Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 8.054
Filtrar
1.
Carbohydr Polym ; 260: 117840, 2021 May 15.
Artículo en Inglés | MEDLINE | ID: mdl-33712175

RESUMEN

Highly efficient shielding materials with an excellent electromagnetic wave absorption have gained increased attention. A new design was used to provide cellulose paper with a high electromagnetic shielding effectiveness (EMI SE) and improve the absorption performance by constructing an asymmetry sandwich structure that consisted of a dense nickel coating, Fe3O4 nanoparticles and a porous nickel layer. This unique structure caused a "multiple reflection-absorb-reflection" process when the electromagnetic waves penetrated the sample. The EMI absorption (SEA) and total SE (SET) increased with Fe3O4 absorption time increasing at 8.2-12.4 GHz, which was attributed to the synergistic effect between porous nickel layer and Fe3O4 nanoparticles. The SEA and SET of the sample with a thickness of 0.195 mm can achieved 18.57 and 41.88 dB, respectively. The design was conducive to improving the magnetic and corrosion resistance properties. This study provided a novel path to obtain a low cost and lightweight electromagnetic shielding material that can reduce secondary radiation.


Asunto(s)
Celulosa/química , Óxido Ferrosoférrico/química , Níquel/química , Protectores contra Radiación/química , Conductividad Eléctrica , Campos Electromagnéticos , Magnetismo , Nanopartículas del Metal/química , Porosidad , Propiedades de Superficie , Temperatura
2.
Nat Commun ; 12(1): 1868, 2021 03 25.
Artículo en Inglés | MEDLINE | ID: mdl-33767166

RESUMEN

It is very attractive yet underexplored to synthesize heterocyclic moieties pertaining to biologically active molecules from biomass-based starting compounds. Herein, we report an electrocatalytic Achmatowicz reaction for the synthesis of hydropyranones from furfuryl alcohols, which can be readily produced from biomass-derived and industrially available furfural. Taking advantage of photo-induced polymerization of a bipyridyl ligand, we demonstrate the facile preparation of a heterogenized nickel electrocatalyst, which effectively drives the Achmatowicz reaction electrochemically. A suite of characterization techniques and density functional theory computations were performed to aid the understanding of the reaction mechanism. It is rationalized that the unsaturated coordination sphere of nickel sites in our electrocatalyst plays an important role at low applied potential, not only allowing the intimate interaction between the nickel center and furfuryl alcohol but also enabling the transfer of hydroxide from nickel to the bound furfuryl alcohol.


Asunto(s)
Técnicas Electroquímicas/métodos , Furanos/química , 2,2'-Dipiridil/química , Biomasa , Catálisis , Níquel/química
3.
Food Chem ; 349: 129202, 2021 Jul 01.
Artículo en Inglés | MEDLINE | ID: mdl-33582540

RESUMEN

In this work, we propose a electrochemical enzyme-free glucose sensor by direct growth of conductive Ni/Co bimetal MOF on carbon cloth [Ni/Co(HHTP)MOF/CC] via a facile hydrothermal method. Due to excellent conductivity between Ni/Co(HHTP)MOF and CC, synergic catalytic effect of Ni and Co elements, the Ni/Co(HHTP)MOF/CC not only provides larger surface area and more effective active sites, but also boosts the charge transports and electro-catalytic performance. Under optimized conditions, the Ni/Co(HHTP)MOF/CC shows excellent activity with a linear range of 0.3 µM-2.312 mM, a low detection limit of 100 nM (S/N = 3), a fast response time of 2 s and a high sensitivity of 3250 µA mM-1 cm-2. Furthermore, the Ni/Co(HHTP)MOF/CC was successfully applied for the detection of glucose in real serum and beverages with competitive performances. This facile and cost-effective method provides a novel strategy for monitoring of glucose in biological and food samples.


Asunto(s)
Bebidas/análisis , Carbono/química , Cobalto/química , Electroquímica/instrumentación , Glucosa/análisis , Estructuras Metalorgánicas/química , Níquel/química , Glucemia/análisis , Catálisis , Conductividad Eléctrica , Humanos , Límite de Detección
4.
Nat Commun ; 12(1): 299, 2021 01 12.
Artículo en Inglés | MEDLINE | ID: mdl-33436637

RESUMEN

Chiral acetylenic derivatives are found in many bioactive compounds and are versatile functional groups in organic chemistry. Here, we describe an enantioselective nickel/Lewis acid-catalyzed asymmetric propargylic substitution reaction from simple achiral materials under mild condition. The introduction of a Lewis acid cocatalyst is crucial to the efficiency of the transformation. Notably, we investigate this asymmetric propargylic substitution reaction for the development of a range of structurally diverse natural products. The power of this strategy is highlighted by the collective synthesis of seven biologically active compounds: (-)-Thiohexital, (+)-Thiopental, (+)-Pentobarbital, (-)-AMG 837, (+)-Phenoxanol, (+)-Citralis, and (-)-Citralis Nitrile.


Asunto(s)
Alquinos/síntesis química , Ácidos de Lewis/química , Níquel/química , Preparaciones Farmacéuticas/síntesis química , Alquilación , Catálisis , Ésteres/química , Malonatos/química , Estereoisomerismo
5.
J Mater Chem B ; 9(4): 983-991, 2021 01 28.
Artículo en Inglés | MEDLINE | ID: mdl-33393541

RESUMEN

The major obstacle to developing nanozymes which are considered as promising alternatives to natural enzymes is their moderate performance, including poor affinity for substrates, low catalytic activity, and severe pH-dependence. To address these issues, herein, we synthesize ultrathin layered double hydroxide (LDH) nanosheets with a thickness of 1.4 nm and an average lateral size of 23 nm using a fast-precipitation method. Through the rational design of their compositions, it is found that NiMn LDHs exhibit the optimum peroxidase mimicking performance with excellent substrate affinity, high catalytic activity (a limit of detection (LOD) of 0.04 µM H2O2) and robustness in a wide pH range (from 2.6 to 9.0), which is superior to that of natural horseradish peroxidase (HRP). The main active centers are identified as Mn sites because of their strong Lewis acidity and low redox potential. Furthermore, a series of disposable paper bioassays based on NiMn LDH nanozymes are designed and used for the highly sensitive detection of H2O2 and ascorbic acid (AA).


Asunto(s)
Peroxidasa de Rábano Silvestre/química , Hidróxidos/química , Manganeso/química , Nanopartículas/química , Níquel/química , Papel , Ácido Ascórbico/análisis , Bioensayo , Técnicas Biosensibles , Peroxidasa de Rábano Silvestre/metabolismo , Peróxido de Hidrógeno/análisis , Hidróxidos/metabolismo , Manganeso/metabolismo , Níquel/metabolismo , Tamaño de la Partícula , Propiedades de Superficie
6.
Nat Commun ; 12(1): 412, 2021 01 18.
Artículo en Inglés | MEDLINE | ID: mdl-33462244

RESUMEN

gem-Difluoroalkene is a bioisostere of carbonyl group for improving bioavailability of drug candidates. Herein we develop structurally diverse 2,2-difluorovinyl benzoates (BzO-DFs) as versatile building blocks for modular synthesis of gem-difluoroenol ethers (44 examples) and gem-difluoroalkenes (2 examples) by Ni-catalyzed cross coupling reactions. Diverse BzO-DFs derivatives bearing sensitive functional groups (e.g., C = C, TMS, strained carbocycles) are readily prepared from their bromodifluoroacetates and bromodifluoroketones precursors using metallic zinc as reductant. With Ni(COD)2 and dppf [1,1'-bis(diphenylphosphino)ferrocene] as catalyst, reactions of BzO-DFs with arylboronic acids and arylmagnesium/alkylzinc reagents afforded the desired gem-difluoroenol ethers and gem-difluoroalkenes in good yields. The Ni-catalyzed coupling reactions features highly regioselective C(vinyl)-O(benzoate) bond activation of the BzO-DFs. Results from control experiments and DFT calculations are consistent with a mechanism involving initial oxidative addition of the BzO-DFs by the Ni(0) complex. By virtue of diversity of the BzO-DFs and excellent functional group tolerance, this method is amenable to late-stage functionalization of multifunctionalized bioactive molecules.


Asunto(s)
Química Farmacéutica/métodos , Éteres/síntesis química , Níquel/química , Benzoatos , Disponibilidad Biológica , Catálisis , Teoría Funcional de la Densidad , Estudios de Factibilidad , Estructura Molecular
7.
Food Chem ; 340: 127927, 2021 Mar 15.
Artículo en Inglés | MEDLINE | ID: mdl-32889214

RESUMEN

The effects of the support on the catalytic performance of supported Ni catalysts for the hydrogenation of soybean oil were examined. The turnover frequency (TOF) for Ni/TiO2 was greater than those for other Ni catalysts. Among the examined Ni catalysts, the Ni/TiO2 catalysts were effective for the reduction of trans fatty acid (TFA) levels (minimum 10.5%) in hydrogenated oils at an iodine value (IV) of 70, independent of the difference in the crystalline structure of TiO2. In addition, the oils hydrogenated by Ni/TiO2 had suitable properties for feedstock of margarine and vegetable shortening. The highly dispersed Ni nanoparticles formed by reduction of the NiO monolayer on the surface of TiO2 contribute to increasing the catalytic activity and to reducing the TFA levels.


Asunto(s)
Níquel/química , Aceite de Soja/química , Titanio/química , Ácidos Grasos Trans/química , Catálisis , Hidrogenación , Margarina , Nanopartículas del Metal
8.
Food Chem ; 336: 127675, 2021 Jan 30.
Artículo en Inglés | MEDLINE | ID: mdl-32795781

RESUMEN

The present study explores the biosorption potential of Pleurotus ostreatus immobilized magnetic iron oxide nanoparticles for solid-phase extractions of Ni(II) and Pb(II) ions from the water and food samples. It was characterized using FTIR, FE-SEM/EDX before and after analyte ions biosorption. Important operational parameters including the effect of initial pH, the flow rate of the sample solution and volume, amount of biomass and support material, interfering ions, best eluent, column reusability were studied. The biosorption capacities of fungus immobilized iron oxide nanoparticles were found as 28.6 and 32.1 mg g-1 for Ni(II) and Pb(II), respectively. The limit of detection (LOD) and limit of quantitation (LOQ) were achieved as 0.019 and 0.062 ng mL-1 for Ni(II), 0.041 and 0.14 ng mL-1 for Pb(II), respectively. The proposed method was validated by applying to certified reference materials and successfully applied for the preconcentrations of Ni(II) and Pb(II) ions from water and food samples by ICP-OES.


Asunto(s)
Plomo/aislamiento & purificación , Nanopartículas/química , Níquel/aislamiento & purificación , Pleurotus/química , Extracción en Fase Sólida/métodos , Contaminantes Químicos del Agua/aislamiento & purificación , Adsorción , Células Inmovilizadas , Compuestos Férricos/química , Análisis de los Alimentos/instrumentación , Análisis de los Alimentos/métodos , Contaminación de Alimentos/análisis , Concentración de Iones de Hidrógeno , Límite de Detección , Fenómenos Magnéticos , Níquel/química , Reproducibilidad de los Resultados , Extracción en Fase Sólida/instrumentación , Contaminantes Químicos del Agua/química
9.
Methods Mol Biol ; 2178: 329-344, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-33128759

RESUMEN

The bacterium Escherichia coli is still considered the first option as a microbial cell factory for recombinant protein production, and affinity chromatography is by far the preferred technique for initial purification after protein expression and cell lysis. In this chapter, we describe the methodology to express and purify recombinant proteins in E. coli tagged with the first two metal-binding proteins proposed as fusion partners. They are the small metal-binding protein SmbP and a mutant of the copper resistance protein CusF3H+. There are several advantages of using them as protein tags: they prevent the formation of inclusion bodies by increasing solubility of the target proteins, they enable purification by immobilized metal-affinity chromatography using Ni(II) ions with high purity, and because of their low molecular weights, excellent final yields are obtained for the target proteins after cleavage and removal of the protein tag. Here we also describe the protocol for the production of proteins in the periplasm of E. coli tagged with two SmbP variants that include the PelB or the TorA signal sequences for transport via the Sec or the Tat pathway, respectively. Based on these methods, we consider CusF3H+ and SmbP excellent alternatives as fusion proteins for the production of recombinant proteins in E. coli.


Asunto(s)
Cromatografía de Afinidad , Proteínas Transportadoras de Cobre , Proteínas de Escherichia coli , Escherichia coli/química , Níquel/química , Periplasma/química , Proteínas Transportadoras de Cobre/química , Proteínas Transportadoras de Cobre/genética , Escherichia coli/genética , Proteínas de Escherichia coli/química , Proteínas de Escherichia coli/genética , Periplasma/genética , Proteínas Recombinantes de Fusión/química , Proteínas Recombinantes de Fusión/genética , Proteínas Recombinantes de Fusión/aislamiento & purificación
10.
Methods Mol Biol ; 2178: 405-416, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-33128763

RESUMEN

Affinity chromatography is one way to measure the binding constants of a protein-ligand interaction. Here, we describe a method of measuring a binding constant using Ni-NTA resin to immobilize a His-tagged enzyme and the method of frontal analysis. While other methods of immobilization are possible, using the strong affinity interaction between His-tagged proteins and Ni-NTA supports results in a fast, easy, and gentle method of immobilization. Once the affinity support is created, frontal analysis can be used to measure the binding constant between the protein and various analytes.


Asunto(s)
Cromatografía de Afinidad , Histidina/química , Níquel/química , Proteínas Recombinantes de Fusión/química , Proteínas Recombinantes de Fusión/aislamiento & purificación , Histidina/genética , Proteínas Recombinantes de Fusión/genética
11.
Chem Commun (Camb) ; 57(4): 476-479, 2021 Jan 14.
Artículo en Inglés | MEDLINE | ID: mdl-33326521

RESUMEN

Replacing coenzyme F430, an Ni(i) F430-like cofactor derived from vitamin B12 (F430-B12) is revealed by DFT calculations to be able to catalyze methane formation in methyl-coenzyme M reductase with a barrier of 13.3 kcal mol-1, demonstrating the correctness of the route starting from vitamin B12. The structure-activity relationships of F430 and F430-B12 (especially the roles of the F ring) are discovered and several sources of inspiration promoting the application of F430-B12 are also obtained, coming closer to using F430 chemistry in man-made catalysis.


Asunto(s)
Metaloporfirinas/química , Oxidorreductasas/química , Vitamina B 12/análogos & derivados , Proteínas Arqueales/química , Proteínas Arqueales/metabolismo , Dominio Catalítico , Cristalografía por Rayos X , Teoría Funcional de la Densidad , Metaloporfirinas/metabolismo , Metano/biosíntesis , Methanobacteriaceae/enzimología , Modelos Químicos , Estructura Molecular , Níquel/química , Oxidorreductasas/metabolismo , Unión Proteica , Relación Estructura-Actividad , Termodinámica , Vitamina B 12/metabolismo
12.
J Vis Exp ; (165)2020 11 30.
Artículo en Inglés | MEDLINE | ID: mdl-33311433

RESUMEN

The development of chemically recyclable biopolymers offers opportunities within the pursuit of a circular economy. Chemically recyclable biopolymers make a positive effort to solve the issue of polymer materials in the disposal phase after the use phase. In this paper, the production of biobased semi-aromatic polyesters, which can be extracted entirely from biomass such as lignin, is described and visualized. The polymer poly-S described in this paper has thermal properties similar to certain commonly used plastics, such as PET. We developed a Green Knoevenagel reaction, which can efficiently produce monomers from aromatic aldehydes and malonic acid. This reaction has been proven to be scalable and has a remarkably low calculated E-factor. These polyesters with ligno-phytochemicals as a starting point show an efficient molecular recycling with minimal losses. The polyester poly(dihydrosinapinic acid) (poly-S) is presented as an example of these semi-aromatic polyesters, and the polymerization, depolymerization, and re-polymerization are described.


Asunto(s)
Lignina/química , Acetilación , Álcalis/química , Biomasa , Rastreo Diferencial de Calorimetría , Ácidos Cumáricos/química , Hidrogenación , Hidrólisis , Níquel/química , Polimerizacion , Espectroscopía de Protones por Resonancia Magnética
13.
Int J Nanomedicine ; 15: 8357-8367, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-33149580

RESUMEN

Introduction: Water contamination from dye effluents from various industrial sources has become a major challenge of the scientific community that is difficult to remediate using orthodox chemical and biological procedures. As such, there is a need for more suitable and cost-effective ways to treat such effluents. The present work describes a green-synthesis approach for preparation of three types of Ni-based oxides as effective catalytic materials to remove environmental pollutants. Metal oxide nanomaterials are cheap, abundant, and ecofriendly earth metals, and thus are promising materials for catalytic applications for environmental detoxification. Methods: An aqueous leaf extract of Prunus persica was used as a reducing agent for the synthesis of NiO, NiO-PdO, and NiO-ZnO nanoparticles (NPs). The leaf extract was treated with each metal-salt precursor based on sol-gel synthesis, and then the final procured NPs were analyzed by spectroscopic techniques for structural and morphological makeup. The pure NPs were further explored for catalytic degradation of hazardous aqueous dye at ambient conditions, instead of following any sophisticated experimental conditions. Results and Discussion: Morphological features revealed the pure formation of NiO, NiO-ZnO, and NiO-PdO NPs of size <100nm, characterized by X-ray diffraction spectroscopy and scanning electron microscopy. Catalytic tests with methyl orange revealed the remediation potential of synthesized material, showing the pseudo-first order kinetics (R 2<1) for NiO, NiO-PdO, and NiO-ZnO. NiO-ZnO gave outstanding results both in dark (R 2=0.88) and light (R 2=0.82) with degradation percentage of 99% (dark) in comparison with the other two catalysts. Moreover, excellent catalyst stability for NiO-ZnO) was observed, even after the fourth cycle, under both light and dark conditions and was separated easily during centrifugation. Conclusion: Although all three materials depicted the degradation potential with good stability, but the NiO-ZnO catalyst was the best catalytic material in the present investigation, with prominent degradation percentage, and can be considered as an efficient catalytic material. Thus, we conclude that P. persica-inspired catalytic material could pave the path toward environmental remediation, alternative clean energy, and other biological applications.


Asunto(s)
Biotecnología , Descontaminación , Nanopartículas/química , Nanotecnología , Níquel/química , Compuestos Azo/química , Catálisis , Colorantes/química , Cromatografía de Gases y Espectrometría de Masas , Nanopartículas/ultraestructura , Óxidos/química , Paladio/química , Espectrofotometría Ultravioleta , Espectroscopía Infrarroja por Transformada de Fourier , Espectrometría Raman , Difracción de Rayos X , Óxido de Zinc/química
14.
Nat Commun ; 11(1): 5101, 2020 10 09.
Artículo en Inglés | MEDLINE | ID: mdl-33037208

RESUMEN

Urease converts urea into ammonia and carbon dioxide and makes urea available as a nitrogen source for all forms of life except animals. In human bacterial pathogens, ureases also aid in the invasion of acidic environments such as the stomach by raising the surrounding pH. Here, we report the structure of urease from the pathogen Yersinia enterocolitica at 2 Å resolution from cryo-electron microscopy. Y. enterocolitica urease is a dodecameric assembly of a trimer of three protein chains, ureA, ureB and ureC. The high data quality enables detailed visualization of the urease bimetal active site and of the impact of radiation damage. The obtained structure is of sufficient quality to support drug development efforts.


Asunto(s)
Proteínas Bacterianas/química , Proteínas Bacterianas/metabolismo , Ureasa/química , Ureasa/metabolismo , Yersinia enterocolitica/enzimología , Dominio Catalítico , Microscopía por Crioelectrón , Lisina/metabolismo , Modelos Moleculares , Níquel/química , Níquel/metabolismo , Conformación Proteica , Dominios Proteicos , Agua/química
15.
J Oleo Sci ; 69(10): 1191-1198, 2020 Oct 07.
Artículo en Inglés | MEDLINE | ID: mdl-32908091

RESUMEN

The kinetics of catalytic transfer hydrogenation (CTH) of low-erucic-acid rapeseed oil using ammonium formate as a hydrogen donor over a Ni-Ag0.15/SBA15 catalyst were studied. Then, a kinetic model for the hydrogenation of low-erucic-acid rapeseed oil was established, and it was found that the reaction rate constants of hydrogenations of 9c-18:1 and 12c-18:1 oleic acid were 0.1262 and 0.0148, and the catalytic selectivity of linoleic acid was 2.04. For the catalyst loading of 0.23%, the hydrogenation temperature was 80°C, the ammonium formate concentration was 0.32 mol/50 mL, and the low-erucic-acid rapeseed oil was hydrogenated in 90 min; it was also found that the iodine value of low-erucic-acid rapeseed oil was 80 g I2/100 g, the oleic acid content was 65%, and the trans fatty acids (TFAs) content was only 6.7%. Therefore, CTH may be widely used in the modification of oils and fats.


Asunto(s)
Ácidos Erucicos , Cinética , Níquel/química , Aceite de Brassica napus/química , Plata/química , Catálisis , Formiatos/química , Calor , Hidrogenación , Yodo/análisis , Ácido Linoleico/análisis , Ácido Linoleico/química , Ácido Oléico/análisis , Ácido Oléico/química , Ácidos Grasos Trans/análisis
16.
Chemosphere ; 254: 126869, 2020 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-32957283

RESUMEN

This paper presents the results of Co(II) and Ni(II) extraction from model and real solutions using bis(2,4,4-trimethylpentyl)phosphinic acid (i.e. Cyanex 272) that are in agreement with waste-to-resources approach, i.e. the recovery of valuable components from wastes. The results from this study shows that, extraction using Cyanex 272 is an efficient method to recover Co(II) selectively from sulfate electrolytes obtained from the leaching of steel scraps of aircraft engines. The highest selectivity value (∼160) of Co(II) extraction over Ni(II) was obtained at a pH of 4.8, the lowest selectivity value (∼30) was observed at a pH of 5.5, while above this value the selectivity only increased slightly with increasing pH. A pH of 5.2 was selected as a compromise between Co(II) selectivity and Ni(II) amount in the organic phase. The essence of the investigation is to propose important parameters to extract Co(II) from real leach solutions, and to further recover valuable Co(II) from the loaded organic phase by stripping with 1 M H2SO4, thus producing an electrolyte of Co(II) for electrowinning - a possible alternative route for resource recovery. Small volume of the stripping phase (w/o = 1:5) used in this study, lead to an enrichment of sulfate electrolyte in Co(II), resulting in ∼50 g/dm3 of Co(II) in the solution, which is a great advantage of the approach proposed. Such a solution is a valuable source for the electrowinning of metallic cobalt, which can be used for the production of steel alloys, Li-ion batteries or catalysts.


Asunto(s)
Cobalto/química , Modelos Químicos , Níquel/química , Ácidos Fosfínicos/química , Suministros de Energía Eléctrica , Litio , Sulfatos
17.
Int J Nanomedicine ; 15: 6239-6245, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-32904074

RESUMEN

Background: As a key component in artificial intelligence computing, a transistor design is updated here as a potential alternative candidate for artificial synaptic behavior implementation. However, further updates are needed to better control artificial synaptic behavior. Here, an updated channel-electrode transistor design is proposed as an artificial synapse device; this structure is different from previously published designs by other groups. Methods: A semiconductor characterization system was used in order to simulate the artificial synaptic behavior and a scanning electron microscope was used to characterize the device structure. Results: It was found that the electrode added to the transistor channel had a strong impact on the representative transmission behavior of such artificial synaptic devices, such as excitatory postsynaptic current (EPSC) and the paired-pulse facilitation (PPF) index. Conclusion: These behaviors were tuned effectively and the impact of the channel electrode is explained by the combined effects of the joint channel electrode and conventional gate. The voltage dependence of such oxide devices suggests more capability to emulate various synaptic behaviors for numerous medical and non-medical applications. This is extremely helpful for future neuromorphic computational system implementation.


Asunto(s)
Electrofisiología/instrumentación , Neuronas/fisiología , Sinapsis/fisiología , Inteligencia Artificial , Electrodos , Electrofisiología/métodos , Diseño de Equipo , Oro/química , Microscopía Electrónica de Rastreo/instrumentación , Níquel/química , Semiconductores , Sinapsis/química , Transmisión Sináptica
18.
Nat Commun ; 11(1): 4557, 2020 09 11.
Artículo en Inglés | MEDLINE | ID: mdl-32917908

RESUMEN

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.


Asunto(s)
Anhidrasas Carbónicas/química , Iones/química , Metaloproteínas/química , Metales/química , Sitios de Unión , Anhidrasa Carbónica II/química , Anhidrasa Carbónica II/metabolismo , Anhidrasas Carbónicas/metabolismo , Catálisis , Dominio Catalítico , Cobalto/química , Cobre/química , Cristalografía por Rayos X , Humanos , Iones/metabolismo , Cinética , Metaloproteínas/metabolismo , Metales/metabolismo , Modelos Moleculares , Níquel/química , Conformación Proteica , Relación Estructura-Actividad , Especificidad por Sustrato , Zinc/química
19.
J Vis Exp ; (161)2020 07 28.
Artículo en Inglés | MEDLINE | ID: mdl-32804166

RESUMEN

Direct alteration of material structure/function through strain is a growing area of research that has allowed for novel properties of materials to emerge. Tuning material structure can be achieved by controlling an external force imposed on materials and inducing stress-strain responses (i.e., applying dynamic strain). Electroactive thin films are typically deposited on shape or volume tunable elastic substrates, where mechanical loading (i.e., compression or tension) can affect film structure and function through imposed strain. Here, we summarize methods for straining n-type doped titanium dioxide (TiO2) films prepared by a thermal treatment of a pseudo-elastic nickel-titanium alloy (Nitinol). The main purpose of the described methods is to study how strain affects electrocatalytic activities of metal oxide, specifically hydrogen evolution and oxygen evolution reactions. The same system can be adapted to study the effect of strain more broadly. Strain engineering can be applied for optimization of a material function, as well as for design of adjustable, multifunctional (photo)electrocatalytic materials under external stress control.


Asunto(s)
Elasticidad , Ensayo de Materiales , Níquel/química , Óxidos/química , Titanio/química , Aleaciones/química , Impedancia Eléctrica , Electroquímica , Electrodos , Oxidación-Reducción , Estrés Mecánico , Propiedades de Superficie , Resistencia a la Tracción
20.
Int J Nanomedicine ; 15: 5591-5602, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-32848389

RESUMEN

Introduction: The catalytic behavior of metal oxide nanomaterials for removal of organic pollutants under dark ambient conditions, without any additional stimulant, is of great interest among the scientific community. Methods: In this account, a nanomaterial of ternary metal oxides (MoO3-NiO-PdO-Pd) was synthesized via greener approach and was explored for degradation of methyl orange in water environment in dark ambient conditions in comparison with light conditions. The biochemical species of Abies pindrow were treated with aqueous solution of precursor's salt following sol gel synthesis strategy. We further attuned morphology and chemistry of MoO3-NiO-PdO-Pd by incorporating bioactive compounds of A. pindrow. Result and Discussion: The bio-fabricated MoO3-NiO-PdO-Pd revealed outstanding catalytic behavior with 92% degradation of methyl orange within 15 min in the dark at ambient temperature and pressure. Whereas, in the presence of visible light irritation, the catalyst degraded 97% of methyl orange in 15 min. According to the reaction kinetics of degradation, the catalysts illustrated good stability in light (R2=0.93) as well as in dark conditions (R2=0.98). Furthermore, the outstanding reusability and recyclability of the synthesized nanomaterial was observed for four runs of the experiment under dark and light conditions. Conclusion: Therefore, A. pindrow-synthesized MoO3-NiO-PdO-Pd nanocatalyst demonstrated significant potential for detoxification of organic pollutants for water remediation.


Asunto(s)
Nanoestructuras/química , Contaminantes Químicos del Agua/química , Abies/química , Compuestos Azo/química , Catálisis , Luz , Molibdeno/química , Níquel/química , Óxidos/química , Paladio/química , Presión , Temperatura
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA
...