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At least 19 recordsLinked to original sources
PubMed2001

Effects of gaseous NO2 on cells of Nitrosomonas eutropha previously incapable of using ammonia as an energy source.

Cells of Nitrosomonas eutropha grown under anoxic conditions with hydrogen as electron donor and nitrite as electron acceptor were initially unable to oxidize ammonia (ammonium) and hydroxylamine when transferred to oxic conditions. Recovery of ammonia and hydroxylamine oxidation activity was dependent on the presence of NO2. Under oxic conditions, without addition of NO2, ammonia consumption started after 8 - 9 days, and small amounts of NO and NO2 were detectable in the gas atmosphere. Removing these nitrogen oxides by intensive aeration, ammonia oxidation activity decreased and broke off after 15 days. Addition of gaseous NO2 (25 ppm1) led to a fast recovery of ammonia oxidation (3 days). Simultaneously, the arrangement of intracytoplasmic membranes (ICM) changed from circular to flattened vesicles, the protein pattern revealed an increase in the concentration of a 27 and a 30 kDa polypeptide, and the cytochrome c content increased significantly.

Aerobiosis↗
PubMed1998

High rate of aerobic nitrification and denitrification by Nitrosomonas eutropha grown in a fermentor with complete biomass retention in the presence of gaseous NO2 or NO.

A pure culture of the obligately lithoautotrophic ammonia-oxidizer Nitrosomonas eutropha was grown in a laboratory-scale bioreactor with complete biomass retention. The air supply was supplemented with nitrogen dioxide (NO2; 25 or 50 ppm) or nitric oxide (NO; 25 or 50 ppm). Compared to cultures grown without these nitrogenous oxides, the addition of NO2 or NO to the culture resulted in a significant increase of the nitrification rate, specific activity of ammonia oxidation, growth rate, and maximum cell densities. In contrast, the growth yield slightly decreased in the presence of NO or NO2. Maximum cell densities of about 2 x 10(10) cells ml-1 and a maximum nitrification rate of about 221 mmol NH4+ l-1 day-1 were obtained after 3 weeks in the presence of 50 ppm NO2. Furthermore, in the stationary phase about 50% of the nitrite produced was aerobically denitrified to dinitrogen (N2) and traces of nitrous oxide (N2O). When cells were supplemented with NO, a high rate of aerobic denitrification occurred only during the first days of the exponential growth phase.

Aerobiosis↗
PubMed2005

Photochemical production and release of gaseous NO2 from nitrate-doped water ice.

Temperature-programmed NO2 emissions from frozen aqueous NaNO3 solutions irradiated at 313 nm were monitored as function of nitrate concentration and heating rate, H, above -30 degrees C. Emissions increase nonmonotonically with temperature, displaying transitions suggestive of underlying metamorphic transformations. Thus, NO2 emissions surge at ca. -8 degrees C in frozen [NO3-] > 200 microM samples warmed at H = 0.70 degrees C min(-1) under continuous irradiation, and also in the dark from samples that had been photolyzed at -30 degrees C. The amounts of NO2 released in individual thermograms, SigmaN, increase less than linearly with [NO3-] or the duration of experiments, revealing the significant loss of photogenerated NO2. The actual SigmaN proportional, variant [NO3-]1/2 dependence (at constant H) is consistent with NO2 hydrolysis: 2NO2 + H2O --> NO3- + NO2- + 2H+, overtaking NO2 desorption, even below the eutectic point (-18 degrees C for aqueous NaNO3). The increasingly larger NO2 losses detected in longer experiments (at constant [NO3-]) are ascribed to secondary photolysis of trapped NO2. The relevance of present results to the interpretation of polar NO2 measurements is briefly analyzed.

Journal Article↗
PubMed2001

Gaseous NO2 as a regulator for ammonia oxidation of Nitrosomonas eutropha.

Cells of Nitrosomonas eutropha strain N904 that were denitrifying under anoxic conditions with hydrogen as electron donor and nitrite as electron acceptor were unable to utilize ammonium (ammonia) as an energy source. The recovery of ammonia oxidation activity was dependent on the presence of NO2. Anaerobic ammonia oxidation activity was observed in a helium atmosphere supplemented with 25 ppm NO2 after 20 h. Ammonia oxidation activity was detected after 2-3 days using an oxic atmosphere with 25 ppm NO2. In contrast, ammonia consumption started after 8-9 days under oxic conditions without the addition of NO2; in this case, small amounts of NO and NO2 were detected and their concentrations increased with increasing ammonia oxidation activities. Hardly any ammonia oxidation was detected when nitrogen oxides were removed by intensive aeration. It would seem, therefore, that NO2 is the master regulatory signal for ammonia oxidation in Nitrosomonas eutropha. Anaerobic ammonia oxidation activity was inhibited by the addition of NO. This inhibition was partly compensated by either increasing the NO2 concentration or by using 2,3-dimercapto-1-propane-sulfonic acid as a NO binding substrate. DMPS was inhibitory to nitrification under oxic conditions, while increased amounts of NO or NO2 led to increased oxidation activities.

Aerobiosis↗
PubMed2005

Photoenhanced uptake of gaseous NO2 on solid organic compounds: a photochemical source of HONO?

In several recent field campaigns the existence of a strong daytime source of nitrous acid was demonstrated. The mechanism of this source remains unclear. Accordingly, in the present laboratory study, the effect of light (in the range 300-500 nm) on the uptake kinetics of NO2 on various surfaces taken as proxies for organic surfaces encountered in the troposphere (as organic aerosol but also ground surfaces) was investigated. In this collaborative study, the uptake kinetics and product formation rate were measured by different flow tube reactors in combination with a sensitive HONO instrument. Uptake on light absorbing aromatic compounds was significantly enhanced when irradiated with light of 300-420 nm, and HONO was formed with high yield when the gas was humidified. Especially organic substrates containing a combination of electron donors, such as phenols, and of compounds yielding excited triplet states, such as aromatic ketones, showed a high reactivity towards NO2. Based on the results reported a mechanism is suggested, in which photosensitised electron transfer is occurring. The results show that HONO can be efficiently formed during the day in the atmosphere at much longer wavelengths compared to the recently proposed nitrate photolysis.

Aerosols↗
PubMed1982

Amine nitration and nitrosation by gaseous nitrogen dioxide.

Reaction of N-methylaniline in solution with ca. 100,000 ppm gaseous NO2 leads to significant amounts of ring- and N-nitro products, in addition to N-methyl-N-nitrosoaniline. Reaction of heterocyclic amines in solution with 5-1000 ppm gaseous NO2 gives significant amounts of N-nitrosamines and much higher amounts of N-nitramines than those obtained from concentrated gaseous NO2. The results are interpreted as evidence that N-nitrosation proceeds via an unsymmetrical ON-ONO2 dimer, whereas N-nitration may involve a free-radical process involving NO2, itself.

Amines↗
PubMed2004

Mechanism of the NO2 conversion to NO2- in an alkaline solution.

The reaction of NO2 and NaOH aqueous solution at room temperature was studied for elucidating the behavior of gaseous NO2 in an alkaline solution. Experimental runs related to NO2 absorption have been carried out in various pH solutions. The nitrite and nitrate ions formed in these absorption solutions were quantitatively analyzed. In the case of pH 5-12, both of the nitrite and nitrate ions were formed simultaneously. On the other hand, only the nitrite ion was formed when the pH of the absorption solution was higher than 13. In this paper, a new reaction mechanism was proposed to explain the selective formation of nitrite ion in the 10 M alkaline solution. In order to confirm the new reaction mechanism, H2(18)O was used as part of the absorption solution for detecting oxygen gas production. The amounts of reaction products: (18)O(18)O, (18)O(16)O and (16)O(16)O, were quantitatively determined. It was confirmed that the new reaction proceeds mainly in the 10 M alkaline solution.

Journal Article↗
PubMed2001

IR detection of NO2 using p+ porous silicon as a high sensitivity sensor.

Mesoporous silicon doped with 3.0 x 10(19) B atoms cm-3 (p(+)-type) is an insulating material which dramatically increases its electrical conductivity when exposed to traces of gaseous NO2; nitrogen dioxide chemisorption at the surface generates carriers, the population of which is readily evaluated through the intensity of IR absorption.

Journal Article↗
PubMed1989

Effect of altered dose rate on NO2 uptake and transformation in isolated lungs.

While the pulmonary toxicity of NO2 is clearly established, the mechanism by which it is removed from inspired air is poorly understood. Uptake is most likely dependent on chemical reaction since, despite limited per se gaseous NO2 aqueous solubility, uptake proceeds rapidly without ready saturation. We utilized an isolated perfused rat lung model to characterize the effect of dose rate on uptake and transformation. Dose rate was varied via alterations in inspired concentration, tidal volume, and ventilation frequency. Dose equaled the total amount inhaled, uptake the amount removed from inspired air, and transformation the amount of NO2- that accumulated in the perfusate. We found a linear proportionality between both inspired concentration (4-20 ppm) and minute ventilation (45-130 ml/min) and uptake. Fractional uptakes (65%) were similar for all groups. Regression of combined concentration and minute ventilation data yielded a linear relationship between total inspired dose (25-330 micrograms NO2) and both uptake (r2 = 0.99) and transformation (r2 = 0.98). Testing of the functional descriptions resulted in measured uptakes and transformation that fell within a few percentage points of those predicted. We conclude that in acutely exposed isolated lungs (1) NO2 uptake is dependent on total inhaled dose rather than on the variables which serve to affect dose rate, (2) transformation is related to both total inspired dose and uptake, and (3) uptake is more accurately described using a regression equation rather than by use of fractional uptakes.

Animals↗
PubMed2005

Reactions of *NO2 with chromium(III) complexes with histamine and pyridoxamine ligands studied by the stopped-flow technique.

This study demonstrated the direct formation of the nitrogen dioxide (*NO2) radical during the decomposition of 3-morpholinosydnonimine (SIN-1) in biological buffer 4-morpholinoethanosulfone acid solution. Consequently, at approximately pH 4, SIN-1 can be used successfully as a source of *NO2. This conclusion is drawn from a comparison of the reactions of cis-[Cr(C2O4)(L- L)(OH2)2]+, where L-L denotes pyridoxamine (Hpm) or histamine (hm), with the gaseous *NO2 radical obtained by two methods: from SIN-1 and from a simple redox reaction. These reactions were investigated using the stopped-flow technique. The measurements were carried out at temperatures ranging from 5 to 25 degrees C over a pH range from 6.52 to 9.11 for cis-[Cr(C2O4)(Hpm) (OH2)2]+ and from 6.03 to 8.15 for cis-[Cr(C2O4)(hm)(OH2)2] +. We also determined the thermodynamic activation parameter (E(a)) and the uptake mechanism for each of the coordination compounds studied.

Chromium↗
PubMed1980

Reaction of solid carrier-adsorbed polycyclic aromatic hydrocarbons with gaseous low-concentrated nitrogen dioxide.

The interaction of gaseous NO2 with solid carrier-adsorbed polycyclic aromatic hydrocarbons was studied under laboratory conditions with a specific attention to factors that might possibly influence this reaction, such as type of carrier lighting conditions, NO2 concentration, exposure time, and temperature. At the NO2 concentration of 1.33 ppm there were detected the following nitro derivatives: nitroanthracene, nitropyrene, nitrochrysene, two mononitro derivatives of benzo/a/pyrene, and dinitrobenzo/a/pyrene. The experimental data suggest that the formation of nitroaromates in atmospheric environment is to be expected, provided that there are present, besides polycyclic aromatic hydrocarbons and nitrogen oxides, also suitable types of sorbents, such as silica gel or fly ash.

Air Pollutants↗
PubMed1987

A Fourier transform infrared spectrometry study of the reactions of phosphatidylcholines with gaseous N2O5 and NO2.

The liquid lining of the alveolar region of the lung contains a surfactant which lowers the surface tension. The major active surface-tension-lowering compounds are phosphatidylcholines, some of which contain unsaturated fatty acid components. In order to determine whether these unsaturated moieties react with the gaseous air pollutant N2O5, which may be present in urban atmospheres at concentrations up to 15 ppb, phosphatidylcholines adsorbed on glass at 25 degrees C were exposed to mixtures of approximately 2 Toor (approximately 2600 ppm) N2O5 in 1 atm of air or argon in the gas phase. Nitronitrates were identified as products of the reactions of N2O5 with beta-oleoyl-gamma-palmitoyl L-alpha-phosphatidylcholine (OPPC) and dioleoyl L-alpha-phosphatidylcholine (DOPC) using Fourier transform infrared (FTIR) spectrometry and in the case of DOPC, fast atom bombardment mass spectrometry. FTIR studies also show that 2 Torr (approximately 2600 ppm) NO2 in 1 atm of air reacts with OPPC and DOPC to give new bands tentatively identified as nitronitrates. Finally, HNO3 was shown to react with OPPC, DOPC, and the saturated dipalmitoyl L-alpha-phosphatidylcholine to give products tentatively identified as nitrate salts and glycerol. These studies suggest that inhaled N2O5, if it reaches the alveolar region, is likely to react with unsaturated C = C groups in surfactant to form nitronitrates.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1981

Chromosomal aberrations and sister-chromatid exchanges induced by gaseous nitrogen dioxide in cultured Chinese hamster cells.

Effects of gaseous nitrogen dioxide (NO2) on chromosomal morphology of cultured Chinese hamster V79-H3 cells were investigated. Chinese hamster cells were exposed to NO2 gas in N2 gas at NO2 concentrations of 0, 5, 10, 20, 50 and 100 ppm (v/v) for 10 min at a gas flow rate of 1000 ml/min. Both chromosomal aberrations and sister-chromatid exchanges were increased depending on the NO2 concentration. The effects of sodium nitrite (NaNO2) were also examined in comparison with those of gaseous NO2, and it was found that the effects of gaseous NO2 could not be ascribed to those of nitrous acid. The gas-exposure apparatus used in this experiments seems to be useful for quantitative investigation of the effects of various gaseous materials on cultured mammalian cells or bacterial cells.

Animals↗
PubMed1982

Changes of gaseous exchange in the lung of mice acutely exposed to nitrogen dioxide.

To clarify the acute effects of NO2 on gaseous exchange in the lung of mice, O2 and CO2 concentrations in respiratory gas, respiratory rate (RR), arterial blood pH, PaCO2, PaO2, lung wet weight and lung water content were examined using the head-enclosed method. The results of the present study indicate that in mice exposed to 5 ppm NO2 for 24 h the gaseous exchange in the lung and metabolic rate of O2 and CO2 in the body are accelerated, whereas in mice exposed to 10 ppm and 20 ppm NO2 the gaseous exchange in the lung is inhibited to change the gaseous metabolism.

Animals↗
PubMedDate not supplied

Anaerobic ammonia oxidation with nitrogen dioxide by Nitrosomonas eutropha.

Nitrosomonas eutropha, an obligately lithoautotrophic bacterium, was able to nitrify and denitrify simultaneously under anoxic conditions when gaseous nitrogen dioxide (NO2) was supplemented to the atmosphere. In the presence of gaseous NO2, ammonia was oxidized, nitrite and nitric oxide (NO) were formed, and hydroxylamine occurred as an intermediate. Between 40 and 60% of the produced nitrite was denitrified to dinitrogen (N2). Nitrous oxide (N2O) was shown to be an intermediate of denitrification. Under an N2 atmosphere supplemented with 25 ppm NO2 and 300 ppm CO2, the amount of cell protein increased by 0.87 mg protein per mmol ammonia oxidized, and the cell number of N. eutropha increased by 5.8 x 10(9) cells per mmol ammonia oxidized. In addition, the ATP and NADH content increased by 4.3 micromol ATP (g protein)-1 and 6.3 micromol NADH (g protein)-1 and was about the same in both anaerobically and aerobically grown cells. Without NO2, the ATP content decreased by 0.7 micromol (g protein)-1, and the NADH content decreased by 1.2 micromol (g protein)-1. NO was shown to inhibit anaerobic ammonia oxidation.

Adenosine Triphosphate↗
PubMed1986

Induction of SOS functions by nitrogen dioxide in Escherichia coli with different DNA-repair capacities.

The effect of gaseous nitrogen dioxide (NO2) on cytotoxicity, induction of synthesis of UmuC and RecA proteins, and mutagenesis was studied in Escherichia coli strains with different capacities of DNA repair. Gaseous NO2 (90, 180 microliter/l) killed Escherichia coli. The recA mutant was most sensitive, the lexA mutant moderately sensitive, and the uvrA mutant and the wild-type the least sensitive. When 90 microliter/l NO2 gas was bubbled into bacterial suspensions for 30 min at a flow rate of 100 ml/min, the induction of umuC gene expression increased in the wild-type strain. NO2 also induced the recA gene expression in the wild-type strain. The synthesis of neither RecA nor UmuC proteins was induced in the recA and lexA mutants. We further investigated the NO2 mutagenesis in the cells treated with bubbling of NO2 gas. NO2 caused mutation to Trp+ of WP2.

DNA Repair↗