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1.
Chemosphere ; 254: 126869, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32957283

RESUMO

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.


Assuntos
Cobalto/química , Modelos Químicos , Níquel/química , Ácidos Fosfínicos/química , Fontes de Energia Elétrica , Lítio , Sulfatos
2.
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
3.
J Chromatogr A ; 1626: 461358, 2020 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-32797837

RESUMO

In this study, the in-situ conversion of the synthesized Co-Al layered double hydroxide (Co-Al LDH) nanosheets to three dimensional hierarchical zeolitic imidazolate framework-67 (3D HZIF-67) was presented as a cost-effective, highly efficient, flexible and robust sorbent to carry out the microextraction process. In the first stage, the anodized aluminum foil was prepared electrochemically. Then, the Co-Al LDH precursor was constructed on the surface of the previously-prepared anodized Al foil applying in-situ formation approach. The procedure is followed by the conversion of the prepared Co-Al LDH film to 3D HZIF-67 film via a facile solvothermal method without adding cobalt salt. The in-situ prepared 3D HZIF-67-anodized Al was used for the thin film microextraction (TFME) of caffeine. The effective factors in TFME procedure were investigated and optimized through applying Central Composite Design (CCD). In the obtained optimal condition, the calibration curves for TFME-HPLC-UV of caffeine were linear in the range of 1-200 µg L-1 with the coefficient of determination (r2) higher than 0.9915. The limits of detection were 0.33 and 0.38 µg L-1, in water and urine matrices, respectively. Moreover, the enrichment factors (EFs) and absolute recoveries (%AR) were also calculated as 173-198 and 57.1%-65.3%, respectively. The inter-day relative standard deviations (RSDs) were evaluated as the method precision for 20 and 200 µg L-1 of spiked sample and were between 4.9-6.1%. The repeatability of the preparation step was investigated as batch-to-batch reproducibility and it was found to be 4.9%; as a result, the reproducibility of the presented film was approved. Finally, the proposed method was utilized to determine caffeine (as the model analyte) from different types of real samples including urine, coffee, beverage (Pepsi) and shampoo. The obtained recoveries (higher than 88%) confirmed the capability of the method for real sample analysis.


Assuntos
Alumínio/química , Cafeína/isolamento & purificação , Cromatografia Líquida de Alta Pressão/métodos , Cobalto/química , Hidróxidos/química , Imidazóis/química , Raios Ultravioleta , Zeolitas/química , Adsorção , Eletrodos , Limite de Detecção , Microscopia de Força Atômica , Porosidade , Reprodutibilidade dos Testes , Solventes/química , Propriedades de Superfície
4.
Acta Crystallogr C Struct Chem ; 76(Pt 7): 663-672, 2020 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-32624513

RESUMO

The reactivity of the cobalt(III) complexes dichlorido[tris(2-aminoethyl)amine]cobalt(III) chloride, [CoCl2(tren)]Cl, and dichlorido(triethylenetetramine)cobalt(III) chloride, [CoCl2(trien)]Cl, towards different amino acids (L-proline, L-asparagine, L-histidine and L-aspartic acid) was explored in detail. This study presents the crystal structures of three amino acidate cobalt(III) complexes, namely, (L-prolinato-κ2N,O)[tris(2-aminoethyl)amine-κ4N,N',N'',N''']cobalt(III) diiodide monohydrate, [Co(C5H8NO2)(C6H18N4)]I2·H2O, I, (L-asparaginato-κ2N,O)[tris(2-aminoethyl)amine-κ4N,N',N'',N''']cobalt(III) chloride perchlorate, [Co(C4H7N2O3)(C6H18N4)](Cl)(ClO4), II, and (L-prolinato-κ2N,O)(triethylenetetramine-κ4N,N',N'',N''')cobalt(III) chloride perchlorate, [Co(C4H7N2O3)(C6H18N4)](Cl)(ClO4), V. The syntheses of the complexes were followed by characterization using UV-Vis spectroscopy of the reaction mixtures and the initial rates of reaction were obtained by calculating the slopes of absorbance versus time plots. The initial rates suggest a stronger reactivity and hence greater affinity of the cobalt(III) complexes towards basic amino acids. The biocompatibility of the complexes was also assessed by evaluating the cytotoxicity of the complexes on cultured normal human fibroblast cells (WS1) in vitro. The compounds were found to be nontoxic after 24 h of incubation at concentrations up to 25 mM.


Assuntos
Cobalto/química , Complexos de Coordenação/química , Histidina/química , Aminoácidos/química , Cristalografia por Raios X , Ligantes , Percloratos/química
5.
Int J Nanomedicine ; 15: 4607-4623, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32636621

RESUMO

Aim: The interaction of NPs with biological systems may reveal useful details about their pharmacodynamic, anticancer and antibacterial effects. Methods: Herein, the interaction of as-synthesized Co3O4 NPs with HSA was explored by different kinds of fluorescence and CD spectroscopic methods, as well as molecular docking studies. Also, the anticancer effect of Co3O4 NPs against leukemia K562 cells was investigated by MTT, LDH, caspase, real-time PCR, ROS, cell cycle, and apoptosis assays. Afterwards, the antibacterial effects of Co3O4 NPs against three pathogenic bacteria were disclosed by antibacterial assays. Results: Different characterization methods such as TEM, DLS, zeta potential and XRD studies proved that fabricated Co3O4 NPs by sol-gel method have a diameter of around 50 nm, hydrodynamic radius of 177 nm with a charge distribution of -33.04 mV and a well-defined crystalline phase. Intrinsic, extrinsic, and synchronous fluorescence as well as CD studies, respectively, showed that the HSA undergoes some fluorescence quenching, minor conformational changes, microenvironmental changes as well as no structural changes in the secondary structure, after interaction with Co3O4 NPs. Molecular docking results also verified that the spherical clusters with a dimension of 1.5 nm exhibit the most binding energy with HSA molecules. Anticancer assays demonstrated that Co3O4 NPs can selectively lead to the reduction of K562 cell viability through the cell membrane damage, activation of caspase-9, -8 and -3, elevation of Bax/Bcl-2 mRNA ratio, ROS production, cell cycle arrest, and apoptosis. Finally, antibacterial assays disclosed that Co3O4 NPs can stimulate a promising antibacterial effect against pathogenic bacteria. Conclusion: In general, these observations can provide useful information for the early stages of nanomaterial applications in therapeutic platforms.


Assuntos
Antibacterianos/farmacologia , Antineoplásicos/farmacologia , Cobalto/química , Cobalto/farmacologia , Nanopartículas Metálicas/química , Óxidos/química , Óxidos/farmacologia , Albumina Sérica Humana/metabolismo , Antibacterianos/química , Antibacterianos/metabolismo , Antineoplásicos/química , Antineoplásicos/metabolismo , Apoptose/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Cobalto/metabolismo , Escherichia coli/efeitos dos fármacos , Humanos , Células K562 , Testes de Sensibilidade Microbiana , Simulação de Acoplamento Molecular , Óxidos/metabolismo , Pseudomonas aeruginosa/efeitos dos fármacos , Albumina Sérica Humana/química , Staphylococcus aureus/efeitos dos fármacos , Difração de Raios X
6.
J Chromatogr A ; 1624: 461229, 2020 Aug 02.
Artigo em Inglês | MEDLINE | ID: mdl-32540071

RESUMO

This work describes a sensitive and rapid analytical method for trace determination of polycyclic aromatic hydrocarbons (PAHs) in cosmetic samples. The proposed method is based on stir bar sorptive-dispersive microextraction (SBSDME). A magnetic composite made of CoFe2O4 magnetic nanoparticles embedded into reduced graphene oxide sheets is used as sorbent phase. After the extraction, the target analytes are desorbed in toluene and then analyzed by gas chromatography-mass spectrometry (GC-MS). The main parameters involved in the extraction procedure (i.e., composite amount, extraction time and desorption time) were evaluated and optimized to provide the best extraction efficiency. The method was successfully validated under the selected conditions, showing a linear range of at least up to 125 ng mL-1, instrumental and method limits of detection from 0.02 to 2.50 ng mL-1 and from 0.15 to 24.22 ng g-1, respectively, and relative standard deviations (RSD) below 10 % for all the target analytes. Standard addition combined with internal standard calibration was employed for quantification. The proposed method was successfully applied to the analysis of ten PAHs in four cosmetic products of different matrix. Several analytes between 14 and 464 ng g-1 were found, some of them prohibited in cosmetic products. This work expands the analytical potential of SBSDME technique to other analytes and to the use of new sorbent phases, showing the great versatility of this approach depending on the characteristics of the analytes.


Assuntos
Cosméticos/análise , Cromatografia Gasosa-Espectrometria de Massas , Grafite/química , Hidrocarbonetos Policíclicos Aromáticos/análise , Microextração em Fase Sólida/métodos , Cobalto/química , Compostos Férricos/química , Limite de Detecção , Magnetismo , Hidrocarbonetos Policíclicos Aromáticos/isolamento & purificação
7.
Chemosphere ; 259: 127431, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32593823

RESUMO

Designing heterostructure of photocatalyst as an efficient approach to boost visible light-driven photocatalytic degradation, we prepared a series of cobalt-based ZIF coordinated with defective TiO2-x, denoted as B-TiO2-x@ZIF-67 composites, through wrapping defective B-TiO2-x on ZIF-67 for promoting photocatalytic degradation efficiency of biphenyl A. The B-TiO2-x@ZIF-67 composites displayed superior photocatalytic performance to pure TiO2-x or ZIF-67 because of faster separation of photogenerated charge carriers and more suitable redox potentials. Such a novel photo-Fenton-like system composed of B-TiO2-x@ZIF-67/H2O2/visible light accelerated the peroxidative degradation of biphenyl An up to a removal efficiency of 95.30%, which is also higher than that of photocatalysis or Fenton-like reaction alone. In addition, the degradation efficiency of biphenyl A is unchanged after catalyst reuse of four cycles. Integrating the trapping experiments and electrochemical analysis, we found the oxygen vacancy on B-TiO2-x capturing the electrons to promote the separation of photogenerated charges, meanwhile the Co(II) in the composite decomposed hydrogen peroxide (H2O2) to produce more •OH radical. Both of them mutually boosted the removal efficiency. Finally, feasible degradation pathways of biphenyl A were proposed based on the assay of LC-MS spectrometry. This strategy offers a novel insight into fabrication of Co-ZIF-based TiO2-x materials and application to visible light-driven photocatalytic and Fenton-like degradation reaction.


Assuntos
Compostos Benzidrílicos/química , Cobalto/química , Fenóis/química , Catálise , Peróxido de Hidrogênio/química , Luz , Processos Fotoquímicos , Titânio/química
8.
Chemosphere ; 256: 127061, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32470729

RESUMO

Cobalt is part of vitamin B12, which is essential to maintain human health, and trace levels of cobalt ions are ubiquitous in water and soil environments. In this study, the destruction of 1,4-dioxane (1,4-D) by peroxymonosulfate (PMS) under the catalysis of trace levels of Co2+ was investigated under buffered conditions. The results showed that near 100% removal of 1,4-D was achieved after reaction for 6 and 10 min with 50 and 25 µg/L Co2+, respectively, in the presence of 5 mM phosphate ions. Mechanism studies revealed that radicals mediated the destruction of 1,4-D and sulfate radicals were the primary reactive species. The traces of Co2+ had the greatest reactivity for the catalysis of PMS in neutral environments (pH 7.0). However, pH 5.5 was observed to be the best condition for 1,4-D destruction, which was probably caused by the involvement of phosphate radicals. Common water components including chloride ions and bicarbonate ions were observed to have promoting and inhibiting effects, respectively, on the removal of 1,4-D. To further demonstrate the potential of Co2+-PMS in practical applications, we explored the simultaneous degradation of 20 antibiotics using trace levels of Co2+. The results showed that all the investigated antibiotics, except for lomefloxacin, could be efficiently degraded by Co2+-PMS with removal rates of greater than 97%. The findings from this study demonstrate the promise of using trace levels of cobalt for environmental remediation applications, even when high concentrations of phosphate ions are co-present.


Assuntos
Cobalto/química , Recuperação e Remediação Ambiental , Sulfatos/química , Catálise , Dioxanos , Oxirredução , Peróxidos
9.
Chemosphere ; 255: 126878, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32387727

RESUMO

Cobalt (Co) co-doped TiO2 photo-catalysis were synthesized, characterized and tested toward solar photocatalytic oxidation of toluene (TOL). A multi-technique approach was used to characterize and relate the photo-catalytic property to photo-oxidation performance. Adding Co to TiO2 significantly changed crystal size and surface morphology (surface area, pore-volume, and pore size), reduced the bandgap energy of TiO2 and improved the solar photo-oxidation of TOL. Up to 96.5% of TOL conversion (%TNconv) was achieved by using Co-TiO2 compared with 28.5% with naked TiO2. The maximum %TNconv was achieved at high hydraulic retention time (HRT) ≥ 100 s, Co content in the photo-catalyst of 5 wt% and relative humidity (%RH) of 50%. The mechanism of TOL solar oxidation was related to the concentration of OH• and •O2-. radicals produced from the generated electrons and holes on the surface of Co-TiO2. The products formed during the photo-catalytic oxidation of TOL were mainly CO2 and water, and minor concentration of benzene and benzaldehyde. Overall, the Co-TiO2 could be used as a potential photo-catalyst for the oxidation of toluene in gas-phase streams on an industrial scale.


Assuntos
Cobalto/química , Tolueno/química , Benzeno/química , Catálise , Oxirredução , Processos Fotoquímicos , Luz Solar , Titânio/química
10.
Chemosphere ; 256: 127160, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32464363

RESUMO

Bimetallic oxide nanomaterials have received much attention owing to their competing performances in heterogeneous catalysis. Herein, hierarchically porous cobalt-iron oxide nanosheets were successfully prepared using NaBH4 as a reductant and high concentration cetyl trimethylammonium bromide (CTAB) as a surfactant. Characterization results showed that the CTAB would induce the form of a bilayer structure while NaBH4 would promote the generation of enriched oxygen vacancies. As a result, the as-prepared Co1Fe1-300 exhibited high activity for activating peroxymonosulfate and achieved 100% phenol degradation within 30 min. This excellent catalytic activity can be attributed to its hierarchically porous structure, more active sites and oxygen vacancies. Co leaching test indicated that the Co1Fe1-300 exhibited excellent catalytic stability. Mechanistic studies suggested that two main degradation pathways were involved during phenol oxidation process, in which SO4•- played a significant role. This work may offer a novel strategy for the synthesis of high activity catalysts and a promising system for the remediation of environmental pollutant.


Assuntos
Cobalto/química , Recuperação e Remediação Ambiental/métodos , Compostos Férricos/química , Óxidos/química , Peróxidos/química , Fenol/análise , Fenol/metabolismo , Catálise , Ferro/química , Nanopartículas Metálicas/química , Compostos Orgânicos , Oxirredução , Fenóis , Porosidade
11.
Chemosphere ; 253: 126767, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32464763

RESUMO

Herein, the potential of bimetallic MOFs in catalytic ozonation was investigated for the first time. Three novel ozonation catalysts, i.e. cobalt-based, nickel-based and cobalt/nickel-based metal-organic frameworks (Co-MOF, Ni-MOF and Co/Ni-MOF), were synthesized, characterized by XRD, SEM, N2 sorption-desorption isotherms, FTIR and XPS, and applied in catalytic ozonation for atrazine removal. It was found that the catalysts showed outstanding performance in the catalytic ozonation, especially Co/Ni-MOF which was attributed to multiple metal sites, higher coordination unsaturation, metal centers with larger electron density, and better efficiency in electron transfer than its single-metal counterparts. Under specific experimental conditions, 47.8%, 67.0%, 75.5%, and 93.9% of atrazine were removed after adsorption and degradation in the ozonation system without catalyst, and the catalytic ozonation systems with Co-MOF, Ni-MOF and Co/Ni-MOF, respectively. Higher removal rates could be achieved by growing initial pH, increasing oxidant dosage and reducing pollutant concentration, while an excess of Co/Ni-MOF was not favorable for the catalytic ozonation. Surface hydroxyl groups and acid sites were considered as the critical catalytic sites on Co/Ni-MOF. From the results of EPR tests, O2·-, 1O2 and ·OH were ascertained as the main reactive species in the degradation. It was suspected that O2·- and H2O2 played important roles in the formation of ·OH and the cycle of Co(II)/Co(III) and Ni(II)/Ni(III). Additionally, Co/Ni-MOF displayed good stability and reusability in cycling experiments, ascribed to the enhancement of the porosity and pore hydrophobicity. Finally, based on MS/MS analysis at different reaction times, major degradation pathways for atrazine were proposed.


Assuntos
Atrazina/química , Adsorção , Catálise , Cobalto/química , Transporte de Elétrons , Peróxido de Hidrogênio , Estruturas Metalorgânicas/química , Níquel/química , Oxidantes , Ozônio/química , Espectrometria de Massas em Tandem
12.
Artigo em Inglês | MEDLINE | ID: mdl-32248046

RESUMO

The present study is the first report of in-situ growth and application of nanorods-flower like Co3O4 nanosorbent coated on the anodized aluminum substrate for thin film microextraction (TFME) approach. The flower like Co3O4 was successfully fabricated by conversion of Co-Al layered double hydroxide (LDH) precursor to Co3O4 using the simple calcinations process. The cheap and available aluminum foil was electrochemically anodized and used as a porous substrate. Response surface methodology (RSM) was explored for optimization step. Different acidic drugs, including: paracetamol, ibuprofen, aspirin and diclofenac were extracted from biological fluids in order to investigate the capability of the prepared sorbent. The extracted analytes were then analyzed using high performance liquid chromatography-ultraviolet detection (HPLC-UV). Under the optimized conditions, the limits of detection were between 0.2 and 1.7 µg L-1 in different selected matrices. The obtained limits of quantification were also calculated to be between 0.8 and 5.1 µg L-1 in the selected matrices. In addition the enrichment factors were also in the range of 105-169. Batch-to-batch reproducibility at 100 µg L-1 concentration level was also evaluated to be lower than 5.2% (n = 3). Finally, the method was successfully used for analysis of these compounds in the biological fluids.


Assuntos
Ácidos/urina , Alumínio/química , Cobalto/química , Nanotubos/química , Óxidos/química , Acetaminofen/urina , Adsorção , Adulto , Aspirina/urina , Cromatografia Líquida de Alta Pressão , Diclofenaco/urina , Técnicas Eletroquímicas , Eletrodos , Feminino , Humanos , Hidróxidos/química , Ibuprofeno/urina , Limite de Detecção , Masculino , Reprodutibilidade dos Testes , Microextração em Fase Sólida , Propriedades de Superfície
13.
Nat Protoc ; 15(5): 1760-1774, 2020 05.
Artigo em Inglês | MEDLINE | ID: mdl-32296151

RESUMO

The direct cleavage of otherwise inert C-H bonds has emerged as a sustainable approach for organic synthesis; in contrast to other approaches, these reactions result in the formation of fewer undesired by-products and do not require pre-functionalization steps. In recent years, oxidative C-H/N-H alkyne annulations and C-H oxygenations were realized by 3d metals. Unfortunately, most of these reactions require stoichiometric amounts of often toxic chemical oxidants. This protocol provides a general method for cobaltaelectro-catalyzed C-H activations of benzamides. Here, anodic oxidation obviates the need for a chemical oxidant and uses 10-20% of a more environmentally benign, inexpensive catalyst. We outline a detailed and precise description of the designed electrolytic cell for metallaelectrocatalysis, including readily available electrode materials and electrode holders. The custom-made device is further compared with the commercially available and standardized ElectraSyn 2.0 electrochemistry kit. As example applications of this approach, we describe cobaltaelectro-catalyzed C-H activation protocols for the direct C-H oxygenation of benzamides and resource-economical synthesis of isoquinolones. The cobaltaelectrocatalysis setup and reaction take about 17 h, while an additional 5 h have to be anticipated for workup and chromatographic purification. The methods described herein feature broad functional group tolerance, operational simplicity, low waste-product formation and an overall exceptional level of resource economy.


Assuntos
Benzamidas/química , Técnicas de Química Sintética/métodos , Cobalto/química , Técnicas Eletroquímicas/métodos , Catálise , Oxirredução
14.
Chemistry ; 26(34): 7595-7601, 2020 Jun 18.
Artigo em Inglês | MEDLINE | ID: mdl-32302020

RESUMO

We propose post-metalation modification as a useful strategy to control the guest recognition behavior of a metal-containing macrocyclic host. This is based on the ligand exchange of the axial ligands of a cobalt(III) dinuclear macrocyclic host, [LCo2 X4 ]2+ (X=axial amine ligand). Four piperidine ligands in [LCo2 (pip)4 ]2+ (pip=piperidine) were site-selectively replaced with primary amines. The competitive experiments revealed that the order of the affinity toward the cobalt centers in [LCo2 X4 ]2+ is primary amine > secondary amine > tertiary amine and that the piperidine-coordinating complex, [LCo2 (pip)4 ]2+ , was reasonably reactive among the isolable complexes. Indeed, two piperidine ligands at the diagonal positions in [LCo2 (pip)4 ]2+ were site-selectively replaced with pyridine or acetate ion. The replacement of piperidine with acetate ion significantly enhanced the recognition ability towards Na+ .


Assuntos
Aminas/química , Cobalto/química , Complexos de Coordenação/química , Piridinas/química , Complexos de Coordenação/síntese química , Cristalografia por Raios X , Ligantes , Metais , Estrutura Molecular
15.
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
16.
Nat Protoc ; 15(4): 1313-1337, 2020 04.
Artigo em Inglês | MEDLINE | ID: mdl-32203487

RESUMO

Reductive aminations are an essential class of reactions widely applied for the preparation of different kinds of amines, as well as a number of pharmaceuticals and industrially relevant compounds. In such reactions, carbonyl compounds (aldehydes, ketones) react with ammonia or amines in the presence of a reducing agent and form corresponding amines. Common catalysts used for reductive aminations, especially for the synthesis of primary amines, are based on precious metals or Raney nickel. However, their drawbacks and limited applicability inspired us to look for alternative catalysts. The development of base-metal nanostructured catalysts is highly preferable and is crucial to the advancement of sustainable and cost-effective reductive amination processes. In this protocol, we describe the preparation of carbon-supported cobalt-based nanoparticles as efficient and practical catalysts for synthesis of different kinds of amines by reductive aminations. Template synthesis of a cobalt-triethylenediamine-terephthalic acid metal-organic framework on carbon and subsequent pyrolysis to remove the organic template resulted in the formation of supported single cobalt atoms and nanoparticles. Applying these catalysts, we have synthesized structurally diverse benzylic, aliphatic and heterocyclic primary, secondary and tertiary amines, including pharmaceutically relevant products, starting from inexpensive and easily accessible carbonyl compounds with ammonia, nitro compounds or amines and molecular hydrogen. To prepare this cobalt-based catalyst takes 26 h, and the reported catalytic reductive amination reactions can be carried out within 18-28 h.


Assuntos
Aminas , Técnicas de Química Sintética/métodos , Cobalto/química , Nanopartículas Metálicas/química , Aminação , Aminas/síntese química , Aminas/química , Estruturas Metalorgânicas/química
17.
Biochemistry ; 59(12): 1289-1297, 2020 03 31.
Artigo em Inglês | MEDLINE | ID: mdl-32167292

RESUMO

Cobalt-mimochrome VI*a (CoMC6*a) is a synthetic mini-protein that catalyzes aqueous proton reduction to hydrogen (H2). In buffered water, there are multiple possible proton donors, complicating the elucidation of the mechanism. We have found that the buffer pKa and sterics have significant effects on activity, evaluated via cyclic voltammetry (CV). Protonated buffer is proposed to act as the primary proton donor to the catalyst, specifically through the protonated amine of the buffers that were tested. At a constant pH of 6.5, catalytic H2 evolution in the presence of buffer acids with pKa values ranging from 5.8 to 11.6 was investigated, giving rise to a potential-pKa relationship that can be divided into two regions. For acids with pKa values of ≤8.7, the half-wave catalytic potential (Eh) changes as a function of pKa with a slope of -128 mV/pKa unit, and for acids with pKa of ≥8.7, Eh changes as a function of pKa with a slope of -39 mV/pKa unit. In addition, a series of buffer acids were synthesized to explore the influence of steric bulk around the acidic proton on catalysis. The catalytic current in CV shows a significant decrease in the presence of the sterically hindered buffer acids compared to those of their parent compounds, also consistent with the added buffer acid acting as the primary proton donor to the catalyst and showing that acid structure in addition to pKa impacts activity. These results demonstrate that buffer acidity and structure are important considerations when optimizing and evaluating systems for proton-dependent catalysis in water.


Assuntos
Cobalto/química , Deuteroporfirinas/química , Hidrogênio/química , Metaloproteínas/química , Prótons , Tampões (Química) , Catálise , Concentração de Íons de Hidrogênio , Água/química
18.
Biochemistry ; 59(10): 1124-1136, 2020 03 17.
Artigo em Inglês | MEDLINE | ID: mdl-32125848

RESUMO

ATP:Co(I)rrinoid adenosyltransferases (ACATs) catalyze the transfer of the adenosyl moiety from co-substrate ATP to a corrinoid substrate. ACATs are grouped into three families, namely, CobA, PduO, and EutT. The EutT family of enzymes is further divided into two classes, depending on whether they require a divalent metal ion for activity (class I and class II). To date, a structure has not been elucidated for either class of the EutT family of ACATs. In this work, results of bioinformatics analyses revealed several conserved residues between the C-terminus of EutT homologues and the structurally characterized Lactobacillus reuteri PduO (LrPduO) homologue. In LrPduO, these residues are associated with ATP binding and formation of an intersubunit salt bridge. These residues were substituted, and in vivo and in vitro data support the conclusion that the equivalent residues in the metal-free (i.e., class II) Listeria monocytogenes EutT (LmEutT) enzyme affect ATP binding. Results of in vivo and in vitro analyses of LmEutT variants with substitutions at phenylalanine and tryptophan residues revealed that replacement of the phenylalanine residue at position 72 affected access to the substrate-binding site and replacement of a tryptophan residue at position 238 affected binding of the Cbl substrate to the active site. Unlike the PduO family of ACATs, a single phenylalanine residue is not responsible for displacement of the α-ligand. Together, these data suggest that while EutT enzymes share a conserved ATP-binding motif and an intersubunit salt bridge with PduO family ACATs, class II EutT family ACATs utilize an unidentified mechanism for Cbl lower-ligand displacement and reduction that is different from that of PduO and CobA family ACATs.


Assuntos
Corrinoides/metabolismo , Listeria monocytogenes/enzimologia , Aciltransferases/metabolismo , Trifosfato de Adenosina/metabolismo , Aldeído Oxirredutases/genética , Aldeído Oxirredutases/metabolismo , Aldeído Oxirredutases/ultraestrutura , Alquil e Aril Transferases/metabolismo , Proteínas de Bactérias/química , Sítios de Ligação , Catálise , Domínio Catalítico , Cobalto/química , Cobamidas/metabolismo , Cinética , Lactobacillus reuteri/metabolismo , Listeria monocytogenes/genética , Listeria monocytogenes/metabolismo , Modelos Moleculares , Mutação , Transferases/metabolismo
19.
Environ Pollut ; 259: 113874, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32032982

RESUMO

Pieces of glass as solid wastes were recycled in the synthesis of highly order MCM-41 that decorated by green fabricated Co3O4 nanoparticles using the green extract of green tea leaves forming novel green nano-composite. The synthetic Co3O4/MCM-41 exhibit high surface area, low bandgap energy (1.63 eV), and typical spherical morphology decorated by Co3O4 nanoparticles. The composite was evaluated as green photocatalyst in effective oxidation of methyl parathion pesticide in the presence of a visible light source. The degradation results revealed complete removal of 50 mg/L and 100 mg/L after 60 min and 90 min, respectively using 0.25 of the catalyst at pH 8. The detection of the TOC in the treated methyl parathion solution gives strong indications about the formation of organic intermediate compounds during the oxidation steps. The main detected intermediate compound are C6H5OH(NO2), C6H5OH, (CH3O)3P(S), C6H4(OH)2, C6H3(OH)3, C6H4(NH2)OP(O)(OCH3)2, (CH3O)2P(O)OH, (CH2)2C(OH)OH(CHO)OC(O), and HO2C(CH2)2C(O)CHO. The detected intermediate compounds converted into SO42-, PO43-, NO3-, and CO2 under the extensive photocatalytic of them over Co3O4/MCM-41. The oxidizing species trapping test verified the controlling of the methyl parathion degradation pathway by the hydroxyl radicals. Finally, the composite showed significant reusability properties and applied five times in the oxidation of methyl parathion with considerable degradation percentages.


Assuntos
Cobalto , Metil Paration , Nanopartículas , Óxidos , Praguicidas , Dióxido de Silício , Purificação da Água , Água , Cobalto/química , Vidro/química , Metil Paration/química , Nanopartículas/química , Oxirredução , Óxidos/química , Praguicidas/química , Dióxido de Silício/química , Água/química , Purificação da Água/métodos
20.
PLoS One ; 15(2): e0228483, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32027722

RESUMO

The aim of this study was to select a candidate deep-sea amphipod species suitable for connectivity analyses in areas around cobalt-rich ferromanganese crusts (CRCs). We applied DNA barcoding based on the mitochondrial protein-coding gene, cytochrome c oxidase subunit I (COI), to specimens collected from the Xufu Guyot (the JA06 Seamount) off southeastern Minami-Torishima Island in the North Pacific, where CRCs are distributed. We used baited traps to collect 37 specimens. Comparison of COI sequences with public reference databases (GenBank, BOLD) showed that almost all of the specimens belonged to the superfamily Lysianassoidea, which is known to be ubiquitous in deep-sea areas. In a molecular taxonomic analysis of these sequences, we detected 11 clades. One of these clades (group 9) composed of 18 sequences and was identified by DNA barcoding as a putative species belonging to Abyssorchomene, which has been reported from the New Hebrides Trench in the South Pacific. We considered this species to be a candidate for connectivity analysis and analyzed its genome by restriction site-associated DNA sequencing. The results showed that the genetic variation in this species is adequate for analyzing connectivity patterns in CRC areas in the future.


Assuntos
Anfípodes/classificação , Anfípodes/genética , Cobalto/química , Código de Barras de DNA Taxonômico/métodos , Sedimentos Geológicos/química , Ferro/química , Manganês/química , Animais , Variação Genética , Japão , Oceanos e Mares , Filogenia , Análise de Sequência de DNA/veterinária , Especificidade da Espécie , Vanuatu
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