Showing papers on "Nitrite published in 1989"

Nanogram nitrite and nitrate determination in environmental and biological materials by vanadium (III) reduction with chemiluminescence detection.

Abstract: Nitrite in environmental water samples is reduced at room temperature to nitric oxide in acidic medium containing vanadium (III). Nitrate is also rapidly reduced after heating to 80-90 degrees C. Nitric oxide is removed from the reaction solution by scrubbing with helium carrier gas and is detected by means of a chemiluminescence NOx analyzer. Nanogram detection limits are obtained. The method has the advantage of not requiring highly acidic solutions for nitrate reduction and has been applied to the analysis of a variety of environmental waters, sediment, plant materials, and human urine and blood serum.

Expression of denitrification enzymes in response to the dissolved oxygen level and respiratory substrate in continuous culture of Pseudomonas stutzeri.

Abstract: The onset and cessation of the synthesis of denitrification enzymes of Pseudomonas stutzeri were investigated by using continuous culture and defined dissolved oxygen levels covering the full range of transition from air saturation to complete anaerobiosis Expression of nitrate reductase, nitrite reductase (cytochrome cd1), and N2O reductase was controlled by discrete oxygen levels and by the nature of the nitrogenous oxide available for respiration N2O reductase was synthesized constitutively at a low level; for enhanced expression, oxygen concentrations were required to decrease below 5 mg of O2 per liter The threshold values for synthesis of nitrate reductase and cytochrome cd1 in the presence of nitrate were ca 5 and ca 25 mg of O2 per liter, respectively With nitrous oxide as the respiratory substrate, nitrite reductase was again the most sensitive to oxygen concentration; however, thresholds for all denitrification enzymes shifted to lower oxygen levels Whereas the presence of nitrate resulted in maximum expression and nearly uniform induction of all reductases, nitrite and nitrous oxide stimulated preferably the respective enzyme catalyzing reduction In the absence of a nitrogenous oxide, anaerobiosis did not induce enzyme synthesis to any significant degree The accumulation of nitrite seen during both the aerobic-anaerobic and anaerobic-aerobic transition phases was caused by the differences in onset or cessation of synthesis of nitrate and nitrite reductases and an inhibitory effect of nitrate on nitrite reduction

Electrocatalytic reduction of nitrite and nitric oxide to ammonia with iron-substituted polyoxotungstates

Abstract: Heteropolytungstates in which one of the positions normally occupied by a tungsten cation is occupied instead by an iron cation are shown to be catalysts for the electroreduction of nitrite to ammonia. The lacunary derivatives in which the empty tungsten site is unoccupied show no catalytic activity. The catalytic mechanism involves the intermediate formation of a nitrosyl complex of the Fe(II) form of the catalyst. The pH dependence of the rate of formation of the nitrosyl complex shows that nitrous acid is the reactive form of nitrite between pH 2 and 8. The catalyzed reduction does not produce hydroxylamine as an intermediate and appears to depend upon the ability of the multiply reduced heteropolytungstates to deliver electrons to the NO group bound to the iron center in a concerted, multiple-electron step. The iron-substituted heteropolytungstates are not degraded by repeated cycling between their oxidized and reduced states. A particularly valuable feature of the heteropolytungstate is the ease with which the formal potentials of the several redox couples they exhibit may be shifted by changing the identity of the central heteroatom. Exploitation of this feature provides diagnostic information that can be decisive in establishing the mechanism of electrocatalytic processes.

Nitrous oxide reductase from Pseudomonas stutzeri. Redox properties and spectroscopic characterization of different forms of the multicopper enzyme.

Abstract: The oxidation-reduction and spectroscopic properties of various forms of nitrous oxide reductase from Pseudomonas stutzeri were investigated. The high-activity form I of the enzyme (purple, 8 Cu, Mr 140,000) was reduced by a large variety of cationic, anionic and photochemically generated agents. The blue form III was the only product found in these experiments under anaerobic conditions. Reductive (dithionite) and oxidative (ferricyanide) titrations showed that the conversion of the purple form I to the blue species III was fully reversible in the absence of dioxygen. Two kinetically different phases of the reaction of form I with a stoichiometric amount of dithionite (1e- -equivalent/Cu) were detected: in the fast phase (seconds), the purple chromophore with lamba max at 540 nm disappeared almost completely, whereas in the slower phase (minutes) the blue species with lambda max around 650 nm was generated. Irrespective of the nature of the reductant the blue species did not react even at large excess of reductant. It was reoxidized by ferricyanide, hydrogen peroxide and nitric oxide. A new, catalytically inactive derivative of nitrous oxide reductase (form V, 2 Cu, Mr 140,000) was isolated from a transposon Tn5-induced mutant with defective chromophore biosynthesis. The pink color of the mutant protein faded almost completely after addition of 0.5e- -equivalent/Cu. In this case no blue species was found, similar to earlier observations for the regenerated, catalytically inactive protein. Varying with the sample and the pH, 50-80% of the total copper of form I was in an electron-paramagnetic-resonance-(EPR)-silent state as compared to 47% in the mutant protein. The broad, featureless EPR signal recorded at 9.32 GHz for the blue, reduced form III of nitrous oxide reductase represented approximately 20% of the total copper. For the blue species no resolution enhancement was achieved at 34 GHz. At this frequency both forms I and V showed similar EPR signals with apparent g-values at 2.16 and 1.99. At 9.32 GHz, form V had an EPR signal with gII at 2.18, AII = 3.55 mT (4 or 5 lines, in contrast to form I) and gI at 2.03. Above 100 K the splitting of the gII region into seven equidistant lines in the EPR signal of the high-activity form I and the hyperfine structure of the perpendicular transition disappeared. Carbon monoxide and nitric oxide, but not nitrous oxide, had marked effects on the spectroscopic properties of the purple form I. Marked effects were also obtained for the exogenous ligands nitrite, azide, cyanate and thiocyanate.(ABSTRACT TRUNCATED AT 400 WORDS)

Nitrite reduction and carbohydrate metabolism in plastids purified from roots of Pisum sativum L.

Abstract: Intact preparations of plastids from pea (Pisum sativum L.) roots have been used to investigate the metabolism of glucose-6-phosphate and reduction of inorganic nitrite within these organelles. The ability of hexose-phosphates to support nitrite reduction was dependent on the integrity of the preparation and was barely measurable in broken organelles. In intact plastids, nitrite was reduced most effectively in the presence of glucose-6-phosphate (Glc6P), fructose-6-phosphate and ribose-5-phosphate and to a lesser extent glucose-1-phosphate. The Km (Glc6P) of plastid-located Glc6P dehydrogenase (EC 1.1.1.49) and Glc6P-dependent nitrite reduction were virtually identical (0.68 and 0.66 mM respectively) and a similar relationship was observed between fructose-6-phosphate, hexose-phosphate isomerase (EC 5.3.1.9) and nitrite reduction. The pattern of release of CO2 from different carbon atoms of Glc6P supplied to root plastids, indicates the operation of both glycolysis and the oxidative pentose-phosphate pathway with some recycling in the latter. During nitrite reduction the evolution of CO2 from carbon atom 1 of Glc6P was stimulated but not from carbon atoms 2, 3, 4, or 6. The importance of these results with regard to the regulation of the pathways of carbohydrate oxidation and nitrogen assimilation within root plastids is discussed.

Effects of oxygen on each step of denitrification on Pseudomonas nautica

Abstract: Studies on the effect of oxygen on denitrification have shown that denitrification on Pseudomonas nautica 617 can take place in the presence of oxygen. The enzymes associated with denitrification are affected differently with respect to oxygen concentration. Nitrate reductase was less sensitive toward oxygen than nitrite and nitrous oxide reductases. Nitrate reductase activity was completely blocked at an oxygen concentration greater than 4.05 mg/L, compared with 2.15 and 0.25 mg/L for nitrite and nitrous oxide reductases, respectively. After an aerobic–anaerobic shift, nitrate reductase activity remained unchanged whereas the rate of nitrite reductase activity rose to a value only 20% that of the original rate.Key words: denitrification, oxygen, Pseudomonas.

The energy-conserving nitric-oxide-reductase system in Paracoccus denitrificans. Distinction from the nitrite reductase that catalyses synthesis of nitric oxide and evidence from trapping experiments for nitric oxide as a free intermediate during denitrification.

Abstract: 1. A Clark-type electrode that responds to nitric oxide has been used to show that cytoplasmic membrane vesicles of Paracoccus denitrificans have a nitric-oxide reductase activity. Nitrous oxide is the reaction product. NADH, succinate or isoascorbate plus 2,3,5,6-tetramethyl-1,4-phenylene diamine can act as reductants. The NADH-dependent activity is resistant to freezing of the vesicles and thus the NADH:nitric-oxide oxidoreductase activity of stored frozen vesicles provides a method for calibrating the electrode by titration of dissolved nitric oxide with NADH. The periplasmic nitrite reductase and nitrous-oxide reductase enzymes are absent from the vesicles which indicates that nitric-oxide reductase is a discrete enzyme associated with the denitrification process. This conclusion was supported by the finding that nitric-oxide reductase activity was absent from both membranes prepared from aerobically grown P. denitrificans and bovine heart submitochondrial particles. 2. The NADH: nitric-oxide oxidoreductase activity was inhibited by concentrations of antimycin or myxothiazol that were just sufficient to inhibit the cytochrome bc1 complex of the ubiquinol--cytochrome-c oxidoreductase. The activity was deduced to be proton translocating by the observations of: (a) up to 3.5-fold stimulation upon addition of an uncoupler; and (b) ATP synthesis with a P:2e ratio of 0.75. 3. Nitrite reductase of cytochrome cd1 type was highly purified from P. denitrificans in a new, high-yield, rapid two- or three-step procedure. This enzyme catalysed stoichiometric synthesis of nitric oxide. This observation, taken together with the finding that the maximum rate of NADH:nitric-oxide oxidoreductase activity catalysed by the vesicles was comparable with that of NADH:nitrate-oxidoreductase, is consistent with a role for nitric-oxide reductase in the physiological conversion of nitrate or nitrite to dinitrogen gas. 4. Intact cells of P. denitrificans also reduced nitric oxide in an antimycin- or myxothiazol-sensitive manner. However, nitric oxide was not detected by the electrode during the reduction of nitrate. Nitric-oxide synthesis from nitrate could be detected with cells in the presence of very low concentrations of Triton X-100 which selectively inhibits nitric-oxide reductase activity. 5. Nitric oxide was detected as an intermediate in denitrification by including haemoglobin with an anaerobic suspension of cells that was reducing nitrate. The characteristic spectrum of the nitric oxide derivative of haemoglobin was observed.(ABSTRACT TRUNCATED AT 400 WORDS)

Nitrosation by stimulated macrophages. Inhibitors, enhancers and substrates

Abstract: Macrophages and their immortalized cell lines can be activated to form nitrite and nitrate via oxidation of arginine and this is accompanied by the formation of N-nitroso compounds. The mechanism of nitrosamine formation has been investigated through the use of compounds which are known either to inhibit or enhance acid-catalyzed nitrosation. The range of nitrogen acceptors has been expanded to include ureas as well as amines of varying pKa and structure. The results are consistent with a mechanism in which NO is oxidized to N2O3 and N2O4, which are capable of nitrosating amines, but not ureas or amides, at neutral pH. This is in agreement with a recent observation that macrophage cell-free extracts can oxidize arginine to NO. The effect of ascorbic acid on intact activated macrophages is complex since nitrite formation is enhanced over a very wide range of ascorbate concentrations (5-500 microM) while nitrosation is inhibited at ascorbate concentrations greater than 50 microM.

Polarographic methods for ultratrace cobalt determination based on adsorption-catalytic effects in cobalt (II)-dioxime-nitrite systems

Abstract: L'augmentation d'un facteur 3 ou 4 des courants continus (DC) et differentiels (DPP) dans les systemes Cobalt (II)-dioxime-NaNO 2 permet de doser le cobalt avec precision, selectivite et une tres grande sensibilite

A Halophilic Denitrifier, Bacillus halodenitrificans sp. nov.

Abstract: A new halotolerant denitrifier, which was isolated from a solar saltern by enrichment culture in liquid medium supplemented with 1.06 M (9%) NaNO3, grew optimally in media containing 0.5 to 1.35 M NaCl, survived and multiplied in media ranging in salinity from 0.35 to 4.25 M NaCl, and tolerated high nitrite ion concentrations, as well as high nitrate ion concentrations. The salt requirement could be provided by 1 M KNO3 or KCl instead of NaCl. For this nonfermentative organism, nitrate and nitrite were the only electron acceptors tested that supported anaerobic growth on a complex medium. Washed cells reduced both nitrate and nitrite at significant rates. The isolate lacked a nitrous oxide reductase activity, utilized a variety of substrates as carbon and energy sources, and required both growth factors and organic (reduced) sulfur. Ammonia served as a nitrogen source for growth, but nitrate did not. Despite the failure of the organism to sporulate, assignment to the genus Bacillus appeared to be consistent with results of cell constituent analyses and partial 16S ribosomal ribonucleic acid sequencing. We propose the name Bacillus halodenitrificans for this organism. A type culture has been deposited with the American Type Culture Collection, Rockville, Md., as strain ATCC 49067.

Effect of different levels of nitrite and nitrate on the survival of Listeria monocytogenes during the manufacture of fermented sausage

Abstract: The fate of L. monocytogenes during the fermentation of Finnish fermented sausage was examined. L. monocytogenes was able to survive during a 21 d fermentation of sausage with levels of nitrite and salt commonly used in the meat industry today (120 ppm NaNO2 and 3.0% NaCl). Initial numbers of Listeria (103 CFU/g and 105 CFU/g) decreased approximately 1 log 10 CFU/g during the manufacture. Increasing the levels of nitrite/nitrate to those used 30 years ago in meat products had a marked effect on the elimination of Listeria . The numbers of survivors in the sausages was reduced 2.0 log 10 CFU/g during the fermentation of 3 weeks with a combination of 200 ppm NaNO2 and 300 ppm KNO3. With 1000 ppm KNO3, the decrease was 3.3 log 10 CFU/g. L. monocytogenes could not be totally eliminated from highly contaminated sausage by increasing only the levels of nitrite and nitrate. Levels of these additives with best bacteriostatic effect on Listeria are no longer permitted in food.

N-nitroso compound formation in human gastric juice.

Abstract: The gastric formation of N-nitroso compounds probably constitutes a major source of human exposure to this important class of environmental carcinogens. Following reduction of nitrate to nitrite by oral or gastric bacteria, reaction with nitrogenous constituents of gastric juice can occur leading to the in situ formation of N-nitroso compounds, probably primarily derived from amides, ureas or aromatic amines. While gastric nitrite concentrations are raised in the achlorhydric relative to the normal stomach, the latter, owing to its acidity, offers a particularly favourable environment for the formation of N-nitroso compounds, as indicated by the finding of greatly increased gastric concentrations of N-nitroso compounds following an oral dose of nitrate. This illustrates the importance of the dynamic nature of the relationships between the various parameters involved in the formation of N-nitroso compounds. While in principle the same is true of the process of inhibition of nitrosation by reducing agents such as ascorbic acid (since, depending on the relative concentrations of reducing agent, nitrite and oxygen, inhibition or catalysis of nitrosation can occur), ingestion of 1 g ascorbic acid brings about a significant reduction in the gastric concentration of N-nitroso compounds.

Genetic regulation of nitrate assimilation in Klebsiella pneumoniae M5al.

Abstract: We isolated Mu dI1734 insertion mutants of Klebsiella pneumoniae that were unable to assimilate nitrate or nitrite as the sole nitrogen source during aerobic growth (Nas- phenotype). The mutants were not altered in respiratory (anaerobic) nitrate and nitrite reduction or in general nitrogen control. The mutations were linked and thus defined a single locus (nas) containing genes required for nitrate assimilation. beta-Galactosidase synthesis in nas+/phi(nas-lacZ) merodiploid strains was induced by nitrate or nitrite and was inhibited by exogenous ammonia or by anaerobiosis. beta-Galactosidase synthesis in phi(nas-lacZ) haploid (Nas-) strains was nearly constitutive during nitrogen-limited aerobic growth and uninducible during anaerobic growth. A general nitrogen control regulatory mutation (ntrB4) allowed nitrate induction of phi(nas-lacZ) expression during anaerobic growth. This and other results suggest that the apparent anaerobic inhibition of phi(nas-lacZ) expression was due to general nitrogen control, exerted in response to ammonia generated by anaerobic (respiratory) nitrate reduction.

Influence of temperature and humidity on the accumulation of tobacco-specific nitrosamines in stored burley tobacco

Abstract: Alkaloid and nitrate concentrations were dramatically decreased during the 21-day storage at 32 o C/90% RH. Treatment of the tobaccos with streptomycin and rifampicin did not inhibit nitrite or nitrosamine formation. During this 21-day period, approximately half of the original weight was lost due to microbial activity and leaching. Storage at 32 o C/83% RH resulted in a reduction of alkaloids but no increase of nitrite or tobacco-specific nitrosamines (TSNA) and no change in nitrate concentration over a 28-day period

Effects of phosphoroamides on ammonia volatilization and nitrite accumulation in soils treated with urea

Abstract: We compared the effects of N-(n-butyl) thiophosphoric triamide (NBPT), N-(diaminophosphinyl)-cyclohexylamine (DPCA), phenylphosphorodiamidate (PPD), and hydroquinone on transformations of urea N in soils. The ability of these urease inhibitors to retard urea hydrolysis, ammonia volatilization, and nitrite accumulation in soils treated with urea-decreased in the order NBPT > DPCA ≫ PPD > HQ. When five soils were incubated at 30°C for 14 days after treatment with urea (1 mg urea N g−1 soil), on average, the gaseous loss of urea N as ammonia and the accumulation of urea N as nitrite were decreased from 52 to 5 % and from 11 to 1%, respectively, by addition of NBPT at the rate of 10 μg g−1 soil (0.47 parts of NBPT per 100 parts of urea). The data obtained support previous evidence that NBPT is more effective than PPD for reduction of the problems encountered in using urea as a fertilizer and deserves consideration as a fertilizer amendment for retarding hydrolysis of urea fertilizer in soil.

Method for inhibiting corrosion in cooling systems and compositions therefor, containing a nitrite corrosion inhibitor and bromosulfamate

Abstract: The method of adding to a nitrite corrosion inhibitor composition an effective amount of a bromosulfamate which is stable with respect to the nitrite corrosion inhibitor and provides an effective biocide, bactericide and fungicide. The composition using this bromosulfamate component to nitrite is utilized at about 0.1 to 10 ppm (residual) with an optimum of about 0.2 ppm of bromosulfamate. The bromosulfamate composition comprises reacting together sodium bromide (NaBr), sodium hypochlorite (NaOCl) or chlorine, and sodium sulfamate (NaSO3 NH2) or sulfamic acid, and using the product "fresh" in treating the nitrite solution.

Determination of nitrite, sulphate, bromide and nitrate in human serum by ion chromatography

Abstract: An ion chromatographic method has been developed for the determination of trace amounts of nitrite, sulphate, bromide and nitrate in human serum, using an ODS column dynamically coated with cetylpyridinium chloride. The anions studied were eluted with 1 mM citrate-2.5% methanol (pH 6.5) as the mobile phase and detected by an ultraviolet detector. The interfering proteins in human serum were removed by an initial filtration through an ultrafilter-paper. The many inorganic and organic anions commonly found in serum had little effect on the determination of the four anions. Recoveries of nitrite, sulphate, bromide and nitrate in serum were 107–110, 94–106, 106–110 and 92–100%, respectively. The proposed method was also applied to human saliva and urine.

Inhibitory effects of sulphur compounds, copper and tungsten on nitrate reduction by mixed rumen micro-organisms.

Abstract: 1. The inhibitory effects of inorganic and organic sulphur-containing compounds, copper and tungsten on nitrate reduction by mixed rumen micro-organisms were investigated in two in vitro studies. 2. Coarsely strained rumen fluid from nitrate-adapted (Expt 1) or non-adapted (Expt 2) Suffolk Down wethers maintained on lucerne (Medicago sativa) cubes was used as an inoculum. In Expt 1, anaerobic incubation was carried out for 24 h for each medium supplemented with 10 mM-sodium nitrate and the following chemicals: 0, 1, 2, 3, 5, 8 and 10 mM-sodium sulphide, 1 and 10 mM-sodium sulphite, 1 and 10 mM-sodium sulphate, 1 and 10 mM-L-cysteine, 1 and 10 mM-DL-methionine, 1 mM-sodium tungstate and 1 mM-copper sulphate. In Expt 2, 1 and 10 mM-Na2S, 1 and 10 mM-L-cysteine, 1 mM-Na2WO4, and 1 mM-CuSO4 were added to incubation media to test for chemical inhibition of microbial reduction of nitrate. 3. In Expt 1, the amount of nitrite formed decreased with increasing concentration of sulphide-S added. The additions of L-cysteine, W and Cu suppressed nitrite formation in media from both nitrate-adapted and non-adapted sheep. 4. In contrast to the effects of sulphide, L-cysteine and W counteracted, to some degree, nitrate-induced reduction of volatile fatty acid (VFA) production. Addition of Cu to the media resulted in a further depression of VFA production.