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1.
Food Chem ; 333: 127540, 2020 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-32682226

RESUMO

A novel of magnetic dummy-template molecularly imprinted polymers (mag-MWCNTs-DMIPs) were prepared by surface molecular imprinting technique. The structure of polymers were characterized and the binding properties were assessed by adsorption experiments. The synthetic mag-MWCNTs-DMIPs exhibit satisfying adsorption capacity, excellent selectivity and fast adsorption rate toward phenoxy carboxylic acid (PCA) herbicides. Afterwards, a reliable analytical method for selective separation and determination of trace PCA herbicides in cereals was established by using magnetic solid-phase extraction (mag-MWCNTs-DMIPs as magnetic adsorbent) and UPLC-MS/MS detection. A series of requisite factors were optimized in detail to achieve expected extraction performance. Under the optimum MSPE parameters, the mean spiked recoveries for analytes in different cereals ranged from 86.7% to 95.2% with intra- and inter-day precision not greater than 8.5% and 10.6%, respectively. At last, the developed method was successfully utilized for determination the four PCA herbicides in actual cereals.


Assuntos
Ácidos Carboxílicos/análise , Ácidos Carboxílicos/isolamento & purificação , Grão Comestível/química , Herbicidas/química , Impressão Molecular , Nanotubos de Carbono/química , Extração em Fase Sólida/métodos , Adsorção , Ácidos Carboxílicos/química , Contaminação de Alimentos/análise , Imãs/química , Polímeros/síntese química , Polímeros/química , Fatores de Tempo
2.
Sci Total Environ ; 729: 138119, 2020 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-32498147

RESUMO

Oil refining produces vast quantities of wastewater with harmful contaminants that can be released back into the environment with a possible risk of toxicity to aquatic wildlife and human populations. Hence the importance of adequate wastewater treatment to achieve safe effluents that protect both ecological and human health. However, some refining effluents are linked to serious pollution problems even after treatment, partly because little progress has been made in determining the causative agents of the observed biological effects, resulting in non-targeted treatment. Here, we followed an effect-directed analysis (EDA) approach using Aliivibrio fischeri as biosensor to show that naphthenic acids (NAs) are important components of refining wastewater resulting from the processing of heavy crude oil. Furthermore, we demonstrate that besides mixture effects, NAs have a significant contribution to the toxicity exerted by these effluents. Profiling of the NA mixture was conducted using high resolution liquid chromatography-Orbitrap, which evidenced that O2 NAs corresponded to 90% of the NAs detected. Our findings contrast with previous reports where classic NAs have been found between 15% and 72% and could explain the significant biological effects observed in A. fischeri. This study broadens the body of evidence pointing at mixture effects and low-concentration pollutants as the cause of toxicity from RWW, in addition to NAs resulting from the processing of heavy crude oil. Our results can serve as a starting point for setting better effluent discharge standards relevant to oil refining wastewater resulting from heavy crude oil and help improve wastewater treatment plants to reduce effluent toxicity.


Assuntos
Ácidos Carboxílicos/química , Aliivibrio fischeri , Campos de Petróleo e Gás , Águas Residuárias , Poluentes Químicos da Água
3.
Chemosphere ; 258: 127281, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32540545

RESUMO

Development of Alberta's oil sands requires large volumes of water, leading to the abundance of oil sands process affected water (OSPW) that must be remediated prior to discharge or reuse. OSPW contains a variety of dissolved organic compounds, however naphthenic acids (NAs) have been found to contribute significantly to the toxicity of OSPW. A fungus, Trichoderma harzianum, isolated directly from OSPW, has previously demonstrated a high tolerance and capacity for growth in the presence of commercial NAs. This study conducted microcosm experiments to elucidate and characterize the capacity of T. harzianum to degrade labile commercial NAs (Merichem), and OSPW-sourced naphthenic acid fraction compounds (NAFCs). Additionally, two model NA compounds, the simple single ring cyclohexane carboxylic acid (CHCA) and complex diamondoid 1-adamanatane carboxylic acid (ADA), were utilized to determine the influence of NA structure on degradation. T. harzianum degraded 14% of CHCA, 13% of ADA, and 23-47% of Merichem NAs. Additionally, Orbitrap mass spectrometry revealed a large change in Z-series within NAFCs. This removal and shift in composition correlated to a 59% and 52% drop in toxicity as per Microtox, for Merichem NAs and NAFCs respectively. This proof of concept experiment confirms that the fungal species T. harzianum can contribute to the biodegradation of complex dissolved organics found in OSPW, including cyclic and diamondoid structures.


Assuntos
Ácidos Carboxílicos/metabolismo , Recuperação e Remediação Ambiental/métodos , Campos de Petróleo e Gás , Trichoderma/metabolismo , Águas Residuárias/microbiologia , Poluentes Químicos da Água/metabolismo , Adamantano/química , Adamantano/metabolismo , Alberta , Biodegradação Ambiental , Ácidos Carboxílicos/química , Cicloexanos/química , Cicloexanos/metabolismo
4.
Chemosphere ; 254: 126803, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32361540

RESUMO

Dehalogenation is one of the most important reactions in environmental pollution control, for instance, the degradation of persistent organic pollutants (POPs). Recently, fluoroacetate dehalogenase (FAcD) has been reported to catalyze the dehalogenation reactions, which shows great potential in treating halogenated pollutants. Here the dehalogenation mechanism catalyzed by FAcD was fully deciphered with the aid of quantum mechanics/molecular mechanics method. The results show that FAcD catalyzed dehalogenation efficiency follows the order of defluorination > dechlorination > debromination. The corresponding Boltzmann-weighted average barriers are 10.1, 19.7, and 20.9 kcal mol-1. Positive/negative correlations between activation barriers and structural parameters (e.g. distance and angle) for FAcD catalyzed dechlorination and debromination were established. Based on the structure-energy relationship, we propose that mutation of the binding pocket amino acids (e.g. His155, Trp156, Tyr219) to smaller proton donor amino acids (e.g. Serine, Threonine, Cysteine, Asparagine) may increase the efficiency for dechlorination and debromination. The results may of practical value for the efficient degradation of chlorined and bromined pollutants by harnessing FAcD.


Assuntos
Ácidos Carboxílicos/química , Hidrolases/química , Aminoácidos/metabolismo , Catálise , Poluentes Ambientais , Halogenação , Simulação de Dinâmica Molecular
5.
Chemosphere ; 249: 126171, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32087452

RESUMO

Carbon-based materials including multiwall carbon nanotubes (MWCNTs) have been recently implicated in a number of reports dealing with their potential use in agriculture, leading to contradictory findings. In this study, MWCNTs were successfully functionalized with carboxylic acid groups (MWCNTs-COOH) in order to increase water dispersion. Hydroponically cultured sweet basil (Ocimum basilicum L.) seedlings were subjected to four concentrations (0, 25, 50 and 100 mg L-1) of MWCNTs-COOH under three salt stress levels (0, 50 and 100 mM NaCl). An array of agronomic, physiological, analytical and biochemical parameters were evaluated in an attempt to examine the potential use of MWCNTs in plants under optimal and abiotic stress conditions. Application of MWCNTs-COOH at optimum concentration (50 mg L-1) could ameliorate the negative effects of salinity stress by increasing chlorophyll and carotenoids content and inducing non-enzymatic (i.e. phenolic content) and enzymatic antioxidant components (i.e. ascorbate peroxidase (APX), catalase (CAT) and guaiacol peroxidase (GP) activity). Furthermore, MWCNTs-COOH treatments under optimal conditions induced plant growth, while a significant increase (P ≤ 0.01) was recorded in essential oil content and compound profile. On the other hand, biochemical and epifluorescence microscopy evidence suggested that high dosage (100 mg L-1) of MWCNTs-COOH leads to toxicity effects in plant tissue. Overall, the positive response of plants to low concentrations of MWCNTs-COOH under control and abiotic stress conditions renders them as potential novel plant growth promoting and stress protecting agents, opening up new perspectives for their use in agriculture.


Assuntos
Nanotubos de Carbono/toxicidade , Ocimum basilicum/fisiologia , Antioxidantes/metabolismo , Ascorbato Peroxidases , Ácidos Carboxílicos/química , Carotenoides , Catalase , Clorofila , Nanotubos de Carbono/química , Ocimum basilicum/efeitos dos fármacos , Óleos Voláteis/metabolismo , Fenóis/metabolismo , Desenvolvimento Vegetal , Plântula/efeitos dos fármacos , Estresse Fisiológico
6.
Nat Commun ; 11(1): 982, 2020 02 20.
Artigo em Inglês | MEDLINE | ID: mdl-32080186

RESUMO

Although peptide chemistry has made great progress, the frequent occurrence of aspartimide formation during peptide synthesis remains a formidable challenge. Aspartimide formation leads to low yields in addition to costly purification or even inaccessible peptide sequences. Here, we report an alternative approach to address this longstanding challenge of peptide synthesis by utilizing cyanosulfurylides to mask carboxylic acids by a stable C-C bond. These functional groups-formally zwitterionic species-are exceptionally stable to all common manipulations and impart improved solubility during synthesis. Deprotection is readily and rapidly achieved under aqueous conditions with electrophilic halogenating agents via a highly selective C-C bond cleavage reaction. This protecting group is employed for the synthesis of a range of peptides and proteins including teduglutide, ubiquitin, and the low-density lipoprotein class A. This protecting group strategy has the potential to overcome one of the most difficult aspects of modern peptide chemistry.


Assuntos
Peptídeos/química , Peptídeos/síntese química , Técnicas de Síntese em Fase Sólida/métodos , Ácido Aspártico/análogos & derivados , Ácido Aspártico/síntese química , Ácido Aspártico/química , Ácidos Carboxílicos/química , Cianetos/química , Lipoproteínas LDL/síntese química , Lipoproteínas LDL/química , Dobramento de Proteína , Ubiquitina/química
7.
Org Biomol Chem ; 18(7): 1279-1336, 2020 02 19.
Artigo em Inglês | MEDLINE | ID: mdl-32025682

RESUMO

Enantio- and diastereodivergent routes to marine-origin natural products with different sizes of cyclic ethers and lactones have been used in order to assign stereochemical features. Kainoid amino acids such as isodomoic acids have been synthesized using diastereodivergent routes. The bis(indole) alkaloid dragmacidin F has been prepared by enantiodivergent strategies as well as furanoterpenes and the tetracyclic agelastatin A. Natural products containing five-membered lactones like quercus lactones, muricatacins, goniofufuranones, methylenolactocins and frenolicin B have been synthesized using stereodivergent routes. Macrolides are very abundant lactones and have been mainly prepared from the corresponding seco-acids by lactonization, such as lasiodiplodin, zaeralanes, macrosphelides and haloprins, or by ring-closing metathesis, such as aspercyclides, microcarpalides, macrolides FD-891 and 892, and tetradic-5-en-9-olides. Other natural products including cyclic ethers (such as sesamin, asarinin, acetogenins, centrolobines and nabilones), alcohols (such as sulcatol), esters (such as methyl jasmonates), polycyclic precursors of fredericamycin, amino alcohols (such as ambroxol and sphingosines), isoprostanes, isofurans, polyketide precursors of anachelins, brevicomins, gummiferol, shikimic acid and the related compounds, and the pheromone disparlure have been synthesized stereodivergently. Heterocyclic systems such as epoxides, theobroxides and bromoxones, oxetan-3-ones, 5- to 8-membered cyclic ethers, azetidones, γ-lactams, oxazolidinones, bis(oxazolines), dihydropyridoisoindolines and octahydroisoquinolines have been prepared following stereodivergent routes. Stereodivergent routes to unnatural compounds such as alkenes, dienes, allenes, cyclopropanes, alcohols, aldols, amines, amino alcohols, ß-amino acids, carboxylic acids, lactones, nitriles and α-amino nitriles have been considered as well.


Assuntos
Produtos Biológicos/síntese química , Compostos Heterocíclicos/síntese química , Lactonas/síntese química , Álcoois/síntese química , Álcoois/química , Alcenos/síntese química , Alcenos/química , Aminas/síntese química , Aminas/química , Aminoácidos/síntese química , Aminoácidos/química , Produtos Biológicos/química , Ácidos Carboxílicos/síntese química , Ácidos Carboxílicos/química , Compostos Heterocíclicos/química , Lactonas/química , Estrutura Molecular , Nitrilos/síntese química , Nitrilos/química , Estereoisomerismo
8.
Phys Chem Chem Phys ; 22(6): 3490-3498, 2020 Feb 14.
Artigo em Inglês | MEDLINE | ID: mdl-31990285

RESUMO

The liquid structures of six choline carboxylate/amino acid ionic liquids (bio-ILs) and their mixtures with water and various n-alkanols have been investigated by small-angle X-ray scattering (SAXS). The ILs exhibit long-range amphiphilic nanostructure comprised of polar and apolar domains that can be controlled by choice of anion, and which is tolerant to water dilution. Mixtures with n-alkanols can lead to marked changes in domain size and ordering. Utilising the Teubner-Strey model, we find amphiphilicity factors in many of these mixtures are comparable to those observed in conventional microemulsions, and that cooperative assembly in bio-IL/alkanol mixtures can enhance amphiphilicity, with potential to improve performance in a range of applications.


Assuntos
Aminoácidos/química , Ácidos Carboxílicos/química , Colina/química , Líquidos Iônicos/química , Nanoestruturas/química , Tensoativos/química
9.
Chemosphere ; 242: 125291, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31896181

RESUMO

The huge usage of rechargeable batteries in electronics has added to a recurrent problem worldwide in generating tonnage of spent lithium-ion batteries (LIBs). The inadequacy of the resources of the depleting critical metals has also been described in vogue. The environmental assessment of the life cycle of the LIBs has been elucidated vis-a-vis the effects of raw material supply, transportation, and recycling. Based on the available work for recycling technologies, this review also attempts to elicit the various methods practiced in discharging/dismantling, classification, and separation of components followed by metal recovery. The authors have reviewed the major developments in the area of recycling of cathode material by using various acids for extraction of metals from spent LIBs, compared the merits and demerits of acids used and presented a comprehensive outlook to the processes formulated vis-à-vis imperative need for using green techniques. The necessity for benign recycling methods is stressed upon to alleviate the need for high temperature and oxidative acid leaching conditions. The various green lixiviants (organic acids) attempted to extract metals from spent LIBs have been discussed in detail with respect to the mechanism, efficacies as well as the various factors (selectivity, cost, etc.) that govern the use of organic acids in battery recycling. It was ascertained that the GHG emissions to extract Co using organic acids stand 1/8 of that using an inorganic acid leaching process. Efforts need to be envisaged in separating the leached metals from these lixiviants ensuring economics and environmental benefits.


Assuntos
Ácidos Carboxílicos/química , Fontes de Energia Elétrica , Resíduo Eletrônico/análise , Poluentes Ambientais/análise , Lítio/análise , Reciclagem/métodos , Eletrodos , Íons
10.
Anal Chim Acta ; 1097: 186-195, 2020 Feb 08.
Artigo em Inglês | MEDLINE | ID: mdl-31910959

RESUMO

A simple electrochemical strategy has been designed for the analysis of MUC1 using electrodeposited gold platinum bimetallic nanoparticles (Au-PtBNPs) on the surface of carboxylated graphene oxide (CGO)/FTO electrode as a signal amplification platform. The carboxylic groups of CGO were activated with EDS-NHS linker and subsequently immobilized with streptavidin for further deposition of biotin labelled aptamer. All the modification steps were characterized by FE-SEM, EDS mapping, FT-IR, contact angle measurements and electrochemical methods. After incubating with target protein MUC1, the aptaelectrode produced some concentration dependent responses which were measured electrochemically by DPV assay. The prepared aptasensor exhibits wide linear range from 1 fM-100 nM with detection limit of 0.79 fM under optimal experimental conditions. The performance of this aptaelectrode was also evaluated showing good selectivity, storage stability (15 days), reproducibility and reusability (up to 3 times). Furthermore, the applicability of the aptasensor for spiked serum samples showed recovery range from 92% to 97%.


Assuntos
Aptâmeros de Nucleotídeos/química , Técnicas Biossensoriais , Técnicas Eletroquímicas , Grafite/química , Nanopartículas Metálicas/química , Mucina-1/análise , Ácidos Carboxílicos/química , Ouro/química , Humanos , Tamanho da Partícula , Platina/química , Propriedades de Superfície
11.
Arch Biochem Biophys ; 683: 108276, 2020 04 15.
Artigo em Inglês | MEDLINE | ID: mdl-31978400

RESUMO

A Pseudomonas CoA ligase (BadA) biocatalyzed aroyl CoA thioesters used by a downstream N-benzoyltransferase (NDTNBT) in a cascade reaction made aroyl analogs of the anticancer drug paclitaxel. BadA kept the high-cost aroyl CoA substrates at saturation for the downstream NDTNBT by recycling CoA when it was added as the limiting reactant. A deacylated taxane substrate N-debenzoyl-2'-deoxypaclitaxel was converted to its benzoylated product at a higher yield, compared to the converted yield in assays in which the BadA ligase chemistry was omitted, and benzoyl CoA was added as a cosubstrate. The resulting benzoylated product 2'-deoxypaclitaxel was made at 196% over the theoretical yield of product that could be made from the CoA added at 50 µM, and the cosubstrates benzoic acid (100 µM), and N-debenzoyl-2'-deoxypaclitaxel (500 µM) added in excess. In addition, a 2-O-benzoyltransferase (mTBT) was incubated with BadA, aroyl acids, CoA, a 2-O-debenzoylated taxane substrate, and cofactors under the CoA-recycling conditions established for the NDTNBT/BadA cascade. The mTBT/BadA combination also made various 2-O-aroylated products that could potentially function as next-generation baccatin III compounds. These ligase/benzoyltransferase cascade reactions show the feasibility of recycling aroyl CoA thioesters in vitro to make bioactive acyl analogs of paclitaxel precursors.


Assuntos
Alcaloides/química , Antineoplásicos/química , Coenzima A Ligases/metabolismo , Paclitaxel/análogos & derivados , Taxoides/química , Ácido Benzoico/química , Biocatálise , Hidrocarbonetos Aromáticos com Pontes , Ácidos Carboxílicos/química , Catálise , Escherichia coli , Cinética , Paclitaxel/química , Rodopseudomonas/enzimologia , Especificidade por Substrato
12.
Molecules ; 25(1)2020 Jan 03.
Artigo em Inglês | MEDLINE | ID: mdl-31947805

RESUMO

Thermal reactions of cobalt(II) salts with flexible N,N'-bis(pyrid-3-ylmethyl)adipoamide (L) and angular 4,4'-sulfonyldibenzoic acid (H2SDA) in H2O and CH3OH afforded a pair of supramolecular isomers: [Co2(L)(SDA)2], 1, and [Co2(L)(SDA)2]⋅CH3OH⋅H2O, 2. The structure of complex 1 can be simplified as a one-dimensional (1D) looped chain with L ligands penetrating into the middles of squares, forming a new type of self-catenated net with the (42⋅54)(4)2(5)2 topology, whereas complex 2 displays a 2-fold interpenetrated 2D net with the rare (42⋅68⋅8⋅104)(4)2-2,6L1 topology. While both complexes 1 and 2 display antiferromagnetism with strong spin-orbital coupling, the antiferromagnetism of 2 is accompanied by a cross-over behavior and probably a spin canting phenomenon.


Assuntos
Amidas/química , Ácidos Carboxílicos/química , Cobalto/química , Complexos de Coordenação , Modelos Químicos , Complexos de Coordenação/síntese química , Complexos de Coordenação/química , Estrutura Molecular
13.
Molecules ; 25(2)2020 Jan 16.
Artigo em Inglês | MEDLINE | ID: mdl-31963148

RESUMO

The oxidation of primary alcohols under mechanochemical conditions in a Spex8000M Mixer/Mill was investigated. To facilitate ease of separation and recyclability, a polystyrene-bound version of a TEMPO catalyst was employed. When paired with Oxone® in a stainless-steel vial with a stainless-steel ball, several primary alcohols were successfully oxidized to the corresponding carboxylic acids. The product was isolated using gravity filtration, which also allowed for the polystyrene-bound TEMPO catalyst to be recovered and reused in subsequent oxidation reactions. Furthermore, it was demonstrated that the size and steric hindrance of the primary alcohol does not hinder the rate of the reaction. Finally, the aldehyde was selectively obtained from a primary alcohol under ball milling conditions by using a combination of non-supported TEMPO with a copper vial and copper ball.


Assuntos
Álcoois/química , Ácidos Carboxílicos/química , Oxirredução , Catálise , Fenômenos Químicos , Fenômenos Mecânicos , Metais/química , Estrutura Molecular , Temperatura
14.
IET Nanobiotechnol ; 14(1): 40-46, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31935676

RESUMO

The present study demonstrated the preparation of three different acid-functionalised magnetic nanoparticles (MNPs) and evaluation for their catalytic efficacy in hydrolysis of cellobiose. Initially, iron oxide (Fe3O4)MNPs were synthesised, which further modified by applying silica coating (Fe3O4-MNPs@Si) and functionalised with alkylsulfonic acid (Fe3O4-MNPs@Si@AS), butylcarboxylic acid (Fe3O4-MNPs@Si@BCOOH) and sulphonic acid (Fe3O4-MNPs@Si@SO3H) groups. The Fourier transform infrared analysis confirmed the presence of above-mentioned acid functional groups on MNPs. Similarly, X-ray diffraction pattern and energy dispersive X-ray spectroscopy analysis confirmed the crystalline nature and elemental composition of MNPs, respectively. TEM micrographs showed the synthesis of spherical and polydispersed nanoparticles having diameter size in the range of 20-80 nm. Cellobiose hydrolysis was used as a model reaction to evaluate the catalytic efficacy of acid-functionalised nanoparticles. A maximum 74.8% cellobiose conversion was reported in case of Fe3O4-MNPs@Si@SO3H in first cycle of hydrolysis. Moreover, thus used acid-functionalised MNPs were magnetically separated and reused. In second cycle of hydrolysis, Fe3O4-MNPs@Si@SO3H showed 49.8% cellobiose conversion followed by Fe3O4-MNPs@Si@AS (45%) and Fe3O4-MNPs@Si@BCOOH (18.3%). However, similar pattern was reported in case of third cycle of hydrolysis. The proposed approach is considered as rapid and convenient. Moreover, reuse of acid-functionalised MNPs makes the process economically viable.


Assuntos
Celobiose/química , Nanopartículas de Magnetita/química , Ácidos Sulfônicos/química , Ácidos Carboxílicos/química , Celobiose/análise , Hidrólise , Espectroscopia de Infravermelho com Transformada de Fourier
15.
Chemistry ; 26(13): 2808-2812, 2020 Mar 02.
Artigo em Inglês | MEDLINE | ID: mdl-31823414

RESUMO

Bicyclo[1.1.0]butanes (BCBs) are highly strained carbocycles that have emerged as versatile synthetic tools, particularly for the construction of functionalized small molecules. This work reports two efficient pathways for the rapid preparation of over 20 structurally diverse BCB ketones, encompassing simple alkyl and aryl derivatives, as well as unprecedented amino acid, dipeptide, bioisostere, and bifunctional linchpin reagents currently inaccessible using literature methods. Analogues are readily forged in two steps and in high yields from simple carboxylic acids or through unsymmetrical ketone synthesis beginning with a convenient carbonyl dication equivalent. The utility of this novel toolbox of strained electrophiles for the selective modification of proteinogenic nucleophiles is highlighted.


Assuntos
Compostos Bicíclicos com Pontes/química , Butanos/química , Ácidos Carboxílicos/química , Catálise , Estrutura Molecular
16.
Food Chem ; 310: 125741, 2020 Apr 25.
Artigo em Inglês | MEDLINE | ID: mdl-31806389

RESUMO

Polyphenol oxidase (PPO), also known as tyrosinase and catechol oxidase, is the enzyme responsible for enzymatic browning in foods. It causes undesirable organoleptic, nutritional and colour changes. Here, we report the preparation of five nanomaterials and a study of their ability to modulate PPO enzyme activity. The materials consist of UVM-7 supports (a mesoporous silica material) modified with diverse functional groups (i.e. amine, carboxylic acid, isocyanate, alkane and pyridine). We also studied the PPO immobilisation capability of the materials. All the materials, except the carboxylic acid functionalised one, offer high PPO loading capabilities and the immobilisation speed increases with functionalisation. Nevertheless, only a minor effect of the inhibition of enzymatic browning was produced. Furthermore, the amine containing material was able to capture not only PPO, but also the oxidation products. Such behaviour was validated with fresh apple juice in which browning was avoided, even 90 min in the presence of oxygen at room temperature.


Assuntos
Catecol Oxidase/química , Catecol Oxidase/metabolismo , Sucos de Frutas e Vegetais , Nanoestruturas/química , Dióxido de Silício/química , Ácidos Carboxílicos/química , Ácido Edético/química , Enzimas Imobilizadas/química , Enzimas Imobilizadas/metabolismo , Malus/química , Oxirredução , Oxigênio/química , Oxigênio/metabolismo , Piridinas/química , Propriedades de Superfície
17.
Sci Total Environ ; 705: 135832, 2020 Feb 25.
Artigo em Inglês | MEDLINE | ID: mdl-31831231

RESUMO

The emission of per- and polyfluoroalkyl substances (PFASs) from municipal solid wastes (MSW) disposal raises concerns for their potential of long-term release and risks. In this study, the occurrence of PFASs was investigated in ambient air and leachate from seven MSW disposal facilities including three landfills, two incineration plants, and two MSW transfer stations in Tianjin, China. Mass loads of PFASs (≥C4) released to the atmosphere were estimated at 0.007-0.97 kg/y/site, which were much lower than those to leachate (0.04-1.3 kg/y/site), while emission to the atmosphere at landfills was more considerable. With total oxidizable precursor (TOP) assay, unknown C4-C12 perfluoroalkyl acids (PFAAs)-precursors were found contributing 10-97 mol% in leachate and accounting for additional 15%-43% mass loads. Using IC-Ba/Ag/H cartridges, trifluoroacetic acid (C2) and perfluoropropionic acid (C3) were recovered in leachate for TOP assay (62%-78%) and determined at dominant levels of 19-81 µg/L, which accounted for mass loads of 0.08-2.6 kg/y/site. Unknown C2-C3 PFAA-precursors contributed 12-93 mol% with mass loads of 0.10-3.0 kg/y/site. Overall, unknown C2-C12 PFAA-precursors remained contributing 0.35-68 mol% in biochemically treated leachate. This study emphasizes that the profiles of unknown PFAA-precursors released during MSW disposal are to be identified, which is essential for their environmental risk assessment.


Assuntos
Ácidos Carboxílicos/química , Eliminação de Resíduos , China , Monitoramento Ambiental , Fluorcarbonetos , Resíduos Sólidos , Instalações de Eliminação de Resíduos , Poluentes Químicos da Água
18.
Eur J Med Chem ; 186: 111883, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31761385

RESUMO

As part of a continuing study, we designed and synthesized four series of 1-phenylimidazole-4-carboxylic acid derivatives as xanthine oxidoreductase (XOR) inhibitors, evaluated their in vitro inhibitory potencies against XOR and hypouricemic effects in mice, and determined their structure-activity relationships (SARs). Most of the compounds exhibited in vitro XOR inhibition at the nanomolar level. In comparison to febuxostat (half-maximal inhibitory concentration [IC50] value of 7.0 nM), compounds Ie and IVa exhibited the most promising XOR inhibitory effects with IC50 values of 8.0 and 7.2 nM, respectively. In the potassium oxonate/hypoxanthine-induced acute and long-term hyperuricemia mouse models, compounds Ie and IVa displayed significant hypouricemic potencies (P < 0.05), that were slightly weaker than and similar to febuxostat, respectively. More interestingly, both compounds showed a capacity to improve kidney damage by decreasing creatinine and urea nitrogen levels compared to the long-term hyperuricemia mouse group (P < 0.05), while febuxostat showed no significant effect.


Assuntos
Ácidos Carboxílicos/farmacologia , Inibidores Enzimáticos/farmacologia , Imidazóis/farmacologia , Xantina Desidrogenase/antagonistas & inibidores , Animais , Ácidos Carboxílicos/síntese química , Ácidos Carboxílicos/química , Relação Dose-Resposta a Droga , Inibidores Enzimáticos/síntese química , Inibidores Enzimáticos/química , Hiperuricemia/induzido quimicamente , Hiperuricemia/tratamento farmacológico , Hiperuricemia/metabolismo , Imidazóis/síntese química , Imidazóis/química , Camundongos , Camundongos Endogâmicos ICR , Modelos Moleculares , Estrutura Molecular , Relação Estrutura-Atividade , Xantina Desidrogenase/metabolismo
19.
Anal Bioanal Chem ; 412(2): 499-506, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31807805

RESUMO

Although a massive research has been devoted on the exploration of noble metal-based nanozyme, less progress has been made in the investigation of palladium (Pd) nanozyme and the interaction between ions and Pd nanozyme. In this study, a new type of Pd nanozyme was prepared by a facile one-pot approach by using carboxylated chitosan as the stabilizer. Owing to the synergistic effect of carboxylated chitosan stabilized Pd nanoparticles (CC-PdNPs) can effectively catalyze the H2O2-mediated oxidation of 3,3',5,5'-tetramethylbenzidine sulfate (TMB) accompanied by a blue color change (oxidized TMB), indicating the peroxidase-like activity of CC-PdNPs. Furthermore, the Michaelis-Menten constants and catalytic stability of CC-PdNPs render them suitable for environmental analysis and bio-detection. Here, we found that while introducing the iodine ions (I-) into the reaction medium, the peroxidase-like activity of CC-PdNPs has been rapidly and effectively inhibited through the formation of Pd-I bond; thus, the active sites of PdNPs can be blocked by I-. Based on this specific inhibition by I-, a facile colorimetric assay has been performed for the detection of I- with an extremely low limit of detection (0.19 nM). Furthermore, the practicality of the proposed sensor also has been demonstrated in tap water, and the satisfactory recoveries were obtained. Our study not only demonstrated a novel Pd-based nanozyme but also provided guidance for I- sensing for environmental analysis, food inspection, and bio-detection. Graphical abstract.


Assuntos
Ácidos Carboxílicos/química , Quitosana/química , Colorimetria/instrumentação , Enzimas/química , Iodo/análise , Nanoestruturas/química , Paládio/química , Ânions , Limite de Detecção , Abastecimento de Água
20.
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
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