Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 5.778
Filtrar
1.
Molecules ; 26(17)2021 Aug 27.
Artigo em Inglês | MEDLINE | ID: mdl-34500638

RESUMO

The effect of humidity on sheep wool during irradiation by an accelerated electron beam was examined. Each of the samples with 10%, 53%, and 97% relative humidity (RH) absorbed a dose of 0, 109, and 257 kGy, respectively. After being freely kept in common laboratory conditions, the samples were subjected to batch Co(II) sorption experiments monitored with VIS spectrometry for different lapses from electron beam exposure. Along with the sorption, FTIR spectral analysis of the wool samples was conducted for cysteic acid and cystine monoxide, and later, the examination was completed, with pH measuring 0.05 molar KCl extract from the wool samples. Besides a relationship to the absorbed dose and lapse, the sorptivity results showed considerable dependence on wool humidity under exposure. When humidity was deficient (10% RH), the sorptivity was lower due to limited transformation of cystine monoxide to cysteic acid. The wool pre-conditioned at 53% RH, which is the humidity close to common environmental conditions, demonstrated the best Co(II) sorptivity in any case. This finding enables the elimination of pre-exposure wool conditioning in practice. Under excessive humidity of 97% RH and enough high dose of 257 kGy, radiolysis of water occurred, deteriorating the sorptivity. Each wool humidity, dose, and lapse showed a particular scenario. The time and humidity variations in the sorptivity for the non-irradiated sample were a little surprising; despite the absence of electron irradiation, relevant results indicated a strong sensitivity to pre-condition humidity and lapse from the start of the monitoring.


Assuntos
Cobalto/química , Íons/química , Ovinos/metabolismo , Lã/química , Adsorção/fisiologia , Animais , Cistina/química , Elétrons , Umidade , Água/química
2.
Inorg Chem ; 60(17): 12681-12684, 2021 Sep 06.
Artigo em Inglês | MEDLINE | ID: mdl-34382784

RESUMO

Aquacobalamin binds hydrogen peroxide reversibly to form a cobalt(III) hydroperoxo adduct with a 0.25 mM dissociation constant, as evidenced by UV-vis absorption spectroscopy and corroborated by NMR, Raman spectroscopy, stopped-flow UV-vis measurements, and density functional theory calculations.


Assuntos
Peróxido de Hidrogênio/química , Vitamina B 12/análogos & derivados , Cobalto/química , Teoria da Densidade Funcional , Espectroscopia de Ressonância Magnética , Modelos Químicos , Espectrofotometria Ultravioleta , Análise Espectral Raman , Vitamina B 12/química
3.
ACS Appl Mater Interfaces ; 13(27): 31799-31807, 2021 Jul 14.
Artigo em Inglês | MEDLINE | ID: mdl-34197068

RESUMO

Catalytic conversion of a biomass derivative (levulinic acid, LA) to a high value-added product (γ-valerolactone, GVL) has attracted much attention, in which the control of catalytic selectivity plays an important role. Herein, a stepwise method was developed to prepare Co-MoOx catalysts via topological transformation (calcination reduction) from layered double hydroxide (Mo/CoAl-LDH) precursors. X-ray diffraction, high-resolution transmission electron microscopy, and hydrogen temperature-programmed reduction demonstrate the formation of MoOx-decorated Co structures of Co-MoOx samples. Remarkably, the sample that is reduced at 500 °C is featured with the most abundant interfacial Coδ+ (denoted as Co-MoOx-500), which exhibits an excellent catalytic performance toward the hydrodeoxygenation (HDO) reaction of several biomass-derived platform molecules (furfural, FAL; succinic acid, SA; 5-hydroxymethyl-furfural, HMF; and levulinic acid, LA). Especially, this optimal catalyst displays a high yield (99%) toward the HDO reaction of LA to GVL, which stands at the highest level among non-noble metal catalysts. The combination of in situ FT-IR characterization and theoretical calculation further confirms that interfacial Coδ+ sites in Co-MoOx-500 act as adsorption active sites for the polarization of a C═O bond in an LA molecule, which simultaneously promotes C═O hydrogenation and C-O cleavage. Moreover, the MoOx overlayer suppresses the formation of byproducts by covering the Co0 sites. This work offers a cost-effective and efficient catalyst, which can be potentially applied in catalytic conversion of biomass-derived platform molecules.


Assuntos
Biomassa , Cobalto/química , Ácidos Levulínicos/química , Tilidina/química , Catálise , Hidrogenação , Temperatura
4.
Molecules ; 26(12)2021 Jun 14.
Artigo em Inglês | MEDLINE | ID: mdl-34198604

RESUMO

Two penta-coordinated [Co(MorphBPT)Cl2]; 1 and [Co(PipBPT)Cl2]; 2 complexes with the bis-pyrazolyl-s-triazine pincer ligands MorphBPT and PipBPT were synthesized and characterized. Both MorphBPT and PipBPT act as NNN-tridentate pincer chelates coordinating the Co(II) center with one short Co-N(s-triazine) and two longer Co-N(pyrazole) bonds. The coordination number of Co(II) is five in both complexes, and the geometry around Co(II) ion is a distorted square pyramidal in 1, while 2 shows more distortion. In both complexes, the packing is dominated by Cl…H, C-H…π, and Cl…C (anion-π stacking) interactions in addition to O…H interactions, which are found only in 1. The UV-Vis spectral band at 564 nm was assigned to metal-ligand charge transfer transitions based on TD-DFT calculations. Complexes 1 and 2 showed higher antimicrobial activity compared to the respective free ligand MorphBPT and PipBPT, which were not active. MIC values indicated that 2 had better activity against S. aureus, B. subtilis, and P. vulgaris than 1. DPPH free radical scavenging assay revealed that all the studied compounds showed weak to moderate antioxidant activity where the nature of the substituent at the s-triazine core has a significant impact on the antioxidant activity.


Assuntos
Antibacterianos/farmacologia , Antioxidantes/farmacologia , Cobalto/química , Complexos de Coordenação/síntese química , Cristalografia por Raios X/métodos , Pirazóis/química , Triazinas/química , Antibacterianos/síntese química , Antioxidantes/química , Complexos de Coordenação/farmacologia , Ligantes , Testes de Sensibilidade Microbiana/métodos , Modelos Moleculares
5.
Int J Mol Sci ; 22(13)2021 Jun 29.
Artigo em Inglês | MEDLINE | ID: mdl-34210014

RESUMO

Human serum transferrin (HST) is a glycoprotein involved in iron transport that may be a candidate for functionalized nanoparticles to bind and target cancer cells. In this study, the effects of the simple and doped with cobalt (Co) and copper (Cu) ferrihydrite nanoparticles (Fh-NPs, Cu-Fh-NPs, and Co-Fh-NPs) were studied by spectroscopic and molecular approaches. Fluorescence spectroscopy revealed a static quenching mechanism for all three types of Fh-NPs. All Fh-NPs interacted with HST with low affinity, and the binding was driven by hydrogen bonding and van der Waals forces for simple Fh-NPs and by hydrophobic interactions for Cu-Fh-NPs and Co-Fh-NPs binding, respectively. Of all samples, simple Fh-NPs bound the most to the HST binding site. Fluorescence resonance energy transfer (FRET) allowed the efficient determination of the energy transfer between HST and NPs and the distance at which the transfer takes place and confirmed the mechanism of quenching. The denaturation of the HST is an endothermic process, both in the case of apo HST and HST in the presence of the three types of Fh-NPs. Molecular docking studies revealed that Fh binds with a low affinity to HST (Ka = 9.17 × 103 M-1) in accord with the fluorescence results, where the interaction between simple Fh-NPs and HST was described by a binding constant of 9.54 × 103 M-1.


Assuntos
Cobalto/química , Compostos Férricos/síntese química , Transferrina/química , Transferrina/metabolismo , Cobre/química , Compostos Férricos/química , Transferência Ressonante de Energia de Fluorescência , Humanos , Ligação de Hidrogênio , Modelos Moleculares , Simulação de Acoplamento Molecular , Nanopartículas , Ligação Proteica , Conformação Proteica , Espectrometria de Fluorescência , Termodinâmica
6.
Molecules ; 26(10)2021 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-34065538

RESUMO

New Co(II), Ni(II), and Cu(II) complexes were synthesized with the Schiff base ligand obtained by the condensation of sulfathiazole with salicylaldehyde. Their characterization was performed by elemental analysis, molar conductance, spectroscopic techniques (IR, diffuse reflectance and UV-Vis-NIR), magnetic moments, thermal analysis, and calorimetry (thermogravimetry/derivative thermogravimetry/differential scanning calorimetry), while their morphological and crystal systems were explained on the basis of powder X-ray diffraction results. The IR data indicated that the Schiff base ligand is tridentate coordinated to the metallic ion with two N atoms from azomethine group and thiazole ring and one O atom from phenolic group. The composition of the complexes was found to be of the [ML2]∙nH2O (M = Co, n = 1.5 (1); M = Ni, n = 1 (2); M = Cu, n = 4.5 (3)) type, having an octahedral geometry for the Co(II) and Ni(II) complexes and a tetragonally distorted octahedral geometry for the Cu(II) complex. The presence of lattice water molecules was confirmed by thermal analysis. XRD analysis evidenced the polycrystalline nature of the powders, with a monoclinic structure. The unit cell volume of the complexes was found to increase in the order of (2) < (1) < (3). SEM evidenced hard agglomerates with micrometric-range sizes for all the investigated samples (ligand and complexes). EDS analysis showed that the N:S and N:M atomic ratios were close to the theoretical ones (1.5 and 6.0, respectively). The geometric and electronic structures of the Schiff base ligand 4-((2-hydroxybenzylidene) amino)-N-(thiazol-2-yl) benzenesulfonamide (HL) was computationally investigated by the density functional theory (DFT) method. The predictive molecular properties of the chemical reactivity of the HL and Cu(II) complex were determined by a DFT calculation. The Schiff base and its metal complexes were tested against some bacterial strains (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Bacillus subtilis). The results indicated that the antibacterial activity of all metal complexes is better than that of the Schiff base.


Assuntos
Cobalto/química , Cobre/química , Níquel/química , Bases de Schiff/química , Sulfatiazóis/química , Antibacterianos/química , Análise Espectral/métodos
7.
J Mater Chem B ; 9(24): 4915-4928, 2021 06 23.
Artigo em Inglês | MEDLINE | ID: mdl-34100480

RESUMO

The promise of biocompatible magnetic nanoparticles with high magnetic saturation in the implementation as drug carriers and hyperthermia agents has generated significant interest in functionalised cobalt nanoparticles. Carboxylic acid coatings on metallic nanoparticles have been shown as an attractive option owing to their respectable stability and biocompatibility. However, only limited information is available on the molecular mechanism leading to the formation of such protective coatings. In this study, ab initio molecular dynamics simulations have been used to unravel the functionalisation mechanism starting from a neutral cobalt cluster and valeric acid molecules. Three stages were detected in the coating process: (i) rapid initial adsorption of acid molecules, (ii) simultaneous adsorption of new molecules and dissociation of those already interacting with the cluster, and, finally, (iii) grouping of dissociated hydrogen atoms and subsequent desorption of acid molecules. The fate of the hydrogen atoms was probed through a combination of static and dynamic ab initio modelling approaches, which predicted H2 generation with favourable energetics. A better understanding of the functionalisation and interaction mechanisms will aid the rational design of biocompatible cobalt nanoparticles for various applications.


Assuntos
Ácidos Carboxílicos/química , Cobalto/química , Nanopartículas Metálicas/química , Adsorção , Nanopartículas de Magnetita/química , Modelos Moleculares , Conformação Molecular , Tamanho da Partícula , Propriedades de Superfície
8.
Ecotoxicol Environ Saf ; 220: 112381, 2021 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-34091184

RESUMO

Developing monolithic carbon-based catalyst with low cost, easy separation and high performance to degrade pollutants via PMS activation is crucial. In this work, a series of novel monolithic Me-CA catalysts based on biomass derived carbon aerogel were prepared by hydrothermal method using waste watermelon peel as raw material. Co-CA catalyst showed excellent performance to activate PMS for 2, 4-DCP degradation in different temperature and different water matrices. Different pollutants, such as ciprofloxacin (CIP), bisphenol A (BPA), and 2, 4-dichlorophenoxyacetic acid (2, 4-D) could also be removed in the Co-CA/PMS system. As expected, Co-CA could be easily separated from degraded solution, and show high stability and reusability for PMS activation with a lower cobalt leaching. Based on the results of the quenching tests, electron paramagnetic resonance (EPR) spectra, Chronoamperometric test (i-t curves) and electro-chemical impedance spectroscopy (EIS), the PMS activation mechanism was proposed. The phytotoxicity assessment determined by germination situation of mung bean indicated that PMS activation could eliminate the hazards of 2, 4-D. Therefore, this study provides a low cost, efficient and environmental-friendly monolithic biomass carbon aerogel catalyst for different pollutants degradation, which further advances monolithic catalyst for practical wastewater treatment.


Assuntos
Carbono/química , Cobalto/química , Recuperação e Remediação Ambiental/métodos , Peróxidos/química , Ácido 2,4-Diclorofenoxiacético/química , Ácido 2,4-Diclorofenoxiacético/toxicidade , Biomassa , Catálise , Poluentes Ambientais/química , Poluentes Ambientais/toxicidade , Eliminação de Resíduos , Vigna/efeitos dos fármacos
9.
Molecules ; 26(11)2021 May 28.
Artigo em Inglês | MEDLINE | ID: mdl-34071361

RESUMO

Nuclear receptor REV-ERBß is an overexpressed oncoprotein that has been used as a target for cancer treatment. The metal-complex nature of its ligand, iron protoporphyrin IX (Heme), enables the REV-ERBß to be used for multiple therapeutic modalities as a photonuclease, a photosensitizer, or a fluorescence imaging agent. The replacement of iron with cobalt as the metal center of protoporphyrin IX changes the ligand from an agonist to an antagonist of REV-ERBß. The mechanism behind that phenomenon is still unclear, despite the availability of crystal structures of REV-ERBß in complex with Heme and cobalt protoporphyrin IX (CoPP). This study used molecular dynamic simulations to compare the effects of REV-ERBß binding to Heme and CoPP, respectively. The initial poses of Heme and CoPP in complex with agonist and antagonist forms of REV-ERBß were predicted using molecular docking. The binding energies of each ligand were calculated using the MM/PBSA method. The computed binding affinity of Heme to REV-ERBß was stronger than that of CoPP, in agreement with experimental results. CoPP altered the conformation of the ligand-binding site of REV-ERBß, disrupting the binding site for nuclear receptor corepressor, which is required for REV-ERBß to regulate the transcription of downstream target genes. Those results suggest that a subtle change in the metal center of porphyrin can change the behavior of porphyrin in cancer cell signaling. Therefore, modification of porphyrin-based agents for cancer therapy should be conducted carefully to avoid triggering unfavorable effects.


Assuntos
Cobalto/química , Neoplasias/tratamento farmacológico , Protoporfirinas/antagonistas & inibidores , Receptores Citoplasmáticos e Nucleares/química , Proteínas Repressoras/química , Sítios de Ligação , Química Farmacêutica/métodos , Heme/química , Humanos , Ferro/química , Cinética , Ligantes , Metais , Conformação Molecular , Simulação de Acoplamento Molecular , Simulação de Dinâmica Molecular , Peptídeos/química , Fármacos Fotossensibilizantes/química , Porfirinas/química , Ligação Proteica , Receptores Citoplasmáticos e Nucleares/antagonistas & inibidores , Receptores Citoplasmáticos e Nucleares/metabolismo , Proteínas Repressoras/antagonistas & inibidores , Proteínas Repressoras/genética , Transdução de Sinais
10.
Inorg Chem ; 60(13): 10056-10063, 2021 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-34138555

RESUMO

Rapid industrialization has led to the release of hexavalent chromium (Cr(VI)), a "Class A" human carcinogen, mutagen, and teratogen in biological systems. Current adsorbents like anionic exchange resins and metal-organic frameworks can remove harmful heavy metal oxyanions from water but are not stable in a broad pH range, suffer from selectivity, and cannot capture them from trace values below the tolerance limits given by the U.S. EPA (100 ppb) and WHO (50 ppb). Herein, we have synthesized nature-inspired coral-like three-dimensional hierarchical structures of [Co0.79Al0.21(OH)2(CO3)0.11]·mH2O (CoAl-LDH) that sets a new benchmark for sequestering oxyanions of Cr(VI). CoAl-LDH shows a broad pH working range (1.93-12.22), high selectivity toward saturated water samples containing monovalent (Cl-, F-, Br-, and NO3-) and divalent (SO42-) anions with fast kinetics (reaches equilibrium within a minute), high capacity (93.4 ± 7.8 mg g-1), and high distribution coefficient of 1.09 × 106 mL g-1. Unlike other materials, it can decrease Cr(VI) concentration up to 0.012 ppb. This high selectivity for Cr(VI) is linked to the weak bonding interaction between Cr2O72- and brucite-like layers, as revealed from thermogravimetric and infrared spectroscopy. With these remarkable features coupled with low cost and an environmentally friendly nature, we have also designed an anion exchange column that can remove >99% Cr(VI) with just 1 wt % of CoAl-LDH and 99 wt % of sand and is a prominent candidate for the elimination of Cr(VI) from industrial effluents.


Assuntos
Alumínio/química , Monóxido de Carbono/química , Cromo/análise , Cobalto/química , Hidróxidos/química , Poluentes Químicos da Água/análise , Adsorção , Concentração de Íons de Hidrogênio , Cinética , Tamanho da Partícula , Propriedades de Superfície , Água/química
11.
Chem Asian J ; 16(13): 1820-1831, 2021 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-34014032

RESUMO

In this investigation, a melamine electrochemical sensor has been developed by using wet-chemically synthesized low-dimensional aggregated nanoparticles (NPs) of ZnO-doped Co3 O4 as sensing substrate that were decorated onto flat glassy carbon electrode (GCE). The characterization of NPs such as UV-Vis, FTIR, XRD, XPS, EDS, and FESEM was done for detailed investigations in optical, functional, structural, elemental, and morphological analyses. The ZnO-doped Co3 O4 NPs decorated GCE was used as a sensing probe to analyze the target chemical melamine in a phosphate buffer at pH 5.7 by applying differential pulse voltammetry (DPV). It exhibited good performances in terms of sensor analytical parameters such as large linear dynamic range (LDR; 0.15-1.35 mM) of melamine detection, high sensitivity (80.6 µA mM-1 cm-2 ), low limit of detection (LOD; 0.118±0.005 mM), low limit of quantification (LOQ; 0.393 mM), and fast response time (30 s). Besides this, the good reproducibility (in several hours) and repeatability were investigated under identical conditions. Moreover, it was implemented to measure the long-time stability, electron mobility, less charge-transfer resistance, and analyzed diffusion-controlled process for the oxidation reaction of the NPs assembled working GCE electrode, which showed outstanding chemical sensor performances. For validation, real environmental samples were collected from various water sources and investigated successfully with regard to the reliability of the selective melamine detection with prepared NPs coated sensor probe. Therefore, this approach might be introduced as an alternative route in the sensor technology to detect selectively unsafe chemicals by an electrochemical method with nanostructure-doped materials for the safety of environmental, ecological, healthcare fields in a broad scale.


Assuntos
Carbono/química , Cobalto/química , Nanopartículas Metálicas/química , Óxidos/química , Triazinas/química , Água/química , Óxido de Zinco/química , Técnicas Eletroquímicas/instrumentação , Técnicas Eletroquímicas/métodos , Eletrodos , Monitoramento Ambiental , Reprodutibilidade dos Testes , Poluentes Químicos da Água/química
12.
J Mater Chem B ; 9(23): 4643-4653, 2021 06 16.
Artigo em Inglês | MEDLINE | ID: mdl-34009230

RESUMO

Radiotherapy, as well as chemotherapy and surgery, occupies an essential position in tumor treatment. Nonetheless, insufficient radiation deposition and hypoxia-related radioresistance of cancer cells still are serious challenges in radiotherapy. Herein, we proposed a hollow PtCo nanosphere (PtCo NS)-based novel radiosensitizer with three advantages to sensitize tumor radiotherapy: (i) the high-Z element Pt ensured higher radiation absorption to cause more DNA damage, (ii) the platinum (Pt) and cobalt (Co) elements exhibited a dual catalase-like enzymatic activity to convert endogenic H2O2 to O2 efficiently, and (iii) the unique hollow nature of the PtCo NS provided a large specific surface area, which could amplify the catalytic reaction of H2O2 to induce reactive oxygen species and cancer cell apoptosis upon combination with radiation. Both in vivo and in vitro studies showed that the hollow PtCo NS could significantly inhibit tumor growth, simultaneously relieving tumor hypoxia with good biocompatibility and biosafety. This work presents a simple but multifunctional radiosensitizer with a unique hollow structure for radiotherapy enhancement.


Assuntos
Carcinoma Pulmonar de Células não Pequenas/radioterapia , Catalase/metabolismo , Cobalto/química , Neoplasias Pulmonares/radioterapia , Nanopartículas Metálicas/química , Nanosferas/química , Oxigênio/metabolismo , Platina/química , Animais , Linhagem Celular Tumoral , Humanos , Camundongos , Camundongos Endogâmicos C57BL , Microscopia Eletrônica de Transmissão , Difração de Pó , Ensaios Antitumorais Modelo de Xenoenxerto
13.
Chem Commun (Camb) ; 57(50): 6161-6164, 2021 Jun 22.
Artigo em Inglês | MEDLINE | ID: mdl-34042919

RESUMO

We report our investigation into the MCU-inhibitory activity of Co3+ complexes in comparison to Ru265. These compounds reversibly inhibit the MCU with nanomolar potency. Mutagenesis studies and molecular docking simulations suggest that the complexes operate through interactions with the DIME motif of the MCU pore.


Assuntos
Aminas/farmacologia , Canais de Cálcio/metabolismo , Cobalto/farmacologia , Complexos de Coordenação/farmacologia , Aminas/química , Cobalto/química , Complexos de Coordenação/química , Células HEK293 , Células HeLa , Humanos , Conformação Molecular , Simulação de Acoplamento Molecular
14.
Bone Joint J ; 103-B(6 Supple A): 94-101, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-34053284

RESUMO

AIMS: The aims of this study were to evaluate wear on the surface of cobalt-chromium (CoCr) femoral components used in total knee arthroplasty (TKA) and compare the wear of these components with that of ceramic femoral components. METHODS: Optical profilometry was used to evaluate surface roughness and to examine the features created by the wear process in a knee wear simulator. We developed a method of measuring surface changes on five CoCr femoral components and quantifying the loss of material from the articular surface during the wear process. We also examined the articular surface of three ceramic femoral components from a previous test for evidence of surface damage, and compared it with that of CoCr components. RESULTS: We found that the surface roughness of CoCr components rapidly increased during the first 1,000 wear cycles, then reached a steady state, but material loss from the surface continued at a rate of 1,778,000 µm3 per million cycles as carbides were removed from its matrix. These carbides formed third-body wear particles, leading to the formation of new scratches even as older scratches were worn away. In contrast, no scratching, loss of material, or other surface damage, when evaluated with one nanometer resolution, was found on the surface of the ceramic components after a 15 M wear cycle test. CONCLUSION: This study showed wear and loss of CoCr material from scratching and microabrasive wear in TKA. The material loss from the surface continued in a linear relationship with increasing cycles. We also found the absence of scratching and roughening of ceramic femoral components in simulated wear, suggesting an advantage in wear rate and avoiding metal sensitivity. This may have implications in the management of persistent pain after TKA. Cite this article: Bone Joint J 2021;103-B(6 Supple A):94-101.


Assuntos
Artroplastia do Joelho/instrumentação , Cerâmica/química , Cromo/química , Cobalto/química , Fêmur/cirurgia , Prótese do Joelho , Falha de Prótese , Humanos , Teste de Materiais , Desenho de Prótese , Propriedades de Superfície
15.
Chemphyschem ; 22(12): 1208-1218, 2021 06 16.
Artigo em Inglês | MEDLINE | ID: mdl-33851772

RESUMO

The cobalt substituted polyoxotungstate [Co6 (H2 O)2 (α-B-PW9 O34 )2 (PW6 O26 )]17- (Co6) displays fast electron transfer (ET) kinetics to photogenerated RuIII (bpy)3 3+ , 4 to 5 orders of magnitude faster than the corresponding ET observed for cobalt oxide nanoparticles. Mechanistic evidence has been acquired indicating that: (i) the one-electron oxidation of Co6 involves Co(II) aquo or Co(II) hydroxo groups (abbreviated as Co6(II)-OH2 and Co6(II)-OH, respectively, whose speciation in aqueous solution is associated to a pKa of 7.6), and generates a Co(III)-OH moiety (Co6(III)-OH), as proven by transient absorption spectroscopy; (ii) at pH>pKa , the Co6(II)-OH→RuIII (bpy)3 3+ ET occurs via bimolecular kinetics, with a rate constant k close to the diffusion limit and dependent on the ionic strength of the medium, consistent with reaction between charged species; (iii) at pH

Assuntos
Complexos de Coordenação/química , Elétrons , Compostos Organometálicos/química , Polímeros/química , Prótons , Compostos de Tungstênio/química , Cobalto/química , Complexos de Coordenação/síntese química , Cinética , Luz , Compostos Organometálicos/efeitos da radiação , Oxidantes/química , Oxidantes/efeitos da radiação , Oxirredução , Polímeros/síntese química , Rutênio/química , Rutênio/efeitos da radiação , Compostos de Tungstênio/síntese química , Água/química
16.
Acc Chem Res ; 54(8): 2003-2013, 2021 04 20.
Artigo em Inglês | MEDLINE | ID: mdl-33797888

RESUMO

Metals are partners for an estimated one-third of the proteome and vary in complexity from mononuclear centers to organometallic cofactors. Vitamin B12 or cobalamin represents the epitome of this complexity and is the product of an assembly line comprising some 30 enzymes. Unable to biosynthesize cobalamin, mammals rely on dietary provision of this essential cofactor, which is needed by just two enzymes, one each in the cytoplasm (methionine synthase) and the mitochondrion (methylmalonyl-CoA mutase). Brilliant clinical genetics studies on patients with inborn errors of cobalamin metabolism spanning several decades had identified at least seven genetic loci in addition to the two encoding B12 enzymes. While cells are known to house a cadre of chaperones dedicated to metal trafficking pathways that contain metal reactivity and confer targeting specificity, the seemingly supernumerary chaperones in the B12 pathway had raised obvious questions as to the rationale for their existence.With the discovery of the genes underlying cobalamin disorders, our laboratory has been at the forefront of ascribing functions to B12 chaperones and elucidating the intricate redox-linked coordination chemistry and protein-linked cofactor conformational dynamics that orchestrate the processing and translocation of cargo along the trafficking pathway. These studies have uncovered novel chemistry that exploits the innate chemical versatility of alkylcobalamins, i.e., the ability to form and dismantle the cobalt-carbon bond using homolytic or heterolytic chemistry. In addition, they have revealed the practical utility of the dimethylbenzimidazole tail, an appendage unique to cobalamins and absent in the structural cousins, porphyrin, chlorin, and corphin, as an instrument for facilitating cofactor transfer between active sites.In this Account, we navigate the chemistry of the B12 trafficking pathway from its point of entry into cells, through lysosomes, and into the cytoplasm, where incoming cobalamin derivatives with a diversity of upper ligands are denuded by the ß-ligand transferase activity of CblC to the common cob(II)alamin intermediate. The broad reaction and lax substrate specificity of CblC also enables conversion of cyanocobalamin (technically, vitamin B12, i.e., the form of the cofactor in one-a-day supplements), to cob(II)alamin. CblD then hitches up with CblC via a unique Co-sulfur bond to cob(II)alamin at a bifurcation point, leading to the cytoplasmic methylcobalamin or mitochondrial 5'-deoxyadenosylcobalamin branch. Mutations at loci upstream of the junction point typically affect both branches, leading to homocystinuria and methylmalonic aciduria, whereas mutations in downstream loci lead to one or the other disease. Elucidation of the biochemical penalties associated with individual mutations is providing molecular insights into the clinical data and, in some instances, identifying which cobalamin derivative(s) might be therapeutically beneficial.Our studies on B12 trafficking are revealing strategies for cofactor sequestration and mobilization from low- to high-affinity and low- to high-coordination-number sites, which in turn are regulated by protein dynamics that constructs ergonomic cofactor binding pockets. While these B12 lessons might be broadly relevant to other metal trafficking pathways, much remains to be learned. This Account concludes by identifying some of the major gaps and challenges that are needed to complete our understanding of B12 trafficking.


Assuntos
Complexos de Coordenação/química , Vitamina B 12/metabolismo , Cobalto/química , Cobamidas/química , Humanos , Lisossomos/metabolismo , Metilmalonil-CoA Mutase/química , Metilmalonil-CoA Mutase/metabolismo , Metiltransferases/química , Metiltransferases/metabolismo , Mitocôndrias/metabolismo , Oxirredução , Estrutura Terciária de Proteína , Vitamina B 12/análogos & derivados , Vitamina B 12/química
17.
J Mater Chem B ; 9(17): 3716-3726, 2021 05 05.
Artigo em Inglês | MEDLINE | ID: mdl-33900347

RESUMO

Over the past decade, there has been a dramatic increase in the number of studies focused on sensors for cysteine (Cys) as a crucial factor in physiological function and disease diagnosis. Among those sensors, nanomaterial-based peroxidase mimetics have received particular attention from researchers. This study introduces a new series of mesoporous silica nanoparticles (MSNs) incorporated with iron and cobalt (Co/Fe-MSN) with a molar ratio of Si/Fe = 10 and cobalt species at 1, 3, and 5 wt% that have great potential in the sensing application. These nanomaterial characterization was investigated by FTIR spectroscopy, SEM, TEM, XRD, and nitrogen adsorption-desorption. The peroxidase activity of these nanomaterials was studied through kinetic analysis. The findings revealed that Co/Fe-MSN (1%) showed higher peroxidatic activity than the others towards the common chromogenic substrate 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) diammonium salt. Based on the enzymatic activity of Co/Fe-MSN (1%), a colorimetric sensing platform was designed to detect H2O2 and Cys. The limit of detection (LOD) for H2O2 and Cys was determined to be 1.1 µM and 0.89 nM, respectively. The results indicated that the proposed enzyme mimic exhibited excellent potential as a sensor in medical diagnostics and biological systems.


Assuntos
Cobalto/química , Corantes/química , Cisteína/análise , Ferro/química , Nanopartículas/química , Dióxido de Silício/química , Adsorção , Benzotiazóis/química , Materiais Biomiméticos/química , Técnicas Biossensoriais , Colorimetria , Peróxido de Hidrogênio/química , Cinética , Limite de Detecção , Nitrogênio/química , Peroxidase/química , Porosidade , Ácidos Sulfônicos/química , Propriedades de Superfície
18.
Inorg Chem ; 60(9): 6649-6662, 2021 May 03.
Artigo em Inglês | MEDLINE | ID: mdl-33855849

RESUMO

The bioessential nature of cobalt and the rich photochemistry of its coordination complexes can be exploited to develop potential next-generation photochemotherapeutics. A series of six novel mixed-ligand cobalt(III) complexes of the formulation [Co(B)2(L)]ClO4 (1-6), where B is an N,N-donor phenanthroline base, namely, 1,10-phenanthroline (phen in 1 and 4), dipyrido[3,2-d:2',3'-f]quinoxaline (dpq in 2 and 5), and dipyrido[3,2-a:2',3'-c]phenazine (dppz in 3 and 6), and L is an O,O-donor dianionic ligand derived from catechol (1,2-dihydroxybenzene, cat2-, in 1-3) or esculetin (6,7-dihydoxycoumarin, esc2-, in 4-6), have been prepared and characterized, and their light-triggered cytotoxicity has been studied in cancer cells. The single-crystal X-ray diffraction structures of complexes 1 (as PF6- salt, 1a) and 2 show distorted octahedral geometries around the cobalt(III) center formed by the set of N4O2 donor atoms. The low-spin and 1:1 electrolytic complexes 1-6 display a d-d transition around 700 nm. Complexes 4-6 with a coordinated esc2- ligand additionally display a π → π* intraligand transition centered at 403 nm. Complexes 4-6 possessing a naturally occurring and photoactive esc2- ligand show high visible-light-triggered cytotoxicity against HeLa and MCF-7 cancer cells, yielding remarkably low micromolar IC50 values while being much less toxic under dark conditions. Control complexes 1-3 possessing the photoinactive cat2- ligand show significantly less cytotoxicity either in the presence of light or in the dark. The complex-induced cell death is apoptotic in nature caused by the formation of reactive oxygen species via a type 1 photoredox pathway. Fluorescence microscopy of HeLa cells treated with complex 6 reveals mitochondrial localization of the complex. A significant decrease in the dark toxicity of free esculetin and dppz base is observed upon coordination to cobalt(III). Complexes bind to calf-thymus DNA with significant affinity, but 6 binds with the greatest affinity. Complex 6 efficiently photocleaves supercoiled DNA to its nicked circular form when irradiated with visible light via a photoredox type 1 pathway involving hydroxyl radicals (HO•). Thus, complex 6 showing remarkable visible-light-triggered cytotoxicity but negligible toxicity in the dark is a good candidate for cancer photochemotherapy applications.


Assuntos
Antineoplásicos/farmacologia , Complexos de Coordenação/farmacologia , Mitocôndrias/efeitos dos fármacos , Fotoquímica , Antineoplásicos/síntese química , Antineoplásicos/química , Proliferação de Células/efeitos dos fármacos , Cobalto/química , Cobalto/farmacologia , Complexos de Coordenação/síntese química , Complexos de Coordenação/química , Cumarínicos/química , Cumarínicos/farmacologia , Cristalografia por Raios X , Teoria da Densidade Funcional , Ensaios de Seleção de Medicamentos Antitumorais , Humanos , Ligantes , Mitocôndrias/metabolismo , Modelos Moleculares , Estrutura Molecular , Fenantrolinas/química , Fenantrolinas/farmacologia , Células Tumorais Cultivadas
19.
Int J Biol Macromol ; 182: 722-729, 2021 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-33862074

RESUMO

Designing of eco-friendly, low cost, and thermally stable stabilizing/supporting agents are always desired for production of catalyst systems which provide good catalytic performance in organic reactions. In this study, a novel, green, and efficient stabilizer containing chitosan/Co3O4 microspheres (CS/Co3O4) was developed. Palladium nanoparticles (Pd NPs) were then successfully immobilized on CS/Co3O4 as a heterogeneous nanocatalyst (Pd NPs/CS/Co3O4). Characterization of the designed materials were performed by FT-IR, TEM, FE-SEM, XRD, and EDS and it was determined that Pd NPs formed as approximately 20 nm. Catalytic behavior of Pd NPs/CS/Co3O4 was investigated in the production of different substituted benzonitriles via aryl halide cyanation. Catalytic studies indicate that electron-rich or poor aromatic halides were smoothly cyanated with good reaction yields by Pd NPs/CS/Co3O4 nanocatalyst by using K4[Fe(CN)6] as the cyanating agent. Moreover, it was found that Pd NPs/CS/Co3O4 nanocatalyst provided not only good reaction yields and but also good recovery/reusability for six times in the aryl halide cyanations. This paper displays that Pd NPs/CS/Co3O4 nanocatalyst has a great catalytic and recycling potential for aryl halide cyanations.


Assuntos
Quitosana/análogos & derivados , Cobalto/química , Nanopartículas/química , Nitrilas/síntese química , Óxidos/química , Paládio/química , Catálise , Microesferas
20.
Chem Commun (Camb) ; 57(40): 4934-4937, 2021 May 18.
Artigo em Inglês | MEDLINE | ID: mdl-33870988

RESUMO

This study demonstrates the screening of a collection of twelve 19F-tagged metal-binding pharmacophores (MBPs) against the Zn(ii)-dependent metalloenzyme human carbonic anhydrase II (hCAII) by 19F NMR. The isomorphous replacement of Zn(ii) by Co(ii) in hCAII produces enhanced sensitivity and reveals the potential of 19F NMR-based techniques for metalloenzyme ligand discovery.


Assuntos
Anidrase Carbônica II/antagonistas & inibidores , Inibidores da Anidrase Carbônica/farmacologia , Cobalto/farmacologia , Ressonância Magnética Nuclear Biomolecular , Compostos Organometálicos/farmacologia , Zinco/farmacologia , Anidrase Carbônica II/metabolismo , Inibidores da Anidrase Carbônica/química , Cobalto/química , Relação Dose-Resposta a Droga , Flúor , Humanos , Ligantes , Estrutura Molecular , Compostos Organometálicos/química , Zinco/química
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...