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1.
Nat Commun ; 11(1): 2706, 2020 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-32483217

RESUMO

Aldehyde is one of most synthetically versatile functional groups and can participate in numerous chemical transformations. While a variety of simple aromatic aldehydes are commercially available, those with a more complex substitution pattern are often difficult to obtain. Benzylic oxygenation of methylarenes is a highly attractive method for aldehyde synthesis as the starting materials are easy to obtain and handle. However, regioselective oxidation of functionalized methylarenes, especially those that contain heterocyclic moieties, to aromatic aldehydes remains a significant challenge. Here we show an efficient electrochemical method that achieves site-selective electrooxidation of methyl benzoheterocycles to aromatic acetals without using chemical oxidants or transition-metal catalysts. The acetals can be converted to the corresponding aldehydes through hydrolysis in one-pot or in a separate step. The synthetic utility of our method is highlighted by its application to the efficient preparation of the antihypertensive drug telmisartan.


Assuntos
Acetais/química , Aldeídos/química , Técnicas Eletroquímicas/métodos , Hidrocarbonetos Aromáticos/química , Modelos Químicos , Acetais/síntese química , Aldeídos/síntese química , Amidinas/química , Benzimidazóis/química , Catálise , Hidrocarbonetos Aromáticos/síntese química , Hidrólise , Estrutura Molecular , Oxidantes/química , Oxirredução
2.
Chemosphere ; 258: 127268, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32569955

RESUMO

In this work, UVA radiation that is part of solar light is taken as the irradiation source and radicals (HO, SO4- and HO2/O2-) are generated through activation of hydrogen peroxide (H2O2), sodium persulfate (Na2S2O8) and Bismuth catalyst (BiOCl), respectively. The distinguished performance in removing acetaminophen (ACTP), a model pharmaceutical pollutant, by these three radicals was compared for the first time. Effect of pH, halide ions concentration and interfacial mechanism have been investigated in detail. Interestingly, results show that heterogeneous UVA/BiOCl process has higher degradation efficiency than homogeneous UVA/H2O2 and UVA/Na2S2O8 systems whatever the solution's pH. To explain these results, second order reaction rate constant (kradical, ACTP) have been determined with laser flash photolysis (LFP) or radical scavenging experiments. The strongly interfacial-depended HO2/O2- radicals have the lowest second order rate constant with ACTP but highest steady state concentration. BiOCl is much easier activated by UVA, and outstanding ACTP mineralization can be achieved. Combination of BiOCl and Na2S2O8 exhibits synergistic effects rather than antagonism effects with H2O2. This study highlights the relative effective utilization of solar light through interfacial directed BiOCl photocatalysis and its synergistic effects with traditional oxidants.


Assuntos
Acetaminofen/análise , Peróxido de Hidrogênio/química , Oxidantes/química , Compostos de Sódio/química , Sulfatos/química , Raios Ultravioleta , Poluentes Químicos da Água/análise , Bismuto/química , Catálise , Radical Hidroxila/química , Modelos Teóricos , Oxirredução
3.
Chemosphere ; 248: 125912, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32006826

RESUMO

Novel meso-zero valent iron (mZVI) was investigated for treating complex wastewater containing toxic heavy metal Cr6+ and organic compound phenol. This study is first of its kind illustrating coupled removal in single-step with H2O2 playing a major role as an oxidant and reductant. The mechanism involved was electron transfer from Fe0/2+ to Cr6+ resulting in Fe2+/3+ which in turn was consumed for phenol oxidation returning as Fe2+ into the system for further Cr6+ reduction. While comparing, single-step simultaneous removal of Cr6+ and phenol showed better performance in terms of pollutant removal, Fe2+/3+ recurrent reaction and precipitation generation, double-tep sequential removal performed better in iron active-corrosion time. It was also observed that the entire redox cycle of Cr6+-Cr3+-Cr6+ was reusable for co-contaminant phenol degradation at all pH with the recurrence of Fe2+-Fe3+-Fe2+. The proposed technique was checked for its viability in a single batch reactor and the complex chemistry of the reactions are unfolded by conducting chemical speciation and mass balance study at every stage of reaction. The unique functioning of mZVI was proven with micro-analysis of ZVI's surface and compared with granular ZVI, cZVI. The results obtained from this study open the door for a safer and cleaner single treatment system in removing both toxic heavy metals and organic compounds from contaminated surface water, groundwater and many such industrial effluents.


Assuntos
Cromo/química , Fenol/química , Eliminação de Resíduos Líquidos , Poluentes Químicos da Água/química , Corrosão , Água Subterrânea/química , Peróxido de Hidrogênio/química , Ferro/química , Oxidantes/química , Oxirredução , Fenóis/análise , Águas Residuárias/química , Poluentes Químicos da Água/análise
4.
Chemosphere ; 247: 125954, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32069725

RESUMO

Landfill leachate is challenging to treat due to its complex composition. Advanced oxidation processes such as Fenton process can be effective to treat leachate. Herein, a previously developed membrane electrochemical reactor (MER) was coupled with Fenton oxidation through providing synergistic benefits with the low solution pH, reduced organics, and ammonia removal/recovery. This two-stage coupled system reduced the leachate COD by 88%, much higher than that from the standalone Fenton process treating raw leachate. In addition, the usage of chemical reagents has been greatly reduced. At a dimensionless oxidant dose of 1.0, the coupled MER-Fenton system reduced the consumption of both FeSO4⋅7H2O and H2O2 by 39%, H2SO4 by 100%, and NaOH by 55%. Consequently, the sludge production was reduced by 51% in weight and 12% in volume. Despite electricity consumption by the MER, the coupled system cost $4.76 per m3 leachate less than the standalone Fenton treatment. More notably, direct Fenton oxidation removed only 21% of ammonia; in comparison the MER-Fenton system removed ammonia by 98% with the possibility for recovery at a rate of 30.6-55.2 kg N m-3 reactor d-1. Those results demonstrate that coupling MER with Fenton process could mitigate some inherent drawbacks of Fenton oxidation such as ineffective ammonia removal, high acid and chemical reagents dose requirements, and a large amount of sludge generation. This system may be moved towards practical applications by addressing a few challenges such as using renewable energy to power MER.


Assuntos
Técnicas Eletroquímicas/métodos , Peróxido de Hidrogênio/química , Poluentes Químicos da Água/química , Purificação da Água/métodos , Amônia/isolamento & purificação , Ferro/química , Oxidantes/química , Oxirredução , Esgotos , Poluentes Químicos da Água/análise , Purificação da Água/economia
5.
Chemosphere ; 247: 125848, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-31958648

RESUMO

A Monitored Natural Attenuation (MNA) assessment approach typically used for contaminant remediation feasibility assessment was developed here for remediation-reagent delivery assessment. Subsurface delivery of oxidants, such as aqueous ozone (O3) for in situ chemical oxidation (ISCO) of groundwater contaminants, is naturally attenuated by oxidant demand and reactivity. We compared mixed reactor kinetic experiments, sand column tracer transport experiments, and reactive transport modeling and assessment methods to quantify natural attenuation kinetics, aqueous O3 solute transport, oxidant demand kinetics, and ISCO reagent delivery limitations. Sorption of aqueous O3 to quartz sand was observed during transport of O3 through water-saturated porous media. Pseudo 1st order decomposition rate constants of O3 bulk attenuation with transport were comparable to mixed reactor experiments without transport, and reactive transport modeling of miscible-displacement column experiments was used to quantify each attenuation process. Aqueous ionic strength was correlated with O3 decomposition rate constants, which was the dominant reagent delivery attenuation process. These results suggest that aqueous O3 decomposition and oxidant delivery attenuation can be predictable upon characterization of the sediment oxidant demand and dispersion, and increasing groundwater velocity during aqueous O3 injection can maximize transport distance for reagent delivery.


Assuntos
Recuperação e Remediação Ambiental/métodos , Ozônio/química , Poluentes Químicos da Água/química , Água Subterrânea/química , Cinética , Oxidantes/química , Oxirredução , Porosidade , Soluções , Água/química , Poluentes Químicos da Água/análise
6.
Artigo em Inglês | MEDLINE | ID: mdl-31724470

RESUMO

Combined sewer overflow (CSO) water introduces pathogens to receiving waters. To control pathogenic releases, chlorine may be added to disinfect CSO water. The added chlorine may react with water constituents to form oxidative species known as chlorine-produced oxidants (CPO). CPO are the sum of free and combined oxidative species that form upon adding free chlorine-bearing compounds (e.g. gaseous chlorine or hypochlorite) to water. CPO discharge is often regulated by governing agencies. Current methods to model CPO behavior do not account for CPO decay and dilution simultaneously in receiving water. This study creates a novel model for CPO demand and dilution in receiving water from chlorinated effluent in order to determine site-specific practices for implementation of a CSO water disinfection regime. To do this, representative receiving water was collected and dosed with 1, 2, and 4 mg/L chlorine. The residual chlorine was measured at intervals up to 30 min after dosing. The immediate and subsequent chlorine demand was calculated, with the subsequent demand modeled by simultaneous application of dilution and decay using pseudo-first-order decay kinetics. A comparison of model calculations indicates that application of dilution before decay underestimates CPO demand, while application of decay before dilution overestimates CPO demand.


Assuntos
Cloro/química , Desinfetantes/química , Desinfecção/métodos , Oxidantes/química , Esgotos/química , Compostos Clorados/química , Modelos Químicos , Purificação da Água
7.
Environ Sci Pollut Res Int ; 27(1): 704-716, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31808080

RESUMO

In situ chemical oxidations are known to remediate PAH contaminations in groundwater and soils. In this study, batch-scale oxidations aim to compare the PAC (polycyclic aromatic compound) degradation of three oxidation processes traditionally applied for soil treatment: permanganate, heat-activated persulfate (60 °C) and Fenton-like activated by magnetite, to results obtained with ferrates (FeVI). Widely studied for water treatments, ferrates are efficient on a wide range of pollutants with the advantage of producing nontoxic ferric sludge after reaction. However, fewer works focus on their action on soil, especially on semi-industrial grade ferrates (compatible with field application). Oxidations were carried out on sand spiked with dense non-aqueous phase liquid (DNAPL) sampled in the groundwater of a former coking plant. Conventional 16 US-EPA PAHs and polar PACs were monitored, especially potential oxygenated by-products that can be more harmful than parent-PAHs. After seven reaction days, only the Fenton-like showed limited degradation. Highest efficiencies were obtained for heat-activated persulfate with no O-PAC ketones formed. Permanganate gave important degradation, but ketones were generated in large amount. The tested ferrates not only gave slightly lower yields due to their auto-decomposition but also induced O-PAC ketone production, suggesting a reactional pathway dominated by oxidoreductive electron transfer, rather than a radical one.


Assuntos
Ferro/química , Hidrocarbonetos Policíclicos Aromáticos/análise , Poluentes do Solo/análise , Coque , Óxido Ferroso-Férrico/química , Água Subterrânea , Compostos de Manganês , Modelos Químicos , Oxidantes/química , Oxirredução , Óxidos , Oxigênio , Compostos Policíclicos/análise , Areia , Solo/química
8.
Nature ; 577(7792): 656-659, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31825951

RESUMO

Functionalization of the ß-C-H bonds of aliphatic acids is emerging as a valuable synthetic disconnection that complements a wide range of conjugate addition reactions1-5. Despite efforts for ß-C-H functionalization in carbon-carbon and carbon-heteroatom bond-forming reactions, these have numerous crucial limitations, especially for industrial-scale applications, including lack of mono-selectivity, use of expensive oxidants and limited scope6-13. Notably, the majority of these reactions are incompatible with free aliphatic acids without exogenous directing groups. Considering the challenge of developing C-H activation reactions, it is not surprising that achieving different transformations requires independent catalyst design and directing group optimizations in each case. Here we report a Pd-catalysed ß-C(sp3)-H lactonization of aliphatic acids enabled by a mono-N-protected ß-amino acid ligand. The highly strained and reactive ß-lactone products are versatile linchpins for the mono-selective installation of diverse alkyl, alkenyl, aryl, alkynyl, fluoro, hydroxyl and amino groups at the ß position of the parent acid, thus providing a route to many carboxylic acids. The use of inexpensive tert-butyl hydrogen peroxide as the oxidant to promote the desired selective reductive elimination from the Pd(IV) centre, as well as the ease of product purification without column chromatography, render this reaction amenable to tonne-scale manufacturing.


Assuntos
Carbono/química , Hidrogênio/química , Lactonas/química , Alquilação , Aminoácidos/química , Ácidos Carboxílicos/síntese química , Ácidos Carboxílicos/química , Catálise , Técnicas de Química Sintética , Genfibrozila/química , Ligantes , Oxidantes/química , Oxirredução , Paládio/química , terc-Butil Hidroperóxido/química
9.
Environ Sci Pollut Res Int ; 27(1): 907-920, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31820248

RESUMO

To understand the atmospheric chemistry of hydrofluoroethers, we have studied the oxidation of a highly fluorinated compound n-C2F5CF(OCH3)CF(CF3)2 (HFE-7300) by OH/Cl oxidants. Here, we have employed M06-2X functional along with a 6-31 + G(d,p) basis set to obtain the optimized structures, various forms of energies, and different modes of frequencies for all species. We have characterized energies of all species on the potential energy surface, and it indicates that H-abstraction from n-C2F5CF(OCH3)CF(CF3)2 by Cl atom is kinetically more dominant than the H-abstraction reaction initiated by OH radical. In contrast, the calculated energy change (ΔrH°298 and ΔrG°298) results govern that OH-initiated H-abstraction reaction is highly exothermic and spontaneous compared to the Cl-initiated H-abstraction reaction. Rate constants are estimated using transition state theory as well as canonical variation transition state theory at the temperature range 200-1000 K and 1 atm pressure. The calculated rate constants of the H-abstraction channels are found to be in good agreement with the reported experimental rate constant at 298 K. Moreover, we have estimated the atmospheric lifetimes of HFE-7300 for the reaction with OH radical and Cl atom and are found to be 1.75 and 153.93 years, respectively. Additionally, the global warming potentials for HFE-7300 molecule are also estimated for 20-, 100-, and 500-year time horizons. Further, subsequent aerial oxidation of product radical (n-C2F5CF(OCH2)CF(CF3)2) in the presence of NO radical is performed, and it produced alkoxy radical via formation of peroxy radical. This alkoxy radical undergoes unimolecular decompositions via two different ways and formed n-C2F5CF(OCHO)CF(CF3)2 and n-C2F5CF(OH) CF(CF3)2 products.


Assuntos
Poluentes Atmosféricos/química , Éteres/química , Oxidantes/química , Atmosfera/química , Aquecimento Global , Radical Hidroxila/química , Cinética , Modelos Químicos , Oxirredução , Termodinâmica
10.
Chemosphere ; 241: 125005, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31605994

RESUMO

Iron dipicolinamide (Fedpa), as an efficient Fenton-like catalyst, was fabricated to excite hydrogen peroxide (H2O2) for the removal of 2,4-dichlorophenol (2,4-DCP). The unique structures and the electronic properties of Fedpa were contributed to its excellent catalytic performance in alkaline Fenton process. Fe was chelated with dpa by four Fe-N bonds leaved two labile sites, which reduced the oxidation potential of dpa[FeIII/FeII], dpa[FeV/FeIII] or dpa[FeIV/FeII] to 0.316 V and 1.189 V respectively, and made it easily be bound with H2O2 to initiate the reaction. The results showed that 99.5% removal rate of 2,4-DCP (0.58 mM) was achieved by using 0.027 g/L Fedpa and 5.8 mM H2O2 in 60 min at pH 9.9. The coordination between Fe and dpa enhanced the catalytic efficiency of FeII. The active species generated in Fedpa/H2O2 system contained the iron-oxo species (dpaFeV = O or dpaIV = O), O2- and HO. The iron-oxo species was the main non-radical reactive species for the degradation of 2,4-DCP and some degradation intermediates were detected by GC-QTOF. Furthermore, the influence of factors, such as Fedpa loading, solution pH, temperature and anions (F-, Cl-, SO42-, NO3- and PO43-) on the catalytic performance of Fedpa were also discussed. This process of complexation between Fe and dpa combined with a green oxidant H2O2 presents a new insight for the use of Fenton-like system in the degradation of refractory organics.


Assuntos
Clorofenóis/isolamento & purificação , Peróxido de Hidrogênio/química , Ferro/química , Poluentes da Água/isolamento & purificação , Catálise , Clorofenóis/química , Nitrogênio/química , Oxidantes/química , Oxirredução , Poluentes da Água/química
11.
Talanta ; 208: 120425, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31816696

RESUMO

A chicken egg white protein-protected gold nanocluster (CEW-AuNC) based fluorogenic biosensor, where protein was used as both reducing and protecting agent, was developed to determine the Cu(II)-induced prooxidant activity of natural antioxidants abundant in food and biological samples. Gold nanoclusters, prepared using egg white proteins, exhibited strong fluorescence. The prooxidant activity of the tested antioxidants was indirectly measured by their reducing action on Cu(II) to Cu(I), and the reduced cuprous ion was bound to the thiol groups in the CEW-AuNC structure, causing a decrease in fluorescence intensity. Epicatechin, catechin, epigallocatechin gallate, morin, rutin, quercetin, gallic, chlorogenic, and rosmarinic acids, glutathione, cysteine, N-acetyl cysteine, bilirubin, resveratrol, and α-tocopherol were studied as natural antioxidants. A fluorometric method showing a large Stokes shift with excitation/emission maxima at 360∕640 nm was developed to sensitively measure the decrease in the fluorescence of CEW-AuNC associated with the binding of copper(I) to the protein structure. Total prooxidant activities of the binary, ternary, and quaternary synthetic mixtures and of some food and synthetic serum samples were determined. The biosensor response was statistically compared to that of its spectrophotometric counterpart. This method can be used for the control of the oxidative stability of foods with a prolonged shelf life.


Assuntos
Técnicas Biossensoriais , Ouro/química , Nanoestruturas/química , Oxidantes/química , Ácidos Carbocíclicos/química , Antioxidantes/química , Bilirrubina/química , Mirtilos Azuis (Planta) , Cobre/química , Proteínas do Ovo/química , Flavonoides/química , Fluorometria , Sucos de Frutas e Vegetais , Malus , Oxirredução , Extratos Vegetais , Resveratrol/química , Compostos de Sulfidrila/química , Chá , Vinho
12.
Chemosphere ; 239: 124763, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31526989

RESUMO

Nonredox metal ions have been widely recognized to be important in a wide range of biological and chemical oxidations as Lewis acids (LA). However, the role of LA in peroxymonosulfate (PMS) activation for wastewater treatment has not been considered until now. This study shows that oxidizing power of PMS can be promoted after binding nonredox metal ions such as Ca2+ as LA, leading to the easier reduction of the oxidant to radicals and substantial enhancement of dye degradation by employing manganese oxides OMS-2 as model catalysts. Increased with Lewis acidity of the metal ion, the rate of PMS decomposition enhanced linearly, while the dye degradation rate first increased and then declined due to the formation of a larger amount of dioxygen. The interactions between Ca2+ and PMS were further investigated by Raman, cyclic voltammetry and XPS; and the detailed mechanism of PMS activation was proposed. The performance of Ca2++OMS-2/PMS system under different conditions was also studied. The findings indicate the importance of LA in PMS activation reaction and their role must be considered in other transition metal oxides/PMS systems. It will be also helpful to design new and highly active catalysts for the reactions.


Assuntos
Ácidos de Lewis/química , Compostos de Manganês/química , Óxidos/química , Peróxidos/química , Poluentes Químicos da Água/química , Cálcio/química , Catálise , Corantes/química , Oxidantes/química , Oxirredução , Soluções , Eliminação de Resíduos Líquidos/métodos , Águas Residuárias/química
13.
Chemosphere ; 238: 124575, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31446274

RESUMO

Significance of surface and ground water contamination by synthetic organic compounds has been pointed out in a very high number of papers worldwide, as well as the need of application of treatment technologies capable to assure their complete removal. Among these processes, the electrochemical advanced oxidation is an interesting option, especially when irradiated with UVC light (photo-electrochemical, P-EC) to promote homolysis of electrogenerated oxidants. In this work, the herbicide glyphosate (GLP) was used as model compound and it was electrochemically treated under UVC irradiation in the presence of NaCl and using a DSA® and BDD anodes. Total organic carbon concentration was measured throughout the electrolysis, as well as the concentration of short chain carboxylic acids and inorganic ions (NO3-, PO43-,ClO-, ClO3- and ClO4-). The synergism of the P-EC was more pronounced when using a DSA® electrode, which led to complete GLP mineralization in 1 h (0.52 A h L-1), as also confirmed by the stoichiometric formation of NO3- and PO43- ions, with an energy consumption as low as 1.25 kW h g-1. Unexpectedly, the concentration evolution of oxyhalides for the P-EC process using both anodes, especially for DSA® at 10 mA cm-2, showed the production of ClO3-, whereas detection of ClO4- species was only found when using BDD at 100 mA cm-2 for the electrochemical process. Finally, small amounts of carboxylic acids were detected, including dichloroacetic acid, especially when using a BDD electrode.


Assuntos
Técnicas Eletroquímicas/métodos , Glicina/análogos & derivados , Água Subterrânea/química , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/química , Purificação da Água/métodos , Ácidos Carboxílicos/análise , Diamante/química , Eletrodos , Glicina/análise , Oxidantes/química , Oxirredução , Raios Ultravioleta
14.
Chemosphere ; 240: 124928, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31563101

RESUMO

Oxidation is an attractive treatment method to effectively remove organic contaminants in water. In this study, degradation of 30 organic compounds in different oxidation systems was evaluated, including oxygen (O2), hydrogen peroxide (H2O2), ozone (O3) and hydroxyl radical (HO). First, a quantitative structure-activity relationship (QSAR) model for oxidation-reduction potentials (ORPs) of organics was developed and exhibited a good performance to predict ORP values of organics with evaluation indices of squared correlation coefficient (R2) = 0.866, internal validation (q2) = 0.811 and external validation (Qext2) = 0.669. Four quantum parameters, including f(+)n, f(-)n, EHOMO and EB3LYP dominate the ORP values. Subsequently, a relationship between reaction rates (k) and the difference of ORP for oxidants and organics (ΔEoxi-org) was established, however, which was limited (R2= 0.697). Therefore, two new predictors (slopes and intercepts) are proposed based on the linear relationships between k values and ORPs of oxidants. These new predictors can be applied to estimate the reaction rates and minimum oxidation potential for organic compounds. Afterwards, to express the two predictors, QSAR models were established. The two optimal QSAR models fitted very well with experimental values and were demonstrated to be stable and accurate based on R2 (0.982 and 0.965), q2 (0.950 and 0.950) and Qext2 (0.985 and 0.989). BOx, q(H)+ and q(C)x were main factors influencing the slopes and intercepts. This study developed methods to predict ORPs of organics and established two new predictors to estimate the reaction rates undergoing different oxidation processes, offering new insights into the oxidant selection.


Assuntos
Modelos Teóricos , Compostos Orgânicos/análise , Relação Quantitativa Estrutura-Atividade , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Peróxido de Hidrogênio/química , Radical Hidroxila/química , Oxidantes/química , Oxirredução , Oxigênio/química , Ozônio/química , Águas Residuárias/química , Água
15.
Biochim Biophys Acta Gen Subj ; 1864(2): 129401, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-31348988

RESUMO

BACKGROUND: Mutants of Cu,Zn-superoxide dismutase (SOD1) exhibit cytotoxicity such as aggregation and pro-oxidation after denaturation, which is thought to be involved in the pathogenesis of amyotrophic lateral sclerosis (ALS). In the present study, we investigated the possibility of the acquisition of toxic properties for wild-type SOD1 (WT) in the demetalated (apo) form after denaturation. METHODS: Denaturation and subsequent pro-oxidant activity of SOD1 were confirmed by circular dichroism (CD) spectroscopy and fluorescence assay, respectively. The aggregation of SOD1 was investigated by native polyacrylamide gel electrophoresis (PAGE). Crowding environment was prepared by the addition of polyethylene glycol (PEG) into buffer solution. RESULTS: The structural stability of SOD1 is reduced by demetallation. Nevertheless, high temperatures around 45 °C are required to induce denaturation of apo-WT. The generated denaturated apo-WT exhibits pro-oxidant activity after the rebinding of Cu2+. In molecular crowding environment mimicked by PEG, apo-WT is found to exhibit denaturation even at physiological temperature. The denatured WT in molecular crowding environment has both the activities of pro-oxidation and aggregation. The acquisition of the pro-oxidant activity is accelerated for H43R, which is an ALS-related mutant, in molecular crowding environment. CONCLUSIONS: Apo-WT acquires the toxic properties at physiological temperature when subjected to molecular crowding environment. Molecular crowding environment also accelerates the induction of the toxicity for H43R. GENERAL SIGNIFICANCE: Molecular crowding environment in living cells becomes an instability factor inducing denaturation and subsequent toxicity for SOD1. Apo-WT also has the toxic properties in molecular crowding environment, which can be related to the pathogenesis of ALS.


Assuntos
Esclerose Amiotrófica Lateral/metabolismo , Oxidantes/química , Superóxido Dismutase-1/química , Dicroísmo Circular , Eletroforese em Gel de Poliacrilamida , Humanos , Peso Molecular , Mutação , Oxirredução , Polietilenoglicóis/química , Conformação Proteica , Desnaturação Proteica , Espécies Reativas de Oxigênio/química , Proteínas Recombinantes/química , Temperatura
16.
J Recept Signal Transduct Res ; 39(4): 373-381, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31726019

RESUMO

A series of new urea and thiourea derivatives of 5-hydroxy tryptophan 3a-l was designed and synthesized from 5-hydroxy tryptophan (1) by treating various isocyanates 2a-g and isothiocyanates 2h-l in the presence of triethylamine (TEA) as a base. The antioxidant activities of the newly synthesized compounds were evaluated by using different in vitro assays such as 1, 1-diphenyl-2-picrylhydrazyl (DPPH), hydrogen peroxide (H2O2) and superoxide. The results obtained from the in vitro studies revealed that the compounds 3a, 3g, 3h, and 3l exhibited the significant high content of antioxidant activity. Besides, molecular docking studies indicated that, all the compounds 3a-l have formed higher binding energies with 3MNG protein than the reference compound 1. Among all the synthesized compounds, 3a, 3l, 3g, 3b, 3c and 3h have exhibited the highest dock scores than the rest of the compounds including the reference compound. Hence, it is concluded that the title compounds will open new vistas for the discovery of strong antioxidants and will stand as remarkable antioxidant moieties in future.


Assuntos
5-Hidroxitriptofano/química , Antioxidantes/química , Antioxidantes/farmacologia , Proteínas/metabolismo , Tioureia/química , Ureia/química , Simulação por Computador , Humanos , Peróxido de Hidrogênio/química , Peróxido de Hidrogênio/metabolismo , Técnicas In Vitro , Simulação de Acoplamento Molecular , Oxidantes/química , Oxidantes/metabolismo , Conformação Proteica , Proteínas/química
17.
Proc Natl Acad Sci U S A ; 116(48): 24359-24365, 2019 11 26.
Artigo em Inglês | MEDLINE | ID: mdl-31719194

RESUMO

Thermosensitive transient receptor potential (TRP) ion channels detect changes in ambient temperature to regulate body temperature and temperature-dependent cellular activity. Rodent orthologs of TRP vanilloid 2 (TRPV2) are activated by nonphysiological heat exceeding 50 °C, and human TRPV2 is heat-insensitive. TRPV2 is required for phagocytic activity of macrophages which are rarely exposed to excessive heat, but what activates TRPV2 in vivo remains elusive. Here we describe the molecular mechanism of an oxidation-induced temperature-dependent gating of TRPV2. While high concentrations of H2O2 induce a modest sensitization of heat-induced inward currents, the oxidant chloramine-T (ChT), ultraviolet A light, and photosensitizing agents producing reactive oxygen species (ROS) activate and sensitize TRPV2. This oxidation-induced activation also occurs in excised inside-out membrane patches, indicating a direct effect on TRPV2. The reducing agent dithiothreitol (DTT) in combination with methionine sulfoxide reductase partially reverses ChT-induced sensitization, and the substitution of the methionine (M) residues M528 and M607 to isoleucine almost abolishes oxidation-induced gating of rat TRPV2. Mass spectrometry on purified rat TRPV2 protein confirms oxidation of these residues. Finally, macrophages generate TRPV2-like heat-induced inward currents upon oxidation and exhibit reduced phagocytosis when exposed to the TRP channel inhibitor ruthenium red (RR) or to DTT. In summary, our data reveal a methionine-dependent redox sensitivity of TRPV2 which may be an important endogenous mechanism for regulation of TRPV2 activity and account for its pivotal role for phagocytosis in macrophages.


Assuntos
Metionina/metabolismo , Canais de Cátion TRPV/química , Canais de Cátion TRPV/metabolismo , Canais de Cálcio/química , Canais de Cálcio/genética , Canais de Cálcio/metabolismo , Cloraminas/química , Escherichia coli/genética , Temperatura Alta , Humanos , Peróxido de Hidrogênio/química , Macrófagos , Metionina/química , Mutação , Oxidantes/química , Oxirredução , Técnicas de Patch-Clamp , Fagocitose , Canais de Cátion TRPM/química , Canais de Cátion TRPM/metabolismo , Canais de Cátion TRPV/genética , Compostos de Tosil/química
18.
Molecules ; 24(22)2019 Nov 16.
Artigo em Inglês | MEDLINE | ID: mdl-31744122

RESUMO

Oxidation of alcohols plays an important role in industrial chemistry. Novel green techniques, such as sonochemistry, could be economically interesting by improving industrial synthesis yield. In this paper, we studied the selective oxidation of benzyl alcohol as a model of aromatic alcohol compound under various experimental parameters such as substrate concentration, oxidant nature and concentration, catalyst nature and concentration, temperature, pH, reaction duration, and ultrasound frequency. The influence of each parameter was studied with and without ultrasound to identify the individual sonochemical effect on the transformation. Our main finding was an increase in the yield and selectivity for benzaldehyde under ultrasonic conditions. Hydrogen peroxide and iron sulfate were used as green oxidant and catalyst. Coupled with ultrasound, these conditions increased the benzaldehyde yield by +45% compared to silent conditions. Investigation concerning the transformation mechanism revealed the involvement of radical species.


Assuntos
Benzaldeídos/química , Álcool Benzílico/química , Oxirredução , Ondas Ultrassônicas , Catálise , Concentração de Íons de Hidrogênio , Cinética , Oxidantes/química , Temperatura
19.
J Photochem Photobiol B ; 200: 111647, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31648133

RESUMO

Photoactive materials called photosensitizers can be used for treatment of different types of cancer in combination with light source. In this paper, we have investigated pro-oxidant and antioxidant potentials of four graphene based nanomaterials (graphene oxide-GO, graphene quantum dots-GQDs, carbon quantum dots-CQDs and N-doped carbon quantum dots-N-CQDs) depending on the presence/absence of visible light source. Structural and optical properties of these materials and their potentials for reactive oxygen species generation/quenching are investigated by applying different microscopy and spectroscopy techniques (transmission electron microscopy, FTIR, UV-Vis, photoluminescence, electron paramagnetic resonance). Results show that all types of quantum dots has pro-oxidant and antioxidant potentials whereas GO demonstrated only moderate antioxidant effect. The best free radical scavenger is CQDs sample in the absence of light. CQDs are the best singlet oxygen generator under blue light irradiation as well. To check photo-cytotoxicity of these materials, photo-cytotoxic concentrations of the GO, GQDs, CQDs and N-CQDs were determined for three cellular lines: human rhabdomyosarcoma (RD), cell line derived from human cervix carcinoma Hep2c (HeLa) and fibroblast cell line from murine (L2OB). Cytotoxicity test has indicated that all samples are much less photocytotoxic than cis-diamminedichloroplatinum (cis-DPP). The production method and doping of quantum dots affect the photodynamic activity of tested samples very much.


Assuntos
Antioxidantes/química , Grafite/química , Oxidantes/química , Carbono/química , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Grafite/toxicidade , Humanos , Microscopia Confocal , Pontos Quânticos/química , Pontos Quânticos/toxicidade , Oxigênio Singlete/química , Oxigênio Singlete/metabolismo
20.
Macromol Rapid Commun ; 40(22): e1900328, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31637803

RESUMO

The incorporation of an extraneous on-off braking system is necessary for the effective motion control of the next generation of micrometer-sized motors. Here, the design and synthesis of micromotors is reported based on mesoporous silica particles containing bipyridine groups, introduced by cocondensation, for entrapping catalytic cobalt(II) ions within the mesochannels, and functionalized on the surface with silane-derived temperature responsive bottle-brush polyphosphazene. Switching the polymers in a narrow temperature window of 25-30 °C between the swollen and collapsed state, allows the access for the fuel H2 O2 contained in the dispersion medium to cobalt(II) bipyridinato catalyst sites. The decomposition of hydrogen peroxide is monitored by optical microscopy, and effectively operated by reversibly closing or opening the pores by the grafted gate-like polyphosphazene, to control on demand the oxygen bubble generation. This design represents one of the few examples using temperature as a trigger for the reversible on-off external switching of mesoporous silica micromotors.


Assuntos
Compostos Organofosforados/química , Polímeros/química , Silanos/química , Dióxido de Silício/química , Catálise , Cobalto/química , Peróxido de Hidrogênio/química , Microscopia Eletrônica de Transmissão , Estrutura Molecular , Nanopartículas/química , Nanopartículas/ultraestrutura , Oxidantes/química , Tamanho da Partícula , Porosidade , Temperatura
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