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1.
Phys Chem Chem Phys ; 22(5): 2878-2886, 2020 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-31950118

RESUMO

Keggin-type polyoxometalate derived ionic liquids (POM-ILs) have recently been presented as effective solvent systems for biomass delignification. To investigate the mechanism of lignin dissolution in POM-ILs, the system involving POM-IL ([C4C1Im]3[PW12O40]) and guaiacyl glycerol-ß-guaiacyl ether (GGE), which contains a ß-O-4 bond (the most dominant bond moiety in lignin), was studied using quantum mechanical calculations and molecular dynamics simulations. These studies show that more stable POM-IL structures are formed when [C4C1Im]+ is anchored in the connecting four terminal oxygen region of the [PW12O40]3- surface. The cations in POM-ILs appear to stabilize the geometry by offering strong and positively charged sites, and the POM anion is a good H-bond acceptor. Calculations of POM-IL interacting with GGE show the POM anion interacts strongly with GGE through many H-bonds and π-π interactions which are the main interactions between the POM-IL anion and GGE and are strong enough to force GGE into highly bent conformations. These simulations provide fundamental models of the dissolution mechanism of lignin by POM-IL, which is promoted by strong interactions of the POM-IL anion with lignin.


Assuntos
Líquidos Iônicos/química , Lignina/química , Simulação de Dinâmica Molecular , Teoria Quântica , Compostos de Tungstênio/química , Guaifenesina/análogos & derivados , Guaifenesina/química , Ligações de Hidrogênio , Lignina/metabolismo , Solubilidade , Eletricidade Estática
2.
Anal Chim Acta ; 1082: 152-164, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31472704

RESUMO

Development of simultaneous bacteria detection and eradication with simple, rapid, and reusable material is important in addressing bacterial contamination issues. In this study, we utilized the expression of alkaline phosphatase (ALP) from bacteria to design fluorescence ON/OFF system for bacteria detection, also using metal oxide nanoparticle for obtaining antibacterial activity and recyclability. The fluorescent-based biosensor with antibacterial activity was prepared by intercalating ALP-sensitive polymer dot (PD) containing ß-cyclodextrin (ß-CD) onto montmorillonite (MMT) as loading matrix via ionic exchange reaction, followed by immobilization of magnetic iron oxide (Fe3O4) and NIR-responsive cesium tungsten oxide (CsWO3). The PD-ßCD-MMT/Fe3O4-CsWO3 nanocomposite exhibited strong fluorescence intensity, which was quenched in the presence of bacterial ALP (0-1000 U/L) due to hydrolysis of p-nitrophenyl phosphate (NPP) into p-nitrophenol (NP) in the hydrophobic site of ß-CD. Furthermore, the nanocomposite could detect both gram-negative Escherichia coli and gram-positive Staphylococcus aureus in the range of 101-107 CFU/mL (LOD 5.09 and 4.62 CFU/mL, respectively), and showed high antibacterial activity against bacteria by generating photothermal heat under 5 min NIR irradiation, causing damage to bacterial cells. This material also demonstrated recyclability via magnetic field exposure due to the presence of Fe3O4. In addition, the fluorescence can be recovered following pH shock and re-conjugation of ß-CD molecules. After 4 cycles, nanocomposite still showed stable photothermal effects and fluorescence-based bacteria detection. Thus, this reusable material offers promising approach for simultaneous bacteria detection and killing, which is simple, rapid, and effective.


Assuntos
Fosfatase Alcalina/química , Antibacterianos/farmacologia , Escherichia coli/isolamento & purificação , Nanopartículas de Magnetita/química , Pontos Quânticos/química , Staphylococcus aureus/isolamento & purificação , Antibacterianos/química , Bentonita/química , Césio/química , Césio/efeitos da radiação , Colorimetria/instrumentação , Colorimetria/métodos , Reutilização de Equipamento , Escherichia coli/efeitos dos fármacos , Calefação , Raios Infravermelhos , Limite de Detecção , Nanopartículas de Magnetita/efeitos da radiação , Testes de Sensibilidade Microbiana/instrumentação , Testes de Sensibilidade Microbiana/métodos , Nanocompostos/química , Nitrofenóis/química , Compostos Organofosforados/química , Polímeros/química , Staphylococcus aureus/efeitos dos fármacos , Compostos de Tungstênio/química , Compostos de Tungstênio/efeitos da radiação , beta-Ciclodextrinas/química
3.
Nanoscale ; 11(32): 15326-15338, 2019 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-31386732

RESUMO

All-in-one nanoagents with a single-component and all-required functions have attracted increasing attention for the imaging-guided therapy of tumors, but the design and preparation of such nanoagents remain a challenge. Herein, we report the introduction of oxygen vacancies to traditional semiconductors with heavy-metal elements for tuning photoabsorption in the near infrared (NIR) region, by using Bi2WO6 (band-gap: ∼2.7 eV) as a model. Bi2WO6-x nanodots with sizes of ∼3 or ∼8 nm have been prepared by a facile coprecipitation-solvothermal method assisted by citric acid (CA, 0.1-1.5 g) as the reduction agent. CA confers the removal of O atoms from the [Bi2O2]2+ layer during the solvothermal process, resulting in the formation of plenty of oxygen vacancies in the Bi2WO6-x crystal. As a result, NIR photoabsorption of Bi2WO6-x nanodots can be remarkably enhanced with the increase of the CA amount from 0 to 1.0 g. Under irradiation of a single-wavelength (808 nm, 1.0 W cm-2) NIR laser, black Bi2WO6-x-CA1.0 nanodots can not only efficiently produce a sufficient amount of heat with a photothermal conversion efficiency of 45.1% for photothermal therapy, but also generate singlet oxygen (1O2) for photodynamic therapy. Furthermore, due to the presence of heavy-metal (Bi and W) elements, Bi2WO6-x-CA1.0 nanodots have high X-ray attenuation ability for CT imaging. After the Bi2WO6-x-CA1.0 nanodot dispersion is injected into the tumor-bearing mice, the tumor can be imaged by using CT and an IR thermal camera. After irradiation with a single-wavelength (808 nm, 1.0 W cm-2, 10 min) NIR laser, the tumor can be completely suppressed by the synergic photothermal and photodynamic effects of Bi2WO6-x-CA1.0 nanodots, without recurrence and treatment-induced toxicity. Therefore, Bi2WO6-x nanodots have great potential as a novel all-in-one nanoagent for the imaging and phototherapy of tumors.


Assuntos
Bismuto/química , Nanoestruturas/química , Oxigênio/química , Compostos de Tungstênio/química , Animais , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Sobrevivência Celular/efeitos da radiação , Raios Infravermelhos , Iohexol/análogos & derivados , Iohexol/química , Iohexol/farmacologia , Camundongos , Nanoestruturas/uso terapêutico , Nanoestruturas/toxicidade , Neoplasias/diagnóstico , Neoplasias/patologia , Neoplasias/terapia , Fotoquimioterapia , Fototerapia , Oxigênio Singlete/química , Oxigênio Singlete/metabolismo , Temperatura Ambiente , Distribuição Tecidual , Tomografia Computadorizada por Raios X
4.
Molecules ; 24(17)2019 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-31466314

RESUMO

The magnetic adsorbent, Fe3O4@[Ni(HL)2]2H2[P2Mo5O23]·2H2O (Fe3O4@1), is synthesized by employing the nanoparticles Fe3O4 and polyoxometalate hybrid 1. Zero-field-cooled (ZFC) and field-cooled (FC) curves show that the blocking temperature of Fe3O4@1 was at 120 K. Studies of Fe3O4@1 removing cationic and anionic dyes from water have been explored. The characterization of Fe3O4@1, effects of critical factors such as dosage, the concentration of methylene blue (MB), pH, adsorption kinetics, isotherm, the removal selectivity of substrate and the reusability of Fe3O4@1 were assessed. The magnetic adsorbent displayed an outstanding removal activity for the cationic dye at a broad range of pH. The adsorption kinetics and isotherm models revealed that the adsorption process of Fe3O4@1 was mainly governed via chemisorption. The maximum capacity of Fe3O4@1 adsorbing substance was 41.91 mg g-1. Furthermore, Fe3O4@1 showed its high stability by remaining for seven runs of the adsorption-desorption process with an effective MB removal rate, and could also be developed as a valuable adsorbent for dyes elimination from aqueous system.


Assuntos
Corantes/análise , Compostos Ferrosos/química , Compostos de Tungstênio/química , Adsorção , Concentração de Íons de Hidrogênio , Estrutura Molecular , Nanopartículas , Purificação da Água
5.
Chemistry ; 25(63): 14370-14381, 2019 Nov 13.
Artigo em Inglês | MEDLINE | ID: mdl-31469197

RESUMO

Creating efficient and residue-directed artificial proteases is a challenging task due to the extreme inertness of the peptide bond, combined with the difficulty of achieving specific interactions between the catalysts and the protein side chains. Herein we report strictly site-selective hydrolysis of a multi-subunit globular protein, hemoglobin (Hb) from bovine blood, by a range of ZrIV -substituted polyoxometalates (Zr-POMs) in mildly acidic and physiological pH solutions. Among 570 peptide bonds in Hb, selective cleavage was observed at only eleven sites, each occurring at Asp-X peptide bonds located in the positive patches on the protein surface. The molecular origins of the observed Asp-X selectivity were rationalized by means of molecular docking, DFT-based binding, and mechanistic studies on model peptides. The proposed mechanism of hydrolysis involves coordination of the amide oxygen to ZrIV followed by a direct nucleophilic attack of the side chain carboxylate group on the C-terminal amide carbon atom with formation of a cyclic anhydride, which is further hydrolyzed to give the reaction products. The activation energy for the cleavage of the structurally related Glu-X sequence compared to Asp-X was calculated to be higher by 1.4 kcal mol-1 , which corresponds to a difference of about one order of magnitude in the rates of hydrolysis. The higher activation energy is attributed to the higher strain present in the six-membered ring of glutaric anhydride (Glu-X), as compared to the five-membered ring of the succinic anhydride (Asp-X) intermediate. Similarly, the cleavage at X-Asp and X-Glu bonds are predicted to be kinetically less likely as the corresponding activation energies were 6 kcal mol-1 higher, explaining the experimentally observed selectivity. The synergy between the negatively charged polyoxometalate cluster, which binds at positive patches on protein surfaces, and selective activation of Asp-X peptide bonds located in these regions by ZrIV ions, results in a novel class of artificial proteases with aspartate-directed reactivity, which is very rare among naturally occurring proteases.


Assuntos
Ácido Aspártico/química , Materiais Biomiméticos/química , Complexos de Coordenação/química , Compostos de Tungstênio/química , Zircônio/química , Sequência de Aminoácidos , Sítios de Ligação , Materiais Biomiméticos/metabolismo , Catálise , Complexos de Coordenação/metabolismo , Hemoglobinas/química , Hemoglobinas/metabolismo , Hidrólise , Espectroscopia de Ressonância Magnética , Conformação Molecular , Simulação de Acoplamento Molecular , Peptídeo Hidrolases/química , Peptídeo Hidrolases/metabolismo , Termodinâmica
6.
J Colloid Interface Sci ; 554: 520-530, 2019 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-31330425

RESUMO

A one-pot simple procedure for the synthesis of uniform, ellipsoidal Eu3+-doped sodium lanthanum tungstate and molybdate (NaLa(XO4)2, X  = W, Mo) nanophosphors, functionalized with carboxylate groups, is described. The method is based on a homogeneous precipitation process at 120 °C from appropriate Na+, Ln3+ and tungstate or molybdate precursors dissolved in ethylene glycol/water mixtures containing polyacrylic acid. A comparative study of the luminescent properties of both luminescent materials as a function of the Eu3+ doping level has been performed to find the optimum nanophosphor, whose efficiency as X-ray computed tomography contrast agent is also evaluated and compared with that of a commercial probe. Finally, the cell viability and colloidal stability in physiological pH medium of the optimum samples have also been studied to assess their suitability for biomedical applications.


Assuntos
Meios de Contraste/química , Európio/química , Lantânio/química , Substâncias Luminescentes/química , Molibdênio/química , Compostos de Tungstênio/química , Animais , Meios de Contraste/síntese química , Substâncias Luminescentes/síntese química , Tomografia Computadorizada por Raios X , Compostos de Tungstênio/síntese química , Células Vero
7.
Soft Matter ; 15(27): 5375-5379, 2019 Jul 10.
Artigo em Inglês | MEDLINE | ID: mdl-31259985

RESUMO

Herein, a novel photothermal agent based on polyoxometalate clusters and food-borne antioxidant peptides was exploited to overcome the inherent problems of poor photothermal stability of polyoxometalate photothermal materials, which commonly appear in the current stage of development, and the inevitable simultaneous inflammatory responses during the therapeutic process.


Assuntos
Antibacterianos/química , Antioxidantes/química , Materiais Biocompatíveis/química , Nanopartículas/química , Oligopeptídeos/química , Compostos de Tungstênio/química , Antibacterianos/farmacologia , Sobrevivência Celular/efeitos dos fármacos , Estabilidade de Medicamentos , Escherichia coli/efeitos dos fármacos , Células Hep G2 , Humanos , Hipertermia Induzida , Raios Infravermelhos , Fototerapia/métodos , Temperatura Ambiente
8.
Biosens Bioelectron ; 140: 111349, 2019 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-31150983

RESUMO

In this report, enhanced organic-inorganic heterojunction of polypyrrole@Bi2WO6 was fabricated and applied for sensitive photoelectrochemical (PEC) immunoassay of creatine kinase-MB (CK-MB). Specifically, heterostructured polypyrrole@Bi2WO6 photoelectrode was prepared and sandwich immunorecognition were integrated for the CK-MB immunoassay. In the detection, with the aid of alkaline phosphate (ALP)-induced biocatalytic precipitation (BCP), the precipitation-dependent suppression of the photocurrent can be recorded due to the impediment of the interfacial mass and electron transfer. On the basis of target-controlled BCP formation, a novel PEC immunoassay could be developed for the sensitive and specific CK-MB detection. This work manifested the great potential of polypyrrole@Bi2WO6 heterojunction as a novel platform for PEC bioanalysis development and also a PEC method for CK-MB detection. This work is expected to stimulate more interest in the design and implementation of numerous other organic-inorganic heterojunction for advanced PEC bioanalysis development.


Assuntos
Bismuto/química , Creatina Quinase Forma MB/análise , Polímeros/química , Pirróis/química , Compostos de Tungstênio/química , Animais , Anticorpos Imobilizados/química , Técnicas Biossensoriais/métodos , Técnicas Eletroquímicas/métodos , Humanos , Imunoensaio/métodos
9.
Molecules ; 24(11)2019 May 30.
Artigo em Inglês | MEDLINE | ID: mdl-31151282

RESUMO

Polyoxometalates (POMs) are a diverse class of anionic metal-oxo clusters with intriguing chemical and physical properties. Owing to unrivaled versatility and structural variation, POMs have been extensively utilized for catalysis for a plethora of reactions. In this focused review, the applications of POMs as promising catalysts or co-catalysts for CO2 conversion, including CO2 photo/electro reduction and CO2 as a carbonyl source for the carbonylation process are summarized. A brief perspective on the potentiality in this field is proposed.


Assuntos
Dióxido de Carbono/química , Compostos de Tungstênio/química , Monóxido de Carbono/química , Catálise , Cristais Líquidos , Modelos Moleculares , Conformação Molecular , Estrutura Molecular , Oxirredução , Processos Fotoquímicos
10.
Food Chem ; 293: 127-133, 2019 Sep 30.
Artigo em Inglês | MEDLINE | ID: mdl-31151592

RESUMO

Dried persimmon is thought to be a rich source of non-extractable polyphenols (NEPPs). Here, we analyzed the NEPP content of dried persimmon and its bile acid-binding activity in vitro. To determine total NEPP content and epicatechin equivalent (ECE) of intact NEPPs, acid hydrolysis and non-destructive methods with 70% (v/v) acetone-insoluble solids (AIS), respectively, were conducted using Folin-Ciocalteu reagent. The ECE of intact NEPPs exceeded 1000 mg/100 g in the non-destructive method, but total NEPP content was approximately 3900 mg/100 g with the acid hydrolysis method. Thiolysis showed that the non-extractable proanthocyanidins in dried persimmon mainly comprised epigallocatechin-gallate, epigallocatechin, epicatechin, and epicatechin-gallate. AIS from dried persimmon showed stronger bile acid-binding activity than AIS from apple, quince, and fresh astringent persimmon. These results suggest that the high content of NEPPs in dried persimmon may contribute to a strong bile acid-binding activity.


Assuntos
Ácidos e Sais Biliares/química , Diospyros/química , Polifenóis/química , Cromatografia Líquida de Alta Pressão , Diospyros/metabolismo , Frutas/química , Frutas/metabolismo , Hidrólise , Espectrometria de Massas , Molibdênio/química , Polifenóis/análise , Proantocianidinas/análise , Proantocianidinas/química , Compostos de Tungstênio/química
11.
Dalton Trans ; 48(28): 10537-10546, 2019 Jul 16.
Artigo em Inglês | MEDLINE | ID: mdl-31214676

RESUMO

Rare earth ion-doped fluoride upconversion nanoparticles (UCNPs), emerging as a novel class of probes and drug carriers, exhibit superior promise for bio-applications in diagnostics and treatment on account of their strong luminescence, fine biocompatibility, and high drug loading. However, the fine control and manipulation of particle size and the distribution of rare earth ion-doped oxides has remained an insurmountable challenge to date. In this work, we construct and synthesize silica-coated Gd2(WO4)3:Yb3+/Ho3+ nanoparticles by one-pot co-precipitation, with uniform distribution (∼130 nm) and enhanced yellow fluorescence. Particularly, the nanoparticles not only possess outstanding temperature sensing performance at biological temperatures in water by utilizing the fluorescence intensity ratio (FIR) method, but also allow a further serviceable contrast effect in vitro and in vivo based on the prominent T1-weighted magnetic resonance (MR) signal of Gd3+. Compared with cisplatin and platinum(iv) (DSP), the Gd2(WO4)3@SiO2 nanoparticles functionalized with DSP (Gd2(WO4)3@SiO2-Pt-PEG) exert higher lethality against CT26 cells and significantly inhibit the growth of tumors at the same concentration of Pt. This effect occurs through the greater level of cell endocytosis. The lethality value of the latter is 10 times higher than the former after the same length of time according to inductively coupled plasma-mass spectrometry (ICP-MS) results. In short, the monodisperse and strongly fluorescent Gd2(WO4)3@SiO2-Pt-PEG nanoparticles are endowed with dual-mode imaging, temperature sensing and anticancer functions, which provide a significant guide for synthesis and bio-application of lanthanide ion-doped oxides.


Assuntos
Antineoplásicos/farmacologia , Corantes Fluorescentes/farmacologia , Nanopartículas/química , Imagem Óptica , Dióxido de Silício/química , Temperatura Ambiente , Animais , Antineoplásicos/síntese química , Antineoplásicos/química , Apoptose/efeitos dos fármacos , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Relação Dose-Resposta a Droga , Ensaios de Seleção de Medicamentos Antitumorais , Corantes Fluorescentes/síntese química , Corantes Fluorescentes/química , Gadolínio/química , Hólmio/química , Camundongos , Estrutura Molecular , Relação Estrutura-Atividade , Compostos de Tungstênio/química , Itérbio/química
12.
ACS Appl Mater Interfaces ; 11(21): 18942-18952, 2019 May 29.
Artigo em Inglês | MEDLINE | ID: mdl-31058495

RESUMO

The radioresistance of tumor cells is considered to be an Achilles' heel of cancer radiotherapy. Thus, an effective and biosafe radiosensitizer is highly desired but hitherto remains a big challenge. With the rapid progress of nanomedicine, multifunctional inorganic nanoradiosensitizers offer a new route to overcome the radioresistance and enhance the efficacy of radiotherapy. Herein, poly(vinylpyrrolidone) (PVP)-modified Bi2WO6 nanoplates with good biocompatibility were synthesized through a simple hydrothermal process and applied as a radiosensitizer for the enhancement of radiotherapy for the first time. On the one hand, the high- Z elements Bi ( Z = 83) and W ( Z = 74) endow PVP-Bi2WO6 with better X-ray energy deposition performance and thus enhance radiation-induced DNA damages. On the other hand, Bi2WO6 semiconductors exhibit significant photocurrent and photocatalytic-like radiocatalytic activity under X-ray irradiation, giving rise to the effective separation of electron/hole (e-/h+) pairs and subsequently promoting the generation of cytotoxic reactive oxygen species, especially hydroxyl radicals (•OH). The γ-H2AX and clonogenic assays demonstrated that PVP-Bi2WO6 could efficiently increase cellular DNA damages and colony formations under X-ray irradiation. These versatile features endowed PVP-Bi2WO6 nanoplates with enhanced radiotherapy efficacy in animal models. In addition, Bi2WO6 nanoplates can also serve as good X-ray computed tomography imaging contrast agents. Our findings provide an alternative nanotechnology strategy for tumor radiosensitization through simultaneous radiation energy deposition and radiocatalysis.


Assuntos
Bismuto/química , Nanopartículas/química , Neoplasias/patologia , Radiossensibilizantes/farmacologia , Semicondutores , Compostos de Tungstênio/química , Animais , Catálise , Morte Celular/efeitos dos fármacos , Endocitose/efeitos dos fármacos , Feminino , Células HeLa , Células Endoteliais da Veia Umbilical Humana/efeitos dos fármacos , Células Endoteliais da Veia Umbilical Humana/metabolismo , Humanos , Camundongos Endogâmicos BALB C , Camundongos Nus , Nanopartículas/ultraestrutura , Povidona/química , Espécies Reativas de Oxigênio/metabolismo , Raios X
13.
Nanoscale ; 11(21): 10209-10219, 2019 May 30.
Artigo em Inglês | MEDLINE | ID: mdl-31112183

RESUMO

Photothermal therapy has emerged as a potential minimally invasive technique to destroy malignant cells with high selectivity. It utilizes low band gap nanoscale materials as photothermal agents dispersed at the affected area to increase the temperature locally by absorbing radiation in the near infrared (NIR) region and destroys the cells. In an effort to develop a photothermal agent with high efficacy for photothermal therapy, we found that (NH4)xWO3 nanorods of length 0.5-1.0 µm and diameter ∼100 nm could destroy breast cancer cells rapidly when irradiated with a wavelength in the therapeutic window. The material was prepared using a solvothermal route followed by PEGylation for improving the biocompatibility. X-ray diffraction and transmission electron microscopy studies revealed the hexagonal crystal lattice of the material. The uniform wrapping of polyethylene glycol (PEG) around the nanorods was confirmed using energy dispersive spectroscopy elemental mapping. An 808 nm laser was used to investigate the photothermal responses of the material on SUM-159 and MCF-7 breast cancer cells in vitro. The PEGylated-(NH4)xWO3 nanorods exhibited rapid temperature elevation from 20 °C to 60 °C within 3 min upon irradiation. A significant growth inhibition of SUM-159 and MCF-7 breast cancer cells with photonecrosis was observed. PEGylated (NH4)xWO3 nanorods could potentially be used in cancer therapy due to their strong photonecrotic properties at specific NIR wavelengths that suffer from minimal attenuation while passing through biological tissues.


Assuntos
Neoplasias da Mama/terapia , Hipertermia Induzida , Nanotubos/química , Fototerapia , Polietilenoglicóis , Compostos de Tungstênio , Amônia/química , Amônia/farmacologia , Neoplasias da Mama/metabolismo , Neoplasias da Mama/patologia , Feminino , Humanos , Células MCF-7 , Polietilenoglicóis/química , Polietilenoglicóis/farmacologia , Compostos de Tungstênio/química , Compostos de Tungstênio/farmacologia
14.
Int J Biol Macromol ; 135: 171-179, 2019 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-31125654

RESUMO

It is of great importance to develop new pathways for low-cost, high-selectivity conversion of lignin into aromatics. In this work, a series of cesium exchanged and transition-metal substituted heterogeneous polyoxometalates were prepared and applied as efficient catalysts for lignin depolymerization. The catalytic oxidation of lignin has been monitored by GPC, 2D NMR HSQC, and GC/MS technologies, and the reaction pathway was also confirmed by the examination with a dimeric ß-O-4 lignin model compound. Under optimal conditions, these catalysts showed high activity toward oxidative cleavage of ß-O-4 linkages, as well as ß-5 and ß-ß CC linkages. In particular, the Co substituted polyoxometalates gave high yield of ca. 9.58% monomeric products at 150°C within 3h under an oxygen atmosphere. Results demonstrated the catalyst was easily separated from products and could be repeatedly used at least five cycles without significant loss of activity. Further, the possible reaction mechanism was proposed by a two-step oxygen-based electron transfer and oxygen transfer reaction mechanism. The design and application of the multifunctional POMs based heterogeneous catalytic system make this strategy of great interest in the production of aromatic products from lignin and inspire a new insight to utilize the entire lignocellulosic biomass.


Assuntos
Césio/química , Lignina/química , Compostos de Tungstênio/química , Betula/química , Catálise , Estrutura Molecular , Oxirredução , Polimerização , Análise Espectral , Temperatura Ambiente
15.
Chem Commun (Camb) ; 55(32): 4711-4714, 2019 Apr 16.
Artigo em Inglês | MEDLINE | ID: mdl-30942240

RESUMO

Induced circular dichroism (ICD) of polyoxomolybdates and polyoxotungstates was realized in three kinds of natural polysaccharide hydrogels possessing hierarchical chirality. Interestingly, the extrinsic chiral factors were dominant in ionic κ/ι-carrageenan hybrids, while the ICD of clusters was dominantly influenced by the intrinsic alternating bond length (ABL) distortions of polyoxometalates in agarose hybrid. The optical activity of the POMs shows sensitive response to multiple stimuli, such as temperature, K+ salts, UV irradiation and redox agents.


Assuntos
Carragenina/química , Hidrogéis/química , Molibdênio/química , Sefarose/química , Compostos de Tungstênio/química , Dicroísmo Circular , Hidrogéis/efeitos da radiação , Luz , Conformação Molecular , Molibdênio/efeitos da radiação , Rotação Ocular , Oxirredução , Estereoisomerismo , Temperatura Ambiente , Compostos de Tungstênio/efeitos da radiação
16.
ACS Appl Mater Interfaces ; 11(18): 16896-16904, 2019 May 08.
Artigo em Inglês | MEDLINE | ID: mdl-30990012

RESUMO

In order to explore novel colorimetric biosensors with high sensibility and selectivity, two new Keggin polyoxometalates (POMs)-based Cu-trz (1,2,4-triazole) metal-organic frameworks (MOFs) with suitable specific surface areas and multiple active sites were favorably fabricated; then single-walled carbon nanotubes (SWNTs) were merged with new POMOFs to construct POMOF/SWNT nanocomposites. Herein, POMOF/SWNT nanocomposites as peroxidase mimics were explored for the first time, and the peroxidase-mimicking activity of the prepared POMOF/SWNT nanocomposites is heavily dependent on the mass ratio of POMOFs and SWNTs, in which the maximum activity is achieved at the mass ratio of 2.5:1 (named PMNT-2). More importantly, PMNT-2 exhibits the lowest limit of detection (0.103 µM) among all reported materials to date and the assumable selectivity toward l-cysteine (l-Cys) detection. With these findings, a convenient, sensitive, and effective "on-off switch" colorimetric platform for l-Cys detection has been successfully developed, providing a promising prospect in the biosensors and clinical diagnosis fields.


Assuntos
Técnicas Biossensoriais , Colorimetria/métodos , Cisteína/isolamento & purificação , Nanotubos de Carbono/química , Catálise , Cobre/química , Cisteína/química , Estruturas Metalorgânicas/química , Nanocompostos/química , Oxirredução , Peroxidase/química , Triazóis/química , Compostos de Tungstênio/química
17.
Inorg Chem ; 58(9): 6000-6007, 2019 May 06.
Artigo em Inglês | MEDLINE | ID: mdl-31021616

RESUMO

Two transition-metal-substituted compounds K10H10{[Co(H2O)2]2[Co(H2O)3]2(Ge4W36O130)}·32H2O (1Co) and K10H10{[Ni(H2O)2]2[Ni(H2O)3]2(Ge4W36O130)}·32H2O (2Ni), have been successfully synthesized, both of which consist of the S-shaped tetrameric structure {Ge4W36} constructed from trivacant Keggin-type germanotungstate precursor K8Na2[ A-α-GeW9O34]·25H2O. These compounds were characterized by single crystal X-ray diffraction crystallography, X-ray powder diffraction (XRD), Raman spectra, thermogravimetric analysis (TGA), electrochemistry, and IR spectra. In addition, the UV spectra and the electrospray-ionization mass spectra (ESI-MS) were employed to investigated the stable pH value range of 1Co and 2Ni in aqueous solution.


Assuntos
Cobalto/química , Germânio/química , Níquel/química , Compostos de Tungstênio/química , Ânions/síntese química , Ânions/química , Cristalografia por Raios X , Modelos Moleculares , Difração de Pó , Compostos de Tungstênio/síntese química , Difração de Raios X
18.
Anal Chim Acta ; 1066: 58-68, 2019 Aug 20.
Artigo em Inglês | MEDLINE | ID: mdl-31027535

RESUMO

Highly efficient enrichment of phosphopeptides in low abundance prior to mass spectrometry analysis is essential in phosphopeptidomics analysis. Herein, an affinity probe possessing both interactions of polyoxometalates (POMs) and hydrophilic interaction chromatography (HILIC) was facilely prepared. POMs and cysteamine hydrochloride-modified chitosan (CYECS) were assembled onto magnetic nanoparticles (MNPs) via a layer-by-layer approach. The developed MNPs-(POM/CYECS) material owned merits of large metal oxide surfaces, positive charge, and hydrophilicity as well as superparamagnetism. By combining with matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS), the prepared material was utilized for effective enrichment of phosphopeptides. High selectivity (mass ratio of ß-casein and bovine serum albumin digests of 1:5000) and low detection limit (0.02 fmol) toward phosphopeptides were achieved. The recovery of phosphopeptides was measured to be 92.6%. The specific enrichment of phosphopeptides from complex samples (nonfat milk, human saliva, serum, and A549 cell lysate) with MNPs-(POM/CYECS) material further confirmed its bright prospects for isolation of phosphopeptides from biological samples.


Assuntos
Quitosana/química , Cisteamina/química , Fosfopeptídeos/química , Fosfopeptídeos/isolamento & purificação , Compostos de Tungstênio/química , Adsorção , Quitosana/síntese química , Humanos , Modelos Moleculares , Estrutura Molecular , Propriedades de Superfície
19.
Environ Sci Pollut Res Int ; 26(16): 16105-16114, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30972679

RESUMO

To reduce the environmental pollution caused by ammonium paratungstate (APT) production in the Ganzhou area in China, simulated experiments in laboratory and field experiments in cement kilns were performed. The migration characteristics of As in secondary residues (thermometallurgy and hydrometallurgy residues) from APT production in cement kilns were similar, and As in the residues existed in the form of sulfides. When the residues were fed at the kiln inlet, the As in the residues was completely distributed in the clinker after a new mass balance of As was reestablished in a very short time. When the residues were fed at the raw mill, the total input rate of As was far higher than the total output rate. Therefore, a part of As was circulated in the cement kiln, and only a small part of As was distributed in the clinker. In addition, the As concentration in the flue gas and the leaching concentration of As in the clinker were far below the limit value in the Chinese standard. For feeding rates below that are used in the field experiment, co-processing of secondary residues in a cement kiln fed at the kiln inlet is environmentally safe. However, if the secondary residues are consistently fed at the raw mill, the As concentration in the flue gas may gradually increase.


Assuntos
Arsênico/análise , Materiais de Construção , Poluentes Ambientais/análise , Compostos de Tungstênio/análise , Poluentes Atmosféricos/análise , Poluentes Atmosféricos/química , Arsênico/química , China , Poluentes Ambientais/química , Metalurgia , Compostos de Tungstênio/química , Volatilização
20.
J Appl Oral Sci ; 27: e20180429, 2019 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-30970115

RESUMO

OBJECTIVES: To evaluate the radiopacity of Biodentine (BD) and BD associated with 15% calcium tungstate (BDCaWO4) or zirconium oxide (BDZrO2), by using conventional and digital radiography systems, and their physicochemical and biological properties. MATERIALS AND METHODS: Radiopacity was evaluated by taking radiographs of cement specimens (n=8) using occlusal film, photostimulable phosphor plates or digital sensors. Solubility, setting time, pH, cytocompatibility and osteogenic potential were also evaluated. Data were analyzed using one-way ANOVA and Tukey post-test or two-way ANOVA and Bonferroni post-test (α=0.05). RESULTS: BD radiopacity was lower than 3 mm Al, while BD ZrO2 and BD CaWO4 radiopacity was higher than 3 mm Al in all radiography systems. The cements showed low solubility, except for BDCaWO4. All cements showed alkaline pH and setting time lower than 34 minutes. MTT and NR assays revealed that cements had greater or similar cytocompatibility in comparison with control. The ALP activity in all groups was similar or greater than the control. All cements induced greater production of mineralized nodules than control. CONCLUSIONS: Addition of 15% ZrO2 or CaWO4 was sufficient to increase the radiopacity of BD to values higher than 3 mm Al. BD associated with radiopacifiers showed suitable properties of setting time, pH and solubility, except for BDCaWO4, which showed the highest solubility. All cements had cytocompatibility and potential to induce mineralization in Saos-2 cells. The results showed that adding 15% ZrO2 increases the radiopacity of BD, allowing its radiography detection without altering its physicochemical and biological properties.


Assuntos
Compostos de Cálcio/química , Radiografia Dentária Digital/métodos , Silicatos/química , Compostos de Tungstênio/química , Zircônio/química , Fosfatase Alcalina/análise , Análise de Variância , Antraquinonas , Compostos de Cálcio/farmacologia , Sobrevivência Celular/efeitos dos fármacos , Humanos , Concentração de Íons de Hidrogênio , Teste de Materiais , Osteoblastos/efeitos dos fármacos , Valores de Referência , Reprodutibilidade dos Testes , Silicatos/farmacologia , Solubilidade , Fatores de Tempo , Compostos de Tungstênio/farmacologia , Zircônio/farmacologia
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