This study aimed to evaluate the quality of water from village boreholes by measuring physicochemical parameters such as nitrates, nitrites, and total organic carbon (TOC). Forty-five (45) village pumps from the South...This study aimed to evaluate the quality of water from village boreholes by measuring physicochemical parameters such as nitrates, nitrites, and total organic carbon (TOC). Forty-five (45) village pumps from the Southern (Basse Côte) and the Northern (Korhogo) region of Cte d’Ivoire (west Africa) were sampled. Physicochemical parameters such as temperature, pH, conductivity at 25˚C, and turbidity were determined in situ, while nitrite and nitrate were analyzed according to ISO 10304-1 (2007) standard and total organic carbon (TOC) by NF EN 1484 (1997) standard. The results showed that the borehole waters of the Basse Côte and Korhogo analyzed are acidic, with an average temperature of 27.51˚C ± 0.16˚C and 29.95˚C ± 0.51˚C respectively for the Basse Côte and Korhogo regions. The borehole waters of the Basse Côtedo not contain nitrites, while those of Korhogo have average nitrite contents of 0.32 mg/l. The average nitrate rate in the waters of the Basse Côte and Korhogo are 12.08 ± 2.11 mg/l and 11.03 ± 3.18 mg/l respectively. The average TOC concentration of the waters of the Basse Côte is 1.28 ± 0.32 mg/l and that of Korhogo is 0.56 ± 0.09 mg/L. The study showed that the borehole waters of the Basse Côte and Korhogo have average temperatures between 27.4˚C and 29.95˚C with a slightly acidic pH value and acceptable salinity. The TOC concentrations obtained at the different sampling points were all below the French standard (2 mg/L) except for certains pumps of the Basse Côte. The water samples from the Basse Côte were devoid of nitrite. On the other hand, those from Korhogo revealed the presence of nitrite. Also, the borehole waters of the regions of the Basse Côte and Korhogo contain relatively high nitrate contents, presumably due to anthropometric activity. Overall, our study on the quality of drinking water showed that the waters analyzed are in compliance with international standards and safe for consumption.展开更多
Food safety problems caused by excessive nitrite addition have been frequently reported and the detection of nitrite in food is particularly important. The standing time during the pretreatment of primary sample has a...Food safety problems caused by excessive nitrite addition have been frequently reported and the detection of nitrite in food is particularly important. The standing time during the pretreatment of primary sample has a great influence on the concentration of nitrite tested by spectrophotometric method. In this context, three kinds of food samples are prepared, including canned mustard, canned fish and home-made pickled water. A series of standing times are placed during the sample pretreatments and the corresponding nitrite contents in these samples are detected by spectrophotometric method based on N-ethylenediamine dihydrochloride. This study aims to find out a reasonable standing time during the pretreatment of food sample, providing influence factor for precise detection of nitrite.展开更多
To effectively separate and recover Co(Ⅱ) from the leachate of spent lithium-ion battery cathodes,we investigated solvent extraction with quaternary ammonium salt N263 in the sodium nitrite system.NO_(2)^(-)combines ...To effectively separate and recover Co(Ⅱ) from the leachate of spent lithium-ion battery cathodes,we investigated solvent extraction with quaternary ammonium salt N263 in the sodium nitrite system.NO_(2)^(-)combines with Co(Ⅱ) to form an anion [Co(NO_(2))_(3)]^(-),and it is then extracted by N263.The extraction of Co(Ⅱ) is related to the concentration of NO_(2)^(-).The extraction efficiency of Co(Ⅱ) reaches the maximum of99.16%,while the extraction efficiencies of Ni(Ⅱ),Mn(Ⅱ),and Li(Ⅰ) are 9.27%-9.80% under the following conditions:30vol% of N263 and15vol% of iso-propyl alcohol in sulfonated kerosene,the volume ratio of the aqueous-to-organic phase is 2:1,the extraction time is 30 min,and1 M sodium nitrite in 0.1 MHNO_(3).The theoretical stages require for the Co(Ⅱ) extraction are performed in the McCabe–Thiele diagram,and the extraction efficiency of Co(Ⅱ) reaches more than 99.00% after three-stage counter-current extraction with Co(Ⅱ) concentration of 2544mg/L.When the HCl concentration is 1.5 M,the volume ratio of the aqueous-to-organic phase is 1:1,the back-extraction efficiency of Co(Ⅱ)achieves 91.41%.After five extraction and back-extraction cycles,the Co(Ⅱ) extraction efficiency can still reach 93.89%.The Co(Ⅱ) extraction efficiency in the actual leaching solution reaches 100%.展开更多
In this study,the nitrogen and oxygen isotope compositions of nitrite in the upper 150 m water column of the Amundsen Sea in the summer of 2019 and 2020 were measured to reveal the distribution and transformation of n...In this study,the nitrogen and oxygen isotope compositions of nitrite in the upper 150 m water column of the Amundsen Sea in the summer of 2019 and 2020 were measured to reveal the distribution and transformation of nitrite in the euphotic zone of the Southern Ocean.We found that primary nitrite maxima(PNMs)are widely present in the Amundsen Sea,where the depth of occurrence deepens from east to west and nitrite concentrations increases.Evidence from dual isotopes suggests that the formation of PNMs in all regions of the Amundsen Sea is dominated by ammonia oxidation.More importantly,the nitrogen and oxygen isotope compositions of nitrite in the Amundsen Sea mixed layer are abnormal,and their depth profiles are mirror symmetrical.Isotopic anomalies exhibit spatial variations,with central surface water having the lowest nitrogen isotope composition(−89.9‰±0.2‰)and western surface water having the highest oxygen isotope composition(63.3‰±0.3‰).Isotopic exchange reaction between nitrate and nitrite is responsible for these isotope anomalies,as both nitrogen and oxygen isotopes have large isotopic fractionation and opposite enrichment effects.This proves that isotopic exchange reaction operates extensively in different regions of the Amundsen Sea.Our study highlights the unique role of dual isotopes of nitrite in deepening the understanding of nitrogen cycle.Further studies on ammonia oxidation and isotopic exchange between nitrate and nitrite are warranted in the future to understand their roles in the nitrogen cycle in the Southern Ocean.展开更多
Implant-associated infections caused by biomedical catheters severely threaten patients'health.The use of electrochemical control on NO release from benign nitrite equipped in the catheter can potentially resolve ...Implant-associated infections caused by biomedical catheters severely threaten patients'health.The use of electrochemical control on NO release from benign nitrite equipped in the catheter can potentially resolve this issue with excellent biocompatibility.Inspired by nitrite reductase,a Cu-BDC(BDC:benzene-1,4-dicarboxylic acid)catalyst with coordinated Cu(Ⅱ)sites was constructed as a heterogeneous electrocatalyst to control nitrite reduction to nitric oxide for catheter antibacteria.The combined results of in situ and ex situ tests unveil the key function of interconversion between Cu(Ⅱ)and Cu(Ⅰ)species in NO_(2)^(-)reduction to NO.After being incorporated into the actual catheter,the Cu-BDC catalyst exhibits high electrocatalytic activity toward NO_(2)^(-)reduction to NO and excellent antibacteria efficacy with a sterilizing rate of 99.9%,paving the way for the development of advanced metal-organic frameworks(MOFs)electrocatalysts for catheter antibacteria.展开更多
Inhaled nitrites have been used recreationally for centuries,particularly among men who have sex with men (MSM).^([1])After inhalation,this substance quickly enters the blood;within seconds,it can produce a temporary ...Inhaled nitrites have been used recreationally for centuries,particularly among men who have sex with men (MSM).^([1])After inhalation,this substance quickly enters the blood;within seconds,it can produce a temporary sense of warmth and pleasure,and relax the anal sphincter to relieve the pain of anal sex.^([2,3])“Popper”and“rush”are slang terms given to drugs of the chemical class called amyl nitrite or isobutyl nitrite.Nitrites oxidize hemoglobin to methemoglobins and may increase proteolytic susceptibility of hemoglobin,leading to oxidative hemolysis.Thus,their use is associated with methemoglobinemia and hemolytic anemia,^([4])although nitrite-induced hemolytic anemia has been described only in rare cases (supplementary Table 1).^([4-9])Herein,we report a case of acute hemolytic anemia associated with the use of amyl nitrite.展开更多
Nitrite is a commonly used additive in cured foods and its sensitive detection is important to human health.In this work,a simple but sensitive electrochemical sensor for nitrite was developed.Conductive carbon black(...Nitrite is a commonly used additive in cured foods and its sensitive detection is important to human health.In this work,a simple but sensitive electrochemical sensor for nitrite was developed.Conductive carbon black(VXC-72R)functionalized with a cationic surfactant cetyltrimethylammonium bromide(CTAB)was used as an electrode material,and was coated on a glassy carbon electrode(GCE)to fabricate the electrochemical sensor(CTAB/VXC-72R/GCE)for nitrite.Zeta potential characterization and a series of electrochemical tests were carried out on several materials.It was found that the present sensor showed an enhanced sensitivity towards nitrite detection due to the enhanced surface positive charge revealed by the Zeta potential.Under optimal conditions,the ranges of good linear relationship between the peak current and the nitrite concentration were obtained to be 0.5-5.0μmol/L and 5.0-1087.0μmol/L with a lower detection limit of 0.30μmol/L.It was also successfully used for the determination of nitrite in cured food samples with excellent reproducibility,stability and selectivity.展开更多
[Objectives]This study was conducted to store and consume overnight vegetables more safely and reasonably.[Methods]Fried cabbage and barbecue was selected as raw materials,which were determine by Griess reagent colori...[Objectives]This study was conducted to store and consume overnight vegetables more safely and reasonably.[Methods]Fried cabbage and barbecue was selected as raw materials,which were determine by Griess reagent colorimetry for the effects of storage time,storage temperature and storage method on the changes in nitrite content in the two foods.[Results]The nitrite content in fried cabbage and barbecue increased with the prolongation of storage time.Both types of food,whether stored in a sealed or open manner,had a nitrite content that increased with the storage temperature.When barbecue was stored in an open manner,its nitrite content was greater than that in sealed storage.The condition of stir-fried cabbage was the same as barbecue when stored at 10℃,but the situation was opposite when stored at 20 and 30℃.In this study,except for the slightly excessive nitrite content in stir-fried cabbage stored at 30℃in open and sealed conditions for 72 h,the nitrite contents in both foods under other storage conditions all met the national standard limit.[Conclusions]This study provides a theoretical basis for the safe and reasonable storage and use of leftovers.展开更多
Electrochemical reduction is one of the most suitable methods for the treatment of highly nitrate-contaminated solutions. This work focuses on the optimization of parameters influencing the electrochemical denitrifica...Electrochemical reduction is one of the most suitable methods for the treatment of highly nitrate-contaminated solutions. This work focuses on the optimization of parameters influencing the electrochemical denitrification of water by the Ti/RuO<sub>2</sub> + IrO<sub>2</sub> electrode. The methodological approach used consists in carrying out a series of electrolysis by scrutinizing the reaction selectivity according to the experimental conditions. For this study, the ions concentrations before and after electrolysis were determined by UV-vis absorption spectroscopy. The results of the process optimization showed that the electrochemical reduction ofis efficient at neutral pH after 120 mn of electrolysis at -100 mA. In contrast to works found in the literature, this study highlighted the process modeling that could open interesting perspectives to develop new treatment methods of polluted waters.展开更多
Sodium nitrite(Na NO2) is an inorganic salt used broadly in chemical industry. Na NO2 is highly reactive with hemoglobin causing hypoxia. Mesenchymal stem cells(MSCs) are capable of differentiating into a variety of t...Sodium nitrite(Na NO2) is an inorganic salt used broadly in chemical industry. Na NO2 is highly reactive with hemoglobin causing hypoxia. Mesenchymal stem cells(MSCs) are capable of differentiating into a variety of tissue specific cells and MSC therapy is a potential method for improving brain functions. This work aims to investigate the possible therapeutic role of bone marrow-derived MSCs against Na NO2 induced hypoxic brain injury. Rats were divided into control group(treated for 3 or 6 weeks), hypoxic(HP) group(subcutaneous injection of 35 mg/kg Na NO2 for 3 weeks to induce hypoxic brain injury), HP recovery groups N-2 w R and N-3 w R(treated with the same dose of Na NO2 for 2 and 3 weeks respectively, followed by 4-week or 3-week self-recovery respectively), and MSCs treated groups N-2 w SC and N-3 w SC(treated with the same dose of Na NO2 for 2 and 3 weeks respectively, followed by one injection of 2 × 106 MSCs via the tail vein in combination with 4 week self-recovery or intravenous injection of Na NO2 for 1 week in combination with 3 week self-recovery). The levels of neurotransmitters(norepinephrine, dopamine, serotonin), energy substances(adenosine monophosphate, adenosine diphosphate, adenosine triphosphate), and oxidative stress markers(malondialdehyde, nitric oxide, 8-hydroxy-2′-deoxyguanosine, glutathione reduced form, and oxidized glutathione) in the frontal cortex and midbrain were measured using high performance liquid chromatography. At the same time, hematoxylin-eosin staining was performed to observe the pathological change of the injured brain tissue. Compared with HP group, pathological change of brain tissue was milder, the levels of malondialdehyde, nitric oxide, oxidized glutathione, 8-hydroxy-2′-deoxyguanosine, norepinephrine, serotonin, glutathione reduced form, and adenosine triphosphate in the frontal cortex and midbrain were significantly decreased, and glutathione reduced form/oxidized glutathione and adenosine monophosphate/adenosine triphosphate ratio were significantly increased in the MSCs treated groups. These findings suggest that bone marrow-derived MSCs exhibit neuroprotective effects against Na NO2-induced hypoxic brain injury through exerting anti-oxidative effects and providing energy to the brain.展开更多
AIM:To investigate whether nitrite administered prior to ischemia/reperfusion(I/R)reduces liver injury.METHODS:Thirty-six male Sprague-Dawley rats were randomized to 3 groups,including sham operated(n=8),45-min segmen...AIM:To investigate whether nitrite administered prior to ischemia/reperfusion(I/R)reduces liver injury.METHODS:Thirty-six male Sprague-Dawley rats were randomized to 3 groups,including sham operated(n=8),45-min segmental ischemia of the left liver lobe(IR,n=14)and ischemia/reperfusion(I/R)preceded by the administration of 480 nmol of nitrite(n=14).Serum transaminases were measured after 4 h of reperfusion.Liver microdialysate(MD)was sampled in 30-min intervals and analyzed for glucose,lactate,pyruvate and glycerol as well as the total nitrite and nitrate(NOx).The NOx was measured in serum.RESULTS:Aspartate aminotransferase(AST)at the end of reperfusion was higher in the IR group than in the nitrite group(40±6.8μkat/L vs 22±2.6μkat/L,P=0.022).Similarly,alanine aminotransferase(ALT)was also higher in the I/R group than in the nitrite group(34±6μkat vs 14±1.5μkat,P=0.0045).The NOx in MD was significantly higher in the nitrite group than in the I/R group(10.1±2.9μmol/L vs 3.2±0.9μmol/L,P=0.031)after the administration of nitrite.During ischemia,the levels decreased in both groups and then increased again during reperfusion.At the end of reperfusion,there was a tendency towards a higher NOx in the I/R group than in the nitrite group(11.6±0.7μmol/L vs 9.2±1.1μmol/L,P=0.067).Lactate in MD was significantly higher in the IR group than in the nitrite group(3.37±0.18 mmol/L vs 2.8±0.12 mmol/L,P=0.01)during ischemia and the first 30 min of reperfusion.During the same period,glycerol was also higher in the IRI group than in the nitrite group(464±38μmol/L vs 367±31μmol/L,P=0.049).With respect to histology,there were more signs of tissue damage in the I/R group than in the nitrite group,and29%of the animals in the I/R group exhibited necrosis compared with none in the nitrite group.Inducible nitric oxide synthase transcription increased between early ischemia(t=15)and the end of reperfusion in both groups.CONCLUSION:Nitrite administered before liver ischemia in the rat liver reduces anaerobic metabolism and cell necrosis,which could be important in the clinical setting.展开更多
It was demonstrated that xanthine oxidoreductase （XOR）, during ischemia, catalyzes the formation of nitric oxide （NO） from nitrite （NO<sub>2</sub><sup>-</sup>） and this NO<sub>2<...It was demonstrated that xanthine oxidoreductase （XOR）, during ischemia, catalyzes the formation of nitric oxide （NO） from nitrite （NO<sub>2</sub><sup>-</sup>） and this NO<sub>2</sub><sup>-</sup>-derived NO protects the isolated perfused rat heart against the damaging effects of ischemia-reperfusion （I/R） when conventional nitric oxide synthase （NOS） -dependent NO production is impaired. Liver is one of the organs with the highest XOR concentration. This study was designed to determine whether NO<sub>2</sub><sup>-</sup>-derived NO by XOR protects liver against I/R injury in vivo. For its minute amounts and active reactivity, NO can not be detected directly in real time in vivo by this time. We have to prove the above hypothesis indirectly. METHODS:Wistar rats were pretreated with saline, NOS inhibitor L-NAME （10 mg/kg intravenously）, XOR inhibitor allopurinol （1.5 mg/kg orally）, L-NAME +allopurinol and NO scavenger carboxy-PTIO （0.6 mg/kg intravenously） respectively （12 animals per group）. And then, they were subjected to total liver ischemia for 40 minutes followed by reperfusion. Blood samples and liver tissues were obtained for analysis after 3 hours of reperfusion. Survival was also investigated. RESULTS:Allopurinol-treated animals exhibited further increased serum alanine aminotransferase （ALT） levels and liver myeloperoxidase （MPO） activities, but further decreased liver adenosine triphosphate （ATP） stores after I/R compared to saline-treated counterparts （830.5±108.3 U/L, 56.5±11.0 U/mg protein and 1.93±0.47 μmol/g vs. 505.8± 184.2 U/L, 41.5±10.2 U/mg protein and 3.05±0.55 μmol/g respectively, P【0.01, P【0.05 and P【0.01 respectively）. The hepatocyte injury was further exacerbated and the overall survival rate was significantly decreased after I/R in animals given by allopurinol compared to those pretreated by saline （P【0.05）. L-NAME and allopurinol co-treated animals exhibited more severe liver injury （P【0.05 and P【0.01） and a further decreased overall survival rate （P【0.05） compared to L-NAME or allopurinol alone-treated counterparts, but they were not different from carboxy-PTIO treated animals （P】0.05）. CONCLUSION:NO<sub>2</sub><sup>-</sup>-derived NO by XOR in the hypoxic and acidic environment induced by hepatic I/R protects the liver against I/R injury in vivo.展开更多
The potential toxic effects of nitrate-nitrite-nitrosamine on pancreatic β cell have remained a controversial issue over the past two decades. In this study, we reviewed epidemiological studies investigated the assoc...The potential toxic effects of nitrate-nitrite-nitrosamine on pancreatic β cell have remained a controversial issue over the past two decades. In this study, we reviewed epidemiological studies investigated the associations between nitrate-nitrite-nitrosamines exposure, from both diet and drinking water to ascertain whether these compounds may contribute to development of type 1 diabetes. To identify relevant studies, a systematic search strategy of Pub Med, Scopus, and Science Direct was conducted using queries including the key words "nitrate", "nitrite", "nitrosamine" with "type 1 diabetes" or "insulin dependent diabetes mellitus". All searches were limited to studies published in English. Ecologic surveys, case-control and cohort studies have indicated conflicting results in relation to nitrate-nitrite exposure from drinking water and the risk of type 1 diabetes. A null, sometimes even negative association has been mainly reported in regions with a mean nitrate levels < 25 mg/L in drinking water, while increased risk of type 1 diabetes was observed in those with a maximum nitrate levels > 40-80 mg/L. Limited data are available regarding the potential diabetogenic effect of nitrite from drinking water, although there is evidence indicating dietary nitrite could be a risk factor for development of type 1 diabetes, an effect however that seems to be significant in a higher range of acceptable limit for nitrate/nitrite. Current data regarding dietary exposure of nitrosamine and development of type 1 diabetes is also inconsistent. Considering to an increasing trend of type 1 diabetes mellitus(T1DM) along with an elevated nitrate-nitrite exposure, additional research is critical to clarify potential harmful effects of nitrate-nitritenitrosamine exposure on β-cell autoimmunity and the risk of T1DM.展开更多
In this study,a novel culture medium that simulates shrimp pond conditions was established to screen nitrite-degrading isolates.The medium was supplemented with nitrite as a nitrogen source and shrimp feed as the majo...In this study,a novel culture medium that simulates shrimp pond conditions was established to screen nitrite-degrading isolates.The medium was supplemented with nitrite as a nitrogen source and shrimp feed as the major carbon source,to achieve the high nitrogen and low carbon nutritional status found in shrimp farming ponds.Screening using this medium identified potent denitrifying Bacillus isolates,among which Bacillus subtilis M7-1 was considered best.M7-1 was able to completely degrade nitrite-N in 24 h without much consumption of dissolved oxygen.Efficient denitrification activity took place in liquid cultures within a set of non-stringent ranges of pH(5.0–9.0),salinity(0–30)and temperature(25–35℃).The denitrifying enzyme gene was amplified,sequenced and further identified as nirS type.In biosecurity assessments,M7-1 had no negative effects on shrimps at a dose of 106 cfu mL−1.M7-1 could therefore be used in aquaculture to reduce and control the nitrogen concentration,and to promote the development of sustainable and healthy culture systems.展开更多
The curing of meat is a conservation technique widely used since ancient times to prolong shelf-life. It consists in exposing meat to a mixture of sodium chloride and nitrate/nitrite. Sodium chloride affects the flavo...The curing of meat is a conservation technique widely used since ancient times to prolong shelf-life. It consists in exposing meat to a mixture of sodium chloride and nitrate/nitrite. Sodium chloride affects the flavor, texture and shelf-life of meat products. Animal fat mainly affects the flavor and texture, and nitrate and nitrite affect the color and flavor, and give cured meat products their typical aroma. Excessive intake of sodium has been linked to arterial hypertension and increased risk of cardiovascular diseases. Excessive intakes of saturated fatty acids in pork fat, and also of nitrite, have been identified as factors promoting some cancers. There is consequently an increasing consumer demand to reduce these ingredients in processed meat and so develop healthier cured meat products. This paper reviews how and to what extent sodium, animal fat rich in saturated fatty acids, and nitrite contents can be reduced in the production of dry-cured hams and dry-fermented sausages.展开更多
Iron-doped titania nanoparticles exhibit a higher photocatalytic activity than pure TiO2 for the degradation of nitrite. The optimum Fe-doped content in terms of activity is approximately 0. 5 %. The increase in photo...Iron-doped titania nanoparticles exhibit a higher photocatalytic activity than pure TiO2 for the degradation of nitrite. The optimum Fe-doped content in terms of activity is approximately 0. 5 %. The increase in photoactivity is probably due to the higher adsorption and the inhibition of electron-hole recombination. The photocatalytic oxidation reaction of nitrite over the Fe-doped TiO2 catalyst follows zero-order kinetics, which is different from that over pure TiO2. The reaction rate decreases linearly with the increase of the pH of the solution.展开更多
The thermal hazards of methyl nitrite(MN)were investigated in the present study.The determination and evaluation of MN decomposition were conducted using a C600 micro thermometer.The thermal runaway reaction character...The thermal hazards of methyl nitrite(MN)were investigated in the present study.The determination and evaluation of MN decomposition were conducted using a C600 micro thermometer.The thermal runaway reaction characteristics of the compound under different initial pressures were obtained using a VSP2 calorimeter.The kinetic parameters of MN were obtained by regression fitting and calculation of the microthermal experimental data.The experimental and calculated results demonstrated that the potential explosion risk of MN is very high.In addition,there was a high energy barrier in the early stage of the uncontrolled decomposition of MN;however,once the decomposition reaction was initiated,the subsequent decomposition was easily conducted.Under the conditions of adiabatic simulation,the possibility that the reaction was uncontrolled increases with the initial temperature and pressure of the system,and there is a great potential safety risk.展开更多
The effects of pre-processing steps (washing, blanching and cooking) and combination preservation of irradiation (10 kGy) and nitrite (0, 50, 100, 150 and 200 mg·kg–1) on the survival of Clostridium sporogenes s...The effects of pre-processing steps (washing, blanching and cooking) and combination preservation of irradiation (10 kGy) and nitrite (0, 50, 100, 150 and 200 mg·kg–1) on the survival of Clostridium sporogenes spores in a ready-to-eat (RTE) spinach relish and sorghum porridge meal were investigated. Chlorine wash (250 mg–1) reduced the C. sporogenes counts in spinach by 1.6 log cycles. Blanching following the chlorine wash caused no significant decrease in the spore counts in spinach. On the other hand, cooking significantly reduced the counts in the porridge by about 1.7 log cycles. In both components of the meal, there was a significant decrease in the Clostridia counts with increased sodium nitrite levels. However, the counts increased in the sorghum porridge component after 12 d of storage at 10℃. Cooking alone significantly reduced the final nitrite levels in both components of the meal. In both components of the meal, nitrite in combination with irradiation reduced the C. sporogenes counts to less than 10 cfu/g. A safe RTE spinach relish and sorghum porridge meal could be expected when a pre-processing, followed by a combination treatment of at least 50 mg·kg–1 sodium nitrite and a target dose of 10 kGy is applied.展开更多
Even though the nitrate assimilation operon has been extensively studied in Phormidium laminosum, some aspects still remain unclear. The genetic manipulation of this cyanobacterium is problematic that hinders the eluc...Even though the nitrate assimilation operon has been extensively studied in Phormidium laminosum, some aspects still remain unclear. The genetic manipulation of this cyanobacterium is problematic that hinders the elucidation of further aspects of nitrogen metabolism. To circumvent this, Thermosynechococcus elongatus BP-1 was selected as a surrogate host and its nirA gene was substituted by the homologous gene of P. laminosum. This process, based on Long Flanking Homology Polymerase Chain Reaction and the natural competence of T. elongatus BP-1, required an intermediate T. elongatus BP-1 ΔnirA::kat mutant, which carries a gene encoding a thermostable kanamycin nucleotidyl transferase in place of nirA_Te. In the presence of nirA_Pl, nirA defective mutants of T. elongatus BP-1 recovered the ability to grow with nitrate as the sole nitrogen source, and showed a phenotype similar to that observed in wild-type cells. The procedure could be useful to substitute other genes from T. elongatus BP-1 with the homologues from P. laminosum in order to study this particular operon. Furthermore, it may be used as a general tool to explore phenotypic changes due to the exchange of a single gene between cyanobacteria.展开更多
Nitrite reductase (NirA, EC 1.7.7.1) from the thermophilic, unicellular, non-N2-fixing cyanobacte-rium Thermosynechococcus elongatus BP-1 has been cloned and expressed in Escherichia coli. Analysis by SDS-PAGE of the ...Nitrite reductase (NirA, EC 1.7.7.1) from the thermophilic, unicellular, non-N2-fixing cyanobacte-rium Thermosynechococcus elongatus BP-1 has been cloned and expressed in Escherichia coli. Analysis by SDS-PAGE of the pure recombinant protein (His6NirA) showed two protein bands, one of 58 kDa (corresponding to the theoretical His6NirA molecular mass) and another of 44 kDa. Western blotting and mass spectrometry analyses confirmed that the 44 kDa protein resulted from proteolysis of the intact His6NirA, and suggested the existence, at the C-terminal domain of the 58 kDa form, of a region particularly sensible to proteolysis or accessible to proteases. A sample of both forms of His6NirA was used to obtain anti-NirA polyclonal antibodies. These antibodies were used to assess, by SDS-PAGE followed by Western blotting, the in vivo expression of NirA in wild-type cells of T. elongatus BP-1 growing in cultures with nitrate, nitrite or ammonium which were inoculated with cells grown with different nitrogen sources. These analyses revealed that protein bands corresponding to the complete (58 kDa) and truncated (44 kDa) forms of NirA can also be detected in solubilized cells. Moreover, the presence of each of these forms depended on the nitrogen source used to grow cells. Thus, expression of the complete NirA generally predominates in cells growing in medium with nitrate or nitrite. However, the truncated form prevails in cells grown in nitrate or nitrite and then transferred to medium with ammonium. The fact that the patterns of in vivo expression of NirA are different depending on the nitrogen source used possibly relies on a post-translational regulatory mechanism by proteolysis.展开更多
文摘This study aimed to evaluate the quality of water from village boreholes by measuring physicochemical parameters such as nitrates, nitrites, and total organic carbon (TOC). Forty-five (45) village pumps from the Southern (Basse Côte) and the Northern (Korhogo) region of Cte d’Ivoire (west Africa) were sampled. Physicochemical parameters such as temperature, pH, conductivity at 25˚C, and turbidity were determined in situ, while nitrite and nitrate were analyzed according to ISO 10304-1 (2007) standard and total organic carbon (TOC) by NF EN 1484 (1997) standard. The results showed that the borehole waters of the Basse Côte and Korhogo analyzed are acidic, with an average temperature of 27.51˚C ± 0.16˚C and 29.95˚C ± 0.51˚C respectively for the Basse Côte and Korhogo regions. The borehole waters of the Basse Côtedo not contain nitrites, while those of Korhogo have average nitrite contents of 0.32 mg/l. The average nitrate rate in the waters of the Basse Côte and Korhogo are 12.08 ± 2.11 mg/l and 11.03 ± 3.18 mg/l respectively. The average TOC concentration of the waters of the Basse Côte is 1.28 ± 0.32 mg/l and that of Korhogo is 0.56 ± 0.09 mg/L. The study showed that the borehole waters of the Basse Côte and Korhogo have average temperatures between 27.4˚C and 29.95˚C with a slightly acidic pH value and acceptable salinity. The TOC concentrations obtained at the different sampling points were all below the French standard (2 mg/L) except for certains pumps of the Basse Côte. The water samples from the Basse Côte were devoid of nitrite. On the other hand, those from Korhogo revealed the presence of nitrite. Also, the borehole waters of the regions of the Basse Côte and Korhogo contain relatively high nitrate contents, presumably due to anthropometric activity. Overall, our study on the quality of drinking water showed that the waters analyzed are in compliance with international standards and safe for consumption.
文摘Food safety problems caused by excessive nitrite addition have been frequently reported and the detection of nitrite in food is particularly important. The standing time during the pretreatment of primary sample has a great influence on the concentration of nitrite tested by spectrophotometric method. In this context, three kinds of food samples are prepared, including canned mustard, canned fish and home-made pickled water. A series of standing times are placed during the sample pretreatments and the corresponding nitrite contents in these samples are detected by spectrophotometric method based on N-ethylenediamine dihydrochloride. This study aims to find out a reasonable standing time during the pretreatment of food sample, providing influence factor for precise detection of nitrite.
基金financially supported by the National Natural Science Foundation of China(No.51804084)the Natural Science Foundation of Guangxi Province,China(No.2021GXNSFAA220096)the Science and Technology Major Project of Guangxi Province,China(No.AA17204100)。
文摘To effectively separate and recover Co(Ⅱ) from the leachate of spent lithium-ion battery cathodes,we investigated solvent extraction with quaternary ammonium salt N263 in the sodium nitrite system.NO_(2)^(-)combines with Co(Ⅱ) to form an anion [Co(NO_(2))_(3)]^(-),and it is then extracted by N263.The extraction of Co(Ⅱ) is related to the concentration of NO_(2)^(-).The extraction efficiency of Co(Ⅱ) reaches the maximum of99.16%,while the extraction efficiencies of Ni(Ⅱ),Mn(Ⅱ),and Li(Ⅰ) are 9.27%-9.80% under the following conditions:30vol% of N263 and15vol% of iso-propyl alcohol in sulfonated kerosene,the volume ratio of the aqueous-to-organic phase is 2:1,the extraction time is 30 min,and1 M sodium nitrite in 0.1 MHNO_(3).The theoretical stages require for the Co(Ⅱ) extraction are performed in the McCabe–Thiele diagram,and the extraction efficiency of Co(Ⅱ) reaches more than 99.00% after three-stage counter-current extraction with Co(Ⅱ) concentration of 2544mg/L.When the HCl concentration is 1.5 M,the volume ratio of the aqueous-to-organic phase is 1:1,the back-extraction efficiency of Co(Ⅱ)achieves 91.41%.After five extraction and back-extraction cycles,the Co(Ⅱ) extraction efficiency can still reach 93.89%.The Co(Ⅱ) extraction efficiency in the actual leaching solution reaches 100%.
基金The Impact and Response of Antarctic Seas to Climate Change under contract Nos IRASCC 02-01-01 and IRASCC 01-01-02Cthe National Natural Science Foundation of China under contract No.41721005.
文摘In this study,the nitrogen and oxygen isotope compositions of nitrite in the upper 150 m water column of the Amundsen Sea in the summer of 2019 and 2020 were measured to reveal the distribution and transformation of nitrite in the euphotic zone of the Southern Ocean.We found that primary nitrite maxima(PNMs)are widely present in the Amundsen Sea,where the depth of occurrence deepens from east to west and nitrite concentrations increases.Evidence from dual isotopes suggests that the formation of PNMs in all regions of the Amundsen Sea is dominated by ammonia oxidation.More importantly,the nitrogen and oxygen isotope compositions of nitrite in the Amundsen Sea mixed layer are abnormal,and their depth profiles are mirror symmetrical.Isotopic anomalies exhibit spatial variations,with central surface water having the lowest nitrogen isotope composition(−89.9‰±0.2‰)and western surface water having the highest oxygen isotope composition(63.3‰±0.3‰).Isotopic exchange reaction between nitrate and nitrite is responsible for these isotope anomalies,as both nitrogen and oxygen isotopes have large isotopic fractionation and opposite enrichment effects.This proves that isotopic exchange reaction operates extensively in different regions of the Amundsen Sea.Our study highlights the unique role of dual isotopes of nitrite in deepening the understanding of nitrogen cycle.Further studies on ammonia oxidation and isotopic exchange between nitrate and nitrite are warranted in the future to understand their roles in the nitrogen cycle in the Southern Ocean.
基金the financial support from National Postdoctoral Science Foundation of China(Nos.2021M702436 and BX2021211)Haihe Laboratory of Sustainable Chemical Transformations+1 种基金National Natural Science Foundation of China(Nos.22101202 and 22071173)Tianjin Science and Technology Programme(Nos.20JCJQJC00050 and 22ZYJDSS00060)。
文摘Implant-associated infections caused by biomedical catheters severely threaten patients'health.The use of electrochemical control on NO release from benign nitrite equipped in the catheter can potentially resolve this issue with excellent biocompatibility.Inspired by nitrite reductase,a Cu-BDC(BDC:benzene-1,4-dicarboxylic acid)catalyst with coordinated Cu(Ⅱ)sites was constructed as a heterogeneous electrocatalyst to control nitrite reduction to nitric oxide for catheter antibacteria.The combined results of in situ and ex situ tests unveil the key function of interconversion between Cu(Ⅱ)and Cu(Ⅰ)species in NO_(2)^(-)reduction to NO.After being incorporated into the actual catheter,the Cu-BDC catalyst exhibits high electrocatalytic activity toward NO_(2)^(-)reduction to NO and excellent antibacteria efficacy with a sterilizing rate of 99.9%,paving the way for the development of advanced metal-organic frameworks(MOFs)electrocatalysts for catheter antibacteria.
基金supported by a grant from Natural Science Foundation of Hunan Province (2022JJ30938)。
文摘Inhaled nitrites have been used recreationally for centuries,particularly among men who have sex with men (MSM).^([1])After inhalation,this substance quickly enters the blood;within seconds,it can produce a temporary sense of warmth and pleasure,and relax the anal sphincter to relieve the pain of anal sex.^([2,3])“Popper”and“rush”are slang terms given to drugs of the chemical class called amyl nitrite or isobutyl nitrite.Nitrites oxidize hemoglobin to methemoglobins and may increase proteolytic susceptibility of hemoglobin,leading to oxidative hemolysis.Thus,their use is associated with methemoglobinemia and hemolytic anemia,^([4])although nitrite-induced hemolytic anemia has been described only in rare cases (supplementary Table 1).^([4-9])Herein,we report a case of acute hemolytic anemia associated with the use of amyl nitrite.
基金Research Foundation from National Innovation Center of Advanced Dyeing&Finishing Technology,China(No.2022GCJJ10)。
文摘Nitrite is a commonly used additive in cured foods and its sensitive detection is important to human health.In this work,a simple but sensitive electrochemical sensor for nitrite was developed.Conductive carbon black(VXC-72R)functionalized with a cationic surfactant cetyltrimethylammonium bromide(CTAB)was used as an electrode material,and was coated on a glassy carbon electrode(GCE)to fabricate the electrochemical sensor(CTAB/VXC-72R/GCE)for nitrite.Zeta potential characterization and a series of electrochemical tests were carried out on several materials.It was found that the present sensor showed an enhanced sensitivity towards nitrite detection due to the enhanced surface positive charge revealed by the Zeta potential.Under optimal conditions,the ranges of good linear relationship between the peak current and the nitrite concentration were obtained to be 0.5-5.0μmol/L and 5.0-1087.0μmol/L with a lower detection limit of 0.30μmol/L.It was also successfully used for the determination of nitrite in cured food samples with excellent reproducibility,stability and selectivity.
基金Supported by College Students Innovation Training Program of Zhaoqing University (X202210580139).
文摘[Objectives]This study was conducted to store and consume overnight vegetables more safely and reasonably.[Methods]Fried cabbage and barbecue was selected as raw materials,which were determine by Griess reagent colorimetry for the effects of storage time,storage temperature and storage method on the changes in nitrite content in the two foods.[Results]The nitrite content in fried cabbage and barbecue increased with the prolongation of storage time.Both types of food,whether stored in a sealed or open manner,had a nitrite content that increased with the storage temperature.When barbecue was stored in an open manner,its nitrite content was greater than that in sealed storage.The condition of stir-fried cabbage was the same as barbecue when stored at 10℃,but the situation was opposite when stored at 20 and 30℃.In this study,except for the slightly excessive nitrite content in stir-fried cabbage stored at 30℃in open and sealed conditions for 72 h,the nitrite contents in both foods under other storage conditions all met the national standard limit.[Conclusions]This study provides a theoretical basis for the safe and reasonable storage and use of leftovers.
文摘Electrochemical reduction is one of the most suitable methods for the treatment of highly nitrate-contaminated solutions. This work focuses on the optimization of parameters influencing the electrochemical denitrification of water by the Ti/RuO<sub>2</sub> + IrO<sub>2</sub> electrode. The methodological approach used consists in carrying out a series of electrolysis by scrutinizing the reaction selectivity according to the experimental conditions. For this study, the ions concentrations before and after electrolysis were determined by UV-vis absorption spectroscopy. The results of the process optimization showed that the electrochemical reduction ofis efficient at neutral pH after 120 mn of electrolysis at -100 mA. In contrast to works found in the literature, this study highlighted the process modeling that could open interesting perspectives to develop new treatment methods of polluted waters.
文摘Sodium nitrite(Na NO2) is an inorganic salt used broadly in chemical industry. Na NO2 is highly reactive with hemoglobin causing hypoxia. Mesenchymal stem cells(MSCs) are capable of differentiating into a variety of tissue specific cells and MSC therapy is a potential method for improving brain functions. This work aims to investigate the possible therapeutic role of bone marrow-derived MSCs against Na NO2 induced hypoxic brain injury. Rats were divided into control group(treated for 3 or 6 weeks), hypoxic(HP) group(subcutaneous injection of 35 mg/kg Na NO2 for 3 weeks to induce hypoxic brain injury), HP recovery groups N-2 w R and N-3 w R(treated with the same dose of Na NO2 for 2 and 3 weeks respectively, followed by 4-week or 3-week self-recovery respectively), and MSCs treated groups N-2 w SC and N-3 w SC(treated with the same dose of Na NO2 for 2 and 3 weeks respectively, followed by one injection of 2 × 106 MSCs via the tail vein in combination with 4 week self-recovery or intravenous injection of Na NO2 for 1 week in combination with 3 week self-recovery). The levels of neurotransmitters(norepinephrine, dopamine, serotonin), energy substances(adenosine monophosphate, adenosine diphosphate, adenosine triphosphate), and oxidative stress markers(malondialdehyde, nitric oxide, 8-hydroxy-2′-deoxyguanosine, glutathione reduced form, and oxidized glutathione) in the frontal cortex and midbrain were measured using high performance liquid chromatography. At the same time, hematoxylin-eosin staining was performed to observe the pathological change of the injured brain tissue. Compared with HP group, pathological change of brain tissue was milder, the levels of malondialdehyde, nitric oxide, oxidized glutathione, 8-hydroxy-2′-deoxyguanosine, norepinephrine, serotonin, glutathione reduced form, and adenosine triphosphate in the frontal cortex and midbrain were significantly decreased, and glutathione reduced form/oxidized glutathione and adenosine monophosphate/adenosine triphosphate ratio were significantly increased in the MSCs treated groups. These findings suggest that bone marrow-derived MSCs exhibit neuroprotective effects against Na NO2-induced hypoxic brain injury through exerting anti-oxidative effects and providing energy to the brain.
文摘AIM:To investigate whether nitrite administered prior to ischemia/reperfusion(I/R)reduces liver injury.METHODS:Thirty-six male Sprague-Dawley rats were randomized to 3 groups,including sham operated(n=8),45-min segmental ischemia of the left liver lobe(IR,n=14)and ischemia/reperfusion(I/R)preceded by the administration of 480 nmol of nitrite(n=14).Serum transaminases were measured after 4 h of reperfusion.Liver microdialysate(MD)was sampled in 30-min intervals and analyzed for glucose,lactate,pyruvate and glycerol as well as the total nitrite and nitrate(NOx).The NOx was measured in serum.RESULTS:Aspartate aminotransferase(AST)at the end of reperfusion was higher in the IR group than in the nitrite group(40±6.8μkat/L vs 22±2.6μkat/L,P=0.022).Similarly,alanine aminotransferase(ALT)was also higher in the I/R group than in the nitrite group(34±6μkat vs 14±1.5μkat,P=0.0045).The NOx in MD was significantly higher in the nitrite group than in the I/R group(10.1±2.9μmol/L vs 3.2±0.9μmol/L,P=0.031)after the administration of nitrite.During ischemia,the levels decreased in both groups and then increased again during reperfusion.At the end of reperfusion,there was a tendency towards a higher NOx in the I/R group than in the nitrite group(11.6±0.7μmol/L vs 9.2±1.1μmol/L,P=0.067).Lactate in MD was significantly higher in the IR group than in the nitrite group(3.37±0.18 mmol/L vs 2.8±0.12 mmol/L,P=0.01)during ischemia and the first 30 min of reperfusion.During the same period,glycerol was also higher in the IRI group than in the nitrite group(464±38μmol/L vs 367±31μmol/L,P=0.049).With respect to histology,there were more signs of tissue damage in the I/R group than in the nitrite group,and29%of the animals in the I/R group exhibited necrosis compared with none in the nitrite group.Inducible nitric oxide synthase transcription increased between early ischemia(t=15)and the end of reperfusion in both groups.CONCLUSION:Nitrite administered before liver ischemia in the rat liver reduces anaerobic metabolism and cell necrosis,which could be important in the clinical setting.
文摘It was demonstrated that xanthine oxidoreductase （XOR）, during ischemia, catalyzes the formation of nitric oxide （NO） from nitrite （NO<sub>2</sub><sup>-</sup>） and this NO<sub>2</sub><sup>-</sup>-derived NO protects the isolated perfused rat heart against the damaging effects of ischemia-reperfusion （I/R） when conventional nitric oxide synthase （NOS） -dependent NO production is impaired. Liver is one of the organs with the highest XOR concentration. This study was designed to determine whether NO<sub>2</sub><sup>-</sup>-derived NO by XOR protects liver against I/R injury in vivo. For its minute amounts and active reactivity, NO can not be detected directly in real time in vivo by this time. We have to prove the above hypothesis indirectly. METHODS:Wistar rats were pretreated with saline, NOS inhibitor L-NAME （10 mg/kg intravenously）, XOR inhibitor allopurinol （1.5 mg/kg orally）, L-NAME +allopurinol and NO scavenger carboxy-PTIO （0.6 mg/kg intravenously） respectively （12 animals per group）. And then, they were subjected to total liver ischemia for 40 minutes followed by reperfusion. Blood samples and liver tissues were obtained for analysis after 3 hours of reperfusion. Survival was also investigated. RESULTS:Allopurinol-treated animals exhibited further increased serum alanine aminotransferase （ALT） levels and liver myeloperoxidase （MPO） activities, but further decreased liver adenosine triphosphate （ATP） stores after I/R compared to saline-treated counterparts （830.5±108.3 U/L, 56.5±11.0 U/mg protein and 1.93±0.47 μmol/g vs. 505.8± 184.2 U/L, 41.5±10.2 U/mg protein and 3.05±0.55 μmol/g respectively, P【0.01, P【0.05 and P【0.01 respectively）. The hepatocyte injury was further exacerbated and the overall survival rate was significantly decreased after I/R in animals given by allopurinol compared to those pretreated by saline （P【0.05）. L-NAME and allopurinol co-treated animals exhibited more severe liver injury （P【0.05 and P【0.01） and a further decreased overall survival rate （P【0.05） compared to L-NAME or allopurinol alone-treated counterparts, but they were not different from carboxy-PTIO treated animals （P】0.05）. CONCLUSION:NO<sub>2</sub><sup>-</sup>-derived NO by XOR in the hypoxic and acidic environment induced by hepatic I/R protects the liver against I/R injury in vivo.
基金supported by the Research Institute for Endocrine Sciences of Shahid Beheshti University of Medical Sciences
文摘The potential toxic effects of nitrate-nitrite-nitrosamine on pancreatic β cell have remained a controversial issue over the past two decades. In this study, we reviewed epidemiological studies investigated the associations between nitrate-nitrite-nitrosamines exposure, from both diet and drinking water to ascertain whether these compounds may contribute to development of type 1 diabetes. To identify relevant studies, a systematic search strategy of Pub Med, Scopus, and Science Direct was conducted using queries including the key words "nitrate", "nitrite", "nitrosamine" with "type 1 diabetes" or "insulin dependent diabetes mellitus". All searches were limited to studies published in English. Ecologic surveys, case-control and cohort studies have indicated conflicting results in relation to nitrate-nitrite exposure from drinking water and the risk of type 1 diabetes. A null, sometimes even negative association has been mainly reported in regions with a mean nitrate levels < 25 mg/L in drinking water, while increased risk of type 1 diabetes was observed in those with a maximum nitrate levels > 40-80 mg/L. Limited data are available regarding the potential diabetogenic effect of nitrite from drinking water, although there is evidence indicating dietary nitrite could be a risk factor for development of type 1 diabetes, an effect however that seems to be significant in a higher range of acceptable limit for nitrate/nitrite. Current data regarding dietary exposure of nitrosamine and development of type 1 diabetes is also inconsistent. Considering to an increasing trend of type 1 diabetes mellitus(T1DM) along with an elevated nitrate-nitrite exposure, additional research is critical to clarify potential harmful effects of nitrate-nitritenitrosamine exposure on β-cell autoimmunity and the risk of T1DM.
基金supported by the Special Fund for Qingdao Marine Biomedical science and Technology Innovation Center, China (No. 2017-CXZX01-3-13)
文摘In this study,a novel culture medium that simulates shrimp pond conditions was established to screen nitrite-degrading isolates.The medium was supplemented with nitrite as a nitrogen source and shrimp feed as the major carbon source,to achieve the high nitrogen and low carbon nutritional status found in shrimp farming ponds.Screening using this medium identified potent denitrifying Bacillus isolates,among which Bacillus subtilis M7-1 was considered best.M7-1 was able to completely degrade nitrite-N in 24 h without much consumption of dissolved oxygen.Efficient denitrification activity took place in liquid cultures within a set of non-stringent ranges of pH(5.0–9.0),salinity(0–30)and temperature(25–35℃).The denitrifying enzyme gene was amplified,sequenced and further identified as nirS type.In biosecurity assessments,M7-1 had no negative effects on shrimps at a dose of 106 cfu mL−1.M7-1 could therefore be used in aquaculture to reduce and control the nitrogen concentration,and to promote the development of sustainable and healthy culture systems.
文摘The curing of meat is a conservation technique widely used since ancient times to prolong shelf-life. It consists in exposing meat to a mixture of sodium chloride and nitrate/nitrite. Sodium chloride affects the flavor, texture and shelf-life of meat products. Animal fat mainly affects the flavor and texture, and nitrate and nitrite affect the color and flavor, and give cured meat products their typical aroma. Excessive intake of sodium has been linked to arterial hypertension and increased risk of cardiovascular diseases. Excessive intakes of saturated fatty acids in pork fat, and also of nitrite, have been identified as factors promoting some cancers. There is consequently an increasing consumer demand to reduce these ingredients in processed meat and so develop healthier cured meat products. This paper reviews how and to what extent sodium, animal fat rich in saturated fatty acids, and nitrite contents can be reduced in the production of dry-cured hams and dry-fermented sausages.
基金the National Natural Science Foundation of China.
文摘Iron-doped titania nanoparticles exhibit a higher photocatalytic activity than pure TiO2 for the degradation of nitrite. The optimum Fe-doped content in terms of activity is approximately 0. 5 %. The increase in photoactivity is probably due to the higher adsorption and the inhibition of electron-hole recombination. The photocatalytic oxidation reaction of nitrite over the Fe-doped TiO2 catalyst follows zero-order kinetics, which is different from that over pure TiO2. The reaction rate decreases linearly with the increase of the pH of the solution.
文摘The thermal hazards of methyl nitrite(MN)were investigated in the present study.The determination and evaluation of MN decomposition were conducted using a C600 micro thermometer.The thermal runaway reaction characteristics of the compound under different initial pressures were obtained using a VSP2 calorimeter.The kinetic parameters of MN were obtained by regression fitting and calculation of the microthermal experimental data.The experimental and calculated results demonstrated that the potential explosion risk of MN is very high.In addition,there was a high energy barrier in the early stage of the uncontrolled decomposition of MN;however,once the decomposition reaction was initiated,the subsequent decomposition was easily conducted.Under the conditions of adiabatic simulation,the possibility that the reaction was uncontrolled increases with the initial temperature and pressure of the system,and there is a great potential safety risk.
文摘The effects of pre-processing steps (washing, blanching and cooking) and combination preservation of irradiation (10 kGy) and nitrite (0, 50, 100, 150 and 200 mg·kg–1) on the survival of Clostridium sporogenes spores in a ready-to-eat (RTE) spinach relish and sorghum porridge meal were investigated. Chlorine wash (250 mg–1) reduced the C. sporogenes counts in spinach by 1.6 log cycles. Blanching following the chlorine wash caused no significant decrease in the spore counts in spinach. On the other hand, cooking significantly reduced the counts in the porridge by about 1.7 log cycles. In both components of the meal, there was a significant decrease in the Clostridia counts with increased sodium nitrite levels. However, the counts increased in the sorghum porridge component after 12 d of storage at 10℃. Cooking alone significantly reduced the final nitrite levels in both components of the meal. In both components of the meal, nitrite in combination with irradiation reduced the C. sporogenes counts to less than 10 cfu/g. A safe RTE spinach relish and sorghum porridge meal could be expected when a pre-processing, followed by a combination treatment of at least 50 mg·kg–1 sodium nitrite and a target dose of 10 kGy is applied.
文摘Even though the nitrate assimilation operon has been extensively studied in Phormidium laminosum, some aspects still remain unclear. The genetic manipulation of this cyanobacterium is problematic that hinders the elucidation of further aspects of nitrogen metabolism. To circumvent this, Thermosynechococcus elongatus BP-1 was selected as a surrogate host and its nirA gene was substituted by the homologous gene of P. laminosum. This process, based on Long Flanking Homology Polymerase Chain Reaction and the natural competence of T. elongatus BP-1, required an intermediate T. elongatus BP-1 ΔnirA::kat mutant, which carries a gene encoding a thermostable kanamycin nucleotidyl transferase in place of nirA_Te. In the presence of nirA_Pl, nirA defective mutants of T. elongatus BP-1 recovered the ability to grow with nitrate as the sole nitrogen source, and showed a phenotype similar to that observed in wild-type cells. The procedure could be useful to substitute other genes from T. elongatus BP-1 with the homologues from P. laminosum in order to study this particular operon. Furthermore, it may be used as a general tool to explore phenotypic changes due to the exchange of a single gene between cyanobacteria.
文摘Nitrite reductase (NirA, EC 1.7.7.1) from the thermophilic, unicellular, non-N2-fixing cyanobacte-rium Thermosynechococcus elongatus BP-1 has been cloned and expressed in Escherichia coli. Analysis by SDS-PAGE of the pure recombinant protein (His6NirA) showed two protein bands, one of 58 kDa (corresponding to the theoretical His6NirA molecular mass) and another of 44 kDa. Western blotting and mass spectrometry analyses confirmed that the 44 kDa protein resulted from proteolysis of the intact His6NirA, and suggested the existence, at the C-terminal domain of the 58 kDa form, of a region particularly sensible to proteolysis or accessible to proteases. A sample of both forms of His6NirA was used to obtain anti-NirA polyclonal antibodies. These antibodies were used to assess, by SDS-PAGE followed by Western blotting, the in vivo expression of NirA in wild-type cells of T. elongatus BP-1 growing in cultures with nitrate, nitrite or ammonium which were inoculated with cells grown with different nitrogen sources. These analyses revealed that protein bands corresponding to the complete (58 kDa) and truncated (44 kDa) forms of NirA can also be detected in solubilized cells. Moreover, the presence of each of these forms depended on the nitrogen source used to grow cells. Thus, expression of the complete NirA generally predominates in cells growing in medium with nitrate or nitrite. However, the truncated form prevails in cells grown in nitrate or nitrite and then transferred to medium with ammonium. The fact that the patterns of in vivo expression of NirA are different depending on the nitrogen source used possibly relies on a post-translational regulatory mechanism by proteolysis.
