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Sample records for adenine dinucleotide hydride

  1. Nicotinamide adenine dinucleotide biosynthesis promotes liver regeneration.

    PubMed

    Mukherjee, Sarmistha; Chellappa, Karthikeyani; Moffitt, Andrea; Ndungu, Joan; Dellinger, Ryan W; Davis, James G; Agarwal, Beamon; Baur, Joseph A

    2017-02-01

    The regenerative capacity of the liver is essential for recovery from surgical resection or injuries induced by trauma or toxins. During liver regeneration, the concentration of nicotinamide adenine dinucleotide (NAD) falls, at least in part due to metabolic competition for precursors. To test whether NAD availability restricts the rate of liver regeneration, we supplied nicotinamide riboside (NR), an NAD precursor, in the drinking water of mice subjected to partial hepatectomy. NR increased DNA synthesis, mitotic index, and mass restoration in the regenerating livers. Intriguingly, NR also ameliorated the steatosis that normally accompanies liver regeneration. To distinguish the role of hepatocyte NAD levels from any systemic effects of NR, we generated mice overexpressing nicotinamide phosphoribosyltransferase, a rate-limiting enzyme for NAD synthesis, specifically in the liver. Nicotinamide phosphoribosyltransferase overexpressing mice were mildly hyperglycemic at baseline and, similar to mice treated with NR, exhibited enhanced liver regeneration and reduced steatosis following partial hepatectomy. Conversely, mice lacking nicotinamide phosphoribosyltransferase in hepatocytes exhibited impaired regenerative capacity that was completely rescued by administering NR.

  2. Regulation of the Nicotinamide Adenine Dinucleotide- and Nicotinamide Adenine Dinucleotide Phosphate-Dependent Glutamate Dehydrogenases of Saccharomyces cerevisiae

    PubMed Central

    Roon, Robert J.; Even, Harvey L.

    1973-01-01

    Saccharomyces cerevisiae contains two distinct l-glutamate dehydrogenases. These enzymes are affected in a reciprocal fashion by growth on ammonia or dicarboxylic amino acids as the nitrogen source. The specific activity of the nicotinamide adenine dinucleotide phosphate (NADP) (anabolic) enzyme is highest in ammonia-grown cells and is reduced in cells grown on glutamate or aspartate. Conversely, the specific activity of the nicotinamide adenine dinucleotide (NAD) (catabolic) glutamate dehydrogenase is highest in cells grown on glutamate or aspartate and is much lower in cells grown on ammonia. The specific activity of both enzymes is very low in nitrogen-starved yeast. Addition of the ammonia analogue methylamine to the growth medium reduces the specific activity of the NAD-dependent enzyme and increases the specific activity of the NADP-dependent enzyme. PMID:4147647

  3. Isotope effect studies of the chemical mechanism of nicotinamide adenine dinucleotide malic enzyme from Crassula

    SciTech Connect

    Grissom, C.B.; Willeford, O.; Wedding, R.T.

    1987-05-05

    The /sup 13/C primary kinetic isotope effect on the decarboxylation of malate by nicotinamide adenine dinucleotide malic enzyme from Crassula argentea is 1.0199 +/- 0.0006 with proteo L-malate-2-H and 1.0162 +/- 0.0003 with malate-2-d. The primary deuterium isotope effect is 1.45 +/- 0.10 on V/K and 1.93 +/- 0.13 on V/sub max/. This indicates a stepwise conversion of malate to pyruvate and CO/sub 2/ with hydride transfer preceding decarboxylation, thereby suggesting a discrete oxaloacetate intermediate. This is in agreement with the stepwise nature of the chemical mechanism of other malic enzymes despite the Crassula enzyme's inability to reduce or decarboxylate oxaloacetate. Differences in morphology and allosteric regulation between enzymes suggest specialization of the Crassula malic enzyme for the physiology of crassulacean and acid metabolism while maintaining the catalytic events founds in malic enzymes from animal sources.

  4. Flavin Adenine Dinucleotide Structural Motifs: From Solution to Gas Phase

    PubMed Central

    2015-01-01

    Flavin adenine dinucleotide (FAD) is involved in important metabolic reactions where the biological function is intrinsically related to changes in conformation. In the present work, FAD conformational changes were studied in solution and in gas phase by measuring the fluorescence decay time and ion-neutral collision cross sections (CCS, in a trapped ion mobility spectrometer, TIMS) as a function of the solvent conditions (i.e., organic content) and gas-phase collisional partner (i.e., N2 doped with organic molecules). Changes in the fluorescence decay suggest that FAD can exist in four conformations in solution, where the abundance of the extended conformations increases with the organic content. TIMS-MS experiments showed that FAD can exist in the gas phase as deprotonated (M = C27H31N9O15P2) and protonated forms (M = C27H33N9O15P2) and that multiple conformations (up to 12) can be observed as a function of the starting solution for the [M + H]+ and [M + Na]+molecular ions. In addition, changes in the relative abundances of the gas-phase structures were observed from a “stack” to a “close” conformation when organic molecules were introduced in the TIMS cell as collision partners. Candidate structures optimized at the DFT/B3LYP/6-31G(d,p) were proposed for each IMS band, and results showed that the most abundant IMS band corresponds to the most stable candidate structure. Solution and gas-phase experiments suggest that the driving force that stabilizes the different conformations is based on the interaction of the adenine and isoalloxazine rings that can be tailored by the “solvation” effect created with the organic molecules. PMID:25222439

  5. The chemistry of nicotinamide adenine dinucleotide (NAD) analogues containing C-nucleosides related to nicotinamide riboside.

    PubMed

    Pankiewicz, Krzysztof W; Watanabe, Kyoichi A; Lesiak-Watanabe, Krystyna; Goldstein, Barry M; Jayaram, Hiremagalur N

    2002-04-01

    Oncolytic C-nucleosides, tiazofurin (2-beta-D-ribofuranosylthiazole-4-carboxamide) and benzamide riboside (3-beta-D-ribofuranosylbenzamide) are converted in cell into active metabolites thiazole-4-carboxamide- and benzamide adenine dinucleotide, TAD and BAD, respectively. TAD and BAD as NAD analogues were found to bind at the nicotinamide adenine dinucleotide (cofactor NAD) site of inosine monophosphate dehydrogenase (IMPDH), an important target in cancer treatment. The synthesis and evaluation of anticancer activity of a number of C-nucleosides related to tiazofurin and nicotinamide riboside then followed and are reviewed herein. Interestingly, pyridine C-nucleosides (such as C-nicotinamide riboside) are not metabolized into the corresponding NAD analogues in cell. Their conversion by chemical methods is described. As dinucleotides these compounds show inhibition of IMPDH in low micromolar level. Also, the synthesis of BAD in metabolically stable bis(phosphonate) form is discussed indicating the usefulness of such preformed inhibitors in drug development. Among tiazofurin analogues, Franchetti and Grifantini found, that the replacement of the sulfur by oxygen (as in oxazafurin) but not the removal of nitrogen (tiophenfurin) of the thiazole ring resulted in inactive compounds. The anti cancer activity of their synthetic dinucleotide analogues indicate that inactive compounds are not only poorly metabolized in cell but also are weak inhibitors of IMPDH as dinucleotides.

  6. Properties of Nicotinamide Adenine Dinucleotide Phosphate-Dependent Formate Dehydrogenase from Clostridium thermoaceticum

    PubMed Central

    Li, Lan-Fun; Ljungdahl, Lars; Wood, Harland G.

    1966-01-01

    Li, Lan-Fun (Western Reserve University School of Medicine, Cleveland, Ohio), Lars Ljungdahl, and Harland G. Wood. Properties of nicotinamide adenine dinucleotide phosphate-dependent formate dehydrogenase from Clostridium thermoaceticum. J. Bacteriol. 92: 405–412. 1966.—A nicotinamide adenine dinucleotide phosphate (NADP)-dependent formate dehydrogenase has been isolated from C. thermoaceticum. The enzyme is very sensitive to oxygen and requires sulfhydryl compounds for activity. The apparent Km at 50 C and pH 7.0 for NADP is 5.9 × 10−5m and for formate, 2.2 × 10−4m. The enzyme is most active at about 60 C and at pH values between 7.0 and 9.0. The enzyme catalyzes an exchange between C14O2 and formate, which requires NADP, but net synthesis of formate from CO2 and reduced nicotinamide adenine dinucleotide phosphate could not be demonstrated. The reaction does not involve ferredoxin. PMID:16562128

  7. Physical Separation of Streptococcal Nicotinamide Adenine Dinucleotide Glycohydrolase from Streptolysin O

    PubMed Central

    Shany, S.; Grushoff, Phyllis S.; Bernheimer, Alan W.

    1973-01-01

    Streptococcal nicotinamide adenine dinucleotide glycohydrolase (NADase) with a molecular weight of about 55,000 and an isoelectric pH of 8.55 was isolated from crude streptolysin O (SLO) preparations. NADase differed from SLO in size, charge, and immunological behavior. Streptococcal NADase is considered to have no role in the hemolytic process because it has no hemolytic activity; conversely, partially purified SLO showed no NADase activity. The hemolytic activity of crude SLO was completely inhibited by anti-tetanolysin, whereas the NADase activity in the same reaction mixture was unaffected. Experiments involving double diffusion in agar also demonstrated immunological nonidentity of the two proteins. Images PMID:4357989

  8. Conformational behavior of flavin adenine dinucleotide: conserved stereochemistry in bound and free states.

    PubMed

    Kuppuraj, Gopi; Kruise, Dennis; Yura, Kei

    2014-11-26

    Metabolic enzymes utilize the cofactor flavin adenine dinucleotide (FAD) to catalyze essential biochemical reactions. Because these enzymes have been implicated in disease pathways, it will be necessary to target them via FAD-based structural analogues that can either activate/inhibit the enzymatic activity. To achieve this, it is important to explore the conformational space of FAD in the enzyme-bound and free states. Herein, we analyze X-ray crystallographic data of the enzyme-bound FAD conformations and sample conformations of the molecule in explicit water by molecular dynamics (MD) simulations. Enzyme-bound FAD conformations segregate into five distinct groups based on dihedral angle principal component analysis (PCA). A notable feature in the bound FADs is that the adenine base and isoalloxazine ring are oppositely oriented relative to the pyrophosphate axis characterized by near trans hypothetical dihedral angle "δV" values. Not surprisingly, MD simulations in water show final compact but not perfectly stacked ring structures in FAD. Simulation data did not reveal noticeable changes in overall conformational dynamics of the dinucleotide in reduced and oxidized forms and in the presence and/or absence of ions. During unfolding-folding dynamics, the riboflavin moiety is more flexible than the adenosine monophosphate group in the molecule. Conversely, the isoalloxazine ring is more stable than the variable adenine base. The pyrophosphate group depicts an unusually highly organized fluctuation illustrated by its dihedral angle distribution. Conformations sampled from enzymes and MD are quantified. The extent to which the protein shifts the distribution from the unbound state is discussed in terms of prevalent FAD shapes and dihedral angle population.

  9. Unusual folded conformation of nicotinamide adenine dinucleotide bound to flavin reductase P.

    PubMed Central

    Tanner, J. J.; Tu, S. C.; Barbour, L. J.; Barnes, C. L.; Krause, K. L.

    1999-01-01

    The 2.1 A resolution crystal structure of flavin reductase P with the inhibitor nicotinamide adenine dinucleotide (NAD) bound in the active site has been determined. NAD adopts a novel, folded conformation in which the nicotinamide and adenine rings stack in parallel with an inter-ring distance of 3.6 A. The pyrophosphate binds next to the flavin cofactor isoalloxazine, while the stacked nicotinamide/adenine moiety faces away from the flavin. The observed NAD conformation is quite different from the extended conformations observed in other enzyme/NAD(P) structures; however, it resembles the conformation proposed for NAD in solution. The flavin reductase P/NAD structure provides new information about the conformational diversity of NAD, which is important for understanding catalysis. This structure offers the first crystallographic evidence of a folded NAD with ring stacking, and it is the first enzyme structure containing an FMN cofactor interacting with NAD(P). Analysis of the structure suggests a possible dynamic mechanism underlying NADPH substrate specificity and product release that involves unfolding and folding of NADP(H). PMID:10493573

  10. Nicotinic acid adenine dinucleotide phosphate-mediated calcium signalling in effector T cells regulates autoimmunity of the central nervous system

    PubMed Central

    Cordiglieri, Chiara; Odoardi, Francesca; Zhang, Bo; Nebel, Merle; Kawakami, Naoto; Klinkert, Wolfgang E. F.; Lodygin, Dimtri; Lühder, Fred; Breunig, Esther; Schild, Detlev; Ulaganathan, Vijay Kumar; Dornmair, Klaus; Dammermann, Werner; Potter, Barry V. L.; Guse, Andreas H.

    2010-01-01

    Nicotinic acid adenine dinucleotide phosphate represents a newly identified second messenger in T cells involved in antigen receptor-mediated calcium signalling. Its function in vivo is, however, unknown due to the lack of biocompatible inhibitors. Using a recently developed inhibitor, we explored the role of nicotinic acid adenine dinucleotide phosphate in autoreactive effector T cells during experimental autoimmune encephalomyelitis, the animal model for multiple sclerosis. We provide in vitro and in vivo evidence that calcium signalling controlled by nicotinic acid adenine dinucleotide phosphate is relevant for the pathogenic potential of autoimmune effector T cells. Live two photon imaging and molecular analyses revealed that nicotinic acid adenine dinucleotide phosphate signalling regulates T cell motility and re-activation upon arrival in the nervous tissues. Treatment with the nicotinic acid adenine dinucleotide phosphate inhibitor significantly reduced both the number of stable arrests of effector T cells and their invasive capacity. The levels of pro-inflammatory cytokines interferon-gamma and interleukin-17 were strongly diminished. Consecutively, the clinical symptoms of experimental autoimmune encephalomyelitis were ameliorated. In vitro, antigen-triggered T cell proliferation and cytokine production were evenly suppressed. These inhibitory effects were reversible: after wash-out of the nicotinic acid adenine dinucleotide phosphate antagonist, the effector T cells fully regained their functions. The nicotinic acid derivative BZ194 induced this transient state of non-responsiveness specifically in post-activated effector T cells. Naïve and long-lived memory T cells, which express lower levels of the putative nicotinic acid adenine dinucleotide phosphate receptor, type 1 ryanodine receptor, were not targeted. T cell priming and recall responses in vivo were not reduced. These data indicate that the nicotinic acid adenine dinucleotide phosphate

  11. Bacterial degradation of styrene involving a novel flavin adenine dinucleotide-dependent styrene monooxygenase.

    PubMed Central

    Hartmans, S; van der Werf, M J; de Bont, J A

    1990-01-01

    By using styrene as the sole source of carbon and energy in concentrations of 10 to 500 microM, 14 strains of aerobic bacteria and two strains of fungi were isolated from various soil and water samples. In cell extracts of 11 of the bacterial isolates, a novel flavin adenine dinucleotide-requiring styrene monooxygenase activity that oxidized styrene to styrene oxide (phenyl oxirane) was detected. In one bacterial strain (S5), styrene metabolism was studied in more detail. In addition to styrene monooxygenase, cell extracts from strain S5 contained styrene oxide isomerase and phenylacetaldehyde dehydrogenase activities. A pathway for styrene degradation via styrene oxide and phenylacetaldehyde to phenylacetic acid is proposed. PMID:2339888

  12. Conducting polymer and its composite materials based electrochemical sensor for Nicotinamide Adenine Dinucleotide (NADH).

    PubMed

    Omar, Fatin Saiha; Duraisamy, Navaneethan; Ramesh, K; Ramesh, S

    2016-05-15

    Nicotinamide Adenine Dinucleotide (NADH) is an important coenzyme in the human body that participates in many metabolic reactions. The impact of abnormal concentrations of NADH significantly causes different diseases in human body. Electrochemical detection of NADH using bare electrode is a challenging task especially in the presence of main electroactive interferences such as ascorbic acid (AA), uric acid (UA) and dopamine (DA). Modified electrodes have been widely explored to overcome the problems of poor sensitivity and selectivity occurred from bare electrodes. This review gives an overview on the progress of using conducting polymers, polyelectrolyte and its composites (co-polymer, carbonaceous, metal, metal oxide and clay) based modified electrodes for the sensing of NADH. In addition, developments on the fabrication of numerous conducting polymer composites based modified electrodes are clearly described.

  13. Evidence for two-step binding of reduced nicotinamide-adenine dinucleotide to aldehyde dehydrogenase.

    PubMed Central

    MacGibbon, A K; Buckley, P D; Blackwell, L F

    1977-01-01

    The displacement of NADH from cytoplasmic aldehyde dehydrogenase (EC 1.2.1.3) from sheep liver was studied by using NAD+, 1,10-phenanthroline, ADP-ribose, deamino-NAD+ and pyridine-3-aldehyde-adenine dinucleotide as displacing agents, by following the decrease in fluorescence as a function of time. The data obtained could be fitted by assuming two first-order processes were occurring, a faster process with an apparent rate constant of 0.85 +/- 0.20 s-1 and a relative amplitude of 60 +/- 10% and a slower process with an apparent rate constant of 0.20 +/- 0.05 s-1 and a relative amplitude of 40 +/- 10% (except for pyridine-3-aldehyde-adenine dinucleotide, where the apparent rate constant for the slow process was 0.05 s-1). The displacement rates did not change significantly when the pH was varied from 6.0 to 9.0. Kinetic data are also reported for the dependence of the rate of binding of NADH to the enzyme on the total concentration of NADH. Detailed arguments are presented based on the isolation and purification procedures, the equilibrium coenzyme-binding studies and the kinetic data, which lead to the following model for the release of NADH from the enzyme: (formula: see article). The parameters that best fit the data are: k + 1 = 0.2 s-1; k - 1 = 0.05 s-1; k + 2 = 0.8 s-1 and k - 2 = 5 X 10(5)litre-mol-1-s-1. The slow phase of the NADH release is similar to the steady-state turnover number for substrates such as acetaldehyde and propionaldehyde and appears to contribute significantly to the limitation of the steady-state rate. Images Fig. 1. Fig. 2. Fig. 3. Fig. 5. PMID:21657

  14. Stimulation of nicotinamide adenine dinucleotide biosynthetic pathways delays axonal degeneration after axotomy.

    PubMed

    Sasaki, Yo; Araki, Toshiyuki; Milbrandt, Jeffrey

    2006-08-16

    Axonal degeneration occurs in many neurodegenerative diseases and after traumatic injury and is a self-destructive program independent from programmed cell death. Previous studies demonstrated that overexpression of nicotinamide mononucleotide adenylyltransferase 1 (Nmnat1) or exogenous application of nicotinamide adenine dinucleotide (NAD) can protect axons of cultured dorsal root ganglion (DRG) neurons from degeneration caused by mechanical or neurotoxic injury. In mammalian cells, NAD can be synthesized from multiple precursors, including tryptophan, nicotinic acid, nicotinamide, and nicotinamide riboside (NmR), via multiple enzymatic steps. To determine whether other components of these NAD biosynthetic pathways are capable of delaying axonal degeneration, we overexpressed each of the enzymes involved in each pathway and/or exogenously administered their respective substrates in DRG cultures and assessed their capacity to protect axons after axotomy. Among the enzymes tested, Nmnat1 had the strongest protective effects, whereas nicotinamide phosphoribosyl transferase and nicotinic acid phosphoribosyl transferase showed moderate protective activity in the presence of their substrates. Strong axonal protection was also provided by Nmnat3, which is predominantly located in mitochondria, and an Nmnat1 mutant localized to the cytoplasm, indicating that the subcellular location of NAD production is not crucial for protective activity. In addition, we showed that exogenous application of the NAD precursors that are the substrates of these enzymes, including nicotinic acid mononucleotide, nicotinamide mononucleotide, and NmR, can also delay axonal degeneration. These results indicate that stimulation of NAD biosynthetic pathways via a variety of interventions may be useful in preventing or delaying axonal degeneration.

  15. Preclinical evidence of mitochondrial nicotinamide adenine dinucleotide as an effective alarm parameter under hypoxia

    NASA Astrophysics Data System (ADS)

    Shi, Hua; Sun, Nannan; Mayevsky, Avraham; Zhang, Zhihong; Luo, Qingming

    2014-01-01

    Early detection of tissue hypoxia in the intensive care unit is essential for effective treatment. Reduced nicotinamide adenine dinucleotide (NADH) has been suggested to be the most sensitive indicator of tissue oxygenation at the mitochondrial level. However, no experimental evidence comparing the kinetics of changes in NADH and other physiological parameters has been provided. The aim of this study is to obtain the missing data in a systematic and reliable manner. We constructed four acute hypoxia models, including hypoxic hypoxia, hypemic hypoxia, circulatory hypoxia, and histogenous hypoxia, and measured NADH fluorescence, tissue reflectance, cerebral blood flow, respiration, and electrocardiography simultaneously from the induction of hypoxia until death. We found that NADH was not always the first onset parameter responding to hypoxia. The order of responses was mainly affected by the cause of hypoxia. However, NADH reached its alarm level earlier than the other monitored parameters, ranging from several seconds to >10 min. As such, we suggest that the NADH can be used as a hypoxia indicator, although the exact level that should be used must be further investigated. When the NADH alarm is detected, the body still has a chance to recover if appropriate and timely treatment is provided.

  16. Flavin adenine dinucleotide as a chromophore of the Xenopus (6-4)photolyase.

    PubMed Central

    Todo, T; Kim, S T; Hitomi, K; Otoshi, E; Inui, T; Morioka, H; Kobayashi, H; Ohtsuka, E; Toh, H; Ikenaga, M

    1997-01-01

    Two types of enzyme utilizing light from the blue and near-UV spectral range (320-520 nm) are known to have related primary structures: DNA photolyase, which repairs UV-induced DNA damage in a light-dependent manner, and the blue light photoreceptor of plants, which mediates light-dependent regulation of seedling development. Cyclobutane pyrimidine dimers (CPDs) and pyrimidine (6-4) pyrimidone photoproducts [(6-4)photoproducts] are the two major photoproducts produced in DNA by UV irradiation. Two types of photolyases have been identified, one specific for CPDs (CPD photolyase) and another specific for (6-4)photoproducts [(6-4)photolyase]. (6-4)Photolyase activity was first found in Drosophila melanogaster and to date this gene has been cloned only from this organism. The deduced amino acid sequence of the cloned gene shows that (6-4)photolyase is a member of the CPD photolyase/blue light photoreceptor family. Both CPD photolyase and blue light photoreceptor are flavoproteins and bound flavin adenine dinucleotides (FADs) are essential for their catalytic activity. Here we report isolation of a Xenopus laevis(6-4)photolyase gene and show that the (6-4)photolyase binds non- covalently to stoichiometric amounts of FAD. This is the first indication of FAD as the chromophore of (6-4)photolyase. PMID:9016626

  17. Magnitude of malate-aspartate reduced nicotinamide adenine dinucleotide shuttle activity in intact respiring tumor cells.

    PubMed

    Greenhouse, W V; Lehninger, A L

    1977-11-01

    Measurements of respiration, CO2 and lactate production, and changes in the levels of various key metabolites of the glycolytic sequence and tricarboxylic acid cycle were made on five lines of rodent ascites tumor cells (two strains of Ehrlich ascites tumor cells, Krebs II carcinoma, AS-30D carcinoma, and L1210 cells) incubated aerobically in the presence of uniformly labeled D-[14C]glucose. From these data, as well as earlier evidence demonstrating that the reduced nicotinamide adenine dinucleotide (NADH) shuttle in these cells requires a transaminase step and is thus identified as the malate-aspartate shuttle (W.V.V. Greenhouse and A.L. Lehninger, Cancer Res., 36: 1392-1396, 1976), metabolic flux diagrams were constructed for the five cell lines. These diagrams show the relative rates of glycolysis, the tricarboxylic acid cycle, electron transport, and the malate-aspartate shuttle in these tumors. Large amounts of cytosolic NADH were oxidized by the mitochondrial respiratory chain via the NADH shuttle, comprising anywhere from about 20 to 80% of the total flow of reducing equivalents to oxygen in these tumors. Calculations of the sources of energy for adenosine triphosphate synthesis indicated that on the average about one-third of the respiratory adenosine triphosphate is generated by electron flow originating from cytosolic NADH via the malate-aspartate shuttle.

  18. Intracellular nicotinamide adenine dinucleotide promotes TNF-induced necroptosis in a sirtuin-dependent manner

    PubMed Central

    Preyat, N; Rossi, M; Kers, J; Chen, L; Bertin, J; Gough, P J; Le Moine, A; Rongvaux, A; Van Gool, F; Leo, O

    2016-01-01

    Cellular necrosis has long been regarded as an incidental and uncontrolled form of cell death. However, a regulated form of cell death termed necroptosis has been identified recently. Necroptosis can be induced by extracellular cytokines, pathogens and several pharmacological compounds, which share the property of triggering the formation of a RIPK3-containing molecular complex supporting cell death. Of interest, most ligands known to induce necroptosis (including notably TNF and FASL) can also promote apoptosis, and the mechanisms regulating the decision of cells to commit to one form of cell death or the other are still poorly defined. We demonstrate herein that intracellular nicotinamide adenine dinucleotide (NAD+) has an important role in supporting cell progression to necroptosis. Using a panel of pharmacological and genetic approaches, we show that intracellular NAD+ promotes necroptosis of the L929 cell line in response to TNF. Use of a pan-sirtuin inhibitor and shRNA-mediated protein knockdown led us to uncover a role for the NAD+-dependent family of sirtuins, and in particular for SIRT2 and SIRT5, in the regulation of the necroptotic cell death program. Thus, and in contrast to a generally held view, intracellular NAD+ does not represent a universal pro-survival factor, but rather acts as a key metabolite regulating the choice of cell demise in response to both intrinsic and extrinsic factors. PMID:26001219

  19. Decrease in nicotinamide adenine dinucleotide dehydrogenase is related to skin pigmentation.

    PubMed

    Nakama, Mitsuo; Murakami, Yuhko; Tanaka, Hiroshi; Nakata, Satoru

    2012-03-01

    Skin pigmentation is caused by various physical and chemical factors. It might also be influenced by changes in the physiological function of skin with aging. Nicotinamide adenine dinucleotide (NADH) dehydrogenase is an enzyme related to the mitochondrial electron transport system and plays a key role in cellular energy production. It has been reported that the functional decrease in this system causes Parkinson's disease. Another study reports that the amount of NADH dehydrogenase in heart and skeletal muscle decreases with aging. A similar decrease in the skin would probably affect its physiological function. However, no reports have examined the age-related change in levels of NADH dehydrogenase in human skin. In this study, we investigated this change and its effect on skin pigmentation using cultured human epidermal keratinocytes. The mRNA expression of NDUFA1, NDUFB7, and NDUFS2, subunits of NADH dehydrogenase, and its activity were significantly decreased in late passage keratinocytes compared to early passage cells. Conversely, the mRNA expression of melanocyte-stimulating cytokines, interleukin-1 alpha and endothelin 1, was increased in late passage cells. On the other hand, the inhibition of NADH dehydrogenase upregulated the mRNA expression of melanocyte-stimulating cytokines. Moreover, the level of NDUFB7 mRNA was lower in pigmented than in nonpigmented regions of skin in vivo. These results suggest the decrease in NADH dehydrogenase with aging to be involved in skin pigmentation.

  20. Studies of yeast cell oxygenation and energetics by laser fluorometry of reduced nicotinamide adenine dinucleotide

    NASA Astrophysics Data System (ADS)

    Pan, Fu-shih; Chen, Stephen; Mintzer, Robert A.; Chen, Chin-Tu; Schumacker, Paul

    1991-03-01

    It is of fundamental importance for biological scientists to assess cellular energetics. Under aerobic conditions, the tricarboxylic acid cycle (TCA cycle) is coupled with the mitochondrial electron cascade pathway to provide the cell with energy. The nicotinamide adenine dinucleotide-conjugated pair (NAD and NADH) is the coenzyme in numerous important biomedical reactions which include several important dehydrogenase reactions in the TCA cycle. Based on Le Chatelier's principle, NADH will accumulate when this energy production mechanism is impaired. The relative amounts of NAD and NADH in a cell are defined as the redox state of the cell (Williamson et.al. 1967) which provides a valuable index of cellular energetics. The sum of the amounts of NAD and NADH in a cell may be assumed to be constant during a finite time; therefore, a reliable means of measuring the NADH concentration would provide us with a useful indicator of tissue viability. Traditionally, the quantities of NADH and NAD may be measured by chemical assay methods. We can avoid these tediois analyses by exploiting the significant difference between the ultraviolet absorption spectra of this redox pair. However, because of the opacity of biological samples and the interference of other biochemicals that also absorb ultraviolet radiation, measurement of NADH and NAD+ concentrations in vivo by absorption spectroscopy is not feasible.

  1. Nicotinamide adenine dinucleotide homeostasis and signalling in heart disease: Pathophysiological implications and therapeutic potential.

    PubMed

    Mericskay, Mathias

    2016-03-01

    Heart failure is a highly morbid syndrome generating enormous socio-economic costs. The failing heart is characterized by a state of deficient bioenergetics that is not currently addressed by classical clinical approaches. Nicotinamide adenine dinucleotide (NAD(+)/NADH) is a major coenzyme for oxidoreduction reactions in energy metabolism; it has recently emerged as a signalling molecule with a broad range of activities, ranging from calcium (Ca(2+)) signalling (CD38 ectoenzyme) to the epigenetic regulation of gene expression involved in the oxidative stress response, catabolic metabolism and mitochondrial biogenesis (sirtuins, poly[adenosine diphosphate-ribose] polymerases [PARPs]). Here, we review current knowledge regarding alterations to myocardial NAD homeostasis that have been observed in various models of heart failure, and their effect on mitochondrial functions, Ca(2+), sirtuin and PARP signalling. We highlight the therapeutic approaches that are currently in use or in development, which inhibit or stimulate NAD(+)-consuming enzymes, and emerging approaches aimed at stimulating NAD biosynthesis in the failing heart.

  2. Naturally Occurring β-Nicotinamide Adenine Dinucleotide-Independent Avibacterium paragallinarum Isolate in Peru.

    PubMed

    Falconi-Agapito, Francesca; Saravia, Luis E; Flores-Pérez, Aldo; Fernández-Díaz, Manolo

    2015-06-01

    The β-nicotinamide adenine dinucleotide (NAD) requirement has been considered to be essential for the isolation of the causal agent of infectious coryza, Avibacterium paragallinarum. Nevertheless, NAD-independent reports from South Africa and Mexico dismissed this paradigm. It is now accepted that both NAD-dependent and NAD-independent agents are able to cause infectious coryza and thus belong to the species A. paragallinarum. Here, we report for the first time in Peru a NAD-independent isolate from broiler chickens with typical signs of infectious coryza that have received a trivalent inactivated vaccine against infectious coryza. The isolate was identified based on its morphology, biochemical and serologic tests, and PCR results. Partial 16S rRNA gene sequence analysis confirmed the isolate as A. paragallinarum. There have been no cases of NAD-independent A. paragallinarum isolates reported in South America. Increasing reports around the world highlight not only the need to reconsider the in vitro nutritional requirements of this species for its correct isolation but also the cross-protection conferred by commercial infectious coryza vaccines against NAD-independent isolates.

  3. Eco-synthesis of graphene and its use in dihydronicotinamide adenine dinucleotide sensing.

    PubMed

    Amouzadeh Tabrizi, Mahmoud; Jalilzadeh Azar, Somayeh; Nadali Varkani, Javad

    2014-09-01

    In this paper, we report a green and eco-friendly approach to synthesize reduced graphene oxide (rGO) via a mild hydrothermal process using malt as a reduced agent. The proposed method is based on the reduction of graphene oxide (GO) in malt solution by making use of the reducing capability of phenolic compounds contained in malt solution. The obtained rGO was characterized by atomic force microscopy (AFM), ultraviolet-visible (UV-vis) absorption spectroscopy, X-ray diffraction spectroscopy (XRD), Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Electrochemical impedance spectroscopy analysis revealed that the charge transfer resistance of rGO modified glassy carbon (GC) electrode was much lower than that of the GC electrode. The electrochemical behavior of dihydronicotinamide adenine dinucleotide (NADH) on rGO modified GC electrode was investigated by cyclic voltammetry and amperometry. Electrochemical experiments indicated that rGO/GC electrode exhibited excellent electrocatalytic activity toward the NADH, which can be attributed to excellent electrical conductivity and high specific surface area of the rGO composite. The resulting biosensor showed highly sensitive amperometric response to NADH with a low detection limit (0.33μM).

  4. Nicotinamide Adenine Dinucleotide Protects against Spinal Cord Ischemia Reperfusion Injury-Induced Apoptosis by Blocking Autophagy

    PubMed Central

    Yu, Sifei; Wang, Zhenfei; Yang, Kai; Liu, Zhuochao

    2017-01-01

    The role of autophagy, neuroprotective mechanisms of nicotinamide adenine dinucleotide (NAD+), and their relationship in spinal cord ischemic reperfusion injury (SCIR) was assessed. Forty-eight Sprague-Dawley rats were divided into four groups: sham, ischemia reperfusion (I/R), 10 mg/kg NAD+, and 75 mg/kg NAD+. Western blotting, immunofluorescence, and immunohistochemistry were used to assess autophagy and apoptosis. Basso, Beattie, and Bresnahan (BBB) scores were used to assess neurological function. Expression levels of Beclin-1, Atg12-Atg5, LC3B-II, cleaved caspase 3, and Bax were upregulated in the I/R group and downregulated in the 75 mg/kg NAD+ group; p-mTOR, p-AKT, p62, and Bcl-2 were downregulated in the I/R group and upregulated in the 75 mg/kg NAD+ group. Numbers of LC3B-positive, caspase 3-positive, Bax-positive, and TUNEL-positive cells were significantly increased in the I/R group and decreased in the 75 mg/kg NAD+ group. The mean integrated option density of Bax increased and that of Nissl decreased in the I/R group, and it decreased and increased, respectively, in the 75 mg/kg NAD+ group. BBB scores significantly increased in the 75 mg/kg NAD+ group relative to the I/R group. No difference was observed between I/R and 10 mg/kg NAD+ groups for these indicators. Therefore, excessive and sustained autophagy aggravates SCIR; administration of NAD+ alleviates injury. PMID:28367271

  5. Nicotinic acid-adenine dinucleotide phosphate activates the skeletal muscle ryanodine receptor.

    PubMed Central

    Hohenegger, Martin; Suko, Josef; Gscheidlinger, Regina; Drobny, Helmut; Zidar, Andreas

    2002-01-01

    Calcium is a universal second messenger. The temporal and spatial information that is encoded in Ca(2+)-transients drives processes as diverse as neurotransmitter secretion, axonal outgrowth, immune responses and muscle contraction. Ca(2+)-release from intracellular Ca(2+) stores can be triggered by diffusible second messengers like Ins P (3), cyclic ADP-ribose or nicotinic acid-adenine dinucleotide phosphate (NAADP). A target has not yet been identified for the latter messenger. In the present study we show that nanomolar concentrations of NAADP trigger Ca(2+)-release from skeletal muscle sarcoplasmic reticulum. This was due to a direct action on the Ca(2+)-release channel/ryanodine receptor type-1, since in single channel recordings, NAADP increased the open probability of the purified channel protein. The effects of NAADP on Ca(2+)-release and open probability of the ryanodine receptor occurred over a similar concentration range (EC(50) approximately 30 nM) and were specific because (i) they were blocked by Ruthenium Red and ryanodine, (ii) the precursor of NAADP, NADP, was ineffective at equimolar concentrations, (iii) NAADP did not affect the conductance and reversal potential of the ryanodine receptor. Finally, we also detected an ADP-ribosyl cyclase activity in the sarcoplasmic reticulum fraction of skeletal muscle. This enzyme was not only capable of synthesizing cyclic GDP-ribose but also NAADP, with an activity of 0.25 nmol/mg/min. Thus, we conclude that NAADP is generated in the vicinity of type 1 ryanodine receptor and leads to activation of this ion channel. PMID:12102654

  6. Photoaffinity labeling of high affinity nicotinic acid adenine dinucleotide phosphate (NAADP)-binding proteins in sea urchin egg.

    PubMed

    Walseth, Timothy F; Lin-Moshier, Yaping; Jain, Pooja; Ruas, Margarida; Parrington, John; Galione, Antony; Marchant, Jonathan S; Slama, James T

    2012-01-20

    Nicotinic acid adenine dinucleotide phosphate (NAADP) is a messenger that regulates calcium release from intracellular acidic stores. Recent studies have identified two-pore channels (TPCs) as endolysosomal channels that are regulated by NAADP; however, the nature of the NAADP receptor binding site is unknown. To further study NAADP binding sites, we have synthesized and characterized [(32)P-5-azido]nicotinic acid adenine dinucleotide phosphate ([(32)P-5N(3)]NAADP) as a photoaffinity probe. Photolysis of sea urchin egg homogenates preincubated with [(32)P-5N(3)]NAADP resulted in specific labeling of 45-, 40-, and 30-kDa proteins, which was prevented by inclusion of nanomolar concentrations of unlabeled NAADP or 5N(3)-NAADP, but not by micromolar concentrations of structurally related nucleotides such as NAD, nicotinic acid adenine dinucleotide, nicotinamide mononucleotide, nicotinic acid, or nicotinamide. [(32)P-5N(3)]NAADP binding was saturable and displayed high affinity (K(d) ∼10 nM) in both binding and photolabeling experiments. [(32)P-5N(3)]NAADP photolabeling was irreversible in a high K(+) buffer, a hallmark feature of NAADP binding in the egg system. The proteins photolabeled by [(32)P-5N(3)]NAADP have molecular masses smaller than the sea urchin TPCs, and antibodies to TPCs do not detect any immunoreactivity that comigrates with either the 45-kDa or the 40-kDa photolabeled proteins. Interestingly, antibodies to TPC1 and TPC3 were able to immunoprecipitate a small fraction of the 45- and 40-kDa photolabeled proteins, suggesting that these proteins associate with TPCs. These data suggest that high affinity NAADP binding sites are distinct from TPCs.

  7. In vivo native fluorescence spectroscopy and nicotinamide adinine dinucleotide/flavin adenine dinucleotide reduction and oxidation states of oral submucous fibrosis for chemopreventive drug monitoring

    NASA Astrophysics Data System (ADS)

    Sivabalan, Shanmugam; Vedeswari, C. Ponranjini; Jayachandran, Sadaksharam; Koteeswaran, Dornadula; Pravda, Chidambaranathan; Aruna, Prakasa Rao; Ganesan, Singaravelu

    2010-01-01

    Native fluorescence spectroscopy has shown potential to characterize and diagnose oral malignancy. We aim at extending the native fluorescence spectroscopy technique to characterize normal and oral submucous fibrosis (OSF) patients under pre- and post-treated conditions, and verify whether this method could also be considered in the monitoring of therapeutic prognosis noninvasively. In this study, 28 normal subjects and 28 clinically proven cases of OSF in the age group of 20 to 40 years are diagnosed using native fluorescence spectroscopy. The OSF patients are given dexamethasone sodium phosphate and hyaluronidase twice a week for 6 weeks, and the therapeutic response is monitored using fluorescence spectroscopy. The fluorescence emission spectra of normal and OSF cases of both pre- and post-treated conditions are recorded in the wavelength region of 350 to 600 nm at an excitation wavelength of 330 nm. The statistical significance is verified using discriminant analysis. The oxidation-reduction ratio of the tissue is also calculated using the fluorescence emission intensities of flavin adenine dinucleotide and nicotinamide adinine dinucleotide at 530 and 440 nm, respectively, and they are compared with conventional physical clinical examinations. This study suggests that native fluorescence spectroscopy could also be extended to OSF diagnosis and therapeutic prognosis.

  8. Nicotinic acid adenine dinucleotide phosphate (NAADP) is a second messenger in muscarinic receptor-induced contraction of guinea pig trachea.

    PubMed

    Aley, Parvinder K; Singh, Nisha; Brailoiu, G Cristina; Brailoiu, Eugen; Churchill, Grant C

    2013-04-19

    Nicotinic acid adenine dinucleotide phosphate (NAADP) is increasingly being demonstrated to be involved in calcium signaling in many cell types and species. Although it has been shown to play a role in smooth muscle cell contraction in several tissues, nothing is known about its possible role in tracheal smooth muscle, a muscle type that is clinically relevant to asthma. To determine whether NAADP functions as a second messenger in tracheal smooth muscle contraction, we used the criteria set out by Sutherland for a molecule to be designated a second messenger. We report that NAADP satisfies all five criteria as follows. First, the NAADP antagonist Ned-19 inhibited contractions in tracheal rings and calcium increases in isolated smooth muscle cells induced by the muscarinic agonist carbachol. Second, NAADP increased cytosolic calcium in isolated cells when microinjected and was blocked by Ned-19. Third, tracheal homogenates could synthesize NAADP by base exchange from exogenous NADP and nicotinic acid and metabolize exogenous NAADP to nicotinic acid adenine dinucleotide by a 2'-phosphatase. Fourth, carbachol induced a rapid and transient increase in endogenous NAADP levels. Fifth, tracheal homogenates contained NAADP-binding sites of high affinity. Taken together, these data demonstrate that NAADP functions as a second messenger in tracheal smooth muscle, and therefore, steps in the NAADP signaling pathway might provide possible new drug targets.

  9. Cleavage of nicotinamide adenine dinucleotide by the ribosome-inactivating protein from Momordica charantia.

    PubMed

    Vinkovic, M; Dunn, G; Wood, G E; Husain, J; Wood, S P; Gill, R

    2015-09-01

    The interaction of momordin, a type 1 ribosome-inactivating protein from Momordica charantia, with NADP(+) and NADPH has been investigated by X-ray diffraction analysis of complexes generated by co-crystallization and crystal soaking. It is known that the proteins of this family readily cleave the adenine-ribose bond of adenosine and related nucleotides in the crystal, leaving the product, adenine, bound to the enzyme active site. Surprisingly, the nicotinamide-ribose bond of oxidized NADP(+) is cleaved, leaving nicotinamide bound in the active site in the same position but in a slightly different orientation to that of the five-membered ring of adenine. No binding or cleavage of NADPH was observed at pH 7.4 in these experiments. These observations are in accord with current views of the enzyme mechanism and may contribute to ongoing searches for effective inhibitors.

  10. Simultaneous quantitation of nicotinamide riboside, nicotinamide mononucleotide and nicotinamide adenine dinucleotide in milk by a novel enzyme-coupled assay.

    PubMed

    Ummarino, Simone; Mozzon, Massimo; Zamporlini, Federica; Amici, Adolfo; Mazzola, Francesca; Orsomando, Giuseppe; Ruggieri, Silverio; Raffaelli, Nadia

    2017-04-15

    Nicotinamide riboside, the most recently discovered form of vitamin B3, and its phosphorylated form nicotinamide mononucleotide, have been shown to be potent supplements boosting intracellular nicotinamide adenine dinucleotide (NAD) levels, thus preventing or ameliorating metabolic and mitochondrial diseases in mouse models. Here we report for the first time on the simultaneous quantitation of nicotinamide riboside, nicotinamide mononucleotide and NAD in milk by means of a fluorometric, enzyme-coupled assay. Application of this assay to milk from different species revealed that the three vitamers were present in human and donkey milk, while being selectively distributed in the other milks. Human milk was the richest source of nicotinamide mononucleotide. Overall, the three vitamers accounted for a significant fraction of total vitamin B3 content. Pasteurization did not affect the bovine milk content of nicotinamide riboside, whereas UHT processing fully destroyed the vitamin. In human milk, NAD levels were significantly affected by the lactation time.

  11. Study on nicotinamide adenine dinucleotide adsorbed at nano-boehmite/water and nano-corundum/water interfaces.

    PubMed

    Li, Li; Xie, Yanfang; Wang, Yanping; Yang, Xiaodi; Chen, Rong Fu; Shen, Ren Fang

    2013-02-01

    In this study, the adsorption behaviors of nicotinamide adenine dinucleotide (NAD(+)) on nano-boehmite (γ-AlOOH) and nano-corundum (γ-Al(2)O(3)) surfaces were investigated. The results showed that NAD(+) was predominantly adsorbed at the boehmite/water and corundum/water interfaces in outer-sphere fashions by electrostatic interaction between NAD(+) phosphate and surface hydroxyl groups. However, the features of ATR-FTIR spectra suggested that some minor inner-sphere complex should be considered at low pH conditions on corundum surface, which was consistent with the effect of NAD(+) on dissolution rate of corundum. In addition, the adsorption data well fitted with Langmuir and Freundlich isotherms on the boehmite and corundum surfaces, respectively. Also, the Gibbs adsorption energy was negative on the boehmite surface, which indicated that the adsorption behavior was spontaneous.

  12. Assembly of alcohol oxidase in peroxisomes of the yeast Hansenula polymorpha requires the cofactor flavin adenine dinucleotide.

    PubMed Central

    Evers, M E; Titorenko, V I; van der Klei, I J; Harder, W; Veenhuis, M

    1994-01-01

    The peroxisomal flavoprotein alcohol oxidase (AO) is an octamer (600 kDa) consisting of eight identical subunits, each of which contains one flavin adenine dinucleotide molecule as a cofactor. Studies on a riboflavin (Rf) auxotrophic mutant of the yeast Hansenula polymorpha revealed that limitation of the cofactor led to drastic effects on AO import and assembly as well as peroxisome proliferation. Compared to wild-type control cells Rf-limitation led to 1) reduced levels of AO protein, 2) reduced levels of correctly assembled and activated AO inside peroxisomes, 3) a partial inhibition of peroxisomal protein import, leading to the accumulation of precursors of matrix proteins in the cytosol, and 4) a significant increase in peroxisome number. We argue that the inhibition of import may result from the saturation of a peroxisomal molecular chaperone under conditions that normal assembly of a major matrix protein inside the target organelle is prevented. Images PMID:7803851

  13. A label-free fluorescence DNA probe based on ligation reaction with quadruplex formation for highly sensitive and selective detection of nicotinamide adenine dinucleotide.

    PubMed

    Zhao, Jingjin; Zhang, Liangliang; Jiang, Jianhui; Shen, Guoli; Yu, Ruqin

    2012-05-11

    A simple label-free fluorescent sensing scheme for sensitive and selective detection of nicotinamide adenine dinucleotide (NAD(+)) has been developed based on DNA ligation reaction with ligand-responsive quadruplex formation. This approach can detect 0.5 nM NAD(+) with high selectivity against other NAD(+) analogs.

  14. The conserved baculovirus protein p33 (Ac92) is a flavin adenine dinucleotide-linked sulfhydryl oxidase

    SciTech Connect

    Long, C.M.; Rohrmann, G.F.; Merrill, G.F.

    2009-06-05

    Open reading frame 92 of the Autographa californica baculovirus (Ac92) is one of about 30 core genes present in all sequenced baculovirus genomes. Computer analyses predicted that the Ac92 encoded protein (called p33) and several of its baculovirus orthologs were related to a family of flavin adenine dinucleotide (FAD)-linked sulfhydryl oxidases. Alignment of these proteins indicated that, although they were highly diverse, a number of amino acids in common with the Erv1p/Alrp family of sulfhydryl oxidases are present. Some of these conserved amino acids are predicted to stack against the isoalloxazine and adenine components of FAD, whereas others are involved in electron transfer. To investigate this relationship, Ac92 was expressed in bacteria as a His-tagged fusion protein, purified, and characterized both spectrophotometrically and for its enzymatic activity. The purified protein was found to have the color (yellow) and absorption spectrum consistent with it being a FAD-containing protein. Furthermore, it was demonstrated to have sulfhydryl oxidase activity using dithiothreitol and thioredoxin as substrates.

  15. A Nicotinamide Adenine Dinucleotide Dispersed Multi-walled Carbon Nanotubes Electrode for Direct and Selective Electrochemical Detection of Uric Acid.

    PubMed

    Chen, Yan; Li, Yiwei; Ma, Yaohong; Meng, Qingjun; Yan, Yan; Shi, Jianguo

    2015-01-01

    A nanocomposite platform built with multi-walled carbon nanotubes (MWCNTs) and nicotinamide adenine dinucleotide (NAD(+)) via a noncovalent interaction between the large π systems in NAD(+) molecules and MWCNTs on a glassy carbon substrate was successfully developed for the sensitive and selective detection of uric acid (UA) in the presence of ascorbic acid (AA), dopamine (DA). NAD(+) has an adenine subunit and a nicotinamide subunit, which enabled interaction with the purine subunit of UA through a strong π-π interaction to enhance the specificity of UA. Compared with a bare glassy carbon electrode (GCE) and MWCNTs/GCE, the MWCNTs-NAD(+)/GCE showed a low background current and a remarkable enhancement of the oxidation peak current of UA. Using differential pulse voltammetry (DPV), a high sensitivity for the determination of UA was explored for the MWCNTs-NAD(+) modified electrode. A linear relationship between the DPV peak current of UA and its concentration could be obtained in the range of 0.05 - 10 μM with the detection limit as low as 10 nM (S/N = 3). This present strategy provides a novel and promising platform for the detection of UA in human urine and serum samples.

  16. Nucleotide sequence of yeast GDH1 encoding nicotinamide adenine dinucleotide phosphate-dependent glutamate dehydrogenase.

    PubMed

    Moye, W S; Amuro, N; Rao, J K; Zalkin, H

    1985-07-15

    The yeast GDH1 gene encodes NADP-dependent glutamate dehydrogenase. This gene was isolated by complementation of an Escherichia coli glutamate auxotroph. NADP-dependent glutamate dehydrogenase was overproduced 6-10-fold in Saccharomyces cerevisiae bearing GDH1 on a multicopy plasmid. The nucleotide sequence of the 1362-base pair coding region and 5' and 3' flanking sequences were determined. Transcription start sites were located by S1 nuclease mapping. Regulation of GDH1 was not maintained when the gene was present on a multicopy plasmid. Protein secondary structure predictions identified a region with potential to form the dinucleotide-binding domain. The amino acid sequences of the yeast and Neurospora crassa enzymes are 63% conserved. Unlike the N. crassa gene, yeast GDH1 has no introns.

  17. Purification and characterization of the enzymes involved in nicotinamide adenine dinucleotide degradation by Penicillium brevicompactum NRC 829.

    PubMed

    Ali, Thanaa Hamed; El-Ghonemy, Dina Helmy

    2016-06-01

    The present study was conducted to investigate a new pathway for the degradation of nicotinamide adenine dinucleotide (NAD) by Penicillium brevicompactum NRC 829 extracts. Enzymes involved in the hydrolysis of NAD, i.e. alkaline phosphatase, aminohydrolase and glycohydrolase were determined. Alkaline phosphatase was found to catalyse the sequential hydrolysis of two phosphate moieties of NAD molecule to nicotinamide riboside plus adenosine. Adenosine was then deaminated by aminohydrolase to inosine and ammonia. While glycohydrolase catalyzed the hydrolysis of the nicotinamide-ribosidic bond of NAD+ to produce nicotinamide and ADP-ribose in equimolar amounts, enzyme purification through a 3-step purification procedure revealed the existence of two peaks of alkaline phosphatases, and one peak contained deaminase and glycohydrolase activities. NAD deaminase was purified to homogeneity as estimated by sodium dodecyl sulphate-polyacrylamide gel electrophoresis with an apparent molecular mass of 91 kDa. Characterization and determination of some of NAD aminohydrolase kinetic properties were conducted due to its biological role in the regulation of cellular NAD level. The results also revealed that NAD did not exert its feedback control on nicotinamide amidase produced by P. brevicompactum.

  18. Electron-transfer studies with a new flavin adenine dinucleotide dependent glucose dehydrogenase and osmium polymers of different redox potentials.

    PubMed

    Zafar, Muhammad Nadeem; Wang, Xiaoju; Sygmund, Christoph; Ludwig, Roland; Leech, Dónal; Gorton, Lo

    2012-01-03

    A new extracellular flavin adenine dinucleotide (FAD)-dependent glucose dehydrogenase from Glomerella cingulata (GcGDH) was electrochemically studied as a recognition element in glucose biosensors. The redox enzyme was recombinantly produced in Pichia pastoris and homogeneously purified, and its glucose-oxidizing properties on spectrographic graphite electrodes were investigated. Six different Os polymers, the redox potentials of which ranged in a broad potential window between +15 and +489 mV versus the normal hydrogen electrode (NHE), were used to immobilize and "wire" GcGDH to the spectrographic graphite electrode's surface. The GcGDH/Os polymer modified electrodes were evaluated by chronoamperometry using flow injection analysis. The current response was investigated using a stepwisely increased applied potential. It was observed that the ratio of GcGDH/Os polymer and the overall loading of the enzyme electrode significantly affect the performance of the enzyme electrode for glucose oxidation. The best-suited Os polymer [Os(4,4'-dimethyl-2,2'-bipyridine)(2)(PVI)Cl](+) had a potential of +309 mV versus NHE, and the optimum GcGDH/Os polymer ratio was 1:2 yielding a maximum current density of 493 μA·cm(-2) at a 30 mM glucose concentration.

  19. 5' End Nicotinamide Adenine Dinucleotide Cap in Human Cells Promotes RNA Decay through DXO-Mediated deNADding.

    PubMed

    Jiao, Xinfu; Doamekpor, Selom K; Bird, Jeremy G; Nickels, Bryce E; Tong, Liang; Hart, Ronald P; Kiledjian, Megerditch

    2017-03-09

    Eukaryotic mRNAs generally possess a 5' end N7 methyl guanosine (m(7)G) cap that promotes their translation and stability. However, mammalian mRNAs can also carry a 5' end nicotinamide adenine dinucleotide (NAD(+)) cap that, in contrast to the m(7)G cap, does not support translation but instead promotes mRNA decay. The mammalian and fungal noncanonical DXO/Rai1 decapping enzymes efficiently remove NAD(+) caps, and cocrystal structures of DXO/Rai1 with 3'-NADP(+) illuminate the molecular mechanism for how the "deNADding" reaction produces NAD(+) and 5' phosphate RNA. Removal of DXO from cells increases NAD(+)-capped mRNA levels and enables detection of NAD(+)-capped intronic small nucleolar RNAs (snoRNAs), suggesting NAD(+) caps can be added to 5'-processed termini. Our findings establish NAD(+) as an alternative mammalian RNA cap and DXO as a deNADding enzyme modulating cellular levels of NAD(+)-capped RNAs. Collectively, these data reveal that mammalian RNAs can harbor a 5' end modification distinct from the classical m(7)G cap that promotes rather than inhibits RNA decay.

  20. Tea polyphenols regulate nicotinamide adenine dinucleotide phosphate oxidase subunit expression and ameliorate angiotensin II-induced hyperpermeability in endothelial cells.

    PubMed

    Ying, Chen-Jiang; Xu, Jin-Wen; Ikeda, Katsumi; Takahashi, Kyoko; Nara, Yasuo; Yamori, Yukio

    2003-10-01

    Out-of-control reactive oxygen species (ROS) signaling is one of the key events in the pathogenesis of endothelial dysfunction and essential hypertension. We observed that tea polyphenols decreased the production of ROS via regulation of the protein expression of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase in bovine carotid artery endothelial cells (BCAECs). Both green tea polyphenols (GTP) and black tea polyphenols (BTP) down-regulated the expression of NADPH oxidase subunits p22phox and p67phox while up-regulating catalase expression (p < 0.05, respectively). Pre-treatment with GTP or BTP for 24 h significantly decreased the superoxide anion level (p < 0.05) and permeable fluorescence intensities in Ang II-stimulated BCAECs. A decrease in cell permeability was also observed by pre-treatment with diphenylene iodonium chloride (DPI) or vitamin E (p < 0.05, respectively). The result demonstrates that tea polyphenols alleviate angiotensin (Ang) II-induced hyperpermeability mainly by decreasing ROS production. Our results suggest that tea polyphenols regulate ROS-related protein expression and may be beneficial in preventing endothelial cell dysfunction and development of cardiovascular diseases, including hypertension.

  1. Redox State of Flavin Adenine Dinucleotide Drives Substrate Binding and Product Release in Escherichia coli Succinate Dehydrogenase

    PubMed Central

    Cheng, Victor W.T.; Piragasam, Ramanaguru Siva; Rothery, Richard A.; Maklashina, Elena; Cecchini, Gary; Weiner, Joel H.

    2016-01-01

    The Complex II family of enzymes, comprising the respiratory succinate dehydrogenases and fumarate reductases, catalyze reversible interconversion of succinate and fumarate. In contrast to the covalent flavin adenine dinucleotide (FAD) cofactor assembled in these enzymes, the soluble fumarate reductases (e.g. that from Shewanella frigidimarina) that assemble a noncovalent FAD cannot catalyze succinate oxidation but retain the ability to reduce fumarate. In this study, an SdhA-H45A variant that eliminates the site of the 8α-N3-histidyl covalent linkage between the protein and the FAD was examined. The variants SdhA-R286A/K/Y and -H242A/Y, that target residues thought to be important for substrate binding and catalysis were also studied. The variants SdhA-H45A and -R286A/K/Y resulted in assembly of a noncovalent FAD cofactor, which led to a significant decrease (−87 mV or more) in its reduction potential. The variant enzymes were studied by electron paramagnetic resonance spectroscopy following stand-alone reduction and potentiometric titrations. The “free” and “occupied” states of the active site were linked to the reduced and oxidized states of the FAD, respectively. Our data allows for a proposed model of succinate oxidation that is consistent with tunnel diode effects observed in the succinate dehydrogenase enzyme and a preference for fumarate reduction catalysis in fumarate reductase homologues that assemble a noncovalent FAD. PMID:25569225

  2. Degradation of pentachlorophenol by a novel peroxidase-catalyzed process in the presence of reduced nicotinamide adenine dinucleotide.

    PubMed

    Li, Haitao; Li, Yuping; Cao, Hongbin; Li, Xingang; Zhang, Yi

    2011-03-01

    A novel horseradish peroxidase (HRP)-catalyzed H₂O₂ process in the presence of reduced nicotinamide adenine dinucleotide (NADH) was applied to remove aqueous pentachlorophenol (PCP). Parameters (pH, H₂O₂ concentration, HRP activity and NADH dosage) on PCP removal were investigated. It was found that initial 0.05mM PCP was removed by 98% in HRP-NADH-H₂O₂ system at pH 5.0 and 30°C for 1h. Addition of O₂ in HRP-NADH-H₂O₂ system enhanced the removal rate of PCP due to promoting hydroxyl radicals (.OH) and superoxide anion radical (.O₂⁻) generation, which were confirmed by electron paramagnetic resonance (EPR)-spin trapping method. PCP removal efficiency decreased when .O₂⁻ and H₂O₂ were scavenged by superoxide dismutase and catalase in HRP-NADH-O₂ system, indicating that .OH/.O₂⁻ played a great role in the degradation of PCP. Gas chromatography-mass spectrometry (GC-MS) analysis revealed that octachlorinated dibenzodioxin (OCDD) in residual solution was reduced after treated by the HRP-NADH-O₂ process, resulting in lower toxicity of treated solution than conventional enzymatic process. Two enzymatic-catalysis pathways were proposed for PCP removal in HRP-NADH-H₂O₂/O₂ system: (i) OH/.O₂⁻ free radical oxidation (ii) conventional phenoxy polymerization.

  3. A computational comparison of electron transfer from reduced ferredoxin to flavin adenine dinucleotide and a gold electrode.

    PubMed

    Walch, Stephen P; Komadina, Jason D; Prinz, Fritz B

    2009-05-21

    We have carried out calculations of the electronic structure of ferredoxin and of the electronic coupling matrix element Hif for electron transfer from reduced ferredoxin to flavin adenine dinucleotide (FAD) and to cluster models of the Au111 surface and a Au111 surface with a mercaptopyridene self-assembled monolayer (SAM). We conclude, based on Hif2, that a gold electrode is approximately 14 times less efficient as an electron acceptor than FAD and that the mercaptopyridine SAM enhances electron transfer. The magnitude of Hif is large enough for these systems that the weak coupling limit approximations may no longer be valid. However, the barrier to electron transfer in the strong coupling limit is computed to be small due to minimal geometry change between oxidized and reduced ferredoxin. MD simulations of the interaction of ferredoxin and protonated pyridine within a water solvation box indicate that the protonated pyridine does strongly orient the ferredoxin, favoring electron transfer as compared to a bare gold surface, where we speculate the orientation of the ferredoxin may be more random.

  4. Development of an enzymatic chromatography strip with nicotinamide adenine dinucleotide-tetrazolium coupling reactions for quantitative l-lactate analysis.

    PubMed

    Kan, Shu-Chen; Chang, Wei-Feng; Lan, Min-Chi; Lin, Chia-Chi; Lai, Wei-Shiang; Shieh, Chwen-Jen; Hsiung, Kuang-Pin; Liu, Yung-Chuan

    2015-02-15

    In this study, a dry assay of l-lactate via the enzymatic chromatographic test (ECT) was developed. An l-lactate dehydrogenase plus a nicotinamide adenine dinucleotide (NADH) regeneration reaction were applied simultaneously. Various tetrazolium salts were screened to reveal visible color intensities capable of determining the lactate concentrations in the sample. The optimal analysis conditions were as follows. The diaphorase (0.5 μl, 2(-6)U/μl) was immobilized in the test line of the ECT strip. Nitrotetrazolium blue chloride (5 μl, 12 mM), l-lactate dehydrogenase (1 μl, 0.25U/μl), and NAD(+) (2μl, 1.5×10(-5)M) were added into the mobile phase (100 μl) composed of 0.1% (w/w) Tween 20 in 10mM phosphate buffer (pH 9.0), and the process was left to run for 10 min. This detection had a linear range of 0.039 to 5mM with a detection limit of 0.047 mM. This quantitative analysis process for l-lactate was easy to operate with good stability and was proper for the point-of-care testing applications.

  5. Localization of nicotinamide adenine dinucleotide phosphate-diaphorase activity in electrosensory and electromotor systems of a gymnotiform teleost, Apteronotus leptorhynchus.

    PubMed

    Turner, R W; Moroz, L L

    1995-05-29

    The distribution of nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) activity was determined in electrosensory and electromotor systems of the weakly electric gymnotiform teleost Apteronotus leptorhynchus as an indicator of putative nitric oxide synthase-containing cells. NADPH-d activity was detected in electroreceptors and in afferent nerves of both ampullary and type I and type II tuberous organs. All cell bodies within the anterior lateral line nerve ganglion were positive for NADPH-d activity, as were the primary afferent axons and termination fields in the medullary electrosensory lateral line lobe. In the corpus cerebelli and valvula cerebelli, NADPH-d label was present in Purkinje cell somata, mossy fiber synaptic glomeruli, granule cells, and parallel fibers. In the midbrain, NADPH-d activity was apparent in layer VIIIB of the torus semicircularis dorsalis and in electrosensory laminae of the optic tectum. NADPH-d was particularly associated with diencephalic electrosensory and electromotor nuclei, including the prepacemaker nucleus, the nucleus subelectrosensorius, and the central posterior nucleus of the thalamus. Intense NADPH-d activity was present in pacemaker and relay cells of the medullary pacemaker nucleus but was absent from a novel class of smaller cells in this structure. Relay cell axons and spinal electromotor neurons and their axons within the electric organ were positive for NADPH-d activity. These results indicate that putative nitric oxide synthase-containing neurons in Apteronotus are localized preferentially to electrosensory and electromotor structures, suggesting a role for nitric oxide in determining the activity of cells involved in detecting or generating weakly electric fields.

  6. Electrochemical behavior of flavin adenine dinucleotide adsorbed onto carbon nanotube and nitrogen-doped carbon nanotube electrodes.

    PubMed

    Goran, Jacob M; Stevenson, Keith J

    2013-11-05

    Flavin adenine dinucleotide (FAD) is a cofactor for many enzymes, but also an informative redox active surface probe for electrode materials such as carbon nanotubes (CNTs) and nitrogen-doped CNTs (N-CNTs). FAD spontaneously adsorbs onto the surface of CNTs and N-CNTs, displaying Langmuir adsorption characteristics. The Langmuir adsorption model provides a means of calculating the electroactive surface area (ESA), the equilibrium constant for the adsorption and desorption processes (K), and the Gibbs free energy of adsorption (ΔG°). Traditional ESA measurements based on the diffusional flux of a redox active molecule to the electrode surface underestimate the ESA of porous materials because pores are not penetrated. Techniques such as gas adsortion (BET) overestimate the ESA because it includes both electroactive and inactive areas. The ESA determined by extrapolation of the Langmuir adsorption model with the electroactive surface probe FAD will penetrate pores and only include electroactive areas. The redox activity of adsorbed FAD also displays a strong dependency on pH, which provides a means of determining the pKa of the surface confined species. The pKa of FAD decreases as the nitrogen content in the CNTs increases, suggesting a decreased hydrophobicity of the N-CNT surface. FAD desorption at N-CNTs slowly transforms the main FAD surface redox reaction with E1/2 at -0.84 V into two new, reversible, surface confined redox reactions with E1/2 at -0.65 and -0.76 V (vs Hg/Hg2SO4), respectively (1.0 M sodium phosphate buffer pH = 6.75). This is the first time these redox reactions have been observed. The new surface confined redox reactions were not observed during FAD desorption from nondoped CNTs.

  7. Cytoprotection of pyruvic acid and reduced beta-nicotinamide adenine dinucleotide against hydrogen peroxide toxicity in neuroblastoma cells.

    PubMed

    Mazzio, Elizabeth A; Soliman, Karam F A

    2003-05-01

    Elevated production of hydrogen peroxide (H2O2) in the central nervous system has been implicated in the pathogenesis of several neurodegenerative diseases, including Parkinson's disease, ischemic reperfusion, stroke, and Alzheimer's disease. Pyruvic acid has a critical role in energy metabolism and a capability to nonenzymatically decarboxylate H2O2 into H2O. This study examined the effects of glycolytic regulation of pyruvic acid on H2O2 toxicity in murine neuroblastoma cells. Glycolytic energy substrates including D-(+)-glucose, D-(-) fructose and the adenosine transport blocker dipyridamole, were not effective in providing protection against H2O2 toxicity, negating energy as a factor. On the other hand, pyruvic acid completely prevented H2O2 toxicity, restoring the loss of ATP and cell viability. H2O2 toxicity was also attenuated by D-fructose 1,6 diphosphate (FBP), phospho (enol) pyruvate (PEP), niacinamide, beta-nicotinamide adenine dinucleotide (beta-NAD+), and reduced form (beta-NADH). Both FBP and PEP exerted positive kinetic effects on pyruvate kinase (PK) activity. Interestingly, only pyruvic acid and beta-NADH exhibited powerful stoichiometric H2O2 antioxidant properties. Further, beta-NADH may exert positive effects on PK activity. Subsequent pyruvic acid accumulation can lead to the recycling of beta-NAD+ through lactate dehydrogenase and beta-NADH through glyceraldehyde-3-phosphate dehydrogenase. It was concluded from these studies that intracellular pyruvic acid and beta-NADH appear to act in concert through glycolysis, to enhance H2O2 intracellular antioxidant capacity in neuroblastoma cells. Future research will be required to examine whether similar effects are observed in primary neuronal culture or intact tissue.

  8. Release of beta-nicotinamide adenine dinucleotide upon stimulation of postganglionic nerve terminals in blood vessels and urinary bladder.

    PubMed

    Smyth, Lisa M; Bobalova, Janette; Mendoza, Michael G; Lew, Christy; Mutafova-Yambolieva, Violeta N

    2004-11-19

    Chemical signaling in autonomic neuromuscular transmission involves agents that function as neurotransmitters and/or neuromodulators. Using high performance liquid chromatography techniques with fluorescence and electrochemical detection we observed that, in addition to ATP and norepinephrine (NE), electrical field stimulation (EFS, 4-16 Hz, 0.1-0.3 ms, 15 V, 60-120 s) of isolated vascular and non-vascular preparations co-releases a previously unidentified compound with apparent nucleotide or nucleoside structure. Extensive screening of more than 25 nucleotides and nucleosides followed by detailed peak identification revealed that beta-nicotinamide adenine dinucleotide (beta-NAD) is released in tissue superfusates upon EFS of canine mesenteric artery (CMA), canine urinary bladder, and murine urinary bladder in the amounts of 7.1 +/- 0.7, 26.5 +/- 4.5, and 15.1 +/- 3.2 fmol/mg of tissue, respectively. Smaller amounts of the beta-NAD metabolites cyclic adenosine 5'-diphosphoribose (cADPR) and ADPR were also present in the superfusates collected during EFS of CMA (2.5 +/- 0.9 and 5.8 +/- 0.8 fmol/mg of tissue, respectively), canine urinary bladder (1.8 +/- 0.5 and 9.0 +/- 6.0 fmol/mg of tissue, respectively), and murine urinary bladder (1.4 +/- 0.1 and 6.2 +/- 2.4 fmol/mg of tissue, respectively). The three nucleotides were also detected in the samples collected before EFS (0.2-1.6 fmol/mg of tissue). Exogenous beta-NAD, cADPR, and ADPR (all 100 nm) reduced the release of NE in CMA at 16 Hz from 27.8 +/- 6.0 fmol/mg of tissue to 15.5 +/- 5.0, 12 +/- 3.0, and 10.0 +/- 4.0 fmol/mg of tissue, respectively. In conclusion, we detected constitutive and nerve-evoked overflow of beta-NAD, cADPR, and ADPR in vascular and non-vascular smooth muscles, beta-NAD being the prevailing compound. These substances modulate the release of NE, implicating novel nucleotide mechanisms of autonomic nervous system control of smooth muscle.

  9. Changes of collagen and nicotinamide adenine dinucleotide in human cancerous and normal prostate tissues studied using native fluorescence spectroscopy with selective excitation wavelength

    NASA Astrophysics Data System (ADS)

    Pu, Yang; Wang, Wubao; Tang, Guichen; Alfano, Robert R.

    2010-07-01

    The fluorescence spectra of human cancerous and normal prostate tissues obtained by the selective excitation wavelength of 340 nm were measured. The contributions of principle biochemical components to tissue fluorescence spectra were investigated using the method of multivariate curve resolution with alternating least squares. The results show that there is a reduced contribution from the emission of collagen and increased contribution from nicotinamide adenine dinucleotide (NADH) in cancerous tissues as compared with normal tissue. This difference is attributed to the changes of relative contents of NADH and collagen during cancer development. This research may present a potential native biomarker for prostate cancer detection.

  10. Reduced nicotinamide adenine dinucleotide fluorescence lifetime detected poly(adenosine-5'-diphosphate-ribose) polymerase-1-mediated cell death and therapeutic effect of pyruvate

    NASA Astrophysics Data System (ADS)

    Guo, Han-Wen; Wei, Yau-Huei; Wang, Hsing-Wen

    2011-06-01

    Noninvasive detection of cell death has the potential for definitive diagnosis and monitoring treatment outcomes in real time. Reduced nicotinamide adenine dinucleotide (NADH) fluorescence intensity has long been used as a noninvasive optical probe of metabolic states. NADH fluorescence lifetime has recently been studied for its potential as an alternative optical probe of cellular metabolic states and cell death. In this study, we investigated the potential using NADH fluorescence intensity and/or lifetime to detect poly(adenosine-5'-diphosphate-ribose) polymerase-1 (PARP-1)-mediated cell death in HeLa cells. We also examined if NADH signals respond to treatment by pyruvate. The mechanism of PARP-1-mediated cell death has been well studied that extensive PARP-1 activation leads to cytosolic nicotinamide adenine dinucleotide depletion resulting in glycolytic inhibition, mitochondrial failure, and death. Pyruvate could restore electron transport chain to prevent energy failure and death. Our results show that NADH fluorescence lifetime, not intensity, responded to PARP-1-mediated cell death and the rescue effect of pyruvate. This lifetime change of NADH fluorescence happened before the collapse of mitochondrial membrane potential and mitochondrial uncoupling. Together with our previous findings in staurosporine-induced cell death, we suggest that NADH fluorescence lifetime increase during cell death is mainly due to increased protein-protein interactions but not the intracellular NADH content.

  11. Changes in phosphorylation of adenosine phosphate and redox state of nicotinamide-adenine dinucleotide (phosphate) in Geobacter sulfurreducens in response to electron acceptor and anode potential variation.

    PubMed

    Rose, Nicholas D; Regan, John M

    2015-12-01

    Geobacter sulfurreducens is one of the dominant bacterial species found in biofilms growing on anodes in bioelectrochemical systems. The intracellular concentrations of reduced and oxidized forms of nicotinamide-adenine dinucleotide (NADH and NAD(+), respectively) and nicotinamide-adenine dinucleotide phosphate (NADPH and NADP(+), respectively) as well as adenosine triphosphate (ATP), adenosine diphosphate (ADP), and adenosine monophosphate (AMP) were measured in G. sulfurreducens using fumarate, Fe(III)-citrate, or anodes poised at different potentials (110, 10, -90, and -190 mV (vs. SHE)) as the electron acceptor. The ratios of CNADH/CNAD+ (0.088±0.022) and CNADPH/CNADP+ (0.268±0.098) were similar under all anode potentials tested and with Fe(III)-citrate (reduced extracellularly). Both ratios significantly increased with fumarate as the electron acceptor (0.331±0.094 for NAD and 1.96±0.37 for NADP). The adenylate energy charge (the fraction of phosphorylation in intracellular adenosine phosphates) was maintained near 0.47 under almost all conditions. Anode-growing biofilms demonstrated a significantly higher molar ratio of ATP/ADP relative to suspended cultures grown on fumarate or Fe(III)-citrate. These results provide evidence that the cellular location of reduction and not the redox potential of the electron acceptor controls the intracellular redox potential in G. sulfurreducens and that biofilm growth alters adenylate phosphorylation.

  12. Facile synthesis of near infrared fluorescent trypsin-stabilized Ag nanoclusters with tunable emission for 1,4-dihydronicotinamide adenine dinucleotide and ethanol sensing.

    PubMed

    Liu, Siyu; Wang, Hui; Cheng, Zhen; Liu, Hongguang

    2015-07-30

    A facile chemical synthetic route was developed to prepare near-infrared fluorescent trypsin-stabilized Ag nanoclusters (Try-Ag NCs). The fluorescence emission wavelength of the produced Try-Ag NCs is tunable by simple adjusting pH value of the synthesis system, and the Try-Ag NCs offer a symmetric fluorescent excitation and emission peak. The fluorescence of Try-Ag NCs remains constant in the presence of various ions and molecules, and it can be effectively quenched by 1,4-dihydronicotinamide adenine dinucleotide (NADH) instead of its oxidized forms nicotinamide adenine dinucleotide (NAD(+)). This property enables the Try-Ag NCs to be a novel analytical platform to monitor biological reaction involved with NADH. In this work, the Try-Ag NCs was also applied to analyze ethanol based on the generation of NADH which was the product of NAD(+) and ethanol in the catalysis of alcohol dehydrogenase. And the proposed platform allowed ethanol to be determined in the range from 10 to 300 μmol/L with 5 μmol/L detection limit.

  13. Urea induced unfolding dynamics of flavin adenine dinucleotide (FAD): spectroscopic and molecular dynamics simulation studies from femto-second to nanosecond regime.

    PubMed

    Sengupta, Abhigyan; Singh, Reman K; Gavvala, Krishna; Koninti, Raj Kumar; Mukherjee, Arnab; Hazra, Partha

    2014-02-20

    Here, we investigate the effect of urea in the unfolding dynamics of flavin adenine dinucleotide (FAD), an important enzymatic cofactor, through steady state, time-resolved fluorescence spectroscopic and molecular dynamics (MD) simulation studies. Steady state results indicate the possibility of urea induced unfolding of FAD, inferred from increasing emission intensity of FAD with urea. The TCSPC and up-conversion results suggest that the stack-unstack dynamics of FAD severely gets affected in the presence of urea and leads to an increase in the unstack conformation population from 15% in pure water to 40% in 12 M urea. Molecular dynamics simulation was employed to understand the nature of the interaction between FAD and urea at the molecular level. Results depict that urea molecules replace many of the water molecules around adenine and isoalloxazine rings of FAD. However, the major driving force for the stability of this unstack conformations arises from the favorable stacking interaction of a significant fraction of the urea molecules with adenine and isoalloxazine rings of FAD, which overcomes the intramolecular stacking interaction between themselves observed in pure water.

  14. Biocomposite based on reduced graphene oxide film modified with phenothiazone and flavin adenine dinucleotide-dependent glucose dehydrogenase for glucose sensing and biofuel cell applications.

    PubMed

    Ravenna, Yehonatan; Xia, Lin; Gun, Jenny; Mikhaylov, Alexey A; Medvedev, Alexander G; Lev, Ovadia; Alfonta, Lital

    2015-10-06

    A novel composite material for the encapsulation of redox enzymes was prepared. Reduced graphene oxide film with adsorbed phenothiazone was used as a highly efficient composite for electron transfer between flavin adenine dinucleotide (FAD)-dependent glucose dehydrogenase and electrodes. Measured redox potential for glucose oxidation was lower than 0 V vs Ag/AgCl electrode. The fabricated biosensor showed high sensitivity of 42 mA M(-1) cm(-2), a linear range of glucose detection of 0.5-12 mM, and good reproducibility and stability as well as high selectivity for different interfering compounds. In a semibiofuel cell configuration, the hybrid film generated high power output of 345 μW cm(-2). These results demonstrate a promising potential for this composition in various bioelectronic applications.

  15. Diabetic complications within the context of aging: Nicotinamide adenine dinucleotide redox, insulin C-peptide, sirtuin 1-liver kinase B1-adenosine monophosphate-activated protein kinase positive feedback and forkhead box O3.

    PubMed

    Ido, Yasuo

    2016-07-01

    Recent research in nutritional control of aging suggests that cytosolic increases in the reduced form of nicotinamide adenine dinucleotide and decreasing nicotinamide adenine dinucleotide metabolism plays a central role in controlling the longevity gene products sirtuin 1 (SIRT1), adenosine monophosphate-activated protein kinase (AMPK) and forkhead box O3 (FOXO3). High nutrition conditions, such as the diabetic milieu, increase the ratio of reduced to oxidized forms of cytosolic nicotinamide adenine dinucleotide through cascades including the polyol pathway. This redox change is associated with insulin resistance and the development of diabetic complications, and might be counteracted by insulin C-peptide. My research and others' suggest that the SIRT1-liver kinase B1-AMPK cascade creates positive feedback through nicotinamide adenine dinucleotide synthesis to help cells cope with metabolic stress. SIRT1 and AMPK can upregulate liver kinase B1 and FOXO3, key factors that help residential stem cells cope with oxidative stress. FOXO3 directly changes epigenetics around transcription start sites, maintaining the health of stem cells. 'Diabetic memory' is likely a result of epigenetic changes caused by high nutritional conditions, which disturb the quiescent state of residential stem cells and impair tissue repair. This could be prevented by restoring SIRT1-AMPK positive feedback through activating FOXO3.

  16. Protonation mechanism and location of rate-determining steps for the Ascaris suum nicotinamide adenine dinucleotide-malic enzyme reaction from isotope effects and pH studies

    SciTech Connect

    Kiick, D.M.; Harris, B.G.; Cook, P.F.

    1986-01-14

    The pH dependence of the kinetic parameters and the primary deuterium isotope effects with nicotinamide adenine dinucleotide (NAD) and also thionicotinamide adenine dinucleotide (thio-NAD) as the nucleotide substrates were determined in order to obtain information about the chemical mechanism and location of rate-determining steps for the Ascaris suum NAD-malic enzyme reaction. The maximum velocity with thio-NAD as the nucleotide is pH-independent from pH 4.2 to 9.6, while with NAD, V decreases below a pK of 4.8. V/K for both nucleotides decreases below a pK of 5.6 and above a pK of 8.9. Both the tartronate pKi and V/Kmalate decrease below a pK of 4.8 and above a pK of 8.9. Oxalate is competitive vs. malate above pH 7 and noncompetitive below pH 7 with NAD as the nucleotide. The oxalate Kis increases from a constant value above a pK of 4.9 to another constant value above a pK of 6.7. The oxalate Kii also increases above a pK of 4.9, and this inhibition is enhanced by NADH. In the presence of thio-NAD the inhibition by oxalate is competitive vs. malate below pH 7. For thio-NAD, both DV and D(V/K) are pH-independent and equal to 1.7. With NAD as the nucleotide, DV decreases to 1.0 below a pK of 4.9, while D(V/KNAD) and D(V/Kmalate) are pH-independent. Above pH 7 the isotope effects on V and the V/K values for NAD and malate are equal to 1.45, the pH-independent value of DV above pH 7. Results indicate that substrates bind to only the correctly protonated form of the enzyme. Two enzyme groups are necessary for binding of substrates and catalysis. Both NAD and malate are released from the Michaelis complex at equal rates which are equal to the rate of NADH release from E-NADH above pH 7. Below pH 7 NADH release becomes more rate-determining as the pH decreases until at pH 4.0 it completely limits the overall rate of the reaction.

  17. Enhancement of anaerobic degradation of azo dye with riboflavin and nicotinamide adenine dinucleotide harvested by osmotic lysis of wasted fermentation yeasts.

    PubMed

    Victral, Davi M; Dias, Heitor R A; Silva, Silvana Q; Baeta, Bruno E L; Aquino, Sérgio F

    2017-02-01

    The study presented here aims at identifying the source of redox mediators (riboflavin), electron carriers nicotinamide adenine dinucleotide (NAD) and carbon to perform decolorization of azo dye under anaerobic conditions after osmotic shock pretreatment of residual yeast from industrial fermentation. Pretreatment conditions were optimized by Doehlert experiment, varying NaCl concentration, temperature, yeast density and time. After the optimization, the riboflavin concentration in the residual yeast lysate (RYL) was 46% higher than the one present in commercial yeast extract. Moreover, similar NAD concentration was observed in both extracts. Subsequently, two decolorization experiments were performed, that is, a batch experiment (48 h) and a kinetic experiment (102 h). The results of the batch experiment showed that the use of the RYL produced by the optimized method increased decolorization rates and led to color removal efficiencies similar to those found when using the commercial extract (∼80%) and from 23% to 50% higher when compared to the control (without redox mediators). Kinetics analysis showed that methane production was also higher in the presence of yeast extract and RYL, and biogas was mostly generated after stabilization of color removal. In all kinetics experiments the azo dye degradation followed the pseudo-second-order model, which suggested that there was a concomitant adsorption/degradation of the dye on the biomass cell surface. Therefore, results showed the possibility of applying the pretreated residual yeast to improve color removal under anaerobic conditions, which is a sustainable process.

  18. A label-free fluorescence strategy for selective detection of nicotinamide adenine dinucleotide based on a dumbbell-like probe with low background noise.

    PubMed

    Chen, Xuexu; Lin, Chunshui; Chen, Yiying; Wang, Yiru; Chen, Xi

    2016-03-15

    In this work we developed a novel label-free fluorescence sensing approach for the detection of nicotinamide adenine dinucleotide (NAD(+)) based on a dumbbell-like DNA probe designed for both ligation reaction and digestion reaction with low background noise. SYBR Green I (SG I), a double-helix dye, was chosen as the readout fluorescence signal. In the absence of NAD(+), the ligation reaction did not occur, but the probe was digested to mononucleotides after the addition of exonuclease I (Exo I) and exonuclease I (Exo III), resulting in a weak fluorescence intensity due to the weak interaction between SG I and mononucleotides. In the presence of NAD(+), the DNA probe was ligated by Escherichia coli DNA ligase, blocking the digestion by Exo I and Exo III. As a result, SG I was intercalated into the stem part of the DNA dumbbell probe and fluorescence enhancement was achieved. This method was simple in design, fast to operate, with good sensitivity and selectivity which could discriminate NAD(+) from its analogs.

  19. Tissue-specific regulation of sirtuin and nicotinamide adenine dinucleotide biosynthetic pathways identified in C57Bl/6 mice in response to high-fat feeding.

    PubMed

    Drew, Janice E; Farquharson, Andrew J; Horgan, Graham W; Williams, Lynda M

    2016-11-01

    The sirtuin (SIRT)/nicotinamide adenine dinucleotide (NAD) system is implicated in development of type 2 diabetes (T2D) and diet-induced obesity, a major risk factor for T2D. Mechanistic links have not yet been defined. SIRT/NAD system gene expression and NAD/NADH levels were measured in liver, white adipose tissue (WAT) and skeletal muscle from mice fed either a low-fat diet or high-fat diet (HFD) for 3 days up to 16 weeks. An in-house custom-designed multiplex gene expression assay assessed all 7 mouse SIRTs (SIRT1-7) and 16 enzymes involved in conversion of tryptophan, niacin, nicotinamide riboside and metabolic precursors to NAD. Significantly altered transcription was correlated with body weight, fat mass, plasma lipids and hormones. Regulation of the SIRT/NAD system was associated with early (SIRT4, SIRT7, NAPRT1 and NMNAT2) and late phases (NMNAT3, NMRK2, ABCA1 and CD38) of glucose intolerance. TDO2 and NNMT were identified as markers of HFD consumption. Altered regulation of the SIRT/NAD system in response to HFD was prominent in liver compared with WAT or muscle. Multiple components of the SIRTs and NAD biosynthetic enzymes network respond to consumption of dietary fat. Novel molecular targets identified above could direct strategies for dietary/therapeutic interventions to limit metabolic dysfunction and development of T2D.

  20. Protective effect of nicotinamide adenine dinucleotide (NAD(+)) against spinal cord ischemia-reperfusion injury via reducing oxidative stress-induced neuronal apoptosis.

    PubMed

    Xie, Lei; Wang, Zhenfei; Li, Changwei; Yang, Kai; Liang, Yu

    2017-02-01

    As previous studies demonstrate that oxidative stress and apoptosis play crucial roles in ischemic pathogenesis and nicotinamide adenine dinucleotide (NAD(+)) treatment attenuates oxidative stress-induced cell death among primary neurons and astrocytes as well as significantly reduce cerebral ischemic injury in rats. We used a spinal cord ischemia injury (SCII) model in rats to verify our hypothesis that NAD(+) could ameliorate oxidative stress-induced neuronal apoptosis. Adult male rats were subjected to transient spinal cord ischemia for 60min, and different doses of NAD(+) were administered intraperitoneally immediately after the start of reperfusion. Neurological function was determined by Basso, Beattie, Bresnahan (BBB) scores. The oxidative stress level was assessed by superoxide dismutase (SOD) activity and malondialdehyde (MDA) content. The degree of apoptosis was analyzed by deoxyuridinetriphosphate nick-end labeling (TUNEL) staining and protein levels of cleaved caspase-3 and AIF (apoptosis inducing factor). The results showed that NAD(+) at 50 or 100mg/kg significantly decreased the oxidative stress level and neuronal apoptosis in the spinal cord of ischemia-reperfusion rats compared with saline, as accompanied with the decreased oxidative stress, NAD(+) administration significantly restrained the neuronal apoptosis after ischemia injury while improved the neurological and motor function. These findings suggested that NAD(+) might protect against spinal cord ischemia-reperfusion via reducing oxidative stress-induced neuronal apoptosis.

  1. Differential effect of pH upon cyclic-ADP-ribose and nicotinate-adenine dinucleotide phosphate-induced Ca2+ release systems.

    PubMed Central

    Chini, E N; Liang, M; Dousa, T P

    1998-01-01

    We investigated the pH dependence and the effects of thimerosal and dithiothreitol (DTT) upon the Ca2+ release induced by cADP-ribose (cADPR) and nicotinate-adenine dinucleotide phosphate (NAADP) in sea urchin egg homogenates. Both Ca2+ release triggered by cADPR and the binding of [3H]cADPR to sea urchin egg homogenates were decreased by alkalization of the assay media from pH 7.2 to 8.9. In contrast, NAADP-triggered Ca2+ release was not influenced by changes in pH. The Ca2+ release induced by cADPR was potentiated by thimerosal and inhibited by DTT, but neither thimerosal nor DTT had any effect upon the Ca2+ release induced by NAADP. We conclude that cADPR-sensitive Ca2+-release mechanisms are dependent on pH of the assay media and are sensitive to thiol group modification. On the other hand, these functional properties are not shared by NAADP-regulated Ca2+ channels. PMID:9794787

  2. Increase of reduced nicotinamide adenine dinucleotide fluorescence lifetime precedes mitochondrial dysfunction in staurosporine-induced apoptosis of HeLa cells

    NASA Astrophysics Data System (ADS)

    Yu, Jia-Sin; Guo, Han-Wen; Wang, Chih-Hao; Wei, Yau-Huei; Wang, Hsing-Wen

    2011-03-01

    In vivo noninvasive detection of apoptosis represents a new tool that may yield a more definite diagnosis, a more accurate prognosis, and help improve therapies for human diseases. The intrinsic fluorescence of reduced nicotinamide adenine dinucleotide (NADH) may be a potential optical biomarker for the apoptosis detection because NADH is involved in the respiration for the mitochondrial membrane potential (ΔΨ) formation and adenosine-5'-triphosphate (ATP) synthesis, and the depletion of ΔΨ and ATP level is the hallmark of apoptosis. We have previously observed the NADH fluorescence lifetime change is associated with staurosporine (STS)-induced mitochondria-mediated apoptosis. However, its relationship with mitochondrial functions such as ΔΨ, ATP, and oxygen consumption rate is not clear. In this study, we investigated this relationship. Our results indicate that the NADH fluorescence lifetime increased when ΔΨ and ATP levels were equal to or higher than their values of controls and decreased before the depletion of ΔΨ and ATP, and the oxygen consumption rate did not change. These findings suggest that the increased NADH fluorescence lifetime in STS-induced cell death occurred before the depletion of ΔΨ and ATP and activation of caspase 3, and was not simply caused by cellular metabolic change. Furthermore, the NADH fluorescence lifetime change is associated with the pace of apoptosis.

  3. Deficiency of the iron-sulfur clusters of mitochondrial reduced nicotinamide-adenine dinucleotide-ubiquinone oxidoreductase (complex I) in an infant with congenital lactic acidosis.

    PubMed

    Moreadith, R W; Batshaw, M L; Ohnishi, T; Kerr, D; Knox, B; Jackson, D; Hruban, R; Olson, J; Reynafarje, B; Lehninger, A L

    1984-09-01

    We report the case of an infant with hypoglycemia, progressive lactic acidosis, an increased serum lactate/pyruvate ratio, and elevated plasma alanine, who had a moderate to profound decrease in the ability of mitochondria from four organs to oxidize pyruvate, malate plus glutamate, citrate, and other NAD+-linked respiratory substrates. The capacity to oxidize the flavin adenine dinucleotide-linked substrate, succinate, was normal. The most pronounced deficiency was in skeletal muscle, the least in kidney mitochondria. Enzymatic assays on isolated mitochondria ruled out defects in complexes II, III, and IV of the respiratory chain. Further studies showed that the defect was localized in the inner membrane mitochondrial NADH-ubiquinone oxidoreductase (complex I). When ferricyanide was used as an artificial electron acceptor, complex I activity was normal, indicating that electrons from NADH could reduce the flavin mononucleotide cofactor. However, electron paramagnetic resonance spectroscopy performed on liver submitochondrial particles showed an almost total loss of the iron-sulfur clusters characteristic of complex I, whereas normal signals were noted for other mitochondrial iron-sulfur clusters. This infant is presented as the first reported case of congenital lactic acidosis caused by a deficiency of the iron-sulfur clusters of complex I of the mitochondrial electron transport chain.

  4. Discovery of Nicotinamide Adenine Dinucleotide Binding Proteins in the Escherichia coli Proteome Using a Combined Energetic- and Structural-Bioinformatics-Based Approach.

    PubMed

    Zeng, Lingfei; Shin, Woong-Hee; Zhu, Xiaolei; Park, Sung Hoon; Park, Chiwook; Tao, W Andy; Kihara, Daisuke

    2017-02-03

    Protein-ligand interaction plays a critical role in regulating the biochemical functions of proteins. Discovering protein targets for ligands is vital to new drug development. Here, we present a strategy that combines experimental and computational approaches to identify ligand-binding proteins in a proteomic scale. For the experimental part, we coupled pulse proteolysis with filter-assisted sample preparation (FASP) and quantitative mass spectrometry. Under denaturing conditions, ligand binding affected protein stability, which resulted in altered protein abundance after pulse proteolysis. For the computational part, we used the software Patch-Surfer2.0. We applied the integrated approach to identify nicotinamide adenine dinucleotide (NAD)-binding proteins in the Escherichia coli proteome, which has over 4200 proteins. Pulse proteolysis and Patch-Surfer2.0 identified 78 and 36 potential NAD-binding proteins, respectively, including 12 proteins that were consistently detected by the two approaches. Interestingly, the 12 proteins included 8 that are not previously known as NAD binders. Further validation of these eight proteins showed that their binding affinities to NAD computed by AutoDock Vina are higher than their cognate ligands and also that their protein ratios in the pulse proteolysis are consistent with known NAD-binding proteins. These results strongly suggest that these eight proteins are indeed newly identified NAD binders.

  5. Detection, distribution, and organohalogen compound discovery implications of the reduced flavin adenine dinucleotide-dependent halogenase gene in major filamentous actinomycete taxonomic groups.

    PubMed

    Gao, Peng; Huang, Ying

    2009-07-01

    Halogenases have been shown to play a significant role in biosynthesis and introducing the bioactivity of many halogenated secondary metabolites. In this study, 54 reduced flavin adenine dinucleotide (FADH(2))-dependent halogenase gene-positive strains were identified after the PCR screening of a large collection of 228 reference strains encompassing all major families and genera of filamentous actinomycetes. The wide distribution of this gene was observed to extend to some rare lineages with higher occurrences and large sequence diversity. Subsequent phylogenetic analyses revealed that strains containing highly homologous halogenases tended to produce halometabolites with similar structures, and halogenase genes are likely to propagate by horizontal gene transfer as well as vertical inheritance within actinomycetes. Higher percentages of halogenase gene-positive strains than those of halogenase gene-negative ones contained polyketide synthase genes and/or nonribosomal peptide synthetase genes or displayed antimicrobial activities in the tests applied, indicating their genetic and physiological potentials for producing secondary metabolites. The robustness of this halogenase gene screening strategy for the discovery of particular biosynthetic gene clusters in rare actinomycetes besides streptomycetes was further supported by genome-walking analysis. The described distribution and phylogenetic implications of the FADH(2)-dependent halogenase gene present a guide for strain selection in the search for novel organohalogen compounds from actinomycetes.

  6. Electrochemical synthesis and characterization of TiO(2) nanoparticles and their use as a platform for flavin adenine dinucleotide immobilization and efficient electrocatalysis.

    PubMed

    Ashok Kumar, S; Lo, Po-Hsun; Chen, Shen-Ming

    2008-06-25

    Here, we report the electrochemical synthesis of TiO(2) nanoparticles (NPs) using the potentiostat method. Synthesized particles have been characterized by using x-ray diffraction (XRD) studies, atomic force microscopy (AFM) and scanning electron microscopy (SEM). The results revealed that the TiO(2) film produced was mainly composed of rutile and that the particles are of a size in the range of 100 ± 50 nm. TiO(2) NPs were used for the modification of a screen printed carbon electrode (SPE). The resulting TiO(2) film coated SPE was used to immobilize flavin adenine dinucleotide (FAD). The flavin enzyme firmly attached onto the metal oxide surface and this modified electrode showed promising electrocatalytic activities towards the reduction of hydrogen peroxide (H(2)O(2)) in physiological conditions. The electrochemistry of FAD confined in the oxide film was investigated. The immobilized FAD displayed a pair of redox peaks with a formal potential of -0.42 V in pH 7.0 oxygen-free phosphate buffers at a scan rate of 50 mV s(-1). The FAD in the nanostructured TiO(2) film retained its bioactivity and exhibited excellent electrocatalytic response to the reduction of H(2)O(2), based on which a mediated biosensor for H(2)O(2) was achieved. The linear range for the determination of H(2)O(2) was from 0.15 × 10(-6) to 3.0 × 10(-3) M with the detection limit of 0.1 × 10(-6) M at a signal-to-noise ratio of 3. The stability and repeatability of the biosensor is also discussed.

  7. Oxidation of C1 Compounds by Particulate fractions from Methylococcus capsulatus: distribution and properties of methane-dependent reduced nicotinamide adenine dinucleotide oxidase (methane hydroxylase).

    PubMed Central

    Ribbons, D W

    1975-01-01

    Cell-free particulate fractions of extracts from the obligate methylotroph Methylococcus capsulatus catalyze the reduced nicotinamide adenine dinucleotide (NADH) and O2-dependent oxidation of methane (methane hydroxylase). The only oxidation product detected was formate. These preparations also catalyze the oxidation of methanol and formaldehyde to formate in the presence or absence of phenazine methosulphate with oxygen as the terminal electron acceptor. Methane hydroxylase activity cannot be reproducibly obtained from disintegrated cell suspensions even though the whole cells actively respired when methane was presented as a substrate. Varying the disintegration method or extraction medium had no significant effect on the activities obtained. When active particles were obtained, hydroxylase activity was stable at 0 C for days. Methane hydroxylase assays were made by measuring the methane-dependent oxidation of NADH by O2. In separate experiments, methane consumption and the accumulation of formate were also demonstrated. Formate is not oxidized by these particulate fractions. The effects of particle concentration, temperature, pH, and phosphate concentration on enzymic activity are described. Ethane is utilized in the presence of NADH and O2. The stoichiometric relationships of the reaction(s) with methane as substrate were not established since (i) the presumed initial product, methanol, is also oxidized to formate, and (ii) the contribution that NADH oxidase activity makes to the observed consumption of reactants could not be assessed in the presence of methane. Studies with known inhibitors of electron transport systems indicate that the path of electron flow from NADH to oxygen is different for the NADH oxidase, methane hydroxylase, and methanol oxidase activities. Images PMID:238946

  8. Spinal Cord Injury Leads to Hyperoxidation and Nitrosylation of Skeletal Muscle Ryanodine Receptor-1 Associated with Upregulation of Nicotinamide Adenine Dinucleotide Phosphate Oxidase 4.

    PubMed

    Liu, Xin-Hua; Harlow, Lauren; Graham, Zachary A; Bauman, William A; Cardozo, Christopher

    2017-02-27

    Spinal cord injury (SCI) results in marked atrophy and dysfunction of skeletal muscle. There are currently no effective treatments for SCI-induced muscle atrophy or the dysfunction of the remaining muscle tissue. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-4 (Nox4) produces reactive oxygen species (ROS) in sarcoplasmic reticulum (SR) and has been identified as an important O2 sensor in skeletal muscle. Ryanodine receptors (RyRs) are calcium (Ca(2+)) channels that are responsible for Ca(2+) release from SR. In skeletal muscle, type1 RyR (RyR1) is predominantly functional. RyR1 is regulated by multiple proteins, including calstabin1, which assures that they close appropriately once contraction has ceased. RyR1 function is also regulated by oxidation and redox-dependent cysteine nitrosylation. Excessive oxidation/nitrosylation of RyR1 is associated with dissociation of calstabin1 and reduced muscle force generation. However, whether Nox4 levels in skeletal muscle are elevated or whether RyR1 is oxidized or nitrosylated after SCI has not been determined. In this study, we examined Nox4 expression, oxidation/nitrolysation status, and association of calstabin1 with RyR1 in skeletal muscle derived from rats that were subjected to T4 complete transection (SCI), and observed elevated expression of Nox4 messenger RNA and protein in muscle after SCI associated with enhanced binding of Nox4 to RyR1, increased oxidation and nitrosylation of RyR1, and dissociation of calstabin1 from RyR1 in SCI rat muscle. Our data suggest that RyR1 dysfunction resulting from excessive oxidation/nitrosylation may contribute to reduced specific force after SCI and suggest that Nox4 may be the source of ROS responsible for increased oxidation and nitrosylation of RyR1.

  9. A novel flavin adenine dinucleotide (FAD) containing d-lactate dehydrogenase from the thermoacidophilic crenarchaeota Sulfolobus tokodaii strain 7: purification, characterization and expression in Escherichia coli.

    PubMed

    Satomura, Takenori; Kawakami, Ryushi; Sakuraba, Haruhiko; Ohshima, Toshihisa

    2008-07-01

    Dye-linked D-lactate dehydrogenase activity was found in the crude extract of a continental thermoacidophilic crenarchaeota, Sulfolobus tokodaii strain 7, and was purified 375-fold through four sequential chromatography steps. With a molecular mass of about 93 kDa, this enzyme was a homodimer comprised of identical subunits with molecular masses of about 48 kDa. The enzyme retained its full activity after incubation at 80 degrees C for 10 min and after incubation at pHs ranging from 6.5 to 10.0 for 30 min at 50 degrees C. The preferred substrate for this enzyme was D-lactate, with 2,6-dichloroindophenol serving as the electron acceptor. Using high-performance liquid chromatography (HPLC), the enzyme's prosthetic group was determined to be flavin adenine dinucleotide (FAD). Its N-terminal amino acid sequence was MLEGIEYSQGEEREDFVGFKIKPKI. Using that sequence and previously reported genome information, the gene encoding the enzyme (ST0649) was identified. It was subsequently cloned and expressed in Escherichia coli and found to encode a polypeptide of 440 amino acids with a calculated molecular weight of 49,715. The amino acid sequence of this dye-linked D-lactate dehydrogenase showed higher homology (39% identity) with that of a glycolate oxidase subunit homologue from Archaeoglobus fulgidus, but less similarity (32% identity) to D-lactate dehydrogenase from A. fulgidus. Taken together, our findings indicate that the dye-linked D-lactate dehydrogenase from S. tokodaii is a novel type of FAD containing D-lactate dehydrogenase.

  10. Characterization of 4-Hydroxyphenylacetate 3-Hydroxylase (HpaB) of Escherichia coli as a Reduced Flavin Adenine Dinucleotide-Utilizing Monooxygenase

    PubMed Central

    Xun, Luying; Sandvik, Erik R.

    2000-01-01

    4-Hydroxyphenylacetate 3-hydroxylase (HpaB and HpaC) of Escherichia coli W has been reported as a two-component flavin adenine dinucleotide (FAD)-dependent monooxygenase that attacks a broad spectrum of phenolic compounds. However, the function of each component in catalysis is unclear. The large component (HpaB) was demonstrated here to be a reduced FAD (FADH2)-utilizing monooxygenase. When an E. coli flavin reductase (Fre) having no apparent homology with HpaC was used to generate FADH2 in vitro, HpaB was able to use FADH2 and O2 for the oxidation of 4-hydroxyphenylacetate. HpaB also used chemically produced FADH2 for 4-hydroxyphenylacetate oxidation, further demonstrating that HpaB is an FADH2-utilizing monooxygenase. FADH2 generated by Fre was rapidly oxidized by O2 to form H2O2 in the absence of HpaB. When HpaB was included in the reaction mixture without 4-hydroxyphenylacetate, HpaB bound FADH2 and transitorily protected it from rapid autoxidation by O2. When 4-hydroxyphenylacetate was also present, HpaB effectively competed with O2 for FADH2 utilization, leading to 4-hydroxyphenylacetate oxidation. With sufficient amounts of HpaB in the reaction mixture, FADH2 produced by Fre was mainly used by HpaB for the oxidation of 4-hydroxyphenylacetate. At low HpaB concentrations, most FADH2 was autoxidized by O2, causing uncoupling. However, the coupling of the two enzymes' activities was increased by lowering FAD concentrations in the reaction mixture. A database search revealed that HpaB had sequence similarities to several proteins and gene products involved in biosynthesis and biodegradation in both bacteria and archaea. This is the first report of an FADH2-utilizing monooxygenase that uses FADH2 as a substrate rather than as a cofactor. PMID:10653707

  11. A Novel Nicotinamide Adenine Dinucleotide Correction Method for Mitochondrial Ca2+ Measurement with FURA-2-FF in Single Permeabilized Ventricular Myocytes of Rat

    PubMed Central

    Lee, Jeong Hoon; Ha, Jeong Mi

    2015-01-01

    Fura-2 analogs are ratiometric fluoroprobes that are widely used for the quantitative measurement of [Ca2+]. However, the dye usage is intrinsically limited, as the dyes require ultraviolet (UV) excitation, which can also generate great interference, mainly from nicotinamide adenine dinucleotide (NADH) autofluorescence. Specifically, this limitation causes serious problems for the quantitative measurement of mitochondrial [Ca2+], as no available ratiometric dyes are excited in the visible range. Thus, NADH interference cannot be avoided during quantitative measurement of [Ca2+] because the majority of NADH is located in the mitochondria. The emission intensity ratio of two different excitation wavelengths must be constant when the fluorescent dye concentration is the same. In accordance with this principle, we developed a novel online method that corrected NADH and Fura-2-FF interference. We simultaneously measured multiple parameters, including NADH, [Ca2+], and pH/mitochondrial membrane potential; Fura-2-FF for mitochondrial [Ca2+] and TMRE for Ψm or carboxy-SNARF-1 for pH were used. With this novel method, we found that the resting mitochondrial [Ca2+] concentration was 1.03 µM. This 1 µM cytosolic Ca2+ could theoretically increase to more than 100 mM in mitochondria. However, the mitochondrial [Ca2+] increase was limited to ~30 µM in the presence of 1 µM cytosolic Ca2+. Our method solved the problem of NADH signal contamination during the use of Fura-2 analogs, and therefore the method may be useful when NADH interference is expected. PMID:26170742

  12. The distribution of nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) in the medulla oblongata, spinal cord, cranial and spinal nerves of frog, Microhyla ornata.

    PubMed

    Jadhao, Arun G; Biswas, Saikat P; Bhoyar, Rahul C; Pinelli, Claudia

    2017-04-01

    Nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) enzymatic activity has been reported in few amphibian species. In this study, we report its unusual localization in the medulla oblongata, spinal cord, cranial nerves, spinal nerves, and ganglions of the frog, Microhyla ornata. In the rhombencephalon, at the level of facial and vagus nerves, the NADPH-d labeling was noted in the nucleus of the abducent and facial nerves, dorsal nucleus of the vestibulocochlear nerve, the nucleus of hypoglossus nerve, dorsal and lateral column nucleus, the nucleus of the solitary tract, the dorsal field of spinal grey, the lateral and medial motor fields of spinal grey and radix ventralis and dorsalis (2-10). Many ependymal cells around the lining of the fourth ventricle, both facial and vagus nerves and dorsal root ganglion, were intensely labeled with NADPH-d. Most strikingly the NADPH-d activity was seen in small and large sized motoneurons in both medial and lateral motor neuron columns on the right and left sides of the brain. This is the largest stained group observed from the caudal rhombencephalon up to the level of radix dorsalis 10 in the spinal cord. The neurons were either oval or elongated in shape with long processes and showed significant variation in the nuclear and cellular diameter. A massive NADPH-d activity in the medulla oblongata, spinal cord, and spinal nerves implied an important role of this enzyme in the neuronal signaling as well as in the modulation of motor functions in the peripheral nervous systems of the amphibians.

  13. β-Nicotinamide adenine dinucleotide acts at prejunctional adenosine A1 receptors to suppress inhibitory musculomotor neurotransmission in guinea pig colon and human jejunum

    PubMed Central

    Wang, Guo-Du; Wang, Xi-Yu; Liu, Sumei; Xia, Yun; Zou, Fei; Qu, Meihua; Needleman, Bradley J.; Mikami, Dean J.

    2015-01-01

    Intracellular microelectrodes were used to record neurogenic inhibitory junction potentials in the intestinal circular muscle coat. Electrical field stimulation was used to stimulate intramural neurons and evoke contraction of the smooth musculature. Exposure to β-nicotinamide adenine dinucleotide (β-NAD) did not alter smooth muscle membrane potential in guinea pig colon or human jejunum. ATP, ADP, β-NAD, and adenosine, as well as the purinergic P2Y1 receptor antagonists MRS 2179 and MRS 2500 and the adenosine A1 receptor agonist 2-chloro-N6-cyclopentyladenosine, each suppressed inhibitory junction potentials in guinea pig and human preparations. β-NAD suppressed contractile force of twitch-like contractions evoked by electrical field stimulation in guinea pig and human preparations. P2Y1 receptor antagonists did not reverse this action. Stimulation of adenosine A1 receptors with 2-chloro-N6-cyclopentyladenosine suppressed the force of twitch contractions evoked by electrical field stimulation in like manner to the action of β-NAD. Blockade of adenosine A1 receptors with 8-cyclopentyl-1,3-dipropylxanthine suppressed the inhibitory action of β-NAD on the force of electrically evoked contractions. The results do not support an inhibitory neurotransmitter role for β-NAD at intestinal neuromuscular junctions. The data suggest that β-NAD is a ligand for the adenosine A1 receptor subtype expressed by neurons in the enteric nervous system. The influence of β-NAD on intestinal motility emerges from adenosine A1 receptor-mediated suppression of neurotransmitter release at inhibitory neuromuscular junctions. PMID:25813057

  14. Nicotinamide Adenine Dinucleotide Phosphate Oxidase–Mediated Redox Signaling and Vascular Remodeling by 16α-Hydroxyestrone in Human Pulmonary Artery Cells

    PubMed Central

    Hood, Katie Y.; Montezano, Augusto C.; Harvey, Adam P.; Nilsen, Margaret; MacLean, Margaret R.

    2016-01-01

    Estrogen and oxidative stress have been implicated in pulmonary arterial hypertension (PAH). Mechanisms linking these systems are elusive. We hypothesized that estrogen metabolite, 16α-hydroxyestrone (16αOHE1), stimulates nicotinamide adenine dinucleotide phosphate oxidase (Nox)–induced reactive oxygen species (ROS) generation and proliferative responses in human pulmonary artery smooth muscle cells (hPASMCs) and that in PAH aberrant growth signaling promotes vascular remodeling. The pathophysiological significance of estrogen–Nox–dependent processes was studied in female Nox1−/− and Nox4−/− mice with PAH. PASMCs from control subjects (control hPASMCs) and PAH patients (PAH-hPASMCs) were exposed to estrogen and 16αOHE1 in the presence/absence of inhibitors of Nox, cytochrome P450 1B1, and estrogen receptors. Estrogen, through estrogen receptor-α, increased Nox-derived ROS and redox-sensitive growth in hPASMCs, with greater effects in PAH-hPASMCs versus control hPASMCs. Estrogen effects were inhibited by cytochrome P450 1B1 blockade. 16αOHE1 stimulated transient ROS production in hPASMCs, with sustained responses in PAH-hPASMCs. Basal expression of Nox1/Nox4 was potentiated in PAH-hPASMCs. In hPASMCs, 16αOHE1 increased Nox1 expression, stimulated irreversible oxidation of protein tyrosine phosphatases, decreased nuclear factor erythroid–related factor 2 activity and expression of nuclear factor erythroid–related factor 2–regulated antioxidant genes, and promoted proliferation. This was further amplified in PAH-hPASMCs. Nox1−/− but not Nox4−/− mice were protected against PAH and vascular remodeling. Our findings demonstrate that in PAH-hPASMCs, 16αOHE1 stimulates redox-sensitive cell growth primarily through Nox1. Supporting this, in vivo studies exhibited protection against pulmonary hypertension and remodeling in Nox1−/− mice. This study provides new insights through Nox1/ROS and nuclear factor erythroid–related factor 2

  15. Dynamic and static quenching of 1,N6-ethenoadenine fluorescence in nicotinamide 1,N6-ethenoadenine dinucleotide and in 1,N6-etheno-9-(3-(indol-3-yl) propyl) adenine.

    PubMed Central

    Gruber, B A; Leonard, N J

    1975-01-01

    For nicotinamide 1,N6-ethenoadenine dinucleotide (epsilonNAD+), the fluorescent analog of NAD+, in neutral aqueous solution the quantum yield has been determined to be 0.028 and the fluorescent lifetime, 2.1 nsec. Simultaneous determination of quantum yields and lifetimes of epsilonNAD+ and of the "half molecule" epsilonAMP allows the calculation of the percentage of stacked and open conformations of the dinucleotide. At 25 degrees in neutral aqueous solution there is 45 +/- 5% of stacked forms. The value of the fluorescent impurities, especially those containing the epsilon-adenosine moiety, and a purification procedure using high performance liquid chromatography was devised to obtain fluorescently homogeneous preparations. In order to study the effect on epsilon-adenosine fluorescence caused by the possible close proximity of a tryptophan in a polypeptide chain or protein, we have prepared 1,N6-etheno-9-[3-(indol-3-yl)propyl]adenine (epsilonAde9-C3-Ind3), a model compound in which indole is used as a neutral substitute for tryptophan. Fluorescence studies on epsilonAde9-C3-Ind3 show that the formation of an intramolecular complex results in complete quenching of the epsilon-adenine fluorescence. It is therefore predictable that positioning of the epsilon-adenosine of any fluorescent coenzyme moiety (e.q., epsilonATP, epsilonADP) in close proximity to a tryptophan in a protein will result in complete fluorescence quenching of the former. PMID:172889

  16. Evolution of function in the "two dinucleotide binding domains" flavoproteins.

    PubMed

    Ojha, Sunil; Meng, Elaine C; Babbitt, Patricia C

    2007-07-01

    Structural and biochemical constraints force some segments of proteins to evolve more slowly than others, often allowing identification of conserved structural or sequence motifs that can be associated with substrate binding properties, chemical mechanisms, and molecular functions. We have assessed the functional and structural constraints imposed by cofactors on the evolution of new functions in a superfamily of flavoproteins characterized by two-dinucleotide binding domains, the "two dinucleotide binding domains" flavoproteins (tDBDF) superfamily. Although these enzymes catalyze many different types of oxidation/reduction reactions, each is initiated by a stereospecific hydride transfer reaction between two cofactors, a pyridine nucleotide and flavin adenine dinucleotide (FAD). Sequence and structural analysis of more than 1,600 members of the superfamily reveals new members and identifies details of the evolutionary connections among them. Our analysis shows that in all of the highly divergent families within the superfamily, these cofactors adopt a conserved configuration optimal for stereospecific hydride transfer that is stabilized by specific interactions with amino acids from several motifs distributed among both dinucleotide binding domains. The conservation of cofactor configuration in the active site restricts the pyridine nucleotide to interact with FAD from the re-side, limiting the flow of electrons from the re-side to the si-side. This directionality of electron flow constrains interactions with the different partner proteins of different families to occur on the same face of the cofactor binding domains. As a result, superimposing the structures of tDBDFs aligns not only these interacting proteins, but also their constituent electron acceptors, including heme and iron-sulfur clusters. Thus, not only are specific aspects of the cofactor-directed chemical mechanism conserved across the superfamily, the constraints they impose are manifested in the

  17. Molecular characterization of Fasciola hepatica and phylogenetic analysis based on mitochondrial (nicotiamide adenine dinucleotide dehydrogenase subunit I and cytochrome oxidase subunit I) genes from the North-East of Iran

    PubMed Central

    Reaghi, Saber; Haghighi, Ali; Harandi, Majid Fasihi; Spotin, Adel; Arzamani, Kourosh; Rouhani, Soheila

    2016-01-01

    Aim: Fascioliasis is one of the most zoonotic diseases with global extension. As the epidemiological distribution of Fasciola may lead to various genetic patterns of the parasite, the aim of this study is to identify Fasciola hepatica based on spermatogenesis, and phylogenetic analysis using mitochondrial (nicotiamide adenine dinucleotide dehydrogenase subunit I [ND1] and cytochrome oxidase subunit I) gene marker. Materials and Methods: In this study, 90 F. hepatica collected from 30 cattle at slaughterhouse located in three different geographical locations in the North-East of Iran were evaluated based on spermatogenetic ability and internal transcribed spacer 1 gene restriction fragment length polymorphism pattern. Genetic diversity and phylogenetic relationship using mtDNA gene marker for the isolates from the North-East of Iran, and other countries were then analyzed. Results: Partial sequences of mtDNA showed eight haplotypes in both genes. The phylogenic analysis using neighbor joining as well as maximum likelihood methods showed similar topologies of trees. Pairwise fixation index between different F. hepatica populations calculated from the nucleotide data set of ND1 gene are statistically significant and show the genetic difference. Conclusion: F. hepatica found in this region of Iran has different genetic structures through the other Fasciola populations in the world. PMID:27733809

  18. Two-pore Channels (TPC2s) and Nicotinic Acid Adenine Dinucleotide Phosphate (NAADP) at Lysosomal-Sarcoplasmic Reticular Junctions Contribute to Acute and Chronic β-Adrenoceptor Signaling in the Heart*

    PubMed Central

    Capel, Rebecca A.; Bolton, Emma L.; Lin, Wee K.; Aston, Daniel; Wang, Yanwen; Liu, Wei; Wang, Xin; Burton, Rebecca-Ann B.; Bloor-Young, Duncan; Shade, Kai-Ting; Ruas, Margarida; Parrington, John; Churchill, Grant C.; Lei, Ming; Galione, Antony; Terrar, Derek A.

    2015-01-01

    Ca2+-permeable type 2 two-pore channels (TPC2) are lysosomal proteins required for nicotinic acid adenine dinucleotide phosphate (NAADP)-evoked Ca2+ release in many diverse cell types. Here, we investigate the importance of TPC2 proteins for the physiology and pathophysiology of the heart. NAADP-AM failed to enhance Ca2+ responses in cardiac myocytes from Tpcn2−/− mice, unlike myocytes from wild-type (WT) mice. Ca2+/calmodulin-dependent protein kinase II inhibitors suppressed actions of NAADP in myocytes. Ca2+ transients and contractions accompanying action potentials were increased by isoproterenol in myocytes from WT mice, but these effects of β-adrenoreceptor stimulation were reduced in myocytes from Tpcn2−/− mice. Increases in amplitude of L-type Ca2+ currents evoked by isoproterenol remained unchanged in myocytes from Tpcn2−/− mice showing no loss of β-adrenoceptors or coupling mechanisms. Whole hearts from Tpcn2−/− mice also showed reduced inotropic effects of isoproterenol and a reduced tendency for arrhythmias following acute β-adrenoreceptor stimulation. Hearts from Tpcn2−/− mice chronically exposed to isoproterenol showed less cardiac hypertrophy and increased threshold for arrhythmogenesis compared with WT controls. Electron microscopy showed that lysosomes form close contacts with the sarcoplasmic reticulum (separation ∼25 nm). We propose that Ca2+-signaling nanodomains between lysosomes and sarcoplasmic reticulum dependent on NAADP and TPC2 comprise an important element in β-adrenoreceptor signal transduction in cardiac myocytes. In summary, our observations define a role for NAADP and TPC2 at lysosomal/sarcoplasmic reticulum junctions as unexpected but major contributors in the acute actions of β-adrenergic signaling in the heart and also in stress pathways linking chronic stimulation of β-adrenoceptors to hypertrophy and associated arrhythmias. PMID:26438825

  19. Nicotinamide Adenine Dinucleotide Based Therapeutics, Update.

    PubMed

    Pankiewicz, K W; Petrelli, R; Singh, R; Felczak, K

    2015-01-01

    About 500 NAD (P)-dependent enzymes in the cell use NAD (P) as a cofactor or a substrate. This family of broadly diversified enzymes is crucial for maintaining homeostasis of all living organisms. The NAD binding domain of these enzymes is conserved and it was believed that NAD mimics would not be of therapeutic value due to lack of selectivity. Consequently, only mycophenolic acid which selectively binds at the cofactor pocket of NAD-dependent IMP-dehydrogenase (IMPDH) has been approved as an immunosuppressant. Recently, it became clear that the NAD (P)-binding domain was structurally much more diversified than anticipated and numerous highly potent and selective inhibitors of NAD (P) dependent enzymes have been reported. It is likely, that as in the case of protein kinases inhibitors, inhibitors of NAD (P)-dependent enzymes would find soon their way to the clinic. In this review, recent developments of selective inhibitors of NAD-dependent human IMPDH, as well as inhibitors of IMPDHs from parasites, and from bacterial sources are reported. Therapies against Cryptosporidium parvum and the development of new antibiotics that are on the horizon will be discussed. New inhibitors of bacterial NAD-ligases, NAD-kinases, NMN-adenylyl transferases, as well as phosphoribosyl transferases are also described. Although none of these compounds has yet to be approved, the progress in revealing and understanding crucial factors that might allow for designing more potent and efficient drug candidates is enormous and highly encouraging.

  20. Unprecedented head-to-head right-handed cross-links between the antitumor bis(mu-N,N'-di-p-tolylformamidinate) dirhodium(II,II) core and the dinucleotide d(ApA) with the adenine bases in the rare imino form.

    PubMed

    Chifotides, Helen T; Dunbar, Kim R

    2007-10-17

    Reactions of the anticancer active compound cis-[Rh2(DTolF)2(CH3CN)6](BF4)2 with 9-ethyladenine (9-EtAdeH) or the dinucleotide d(ApA) proceed with bridging adenine bases in the rare imino form (A*), spanning the Rh-Rh bond at equatorial positions via N7/N6. The inflection points for the pH-dependent H2 and H8 NMR resonance curves of cis-[Rh2(DTolF)2(9-EtAdeH)2](BF4)2 correspond to N1H deprotonation of the metal-stabilized rare imino tautomer, which takes place at pKa approximately 7.5 in CD3CN-d3, a considerably reduced value as compared to that of the imino form of 9-EtAdeH. Similarly, coordination of the metal atoms to the N7/N6 adenine sites in Rh2(DTolF)2{d(ApA)} induces formation of the rare imino tautomer of the bases with a concomitant substantial decrease in the basicity of the N1H sites (pKa approximately 7.0 in CD3CN-d3), as compared to the imino form of the free dinucleotide. The presence of the adenine bases in the rare imino form, due to bidentate metalation of the N6/N7 sites, is further corroborated by DQF-COSY H2/N1H and ROE N1H/N6H cross-peaks in the 2D NMR spectra of Rh2(DTolF)2{d(ApA)} in CD3CN-d3 at -38 degrees C. Due to the N7/N6 bridging mode of the adenine bases in Rh2(DTolF)2{d(ApA)}, only the anti orientation of the imino tautomer is possible. The imino form A* of adenine in DNA may result in AT-->CG transversions or AT-->GC transitions, which can eventually lead to lethal mutations. The HH arrangement of the bases in Rh2(DTolF)2{d(ApA)} is indicated by the H8/H8 NOE cross-peaks in the 2D ROESY NMR spectrum, whereas the formamidinate bridging groups dictate the presence of one right-handed conformer HH1R in solution. Complete characterization of Rh2(DTolF)2{d(ApA)} by 2D NMR spectroscopy and molecular modeling supports the presence of the HH1R conformer, anti orientation of both sugar residues about the glycosyl bonds, and N-type conformation for the 5'-A base.

  1. A novel modified carbon paste electrode based on NiO/CNTs nanocomposite and (9, 10-dihydro-9, 10-ethanoanthracene-11, 12-dicarboximido)-4-ethylbenzene-1, 2-diol as a mediator for simultaneous determination of cysteamine, nicotinamide adenine dinucleotide and folic acid.

    PubMed

    Karimi-Maleh, Hassan; Biparva, Pourya; Hatami, Mehdi

    2013-10-15

    A carbon paste electrode (CPE) modified with (9, 10-dihydro-9, 10-ethanoanthracene-11, 12-dicarboximido)-4-ethylbenzene-1, 2-diol (DEDE) and NiO/CNTs nanocomposite was used for the sensitive voltammetric determination of cysteamine (CA), nicotinamide adenine dinucleotide (NADH) and folic acid (FA) for the first time. The synthesized materials were characterized with different methods such as XRD, cyclic voltammetry, electrochemical impedance spectroscopy (EIS) and square wave voltammetry (SWV). The modified electrode exhibited a potent and persistent electron mediating behavior followed by well-separated oxidation peaks of CA, NADH and FA. The peak currents were linearly dependent on CA, NADH and FA concentrations using square wave voltammetry (SWV) method in the ranges of 0.01-250, 1.0-500, and 3.0-550 µmol L⁻¹, with detection limits of 0.007, 0.6, and 0.9 µmol L⁻¹, respectively. The modified electrode was used for the determination of CA, NADH and FA in biological and pharmaceutical samples.

  2. Hydrogen storage and evolution catalysed by metal hydride complexes.

    PubMed

    Fukuzumi, Shunichi; Suenobu, Tomoyoshi

    2013-01-07

    The storage and evolution of hydrogen are catalysed by appropriate metal hydride complexes. Hydrogenation of carbon dioxide by hydrogen is catalysed by a [C,N] cyclometalated organoiridium complex, [Ir(III)(Cp*)(4-(1H-pyrazol-1-yl-κN(2))benzoic acid-κC(3))(OH(2))](2)SO(4) [Ir-OH(2)](2)SO(4), under atmospheric pressure of H(2) and CO(2) in weakly basic water (pH 7.5) at room temperature. The reverse reaction, i.e., hydrogen evolution from formate, is also catalysed by [Ir-OH(2)](+) in acidic water (pH 2.8) at room temperature. Thus, interconversion between hydrogen and formic acid in water at ambient temperature and pressure has been achieved by using [Ir-OH(2)](+) as an efficient catalyst in both directions depending on pH. The Ir complex [Ir-OH(2)](+) also catalyses regioselective hydrogenation of the oxidised form of β-nicotinamide adenine dinucleotide (NAD(+)) to produce the 1,4-reduced form (NADH) under atmospheric pressure of H(2) at room temperature in weakly basic water. In weakly acidic water, the complex [Ir-OH(2)](+) also catalyses the reverse reaction, i.e., hydrogen evolution from NADH to produce NAD(+) at room temperature. Thus, interconversion between NADH (and H(+)) and NAD(+) (and H(2)) has also been achieved by using [Ir-OH(2)](+) as an efficient catalyst and by changing pH. The iridium hydride complex formed by the reduction of [Ir-OH(2)](+) by H(2) and NADH is responsible for the hydrogen evolution. Photoirradiation (λ > 330 nm) of an aqueous solution of the Ir-hydride complex produced by the reduction of [Ir-OH(2)](+) with alcohols resulted in the quantitative conversion to a unique [C,C] cyclometalated Ir-hydride complex, which can catalyse hydrogen evolution from alcohols in a basic aqueous solution (pH 11.9). The catalytic mechanisms of the hydrogen storage and evolution are discussed by focusing on the reactivity of Ir-hydride complexes.

  3. Hydriding process

    DOEpatents

    Raymond, J.W.; Taketani, H.

    1973-12-01

    BS>A method is described for hydriding a body of a Group IV-B metal, preferably zirconium, to produce a crack-free metal-hydride bedy of high hydrogen content by cooling the body at the beta to beta + delta boundary, without further addition of hydrogen, to precipitate a fine-grained delta-phase metal hydride in the beta + delta phase region and then resuming the hydriding, preferably preceded by a reheating step. (Official Gazette)

  4. Multiple isotope effects with alternative dinucleotide substrates as a probe of the malic enzyme reaction

    SciTech Connect

    Weiss, P.M.; Urbauer, J.L.; Cleland, W.W. ); Gavva, S.R.; Harris, B.G.; Cook, P.F. )

    1991-06-11

    Deuterium isotope effects and {sup 13}C isotope effects with deuterium- and protium-labeled malate have been obtained for both NAD- and NADP-malic enzymes by using a variety of alternative dinucleotide substrates. With nicotinamide-containing dinucleotides as the oxidizing substrate, the {sup 13}C effect decreases when deuterated malate is the substrate compared to the value obtained with protium-labeled malate. These data are consistent with a stepwise chemical mechanism in which hydride transfer precedes decarboxylation of the oxalacetate intermediate as previously proposed. When dinucleotide substrates such as thio-NAD, 3-nicotinamide rings are used, the {sup 13}C effect increases when deuterated malate is the substrate compared to the value obtained with protium-labeled malate. These data, at face value, are consistent with a change in mechanism from stepwise to concerted for the oxidative decarboxylation portion of the mechanism. However, the increase in the deuterium isotope effect from 1.5 to 3 with a concomitant decrease in the {sup 13}C isotope effect from 1.034 to 1.003 as the dinucleotide substrate is changed suggests that the reaction may still be stepwise with the non-nicotinamide dinucleotides. A more likely explanation is that a {beta}-secondary {sup 13}C isotope effect accompanies hydride transfer as a result of hyperconjugation of the {beta}-carboxyl of malate as the transition state for the hydride transfer step is approached.

  5. Malic enzyme: Tritium isotope effects with alternative dinucleotide substrates and divalent metal ions

    SciTech Connect

    Karsten, W.E.; Harris, B.G.; Cook, P.F. )

    1992-01-01

    The NAD-malic enzyme from Ascaris suum catalyzes the divalent metal ion dependent oxidative decarboxylation of L-malate to yield pyruvate, carbon dioxide and NADH. Multiple isotope effect studies suggest a stepwise chemical mechanism with hydride transfer from L-malate to NAD occurring first to form oxalacetate, followed by decarboxylation. Utilizing L-malate-2-T, tritium V/K isotope effects have been determined for the hydride transfer step using a variety of alternative dinucleotide substrates and divalent metal ions. Combination of these data with deuterium isotope effects data and previously determined [sup 13]C isotope effects has allowed the calculation of intrinsic isotope effects for the malic enzyme catalyzed reaction. The identity of both the dinucleotide substrate and divalent metal ion has an effect of the size of the intrinsic isotope effect for hydride transfer.

  6. Bioluminescent Cell-Based NAD(P)/NAD(P)H Assays for Rapid Dinucleotide Measurement and Inhibitor Screening

    PubMed Central

    Leippe, Donna; Sobol, Mary; Vidugiris, Gediminas; Zhou, Wenhui; Meisenheimer, Poncho; Gautam, Prson; Wennerberg, Krister; Cali, James J.

    2014-01-01

    Abstract The central role of nicotinamide adenine dinucleotides in cellular energy metabolism and signaling makes them important nodes that link the metabolic state of cells with energy homeostasis and gene regulation. In this study, we describe the implementation of cell-based bioluminescence assays for rapid and sensitive measurement of those important redox cofactors. We show that the sensitivity of the assays (limit of detection ∼0.5 nM) enables the selective detection of total amounts of nonphosphorylated or phosphorylated dinucleotides directly in cell lysates. The total amount of NAD+NADH or NADP+NADPH levels can be detected in as low as 300 or 600 cells/well, respectively. The signal remains linear up to 5,000 cells/well with the maximum signal-to-background ratios ranging from 100 to 200 for NAD+NADH and from 50 to 100 for NADP+NADPH detection. The assays are robust (Z′ value >0.7) and the inhibitor response curves generated using a known NAD biosynthetic pathway inhibitor FK866 correlate well with the reported data. More importantly, by multiplexing the dinucleotide detection assays with a fluorescent nonmetabolic cell viability assay, we show that dinucleotide levels can be decreased dramatically (>80%) by FK866 treatment before changes in cell viability are detected. The utility of the assays to identify modulators of intracellular nicotinamide adenine dinucleotide levels was further confirmed using an oncology active compound library, where novel dinucleotide regulating compounds were identified. For example, the histone deacetylase inhibitor entinostat was a potent inhibitor of cellular nicotinamide adenine dinucleotides, whereas the selective estrogen receptor modulator raloxifene unexpectedly caused a twofold increase in cellular nicotinamide adenine dinucleotide levels. PMID:25506801

  7. Search for interstellar adenine

    NASA Astrophysics Data System (ADS)

    Chakrabarti, Sandip K.; Majumdar, Liton; Das, Ankan; Chakrabarti, Sonali

    2015-05-01

    It is long debated if pre-biotic molecules are indeed present in the interstellar medium. Despite substantial works pointing to their existence, pre-biotic molecules are yet to be discovered with a complete confidence. In this paper, our main aim is to study the chemical evolution of interstellar adenine under various circumstances. We prepare a large gas-grain chemical network by considering various pathways for the formation of adenine. Majumdar et al. (New Astron. 20:15, 2013) proposed that in the absence of adenine detection, one could try to trace two precursors of adenine, namely, HCCN and NH2CN. Recently Merz et al. (J. Phys. Chem. A 118:3637-3644, 2014), proposed another route for the formation of adenine in interstellar condition. They proposed two more precursor molecules. But it was not verified by any accurate gas-grain chemical model. Neither was it known if the production rate would be high or low. Our paper fills this important gap. We include this new pathways to find that the contribution through this pathways for the formation of Adenine is the most dominant one in the context of interstellar medium. We propose that observers may look for the two precursors (C3NH and HNCNH) in the interstellar media which are equally important for predicting abundances of adenine. We perform quantum chemical calculations to find out spectral properties of adenine and its two new precursor molecules in infrared, ultraviolet and sub-millimeter region. Our present study would be useful for predicting abundance of adenine.

  8. Hydride compositions

    DOEpatents

    Lee, Myung, W.

    1994-01-01

    Disclosed are a composition for use in storing hydrogen and a method for making the composition. The composition comprises a mixture of two or more hydrides, each hydride having a different series of hydrogen sorption isotherms that contribute to the overall isotherms of the mixture. The hydrides are chosen so that the isotherms of the mixture have regions wherein the H equilibrium pressure increases with increasing hydrogen, preferably linearly. The isotherms of the mixture can be adjusted by selecting hydrides with different isotherms and by varying the amounts of the individual hydrides, or both. Preferably, the mixture is made up of hydrides that have isotherms with substantially flat plateaus and in nearly equimolar amounts. The composition is activated by degassing, exposing to H, and then heating below the softening temperature of any of the constituents. When the composition is used to store hydrogen, its hydrogen content can be found simply by measuring P{sub H}{sub 2} and determining H/M from the isothermic function of the composition.

  9. Hydride compositions

    DOEpatents

    Lee, Myung W.

    1995-01-01

    A composition for use in storing hydrogen, and a method for making the composition. The composition comprises a mixture of two or more hydrides, each hydride having a different series of hydrogen sorption isotherms that contribute to the overall isotherms of the mixture. The hydrides are chosen so that the isotherms of the mixture have regions wherein the hydrogen equilibrium pressure increases with increasing hydrogen, preferably linearly. The isotherms of the mixture can be adjusted by selecting hydrides with different isotherms and by varying the amounts of the individual hydrides, or both. Preferably, the mixture is made up of hydrides that have isotherms with substantially flat plateaus and in nearly equimolar amounts. The composition is activated by degassing, exposing to hydrogen and then heating at a temperature below the softening temperature of any of the. constituents so that their chemical and structural integrity is preserved. When the composition is used to store hydrogen, its hydrogen content can be found simply by measuring P.sub.H.sbsb.2 and determining H/M from the isothermic function of the composition.

  10. Adenine formation without HCN.

    PubMed

    Merz, Kenneth M; Aguiar, Eduardo C; da Silva, Joao Bosco P

    2014-05-22

    From a historic point of view adenine was always presumed to be the product of HCN pentamerization. In this work a new mechanism for adenine synthesis in the gas phase without HCN is proposed. The concept of retrosynthetic analysis was employed to create a tautomer of adenine, which can be reached from previously observed interstellar molecules C3NH and HNCNH and its isomer H2NCN. MP2/6-311++G(2d,2p) calculations were performed to calculate the Gibbs free energy of the minimum and the transition state (TS) structures involved in the six step mechanism. This new mechanism requires a smaller number of steps, the reaction energy is twice as exergonic, and the rate determining TS is lower in energy than the corresponding ones proposed elsewhere in the literature.

  11. Momentum Distribution as a Fingerprint of Quantum Delocalization in Enzymatic Reactions: Open-Chain Path-Integral Simulations of Model Systems and the Hydride Transfer in Dihydrofolate Reductase.

    PubMed

    Engel, Hamutal; Doron, Dvir; Kohen, Amnon; Major, Dan Thomas

    2012-04-10

    The inclusion of nuclear quantum effects such as zero-point energy and tunneling is of great importance in studying condensed phase chemical reactions involving the transfer of protons, hydrogen atoms, and hydride ions. In the current work, we derive an efficient quantum simulation approach for the computation of the momentum distribution in condensed phase chemical reactions. The method is based on a quantum-classical approach wherein quantum and classical simulations are performed separately. The classical simulations use standard sampling techniques, whereas the quantum simulations employ an open polymer chain path integral formulation which is computed using an efficient Monte Carlo staging algorithm. The approach is validated by applying it to a one-dimensional harmonic oscillator and symmetric double-well potential. Subsequently, the method is applied to the dihydrofolate reductase (DHFR) catalyzed reduction of 7,8-dihydrofolate by nicotinamide adenine dinucleotide phosphate hydride (NADPH) to yield S-5,6,7,8-tetrahydrofolate and NADP(+). The key chemical step in the catalytic cycle of DHFR involves a stereospecific hydride transfer. In order to estimate the amount of quantum delocalization, we compute the position and momentum distributions for the transferring hydride ion in the reactant state (RS) and transition state (TS) using a recently developed hybrid semiempirical quantum mechanics-molecular mechanics potential energy surface. Additionally, we examine the effect of compression of the donor-acceptor distance (DAD) in the TS on the momentum distribution. The present results suggest differential quantum delocalization in the RS and TS, as well as reduced tunneling upon DAD compression.

  12. Photoinduced Electron Transfer in DNA: Charge Shift Dynamics Between 8-Oxo-Guanine Anion and Adenine.

    PubMed

    Zhang, Yuyuan; Dood, Jordan; Beckstead, Ashley A; Li, Xi-Bo; Nguyen, Khiem V; Burrows, Cynthia J; Improta, Roberto; Kohler, Bern

    2015-06-18

    Femtosecond time-resolved IR spectroscopy is used to investigate the excited-state dynamics of a dinucleotide containing an 8-oxoguanine anion at the 5'-end and neutral adenine at the 3'-end. UV excitation of the dinucleotide transfers an electron from deprotonated 8-oxoguanine to its π-stacked neighbor adenine in less than 1 ps, generating a neutral 8-oxoguanine radical and an adenine radical anion. These species are identified by the excellent agreement between the experimental and calculated IR difference spectra. The quantum efficiency of this ultrafast charge shift reaction approaches unity. Back electron transfer from the adenine radical anion to the 8-oxguanine neutral radical occurs in 9 ps, or approximately 6 times faster than between the adenine radical anion and the 8-oxoguanine radical cation (Zhang, Y. et al. Proc. Natl. Acad. Sci. U.S.A. 2014, 111, 11612-11617). The large asymmetry in forward and back electron transfer rates is fully rationalized by semiclassical nonadiabatic electron transfer theory. Forward electron transfer is ultrafast because the driving force is nearly equal to the reorganization energy, which is estimated to lie between 1 and 2 eV. Back electron transfer is highly exergonic and takes place much more slowly in the Marcus inverted region.

  13. Maximal dinucleotide and trinucleotide circular codes.

    PubMed

    Michel, Christian J; Pellegrini, Marco; Pirillo, Giuseppe

    2016-01-21

    We determine here the number and the list of maximal dinucleotide and trinucleotide circular codes. We prove that there is no maximal dinucleotide circular code having strictly less than 6 elements (maximum size of dinucleotide circular codes). On the other hand, a computer calculus shows that there are maximal trinucleotide circular codes with less than 20 elements (maximum size of trinucleotide circular codes). More precisely, there are maximal trinucleotide circular codes with 14, 15, 16, 17, 18 and 19 elements and no maximal trinucleotide circular code having less than 14 elements. We give the same information for the maximal self-complementary dinucleotide and trinucleotide circular codes. The amino acid distribution of maximal trinucleotide circular codes is also determined.

  14. Dinucleotide circular codes and bijective transformations.

    PubMed

    Fimmel, Elena; Giannerini, Simone; Gonzalez, Diego Luis; Strüngmann, Lutz

    2015-12-07

    The presence of circular codes in mRNA coding sequences is postulated to be involved in informational mechanisms aimed at detecting and maintaining the normal reading frame during protein synthesis. Most of the recent research is focused on trinucleotide circular codes. However, also dinucleotide circular codes are important since dinucleotides are ubiquitous in genomes and associated to important biological functions. In this work we adopt the group theoretic approach used for trinucleotide codes in Fimmel et al. (2015) to study dinucleotide circular codes and highlight their symmetry properties. Moreover, we characterize such codes in terms of n-circularity and provide a graph representation that allows to visualize them geometrically. The results establish a theoretical framework for the study of the biological implications of dinucleotide circular codes in genomic sequences.

  15. Repertoires of the nucleosome-positioning dinucleotides.

    PubMed

    Bettecken, Thomas; Trifonov, Edward N

    2009-11-02

    It is generally accepted that the organization of eukaryotic DNA into chromatin is strongly governed by a code inherent in the genomic DNA sequence. This code, as well as other codes, is superposed on the triplets coding for amino acids. The history of the chromatin code started three decades ago with the discovery of the periodic appearance of certain dinucleotides, with AA/TT and RR/YY giving the strongest signals, all with a period of 10.4 bases. Every base-pair stack in the DNA duplex has specific deformation properties, thus favoring DNA bending in a specific direction. The appearance of the corresponding dinucleotide at the distance 10.4 xn bases will facilitate DNA bending in that direction, which corresponds to the minimum energy of DNA folding in the nucleosome. We have analyzed the periodic appearances of all 16 dinucleotides in the genomes of thirteen different eukaryotic organisms. Our data show that a large variety of dinucleotides (if not all) are, apparently, contributing to the nucleosome positioning code. The choice of the periodical dinucleotides differs considerably from one organism to another. Among other 10.4 base periodicities, a strong and very regular 10.4 base signal was observed for CG dinucleotides in the genome of the honey bee A. mellifera. Also, the dinucleotide CG appears as the only periodical component in the human genome. This observation seems especially relevant since CpG methylation is well known to modulate chromatin packing and regularity. Thus, the selection of the dinucleotides contributing to the chromatin code is species specific, and may differ from region to region, depending on the sequence context.

  16. Maximal dinucleotide comma-free codes.

    PubMed

    Fimmel, Elena; Strüngmann, Lutz

    2016-01-21

    The problem of retrieval and maintenance of the correct reading frame plays a significant role in RNA transcription. Circular codes, and especially comma-free codes, can help to understand the underlying mechanisms of error-detection in this process. In recent years much attention has been paid to the investigation of trinucleotide circular codes (see, for instance, Fimmel et al., 2014; Fimmel and Strüngmann, 2015a; Michel and Pirillo, 2012; Michel et al., 2012, 2008), while dinucleotide codes had been touched on only marginally, even though dinucleotides are associated to important biological functions. Recently, all maximal dinucleotide circular codes were classified (Fimmel et al., 2015; Michel and Pirillo, 2013). The present paper studies maximal dinucleotide comma-free codes and their close connection to maximal dinucleotide circular codes. We give a construction principle for such codes and provide a graphical representation that allows them to be visualized geometrically. Moreover, we compare the results for dinucleotide codes with the corresponding situation for trinucleotide maximal self-complementary C(3)-codes. Finally, the results obtained are discussed with respect to Crick׳s hypothesis about frame-shift-detecting codes without commas.

  17. Hydride compressor

    DOEpatents

    Powell, James R.; Salzano, Francis J.

    1978-01-01

    Method of producing high energy pressurized gas working fluid power from a low energy, low temperature heat source, wherein the compression energy is gained by using the low energy heat source to desorb hydrogen gas from a metal hydride bed and the desorbed hydrogen for producing power is recycled to the bed, where it is re-adsorbed, with the recycling being powered by the low energy heat source. In one embodiment, the adsorption-desorption cycle provides a chemical compressor that is powered by the low energy heat source, and the compressor is connected to a regenerative gas turbine having a high energy, high temperature heat source with the recycling being powered by the low energy heat source.

  18. Adenine phosphoribosyltransferase deficiency.

    PubMed

    Bollée, Guillaume; Harambat, Jérôme; Bensman, Albert; Knebelmann, Bertrand; Daudon, Michel; Ceballos-Picot, Irène

    2012-09-01

    Complete adenine phosphoribosyltransferase (APRT) deficiency is a rare inherited metabolic disorder that leads to the formation and hyperexcretion of 2,8-dihydroxyadenine (DHA) into urine. The low solubility of DHA results in precipitation of this compound and the formation of urinary crystals and stones. The disease can present as recurrent urolithiasis or nephropathy secondary to crystal precipitation into renal parenchyma (DHA nephropathy). The diagnostic tools available-including stone analysis, crystalluria, and APRT activity measurement-make the diagnosis easy to confirm when APRT deficiency is suspected. However, the disease can present at any age, and the variability of symptoms can present a diagnostic challenge to many physicians. The early recognition and treatment of APRT deficiency are of crucial importance for preventing irreversible loss of renal function, which still occurs in a non-negligible proportion of cases. This review summarizes the genetic and metabolic mechanisms underlying stone formation and renal disease, along with the diagnosis and management of APRT deficiency.

  19. The Responses of Isolated Plant Mitochondria to External Nicotinamide Adenine Dinucleotide 1

    PubMed Central

    Soole, Kathleen L.; Dry, Ian B.; Wiskich, Joseph T.

    1986-01-01

    The effects of added NAD on substrate oxidation by turnip (Brassica rapa L.) and beetroot (Beta vulgaris L.) mitochondria were investigated. State 3 malate and 2-oxoglutarate oxidation rates with turnip mitochondria were stimulated 25 to 40% by external NAD. Following NAD-depletion this stimulation by NAD was increased to 70 to 80%. With purified beetroot mitochondria, state 3 malate and 2-oxoglutarate oxidation rates were only marginally increased (10-15%) by the addition of NAD but after NAD-depletion treatments this stimulation increased to 55%. The effect of added NAD on oxidation rates could be reduced by preloading mitochondria with NAD in the presence of succinate. Oxidation rates were found to be most sensitive to the addition of external NAD when rotenone was present. The uptake of external NAD into beetroot mitochondria appeared to be composed of both an active and a diffusive component. The active component displayed saturation kinetics with an approximate Km of 0.105 ± 0.046 millimolar. These results provide further evidence, reported previously with potato mitochondria, that NAD can move across the inner membrane of plant mitochondria. They are particularly significant with respect to beetroot mitochondria which in contrast to other plant mitochondria, have not demonstrated any response to added NAD. PMID:16664861

  20. Partial purification of nicotinamide adenine dinucleotide (NAD) pyrophosphatase from Salmonella typhimurium

    SciTech Connect

    Putt, M.M.; Foster, J.W.; Kasvinsky, P.J.

    1987-05-01

    NAD is an extremely important compound in cellular physiology. In the pyridine nucleotide cycle of S. typhimurium NAD pyrophosphatase, located in the inner membrane, carries out the cleavage of NAD prior to the transport of nicotinamide mononucleotide (NMN) into the cell. The partial purification of this enzyme is reported here. A cell suspension of S. typhimurium was passed twice through a French pressure cell, centrifugated at 5000 xg, and at 200,000 xg, for 1 hr. The pellet containing the crude membrane fraction was extracted with a novel detergent extraction using the differential solubility of NAD pyrophosphatase at various concentrations of the non-ionic detergent n-octyl glucoside (nOG). Extraction of the membrane fraction with 0.5% nOG in the presence of 10mM MgCl/sub 2/ removed 60% of the protein with no loss in activity. A second extraction with 2% nOG and 10mM MgCl/sub 2/ removed 20% of the protein and 71% of the activity from the membrane fraction. Ammonium sulfate fractionation at 45 to 50% sat. gave a partially purified enzyme preparation having a specific activity of about 2500 units/mg with a 94% recovery compared to the crude extract. One unit of activity is the cleavage of 1 nmole /sup 14/C NAD to /sup 14/C NMN per minute. The enzyme appears to have a MW of 200,000 on Sephacryl S-200, is temperature labile, and stabilized by 1mM Mg/sup + +/ and storage at -70/sup 0/.

  1. Modification of Metabolic Pattern by Variation of Nicotinamide Adenine Dinucleotide Phosphate Level 1

    PubMed Central

    Yamamoto, Yukio

    1969-01-01

    The experiments were designed to get some information on the metabolism controlled by variation of the NADP level, which is known to change with the variation of environmental factors. The exogenous NADP added to the mitochondria prepared from Vigna sesquipedalis cotyledons was associated with and/or penetrated into the mitochondria. The combined NADP served in the operation of the mitochondrial NADP-isocitric acid dehydrogenase. The variation of NADP level by exogenous NADP was observed to modify the rates of metabolic processes. The increase of exogenous NADP in Vigna hypocotyl slices lowered malic- and citric-acid contents and raised the α-ketoglutaric acid content. The incorporation of 14C from acetate-2-14C into lipid, organic acid, amino acid, was promoted with the exogenous NADP. The 14C-incorporation into glycolic acid, malic acid and glutamic acid was accelerated. In the mannitol homogenate of Vigna cotyledon, 14CO2 evolution and 14C-incorporation into lipid, sugar, and glycolic acid from acetate-2-14C were promoted with the exogenous NADP. Endogenous citric acid content was lowered by NADP, while malic acid content was increased. The activation of NADP-enzymes by NADP was discussed to be involved in these variations. PMID:16657076

  2. Grafted Azure A modified electrodes as disposable β-nicotinamide adenine dinucleotide sensors.

    PubMed

    Revenga-Parra, M; Gómez-Anquela, C; García-Mendiola, T; Gonzalez, E; Pariente, F; Lorenzo, E

    2012-10-17

    We report the in situ generation of aryl diazonium cations of Azure A, a redox-active phenothiazine dye, by reaction between the corresponding aromatic aminophenyl group and sodium nitrite in 0.1 M HCl. The subsequent electrochemical reduction of these dye diazonium salts gives rise to conductive electrografted films onto screen-printed carbon (SPC) electrodes. The resulting Azure A films have a very stable and reversible electrochemical response and exhibit potent and persistent electrocatalytic behavior toward NADH oxidation. We have optimized the electrografting conditions in order to obtain SPC modified electrodes with high and stable electrocatalytic response. The kinetic of the reaction between the NADH and the redox active centers in the Azure A film has been characterized using cyclic voltammetry and single step chronoamperometry. The catalytic currents were proportional to the concentration of NADH giving rise to linear calibration plots up to a concentration of 0.5 mM with a detection limit of 0.57±0.03 μM and a sensitivity of 9.48 A mol cm(-2) μM(-1). The precision of chronoamperometric determinations was found to be 2.3% for five replicate determinations of 3.95 μM NADH. The great stability of such modified electrodes makes them ideal for their application in the development of biosensing platforms based on dehydrogenases.

  3. Solution conformation of 2-aminopurine dinucleotide determined by ultraviolet two-dimensional fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Widom, Julia R.; Johnson, Neil P.; von Hippel, Peter H.; Marcus, Andrew H.

    2013-02-01

    We have observed the conformation-dependent electronic coupling between the monomeric subunits of a dinucleotide of 2-aminopurine (2-AP), a fluorescent analogue of the nucleic acid base adenine. This was accomplished by extending two-dimensional fluorescence spectroscopy (2D FS)—a fluorescence-detected variation of 2D electronic spectroscopy—to excite molecular transitions in the ultraviolet (UV) regime. A collinear sequence of four ultrafast laser pulses centered at 323 nm was used to resonantly excite the coupled transitions of 2-AP dinucleotide. The phases of the optical pulses were continuously swept at kilohertz frequencies, and the ensuing nonlinear fluorescence was phase-synchronously detected at 370 nm. Upon optimization of a point-dipole coupling model to our data, we found that in aqueous buffer the 2-AP dinucleotide adopts an average conformation in which the purine bases are non-helically stacked (center-to-center distance R12 = 3.5 ± 0.5 Å , twist angle θ12 = 5° ± 5° ), which differs from the conformation of such adjacent bases in duplex DNA. These experiments establish UV-2D FS as a method for examining the local conformations of an adjacent pair of fluorescent nucleotides substituted into specific DNA or RNA constructs, which will serve as a powerful probe to interpret, in structural terms, biologically significant local conformational changes within the nucleic acid framework of protein-nucleic acid complexes.

  4. Protein modification by adenine propenal.

    PubMed

    Shuck, Sarah C; Wauchope, Orrette R; Rose, Kristie L; Kingsley, Philip J; Rouzer, Carol A; Shell, Steven M; Sugitani, Norie; Chazin, Walter J; Zagol-Ikapitte, Irene; Boutaud, Olivier; Oates, John A; Galligan, James J; Beavers, William N; Marnett, Lawrence J

    2014-10-20

    Base propenals are products of the reaction of DNA with oxidants such as peroxynitrite and bleomycin. The most reactive base propenal, adenine propenal, is mutagenic in Escherichia coli and reacts with DNA to form covalent adducts; however, the reaction of adenine propenal with protein has not yet been investigated. A survey of the reaction of adenine propenal with amino acids revealed that lysine and cysteine form adducts, whereas histidine and arginine do not. N(ε)-Oxopropenyllysine, a lysine-lysine cross-link, and S-oxopropenyl cysteine are the major products. Comprehensive profiling of the reaction of adenine propenal with human serum albumin and the DNA repair protein, XPA, revealed that the only stable adduct is N(ε)-oxopropenyllysine. The most reactive sites for modification in human albumin are K190 and K351. Three sites of modification of XPA are in the DNA-binding domain, and two sites are subject to regulatory acetylation. Modification by adenine propenal dramatically reduces XPA's ability to bind to a DNA substrate.

  5. Trypanosoma brucei adenine-phosphoribosyltransferases mediate adenine salvage and aminopurinol susceptibility but not adenine toxicity.

    PubMed

    Lüscher, Alexandra; Lamprea-Burgunder, Estelle; Graf, Fabrice E; de Koning, Harry P; Mäser, Pascal

    2014-04-01

    African trypanosomes, like all obligate parasitic protozoa, cannot synthesize purines de novo and import purines from their hosts to build nucleic acids. The purine salvage pathways of Trypanosoma brucei being redundant, none of the involved enzymes is likely to be essential. Nevertheless they can be of pharmacological interest due to their role in activation of purine nucleobase or nucleoside analogues, which only become toxic when converted to nucleotides. Aminopurine antimetabolites, in particular, are potent trypanocides and even adenine itself is toxic to trypanosomes at elevated concentrations. Here we report on the T. brucei adenine phosphoribosyltransferases TbAPRT1 and TbAPRT2, encoded by the two genes Tb927.7.1780 and Tb927.7.1790, located in tandem on chromosome seven. The duplication is syntenic in all available Trypanosoma genomes but not in Leishmania. While TbAPRT1 is cytosolic, TbAPRT2 possesses a glycosomal targeting signal and co-localizes with the glycosomal marker aldolase. Interestingly, the distribution of glycosomal targeting signals among trypanosomatid adenine phosphoribosyltransferases is not consistent with their phylogeny, indicating that the acquisition of adenine salvage to the glycosome happened after the radiation of Trypanosoma. Double null mutant T. brucei Δtbaprt1,2 exhibited no growth phenotype but no longer incorporated exogenous adenine into the nucleotide pool. This, however, did not reduce their sensitivity to adenine. The Δtbaprt1,2 trypanosomes were resistant to the adenine isomer aminopurinol, indicating that it is activated by phosphoribosyl transfer. Aminopurinol was about 1000-fold more toxic to bloodstream-form T. brucei than the corresponding hypoxanthine isomer allopurinol. Aminopurinol uptake was not dependent on the aminopurine permease P2 that has been implicated in drug resistance.

  6. Quantum-chemical study of interactions of trans-resveratrol with guanine-thymine dinucleotide and DNA-nucleobases.

    PubMed

    Mikulski, Damian; Szeląg, Małgorzata; Molski, Marcin

    2011-12-01

    Trans-resveratrol, a natural phytoalexin present in red wine and grapes, has gained considerable attention because of its antiproliferative, chemopreventive and proapoptotic activity against human cancer cells. The accurate quantum-chemical computations based on the density functional theory (DFT) and ab initio second-order Møller-Plesset perturbation method (MP2) have been performed for the first time to study interactions of trans-resveratrol with guanine-thymine dinucleotide and DNA-derived nitrogenous bases: adenine, guanine, cytosine and thymine in vacuum and water medium. This compound is found to show high affinity to nitrogenous bases and guanine-thymine dinucleotide. The electrostatic interactions from intermolecular hydrogen bonding increase the stability of complexes studied. In particular, significantly strong hydrogen bonds between 4'-H atom of trans-resveratrol and imidazole nitrogen as well as carbonyl oxygen atoms of nucleobases studied stabilize these systems. The stabilization energies computed reveal that the negatively charged trans-resveratrol-dinucleotide complex is more energetically stable in water medium than in vacuum. MP2 method gives more reliable and significantly high values of stabilization energy of trans-resveratrol-dinucleotide, trans-resveratrol-guanine and trans-resveratrol-thymine complexes than B3LYP exchange-correlation functional because it takes into account London dispersion energy. According to the results, in the presence of trans-resveratrol the 3'-5' phosphodiester bond in dinucleotide can be cleaved and the proton from 4'-OH group of trans-resveratrol migrates to the 3'-O atom of dinucleotide. It is concluded that trans-resveratrol is able to break the DNA strand. Hence, the findings obtained help understand antiproliferative and anticancer properties of this polyphenol.

  7. Automated genotyping of dinucleotide repeat markers

    SciTech Connect

    Perlin, M.W.; Hoffman, E.P. |

    1994-09-01

    The dinucleotide repeats (i.e., microsatellites) such as CA-repeats are a highly polymorphic, highly abundant class of PCR-amplifiable markers that have greatly streamlined genetic mapping experimentation. It is expected that over 30,000 such markers (including tri- and tetranucleotide repeats) will be characterized for routine use in the next few years. Since only size determination, and not sequencing, is required to determine alleles, in principle, dinucleotide repeat genotyping is easily performed on electrophoretic gels, and can be automated using DNA sequencers. Unfortunately, PCR stuttering with these markers generates not one band for each allele, but a pattern of bands. Since closely spaced alleles must be disambiguated by human scoring, this poses a key obstacle to full automation. We have developed methods that overcome this obstacle. Our model is that the observed data is generated by arithmetic superposition (i.e., convolution) of multiple allele patterns. By quantitatively measuring the size of each component band, and exploiting the unique stutter pattern associated with each marker, closely spaced alleles can be deconvolved; this unambiguously reconstructs the {open_quotes}true{close_quotes} allele bands, with stutter artifact removed. We used this approach in a system for automated diagnosis of (X-linked) Duchenne muscular dystrophy; four multiplexed CA-repeats within the dystrophin gene were assayed on a DNA sequencer. Our method accurately detected small variations in gel migration that shifted the allele size estimate. In 167 nonmutated alleles, 89% (149/167) showed no size variation, 9% (15/167) showed 1 bp variation, and 2% (3/167) showed 2 bp variation. We are currently developing a library of dinucleotide repeat patterns; together with our deconvolution methods, this library will enable fully automated genotyping of dinucleotide repeats from sizing data.

  8. Synthesis of ruthenium hydride

    NASA Astrophysics Data System (ADS)

    Kuzovnikov, M. A.; Tkacz, M.

    2016-02-01

    Ruthenium hydride was synthesized at a hydrogen pressure of about 14 GPa in a diamond-anvil cell. Energy-dispersive x-ray diffraction was used to monitor the ruthenium crystal structure as a function of hydrogen pressure up to 30 GPa. The hydride formation was accompanied by phase transition from the original hcp structure of the pristine metal to the fcc structure. Our results confirmed the theoretical prediction of ruthenium hydride formation under hydrogen pressure. The standard Gibbs free energy of the ruthenium hydride formation reaction was calculated assuming the pressure of decomposition as the equilibrium pressure.

  9. Was adenine the first purine?

    NASA Technical Reports Server (NTRS)

    Schwartz, Alan W.; Bakker, C. G.

    1989-01-01

    Oligomerization of HCN (1 molar) in the presence of added formaldehyde (0.5 molar) produced an order of magnitude more 8-hydroxymethyladenine than adenine or any other biologically significant purine. This result suggests that on the prebiotic earth, nucleoside analogs may have been synthesized directly in more complex mixtures of HCN with other aldehydes.

  10. Hysteresis in Metal Hydrides.

    ERIC Educational Resources Information Center

    Flanagan, Ted B., And Others

    1987-01-01

    This paper describes a reproducible process where the irreversibility can be readily evaluated and provides a thermodynamic description of the important phenomenon of hysteresis. A metal hydride is used because hysteresis is observed during the formation and decomposition of the hydride phase. (RH)

  11. Molybdopterin Dinucleotide Biosynthesis in Escherichia coli

    PubMed Central

    Neumann, Meina; Seduk, Farida; Iobbi-Nivol, Chantal; Leimkühler, Silke

    2011-01-01

    The molybdenum cofactor is modified by the addition of GMP or CMP to the C4′ phosphate of molybdopterin forming the molybdopterin guanine dinucleotide or molybdopterin cytosine dinucleotide cofactor, respectively. The two reactions are catalyzed by specific enzymes as follows: the GTP:molybdopterin guanylyltransferase MobA and the CTP:molybdopterin cytidylyltransferase MocA. Both enzymes show 22% amino acid sequence identity and are specific for their respective nucleotides. Crystal structure analysis of MobA revealed two conserved motifs in the N-terminal domain of the protein involved in binding of the guanine base. Based on these motifs, we performed site-directed mutagenesis studies to exchange the amino acids to the sequence found in the paralogue MocA. Using a fully defined in vitro system, we showed that the exchange of five amino acids was enough to obtain activity with both GTP and CTP in either MocA or MobA. Exchange of the complete N-terminal domain of each protein resulted in the total inversion of nucleotide specificity activity, showing that the N-terminal domain determines nucleotide recognition and binding. Analysis of protein-protein interactions showed that the C-terminal domain of either MocA or MobA determines the specific binding to the respective acceptor protein. PMID:21081498

  12. Onset of chiral adenine surface growth.

    PubMed

    Capitán, María Jose; Álvarez, Jesús; Wang, Yang; Otero, Roberto; Alcamí, Manuel; Martín, Fernando; Miranda, Rodolfo

    2013-10-07

    The structure and stability of adenine crystals and thin layers has been studied by using scanning tunneling microscopy, X-ray diffraction, and density functional theory calculations. We have found that adenine crystals can be grown in two phases that are energetically quasi-degenerate, the structure of which can be described as a pile-up of 2D adenine planes. In each plane, the structure can be described as an aggregation of adenine dimers. Under certain conditions, kinetic effects can favor the growth of the less stable phase. These results have been used to understand the growth of adenine thin films on gold under ultra-high vacuum conditions. We have found that the grown phase corresponds to the α-phase, which is composed of stacked prochiral planes. In this way, the adenine nanocrystals exhibit a surface that is enantiopure. These results could open new insight into the applications of adenine in biological, medical, and enantioselective or pharmaceutical fields.

  13. Chemistry of intermetallic hydrides

    SciTech Connect

    Reilly, J.J.

    1991-01-01

    Certain intermetallic hydrides are safe, convenient and inexpensive hydrogen storage compounds. A particular advantage of such compounds is the ease with which their properties can be modified by small changes in alloy composition or preparation. This quality can be exploited to optimize their storage properties for particular applications, e.g. as intermetallic hydride electrodes in batteries. We will be concerned herein with the more important aspects of the thermodynamic and structural principles which regulate the behavior of intermetallic hydrogen systems and then illustrate their application using the archetype hydrides of LaNi5, FeTi and Mg alloys. The practical utility of these classes of materials will be briefly noted.

  14. Supramolecular polymer formation by cyclic dinucleotides and intercalators affects dinucleotide enzymatic processing

    PubMed Central

    Nakayama, Shizuka; Zhou, Jie; Zheng, Yue; Szmacinski, Henryk; Sintim, Herman O

    2016-01-01

    Background: Cyclic dinucleotides form supramolecular aggregates with intercalators, and this property could be utilized in nanotechnology and medicine. Methods & results: Atomic force microscopy and electrophoretic mobility shift assays were used to show that cyclic diguanylic acid (c-di-GMP) forms G-wires in the presence of intercalators. The average fluorescence lifetime of thiazole orange, when bound to c-di-GMP was greater than when bound to DNA G-quadruplexes or dsDNA. The stability of c-di-GMP supramolecular polymers is dependent on both the nature of the cation present and the intercalator. C-di-GMP or cyclic diadenylic acid/intercalator complexes are more resistant to cleavage by YybT, a phosphodiesterase, than the uncomplexed nucleotides. Conclusion: Cleavage of bacterial cyclic dinucleotides could be slowed down via complexation with small molecules and that this could be utilized for diverse applications in nanotechnology and medicine. PMID:28031943

  15. Regenerative Hydride Heat Pump

    NASA Technical Reports Server (NTRS)

    Jones, Jack A.

    1992-01-01

    Hydride heat pump features regenerative heating and single circulation loop. Counterflow heat exchangers accommodate different temperatures of FeTi and LaNi4.7Al0.3 subloops. Heating scheme increases efficiency.

  16. Hydride heat pump

    DOEpatents

    Cottingham, James G.

    1977-01-01

    Method and apparatus for the use of hydrides to exhaust heat from one temperature source and deliver the thermal energy extracted for use at a higher temperature, thereby acting as a heat pump. For this purpose there are employed a pair of hydridable metal compounds having different characteristics working together in a closed pressure system employing a high temperature source to upgrade the heat supplied from a low temperature source.

  17. Solution conformation of 2-aminopurine (2-AP) dinucleotide determined by ultraviolet 2D fluorescence spectroscopy (UV-2D FS).

    PubMed

    Widom, Julia R; Johnson, Neil P; von Hippel, Peter H; Marcus, Andrew H

    2013-02-01

    We have observed the conformation-dependent electronic coupling between the monomeric subunits of a dinucleotide of 2-aminopurine (2-AP), a fluorescent analog of the nucleic acid base adenine. This was accomplished by extending two-dimensional fluorescence spectroscopy (2D FS) - a fluorescence-detected variation of 2D electronic spectroscopy - to excite molecular transitions in the ultraviolet (UV) regime. A collinear sequence of four ultrafast laser pulses centered at 323 nm was used to resonantly excite the coupled transitions of 2-AP dinucleotide. The phases of the optical pulses were continuously swept at kilohertz frequencies, and the ensuing nonlinear fluorescence was phase-synchronously detected at 370 nm. Upon optimization of a point-dipole coupling model to our data, we found that in aqueous buffer the 2-AP dinucleotide adopts an average conformation in which the purine bases are non-helically stacked (center-to-center distance R12 = 3.5 Å ± 0.5 Å, twist angle θ12 = 5° ± 5°), which differs from the conformation of such adjacent bases in duplex DNA. These experiments establish UV-2D FS as a method for examining the local conformations of an adjacent pair of fluorescent nucleotides substituted into specific DNA or RNA constructs, which will serve as a powerful probe to interpret, in structural terms, biologically significant local conformational changes within the nucleic acid framework of protein-nucleic acid complexes.

  18. Vertical Singlet Excitations on Adenine Dimer: A Time Dependent Density Functional Study

    NASA Astrophysics Data System (ADS)

    Crespo-Hernández, Carlos E.; Marai, Christopher N. J.

    2007-12-01

    The condense phase, excited state dynamics of the adenylyl(3'→5')adenine (ApA) dinucleotide has been previously studied using transient absorption spectroscopy with femtosecond time resolution (Crespo-Hernández et al. Chem. Rev. 104, 1977-2019 (2004)). An ultrafast and a long-lived component were observed with time constants of <1 ps and 60±16 ps, respectively. Comparison of the time constants measured for the dinucleotide with that for the adenine nucleotide suggested that the fast component observed in ApA could be assigned to monomer dynamics. The long-lived component observed in ApA was assigned to an excimer state that originates from a fraction of base stacked conformations present at the time of excitation. In this contribution, supermolecule calculations using the time dependent implementation of density functional theory is used to provide more insights on the origin of the initial Franck-Condon excitations. Monomer-like, localized excitations are observed for conformations having negligible base stacking interactions, whereas delocalized excitations are predicted for conformations with significant vertical base-base overlap.

  19. Lightweight hydride storage materials

    SciTech Connect

    Thomas, G.J.; Guthrie, S.E.; Bauer, W.

    1995-09-01

    The need for lightweight hydrides in vehicular applications has prompted considerable research into the use of magnesium and its alloys. Although this earlier work has provided some improved performance in operating temperature and pressure, substantial improvements are needed before these materials will significantly enhance the performance of an engineered system on a vehicle. We are extending the work of previous investigators on Mg alloys to reduce the operating temperature and hydride heat of formation in light weight materials. Two important results will be discussed in this paper: (1) a promising new alloy hydride was found which has better pressure-temperature characteristics than any previous Mg alloy and, (2) a new fabrication process for existing Mg alloys was developed and demonstrated. The new alloy hydride is composed of magnesium, aluminum and nickel. It has an equilibrium hydrogen overpressure of 1.3 atm. at 200{degrees}C and a storage capacity between 3 and 4 wt.% hydrogen. A hydrogen release rate of approximately 5 x 10{sup -4} moles-H{sub 2}/gm-min was measured at 200{degrees}C. The hydride heat of formation was found to be 13.5 - 14 kcal/mole-H{sub 2}, somewhat lower than Mg{sub 2}Ni. The new fabrication method takes advantage of the high vapor transport of magnesium. It was found that Mg{sub 2}Ni produced by our low temperature process was better than conventional materials because it was single phase (no Mg phase) and could be fabricated with very small particle sizes. Hydride measurements on this material showed faster kinetic response than conventional material. The technique could potentially be applied to in-situ hydride bed fabrication with improved packing density, release kinetics, thermal properties and mechanical stability.

  20. Formation of the imidazolides of dinucleotides under potentially prebiotic conditions

    NASA Technical Reports Server (NTRS)

    Sleeper, H. L.; Lohrmann, R.; Orgel, L. E.

    1978-01-01

    Imidazolides of dinucleotides such as ImpApA can be formed from the corresponding dinucleotides in a two-stage process, which gives up to 15% yields under potentially prebiotic conditions. First a solution of the dinucleotide and sodium trimetaphosphate is dried out at constant temperature and humidity. This produces polyphosphates such as p(n)ApA in excellent yield (greater than or equal to 80%). The products are dissolved in water, imidazole is added, and the solution is dried out again. This yields the 5'-phosphorimidazolides.

  1. Adenine and adenosine salvage in Leishmania donovani.

    PubMed

    Boitz, Jan M; Ullman, Buddy

    2013-08-01

    6-aminopurine metabolism in Leishmania is unique among trypanosomatid pathogens since this genus expresses two distinct routes for adenine salvage: adenine phosphoribosyltransferase (APRT) and adenine deaminase (AAH). To evaluate the relative contributions of APRT and AAH, adenine salvage was evaluated in Δaprt, Δaah, and Δaprt/Δaah null mutants of L. donovani. The data confirm that AAH plays the dominant role in adenine metabolism in L. donovani, although either enzyme alone is sufficient for salvage. Adenosine salvage was also evaluated in a cohort of null mutants. Adenosine is also primarily converted to hypoxanthine, either intracellularly or extracellularly, but can also be phosphorylated to the nucleotide level by adenosine kinase when the predominant pathways are genetically or pharmacologically blocked. These data provide genetic verification for the relative contributions of 6-aminopurine metabolizing pathways in L. donovani and demonstrate that all of the pathways can function under appropriate conditions of genetic or pharmacologic perturbation.

  2. Hydrated hydride anion clusters

    NASA Astrophysics Data System (ADS)

    Lee, Han Myoung; Kim, Dongwook; Singh, N. Jiten; Kołaski, Maciej; Kim, Kwang S.

    2007-10-01

    On the basis of density functional theory (DFT) and high level ab initio theory, we report the structures, binding energies, thermodynamic quantities, IR spectra, and electronic properties of the hydride anion hydrated by up to six water molecules. Ground state DFT molecular dynamics simulations (based on the Born-Oppenheimer potential surface) show that as the temperature increases, the surface-bound hydride anion changes to the internally bound structure. Car-Parrinello molecular dynamics simulations are also carried out for the spectral analysis of the monohydrated hydride. Excited-state ab initio molecular dynamics simulations show that the photoinduced charge-transfer-to-solvent phenomena are accompanied by the formation of the excess electron-water clusters and the detachment of the H radical from the clusters. The dynamics of the detachment process of a hydrogen radical upon the excitation is discussed.

  3. Bound Anionic States of Adenine

    SciTech Connect

    Haranczyk, Maciej; Gutowski, Maciej S.; Li, Xiang; Bowen, Kit H.

    2007-03-20

    The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. Anionic states of nucleic acid bases are involved in DNA damage by low-energy electrons and in charge transfer through DNA. Previous gas phase studies of free, unsolvated nucleic acid base parent anions probed only dipole-bound states, which are not present in condensed phase environments, but did not observe valence anionic states, which for purine bases are thought to be adiabatically unbound. Contrary to this expectation, we have demonstrated that some thus far ignored tautomers of adenine, which result from enamine-imine transformations, support valence anionic states with electron vertical detachment energies as large as 2.2 eV, and at least one of these anionic tautomers is adiabatically bound. Moreover, we predict that the new anionic tautomers should also dominate in solutions and should be characterized by larger values of electron vertical detachment energy than the canonical valence anion. All of the newfound anionic tautomers might be formed in the course of dissociative electron attachment followed by a hydrogen atom attachment to a carbon atom, and they might affect the structure and properties of DNA and RNA exposed to low-energy electrons. The new valence states observed here, unlike the dipole-bound state, could exist in condensed phases and might be relevant to radiobiological damage. The discovery of these valence anionic states of adenine was facilitated by the development of (i) an experimental method for preparing parent anions of nucleic acid bases for photoelectron experiments, and (it) a combinatorial/quantum chemical approach for identification of the most stable tautomers of organic molecules.

  4. Adenine Aminohydrolase from Leishmania donovani

    PubMed Central

    Boitz, Jan M.; Strasser, Rona; Hartman, Charles U.; Jardim, Armando; Ullman, Buddy

    2012-01-01

    Adenine aminohydrolase (AAH) is an enzyme that is not present in mammalian cells and is found exclusively in Leishmania among the protozoan parasites that infect humans. AAH plays a paramount role in purine metabolism in this genus by steering 6-aminopurines into 6-oxypurines. Leishmania donovani AAH is 38 and 23% identical to Saccharomyces cerevisiae AAH and human adenosine deaminase enzymes, respectively, catalyzes adenine deamination to hypoxanthine with an apparent Km of 15.4 μm, and does not recognize adenosine as a substrate. Western blot analysis established that AAH is expressed in both life cycle stages of L. donovani, whereas subcellular fractionation and immunofluorescence studies confirmed that AAH is localized to the parasite cytosol. Deletion of the AAH locus in intact parasites established that AAH is not an essential gene and that Δaah cells are capable of salvaging the same range of purine nucleobases and nucleosides as wild type L. donovani. The Δaah null mutant was able to infect murine macrophages in vitro and in mice, although the parasite loads in both model systems were modestly reduced compared with wild type infections. The Δaah lesion was also introduced into a conditionally lethal Δhgprt/Δxprt mutant in which viability was dependent on pharmacologic ablation of AAH by 2′-deoxycoformycin. The Δaah/Δhgprt/Δxprt triple knock-out no longer required 2′-deoxycoformycin for growth and was avirulent in mice with no persistence after a 4-week infection. These genetic studies underscore the paramount importance of AAH to purine salvage by L. donovani. PMID:22238346

  5. Boron hydride polymer coated substrates

    DOEpatents

    Pearson, R.K.; Bystroff, R.I.; Miller, D.E.

    1986-08-27

    A method is disclosed for coating a substrate with a uniformly smooth layer of a boron hydride polymer. The method comprises providing a reaction chamber which contains the substrate and the boron hydride plasma. A boron hydride feed stock is introduced into the chamber simultaneously with the generation of a plasma discharge within the chamber. A boron hydride plasma of ions, electrons and free radicals which is generated by the plasma discharge interacts to form a uniformly smooth boron hydride polymer which is deposited on the substrate.

  6. Boron hydride polymer coated substrates

    DOEpatents

    Pearson, Richard K.; Bystroff, Roman I.; Miller, Dale E.

    1987-01-01

    A method is disclosed for coating a substrate with a uniformly smooth layer of a boron hydride polymer. The method comprises providing a reaction chamber which contains the substrate and the boron hydride plasma. A boron hydride feed stock is introduced into the chamber simultaneously with the generation of a plasma discharge within the chamber. A boron hydride plasma of ions, electrons and free radicals which is generated by the plasma discharge interacts to form a uniformly smooth boron hydride polymer which is deposited on the substrate.

  7. The role of nicotinamide–adenine dinucleotide phosphate-dependent malate dehydrogenase and isocitrate dehydrogenase in the supply of reduced nicotinamide–adenine dinucleotide phosphate for steroidogenesis in the superovulated rat ovary

    PubMed Central

    Flint, A. P. F.; Denton, R. M.

    1970-01-01

    1. Superovulated rat ovary was found to contain high activities of NADP–malate dehydrogenase and NADP–isocitrate dehydrogenase. The activity of each enzyme was approximately four times that of glucose 6-phosphate dehydrogenase and equalled or exceeded the activities reported to be present in other mammalian tissues. Fractionation of a whole tissue homogenate of superovulated rat ovary indicated that both enzymes were exclusively cytoplasmic. The tissue was also found to contain pyruvate carboxylase (exclusively mitochondrial), NAD–malate dehydrogenase and aspartate aminotransferase (both mitochondrial and cytoplasmic) and ATP–citrate lyase (exclusively cytoplasmic). 2. The kinetic properties of glucose 6-phosphate dehydrogenase, NADP–malate dehydrogenase and NADP–isocitrate dehydrogenase were determined and compared with the whole-tissue concentrations of their substrates and NADPH; NADPH is a competitive inhibitor of all three enzymes. The concentrations of glucose 6-phosphate, malate and isocitrate in incubated tissue slices were raised at least tenfold by the addition of glucose to the incubation medium, from the values below to values above the respective Km values of the dehydrogenases. Glucose doubled the tissue concentration of NADPH. 3. Steroidogenesis from acetate is stimulated by glucose in slices of superovulated rat ovary incubated in vitro. It was found that this stimulatory effect of glucose can be mimicked by malate, isocitrate, lactate and pyruvate. 4. It is concluded that NADP–malate dehydrogenase or NADP–isocitrate dehydrogenase or both may play an important role in the formation of NADPH in the superovulated rat ovary. It is suggested that the stimulatory effect of glucose on steroidogenesis from acetate results from an increased rate of NADPH formation through one or both dehydrogenases, brought about by the increases in the concentrations of malate, isocitrate or both. Possible pathways involving the two enzymes are discussed. PMID:4393612

  8. Bound anionic states of adenine

    SciTech Connect

    Haranczyk, Maciej; Gutowski, Maciej S; Li, Xiang; Bowen, Kit H

    2007-03-20

    Anionic states of nucleic acid bases are involved in DNA damage by low-energy electrons and in charge transfer through DNA. Previous gas phase studies of free, unsolvated nucleic acid base parent anions probed only dipole-bound states, which are not present in condensed phase environments, but did not observe valence anionic states, which for purine bases, are thought to be adiabatically unbound. Contrary to this expectation, we have demonstrated that some thus far ignored tautomers of adenine, which result from enamine-imine transformations, support valence anionic states with electron vertical detachment energies as large as 2.2 eV, and at least one of these anionic tautomers is adiabatically bound. Moreover, we predict that the new anionic tautomers should also dominate in solutions and should be characterized by larger values of electron vertical detachment energy than the canonical valence anion. All of the new-found anionic tautomers might be formed in the course of dissociative electron attachment followed by a hydrogen atom attachment to a carbon atom, and they might affect the structure and properties of DNA and RNA exposed to low-energy electrons. The discovery of these valence anionic states of adenine was facilitated by the development of: (i) a new experimental method for preparing parent anions of nucleic acid bases for photoelectron experiments, and (ii) a new combinatorial/ quantum chemical approach for identification of the most stable tautomers of organic molecules. The computational portion of this work was supported by the: (i) Polish State Committee for Scientific Research (KBN) Grants: DS/8000-4-0140-7 (M.G.) and N204 127 31/2963 (M.H.), (ii) European Social Funds (EFS) ZPORR/2.22/II/2.6/ARP/U/2/05 (M.H.), and (iii) US DOE Office of Biological and Environmental Research, Low Dose Radiation Research Program (M.G.). M.H. holds the Foundation for Polish Science (FNP) award for young scientists. The calculations were performed at the Academic

  9. Electrocatalytic oxidation of dihydronicotineamide adenine dinucleotide on gold electrode modified with catechol-terminated alkanethiol self-assembly.

    PubMed

    Nakano, Koji; Ohkubo, Kimihiko; Taira, Hiroaki; Takagi, Makoto; Imato, Toshihiko

    2008-06-30

    Synthesis of a mercaptoundecaneamide derivative having a terminus of catechol is described. FT-IR spectroscopic characterization showed that the new molecular entry simply undergoes molecular self-assembly on Au substrate surfaces promoting intra- and intermolecular hydrogen bonds to form well-packed monolayers. Cyclic voltammetric (CV) measurements on the monolayer-modified Au electrode revealed that the surface adlayer possesses specific electrochemical activity due to the reversible catechol/o-quinone redox reaction having characteristics of a surface process and also pH-dependence in its formal potential (59 mV per pH). Detailed analysis of CVs gave fundamental electrochemical parameters including the electroactive surface coverage (0.20-0.24 nmol cm(-2)), the transfer coefficients (0.24 in oxidation and 0.81 in reduction), and also the electron transfer rate constant (1.10-2.76 s(-1)). These data were almost consistent to those seen in literature. We have also found that the catechol monolayer modified electrode exhibits an electrocatalytic function in NADH oxidation. That is, the faradaic current appeared reinforcingly at around the same potential where catechol function is oxidized in the monolayer and increased with an increase in the NADH concentration from 1 to 5 mM, and then reached to a plateau indicating a catalyzed reaction pathway. Detailed analyses revealed that the present system could be characterized by its weak stability of the intermediate compound formed and prompt reaction rate compared with the previously reported chemically modified electrode (CME) systems. We think this type of achievement should be important for the basics of biosensors that rely on dehydrogenase enzymes.

  10. Syntheses of nicotinamide riboside and derivatives: effective agents for increasing nicotinamide adenine dinucleotide concentrations in mammalian cells.

    PubMed

    Yang, Tianle; Chan, Noel Yan-Ki; Sauve, Anthony A

    2007-12-27

    A new two-step methodology achieves stereoselective synthesis of beta-nicotinamide riboside and a series of related amide, ester, and acid nucleosides. Compounds were prepared through a triacetylated-nicotinate ester nucleoside, via coupling of either ethylnicotinate or phenylnicotinate with 1,2,3,5-tetra-O-acetyl-beta-D-ribofuranose. Nicotinamide riboside, nicotinic acid riboside, O-ethylnicotinate riboside, O-methylnicotinate riboside, and several N-alkyl derivatives increased NAD+ concentrations from 1.2-2.7-fold in several mammalian cell lines. These findings establish bioavailability and potent effects of these nucleosides in stimulating the increase of NAD+ concentrations in mammalian cells.

  11. The ascorbic acid-dependent oxidation of reduced nicotinamide–adenine dinucleotide by ciliary and retinal microsomes

    PubMed Central

    Heath, H.; Fiddick, Rosemary

    1965-01-01

    1. The presence of an ascorbic acid-dependent NADH oxidation in ocular tissues has been established. Subcellular fractionation revealed that the enzyme is localized in the microsomes. The distribution of the enzyme in some ocular tissues has been determined; microsomes from the ciliary processes and the retina have comparable activities, which are much higher than those from the cornea or lens. 2. NADPH cannot replace NADH, and cysteine, reduced glutathione, ergothioneine and dehydroascorbic acid cannot be substituted for ascorbic acid in the reaction. The rate of NADH oxidation was greatly increased in the presence of cucumber ascorbate oxidase, and the enzyme appears to be NADH–monodehydroascorbate transhydrogenase. 3. Cytochrome b5 is present in retinal microsomes. 4. The enzyme is inhibited by p-chloromercuribenzoate and iodoacetate, but not by cyanide, Amytal or malonate. 5. High concentrations of chloroquine cause a partial inhibition of the reaction, probably owing to interaction of this compound with the enzyme thiol groups. Low concentrations of Diamox, comparable with those attained in tissues during therapy with this drug, bring about partial inhibition of the reaction. Eserine, cortisone, hydrocortisone, 11-deoxycorticosterone and dexamethasone have no effect on the rate of oxidation. 6. The possible role of ascorbic acid and NADH–monodehydroascorbate transhydrogenase in the formation of aqueous humour and secretory mechanisms is discussed. PMID:14345883

  12. Enzymatic production by tissue extracts of a metabolite of nicotinamide adenine dinucleotide with calcium-releasing ability

    SciTech Connect

    Tich, N.R.

    1989-01-01

    This research investigated the occurrence and characterization of the metabolite in mammalian tissues. In all mammalian tissues tested, including rabbit liver, heart, spleen, kidney, and brain, the factor to convert NAD into its active metabolite was present. The conversion exhibited many characteristics of an enzymatic process such as temperature sensitivity, concentration dependence and protease sensitivity. Production of the NAD metabolite occurred within a time frame of 15-45 minutes at 37{degree}C, depending upon the particular preparation. The metabolite was isolated using high performance liquid chromatography from all mammalian tissues. This purified metabolite was then tested for its effectiveness in releasing intracellular calcium in an intact cell by microinjecting it into unfertilized sea urchin eggs. These eggs undergo a massive morphological change upon fertilization which is dependent upon the release of calcium from inside the cell. Upon injection of the NAD metabolite into unfertilized eggs, this same morphological change was observed showing indirectly that the metabolite released intracellular calcium from an intact, viable cell. In addition, radioactive studies using {sup 45}Ca{sup 2+} loaded into permeabilized hepatocytes, indicated in preliminary studies that the NAD metabolite could also release calcium from intracellular stores of mammalian cells.

  13. Covalent attachment of flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN) to enzymes: the current state of affairs.

    PubMed Central

    Mewies, M.; McIntire, W. S.; Scrutton, N. S.

    1998-01-01

    The first identified covalent flavoprotein, a component of mammalian succinate dehydrogenase, was reported 42 years ago. Since that time, more than 20 covalent flavoenzymes have been described, each possessing one of five modes of FAD or FMN linkage to protein. Despite the early identification of covalent flavoproteins, the mechanisms of covalent bond formation and the roles of the covalent links are only recently being appreciated. The main focus of this review is, therefore, one of mechanism and function, in addition to surveying the types of linkage observed and the methods employed for their identification. Case studies are presented for a variety of covalent flavoenzymes, from which general findings are beginning to emerge. PMID:9514256

  14. Alternative splicing and differential expression of two transcripts of nicotine adenine dinucleotide phosphate oxidase B gene from Zea mays.

    PubMed

    Lin, Fan; Zhang, Yun; Jiang, Ming-Yi

    2009-03-01

    With the exception of rice, little is known about the existence of respiratory burst oxidase homolog (rboh) gene in cereals. The present study reports the cloning and analysis of a novel rboh gene, termed ZmrbohB, from maize (Zea mays L.). The full-length cDNA of ZmrbohB encodes a 942 amino acid protein containing all of the respiratory burst oxidase homolog catalytically critical motifs. Alternative splicing of ZmrbohB has generated two transcript isoforms, ZmrbohB-alpha and -beta. Spliced transcript ZmrbohB-beta retains an unspliced intron 11 that carries a premature termination codon and probably leads to nonsense-mediated mRNA decay. Expression analysis showed that two splice isoforms were differentially expressed in various tissues and at different developmental stages, and the major product was ZmrbohB-alpha. The transcripts of ZmrbohB-alpha accumulated markedly when the maize seedlings were subjected to various abiotic stimuli, such as wounding, cold (4 degrees C), heat (40 degrees C), UV and salinity stress. In addition, several abiotic stimuli also affected the alternative splicing pattern of ZmrbohB except wounding. These results provide new insight into roles in the expression regulation of plant rboh genes and suggest that ZmrbohB gene may play a role in response to environmental stresses.

  15. The purification and properties of the respiratory-chain reduced nicotinamide–adenine dinucleotide dehydrogenase of Torulopsis utilis

    PubMed Central

    Tottmar, S. O. C.; Ragan, C. I.

    1971-01-01

    1. An NADH–ferricyanide reductase activity has been isolated from the respiratory chain of Torulopsis utilis by using detergents. The isolated enzyme contains non-haem iron, acid-labile sulphide and FMN in the molar proportions 27.5:28.4:1. The preparation is free of FAD and largely free of cytochrome. 2. The enzyme catalyses ferricyanide reduction by NADPH at about 1% of the rate with NADH, and reacts poorly with acceptors other than ferricyanide. The rates of reduction of some acceptors are, as percentages of the rate with ferricyanide: menadione, 0.35%; lipoate, 0.01%; cytochrome c, 0.065%; dichlorophenolindophenol, 0.35%; ubiquinone-1, 0.08%. 3. Several properties of submitochondrial particles of T. utilis (non-haem iron, acid-labile sulphide, FMN and an NADH-reducible electron-paramagnetic-resonance signal) were found to co-purify with the NADH–ferricyanide reductase activity. Thus about 70% of the FMN and, within the limits of accuracy of the experiments, 100% of the non-haem iron and acid-labile sulphide of submitochondrial particles derived from T. utilis cells grown under conditions of glycerol limitation (but relatively low iron availability) can be attributed to the NADH–ferricyanide reductase. 4. It was also shown that the component of submitochondrial particles specifically bleached at 460nm by NADH [species 1 of Ragan & Garland (1971)] co-purifies with the NADH–ferricyanide reductase. 5. This successful purification of an NADH dehydrogenase from T. utilis forms a starting point for investigating the molecular properties of phenotypically modified mitochondrial NADH oxidation pathways that lack energy conservation between NADH and the cytochromes. PMID:4399788

  16. Noncompetitive and irreversible inhibition of xanthine oxidase by benzimidazole analogues acting at the functional flavin adenine dinucleotide cofactor.

    PubMed

    Skibo, E B

    1986-07-29

    Benzimidazole derivatives possessing a leaving group in the 2 alpha-position and either 4,7-dione, 4,7-diol, or 4,7-dimethoxy substituents were examined as inhibitors of buttermilk xanthine oxidase. The quinone and hydroquinone derivatives are not inhibitors of xanthine-oxygen reductase activity, even though the latter is a powerful alkylating agent. The methoxylated hydroquinones are linear noncompetitive inhibitors, the best of which is the 2 alpha-bromo analogue (Ki = 46 microM). During xanthine-oxygen reductase activity, the 2 alpha-bromo analogue irreversibly traps the reduced enzyme. Formation of a C(4a) adduct of the reduced functional FAD cofactor is postulated on the basis of UV-visible spectral evidence and reconstitution of the enzyme after removal of the altered FAD. A probable sequence of events is reversible binding at or near the reduced cofactor followed by adduct formation. It is concluded that potent tight binding inhibitors could be designed that act at the FAD cofactor rather than the purine active site.

  17. Analysing two dinucleotide repeats of FVIII gene in Iranian population.

    PubMed

    Rabbani, B; Rezaeian, A; Khanahmad, H; Bagheri, R; Kamali, E; Zeinali, S

    2007-11-01

    Using dinucleotide repeats for carrier detection and prenatal diagnosis of haemophilia A patients, led us to find different alleles and their frequencies in Iranian population. Polymerase chain reaction (PCR) amplification of two short tandem repeat (STR) loci of factor VIII (FVIII) gene was performed, and the PCR products were resolved on 10% native polyacrylamide gel, and samples were analysed with sequenced DNA markers made of PCR cloning of the dinucleotide FVIII gene fragments. Seven different alleles were observed for intron 13 STR, having 18-24 (CA) repeating units and five alleles for intron 22 STR having 24-28 repeating units of (CACT). Bands produced during dinucleotide study were defined in detail so this could improve the genotyping of heterozygotes and homozygotes. Conformational band produced were characterized to specify the dinucleotide pattern. Our results confirm the Hardy-Weinberg proportions of the heterozygosity rate of the 85 analysed individuals. The observed heterozygosity rate for intron 13 and 22 was 52% and 59% respectively. Our data also indicate that our population is closer to caucasians than to any other populations. Finding different dinucleotide repeat alleles and their frequencies has made it possible to identify carriers and provide prenatal diagnosis with more confidence. This allows antenatal diagnosis to be performed in the vast majority of carriers.

  18. Method for preparing porous metal hydride compacts

    DOEpatents

    Ron, Moshe; Gruen, Dieter M.; Mendelsohn, Marshall H.; Sheft, Irving

    1981-01-01

    A method for preparing porous metallic-matrix hydride compacts which can be repeatedly hydrided and dehydrided without disintegration. A mixture of a finely divided metal hydride and a finely divided matrix metal is contacted with a poison which prevents the metal hydride from dehydriding at room temperature and atmospheric pressure. The mixture of matrix metal and poisoned metal hydride is then compacted under pressure at room temperature to form porous metallic-matrix hydride compacts.

  19. Method for preparing porous metal hydride compacts

    DOEpatents

    Ron, M.; Gruen, D.M.; Mendelsohn, M.H.; Sheft, I.

    1980-01-21

    A method for preparing porous metallic-matrix hydride compacts which can be repeatedly hydrided and dehydrided without disintegration. A mixture of a finely divided metal hydride and a finely divided matrix metal is contacted with a poison which prevents the metal hydride from dehydriding at room temperature and atmospheric pressure. The mixture of matrix metal and poisoned metal hydride is then compacted under pressure at room temperature to form porous metallic-matrix hydride compacts.

  20. Materials engineering of metal hydrides

    SciTech Connect

    Gruen, D.M.; Mendelsohn, M.H.

    1981-01-01

    Intermetallic hydrides of the AB/sub 5/ type have enthalpies in the range valid for chemical heat pumps. A scheme for manufacturing hydrides with optimal properties for a chemical heat pump is described, using LaNi/sub 5-x/Al/sub x/ and ZrV/sub 2x/Cr/sub x as examples. The Laves-phase ternary hydrides appear to be good candidates for gettering hydrogen in the Tokamak Fusion Test Reactor. (DLC)

  1. Superstoichiometric hydride of zirconium

    SciTech Connect

    Kupryazhkin, A.Ya.; Shchepetkin, A.A.; Zabolotskaya, E.V.; Pletnev, R.N.; Alyamovskii, S.I.; Kitaev, G.A.

    1987-12-01

    Superstoichiometric hydrides of zirconium have been obtained all the way up to the composition ZrH/sub 2.4/ by additional hydrogenation of ZrH/sub 2/ as a result of redistribution of hydrogen atoms between t- and o-positions. In the preparation of the hydrides the authors used zirconium iodide with an impurity content no greater than 10/sup -2/ to 10/sup -2/ mole %; the hydrogen and helium used in this work had a minimum purity of 99.95%. The content of hydrogen in the specimens was determined by a volumetric method. The x-ray diffraction analysis was performed in a DRON-2.0 unit (CuK/sub ..cap alpha../ radiation). PMR spectra were recorded in a broad-line spectrometer in the temperature interval 150-450 K.

  2. Hydrogen Outgassing from Lithium Hydride

    SciTech Connect

    Dinh, L N; Schildbach, M A; Smith, R A; Balazs1, B; McLean II, W

    2006-04-20

    Lithium hydride is a nuclear material with a great affinity for moisture. As a result of exposure to water vapor during machining, transportation, storage and assembly, a corrosion layer (oxide and/or hydroxide) always forms on the surface of lithium hydride resulting in the release of hydrogen gas. Thermodynamically, lithium hydride, lithium oxide and lithium hydroxide are all stable. However, lithium hydroxides formed near the lithium hydride substrate (interface hydroxide) and near the sample/vacuum interface (surface hydroxide) are much less thermally stable than their bulk counterpart. In a dry environment, the interface/surface hydroxides slowly degenerate over many years/decades at room temperature into lithium oxide, releasing water vapor and ultimately hydrogen gas through reaction of the water vapor with the lithium hydride substrate. This outgassing can potentially cause metal hydriding and/or compatibility issues elsewhere in the device. In this chapter, the morphology and the chemistry of the corrosion layer grown on lithium hydride (and in some cases, its isotopic cousin, lithium deuteride) as a result of exposure to moisture are investigated. The hydrogen outgassing processes associated with the formation and subsequent degeneration of this corrosion layer are described. Experimental techniques to measure the hydrogen outgassing kinetics from lithium hydride and methods employing the measured kinetics to predict hydrogen outgassing as a function of time and temperature are presented. Finally, practical procedures to mitigate the problem of hydrogen outgassing from lithium hydride are discussed.

  3. On the origin of multiexponential fluorescence decays from 2-aminopurine-labeled dinucleotides

    NASA Astrophysics Data System (ADS)

    Remington, Jacob M.; Philip, Abbey M.; Hariharan, Mahesh; Kohler, Bern

    2016-10-01

    The fluorescent probe 2-aminopurine (2Ap) has been used for decades to study local conformational fluctuations in DNA. Steady-state and time-resolved measurements of 2Ap fluorescence have been used to predict specific conformational states through suitable modeling of the quenching of the fluorescence of a 2Ap residue incorporated site-specifically into a DNA strand. The success of this approach has been limited by a lack of understanding of the precise factors responsible for the complex, multiexponential decays observed experimentally. In this study, dinucleotides composed of 2Ap and adenine were studied by the time-correlated single-photon counting technique to investigate the causes of heterogeneous emission kinetics. Contrary to previous reports, we argue that emission from 2Ap that is stacked with a neighboring base contributes negligibly to the emission signals recorded more than 50 ps after excitation, which are instead dominated by emission from unstacked 2Ap. We find that the decay kinetics can be modeled using a continuous lifetime distribution, which arises from the inherent distance dependence of electron transfer rates without the need to postulate a small number of discrete states with decay times derived from multiexponential fits. These results offer a new perspective on the quenching of 2Ap fluorescence and expand the information that can be obtained from experiments.

  4. On the origin of multiexponential fluorescence decays from 2-aminopurine-labeled dinucleotides.

    PubMed

    Remington, Jacob M; Philip, Abbey M; Hariharan, Mahesh; Kohler, Bern

    2016-10-21

    The fluorescent probe 2-aminopurine (2Ap) has been used for decades to study local conformational fluctuations in DNA. Steady-state and time-resolved measurements of 2Ap fluorescence have been used to predict specific conformational states through suitable modeling of the quenching of the fluorescence of a 2Ap residue incorporated site-specifically into a DNA strand. The success of this approach has been limited by a lack of understanding of the precise factors responsible for the complex, multiexponential decays observed experimentally. In this study, dinucleotides composed of 2Ap and adenine were studied by the time-correlated single-photon counting technique to investigate the causes of heterogeneous emission kinetics. Contrary to previous reports, we argue that emission from 2Ap that is stacked with a neighboring base contributes negligibly to the emission signals recorded more than 50 ps after excitation, which are instead dominated by emission from unstacked 2Ap. We find that the decay kinetics can be modeled using a continuous lifetime distribution, which arises from the inherent distance dependence of electron transfer rates without the need to postulate a small number of discrete states with decay times derived from multiexponential fits. These results offer a new perspective on the quenching of 2Ap fluorescence and expand the information that can be obtained from experiments.

  5. 17. VIEW OF HYDRIDING SYSTEM IN BUILDING 881. THE HYDRIDING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    17. VIEW OF HYDRIDING SYSTEM IN BUILDING 881. THE HYDRIDING SYSTEM WAS PART OF THE FAST ENRICHED URANIUM RECOVERY PROCESS. (11/11/59) - Rocky Flats Plant, General Manufacturing, Support, Records-Central Computing, Southern portion of Plant, Golden, Jefferson County, CO

  6. Photophysical deactivation pathways in adenine oligonucleotides.

    PubMed

    Spata, Vincent A; Matsika, Spiridoula

    2015-12-14

    In this work we study deactivation processes in adenine oligomers after absorption of UV radiation using Quantum Mechanics combined with Molecular Mechanics (QM/MM). Correlated electronic structure methods appropriate for describing the excited states are used to describe a π-stacked dimer of adenine bases incorporated into (dA)20(dT)20. The results of these calculations reveal three different types of excited state minima which play a role in deactivation processes. Within this set of minima there are minima where the excited state is localized on one adenine (monomer-like) as well as minima where the excited state is delocalized on two adenines, forming different types of excimers and bonded excimers of varying but inter-related character. The proximity of their energies reveals that the minima can decay into one another along a flat potential energy surface dependent on the interbase separation. Additionally, analysis of the emissive energies and other physical properties, including theoretical anisotropy calculations, and comparison with fluorescence experiments, provides evidence that excimers play an important role in long-lived signals in adenine oligonucleotides while the subpicosecond decay is attributed to monomer-like minima. The necessity for a close approach of the nucleobases reveals that the deactivation mechanism is tied to macro-molecular motion.

  7. Hydrogenation using hydrides and acid

    DOEpatents

    Bullock, R. Morris

    1990-10-30

    A process for the non-catalytic hydrogenation of organic compounds, which contain at least one reducible functional group, which comprises reacting the organic compound, a hydride complex, preferably a transition metal hydride complex or an organosilane, and a strong acid in a liquid phase.

  8. Dimensionally stable metallic hydride composition

    DOEpatents

    Heung, Leung K.

    1994-01-01

    A stable, metallic hydride composition and a process for making such a composition. The composition comprises a uniformly blended mixture of a metal hydride, kieselguhr, and a ballast metal, all in the form of particles. The composition is made by subjecting a metal hydride to one or more hydrogen absorption/desorption cycles to disintegrate the hydride particles to less than approximately 100 microns in size. The particles are partly oxidized, then blended with the ballast metal and the kieselguhr to form a uniform mixture. The mixture is compressed into pellets and calcined. Preferably, the mixture includes approximately 10 vol. % or more kieselguhr and approximately 50 vol. % or more ballast. Metal hydrides that can be used in the composition include Zr, Ti, V, Nb, Pd, as well as binary, tertiary, and more complex alloys of La, Al, Cu, Ti, Co, Ni, Fe, Zr, Mg, Ca, Mn, and mixtures and other combinations thereof. Ballast metals include Al, Cu and Ni.

  9. Adenine auxotrophy--be aware: some effects of adenine auxotrophy in Saccharomyces cerevisiae strain W303-1A.

    PubMed

    Kokina, Agnese; Kibilds, Juris; Liepins, Janis

    2014-08-01

    Adenine auxotrophy is a commonly used genetic marker in haploid yeast strains. Strain W303-1A, which carries the ade2-1 mutation, is widely used in physiological and genetic research. Yeast extract-based rich medium contains a low level of adenine, so that adenine is often depleted before glucose. This could affect the cell physiology of adenine auxotrophs grown in rich medium. The aim of our study was to assess the effects of adenine auxotrophy on cell morphology and stress physiology. Our results show that adenine depletion halts cell division, but that culture optical density continues to increase due to cell swelling. Accumulation of trehalose and a coincident 10-fold increase in desiccation stress tolerance is observed in adenine auxotrophs after adenine depletion, when compared to prototrophs. Under adenine starvation, long-term survival of W303-1A is lower than during carbon starvation, but higher than during leucine starvation. We observed drastic adenine-dependent changes in cell stress physiology, suggesting that results may be biased when adenine auxotrophs are grown in rich media without adenine supplementation.

  10. Hydride development for hydrogen storage

    SciTech Connect

    Thomas, G.J.; Guthrie, S.E.; Bauer, W.; Yang, N.Y.C.; Sandrock, G.

    1996-10-01

    The purpose of this project is to develop and demonstrate improved hydride materials for hydrogen storage. The work currently is organized into four tasks: hydride development, bed fabrication, materials support for engineering systems, and IEA Annex 12 activities. At the present time, hydride development is focused on Mg alloys. These materials generally have higher weight densities for storing hydrogen than rare earth or transition metal alloys, but suffer from high operating temperatures, slow kinetic behavior and material stability. The authors approach is to study bulk alloy additions which increase equilibrium overpressure, in combination with stable surface alloy modification and particle size control to improve kinetic properties. This work attempts to build on the considerable previous research in this area, but examines specific alloy systems in greater detail, with attention to known phase properties and structures. The authors have found that specific phases can be produced which have significantly improved hydride properties compared to previous studies.

  11. Complex Hydrides for Hydrogen Storage

    SciTech Connect

    Slattery, Darlene; Hampton, Michael

    2003-03-10

    This report describes research into the use of complex hydrides for hydrogen storage. The synthesis of a number of alanates, (AIH4) compounds, was investigated. Both wet chemical and mechano-chemical methods were studied.

  12. Cyclic Dinucleotide-Controlled Regulatory Pathways in Streptomyces Species

    PubMed Central

    2015-01-01

    The cyclic dinucleotides cyclic 3′,5′-diguanylate (c-di-GMP) and cyclic 3′,5′-diadenylate (c-di-AMP) have emerged as key components of bacterial signal transduction networks. These closely related second messengers follow the classical general principles of nucleotide signaling by integrating diverse signals into regulatory pathways that control cellular responses to changing environments. They impact distinct cellular processes, with c-di-GMP having an established role in promoting bacterial adhesion and inhibiting motility and c-di-AMP being involved in cell wall metabolism, potassium homeostasis, and DNA repair. The involvement of c-dinucleotides in the physiology of the filamentous, nonmotile streptomycetes remained obscure until recent discoveries showed that c-di-GMP controls the activity of the developmental master regulator BldD and that c-di-AMP determines the level of the resuscitation-promoting factor A(RpfA) cell wall-remodelling enzyme. Here, I summarize our current knowledge of c-dinucleotide signaling in Streptomyces species and highlight the important roles of c-di-GMP and c-di-AMP in the biology of these antibiotic-producing, multicellular bacteria. PMID:26216850

  13. Graphene-Enhanced Raman Scattering from the Adenine Molecules

    NASA Astrophysics Data System (ADS)

    Dolgov, Leonid; Pidhirnyi, Denys; Dovbeshko, Galyna; Lebedieva, Tetiana; Kiisk, Valter; Heinsalu, Siim; Lange, Sven; Jaaniso, Raivo; Sildos, Ilmo

    2016-04-01

    An enhanced Raman scattering from a thin layer of adenine molecules deposited on graphene substrate was detected. The value of enhancement depends on the photon energy of the exciting light. The benzene ring in the structure of adenine molecule suggests π-stacking of adenine molecule on top of graphene. So, it is proposed that the enhancement in the adenine Raman signal is explained by the resonance electron transfer from the Fermi level of graphene to the lowest unoccupied molecular orbital (LUMO) level of adenine.

  14. Low density metal hydride foams

    DOEpatents

    Maienschein, Jon L.; Barry, Patrick E.

    1991-01-01

    Disclosed is a low density foam having a porosity of from 0 to 98% and a density less than about 0.67 gm/cc, prepared by heating a mixture of powered lithium hydride and beryllium hydride in an inert atmosphere at a temperature ranging from about 455 to about 490 K for a period of time sufficient to cause foaming of said mixture, and cooling the foam thus produced. Also disclosed is the process of making the foam.

  15. Atomic substitution reveals the structural basis for substrate adenine recognition and removal by adenine DNA glycosylase

    SciTech Connect

    Lee, Seongmin; Verdine, Gregory L.

    2010-01-14

    Adenine DNA glycosylase catalyzes the glycolytic removal of adenine from the promutagenic A {center_dot} oxoG base pair in DNA. The general features of DNA recognition by an adenine DNA glycosylase, Bacillus stearothermophilus MutY, have previously been revealed via the X-ray structure of a catalytically inactive mutant protein bound to an A:oxoG-containing DNA duplex. Although the structure revealed the substrate adenine to be, as expected, extruded from the DNA helix and inserted into an extrahelical active site pocket on the enzyme, the substrate adenine engaged in no direct contacts with active site residues. This feature was paradoxical, because other glycosylases have been observed to engage their substrates primarily through direct contacts. The lack of direct contacts in the case of MutY suggested that either MutY uses a distinctive logic for substrate recognition or that the X-ray structure had captured a noncatalytically competent state in lesion recognition. To gain further insight into this issue, we crystallized wild-type MutY bound to DNA containing a catalytically inactive analog of 2'-deoxyadenosine in which a single 2'-H atom was replaced by fluorine. The structure of this fluorinated lesion-recognition complex (FLRC) reveals the substrate adenine buried more deeply into the active site pocket than in the prior structure and now engaged in multiple direct hydrogen bonding and hydrophobic interactions. This structure appears to capture the catalytically competent state of adenine DNA glycosylases, and it suggests a catalytic mechanism for this class of enzymes, one in which general acid-catalyzed protonation of the nucleobase promotes glycosidic bond cleavage.

  16. The catalase activity of diiron adenine deaminase

    SciTech Connect

    Kamat S. S.; Swaminathan S.; Holmes-Hampton, G. P.; Bagaria, A.; Kumaran, D.; Tichy, S. E.; Gheyi, T.; Zheng, X.; Bain, K.; Groshong, C.; Emtage, S.; Sauder, J. M.; Burley, S. K.; Lindahl, P. A.; Raushel, F. M.

    2011-12-01

    Adenine deaminase (ADE) from the amidohydrolase superfamily (AHS) of enzymes catalyzes the conversion of adenine to hypoxanthine and ammonia. Enzyme isolated from Escherichia coli was largely inactive toward the deamination of adenine. Molecular weight determinations by mass spectrometry provided evidence that multiple histidine and methionine residues were oxygenated. When iron was sequestered with a metal chelator and the growth medium supplemented with Mn{sup 2+} before induction, the post-translational modifications disappeared. Enzyme expressed and purified under these conditions was substantially more active for adenine deamination. Apo-enzyme was prepared and reconstituted with two equivalents of FeSO{sub 4}. Inductively coupled plasma mass spectrometry and Moessbauer spectroscopy demonstrated that this protein contained two high-spin ferrous ions per monomer of ADE. In addition to the adenine deaminase activity, [Fe{sup II}/Fe{sup II}]-ADE catalyzed the conversion of H{sub 2}O{sub 2} to O{sub 2} and H{sub 2}O. The values of k{sub cat} and k{sub cat}/K{sub m} for the catalase activity are 200 s{sup -1} and 2.4 x 10{sup 4} M{sup -1} s{sup -1}, respectively. [Fe{sup II}/Fe{sup II}]-ADE underwent more than 100 turnovers with H{sub 2}O{sub 2} before the enzyme was inactivated due to oxygenation of histidine residues critical for metal binding. The iron in the inactive enzyme was high-spin ferric with g{sub ave} = 4.3 EPR signal and no evidence of anti-ferromagnetic spin-coupling. A model is proposed for the disproportionation of H{sub 2}O{sub 2} by [Fe{sup II}/Fe{sup II}]-ADE that involves the cycling of the binuclear metal center between the di-ferric and di-ferrous oxidation states. Oxygenation of active site residues occurs via release of hydroxyl radicals. These findings represent the first report of redox reaction catalysis by any member of the AHS.

  17. Complex and liquid hydrides for energy storage

    NASA Astrophysics Data System (ADS)

    Callini, Elsa; Atakli, Zuleyha Özlem Kocabas; Hauback, Bjørn C.; Orimo, Shin-ichi; Jensen, Craig; Dornheim, Martin; Grant, David; Cho, Young Whan; Chen, Ping; Hjörvarsson, Bjørgvin; de Jongh, Petra; Weidenthaler, Claudia; Baricco, Marcello; Paskevicius, Mark; Jensen, Torben R.; Bowden, Mark E.; Autrey, Thomas S.; Züttel, Andreas

    2016-04-01

    The research on complex hydrides for hydrogen storage was initiated by the discovery of Ti as a hydrogen sorption catalyst in NaAlH4 by Boris Bogdanovic in 1996. A large number of new complex hydride materials in various forms and combinations have been synthesized and characterized, and the knowledge regarding the properties of complex hydrides and the synthesis methods has grown enormously since then. A significant portion of the research groups active in the field of complex hydrides is collaborators in the International Energy Agreement Task 32. This paper reports about the important issues in the field of complex hydride research, i.e. the synthesis of borohydrides, the thermodynamics of complex hydrides, the effects of size and confinement, the hydrogen sorption mechanism and the complex hydride composites as well as the properties of liquid complex hydrides. This paper is the result of the collaboration of several groups and is an excellent summary of the recent achievements.

  18. Complex and liquid hydrides for energy storage

    SciTech Connect

    Callini, Elsa; Atakli, Zuleyha Özlem Kocabas; Hauback, Bjørn C.; Orimo, Shin-ichi; Jensen, Craig; Dornheim, Martin; Grant, David; Cho, Young Whan; Chen, Ping; Hjörvarsson, Bjørgvin; de Jongh, Petra; Weidenthaler, Claudia; Baricco, Marcello; Paskevicius, Mark; Jensen, Torben R.; Bowden, Mark E.; Autrey, Thomas S.; Züttel, Andreas

    2016-03-10

    The research on complex hydrides for hydrogen storage was imitated by the discovery of Ti as a hydrogen sorption catalyst in NaAlH4 by Boris Bogdanovic in 1996. A large number of new complex hydride materials in various forms and combinations have been synthesized and characterized and the knowledge on the properties of complex hydrides and the synthesis methods has grown enormously since then. A significant part of the research groups active in the field of complex hydrides are collaborators in the IEA task 32. This paper reports about the important issues in the field of the complex hydride research, i.e. the synthesis of borohydrides, the thermodynamics of complex hydrides and their thermodynamic properties, the effects of size and confinement, the hydrogen sorption mechanism and the complex hydride composites as well as the properties of liquid complex hydrides. This paper is the result of the collaboration of several groups and excellent summary of the recent achievements.

  19. A new route to metal hydrides

    SciTech Connect

    Murphy, D.W.; Zahurak, S.M.; Vyas, B.; Thomas, M.; Badding, M.E.; Fang, W.C. )

    1993-06-01

    Aqueous borohydride is shown to be an effective reagent for hydriding metals and intermetallics. It is the hydriding equivalent of 20-30 atm of H[sub 2]. The reaction is a convenient way to screen materials for hydride formation and possible utility in applications such as nickel-metal hydride batteries. The reaction is also a convenient alternative to decrepitation for the production of free flowing powders. 16 refs., 1 fig., 1 tab.

  20. Gas-phase acidities of binary hydrides.

    NASA Technical Reports Server (NTRS)

    Brauman, J. I.; Eyler, J. R.; Blair, L. K.; White, M. J.; Comisarow, M. B.; Smyth, K. C.

    1971-01-01

    The preferred direction of proton transfer in a reaction between a hydride molecule and a hydride ion was studied in order to determine the relative acidities of some binary hydrides. Sufficient data are presented to make clear the periodic trends in acidities and the underlying trends in other fundamental thermochemical quantities which influence acidity. The bond dissociation energies and electron affinities of the hydrides considered are listed in a table.

  1. Photochemistry of Transition Metal Hydrides.

    PubMed

    Perutz, Robin N; Procacci, Barbara

    2016-08-10

    Photochemical reactivity associated with metal-hydrogen bonds is widespread among metal hydride complexes and has played a critical part in opening up C-H bond activation. It has been exploited to design different types of photocatalytic reactions and to obtain NMR spectra of dilute solutions with a single pulse of an NMR spectrometer. Because photolysis can be performed on fast time scales and at low temperature, metal-hydride photochemistry has enabled determination of the molecular structure and rates of reaction of highly reactive intermediates. We identify five characteristic photoprocesses of metal monohydride complexes associated with the M-H bond, of which the most widespread are M-H homolysis and R-H reductive elimination. For metal dihydride complexes, the dominant photoprocess is reductive elimination of H2. Dihydrogen complexes typically lose H2 photochemically. The majority of photochemical reactions are likely to be dissociative, but hydride complexes may be designed with equilibrated excited states that undergo different photochemical reactions, including proton transfer or hydride transfer. The photochemical mechanisms of a few reactions have been analyzed by computational methods, including quantum dynamics. A section on specialist methods (time-resolved spectroscopy, matrix isolation, NMR, and computational methods) and a survey of transition metal hydride photochemistry organized by transition metal group complete the Review.

  2. Methods for detection of methyl-CpG dinucleotides

    DOEpatents

    Dunn, John J

    2013-11-26

    The invention provides methods for enriching methyl-CpG sequences from a DNA sample. The method makes use of conversion of cytosine residues to uracil under conditions in which methyl-cytosine residues are preserved. Additional methods of the invention enable to preservation of the context of me-CpG dinucleotides. The invention also provides a recombinant, full length and substantially pure McrA protein (rMcrA) for binding and isolation of DNA fragments containing the sequence 5'-C.sup.MeCpGG-3'. Methods for making and using the rMcrA protein, and derivatives thereof are provided.

  3. Methods for detection of methyl-CpG dinucleotides

    DOEpatents

    Dunn, John J.

    2013-01-29

    The invention provides methods for enriching methyl-CpG sequences from a DNA sample. The method makes use of conversion of cytosine residues to uracil under conditions in which methyl-cytosine residues are preserved. Additional methods of the invention enable to preservation of the context of me-CpG dinucleotides. The invention also provides a recombinant, full length and substantially pure McrA protein (rMcrA) for binding and isolation of DNA fragments containing the sequence 5'-C.sup.MeCpGG-3'. Methods for making and using the rMcrA protein, and derivatives thereof are provided.

  4. Methods for detection of methyl-CpG dinucleotides

    DOEpatents

    Dunn, John J.

    2012-09-11

    The invention provides methods for enriching methyl-CpG sequences from a DNA sample. The method makes use of conversion of cytosine residues to uracil under conditions in which methyl-cytosine residues are preserved. Additional methods of the invention enable to preservation of the context of me-CpG dinucleotides. The invention also provides a recombinant, full length and substantially pure McrA protein (rMcrA) for binding and isolation of DNA fragments containing the sequence 5'-C.sup.MeCpGG-3'. Methods for making and using the rMcrA protein, and derivatives thereof are provided.

  5. Hydrogen, lithium, and lithium hydride production

    DOEpatents

    Brown, Sam W; Spencer, Larry S; Phillips, Michael R; Powell, G. Louis; Campbell, Peggy J

    2014-03-25

    A method of producing high purity lithium metal is provided, where gaseous-phase lithium metal is extracted from lithium hydride and condensed to form solid high purity lithium metal. The high purity lithium metal may be hydrided to provide high purity lithium hydride.

  6. Vanadium hydride deuterium-tritium generator

    DOEpatents

    Christensen, Leslie D.

    1982-01-01

    A pressure controlled vanadium hydride gas generator to provide deuterium-tritium gas in a series of pressure increments. A high pressure chamber filled with vanadium-deuterium-tritium hydride is surrounded by a heater which controls the hydride temperature. The heater is actuated by a power controller which responds to the difference signal between the actual pressure signal and a programmed pressure signal.

  7. Method of producing a chemical hydride

    DOEpatents

    Klingler, Kerry M.; Zollinger, William T.; Wilding, Bruce M.; Bingham, Dennis N.; Wendt, Kraig M.

    2007-11-13

    A method of producing a chemical hydride is described and which includes selecting a composition having chemical bonds and which is capable of forming a chemical hydride; providing a source of a hydrocarbon; and reacting the composition with the source of the hydrocarbon to generate a chemical hydride.

  8. Exploration of Excited State Deactivation Pathways of Adenine Monohydrates.

    PubMed

    Chaiwongwattana, Sermsiri; Sapunar, Marin; Ponzi, Aurora; Decleva, Piero; Došlić, Nađa

    2015-10-29

    Binding of a single water molecule has a dramatic effect on the excited state lifetime of adenine. Here we report a joint nonadiabatic dynamics and reaction paths study aimed at understanding the sub-100 fs lifetime of adenine in the monohydrates. Our nonadiabatic dynamics simulations, performed using the ADC(2) electronic structure method, show a shortening of the excited state lifetime in the monohydrates with respect to bare adenine. However, the computed lifetimes were found to be significantly longer that the observed one. By comparing the reaction pathways of several excited state deactivation processes in adenine and adenine monohydrates, we show that electron-driven proton transfer from water to nitrogen atom N3 of the adenine ring may be the process responsible for the observed ultrafast decay. The inaccessibility of the electron-driven proton transfer pathway to trajectory-based nonadiabatic dynamics simulation is discussed.

  9. Characteristics and Applications of Metal Hydrides

    NASA Technical Reports Server (NTRS)

    Egan, G. J.; Lynch, F. E.

    1987-01-01

    Report discusses engineering principles of uses of metal hydrides in spacecraft. Metal hydrides absorb, store, pump, compress, and expand hydrogen gas. Additionally, they release or absorb sizeable amounts of heat as they form and decompose - property adapted for thermal-energy management or for propulsion. Describes efforts to: Identify heat sources and sinks suitable for driving metal hydride thermal cycles in spacecraft; develop concepts for hydride subsystems employing available heating and cooling methods; and produce data base on estimated sizes, masses, and performances of hydride devices for spacecraft.

  10. Characterization of hydrides and delayed hydride cracking in zirconium alloys

    NASA Astrophysics Data System (ADS)

    Fang, Qiang

    This thesis tries to fill some of the missing gaps in the study of zirconium hydrides with state-of-art experiments, cutting edge tomographical technique, and a novel numerical algorithm. A new hydriding procedure is proposed. The new anode material and solution combination overcomes many drawbacks of the AECLRTM hydriding method and leads to superior hydriding result compared to the AECL RTM hydriding procedure. The DHC crack growth velocity of as-received Excel alloy and Zr-2.5Nb alloy together with several different heat treated Excel alloy samples are measured. While it already known that the DHC crack growth velocity increases with the increase of base metal strength, the finding that the transverse plane is the weaker plane for fatigue crack growth despite having higher resistance to DHC crack growth was unexpected. The morphologies of hydrides in a coarse grained Zircally-2 sample have been studied using synchrotron x-rays at ESRF with a new technique called Diffraction Contrast Tomography that uses simultaneous collection of tomographic data and diffraction data to determine the crystallographic orientation of crystallites (grains) in 3D. It has been previously limited to light metals such as Al or Mg (due to the use of low energy x-rays). Here we show the first DCT measurements using high energy x-rays (60 keV), allowing measurements in zirconium. A new algorithm of a computationally effcient way to characterize distributions of hydrides - in particular their orientation and/or connectivity - has been proposed. It is a modification of the standard Hough transform, which is an extension of the Hough transform widely used in the line detection of EBSD patterns. Finally, a basic model of hydrogen migration is built using ABAQUS RTM, which is a mature finite element package with tested modeling modules of a variety of physical laws. The coupling of hydrogen diffusion, lattice expansion, matrix deformation and phase transformation is investigated under

  11. The relationship between periodic dinucleotides and the nucleosomal DNA deformation revealed by normal mode analysis

    NASA Astrophysics Data System (ADS)

    Wang, Debby D.; Yan, Hong

    2011-12-01

    Nucleosomes, which contain DNA and proteins, are the basic unit of eukaryotic chromatins. Polymers such as DNA and proteins are dynamic, and their conformational changes can lead to functional changes. Periodic dinucleotide patterns exist in nucleosomal DNA chains and play an important role in the nucleosome structure. In this paper, we use normal mode analysis to detect significant structural deformations of nucleosomal DNA and investigate the relationship between periodic dinucleotides and DNA motions. We have found that periodic dinucleotides are usually located at the peaks or valleys of DNA and protein motions, revealing that they dominate the nucleosome dynamics. Also, a specific dinucleotide pattern CA/TG appears most frequently.

  12. CpG Dinucleotide Frequencies Reveal the Role of Host Methylation Capabilities in Parvovirus Evolution

    PubMed Central

    Upadhyay, Mohita; Samal, Jasmine; Kandpal, Manish; Vasaikar, Suhas; Biswas, Banhi; Gomes, James

    2013-01-01

    Parvoviruses are rapidly evolving viruses that infect a wide range of hosts, including vertebrates and invertebrates. Extensive methylation of the parvovirus genome has been recently demonstrated. A global pattern of methylation of CpG dinucleotides is seen in vertebrate genomes, compared to “fractional” methylation patterns in invertebrate genomes. It remains unknown if the loss of CpG dinucleotides occurs in all viruses of a given DNA virus family that infect host species spanning across vertebrates and invertebrates. We investigated the link between the extent of CpG dinucleotide depletion among autonomous parvoviruses and the evolutionary lineage of the infected host. We demonstrate major differences in the relative abundance of CpG dinucleotides among autonomous parvoviruses which share similar genome organization and common ancestry, depending on the infected host species. Parvoviruses infecting vertebrate hosts had significantly lower relative abundance of CpG dinucleotides than parvoviruses infecting invertebrate hosts. The strong correlation of CpG dinucleotide depletion with the gain in TpG/CpA dinucleotides and the loss of TpA dinucleotides among parvoviruses suggests a major role for CpG methylation in the evolution of parvoviruses. Our data present evidence that links the relative abundance of CpG dinucleotides in parvoviruses to the methylation capabilities of the infected host. In sum, our findings support a novel perspective of host-driven evolution among autonomous parvoviruses. PMID:24109231

  13. CpG dinucleotide frequencies reveal the role of host methylation capabilities in parvovirus evolution.

    PubMed

    Upadhyay, Mohita; Samal, Jasmine; Kandpal, Manish; Vasaikar, Suhas; Biswas, Banhi; Gomes, James; Vivekanandan, Perumal

    2013-12-01

    Parvoviruses are rapidly evolving viruses that infect a wide range of hosts, including vertebrates and invertebrates. Extensive methylation of the parvovirus genome has been recently demonstrated. A global pattern of methylation of CpG dinucleotides is seen in vertebrate genomes, compared to "fractional" methylation patterns in invertebrate genomes. It remains unknown if the loss of CpG dinucleotides occurs in all viruses of a given DNA virus family that infect host species spanning across vertebrates and invertebrates. We investigated the link between the extent of CpG dinucleotide depletion among autonomous parvoviruses and the evolutionary lineage of the infected host. We demonstrate major differences in the relative abundance of CpG dinucleotides among autonomous parvoviruses which share similar genome organization and common ancestry, depending on the infected host species. Parvoviruses infecting vertebrate hosts had significantly lower relative abundance of CpG dinucleotides than parvoviruses infecting invertebrate hosts. The strong correlation of CpG dinucleotide depletion with the gain in TpG/CpA dinucleotides and the loss of TpA dinucleotides among parvoviruses suggests a major role for CpG methylation in the evolution of parvoviruses. Our data present evidence that links the relative abundance of CpG dinucleotides in parvoviruses to the methylation capabilities of the infected host. In sum, our findings support a novel perspective of host-driven evolution among autonomous parvoviruses.

  14. Cheaper Hydride-Forming Cathodes

    NASA Technical Reports Server (NTRS)

    Jones, Jack A.; Blue, Gary

    1990-01-01

    Hydride-forming cathodes for electrochemical experiments made of materials or combinations of materials cheaper and more abundant than pure palladium, according to proposal. Concept prompted by needs of experimenters in now-discredited concept of electrochemical nuclear fusion, cathodes useful in other electrochemical applications involving generation or storage of hydrogen, deuterium, or tritium.

  15. Properties of nanoscale metal hydrides.

    PubMed

    Fichtner, Maximilian

    2009-05-20

    Nanoscale hydride particles may exhibit chemical stabilities which differ from those of a macroscopic system. The stabilities are mainly influenced by a surface energy term which contains size-dependent values of the surface tension, the molar volume and an additional term which takes into account a potential reduction of the excess surface energy. Thus, the equilibrium of a nanoparticular hydride system may be shifted to the hydrogenated or to the dehydrogenated side, depending on the size and on the prefix of the surface energy term of the hydrogenated and dehydrogenated material. Additional complexity appears when solid-state reactions of complex hydrides are considered and phase segregation has to be taken into account. In such a case the reversibility of complex hydrides may be reduced if the nanoparticles are free standing on a surface. However, it may be enhanced if the system is enclosed by a nanoscale void which prevents the reaction partners on the dehydrogenated side from diffusing away from each other. Moreover, the generally enhanced diffusivity in nanocrystalline systems may lower the kinetic barriers for the material's transformation and, thus, facilitate hydrogen absorption and desorption.

  16. Dinucleotide Composition in Animal RNA Viruses Is Shaped More by Virus Family than by Host Species.

    PubMed

    Di Giallonardo, Francesca; Schlub, Timothy E; Shi, Mang; Holmes, Edward C

    2017-04-15

    Viruses use the cellular machinery of their hosts for replication. It has therefore been proposed that the nucleotide and dinucleotide compositions of viruses should match those of their host species. If this is upheld, it may then be possible to use dinucleotide composition to predict the true host species of viruses sampled in metagenomic surveys. However, it is also clear that different taxonomic groups of viruses tend to have distinctive patterns of dinucleotide composition that may be independent of host species. To determine the relative strength of the effect of host versus virus family in shaping dinucleotide composition, we performed a comparative analysis of 20 RNA virus families from 15 host groupings, spanning two animal phyla and more than 900 virus species. In particular, we determined the odds ratios for the 16 possible dinucleotides and performed a discriminant analysis to evaluate the capability of virus dinucleotide composition to predict the correct virus family or host taxon from which it was isolated. Notably, while 81% of the data analyzed here were predicted to the correct virus family, only 62% of these data were predicted to their correct subphylum/class host and a mere 32% to their correct mammalian order. Similarly, dinucleotide composition has a weak predictive power for different hosts within individual virus families. We therefore conclude that dinucleotide composition is generally uniform within a virus family but less well reflects that of its host species. This has obvious implications for attempts to accurately predict host species from virus genome sequences alone.IMPORTANCE Determining the processes that shape virus genomes is central to understanding virus evolution and emergence. One question of particular importance is why nucleotide and dinucleotide frequencies differ so markedly between viruses. In particular, it is currently unclear whether host species or virus family has the biggest impact on dinucleotide frequencies and

  17. Microstructure of surface cerium hydride growth sites

    SciTech Connect

    Brierley, Martin; Knowles, John; Montgomery, Neil; Preuss, Michael

    2014-05-15

    Samples of cerium were exposed to hydrogen under controlled conditions causing cerium hydride sites to nucleate and grow on the surface. The hydriding rate was measured in situ, and the hydrides were characterised using secondary ion mass spectrometry, scanning electron microscopy, and optical microscopy. The results show that the hydriding rate proceeded more quickly than earlier studies. Characterisation confirmed that the hydrogen is confined to the sites. The morphology of the hydrides was confirmed to be oblate, and stressed material was observed surrounding the hydride, in a number of cases lathlike features were observed surrounding the hydride sites laterally with cracking in the surface oxide above them. It is proposed that during growth the increased lattice parameter of the CeH{sub 2} induces a lateral compressive stress around the hydride, which relieves by the ca. 16% volume collapse of the γ-Ce to α-Ce pressure induced phase transition. Cracking of the surface oxide above the laths reduces the diffusion barrier to hydrogen reaching the metal/oxide interface surrounding the hydride site and contributes to the anisotropic growth of the hydrides.

  18. Adenine suppresses IgE-mediated mast cell activation.

    PubMed

    Silwal, Prashanta; Shin, Keuna; Choi, Seulgi; Kang, Seong Wook; Park, Jin Bong; Lee, Hyang-Joo; Koo, Suk-Jin; Chung, Kun-Hoe; Namgung, Uk; Lim, Kyu; Heo, Jun-Young; Park, Jong Il; Park, Seung-Kiel

    2015-06-01

    Nucleobase adenine is produced by dividing human lymphoblasts mainly from polyamine synthesis and inhibits immunological functions of lymphocytes. We investigated the anti-allergic effect of adenine on IgE-mediated mast cell activation in vitro and passive cutaneous anaphylaxis (PCA) in mice. Intraperitoneal injection of adenine to IgE-sensitized mice attenuated IgE-mediated PCA reaction in a dose dependent manner, resulting in a median effective concentration of 4.21 mg/kg. In mast cell cultures, only adenine among cytosine, adenine, adenosine, ADP and ATP dose-dependently suppressed FcɛRI (a high affinity receptor for IgE)-mediated degranulation with a median inhibitory concentration of 1.6mM. It also blocked the production of LTB4, an inflammatory lipid mediator, and inflammatory cytokines TNF-α and IL-4. In addition, adenine blocked thapsigargin-induced degranulation which is FcɛRI-independent but shares FcɛRI-dependent signaling events. Adenine inhibited the phosphorylation of signaling molecules important to FcɛRI-mediated allergic reactions such as Syk, PLCγ2, Gab2, Akt, and mitogen activated protein kinases ERK and JNK. From this result, we report for the first time that adenine inhibits PCA in mice and allergic reaction by inhibiting FcɛRI-mediated signaling events in mast cells. Therefore, adenine may be useful for the treatment of mast cell-mediated allergic diseases. Also, the upregulation of adenine production may provide another mechanism for suppressing mast cell activity especially at inflammatory sites.

  19. Radiation and thermal stabilities of adenine nucleotides.

    PubMed

    Demidov, V V; Potaman, V N; Solyanina, I P; Trofimov, V I

    1995-03-01

    We have investigated in detail radiation and thermal stabilities and transformations of adenosine mono- and triphosphates in liquid and frozen solid aqueous solutions within a wide range of absorbed radiation dose (up to 75 kGy) and temperature (up to 160 degrees C). Dephosphorylation is the main pathway of high temperature hydrolysis of adenine nucleotides. Basic thermodynamic and kinetic parameters of this process have been determined. Radiolysis of investigated compounds at room temperature results in scission of N-glycosidic bond with a radiation yield about of 1 mol/100 eV. Solution freezing significantly enhances radiation stability of nucleotides as well as other biomolecules. This circumstance is essential in the discussion of panspermia concepts.

  20. The renaissance of hydrides as energy materials

    NASA Astrophysics Data System (ADS)

    Mohtadi, Rana; Orimo, Shin-Ichi

    2016-12-01

    Materials based on hydrides have been the linchpin in the development of several practical energy storage technologies, of which the most prominent example is nickel-metal hydride batteries. Motivated by the need to meet the future's energy demand, the past decade has witnessed substantial advancements in the research and development of hydrides as media for hydrogen energy storage. More recently, new and rapidly evolving discoveries have positioned hydrides as highly promising materials for future electrochemical energy storage, such as electrolytes for mono- and divalent batteries, and anodes for lithium-ion batteries. In addition, the potential of hydrides in efficient power transmission has been recently revealed. In this Review, we highlight key advances and illustrate how the versatility of hydrides has not only yielded a meaningful past, but also ensures a very bright future.

  1. Rechargeable metal hydrides for spacecraft application

    NASA Astrophysics Data System (ADS)

    Perry, J. L.

    1988-09-01

    Storing hydrogen on board the Space Station presents both safety and logistics problems. Conventional storage using pressurized bottles requires large masses, pressures, and volumes to handle the hydrogen to be used in experiments in the U.S. Laboratory Module and residual hydrogen generated by the ECLSS. Rechargeable metal hydrides may be competitive with conventional storage techniques. The basic theory of hydride behavior is presented and the engineering properties of LaNi5 are discussed to gain a clear understanding of the potential of metal hydrides for handling spacecraft hydrogen resources. Applications to Space Station and the safety of metal hydrides are presented and compared to conventional hydride storage. This comparison indicates that metal hydrides may be safer and require lower pressures, less volume, and less mass to store an equivalent mass of hydrogen.

  2. Rechargeable metal hydrides for spacecraft application

    NASA Technical Reports Server (NTRS)

    Perry, J. L.

    1988-01-01

    Storing hydrogen on board the Space Station presents both safety and logistics problems. Conventional storage using pressurized bottles requires large masses, pressures, and volumes to handle the hydrogen to be used in experiments in the U.S. Laboratory Module and residual hydrogen generated by the ECLSS. Rechargeable metal hydrides may be competitive with conventional storage techniques. The basic theory of hydride behavior is presented and the engineering properties of LaNi5 are discussed to gain a clear understanding of the potential of metal hydrides for handling spacecraft hydrogen resources. Applications to Space Station and the safety of metal hydrides are presented and compared to conventional hydride storage. This comparison indicates that metal hydrides may be safer and require lower pressures, less volume, and less mass to store an equivalent mass of hydrogen.

  3. Use of reversible hydrides for hydrogen storage

    NASA Technical Reports Server (NTRS)

    Darriet, B.; Pezat, M.; Hagenmuller, P.

    1980-01-01

    The addition of metals or alloys whose hydrides have a high dissociation pressure allows a considerable increase in the hydrogenation rate of magnesium. The influence of temperature and hydrogen pressure on the reaction rate were studied. Results concerning the hydriding of magnesium rich alloys such as Mg2Ca, La2Mg17 and CeMg12 are presented. The hydriding mechanism of La2Mg17 and CeMg12 alloys is given.

  4. Hydrogen /Hydride/-air secondary battery

    NASA Technical Reports Server (NTRS)

    Sarradin, J.; Bronoel, G.; Percheron-Guegan, A.; Achard, J. C.

    1979-01-01

    The use of metal hydrides as negative electrodes in a hydrogen-air secondary battery seems promising. However, in an unpressurized cell, more stable hydrides that LaNi5H6 must be selected. Partial substitutions of nickel by aluminium or manganese increase the stability of hydrides. Combined with an air reversible electrode, a specific energy close to 100 Wh/kg can be expected.

  5. Inhibited solid propellant composition containing beryllium hydride

    NASA Technical Reports Server (NTRS)

    Thompson, W. W. (Inventor)

    1978-01-01

    An object of this invention is to provide a composition of beryllium hydride and carboxy-terminated polybutadiene which is stable. Another object of this invention is to provide a method for inhibiting the reactivity of beryllium hydride toward carboxy-terminated polybutadiene. It was found that a small amount of lecithin inhibits the reaction of beryllium hydride with the acid groups in carboxy terminated polybutadiene.

  6. Multi-stage hydride-hydrogen compressor

    NASA Astrophysics Data System (ADS)

    Golben, P. M.

    A 4-stage metal hydride/hydrogen compressor that uses low temperature hot water (75 C) as its energy source has been built and tested. The compressor utilizes a new hydride heat exchanger technique that has achieved fast cycling time (with 20 C cooling water) on the order of 1 min. This refinement substantially decreases the size, weight and cost of the unit when compared to previous hydride compressors or even conventional mechanical diaphragm compressors.

  7. Vanadium hydride deuterium-tritium generator

    DOEpatents

    Christensen, L.D.

    1980-03-13

    A pressure controlled vanadium hydride gas generator was designed to provide deuterium-tritium gas in a series of pressure increments. A high pressure chamber filled with vanadium-deuterium-tritium hydride is surrounded by a heater which controls the hydride temperature. The heater is actuated by a power controller which responds to the difference signal between the actual pressure signal and a programmed pressure signal.

  8. Adenine oxidation by pyrite-generated hydroxyl radicals.

    PubMed

    Cohn, Corey A; Fisher, Shawn C; Brownawell, Bruce J; Schoonen, Martin Aa

    2010-04-26

    Cellular exposure to particulate matter with concomitant formation of reactive oxygen species (ROS) and oxidization of biomolecules may lead to negative health outcomes. Evaluating the particle-induced formation of ROS and the oxidation products from reaction of ROS with biomolecules is useful for gaining a mechanistic understanding of particle-induced oxidative stress. Aqueous suspensions of pyrite particles have been shown to form hydroxyl radicals and degrade nucleic acids. Reactions between pyrite-induced hydroxyl radicals and nucleic acid bases, however, remain to be determined. Here, we compared the oxidation of adenine by Fenton-generated (i.e., ferrous iron and hydrogen peroxide) hydroxyl radicals to adenine oxidation by hydroxyl radicals generated in pyrite aqueous suspensions. Results show that adenine oxidizes in the presence of pyrite (without the addition of hydrogen peroxide) and that the rate of oxidation is dependent on the pyrite loading. Adenine oxidation was prevented by addition of either catalase or ethanol to the pyrite/adenine suspensions, which implies that hydrogen peroxide and hydroxyl radicals are causing the adenine oxidation. The adenine oxidation products, 8-oxoadenine and 2-hydroxyadenine, were the same whether hydroxyl radicals were generated by Fenton or pyrite-initiated reactions. Although nucleic acid bases are unlikely to be directly exposed to pyrite particles, the formation of ROS in the vicinity of cells may lead to oxidative stress.

  9. Ten degree Kelvin hydride refrigerator

    NASA Technical Reports Server (NTRS)

    Jones, Jack A. (Inventor)

    1987-01-01

    A compact hydride absorption refrigeration system with few moving parts for 10 Kelvin operation is disclosed and comprises liquid hydrogen producing means in combination with means for solidifying and subliming the liquid hydrogen produced. The liquid hydrogen is sublimed at about 10 Kelvin. By using a symmetrical all hydrogen redundant loop system, a 10 Kelvin refrigeration system can be operated for many years with only a fraction of the power required for prior art systems.

  10. Complex hydrides for hydrogen storage

    DOEpatents

    Zidan, Ragaiy

    2006-08-22

    A hydrogen storage material and process of forming the material is provided in which complex hydrides are combined under conditions of elevated temperatures and/or elevated temperature and pressure with a titanium metal such as titanium butoxide. The resulting fused product exhibits hydrogen desorption kinetics having a first hydrogen release point which occurs at normal atmospheres and at a temperature between 50.degree. C. and 90.degree. C.

  11. Coinage Metal Hydrides: Synthesis, Characterization, and Reactivity.

    PubMed

    Jordan, Abraham J; Lalic, Gojko; Sadighi, Joseph P

    2016-08-10

    Hydride complexes of copper, silver, and gold encompass a broad array of structures, and their distinctive reactivity has enabled dramatic recent advances in synthesis and catalysis. This Review summarizes the synthesis, characterization, and key stoichiometric reactions of isolable or observable coinage metal hydrides. It discusses catalytic processes in which coinage metal hydrides are known or probable intermediates, and presents mechanistic studies of selected catalytic reactions. The purpose of this Review is to convey how developments in coinage metal hydride chemistry have led to new organic transformations, and how developments in catalysis have in turn inspired the synthesis of reactive new complexes.

  12. Thermodynamic Hydricity of Transition Metal Hydrides.

    PubMed

    Wiedner, Eric S; Chambers, Matthew B; Pitman, Catherine L; Bullock, R Morris; Miller, Alexander J M; Appel, Aaron M

    2016-08-10

    Transition metal hydrides play a critical role in stoichiometric and catalytic transformations. Knowledge of free energies for cleaving metal hydride bonds enables the prediction of chemical reactivity, such as for the bond-forming and bond-breaking events that occur in a catalytic reaction. Thermodynamic hydricity is the free energy required to cleave an M-H bond to generate a hydride ion (H(-)). Three primary methods have been developed for hydricity determination: the hydride transfer method establishes hydride transfer equilibrium with a hydride donor/acceptor pair of known hydricity, the H2 heterolysis method involves measuring the equilibrium of heterolytic cleavage of H2 in the presence of a base, and the potential-pKa method considers stepwise transfer of a proton and two electrons to give a net hydride transfer. Using these methods, over 100 thermodynamic hydricity values for transition metal hydrides have been determined in acetonitrile or water. In acetonitrile, the hydricity of metal hydrides spans a range of more than 50 kcal/mol. Methods for using hydricity values to predict chemical reactivity are also discussed, including organic transformations, the reduction of CO2, and the production and oxidation of hydrogen.

  13. Fundamental experiments on hydride reorientation in zircaloy

    NASA Astrophysics Data System (ADS)

    Colas, Kimberly B.

    In the current study, an in-situ X-ray diffraction technique using synchrotron radiation was used to follow directly the kinetics of hydride dissolution and precipitation during thermomechanical cycles. This technique was combined with conventional microscopy (optical, SEM and TEM) to gain an overall understanding of the process of hydride reorientation. Thus this part of the study emphasized the time-dependent nature of the process, studying large volume of hydrides in the material. In addition, a micro-diffraction technique was also used to study the spatial distribution of hydrides near stress concentrations. This part of the study emphasized the spatial variation of hydride characteristics such as strain and morphology. Hydrided samples in the shape of tensile dog-bones were used in the time-dependent part of the study. Compact tension specimens were used during the spatial dependence part of the study. The hydride elastic strains from peak shift and size and strain broadening were studied as a function of time for precipitating hydrides. The hydrides precipitate in a very compressed state of stress, as measured by the shift in lattice spacing. As precipitation proceeds the average shift decreases, indicating average stress is reduced, likely due to plastic deformation and morphology changes. When nucleation ends the hydrides follow the zirconium matrix thermal contraction. When stress is applied below the threshold stress for reorientation, hydrides first nucleate in a very compressed state similar to that of unstressed hydrides. After reducing the average strain similarly to unstressed hydrides, the average hydride strain reaches a constant value during cool-down to room temperature. This could be due to a greater ease of deforming the matrix due to the applied far-field strain which would compensate for the strains due to thermal contraction. Finally when hydrides reorient, the average hydride strains become tensile during the first precipitation regime and

  14. Discrepancy variation of dinucleotide microsatellite repeats in eukaryotic genomes.

    PubMed

    Gao, Huan; Cai, Shengli; Yan, Binlun; Chen, Baiyao; Yu, Fei

    2009-01-01

    To address whether there are differences of variation among repeat motif types and among taxonomic groups, we present here an analysis of variation and correlation of dinucleotide microsatellite repeats in eukaryotic genomes. Ten taxonomic groups were compared, those being primates, mammalia (excluding primates and rodentia), rodentia, birds, fish, amphibians and reptiles, insects, molluscs, plants and fungi, respectively. The data used in the analysis is from the literature published in the Journal of Molecular Ecology Notes. Analysis of variation reveals that there are no significant differences between AC and AG repeat motif types. Moreover, the number of alleles correlates positively with the copy number in both AG and AC repeats. Similar conclusions can be obtained from each taxonomic group. These results strongly suggest that the increase of SSR variation is almost linear with the increase of the copy number of each repeat motif. As well, the results suggest that the variability of SSR in the genomes of low-ranking species seem to be more than that of high-ranking species, excluding primates and fungi.

  15. Butyrate influences intracellular levels of adenine and adenine derivatives in the fungus Penicillium restrictum.

    PubMed

    Zutz, Christoph; Chiang, Yi Ming; Faehnrich, Bettina; Bacher, Markus; Hellinger, Roland; Kluger, Bernhard; Wagner, Martin; Strauss, Joseph; Rychli, Kathrin

    2017-04-01

    Butyrate, a small fatty acid, has an important role in the colon of ruminants and mammalians including the inhibition of inflammation and the regulation of cell proliferation. There is also growing evidence that butyrate is influencing the histone structure in mammalian cells by inhibition of histone deacetylation. Butyrate shows furthermore an antimicrobial activity against fungi, yeast and bacteria, which is linked to its toxicity at a high concentration. In fungi there are indications that butyrate induces the production of secondary metabolites potentially via inhibition of histone deacetylases. However, information about the influence of butyrate on growth, primary metabolite production and metabolism, besides lipid catabolism, in fungi is scarce. We have identified the filamentous fungus Penicillium (P.) restrictum as a susceptible target for butyrate treatment in an antimicrobial activity screen. The antimicrobial activity was detected only in the mycelium of the butyrate treated culture. We investigated the effect of butyrate ranging from low (0.001mM) to high (30mM), potentially toxic, concentrations on biomass and antimicrobial activity. Butyrate at high concentrations (3 and 30mM) significantly reduced the fungal biomass. In contrast P. restrictum treated with 0.03mM of butyrate showed the highest antimicrobial activity. We isolated three antimicrobial active compounds, active against Staphylococcus aureus, from P. restrictum cellular extracts treated with butyrate: adenine, its derivate hypoxanthine and the nucleoside derivate adenosine. Production of all three compounds was increased at low butyrate concentrations. Furthermore we found that butyrate influences the intracellular level of the adenine nucleoside derivate cAMP, an important signalling molecule in fungi and various organisms. In conclusion butyrate treatment increases the intracellular levels of adenine and its respective derivatives.

  16. Adenine adlayers on Cu(111): XPS and NEXAFS study.

    PubMed

    Tsud, Nataliya; Bercha, Sofiia; Ševčíková, Klára; Acres, Robert G; Prince, Kevin C; Matolín, Vladimír

    2015-11-07

    The adsorption of adenine on Cu(111) was studied by photoelectron and near edge x-ray absorption fine structure spectroscopy. Disordered molecular films were deposited by means of physical vapor deposition on the substrate at room temperature. Adenine chemisorbs on the Cu(111) surface with strong rehybridization of the molecular orbitals and the Cu 3d states. Annealing at 150 °C caused the desorption of weakly bonded molecules accompanied by formation of a short-range ordered molecular adlayer. The interface is characterized by the formation of new states in the valence band at 1.5, 7, and 9 eV. The present work complements and refines existing knowledge of adenine interaction with this surface. The coverage is not the main parameter that defines the adenine geometry and adsorption properties on Cu(111). Excess thermal energy can further rearrange the molecular adlayer and, independent of the initial coverage, the flat lying stable molecular adlayer is formed.

  17. Adenine adlayers on Cu(111): XPS and NEXAFS study

    SciTech Connect

    Tsud, Nataliya; Bercha, Sofiia; Ševčíková, Klára; Matolín, Vladimír; Acres, Robert G.; Prince, Kevin C.

    2015-11-07

    The adsorption of adenine on Cu(111) was studied by photoelectron and near edge x-ray absorption fine structure spectroscopy. Disordered molecular films were deposited by means of physical vapor deposition on the substrate at room temperature. Adenine chemisorbs on the Cu(111) surface with strong rehybridization of the molecular orbitals and the Cu 3d states. Annealing at 150 °C caused the desorption of weakly bonded molecules accompanied by formation of a short-range ordered molecular adlayer. The interface is characterized by the formation of new states in the valence band at 1.5, 7, and 9 eV. The present work complements and refines existing knowledge of adenine interaction with this surface. The coverage is not the main parameter that defines the adenine geometry and adsorption properties on Cu(111). Excess thermal energy can further rearrange the molecular adlayer and, independent of the initial coverage, the flat lying stable molecular adlayer is formed.

  18. Intermolecular band dispersion in quasi-one-dimensional adenine assemblies.

    PubMed

    Wang, Ying; Fleurence, Antoine; Yamada-Takamura, Yukiko; Friedlein, Rainer

    2011-12-07

    Highly-ordered, hydrated adenine multilayer films grown on the surface of highly-oriented pyrolytic graphite, HOPG(0001), display extended electronic states, affording anisotropic band-like charge transport along the π-π stacking direction.

  19. A three-state model for the photophysics of adenine.

    PubMed

    Serrano-Andrés, Luis; Merchán, Manuela; Borin, Antonio Carlos

    2006-08-25

    An ab initio theoretical study at the CASPT2 level is reported on minimum energy reaction paths, state minima, transition states, reaction barriers, and conical intersections on the potential energy hypersurfaces of two tautomers of adenine: 9H- and 7H-adenine. The obtained results led to a complete interpretation of the photophysics of adenine and derivatives, both under jet-cooled conditions and in solution, within a three-state model. The ultrafast subpicosecond fluorescence decay measured in adenine is attributed to the low-lying conical intersection (gs/pipi* La)(CI), reached from the initially populated 1(pipi* La) state along a path which is found to be barrierless only in 9H-adenine, while for the 7H tautomer the presence of an intermediate plateau corresponding to an NH2-twisted conformation may explain the absence of ultrafast decay in 7-substituted compounds. A secondary picosecond decay is assigned to a path involving switches towards two other states, 1(pipi* Lb) and 1(npi*), ultimately leading to another conical intersection with the ground state, (gs/npi*), with a perpendicular disposition of the amino group. The topology of the hypersurfaces and the state properties explain the absence of secondary decay in 9-substituted adenines in water in terms of the higher position of the 1(npi*) state and also that the 1(pipi* Lb) state of 7H-adenine is responsible for the observed fluorescence in water. A detailed discussion comparing recent experimental and theoretical findings is given. As for other nucleobases, the predominant role of a pipi*-type state in the ultrafast deactivation of adenine is confirmed.

  20. Erbium hydride thermal desorption : controlling kinetics.

    SciTech Connect

    Ferrizz, Robert Matthew

    2007-08-01

    Thermal desorption spectroscopy (TDS) is used to study the decomposition kinetics of erbium hydride thin films. The TDS results presented in this report show that hydride film processing parameters directly impact thermal stability. Issues to be addressed include desorption kinetics for dihydrides and trihydrides, and the effect of film growth parameters, loading parameters, and substrate selection on desorption kinetics.

  1. Direct synthesis of catalyzed hydride compounds

    DOEpatents

    Gross, Karl J.; Majzoub, Eric

    2004-09-21

    A method is disclosed for directly preparing alkali metal aluminum hydrides such as NaAlH.sub.4 and Na.sub.3 AlH.sub.6 from either the alkali metal or its hydride, and aluminum. The hydride thus prepared is doped with a small portion of a transition metal catalyst compound, such as TiCl.sub.3, TiF.sub.3, or a mixture of these materials, in order to render them reversibly hydridable. The process provides for mechanically mixing the dry reagents under an inert atmosphere followed by charging the mixed materials with high pressure hydrogen while heating the mixture to about 125.degree. C. The method is relatively simple and inexpensive and provides reversible hydride compounds which are free of the usual contamination introduced by prior art wet chemical methods.

  2. Zirconium hydride containing explosive composition

    DOEpatents

    Walker, Franklin E.; Wasley, Richard J.

    1981-01-01

    An improved explosive composition is disclosed and comprises a major portion of an explosive having a detonation velocity between about 1500 and 10,000 meters per second and a minor amount of a donor additive comprising a non-explosive compound or mixture of non-explosive compounds which when subjected to an energy fluence of 1000 calories/cm.sup.2 or less is capable of releasing free radicals each having a molecular weight between 1 and 120. Exemplary donor additives are dibasic acids, polyamines and metal hydrides.

  3. Activated aluminum hydride hydrogen storage compositions and uses thereof

    DOEpatents

    Sandrock, Gary; Reilly, James; Graetz, Jason; Wegrzyn, James E.

    2010-11-23

    In one aspect, the invention relates to activated aluminum hydride hydrogen storage compositions containing aluminum hydride in the presence of, or absence of, hydrogen desorption stimulants. The invention particularly relates to such compositions having one or more hydrogen desorption stimulants selected from metal hydrides and metal aluminum hydrides. In another aspect, the invention relates to methods for generating hydrogen from such hydrogen storage compositions.

  4. Renal reduced nicotinamide adenine dinucleotide phosphate:cytochrome c reductase-mediated metabolism of the carcinogen N-(4-(5-nitro-2-furyl)-2-thiazolyl)acetamide

    SciTech Connect

    Mattammal, M.B.; Zenser, T.V.; Palmier, M.O.; Davis, B.B.

    1985-01-01

    N-(4-(5-Nitro-2-furyl)-2-thiazolyl)acetamide (NFTA) metabolism was examined in vitro using microsomes prepared from rat liver and renal cortex and from rabbit liver and renal cortex and outer and inner medulla. NFTA nitroreduction was observed with each tissue. Three mol of NADPH were used per mol of NFTA reduced. Substrate and inhibitor specificity suggested that the microsomal nitroreduction was due to NADPH:cytochrome c reductase. Metabolite(s) formed bound to protein, RNA, DNA, and synthetic polyribonucleotides. Maximum covalent binding was seen with polyguanylic acid. A guanosine-NFTA adduct was isolated. Binding was inhibited by sulfhydryl compounds and vitamin E. The (/sup 14/C)NFTA:glutathione or (/sup 3/H)glutathione:NFTA conjugates obtained from microsomal incubations showed identical chromatographic properties as the product obtained by the reaction of synthetic N-hydroxy-NFTA with (/sup 3/H)glutathione. Structures of synthetic N-hydroxy-NFTA and the microsomal reduction product 1-(4-(2-acetylaminothiazolyl))-3-cyano-1-propanone were established by mass spectrometry. The latter reduction product did not bind macromolecules. These results suggest that renal NADPH:cytochrome c reductase reduces NFTA to an N-hydroxy-NFTA intermediate that binds nucleophilic sites on macromolecules.

  5. Effect of Exogenous Extracellular Nicotinamide Adenine Dinucleotide (NAD⁺) on Bioelectric Activity of the Pacemaker and Conduction System of the Heart.

    PubMed

    Pustovit, K B; Kuz'min, V S; Sukhova, G S

    2015-06-01

    In rat sinoatrial node, NAD(+) (10 μM) reduced the rate of spontaneous action potentials, duration of action potentials, and the velocity of slow diastolic depolarization, but the rate of action potential front propagation increases. In passed rabbit Purkinje fibers, NAD(+) (10 μM) reduced the duration of action potentials. Under conditions of spontaneous activity of Purkinje fibers, NAD(+) reduced the fi ring rate and the rate of slow diastolic depolarization. The effects of extracellular NAD(+) on bioelectric activity of the pacemaker (sinoatrial node) and conduction system of the heart (Purkinje fibers) are probably related to activation of P1 and P2 purinoceptors.

  6. Pharmacological inhibition of inducible nitric oxide synthase (iNOS) and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, convalesce behavior and biochemistry of hypertension induced vascular dementia in rats.

    PubMed

    Sharma, Bhupesh; Singh, Nirmal

    2013-02-01

    Cognitive disorders are likely to increase over the coming years (5-10). Vascular dementia (VaD) has heterogeneous pathology and is a challenge for clinicians. Current Alzheimer's disease drugs have had limited clinical efficacy in treating VaD and none have been approved by major regulatory authorities specifically for this disease. Role of iNOS and NADPH-oxidase has been reported in various pathological conditions but there role in hypertension (Hypt) induced VaD is still unclear. This research work investigates the salutiferous effect of aminoguanidine (AG), an iNOS inhibitor and 4'-hydroxy-3'-methoxyacetophenone (HMAP), a NADPH oxidase inhibitor in Hypt induced VaD in rats. Deoxycorticosterone acetate-salt (DOCA-S) hypertension has been used for development of VaD in rats. Morris water-maze was used for testing learning and memory. Vascular system assessment was done by testing endothelial function. Mean arterial blood pressure (MABP), oxidative stress [aortic superoxide anion, serum and brain thiobarbituric acid reactive species (TBARS) and brain glutathione (GSH)], nitric oxide levels (serum nitrite/nitrate) and cholinergic activity (brain acetyl cholinesterase activity-AChE) were also measured. DOCA-S treated rats have shown increased MABP with impairment of endothelial function, learning and memory, reduction in serum nitrite/nitrate & brain GSH levels along with increase in serum & brain TBARS, and brain AChE activity. AG as well as HMAP significantly convalesce Hypt induced impairment of learning, memory, endothelial function, and alterations in various biochemical parameters. It may be concluded that AG, an iNOS inhibitor and HMAP, a NADPH-oxidase inhibitor may be considered as potential agents for the management of Hypt induced VaD.

  7. Effect of sulphate-limited growth on mitochondrial electron transfer and energy conservation between reduced nicotinamide–adenine dinucleotide and the cytochromes in Torulopsis utilis

    PubMed Central

    Haddock, B. A.; Garland, P. B.

    1971-01-01

    1. Conditions have been established for the sulphate-limited growth of Torulopsis utilis in continuous culture. 2. Mitochondria prepared from sulphate-limited cells lack both piericidin A sensitivity and the first energy-conservation site (site 1). Sensitivity to antimycin A or cyanide and the second and third energy-conservation sites were apparently unaffected by sulphate-limited growth. 3. Aerobic incubation for 8h of sulphate-limited cells with a low concentration of sulphate (50μm or less) resulted in the recovery of mitochondrial piericidin A sensitivity and site 1. The use of higher concentrations of sulphate (250μm or more) still resulted in the recovery of mitochondrial piericidin A sensitivity and site 1, but also resulted in the appearance of a non-phosphorylating oxidase, which mediated oxidation of the respiratory chain at about the level of cytochrome b in an antimycin A- and cyanide-insensitive manner. Both this alternative route and the conventional normal route of respiration were shown to coexist and to intercommunicate at the level of cytochrome b. 4. Low-temperature spectroscopy failed to identify any new respiratory component to explain the alternative route. 5. The apparent affinity of the alternative route for oxygen was similar to that for the conventional route through cytochrome oxidase, namely half-maximal activity at 0.1μm-oxygen or less. 6. The non-haem iron concentration of submitochondrial particles was unaffected by sulphate limitation, whereas the acid-labile sulphide concentration was lowered tenfold. Marked increases (between four- and 30-fold) in the acid-labile sulphide concentration of submitochondrial particles were observed in sulphate-limited cells after aerobic incubation with various concentrations of sulphate. The lowest increase (fourfold) was observed without added sulphate, the highest (30-fold) with 1.0mm added sulphate. 7. The ratio of non-haem iron to acid-labile sulphide in submitochondrial particles varied with different growth conditions from a maximum of 15.0 to a minimum of 0.72. It is suggested that analytical measurements of non-haem iron are an inadequate guide to the concentration of iron–sulphur protein in complex systems. 8. The effects of sulphate-limited growth on site 1 and piericidin sensitivity are interpreted to indicate a role for iron–sulphur protein in these properties. 9. The aerobic incubation of sulphate-limited cells with cycloheximide resulted in the recovery by mitochondria of site 1 but not of piericidin sensitivity. 10. The appearance of the alternative route for cyanide- and antimycin-A (but not piericidin A-) insensitive respiration on incubating sulphate-limited cells with sulphate concentrations higher than 250μm indicates that the alternative route involves an iron–sulphur protein. PMID:4399517

  8. HIV-1 trans activator of transcription protein elicits mitochondrial hyperpolarization and respiratory deficit, with dysregulation of complex IV and nicotinamide adenine dinucleotide homeostasis in cortical neurons.

    PubMed

    Norman, John P; Perry, Seth W; Kasischke, Karl A; Volsky, David J; Gelbard, Harris A

    2007-01-15

    HIV-1 causes a common, progressive neurological disorder known as HIV-associated dementia (HAD). The prevalence of this disorder has increased despite the use of highly active antiretroviral therapy, and its underlying pathogenesis remains poorly understood. However, evidence suggests that some aspects of HAD may be reversible. To model the reversible aspects of HAD, we have used the HIV-1 neurotoxin trans activator of transcription protein (Tat) to investigate nonlethal changes in cultured neurons. Exposure of rodent cortical neurons to sublethal concentrations of Tat elicits mitochondrial hyperpolarization. In this study, we used the cationic lipophilic dye rhodamine 123 to confirm this observation, and then performed follow-up studies to examine the mechanism involved. In intact neurons, we found Tat elicited a rapid drop in internal mitochondrial pH, and addition of Tat to purified mitochondrial extracts inhibited complex IV of the electron transport chain. To correlate enzyme activity in mitochondrial extracts with results in intact cells, we measured neuronal respiration following Tat exposure. Cortical neurons demonstrated decreased respiration upon Tat treatment, consistent with inhibition of complex IV. We examined mitochondrial Ca(2+) homeostasis using a mitochondrial targeted enhanced yellow fluorescent protein-calmodulin construct. We detected a decrease in mitochondrial calcium concentration following exposure to Tat. Finally, we measured the energy intermediate NAD(P)H after Tat treatment, and found a 20% decrease in the autofluorescence. Based on these findings, we suggest that decreased NADPH and calcium concentration contribute to subsequent respiratory decline after exposure to Tat, with detrimental effects on neuronal signaling.

  9. Towards understanding the origins of the different specificities of binding the reduced (NADPH) and oxidised (NADP +) forms of nicotinamide adenine dinucleotide phosphate coenzyme to dihydrofolate reductase

    NASA Astrophysics Data System (ADS)

    Polshakov, Vladimir I.; Biekofsky, Rodolfo R.; Birdsall, Berry; Feeney, James

    2002-01-01

    Lactobacillus casei dihydrofolate reductase (DHFR) binds more than a thousand times tighter to NADPH than to NADP +. The origins of the difference in binding affinity to DHFR between NADPH and NADP + are investigated in the present study using experimental NMR data and hybrid density functional, B3LYP, calculations. Certain protein residues (Ala 6, Gln 7, Ile 13 and Gly 14) that are directly involved in hydrogen bonding with the nicotinamide carboxamide group show consistent differences in 1H and 15N chemical shift between NADPH and NADP + in a variety of ternary complexes. B3LYP calculations in model systems of protein-coenzyme interactions show differences in the H-bond geometry and differences in charge distribution between the oxidised and reduced forms of the nicotinamide ring. GIAO isotropic nuclear shieldings calculated for nuclei in these systems reproduce the experimentally observed trends in magnitudes and signs of the chemical shifts. The experimentally observed reduction in binding of NADP + compared with NADPH results partly from NADP + having to change its nicotinamide amide group from a cis- to a trans-conformation on binding and partly from the oxidised nicotinamide ring of NADP + being unable to take up its optimal hydrogen bonding geometry in its interactions with protein residues.

  10. The role of Val-265 for flavin adenine dinucleotide (FAD) binding in pyruvate oxidase: FTIR, kinetic, and crystallographic studies on the enzyme variant V265A.

    PubMed

    Wille, Georg; Ritter, Michaela; Weiss, Manfred S; König, Stephan; Mäntele, Werner; Hübner, Gerhard

    2005-04-05

    In pyruvate oxidase (POX) from Lactobacillus plantarum, valine 265 participates in binding the cofactor FAD and is responsible for the strained conformation of its isoalloxazine moiety that is visible in the crystal structure of POX. The contrasting effects of the conservative amino acid exchange V265A on the enzyme's catalytic properties, cofactor affinity, and protein structure were investigated. The most prominent effect of the exchange was observed in the 2.2 A crystal structure of the mutant POX. While the overall structures of the wild-type and the variant are similar, flavin binding in particular is clearly different. Local disorder at the isoalloxazine binding site prevents modeling of the complete FAD cofactor and two protein loops of the binding site. Only the ADP moiety shows well-defined electron density, indicating an "anchor" function for this part of the molecule. This notion is corroborated by competition experiments where ADP was used to displace FAD from the variant enzyme. Despite the fact that the affinity of FAD binding in the variant is reduced, the catalytic properties are very similar to the wild-type, and the redox potential of the bound flavin is the same for both proteins. The rate of electron transfer toward the flavin during turnover is reduced to one-third compared to the wild-type, but k(cat) remains unchanged. Redox-triggered FTIR difference spectroscopy of free FAD shows the nu(C(10a)=N(1)) band at 1548 cm(-)(1). In POX-V265A, this band is found at 1538 cm(-)(1) and thus shifted less strongly than in wild-type POX where it is found at 1534 cm(-)(1). Taking these observations together, the conservative exchange V265A in POX has a surprisingly small effect on the catalytic properties of the enzyme, whereas the effect on the three-dimensional structure is rather big.

  11. New approach to biosensing of co-enzyme nicotinamide adenine dinucleotide (NADH) by incorporation of neutral red in aluminum doped nanostructured ZnO thin films.

    PubMed

    V T, Fidal; T S, Chandra

    2017-01-04

    Biosensing of NADH on bare electrodes has drawbacks such as high over-potential and poisoning during the oxidation reaction. To overcome this challenge a different approach has been undertaken by incorporating neutral red (NR) in Al doped ZnO (AZO) thin films using one-pot chemical bath deposition (CBD). The surface morphology of the films was hexagonal nanorods along the c-axis, perpendicular to the substrate. The thickness of the thin films were ranging from 400 to 3000nm varying dependent on time of deposition (30 to 150min). The average diameter of the nanorods was larger in the presence of neutral red (NR-AZO) with ~300nm in contrast to its absence (AZO) with ~200nm. The density of the packing of nanorods was dependent on the citrate concentration used during deposition. Control over the dopant concentration in the films was achieved by varying the area of Al foil used in the deposition solution. The selected area diffraction (SAED) and X-ray diffraction (XRD) indicated 002 plane of orientation in the nanorods. FTIR and FT-Raman analysis revealed conserved structure of NR and AZO. Chronoamperometric (CA) analysis showed a sensitivity of 0.45μAcm(-2)mM(-1) and LoD of 22μM within the range 0.075-4mM of NADH. The biological sensing of NADH was validated by physical adsorption of NAD(+) dependent-lactate dehydrogenase (LDH) on NR-AZO. CA showed sensitivity of 0.56μAcm(-2)mM(-1) and LoD for lactate was 27μM in the range of 0.1-1mM of lactate. Further validation with real-time serum sample shows that LDH/NR-AZO correlates with the clinical values. The distinction in this study is that the organic mediator like neutral red has been incorporated into the grain structure of the ZnO thin film whereas other study with the mediators have only attempted surface functionalization. This article is part of a Special Issue entitled "Recent Advances in Bionanomaterials" Guest Editor: Dr. Marie-Louise Saboungi and Dr. Samuel D. Bader.

  12. A Mutation in the Flavin Adenine Dinucleotide-Dependent Oxidoreductase FOXRED1 Results in Cell-Type-Specific Assembly Defects in Oxidative Phosphorylation Complexes I and II

    PubMed Central

    Zurita Rendón, Olga; Antonicka, Hana; Horvath, Rita

    2016-01-01

    Complex I (NADH ubiquinone oxidoreductase) is a large multisubunit enzyme that catalyzes the first step in oxidative phosphorylation (OXPHOS). In mammals, complex I biogenesis occurs in a stepwise manner, a process that requires the participation of several nucleus-encoded accessory proteins. The FAD-dependent oxidoreductase-containing domain 1 (FOXRED1) protein is a complex I assembly factor; however, its specific role in the assembly pathway remains poorly understood. We identified a homozygous missense mutation, c.1308 G→A (p.V421M) in FOXRED1 in a patient who presented with epilepsy and severe psychomotor retardation. A patient myoblast line showed a severe reduction in complex I, associated with the accumulation of subassemblies centered around ∼340 kDa, and a milder decrease in complex II, all of which were rescued by retroviral expression of wild-type FOXRED1. Two additional assembly factors, AIFM1 and ACAD9, coimmunoprecipitated with FOXRED1, and all were associated with a 370-kDa complex I subassembly that, together with a 315-kDa subassembly, forms the 550-kDa subcomplex. Loss of FOXRED1 function prevents efficient formation of this midassembly subcomplex. Although we could not identify subassemblies of complex II, our results establish that FOXRED1 function is both broader than expected, involving the assembly of two flavoprotein-containing OXPHOS complexes, and cell type specific. PMID:27215383

  13. Nicotinic Acid Adenine Dinucleotide Phosphate (NAADP) and Cyclic ADP-Ribose (cADPR) Mediate Ca2+ Signaling in Cardiac Hypertrophy Induced by β-Adrenergic Stimulation

    PubMed Central

    Shawl, Asif Iqbal; Im, Soo-Yeul; Nam, Tae-Sik; Lee, Sun-Hwa; Ko, Jae-Ki; Jang, Kyu Yoon; Kim, Donghee; Kim, Uh-Hyun

    2016-01-01

    Ca2+ signaling plays a fundamental role in cardiac hypertrophic remodeling, but the underlying mechanisms remain poorly understood. We investigated the role of Ca2+-mobilizing second messengers, NAADP and cADPR, in the cardiac hypertrophy induced by β-adrenergic stimulation by isoproterenol. Isoproterenol induced an initial Ca2+ transients followed by sustained Ca2+ rises. Inhibition of the cADPR pathway with 8-Br-cADPR abolished only the sustained Ca2+ increase, whereas inhibition of the NAADP pathway with bafilomycin-A1 abolished both rapid and sustained phases of the isoproterenol-mediated signal, indicating that the Ca2+ signal is mediated by a sequential action of NAADP and cADPR. The sequential production of NAADP and cADPR was confirmed biochemically. The isoproterenol-mediated Ca2+ increase and cADPR production, but not NAADP production, were markedly reduced in cardiomyocytes obtained from CD38 knockout mice. CD38 knockout mice were rescued from chronic isoproterenol infusion-induced myocardial hypertrophy, interstitial fibrosis, and decrease in fractional shortening and ejection fraction. Thus, our findings indicate that β-adrenergic stimulation contributes to the development of maladaptive cardiac hypertrophy via Ca2+ signaling mediated by NAADP-synthesizing enzyme and CD38 that produce NAADP and cADPR, respectively. PMID:26959359

  14. Novel concept of enzyme selective nicotinamide adenine dinucleotide (NAD)-modified inhibitors based on enzyme taxonomy from the diphosphate conformation of NAD.

    PubMed

    Fujii, Mikio; Kitagawa, Yasuyuki; Iida, Shui; Kato, Keisuke; Ono, Machiko

    2015-11-15

    The dihedral angle θ of the diphosphate part of NAD(P) were investigated to distinguish the differences in the binding-conformation of NAD(P) to enzymes and to create an enzyme taxonomy. Furthermore, new inhibitors with fixed dihedral angles showed that enzymes could recognize the differences in the dihedral angle θ. We suggest the taxonomy and the dihedral angle θ are important values for chemists to consider when designing inhibitors and drugs that target enzymes.

  15. Enhanced Reduced Nicotinamide Adenine Dinucleotide electrocatalysis onto multi-walled carbon nanotubes-decorated gold nanoparticles and their use in hybrid biofuel cell

    NASA Astrophysics Data System (ADS)

    Aquino Neto, S.; Almeida, T. S.; Belnap, D. M.; Minteer, S. D.; De Andrade, A. R.

    2015-01-01

    We report the preparation of Au nanoparticles synthetized by different protocols and supported on the surface of multi-walled carbon nanotubes containing different functional groups, focusing on their electrochemical performance towards NADH oxidation, ethanol bioelectrocatalysis, and ethanol/O2 biofuel cell. We describe four different synthesis protocols: microwave-assisted heating, water-in-oil, and dendrimer-encapsulated nanoparticles using acid or thiol species in the extraction step. The physical characterization of the metallic nanoparticles indicated that both the synthetic protocol as well as the type of functional groups on the carbon nanotubes affect the final particle size (varying from 13.4 to 2.4 nm) and their distribution onto the carbon surface. Moreover, the electrochemical data indicated that these two factors also influence their performance toward the electrooxidation of NADH. We observed that the samples containing Au nanoparticles with smaller size leads to higher catalytic currents and also shifts the oxidation potential of the targeted reaction, which varied from 0.13 to -0.06 V vs Ag/AgCl. Ethanol/O2 biofuel cell tests indicated that the hybrid bioelectrodes containing smaller and better distributed Au nanoparticles on the surface of carbon nanotubes generates higher power output, confirming that the electrochemical regeneration of NAD+ plays an important role in the overall biofuel cell performance.

  16. Dehydrogenation of androsterone by purified 3α-hydroxy steroid-dependent nicotinamide–adenine dinucleotide (phosphate)-transhydrogenating enzyme of rat liver

    PubMed Central

    Pietruszko, Regina; Baron, D. N.

    1965-01-01

    1. An enzyme from rat liver, catalysing 3α-hydroxy steroid-dependent NAD(P) transhydrogenation and NAD-linked and NADP-linked dehydrogenation of 3α-hydroxy steroids, has been purified 100-fold by chromatography on DEAE-cellulose and calcium phosphate gel. 2. No separation of these activities into different protein fractions has been achieved. 3. The properties of the enzyme in catalysing NAD-linked and NADP-linked dehydrogenation have been compared, with androsterone as substrate. Differences were found in pH optima, affinity for coenzyme and steroid, equilibrium constants and effects of salts. 4. NAD-linked dehydrogenation is inhibited by NADPH2 but is protected from this inhibition by chloride, which alone is itself an inhibitor. 5. The relevance of these findings to the problem of the number of enzymes involved in catalysis of 3α-hydroxy steroid-dependent transhydrogenation is discussed. PMID:4378709

  17. Mature microsatellites: mechanisms underlying dinucleotide microsatellite mutational biases in human cells.

    PubMed

    Baptiste, Beverly A; Ananda, Guruprasad; Strubczewski, Noelle; Lutzkanin, Andrew; Khoo, Su Jen; Srikanth, Abhinaya; Kim, Nari; Makova, Kateryna D; Krasilnikova, Maria M; Eckert, Kristin A

    2013-03-01

    Dinucleotide microsatellites are dynamic DNA sequences that affect genome stability. Here, we focused on mature microsatellites, defined as pure repeats of lengths above the threshold and unlikely to mutate below it in a single mutational event. We investigated the prevalence and mutational behavior of these sequences by using human genome sequence data, human cells in culture, and purified DNA polymerases. Mature dinucleotides (≥10 units) are present within exonic sequences of >350 genes, resulting in vulnerability to cellular genetic integrity. Mature dinucleotide mutagenesis was examined experimentally using ex vivo and in vitro approaches. We observe an expansion bias for dinucleotide microsatellites up to 20 units in length in somatic human cells, in agreement with previous computational analyses of germ-line biases. Using purified DNA polymerases and human cell lines deficient for mismatch repair (MMR), we show that the expansion bias is caused by functional MMR and is not due to DNA polymerase error biases. Specifically, we observe that the MutSα and MutLα complexes protect against expansion mutations. Our data support a model wherein different MMR complexes shift the balance of mutations toward deletion or expansion. Finally, we show that replication fork progression is stalled within long dinucleotides, suggesting that mutational mechanisms within long repeats may be distinct from shorter lengths, depending on the biochemistry of fork resolution. Our work combines computational and experimental approaches to explain the complex mutational behavior of dinucleotide microsatellites in humans.

  18. Implications of Dna-Nanostructures by Hoogsteen-Dinucleotides on Transcription Factor Binding

    NASA Astrophysics Data System (ADS)

    Wanke, Dierk; Brand, Luise H.; Fischer, Nina M.; Peschke, Florian; Kilian, Joachim; Berendzen, Kenneth W.

    2013-01-01

    Recent findings showed that non-harmonic DNA-nanostructures are formed by Hoogsteen (HG) dinucleotides in vivo. In contrast to Waston-Crick (WC) base pairing, the purine base component is flipped from anti- to syn-conformation. This change consequently alters the width of the DNA-helix, the sizes of minor and major groove and biophysical properties, such as the melting temperature. Three dinucleotides (CA, TG and TA) have been identified that form stable HG conformations. Functional data and structural models imply that transcription factors specifically bind DNA-motifs that consist of both HG and WC base pairs - especially at the topological transition between HG and WC dinucleotides. We could show that most know cis -regulatory elements contain at least one HG dinucleotide. In addition, we focused our work on human promoter sequences that encode gene regulatory information within double stranded DNA. We compared occurrences of HG dinucleotides to all 16 dinucleotides. These ratios differed most in sequences closer to gene transcripts, where the promoters are located. These findings imply that transcription factors might explicitly recognize their DNA-motifs in regulatory promoter sequences that exhibit HG nanostructure islands.

  19. Hydrogen-storing hydride complexes

    DOEpatents

    Srinivasan, Sesha S [Tampa, FL; Niemann, Michael U [Venice, FL; Goswami, D Yogi [Tampa, FL; Stefanakos, Elias K [Tampa, FL

    2012-04-10

    A ternary hydrogen storage system having a constant stoichiometric molar ratio of LiNH.sub.2:MgH.sub.2:LiBH.sub.4 of 2:1:1. It was found that the incorporation of MgH.sub.2 particles of approximately 10 nm to 20 nm exhibit a lower initial hydrogen release temperature of 150.degree. C. Furthermore, it is observed that the particle size of LiBNH quaternary hydride has a significant effect on the hydrogen sorption concentration with an optimum size of 28 nm. The as-synthesized hydrides exhibit two main hydrogen release temperatures, one around 160.degree. C. and the other around 300.degree. C., with the main hydrogen release temperature reduced from 310.degree. C. to 270.degree. C., while hydrogen is first reversibly released at temperatures as low as 150.degree. C. with a total hydrogen capacity of 6 wt. % to 8 wt. %. Detailed thermal, capacity, structural and microstructural properties have been demonstrated and correlated with the activation energies of these materials.

  20. Liquid suspensions of reversible metal hydrides

    DOEpatents

    Reilly, J.J.; Grohse, E.W.; Winsche, W.E.

    1983-12-08

    The reversibility of the process M + x/2 H/sub 2/ ..-->.. MH/sub x/, where M is a metal hydride former that forms a hydride MH/sub x/ in the presence of H/sub 2/, generally used to store and recall H/sub 2/, is found to proceed under a liquid, thereby to reduce contamination, provide better temperature control and provide in situ mobility of the reactants. Thus, a slurry of particles of a metal hydride former with an inert solvent is subjected to temperature and pressure controlled atmosphere containing H/sub 2/, to store hydrogen (at high pressures) and to release (at low pressures) previously stored hydrogen. The direction of the flow of the H/sub 2/ through the liquid is dependent upon the H/sub 2/ pressure in the gas phase at a given temperature. When the former is above the equilibrium absorption pressure of the respective hydride the reaction proceeds to the right, i.e., the metal hydride is formed and hydrogen is stored in the solid particle. When the H/sub 2/ pressure in the gas phase is below the equilibrium dissociation pressure of the respective hydride the reaction proceeds to the left, the metal hydride is decomposed and hydrogen is released into the gas phase.

  1. Kidney Disease in Adenine Phosphoribosyltransferase Deficiency

    PubMed Central

    Runolfsdottir, Hrafnhildur Linnet; Palsson, Runolfur; Sch. Agustsdottir, Inger M.; Indridason, Olafur S.; Edvardsson, Vidar O.

    2015-01-01

    Background Adenine phosphoribosyltransferase (APRT) deficiency is a purine metabolism disorder causing kidney stones and chronic kidney disease (CKD). The course of nephrolithiasis and CKD has not been well characterized. The objective of this study was to examine long-term kidney outcomes in patients with APRT deficiency. Study Design An observational cohort study. Setting & Participants All patients enrolled in the APRT Deficiency Registry of the Rare Kidney Stone Consortium. Outcomes Kidney stones, acute kidney injury (AKI), stage of CKD and kidney failure, estimated glomerular filtration rate (eGFR) and changes in eGFR. Measurements Serum creatinine and eGFR calculated using creatinine-based equations. Results Of 53 patients, 30 (57%) were female and median age at diagnosis was 37.0 (range, 0.6–67.9) years. The median duration of follow-up was 10.3 (range, 0.0–31.5) years. At diagnosis, kidney stones had developed in 29 patients (55%) and 20 (38%) had CKD stages 3–5, including 11 patients (21%) with stage 5. At latest follow-up, 33 patients (62%) had had kidney stones; 18 (34%), AKI; and 22 (42%), CKD stage 3–5. Of the 14 (26%) patients with CKD stage 5, 12 had initiated renal replacement therapy. Kidney stones recurred in 18 of 33 patients (55%). The median eGFR slope was −0.38 (range, −21.99 to 1.42) mL/min/1.73 m2 per year in patients receiving treatment with xanthine dehydrogenase inhibitor and −5.74 (range, −75.8 to −0.10) mL/min/1.73 m2 per year in those not treated prior to the development of stage 5 CKD (p=0.001). Limitations Use of observational registry data. Conclusions Progressive CKD and AKI episodes are major features of APRT deficiency, while nephrolithiasis is the most common presentation. Advanced CKD without history of kidney stones is more prevalent than previously reported. Our data suggest that timely therapy may retard CKD progression. PMID:26724837

  2. Hydride heat pump with heat regenerator

    NASA Technical Reports Server (NTRS)

    Jones, Jack A. (Inventor)

    1991-01-01

    A regenerative hydride heat pump process and system is provided which can regenerate a high percentage of the sensible heat of the system. A series of at least four canisters containing a lower temperature performing hydride and a series of at least four canisters containing a higher temperature performing hydride is provided. Each canister contains a heat conductive passageway through which a heat transfer fluid is circulated so that sensible heat is regenerated. The process and system are useful for air conditioning rooms, providing room heat in the winter or for hot water heating throughout the year, and, in general, for pumping heat from a lower temperature to a higher temperature.

  3. High-pressure synthesis of lithium hydride

    NASA Astrophysics Data System (ADS)

    Howie, Ross T.; Narygina, Olga; Guillaume, Christophe L.; Evans, Shaun; Gregoryanz, Eugene

    2012-08-01

    By compressing elemental lithium and hydrogen in a diamond anvil cell, we have synthesized lithium hydride (LiH) at pressures as low as 50 MPa at room temperature. Combined Raman spectroscopy and synchrotron x-ray diffraction measurements reveal that, once synthesized, LiH remains stable at 300 K up to 160 GPa in the presence of molecular hydrogen. The mixture of lithium hydride and molecular hydrogen and application of pressure alone cannot form a higher H2 content hydride (LiHx, x>1) as was suggested from the theoretical ab initio calculations and therefore, cannot be considered as a route to low-pressure hydrogen rich material metallization.

  4. [Study of some pharmacological properties of a new adenine derivative].

    PubMed

    Iasnetsov; Ozerov, A A; Motin, V G; Iasnetsov, Vik V; Karsanova, S K; Ivanov, Iu V; Chel'naia, N A

    2014-01-01

    It is established that the new compound, 9-[2-(4-isopropylphenoxy)ethyl]adenine (9-IPE-adenine) in a dose of 10 mg/kg per day produces neuroprotective effect in rats with brain ischemia model. 9-IPE-adenine decreased the neurologic deficiency 1.2 times more effectively (p < 0.05) than the reference drug mexidol in analogous dose, and had equal effect with this drug at 25 mg/kg per day on the neurologic deficiency and survival of animals. Electrophysiological studies in hippocampal slices in rats showed that 9-IPE-adenine depressed orthodromic population spikes in CA1 area by 42 ± 4%. Non-competitive antagonist of NMDA receptor complex MK-801, in contrast to D-AP5 (competitive NMDA receptor antagonist) and CNQX (competitive AMPA receptor antagonist), enhanced the depressive effect of the new drug more than two times. These ese results are indicative of the ability of 9-IPE-adenine to modulate the ion channel of NMDA receptor complex.

  5. DNA adenine hypomethylation leads to metabolic rewiring in Deinococcus radiodurans.

    PubMed

    Shaiwale, Nayana S; Basu, Bhakti; Deobagkar, Deepti D; Deobagkar, Dileep N; Apte, Shree K

    2015-08-03

    The protein encoded by DR_0643 gene from Deinococcus radiodurans was shown to be an active N-6 adenine-specific DNA methyltransferase (Dam). Deletion of corresponding protein reduced adenine methylation in the genome by 60% and resulted in slow-growth phenotype. Proteomic changes induced by DNA adenine hypomethylation were mapped by two-dimensional protein electrophoresis coupled with mass spectrometry. As compared to wild type D. radiodurans cells, at least 54 proteins were differentially expressed in Δdam mutant. Among these, 39 metabolic enzymes were differentially expressed in Δdam mutant. The most prominent change was DNA adenine hypomethylation induced de-repression of pyruvate dehydrogenase complex, E1 component (aceE) gene resulting in 10 fold increase in the abundance of corresponding protein. The observed differential expression profile of metabolic enzymes included increased abundance of enzymes involved in fatty acid and amino acid degradation to replenish acetyl Co-A and TCA cycle intermediates and diversion of phosphoenolpyruvate and pyruvate into amino acid biosynthesis, a metabolic rewiring attempt by Δdam mutant to restore energy generation via glycolysis-TCA cycle axis. This is the first report of DNA adenine hypomethylation mediated rewiring of metabolic pathways in prokaryotes.

  6. Theoretical study on absorption and emission spectra of adenine analogues.

    PubMed

    Liu, Hongxia; Song, Qixia; Yang, Yan; Li, Yan; Wang, Haijun

    2014-04-01

    Fluorescent nucleoside analogues have attracted much attention in studying the structure and dynamics of nucleic acids in recent years. In the present work, we use theoretical calculations to investigate the structural and optical properties of four adenine analogues (termed as A1, A2, A3, and A4), and also consider the effects of aqueous solution and base pairing. The results show that the fluorescent adenine analogues can pair with thymine to form stable H-bonded WC base pairs. The excited geometries of both adenine analogues and WC base pairs are similar to the ground geometries. The absorption and emission maxima of adenine analogues are greatly red shifted compared with nature adenine, the oscillator strengths of A1 and A2 are stronger than A3 and A4 in both absorption and emission spectra. The calculated low-energy peaks in the absorption spectra are in good agreement with the experimental data. In general, the aqueous solution and base pairing can slightly red-shift both the absorption and emission maxima, and can increase the oscillator strengths of absorption spectra, but significantly decrease the oscillator strengths of A3 in emission spectra.

  7. Computational Modeling of Uranium Hydriding and Complexes

    SciTech Connect

    Balasubramanian, K; Siekhaus, W J; McLean, W

    2003-02-03

    Uranium hydriding is one of the most important processes that has received considerable attention over many years. Although many experimental and modeling studies have been carried out concerning thermochemistry, diffusion kinetics and mechanisms of U-hydriding, very little is known about the electronic structure and electronic features that govern the U-hydriding process. Yet it is the electronic feature that controls the activation barrier and thus the rate of hydriding. Moreover the role of impurities and the role of the product UH{sub 3} on hydriding rating are not fully understood. An early study by Condon and Larson concerns with the kinetics of U-hydrogen system and a mathematical model for the U-hydriding process. They proposed that diffusion in the reactant phase by hydrogen before nucleation to form hydride phase and that the reaction is first order for hydriding and zero order for dehydriding. Condon has also calculated and measures the reaction rates of U-hydriding and proposed a diffusion model for the U-hydriding. This model was found to be in excellent agreement with the experimental reaction rates. From the slopes of the Arrhenius plot the activation energy was calculated as 6.35 kcal/mole. In a subsequent study Kirkpatrick formulated a close-form for approximate solution to Condon's equation. Bloch and Mintz have proposed the kinetics and mechanism for the U-H reaction over a wide range of pressures and temperatures. They have discussed their results through two models, one, which considers hydrogen diffusion through a protective UH{sub 3} product layer, and the second where hydride growth occurs at the hydride-metal interface. These authors obtained two-dimensional fits of experimental data to the pressure-temperature reactions. Kirkpatrick and Condon have obtained a linear solution to hydriding of uranium. These authors showed that the calculated reaction rates compared quite well with the experimental data at a hydrogen pressure of 1 atm. Powell

  8. Cerulenin-mediated apoptosis is involved in adenine metabolic pathway

    SciTech Connect

    Chung, Kyung-Sook; Sun, Nam-Kyu; Lee, Seung-Hee; Lee, Hyun-Jee; Choi, Shin-Jung; Kim, Sun-Kyung; Song, Ju-Hyun; Jang, Young-Joo; Song, Kyung-Bin; Yoo, Hyang-Sook; Simon, Julian . E-mail: jsimon@fhcrc.org; Won, Misun . E-mail: misun@kribb.re.kr

    2006-10-27

    Cerulenin, a fatty acid synthase (FAS) inhibitor, induces apoptosis of variety of tumor cells. To elucidate mode of action by cerulenin, we employed the proteomics approach using Schizosaccharomyces pombe. The differential protein expression profile of S. pombe revealed that cerulenin modulated the expressions of proteins involved in stresses and metabolism, including both ade10 and adk1 proteins. The nutrient supplementation assay demonstrated that cerulenin affected enzymatic steps transferring a phosphoribosyl group. This result suggests that cerulenin accumulates AMP and p-ribosyl-s-amino-imidazole carboxamide (AICAR) and reduces other necessary nucleotides, which induces feedback inhibition of enzymes and the transcriptional regulation of related genes in de novo and salvage adenine metabolic pathway. Furthermore, the deregulation of adenine nucleotide synthesis may interfere ribonucleotide reductase and cause defects in cell cycle progression and chromosome segregation. In conclusion, cerulenin induces apoptosis through deregulation of adenine nucleotide biosynthesis resulting in nuclear division defects in S. pombe.

  9. Method of forming metal hydride films

    NASA Technical Reports Server (NTRS)

    Steinberg, R.; Alger, D. L.; Cooper, D. W. (Inventor)

    1977-01-01

    The substrate to be coated (which may be of metal, glass or the like) is cleaned, both chemically and by off-sputtering in a vacuum chamber. In an ultra-high vacuum system, vapor deposition by a sublimator or vaporizer coats a cooled shroud disposed around the substrate with a thin film of hydride forming metal which getters any contaminant gas molecules. A shutter is then opened to allow hydride forming metal to be deposited as a film or coating on the substrate. After the hydride forming metal coating is formed, deuterium or other hydrogen isotopes are bled into the vacuum system and diffused into the metal film or coating to form a hydride of metal film. Higher substrate temperatures and pressures may be used if various parameters are appropriately adjusted.

  10. Sealed aerospace metal-hydride batteries

    NASA Technical Reports Server (NTRS)

    Coates, Dwaine

    1992-01-01

    Nickel metal hydride and silver metal hydride batteries are being developed for aerospace applications. There is a growing market for smaller, lower cost satellites which require higher energy density power sources than aerospace nickel-cadmium at a lower cost than space nickel-hydrogen. These include small LEO satellites, tactical military satellites and satellite constellation programs such as Iridium and Brilliant Pebbles. Small satellites typically do not have the spacecraft volume or the budget required for nickel-hydrogen batteries. NiCd's do not have adequate energy density as well as other problems such as overcharge capability and memory effort. Metal hydride batteries provide the ideal solution for these applications. Metal hydride batteries offer a number of advantages over other aerospace battery systems.

  11. A classical but new kinetic equation for hydride transfer reactions.

    PubMed

    Zhu, Xiao-Qing; Deng, Fei-Huang; Yang, Jin-Dong; Li, Xiu-Tao; Chen, Qiang; Lei, Nan-Ping; Meng, Fan-Kun; Zhao, Xiao-Peng; Han, Su-Hui; Hao, Er-Jun; Mu, Yuan-Yuan

    2013-09-28

    A classical but new kinetic equation to estimate activation energies of various hydride transfer reactions was developed according to transition state theory using the Morse-type free energy curves of hydride donors to release a hydride anion and hydride acceptors to capture a hydride anion and by which the activation energies of 187 typical hydride self-exchange reactions and more than thirty thousand hydride cross transfer reactions in acetonitrile were safely estimated in this work. Since the development of the kinetic equation is only on the basis of the related chemical bond changes of the hydride transfer reactants, the kinetic equation should be also suitable for proton transfer reactions, hydrogen atom transfer reactions and all the other chemical reactions involved with breaking and formation of chemical bonds. One of the most important contributions of this work is to have achieved the perfect unity of the kinetic equation and thermodynamic equation for hydride transfer reactions.

  12. Adenine and 2-aminopurine: paradigms of modern theoretical photochemistry.

    PubMed

    Serrano-Andrés, Luis; Merchán, Manuela; Borin, Antonio C

    2006-06-06

    Distinct photophysical behavior of nucleobase adenine and its constitutional isomer, 2-aminopurine, has been studied by using quantum chemical methods, in particular an accurate ab initio multiconfigurational second-order perturbation theory. After light irradiation, the efficient, ultrafast energy dissipation observed for nonfluorescent 9H-adenine is explained here by the nonradiative internal conversion process taking place along a barrierless reaction path from the initially populated 1(pipi* La) excited state toward a low-lying conical intersection (CI) connected with the ground state. In contrast, the strong fluorescence recorded for 2-aminopurine at 4.0 eV with large decay lifetime is interpreted by the presence of a minimum in the 1(pipi* La) hypersurface lying below the lowest CI and the subsequent potential energy barrier required to reach the funnel to the ground state. Secondary deactivation channels were found in the two systems related to additional CIs involving the 1(pipi* Lb) and 1(npi*) states. Although in 9H-adenine a population switch between both states is proposed, in 7H-adenine this may be perturbed by a relatively larger barrier to access the 1(npi*) state, and, therefore, the 1(pipi* Lb) state becomes responsible for the weak fluorescence measured in aqueous adenine at approximately 4.5 eV. In contrast to previous models that explained fluorescence quenching in adenine, unlike in 2-aminopurine, on the basis of the vibronic coupling of the nearby 1(pipi*) and 1(npi*) states, the present results indicate that the 1(npi*) state does not contribute to the leading photophysical event and establish the prevalence of a model based on the CI concept in modern photochemistry.

  13. Negative ion formation in potassium-adenine collisions

    NASA Astrophysics Data System (ADS)

    Chunha, T.; Mendes, M.; Ferreira da Silva, F.; García, G.; Limáo Vieira, P.

    2016-09-01

    We have devoted experimental studies to time-of-flight negative ion formation in electron transfer experiments from neutral potassium atoms with neutral adenine molecules1. Total partial cross sections have been obtained as a function of the collision energy, together with branching ratios for the most relevant fragment anions. Additional set of measurements in adenine derivatives have been performed in order to probe the role of negative ions as well as to probe whether site- and bond-selective excision is also a prevalent mechanism within electron transfer in atom-molecule collision experiments.

  14. Metastable Metal Hydrides for Hydrogen Storage

    DOE PAGES

    Graetz, Jason

    2012-01-01

    The possibility of using hydrogen as a reliable energy carrier for both stationary and mobile applications has gained renewed interest in recent years due to improvements in high temperature fuel cells and a reduction in hydrogen production costs. However, a number of challenges remain and new media are needed that are capable of safely storing hydrogen with high gravimetric and volumetric densities. Metal hydrides and complex metal hydrides offer some hope of overcoming these challenges; however, many of the high capacity “reversible” hydrides exhibit a large endothermic decomposition enthalpy making it difficult to release the hydrogen at low temperatures. Onmore » the other hand, the metastable hydrides are characterized by a low reaction enthalpy and a decomposition reaction that is thermodynamically favorable under ambient conditions. The rapid, low temperature hydrogen evolution rates that can be achieved with these materials offer much promise for mobile PEM fuel cell applications. However, a critical challenge exists to develop new methods to regenerate these hydrides directly from the reactants and hydrogen gas. This spotlight paper presents an overview of some of the metastable metal hydrides for hydrogen storage and a few new approaches being investigated to address the key challenges associated with these materials.« less

  15. Some aspects of adenosine triphosphate synthesis from adenine and adenosine in human red blood cells

    PubMed Central

    Whittam, R.; Wiley, J. S.

    1968-01-01

    1. The synthesis of ATP has been studied in human erythrocytes. Fresh cells showed no net synthesis of ATP when incubated with adenine or adenosine, although labelled adenine was incorporated into ATP in small amounts. 2. Cold-stored cells (3-6 weeks old) became progressively depleted of adenine nucleotides but incubation with adenosine or adenine plus inosine restored the ATP concentration to normal within 4 hr. Incorporation of labelled adenine or adenosine into the ATP of incubated stored cells corresponded to net ATP synthesis by these cells. 3. Synthesis of ATP from adenosine plus adenine together was 75% derived from adenine and only 25% from adenosine, indicating that nucleotide synthesis from adenine inhibits the simultaneous synthesis of nucleotide from adenosine. PMID:5723519

  16. Base excision repair of tandem modifications in a methylated CpG dinucleotide.

    PubMed

    Sassa, Akira; Çağlayan, Melike; Dyrkheeva, Nadezhda S; Beard, William A; Wilson, Samuel H

    2014-05-16

    Cytosine methylation and demethylation in tracks of CpG dinucleotides is an epigenetic mechanism for control of gene expression. The initial step in the demethylation process can be deamination of 5-methylcytosine producing the TpG alteration and T:G mispair, and this step is followed by thymine DNA glycosylase (TDG) initiated base excision repair (BER). A further consideration is that guanine in the CpG dinucleotide may become oxidized to 7,8-dihydro-8-oxoguanine (8-oxoG), and this could affect the demethylation process involving TDG-initiated BER. However, little is known about the enzymology of BER of altered in-tandem CpG dinucleotides; e.g. Tp8-oxoG. Here, we investigated interactions between this altered dinucleotide and purified BER enzymes, the DNA glycosylases TDG and 8-oxoG DNA glycosylase 1 (OGG1), apurinic/apyrimidinic (AP) endonuclease 1, DNA polymerase β, and DNA ligases. The overall TDG-initiated BER of the Tp8-oxoG dinucleotide is significantly reduced. Specifically, TDG and DNA ligase activities are reduced by a 3'-flanking 8-oxoG. In contrast, the OGG1-initiated BER pathway is blocked due to the 5'-flanking T:G mispair; this reduces OGG1, AP endonuclease 1, and DNA polymerase β activities. Furthermore, in TDG-initiated BER, TDG remains bound to its product AP site blocking OGG1 access to the adjacent 8-oxoG. These results reveal BER enzyme specificities enabling suppression of OGG1-initiated BER and coordination of TDG-initiated BER at this tandem alteration in the CpG dinucleotide.

  17. Detection of electronically equivalent tautomers of adenine base: DFT study

    SciTech Connect

    Siddiqui, Shamoon Ahmad; Bouarissa, Nadir; Rasheed, Tabish; Al-Assiri, M.S.; Al-Hajry, A.

    2014-03-01

    Graphical abstract: - Highlights: • DFT calculations have been performed on adenine and its rare tautomer Cu{sup 2+} complexes. • Interaction of A-Cu{sup 2+} and rA-Cu{sup 2+} complexes with AlN modified fullerene (C{sub 60}) have been studied briefly. • It is found that AlN modified C{sub 60} could be used as a nanoscale sensor to detect these two A-Cu{sup 2+} and rA-Cu{sup 2+} complexes. - Abstract: In the present study, quantum chemical calculations were carried out to investigate the electronic structures and stabilities of adenine and its rare tautomer along with their Cu{sup 2+} complexes. Density Functional Theory (B3LYP method) was used in all calculations. The two Cu{sup 2+} complexes of adenine have almost similar energies and electronic structures; hence, their chemical differentiation is very difficult. For this purpose, interactions of these complexes with AlN modified fullerene (C{sub 60}) have been studied. Theoretical investigations reveal that AlN-doped C{sub 60} may serve as a potentially viable nanoscale sensor for detection of the two Cu{sup 2+} complexes of adenine.

  18. Catalytic Mechanism and Three-Dimensional Structure of Adenine Deaminase

    SciTech Connect

    S Kamat; A Bagaria; D Kumaran; G Holmes-Hampton; H Fan; A Sali; J Sauder; S Burley; P Lindahl; et. al.

    2011-12-31

    Adenine deaminase (ADE) catalyzes the conversion of adenine to hypoxanthine and ammonia. The enzyme isolated from Escherichia coli using standard expression conditions was low for the deamination of adenine (k{sub cat} = 2.0 s{sup -1}; k{sub cat}/K{sub m} = 2.5 x 10{sup 3} M{sup -1} s{sup -1}). However, when iron was sequestered with a metal chelator and the growth medium was supplemented with Mn{sup 2+} prior to induction, the purified enzyme was substantially more active for the deamination of adenine with k{sub cat} and k{sub cat}/K{sub m} values of 200 s{sup -1} and 5 x 10{sup 5} M{sup -1} s{sup -1}, respectively. The apoenzyme was prepared and reconstituted with Fe{sup 2+}, Zn{sup 2+}, or Mn{sup 2+}. In each case, two enzyme equivalents of metal were necessary for reconstitution of the deaminase activity. This work provides the first example of any member of the deaminase subfamily of the amidohydrolase superfamily to utilize a binuclear metal center for the catalysis of a deamination reaction. [Fe{sup II}/Fe{sup II}]-ADE was oxidized to [Fe{sup III}/Fe{sup III}]-ADE with ferricyanide with inactivation of the deaminase activity. Reducing [Fe{sup III}/Fe{sup III}]-ADE with dithionite restored the deaminase activity, and thus, the diferrous form of the enzyme is essential for catalytic activity. No evidence of spin coupling between metal ions was evident by electron paramagnetic resonance or Moessbauer spectroscopy. The three-dimensional structure of adenine deaminase from Agrobacterium tumefaciens (Atu4426) was determined by X-ray crystallography at 2.2 {angstrom} resolution, and adenine was modeled into the active site on the basis of homology to other members of the amidohydrolase superfamily. On the basis of the model of the adenine-ADE complex and subsequent mutagenesis experiments, the roles for each of the highly conserved residues were proposed. Solvent isotope effects, pH-rate profiles, and solvent viscosity were utilized to propose a chemical reaction

  19. Catalytic Mechanism and Three-Dimensional Structure of Adenine Deaminase

    SciTech Connect

    Kamat, S.S.; Swaminathan, S.; Bagaria, A.; Kumaran, D.; Holmes-Hampton, G. P.; Fan, H.; Sali, A.; Sauder, J. M.; Burley, S. K.; Lindahl, P. A.; Raushel, F. M.

    2011-03-22

    Adenine deaminase (ADE) catalyzes the conversion of adenine to hypoxanthine and ammonia. The enzyme isolated from Escherichia coli using standard expression conditions was low for the deamination of adenine (k{sub cat} = 2.0 s{sup -1}; k{sub cat}/K{sub m} = 2.5 x 10{sup 3} M{sup -1} s{sup -1}). However, when iron was sequestered with a metal chelator and the growth medium was supplemented with Mn{sup 2+} prior to induction, the purified enzyme was substantially more active for the deamination of adenine with kcat and kcat/Km values of 200 s{sup -1} and 5 x 10{sup 5} M{sup -1} s{sup -1}, respectively. The apoenzyme was prepared and reconstituted with Fe{sup 2+}, Zn{sup 2+}, or Mn{sup 2+}. In each case, two enzyme equivalents of metal were necessary for reconstitution of the deaminase activity. This work provides the first example of any member of the deaminase subfamily of the amidohydrolase superfamily to utilize a binuclear metal center for the catalysis of a deamination reaction. [Fe{sup II}/Fe{sup II}]-ADE was oxidized to [Fe{sup III}/Fe{sup III}]-ADE with ferricyanide with inactivation of the deaminase activity. Reducing [Fe{sup III}/Fe{sup III}]-ADE with dithionite restored the deaminase activity, and thus, the diferrous form of the enzyme is essential for catalytic activity. No evidence of spin coupling between metal ions was evident by electron paramagnetic resonance or Moessbauer spectroscopy. The three-dimensional structure of adenine deaminase from Agrobacterium tumefaciens (Atu4426) was determined by X-ray crystallography at 2.2 {angstrom} resolution, and adenine was modeled into the active site on the basis of homology to other members of the amidohydrolase superfamily. On the basis of the model of the adenine-ADE complex and subsequent mutagenesis experiments, the roles for each of the highly conserved residues were proposed. Solvent isotope effects, pH-rate profiles, and solvent viscosity were utilized to propose a chemical reaction mechanism and the

  20. Relationship between periodic dinucleotides and the nucleosome structure revealed by alpha shape modeling

    NASA Astrophysics Data System (ADS)

    Zhou, Weiqiang; Yan, Hong

    2010-04-01

    As the fundamental repeating units in eukaryotic chromatin, nucleosomes play an important role in many biological processes. For this reason, the study of the structure of nucleosomes may help to reveal some of the crucial principals of these processes. In our research, we have used alpha shapes to model nucleosome structure and discovered that the periodic DNA dinucleotides AA, TT and GC occupy special positions in nucleosome structure with one nucleotide inside and the other outside the nucleosome surface. This structural feature and other dinucleotide characteristics can provide useful information for the study of nucleosome positioning.

  1. In vitro adenine nucleotide catabolism in African catfish spermatozoa.

    PubMed

    Zietara, Marek S; Słomińska, Ewa; Rurangwa, Eugene; Ollevier, Frans; Swierczyński, Julian; Skorkowski, Edward F

    2004-08-01

    It has been shown recently that African catfish (Clarias gariepinus) spermatozoa possess relatively low ATP content and low adenylate energy charge (AEC). One of the possible explanations for this phenomenon is that the spermatozoa actively catabolize adenine nucleotides. A relatively high rate of such catabolism could then contribute to the low ATP concentration and low adenylate energy charge observed in the spermatozoa in vitro. To check this hypothesis, we investigated ATP content and adenine nucleotide catabolism in African catfish spermatozoa stored at 4 degrees C in the presence of glycine as an energetic substrate. Our results indicate that the storage of African catfish sperm at 4 degrees C in the presence of glycine causes time-dependent ATP depletion. In contrast to ATP, the AMP content increases significantly during the same period of sperm storage, while the ADP increases only slightly. Moreover, a significant increase of inosine and hypoxanthine content was also found. Hypoxanthine was accumulated in the storage medium, but xanthine was found neither in spermatozoa nor in the storage medium. It indicates that hypoxanthine is not converted to xanthine, probably due to lack of xanthine oxidase activity in catfish spermatozoa. Present results suggest that adenine nucleotides may be converted to hypoxanthine according to the following pathway: ATP-->ADP-->AMP (adenosine/IMP)-->inosine-->hypoxanthine. Moreover, hypoxanthine seems to be the end product of adenine nucleotide catabolism in African catfish spermatozoa. In conclusion, our results suggest that a relatively high rate of adenine nucleotide catabolism contributes to the low ATP concentration and low adenylate energy charge observed in African catfish spermatozoa in vitro.

  2. Hydride fuel behavior in LWRs

    NASA Astrophysics Data System (ADS)

    Olander, Donald R.; Ng, Marowen

    2005-11-01

    The U-Zr hydride U 0.31ZrH 1.6 offers a number of advantages over oxide fuel for light-water reactors. Fission-gas release appears to be very small (release fraction ˜10 -4) up to 600 °C, which is close to the maximum fuel temperature. Initial irradiation-induced swelling can be as large as 5% for temperatures exceeding 650 °C. Hydrogen redistributes due to the non-uniform temperature in the fuel from the as-fabricated H/Zr of 1.6 to one that is higher at the pellet periphery than at the centerline. Radial redistribution produces 'hydrogen' stresses in the pellet which add to the usual thermal stresses. In a helium-bonded fuel rod, the total stresses are less than the fracture stress; in a liquid-metal-bonded fuel rod, the fracture stress is exceeded in the central portion of the pellet, but the surface remains in compression. Axial redistribution moves substantial quantities of hydrogen from the middle portion of the fuel stack to the ends. The neutronic effect of this displacement of the moderator is unknown.

  3. Thin-film metal hydrides.

    PubMed

    Remhof, Arndt; Borgschulte, Andreas

    2008-12-01

    The goal of the medieval alchemist, the chemical transformation of common metals into nobel metals, will forever be a dream. However, key characteristics of metals, such as their electronic band structure and, consequently, their electric, magnetic and optical properties, can be tailored by controlled hydrogen doping. Due to their morphology and well-defined geometry with flat, coplanar surfaces/interfaces, novel phenomena may be observed in thin films. Prominent examples are the eye-catching hydrogen switchable mirror effect, the visualization of solid-state diffusion and the formation of complex surface morphologies. Thin films do not suffer as much from embrittlement and/or decrepitation as bulk materials, allowing the study of cyclic absorption and desorption. Therefore, thin-metal hydride films are used as model systems to study metal-insulator transitions, for high throughput combinatorial research or they may be used as indicator layers to study hydrogen diffusion. They can be found in technological applications as hydrogen sensors, in electrochromic and thermochromic devices. In this review, we discuss the effect of hydrogen loading of thin niobium and yttrium films as archetypical examples of a transition metal and a rare earth metal, respectively. Our focus thereby lies on the hydrogen induced changes of the electronic structure and the morphology of the thin films, their optical properties, the visualization and the control of hydrogen diffusion and on the study of surface phenomena and catalysis.

  4. Metal Hydride Heat Storage Technology for Directed Energy Weapon Systems

    DTIC Science & Technology

    2007-11-16

    over time after the pulse operation. A compressor -driven metal hydride heat storage system was developed for efficient, compact heat storage and...principle and heat storage performance results of the compressor -driven metal hydride heat storage system through system modeling and prototype testing. The...hyd/m³] Subscripts A Metal hydride reactor B Hydrogen container C Hydrogen compressor s Hydrogen solid phase in hydride f Hydrogen fluid phase

  5. High H- ionic conductivity in barium hydride

    NASA Astrophysics Data System (ADS)

    Verbraeken, Maarten C.; Cheung, Chaksum; Suard, Emmanuelle; Irvine, John T. S.

    2015-01-01

    With hydrogen being seen as a key renewable energy vector, the search for materials exhibiting fast hydrogen transport becomes ever more important. Not only do hydrogen storage materials require high mobility of hydrogen in the solid state, but the efficiency of electrochemical devices is also largely determined by fast ionic transport. Although the heavy alkaline-earth hydrides are of limited interest for their hydrogen storage potential, owing to low gravimetric densities, their ionic nature may prove useful in new electrochemical applications, especially as an ionically conducting electrolyte material. Here we show that barium hydride shows fast pure ionic transport of hydride ions (H-) in the high-temperature, high-symmetry phase. Although some conductivity studies have been reported on related materials previously, the nature of the charge carriers has not been determined. BaH2 gives rise to hydride ion conductivity of 0.2 S cm-1 at 630 °C. This is an order of magnitude larger than that of state-of-the-art proton-conducting perovskites or oxide ion conductors at this temperature. These results suggest that the alkaline-earth hydrides form an important new family of materials, with potential use in a number of applications, such as separation membranes, electrochemical reactors and so on.

  6. Reactivity of yttrium carboxylates toward alkylaluminum hydrides.

    PubMed

    Schädle, Christoph; Fischbach, Andreas; Herdtweck, Eberhardt; Törnroos, Karl W; Anwander, Reiner

    2013-11-25

    Yttrocene-carboxylate complex [Cp*2Y(OOCAr(Me))] (Cp*=C5Me5, Ar(Me) =C6H2Me3-2,4,6) was synthesized as a spectroscopically versatile model system for investigating the reactivity of alkylaluminum hydrides towards rare-earth-metal carboxylates. Equimolar reactions with bis-neosilylaluminum hydride and dimethylaluminum hydride gave adduct complexes of the general formula [Cp*2Y(μ-OOCAr(Me))(μ-H)AlR2] (R=CH2SiMe3, Me). The use of an excess of the respective aluminum hydride led to the formation of product mixtures, from which the yttrium-aluminum-hydride complex [{Cp*2Y(μ-H)AlMe2(μ-H)AlMe2(μ-CH3)}2] could be isolated, which features a 12-membered-ring structure. The adduct complexes [Cp*2Y(μ-OOCAr(Me))(μ-H)AlR2] display identical (1)J(Y,H) coupling constants of 24.5 Hz for the bridging hydrido ligands and similar (89)Y NMR shifts of δ=-88.1 ppm (R=CH2SiMe3) and δ=-86.3 ppm (R=Me) in the (89)Y DEPT45 NMR experiments.

  7. 49 CFR 173.311 - Metal hydride storage systems.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 2 2014-10-01 2014-10-01 false Metal hydride storage systems. 173.311 Section 173... REQUIREMENTS FOR SHIPMENTS AND PACKAGINGS Gases; Preparation and Packaging § 173.311 Metal hydride storage systems. The following packing instruction is applicable to transportable UN Metal hydride storage...

  8. 49 CFR 173.311 - Metal hydride storage systems.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 2 2011-10-01 2011-10-01 false Metal hydride storage systems. 173.311 Section 173... REQUIREMENTS FOR SHIPMENTS AND PACKAGINGS Gases; Preparation and Packaging § 173.311 Metal hydride storage systems. The following packing instruction is applicable to transportable UN Metal hydride storage...

  9. 49 CFR 173.311 - Metal hydride storage systems.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 2 2012-10-01 2012-10-01 false Metal hydride storage systems. 173.311 Section 173... REQUIREMENTS FOR SHIPMENTS AND PACKAGINGS Gases; Preparation and Packaging § 173.311 Metal hydride storage systems. The following packing instruction is applicable to transportable UN Metal hydride storage...

  10. 49 CFR 173.311 - Metal hydride storage systems.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 2 2013-10-01 2013-10-01 false Metal hydride storage systems. 173.311 Section 173... REQUIREMENTS FOR SHIPMENTS AND PACKAGINGS Gases; Preparation and Packaging § 173.311 Metal hydride storage systems. The following packing instruction is applicable to transportable UN Metal hydride storage...

  11. Improved predictive test for MEN2, using flanking dinucleotide repeats and RFLPs

    SciTech Connect

    Howe, J.R.; Lairmore, T.C.; Mishra, S.K.; Shenshen Dou; Veile, R.; Wells, S.A. Jr.; Donis-Keller, H. )

    1992-12-01

    Gene(s) for the autosomal dominant endocrine cancer syndromes, multiple endocrine neoplasia type 2A (MEN2A), multiple endocrine neoplasia type 2B (MEN2B), and familial medullary thyroid carcinoma (MTC1) all map to the pericentromeric region of chromosome 10. Predictive testing for the inheritance of mutant alleles in individuals at risk for these disorders has been limited by the availability of highly informative and closely linked flanking markers. The authors describe the development of eight new markers, including two PCR-based dinucleotide repeat polymorphisms and six RFLPs that flank the disease loci. One of the dinucleotide repeat markers (sJRH-1) derives from the RBP3 locus on 10q11.2 and has a PIC of .88. The other dinucleotide repeat (sTCL-1) defines a new locus, D10S176, that maps by in situ hybridization to 10p11.2 and has a PIC of .68. The authors have constructed a new genetic linkage map of the pericentromeric region of chromosome 10, on the basis of 13 polymorphisms at six loci, which places the MEN2A locus between the dinucleotide repeat markers, with odds of 5,750:1 over the next most likely position. Using this set of markers, predictive genetic testing of 130 at-risk individuals from six families segregating MEN2A revealed that 95% were jointly informative with flanking markers, representing a significant improvement in genetic testing capabilities. 42 refs., 6 figs., 3 tabs.

  12. Study on the oxidation form of adenine in phosphate buffer solution.

    PubMed

    Song, Yuan-Zhi; Zhou, Jian-Feng; Zhu, Feng-Xia; Ye, Yong; Xie, Ji-Min

    2010-07-01

    The oxidation of adenine in phosphate buffer solution is investigated using square-wave voltammetry and in situ UV spectroelectrochemistry. The geometry of adenine and the derivatives optimized at DFTB3LYP-6-31G (d, p)-PCM level is in agreement with the crystal structure, and the imitated UV spectra of adenine and the product at electrode are consistent with the in situ UV spectra. The relationship between the electrochemical property and the molecular structure is also discussed. The experimental and theoretical results show that the adenine oxidation origins from the neutral adenine.

  13. Iron Group Hydrides in Noyori Bifunctional Catalysis.

    PubMed

    Morris, Robert H

    2016-12-01

    This is an overview of the hydride-containing catalysts prepared in the Morris group for the efficient hydrogenation of simple ketones, imines, nitriles and esters and the asymmetric hydrogenation and transfer hydrogenation of prochiral ketones and imines. The work was inspired by and makes use of Noyori metal-ligand bifunctional concepts involving the hydride-ruthenium amine-hydrogen HRuNH design. It describes the synthesis and some catalytic properties of hydridochloro, dihydride and amide complexes of ruthenium and in one case, osmium, with monodentate, bidentate and tetradentate phosphorus and nitrogen donor ligands. The iron hydride that has been identified in a very effective asymmetric transfer hydrogenation process is also mentioned. The link between the HMNH structure and the sense of enantioinduction is demonstrated by use of simple transition state models.

  14. Stacking interactions in RNA and DNA: Roll-slide energy hyperspace for ten unique dinucleotide steps.

    PubMed

    Mukherjee, Sanchita; Kailasam, Senthilkumar; Bansal, Manju; Bhattacharyya, Dhananjay

    2015-03-01

    Understanding dinucleotide sequence directed structures of nuleic acids and their variability from experimental observation remained ineffective due to unavailability of statistically meaningful data. We have attempted to understand this from energy scan along twist, roll, and slide degrees of freedom which are mostly dependent on dinucleotide sequence using ab initio density functional theory. We have carried out stacking energy analysis in these dinucleotide parameter phase space for all ten unique dinucleotide steps in DNA and RNA using DFT-D by ωB97X-D/6-31G(2d,2p), which appears to satisfactorily explain conformational preferences for AU/AU step in our recent study. We show that values of roll, slide, and twist of most of the dinucleotide sequences in crystal structures fall in the low energy region. The minimum energy regions with large twist values are associated with the roll and slide values of B-DNA, whereas, smaller twist values correspond to higher stability to RNA and A-DNA like conformations. Incorporation of solvent effect by CPCM method could explain the preference shown by some sequences to occur in B-DNA or A-DNA conformations. Conformational preference of BII sub-state in B-DNA is preferentially displayed mainly by pyrimidine-purine steps and partly by purine-purine steps. The purine-pyrimidine steps show largest effect of 5-methyl group of thymine in stacking energy and the introduction of solvent reduces this effect significantly. These predicted structures and variabilities can explain the effect of sequence on DNA and RNA functionality.

  15. 1. VIEW OF A PORTION OF THE HYDRIDE PROCESSING LABORATORY. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. VIEW OF A PORTION OF THE HYDRIDE PROCESSING LABORATORY. OPERATIONS IN THE GLOVE BOX IN THE BACKGROUND OF THE PHOTOGRAPH INCLUDED HYDRIDING OF PLUTONIUM AND HYDRIDE SEPARATION. IN THE FOREGROUND, THE VACUUM MONITOR CONTROL PANEL MEASURED TEMPERATURES WITHIN THE GLOVEBOX. THE CENTER CONTROL PANEL REGULATED THE FURNACE INSIDE THE GLOVE BOX USED IN THE HYDRIDING PROCESSES. THIS EQUIPMENT WAS ESSENTIAL TO THE HYDRIDING PROCESS, AS WELL AS OTHER GLOVE BOX OPERATIONS. - Rocky Flats Plant, Plutonium Laboratory, North-central section of industrial area at 79 Drive, Golden, Jefferson County, CO

  16. Excited State Pathways Leading to Formation of Adenine Dimers.

    PubMed

    Banyasz, Akos; Martinez-Fernandez, Lara; Ketola, Tiia-Maaria; Muñoz-Losa, Aurora; Esposito, Luciana; Markovitsi, Dimitra; Improta, Roberto

    2016-06-02

    The reaction intermediate in the path leading to UV-induced formation of adenine dimers A═A and AA* is identified for the first time quantum mechanically, using PCM/TD-DFT calculations on (dA)2 (dA: 2'deoxyadenosine). In parallel, its fingerprint is detected in the absorption spectra recorded on the millisecond time-scale for the single strand (dA)20 (dA: 2'deoxyadenosine).

  17. High resolution dissociative electron attachment to gas phase adenine

    SciTech Connect

    Huber, D.; Beikircher, M.; Denifl, S.; Zappa, F.; Matejcik, S.; Bacher, A.; Grill, V.; Maerk, T. D.; Scheier, P.

    2006-08-28

    The dissociative electron attachment to the gas phase nucleobase adenine is studied using two different experiments. A double focusing sector field mass spectrometer is utilized for measurements requiring high mass resolution, high sensitivity, and relative ion yields for all the fragment anions and a hemispherical electron monochromator instrument for high electron energy resolution. The negative ion mass spectra are discussed at two different electron energies of 2 and 6 eV. In contrast to previous gas phase studies a number of new negative ions are discovered in the mass spectra. The ion efficiency curves for the negative ions of adenine are measured for the electron energy range from about 0 to 15 eV with an electron energy resolution of about 100 meV. The total anion yield derived via the summation of all measured fragment anions is compared with the total cross section for negative ion formation measured recently without mass spectrometry. For adenine the shape of the two cross section curves agrees well, taking into account the different electron energy resolutions; however, for thymine some peculiar differences are observed.

  18. The nucleobase adenine as a signalling molecule in the kidney.

    PubMed

    Thimm, D; Schiedel, A C; Peti-Peterdi, J; Kishore, B K; Müller, C E

    2015-04-01

    In 2002, the first receptor activated by the nucleobase adenine was discovered in rats. In the past years, two adenine receptors (AdeRs) in mice and one in Chinese hamsters, all of which belong to the family of G protein-coupled receptors (GPCRs), were cloned and pharmacologically characterized. Based on the nomenclature for other purinergic receptor families (P1 for adenosine receptors and P2 for nucleotide, e.g. ATP, receptors), AdeRs were designated P0 receptors. Pharmacological data indicate the existence of G protein-coupled AdeRs in pigs and humans as well; however, those have not been cloned so far. Current data suggest a role for adenine and AdeRs in renal proximal tubules. Furthermore, AdeRs are suggested to be functional counterplayers of vasopressin in the collecting duct system, thus exerting diuretic effects. We are only at the beginning of understanding the significance of this new class of purinergic receptors, which might become future drug targets.

  19. Fragmentation mechanisms of cytosine, adenine and guanine ionized bases.

    PubMed

    Sadr-Arani, Leila; Mignon, Pierre; Chermette, Henry; Abdoul-Carime, Hassan; Farizon, Bernadette; Farizon, Michel

    2015-05-07

    The different fragmentation channels of cytosine, adenine and guanine have been studied through DFT calculations. The electronic structure of bases, their cations, and the fragments obtained by breaking bonds provides a good understanding of the fragmentation process that can complete the experimental approach. The calculations allow assigning various fragments to the given peaks. The comparison between the energy required for the formation of fragments and the peak intensity in the mass spectrum is used. For cytosine and guanine the elimination of the HNCO molecule is a major route of dissociation, while for adenine multiple loss of HCN or HNC can be followed up to small fragments. For cytosine, this corresponds to the initial bond cleavage of N3-C4/N1-C2, which represents the main dissociation route. For guanine the release of HNCO is obtained through the N1-C2/C5-C6 bond cleavage (reverse order also possible) leading to the largest peak of the spectrum. The corresponding energies of 3.5 and 3.9 eV are typically in the range available in the experiments. The loss of NH3 or HCN is also possible but requires more energy. For adenine, fragmentation consists of multiple loss of the HCN molecule and the main route corresponding to HC8N9 loss is followed by the release of HC2N1.

  20. Hydride formation on deformation twin in zirconium alloy

    NASA Astrophysics Data System (ADS)

    Kim, Ju-Seong; Kim, Sung-Dae; Yoon, Jonghun

    2016-12-01

    Hydrides deteriorate the mechanical properties of zirconium (Zr) alloys used in nuclear reactors. Intergranular hydrides that form along grain boundaries have been extensively studied due to their detrimental effects on cracking. However, it has been little concerns on formation of Zr hydrides correlated with deformation twins which is distinctive heterogeneous nucleation site in hexagonal close-packed metals. In this paper, the heterogeneous precipitation of Zr hydrides at the twin boundaries was visualized using transmission electron microscopy. It demonstrates that intragranular hydrides in the twinned region precipitates on the rotated habit plane by the twinning and intergranular hydrides precipitate along the coherent low energy twin boundaries independent of the conventional habit planes. Interestingly, dislocations around the twin boundaries play a substantial role in the nucleation of Zr hydrides by reducing the misfit strain energy.

  1. Hydridable material for the negative electrode in a nickel-metal hydride storage battery

    DOEpatents

    Knosp, Bernard; Bouet, Jacques; Jordy, Christian; Mimoun, Michel; Gicquel, Daniel

    1997-01-01

    A monophase hydridable material for the negative electrode of a nickel-metal hydride storage battery with a "Lave's phase" structure of hexagonal C14 type (MgZn.sub.2) has the general formula: Zr.sub.1-x Ti.sub.x Ni.sub.a Mn.sub.b Al.sub.c Co.sub.d V.sub.e where ##EQU1##

  2. Ductility Evaluation of As-Hydrided and Hydride Reoriented Zircaloy-4 Cladding under Simulated Dry-Storage Condition

    SciTech Connect

    Yan, Yong; Plummer, Lee K; Ray, Holly B; Cook, Tyler S; Bilheux, Hassina Z

    2014-01-01

    Pre-storage drying-transfer operations and early stage storage expose cladding to higher temperatures and much higher pressure-induced tensile hoop stresses relative to normal operation in-reactor and pool storage under these conditions. Radial hydrides could precipitate during slow cooling and provide an additional embrittlement mechanism as the cladding temperature decreases below the ductile-to-brittle transition temperature. As a means of simulating this behavior, unirradiated hydrided Zircaloy-4 samples were fabricated by a gas charging method to levels that encompass the range of hydrogen concentrations observed in current used fuel. Mechanical testing was carried out by the ring compression test (RCT) method at various temperatures to evaluate the sample s ductility for both as-hydrided and post-hydride reorientation treated specimens. As-hydrided samples with higher hydrogen concentration (>800 ppm) resulted in lower strain before fracture and reduced maximum load. Increasing RCT temperatures resulted in increased ductility of the as-hydrided cladding. A systematic radial hydride treatment was conducted at various pressures and temperatures for the hydrided samples with H content around 200 ppm. Following the radial hydride treatment, RCTs on the hydride reoriented samples were conducted and exhibited lower ductility compared to as-hydrided samples.

  3. A thermokinetically driven metal-hydride actuator

    NASA Astrophysics Data System (ADS)

    Jung, Kwangmok; Kim, Kwang J.

    2008-03-01

    The purpose of this study is to develop a novel thermokinetically-driven actuator technology based on the physics of metal hydrides (MH's). A metal hydride absorbs and desorbs hydrogen due to the imposed temperature swing(s). The MH can also work as an effective thermally-driven hydrogen compressor producing more than 5,000 psia net pressure swing. The MH actuation system can be built in a simple structure, exhibits high power, produces soft actuating, and is essentially noiseless. Moreover, it is much more powerful and compact than conventional pneumatic systems that require bulky auxiliary systems. It is our belief that the MH actuators are useful for many emerging industrial, biorobotic, and civil structural applications. In this paper, we report the recent preliminary experimental results for a laboratory-prototyped MH actuation system. In particular, the dynamic response characteristics, enhanced controllability, thermodynamic performances, and reliability of the metal hydride actuator were studied in order to estimate the actuation capability of the MH actuator. A unique design of the MH actuator was created. It encases a so-called "porous metal hydride (PMH)" in the reactor to effectively achieve desirable performance by improving overall thermal conductance.

  4. X-Ray Topography of Hydride Domains.

    DTIC Science & Technology

    1983-04-01

    boundaries between hydride (deuteride) domains, and the irregular boundaries correspond to incoherent twin boundaries . Trace analysis of the coherent...topographs of the NbHo.78 and NbO 0 .75 crystals. As discussed by Schober and Linke (1976b), the straight boundaries correspond to coherent twin

  5. Metal hydride fuel storage and method thereof

    DOEpatents

    Morse, Jeffrey D.; Jankowski, Alan F.; Yu, Conrad

    2006-10-17

    Disclosed herein is a metal hydride fuel storage cartridge having integrated resistive heaters that can be used in conjunction with fuel cells such as MEMS-based fuel cells. The cartridge is fabricated using micromachining methods and thin/thick film materials synthesis techniques.

  6. Metal hydride fuel storage and method thereof

    DOEpatents

    Morse, Jeffrey D [Martinez, CA; Jankowski, Alan F [Livermore, CA; Yu, Conrad [Antioch, CA

    2009-05-05

    Disclosed herein is a metal hydride fuel storage cartridge having integrated resistive heaters that can be used in conjunction with fuel cells such as MEMS-based fuel cells. The cartridge is fabricated using micromachining methods and thin/thick film materials synthesis techniques.

  7. A Highly Reactive Imidazolium-Bridged Dinucleotide Intermediate in Nonenzymatic RNA Primer Extension.

    PubMed

    Walton, Travis; Szostak, Jack W

    2016-09-14

    Because of its importance for the origin of life, the nonenzymatic copying of RNA templates has been the subject of intense study for several decades. Previous characterizations of template-directed primer extension using 5'-phosphoryl-2-methylimidazole-activated nucleotides (2-MeImpNs) as substrates have assumed a classical in-line nucleophilic substitution mechanism, in which the 3'-hydroxyl of the primer attacks the phosphate of the incoming monomer, displacing the 2-methylimidazole leaving group. However, we have found that the initial rate of primer extension depends on the pH and concentration at which the activated monomer is maintained prior to the primer extension reaction. These and other results suggest an alternative mechanism, in which two monomers react with each other to form an imidazolium-bridged dinucleotide intermediate, which then binds to the template. Subsequent attack of the 3'-hydroxyl of the primer displaces an activated nucleotide as the leaving group and results in extension of the primer by one nucleotide. Analysis of monomer solutions by NMR indicates formation of the proposed imidazolium-bridged dinucleotide in the expected pH-dependent manner. We have used synthetic methods to prepare material that is enriched in this proposed intermediate and show that it is a highly reactive substrate for primer extension. The formation of an imidazolium-bridged dinucleotide intermediate provides a mechanistic interpretation of previously observed catalysis by an activated nucleotide located downstream from the site of primer extension.

  8. Progress in Understanding the Molecular Basis Underlying Functional Diversification of Cyclic Dinucleotide Turnover Proteins.

    PubMed

    Römling, Ute; Liang, Zhao-Xun; Dow, J Maxwell

    2017-03-01

    Cyclic di-GMP was the first cyclic dinucleotide second messenger described, presaging the discovery of additional cyclic dinucleotide messengers in bacteria and eukaryotes. The GGDEF diguanylate cyclase (DGC) and EAL and HD-GYP phosphodiesterase (PDE) domains conduct the turnover of cyclic di-GMP. These three unrelated domains belong to superfamilies that exhibit significant variations in function, and they include both enzymatically active and inactive members, with a subset involved in synthesis and degradation of other cyclic dinucleotides. Here, we summarize current knowledge of sequence and structural variations that underpin the functional diversification of cyclic di-GMP turnover proteins. Moreover, we highlight that superfamily diversification is not restricted to cyclic di-GMP signaling domains, as particular DHH/DHHA1 domain and HD domain proteins have been shown to act as cyclic di-AMP phosphodiesterases. We conclude with a consideration of the current limitations that such diversity of action places on bioinformatic prediction of the roles of GGDEF, EAL, and HD-GYP domain proteins.

  9. Effects of spinally administered adenine on dorsal horn neuronal responses in a rat model of inflammation.

    PubMed

    Matthews, Elizabeth A; Dickenson, Anthony H

    2004-02-19

    A novel G-protein-coupled receptor with adenine identified as the endogenous ligand has recently been described. In vivo electrophysiological techniques in the rat were used to record the response of dorsal horn neurones in response to transcutaneous electrical stimulation to the hindpaw receptive field. Spinal adenine (1-1000 microg) exerted facilitatory effects on the electrically-evoked neuronal responses, in a mildly dose-related manner. After establishment of carrageenan-induced inflammation to the hindpaw this excitatory effect of adenine was still apparent, yet reduced. C-fibre-evoked responses and other nociceptive related measures were most susceptible to the effects of adenine, whereas non-nociceptive Abeta-fibre evoked activity remained unaffected. Thus, activation of the adenine receptor site, via spinally applied adenine, suggests a pronociceptive role in nociceptive sensory transmission.

  10. Influence of hydrogen bonding on the geometry of the adenine fragment

    NASA Astrophysics Data System (ADS)

    Słowikowska, Joanna Maria; Woźniak, Krzysztof

    1996-01-01

    The crystal structures of two adenine derivatives, N(6),9-dimethyl-8-butyladenine (I) and its hydrate (1 : 1) (II), have been determined by single-crystal X-ray diffraction. The geometrical features of both structures are discussed. The influence of protonation, substitution and hydrogen bond formation on the geometry of the adenine fragment was studied, based on data retrieved from the Cambridge Structural Database. Total correlation analysis showed mutual correlation between the structural parameters in the adenine ring system; partial correlation calculations for the adenine nucleoside fragments suggest intercorrelation between the parameters of the hydrogen bonding involved in base pairing and the N(adenine)-C(sugar) bond through the adenine fragment; few such correlations were found for fragments without the sugar substituent.

  11. Sulfur and adenine metabolisms are linked, and both modulate sulfite resistance in wine yeast.

    PubMed

    Aranda, Agustín; Jiménez-Martí, Elena; Orozco, Helena; Matallana, Emilia; Del Olmo, Marcellí

    2006-08-09

    Sulfite treatment is the most common way to prevent grape must spoilage in winemaking because the yeast Saccharomyces cerevisiae is particularly resistant to this chemical. In this paper we report that sulfite resistance depends on sulfur and adenine metabolism. The amount of adenine and methionine in a chemically defined growth medium modulates sulfite resistance of wine yeasts. Mutations in the adenine biosynthetic pathway or the presence of adenine in a synthetic minimal culture medium increase sulfite resistance. The presence of methionine has the opposite effect, inducing a higher sensitivity to SO(2). The concentration of methionine, adenine, and sulfite in a synthetic grape must influences the progress of fermentation and at the transcriptional level the expression of genes involved in sulfur (MET16), adenine (ADE4), and acetaldehyde (ALD6) metabolism. Sulfite alters the pattern of expression of all these genes. This fact indicates that the response to this stress is complex and involves several metabolic pathways.

  12. HYDROGEN-BONDED DIMERS OF ADENINE AND URACIL DERIVATIVES.

    PubMed

    HAMLIN, R M; LORD, R C; RICH, A

    1965-06-25

    In concentrated solutions of either 9-ethyladenine or 1-cyclohexyluracil in deuterochloroform, absorption bands in the infrared spectrum demonstrate hydrogen bonding of the adenine and uracil derivatives with themselves. In dilute solutions, there is very little hydrogen bonding. However, when dilute solutions of 9-ethyladenine and 1-cyclohexyluracil are mixed, a series of bands appear which show that these molecules are hydrogen-bonding with each other much more strongly than with themselves. A study of the stoichiometry of this association indicates formation of 1:1 hydrogen-bonded pairs in solution.

  13. Purines 2010: Adenine Nucleosides and Nucleotides in Biomedicine.

    PubMed

    Sereda, Michal J

    2010-08-01

    The Purines 2010: Adenine Nucleosides and Nucleotides in Biomedicine meeting, held in Tarragona, Spain, included topics covering new findings in the field of purinergic signaling and the development of purine-based drugs. This conference report highlights selected presentations on developments in purinerigic signaling, medicinal chemistry, the therapeutic potential of purine-based drugs, and the role of purines and adenosine receptors in neurodegenerative disorders, sickle cell disease, bone homeostasis, pulmonary fibrosis and pain. Investigational drugs discussed include CF-101 (Can-Fite BioPharma Ltd/NIH/Kwang Dong Pharmaceutical Co Ltd/Seikagaku Corp) and denufosol tetrasodium (Cystic Fibrosis Foundation Therapeutics Inc/Inspire Pharmaceuticals Inc).

  14. Dynamic changes in nicotinamide pyridine dinucleotide content in normal human epidermal keratinocytes and their effect on retinoic acid biosynthesis

    SciTech Connect

    Pinkas-Sarafova, Adriana . E-mail: apinkassaraf@notes.cc.sunysb.edu; Markova, N.G. . E-mail: nmarkova@notes.cc.sunysb.edu; Simon, M. . E-mail: marsimon@notes.cc.sunysb.edu

    2005-10-21

    The function of many enzymes that regulate metabolism and transcription depends critically on the nicotinamide pyridine dinucleotides. To understand the role of NAD(P)(H) in physiology and pathophysiology, it is imperative to estimate both their amount and ratios in a given cell type. In human epidermis and in cultured epidermal keratinocytes, we found that the total dinucleotide content is in the low millimolar range. The dinucleotide pattern changes during proliferation and maturation of keratinocytes in culture. Differences in the concentrations of NAD(P)(H) of 1.5- to 12-fold were observed. This resulted in alteration of the NAD(P)H/NAD(P) ratio, which could impact the differential regulation of both transcriptional and metabolic processes. In support of this notion, we provide evidence that the two-step oxidation of retinol to retinoic acid, a nuclear hormone critical for epidermal homeostasis, can be regulated by the relative physiological amounts of the pyridine dinucleotides.

  15. Investigation of coordination properties of isolated adenine to copper metal: a systematic spectroscopic and DFT study.

    PubMed

    Prakash, Om; Singh, Sachin Kumar; Singh, Bachcha; Singh, Ranjan K

    2013-08-01

    The coordination properties of copper with adenine have been studied by the analyzing the changes in Fourier Transform Infra-red (FTIR) and Raman spectra of adenine and adenine-copper complex. The geometry of adenine and adenine copper complex were optimized and theoretical Infra-red and Raman spectra of the optimized structures were calculated using Density Functional Theory (DFT). During synthesis of adenine-copper complex specific procedure was adopted to attach the Cu atom with particular N-atom of adenine (N9). The results of Raman and DFT confirmed the attachment. The Raman bands at 625, 330 and 230 cm(-1) of adenine-copper complex contain significant contribution of the vibrational motions of Cu metal coordinated to N9 and Cl atoms. The DFT calculations give additional vibrational modes containing the Cu, N9 and N9* atoms, which are not observed in FTIR and Raman spectra. The Raman, IR and DFT study confirm that Cu metal has good binding affinity to the isolated adenine base.

  16. METHOD OF FABRICATING A URANIUM-ZIRCONIUM HYDRIDE REACTOR CORE

    DOEpatents

    Weeks, I.F.; Goeddel, W.V.

    1960-03-22

    A method is described of evenly dispersing uranlum metal in a zirconium hydride moderator to produce a fuel element for nuclear reactors. According to the invention enriched uranium hydride and zirconium hydride powders of 200 mesh particle size are thoroughly admixed to form a mixture containing 0.1 to 3% by weight of U/sup 235/ hydride. The mixed powders are placed in a die and pressed at 100 tons per square inch at room temperature. The resultant compacts are heated in a vacuum to 300 deg C, whereby the uranium hydride deoomposes into uranium metal and hydrogen gas. The escaping hydrogen gas forms a porous matrix of zirconium hydride, with uramum metal evenly dispersed therethrough. The advantage of the invention is that the porosity and uranium distribution of the final fuel element can be more closely determined and controlled than was possible using prior methods of producing such fuel ele- ments.

  17. Synthesis and properties of platinum hydride

    NASA Astrophysics Data System (ADS)

    Scheler, Thomas; Degtyareva, Olga; Marqués, Miriam; Guillaume, Christophe L.; Proctor, John E.; Evans, Shaun; Gregoryanz, Eugene

    2011-06-01

    Synchrotron x-ray diffraction experiments on compressed platinum-hydrogen mixtures reveal the formation of platinum hydride at a pressure of 27(1) GPa at room temperature. This compound exhibits two phases, PtH-I and PtH-II, coexisting up to the pressure of 42 GPa, above which the single phase of PtH-II is observed. Pt atoms in the PtH-II phase are shown to form a hexagonal closed-packed structure. This phase exhibits a high bulk modulus of 310 (10) GPa and is stable up to at least 53 GPa. Ab initio calculations show that PtH-II is superconducting with Tc = 12 K at 90 GPa, the highest temperature of superconducting transition among any known metal hydride.

  18. Unoccupied electronic states in cerium hydrides

    NASA Astrophysics Data System (ADS)

    Osterwalder, J.; Schlapbach, L.

    1985-05-01

    We present UV isochromat spectra of polycrystalline CeH 2.1 and CeH 2.9. The intensity at EF is small in CeH 2.1 and vanishes in CeH 2.9 as it is expected from XPS, UPS and conductivity data. In both hydrides broad features (≈2 eV FWHM) appear between 4 and 5 eV above EF. This is in qualitative agreement with bandstructure calculations.

  19. Dissipative hydride precipitates in superconducting niobium cavities

    SciTech Connect

    Romanenko, A.; Cooley, L.D.; Ciovati, G.; Wu, G.; /Argonne

    2011-10-01

    We report the first direct observation of the microstructural features exhibiting RF losses at high surface magnetic fields of above 100 mT in field emission free superconducting niobium cavities. The lossy areas were identified by advanced thermometry. Surface investigations using different techniques were carried out on cutout samples from lossy areas and showed the presence of dendritic niobium hydrides. This finding has possible implications to the mechanisms of RF losses in superconducting niobium at all field levels.

  20. Nickel metal hydride LEO cycle testing

    NASA Technical Reports Server (NTRS)

    Lowery, Eric

    1995-01-01

    The George C. Marshall Space Flight Center is working to characterize aerospace AB5 Nickel Metal Hydride (NiMH) cells. The cells are being evaluated in terms of storage, low earth orbit (LEO) cycling, and response to parametric testing (high rate charge and discharge, charge retention, pulse current ability, etc.). Cells manufactured by Eagle Picher are the subjects of the evaluation. There is speculation that NiMH cells may become direct replacements for current Nickel Cadmium cells in the near future.

  1. Materials compatibility of hydride storage materials with austenitic stainless steels

    SciTech Connect

    Clark, E.A.

    1992-09-21

    This task evaluated the materials compatibility of LaNi[sub 5-x]Al[sub x] (x= 0.3, 0.75) hydrides and palladium coated kieselguhr with austenitic stainless steel in hydrogen and tritium process environments. Based on observations of retired prototype hydride storage beds and materials exposure testing samples designed for this study, no materials compatibility problem was indicated. Scanning electron microscopy observations of features on stainless steel surfaces after exposure to hydrides are also commonly found on as-received materials before hydriding. These features are caused by either normal heat treating and acid cleaning of stainless steel or reflect the final machining operation.

  2. Materials compatibility of hydride storage materials with austenitic stainless steels

    SciTech Connect

    Clark, E.A.

    1992-09-21

    This task evaluated the materials compatibility of LaNi{sub 5-x}Al{sub x} (x= 0.3, 0.75) hydrides and palladium coated kieselguhr with austenitic stainless steel in hydrogen and tritium process environments. Based on observations of retired prototype hydride storage beds and materials exposure testing samples designed for this study, no materials compatibility problem was indicated. Scanning electron microscopy observations of features on stainless steel surfaces after exposure to hydrides are also commonly found on as-received materials before hydriding. These features are caused by either normal heat treating and acid cleaning of stainless steel or reflect the final machining operation.

  3. Storing hydrogen in the form of light alloy hydrides

    NASA Technical Reports Server (NTRS)

    Freund, E.; Gillerm, C.

    1981-01-01

    Different hydrides are investigated to find a system with a sufficiently high storage density (at least 3%). The formation of hydrides with light alloys is examined. Reaction kinetics for hydride formation were defined and applied to the systems Mg-Al-H, Mg-Al-Cu-H, Ti-Al-H, Ti-Al-Cu-H, and Ti-Al-Ni-H. Results indicate that the addition of Al destabilizes MgH2 and TiH2 hydrides while having only a limited effect on the storage density.

  4. METHOD AND APPARATUS FOR MAKING URANIUM-HYDRIDE COMPACTS

    DOEpatents

    Wellborn, W.; Armstrong, J.R.

    1959-03-10

    A method and apparatus are presented for making compacts of pyrophoric hydrides in a continuous operation out of contact with air. It is particularly useful for the preparation of a canned compact of uranium hydride possessing high density and purity. The metallic uranium is enclosed in a container, positioned in a die body evacuated and nvert the uranium to the hydride is admitted and the container sealed. Heat is applied to bring about the formation of the hydride, following which compression is used to form the compact sealed in a container ready for use.

  5. PA0148 from Pseudomonas aeruginosa Catalyzes the Deamination of Adenine

    SciTech Connect

    Goble, A.M.; Swaminathan, S.; Zhang, Z.; Sauder, J. M.; Burley, S. K.; Raushel, F. M.

    2011-08-02

    Four proteins from NCBI cog1816, previously annotated as adenosine deaminases, have been subjected to structural and functional characterization. Pa0148 (Pseudomonas aeruginosa PAO1), AAur1117 (Arthrobacter aurescens TC1), Sgx9403e, and Sgx9403g have been purified and their substrate profiles determined. Adenosine is not a substrate for any of these enzymes. All of these proteins will deaminate adenine to produce hypoxanthine with k{sub cat}/K{sub m} values that exceed 10{sup 5} M{sup -1} s{sup -1}. These enzymes will also accept 6-chloropurine, 6-methoxypurine, N-6-methyladenine, and 2,6-diaminopurine as alternate substrates. X-ray structures of Pa0148 and AAur1117 have been determined and reveal nearly identical distorted ({beta}/{alpha}){sub 8} barrels with a single zinc ion that is characteristic of members of the amidohydrolase superfamily. Structures of Pa0148 with adenine, 6-chloropurine, and hypoxanthine were also determined, thereby permitting identification of the residues responsible for coordinating the substrate and product.

  6. Pa0148 from Pseudomonas aeruginosa Catalyzes the Deamination of Adenine

    SciTech Connect

    A Goble; Z Zhang; J Sauder; S Burley; S Swaminathan; F Raushel

    2011-12-31

    Four proteins from NCBI cog1816, previously annotated as adenosine deaminases, have been subjected to structural and functional characterization. Pa0148 (Pseudomonas aeruginosa PAO1), AAur1117 (Arthrobacter aurescens TC1), Sgx9403e, and Sgx9403g have been purified and their substrate profiles determined. Adenosine is not a substrate for any of these enzymes. All of these proteins will deaminate adenine to produce hypoxanthine with k{sub cat}/K{sub m} values that exceed 10{sup 5} M{sup -1} s{sup -1}. These enzymes will also accept 6-chloropurine, 6-methoxypurine, N-6-methyladenine, and 2,6-diaminopurine as alternate substrates. X-ray structures of Pa0148 and AAur1117 have been determined and reveal nearly identical distorted ({beta}/{alpha}){sub 8} barrels with a single zinc ion that is characteristic of members of the amidohydrolase superfamily. Structures of Pa0148 with adenine, 6-chloropurine, and hypoxanthine were also determined, thereby permitting identification of the residues responsible for coordinating the substrate and product.

  7. A9145, a New Adenine-Containing Antifungal Antibiotic: Fermentation

    PubMed Central

    Boeck, L. D.; Clem, G. M.; Wilson, M. M.; Westhead, J. E.

    1973-01-01

    A9145 is a basic, water-soluble, antifungal antibiotic which is produced in a complex organic medium by Streptomyces griseolus. The metabolite has a molecular weight of 510, and contains adenine as well as sugar hydroxyl and amino groups. Although glucose, fructose, glucose polymers, and some long-chain fatty acid methyl esters supported biosynthesis, oils were superior, with cottonseed oil being preferred. Several ions and salts, especially Co2+, PO43−, and CaCO3, were stimulatory. Adenine, nucleosides, and some amino acids increased the accumulation of A9145 in shaken-flask fermentors. Enrichment of the culture medium with tyrosine afforded maximal enhancement of antibiotic production in both flask and tank fermentors. Control of the dissolved O2 level was also critical, the optimal concentration being 3 × 10−2 to 4.5 × 10−2 μmole of O2/ml. Optimization of various fermentation parameters increased antibiotic titers approximately 135-fold in shaken flask fermentors and 225-fold in stirred vessels. PMID:4208279

  8. A9145, a new adenine-containing antifungal antibiotic: fermentation.

    PubMed

    Boeck, L D; Clem, G M; Wilson, M M; Westhead, J E

    1973-01-01

    A9145 is a basic, water-soluble, antifungal antibiotic which is produced in a complex organic medium by Streptomyces griseolus. The metabolite has a molecular weight of 510, and contains adenine as well as sugar hydroxyl and amino groups. Although glucose, fructose, glucose polymers, and some long-chain fatty acid methyl esters supported biosynthesis, oils were superior, with cottonseed oil being preferred. Several ions and salts, especially Co(2+), PO(4) (3-), and CaCO(3), were stimulatory. Adenine, nucleosides, and some amino acids increased the accumulation of A9145 in shaken-flask fermentors. Enrichment of the culture medium with tyrosine afforded maximal enhancement of antibiotic production in both flask and tank fermentors. Control of the dissolved O(2) level was also critical, the optimal concentration being 3 x 10(-2) to 4.5 x 10(-2) mumole of O(2)/ml. Optimization of various fermentation parameters increased antibiotic titers approximately 135-fold in shaken flask fermentors and 225-fold in stirred vessels.

  9. On the deactivation mechanisms of adenine-thymine base pair.

    PubMed

    Gobbo, João Paulo; Saurí, Vicenta; Roca-Sanjuán, Daniel; Serrano-Andrés, Luis; Merchán, Manuela; Borin, Antonio Carlos

    2012-04-05

    In this contribution, the multiconfigurational second-order perturbation theory method based on a complete active space reference wave function (CASSCF/CASPT2) is applied to study all possible single and double proton/hydrogen transfers between the nucleobases in the adenine-thymine (AT) base pair, analyzing the role of excited states with different nature [localized (LE) and charge transfer (CT)], and considering concerted as well as step-wise mechanisms. According to the findings, once the lowest excited states, localized in adenine, are populated during UV irradiation of the Watson-Crick base pair, the proton transfer in the N-O bridge does not require high energy in order to populate a CT state. The latter state will immediately relax toward a crossing with the ground state, which will funnel the system to either the canonical structure or the imino-enol tautomer. The base pair is also capable of repairing itself easily since the imino-enol species is unstable to thermal conversion.

  10. Nonselective enrichment for yeast adenine mutants by flow cytometry

    NASA Technical Reports Server (NTRS)

    Bruschi, C. V.; Chuba, P. J.

    1988-01-01

    The expression of certain adenine biosynthetic mutations in the yeast Saccharomyces cerevisiae results in a red colony color. This phenomenon has historically provided an ideal genetic marker for the study of mutation, recombination, and aneuploidy in lower eukaryotes by classical genetic analysis. In this paper, it is reported that cells carrying ade1 and/or ade2 mutations exhibit primary fluorescence. Based on this observation, the nonselective enrichment of yeast cultures for viable adenine mutants by using the fluorescence-activated cell sorter has been achieved. The advantages of this approach over conventional genetic analysis of mutation, recombination, and mitotic chromosomal stability include speed and accuracy in acquiring data for large numbers of clones. By using appropriate strains, the cell sorter has been used for the isolation of both forward mutations and chromosomal loss events in S. cerevisiae. The resolving power of this system and its noninvasiveness can easily be extended to more complex organisms, including mammalian cells, in which analogous metabolic mutants are available.

  11. METAL HYDRIDE HYDROGEN COMPRESSORS: A REVIEW

    SciTech Connect

    Bowman Jr, Robert C; Yartys, Dr. Volodymyr A.; Lototskyy, Dr. Michael V; Pollet, Dr. B.G.

    2014-01-01

    Metal hydride (MH) thermal sorption compression is an efficient and reliable method allowing a conversion of energy from heat into a compressed hydrogen gas. The most important component of such a thermal engine the metal hydride material itself should possess several material features in order to achieve an efficient performance in the hydrogen compression. Apart from the hydrogen storage characteristics important for every solid H storage material (e.g. gravimetric and volumetric efficiency of H storage, hydrogen sorption kinetics and effective thermal conductivity), the thermodynamics of the metal-hydrogen systems is of primary importance resulting in a temperature dependence of the absorption/desorption pressures). Several specific features should be optimized to govern the performance of the MH-compressors including synchronisation of the pressure plateaus for multi-stage compressors, reduction of slope of the isotherms and hysteresis, increase of cycling stability and life time, together with challenges in system design associated with volume expansion of the metal matrix during the hydrogenation. The present review summarises numerous papers and patent literature dealing with MH hydrogen compression technology. The review considers (a) fundamental aspects of materials development with a focus on structure and phase equilibria in the metal-hydrogen systems suitable for the hydrogen compression; and (b) applied aspects, including their consideration from the applied thermodynamic viewpoint, system design features and performances of the metal hydride compressors and major applications.

  12. Plasmonic hydrogen sensing with nanostructured metal hydrides.

    PubMed

    Wadell, Carl; Syrenova, Svetlana; Langhammer, Christoph

    2014-12-23

    In this review, we discuss the evolution of localized surface plasmon resonance and surface plasmon resonance hydrogen sensors based on nanostructured metal hydrides, which has accelerated significantly during the past 5 years. We put particular focus on how, conceptually, plasmonic resonances can be used to study metal-hydrogen interactions at the nanoscale, both at the ensemble and at the single-nanoparticle level. Such efforts are motivated by a fundamental interest in understanding the role of nanosizing on metal hydride formation processes in the quest to develop efficient solid-state hydrogen storage materials with fast response times, reasonable thermodynamics, and acceptable long-term stability. Therefore, a brief introduction to the thermodynamics of metal hydride formation is also given. However, plasmonic hydrogen sensors not only are of academic interest as research tool in materials science but also are predicted to find more practical use as all-optical gas detectors in industrial and medical applications, as well as in a future hydrogen economy, where hydrogen is used as a carbon free energy carrier. Therefore, the wide range of different plasmonic hydrogen sensor designs already available is reviewed together with theoretical efforts to understand their fundamentals and optimize their performance in terms of sensitivity. In this context, we also highlight important challenges to be addressed in the future to take plasmonic hydrogen sensors from the laboratory to real applications in devices, including poisoning/deactivation of the active materials, sensor lifetime, and cross-sensitivity toward other gas species.

  13. Hydride phase formation in carbon supported palladium hydride nanoparticles by in situ EXAFS and XRD

    NASA Astrophysics Data System (ADS)

    Bugaev, A. L.; Guda, A. A.; Lomachenko, K. A.; Lazzarini, A.; Srabionyan, V. V.; Vitillo, J. G.; Piovano, A.; Groppo, E.; Bugaev, L. A.; Soldatov, A. V.; Dmitriev, V. P.; Pellegrini, R.; van Bokhoven, J. A.; Lamberti, C.

    2016-05-01

    In the current work we present a detailed analysis of the hydride phase formation in industrial Pd/C nanocatalysts by means of combined in situ X-ray absorption spectroscopy (EXAFS), X-ray diffraction (XRD) and volumetric measurements for the temperatures from - 10 to 50 °C in the hydrogen pressure range from 0 to 1000 mbar. α- and β- hydride phases are clearly distinguished in XRD. For the first time, H/Pd atomic ratio were obtained by theoretical fitting of the near-edge region of the absorption spectra (XANES) and compared with volumetric measurements.

  14. Adenine attenuates the Ca(2+) contraction-signaling pathway via adenine receptor-mediated signaling in rat vascular smooth muscle cells.

    PubMed

    Fukuda, Toshihiko; Kuroda, Takahiro; Kono, Miki; Hyoguchi, Mai; Tajiri, Satoshi; Tanaka, Mitsuru; Mine, Yoshinori; Matsui, Toshiro

    2016-09-01

    Our previous study demonstrated that adenine (6-amino-6H-purine) relaxed contracted rat aorta rings in an endothelial-independent manner. Although adenine receptors (AdeRs) are expressed in diverse tissues, aortic AdeR expression has not been ascertained. Thus, the aims of this study were to clarify the expression of AdeR in rat vascular smooth muscle cells (VSMCs) and to investigate the adenine-induced vasorelaxation mechanism(s). VSMCs were isolated from 8-week-old male Wistar-Kyoto rats and used in this study. Phosphorylation of myosin light chain (p-MLC) was measured by western blot. AdeR mRNA was detected by RT-PCR. Intracellular Ca(2+) concentration ([Ca(2+)]i) was measured by using Fura-2/AM. Vasorelaxant adenine (10-100 μM) significantly reduced p-MLC by angiotensin II (Ang II, 10 μM) in VSMCs (P < 0.05). We confirmed the expression of aortic AdeR mRNA and the activation of PKA in VSMCs through stimulation of AdeR by adenine by ELISA. Intracellular Ca(2+) concentration ([Ca(2+)]i) measurement demonstrated that adenine inhibits Ang II- and m-3M3FBS (PLC agonist)-induced [Ca(2+)]i elevation. In AdeR-knockdown VSMCs, PKA activation and p-MLC reduction by adenine were completely abolished. These results firstly demonstrated that vasorelaxant adenine can suppress Ca(2+) contraction signaling pathways via aortic AdeR/PKA activation in VSMCs.

  15. Renoprotective effects of aliskiren on adenine-induced tubulointerstitial nephropathy: possible underlying mechanisms.

    PubMed

    Hussein, Abdelaziz M; Malek, Hala Abdel; Saad, Mohamed-Ahdy

    2016-08-01

    The present study investigated the possible renoprotective effect of direct renin inhibitor (aliskiren) on renal dysfunctions, as well as its underlying mechanisms in rat model of adenine-induced tubulointerstitial nephropathy. Forty male Sprague-Dawley rats were randomized into 4 groups; normal group, aliskiren group (normal rats received 10 mg/kg aliskiren), adenine group (animals received high-adenine diet for 4 weeks and saline for 12 weeks), and adenine + aliskiren group (animals received adenine for 4 weeks and aliskiren 10 mg/kg for 12 weeks). It was found that adenine caused significant decrease in body mass, Hb, HR, serum Ca(2+), eNOS and nrf2 expression, GSH, and catalase in kidney tissues with significant increase in arterial blood pressure (ABP), serum creatinine, BUN, plasma renin activity (PRA), K(+) and P, urinary albumin excretion (UAE), caspase-3, and MDA (lipid peroxidation marker) in kidney tissues compared to normal group (p < 0.05). Administration of aliskiren caused significant improvement in all studied parameters compared to adenine group (p < 0.05). We concluded that aliskiren has renoprotective effect against adenine-induced nephropathy. This might be due to inhibition of PRA, attenuation of oxidative stress, activation of Nrf2 and eNOS genes, and suppression of caspase-3.

  16. Major and minor groove conformations of DNA trimers modified on guanine or adenine by 4-aminobiphenyl: Adenine adducts favor the minor groove

    SciTech Connect

    Shapiro, R.; Ellis, S.; Hingerty, B.E.

    1995-01-01

    We have studied the conformational effects of 4-aminobiphenyl modification at C-8 of guanine or adenine on double-stranded DNA trimers. We used sequences with the modified purine at the central base pair and all 16 possible neighboring sequences at the outer pairs. Minimized potential energy calculations were carried out using the molecular mechanics program DUPLEX to survey the conformation space of these adducts, using a total of 1280 starting structures both in the modified guanine series and in the modified adenine series. Conformer families in which the bound 4-aminobiphenyl was located in the DNA major groove, and in the minor groove, were located for both adenine and guanine modification. In the modified guanine series, the major and minor groove families were roughly comparable in energy, and the sequence context determined which was more stable in a particular case. In the modified adenine series, however, the minor groove structure was more that 10 kcal/mol more stable than the major groove for all sequences. As a result, minor groove adducts provided most of the global minima in the adenine-modified series. This result may be relevant to a previous mutagenesis study [Lasko et al. (1988) J. Biol. Chem. 263, 15429-15435] in which the hot spot of most frequent occurrence was located at an adenine, in the sequence GAT. 25 refs., 9 figs., 4 tabs.

  17. Single nucleotide polymorphisms of human STING can affect innate immune response to cyclic dinucleotides.

    PubMed

    Yi, Guanghui; Brendel, Volker P; Shu, Chang; Li, Pingwei; Palanathan, Satheesh; Cheng Kao, C

    2013-01-01

    The STING (stimulator of interferon genes) protein can bind cyclic dinucleotides to activate the production of type I interferons and inflammatory cytokines. The cyclic dinucleotides can be bacterial second messengers c-di-GMP and c-di-AMP, 3'5'-3'5' cyclic GMP-AMP (3'3' cGAMP) produced by Vibrio cholerae and metazoan second messenger 2'5'-3'5' Cyclic GMP-AMP (2'3' cGAMP). Analysis of single nucleotide polymorphism (SNP) data from the 1000 Genome Project revealed that R71H-G230A-R293Q (HAQ) occurs in 20.4%, R232H in 13.7%, G230A-R293Q (AQ) in 5.2%, and R293Q in 1.5% of human population. In the absence of exogenous ligands, the R232H, R293Q and AQ SNPs had only modest effect on the stimulation of IFN-β and NF-κB promoter activities in HEK293T cells, while HAQ had significantly lower intrinsic activity. The decrease was primarily due to the R71H substitution. The SNPs also affected the response to the cyclic dinucleotides. In the presence of c-di-GMP, the R232H variant partially decreased the ability to activate IFN-βsignaling, while it was defective for the response to c-di-AMP and 3'3' cGAMP. The R293Q dramatically decreased the stimulatory response to all bacterial ligands. Surprisingly, the AQ and HAQ variants maintained partial abilities to activate the IFN-β signaling in the presence of ligands due primarily to the G230A substitution. Biochemical analysis revealed that the recombinant G230A protein could affect the conformation of the C-terminal domain of STING and the binding to c-di-GMP. Comparison of G230A structure with that of WT revealed that the conformation of the lid region that clamps onto the c-di-GMP was significantly altered. These results suggest that hSTING variation can affect innate immune signaling and that the common HAQ haplotype expresses a STING protein with reduced intrinsic signaling activity but retained the ability to response to bacterial cyclic dinucleotides.

  18. Vectorette PCR isolation of microsatellite repeat sequences using anchored dinucleotide repeat primers.

    PubMed Central

    Lench, N J; Norris, A; Bailey, A; Booth, A; Markham, A F

    1996-01-01

    We have developed a vectorette PCR approach to provide an improved method for isolation of microsatellite repeats. The modified procedure relies on PCR amplification using a vectorette-specific primer in combination with one of a panel of anchored dinucleotide repeat primers. The target DNA to be screened for microsatellite sequences can be from YAC, P1, cosmid, bacteriophage or plasmid clones. We have used this technique to isolate novel, polymorphic microsatellite repeats from clones containing the amelogenin gene (AMGX) located on human chromosome Xp22.3. PMID:8668553

  19. Interaction of sulfanilamide and sulfamethoxazole with bovine serum albumin and adenine: Spectroscopic and molecular docking investigations

    NASA Astrophysics Data System (ADS)

    Rajendiran, N.; Thulasidhasan, J.

    2015-06-01

    Interaction between sulfanilamide (SAM) and sulfamethoxazole (SMO) with BSA and DNA base (adenine) was investigated by UV-visible, fluorescence, cyclic voltammetry and molecular docking studies. Stern-Volmer fluorescence quenching constant (Ka) suggests SMO is more quenched with BSA/adenine than that of SAM. The distance r between donor (BSA/adenine) and acceptor (SAM and SMO) was obtained according to fluorescence resonance energy transfer (FRET). The results showed that hydrophobic forces, electrostatic interactions, and hydrogen bonds played vital roles in the SAM and SMO with BSA/adenine binding interaction. During the interaction, sulfa drugs could insert into the hydrophobic pocket, where the non-radioactive energy transfer from BSA/adenine to sulfa drugs occurred with high possibility. Cyclic voltammetry results suggested that when the drug concentration is increased, the anodic electrode potential deceased. The docking method indicates aniline group is interacted with the BSA molecules.

  20. Electrochemical characterization of redox polymer modified electrode developed for monitoring of adenine.

    PubMed

    Kuralay, Filiz; Erdem, Arzum; Abacı, Serdar; Ozyörük, Haluk

    2013-05-01

    Electrochemical characterization of redox polymer for monitoring of adenine was described in this study using poly(vinylferrocenium) (PVF(+)) modified platinum (Pt) electrode. Scanning electron microscope (SEM) was used for the surface characterization. The electrochemical behaviors of polymer modified and adenine immobilized polymer modified electrodes were investigated by using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). In order to obtain more sensitive and improved electrochemical signals, analytical parameters such as the effects of polymeric film thickness, immobilization time of adenine, pH and adenine concentration were examined on the response of the polymer modified electrode. Alternating current (AC) impedance spectroscopy was used for the characterization of polymer modified and adenine immobilized polymer modified electrodes. The effect of possible interferents on the response of the electrode was examined.

  1. Interaction of sulfanilamide and sulfamethoxazole with bovine serum albumin and adenine: spectroscopic and molecular docking investigations.

    PubMed

    Rajendiran, N; Thulasidhasan, J

    2015-06-05

    Interaction between sulfanilamide (SAM) and sulfamethoxazole (SMO) with BSA and DNA base (adenine) was investigated by UV-visible, fluorescence, cyclic voltammetry and molecular docking studies. Stern-Volmer fluorescence quenching constant (Ka) suggests SMO is more quenched with BSA/adenine than that of SAM. The distance r between donor (BSA/adenine) and acceptor (SAM and SMO) was obtained according to fluorescence resonance energy transfer (FRET). The results showed that hydrophobic forces, electrostatic interactions, and hydrogen bonds played vital roles in the SAM and SMO with BSA/adenine binding interaction. During the interaction, sulfa drugs could insert into the hydrophobic pocket, where the non-radioactive energy transfer from BSA/adenine to sulfa drugs occurred with high possibility. Cyclic voltammetry results suggested that when the drug concentration is increased, the anodic electrode potential deceased. The docking method indicates aniline group is interacted with the BSA molecules.

  2. Metal Hydrides for High-Temperature Power Generation

    DOE PAGES

    Ronnebro, Ewa; Whyatt, Greg A.; Powell, Michael R.; ...

    2015-08-10

    Metal hydrides can be utilized for hydrogen storage and for thermal energy storage (TES) applications. By using TES with solar technologies, heat can be stored from sun energy to be used later which enables continuous power generation. We are developing a TES technology based on a dual-bed metal hydride system, which has a high-temperature (HT) metal hydride operating reversibly at 600-800°C to generate heat as well as a low-temperature (LT) hydride near room temperature that is used for hydrogen storage during sun hours until there is a need to produce electricity, such as during night time, a cloudy day, ormore » during peak hours. We proceeded from selecting a high-energy density, low-cost HT-hydride based on performance characterization on gram size samples, to scale-up to kilogram quantities and design, fabrication and testing of a 1.5kWh, 200kWh/m3 bench-scale TES prototype based on a HT-bed of titanium hydride and a hydrogen gas storage instead of a LT-hydride. COMSOL Multiphysics was used to make performance predictions for cylindrical hydride beds with varying diameters and thermal conductivities. Based on experimental and modeling results, a bench-scale prototype was designed and fabricated and we successfully showed feasibility to meet or exceed all performance targets.« less

  3. Metal-hydride energy-technological processing of hydrogen

    NASA Astrophysics Data System (ADS)

    Solovei, V. V.

    1983-03-01

    The external and internal irreversibility of the thermochemical hydrogen compression cycle is analyzed in relation to the efficiency of heat utilization in a metal-hydride energy system. The properties of the working fluid and the design of the metal-hydride elements are shown to have a considerable effect on the thermodynamic performance of a heat-utilizing installation for hydrogen processing.

  4. Hydrogen storage in the form of metal hydrides

    NASA Technical Reports Server (NTRS)

    Zwanziger, M. G.; Santana, C. C.; Santos, S. C.

    1984-01-01

    Reversible reactions between hydrogen and such materials as iron/titanium and magnesium/ nickel alloy may provide a means for storing hydrogen fuel. A demonstration model of an iron/titanium hydride storage bed is described. Hydrogen from the hydride storage bed powers a converted gasoline electric generator.

  5. Method of making crack-free zirconium hydride

    DOEpatents

    Sullivan, Richard W.

    1980-01-01

    Crack-free hydrides of zirconium and zirconium-uranium alloys are produced by alloying the zirconium or zirconium-uranium alloy with beryllium, or nickel, or beryllium and scandium, or nickel and scandium, or beryllium and nickel, or beryllium, nickel and scandium and thereafter hydriding.

  6. Metal Hydrides for High-Temperature Power Generation

    SciTech Connect

    Ronnebro, Ewa; Whyatt, Greg A.; Powell, Michael R.; Westman, Matthew P.; Zheng, Feng; Fang, Zhigang Zak

    2015-08-10

    Metal hydrides can be utilized for hydrogen storage and for thermal energy storage (TES) applications. By using TES with solar technologies, heat can be stored from sun energy to be used later which enables continuous power generation. We are developing a TES technology based on a dual-bed metal hydride system, which has a high-temperature (HT) metal hydride operating reversibly at 600-800°C to generate heat as well as a low-temperature (LT) hydride near room temperature that is used for hydrogen storage during sun hours until there is a need to produce electricity, such as during night time, a cloudy day, or during peak hours. We proceeded from selecting a high-energy density, low-cost HT-hydride based on performance characterization on gram size samples, to scale-up to kilogram quantities and design, fabrication and testing of a 1.5kWh, 200kWh/m3 bench-scale TES prototype based on a HT-bed of titanium hydride and a hydrogen gas storage instead of a LT-hydride. COMSOL Multiphysics was used to make performance predictions for cylindrical hydride beds with varying diameters and thermal conductivities. Based on experimental and modeling results, a bench-scale prototype was designed and fabricated and we successfully showed feasibility to meet or exceed all performance targets.

  7. High energy density battery based on complex hydrides

    DOEpatents

    Zidan, Ragaiy

    2016-04-26

    A battery and process of operating a battery system is provided using high hydrogen capacity complex hydrides in an organic non-aqueous solvent that allows the transport of hydride ions such as AlH.sub.4.sup.- and metal ions during respective discharging and charging steps.

  8. Gender differences in adenine-induced chronic kidney disease and cardiovascular complications in rats.

    PubMed

    Diwan, Vishal; Small, David; Kauter, Kate; Gobe, Glenda C; Brown, Lindsay

    2014-12-01

    Gender contributes to differences in incidence and progression of chronic kidney disease (CKD) and associated cardiovascular disease. To induce kidney damage in male and female Wistar rats (n = 12/group), a 0.25% adenine diet for 16 wk was used. Kidney function (blood urea nitrogen, plasma creatinine, proteinuria) and structure (glomerular damage, tubulointerstitial atrophy, fibrosis, inflammation); cardiovascular function (blood pressure, ventricular stiffness, vascular responses, echocardiography) and structure (cardiac fibrosis); plasma testosterone and estrogen concentrations; and protein expression for oxidative stress [heme oxygenase-1, inflammation (TNF-α), fibrosis (transforming growth factor-β), ERK1/2, and estrogen receptor-α (ER-α)] were compared in males and females. Adenine-fed females had less decline in kidney function than adenine-fed males, although kidney atrophy, inflammation, and fibrosis were similar. Plasma estrogen concentrations increased and plasma testosterone concentrations decreased in adenine-fed males, with smaller changes in females. CKD-associated molecular changes in kidneys were more pronounced in males than females except for expression of ER-α in the kidney, which was completely suppressed in adenine-fed males but unchanged in adenine-fed females. Both genders showed increased blood pressure, ventricular stiffness, and cardiac fibrosis with the adenine diet. Cardiovascular changes with adenine were similar in males and females, except males developed concentric, and females eccentric cardiac hypertrophy. In hearts from adenine-fed male and female rats, expression of ER-α and activation of the ERK1/2 pathway were increased, in part explaining changes in cardiac hypertrophy. In summary, adenine-induced kidney damage may be increased in males due to the suppression of ER-α.

  9. Hydride morphology and striation formation during delayed hydride cracking in Zr-2.5% Nb

    NASA Astrophysics Data System (ADS)

    Shek, G. K.; Jovanoviċ, M. T.; Seahra, H.; Ma, Y.; Li, D.; Eadie, R. L.

    1996-08-01

    These experiments were designed to study hydride formation at the crack tip, acoustic emission (AE), potential drop (PD) and striation formation during DHC (delayed hydride cracking) in Zr-2.5% Nb. The test material was taken from an especially extrude pressure tube, which showed similar strength properties to normal pressure tube material but somewhat coarser microstructure. In testing at KI below 12 MPa √m at both 200 and 250°C very large striations (> 40 μ at 200 and >50 μm at 250°C) were produced. In simultaneous monitoring with acoustic emission and potential drop, both AE and PD jumps were shown to be monolithic. The number of striations on the fracture surface corresponded to the number of monolithic AE/PD jumps. Tapered shaped hydrides with the thick end adjacent to the crack tip were observed. These hydrides grew in size during the incubation period until they reached the striation length and then fractured monolithically. However, when KI was increased beyond about 12 MPa √m for these same specimens, the striation spacing decreased below 30 μ, the monolithic jumping dissolved into more continuous changes in signals, although the smaller striations were still visible on the fracture surface.

  10. ORNL Interim Progress Report on Hydride Reorientation CIRFT Tests

    SciTech Connect

    Wang, Jy-An John; Yan, Yong; Wang, Hong

    2016-10-28

    A systematic study of H. B. Robinson (HBR) high burnup spent nuclear fuel (SNF) vibration integrity was performed in Phase I project under simulated transportation environments, using the Cyclic Integrated Reversible-Bending Fatigue Tester (CIRFT) hot cell testing technology developed at Oak Ridge National Laboratory in 2013–14. The data analysis on the as-irradiated HBR SNF rods demonstrated that the load amplitude is the dominant factor that controls the fatigue life of bending rods. However, previous studies have shown that the hydrogen content and hydride morphology has an important effect on zirconium alloy mechanical properties. To address the effect of radial hydrides in SNF rods, in Phase II a test procedure was developed to simulate the effects of elevated temperatures, pressures, and stresses during transfer-drying operations. Pressurized and sealed fuel segments were heated to the target temperature for a preset hold time and slow-cooled at a controlled rate. The procedure was applied to both non-irradiated/prehydrided and high-burnup Zircaloy-4 fueled cladding segments using the Nuclear Regulatory Commission-recommended 400°C maximum temperature limit at various cooling rates. Before testing high-burnup cladding, four out-of-cell tests were conducted to optimize the hydride reorientation (R) test condition with pre-hydride Zircaloy-4 cladding, which has the same geometry as the high burnup fuel samples. Test HR-HBR#1 was conducted at the maximum hoop stress of 145 MPa, at a 400°C maximum temperature and a 5°C/h cooling rate. On the other hand, thermal cycling was performed for tests HR-HBR#2, HR-HBR#3, and HR-HBR#4 to generate more radial hydrides. It is clear that thermal cycling increases the ratio of the radial hydride to circumferential hydrides. The internal pressure also has a significant effect on the radial hydride morphology. This report describes a procedure and experimental results of the four out-of-cell hydride reorientation tests of

  11. Ultraviolet absorption and luminescence of matrix-isolated adenine

    SciTech Connect

    Polewski, K.; Sutherland, J.; Zinger, D.; Trunk, J.

    2011-10-01

    We have investigated the absorption, the fluorescence and phosphorescence emission and the fluorescence lifetimes of adenine in low-temperature argon and nitrogen matrices at 15 K. Compared to other environments the absorption spectrum shows higher intensity at the shortest wavelengths, and a weak apparent absorption peak is observed at 280 nm. The resolved fluorescence excitation spectrum has five peaks at positions corresponding to those observed in the absorption spectrum. The position of the fluorescence maximum depends on the excitation wavelength. Excitation below 220 nm displays a fluorescence maximum at 305 nm, while for excitations at higher wavelengths the maximum occurs at 335 nm. The results suggest that multiple-emission excited electronic states are populated in low-temperature gas matrices. Excitation at 265 nm produces a phosphorescence spectrum with a well-resolved vibrational structure and a maximum at 415 nm. The fluorescence decays corresponding to excitation at increasing energy of each resolved band could be fit with a double exponential, with the shorter and longer lifetimes ranging from 1.7 to 3.3 ns and from 12 to 23 ns, respectively. Only for the excitation at 180 nm one exponential is required, with the calculated lifetimes of 3.3 ns. The presented results provide an experimental evidence of the existence of multiple site-selected excited electronic states, and may help elucidate the possible deexcitation pathways of adenine. The additional application of synchrotron radiation proved to result in a significant enhancement of the resolution and spectral range of the phenomena under investigation.

  12. A novel plating process for microencapsulating metal hydrides

    SciTech Connect

    Law, H.H.; Vyas, B.; Zahurak, S.M.; Kammlott, G.W.

    1996-08-01

    One approach to increasing the lifetime of the metal hydride electrode has been the use of conventional electroless plating to produce a coating of copper or nickel on the surface of the metal hydride powders. In this paper, a novel method for microencapsulating the active electrode powders is presented. This new plating technique takes advantage of the reducing power of hydrogen already stored inside the metal hydride to plate a variety of metals onto metal hydride materials. This method greatly simplifies electroless plating for these powders, eliminating the need for stabilizers and additives typically required for conventional electroless plating solutions. Metals that can be electrolessly plated with stored hydrogen have been identified based on thermodynamic considerations. Experimentally, micrometers thick coatings of copper, silver, and nickel have been plated on several metal hydrides.

  13. Porous metal hydride composite and preparation and uses thereof

    DOEpatents

    Steyert, William A.; Olsen, Clayton E.

    1982-01-01

    A composite formed from large pieces of aggregate formed from (1) metal hydride (or hydride-former) powder and (2) either metal powder or plastic powder or both is prepared. The composite has large macroscopic interconnected pores (much larger than the sizes of the powders which are used) and will have a very fast heat transfer rate and low windage loss. It will be useful, for example, in heat engines, hydrogen storage devices, and refrigerator components which depend for their utility upon both a fast rate of hydriding and dehydriding. Additionally, a method of preparing the composite and a method of increasing the rates of hydriding and dehydriding of metal hydrides are also given.

  14. Porous metal hydride composite and preparation and uses thereof

    DOEpatents

    Steyert, W.A.; Olsen, C.E.

    1980-03-12

    A composite formed from large pieces of aggregate formed from (1) metal hydride (or hydride-former) powder and (2) either metal powder or plastic powder or both is prepared. The composite has large macroscopic interconnected pores (much larger than the sizes of the powders which are used) and will have a very fast heat transfer rate and low windage loss. It will be useful, for example, in heat engines, hydrogen storage devices, and refrigerator components which depend for their utility upon both a fast rate of hydriding and dehydriding. Additionally, a method of preparing the composite and a method of increasing the rates of hydriding and dehydriding of metal hydrides are also given.

  15. Metal hydrides for concentrating solar thermal power energy storage

    NASA Astrophysics Data System (ADS)

    Sheppard, D. A.; Paskevicius, M.; Humphries, T. D.; Felderhoff, M.; Capurso, G.; Bellosta von Colbe, J.; Dornheim, M.; Klassen, T.; Ward, P. A.; Teprovich, J. A.; Corgnale, C.; Zidan, R.; Grant, D. M.; Buckley, C. E.

    2016-04-01

    The development of alternative methods for thermal energy storage is important for improving the efficiency and decreasing the cost of concentrating solar thermal power. We focus on the underlying technology that allows metal hydrides to function as thermal energy storage (TES) systems and highlight the current state-of-the-art materials that can operate at temperatures as low as room temperature and as high as 1100 °C. The potential of metal hydrides for thermal storage is explored, while current knowledge gaps about hydride properties, such as hydride thermodynamics, intrinsic kinetics and cyclic stability, are identified. The engineering challenges associated with utilising metal hydrides for high-temperature TES are also addressed.

  16. Recent advances in metal hydrides for clean energy applications

    SciTech Connect

    Ronnebro, Ewa; Majzoub, Eric H.

    2013-06-01

    Metal hydrides are a fascinating class of materials that can be utilized for a surprising variety of clean energy applications, including smart solar collectors, smart windows, sensors, thermal energy storage, and batteries, in addition to their traditional application for hydrogen storage. Over the past decade, research on metal hydrides for hydrogen storage increased due to global governmental incentives and an increased focus on hydrogen storage research for polymer electrolyte membrane fuel cell operation. Tremendous progress has been made in so-called complex metal hydrides for hydrogen storage applications with the discovery of many new hydrides containing covalently bound complex anions. Many of these materials have applications beyond hydrogen storage and are being investigated for lithium-ion battery separator and anode materials. In this issue of MRS Bulletin , we present the state of the art of key evolving metal-hydride-based clean energy technologies with an outlook toward future needs.

  17. Helium trapping at erbium oxide precipitates in erbium hydride

    SciTech Connect

    Foiles, Stephen M.; Battaile, Corbett Chandler

    2016-02-01

    The formation of He bubbles in erbium tritides is a significant process in the aging of these materials. Due to the long-standing uncertainty about the initial nucleation process of these bubbles, there is interest in mechanisms that can lead to the localization of He in erbium hydrides. Previous work has been unable to identify nucleation sites in homogeneous erbium hydride. This work builds on the experimental observation that erbium hydrides have nano- scale erbium oxide precipitates due to the high thermodynamic stability of erbium oxide and the ubiquitous presence of oxygen during materials processing. Fundamental DFT calculations indicate that the He is energetically favored in the oxide relative to the bulk hydride. Activation energies for the motion of He in the oxide and at the oxide-hydride interface indicate that trapping is kinetically feasible. A simple kinetic Monte Carlo model is developed that demonstrates the degree of trapping of He as a function of temperature and oxide fraction.

  18. Evolutionary mechanism and biological functions of 8-mers containing CG dinucleotide in yeast.

    PubMed

    Zheng, Yan; Li, Hong; Wang, Yue; Meng, Hu; Zhang, Qiang; Zhao, Xiaoqing

    2017-02-09

    The rules of k-mer non-random usage and the biological functions are worthy of special attention. Firstly, the article studied human 8-mer spectra and found that only the spectra of cytosine-guanine (CG) dinucleotide classification formed independent unimodal distributions when the 8-mers were classified into three subsets under 16 dinucleotide classifications. Secondly, the distribution rules were reproduced by other seven species including yeast, which showed that the evolution phenomenon had species universality. It followed that we proposed two theoretical conjectures: (1) CG1 motifs (8-mers including 1 CG) are the nucleosome-binding motifs. (2) CG2 motifs (8-mers including two or more than two CG) are the modular units of CpG islands. Our conjectures were confirmed in yeast by the following results: a maximum of average area under the receiver operating characteristic (AUC) resulted from CG1 information during nucleosome core sequences, and linker sequences were distinguished by three CG subsets; there was a one-to-one relationship between abundant CG1 signal regions and histone positions; the sequence changing of squeezed nucleosomes was relevant with the strength of CG1 signals; and the AUC value of 0.986 was based on CG2 information when CpG islands and non-CpG islands were distinguished by the three CG subsets.

  19. CG dinucleotide clustering is a species-specific property of the genome.

    PubMed

    Glass, Jacob L; Thompson, Reid F; Khulan, Batbayar; Figueroa, Maria E; Olivier, Emmanuel N; Oakley, Erin J; Van Zant, Gary; Bouhassira, Eric E; Melnick, Ari; Golden, Aaron; Fazzari, Melissa J; Greally, John M

    2007-01-01

    Cytosines at cytosine-guanine (CG) dinucleotides are the near-exclusive target of DNA methyltransferases in mammalian genomes. Spontaneous deamination of methylcytosine to thymine makes methylated cytosines unusually susceptible to mutation and consequent depletion. The loci where CG dinucleotides remain relatively enriched, presumably due to their unmethylated status during the germ cell cycle, have been referred to as CpG islands. Currently, CpG islands are solely defined by base compositional criteria, allowing annotation of any sequenced genome. Using a novel bioinformatic approach, we show that CG clusters can be identified as an inherent property of genomic sequence without imposing a base compositional a priori assumption. We also show that the CG clusters co-localize in the human genome with hypomethylated loci and annotated transcription start sites to a greater extent than annotations produced by prior CpG island definitions. Moreover, this new approach allows CG clusters to be identified in a species-specific manner, revealing a degree of orthologous conservation that is not revealed by current base compositional approaches. Finally, our approach is able to identify methylating genomes (such as Takifugu rubripes) that lack CG clustering entirely, in which it is inappropriate to annotate CpG islands or CG clusters.

  20. Identification of a Soybean Protein That Interacts with GAGA Element Dinucleotide Repeat DNA1

    PubMed Central

    Sangwan, Indu; O'Brian, Mark R.

    2002-01-01

    Dinucleotide repeat DNA with the pattern (GA)n/(TC)n, so-called GAGA elements, control gene expression in animals, and are recognized by a specific regulatory protein. Here, a yeast one-hybrid screen was used to isolate soybean (Glycine max) cDNA encoding a GAGA-binding protein (GBP) that binds to (GA)n/(CT)n DNA. Soybean GBP was dissimilar from the GAGA factor of Drosophila melanogaster. Recombinant GBP protein did not bind to dinucleotide repeat sequences other than (GA)n/(CT)n. GBP bound to the promoter of the heme and chlorophyll synthesis gene Gsa1, which contains a GAGA element. Removal of that GAGA element abrogated binding of GBP to the promoter. Furthermore, insertion of the GAGA element to a nonspecific DNA conferred GBP-binding activity on that DNA. Thus, the GAGA element of the Gsa1 promoter is both necessary and sufficient for GBP binding. Gbp mRNA was expressed in leaves and was induced in symbiotic root nodules elicited by the bacterium Bradyrhizobium japonicum. In addition, Gbp transcripts were much higher in leaves of dark-treated etiolated plantlets than in those exposed to light for 24 h. Homologs of GBP were found in other dicots and in the monocot rice (Oryza sativa), as well. We suggest that interaction between GAGA elements and GBP-like proteins is a regulatory feature in plants. PMID:12177492

  1. The tungsten formylmethanofuran dehydrogenase from Methanobacterium thermoautotrophicum contains sequence motifs characteristic for enzymes containing molybdopterin dinucleotide.

    PubMed

    Hochheimer, A; Schmitz, R A; Thauer, R K; Hedderich, R

    1995-12-15

    Formylmethanofuran dehydrogenases are molybdenum or tungsten iron-sulfur proteins containing a pterin dinucleotide cofactor. We report here on the primary structures of the four subunits FwdABCD of the tungsten enzyme from Methanobacterium thermoautotrophicum which were determined by cloning and sequencing the encoding genes fwdABCD. FwdB was found to contain sequence motifs characteristic for molybdopterin-dinucleotide-containing enzymes indicating that this subunit harbors the active site. FwdA, FwdC and FwdD showed no significant sequence similarity to proteins in the data bases. Northern blot analysis revealed that the four fwd genes form a transcription unit together with three additional genes designated fwdE, fwdF and fwdG. A 17.8-kDa protein and an 8.6-kDa protein, both containing two [4Fe-4S] cluster binding motifs, were deduced from fwdE and fwdG. The open reading frame fwdF encodes a 38.6-kDa protein containing eight binding motifs for [4Fe-4S] clusters suggesting the gene product to be a novel polyferredoxin. All seven fwd genes were expressed in Escherichia coli yielding proteins of the expected size. The fwd operon was found to be located in a region of the M. thermoautotrophicum genome encoding molybdenum enzymes and proteins involved in molybdopterin biosynthesis.

  2. Base-boronated dinucleotides: synthesis and effect of N7-cyanoborane substitution on the base protons.

    PubMed Central

    Hasan, A; Li, H; Tomasz, J; Shaw, B R

    1996-01-01

    Boron-modified nucleic acids comprise a new set of DNA mimics that have potential biological and therapeutic applications. A series of nine dinucleotides containing N7-cyanoborane-2'-deoxyguanosine ((7b)dG) at the 3', 5' or both positions of the phosphodiester linkage have been synthesized using solution phase phosphoramidite chemistry. Fmoc was used as the 5'-protecting group because of incompatibility of the cyanoborane moiety with 5'-DMT cations generated during the deprotection step. The presence of the cyanoborane group was confirmed on the basis of Fab-MS and 1H NMR spectroscopy. The H-8 proton of (7b)dG in the dinucleotides shifted 0.35-0.80 p.p.m. downfield relative to that of unmodified dG. A comparison of the D20 exchange kinetics of the H-8 proton at 60 degrees C showed that H-8 of (7b)dG is very labile relative to unmodified dG, indicating that the N7-cyanoborane modification increases the acidity of the H-8 proton of (7b)dG. These studies illustrate the feasibility of synthesizing boron-containing oligonucleotides which are modified at the N7-guanine to block Hoogsteen pairing in the DNA major groove. PMID:8668548

  3. Structure-guided reprogramming of human cGAS dinucleotide linkage specificity.

    PubMed

    Kranzusch, Philip J; Lee, Amy S Y; Wilson, Stephen C; Solovykh, Mikhail S; Vance, Russell E; Berger, James M; Doudna, Jennifer A

    2014-08-28

    Cyclic dinucleotides (CDNs) play central roles in bacterial pathogenesis and innate immunity. The mammalian enzyme cGAS synthesizes a unique cyclic dinucleotide (cGAMP) containing a 2'-5' phosphodiester linkage essential for optimal immune stimulation, but the molecular basis for linkage specificity is unknown. Here, we show that the Vibrio cholerae pathogenicity factor DncV is a prokaryotic cGAS-like enzyme whose activity provides a mechanistic rationale for the unique ability of cGAS to produce 2'-5' cGAMP. Three high-resolution crystal structures show that DncV and human cGAS generate CDNs in sequential reactions that proceed in opposing directions. We explain 2' and 3' linkage specificity and test this model by reprogramming the human cGAS active site to produce 3'-5' cGAMP, leading to selective stimulation of alternative STING adaptor alleles in cells. These results demonstrate mechanistic homology between bacterial signaling and mammalian innate immunity and explain how active site configuration controls linkage chemistry for pathway-specific signaling.

  4. Results of NDE Technique Evaluation of Clad Hydrides

    SciTech Connect

    Kunerth, Dennis C.

    2014-09-01

    This report fulfills the M4 milestone, M4FT-14IN0805023, Results of NDE Technique Evaluation of Clad Hydrides, under Work Package Number FT-14IN080502. During service, zirconium alloy fuel cladding will degrade via corrosion/oxidation. Hydrogen, a byproduct of the oxidation process, will be absorbed into the cladding and eventually form hydrides due to low hydrogen solubility limits. The hydride phase is detrimental to the mechanical properties of the cladding and therefore it is important to be able to detect and characterize the presence of this constituent within the cladding. Presently, hydrides are evaluated using destructive examination. If nondestructive evaluation techniques can be used to detect and characterize the hydrides, the potential exists to significantly increase test sample coverage while reducing evaluation time and cost. To demonstrate the viability this approach, an initial evaluation of eddy current and ultrasonic techniques were performed to demonstrate the basic ability to these techniques to detect hydrides or their effects on the microstructure. Conventional continuous wave eddy current techniques were applied to zirconium based cladding test samples thermally processed with hydrogen gas to promote the absorption of hydrogen and subsequent formation of hydrides. The results of the evaluation demonstrate that eddy current inspection approaches have the potential to detect both the physical damage induced by hydrides, e.g. blisters and cracking, as well as the combined effects of absorbed hydrogen and hydride precipitates on the electrical properties of the zirconium alloy. Similarly, measurements of ultrasonic wave velocities indicate changes in the elastic properties resulting from the combined effects of absorbed hydrogen and hydride precipitates as well as changes in geometry in regions of severe degradation. However, for both approaches, the signal responses intended to make the desired measurement incorporate a number of contributing

  5. Highly Concentrated Palladium Hydrides/Deuterides; Theory

    SciTech Connect

    Papaconstantopoulos, Dimitrios

    2013-11-26

    Accomplishments are reported in these areas: tight-binding molecular dynamics study of palladium; First-principles calculations and tight-binding molecular dynamics simulations of the palladium-hydrogen system; tight-binding studies of bulk properties and hydrogen vacancies in KBH{sub 4}; tight-binding study of boron structures; development of angular dependent potentials for Pd-H; and density functional and tight-binding calculations for the light-hydrides NaAlH4 and NaBH4

  6. Lithium hydride - A space age shielding material

    NASA Technical Reports Server (NTRS)

    Welch, F. H.

    1974-01-01

    Men and materials performing in the environment of an operating nuclear reactor require shielding from the escaping neutron particles and gamma rays. For efficient shielding from gamma rays, dense, high atomic number elements such as iron, lead, or tungsten are required, whereas light, low atomic number elements such as hydrogen, lithium, or beryllium are required for efficient neutron shielding. The use of lithium hydride (LiH) as a highly efficient neutron-shielding material is considered. It contains, combined into a single, stable compound, two of the elements most effective in attenuating and absorbing neutrons.

  7. Metal hydride fuel storage and method thereof

    DOEpatents

    Morse, Jeffrey D.; Jankowski, Alan F.; Yu, Conrad

    2010-08-10

    An apparatus having a first substrate having (1) a cavity, (2) one or more resistive heaters, and (3) one or more coatings forming a diffusion barrier to hydrogen; a second substrate having (1) an outlet valve comprising a pressure relief structure and (2) one or more coatings forming a diffusion barrier to hydrogen, wherein said second substrate is coupled to said first substrate forming a sealed volume in said cavity; a metal hydride material contained within said cavity; and a gas distribution system formed by coupling a microfluidic interconnect to said pressure relief structure. Additional apparatuses and methods are also disclosed.

  8. Development of nickel-metal hydride cell

    NASA Technical Reports Server (NTRS)

    Kuwajima, Saburo; Kamimori, Nolimits; Nakatani, Kensuke; Yano, Yoshiaki

    1993-01-01

    National Space Development Agency of Japan (NASDA) has conducted the research and development (R&D) of battery cells for space use. A new R&D program about a Nickel-Metal Hydride (Ni-MH) cell for space use from this year, based on good results in evaluations of commercial Ni-MH cells in Tsukuba Space Center (TKSC), was started. The results of those commercial Ni-MH cell's evaluations and recent status about the development of Ni-MH cells for space use are described.

  9. Pressure-stabilized superconductive yttrium hydrides

    NASA Astrophysics Data System (ADS)

    Li, Yinwei; Hao, Jian; Liu, Hanyu; Tse, John S.; Wang, Yanchao; Ma, Yanming

    2015-05-01

    The search for high-temperature superconductors has been focused on compounds containing a large fraction of hydrogen, such as SiH4(H2)2, CaH6 and KH6. Through a systematic investigation of yttrium hydrides at different hydrogen contents using an structure prediction method based on the particle swarm optimization algorithm, we have predicted two new yttrium hydrides (YH4 andYH6), which are stable above 110 GPa. Three types of hydrogen species with increased H contents were found, monatomic H in YH3, monatomic H+molecular “H2” in YH4 and hexagonal “H6” unit in YH6. Interestingly, H atoms in YH6 form sodalite-like cage sublattice with centered Y atom. Electron-phonon calculations revealed the superconductive potential of YH4 and YH6 with estimated transition temperatures (Tc) of 84-95 K and 251-264 K at 120 GPa, respectively. These values are higher than the predicted maximal Tc of 40 K in YH3.

  10. Pressure-stabilized superconductive yttrium hydrides.

    PubMed

    Li, Yinwei; Hao, Jian; Liu, Hanyu; Tse, John S; Wang, Yanchao; Ma, Yanming

    2015-05-05

    The search for high-temperature superconductors has been focused on compounds containing a large fraction of hydrogen, such as SiH4(H2)2, CaH6 and KH6. Through a systematic investigation of yttrium hydrides at different hydrogen contents using an structure prediction method based on the particle swarm optimization algorithm, we have predicted two new yttrium hydrides (YH4 andYH6), which are stable above 110 GPa. Three types of hydrogen species with increased H contents were found, monatomic H in YH3, monatomic H+molecular "H2" in YH4 and hexagonal "H6" unit in YH6. Interestingly, H atoms in YH6 form sodalite-like cage sublattice with centered Y atom. Electron-phonon calculations revealed the superconductive potential of YH4 and YH6 with estimated transition temperatures (Tc) of 84-95 K and 251-264 K at 120 GPa, respectively. These values are higher than the predicted maximal Tc of 40 K in YH3.

  11. Pressure-stabilized superconductive yttrium hydrides

    PubMed Central

    Li, Yinwei; Hao, Jian; Liu, Hanyu; Tse, John S.; Wang, Yanchao; Ma, Yanming

    2015-01-01

    The search for high-temperature superconductors has been focused on compounds containing a large fraction of hydrogen, such as SiH4(H2)2, CaH6 and KH6. Through a systematic investigation of yttrium hydrides at different hydrogen contents using an structure prediction method based on the particle swarm optimization algorithm, we have predicted two new yttrium hydrides (YH4 andYH6), which are stable above 110 GPa. Three types of hydrogen species with increased H contents were found, monatomic H in YH3, monatomic H+molecular “H2” in YH4 and hexagonal “H6” unit in YH6. Interestingly, H atoms in YH6 form sodalite-like cage sublattice with centered Y atom. Electron-phonon calculations revealed the superconductive potential of YH4 and YH6 with estimated transition temperatures (Tc) of 84–95 K and 251–264 K at 120 GPa, respectively. These values are higher than the predicted maximal Tc of 40 K in YH3. PMID:25942452

  12. Metal hydrides for lithium-ion batteries.

    PubMed

    Oumellal, Y; Rougier, A; Nazri, G A; Tarascon, J-M; Aymard, L

    2008-11-01

    Classical electrodes for Li-ion technology operate via an insertion/de-insertion process. Recently, conversion electrodes have shown the capability of greater capacity, but have so far suffered from a marked hysteresis in voltage between charge and discharge, leading to poor energy efficiency and voltages. Here, we present the electrochemical reactivity of MgH(2) with Li that constitutes the first use of a metal-hydride electrode for Li-ion batteries. The MgH(2) electrode shows a large, reversible capacity of 1,480 mAh g(-1) at an average voltage of 0.5 V versus Li(+)/Li(o) which is suitable for the negative electrode. In addition, it shows the lowest polarization for conversion electrodes. The electrochemical reaction results in formation of a composite containing Mg embedded in a LiH matrix, which on charging converts back to MgH(2). Furthermore, the reaction is not specific to MgH(2), as other metal or intermetallic hydrides show similar reactivity towards Li. Equally promising, the reaction produces nanosized Mg and MgH(2), which show enhanced hydrogen sorption/desorption kinetics. We hope that such findings can pave the way for designing nanoscale active metal elements with applications in hydrogen storage and lithium-ion batteries.

  13. Regeneration of Aluminum Hydride Using Trimethylamine

    SciTech Connect

    D Lacina; J Reilly; Y Celebi; J Wegrzyn; J Johnson; J Graetz

    2011-12-31

    Aluminum hydride is an attractive reducing agent and energy storage compound possessing a low decomposition temperature and a high gravimetric and volumetric hydrogen density. However, it is thermodynamically unstable at room temperature and requires extremely high pressures to form the hydride from aluminum and hydrogen gas. Here, we describe an alternate method of synthesizing AlH{sub 3} using Ti-catalyzed Al powder, H{sub 2}, and trimethylamine (TMA) to form an alane adduct. The formation of trimethylamine alane occurs at modest hydrogen pressures ({approx}100 bar), forming the 2:1 bis complex (2 trimethylamine/AlH{sub 3}). Along with the hydrogenation product, mono (1:1) and bis (2:1) standards of TMA-AlH{sub 3} were prepared and characterized using X-ray diffraction and Raman spectroscopy. X-ray absorption spectroscopy of the reaction products showed that the Ti catalyst remains with the unreacted Al powder after hydrogenation and is not present in the alane adduct. We also demonstrate that TMA can be transaminated with triethylamine to form triethylamine alane, which can easily be separated to recover AlH{sub 3}.

  14. Molecular rare-earth-metal hydrides in non-cyclopentadienyl environments.

    PubMed

    Fegler, Waldemar; Venugopal, Ajay; Kramer, Mathias; Okuda, Jun

    2015-02-02

    Molecular hydrides of the rare-earth metals play an important role as homogeneous catalysts and as counterparts of solid-state interstitial hydrides. Structurally well-characterized non-metallocene-type hydride complexes allow the study of elementary reactions that occur at rare-earth-metal centers and of catalytic reactions involving bonds between rare-earth metals and hydrides. In addition to neutral hydrides, cationic derivatives have now become available.

  15. The development of metal hydrides using as concentrating solar thermal storage materials

    NASA Astrophysics Data System (ADS)

    Qu, Xuanhui; Li, Yang; Li, Ping; Wan, Qi; Zhai, Fuqiang

    2015-12-01

    Metal hydrides high temperature thermal heat storage technique has great promising future prospects in solar power generation, industrial waste heat utilization and peak load regulating of power system. This article introduces basic principle of metal hydrides for thermal storage, and summarizes developments in advanced metal hydrides high-temperature thermal storage materials, numerical simulation and thermodynamic calculation in thermal storage systems, and metal hydrides thermal storage prototypes. Finally, the future metal hydrides high temperature thermal heat storage technique is been looked ahead.

  16. A study of hydriding kinetics of metal hydrides using a physically based model

    NASA Astrophysics Data System (ADS)

    Voskuilen, Tyler G.

    The reaction of hydrogen with metals to form metal hydrides has numerous potential energy storage and management applications. The metal hydrogen system has a high volumetric energy density and is often reversible with a high cycle life. The stored hydrogen can be used to produce energy through combustion, reaction in a fuel cell, or electrochemically in metal hydride batteries. The high enthalpy of the metal-hydrogen reaction can also be used for rapid heat removal or delivery. However, improving the often poor gravimetric performance of such systems through the use of lightweight metals usually comes at the cost of reduced reaction rates or the requirement of pressure and temperature conditions far from the desired operating conditions. In this work, a 700 bar Sievert system was developed at the Purdue Hydrogen Systems Laboratory to study the kinetic and thermodynamic behavior of high pressure hydrogen absorption under near-ambient temperatures. This system was used to determine the kinetic and thermodynamic properties of TiCrMn, an intermetallic metal hydride of interest due to its ambient temperature performance for vehicular applications. A commonly studied intermetallic hydride, LaNi5, was also characterized as a base case for the phase field model. The analysis of the data obtained from such a system necessitate the use of specialized techniques to decouple the measured reaction rates from experimental conditions. These techniques were also developed as a part of this work. Finally, a phase field model of metal hydride formation in mass-transport limited interstitial solute reactions based on the regular solution model was developed and compared with measured kinetics of LaNi5 and TiCrMn. This model aided in the identification of key reaction features and was used to verify the proposed technique for the analysis of gas-solid reaction rates determined volumetrically. Additionally, the phase field model provided detailed quantitative predictions of the

  17. Synthesis and hydride transfer reactions of cobalt and nickel hydride complexes to BX3 compounds.

    PubMed

    Mock, Michael T; Potter, Robert G; O'Hagan, Molly J; Camaioni, Donald M; Dougherty, William G; Kassel, W Scott; DuBois, Daniel L

    2011-12-05

    Hydrides of numerous transition metal complexes can be generated by the heterolytic cleavage of H(2) gas such that they offer alternatives to using main group hydrides in the regeneration of ammonia borane, a compound that has been intensely studied for hydrogen storage applications. Previously, we reported that HRh(dmpe)(2) (dmpe = 1,2-bis(dimethylphosphinoethane)) was capable of reducing a variety of BX(3) compounds having a hydride affinity (HA) greater than or equal to the HA of BEt(3). This study examines the reactivity of less expensive cobalt and nickel hydride complexes, HCo(dmpe)(2) and [HNi(dmpe)(2)](+), to form B-H bonds. The hydride donor abilities (ΔG(H(-))°) of HCo(dmpe)(2) and [HNi(dmpe)(2)](+) were positioned on a previously established scale in acetonitrile that is cross-referenced with calculated HAs of BX(3) compounds. The collective data guided our selection of BX(3) compounds to investigate and aided our analysis of factors that determine favorability of hydride transfer. HCo(dmpe)(2) was observed to transfer H(-) to BX(3) compounds with X = H, OC(6)F(5), and SPh. The reaction with B(SPh)(3) is accompanied by the formation of dmpe-(BH(3))(2) and dmpe-(BH(2)(SPh))(2) products that follow from a reduction of multiple B-SPh bonds and a loss of dmpe ligands from cobalt. Reactions between HCo(dmpe)(2) and B(SPh)(3) in the presence of triethylamine result in the formation of Et(3)N-BH(2)SPh and Et(3)N-BH(3) with no loss of a dmpe ligand. Reactions of the cationic complex [HNi(dmpe)(2)](+) with B(SPh)(3) under analogous conditions give Et(3)N-BH(2)SPh as the final product along with the nickel-thiolate complex [Ni(dmpe)(2)(SPh)](+). The synthesis and characterization of HCo(dedpe)(2) (dedpe = Et(2)PCH(2)CH(2)PPh(2)) from H(2) and a base is also discussed, including the formation of an uncommon trans dihydride species, trans-[(H)(2)Co(dedpe)(2)][BF(4)].

  18. Synthesis and Hydride Transfer Reactions of Cobalt and Nickel Hydride Complexes to BX₃ Compounds

    SciTech Connect

    Mock, Michael T.; Potter, Robert G.; O'Hagan, Molly; Camaioni, Donald M.; Dougherty, William G.; Kassel, W. Scott; DuBois, Daniel L.

    2011-10-31

    Hydrides of numerous transition metal complexes can be generated by the heterolytic cleavage of H₂ gas such that they offer alternatives to using main group hydrides in the regeneration of ammonia borane, a compound that has been intensely studied for hydrogen storage applications. Previously, we reported that HRh(dmpe)₂ (dmpe = 1,2-bis(dimethylphosphinoethane)) was capable of reducing a variety of BX₃ compounds having a hydride affinity (HA) greater than or equal to the HA of BEt₃. This study examines the reactivity of less expensive cobalt and nickel hydride complexes, HCo(dmpe)₂ and [HNi(dmpe)₂]+, to form B–H bonds. The hydride donor abilities (ΔGH °) of HCo(dmpe)₂ and [HNi(dmpe)₂]+ were positioned on a previously established scale in acetonitrile that is cross-referenced with calculated HAs of BX₃ compounds. The collective data guided our selection of BX₃ compounds to investigate and aided our analysis of factors that determine favorability of hydride transfer. HCo(dmpe)₂ was observed to transfer H to BX₃ compounds with X = H, OC₆F₅, and SPh. The reaction with B(SPh)₃ is accompanied by the formation of dmpe-(BH₃)₂ and dmpe-(BH₂(SPh))₂ products that follow from a reduction of multiple B–SPh bonds and a loss of dmpe ligands from cobalt. Reactions between HCo(dmpe)₂ and B(SPh)₃ in the presence of triethylamine result in the formation of Et₃N–BH₂SPh and Et₃N–BH₃ with no loss of a dmpe ligand. Reactions of the cationic complex [HNi(dmpe)₂]+ with B(SPh)₃ under analogous conditions give Et₃N–BH₂SPh as the final product along with the nickel–thiolate complex [Ni(dmpe)₂(SPh)]+. The synthesis and characterization of HCo(dedpe)₂ (dedpe = Et₂PCH₂CH₂PPh₂) from H₂ and a base is also discussed, including the formation of an uncommon trans dihydride species, trans-[(H)₂Co(dedpe)₂][BF₄].

  19. Synthesis and Hydride Transfer Reactions of Cobalt and Nickel Hydride Complexes to BX3 Compounds

    SciTech Connect

    Mock, Michael T.; Potter, Robert G.; O'Hagan, Molly J.; Camaioni, Donald M.; Dougherty, William G.; Kassel, W. S.; DuBois, Daniel L.

    2011-12-05

    Hydrides of numerous transition metal complexes can be generated by the heterolytic cleavage of H{sub 2} gas such that they offer alternatives to using main group hydrides in the regeneration of ammonia borane, a compound that has been intensely studied for hydrogen storage applications. Previously, we reported that HRh(dmpe){sub 2}, dmpe = 1,2-bis(dimethylphosphinoethane) was capable of reducing a variety of BX{sub 3} compounds having hydride affinity (HA) greater than or equal to HA of BEt{sub 3}. This study examines the reactivity of less expensive cobalt and nickel hydride complexes, (HCo(dmpe){sub 2} and [HNi(dmpe){sub 2}]{sup +}), to form B-H bonds. The hydride donor abilities ({Delta}G{sub H{sup -}}{sup o}) of HCo(dmpe){sub 2} and [HNi(dmpe){sub 2}]{sup +} were positioned on a previously established scale in acetonitrile that is cross-referenced with calculated HAs of BX{sub 3} compounds. The collective data guided our selection of BX{sub 3} compounds to investigate and aided our analysis of factors that determine favorability of hydride transfer. HCo(dmpe){sub 2} was observed to transfer H{sup -} to BX{sub 3} compounds with X = H, OC{sub 6}F{sub 5} and SPh. The reaction with B(SPh){sub 3} is accompanied by formation of (BH{sub 3}){sub 2}-dmpe and (BH{sub 2}SPh){sub 2}-dmpe products that follow from reduction of multiple BSPh bonds and loss of a dmpe ligand from Co. Reactions between HCo(dmpe){sub 2} and B(SPh){sub 3} in the presence of triethylamine result in formation of Et{sub 3}N-BH{sub 2}SPh and Et{sub 3}N-BH{sub 3} with no loss of dmpe ligand. Reactions of the cationic complex [HNi(dmpe){sub 2}]{sup +} with B(SPh){sub 3} under analogous conditions give Et{sub 3}N-BH{sub 2}SPh as the final product along with the nickel-thiolate complex [Ni(dmpe){sub 2}(SPh)]{sup +}. The synthesis and characterization of HCo(dedpe){sub 2} (dedpe = diethyldiphenyl(phosphino)ethane) from H{sub 2} and a base is also discussed; including the formation of an uncommon trans

  20. Hot temperatures line lists for metal hydrides

    NASA Astrophysics Data System (ADS)

    Gorman, M.; Lodi, L.; Leyland, P. pC; Hill, C.; Yurchenko, S. N.; Tennyson, J.

    2013-09-01

    The ExoMol project is an ERC funded project set up with the purpose of calculating high quality theoretical molecular line list data to facilitate the emerging field of exoplanet and cool star atmospheric haracterisation [1]. Metal hydrides are important building blocks of interstellar physical chemistry. For molecular identification and characterisation in astrophysical sources, one requires accurate and complete spectroscopic data including transitional frequencies and intensities in the form of a line list. The ab initio methods offer the best opportunity for detailed theoretical studies of free diatomic metal hydrides and other simple hydride molecules. In this contribution we present progress on theoretical line lists for AlH, CrH, MgH, NiH, NaH and TiH obtained from first principles, applicable for a large range of temperatures up to 3500 K. Among the hydrides, AlH is of special interest because of a relatively high cosmic abundance of aluminium. The presence of AlH has been detected in the spectra of M-type and S-type stars as well as in sunspots (See [2] and references therein). CrH is a molecule of astrophysical interest; under the classification scheme developed by Kirkpatrick et al [3], CrH is of importance in distinguishing L type brown dwarfs. It has been proposed that theoretical line-lists of CrH and CrD could be used to facilitate a 'Deuterium test' for use in distinguishing planets, brown dwarfs and stars [5] and also it has been speculated that CrH exists in sunspots [4] but a higherquality hot-temperature line-list is needed to confirm this finding. The presence of MgH in stellar spectra is well documented through observation of the A2 ! X 2+ and B0 2+ ! X 2+ transitions. Different spectral features of MgH have been used as an indicator for the magnesium isotope abundances in the atmospheres of different stars from giants to dwarfs including the Sun, to measure the temperature of stars, surface gravity, stars' metal abundance, gravitational, as

  1. Slow deactivation channels in UV-photoexcited adenine DNA.

    PubMed

    Chen, Xuebo; Fang, Weihai; Wang, Haobin

    2014-03-07

    The molecular mechanism for removing the excess energy in DNA bases is responsible for the high photostability of DNA and is thus the subject of intense theoretical/computational investigation. To understand why the excited state decay of the stacked bases is significantly longer than that of the monomers, we carried out electronic structure calculations on an adenine monomer and an aqueous (dA)5 oligonucleotide employing the CASPT2//CASSCF and CASPT2//CASSCF/AMBER levels of theory. The newly-found bright excited state pair Sstack1((1)ππ*) and Sstack2((1)ππ*) of d(A)5, originated from base stacking, is of intra-base charge transfer nature and occurs in different stacked bases with charge transfer along opposite directions. Two slow deactivation channels of d(A)5 were proposed as a result of the sizable barriers along the relaxation paths starting from the FC point of the Sstack1((1)ππ*) state. The SN1P((1)nπ*) state of d(A)5 serves as an intermediate state in one relaxation channel, to which a nonadiabatic decay from the Sstack1((1)ππ*) state occurs in an energy degeneracy region. A relatively high barrier in this state is found and attributed to the steric hindrance of the DNA environment due to the large NH2 group twisting, which gives a weak and red-shifted fluorescence. Another direct relaxation channel, induced by the C2-H2 bond twisting motion, is found to go through a conical intersection between the Sstack1((1)ππ*) and the ground state. The barrier found here enables fluorescence from the Sstack1((1)ππ*) state and may explain the bright state emission observed in the fluorescence upconversion measurements. The inter-molecular SCT((1)ππ*) state may be involved in the slow relaxation process of the photoexcited adenine oligomers through efficient internal conversion to the intra-base Sstack1((1)ππ*) state.

  2. Synthesis and some reactions of dibutyltin (S)- and (R)-camphorsulfonyl hydrides.

    PubMed

    Kinart, Wojciech J; Kinart, Cezary M; Kozak, Monika; Kinart, Andrzej; Sendecki, Marcin; Matczak, Piotr

    2009-08-01

    The synthesis and physical properties of dibutyltin (S)-camphorsulfonyl hydride (1) and dibutyltin (R)-camphorsulfonyl hydride (2), and diphenyltin (S)-camphorsulfonyl hydride (3) as well as that of their organotin precursors are described. Their reactivity with different amines as triethylamine, morpholine and pyridine has been compared with other mixed hydrides as dibutyltin chloride hydride, dibutyltin acetate hydride and dibutyltin dihydride. It has been studied also the possibility of using of dibutyltin (R)- or (S)-camphorsulfonyl hydrides for the stereoselective reduction of different ketones as acetophenone, menthon, camphor and cyclopropyl-(4-metoxyphenyl)-methanone. The reduction of acetophenone with studied camphorsulfonyl hydrides carried out in benzene at room temperature afforded 1-phenylethanol with relatively low enantioselectivity. Addition of 10 equiv. of MnCl(2)*4H(2)O or ZnCl(2) to the reduction mixture involving dibutyltin (S)-camphorsulfonyl hydride (1) and acetophenone and carried out in methanol and tetrahydrofuran, respectively, resulted in remarkable increase in enantioselectivity. The comparative kinetic studies of reduction of acetophenone by different hydrides proved that dibutyltin camphorsulfonyl hydride is significantly more reactive in comparison with dibutyltin chloro hydride and dibutyltin acetate hydride. Analogous results have been obtained from kinetic studies for different tin hydrides with chosen amines. The outcome of these studies supported by theoretical calculations led to the conclusion that the order of reactivity of the studied hydrides correlates with the rate of their homolytic decomposition at room temperature.

  3. Technical and economic aspects of hydrogen storage in metal hydrides

    NASA Technical Reports Server (NTRS)

    Schmitt, R.

    1981-01-01

    The recovery of hydrogen from such metal hydrides as LiH, MgH2, TiH2, CaH2 and FeTiH compounds is studied, with the aim of evaluating the viability of the technique for the storage of hydrogen fuel. The pressure-temperature dependence of the reactions, enthalpies of formation, the kinetics of the hydrogen absorption and desorption, and the mechanical and chemical stability of the metal hydrides are taken into account in the evaluation. Economic aspects are considered. Development of portable metal hydride hydrogen storage reservoirs is also mentioned.

  4. Structural Characterization of Metal Hydrides for Energy Applications

    NASA Astrophysics Data System (ADS)

    George, Lyci

    Hydrogen can be an unlimited source of clean energy for future because of its very high energy density compared to the conventional fuels like gasoline. An efficient and safer way of storing hydrogen is in metals and alloys as hydrides. Light metal hydrides, alanates and borohydrides have very good hydrogen storage capacity, but high operation temperatures hinder their application. Improvement of thermodynamic properties of these hydrides is important for their commercial use as a source of energy. Application of pressure on materials can have influence on their properties favoring hydrogen storage. Hydrogen desorption in many complex hydrides occurs above the transition temperature. Therefore, it is important to study the physical properties of the hydride compounds at ambient and high pressure and/or high temperature conditions, which can assist in the design of suitable storage materials with desired thermodynamic properties. The high pressure-temperature phase diagram, thermal expansion and compressibility have only been evaluated for a limited number of hydrides so far. This situation serves as a main motivation for studying such properties of a number of technologically important hydrides. Focus of this dissertation was on X-ray diffraction and Raman spectroscopy studies of Mg2FeH6, Ca(BH4) 2, Mg(BH4)2, NaBH4, NaAlH4, LiAlH4, LiNH2BH3 and mixture of MgH 2 with AlH3 or Si, at different conditions of pressure and temperature, to obtain their bulk modulus and thermal expansion coefficient. These data are potential source of information regarding inter-atomic forces and also serve as a basis for developing theoretical models. Some high pressure phases were identified for the complex hydrides in this study which may have better hydrogen storage properties than the ambient phase. The results showed that the highly compressible B-H or Al-H bonds and the associated bond disordering under pressure is responsible for phase transitions observed in brorohydrides or

  5. Design of laser pulses for selective vibrational excitation of the N6-H bond of adenine and adenine-thymine base pair using optimal control theory.

    PubMed

    Sharma, Sitansh; Sharma, Purshotam; Singh, Harjinder; Balint-Kurti, Gabriel G

    2009-06-01

    Time dependent quantum dynamics and optimal control theory are used for selective vibrational excitation of the N6-H (amino N-H) bond in free adenine and in the adenine-thymine (A-T) base pair. For the N6-H bond in free adenine we have used a one dimensional model while for the hydrogen bond, N6-H(A)...O4(T), present in the A-T base pair, a two mathematical dimensional model is employed. The conjugate gradient method is used for the optimization of the field dependent cost functional. Optimal laser fields are obtained for selective population transfer in both the model systems, which give virtually 100% excitation probability to preselected vibrational levels. The effect of the optimized laser field on the other hydrogen bond, N1(A)...H-N3(T), present in A-T base pair is also investigated.

  6. The Oxidation Products of Aluminum Hydride and Boron Aluminum Hydride Clusters

    DTIC Science & Technology

    2016-01-04

    a solid with six crystalline phases. In principle, alane is a promising propellant . The specific impulse of an AP/HTPB propellant mixed with alane...Distribution approved for public release. 2     Introduction Boranes (boron hydrides) were once thought to be promising propellants .1-14 The reasons...diborane, hydrogen, and a white solid . Whatley et al.8 studied the products of diborane oxidation. Roth and co-workers9 found HOBO to be the main

  7. DNA methylation on N6-adenine in C. elegans

    PubMed Central

    Greer, Eric Lieberman; Blanco, Mario Andres; Gu, Lei; Sendinc, Erdem; Liu, Jianzhao; Aristizábal-Corrales, David; Hsu, Chih-Hung; Aravind, L.; He, Chuan; Shi, Yang

    2015-01-01

    Summary In mammalian cells, DNA methylation on the 5th position of cytosine (5mC) plays an important role as an epigenetic mark. However, DNA methylation was considered to be absent in C. elegans because of the lack of detectable 5mC as well as homologs of the cytosine DNA methyltransferases. Here, using multiple approaches, we demonstrate the presence of adenine N6-methylation (6mA) in C. elegans DNA. We further demonstrate that this modification increases trans-generationally in a paradigm of epigenetic inheritance. Importantly, we identify a DNA demethylase, NMAD-1, and a potential DNA methyltransferase, DAMT-1, which regulate 6mA levels and crosstalk between methylation of histone H3K4me2 and 6mA, and control the epigenetic inheritance of phenotypes associated with the loss of the H3K4me2 demethylase spr-5. Together, these data identify a DNA modification in C. elegans and raise the exciting possibility that 6mA may be a carrier of heritable epigenetic information in eukaryotes. PMID:25936839

  8. Radiolysis of aqueous adenine (vitamin B4) and 8-hydroxyadenine

    NASA Astrophysics Data System (ADS)

    Hartmann, J.; Quint, R. M.; Getoff, N.

    2007-05-01

    The radiolysis of adenine (vitamin B4) was studied in aqueous solution (pH˜7.4) saturated either with argon (operating radicals: 44% e -aq, 46% OH, 10% H) or with air (46% OH, 54% O 2rad - ) and with N 2O (90% OH, 10% H), respectively. The obtained initial Gi-values are: 0.88, 1.16 and 1.45. As main radiolytic product was determined 8-hydroxyadenine (8-HOA), whose yield depends on the OH concentration in the reacting media. Hence, under the same experimental conditions the Gi-values are in media saturated with argon: 0.1, in air: 0.15 and in N 2O: 0.29. In aerated solution also a mixture of aldehydes as well as of carboxylic acids were formed, but they were not identified. 8-HOA is of some biological interest; therefore, its radiolysis was also investigated under the same conditions. The determined Gi(-8HOA)-values were in airfree solution negligible, in aerated solutions: 3.1 and in the presence of N 2O: 4.0. For explanation of the product formation some probable reaction mechanisms were given.

  9. ENVIRONMENTAL REACTIVITY OF SOLID STATE HYDRIDE MATERIALS

    SciTech Connect

    Gray, J; Donald Anton, D

    2009-04-23

    In searching for high gravimetric and volumetric density hydrogen storage systems, it is inevitable that higher energy density materials will be used. In order to make safe and commercially acceptable condensed phase hydrogen storage systems, it is important to understand quantitatively the risks involved in using and handling these materials and to develop appropriate mitigation strategies to handle potential material exposure events. A crucial aspect of the development of risk identification and mitigation strategies is the development of rigorous environmental reactivity testing standards and procedures. This will allow for the identification of potential risks and implementation of risk mitigation strategies. Modified testing procedures for shipping air and/or water sensitive materials, as codified by the United Nations, have been used to evaluate two potential hydrogen storage materials, 2LiBH{sub 4} {center_dot} MgH{sub 2} and NH{sub 3}BH{sub 3}. The modified U.N. procedures include identification of self-reactive substances, pyrophoric substances, and gas-emitting substances with water contact. The results of these tests for air and water contact sensitivity will be compared to the pure material components where appropriate (e.g. LiBH{sub 4} and MgH{sub 2}). The water contact tests are divided into two scenarios dependent on the hydride to water mole ratio and heat transport characteristics. Air contact tests were run to determine whether a substance will spontaneously react with air in a packed or dispersed form. In the case of the 2LiBH{sub 4} {center_dot} MgH{sub 2} material, the results from the hydride mixture compared to the pure materials results showed the MgH{sub 2} to be the least reactive component and LiBH{sub 4} the more reactive. The combined 2LiBH{sub 4} {center_dot} MgH{sub 2} resulted in a material having environmental reactivity between these two materials. Relative to 2LiBH{sub 4} {center_dot} MgH{sub 2}, the chemical hydride NH{sub 3}BH

  10. Spin-dependent electron transport in zinc- and manganese-doped adenine molecules

    SciTech Connect

    Simchi, Hamidreza; Esmaeilzadeh, Mahdi Mazidabadi, Hossein

    2014-01-28

    The spin-dependent electron transport properties of zinc- and manganese-doped adenine molecules connected to zigzag graphene leads are studied in the zero bias regime using the non-equilibrium Green's function method. The conductance of the adenine molecule increased and became spin-dependent when a zinc or manganese atom was doped into the molecules. The effects of a transverse electric field on the spin-polarization of the transmitted electrons were investigated and the spin-polarization was controlled by changing the transverse electric field. Under the presence of a transverse electric field, both the zinc- and manganese-doped adenine molecules acted as spin-filters. The maximum spin-polarization of the manganese-doped adenine molecule was greater than the molecule doped with zinc.

  11. Adenine and guanine nucleotide metabolism during platelet storage at 22 degree C

    SciTech Connect

    Edenbrandt, C.M.; Murphy, S. )

    1990-11-01

    Adenine and guanine nucleotide metabolism of platelet concentrates (PCs) was studied during storage for transfusion at 22 +/- 2 degrees C over a 7-day period using high-pressure liquid chromatography. There was a steady decrease in platelet adenosine triphosphate (ATP) and adenosine diphosphate (ADP), which was balanced quantitatively by an increase in plasma hypoxanthine. As expected, ammonia accumulated along with hypoxanthine but at a far greater rate. A fall in platelet guanosine triphosphate (GTP) and guanosine diphosphate (GDP) paralleled the fall in ATP + ADP. When adenine was present in the primary anticoagulant, it was carried over into the PC and metabolized. ATP, GTP, total adenine nucleotides, and total guanine nucleotides declined more slowly in the presence of adenine than in its absence. With adenine, the increase in hypoxanthine concentration was more rapid and quantitatively balanced the decrease in adenine and platelet ATP + ADP. Plasma xanthine rose during storage but at a rate that exceeded the decline in GTP + GDP. When platelet ATP + ADP was labeled with 14C-adenine at the initiation of storage, half of the radioactivity was transferred to hypoxanthine (45%) and GTP + GDP + xanthine (5%) by the time storage was completed. The isotopic data were consistent with the presence of a radioactive (metabolic) and a nonradioactive (storage) pool of ATP + ADP at the initiation of storage with each pool contributing approximately equally to the decline in ATP + ADP during storage. The results suggested a continuing synthesis of GTP + GDP from ATP + ADP, explaining the slower rate of fall of GTP + GDP relative to the rate of rise of plasma xanthine. Throughout storage, platelets were able to incorporate 14C-hypoxanthine into both adenine and guanine nucleotides but at a rate that was only one fourth the rate of hypoxanthine accumulation.

  12. Structural and biochemical characterization of linear dinucleotide analogs bound to the c-di-GMP-I aptamer†,‡

    PubMed Central

    Smith, Kathryn D.; Lipchock, Sarah V.; Strobel, Scott A.

    2011-01-01

    The cyclic dinucleotide c-di-GMP regulates lifestyle transitions in many bacteria, such as the change from a free motile state to a biofilm-forming community. Riboswitches that bind this second messenger are important downstream targets in this bacterial signaling pathway. The breakdown of c-di-GMP in the cell is accomplished enzymatically and results in the linear dinucleotide pGpG. The c-di-GMP-binding riboswitches must be able to discriminate between their cognate cyclic ligand and linear dinucleotides in order to be selective biological switches. It has been reported that the cdi-GMP-I riboswitch binds c-di-GMP five orders of magnitude better than the linear pGpG, but the cause of this large energetic difference in binding is unknown. Here we report binding data and crystal structures of several linear c-di-GMP analogs in complex with the c-di-GMP-I riboswitch. These data reveal the parameters for phosphate recognition and the structural basis of linear dinucleotide binding to the riboswitch. Additionally, the pH dependence of binding shows that exclusion of pGpG is not due to the additional negative charge on the ligand. These data reveal principles that, along with published work, will contribute to the design of c-di-GMP analogs with properties desirable for use as chemical tools and potential therapeutics. PMID:22148472

  13. Relativistic effects on sixth group hydrides

    NASA Astrophysics Data System (ADS)

    Pisani, L.; Clementi, E.

    1994-08-01

    Dirac-Fock (DF) and Hartree-Fock (HF) calculations have been performed for the ground state configuration of the H2O, H2S, H2Se, H2Te, and H2Po molecules. Equilibrium geometries, atomization energies, and molecular orbitals energies are evaluated with both methods, compared and discussed with the help of population analysis and atomic orbital energies. Particular attention has been given to a qualitative understanding of the relativistic effects. Molecular spin-orbits corrections appear to be essential to a description of some in the sixth group hydrides set. A description of the relativistic computer program is presented elsewhere [L. Pisani and E. Clementi, J. Comput. Chem. (in press)].

  14. Zirconium Hydride Space Power Reactor design.

    NASA Technical Reports Server (NTRS)

    Asquith, J. G.; Mason, D. G.; Stamp, S.

    1972-01-01

    The Zirconium Hydride Space Power Reactor being designed and fabricated at Atomics International is intended for a wide range of potential applications. Throughout the program a series of reactor designs have been evaluated to establish the unique requirements imposed by coupling with various power conversion systems and for specific applications. Current design and development emphasis is upon a 100 kilowatt thermal reactor for application in a 5 kwe thermoelectric space power generating system, which is scheduled to be fabricated and ground tested in the mid 70s. The reactor design considerations reviewed in this paper will be discussed in the context of this 100 kwt reactor and a 300 kwt reactor previously designed for larger power demand applications.

  15. Far-infrared spectrum of sodium hydride

    NASA Astrophysics Data System (ADS)

    Leopold, K. R.; Zink, L. R.; Evenson, K. M.; Jennings, D. A.

    1987-03-01

    Rotational spectra in the v = 0, 1, 2, and 3 levels of the ground ( 1Σ) state of sodium hydride have been observed using tunable far-infrared radiation generated from the difference frequency between two CO 2 lasers. The Dunham coefficients, which have been determined without the use of optical data or isotopic scaling relations, are Y01 = 146 999.138(38) MHz, Y02 = -10.29481(54) MHz, Y03 = 6.243(49) × 10 -4 MHz, Y11 = -4109.912(68) MHz, Y12 = 0.14695(68) MHz, Y21 = 33.341(34) MHz, Y22 = -2.69(20) × 10 -3 MHz, and Y31 = -1.0517(55) MHz. The constants are typically an order of magnitude more accurate than the best values previously available, and where comparison is possible, agreement is found to be excellent.

  16. Ni/metal hydride secondary element

    DOEpatents

    Bauerlein, Peter

    2005-04-19

    A Ni/metal hydride secondary element having a positive nickel hydroxide electrode, a negative electrode having a hydrogen storage alloy, and an alkaline electrolyte, the positive electrode, provided with a three-dimensional metallic conductive structure, also contains an aluminum compound which is soluble in the electrolyte, in addition to nickel hydroxide and cobalt oxide. The aluminum compound is aluminum hydroxide and/or aluminum oxide, and the mass of the aluminum compound which is present in the positive bulk material mixture is 0.1 to 2% by weight relative to the mass of the nickel hydroxide which is present. In combination with aluminum hydroxide or aluminum oxide, the positive electrode further contains lanthanoid oxidic compounds Y.sub.2 O.sub.3, La.sub.2 O.sub.3 and Ca(OH).sub.2, as well as mixtures of these compounds.

  17. Process for production of a metal hydride

    SciTech Connect

    Allen, Nathan Tait; Butterick, III, Robert; Chin, Arthur Achhing; Millar, Dean Michael; Molzahn, David Craig

    2014-08-12

    A process for production of a metal hydride compound MH.sub.x, wherein x is one or two and M is an alkali metal, Be or Mg. The process comprises combining a compound of formula (R.sup.1O).sub.xM with aluminum, hydrogen and at least one metal selected from among titanium, zirconium, hafnium, niobium, vanadium, tantalum and iron to produce a compound of formula MH.sub.x. R.sup.1 is phenyl or phenyl substituted by at least one alkyl or alkoxy group. A mole ratio of aluminum to (R.sup.1O).sub.xM is from 0.1:1 to 1:1. The catalyst is present at a level of at least 200 ppm based on weight of aluminum.

  18. Self-Consistent-Field Calculation on Lithium Hydride for Undergraduates.

    ERIC Educational Resources Information Center

    Rioux, Frank; Harriss, Donald K.

    1980-01-01

    Describes a self-consistent-field-linear combination of atomic orbitals-molecular orbital calculation on the valence electrons of lithium hydride using the method of Roothaan. This description is intended for undergraduate physics students.

  19. Thermally unstable hydrides of titanium aluminide Ti3Al

    NASA Astrophysics Data System (ADS)

    Kazantseva, N. V.; Popov, A. G.; Mushnikov, N. V.; Skripov, A. V.; Soloninin, A. V.; Aleksashin, B. A.; Novozhenov, V. I.; Sazonova, V. A.; Kharisova, A. G.

    2011-04-01

    The hydrogen capacity of (Ti, Nb)3Al titanium aluminides subjected to mechanical activation in a hydrogen atmosphere has been studied. It has been shown that the application of this procedure allows one to prepare thermally unstable titanium aluminide (Ti3Al) hydrides with a high hydrogen content (to 2.6 wt %) at room temperature and normal pressure; in this case, no special requirements for the hydrogen purity are placed. The thermally unstable nanostructured Ti3Al hydrides were found to exhibit a higher hydrogen mobility as compared to that of the microcrystalline hydrides. Low niobium additions (to 2.1 at %) have been found to decrease the hydrogen capacity. Experiments on the preparation of bulk samples from the hydride powders obtained were performed.

  20. Life test results of hydride compressors for cryogenic refrigerators

    NASA Astrophysics Data System (ADS)

    Jones, J. A.; Golben, P. M.

    1984-01-01

    A development status assessment is made, from the viewpoint of system durability, for the hydride compressors used in such cryogenic refrigerators as that of the JPL, which has operated at 29 K for 500 hours and at lower temperatures for over 1000. Attention is given to a novel hydride compressor unit which has operated through 35,000 cycles and exhibits negligible degradation of check valves, hydride particle size, and expansion valves. The power requirement for liquid hydrogen cooling can be halved through the use of recuperative hot water heating methods, making this system comparable in power use to liquid hydrogen refrigeration systems operating on electricity. Due to the lack of moving parts in hydride refrigerator designs, potential service lifetimes of many years, and perhaps decades, are being projected.

  1. High-pressure synthesis of noble metal hydrides

    NASA Astrophysics Data System (ADS)

    Donnerer, Christian; Scheler, Thomas; Gregoryanz, Eugene

    2013-04-01

    The formation of hydride phases in the noble metals copper, silver, and gold was investigated by in situ x-ray diffraction at high hydrogen pressures. In the case of copper, a novel hexagonal hydride phase, Cu2H, was synthesised at pressures above 18.6 GPa. This compound exhibits an anti-CdI2-type structure, where hydrogen atoms occupy every second layer of octahedral interstitial sites. In contrast to chemically produced CuH, this phase does not show a change in compressibility compared to pure copper. Furthermore, repeated compression (after decomposition of Cu2H) led to the formation of cubic copper hydride at 12.5 GPa, a phenomenon attributed to an alteration of the microstructure during dehydrogenation. No hydrides of silver (up to 87 GPa) or gold (up to 113 GPa) were found at both room and high temperatures.

  2. The development of lightweight hydride alloys based on magnesium

    SciTech Connect

    Guthrie, S.E.; Thomas, G.J.; Yang, N.Y.C.; Bauer, W.

    1996-02-01

    The development of a magnesium based hydride material is explored for use as a lightweight hydrogen storage medium. It is found that the vapor transport of magnesium during hydrogen uptake greatly influences the surface and hydride reactions in these alloys. This is exploited by purposely forming near-surface phases of Mg{sub 2}Ni on bulk Mg-Al-Zn alloys which result in improved hydrogen adsorption and desorption behavior. Conditions were found where these near-surface reactions yielded a complex and heterogeneous microstructure that coincided with excellent bulk hydride behavior. A Mg-Al alloy hydride is reported with near atmospheric plateau pressures at temperatures below 200{degrees}C. Additionally, a scheme is described for low temperature in-situ fabrication of Mg{sub 2}Ni single phase alloys utilizing the high vapor pressure of Mg.

  3. Metal hydrides as negative electrode materials for Ni- MH batteries

    NASA Astrophysics Data System (ADS)

    Yartys, V.; Noreus, D.; Latroche, M.

    2016-01-01

    Structural, thermodynamical and electrochemical properties of metallic hydrides belonging to the pseudo-binary family A-Mg-Ni ( A: rare earths) are reviewed and compared. Technology aspects of bipolar cells are also discussed.

  4. Nonaqueous actinide hydride dissolution and production of actinide $beta$- diketonates

    DOEpatents

    Crisler, L.R.

    1975-11-11

    Actinide beta-diketonate complex molecular compounds are produced by reacting a beta-diketone compound with a hydride of the actinide material in a mixture of carbon tetrachloride and methanol. (auth)

  5. Artificial exomuscle investigations for applications--metal hydride.

    PubMed

    Crevier, Marie-Charlotte; Richard, Martin; Rittenhouse, D Matheson; Roy, Pierre-Olivier; Bédard, Stéphane

    2007-03-01

    In pursuing the development of bionic devices, Victhom identified a need for technologies that could replace current motorized systems and be better integrated into the human body motion. The actuators used to obtain large displacements are noisy, heavy, and do not adequately reproduce human muscle behavior. Subsequently, a project at Victhom was devoted to the development of active materials to obtain an artificial exomuscle actuator. An exhaustive literature review was done at Victhom to identify promising active materials for the development of artificial muscles. According to this review, metal hydrides were identified as a promising technology for artificial muscle development. Victhom's investigations focused on determining metal hydride actuator potential in the context of bionics technology. Based on metal hydride properties and artificial muscle requirements such as force, displacement and rise time, an exomuscle was built. In addition, a finite element model, including heat and mass transfer in the metal hydride, was developed and implemented in FEMLAB software.

  6. Bipolar Nickel-Metal Hydride Battery Being Developed

    NASA Technical Reports Server (NTRS)

    Manzo, Michelle A.

    1998-01-01

    The NASA Lewis Research Center has contracted with Electro Energy, Inc., to develop a bipolar nickel-metal hydride battery design for energy storage on low-Earth-orbit satellites. The objective of the bipolar nickel-metal hydride battery development program is to approach advanced battery development from a systems level while incorporating technology advances from the lightweight nickel electrode field, hydride development, and design developments from nickel-hydrogen systems. This will result in a low-volume, simplified, less-expensive battery system that is ideal for small spacecraft applications. The goals of the program are to develop a 1-kilowatt, 28-volt (V), bipolar nickel-metal hydride battery with a specific energy of 100 watt-hours per kilogram (W-hr/kg), an energy density of 250 W-hr/liter and a 5-year life in low Earth orbit at 40-percent depth-of-discharge.

  7. High-pressure synthesis of noble metal hydrides.

    PubMed

    Donnerer, Christian; Scheler, Thomas; Gregoryanz, Eugene

    2013-04-07

    The formation of hydride phases in the noble metals copper, silver, and gold was investigated by in situ x-ray diffraction at high hydrogen pressures. In the case of copper, a novel hexagonal hydride phase, Cu2H, was synthesised at pressures above 18.6 GPa. This compound exhibits an anti-CdI2-type structure, where hydrogen atoms occupy every second layer of octahedral interstitial sites. In contrast to chemically produced CuH, this phase does not show a change in compressibility compared to pure copper. Furthermore, repeated compression (after decomposition of Cu2H) led to the formation of cubic copper hydride at 12.5 GPa, a phenomenon attributed to an alteration of the microstructure during dehydrogenation. No hydrides of silver (up to 87 GPa) or gold (up to 113 GPa) were found at both room and high temperatures.

  8. Precipitation of hydrides in high purity niobium after different treatments

    SciTech Connect

    Barkov, F.; Romanenko, A.; Trenikhina, Y.; Grassellino, A.

    2013-01-01

    Precipitation of lossy non-superconducting niobium hydrides represents a known problem for high purity niobium in superconducting applications. Using cryogenic optical and laser confocal scanning microscopy we have directly observed surface precipitation and evolution of niobium hydrides in samples after different treatments used for superconducting RF cavities for particle acceleration. Precipitation is shown to occur throughout the sample volume, and the growth of hydrides is well described by the fast diffusion-controlled process in which almost all hydrogen is precipitated at $T=140$~K within $\\sim30$~min. 120$^{\\circ}$C baking and mechanical deformation are found to affect hydride precipitation through their influence on the number of nucleation and trapping centers.

  9. Process for massively hydriding zirconium--uranium fuel elements

    DOEpatents

    Katz, N.H.

    1973-12-01

    A method is described of hydriding uranium-zirconium alloy by heating the alloy in a vacuum, introducing hydrogen and maintaining an elevated temperature until occurrence of the beta--delta phase transformation and isobarically cooling the composition. (Official Gazette)

  10. Neutrophil gelatinase-associated lipocalin in a triphasic rat model of adenine-induced kidney injury.

    PubMed

    Gil, Amnon; Brod, Vera; Awad, Hoda; Heyman, Samuel N; Abassi, Zaid; Frajewicki, Victor

    2016-10-01

    The aim of this study is to investigate whether NGAL, given its advantages over traditional biomarkers, can be used to describe the dynamic characteristics of the renal tubulointerstitial insult caused by adenine. Subsequently, it will be possible to assess NGAL as a biomarker of any acute kidney injury, on top of chronic interstitial disease, if NGAL levels are stable through the chronic phase of our adenine model. Study group rats were fed an adenine diet, and control group rats were fed a regular diet only. Blood and urine samples for urea, creatinine and NGAL were drawn from each rat at the beginning of the study and after 1, 3, 4, 5, 6, 7 and 8 weeks. Kidney slices from these rats were stained with Hematoxylin-eosin (HE) and β-actin stainings. Serum urea, creatinine and NGAL levels and urinary NGAL/creatinine ratio in the study group were higher than baseline and than in the control group; these differences were statistically significant in some of the intervals. Tubulointerstitial changes and adenine crystals were evident in the study group rats. In the rats fed adenine, serum urea, creatinine and NGAL levels and urinary NGAL/creatinine ratio followed a triphasic pattern of kidney injury: an acute phase while on the adenine diet, a partial recovery phase after switching to the regular diet and a chronic kidney disease phase after stabilization of renal function. NGAL can serve a biomarker for acute kidney injury and possibly for chronic kidney disease in the tubulointerstitial rat model.

  11. Improved growth and stress tolerance in the Arabidopsis oxt1 mutant triggered by altered adenine metabolism.

    PubMed

    Sukrong, Suchada; Yun, Kil-Young; Stadler, Patrizia; Kumar, Charan; Facciuolo, Tony; Moffatt, Barbara A; Falcone, Deane L

    2012-11-01

    Plants perceive and respond to environmental stresses with complex mechanisms that are often associated with the activation of antioxidant defenses. A genetic screen aimed at isolating oxidative stress-tolerant lines of Arabidopsis thaliana has identified oxt1, a line that exhibits improved tolerance to oxidative stress and elevated temperature but displays no apparent deleterious growth effects under non-stress conditions. Oxt1 harbors a mutation that arises from the altered expression of a gene encoding adenine phosphoribosyltransferase (APT1), an enzyme that converts adenine to adenosine monophosphate (AMP), indicating a link between purine metabolism, whole-plant growth responses, and stress acclimation. The oxt1 mutation results in decreased APT1 expression that leads to reduced enzymatic activity. Correspondingly, oxt1 plants possess elevated levels of adenine. Decreased APT enzyme activity directly correlates with stress resistance in transgenic lines that ectopically express APT1. The metabolic alteration in oxt1 plants also alters the expression of several antioxidant defense genes and the response of these genes to oxidative challenge. Finally, it is shown that manipulation of adenine levels can induce stress tolerance to wild-type plants. Collectively, these results show that alterations in cellular adenine levels can trigger stress tolerance and improve growth, leading to increases in plant biomass. The results also suggest that adenine might play a part in the signals that modulate responses to abiotic stress and plant growth.

  12. Benchmark Thermochemistry for Biologically Relevant Adenine and Cytosine. A Combined Experimental and Theoretical Study.

    PubMed

    Emel'yanenko, Vladimir N; Zaitsau, Dzmitry H; Shoifet, Evgeni; Meurer, Florian; Verevkin, Sergey P; Schick, Christoph; Held, Christoph

    2015-09-17

    The thermochemical properties available in the literature for adenine and cytosine are in disarray. A new condensed phase standard (p° = 0.1 MPa) molar enthalpy of formation at T = 298.15 K was measured by using combustion calorimetry. New molar enthalpies of sublimation were derived from the temperature dependence of vapor pressure measured by transpiration and by the quarz-crystal microbalance technique. The heat capacities of crystalline adenine and cytosine were measured by temperature-modulated DSC. Thermodynamic data on adenine and cytosine available in the literature were collected, evaluated, and combined with our experimental results. Thus, the evaluated collection of data together with the new experimental results reported here has helped to resolve contradictions in the available enthalpies of formation. A set of reliable thermochemical data is recommended for adenine and cytosine for further thermochemical calculations. Quantum-chemical calculations of the gas phase molar enthalpies of formation of adenine and cytosine have been performed by using the G4 method and results were in excellent agreement with the recommended experimental data. The standard molar entropies of formation and the standard molar Gibbs functions of formation in crystal and gas state have been calculated. Experimental vapor-pressure data measured in this work were used to estimate pure-component PC-SAFT parameters. This allowed modeling solubility of adenine and cytosine in water over the temperature interval 278-310 K.

  13. Hydrogen storage in sodium aluminum hydride.

    SciTech Connect

    Ozolins, Vidvuds; Herberg, J.L. (Lawrence Livermore National Laboratories, Livermore, CA); McCarty, Kevin F.; Maxwell, Robert S. (Lawrence Livermore National Laboratories, Livermore, CA); Stumpf, Roland Rudolph; Majzoub, Eric H.

    2005-11-01

    Sodium aluminum hydride, NaAlH{sub 4}, has been studied for use as a hydrogen storage material. The effect of Ti, as a few mol. % dopant in the system to increase kinetics of hydrogen sorption, is studied with respect to changes in lattice structure of the crystal. No Ti substitution is found in the crystal lattice. Electronic structure calculations indicate that the NaAlH{sub 4} and Na{sub 3}AlH{sub 6} structures are complex-ionic hydrides with Na{sup +} cations and AlH{sub 4}{sup -} and AlH{sub 6}{sup 3-} anions, respectively. Compound formation studies indicate the primary Ti-compound formed when doping the material at 33 at. % is TiAl{sub 3} , and likely Ti-Al compounds at lower doping rates. A general study of sorption kinetics of NaAlH{sub 4}, when doped with a variety of Ti-halide compounds, indicates a uniform response with the kinetics similar for all dopants. NMR multiple quantum studies of solution-doped samples indicate solvent interaction with the doped alanate. Raman spectroscopy was used to study the lattice dynamics of NaAlH{sub 4}, and illustrated the molecular ionic nature of the lattice as a separation of vibrational modes between the AlH{sub 4}{sup -} anion-modes and lattice-modes. In-situ Raman measurements indicate a stable AlH{sub 4}{sup -} anion that is stable at the melting temperature of NaAlH{sub 4}, indicating that Ti-dopants must affect the Al-H bond strength.

  14. Ab-Initio Study of the Group 2 Hydride Anions

    NASA Astrophysics Data System (ADS)

    Harris, Joe P.; Wright, Timothy G.; Manship, Daniel R.

    2013-06-01

    The beryllium hydride (BeH)- dimer has recently been shown to be surprisingly strongly bound, with an electronic structure which is highly dependent on internuclear separation. At the equilibrium distance, the negative charge is to be found on the beryllium atom, despite the higher electronegativity of the hydrogen. The current study expands this investigation to the other Group 2 hydrides, and attempts to explain these effects. M. Verdicchio, G. L. Bendazzoli, S. Evangelisti, T. Leininger J. Phys. Chem. A, 117, 192, (2013)

  15. Method of selective reduction of polyhalosilanes with alkyltin hydrides

    DOEpatents

    Sharp, Kenneth G.; D'Errico, John J.

    1989-01-01

    The invention relates to the selective and stepwise reduction of polyhalosilanes by reacting at room temperature or below with alkyltin hydrides without the use of free radical intermediates. Alkyltin hydrides selectively and stepwise reduce the Si--Br, Si--Cl, or Si--I bonds while leaving intact any Si--F bonds. When two or more different halogens are present on the polyhalosilane, the halogen with the highest atomic weight is preferentially reduced.

  16. Development of the Low-Pressure Hydride/Dehydride Process

    SciTech Connect

    Rueben L. Gutierrez

    2001-04-01

    The low-pressure hydride/dehydride process was developed from the need to recover thin-film coatings of plutonium metal from the inner walls of an isotope separation chamber located at Los Alamos and to improve the safety operation of a hydride recovery process using hydrogen at a pressure of 0.7 atm at Rocky Flats. This process is now the heart of the Advanced Recovery and Integrated Extraction System (ARIES) project.

  17. Tellurium Hydrides at High Pressures: High-Temperature Superconductors

    NASA Astrophysics Data System (ADS)

    Zhong, Xin; Wang, Hui; Zhang, Jurong; Liu, Hanyu; Zhang, Shoutao; Song, Hai-Feng; Yang, Guochun; Zhang, Lijun; Ma, Yanming

    2016-02-01

    Observation of high-temperature superconductivity in compressed sulfur hydrides has generated an irresistible wave of searches for new hydrogen-containing superconductors. We herein report the prediction of high-Tc superconductivity in tellurium hydrides stabilized at megabar pressures identified by first-principles calculations in combination with a swarm structure search. Although tellurium is isoelectronic to sulfur or selenium, its heavier atomic mass and weaker electronegativity makes tellurium hydrides fundamentally distinct from sulfur or selenium hydrides in stoichiometries, structures, and chemical bondings. We identify three metallic stoichiometries of H4Te , H5Te2 , and HTe3 , which are not predicted or known stable structures for sulfur or selenium hydrides. The two hydrogen-rich H4Te and H5Te2 phases are primarily ionic and contain exotic quasimolecular H2 and linear H3 units, respectively. Their high-Tc (e.g., 104 K for H4Te at 170 GPa) superconductivity originates from the strong electron-phonon couplings associated with intermediate-frequency H-derived wagging and bending modes, a superconducting mechanism which differs substantially with those in sulfur or selenium hydrides where the high-frequency H-stretching vibrations make considerable contributions.

  18. Novel fuel cell stack with coupled metal hydride containers

    NASA Astrophysics Data System (ADS)

    Liu, Zhixiang; Li, Yan; Bu, Qingyuan; Guzy, Christopher J.; Li, Qi; Chen, Weirong; Wang, Cheng

    2016-10-01

    Air-cooled, self-humidifying hydrogen fuel cells are often used for backup and portable power sources, with a metal hydride used as the hydrogen storage material. To provide a stable hydrogen flow to the fuel cell stack, heat must be provided to the metal hydride. Conventionally, the heat released from the exothermic reaction of hydrogen and oxygen in the fuel cell stack to the exhaust air is used to heat a separate metal hydride container. In this case, the heat is only partially used instead of being more closely coupled because of the heat transfer resistances in the system. To achieve better heat integration, a novel scheme is proposed whereby hydrogen storage and single fuel cells are more closely coupled. Based on this idea, metal hydride containers in the form of cooling plates were assembled between each pair of cells in the stack so that the heat could be directly transferred to a metal hydride container of much larger surface-to-volume ratio than conventional separate containers. A heat coupled fuel cell portable power source with 10 cells and 11 metal hydride containers was constructed and the experimental results show that this scheme is beneficial for the heat management of fuel cell stack.

  19. Optimization of Hydride Rim Formation in Unirradiated Zr 4 Cladding

    SciTech Connect

    Shimskey, Rick W.; Hanson, Brady D.; MacFarlan, Paul J.

    2013-09-30

    The purpose of this work is to build on the results reported in the M2 milestone M2FT 13PN0805051, document number FCRD-USED-2013-000151 (Hanson, 2013). In that work, it was demonstrated that unirradiated samples of zircaloy-4 cladding could be pre-hydrided at temperatures below 400°C in pure hydrogen gas and that the growth of hydrides on the surface could be controlled by changing the surface condition of the samples and form a desired hydride rim on the outside diameter of the cladding. The work performed at Pacific Northwest National Laboratory since the issuing of the M2 milestone has focused its efforts to optimize the formation of a hydride rim on available zircaloy-4 cladding samples by controlling temperature variation and gas flow control during pre-hydriding treatments. Surface conditioning of the outside surface was also examined as a variable. The results of test indicate that much of the variability in the hydride thickness is due to temperature variation occurring in the furnaces as well as how hydrogen gas flows across the sample surface. Efforts to examine other alloys, gas concentrations, and different surface conditioning plan to be pursed in the next FY as more cladding samples become available

  20. Effect of niobium additions on initial hydriding kinetics of uranium

    NASA Astrophysics Data System (ADS)

    Li, Ruiwen; Wang, Xiaolin

    2014-06-01

    To study the behavior of hydrogen corrosion at the surface of U, U-2.5 wt%Nb alloy and U-5.7 wt%Nb, a gas-solid reaction system with an in situ microscope was designed. The nucleation and growth of the hydride of the alloy were continuously observed and recorded by a computer. The different characteristics of the hydrides on U metal and U-2.5 wt%Nb showed that the later alloy is more susceptible to hydrogen corrosion than the former. The growth rate of hydride of U-2.5 wt%Nb, calculated by measuring the perimeter of the hydride spots recorded by the in situ microscope, exhibited a reaction temperature dependency in the range of 40-160 °C, for pressure of 0.8 × 105 Pa. An Arrhenius plot for growth rate versus temperature yielded activation energy of 24.34 kJ/mol for the hydriding of U-2.5 wt%Nb alloy. The maximum hydriding rate was obtained at 125 °C, whose thermodynamics reason was discussed.

  1. Thiaminylated adenine nucleotides. Chemical synthesis, structural characterization and natural occurrence.

    PubMed

    Frédérich, Michel; Delvaux, David; Gigliobianco, Tiziana; Gangolf, Marjorie; Dive, Georges; Mazzucchelli, Gabriel; Elias, Benjamin; De Pauw, Edwin; Angenot, Luc; Wins, Pierre; Bettendorff, Lucien

    2009-06-01

    Thiamine and its three phosphorylated derivatives (mono-, di- and triphosphate) occur naturally in most cells. Recently, we reported the presence of a fourth thiamine derivative, adenosine thiamine triphosphate, produced in Escherichia coli in response to carbon starvation. Here, we show that the chemical synthesis of adenosine thiamine triphosphate leads to another new compound, adenosine thiamine diphosphate, as a side product. The structure of both compounds was confirmed by MS analysis and 1H-, 13C- and 31P-NMR, and some of their chemical properties were determined. Our results show an upfield shifting of the C-2 proton of the thiazolium ring in adenosine thiamine derivatives compared with conventional thiamine phosphate derivatives. This modification of the electronic environment of the C-2 proton might be explained by a through-space interaction with the adenosine moiety, suggesting U-shaped folding of adenosine thiamine derivatives. Such a structure in which the C-2 proton is embedded in a closed conformation can be located using molecular modeling as an energy minimum. In E. coli, adenosine thiamine triphosphate may account for 15% of the total thiamine under energy stress. It is less abundant in eukaryotic organisms, but is consistently found in mammalian tissues and some cell lines. Using HPLC, we show for the first time that adenosine thiamine diphosphate may also occur in small amounts in E. coli and in vertebrate liver. The discovery of two natural thiamine adenine compounds further highlights the complexity and diversity of thiamine biochemistry, which is not restricted to the cofactor role of thiamine diphosphate.

  2. Labeling of mitochondrial adenine nucleotides of bovine sperm

    SciTech Connect

    Cheetham, J.; Lardy, H.A.

    1986-05-01

    Incorporation of /sup 32/P/sub i/ into the adenine nucleotide pool of intact bovine spermatozoa utilizing endogenous substrates results in a specific activity (S.A.) ratio ATP/ADP of 0.3 to 0.5, suggesting compartmentation of nucleotide pools or a pathway for phosphorylation of AMP in addition to the myokinase reaction. Incubation of filipin-permeabilized cells with pyruvate, acetylcarnitine, or ..cap alpha..-ketoglutarate (..cap alpha..KG) resulted in ATP-ADP S.A. ratios of 0.5, 0.8, and 1.6, respectively, for mitochondrial nucleotides. However, when malate was included with pyruvate or acetylcarnitine, the ATP/ADP S.A. ratio increased by 400% to 2.0 for pyruvate/malate and by 290% to 2.8 for acetylcarnitine/malate, while the ATP/ADP ratio increased by less than 100% in both cases. These results may indicate that under conditions of limited flux through the citric acid cycle a pathway for phosphorylation of AMP from a precursor other than ATP exists or that ATP is compartmented within the mitochondrion. In the presence of uncoupler and oligomycin with ..cap alpha..KG, pyruvate/malate, or acetylcarnitine/malate, /sup 32/P/sub i/ is incorporated primarily into ATP, resulting in an ATP/ADP S.A. ratio of 4.0 for ..cap alpha..KG, 2.7 for pyruvate/malate, and 2.8 for acetylcarnitine/malate. These data are consistent with phosphorylation of ADP during substrate level phosphorylation in the citric acid cycle.

  3. Phenotype and Genotype Characterization of Adenine Phosphoribosyltransferase Deficiency

    PubMed Central

    Bollée, Guillaume; Dollinger, Cécile; Boutaud, Lucile; Guillemot, Delphine; Bensman, Albert; Harambat, Jérôme; Deteix, Patrice; Daudon, Michel; Knebelmann, Bertrand

    2010-01-01

    Adenine phosphoribosyltransferase (APRT) deficiency is a rare autosomal recessive disorder causing 2,8-dihydroxyadenine stones and renal failure secondary to intratubular crystalline precipitation. Little is known regarding the clinical presentation of APRT deficiency, especially in the white population. We retrospectively reviewed all 53 cases of APRT deficiency (from 43 families) identified at a single institution between 1978 and 2009. The median age at diagnosis was 36.3 years (range 0.5 to 78.0 years). In many patients, a several-year delay separated the onset of symptoms and diagnosis. Of the 40 patients from 33 families with full clinical data available, 14 (35%) had decreased renal function at diagnosis. Diagnosis occurred in six (15%) patients after reaching ESRD, with five diagnoses made at the time of disease recurrence in a renal allograft. Eight (20%) patients reached ESRD during a median follow-up of 74 months. Thirty-one families underwent APRT sequencing, which identified 54 (87%) mutant alleles on the 62 chromosomes analyzed. We identified 18 distinct mutations. A single T insertion in a splice donor site in intron 4 (IVS4 + 2insT), which produces a truncated protein, accounted for 40.3% of the mutations. We detected the IVS4 + 2insT mutation in two (0.98%) of 204 chromosomes of healthy newborns. This report, which is the largest published series of APRT deficiency to date, highlights the underdiagnosis and potential severity of this disease. Early diagnosis is crucial for initiation of effective treatment with allopurinol and for prevention of renal complications. PMID:20150536

  4. Trialkylborane-Assisted CO(2) Reduction by Late Transition Metal Hydrides.

    PubMed

    Miller, Alexander J M; Labinger, Jay A; Bercaw, John E

    2011-01-01

    Trialkylborane additives promote reduction of CO(2) to formate by bis(diphosphine) Ni(II) and Rh(III) hydride complexes. The late transition metal hydrides, which can be formed from dihydrogen, transfer hydride to CO(2) to give a formate-borane adduct. The borane must be of appropriate Lewis acidity: weaker acids do not show significant hydride transfer enhancement, while stronger acids abstract hydride without CO(2) reduction. The mechanism likely involves a pre-equilibrium hydride transfer followed by formation of a stabilizing formate-borane adduct.

  5. Chemical probing of adenine residues within the secondary structure of rabbit /sup 18/S ribosomal RNA

    SciTech Connect

    Rairkar, A.; Rubino, H.M.; Lockard, R.E.

    1988-01-26

    The location of unpaired adenine residues within the secondary structure of rabbit /sup 18/S ribosomal RNA was determined by chemical probing. Naked /sup 18/S rRNA was first prepared by digestion of purified 40S subunits with matrix-bound proteinase K in sodium dodecyl sulfate, thereby omitting the use of nucleic acid denaturants. Adenines within naked /sup 18/S rRNA were chemically probed by using either diethyl pyrocarbonate or dimethyl sulfate, which specifically react with unpaired nucleotides. Adenine modification sites were identified by polyacrylamide sequencing gel electrophoresis either upon aniline-induced strand scission of /sup 32/P-end-labeled intact and fragmented rRNA or by primer extension using sequence-specific DNA oligomers with reverse transcriptase. The data indicate good agreement between the general pattern of adenine reactivity and the location of unpaired regions in /sup 18/S rRNA determined by comparative sequence analysis. The overall reactivity of adenine residues toward single-strand-specific chemical probes was, also, similar for both rabbit and Escherichia coli small rRNA. The number of strongly reactive adenines appearing within phylogenetically determined helical segments, however, was greater in rabbit /sup 18/S rRNA than for E. coli /sup 16/S rRNA. Some of these adenines were found clustered in specific helices. Such differences suggest a greater irregularity of many of the helical elements within mammalian /sup 18/S rRNA, as compared with prokaryotic /sup 16/S rRNA. These helical irregularities could be important for protein association and also may represent biologically relevant flexible regions of the molecule.

  6. Dissection of the PHO pathway in Schizosaccharomyces pombe using epistasis and the alternate repressor adenine.

    PubMed

    Estill, Molly; Kerwin-Iosue, Christine L; Wykoff, Dennis D

    2015-05-01

    In Saccharomyces cerevisiae, intracellular phosphate levels are maintained by the PHO pathway, activation of which is assayed by increased phosphatase activity. The PHO pathway of Schizosaccharomyces pombe upregulates phosphatase activity (encoded by pho1 (+)) during low extracellular phosphate levels, but the underlying mechanism is poorly understood. We utilized an alternate repressor of pho1 (+) expression (adenine supplementation) along with epistasis analysis to develop a model of how S. pombe PHO pathway components interact. Analyzing Pho1 activity in S. pombe PHO pathway deletion mutants during adenine starvation, we observed most mutants with a phosphatase defect in phosphate starvation also had a defect in adenine starvation. Pho7, a transcription factor in the PHO pathway, is necessary for an adenine starvation-mediated increase in Pho1 activity. Comparing adenine starvation to phosphate starvation, there are differences in the degree to which individual mutants regulate the two responses. Through epistasis studies, we identified two positive regulatory arms and one repressive arm of the PHO pathway. PKA activation is a positive regulator of Pho1 activity under both environmental conditions and is critical for transducing adenine concentrations in the cell. The synthesis of IP7 also appears critical for the induction of Pho1 activity during adenine starvation, but IP7 is not critical during phosphate starvation, which differs from S. cerevisiae. Finally, Csk1 is critical for repression of pho1 (+) expression during phosphate starvation. We believe all of these regulatory arms converge to increase transcription of pho1 (+) and some of the regulation acts through pho7 (+).

  7. Designing metal hydride complexes for water splitting reactions: a molecular electrostatic potential approach.

    PubMed

    Sandhya, K S; Suresh, Cherumuttathu H

    2014-08-28

    The hydridic character of octahedral metal hydride complexes of groups VI, VII and VIII has been systematically studied using molecular electrostatic potential (MESP) topography. The absolute minimum of MESP at the hydride ligand (Vmin) and the MESP value at the hydride nucleus (VH) are found to be very good measures of the hydridic character of the hydride ligand. The increasing/decreasing electron donating feature of the ligand environment is clearly reflected in the increasing/decreasing negative character of Vmin and VH. The formation of an outer sphere metal hydride-water complex showing the HH dihydrogen interaction is supported by the location and the value of Vmin near the hydride ligand. A higher negative MESP suggested lower activation energy for H2 elimination. Thus, MESP features provided a way to fine-tune the ligand environment of a metal-hydride complex to achieve high hydridicity for the hydride ligand. The applicability of an MESP based hydridic descriptor in designing water splitting reactions is tested for group VI metal hydride model complexes of tungsten.

  8. Chemical Hydride Slurry for Hydrogen Production and Storage

    SciTech Connect

    McClaine, Andrew W

    2008-09-30

    The purpose of this project was to investigate and evaluate the attractiveness of using a magnesium chemical hydride slurry as a hydrogen storage, delivery, and production medium for automobiles. To fully evaluate the potential for magnesium hydride slurry to act as a carrier of hydrogen, potential slurry compositions, potential hydrogen release techniques, and the processes (and their costs) that will be used to recycle the byproducts back to a high hydrogen content slurry were evaluated. A 75% MgH2 slurry was demonstrated, which was just short of the 76% goal. This slurry is pumpable and storable for months at a time at room temperature and pressure conditions and it has the consistency of paint. Two techniques were demonstrated for reacting the slurry with water to release hydrogen. The first technique was a continuous mixing process that was tested for several hours at a time and demonstrated operation without external heat addition. Further work will be required to reduce this design to a reliable, robust system. The second technique was a semi-continuous process. It was demonstrated on a 2 kWh scale. This system operated continuously and reliably for hours at a time, including starts and stops. This process could be readily reduced to practice for commercial applications. The processes and costs associated with recycling the byproducts of the water/slurry reaction were also evaluated. This included recovering and recycling the oils of the slurry, reforming the magnesium hydroxide and magnesium oxide byproduct to magnesium metal, hydriding the magnesium metal with hydrogen to form magnesium hydride, and preparing the slurry. We found that the SOM process, under development by Boston University, offers the lowest cost alternative for producing and recycling the slurry. Using the H2A framework, a total cost of production, delivery, and distribution of $4.50/kg of hydrogen delivered or $4.50/gge was determined. Experiments performed at Boston

  9. Glibenclamide improves kidney and heart structure and function in the adenine-diet model of chronic kidney disease.

    PubMed

    Diwan, Vishal; Gobe, Glenda; Brown, Lindsay

    2014-01-01

    The development of chronic kidney disease (CKD) and associated cardiovascular disease involves free radical damage and inflammation. Addition of adenine to the diet induces inflammation followed by CKD and cardiovascular disease. NOD-like receptor protein-3 (NLRP-3) is pro-inflammatory in the kidney; glibenclamide inhibits production of NLRP-3. Male Wistar rats were fed either control rat food or adenine (0.25%) in this food for 16 weeks. Glibenclamide (10 mg/kg/day) was administered to two groups with and without adenine for the final 8 weeks. Kidney function (blood urea nitrogen/BUN, plasma creatinine/PCr, plasma uric acid, proteinuria), kidney structure (fibrosis, inflammation), cardiovascular parameters (blood pressure, left ventricular stiffness, vascular responses and echocardiography) and protein expression of markers for oxidative stress (HO-1), and inflammation (TNF-α, NLRP-3) were assessed. In adenine-fed rats, glibenclamide decreased BUN (controls: 6±0.6; adenine: 56.6±5.4; adenine+glibenclamide: 19.4±2.7 mmol/L), PCr (controls: 42±2.8; adenine: 268±23; adenine+glibenclamide: 81±10 μmol/L), proteinuria (controls: 150±7.4; adenine: 303±19; adenine+glibenclamide: 220±13 μmol/L) (all p<0.05). Glibenclamide decreased infiltration of chronic inflammatory cells, fibrosis, tubular damage and expression of HO-1, TNF-α and NLRP-3 in the kidney. Glibenclamide did not alter plasma uric acid concentrations (controls: 38±1; adenine: 63±4; adenine+glibenclamide: 69±14 μmol/L). Cardiovascular changes included decreased systolic blood pressure and improved vascular responses although cardiac fibrosis, left ventricular stiffness and hypertrophy were not reduced. Glibenclamide improved kidney structure and function in CKD and decreased some cardiovascular parameters. Inflammatory markers and cell populations were attenuated by glibenclamide in kidneys.

  10. Influence of uranium hydride oxidation on uranium metal behaviour

    SciTech Connect

    Patel, N.; Hambley, D.; Clarke, S.A.; Simpson, K.

    2013-07-01

    This work addresses concerns that the rapid, exothermic oxidation of active uranium hydride in air could stimulate an exothermic reaction (burning) involving any adjacent uranium metal, so as to increase the potential hazard arising from a hydride reaction. The effect of the thermal reaction of active uranium hydride, especially in contact with uranium metal, does not increase in proportion with hydride mass, particularly when considering large quantities of hydride. Whether uranium metal continues to burn in the long term is a function of the uranium metal and its surroundings. The source of the initial heat input to the uranium, if sufficient to cause ignition, is not important. Sustained burning of uranium requires the rate of heat generation to be sufficient to offset the total rate of heat loss so as to maintain an elevated temperature. For dense uranium, this is very difficult to achieve in naturally occurring circumstances. Areas of the uranium surface can lose heat but not generate heat. Heat can be lost by conduction, through contact with other materials, and by convection and radiation, e.g. from areas where the uranium surface is covered with a layer of oxidised material, such as burned-out hydride or from fuel cladding. These rates of heat loss are highly significant in relation to the rate of heat generation by sustained oxidation of uranium in air. Finite volume modelling has been used to examine the behaviour of a magnesium-clad uranium metal fuel element within a bottle surrounded by other un-bottled fuel elements. In the event that the bottle is breached, suddenly, in air, it can be concluded that the bulk uranium metal oxidation reaction will not reach a self-sustaining level and the mass of uranium oxidised will likely to be small in relation to mass of uranium hydride oxidised. (authors)

  11. Evolution of hypervariable microsatellites in apomictic polyploid lineages of Ranunculus carpaticola: directional bias at dinucleotide loci.

    PubMed

    Paun, Ovidiu; Hörandl, Elvira

    2006-09-01

    Microsatellites are widely used in genetic and evolutionary analyses, but their own evolution is far from simple. The mechanisms maintaining the mutational patterns of simple repeats and the typical stable allele-frequency distributions are still poorly understood. Asexual lineages may provide particularly informative models for the indirect study of microsatellite evolution, because their genomes act as complete linkage groups, with mutations being the only source of genetic variation. Here, we study the direction of accumulated dinucleotide microsatellite mutations in wild asexual lineages of hexaploid Ranunculus carpaticola. Whereas the overall number of contractions is not significantly different from that of expansions, the within-locus frequency of contractions, but not of expansions, significantly increases with allele length. Moreover, within-locus polymorphism is positively correlated with allele length, but this relationship is due solely to the influence of contraction mutations. Such asymmetries may explain length constraints generally observed with microsatellites and are consistent with stable, bell-shaped allele-frequency distributions. Although apomictic and allohexaploid, the R. carpaticola lineages show mutational patterns resembling the trends observed in a broad range of organisms, including sexuals and diploids, suggesting that, even if not of germline origin, the mutations in these apomicts may be the consequence of similar mechanisms.

  12. Detection of mercury-TpT dinucleotide binding by Raman spectra: a computational study.

    PubMed

    Benda, Ladislav; Straka, Michal; Sychrovský, Vladimír; Bouř, Petr; Tanaka, Yoshiyuki

    2012-08-16

    The Hg(2+) ion stabilizes the thymine-thymine mismatched base pair and provides new ways of creating various DNA structures. Recently, such T-Hg-T binding was detected by the Raman spectroscopy. In this work, detailed differences in vibrational frequencies and Raman intensity patterns in the free TpT dinucleotide and its metal-mediated complex (TpT·Hg)(2) are interpreted on the basis of quantum chemical modeling. The computations verified specific marker Raman bands indicating the effect of mercury binding to DNA. Although the B3LYP functional well-describes the Raman frequencies, a dispersion correction had to be added for all atoms including mercury to obtain realistic geometry of the (TpT·Hg)(2) dimer. Only then, the DFT complex structure agreed with those obtained with the wave function-based MP2 method. The aqueous solvent modeled as a polarizable continuum had a minor effect on the dispersion interaction, but it stabilized conformations of the sugar and phosphate parts. A generalized definition of internal coordinate force field was introduced to monitor covalent bond mechanical strengthening and weakening upon the Hg(2+) binding. Induced vibrational frequency shifts were rationalized in terms of changes in electronic structure. The simulations thus also provided reliable insight into the complex structure and stability.

  13. Predicting DNA Methylation State of CpG Dinucleotide Using Genome Topological Features and Deep Networks.

    PubMed

    Wang, Yiheng; Liu, Tong; Xu, Dong; Shi, Huidong; Zhang, Chaoyang; Mo, Yin-Yuan; Wang, Zheng

    2016-01-22

    The hypo- or hyper-methylation of the human genome is one of the epigenetic features of leukemia. However, experimental approaches have only determined the methylation state of a small portion of the human genome. We developed deep learning based (stacked denoising autoencoders, or SdAs) software named "DeepMethyl" to predict the methylation state of DNA CpG dinucleotides using features inferred from three-dimensional genome topology (based on Hi-C) and DNA sequence patterns. We used the experimental data from immortalised myelogenous leukemia (K562) and healthy lymphoblastoid (GM12878) cell lines to train the learning models and assess prediction performance. We have tested various SdA architectures with different configurations of hidden layer(s) and amount of pre-training data and compared the performance of deep networks relative to support vector machines (SVMs). Using the methylation states of sequentially neighboring regions as one of the learning features, an SdA achieved a blind test accuracy of 89.7% for GM12878 and 88.6% for K562. When the methylation states of sequentially neighboring regions are unknown, the accuracies are 84.82% for GM12878 and 72.01% for K562. We also analyzed the contribution of genome topological features inferred from Hi-C. DeepMethyl can be accessed at http://dna.cs.usm.edu/deepmethyl/.

  14. Predicting DNA Methylation State of CpG Dinucleotide Using Genome Topological Features and Deep Networks

    NASA Astrophysics Data System (ADS)

    Wang, Yiheng; Liu, Tong; Xu, Dong; Shi, Huidong; Zhang, Chaoyang; Mo, Yin-Yuan; Wang, Zheng

    2016-01-01

    The hypo- or hyper-methylation of the human genome is one of the epigenetic features of leukemia. However, experimental approaches have only determined the methylation state of a small portion of the human genome. We developed deep learning based (stacked denoising autoencoders, or SdAs) software named “DeepMethyl” to predict the methylation state of DNA CpG dinucleotides using features inferred from three-dimensional genome topology (based on Hi-C) and DNA sequence patterns. We used the experimental data from immortalised myelogenous leukemia (K562) and healthy lymphoblastoid (GM12878) cell lines to train the learning models and assess prediction performance. We have tested various SdA architectures with different configurations of hidden layer(s) and amount of pre-training data and compared the performance of deep networks relative to support vector machines (SVMs). Using the methylation states of sequentially neighboring regions as one of the learning features, an SdA achieved a blind test accuracy of 89.7% for GM12878 and 88.6% for K562. When the methylation states of sequentially neighboring regions are unknown, the accuracies are 84.82% for GM12878 and 72.01% for K562. We also analyzed the contribution of genome topological features inferred from Hi-C. DeepMethyl can be accessed at http://dna.cs.usm.edu/deepmethyl/.

  15. Efficient UV-induced charge separation and recombination in an 8-oxoguanine-containing dinucleotide

    PubMed Central

    Zhang, Yuyuan; Dood, Jordan; Beckstead, Ashley A.; Li, Xi-Bo; Nguyen, Khiem V.; Burrows, Cynthia J.; Improta, Roberto; Kohler, Bern

    2014-01-01

    During the early evolution of life, 8-oxo-7,8-dihydro-2′-deoxyguanosine (O) may have functioned as a proto-flavin capable of repairing cyclobutane pyrimidine dimers in DNA or RNA by photoinduced electron transfer using longer wavelength UVB radiation. To investigate the ability of O to act as an excited-state electron donor, a dinucleotide mimic of the FADH2 cofactor containing O at the 5′-end and 2′-deoxyadenosine at the 3′-end was studied by femtosecond transient absorption spectroscopy in aqueous solution. Following excitation with a UV pulse, a broadband mid-IR pulse probed vibrational modes of ground-state and electronically excited molecules in the double-bond stretching region. Global analysis of time- and frequency-resolved transient absorption data coupled with ab initio quantum mechanical calculations reveal vibrational marker bands of nucleobase radical ions formed by electron transfer from O to 2′-deoxyadenosine. The quantum yield of charge separation is 0.4 at 265 nm, but decreases to 0.1 at 295 nm. Charge recombination occurs in 60 ps before the O radical cation can lose a deuteron to water. Kinetic and thermodynamic considerations strongly suggest that all nucleobases can undergo ultrafast charge separation when π-stacked in DNA or RNA. Interbase charge transfer is proposed to be a major decay pathway for UV excited states of nucleic acids of great importance for photostability as well as photoredox activity. PMID:25071180

  16. DNA Adenine Methyltransferase Influences the Virulence of Aeromonas hydrophila

    PubMed Central

    Erova, Tatiana E.; Pillai, Lakshmi; Fadl, Amin A.; Sha, Jian; Wang, Shaofei; Galindo, Cristi L.; Chopra, Ashok K.

    2006-01-01

    Among the various virulence factors produced by Aeromonas hydrophila, a type II secretion system (T2SS)-secreted cytotoxic enterotoxin (Act) and the T3SS are crucial in the pathogenesis of Aeromonas-associated infections. Our laboratory molecularly characterized both Act and the T3SS from a diarrheal isolate, SSU of A. hydrophila, and defined the role of some regulatory genes in modulating the biological effects of Act. In this study, we cloned, sequenced, and expressed the DNA adenine methyltransferase gene of A. hydrophila SSU (damAhSSU) in a T7 promoter-based vector system using Escherichia coli ER2566 as a host strain, which could alter the virulence potential of A. hydrophila. Recombinant Dam, designated as M.AhySSUDam, was produced as a histidine-tagged fusion protein and purified from an E. coli cell lysate using nickel affinity chromatography. The purified Dam had methyltransferase activity, based on its ability to transfer a methyl group from S-adenosyl-l-methionine to N6-methyladenine-free lambda DNA and to protect methylated lambda DNA from digestion with DpnII but not against the DpnI restriction enzyme. The dam gene was essential for the viability of the bacterium, and overproduction of Dam in A. hydrophila SSU, using an arabinose-inducible, PBAD promoter-based system, reduced the virulence of this pathogen. Specifically, overproduction of M.AhySSUDam decreased the motility of the bacterium by 58%. Likewise, the T3SS-associated cytotoxicity, as measured by the release of lactate dehydrogenase enzyme in murine macrophages infected with the Dam-overproducing strain, was diminished by 55% compared to that of a control A. hydrophila SSU strain harboring the pBAD vector alone. On the contrary, cytotoxic and hemolytic activities associated with Act as well as the protease activity in the culture supernatant of a Dam-overproducing strain were increased by 10-, 3-, and 2.4-fold, respectively, compared to those of the control A. hydrophila SSU strain. The Dam

  17. Diabetes and the control of pyruvate dehydrogenase in rat heart mitochondria by concentration ratios of adenosine triphosphate/adenosine diphosphate, of reduced/oxidized nicotinamide-adenine dinucleotide and of acetyl-coenzyme A/coenzyme A.

    PubMed Central

    Kerbey, A L; Radcliffe, P M; Randle, P J

    1977-01-01

    1. The proportion of active (dephosphorylated) pyruvate dehydrogenase in rat heart mitochondria was correlated with total concentration ratios of ATP/ADP, NADH/NAD+ and acetyl-CoA/CoA. These metabolites were measured with ATP-dependent and NADH-dependent luciferases. 2. Increase in the concentration ratio of NADH/NAD+ at constant [ATP]/[ADP] and [acetyl-CoA]/[CoA] was associated with increased phosphorylation and inactivation of pyruvate dehydrogenase. This was based on comparison between mitochondria incubated with 0.4mM- or 1mM-succinate and mitochondria incubated with 0.4mM-succinate+/-rotenone. 3. Increase in the concentration ratio acetyl-CoA/CoA at constant [ATP]/[ADP] and [NADH][NAD+] was associated with increased phosphorylation and inactivation of pyruvate dehydrogenase. This was based on comparison between incubations in 50 micrometer-palmitotoyl-L-carnitine and in 250 micrometer-2-oxoglutarate +50 micrometer-L-malate. 4. These findings are consistent with activation of the pyruvate dehydrogenase kinase reaction by high ratios of [NADH]/[NAD+] and of [acetyl-CoA]/[CoA]. 5. Comparison between mitochondria from hearts of diabetic and non-diabetic rats shows that phosphorylation and inactivation of pyruvate dehydrogenase is enhanced in alloxan-diabetes by some factor other than concentration ratios of ATP/ADP, NADH/NAD+ or acetyl-CoA/CoA. PMID:196589

  18. Ultra-performance liquid chromatography tandem mass-spectrometry (uplc-ms/ms) for the rapid, simultaneous analysis of thiamin, riboflavin, flavin adenine dinucleotide, nicotinamide and pyridoxal in human milk

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A novel, rapid and sensitive Ultra Performance Liquid-Chromatography tandem Mass-Spectrometry (UPLC-MS/MS) method for the simultaneous determination of several B-vitamins in human milk was developed. Resolution by retention time or multiple reaction monitoring (MRM) for thiamin, riboflavin, flavin a...

  19. The metabolic fate of the products of citrate cleavage. Adenosine triphosphate citrate lyase and nicotinamide–adenine dinucleotide phosphate-linked malate dehydrogenase in foetal and adult liver from ruminants and non-ruminants

    PubMed Central

    Hanson, R. W.; Ballard, F. J.

    1968-01-01

    1. Foetal rat liver slices incorporate the C-3 of aspartate and C-2 of glutamate into fatty acids at rates equal to those observed with adult rat liver slices. Incorporation of either of these labelled carbon atoms into fatty acids would require a functioning citrate-cleavage pathway which consists of the enzymes ATP–citrate lyase, NAD–malate dehydrogenase and NADP–malate dehydrogenase. However, NADP–malate dehydrogenase is present in foetal rat liver at only 5% of the activity detectable in adult rat liver. 2. From these findings and the effect of cofactors on the formation of 14CO2 from [1,5-14C2]citrate in liver supernatant fractions (100000g), it is suggested that NADP–malate dehydrogenase limits the citrate-cleavage sequence. 3. Measurement of the citrate-cleavage pathway by incorporation studies with [3-14C]aspartate and [U-14C]glucose and by determining the activities of ATP–citrate lyase and NADP–malate dehydrogenase have shown that this sequence of reactions is present in the liver of the bovine foetus but not in the adult. However, C-2 of glutamate is not incorporated into fatty acids or non-saponifiable lipid by bovine liver slices. This finding as well as those presented above for the adult and foetal rat liver are interpreted on the basis of a competition between phosphoenolpyruvate carboxykinase and NAD–malate dehydrogenase for oxaloacetate produced by the cleavage of citrate in the cytosol. PMID:4386407

  20. Hydrogen storage as a hydride. Citations from the International Aerospace Abstracts data base

    NASA Technical Reports Server (NTRS)

    Zollars, G. F.

    1980-01-01

    These citations from the international literature concern the storage of hydrogen in various metal hydrides. Binary and intermetallic hydrides are considered. Specific alloys discussed are iron titanium, lanthanium nickel, magnesium copper and magnesium nickel among others.

  1. One-pot synthesis of fluorescent polysaccharides: adenine grafted agarose and carrageenan.

    PubMed

    Oza, Mihir D; Prasad, Kamalesh; Siddhanta, A K

    2012-08-01

    New fluorescent polysaccharides were synthesized by grafting the nucleobase adenine on to the backbones of agarose and κ-carrageenan, which were characterized by FT-IR, (13)C NMR, TGA, XRD, UV, and fluorescence properties. The synthesis involved a rapid water based potassium persulfate (KPS) initiated method under microwave irradiation. The emission spectra of adenine grafted agarose and κ-carrageenan were recorded in aqueous (5×10(-5) M) solution, exhibiting λ(em,max) 347 nm by excitation at 261 nm, affording ca. 30% and 40% enhanced emission intensities, respectively compared to that of pure adenine solution in the same concentration. Similar emission intensity was recorded in the pure adenine solution at its molar equivalent concentrations present in the 5×10(-5) M solution of the agarose and carrageenan grafted products, that is, 3.28×10(-5) M and 4.5×10(-5) M respectively. These fluorescent adenine grafted products may have potential utility in various sensor applications.

  2. Determination of adenine based on the fluorescence recovery of the L-Tryptophan-Cu2+ complex

    NASA Astrophysics Data System (ADS)

    Duan, Ruilin; Li, Chunyan; Liu, Shaopu; Liu, Zhongfang; Li, Yuanfang; Yuan, Yusheng; Hu, Xiaoli

    2016-01-01

    A simple and sensitive method for determination of adenine was developed based on fluorescence quenching and recovery of L-Tryptophan (L-Trp). The fluorescence of L-Trp could efficiently quenched by copper ion compared with other common metal ions. Upon addition of adenine (Ade) in L-Trp-Cu(II) system, the fluorescence was reoccurred. Under the optimum conditions, the recovery fluorescence intensity was linearly correlated with the concentration of adenine in the range from 0.34 to 25.0 μmol L-1, with a correlation coefficient (R2) of 0.9994. The detection limit (3σ/k) was 0.046 μmol L-1, indicating that this method could applied to detect trace adenine. In this study, amino acids including L-Trp, D-Trp, L-Tyr, D-Tyr, L-Phe, D-Phe were investigated and only L-Trp could well chelated copper ion. Additionally, the mechanism of quench and recovery also were discussed and the method was successfully applied to detect the adenine in DNA with satisfactory results.

  3. Spectroscopic investigation on cocrystal formation between adenine and fumaric acid based on infrared and Raman techniques.

    PubMed

    Du, Yong; Fang, Hong Xia; Zhang, Qi; Zhang, Hui Li; Hong, Zhi

    2016-01-15

    As an important component of double-stranded DNA, adenine has powerful hydrogen-bond capability, due to rich hydrogen bond donors and acceptors existing within its molecular structure. Therefore, it is easy to form cocrystal between adenine and other small molecules with intermolecular hydrogen-bond effect. In this work, cocrystal of adenine and fumaric acid has been characterized as model system by FT-IR and FT-Raman spectral techniques. The experimental results show that the cocrystal formed between adenine and fumaric acid possesses unique spectroscopical characteristic compared with that of starting materials. Density functional theory (DFT) calculation has been performed to optimize the molecular structures and simulate vibrational modes of adenine, fumaric acid and the corresponding cocrystal. Combining the theoretical and experimental vibrational results, the characteristic bands corresponding to bending and stretching vibrations of amino and carbonyl groups within cocrystal are shifted into lower frequencies upon cocrystal formation, and the corresponding bond lengths show some increase due to the effect of intermolecular hydrogen bonding. Different vibrational modes shown in the experimental spectra have been assigned based on the simulation DFT results. The study could provide experimental and theoretical benchmarks to characterize cocrystal formed between active ingredients and cocrystal formers and also the intermolecular hydrogen-bond effect within cocrystal formation process by vibrational spectroscopic techniques.

  4. Determination of adenine based on the fluorescence recovery of the L-Tryptophan-Cu(2+) complex.

    PubMed

    Duan, Ruilin; Li, Chunyan; Liu, Shaopu; Liu, Zhongfang; Li, Yuanfang; Yuan, Yusheng; Hu, Xiaoli

    2016-01-05

    A simple and sensitive method for determination of adenine was developed based on fluorescence quenching and recovery of L-Tryptophan (L-Trp). The fluorescence of L-Trp could efficiently quenched by copper ion compared with other common metal ions. Upon addition of adenine (Ade) in L-Trp-Cu(II) system, the fluorescence was reoccurred. Under the optimum conditions, the recovery fluorescence intensity was linearly correlated with the concentration of adenine in the range from 0.34 to 25.0μmolL(-1), with a correlation coefficient (R(2)) of 0.9994. The detection limit (3σ/k) was 0.046μmolL(-1), indicating that this method could applied to detect trace adenine. In this study, amino acids including L-Trp, D-Trp, L-Tyr, D-Tyr, L-Phe, D-Phe were investigated and only L-Trp could well chelated copper ion. Additionally, the mechanism of quench and recovery also were discussed and the method was successfully applied to detect the adenine in DNA with satisfactory results.

  5. Binding of adenine to Stx2, the protein toxin from Escherichia coli O157:H7

    SciTech Connect

    Fraser, Marie E.; Cherney, Maia M.; Marcato, Paola; Mulvey, George L.; Armstrong, Glen D.; James, Michael N. G.

    2006-07-01

    Crystals of Stx2 were grown in the presence of adenosine and adenine. In both cases, the resulting electron density showed only adenine bound at the active site of the A subunit, proving that the holotoxin is an active N-glycosidase. Stx2 is a protein toxin whose catalytic subunit acts as an N-glycosidase to depurinate a specific adenine base from 28S rRNA. In the holotoxin, the catalytic portion, A1, is linked to the rest of the A subunit, A2, and A2 interacts with the pentameric ring formed by the five B subunits. In order to test whether the holotoxin is active as an N-glycosidase, Stx2 was crystallized in the presence of adenosine and adenine. The crystals diffracted to ∼1.8 Å and showed clear electron density for adenine in the active site. Adenosine had been cleaved, proving that Stx2 is an active N-glycosidase. While the holotoxin is active against small substrates, it would be expected that the B subunits would interfere with the binding of the 28S rRNA.

  6. Spectroscopic investigation on cocrystal formation between adenine and fumaric acid based on infrared and Raman techniques

    NASA Astrophysics Data System (ADS)

    Du, Yong; Fang, Hong Xia; Zhang, Qi; Zhang, Hui Li; Hong, Zhi

    2016-01-01

    As an important component of double-stranded DNA, adenine has powerful hydrogen-bond capability, due to rich hydrogen bond donors and acceptors existing within its molecular structure. Therefore, it is easy to form cocrystal between adenine and other small molecules with intermolecular hydrogen-bond effect. In this work, cocrystal of adenine and fumaric acid has been characterized as model system by FT-IR and FT-Raman spectral techniques. The experimental results show that the cocrystal formed between adenine and fumaric acid possesses unique spectroscopical characteristic compared with that of starting materials. Density functional theory (DFT) calculation has been performed to optimize the molecular structures and simulate vibrational modes of adenine, fumaric acid and the corresponding cocrystal. Combining the theoretical and experimental vibrational results, the characteristic bands corresponding to bending and stretching vibrations of amino and carbonyl groups within cocrystal are shifted into lower frequencies upon cocrystal formation, and the corresponding bond lengths show some increase due to the effect of intermolecular hydrogen bonding. Different vibrational modes shown in the experimental spectra have been assigned based on the simulation DFT results. The study could provide experimental and theoretical benchmarks to characterize cocrystal formed between active ingredients and cocrystal formers and also the intermolecular hydrogen-bond effect within cocrystal formation process by vibrational spectroscopic techniques.

  7. Electrochemical studies on the oxidation of guanine and adenine at cyclodextrin modified electrodes.

    PubMed

    Abbaspour, Abdolkarim; Noori, Abolhassan

    2008-12-01

    An electrochemical sensor for guanine and adenine using cyclodextrin-modified poly(N-acetylaniline) (PNAANI) on a carbon paste electrode has been developed. The oxidation mechanism of guanine and adenine on the surface of the electrode was investigated by cyclic voltammetry. It was found that the electrode processes are irreversible, pH dependent, and involve several reaction products. The electron transfer process occurs in consecutive steps with the formation of a strongly adsorbed intermediate on the electrode surface. Also, a new method for estimating the apparent formation constants of guanine and adenine with the immobilized cyclodextrins, through the change of surface coverage of studied analytes has been reported. Both guanine and adenine showed linear concentrations in the range of 0.1-10 microM by using differential pulse voltammetry, with an experimental limit of detection down to 0.05 microM. Linear concentration ranges of 2-150 microM for guanine and 6-104 microM for adenine have been found when cyclic voltammetry was used for determination of both analytes.

  8. Alkylation by propylene oxide of deoxyribonucleic acid, adenine, guanosine and deoxyguanylic acid

    PubMed Central

    Lawley, P. D.; Jarman, M.

    1972-01-01

    1. Propylene oxide reacts with DNA in aqueous buffer solution at about neutral pH to yield two principal products, identified as 7-(2-hydroxypropyl)guanine and 3-(2-hydroxypropyl)adenine, which hydrolyse out of the alkylated DNA at neutral pH values at 37°C. 2. These products were obtained in quantity by reactions between propylene oxide and guanosine or adenine respectively. 3. The reactions between propylene oxide and adenine in acetic acid were parallel to those between dimethyl sulphate and adenine in neutral aqueous solution; the alkylated positions in adenine in order of decreasing reactivity were N-3, N-1 and N-9. A method for separating these alkyladenines is described. 4. Deoxyguanylic acid sodium salt was alkylated at N-7 by propylene oxide in neutral aqueous solution. 5. The nature of the side chain in the principal alkylation products was established by mass spectrometry, and the nature of the products is consistent with their formation by the bimolecular reaction mechanism. PMID:5073240

  9. Fatigue crack growth in lithium hydride

    SciTech Connect

    Healy, T.E.

    1993-09-01

    Subcritical fatigue crack growth, from cyclic tensile loading, was demonstrated in warm pressed Polycrystalline lithium hydride. Experiments were performed with cyclic tension-tension crack opening (mode I) loads applied to a pre-cracked compact type specimen in an argon environment at a temperature of 21C (70F). The fatigue crack growth was found to occur between 7.56 {times} 10{sup {minus}ll} M/cycle (2.98 {times} l0{sup {minus}9} in/cycle) and 2.35 {times} l0{sup {minus}8} m/cycle (9.24{times}10{sup {minus}7} in/cycle) for a range of stress intensity factors between 1.04 MPa{center_dot}{radical}m (0.95 ksi{center_dot}{radical}in) and 1.49 MPa{center_dot}{radical}m (1.36 ksi{center_dot}{radical}in). The rate of fatigue crack growth from cyclic tensile loading was found to be in excess of crack growth from sustained loading at an equivalent stress intensity factor. Furthermore, a fatigue threshold was not evident from the acquired data.

  10. Permeation rates for RTF metal hydride vessels

    SciTech Connect

    Klein, J.E.

    1992-05-21

    Contamination rates have been estimated for the RTF nitrogen heating and cooling system (NH and CS) due to tritium permeation through the walls of metal hydride vessels. Tritium contamination of the NH and CS will be seen shortly after start-up of the RTF with the majority of it coming from the TCAP units. Contamination rates of the NH and CS are estimated to exceed 400 Ci/year after three years of operation and will elevate tritium concentrations in the NH and CS above 6 {times} 10{sup {minus}3} {mu}Ci/cc. To reduce tritium activity in the NH and CS, a stripper or ``getter`` bed may need to be installed in the NH and CS. Increasing the purge rate of nitrogen from the NH and CS is shown to be an impractical method for reducing tritium activity due to the high purge rates required. Stripping of the NH and CS nitrogen in the glove box stripper system will give a temporary lowering of tritium activity in the NH and CS, but tritium activity will return to its previous level in approximately two weeks.

  11. Transition-Metal Hydride Radical Cations.

    PubMed

    Hu, Yue; Shaw, Anthony P; Estes, Deven P; Norton, Jack R

    2016-08-10

    Transition-metal hydride radical cations (TMHRCs) are involved in a variety of chemical and biochemical reactions, making a more thorough understanding of their properties essential for explaining observed reactivity and for the eventual development of new applications. Generally, these species may be treated as the ones formed by one-electron oxidation of diamagnetic analogues that are neutral or cationic. Despite the importance of TMHRCs, the generally sensitive nature of these complexes has hindered their development. However, over the last four decades, many more TMHRCs have been synthesized, characterized, isolated, or hypothesized as reaction intermediates. This comprehensive review focuses on experimental studies of TMHRCs reported through the year 2014, with an emphasis on isolated and observed species. The methods used for the generation or synthesis of TMHRCs are surveyed, followed by a discussion about the stability of these complexes. The fundamental properties of TMHRCs, especially those pertaining to the M-H bond, are described, followed by a detailed treatment of decomposition pathways. Finally, reactions involving TMHRCs as intermediates are described.

  12. Charging efficiency of metal-hydride electrodes

    NASA Astrophysics Data System (ADS)

    Chen, J.; Dou, S. X.; Bradhurst, D.; Liu, H. K.

    The charging efficiencies of MmNi 5, MmNi 4.5Mn 0.5, MmNi 3.8Co 0.7Mn 0.5, ZrV 0.6Ni 1.4, ZrV 0.6Mn 0.4Ni 1.0, ZrV 0.6Mn 0.4Co 0.2Ni 0.8 allay electrodes (Mm = Mischmetal) are investigated in terms of hydrogen evolution. Experiments are conducted to optimize: (i) elemental composition of the MmNi 5 system and Zr-based Laves-phase hydrogen storage alloys; (ii) additive materials, such as cobalt powder, nickel powder, Teflonized carbons, and acetylene black; (iii) the proportion of the additives in the alloy; (iv) the best percentage of the composite additives in the metal-hydride electrodes. The results show that the electrode activation, charging efficiency and high-rate discharge depend greatly on the active materials, as well as the type and the amount of the additives in the electrodes.

  13. Hydrides in Space: Past, Present, and Future

    NASA Astrophysics Data System (ADS)

    Lis, D. C.; Goldsmith, P. F.; Bergin, E. A.; Falgarone, E.; Gerin, M.; Roueff, E.

    2009-12-01

    One of the central questions of modern astrophysics concerns the life cycle of molecules in the Universe—from the diffuse interstellar medium to planetary systems—and the chemical pathways leading from simple atoms and diatomic molecules to complex organic species. In the past two decades, the Caltech Submillimeter Observatory (CSO) has contributed a number of key discoveries on these topics. Light hydrides are of particular interest for astrochemistry, as the basic building blocks of the chemical networks in both diffuse and dense clouds. Ongoing and planned submillimeter wide-field continuum surveys will yield hundreds of potential galactic targets suitable for detailed spectroscopic follow-ups. Recent advances in detector and digital spectrometer technologies promise to truly revolutionize further the field of high-resolution submillimeter spectroscopy and its application to the study of the life cycle of molecules. This will greatly improve our understanding of astrochemistry, astrobiology, the origin of life on Earth, and allow assessing the possibilities of life in other planetary systems.

  14. Comparison of the interactions in the rare gas hydride and Group 2 metal hydride anions.

    PubMed

    Harris, Joe P; Manship, Daniel R; Breckenridge, W H; Wright, Timothy G

    2014-02-28

    We study both the rare gas hydride anions, RG-H(-) (RG = He-Rn) and Group 2 (Group IIa) metal hydride anions, MIIaH(-) (MIIa = Be-Ra), calculating potential energy curves at the CCSD(T) level with augmented quadruple and quintuple basis sets, and extrapolating the results to the basis set limit. We report spectroscopic parameters obtained from these curves; additionally, we study the Be-He complex. While the RG-H(-) and Be-He species are weakly bound, we show that, as with the previously studied BeH(-) and MgH(-) species, the other MIIaH(-) species are strongly bound, despite the interactions nominally also being between two closed shell species: M(ns(2)) and H(-)(1s(2)). We gain insight into the interactions using contour plots of the electron density changes and population analyses. For both series, the calculated dissociation energy is significantly less than the ion/induced-dipole attraction term, confirming that electron repulsion is important in these species; this effect is more dramatic for the MIIaH(-) species than for RG-H(-). Our analyses lead us to conclude that the stronger interaction in the case of the MIIaH(-) species arises from sp and spd hybridization, which allows electron density on the MIIa atom to move away from the incoming H(-).

  15. Multidimensional simulations of hydrides during fuel rod lifecycle

    NASA Astrophysics Data System (ADS)

    Stafford, D. S.

    2015-11-01

    In light water reactor fuel rods, waterside corrosion of zirconium-alloy cladding introduces hydrogen into the cladding, where it is slightly soluble. When the solubility limit is reached, the hydrogen precipitates into crystals of zirconium hydride which decrease the ductility of the cladding and may lead to cladding failure during dry storage or transportation events. The distribution of the hydride phase and the orientation of the crystals depend on the history of the spatial temperature and stress profiles in the cladding. In this work, we have expanded the existing hydride modeling capability in the BISON fuel performance code with the goal of predicting both global and local effects on the radial, azimuthal and axial distribution of the hydride phase. We compare results from 1D simulations to published experimental data. We demonstrate the new capability by simulating in 2D a fuel rod throughout a lifecycle that includes irradiation, short-term storage in the spent fuel pool, drying, and interim storage in a dry cask. Using the 2D simulations, we present qualitative predictions of the effects of the inter-pellet gap and the drying conditions on the growth of a hydride rim.

  16. Sodium-based hydrides for thermal energy applications

    NASA Astrophysics Data System (ADS)

    Sheppard, D. A.; Humphries, T. D.; Buckley, C. E.

    2016-04-01

    Concentrating solar-thermal power (CSP) with thermal energy storage (TES) represents an attractive alternative to conventional fossil fuels for base-load power generation. Sodium alanate (NaAlH4) is a well-known sodium-based complex metal hydride but, more recently, high-temperature sodium-based complex metal hydrides have been considered for TES. This review considers the current state of the art for NaH, NaMgH3- x F x , Na-based transition metal hydrides, NaBH4 and Na3AlH6 for TES and heat pumping applications. These metal hydrides have a number of advantages over other classes of heat storage materials such as high thermal energy storage capacity, low volume, relatively low cost and a wide range of operating temperatures (100 °C to more than 650 °C). Potential safety issues associated with the use of high-temperature sodium-based hydrides are also addressed.

  17. Investigation of metal hydride materials as hydrogen reservoirs for metal-hydrogen batteries

    NASA Technical Reports Server (NTRS)

    ONISCHAK

    1976-01-01

    The performance and suitability of various metal hydride materials were examined for use as possible hydrogen storage reservoirs for secondary metal-hydrogen batteries. Lanthanum pentanickel hydride appears as a probable candidate in terms of stable hydrogen supply under feasible thermal conditions. A kinetic model describing the decomposition rate data of the hydride has been developed.

  18. The coordination chemistry of organo-hydride donors: new prospects for efficient multi-electron reduction.

    PubMed

    McSkimming, Alex; Colbran, Stephen B

    2013-06-21

    In biological reduction processes the dihydronicotinamides NAD(P)H often transfer hydride to an unsaturated substrate bound within an enzyme active site. In many cases, metal ions in the active site bind, polarize and thereby activate the substrate to direct attack by hydride from NAD(P)H cofactor. This review looks more widely at the metal coordination chemistry of organic donors of hydride ion--organo-hydrides--such as dihydronicotinamides, other dihydropyridines including Hantzsch's ester and dihydroacridine derivatives, those derived from five-membered heterocycles including the benzimidazolines and benzoxazolines, and all-aliphatic hydride donors such as hexadiene and hexadienyl anion derivatives. The hydride donor properties--hydricities--of organo-hydrides and how these are affected by metal ions are discussed. The coordination chemistry of organo-hydrides is critically surveyed and the use of metal-organo-hydride systems in electrochemically-, photochemically- and chemically-driven reductions of unsaturated organic and inorganic (e.g. carbon dioxide) substrates is highlighted. The sustainable electrocatalytic, photochemical or chemical regeneration of organo-hydrides such as NAD(P)H, including for driving enzyme-catalysed reactions, is summarised and opportunities for development are indicated. Finally, new prospects are identified for metal-organo-hydride systems as catalysts for organic transformations involving 'hydride-borrowing' and for sustainable multi-electron reductions of unsaturated organic and inorganic substrates directly driven by electricity or light or by renewable reductants such as formate/formic acid.

  19. Excited-state lifetime of adenine near the first electronic band origin

    NASA Astrophysics Data System (ADS)

    Kang, Hyuk; Chang, Jinyoung; Lee, Sang Hak; Ahn, Tae Kyu; Kim, Nam Joon; Kim, Seong Keun

    2010-10-01

    The excited-state lifetime of supersonically cooled adenine was measured in the gas phase by femtosecond pump-probe transient ionization as a function of excitation energy between 36 100 and 37 500 cm-1. The excited-state lifetime of adenine is ˜2 ps around the 0-0 band of the L1b ππ ∗ state (36 105 cm-1). The lifetime drops to ˜1 ps when adenine is excited to the L1a ππ ∗ state with the pump energy at 36 800 cm-1 and above. The excited-state lifetimes of L1a and L1b ππ∗ states are differentiated in accordance with previous frequency-resolved and computational studies.

  20. Adenine phosphoribosyltransferase deficiency as a rare cause of renal allograft dysfunction.

    PubMed

    Kaartinen, Kati; Hemmilä, Ulla; Salmela, Kaija; Räisänen-Sokolowski, Anne; Kouri, Timo; Mäkelä, Satu

    2014-04-01

    Adenine phosphoribosyltransferase deficiency is a rare autosomal recessive disorder manifesting as urolithiasis or crystalline nephropathy. It leads to the generation of large amounts of poorly soluble 2,8-dihydroxyadenine excreted in urine, yielding kidney injury and in some patients, kidney failure. Early recognition of the disease, institution of xanthine analog therapy to block the formation of 2,8-dihydroxyadenine, high fluid intake, and low purine diet prevent CKD. Because of symptom variability and lack of awareness, however, the diagnosis is sometimes extremely deferred. We describe a patient with adenine phosphoribosyltransferase deficiency who was diagnosed during evaluation of a poorly functioning second kidney allograft. This report highlights the risk of renal allograft loss in patients with undiagnosed adenine phosphoribosyltransferase deficiency and the need for improved early detection of this disease.

  1. The basal proton conductance of mitochondria depends on adenine nucleotide translocase content

    PubMed Central

    2005-01-01

    The basal proton conductance of mitochondria causes mild uncoupling and may be an important contributor to metabolic rate. The molecular nature of the proton-conductance pathway is unknown. We show that the proton conductance of muscle mitochondria from mice in which isoform 1 of the adenine nucleotide translocase has been ablated is half that of wild-type controls. Overexpression of the adenine nucleotide translocase encoded by the stress-sensitive B gene in Drosophila mitochondria increases proton conductance, and underexpression decreases it, even when the carrier is fully inhibited using carboxyatractylate. We conclude that half to two-thirds of the basal proton conductance of mitochondria is catalysed by the adenine nucleotide carrier, independently of its ATP/ADP exchange or fatty-acid-dependent proton-leak functions. PMID:16076285

  2. Unique modification of adenine in genomic DNA of the marine cyanobacterium Trichodesmium sp. strain NIBB 1067.

    PubMed Central

    Zehr, J P; Ohki, K; Fujita, Y; Landry, D

    1991-01-01

    The genomic DNA of the marine nonheterocystous nitrogen-fixing cyanobacterium Trichodesmium sp. strain NIBB 1067 was found to be highly resistant to DNA restriction endonucleases. The DNA was digested extensively by the restriction enzyme DpnI, which requires adenine methylation for activity. The DNA composition, determined by high-performance liquid chromatography (HPLC), was found to be 69% AT. Surprisingly, it was found that a modified adenine which was not methylated at the usual N6 position was present and made up 4.7 mol% of the nucleosides in Trichodesmium DNA (15 mol% of deoxyadenosine). In order for adenine residues to be modified at this many positions, there must be many modifying enzymes or at least one of the modifying enzymes must have a degenerate recognition site. The reason(s) for this extensive methylation has not yet been determined but may have implications for the ecological success of this microorganism in nature. Images FIG. 1 FIG. 2 PMID:1657876

  3. A study of advanced magnesium-based hydride and development of a metal hydride thermal battery system

    NASA Astrophysics Data System (ADS)

    Zhou, Chengshang

    Metal hydrides are a group of important materials known as energy carriers for renewable energy and thermal energy storage. A concept of thermal battery based on advanced metal hydrides is studied for heating and cooling of cabins in electric vehicles. The system utilizes a pair of thermodynamically matched metal hydrides as energy storage media. The hot hydride that is identified and developed is catalyzed MgH2 due to its high energy density and enhanced kinetics. TiV0.62Mn1.5, TiMn2, and LaNi5 alloys are selected as the matching cold hydride. A systematic experimental survey is carried out in this study to compare a wide range of additives including transitions metals, transition metal oxides, hydrides, intermetallic compounds, and carbon materials, with respect to their effects on dehydrogenation properties of MgH2. The results show that additives such as Ti and V-based metals, hydride, and certain intermetallic compounds have strong catalytic effects. Solid solution alloys of magnesium are exploited as a way to destabilize magnesium hydride thermodynamically. Various elements are alloyed with magnesium to form solid solutions, including indium and aluminum. Thermodynamic properties of the reactions between the magnesium solid solution alloys and hydrogen are investigated, showing that all the solid solution alloys that are investigated in this work have higher equilibrium hydrogen pressures than that of pure magnesium. Cyclic stability of catalyzed MgH2 is characterized and analyzed using a PCT Sievert-type apparatus. Three systems, including MgH2-TiH 2, MgH2-TiMn2, and MgH2-VTiCr, are examined. The hydrogenating and dehydrogenating kinetics at 300°C are stable after 100 cycles. However, the low temperature (25°C to 150°C) hydrogenation kinetics suffer a severe degradation during hydrogen cycling. Further experiments confirm that the low temperature kinetic degradation can be mainly related the extended hydrogenation-dehydrogenation reactions. Proof

  4. De novo synthesis of adenine nucleotides in different skeletal muscle fiber types

    SciTech Connect

    Tullson, P.C.; John-Alder, H.B.; Hood, D.A.; Terjung, R.L.

    1988-09-01

    Management of adenine nucleotide catabolism differs among skeletal muscle fiber types. This study evaluated whether there are corresponding differences in the rates of de novo synthesis of adenine nucleotide among fiber type sections of skeletal muscle using an isolated perfused rat hindquarter preparation. Label incorporation into adenine nucleotides from the (1-14C)glycine precursor was determined and used to calculate synthesis rates based on the intracellular glycine specific radioactivity. Results show that intracellular glycine is closely related to the direct precursor pool. Rates of de novo synthesis were highest in fast-twitch red muscle (57.0 +/- 4.0, 58.2 +/- 4.4 nmol.h-1.g-1; deep red gastrocnemius and vastus lateralis), relatively high in slow-twitch red muscle (47.0 +/- 3.1; soleus), and low in fast-twitch white muscle (26.1 +/- 2.0 and 21.6 +/- 2.3; superficial white gastrocnemius and vastus lateralis). Rates for four mixed muscles were intermediate, ranging between 32.3 and 37.3. Specific de novo synthesis rates exhibited a strong correlation (r = 0.986) with muscle section citrate synthase activity. Turnover rates (de novo synthesis rate/adenine nucleotide pool size) were highest in high oxidative muscle (0.82-1.06%/h), lowest in low oxidative muscle (0.30-0.35%/h), and intermediate in mixed muscle (0.44-0.55%/h). Our results demonstrate that differences in adenine nucleotide management among fiber types extends to the process of de novo adenine nucleotide synthesis.

  5. Efficacy of the acyclic nucleoside phosphonates (S)-9-(3-fluoro-2-phosphonylmethoxypropyl)adenine (FPMPA) and 9-(2-phosphonylmethoxyethyl)adenine (PMEA) against feline immunodeficiency virus.

    PubMed

    Hartmann, K; Kuffer, M; Balzarini, J; Naesens, L; Goldberg, M; Erfle, V; Goebel, F D; De Clercq, E; Jindrich, J; Holy, A; Bischofberger, N; Kraft, W

    1998-02-01

    The acyclic nucleoside phosphonates (S)-9-(3-fluoro-2-phosphonylmethoxypropyl)adenine (FPMPA) and 9-(2-phosphonylmethoxyethyl)adenine (PMEA) were evaluated for their efficacy and side effects in a double-blind placebo-controlled trial using naturally occurring feline immunodeficiency virus (FIV)-infected cats. This natural retrovirus animal model is considered highly relevant for the pathogenesis and chemotherapy of HIV in humans. Both PMEA and FPMPA proved effective in ameliorating the clinical symptoms of FIV-infected cats, as measured by several clinical parameters including the incidence and severity of stomatitis, Karnofsky's score, immunologic parameters such as relative and absolute CD4+ lymphocyte counts, and virologic parameters including proviral DNA levels in peripheral blood mononuclear cells (PBMC) of drug-treated animals. In contrast with PMEA, FPMPA showed no hematologic side effects at a dose that was 2.5-fold higher than PMEA.

  6. A nickel metal hydride battery for electric vehicles.

    PubMed

    Ovshinsky, S R; Fetcenko, M A; Ross, J

    1993-04-09

    Widespread use of electric vehicles can have significant impact on urban air quality, national energy independence, and international balance of trade. An efficient battery is the key technological element to the development of practical electric vehicles. The science and technology of a nickel metal hydride battery, which stores hydrogen in the solid hydride phase and has high energy density, high power, long life, tolerance to abuse, a wide range of operating temperature, quick-charge capability, and totally sealed maintenance-free operation, is described. A broad range of multi-element metal hydride materials that use structural and compositional disorder on several scales of length has been engineered for use as the negative electrode in this battery. The battery operates at ambient temperature, is made of nontoxic materials, and is recyclable. Demonstration of the manufacturing technology has been achieved.

  7. Investigation of metal hydride nanoparticles templated in metal organic frameworks.

    SciTech Connect

    Jacobs, Benjamin W.; Herberg, Julie L.; Highley, Aaron M.; Grossman, Jeffrey; Wagner, Lucas; Bhakta, Raghu; Peaslee, D.; Allendorf, Mark D.; Liu, X.; Behrens, Richard, Jr.; Majzoub, Eric H.

    2010-11-01

    Hydrogen is proposed as an ideal carrier for storage, transport, and conversion of energy. However, its storage is a key problem in the development of hydrogen economy. Metal hydrides hold promise in effectively storing hydrogen. For this reason, metal hydrides have been the focus of intensive research. The chemical bonds in light metal hydrides are predominantly covalent, polar covalent or ionic. These bonds are often strong, resulting in high thermodynamic stability and low equilibrium hydrogen pressures. In addition, the directionality of the covalent/ionic bonds in these systems leads to large activation barriers for atomic motion, resulting in slow hydrogen sorption kinetics and limited reversibility. One method for enhancing reaction kinetics is to reduce the size of the metal hydrides to nano scale. This method exploits the short diffusion distances and constrained environment that exist in nanoscale hydride materials. In order to reduce the particle size of metal hydrides, mechanical ball milling is widely used. However, microscopic mechanisms responsible for the changes in kinetics resulting from ball milling are still being investigated. The objective of this work is to use metal organic frameworks (MOFs) as templates for the synthesis of nano-scale NaAlH4 particles, to measure the H2 desorption kinetics and thermodynamics, and to determine quantitative differences from corresponding bulk properties. Metal-organic frameworks (MOFs) offer an attractive alternative to traditional scaffolds because their ordered crystalline lattice provides a highly controlled and understandable environment. The present work demonstrates that MOFs are stable hosts for metal hydrides and their reactive precursors and that they can be used as templates to form metal hydride nanoclusters on the scale of their pores (1-2 nm). We find that using the MOF HKUST-1 as template, NaAlH4 nanoclusters as small as 8 formula units can be synthesized inside the pores. A detailed picture of

  8. CO2 hydrogenation on a metal hydride surface.

    PubMed

    Kato, Shunsuke; Borgschulte, Andreas; Ferri, Davide; Bielmann, Michael; Crivello, Jean-Claude; Wiedenmann, Daniel; Parlinska-Wojtan, Magdalena; Rossbach, Peggy; Lu, Ye; Remhof, Arndt; Züttel, Andreas

    2012-04-28

    The catalytic hydrogenation of CO(2) at the surface of a metal hydride and the corresponding surface segregation were investigated. The surface processes on Mg(2)NiH(4) were analyzed by in situ X-ray photoelectron spectroscopy (XPS) combined with thermal desorption spectroscopy (TDS) and mass spectrometry (MS), and time-of-flight secondary ion mass spectrometry (ToF-SIMS). CO(2) hydrogenation on the hydride surface during hydrogen desorption was analyzed by catalytic activity measurement with a flow reactor, a gas chromatograph (GC) and MS. We conclude that for the CO(2) methanation reaction, the dissociation of H(2) molecules at the surface is not the rate controlling step but the dissociative adsorption of CO(2) molecules on the hydride surface.

  9. Metal hydride hydrogen compression: Recent advances and future prospects

    DOE PAGES

    Bowman, Jr., Robert C.; Yartys, Volodymyr A.; Lototskyy, Mykhaylo V.; ...

    2016-03-17

    Metal hydride (MH) thermal sorption compression is one of the more important applications of the metal hydrides. The present paper reviews recent advances in the field based on the analysis of the fundamental principles of this technology. The performances when boosting hydrogen pressure, along with two- and three-step compression units are analyzed. The paper includes also a theoretical modeling of a two-stage compressor aimed at both describing the performance of the experimentally studied systems, but, also, on their optimization and design of more advanced MH compressors. Business developments in the field are reviewed for the Norwegian company HYSTORSYS AS andmore » the South African Institute for Advanced Materials Chemistry. Finally, future prospects are outlined presenting the role of the metal hydride compression in the overall development of the hydrogen driven energy systems. Lastly, the work is based on the analysis of the development of the technology in Europe, USA and South Africa.« less

  10. Metal hydride hydrogen compression: Recent advances and future prospects

    SciTech Connect

    Bowman, Jr., Robert C.; Yartys, Volodymyr A.; Lototskyy, Mykhaylo V.; Linkov, Vladimir; Grant, David; Stuart, Alastair; Eriksen, Jon; Denys, Roman

    2016-03-17

    Metal hydride (MH) thermal sorption compression is one of the more important applications of the metal hydrides. The present paper reviews recent advances in the field based on the analysis of the fundamental principles of this technology. The performances when boosting hydrogen pressure, along with two- and three-step compression units are analyzed. The paper includes also a theoretical modeling of a two-stage compressor aimed at both describing the performance of the experimentally studied systems, but, also, on their optimization and design of more advanced MH compressors. Business developments in the field are reviewed for the Norwegian company HYSTORSYS AS and the South African Institute for Advanced Materials Chemistry. Finally, future prospects are outlined presenting the role of the metal hydride compression in the overall development of the hydrogen driven energy systems. Lastly, the work is based on the analysis of the development of the technology in Europe, USA and South Africa.

  11. Comparative study of spontaneous deamination of adenine and cytosine in unbuffered aqueous solution at room temperature

    NASA Astrophysics Data System (ADS)

    Wang, Shiliang; Hu, Anguang

    2016-06-01

    Adenine in unbuffered nanopure water at a concentration of 2 mM is completely deaminated (>99%) to hypoxanthine at room temperature in ca. 10 weeks, with an estimated half-life (t1/2) less than 10 days, about six orders of magnitude faster than previously reported. Cytosine is not deaminated under the same condition, even after 3 years. This is in contrast to previous observations that cytosine deaminates 20-40 times faster than adenine free base, in nucleoside, in nucleotide and in single-stranded DNA in buffered neutral aqueous solutions.

  12. Ricin Activity Assay by Direct Analysis in Real Time Mass Spectrometry Detection of Adenine Release

    DTIC Science & Technology

    2010-02-01

    direct analysis in real time mass spectrometry. The release of adenine from the inhomo- geneous substrate herring sperm DNA by ricin was determined to...chain catalyzes cleavage at adenosine 4324 (in rat RNA) of 28S rRNA to release adenine.10 This action inhibits protein synthesis, leading to cell...death. In addition to RNA, herring sperm DNA (hsDNA) is a substrate for ricin.11 We chose to employ hsDNA for this assay because it is relatively stable

  13. High-Spin Cobalt Hydrides for Catalysis

    SciTech Connect

    Holland, Patrick L.

    2013-08-29

    Organometallic chemists have traditionally used catalysts with strong-field ligands that give low-spin complexes. However, complexes with a weak ligand field have weaker bonds and lower barriers to geometric changes, suggesting that they may lead to more rapid catalytic reactions. Developing our understanding of high-spin complexes requires the use of a broader range of spectroscopic techniques, but has the promise of changing the mechanism and/or selectivity of known catalytic reactions. These changes may enable the more efficient utilization of chemical resources. A special advantage of cobalt and iron catalysts is that the metals are more abundant and cheaper than those currently used for major industrial processes that convert unsaturated organic molecules and biofeedstocks into useful chemicals. This project specifically evaluated the potential of high-spin cobalt complexes for small-molecule reactions for bond rearrangement and cleavage reactions relevant to hydrocarbon transformations. We have learned that many of these reactions proceed through crossing to different spin states: for example, high-spin complexes can flip one electron spin to access a lower-energy reaction pathway for beta-hydride elimination. This reaction enables new, selective olefin isomerization catalysis. The high-spin cobalt complexes also cleave the C-O bond of CO2 and the C-F bonds of fluoroarenes. In each case, the detailed mechanism of the reaction has been determined. Importantly, we have discovered that the cobalt catalysts described here give distinctive selectivities that are better than known catalysts. These selectivities come from a synergy between supporting ligand design and electronic control of the spin-state crossing in the reactions.

  14. Method for preparing hydride configurations and reactive metal surfaces

    DOEpatents

    Silver, G.L.

    1984-05-18

    A method for preparing reactive metal surfaces, particularly uranium surfaces is disclosed, whereby the metal is immediately reactive to hydrogen gas at room temperature and low pressure. The metal surfaces are first pretreated by exposure to an acid which forms an adherent hydride-bearing composition on the metal surface. Subsequent heating of the pretreated metal at a temperature sufficient to decompose the hydride coating in vacuum or inert gas renders the metal surface instantaneously reactive to hydrogen gas at room temperature and low pressure.

  15. Phase I. Lanthanum-based Start Materials for Hydride Batteries

    SciTech Connect

    Gschneidner, K. A.; Schmidt, F. A.; Frerichs, A. E.; Ament, K. A.

    2013-08-20

    The purpose of Phase I of this work is to focus on developing a La-based start material for making nickel-metal (lanthanum)-hydride batteries based on our carbothermic-silicon process. The goal is to develop a protocol for the manufacture of (La1-xRx)(Ni1-yMy)(Siz), where R is a rare earth metal and M is a non-rare earth metal, to be utilized as the negative electrode in nickel-metal hydride (NiMH) rechargeable batteries.

  16. Hydride formation in core-shell alloyed metal nanoparticles

    NASA Astrophysics Data System (ADS)

    Zhdanov, Vladimir P.

    2016-07-01

    The model and analysis presented are focused on hydride formation in nanoparticles with a Pd shell and a core formed by another metal. The arrangement of metal atoms is assumed to be coherent (no dislocations). The lattice strain distribution, elastic energy, and chemical potential of hydrogen atoms are scrutinized. The slope of the chemical potential (as a function of hydrogen uptake) is demonstrated to decrease with increasing the core volume, and accordingly the critical temperature for hydride formation and the corresponding hysteresis loops are predicted to decrease as well.

  17. METHOD OF PREPARING SINTERED ZIRCONIUM METAL FROM ITS HYDRIDES

    DOEpatents

    Angier, R.P.

    1958-02-11

    The invention relates to the preparation of metal shapes from zirconium hydride by powder metallurgical techniques. The zirconium hydride powder which is to be used for this purpose can be prepared by rendering massive pieces of crystal bar zirconium friable by heat treatment in purified hydrogen. This any then be ground into powder and powder can be handled in the air without danger of it igniting. It may then be compacted in the normal manner by being piaced in a die. The compact is sintered under vacuum conditions preferably at a temperature ranging from 1200 to 1300 deg C and for periods of one to three hours.

  18. Ab-initio study of transition metal hydrides

    SciTech Connect

    Sharma, Ramesh; Shukla, Seema Dwivedi, Shalini Sharma, Yamini

    2014-04-24

    We have performed ab initio self consistent calculations based on Full potential linearized augmented plane wave (FP-LAPW) method to investigate the optical and thermal properties of yttrium hydrides. From the band structure and density of states, the optical absorption spectra and specific heats have been calculated. The band structure of Yttrium metal changes dramatically due to hybridization of Y sp orbitals with H s orbitals and there is a net charge transfer from metal to hydrogen site. The electrical resistivity and specific heats of yttrium hydrides are lowered but the thermal conductivity is slightly enhanced due to increase in scattering from hydrogen sites.

  19. Affinity of a galactose-specific legume lectin from Dolichos lablab to adenine revealed by X-ray cystallography.

    PubMed

    Shetty, Kartika N; Latha, Vakada Lavanya; Rao, Rameshwaram Nagender; Nadimpalli, Siva Kumar; Suguna, Kaza

    2013-07-01

    Crystal structure analysis of a galactose-specific lectin from a leguminous food crop Dolichos lablab (Indian lablab beans) has been carried out to obtain insights into its quaternary association and lectin-carbohydrate interactions. The analysis led to the identification of adenine binding sites at the dimeric interfaces of the heterotetrameric lectin. Structural details of similar adenine binding were reported in only one legume lectin, Dolichos biflorus, before this study. Here, we present the structure of the galactose-binding D. lablab lectin at different pH values in the native form and in complex with galactose and adenine. This first structure report on this lectin also provides a high resolution atomic view of legume lectin-adenine interactions. The tetramer has two canonical and two DB58-like interfaces. The binding of adenine, a non-carbohydrate ligand, is found to occur at four hydrophobic sites at the core of the tetramer at the DB58-like dimeric interfaces and does not interfere with the carbohydrate-binding site. To support the crystallographic observations, the adenine binding was further quantified by carrying out isothermal calorimetric titration. By this method, we not only estimated the affinity of the lectin to adenine but also showed that adenine binds with negative cooperativity in solution.

  20. Exploring "aerogen-hydride" interactions between ZOF2 (Z = Kr, Xe) and metal hydrides: An ab initio study

    NASA Astrophysics Data System (ADS)

    Esrafili, Mehdi D.; Mohammadian-Sabet, Fariba

    2016-06-01

    In this work, a new σ-hole interaction formed between ZOF2 (Z = Kr and Xe) as the Lewis acid and a series of metal-hydrides HMX (M = Be, Mg, Zn and X = H, F, CN, CH3) is reported. The nature of this interaction, called "aerogen-hydride" interaction, is unveiled by molecular electrostatic potential, non-covalent interaction, quantum theory of atoms in molecules and natural bond orbital analyses. Our results indicate that the aerogen-hydride interactions are quite strong and can be comparable in strength to other σ-hole bonds. An important charge-transfer interaction is also associated with the formation of OF2Z⋯HMX complexes.

  1. Uranium Hydride Nucleation and Growth Model FY'16 ESC Annual Report

    SciTech Connect

    Hill, Mary Ann; Richards, Andrew Walter; Holby, Edward F.; Schulze, Roland K.

    2016-12-20

    Uranium hydride corrosion is of great interest to the nuclear industry. Uranium reacts with water and/or hydrogen to form uranium hydride which adversely affects material performance. Hydride nucleation is influenced by thermal history, mechanical defects, oxide thickness, and chemical defects. Information has been gathered from past hydride experiments to formulate a uranium hydride model to be used in a Canned Subassembly (CSA) lifetime prediction model. This multi-scale computer modeling effort started in FY’13 and the fourth generation model is now complete. Additional high resolution experiments will be run to further test the model.

  2. Synthesis, cyclopolymerization and cyclo-copolymerization of 9-(2-diallylaminoethyl)adenine and its hydrochloride salt.

    PubMed

    Bouhadir, Kamal H; Abramian, Lara; Ezzeddine, Alaa; Usher, Karyn; Vladimirov, Nikolay

    2012-11-08

    We report herein the synthesis and characterization of 9-(2-diallylaminoethyl) adenine. We evaluated two different synthetic routes starting with adenine where the optimal route was achieved through coupling of 9-(2-chloroethyl)adenine with diallylamine. The cyclopolymerization and cyclo-copolymerization of 9-(2-diallylaminoethyl)adenine hydrochloride salt resulted in low molecular weight oligomers in low yields. In contrast, 9-(2-diallylaminoethyl)adenine failed to cyclopolymerize, however, it formed a copolymer with SO₂ in relatively good yields. The molecular weights of the cyclopolymers were around 1,700-6,000 g/mol, as estimated by SEC. The cyclo-copolymer was stable up to 226 °C. To the best of our knowledge, this is the first example of a free-radical cyclo-copolymerization of a neutral alkyldiallylamine derivative with SO₂. These polymers represent a novel class of carbocyclic polynucleotides.

  3. Caffeine biosynthesis and adenine metabolism in transgenic Coffea canephora plants with reduced expression of N-methyltransferase genes.

    PubMed

    Ashihara, Hiroshi; Zheng, Xin-Qiang; Katahira, Riko; Morimoto, Masayuki; Ogita, Shinjiro; Sano, Hiroshi

    2006-05-01

    In anti-sense and RNA interference transgenic plants of Coffea canephora in which the expression of CaMXMT1 was suppressed, caffeine biosynthesis from [8-(14)C]adenine was investigated, together with the overall metabolism of [8-(14)C]adenine. Compared with wild type control plants, total purine alkaloid biosynthesis from adenine and conversion of theobromine to caffeine were both reduced in the transgenic plants. As found previously, [8-(14)C]adenine was metabolised to salvage products (nucleotides and RNA), to degradation products (ureides and CO(2)) and to purine alkaloids (theobromine and caffeine). In the transgenic plants, metabolism of [8-(14)C]adenine shifted from purine alkaloid synthesis to purine catabolism or salvage for nucleotides. HPLC analysis revealed a significantly reduced caffeine content in the transgenic plants. A small quantity (less than 20 nmol g(-1) fresh weight) of xanthosine had accumulated in at least one of the transgenic plants.

  4. Heat-mass flow enhancement system for a metal hydride assembly

    NASA Astrophysics Data System (ADS)

    Argabright, T. A.

    1985-02-01

    Southern California Gas Company and Solar Turbines Incorporated are cooperating in the development and demonstration of a metal hydride/chemical heat pump (MHHP). In the design of the MHHP, heat transfer was considered to be the key technical study area. The goal of this effort is improved heat transfer and reduced thermal mass in a hydride heat exchanger/containment assembly. Phase 1 resulted in the detailed design of an advanced hydride heat exchanger. Phase 2 consisted of the experimental verification of the hydride alloy design data, fabrication of the hydride heat exchanger module components, heat transfer testing of the single heat exchanger element and preliminary performance testing of the entire module. Phase 3 was devoted to the complete characterization of the hydride heat exchanger modules through further operation and testing. A review of other possible hydride heat transfer concepts was also conducted in Phase 2.

  5. Diminution in adenine nucleotide hydrolysis by platelets and serum from rats submitted to Walker 256 tumour.

    PubMed

    Buffon, Andréia; Ribeiro, Vanessa B; Schanoski, Alessandra S; Sarkis, João J F

    2006-01-01

    Extracellular adenine nucleotide hydrolysis in the circulation is mediated by the action of an NTPDase (CD39, apyrase) and of a 5'-nucleotidase (CD73), presenting as a final product, adenosine. Among other properties described for adenine nucleotides, an anti-cancer activity is suggested, since ATP is considered a cytotoxic molecule in several tumour cell systems. Conversely, some studies demonstrate that adenosine presents a tumour-promoting activity. In this study, we evaluated the pattern of adenine nucleotide hydrolysis by serum and platelets from rats submitted to the Walker 256 tumour model. Extracellular adenine nucleotide hydrolysis by blood serum and platelets obtained from rats at, 6, 10 and 15 days after the subcutaneous Walker 256 tumour inoculation, was evaluated. Our results demonstrate a significant reduction in ATP, ADP and AMP hydrolysis in blood serum at 6, 10 and 15 days after tumour induction. In platelets, a significant reduction in ATP and AMP hydrolysis was observed at 10 and 15 days after tumour induction, while an inhibition of ADP hydrolysis was observed at all times studied. Based on these results, it is possible to suggest a physiologic protection mechanism against the tumoral process in circulation. The inhibition in nucleotide hydrolysis observed probably maintains ATP levels elevated (cytotoxic compound) and, at the same time, reduces the adenosine production (tumour-promoting molecule) in the circulation.

  6. Ameliorative Effect of Chrysin on Adenine-Induced Chronic Kidney Disease in Rats

    PubMed Central

    Ali, Badreldin H.; Adham, Sirin A.; Al Za’abi, Mohammed; Waly, Mostafa I.; Yasin, Javed; Nemmar, Abderrahim; Schupp, Nicole

    2015-01-01

    Chrysin (5, 7- dihydroxyflavone) is a flavonoid with several pharmacological properties that include antioxidant, anti-inflammatory and antiapoptotic activities. in this work, we investigated some effects of three graded oral doses of chrysin (10, 50 and 250 mg/kg) on kidney structure and function in rats with experimental chronic renal disease (CKD) induced by adenine (0.25% w/w in feed for 35 days), which is known to involve inflammation and oxidative stress. Using several indices in plasma, urine and kidney homogenates, adenine was found to impair kidney function as it lowered creatinine clearance and increased plasma concentrations of creatinine, urea, neutrophil gelatinase-associated lipocalin and N-Acetyl-beta-D-glucosaminidase activity. Furthermore, it raised plasma concentrations of the uremic toxin indoxyl sulfate, some inflammatory cytokines and urinary albumin concentration. Renal morphology was severely damaged and histopathological markers of inflammation and fibrosis were especially increased. In renal homogenates, antioxidant indices, including superoxide dismutase and catalase activities, total antioxidant capacity and reduced glutathione were all adversely affected. Most of these adenine – induced actions were moderately and dose -dependently mitigated by chrysin, especially at the highest dose. Chrysin did not cause any overt adverse effect on the treated rats. The results suggest that different doses of chrysin produce variable salutary effects against adenine-induced CKD in rats, and that, pending further pharmacological and toxicological studies, its usability as a possible ameliorative agent in human CKD should be considered. PMID:25909514

  7. Ameliorative effect of chrysin on adenine-induced chronic kidney disease in rats.

    PubMed

    Ali, Badreldin H; Adham, Sirin A; Al Za'abi, Mohammed; Waly, Mostafa I; Yasin, Javed; Nemmar, Abderrahim; Schupp, Nicole

    2015-01-01

    Chrysin (5, 7- dihydroxyflavone) is a flavonoid with several pharmacological properties that include antioxidant, anti-inflammatory and antiapoptotic activities. in this work, we investigated some effects of three graded oral doses of chrysin (10, 50 and 250 mg/kg) on kidney structure and function in rats with experimental chronic renal disease (CKD) induced by adenine (0.25% w/w in feed for 35 days), which is known to involve inflammation and oxidative stress. Using several indices in plasma, urine and kidney homogenates, adenine was found to impair kidney function as it lowered creatinine clearance and increased plasma concentrations of creatinine, urea, neutrophil gelatinase-associated lipocalin and N-Acetyl-beta-D-glucosaminidase activity. Furthermore, it raised plasma concentrations of the uremic toxin indoxyl sulfate, some inflammatory cytokines and urinary albumin concentration. Renal morphology was severely damaged and histopathological markers of inflammation and fibrosis were especially increased. In renal homogenates, antioxidant indices, including superoxide dismutase and catalase activities, total antioxidant capacity and reduced glutathione were all adversely affected. Most of these adenine - induced actions were moderately and dose -dependently mitigated by chrysin, especially at the highest dose. Chrysin did not cause any overt adverse effect on the treated rats. The results suggest that different doses of chrysin produce variable salutary effects against adenine-induced CKD in rats, and that, pending further pharmacological and toxicological studies, its usability as a possible ameliorative agent in human CKD should be considered.

  8. Effect of atracylodes rhizome polysaccharide in rats with adenine-induced chronic renal failure.

    PubMed

    Yang, C; Liu, C; Zhou, Q; Xie, Y C; Qiu, X M; Feng, X

    2015-01-01

    The aim of the study was to elucidate the therapeutic effects of Atracylodes rhizome polysaccharide on adenine-induced chronic renal failure in rats. Fifty male Sprague Dawley rats were selected and randomly divided in to 5 groups (n=10 rats per group): The normal control group, the chronic renal failure pathological control group, the dexamethasone treatment group and two Atracylodes rhizome polysaccharide treatment groups, treated with two different concentrations of the polysaccharide, the Atracylodes rhizome polysaccharide high group and the Atracylodes rhizome polysaccharide low group. All the rats, except those in the normal control group were fed adenine-enriched diets, containing 10 g adenine per kg food for 3 weeks. After being fed with adenine, the dexamethasone treatment group, Atracylodes rhizome polysaccharide high group and Atracylodes rhizome polysaccharide low group rats were administered the drug orally for 2 weeks. On day 35, the kidney coefficient of the rats and the serum levels of creatinine, blood urea nitrogen, total protein and hemalbumin were determined. Subsequent to experimentation on a model of chronic renal failure in rats, the preparation was proven to be able to reduce serum levels of creatinine, blood urea nitrogen and hemalbumin levels (P<0.05) and improve renal function. Atracylodes rhizome polysaccharide had reversed the majority of the indices of chronic renal failure in rats.

  9. The Effect of Adenine Repeats on G-quadruplex/hemin Peroxidase Mimicking DNAzyme Activity.

    PubMed

    Chen, Jielin; Guo, Yuehua; Zhou, Jun; Ju, Huangxian

    2017-03-23

    The catalytic activity of G-quadruplex/hemin is much lower than that of proteinous enzymes, so it is very important to increase its activity. Very recently, flanking sequences, which can be regarded as an external part of G-quadruplexes, were found to enhance the activity of G-quadruplex/hemin DNAzyme. However, little is known about the effect of internal parts, such as loop sequences and linkers, on the activity. In the present study, adenine repeats were incorporated into several designed G-quadruplex structures either in the loops, bulges, or linkers, and the constructed G-quadruplex/hemin DNAzyme exhibit about fivefold improvement in peroxidase-mimicking activity in some cases. The enhancement effect may result from the formation of compound I, protoporphyrin⋅Fe(IV) =O(.+) , accelerated by dA repeats, which was demonstrated by H2 O2 decay kinetics and pH dependency analysis. The novel enhancement methods described here may help in the development of high-activity DNAzymes, illustrated by a dimer G-quadruplex with flanking adenine at one end, a relatively long adenine run in one loop, and another adenine run in the linker.

  10. Macrophage Trafficking as Key Mediator of Adenine-Induced Kidney Injury

    PubMed Central

    Braga, Tárcio Teodoro; Felizardo, Raphael José Ferreira; Andrade-Oliveira, Vinícius; Hiyane, Meire Ioshie; da Silva, João Santana; Câmara, Niels Olsen Saraiva

    2014-01-01

    Macrophages play a special role in the onset of several diseases, including acute and chronic kidney injuries. In this sense, tubule interstitial nephritis (TIN) represents an underestimated insult, which can be triggered by different stimuli and, in the absence of a proper regulation, can lead to fibrosis deposition. Based on this perception, we evaluated the participation of macrophage recruitment in the development of TIN. Initially, we provided adenine-enriched food to WT and searched for macrophage presence and action in the kidney. Also, a group of animals were depleted of macrophages with the clodronate liposome while receiving adenine-enriched diet. We collected blood and renal tissue from these animals and renal function, inflammation, and fibrosis were evaluated. We observed higher expression of chemokines in the kidneys of adenine-fed mice and a substantial protection when macrophages were depleted. Then, we specifically investigated the role of some key chemokines, CCR5 and CCL3, in this TIN experimental model. Interestingly, CCR5 KO and CCL3 KO animals showed less renal dysfunction and a decreased proinflammatory profile. Furthermore, in those animals, there was less profibrotic signaling. In conclusion, we can suggest that macrophage infiltration is important for the onset of renal injury in the adenine-induced TIN. PMID:25132730

  11. The effect of activated charcoal on adenine-induced chronic renal failure in rats.

    PubMed

    Ali, Badreldin H; Alza'abi, Mohamed; Ramkumar, Aishwarya; Al-Lawati, Intisar; Waly, Mostafa I; Beegam, Sumaya; Nemmar, Abderrahim; Brand, Susanne; Schupp, Nicole

    2014-03-01

    Activated charcoal (AC) is a sorbent that has been shown to remove urinary toxins like urea and indoxyl sulfate. Here, the influence of AC on kidney function of rats with experimental chronic renal failure (CRF) is investigated. CRF was induced in rats by feeding adenine (0.75%) for four weeks. As an intervention, AC was added to the feed at concentrations of 10%, 15% or 20%. Adenine treatment impaired kidney function: it lowered creatinine clearance and increased plasma concentrations of creatinine, urea, neutrophil gelatinase-associated lipocalin and vanin-1. Furthermore, it raised plasma concentrations of the uremic toxins indoxyl sulfate, phosphate and uric acid. Renal morphology was severely damaged and histopathological markers of inflammation and fibrosis were especially increased. In renal homogenates, antioxidant indices, including superoxide dismutase and catalase activity, total antioxidant capacity and reduced glutathione were adversely affected. Most of these changes were significantly ameliorated by dietary administration of AC at a concentration of 20%, while effects induced by lower doses of dietary AC on adenine nephrotoxicity were not statistically significant. The results suggest that charcoal is a useful sorbent agent in dietary adenine-induced CRF in rats and that its usability as a nephroprotective agent in human kidney disease should be studied.

  12. High membrane potential promotes alkenal-induced mitochondrial uncoupling and influences adenine nucleotide translocase conformation.

    PubMed

    Azzu, Vian; Parker, Nadeene; Brand, Martin D

    2008-07-15

    Mitochondria generate reactive oxygen species, whose downstream lipid peroxidation products, such as 4-hydroxynonenal, induce uncoupling of oxidative phosphorylation by increasing proton leak through mitochondrial inner membrane proteins such as the uncoupling proteins and adenine nucleotide translocase. Using mitochondria from rat liver, which lack uncoupling proteins, in the present study we show that energization (specifically, high membrane potential) is required for 4-hydroxynonenal to activate proton conductance mediated by adenine nucleotide translocase. Prolonging the time at high membrane potential promotes greater uncoupling. 4-Hydroxynonenal-induced uncoupling via adenine nucleotide translocase is prevented but not readily reversed by addition of carboxyatractylate, suggesting a permanent change (such as adduct formation) that renders the translocase leaky to protons. In contrast with the irreversibility of proton conductance, carboxyatractylate added after 4-hydroxynonenal still inhibits nucleotide translocation, implying that the proton conductance and nucleotide translocation pathways are different. We propose a model to relate adenine nucleotide translocase conformation to proton conductance in the presence or absence of 4-hydroxynonenal and/or carboxyatractylate.

  13. Hydride vapor phase epitaxy of aluminum nitride

    NASA Astrophysics Data System (ADS)

    Kamber, Derrick Shane

    AlN is a promising substrate material for AlGaN-based UV optoelectronic devices and high-power, high-frequency electronic devices. Since large-area bulk AlN crystals are not readily available, one approach to prepare AlN substrates is to heteroepitaxially deposit thick (e.g., 10-300+ mum) AlN layers by hydride vapor phase epitaxy. Initial efforts focused on growing AlN layers on sapphire substrates with growth rates up to 75 mum/hr. The resulting layers were colorless, smooth, and specular. Subsurface cracking, attributed to the plastic relief of tensile strain from island coalescence, was observed but did not adversely affect the surface morphology of the AlN layers. The surfaces possessed rms roughnesses as low as 0.316 nm over 5 x 5 mum2 sampling areas, but hexagonal hillock formation was observed for thick films grown at high growth rates. TEM revealed that the threading dislocation (TD) density of the films was 2 x 109 cm-2. The high TD densities for direct growth of AlN films on foreign substrates motivated the development of lateral epitaxial overgrowth approaches for defect reduction. Growth of AlN layers on patterned SiC substrates produced coalesced AlN films possessing TD densities below 8.3 x 106 cm -2 in the laterally grown wing regions, as compared to 1.8 x 109 cm-2 in the seed regions. These films, however, cracked on cooldown due to the difference in thermal expansion coefficients for AlN and SiC. To avoid this cracking, AlN layers were grown on patterned sapphire substrates. Although the films were able to be coalesced and contained few or no cracks, the TDs in these films were not confined to the seed regions. This produced a relatively uniform distribution of TDs over the surfaces of the films, with only a modest reduction in the TD density of 1 x 10 8 cm-2. Selective area growth of AlN was also pursued using Si3N4, SiO2, and Ti masks. Growth selectivity and film coalescence was observed for films grown on each masking material, but none of the

  14. KNH2-KH: a metal amide-hydride solid solution.

    PubMed

    Santoru, Antonio; Pistidda, Claudio; Sørby, Magnus H; Chierotti, Michele R; Garroni, Sebastiano; Pinatel, Eugenio; Karimi, Fahim; Cao, Hujun; Bergemann, Nils; Le, Thi T; Puszkiel, Julián; Gobetto, Roberto; Baricco, Marcello; Hauback, Bjørn C; Klassen, Thomas; Dornheim, Martin

    2016-09-27

    We report for the first time the formation of a metal amide-hydride solid solution. The dissolution of KH into KNH2 leads to an anionic substitution, which decreases the interaction among NH2(-) ions. The rotational properties of the high temperature polymorphs of KNH2 are thereby retained down to room temperature.

  15. Process of forming a sol-gel/metal hydride composite

    DOEpatents

    Congdon, James W.

    2009-03-17

    An external gelation process is described which produces granules of metal hydride particles contained within a sol-gel matrix. The resulting granules are dimensionally stable and are useful for applications such as hydrogen separation and hydrogen purification. An additional coating technique for strengthening the granules is also provided.

  16. Cascades for hydrogen isotope separation using metal hydrides

    SciTech Connect

    Hill, F.B.; Grzetic, V.

    1982-01-01

    Designs are presented for continuous countercurrent hydrogen isotope separation cascades based on the use of metal hydrides. The cascades are made up of pressure swing adsorption (PSA) or temperature swing adsorption (TSA) stages. The designs were evolved from consideration of previously conducted studies of the separation performance of four types of PSA and TSA processes.

  17. Electronic Principles of Some Trends in Properties of Metallic Hydrides

    NASA Astrophysics Data System (ADS)

    Ivanović, Nenad; Novaković, Nikola; Colognesi, Daniele; Radisavljević, Ivana; Ostojić, Stanko

    Due to their extensive present, important and versatile potential applications, metal hydrides (MH) are among the most investigated solid-state systems. Theoretical, numerical and experimental studies have provided a considerable knowledge about their structure and properties, but in spite of that, the basic electronic principles of various interactions present in MH have not yet been completely resolved. Even in the simplest MH, i.e. alkali hydrides (Alk-H), some trends in physical properties, and especially their deviations, are not well understood. Similar doubts exist for the alkaline-earth hydride (AlkE-H) series, and are even more pronounced for complex systems, like transition metal-doped AlkE-H, alanates and borohydrides. This work is an attempt of explaining some trends in the physical properties of Alk-H and AlkE-H, employing the Bader analysis of the charge distribution topology evaluated by first-principle all-electron calculations. These results are related to some variables commonly used in the explanation of experimental and calculated results, and are also accompanied by simple tight-binding estimations. Such an approach provides a valuable insight in the characteristics of M-H and H-H interactions in these hydrides, and their possible changes along with external parameters, like temperature, pressure, defect or impurity introduction. The knowledge of these basic interactions and processes taking place in simple MH are essential for the design and optimisation of complex MH-systems interesting for practical hydrogen storage applications.

  18. Hydrogen and dihydrogen bonding of transition metal hydrides

    NASA Astrophysics Data System (ADS)

    Jacobsen, Heiko

    2008-04-01

    Intermolecular interactions between a prototypical transition metal hydride WH(CO) 2NO(PH 3) 2 and a small proton donor H 2O have been studied using DFT methodology. The hydride, nitrosyl and carbonyl ligand have been considered as site of protonation. Further, DFT-D calculations in which empirical corrections for the dispersion energy are included, have been carried out. A variety of pure and hybrid density functionals (BP86, PW91, PBE, BLYP, OLYP, B3LYP, B1PW91, PBE0, X3LYP) have been considered, and our calculations indicate the PBE functional and its hybrid variation are well suited for the calculation of transition metal hydride hydrogen and dihydrogen bonding. Dispersive interactions make up for a sizeable portion of the intermolecular interaction, and amount to 20-30% of the bond energy and to 30-40% of the bond enthalpy. An energy decomposition analysis reveals that the H⋯H bond of transition metal hydrides contains both covalent and electrostatic contributions.

  19. Hydride encapsulation by molecular alkali-metal clusters.

    PubMed

    Haywood, Joanna; Wheatley, Andrew E H

    2008-07-14

    The sequential treatment of group 12 and 13 Lewis acids with alkali-metal organometallics is well established to yield so-called ''ate' complexes, whereby the Lewis-acid metal undergoes nucleophilic attack to give an anion, at least one group 1 metal acting to counter this charge. However, an alternative, less well recognised, reaction pathway involves the Lewis acid abstracting hydride from the organolithium reagent via a beta-elimination mechanism. It has recently been shown that in the presence of N,N'-bidentate ligands this chemistry can be harnessed to yield a new type of molecular main-group metal cluster in which the abstracted LiH is effectively trapped, with the hydride ion occupying an interstitial site in the cluster core. Discussion focuses on the development of this field, detailing advances in our understanding of the roles of Lewis acid, organolithium, and amine substrates in the syntheses of these compounds. Structure-types are discussed, as are efforts to manipulate cluster geometry and composition as well as hydride-coordination. Embryonic mechanistic studies are reported, as well as attempts to generate hydride-encapsulation clusters under catalytic control.

  20. Optimizing Misch-Metal Compositions In Metal Hydride Anodes

    NASA Technical Reports Server (NTRS)

    Bugga, Ratnakumar V.; Halpert, Gerald

    1995-01-01

    Electrochemical cells based on metal hydride anodes investigated experimentally in effort to find anode compositions maximizing charge/discharge-cycle performances. Experimental anodes contained misch metal alloyed with various proportions of Ni, Co, Mn, and Al, and experiments directed toward optimization of composition of misch metal.

  1. Well-defined transition metal hydrides in catalytic isomerizations.

    PubMed

    Larionov, Evgeny; Li, Houhua; Mazet, Clément

    2014-09-07

    This Feature Article intends to provide an overview of a variety of catalytic isomerization reactions that have been performed using well-defined transition metal hydride precatalysts. A particular emphasis is placed on the underlying mechanistic features of the transformations discussed. These have been categorized depending upon the nature of the substrate and in most cases discussed following a chronological order.

  2. Hydride generation from the Exide load-leveling cells

    NASA Astrophysics Data System (ADS)

    Marr, J. J.; Smaga, J. A.

    1987-05-01

    Stibine and arsine evolution from lead-acid cells in a 36-kWh Exide load-leveling module was measured as this module approached 1900 cycles of operation. A gas-collection apparatus enabled us to determine the maximum and average rates for evolution of both toxic hydrides. Hydride generation began once the cell voltage exceeded 2.4 V. The maximum rate for arsine occurred just above 2.5 V and consistently preceded the peak rate for stibine for each sampled cell. The average rates of hydride generation were found to be 175 g/min for stibine and 12.6 g/min for arsine. The former rate proved to be the critical value in determining safe ventilation requirements for cell off-gases. The minimum airflow requirement was calculated to be 340 L/min per cell. Projections for a hypothetical 1-MWh Exide battery without an abatement system indicated that the normal ventilation capacity in the Battery Energy Storage Test facility provides nearly five times the airflow needed for safe hydride removal.

  3. Administration of α-Galactosylceramide Improves Adenine-Induced Renal Injury.

    PubMed

    Aguiar, Cristhiane Favero; Naffah-de-Souza, Cristiane; Castoldi, Angela; Corrêa-Costa, Matheus; Braga, Tárcio T; Naka, Érika L; Amano, Mariane T; Abate, Débora T R S; Hiyane, Meire I; Cenedeze, Marcos A; Pacheco e Silva Filho, Alvaro; Câmara, Niels O S

    2015-06-18

    Natural killer T (NKT) cells are a subset of lymphocytes that reacts to glycolipids presented by CD1d. Invariant NKT cells (iNKT) correspond to >90% of the total population of NKTs and reacts to α-galactosylceramide (αGalCer). αGalCer promotes a complex mixture of Th1 and Th2 cytokines, as interferon (IFN)-γ and interleukin (IL)-4. NKT cells and IFN-γ are known to participate in some models of renal diseases, but further studies are still necessary to elucidate their mechanisms. The aim of our study was to analyze the participation of iNKT cells in an experimental model of tubule-interstitial nephritis. We used 8-wk-old C57BL/6j, Jα18KO and IFN-γKO mice. They were fed a 0.25% adenine diet for 10 d. Both adenine-fed wild-type (WT) and Jα18KO mice exhibited renal dysfunction, but adenine-fed Jα18KO mice presented higher expression of kidney injury molecule-1 (KIM-1), tumor necrosis factor (TNF)-α and type I collagen. To analyze the role of activated iNKT cells in our model, we administered αGalCer in WT mice during adenine ingestion. After αGalCer injection, we observed a significant reduction in serum creatinine, proinflammatory cytokines and renal fibrosis. However, this improvement in renal function was not observed in IFN-γKO mice after αGalCer treatment and adenine feeding, illustrating that this cytokine plays a role in our model. Our findings may suggest that IFN-γ production is one of the factors contributing to improved renal function after αGalCer administration.

  4. ON THE INTERACTION OF ADENINE WITH IONIZING RADIATION: MECHANISTICAL STUDIES AND ASTROBIOLOGICAL IMPLICATIONS

    SciTech Connect

    Evans, Nicholas L.; Ullrich, Susanne; Bennett, Chris J.; Kaiser, Ralf I.

    2011-04-01

    The molecular inventory available on the prebiotic Earth was likely derived from both terrestrial and extraterrestrial sources. A complete description of which extraterrestrial molecules may have seeded early Earth is therefore necessary to fully understand the prebiotic evolution which led to life. Galactic cosmic rays (GCRs) are expected to cause both the formation and destruction of important biomolecules-including nucleic acid bases such as adenine-in the interstellar medium within the ices condensed on interstellar grains. The interstellar ultraviolet (UV) component is expected to photochemically degrade gas-phase adenine on a short timescale of only several years. However, the destruction rate is expected to be significantly reduced when adenine is shielded in dense molecular clouds or even within the ices of interstellar grains. Here, biomolecule destruction by the energetic charged particle component of the GCR becomes important as it is not fully attenuated. Presented here are results on the destruction rate of the nucleobase adenine in the solid state at 10 K by energetic electrons, as generated in the track of cosmic ray particles as they penetrate ices. When both UV and energetic charged particle destructive processes are taken into account, the half-life of adenine within dense interstellar clouds is found to be {approx}6 Myr, which is on the order of a star-forming molecular cloud. We also discuss chemical reaction pathways within the ices to explain the production of observed species, including the formation of nitriles (R-C{identical_to}N), epoxides (C-O-C), and carbonyl functions (R-C=O).

  5. Administration of α-Galactosylceramide Improves Adenine-Induced Renal Injury

    PubMed Central

    Aguiar, Cristhiane Favero; Naffah-de-Souza, Cristiane; Castoldi, Angela; Corrêa-Costa, Matheus; Braga, Tárcio T; Naka, Érika L; Amano, Mariane T; Abate, Débora T R S; Hiyane, Meire I; Cenedeze, Marcos A; Filho, Alvaro Pacheco e Silva; Câmara, Niels O S

    2015-01-01

    Natural killer T (NKT) cells are a subset of lymphocytes that reacts to glycolipids presented by CD1d. Invariant NKT cells (iNKT) correspond to >90% of the total population of NKTs and reacts to α-galactosylceramide (αGalCer). αGalCer promotes a complex mixture of Th1 and Th2 cytokines, as interferon (IFN)-γ and interleukin (IL)-4. NKT cells and IFN-γ are known to participate in some models of renal diseases, but further studies are still necessary to elucidate their mechanisms. The aim of our study was to analyze the participation of iNKT cells in an experimental model of tubule-interstitial nephritis. We used 8-wk-old C57BL/6j, Jα18KO and IFN-γKO mice. They were fed a 0.25% adenine diet for 10 d. Both adenine-fed wild-type (WT) and Jα18KO mice exhibited renal dysfunction, but adenine-fed Jα18KO mice presented higher expression of kidney injury molecule-1 (KIM-1), tumor necrosis factor (TNF)-α and type I collagen. To analyze the role of activated iNKT cells in our model, we administered αGalCer in WT mice during adenine ingestion. After αGalCer injection, we observed a significant reduction in serum creatinine, proinflammatory cytokines and renal fibrosis. However, this improvement in renal function was not observed in IFN-γKO mice after αGalCer treatment and adenine feeding, illustrating that this cytokine plays a role in our model. Our findings may suggest that IFN-γ production is one of the factors contributing to improved renal function after αGalCer administration. PMID:26101952

  6. Hydride Compressor Sorption Cooler and Surface Contamination Issues

    NASA Astrophysics Data System (ADS)

    Bowman, R. C.; Reiter, J. W.; Prina, M.; Kulleck, J. G.; Lanford, W. A.

    2003-07-01

    A continuous-duty hydrogen sorption cryocooler is being developed for the Planck spacecraft, a mission to map the cosmic microwave background beginning in 2007. This cryocooler uses six individual compressor elements (CEs) filled with the hydriding alloy LaNi4.78Sn0.22 to provide high-pressure (50 bar) hydrogen to a Joule-Thomson (J-T) expander and to absorb low-pressure (˜0.3 bar) gas from liquid hydrogen reservoirs cooled to ˜18K. Quadrupole Mass Spectrometry (QMS) showed methane in these hydride beds after cycling during initial operation of laboratory tests of the Planck engineering breadboard (EBB) cooler. These contaminants have caused problems involving plugged J-T expanders. The contaminants probably come from reactions with residual hydrocarbon species on surfaces inside the hydride bed. The hydride bed in each CE is contained in an annular volume called a "gas-gap heat switch," which serves as a reversible, intermittent thermal path to the spacecraft radiator. The gas-gap is either "off" (i.e., its pressure <1.3 Pa), or "on" (i.e., hydrogen gas at ˜4 kPa). The hydrogen pressure is varied with an independent hydride actuator containing ZrNiHx. Early EBB cooler tests showed increasing parasitic heat losses from the inner beds, suggesting residual pressures in the gas gap during its "off" state. The pressure was shown to be due to hydrogen from outgassing from metallic surfaces in the gas gap and hydrogen permeation through the inner sorbent bed wall. This gas accumulation has serious end-of-life implications, as the ZrNi actuator has limited storage capacity and any excess hydrogen would necessarily affect its operation. This paper summarizes experiments on the behavior of hydrogen in the gas gap switch and formation of methane in the CE sorbent beds.

  7. Metal Hydrides as hot carrier cell absorber materials

    NASA Astrophysics Data System (ADS)

    Wang, Pei; Wen, Xiaoming; Shrestha, Santosh; Conibeer, Gavin; Aguey-Zinsou, Kondo-Francois

    2016-09-01

    The hot Carrier Solar Cell (HCSC) allows the photon-induced hot carriers (the carriers with energy larger than the band gap) to be collected before they completely thermalise. The absorber of the HCSC should have a large phononic band gap to supress Klemens Decay, which results in a slow carrier cooling speed. In fact, a large phononic band gap likely exists in a binary compound whose constituent elements have a large mass ratio between each other. Binary hydrides with their overwhelming mass ratio of the constituent elements are important absorber candidates. Study on different types of binary hydrides as potential absorber candidates is presented in this paper. Many binary transition metal hydrides have reported theoretical or experimental phonon dispersion charts which show large phononic band gaps. Among these hydrides, the titanium hydride (TiHX) is outstanding because of its low cost, easy fabrication process and is relatively inert to air and water. A TiHX thin film is fabricated by directly hydrogenating an evaporated titanium thin film. Characterisation shows good crystal quality and the hydrogenation process is believed to be successful. Ultrafast transient absorption (TA) spectroscopy is used to study the electron cooling time of TiHX. The result is very noisy due to the low absorption and transmission of the sample. The evolution of the TA curves has been explained by band to band transition using the calculated band structure of TiH2. Though not reliable due to the high noise, decay time fitting at 700nm and 600nm shows a considerably slow carrier cooling speed of the sample.

  8. Inert blanketing of a hydride bed using typical grade protium

    SciTech Connect

    Klein, J.E.

    2015-03-15

    This paper describes the impact of 500 ppm (0.05%) impurities in protium on the absorption rate of a 9.66 kg LaNi{sub 4.25}Al{sub 0.75} (LANA0.75) metal hydride bed. The presence of 500 ppm or less inerts (i.e. non-hydrogen isotopes) can significantly impact hydrogen bed absorption rates. The impact on reducing absorption rates is significantly greater than predicted assuming uniform temperature, pressure, and compositions throughout the bed. Possible explanations are discussed. One possibility considered was the feed gas contained impurity levels higher than 500 ppm. It was shown that a level of 5000 ppm of inerts would have been necessary to fit the experimental result so this possibility wa dismissed. Another possibility is that the impurities in the protium supply reacted with the hydride material and partially poisoned the hydride. If the hydride were poisoned with CO or another impurity, the removal of the over-pressure gas in the bed would not be expected to allow the hydride loading of the bed to continue as the experimental results showed, so this possibility was also dismissed. The last possibility questions the validity of the calculations. It is assumed in all the calculations that the gas phase composition, temperature, and pressure are uniform throughout the bed. These assumptions are less valid for large beds where there can be large temperature, pressure, and composition gradients throughout the bed. Eventually the impact of 0.05% inerts in protium on bed absorption rate is shown and explained in terms of an increase in inert partial pressure as the bed was loaded.

  9. Hydride transfer during catalysis by dihydrofolate reductase from Thermotoga maritima.

    PubMed Central

    Maglia, Giovanni; Javed, Masood H; Allemann, Rudolf K

    2003-01-01

    DHFR (dihydrofolate reductase) catalyses the metabolically important reduction of 7,8-dihydrofolate by NADPH. DHFR from the hyperthermophilic bacterium Thermotoga maritima (TmDHFR), which shares similarity with DHFR from Escherichia coli, has previously been characterized structurally. Its tertiary structure is similar to that of DHFR from E. coli but it is the only DHFR characterized so far that relies on dimerization for stability. The midpoint of the thermal unfolding of TmDHFR was at approx. 83 degrees C, which was 30 degrees C higher than the melting temperature of DHFR from E. coli. The turnover and the hydride-transfer rates in the kinetic scheme of TmDHFR were derived from measurements of the steady-state and pre-steady-state kinetics using absorbance and stopped-flow fluorescence spectroscopy. The rate constant for hydride transfer was found to depend strongly on the temperature and the pH of the solution. Hydride transfer was slow (0.14 s(-1) at 25 degrees C) and at least partially rate limiting at low temperatures but increased dramatically with temperature. At 80 degrees C the hydride-transfer rate of TmDHFR was 20 times lower than that observed for the E. coli enzyme at its physiological temperature. Hydride transfer depended on ionization of a single group in the active site with a p K(a) of 6.0. While at 30 degrees C, turnover of substrate by TmDHFR was almost two orders of magnitude slower than by DHFR from E. coli; the steady-state rates of the two enzymes differed only 8-fold at their respective working temperatures. PMID:12765545

  10. 5-year review of Metal Hydride Center of Excellence.

    SciTech Connect

    Keller, Jay O.; Klebanoff, Leonard E.

    2010-05-01

    The purpose of the DOE Metal Hydride Center of Excellence (MHCoE) is to develop hydrogen storage materials with engineering properties that allow the use of these materials in a way that satisfies the DOE/FreedomCAR Program system requirements for automotive hydrogen storage. The Center is a multidisciplinary and collaborative effort with technical interactions divided into two broad areas: (1) mechanisms and modeling (which provide a theoretically driven basis for pursuing new materials) and (2) materials development (in which new materials are synthesized and characterized). Driving all of this work are the hydrogen storage system specifications outlined by the FreedomCAR Program for 2010 and 2015. The organization of the MHCoE during the past year is show in Figure 1. During the past year, the technical work was divided into four project areas. The purpose of the project areas is to organize the MHCoE technical work along appropriate and flexible technical lines. The four areas summarized are: (1) Project A - Destabilized Hydrides, The objective of this project is to controllably modify the thermodynamics of hydrogen sorption reactions in light metal hydrides using hydride destabilization strategies; (2) Project B - Complex Anionic Materials, The objective is to predict and synthesize highly promising new anionic hydride materials; (3) Project C - Amides/Imides Storage Materials, The objective of Project C is to assess the viability of amides and imides (inorganic materials containing NH{sub 2} and NH moieties, respectively) for onboard hydrogen storage; and (4) Project D - Alane, AlH{sub 3}, The objective of Project D is to understand the sorption and regeneration properties of AlH{sub 3} for hydrogen storage.

  11. Kinetic and mechanistic analysis of dinucleotide and oligonucleotide formation from the 5'-phosphorimidazolide of adenosine on Na(+)-montmorillonite

    NASA Technical Reports Server (NTRS)

    Kawamura, K.; Ferris, J. P.

    1994-01-01

    The rate constants for the condensation reaction of the 5'-phosphorimidazolide of adenosine (ImpA) to form dinucleotides and oligonucleotides have been measured in the presence of Na(+)-volclay (a Na(+)-montmorillonite) in pH 8 aqueous solution at 25 degrees C. The rates of the reaction of ImpA with an excess of adenosine 5'-monophosphoramidate (NH2pA), P1,P2-diadenosine 5',5'-pyrophosphate (A5'ppA), or adenosine 5'-monophosphate (5'-AMP or pA) in the presence of the montmorillonite to form NH2pA3'pA, A5'ppA3'pA, and pA3'pA, respectively, were measured. Only 3',5'-linked products were observed. The magnitude of the rate constants decrease in the order NH2pA3'pA > A5'-ppA3'pA > pA3'pA. The binding of ImpA to montmorillonite was measured, and the adsorption isotherm was determined. The binding of ImpA to montmorillonite and the formation of higher oligonucleotides is not observed in the absence of salts. Mg2+ enhances binding and oligonucleotide formation more than Ca2+ and Na+. The rate constants for the oligonucleotide formation were determined from the reaction products formed from 10 to 40 mM ImpA in the presence of Na(+)-montmorillonite using the computer program SIMFIT. The magnitudes of the rate constants for the formation of oligonucleotides increased in the order 2-mer < 3-mer < 4-mer ... 7-mer. The rate constants for dinucleotide and trinucleotide formation are more than 1000 times larger than those measured in the absence of montmorillonite. The rate constants for the formation of dinucleotide, trinucleotide, and tetranucleotide are 41,2.6, and 3.7 times larger than those for the formation of oligo(G)s with a poly(C) template. The hydrolysis of ImpA was accelerated 35 times in the presence of the montmorillonite. The catalytic ability of montmorillonite to form dinucleotides and oligonucleotides is quantitatively evaluated and possible pathways for oligo(A) formation are proposed.

  12. Supramolecular polymeric chemosensor for biomedical applications: design and synthesis of a luminescent zinc metallopolymer as a chemosensor for adenine detection.

    PubMed

    Chow, Cheuk-Fai

    2012-11-01

    Adenine is an important bio-molecule that plays many crucial roles in food safety and biomedical diagnostics. Differentiating adenine from a mixture of adenosine and other nucleic bases (guanine, thymine, cytosine, and uracil) is particularly important for both biological and clinical applications. A neutral Zn(II) metallosupramolecular polymer based on acyl hydrazone derived coordination centres (P1) were generated through self-assembly polymerization. It is a linear coordination polymer that behaves like self-standing film. The synthesis, (1)H-NMR characterization, and spectroscopic properties of this supramolecular material are reported. P1 was found to be a chemosensor specific to adenine, with a luminescent enhancement. The binding properties of P1 with common nucleic bases and nucleosides reveal that this supramolecular polymer is very selective to adenine molecules (~20 to 420 times more selectivity than other nucleic bases). The formation constant (K) of P1 to adenine was found to be log K = 4.10 ± 0.02. This polymeric chemosensor produces a specific response to adenine down to 90 ppb. Spectrofluorimetric and (1)H-NMR titration studies showed that the P1 polymer allows each Zn(II) coordination centre to bind to two adenine molecules through hydrogen bonding with their imine and hydrazone protons.

  13. Hydriding performances and modeling of a small-scale ZrCo bed

    SciTech Connect

    Koo, D.; Lee, J.; Park, J.; Paek, S.; Chung, H.; Chang, M.H.; Yun, S.H.; Cho, S.; Jung, K.J.

    2015-03-15

    In order to evaluate the performance of the hydriding of a ZrCo bed, a small-scale getter bed of ZrCo was designed and fabricated. The results show that the hydriding time at room temperature was somewhat shorter than that at higher temperatures of ZrCo and that the performance of hydriding at low temperatures of ZrCo was better than that at high temperatures of ZrCo. The experimental results of the hydrogen pressure of hydriding (ZrCoH{sub 2.8}) at different temperatures were in agreement with the computed values using a numerical modeling equation but with a small difference during the first 10 minutes of the hydriding of ZrCo. The model is based on the Kozeny-Carman equation. The effect of a helium blanket on hydriding was measured and analyzed. The hydriding with no helium blanket in the primary vessel of ZrCo is much faster than that with a helium blanket. The hydriding at a helium concentration of 8% is slower than that at 0%. As the helium concentration increases, the hydriding of ZrCo decreases. The experimental results of the hydriding with 0 %, 4%, and 8% of helium concentration are in agreement with the calculated values but with minimal differences during the first 10 minutes.

  14. Hydride structures in Ti-aluminides subjected to high temperature and hydrogen pressure charging conditions

    NASA Technical Reports Server (NTRS)

    Legzdina, D.; Robertson, I. M.; Birnbaum, H. K.

    1991-01-01

    The distribution and chemistry of hydrides produced in single and dual phase alloys with a composition near TiAl have been investigated by using a combination of TEM and X-ray diffraction techniques. The alloys were exposed at 650 C to 13.8 MPa of gaseous H2 for 100 h. In the single-phase gamma alloy, large hydrides preferentially nucleated on the grain boundaries and matrix dislocations and a population of small hydrides was distributed throughout the matrix. X-ray and electron diffraction patterns from these hydrides indicated that they have an fcc structure with a lattice parameter of 0.45 nm. EDAX analysis of the hydrides showed that they were enriched in Ti. The hydrides were mostly removed by vacuum annealing at 800 C for 24 h. On dissolution of the hydrides, the chemistry of hydride-free regions of the grain boundary returned to the matrix composition, suggesting that Ti segregation accompanied the hydride formation rather than Ti enrichment causing the formation of the hydride.

  15. Differences in Electrostatic Potential Around DNA Fragments Containing Adenine and 8-oxo-Adenine. An Analysis Based on Regular Cylindrical Projection

    SciTech Connect

    Haranczyk, Maciej; Miller, John H; Gutowski, Maciej S

    2007-07-01

    Changes of electrostatic potential (EP) around the DNA molecule resulting from chemical modifications of nucleotides may play a role in enzymatic recognition of damaged sites. Effects of chemical modifications of nucleotides on the structure of DNA have been characterized through large scale density functional theory computations. Quantum mechanical structural optimizations of DNA fragments with three pairs of nucleotides and accompanying counteractions were performed with a B3LYP exchange-correlation functional and 6-31G** basis sets. The “intact” DNA fragment contained adenine in the middle layer, while the “damaged” fragment had the adenine replaced with 8-oxo-adenine. The electrostatic potential around these DNA fragments was projected on a cylindrical surface around the double helix. The two-dimensional maps of EP of the intact and damaged DNA fragments were analyzed to identify these modifications of EP that result from the occurrence of 8-oxo-adenine (8oA). It was found that distortions of a phosphate group neighboring 8oA and displacements of the accompanying countercation are clearly reflected in the EP maps. Helpful discussions Michel Dupuis are gratefully acknowledged. Authors wish to thank Marcel Swart for directing us to a compilation of van der Waals radii. This work was supported by the: (i) US DOE Office of Biological and Environmental Research, Low Dose Radiation Research Program (M.G. and M.H.), (ii) the Office of Science (BER), U. S. Department of Energy, Grant No. DE-FG03-02ER63470 (JHM), (iii) Polish State Committee for Scientific Research (KBN) Grant DS/8221-4-0140-6 (MG), (iv) European Social Funds (EFS) ZPORR/2.22/II/2.6/ARP/U/2/05 (M.H.). M.H. holds the Foundation for Polish Science (FNP) award for young scientists. The calculations were performed at the Academic Computer Center in Gdansk (TASK) and at the Molecular Science Computing Facility (MSCF) in the William R. Wiley Environmental Molecular Sciences Laboratory, a national

  16. Dissociation potential curves of low-lying states in transition metal hydrides. 3. Hydrides of groups 6 and 7.

    PubMed

    Koseki, Shiro; Matsushita, Takeshi; Gordon, Mark S

    2006-02-23

    The dissociation curves of low-lying spin-mixed states in monohydrides of groups 6 and 7 were calculated by using an effective core potential (ECP) approach. This approach is based on the multiconfiguration self-consistent field (MCSCF) method, followed by first-order configuration interaction (FOCI) calculations, in which the method employs an ECP basis set proposed by Stevens and co-workers (SBKJC) augmented by a set of polarization functions. Spin-orbit coupling (SOC) effects are estimated within the one-electron approximation by using effective nuclear charges, since SOC splittings obtained with the full Breit-Pauli Hamitonian are underestimated when ECP basis sets are used. The ground states of group 6 hydrides have Omega = (1)/(2)(X(6)Sigma(+)(1/2)), where Omega is the z component of the total angular momentum quantum number. Although the ground states of group 7 hydrides have Omega = 0(+), their main adiabatic components are different; the ground state in MnH originates from the lowest (7)Sigma(+), while in TcH and ReH the main component of the ground state is the lowest (5)Sigma(+). The present paper reports a comprehensive set of theoretical results including the dissociation energies, equilibrium distances, electronic transition energies, harmonic frequencies, anharmonicities, and rotational constants for several low-lying spin-mixed states in these hydrides. Transition dipole moments were also computed among the spin-mixed states and large peak positions of electronic transitions are suggested theoretically for these hydrides. The periodic trends of physical properties of metal hydrides are discussed, based on the results reported in this and other recent studies.

  17. Composite Materials for Hazard Mitigation of Reactive Metal Hydrides.

    SciTech Connect

    Pratt, Joseph William; Cordaro, Joseph Gabriel; Sartor, George B.; Dedrick, Daniel E.; Reeder, Craig L.

    2012-02-01

    In an attempt to mitigate the hazards associated with storing large quantities of reactive metal hydrides, polymer composite materials were synthesized and tested under simulated usage and accident conditions. The composites were made by polymerizing vinyl monomers using free-radical polymerization chemistry, in the presence of the metal hydride. Composites with vinyl-containing siloxane oligomers were also polymerized with and without added styrene and divinyl benzene. Hydrogen capacity measurements revealed that addition of the polymer to the metal hydride reduced the inherent hydrogen storage capacity of the material. The composites were found to be initially effective at reducing the amount of heat released during oxidation. However, upon cycling the composites, the mitigating behavior was lost. While the polymer composites we investigated have mitigating potential and are physically robust, they undergo a chemical change upon cycling that makes them subsequently ineffective at mitigating heat release upon oxidation of the metal hydride. Acknowledgements The authors would like to thank the following people who participated in this project: Ned Stetson (U.S. Department of Energy) for sponsorship and support of the project. Ken Stewart (Sandia) for building the flow-through calorimeter and cycling test stations. Isidro Ruvalcaba, Jr. (Sandia) for qualitative experiments on the interaction of sodium alanate with water. Terry Johnson (Sandia) for sharing his expertise and knowledge of metal hydrides, and sodium alanate in particular. Marcina Moreno (Sandia) for programmatic assistance. John Khalil (United Technologies Research Corp) for insight into the hazards of reactive metal hydrides and real-world accident scenario experiments. Summary In an attempt to mitigate and/or manage hazards associated with storing bulk quantities of reactive metal hydrides, polymer composite materials (a mixture of a mitigating polymer and a metal hydride) were synthesized and tested

  18. SPECIATION OF ARSENIC COMPOUNDS IN DRINKING WATER BY CAPILLARY ELECTROPHORESIS WITH HYDRODYNAMICALLY MODIFIED ELECTROOSMOTIC FLOW DETECTED THROUGH HYDRIDE GENERATION INDUCTIVELY COUPLED PLASMA MASS..

    EPA Science Inventory

    Capillary electrophoresis (CE) was used to speciate four environmentally significant, toxic forms of arsenic: arsenite, arsenate, monomethylarsonic acid and dimethylarsinic acid. Hydride generation (HG) was used to convert the species into their respective hydrides. The hydride ...

  19. SPECIATION OF ARSENIC COMPOUNDS IN DRINKING WATER BY CAPILLARY ELECTROPHORESIS WITH HYDRODYNAMICALLY MODIFIED ELECTROOSMOTIC FLOW DETECTED THROUGH HYDRIDE GENERATION INDUCTIVELY COUPLED PLASMA MASS...

    EPA Science Inventory

    Capillary electrophoresis (CE) was used to speciate four environmentally significant, toxic forms of arsenic: arsenite, arsenate, monomethylarsonic acid and dimethylarsinic acid. Hydride generation (HG) was used to convert the species into their respective hydrides. The hydride s...

  20. Effect of thermo-mechanical cycling on zirconium hydride reorientation studied in situ with synchrotron X-ray diffraction

    NASA Astrophysics Data System (ADS)

    Colas, Kimberly B.; Motta, Arthur T.; Daymond, Mark R.; Almer, Jonathan D.

    2013-09-01

    The circumferential hydrides normally present in nuclear reactor fuel cladding after reactor exposure may dissolve during drying for dry storage and re-precipitate when cooled under load into a more radial orientation, which could embrittle the fuel cladding. It is necessary to study the rates and conditions under which hydride reorientation may happen in order to assess fuel integrity in dry storage. The objective of this work is to study the effect of applied stress and thermal cycling on the hydride morphology in cold-worked stress-relieved Zircaloy-4 by combining conventional metallography and in situ X-ray diffraction techniques. Metallography is used to study the evolution of hydride morphology after several thermo-mechanical cycles. In situ X-ray diffraction performed at the Advanced Photon Source synchrotron provides real-time information on the process of hydride dissolution and precipitation under stress during several thermal cycles. The detailed study of diffracted intensity, peak position and full-width at half-maximum provides information on precipitation kinetics, elastic strains and other characteristics of the hydride precipitation process. The results show that thermo-mechanical cycling significantly increases the radial hydride fraction as well as the hydride length and connectivity. The radial hydrides are observed to precipitate at a lower temperature than circumferential hydrides. Variations in the magnitude and range of hydride strains due to reorientation and cycling have also been observed. These results are discussed in light of existing models and experiments on hydride reorientation. The study of hydride elastic strains during precipitation shows marked differences between circumferential and radial hydrides, which can be used to investigate the reorientation process. Cycling under stress above the threshold stress for reorientation drastically increases both the reoriented hydride fraction and the hydride size. The reoriented hydride

  1. FEASIBILITY OF RECYCLING PLUTONIUM AND MINOR ACTINIDES IN LIGHT WATER REACTORS USING HYDRIDE FUEL

    SciTech Connect

    Greenspan, Ehud; Todreas, Neil; Taiwo, Temitope

    2009-03-10

    The objective of this DOE NERI program sponsored project was to assess the feasibility of improving the plutonium (Pu) and minor actinide (MA) recycling capabilities of pressurized water reactors (PWRs) by using hydride instead of oxide fuels. There are four general parts to this assessment: 1) Identifying promising hydride fuel assembly designs for recycling Pu and MAs in PWRs 2) Performing a comprehensive systems analysis that compares the fuel cycle characteristics of Pu and MA recycling in PWRs using the promising hydride fuel assembly designs identified in Part 1 versus using oxide fuel assembly designs 3) Conducting a safety analysis to assess the likelihood of licensing hydride fuel assembly designs 4) Assessing the compatibility of hydride fuel with cladding materials and water under typical PWR operating conditions Hydride fuel was found to offer promising transmutation characteristics and is recommended for further examination as a possible preferred option for recycling plutonium in PWRs.

  2. The free-energy barrier to hydride transfer across a dipalladium complex.

    PubMed

    Vanston, C R; Kearley, G J; Edwards, A J; Darwish, T A; de Souza, N R; Ramirez-Cuesta, A J; Gardiner, M G

    2015-01-01

    We use density-functional theory molecular dynamics (DFT-MD) simulations to determine the hydride transfer coordinate between palladium centres of the crystallographically observed terminal hydride locations, Pd-Pd-H, originally postulated for the solution dynamics of the complex bis-NHC dipalladium hydride [{(MesIm)2CH2}2Pd2H][PF6], and then calculate the free-energy along this coordinate. We estimate the transfer barrier-height to be about 20 kcal mol(-1) with a hydride transfer rate in the order of seconds at room temperature. We validate our DFT-MD modelling using inelastic neutron scattering which reveals anharmonicity of the hydride environment that is so pronounced that there is complete failure of the harmonic model for the hydride ligand. The simulations are extended to high temperature to bring the H-transfer to a rate that is accessible to the simulation technique.

  3. The free-energy barrier to hydride transfer across a dipalladium complex

    SciTech Connect

    Ramirez-Cuesta, Anibal J

    2015-01-01

    We use density-functional theory molecular dynamics (DFT-MD) simulations to determine the hydride transfer coordinate between palladium centres of the crystallographically observed terminal hydride locations, Pd-Pd-H, originally postulated for the solution dynamics of the complex bis-NHC dipalladium hydride [{(MesIm)(2)CH2}(2)Pd2H][PF6], and then calculate the free-energy along this coordinate. We estimate the transfer barrier-height to be about 20 kcal mol(-1) with a hydride transfer rate in the order of seconds at room temperature. We validate our DFT-MD modelling using inelastic neutron scattering which reveals anharmonicity of the hydride environment that is so pronounced that there is complete failure of the harmonic model for the hydride ligand. The simulations are extended to high temperature to bring the H-transfer to a rate that is accessible to the simulation technique.

  4. In situ synchrotron X-ray diffraction study of hydrides in Zircaloy-4 during thermomechanical cycling

    NASA Astrophysics Data System (ADS)

    Cinbiz, Mahmut N.; Koss, Donald A.; Motta, Arthur T.; Park, Jun-Sang; Almer, Jonathan D.

    2017-04-01

    The d-spacing evolution of both in-plane and out-of-plane hydrides has been studied using in situ synchrotron radiation X-ray diffraction during thermo-mechanical cycling of cold-worked stress-relieved Zircaloy-4. The structure of the hydride precipitates is such that the δ{111} d-spacing of the planes aligned with the hydride platelet face is greater than the d-spacing of the 111 planes aligned with the platelet edges. Upon heating from room temperature, the δ{111} planes aligned with hydride plate edges exhibit bi-linear thermally-induced expansion. In contrast, the d-spacing of the (111) plane aligned with the hydride plate face initially contracts upon heating. These experimental results can be understood in terms of a reversal of stress state associated with precipitating or dissolving hydride platelets within the α-zirconium matrix.

  5. The free-energy barrier to hydride transfer across a dipalladium complex

    DOE PAGES

    Ramirez-Cuesta, Anibal J

    2015-01-01

    We use density-functional theory molecular dynamics (DFT-MD) simulations to determine the hydride transfer coordinate between palladium centres of the crystallographically observed terminal hydride locations, Pd-Pd-H, originally postulated for the solution dynamics of the complex bis-NHC dipalladium hydride [{(MesIm)(2)CH2}(2)Pd2H][PF6], and then calculate the free-energy along this coordinate. We estimate the transfer barrier-height to be about 20 kcal mol(-1) with a hydride transfer rate in the order of seconds at room temperature. We validate our DFT-MD modelling using inelastic neutron scattering which reveals anharmonicity of the hydride environment that is so pronounced that there is complete failure of the harmonic model formore » the hydride ligand. The simulations are extended to high temperature to bring the H-transfer to a rate that is accessible to the simulation technique.« less

  6. Heat transfer analysis of metal hydrides in metal-hydrogen secondary batteries

    NASA Technical Reports Server (NTRS)

    Onischak, M.; Dharia, D.; Gidaspow, D.

    1976-01-01

    The heat transfer between a metal-hydrogen secondary battery and a hydrogen-storing metal hydride was studied. Temperature profiles of the endothermic metal hydrides and the metal-hydrogen battery were obtained during discharging of the batteries assuming an adiabatic system. Two hydride materials were considered in two physical arrangements within the battery system. In one case the hydride is positioned in a thin annular region about the battery stack; in the other the hydride is held in a tube down the center of the stack. The results show that for a typical 20 ampere-hour battery system with lanthanum pentanickel hydride as the hydrogen reservoir the system could perform successfully.

  7. Molecular early main group metal hydrides: synthetic challenge, structures and applications.

    PubMed

    Harder, Sjoerd

    2012-11-25

    Within the general area of early main group metal chemistry, the controlled synthesis of well-defined metal hydride complexes is a rapidly developing research field. As group 1 and 2 metal complexes are generally highly dynamic and lattice energies for their [MH](∞) and [MH(2)](∞) salts are high, the synthesis of well-defined soluble hydride complexes is an obvious challenge. Access to molecular early main group metal hydrides, however, is rewarding: these hydrocarbon-soluble metal hydrides are highly reactive, have found use in early main group metal catalysis and are potentially also valuable molecular model systems for polar metal hydrides as a hydrogen storage material. The article focusses specifically on alkali and alkaline-earth metal hydride complexes and discusses the synthetic challenge, molecular structures, reactivity and applications.

  8. Effect of hydride orientation on fracture toughness of Zircaloy-4 cladding

    NASA Astrophysics Data System (ADS)

    Hsu, Hsiao-Hung; Tsay, Leu-Wen

    2011-01-01

    Hydrogen embrittlement is one of the major degradation mechanisms for high burnup fuel cladding during reactor service and spent fuel dry storage, which is related to the hydrogen concentration, morphology and orientation of zirconium hydrides. In this work, the J-integral values for X-specimens with different hydride orientations are measured to evaluate the fracture toughness of Zircaloy-4 (Zry-4) cladding. The toughness values for Zry-4 cladding with various percentages of radial hydrides are much smaller than those with circumferential hydrides only in the same hydrogen content level at 25 °C. The fractograghic features reveal that the crack path is influenced by the orientation of zirconium hydride. Moreover, the fracture toughness measurements for X-specimens at 300 °C are not sensitive to a variation in hydride orientation but to hydrogen concentration.

  9. Particular behavior of the adenine and guanine ring-breathing modes upon the DNA conformational transitions.

    PubMed

    Ghomi, M; Letellier, R; Taillandier, E

    1988-06-01

    Harmonic dynamics calculations performed on the deoxyguanosine (dG) and deoxyadenosine (dA) residues, based on a reliable force field, show that the breathing motions of both guanine and adenine residues are involved in two different vibration modes (750-500 cm-1 spectral region). The calculated results reveal a strong coupling of these modes with the sugar pucker motions. This effect has been verified for the dG residue by the Raman spectra of polyd(G-C). As far as the dA residue is concerned, the particular behavior of the adenine residue breathing mode predicted by these calculations, has been confirmed by Raman spectra of polyd(A-T) undergoing a B----Z conformational transition.

  10. Neonatal hypothyroidism affects the adenine nucleotides metabolism in astrocyte cultures from rat brain.

    PubMed

    Braganhol, Elizandra; Bruno, Alessandra Nejar; Bavaresco, Luci; Barreto-Chaves, Maria Luiza M; Sarkis, João José Freitas; Battastini, Ana Maria Oliveira

    2006-04-01

    Neonatal hypothyroidism is associated with multiple and severe brain alterations. We recently demonstrated a significant increase in hydrolysis of AMP to adenosine in brain of hypothyroid rats at different ages. However, the origin of this effect was unclear. Considering the effects of adenine nucleotides to brain functions and the harmful effects of neonatal hypothyroidism to normal development of the central nervous system, in this study we investigated the metabolism of adenine nucleotides in hippocampal, cortical and cerebellar astrocyte cultures from rats submitted to neonatal hypothyroidism. ATP and AMP hydrolysis were enhanced by 52 and 210%, respectively, in cerebellar astrocytes from hypothyroid rats. In hippocampus of hypothyroid rats, the 47% increase in AMP hydrolysis was significantly reverted when the astrocytes were treated with T3. Therefore, the imbalance in the ATP and adenosine levels in astrocytes, during brain development, may contribute to some of the effects described in neonatal hypothyroidism.

  11. BII stability and base step flexibility of N6-adenine methylated GATC motifs.

    PubMed

    Karolak, Aleksandra; van der Vaart, Arjan

    2015-01-01

    The effect of N6-adenine methylation on the flexibility and shape of palindromic GATC sequences has been investigated by molecular dynamics simulations. Variations in DNA backbone geometry were observed, which were dependent on the degree of methylation and the identity of the bases. While the effect was small, more frequent BI to BII conversions were observed in the GA step of hemimethylated DNA. The increased BII population of the hemimethylated system positively correlated with increased stacking interactions between methylated adenine and guanine, while stacking interactions decreased at the TC step for the fully methylated strand. The flexibility of the AT and TC steps was marginally affected by methylation, in a fashion that was correlated with stacking interactions. The facilitated BI to BII conversion in hemimethylated strands might be of importance for SeqA selectivity and binding.

  12. From formamide to adenine: a self-catalytic mechanism for an abiotic approach.

    PubMed

    Wang, Jing; Gu, Jiande; Nguyen, Minh Tho; Springsteen, Greg; Leszczynski, Jerzy

    2013-11-14

    Mechanisms for abiotic reaction pathways from formamide (H2NCHO) to adenine are presented herein. Formamide is a simple C1 building block hypothesized to be a precursor to many protometabolic compounds. On the basis of a step-by-step mechanism of the reaction pathways, formamide is suggested to be more reactive in addition reactions than HCN. In addition to its simplicity, the formamide self-catalyzed mechanism is energetically (kinetically) more viable than either a water-catalyzed mechanism or noncatalyzed processes. Moreover, this self-catalyzed mechanism accounts for the yields of purine and adenine previously observed in experiments. This mechanism may elucidate processes that were vital for the emergence of life on the early earth.

  13. Critical appraisal of excited state nonadiabatic dynamics simulations of 9H-adenine.

    PubMed

    Barbatti, Mario; Lan, Zhenggang; Crespo-Otero, Rachel; Szymczak, Jaroslaw J; Lischka, Hans; Thiel, Walter

    2012-12-14

    In spite of the importance of nonadiabatic dynamics simulations for the understanding of ultrafast photo-induced phenomena, simulations based on different methodologies have often led to contradictory results. In this work, we proceed through a comprehensive investigation of on-the-fly surface-hopping simulations of 9H-adenine in the gas phase using different electronic structure theories (ab initio, semi-empirical, and density functional methods). Simulations that employ ab initio and semi-empirical multireference configuration interaction methods predict the experimentally observed ultrafast deactivation of 9H-adenine with similar time scales, however, through different internal conversion channels. Simulations based on time-dependent density functional theory with six different hybrid and range-corrected functionals fail to predict the ultrafast deactivation. The origin of these differences is analyzed by systematic calculations of the relevant reaction pathways, which show that these discrepancies can always be traced back to topographical features of the underlying potential energy surfaces.

  14. Theoretical Study of Tautomerization Reactions for the Ground and First Excited Electronic States of Adenine

    NASA Technical Reports Server (NTRS)

    Salter, Latasha M.; Chaban, Galina M.; Kwak, Dochan (Technical Monitor)

    2002-01-01

    Geometrical structures and energetic properties for different tautomers of adenine are calculated in this study, using multi-configurational wave functions. Both the ground and the lowest singlet excited state potential energy surfaces are studied. Four tautomeric forms are considered, and their energetic order is found to be different on the ground and the excited state potential energy surfaces. Minimum energy reaction paths are obtained for hydrogen atom transfer (tautomerization) reactions in the ground and the lowest excited electronic states. It is found that the barrier heights and the shapes of the reaction paths are different for the ground and the excited electronic states, suggesting that the probability of such tautomerization reaction is higher on the excited state potential energy surface. This tautomerization process should become possible in the presence of water or other polar solvent molecules and should play an important role in the photochemistry of adenine.

  15. Induction of nucleoside phosphorylase in Enterobacter aerogenes and enzymatic synthesis of adenine arabinoside.

    PubMed

    Wei, Xiao-Kun; Ding, Qing-Bao; Zhang, Lu; Guo, Yong-Li; Ou, Lin; Wang, Chang-Lu

    2008-07-01

    Nucleoside phosphorylases (NPases) were found to be induced in Enterobacter aerogenes DGO-04, and cytidine and cytidine 5'-monophosphate (CMP) were the best inducers. Five mmol/L to fifteen mmol/L cytidine or CMP could distinctly increase the activities of purine nucleoside phosphorylase (PNPase), uridine phosphorylase (UPase) and thymidine phosphorylase (TPase) when they were added into medium from 0 to 8 h. In the process of enzymatic synthesis of adenine arabinoside from adenine and uracil arabinoside with wet cells of Enterobacter aerogenes DGO-04 induced by cytidine or CMP, the reaction time could be shortened from 36 to 6 h. After enzymatic reaction the activity of NPase in the cells induced remained higher than that in the cells uninduced.

  16. Orbital-like motion of hydride ligands around low-coordinate metal centers.

    PubMed

    Ortuño, Manuel A; Vidossich, Pietro; Conejero, Salvador; Lledós, Agustí

    2014-12-15

    Hydrogen atoms in the coordination sphere of a transition metal are highly mobile ligands. Here, a new type of dynamic process involving hydrides has been characterized by computational means. This dynamic event consists of an orbital-like motion of hydride ligands around low-coordinate metal centers containing N-heterocyclic carbenes. The hydride movement around the carbene-metal-carbene axis is the lowest energy mode connecting energy equivalent isomers. This understanding provides crucial information for the interpretation of NMR spectra.

  17. Neutral binuclear rare-earth metal complexes with four μ₂-bridging hydrides.

    PubMed

    Rong, Weifeng; He, Dongliang; Wang, Meiyan; Mou, Zehuai; Cheng, Jianhua; Yao, Changguang; Li, Shihui; Trifonov, Alexander A; Lyubov, Dmitrii M; Cui, Dongmei

    2015-03-25

    The first neutral rare-earth metal dinuclear dihydrido complexes [(NPNPN)LnH2]2 (2-Ln; Ln = Y, Lu; NPNPN: N[Ph2PNC6H3((i)Pr)2]2) bearing μ2-bridging hydride ligands have been synthesized. In the presence of THF, 2-Y undergoes intramolecular activation of the sp(2) C-H bond to form dinuclear aryl-hydride complex 3-Y containing three μ2-bridging hydride ligands.

  18. High temperature metal hydrides as heat storage materials for solar and related applications.

    PubMed

    Felderhoff, Michael; Bogdanović, Borislav

    2009-01-01

    For the continuous production of electricity with solar heat power plants the storage of heat at a temperature level around 400 degrees C is essential. High temperature metal hydrides offer high heat storage capacities around this temperature. Based on Mg-compounds, these hydrides are in principle low-cost materials with excellent cycling stability. Relevant properties of these hydrides and their possible applications as heat storage materials are described.

  19. Thermodynamic studies and hydride transfer reactions from a rhodium complex to BX3 compounds.

    PubMed

    Mock, Michael T; Potter, Robert G; Camaioni, Donald M; Li, Jun; Dougherty, William G; Kassel, W Scott; Twamley, Brendan; DuBois, Daniel L

    2009-10-14

    This study examines the use of transition-metal hydride complexes that can be generated by the heterolytic cleavage of H(2) gas to form B-H bonds. Specifically, these studies are focused on providing a reliable and quantitative method for determining when hydride transfer from transition-metal hydrides to three-coordinate BX(3) (X = OR, SPh, F, H; R = Ph, p-C(6)H(4)OMe, C(6)F(5), (t)Bu, Si(Me)(3)) compounds will be favorable. This involves both experimental and theoretical determinations of hydride transfer abilities. Thermodynamic hydride donor abilities (DeltaG(o)(H(-))) were determined for HRh(dmpe)(2) and HRh(depe)(2), where dmpe = 1,2-bis(dimethylphosphinoethane) and depe = 1,2-bis(diethylphosphinoethane), on a previously established scale in acetonitrile. This hydride donor ability was used to determine the hydride donor ability of [HBEt(3)](-) on this scale. Isodesmic reactions between [HBEt(3)](-) and selected BX(3) compounds to form BEt(3) and [HBX(3)](-) were examined computationally to determine their relative hydride affinities. The use of these scales of hydride donor abilities and hydride affinities for transition-metal hydrides and BX(3) compounds is illustrated with a few selected reactions relevant to the regeneration of ammonia borane. Our findings indicate that it is possible to form B-H bonds from B-X bonds, and the extent to which BX(3) compounds are reduced by transition-metal hydride complexes forming species containing multiple B-H bonds depends on the heterolytic B-X bond energy. An example is the reduction of B(SPh)(3) using HRh(dmpe)(2) in the presence of triethylamine to form Et(3)N-BH(3) in high yields.

  20. High Temperature Metal Hydrides as Heat Storage Materials for Solar and Related Applications

    PubMed Central

    Felderhoff, Michael; Bogdanović, Borislav

    2009-01-01

    For the continuous production of electricity with solar heat power plants the storage of heat at a temperature level around 400 °C is essential. High temperature metal hydrides offer high heat storage capacities around this temperature. Based on Mg-compounds, these hydrides are in principle low-cost materials with excellent cycling stability. Relevant properties of these hydrides and their possible applications as heat storage materials are described. PMID:19333448