Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 60
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Chemosphere ; : 135872, 2022 Aug 04.
Artigo em Inglês | MEDLINE | ID: mdl-35934094

RESUMO

This work reports a mechanochemical (MC) method for complete defluorination of perfluorooctanoic acid (PFOA) by using Al and Al2O3 as milling agents. Both the Al/Al2O3 molar ratio ( [Formula: see text] ) and the pre-thermal treatment of Al2O3 strongly influenced the defluorination of PFOA. When commercial γ-Al2O3 was pre-treated at 1200 °C, the use of Al and heat-treated γ-Al2O3 with [Formula: see text] of 1: 1 led to PFOA defluorination of 100% after ball milling for 26 min at 350 rpm, being much higher than those (8.3%-58.1%) for using singlet milling agents or binary milling agents containing γ-Al2O3 pre-heated at temperatures lower than 700 °C. It was clarified that the carboxylate-mediated adsorption of PFOA on Al2O3 was essential for the MC decarboxylation as a degradation initiation step, and the in-situ generated electron on milled Al consequently caused the reductive dissociation of C-F bonds in the decarboxylation intermediate. A larger [Formula: see text] increased the in-situ electron generation rate (re), and a higher heat-treatment temperature decreased OH-/H2O adsorbed on Al2O3 to low the PFOA decarboxylation rate (rdec). The re/rdec ratio determined defluorination pathways, and the percentage of the defluorination of PFOA in its total degradation including the generation of any degradation intermediates increased linearly with increasing re/rdec.

2.
J Hazard Mater ; 411: 125124, 2021 06 05.
Artigo em Inglês | MEDLINE | ID: mdl-33858098

RESUMO

It is of great importance to predict the adsorption of micropollutants onto CNTs, which is not only useful for exploring their potential adsorbent applications, but also helpful for better understanding their fate and risks in aquatic environments. This study experimentally examined the adsorption affinities of thirty-one micropollutants on four multi-walled CNTs (MWCNTs) with different functional groups (non-functionalized, -COOH, -OH, and -NH2). The properties of each adsorbent were predicted based on the linear free energy relationship (LFER) model. The experimental results showed that MWCNTs-COOH has remarkable adsorption affinities for positively charged compounds (1.996-3.203 log unit), whereas MWCNTs-NH2 has high adsorption affinities for negatively charged compounds (1.360-3.073 log unit). Regarding neutral compounds, there was no significant difference in adsorption affinities of all types of CNTs. According to modeling results, the adsorption affinity can be accurately predicted using LFER models with R2 in the range of 0.81-0.91. Based on the developed models, the adsorption mechanism and contribution of individual intermolecular interactions to the overall adsorption were interpreted. For non-functionalized MWCNTs, molecular interactions induced by molecular volume and H-bonding basicity predominantly contribute to adsorption, whereas for functionalized MWCNTs, the Coulombic interaction due to the charges is an important factor.

3.
Materials (Basel) ; 13(11)2020 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-32532093

RESUMO

This work is about the influence rule of inclination of welding torch on the formation and characteristics of weld bead during the pulsed-gas metal arc welding (GMAW) process based on the robotic operation. The inclination of welding torch was an important operation condition during the pulsed-GMAW process, because it can affect the formation and quality of weld bead, which was the output of the process. In this work, the different inclination modes and values were employed to conduct actual welding experiments, and some influence rules can be obtained according to examine the surface topography and cross section. Then, to obtain further rules, serious measurements for the geometry characteristic parameters were conducted and corresponding curve fitting equations between inclination angles and the bead width, penetration and bead height were obtained, and the largest error of these curve fitting equations was 0.117 mm, whose corresponding mean squared error (MSE) was 0.0103. Corresponding verification experiments validated the effectiveness of the curve fittings and showed the second order polynomials were proper, and the largest errors between measurements and curve fitting equations for inclination angle under backward mode were larger than those under forward mode, and were 0.10 mm and 0.15 mm, respectively, which corresponded to the penetration and were below 10%, therefore the equations can be used to predict the geometry of the weld bead. This work can benefit the process and operation optimization of the pulsed-GMAW process, both in the academic researches and actual industrial production.

4.
Anal Chim Acta ; 1082: 49-55, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31472712

RESUMO

A new determination method for total bromine in electronic devices was developed by using ultrasound assisted extraction, copper-catalyzed reductive debromination and ion chromatography (UAE-RD-IC). It was found that all the added brominated flame retardants (polybrominateddiphenyl ethers, polybrominated biphenyls, tetrabromobisphenol A, and hexabromocyclododecane) could be completely debrominated by using copper-based catalysts and reducing agent N2H4•H2O. The complete debromination of brominated flame retardants released all of their bromine in the form of bromide ions, which could be determined by ion chromatography. After the extraction parameters were optimized by achieving the maximum IC signal in the certified reference material GBW(E) 082725, the UAE-RD-IC method was established for the determination of total bromine in solid samples. By analyzing the certified reference material, the Br content was obtained as 695.3 ±â€¯16.0 mg kg-1, being well consistent with its standard value (694.54 ±â€¯30.63 mg kg-1). The relative standard deviation (RSD) of five parallel determinations was 1.7%, indicating the good repeatability of the developed method. The proposed method was further applied to analyze the samples of cables and computer mouse shells. For all these practical samples, the Br contents obtained by the UAE-RD-IC method were in good agreement with that obtained by the standard oxygen bomb combustion-IC method. It was noted that the new method has a detection limit of Br of about 20 mg kg-1, being much lower than that (75 mg kg-1) of the traditional oxygen bomb combustion-IC method for total bromine detection. Therefore, the proposed method was qualified as a practical method to measure total bromine content in actual electronic devices with good analytical performances of accuracy, precision and sensitivity.

5.
Materials (Basel) ; 12(17)2019 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-31466353

RESUMO

This study focuses on the characteristics of the ripples of the weld bead formed during the double-pulsed gas metal arc welding (DP-GMAW) process. As a special output of the process, ripples include many useful information and can reflect the quality of the welding process. The work analyzed the operational characteristics of the DP-GMAW process based on robot operation which used the latest twinpulse XT DP control process, and then selected five key operational parameters, such as average current, welding speed, twin pulse frequency, twin pulse relation, and twin pulse current change in percent, to explore their effects on the formation and characteristics of ripples. A reliable method of measuring the distance of the ripples was used to provide convincing data. According to a series of experimental observations and analyses, the distance of ripples and appearance under different conditions were obtained. Also, curve fitting equations between each operational parameter and corresponding distances of ripples was obtained. To testify the effectiveness of the curve fitting equations, corresponding verifying experiments were conducted, and the results showed that all the errors were below 10%. In addition, the different levels of the operational parameters on the formation and characteristics of ripples were provided. This work can be a reference for the process and quality control improvement for the DP-GMAW process.

6.
Analyst ; 144(18): 5528-5537, 2019 Sep 09.
Artigo em Inglês | MEDLINE | ID: mdl-31402359

RESUMO

The fast inspection of the pesticide residues on fruits and vegetables requires the development of facile, sensitive and accurate methods. Surface enhanced Raman scattering (SERS) is a promising way to provide a fast inspection method, which requires significant improvements in the reproducibility and feasibility. In the present work, an SERS method was developed for the fast inspection of pesticides on fruit peels in conjunction with surface extraction and coordination transferring. In this new method, the residual pesticides were directly extracted from fruit peels with an appropriate extraction solution and then quantitatively transferred onto an organic solvent-compatible Au array SERS chip through the strong chemical interactions between the heteroatoms in the pesticides and the gold surface. The functional SERS chip was fabricated by the interfacial assembly of an Au array on a membrane, which produced dense and uniformly distributed SERS hot spots and enabled compatibility with random curvature surfaces and handheld Raman spectrometers. As a proof of concept, sulfur atoms containing thiram on apples were detected at a concentration as low as 5 ng cm-2 with good reproducibility (relative standard deviation lower than 10%). The strong interactions between the sulfur atoms and gold surface during the coordination transferring process were confirmed by the enhanced vibrations of the specified bands occurring in both the Raman and IR spectra. This surface extraction-coordination transferring-based method holds wide applicability for heteroatom-containing pesticides, as demonstrated by the detection of various S- and P-containing pesticides.

7.
Environ Sci Technol ; 53(14): 8302-8313, 2019 Jul 16.
Artigo em Inglês | MEDLINE | ID: mdl-31149813

RESUMO

Perfluorooctanoic acid (PFOA) is a persistent organic pollutant that has received concerns worldwide due to its extreme resistance to conventional degradation. A mechanochemical (MC) method was developed for complete degradation of PFOA by using alumina (Al2O3) and potassium persulfate (PS) as comilling agents. After ball milling for 2 h, the MC treatment using Al2O3 or PS caused conversion of PFOA to either 1-H-1-perfluoroheptene or dimers with a defluorination efficiency lower than 20%, but that using both Al2O3 and PS caused degradation of PFOA with a defluorination of 100% and a mineralization of 98%. This method also caused complete defluorination of other C3∼C6 homologues of PFOA. The complete defluorination of PFOA attributes to Al2O3 and PS led to the weakening of the C-F bond in PFOA and the generation of hydroxyl radical (•OH), respectively. During the MC degradation, Al2O3 strongly anchors PFOA through COO--Al coordination and in situ formed from Lewis-base interaction and PS through hydrogen bond. Meanwhile, mechanical effects induce the homolytic cleavage of PS to produce SO4•-, which reacts with OH group of Al2O3 to generate •OH. The degradation of PFOA is initiated by decarboxylation as a result of weakened C-COO- due to Al3+ coordination. The subsequent addition of •OH, elimination of HF, and reaction with water induce the stepwise removal of all carboxyl groups and F atoms as CO2 and F-, respectively. Thus, complete defluorination and mineralization are achieved.


Assuntos
Óxido de Alumínio , Fluorcarbonetos , Caprilatos , Radical Hidroxila
8.
J Hazard Mater ; 371: 456-462, 2019 06 05.
Artigo em Inglês | MEDLINE | ID: mdl-30875573

RESUMO

Dissolved cobalt ions (Co2+) are an excellent catalyst for activating peroxymonosulfate (PMS) to generate SO4- for the degradation of organic pollutants, but fairly high level of Co2+ is generally required, which may cause secondary pollution due to its toxicity. Herein, we demonstrate a novel strategy for this catalytic oxidation treatment in which the required Co2+ addition is very small, being much less than the emission limit of 17 µmol L-1. This new strategy is based on the much enhanced catalytic effect by the addition of small organic acids (SOAs). In a typical case, all the added diclofenac (30 µmol L-1) was degraded in 20 min by using 2 µmol L-1 Co2+, 0.15 mmol L-1 PMS and 0.5 mmol L-1 acetate with a degradation rate constant of 0.482 min-1, which was about 10 times higher than that (0.048 min-1) of equivalent Co2+-PMS system without acetate. The formation of SO4- was greatly enhanced by introducing acetate, and this novel system is universal for enhanced degradation of various organic pollutants. Similarly, formate, propionate, and butyrate also exhibited enhancing effects on the catalytic ability of Co2+. The enhancement mechanism of SOAs on catalytic activation of PMS by low-level Co2+ was also proposed.

9.
Environ Sci Technol ; 53(8): 4433-4439, 2019 04 16.
Artigo em Inglês | MEDLINE | ID: mdl-30912444

RESUMO

Reductive debromination has been widely studied for the degradation of polybrominated diphenyl ethers (PBDEs), although the reaction mechanisms are not so clear. In the present study, the photocatalytic degradation and debromination of ten PBDEs were carried out with CuO/TiO2 nanocomposites as the photocatalyst under an anaerobic condition. The pseudo-first-order rate constants were obtained for the photocatalytic debromination of PBDEs, and their relative rate constants ( kR) were evaluated against kR= 1 for BDE209. Unlike the generally accepted summary that kR is dependent on the total Br number ( N) of PBDEs, kR is found to depend on the Br number on a phenyl ring with more Br atoms than the other one. In other words, a phenyl ring substituted by more Br is more reactive for the reductive debromination. The calculated LUMO energies ( ELUMO) of all PBDEs are well correlated to the more reactive phenyl ring with more Br, compared with the N of two phenyl rings. The result was explained by LUMO localization on the Br-rich phenyl ring, suggesting that the reductive debromination occurs on the phenyl ring.


Assuntos
Éteres Difenil Halogenados , Éteres Fenílicos
10.
J Environ Sci (China) ; 78: 1-12, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30665628

RESUMO

Ibuprofen (IBU), a nonsteroidal anti-inflammatory drug, is becoming an important member of pharmaceuticals and personal care products (PPCPs) as emerging pollutants. To degrade IBU, magnetic Fe3C nanoparticles embedded on N-doped carbon (Fe3C/NC) were prepared as a catalyst by a sol-gel combustion method. As characterized, the Fe3C/NC nanoparticles were composed of a NC nano-sheet and capsulated Fe3C particles on the sheet. The Fe3C/NC nanoparticles were confirmed an efficient catalyst for peroxymonosulfate (PMS) activation to generate sulfate radicals (SO4•-), single oxygen (1O2) and hydroxyl radicals (•OH) toward the degradation of IBU. The added IBU (10 mg/L) was almost completely removed in 30 min by using 0.1 g/L Fe3C/NC and 2 g/L PMS. The catalyst was confirmed to have good ability and excellent reusability through leaching measurements and cycle experiments. A catalytic mechanism was proposed for the catalytic activation of PMS on Fe3C/NC, which involves both Fe3C reactive sites and N-doped carbon matrix as reactive sites in Fe3C/NC. Moreover, the degradation pathway of IBU in the Fe3C/NC-PMS system was proposed according to the detections of degradation intermediates.


Assuntos
Ibuprofeno/química , Modelos Químicos , Poluentes Químicos da Água/química , Carbono/química , Catálise , Compostos Férricos/química , Peróxidos/química
11.
J Hazard Mater ; 364: 59-68, 2019 02 15.
Artigo em Inglês | MEDLINE | ID: mdl-30339933

RESUMO

Chalcopyrite nanoparticles (CuFeS2 NPs) with abundant surface bonded ferrous were successfully prepared, characterized and used as a catalyst for peroxymonosulfate (PMS) activation and BPA degradation. The effect of reaction parameters such as initial pH, catalyst load, PMS concentration, initial BPA concentration and reaction temperature on BPA degradation in CuFeS2-PMS system was systematically investigated. As a bimetallic sulfide, CuFeS2 exhibits ultra-high activity for PMS activation compared with Cu2S, FeS2, CuFeO2 and Co3O4. It was found that by co-use of 0.1 g L-1 CuFeS2 and 0.3 mmol L-1 PMS, 20 mg L-1 of BPA was almost completely degraded (99.7%) and reached a mineralization rate of 75% within 20 min. The highly catalytic activity of CuFeS2 is closely related to two aspects: one is that S2- in the catalysts promotes the cycling of Fe3+/Fe2+ and Cu2+/Cu+ cycles on the surface, and the other is the synergistic effect of Fe3+/Fe2+ and Cu2+/Cu+ cycles in the PMS activation. These interesting findings shed some new insight on the development of metal sulfides for the oxidative treatment of organic contaminants.

12.
Environ Sci Technol ; 52(20): 11743-11751, 2018 10 16.
Artigo em Inglês | MEDLINE | ID: mdl-30207447

RESUMO

Fast and deep debromination of polybrominated diphenyl ethers (PBDEs) under mild conditions is a challenge in the field of pollution control. A strategy was developed to achieve it by exploiting Cu/TiO2 composites as a noble-metal-free catalyst. Toward the debromination of 2,2',4,4'-tetrabromodiphenyl ether (BDE47) as a typical PBDE, the use of Cu/TiO2 as a catalyst and hydrazine hydrate (N2H4·H2O) as a reducing agent yielded a degradation removal of 100% and a debromination efficiency of 87.7% in 3 s. A complete debromination of BDE47 at 1500 mg L-1 was possible by successively adding N2H4·H2O. A debromination pathway involving active H atom species was proposed for the catalytic transfer hydrogenation (CTH) of PBDEs according to the identified degradation intermediates. A mechanism was further clarified by density functional theory calculations: electrons are delivered from N2H4·H2O to the metallic Cu atom via a coordination of N in N2H4·H2O with Cu atoms. The electron-trapped Cu atom interacts with adsorbed BDE47 to form a transition complex, and then the debromination of this complex occurs on the surface of Cu nanoparticles due to the hydrogen donation of N2H4·H2O through the CTH process. The new method provides a highly efficient method to remove brominated pollutants.


Assuntos
Nanocompostos , Catálise , Éter , Éteres Difenil Halogenados , Ferro , Metais
13.
Chemosphere ; 205: 531-539, 2018 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-29709803

RESUMO

In this work, we report metal ions catalyzed oxidative degradation of three typical fluoroquinolones norfloxacin (NOR), ofloxacin (OFL) and ciprofloxacin (CIP) by using NaBiO3 nanosheets. It was found that variable-valence metal ions such as Cu2+, Fe2+, Mn2+, Ce3+, Ag+ and Co2+ could obviously enhanced degradation of NOR, OFL and CIP by NaBiO3. The pseudo-first-order kinetic rate for the degradation of 20 µmol L-1 NOR by NaBiO3 (2 mmol L-1) in the presence of 0.1 mmol L-1 Cu2+, Fe2+, Mn2+, Ce3+, Ag+ and Co2+ was 0.021, 0.084, 0.019, 0.23, 0.25 and 0.28 min-1, 2.1, 8.4, 19, 23, 25 and 28 times that by NaBiO3 without any metal ions. In comparison, Ca2+ and Fe3+ exhibited no obviously promotive or depressive effect for the degradation of NOR by NaBiO3. Singlet oxygen (1O2) was suggested as the main reactive species from NaBiO3 in the presence of metal ions by electron spin resonance technology and radicals scavenging experiments. The evolution of NaBiO3 was tracked with scanning electron microscope, energy dispersive spectrometer, X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectroscopy. It was found that the metal ions were embedded into the crystal structure of NaBiO3 through ion-exchange between Na in NaBiO3 and metal ions. In the subsequent step, an electron transformation from lattice oxygen to Bi(V) sites was mediated by embedded variable-valence metal species, resulting in an enhanced generation of 1O2 from the crystal structure of NaBiO3. These results can shed light on the application of NaBiO3 for the organic pollutant decontamination.


Assuntos
Bismuto/química , Ciprofloxacina/química , Metais/química , Norfloxacino/química , Ofloxacino/química , Catálise , Nanoestruturas , Oxirredução , Estresse Oxidativo , Oxigênio/química , Sódio , Difração de Raios X
14.
Langmuir ; 34(8): 2841-2848, 2018 02 27.
Artigo em Inglês | MEDLINE | ID: mdl-29406720

RESUMO

The wetting property of nanomaterials is of great importance to both fundamental understanding and potential applications. However, the study on the intrinsic wetting property of nanomaterials is interfered by organic capping agents, which are often used to lower the surface energy of nanomaterials and avoid their irreversible agglomeration. In this work, the wetting property of the nanostructured polyaniline that requires no organic capping agents is investigated. Compared to hydrophilic granular particulates, polyaniline nanofibers are amphiphilic and have an excellent capability of creating Pickering emulsions at a wide range of pH. It is suggested that polyaniline nanofibers can be easily wetted by water and oil. Furthermore, the amphiphilic polyaniline nanofibers as building blocks can be used to construct filtration membranes with a small pore size. The wetting layer of the continuous phase of emulsions in the porous nanochannels efficiently prevents the permeation of the dispersed phase, realizing high-efficiency on-demand emulsion separation.

15.
Sensors (Basel) ; 17(7)2017 Jul 10.
Artigo em Inglês | MEDLINE | ID: mdl-28698502

RESUMO

Sibutramine hydrochloride (SH) is a banned weight-loss drug, but its illegal addition to health products is still rampant. This suggests a very urgent need for a fast and precise detection method for SH. Surface Enhanced Raman Scattering (SERS) is a promising candidate for this purpose, but the weak affinity between SH and bare metal limits its direct SERS detection. In the present work, ß-cyclodextrin was capped in situ onto the surface of Ag nanoparticles to function as a scaffold to capture SH. The obtained Ag nanoparticles were encapsulated into polyvinyl alcohol (PVA) to fabricate a SERS active hydrogel with excellent reproducibility. A facile SERS strategy based on such substrate was proposed for trace SH quantification with a linear range of 7.0-150.0 µg·mL-1, and a detection limit low to 3.0 µg·mL-1. It was applied to analyze seven types of commercial slimming capsules with satisfactory results, showing good prospect for real applications.


Assuntos
Análise Espectral Raman , Cápsulas , Ciclobutanos , Hidrogel de Polietilenoglicol-Dimetacrilato , Nanopartículas Metálicas , Álcool de Polivinil , Reprodutibilidade dos Testes , Prata , beta-Ciclodextrinas
16.
Molecules ; 21(8)2016 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-27517896

RESUMO

Graphene oxide/Fe3O4 (GO/Fe3O4) nanoparticles were synthesized by an ultrasonic-assisted reverse co-precipitation method, and then horseradish peroxidase (HRP) was covalently immobilized onto GO/Fe3O4 with 1-ethyl-3-(3-dimethyaminopropyl)carbodiimide (EDC) as a cross-linking agent. In order to enhance the phenol removal efficiency and prevent the inactivation of the enzyme, the polyethylene glycol with highly hydrophilicity was added in this reaction, because the adsorption capacity for the polymer by degradation was stronger than the HRP. The results showed that the immobilized enzyme removed over 95% of phenol from aqueous solution. The catalytic condition was extensively optimized among the range of pH, mass ratio of PEG/phenol as well as initial concentration of immobilized enzyme and H2O2. The HRP immobilized on GO/Fe3O4 composite could be easily separated under a magnetic field from the reaction solution and reused.


Assuntos
Clorofenóis/química , Enzimas Imobilizadas , Compostos Férricos/química , Grafite/química , Peroxidase do Rábano Silvestre/química , Fenóis/química , Catálise , Peróxido de Hidrogênio/química , Nanopartículas de Magnetita/química , Nanopartículas de Magnetita/ultraestrutura , Oxirredução , Polietilenoglicóis/química , Difração de Raios X
17.
J Hazard Mater ; 317: 686-694, 2016 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-27329789

RESUMO

Microscaled CuFeO2 particles (micro-CuFeO2) were rapidly prepared via a microwave-assisted hydrothermal method and characterized by scanning electron microscopy, X-ray powder diffraction and X-ray photoelectron spectroscopy. It was found that the micro-CuFeO2 was of pure phase and a rhombohedral structure with size in the range of 2.8±0.6µm. The micro-CuFeO2 efficiently catalyzed the activation of peroxymonosulfate (PMS) to generate sulfate radicals (SO4-), causing the fast degradation of carbamazepine (CBZ). The catalytic activity of micro-CuFeO2 was observed to be 6.9 and 25.3 times that of micro-Cu2O and micro-Fe2O3, respectively. The enhanced activity of micro-CuFeO2 for the activation of PMS was confirmed to be attributed to synergistic effect of surface bonded Cu(I) and Fe(III). Sulfate radical was the primary radical species responsible for the CBZ degradation. As a microscaled catalyst, micro-CuFeO2 can be easily recovered by gravity settlement and exhibited improved catalytic stability compared with micro-Cu2O during five successive degradation cycles. Oxidative degradation of CBZ by the couple of PMS/CuFeO2 was effective in the studied actual aqueous environmental systems.


Assuntos
Carbamazepina/análise , Cobre/química , Compostos Ferrosos/química , Peróxidos/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Catálise , Tamanho da Partícula , Reciclagem , Propriedades de Superfície
18.
DNA Cell Biol ; 35(9): 498-505, 2016 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-27351590

RESUMO

Hepatic fibrosis is a reversible process involving plenty of transcription factors and pathways. Vitamin D receptor (VDR) as a member of ligand-induced transcription factors can interact with 9-cis retinoid X receptor (RXR) and VDR-interacting repressor (VDIR) to mediate transactivation or transrepression in the absence or in the presence of VDR ligand to regulate the expression of VDR target genes. The active form of vitamin D [1α,25(OH)2D3] can downregulate the expression of type I collagen both α1 and α2 (COLIα1 and COLIα2) in hepatic stellate cells (HSC-T6) in a time-dependent fashion, which provides a new direction for hepatic fibrosis therapy. As one of VDR target genes, rat COLIα1 gene contains 1αnVDRE (E-box1 and E-box2) in its promoter, and unliganded VDR/RXR may bind to 1αnVDRE through VDIR to mediate transactivation, whereas liganded VDR/RXR may bind to 1αnVDRE through VDIR for transrepression. The results suggested a sort of relying on each other relationship between VDR/RXR and VDIR in regulating the expression of COLIα1 gene in HSC-T6 cells, which established VDR as a potential target for blocking and even reversing hepatic fibrosis.


Assuntos
Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Colágeno Tipo I/genética , Células Estreladas do Fígado/metabolismo , Receptores de Calcitriol/genética , Receptores X de Retinoides/genética , Animais , Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Sítios de Ligação , Linhagem Celular , Colágeno Tipo I/metabolismo , Regulação da Expressão Gênica , Células Estreladas do Fígado/citologia , Ligantes , Regiões Promotoras Genéticas , Ligação Proteica , Ratos , Receptores de Calcitriol/metabolismo , Receptores X de Retinoides/metabolismo , Transdução de Sinais , Vitamina D/metabolismo
19.
Cell Biosci ; 6: 31, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27175276

RESUMO

BACKGROUND: The excessive accumulation of extracellular matrix of hepatic fibrosis is positively correlated with tissue inhibitors of metalloproteinase 1 (TIMP1). Here we aimed to investigate whether TIMP1 may be down-regulated by Decoy ODNs strategy to capture transcriptional factor upstream TIMP1 element 1 (UTE1) and specificity protein 1(SP1). RESULTS: By luciferase reporter assays, we confirmed that these Decoy ODNs could influence the promoter activation of TIMP-1, α-SMA and Collagen Iα2 (COLΙα2) genes as well as the enhancer activation of TRE in HSC-T6 cells, and the combination tended to be more effective than SP1 or UTE1 Decoy ODN alone. Western blot analysis also demonstrated down-regulation of the expression of those target genes except for TGF-ß. Furthermore, we observed that the viability of HSC-T6 cells at 72 h was significantly in decline in combination group. CONCLUSION: The combination of SP1 and UTE1 Decoy ODNs treatments inhibit the activation and proliferation of HSCs more effectively than one of the Decoy ODNs through co-regulation of TIMP1 and TGF-ß signal pathway but not the expression of TGF-ß itself.

20.
Chemosphere ; 150: 536-544, 2016 May.
Artigo em Inglês | MEDLINE | ID: mdl-26546118

RESUMO

As a typical moderately-brominated diphenylethers, 2,2',4,4'-tetrabromodiphenyl ether (BDE47) is hardly debrominated by a conventional TiO2-mediated photocatalysis. However, its reductive debromination was rapid achieved over silver nanoparticle-loaded TiO2 (Ag/TiO2) in UV-irradiated anoxic acetonitrile-water within 13 min. An "Ag-promoted electron transfer and C-Br cleavage" concept was proposed based on experimental results and density functional theory calculations. Ag(0) exerted affinity interaction with bromine atoms, and the storing of electrons on Ag(0) increased the binding interaction, which elongated the C-Br bond of BDE47 and facilitated its cleavage. The initiating of the BDE47 debromination on Ag(0) required an induction period to enrich a critical amount of electrons, leading to a stronger driving force for both injecting electron to BDE47 and stretching the C-Br bond. Stronger photo-excitation, higher polar solvent, and a moderate Ag(0) load strengthened the interfacial electron transfer over Ag/TiO2, and thereby shortening the induction time and accelerating the BDE47 degradation.


Assuntos
Bromo/química , Éteres Difenil Halogenados/química , Nanopartículas Metálicas/química , Prata/química , Titânio/química , Raios Ultravioleta , Catálise , Titânio/efeitos da radiação
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...