Small Amounts Of Nitric Oxide Research Articles

Emissions of nitrogen oxide gases during aerobic treatment of animal slurries

Abstract Quantities of nitrous oxide, N 2 O, an important greenhouse gas, were found in the effluent gases from controlled continuous aerobic treatment of pig slurry. Where nitrifying-denitrifying conditions were encouraged (4-day treatment time and aeration to a redox potential of −50 mV E cal ), concentrations of this gas at times exceeded 1500 ppm and accounted for 19% of the nitrogen lost from the slurry. Smaller concentrations of the gas (170 ppm) were found during short treatments (1·5 days) where nitrifying activity would not be expected; partial nitrification is a possible explanation. Quantities of nitric oxide (NO) (up to 100 ppm), and even small amounts of NO 2 , were also found, suggesting these previously unquantified nitrogen transformation routes in the traditional nitrogen cycle exist in aerobic treatment processes.

Inducible nitric oxide synthase activity in hepatocytes is dependent on the coinduction of tetrahydrobiopterin synthesis.

Nitric oxide (NO) is a short-lived radical derived from the oxidation of one of the two chemically equivalent quanido nitrogens of L-arginine1. Three isoforms of the enzyme which produces NO, NO synthase (NOS), have been identified thus far. Two NOS isoforms, endothelial and neuronal are expressed constitutively (cNOS) and release relatively small amounts of NO immediately upon stimulation. A third isoform has been termed inducible NOS (iNOS) because it is not present in resting cells but is expressed if cells are exposed to inflammatory stimuli, such as bacterial lipopolysaccharide (LPS) and/or cytokines. Upon purification all three isoforms are known to be dependent on tetrahydrobiopterin (BH4) for maximal activity2–5. This observation adds to the list of four enzymes previously known to be dependent on BH4. Although the precise role of BH4 in the five-electroh oxidation of L-arginine to NO and citrulline remains uncertain, recent reports using intact cells in culture indicate that both endothelial cNOS6 and smooth muscle cell7 isoforms are dependent on BH4 availability.

Kinetic Explanation for Accumulation of Nitrite, Nitric Oxide, and Nitrous Oxide During Bacterial Denitrification

The kinetics of denitrification and the causes of nitrite and nitrous oxide accumulation were examined in resting cell suspensions of three denitrifiers. An Alcaligenes species and a Pseudomonas fluorescens isolate characteristically accumulated nitrite when reducing nitrate; a Flavobacterium isolate did not. Nitrate did not inhibit nitrite reduction in cultures grown with tungstate to prevent formation of an active nitrate reductase; rather, accumulation of nitrite seemed to depend on the relative rates of nitrate and nitrite reduction. Each isolate rapidly reduced nitrous oxide even when nitrate or nitrite had been included in the incubation mixture. Nitrate also did not inhibit nitrous oxide reduction in Alcaligenes odorans, an organism incapable of nitrate reduction. Thus, added nitrate or nitrite does not always cause nitrous oxide accumulation, as has often been reported for denitrifying soils. All strains produced small amounts of nitric oxide during denitrification in a pattern suggesting that nitric oxide was also under kinetic control similar to that of nitrite and nitrous oxide. Apparent K(m) values for nitrate and nitrite reduction were 15 muM or less for each isolate. The K(m) value for nitrous oxide reduction by Flavobacterium sp. was 0.5 muM. Numerical solutions to a mathematical model of denitrification based on Michaelis-Menten kinetics showed that differences in reduction rates of the nitrogenous compounds were sufficient to account for the observed patterns of nitrite, nitric oxide, and nitrous oxide accumulation. Addition of oxygen inhibited gas production from NO(3) by Alcaligenes sp. and P. fluorescens, but it did not reduce gas production by Flavobacterium sp. However, all three isolates produced higher ratios of nitrous oxide to dinitrogen as the oxygen tension increased. Inclusion of oxygen in the model as a nonspecific inhibitor of each step in denitrification resulted in decreased gas production but increased ratios of nitrous oxide to dinitrogen, as observed experimentally. The simplicity of this kinetic model of denitrification and its ability to unify disparate observations should make the model a useful guide in research on the physiology of denitrifier response to environmental effectors.

Effect of increased nitrogen fixation on stratospheric ozone

Effect of increased nitrogen fixation on stratospheric ozone

Dissimilatory Nitrate and Nitrite Reduction under Aerobic Conditions by an Aerobically and Anaerobically Grown Alcaligenes sp. and by Activated Sludge

The oxygen uptake of an Alcaligenes sp., isolated from activated sludge, was inhibited by small amounts of nitric oxide. The occurrence of this inhibition was dependent on the growth conditions and the pretreatment of the cells. Anaerobically grown cells, which had subsequently been aerated in a nitrogen‐free medium, accumulated nitric oxide, after the addition of nitrate or nitrite. When the oxygen uptake was inhibited by nitric oxide, dissimilatory reduction of nitrate and nitrite proceeded under aerobic conditions at the same rate as in the absence of oxygen. Activated sludge removed nitric oxide actively under aerobic conditions and as a consequence the oxygen uptake of the sludge was not inhibited in the presence of nitrite. The rate of nitrate reduction under aerobic conditions was about 20% of that in the absence of oxygen.

Adsorption in AgX and AgY zeolites by carbon monoxide and other simple molecules

Carbon monoxide was strongly adsorbed in AgX and AgY zeolites to the extent of four molecules per supercage at 25 °C. An intense infrared absorption band was observed at 2195 cm −1, which was only slightly affected by preadsorbed ammonia. The isosteric heats of adsorption were 19.2 kcal/mole for AgX and 15.1 kcal/mole for AgY at very low coverages. More nitrogen was adsorbed in AgX than in AgY with heat of adsorption as high as 8.2 kcal/mole at a coverage of 0.1 mmole/g. In the AgY sample, the heat was only 4.6 kcal/mole. The specific adsorption was due to higher silver content in the AgX zeolite, which also had higher heats for the adsorption of carbon monoxide and carbon dioxide. The adsorption of oxygen at 25 °C in both zeolites was negligibly small. In addition to the initial reversible adsorption, a small amount of nitric oxide was slowly adsorbed in AgY. No migration of silver ions, when ammonia was adsorbed, could be inferred from adsorption measurement. No specific adsorption of carbon monoxide in AgX and AgY and of nitrogen in AgX was observed when the samples had been treated with carbon monoxide at 350 °C. Silver ions were probably reduced after this treatment.

Amplified laser absorption: detection of nitric oxide

Experimental results are reported for the power loss of a carbon monoxide gas laser due to the absorption of small amounts of nitric oxide placed in an intra-laser-cavity absorption cell. It was found, for the particular experimental conditions employed, that the absorption coefficient of nitric oxide at 1900.04/cm is enhanced more than two orders of magnitude when it is in the intracavity cell. Finally, the experimental results are compared with theoretical calculations.

Newly recognized vital nitrogen cycle.

Soil and sea bacteria produce a small amount of nitrous oxide (N(2)O); a small part of this N(2)O is photochemically converted to nitric oxide (NO) in the stratosphere. This process has recently been shown to be the principal source of the active oxides of nitrogen (NO and NO(2)) in the stratosphere. The active oxides of nitrogen catalytically destroy ozone, and NO and NO(2) appear to be a principal factor in the natural ozone balance. Stratospheric ozone is the only effective shield for the surface of the Earth against the harsh ultraviolet radiation between 300 and 250 nm. Thus, soil bacteria indirectly control the intensity of ultraviolet radiation reaching the Earth's surface. This subcycle of the major nitrogen cycle involves a relatively small amount of nitric oxide, estimated to be between 0.26 and 1.2 x 10(9) kg of NO per year on a worldwide basis. A recent estimate of the future nitric oxide emission in the stratosphere by the Concord supersonic transport is 0.37 x 10(9) kg/year on a world-wide basis, which is similar to the amount estimated from the natural source.

Gas-phase pyrolysis of 1,2-dichloropropane

The gas-phase pyrolysis of 1,2-dichloropropane has been studied at temperatures from 393 to 470°C and initial pressures from 0.2 to 26.0 Torr. In a 1-1. silica reaction vessel of low surface/volume ratio, the products are the four monochloropropenes and hydrogen chloride. Above 440°C the product ratios show only a small dependence on temperature and the relative amounts of the various isomers at 457°C are (expressed as percentage of the total chloropropenes), 3-chloropropene 63.6%, cis-1-chloropropene 22.9 %, trans-1-chloropropene 12.7 %, 2-chloropropene 0.8 %. The overall reaction is closely represented by the pressure change which leads to the overall rate-constant log10k(s–1)=(13.78 ±0.21)–(54 760 ±440)/4.576 T. Arrhenius parameters have been derived for each of the chloropropene products from the above expression and the product ratios at various temperatures (extrapolated to zero time). Additions of small amounts of nitric oxide and propene had virtually no effect upon the overall rate. The reaction has also been studied at low temperatures (300–380°C) and in various packed reaction vessels. The product ratios (extrapolated to zero time and corrected for the concurrent homogeneous reaction at the higher temperatures) show increased proportions of 2-chloropropene and cis-1-chloropropene and also formation of propene which can constitute up to 15 mol % of the total organic products. The results are consistent with four parallel unimolecular reactions occurring homogeneously at high temperatures. The heterogeneous reactions are more complicated although similarities are noted with the elimination reactions of other alkyl halides at glass surfaces.

Factors Affecting Turkey Meat Color

INTRODUCTIONCOLOR in poulty products strongly influences consumer acceptance. Two closely related heme pigments, myoglobin and hemoglobin, make uncooked poultry flesh pink to red. Consumers often object to variation from that normal appearance of uncooked meat or from the normal white to golden-brown of cooked turkey. Pool (1956) reported that turkey meat acquired a pink color when oven roasted in an uncovered container. He concluded this discoloration resulted from small amounts of nitric oxide and carbon monoxide (frequently found in oven atmosphere) combining with heme pigments of the bird.Froning and Hartung (1967) studied effects of age, sex and strain on color and texture of turkey meat, reporting that Gardner L values of uncooked and cooked meat decreased (meat darkened) with age of the bird. (Gardner L refers to light reflectance, aL to redness and bL to yellowness.) They found that uncooked dark meat had significantly more redness (higher aL…

A nitrate reductase from Micrococcus denitrificans

A nitrate reductase from Micrococcus denitrificans (N.C.I.B. 8944) was associated with cell membranes. This particulate system utilized NADH and succinate as electron donors for the reduction of nitrate to nitrite. Small amounts of nitric oxide, nitrous oxide and nitrogen gas were also produced. The K m for NADH using nitrate and oxygen as acceptors were 1.8 ·10 −5 M and 2·10 −5 M, respectively. The solubilized nitrate reductase purified 108-fold converts nitrate to nitrite stoichiometrically with reduced benzyl viologen as the electron donor. Reduced methyl viologen was also effective, but NADH, succinate and reduced cytochrome c were not utilized. The purified enzyme contained Mo as shown by isotope labelling. Its involvement in enzyme action is indicated by strong inhibition by KCNS and dithiol. Idoacetamide and p-Chloromercuribenzoate also inhibited the enzyme, and the effect in the latter case was reversed by reduced glutathione. The purified enzyme did not contain any cytochrome or flavin. Maximum enzyme activity was observed at pH 6.3 and a K m of 9.6·10 −4 M was recorded for nitrate when reduced benzyl viologen was the electron donor.

Effect of Automobile Exhaust Fume Inhalation by Poultry Immediately Prior to Slaughter on Color of Meat

RECENT research has indicated that various factors may influence poultry meat color. Froning and Hartung (1967) studied the effect of age, sex and strain on the color of turkey meat. Meat color was noted to become darker and to increase in redness (higher aL values) with advancing age of the bird. Some strain differences in redness were also observed.The effect of dietary nitrates and nitrites on development of pink color reaction in processed poultry meat was investigated by Froning et al. (1967, 1968). Nitrates and nitrites fed at higher levels were shown to increase the visual redness and aL values of chicken and turkey meat.Pool (1956) reported that small amounts of nitric oxide and carbon monoxide from oven gases will produce an undesirable pink surface reaction in cooked poultry meat. Exhaust fumes from internal combustion engines contain oxides of nitrogen (nitric oxide+nitrogen dioxide) and carbon monoxide (Abelson, 1967;…

KINETICS AND MECHANISMS OF THE THERMAL DECOMPOSITION OF PROPIONALDEHYDE: PART II. THE REACTION IN THE PRESENCE OF NITRIC OXIDE

The decomposition of propionaldehyde in the presence of various amounts of nitric oxide has been studied in the temperature range 520–560 °C and at propionaldehyde pressures from 30 to 300 mm Hg. The reaction is inhibited by small amounts of nitric oxide, and larger amounts give rise to strong catalysis. The order of the maximally inhibited reaction is 1.5 and the degree of inhibition decreases with an increase of propionaldehyde pressure. In the catalytic region the order of the overall reaction is 1.25 with respect to propionaldehyde, and the relative rate (the ratio of rates in the presence and absence of nitric oxide) is independent of propionaldehyde pressure. The overall rate in the catalytic region can be expressed as[Formula: see text]the unit of concentration being mole per cc. A mechanism in which nitric oxide initiates chains by the reaction C2H5CHO + NO → C2H5CO + HNO, propagates them by C2H5NO + C2H5CHO → C2H6 + C2H5CO + NO, and terminates them by C2H5 + C2H5NO → C4H10 + NO and C2H6 + C2H4 + NO and C2H5NO + C2H5NO → C4H10 + 2NO or C2H6 + C2H4 + 2NO is proposed and is shown to be consistent with the results.

The thermal decomposition of aliphatic aldehydes

The thermal decomposition of acetaldehyde, propionaldehyde, n -butyraldehyde and iso-butyraldehyde, as investigated by the static method, is essentially homogeneous, inhibitable by propylene, isobutene and small amounts of nitric oxide, and generally catalyzed at high inhibitor concentrations. The kinetic order of the uninhibited decomposition exhibits little obvious regularity, but that of the maximally inhibited reaction is approximately 1.5 for all three inhibitors. Kates of the uninhibited decomposition do not follow the sequence in the homologous series, and there is no systematic variation in the extent of inhibition from one aldehyde to another. For each aldehyde, the minimum rates for the three inhibitors in general are not identical, nevertheless exhibit a correspondence probably close enough to eliminate chance coincidence. The kinetic and analytical results of the uninhibited decomposition can be approximately described by a Kice-Herzfeld-type mechanism, with the kinetics in each case largely determined by the stability of radicals and their reactions in chain propagation and termination. The question whether the maximally inhibited reaction is a molecular reaction or a chain reaction is surveyed. Although the results cannot be completely accounted for by a molecular reaction alone, a chain mechanism for propylene inhibition involving allyl radicals likewise has only limited success. For nitric-oxide inhibition, it is not certain how far the results are affected by the occurrence of the subsequent catalyzed reaction. No definite conclusion can thus be reached about the nature of the maximally inhibited reaction.

Free Electrons in Active Nitrogen

The resonance shift in an S-band cavity was used to measure the free-electron density [n] in a continuous flow of rf-excited active nitrogen in the mm Hg pressure range. [n] varied between 107 and 6×109 cm—3 and depended distinctly on the oxygen contamination. The ions formed presumably are NO+. By admixing known small amounts of nitric oxide to the stream it could be demonstrated that the ionization rate indeed varied linearly with the amount of NO added. At high pressures and large [n] the electron removal was by recombination, and at low pressures and small [n] it was governed by ambipolar diffusion. The value of Dp/α was estimated at 109 mm Hg/cm. Since the NO must be practically completely dissociated by the active nitrogen, the required large ionization rate indicates that the mechanism probably involves formation of excited nitrogen molecules as an intermediate step.

PRIMARY QUANTUM EFFICIENCIES IN THE REACTION OF CYCLOPENTANE WITH MERCURY 6(3P1) ATOMS

An investigation has been made of the reaction of cyclopentane with Hg 6(3P1) atoms at a substrate pressure of 107 mm, under static conditions at 24 °C. Low light intensities were used in order to minimize secondary reactions.The products of the reaction, for small extents of decomposition, have been shown to be exclusively hydrogen, bicyclopentyl, and cyclopentene. With increasing duration of exposure, the cyclopentene-to-cyclopentane ratio achieves a steady-state value of 5.7 × 10−3. Furthermore, it has been found that the same ratio is ultimately reached, upon prolonged exposure of a substrate initially containing cyclopentene at a concentration higher than the steady-state value. In the runs with added cyclopentene, a fourth product appeared in measurable quantities. Its molecular weight corresponded to the formula, C10H16, and it was assumed to be a cyclopentyl cyclopentene. The same compound appears in extensive decomposition of the pure substrate.The addition of small amounts of nitric oxide was found to have a marked inhibiting effect on the reaction. Bicyclopentyl formation was completely suppressed when 0.7 mole% of nitric oxide was present; and the cyclopentene yield was reduced to one-fifth of its value for the pure substrate, by adding 0.98 mole% of nitric oxide.In order to obtain primary quantum yields for the reaction, a series of runs were performed of 1 to 33 minutes in duration, with a cyclopentane which had been purified by gas–liquid chromatography. By a short extrapolation of the mean quantum yields of product formation to zero extent of reaction, it was found that the primary quantum yields for hydrogen, bicyclopentyl, and cyclopentene were respectively 0.8, 0.4, and 0.4.On the basis of a simple four-step paraffinic mechanism, taken in conjunction with the primary quantum yield data, it is concluded that the reaction has a primary quantum yield of substrate decomposition of 0.8, and that cyclopentyl radicals have the same rates for disproportionation and recombination at 24 °C.

The photochemical decomposition of methyl iodide in presence of nitric oxide - II. Reactions of nitrosomethane

A product of the photolysis, in presence of a small quantity of nitric oxide, of methyl iodide reacts with excess nitric oxide to form a substance(s), Y , which absorbs light throughout the wavelength region 2300 to 5300 Å. The initial products of the photolysis, in presence of small quantities of nitric oxide, of both acetone and acetaldehyde react similarly. The species undergoing the reaction is believed to be monomeric nitrosomethane, formed by the association of methyl radicals with nitric oxide. The order of the reaction to form Y , as determined by the initial rate method, is one with respect to nitrosomethane and two with respect to nitric oxide. The extent of the reaction, which can be used as a measure of nitrosomethane concentration, depends on the concentration of nitric oxide. In absence of excess nitric oxide the monomer disappears slowly from the gas phase in a second-order reaction, which is thought to be the dimerization to nitrosomethane dimer.

The photochemical decomposition of methyl iodide in presence of nitric oxide I. The reaction of methyl radicals with nitric oxide

The quantum yield of molecular iodine produced in the photolysis of gaseous methyl iodide is markedly increased by the presence of small quantities of nitric oxide. The yield of iodine is determined by the competition between reactions of methyl radicals with iodine molecules to reform methyl iodide and of methyl radicals with nitric oxide to form nitrosomethane. The latter reaction is pressure-dependent and the kinetics may be interpreted in terms of the following steps: CH 3 + NO = CH 3 NO' ( k a ). CH 3 NO' = CH 3 + NO ( k b ), CH 3 NO' + M = CH 3 NO + M' ( k c,M ). The apparent third-order constant at low pressure { = ( k c, M k a ) / k b } is 50 times as great as that measured for the association of methyl radicals with oxygen in the same gas mixture. The minimum lifetime of the energy-rich CH 3 NO' complex is 10 -8 s. The absolute value of k a , the limiting value of the apparent second-order constant for the association, is estimated to be 7 x 10 11 ml. mole -1 s -1 , with an uncertainty factor of 3.

The concentration of hydroxyl and of oxygen atoms in gases from lean hydrogen-air flames

Measurements of OH concentrations in flame gases from lean hydrogen-air flames held on porous burners are reported. [ OH] is always found to be in excess of equilibrium near the flame and to decay downstream. The decay is formally second order in OH and the rate constant is relatively insensitive to pressure, temperature and composition, and has an average value of about 10 −13 cm 3/molecule sec. The effects of the addition of small amounts of nitric oxide have been studied. Data are presented on the relationship between the intensity of light emitted from nitric oxide containing nearly stoichiometric flames and [ OH], and it is argued that these provide strong evidence that the nitric oxide test for O atoms is quantitative. The light-producing reaction is probably NO+ O→ NO 2+hv with a rate constant, k 10, equal to 2 × 10 −18 cm 3 / molecule sec. By means of this test it is shown that under all of the conditions studied oxygen atoms and hydroxyl radicals are equilibrated according to the reaction 2 OH⇌ H 2 O+ O

The thermal decomposition of diethyl ether. III. The action of inhibitors and the mechanism of the reaction

Small quantities of nitric oxide reduce the rate of thermal decomposition of diethyl ether at 525 °C to about one-quarter. Much larger amounts accelerate the decomposition, but the concentration ranges in which the ‘ maximally inhibited ’ reaction and the ‘ nitric-oxide-induced’ reaction can be studied are so widely separated that these reactions can be treated as two distinct entities. The ‘uninhibited’ reaction constitutes a third. Reaction products and kinetics are recorded for all three, and nitric oxide consumption is measured for the first two. In all three the major products are the same, with secondary differences which are discussed. In the presence of nitric oxide small amounts of cyanides and other compounds are formed. In the nitric-oxide-induced reaction 1.4 molecules of ether are decomposed for each molecule of nitric oxide used up: in the maximally inhibited reaction the ratio, which is dependent on the ether pressure, is very much greater. The rate of the maximally inhibited reaction is independent of the concentration of nitric oxide, or of propylene, and the same for the two inhibitors (as is now proved by direct analysis). The first-order rate constant varies with the initial pressure of ether according to the equation k inhib. = ( A [ether])/(1 + B [ether]) + C [ether]. The rate constant of the uninhibited reaction varies with ether pressure according to an expression which, although probably of different algebraical form, is empirically similar to the above over a considerable range. The nitric-oxide-induced reaction is nearly of the first order with respect both to ether pressure and to nitric oxide pressure. The maximally inhibited reaction is shown to be most probably a molecular decomposition of the ether. The uninhibited reaction is predominantly a chain reaction, the mechanism of which is discussed. The nitric-oxide-induced reaction, it is suggested on the basis of the experimental evidence, is largely initiated by a generation of radicals in an attack of nitric oxide on ether. It is possibly also in part a molecular decomposition of ether caused by collision with nitric oxide.