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1.
Food Chem ; 336: 127675, 2021 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-32795781

RESUMO

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.


Assuntos
Chumbo/isolamento & purificação , Nanopartículas/química , Níquel/isolamento & purificação , Pleurotus/química , Extração em Fase Sólida/métodos , Poluentes Químicos da Água/isolamento & purificação , Adsorção , Células Imobilizadas , Compostos Férricos/química , Análise de Alimentos/instrumentação , Análise de Alimentos/métodos , Contaminação de Alimentos/análise , Concentração de Íons de Hidrogênio , Limite de Detecção , Fenômenos Magnéticos , Níquel/química , Reprodutibilidade dos Testes , Extração em Fase Sólida/instrumentação , Poluentes Químicos da Água/química
2.
Nat Commun ; 11(1): 5101, 2020 10 09.
Artigo em Inglês | MEDLINE | ID: mdl-33037208

RESUMO

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.


Assuntos
Proteínas de Bactérias/química , Proteínas de Bactérias/metabolismo , Urease/química , Urease/metabolismo , Yersinia enterocolitica/enzimologia , Domínio Catalítico , Microscopia Crioeletrônica , Lisina/metabolismo , Modelos Moleculares , Níquel/química , Níquel/metabolismo , Conformação Proteica , Domínios Proteicos , Água/química
3.
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
4.
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
5.
Int J Nanomedicine ; 15: 6239-6245, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32904074

RESUMO

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.


Assuntos
Eletrofisiologia/instrumentação , Neurônios/fisiologia , Sinapses/fisiologia , Inteligência Artificial , Eletrodos , Eletrofisiologia/métodos , Desenho de Equipamento , Ouro/química , Microscopia Eletrônica de Varredura/instrumentação , Níquel/química , Semicondutores , Sinapses/química , Transmissão Sináptica
6.
J Oleo Sci ; 69(10): 1191-1198, 2020 Oct 07.
Artigo em Inglês | MEDLINE | ID: mdl-32908091

RESUMO

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.


Assuntos
Ácidos Erúcicos , Cinética , Níquel/química , Óleo de Brassica napus/química , Prata/química , Catálise , Formiatos/química , Temperatura Alta , Hidrogenação , Iodo/análise , Ácido Linoleico/análise , Ácido Linoleico/química , Ácido Oleico/análise , Ácido Oleico/química , Ácidos Graxos Trans/análise
7.
J Vis Exp ; (161)2020 07 28.
Artigo em Inglês | MEDLINE | ID: mdl-32804166

RESUMO

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.


Assuntos
Elasticidade , Teste de Materiais , Níquel/química , Óxidos/química , Titânio/química , Ligas/química , Impedância Elétrica , Eletroquímica , Eletrodos , Oxirredução , Estresse Mecânico , Propriedades de Superfície , Resistência à Tração
8.
Int J Nanomedicine ; 15: 5591-5602, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32848389

RESUMO

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.


Assuntos
Nanoestruturas/química , Poluentes Químicos da Água/química , Abies/química , Compostos Azo/química , Catálise , Luz , Molibdênio/química , Níquel/química , Óxidos/química , Paládio/química , Pressão , Temperatura
9.
Nat Commun ; 11(1): 3188, 2020 06 24.
Artigo em Inglês | MEDLINE | ID: mdl-32581225

RESUMO

Nitric oxide (NO) has been implicated in a variety of physiological and pathological processes. Monitoring cellular levels of NO requires a sensor to feature adequate sensitivity, transient recording ability and biocompatibility. Herein we report a single-atom catalysts (SACs)-based electrochemical sensor for the detection of NO in live cellular environment. The system employs nickel single atoms anchored on N-doped hollow carbon spheres (Ni SACs/N-C) that act as an excellent catalyst for electrochemical oxidation of NO. Notably, Ni SACs/N-C shows superior electrocatalytic performance to the commonly used Ni based nanomaterials, attributing from the greatly reduced Gibbs free energy that are required for Ni SACs/N-C in activating NO oxidation. Moreover, Ni SACs-based flexible and stretchable sensor shows high biocompatibility and low nanomolar sensitivity, enabling the real-time monitoring of NO release from cells upon drug and stretch stimulation. Our results demonstrate a promising means of using SACs for electrochemical sensing applications.


Assuntos
Técnicas Biossensoriais/métodos , Níquel/química , Óxido Nítrico/análise , Nitrogênio/química , Técnicas Biossensoriais/instrumentação , Carbono/química , Catálise , Eletroquímica , Células Endoteliais da Veia Umbilical Humana/metabolismo , Humanos , Nanoestruturas/química , Nanoestruturas/ultraestrutura , Óxido Nítrico/metabolismo , Oxirredução
10.
Artigo em Inglês | MEDLINE | ID: mdl-32532180

RESUMO

In the present investigation, physico-chemical characterization of composite material revealed the presence of fluffy surface structure with crystalline look and negatively charged surface functional groups. The study of adsorption flux by using dimensionless numbers φ (2.62), Nk (62.68) and λ (1.17 × 10-5) proved that adsorption of nickel ions on the surface of composite material was mostly film diffusion-limited with maximum surface area coverage coupled with weakened surface tension. The results of intraparticle diffusivity and Boyd plot model showed that at the onset of process, film diffusion was the primary mechanism involved and at the later stage intraparticle diffusion played a critical role as rate governing step. The values of film (0.65 × 10-8 cm2 sec-1) and pore diffusivity (1.8 × 10-12 cm2 sec-1) coefficients showed that the adsorption process is dependent upon two different types of diffusion namely film and pore diffusion. Overall, transport and reshuffling mechanism had no substantial role in adsorption dynamics of nickel ions on the surface of composite material. Sorption isotherm and kinetics modeling showed higher values of regression coefficients for Langmuir isotherm (R2 = 0.99) and pseudo-second-order kinetic model (R2 = 0.99) compared to other models. This showed that sorption of nickel followed monolayer coverage with chemisorption at optimized process parameters like pH 6, biosorbent dose 0.1 g/L, temperature 50 °C, agitation rate180 rpm, adsorbate concentration100 mg/L and contact time 60 minutes. The positive value of enthalpy of adsorption (ΔH = + 10.41 kJ/mole) and entropy (ΔS = +58.19 J/mol K) showed that binding of nickel ions on the surface of the composite material was endothermic with improved randomness at solid-liquid interface. The negative value of (ΔG = -6.4 to -8.67 kJ/mol) showed spontaneous nature of nickel adsorption on composite material in the liquid phase.


Assuntos
Bentonita/química , Argila/química , Modelos Teóricos , Níquel/análise , Águas Residuárias/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Adsorção , Difusão , Concentração de Íons de Hidrogênio , Íons , Cinética , Níquel/química , Soluções , Propriedades de Superfície , Termodinâmica , Poluentes Químicos da Água/química
11.
Nat Chem Biol ; 16(9): 1006-1012, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32514183

RESUMO

In proteins where conformational changes are functionally important, the number of accessible states and their dynamics are often difficult to establish. Here we describe a novel 19F-NMR spectroscopy approach to probe dynamics of large membrane proteins. We labeled a glutamate transporter homolog with a 19F probe via cysteine chemistry and with a Ni2+ ion via chelation by a di-histidine motif. We used distance-dependent enhancement of the longitudinal relaxation of 19F nuclei by the paramagnetic metal to assign the observed resonances. We identified one inward- and two outward-facing states of the transporter, in which the substrate-binding site is near the extracellular and intracellular solutions, respectively. We then resolved the structure of the unanticipated second outward-facing state by cryo-EM. Finally, we showed that the rates of the conformational exchange are accessible from measurements of the metal-enhanced longitudinal relaxation of 19F nuclei.


Assuntos
Sistema X-AG de Transporte de Aminoácidos/química , Espectroscopia de Ressonância Magnética , Sistema X-AG de Transporte de Aminoácidos/genética , Sistema X-AG de Transporte de Aminoácidos/metabolismo , Microscopia Crioeletrônica , Cisteína/química , Flúor , Histidina/química , Modelos Moleculares , Mutação , Níquel/química , Conformação Proteica , Domínios Proteicos , Pyrococcus horikoshii/química
12.
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
13.
BMC Surg ; 20(1): 103, 2020 May 13.
Artigo em Inglês | MEDLINE | ID: mdl-32404137

RESUMO

BACKGROUND: Development of multiple rib fractures leading to bilateral flail chest in Cronkhite-Canada Syndrome (CCS) has not been reported. CASE PRESENTATION: A 59-year-old man presented with complaints of fatigue, chest pain, respiratory distress and orthopnea requiring ventilatory support to maintain oxygenation. CCS with bilateral anterior and posterior flail chest due to multiple rib fractures (2nd-10th on the right side and 2nd-11th on the left side). He underwent open reduction and anterior and posterior internal fixation using a titanium alloy fixator and a nickel-titanium memory alloy embracing fixator for chest wall reconstruction. He recovered gradually from the ventilator and showed improvement in his symptoms. He gained about 20 kg of weight in the follow up period (6 months after discharge from the hospital). CONCLUSION: CCS is a rare, complex disease that increases the risk of developing multiple rib fractures, which can be successfully treated with open reduction and internal fixation.


Assuntos
Tórax Fundido/cirurgia , Polipose Intestinal/cirurgia , Fraturas das Costelas/cirurgia , Fixação Interna de Fraturas/métodos , Humanos , Masculino , Pessoa de Meia-Idade , Níquel/química , Redução Aberta , Parede Torácica , Titânio/química
14.
Chemosphere ; 250: 126298, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32234622

RESUMO

Chlorophenol (CP) is considered as environmentally hazardous material due to its acute toxicity, persistent nature and strong bioaccumulation. The dechlorination of 4-CP was investigated by using various catalysts such as bimetallic (Fe0/Cu0, Al0/Fe0), Pd/C, Raney Ni and Fe0 at room temperature. Among the catalysts studied, Raney Ni proved to be very economical and efficient catalyst that worked without the use of an external reducing agent. The dechlorination of 4-CP by Raney Ni was therefore further explored. Complete dechlorination of 4-CP (30 mg L-1) was achieved in 6 h at an optimum Raney Ni catalyst loading of 3 g L-1. The effect of triethylamine (TEA) and tripropylamine (TPA) was also investigated and it was observed that 100% dechlorination is possible in presence of 45 mg L-1 of TEA. The kinetics of dechlorination of 4-CP was investigated and found to be first order with a rate constant of 0.017 min-1 at 50 οC, and it enhances to 0.109 min-1 with addition of TEA. In the absence of a reducing agent, acidic to neutral pH favors dechlorination of 4-CP. The final product of dechlorination was estimated to be phenol by performing HPLC, LCMS and NMR analysis. Based on the results, a probable dechlorination mechanism of 4-CP is also proposed. It can be concluded that the catalytic hydrodechlorination is an effective and economical technique for dechlorination of 4-CP and it has a potential for the dechlorination of other toxic derivatives of chlorinated aromatics.


Assuntos
Clorofenóis/química , Modelos Químicos , Níquel/química , Catálise , Halogenação , Concentração de Íons de Hidrogênio , Cinética , Substâncias Redutoras
15.
Chemistry ; 26(41): 8875-8878, 2020 Jul 22.
Artigo em Inglês | MEDLINE | ID: mdl-32237247

RESUMO

The nickel(II)-mediated self-assembly of a multimeric DNA binder is described. The binder is composed of two metal-chelating peptides derived from a bZIP transcription factor (brHis2 ) and one short AT-hook domain equipped with two bipyridine ligands (HkBpy2 ). These peptides reversibly assemble in the presence of NiII ions at selected DNA sequences of 13 base pairs.


Assuntos
Complexos de Coordenação/química , DNA/química , Níquel/química , Peptídeos/química , Fatores de Transcrição/química , Complexos de Coordenação/síntese química , Íons/química , Ligantes
16.
J Phys Chem Lett ; 11(8): 2941-2948, 2020 Apr 16.
Artigo em Inglês | MEDLINE | ID: mdl-32223169

RESUMO

A highly efficient CO2 electrolysis system could be created by introducing biomass oxidation as an alternative anodic reaction to the sluggish oxygen evolution reaction in a CO2-saturated and near-neutral electrolyte. Here, we successfully demonstrate anodic biomass oxidation by synthesizing 5 nm nickel oxide nanoparticles (NiO NPs). NiO NPs show a unique electrocatalytic activity for 5-hydroxymethylfurfural (HMF) oxidation under near-neutral conditions, exhibiting an anodic current onset (1 mA cm-2) at 1.524 V versus the reversible hydrogen electrode and a total Faradaic efficiency of ≤70%. Electrokinetic and in situ ultraviolet-visible spectroscopic analyses suggest that a redox active nickel hydroxide species is formed on the surface of NiO electrocatalysts during HMF oxidation, and this oxidation of Ni(II) hydroxide to Ni(III) oxyhydroxide could be the rate-determining step. This mechanistic study of biomass oxidation in a CO2-saturated electrolyte provides insight into constructing a highly efficient system for the paired electrolysis of CO2 reduction and biomass oxidation.


Assuntos
Biomassa , Dióxido de Carbono/química , Eletrólise/métodos , Eletrólitos/química , Nanopartículas Metálicas/química , Níquel/química , Dióxido de Carbono/metabolismo , Técnicas Eletroquímicas/métodos , Eletrólitos/metabolismo , Níquel/metabolismo , Oxirredução
17.
Chemistry ; 26(31): 7074-7082, 2020 Jun 02.
Artigo em Inglês | MEDLINE | ID: mdl-32187746

RESUMO

The results of extended comparative investigation of nickel(II) Schiff base complexes (containing various auxiliary chiral moieties) commonly used as a methodological platform for the asymmetric synthesis of tailor-made α-amino acids are provided. The following issues are addressed: 1) redox activity (determining the possibility for electrochemically induced reactions); 2) quantitative estimation of the reactivity of deprotonated complexes towards electrophiles; and 3) quantum-chemical estimation of noncovalent interactions in the metal coordination environment (which shed light on the origin of the stereochemical outcome observed for different stereoinductors). Possible mechanisms that determine the relationship between the stereochemical configuration of a molecule and its electronic structure are discussed. The DFT-calculated HOMO-LUMO energies and localization, as well as relative energies for the (S)- and (R)-alanine derivatives, that determine the stereoinduction efficiency in thermodynamically controlled reactions in nickel(II) coordination are provided. The computational data are supported by experimental results on the monobenzylation of glycine derivatives.


Assuntos
Aminoácidos/química , Complexos de Coordenação/química , Bases de Schiff/química , Alanina/química , Glicina/química , Níquel/química , Estereoisomerismo , Termodinâmica
18.
Chem Pharm Bull (Tokyo) ; 68(3): 292-297, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32115537

RESUMO

In this study, the adsorption capability of phosphate ion using a novel tri-metals complex hydroxide was evaluated for preventing the eutrophication in water environment. A nickel-aluminum-zirconium complex hydroxide (NAZ) was synthesized using each inorganic sulfate mixing ratio of 0.9 : 1.0 : 0.1 and was calcined at different temperatures. The characteristics of the NAZ were analyzed by scanning electron microscopy images, X-ray diffraction analysis, elemental distribution, and binding energy. Moreover, the amount adsorbed of phosphate ion onto uncalcined and calcined NAZ was measured. That of phosphate ions onto the uncalcined was the largest of all. These results suggested that the adsorption of phosphate ions tends to depend on the physicochemical properties (e.g., amount of hydroxyl groups, pore volumes, and pH) of the adsorbents. Moreover, the adsorption mechanism of phosphate ions was evaluated on the basis of binding energy and elemental analysis. After adsorption, the binding energy of phosphorus P (2s and 2p) peaked and the sulfur peak intensity S(2s) reduced. This result indicated that the adsorption mechanism of phosphate would be exchanged with sulfate ions.


Assuntos
Alumínio/química , Complexos de Coordenação/química , Hidróxidos/química , Níquel/química , Fosfatos/química , Zircônio/química , Adsorção , Complexos de Coordenação/síntese química , Tamanho da Partícula , Propriedades de Superfície
19.
Inorg Chem ; 59(7): 4772-4780, 2020 Apr 06.
Artigo em Inglês | MEDLINE | ID: mdl-32207613

RESUMO

Detailed equilibrium, spectroscopic, and SOD activity studies are reported on nickel(II) complexes formed with the N-terminally free HHDLPCGVY-NH2 (NiSODHH) and HCDLPHGVY-NH2 (NiSODHC) peptides mimicking the nickel binding loop in NiSOD. In these model peptides, cysteine was incorporated in different positions in order to gain better insight into the role of the cysteine residues in NiSOD. The results are compared with those obtained with the wild-type fragment of NiSOD. The complex formation equilibria of nickel(II) with the two peptides exhibit different features. In the case of NiSODHH, the ligand field of the (NH2,NIm,NIm,S-) donor set is not strong enough to cause spin pairing and an octahedral paramagnetic complex is formed under physiological conditions. In contrast, NiSODHC forms a square-planar diamagnetic complex with (NH2,N-,S-,NIm) donors which exhibits remarkable SOD activity. Our results unambiguously prove that the presence of cysteine in the secondary position of the peptide chain is crucial to establish the square-planar geometry in the reduced form of NiSOD, while the distant cysteine affects the redox properties of the Ni(II)/Ni(III) couple. Compared to the model systems, the Ni(II) complex with the wild-type fragment of NiSOD exhibits superior SOD activity. This confirms that both cysteinyl residues are essential in the efficient degradation of superoxide ion. The enzyme mimetic complexes are also capable of assisting the decomposition of superoxide ion; however, they show considerably smaller catalytic activity due to the absence of one of the cysteine residues.


Assuntos
Complexos de Coordenação/química , Cisteína/química , Níquel/química , Fragmentos de Peptídeos/química , Superóxido Dismutase/química , Catálise , Complexos de Coordenação/metabolismo , Cisteína/metabolismo , Níquel/metabolismo , Fragmentos de Peptídeos/metabolismo , Ligação Proteica , Conformação Proteica , Estrutura Secundária de Proteína , Superóxido Dismutase/metabolismo , Superóxidos/química
20.
Biochim Biophys Acta Biomembr ; 1862(7): 183236, 2020 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-32126226

RESUMO

Piscidins are host-defense peptides (HDPs) from fish that exhibit antimicrobial, antiviral, anti-cancer, anti-inflammatory, and wound-healing properties. They are distinctively rich in histidine and contain an amino terminal copper and nickel (ATCUN) binding motif due to the presence of a conserved histidine at position 3. Metallation lowers their total charge and provides a redox center for the formation of radicals that can convert unsaturated fatty acids (UFAs) into membrane-destabilizing oxidized phospholipids (OxPLs). Here, we focus on P1, a particularly membrane-active isoform, and investigate how metallating it and making OxPL available influence its membrane activity. First, we quantify through dye leakage experiments the permeabilization of the apo- and holo-forms of P1 on model membranes containing a fixed ratio of anionic phosphatidylglycerol (PG) and zwitterionic phosphatidylcholine (PC) but varying amounts of Aldo-PC, an OxPL derived from the degradation of several UFAs. Remarkably, metallating P1 increases membranolysis by a factor of five in each lipid system. Conversely, making Aldo-PC available improves permeabilization by a factor of two for each peptide form. Second, we demonstrate through CD-monitored titrations that the strength of the peptide-membrane interactions is similar in PC/PG and PC/PG/Aldo-PC. Thus, peptide-induced membrane activity is boosted by properties intrinsic to the peptide (e.g., charge and structural changes associated with metallation) and bilayer (e.g., reversal of sn-2 chain due to oxidation). Third, we show using oriented-sample 15N solid-state NMR that the helical portion of P1 lies parallel to the bilayer surface in both lipid systems. 31P NMR experiments show that both the apo- and holo-states interact more readily with PC in PC/PG. However, the presence of Aldo-PC renders the holo-, but not the apo-state, more specific to PG. Hence, the membrane disruptive effects of P1 and its specificity for the anionic lipids found on pathogenic cell membrane surfaces are simultaneously optimized when it is metallated and the OxPL is present. Overall, this study deepens our insights into how OxPLs affect peptide-lipid interactions and how host defense metallopeptides could help integrate the effects of antimicrobial agents.


Assuntos
Peptídeos Catiônicos Antimicrobianos/química , Ácidos Graxos Insaturados/química , Proteínas de Peixes/genética , Metais/química , Animais , Anti-Infecciosos/química , Peptídeos Catiônicos Antimicrobianos/genética , Sítios de Ligação , Membrana Celular , Cobre/química , Ácidos Graxos Insaturados/genética , Proteínas de Peixes/química , Histidina/química , Histidina/genética , Humanos , Bicamadas Lipídicas/química , Lipídeos de Membrana/química , Lipídeos de Membrana/genética , Níquel/química , Fosfolipídeos/química , Fosfolipídeos/genética
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