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1.
Chem Commun (Camb) ; 56(11): 1705-1708, 2020 Feb 06.
Artigo em Inglês | MEDLINE | ID: mdl-31942910

RESUMO

We report ultrathin organic photovoltaic elements optimized to run photofaradaic reactions in biological conditions. We demonstrate concurrent oxygen reduction to hydrogen peroxide and glucose oxidation. The devices are powered by deep-red irradiation in the tissue transparency window. We utilize bilayers of phthalocyanine, acting as the light absorber, and perylene diimide, functioning as both electron-acceptor and the hydrogen peroxide evolution electrocatalyst. These heterojunction bilayers are stable when irradiated in simulated physiological conditions, producing photovoltages sufficient to simultaneously drive cathodic oxygen reduction to H2O2 and anodic oxidation of glucose. We find that optimization of the anode metal is critical for sustained photofaradaic reactivity. Our results demonstrate a robust "wet" thin film photovoltaic with potential for physiological applications where localized electrochemical manipulation is desired, in particular the delivery of reactive oxygen species.


Assuntos
Técnicas Eletroquímicas/métodos , Peróxido de Hidrogênio/síntese química , Imidas/química , Indóis/química , Perileno/análogos & derivados , Técnicas Eletroquímicas/instrumentação , Desenho de Equipamento , Glucose/química , Ouro/química , Imidas/efeitos da radiação , Indóis/efeitos da radiação , Luz , Membranas Artificiais , Oxirredução , Oxigênio/química , Perileno/química , Perileno/efeitos da radiação , Fotoquímica/métodos
2.
Chemosphere ; 238: 124854, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31549676

RESUMO

This work focusses on the production of hydrogen peroxide and in the removal of bromacil by the electro-Fenton process using two different electrochemical cells: mixed tank cell (MTC) and flow-through cell (FTC). Both cells use boron doped diamond (BDD) as anode and carbon felt as cathode to promote the formation of hydrogen peroxide. In the case of the MTC, two surface area ratios, Acathode/Aanode, have been used. Results show that the H2O2 produced by MTC and FTCPSC increases with the time until a stabilization state. For the FTCPSC, the average hydrogen peroxide concentration produced increases progressively with the current, while for MTC the maximum values are found in applying very low current densities. In addition, the FTCPSC provides higher concentrations of hydrogen peroxide for the same current density applied. Regarding the MTC, it can be stated that the higher the area of the cathode, the higher is the amount of H2O2 produced and the lower is the cell voltage (because of a more efficient current lines distribution). The initial oxidation of bromacil is very efficiently attained being rapidly depleted from wastewater. However, the higher production of hydrogen peroxide obtained by the FTCPSC cell does not reflect on a better performance of the electro-Fenton process. Thus, bromacil is better mineralized using the MTC cell with the lowest cathode area. This observation has been explained because larger concentrations of produced hydrogen peroxide seems to benefit the oxidation of intermediates and not the mineralization.


Assuntos
Bromouracila/análogos & derivados , Diamante/química , Peróxido de Hidrogênio/síntese química , Águas Residuárias/química , Poluentes Químicos da Água/análise , Boro/química , Bromouracila/análise , Carbono/química , Condutividade Elétrica , Ferro/química , Oxirredução
3.
Inorg Chem ; 58(21): 14294-14298, 2019 Nov 04.
Artigo em Inglês | MEDLINE | ID: mdl-31599154

RESUMO

Metal complexes to promote oxidative DNA cleavage by H2O2 are desirable as anticancer drugs. A dicopper(II) complex of known p-cresol-derived methylene-tether ligand Hbcc [Cu2(bcc)]3+ did not promote DNA cleavage by H2O2. Here, we synthesized a new p-cresol-derived amide-tether one, 2,6-bis(1,4,7,10-tetrazacyclododecyl-1-carboxyamide)-p-cresol (Hbcamide). A dicopper(II) complex of the new ligand [Cu2(µ-OH)(bcamide)]2+ was structurally characterized. This complex promoted the oxidative cleavage of supercoiled plasmid pUC19 DNA (Form I) with H2O2 at pH 6.0-8.2 to give Forms II and III. The reaction was largely accelerated in a high pH region. A µ-1,1-hydroperoxo species was formed as the active species and spectroscopically identified. The amide-tether complex is more effective in cytotoxicity against HeLa cells than the methylene-tether one.


Assuntos
Amidas/farmacologia , Antineoplásicos/farmacologia , Complexos de Coordenação/farmacologia , Cobre/farmacologia , Cresóis/farmacologia , Peróxido de Hidrogênio/farmacologia , Amidas/química , Antineoplásicos/síntese química , Antineoplásicos/química , Proliferação de Células/efeitos dos fármacos , Complexos de Coordenação/síntese química , Complexos de Coordenação/química , Cobre/química , Cresóis/química , Clivagem do DNA , Ensaios de Seleção de Medicamentos Antitumorais , Células HeLa , Humanos , Peróxido de Hidrogênio/síntese química , Peróxido de Hidrogênio/química , Ligantes , Estrutura Molecular , Oxirredução
4.
Chemosphere ; 234: 471-477, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31229707

RESUMO

Sodium Dodecyl Benzene Sulfonate (SDBS) is a major anionic surfactant and is widely used in the detergent industry. The large amount of SDBS discharged into water bodies can cause eutrophication of water bodies and produce toxic effects in aquatic organisms. In this study, the degradation of SDBS and variation in toxicity during the plasma treatment process were evaluated using gas-liquid interface discharge. The experimental results showed that SDBS could be removed effectively after discharge for 8 min at an initial concentration of 30 mg/L. The SDBS removal could be fitted by the first-order kinetic model. The plasma voltage and initial pH had great effects on the removal of SDBS. At the same voltage, SDBS could be removed faster under alkaline conditions. Compared to ozonation, much higher SDBS and TOC removal performance was achieved by plasma treatment. HO, which was mainly derived from the reaction of H2O2 and ozone in the solutions, played a major role in the oxidation process. The toxicity evaluation showed that plasma treatment could reduce the acute toxicity effectively initially, and also indicated that the formed intermediates of formate, oxalate, malonate and sulfate had no negative effects. However, further treatment caused an increase in toxicity, which was mainly correlated with the excessive residual H2O2 formed during the plasma process. This study indicated that while applying plasma treatment, the conditions should be optimized comprehensively to maintain a low H2O2 residual in the effluent.


Assuntos
Benzenossulfonatos/química , Gases em Plasma/química , Purificação da Água/métodos , Benzenossulfonatos/toxicidade , Peróxido de Hidrogênio/análise , Peróxido de Hidrogênio/síntese química , Cinética , Oxirredução , Ozônio/química , Tensoativos/química , Tensoativos/toxicidade
5.
Chemosphere ; 225: 588-607, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30903840

RESUMO

The electrochemical production of hydrogen peroxide (H2O2) by 2-electron oxygen reduction reaction (ORR) is an attractive alternative to the present complex anthraquinone process. The objective of this paper is to provide a state-of-the-arts review of the most important aspects of this process. First, recent advances in H2O2 production are reviewed and the advantages of H2O2 electrogeneration via 2-electron ORR are highlighted. Second, the selectivity of the ORR pathway towards H2O2 formation as well as the development process of H2O2 production are presented. The cathode characteristics are the decisive factors of H2O2 production. Thus the focus is shifted to the introduction of commonly used carbon cathodes and their modification methods, including the introduction of other active carbon materials, hetero-atoms doping (i.e., O, N, F, B, and P) and decoration with metal oxides. Cathode stability is evaluated due to its significance for long-term application. Effects of various operational parameters, such as electrode potential/current density, supporting electrolyte, electrolyte pH, temperature, dissolved oxygen, and current mode on H2O2 production are then discussed. Additionally, the environmental application of electrogenerated H2O2 on aqueous and gaseous contaminants removal, including dyes, pesticides, herbicides, phenolic compounds, drugs, VOCs, SO2, NO, and Hg0, are described. Finally, a brief conclusion about the recent progress achieved in H2O2 electrogeneration via 2-electron ORR and an outlook on future research challenges are proposed.


Assuntos
Recuperação e Remediação Ambiental/métodos , Peróxido de Hidrogênio/síntese química , Oxigênio/química , Eletrodos , Peróxido de Hidrogênio/química , Peróxido de Hidrogênio/farmacologia , Oxirredução
6.
Chemosphere ; 222: 141-148, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30703653

RESUMO

The degradation of organic pollutants in saline wastewater has been a challenge for environmental remediation. In this study, a two-chamber cell was structured to simultaneously degrade organic contaminants (bisphenol A, BPA) from saline wastewater and produce hydrogen peroxide (H2O2). In the anode chamber, a new solar-light-driven system was devised using chloride ions (Cl‾) as a medium and WO3 photoanode as a radical initiator. Under solar light irradiation, photogenerated holes yielded at the WO3 photoanode promoted the conversion of Cl‾ to reactive chlorine species, which could oxidize BPA more rapidly. The results indicated that the BPA removal can be significantly enhanced by increasing pH to 10.8 or increasing the Cl‾ concentration to 200 mM. At these conditions, 92% BPA was degraded into CO2 and H2O in 120 min. In the cathode chamber, a new dopamine modified carbon felt (CF-DPA) cathode was employed to produce H2O2, obtaining a high concentration of 5.4 mM under optimum conditions. The electrochemical analyses for CF-DPA revealed that dopamine modification promoted electron transfer and enhanced the two-electron oxygen reduction to increase H2O2 yields.


Assuntos
Compostos Benzidrílicos/química , Peróxido de Hidrogênio/síntese química , Fenóis/química , Processos Fotoquímicos , Águas Residuárias/química , Purificação da Água/métodos , Catálise , Recuperação e Remediação Ambiental , Águas Salinas , Luz Solar , Poluentes Químicos da Água
7.
Z Naturforsch C J Biosci ; 74(3-4): 101-104, 2019 Feb 25.
Artigo em Inglês | MEDLINE | ID: mdl-30379645

RESUMO

There is an increasing interest in the application of peroxygenases in biocatalysis, because of their ability to catalyse the oxyfunctionalisation reaction in a stereoselective fashion and with high catalytic efficiencies, while using hydrogen peroxide or organic peroxides as oxidant. However, enzymes belonging to this class exhibit a very low stability in the presence of peroxides. With the aim of bypassing this fast and irreversible inactivation, we study the use of a gradual supply of hydrogen peroxide to maintain its concentration at stoichiometric levels. In this contribution, we report a multienzymatic cascade for in situ generation of hydrogen peroxide. In the first step, in the presence of NAD+ cofactor, formate dehydrogenase from Candida boidinii (FDH) catalysed the oxidation of formate yielding CO2. Reduced NADH was reoxidised by the reduction of the flavin mononucleotide cofactor bound to an old yellow enzyme homologue from Bacillus subtilis (YqjM), which subsequently reacts with molecular oxygen yielding hydrogen peroxide. Finally, this system was coupled to the hydroxylation of ethylbenzene reaction catalysed by an evolved peroxygenase from Agrocybe aegerita (rAaeUPO). Additionally, we studied the influence of different reaction parameters on the performance of the cascade with the aim of improving the turnover of the hydroxylation reaction.


Assuntos
Proteínas de Bactérias/química , FMN Redutase/química , Formiato Desidrogenases/química , Proteínas Fúngicas/química , Peróxido de Hidrogênio/síntese química , Oxigenases de Função Mista/química , Agrocybe/química , Agrocybe/enzimologia , Bacillus subtilis/química , Bacillus subtilis/enzimologia , Proteínas de Bactérias/metabolismo , Derivados de Benzeno/química , Derivados de Benzeno/metabolismo , Biocatálise , Candida/química , Candida/enzimologia , Dióxido de Carbono/química , Dióxido de Carbono/metabolismo , Coenzimas/química , Coenzimas/metabolismo , FMN Redutase/metabolismo , Mononucleotídeo de Flavina/química , Mononucleotídeo de Flavina/metabolismo , Formiato Desidrogenases/metabolismo , Formiatos/química , Formiatos/metabolismo , Proteínas Fúngicas/metabolismo , Peróxido de Hidrogênio/metabolismo , Hidroxilação , Cinética , Oxigenases de Função Mista/metabolismo , NAD/química , NAD/metabolismo , Oxirredução , Oxigênio/química , Oxigênio/metabolismo , Estereoisomerismo
8.
Chem Res Toxicol ; 32(1): 100-112, 2019 01 22.
Artigo em Inglês | MEDLINE | ID: mdl-30560658

RESUMO

Stimulus-responsive cleavage reactions have found broad use to direct drug release at a particular target disease area. Increased levels of reactive oxygen species (ROS) have been associated with the development and progression of cancer and several other disease states, motivating the development of drug conjugates that can undergo a chemoselective ROS-triggered release. Melatonin (MLT) and the reactive electrophile p-benzoquinone methide ( p-QM) have evidenced either cytoprotective or cytotoxic effects in biological systems, depending on the dose, cellular targets, and time of exposure. In this study, we report the synthesis and biological activity of two MLT derivatives linked to ROS-responsive arylboronate triggers (P1 and P2), which can be activated by endogenously generated hydrogen peroxide (H2O2) to release MLT, or 5-methoxytryptamine (5-MeOT), and p-QM-intermediates. Their H2O2-induced activation mechanism was studied by HPLC-DAD-MS. P1, which rapidly releases MLT and p-QM, was able to strongly induce the Nrf2 antioxidant signaling pathway, but was ineffective to provide protection against H2O2-mediated oxidative damage. By contrast, P1 exhibited strong toxic effects in HeLa cancer cells, without causing significant toxicity to normal NCTC-2544 cells. Similar, although more limited, effects were exerted by P2. In both cases, cytotoxicity was accompanied by depletion of cellular glutathione (GSH), probably as a consequence of p-QM release, and increased ROS levels. A role for MLT in toxicity was also observed, suggesting that the P1 released products, MLT and p-QM, contributed additively to promote cell death.


Assuntos
Ácidos Borônicos/farmacologia , Desenho de Fármacos , Peróxido de Hidrogênio/farmacologia , Melatonina/farmacologia , Ácidos Borônicos/síntese química , Ácidos Borônicos/química , Morte Celular/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Células HeLa , Humanos , Peróxido de Hidrogênio/síntese química , Peróxido de Hidrogênio/química , Melatonina/síntese química , Melatonina/química , Estrutura Molecular , Fator 2 Relacionado a NF-E2/metabolismo , Estresse Oxidativo/efeitos dos fármacos , Espécies Reativas de Oxigênio/metabolismo
9.
Free Radic Res ; 52(9): 1040-1051, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-30173586

RESUMO

Fenton-reaction initiated in vitro oxidation and in vivo oxidative biotransformation of salicylic acid was investigated by HPLC-UV-Vis method. By means of the developed high performance liquid chromatography (HPLC) method salicylic acid, catechol, and all the possible monohydroxylated derivatives of salicylic acid can be separated. Fenton oxidations were performed in acidic medium (pH 3.0) with two reagent molar ratios: (1) salicylic acid: iron: hydrogen peroxide 1:3:1 and (2) 1:0.3:1. The incubation samples were analysed at different time points of the reactions. The biological effect of elevated reactive oxygen species concentration on the intestinal metabolism of salicylic acid was investigated by an experimental diabetic rat model. HPLC-MS analysis of the in vitro samples revealed presence of 2,3- and 2,5-dihydroxybenzoic acids. The results give evidence for nonenzyme catalysed intestinal hydroxylation of xenobiotics.


Assuntos
Diabetes Mellitus Experimental/tratamento farmacológico , Peróxido de Hidrogênio/química , Ferro/química , Estresse Oxidativo/efeitos dos fármacos , Ácido Salicílico/química , Animais , Biotransformação/efeitos dos fármacos , Catecóis/síntese química , Catecóis/química , Cromatografia Líquida de Alta Pressão , Diabetes Mellitus Experimental/patologia , Humanos , Peróxido de Hidrogênio/administração & dosagem , Peróxido de Hidrogênio/síntese química , Intestinos/efeitos dos fármacos , Ferro/administração & dosagem , Oxirredução , Ratos , Espécies Reativas de Oxigênio/química , Ácido Salicílico/administração & dosagem , Ácido Salicílico/síntese química
10.
Chem Commun (Camb) ; 54(79): 11176-11179, 2018 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-30229245

RESUMO

An enzyme-immobilized metal-organic framework (MOF) nanosheet system was developed as a tandem catalyst, which converted glucose into gluconic acid and H2O2, and sequentially the latter could be used to catalyze the oxidation of l-arginine to generate nitric oxide in the presence of porphyrinic MOFs as artificial enzymes under physiological pH, showing great potential in cancer depleting glucose for starving-like/gas therapy.


Assuntos
Enzimas Imobilizadas/química , Glucose Oxidase/química , Estruturas Metalorgânicas/química , Nanoconjugados/química , Óxido Nítrico/síntese química , Animais , Arginina/química , Materiais Biocompatíveis/química , Catálise , Cobalto/química , Gluconatos/síntese química , Glucose/química , Peróxido de Hidrogênio/síntese química , Ferro/química , Cinética , Metaloporfirinas/química , Oxirredução , Coelhos
11.
Talanta ; 188: 708-713, 2018 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-30029436

RESUMO

A novel ratiometric fluorescence sensing system based on cholesterol oxidase-functionalized dual-color mesoporous silica nanoparticles (MSNs)@metal-organic framework core-shell nanocomposite is demonstrated for cholesterol detection. MSNs were first loaded with 5-aminofluorescein (AF) inside pores and then wrapped with red-emission CdTe quantum dots (QDs) on the surface to seal in the dye molecules, forming the signal displaying unit (AF-MSN-QDs). Next, AF-MSN-QDs were encapsulated with zeolitic imidazolate framework (ZIF-8) to form a transition layer with distinct size-selectivity, which not only protected the cores from corrosion but also greatly decreased background interference from large molecules. More significantly, the ZIF-8 shells showed high affinity for most enzymes, which made it possible for cholesterol oxidase (ChOx) to self-organize on the surface of ZIF-8-encapsulated AF-MSN-QDs via chemo-physical adsorption, forming novel core-shell nanocomposites (AF-MSN-QD@ZIF-8-ChOx) as a sensing platform for cholesterol detection. The detectable signal was monitored by enzymatic product-quenching fluorescence of the QDs. The fluorescence changes of I520/I618 showed excellent linearity with H2O2 concentrations in the range of 5-100 nM, with a limit of detection (LOD) as low as 0.89 nM. As a proof-of-concept, cholesterol was selectively detected with beneficial LOD as low as 0.923 µg/mL, demonstrating the great potential of this biosensor platform for other biologically important molecules with H2O2-producing oxidases.


Assuntos
Colesterol Oxidase/química , Colesterol/análise , Corantes Fluorescentes/química , Nanocompostos/química , Nanopartículas/química , Dióxido de Silício/química , Adsorção , Técnicas Biossensoriais/métodos , Cádmio/química , Colesterol/metabolismo , Fluoresceínas/química , Fluorescência , Peróxido de Hidrogênio/síntese química , Imidazóis/química , Limite de Detecção , Pontos Quânticos/química , Telúrio/química , Zeolitas/química
12.
Chemosphere ; 208: 665-673, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-29894967

RESUMO

A novel Zn0-CNTs-Fe3O4 composite was synthesized by the chemical co-precipitation combined with high sintering process at nitrogen atmosphere. The as-prepared composite was characterized by SEM, EDS, XRD, XPS, VSM and N2 adsorption/desorption experiments. A novel heterogeneous Fenton-like system, composed of Zn0-CNTs-Fe3O4 composite and dissolved oxygen (O2) in solution, which can in situ generate H2O2 and OH, was used for the degradation of 4-chlorophenol (4-CP). The influences of various operational parameters, including the initial pH, dosage of Zn0-CNTs-Fe3O4 and initial concentration of 4-CP on the removal of 4-CP were investigated. The removal efficiencies of 4-CP and total organic carbon (TOC) were 99% and 57%, respectively, at the initial pH of 1.5, Zn0-CNTs-Fe3O4 dosage of 2 g/L, 4-CP initial concentration of 50 mg/L and oxygen flow rate of 400 mL/min. Based on the results of the radical scavenger effect study, the hydroxyl radical was considered as the main reactive oxidants in Zn0-CNTs-Fe3O4/O2 system and a possible degradation pathway of 4-CP was proposed.


Assuntos
Clorofenóis/química , Peróxido de Hidrogênio/síntese química , Adsorção , Anti-Infecciosos/química , Catálise , Recuperação e Remediação Ambiental/métodos , Peróxido de Hidrogênio/química , Radical Hidroxila/química , Oxigênio/química
13.
Chemistry ; 24(57): 15227-15235, 2018 Oct 12.
Artigo em Inglês | MEDLINE | ID: mdl-29904959

RESUMO

This work reports a combination of aryl diselenides/hydrogen peroxide and carbon-nanotube (CNT)/rhodium nanohybrids (RhCNT) for naphthol oxidation towards the synthesis of 1,4-naphthoquinones and evaluation of their relevant trypanocidal activity. Under a combination of (PhSe)2 /H2 O2 in the presence of O2 in iPrOH/hexane, several benzenoid (A-ring)-substituted quinones were prepared in moderate to high yields. We also studied the contribution of RhCNT as co-catalyst in this process and, in some cases, yields were improved. This method provides an efficient and versatile alternative for preparing A-ring-modified naphthoquinonoid compounds with relevant biological profile.


Assuntos
Peróxido de Hidrogênio/química , Nanotubos de Carbono/química , Naftóis/química , Naftoquinonas/síntese química , Ródio/química , Tripanossomicidas/síntese química , Doença de Chagas/tratamento farmacológico , Humanos , Peróxido de Hidrogênio/síntese química , Modelos Moleculares , Naftóis/síntese química , Naftoquinonas/química , Naftoquinonas/farmacologia , Compostos Organosselênicos/química , Oxirredução , Tripanossomicidas/química , Tripanossomicidas/farmacologia , Trypanosoma cruzi/efeitos dos fármacos
14.
J Agric Food Chem ; 66(23): 5812-5820, 2018 Jun 13.
Artigo em Inglês | MEDLINE | ID: mdl-29758984

RESUMO

Reactive dicarbonyl species (RCS) such as methylglyoxal (MGO) and glyoxal (GO) are common intermediates in protein damage, leading to the formation of advanced glycation end products (AGEs) through nonenzymatic glycation. (+)-Catechin, a natural plant extract from tea, has been evaluated for its ability in trapping GO and MGO. However, (+)-catechin is also reported to have both antioxidant ability and pro-oxidant properties. Until now, whether (+)-catechin can inhibit the formation of nonenzymatic glycation and the mechanism of the inhibition in nucleoprotein nonenzymatic glycation is still unclear. In the present study, histone H1 and MGO were used to establish an in vitro (100 mM phosphate buffer solution (PBS), pH 7.4, 37 °C) protein glycation model to study the trapping ability of (+)-catechin. Our data show that MGO caused dose-dependent protein damage, and the content of MGO-induced Schiff base formation was inhibited by (+)-catechin when the molecular ratio of catechin:MGO was 1:6. The formation of Nε-carboxymethyllysine (CML) was reduced significantly when the ratio of (+)-catechin and MGO was 1:1, which was similar to the inhibition effect of aminoguanidine (AG). The formation of CML under in vitro conditions can be inhibited by low concentration (12.5-100 µM) of (+)-catechin but not with high concentration (200-800 µM) of (+)-catechin. The reason is that the high concentration of (+)-catechin did not inhibit CML formations due to H2O2 produced by (+)-catechin. In the presence of catalase, catechin can inhibit MGO-induced CML formation. In conclusion, the trapping ability of (+)-catechin may be more effective at the early stage of nonenzymatic glycation. However, a high concentration (200-800 µM) of (+)-catechin may not inhibit the formation of CML because it induced the increase of H2O2 formation.


Assuntos
Catequina/administração & dosagem , Histonas/síntese química , Lisina/análogos & derivados , Aldeído Pirúvico/administração & dosagem , Catequina/química , Produtos Finais de Glicação Avançada/síntese química , Peróxido de Hidrogênio/síntese química , Lisina/síntese química , Bases de Schiff/síntese química
15.
ChemMedChem ; 13(7): 684-704, 2018 04 06.
Artigo em Inglês | MEDLINE | ID: mdl-29420864

RESUMO

The uncontrolled redox activity of metal ions, especially copper, in the brains of patients with Alzheimer's disease (AD) should be considered the origin of intense oxidative damage to neurons in the AD brain. To obtain low-molecular-weight copper chelators that act as tetradentate ligands, we designed new compounds based on an 8-aminoquinoline motif with a lateral chain attached at the 2-position of the aromatic ring. Some of these new ligands, termed TDMQ for TetraDentate MonoQuinolines, are specific for copper chelation. Full characterization of these ligands is reported, as well as their affinities for CuII , and their capacities to inhibit oxidative stress induced by copper-amyloids activated by a reductant. Such metal ligands can be considered as potential anti-AD agents, as they should be able to regulate the homeostasis of copper in brain tissue.


Assuntos
Aminoquinolinas/química , Quelantes/química , Cobre/química , Doença de Alzheimer/tratamento farmacológico , Aminoquinolinas/síntese química , Peptídeos beta-Amiloides/química , Ácido Ascórbico/química , Quelantes/síntese química , Complexos de Coordenação/química , Glutationa/química , Peróxido de Hidrogênio/síntese química , Ligantes , Estrutura Molecular , Oxirredução , Fragmentos de Peptídeos/química , Zinco/química
16.
Anal Chem ; 89(24): 13349-13356, 2017 12 19.
Artigo em Inglês | MEDLINE | ID: mdl-29211446

RESUMO

Nanomaterials themselves as redox probes and nanocatalysts have many advantages for electrochemical biosensors. However, most nanomaterials with excellent catalytic activity cannot be directly used as redox probe to construct electrochemical biosensor because the redox signal of these nanomaterials can only be obtained in strong acid or alkali solution at high positive or negative potential, which greatly limits their applications in biologic assay. In this study, Cu/Mn double-doped CeO2 nanocomposite (CuMn-CeO2) was synthesized to use as signal tags and signal amplifiers for the construction of electrochemical immunosensor for sensitive assay of procalcitonin (PCT). Herein, CuMn-CeO2 not only possesses excellent catalytic activity toward H2O2 for signal amplification, but also can be directly used as redox probe for electrochemical signal readout achieved in neutral mild buffer solution at low positive potential. Importantly, since doping Cu, Mn into CeO2 lattice structure can generate extra oxygen vacancies, the redox and catalytic performance of obtained CuMn-CeO2 was much better than that of pure CeO2, which improves the performance of proposed immunosensor. Furthermore, CuMn-CeO2 can be implemented as a matrix for immobilizing amounts of secondary antibody anti-PCT by forming ester-like bridging between carboxylic groups of Ab2 and CeO2 without extra chemical modifications, which greatly simplifies the preparative steps. The prepared immunosensor exhibited a wide linear range of 0.1 pg mL-1 to 36.0 ng mL-1 with a low detection limit of 0.03 pg mL-1. This study implements nanomaterial themselves as redox probes and signal amplifiers and paves a new way for constructing electrochemical immunosensor.


Assuntos
Cério/química , Cobre/química , Técnicas Eletroquímicas , Manganês/química , Nanocompostos/química , Pró-Calcitonina/análise , Catálise , Peróxido de Hidrogênio/síntese química , Peróxido de Hidrogênio/química , Tamanho da Partícula , Propriedades de Superfície
17.
Chem Asian J ; 12(24): 3098-3109, 2017 Dec 14.
Artigo em Inglês | MEDLINE | ID: mdl-29044983

RESUMO

Horseradish peroxidase (HRP)-catalyzed hydrogelation has attracted much attention owing to the ease of handling, high biocompatibility, and processability. This review summarizes recent developments, including cutting-edge research into the use of HRP-mediated hydrogelation toward biomedical, biopharmaceutical, and biofabrication applications. From the viewpoint of polymer chemistry, the basic chemistry behind hydrogelation, the structure-property relationship, and hybridization of multiple materials by using HRP-catalyzed hydrogelation are summarized. From the chemical engineering perspective, strategies for controlling hydrogelation kinetics, hydrogel characteristics, and hydrogelation processes are summarized and discussed in detail. Strategies for obtaining biomaterials for medical and pharmaceutical use, and biofabrication for tissue engineering and regenerative medicine emerge by unifying the aspects of HRP-mediated hydrogelation.


Assuntos
Materiais Biocompatíveis/síntese química , Peroxidase do Rábano Silvestre/química , Hidrogéis/síntese química , Animais , Materiais Biocompatíveis/química , Catálise , Humanos , Hidrogéis/química , Peróxido de Hidrogênio/síntese química , Peróxido de Hidrogênio/química
18.
ChemSusChem ; 10(17): 3342-3346, 2017 09 11.
Artigo em Inglês | MEDLINE | ID: mdl-28752581

RESUMO

Highly selective hydrogen peroxide (H2 O2 ) synthesis directly from H2 and O2 is a strongly desired reaction for green processes. Herein a highly efficient palladium-tellurium (Pd-Te/TiO2 ) catalyst with a selectivity of nearly 100 % toward H2 O2 under mild conditions (283 K, 0.1 MPa, and a semi-batch continuous flow reactor) is reported. The size of Pd particles was remarkably reduced from 2.1 nm to 1.4 nm with the addition of Te. The Te-modified Pd surface could significantly weaken the dissociative activation of O2 , leading to the non-dissociative hydrogenation of O2 . Density functional theory calculations illuminated the critical role of Te in the selective hydrogenation of O2 , in that the active sites composed of Pd and Te could significantly restrain side reactions. This work has made significant progress on the development of high-selectivity catalysts for the direct synthesis of H2 O2 at ambient pressure.


Assuntos
Peróxido de Hidrogênio/química , Peróxido de Hidrogênio/síntese química , Paládio/química , Pressão , Telúrio/química , Catálise , Técnicas de Química Sintética , Modelos Moleculares , Conformação Molecular
19.
J Am Chem Soc ; 139(27): 9108-9111, 2017 07 12.
Artigo em Inglês | MEDLINE | ID: mdl-28587453

RESUMO

Toward the development of structural and functional models of the oxygen evolving complex (OEC) of photosystem II, we report the synthesis of site-differentiated tetranuclear manganese complexes featuring three six-coordinate and one five-coordinate Mn centers. To incorporate biologically relevant second coordination sphere interactions, substituents capable of hydrogen bonding are included as pyrazolates with arylamine substituents. Complexes with terminal anionic ligands, OH- or Cl-, bound to the lower coordinate metal center are supported through the hydrogen-bonding network in a fashion reminiscent of the enzymatic active site. The hydroxide complex was found to be a competent electrocatalyst for O-O bond formation, a key transformation pertinent to the OEC. In an acetonitrile-water mixture, at neutral pH, electrochemical water oxidation to hydrogen peroxide was observed, albeit with low (15%) Faradaic yield, likely due to competing reactions with organics. In agreement, 9,10-dihydroanthracene is electrochemically oxidized in the presence of this cluster both via H-atom abstraction and oxygenation with ∼50% combined Faradaic yield.


Assuntos
Complexos de Coordenação/química , Técnicas Eletroquímicas , Peróxido de Hidrogênio/síntese química , Manganês/química , Oxigênio/química , Água/química , Catálise , Ligação de Hidrogênio , Peróxido de Hidrogênio/química , Modelos Moleculares , Conformação Molecular , Oxirredução
20.
ChemSusChem ; 10(9): 1909-1915, 2017 05 09.
Artigo em Inglês | MEDLINE | ID: mdl-28322007

RESUMO

We report herein a new molecular catalyst for efficient water splitting, aluminum porphyrins (tetra-methylpyridiniumylporphyrinatealuminum: AlTMPyP), containing earth's most abundant metal as the central ion. One-electron oxidation of the aluminum porphyrin initiates the two-electron oxidation of water to form hydrogen peroxide as the primary reaction product with the lowest known overpotential (97 mV). The aluminum-peroxo complex was detected by a cold-spray ionization mass-spectrometry in high-resolution MS (HRMS) mode and the structure of the intermediate species was further confirmed using laser Raman spectroscopy, indicating the hydroperoxy complex of AlTMPyP to be the key intermediate in the reaction. The two-electron oxidation of water to form hydrogen peroxide was essentially quantitative, with a Faradaic efficiency of 99 %. The catalytic reaction was found to be highly efficient, with a turnover frequency up to ∼2×104  s-1 . A reaction mechanism is proposed involving oxygen-oxygen bond formation by the attack of a hydroxide ion on the oxyl-radical-like axial ligand oxygen atom in the one-electron-oxidized form of AlTMPyP(O- )2 , followed by a second electron transfer to the electrode.


Assuntos
Alumínio/química , Elétrons , Peróxido de Hidrogênio/síntese química , Porfirinas/química , Água/química , Catálise , Peróxido de Hidrogênio/química , Estrutura Molecular , Oxirredução , Espectrometria de Massas por Ionização por Electrospray , Análise Espectral Raman
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