01

    Fermentative hydrogen production is a promising biochemical route to produce renewable H2. The effect of organic loading rate on the biohydrogen production during the start-up phase and effect of Fe2+ and Mg2+ concentration on biohydrogen production of a continuous stirred tank reactor using molasses wastewater as substrate were investigated. It was found that an initial biomass of 14.07 gVSS/L and an organic loading rate of 6.0 kgCOD/m3ṡd, an equilibrial microbial community in the butyric-type fermentation could be established with in 30 days. It was demonstrated that both Fe2+ and Mg2+ were able to enhance the hydrogen production capacity of microorganism flora. Different concentration of Fe2+ was added to the biohydrogen producing system (50 mg/L, 100 mg/L, 200 mg/L and 500 mg/L), the maximum biogas production yield of 6.78 L/d and the maximum specific hydrogen production rate of 10.1 ml/gVSSṡh were obtained at Fe2+ concentration of 500 mg/L and 200 mg/L, respectively. The maximum biogas production yield of 6.84 L/d and the maximum specific hydrogen production rate of 10.2 ml/gVSSṡh were obtained at Mg2+ concentration of 100 mg/L and 50 mg/L, respectively.

  10. Protective effect of hydrogen sulfide on renal injury in the experimental unilateral ureteral obstruction

    PubMed Central

    Dursun, Murat; Otunctemur, Alper; Ozbek, Emin; Sahin, Suleyman; Besiroglu, Huseyin; Ozsoy, Ozgur Doga; Cekmen, Mustafa; Somay, Adnan; Ozbay, Nurver

    2015-01-01

    ABSTRACT Introduction/Objective: Ureteral obstruction is a common pathology and causes kidney fibrosis and dysfunction at late period. In this present study, we investigated the antifibrotic and antiinflammatory effects of hydrogen sulfide on kidney damage after unilateral ureteral obstruction (UUO) in rats. Materials and Methods: 24 rats were divided into four groups. Group 1 was control, group 2 was sham, group 3 included rats with UUO and group 4 rats with UUO which were given sodium hydrogen sulfide (NaHS)-exogenous donor of hydrogen sulfide (intraperitoneally 56μmoL/kg/day). After 14 days, rats were killed and their kidneys were taken and blood analysis was performed. Tubular necrosis, mononuclear cell infiltration and interstitial fibrosis were determined histopathologically in a part of the kidneys; nitric oxide (NO), malondialdehyde (MDA) and reduced glutathione (GSH) levels were determined in the other part of the kidneys. Urea-creatinine levels were investigated by blood analysis. Statistical analyses were made by the Chi-square test and one-way analysis of variance (ANOVA). Results: There was no significantly difference for urea-creatinine levels among groups. Pathologically, there was serious tubular necrosis and fibrosis in group 3 and there was significantly decreasing of tubular necrosis and fibrosis in group 4 (p<0.005). Also, there was significantly increase of NO and MDA levels and decrease of GSH levels in group 3 compared to other groups (p<0.005). Conclusions: hydrogen sulfide prevents kidney damage with antioxidant and antiinflammatory effect. PMID:26742979

  11. Modulation of the chloroplast ATPase by tight ADP binding. Effect of uncouplers and ATP.

    PubMed

    Bar-Zvi, D; Shavit, N

    1982-12-01

    Inactivation of the membrane-bound ATPase by tight ADP binding was studied under nonenergized conditions. The energy state of the system was controlled either by omitting MgCl2, preventing ATP hydrolysis, or by addition of an uncoupler which dissipates the delta mu H+. In the absence of Mg2+, ATP prevents the inactivation of the enzyme by ADP, in a competitive manner. This effect of ATP resembles that of GDP with Mg2+ present. In the presence of nigericin, Mg2+, and ATP, inactivation occurs after a 10-15-sec interval, during which the enzyme is able to hydrolyze ATP at a relatively rapid rate. The degree of inactivation is proportional to the level of bound ADP detected. This behavior is different from that of the coupled ATPase (no uncoupler added), where inactivation is attained only upon exhaustion of the ATP by its hydrolysis, despite the finding that ADP binds tightly to the active ATPase at all stages of the reaction. Higher levels of tightly bound ADP were detected in the presence of an uncoupler. We suggest that the interval during which the enzyme becomes inactive is that required for the enzyme to generate and bind ADP, and to change from the active to the inactive conformation. These results support the mechanism suggested previously for the modulation of the ATPase by tight nucleotide binding. PMID:6219104

  12. Partial MHC class II constructs inhibit MIF/CD74 binding and downstream effects.

    PubMed

    Benedek, Gil; Meza-Romero, Roberto; Andrew, Shayne; Leng, Lin; Burrows, Gregory G; Bourdette, Dennis; Offner, Halina; Bucala, Richard; Vandenbark, Arthur A

    2013-05-01

    MIF and its receptor, CD74, are pivotal regulators of the immune system. Here, we demonstrate for the first time that partial MHC class II constructs comprised of linked β1α1 domains with covalently attached antigenic peptides (also referred to as recombinant T-cell receptor ligands - RTLs) can inhibit MIF activity by not only blocking the binding of rhMIF to immunopurified CD74, but also downregulating CD74 cell-surface expression. This bifunctional inhibition of MIF/CD74 interactions blocked downstream MIF effects, including enhanced secretion of proinflammatory cytokines, anti-apoptotic activity, and inhibition of random migration that all contribute to the reversal of clinical and histological signs of EAE. Moreover, we demonstrate that enhanced CD74 cell-surface expression on monocytes in mice with EAE and subjects with multiple sclerosis can be downregulated by humanized RTLs, resulting in reduced MIF binding to the cells. Thus, binding of partial MHC complexes to CD74 blocks both the accessibility and availability of CD74 for MIF binding and downstream inflammatory activity. PMID:23576302

  13. Effect of diet on insulin binding and glucose transport in rat sarcolemmal vesicles

    SciTech Connect

    Grimditch, G.K.; Barnard, R.J.; Sternlicht, E.; Whitson, R.H.; Kaplan, S.A.

    1987-03-01

    The purpose of this study was to compare the effects of a high-fat, high-sucrose diet (HFS) and a low-fat, high-complex carbohydrate diet (LFC) on glucose tolerance, insulin binding, and glucose transport in rat skeletal muscle. During the intravenous glucose tolerance test, peak glucose values at 5 min were significantly higher in the HFS group; 0-, 20-, and 60-min values were similar. Insulin values were significantly higher in the HFS group at all time points (except 60 min), indicating whole-body insulin resistance. Skeletal muscle was responsible, in part, for this insulin resistance, because specific D-glucose transport in isolated sarcolemmal (SL) vesicles under basal conditions was similar between LFC and HFS rats, despite the higher plasma insulin levels. Scatchard analyses of insulin binding curves to sarcolemmal vesicles revealed that the K/sub a/ of the high-affinity binding sites was significantly reduced by the HFS diet; no other binding changes were noted. Specific D-glucose transport in SL vesicles after maximum insulin stimulation (1 U/kg) was significantly depressed in the HFS group, indicating that HFS feeding also caused a postbinding defect. These results indicate that the insulin resistance in skeletal muscle associated with a HFS diet is due to both a decrease in the K/sub a/ of the high-affinity insulin receptors and a postbinding defect.

  14. Control of glycolytic enzyme binding: effect of changing enzyme substrate concentrations on in vivo enzyme distributions.

    PubMed

    Brooks, S P; Storey, K B

    1993-05-12

    The effect of changing concentrations of glycolytic intermediates on the binding of phosphofructokinase, aldolase and pyruvate kinase to cellular particulate matter was investigated. Concentrations of glycolytic intermediates were altered by adding 2 mM iodoacetic acid (IAA) to an incubation medium containing tissues isolated from the channelled whelk Busycon canaliculatum. Iodoacetic acid inhibited glyceraldehyde 3-phosphate dehydrogenase activity causing a 100-400 fold increase in the concentration of fructose 1,6-bisphosphate as well as 3-20 fold increases in glucose 6-phosphate, fructose 6-phosphate, and dihydroxyacetone phosphate levels depending on the experimental protocol. Cellular pH values were not statistically different in the presence of IAA. Measurement of enzyme binding to particulate matter showed that the binding of phosphofructokinase, aldolase and pyruvate kinase was unaffected by iodoacetic acid under any experimental condition. These results show that changes in the tissue concentrations of enzyme substrates and products do not regulate enzyme binding to particulate matter in the cell. PMID:8350861

  15. Partial MHC class II constructs inhibit MIF/CD74 binding and downstream effects

    PubMed Central

    Benedek, Gil; Meza-Romero, Roberto; Andrew, Shayne; Leng, Lin; Burrows, Gregory G.; Bourdette, Dennis; Offner, Halina; Bucala, Richard; Vandenbark, Arthur A.

    2013-01-01

    Macrophage migration inhibitory factor (MIF) and its receptor, CD74, are pivotal regulators of the immune system. Here we demonstrate for the first time that partial MHC class II constructs comprised of linked β1α1 domains with covalently attached antigenic peptides (also referred to as recombinant T-cell receptor ligands - RTLs) can inhibit MIF activity by not only blocking the binding of rhMIF to immunopurified CD74, but also down-regulating CD74 cell-surface expression. This bi-functional inhibition of MIF/CD74 interactions blocked downstream MIF effects, including enhanced secretion of proinflammatory cytokines, anti-apoptotic activity and inhibition of random migration that all contribute to the reversal of clinical and histological signs of experimental autoimmune encephalomyelitis (EAE). Moreover, we demonstrate that enhanced CD74 cell surface expression on monocytes in mice with EAE and subjects with multiple sclerosis (MS) can be down-regulated by humanized RTLs, resulting in reduced MIF binding to the cells. Thus, binding of partial MHC complexes to CD74 blocks both the accessibility and availability of CD74 for MIF binding and downstream inflammatory activity. PMID:23576302

  16. Comparison of Binding Properties and Early Biological Effects of Elicitins in Tobacco Cells1

    PubMed Central

    Bourque, Stéphane; Ponchet, Michel; Binet, Marie-Noëlle; Ricci, Pierre; Pugin, Alain; Lebrun-Garcia, Angela

    1998-01-01

    Elicitins are a family of small proteins secreted by Phytophthora species that have a high degree of homology and elicit defense reactions in tobacco (Nicotiana tabacum). They display acidic or basic characteristics, the acidic elicitins being less efficient in inducing plant necrosis. In this study we compared the binding properties of four elicitins (two basic and two acidic) and early-induced signal transduction events (Ca2+ influx, extracellular medium alkalinization, and active oxygen species production). The affinity for tobacco plasma membrane-binding sites and the number of binding sites were similar for all four elicitins. Furthermore, elicitins compete with one another for binding sites, suggesting that they interact with the same receptor. The four elicitins induced Ca2+ influx, extracellular medium alkalinization, and the production of active oxygen species in tobacco cell suspensions, but the intensity and kinetics of these effects were different from one elicitin to another. As a general observation the concentrations that induce similar levels of biological activities were lower for basic elicitins (with the exception of cinnamomin-induced Ca2+ uptake). The qualitative similarity of early events induced by elicitins indicates a common transduction scheme, whereas fine signal transduction tuning is different in each elicitin. PMID:9847105

  17. The effect of hyperthyroidism on opiate receptor binding and pain sensitivity

    SciTech Connect

    Edmondson, E.A. ); Bonnet, K.A.; Friedhoff, A.J. )

    1990-01-01

    This study was conducted to determine the effect of thyroid hormone on opiate receptor ligand-binding and pain sensitivity. Specific opiate receptor-binding was performed on brain homogenates of Swiss-Webster mice. There was a significant increase in {sup 3}H-naloxone-binding in thyroxine-fed subjects (hyperthyroid). Scatchard analysis revealed that the number of opiate receptors was increased in hyperthyroid mice (Bmax = 0.238 nM for hyperthyroid samples vs. 0.174 nM for controls). Binding affinity was unaffected (Kd = 1.54 nM for hyperthyroid and 1.58 nM for control samples). When mice were subjected to hotplate stimulation, the hyperthyroid mice were noted to be more sensitive as judged by pain aversion response latencies which were half that of control animals. After morphine administration, the hyperthyroid animals demonstrated a shorter duration of analgesia. These findings demonstrate that thyroxine increases opiate receptor number and native pain sensitivity but decreases the duration of analgesia from morphine.

  18. Inverse Ubbelohde effect in the short hydrogen bond of photosystem II: Relation between H/D isotope effect and symmetry in potential energy profile.

    PubMed

    Kanematsu, Yusuke; Tachikawa, Masanori; Takano, Yu

    2016-09-01

    The short hydrogen bond between tyrosine Yz and D1-His190 of photosystem II (PSII) was investigated using multicomponent quantum mechanics, where the quantum fluctuation of a hydrogen nucleus was incorporated into electronic structure calculation. Our computation demonstrated that the deuteration for hydrogen in the short hydrogen bond of PSII led to the reduction of the O…N distance. It indicated an inverse Ubbelohde effect typically recognized in strong and symmetric hydrogen-bonding clusters such as FHF(-) and H3O2-. We confirmed that the relation between the geometric isotope effect and the symmetry of the potential energy profile of FHF(-) was reasonably agreed with that of PSII. According to this agreement, the short hydrogen bond in PSII can be regarded as a short strong hydrogen bond. © 2016 Wiley Periodicals, Inc. PMID:27349328

  19. Protein binding of chlorpromazine in vivo and in vitro: effect of chlorpromazine metabolite on chlorpromazine protein binding in rat.

    PubMed

    Sato, S; Koshiro, A

    1995-04-01

    The serum protein binding curve of chlorpromazine (CPZ) on the Scatchard plot in vitro was a two-phase downward curve. However, after i.v. administration of CPZ the curve was altered to an upward curve. To clarify the reasons for these in vivo changes, the influence of chlorpromazine S-oxide (CPZSO), chlorpromazine N-oxide (CPZNO), desmethylchlorpromazine (nor1-CPZ), chlorpromazine sulfone (sul-CPZ) and 7-hydroxychlorpromazine (7-OH-CPZ) on CPZ protein binding were studied in vitro. The results indicated that the characteristics of the CPZ protein binding are altered by the combination of CPZSO or CPZNO or by either of them. Since it was very difficult to explain the relationship between serum total and free concentrations of CPZ in vivo using mass-balance equations like Hill's equation or a competitive inhibition equation on the multiple binding sites for drug, the correlation between the ratio ot total concentration of CPZ metabolites and CPZ (CPZSO/CPZ or CPZNO/CPZ) and the free fraction of CPZ was examined using the in vitro and in vivo data. The correlation between the ratio of CPZSO/CPZ and the free fraction of CPZ was good in both the in vivo and the in vitro studies. There was no statistically significant difference between the population regression coefficient of the two studies. The values of the slope and the intercept became almost the same as those obtained using the in vivo studies when combined with CPZNO.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7655433

  20. Theoretical study of binding interactions and vibrational Raman spectra of water in hydrogen-bonded anionic complexes: (H2O)n- (n = 2 and 3), H2O...X- (X = F, Cl, Br, and I), and H2O...M- (M = Cu, Ag, and Au).

    PubMed

    Wu, De-Yin; Duan, Sai; Liu, Xiu-Min; Xu, Yong-Chun; Jiang, Yu-Xiong; Ren, Bin; Xu, Xin; Lin, S H; Tian, Zhong-Qun

    2008-02-14

    Binding interactions and Raman spectra of water in hydrogen-bonded anionic complexes have been studied by using the hybrid density functional theory method (B3LYP) and ab initio (MP2) method. In order to explore the influence of hydrogen bond interactions and the anionic effect on the Raman intensities of water, model complexes, such as the negatively charged water clusters ((H2O)n-, n = 2 and 3), the water...halide anions (H2O...X-, X = F, Cl, Br, and I), and the water-metal atom anionic complexes (H2O...M-, M = Cu, Ag, and Au), have been employed in the present calculations. These model complexes contained different types of hydrogen bonds, such as O-H...X-, O-H...M-, O-H...O, and O-H...e-. In particular, the last one is a dipole-bound electron involved in the anionic water clusters. Our results showed that there exists a large enhancement in the off-resonance Raman intensities of both the H-O-H bending mode and the hydrogen-bonded O-H stretching mode, and the enhancement factor is more significant for the former than for the latter. The reasons for these spectral properties can be attributed to the strong polarization effect of the proton acceptors (X-, M-, O, and e-) in these hydrogen-bonded complexes. We proposed that the strong Raman signal of the H-O-H bending mode may be used as a fingerprint to address the local microstructures of water molecules in the chemical and biological systems. PMID:18215023

  1. Beneficial Effects of Hydrogen-Rich Saline on Early Burn-Wound Progression in Rats

    PubMed Central

    Guo, Song Xue; Jin, Yun Yun; Fang, Quan; You, Chuan Gang; Wang, Xin Gang; Hu, Xin Lei; Han, Chun-Mao

    2015-01-01

    Introduction Deep burn wounds undergo a dynamic process known as wound progression that results in a deepening and extension of the initial burn area. The zone of stasis is more likely to develop more severe during wound progression in the presence of hypoperfusion. Hydrogen has been reported to alleviate injury triggered by ischaemia/reperfusion and burns in various organs by selectively quenching oxygen free radicals. The aim of this study was to investigate the possible protective effects of hydrogen against early burn-wound progression. Methods Deep-burn models were established through contact with a boiled, rectangular, brass comb for 20 s. Fifty-six Sprague-Dawley rats were randomly divided into sham, burn plus saline, and burn plus hydrogen-rich saline (HS) groups with sacrifice and analysis at various time windows (6 h, 24 h, 48 h) post burn. Indexes of oxidative stress, apoptosis and autophagy were measured in each group. The zone of stasis was evaluated using immunofluorescence staining, ELISA, and Western blot to explore the underlying effects and mechanisms post burn. Results The burn-induced increase in malondialdehyde was markedly reduced with HS, while the activities of endogenous antioxidant enzymes were significantly increased. Moreover, HS treatment attenuated increases in apoptosis and autophagy postburn in wounds, according to the TUNEL staining results and the expression analysis of Bax, Bcl-2, caspase-3, Beclin-1 and Atg-5 proteins. Additionally, HS lowered the level of myeloperoxidase and expression of TNF-α, IL-1β, and IL-6 in the zone of stasis while augmenting IL-10. The elevated levels of Akt phosphorylation and NF-κB p65 expression post burn were also downregulated by HS management. Conclusion Hydrogen can attenuate early wound progression following deep burn injury. The beneficial effect of hydrogen was mediated by attenuating oxidative stress, which inhibited apoptosis and inflammation, and the Akt/NF-κB signalling pathway may be

  2. Hydrogen/Deuterium Exchange Kinetics Demonstrate Long Range Allosteric Effects of Thumb Site 2 Inhibitors of Hepatitis C Viral RNA-dependent RNA Polymerase.

    PubMed

    Deredge, Daniel; Li, Jiawen; Johnson, Kenneth A; Wintrode, Patrick L

    2016-05-01

    New nonnucleoside analogs are being developed as part of a multi-drug regimen to treat hepatitis C viral infections. Particularly promising are inhibitors that bind to the surface of the thumb domain of the viral RNA-dependent RNA polymerase (NS5B). Numerous crystal structures have been solved showing small molecule non-nucleoside inhibitors bound to the hepatitis C viral polymerase, but these structures alone do not define the mechanism of inhibition. Our prior kinetic analysis showed that nonnucleoside inhibitors binding to thumb site-2 (NNI2) do not block initiation or elongation of RNA synthesis; rather, they block the transition from the initiation to elongation, which is thought to proceed with significant structural rearrangement of the enzyme-RNA complex. Here we have mapped the effect of three NNI2 inhibitors on the conformational dynamics of the enzyme using hydrogen/deuterium exchange kinetics. All three inhibitors rigidify an extensive allosteric network extending >40 Å from the binding site, thus providing a structural rationale for the observed disruption of the transition from distributive initiation to processive elongation. The two more potent inhibitors also suppress slow cooperative unfolding in the fingers extension-thumb interface and primer grip, which may contribute their stronger inhibition. These results establish that NNI2 inhibitors act through long range allosteric effects, reveal important conformational changes underlying normal polymerase function, and point the way to the design of more effective allosteric inhibitors that exploit this new information. PMID:27006396

  3. Voluntary action and tactile sensory feedback in the intentional binding effect.

    PubMed

    Zhao, Ke; Hu, Li; Qu, Fangbing; Cui, Qian; Piao, Qiuhong; Xu, Hui; Li, Yanyan; Wang, Liang; Fu, Xiaolan

    2016-08-01

    The intentional binding effect refers to a subjective compression over a temporal interval between the start point initialized by a voluntary action and the endpoint signaled by an external sensory (visual or audio) feedback. The present study aimed to explore the influence of tactile sensory feedback on this binding effect by comparing voluntary key-press actions with voluntary key-release actions. In experiment 1, each participant was instructed to report the perceived interval (in ms) between an action and the subsequent visual sensory feedback. In this task, either the action (key-press or key-release) was voluntarily performed by the participant or a kinematically identical movement was passively applied to the left index finger of the participant. In experiment 2, we explored whether the difference in the perception of time was affected by the direction of action. In experiment 3, we developed an apparatus in which two parallel laser beams were generated by a laser emission unit and detected by a laser receiver unit; this allowed the movement of the left index finger to be detected without it touching a keyboard (i.e., without any tactile sensory feedback). Convergent results from all of the experiments showed that the temporal binding effect was only observed when the action was both voluntary and involved physical contact with the key, suggesting that the combination of intention and tactile sensory feedback, as a form of top-down processing, likely distracted attention from temporal events and caused the different binding effects. PMID:27038203

  4. Assessment of shock effects on amphibole water contents and hydrogen isotope compositions: 1. Amphibolite experiments

    NASA Astrophysics Data System (ADS)

    Minitti, Michelle E.; Rutherford, Malcolm J.; Taylor, Bruce E.; Dyar, M. Darby; Schultz, Peter H.

    2008-02-01

    ). Extrapolating the shock signature of the regrouped data to grains that experienced Martian meteorite-like shock pressures suggests that shock-induced water losses and hydrogen isotope enrichments could approach 1 wt.% H 2O and Δ D = + 100‰, respectively. If these values are valid, then impact shock effects could explain a substantial fraction of the low water contents and variable hydrogen isotope compositions of the Martian meteorite kaersutites.

  5. Effect of B-site europium doping on the hydrogen transport properties of barium cerate

    NASA Astrophysics Data System (ADS)

    Rhodes, James Michael

    Barium cerate doped with europium on the Ce-site (B-site of the ABO3 perovskite structure) has been investigated as a potential material for hydrogen separation. Barium cerate doped with 15 mol% europium (BaCe0.85Eu0.15O3-delta) demonstrated higher electrical conductivity in a hydrogen-containing gas stream than gadolinium-doped barium cerate (BaCe0.85Gd0.15O3-delta), which was known to have one of the highest conductivities (0.027 S/cm 2 compared to 0.021 S/cm2 at 800°C). For europium dopant levels between 5 to 25 mol%, the sample doped with 15 mol% demonstrated higher electrical conductivities in dry forming gas (4% H2/96% N2) dry air, and wet nitrogen. The activation energies in dry air (˜0.60 eV) were indicative of p-type electronic conduction, and the activation energies in hydrogen-containing gases (˜0.35--0.45 eV) were indicative of protonic conduction. With BaCe0.85Eu0.15O3-delta , the onset of n-type electronic conductivity necessary for hydrogen separation was shown to occur at ˜600°C. A gas-tight glass seal was developed to study the hydrogen permeation properties of BaCe0.85Eu0.15O3-delta. The glass seal was a composite of a glass containing strontium oxide, boron oxide, silicon oxide, aluminum oxide, and lanthanum oxide mixed with doped barium cerate powder. The seal would form at temperatures >875°C, allowing for testing down to 650°C. The effect of temperature, feed-side hydrogen partial pressure, and membrane thickness on hydrogen permeation flux of BaCe0.85Eu0.15O 3-delta was investigated. For the range of thicknesses studied (0.75 to 2.00 mm), the performance of BaCe0.85Eu0.15O 3-delta membranes is under mixed control of bulk diffusion and surface kinetics. This mixed control indicates that investigating BaCe 0.85Eu0.15O3-delta membranes thinner than 0.75 mm would result in a limited increase in hydrogen permeation flux unless measures were taken to improve surface kinetics. The need for improved surface kinetics was confirmed when surface

  6. Effect of odd hydrogen on ozone depletion by chlorine reactions

    NASA Technical Reports Server (NTRS)

    Donahue, T. M.; Cicerone, R. J.; Liu, S. C.; Chameides, W. L.

    1976-01-01

    The present paper discusses how the shape of the ozone layer changes under the influence of injected ClX for several choices of two key HOx reaction rates. The two HOx reactions are: OH + HO2 yields H2O + O2 and O + HO2 yields OH + O2. Results of calculations are presented which show that the two reaction rates determine the stratospheric concentrations of OH and HO2, and that these concentrations regulate the amount by which the stratospheric ozone column can be reduced due to injections of odd chlorine. It is concluded that the amount of ozone reduction by a given mixing ratio of ClX will remain very uncertain until the significance of several possible feedback effects involving HOx in a chlorine-polluted atmosphere are determined and measurements of the reaction rates and HOx concentrations are made at the relevant temperatures.

  7. Probing nucleotide-binding effects on backbone dynamics and folding of the nucleotide-binding domain of the sarcoplasmic/endoplasmic-reticulum Ca2+-ATPase.

    PubMed Central

    Abu-Abed, Mona; Millet, Oscar; MacLennan, David H; Ikura, Mitsuhiko

    2004-01-01

    In muscle cells, SERCA (sarcoplasmic/endoplasmic-reticulum Ca2+-ATPase) plays a key role in restoring cytoplasmic Ca2+ levels to resting concentrations after transient surges caused by excitation-coupling cycles. The mechanism by which Ca2+ is translocated to the lumen of the ER (endoplasmic reticulum) involves major conformational rearrangements among the three cytoplasmic domains: actuator (A), nucleotide-binding (N) and phosphorylation (P) domains; and within the transmembrane Ca2+-binding domain of SERCA. CD, fluorescence spectroscopy and NMR spectroscopy were used in the present study to probe the conformation and stability of the isolated N domain of SERCA (SERCA-N), in the presence and absence of AMP-PNP (adenosine 5'-[beta,gamma-imido]triphosphate). CD and tryptophan fluorescence spectroscopy results established that the effects of nucleotide binding were not readily manifested on the global fold and structural stability of SERCA-N. 15N-backbone-relaxation experiments revealed site-specific changes in backbone dynamics that converge on the central beta-sheet domain. Nucleotide binding produced diverse effects on dynamics, with enhanced mobility observed for Ile369, Cys420, Arg467, Asp568, Phe593 and Gly598, whereas rigidifying effects were found for Ser383, Leu419, Thr484 and Thr532. These results demonstrate that the overall fold and backbone motional properties of SERCA-N remained essentially the same in the presence of AMP-PNP, yet revealing evidence for internal counter-balancing effects on backbone dynamics upon binding the nucleotide, which propagate through the central beta-sheet. PMID:14987197

  8. Effects of hydrogen adsorption on the properties of double wall BN and (BN)xCy nanotubes

    NASA Astrophysics Data System (ADS)

    Freitas, A.; Azevedo, S.; Kaschny, J. R.

    2016-01-01

    In the present contribution, we apply first-principles calculations, based on the density functional theory, to study the effects of hydrogen adsorption on the structural and electronic properties of boron nitride and hybrid carbon-boron nitride double wall nanotubes. The results demonstrate that the hydrogen decoration induces significant structural deformation and an appreciable reduction in the gap energy. When the number of hydrogen atoms introduced on the outer wall is increased, desorption of hydrogen pairs are observed. The calculations indicate that each adsorbed hydrogen atom induces a structural deformation with an energetic cost of about 68 meV/atom. It is also found that the introduction of hydrogen atoms can be applied as an efficient tool for tuning the electronic properties of such structures.

  9. Effects of Buoyancy in Hydrogen Jet Diffusion Flames

    NASA Technical Reports Server (NTRS)

    Agrawal, A. K.; Al-Ammar, K.; Gollahalli, S. R.; Griffin, D. W.

    1999-01-01

    This project was carried out to understand the effects of heat release and buoyancy on the flame structure of diffusion flames. Experiments were conducted at atmospheric pressure in both normal gravity and microgravity conditions in the NASA LeRC 2.2 s drop tower. Experiments were also conducted in a variable pressure combustion facility in normal gravity to scale buoyancy and thus, to supplement the drop tower experiments. Pure H2 or H2 mixed with He was used as the jet fluid to avoid the complexities associated with soot formation. Fuel jet burning in quiescent air was visualized and quantified by the Rainbow Schlieren Deflectometry (RSD) to obtain scalar profiles (temperature, oxygen concentration) within the flame. Burner tube diameter (d) was varied from 0.3 to 1.19 mm producing jet exit Reynolds numbers ranging from 40 to 1900, and generating flames encompassing laminar and transitional (laminar to turbulent) flow structure. Some experiments were also complemented with the CFD analysis. In a previous paper, we have presented details of the RSD technique, comparison of computed and measured scalar distributions, and effects of buoyancy on laminar and transitional H2 gas-jet diffusion flames. Results obtained from the RSD technique, variable pressure combustion chamber, and theoretical models have been published. Subsequently, we have developed a new drop rig with improved optical and image acquisition. In this set up, the schlieren images are acquired in real time and stored digitally in RAM of an onboard computer. This paper deals with laminar diffusion flames of pure H2 in normal and microgravity.

  10. Strain Effects on Enhanced Hydrogen Sulphide Detection Capability of Ag-DECORATED Defective Graphene: a First-Principles Investigation

    NASA Astrophysics Data System (ADS)

    Qin, Xian; Meng, Qingyuan; Feng, Yuan Ping

    2012-10-01

    Strain effects on hydrogen sulphide (H2S) adsorption on Ag-decorated Stone-Wales (SW) defect in graphene were investigated by density functional theory calculations. The results indicate that an Ag adatom is easily pinned chemically on the top of the most stretched C-C bond at the SW defect in graphene without mechanical strains. A modest uniform tensile strain (8%) applied in defective graphene greatly increases the binding energy of Ag by 44%, indicating the strain enhanced stabilization of Ag on SW defect. Using the resulting Ag-decorated defective graphene (Ag-SW-g) composite as a model for H2S molecule detection, we found that the tensile strain has little effects on the interaction between the molecule and the composite, and the adsorption energies of H2S around 1.6 eV which is six times larger than that on pristine graphene are produced. The enhanced H2S adsorption on Ag-SW-g is attributed to charge transfer from the molecule to the graphene through the bridge-like Ag adatom. In addition, the electronic property of the Ag-SW-g under different strains changes from a metallic state to a semiconductor state upon H2S adsorption, which should lead to an observable change in its conductivity. These findings pave the way for future development of graphene-based gas sensor.

  11. Effect of platinum nanoparticle deposition parameters on hydrogen peroxide transduction for applications in wearable electrochemical glucose biosensors

    NASA Astrophysics Data System (ADS)

    Cargill, Allison A.; Neil, Kathrine M.; Hondred, John A.; McLamore, Eric S.; Claussen, Jonathan C.

    2016-05-01

    Enhanced interest in wearable biosensor technology over the past decade is directly related to the increasing prevalence of diabetes and the associated requirement of daily blood glucose monitoring. In this work we investigate the platinum-carbon transduction element used in traditional first-generation glucose biosensors which rely on the concentration of hydrogen peroxide produced by the glucose-glucose oxidase binding scheme. We electrodeposit platinum nanoparticles on a commercially-available screen printed carbon electrode by stepping an applied current between 0 and 7.12 mA/cm2 for a varying number of cycles. Next, we examine the trends in deposition and the effect that the number of deposition cycles has on the sensitivity of electrochemical glucose sensing. Results from this work indicate that applying platinum nanoparticles to screen printed carbon via electrodeposition from a metal salt solution improves overall biosensor sensitivity. This work also pinpoints the amount of platinum (i.e., number of deposition cycles) that maximizes biosensor sensitivity in an effort to minimize the use of the precious metals, viz., platinum, in electrode fabrication. In summary, this work quantifies the relationship between platinum electrodeposition and sensor performance, which is crucial in designing and producing cost-effective sensors.

  12. [Transthyretin-binding activity of hexabromocyclododecanes (HBCDs) and its thyroid hormone disrupting effects after developmental exposure].

    PubMed

    Ji, Xiu-Ling; Liu, Yang; Liu, Fang; Lu, Yue; Zhong, Gao-Ren

    2010-09-01

    In vivo and in vitro research approaches were carried out to survey the potential health risk of environmental exposure by hexabromocyclododecanes (HBCDs). Transthyretin-binding assay was designed to test for the potency of HBCDs to compete with thyroxine (T4) for binding to the transport protein. The results showed that the binding of 25I-T4 and T4 was only slightly inhabited even at the highest competitive concentration of HBCDs (75.08%, 80 micromol x L(-1)), indicating the marginally interfere potency of HBCDs in the transportation of T4. Sprague-Dawley rats of 3-days old were exposed to 0.2 mg/kg and 1 mg/kg HBCDs for 21 d to examine the thyroid hormones (THs) disrupting effects of HBCDs after developmental exposure. Compared with the controls, levels of total 3,3',5-triiodothyronine (TT3), free 3,3',5-triiodothyronine (FT3), increased significantly (p < 0.05, p < 0.05) in low- and high-dose exposures, thyroid stimulating hormone (TSH) also increased slightly while the total thyroxine (TT4), free thyroxine (FT4) had a decline about two-fold inversely. Combined both the in vivo and in vitro results, the possible mode of action of HBCDs on THs disruption may through the synergy or substitution effect of T3. The findings support further investigation of the potential THs disrupting effects of HBCDs on public health, especially on children during brain development. PMID:21072945

  13. Exciton Binding energies and effective masses in Organo-lead Tri-Halide Perovskites

    NASA Astrophysics Data System (ADS)

    Portugall, Oliver; Miyata, Atsuhiko; Mitioglu, Anatol; Plochocka, Paulina; Wang, Jacob Tse-Wei; Stranks, Samuel; Snaith, Henry; Nicholas, Robin; Lncmi Toulouse Team; Oxford University Team

    2015-03-01

    Solid-state perovskite-based solar cells have made a dramatic impact on emerging PV research with efficiencies of over 17% already achieved. However, to date the basic electronic properties of the perovskites such as the electron and hole effective masses and the exciton binding energy are not well known. We have measured both for methyl ammonium lead tri-iodide using magneto absorption in very high magnetic fields up to 150T showing that the exciton binding energy at low temperatures is only 16 meV, a value three times smaller than previously thought and sufficiently small to completely transform the way in which the devices must operate. Landau level spectroscopy shows that the reduced effective mass of 0.104 me is also smaller than previously thought. In addition by using a fast pulse 150T magnet we measure the band structure change due to the structural phase transition that occurs in this system at around 160K. We also observe Landau levels in the high temperature phase as used for device production, which has a very similar effective mass and the analysis suggests an exciton binding energy which is even smaller than in the low temperature phase.

  14. Effects of Local Protein Environment on the Binding of Diatomic Molecules to Heme in Myoglobins. DFT and Dispersion-Corrected DFT Studies

    PubMed Central

    Liao, Meng-Sheng; Huang, Ming-Ju; Watts, John D.

    2013-01-01

    The heme-AB binding energies (AB = CO, O2) in a wild-type myoglobin (Mb) and two mutants (H64L, V68N) of Mb have been investigated in detail with both DFT and dispersioncorrected DFT methods, where H64L and V68N represent two different, opposite situations. Several dispersion correction approaches were tested in the calculations. The effects of the local protein environment were accounted for by including the five nearest surrounding residues in the calculated systems. The specific role of histidine-64 in the distal pocket was examined in more detail in this study than in other studies in the literature. Although the present calculated results do not change the previous conclusion that the hydrogen bonding by the distal histidine-64 residue plays a major role in the O2/CO discrimination by Mb, more details about the interaction between the protein environment and the bound ligand have been revealed in this study by comparing the binding energies of AB to a porphyrin and the various myoglobins. The changes in the experimental binding energies from one system to another are well reproduced by the calculations. Without constraints on the residues in geometry optimization, the dispersion correction is necessary, since it improves the calculated structures and energetic results significantly. PMID:23661270

  15. Ice-binding mechanism of winter flounder antifreeze proteins.

    PubMed Central

    Cheng, A; Merz, K M

    1997-01-01

    We have studied the winter flounder antifreeze protein (AFP) and two of its mutants using molecular dynamics simulation techniques. The simulations were performed under four conditions: in the gas phase, solvated by water, adsorbed on the ice (2021) crystal plane in the gas phase and in aqueous solution. This study provided details of the ice-binding pattern of the winter flounder AFP. Simulation results indicated that the Asp, Asn, and Thr residues in the AFP are important in ice binding and that Asn and Thr as a group bind cooperatively to the ice surface. These ice-binding residues can be collected into four distinct ice-binding regions: Asp-1/Thr-2/Asp-5, Thr-13/Asn-16, Thr-24/Asn-27, and Thr-35/Arg-37. These four regions are 11 residues apart and the repeat distance between them matches the ice lattice constant along the (1102) direction. This match is crucial to ensure that all four groups can interact with the ice surface simultaneously, thereby, enhancing ice binding. These Asx (x = p or n)/Thr regions each form 5-6 hydrogen bonds with the ice surface: Asn forms about three hydrogen bonds with ice molecules located in the step region while Thr forms one to two hydrogen bonds with the ice molecules in the ridge of the (2021) crystal plane. Both the distance between Thr and Asn and the ordering of the two residues are crucial for effective ice binding. The proper sequence is necessary to generate a binding surface that is compatible with the ice surface topology, thus providing a perfect "host/guest" interaction that simultaneously satisfies both hydrogen bonding and van der Waals interactions. The results also show the relation among binding energy, the number of hydrogen bonds, and the activity. The activity is correlated to the binding energy, and in the case of the mutants we have studied the number of hydrogen bonds. The greater the number of the hydrogen bonds the greater the antifreeze activity. The roles van der Waals interactions and the hydrophobic

  16. Effects of class I heparin binding growth factor and fibronectin on platelet adhesion and aggregation

    SciTech Connect

    Greisler, H.P.; Klosak, J.J.; Steinam, S.J.; Lam, T.M.; Burgess, W.H.; Kim, D.U. )

    1990-05-01

    Fibronectin and heparin binding growth factor-type 1 have been affixed to vascular graft surfaces to enhance the attachment and the proliferation of transplanted endothelial cells, respectively. The current study examines the effect of fibronectin and heparin binding growth factor-type 1 on platelet adhesion and activation in vivo and on platelet aggregation in vitro. Expanded polytetrafluoroethylene prostheses (5 cm x 4 mm internal diameter) were treated either with fibronectin (n = 9), fibronectin/heparin/heparin binding growth factor-type 1/heparin (n = 12), or neither (n = 13) and were interposed into canine aortoiliac systems bilaterally. Autogenous radiolabeled (Indium 111 oxine, 650 microCi) platelets were injected intravenously before reestablishment of circulation. Perfusion was maintained for 30 minutes, and prostheses were removed with segments of native aorta and distal iliac arteries bilaterally. Specimens were examined for thrombus-free surface area, by gamma well counting for adherent radiolabeled platelets, and by light microscopy and transmission and scanning electron microscopic techniques. Results showed that both the fibronectin and fibronectin/heparin/heparin binding growth factor-type 1/heparin pretreated prostheses contained significantly greater numbers of platelets and adherent radioactivity than did control graft segments when normalized to their ipsilateral iliac arteries. Fibronectin/heparin/heparin binding growth factor-type 1/heparin pretreated prostheses contained 27 +/- 16 times more radioactivity per square millimeter than ipsilateral iliac arteries, fibronectin pretreated prostheses had 13 +/- 8 times more radioactivity per square millimeter than ipsilateral iliac arteries, and untreated expanded polytetrafluoroethylene had 4 +/- 3 times more radioactivity per square millimeter than ipsilateral iliac arteries.

  17. Study of volume and surface effects in pure hydrogen discharges

    SciTech Connect

    Taccogna, F.; Schneider, R.; Fantz, U.; Longo, S.; Capitelli, M.

    2007-08-10

    The work concerns the simulation of negative ion formation and acceleration in a radio-frequency discharge for neutral beam injection system for ITER, with particular emphasis on the IPP negative ion source. To generate intense beams of negative ions and to optimize the negative ion source, understanding of transport properties of negative ions H- is indispensable. To study this effect, we have developed a 1D(z)-3V Particle-in-Cell electrostatic model of the production and extraction regions. The motion of charged particles (e, H+, H{sub 2}{sup +} and H-) in their self-consistent electric field and of neutral particles (H(n=1,2,3) and H2(X{sup 1}{sigma}{sub g}{sup +}, {nu}=0,...,14)) is simulated. Surface and volumetric processes involving plasma and neutral systems have been included by using different Monte Carlo Collision methods. Comparisons between numerical and experimental results have been done in order to validate the code.

  18. Effects of plasma hydrogenation on trapping properties of dislocations in heteroepitaxial InP/GaAs

    NASA Technical Reports Server (NTRS)

    Ringel, S. A.; Chatterjee, B.

    1994-01-01

    In previous work, we have demonstrated the effectiveness of a post-growth hydrogen plasma treatment for passivating the electrical activity of dislocations in metalorganic chemical vapor deposition (MOCVD) grown InP on GaAs substrates by a more than two order of magnitude reduction in deep level concentration and an improvement in reverse bias leakage current by a factor of approximately 20. These results make plasma hydrogenation an extremely promising technique for achieving high efficiency large area and light weight heteroepitaxial InP solar cells for space applications. In this work we investigate the carrier trapping process by dislocations in heteroepitaxial InP/GaAs and the role of hydrogen passivation on this process. It is shown that the charge trapping kinetics of dislocations after hydrogen passivation are significantly altered, approaching point defect-like behavior consistent with a transformation from a high concentration of dislocation-related defect bands within the InP bandgap to a low concentration of individual dislocation related deep levels, before and after passivation. It is further shown that the 'apparent' activation energies of dislocation related deep levels, before and after passivation, reduce by approximately 70 meV as DLTS fill pulse times are increased from 1 microsecond to 1 millisecond. A model is proposed which explains these effects based on a reduction of Coulombic interaction between individual core sites along the dislocation cores by hydrogen incorporation. Knowledge of the trapping properties in these specific structures is important to develop optimum, low loss heteroepitaxial InP cells.

  19. Three dimensional simulation on binding efficiency of immunoassay for a biosensor with applying electrothermal effect

    NASA Astrophysics Data System (ADS)

    Huang, Kuan-Rong; Chang, Jeng-Shian

    2013-11-01

    In this work, we perform three dimensional finite element simulations on the binding reaction kinetics of the commonly used analyte-ligand protein pairs, namely, C-reactive protein (CRP) and anti-CRP, in a reaction chamber (microchannel) of a biosensor. For the diffusion limited binding biomolecular pairs, due to the slower transport speed of the analyte and the faster reaction rate of analyte-ligand complex, diffusion boundary layers often develop on the reaction surface. To enhance the performance of a biosensor by accelerating the transport speed, a non-uniform AC electric field is applied to induce the electrothermal force to stir the flow field. The swirling flow in the fluid can accelerate the transport of the analyte to and from the reaction surface and hence enhance the association and dissociation of analyte-ligand complex. Four types of biosensors with different arrangements of the geometric locations of the electrode pair and the reaction surface are designed to study the effects of varying geometric configuration on the binding efficiency. The simulation results show that the performance of a biosensor can be better improved by placing the electrodes and the reaction surface on the same side of the microchannel against the opposite side. For the best case studied in this work, the maximum initial slope of the binding curve can be raised up to 6.94 times (with respect to the field-free value) in the association phase, under applying AC field of 15 Vrms and operating frequency of 100 kHz. Another important result with applying electrothermal effect is that it is feasible to use the slower sample flow in the microchannel to save a lot of sample consumption without sacrificing the performance of a biosensor. Several control factors not studied in our previous works such as the thermal boundary condition and the effect of electrical conductivity are also discussed.

  20. Effect of Na+ binding on the conformation, stability and molecular recognition properties of thrombin

    PubMed Central

    De Filippis, Vincenzo; De Dea, Elisa; Lucatello, Filippo; Frasson, Roberta

    2005-01-01

    In the present work, the effect of Na+ binding on the conformational, stability and molecular recognition properties of thrombin was investigated. The binding of Na+ reduces the CD signal in the far-UV region, while increasing the intensity of the near-UV CD and fluorescence spectra. These spectroscopic changes have been assigned to perturbations in the environment of aromatic residues at the level of the S2 and S3 sites, as a result of global rigidification of the thrombin molecule. Indeed, the Na+-bound form is more stable to urea denaturation than the Na+-free form by ∼2 kcal/mol (1 cal≡4.184 J). Notably, the effects of cation binding on thrombin conformation and stability are specific to Na+ and parallel the affinity order of univalent cations for the enzyme. The Na+-bound form is even more resistant to limited proteolysis by subtilisin, at the level of the 148-loop, which is suggestive of the more rigid conformation this segment assumes in the ‘fast’ form. Finally, we have used hirudin fragment 1–47 as a molecular probe of the conformation of thrombin recognition sites in the fast and ‘slow’ form. From the effects of amino acid substitutions on the affinity of fragment 1–47 for the enzyme allosteric forms, we concluded that the specificity sites of thrombin in the Na+-bound form are in a more open and permissible conformation, compared with the more closed structure they assume in the slow form. Taken together, our results indicate that the binding of Na+ to thrombin serves to stabilize the enzyme into a more open and rigid conformation. PMID:15971999

  1. Effect of controlled deactivation on the thermochemical characteristics of hydrogen adsorption on skeletal nickel from sodium hydroxide-water solutions

    NASA Astrophysics Data System (ADS)

    Prozorov, D. A.; Lukin, M. V.; Ulitin, M. V.

    2013-04-01

    Differential heats of adsorption in a wide range of surface coverage and maximum amounts of adsorbed hydrogen are determined by adsorption calorimetry on partially deactivated skeletal nickel from aqueous solutions of sodium hydroxide. The effect of the composition of solutions on the values of limiting adsorption and adsorption equilibria of individual forms of hydrogen is shown.

  2. The effects of heat treatment and hydrogen on the SCC behavior of superalloy 718

    SciTech Connect

    Wang, C.P.; Yu, G.P.; Huang, J.H.

    1996-10-01

    The effects of heat treatment and cathodically hydrogen charging on susceptibility of nickel-based superalloy 718 to stress corrosion cracking were studied. Two conditions of solution-annealed (SA) and heat-treated (HT) materials were considered. Slow strain rate tensile tests with strain rates of 1 x 10{sup {minus}6} sec{sup {minus}1} were performed in 0.1M NaCl solution at room temperature on tensile specimens. Cathodic charging of hydrogen with the potential ranging from {minus}900 mV{sub SCE} to {minus}1,350 mV{sub SCE} were applied during SSRT tests. Reduction of area and ultimate tensile strength were used to correlate the relative susceptibility to different hydrogen charging conditions. Fractography of alloy 718 was usually transgranular, and there was a transition from dimpled microvoid coalescence to intergranular-like failure (transgranular failure adjacent to grain boundaries) as cathodic potential increased. Identification of grain boundary precipitates were carried out by the EDS technique on SEM and XRD of electrolytically extracted phases. MC carbides coalescence with microcracks acted as a preferred crack initiation and propagation site, and promoted crack tip deformation. The HT alloy 718 suffered more hydrogen damage than SA one because large amount of MC carbides precipitated in HT material.

  3. Effect of Hydrogen on Interfacial Structure and Adhesion of Metal/Al_2O_3

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-Gang; Scheffler, Matthias

    2001-03-01

    Metal/sapphire interfaces have been intensively studying because of their importance in many technological applications. A large work of adhesion was found for the oxygen-terminated Al_2O_3(0001)/metal interfaces. As well known, the clean oxygen-terminated Al_2O3 surface is not stable even under a high oxygen pressure[1]. The understanding of how the oxygen-terminated interfaces can be formed is limited. Using an ab initio full-potential linearized augmented plane wave method, we investigated the effect of hydrogen on the formation of metal/Al_2O_3(0001) interfaces. Our results reveal that hydrogen plays an important role in the formation of the oxygen-terminated interfaces. Hydrogen impurities greatly decrease the work of adhesion. The behavior of hydrogen in deposition process of ultrathin metal films on sapphire substrates and the possible structures of the ultrathin films are discussed also. [1] Xiao-Gang Wang, Anne Chaka, Matthias Scheffler, Phys. Rev. Lett. 84, 3650 (2000).

  4. The effects of cations and anions on hydrogen chemisorption at Pt

    NASA Technical Reports Server (NTRS)

    Huang, J. C.; Ogrady, W. E.; Yeager, E.

    1977-01-01

    Experimental evidence based on linear sweep voltammetry is presented to substantiate the view that ionic adsorption substantially shifts electrode potentials in addition to the relative heights of the hydrogen adsorption peaks. HClO4 and HF are chosen as better reference electrolytes for anion studies. The voltammetry curves for 0.1M HF and 0.1M HClO4 as well as the effect of adding successively increasing amounts of H2SO4 to these electrolytes are discussed. The measurements are also extended to alkaline solutions. Mechanisms whereby the addition of various cations and anions to electrolytes such as HF and HClO4 can induce changes in the structure of the hydrogen adsorption region in the voltammetry curves are identified: (1) blocking of sites by anion adsorption and coupling of hydrogen adsorption and anion desorption, (2) modification in the hydrogen adsorption energies for sites adjacent to adsorbed anions, (3) changes in the potential distribution across the interface, and (4) surface restructuring.

  5. Computational insights into the photocyclization of diclofenac in solution: effects of halogen and hydrogen bonding.

    PubMed

    Bani-Yaseen, Abdulilah Dawoud

    2016-08-21

    The effects of noncovalent interactions, namely halogen and hydrogen bonding, on the photochemical conversion of the photosensitizing drug diclofenac (DCF) in solution were investigated computationally. Both explicit and implicit solvent effects were qualitatively and quantitatively assessed employing the DFT/6-31+G(d) and SQM(PM7) levels of theory. Full geometry optimizations were performed in solution for the reactant DCF, hypothesized radical-based intermediates, and the main product at both levels of theories. Notably, in good agreement with previous experimental results concerning the intermolecular halogen bonding of DCF, the SQM(PM7) method revealed different values for d(ClO, Å) and ∠(C-ClO, °) for the two chlorine-substituents of DCF, with values of 2.63 Å/162° and 3.13 Å/142° for the trans and cis orientations, respectively. Employing the DFT/6-31+G(d) method with implicit solvent effects was not conclusive; however, explicit solvent effects confirmed the key contribution of hydrogen and halogen bonding in stabilizing/destabilizing the reactant and hypothesized intermediates. Interestingly, the obtained results revealed that a protic solvent such as water can increase the rate of photocyclization of DCF not only through hydrogen bonding effects, but also through halogen bonding. Furthermore, the atomic charges of atoms majorly involved in the photocyclization of DCF were calculated using different methods, namely Mulliken, Hirshfeld, and natural bond orbital (NBO). The obtained results revealed that in all cases there is a notable nonequivalency in the noncovalent intermolecular interactions of the two chlorine substituents of DCF and the radical intermediates with the solvent, which in turn may account for the discrepancy of their reactivity in different media. These computational results provide insight into the importance of halogen and hydrogen bonding throughout the progression of the photochemical conversion of DCF in solution. PMID:27424600

  6. Sustained hydrogen photoproduction by Chlamydomonas reinhardtii: Effects of culture parameters.

    PubMed

    Kosourov, Sergey; Tsygankov, Anatoly; Seibert, Michael; Ghirardi, Maria L

    2002-06-30

    The green alga, Chlamydomonas reinhardtii, is capable of sustained H(2) photoproduction when grown under sulfur-deprived conditions. This phenomenon is a result of the partial deactivation of photosynthetic O(2)-evolution activity in response to sulfur deprivation. At these reduced rates of water-oxidation, oxidative respiration under continuous illumination can establish an anaerobic environment in the culture. After 10-15 hours of anaerobiosis, sulfur-deprived algal cells induce a reversible hydrogenase and start to evolve H(2) gas in the light. Using a computer-monitored photobioreactor system, we investigated the behavior of sulfur-deprived algae and found that: (1) the cultures transition through five consecutive phases: an aerobic phase, an O(2)-consumption phase, an anaerobic phase, a H(2)-production phase and a termination phase; (2) synchronization of cell division during pre-growth with 14:10 h light:dark cycles leads to earlier establishment of anaerobiosis in the cultures and to earlier onset of the H(2)-production phase; (3) re-addition of small quantities of sulfate (12.5-50 microM MgSO(4), final concentration) to either synchronized or unsynchronized cell suspensions results in an initial increase in culture density, a higher initial specific rate of H(2) production, an increase in the length of the H(2)-production phase, and an increase in the total amount of H(2) produced; and (4) increases in the culture optical density in the presence of 50 microM sulfate result in a decrease in the initial specific rates of H(2) production and in an earlier start of the H(2)-production phase with unsynchronized cells. We suggest that the effects of sulfur re-addition on H(2) production, up to an optimal concentration, are due to an increase in the residual water-oxidation activity of the algal cells. We also demonstrate that, in principle, cells synchronized by growth under light:dark cycles can be used in an outdoor H(2)-production system without loss of

  7. Confinement effects of magnetic field on two-dimensional hydrogen atom in plasmas

    NASA Astrophysics Data System (ADS)

    Bahar, M. K.; Soylu, A.

    2015-05-01

    In this study, for the first time, the Schrödinger equation with more general exponential cosine screened Coulomb (MGECSC) potential is solved numerically in the presence and in the absence of an external magnetic field within two-dimensional formalism using the asymptotic iteration method. The MGECSC potential includes four different potential forms when considering different sets of the parameters in the potential. The plasma screening effects in the weak and strong magnetic field regimes as well as the confinement effects of magnetic field on the two-dimensional hydrogen atom in Debye and quantum plasmas are investigated by solving the corresponding equations. It is found that applying a uniform magnetic field on the hydrogen atom embedded in a plasma leads to change in the profile of the total interaction potential. Thus, confinement effects of magnetic field on hydrogen atom embedded in Debye and quantum plasmas modeled by a MGECSC potential lead to shift bound state energies. This effect would be important to isolate the plasma from the external environment in the experimental applications of plasma physics.

  8. Effect of micro cooling channels on a hydrogen peroxide monopropellant microthruster performance

    NASA Astrophysics Data System (ADS)

    Huh, Jeongmoo; Kwon, Sejin

    2015-12-01

    In this paper, a hydrogen peroxide monopropellant microthrusters with and without regenerative micro cooling channels were fabricated and performance test results were compared to determine cooling effect of the regenerative micro cooling channels. Photosensitive glass was used as microfabrication material, which is cost-effective for MEMS fabrication process. Nine photosensitive glasses was integrated using UV and thermal bonding and composed the microthrusters. 90wt% hydrogen peroxide was used both as monopropellant and cooling fluid. For hydrogen peroxide decomposition, catalyst was fabricated and inserted into the microchamber. Platinum was used as the catalyst active material and γ-alumina was used as catalyst support. Experimental testing was conducted to determine effect of the cooling channels and the chamber pressure, temperature and surface temperature were measured. The performance test results showed that it was possible to relieve the thermal shock of the micro thruster structure by as much as 64% by adding regenerative micro cooling channels on both sides of the microthruster chamber. However, the chamber pressure and temperature decreased by regenerative cooling channels due to excessive cooling effects.

  9. Confinement effects of magnetic field on two-dimensional hydrogen atom in plasmas

    SciTech Connect

    Bahar, M. K.; Soylu, A.

    2015-05-15

    In this study, for the first time, the Schrödinger equation with more general exponential cosine screened Coulomb (MGECSC) potential is solved numerically in the presence and in the absence of an external magnetic field within two-dimensional formalism using the asymptotic iteration method. The MGECSC potential includes four different potential forms when considering different sets of the parameters in the potential. The plasma screening effects in the weak and strong magnetic field regimes as well as the confinement effects of magnetic field on the two-dimensional hydrogen atom in Debye and quantum plasmas are investigated by solving the corresponding equations. It is found that applying a uniform magnetic field on the hydrogen atom embedded in a plasma leads to change in the profile of the total interaction potential. Thus, confinement effects of magnetic field on hydrogen atom embedded in Debye and quantum plasmas modeled by a MGECSC potential lead to shift bound state energies. This effect would be important to isolate the plasma from the external environment in the experimental applications of plasma physics.

  10. Hyper-Binding across Time: Age Differences in the Effect of Temporal Proximity on Paired-Associate Learning

    ERIC Educational Resources Information Center

    Campbell, Karen L.; Trelle, Alexandra; Hasher, Lynn

    2014-01-01

    Older adults show hyper- (or excessive) binding effects for simultaneously and sequentially presented distraction. Here, we addressed the potential role of hyper-binding in paired-associate learning. Older and younger adults learned a list of word pairs and then received an associative recognition task in which rearranged pairs were formed from…

  11. Assessment of the in vitro binding of JHW 007, a dopamine transport inhibitor that blocks the effects of cocaine

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Benztropine (BZT) and its analogues, like cocaine, bind to the dopamine transporter and block dopamine uptake. However, while BZT analogues bind the DAT with high affinity, they generally do not have cocaine-like behavioral effects. JHW 007 is a BZT analogue that displaces [3H]WIN 35,428 from the D...

  12. Effects of van der Waals density functional corrections on trends in furfural adsorption and hydrogenation on close-packed transition metal surfaces

    NASA Astrophysics Data System (ADS)

    Liu, Bin; Cheng, Lei; Curtiss, Larry; Greeley, Jeffrey

    2014-04-01

    The hydrogenation of furfural to furfuryl alcohol on Pd(111), Cu(111) and Pt(111) is studied with both standard Density Functional Theory (DFT)-GGA functionals and with van der Waals-corrected density functionals. VdW-DF functionals, including optPBE, optB88, optB86b, and Grimme's method, are used to optimize the adsorption configurations of furfural, furfuryl alcohol, and related intermediates resulting from hydrogenation of furfural, and the results are compared to corresponding values determined with GGA functionals, including PW91 and PBE. On Pd(111) and Pt(111), the adsorption geometries of the intermediates are not noticeably different between the two classes of functionals, while on Cu(111), modest changes are seen in both the perpendicular distance and the orientation of the aromatic ring with respect to the planar surface. In general, the binding energies increase substantially in magnitude as a result of van der Waals contributions on all metals. In contrast, however, dispersion effects on the kinetics of hydrogenation are relatively small. It is found that activation barriers are not significantly affected by the inclusion of dispersion effects, and a Brønsted-Evans-Polanyi relationship developed solely from PW91 calculations on Pd(111) is capable of describing corresponding results on Cu(111) and Pt(111), even when the dispersion effects are included. Finally, the reaction energies and barriers derived from the dispersion-corrected and pure GGA calculations are used to plot simple potential energy profiles for furfural hydrogenation to furfuryl alcohol on the three considered metals, and an approximately constant downshift of the energetics due to the dispersion corrections is observed.

  13. Effects of van der Waals Density Functional Corrections on Trends in Furfural Adsorption and Hydrogenation on Close-Packed Transition Metal Surfaces

    SciTech Connect

    Liu, Bin; Cheng, Lei; Curtiss, Larry A.; Greeley, Jeffrey P.

    2014-04-01

    The hydrogenation of furfural to furfuryl alcohol on Pd(111), Cu(111) and Pt(111) is studied with both standard Density Functional Theory (DFT)-GGA functionals and with van der Waals-corrected density functionals. VdWDF functionals, including optPBE, optB88, optB86b, and Grimme's method, are used to optimize the adsorption configurations of furfural, furfuryl alcohol, and related intermediates resulting from hydrogenation of furfural, and the results are compared to corresponding values determined with GGA functionals, including PW91 and PBE. On Pd(111) and Pt(111), the adsorption geometries of the intermediates are not noticeably different between the two classes of functionals, while on Cu(111), modest changes are seen in both the erpendicular distance and the orientation of the aromatic ringwith respect to the planar surface. In general, the binding energies increase substantially in magnitude as a result of van derWaals contributions on all metals. In contrast, however, dispersion effects on the kinetics of hydrogenation are relatively small. It is found that activation barriers are not significantly affected by the inclusion of dispersion effects, and a Brønsted–Evans–Polanyi relationship developed solely fromPW91 calculations on Pd(111) is capable of describing corresponding results on Cu(111) and Pt(111), even when the dispersion effects are included. Finally, the reaction energies and barriers derived from the dispersion-corrected and pure GGA calculations are used to plot simple potential energy profiles for furfural hydrogenation to furfuryl alcohol on the three considered metals, and an approximately constant downshift of the energetics due to the dispersion corrections is observed.

  14. The vitamin B12 analog cobinamide is an effective hydrogen sulfide antidote in a lethal rabbit model

    PubMed Central

    BRENNER, M.; BENAVIDES, S.; MAHON, S. B.; LEE, J.; YOON, D.; MUKAI, D.; VISEROI, M.; CHAN, A.; JIANG, J.; NARULA, N.; AZER, S. M.; ALEXANDER, C.; BOSS, G. R.

    2014-01-01

    Background and purpose Hydrogen sulfide (H2S) is a highly toxic gas for which no effective antidotes exist. It acts, at least in part, by binding to cytochrome c oxidase, causing cellular asphyxiation and anoxia. We investigated the effects of three different ligand forms of cobinamide, a vitamin B12 analog, to reverse sulfide (NaHS) toxicity. Methods New Zealand white rabbits received a continuous intravenous (IV) infusion of NaHS (3 mg/min) until expiration or a maximum 270 mg dose. Animals received six different treatments, administered at the time when they developed signs of severe toxicity: Group 1—saline (placebo group, N = 9); Group 2—IV hydroxocobalamin (N = 7); Group 3—IV aquohydroxocobinamide (N = 6); Group 4—IV sulfitocobinamide (N = 6); Group 5—intramuscular (IM) sulfitocobinamide (N = 6); and Group 6—IM dinitrocobinamide (N = 8). Blood was sampled intermittently, and systemic blood pressure and deoxygenated and oxygenated hemoglobin were measured continuously in peripheral muscle and over the brain region; the latter were measured by diffuse optical spectroscopy (DOS) and continuous wave near infrared spectroscopy (CWNIRS). Results Compared with the saline controls, all cobinamide derivatives significantly increased survival time and the amount of NaHS that was tolerated. Aquohydroxocobinamide was most effective (261.5 ± 2.4 mg NaHS tolerated vs. 93.8 ± 6.2 mg in controls, p < 0.0001). Dinitrocobinamide was more effective than sulfitocobinamide. Hydroxocobalamin was not significantly more effective than the saline control. Conclusions Cobinamide is an effective agent for inhibiting lethal sulfide exposure in this rabbit model. Further studies are needed to determine the optimal dose and form of cobinamide and route of administration. PMID:24716792

  15. Actin-binding proteins coronin-1a and IBA-1 are effective microglial markers for immunohistochemistry.

    PubMed

    Ahmed, Zeshan; Shaw, Gerry; Sharma, Ved P; Yang, Cui; McGowan, Eileen; Dickson, Dennis W

    2007-07-01

    This study identifies the actin-binding protein, coronin-1a, as a novel and effective immunohistochemical marker for microglia in both cell cultures and in formaldehyde-fixed, paraffin-embedded tissue. Antibodies to coronin-1a effectively immunostained microglia in human, monkey, horse, rat, and mouse tissues, even in tissues stored for long periods of time. The identity of coronin-1a-immunoreactive cells as microglia was confirmed using double immunolabeling with cell type-specific markers as well as by morphological features and the distribution of immunoreactive cells. These properties are shared by another actin-binding protein, IBA-1. Unlike IBA-1, coronin-1a immunoreactivity was also detected in lymphocytes and certain other hematopoietic cells. The results indicate that both coronin-1a and IBA-1 are robust markers for microglia that can be used in routinely processed tissue of humans and animals. Because both coronin-1a and IBA-1 are actin-binding proteins that play a role in rearrangement of the membrane cytoskeleton, it suggests that these proteins are critical to dynamic properties of microglia. PMID:17341475

  16. Binding energies of exciton complexes in transition metal dichalcogenide monolayers and effect of dielectric environment

    NASA Astrophysics Data System (ADS)

    Kylänpää, Ilkka; Komsa, Hannu-Pekka

    2015-11-01

    Excitons, trions, biexcitons, and exciton-trion complexes in two-dimensional transition metal dichalcogenide sheets of MoS2, MoSe2, MoTe2, WS2, and WSe2 are studied by means of density functional theory and path-integral Monte Carlo method in order to accurately account for the particle-particle correlations. In addition, the effect of dielectric environment on the properties of these exciton complexes is studied by modifying the effective interaction potential between particles. Calculated exciton and trion binding energies are consistent with previous experimental and computational studies, and larger systems such as biexciton and exciton-trion complex are found highly stable. Binding energies of biexcitons are similar to or higher than those of trions, but the binding energy of the trion depends significantly stronger on the dielectric environment than that of biexciton. Therefore, as a function of an increasing dielectric constant of the environment the exciton-trion complex "dissociates" to a biexciton rather than to an exciton and a trion.

  17. Molecular crowding effect on dynamics of DNA-binding proteins search for their targets

    NASA Astrophysics Data System (ADS)

    Liu, Lin; Luo, Kaifu

    2014-12-01

    DNA-binding proteins locate and bind their target sequences positioned on DNA in crowded environments, but the molecular crowding effect on this search process is not clear. Using analytical techniques and Langevin dynamics simulations in two dimensions (2D), we find that the essential physics for facilitated diffusion in 2D search and 3D search is the same. We observe that the average search times have minima at the same optimal nonspecific binding energy for the cases with and without the crowding particle. Moreover, the molecular crowding increases the search time by increasing the average search rounds and the one-dimensional (1D) sliding time of a round, but almost not changing the average 2D diffusion time of a round. In addition, the fraction of 1D sliding time out of the total search time increases with increasing the concentration of crowders. For 2D diffusion, the molecular crowding decreases the jumping length and narrows its distribution due to the cage effect from crowders. These results shed light on the role of facilitated diffusion in DNA targeting kinetics in living cells.

  18. Effect of Osmolytes on the Binding of EGR1 Transcription Factor to DNA

    PubMed Central

    Mikles, David C.; Bhat, Vikas; Schuchardt, Brett J.; McDonald, Caleb B.; Farooq, Amjad

    2014-01-01

    Osmolytes play a key role in maintaining protein stability and mediating macromolecular interactions within the intracellular environment of the cell. Herein, we show that osmolytes such as glycerol, sucrose and PEG400 mitigate the binding of EGR1 transcription factor to DNA in a differential manner. Thus, while physiological concentrations of glycerol only moderately reduce the binding affinity, addition of sucrose and PEG400 is concomitant with a loss in the binding affinity by an order of magnitude. This salient observation suggests that EGR1 is most likely subject to conformational equilibrium and that the osmolytes exert their effect via favorable interactions with the unliganded conformation. Consistent with this notion, our analysis reveals that while EGR1 displays rather high structural stability in complex with DNA, the unliganded conformation becomes significantly destabilized in solution. In particular, while liganded EGR1 adopts a well-defined arc-like architecture, the unliganded protein samples a comparatively large conformational space between two distinct states that periodically interconvert between an elongated rod-like shape and an arc-like conformation on a sub-microsecond time scale. Consequently, the ability of osmolytes to favorably interact with the unliganded conformation so as to stabilize it could account for the negative effect of osmotic stress on EGR1-DNA interaction observed here. Taken together, our study sheds new light on the role of osmolytes in modulating a key protein-DNA interaction. PMID:25269753

  19. Effect of hydrogen passivation on the photoluminescence of Tb ions in silicon rich silicon oxide films

    NASA Astrophysics Data System (ADS)

    Zatryb, G.; Klak, M. M.; Wojcik, J.; Misiewicz, J.; Mascher, P.; Podhorodecki, A.

    2015-12-01

    In this work, silicon-rich silicon oxide films containing terbium were prepared by means of plasma enhanced chemical vapor deposition. The influence of hydrogen passivation on defects-mediated non-radiative recombination of excited Tb3+ ions was investigated by photoluminescence, photoluminescence excitation, and photoluminescence decay measurements. Passivation was found to have no effect on shape and spectral position of the excitation spectra. In contrast, a gradual increase in photoluminescence intensity and photoluminescence decay time was observed upon passivation for the main 5D4-7F5 transition of Tb3+ ions. This observation was attributed to passivation of non-radiative recombination defects centers with hydrogen. It was found that the number of emitted photons increases upon passivation as a result of two effects: (1) longer Tb3+ lifetime in the 5D4 excited state and (2) optical activation of new Tb3+ emitters. The obtained results were discussed and compared with other experimental reports.

  20. Solar wind heating beyond 1 AU. [interplanetary atomic hydrogen gas effect on protons and electrons

    NASA Technical Reports Server (NTRS)

    Holzer, T. E.; Leer, E.

    1973-01-01

    The effect of an interplanetary atomic hydrogen gas on solar wind proton, electron and alpha-particle temperatures beyond 1 AU is considered. It is shown that the proton temperature (and probably also the alpha-particle temperature) reaches a minimum between 2 AU and 4 AU, depending on values chosen for solar wind and interstellar gas parameters. Heating of the electron gas depends primarily on the thermal coupling of the protons and electrons. For strong coupling, the electron temperature reaches a minimum between 4 AU and 8 AU, but for weak coupling (Coulomb collisions only), the electron temperature continues to decrease throughout the inner solar system. A spacecraft travelling to Jupiter should be able to observe the heating effect of the solar wind-interplanetary hydrogen interaction, and from such observations it may be possible of infer some properties of the interstellar neutral gas.