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1.
Nitric Oxide ; 103: 29-30, 2020 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-32712272

RESUMO

Most outcomes of COVID-19 are associated with dysfunction of the vascular system, particularly in the lung. Inhalation of nitric oxide (NO) gas is currently being investigated as a treatment for patients with moderate to severe COVID-19. In addition to the expected vasodilation effect, it has been also suggested that NO potentially prevents infection by SARS-CoV-2. Since NO is an unstable radical molecule that is easily oxidized by multiple mechanisms in the human body, it is practically difficult to control its concentration at lesions that need NO. Inorganic nitrate and/or nitrite are known as precursors of NO that can be produced through chemical as well enzymatic reduction. It appears that this NO synthase (NOS)-independent mechanism has been overlooked in the current developing of clinical treatments. Here, I suggest the missing link between nitrate and COVID-19 in terms of hypoxic NO generation.


Assuntos
Betacoronavirus/efeitos dos fármacos , Infecções por Coronavirus/tratamento farmacológico , Nitratos/metabolismo , Óxido Nítrico/metabolismo , Nitritos/metabolismo , Pneumonia Viral/tratamento farmacológico , Antivirais/metabolismo , Ácido Ascórbico/química , Ácido Ascórbico/uso terapêutico , Infecções por Coronavirus/metabolismo , Infecções por Coronavirus/prevenção & controle , Fatores Relaxantes Dependentes do Endotélio/metabolismo , Humanos , Nitratos/sangue , Nitritos/sangue , Nitritos/química , Pandemias/prevenção & controle , Pneumonia Viral/metabolismo , Pneumonia Viral/prevenção & controle , Vasodilatação/efeitos dos fármacos
2.
DNA Cell Biol ; 39(9): 1473-1477, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32721230

RESUMO

Global antibiotic resistance, driven by intensive antibiotic exposure/abuse, constitutes a serious challenge to all health care, particularly in an era when new antimicrobial development has slowed to a trickle. Recently, we published work demonstrating the discovery and partial mechanism of action of a novel bactericidal agent that is effective against both gram-positive and gram-negative multidrug-resistant bacteria. This drug, called AB569, consists of acidified nitrite (A-NO2-) and EDTA, of which there is no mechanism of resistance. Using both chemistry-, genetic-, and bioinformatics-based techniques, we first discovered that AB569 was able to generate bactericidal levels of nitric oxide (NO), while the EDTA component stabilized S-nitrosyl thiols, thereby furthering NO and downstream reactive nitrogen species production. This elegant chemistry triggered a paralytic downregulation of vital genes using RNA-seq involved in the synthesis of DNA, RNA, ATP, and protein in the representative ESKAPE pathogen, Pseudomonas aeruginosa.


Assuntos
Antibacterianos/farmacologia , Bactérias Gram-Negativas/efeitos dos fármacos , Bactérias Gram-Positivas/efeitos dos fármacos , Antibacterianos/química , Farmacorresistência Bacteriana , Ácido Edético/química , Bactérias Gram-Negativas/genética , Bactérias Gram-Positivas/genética , Nitritos/química
3.
Chemosphere ; 260: 127554, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32688313

RESUMO

Estuarine sediments are often characterized by abundant iron oxides, organic matter, and anthropogenic nitrogen compounds (e.g., nitrate and nitrite). Anoxic dissimilatory iron reducing bacteria (e.g., Shewanella loihica) are ubiquitous in these environments where they can catalyze the reduction of Fe(III) (oxyhydr)oxides, thereby releasing aqueous Fe(II). The biologically produced Fe(II) can later reduce nitrite to form nitrous oxide. The effect on nitrite reduction by both biologically produced and artificially amended Fe(II) was examined experimentally. Ferrihydrite was reduced by Shewanella loihica in a batch reaction with an anoxic synthetic sea water medium. Some of the Fe(II) released by S. loihica adsorbed onto ferrihydrite, which was involved in the transformation of ferrihydrite to magnetite. In a second set of experiments with identical medium, no microorganism was present, instead, Fe(II) was amended. The amount of solid-bound Fe(II) in the experiments with bioproduced Fe(II) increased the rate of abiotic NO2- reduction with respect to that with synthetic Fe(II), yielding half-lives of 0.07 and 0.47 d, respectively. The δ18O and δ15N of NO2- was measured through time for both the abiotic and innoculated experiments. The ratio of ε18O/ε15N was 0.6 for the abiotic experiments and 3.1 when NO2- was reduced by S. loihica, thus indicating two different mechanisms for the NO2- reduction. Notably, there is a wide range of the ε18O/ε15N values in the literature for abiotic and biotic NO2- reduction, as such, the use of this ratio to distinguish between reduction mechanisms in natural systems should be taken with caution. Therefore, we suggest an additional constraint to identify the mechanisms (i.e. abiotic/biotic) controlling NO2- reduction in natural settings through the correlation of δ15N-NO2- and the aqueous Fe(II) concentration.


Assuntos
Compostos Férricos/química , Nitritos/química , Poluentes Químicos da Água/química , Catálise , Óxido Ferroso-Férrico , Nitratos , Óxido Nitroso , Oxirredução , Óxidos , Shewanella
4.
Food Chem ; 333: 127532, 2020 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-32668396

RESUMO

Poly(melamine) (PMel) was synthesized via the electropolymerization of melamine monomer, which was then characterized by field-emission scanning electron microscopy (FESEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The possible polymerization mechanisms of melamine were also revealed by FT-IR spectroscopy and UV-Vis spectroscopy. Next, the PMel modified GCE (PMel/GCE) was used for the simultaneous determination of nitrite (NO2-) and tartrazine, and the parameters were optimized. The kinetic study showed that the electrochemical oxidation of nitrite and tartrazine at the surface of PMel/GCE is a typical surface-controlled electrode process. Under the optimun conditions, the developed sensor outperformed those previously reported, and it also exhibited high selectivity and reproducibility. Finally, the PMel/GCE was used for the simultaneous determination of nitrite and tartrazine in foodstuffs, and the results indicated that the proposed sensor could be a promising candidate for accurate determination of nitrite and tartrazine in real food samples.


Assuntos
Nitritos/análise , Polimerização , Tartrazina/análise , Triazinas/química , Espectroscopia Dielétrica , Eletroquímica , Eletrodos , Microscopia Eletrônica de Varredura , Nitritos/química , Oxirredução , Reprodutibilidade dos Testes , Tartrazina/química , Fatores de Tempo
5.
Inorg Chem ; 59(12): 8308-8319, 2020 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-32437613

RESUMO

Despite a comprehensive study on the biosynthesis and function of nitric oxide, biological metabolism of nitric oxide, especially when its concentration exceeds the cytotoxic level, remains elusive. Oxidation of nitric oxide by O2 in aqueous solution has been known to yield NO2-. On the other hand, a biomimetic study on the metal-mediated conversion of NO to NO2-/NO3- via O2 reactivity disclosed a conceivable pathway for aerobic metabolism of NO. During the NO-to-NO3- conversion, transient formation of metal-bound peroxynitrite and subsequent release of •NO2 via O-O bond cleavage were evidenced by nitration of tyrosine residue or 2,4-di-tert-butylphenol (DTBP). However, the synthetic/catalytic/enzymatic cycle for conversion of nitric oxide into a nitrite pool is not reported. In this study, sequential reaction of the ferrous complex [(PMDTA)Fe(κ2-O,O'-NO2)(κ1-O-NO2)] (3; PMDTA = pentamethyldiethylenetriamine) with NO(g), KC8, and O2 established a synthetic cycle, complex 3 → {Fe(NO)2}9 DNIC [(PMDTA)Fe(NO)2][NO2] (4) → {Fe(NO)2}10 DNIC [(PMDTA)Fe(NO)2] (1) → [(PMDTA)(NO)Fe(κ2-O,N-ONOO)] (2) → complex 3, for the transformation of nitric oxide into nitrite. In contrast to the reported reactivity of metal-bound peroxynitrite toward nitration of DTBP, peroxynitrite-bound MNIC 2 lacks phenol nitration reactivity toward DTBP. Presumably, the [(PMDTA)Fe] core in {Fe(NO)}8 MNIC 2 provides a mononuclear template for intramolecular interaction between Fe-bound peroxynitrite and Fe-bound NO-, yielding Fe-bound nitrite stabilized in the form of complex 3. This [(PMDTA)Fe]-core-mediated concerted peroxynitrite homolytic O-O bond cleavage and combination of the O atom with Fe-bound NO- reveals a novel and effective pathway for NO-to-NO2- transformation. Regarding the reported assembly of the dinitrosyliron unit (DNIU) [Fe(NO)2] in the biological system, this synthetic cycle highlights DNIU as a potential intermediate for nitric oxide monooxygenation activity in a nonheme iron system.


Assuntos
Complexos de Coordenação/química , Compostos Férricos/química , Compostos Ferrosos/química , Óxido Nítrico/química , Nitritos/química , Poliaminas/química , Complexos de Coordenação/síntese química , Estrutura Molecular , Oxigênio/química
6.
Environ Pollut ; 261: 114242, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32220756

RESUMO

Sulfate radical (SO4-)-based advanced oxidation processes (SR-AOPs) are promising in-situ chemical oxidation technologies widely applied for soil/groundwater remediation. The presence of non-target water constituents may interfere the abatement of contaminants by SR-AOPs as well as result in the formation of unintended byproducts. Herein, we reported the formation of toxic chloronitrophenols during thermally activated persulfate oxidation of 2-chlorophenol (2CP) in the presence of nitrite (NO2-). 2-Chloro-4-nitrophenol (2C4NP) and 2-chloro-6-nitrophenol (2C6NP) were identified as nitrated byproducts of 2CP with total yield up to 90%. The formation of nitrated byproducts is a result of coupling reaction between 2CP phenoxyl radical (ClPhO) and nitrogen dioxide radical (NO2). As a critical step, the formation of ClPhO was supported by density functional theory (DFT) computation. Both 2C4NP and 2C6NP could convert to 2-chloro-4,6-dinitrophenol (2C46DNP) upon further treatment via a denitration-renitration process. The formation rate of 2C4NP and 2C6NP was closely dependent on the concentration of NO2-, solution pH, and natural water constituents. ECOSAR calculation suggests that chloronitrophenols are generally more hydrophobic and ecotoxic than 2CP. Our result therefore reveals the potential risks in the abatement of chlorophenols by SR-AOP, particularly when high level of NO2- is present in water matrix.


Assuntos
Clorofenóis , Nitritos , Sulfatos , Poluentes Químicos da Água , Clorofenóis/química , Nitritos/química , Oxirredução , Sulfatos/química , Poluentes Químicos da Água/síntese química
7.
Food Chem ; 317: 126456, 2020 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-32109661

RESUMO

In recent years, gold nanoclusters (AuNCs) have received considerable attention as optical transducers in chemo/biosensors. Herein, a facile and efficient assay for NO2- has been successfully developed based on the fluorescence quenching of AuNCs co-modified by bovine serum albumin and 3-mercaptopropionic acid (BSA/MPA-AuNCs). In the presence of NO2- under acidic conditions, Fe2+ can be readily oxidized and transformed to Fe3+, which can significantly suppress the fluorescence of BSA/MPA-AuNCs via non-radiative electron-transfer mechanism. The linear range and detection limit for this system were found to be 5-30 µM (r = 0.9975) and 0.7 µM, respectively. Other common anions and cations showed only very minor interference with the NO2- detection. Furthermore, the effectiveness of the proposed sensing strategy was validated by the demonstration of good performance in the determination of the amount of NO2- in ham samples, rendering it a powerful tool for the assessment of food security and water quality.


Assuntos
Análise de Alimentos/métodos , Ferro/química , Nanoestruturas/química , Nitritos/análise , Ácido 3-Mercaptopropiônico/química , Técnicas Biossensoriais , Fluorescência , Corantes Fluorescentes/química , Análise de Alimentos/instrumentação , Ouro/química , Limite de Detecção , Nitritos/química , Oxirredução , Carne de Porco/análise , Sensibilidade e Especificidade , Soroalbumina Bovina/química , Espectrometria de Fluorescência
8.
Food Chem ; 317: 126361, 2020 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-32070846

RESUMO

A rapid, sensitive, and highly selective method for determining nitrite in food has been developed. This method is based on the reaction of nitrite with the amino group of 3,3,5,5-tetramethylbenzidine (TMB) to form a diazonium salt, and then the diazonium salt and glucosamine hydrochloride are coupled to each other to form an orange compound. The optimal conditions for maximum color and other analytical parameters were studied. A colorimetric method for nitrite detection has been developed with an outstanding correlation coefficient (R2 = 0.9944), a wide linear range (1-75 µM) and 0.73 µM limit of detection (at S/N = 3) for nitrite ions. This method was successfully applied to the determination of nitrite in a variety of foods and gave recoveries in the range between 100.16% and 103.07%, demonstrating that the accuracy, reliability and potential application of this assay for monitoring nitrite in foods.


Assuntos
Benzidinas/química , Análise de Alimentos/métodos , Nitritos/análise , Colorimetria/métodos , Glucosamina/química , Concentração de Íons de Hidrogênio , Limite de Detecção , Nitritos/química , Reprodutibilidade dos Testes
9.
Proc Natl Acad Sci U S A ; 117(9): 4921-4930, 2020 03 03.
Artigo em Inglês | MEDLINE | ID: mdl-32071223

RESUMO

Antibiotic-resistant superbug bacteria represent a global health problem with no imminent solutions. Here we demonstrate that the combination (termed AB569) of acidified nitrite (A-NO2 -) and Na2-EDTA (disodium ethylenediaminetetraacetic acid) inhibited all Gram-negative and Gram-positive bacteria tested. AB569 was also efficacious at killing the model organism Pseudomonas aeruginosa in biofilms and in a murine chronic lung infection model. AB569 was not toxic to human cell lines at bactericidal concentrations using a basic viability assay. RNA-Seq analyses upon treatment of P. aeruginosa with AB569 revealed a catastrophic loss of the ability to support core pathways encompassing DNA, RNA, protein, ATP biosynthesis, and iron metabolism. Electrochemical analyses elucidated that AB569 produced more stable SNO proteins, potentially explaining one mechanism of bacterial killing. Our data implicate that AB569 is a safe and effective means to kill pathogenic bacteria, suggesting that simple strategies could be applied with highly advantageous therapeutic/toxicity index ratios to pathogens associated with a myriad of periepithelial infections and related disease scenarios.


Assuntos
Antibacterianos/química , Antibacterianos/farmacologia , Bactérias/efeitos dos fármacos , Ácido Edético/farmacologia , Nitrito de Sódio/farmacologia , Animais , Antibacterianos/uso terapêutico , Biofilmes/efeitos dos fármacos , Modelos Animais de Doenças , Regulação para Baixo , Farmacorresistência Bacteriana/efeitos dos fármacos , Ácido Edético/química , Pneumopatias/tratamento farmacológico , Pneumopatias/microbiologia , Redes e Vias Metabólicas , Camundongos , Nitritos/química , Nitritos/farmacologia , Pseudomonas aeruginosa/efeitos dos fármacos
10.
Food Chem ; 312: 126089, 2020 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-31896452

RESUMO

A fluorometric and colorimetric dual-mode sensing platform based on graphitic carbon nitrite quantum dots (g-CNQDs) and Fe (II)-bathophenanthroline complex (BPS-Fe2+) was designed to the sensitive detection of nitrite (NO2-) in sausage and water. In this system, the fluorescence of g-CNQDs was quenched by BPS-Fe2+ complex due to the inner filter effect (IFE). When NO2- was present, Fe2+ was oxidized by nitrite to form BPS-Fe3+ complex with BPS, leading to the recovery of the fluorescence from g-CNQDs. Therefore, we constructed a "turn-off-on" fluorescence probe for detection of NO2-. Moreover, with the increase of NO2- concentration, the color of the solution changed from red to colorless, so the UV-vis measurements and on-site visual detection were realized. The method is capable of detecting NO2- in the concentration range of 2.32-34.8 µM with good selectivity and high sensitivity. In addition, the method has the potential to determine NO2- in water samples and sausage samples.


Assuntos
Carbono/química , Grafite/química , Produtos da Carne/análise , Nitritos/química , Fenantrolinas/química , Pontos Quânticos , Água/química , Colorimetria , Fluorescência , Corantes Fluorescentes , Fluorometria , Compostos de Ferro/química
11.
Chemosphere ; 243: 125433, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31995883

RESUMO

Biomass detachment generally occurred in granular sludge systems. However, little is known about the influence of biomass detachment on the granules performing nitritation. Here, a granular sludge reactor with high loading rates (6.8 ± 0.4 kg N·m-3·d-1) was achieved at mainstream conditions. Though the low ratio control strategy was maintained, the deterioration of nitritation performance was observed after the further increase of air supply rates to 3.4 ± 0.2 L min-1. In parallel with that, the loss of AOB and the proliferation of NOB was observed. Additionally, with the decrease of granules size and biomass concentration, the incomplete stratification of nitrifiers in the granules was confirmed by batch tests. All these results suggested that granules abrasion under the high shear stress conditions caused the detachment of external AOB and hence resulted in the deteriorated stratified structure of nitrifiers, which subsequently contributed to the proliferation of the internal NOB and the deterioration of nitritation. These findings highlight that the granules abrasion should be well controlled in the development of high-rate nitritation process with granular sludge.


Assuntos
Biomassa , Nitritos/química , Nitrogênio/química , Esgotos/química , Reatores Biológicos
12.
Molecules ; 25(2)2020 Jan 09.
Artigo em Inglês | MEDLINE | ID: mdl-31936442

RESUMO

A novel generation of indole-2,3-quinodimethanes via the deamination of 1,2,3,4-tetrahydropyrrolo[s3,4-b]indoles is reported.


Assuntos
Indóis/química , Pirróis/química , Desaminação , Indóis/síntese química , Nitritos/química , Pirróis/síntese química
13.
Environ Sci Pollut Res Int ; 27(2): 1956-1968, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31768960

RESUMO

Membrane separation processes are being currently applied to produce drinking water from water contaminated with nitrate. The overall process generates a brine with high nitrate/nitrite concentration that is usually send back to a conventional wastewater treatment plant. Catalytic processes to nitrate reduction are being studied, but the main goal of achieving a high selectivity to nitrogen production is still a matter of research. In this work, a two-step process was evaluated, aiming to verify the best combination of operational parameters to efficiently reduce nitrate to nitrogen. In the first step, the nitrate was reduced to nitrite by electroreduction, applying a copper electrode and different cell potentials. A second step of the process was carried out by reducing the generated nitrite with a catalytic process by hydrogenation. The results showed that the highest nitrate reduction (89%) occurred when a cell potential of 11 V was applied. In this condition, the nitrite ion was generated with all experimental conditions evaluated. Then, to reduce the nitrite ion formed by catalytic reduction, activated carbon fibers (ACF) and powder γ-alumina (γ-Al2O3) were tested as supports for palladium (Pd). With both catalysts, the total nitrite conversion was obtained, being the selectivity to gaseous compounds 94% and 97% for Pd/Al2O3 and Pd/ACF, respectively. Considering the results obtained, a two-stage treatment setup to brine denitrification may be proposed. With electrochemistry, an operating condition was achieved in which ammonium production can be controlled to very low values, but the reduction is predominant to nitrite. With the second step, all nitrite is converted to nitrogen gas and just 3% of ammonium is produced with the most selective catalyst. The main novelty of this work is associated to the use of a two-stage process enabling 89% of nitrate reduction and 100% of nitrite reduction.


Assuntos
Desnitrificação , Nitratos/química , Nitritos/química , Sais/química , Catálise , Nitrogênio , Oxirredução
14.
Chemosphere ; 241: 125089, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31629234

RESUMO

The Pantanal (Brazil) is a wetland region characterized by seasonal flooding. Hydrological cycles influence the water physicochemical parameters, causing seasonal variations in pH and nitrites. Thus, the objective of this study was to evaluate the effects of varying pH and nitrite concentrations on the toxicity of the cypermethrin-based pesticide Barrage®, considering both lethal (mortality) and sublethal endpoints (growth and development). Larvae of the endemic shrimp Macrobrachium pantanalense and of the estuarine Amazonian congener Macrobrachium amazonicum were exposed to cypermethrin (through Barrage®) under several pH levels (6.5, 7.5 and 8.5) or nitrite concentrations (0.1, 0.2 and 0.4 mg/L). The pH had direct effects on all the tested endpoints for both species. For M. pantanalense, the lethal effects of the cypermethrin formulation were more pronounced at low pH (96-h LC50 = 0.004 µg/L at pH 6.5, and 0.146 µg/L at pH 8.5). For M. amazonicum, an opposite response was observed, with increased toxicity of the formulation at high pH (96-h LC50 = 0.110 µg/L at pH 6.5 and 0.044 µg/L at pH 8.5). Variations in pH also seemed to modify the sublethal effects of the formulation on larval growth and development of M. pantanalense. Nitrite concentrations affected larval growth of both species, modifying also the effects of the cypermethrin formulation on the larval development of M. amazonicum. This work shows the importance of considering abiotic factors for risk assessment either due to possible direct effects on the physiology of organisms and/or due to interactions with other stressors, particularly in fragile biomes such as Pantanal.


Assuntos
Água Doce/química , Palaemonidae/efeitos dos fármacos , Praguicidas/toxicidade , Piretrinas/toxicidade , Poluentes Químicos da Água/toxicidade , Animais , Brasil , Ecotoxicologia , Feminino , Água Doce/análise , Concentração de Íons de Hidrogênio , Larva/efeitos dos fármacos , Larva/crescimento & desenvolvimento , Dose Letal Mediana , Mortalidade , Nitritos/análise , Nitritos/química , Palaemonidae/crescimento & desenvolvimento , Praguicidas/química , Piretrinas/química , Especificidade da Espécie , Testes de Toxicidade Aguda , Áreas Alagadas
15.
Meat Sci ; 159: 107917, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31494521

RESUMO

In this study, effects of ingoing nitrite level (0, 50, 100 and 150 mg/kg), use of sodium ascorbate, addition of starter culture (Lactobacillus plantarum GM77 + Staphylococcus xylosus GM92) and cooking level (control, medium, medium well, well done and very well done) on nitrosamine formation in heat-treated sucuk, a type of semi-dry fermented sausage, were investigated. The use of ascorbate had no significant effect on NDMA (N-Nitrosodimethylamine) and NPIP (N-Nitrosopiperidine) contents in the presence of starter culture. A higher NPYR (N- Nitrosopyrrolidine) content was detected in the group with starter culture at 150 mg/kg nitrite level in comparison to the group without starter culture. Cooking level affected all identified nitrosamines very significantly. Ingoing nitrite level × cooking level interaction was only effective on NPIP and advanced cooking levels (well done and very well done) at higher ingoing nitrite levels (100 and 150 mg/kg) resulted in significant increases in NPIP content.


Assuntos
Ácido Ascórbico/química , Culinária , Dimetilnitrosamina/química , Produtos da Carne/análise , Nitritos/química , Animais , Bacteriocinas , Bovinos , Microbiologia de Alimentos , Temperatura Alta , Fosfatos de Inositol , Lactobacillus plantarum/metabolismo , Produtos da Carne/microbiologia , Carne Vermelha , Staphylococcus/metabolismo
16.
Chemosphere ; 238: 124654, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31524611

RESUMO

Nitrate is a byproduct of the anaerobic ammonium oxidation (anammox) process and is related to its electron transfer. However, little is known about the influence of nitrate on the anammox process. In this work, the biphasic effect of exogenous nitrate on the anammox process was investigated in an upflow biofilter (UBF) reactor with ammonium as the sole electron donor. The responses of anammox to increased nitrate were analyzed by one-way ANOVA test and found to be significantly different under a constant and decreased nitrite condition (p < 0.01). With a single increase in nitrate and constant ammonium and nitrite in the influent, the total nitrogen removal rate (TNRR) of anammox was uninhibited, but stoichiometry deviated and nitrate production always showed a linear decrease. In contrast, anammox exhibited a range of activity with constant ammonium and simultaneously increased nitrate and decreased nitrite in the influent, including a continuous reduction of TNRR, a nonpersistent ammonium overconsumption and a pronounced nonlinear response of nitrate production. Correlation analysis shows that the lack of ammonium overconsumption was accompanied by the disappearance of nitrate underproduction. Kinetic models of product formation were effectively used to explore the nitrate production behavior of anammox subjected to increased nitrate, and the metabolite of nitrate was divided into a growth negative coupling type and growth (partial) coupling type under a constant and decreased nitrite condition, respectively. These findings collectively suggest that nitrate has a biphasic effect on the anammox process and is correlated with the availability of nitrite.


Assuntos
Compostos de Amônio/química , Anaerobiose/efeitos dos fármacos , Nitratos/farmacologia , Reatores Biológicos , Desnitrificação , Cinética , Nitratos/química , Nitritos/química , Nitrogênio/química , Oxirredução
17.
Chemosphere ; 239: 124803, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31520973

RESUMO

Nitrogen biogeochemistry occupies a central role in nitrogen cycles and exerts a significant influence on primary productivity and global carbon cycles. In order to better understand the nitrogen biogeochemistry in coastal regions, spatiotemporal nitrogen fixation, denitrification and anammox were investigated in the coastal regions of northern Beibu Gulf (NBG), South China Sea (SCS). Nitrogen fixation was mainly detected in the water column of outer bays, attributed to the low nitrate concentration and low N/P (N/P < 16). Comparisons of the nitrogen fixation rates between unicellular (<10 mm) and the filamentous diazotrophs (>10 mm) indicated that the contribution of unicellular diazotrophs was more important than filamentous diazotrophs. Besides, field investigation revealed that Richelia was the dominant species in filamentous diazotrophs. On the other hand, both denitrification and anammox were found in the surface sediment and denitrification dominated the nitrogen loss process. Denitrification was mainly related to the nitrate concentration in pore water and organic matter in the sediment, while anammox was mainly regulated by the concentration of nitrate and nitrite in pore water. Additionally, temperature, dissolved oxygen (DO) and salinity also had an impact on denitrification and anammox. The net areal yield of nitrogen biogeochemical processes was estimated to be -1079t/a, as an important pathway of nitrogen removal. This study adds to the knowledge of nitrogen biogeochemistry in the nutrient-replete coastal region and highlights its significance in such an environment.


Assuntos
Baías/química , Ciclo do Nitrogênio , Nitrogênio/química , Baías/microbiologia , Ciclo do Carbono , China , Cianobactérias/metabolismo , Desnitrificação , Nitratos/química , Nitritos/química , Nitrogênio/análise , Fixação de Nitrogênio , Oxigênio/química , Salinidade , Análise Espaço-Temporal
18.
Methods Mol Biol ; 2057: 37-43, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31595468

RESUMO

Accumulating experimental evidence indicates that S-nitrosylation (technically S-nitrosation) events have a central role in plant biology, presumably accounting for much of the widespread influence of nitric oxide (NO) on developmental, metabolic, and stress-related plant responses. Therefore, the accurate detection and quantification of S-nitrosylated proteins and peptides can be particularly useful to determine the relevance of this class of compounds in the ever-increasing number of NO-dependent signaling events described in plant systems. Up to now, the quantification of S-nitrosothiols (SNOs) in plant samples has mostly relied on the Saville reaction and the ozone-based chemiluminescence method, which lacks sensitivity and are very time-consuming, respectively. Taking advantage of the photolytic properties of S-nitrosylated proteins and peptides, the method described in this chapter allows simple, fast, and high-throughput detection of SNOs in plant samples.


Assuntos
Fluorometria/métodos , Óxido Nítrico/metabolismo , Proteínas de Plantas/metabolismo , Plantas/metabolismo , S-Nitrosotióis/análise , Fluorometria/instrumentação , Medições Luminescentes/métodos , Óxido Nítrico/efeitos da radiação , Nitritos/química , Nitrosação , Plantas/química , Rodaminas/química , Rodaminas/efeitos da radiação , S-Nitrosoglutationa/metabolismo , Raios Ultravioleta , Fluxo de Trabalho
19.
Methods Mol Biol ; 1980: 71-80, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-29582371

RESUMO

Nitrogen (N) is one of the key nutrients for algal growth and is an integral part of many cellular components, for example in proteins. Being able to determine the inorganic and organic pools of N is consequently critical for algal cultivation. In this chapter we present the methods we use for determining dissolved inorganic nitrogen (DIN), dissolved organic nitrogen (DON), and particulate organic nitrogen (PON). The methods presented here for DIN rely on colorimetric methods and those of DON and PON on filtration and high temperature catalytic oxidation.


Assuntos
Compostos Inorgânicos/análise , Nitrogênio/análise , Nitrogênio/química , Compostos Orgânicos/análise , Compostos de Amônio/análise , Compostos de Amônio/química , Nitratos/análise , Nitratos/química , Nitritos/análise , Nitritos/química , Solubilidade
20.
BMC Mol Cell Biol ; 20(Suppl 3): 52, 2019 12 11.
Artigo em Inglês | MEDLINE | ID: mdl-31823720

RESUMO

BACKGROUND: Proteins perform their functions by interacting with acid radical ions. Recently, it was a challenging work to precisely predict the binding residues of acid radical ion ligands in the research field of molecular drug design. RESULTS: In this study, we proposed an improved method to predict the acid radical ion binding residues by using K-nearest Neighbors classifier. Meanwhile, we constructed datasets of four acid radical ion ligand (NO2-, CO32-, SO42-, PO43-) binding residues from BioLip database. Then, based on the optimal window length for each acid radical ion ligand, we refined composition information and position conservative information and extracted them as feature parameters for K-nearest Neighbors classifier. In the results of 5-fold cross-validation, the Matthew's correlation coefficient was higher than 0.45, the values of accuracy, sensitivity and specificity were all higher than 69.2%, and the false positive rate was lower than 30.8%. Further, we also performed an independent test to test the practicability of the proposed method. In the obtained results, the sensitivity was higher than 40.9%, the values of accuracy and specificity were higher than 84.2%, the Matthew's correlation coefficient was higher than 0.116, and the false positive rate was lower than 15.4%. Finally, we identified binding residues of the six metal ion ligands. In the predicted results, the values of accuracy, sensitivity and specificity were all higher than 77.6%, the Matthew's correlation coefficient was higher than 0.6, and the false positive rate was lower than 19.6%. CONCLUSIONS: Taken together, the good results of our prediction method added new insights in the prediction of the binding residues of acid radical ion ligands.


Assuntos
Carbonatos/química , Biologia Computacional/métodos , Nitritos/química , Fosfatos/química , Proteínas/química , Proteínas/metabolismo , Sulfatos/química , Sítios de Ligação , Carbonatos/metabolismo , Bases de Dados de Proteínas , Ligantes , Nitritos/metabolismo , Fosfatos/metabolismo , Sulfatos/metabolismo
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