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1.
Nat Commun ; 11(1): 4557, 2020 09 11.
Artigo em Inglês | MEDLINE | ID: mdl-32917908

RESUMO

Why metalloenzymes often show dramatic changes in their catalytic activity when subjected to chemically similar but non-native metal substitutions is a long-standing puzzle. Here, we report on the catalytic roles of metal ions in a model metalloenzyme system, human carbonic anhydrase II (CA II). Through a comparative study on the intermediate states of the zinc-bound native CA II and non-native metal-substituted CA IIs, we demonstrate that the characteristic metal ion coordination geometries (tetrahedral for Zn2+, tetrahedral to octahedral conversion for Co2+, octahedral for Ni2+, and trigonal bipyramidal for Cu2+) directly modulate the catalytic efficacy. In addition, we reveal that the metal ions have a long-range (~10 Å) electrostatic effect on restructuring water network in the active site. Our study provides evidence that the metal ions in metalloenzymes have a crucial impact on the catalytic mechanism beyond their primary chemical properties.


Assuntos
Anidrases Carbônicas/química , Íons/química , Metaloproteínas/química , Metais/química , Sítios de Ligação , Anidrase Carbônica II/química , Anidrase Carbônica II/metabolismo , Anidrases Carbônicas/metabolismo , Catálise , Domínio Catalítico , Cobalto/química , Cobre/química , Cristalografia por Raios X , Humanos , Íons/metabolismo , Cinética , Metaloproteínas/metabolismo , Metais/metabolismo , Modelos Moleculares , Níquel/química , Conformação Proteica , Relação Estrutura-Atividade , Especificidade por Substrato , Zinco/química
2.
PLoS Pathog ; 16(8): e1008707, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32780778

RESUMO

Proteus mirabilis, a Gram-negative uropathogen, is a major causative agent in catheter-associated urinary tract infections (CAUTI). Mannose-resistant Proteus-like fimbriae (MR/P) are crucially important for P. mirabilis infectivity and are required for biofilm formation and auto-aggregation, as well as for bladder and kidney colonization. Here, the X-ray crystal structure of the MR/P tip adhesin, MrpH, is reported. The structure has a fold not previously described and contains a transition metal center with Zn2+ coordinated by three conserved histidine residues and a ligand. Using biofilm assays, chelation, metal complementation, and site-directed mutagenesis of the three histidines, we show that an intact metal binding site occupied by zinc is essential for MR/P fimbria-mediated biofilm formation, and furthermore, that P. mirabilis biofilm formation is reversible in a zinc-dependent manner. Zinc is also required for MR/P-dependent agglutination of erythrocytes, and mutation of the metal binding site renders P. mirabilis unfit in a mouse model of UTI. The studies presented here provide important clues as to the mechanism of MR/P-mediated biofilm formation and serve as a starting point for identifying the physiological MR/P fimbrial receptor.


Assuntos
Adesinas Bacterianas/metabolismo , Biofilmes , Proteínas de Fímbrias/metabolismo , Proteus mirabilis/metabolismo , Infecções Urinárias/microbiologia , Zinco/metabolismo , Adesinas Bacterianas/química , Adesinas Bacterianas/genética , Sequência de Aminoácidos , Proteínas de Fímbrias/química , Proteínas de Fímbrias/genética , Humanos , Infecções por Proteus/metabolismo , Infecções por Proteus/microbiologia , Proteus mirabilis/química , Proteus mirabilis/genética , Alinhamento de Sequência , Infecções Urinárias/metabolismo , Zinco/química
3.
Chemosphere ; 260: 127574, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32688316

RESUMO

Artisanal and small-scale gold mining (ASGM) operations are major contributors to the Philippines' annual gold (Au) output (at least 60%). Unfortunately, these ASGM activities lacked adequate tailings management strategies, so contamination of the environment is prevalent. In this study, soil contamination with copper (Cu), lead (Pb), zinc (Zn) and arsenic (As) due to ASGM activities in Nabunturan, Davao de Oro, Philippines was investigated. The results showed that ASGM-impacted soils had Cu, Pb, Zn and As up to 3.6, 83, 73 and 68 times higher than background levels, respectively and were classified as 'extremely' polluted (CD = 30-228; PLI = 5.5-34.8). Minerals typically found in porphyry copper-gold ores like pyrite, chalcopyrite, malachite, galena, sphalerite and goethite were identified by XRD and SEM-EDS analyses. Furthermore, sequential extraction results indicate substantial Cu (up to 90%), Pb (up to 50%), Zn (up to 65%) and As (up to 48%) partitioned with strongly adsorbed, weak acid soluble, reducible and oxidisable fractions, which are considered as 'geochemically mobile' phases in the environment. Although very high Pb and Zn were found in ASGM-impacted soils, they were relatively immobile under oxidising conditions around pH 8.5 because of their retention via adsorption to hydrous ferric oxides (HFOs), montmorillonite and kaolinite. In contrast, Cu and As release from the historic ASGM site samples exceeded the environmental limits for Class A and Class C effluents, which could be attributed to the removal of calcite and dolomite by weathering. The enhanced desorption of As at around pH 8.5 also likely contributed to its release from these soils.


Assuntos
Mineração , Poluentes do Solo/análise , Poluentes do Solo/química , Solo/química , Arsênico/análise , Arsênico/química , Cobre/análise , Cobre/química , Ouro/análise , Ferro/química , Compostos de Ferro/química , Chumbo/análise , Chumbo/química , Minerais/química , Filipinas , Sulfetos/química , Difração de Raios X , Zinco/análise , Zinco/química
4.
Chemosphere ; 260: 127583, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32698115

RESUMO

A series of superhydrophobic polycarbonate porous monoliths modified with metal organic framework (Z8/PC) were firstly fabricated through a facile thermally impacted non-solvent induced phase separation method for efficient selective oil/water separation. The performance of the monoliths on oil/water separation was evaluated in terms of selectivity, equilibrium adsorption capacity, corrosion resistance, kinetics, and circulation. The results showed that the use of ZIF-8 significantly compensated for the shortage of pure monolith. Compared with pure PC monolith, the hydrophobic angle of the Z8/PC-2 monolith promoted from 136.18° to 154.25° due to the micro-nano flower surface. Meanwhile, the Z8/PC-2 monolith displayed a more intricate and continuous interconnected 3D hierarchical micro-nano structure, which possessed the monolith a higher specific surface area of 146.84 m2 g-1 and porosity of 89.5%. What's more, more superior oil/water separation abilities of Z8/PC-2 monolith were manifested by the selective removal of oil or organic solvent from water within 30s, high equilibrium adsorption capacity, and excellent corrosion resistance. In addition, the ten-cycle regeneration of porous monoliths via centrifugation or evaporation displayed additional attractiveness. Therefore, porous Z8/PC monolith will be a promising candidate for the efficient selective oil/water separation of oil spills and organic solvents.


Assuntos
Estruturas Metalorgânicas/química , Nanoestruturas/química , Poluição por Petróleo/análise , Cimento de Policarboxilato/química , Águas Residuárias/química , Poluentes Químicos da Água/análise , Zinco/química , Adsorção , Interações Hidrofóbicas e Hidrofílicas , Modelos Teóricos , Porosidade
5.
Nat Commun ; 11(1): 2903, 2020 06 09.
Artigo em Inglês | MEDLINE | ID: mdl-32518257

RESUMO

Direct transfer of protons and electrons between two tandem reactions is still a great challenge, because overall reaction kinetics is seriously affected by diffusion rate of the proton and electron carriers. We herein report a host-guest supramolecular strategy based on the incorporation of NADH mimics onto the surface of a metal-organic capsule to encapsulate flavin analogues for catalytic biomimetic monooxygenations in conjunction with enzymes. Coupling an artificial catalysis and a natural enzymatic catalysis in the pocket of an enzyme, this host-guest catalyst-enzyme system allows direct proton and electron transport between two catalytic processes via NADH mimics for the monooxygenation of both cyclobutanones and thioethers. This host-guest approach, which involves the direct coupling of abiotic and biotic catalysts via a NADH-containing host, is quite promising compared to normal catalyst-enzyme systems, as it offers the key advantages of supramolecular catalysis in integrated chemical and biological synthetic sequences.


Assuntos
Biomimética , Oxigênio/química , Catálise , Domínio Catalítico , Cristalografia por Raios X , Transporte de Elétrons , Enzimas/química , Ligação de Hidrogênio , Íons , Cinética , Ligantes , NAD/química , Solventes/química , Zinco/química
6.
Int J Nanomedicine ; 15: 3921-3936, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32581537

RESUMO

Background: Mesoporous calcium-silicate nanoparticles (MCSNs) have good prospects in the medical field due to their great physicochemical characteristics, antibacterial activity and drug delivery capacity. This study was to analyze the antibiofilm activity and mechanisms of silver (Ag) and zinc (Zn) incorporated MCSNs (Ag/Zn-MCSNs) with different percentages of Ag and Zn. Methods: Ag/Zn(1:9, molar ratio)-MCSNs and Ag/Zn(9:1, molar ratio)-MCSNs were prepared and characterized. Endocytosis of nanoparticles by Enterococcus faecalis (E. faecalis) treated with Ag/Zn-MCSNs was observed using TEM to explore the antibacterial mechanisms. The antibiofilm activity of Ag/Zn-MCSNs with different ratios of Ag and Zn was tested by E. faecalis biofilm model in human roots. The human roots pretreated by different Ag/Zn-MCSNs were cultured with E. faecalis. Then, SEM and CLSM were used to observe the survival of E. faecalis on the root canal wall. Cytotoxicity of the nanoparticles was tested by CCK8 kits. Results: The Ag/Zn-MCSNs release Ag+ and destroy the cell membranes to kill bacteria. The MCSNs containing Ag showed antibacterial activity against E. faecalis biofilms in different degrees, and they can adhere to dentin surfaces to get a continuous antibacterial effect. However, MTA, MCSNs and Zn-MCSNs could not disrupt the bacterial biofilms obviously. MCSNs, Ag/Zn(1:1, molar ratio)-MCSNs and Ag/Zn(1:9)-MCSNs showed no obvious cytotoxicity, while Ag-MCSNs and Ag/Zn(9:1)-MCSNs showed cytotoxicity. Zn-MCSNs can slightly promote cell proliferation. Conclusion: Ag/Zn-MCSNs have good antibiofilm activity. They might achieve an appropriate balance between the antibacterial activity and cytotoxicity by adjusting the ratio of Ag and Zn. Ag/Zn-MCSNs are expected to be a new type of root canal disinfectant or sealer for root canal treatment.


Assuntos
Antibacterianos/farmacologia , Enterococcus faecalis/efeitos dos fármacos , Nanopartículas/química , Prata/química , Zinco/química , Animais , Antibacterianos/química , Biofilmes/efeitos dos fármacos , Compostos de Cálcio/química , Cavidade Pulpar/microbiologia , Dentina/efeitos dos fármacos , Endocitose/efeitos dos fármacos , Enterococcus faecalis/fisiologia , Infecções por Bactérias Gram-Positivas/prevenção & controle , Humanos , Camundongos , Osteoblastos/efeitos dos fármacos , Porosidade , Silicatos/química , Prata/farmacologia , Zinco/farmacologia
7.
Life Sci ; 256: 117993, 2020 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-32574664

RESUMO

Flavonoids are known for their wide range of bioactive properties including beneficial effect on bone formation. Their intense metal ion chelating capacity endorsed their nomination as a new biomaterial for biomedical applications. The present study examined the functional role of Kaemferal-Zinc(II) (Kaem-Zn) complex in bone formation, in vitro and in vivo. The cyto-compatibility assay confirmed that upto 25 µM of Kaem and Kaem-Zn complex was non-toxic. In fact, it facilitates ALP activity and accumulation of calcium in osteoblast; it was confirmed by Alizarin red and von Kossa staining. In addition to this, osteoblast markers, Runx2, type 1 col., ALP mRNAs expression, and osteocalcin and osteonectin secretory proteins level were also induced by the Kaem-Zn complex. Furthermore, bone forming ability of Kaem and Kaem-Zn was assessed by zebrafish model. The optimal concentration of Kaem and Kaem-Zn was determined by the viability assay of Zebrafish larvae. Osteoblasts distribution in scale, vertebrae and caudal fin ossification was studied by alizarin red staining accompanied by confocal imaging were carried out in adult zebrafish exposed to Kaem and Kaem-Zn complex. To sum up, our findings showed that Kaem promotes bone growth, and Kaem-Zn complex has further strengthened it. Kaem-Zn complex could be an effectively explored and used use in bone tissue engineering.


Assuntos
Quempferóis/administração & dosagem , Quempferóis/síntese química , Osteogênese/efeitos dos fármacos , Osteogênese/fisiologia , Zinco/administração & dosagem , Animais , Relação Dose-Resposta a Droga , Peixe-Zebra , Zinco/química
8.
Environ Monit Assess ; 192(6): 345, 2020 May 08.
Artigo em Inglês | MEDLINE | ID: mdl-32385719

RESUMO

Zinc is a toxic metal ion and is of importance in water and wastewater because it causes dizziness as well as lethargy when ingested by man. In the current study, the groundnut husk ash was investigated as a potential adsorbent for adsorption of zinc(II) ions from industrial wastewater. Groundnut husk ash was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and proximate analysis to identify the presence of the functional groups, surface morphology and the carbon content in the adsorbent respectively. To optimize the process parameters affecting the percentage removal of zinc(II) onto groundnut husk ash, the central composite design was used. The result of the optimization study showed an optimal percentage removal of 80.00%, with the optimal conditions of 1400 µm, 100 min, 25 °C, 40 mg/l and 20 mg for particle size, contact time, temperature, initial zinc concentration and adsorbent dosage respectively. The equilibrium data showed a better fit for Langmuir isotherm, when compared to Freundlich, Temkin and Dubinin-Radushkevich isotherms, with R2 of 0.965. The adsorption kinetics was best described by pseudo-second-order kinetics with R2 of 0.987. The thermodynamic study, on the other hand, showed a negative value of enthalpy change(∆H = - 27.021), indicating an exothermic as well as a spontaneous reaction, with the degree of spontaneity of the reaction ranging from - 55.487 ≤ ∆G ≤ - 56.427, which showed a corresponding increase in Gibb's free energy (∆G) with an increase in temperature.


Assuntos
Poluentes Químicos da Água , Purificação da Água , Zinco/química , Adsorção , Concentração de Íons de Hidrogênio , Cinética , Espectroscopia de Infravermelho com Transformada de Fourier , Temperatura , Termodinâmica , Águas Residuárias
9.
Food Chem ; 327: 127080, 2020 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-32454274

RESUMO

A hydrazone based Schiff base (SB) has been synthesized and investigated for the detection, quantification and degradation of selective organophosphates (i.e diethyl chlorophosphate, diethyl cyanophosphonate, tris (2-chloroethyl) phosphate and dichlorvos). The organophosphates (OPs) form a covalent bond with -OH groups of SB and form SB-OP which quenches emission signal at 533 nm. Therefore, it can be used for the spectrofluorimetric detection and quantification of OPs upto the detection limits of 10.2, 158.2, 10.3 and 122.7 nM, respectively. Besides, the SB-OP duo undergoes degradation to non-toxic species in the presence of Zn2+ ions. The mechanism of interaction between SB-OP-Zn2+ trio is investigated by spectrofluorometric, spectroscopic, chromatographic and spectrometric experiments. The optimized recognition and degradation protocols were found accurate and precise when applied to fruits, vegetable and soil samples. Overall, the developed protocols prove SB as highly sensitive, selective and recyclable 'pick and degrade' probe for the recognition and degradation of OPs.


Assuntos
Retardadores de Chama/análise , Frutas/química , Organofosfatos/química , Verduras/química , Zinco/química , Cátions Bivalentes , Fosfatos , Bases de Schiff/química
10.
Acta Crystallogr C Struct Chem ; 76(Pt 5): 476-482, 2020 05 01.
Artigo em Inglês | MEDLINE | ID: mdl-32367829

RESUMO

Reaction of N,N'-(cyclohexane-1,2-diylidene)bis(4-fluorobenzohydrazide), C20H18F2N4O2, (LF), with zinc chloride and mercury(II) chloride produced different types and shapes of neutral coordination complexes, namely, dichlorido[N,N'-(cyclohexane-1,2-diylidene)bis(4-fluorobenzohydrazide)-κ2N,O]zinc(II), [ZnCl2(C20H18F2N4O2)], (1), and dichlorido[N,N'-(cyclohexane-1,2-diylidene)bis(4-fluorobenzohydrazide)-κ4O,N,N',O']mercury(II), [HgCl2(C20H18F2N4O2)], (2). The organic ligand and its metal complexes are characterized using various techniques: IR, UV-Vis and nuclear magnetic resonance (NMR) spectroscopies, in addition to powder X-ray diffraction (PXRD), single-crystal X-ray crystallography and microelemental analysis. Depending upon the data from these analyses and measurements, a typical tetrahedral geometry was confirmed for zinc complex (1), in which the ZnII atom is located outside the bis(benzhydrazone) core. The HgII atom in (2) is found within the core and has a common octahedral structure. The in vitro antibacterial activities of the prepared compounds were evaluated against two different bacterial strains, i.e. gram positive Bacillus subtilis and gram negative Pseudomonas aeruginosa bacteria. The prepared compounds exhibited differentiated growth-inhibitory activities against these two bacterial strains based on the difference in their lipophilic nature and structural features.


Assuntos
Antibacterianos/síntese química , Antibacterianos/farmacologia , Cloretos/farmacologia , Mercúrio/química , Compostos de Zinco/farmacologia , Zinco/química , Antibacterianos/química , Cloretos/química , Complexos de Coordenação/química , Cristalografia por Raios X , Difração de Raios X , Compostos de Zinco/química
11.
Int J Nanomedicine ; 15: 2095-2118, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32273705

RESUMO

Purpose: Zinc (Zn), an essential trace element in the body, has stable chemical properties, excellent osteogenic ability and moderate immunomodulatory property. In the present study, a Zn-incorporated TiO2 nanotube (TNT) was fabricated on titanium (Ti) implant material. We aimed to evaluate the influence of nano-scale topography and Zn on behaviors of murine RAW 264.7 macrophages. Moreover, the effects of Zn-incorporated TNT surface-regulated macrophages on the behaviors and osteogenic differentiation of murine MC3T3-E1 osteoblasts were also investigated. Methods: TNT coatings were firstly fabricated on a pure Ti surface using anodic oxidation, and then nano-scale Zn particles were incorporated onto TNTs by the hydrothermal method. Surface topography, chemical composition, roughness, hydrophilicity, Zn release pattern and protein adsorption ability of the Zn-incorporated TiO2 nanotube surface were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), surface profiler, contact angle test, Zn release test and protein adsorption test. The cell behaviors and both pro-inflammatory (M1) and pro-regenerative (M2) marker gene and protein levels in macrophages cultured on Zn-incorporated TNTs surfaces with different TNT diameters were detected. The supernatants of macrophages were extracted and preserved as conditioned medium (CM). Furthermore, the behaviors and osteogenic properties of osteoblasts cultured in CM on various surfaces were evaluated. Results: The release profile of Zn on Zn-incorporated TNT surfaces revealed a controlled release pattern. Macrophages cultured on Zn-incorporated TNT surfaces displayed enhanced gene and protein expression of M2 markers, and M1 markers were moderately inhibited, compared with the LPS group (the inflammation model). When cultured in CM, osteoblasts cultured on Zn-incorporated TNTs showed strengthened cell proliferation, adhesion, osteogenesis-related gene expression, alkaline phosphatase activity and extracellular mineralization, compared with their TNT counterparts and the Ti group. Conclusion: This study suggests that the application of Zn-incorporated TNT surfaces may establish an osteogenic microenvironment and accelerate bone formation. It provided a promising strategy of Ti surface modification for a better applicable prospect.


Assuntos
Fatores Imunológicos/farmacologia , Macrófagos/efeitos dos fármacos , Nanotubos , Osteoblastos/efeitos dos fármacos , Osteogênese/efeitos dos fármacos , Zinco/farmacocinética , Animais , Diferenciação Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Meios de Cultivo Condicionados/farmacologia , Regulação da Expressão Gênica/efeitos dos fármacos , Macrófagos/imunologia , Camundongos , Microscopia Eletrônica de Varredura , Nanotubos/química , Osteoblastos/citologia , Osteogênese/genética , Espectroscopia Fotoeletrônica , Células RAW 264.7 , Propriedades de Superfície , Titânio/química , Difração de Raios X , Zinco/química
12.
Ecotoxicol Environ Saf ; 196: 110550, 2020 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-32247244

RESUMO

Iron/zinc (Fe/Zn), phosphoric acid (H3PO4) or in combination (Fe/Zn + H3PO4) modified sludge biochar (SBC) were prepared and tested in this study to adsorb fluoroquinolones antibiotics including ciprofloxacin (CIP), norfloxacin (NOR) and ofloxacin (OFL) from water. Fe/Zn + H3PO4-SBC had an increased surface area (SBET), total pore volume (Vtot), mesoporous volume (Vmes), pore diameter (Dp) and oxygen-containing functional groups. It exhibited superior adsorption performance for CIP, NOR and OFL with the maximum adsorption amount of 83.7, 39.3, 25.4 mg g-1, respectively. Pseudo-second kinetic and Freundlich isotherm model presented the better fitting. The results of models and characterization analysis in combination indicated that physisorption and chemisorption, including pore filling, hydrogen bonding, π-π interaction, electrostatic interaction and functional groups complexation on a heterogeneous surface were the dominant process and mechanism. Liquid film diffusion was the main rate-limiting step. The adsorption process of CIP, NOR and OFL onto Fe/Zn + H3PO4-SBC were a spontaneous endothermic process. This study demonstrated that Fe/Zn + H3PO4 modified SBC exhibited high adsorption capacity, which was a promising adsorbent for fluoroquinolones as well as for other antibiotics effective removal from waters.


Assuntos
Antibacterianos/análise , Carvão Vegetal/química , Fluoroquinolonas/análise , Esgotos/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Adsorção , Ferro/química , Cinética , Modelos Teóricos , Ácidos Fosfóricos/química , Propriedades de Superfície , Zinco/química
13.
Chemosphere ; 253: 126726, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32302906

RESUMO

We synthesized a novel material, namely palladized zero-valent zinc (Pd/ZVZ), and investigated its efficiency for the degradation of polybrominated diphenyl ethers (PBDEs). The plated Pd significantly enhances the degradation rate of PBDEs by ZVZ at the optimum loading of 1% by weight. In the Pd/ZVZ system, very few lower BDEs were accumulated during the degradation of 2,2',4,4'- tetrabromodiphenyl ether (BDE-47) and the final product is diphenyl ether, whereas the ZVZ system only debrominates BDE-47 to di-BDE and further debromination becomes very difficult. The degradation rates of BDEs by ZVZ greatly decreased with decreased bromination level, while in Pd/ZVZ system, the degradation rates of PBDEs did not show a significant difference. These indicate different mechanisms. This was confirmed by investigating the debromination pathways of the PBDEs in both systems. We determined that a H-transfer was the dominant mechanism in the Pd/ZVZ system. In addition, the reactivity of Pd/ZVZ to BDE-47 is pH-independent, which has a great advantage for various applications over ZVZ alone. Our study provides a new approach for the remediation of the PBDEs pollution.


Assuntos
Poluentes Ambientais/análise , Retardadores de Chama/análise , Éteres Difenil Halogenados/análise , Ferro/química , Paládio/química , Bifenil Polibromatos/análise , Zinco/química , Halogenação , Cinética , Tamanho da Partícula , Éteres Fenílicos/análise , Pós
14.
J Vis Exp ; (157)2020 03 19.
Artigo em Inglês | MEDLINE | ID: mdl-32250360

RESUMO

Chemical model complexes are prepared to represent the active site of an enzyme. In this protocol, a family of tridentate pincer ligand precursors (each possessing two sulfur and one nitrogen donor atom functionalities (SNS) and based on bis-imidazole or bis-triazole compounds) are metallated with CoCl2·6H2O to afford tridentate SNS pincer cobalt(II) complexes. Preparation of the cobalt(II) model complexes for liver alcohol dehydrogenase is facile. Based on a quick color change upon adding the CoCl2·6H2O to acetonitrile solution that contains the ligand precursor, the complex forms rapidly. Formation of the metal complex is complete after allowing the solution to reflux overnight. These cobalt(II) complexes serve as models for the zinc active site in liver alcohol dehydrogenase (LADH). The complexes are characterized using single crystal X-ray diffraction, electrospray mass spectrometry, ultra-violet visible spectroscopy, and elemental analysis. To accurately determine the structure of the complex, its single crystal structure must be determined. Single crystals of the complexes that are suitable for X-ray diffraction are then grown via slow vapor diffusion of diethyl ether into an acetonitrile solution that contains the cobalt(II) complex. For high quality crystals, recrystallization typically takes place over a 1 week period, or longer. The method can be applied to the preparation of other model coordination complexes and can be used in undergraduate teaching laboratories. Finally, it is believed that others may find this recrystallization method to obtain single crystals beneficial to their research.


Assuntos
Álcool Desidrogenase/química , Cobalto/química , Complexos de Coordenação/química , Fígado/enzimologia , Modelos Químicos , Cristalografia por Raios X , Imidazóis , Ligantes , Nitrogênio/química , Espectrometria de Massas por Ionização por Electrospray , Enxofre/química , Zinco/química
15.
Dalton Trans ; 49(19): 6249-6258, 2020 May 19.
Artigo em Inglês | MEDLINE | ID: mdl-32329503

RESUMO

Copper-based radiopharmaceuticals are of high interest these days owing to the decay properties of copper radioisotopes. In contrast, labeled zinc compounds have been less studied for applications in nuclear medicine. In this study, the stability of labeled zinc and copper complexes with two azacrown ether ligands was investigated and compared. Then, the in vitro and in vivo stability of the studied zinc complexes was demonstrated, with the complexes showing promise for biomedical applications. In contrast, analogous copper complexes quickly dissociated in the presence of serum proteins. Furthermore, a simple method for the production of radiochemically pure 65Zn was proposed, and the opportunity for its use as a surrogate radionuclide for research into potential zinc-containing radiopharmaceuticals was demonstrated.


Assuntos
Complexos de Coordenação/química , Cobre/química , Éteres de Coroa/química , Zinco/química , Animais , Complexos de Coordenação/sangue , Complexos de Coordenação/urina , Cristalografia por Raios X , Ligantes , Espectroscopia de Ressonância Magnética , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Conformação Molecular , Radioisótopos de Zinco/química
16.
Biofouling ; 36(3): 245-255, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-32326753

RESUMO

Dental plaque is a biofilm composed of a complex oral microbial community. The accumulation of plaque in the pit and fissures of dental elements often leads to the development of tooth decay (dental caries). Here, potent anti-biofilm materials were developed by incorporating zinc methacrylates or di-n-butyl-dimethacrylate-tin into the light-curable sealant and their physical, mechanical, and biological properties were evaluated. The data revealed that 5% di-n-butyl-dimethacrylate-tin (SnM 5%) incorporated sealant showed strong anti-biofilm efficacy against various single-species (Streptococcus mutans or Streptococcus oralis or Candida albicans) and S. mutans-C. albicans cross-kingdom dual-species biofilms without either impairing the mechanical properties of the sealant or causing cytotoxicities against mouse fibroblasts. The findings indicate that the incorporation of SnM 5% in the experimental pit and fissure self-adhesive sealant may have the potential to be part of current chemotherapeutic strategies to prevent the formation of cariogenic oral biofilms that cause dental caries.


Assuntos
Adesivos/farmacologia , Biofilmes/efeitos dos fármacos , Cárie Dentária/prevenção & controle , Selantes de Fossas e Fissuras/farmacologia , Zinco/química , Adesivos/química , Animais , Biofilmes/crescimento & desenvolvimento , Candida albicans/efeitos dos fármacos , Candida albicans/crescimento & desenvolvimento , Cárie Dentária/microbiologia , Humanos , Metacrilatos/química , Camundongos , Microbiota/efeitos dos fármacos , Selantes de Fossas e Fissuras/química , Streptococcus mutans/efeitos dos fármacos , Streptococcus mutans/crescimento & desenvolvimento , Streptococcus oralis/efeitos dos fármacos , Streptococcus oralis/crescimento & desenvolvimento
17.
Chemosphere ; 249: 126341, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32213393

RESUMO

Current mechanism studies in plant heavy metal tolerance do not consider the effects of different phenolic acids on the bioavailability of heavy metals and the comparison with antioxidant enzyme system in the hydroxyl radical scavenging capacity. In present study, by a set of pot culture experiments with adding cadmium (Cd) and zinc (Zn) to the sediments, the effects of different phenolic acids on the toxicity of Cd and Zn in Kandelia obovata and the dominant role in scavenging hydroxyl radicals were evaluated. The results showed that 100 mg kg-1 Zn treatment promoted the growth of plant under high concentrations of Cd and Zn stress. Under the stress of Cd and Zn, the phenolic acids were mainly metabolized by phenylpropanoid and flavonoid pathways, supplemented by shikimate and monolignol pathways in K. obovata. Eleven phenolic acids with different abilities of scavenging free radicals were detected in the plant, including pyrogallic acid (Gal), coumaric acid (Cou), protocatechuic acid (Pro), chlorogenic acid (Chl), 4-hydroxy benzoic acid (Hyd), caffeic acid (Caf), vanillic acid (Van), ferulic acid (Fer), benzoic acid (Ben), and salicylic acid (Sal). By adding phenolic acids to the sediments, chlorogenic acid (Chl), pyrogallic acid (Gal), cinnamic acid (Cin), and coumaric acid (Cou) behave as more reactive in changing Cd or Zn into residual fractions than the others, and chlorogenic acid (Chl), pyrogallic acid (Gal), ferulic acid (Fer) and caffeic acid (Caf) have higher ability of scavenging hydroxyl radicals than the others. In summary, K. obovata tends to synthesize phenolic acids with strong scavenging ability of free radicals and changing the bioavailability of Cd and Zn under high concentration of Cd and Zn stress. Phenolic acids played a crucial role in the mitigative effect of heavy metal stress via scavenging free radicals and involving in the process of Cd and Zn uptake and tolerance. The results will provide important theoretical basis and method guidance for mangrove wetland conservation.


Assuntos
Hidroxibenzoatos/química , Metais Pesados/química , Rhizophoraceae/fisiologia , Antioxidantes/metabolismo , Disponibilidade Biológica , Cádmio/química , Cádmio/metabolismo , Ácidos Cafeicos , Ácidos Cumáricos , Metais Pesados/metabolismo , Rhizophoraceae/efeitos dos fármacos , Áreas Alagadas , Zinco/química , Zinco/metabolismo
18.
Phys Chem Chem Phys ; 22(11): 6457-6467, 2020 Mar 21.
Artigo em Inglês | MEDLINE | ID: mdl-32152610

RESUMO

Chloracidobacterium (C.) thermophilum is a microaerophilic, chlorophototrophic species in the phylum Acidobacteria that uses homodimeric type-1 reaction centers (RC) to convert light energy into chemical energy using (bacterio)chlorophyll ((B)Chl) cofactors. Pigment analyses show that these RCs contain BChl aP, Chl aPD, and Zn2+-BChl aP' in the approximate ratio 7.1 : 5.4 : 1. However, the functional roles of these three different Chl species are not yet fully understood. It was recently demonstrated that Chl aPD is the primary electron acceptor. Because Zn2+-(B)Chl aP' is present at low abundance, it was suggested that the primary electron donor might be a dimer of Zn2+-BChl aP' molecules. In this study, we utilize isotopic enrichment and high-resolution two-dimensional (2D) 14N and 67Zn hyperfine sublevel correlation (HYSCORE) spectroscopy to demonstrate that the primary donor cation, P840+, in the C. thermophilum RC is indeed a Zn2+-BChl aP' dimer. Density functional theory (DFT) calculations and the measured electron-nuclear hyperfine parameters of P840+ indicate that the electron spin density on P840+ is distributed nearly symmetrically over two Zn2+-(B)Chl aP' molecules as expected in a homodimeric RC. To our knowledge this is the only example of a photochemical RC in which the Chl molecules of the primary donor are metallated differently than those of the antenna.


Assuntos
Acidobacteria/química , Bacterioclorofila A/química , Processos Fotoquímicos , Zinco/química , Metabolismo Energético , Luz , Análise Espectral
19.
Chemosphere ; 251: 126419, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32171133

RESUMO

Due to their release into the environment, zinc oxide nanoparticles (ZnO NPs) may come in contact with plants. In elevated concentrations, ZnO NPs induce reactive oxygen species (ROS) production, but the metabolism of reactive nitrogen species (RNS) and the consequent nitro-oxidative signalling has not been examined so far. In this work, Brassica napus and Brassica juncea seedlings were treated with chemically synthetized ZnO NPs (∼8 nm, 0, 25 or 100 mg/L). At low dose (25 mg/L) ZnO NP exerted a positive effect, while at elevated concentration (100 mg/L) it was toxic to both species. Additionally, B. juncea was more tolerant to ZnO NPs than B. napus. The ZnO NPs could enter the root cells due to their small (∼8 nm) size which resulted in the release of Zn2+ and subsequently increased Zn2+ content in the plant organs. ZnO NPs disturbed superoxide radical and hydrogen peroxide homeostasis and modulated ROS metabolic enzymes (NADPH oxidase, superoxide dismutase, ascorbate peroxidase) and non-enzymatic antioxidants (ascorbate and glutathione) inducing similar changes in oxidative signalling in both Brassica species. The homeostasis of RNS (nitric oxide, peroxynitrite and S-nitrosoglutathione) was also altered by ZnO NPs; however, changes in nitrosative signalling proved to be different in the examined species. Moreover, ZnO NPs triggered changes in protein carbonylation and nitration. These results suggest that ZnO NPs induce changes in nitro-oxidative signalling which may contribute to ZnO NP toxicity. Furthermore, difference in ZnO NP tolerance of Brassica species is more likely related to nitrosative than to oxidative signalling.


Assuntos
Brassica/fisiologia , Nanopartículas/toxicidade , Óxido de Zinco/toxicidade , Antioxidantes/metabolismo , Ascorbato Peroxidases/metabolismo , Brassica napus/metabolismo , Glutationa/metabolismo , Mostardeira/metabolismo , Nanopartículas/química , Oxirredução , Raízes de Plantas/metabolismo , Espécies Reativas de Nitrogênio , Espécies Reativas de Oxigênio/metabolismo , Plântula/efeitos dos fármacos , Transdução de Sinais/efeitos dos fármacos , Superóxido Dismutase/metabolismo , Zinco/química , Óxido de Zinco/química
20.
Chemosphere ; 252: 126516, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32217408

RESUMO

Contaminated mining sediment may cause environmental and human health risk due to potentially hazardous elements (PHEs) leaching into groundwater, especially under very acid (pH ≤ 3) conditions. The capability of Chinese loess to immobilise and retain copper (Cu), zinc (Zn), cadmium (Cd) and lead (Pb) from element contaminated mining sediment was explored by a column leaching experiment. Results showed that loess could effectively reduce Cu geomobility, and their leachate concentrations were lower than the quality standard (1.0 mg L-1) for ground water in China. The sierozem showed strong adsorption for Zn, Cd and Pb. The geomobility of Cu, Zn, Cd and Pb were affected by pH, electrical conductivity, organic matter and carbonate content of sediment/loess-amended sediment and sierozem. The long-term leaching of PHEs in loess-amended sediment may pose a potential risk to sierozem and groundwater in the region. This study highlights the need to develop a remediation technique to minimise the concentration level of hazardous elements in the mining sediment.


Assuntos
Monitoramento Ambiental , Substâncias Perigosas/análise , Mineração , Poluentes do Solo/análise , Adsorção , Cádmio , China , Cobre/análise , Água Subterrânea , Metais Pesados/análise , Zinco/química
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