Higher plant m utants defective in nitrite reduction should be of use in dissecting this step at the genetic level as m utations in a num ber of loci w ould be likely to lead to a defect in nitrite reduction, such as w ithin the nitrite reductase structural gene, affecting either catalytic activity or the proper functioning of the transit sequence required for chloroplast targeting; in the chloroplast envelope affecting recognition of the transit sequence and thus preventing im port of the nitrite reductase protein into the chloroplast; in stromal proteinases; in prosthetic group synthesis; in transport of nitrite into the chloroplast (if this m echanism is protein m ediated); in electron donation to nitrite reductase and in a component of the signal transduction pathw ay through which nitrate, light and the plastidic factor operate to regulate synthesis of nitrite reductase. However, mutations in some of these components of nitrite reduction could be lethal and unselectable.
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Since nitrite reduction is considered to occur within the chloroplasts several workers have attempted to determine whether the nitrite reductase structural gene is coded by DNA within the nucleus or wdthin the plant organelles. Attempts have been made to infer the origin of nitrite reductase mRNA using the protein synthesis inhibitors cycloheximide and chloramphenicol which inhibit the peptidyl transferase activity of the nuclear and organellar small ribosomal subunits respectively. Cycloheximide inhibits the induction of nitrite reductase activity in Lemna minor when presented to the tissue before nitrate (Stewart, 1967). When cycloheximide was added after exposure to nitrate all further induction of nitrite reductase activity was prevented, suggesting that nitrite reductase was synthesised on cytoplasmic ribosomes and was coded by nuclear DNA. This view was supported by Sluiters-Scholten, (1973) who showed that the induction of nitrite reductase activity by nitrate in green leaves of Phaseolus vulgaris in the light was inhibited by cycloheximide. Both cycloheximide and chloramphenicol inhibited the induction of nitrite reductase activity in etiolated leaves (Sluiters-Scholten, 1973). However, chloramphenicol did not inhibit the induction of nitrite reductase activity when presented to seedlings after 24 hours illumination. Sluiters-Scholten (1973) concluded that nitrite reductase was synthesised on cytoplasmic ribosomes, and therefore presumably coded by nuclear DNA, but some form of chloroplast development is required before production of nitrite reductase molecules can occur.
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In this work, the experimental assessment of the performance of a new catalytic hollow fiber reactor with supported Pd catalyst for nitrite removal from polluted waters has been reported. The proposed reactor configuration facilitates working at low flowrate and hydrogen concentrations in order to improve the selectivity of the reduction reaction towards nitrogen, thus, inhibiting the formation of ammonia. Pd catalyst was supported on propylene and polyethersulfone hollow fibers following a simple impregnation method; the stability of the supported catalyst was checked along the operation time. Experiments of nitrite reduction were carried out in the range of 0.075-1 bar of H 2 partial pressure, 0.3-0.4 bar of
Hypoxic vasodilation is a fundamental, highly conserved physiological response that requires oxygen and/or pH sensing coupled to vasodilation. While this process was first characterized more than 80 years ago, the precise identity and mechanism of the oxygen sensor and mediators of vasodilation remain uncertain. In sup- port of a possible role for hemoglobin (Hb) as a sensor and effector of hypoxic vasodilation, here we show biochemical evidence that Hb exhibits enzymatic behavior as a nitrite reductase, with maximal NO generation rates occurring near the oxy-to-deoxy (R-to-T) allosteric structural transition of the protein. The observed rate of nitrite reduction by Hb deviates from second-order kinetics, and sigmoidal reaction progress is determined by a balance between 2 opposing chemistries of the heme in the R (oxygenated conformation) and T (deoxygen- ated conformation) allosteric quaternary structures of the Hb tetramer — the greater reductive potential of deoxyheme in the R state tetramer and the number of unligated deoxyheme sites necessary for nitrite binding, which are more plentiful in the T state tetramer. These opposing chemistries result in a maximal nitrite reduc- tion rate when Hb is 40–60% saturated with oxygen (near the Hb P 50 ), an apparent ideal set point for hypoxia-
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The development of analytical techniques for nitrite determination has been reviewed , of which electrochemical analyses are very promising. Electrochemical assays possess good analytical features, such as fast responses, cheap instrumentation and simple operation . Nitrite is electro- oxidized at solid electrodes, however, a high overpotential is required . The high overpotential for nitrite oxidation usually suffers interferences from other readily oxidizable compounds, and leads to unexpected reactions and electrode surface passivation [3-9]. Lowering the applied potential for the determination of nitrite could be achieved by modification of electrode surfaces with suitable electrocatlysts, including metal oxide , metal complexes , graphene , single-walled carbon nanotubes , multi-walled carbon nanotubes , polymer film , and gold nanoparticle-polymer composite . Electrochemical reduction approaches have also presented some difficulties for the determination of nitrite. In order to reduce overpotential for nitrite reduction, several kinds of materials have been fabricated onto electrode surfaces. These include polymeric metalloporphyrin , polymer composites , polyaniline/carbon nanotube , Cu nanoparticle composites [13-15], carbon nanotube/Cu 2+ -DNA  and enzyme composites [17-21]. Typically, the electro-reduction of nitrite has the drawbacks of low sensitivity. Biosensors for nitrite determinations suffer from the denaturing of enzymes or withdrawing of modifiers from the sensing surface [17-20]. Interference from dissolved oxygen and coexisting substances have operational disadvantages for the determination of nitrite in real samples [10-21].
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based on tripodal N-donor ligands coordinated to a Cu center. 11,13−45 In many cases, these analogues also encapsulate the functionality of CuNIR (and so can mediate the reduction of nitrite to NO), normally with the use of stoichiometric sacri ﬁ cial electron donors. There is also a distinct subset of such Cu − N donor complexes that can mediate the electrocatalytic reduction of nitrite to NO. 46−51 In these latter cases in particular, the role of solution pH (or the presence of additional proton sources in nonaqueous media) has been shown to be critical, with acidic regimes being essential for catalytic reduction of nitrite to NO. This is perhaps not surprising, given the dependence of eq 1 on the presence of protons. More surprising to us, especially considering that protons are required for this reduction, was the relative dearth of studies on the role of proton-relay units that might mediate proton-coupled electron transfer (PCET) 52−56 during catalytic nitrite reduction with such CuNIR mimics.
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Biologic denitrifying activities were once thought to be uniquely characteristic of prokaryotes, before the dis- covery of the fungal denitrification systems . They are induced under the same conditions as those inducing the bacterial systems, i.e., the presence of nitrite and a low oxygen-fugacity micro-environment that permits anaero- bic ammonium oxidation. Nitrite reductase has been de- tected in the mitochondrial fraction from denitrifying cells. Respiratory substrates such as malate, peruvate and succinate, were effective donors of electrons to these activities in the mitochondrial fractions. Nitrite reduction is coupled to the systems to produce ATP energy.
centration values recorded at each of these times in each group of animals were plotted (Figures 3 and 4). Each of the graphs shows that blood nitrate and nitrite levels in- creased up to a peak value following administration, and started to drop beyond this value. This created two phases in the kinetics of nitrates and nitrites in the rats. These are the phases before and after the attainment of peak value which can be referred to as the absorption and elimination phases respectively. Peak concentrations var- ied proportionately across groups with administered quan- tities of nitrate and nitrite (Table 5). Animal groups which received higher nitrate and nitrite quantities had higher peak values of these analytes in their blood.
Sodium nitrite and potassium nitrate have a long history of use as curing ingredients, and by the close of the 19th century the scientific basis of the process were becoming well understood. It was realized, for example, that nitrate must be converted to nitrite which help the curing process to proceed. This process has two purposes. One is “cosmetic”, where they give the meat a pinkish-reddish color and prevent it from turning brown. The second is the prevention of clostridium botulinum growth, the microorganism that produces the deadly botulism toxin (Borchert and Cassens, 1998). Sodium nitrite (NaNO 2 ) is commonly added to meat products which are kept
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A total of 578 patients were included in the study, 154 (26.7%) males and 424 (73.4%) females. The mean age was 4.84 ± 3.94 months (range: 4 days – 16 years). The most commonly identified underlying condition was VUR (n=62, 10.7%). There were 229 patients (39.6%) with a previous history of UTI. One hundred fifty- four patients (26.6%) were on prophylaxis and 257 (44.5%) had recent/current antibiotics. The most common symptom was fever (n=225, 44.1%). Most sample were clean catch midstream urine (n=236, 40.8%). Four hundred twenty-one samples showed some kind of antimicrobial resistance (n=72.8%). There were 225 patients (38.9%) who were nitrite positive. (Table 1)
carbonation suppression effect owing to the densification of the structure . In particular, when 5% calcium nitrite was added, the quality criterion of KS F 4042  for the carbonation depth of polymer cement mortar for repairing concrete structures (less than 2 mm carbonation depth at four weeks of age) could be met.
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In this research, we introduced a powerful electrochemical sensor (based carbon paste electrode) for analysis of nitrite in foodstuff, using CdO decorated single wall carbon nanotube incorporated with 1- methyl-3-butylimidazolium bromide (CdO/SWCNTs/1-3-MBIB/CPE). Our results revealed that CdO/SWCNTs/1-3-MBIB/CPE shows excellent electro-catalytic activity towards electro-oxidation of nitrite. The obtained data illustrated an irreversible oxidation peak current at 0.92 V, pointing to the oxidation of nitrite. The CdO/SWCNTs/1-3-MBIB/CPE exhibited a linear response from 0.1 μM to 900.0 μM of nitrite with no interfering from other food compounds. The CdO/SWCNTs/1-3- MBIB/CPE desb aaeb sah for determination of nitrite in real samples.
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Results: Compared to the model group, the lipid and vWF plasma levels were significantly lower, the plasma nitrite levels were significantly higher, the fatty streaks of aortic lesions were significantly lower, and the endothelium dependent relaxation was significantly higher after both phase studies (P , 0.05). The DFMG supplementation led to significant plasma nitrite increment in all groups after both phase studies (P , 0.05).There were significantly decreased fatty streaks of aortic lesions in DFMG-prevented and DFMG-treated mice (P , 0.05). There was a significant increase in EDR in all prophylactic treatment groups and treatment groups (P , 0.05). We further demonstrated that the preventative effect was more obvious than the therapeutic effect. Conclusion: Our results suggest that DFMG could work in prophylactic and therapeutic treat- ments for atherosclerosis development.
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which appears as the upper band in samples analyzed by SDS-PAGE. Moreover, fractions containing both pro- teins show NirA activity, indicating that the siroheme and [4Fe-4S] groups are linked to the mature protein, and that the level of prosthetic groups is enough to provide some enzyme activity, even when the recombinant pro- tein is expressed in E. coli cells. However, as occurred when other nitrite and sulphite reductases were expressed in E. coli cells , some of the newly synthesized apoprotein remains inactive due to the loss of siroheme in some enzyme molecules during the purification procedure, or because the amount of siroheme and/or [4Fe-4S] cluster available in E. coli cells is insufficient to assemble with all the de novo synthesized apoprotein providing the fully active holoprotein.
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As shown in Figure 1: Schematic representation of the problem cluster, the waste of nitrite salt and the waste of time are the main causes of the inefficient nitrite measurement. The new nitrite measurement system needs to minimize these different forms of waste. As already is defined by Nave D. (2002)  Lean is focused on the removal of all forms of waste. The other process optimization methods are focused on other concepts, such as quality or restructuring of the business. Lean is therefore the process optimization method that fits the best with our goal. What does Lean mean?
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The nitrate and nitrite content were determined for the samples according to the ISO 6635. 22 The method involves extraction of the test portion with hot water (approximately 10 g of the test sample weighed to the nearest 1 mg), precipitation of the proteins, and filtration. Addition of sulfanilamide chloride and N-(1- naphthyl) ethylenediamine dihydrochloride to the portion of the filtrate, and spectrometric measurement of the red complex obtained in the presence of nitrite at a wavelength of 538 nm compared with standard nitrite solutions by using Spectronic Genesys 2 spectrophotometer. For nitrate determination, a reduction to nitrite was done in a portion of the filtrate by means of metallic cadmium. Nitrate content was calculated taking into consideration the difference between these two analytical results. All reagents were of analytical grade quality. Deionized water was used throughout the procedure. The method was continuously tested by standard addition of nitrate and nitrite. Recoveries have been found to be between 98 and 102%. The limit of detection was 0.34 ppm for nitrate and 0.05 ppm for nitrite. Analyses were run in duplicate.
FIGURE 5 | Non-metric multi-dimensional scaling (NMDS) ordination of T-RFLP profiles for (A) collective denitrification genes (nirK, nirS, nosZ-I, and nosZ-II); (B) nitrite-reduction genes (nirK and nirS); and (C) N 2 O-reduction genes (nosZ-I and nosZ-II). Each point represents the T-RFLP profile of one field plot. Environmental vectors that were significantly correlated to shifts in T-RFLP profiles (p < 0.05) were fitted to the ordination and presented as gradients: black solid lines represent cumulative N 2 O emissions (g N 2 O-N ha − 1 ), and gray dashed lines represent average soil NO −
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Comparison among the average values measured in the 12 stations and acceptance threshold for culturing rainbow trout (Table 4) was carried out by analysis of One-Sample T-test. There were significant differences between nitrite (p≤0.001), nitrate (p=0.002), ammonium (p≤0.001), sulphide (p=0.002), phosphate (p≤0.001) concentrations and acceptance threshold for culturing rainbow trout.
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investigated preliminarily and the corresponding results are shown in Fig.6. It can be observed obviously that the response currents decrease with the addition of the nitrite, which implies PANI/nano-TiC has electrocatalytic ability to the reduction of nitrite. This work studies the sensing function of PANI/nano-TiC against nitrite and compared with the other work, the sensitivity result of our work is better.
This work deals with the determination of electrochemical behaviour of cobalt- dimethylglyoxime (Co-DMG) in different electrolyte media. The polarographic and voltammetric behaviour at the SMDE and HMDE has been studied in aqueous by using SWV and DPP techniques. At the same time, catalytic effect of nitrite, on the Co-DMG complex were investigated depended on different parameters. It has been determined optimum conditions by using SWV, DPV and stripping techniques. This study contributes to previous studies on the electrochemistry of Co-DMG complex.