Showing papers on "Ammonia published in 1984"

Influence of pathological concentrations of ammonia on metabolic fate of 14C-labeled glutamate in astrocytes in primary cultures

Abstract: Rates of glutamine formation and of carbon dioxide production (as an indication of oxidative deamination of glutamate) were determined in primary cultures of astrocytes exposed to 50 microM labeled glutamate in the absence or presence of added ammonia (0.1-3 mM). Glutamine formation (1.7 nmol/min/mg protein) was unaffected by all concentrations of added ammonia. This probably reflects the presence of a low content of ammonia (0.1-0.2 mM), originating from degradation of glutamine, in the cells even in the absence of added ammonia, and it shows that pathophysiological concentrations of ammonia do not increase the formation of glutamine from exogenous glutamate. The carbon dioxide production rate was 5.9 nmol/min/mg protein, i.e., three to four times higher than the rate of glutamine formation. It was significantly reduced (to 3.5 nmol/min/mg protein) in the presence of 1 mM or more of ammonia. This is in keeping with suggestions by others that toxic levels of ammonia affect oxidative metabolism.

Theoretical study of silylene insertion into nitrogen-hydrogen, oxygen-hydrogen, fluorine-hydrogen, phosphorus-hydrogen, sulfur-hydrogen, and chlorine-hydrogen bonds

Abstract: Surfaces d'energie potentielle pour les reactions d'insertion du silylene dans NH 3 , H 2 O, HF, PH 3 , H 2 S et HCl

Ethylene oxidation by Nitrosomonas europaea

Abstract: Incubation of whole cells of the nitrifying bacterium Nitrosomonas europaea with ethylene led to the formation of ethylene oxide. Ethylene oxide production was prevented by inhibitors of ammonium ion oxidation, and showed properties implying that ethylene is a substrate for the ammonia oxidising enzyme, ammonia monooxygenase. Endogenous substrates, hydroxylamine, hydrazine and ammonium ions were compared as sources of reducing power in terms of rates and stoichiometries of ethylene oxidation. The highest rates of ethylene oxide formation (15 μmol h-1 mg protein-1) were obtained with hydrazine as donor. The data suggest that at high concentrations of ethylene the rate of oxidation is limited by the rate at which reducing power can be supplied to the monooxygenase, not by an intrinsic V max. Ethylene had an inhibitory effect on the rate of ammonium ion utilisation; an approximate K i of 80 μM was derived, but the results deviated from simple competitive behaviour. Measurement of relative rates of ethylene oxide formation and ammonium ion utilization led to a k cat/K m value for ethylene of 1.1 relative to NH 4 + , or 0.04 relative to the true natural substrate, NH3. The effects of higher concentrations of ethylene oxide on oxygen uptake rates were also investigated. The results imply that ethylene oxide is also a substrate for the monooxygenase, but with a much lower affinity than ethylene.

Ammonia decomposition on (1 1 10) and (0 0 1) surfaces of ruthenium

Abstract: The decomposition of ammonia on stepped Ru(1 1 10) and flat Ru(0 0 1) surfaces has been investigated by Auger electron spectroscopy, low-energy electron diffraction, thermal-desorption studies and kinetic studies. The reaction takes place at ca. 400 K, and N2 and H2 are formed stoichiometrically. At lower temperatures ( 600 K) the rate of reaction is linearly dependent on ammonia pressure only and independent of hydrogen and nitrogen pressures; the amount of adsorbed hydrogen on the surface was negligible. Since no isotope effect was observed, the reaction is thought to proceed through the recombination of N(ads) on the surface.

Strongly hydrogen-bonded molecular complexes studied by matrix-isolation vibrational spectroscopy. Part 2.—Amine–hydrogen chloride complexes

Abstract: Infrared spectra are reported of a strongly hydrogen-bonded complex between ammonia and hydrogen chloride trapped in argon and nitrogen matrices. There are substantial differences between the spectra of the complex in the two matrices, and these are attributed to increased proton transfer from hydrogen chloride to ammonia in the more polar nitrogen matrix. The corresponding gas-phase complex would be expected to display less proton transfer than the complex in an argon matrix.

Ammonia reduction-denitration process and apparatus therefor

Abstract: An ammonia reduction-denitration process for exhaust gases containing NOx consisting mainly of NO2, and an apparatus therefor are provided, which process comprises treating the exhaust gases with ammonia using a catalyst which is active to both a reaction of (NO2 +NH3 →N2 +N2 O+H2 O) and a reaction of (N2 O+NH3 →N2 +H2 O) at an area velocity of 3 m/h or less and in a concentration ratio of NH3 /NO2 of 1.3 or more. According to this process, it is possible to reduce NO2 contained in the exhaust gases with ammonia at one stage without by-producing N2 O.

Steam injection method

Abstract: A method is disclosed for inhibiting silica dissolution during steam injection into a formation. In the method, there is added to the steam, or to feedwater used to generate the steam, a mixture comprising: (a) a compound selected from the group consisting of ammonium salts of inorganic acids, ammonium salts of carboxylic acids, quaternary ammonium halides, amine or substituted amine hydrochlorides, and mixtures thereof; and (b) a compound selected from the group consisting of ammonia, salts which decompose in steam to form acid neutralizers or buffers having alkaline pH values, amides of carbamic acid or thiocarbamic acid and derivatives of such amides, tertiary carboxylic acid amides and their substituted and alkylated derivatives, and mixtures thereof. In steam, the compound of (a) decomposes to form a proton, which neutralizes hydroxide generated by ions in the steam generator feedwater. The compound of (b) neutralizes or buffers the steam to prevent acidic pH values which would be obtained from overtreatment with compound (a) above.

Effect of L-Methionine Sulphoximine on the Products of Photosynthesis in Wheat (Triticum aestivum) Leaves

Abstract: Methionine sulphoximine, an inhibitor of glutamine synthetase, caused ammonia accumulation in detached wheat leaves. The rate was increased by increased oxygen in the atmosphere and by simultaneously supplying glycine or giving extra nitrate; it was decreased by isonicotinyl hydrazide. Ammonia production was light-dependent and continued at a constant rate in air for at least 2 h. Photosynthesis was progressively inhibited after the first hour; this inhibition was not because of increased stomatal resistance. Leaves supplied with 30 mol m~3 ammonium chloride, without methionine sulphoximine, accumulated more ammonia than leaves treated with the inhibitor but showed less inhibition of photosynthesis. The inhibitor decreased synthesis of [14C] amino acids from 14C02 in the light but increased the synthesis of [14C] malate and, relatively, the incorporation of 14C into sugar phosphates. In the absence of inhibitor, nitrate increased and ammonium ion decreased synthesis of malate. Methionine sulphoximine, by causing a shortage of amino acids, probably inhibited photosynthesis in part by decreasing the recycling of carbon from the photorespiratory cycle back to the Calvin cycle.

Nitrate content and nitrate reductase activity in Rumex obtusifolius L. : II. Responses to nitrate starvation and nitrogen fertilization.

Abstract: The aim of this work was to investigate the effect of nitrogen starvation and subsequent fentilization with nitrate or ammonium on nitrate content and nitrate reductase activity of Rumex obtusifolius L. under natural conditions.When plants were transplanted to nitrate-poor media, endogenous nitrate was reduced within a few days. In parallel, nitrage reductase activities dropped to about 25% of the initial values. As a consequence of nitrate fertilization (1; 10 or 100 mmol KNO3/l substrate), endogenous nitrate content of the plant abruptly increased within one day. In extreme cases, nitrate concentrations of up to 10% of plant dry weight could be observed without being lethal. High external nitrate concentrations caused an inhibition of nitrate reductase within the leaves, while low external concentrations provoked an increase in the enzyme activity of about 450% within one day. Ammonium fertilization (5 mmol (NH4)2SO4/l substrate) also caused an increase in nitrate reductase activity and nitrate content within leaf blades. This observation indicates a rapid nitrification of ammonium in the substrate. When plants were fertilized with ammonium plus nitrate (2.5 mmol (NH4)2SO4+ 5 mmol KNO3/l substrate), an extremely high and long term increase in nitrate reduction could be observed. Due to an intensive enzymatic nitrate turnover, the nitrate content of leaf blades then remained relatively low. Our observations do not point to an inhibition of nitrate reductase activity in leaves of Rumex obtusifolius by ammonium. Despite temporarily high endogenous nitrate concentrations, Rumex obtusifolius may not be termed as a "nitrate storage" plant, since the accumulation of nitrate is a short term process only.

Polyalkylene polyamines from alkanolamine and ammonia or amines using group IIIB metal acid phosphate catalysts

Abstract: A process for preparing polyalkylene polyamine compounds is disclosed wherein ammonia or a primary or secondary amine and an alkanolamine compound are reacted in the presence of an effective amount of a Group IIIB metal acid phosphate at a temperature from about 175 to 400°C under a pressure sufficient to maintain a substantial amount of the ammonia or amine in the reaction zone. The polyalkylene polyamines thus formed are recovered from the reaction mixture.

Oxidation of ammonia and hydroxylamine to nitrate in the rat and in vitro

Abstract: We have demonstrated that ammonia is oxidized to nitrate in the rat. Male Sprague-Dawley rats gavaged with 1000 mumol N-15-ammonium chloride each day for 5 days were found to excrete low, but significant amounts of excess N-15-nitrate in their urines on the five days of treatment and on the five subsequent days. We recovered a total of 0.28 +/- 0.03 mumol excess N-15-nitrate (mean +/- SE) per rat, which indicates that ammonia is converted to nitrate in a yield of approximately 0.0080%. The oxidation of N-15-labeled glycine and L-glutamic acid to N-15-nitrate could not be detected. N-15-Hydroxylamine was oxidized in the rat to N-15-nitrate in a yield of 4.7%, which shows that hydroxylamine is a possible intermediate in the ammonia oxidation process. Injection of rats with Arochlor 1254, an inducer of several isozymes of cytochrome P-450, did not significantly affect the rate of endogeneous nitrate synthesis. Carbon tetrachloride, which causes hepatic lipid peroxidation, produced a small but significant increase in nitrate synthesis. We confirmed the observation that a bacterial endotoxin can greatly stimulate nitrate synthesis, and we showed that concurrent treatment with superoxide dismutase does not modify the effect of the endotoxin. An in vitro chemical model system was used to demonstrate that oxidation of ammonia to nitrate by the hydroxyl radical at physiological pH is chemically feasible. Our results are consistent with the hypothesis that ammonia is oxidized to nitrate in vivo by a non-enzymatic process which involves active oxygen species such as the hydroxyl radical. We estimate that a 215 g rat produces 3.0 mumol of nitrate per day via ammonia oxidation.

Sustained Photoproduction of Ammonia from Dinitrogen and Water by the Nitrogen-Fixing Cyanobacterium Anabaena sp. Strain ATCC 33047.

Abstract: Conditions have been developed that lengthen the time during which photosynthetic dinitrogen fixation by filaments of the cyanobacterium Anabaena sp. strain ATCC 33047 proceeds freely, whereas the subsequent conversion of ammonia into organic nitrogen remains blocked, with the resulting ammonia released to the outer medium. When l-methionine-dl-sulfoximine was added every 20 h, maximal rates of ammonia production (25 to 30 μmol/mg of chlorophyll per h) were maintained for about 50 h. After this time, ammonia production ceased due to a deficiency of glutamine and other nitrogenous compounds in the filaments, conditions which finally led to cell lysis. The effective ammonia production period could be further extended to about 7 days by adding a small amount of glutamine at the end of a 40-h production period or by allowing the cells to recover for 8 h in the absence of l-methionine-dl-sulfoximine after every 40-h period in the presence of the inhibitor. A more prolonged steady production of ammonia, lasting for longer than 2 weeks, was achieved by alternating treatments with the glutamine synthetase inhibitors l-methionine-dl-sulfoximine and phosphinothricin, provided that 8-h recovery periods in the absence of either compound were also alternated throughout. The biochemically manipulated cyanobacterial filaments thus represent a system that is relatively stable with time for the conversion of light energy into chemical energy, with the net generation of a valuable fuel and fertilizer through the photoreduction of dinitrogen to ammonia.

Leaching metals from spent hydroprocessing catalysts with ammonium sulfate

Abstract: A process for enhancing recovery of metals, especially cobalt, from spent hydroprocessing catalysts when the spent catalyst particles are first roasted at between 400° C. and 600° C. and then contacted with a first aqueous solution of ammonia and an ammonium salt to recover nickel, cobalt, molybdenum, tungsten, and vanadium. The once-leached spent hydroprocessing catalysts are again leached by contacting them with a second aqueous solution of ammonium sulfate at a pH of 1 to 4.

On the abiotic formation of amino acids. I: HCN as a precursor of amino acids detected in extracts of lunar samples. ― II: Formation of HCN and amino acids from simulated mixtures of gases released from lunar samples

Abstract: Two studies on the abiotic formation of amino acids are presented. The first study demonstrates the role of hydrogen cyanide as a precursor of amino acids detected in extracts of lunar samples. The formation of several amino acids, including glycine, alanine, aspartic acid, and glutamic acid, under conditions similar to those used for the analysis of lunar samples is demonstrated. The second study investigates the formation of hydrogen cyanide as well as amino acids from lunar-sample gas mixtures under electrical discharge conditions. These results extend the possibility of synthesis of amino acids to planetary bodies with primordial atmospheres less reducing than a mixture of methane, ammonia, hydrogen and water.