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Sample records for effect hydrogen binding

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

    PubMed

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

    2006-03-03

    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

  2. Interrelationship among Fe-His Bond Strengths, Oxygen Affinities, and Intersubunit Hydrogen Bonding Changes upon Ligand Binding in the β Subunit of Human Hemoglobin: The Alkaline Bohr Effect.

    PubMed

    Nagatomo, Shigenori; Okumura, Miki; Saito, Kazuya; Ogura, Takashi; Kitagawa, Teizo; Nagai, Masako

    2017-03-07

    Regulation of the oxygen affinity of human adult hemoglobin (Hb A) at high pH, known as the alkaline Bohr effect, is essential for its physiological function. In this study, structural mechanisms of the alkaline Bohr effect and pH-dependent O2 affinity changes were investigated via (1)H nuclear magnetic resonance and visible and UV resonance Raman spectra of mutant Hbs, Hb M Iwate (αH87Y) and Hb M Boston (αH58Y). It was found that even though the binding of O2 to the α subunits is forbidden in the mutant Hbs, the O2 affinity was higher at alkaline pH than at neutral pH, and concomitantly, the Fe-His stretching frequency of the β subunits was shifted to higher values. Thus, it was confirmed for the β subunits that the stronger the Fe-His bond, the higher the O2 affinity. It was found in this study that the quaternary structure of α(Fe(3+))β(Fe(2+)-CO) of the mutant Hb is closer to T than to the ordinary R at neutral pH. The retained Aspβ94-Hisβ146 hydrogen bond makes the extent of proton release smaller upon ligand binding from Hisβ146, known as one of residues contributing to the alkaline Bohr effect. For these T structures, the Aspα94-Trpβ37 hydrogen bond in the hinge region and the Tyrα42-Aspβ99 hydrogen bond in the switch region of the α1-β2 interface are maintained but elongated at alkaline pH. Thus, a decrease in tension in the Fe-His bond of the β subunits at alkaline pH causes a substantial increase in the change in global structure upon binding of CO to the β subunit.

  3. 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.

  4. How are hydrogen bonds modified by metal binding?

    PubMed

    Husberg, Charlotte; Ryde, Ulf

    2013-06-01

    We have used density functional theory calculations to investigate how the hydrogen-bond strength is modified when a ligand is bound to a metal using over 60 model systems involving six metals and eight ligands frequently encountered in metalloproteins. We study how the hydrogen-bond geometry and energy vary with the nature of metal, the oxidation state, the coordination number, the ligand involved in the hydrogen bond, other first-sphere ligands, and different hydrogen-bond probe molecules. The results show that, in general, the hydrogen-bond strength is increased for neutral ligands and decreased for negatively charged ligands. The size of the effect is mainly determined by the net charge of the metal complex, and all effects are typically decreased when the model is solvated. In water solution, the hydrogen-bond strength can increase by up to 37 kJ/mol for neutral ligands, and that of negatively charged ligands can increase (for complexes with a negative net charge) or decrease (for positively charged complexes). If the net charge of the complex does not change, there is normally little difference between different metals or different types of complexes. The only exception is observed for sulphur-containing ligands (Met and Cys) and if the ligand is redox-active (e.g. high-valence Fe-O complexes).

  5. 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.

  6. 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.

  7. 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.

  8. Effects of retinoic acid and hydrogen peroxide on sterol regulatory element-binding protein-1a activation during adipogenic differentiation of 3T3-L1 cells.

    PubMed

    Abd Eldaim, Mabrouk A; Okamatsu-Ogura, Yuko; Terao, Akira; Kimura, Kazuhiro

    2010-11-01

    Both retinoic acid (RA) and oxidative stress (H2O2) increased transcription and cleavage of membrane-bound sterol regulatory element-binding protein (SREBP)-1, leading to enhanced transcription of fatty acid synthase (FAS) in hepatoma cells. On the other hand, RA and H2O2 decreased and increased lipogenesis in adipocytes, respectively, although roles of SREBP-1 activation in these effects remain to be elucidated. To elucidate its involvement, we examined the activation of SREBP-la, expression of FAS genes and lipid accumulation in 3T3-L1 cells in the presence of RA and/or H2O2. RA (1 microM) treatment suppressed expression of SREBP-1a and FAS genes and lipid accumulation. H2O2 (2 microM) treatment induced increased cleavage of SREBP-1a, without affecting amounts of SREBP-1a mRNA and precursor protein, and enhanced expression of FAS gene and lipid accumulation. Increased cleavage of SREBP-1a by H2O2 was also observed even in the presence of RA. These results suggest that H2O2, enhances a cleavage of SREBP-1a precursor protein, which independently occurs with the RA suppression of SREBP-1a gene expression, and that RA itself has no role in the SREBP-1a activation in adipocytes.

  9. 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

  10. Benzene selectivity in competitive arene hydrogenation: Effects of single-site catalyst···acidic oxide surface binding geometry

    DOE PAGES

    Gu, Weixing; Stalzer, Madelyn Marie; Nicholas, Christopher P.; ...

    2015-04-17

    Organozirconium complexes are chemisorbed on Brønsted acidic sulfated ZrO2 (ZrS), sulfated Al2O3 (AlS), and ZrO2–WO3 (ZrW). Under mild conditions (25 °C, 1 atm H2), the supported Cp*ZrMe3, Cp*ZrBz3, and Cp*ZrPh3 catalysts are very active for benzene hydrogenation with activities declining with decreasing acidity, ZrS >> AlS ≈ ZrW, arguing that more Brønsted acidic oxides (those having weaker corresponding conjugate bases) yield stronger surface organometallic electrophiles and for this reason have higher benzene hydrogenation activity. Benzene selective hydrogenation, a potential approach for carcinogenic benzene removal from gasoline, is probed using benzene/toluene mixtures, and selectivities for benzene hydrogenation vary with catalyst asmore » ZrBz3+/ZrS–, 83% > Cp*ZrMe2+/ZrS–, 80% > Cp*ZrBz2+/ZrS–, 67% > Cp*ZrPh2+/ZrS–, 57%. For Cp*ZrBz2+/ZrS–, which displays the highest benzene hydrogenation activity with moderate selectivity in benzene/toluene mixtures. Other benzene/arene mixtures are examined, and benzene selectivities vary with arene as mesitylene, 99%, > ethylbenzene, 86% > toluene, 67%. Structural and computational studies by solid-state NMR spectroscopy, XAS, and periodic DFT methods applied to supported Cp*ZrMe3 and Cp*ZrBz3 indicate that larger Zr···surface distances are present in more sterically encumbered Cp*ZrBz2+/AlS– vs Cp*ZrMe2+/AlS–. Furthermore, the combined XAS, solid state NMR, and DFT data argue that the bulky catalyst benzyl groups expand the “cationic” metal center–anionic sulfated oxide surface distances, and this separation/weakened ion-pairing enables the activation/insertion of more sterically encumbered arenes and influences hydrogenation rates and selectivity patterns.« less

  11. Computational study of hydrogen binding by metal-organic framework-5

    NASA Astrophysics Data System (ADS)

    Sagara, Tatsuhiko; Klassen, James; Ganz, Eric

    2004-12-01

    We report the results of quantum chemistry calculations on H2 binding by the metal-organic framework-5 (MOF)-5. Density functional theory calculations were used to calculate the atomic positions, lattice constant, and effective atomic charges from the electrostatic potential for the MOF-5 crystal structure. Second-order Møller-Plesset perturbation theory was used to calculate the binding energy of H2 to benzene and H2-1,4-benzenedicarboxylate-H2. To achieve the necessary accuracy, the large Dunning basis sets aug-cc-pVTZ, and aug-cc-pVQZ were used, and the results were extrapolated to the basis set limit. The binding energy results were 4.77 kJ/mol for benzene, 5.27 kJ/mol for H2-1,4-benzenedicarboxylate-H2. We also estimate binding of 5.38 kJ/mol for Li-1,4-benzenedicarboxylate-Li and 6.86 kJ/mol at the zinc oxide corners using second-order Møller-Plesset perturbation theory. In order to compare our theoretical calculations to the experimental hydrogen storage results, grand canonical Monte Carlo calculations were performed. The Monte Carlo simulations identify a high energy binding site at the corners that quickly saturated with 1.27 H2 molecules at 78 K. At 300 K, a broad range of binding sites are observed.

  12. Computational study of hydrogen binding by metal-organic framework-5.

    PubMed

    Sagara, Tatsuhiko; Klassen, James; Ganz, Eric

    2004-12-22

    We report the results of quantum chemistry calculations on H(2) binding by the metal-organic framework-5 (MOF)-5. Density functional theory calculations were used to calculate the atomic positions, lattice constant, and effective atomic charges from the electrostatic potential for the MOF-5 crystal structure. Second-order Møller-Plesset perturbation theory was used to calculate the binding energy of H(2) to benzene and H(2)-1,4-benzenedicarboxylate-H(2). To achieve the necessary accuracy, the large Dunning basis sets aug-cc-pVTZ, and aug-cc-pVQZ were used, and the results were extrapolated to the basis set limit. The binding energy results were 4.77 kJ/mol for benzene, 5.27 kJ/mol for H(2)-1,4-benzenedicarboxylate-H(2). We also estimate binding of 5.38 kJ/mol for Li-1,4-benzenedicarboxylate-Li and 6.86 kJ/mol at the zinc oxide corners using second-order Møller-Plesset perturbation theory. In order to compare our theoretical calculations to the experimental hydrogen storage results, grand canonical Monte Carlo calculations were performed. The Monte Carlo simulations identify a high energy binding site at the corners that quickly saturated with 1.27 H(2) molecules at 78 K. At 300 K, a broad range of binding sites are observed. (c) 2004 American Institute of Physics.

  13. 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.

  14. 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.

  15. 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.

  16. 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. Copyright © 2014 Elsevier B.V. All rights reserved.

  17. 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

  18. 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.

  19. Binding energies of hydrogen molecules to isoreticular metal-organic framework materials.

    PubMed

    Sagara, Tatsuhiko; Klassen, James; Ortony, Julia; Ganz, Eric

    2005-07-01

    Recently, several novel isoreticular metal-organic framework (IRMOF) structures have been fabricated and tested for hydrogen storage applications. To improve our understanding of these materials, and to promote quantitative calculations and simulations, the binding energies of hydrogen molecules to the MOF have been studied. High-quality second-order Moller-Plesset (MP2) calculations using the resolution of the identity approximation and the quadruple zeta QZVPP basis set were used. These calculations use terminated molecular fragments from the MOF materials. For H2 on the zinc oxide corners, the MP2 binding energy using Zn4O(HCO2)6 molecule is 6.28 kJ/mol. For H2 on the linkers, the binding energy is calculated using lithium-terminated molecular fragments. The MP2 results with coupled-cluster singles and doubles and noniterative triples method corrections and charge-transfer corrections are 4.16 kJ/mol for IRMOF-1, 4.72 kJ/mol for IRMOF-3, 4.86 kJ/mol for IRMOF-6, 4.54 kJ/mol for IRMOF-8, 5.50 and 4.90 kJ/mol for IRMOF-12, 4.87 and 4.84 kJ/mol for IRMOF-14, 5.42 kJ/mol for IRMOF-18, and 4.97 and 4.66 kJ/mol for IRMOF-993. The larger linkers are all able to bind multiple hydrogen molecules per side. The linkers of IRMOF-12, IRMOF-993, and IRMOF-14 can bind two to three, three, and four hydrogen molecules per side, respectively. In general, the larger linkers have the largest binding energies, and, together with the enhanced surface area available for binding, will provide increased hydrogen storage. We also find that adding up NH2 or CH3 groups to each linker can provide up to a 33% increase in the binding energy.

  20. Binding energies of hydrogen molecules to isoreticular metal-organic framework materials

    NASA Astrophysics Data System (ADS)

    Sagara, Tatsuhiko; Klassen, James; Ortony, Julia; Ganz, Eric

    2005-07-01

    Recently, several novel isoreticular metal-organic framework (IRMOF) structures have been fabricated and tested for hydrogen storage applications. To improve our understanding of these materials, and to promote quantitative calculations and simulations, the binding energies of hydrogen molecules to the MOF have been studied. High-quality second-order Møller-Plesset (MP2) calculations using the resolution of the identity approximation and the quadruple zeta QZVPP basis set were used. These calculations use terminated molecular fragments from the MOF materials. For H2 on the zinc oxide corners, the MP2 binding energy using Zn4O(HCO2)6 molecule is 6.28kJ/mol. For H2 on the linkers, the binding energy is calculated using lithium-terminated molecular fragments. The MP2 results with coupled-cluster singles and doubles and noniterative triples method corrections and charge-transfer corrections are 4.16kJ/mol for IRMOF-1, 4.72kJ/mol for IRMOF-3, 4.86kJ/mol for IRMOF-6, 4.54kJ/mol for IRMOF-8, 5.50 and 4.90kJ/mol for IRMOF-12, 4.87 and 4.84kJ/mol for IRMOF-14, 5.42kJ/mol for IRMOF-18, and 4.97 and 4.66kJ/mol for IRMOF-993. The larger linkers are all able to bind multiple hydrogen molecules per side. The linkers of IRMOF-12, IRMOF-993, and IRMOF-14 can bind two to three, three, and four hydrogen molecules per side, respectively. In general, the larger linkers have the largest binding energies, and, together with the enhanced surface area available for binding, will provide increased hydrogen storage. We also find that adding up NH2 or CH3 groups to each linker can provide up to a 33% increase in the binding energy.

  1. Hydrogen effects in 001-line oriented nickel-base superalloy single crystals

    NASA Technical Reports Server (NTRS)

    Baker, C. L.; Chene, J.; Bernstein, I. M.; Williams, J. C.

    1988-01-01

    The entry and subsequent interaction of hydrogen on the mechanical properties of the single crystal nickel-base superalloy CMSX-2 has been studied. Significant amounts of hydrogen were introduced by high temperature hydrogen charging in molten salts which led to an increased lattice parameter and microhardness and to a degradation in tensile elongation to failure whose extent scales with the depth of the hydrogenated zone. In this region a fracture mode change from a 111 to a 100 plane type also occurred. The values of the binding energy of hydrogen to solidification voids and the effective hydrogen pressure in the voids were estimated.

  2. Enthalpy of hydrogen bond formation in a protein-ligand binding reaction.

    PubMed Central

    Connelly, P R; Aldape, R A; Bruzzese, F J; Chambers, S P; Fitzgibbon, M J; Fleming, M A; Itoh, S; Livingston, D J; Navia, M A; Thomson, J A

    1994-01-01

    Parallel measurements of the thermodynamics (free-energy, enthalpy, entropy and heat-capacity changes) of ligand binding to FK506 binding protein (FKBP-12) in H2O and D2O have been performed in an effort to probe the energetic contributions of single protein-ligand hydrogen bonds formed in the binding reactions. Changing tyrosine-82 to phenylalanine in FKBP-12 abolishes protein-ligand hydrogen bond interactions in the FKBP-12 complexes with tacrolimus or rapamycin and leads to a large apparent enthalpic stabilization of binding in both H2O and D2O. High-resolution crystallographic analysis reveals that two water molecules bound to the tyrosine-82 hydroxyl group in unliganded FKBP-12 are displaced upon formation of the protein-ligand complexes. A thermodynamic analysis is presented that suggests that the removal of polar atoms from water contributes a highly unfavorable enthalpy change to the formation of C=O...HO hydrogen bonds as they occur in the processes of protein folding and ligand binding. Despite the less favorable enthalpy change, the entropic advantage of displacing two water molecules upon binding leads to a slightly more favorable free-energy change of binding in the reactions with wild-type FKBP-12. Images PMID:7510408

  3. Enthalpy of hydrogen bond formation in a protein-ligand binding reaction.

    PubMed

    Connelly, P R; Aldape, R A; Bruzzese, F J; Chambers, S P; Fitzgibbon, M J; Fleming, M A; Itoh, S; Livingston, D J; Navia, M A; Thomson, J A

    1994-03-01

    Parallel measurements of the thermodynamics (free-energy, enthalpy, entropy and heat-capacity changes) of ligand binding to FK506 binding protein (FKBP-12) in H2O and D2O have been performed in an effort to probe the energetic contributions of single protein-ligand hydrogen bonds formed in the binding reactions. Changing tyrosine-82 to phenylalanine in FKBP-12 abolishes protein-ligand hydrogen bond interactions in the FKBP-12 complexes with tacrolimus or rapamycin and leads to a large apparent enthalpic stabilization of binding in both H2O and D2O. High-resolution crystallographic analysis reveals that two water molecules bound to the tyrosine-82 hydroxyl group in unliganded FKBP-12 are displaced upon formation of the protein-ligand complexes. A thermodynamic analysis is presented that suggests that the removal of polar atoms from water contributes a highly unfavorable enthalpy change to the formation of C=O...HO hydrogen bonds as they occur in the processes of protein folding and ligand binding. Despite the less favorable enthalpy change, the entropic advantage of displacing two water molecules upon binding leads to a slightly more favorable free-energy change of binding in the reactions with wild-type FKBP-12.

  4. Density functional study of hydrogen binding on gold and silver-gold clusters.

    PubMed

    Zhao, Shuang; Ren, YunLi; Ren, YunLai; Wang, JianJi; Yin, WeiPing

    2010-04-15

    A theoretical study was carried out on the binding of hydrogen on small bimetallic Ag(m)Au(n) (m + n < or = 5) and pure Au(n) (n < or = 5) clusters with neutral, negative, and positive charge state. It is found that the composition and charge state of clusters have strong influence on the most favorable binding site. The adiabatic ionization potentials, electron affinities, and hydrogen binding energies of cluster hydrides increase with the Au content increasing for the given cluster size. The cationic silver-gold cluster hydrides prefer ejection of Au-containing products whereas the anionic silver-gold cluster hydrides prefer ejection of Ag-containing products. The magnitude of metal-H frequency in combination with the metal-H bond length indicates that, with the same type of the binding site, the Au-H interaction is stronger than the Ag-H interaction.

  5. The role of multiple hydrogen-bonding groups in specific alcohol binding sites in proteins: insights from structural studies of LUSH.

    PubMed

    Thode, Anna B; Kruse, Schoen W; Nix, Jay C; Jones, David N M

    2008-03-07

    It is now generally accepted that many of the physiological effects of alcohol consumption are a direct result of binding to specific sites in neuronal proteins such as ion channels or other components of neuronal signaling cascades. Binding to these targets generally occurs in water-filled pockets and leads to alterations in protein structure and dynamics. However, the precise interactions required to confer alcohol sensitivity to a particular protein remain undefined. Using information from the previously solved crystal structures of the Drosophila melanogaster protein LUSH in complexes with short-chain alcohols, we have designed and tested the effects of specific amino acid substitutions on alcohol binding. The effects of these substitutions, specifically S52A, T57S, and T57A, were examined using a combination of molecular dynamics, X-ray crystallography, fluorescence spectroscopy, and thermal unfolding. These studies reveal that the binding of ethanol is highly sensitive to small changes in the composition of the alcohol binding site. We find that T57 is the most critical residue for binding alcohols; the T57A substitution completely abolishes binding, while the T57S substitution differentially affects ethanol binding compared to longer-chain alcohols. The additional requirement for a potential hydrogen-bond acceptor at position 52 suggests that both the presence of multiple hydrogen-bonding groups and the identity of the hydrogen-bonding residues are critical for defining an ethanol binding site. These results provide new insights into the detailed chemistry of alcohol's interactions with proteins.

  6. Yeast ribonuclease III uses a network of multiple hydrogen bonds for RNA binding and cleavage.

    PubMed

    Lavoie, Mathieu; Abou Elela, Sherif

    2008-08-19

    Members of the bacterial RNase III family recognize a variety of short structured RNAs with few common features. It is not clear how this group of enzymes supports high cleavage fidelity while maintaining a broad base of substrates. Here we show that the yeast orthologue of RNase III (Rnt1p) uses a network of 2'-OH-dependent interactions to recognize substrates with different structures. We designed a series of bipartite substrates permitting the distinction between binding and cleavage defects. Each substrate was engineered to carry a single or multiple 2'- O-methyl or 2'-fluoro ribonucleotide substitutions to prevent the formation of hydrogen bonds with a specific nucleotide or group of nucleotides. Interestingly, introduction of 2'- O-methyl ribonucleotides near the cleavage site increased the rate of catalysis, indicating that 2'-OH are not required for cleavage. Substitution of nucleotides in known Rnt1p binding site with 2'- O-methyl ribonucleotides inhibited cleavage while single 2'-fluoro ribonucleotide substitutions did not. This indicates that while no single 2'-OH is essential for Rnt1p cleavage, small changes in the substrate structure are not tolerated. Strikingly, several nucleotide substitutions greatly increased the substrate dissociation constant with little or no effect on the Michaelis-Menten constant or rate of catalysis. Together, the results indicate that Rnt1p uses a network of nucleotide interactions to identify its substrate and support two distinct modes of binding. One mode is primarily mediated by the dsRNA binding domain and leads to the formation of stable RNA/protein complex, while the other requires the presence of the nuclease and N-terminal domains and leads to RNA cleavage.

  7. Hydrogen Bond Dynamic Propensity Studies for Protein Binding and Drug Design

    PubMed Central

    2016-01-01

    We study the dynamic propensity of the backbone hydrogen bonds of the protein MDM2 (the natural regulator of the tumor suppressor p53) in order to determine its binding properties. This approach is fostered by the observation that certain backbone hydrogen bonds at the p53-binding site exhibit a dynamical propensity in simulations that differs markedly form their state-value (that is, formed/not formed) in the PDB structure of the apo protein. To this end, we conduct a series of hydrogen bond propensity calculations in different contexts: 1) computational alanine-scanning studies of the MDM2-p53 interface; 2) the formation of the complex of MDM2 with the disruptive small molecule Nutlin-3a (dissecting the contribution of the different molecular fragments) and 3) the binding of a series of small molecules (drugs) with different affinities for MDM2. Thus, the relevance of the hydrogen bond propensity analysis for protein binding studies and as a useful tool to complement existing methods for drug design and optimization will be made evident. PMID:27792778

  8. 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.

  9. QM/MM (ONIOM) study of glycerol binding and hydrogen abstraction by the coenzyme B12-independent dehydratase.

    PubMed

    Liu, Yuemin; Gallo, August A; Florián, Jan; Liu, Yen-Shan; Mora, Sandeep; Xu, Wu

    2010-04-29

    Glycerol binding and the radical-initiated hydrogen transfer by the coenzyme B(12)-independent glycerol dehydratase from Clostridium butyricum were investigated by using quantum mechanical/molecular mechanical (QM/MM) calculations based on the high-resolution crystal structure (PDB code: 1r9d). Our QM/MM calculations of enzyme catalysis considered the electrostatic coupling between the quantum-mechanical and molecular-mechanical subsystems and two alternative mechanisms. In addition to performing QM/MM calculations in the enzyme, we evaluated energetics along the same reaction pathway in aqueous solution modeled by the polarized dielectric and in the virtual enzyme site that included full steric component from the enzyme residues described by molecular mechanics but lacked the electrostatic contribution of these residues. In this way, we established significant enzyme catalytic effect with respect to reference reactions in both an aqueous solution and a nonpolar cavity. Structurally, four hydrogen bonds formed between glycerol and H164, S282, E435, and D447 anchor glycerol for hydrogen abstraction by thiyl radical on C433. These hydrogen-bond partners orient glycerol molecule to facilitate the formation of the transition state for hydrogen abstraction from carbon C1. This reaction then proceeds with the activation free energy of 6.3 kcal/mol and the reaction free energy of 6.1 kcal/mol. The polarization effects imposed by these hydrogen bonds represent a predominant contribution to a 7.5 kcal/mol enzyme catalytic effect. These results demonstrate the importance of electrostatic catalysis and hydrogen-bonding in enzyme-catalyzed radical reactions and advance our understanding of the catalytic mechanism of B(12)-independent glycerol dehydratases.

  10. Hydrogen bonding in the protic ionic liquid triethylammonium nitrate explored by density functional tight binding simulations

    NASA Astrophysics Data System (ADS)

    Zentel, Tobias; Kühn, Oliver

    2016-12-01

    The applicability of the density functional based tight binding (DFTB) method to the description of hydrogen bond dynamics and infrared (IR) spectroscopy is addressed for the exemplary protic ionic liquid triethylammonium nitrate. Potential energy curves for proton transfer in gas and liquid phases are shown to be comparable to the high level coupled cluster theory in the thermally accessible range of bond lengths. Geometric correlations in the hydrogen bond dynamics are analyzed for a cluster of six ion pairs. Comparing DFTB and DFT data lends further support for the reliability of the DFTB method. Therefore, DFTB bulk simulations are performed to quantify the extent of geometric correlations in terms of Pauling's bond order model. Further, IR absorption spectra are obtained using DFTB and analyzed putting emphasis on the signatures of hydrogen bonding in the NH-stretching and far IR hydrogen bond range.

  11. 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. Copyright © 2013 Elsevier Ltd. All rights reserved.

  12. C-H…O hydrogen bonds in FK506-binding protein-ligand interactions.

    PubMed

    Rajan, Sreekanth; Baek, Kwanghee; Yoon, Ho Sup

    2013-11-01

    Hydrogen bonds are important interaction forces observed in protein structures. They can be classified as stronger or weaker depending on their energy, thereby reflecting on the type of donor. The contribution of weak hydrogen bonds is deemed as an important factor toward structure stability along with the stronger bonds. One such bond, the C-H…O type hydrogen bond, is shown to make a contribution in maintaining three dimensional structures of proteins. Apart from their presence within protein structures, the role of these bonds in protein-ligand interactions is also noteworthy. In this study, we present a statistical analysis on the presence of C-H…O hydrogen bonds observed between FKBPs and their cognate ligands. The FK506-binding proteins (FKBPs) carry peptidyl cis-trans isomerase activity apart from the immunosuppressive property by binding to the immunosuppressive drugs FK506 or rapamycin. Because the active site of FKBPs is lined up by many hydrophobic residues, we speculated that the prevalence of C-H…O hydrogen bonds will be considerable. In a total of 25 structures analyzed, a higher frequency of C-H…O hydrogen bonds is observed in comparison with the stronger hydrogen bonds. These C-H…O hydrogen bonds are dominated by a highly conserved donor, the C(α/β) of Val55 and an acceptor, the backbone oxygen of Glu54. Both these residues are positioned in the β4-α1 loop, whereas the other residues Tyr26, Phe36 and Phe99 with higher frequencies are lined up at the opposite face of the active site. These preferences could be implicated in FKBP pharmacophore models toward enhancing the ligand affinity. This study could be a prelude to studying other proteins with hydrophobic pockets to gain better insights into ligand recognition.

  13. The hydrostatic pressure and temperature effects on hydrogenic impurity binding energies in lattice matched InP/In0.53Ga0.47As/InP square quantum well

    NASA Astrophysics Data System (ADS)

    Başer, P.; Elagoz, S.

    2017-02-01

    The on-center shallow-donor impurity binding energy in lattice matched InP/In0.53Ga0.47As square quantum well structure have been theoretically investigated using effective mass and variational techniques. The effects of hydrostatic pressure, temperature and well width has been calculated and the results are discussed.

  14. 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.

  15. Catalyst support effects on hydrogen spillover

    NASA Astrophysics Data System (ADS)

    Karim, Waiz; Spreafico, Clelia; Kleibert, Armin; Gobrecht, Jens; Vandevondele, Joost; Ekinci, Yasin; van Bokhoven, Jeroen A.

    2017-01-01

    Hydrogen spillover is the surface migration of activated hydrogen atoms from a metal catalyst particle, on which they are generated, onto the catalyst support. The phenomenon has been much studied and its occurrence on reducible supports such as titanium oxide is established, yet questions remain about whether hydrogen spillover can take place on nonreducible supports such as aluminium oxide. Here we use the enhanced precision of top-down nanofabrication to prepare controlled and precisely tunable model systems that allow us to quantify the efficiency and spatial extent of hydrogen spillover on both reducible and nonreducible supports. We place multiple pairs of iron oxide and platinum nanoparticles on titanium oxide and aluminium oxide supports, varying the distance between the pairs from zero to 45 nanometres with a precision of one nanometre. We then observe the extent of the reduction of the iron oxide particles by hydrogen atoms generated on the platinum using single-particle in situ X-ray absorption spectromicroscopy applied simultaneously to all particle pairs. The data, in conjunction with density functional theory calculations, reveal fast hydrogen spillover on titanium oxide that reduces remote iron oxide nanoparticles via coupled proton-electron transfer. In contrast, spillover on aluminium oxide is mediated by three-coordinated aluminium centres that also interact with water and that give rise to hydrogen mobility competing with hydrogen desorption; this results in hydrogen spillover about ten orders of magnitude slower than on titanium oxide and restricted to very short distances from the platinum particle. We anticipate that these observations will improve our understanding of hydrogen storage and catalytic reactions involving hydrogen, and that our approach to creating and probing model catalyst systems will provide opportunities for studying the origin of synergistic effects in supported catalysts that combine multiple functionalities.

  16. 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.

  17. 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.

  18. Membrane adsorption and binding, cellular uptake and cytotoxicity of cell-penetrating peptidomimetics with α-peptide/β-peptoid backbone: effects of hydrogen bonding and α-chirality in the β-peptoid residues.

    PubMed

    Jing, Xiaona; Yang, Mingjun; Kasimova, Marina R; Malmsten, Martin; Franzyk, Henrik; Jorgensen, Lene; Foged, Camilla; Nielsen, Hanne M

    2012-11-01

    Cell-penetrating peptides (CPPs) provide a promising approach for enhancing intracellular delivery of therapeutic biomacromolecules by increasing transport through membrane barriers. Here, proteolytically stable cell-penetrating peptidomimetics with α-peptide/β-peptoid backbone were studied to evaluate the effect of α-chirality in the β-peptoid residues and the presence of guanidinium groups in the α-amino acid residues on membrane interaction. The molecular properties of the peptidomimetics in solution (surface and intramolecular hydrogen bonding, aqueous diffusion rate and molecular size) were studied along with their adsorption to lipid bilayers, cellular uptake, and toxicity. The surface hydrogen bonding ability of the peptidomimetics reflected their adsorbed amounts onto lipid bilayers as well as with their cellular uptake, indicating the importance of hydrogen bonding for their membrane interaction and cellular uptake. Ellipsometry studies further demonstrated that the presence of chiral centers in the β-peptoid residues promotes a higher adsorption to anionic lipid bilayers, whereas circular dichroism results showed that α-chirality influences their overall mean residue ellipticity. The presence of guanidinium groups and α-chiral β-peptoid residues was also found to have a significant positive effect on uptake in living cells. Together, the findings provide an improved understanding on the behavior of cell-penetrating peptidomimetics in the presence of lipid bilayers and live cells.

  19. 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. Copyright © 2015 Elsevier Ltd. All rights reserved.

  20. Effects of electrolytic hydrogen in bcc metals

    SciTech Connect

    Armacanqui Tipacti, M.E.

    1986-01-01

    Lattice defects produced in polycrystalline bcc Ti-30Mo, tantalum, and niobium by hydrogen concentration gradients established by cathodic charging were studied. Anomalous hydrogen diffusion in these metals is revealed by x-ray diffraction and hydrogen permeation experiments. There are four main effects observed during cathodic charging: (a) much slower kinetics of the lattice parameter change compared with diffusion-controlled kinetics, (b) nonuniform lattice parameter, depending on grain orientation, (c) change in angle of diffraction, suggesting grain rotation, and (d) appearance of diffraction subpeaks. Hydrogen concentration profiles on charged samples determined by hot vacuum extraction indicate the presence of peaks of high hydrogen content throughout the sample thickness suggesting hydrogen trapping at various locations within the lattice. The traps were identified as dislocations by TEM. Hydrogen permeation experiments carried out to study the observed anomalies indicate that defects are not generated at current densities below 250 ..mu..A/cm/sup 2/ in a solution of 0.1 N NaOH. The calculated magnitude of the stresses at the entry surface sufficient to cause generation of dislocations is found to be a very small fraction of the materials' yield stress. The effects of cathodic charging on thin films of iron, titanium, and tantalum were also studied.

  1. "Chameleonic" backbone hydrogen bonds in protein binding and as drug targets.

    PubMed

    Menéndez, C A; Accordino, S R; Gerbino, D C; Appignanesi, G A

    2015-10-01

    We carry out a time-averaged contact matrix study to reveal the existence of protein backbone hydrogen bonds (BHBs) whose net persistence in time differs markedly form their corresponding PDB-reported state. We term such interactions as "chameleonic" BHBs, CBHBs, precisely to account for their tendency to change the structural prescription of the PDB for the opposite bonding propensity in solution. We also find a significant enrichment of protein binding sites in CBHBs, relate them to local water exposure and analyze their behavior as ligand/drug targets. Thus, the dynamic analysis of hydrogen bond propensity might lay the foundations for new tools of interest in protein binding-site prediction and in lead optimization for drug design.

  2. 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.

  3. Tight-binding quantum molecular-dynamics simulations of hydrogen in silicon

    NASA Astrophysics Data System (ADS)

    Boucher, Derrick E.; Deleo, Gary G.

    1994-08-01

    We have carried out molecular-dynamics simulations of neutral hydrogen in crystalline silicon using tight-binding (TB) quantum-mechanical total energies and forces. A well-established model due to Goodwin et al. is used for the Si-Si interactions. For the Si-H interactions, we have fit our Harrison-type TB model to the known properties of silane and to both theoretical and experimental information about hydrogen in crystalline silicon. Several simulations performed in the temperature range of 1050 to 2000 K yield a diffusion curve in good agreement with experiment. The H diffusion is found to be jumplike between bond-centered (BC) sites, and the trapping of H at the BC site is mediated by a metastable onefold coordinated H configuration which weakens adjacent Si-Si bonds, allowing the H to enter the BC site. Vibrational frequencies for hydrogen at the BC site are also calculated and isotopic frequency shifts are discussed.

  4. 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})

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

    PubMed

    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(-1) upon dimerization, somewhat more than in the anharmonic experiment (-111 cm(-1)).

  6. The Influence of Hydrogen Ion Concentration on Calcium Binding and Release by Skeletal Muscle Sarcoplasmic Reticulum

    PubMed Central

    Nakamaru, Yoshiaki; Schwartz, Arnold

    1972-01-01

    Calcium release and binding produced by alterations in pH were investigated in isolated sarcoplasmic reticulum (SR) from skeletal muscle. When the pH was abruptly increased from 6.46 to 7.82, after calcium loading for 30 sec, 80–90 nanomoles (nmole) of calcium/mg protein were released. When the pH was abruptly decreased from 7.56 to 6.46, after calcium loading for 30 sec, 25–30 nmole of calcium/mg protein were rebound. The calcium release process was shown to be a function of pH change: 57 nmole of calcium were released per 1 pH unit change per mg protein. The amount of adenosine triphosphate (ATP) bound to the SR was not altered by the pH changes. The release phenomenon was not due to alteration of ATP concentration by the increased pH. Native actomyosin was combined with SR in order to study the effectiveness of calcium release from the SR by pH change in inducing super-precipitation of actomyosin. It was found that SR, in an amount high enough to inhibit superprecipitation at pH 6.5, did not prevent the process when the pH was suddenly increased to 7.3, indicating that the affinity of SR for calcium depends specifically on pH. These data suggest the possible participation of hydrogen ion concentration in excitation-contraction coupling. PMID:5007263

  7. Significant Quantum Effects in Hydrogen Activation

    SciTech Connect

    Kyriakou, Georgios; Davidson, Erlend R. M.; 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. Here, 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.

  8. Significant Quantum Effects in Hydrogen Activation

    DOE PAGES

    Kyriakou, Georgios; Davidson, Erlend R. M.; Peng, Guowen; ...

    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 revealmore » 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. Here, 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.« less

  9. 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.

  10. 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

  11. Introducing ligand-based hydrogen bond donors to a receptor: both selectivity and binding affinity for anion recognition in water can be improved.

    PubMed

    Huang, Feihu; Cheng, Chen; Feng, Guoqiang

    2012-12-21

    Introducing hydrogen bond donors to a receptor was found to be an effective approach to improve both its selectivity and binding affinity for pyrophosphate in water. The crystal structure of Zn3-ADP complex showed the improvements come from the combination of H-bonding and metal coordination in a manner similar to many metalloenzymes.

  12. Hydrogen Bonding Motifs in MutSaphla and their response to binding damaged DNA

    NASA Astrophysics Data System (ADS)

    Negureanu, Lacra; Salsbury, Freddie

    2013-03-01

    Over the past decade, there has been a growing interest in studying the binding of damaged DNA to the MutSalpha protein complex. This protein complex, the Msh2/Msh6 complex in humans, is the initial complex that binds mismatched DNA and other DNA defects that occur during replication. This complex has also been shown to bind at least some types of damaged DNA. As a result of this interest, multiple studies have contrasted the interactions of MutSalpha with its normal mismatched substrate and with the interactions of MutsSalpha to DNA damaged by the chemotherapeutic cisplatin. To complement these studies, we examined the interaction between MutSalpha and DNA damaged by carboplatin via all-atom molecular dynamics simulations. These simulations provide evidence for different hydrogen bonding interactions at the protein/DNA and protein/protein interface. The hydrogen bonding motifs found are broadly similar to those found in binding to the adduct from cis-platin, but have distinct differences. These subtle differences may play a role in the way the different damages are signaled by MutS.

  13. 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

  14. 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.

  15. AIScore chemically diverse empirical scoring function employing quantum chemical binding energies of hydrogen-bonded complexes.

    PubMed

    Raub, Stephan; Steffen, Andreas; Kämper, Andreas; Marian, Christel M

    2008-07-01

    In this work we report on a novel scoring function that is based on the LUDI model and focuses on the prediction of binding affinities. AIScore extends the original FlexX scoring function using a chemically diverse set of hydrogen-bonded interactions derived from extensive quantum chemical ab initio calculations. Furthermore, we introduce an algorithmic extension for the treatment of multifurcated hydrogen bonds (XFurcate). Charged and resonance-assisted hydrogen bond energies and hydrophobic interactions as well as a scaling factor for implicit solvation were fitted to experimental data. To this end, we assembled a set of 101 protein-ligand complexes with known experimental binding affinities. Tightly bound water molecules in the active site were considered to be an integral part of the binding pocket. Compared to the original FlexX scoring function, AIScore significantly improves the prediction of the binding free energies of the complexes in their native crystal structures. In combination with XFurcate, AIScore yields a Pearson correlation coefficient of R P = 0.87 on the training set. In a validation run on the PDBbind test set we achieved an R P value of 0.46 for 799 attractively scored complexes, compared to a value of R P = 0.17 and 739 bound complexes obtained with the FlexX original scoring function. The redocking capability of AIScore, on the other hand, does not fully reach the good performance of the original FlexX scoring function. This finding suggests that AIScore should rather be used for postscoring in combination with the standard FlexX incremental ligand construction scheme.

  16. Regulation of phenylalanine hydroxylase: conformational changes upon phenylalanine binding detected by hydrogen/deuterium exchange and mass spectrometry.

    PubMed

    Li, Jun; Dangott, Lawrence J; Fitzpatrick, Paul F

    2010-04-20

    Phenylalanine acts as an allosteric activator of the tetrahydropterin-dependent enzyme phenylalanine hydroxylase. Hydrogen/deuterium exchange monitored by mass spectrometry has been used to gain insight into local conformational changes accompanying activation of rat phenylalanine hydroxylase by phenylalanine. Peptides in the regulatory and catalytic domains that lie in the interface between these two domains show large increases in the extent of deuterium incorporation from solvent in the presence of phenylalanine. In contrast, the effects of phenylalanine on the exchange kinetics of a mutant enzyme lacking the regulatory domain are limited to peptides surrounding the binding site for the amino acid substrate. These results support a model in which the N-terminus of the protein acts as an inhibitory peptide, with phenylalanine binding causing a conformational change in the regulatory domain that alters the interaction between the catalytic and regulatory domains.

  17. Effect of Ion Binding in Palmitoyl-Oleoyl Phosphatidylserine Monolayers

    NASA Astrophysics Data System (ADS)

    Eckler, Matthew; Matysiak, Silvina

    2013-03-01

    Molecular dynamics simulations of palmitoyl-oleoyl phosphatidylserine (POPS) monolayers at the air-water interface were performed with different ionic strengths with the aim of determining the specific organization and dynamics of counterion binding events. Na + ions penetrated the monolayers into both the ester carbonyl and carboxylate regions of the phospholipids. The binding events increase with the addition of salt. Differences in lipid order parameter, headgroup orientation, and prevalence of inter- and intramolecular hydrogen bonding events between the amine group of the lipid and oxygen groups are observed depending on whether the Na + is binding near the carboxylate or ester region of the lipid. The observed changes are explained in terms of the salting-out effect.

  18. Hydrogen effect on the properties of sapphire

    NASA Astrophysics Data System (ADS)

    Mogilevsky, Radion N.; Sharafutdinova, Liudmila G.; Nedilko, Sergiy; Gavrilov, Valeriy; Verbilo, Dmitriy; Mittl, Scott D.

    2009-05-01

    Sapphire is a widely used material for optical, electronic and semiconductor applications due to its excellent optical properties and very high durability. Optical and mechanical properties of sapphire depend on many factors such as the starting materials that are used to grow crystals, methods to grow sapphire crystals, etc. Demand for highest purity and quality of sapphire crystals increased ten fold for the last several years due to new applications for this material. In this work we studied the effect of starting materials and crystal growth methods on the optical and mechanical properties of sapphire, especially concentrating on the effect of hydrogen on the properties of sapphire. It was found that the infrared (IR) absorption which is traditionally used to measure the hydrogen content in sapphire crystals cannot be reliably used and the data obtained by this method provides a much lower hydrogen concentration than actual. We have shown for the first time that Nuclear Magnetic Resonance techniques can be successfully used to determine hydrogen concentration in sapphire crystals. We have shown that hydrogen concentration in sapphire can reach thousands of ppm if these crystals are grown from Verneuil starting material or aluminum oxide powder. Alternatively, the hydrogen concentration is very low if sapphire crystals are grown from High Purity Densified Alumina (HPDA®) as a starting material. HPDA® is produced by EMT, Inc through their proprietary patented technology. It was found that optical and mechanical properties of sapphire crystals grown using EMT HPDA® starting material are much better than those sapphire crystals grown using a starting material of Verneuil crystals or aluminum oxide powder.

  19. 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.

  20. 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.

  1. 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.

  2. Insights into a highly conserved network of hydrogen bonds in the agonist binding site of nicotinic acetylcholine receptors: a structural and theoretical study.

    PubMed

    Atkinson, Alexandre; Graton, Jérôme; Le Questel, Jean-Yves

    2014-10-01

    Structural and theoretical studies on the geometrical features of a hydrogen-bond network occurring in the binding site of nicotinic acetylcholine receptors (nAChRs) and composed of interconnected WxPD (Trp-x-Pro-Asp) and SWyz (Ser-Trp-yz) sequences from loops A and B, respectively, have been carried out. Multiple sequence alignments using as template the sequence of the apoform of Aplysia californica acetylcholine binding protein (Ac-AChBP) show the strict conservation of serine and tryptophan residues of the loop B SWyz sequence. Considering a sample of 19 high resolution AChBP structures, the strong conformational preferences of the key tryptophan residue has been pointing out, whatever the form, free or bounded, of AChBP. The geometry of the motif hydrogen-bond network has been characterized through the analyses of seven distances. The robustness of the various hydrogen-bond interactions is pointed out, the one involving the aspartate carboxylate group and the serine residue being the shortest of the network. The role of a cooperative effect involving a NH(His145)…OH (Ser142) hydrogen bond is highlighted. Density functional theory calculations on several simplified models based on the motif hydrogen-bond network allow probing the importance of the various hydrogen-bond interactions. The removal of the Ser142 hydroxyl group induces strong structural rearrangements, in agreement with the structural observations. Molecular electrostatic potential calculations on model systems highlight the importance of a cooperative effect in the whole hydrogen-bond network. More precisely, the key role of the Ser142 hydroxyl group, involved in several hydrogen bonds, is underlined.

  3. Effect Of Water On Permeation By Hydrogen

    NASA Technical Reports Server (NTRS)

    Tomazic, William A.; Hulligan, David

    1988-01-01

    Water vapor in working fluid equilibrates with permeability-reducing oxides in metal parts. Report describes study of effects of water on permeation of heater-head tubes by hydrogen in Stirling engine. Experiments performed to determine minimum concentration of oxygen and/or oxygen-bearing gas maintaining oxide coverage adequate for low permeability. Tests showed 750 ppm or more of water effective in maintaining stable, low permeability.

  4. Halide binding by the D212N mutant of Bacteriorhodopsin affects hydrogen bonding of water in the active site.

    PubMed

    Shibata, Mikihiro; Yoshitsugu, Maiko; Mizuide, Noriko; Ihara, Kunio; Kandori, Hideki

    2007-06-26

    Bacteriorhodopsin (BR), a membrane protein found in Halobacterium salinarum, functions as a light-driven proton pump. The Schiff base region has a quadrupolar structure with positive charges located at the protonated Schiff base and Arg82, and the counterbalancing negative charges located at Asp85 and Asp212. The quadropole inside the protein is stabilized by three water molecules, forming a roughly planar pentagonal cluster composed of these waters and two oxygens of Asp85 and Asp212 (one from each carboxylate side chain). It is known that BR lacks proton-pumping activity if Asp85 or Asp212 is neutralized by mutation, but binding of Cl- has different functional effects in mutants at these positions. Binding of Cl- to D85T converts into a chloride ion pump (Sasaki, J., Brown, L. S., Chon, Y.-S., Kandori, H., Maeda, A., Needleman, R., and Lanyi, J. K. (1995) Science 269, 73-75). On the other hand, photovoltage measurements suggested that binding of Cl- to D212N restores the proton-pumping activity at low pH (Moltke, S., Krebs, M. P., Mollaaghababa, R., Khorana, H. G., and Heyn, M. P. (1995) Biophys. J. 69, 2074-2083). In this paper, we studied halide-bound D212N mutant BR in detail. Light-induced pH changes in a suspension of proteoliposomes containing D212N(Cl-) at pH 5 clearly showed that Cl- restores the proton-pumping activity. Spectral blue-shift induced by halide binding to D212N indicates that halides affect the counterion of the protonated Schiff base, whereas much smaller halide dependence of the lambdamax than in D85T suggests that the binding site is distant from the chromophore. In fact, the K minus BR difference Fourier-transform infrared (FTIR) spectra of D212N at 77 K exhibit little halide dependence for vibrational bands of retinal and protein. The only halide-dependent bands were the C=N stretch of Arg82 and some water O-D stretches, suggesting that these groups constitute a halide-binding pocket. A strongly hydrogen-bonded water molecule is

  5. Cooperative enhancement of water binding to crownophane by multiple hydrogen bonds: analysis by high level ab initio calculations.

    PubMed

    Tsuzuki, S; Houjou, H; Nagawa, Y; Goto, M; Hiratani, K

    2001-05-09

    The intermolecular interaction energy of the model system of the water-crownophane complex was analyzed. The water molecule has four hydrogen bonds, with the two hydrogen-donating phenolic hydroxy groups and two hydrogen-accepting oxygen atoms of the poly-oxyethylene chain of the crownophane in the complex. The MP2/6-311G(2d,2p) level calculations of the model system of the complex (hydrogen donating unit + hydrogen accepting unit + water) indicate that the binding energy of the water is 21.85 kcal/mol and that the hydrogen bond cooperativity increases the binding energy as much as 3.67 kcal/mol. The calculated interaction energies depend on the basis set, while the basis set dependence of the cooperative increment is negligible. Most of the cooperative increment is covered by the HF level calculation, which suggests that the major source of the hydrogen bond cooperativity in this system has its origin in induction. The BLYP/6-311G** and PW91/6-311G** level interaction energies of the model system are close to the MP2/6-311G** interaction energies, which suggests that the DFT calculations with these functionals are useful methods to evaluated the interactions of hydrogen bonded systems.

  6. Asn792 participates in the hydrogen bond network around the K+-binding pocket of gastric H,K-ATPase.

    PubMed

    Swarts, Herman G P; Koenderink, Jan B; Willems, Peter H G M; Krieger, Elmar; De Pont, Jan Joep H H M

    2005-03-25

    Asn792 present in M5 of gastric H,K-ATPase is highly conserved within the P-type ATPase family. A direct role in K+ binding was postulated for Na,K-ATPase but was not found in a recent model for gastric H,K-ATPase (Koenderink, J. B., Swarts, H. G. P., Willems, P. H. G. M., Krieger, E., and De Pont, J. J. H. H. M. (2004) J. Biol. Chem. 279, 16417-16424). Therefore, its role in K+ binding and E1/E2 conformational equilibrium in gastric H,K-ATPase was studied by site-directed mutagenesis and expression in Sf9 cells. N792Q and N792A, but not N792D and N792E, had a markedly reduced K+ affinity in both the ATPase and dephosphorylation reactions. In addition, N792A shifted the conformational equilibrium to the E1 form. In double mutants, the effect of N792A on K+ sensitivity was overruled by either E820Q (K(+)-independent activity) or E343D (no dephosphorylation activity). Models were made for the mutants based on the E2 structure of Ca(2+)-ATPase. In the wild-type model the acid amide group of Asn792 has hydrogen bridges to Lys791, Ala339, and Val341. Comparison of the effects of the various mutants suggests that the hydrogen bridge between the carbonyl oxygen of Asn792 and the amino group of Lys791 is essential for the K+ sensitivity and the E2 preference of wild-type enzyme. Moreover, there was a high positive correlation (r = 0.98) between the in silico calculated energy difference of the E2 form (mutants versus wild type) and the experimentally measured IC50 values for vanadate, which reflects the direction of the E2<-->E1 conformational equilibrium. These data strongly support the validity of the model in which Asn792 participates in the hydrogen bond network around the K(+)-binding pocket.

  7. 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.

  8. Tunability of the Adsorbate Binding on Bimetallic Alloy Nanoparticles for the Optimization of Catalytic Hydrogenation.

    PubMed

    Luo, Long; Duan, Zhiyao; Li, Hao; Kim, Joohoon; Henkelman, Graeme; Crooks, Richard M

    2017-04-07

    In this paper, we show that PtAu and PdAu random alloy dendrimer-encapsulated nanoparticles with an average size of ∼1.6 nm have different catalytic activity trends for allyl alcohol hydrogenation. Specifically, PtAu nanoparticles exhibit a linear increase in activity with increasing Pt content, whereas PdAu dendrimer-encapsulated nanoparticles show a maximum activity at a Pd content of ∼60%. Both experimental and theoretical results suggest that this contrasting behavior is caused by differences in the strength of H binding on the PtAu and PdAu alloy surfaces. The results have significant implications for predicting the catalytic performance of bimetallic nanoparticles on the basis of density functional theory calculations.

  9. 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.

  10. Amine-hydrogen halide complexes: experimental electric dipole moments and a theoretical decomposition of dipole moments and binding energies.

    PubMed

    Brauer, Carolyn S; Craddock, Matthew B; Kilian, Jacob; Grumstrup, Erik M; Orilall, M Christopher; Mo, Yirong; Gao, Jiali; Leopold, Kenneth R

    2006-08-24

    The Stark effect has been observed in the rotational spectra of several gas-phase amine-hydrogen halide complexes and the following electric dipole moments have been determined: H(3)(15)N-H(35)Cl (4.05865 +/- 0.00095 D), (CH(3))(3)(15)N-H(35)Cl (7.128 +/- 0.012 D), H(3)(15)N-H(79)Br (4.2577 +/- 0.0022 D), and (CH(3))(3)(15)N-H(79)Br (8.397 +/- 0.014 D). Calculations of the binding energies and electric dipole moments for the full set of complexes R(n)()(CH(3))(3)(-)(n)()N-HX (n = 0-3; X = F, Cl, Br) at the MP2/aug-cc-pVDZ level are also reported. The block localized wave function (BLW) energy decomposition method has been used to partition the binding energies into contributions from electrostatic, exchange, distortion, polarization, and charge-transfer terms. Similarly, the calculated dipole moments have been decomposed into distortion, polarization, and charge-transfer components. The complexes studied range from hydrogen-bonded systems to proton-transferred ion pairs, and the total interaction energies vary from 7 to 17 kcal/mol across the series. The individual energy components show a much wider variation than this, but cancellation of terms accounts for the relatively narrow range of net binding energies. For both the hydrogen-bonded complexes and the proton-transferred ion pairs, the electrostatic and exchange terms have magnitudes that increase with the degree of proton transfer but are of opposite sign, leaving most of the net stabilization to arise from polarization and charge transfer. In all of the systems studied, the polarization terms contribute the most to the induced dipole moment, followed by smaller but still significant contributions from charge transfer. A significant contribution to the induced moment of the ion pairs also arises from distortion of the HX monomer.

  11. Polaronic effects on diamagnetic susceptibility of a hydrogenic donor in nanostructures

    NASA Astrophysics Data System (ADS)

    Jeice, A. R.; Jayam G., Sr.; Wilson, K. S. J.

    2016-07-01

    The binding energy and diamagnetic susceptibility of a hydrogenic donor in nanostructures like quantum well, quantum wire and quantum dot have been calculated for the finite and infinite barrier square well potential and are computed using variational technique. The binding energy of cubic nanostructures formed by GaAs/Ga1- x Al x As has also been obtained using conduction band non-parabolicity and polaronic correction. Our results demonstrate that the effect of polaronic mass and band non-parabolicity which exhibits effective binding energy and diamagnetic susceptibility for the nanostructures having narrow width sizes and it is not significant to the low dimensional nanostructures.

  12. 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.

  13. Probing the binding and spatial arrangement of molecular hydrogen in porous hosts via neutron Compton scattering.

    PubMed

    Krzystyniak, Maciej; Adams, Mark A; Lovell, Arthur; Skipper, Neal T; Bennington, Stephen M; Mayers, Jerry; Fernandez-Alonso, Felix

    2011-01-01

    The adsorption of molecular hydrogen (H2) in the alkali-graphite intercalate KC24 has been studied using simultaneous neutron diffraction and Compton scattering. Neutron Compton scattering data for the (H2)xKC24 system (x = 0-2.5) were measured at T = 1.5 K as a function of the relative orientation between the neutron beam and the intercalate c-axis. Synchronous with the above proton-recoil measurements, high-resolution diffraction patterns were measured in backscattering geometry. From these diffraction measurements, the intrinsic mosaicity of the Papyex-based intercalate was determined to be approximately 15 degrees half-width-at-half-maximum, in good agreement with previous studies [Finkelstein et al., Physica B, 2000, 291, 213]. Hydrogen uptake by the intercalate leads to a distinct and readily detectable broadening of the isotropic Compton profile compared to bulk H2, indicative of an enhanced interaction of the H2 molecule with the surrounding solid-state environment. Total proton-recoil intensities also scale linearly with the amount of adsorbed hydrogen. Taking as our starting point previous experimental and theoretical results, the isotropic widths of the proton momentum distributions can be explained on the basis of three energy scales, namely, intramolecular H-H vibrations, followed by H-H librations and H2 centre-of-mass translations. From the coverage dependence of these neutron data, we also establish an upper bound of approximately 10 meV for intermolecular hydrogen-hydrogen interactions. Finally, we observe a weak anisotropy of the width of the proton momentum distributions. Comparison of these experimental data with first-principles predictions indicates that subtle quantum mechanical effects associated with particle delocalisation and exchange lie at the heart of the observed behaviour. Overall, these results demonstrate the suitability and largely untapped potential of neutron Compton scattering to explore H2 uptake by solid-state hosts.

  14. 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.

  15. Unique Ligand Binding Patterns Between Estrogen Receptor α and β Revealed by Hydrogen/Deuterium Exchange

    PubMed Central

    Dai, Susie Y.; Burris, Thomas P.; Dodge, Jeffrey A.; Montrose-Rafizadeh, Chahrzad; Wang, Yong; Pascal, Bruce D.; Chalmers, Michael J.; Griffin, Patrick R.

    2009-01-01

    Here we present the use of hydrogen/deuterium exchange (HDX) mass spectrometry to analyze the estrogen receptor β ligand binding domain (ERβLBD) in the absence and presence of a variety of chemical compounds with different binding modes and pharmacological properties. Previously, we reported the use of HDX as a method to predict the tissue selectivity of ERα ligands. HDX profiles of ERαLBD in complex with ligand could differentiate compounds of the same chemotype. In contrast, similar analysis of ERβLBD showed correlation to the compound chemical structures but little correlation with compound tissue selectivity. The different HDX patterns observed for ERβLBD when compared to ERαLBD bound to the same chemical compounds serves as an indication that ERβLBD undergoes a different structural response to the same ligand when compared to ERαLBD. The conformational dynamics revealed by HDX forz ERβLBD together with those for ERαLBD shed light into ER ligand interactions and offer new structural insights. The compound specific perturbations in HDX kinetics observed for each of the two isoforms should aid the development of subtype selective ER ligands. PMID:19739677

  16. Nuclear quantum effects and hydrogen bonding in liquids.

    PubMed

    Raugei, Simone; Klein, Michael L

    2003-07-30

    We have employed ab initio path integral molecular dynamics simulations to investigate the role of nuclear quantum effects on the strength of hydrogen bonds in liquid hydrogen fluoride. Nuclear quantum effects are shown to be responsible for a stronger hydrogen bond and an enhanced dipole-dipole interaction, which lead, in turn, to a shortening of the H...F intrachain distance. The simulation results are analyzed in terms of the electronic density shifts with respect to a purely classical treatment of the nuclei. The observed enhanced hydrogen-bond interaction, which arises from a coupling of intra- and intermolecular effects, should be a general phenomenon occurring in all hydrogen-bonded systems.

  17. Effect of Various Factors on Hydrogen Embrittlement of Structural Steels

    NASA Astrophysics Data System (ADS)

    Khanzhin, V. G.; Turilina, V. Yu.; Rogachev, S. O.; Nikitin, A. V.; Belov, V. A.

    2015-07-01

    Results of studies of hydrogen embrittlement of structural steels of different strength are presented. The effect of various factors on delayed hydrogen fracture is analyzed using the results of investigations by the methods of acoustic emission, metallography and fractography of bolts under the conditions of tension with bending after galvanic hydrogen charging.

  18. 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

  19. Effective field theories for muonic hydrogen

    NASA Astrophysics Data System (ADS)

    Peset, Clara

    2017-03-01

    Experimental measurements of muonic hydrogen bound states have recently started to take place and provide a powerful setting in which to study the properties of QCD. We profit from the power of effective field theories (EFTs) to provide a theoretical framework in which to study muonic hydrogen in a model independent fashion. In particular, we compute expressions for the Lamb shift and the hyperfine splitting. These expressions include the leading logarithmic O(mμα6) terms, as well as the leading {\\cal O}≤ft( {{m_μ }{α ^5}{{m_μ ^2} \\over {Λ {{QCD}}^2}}} \\right) hadronic effects. Most remarkably, our analyses include the determination of the spin-dependent and spin-independent structure functions of the forward virtualphoton Compton tensor of the proton to O(p3) in HBET and including the Delta particle. Using these results we obtain the leading hadronic contributions to the Wilson coeffcients of the lepton-proton four fermion operators in NRQED. The spin-independent coeffcient yields a pure prediction for the two-photon exchange contribution to the muonic hydrogen Lamb shift, which is the main source of uncertainty in our computation. The spindependent coeffcient yields the prediction of the hyperfine splitting. The use of EFTs crucially helps us organizing the computation, in such a way that we can clearly address the parametric accuracy of our result. Furthermore, we review in the context of NRQED all the contributions to the energy shift of O(mμα5, as well as those that scale like mrα6× logarithms.

  20. 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

    2011-10-05

    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.

  1. Hydrogen molecule binding to unsaturated metal sites in metal-organic frameworks studied by neutron powder diffraction and inelastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Liu, Yun; Brown, Craig; Neumann, Dan; Dinca, Mircea; Long, Jeffrey; Peterson, Vanessa; Kepert, Cameron

    2007-03-01

    Metal organic framework (MOF) materials have shown considerable potential for hydrogen storage arising from very large surface areas. However, the low binding energy of hydrogen molecules limits its storage capability to very low temperatures (< 77 K), which is impractical for industrial applications. Using neutron powder diffraction (NPD), we have characterized the hydrogen adsorption sites in a selected series of MOF materials with exposed unsaturated metal ions. Direct binding between the unsaturated metal ions and hydrogen molecules is observed and responsible for the enhanced initial hydrogen adsorption enthalpy. The different metals centers in these MOFs show different binding strength and interaction distances between the hydrogen molecule and metal ions. The organic linker also affects the overall H2 binding strength. Inelastic neutron scattering spectra of H2 in these MOFs are also discussed.

  2. Nucleotides of transcription factor binding sites exert interdependent effects on the binding affinities of transcription factors

    PubMed Central

    Bulyk, Martha L.; Johnson, Philip L. F.; Church, George M.

    2002-01-01

    We can determine the effects of many possible sequence variations in transcription factor binding sites using microarray binding experiments. Analysis of wild-type and mutant Zif268 (Egr1) zinc fingers bound to microarrays containing all possible central 3 bp triplet binding sites indicates that the nucleotides of transcription factor binding sites cannot be treated independently. This indicates that the current practice of characterizing transcription factor binding sites by mutating individual positions of binding sites one base pair at a time does not provide a true picture of the sequence specificity. Similarly, current bioinformatic practices using either just a consensus sequence, or even mononucleotide frequency weight matrices to provide more complete descriptions of transcription factor binding sites, are not accurate in depicting the true binding site specificities, since these methods rely upon the assumption that the nucleotides of binding sites exert independent effects on binding affinity. Our results stress the importance of complete reference tables of all possible binding sites for comparing protein binding preferences for various DNA sequences. We also show results suggesting that microarray binding data using particular subsets of all possible binding sites can be used to extrapolate the relative binding affinities of all possible full-length binding sites, given a known binding site for use as a starting sequence for site preference refinement. PMID:11861919

  3. Strengthening of hydrogen bonding with the push-pull effect

    NASA Astrophysics Data System (ADS)

    Tao, Yunwen; Zou, Wenli; Kraka, Elfi

    2017-10-01

    Theoretical studies of hydrogen-bonding based on cluster models tend to overlook the peripheral monomers which are influential. By revisiting thirteen hydrogen-bonded complexes of H2O, HF and NH3, the "push-pull" effect is identified as a general mechanism that strengthens a hydrogen bond. Enhanced Lp (X) →σ∗ (X‧ - H) charge transfer is proved to be the core of the "push-pull" effect. The charge transfer can convert an electrostatic hydrogen bond into a covalent hydrogen bond.

  4. Ligation-state hydrogen exchange: coupled binding and folding equilibria in ribonuclease P protein.

    PubMed

    Henkels, Christopher H; Oas, Terrence G

    2006-06-21

    Bacillus subtilis ribonuclease P protein (P protein) is predominantly unfolded (D) at physiological pH and low ionic strength; however, small molecule anionic ligands (e.g., sulfate) directly bind to and stabilize the folded state (NL2). Because the D + 2L <--> NL2 transition is experimentally two-state, high-energy states such as the singly bound, folded species (NL) and the unliganded folded species (N) are generally difficult to detect at equilibrium. To study the conformational properties of these ensembles, NMR-detected amide hydrogen exchange (HX) rates of P protein were measured at four sulfate (i.e., ligand) concentrations, a method we denote "ligation-state hydrogen exchange". The ligand concentration dependence of the HX rate of 47 residues was fit to a model with four possible HX pathways, corresponding to the local and/or global opening reactions from NL2 and NL, the local opening of N, and the global opening of N to D. Data analysis permits the calculation of the residue-specific free energy of opening from each ensemble as well as the fractional amide HX flux through each pathway. Results indicate that the predominant route of HX is through the NL and N states, which represent only 0.45% and 0.0005% of the total protein population in 20 mM sodium sulfate, respectively. Despite the low population of N, a region of protected amides was identified. Therefore, exchange through unliganded forms must be accounted for prior to the interpretation of HX-based protein-interaction studies. We offer a simple test to determine if HX occurs through the liganded or unliganded form.

  5. Binding.

    ERIC Educational Resources Information Center

    Rebsamen, Werner

    1981-01-01

    Categorizes contemporary methods of binding printed materials in terms of physical preservation--hand binding (archival restoration), edition binding (paperback, hardcover), publication binding (magazines), textbook binding (sidesewn), single-sheet binding (loose-leaf, mechanical), and library binding (oversewn, sidesewn). Seven references are…

  6. Nature of the Hydrogen Binding in Metal Organic Frameworks with Exposed Transition Metal Sites

    NASA Astrophysics Data System (ADS)

    Zhou, Wei; Yildirim, Taner

    2008-03-01

    MOFs with exposed transition metal (TM) sites were recently found to exhibit significantly larger experimental heat of H2 adsorption than classical MOFs, thus attracted great attention. [1, 2] Understanding the nature of the H2 interaction with the exposed metal sites is of critical importance for the further development of these materials. Using Mn4Cl-MOF as an example, here we show that the H2 binding with the exposed TM site is not of the expected Kubas type, in strong contrast to ``similar'' systems investigated previously (e.g., ref. [3] and [4]). In Mn4Cl-MOF, there are a) no charge transfer from TM to H2, b) no significant H-H bond elongation, and c) no evidence of any H2-σ^* Mn-d orbital hybridization. We also study the H2 binding as a function of Mn4-magnetic spin configurations, and find no significant effect of the magnetic state on the binding energy. We further reveal that the major contribution to the overall binding is classical Coulomb interaction arising from the small charge overlap of H2-σ and Mn-d orbitals. This coulomb interaction is very anisotropic, and when the quantum nature of H2-orientation is taken into account, the actual binding energy is significantly reduced from the calculated classical binding energy. [1] J. Am. Chem. Soc. 128, 16876 (2006). [2] Angew. Chem. Int. Ed. 46, 1419 (2007). [3] Phys. Rev. Lett. 94, 087205 (2005). [4] Phys. Rev. B 76, 085434 (2007).

  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. Magnetic effects of interstitial hydrogen in nickel

    NASA Astrophysics Data System (ADS)

    León, Andrea; Velásquez, E. A.; Mazo-Zuluaga, J.; Mejía-López, J.; Florez, J. M.; Vargas, P.

    2017-01-01

    Hydrogen storage in materials is among the most relevant fields when thinking about energy conversion and storage. In this work we present a study that responds to a couple of questions concerning induced electronic changes that H produces in ferromagnetic nickel (Ni) host. We calculate and explain the change of magnetic properties of Ni with different concentrations of H. Density functional theory calculations (DFT) were performed for super-cells of fcc Ni with interstitial H in octahedral sites at different concentrations. In order to physically explain the effect of magnetization diminishing as the hydrogen concentration increases, we propose a simple Stoner type of model to describe the influence of the H impurity on the magnetic properties of Ni. The exchange splitting reduction, as shown in first principles calculations, is clearly explained within this physical model. Using a paramagnetic Ni fcc band with variable number of electrons and a Stoner model allow us to obtain the correct trend for the magnetic moment of the system as a function of the H concentration.

  9. Do Halogen-Hydrogen Bond Donor Interactions Dominate the Favorable Contribution of Halogens to Ligand-Protein Binding?

    PubMed

    Lin, Fang-Yu; MacKerell, Alexander D

    2017-07-20

    Halogens are present in a significant number of drugs, contributing favorably to ligand-protein binding. Currently, the contribution of halogens, most notably chlorine and bromine, is largely attributed to halogen bonds involving favorable interactions with hydrogen bond acceptors. However, we show that halogens acting as hydrogen bond acceptors potentially make a more favorable contribution to ligand binding than halogen bonds based on quantum mechanical calculations. In addition, bioinformatics analysis of ligand-protein crystal structures shows the presence of significant numbers of such interactions. It is shown that interactions between halogens and hydrogen bond donors (HBDs) are dominated by perpendicular C-X···HBD orientations. Notably, the orientation dependence of the halogen-HBD (X-HBD) interactions is minimal over greater than 100° with favorable interaction energies ranging from -2 to -14 kcal/mol. This contrasts halogen bonds in that X-HBD interactions are substantially more favorable, being comparable to canonical hydrogen bonds, with a smaller orientation dependence, such that they make significant, favorable contributions to ligand-protein binding and, therefore, should be actively considered during rational ligand design.

  10. Colonic hydrogen absorption: quantification of its effect on hydrogen accumulation caused by bacterial fermentation of carbohydrates.

    PubMed Central

    Hammer, H F

    1993-01-01

    The aim of the study was to assess (quantitatively) colonic hydrogen absorption. Hydrogen volumes in flatus and breath were measured over periods of six hours in normal subjects during fasting and after ingestion of the non-absorbable carbohydrate lactulose to simulate the effect of fermentable dietary fibres. If less than 76 ml/6 h of hydrogen accumulated in the colon then all of it was absorbed, as suggested by the intercept of the regression line of the correlation between hydrogen volumes in flatus and breath after ingestion of lactulose. As total flatus volume increased, efficiency of colonic hydrogen absorption decreased from 90% to 20%. The positive correlation between hydrogen volumes of flatus and breath showed that the eightfold interindividual differences in flatus volume after ingestion of 12.5 g of lactulose were caused by differences in bacterial net gas production, not gas absorption. Differences in colonic gas emptying rate are the consequence rather than the cause of interindividual differences in flatus volume. In conclusion: (1) colonic hydrogen absorption is highly effective at low colonic hydrogen accumulation rates, but not at higher accumulation rates; (2) ineffective colonic gas absorption is the consequence and not the cause of high colonic gas accumulation rate after ingestion of non-absorbable carbohydrates; and (3) future therapeutic approaches to the large interindividual variability in colonic gas accumulation after ingestion of poorly absorbable fermentable carbohydrates, such as some kinds of dietary fibres, should be directed towards altering colonic bacterial metabolism. PMID:8314516

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

    DOE PAGES

    Kolasinski, R. D.; Hammond, K. D.; Whaley, J. A.; ...

    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

  12. Effect of Temperature on Tolbutamide Binding to Glycated Serum Albumin.

    PubMed

    Szkudlarek, Agnieszka; Pentak, Danuta; Ploch, Anna; Pożycka, Jadwiga; Maciążek-Jurczyk, Małgorzata

    2017-03-31

    Glycation process occurs in protein and becomes more pronounced in diabetes when an increased amount of reducing sugar is present in bloodstream. Glycation of protein may cause conformational changes resulting in the alterations of its binding properties even though they occur at a distance from the binding sites. The changes in protein properties could be related to several pathological consequences such as diabetic and nondiabetic cardiovascular diseases, cataract, renal dysfunction and Alzheimer's disease. The experiment was designed to test the impact of glycation process on sulfonylurea drug tolbutamide-albumin binding under physiological (T = 309 K) and inflammatory (T = 311 K and T = 313 K) states using fluorescence and UV-VIS spectroscopies. It was found in fluorescence analysis experiments that the modification of serum albumin in tryptophanyl and tyrosyl residues environment may affect the tolbutamide (TB) binding to albumin in subdomain IIA and/or IIIA (Sudlow's site I and/or II), and also in subdomains IB and IIB. We estimated the binding of tolbutamide to albumin described by a mixed nature of interaction (specific and nonspecific). The association constants Ka (L∙mol(-1)) for tolbutamide at its high affinity sites on non-glycated albumin were in the range of 1.98-7.88 × 10⁴ L∙mol(-1) (λex = 275 nm), 1.20-1.64 × 10⁴ L∙mol(-1) (λex = 295 nm) and decreased to 1.24-0.42 × 10⁴ L∙mol(-1) at λex = 275 nm (T = 309 K and T = 311 K) and increased to 2.79 × 10⁴ L∙mol(-1) at λex = 275 nm (T = 313 K) and to 4.43-6.61 × 10⁴ L∙mol(-1) at λex = 295 nm due to the glycation process. Temperature dependence suggests the important role of van der Waals forces and hydrogen bonding in hydrophobic interactions between tolbutamide and both glycated and non-glycated albumin. We concluded that the changes in the environment of TB binding of albumin in subdomain IIA and/or IIIA as well as in subdomains IB and IIB influence on therapeutic effect

  13. Hydrogen Bonding in the Active Site of Ketosteroid Isomerase: Electronic Inductive Effects and Hydrogen Bond Coupling

    PubMed Central

    Hanoian, Philip; Sigala, Paul A.; Herschlag, Daniel; Hammes-Schiffer, Sharon

    2010-01-01

    Computational studies are performed to analyze the physical properties of hydrogen bonds donated by Tyr16 and Asp103 to a series of substituted phenolate inhibitors bound in the active site of ketosteroid isomerase (KSI). As the solution pKa of the phenolate increases, these hydrogen bond distances decrease, the associated NMR chemical shifts increase, and the fraction of protonated inhibitor increases, in agreement with prior experiments. The quantum mechanical/molecular mechanical calculations provide insight into the electronic inductive effects along the hydrogen-bonding network that includes Tyr16, Tyr57, and Tyr32, as well as insight into hydrogen bond coupling in the active site. The calculations predict that the most-downfield NMR chemical shift observed experimentally corresponds to the Tyr16-phenolate hydrogen bond and that Tyr16 is the proton donor when a bound naphtholate inhibitor is observed to be protonated in electronic absorption experiments. According to these calculations, the electronic inductive effects along the hydrogen-bonding network of tyrosines cause the Tyr16 hydroxyl to be more acidic than the Asp103 carboxylic acid moiety, which is immersed in a relatively nonpolar environment. When one of the distal tyrosine residues in the network is mutated to phenylalanine, thereby diminishing this inductive effect, the Tyr16-phenolate hydrogen bond lengthens, and the Asp103-phenolate hydrogen bond shortens, as observed in NMR experiments. Furthermore, the calculations suggest that the differences in the experimental NMR data and electronic absorption spectra for pKSI and tKSI, two homologous bacterial forms of the enzyme, are due predominantly to the third tyrosine that is present in the hydrogen-bonding network of pKSI but not tKSI. These studies also provide experimentally testable predictions about the impact of mutating the distal tyrosine residues in this hydrogen-bonding network on the NMR chemical shifts and electronic absorption spectra

  14. 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.

  15. Hydrogen-Deuterium Exchange Mass Spectrometry Reveals Calcium Binding Properties and Allosteric Regulation of Downstream Regulatory Element Antagonist Modulator (DREAM).

    PubMed

    Zhang, Jun; Li, Jing; Craig, Theodore A; Kumar, Rajiv; Gross, Michael L

    2017-07-18

    Downstream regulatory element antagonist modulator (DREAM) is an EF-hand Ca(2+)-binding protein that also binds to a specific DNA sequence, downstream regulatory elements (DRE), and thereby regulates transcription in a calcium-dependent fashion. DREAM binds to DRE in the absence of Ca(2+) but detaches from DRE under Ca(2+) stimulation, allowing gene expression. The Ca(2+) binding properties of DREAM and the consequences of the binding on protein structure are key to understanding the function of DREAM. Here we describe the application of hydrogen-deuterium exchange mass spectrometry (HDX-MS) and site-directed mutagenesis to investigate the Ca(2+) binding properties and the subsequent conformational changes of full-length DREAM. We demonstrate that all EF-hands undergo large conformation changes upon calcium binding even though the EF-1 hand is not capable of binding to Ca(2+). Moreover, EF-2 is a lower-affinity site compared to EF-3 and -4 hands. Comparison of HDX profiles between wild-type DREAM and two EF-1 mutated constructs illustrates that the conformational changes in the EF-1 hand are induced by long-range structural interactions. HDX analyses also reveal a conformational change in an N-terminal leucine-charged residue-rich domain (LCD) remote from Ca(2+)-binding EF-hands. This LCD domain is responsible for the direct interaction between DREAM and cAMP response element-binding protein (CREB) and regulates the recruitment of the co-activator, CREB-binding protein. These long-range interactions strongly suggest how conformational changes transmit the Ca(2+) signal to CREB-mediated gene transcription.

  16. 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

  17. Ammonium Additives to Dissolve Lithium Sulfide through Hydrogen Binding for High-Energy Lithium-Sulfur Batteries.

    PubMed

    Pan, Huilin; Han, Kee Sung; Vijayakumar, M; Xiao, Jie; Cao, Ruiguo; Chen, Junzheng; Zhang, Jiguang; Mueller, Karl T; Shao, Yuyan; Liu, Jun

    2017-02-08

    In rechargeable Li-S batteries, the uncontrollable passivation of electrodes by highly insulating Li2S limits sulfur utilization, increases polarization, and decreases cycling stability. Dissolving Li2S in organic electrolyte is a facile solution to maintain the active reaction interface between electrolyte and sulfur cathode, and thus address the above issues. Herein, ammonium salts are demonstrated as effective additives to promote the dissolution of Li2S to 1.25 M in DMSO solvent at room temperature. NMR measurements show that the strong hydrogen binding effect of N-H groups plays a critical role in dissolving Li2S by forming complex ligands with S(2-) anions coupled with the solvent's solvating surrounding. Ammonium additives in electrolyte can also significantly improve the oxidation kinetics of Li2S, and therefore enable the direct use of Li2S as cathode material in Li-S battery system in the future. This provides a new approach to manage the solubility of lithium sulfides through cation coordination with sulfide anion.

  18. Ammonium Additives to Dissolve Lithium Sulfide through Hydrogen Binding for High-Energy Lithium–Sulfur Batteries

    SciTech Connect

    Pan, Huilin; Han, Kee Sung; Vijayakumar, M.; Xiao, Jie; Cao, Ruiguo; Chen, Junzheng; Zhang, Jiguang; Mueller, Karl T.; Shao, Yuyan; Liu, Jun

    2016-07-01

    In rechargeable Li-S batteries, the uncontrollable passivation of electrodes by highly insulating Li2S limits sulfur utilization, increases polarization and decreases cycling stability. Dissolving Li2S in organic electrolyte is a facile solution to maintain the active reaction interface between electrolyte and sulfur cathode, and thus address the above issues. Herein, ammonium salts are demonstrated as effective additives to promote the dissolution of Li2S to 1.25 M in DMSO solvent at room temperature. NMR measurements show that the strong hydrogen binding effect of N-H groups plays a critical role in dissolving Li2S by forming complex ligands with S2- anions coupled with the solvent’s solvating surrounding. Ammonium additives in electrolyte can also significantly improve the oxidation kinetics of Li2S, therefore enables the direct use of Li2S as cathode material in Li-S battery system in the future. This provides a new approach to manage the solubility of lithium sulfides through cation coordination with sulfide anion.

  19. Causal binding of actions to their effects.

    PubMed

    Buehner, Marc J; Humphreys, Gruffydd R

    2009-10-01

    According to widely held views in cognitive science harking back to David Hume, causality cannot be perceived directly, but instead is inferred from patterns of sensory experience, and the quality of these inferences is determined by perceivable quantities such as contingency and contiguity. We report results that suggest a reversal of Hume's conjecture: People's sense of time is warped by the experience of causality. In a stimulus-anticipation task, participants' response behavior reflected a shortened experience of time in the case of target stimuli participants themselves had generated, relative to equidistant, equally predictable stimuli they had not caused. These findings suggest that causality in the mind leads to temporal binding of cause and effect, and extend and generalize beyond earlier claims of intentional binding between action and outcome.

  20. Hydrogen effects in non-ferrous alloys: discussion

    NASA Astrophysics Data System (ADS)

    Patel, Mitesh; Stopher, Miles A.

    2017-06-01

    This is a transcript of the discussion session on the effects of hydrogen in the non-ferrous alloys of zirconium and titanium, which are anisotropic hydride-forming metals. The four talks focus on the hydrogen embrittlement mechanisms that affect zirconium and titanium components, which are respectively used in the nuclear and aerospace industries. Two specific mechanisms are delayed hydride cracking and stress corrosion cracking. This article is part of the themed issue 'The challenges of hydrogen and metals'.

  1. 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.

  2. Ortho-substituted catechol derivatives: the effect of intramolecular hydrogen-bonding pathways on chloride anion recognition.

    PubMed

    Winstanley, Keith J; Smith, David K

    2007-04-13

    This paper reports a series of chloride anion receptors containing two catechol head groups connected through their ortho-positions via a spacer chain. The linking group chosen to attach the spacer chain to the catechol units has a major impact on the anion-binding potential of the receptor. Linking groups that are capable of forming stable six-membered intramolecular hydrogen-bonded rings with the catechol O-H groups significantly inhibit the ability of the catechol units to hydrogen bond to chloride anions. However, where the linking groups are only capable of forming five- or seven-membered intramolecular hydrogen-bonded rings, then anion binding via hydrogen bonding through the catechol O-H groups becomes a possibility. This process is solvent dependent; the presence of competitive solvent (e.g., DMSO-d6) disrupts the intramolecular hydrogen-bonding pattern and enhances anion binding relative to simple unfunctionalized catechol. The most effective receptor is that in which the hydrogen-bonding linker (-CH2CONH-) is most distant from the catechol units and can only form a seven-membered intramolecular hydrogen-bonded ring. In this case, the receptor, which contains two catechol units, is a more effective chloride anion binder than simple unfunctionalized catechol, demonstrating that the two head groups, in combination with the N-H groups in the linker, act cooperatively and enhance the degree of anion binding. In summary, this paper provides insight into the hydrogen-bonding patterns in ortho-functionalized catechols and the impact these have on the potential of the catechol O-H groups to hydrogen bond to a chloride anion.

  3. Optimizing Binding Energies of Key Intermediates for CO 2 Hydrogenation to Methanol over Oxide-Supported Copper

    SciTech Connect

    None, None

    2016-08-29

    Rational optimization of catalytic performance has been one of the major challenges in catalysis. We report a bottom-up study on the ability of TiO2 and ZrO2 to optimize the CO2 conversion to methanol on Cu, using combined density functional theory (DFT) calculations, kinetic Monte Carlo (KMC) simulations, in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements, and steady-state flow reactor tests. Furthermore, the theoretical results from DFT and KMC agree with in situ DRIFTS measurements, showing that both TiO2 and ZrO2 help to promote methanol synthesis on Cu via carboxyl intermediates and the reverse water–gas-shift (RWGS) pathway; the formate intermediates, on the other hand, likely act as a spectator eventually. The origin of the superior promoting effect of ZrO2 is associated with the fine-tuning capability of reduced Zr3+ at the interface, being able to bind the key reaction intermediates, e.g. *CO2, *CO, *HCO, and *H2CO, moderately to facilitate methanol formation. Our study demonstrates the importance of synergy between theory and experiments to elucidate the complex reaction mechanisms of CO2 hydrogenation for the realization of a better catalyst by design.

  4. Optimizing Binding Energies of Key Intermediates for CO2 Hydrogenation to Methanol over Oxide-Supported Copper.

    PubMed

    Kattel, Shyam; Yan, Binhang; Yang, Yixiong; Chen, Jingguang G; Liu, Ping

    2016-09-28

    Rational optimization of catalytic performance has been one of the major challenges in catalysis. Here we report a bottom-up study on the ability of TiO2 and ZrO2 to optimize the CO2 conversion to methanol on Cu, using combined density functional theory (DFT) calculations, kinetic Monte Carlo (KMC) simulations, in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements, and steady-state flow reactor tests. The theoretical results from DFT and KMC agree with in situ DRIFTS measurements, showing that both TiO2 and ZrO2 help to promote methanol synthesis on Cu via carboxyl intermediates and the reverse water-gas-shift (RWGS) pathway; the formate intermediates, on the other hand, likely act as a spectator eventually. The origin of the superior promoting effect of ZrO2 is associated with the fine-tuning capability of reduced Zr(3+) at the interface, being able to bind the key reaction intermediates, e.g. *CO2, *CO, *HCO, and *H2CO, moderately to facilitate methanol formation. This study demonstrates the importance of synergy between theory and experiments to elucidate the complex reaction mechanisms of CO2 hydrogenation for the realization of a better catalyst by design.

  5. Optimizing Binding Energies of Key Intermediates for CO 2 Hydrogenation to Methanol over Oxide-Supported Copper

    SciTech Connect

    None, None

    2016-08-29

    Rational optimization of catalytic performance has been one of the major challenges in catalysis. We report a bottom-up study on the ability of TiO2 and ZrO2 to optimize the CO2 conversion to methanol on Cu, using combined density functional theory (DFT) calculations, kinetic Monte Carlo (KMC) simulations, in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements, and steady-state flow reactor tests. Furthermore, the theoretical results from DFT and KMC agree with in situ DRIFTS measurements, showing that both TiO2 and ZrO2 help to promote methanol synthesis on Cu via carboxyl intermediates and the reverse water–gas-shift (RWGS) pathway; the formate intermediates, on the other hand, likely act as a spectator eventually. The origin of the superior promoting effect of ZrO2 is associated with the fine-tuning capability of reduced Zr3+ at the interface, being able to bind the key reaction intermediates, e.g. *CO2, *CO, *HCO, and *H2CO, moderately to facilitate methanol formation. Our study demonstrates the importance of synergy between theory and experiments to elucidate the complex reaction mechanisms of CO2 hydrogenation for the realization of a better catalyst by design.

  6. Optimizing Binding Energies of Key Intermediates for CO 2 Hydrogenation to Methanol over Oxide-Supported Copper

    DOE PAGES

    None, None

    2016-08-29

    Rational optimization of catalytic performance has been one of the major challenges in catalysis. We report a bottom-up study on the ability of TiO2 and ZrO2 to optimize the CO2 conversion to methanol on Cu, using combined density functional theory (DFT) calculations, kinetic Monte Carlo (KMC) simulations, in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements, and steady-state flow reactor tests. Furthermore, the theoretical results from DFT and KMC agree with in situ DRIFTS measurements, showing that both TiO2 and ZrO2 help to promote methanol synthesis on Cu via carboxyl intermediates and the reverse water–gas-shift (RWGS) pathway; the formatemore » intermediates, on the other hand, likely act as a spectator eventually. The origin of the superior promoting effect of ZrO2 is associated with the fine-tuning capability of reduced Zr3+ at the interface, being able to bind the key reaction intermediates, e.g. *CO2, *CO, *HCO, and *H2CO, moderately to facilitate methanol formation. Our study demonstrates the importance of synergy between theory and experiments to elucidate the complex reaction mechanisms of CO2 hydrogenation for the realization of a better catalyst by design.« less

  7. The effects of hydrogen in sealed electrical contacts

    NASA Astrophysics Data System (ADS)

    Schubert, Rudolf; Gray, Eoin W.

    1985-12-01

    Hydrogen has been an integral atmospheric component of sealed electrical contacts for decades because of its effect on reliability. It is well known that hydrogen is a needed component to prevent high contact resistance due to carbon-spot formation. This hydrogen benefit has been attributed to hydrogenation of hydrocarbons (HC), enhanced volatilization of previously deposited carbon, enhanced catalytic activity, and thermal cooling. By a variety of physical and chemical laboratory techniques, this paper shows that the hydrogen is not itself directly active. However, some of the hydrogen is converted to water during the glass sealing process. It is this water which plays the active role in the process of quenching carbon formation from hydrocarbon impurities and also acts as a diluent of HC's adsorbed on the contact surface and in the arcing volume. This limits the carbon accumulation on the contacts and increases lifetime reliability.

  8. 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.

  9. Amide-mediated hydrogen bonding at organic crystal/water interfaces enables selective endotoxin binding with picomolar affinity.

    PubMed

    Vagenende, Vincent; Ching, Tim-Jang; Chua, Rui-Jing; Thirumoorthi, Navanita; Gagnon, Pete

    2013-05-22

    Since the discovery of endotoxins as the primary toxic component of Gram-negative bacteria, researchers have pursued the quest for molecules that detect, neutralize, and remove endotoxins. Selective removal of endotoxins is particularly challenging for protein solutions and, to this day, no general method is available. Here, we report that crystals of the purine-derived compound allantoin selectively adsorb endotoxins with picomolar affinity through amide-mediated hydrogen bonding in aqueous solutions. Atom force microscopy and chemical inhibition experiments indicate that endotoxin adsorption is largely independent from hydrophobic and ionic interactions with allantoin crystals and is mediated by hydrogen bonding with amide groups at flat crystal surfaces. The small size (500 nm) and large specific surface area of allantoin crystals results in a very high endotoxin-binding capacity (3 × 10(7) EU/g) which compares favorably with known endotoxin-binding materials. These results provide a proof-of-concept for hydrogen bond-based molecular recognition processes in aqueous solutions and establish a practical method for removing endotoxins from protein solutions.

  10. 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.

  11. Cosolvent Effects on Solute-Solvent Hydrogen-Bond Dynamics: Ultrafast 2D IR Investigations.

    PubMed

    Kashid, Somnath M; Jin, Geun Young; Bagchi, Sayan; Kim, Yung Sam

    2015-12-10

    Cosolvents strongly influence the solute-solvent interactions of biomolecules in aqueous environments and have profound effects on the stability and activity of several proteins and enzymes. Experimental studies have previously reported on the hydrogen-bond dynamics of water molecules in the presence of a cosolvent, but understanding the effects from a solute's perspective could provide greater insight into protein stability. Because carbonyl groups are abundant in biomolecules, the current study used 2D IR spectroscopy and molecular dynamics simulations to compare the hydrogen-bond dynamics of the solute's carbonyl group in aqueous solution, with and without the presence of DMSO as a cosolvent. 2D IR spectroscopy was used to quantitatively estimate the time scales of the hydrogen-bond dynamics of the carbonyl group in neat water and 1:1 DMSO/water solution. The 2D IR results show spectral signatures of a chemical exchange process: The presence of the cosolvent was found to lower the hydrogen-bond exchange rate by a factor of 5. The measured exchange rates were 7.50 × 10(11) and 1.48 × 10(11) s(-1) in neat water and 1:1 DMSO/water, respectively. Molecular dynamics simulations predict a significantly shorter carbonyl hydrogen-bond lifetime in neat water than in 1:1 DMSO/water and provide molecular insights into the exchange mechanism. The binding of the cosolvent to the solute was found to be accompanied by the release of hydrogen-bonded water molecules to the bulk. The widely different hydrogen-bond lifetimes and exchange rates with and without DMSO indicate a significant change in the ultrafast hydrogen-bond dynamics in the presence of a cosolvent, which, in turn, might play an important role in the stability and activity of biomolecules.

  12. The effects of hydrogen bonds on metal-mediated O2 activation and related processes

    PubMed Central

    Shook, Ryan L.; Borovik, A. S.

    2009-01-01

    Hydrogen bonds stabilize and direct chemistry performed by metalloenzymes. With inspiration from enzymes, we will utilize an approach that incorporates intramolecular hydrogen bond donors to determine their effects on the stability and reactivity of metal complexes. Our premise is that control of secondary coordination sphere interactions will promote new function in synthetic metal complexes. Multidentate ligands have been developed that create rigid organic structures around metal ions. These ligands place hydrogen bond (H-bond) donors proximal to the metal centers, forming specific microenvironments. One distinguishing attribute of these systems is that site-specific modulations in structure can be readily accomplished, in order to evaluate correlations with reactivity. A focus of this research is consideration of dioxygen binding and activation by metal complexes, including developing structure–function relationships in metal-assisted oxidative catalysis. PMID:19082087

  13. Effects of multiple ligand binding on kinetic isotope effects in PQQ-dependent methanol dehydrogenase.

    PubMed

    Hothi, Parvinder; Basran, Jaswir; Sutcliffe, Michael J; Scrutton, Nigel S

    2003-04-08

    The reaction of PQQ-dependent methanol dehydrogenase (MDH) from Methylophilus methylotrophus has been studied by steady-state and stopped-flow kinetic methods, with particular reference to multiple ligand binding and the kinetic isotope effect (KIE) for PQQ reduction. Phenazine ethosulfate (PES; an artificial electron acceptor) and cyanide (a suppressant of endogenous activity), but not ammonium (an activator of MDH), compete for binding at the catalytic methanol-binding site. Cyanide does not activate turnover in M. methylotrophus MDH, as reported previously for the Paracoccus denitrificans enzyme. Activity is dependent on activation by ammonium but is inhibited at high ammonium concentrations. PES and methanol also influence the stimulatory and inhibitory effects of ammonium through competitive binding. Reaction profiles as a function of ammonium and PES concentration differ between methanol and deuterated methanol, owing to force constant effects on the binding of methanol to the stimulatory and inhibitory ammonium binding sites. Differential binding gives rise to unusual KIEs for PQQ reduction as a function of ammonium and PES concentration. The observed KIEs at different ligand concentrations are independent of temperature, consistent with their origin in differential binding affinities of protiated and deuterated substrate at the ammonium binding sites. Stopped-flow studies indicate that enzyme oxidation is not rate-limiting at low ammonium concentrations (<4 mM) during steady-state turnover. At higher ammonium concentrations (>20 mM), the low effective concentration of PES in the active site owing to the competitive binding of ammonium lowers the second-order rate constant for enzyme oxidation, and the oxidative half-reaction becomes more rate limiting. A sequential stopped-flow method is reported that has enabled, for the first time, a detailed study of the reductive half-reaction of MDH and comparison with steady-state data. The limiting rate of PQQ

  14. 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

  15. 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.

  16. Side-chain rotamer changes upon ligand binding: common, crucial, correlate with entropy and rearrange hydrogen bonding

    PubMed Central

    Gaudreault, Francis; Chartier, Matthieu; Najmanovich, Rafael

    2012-01-01

    Motivation: Protein movements form a continuum from large domain rearrangements (including folding and restructuring) to side-chain rotamer changes and small rearrangements. Understanding side-chain flexibility upon binding is important to understand molecular recognition events and predict ligand binding. Methods: In the present work, we developed a well-curated non-redundant dataset of 188 proteins in pairs of structures in the Apo (unbound) and Holo (bound) forms to study the extent and the factors that guide side-chain rotamer changes upon binding. Results: Our analysis shows that side-chain rotamer changes are widespread with only 10% of binding sites displaying no conformational changes. Overall, at most five rotamer changes account for the observed movements in 90% of the cases. Furthermore, rotamer changes are essential in 32% of flexible binding sites. The different amino acids have a 11-fold difference in their probability to undergo changes. Side-chain flexibility represents an intrinsic property of amino acids as it correlates well with configurational entropy differences. Furthermore, on average b-factors and solvent accessible surface areas can discriminate flexible side-chains in the Apo form. Finally, there is a rearrangement of the hydrogen-bonding network upon binding primarily with a loss of H-bonds with water molecules and a gain of H-bonds with protein residues for flexible residues. Interestingly, only 25% of side chains capable of forming H-bonds do so with the ligand upon binding. In terms of drug design, this last result shows that there is a large number of potential interactions that may be exploited to modulate the specificity and sensitivity of inhibitors. Contact: rafael.najmanovich@usherbrooke.ca PMID:22962462

  17. Ab initio design of Ca-decorated organic frameworks for high capacity molecular hydrogen storage with enhanced binding

    NASA Astrophysics Data System (ADS)

    Sun, Y. Y.; Lee, Kyuho; Kim, Yong-Hyun; Zhang, S. B.

    2009-07-01

    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 (H2) 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-α, with decorated Ca. Both density functional theory and second-order Møller-Plesset perturbation calculations show that the H2 binding in these systems is significantly stronger than the van der Waals interactions, which is required for H2 storage at near ambient conditions.

  18. 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.

  19. Hydrogen

    PubMed Central

    Bockris, John O’M.

    2011-01-01

    The idea of a “Hydrogen Economy” is that carbon containing fuels should be replaced by hydrogen, thus eliminating air pollution and growth of CO2 in the atmosphere. However, storage of a gas, its transport and reconversion to electricity doubles the cost of H2 from the electrolyzer. Methanol made with CO2 from the atmosphere is a zero carbon fuel created from inexhaustible components from the atmosphere. Extensive work on the splitting of water by bacteria shows that if wastes are used as the origin of feed for certain bacteria, the cost for hydrogen becomes lower than any yet known. The first creation of hydrogen and electricity from light was carried out in 1976 by Ohashi et al. at Flinders University in Australia. Improvements in knowledge of the structure of the semiconductor-solution system used in a solar breakdown of water has led to the discovery of surface states which take part in giving rise to hydrogen (Khan). Photoelectrocatalysis made a ten times increase in the efficiency of the photo production of hydrogen from water. The use of two electrode cells; p and n semiconductors respectively, was first introduced by Uosaki in 1978. Most photoanodes decompose during the photoelectrolysis. To avoid this, it has been necessary to create a transparent shield between the semiconductor and its electronic properties and the solution. In this way, 8.5% at 25 °C and 9.5% at 50 °C has been reached in the photo dissociation of water (GaP and InAs) by Kainthla and Barbara Zeleney in 1989. A large consortium has been funded by the US government at the California Institute of Technology under the direction of Nathan Lewis. The decomposition of water by light is the main aim of this group. Whether light will be the origin of the post fossil fuel supply of energy may be questionable, but the maximum program in this direction is likely to come from Cal. Tech. PMID:28824125

  20. 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.

  1. Hydrogen effects in non-ferrous alloys: discussion.

    PubMed

    Patel, Mitesh; Stopher, Miles A

    2017-07-28

    This is a transcript of the discussion session on the effects of hydrogen in the non-ferrous alloys of zirconium and titanium, which are anisotropic hydride-forming metals. The four talks focus on the hydrogen embrittlement mechanisms that affect zirconium and titanium components, which are respectively used in the nuclear and aerospace industries. Two specific mechanisms are delayed hydride cracking and stress corrosion cracking.This article is part of the themed issue 'The challenges of hydrogen and metals'. © 2017 The Author(s).

  2. Retroactivity effects dependency on the transcription factors binding mechanisms.

    PubMed

    Pantoja-Hernández, Libertad; Álvarez-Buylla, Elena; Aguilar-Ibáñez, Carlos F; Garay-Arroyo, Adriana; Soria-López, Alberto; Martínez-García, Juan Carlos

    2016-12-07

    Downstream connection effects on transcription are caused by retroactivity. When biomolecular dynamical systems interconnect retroactivity is a property that becomes important. The biological functional meaning of these effects is increasingly becoming an area of interest. Downstream targets, which are operator binding sites in transcriptional networks, may induce behaviors such as ultrasensitive responses or even represent an undesired issue in regulation. To the best of our knowledge, the role of the binding mechanisms of transcription factors in relation to minimizing - or enhancing - retroactivity effects has not been previously addressed. Our aim is to evaluate retroactivity effects considering how the binding mechanism impacts the number of free functional transcription factor (FFTF) molecules using a simple model via deterministic and stochastic simulations. We study four transcription factor binding mechanisms (BM): simple monomer binding (SMB), dimer binding (DB), cooperative sequential binding (CSB) and cooperative sequential binding with dimerization (CSB_D). We consider weak and strong binding regimes for each mechanism, where we contrast the cases when the FFTF is bound or unbound to the downstream loads. Upon interconnection, the number of FFTF molecules changed less for the SMB mechanism while for DB they changed the most. Our results show that for the chosen mechanisms (in terms of the corresponding described dynamics), retroactivity effects depend on transcription binding mechanisms. This contributes to the understanding of how the transcription factor regulatory function-such as decision making-and its dynamic needs for the response, may determine the nature of the selected binding mechanism.

  3. 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.

  4. Effective binding of perhalogenated closo-borates to serum albumins revealed by spectroscopic and ITC studies

    NASA Astrophysics Data System (ADS)

    Kuperman, Marina V.; Losytskyy, Mykhaylo Yu.; Bykov, Alexander Yu.; Yarmoluk, Sergiy M.; Zhizhin, Konstantin Yu.; Kuznetsov, Nikolay T.; Varzatskii, Oleg A.; Gumienna-Kontecka, Elzbieta; Kovalska, Vladyslava B.

    2017-08-01

    The interactions of boron cluster compounds closo-borates with biomolecules are widely studied due to their efficiency as agents for boron neutron capture therapy of cancer. In present work the binding abilities of anionic halogen closo-borates [B10Hal10]2- (Hal = Cl, Br, I) and [B12Hal12]2- (Hal = Cl, I) towards bovine and human serum albumins were investigated by spectroscopic and isothermal titration calorimetry (ITC) methods. The protein fluorescence quenching method and ITC studies confirmed the complex formation. The degree of protein fluorescence quenching increased from chlorine to iodine boron derivatives that is attributed to external heavy atom effect. The ITC data point on the existence in the protein structure of two types of binding sites: with higher and lower affinity to closo-borates. Albumin-closo-borate complex binding ratio, n (4-5 anions per protein molecule) is higher than for the parent hydrogen closo-borates (2 anions per protein molecule). Binding constants estimated by fluorescent and ITC methods indicate higher affinity of halogen closo-borates to albumins (K in the range of 104-106 M-1) comparing to that of the hydrogen closo-borate (K about 103 M-1). Due to their high affinity and high binding ratio to albumins halogen closo-borates are proposed for further studies as agents for boron neutron capture therapy.

  5. 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.

  6. Effect of a liquid phase on spillover of hydrogen

    SciTech Connect

    Kildibekova, G.A.; Zavyalov, S.A.; Mikhailenko, S.D.

    1995-03-01

    Spillover of hydrogen in Pt/ZnO is studied by measuring conductance of semiconductor sensors in the presence of water and alcohol vapors. The sensor conductance is found to increase sharply at low solvent pressures and to decrease significantly with increasing pressure. The effects observed are interpreted from the standpoint of accelerating the transfer of atomic hydrogen by solvation and desolvation of a proton.

  7. Selective binding of hydrogen chloride and its trapping through supramolecular gelation.

    PubMed

    Basak, Shibaji; Nandi, Nibedita; Banerjee, Arindam

    2014-07-04

    A pyridine containing amino acid based gelator forms gel in aqueous media in the presence of hydrochloric acid and the chloride ion is found to be very selective for gelation. The gelator is successfully applied for the detection and trapping of hydrogen chloride gas and this indicates its probable application for removing hazardous HCl gas from the environment.

  8. 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.

  9. Effect of hydrogen bonds on optical nonlinearities of inorganic crystals

    NASA Astrophysics Data System (ADS)

    Xue, Dongfeng; Zhang, Siyuan

    1999-03-01

    This work probes the role of hydrogen bonds (such as O-H⋯O and N-H⋯O) in some inorganic nonlinear optical (NLO) crystals, such as HIO 3, NH 4H 2PO 4 (ADP), K[B 5O 6(OH) 4]·2H 2O (KB 5) and K 2La(NO 3) 5·2H 2O (KLN), from the chemical bond standpoint. Second order NLO behaviors of these four typical inorganic crystals have been quantitatively studied, results show hydrogen bonds play a very important role in NLO contributions to the total nonlinearity. Conclusions derived here concerning the effect of hydrogen bonds on optical nonlinearities of inorganic crystals have important implications with regard to the utilization of hydrogen bonds in the structural design of inorganic NLO crystals.

  10. 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.

  11. 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.

  12. 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

  13. The binding and release of oxygen and hydrogen peroxide are directed by a hydrophobic tunnel in cholesterol oxidase†

    PubMed Central

    Chen, Lin; Lyubimov, Artem Y.; Brammer, Leighanne; Vrielink, Alice; Sampson, Nicole S.

    2008-01-01

    The usage by enzymes of specific binding pathways for gaseous substrates or products is debated. The crystal structure of the redox enzyme cholesterol oxidase, solved at sub-Ångstrom 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 understand 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 the tunnel residues Phe359 or Gly347 to Trp or Asn, reduces the catalytic efficiency of oxidation. The KmO2 increases from 300 ± 35 μM for the wild-type enzyme to 617 ± 15 μM for the F359W mutant. The kcat for the F359W mutant catalyzed reaction decreases 13-fold relative to the wild-type catalyzed reaction. The N485D and G347N mutants could not be saturated with oxygen. Hydride transfer 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 are consistent with the cooperative kinetics. In the atomic resolution structure of F359W, the indole ring of the tryptophan completely fills the tunnel and is only observed in 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 substrate binding and

  14. 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.

  15. Interaction of molecular hydrogen with open transition metal centers for enhanced binding in metal-organic frameworks: a computational study.

    PubMed

    Lochan, Rohini C; Khaliullin, Rustam Z; Head-Gordon, Martin

    2008-05-19

    Molecular hydrogen is known to form stable, "nonclassical" sigma complexes with transition metal centers that are stabilized by donor-acceptor interactions and electrostatics. In this computational study, we establish that strong H2 sorption sites can be obtained in metal-organic frameworks by incorporating open transition metal sites on the organic linkers. Using density functional theory and energy decomposition analysis, we investigate the nature and characteristics of the H2 interaction with models of exposed open metal binding sites {half-sandwich piano-stool shaped complexes of the form (Arene)ML(3- n)(H2)n [M=Cr, Mo, V(-), Mn(+); Arene = C6H5X (X=H, F, Cl, OCH3, NH2, CH3, CF3) or C6H3Y2X (Y=COOH, X=CF3, Cl; L=CO; n=1-3]}. The metal-H2 bond dissociation energy of the studied complexes is calculated to be between 48 and 84 kJ/mol, based on the introduction of arene substituents, changes to the metal core, and of charge-balancing ligands. Thus, design of the binding site controls the H2 binding affinity and could be potentially used to control the magnitude of the H2 interaction energy to achieve reversible sorption characteristics at ambient conditions. Energy decomposition analysis illuminates both the possibilities and present challenges associated with rational materials design.

  16. Effects of formate on fermentative hydrogen production by Enterobacter aerogenes.

    PubMed

    Kurokawa, Tatsuo; Tanisho, Shigeharu

    2005-01-01

    This paper describes the effects of formate on fermentative hydrogen production by Enterobacter aerogenes by way of batch culture. When 20 mM formate was added to pH 6.3 and pH 5.8 E. aerogenes glucose cultures (formate culture) at the beginning of cultivation, hydrogen evolution through both glucose consumption and decomposition of the extrinsic formate occurred together, while hydrogen evolution occurred only through glucose consumption in the control cultures. The hydrogen evolution rates in the formate cultures were faster than in the control cultures, although cell growth and glucose consumption rates in the formate cultures were slower than the control cultures'. The decomposition rate of the extrinsic formate in the pH 5.8 formate culture was faster than in the pH 6.3 formate culture. The hydrogen yield from glucose in the pH 6.3 formate culture increased due to the increasing amount of the nicotinamide adenine dinucleotide for hydrogen production.

  17. 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.

  18. Effects of the central potassium ions on the G-quadruplex and stabilizer binding.

    PubMed

    Wang, Zhiguo; Liu, Jun-Ping

    2017-03-01

    Human telomeres undertake the structure of intra-molecular parallel G-quadruplex in the presence of K(+) in eukaryotic cell. Stabilization of the telomere G-quadruplex represents a potential strategy to prevent telomere lengthening by telomerase in cancer therapy. Current work demonstrates that the binding of central K(+) with the parallel G-quadruplex is a coordinated water directed step-wise process. The K(+) above the top G-tetrad is prone to leak into environment and the 5'-adenine quickly flips over the top G-tetrad, leading to the bottom gate of G-tetrads as the only viable pathway of K(+) binding. Present molecular dynamics studies on the two most potent stabilizers RHPS4 and BRACO-19 reveal that the central K(+) has little influence on the binding conformations of the bound stabilizers. But without the central K(+), either RHPS4 or BRACO-19 cannot stabilize the structure of G-quadruplex. The binding strength of stabilizers evaluated by the MM-PBSA method follows the order of BRACO-19> RHPS4, which agrees with the experimental results. The difference in binding affinities between RHPS4 and BRACO-19 is probably related to the ability to form intramolecular hydrogen bonds and favorable van del Waals interactions with G-quadruplex. In the models that have one central K(+) located at the upper/lower binding site, the corresponding top/bottom stacked stabilizers show more favorable binding affinities, indicating the apparent promoting effect of central K(+) on the stabilizer binding. Our findings provide further insights into the regulatory effect of K(+) on the G-quadruplex targeted binding, which is meaningful to the development of G-quadruplex stabilizers. Copyright © 2017 Elsevier Inc. All rights reserved.

  19. Dendritic biomimicry: microenvironmental hydrogen-bonding effects on tryptophan fluorescence.

    PubMed

    Koenig, S; Müller, L; Smith, D K

    2001-03-02

    Two series of dendritically modified tryptophan derivatives have been synthesised and their emission spectra measured in a range of different solvents. This paper presents the syntheses of these novel dendritic structures and discusses their emission spectra in terms of both solvent and dendritic effects. In the first series of dendrimers, the NH group of the indole ring is available for hydrogen bonding, whilst in the second series, the indole NH group has been converted to NMe. Direct comparison of the emission wavelengths of analogous NH and NMe derivatives indicates the importance of the Kamlet-Taft solvent beta3 parameter, which reflects the ability of the solvent to accept a hydrogen bond from the NH group, an effect not possible for the NMe series of dendrimers. For the NH dendrimers, the attachment of a dendritic shell to the tryptophan subunit leads to a red shift in emission wavelength. This dendritic effect only operates in non-hydrogen-bonding solvents. For the NMe dendrimers, however, the attachment of a dendritic shell has no effect on the emission spectra of the indole ring. This proves the importance of hydrogen bonding between the branched shell and the indole NH group in causing the dendritic effect. This is the first time a dendritic effect has been unambiguously assigned to individual hydrogen-bonding interactions and indicates that such intramolecular interactions are important in dendrimers, just as they are in proteins. Furthermore, this paper sheds light on the use of tryptophan residues as a probe of the microenvironment within proteins--in particular, it stresses the importance of hydrogen bonds formed by the indole NH group.

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

    PubMed

    Martínez-González, Eduardo; Frontana, Carlos

    2014-05-07

    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.

  1. Effect of some isothiocyanates on the hydrogenation of canola oil

    SciTech Connect

    Abraham, V.; de Man, J.M.

    1987-06-01

    Sulfur compounds were added to refined and bleached canola oil before hydrogenation in the form of allyl, heptyl and 2-phenethyl isothiocyanates, and the effects on hydrogenation rate, solid fat content and percentage trans fatty acids were determined. The poisoning effect was most pronounced with allyl isothiocyanate and least phenethyl isothiocyanate. As the amount of added sulfur increased, the hydrogenation rate decreased. Of the three isothiocyanates used, allyl isothiocyanate caused formation of larger amounts of trans isomers. An increased sulfur level in the oil resulted in increased solid fat content and trans isomer level. Allyl isothiocyanate also caused formation of larger amounts of solid fat than other isothiocyanates at all levels of sulfur addition. (Refs. 24).

  2. Kinetic effect of Pd additions on the hydrogen uptake of chemically activated, ultramicroporous carbon

    SciTech Connect

    Bhat, Vinay V; Contescu, Cristian I; Gallego, Nidia C

    2010-01-01

    The effect of mixing chemically-activated ultramicroporous carbon (UMC) with Pd nanopowder is investigated. Results show that Pd addition doubles the rate of hydrogen uptake, but does not enhance the hydrogen capacity or improve desorption kinetics. The effect of Pd on the rate of hydrogen adsorption supports the occurrence of the hydrogen spillover mechanism in the Pd - UMC system.

  3. 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.

  4. Effects of hydrogen sulphide in smooth muscle.

    PubMed

    Dunn, William R; Alexander, Stephen P H; Ralevic, Vera; Roberts, Richard E

    2016-02-01

    In recent years, it has become apparent that the gaseous pollutant, hydrogen sulphide (H2S) can be synthesised in the body and has a multitude of biological actions. This review summarizes some of the actions of this 'gasotransmitter' in influencing the smooth muscle that is responsible for controlling muscular activity of hollow organs. In the vasculature, while H2S can cause vasoconstriction by complex interactions with other biologically important gases, such as nitric oxide, the prevailing response is vasorelaxation. While most vasorelaxation responses occur by a direct action of H2S on smooth muscle cells, it has recently been proposed to be an endothelium-derived hyperpolarizing factor. H2S also promotes relaxation in other smooth muscle preparations including bronchioles, the bladder, gastrointestinal tract and myometrium, opening up the opportunity of exploiting the pharmacology of H2S in the treatment of conditions where smooth muscle tone is excessive. The original concept, that H2S caused smooth muscle relaxation by activating ATP-sensitive K(+) channels, has been supplemented with observations that H2S can also modify the activity of other potassium channels, intracellular pH, phosphodiesterase activity and transient receptor potential channels on sensory nerves. While the enzymes responsible for generating endogenous H2S are widely expressed in smooth muscle preparations, it is much less clear what the physiological role of H2S is in determining smooth muscle contractility. Clarification of this requires the development of potent and selective inhibitors of H2S-generating enzymes. Copyright © 2015 Elsevier Inc. All rights reserved.

  5. Investigating the effect of heat treatment on hydrogen permeation behavior of API X-70 steel

    NASA Astrophysics Data System (ADS)

    Shirband, Zeynab; Shishesaz, Mohammad Reza; Ashrafi, Ali

    2012-06-01

    Pipeline steels absorb different amounts of hydrogen during transportation of sour oil and gas. Since hydrogen-related damages such as hydrogen-induced cracking are strongly affected by hydrogen permeation behavior of steels, the purpose of this study determined to investigate hydrogen permeation behavior in API X-70 pipeline steel using electrochemical permeation method. The effect of heat treatment was also considered. It was found that hydrogen diffusivity increased by annealing the X-70 and it was decreased by normalizing. The condition was reverse for hydrogen apparent solubility. Finally, it was concluded that change in hydrogen diffusivity can be attributed to changes in grain size due to heat treatment.

  6. Synthesis and anion binding studies of tris(3-aminopropyl)amine-based tripodal urea and thiourea receptors: Proton transfer-induced selectivity for hydrogen sulfate over sulfate

    PubMed Central

    Khansari, Maryam Emami; Johnson, Corey R.; Basaran, Ismet; Nafis, Aemal; Wang, Jing

    2015-01-01

    Tris(3-aminopropyl)amine-based tripodal urea and thiourea receptors, tris([(4-cyanophenyl)amino]propyl)urea (L1) and tris([(4-cyanophenyl)amino]propyl)thiourea (L2), have been synthesized and their anion binding properties have been investigated for halides and oxoanions. As investigated by 1H NMR titrations, each receptor binds an anion with a 1:1 stoichiometry via hydrogen-bonding interactions (NH⋯anion), showing the binding trend in the order of F− > H2PO4− > HCO3− > HSO4− > CH3COO− > SO42− > Cl− > Br− > I in DMSO-d6. The interactions of the receptors were further studied by 2D NOESY, showing the loss of NOESY contacts of two NH resonances for the complexes of F−, H2PO4−, HCO3−, HSO4− or CH3COO− due to the strong NH⋯anion interactions. The observed higher binding affinity for HSO4− than SO42− is attributed to the proton transfer from HSO4− to the central nitrogen of L1 or L2 which was also supported by the DFT calculations, leading to the secondary acid-base interactions. The thiourea receptor L2 has a general trend to show a higher affinity for an anion as compared to the urea receptor L1 for the corresponding anion in DMSO-d6. In addition, the compound L2 has been exploited for its extraction properties for fluoride in water using a liquid-liquid extraction technique, and the results indicate that the receptor effectively extracts fluoride from water showing ca. 99% efficiency (based on L2). PMID:28184300

  7. 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.

  8. 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.

  9. Hydrogen Atoms Cause Long-Range Electronic Effects on Graphite

    NASA Astrophysics Data System (ADS)

    Ruffieux, P.; Gröning, O.; Schwaller, P.; Schlapbach, L.; Gröning, P.

    2000-05-01

    We report on long-range electronic effects caused by hydrogen-carbon interaction at the graphite surface. Two types of defects could be distinguished with a combined mode of scanning tunneling microscopy and atomic force microscopy: chemisorption of hydrogen on the basal plane of graphite and atomic vacancy formation. Both types show a \\(3×3\\)R30° superlattice in the local density of states but have a different topographic structure. The range of modifications in the electronic structure, of fundamental importance for electronic devices based on carbon nanostructures, has been found to be of the order of 20-25 lattice constants.

  10. 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.

  11. Effects of crossover hydrogen on platinum dissolution and agglomeration

    NASA Astrophysics Data System (ADS)

    Cheng, Tommy T. H.; Rogers, Erin; Young, Alan P.; Ye, Siyu; Colbow, Vesna; Wessel, Silvia

    2011-10-01

    The durability of catalysts in the polymer-electrolyte membrane fuel cell (PEMFC) is identified as a critical limiting factor for wide commercialization of fuel cells. Even though much progress has been made in understanding the degradation mechanisms, the phenomena of Pt dissolution and agglomeration and their contributing factors are not fully understood. In the present investigation, the effects of crossover hydrogen on Pt degradation are studied using an accelerated stress test (AST). The end-of-test (EOT) membrane-electrode-assemblies (MEAs) were characterized by X-ray diffraction (XRD), scanning-electron microscopy (SEM), and energy-dispersive X-ray (EDX). The results provided mechanistic understanding of Pt dissolution and agglomeration: Pt growth and agglomeration were found to be less severe with more crossover hydrogen due likely to the chemical reduction of Pt oxides by crossover hydrogen and the subsequently decrease in the amount of Pt ions formed via the oxide pathway.

  12. Cooperative hydrogen bonds of macromolecules. 2. Two-dimensional cooperativity in the binding of poly(4-vinylpyridine) to poly(4-vinylphenol).

    PubMed

    Kríz, Jaroslav; Dybal, Jirí; Brus, Jirí

    2006-09-21

    The hydrogen bond interaction of poly(4-vinylphenol) (PVF), ligated by a 20 mol/mol excess of pyridine-d(5) (PD) in tetrahydrofuran-d(8), with poly(4-vinylpyridine) (PVP) was studied using liquid and solid-state NMR and quantum mechanical calculations. Because of its cooperative interaction, PVP substitutes PD in its hydrogen bond with PVF, thus forming a PVF-PVP complex, which gradually precipitates from solution. On the basis of the 1H/13C NMR spin-diffusion experiments and density functional theory quantum calculations, the complex is shown to have the fairly regular structure of a polymer sheet with intermittent H-bond links between PVF and PVP chains. The cooperativity of PVP interaction with PVF was studied by measuring the dependence of the binding degree alpha of PVP on its polymerization degree (P(n), being 10, 17, 30, 36, 48, 65, and 84) at various PVP/PVF molar ratios. The value of alpha was established indirectly by measuring the fraction of liberated PD using its 2H quadrupolar relaxation and pulsed field-gradient spin-echo measurement of self-diffusion. The cooperativity is shown to be of a higher order and two-dimensional, that is, dependent on both the polymerization degree of PVP and its ratio to PVF. A mathematical model of such two-dimensional cooperativity based chiefly on a proximity effect is suggested.

  13. Cholesterol accelerates the binding of Alzheimer's β-amyloid peptide to ganglioside GM1 through a universal hydrogen-bond-dependent sterol tuning of glycolipid conformation

    PubMed Central

    Fantini, Jacques; Yahi, Nouara; Garmy, Nicolas

    2013-01-01

    Age-related alterations of membrane lipids in brain cell membranes together with high blood cholesterol are considered as major risk factors for Alzheimer's disease. Yet the molecular mechanisms by which these factors increase Alzheimer's risk are mostly unknown. In lipid raft domains of the plasma membrane, neurotoxic Alzheimer's beta-amyloid (Abeta) peptides interact with both cholesterol and ganglioside GM1. Recent data also suggested that cholesterol could stimulate the binding of Abeta to GM1 through conformational modulation of the ganglioside headgroup. Here we used a combination of physicochemical and molecular modeling approaches to decipher the mechanisms of cholesterol-assisted binding of Abeta to GM1. With the aim of decoupling the effect of cholesterol on GM1 from direct Abeta-cholesterol interactions, we designed a minimal peptide (Abeta5-16) containing the GM1-binding domain but lacking the amino acid residues involved in cholesterol recognition. Using the Langmuir technique, we showed that cholesterol (but not phosphatidylcholine or sphingomyelin) significantly accelerates the interaction of Abeta5-16 with GM1. Molecular dynamics simulations suggested that Abeta5-16 interacts with a cholesterol-stabilized dimer of GM1. The main structural effect of cholesterol is to establish a hydrogen-bond between its own OH group and the glycosidic-bond linking ceramide to the glycone part of GM1, thereby inducing a tilt in the glycolipid headgroup. This fine conformational tuning stabilizes the active conformation of the GM1 dimer whose headgroups, oriented in two opposite directions, form a chalice-shaped receptacle for Abeta. These data give new mechanistic insights into the stimulatory effect of cholesterol on Abeta/GM1 interactions. They also support the emerging concept that cholesterol is a universal modulator of protein-glycolipid interactions in the broader context of membrane recognition processes. PMID:23772214

  14. Cholesterol accelerates the binding of Alzheimer's β-amyloid peptide to ganglioside GM1 through a universal hydrogen-bond-dependent sterol tuning of glycolipid conformation.

    PubMed

    Fantini, Jacques; Yahi, Nouara; Garmy, Nicolas

    2013-01-01

    Age-related alterations of membrane lipids in brain cell membranes together with high blood cholesterol are considered as major risk factors for Alzheimer's disease. Yet the molecular mechanisms by which these factors increase Alzheimer's risk are mostly unknown. In lipid raft domains of the plasma membrane, neurotoxic Alzheimer's beta-amyloid (Abeta) peptides interact with both cholesterol and ganglioside GM1. Recent data also suggested that cholesterol could stimulate the binding of Abeta to GM1 through conformational modulation of the ganglioside headgroup. Here we used a combination of physicochemical and molecular modeling approaches to decipher the mechanisms of cholesterol-assisted binding of Abeta to GM1. With the aim of decoupling the effect of cholesterol on GM1 from direct Abeta-cholesterol interactions, we designed a minimal peptide (Abeta5-16) containing the GM1-binding domain but lacking the amino acid residues involved in cholesterol recognition. Using the Langmuir technique, we showed that cholesterol (but not phosphatidylcholine or sphingomyelin) significantly accelerates the interaction of Abeta5-16 with GM1. Molecular dynamics simulations suggested that Abeta5-16 interacts with a cholesterol-stabilized dimer of GM1. The main structural effect of cholesterol is to establish a hydrogen-bond between its own OH group and the glycosidic-bond linking ceramide to the glycone part of GM1, thereby inducing a tilt in the glycolipid headgroup. This fine conformational tuning stabilizes the active conformation of the GM1 dimer whose headgroups, oriented in two opposite directions, form a chalice-shaped receptacle for Abeta. These data give new mechanistic insights into the stimulatory effect of cholesterol on Abeta/GM1 interactions. They also support the emerging concept that cholesterol is a universal modulator of protein-glycolipid interactions in the broader context of membrane recognition processes.

  15. Nuclear quantum effect on intramolecular hydrogen bond of hydrogen maleate anion: An ab initio path integral molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Kawashima, Yukio; Tachikawa, Masanori

    2013-05-01

    Ab initio path integral molecular dynamics simulation was performed to understand the nuclear quantum effect on the hydrogen bond of hydrogen malonate anion. Static calculation predicted the proton transfer barrier as 0.12 kcal/mol. Conventional ab initio molecular dynamics simulation at 300 K found proton distribution with a double peak on the proton transfer coordinate. Inclusion of thermal effect alone elongates the hydrogen bond length, which increases the barrier height. Inclusion of nuclear quantum effect washes out this barrier, and distributes a single broad peak in the center. H/D isotope effect on the proton transfer is also discussed.

  16. 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

  17. 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.

  18. Catalytic and ligand binding properties of the FK506 binding protein FKBP12: effects of the single amino acid substitution of Tyr82 to Leu.

    PubMed Central

    Bossard, M J; Bergsma, D J; Brandt, M; Livi, G P; Eng, W K; Johnson, R K; Levy, M A

    1994-01-01

    The binding of FK506 and rapamycin to their cytosolic receptor FKBP12 is an intermediate step in the paths leading to their potent immunosuppressive properties. One of the amino acids defining the hydrophobic binding cleft for the macrocycles is Tyr82, which is thought to form a hydrogen bond with the amide oxygens of the common pipecolyl structural element within the two macrolides. To understand better the influence of this amino acid residue in catalytic activity (cis-trans peptidyl prolyl isomerization) and ligand binding properties, a Tyr82 to Leu site-specific modification of FKBP12 was prepared, purified and characterized. Kinetic experiments have demonstrated that the Tyr82 to Leu modification has a greater effect on catalytic properties than on ligand binding affinities, a result which indicates that these inhibitors may not be binding as true transition-state analogues. In an additional test for cellular function, expression of both wild-type and mutant human FKBP12 in a strain of Saccharomyces cerevisiae rendered resistant to rapamycin by deletion of the gene encoding a cytosolic rapamycin binding protein (RPB1), the yeast homologue of FKBP12, restored wild-type drug sensitivity. PMID:7507662

  19. Resolution of Unresolved Safety Issue A-48, Hydrogen control measures and effects of hydrogen burns on safety equipment

    SciTech Connect

    Ferrell, C.M.; Soffer, L.

    1989-09-01

    Unresolved Safety Issue (USI) A-48 arose as a result of the large amount of hydrogen generated and burned within containment during the Three Mile Island accident. This issue covers hydrogen control measures for recoverable degraded-core accidents for all boiling-water reactors (BWRs) and those pressurized-water reactors (PWRs) with ice-condenser containments. The Commission and the nuclear industry have sponsored extensive research in this area, which has led to significant revision of the Commission's hydrogen control regulations, given in Title 10, Code of Federal Regulations, Part 50 (10 CFR 50), Section 50.44. BWRs having Mark I and II containments are presently required to operate with inerted containment atmospheres that effectively prevent hydrogen combustion. BWRs with Mark III containments and PWRs with ice-condenser containments are now required to be equipped with hydrogen control systems to protect containment integrity and safety systems inside containment. Industry has chosen to use hydrogen igniter systems to burn hydrogen produced in a controlled fashion to prevent damage. An independent review by a Committee of the National Research Council concluded that, for most accident scenarios, current regulatory requirements make it highly unlikely that hydrogen detonation would be the cause of containment failure. On the basis of the extensive research effort conducted and current regulatory requirements, including their implementation, the staff concludes that no new regulatory guidance on hydrogen control for recoverable degraded-core accidents for these types of plants is necessary and that USI A-48 is resolved.

  20. Interdependence of coenzyme-induced conformational work and binding potential in yeast alcohol and porcine heart lactate dehydrogenases: a hydrogen-deuterium exchange study

    SciTech Connect

    De Weck, Z.; Pande, J.; Kaegi, J.H.R.

    1987-07-28

    Binding of NAD coenzymes to yeast alcohol dehydrogenase (YADH) and porcine heart lactate dehydrogenase (PHLDH) was studied by hydrogen-deuterium exchange with the infrared technique. Conformational changes in the enzymes specific to the coenzymes and their fragments were observed, and the pH dependence of the exchange reaction shows that it conforms to the EX-2 scheme. In both YADH and PHLDH the magnitude of the conformational change as measured by exchange retardation is considerably larger for the NAD/sup +/ than for NADH. Studies with coenzyme fragments like ADP-ribose, ADP, and AMP also highlight the lack of rigorous correlation between structural features such as charge and size and their influence on exchange behavior. Ternary complexes such as YADH-NAD/sup +/-pyrazole, PHLDH-NAD/sup +/-oxalate, and PHLDH-NADH-oxamate, which mimic the transition state, have a significantly more pronounced effect on exchange rates than the corresponding binary complexes. The outstanding feature of this study is the demonstration that in the binary enzyme-coenzyme complexes the more loosely bound NAD/sup +/ is more effective in retarding exchange than the more firmly bound NADH. These differences are attributed to the unequal structural constraints exerted by the two coenzymes upon the enzymes, which translate to unequal expenditure of transconformational work in the formation of the two complexes. The opposing variation in the free energy of binding and the transconformational work expended can be viewed as an unequal partitioning of the net free energy gain resulting from the protein-ligand interaction into a binding term and that required for conformational change.

  1. Interdependence of coenzyme-induced conformational work and binding potential in yeast alcohol and porcine heart lactate dehydrogenases: a hydrogen-deuterium exchange study.

    PubMed

    De Weck, Z; Pande, J; Kägi, J H

    1987-07-28

    Binding of NAD coenzymes to yeast alcohol dehydrogenase (YADH) and porcine heart lactate dehydrogenase (PHLDH) was studied by hydrogen-deuterium exchange with the infrared technique. Conformational changes in the enzymes specific to the coenzymes and their fragments were observed, and the pH dependence of the exchange reaction shows that it conforms to the EX-2 scheme. In both YADH and PHLDH the magnitude of the conformational change of measured by exchange retardation is considerably larger for NAD+ than for NADH. Studies with coenzyme fragments like ADP-ribose, ADP, and AMP also highlight the lack of rigorous correlation between structural features such as charge and size and their influence on exchange behavior. Ternary complexes such as YADH-NAD+-pyrazole, PHLDH-NAD+-oxalate, and PHLDH-NADH-oxamate, which mimic the transition state, have a significantly more pronounced effect on exchange rates than the corresponding binary complexes. The outstanding feature of this study is the demonstration that in the binary enzyme-coenzyme complexes the more loosely bound NAD+ is more effective in retarding exchange than the more firmly bound NADH. These differences are attributed to the unequal structural constraints exerted by the two coenzymes upon the enzymes, which translate to unequal expenditure of transconformational work in the formation of the two complexes. The opposing variation in the free energy of binding and the transconformational work expended can be viewed as an unequal partitioning of the net free energy gain resulting from the protein-ligand interaction into a binding term and that required for conformational change.

  2. Primary Structure Effects on Peptide Group Hydrogen Exchange

    PubMed Central

    Bai, Yawen; Milne, John S.; Mayne, Leland; Englander, S. Walter

    2012-01-01

    The rate of exchange of peptide group NH hydrogens with the hydrogens of aqueous solvent is sensitive to neighboring side chains. To evaluate the effects of protein side chains, all 20 naturally occurring amino acids were studied using dipeptide models. Both inductive and steric blocking effects are apparent. The additivity of nearest-neighbor blocking and inductive effects was tested in oligo-and polypeptides and, surprisingly, confirmed. Reference rates for alanine-containing peptides were determined and effects of temperature considered. These results provide the information necessary to evaluate measured protein NH to ND exchange rates by comparing them with rates to be expected for the same amino acid sequence is unstructured oligo- and polypeptides. The application of this approach to protein studies is discussed. PMID:8234246

  3. Copper(ii)-directed synthesis of neutral heteroditopic [2]rotaxane ion-pair host systems incorporating hydrogen and halogen bonding anion binding cavities.

    PubMed

    Brown, Asha; Mennie, Katrina M; Mason, Owen; White, Nicholas G; Beer, Paul D

    2017-09-27

    Neutral heteroditopic [2]rotaxane ion-pair host systems were synthesised via a Cu(ii) directed passive metal template strategy. Each rotaxane contains discrete, axle-separated interlocked binding sites for a guest anion and a transition metal countercation. The anion binding sites are composed of convergent X-H (X = C, N) hydrogen bond donor groups, or mixed X-H and C-I hydrogen and halogen bond donor groups, whereas an equivalent three-dimensional array of amine, pyridine and carbonyl oxygen donor groups comprise the transition metal binding site. (1)H NMR titrations experiments in CDCl3/CD3OD or CDCl3/CD3OD/D2O solvent mixtures reveal that the heteroditopic [2]rotaxane host systems are capable of cooperative anion recognition in the presence of a co-bound Zn(ii) cation.

  4. Mannobiose Binding Induces Changes in Hydrogen Bonding and Protonation States of Acidic Residues in Concanavalin A As Revealed by Neutron Crystallography.

    PubMed

    Gerlits, Oksana O; Coates, Leighton; Woods, Robert J; Kovalevsky, Andrey

    2017-08-30

    Plant lectins are carbohydrate-binding proteins with various biomedical applications. Concanavalin A (Con A) holds promise in treating cancerous tumors. To better understand the Con A carbohydrate binding specificity, we obtained a room-temperature neutron structure of this legume lectin in complex with a disaccharide Manα1-2Man, mannobiose. The neutron structure afforded direct visualization of the hydrogen bonding between the protein and ligand, showing that the ligand is able to alter both protonation states and interactions for residues located close to and distant from the binding site. An unprecedented low-barrier hydrogen bond was observed forming between the carboxylic side chains of Asp28 and Glu8, with the D atom positioned equidistant from the oxygen atoms having an O···D···O angle of 101.5°.

  5. Polycation binding to glomerular basement membrane. Effect of biochemical modification.

    PubMed

    Bertolatus, J A; Hunsicker, L G

    1987-02-01

    The polycation hexadimethrine (HDM) binds to anionic sites in the glomerular basement membrane (GBM) and causes heavy proteinuria when infused in vivo. An in vitro assay of 3H-HDM binding to isolated dog GBM was developed, to permit further analysis of the GBM components binding HDM. 3H-HDM binding to isolated GBM was saturable, reversible in dose-dependent fashion by competing polycations, and inhibited by increasing salt concentration and low pH. The pH dependence of binding suggested that most of the HDM binds to carboxyl groups rather than to the sulfate groups of proteoglycans. Removal of heparan sulfate by heparinase or purified heparatinase had no detectable effect on HDM binding. Treatment of GBM with neuraminidase, hyaluronidase, or chondroitinase reduced binding of HDM by a maximum of 20 to 38%. However, substitution of carboxyl anions with nonionizable glycine methyl ester residues resulted in complete elimination of HDM binding. Parallel results were obtained in studies of glomerular localization of cationized ferritin (CatF), pI 8.5. After carboxyl substitution, GBM did not bind CatF; heparinase-treated GBM bound CatF in a distribution not demonstrably different from normal. Cellulose acetate electrophoresis of glycosaminoglycan fractions prepared from treated GBM confirmed that carboxyl modification did not alter the content or charge of the heparan sulfate of GBM, but heparinase treatment removed at least 90% of heparan sulfate. The results indicate that carboxyl groups are quantitatively more important than heparan sulfate for binding of HDM in vitro. Since HDM causes proteinuria in vivo, carboxyl groups may be important for maintenance of normal permselectivity.

  6. 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.

  7. 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.

  8. 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.

  9. Effect of hydrogen peroxide on human tendon allograft.

    PubMed

    Gardner, E M H; VonderHeide, N; Fisher, R; Brooker, G; Yates, P J

    2013-12-01

    Bacterial contamination of tendon allografts at the completion of processing has historically been about 2 %, with tendons that are found to be culture positive being discarded. Treatment of tendon allograft with hydrogen peroxide at the beginning of tissue processing may reduce bacterial contamination, however, the potential side effects of hydrogen peroxide treatment include hydrolysis of the collagen and this may alter the mechanical properties of the graft. Pairs of human tendons were used. One was washed in 3 % hydrogen peroxide for 5 min and the untreated tendon was used as a control. The ultimate tensile strength of the tendons was determined using a material testing machine. A freeze clamp technique was used to hold the tendons securely at the high loads required to cause tendon failure. There was no statistical difference in the ultimate tensile strength between the treated and untreated tendons. Mean strength ranged from Extensor Hallucis Longus at 588 Newtons to Tibialis Posterior at 2,366 Newtons. Hydrogen peroxide washing may reduce bacterial contamination of tendon allograft and does not affect the strength of the tendon.

  10. Aromaticity, closed-shell effects, and metallization of hydrogen.

    PubMed

    Naumov, Ivan I; Hemley, Russell J

    2014-12-16

    CONSPECTUS: Recent theoretical and experimental studies reveal that compressed molecular hydrogen at 200-350 GPa transforms to layered structures consisting of distorted graphene sheets. The discovery of chemical bonding motifs in these phases that are far from close-packed contrasts with the long-held view that hydrogen should form simple, symmetric, ambient alkali-metal-like structures at these pressures. Chemical bonding considerations indicate that the realization of such unexpected structures can be explained by consideration of simple low-dimensional model systems based on H6 rings and graphene-like monolayers. Both molecular quantum chemistry and solid-state physics approaches show that these model systems exhibit a special stability, associated with the completely filled set of bonding orbitals or valence bands. This closed-shell effect persists in the experimentally observed layered structures where it prevents the energy gap from closing, thus delaying the pressure-induced metallization. Metallization occurs upon further compression by destroying the closed shell electronic structure, which is mainly determined by the 1s electrons via lowering of the bonding bands stemming from the unoccupied atomic 2s and 2p orbitals. Because enhanced diamagnetic susceptibility is a fingerprint of aromaticity, magnetic measurements provide a potentially important tool for further characterization of compressed hydrogen. The results indicate that the properties of dense hydrogen are controlled by chemical bonding forces over a much broader range of conditions than previously considered.

  11. Enhancement effect of hematite nanoparticles on fermentative hydrogen production.

    PubMed

    Han, Hongliang; Cui, Maojin; Wei, Liling; Yang, Haijun; Shen, Jianquan

    2011-09-01

    The effects of hematite nanoparticles concentration (0-1600 mg/L) and initial pH (4.0-10.0) on hydrogen production were investigated in batch assays using sucrose-fed anaerobic mixed bacteria at 35°C. The optimum hematite nanoparticles concentration with an initial pH 8.48 was 200mg/L, with the maximum hydrogen yield of 3.21 mol H(2)/mol sucrose which was 32.64% higher than the blank test. At 200mg/L hematite nanoparticles concentration, further initial pH optimization experiments indicated that at pH 6.0 the maximum hydrogen yield reached to 3.57 mol H(2)/mol sucrose and hydrogen content was 66.1%. The slow release of hematite nanoparticles had been recorded by transmission electron microscopy (TEM). In addition, TEM analysis indicated that the hematite nanoparticles can affect the shape of bacteria, namely, its length increased from ca. 2.0-3.6 μm to ca. 2.6-5.6 μm, and width became narrower.

  12. 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.

  13. Thermal effects in dynamic storage of hydrogen by adsorption

    SciTech Connect

    Lamari, M.; Aoufi, A.; Malbrunot, P.

    2000-03-01

    Thermal effects in dynamic hydrogen storage by adsorption at room temperature and high pressure are studied theoretically and experimentally. The system of adsorbate-adsorbent used was hydrogen in granular activated carbon. The theoretical analysis was based on heat- and mass-transfer modeling in a packed-bed adsorber, with particular emphasis on the thermal effects occurring during charge and discharge steps. The influence of gas flow rate and storage pressure (up to 15 MPa) on the total amount stored or delivered was investigated. Operating conditions were compatible with practical application for onboard vehicle storage. The experimental study was carried out in cylindrical 2-L reservoirs filled with granular activated carbon in which the bed temperature was measured at various positions. The temperature changes during both charge and discharge agreed well with the model predictions.

  14. Metal-support effects on acetone hydrogenation over platinum catalysts

    SciTech Connect

    Sen, B.; Vannice, M.A. )

    1988-09-01

    Acetone hydrogenation was studied over Pt/TiO{sub 2}, Pt/{eta}-Al{sub 2}O{sub 3}, Pt/SiO{sub 2}, Pt powder, and Pt/Au catalysts to test the hypothesis that the metal-support effect responsible for higher CO hydrogenation rates over certain metal/TiO{sub 2} catalysts represents a phenomenon capable of activating carbonyl bonds in general. Compared with the other catalysts, the high-temperature reduced (HTR) Pt/TiO{sub 2} samples had turnover frequencies more than 500 times higher than those of unsupported Pt and Pt/SiO{sub 2} catalysts, and the specific activity (per g Pt) of the Pt/TiO{sub 2} catalyst was 10 times that of a Pt/SiO{sub 2} catalyst with comparable dispersion. Complete hydrogenation to C{sub 3}H{sub 8} and H{sub 2}O occurred only on large, unsupported Pt crystallites; however, partial hydrogenation to isopropyl alcohol appeared to be structure insensitive and activation energies were similar over all catalysts, as were pressure dependencies, which associates the higher activity with a larger preexponential factor. Only one Langmuir-Hinshelwood model provided a rate expression consistent with experimental results - that which assumed competitive adsorption of H{sub 2} and acetone on the same sites and addition of the second H atom as the rate-determining step. This model is consistent with previous TPD, IR, and EELs studies and is also substantiated by theoretical calculations based on the bond-order conservation method. The much higher activities over Pt/TiO{sub 2} catalysts are attributed to an increase in the active site concentration in the Pt-titania interface region. These special sites are presumed to be defects on the titania surface near the Pt that can activate the carbonyl bond in the presence of atomic hydrogen provided by the Pt. 131 refs.

  15. Strong parallel magnetic field effects on the hydrogen molecular ion

    NASA Astrophysics Data System (ADS)

    Guan, Xiaoxu; Li, Baiwen; Taylor, K. T.

    2003-09-01

    Equilibrium distances, binding energies and dissociation energies for the ground and low-lying states of the hydrogen molecular ion in a strong magnetic field parallel to the internuclear axis are calculated and refined, by using the two-dimensional pseudospectral method. High-precision results are presented for the binding energies over a wider field regime than already given in the literature (Kravchenko and Liberman 1997 Phys. Rev. A 55 2701). The present work removes a long-standing discrepancy for the Req value in the 1sigmau state at a field strength of 1.0 × 106 T. The dissociation energies of the antibonding 1pig state induced by magnetic fields are determined accurately. We have also observed that the antibonding 1pig potential energy curve develops a minimum if the field is sufficiently strong. Some unreliable results in the literature are pointed out and discussed. A way to efficiently treat vibrational processes and coupling between the nuclear and the electronic motions in magnetic fields is also suggested within a three-dimensional pseudospectral scheme.

  16. 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.

  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. 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.

  19. Secondary hydrogen isotope effects on the structure and stability of cation-pi complexes (cation = Li(+), Na(+), K(+) and pi = acetylene, ethylene, benzene).

    PubMed

    Moreno, Diego V; González, Sergio A; Reyes, Andrés

    2010-09-02

    Secondary hydrogen isotope effects on the geometries, electronic wave functions and binding energies of cation-pi complexes (cation = Li(+), Na(+), K(+) and pi = acetylene, ethylene, benzene) are investigated with NEO/HF and NEO/MP2 methods. These methods determine both electronic and nuclear wave functions simultaneously. Our results show that an increase of the hydrogen nuclear mass leads to the elongation of the cation-pi bond distance and the decrease in its binding energy. An explanation to this behavior is given in terms of the changes in the pi-molecule electronic structure and electrostatic potential induced by isotopic substitutions.

  20. Action-effect binding by observational learning.

    PubMed

    Paulus, Markus; van Dam, Wessel; Hunnius, Sabine; Lindemann, Oliver; Bekkering, Harold

    2011-10-01

    The acquisition of bidirectional action-effect associations plays a central role in the ability to intentionally control actions. Humans learn about actions not only through active experience, but also through observing the actions of others. In Experiment 1, we examined whether action-effect associations can be acquired by observational learning. To this end, participants observed how a model repeatedly pressed two buttons during an observation phase. Each of the buttonpresses led to a specific tone (action effect). In a subsequent test phase, the tones served as target stimuli to which the participants had to respond with buttonpresses. Reaction times were shorter if the stimulus-response mapping in the test phase was compatible with the action-effect association in the observation phase. Experiment 2 excluded the possibility that the impact of perceived action effects on own actions was driven merely by an association of spatial features with the particular tones. Furthermore, we demonstrated that the presence of an agent is necessary to acquire novel action-effect associations through observation. Altogether, the study provides evidence for the claim that bidirectional action-effect associations can be acquired by observational learning. Our findings are discussed in the context of the idea that the acquisition of action-effect associations through observation is an important cognitive mechanism subserving the human ability for social learning.

  1. 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

  2. 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.

  3. New effect in Stark spectroscopy of atomic hydrogen: dynamic resonance

    SciTech Connect

    Gavrilenko, V.P.; Oks, E.A.

    1981-06-01

    We investigate analytically the spectrum of the hydrogen atom in an electric field E(t) = E/sub 0/ cos ..omega..t+F, where FperpendicularE/sub 0/. In the case when the splitting in the time-averaged field < E(t) > coincides with (2--1) ..omega.., where perpendicular = 1, 2, 3..., an effect called dynamic resonance is produced. The resonance occurs between the quasienergy states and is multiparticle and multiphoton. The hydrogen spectral lines undergo additional splitting under these conditions. The theory of dynamic resonance provides a physical explanation of the results of the numerical calculation of the L/sub ..cap alpha../ spectrum in crossed electric fields E/sub 0/ cos ..omega..t and F, as reported by Cohn, Bakshi, and Kalman (Phys. Rev. Lett. 29, 324 (1974)). We show also that fields with fixed phases and fields with random phases can exert different resonant action on the hydrogen spectral lines that start from levels with n> or =3. The dynamic resonance effect can be experimentally observed ad used both in laser physics and in plasma physics (in particular, to detect Langmuir solitons).

  4. Protective Effects of Hydrogen Sulfide in the Ageing Kidney

    PubMed Central

    Hou, Cui-Lan; Wang, Ming-Jie; Sun, Chen; Huang, Yong; Jin, Sheng; Mu, Xue-Pan; Chen, Ying

    2016-01-01

    Aims. The study aimed to examine whether hydrogen sulfide (H2S) generation changed in the kidney of the ageing mouse and its relationship with impaired kidney function. Results. H2S levels in the plasma, urine, and kidney decreased significantly in ageing mice. The expression of two known H2S-producing enzymes in kidney, cystathionine γ-lyase (CSE) and cystathionine-β-synthase (CBS), decreased significantly during ageing. Chronic H2S donor (NaHS, 50 μmol/kg/day, 10 weeks) treatment could alleviate oxidative stress levels and renal tubular interstitial collagen deposition. These protective effects may relate to transcription factor Nrf2 activation and antioxidant proteins such as HO-1, SIRT1, SOD1, and SOD2 expression upregulation in the ageing kidney after NaHS treatment. Furthermore, the expression of H2S-producing enzymes changed with exogenous H2S administration and contributed to elevated H2S levels in the ageing kidney. Conclusions. Endogenous hydrogen sulfide production in the ageing kidney is insufficient. Exogenous H2S can partially rescue ageing-related kidney dysfunction by reducing oxidative stress, decreasing collagen deposition, and enhancing Nrf2 nuclear translocation. Recovery of endogenous hydrogen sulfide production may also contribute to the beneficial effects of NaHS treatment. PMID:27882191

  5. Protective Effects of Hydrogen Sulfide in the Ageing Kidney.

    PubMed

    Hou, Cui-Lan; Wang, Ming-Jie; Sun, Chen; Huang, Yong; Jin, Sheng; Mu, Xue-Pan; Chen, Ying; Zhu, Yi-Chun

    2016-01-01

    Aims. The study aimed to examine whether hydrogen sulfide (H2S) generation changed in the kidney of the ageing mouse and its relationship with impaired kidney function. Results. H2S levels in the plasma, urine, and kidney decreased significantly in ageing mice. The expression of two known H2S-producing enzymes in kidney, cystathionine γ-lyase (CSE) and cystathionine-β-synthase (CBS), decreased significantly during ageing. Chronic H2S donor (NaHS, 50 μmol/kg/day, 10 weeks) treatment could alleviate oxidative stress levels and renal tubular interstitial collagen deposition. These protective effects may relate to transcription factor Nrf2 activation and antioxidant proteins such as HO-1, SIRT1, SOD1, and SOD2 expression upregulation in the ageing kidney after NaHS treatment. Furthermore, the expression of H2S-producing enzymes changed with exogenous H2S administration and contributed to elevated H2S levels in the ageing kidney. Conclusions. Endogenous hydrogen sulfide production in the ageing kidney is insufficient. Exogenous H2S can partially rescue ageing-related kidney dysfunction by reducing oxidative stress, decreasing collagen deposition, and enhancing Nrf2 nuclear translocation. Recovery of endogenous hydrogen sulfide production may also contribute to the beneficial effects of NaHS treatment.

  6. Nuclear quantum effects and hydrogen bond fluctuations in water.

    PubMed

    Ceriotti, Michele; Cuny, Jérôme; Parrinello, Michele; Manolopoulos, David E

    2013-09-24

    The hydrogen bond (HB) is central to our understanding of the properties of water. However, despite intense theoretical and experimental study, it continues to hold some surprises. Here, we show from an analysis of ab initio simulations that take proper account of nuclear quantum effects that the hydrogen-bonded protons in liquid water experience significant excursions in the direction of the acceptor oxygen atoms. This generates a small but nonnegligible fraction of transient autoprotolysis events that are not seen in simulations with classical nuclei. These events are associated with major rearrangements of the electronic density, as revealed by an analysis of the computed Wannier centers and (1)H chemical shifts. We also show that the quantum fluctuations exhibit significant correlations across neighboring HBs, consistent with an ephemeral shuttling of protons along water wires. We end by suggesting possible implications for our understanding of how perturbations (solvated ions, interfaces, and confinement) might affect the HB network in water.

  7. Mg NMR in DNA solutions: Dominance of site binding effects.

    PubMed

    Rose, D M; Bleam, M L; Record, M T; Bryant, R G

    1980-11-01

    (25)Mg NMR spectroscopy is applied to a study of magnesium ion interactions with DNA, which is considered as a model for a linear polyelectrolyte. It is demonstrated that the magnesium ion spectrum is complicated by a non-Lorent-zian line shape and is dominated by the effects of chemical exchange with macromolecule binding sites. A distinction is made between specific-site interactions in which the magnesium ion loses a water molecule from the first coordination sphere on binding and those interactions, referred to as territorial binding, in which the ion maintains its first coordination sphere complement of solvent. The first type of site-binding interactions are shown to dominate the magnesium ion NMR spectrum, based on a consideration of the magnitudes of the observed (25)Mg relaxation rates compared with (23)Na relaxation rates, the clear contributions of chemical exchange-limited relaxation, and an ion displacement experiment employing sodium.

  8. Transport effects on the kinetics of protein-surface binding.

    PubMed Central

    Balgi, G; Leckband, D E; Nitsche, J M

    1995-01-01

    A detailed model is presented for protein binding to active surfaces, with application to the binding of avidin molecules to a biotin-functionalized fiber optic sensor in experiments reported by S. Zhao and W. M. Reichert (American Chemical Society Symposium Series 493, 1992). Kinetic data for binding in solution are used to assign an intrinsic catalytic rate coefficient k to the biotin-avidin pair, deconvoluted from transport and electrostatic factors via application of coagulation theory. This intrinsic chemical constant is built into a reaction-diffusion analysis of surface binding where activity is restricted to localized sites (representing immobilized biotin molecules). The analysis leads to an effective catalytic rate coefficient keff characterizing the active surface. Thereafter, solution of the transport problem describing absorption of avidin molecules by the macroscopic sensor surface leads to predictions of the avidin flux, which are found to be in good agreement with the experimental data. The analysis suggests the following conclusions. 1) Translational diffusion limitations are negligible for avidin-biotin binding in solution owing to the small (kinetically limiting) value k = 0.00045 m/s. 2) The sparse distribution of biotin molecules and the presence of a repulsive hydration force produce an effective surface-average catalytic rate coefficient keff of order 10(-7) m/s, much smaller than k. 3) Avidin binding to the fiber optic sensor occurs in an intermediate regime where the rate is influenced by both kinetics and diffusion. Images FIGURE 1 FIGURE 3 PMID:7647232

  9. 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.

  10. Hydrogen embrittlement I. Analysis of hydrogen-enhanced localized plasticity: Effect of hydrogen on the velocity of screw dislocations in α -Fe

    NASA Astrophysics Data System (ADS)

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

    2017-08-01

    We demonstrate a kinetic Monte Carlo simulation tool, based on published data using first-principles quantum mechanics, applied to answer the question: under which conditions of stress, temperature, and nominal hydrogen concentration does the presence of hydrogen in iron increase or decrease the screw dislocation velocity? Furthermore, we examine the conditions under which hydrogen-induced shear localization is likely to occur. Our simulations yield quantitative data on dislocation velocity and the ranges of hydrogen concentration within which a large gradient of velocity as a function of concentration is expected to be observed and thereby contribute to a self-perpetuating localization of plasticity—a phenomenon that has been linked to hydrogen-induced fracture and fatigue failure in ultrahigh strength steel. We predict the effect of hydrogen in generating debris made up of edge dipoles trailing in the wake of gliding screw dislocations and their role in pinning. We also simulate the competing effects of softening by enhanced kink-pair generation and hardening by solute pinning. Our simulations act as a bridge between first-principles quantum mechanics and discrete dislocation dynamics, and at the same time offer the prospect of a fully physics-based dislocation dynamics method.

  11. Beyond feature binding: interference from episodic context binding creates the bivalency effect in task-switching.

    PubMed

    Meier, Beat; Rey-Mermet, Alodie

    2012-01-01

    When switching between different tasks and bivalent stimuli occur only occasionally on one of them, performance is slowed on subsequent univalent trials even if they have no overlapping features with the bivalent stimulus. This phenomenon has been labeled the "bivalency effect." Recent evidence has revealed that this effect is robust, general, and enduring. Moreover, it challenges current theories of task-switching and cognitive control. Here, we review these theories and propose a new, episodic context binding account. According to this account, binding does not only occur between stimuli, responses, and tasks, but also for the more general context in which the stimuli occur. The result of this binding process is a complex representation that includes each of these components. When bivalent stimuli occur, the resulting conflict is associated with the general context, creating a new conflict-loaded representation. The reactivation of this representation causes interference on subsequent trials, that is, the bivalency effect. We evaluate this account in light of the empirical evidence.

  12. Polyclonal and monoclonal IgG binding on Protein A resins - Evidence of competitive binding effects.

    PubMed

    Weinberg, Justin; Zhang, Shaojie; Crews, Gillian; Healy, Edward; Carta, Giorgio; Przybycien, Todd

    2017-03-14

    Protein A (ProA) chromatography is used extensively in the biopharmaceutical industry for the selective capture of both polyclonal and monoclonal antibodies (mAbs). This work provides a comparison of the adsorptive behavior of a highly heterogeneous polyclonal hIgG versus that of a mAb as well as the behavior of their mixtures on representative ProA resins. Both pH gradient elution and frontal loading experiments using human polyclonal IgG (hIgG) reveal a distribution of IgG-ProA binding strengths likely associated with multiple IgG subclasses and the heterogeneity of the variable region. pH gradient analysis of fractions collected along the breakthrough curve demonstrate a clear progression from weaker binding (higher pH eluting) to stronger binding (lower pH eluting) IgG species leaving the column suggesting the possibility of stronger binding species displacing the weaker binding ones. Displacement is directly observed by visualizing the adsorption of fluorescently labeled mAb and hIgG using confocal laser scanning microscopy (CLSM). Here, the displacement of hIgG results in a broad adsorption front compared to the sharp, 'shrinking core' behavior typically observed with mAbs. Sequential CLSM adsorption experiments with a mAb and hIgG confirm that stronger or equivalent-binding hIgG species are able to displace and desorb bound mAb molecules. These phenomena are examined using a variety of ProA resins including CaptivA PriMAB, MabSelect, and MabSelect SuRe to understand the effect of different ligand properties on binding strength and competition among different IgG species. The results of these comparisons suggest that the competition kinetics are slower with ligands that have a single-point covalent attachment to the base matrix compared to a multi-point attachment. This article is protected by copyright. All rights reserved.

  13. 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.

  14. 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

  15. 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.

  16. Fate of methanol molecule sandwiched between hydrogen-terminated diamond-like carbon films by tribochemical reactions: tight-binding quantum chemical molecular dynamics study.

    PubMed

    Hayashi, Kentaro; Sato, Seiichiro; Bai, Shandan; Higuchi, Yuji; Ozawa, Nobuki; Shimazaki, Tomomi; Adachi, Koshi; Martin, Jean-Michel; Kubo, Momoji

    2012-01-01

    Recently, much attention has been given to diamond-like carbon (DLC) as a solid-state lubricant, because it exhibits high resistance to wear, low friction and low abrasion. Experimentally it is reported that gas environments are very important for improving the tribological characteristics of DLC films. Recently one of the authors in the present paper, J.-M. Martin, experimentally observed that the low friction of DLC films is realized under alcohol environments. In the present paper, we aim to clarify the low-friction mechanism of the DLC films under methanol environments by using our tight-binding quantum chemical molecular dynamics method. We constructed the simulation model in which one methanol molecule is sandwiched between two hydrogen-terminated DLC films. Then, we performed sliding simulations of the DLC films. We observed the chemical reaction of the methanol molecule under sliding conditions. The methanol molecule decomposed and then OH-termination of the DLC was realized and the CH3 species was incorporated into the DLC film. We already reported that the OH-terminated DLC film is very effective to achieve good low-friction properties under high pressure conditions, compared to H-terminated DLC films. Here, we suggest that methanol environments are very effective to realize the OH-termination of DLC films which leads to the good low-friction properties.

  17. Effect of methane concentration in hydrogen plasma on hydrogen impurity incorporation in thick large-grained polycrystalline diamond films

    NASA Astrophysics Data System (ADS)

    Tang, C. J.; Fernandes, A. J. S.; Jiang, X. F.; Pinto, J. L.; Ye, H.

    2015-09-01

    We investigate the impact of methane concentration in hydrogen plasma on the growth of large-grained polycrystalline diamond (PCD) films and its hydrogen impurity incorporation. The diamond samples were produced using high CH4 concentration in H2 plasma and high power up to 4350 W and high pressure (either 105 or 110 Torr) in a microwave plasma chemical vapor deposition (MPCVD) system. The thickness of the free-standing diamond films varies from 165 μm to 430 μm. Scanning electron microscopy (SEM), micro-Raman spectroscopy and Fourier-transform infrared (FTIR) spectroscopy were used to characterize the morphology, crystalline and optical quality of the diamond samples, and bonded hydrogen impurity in the diamond films, respectively. Under the conditions employed here, when methane concentration in the gas phase increases from 3.75% to 7.5%, the growth rate of the PCD films rises from around 3.0 μm/h up to 8.5 μm/h, and the optical active bonded hydrogen impurity content also increases more than one times, especially the two CVD diamond specific H related infrared absorption peaks at 2818 and 2828 cm-1 rise strongly; while the crystalline and optical quality of the MCD films decreases significantly, namely structural defects and non-diamond carbon phase content also increases a lot with increasing of methane concentration. Based on the results, the relationship between methane concentration and diamond growth rate and hydrogen impurity incorporation including the form of bonded infrared active hydrogen impurity in CVD diamonds was analyzed and discussed. The effect of substrate temperature on diamond growth was also briefly discussed. The experimental findings indicate that bonded hydrogen impurity in CVD diamond films mainly comes from methane rather than hydrogen in the gas source, and thus can provide experimental evidence for the theoretical study of the standard methyl species dominated growth mechanism of CVD diamonds grown with methane/hydrogen mixtures.

  18. 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.

  19. Effects of exercise on insulin binding to human muscle

    SciTech Connect

    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 O/sub 2/ consumption (VO/sub 2/max). 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% VO/sub 2/max (n = 5) no change in insulin binding occurred (P greater than 0.05). However, when exercise occurred at greater than or equal to 69% VO/sub 2/max (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% VO/sub 2/max but that a marked decrement occurs when exercise is greater than or equal to 69% VO/sub 2/max.

  20. Adsorption of 2 Chloroethyl Ethyl Sulfide on Silica: Binding Mechanism and Energy of a Bifunctional Hydrogen-Bond Acceptor at the Gas Surface Interface

    DTIC Science & Technology

    2014-11-19

    and reveals two distinct types of charge donors (lone-pair hydrogen-bond acceptors) within 2-CEES. The chlorine and sulfur moieties within the 2-CEES...sulfur than through the chlorine constituents of the molecule and that both types of interactions occur for 2-CEES. However, the extent of charge...formation through the sulfur or the chlorine component likely leads to very similar binding strengths (similar to those of diethyl sulfide and chlorobutane

  1. Molecular dynamics simulation of effect of hydrogen atoms on crack propagation behavior of α-Fe

    NASA Astrophysics Data System (ADS)

    Song, H. Y.; Zhang, L.; Xiao, M. X.

    2016-12-01

    The effect of the hydrogen concentration and hydrogen distribution on the mechanical properties of α-Fe with a pre-existing unilateral crack under tensile loading is investigated by molecular dynamics simulation. The results reveal that the models present good ductility when the front region of crack tip has high local hydrogen concentration. The peak stress of α-Fe decreases with increasing hydrogen concentration. The studies also indicate that for the samples with hydrogen atoms, the crack propagation behavior is independent of the model size and boundaries. In addition, the crack propagation behavior is significantly influenced by the distribution of hydrogen atoms.

  2. Effects of hydrogen on mechanical properties in irradiated austenitic stainless steels

    NASA Astrophysics Data System (ADS)

    Morisawa, J.; Kodama, M.; Nishimura, S.; Asano, K.; Nakata, K.; Shima, S.

    1994-09-01

    To investigate the hydrogen effect on mechanical properties of solution annealed Type 304 stainless steel, tensile tests of neutron irradiated materials were conducted after a hydrogen charging and discharging process (hydrogen treatment). Elongation was less with increasing neutron fluence after hydrogen treatment than that of as-irradiated specimens. Intergranular cracking occurred by the hydrogen treatment in heavier irradiated specimens, in which the Cr depleted zone along grain boundary was observed. Embrittlement and intergranular cracking after the hydrogen treatment were estimated to be attributed to the Cr depleted zone at the grain boundary due to neutron irradiation.

  3. 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.

  4. Inhibitory heterotrimeric GTP-binding proteins inhibit hydrogen peroxide-induced apoptosis by up-regulation of Bcl-2 via NF-kappaB in H1299 human lung cancer cells.

    PubMed

    Seo, Miran; 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 (Galphai1QL), Gi2, or Gi3 inhibited hydrogen peroxide-induced apoptosis. The expression of Galphai1QL up-regulated Bcl-2 expression, and the knockdown of Bcl-2 with siRNA abolished the anti-apoptotic effect of Galphai1QL. Galphai1 induced the transcription of Bcl-2 by activation of NF-kappaB, which resulted from an increase in NF-kappaB p50 protein. We conclude that Galphai1 inhibits hydrogen peroxide-induced apoptosis of H1299 lung cancer cells by up-regulating the transcription of Bcl-2 through a p50-mediated NF-kappaB activation.

  5. 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

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

    PubMed Central

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

    2013-01-01

    Infection of humans by hepatitis B virus (HBV) induces the copious production of antibodies directed against the capsid protein (Cp). A large variety of anti-capsid 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 outwards-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 sub-stoichiometric 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

  7. 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.

  8. Binding characteristics of homogeneous molecularly imprinted polymers for acyclovir using an (acceptor-donor-donor)-(donor-acceptor-acceptor) hydrogen-bond strategy, and analytical applications for serum samples.

    PubMed

    Wu, Suqin; Tan, Lei; Wang, Ganquan; Peng, Guiming; Kang, Chengcheng; Tang, Youwen

    2013-04-12

    This paper demonstrates a novel approach to assembling homogeneous molecularly imprinted polymers (MIPs) based on mimicking multiple hydrogen bonds between nucleotide bases by preparing acyclovir (ACV) as a template and using coatings grafted on silica supports. (1)H NMR studies confirmed the AAD-DDA (A for acceptor, D for donor) hydrogen-bond array between template and functional monomer, while the resultant monodisperse molecularly imprinted microspheres (MIMs) were evaluated using a binding experiment, high performance liquid chromatography (HPLC), and solid phase extraction. The Langmuir isothermal model and the Langmuir-Freundlich isothermal model suggest that ACV-MIMs have more homogeneous binding sites than MIPs prepared through normal imprinting. In contrast to previous MIP-HPLC columns, there were no apparent tailings for the ACV peaks, and ACV-MIMs had excellent specific binding properties with a Ka peak of 3.44 × 10(5)M(-1). A complete baseline separation is obtained for ACV and structurally similar compounds. This work also successfully used MIMs as a specific sorbent for capturing ACV from serum samples. The detection limit and mean recovery of ACV was 1.8 ng/mL(-1) and 95.6%, respectively, for molecularly imprinted solid phase extraction coupled with HPLC. To our knowledge, this was the first example of MIPs using AAD-DDA hydrogen bonds.

  9. Effect of clustered peptide binding on DNA condensation.

    PubMed

    Haley, Jennifer; Kabiru, Paul; Geng, Yan

    2010-01-01

    DNA condensation in-vitro has been studied as a model system to reveal common principles underlying gene packaging in biology, and as the critical first step towards the development of non-viral gene delivery vectors. In this study, we use a bio-inspired approach, where small DNA-binding peptides are controllably clustered by an amphiphilic block copolymer scaffold, to reveal the effect of clustered peptide binding on the energetics, size, shape and physical properties of DNA condensation in-vitro. This provides insights into the general architectural effect of gene-binding proteins on DNA condensation process. Moreover, the versatility afforded by regulating the clustering density and composition of peptides may provide a novel design platform for gene delivery applications in the future.

  10. 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.

  11. 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.

  12. Dopant-vacancy binding effects in Li-doped magnesium hydride

    NASA Astrophysics Data System (ADS)

    Smith, Kyle C.; Fisher, Timothy S.; Waghmare, Umesh V.; Grau-Crespo, Ricardo

    2010-10-01

    We use a combination of ab initio calculations and statistical mechanics to investigate the substitution of Li+ for Mg2+ in magnesium hydride (MgH2) accompanied by the formation of hydrogen vacancies with positive charge (with respect to the original ion at the site). We show that the binding energy between dopants and vacancy defects leads to a significant fraction of trapped vacancies and therefore a dramatic reduction in the number of free vacancies available for diffusion. The concentration of free vacancies initially increases with dopant concentration but reaches a maximum at around 1mol% Li doping and slowly decreases with further doping. At the optimal level of doping, the corresponding concentration of free vacancies is much higher than the equilibrium concentrations of charged and neutral vacancies in pure MgH2 at typical hydrogen storage conditions. We also show that Li-doped MgH2 is thermodynamically metastable with respect to phase separation into pure magnesium and lithium hydrides at any significant Li concentration, even after considering the stabilization provided by dopant-vacancy interactions and configurational entropic effects. Our results suggest that lithium doping may enhance hydrogen diffusion hydride but only to a limited extent determined by an optimal dopant concentration and conditioned to the stability of the doped phase.

  13. SIRT3 Mediates the Antioxidant Effect of Hydrogen Sulfide in Endothelial Cells

    PubMed Central

    Xie, Liping; Feng, Haihua; Li, Sha; Meng, Guoliang; Liu, Shangmin; Tang, Xin; Ma, Yan; Han, Yi; Xiao, Yujiao; Gu, Yue; Shao, Yongfeng; Park, Chung-Min; Xian, Ming; Huang, Yu; Ferro, Albert; Wang, Rui; Moore, Philip K.

    2016-01-01

    Abstract Aim: Oxidative stress is a key contributor to endothelial dysfunction and associated cardiovascular pathogenesis. Hydrogen sulfide (H2S) is an antioxidant gasotransmitter that protects endothelial cells against oxidative stress. Sirtuin3 (SIRT3), which belongs to the silent information regulator 2 (SIR2) family, is an important deacetylase under oxidative stress. H2S is able to regulate the activity of several sirtuins. The present study aims to investigate the role of SIRT3 in the antioxidant effect of H2S in endothelial cells. Results: Cultured EA.hy926 endothelial cells were exposed to hydrogen peroxide (H2O2) as a model of oxidative stress-induced cell injury. GYY4137, a slow-releasing H2S donor, improved cell viability, reduced oxidative stress and apoptosis, and improved mitochondrial function following H2O2 treatment. H2S reversed the stimulation of MAPK phosphorylation, downregulation of SIRT3 mRNA and reduction of the superoxide dismutase 2 and isocitrate dehydrogenase 2 expression which were induced by H2O2. H2S also increased activator protein 1 (AP-1) binding activity with SIRT3 promoter and this effect was absent in the presence of the specific AP-1 inhibitor, SR11302 or curcumin. Paraquat administration to mice induced a defected endothelium-dependent aortic vasodilatation and increased oxidative stress in both mouse aorta and small mesenteric artery, which were alleviated by GYY4137 treatment. This vasoprotective effect of H2S was absent in SIRT3 knockout mice. Innovation: The present results highlight a novel role for SIRT3 in the protective effect of H2S against oxidant damage in the endothelium both in vitro and in vivo. Conclusion: H2S enhances AP-1 binding activity with the SIRT3 promoter, thereby upregulating SIRT3 expression and ultimately reducing oxidant-provoked vascular endothelial dysfunction. Antioxid. Redox Signal. 24, 329–343. PMID:26422756

  14. 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.

  15. Effect of VGs on a turbulent hydrogen jet

    NASA Astrophysics Data System (ADS)

    Senouci, M.; Hibbo, H.; Hammoudi, B.; Kadi, M.; Imine, B.

    2016-03-01

    The aim of this study is to investigate numerically the effects of four vortices on the dynamic, scalar, and turbulent fields of the hydrogen jet. These vortices, which appear in the vicinities of the nozzle, are created by the vortex generators (VGs), and they are assembled with periodicity or symmetry in order, respectively, to give four vortices of the same or opposite direction. A second-order Reynolds stress model is used to investigate asymmetric turbulent jet. The results indicate that the presence of the vortex near the emission jet section noticeably enhances mixing to ensure a good combustion.

  16. Atomic hydrogen adsorption on a Stone Wales defect in graphite

    NASA Astrophysics Data System (ADS)

    Letardi, Sara; Celino, Massimo; Cleri, Fabrizio; Rosato, Vittorio

    2002-01-01

    Ab initio electronic structure calculations have been used to evaluate the binding energy of atomic hydrogen to graphite lattice defects. Results show that carbon sites belonging to a Stone-Wales defect are preferred binding sites with respect to undefected sites. Upon hydrogen adsorption, carbon sites undergo a sizeable tetragonalization effect which is more pronounced on the defected sizes.

  17. Human recombinant [C22A] FK506-binding protein amide hydrogen exchange rates from mass spectrometry match and extend those from NMR.

    PubMed Central

    Zhang, Z.; Li, W.; Logan, T. M.; Li, M.; Marshall, A. G.

    1997-01-01

    Hydrogen/deuterium exchange behavior of human recombinant [C22A] FK506 binding protein (C22A FKBP) has been determined by protein fragmentation, combined with electrospray Fourier transform ion cyclotron resonance mass spectrometry (MS). After a specified period of H/D exchange in solution, C22A FKBP was digested by pepsin under slow exchange conditions (pH 2.4, 0 degree C), and then subjected to on-line HPLC/MS for deuterium analysis of each proteolytic peptide. The hydrogen exchange rate of each individual amide hydrogen was then determined independently by heteronuclear two-dimensional NMR on 15N-enriched C22A FKBP. A maximum entropy method (MEM) algorithm makes it possible to derive the distributions of hydrogen exchange rate constants from the MS-determined deuterium exchange-in curves in either the holoprotein or its proteolytic segments. The MEM-derived rate constant distributions of C22A FKBP and different segments of C22A FKBP are compared to the rate constants determined by NMR for individual amide protons. The rate constant distributions determined by both methods are consistent and complementary, thereby validating protein fragmentation/mass spectrometry as a reliable measure of hydrogen exchange in proteins. PMID:9336843

  18. Ionic association of hydroperoxide anion HO2- in the binding mean spherical approximation. Spectroscopic study of hydrogen peroxide in concentrated sodium hydroxide solutions.

    PubMed

    Chlistunoff, Jerzy; Simonin, Jean-Pierre

    2006-12-28

    The ultraviolet-visible (UV-vis) spectroscopy of hydrogen peroxide in concentrated sodium hydroxide solutions was studied. The peroxide band in the UV range shifts from approximately 214 nm to approximately 236 nm as the NaOH concentration increases from 0.338 mol dm-3 to 13.1 mol dm-3. The band originates from an intramolecular electronic transition of the hydroperoxide anion HO2-, as indicated by the negligible temperature effect on the band position and confirmed by ab initio quantum mechanical calculations. It is postulated that the bathochromic shift of the peroxide band that accompanies the increase in NaOH concentration originates from the formation of the ion pair (Na+HO2-). The equilibrium constant for the ion association reaction (0.048 mol-1 dm3) and the characteristics of the individual absorption bands of the hydroperoxide anion and its associate with Na+ were determined from the numerical modeling of the absorbance data, using the binding mean spherical approximation (BIMSA).

  19. Enhanced Binding Affinity via Destabilization of the Unbound State: A Millisecond Hydrogen-Deuterium Exchange Study of the Interaction between p53 and a Pleckstrin Homology Domain.

    PubMed

    Zhu, Shaolong; Khatun, Rahima; Lento, Cristina; Sheng, Yi; Wilson, Derek J

    2017-08-15

    The incorporation of intrinsically disordered domains enables proteins to engage a wide variety of targets, with phosphorylation often modulating target specificity and affinity. Although phosphorylation can clearly act as a chemical driver of complexation in structured proteins, e.g., by abrogating or permitting new charge-charge interactions, the basis for enhancement of the hydrophobically driven interactions that are typical of disordered protein-target complexation is less clear. To determine how phosphorylation can positively impact target recruitment in disordered domains, we have examined the interaction between the disordered N-terminal transactivation domain (TAD) of p53 and the pleckstrin homology (PH) domain of p62. Using time-resolved electrospray ionization with hydrogen-deuterium exchange, we demonstrate that phosphorylation has little effect on the conformation of the p53 TAD when it is bound to the PH domain but instead increases the degree of conformational disorder in the unbound state. We propose that this increase in the degree of disorder creates a wider free energy gap between the free and bound states, providing a target-independent mechanism for enhanced binding when the phosphorylated and unphosphorylated p53-target complexes have similar free energies.

  20. Effects of OLRs and HRTs on hydrogen production from high salinity substrate by halophilic hydrogen producing bacterium (HHPB).

    PubMed

    Zhang, Shan; Lee, Yunhee; Kim, Tae-Hyeong; Hwang, Sun-Jin

    2013-08-01

    The effects of hydraulic retention time (HRT) and organic loading rate (OLR) on hydrogen production were investigated with glucose medium containing 2% NaCl. Halophilic hydrogen producing bacterium (HHPB) Clostridium bifermentans 3AT-ma, which can survive under high salt conditions, was used. Sponge media were used as 20% of working volume. The OLR and HRT were varied in 10-60 g-glucose/L-reactor/day and 24-6h. With OLR of 20 g-glucose/L/day, shorter HRT resulted in higher hydrogen producing rate and yield. When the OLR was increased from 20 to 60 g-glucose/L-reactor/day at HRT 6h, the hydrogen production rate increased, while the hydrogen production yield decreased due to the increase and accumulation of volatile fatty acids. Biohydrogen production was possible from the salinity substrate using HHPB, and the maximum hydrogen production yield was 1.1 mol-H₂/mol-glucose with optimal conditions of OLR of 20 g-glucose/L/day and HRT of 12h.

  1. Effect of Hydrogen Peroxide on the Antibacterial Substantivity of Chlorhexidine

    PubMed Central

    Shahriari, Shahriar; Mohammadi, Zahed; Mokhtari, Mohammadi Mehdi; Yousefi, Rasoul

    2010-01-01

    The purpose of this in vitro study was to assess the effect of hydrogen peroxide on the antibacterial substantivity of chlorhexidine (CHX). Seventy-five dentine tubes prepared from human maxillary central and lateral incisor teeth were used. After contamination with Enterococcus faecalis for 14 days, the specimens were divided into five groups as follows: CHX, H2O2, CHX + H2O2, infected dentine tubes (positive control), and sterile dentine tubes (negative control). Dentine chips were collected with round burs into tryptic soy broth, and after culturing, the number of colony-forming units (CFU) was counted. The number of CFU was minimum in the first cultures in all experimental groups, and the results obtained were significantly different from each other at any time period (P < .05). At the first culture, the number of CFU in the CHX + H2O2 group was lower than other two groups. At the other experimental periods, the CHX group showed the most effective antibacterial action (P < .05). Hydrogen peroxide group showed the worst result at all periods. In each group, the number of CFU increased significantly by time lapse (P < .05). In conclusion, H2O2 had no additive effect on the residual antibacterial activity of CHX. PMID:21318180

  2. Effect of anion binding on iodopsin studied by low-temperature fourier transform infrared spectroscopy.

    PubMed

    Imamoto, Y; Hirano, T; Imai, H; Kandori, H; Maeda, A; Yoshizawa, T; Groesbeek, M; Lugtenburg, J; Shichida, Y

    1999-09-07

    The effect of anion binding on iodopsin, the chicken red-sensitive cone visual pigment, was studied by measurements of the Fourier transform infrared spectra of chloride- and nitrate-bound forms of iodopsin at 77 K. In addition to the blue shift of the absorption maximum upon substituting nitrate for chloride, the C=C stretching vibrations of iodopsin and its photoproducts were upshifted 5-6 cm(-)(1). The C=NH and C=ND stretching vibrations were the same in wavenumber between the chloride- and nitrate-bound forms, indicating that the binding of either chloride or nitrate has no effect on the interaction between the protonated Schiff base and the counterion. The vibrational bands of iodopsin in the fingerprint and the hydrogen out-of-plane wagging regions were insensitive to anion substitution, suggesting that local chromophore interactions with the anions are not crucial for the absorption spectral shift. In contrast, bathoiodopsin in the chloride-bound form exhibited an intense C(14)H wagging mode, whose intensity was considerably weakened upon substitution of nitrate for chloride. These results suggest that binding of chloride changes the environment near the C(14) position of the chromophore, which could be one of the factors in the thermal reverse reaction of bathoiodopsin to iodopsin in the chloride-bound form.

  3. Binding Energy of Hydrogen-Like Impurities in Quantum Well Wires of InSb/GaAs in a Magnetic Field

    PubMed Central

    2007-01-01

    The binding energy of a hydrogen-like impurity in a thin size-quantized wire of the InSb/GaAs semiconductors with Kane’s dispersion law in a magnetic fieldBparallel to the wire axis has been calculated as a function of the radius of the wire and magnitude ofB, using a variational approach. It is shown that when wire radius is less than the Bohr radius of the impurity, the nonparabolicity of dispersion law of charge carriers leads to a considerable increase of the binding energy in the magnetic field, as well as to a more rapid growth of binding energy with growth ofB.

  4. Influence of halide binding on the hydrogen bonding network in the active site of Salinibacter sensory rhodopsin I.

    PubMed

    Reissig, Louisa; Iwata, Tatsuya; Kikukawa, Takashi; Demura, Makoto; Kamo, Naoki; Kandori, Hideki; Sudo, Yuki

    2012-11-06

    In nature, organisms are subjected to a variety of environmental stimuli to which they respond and adapt. They can show avoidance or attractive behaviors away from or toward such stimuli in order to survive in the various environments in which they live. One such stimuli is light, to which, for example, the receptor sensory rhodopsin I (SRI) has been found to respond by regulating both negative and positive phototaxis in, e.g., the archaeon Halobacterium salinarum. Interestingly, to date, all organisms having SRI-like proteins live in highly halophilic environments, suggesting that salt significantly influences the properties of SRIs. Taking advantage of the discovery of the highly stable SRI homologue from Salinibacter ruber (SrSRI), which maintains its color even in the absence of salt, the importance of the chloride ion for the color tuning and for the slow M-decay, which is thought to be essential for the phototaxis function of SRIs, has been reported previously [Suzuki, D., et al. (2009) J. Mol. Biol.392, 48-62]. Here the effects of the anion binding on the structure and structural changes of SRI during its photocycle are investigated by means of Fourier transform infrared (FTIR) spectroscopy and electrochemical experiments. Our results reveal that, among other things, the structural change and proton movement of a characteristic amino acid residue, Asp102 in SrSRI, is suppressed by the binding of an anion in its vicinity, both in the K- and M-intermediate. The presence of this anion also effects the extent of chromophore distrotion, and tentative results indicate an influence on the number and/or properties of internal water molecules. In addition, a photoinduced proton transfer could only be observed in the absence of the bound anion. Possible proton movement pathways, including the residues Asp102 and the putative Cl binding site His131, are discussed. In conclusion, the results show that the anion binding to SRI is not only important for the color tuning

  5. Effect of ammonia concentration on fermentative hydrogen production by mixed cultures.

    PubMed

    Wang, Bo; Wan, Wei; Wang, Jianlong

    2009-02-01

    The effect of ammonia concentration ranging from 0 to 10 g N/L on fermentative hydrogen production by mixed cultures was investigated in batch tests using glucose as substrate at 35 degrees C and initial pH 7.0. The experimental results showed that during the fermentative hydrogen production, the substrate degradation efficiency increased with increasing ammonia concentration from 0 to 0.01 g N/L. The hydrogen production potential, hydrogen yield and average hydrogen production rate increased with increasing ammonia concentration from 0 to 0.1g N/L. The maximum hydrogen production potential of 291.4 mL, maximum hydrogen yield of 298.8 mL/g glucose and maximum average hydrogen production rate of 8.5 mL/h were all obtained at the ammonia concentration of 0.1g N/L.

  6. 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.

  7. Effects of hydrogen on iron/nickel/cobalt/alloy

    NASA Technical Reports Server (NTRS)

    Harris, J. A.; Mucci, J.

    1977-01-01

    Commercially available alloy, Incoloy 903, is candidate for various high-pressure, high-temperature applications. Recent study of properties in hydrogen and helium atmospheres under extreme environments indicates that alloy can be degraded by gaseous hydrogen, particularly at elevated temperatures. Study also reports that water vapor added to hydrogen environments causes reductions in low-cycle fatigue life of material.

  8. 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

    2014-04-07

    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.

  9. Effect of chloride ions on adsorption and permeation of hydrogen in iron

    SciTech Connect

    Allam, A.M.; Pickering, H.W.; Ateya, B.G.

    1997-04-01

    Effects of chloride ions on hydrogen absorption into iron and on the hydrogen evolution reaction (HER) on an iron surface were studied in acid and alkaline solutions at 23 C using the permeation method of Devanathan and Stachurski. Cl{sup {minus}} ions reduced the overpotential ({eta}) for HER and, in turn, reduced hydrogen coverage and permeation.Effects on hydrogen permeation were more pronounced in alkaline than in acid solutions. Permeation transients at constant electrode potential of he charging surface and subsequent surface analyses of the uppermost atom layers of the hydrogen-charged iron surface indicated a reversible or low coverage with Cl{sup {minus}} ions, a low hydrogen coverage that was not influenced significantly by Cl{sup {minus}} ion concentration at low {eta}, and a marked effect of Cl{sup {minus}} ions in reducing hydrogen coverage of the surface and permeability in alkaline solutions at high cathodic polarizations.

  10. Effects of hydrogen bond on 2-aminopyridine and its derivatives complexes in methanol solvent.

    PubMed

    Zhao, Jinfeng; Song, Peng; Cui, Yanling; Liu, Xuemei; Sun, Shaowu; Hou, Siyao; Ma, Fengcai

    2014-10-15

    In the present work, the time-dependent density functional theory (TD-DFT) method was adopted to investigate the excited state hydrogen-bond dynamics of 2-aminopyridine monomer (2AP) and its derivatives in hydrogen donating methanol solvent. The calculated steady-state absorption and fluorescence spectra agree well with the experimental results. Theoretical results state that the bond lengths of both O-H and N-H bands are lengthened, while the intermolecular hydrogen bond lengths are shortened in the excited state. Further, the intermolecular hydrogen bonds are proved to be strengthened according to the calculated binding energy. As a reasonable explanation, the hydrogen bonds binding energy increases with multiple hydrogen-bonding interactions in the electronically excited state. In addition, the hydrogen bonding dynamics in the excited state were visualized by the spectral shifts of vibrational modes. The calculated infrared spectra of both O-H and N-H stretching vibrational regions revealed that the O-H and N-H stretching bands red-shift.

  11. A new polymorph of triphenylmethylamine: the effect of hydrogen bonding.

    PubMed

    Khrustalev, Victor N; Borisova, Irina V; Zemlyansky, Nikolai N; Antipin, M Yu

    2009-02-01

    Crystallization of the hexane reaction mixture after treatment of LiGe(OCH(2)CH(2)NMe(2))(3) with Ph(3)CN(3) gives rise to a new triclinic (space group P\\overline{1}) polymorph of triphenylmethylamine, C(19)H(17)N, (I), containing dimers formed by N-H...N hydrogen bonds, whereas the structure of the known orthorhombic (space group P2(1)2(1)2(1)) polymorph of this compound, (II), consists of isolated molecules. While the dimers in (I) lie across crystallographic inversion centres, the molecules are not truly related by them. The centrosymmetric structure is due to the statistical disordering of the amino H atoms participating in the N-H...N hydrogen-bonding interactions, and thus the inversion centre is superpositional. The conformations and geometric parameters of the molecules in (I) and (II) are very similar. It was found that the polarity of the solvent does not affect the capability of triphenylmethylamine to crystallize in the different polymorphic modifications. The orthorhombic polymorph, (II), is more thermodynamically stable under normal conditions than the triclinic polymorph, (I). The experimental data indicate the absence of a phase transition in the temperature interval 120-293 K. The densities of (I) (1.235 Mg m(-3)) and (II) (1.231 Mg m(-3)) at 120 K are practically equal. It would seem that either the kinetic factors or the effects of the other products of the reaction facilitating the hydrogen-bonded dimerization of triphenylmethylamine molecules are the determining factor for the isolation of the triclinic polymorph (I) of triphenylmethylamine.

  12. The Search for a Diurnal Effect in Lunar Hydrogen Abundance

    NASA Astrophysics Data System (ADS)

    Teodoro, L. A.; Lawrence, D. J.; Elphic, R. C.; Eke, V. R.; Feldman, W. C.; Maurice, S.

    2014-12-01

    Mapping the abundance of hydrogen-bearing materials has led to significant advances in our understanding of the sequestration of volatiles at the poles of the Moon. Neutron spectroscopy, and especially mapping of epithermal neutron fluxes, has been central to this endeavor (e.g., Feldman et al., Science, 1998). In this talk we present a study of the diurnal variation of the Lunar Prospector neutron spectrometer (LPNS) measurements to search for the possible low-latitude mobility of water molecules. This study is prompted by reports of local-time-varying concentrations of H2O/OH, based on near-infrared spectral reflectance data (e.g., Sunshine et al., Science, 2009), as well as reports of a diurnal hydrogen signature in the Lunar Exploration Neutron Detector epithermal neutron fluxes (eg., Livengood et al., ESF, 2014). While the spectral reflectance signatures could be due to small amounts of surficial water or hydroxyl molecules within the instrument view, the neutron result implies the diurnal mobility of volumetrically significant amounts of water and/or hydroxyl. Such an extraordinary finding, if confirmed, could have significant ramifications for our understanding of the H2O/OH distribution and mobility at the lunar surface. In this talk, we will show that Lunar Prospector epithermal neutron data exhibit diurnal variations of the same magnitude (1-2% of the average lunar epithermal neutron flux) as those reported by Livengood et al., 2014, but the LPNS variations do not follow the same diurnal trend. Instead, the LPNS variations are systemically anti-correlated with instrument temperature, and are related to very small changes in instrument gain. These findings suggest that, rather than reflecting diurnal changes in hydrogen, the temporal fluctuations in the count rates are due to small residual systematic effects in the data reduction.

  13. 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

  14. Hydrogen bonding plays a significant role in the binding of coomassie brilliant blue-R to hemoglobin: FT-IR, fluorescence and molecular dynamics studies.

    PubMed

    Maity, Mritunjoy; Dolui, Sandip; Maiti, Nakul C

    2015-12-14

    An analog of coomassie brilliant blue-R (CBB-R) was recently found to act as an antagonist to ATP-sensitive purinergic receptors (P2X7R) and has potential to be used in medicine. With the aim of understanding its transportation and distribution through blood, in this investigation, we measured the binding parameters of CBB-R with bovine hemoglobin (BHG). The molecule specifically bound to a single binding site of the protein with a stoichiometric ratio of 1 : 1 and the observed binding constant Ka was 3.5, 2.5, 2.0 and 1.5 × 10(5) M(-1) at 20 °C, 27 °C, 37 °C and 45 °C, respectively. The measured respective ΔG(0) values of the binding at four temperatures were -30.45, -22.44, -18.04 and -11.95 kJ mol(-1). The ΔH(0) (change in enthalpy) and ΔS(0) (change in entropy) values were -23.6 kJ mol(-1) and -70.66 J mol(-1) respectively in the binding process. The negative value of ΔH(0) and ΔS(0) indicated that the binding of the molecule was thermodynamically favorable. The best energy structure in the molecular docking analysis revealed that CBB-R preferred to be intercalated in the cavity among the α2, β1 and β2 subunits and the binding location was 7.4 Å away from Trp37 in the β2 subunit. The binding of the molecule with the protein was stabilized by hydrogen bonds involving the side chain of two amino acid residues. The residues were Lys104 and Glu101 in the β2 subunit. The binding was further stabilized via hydrogen bond formation between the amide group of the peptide backbone (residue Tyr145 of the β1 subunit) and CBB-R. A shift of the amide I (-C=O stretching) band frequency of ∼8 cm(-1) to low energy was ascribed to the hydrogen bond interaction involving the polypeptide carbonyl of the protein and the CBB-R molecule. In addition, two π-cation interactions between Lys99 of the α2 subunit and Lys104 of the β2 subunit and CBB-R contributed favorably in the binding processes. No substantial change in the soret and Q absorption bands of BHG

  15. Nitrendipine: effects on vascular responses and myocardial binding.

    PubMed

    McBride, W; Mukherjee, A; Haghani, Z; Wheeler-Clark, E; Brady, J; Gandler, T; Bush, L; Buja, L M; Willerson, J T

    1984-11-01

    We have further defined the binding characteristics of [3H]nitrendipine to myocardial microsomal membranes of cats, dogs, rats, and rabbits and to canine coronary vasculature (1.5-3.0 mm OD), and we have studied nitrendipine's effect on contractile responses in isolated feline cardiac muscle and canine coronary arteries. [3H]nitrendipine binding is rapid, saturable, and reversible in all four species and in all of these tissues. Feline myocardium has a single binding site with a dissociation constant (KD) of 1.94 nM. Canine myocardium may have two classes of binding sites, with the high-affinity site having a KD of 0.17 nM. Nitrendipine depresses contractility in isolated feline cardiac muscle and canine coronary arteries in a dose-dependent manner [half-maximal dose (ED50) 0.20 microM in isolated feline cardiac muscle and 1.6-6.3 nM for potential dependent contractile responses in isolated canine coronary arteries] and severely blunts the contractile response to increases in extracellular calcium concentration in isolated feline papillary muscles. In contrast to verapamil and D 600, nitrendipine does not prevent the treppe phenomenon. In isolated feline cardiac muscle and large canine coronary arteries, the minimal nitrendipine concentration required for specific binding and for depression of contractile responses is similar. However, only in large canine coronary arteries is the ED50 for nifedipine's depression of contractility similar to the KD for [3H]nitrendipine binding in the respective tissue.

  16. Effect of Li Termination on the Electronic and Hydrogen Storage Properties of Linear Carbon Chains: A TAO-DFT Study.

    PubMed

    Seenithurai, Sonai; Chai, Jeng-Da

    2017-07-10

    Accurate prediction of the electronic and hydrogen storage properties of linear carbon chains (C n ) and Li-terminated linear carbon chains (Li2C n ), with n carbon atoms (n = 5-10), has been very challenging for traditional electronic structure methods, due to the presence of strong static correlation effects. To meet the challenge, we study these properties using our newly developed thermally-assisted-occupation density functional theory (TAO-DFT), a very efficient electronic structure method for the study of large systems with strong static correlation effects. Owing to the alteration of the reactivity of C n and Li2C n with n, odd-even oscillations in their electronic properties are found. In contrast to C n , the binding energies of H2 molecules on Li2C n are in (or close to) the ideal binding energy range (about 20 to 40 kJ/mol per H2). In addition, the H2 gravimetric storage capacities of Li2C n are in the range of 10.7 to 17.9 wt%, satisfying the United States Department of Energy (USDOE) ultimate target of 7.5 wt%. On the basis of our results, Li2C n can be high-capacity hydrogen storage materials that can uptake and release hydrogen at temperatures well above the easily achieved temperature of liquid nitrogen.

  17. 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

    2014-09-05

    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.

  18. 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.

  19. 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

    1999-02-05

    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.

  20. 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.

  1. Effect of electric and magnetic fields on impurity binding energy in zinc-blend symmetric InGaN/GaN multiple quantum dots.

    PubMed

    Sadeghi, Ebrahim; Naghdi, Elham

    2014-01-01

    The binding energy of ground state for hydrogenic impurity in multiple quantum dots is calculated in the framework of effective-mass approximation and using a variational method. It is shown that the binding energy is a function of the size of dots, impurity position and external fields strength. The binding energy has a maximum value when the impurity is located on the center of dots and decreases for other impurity positions. The external electric and magnetic fields change the magnitude and the position of peaks. PACS Codes 73.20.D; 71.21.La; 71.55.Eq.

  2. Anisotropy of hydrogen diffusion in nickel single crystals: the effects of self-stress and hydrogen concentration on diffusion.

    PubMed

    Li, J; Oudriss, A; Metsue, A; Bouhattate, J; Feaugas, X

    2017-03-22

    Hydrogen diffusion has an important role in solute-dependent hydrogen embrittlement in metals and metallic alloys. In spite of extensive studies, the complexity of hydrogen diffusion in solids remains a phenomenon that needs to be clarified. In this paper, we investigate the anisotropy of hydrogen diffusion in pure nickel single crystals using both an experimental approach and a thermodynamic development. As a first approximation, experimental data from electrochemical permeation and thermal desorption spectroscopy are described using the classical Fick's laws and an apparent diffusion tensor. Within a thermodynamic framework, the diffusion equation can be derived from Fick's laws with an apparent diffusion coefficient which contains an added solute content dependent term β. This term is due to the elastic strain field associated with the insertion of solute atoms. For nickel crystals, the dependence of β on the crystallographic orientation arises from the elastic anisotropy. Additionally, our results elucidate the discrepancies between the thermodynamic model and experimental observations of the effect of the solute concentration on the diffusion process. Moreover, this highlights the importance of the impact of hydrogen on vacancy formation and the subsequent consequences on the anisotropy of the apparent diffusion coefficient.

  3. Anisotropy of hydrogen diffusion in nickel single crystals: the effects of self-stress and hydrogen concentration on diffusion

    PubMed Central

    Li, J.; Oudriss, A.; Metsue, A.; Bouhattate, J.; Feaugas, X.

    2017-01-01

    Hydrogen diffusion has an important role in solute-dependent hydrogen embrittlement in metals and metallic alloys. In spite of extensive studies, the complexity of hydrogen diffusion in solids remains a phenomenon that needs to be clarified. In this paper, we investigate the anisotropy of hydrogen diffusion in pure nickel single crystals using both an experimental approach and a thermodynamic development. As a first approximation, experimental data from electrochemical permeation and thermal desorption spectroscopy are described using the classical Fick’s laws and an apparent diffusion tensor. Within a thermodynamic framework, the diffusion equation can be derived from Fick’s laws with an apparent diffusion coefficient which contains an added solute content dependent term β. This term is due to the elastic strain field associated with the insertion of solute atoms. For nickel crystals, the dependence of β on the crystallographic orientation arises from the elastic anisotropy. Additionally, our results elucidate the discrepancies between the thermodynamic model and experimental observations of the effect of the solute concentration on the diffusion process. Moreover, this highlights the importance of the impact of hydrogen on vacancy formation and the subsequent consequences on the anisotropy of the apparent diffusion coefficient. PMID:28327592

  4. Anisotropy of hydrogen diffusion in nickel single crystals: the effects of self-stress and hydrogen concentration on diffusion

    NASA Astrophysics Data System (ADS)

    Li, J.; Oudriss, A.; Metsue, A.; Bouhattate, J.; Feaugas, X.

    2017-03-01

    Hydrogen diffusion has an important role in solute-dependent hydrogen embrittlement in metals and metallic alloys. In spite of extensive studies, the complexity of hydrogen diffusion in solids remains a phenomenon that needs to be clarified. In this paper, we investigate the anisotropy of hydrogen diffusion in pure nickel single crystals using both an experimental approach and a thermodynamic development. As a first approximation, experimental data from electrochemical permeation and thermal desorption spectroscopy are described using the classical Fick’s laws and an apparent diffusion tensor. Within a thermodynamic framework, the diffusion equation can be derived from Fick’s laws with an apparent diffusion coefficient which contains an added solute content dependent term β. This term is due to the elastic strain field associated with the insertion of solute atoms. For nickel crystals, the dependence of β on the crystallographic orientation arises from the elastic anisotropy. Additionally, our results elucidate the discrepancies between the thermodynamic model and experimental observations of the effect of the solute concentration on the diffusion process. Moreover, this highlights the importance of the impact of hydrogen on vacancy formation and the subsequent consequences on the anisotropy of the apparent diffusion coefficient.

  5. Bioconversion of wheat stalk to hydrogen by dark fermentation: effect of different mixed microflora on hydrogen yield and cellulose solubilisation.

    PubMed

    Wei, Yueli; Yuan, Xianzheng; Shi, Xiaoshuang; Chu, Yongbao; Guo, Rongbo

    2011-02-01

    This study determined hydrogen production, volatile fatty acids (VFAs) generation and cellulose solubilisation from anaerobic dark fermentation of wheat stalk and showed the effect of different mixed microflora. The cumulative hydrogen yields of anaerobic digested activated sludge (AS)-inoculated and anaerobic digested dairy manure (DM)-inoculated system were 23.3 and 37.0 mL/g VS at 204 h, respectively. A modified Gompertz equation was able to adequately describe the production of hydrogen from the batch fermentation by both mixed microflora. During the process, acetate and butyrate accounted for more than 76.1% of total VFAs for both fermentations. The extent of cellulose solubilisation approached 46.6% and 75.2% for AS- and DM-inoculated fermentation, respectively. The X-ray diffraction (XRD) showed that the crystallinities of both fermented stalks were partly disrupted by the mixed microflora, and DM-inoculated fermentation had more disruption than AS-inoculated one.

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

    PubMed

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

    2015-11-05

    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.

  7. Effect of edge structure on the activity for hydrogen evolution reaction in MoS2 nanoribbons

    NASA Astrophysics Data System (ADS)

    Liu, Lili; Li, Xiuyan; Xu, Li-Chun; Liu, Ruiping; Yang, Zhi

    2017-02-01

    Density functional theory (DFT) was carried out to investigate the effect of edge structure on the catalytic activity and electronic properties of MoS2 nanoribbons for hydrogen evolution reaction (HER). There are two stable configurations of MoS2 nanoribbons, MoS2NR-L and MoS2NR-R, with an energy barrier of 0.035 eV. Four hydrogen adsorbed configurations are obtained by adsorbing the hydrogen atom at the different adsorption sites of two configurations. By calculating the Gibbs free energy and exchange current densities, it is found that these four adsorbed configurations have varied catalytic activity for HER, which demonstrates that location of edge atoms has significantly effect on the catalytic activity for HER. The optimization in HER activities originates from the suitable binding between hydrogen atom and S atom, corresponding to that Gibbs free energy is close to zero. Our results signify that the edge structures play a key role on the HER activity in MoS2 nanoribbons.

  8. 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.

  9. Many-body effect in ion binding to RNA

    PubMed Central

    Zhu, Yuhong; Chen, Shi-Jie

    2014-01-01

    Ion-mediated electrostatic interactions play an important role in RNA folding stability. For a RNA in a solution with higher Mg2+ ion concentration, more counterions in the solution can bind to the RNA, causing a strong many-body coupling between the bound ions. The many-body effect can change the effective potential of mean force between the tightly bound ions. This effect tends to dampen ion binding and lower RNA folding stability. Neglecting the many-body effect leads to a systematic error (over-estimation) of RNA folding stability at high Mg2+ ion concentrations. Using the tightly bound ion model combined with a conformational ensemble model, we investigate the influence of the many-body effect on the ion-dependent RNA folding stability. Comparisons with the experimental data indicate that including the many-body effect led to much improved predictions for RNA folding stability at high Mg2+ ion concentrations. The results suggest that the many-body effect can be important for RNA folding in high concentrations of multivalent ions. Further investigation showed that the many-body effect can influence the spatial distribution of the tightly bound ions and the effect is more pronounced for compact RNA structures and structures prone to the formation of local clustering of ions. PMID:25106614

  10. Hydrogenation of magnesium nanoblades: The effect of concentration dependent hydrogen diffusion

    NASA Astrophysics Data System (ADS)

    Yang, B.; He, Y.-P.; Zhao, Y.-P.

    2011-02-01

    By assuming the H diffusion coefficient and H adsorption rate to be exponentially and linearly dependent on concentration, a physical model is developed to predict the hydrogenation process of Mg nanoblades. The predicted H uptake curves agree well with the experimental data from V-coated Mg nanoblades. The obtained H diffusion coefficients in MgHx between Mg and MgH2 have nearly three orders of magnitude variation. The characteristic time of H surface adsorption is longer than that of H diffusion in Mg but shorter than that in MgH2 for 100 nm thick nanoblades. A hydride shell is not formed during the hydrogenation.

  11. Geometric phase effects in ultracold hydrogen exchange reaction

    NASA Astrophysics Data System (ADS)

    Hazra, Jisha; Kendrick, Brian K.; Balakrishnan, N.

    2016-10-01

    The role of the geometric phase effect on chemical reaction dynamics is explored by examining the hydrogen exchange process in the fundamental H+HD reaction. Results are presented for vibrationally excited HD molecules in the v = 4 vibrational level and for collision energies ranging from 1 μK to 100 K. It is found that, for collision energies below 3 K, inclusion of the geometric phase leads to dramatic enhancement or suppression of the reaction rates depending on the final quantum state of the HD molecule. The effect was found to be the most prominent for rotationally resolved integral and differential cross sections but it persists to a lesser extent in the vibrationally resolved and total reaction rate coefficients. However, no significant GP effect is present in the reactive channel leading to the D+H2 product or in the D+H2 (v=4,j=0) \\to HD+H reaction. A simple interference mechanism involving inelastic (nonreactive) and exchange scattering amplitudes is invoked to account for the observed GP effects. The computed results also reveal a shape resonance in the H+HD reaction near 1 K and the GP effect is found to influence the magnitude of the resonant part of the cross section. Experimental detection of the resonance may allow a sensitive probe of the GP effect in the H+HD reaction.

  12. Geometric phase effects in ultracold hydrogen exchange reaction

    SciTech Connect

    Hazra, Jisha; Kendrick, Brian K.; Balakrishnan, Naduvalath

    2016-10-14

    The role of the geometric phase effect on chemical reaction dynamics is explored by examining the hydrogen exchange process in the fundamental H+HD reaction. Results are presented for vibrationally excited HD molecules in the v = 4 vibrational level and for collision energies ranging from 1 μK to 100 K. It is found that, for collision energies below 3 K, inclusion of the geometric phase leads to dramatic enhancement or suppression of the reaction rates depending on the final quantum state of the HD molecule. The effect was found to be the most prominent for rotationally resolved integral and differential cross sections but it persists to a lesser extent in the vibrationally resolved and total reaction rate coefficients. However, no significant GP effect is present in the reactive channel leading to the D+H2 product or in the D+H2 $(v=4,j=0)\\,\\to $ HD+H reaction. A simple interference mechanism involving inelastic (nonreactive) and exchange scattering amplitudes is invoked to account for the observed GP effects. The computed results also reveal a shape resonance in the H+HD reaction near 1 K and the GP effect is found to influence the magnitude of the resonant part of the cross section. In conclusion, experimental detection of the resonance may allow a sensitive probe of the GP effect in the H+HD reaction.

  13. Geometric phase effects in ultracold hydrogen exchange reaction

    DOE PAGES

    Hazra, Jisha; Kendrick, Brian K.; Balakrishnan, Naduvalath

    2016-10-14

    The role of the geometric phase effect on chemical reaction dynamics is explored by examining the hydrogen exchange process in the fundamental H+HD reaction. Results are presented for vibrationally excited HD molecules in the v = 4 vibrational level and for collision energies ranging from 1 μK to 100 K. It is found that, for collision energies below 3 K, inclusion of the geometric phase leads to dramatic enhancement or suppression of the reaction rates depending on the final quantum state of the HD molecule. The effect was found to be the most prominent for rotationally resolved integral and differential cross sections but it persists to a lesser extent in the vibrationally resolved and total reaction rate coefficients. However, no significant GP effect is present in the reactive channel leading to the D+H2 product or in the D+H2more » $$(v=4,j=0)\\,\\to $$ HD+H reaction. A simple interference mechanism involving inelastic (nonreactive) and exchange scattering amplitudes is invoked to account for the observed GP effects. The computed results also reveal a shape resonance in the H+HD reaction near 1 K and the GP effect is found to influence the magnitude of the resonant part of the cross section. In conclusion, experimental detection of the resonance may allow a sensitive probe of the GP effect in the H+HD reaction.« less

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Effect of Nanosized NbC Precipitates on Hydrogen Diffusion in X80 Pipeline Steel

    PubMed Central

    Wu, Junsheng; Xie, Donghan; Wu, Xiaoguang; Huang, Yunhua; Li, Xiaogang

    2017-01-01

    In this paper, the effects of dispersed 3~10 nm NbC precipitates on hydrogen diffusion in X80 pipeline steel were investigated by means of high resolution transmission electron microscopy (HRTEM), electrochemical hydrogen permeation, and thermal desorption spectroscopy (TDS). The relationship between hydrogen diffusion and temperature was determined for Nb-free X80 and 0.055 wt% Nb X80 steel. The temperature dividing reversible and irreversible traps was measured, and the quantity of hydrogen captured by different traps was calculated. Three types of hydrogen trap were designed and applied in the test, and the results revealed that irreversible hydrogen traps formed by nanosized and coherent NbC precipitates markedly hindered hydrogen diffusion, and prolonged breakthrough time in Nb-bearing X80 steel. PMID:28773079

  19. 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.

  20. Effect of Nanosized NbC Precipitates on Hydrogen Diffusion in X80 Pipeline Steel.

    PubMed

    Cui, Qiaoqi; Wu, Junsheng; Xie, Donghan; Wu, Xiaoguang; Huang, Yunhua; Li, Xiaogang

    2017-06-28

    In this paper, the effects of dispersed 3~10 nm NbC precipitates on hydrogen diffusion in X80 pipeline steel were investigated by means of high resolution transmission electron microscopy (HRTEM), electrochemical hydrogen permeation, and thermal desorption spectroscopy (TDS). The relationship between hydrogen diffusion and temperature was determined for Nb-free X80 and 0.055 wt% Nb X80 steel. The temperature dividing reversible and irreversible traps was measured, and the quantity of hydrogen captured by different traps was calculated. Three types of hydrogen trap were designed and applied in the test, and the results revealed that irreversible hydrogen traps formed by nanosized and coherent NbC precipitates markedly hindered hydrogen diffusion, and prolonged breakthrough time in Nb-bearing X80 steel.

  1. Highly effective recognition of carbohydrates by phenanthroline-based receptors: alpha- versus beta-anomer binding preference.

    PubMed

    Mazik, Monika; Hartmann, Andrè; Jones, Peter G

    2009-09-14

    (1)H NMR spectroscopic titrations in competitive and non-competitive media, as well as binding studies in two-phase systems, such as phase transfer of sugars from aqueous into organic solvents and dissolution of solid carbohydrates in apolar media revealed both highly effective recognition of neutral carbohydrates and interesting binding preferences of an acyclic phenanthroline-based receptor 1. Compared to the previously described acyclic receptors, compound 1 displays significantly higher binding affinities, the rare capability to extract sugars from water into non-polar organic solutions and alpha- versus beta-anomer binding preference in the recognition of glycosides, which differs from those observed for other receptor systems. X-ray crystallographic investigations revealed the presence of water molecules in the binding pocket of 1 that are engaged in the formation of hydrogen-bonding motifs similar to those suggested by molecular modelling for the sugar OH groups in the receptor-sugar complexes. The molecular modelling calculations, synthesis, crystal structure and binding properties of 1 are described and compared with those of the previously described receptors.

  2. 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

  3. Thiosulfate Mediates Cytoprotective Effects of Hydrogen Sulfide Against Neuronal Ischemia.

    PubMed

    Marutani, Eizo; Yamada, Marina; Ida, Tomoaki; Tokuda, Kentaro; Ikeda, Kohei; Kai, Shinichi; Shirozu, Kazuhiro; Hayashida, Kei; Kosugi, Shizuko; Hanaoka, Kenjiro; Kaneki, Masao; Akaike, Takaaki; Ichinose, Fumito

    2015-11-06

    Hydrogen sulfide (H2S) exhibits protective effects in various disease models including cerebral ischemia-reperfusion (I/R) injury. Nonetheless, mechanisms and identity of molecules responsible for neuroprotective effects of H2S remain incompletely defined. In the current study, we observed that thiosulfate, an oxidation product of H2S, mediates protective effects of an H2S donor compound sodium sulfide (Na2S) against neuronal I/R injury. We observed that thiosulfate in cell culture medium is not only required but also sufficient to mediate cytoprotective effects of Na2S against oxygen glucose deprivation and reoxygenation of human neuroblastoma cell line (SH-SY5Y) and murine primary cortical neurons. Systemic administration of sodium thiosulfate (STS) improved survival and neurological function of mice subjected to global cerebral I/R injury. Beneficial effects of STS, as well as Na2S, were associated with marked increase of thiosulfate, but not H2S, in plasma and brain tissues. These results suggest that thiosulfate is a circulating "carrier" molecule of beneficial effects of H2S. Protective effects of thiosulfate were associated with inhibition of caspase-3 activity by persulfidation at Cys163 in caspase-3. We discovered that an SLC13 family protein, sodium sulfate cotransporter 2 (SLC13A4, NaS-2), facilitates transport of thiosulfate, but not sulfide, across the cell membrane, regulating intracellular concentrations and thus mediating cytoprotective effects of Na2S and STS. The protective effects of H2S are mediated by thiosulfate that is transported across cell membrane by NaS-2 and exerts antiapoptotic effects via persulfidation of caspase-3. Given the established safety track record, thiosulfate may be therapeutic against ischemic brain injury. © 2015 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley Blackwell.

  4. 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

  5. Effects of Flux and Energy of Neutral Beam on Hydrogenation of Graphene

    NASA Astrophysics Data System (ADS)

    Okada, Takeru; Samukawa, Seiji

    2015-09-01

    Hydrogen modification, hydrogenation, of graphene, has attracted due to the possibility of hydrogen storage. Chemisorbed hydrogen has strong interaction with graphene surface and sp3 bond forms. Surprisingly, ideal structure of graphene shows reversible absorption of hydrogen and it leads to effective designing of hydrogen storage material. In this paper, we have demonstrated neutral beam (NB) technique for hydrogenation of graphene instead of conventional plasma method. NB system consists of a plasma generation chamber and a process chamber, which are separated by a carbon plate with many apertures. The charged particles can be effectively neutralized by collision with the sidewall of the apertures when passing through them to the process chamber. Development of the D-band and blue shift of G-band were observed after hydrogen NB irradiation by Raman spectroscopy. FTIR analysis reveals CH bending mode was appeared and it depends on beam energy, thus CH formation has reaction threshold and potential to control it. In addition, it is shown that beam flux affects hydrogenation and additional effect is also included in reaction process. We believe our investigation will provide development of hydrogenated graphene applications.

  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. 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.

  8. Hydrogen storage in a potassium-ion-bound metal-organic framework incorporating crown ether struts as specific cation binding sites.

    PubMed

    Lim, Dae-Woon; Chyun, Seung An; Suh, Myunghyun Paik

    2014-07-21

    To develop a metal-organic framework (MOF) for hydrogen storage, SNU-200 incorporating a 18-crown-6 ether moiety as a specific binding site for selected cations has been synthesized. SNU-200 binds K(+), NH4(+), and methyl viologen (MV(2+)) through single-crystal to single-crystal transformations. It exhibits characteristic gas-sorption properties depending on the bound cation. SNU-200 activated with supercritical CO2 shows a higher isosteric heat (Qst) of H2 adsorption (7.70 kJ mol(-1)) than other zinc-based MOFs. Among the cation inclusions, K(+) is the best for enhancing the isosteric heat of the H2 adsorption (9.92 kJ mol(-1)) as a result of the accessible open metal sites on the K(+) ion. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. 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.

  10. Progress in the study of biological effects of hydrogen on higher plants and its promising application in agriculture.

    PubMed

    Zeng, Jiqing; Ye, Zhouheng; Sun, Xuejun

    2014-01-01

    While the medical effects of hydrogen have been broadly analyzed, research into the effects of hydrogen on higher plants has often been of lesser concern. Recent studies on the botanical effects of hydrogen have shown that it is involved in signal transduction pathways of plant hormones and can improve the resistance of plants to stressors, such as drought, salinity, cold and heavy metals. In addition, hydrogen could delay postharvest ripening and senescence of fruits. Observational evidence has also shown that hydrogen can regulate the flowering time of plants. These results indicate that hydrogen may have great potential applications within agricultural production, indicating that there may be a new 'hydrogen agricultural era' to come.

  11. Binding and Release between Polymeric Carrier and Protein Drug: pH Mediated Interplay of Coulomb forces, Hydrogen Bonding, van der Waals Interactions and Entropy.

    PubMed

    De Luca, Sergio; Chen, Fan; Seal, Prasenjit; Stenzel, Martina H; Smith, Sean C

    2017-09-07

    The accelerating search for new types of drugs and delivery strategies poses the challenge to understand the mechanism of delivery. To this end, a detailed atomistic picture of binding between the drug and the carrier is quintessential. While many studies focus on the electrostatics of drug-vector interactions, it has also been pointed out that entropic factors relating to water and counter ions can play an important role. By carrying out extensive molecular dynamics simulations and subsequently validating with experiment, we shed light herein on the binding in aqueous solution between a protein drug and a polymeric carrier. We examined the complexation between the polymer, poly (ethylene glycol) methyl ether acrylate-b-poly(carboxyethyl acrylate (PEGMEA-b-PCEA) and the protein, egg white lysozyme, a system that acts as a model for polymer-vector / protein-drug delivery systems. The complexation has been visualized and characterized using contact maps and hydrogen bonding analyses for five independent simulations of the complex, each running over 100 ns. Binding at physiological pH is, as expected, mediated by coulombic attraction between the positively charged protein and negatively charged carboxylate groups on the polymer. However, we find that consideration of electrostatics alone is insufficient to explain the complexation behaviour at low pH. Intra-complex hydrogen bonds, van der Waals interactions also water-water interactions dictate that the polymer does not release the protein at pH 4.8 or indeed at pH 3.2, even though the Coulombic attractions are largely removed as carboxylate groups on the polymer become titrated. Experiments in aqueous solution carried out at pH = 7.0, 4.5, and 3.0 confirm the veracity of the computed binding behaviour. Overall, these combined simulation and experimental results illustrate that coulomb interactions need to be complemented with consideration of other entropic forces, mediated by van der Waals interactions and hydrogen

  12. Effect of an acetylene bond on hydrogen adsorption in diamond-like carbon allotropes: from first principles to atomic simulation.

    PubMed

    Wu, Xuanjun; Li, Lei; Fang, Tiange; Wang, YeTong; Cai, Weiquan; Xiang, Zhonghua

    2017-03-29

    By inserting an acetylene bond into the organic linkers of porous materials, hydrogen storage can be significantly enhanced; however, the mechanism of this enhancement remains elusive. Herein, we developed a new diamond-like carbon allotrope (referred as diamond-like diacetylene a.k.a. DDA) with medium pores constructed by inserting -C[triple bond, length as m-dash]C-C[triple bond, length as m-dash]C- ligands into the -C-C- bonds of diamond. The structural, mechanical, and electrical properties, as well as hydrogen storage capacities were investigated for this novel material using density functional theory and Monte Carlo simulations. The optimized geometry of DDA shows a high surface area and free pore volume of ca. 5498.76 m(2) g(-1) and 2.0486 m(3) g(-1), respectively. DDA also exhibits structural stability and special electronic properties. Interestingly, DDA exhibits exceptional gravimetric hydrogen storage capacity as well as volumetric one. The excess gravimetric and volumetric H2 uptakes at 77 K and 2.0 MPa hit a maximum of 14.12 wt% and 603.35 cm(3) (STP) cm(-3), respectively, which substantially exceeds those previously reported for MOF or PAF materials. Even at 243 K and 12 MPa, the total gravimetric H2 uptake of DDA reaches 5.38 wt%. To the best of our knowledge, DDA is one of porous materials with the maximum physical hydrogen uptake. It is also one of the few materials that can be close to meeting hydrogen storage target of the US department of energy at room temperature. Significantly, DDA shows the deliverable hydrogen storage capacity up to 5.28 wt% at room temperature. Through analyzing the effect of the acetylene position in the DLCAs on their hydrogen storage capacities, we found that the high hydrogen adsorption performance of DDA is mainly attributed to its high surface area, large number of adsorption sites, and appropriate binding energy. In summary, the newly developed DDA is a promising candidate for hydrogen storage and provides a new

  13. Effect ofHydrogen Use on Diesel Engine Performance

    NASA Astrophysics Data System (ADS)

    Ceraat, A.; Pana, C.; Negurescu, N.; Nutu, C.; Mirica, I.; Fuiorescu, D.

    2016-11-01

    Necessity of pollutant emissions decreasing, a great interest aspect discussed at 2015 Paris Climate Conference, highlights the necessity of alternative fuels use at diesel engines. Hydrogen is considered a future fuel for the automotive industry due to its properties which define it as the cleanest fuel and due to the production unlimited sources. The use of hydrogen as fuel for diesel engines has a higher degree of complexity because of some hydrogen particularities which lead to specific issues of the hydrogen use at diesel engine: tendency of uncontrolled ignition with inlet backfire, in-cylinder combustion with higher heat release rates and with high NOx level, storage difficulties. Because hydrogen storing on vehicle board implies important difficulties in terms of safety and automotive range, the partial substitution of diesel fuel by hydrogen injected into the inlet manifold represents the most efficient method. The paper presents the results of the experimental researches carried on a truck diesel engine fuelled with diesel fuel and hydrogen, in-cylinder phenomena's study showing the influence of some parameters on combustion, engine performance and pollutant emissions. The paper novelty is defined by the hydrogen fuelling method applied to diesel engine and the efficient control of the engine running.

  14. Hydrogen Response of Palladium Coated Suspended Gate Field Effect Transistor.

    DTIC Science & Technology

    1986-07-30

    abstract wtaered In Mlock 20, It diffrent frog JR*Port) 18. SUPPLEMENTARY NOTES 19. KEY WORDS (Continue on to,,ee, aIde It ncessary a Identity by block...hydrogen is dissolved in the metal, the lattice is strained. The resulting change in dimensions has been used as a means for sensing hydrogen2 2 and has

  15. 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.

  16. 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

  17. 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.

  18. Substituent effects on noncovalent bonds: complexes of ionized benzene derivatives with hydrogen cyanide.

    PubMed

    Attah, Isaac K; Hamid, Ahmed M; Meot-Ner Mautner, Michael; El-Shall, M S; Aziz, Saadullah G; Alyoubi, Abdulrahman O

    2013-10-17

    Here, we report the first experimental and computational study of the noncovalent binding energies and structures of ionized benzenes containing electron-withdrawing substituents solvated by one to four HCN molecules. Measured by ion mobility mass spectrometric equilibrium studies, the bond dissociation enthalpies of the first HCN molecule to the fluorobenzene (C6H5F(•+)), 1,4-difluorobenzene (C6H4F2(•+)), and benzonitrile (C6H5CN(•+)) ions (11.2, 11.2, and 9.2 kcal/mol, respectively) are similar to those of HCN with the benzene (C6H6(•+)) and phenyacetylene (C6H5CCH(•+)) radical cations (9.2 and 10.5 kcal/mol, respectively). DFT calculations at the B3LYP/6-311++G(d,p) level show that HCN can form in-plane hydrogen bonds to ring hydrogens, or bind electrostatically to positively charged carbon centers in the ring. The electron-withdrawing substituents increase the bond energy by increasing the partial positive charge on the ring hydrogens that form CH(δ+)---NCH bonds, and by creating a π hole, as evidenced by positive charge centers on the fluorinated ring carbons for electrostatically bonded isomers. In the complexes of benzonitrile(•+), similar to benzene(•+), hydrogen bonded planar isomers have the lowest energy. In the complexes of (fluorinated benzene)(•+), the lowest energy isomers are electrostatically bonded where HCN is perpendicular to the ring and its dipole points to a positively charged ring carbon. However, in all cases the planar hydrogen-bonded and vertical electrostatic isomers have similar binding energies within 1 kcal/mol, although HCN interacts with different sites of the ionized benzenes in these isomers, suggesting that the observed cluster populations are mixtures of the planar and vertical isomers. Further HCN molecules can bind directly to unoccupied ring CH hydrogens or bind to the first-shell HCN molecules to form linear HCN---HCN--- hydrogen bonded chains. The binding energies decrease stepwise to about 6-7 kcal/mol by

  19. Dissecting the Binding Mode of Low Affinity Phage Display Peptide Ligands to Protein Targets by Hydrogen/Deuterium Exchange Coupled to Mass Spectrometry

    PubMed Central

    2015-01-01

    Phage display (PD) is frequently used to discover peptides capable of binding to biological protein targets. The structural characterization of peptide–protein complexes is often challenging due to their low binding affinities and high structural flexibility. Here, we investigate the use of hydrogen/deuterium exchange mass spectrometry (HDX-MS) to characterize interactions of low affinity peptides with their cognate protein targets. The HDX-MS workflow was optimized to accurately detect low-affinity peptide–protein interactions by use of ion mobility, electron transfer dissociation, nonbinding control peptides, and statistical analysis of replicate data. We show that HDX-MS can identify regions in the two epigenetic regulator proteins KDM4C and KDM1A that are perturbed through weak interactions with PD-identified peptides. Two peptides cause reduced HDX on opposite sides of the active site of KDM4C, indicating distinct binding modes. In contrast, the perturbation site of another PD-selected peptide inhibiting the function of KDM1A maps to a GST-tag. Our results demonstrate that HDX-MS can validate and map weak peptide–protein interactions and pave the way for understanding and optimizing the binding of peptide scaffolds identified through PD and similar ligand discovery approaches. PMID:25325890

  20. Elucidation of the binding sites of sodium dodecyl sulfate to β-lactoglobulin using hydrogen/deuterium exchange mass spectrometry combined with docking simulation.

    PubMed

    Hu, Wenbing; Liu, Jianan; Luo, Qun; Han, Yumiao; Wu, Kui; Lv, Shuang; Xiong, Shaoxiang; Wang, Fuyi

    2011-05-30

    Hydrogen/deuterium exchange mass spectrometry (H/DX MS) has become a powerful tool to investigate protein-protein and protein-ligand interactions, but it is still challenging to localize the interaction regions/sites of ligands with pepsin-resistant proteins such as lipocalins. β-Lactoglobulin (BLG), a member of the lipocalin family, can bind a variety of small hydrophobic molecules including retinols, retinoic acids, and long linear fatty acids. However, whether the binding site of linear molecules locates in the external groove or internal cavity of BLG is controversial. In this study we used H/DX MS combined with docking simulation to localize the interaction sites of a tested ligand, sodium dodecyl sulfate (SDS), binding to BLG. H/DX MS results indicated that SDS can bind to both the external and the internal sites in BLG. However, neither of the sites is saturated with SDS, allowing a dynamic ligand exchange to occur between the sites at equilibrium state. Docking studies revealed that SDS forms H-bonds with Lys69 in the internal site and Lys138 and Lys141 in the external site in BLG via the sulfate group, and interacts with the hydrophobic residues valine, leucine, isoleucine and methionine within both of the sites via its hydrocarbon tail, stabilizing the BLG-SDS complex.

  1. Effect of polarization on HIV-1protease and fluoro-substituted inhibitors binding energies by large scale molecular dynamics simulations

    PubMed Central

    Duan, Li L.; Zhu, T.; Li, Yu C.; Zhang, Qing G.; Zhang, John Z. H.

    2017-01-01

    Molecular dynamics simulations in explicit water are carried out to study the binding of six inhibitors to HIV-1 protease (PR) for up to 700 ns using the standard AMBER force field and polarized protein-specific charge (PPC). PPC is derived from quantum mechanical calculation for protein in solution and therefore it includes electronic polarization effect. Our results show that in all six systems, the bridging water W301 drifts away from the binding pocket in AMBER simulation. However, it is very stable in all six complexes systems using PPC. Especially, intra-protease, protease-inhibitor hydrogen bonds are dynamic stabilized in MD simulation. The computed binding free energies of six complexes have a significantly linear correlation with those experiment values and the correlation coefficient is found to be 0.91 in PPC simulation. However, the result from AMBER simulation shows a weaker correlation with the correlation coefficient of −0.51 due to the lack of polarization effect. Detailed binding interactions of W301, inhibitors with PR are further analyzed and discussed. The present study provides important information to quantitative understanding the interaction mechanism of PR-inhibitor and PR-W301 and these data also emphasizes the importance of both the electronic polarization and the bridging water molecule in predicting precisely binding affinities. PMID:28155907

  2. An investigation into the effects of hydrogen on the fracture and deformation of Alloy X-750

    SciTech Connect

    Symons, Douglas M.

    1994-11-01

    this study investigated the effect of hydrogen on the fracture of a nickel-base superalloy, Alloy X-750 in the solution treated and aged (HTH) condition. The effect of hydrogen was examined through tensile testing and fracture toughness testing incorporating observations from scanning electron microscopy and light microscopy.

  3. Angiotensin receptor binding and pressor effects in cat subretrofacial nucleus

    SciTech Connect

    Allen, A.M.; Dampney, R.A.L.; Mendelsohn, F.A.O. Univ. of Sydney )

    1988-11-01

    Central administration of angiotensin II (ANG II) increases arterial blood pressure via increased sympathetic activity. The authors have examined the possibility that one site of action of ANG II is the subretrofacial (SRF) nucleus in the rostral ventrolateral medulla, since this nucleus is known to play a critical role in the tonic and phasic control of arterial pressure. In vitro autoradiography, employing {sup 125}I-labeled (Sar{sup 1}, Ile{sup 8})ANG II as radioligand, was used to localize binding sites for ANG-II in the cat ventrolateral medulla. A high density of ANG II-receptor binding sites was found confined to the SRF nucleus. In a second group of experiments in anesthetized cats, microinjections of ANG II, in doses ranging from 10 to 50 pmol, were made into histologically identified sites within and outside the SRF nucleus. Microinjections into the nucleus resulted in a dose-dependent increase in arterial pressure, which was abolished by systemic administration of the ganglion-blocking drug hexamethonium bromide. In contrast, microinjections just outside the SRF nucleus had no effect on arterial pressure. It is concluded that activation of ANG II-receptor binding sites within the SRF nucleus leads to an increase in arterial pressure via increased sympathetic efferent activity.

  4. Chemical Binding Effects in Neutron Resonance Scattering and Absorption.

    NASA Astrophysics Data System (ADS)

    Shamaoun, Adib Iskandar

    The Doppler broadening of neutron absorption and scattering resonances is an effect of considerable importance in calculating reactor parameters. This broadening is known to depend upon the state of the atom from which the scattering of the neutron occurs. This dependence is called the chemical binding effect. A key assumption in the usual computations of Doppler broadening is to ignore the dependence of the total resonance width on the chemical binding state of the compound nucleus. This is an excellent approximation for the gamma line. We derive an expression for the neutron line width as a function of the energy of the compound nucleus for an ideal gas. The influence of energy on the width with energy is examined at two different temperatures 4K and 1000K. It is found that these effects are very small, of the order of 10^{4-} . The assumption of constancy of the resonance width is thus shown to be a good approximation for the neutron line width. Also we examine the influence of the crystalline binding on the 6.67 eV resonance energy of U-238 line shape in uranium carbide and uranium dioxide. This model treats the crystal as a gas with an effective temperature and an effective mass determined by harmonic crystal phonon spectrum developed by Koppel and Houston. Based on this model, the line shape of U-238 is Gaussian plus a recoilless part. We also compute the broadening using a harmonic crystal model. As the temperature of U-238 target is decreased, disagreement between the two models becomes pronounced. However the results agree in the limiting case of high temperature. As the nucleus becomes more tightly bound, shifts in the resonance peak to lower energies are also observed. A general formula for the differential scattering cross section is developed starting from the transition probability (T-matrix). The formalism is applied to the gas and harmonic crystal models to determine the chemical binding effect. Although the resonance broadening is determined in

  5. 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.

  6. 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

  7. Effect of hydrogen defects on nanocrystallite layers of Si solar cells by hydrogen implantation

    NASA Astrophysics Data System (ADS)

    Palei, Srikanta; Lim, Gyoungho; Parida, Bhaskar; Choi, Jaeho; Kim, Keunjoo

    2015-11-01

    The Si solar cells were irradiated with high energy hydrogen ions of 10, 30, 60 and 120 keV at the dose rate of 1017 H+ ions (proton)/cm2. The structural, optical and electrical properties of the implanted samples and fabricated cells were studied. The implantation induced defects bringing structural changes before and after annealing was evidenced by the transmission electron microscopy. The Raman spectrum showed a change of crystalline to amorphous state at 480 cm-1 when the sample was implanted by hydrogen ion of 30 keV energy. Formation of nanocrystallite layers were observed after annealing. The electroluminescence images showed that hydrogen-related defect centers were involved in the emission mechanism. The photoluminescence emission from the implanted cells was attributed to nanocrystallite layers. From current-voltage measurements, the conversion efficiencies of implanted Si solar cells were found lower than the un-implanted reference cell. The ion implantation did not passivate the defects rather acted as recombination centers.

  8. Neuroprotective effects of hydrogen sulfide and the underlying signaling pathways.

    PubMed

    Chen, Wen-Lin; Niu, Ying-Ying; Jiang, Wei-Zheng; Tang, Hui-Lan; Zhang, Chong; Xia, Qi-Ming; Tang, Xiao-Qing

    2015-01-01

    Hydrogen sulfide (H2S) is an endogenously produced gas that represents a novel third gaseous signaling molecule, neurotransmitter and cytoprotectant. Cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE), 3-mercaptopyruvate sulfur transferase with cysteine aminotransferase (3-MST/CAT) and 3-mercaptopyruvate sulfur transferase with d-amino acid oxidase (3-MST/DAO) pathways are involved in the generation of endogenous H2S despite the ubiquitous or restricted distribution of those enzymes. CBS, 3-MST/CAT and 3-MST/DAO can be found in the brain, while CSE is widely located in other organs. There also exist up-taking or recycling and scavenging mechanisms in H2S metabolism to maintain its persistence for physiological function. In recent years, investigating the role that H2S plays in the central nervous system and cardiovascular system has always been a hotspot. To date, effects of H2S are at least partially verified in multiple animal models or neuron cell lines of Alzheimer's disease, Parkinson's disease, cerebral ischemia, major depression disorders and febrile seizure, although subsequent studies are still badly needed. This article presents an overview of current knowledge of H2S focusing on its neuroprotective effects and corresponding signaling pathways, together with connections to potential therapeutic strategies in the clinic.

  9. Effect of thermal nonequilibrium on reactions in hydrogen combustion

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

    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.

  10. 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.

  11. 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.

  12. 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

  13. The effect of pearlite on the hydrogen-induced ductility loss in ductile cast irons

    NASA Astrophysics Data System (ADS)

    Matsuo, T.

    2017-05-01

    Hydrogen energy systems, such as a hydrogen fuel cell vehicle and a hydrogen station, are rapidly developing to solve global environmental problems and resource problems. The available structural materials used for hydrogen equipments have been limited to only a few relatively expensive metallic materials that are tolerant for hydrogen embrittlement. Therefore, for the realization of a hydrogen society, it is important to expand the range of materials available for hydrogen equipment and thereby to enable the use of inexpensive common materials. Therefore, ductile cast iron was, in this study, focused as a structural material that could contribute to cost reduction of hydrogen equipment, because it is a low-cost material having good mechanical property comparable to carbon steels in addition to good castability and machinability. The strength and ductility of common ductile cast irons with a ferritic-pearlitic matrix can be controlled by the volume fraction of pearlitic phase. In the case of carbon steels, the susceptibility to hydrogen embrittlement increases with increase in the pearlite fraction. Toward the development of ferritic-pearlitic ductile cast iron with reasonable strength for hydrogen equipment, it is necessary to figure out the effect of pearlite on the hydrogen embrittlement of this cast iron. In this study, the tensile tests were conducted using hydrogen-precharged specimens of three kinds of ferritic-pearlitic ductile cast irons, JIS-FCD400, JIS-FCD450 and JIS-FCD700. Based on the results, the role of pearlite in characterizing the hydrogen embrittlement of ductile cast iron was discussed.

  14. The study of synergistic effects of alcohols on the catalytic hydrogenation of brown coal

    SciTech Connect

    Kuznetsov, P.N.; Kuznetsova, L.I.; Kartseva, N.V.

    1998-12-31

    The hydrogenation of brown coal in methanol, ethanol and isopropanol containing medium in the presence of catalysts was studied. The effects of different catalysts, alcohols, the proportion between the quantity of hydrogen, alcohols and tetralin on the conversion of coal, product yields, composition and molecular weight of solubles were analyzed. The synergistic effects of the mixtures of methanol and ethanol with tetralin and with hydrogen on the conversion of brown coal were observed at 380 C and 430 C in the presence of supported Fe, Fe-Mo, Ni, and Co hydroxide catalysts. Small amounts of methanol and ethanol additives induced the improved coal swelling and conversion into soluble products with diminished molecular weight. Synergistic effect was found to depend on the catalyst concentration, hydrogen pressure and alcohol structure. Coal swelling, hydrogenation and alkylation reactions were evaluated. The nature of the promoting effect of alcohols on coal liquefaction is discussed.

  15. Alterations of the colonic flora and their effect on the hydrogen breath test.

    PubMed

    Gilat, T; Ben Hur, H; Gelman-Malachi, E; Terdiman, R; Peled, Y

    1978-07-01

    The hydrogen breath test was performed by ingestion of 20 g lactulose and analysis of end-expiratory air. Eighteen patients undergoing colonoscopy, 17 receiving antibiotics, 12 prepared for colon surgery, and 15 controls were examined. The test was repeated under control conditions in the treated patients. Eleven of 55 subjects failed to produce significant amounts of hydrogen under control conditions. This 20% proportion of non-hydrogen producers is much higher than that reported by other investigators. The hydrogen production was very markedly depressed after preparation for colonscopy and antibiotic therapy. The effect of neomycin and enemata as used in preparation for colon surgery was less marked. Hydrogen production by the colonic flora is thus subject to individual variations and may be affected by various therapeutic regimens. All these may cause false negative results when using the hydrogen breath test to evaluate carbohydrate absorption. The test should therefore not be performed for a considerable time after therapeutic manipulation of the colonic flora.

  16. Regulatory effect of hydrogen on nitrogenase activity of the blue-green alga (cyanobacterium) Nostoc muscorum.

    PubMed

    Scherer, S; Kerfin, W; Böger, P

    1980-03-01

    Preincubation of the blue-green alga (cyanobacterium) Nostoc muscorum under an atmosphere of argon plus acetylene in the light led to a greater than fourfold increase of light-induced hydrogen evolution and to a 50% increase of acetylene reduction, as compared to cells that had not been preconditioned. The basic and the increased hydrogen evolution were both due to nitrogenase activity. Furthermore, after preincubation the hydrogen uptake, usually observed with unconditional cells, was abolished. Nostoc preincubated under acetylene evolved hydrogen in the light even in the presence of nitrogen for at least 2 h, with a 15-fold increase as compared to the unconditioned cells. These acetylene effects could be completely abolished by the presence of hydrogen during acetylene preincubation. These findings indicate that the hydrogen concentration in N. muscorum cells plays a role in regulation of nitrogenase activity.

  17. Effects due to adsorbed atoms upon angular and energy distributions of surface produced negative hydrogen ions

    NASA Astrophysics Data System (ADS)

    Wada, M.; Bacal, M.; Kasuya, T.; Kato, S.; Kenmotsu, T.; Sasao, M.

    2013-02-01

    Exposure to Cs added hydrogen discharge makes surface of plasma grid of a negative hydrogen ion source covered with Cs and hydrogen. A Monte-Carlo particle simulation code ACAT was run to evaluate the effects due to adsorbed Cs and H atoms upon the angular and energy distributions of H atoms leaving the surface. Accumulation of H atoms on the surface reduces particle reflection coefficients and the mean energy of backscattered H atoms. Angular distributions of H atoms reflected from the hydrogen covered surface tend to be under-cosine at lower energies. Desorption of adsorbed H atoms is more efficient for hydrogen positive ions than for Cs positive ions at lower incident energy. At higher energy more than 100 eV, Cs ions desorb adsorbed H atoms more efficiently than hydrogen ions.

  18. 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.

  19. Host Plant Cultivar Effects on Hydrogen Evolution by Rhizobium leguminosarum.

    PubMed

    Bedmar, E J; Edie, S A; Phillips, D A

    1983-08-01

    The effect of host plant cultivar on H(2) evolution by root nodules was examined in symbioses between Pisum sativum L. and selected strains of Rhizobium leguminosarum. Hydrogen evolution from root nodules containing Rhizobium represents the sum of H(2) produced by the nitrogenase enzyme complex and H(2) oxidized by any uptake hydrogenase present in those bacterial cells. Relative efficiency (RE) calculated as RE = 1 - (H(2) evolved in air/C(2) H(2) reduced) did not vary significantly among ;Feltham First,' ;Alaska,' and ;JI1205' peas inoculated with R. leguminosarum strain 300, which lacks uptake hydrogenase activity (Hup(-)). That observation suggests that the three host cultivars had no effect on H(2) production by nitrogenase. However, RE of strain 128C53 was significantly (P effects on H(2) uptake capacity of both strain 128C53 and the genetically related strain 3960. The (3)H(2) incorporation assay showed that strains 128C53 and 3960 in symbiosis with Feltham First had about 10% of the uptake hydrogenase activity measured in root nodules of Alaska or JI1205. These data are the first demonstration of significant host plant effects on rhizobial uptake hydrogenase in a single plant species.

  20. 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.

  1. Microcavity effects in the photoluminescence of hydrogenated amorphous silicon nitride

    NASA Astrophysics Data System (ADS)

    Serpenguzel, Ali; Aydinli, Atilla; Bek, Alpan

    1998-07-01

    Fabry-Perot microcavities are used for the alteration of photoluminescence in hydrogenated amorphous silicon nitride grown with and without ammonia. The photoluminescence is red-near-infrared for the samples grown without ammonia, and blue-green for the samples grown with ammonia. In the Fabry- Perot microcavities, the amplitude of the photoluminescence is enhanced, while its linewidth is reduced with respect to the bulk hydrogenated amorphous silicon nitride. The microcavity was realized by a metallic back mirror and a hydrogenated amorphous silicon nitride--air or a metallic front mirror. The transmittance, reflectance, and absorbance spectra were also measured and calculated. The calculated spectra agree well with the experimental spectra. The hydrogenated amorphous silicon nitride microcavity has potential for becoming a versatile silicon based optoelectronic device such as a color flat panel display, a resonant cavity enhanced light emitting diode, or a laser.

  2. 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.

  3. Effect of oxide films on hydrogen permeability of candidate Stirling heater head tube alloys

    SciTech Connect

    Schuon, S R; Misencik, J A

    1981-01-01

    High pressure hydrogen has been selected as the working fluid for the developmental automotive Stirling engine. Containment of the working fluid during operation of the engine at high temperatures and at high hydrogen gas pressures is essential for the acceptance of the Stirling engine as an alternative to the internal combustion engine. Most commercial alloys are extremely permeable to pure hydrogen at high temperatures. A program was undertaken at NASA Lewis Research Center (LeRC) to reduce hydrogen permeability in the Stirling engine heater head tubes by doping the hydrogen working fluid with CO or CO/sub 2/. Small additions of these gases were shown to form an oxide on the inside tube wall and thus reduce hydrogen permeability. A study of the effects of dopant concentration, alloy composition, and effects of surface oxides on hydrogen permeability in candidate heater head tube alloys is summarized. Results showed that hydrogen permeability was similar for iron-base alloys (N-155, A286, IN800, 19-9DL, and Nitronic 40), cobalt-base alloys (HS-188) and nickel-base alloys (IN718). In general, the permeability of the alloys decreased with increasing concentration of CO or CO/sub 2/ dopant, with increasing oxide thickness, and decreasing oxide porosity. At high levels of dopants, highly permeable liquid oxides formed on those alloys with greater than 50% Fe content. Furthermore, highly reactive minor alloying elements (Ti, Al, Nb, and La) had a strong influence on reducing hydrogen permeability.

  4. Effect of knots on binding of intercalators to DNA

    NASA Astrophysics Data System (ADS)

    Medalion, Shlomi; Rabin, Yitzhak

    2014-05-01

    We study the effect of knots in circular dsDNA molecules on the binding of intercalating ligands. Using Monte Carlo simulations we show that depending on their handedness, the presence of knots can either suppress or enhance intercalation in supercoiled DNA. When the occupancy of intercalators on DNA is low, the effect of knots on intercalation can be captured by introducing a shift in the mean writhe of the chain that accounts for the writhe of the corresponding ideal knot. In the limit of high intercalator occupancy, the writhe distribution of different knots is strongly affected by excluded volume effects and therefore by salt concentration. Based on the finding that different knots yield well-separated probability distributions of bound intercalators, we propose a new experimental approach to determine DNA topology by monitoring the intensity of fluorescence emitted by dye molecules intercalated into knotted DNA molecules.

  5. Effective Hamiltonians for fastly driven tight-binding chains

    NASA Astrophysics Data System (ADS)

    Itin, A. P.; Neishtadt, A. I.

    2014-02-01

    We consider a single particle tunnelling in a tight-binding model with nearest-neighbour couplings, in the presence of a periodic high-frequency force. An effective Hamiltonian for the particle is derived using an averaging method resembling classical canonical perturbation theory. Three cases are considered: uniform lattice with periodic and open boundary conditions, and lattice with a parabolic potential. We find that in the latter case, interplay of the potential and driving leads to appearance of the effective next-nearest neighbour couplings. In the uniform case with periodic boundary conditions the second- and third-order corrections to the averaged Hamiltonian are completely absent, while in the case with open boundary conditions they have a very simple form, found before in some particular cases by S. Longhi (2008) [10]. These general results may found applications in designing effective Hamiltonian models in experiments with ultracold atoms in optical lattices, e.g. for simulating solid-state phenomena.

  6. 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.

  7. 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.

  8. 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

  9. Protective Effects of Hydrogen Gas on Experimental Acute Pancreatitis.

    PubMed

    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.

  10. Numerical study of influence of hydrogen backflow on krypton Hall effect thruster plasma focusing

    NASA Astrophysics Data System (ADS)

    Yan, Shilin; Ding, Yongjie; Wei, Liqiu; Hu, Yanlin; Li, Jie; Ning, Zhongxi; Yu, Daren

    2017-03-01

    The influence of backflow hydrogen on plasma plume focusing of a krypton Hall effect thruster is studied via a numerical simulation method. Theoretical analysis indicates that hydrogen participates in the plasma discharge process, changes the potential and ionization distribution in the thruster discharge cavity, and finally affects the plume focusing within a vacuum vessel.

  11. Hydrogenation effects in metalloporphycenes: synthesis and redox behavior of Ni(II)-tetra(n-propyl)dihydroporphycene.

    PubMed

    Okawara, Toru; Hashimoto, Koichi; Abe, Masaaki; Shimakoshi, Hisashi; Hisaeda, Yoshio

    2012-06-04

    Hydrogenated tetrapropylporphycenes, 2,3-dihydro-2,7,12,17-tetrapropylporphycene 1 and its Ni(II) complex 2, have been prepared and the hydrogenation effects on their electronic structure characterized. A one-electron reduction of 2 promotes dehalogenation of organic halides whose observation is unprecedented for the porphycene compounds.

  12. Geometrical H/D isotope effect on hydrogen bonds in charged water clusters.

    PubMed

    Tachikawa, Masanori; Shiga, Motoyuki

    2005-08-31

    To investigate the proton/deuteron geometrical isotope effect of positively and negatively charged water complexes, H5O2+ and H3O2-, we have carried out accurate ab initio path integral simulations considering the electron correlation effect. It has been found that the isotope effect on the hydrogen bond is different between these two species in that the oxygen separation becomes shorter in H5O2+ while longer in H3O2- by deuteron substitution. This behavior is ascribed to the change in the quantum effect of hydrogen bonds whether the shared hydrogen is on a single or double well potential surface.

  13. EFFECT OF TEMPERATURE AND GLYCEROL ON THE HYDROGEN-BOND DYNAMICS OF WATER

    SciTech Connect

    Ghattyvenkatakrishna, Pavan K; Uberbacher, Edward C

    2013-01-01

    The effect of glycerol, water and glycerol-water binary mixtures on the structure and dynamics of biomolecules has been well studied. However, the effect of varying glycerol concentration and temperature on the dynamics of water has not received due attention. We have studied the effect of concentration and temperature on the hydrogen bonded network formed by water molecules. A strong correlation between the relaxation time of the network and average number of hydrogen bonds per water molecules was found. The radial distribution function of water oxygens and hydrogens clarifies the effect of concentration on the structure and clustering of water.

  14. Can Silicon Carbide Nanotubes Be Effective Storage Medium for Hydrogen Storage

    NASA Astrophysics Data System (ADS)

    Mukherjee, Souptik; Ray, Asok

    2009-03-01

    A systematic study of molecular hydrogen adsorption on three different atomic configurations of armchair SICNTs has been performed. In the first stage of our study, first principles calculations using both density functional theory (DFT) and hybrid density functional theory (HDFT) as well as the finite cluster approximation have been performed to study the adsorption of molecular hydrogen on three types of armchair (9, 9) silicon carbide nanotubes. The distances of molecular hydrogen from the outer wall of the nanotubes have been optimized manually using the B3LYP and PW91 functionals and results have been compared in detail with published literature results. In the second part of our study, hydrogen molecule has been adsorbed from both inside as well as from the outer wall of nanotubes ranging from (3, 3) to (6, 6) for all three types. A detailed comparison of the binding energies, equilibrium positions and Mulliken charges has been performed for all three types of nanotubes and for all possible sites in those nanotubes. In the third phase, co-adsorption of two hydrogen molecules has been carried out. Possibilities of hydrogen storage have been explored in detail.

  15. 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.

  16. BINDING OF THE RESPIRATORY CHAIN INHIBITOR ANTIMYCIN TO THE MITOCHONDRIAL bc1 COMPLEX: A NEW CRYSTAL STRUCTURE REVEALS AN ALTERED INTRAMOLECULAR HYDROGEN-BONDING PATTERN.

    PubMed Central

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

    2006-01-01

    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-salicylamide 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 2.28 Å 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 αA helix. PMID:16024040

  17. 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.

  18. 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.

  19. Effect of pH on pyrazole binding to liver alcohol dehydrogenase.

    PubMed

    Andersson, P; Kvassman, J; Lindström, A; Oldén, B; Pettersson, G

    1981-03-01

    1. Kinetic and equilibrium data have been determined at different pH between 4 and 10 for binding of the inhibitor pyrazole to liver alcohol dehydrogenase and to the binary complexes formed between enzyme and NADH or NAD+. 2. Pyrazole binding to free enzyme requires the protonated form of an ionizing group with a pKa of 9.2, agreeing with the pKa value reported for the water molecule bound at the catalytic zinc ion of the enzyme subunit. The rate of association of the inhibitor to the enzyme . NAD+ complex exhibits a similar pKa-7.6-dependence attributable to ionization of zinc-bound water in the latter binary complex. These observations lend support to the idea that pyrazole combines to the catalytic zinc ion on complex formation with the enzyme, zinc-bound water most likely being displaced by the inhibitor. 3. The rate of dissociation of the inhibitor from the ternary enzyme . NAD+ . pyrazole complex is proportional to the hydrogen ion concentration over the examined pH range (4-8). This effect of pH, which is proposed to reflect ionization of the enzyme-bound inhibitor with a pKa value below 4 (indirectly estimated to 2.4), accounts for the exceptional stability of the ternary complex at neutral and alkaline pH. It is concluded that pyrazole, by analogy to water and alcohol ligands, undergoes a drastic pKa perturbation on binding to the catalytic zinc ion in the enzyme . NAD+ complex.

  20. Effect of fatty acids on the phosphate binding of TRK-390, a novel, highly selective phosphate-binding polymer.

    PubMed

    Nakaki, Junko; Yamaguchi, Shinichi; Torii, Yuichi; Inoue, Atsushi; Minakami, Satoshi; Kanno, Takami; Murakami, Masanori; Tsuzuki, Masahiro; Mochizuki, Hidenori; Suyama, Kazuharu; Miyamoto, Mitsuko

    2013-08-15

    Phosphate binders are used for the treatment of hyperphosphatemia in hemodialysis patients with chronic kidney disease. Sevelamer, a phosphate-binding polymer, has been reported to bind bile acids or fatty acids and thereby decrease its phosphate-binding capacity. The novel phosphate binder TRK-390 is a poly (allylamine) polymer that has been shown to have enhanced phosphate selectivity, with low bile-acid-binding. In this study we evaluated the effect of fatty acids on the phosphate-binding capacity of TRK-390. In the absence of fatty acids and bile acids, the phosphate-binding capacity of TRK-390 was similar to that of sevelamer. In the presence of fatty acids and bile acids, the phosphate-binding capacity of TRK-390 was reduced to 83%; in contrast, that of sevelamer was reduced to 35%. TRK-390 and sevelamer showed a similar effect in lowering urinary phosphate excretion in normal rats fed a normal diet. However, urinary phosphate excretion of rats treated with TRK-390 was reduced by about one half of that obtained with sevelamer, when given with a high-fat diet that had a fat content similar to the diet of hemodialysis patients. TRK-390 was superior in terms of phosphate selectivity in the presence of fatty acids and bile acids in vitro, and the phosphate-binding capacity of TRK-390 in vivo was shown to be less affected by fat in comparison with that of sevelamer. Thus, TRK-390 is expected to be useful as a novel highly selective phosphate binder. © 2013 Elsevier B.V. All rights reserved.

  1. Effects of internal hydrogen on the vacancy loop formation probability in Al

    SciTech Connect

    Bui, T.X.; Sirois, E.; Robertson, I.M. . Dept. of Materials Science and Engineering); Kirk, M.A. )

    1990-04-01

    The effect of internal hydrogen on the formation of vacancy dislocation loops from heavy-ion generated displacement cascades in Al has been investigated. Samples of high-purity aluminum and aluminum containing 900 and 1300 appM of hydrogen were irradiated at room temperature with 50 keV Kr+ ions. The ion dose rate was typically 2 {times} 10{sup 10}ions cm{sup {minus}2} sec{sup {minus}1} and the ion dose was between 10{sup 11} and 10{sup 13} ion cm{sup {minus}2}. Under these irradiation conditions, dislocation loops were observed in all compositions, although the formation probability was relatively low (less than 10 percent of the displacement cascades produced a vacancy loop). The loop formation probability was further reduced by the presence of hydrogen. No difference in the geometry or the size of the loops created in the hydrogen free and hydrogen charged samples was found. These results are difficult to interpret, and the explanation may lie in the distribution and form of the hydrogen. To account for the large hydrogen concentrations and from calculations of the energy associated with hydrogen entry into aluminum, it has been suggested that the hydrogen enters the aluminum lattice with an accompanying vacancy. This will create hydrogen-vacancy complexes in the material; two dimensional complexes have been detected in the hydrogen-charged, but unirradiated, samples by the small-angle x-ray scattering technique. The possibility of these complexes trapping the vacancies produced by the cascade process exists thus lowering the formation probability. However, such a mechanism must occur within the lifetime of the cascade. Alternatively, if a displacement cascade overlaps with the hydrogen-vacancy complexes, the lower atomic density of the region will result in an increase in the cascade volume (decrease in the local vacancy concentration) which will also reduce the loop formation probability.

  2. The effect of hydrogen on the fracture toughness of alloy X-750 at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Symons, Douglas M.

    Ni-Cr-Fe alloys are widely used in pressurized water nuclear reactors (PWR). These alloys are susceptible to stress corrosion cracking (SCC) in PWR environments. There have been numerous mechanisms of crack advance proposed to describe the SCC of the nickel-base alloys in a PWR environment including slip/film rupture/oxidation and hydrogen embrittlement. It has also been suggested that there is not sufficient evidence to implicate hydrogen in the PWR SCC of nickel-base alloys. This program evaluated the effect of hydrogen on the embrittlement of a nickel-base alloy, alloy X-750, at elevated temperatures with a hydrogen concentration typical of what may be developed from the corrosion reaction. Fracture toughness values and the tearing resistance of alloy X-750 were evaluated in hydrogen gas and in air 260°C and 338°C. It was shown that at 260°C and 338°C alloy X-750 was severely embrittled in high pressure hydrogen gas. Further, the fracture morphology changed from predominantly transgranular ductile dimple fracture in air to predominantly intergranular fracture in hydrogen. The fracture morphology in hydrogen was similar to that found for PWR SCC of this material. This work supports a hydrogen-enhanced fracture mechanism contributing to the SCC of nickel-base alloys at elevated temperatures.

  3. 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.

  4. Effect of hydrogen peroxide and sodium perborate on the microhardness of human enamel and dentin.

    PubMed

    Lewinstein, I; Hirschfeld, Z; Stabholz, A; Rotstein, I

    1994-02-01

    The effect of 30% hydrogen peroxide and a paste of sodium perborate mixed with hydrogen peroxide at different temperatures and time intervals on the microhardness of human enamel and dentin was examined. Intact extracted human teeth were sectioned, embedded in acrylic resin, polished, and divided into four test groups related to surface treatment. The groups were 30% hydrogen peroxide at 37 degrees C, 30% hydrogen peroxide at 50 degrees C in an illuminated chamber, a paste of sodium perborate mixed with hydrogen peroxide at 37 degrees C, and a paste of sodium perborate mixed with hydrogen peroxide at 50 degrees C in an illuminated chamber. Teeth treated with distilled water at either 37 degrees C or 50 degrees C served as controls. The results indicated that treatment with 30% hydrogen peroxide reduced the microhardness of both enamel and dentin. This reduction was statistically significant after 5-min treatment for the dentin and after 15-min treatment for the enamel (p < 0.05). Treatment with sodium perborate mixed with hydrogen peroxide did not alter the microhardness of either the enamel or dentin at the tested temperatures and time intervals. It is therefore suggested that the use of high concentrations of hydrogen peroxide for bleaching purposes should be limited. Sodium perborate appears to be a less damaging bleaching agent.

  5. Magnesium ion is an effective inhibitor of the binding of Escherichia coli to heparin

    PubMed Central

    Kang, Jonghoon; Lee, Myung Soog; Gorenstein, David G.

    2007-01-01

    We investigated the effects of ions and temperature on the binding of E. coli to heparin using a chemiluminescence electrophoretic mobility shift assay. We found that magnesium ion is an effective inhibitor of the binding. The method can be readily applied to discover agents that can block the binding. PMID:17967492

  6. The effect of the cellulose-binding domain from Clostridium cellulovorans on the supramolecular structure of cellulose fibers.

    PubMed

    Ciolacu, Diana; Kovac, Janez; Kokol, Vanja

    2010-03-30

    The cellulose-binding domain (CBD) is the second important and the most wide-spread element of cellulase structure involved in cellulose transformation with a great structural diversity and a range of adsorption behavior toward different types of cellulosic materials. The effect of the CBD from Clostridium cellulovorans on the supramolecular structure of three different sources of cellulose (cotton cellulose, spruce dissolving pulp, and cellulose linters) was studied. Fourier-transform infrared spectroscopy (FTIR) was used to record amides I and II absorption bands of cotton cellulose treated with CBD. Structural changes as weakening and splitting of the hydrogen bonds within the cellulose chains after CBD adsorption were observed. The decrease of relative crystallinity index of the treated celluloses was confirmed by FTIR spectroscopy and X-ray diffraction (XRD). X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were used to confirm the binding of the CBD on the cellulose surface and the changing of the cellulose morphology.

  7. 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.

  8. 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.

  9. 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.

  10. 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)).

  11. 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.

  12. 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.

  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. Influence of Intramolecular Charge Transfer and Nuclear Quantum Effects on Intramolecular Hydrogen Bonds in Azopyrimidines.

    PubMed

    Bártová, Kateřina; Čechová, Lucie; Procházková, Eliška; Socha, Ondřej; Janeba, Zlatko; Dračínský, Martin

    2017-10-06

    Intramolecular hydrogen bonds (IMHBs) in 5-azopyrimidines are investigated by NMR spectroscopy and DFT computations that involve nuclear quantum effects. A series of substituted 5-phenylazopyrimidines with one or two hydrogen bond donors able to form IMHBs with the azo group is prepared by azo coupling. The barrier of interconversion between two rotamers of the compounds with two possible IMHBs is determined by variable temperature NMR spectroscopy and it is demonstrated that the barrier is significantly affected by intramolecular charge transfer. Through-hydrogen-bond scalar coupling is investigated in (15)N labeled compounds and the stability of the IMHBs is correlated with experimental NMR parameters and rationalized by path integral molecular dynamics simulations that involve nuclear quantum effects. Detailed information on the hydrogen bond geometry upon hydrogen-to-deuterium isotope exchange is obtained from a comparison of experimental and calculated NMR data.

  15. The effect of hydrogen on the fracture toughness of oxygen-strengthened titanium

    NASA Technical Reports Server (NTRS)

    Wasz, M. L.; Ko, C. C.; Brotzen, F. R.; Mclellan, R. B.

    1990-01-01

    Studies of oxygen-strengthened titanium alloys have indicated that while hydrogen has little effect on tensile properties, it causes a marked decrease in impact strength. It is presently established experimentally that the presence of hydrogen has essentially no effect on the fracture-toughness factor at the onset of crack propagation, in commercial-grade titanium alloys containing either low or high concentrations of oxygen. These findings are congruent with other study results on the tensile properties of these alloys, but contrast with the previously noted pronounced effect of hydrogen on impact resistance.

  16. The Effect of Hydrogen on the Solid Solution Strengthening and Softening of Nickel.

    DTIC Science & Technology

    1981-11-01

    Afl-A108 654e ILLINOIS UNIV AT URBANA DEPT OF METALLURGY AND MININS--ETC F/6 11/6 THE EFFECT OF HYDROGEN ON THE SOLID SOLUTION STRFNSTNFNING ANfl...RESOLUTION TEST CHART NATIONAL HUR[AU OF STANDARDS 1963 A, " , ..... . .... .. i ....... .. .. . t , LEVEL THE EFFECT OF HYDROGEN ON THE SOLID SOLUTION STRENGTHENING...Availability Codes IIAvail and/or Dist Special THE EFFECT OF HYDROGEN ON THE SOLID SOLUTION STRENGTHENING AND SOFTENING OF NICKEL J. Eastman, F. Heuhaum, T

  17. Effect of fiber on breath hydrogen response and symptoms after oral lactose in lactose malabsorbers.

    PubMed

    Nguyen, K N; Welsh, J D; Manion, C V; Ficken, V J

    1982-06-01

    The effect of ingesting cellulose, pectin, and psyllium with orally administered lactose in water or milk was tested in six lactose malabsorbers. Breath hydrogen tests were used to evaluate lactose malabsorption and mouth-to-cecum transit times. Addition of psyllium significantly reduced the breath hydrogen response, and symptoms in each subject; whereas, less diminution of expired hydrogen was seen after cellulose or pectin was added. The effect of each fiber on gastric emptying rates of an equal volume liquid meal was evaluated in three volunteers. Pectin had no effect, while the cellulose and psyllium modestly delayed emptying at approximately 30 min.

  18. 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.

  19. Molecular hydrogen: An inert gas turns clinically effective.

    PubMed

    Ostojic, Sergej M

    2015-06-01

    Molecular hydrogen (H2) appeared as an experimental agent in biomedicine approximately 40 years ago, yet the past 5 years seem to confirm its medicinal value in the clinical environment. H2 improves clinical end-points and surrogate markers in several clinical trials, from metabolic diseases to chronic systemic inflammatory disorders to cancer. However, less information is available concerning its medicinal properties, such as dosage and administration, or adverse reactions and use in specific populations. The present paper overviews the clinical relevance of molecular hydrogen, and summarizes data from clinical trials on this innovative medical agent. Clinical profiles of H2 provide evidence-based direction for practical application and future research on molecular hydrogen for the wider health care community.

  20. Paraquat toxicity and effect of hydrogen peroxide on thermophilic bacteria.

    PubMed

    Allgood, G S; Perry, J J

    1985-01-01

    Paraquat (PQ++) increased cyanide-resistant univalent respiration in cell suspensions of five strains of obligately thermophilic bacteria. PQ++ was reduced by an NADH: or NADPH:paraquat diaphorase and selectivity for NADH, NADPH, or both electron donors varied among the thermophiles. Superoxide anion production that was dependent on the presence of PQ++ was shown by following the superoxide dismutase-inhibitable reduction of cytochrome c. In addition, the PQ++-dependent formation of hydrogen peroxide from superoxide anion was evident in two of the thermophilic strains. Catalase synthesis was induced by adding hydrogen peroxide to the growth medium of the thermophiles. The induction of catalase to eliminate hydrogen peroxide appears to be an important response of these thermophilic bacteria to oxygen toxicity.

  1. Effects of Hydrogen Peroxide on Coral Photosynthesis and Calcification

    NASA Astrophysics Data System (ADS)

    Higuchi, T.; Fujimura, H.; Arakaki, T.; Oomori, T.

    2007-12-01

    The widely-observed decline of coral reefs is considered to be caused by changes in the environment by natural and anthropogenic activities. As one important factor, the run-off of various matters from human activities to the coastal seawater poses stresses to the corals by degrading the quality of the seawater. In Okinawa, Japan, red- soil running off from the developed land has been a major environmental issue since 1980s. Hydrogen peroxide (HOOH), a strong active oxygen species, is one of the photochemically formed chemicals in the red-soil-polluted seawater. Recent photochemical studies of seawater showed that HOOH photo-formation was faster in the red- soil-polluted seawater than clean seawater. We studied the effects of HOOH on corals by studying the changes in coral carbon metabolisms such as photosynthesis and calcification, which are indicators of the physiological state of a coral colony. The corals were exposed to various concentrations of HOOH (0, 0.3, 3 μM). Two massive coral species of Porites sp. and Goniastrea aspera and one branch coral of Galaxea facicularis were used for the exposure experiments. The control experiments showed that when no HOOH was added, metabolisms of each coral colony were relatively stable. On the other hand, when HOOH was added to the seawater, we observed obvious changes in the coral metabolisms in all the coral species. When 0.3 μM HOOH was added, photosynthesis decreased by 14% and calcification decreased by 17% within 3 days, compared with the control. When 3 μM HOOH was added, photosynthesis decreased by 21% and calcification decreased by 41% within 3 days, compared with the control. Our study showed that higher concentrations of HOOH posed more stress to the coral colonies.

  2. Factors influencing rumen fermentation: effect of hydrogen on formation of propionate.

    PubMed

    Schulman, M D; Valentino, D

    1976-08-01

    The effect of hydrogen on fermentation of lactate, pyruvate, fumarate, and succinate by resting rumen microorganisms has been investigated. Under an atmosphere of nitrogen, lactate was fermented to yield acetate as the major product (85 to 100 mole %) and propionate (0 to 17 mole %) and butyrate (0 to 3%) as secondary products. Under hydrogen, there was increased formation of both propionate and total volatile fatty acids. The amount of propionate increased 4 to 8 times and total volatile fatty acids 2.5 to 3.2 times. Propionate formation was proportional to the hydrogen concentration and reached a maximum at a partial pressure of hydrogen of .2 N/m2. With [2-carbon-14] lactate, propionate was formed via the dicarboxylic acid pathway under both nitrogen or hydrogen. Hydrogen did not affect significantly the fermentation of pyruvate or succinate. With fumarate under hydrogen, propionate and total volatile fatty acids increased 6.8 and 2 times while acetate was unchanged. The mechanism by which hydrogen exerts these effects is discussed in relation to the role of methanogenesis in the rumen.

  3. Effects of hydrogen on carbon steels at the Multi-Function Waste Tank Facility

    SciTech Connect

    Carlos, W.C.

    1995-02-08

    Concern has been expressed that hydrogen produced by corrosion, radiolysis, and decomposition of the waste could cause embrittlement of the carbon steel waste tanks at Hanford. The concern centers on the supposition that the hydrogen evolved in many of the existing tanks might penetrate the steel wall of the tank and cause embrittlement that might lead to catastrophic failure. This document reviews literature on the effects of hydrogen on the carbon steel proposed for use in the Multi-Function Waste Tank Facility for the time periods before and during construction as well as for the operational life of the tanks. The document draws several conclusions about these effects. Molecular hydrogen is not a concern because it is not capable of entering the steel tank wall. Nascent hydrogen produced by corrosion reactions will not embrittle the steel because the mild steel used in tank construction is not hard enough to be susceptible to hydrogen stress cracking and the corrosion product hydrogen is not produced at a rate sufficient to cause either loss in tensile ductility or blistering. If the steel intended for use in the tanks is produced to current technology, fabricated in accordance with good construction practice, postweld heat treated, and operated within the operating limits defined, hydrogen will not adversely affect the carbon steel tanks during their 50-year design life. 26 refs.

  4. Effects of heat treatment on microbial communities of granular sludge for biological hydrogen production.

    PubMed

    Alibardi, Luca; Favaro, Lorenzo; Lavagnolo, Maria Cristina; Basaglia, Marina; Casella, Sergio

    2012-01-01

    Dark fermentation shares many features with anaerobic digestion with the exception that to maximize hydrogen production, methanogens and hydrogen-consuming bacteria should be inhibited. Heat treatment is widely applied as an inoculum pre-treatment due to its effectiveness in inhibiting methanogenic microflora but it may not exclusively select for hydrogen-producing bacteria. This work evaluated the effects of heat treatment on microbial viability and structure of anaerobic granular sludge. Heat treatment was carried out on granular sludge at 100 °C with four residence times (0.5, 1, 2 and 4 h). Hydrogen production of treated sludges was studied from glucose by means of batch test at different pH values. Results indicated that each heat treatment strongly influenced the granular sludge resulting in microbial communities having different hydrogen productions. The highest hydrogen yields (2.14 moles of hydrogen per mole of glucose) were obtained at pH 5.5 using the sludge treated for 4 h characterized by the lowest CFU concentration (2.3 × 10(3)CFU/g sludge). This study demonstrated that heat treatment should be carefully defined according to the structure of the sludge microbial community, allowing the selection of highly efficient hydrogen-producing microbes.

  5. 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.

  6. 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

    2016-03-30

    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.

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. 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)

  12. Pressure effect on hydrogen tunneling and vibrational spectrum in α-Mn

    SciTech Connect

    Kolesnikov, Alexander I; Podlesnyak, Andrey A; Sadykov, Ravil A.; Antonov, Vladimir E.; Kuzovnikov, Michael; Ehlers, Georg; Granroth, Garrett E

    2016-10-03

    Here in this paper, the pressure effect on the tunneling mode and vibrational spectra of hydrogen in α-MnH0.07 has been studied by inelastic neutron scattering. Applying hydrostatic pressure of up to 30 kbar is shown to shift both the hydrogen optical modes and the tunneling peak to higher energies. First-principles calculations show that the potential for hydrogen in α-Mn becomes overall steeper with increasing pressure. At the same time, the barrier height and its extent in the direction of tunneling decrease and the calculations predict significant changes of the dynamics of hydrogen in α-Mn at 100 kbar, when the estimated tunneling splitting of the hydrogen ground state exceeds the barrier height.

  13. 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.

  14. Hydrogenated monolayer graphene with reversible and tunable wide band gap and its field-effect transistor

    NASA Astrophysics Data System (ADS)

    Son, Jangyup; Lee, Soogil; Kim, Sang Jin; Park, Byung Cheol; Lee, Han-Koo; Kim, Sanghoon; Kim, Jae Hoon; Hong, Byung Hee; Hong, Jongill

    2016-11-01

    Graphene is currently at the forefront of cutting-edge science and technology due to exceptional electronic, optical, mechanical, and thermal properties. However, the absence of a sizeable band gap in graphene has been a major obstacle for application. To open and control a band gap in functionalized graphene, several gapping strategies have been developed. In particular, hydrogen plasma treatment has triggered a great scientific interest, because it has been known to be an efficient way to modify the surface of single-layered graphene and to apply for standard wafer-scale fabrication. Here we show a monolayer chemical-vapour-deposited graphene hydrogenated by indirect hydrogen plasma without structural defect and we demonstrate that a band gap can be tuned as wide as 3.9 eV by varying hydrogen coverage. We also show a hydrogenated graphene field-effect transistor, showing that on/off ratio changes over three orders of magnitude at room temperature.

  15. Pressure effect on hydrogen tunneling and vibrational spectrum in α-Mn

    SciTech Connect

    Kolesnikov, Alexander I; Podlesnyak, Andrey A; Sadykov, Ravil A.; Antonov, Vladimir E.; Kuzovnikov, Michael; Ehlers, Georg; Granroth, Garrett E

    2016-10-03

    Here in this paper, the pressure effect on the tunneling mode and vibrational spectra of hydrogen in α-MnH0.07 has been studied by inelastic neutron scattering. Applying hydrostatic pressure of up to 30 kbar is shown to shift both the hydrogen optical modes and the tunneling peak to higher energies. First-principles calculations show that the potential for hydrogen in α-Mn becomes overall steeper with increasing pressure. At the same time, the barrier height and its extent in the direction of tunneling decrease and the calculations predict significant changes of the dynamics of hydrogen in α-Mn at 100 kbar, when the estimated tunneling splitting of the hydrogen ground state exceeds the barrier height.

  16. 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.

  17. Strength of effective Coulomb interactions and origin of ferromagnetism in hydrogenated graphene

    NASA Astrophysics Data System (ADS)

    Şaşıoǧlu, E.; Hadipour, H.; Friedrich, C.; Blügel, S.; Mertig, I.

    2017-02-01

    Hydrogenation provides a novel way to tune the electronic properties of graphene. Recent scanning tunneling microscopy experiments have demonstrated that local graphene magnetism can be selectively switched on and off by hydrogen (H) dimers. Employing first-principles calculations in conjunction with the constrained random-phase approximation we determine the strength of the effective Coulomb interaction U in hydrogenated graphene. We find that the calculated U parameters are smaller than the ones in graphene and depend on the H concentration. Moreover, the U parameters are very sensitive to the position of H atoms adsorbed on the graphene lattice. We discuss the instability of the paramagnetic state of the hydrogenated graphene towards the ferromagnetic one on the basis of calculated U parameters within the Stoner model. Spin-polarized calculations reveal that the itinerant ferromagnetism in hydrogenated graphene can be well accounted for by the Stoner model.

  18. Hydrogenated monolayer graphene with reversible and tunable wide band gap and its field-effect transistor

    PubMed Central

    Son, Jangyup; Lee, Soogil; Kim, Sang Jin; Park, Byung Cheol; Lee, Han-Koo; Kim, Sanghoon; Kim, Jae Hoon; Hong, Byung Hee; Hong, Jongill

    2016-01-01

    Graphene is currently at the forefront of cutting-edge science and technology due to exceptional electronic, optical, mechanical, and thermal properties. However, the absence of a sizeable band gap in graphene has been a major obstacle for application. To open and control a band gap in functionalized graphene, several gapping strategies have been developed. In particular, hydrogen plasma treatment has triggered a great scientific interest, because it has been known to be an efficient way to modify the surface of single-layered graphene and to apply for standard wafer-scale fabrication. Here we show a monolayer chemical-vapour-deposited graphene hydrogenated by indirect hydrogen plasma without structural defect and we demonstrate that a band gap can be tuned as wide as 3.9 eV by varying hydrogen coverage. We also show a hydrogenated graphene field-effect transistor, showing that on/off ratio changes over three orders of magnitude at room temperature. PMID:27830748

  19. 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.

  20. Pressure effect on hydrogen tunneling and vibrational spectrum in α-Mn

    DOE PAGES

    Kolesnikov, Alexander I; Podlesnyak, Andrey A; Sadykov, Ravil A.; ...

    2016-10-03

    Here in this paper, the pressure effect on the tunneling mode and vibrational spectra of hydrogen in α-MnH0.07 has been studied by inelastic neutron scattering. Applying hydrostatic pressure of up to 30 kbar is shown to shift both the hydrogen optical modes and the tunneling peak to higher energies. First-principles calculations show that the potential for hydrogen in α-Mn becomes overall steeper with increasing pressure. At the same time, the barrier height and its extent in the direction of tunneling decrease and the calculations predict significant changes of the dynamics of hydrogen in α-Mn at 100 kbar, when the estimatedmore » tunneling splitting of the hydrogen ground state exceeds the barrier height.« less

  1. The effectiveness of ski bindings and their professional adjustment for preventing alpine skiing injuries.

    PubMed

    Finch, C F; Kelsall, H L

    1998-06-01

    This article presents a critical review of the extent to which alpine ski bindings and their adjustment have been formally demonstrated to prevent injuries. It considers a range of evidence, from anecdotal evidence and informed opinion to biomechanical studies, testing of equipment, epidemiological studies and controlled field evaluations. A total of 15 published studies examining the effectiveness of bindings and their adjustment were identified. All of these included anecdotal or informed opinion, and all but one focused on equipment design. Seven studies involved the testing of bindings or binding prototypes, 2 studies presented biomechanical models of the forces involved in binding operation, 6 reported an epidemiological evaluation of ski bindings and 2 considered skiers' behaviours towards binding adjustment. Some of the reviewed articles relate to the study of the biomechanics of ski bindings and their release in response to various loads and loading patterns. Other studies examined the contribution of bindings and binding-release to lower extremity, equipment-related injuries, the effect of various methods of binding adjustment on injury risk and the determinants of skiers' behaviour relating to professional binding adjustment. Most of the evidence suggests that currently used bindings are insufficient for the multidirectional release required to reduce the risk of injury to the lower limb, especially at the knee. This evidence suggests that further technical developments and innovations are required. The standard of the manufacture of bindings and boots also needs to be considered. The optimal adjustment of bindings using a testing device has been shown to be associated with a reduced risk of lower extremity injury. Generally, however, the adjustment of bindings has been shown to be inadequate, especially for children's bindings. Recommendations for further research, development and implementation with respect to ski binding and their adjustment are given

  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. Microwave response of magnetized hydrogen plasma in carbon nanotubes: multiple reflection effects

    SciTech Connect

    Moradi, Afshin

    2010-04-01

    We derived simple sets of equations to describe the microwave response of the magnetized hydrogen plasma slab embedded inside carbon nanotubes, which were grown by iron-catalyzed high-pressure disproportionation. These equations, which are useful when interference effects due to multiple reflections between plasma film interfaces are small, were used to analyze the reflection, absorption, and transmission coefficients of the magnetized hydrogen plasma slab. A discussion on the effects of the continuously changing external magnetic field and hydrogen plasma parameters on the reflected power, absorbed power, and transmitted power in the system is presented.

  4. Microwave response of magnetized hydrogen plasma in carbon nanotubes: multiple reflection effects.

    PubMed

    Moradi, Afshin

    2010-04-01

    We derived simple sets of equations to describe the microwave response of the magnetized hydrogen plasma slab embedded inside carbon nanotubes, which were grown by iron-catalyzed high-pressure disproportionation. These equations, which are useful when interference effects due to multiple reflections between plasma film interfaces are small, were used to analyze the reflection, absorption, and transmission coefficients of the magnetized hydrogen plasma slab. A discussion on the effects of the continuously changing external magnetic field and hydrogen plasma parameters on the reflected power, absorbed power, and transmitted power in the system is presented.

  5. Catalytic effects of TiF3 on hydrogen spillover on Pt/carbon for hydrogen storage.

    PubMed

    Chen, Hao; Yang, Ralph T

    2010-10-05

    Recent studies have shown that using the hydrogen spillover phenomena is a promising approach for developing new materials for hydrogen storage at ambient temperature. However, the rates need to be improved. Significant catalytic effects on both spillover (i.e., adsorption) and reverse spillover (i.e., desorption) on Pt-doped carbon by TiF(3) were found. By doping 2 wt % TiF(3) on the Pt-doped Maxsorb (a superactivated carbon), both adsorption and desorption rates were significantly increased while the storage capacity decreased only slightly due to decreased surface areas. The effect of the heat treatment temperature (473 K vs 673 K) of the doped TiF(3) on its catalytic effects was also studied. XPS analyses showed that C-F bonds were formed upon heat treatment and that the amount of C-F bonds increased with the heat treatment temperature. The catalytic effects also increased with the heat treatment temperature, indicating that the catalytic mechanism possibly involved the formation of C-F bonds on the carbon edge sites. In addition, the issue of proper sample preparation of Pt/carbon was briefly addressed; missteps in metal doping and consequently poor metal dispersion will result in significantly diminished spillover enhancements (Stadie et al.).

  6. Isotope effects on chemical shifts in the study of intramolecular hydrogen bonds.

    PubMed

    Hansen, Poul Erik

    2015-01-30

    The paper deals with the use of isotope effects on chemical shifts in characterizing intramolecular hydrogen bonds. Both so-called resonance-assisted (RAHB) and non-RAHB systems are treated. The importance of RAHB will be discussed. Another very important issue is the borderline between "static" and tautomeric systems. Isotope effects on chemical shifts are particularly useful in such studies. All kinds of intramolecular hydrogen bonded systems will be treated, typical hydrogen bond donors: OH, NH, SH and NH+, typical acceptors C=O, C=N, C=S C=N-. The paper will be deal with both secondary and primary isotope effects on chemical shifts. These two types of isotope effects monitor the same hydrogen bond, but from different angles.

  7. Effects of copper catalytic reactions on the development of supersonic hydrogen flames

    SciTech Connect

    Chang, S.L.; Lottes, S.A.; Berry, G.F.

    1992-10-01

    Copper species are present in hydrogen flames in arc heated supersonic ramjet testing facilities. Homogeneous and heterogeneous copper catalytic reactions may affect the flame development by enhancing the recombination of hydrogen atoms. Computer simulation is used to investigate the effects of the catalytic reactions on the reaction and ignition times of the flames. The simulation uses a modified general chemical kinetics computer program to simulate the development of copper-contaminated hydrogen flames under scramjet testing conditions. Reaction times of hydrogen flames are found to be reduced due to the copper catalytic effects, but ignition times are much less sensitive to such effects. The reduction of reaction time depends on copper concentration, particle size (if copper is in the condensed phase), and Mach number (or initial temperature and pressure). As copper concentration increases or the particle size decreases, reaction time decreases. As Mach number increases (or pressure and temperature decrease), the copper catalytic effects are greater.

  8. Hydrogen effect on compression mechanical properties of TiNb alloys at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Losertová, M.; Štefek, O.; Schindler, I.; Szkandera, L.; Kudela, P.

    2017-02-01

    The study of this work was focused on the hydrogen effect on hot deformation behavior of hydrogen charged TiNb based alloys at three temperatures in comparison with non-charged specimens. The Ti24Nb and Ti26Nb (at.%) alloys were heat treated by three step regime in argon or hydrogen atmospheres. The hot compression tests were performed on a Gleeble 3800 machine at 800, 750 and 700°C with compression strain of 5×10-3 s-1 and deformation degree of 50 %. The microstructure resulting from heat treatment as well as from isothermal compression test was analyzed using optical and scanning electron microscopies. Measurement of microhardness revealed that higher microhardness values for Ti24Nb after thermo-hydrogen treatment corresponded to fine grained microstructure and strengthening by grain boundaries. Hydrogen contents determined using LECO RH600 analyzer showed that Ti26Nb contained higher amount of hydrogen due to the stabilization of beta phase by higher Nb concentration. Based on the hot compression test results, the plasticity at elevated temperatures was evaluated. The evolution of uniaxial compressive test curves showed the stabilization of flow stress due to the hydrogen for high deformations at lower temperatures. The differences in hot compression behavior for both niobium contents on the one hand and for hydrogen charged and non-charged specimens on the other hand were observed.

  9. Effects of Hydrogen on the Critical Conditions for Dynamic Recrystallization of Titanium Alloy During Hot Deformation

    NASA Astrophysics Data System (ADS)

    Zhao, Jingwei; Ding, Hua; Jiang, Zhengyi; Wei, Dongbin; Linghu, Kezhi

    2014-10-01

    Hot deformation tests were performed to study the flow behavior and microstructural evolution of a Ti600 titanium alloy with different hydrogen contents. The effects of hydrogen on the critical conditions for the initiation of dynamic recrystallization (DRX) were investigated. The DRX kinetics models of hydrogenated Ti600 alloy were developed, and the DRX volume fractions were quantified under different deformation conditions. The results indicate that the addition of proper hydrogen (no greater than 0.3 pct) benefits the decrease of both the critical stress and critical strain for the initiation of DRX. The critical stress and critical strain are dependent linearly on the peak stress and the strain to peak stress, respectively. The strain range from the initiation to the completion of DRX increases gradually with hydrogen in the hydrogen range of 0 to 0.3 pct, and a slightly decreased strain range is observed at the hydrogen content of 0.5 pct relative to that of 0.3 pct. The addition of large amounts of hydrogen (0.3 pct or greater) in Ti600 alloy induces incomplete DRX during hot deformation.

  10. Small chemicals with inhibitory effects on PtdIns(3,4,5)P3 binding of Btk PH domain.

    PubMed

    Yoon, Youngdae

    2014-05-15

    Phosphatidylinositol-3,4-5-triphosphates (PtdIns(3,4,5)P3) formed by phosphoinositide-3-kinase (PI3K) had been known as a signaling molecule that plays important roles in diverse cellular processes such as cell signaling, metabolism, cell differentiation, and apoptosis. PtdIns(3,4,5)P3 regulates diverse cellular processes by recruiting effector proteins to the specific cellular locations for correct functions. In this study, we reported the inhibitory effect of small chemicals on the interaction between PtdIns(3,4,5)P3-Btk PH domain. Small chemicals were synthesized based on structural similarity of PtdInsP head-groups, and tested the inhibitory effects in vitro via surface plasmon resonance (SPR). As a result, the chemical 8 showed highest inhibitory effect with 17μM of IC50 value. To elucidate diverse inhibitory effects of different small chemicals we employed in silico docking experiment using molecular modeling and simulation. The result of docking experiments showed chemical 8 has more hydrogen bonding with the residues in PtdIns(3,4,5)P3 binding site of Btk PH domain than others. Overall, our studies demonstrate the efficient approach to develop lipid binding inhibitors, and further we can use these chemicals to regulate effector proteins. In addition, our study would provide new insight that lipid binding domain may be the attractive therapeutic targets to treat severe human diseases.

  11. 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

  12. The effect of melanin on iron associated decomposition of hydrogen peroxide.

    PubMed

    Pilas, B; Sarna, T; Kalyanaraman, B; Swartz, H M

    1988-01-01

    The effects of melanin on the iron-catalyzed decomposition of hydrogen peroxide to hydroxyl radicals and hydroxyl ions have been studied using electron spin resonance, spin trapping and visible light spectrophotometry. Melanin altered these reactions by several different mechanisms and consequently, depending on conditions, can significantly increase or decrease the yield of reactive products, including hydroxyl radicals. For low concentrations of ferrous ions, melanin decreased the yield of hydroxyl radicals due to binding of ferrous ions by melanin; ferrous ions bound to melanin did not decompose H2O2 efficiently. Melanins increased the rate of hydroxyl radical production if the predominant form of iron was ferric, due to the ability of melanin to reduce ferric to ferrous iron. Hydroxyl radical production in the presence of a strong chelator (e.g. EDTA) and melanin was greater than in the presence of a weak chelator (e.g. ADP) and melanin. Melanin also increased the rate of destruction of the DMPO-OH adduct.

  13. Hydrogen bond vs. halogen bond in cation-cation complexes. The effect of the solvent.

    PubMed

    Chalanchi, Saber Mohammadi; Alkorta, Ibon; Elguero, Jose; Quiñonero, David

    2017-09-07

    In this manuscript we have explored the competition between hydrogen- (HB) and halogen-bonded (XB) 4-amonium pyridine and halogenamonium (NHnF3-nX+, n=0-3, X= F, Cl, Br and I) cation-cation complexes by means of DFT theoretical calculations. HB and XB minima structures are found for all systems in gas phase. As the number of fluorine atoms increases the HB complexes are more favored than the XB ones. Proton transfer is generally observed in the complexes with two or more halogen atoms. The XB complexes evolved from traditional ZB, to halogen shared, and to ionic complexes as the number of fluorine atoms increases. The dissociation transition states and their corresponding barriers have also been characterized, increasing as the number of fluorine atoms increases. The results when solvent effects are considered indicate that even in an apolar solvent as n-hexane most of the complexes have favorable binding energies. The ''atoms-in-molecules'' (AIM) theory was used to analyze the complexes, obtaining good correlations between electron density and total electron energy density () values with the intermolecular bond distance. According to the  values obtained, the covalency of these interactions would start manifesting at distances around 72%-74% the sum of the van der Waals radii of the interacting atoms. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Kinetic solvent effects on hydrogen abstraction reactions from carbon by the cumyloxyl radical. The role of hydrogen bonding.

    PubMed

    Bietti, Massimo; Salamone, Michela

    2010-08-20

    A kinetic study of the H-atom abstraction reactions from 1,4-cyclohexadiene and triethylamine by the cumyloxyl radical has been carried out in different solvents. Negligible effects are observed with 1,4-cyclohexadiene, whereas with triethylamine a significant decrease in rate constant (k(H)) is observed on going from benzene to MeOH. A good correlation between log k(H) and the solvent hydrogen bond donor parameter alpha is observed, indicative of an H-bonding interaction between the amine lone pair and the solvent.

  15. Effects of hydrogen and rf power on the structural and electrical properties of rf sputtered hydrogenated amorphous silicon carbide films

    NASA Astrophysics Data System (ADS)

    Choi, W. K.; Loo, F. L.; Loh, F. C.; Tan, K. L.

    1996-08-01

    The effects of the rf power (100 to 600 W) and the hydrogen partial pressure (PH=0.15 to 0.6 Pa.) on the deposition rate and the structural and electrical properties of rf sputtered hydrogenated amorphous silicon carbide (a-Si1-xCx:H) films were investigated. The films were deposited in an argon plus hydrogen ambient. The deposition rate increased with increasing rf power, but decreased with increasing PH. The refractive index increases from 1.85-3.6 as the rf power increases from 100-600 W and from 2.8 to 3.5 as PH increases from 0.15-0.6 Pa. The optical gap increases from 1.5 to 2.15 eV as PH increases from 0.15-0.6 Pa, but decreases from 2.8-1.38 eV as the rf power increases from 100-600 W. The Si-C bond gave the most prominent absorption peak in the infrared spectra, and increased with increasing rf power but not affected by changes in PH. The Si-H bonds increases from 3.06×1021 to 1.64×1022 cm-3 as PH was increased from 0.15-0.6 Pa. The optical gap increases from 1.5-2.15 eV and the conductivity reduces from 7.3×10-9 to 1.9×10-11 Ω-1 cm-1 accordingly. No C-Hn stretching mode was detected in all the films and this was attributed to the low carbon content of the films. We conclude that rf sputtering technique is not effective in varying the carbon content in a-Si1-xCx:H films.

  16. Hydrogen effects on low-cycle fatigue of the single-crystal nickel-base superalloy CMSX-2

    NASA Technical Reports Server (NTRS)

    Dollar, M.; Bernstein, I. M.; Kromp, W.; Domnanovitch, A.; Pinczolits, H.

    1991-01-01

    The effects of hydrogen on the low-cycle fatigue behavior of CMSX-2 (001)-oriented single crystals were examined. Fatigue tests were conducted under constant plastic strain amplitude control. Cyclic stress-strain curves and fatigue life data at different plastic strain amplitudes were determined for hydrogen-free and hydrogen-charged specimens. Two charging procedures, leading to different hydrogen concentrations, were applied. Hydrogen was found to decrease significantly the number of cycles to failure under the various experimental conditions. The increasing hydrogen concentration and ratio of the hydrogen to nonhydrogen-containing volume were found to shorten fatigue life in hydrogen-charged specimens. Based on the analysis of cyclic stress-strain curves and optical and transmission electron microscopy, it was established that hydrogen enhanced strain localization and promoted crystallographic stage I cracking, leading to embrittlement.

  17. CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Spectrum and Binding Energy of an Off-Center Hydrogenic Donor in a Spherical Quantum Dot

    NASA Astrophysics Data System (ADS)

    Yuan, Jian-Hui; Huang, Jin-Sheng; Yin, Miao; Zeng, Qi-Jun; Zhang, Jun-Pei

    2010-08-01

    Off-center impurity effects in a spherical quantum dot are theoretically studied by degenerate perturbation method in strong confinement. The energy levels and binding energies are computed for the typical GaAs material as function of the donor position. The numerical results show the quantum size effect. We note that the energy levels and binding energies are not only related to the position of donor and the strength of confinement, but also related to the fold of degenerate states. We can see obviously that gaps will appear among the degenerate states and the splitting of energy levels and binding energies will appear as the position of the impurity is shifted away off the center.

  18. An actin-binding protein, LlLIM1, mediates calcium and hydrogen regulation of actin dynamics in pollen tubes.

    PubMed

    Wang, Huei-Jing; Wan, Ai-Ru; Jauh, Guang-Yuh

    2008-08-01

    Actin microfilaments are crucial for polar cell tip growth, and their configurations and dynamics are regulated by the actions of various actin-binding proteins (ABPs). We explored the function of a lily (Lilium longiflorum) pollen-enriched LIM domain-containing protein, LlLIM1, in regulating the actin dynamics in elongating pollen tube. Cytological and biochemical assays verified LlLIM1 functioning as an ABP, promoting filamentous actin (F-actin) bundle assembly and protecting F-actin against latrunculin B-mediated depolymerization. Overexpressed LlLIM1 significantly disturbed pollen tube growth and morphology, with multiple tubes protruding from one pollen grain and coaggregation of FM4-64-labeled vesicles and Golgi apparatuses at the subapex of the tube tip. Moderate expression of LlLIM1 induced an oscillatory formation of asterisk-shaped F-actin aggregates that oscillated with growth period but in different phases at the subapical region. These results suggest that the formation of LlLIM1-mediated overstabilized F-actin bundles interfered with endomembrane trafficking to result in growth retardation. Cosedimentation assays revealed that the binding affinity of LlLIM1 to F-actin was simultaneously regulated by both pH and Ca(2+): LlLIM1 showed a preference for F-actin binding under low pH and low Ca(2+) concentration. The potential functions of LlLIM1 as an ABP sensitive to pH and calcium in integrating endomembrane trafficking, oscillatory pH, and calcium circumstances to regulate tip-focused pollen tube growth are discussed.

  19. 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.

  20. Arrhenius curves of hydrogen transfers: tunnel effects, isotope effects and effects of pre-equilibria

    PubMed Central

    Limbach, Hans-Heinrich; Miguel Lopez, Juan; Kohen, Amnon

    2006-01-01

    In this paper, the Arrhenius curves of selected hydrogen-transfer reactions for which kinetic data are available in a large temperature range are reviewed. The curves are discussed in terms of the one-dimensional Bell–Limbach tunnelling model. The main parameters of this model are the barrier heights of the isotopic reactions, barrier width of the H-reaction, tunnelling masses, pre-exponential factor and minimum energy for tunnelling to occur. The model allows one to compare different reactions in a simple way and prepare the kinetic data for more-dimensional treatments. The first type of reactions is concerned with reactions where the geometries of the reacting molecules are well established and the kinetic data of the isotopic reactions are available in a large temperature range. Here, it is possible to study the relation between kinetic isotope effects (KIEs) and chemical structure. Examples are the tautomerism of porphyrin, the porphyrin anion and related compounds exhibiting intramolecular hydrogen bonds of medium strength. We observe pre-exponential factors of the order of kT/h≅1013 s−1 corresponding to vanishing activation entropies in terms of transition state theory. This result is important for the second type of reactions discussed in this paper, referring mostly to liquid solutions. Here, the reacting molecular configurations may be involved in equilibria with non- or less-reactive forms. Several cases are discussed, where the less-reactive forms dominate at low or at high temperature, leading to unusual Arrhenius curves. These cases include examples from small molecule solution chemistry like the base-catalysed intramolecular H-transfer in diaryltriazene, 2-(2′-hydroxyphenyl)-benzoxazole, 2-hydroxy-phenoxyl radicals, as well as in the case of an enzymatic system, thermophilic alcohol dehydrogenase. In the latter case, temperature-dependent KIEs are interpreted in terms of a transition between two regimes with different temperature

  1. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2004-06-01

    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.

  3. Hydrogen effect on remaining life of hydroprocessing reactors

    SciTech Connect

    Iwadate, T.; Nomura, T.; Watanabe, J.

    1988-02-01

    Old vintage 2.25Cr-1Mo steels used for high-temperature/pressure hydroprocessing reactors have a high potential for temper embrittlement. The cracks caused by hydrogen embrittlement (HE) have been experienced in a stainless steel overlay and base metal of hydroprocessing reactors. In this paper, the temper embrittlement behavior during long-term service is discussed using the results of isothermal temper embrittlement tests up to 30,000 h of exposure. HE susceptibility of base metals, i.e., the threshold stress intensity factor K/sub IH/ and hydrogen-assisted crack growth rate behavior are also discussed. Based on the experimental data obtained, the remaining life assessment of a 2.25Cr-1Mo steel hydroprocessing reactor is analyzed from knowledge of HE.

  4. 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.

  5. Enthalpy and entropy effects in hydrogen adsorption on carbon nanotubes.

    PubMed

    Efremenko, Irena; Sheintuch, Moshe

    2005-07-05

    Interaction energies and entropies associated with hydrogen adsorption on the inner and outer surfaces of zigzag single-wall carbon nanotubes (SWCNT) of various diameters are analyzed by means of molecular mechanics, density functional theory, and ab initio calculations. For a single molecule the strongest interaction, which is 3.5 greater than that with the planar graphite sheet, is found inside a (8,0) nanotube. Adsorption on the outer surfaces is weaker than that on graphite. Due to the steric considerations, both processes are accompanied by an extremely strong decline in entropy. Absence of specific adsorption sites and weak attractive interaction between hydrogen molecules within carbon nanotubes results in their close packing at low temperatures. Using the calculated geometric and thermodynamic parameters in Langmuir isotherms we predict the adsorption capacity of SWCNTs at room temperature to be smaller than 1 wt % even at 100 bar.

  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. Inelastic neutron scattering study of binding of para-hydrogen in an ultra-microporous metal-organic framework

    NASA Astrophysics Data System (ADS)

    Yang, Sihai; Ramirez-Cuesta, Anibal J.; Schröder, Martin

    2014-01-01

    Metal-organic framework (MOF) materials show promise for H2 storage and it is widely predicted by computational modelling that MOFs incorporating ultra-micropores are optimal for H2 binding due to enhanced overlapping potentials. We report the investigation using inelastic neutron scattering of the interaction of H2 in an ultra-microporous MOF material showing low H2 uptake capacity. The study has revealed that adsorbed H2 at 5 K has a liquid recoil motion along the channel with very little interaction with the MOF host, consistent with the observed low uptake. The low H2 uptake is not due to incomplete activation or decomposition as the desolvated MOF shows CO2 uptake with a measured pore volume close to that of the single crystal pore volume. This study represents a unique example of surprisingly low H2 uptake within a MOF material, and complements the wide range of studies on systems showing higher uptake capacities and binding interactions.

  8. 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.

  9. Co-operative inhibitory effects of hydrogen peroxide and iodine against bacterial and yeast species

    PubMed Central

    2013-01-01

    Background Hydrogen peroxide and iodine are powerful antimicrobials widely used as antiseptics and disinfectants. Their antimicrobial properties are known to be enhanced by combining them with other compounds. We studied co-operative inhibitory activities (synergism, additive effects and modes of growth inhibition) of hydrogen peroxide and iodine used concurrently against 3 bacterial and 16 yeast species. Results Synergistic or additive inhibitory effects were shown for hydrogen peroxide and iodine mixtures against all 19 species used in the study. Both biocides were mostly cidal individually and in mixtures against Pseudomonas aeruginosa and Staphylococcus aureus. Both compounds manifested static inhibitory effects individually, but their mixtures were synergistically cidal for Saccharomyces cerevisiae and Escherihia coli. Cells of S. cerevisiae treated with hydrogen peroxide and iodine-hydrogen peroxide mixture produced increased numbers of respiratory deficient mutants indicating genotoxic effects. Conclusion Iodine and hydrogen peroxide used concurrently interact synergistically or additively against a range of prokaryotic and eukaryotic microorganisms. The study provides an insight as to how these traditional antimicrobials could be used more effectively for disinfection and antisepsis. In addition, a simple approach is proposed for scoring genotoxicity of different biocides by using the budding yeast system. PMID:23856115

  10. Co-operative inhibitory effects of hydrogen peroxide and iodine against bacterial and yeast species.

    PubMed

    Zubko, Elena I; Zubko, Mikhajlo K

    2013-07-15

    Hydrogen peroxide and iodine are powerful antimicrobials widely used as antiseptics and disinfectants. Their antimicrobial properties are known to be enhanced by combining them with other compounds. We studied co-operative inhibitory activities (synergism, additive effects and modes of growth inhibition) of hydrogen peroxide and iodine used concurrently against 3 bacterial and 16 yeast species. Synergistic or additive inhibitory effects were shown for hydrogen peroxide and iodine mixtures against all 19 species used in the study. Both biocides were mostly cidal individually and in mixtures against Pseudomonas aeruginosa and Staphylococcus aureus. Both compounds manifested static inhibitory effects individually, but their mixtures were synergistically cidal for Saccharomyces cerevisiae and Escherihia coli. Cells of S. cerevisiae treated with hydrogen peroxide and iodine-hydrogen peroxide mixture produced increased numbers of respiratory deficient mutants indicating genotoxic effects. Iodine and hydrogen peroxide used concurrently interact synergistically or additively against a range of prokaryotic and eukaryotic microorganisms. The study provides an insight as to how these traditional antimicrobials could be used more effectively for disinfection and antisepsis. In addition, a simple approach is proposed for scoring genotoxicity of different biocides by using the budding yeast system.

  11. A molecular dynamics study of nuclear quantum effect on diffusivity of hydrogen molecule

    NASA Astrophysics Data System (ADS)

    Nagashima, H.; Tsuda, S.; Tsuboi, N.; Hayashi, A. K.; Tokumasu, T.

    2017-07-01

    In this paper, the nuclear quantum effect of the hydrogen molecule on its diffusivity was analyzed using the molecular dynamics (MD) method. The centroid MD (CMD) method was applied to reproduce the time evolution of the molecules. The diffusion coefficient of hydrogen was calculated using the Green-Kubo method over a wide temperature region, and the temperature dependence of the quantum effect of the hydrogen molecule on its diffusivity was addressed. The calculated results were compared with classical MD results based on the principle of corresponding state (PCS). It was confirmed that the difference in the diffusion coefficient calculated in the CMD and classical MD methods was small, and the PCS appears to be satisfied on the temperature dependence of the diffusion coefficient, even though the quantum effect of the hydrogen molecules was taken into account. It was clarified that this result did not suggest that the quantum effect on the diffusivity of the hydrogen molecule was small but that the two changes in the intermolecular interaction of hydrogen due to the quantum effect offset each other. Moreover, it was found that this tendency was related to the temperature dependence of the ratio of the kinetic energy of the quantum fluctuational motion to the classical kinetic energy.

  12. Biofunctional peptides from milk proteins: mineral binding and cytomodulatory effects.

    PubMed

    Meisel, H; FitzGerald, R J

    2003-01-01

    The protein fraction of milk contains many valuable components and biologically active substances. Moreover, milk proteins are precursors of many different biologically active peptides which are inactive within the sequence of the precursor protein but can be released by enzymatic proteolysis. Many milk protein-derived peptides, such as caseinophosphopeptides, reveal multi-functional bioactivities. Caseinophosphopeptides can form soluble organophosphate salts and may function as carriers for different minerals, especially calcium. Furthermore, they have been shown to exert cytomodulatory effects. Cytomodulatory peptides inhibit cancer cell growth or they stimulate the activity of immunocompetent cells and neonatal intestinal cells, respectively. Several bioactive peptides derived from milk proteins are potential modulators of various regulatory processes in the body and thus may exert beneficial physiological effects. Caseinophosphopeptides are already produced on an industrial-scale and as a consequence these peptides have been considered for application as ingredients in both 'functional foods' and pharmaceutical preparations. Although the physiological significance as exogenous regulatory substances is not yet fully understood, both mineral binding and cytomodulatory peptides derived from bovine milk proteins are claimed to be health enhancing components that can be used to reduce the risk of disease or to enhance a certain physiological function.

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

    NASA Astrophysics Data System (ADS)

    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 1H NMR, 13C NMR, IR and X-ray single-crystal diffraction. The carboxylic acid group forms classic Osbnd H ⋯ O hydrogen bonded dimers in a centrosymmetric R22(8) ring motifs for BAA-Br and BAA-Cl. However, no carboxylic acid group forms classic Osbnd H ⋯ 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 0.5-3.8 kcal/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 4 kcal/mol.

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

    PubMed

    Sen, Ibrahim; Kara, Hulya; Azizoglu, Akın

    2016-10-05

    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.

  15. Effects of helium and hydrogen on radiation-induced microstructural changes in austenitic stainless steel

    NASA Astrophysics Data System (ADS)

    Jin, Hyung-Ha; Ko, Eunsol; Lim, Sangyeop; Kwon, Junhyun

    2015-09-01

    Microstructural changes in austenitic stainless steel by helium, hydrogen, and iron ion irradiation were investigated with transmission electron microscopy. Typical radiation-induced changes, such as the formation of Frank loops in the matrix and radiation-induced segregation (RIS) or depletion at grain boundaries, were observed after ion irradiation. The helium ion irradiation led to the formation of cavities both at grain boundaries and in the matrix, as well as the development of smaller Frank loops. The hydrogen ion irradiation generated stronger RIS behavior at the grain boundaries compared to irradiation with helium and iron ions. The effects of helium and hydrogen on radiation-induced microstructural changes were discussed.

  16. The self limiting effect of hydrogen cluster in gas jet under liquid nitrogen temperature

    SciTech Connect

    Han Jifeng; Yang Chaowen; Miao Jingwei; Fu Pengtao; Luo Xiaobing; Shi Miangong

    2010-09-15

    The generation of hydrogen clusters in gas jet is tested using the Rayleigh scattering method under liquid nitrogen temperature of 79 K. The self limiting effect of hydrogen cluster is studied and it is found that the cluster formation is greatly affected by the number of expanded molecules. The well designed liquid nitrogen cold trap ensured that the hydrogen cluster would keep maximum size for maximum 15 ms during one gas jet. The scattered light intensity exhibits a power scaling on the backing pressure ranging from 5 to 48 bar with the power value of 4.1.

  17. Hydrogen therapy may be an effective and specific novel treatment for acute radiation syndrome.

    PubMed

    Liu, Cong; Cui, Jianguo; Sun, Quan; Cai, Jianming

    2010-01-01

    Hydrogen is the most abundant chemical element in the universe, however, it is seldom regarded as a therapeutic gas. Recent studies show that inhaled hydrogen gas (H(2)) has antioxidant and antiapoptotic activities that protect the brain against ischemia-reperfusion injury and stroke by selectively reducing hydroxyl and peroxynitrite radicals. It is also well known that more than a half of the ionizing radiation-induced cellular damage is caused by hydroxyl radicals. Studies have show that reducing hydroxyl radicals can significantly improve the protection of cells from radiation damage. In like manner, we hypothesize that hydrogen therapy may be an effective, specific and unique treatment for acute radiation syndrome.

  18. Effect of transition-metal additives on hydrogen desorption kinetics of MgH2

    NASA Astrophysics Data System (ADS)

    Roy, Anindya; Janotti, Anderson; Van de Walle, Chris G.

    2013-01-01

    Using first-principles calculations, we study the effect of transition-metal additives (Ti, Fe, Co, and Ni) on the rate of hydrogen desorption in MgH2. The presence of large concentrations of transition-metal impurities causes the Fermi level to shift according to the position of the transition-metal acceptor/donor levels in the band gap. This shift can lower the formation energy of native defects and increase their concentration. The resulting higher rates of hydrogen desorption enhance the prospect of MgH2 as a solid-state hydrogen-storage material.

  19. Substitution effects on the hydrogen storage behavior of AB2 alloys by first principles

    NASA Astrophysics Data System (ADS)

    Li, Fen; Zhao, Ji-jun; Sun, Li-xian

    2011-06-01

    The hydrogen storage behavior of the TiCr2 and ZrCr2 alloys substituted with the third components (Zr, V, Fe, Ni) have been studied using first-principles calculations. The change of the hydrogen absorption energies caused by metal doping is arising from the charge transfer among the doped alloys interior. Zr and V atoms devoted abundant electrons, leading to a great enhancement of the H absorption energy, while Fe and Ni atoms always accepted electrons, yielding a remarkable decrease of the H absorption energy. The hydrogen diffusion energy barrier is closely correlated with the geometry effect rather than the electronic structure.

  20. Hydrogen Embrittlement

    NASA Technical Reports Server (NTRS)

    Woods, Stephen; Lee, Jonathan A.

    2016-01-01

    Hydrogen embrittlement (HE) is a process resulting in a decrease in the fracture toughness or ductility of a metal due to the presence of atomic hydrogen. In addition to pure hydrogen gas as a direct source for the absorption of atomic hydrogen, the damaging effect can manifest itself from other hydrogen-containing gas species such as hydrogen sulfide (H2S), hydrogen chloride (HCl), and hydrogen bromide (HBr) environments. It has been known that H2S environment may result in a much more severe condition of embrittlement than pure hydrogen gas (H2) for certain types of alloys at similar conditions of stress and gas pressure. The reduction of fracture loads can occur at levels well below the yield strength of the material. Hydrogen embrittlement is usually manifest in terms of singular sharp cracks, in contrast to the extensive branching observed for stress corrosion cracking. The initial crack openings and the local deformation associated with crack propagation may be so small that they are difficult to detect except in special nondestructive examinations. Cracks due to HE can grow rapidly with little macroscopic evidence of mechanical deformation in materials that are normally quite ductile. This Technical Memorandum presents a comprehensive review of experimental data for the effects of gaseous Hydrogen Environment Embrittlement (HEE) for several types of metallic materials. Common material screening methods are used to rate the hydrogen degradation of mechanical properties that occur while the material is under an applied stress and exposed to gaseous hydrogen as compared to air or helium, under slow strain rates (SSR) testing. Due to the simplicity and accelerated nature of these tests, the results expressed in terms of HEE index are not intended to necessarily represent true hydrogen service environment for long-term exposure, but rather to provide a practical approach for material screening, which is a useful concept to qualitatively evaluate the severity of

  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. Binding Energies, Effective Masses and Screenings Effects of Fröhlich Bipolarons

    NASA Astrophysics Data System (ADS)

    Cataudella, V.; Iadonisi, G.; Ninno, D.

    1991-01-01

    The bipolaron ground state binding energy and the effective masses are calculated self-consistently in a scheme where the electron-phonon interaction is described by the Fröhlich interaction. We explicitly use the total linear momentum conservation and both two-and three-dimensional systems are considered. We review results for binding energies and show that the bipolaron effective mass increases with the electron-phonon coupling constant α more rapidly than two free polaron masses. As expected, the increase is greater in two than in three dimensions. We estimate the screening effects due to an electronic or hole density n in a range of values such that nR2b ll 1 (here Rb is the bipolaron radius). We find that the bipolaron binding energy decreases with n and eventually becomes positive indicating the existence of a metastable bipolaron state. Finally we discuss the possible connections between our results and high Tc superconductivity.

  3. Effect of metal Additions on the Hydrogen Uptake of Microporous Carbon at Near-Ambient Temperature

    SciTech Connect

    Contescu, Cristian I; Gallego, Nidia C; Bhat, Vinay V

    2010-01-01

    Enhancing the hydrogen sorption capacity of microporous carbon materials at near-ambient temperature continue to be a challenge and the subject of intense research. Physisorption alone on microporous carbons is not strong enough to provide the desired levels of hydrogen uptake. Modifying carbons with small amounts of metals has been proven effective to increase the amounts adsorbed. However, very different mechanisms may be involved when the promoters are transition metals or alkali metals. In this presentation we compare the effect of additions of palladium and/or alkali metals on the hydrogen uptake of microporous carbons, in an attempt to differentiate between the possible mechanisms leading to enhanced hydrogen capacity and fast kinetics.

  4. Effects of hydrogen isotope in coupling between confinement, wall material and SoL turbulence

    NASA Astrophysics Data System (ADS)

    Itoh, K.; Itoh, S.-I.; Sasaki, M.; Kosuga, Y.

    2017-05-01

    The hydrogen isotope effect on confinement is discussed by investigating the coupling between confinement, wall material and scrape-off-layer (SoL) turbulence. An emphasis is placed upon the dependence of the neutral density on the hydrogen mass number. The momentum loss via CX process in the barrier is studied, and its influence on the radial electric field in the barrier (so as to modify the suppression of transport) is discussed. The penetration of slow neutrals and the reflection of fast neutrals on the wall are considered. Combining these processes, the influence of hydrogen mass number on the atomic, molecular, material and plasma interactions is investigated. The penetration of strong fluctuations in the SoL plasma into the confined plasma via the fuelling of neutral particles (i.e. fuelling fuels turbulence) is also discussed. The hydrogen isotope effect on this source of edge turbulence, which can affect the core-confinement, is discussed.

  5. The effect of hydrogen on the low cycle fatigue behavior of a single crystal superalloy

    NASA Technical Reports Server (NTRS)

    Gayda, J.; Gabb, T. P.; Dreshfield, R. L.

    1990-01-01

    The present study compares the room temperature fatigue properties of PWA 1480 single crystals containing either normal or elevated hydrogen levels, giving attention to the effects of various levels of HIPing process-controlled porosity on hydrogen-trapping and fatigue life. Hydrogen charging is found to degrade the fatigue lives of alloy samples by an order of magnitude; the magnitude of this degradation is comparable at both high and low porosity. HIPing accomplished a small beneficial effect on the fatigue life of both the hydrogen-charged and uncharged PWA 1480 samples. Fatigue cracks are noted to have consistently initiated at large, near-surface pores. By reducing the size and frquency of the larger pores, HIPing apparently retarded fatigue-crack initiation.

  6. 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.

  7. Stereoselectivity of the hydrogen-atom transfer in benzophenone-tyrosine dyads: an intramolecular kinetic solvent effect.

    PubMed

    Hörner, Gerald; Hug, Gordon L; Lewandowska, Anna; Kazmierczak, Franciszek; Marciniak, Bronislaw

    2009-01-01

    To be or not to be solvated is the decisive parameter that controls the photoinduced hydrogen-atom transfer in diastereomeric ketone/phenol dyads. A kinetic solvent effect that refers to hydrogen bonding between the phenol and the solvent is suggested to be the main source of the stereoselective discrimination in the hydrogen transfer (see figure).

  8. Effect of Al(OH)3 on the hydrogen generation of aluminum-water system

    NASA Astrophysics Data System (ADS)

    Teng, Hsin-Te; Lee, To-Ying; Chen, Yu-Kuang; Wang, Hong-Wen; Cao, Guozhong

    2012-12-01

    Many metal oxides effectively modify metallic aluminum (Al) powders to produce hydrogen in neutral water at room temperature. In this study, hydrogen is generated even more rapidly from the reacted solution when the by-product Al(OH)3 (bayerite) is present. The influence of Al(OH)3 on the hydrogen generation during the aluminum/water reaction is highly dependent on the surface area and the crystallinity of Al(OH)3. High surface area and poor crystallinity of Al(OH)3 render the system a rapid hydrogen generation rate. The self-catalytic phenomenon can be explained by the formation of AlO(OH) (boehmite) from the reaction of by-product β-Al(OH)3 and the surface passive oxide layer Al2O3. Furthermore, by taking advantage of the exothermic heat from the Al/water reaction, hydrogen yield is able to reach 70% within 30 min in a common aqueous solution (pH < 10) containing fine Al(OH)3. This hydrogen generation technology relies on common, nontoxic, noncorrosive additives and is therefore a very promising system for creating a use-on-demand hydrogen source.

  9. Effect of Water on the Structure and Stability of Hydrogen-Bonded Oxalic Acid Dimer.

    PubMed

    Hu, Yuan-Chun; Zhang, Xiu-Hui; Li, Quan-Song; Zhang, Yun-Hong; Li, Ze-Sheng

    2017-10-06

    As the simplest and the most abundant dicarboxylic acids in the atmosphere, oxalic acid (OA) not only plays a key role in aerosol nucleation, but also acts as a prototypical compound for the investigation of intra- and intermolecular hydrogen bonding interactions. In this work, a systematic theoretical study on the hydrated OA dimers were carried out using density functional theory (DFT) at the M06-2X/6-311++G(3df, 2p) level. The properties of the hydrogen bonds in clusters were inspected through topological analysis using atoms in molecules (AIM) theory. The most stable OA dimer involves a cyclic structure with two intermolecular hydrogen bonds. Our calculations show that one H2O has slightly effect on the hydrogen bonds, while two water molecules weaken and three water molecules even break the two intermolecular hydrogen bonds between OAs. Furthermore, there are no hydrogen bond interactions between OAs in almost all stable clusters when the H2O number increases to four and five. Additionally, the ionization and the isomerization of OA through water-assisted proton transfer phenomena were observed in tetrahydrates and pentahydrates. Our work has provided new insights into the conversion process of anhydrous OA to hydrated clusters, which are helpful for further understanding the atmospheric nucleation process and the nature of hydrogen bond. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Numerical estimation of ultrasonic production of hydrogen: Effect of ideal and real gas based models.

    PubMed

    Kerboua, Kaouther; Hamdaoui, Oualid

    2018-01-01

    Based on two different assumptions regarding the equation describing the state of the gases within an acoustic cavitation bubble, this paper studies the sonochemical production of hydrogen, through two numerical models treating the evolution of a chemical mechanism within a single bubble saturated with oxygen during an oscillation cycle in water. The first approach is built on an ideal gas model, while the second one is founded on Van der Waals equation, and the main objective was to analyze the effect of the considered state equation on the ultrasonic hydrogen production retrieved by simulation under various operating conditions. The obtained results show that even when the second approach gives higher values of temperature, pressure and total free radicals production, yield of hydrogen does not follow the same trend. When comparing the results released by both models regarding hydrogen production, it was noticed that the ratio of the molar amount of hydrogen is frequency and acoustic amplitude dependent. The use of Van der Waals equation leads to higher quantities of hydrogen under low acoustic amplitude and high frequencies, while employing ideal gas law based model gains the upper hand regarding hydrogen production at low frequencies and high acoustic amplitudes. Copyright © 2017 Elsevier B.V. All rights reserved.

  11. 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

  12. 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

  13. 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.

  14. 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.

  15. Effect of pH on the Structure and DNA Binding of the FOXP2 Forkhead Domain.

    PubMed

    Blane, Ashleigh; Fanucchi, Sylvia

    2015-06-30

    Forkhead box P2 (FOXP2) is a transcription factor expressed in cardiovascular, intestinal, and neural tissues during embryonic development and is implicated in language development. FOXP2 like other FOX proteins contains a DNA binding domain known as the forkhead domain (FHD). The FHD interacts with DNA by inserting helix 3 into the major groove. One of these DNA-protein interactions is a direct hydrogen bond that is formed with His554. FOXP2 is localized in the nuclear compartment that has a pH of 7.5. Histidine contains an imidazole side chain in which the amino group typically has a pKa of ~6.5. It seems possible that pH fluctuations around 6.5 may result in changes in the protonation state of His554 and thus the ability of the FOXP2 FHD to bind DNA. To investigate the effect of pH on the FHD, both the structure and the binding affinity were studied in the pH range of 5-9. This was done in the presence and absence of DNA. The structure was assessed using size exclusion chromatography, far-UV circular dichroism, and intrinsic and extrinsic fluorescence. The results indicated that while pH did not affect the secondary structure in the presence or absence of DNA, the tertiary structure was pH sensitive and the protein was less compact at low pH. Furthermore, the presence of DNA caused the protein to become more compact at low pH and also had the potential to increase the dimerization propensity. Fluorescence anisotropy was used to investigate the effect of pH on the FOXP2 FHD DNA binding affinity. It was found that pH had a direct effect on binding affinity. This was attributed to the altered hydrogen bonding patterns upon protonation or deprotonation of His554. These results could implicate pH as a means of regulating transcription by the FOXP2 FHD, which may also have repercussions for the behavior of this protein in cancer cells.

  16. Effects of phenytoin on [3H]diazepam binding in dissociated primary cortical cell culture.

    PubMed

    Gallager, D W; Mallorga, P; Swaiman, K F; Neale, E A; Nelson, P G

    1981-08-10

    The effects of chronic exposure of primary dissociated cerebral cortical cells in culture to the anticonvulsant drug phenytoin have been investigated using benzodiazepine binding techniques. By separating benzodiazepine binding into pharmacologically distinct subtypes, the data indicate that clonazepam-displaceable benzodiazepine binding (associated primarily with neuronal membranes) is significantly decreased by exposure to therapeutic and toxic doses of phenytoin while R05-4864-displaceable benzodiazepine binding (associated principally with non-neuronal elements) is enhanced. The ratio of clonazepam-displaceable to R05-4864-displaceable benzodiazepine binding appears to be the most sensitive indicator for these changes.

  17. Effects of edge hydrogenation on structural stability, electronic, and magnetic properties of WS2 nanoribbons

    NASA Astrophysics Data System (ADS)

    Ouyang, Fangping; Ni, Xiang; Yang, Zhixiong; Chen, Yu; Zheng, Xiaojuan; Xiong, Xiang

    2013-12-01

    Using density functional theory based first-principles, we have investigated the structural stability, electronic, and magnetic properties of tungsten disulfide nanoribbons (WS2NRs). When the edges are bare, Zigzag-edge WS2 nanoribbons (ZWS2NRs) and Armchair-edge WS2 nanoribbons (AWS2NRs) are ferromagnetic metal and nonmagnetic semiconductor, respectively. After edge hydrogenation, WS2NRs exhibit different structural stabilities and electronic structures according the patterns of edge hydrogenation. Hydrogenated ZWS2NRs keep ferromagnetic and metallic while AWS2NRs convert from nonmagnetic to magnetic when at least one edge is partially hydrogenated. The transition of AWS2NRs is contributed to the unpaired valence electrons. With the change of nanoribbon width n, magnetic moment of edge fully hydrogenated ZWS2NRs shows nearly periodical variation, the band gap of bare AWS2NRs oscillates like three distinct families and owing to the ever-present edge effect it converges to 0.5 eV as n increases. Compared with bare AWS2NRs, edge fully hydrogenated AWS2NRs have the same scaling rule of band-gap variation when n ≤12, while the band gap oscillates up and down when n > 12 because of the more obvious edge asymmetric effect than quantum confinement effect. These findings are essential for applications of WS2NRs in nanoelectronics and spintronics.

  18. Effect of hydrogen on cathodic corrosion of titanium aluminide

    SciTech Connect

    Gao, K.W.; Jin, J.W.; Qiao, L.J.; Chu, W.Y.; Hsiao, C.M.

    1996-01-01

    Cathodic corrosion of titanium aluminide (TiAl) during hydrogen charging in various acidic aqueous solutions and in molten salt at 160 C was studied. At constant potential, the rate of cathodic corrosion (V) was much higher than during anodic dissolution, and V increased linearly with increasing current. V was 10 times higher in the acid solution than in the salt solution under the same current. Disruption of the surface film by local hydride formation during cathodic polarization was shown to be the key step.

  19. Effect of acceptor heteroatoms on π-hydrogen bonding interactions: A study of indoleṡṡṡthiophene heterodimer in a supersonic jet

    NASA Astrophysics Data System (ADS)

    Kumar, Sumit; Das, Aloke

    2012-09-01

    Resonant two photon ionization (R2PI), IR-UV, and UV-UV double resonance spectroscopic techniques combined with quantum chemistry calculations have been used to determine the structure of indoleṡṡṡthiophene dimer observed in a supersonic jet. With the help of combined experimental and theoretical IR spectra it has been found that the observed dimer has a N-Hṡṡṡπ hydrogen bonded slanted T-shaped structure. The present study demonstrates the effect of heteroatoms present in the acceptors on the strength of the π-hydrogen bonding interactions. It was concluded by Sherrill and co-workers from their theoretical study of benzeneṡṡṡpyridine dimer that aromatic rings containing heteroatoms are poorest π-hydrogen bond acceptors [E. G. Hohenstein and C. D. Sherrill, J. Phys. Chem. A 113, 878 (2009), 10.1021/jp809062x]. But the current spectroscopic investigation exhibits that five membered aromatic heterocycles are favorable π-hydrogen bond acceptors. In this study, it has also been shown that thiophene is a better π-hydrogen bond acceptor than furan. The present work has immense biological significance as indole is the chromophore of tryptophan residue in the proteins and thiophene derivatives have potential therapeutic applications. Thus, understanding the binding motif between indole and thiophene in the heterodimer studied in this work may help in designing efficient drugs.

  20. Effect of acceptor heteroatoms on π-hydrogen bonding interactions: a study of indole···thiophene heterodimer in a supersonic jet.

    PubMed

    Kumar, Sumit; Das, Aloke

    2012-09-07

    Resonant two photon ionization (R2PI), IR-UV, and UV-UV double resonance spectroscopic techniques combined with quantum chemistry calculations have been used to determine the structure of indole···thiophene dimer observed in a supersonic jet. With the help of combined experimental and theoretical IR spectra it has been found that the observed dimer has a N-H···π hydrogen bonded slanted T-shaped structure. The present study demonstrates the effect of heteroatoms present in the acceptors on the strength of the π-hydrogen bonding interactions. It was concluded by Sherrill and co-workers from their theoretical study of benzene···pyridine dimer that aromatic rings containing heteroatoms are poorest π-hydrogen bond acceptors [E. G. Hohenstein and C. D. Sherrill, J. Phys. Chem. A 113, 878 (2009)]. But the current spectroscopic investigation exhibits that five membered aromatic heterocycles are favorable π-hydrogen bond acceptors. In this study, it has also been shown that thiophene is a better π-hydrogen bond acceptor than furan. The present work has immense biological significance as indole is the chromophore of tryptophan residue in the proteins and thiophene derivatives have potential therapeutic applications. Thus, understanding the binding motif between indole and thiophene in the heterodimer studied in this work may help in designing efficient drugs.

  1. 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

  2. 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.

  3. 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.

  4. The effect of hydrogen on the fracture of alloy x-750

    NASA Astrophysics Data System (ADS)

    Symons, Douglas M.; Thompson, Anthony W.

    1996-01-01

    The effect of hydrogen on the fracture of a nickel-base superalloy, alloy X-750, was investigated in the HTH condition. The effect of hydrogen was examined through tensile testing incorporating observations from scanning electron microscopy and light microscopy. The ductility at 25 °C, as measured by elongation to failure for tensile specimens, was reduced from 21 pct for noncharged specimens to 7.3 pct for 5.7 ppm hydrogen and to 3.5 pct for 65 ppm hydrogen. The elongation to failure was a function of the strain rate and test temperature. For hydrogen-charged specimens, the elongation decreased as the strain rate decreased at a constant temperature, while for a constant strain rate and varying temperature, there was a maximum in embrittlement near 25 °C and no embrittlement at -196 °C. For the noncharged specimens, the elongation monotonically increased as temperature increased, while there was no noticeable effect of strain rate. Prestraining prior to charging dramatically decreased elongation after hydrogen charging. When the strain rate was increased on the prestrained specimens, more plastic deformation was observed prior to failure. Failure did not occur until the flow stress was reached, supporting the proposition that plasticity is required for failure. The intergranular failure mechanism in alloy X-750 was a microvoid initiation process at grain boundary carbides followed by void growth and coalescence. The void initiation strain, as determined from tensile data and from sectioning unfractured specimens, was observed to be much lower in the hydrogen-charged specimens as compared to noncharged specimens. The reduced ductility may be explained by either a reduction of the interfacial strength of the carbide-matrix interface or a local hydrogen pressure at the carbide-matrix interface.

  5. Chelate effects in sulfate binding by amide/urea-based ligands.

    PubMed

    Jia, Chuandong; Wang, Qi-Qiang; Begum, Rowshan Ara; Day, Victor W; Bowman-James, Kristin

    2015-07-07

    The influence of chelate and mini-chelate effects on sulfate binding was explored for six amide-, amide/amine-, urea-, and urea/amine-based ligands. Two of the urea-based hosts were selective for SO4(2-) in water-mixed DMSO-d6 systems. Results indicated that the mini-chelate effect provided by a single urea group with two NH binding sites appears to provide enhanced binding over two amide groups. Furthermore, additional urea binding sites incorporated into the host framework appeared to overcome to some extent competing hydration effects with increasing water content.

  6. Actions of Ethanol on Voltage-Sensitive Sodium Channels: Effects on Neurotoxin Binding

    DTIC Science & Technology

    1987-01-01

    Exprnmantal Trherpeutics Ped in I.SA. Actions of Ethanol on Voltage-Sensitive Sodium Channels: Effects on Neurotoxin Binding1 MICHAEL J. MULLIN 2 and... sodium channels. This indirect allosteric mechanism for inhibition of [H]BTX-B binding. effect orethanol was concentration-dependent and was affected...ethanol increased the equilibrium binding constant without af- that ethanol can affect the voltage-sensitive sodium channels in fecting the apparent

  7. The effect of structural and energetic parameters of MOFs and COFs towards the improvement of their hydrogen storage properties

    NASA Astrophysics Data System (ADS)

    Tylianakis, Emmanuel; Klontzas, Emmanouel; Froudakis, George E.

    2009-05-01

    Open-framework materials have been proposed as potential materials for hydrogen storage. Metal-organic framework (MOF) and covalent-organic framework (COF) materials are under extensive study to discover their storage abilities. In particular the IRMOF family of materials have been considered as ideal to study the effect of different factors that affect the hydrogen storage capacity. In this paper, we analyse the effect of different factors such as surface area, pore volume and the interaction of hydrogen with the molecular framework on the hydrogen uptake of such materials. Through this analysis we propose guidelines to enhance hydrogen storage capacity of already synthesized materials and recommend advanced materials for this application.

  8. The effect of structural and energetic parameters of MOFs and COFs towards the improvement of their hydrogen storage properties.

    PubMed

    Tylianakis, Emmanuel; Klontzas, Emmanouel; Froudakis, George E

    2009-05-20

    Open-framework materials have been proposed as potential materials for hydrogen storage. Metal-organic framework (MOF) and covalent-organic framework (COF) materials are under extensive study to discover their storage abilities. In particular the IRMOF family of materials have been considered as ideal to study the effect of different factors that affect the hydrogen storage capacity. In this paper, we analyse the effect of different factors such as surface area, pore volume and the interaction of hydrogen with the molecular framework on the hydrogen uptake of such materials. Through this analysis we propose guidelines to enhance hydrogen storage capacity of already synthesized materials and recommend advanced materials for this application.

  9. Effects of hydrogen on acceptor activation in ternary nitride semiconductors

    DOE PAGES

    Fioretti, Angela N.; Stokes, Adam; Young, Matthew R.; ...

    2017-02-09

    Doping control is necessary to unlock the scientific and technological potential of many materials, including ternary II-IV-nitride semiconductors, which are closely related to binary GaN. In particular, ZnSnN2 has been reported to have degenerate doping density, despite bandgap energies that are well suited for solar energy conversion. Here, we show that annealing Zn-rich Zn1+xSn1-xN2 grown with added hydrogen reduces its free electron density by orders of magnitude, down to 4 x 1016 cm-3. This experimental observation can be explained by hydrogen passivation of acceptors in Zn1+xSn1-xN2 during growth, lowering the driving force for unintentional donor formation. Lastly, these results indicatemore » that the doping control principles used in GaN can be translated to ZnSnN2, suggesting that other strategies used in binary III-Vs can be applied to accelerate the technological development of ternary II-IV-N2 materials.« less

  10. 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.

  11. Pressure and size effects in endohedrally confined hydrogen clusters.

    PubMed

    Soullard, Jacques; Santamaria, Ruben; Jellinek, Julius

    2008-02-14

    Density functional theory is used to carry out a systematic study of zero-temperature structural and energy properties of endohedrally confined hydrogen clusters as a function of pressure and the cluster size. At low pressures, the most stable structural forms of (H(2))(n) possess rotational symmetry that changes from C(4) through C(5) to C(6) as the cluster grows in size from n=8 through n=12 to n=15. The equilibrium configurational energy of the clusters increases with an increase of the pressure. The rate of this increase, however, as gauged on the per atom basis is different for different clusters sizes. As a consequence, the size dependencies of the configurational energies per atom at different fixed values of pressure are nonmonotonic functions. At high pressures, the molecular (H(2))(n) clusters gradually become atomic or dominantly atomic. The pressure-induced changes in the HOMO-LUMO gap of the clusters indicate a finite-size analog of the pressure-driven metallization of the bulk hydrogen. The ionization potentials of the clusters decrease with the increase of pressure on them.

  12. 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.

  13. 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.

  14. Enhancement Effect of Lithium-Doping Functionalization on Hydrogen Adsorption in Metal-Organic Framework

    NASA Astrophysics Data System (ADS)

    Xia, Liangzhi; Liu, Qing; Wang, Fengling; Li, Yupeng

    Grand canonical Monte-Carlo simulation was carried out to study the effect of linker functionalization by Li atoms. In this work, two new Li-doping structures, MOF-808-Li and MOF-808-OLi were theoretically constructed by physical modification and chemical modification, respectively. The results show that both these methods can improve the hydrogen storage performance significantly, owing to the Li atoms increasing the interaction energy between the hydrogen molecules and the Li-doped MOF-808. Furthermore, MOF-808-OLi shows higher hydrogen capacity in comparison to the H2 adsorption in the MOF-808-Li, this can be attributed to the new adsorption sites created by oxygen atom. The gravimetric adsorption capacity of MOF-808-OLi can reach 3.17wt.% at 77K and 1bar, which are significantly higher than the hydrogen adsorption in the unmodified MOF-808.

  15. 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.

  16. 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.

  17. 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.

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

    DOE PAGES

    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

  19. Design of effective zeolite catalysts for the complete hydrogenation of CO2.

    PubMed

    Chan, Bun; Radom, Leo

    2006-04-26

    Ab initio molecular orbital calculations have been applied to the study of the three-stage zeolite-catalyzed hydrogenation of CO2 to methanol. The results present strong evidence that appropriate chemical modifications to ZSM-5 can lead to significantly lower energy barriers for the three component reactions, that is, hydrogenation of CO2, HCO2H, and CH2O. Zeolites incorporating either Na+ or Ge are more effective catalysts than conventional acidic zeolites for the hydrogenation of CO2 to give HCO2H, but amine-based zeolites do not lead to significantly lower barriers for any of the three hydrogenation reactions. However, we predict that when all three features, namely, Na+, N, and Ge, are incorporated in the zeolite, there is a dramatic improvement in catalytic activity for all three reactions.

  20. Effect of hydrogen peroxide treatment on the properties of wool fabric

    NASA Astrophysics Data System (ADS)

    Wang, Xin; Shen, Xiaolin; Xu, Weilin

    2012-10-01

    In this study, hydrogen peroxide treatment was applied to improve the surface wettability, moisture transfer properties and other related properties of wool fabric. SEM images showed the tip of wool scale was smoothened and parts of the scale were peeled off after hydrogen peroxide treatment. The time for a water droplet to sink into the fabric could decrease to less than 1 s and the wicking properties of wool fabrics were dramatically improved after hydrogen peroxide treatment. Shrinkage and whiteness of the fabric were improved due to the modification of scale and the bleaching effect of hydrogen peroxide, respectively. The fabrics became weaker and ductile with less than 4% weight loss. This study would benefit further application of wool fiber in summer clothing in which the surface wettability and moisture transfer properties are essential and determinative.

  1. 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.

  2. 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.

  3. 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. © 2013 Japanese Society of Animal Science.

  4. Modeling of hydrogen effect on the superelastic behavior of Ni-Ti shape memory alloy wires

    NASA Astrophysics Data System (ADS)

    Lachiguer, Amani; Bouby, Céline; Gamaoun, Fehmi; Bouraoui, Tarak; Ben Zineb, Tarak

    2016-11-01

    Superelastic NiTi wires are widely used in orthodontic treatments, but sometimes fracture can be observed after few months of use in buccal cavity and attributed to the degradation of NiTi mechanical properties due to hydrogen absorption. In this paper, a modeling approach is proposed in order to describe the effect of hydrogen diffusion on the transformation properties of NiTi SMAs. In order to experimentally predict such effects, cathodic hydrogen charging was performed at a current density of 10 A/{m}2 for 6h, 24h, 48h and 72h in 0.9% NaCl aqueous solution at room temperature. Tensile tests were carried out shortly after hydrogen charging. The obtained stress-strain curves showed an increase of yield transformation stresses for forward and reverse martensitic transformations and a decrease of maximum transformation strain. Using Fick’s second law, the transformation temperatures variation can be expressed as a function of the mean concentration of absorbed hydrogen and then taked into account in the SMA constitutive model developed by Chemisky et al (2011). The numerical results are compared to the experimental ones to calibrate the proposed method. Simulations showed that hydrogen diffusion induces a shifting of transfomation temperatures, a decreasing of maximum transformation strain and an increasing of yield transfomation stresses.

  5. Hydrogen Storage Properties of Rigid Three-Dimensional Hofmann Clathrate Derivatives: The Effects of Pore Size

    SciTech Connect

    Culp, Jeffery T.; Natesakhawat, Sittichai; Smith, Milton R.; Bittner, Edward; Matranga, Christopher; Bockrath, Bradley

    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.

  6. The Effect of Teflon Emulsion on Hydrogen Electrode Properties and Performance in Nickel-Hydrogen Cells

    DTIC Science & Technology

    2008-01-30

    include area code) UNCLASSIFIED UNCLASSIFIED UNCLASSIFIED (310)336-2141 Standard Form 296 (Rev. 8-98) P. e=c bed by ANSi Sd. 23S.18 The Effect of...Recrystallization of Pt particles over life - Lowers reactivity and catalyst surface area - Oxidation and dissolution of platinum - Carbon dioxide poisoning...Materials Parameters of Interest - Conductivity - Surface Area - Pore size distribution - Density - KOH retention - Gas permeability - Cracking

  7. Effect of FGF-binding Protein 3 on Vascular Permeability*

    PubMed Central

    Zhang, Wentao; Chen, Yifan; Swift, Matthew R.; Tassi, Elena; Stylianou, Dora C.; Gibby, Krissa A.; Riegel, Anna T.; Wellstein, Anton

    2008-01-01

    Fibroblast growth factor-binding protein 1 (FGF-BP1 is BP1) is involved in the regulation of embryonic development, tumor growth, and angiogenesis by mobilizing endogenous FGFs from their extracellular matrix storage. Here we describe a new member of the FGF-BP family, human BP3. We show that the hBP3 protein is secreted from cells, binds to FGF2 in vitro and in intact cells, and inhibits FGF2 binding to heparin. To determine the function of hBP3 in vivo, hBP3 was transiently expressed in chicken embryos and resulted in >50% lethality within 24 h because of vascular leakage. The onset of vascular permeability was monitored by recording the extravasation kinetics of FITC-labeled 40-kDa dextran microperfused into the vitelline vein of 3-day-old embryos. Vascular permeability increased as early as 8 h after expression of hBP3. The increased vascular permeability caused by hBP3 was prevented by treatment of embryos with PD173074, a selective FGFR kinase inhibitor. Interestingly, a C-terminal 66-amino acid fragment (C66) of hBP3, which contains the predicted FGF binding domain, still inhibited binding of FGF2 to heparin similar to full-length hBP3. However, expression of the C66 fragment did not increase vascular permeability on its own, but required the administration of exogenous FGF2 protein. We conclude that the FGF binding domain and the heparin binding domain are necessary for the hBP3 interaction with endogenous FGF and the activation of FGFR signaling in vivo. PMID:18669637

  8. Effect of halide and acid additives on the direct synthesis of hydrogen peroxide using supported gold-palladium catalysts.

    PubMed

    Ntainjua N, Edwin; Piccinini, Marco; Pritchard, James C; Edwards, Jennifer K; Carley, Albert F; Moulijn, Jacob A; Hutchings, Graham J

    2009-01-01

    The effect of halide and acid addition on the direct synthesis of hydrogen peroxide is studied for magnesium oxide- and carbon-supported bimetallic gold-palladium catalysts. The addition of acids decreases the hydrogenation/decomposition of hydrogen peroxide, and the effect is particularly pronounced for the magnesium oxide-supported catalysts whilst for carbon-supported catalysts the pH requires close control to optimize hydrogen peroxide synthesis. The addition of bromide leads to a marked decrease in the hydrogenation/decomposition of hydrogen peroxide with either catalyst. These effects are discussed in terms of the structure of the gold-palladium alloy nanoparticles and the isoelectric point of the support. We conclude that with the highly active carbon-supported gold-palladium catalysts these additives are not required and that therefore this system presents the potential for the direct synthesis of hydrogen peroxide to be operated using green process technology.

  9. Bleaching effect of activation of hydrogen peroxide using photon-initiated photoacoustic streaming technique.

    PubMed

    Arslan, Hakan; Akcay, Merve; Yasa, Bilal; Hatirli, Huseyin; Saygili, Gökhan

    2015-03-01

    This study aims to investigate the bleaching effectiveness of photon-initiated photoacoustic streaming (PIPS) using 35 % hydrogen peroxide on discolored teeth as compared with different devital bleaching techniques. Fifty extracted human mandibular incisors were collected and artificially stained using sheep's blood. The teeth were then randomly divided into five groups according to the different bleaching procedures to be tested: walking bleach with sodium perborate and with 35 % hydrogen peroxide gel, both for 1 week; PIPS using 35 % hydrogen peroxide liquid for 30 min; and just 35 % hydrogen peroxide, as a liquid and as a gel (again, for 30 min). Spectrophotometric measurements were obtained on the buccal surfaces of the crowns, at the beginning, just after the bleaching procedures had been performed, and the following first, third, and seventh days. The ∆E values were calculated, and the data were analyzed with a two-way analysis of variance (P = 0.05). There were statistically significant differences between the PIPS technique using 35 % hydrogen peroxide liquid and the 35 % hydrogen peroxide liquid and gel without PIPS immediately after the procedures (P < 0.05). On Days 1, 3, and 7, the PIPS technique further bleached specimens more than all of the other techniques (P < 0.05). The PIPS technique using 35 % hydrogen peroxide was found to be more effective than all of the conventional techniques. Within limitations of this study, PIPS technique using hydrogen peroxide was superior to the conventional techniques. Further studies should be conducted to determine if the PIPS technique results in any complications, particularly cervical resorption.

  10. Hydrogen abstraction from cyclic amines by the cumyloxyl and benzyloxyl radicals. The role of stereoelectronic effects and of substrate/radical hydrogen bonding.

    PubMed

    Salamone, Michela; Martella, Roberto; Bietti, Massimo

    2012-10-05

    A kinetic study on the hydrogen abstraction reactions from cyclic amines and diamines (pyrrolidines, piperidines, morpholines, and piperazines) by the cumyloxyl (CumO(•)) and benzyloxyl (BnO(•)) radicals was carried out. The reactions with CumO(•) were described in all cases as direct hydrogen abstractions. The differences in the hydrogen abstraction rate constant (k(H)) were explained in terms of the different number of abstractable hydrogen atoms, the operation of stereoelectronic effects, and, with the morpholines, on the basis of polar effects. Significantly higher k(H) values were measured for the reactions of the amines with BnO(•). This behavior was explained on the basis of a mechanism that proceeds through the rate-determining formation of a hydrogen bonded pre-reaction complex between the radical α-C-H and the nitrogen lone pair followed by hydrogen abstraction within the complex. A decrease in k(H) was observed going from secondary to tertiary amines and, with tertiary amines, on increasing steric hindrance at nitrogen, pointing toward the important role of steric and electronic effects on pre-reaction complex formation. These results expand previous findings contributing to a detailed mechanistic description of the reactions of alkoxyl radicals with amines, showing that structural effects in both the substrate and the radical can play a dramatic role and providing new information on the role of substrate/radical interactions on these processes.

  11. Analysis of Agonist and Antagonist Effects on Thyroid Hormone Receptor Conformation by Hydrogen/Deuterium Exchange

    PubMed Central

    Figueira, A. C. M.; Saidemberg, D. M.; Souza, P. C. T.; Martínez, L.; Scanlan, T. S.; Baxter, J. D.; Skaf, M. S.; Palma, M. S.; Webb, P.; Polikarpov, I.

    2011-01-01

    Thyroid hormone receptors (TRs) are ligand-gated transcription factors with critical roles in development and metabolism. Although x-ray structures of TR ligand-binding domains (LBDs) with agonists are available, comparable structures without ligand (apo-TR) or with antagonists are not. It remains important to understand apo-LBD conformation and the way that it rearranges with ligands to develop better TR pharmaceuticals. In this study, we conducted hydrogen/deuterium exchange on TR LBDs with or without agonist (T3) or antagonist (NH3). Both ligands reduce deuterium incorporation into LBD amide hydrogens, implying tighter overall folding of the domain. As predicted, mass spectroscopic analysis of individual proteolytic peptides after hydrogen/deuterium exchange reveals that ligand increases the degree of solvent protection of regions close to the buried ligand-binding pocket. However, there is also extensive ligand protection of other regions, including the dimer surface at H10–H11, providing evidence for allosteric communication between the ligand-binding pocket and distant interaction surfaces. Surprisingly, C-terminal activation helix H12, which is known to alter position with ligand, remains relatively protected from solvent in all conditions suggesting that it is packed against the LBD irrespective of the presence or type of ligand. T3, but not NH3, increases accessibility of the upper part of H3–H5 to solvent, and we propose that TR H12 interacts with this region in apo-TR and that this interaction is blocked by T3 but not NH3. We present data from site-directed mutagenesis experiments and molecular dynamics simulations that lend support to this structural model of apo-TR and its ligand-dependent conformational changes. PMID:21106879

  12. Visual feature binding in younger and older adults: encoding and suffix interference effects.

    PubMed

    Brown, Louise A; Niven, Elaine H; Logie, Robert H; Rhodes, Stephen; Allen, Richard J

    2017-02-01

    Three experiments investigated younger (18-25 yrs) and older (70-88 yrs) adults' temporary memory for colour-shape combinations (binding). We focused upon estimating the magnitude of the binding cost for each age group across encoding time (Experiment 1; 900/1500 ms), presentation format (Experiment 2; simultaneous/sequential), and interference (Experiment 3; control/suffix) conditions. In Experiment 1, encoding time did not differentially influence binding in the two age groups. In Experiment 2, younger adults exhibited poorer binding performance with sequential relative to simultaneous presentation, and serial position analyses highlighted a particular age-related difficulty remembering the middle item of a series (for all memory conditions). Experiments 1-3 demonstrated small to medium binding effect sizes in older adults across all encoding conditions, with binding less accurate than shape memory. However, younger adults also displayed negative effects of binding (small to large) in two of the experiments. Even when older adults exhibited a greater suffix interference effect in Experiment 3, this was for all memory types, not just binding. We therefore conclude that there is no consistent evidence for a visual binding deficit in healthy older adults. This relative preservation contrasts with the specific and substantial deficits in visual feature binding found in several recent studies of Alzheimer's disease.

  13. 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.

  14. The effect of water displacement on binding thermodynamics: concanavalin A.

    PubMed

    Li, Zheng; Lazaridis, Themis

    2005-01-13

    Interactions at the binding interface of biomolecular complexes are often mediated by ordered water molecules. In this work, we considered two concanavalin A-carbohydrate complexes. In the first, a water molecule is buried at the binding interface. In the second, this water molecule is displaced by a modification of the ligand (Clarke, C.; Woods, R. J.; Gluska, J.; Cooper, A.; Nutley, M. A.; Boons, G. J. J. Am. Chem. Soc. 2001, 123, 12238-12247). We computed the contribution of this water molecule to the thermodynamic properties using statistical mechanical formulas for the energy and entropy and molecular dynamics simulations. Other contributions to the binding affinity, including desolvation, entropy of conformational restriction, and interaction between the ligand and protein, were also computed. The thermodynamic consequences of displacement of the ordered water molecule by ligand modification were in qualitative agreement with experimental data. The free energy contribution of the water molecule (-17.2 kcal/mol; -19.2 enthalpic and +2 entropic) was nearly equivalent to the additional protein-ligand interactions in trimannoside 2 (-18.9 kcal/mol). The two structural ions interact more strongly with the water than with the hydroxyl of trimannoside 2, thus favoring trimannoside 1. The contributions from desolvation and conformational entropy are much smaller but significant, compared to the binding free energy difference. The picture that emerges is that the final outcome of water displacement is sensitive to the details of the binding site and cannot be predicted by simple empirical rules.

  15. 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.

  16. Excitonic Effects and the Optical Absorption Spectrum of Hydrogenated Si Clusters

    SciTech Connect

    Rohlfing, M.; Louie, S.G. |

    1998-04-01

    We calculate the optical absorption spectrum of hydrogen-terminated silicon clusters by solving the Bethe-Salpeter equation for the two-particle Green{close_quote}s function using an {ital ab initio} approach. The one-particle Green{close_quote}s function and the electron-hole interaction kernel are calculated within the GW approximation for the electron self-energy operator. Very large exciton binding energies are observed. Our results for the one-particle properties and the optical absorption spectra of the clusters are in very good agreement with available experimental data. {copyright} {ital 1998} {ital The American Physical Society}

  17. 43 CFR 1810.3 - Effect of laches; authority to bind government.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 43 Public Lands: Interior 2 2014-10-01 2014-10-01 false Effect of laches; authority to bind... GUIDANCE General Rules § 1810.3 Effect of laches; authority to bind government. (a) The authority of the... agents when they enter into an arrangement or agreement to do or cause to be done what the law does...

  18. 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.

  19. Dietary fiber effects on passage rate and breath hydrogen.

    PubMed

    Hanson, C F; Winterfeldt, E A

    1985-07-01

    Fermentation of fiber and passage to the large intestine were monitored by measuring hydrogen gas (H2) concentration in expired breath. Five subjects consumed meals containing no added fiber or 40 g of wheat bran (WB), corn bran (CB), oat bran (OB), or citrus flour (CF) replacing white flour. Breath samples were obtained at 30 min intervals for 9 h after the test meals. Mean H2 concentration (ppm), averaged over the 9 h test period, ranged from 7.5 (CB) to 12.0 (OB) and tended to increase with addition of OB, CF, or WB but decrease with addition of CB. Hours from the meal to the highest H2 peaks were 4.7 (WB), 5.6 (CB), 6.2 (OB), 6.4 (CF), and 8.2 (basal). The gel-like fibers (OB and CF) resulted in greater H2 concentration and less acceleration of passage rate than the particulate fibers (WB and CB).

  20. Effect of metal adatoms on hydrogen adsorption properties of phosphorene

    NASA Astrophysics Data System (ADS)

    Yu, Zhiyuan; Lei, Shuangying; Wan, Neng; Luan, Shan; Shen, Haiyun; Yu, Hong

    2017-04-01

    Based on first-principles density functional theory, we have investigated hydrogen storage on metal adatoms decorated phosphorene. Almost all metals including alkali, alkaline, 3d, 4d and 5d transition metals (TM) as well as post-TMs are considered to decorate phosphorene, and most metals exhibit an enhancement of H2 adsorption energy (E a), except for Zn, Cd, Hg, and all post-TMs. Nine metals show ideal Ea within the energy window 0.2-0.6 eV/H2 for practical application purposes. Among them, Li, Sc, Ti, Y, Zr, and La exhibit superior adsorption abilities of 3-5 H2 per adatom. Based on local density of states and Barder analyses, underlying mechanisms of interaction between phosphorene, metal, and H2 are also discussed.

  1. On the effect of nuclear motion on chemical binding

    NASA Astrophysics Data System (ADS)

    Dohnert, A.

    1985-05-01

    The surfaces defined by Berlin (1951) to characterize the role of intramolecular forces in chemical binding are obtained analytically for the case in which the atomic nuclei are in motion. The generalized equation for the force function is derived from the hypervirial theorem rather than by the method of coordinate scaling as reported by Garcia-Sucre et al. (1984). Numerical results for the lowest vibrational level of the ground state of the H2 molecule are presented in a graph, and the inclusion of nuclear motion is shown to reduce the volume of the spatial 'binding region' and hence to localize the bond and reduce the degree of binding (relative to the fixed-nucleus model).

  2. Effect of mutational alteration of Asn-128 in the putative GTP-binding domain of tetracycline resistance determinant Tet(O) from Campylobacter jejuni.

    PubMed Central

    Grewal, J; Manavathu, E K; Taylor, D E

    1993-01-01

    The deduced amino acid sequence of Campylobacter jejuni Tet(O), cloned in Escherichia coli, has shown that it contains the five highly conserved sequences of the GTP-binding domain found in other GTPases. Asn-128 belongs to the G4 motif of such a domain and is involved in hydrogen bonding with the guanine ring of the nucleotide. Substitution of Asn-128 by 11 other amino acids resulted in a decrease in tetracycline resistance, indicating that tetracycline resistance conferred by Tet(O) is related to GTP binding. The effect of the mutations on the GTP-binding domain is discussed with the EF-Tu-GDP complex as a model. PMID:8109930

  3. Synergistic effect of microwave heating and hydrogen peroxide on inactivation of microorganisms.

    PubMed

    Kuchma, T

    1998-01-01

    Escherichia coli K-12 isogenous strains and Pseudomonas aeruginosa 102 were used to study the synergistic effects of combined microwave heating at short-time processing with low concentrations of hydrogen peroxide. The effect of microwave heating to temperatures of 40, 50 and 60 degrees C, as well as the concentration of hydrogen peroxide (0.05, 0.08 and 0.1%), the sequence of the agents' use, the nature of microorganisms on the survival of cells, DNA damages and interaction factors were studied. A method of anomalous viscosity time dependencies (AVTD) was used for measurement of the changes of genome conformational state (GCS) simultaneously with bacterial survival determination. The synergistic effect of microwave heating and low concentrations of hydrogen peroxide was observed under combined application, and reached a maximum when the cells were exposed to microwave heating to 50 degrees C and 0.08% hydrogen peroxide simultaneously. Both maxima of cell destruction and DNA injuries have been achieved by successive exposure to (MW + 10 min H2O2) to 60 degrees C and 0.08% hydrogen peroxide. The mechanisms of synergistic effects, the role of a disturbance of DNA repair and the interaction of sublethal injuries caused by different agents are discussed.

  4. 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.

  5. 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.

  6. Radiation Effects in Hydrogen-Laden Porous Water Ice Films: Implications for Interstellar Ices

    NASA Astrophysics Data System (ADS)

    Raut, Ujjwal; Baragiola, Raul; Mitchell, Emma; Shi, Jianming

    H _{2} is the dominant gas in the dense clouds of the interstellar medium (ISM). At densities of 10 (5) cm (-3) , an H _{2} molecule arrives at the surface of a 0.1 mum-sized, ice-covered dust grain once every few seconds [1]. At 10 K, H _{2} can diffuse into the pores of the ice mantle and adsorb at high-energy binding sites, loading the ice with hydrogen over the lifetime of the cloud. These icy grains are also impacted by galactic cosmic rays and stellar winds (in clouds with embedded protostar). Based on the available cosmic proton flux spectrum [2], we estimate a small impact rate of nearly 1 hit per year on a 0.1 μm sized grain, or 10 (-7) times the impact frequency of the neutral H _{2}. The energy deposited by such impacts can release the adsorbed H _{2} into the gas phase (impact desorption or sputtering). Recently, we have reported on a new process of ion-induced enhanced adsorption, where molecules from the gas phase are incorporated into the film when irradiation is performed in the presence of ambient gas [3]. The interplay between ion-induced ejection and adsorption can be important in determining the gas-solid balance in the ISM. To understand the effects of cosmic rays/stellar winds impacts on interstellar ice immersed in H _{2} gas, we have performed irradiation of porous amorphous ice films loaded with H _{2} through co-deposition or adsorption following growth. The irradiations were performed with 100 keV H (+) using fluxes of 10 (10) -10 (12) H (+) cm (-2) s (-1) at 7 K, in presence of ambient H _{2} at pressures ranging from 10 (-5) to 10 (-8) Torr. Our initial results show a net loss in adsorbed H _{2} during irradiation, from competing ion-induced ejection and adsorption. The H _{2} loss per ion decreases exponentially with fluence, with a cross-section of 10 (-13) cm (2) . In addition to hydrogen removal, irradiation also leads to trapping of H _{2} in the ice film, from closing of the pores during irradiation [4]. As a result, 2.6 percent

  7. 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.

  8. 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.

  9. [Effect of nitrogen-containing compounds on hydrogen light emission and nitrogen fixation by purple bacteria].

    PubMed

    Kondrat'eva, E N; Gogotov, I N; Gruzinskiĭ, I V

    1979-01-01

    The cells of Rhodospirillum rubrum and Thiocapsa roseopersicina grown in media containing glutamate and arginine, respectively, as well as under conditions of nitrogen fixation evolve H2 in the light. If the cultures were grown in media with NH4+, NO3-, urea, glutamine or asparagine, hydrogen photoevolution by the cells and acetylene reduction started after the lag-phase and proceeded at a low rate. Extracts of such cells did not display the activity of nitrogenase which could be assayed by the ATP-dependent evolution of H2 from dithionite. The data obtained confirm the fact that hydrogen photoevolution by purple bacteria involves nitrogenase whose synthesis is regulated (according to the action of glutamine) with the participation of glutamine synthetase. NH4+, glutamine and asparagine inhibit also hydrogen photoproduction by purple bacteria and acetylene photoreduction. However, they have no effect on hydrogen evolution in the dark by the cells of R. rubrum and T. roseopersicina in the presence of formiate or pyruvate, respectively, whereas carbon monoxide inhibits hydrogen production. Therefore, hydrogen production by purple bacteria in the dark must be catalyzed by hydrogenase.

  10. Critical assessment of hydrogen effects on the slip transmission across grain boundaries in α-Fe

    PubMed Central

    Adlakha, I.; Solanki, K. N.

    2016-01-01

    Grain boundaries (GBs) play a fundamental role in the strengthening mechanism of crystalline structures by acting as an impediment to dislocation motion. However, the presence of an aggressive environment such as hydrogen increases the susceptibility to intergranular fracture. Further, there is a lack of systematic investigations exploring the role of hydrogen on the dislocation–grain-boundary (DGB) interactions. Thus, in this work, the effect of hydrogen on the interactions between a screw dislocation and 〈111〉 tilt GBs in α-Fe were examined. Our simulations reveal that the outcome of the DGB interaction strongly depends on the underlying GB dislocation network. Further, there exists a strong correlation between the GB energy and the energy barrier for slip transmission. In other words, GBs with lower interfacial energy demonstrate a higher barrier for slip transmission. The introduction of hydrogen along the GB causes the energy barrier for slip transmission to increase consistently for all of the GBs examined. The energy balance for a crack initiation in the presence of hydrogen was examined with the help of our observations and previous findings. It was found that the presence of hydrogen increases the strain energy stored within the GB which could lead to a transgranular-to-intergranular fracture mode transition. PMID:26997895

  11. Critical assessment of hydrogen effects on the slip transmission across grain boundaries in α -Fe.

    PubMed

    Adlakha, I; Solanki, K N

    2016-01-01

    Grain boundaries (GBs) play a fundamental role in the strengthening mechanism of crystalline structures by acting as an impediment to dislocation motion. However, the presence of an aggressive environment such as hydrogen increases the susceptibility to intergranular fracture. Further, there is a lack of systematic investigations exploring the role of hydrogen on the dislocation-grain-boundary (DGB) interactions. Thus, in this work, the effect of hydrogen on the interactions between a screw dislocation and 〈111〉 tilt GBs in α-Fe were examined. Our simulations reveal that the outcome of the DGB interaction strongly depends on the underlying GB dislocation network. Further, there exists a strong correlation between the GB energy and the energy barrier for slip transmission. In other words, GBs with lower interfacial energy demonstrate a higher barrier for slip transmission. The introduction of hydrogen along the GB causes the energy barrier for slip transmission to increase consistently for all of the GBs examined. The energy balance for a crack initiation in the presence of hydrogen was examined with the help of our observations and previous findings. It was found that the presence of hydrogen increases the strain energy stored within the GB which could lead to a transgranular-to-intergranular fracture mode transition.

  12. Effects of Hydrogen-Rich Saline on Taurocholate-Induced Acute Pancreatitis in Rat

    PubMed Central

    Zhang, De-qing; Feng, Huang; Chen, Wei-chang

    2013-01-01

    Oxidative stress plays an important role in the pathogenesis of acute pancreatitis (AP). As an ideal exterminator of poisonous free radicals, hydrogen can clearly reduce the degree of oxidative damage caused by severe acute pancreatitis (SAP) and lessen the presence of inflammatory cytokines. The aim of this study was to investigate the effects and mechanism of hydrogen-rich saline on SAP in rats. Serum TNF-α, IL-6, and IL-18 and histopathological score in the pancreas were reduced after hydrogen-rich saline treatment. Malondialdehyde (MDA) and myeloperoxidase (MPO) contents were obviously reduced, while superoxide dismutase (SOD) and glutathione (GSH) contents were increased after hydrogen-rich saline treatment. The expression of mRNA of tumor necrosis factor-α (TNF-α) and intercellular adhesion molecule-1 (ICAM-1) in the pancreas was reduced in hydrogen-rich saline treated group. In conclusion, intravenous hydrogen-rich saline injections could attenuate the severity of AP, probably via inhibiting the oxidative stress and reducing the presence of inflammatory mediators. PMID:23983797

  13. 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.

  14. Effect of expanded graphite lattice in exfoliated graphite nanofibers on hydrogen storage.

    PubMed

    Lueking, Angela D; Pan, Ling; Narayanan, Deepa L; Clifford, Caroline E B

    2005-07-07

    A graphite exfoliation technique, using intercalation of a concentrated sulfuric/nitric acid mixture followed by a thermal shock, has successfully exfoliated a herringbone graphite nanofiber (GNF). The exfoliated GNF retains the overall nanosized dimensions of the original GNF, with the exfoliation temperature determining the degree of induced defects, lattice expansion, and resulting microstructure. High-resolution transmission electron microscopy indicated that the fibers treated at an intermediate temperature of 700 degrees C for 2 min had dislocations in the graphitic structure and a 4% increase in graphitic lattice spacing to 3.5 A. The fibers treated at 1000 degrees C for 36 h were expanded along the fiber axis, with regular intervals of graphitic and amorphous regions ranging from 0.5 to >50 nm in width. The surface area of the starting material was increased from 47 m(2)/g to 67 m(2)/g for the 700- degrees C treatment and to 555 m(2)/g for the 1000- degrees C treatment. Hydrogen uptake measurements at 20 bar indicate that the overall hydrogen uptake and operative adsorption temperature are sensitive to the structural variations and graphitic spacing. The increased surface area after the 1000- degrees C treatment led to a 1.2% hydrogen uptake at 77 K and 20 bar, a 3-fold increase in hydrogen physisorption of the starting material. The uptake of the 700- degrees C-treated material had a 0.29% uptake at 300 K and 20 bar; although low, this was a 14-fold uptake over the starting material and higher than other commonly used pretreatment methods that were tested in parallel. These results suggest that selective exfoliation of a nanofiber is a means by which to control the relative binding energy of the hydrogen interaction with the carbon structure and thus vary the operative adsorption temperature.

  15. 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.

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

    PubMed

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

    2015-08-01

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

  18. Immobilized algal cells used for hydrogen production

    SciTech Connect

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

    2007-10-01

    This paper explores the use of the photosynthetic green alga Chlamydomonas reinhardtii bound to solid support particles to produce hydrogen in a two-step cycle. Bound cells are more easily cycled between growth mode and hydrogen production mode. The data indicate that the presence of silica particles does not inhibit the growth of the algae in the sulfur rich growth media. Filtration experiments reveal that the algae effectively bind to the silica particles, as high removal efficiencies are observed. The silica particles appear to approach saturation algae at a mass-loading ratio of about 0.035. In hydrogen production mode, the bound algae perform about as well as free-floating algae in terms of cumulative hydrogen production. A full-factorial experiment is described in which algae concentration was deemed to have a significant effect on cumulative hydrogen production.

  19. Inhibitory effects of enterococci on the production of hydrogen sulfide by hydrogen sulfide-producing bacteria in raw meat.

    PubMed

    Liu, X; Gong, C; Jiang, X

    2011-07-01

    Applying competitive exclusion micro-organisms to control hydrogen sulfide (H₂S) gas produced by hydrogen sulfide-producing bacteria (SPB) in chicken meat. Five SPB strains, isolated from animal by-products, were used for screening lactic acid bacteria (LAB) that can inhibit the production of H₂S by SPB in trypticase soy broth supplemented with L-cysteine (TSB-L-cys). A sensitive and accurate test strip method was developed for H₂S determination in real time. One LAB strain, isolate L86, from cheese whey, demonstrated the highest inhibitory activity against the production of H₂S by SPB. The isolate L86 was confirmed as Enterococcus faecium that does not possess genes encoding for vancomycin resistance based on PCR analysis. Enterococcus faecium strain L86 reduced (P < 0·05) the yield of H₂S upto 51·2% in 10 h at 35°C in TSB-L-cys medium. In fresh chicken meat, the yield of H₂S produced by the artificially inoculated SPB was reduced (P < 0·05) by 48·6, 49·7 and 69·8% in 10 h at 35, 30 and 25°C, respectively. Enterococcus faecium strain L86 also reduced (P < 0·05) by 53·8% on the yield of H₂S produced by the indigenous SPB in partially spoiled chicken meat at 35°C for 10 h. Enterococcus faecium strain L86 is effective on inhibiting the production of H₂S by SPB. The application of this biological agent to raw animal by-products will provide a safer working environment in rendering processing plants and produce higher-quality rendered products. © 2011 The Authors. Journal of Applied Microbiology © 2011 The Society for Applied Microbiology.

  20. The relationship between the boron dipyrromethene (BODIPY) structure and the effectiveness of homogeneous and heterogeneous solar hydrogen-generating systems as well as DSSCs.

    PubMed

    Luo, Geng-Geng; Lu, Hui; Zhang, Xiao-Long; Dai, Jing-Cao; Wu, Ji-Huai; Wu, Jia-Jia

    2015-04-21

    effective surface binding mode is allowed with this structure. This is also in contrast with the case of dye-sensitized solar H2 generation, in which B3 was the most efficient chromophore. The differences between dye-sensitized hydrogen-generating systems and DSSCs may be due to rates of electron transfer and the dye aggregation tendency.

  1. Electronic and Steric Effects in Binding of Deep Cavitands

    PubMed Central

    Hooley, Richard J.; Shenoy, Siddhartha R.; Rebek, Julius

    2009-01-01

    A deep, self-folding cavitand responds to minor electronic differences between suitably sized adamantane guests. Binding constants range from <0.5 to 4000 M-1 for guests as similar as 1-bromoadamantane and 1-cyanoadamantane. The barriers to guest exchange also vary up to 3 kcal mol-1. PMID:18989966

  2. Hydrogen sulphide.

    PubMed

    Guidotti, T L

    1996-10-01

    Hydrogen sulphide (H2S) is the primary chemical hazard in natural gas production in 'sour' gas fields. It is also a hazard in sewage treatment and manure-containment operations, construction in wetlands, pelt processing, certain types of pulp and paper production, and any situation in which organic material decays or inorganic sulphides exist under reducing conditions. H2S dissociates into free sulphide in the circulation. Sulphide binds to many macromolecules, among them cytochrome oxidase. Although this is undoubtedly an important mechanism of toxicity due to H2S, there may be others H2S provides little opportunity for escape at high concentrations because of the olfactory paralysis it causes, the steep exposure-response relationships, and the characteristically sudden loss of consciousness it can cause which is colloquially termed 'knockdown.' Other effects may include mucosal irritation, which is associated at lower concentrations with a keratoconjunctivitis called 'gas eye' and at higher concentrations with risk of pulmonary oedema. Chronic central nervous system sequelae may possibly follow repeated knockdowns: this is controversial and the primary effects of H2S may be confounded by anoxia or head trauma. Treatment is currently empirical, with a combination of nitrite and hyperbaric oxygen preferred. The treatment regimen is not ideal and carries some risk.

  3. Effect of gravity on the stability and structure of lean hydrogen-air flames

    NASA Technical Reports Server (NTRS)

    Patnaik, G.; Kailasanath, K.

    1991-01-01

    Detailed, time-dependent, 2D numerical simulations with full hydrogen-oxygen chemistry are used to investigate the effects of gravity on the stability and structure of laminar flames in lean, premixed hydrogen-air mixtures. The calculations show that the effects of gravity becomes more important as the lean flammability limit is approached. In a 12 percent hydrogen-air mixture, gravity plays only a secondary role in determining the multidimensional structure of the flame with the stability and structure of the flame controlled primarily by the thermo-diffusive instability mechanism. However, in leaner hydrogen-air mixtures gravity becomes more important. Upward-propagating flames are highly curved and evolve into a bubble rising upwards in the tube. Downward-propagating flames are flat or even oscillate between structures with concave and convex curvatures. The zero-gravity flame shows only cellular structures. Cellular structures which are present in zero gravity can be suppressed by the effect of buoyancy for mixtures leaner than 11 percent hydrogen. These observations are explained on the basis of an interaction between the processes leading to buoyancy-induced Rayleigh-Taylor instability and the thermo-diffusive instability.

  4. Anti-inflammation effects of hydrogen saline in LPS activated macrophages and carrageenan induced paw oedema

    PubMed Central

    2012-01-01

    Background Oxidative stress is thought to play an important role in the pathogenesis of inflammation. Recent studies have found that hydrogen gas has the effect of eliminating free radicals. Whether hydrogen saline (more convenient to be used than hydrogen gas) has the anti-inflammation effect or not is still unknown. Methods Carrageenan-induced paw oedema and LPS-activated macrophages are studied in this article. Injection of carrageenan into the foot of a mouse elicited an acute inflammatory response characterized by increase of foot volume and infiltration of neutrophils. While tumor necrosis factorα(TNF-α) secreted by activated macrophages was determined by ELISA and real-time PCR. Results All parameters of inflammation (foot volume, infiltration of neutrophils, amount of TNF-α and the level of TNF-α's mRNA) were attenuated by the hydrogen saline treatment. Conclusion As a more convenient way than inhaling H2, hydrogen saline exhibits a protective effect against inflammation and it might provide a novel therapeutic approach for inflammatory diseases. PMID:22296736

  5. Effect of gravity on the stability and structure of lean hydrogen-air flames

    NASA Technical Reports Server (NTRS)

    Patnaik, G.; Kailasanath, K.

    1991-01-01

    Detailed, time-dependent, 2D numerical simulations with full hydrogen-oxygen chemistry are used to investigate the effects of gravity on the stability and structure of laminar flames in lean, premixed hydrogen-air mixtures. The calculations show that the effects of gravity becomes more important as the lean flammability limit is approached. In a 12 percent hydrogen-air mixture, gravity plays only a secondary role in determining the multidimensional structure of the flame with the stability and structure of the flame controlled primarily by the thermo-diffusive instability mechanism. However, in leaner hydrogen-air mixtures gravity becomes more important. Upward-propagating flames are highly curved and evolve into a bubble rising upwards in the tube. Downward-propagating flames are flat or even oscillate between structures with concave and convex curvatures. The zero-gravity flame shows only cellular structures. Cellular structures which are present in zero gravity can be suppressed by the effect of buoyancy for mixtures leaner than 11 percent hydrogen. These observations are explained on the basis of an interaction between the processes leading to buoyancy-induced Rayleigh-Taylor instability and the thermo-diffusive instability.

  6. Quantum dynamics study on the binding of a positron to vibrationally excited states of hydrogen cyanide molecule

    NASA Astrophysics Data System (ADS)

    Takayanagi, Toshiyuki; Suzuki, Kento; Yoshida, Takahiko; Kita, Yukiumi; Tachikawa, Masanori

    2017-05-01

    We present computational results of vibrationally enhanced positron annihilation in the e+ + HCN/DCN collisions within a local complex potential model. Vibrationally elastic and inelastic cross sections and effective annihilation rates were calculated by solving a time-dependent complex-potential Schrödinger equation under the ab initio potential energy surface for the positron attached HCN molecule, [HCN; e+], with multi-component configuration interaction level (Kita and Tachikawa, 2014). We discuss the effect of vibrational excitation on the positron affinities from the obtained vibrational resonance features.

  7. Effect of Hydrogen on the Mechnical Properties and Fracture Behavior of High Purity Aluminum.

    DTIC Science & Technology

    1986-07-01

    RD-0171 214 EFFECT OF HYDROGEN ON THE NECHNICAL PROPERTIES AND 1/2 FRACTURE BEHAVIOR OF H.. (U) ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE F...University of Illinois at Urbana -Champaign, 1986 Accesion For NTIS CRA&I DTIC TAB 3 UWanno~r-ced 1 JAificatioil Urbana , Illinois Ditb jtion I orc...and should eventually 2 I RD-0171 214 EFFECT OF HYDROGEN ON THE NECHNXCAL PROPERTIES AND 2/2 FRACTURE BEHAYIOR OF H..(U) ILLINOIS UNIV AT URBANA DEPT

  8. 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.

  9. The effect of hydrogen on the fracture toughness of alloy X-750

    NASA Astrophysics Data System (ADS)

    Symons, Douglas M.; Thompson, Anthony W.

    1997-03-01

    The effect of hydrogen on the fracture toughness behavior of a nickel-base superalloy, Alloy X-750, in the solutionized and aged condition was investigated. Notched bend specimens were tested to determine if the fracture process was stress or strain controlled. The fracture was observed to initiate at a distance between the location of maximum stress and maximum strain, suggesting that fracture required both a critical stress and strain. The effect of hydrogen was further investigated and modeled using fracture toughness testing and fractographic examination. The fracture toughness of the non-charged specimen was 147 MPasqrt m . Charging with hydrogen decreased the fracture toughness, K lc, to 52 MPasqrt m at a rapid loading rate and further decreased the toughness to 42 MPasqrt m for a slow loading rate. This is consistent with the rate-limiting step forthe embrittlement process being hydrogen diffusion. The fracture morphology for the hydrogen-charged specimens was intergranular ductile dimple, while the fracture morphology of noncharged specimens was a mixture of large transgranular dimples and fine intergranular dimples. The intergranular failure mechanism in Alloy X-750 was a microvoid initiation process at grain boundary carbides followed by void growth and coalescence. One role of hydrogen was to reduce the void initiation strain for the fine intergranular carbides. Hydrogen may have also increased the rate of void growth. The conditions ahead of a crack satisfy the critical stress criterion at a much lower applied stress intensity factor than for the critical fracture strain criterion. A model based on a critical fracture strain criterion is shown to predict the fracture behavior.

  10. Green synthesized iron oxide nanoparticles effect on fermentative hydrogen production by Clostridium acetobutylicum.

    PubMed

    Mohanraj, Sundaresan; Kodhaiyolii, Shanmugam; Rengasamy, Mookan; Pugalenthi, Velan

    2014-05-01

    A green synthesis of iron oxide nanoparticles (FeNPs) was developed using Murraya koenigii leaf extract as reducing and stabilizing agent. UV-vis spectra show that the absorption band centred at a wavelength of 277 nm which corresponds to the surface plasmon resonances of synthesized FeNPs. Fourier transform infrared spectroscopy spectrum exhibits that the characteristic band at 580 cm(-1) is assigned to Fe-O of γ-Fe2O3. Transmission electron microscopy image confirms that the spherical with irregular shaped aggregates and average size of nanoparticles was found to be ∼59 nm. The effect of synthesized FeNPs on fermentative hydrogen production was evaluated from glucose by Clostridium acetobutylicum NCIM 2337. The hydrogen yield in control experiment was obtained as 1.74 ± 0.08 mol H2/mol glucose whereas the highest hydrogen yield in FeNPs supplemented experiment was achieved as 2.33 ± 0.09 mol H2/mol glucose at 175 mg/L of FeNPs. In addition, the hydrogen content and hydrogen production rate were also increased from 34 ± 0.8 to 52 ± 0.8 % and 23 to 25.3 mL/h, respectively. The effect of FeNPs was compared with supplementation of FeSO4 on fermentative process. The supplementation of FeNPs enhanced the hydrogen production in comparison with control and FeSO4. The supplementation of FeNPs led to the change of the metabolic pathway towards high hydrogen production due to the enhancement of ferredoxin activity. The fermentation type was shifted from butyrate to acetate/butyrate fermentation type at the addition of FeNPs.

  11. Quantum Calculations On Hydrogen Bonds In Certain Water Clusters Show Cooperative Effects

    PubMed Central

    ZNAMENSKIY, VASILIY S.; GREEN, MICHAEL E.

    2008-01-01

    Water molecules in clefts and small clusters are in a significantly different environment than 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 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 of 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 number of neighboring donor and acceptor molecules. 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. PMID:19169381

  12. Relationship between brain serotonin transporter binding, plasma concentration and behavioural effect of selective serotonin reuptake inhibitors.

    PubMed

    Hirano, Kazufumi; Kimura, Ryohei; Sugimoto, Yumi; Yamada, Jun; Uchida, Shinya; Kato, Yasuhiro; Hashimoto, Hisakuni; Yamada, Shizuo

    2005-03-01

    1. The present study was undertaken to characterise the relationship between in vivo brain serotonin transporter (SERT) binding, plasma concentration and pharmacological effect of selective serotonin reuptake inhibitors (SSRIs) in mice. Oral administration of fluvoxamine, fluoxetine, paroxetine and sertraline at pharmacologically relevant doses exerted dose- and time-dependent binding activity of brain SERT as revealed by significant increases in KD for specific [3H]paroxetine binding, and the in vivo SERT-binding potency was in the order of paroxetine>fluoxetine, sertraline>fluvoxamine. 2. The time courses of brain SERT binding by SSRIs in mice were mostly in parallel to those of their plasma concentrations. Also, norfluoxetine (active metabolite) has been suggested to contribute largely to the long-lasting binding activity of brain SERT after the fluoxetine administration. 3. Oral administration of each SSRI suppressed significantly the marble-burying behaviour with no change in locomotor activity in mice, and the extent and time course of suppression agreed well with those of brain SERT binding. Thus, the pharmacological potencies of SSRIs in the attenuation of marble-burying behaviour correlated significantly with their brain SERT binding activities. 4. In conclusion, the present study has provided the first in vivo evidences to support that fluvoxamine, fluoxetine, paroxetine and sertraline orally administered bind to the pharmacologically relevant brain SERT in mice and that their SERT-binding characteristics is closely associated with the pharmacokinetics and inhibition of marble-burying behaviour.

  13. 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