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1.
Phys Chem Chem Phys ; 22(9): 4875-4879, 2020 Mar 07.
Artigo em Inglês | MEDLINE | ID: mdl-32072999

RESUMO

Structural studies on proteins directly in their native environment are required for a comprehensive understanding of their function. Electron paramagnetic resonance (EPR) spectroscopy and in particular double electron-electron resonance (DEER) distance determination are suited to investigate spin-labeled proteins directly in the cell. The combination of intracellular bioorthogonal labeling with in-cell DEER measurements does not require additional purification or delivery steps of spin-labeled protein to the cells. In this study, we express eGFP in E. coli and use copper-catalyzed azide-alkyne cycloaddition (CuAAC) for the site-directed spin labeling of the protein in vivo, followed by in-cell EPR distance determination. Inter-spin distance measurements of spin-labeled eGFP agree with in vitro measurements and calculations based on the rotamer library of the spin label.


Assuntos
Espectroscopia de Ressonância de Spin Eletrônica , Escherichia coli/metabolismo , Proteínas de Fluorescência Verde/química , Alquinos/química , Azidas/química , Catálise , Cobre/química , Reação de Cicloadição , Proteínas de Fluorescência Verde/genética , Proteínas de Fluorescência Verde/metabolismo , Óxidos de Nitrogênio/química , Marcadores de Spin
2.
Chemosphere ; 242: 125273, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31896195

RESUMO

Atmospheric processing may significantly increase solubility of iron in mineral dust, but the effects of heterogeneous reactions on iron solubility have been poorly understood. In this work, we investigated heterogeneous reaction of NO2 (15 ±â€¯1 and 2.5 ±â€¯0.1 ppmv, equal to ∼3.7 × 1014 and ∼6.2 × 1013 molecule cm-3) with hematite, magnetite and goethite at different relative humidities (RH, 0-90%), and changes in particulate nitrate and soluble iron due to heterogeneous reaction with NO2 were quantified as a function of time (up to 24 h). After reaction with 2.5 ±â€¯0.1 ppmv NO2 for 24 h (or less time), hematite and magnetite were fully saturated, while goethite was only partly deactivated. Nitrate yield was largest for goethite, and the mass ratio of formed nitrate to unreacted mineral only reached ∼1% or less after 24 h reaction. All the three minerals showed low reactivities towards NO2, and the average reactive uptake coefficients of NO2 in the first 3 h were found to be < 5 × 10-8. In addition, the increase in iron solubility was found to be small and in some cases even insignificant for the three minerals after heterogeneous reaction with NO2 for 24 h. Overall, the impacts of heterogeneous reaction of NO2 with hematite, magnetite and goethite on nitrate aerosol formation and iron solubility could be very limited.


Assuntos
Compostos Férricos/química , Óxido Ferroso-Férrico/química , Compostos de Ferro/química , Ferro/química , Minerais/química , Nitratos/análise , Óxidos de Nitrogênio/química , Aerossóis , Poluentes Atmosféricos/análise , Poluentes Atmosféricos/química , Poeira/análise , Modelos Químicos , Solubilidade
3.
J Environ Sci (China) ; 87: 289-298, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31791502

RESUMO

CMK-3 and C-FDU-15 samples were synthesized using hard-templating and evaporation-induced self-assembly (EISA) methods, respectively. The pore structures of CMK-3 and C-FDU-15 as well as commercial activated carbon were characterized by means of X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, and N2 adsorption-desorption. Adsorption of NO was investigated by means of thermogravimetric analysis, temperature-programmed desorption of NO + O2, and in situ diffuse reflectance Fourier transform infrared spectroscopy. The results show that the CMK-3 and C-FDU-15 materials possessed ordered and uniform structures. The co-adsorption capacity of NO and O2 decreased in the sequence CMK-3 (88.6 mg/g) > C-FDU-15 (71.7 mg/g) > AC (25.3 mg/g). There were two main adsorption species on CMK-3 and C-FDU-15: nitrite and nitrate. Nitrite is converted to nitrate easily. However, the adsorption species were more complex on AC, with nitrite being the main species. Moreover, CMK-3 and C-FDU-15 exhibit excellent regeneration efficiency compared with AC. The excellent NO adsorption performance of CMK-3 and C-FDU-15 was associated with their ordered mesoporous structures and high surface areas. The research provides more options for NO adsorption in the future.


Assuntos
Modelos Químicos , Óxidos de Nitrogênio/química , Adsorção , Temperatura Baixa , Microscopia Eletrônica de Varredura , Porosidade , Espectroscopia de Infravermelho com Transformada de Fourier
4.
Mutat Res ; 782: 108283, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31843137

RESUMO

Immuno-spin trapping detection of DNA radicals with the nitrone spin trap 5,5-dimethyl-1-pyrrloine N-oxide (DMPO) has made important contributions towards the understanding of DNA radicalization and genotoxicity at sites of inflammation. At sites of inflammation, one-electron oxidants and chloramines decay induce oxidation of genomic DNA, genotoxicity and cell transformation. Radicalization of DNA can result in either single- or double-strand breaks, or end-oxidation products at the sugar or bases. If not repaired, these modifications can lead to mutations and cell transformation. If trapped with DMPO, DNA-centered radical decay and subsequent formation of end-oxidation products are blocked. Herein we discuss recent literature regarding the use of immuno-spin trapping with DMPO to study DNA-centered radicals and their involvement in genotoxicity. This technique has shown the critical role of DNA radicalization in 8-oxo-dG formation and DNA strand breaks in isolated DNA, cells and in whole animals. Combination of technologies, including immuno-spin trapping and powerful chromatographic and sequencing techniques are needed to move forward the field towards the detection of specific genes that are susceptible to oxidative damage in cells located at sites of inflammation. This is important in order to provide novel information about genotoxicity mechanisms, as well as therapeutic possibilities of DMPO or its derivatives for preventing DNA-centered radical-mediated carcinogenesis.


Assuntos
Óxidos N-Cíclicos/efeitos adversos , Dano ao DNA/efeitos dos fármacos , DNA/efeitos dos fármacos , Radicais Livres/química , Mutagênicos/efeitos adversos , Óxidos de Nitrogênio/efeitos adversos , Óxidos de Nitrogênio/química , Animais , Inflamação/genética , Detecção de Spin/métodos
5.
Environ Sci Process Impacts ; 21(10): 1684-1698, 2019 Oct 16.
Artigo em Inglês | MEDLINE | ID: mdl-31580371

RESUMO

We examined the reactive uptake of dinitrogen pentoxide (N2O5) to authentic biomass-burning aerosol (BBA) using a small chamber reservoir in combination with an entrained aerosol flow tube. BBA was generated from four different fuel types and the reactivity of N2O5 was probed from 30 to 70% relative humidity (RH). The N2O5 reactive uptake coefficient, γ(N2O5), depended upon RH, fuel type, and to a lesser degree on aerosol chloride mass fractions. The γ(N2O5) ranged from 2.0 (±0.4) ×10-3 on black needlerush derived BBA at 30% RH to 6.0 (±0.6) ×10-3 on wiregrass derived BBA at 65% RH. Major N2O5 reaction products were observed including gaseous ClNO2 and HNO3 and particulate nitrate, and used to create a reactive nitrogen budget. Black needlerush BBA had the most particulate chloride, and the only measured ClNO2 yield > 1%. The ClNO2 yield on black needlerush decayed from an initial value of ∼100% to ∼30% over the course of the burn experiment, suggesting a depletion of BBA chloride over time. Black needlerush was also the only fuel for which the reactive nitrogen budget indicated other N-containing products were generated. Generally, the results suggest limited chloride availability for heterogeneous reaction for BBA in the RH range probed here, including BBA with chloride mass fractions on the higher end of previously reported values (∼17-34%). Though less than fresh sea spray aerosol, ∼50%. We use these measured quantities to discuss the implications for nocturnal aerosol nitrate formation, the chemical fate of N2O5(g), and the availability of particulate chloride for activation in biomass burning plumes.


Assuntos
Aerossóis/química , Cloro/química , Óxidos de Nitrogênio/química , Biomassa , Mudança Climática , Cinética , Óxidos de Nitrogênio/análise , Incêndios Florestais
6.
Cell Biochem Biophys ; 77(4): 279-292, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31586291

RESUMO

Here, I present the data testifying that the conversion of free radical NO molecules to nitrosonium ions (NO+), which are necessary for the realization of one of NO biological effects (S-nitrosation), may occur in living organisms after binding NO molecules to loosely bound iron (Fe2+ ions) with the subsequent mutual one-electron oxidation-reduction of NO molecules (their disproportionation). Inclusion of thiol-containing substances as iron ligands into this process prevents hydrolysis of NO+ ions bound to iron thus providing the formation of stable dinitrosyl iron complexes (DNIC) with thiol ligands. Such complexes act in living organisms as donors of NO and NO+, providing stabilization and transfer of these agents via the autocrine and paracrine pathways. Without loosely bound iron (labile iron pool) and thiols participating in the DNIC formation, NO functioning as one of universal regulators of diverse metabolic processes would be impossible.


Assuntos
Óxido Nítrico/metabolismo , Animais , Arginina/química , Glutationa/química , Humanos , Ferro/química , Óxidos de Nitrogênio/química , Oxirredução , S-Nitrosotióis/química , S-Nitrosotióis/metabolismo , Compostos de Sulfidrila/química
7.
Int J Mol Sci ; 20(19)2019 Sep 24.
Artigo em Inglês | MEDLINE | ID: mdl-31554219

RESUMO

Nitroxide-based radicals, having the advantage of firm chemical stability, are usable as probes in the detection of nanoscale details in the chemical environment of various multi-component systems, based on subtle variations in their electron paramagnetic resonance spectra. We propose a systematic walk through the vast area of problems and inquires that are implied by the rationalization of solvent effects on the spectral parameters, by first-principle methods of structural chemistry. Our approach consists of using state-of-the-art procedures, like Density Functional Theory (DFT), on properly designed systems, kept at the border of idealization and chemical realism. Thus, we investigate the case of real solvent molecules intervening in different configurations between two radical molecules, in comparison with radicals taken in vacuum or having the solvent that is treated by surrogate models, such as polarization continuum approximation. In this work, we selected the dichloromethane as solvent and the prototype radicals abbreviated TEMPO ((2,2,6,6-Tetramethylpiperidin-1-yl) oxyl). In another branch of the work, we check the interaction of radicals with large toroidal molecules, ß-cyclodextrin, and cucurbit[6]uril, modeling the interaction energy profile at encapsulation. The drawn synoptic view offers valuable rationales for understanding spectroscopy and energetics of nitroxide radicals in various environments, which are specific to soft chemistry.


Assuntos
Estrutura Molecular , Óxidos de Nitrogênio/química , Óxidos N-Cíclicos/química , Teoria da Densidade Funcional , Espectroscopia de Ressonância de Spin Eletrônica , Modelos Moleculares , Conformação Molecular , Solventes/química
8.
Phys Chem Chem Phys ; 21(35): 19226-19233, 2019 Sep 11.
Artigo em Inglês | MEDLINE | ID: mdl-31441492

RESUMO

As one of the main air pollutants, nitrogen oxides (NOx) have serious effects on human health and the environment. In our previous study, we found that Mn-MOF-74 shows excellent catalytic performance for the selective catalytic reduction (SCR) reaction with NH3 being the reductant (NH3-SCR) at low temperature. To obtain a further understanding of the NH3-SCR mechanism in Mn-MOF-74, in this paper, we investigated two important parts of the NH3-SCR process in Mn-MOF-74 using the density functional theory (DFT) method. On the one hand, the structural characteristics of two types of oxygen vacancies of Mn-MOF-74, namely carboxyl oxygen vacancies and hydroxyl oxygen vacancies, and their adsorption properties to reaction species were calculated. It was found that the oxygen vacancies not only activate the reaction species, but also promote the desorption of NO2 molecules from metal sites for the subsequent rapid SCR reactions. On the other hand, we studied the effect of H2O on the structural stability and catalytic performance of Mn-MOF-74. It was found that the interaction of Mn-O bonds was weakened by H2O. Therefore, the influence of H2O should be considered for the future design of MOF-based catalysts for the SCR process.


Assuntos
Teoria da Densidade Funcional , Estruturas Metalorgânicas/química , Oxigênio/química , Água/química , Poluentes Atmosféricos/química , Poluentes Atmosféricos/isolamento & purificação , Catálise , Óxidos de Nitrogênio/química , Óxidos de Nitrogênio/isolamento & purificação , Substâncias Redutoras/química
9.
Int J Mol Sci ; 20(15)2019 Aug 03.
Artigo em Inglês | MEDLINE | ID: mdl-31382639

RESUMO

This paper reports on dihydroxycoumarins as fluorescent probes suitable for the detection and determination of the nitroxide radical, namely 4-amino-TEMPO. Since 4-amino-TEMPO is used as a spin label for the detection of various radicals and damage caused by these species, its determination under physiological conditions might help us to understand the mechanism of the oxidative stress. Among different coumarins studied, only dihydroxy-substituted derivatives show high sensitivity, specificity, and selectivity for the nitroxide radical. In this assay, dihydroxy-substituted coumarins under the action of 4-amino-TEMPO show a very fast and significant increase in fluorescence intensity and lifetime. Among them 6,7-dihydroxycoumarin (esculetin) exhibits the strongest fluorescence enhancement (up to 40 times), with an estimated limit of detection equal to 16.7 nM-a significantly lower value when compared with UV-Vis or electron paramagnetic resonance (EPR) spectroscopy. The method is characterized by an easy procedure of sample preparation and very short time of analysis. The mechanism of the interaction between 6,7-dihydroxycoumarin and 4-amino-TEMPO has been examined with the use of a series of complementary techniques, such as steady-state and time-resolved fluorescence spectroscopy, UV-Vis spectroscopy, electron paramagnetic resonance spectroscopy, potentiometric titration, and high-performance liquid chromatography. It has been proven that the only route of the reaction in the system studied is a proton transfer from the molecule of esculetin to the amino group of the nitroxide. Biological studies performed on prostate cancer cells, breast cancer cells, and normal skin fibroblasts revealed significant anticancer properties of 6,7-dihydroxycoumarin, which caused a considerable decrease in the viability and number of cancer cells, and affected their morphology, contrary to normal fibroblasts. Furthermore, the experiment performed on prostate cancer cells showed that fluorescence emission of esculetin is closely related to intracellular pH-the higher pH, the higher observed fluorescence intensity (in accordance with a chemical experiment). On the other hand, the studies performed in different pH levels revealed that when pH of the solution increases, the observed fluorescence intensity enhancement under the action of 4-amino-TEMPO decreases (better sensing properties of esculetin towards the nitroxide in lower pH).


Assuntos
Cumarínicos/química , Óxidos N-Cíclicos/química , Óxidos de Nitrogênio/química , Estresse Oxidativo , Cumarínicos/farmacologia , Óxidos N-Cíclicos/isolamento & purificação , Espectroscopia de Ressonância de Spin Eletrônica , Fluorescência , Corantes Fluorescentes/química , Depuradores de Radicais Livres/química , Óxidos de Nitrogênio/isolamento & purificação , Espectrometria de Fluorescência , Marcadores de Spin
10.
Molecules ; 24(13)2019 Jul 04.
Artigo em Inglês | MEDLINE | ID: mdl-31277425

RESUMO

The reactions of 3-isoselenocyanato-2,2,5,5-tetramethylpyrrolidine-1-oxyl, 3-isoselenocyanatomethyl-2,2,5,5-tetramethyl-3-pyrrolidine-1-oxyl, and 4-isoselenocyanato-2,2,6,6-tetramethylpiperidine-1-oxyl with selected amines and alcohols give the corresponding novel nitroxyl selenoureas and selenocarbamates, all bearing a nitroxyl moiety. Synthesized selenoureas and selenocarbamates show significant activity against pathogenic fungi and bacteria. In contrast to piperidine nitroxides, pyrrolidine, five-membered nitroxyl selenoureas and selenocarbamates show excellent antifungal and antibacterial activity against pathogenic fungi and bacteria, respectively.


Assuntos
Antibacterianos/farmacologia , Antifúngicos/farmacologia , Carbamatos/farmacologia , Óxidos de Nitrogênio/síntese química , Óxidos de Nitrogênio/farmacologia , Compostos Organosselênicos/farmacologia , Ureia/análogos & derivados , Bactérias/efeitos dos fármacos , Carbamatos/síntese química , Carbamatos/química , Fungos/efeitos dos fármacos , Testes de Sensibilidade Microbiana , Óxidos de Nitrogênio/química , Compostos Organosselênicos/síntese química , Compostos Organosselênicos/química , Ureia/síntese química , Ureia/química , Ureia/farmacologia
11.
Environ Sci Pollut Res Int ; 26(25): 26071-26081, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31278646

RESUMO

Pd-only three-way catalysts with improved catalytic activity for NO elimination were prepared. In order to explore the catalytic reaction rules of NO reduction under a three-way catalytic system, a series of single reactions related to NO reduction were evaluated. It was found that the reaction temperatures of NO + H2 or NO + CO or NO + C3H6 reactions were below 250 °C, while that of NO + C3H8 was up to 350 °C. Thus, the reaction NO + C3H8 served as the key reaction in determining the purification efficiency of NO at the high-temperature stage. By in situ FTIR, we proposed that three possible steps were involved in NO + C3H8 reaction. The first step was the oxidation of C3H8 and NO to acetone and nitrate species by active oxygen species, respectively (C3H8 + O* → C3H6O, NO + O* → NO3-). XPS results revealed that the amount of active oxygen species in Pd/CeO2-ZrO2-Al2O3 (Pd/CZA, 73.7%) was much higher than that in Pd/CexZr1-xO2+Al2O3 (Pd/CZ+A, 64.1%). This was in line with the higher reaction efficiency of the first step over Pd/CZA. Then the NO + C3H8 reaction was accelerated by the first step, which consequently contributed to the higher NO elimination efficiency of Pd/CZA.


Assuntos
Nitratos/química , Óxidos de Nitrogênio/química , Emissões de Veículos , Catálise , Oxirredução , Temperatura Ambiente
12.
Environ Sci Pollut Res Int ; 26(27): 27888-27896, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31346940

RESUMO

This study evaluated the NOx adsorption and desorption performance as well as the casual relationship underlying a Mn-incorporated catalyst (Pt/Ba/Ce/xMn/γ-Al2O3). NOx adsorption and desorption are regarded as a prominent index for the NOx removal performance of NOx storage and reduction; we utilized NOx storage experiments with various inlet NO and O2 concentrations and cycling adsorption/desorption experiments with a couple of adsorption time protocols for performance evaluation. In-suit DRIFT and NOx-TPD tests were implemented to reveal the instant stored species and their thermal stability. Eight percent of Mn catalyst at 350 °C was adopted in the described experiments for its desirable NOx adsorption characteristics. The optimal NOx storage performance was found under 10% O2, deteriorating when the concentration was further increased. Furthermore, elevating NO concentration impaired the NOx adsorption due to the low NO2/NOx ratio. It was also found that shorter adsorption time facilitated NOx removal via maintaining an unsaturated state for active storage components in terms of a fixed desorption time. The stored species existed as nitrites and nitrates with a good low-temperature thermal stability which however decayed at higher temperatures as exhibited in the DRIFT and NOx-TPD tests. These findings provided invaluable information for the application of Mn-incorporated catalyst for NOx removal in diesel exhaust purification to relieve the aerial pollution.


Assuntos
Metais/química , Nitratos/metabolismo , Óxidos de Nitrogênio/metabolismo , Adsorção , Catálise , Temperatura Baixa , Nitratos/química , Óxidos de Nitrogênio/química , Emissões de Veículos
13.
Environ Sci Pollut Res Int ; 26(27): 27940-27952, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31350690

RESUMO

A series of MnOx/ACFN, Ce-MnOx/ACFN, and Fe-Ce-MnOx/ACFN catalysts on selective catalytic reduction (SCR) of NOx with NH3 at low-middle temperature had been successfully prepared through ultrasonic impregnation method, and the catalysts were characterized by SEM, XRD, BET, H2-TPR, NH3-TPD, XPS, and FT-IR spectroscopy, respectively. The results demonstrated that the 15 wt% Fe(1)-Ce(3)-MnOx(7)/ACFN catalyst achieved 90% NOx conversion (100~300 °C), good water resistance, and stability (175 °C). The excellent catalytic performance of the Fe(1)-Ce(3)-MnOx(7)/ACFN catalyst was mainly attributed to the interaction among Mn, Ce, and Fe. The doping of Fe promoted the dispersion of Ce and Mn and the formation of more Mn4+ and chemisorbed oxygen on the surface of a catalyst. This work laid a foundation for the successful application of active carbon fiber in the field of industrial denitrification, especially in the aspect of denitrification moving bed. Graphic abstract.


Assuntos
Amônia/química , Modelos Químicos , Óxidos de Nitrogênio/química , Catálise , Carvão Vegetal , Temperatura Baixa , Desnitrificação , Oxirredução , Oxigênio , Espectroscopia de Infravermelho com Transformada de Fourier , Temperatura Ambiente , Água
14.
J Mol Model ; 25(8): 225, 2019 Jul 16.
Artigo em Inglês | MEDLINE | ID: mdl-31312984

RESUMO

Lapatinib, an orally active dual tyrosine kinase inhibitor, is efficacious in combination therapy with capecitabine for advanced metastatic breast cancer. Despite its importance, it has been associated with hepatotoxicity observed in clinical trials and postmarketing surveillance. The mechanisms of hepatotoxicity at the chemical and cellular levels may link to drug metabolism. In this study, the N- and α-carbon oxidation processes of lapatinib catalyzed by CYP3A4 were explored by density functional theory method. The calculation results show that oxidation of C6 is the primary metabolic process and carboxylic acid is the main metabolic product. Both hydroxylation of C8 and subsequent formation of primary amines are feasible. However, it is not easy for the primary amines to form active metabolites nitroso, which indicates that there are other paths for the production of nitroso. Carboxylic acid is not the main metabolite of N7 oxidation because of higher hydrolysis energy barrier of intermediate nitrone. It is worthy to study subsequent N-hydroxylation and its downstream reaction, which may be the main pathway for the formation of nitroso. These results lay the foundation for drug design and optimization.


Assuntos
Biocatálise , Carbono/química , Sistema Enzimático do Citocromo P-450/metabolismo , Lapatinib/metabolismo , Modelos Teóricos , Furaldeído/química , Hidrogênio/química , Hidroxilação , Redes e Vias Metabólicas , Conformação Molecular , Óxidos de Nitrogênio/química , Oxirredução , Termodinâmica
15.
Mol Biotechnol ; 61(9): 650-662, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31201604

RESUMO

1-Aminocyclopropane carboxylic acid oxidase (ACCO) catalyzes the last step of ethylene biosynthesis in plants. Although some sets of structures have been described, there are remaining questions on the active conformation of ACCO and in particular, on the conformation and potential flexibility of the C-terminal part of the enzyme. Several techniques based on the introduction of a probe through chemical modification of amino acid residues have been developed for determining the conformation and dynamics of proteins. Cysteine residues are recognized as convenient targets for selective chemical modification of proteins, thanks to their relatively low abundance in protein sequences and to their well-mastered chemical reactivity. ACCOs have generally 3 or 4 cysteine residues in their sequences. By a combination of approaches including directed mutagenesis, activity screening on cell extracts, biophysical and biochemical characterization of purified enzymes, we evaluated the effect of native cysteine replacement and that of insertion of cysteines on the C-terminal part in tomato ACCO. Moreover, we have chosen to use paramagnetic labels targeting cysteine residues to monitor potential conformational changes by electron paramagnetic resonance (EPR). Given the level of conservation of the cysteines in ACCO from different plants, this work provides an essential basis for the use of cysteine as probe-anchoring residues.


Assuntos
Aminoácido Oxirredutases/química , Aminoácidos Cíclicos/química , Cisteína/química , Etilenos/química , Lycopersicon esculentum/enzimologia , Óxidos de Nitrogênio/química , Proteínas de Plantas/química , Aminoácido Oxirredutases/genética , Aminoácido Oxirredutases/metabolismo , Substituição de Aminoácidos , Aminoácidos Cíclicos/metabolismo , Sítios de Ligação , Clonagem Molecular , Cisteína/metabolismo , Espectroscopia de Ressonância de Spin Eletrônica , Escherichia coli/genética , Escherichia coli/metabolismo , Etilenos/biossíntese , Expressão Gênica , Vetores Genéticos/química , Vetores Genéticos/metabolismo , Cinética , Lycopersicon esculentum/química , Modelos Moleculares , Mutagênese Sítio-Dirigida , Óxidos de Nitrogênio/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Ligação Proteica , Conformação Proteica em alfa-Hélice , Conformação Proteica em Folha beta , Domínios e Motivos de Interação entre Proteínas , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Marcadores de Spin , Especificidade por Substrato
16.
Environ Sci Pollut Res Int ; 26(22): 22351-22361, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31154651

RESUMO

A new method was developed for denitrification and desulfurization using hydrogen peroxide with the aid of an ultrasonic nebulizer to obtain high removal efficiency of NOx and SO2. Comparing with the atomizing nozzles having the aperture size of 0.01~0.02 mm, the droplets generated using the ultrasonic nebulizer show the smallest d50 value of 7.2 µm, with 72% possessing the size less than 10 µm. Based on the numerical simulation of the vaporization rate of droplets, it is indicated that the droplets with the size of 7.2 µm can be vaporized totally at very short residence time (0.11 s) under 130 °C. Effects of influence factors including the reaction temperature, the initial H2O2 concentration, pH value, and the flue gas flow rate were studied on the removal efficiencies of NO and SO2. Using the in-series double-oxidation subsystems with H2O2 concentration of 6 wt%, pH 5.0, and the reaction temperature of 130 °C, the removal efficiencies of SO2 and NO are respectively 100% and 89.3% at the short residence time of 1.8 s, and the removal efficiency of NO can be increased to 100% as the residence time is longer than 3.7 s. It is confirmed that the ultrasonically atomized H2O2 can indeed enhance the removal efficiencies of NO and SO2 at the optimal temperature, owing to the fast vaporization rate of fine droplets as well as the formation of more active radicals to be captured by NO and SO2 simultaneously. The results here provide a promising route to remove effectively the emissions of NO and SO2 simultaneously. Graphical abstract.


Assuntos
Peróxido de Hidrogênio/química , Óxidos de Nitrogênio/química , Dióxido de Enxofre/química , Desnitrificação , Nebulizadores e Vaporizadores , Oxirredução , Temperatura Ambiente , Ultrassom
17.
Biochim Biophys Acta Biomembr ; 1861(8): 1489-1501, 2019 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-31247162

RESUMO

Free radical scavengers like α-phenyl-N-tert-butylnitrone (PBN) and 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox) have been widely used as protective agents in various biomimetic and biological models. A series of three amphiphilic Trolox and PBN derivatives have been designed by adding to those molecules a perfluorinated chain as well as a sugar group in order to render them amphiphilic. In this work, we have studied the interactions between these derivatives and lipid membranes to understand how they influence their ability to prevent membrane lipid oxidation. We showed the derivatives better inhibited the AAPH-induced oxidation of 1,2-dilinoleoyl-sn-glycero-3-phosphocholine (DLiPC) small unilamellar vesicles (SUVs) than the parent compounds. One of the derivatives, bearing both PBN and Trolox moieties on the same fluorinated carrier, exhibited a synergistic antioxidant effect by delaying the oxidation process. We next investigated the ability of the derivatives to interact with DLiPC membranes in order to better understand the differences observed regarding the antioxidant properties. Surface tension and fluorescence spectroscopy experiments revealed the derivatives exhibited the ability to form monolayers at the air/water interface and spontaneously penetrated lipid membranes, underlying pronounced hydrophobic properties in comparison to the parent compounds. We observed a correlation between the hydrophobic properties, the depth of penetration and the antioxidant properties and showed that the location of these derivatives in the membrane is a key parameter to rationalize their antioxidant efficiency. Molecular dynamics (MD) simulations supported the understanding of the mechanism of action, highlighting various key physical-chemical descriptors.


Assuntos
Antioxidantes/farmacologia , Cromanos/química , Lipídeos de Membrana/química , Óxidos de Nitrogênio/química , Sinergismo Farmacológico , Flúor/química , Peroxidação de Lipídeos , Membranas Artificiais , Oxirredução
18.
Oxid Med Cell Longev ; 2019: 2798154, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31089406

RESUMO

Hypochlorous acid (HOCl), one of the major precursors of free radicals in body cells and tissues, is endowed with strong prooxidant activity. In living systems, dinitrosyl iron complexes (DNIC) with glutathione ligands play the role of nitric oxide donors and possess a broad range of biological activities. At micromolar concentrations, DNIC effectively inhibit HOCl-induced lysis of red blood cells (RBCs) and manifest an ability to scavenge alkoxyl and alkylperoxyl radicals generated in the reaction of HOCl with tert-butyl hydroperoxide. DNIC proved to be more effective cytoprotective agents and organic free radical scavengers in comparison with reduced glutathione (GSH). At the same time, the kinetics of HOCl-induced oxidation of glutathione ligands in DNIC is slower than in the case of GSH. HOCl-induced oxidative conversions of thiolate ligands cause modification of DNIC, which manifests itself in inclusion of other ligands. It is suggested that the strong inhibiting effect of DNIC with glutathione on HOCl-induced lysis of RBCs is determined by their antioxidant and regulatory properties.


Assuntos
Citoproteção/efeitos dos fármacos , Eritrócitos/efeitos dos fármacos , Glutationa/farmacologia , Hemólise/efeitos dos fármacos , Ácido Hipocloroso/toxicidade , Ferro/farmacologia , Óxidos de Nitrogênio/farmacologia , Substâncias Protetoras/farmacologia , Albuminas/metabolismo , Glutationa/química , Humanos , Ferro/química , Ligantes , Óxidos de Nitrogênio/química , Peroxidase/metabolismo
19.
Oxid Med Cell Longev ; 2019: 6373685, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31089411

RESUMO

The present study was directed to the development of EPR methodology for distinguishing cells with different proliferative activities, using "redox imaging." Three nitroxide radicals were used as redox sensors: (a) mito-TEMPO-cell-penetrating and localized mainly in the mitochondria; (b) methoxy-TEMPO-cell-penetrating and randomly distributed between the cytoplasm and the intracellular organelles; and (c) carboxy-PROXYL-nonpenetrating in living cells and evenly distributed in the extracellular environment. The experiments were conducted on eleven cell lines with different proliferative activities and oxidative capacities, confirmed by conventional analytical tests. The data suggest that cancer cells and noncancer cells are characterized by a completely different redox status. This can be analyzed by EPR spectroscopy using mito-TEMPO and methoxy-TEMPO, but not carboxy-PROXYL. The correlation analysis shows that the EPR signal intensity of mito-TEMPO in cell suspensions is closely related to the superoxide level. The described methodology allows the detection of overproduction of superoxide in living cells and their identification based on the intracellular redox status. The experimental data provide evidences about the role of superoxide and hydroperoxides in cell proliferation and malignancy.


Assuntos
Biomarcadores/metabolismo , Peróxido de Hidrogênio/metabolismo , Superóxidos/metabolismo , Antioxidantes/metabolismo , Linhagem Celular , Proliferação de Células , Óxidos N-Cíclicos/metabolismo , Espectroscopia de Ressonância de Spin Eletrônica , Humanos , Leucemia/metabolismo , Linfócitos/metabolismo , Óxidos de Nitrogênio/química , Óxidos de Nitrogênio/metabolismo , Oxirredução
20.
Environ Sci Process Impacts ; 21(6): 916-929, 2019 Jun 19.
Artigo em Inglês | MEDLINE | ID: mdl-31089656

RESUMO

Ozone (O3), a main component in photochemical smog, is a secondary pollutant formed through complex photochemical reactions involving nitrogen oxides (NOx) and volatile organic compounds (VOCs). In the past few decades, with the rapid economic development, industrialization and urbanization, the mixing ratio of O3 has increased substantially in China. O3 non-attainment days have been frequently observed. Despite great efforts made in the past few years, it is still difficult to alleviate O3 pollution in China, due to its non-linear relationship with the precursors. In view of the severe situation in China, this study presents a comprehensive review on the spatial-temporal variations of the relationship between O3 and its precursors (i.e. O3 formation regime), built upon the previous reviews of the spatial-temporal variations of O3 and its precursor levels. Valuable findings from previous studies are laid out for a better understanding of O3 pollution, followed by implications for the control of O3 pollution. This literature review indicates that O3 formation in most areas of the North China Plain (NCP), Yangtze River Delta (YRD) and Pearl River Delta (PRD) regions is in a VOC-limited regime during the high-O3 seasons due to dramatic emissions from human activities in cities. Outside these metropolitan areas, a NOx-limited regime dominates rural/remote areas. From summer to winter, the O3 formation regime over China shows a tendency to shift to a VOC-limited regime. Furthermore, O3 formation in China shifted toward increasing sensitivity to VOC emissions before the 12th Five-Year-Plan. However, after the 12th Five-Year-Plan, successful reduction of NOx slowed down this trend. Further effective control of VOCs is expected to achieve sustained O3 attainment in the future. To timely solve the current O3 pollution problem, precise control of O3 precursors is proposed, together with the joint prevention and control of regional air pollution.


Assuntos
Poluentes Atmosféricos/química , Ozônio/química , Poluição do Ar/prevenção & controle , China , Óxidos de Nitrogênio/química , Estações do Ano , Compostos Orgânicos Voláteis/química
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