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1.
Phytochemistry ; 166: 112077, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31374519

RESUMO

Radical scavenging activity and subsequent oxidation resulting in quinone products represent one of the important features of phenols occurring in plants and other biological systems. However, corresponding thermochemistry data can be still considered scarce. For phenol and 25 para-substituted phenols, we investigate the thermodynamics of the individual reaction steps, including three subsequent hydrogen atom transfers, as well as hydroxyl HO radical addition, leading to final ortho-quinone formation. The substituent and solvent effect of water on corresponding reactions enthalpies is elucidated. Solvent enhances substituent induced changes in the investigated reaction enthalpies. The reliability of employed computational methods for the thermodynamics of hydrogen atom donating ability of studied phenols and catechols is assessed, too. Obtained linear equations enable estimation of studied reaction enthalpies from Hammett constants of substituents.


Assuntos
Depuradores de Radicais Livres/química , Fenóis/química , Quinonas/química , Radical Hidroxila/química , Isomerismo , Relação Estrutura-Atividade , Termodinâmica
2.
Analyst ; 144(17): 5284-5291, 2019 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-31372627

RESUMO

5,10,15,20-Tetrakis(4-carboxyl phenyl)porphyrin (Por) modified Co(OH)2 deposited on the surface of GO nanocomposites (Por/Co(OH)2/GO) were prepared and characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and XRD. For the first time, H2TCPP/Co(OH)2/GO is found to have enhanced peroxidase-like activity and catalyze the oxidation of the substrate 3,3,5,5-tetramethylbenzidine (TMB) by hydrogen peroxide (H2O2). Notably, the colorless TMB rapidly transformed into blue oxTMB in just 60 s, which was easily observed visually. The catalytic kinetics of H2TCPP/Co(OH)2/GO is in accord with the Michaelis-Menten equation. The catalytic mechanism of H2TCPP/Co(OH)2/GO nanocomposites is attributed to hydroxyl radicals (˙OH), due to decomposition of H2O2, which is verified by using terephthalic acid as a fluorescent probe. What's more, H2O2 can be detected in a wide linear detection range from 5 to 35 mM with a detection limit of 0.385 mM. Furthermore, based on the excellent peroxidase-like activity of H2TCPP/Co(OH)2/GO, a colorimetric sensor is established to sensitively detect glutathione (GSH) in a linear range from 10 to 300 µM with a low detection limit of 9.5 µM.


Assuntos
Cobalto/química , Grafite/química , Hidróxidos/química , Nanocompostos/química , Peroxidases/química , Porfirinas/química , Benzidinas/química , Materiais Biomiméticos , Técnicas Biossensoriais/métodos , Catálise , Glutationa/análise , Peróxido de Hidrogênio/química , Radical Hidroxila/química , Cinética , Limite de Detecção , Oxirredução , Sensibilidade e Especificidade , Propriedades de Superfície
3.
J Agric Food Chem ; 67(28): 7961-7967, 2019 Jul 17.
Artigo em Inglês | MEDLINE | ID: mdl-31260294

RESUMO

Food-derived glycated phospholipids is potentially hazardous to human health. However, there are few studies on the effects of lipids on the formation of glycated phospholipids. In this work, two model systems were established: (1) a model system including 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (PE), glucose, and Fenton reagent and (2) a model system including PE, glucose, and five kind of vegetable oils. The contents of carboxymethyl-PE, carboxyethyl-PE, Amadori-PE, hydroxyl radical (OH•), glyoxal, and methylglyoxal were determined with high-performance liquid chromatography mass spectrometry. The results of the first model system showed that OH• oxidized glucose to produce glyoxal and methylglyoxal, which then reacted with PE to form carboxymethyl-PE and carboxyethyl-PE. OH• also oxidized Amadori-PE to form carboxymethyl-PE. The results of the second model system showed that vegetable oils with higher number of moles of carbon-carbon unsaturated double bond in vegetable oil per kilogram could produce more OH•, which promote the formation of carboxymethyl-PE and carboxyethyl-PE by oxidizing glucose and oil. We elucidated the effects of oils on the formation of glycated phospholipids in terms of OH• and intermediates. This work will contribute to better understanding the formation mechanism of glycated phospholipids with oil.


Assuntos
Radical Hidroxila/química , Lipídeos/química , Fosfolipídeos/química , Cromatografia Líquida de Alta Pressão , Glucose/química , Glicosilação , Glioxal/química , Reação de Maillard , Espectrometria de Massas , Modelos Químicos , Oxirredução , Aldeído Pirúvico/química
4.
Food Chem ; 297: 124941, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31253326

RESUMO

The effect of a hydroxyl radical generating system (HRGS), which contained FeCl3, sodium ascorbate, and different concentrations of H2O2, on the physiochemical properties of myofibrillar protein (MP) from squid mantles, has been investigated. The effect of different exposure times to HRGS was also considered. Compared to non-oxidized MP, a significant (p < 0.05) increase in carbonyl content (more than 50% of its original content) and protein solubility, as well as in surface hydrophobicity, was observed in the oxidative MP. With different treatment times, a sharp decrease (p < 0.05) in sulfhydryl content was detected. In addition, hydroxyl radical treatment significantly reduced the MP gel's texture properties, whiteness and water holding capacity, especially at higher concentrations of H2O2. This observation could be attributed to extensive disorderly and less compact structure of MP gels. The results demonstrate the negative effect of HRGS on the structural and functional properties of MP from squid mantles.


Assuntos
Decapodiformes/metabolismo , Proteínas de Frutos do Mar/química , Animais , Ácido Ascórbico/química , Géis/química , Interações Hidrofóbicas e Hidrofílicas , Radical Hidroxila/química , Oxirredução , Reologia , Proteínas de Frutos do Mar/metabolismo , Solubilidade , Compostos de Sulfidrila/análise , Água/química
5.
Int J Nanomedicine ; 14: 2415-2431, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31040665

RESUMO

Background: Gadolinium-based nanoparticles (GdNPs) have been used as theranostic sensitizers in clinical radiotherapy studies; however, the biomechanisms underlying the radio-sensitizing effects of GdNPs have yet to be determined. In this study, ultra-small gadolinium oxide nanocrystals (GONs) were employed to investigate their radiosensitizing effects and biological mechanisms in non-small-cell lung cancer (NSCLC) cells under X-ray irradiation. Method and materials: GONs were synthesized using polyol method. Hydroxyl radical production, oxidative stress, and clonogenic survival after X-ray irradiation were used to evaluate the radiosensitizing effects of GONs. DNA double-strand breakage, cell cycle phase, and apoptosis and autophagy incidences were investigated in vitro to determine the radiosensitizing biomechanism of GONs under X-ray irradiation. Results: GONs induced hydroxyl radical production and oxidative stress in a dose- and concentration-dependent manner in NSCLC cells after X-ray irradiation. The sensitizer enhancement ratios of GONs ranged between 19.3% and 26.3% for the NSCLC cells under investigation with a 10% survival rate compared with that of the cells treated with irradiation alone. Addition of 3-methyladenine to the cell medium decreased the incidence rate of autophagy and increased cell survival, supporting the idea that the GONs promoted cytostatic autophagy in NSCLC cells under X-ray irradiation. Conclusion: This study examined the biological mechanisms underlying the radiosensitizing effects of GONs on NSCLC cells and presented the first evidence for the radiosensitizing effects of GONs via activation of cytostatic autophagy pathway following X-ray irradiation.


Assuntos
Autofagia , Carcinoma Pulmonar de Células não Pequenas/patologia , Gadolínio/química , Neoplasias Pulmonares/patologia , Nanopartículas/química , Tamanho da Partícula , Apoptose , Morte Celular , Linhagem Celular Tumoral , Sobrevivência Celular , Dano ao DNA , Endocitose , Humanos , Radical Hidroxila/química , Nanopartículas/ultraestrutura , Estresse Oxidativo , Raios X
6.
Chemosphere ; 228: 602-610, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31059958

RESUMO

Recent studies have reported a novel advanced oxidation process (AOP) by combining permanganate (KMnO4) and peroxymonosulfate (PMS) for destruction of organic contaminants (i.e., acid orange 7, trichloroethylene, and benzene), where hydroxyl (•OH) and sulfate radicals (SO4•-) are proposed to be generated from PMS activation by amorphous manganese dioxide (MnO2) formed in situ from KMnO4 reduction. In this work, appreciable degradation of p-chlorobenzoic acid (p-CBA) was confirmed in KMnO4/PMS system, while KMnO4 or PMS alone showed inert reactivity toward p-CBA. Moreover, it was found that pre-synthesized amorphous MnO2 showed invalid PMS activation for p-CBA degradation, and pre-addition of inorganic or organic reducing agents to promote the formation of amorphous MnO2 showed negligible influence on p-CBA degradation as well. In these regards, a tentative mechanism for PMS activation by KMnO4 rather than its product MnO2 was proposed, involving the substitution of oxo atoms of KMnO4 by peroxo groups, subsequent reductive generation of peroxomanganese (VI) complexes, and intramolecular disproportionation of these complexes to generate radicals. Efficient degradation of p-CBA was achieved at acid or basic conditions with a maximum rate occurring at pH 3. The coexisting chloride anions showed suppressive effect on p-CBA degradation for scavenging SO4•- and •OH, while metal ions accelerated the degradation of p-CBA, possibly due to the cation bridging function between negatively-charged MnO4- and HSO5-. Hydroxylated intermediates of p-CBA were identified in KMnO4/PMS system. This work improved the fundamental understanding of a new class of AOPs by combining KMnO4 and PMS for environmental decontamination.


Assuntos
Compostos de Manganês/química , Óxidos/química , Peróxidos/química , Poluentes Químicos da Água/química , Purificação da Água/métodos , Concentração de Íons de Hidrogênio , Radical Hidroxila/química , Compostos Orgânicos/química , Oxirredução , Sulfatos
7.
Chemosphere ; 229: 200-205, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31078034

RESUMO

In the present study, ascorbic acid (AA) induced persulfate activation was investigated for the further exploration of organic pollutants oxidation by persulfate. We interestingly found that AA showed a significant catalytic activity to persulfate. Under neutral pH and room temperature condition, about 71.3% of pentachlorophenol (PCP, 10 mg L-1) was decomposed in 180 min with 40 mmol L-1 persulfate and 1.0 mmol L-1 AA, while only 15.4% and 3.2% of PCP was removed by alone persulfate and AA respectively. The result of EPR spectra identified sulfate radical (SO4•-) and hydroxyl radical (OH) were generated during the reaction between persulfate and AA. Quenching experiments confirmed that both SO4- and OH contributed to the decomposition of PCP. With the addition of AA augmented from 0 to 1 mmol L-1, the PCP degradation ratio continuously increased. However, excess AA could consume the generated reactive oxygen species (ROSs) that led to the inhibition of PCP degradation. Meanwhile, the PCP degradation by persulfate-AA was strongly pH dependent. The PCP degradation rate was declined as the initial pH increased from 3.5 to 10.5. At pH above 12.5, the base activation began to predominate over AA activation of persulfate. Furthermore, it was observed that the AA inducing persulfate activation was related to the extent of AA ionization, while C6H8O6 promoted the highest persulfate activation for the PCP degradation, and C6H6O62- induced the lowest persulfate activation. This study indicates the high potential of AA induced persulfate activation for treatment of organochlorine contaminated water.


Assuntos
Ácido Ascórbico/química , Pentaclorofenol/química , Sulfatos/química , Poluentes Químicos da Água/química , Concentração de Íons de Hidrogênio , Radical Hidroxila/química , Oxirredução
8.
Environ Pollut ; 250: 906-913, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31085477

RESUMO

A novel heterogeneous Fenton-like system (Mg/Fe-O2) which could directly convert oxygen (O2) to hydrogen peroxide/hydroxyl radicals (H2O2/•OH) was developed and used to degrade 4-chlorophenol. The Mg/Fe bimetallic particles were prepared by chemical displacement process and characterized by XRD, SEM and TEM. The in situ continuous production of H2O2/•OH and the effect of the mole ratio of Mg to Fe in the Mg/Fe bimetallic particles and the operating parameters on the degradation 4-chlorophenol in Mg/Fe-O2 system were investigated in detail. It was found that the Mg/Fe bimetallic particles with the mole ratio of Mg to Fe of 32:1 had the best performance for the 4-chlorophenol degradation and the maximum cumulative concentration of H2O2, the degradation efficiency of 4-chlorophenol and the removal efficiency of TOC in Mg/Fe-O2 system were 34.5 mg/L, 100% and 91.8%, respectively, at pH 3, O2 flow rate 400 mL/min, dosage of Mg/Fe bimetallic particles 2 g/L, 4-chlorophenol initial concentration 50 mg/L and reaction time 60 min. It was revealed by radical scavenging experiments that •OH, particularly the surface-bound •OH, were the predominant reactive oxygen species in Mg/Fe-O2 system for the degradation of 4-chlorophenol. The main intermediates of 4-chlorophenol degradation were detected by high-resolution liquid chromatography equipped with time-of-flight mass spectrometry (HRLC-ToF-MS) and ion chromatography (IC). Based the results of control experiments and the electrochemical tests, the possible pathway and mechanism of 4-chlorophenol degradation in Mg/Fe-O2 system were tentatively proposed.


Assuntos
Clorofenóis/análise , Peróxido de Hidrogênio/química , Ferro/química , Magnésio/química , Oxigênio/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Catálise , Eletroquímica , Concentração de Íons de Hidrogênio , Radical Hidroxila/química , Modelos Teóricos , Oxirredução , Propriedades de Superfície
9.
Chemosphere ; 231: 276-286, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31129409

RESUMO

The formation of secondary organic aerosol (SOA) generated by irradiating styrene in the presence and/or absence of OH, NOx, H2O vapour and seed aerosol has been investigated for the first time. Experiments were conducted in a smog chamber at 298 K and atmospheric pressure. Styrene decay was measured by gas chromatography with a mass spectrometric detector (GC-MS), and the temporal evolution of the aerosol was monitored using a fast mobility particle sizer (FMPS). The SOA yield increases as the initial styrene concentration increases, leading to yields ranging from 1.8% to 3.5% for styrene photolysis, and from 2.4% to 5.0% for its photooxidation. In both cases, the organic aerosol formation can be expressed by a one-product gas/particle partitioning absorption model. The particle number concentration, mass and yield decrease in the presence of NOx and seed aerosol but increase at higher relative humidity (RH). The gas phase and SOA composition were analysed offline using a filter/denuder sampling system simultaneously collecting gas- and particle-phase products. Benzaldehyde was confirmed as the main gas-phase product of the reaction. However, although products in the particle phase were detected, they could not be identified. Moreover, the aqueous filter extracts were analysed using UV-Visible spectrophotometry to determine differences in the optical properties of SOA produced in the presence and absence of NOx. The results from this work may be used to discuss the implications of atmospheric SOA generation from styrene degradation.


Assuntos
Aerossóis/química , Radical Hidroxila/química , Estireno/química , Gases , Modelos Químicos , Processos Fotoquímicos , Fotólise , Água
10.
Environ Sci Pollut Res Int ; 26(18): 18411-18420, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31049860

RESUMO

Oxidation flow reactors (OFRs) are increasingly used to study the formation and evolution of secondary organic aerosols (SOA) in the atmosphere. The OH/HO2 and OH/O3 ratios in OFRs are similar to tropospheric ratios. In the present work, we investigated the production of SOA generated by OH oxydation and ozonolysis of limonene in OFR as a function of OH exposure and O3 exposure. The results are compared with those obtained from the simulation chambers. The precursor gas is exposed to OH concentrations ranging from 2.11 × 108 to 1.91 × 109 molec cm-3, with an estimated exposure time in the OFR of 137 s. In the environmental chambers, the precursor was oxidized using OH concentrations between 2.10 × 106 and 2.12 × 107 molec cm-3 over exposure times of several hours. In the overlapping OH exposure region, the highest SOA yields are obtained in the OFR, which is explained by the ozonolysis of limonene in the OFR. However, the yields decrease with the increase of OHexp in both systems.


Assuntos
Aerossóis/análise , Limoneno , Modelos Teóricos , Raios Ultravioleta , Compostos Orgânicos Voláteis/análise , Atmosfera/análise , Desenho de Equipamento , Radical Hidroxila/química , Limoneno/química , Limoneno/efeitos da radiação , Oxirredução , Ozônio/química , Processos Fotoquímicos
11.
Chemosphere ; 228: 769-777, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31075640

RESUMO

As sulfonated aromatic compounds are widely used in industry, they have frequently been detected in aquatic environments. This study evaluated the degradation and mineralization of 2,6-naphthalenedisulfonic acid disodium salt (2,6-NS), sodium 2-naphthalenesulfonate (2-NS), benzenesulfonic acid sodium salt (BS), and 4-vinylbenzene sulfonate sodium (4-VBS) by exposing aqueous solutions of these compounds to Co60 irradiation. The radiolytic degradation of these pollutants was found to follow pseudo-first-order kinetics. The dose required to achieve 90% degradation (D90) of these four sulfonated compounds was 0.480 (2,6-NS), 0.390 (2-NS), 0.194 (BS), and 0.280 kGy (4-VBS). The chemical radiolytic yield (Gvalue) decreased as the absorbed dose increased; moreover, the chemical structures of these compounds affected their radiolytic efficacy. No significant reduction in radiolytic degradation was observed in the presence of inorganic anions (SO42-, Cl-). The radiolytic degradation efficiency was higher when hydrogen peroxide (H2O2, a hydroxyl radical (OH) promoter) was added. The results also showed that combining H2O2, persulfate anions (S2O82-, a sulfate radical anion (SO4-) promoter), or N2O gas (a OH radical promoter) with the sulfonated compounds enhanced the radiolytic mineralization yield and process by reducing the required irradiation energy. In terms of the Co60/O2 system, at an absorbed dose of 12 kGy, the total organic carbon (TOC) removal efficiency was almost 70%, resulting in the observed release of SO42- anions. In addition, the concentration of dissolved oxygen decreased and the pH was lowered. Based on these results, irradiation with Co60 was found to be a useful tool to remedy wastewater containing sulfonated aromatic compounds.


Assuntos
Sulfonatos de Arila/química , Poluentes Químicos da Água/química , Ânions , Sulfonatos de Arila/efeitos da radiação , Biodegradação Ambiental , Carbono/química , Radioisótopos de Cobalto , Relação Dose-Resposta à Radiação , Peróxido de Hidrogênio/química , Radical Hidroxila/química , Cinética , Naftalenossulfonatos/química , Naftalenossulfonatos/efeitos da radiação , Sulfatos/química , Água/química , Poluentes Químicos da Água/efeitos da radiação
12.
Environ Sci Pollut Res Int ; 26(20): 21022-21033, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31119544

RESUMO

Iron- and/or manganese-supported catalysts on granular activated carbons (Fe and/or Mn/GACs) were prepared, and their catalytic activities were evaluated by using them to treat phenol and secondary petrochemical effluent via ozonation. The presence of Fe and/or Mn/GACs significantly improved the degradation and degree of phenol mineralization. Changes in dissolved ozone concentrations and the effects of carbonate and tert-butyl alcohol (TBA) indicated that the prepared catalyst enhanced the decomposition of ozone into hydroxyl radicals (·OH), which was determined to be a key factor in catalyzing the ozonation of phenol. Typical intermediate products were identified by GC-MS and HPLC analysis, and a possible degradation pathway of phenol via catalytic ozonation was proposed. The results of XPS, CV, and other experimental data indicated that introducing Fe and/or Mn increased the rate of ozone decomposition into ·OH, and also enhanced the interfacial electron transfer by Fe2+-Fe3+ and Mn2+-Mn3+-Mn4+ redox cycles, resulting in higher catalytic activity. However, the Fe-Mn/GAC surface was shown to undergo galvanic corrosion between Fe3O4 and MnO2, decreasing the catalytic activity. In addition, catalytic ozonation was used to treat secondary petrochemical effluent. The results demonstrated that the Mn/GAC/O3 system significantly improved the quality of phenol-containing wastewater in terms of its COD, TOC, NH4+-N, water color, and ecotoxicity. This study gives a better understanding of the phenol treatment by catalytic ozonation using Fe and/or Mn/GAC.


Assuntos
Carvão Vegetal/química , Ferro/química , Manganês/química , Fenol/isolamento & purificação , Purificação da Água/métodos , Catálise , Radical Hidroxila/química , Oxirredução , Ozônio/química , Fenol/química , Poluentes Químicos da Água/química , Poluentes Químicos da Água/isolamento & purificação
13.
Carbohydr Polym ; 216: 270-281, 2019 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-31047067

RESUMO

The fine structure and chain conformation of a heteropolysaccharide (PCIPS3) from mycelium of Paecilomyces cicadae were investigated via the analysis of HPLC, IR, methylation, NMR spectroscopy and multiangle light scattering. It was determined to be a 2.23 × 104 g/mol heteropolysaccharide primarily composed of glucose, galactose and mannose in a molar ratio of 23.8:2.1:1.0. The PCIPS3 backbone consisted of 1,4-linked α-d-Glcp and 1,4-linked 6-O-Me-α-d-Glcp residues, which were occasionally interrupted by branched ß-Galf residues through 1,6-linkage. Moreover, the α (0.60) from Mark-Houwink-Sakurada (MHS) equation suggested that PCIPS3 adopted a flexible chain conformation in 0.1 mol/L NaNO3 at 25 °C. The worm-like chains model parameters for PCIPS3 were estimated as following: ML = 437 nm-1, q = 0.46 nm and 0.79 nm, which were further evidenced by AFM. Furthermore, PCIPS3 showed excellent scavenging capacities of 2,2-diphenyl-1-picrylhydrazyl radical, superoxide radical, hydroxyl radical, ORAC radical and moderate immunomodulatory activity.


Assuntos
Depuradores de Radicais Livres/farmacologia , Polissacarídeos Fúngicos/farmacologia , Fatores Imunológicos/farmacologia , Paecilomyces/química , Animais , Configuração de Carboidratos , Sobrevivência Celular/efeitos dos fármacos , Depuradores de Radicais Livres/química , Depuradores de Radicais Livres/isolamento & purificação , Depuradores de Radicais Livres/toxicidade , Polissacarídeos Fúngicos/química , Polissacarídeos Fúngicos/isolamento & purificação , Polissacarídeos Fúngicos/toxicidade , Radical Hidroxila/química , Fatores Imunológicos/química , Fatores Imunológicos/isolamento & purificação , Fatores Imunológicos/toxicidade , Interleucina-1beta/metabolismo , Interleucina-6/metabolismo , Camundongos , Peróxidos/química , Células RAW 264.7 , Superóxidos/química , Fator de Necrose Tumoral alfa/metabolismo
14.
Carbohydr Polym ; 216: 369-375, 2019 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-31047079

RESUMO

Lignocellulosic-like materials are potentially low-cost fermentation substrates, but their pretreatment brings about by-products. This work investigated the effects of furfural on xanthan gum (XG) production, and product quality was evaluated by structure, viscosity and antioxidant capacities. Xanthomonas campestris maintained steady polysaccharide yield (above 13 g·L-1) with enhanced cell growth at low furfural concentrations (below 3.2 g·L-1). The products were verified as XG by FT-IR, XRD, NMR and monosaccharide analysis. Moreover, they were found to have reduced acetyl, rising pyruvate and up-to-down glucuronic acid groups as increasing furfural concentration. Furthermore, XG product with 1 g·L-1 furfural addition showed the best hydroxyl scavenging effects, though reducing powers presented no variation. It was demonstrated that furfural, the common hydrolysis by-product, was not necessarily an inhibitor for fermentation, and an appropriate amount of furfural was beneficial to XG production with steady yield and good quality.


Assuntos
Depuradores de Radicais Livres/metabolismo , Furaldeído/farmacologia , Polissacarídeos Bacterianos/biossíntese , Polissacarídeos Bacterianos/química , Xanthomonas campestris/metabolismo , Fermentação/efeitos dos fármacos , Depuradores de Radicais Livres/química , Radical Hidroxila/química , Viscosidade , Xanthomonas campestris/efeitos dos fármacos
15.
Molecules ; 24(9)2019 May 03.
Artigo em Inglês | MEDLINE | ID: mdl-31058864

RESUMO

In this work, primidone, a high persistent pharmacological drug typically found in urban wastewaters, was degraded by different ozone combined AOPs using TiO2 P25 and commercial WO3 as photocatalyst. The comparison of processes, kinetics, nature of transformation products, and ecotoxicity of treated water samples, as well as the influence of the water matrix (ultrapure water or a secondary effluent), is presented and discussed. In presence of ozone, primidone is rapidly eliminated, with hydroxyl radicals being the main species involved. TiO2 was the most active catalyst regardless of the water matrix and the type of solar (global or visible) radiation applied. The synergy between ozone and photocatalysis (photocatalytic ozonation) for TOC removal was more evident at low O3 doses. In spite of having a lower band gap than TiO2 P25, WO3 did not bring any beneficial effects compared to TiO2 P25 regarding PRM and TOC removal. Based on the transformation products identified during ozonation and photocatalytic ozonation of primidone (hydroxyprimidone, phenyl-ethyl-malonamide, and 5-ethyldihydropirimidine-4,6(1H,5H)-dione), a degradation pathway is proposed. The application of the different processes resulted in an environmentally safe effluent for Daphnia magna.


Assuntos
Óxidos/química , Ozônio/química , Primidona/análise , Titânio/química , Tungstênio/química , Poluentes Químicos da Água/análise , Animais , Catálise , Daphnia/efeitos dos fármacos , Daphnia/crescimento & desenvolvimento , Radical Hidroxila/química , Cinética , Oxirredução , Processos Fotoquímicos , Luz Solar , Raios Ultravioleta , Água/química , Purificação da Água
16.
Molecules ; 24(9)2019 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-31067637

RESUMO

4-hydroxycyanobenzene (4HCB) is a dipolar molecule formed of an aromatic substituted benzene ring with the CN and OH functional groups at the 1 and 4 positions. In the crystalline state, it forms spiral chains via hydrogen bonding, which pack together through π - π interactions. The direct stacking of benzene rings down the a- and b-axes and its π - π interactions throughout the structure gives rise to its semiconductor properties. Here, high-pressure studies are conducted on 4HCB in order to investigate how the packing and intermolecular interactions, related to its semiconductor properties, are affected. High-pressure single-crystal X-ray diffraction was performed with helium and neon as the pressure-transmitting mediums up to 26 and 15 GPa, respectively. The pressure-dependent behaviour of 4HCB in He was dominated by the insertion of He into the structure after 2.4 GPa, giving rise to two phase transitions, and alterations in the π - π interactions above 4 GPa. 4HCB compressed in Ne displayed two phase transitions associated with changes in the orientation of the 4HCB molecules, giving rise to twice as many face-to-face packing of the benzene rings down the b-axis, which could allow for greater charge mobility. In the He loading, the hydrogen bonding interactions steadily decrease without any large deviations, while in the Ne loading, the change in 4HCB orientation causes an increase in the hydrogen bonding interaction distance. Our study highlights how the molecular packing and π - π interactions evolve with pressure as well as with He insertion.


Assuntos
Benzeno/química , Estrutura Molecular , Fenóis/química , Ligações de Hidrogênio , Radical Hidroxila/química , Pressão , Difração de Raios X
17.
Chemosphere ; 228: 54-64, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31022620

RESUMO

Organic degradation by zero-valent metal (ZVM)-activated peroxymonosulfate (PMS) systems has drawn great attention in water treatment. Among various types of ZVM, zero-valent copper (ZVC) showed greatest activating capacity. However, the disadvantages of the released Cu2+ limit the practical utilization of ZVC. In this study, the activation capacity of four normal-sized copper catalysts, namely, copper sheet, graphene-copper sheet, copper foam, and graphene-copper foam, for PMS was investigated using Naproxen (NPX) as the probe compound. Results showed that the degradation efficiency of NPX increased by 10%, while the release of Cu2+ decreased by 30% by coating the copper with graphene. Stability tests showed that all of the four catalysts exhibited considerable stability in PMS activation. Furthermore, we found for the first time that the hydroxyl radical was the dominant species in the degradation of NPX rather than the sulfate radical, which was proved by ESR and radical scavenging experiments. Finally, six intermediates were identified by HPLC-MS/MS, and the degradation pathways were proposed. This study confirmed the feasibility of graphene coating on metals to achieve the enhancement of PMS activation.


Assuntos
Cobre/química , Naproxeno/química , Peróxidos/química , Purificação da Água/métodos , Catálise , Radical Hidroxila/química , Sulfatos/química , Poluentes Químicos da Água/química
18.
Environ Sci Pollut Res Int ; 26(15): 15373-15380, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30937738

RESUMO

Alumina has been used as a catalyst for ozonation, surface hydroxyl on which is regarded as the active center for ozone attack, but the influences of hydroxyl generation are still vague. Here, we prepared alumina with different hydroxyl concentrations by adjusting calcination temperatures, of which the catalytic activity was evaluated with the mineralization degree of phenol, and then revealed the active sites of hydroxyl generation with characterization of XRD, Py-IR, and NH3-TPD. The results show that the greater the hydroxyl concentration, the higher the catalytic activity, demonstrating that surface hydroxyl contributes to its catalytic activity. The effect of calcination temperatures on hydroxyl concentration and catalytic activity is in accordance with the amount of weak Lewis acid sites on the surface of alumina, illustrating the surface hydroxyl derived from the decomposition of water adsorbed on weak Lewis acid sites. However, the catalytic performance of the alumina decreases slowly in a long-term reaction owing to the active center reduction resulted from the coverage by organic acids from phenol degradation. The present work reveals the influences of hydroxyl generation which are beneficial for adjusting surface hydroxyl regarded as active site for ozone attack and the reason of catalyst deactivation, which provides guideline for the rational design of catalyst.


Assuntos
Óxido de Alumínio/química , Radical Hidroxila/química , Ozônio/química , Fenol/química , Poluentes Químicos da Água/química , Adsorção , Catálise , Ácidos de Lewis/química , Temperatura Ambiente , Purificação da Água/métodos , Difração de Raios X
19.
Chemosphere ; 228: 232-240, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31035160

RESUMO

The activities of heterogeneous Fenton and Photo-Fenton processes using pyrite (FeS2) prepared via a solvethermal method were evaluated by oxidation of p-nitrophenol (PNP). PNP could be completely ultrarapidly oxidized by Pyrite-Photo-Fenton (Pyrite-PF) system within 4 min, versus 10 min in Pyrite-Fenton (Pyrite-F) system. The excellent oxidation performance obtained by Pyrite-PF might be due to accelerated circulation between ferrous ions and ferric ions under visible light illumination, which improved generation of reactive oxygen species (ROS). X-ray diffraction (XRD), scanning electron microscope (SEM), high resolution transmission electron microscopy (HRTEM), electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS) were applied to ascertain the morphology and crystal structure of fresh-pyrite as well as used-pyrite. According to these results, the synthesized pyrite particles performed eminent stability, and used-pyrite could even generated more ROS including hydroxyl radicals (OH) and superoxide radicals (O2-). EPR testing and quenching experiments also confirmed the generations of OH, O2- and holes (h+) during oxidation processes of PNP in both Pyrite-F and Pyrite-PF systems. The reaction pathway was proposed based on the detected intermediate products including 4-nitrocatechol, 4-nitropyrogallol, hydroquinone, benzoquinone, 1,2,4-trihydroxybenzene and 2,4-dinitrophenol. The mechanisms of PNP degradation in Pyrite-F and Pyrite-PF systems have also been studied by DFT calculations. Pyrite (111) should be responsible for the generations of free OH and surface OH.


Assuntos
Catálise , Luz , Nitrofenóis/química , Sulfetos/síntese química , Peróxido de Hidrogênio/química , Radical Hidroxila/química , Ferro/química , Oxirredução , Análise Espectral , Sulfetos/química , Superóxidos
20.
J Agric Food Chem ; 67(20): 5866-5873, 2019 May 22.
Artigo em Inglês | MEDLINE | ID: mdl-31026156

RESUMO

The main purpose of this study was to investigate the effects of oxidation in vitro on the biochemical properties of myofibrillar protein isolates (MPIs) from beef muscles. MPIs were incubated at 4 °C for 24 h with hydroxyl-radical-generating systems consisting of 0.01 mM FeCl3 and 0.1 mM ascorbic acid plus 0, 0.2, 1, 5, 10, and 20 mM hydrogen peroxide. The results showed that oxidation caused drastically structural changes in bovine MPIs. The carbonyl content, the surface hydrophobicity, and the particle diameter of MPIs were significantly increased, while the free sulfhydryl group content was dramatically decreased with increasing hydrogen peroxide concentrations. Oxidation caused the protein aggregations through cross-linking between proteins and amino acids. Proteomics study identified protein sites in which they were easy to be oxidized. Oxidized catalytic activities and binding sites of enzymes that were susceptible to oxidation were also identified.


Assuntos
Proteínas Musculares/química , Músculo Esquelético/química , Miofibrilas/química , Animais , Bovinos , Interações Hidrofóbicas e Hidrofílicas , Radical Hidroxila/química , Oxirredução , Carne Vermelha/análise
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