Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 5.520
Filtrar
1.
J Phys Chem Lett ; 11(3): 1178-1188, 2020 Feb 06.
Artigo em Inglês | MEDLINE | ID: mdl-31976669

RESUMO

The lack of long-term stability, the presence of toxic lead, and a low photoluminescence (PL) efficiency are the major obstacles to the commercialization of lead-halide perovskite-based optoelectronic and photovoltaic devices. Herein we report a facile ambient condition doping protocol that addresses all three issues of the CsPbX3 perovskite nanocrystals (NCs) to a substantial extent. We show that the room-temperature treatment of these NCs with MgX2 results in the partial (18-23%) replacement of toxic lead, enhances the PL quantum yield of green-emitting CsPbBr3 (to ∼100% from ∼51%) and violet-emitting CsPbCl3 NCs (to ∼79% from ∼1%), and improves the stability under ambient conditions and in the presence of light and a polar solvent. Ultrafast pump-probe and temperature-dependent PL studies reveal that curing of the intrinsic structural disorder, introduction of some shallow energy levels close to the conduction band edge, and effective passivation of the halide deficiency contribute to the improved properties of the doped systems.


Assuntos
Compostos de Cálcio/química , Magnésio/química , Nanopartículas Metálicas/química , Óxidos/química , Titânio/química , Hexanos/química , Íons/química , Luminescência , Temperatura Ambiente
2.
Chemosphere ; 239: 124741, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31518921

RESUMO

In many parts of the world, wastewater irrigation has become a common practice because of freshwater scarcity and to increase resource reuse efficiency. Wastewater irrigation has positive impacts on livelihoods and at the same time, it has adverse impacts related to environmental pollution. Hydrochemical processes and groundwater behaviour need to be analyzed for a thorough understanding of the geochemical evolution in the wastewater irrigated systems. The current study focuses on a micro-watershed in the peri-urban Hyderabad of India, where farmers practice intensive wastewater irrigation. To evaluate the major factors that control groundwater geochemical processes, we analyzed the chemical composition of the wastewater used for irrigation and groundwater samples on a monthly basis for one hydrological year. The groundwater samples were collected in three settings of the watershed: wastewater irrigated area, groundwater irrigated area and upstream peri-urban area. The collected groundwater and wastewater samples were analyzed for major anions, cations and nutrients. We systematically investigated the anthropogenic influences and hydrogeochemical processes such as cation exchange, precipitation and dissolution of minerals using saturated indices, and freshwater-wastewater mixtures at the aquifer interface. Saturation indices of halite, gypsum and fluorite are exhibiting mineral dissolution and calcite and dolomite display mineral precipitation. Overall, the results suggest that the groundwater geochemistry of the watershed is largely controlled by long-term wastewater irrigation, local rainfall patterns and water-rock interactions. The study results can provide the basis for local decision-makers to develop sustainable groundwater management strategies and to control the aquifer pollution influenced by wastewater irrigation.


Assuntos
Irrigação Agrícola/métodos , Água Subterrânea/química , Águas Residuárias , Ânions/análise , Carbonato de Cálcio/química , Sulfato de Cálcio/química , Cátions/análise , Meio Ambiente , Monitoramento Ambiental/métodos , Água Doce/química , Água Subterrânea/análise , Hidrologia/métodos , Índia , Magnésio/química , Salinidade , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/química , Qualidade da Água
3.
Ecotoxicol Environ Saf ; 188: 109934, 2020 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-31740234

RESUMO

Due to the presence of toxic pollutants, soils in former military areas need remedial actions with environmentally friendly methods. Greenhouse experiments were conducted to investigate the aided phytostabilization of multi-heavy metals (HMs), i.e. Cd, Cr, Cu, Ni, Pb, Zn, in post-military soil by Festuca rubra and three mineral amendments (diatomite, dolomite and halloysite). The amendments were applied at 0 and 3.0% to each pot filled with 5 kg of polluted soil. After seven weeks of the phytostabilization, selected soil properties, biomass yield of F. rubra and immobilization of HMs by their accumulation in plant and redistribution among individual fractions in soil were determined. In addition, ecotoxicology parameters of non-amended and amended soil were established using Phytotoxkit (Sinapsis alba) and Ostracodtoxkit (Heterocypris incongruens) tests. The addition of halloysite significantly increased F. rubra biomass. Diatomite significantly increased both the Cd, Cu, Pb and Cr concentrations in the roots and the pH of the soil. The application of halloysite significantly decreased the Cd and Zn contents of the soil after the completion of the experiment. Dolomite and halloysite were more effective in HM immobilization in soil by decreasing their content in an exchangeable fraction than diatomite. These soil amendments significantly differentiated the length of S. alba roots and had a positive effect on the development of H. incongruens.


Assuntos
Carbonato de Cálcio/química , Argila/química , Recuperação e Remediação Ambiental/métodos , Festuca/crescimento & desenvolvimento , Magnésio/química , Metais Pesados/análise , Instalações Militares , Poluentes do Solo/análise , Biodegradação Ambiental , Biomassa , Festuca/química , Raízes de Plantas/crescimento & desenvolvimento , Solo/química
4.
Food Chem ; 306: 125578, 2020 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-31622835

RESUMO

Oleosomes are storage vehicles of TAGs in plant seeds. They are protected with a phospholipid-protein monolayer and extracted with alkaline aqueous media; however, pH adjustment intensifies the extraction process. Therefore, the aim of this work was to investigate the extraction mechanism of rapeseed oleosomes at pH 7 and at the presence of monovalent and divalent cations (Na+, K+, Mg2+, and Ca+2). The oleosome yield at pH 9.5 was 64 wt%, while the yield at pH 7 with H2O was just 43 wt.%. The presence of cations at pH 7, significantly enhanced the yield, with K+ giving the highest yield (64 wt.%). The cations affected the oleosome interface and their interactions. The presence of monovalent cations resulted in aggregation and minor coalescence, while divalent cations resulted in extensive coalescence. These results help to understand the interactions of oleosomes in their native matrix and design simple extraction processes at neutral conditions.


Assuntos
Brassica/química , Cálcio/química , Magnésio/química , Extratos Vegetais/química , Potássio/química , Sódio/química , Cátions Bivalentes/química , Cátions Monovalentes/química , Concentração de Íons de Hidrogênio , Gotículas Lipídicas , Sementes/química , Água
5.
J Environ Sci (China) ; 86: 65-77, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31787191

RESUMO

This study revealed the relationship between the presence of calcium impurities and ammoniacal nitrogen concentration upon crystallization of struvite. The research hypothesis was that the presence of both calcium and high concentrations of ammoniacal nitrogen (328-1000 mg/L) in waste activated sludge may influence the struvite quality and acid stability. Hence, we studied the impact of Ca:Mg ratio upon morphology, particle size, purity and dissolution of struvite, in the presence of varying levels of excess ammoniacal nitrogen. X-ray diffraction revealed that up to 31.4% amorphous material was made which was assigned to hydroxyapatite. Increasing the ammoniacal nitrogen concentration and elevation of the Mg:Ca ratio maximized the presence of struvite. Struvite particle size was also increased by ammoniacal nitrogen as was twinning of the crystals. Tests with dilute solutions of organic acid revealed the sensitivity of struvite dissolution to the physical characteristics of the struvite. Smaller particles (21.2 µm) dissolved at higher rates than larger particles (35.86 µm). However, struvite dissolved rapidly as the pH was further reduced irrespective of the physical characteristics. Therefore, addition of struvite to low pH soils was not viewed as beneficial in terms of controlled nutrient release. Overall, this study revealed that waste activated sludge effluent with high ammoniacal nitrogen was prospective for synthesis of high quality struvite material.


Assuntos
Cálcio/química , Magnésio/química , Nitrogênio/química , Estruvita/química , Eliminação de Resíduos Líquidos/métodos
6.
J Chem Theory Comput ; 15(12): 6992-7003, 2019 Dec 10.
Artigo em Inglês | MEDLINE | ID: mdl-31714772

RESUMO

Di/triphosphates perform a multitude of essential tasks, being important components of many vital organic cofactors such as adenosine/guanosine di/triphosphate (ADP/GDP, ATP/GTP), flavin adenine dinucleotide, and nicotinamide adenine dinucleotide and its phosphate derivative. They are generally bound to cations inside cells, in particular Mg2+ in the case of ATP/GTP. Yet how their metal-binding modes depend on the number, charge, and solvent exposure of the polyphosphate group and how Mg2+and Ca2+ dications that coexist in cellular fluids compete for di/triphosphates in biological systems remain elusive. Using density functional theory calculations combined with a polarizable continuum model, we have determined the relative free energies and stabilities of the different binding modes of di- and triphosphate groups to Mg2+ and Ca2+. We show that the thermodynamic outcome of the competition between Mg2+ and Ca2+ for cellular di/triphosphates depends mainly on the oligomericity/charge and metal-binding mode of the phosphate ligand as well as the solvent exposure of the binding site. Increasing the charge and thus denticity of the phosphate ligand from bi- to tridentate in a buried binding pocket enhances the affinity of the host system for the stronger charge acceptor, Mg2+. The cellular di/triphosphates's intrinsic properties and the protein matrix allowing them to bind a dication bi/tridentately, along with the higher cytosolic concentration of Mg2+ compared to Ca2+, enables Mg2+ to outcompete Ca2+ in binding to these highly charged anions. This suggests an explanation for why nature has chosen Mg2+ but not Ca2+ to perform most of the essential tasks associated with biological triphosphates.


Assuntos
Difosfato de Adenosina/química , Trifosfato de Adenosina/química , Cálcio , Guanosina Difosfato/química , Guanosina Trifosfato/química , Magnésio/química , Sítios de Ligação , Cálcio/química , Bases de Dados de Proteínas , Teoria da Densidade Funcional , Termodinâmica
7.
Phys Chem Chem Phys ; 21(39): 21798-21805, 2019 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-31573010

RESUMO

Composites of the noble metal Au supported on MgAl-LDHs were prepared by a simple impregnation-reduction method to be used as thermal- and photocatalysts for the photocatalytic degradation of ciprofloxacin and thermocatalytic decomposition of formic acid to produce hydrogen. A collection of techniques, including X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) were employed to determine the structure and morphology properties of the as-prepared Au/MgAl-LDHs. The presence of surface Au(0) in Au/MgAl-LDHs was confirmed by TEM and XPS analyses. For the first time, we compared the effect of the surfactant PVP on the catalyst and found that the Au/MgAl-LDH composite with Au particle size of 2-8 nm had better catalytic activity than the (PVP@Au)/MgAl-LDH composite with Au particle size in the range of 1-5 nm. The sizes of Au NPs in the two catalysts were similar but had different effects on the catalytic performance. This indicated that the addition of PVP had an inhibitory effect on the catalytic activity of the catalyst. To evaluate the photostability of Au/MgAl-LDHs, recycle experiments for the photocatalytic degradation of ciprofloxacin were performed, and it was found that Au/MgAl-LDHs had good stability. Finally, we also applied Au/MgAl-LDHs in environmental catalysis and energy catalysis; we hope that they will be useful in practical applications.


Assuntos
Ligas/química , Alumínio/química , Ouro/química , Hidróxidos/química , Magnésio/química , Nanopartículas Metálicas/química , Adsorção , Catálise , Ciprofloxacino/química , Formiatos/química , Hidrogênio/química , Cinética , Oxirredução , Tamanho da Partícula , Processos Fotoquímicos , Propriedades de Superfície , Poluentes Químicos da Água/química
8.
Chemosphere ; 235: 1015-1021, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31561290

RESUMO

Phosphate is one of the main contaminations in water, so an effective method of decreasing or removing phosphate is needed. The main purpose of this paper is to synthesize CaFe-LDHs and MgFe-LDHs from the mixture of calcined dolomite and ferric chloride to remove orthophosphate and pyrophosphate. The study showed that removal of orthophosphate was attributed to the precipitation by Ca2+ and adsorption by MgFe-LDHs, where the former played a main role. As for pyrophosphate, it was mainly removed by precipitation at the initial pyrophosphate concentration ranging from 3.228 to 17.04 mmol/L. When the initial concentrations became relatively higher, the removal efficiency of pyrophosphate decreased because the complexation effects by Fe3+, Ca2+ and Mg2+ took place.


Assuntos
Carbonato de Cálcio/química , Cloretos/química , Difosfatos/análise , Compostos Férricos/química , Hidróxidos/química , Magnésio/química , Fosfatos/análise , Poluentes Químicos da Água/análise , Difosfatos/isolamento & purificação , Fosfatos/isolamento & purificação , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água/métodos
9.
Biophys Chem ; 254: 106261, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31522070

RESUMO

The study of the pressure response by NMR spectroscopy provides information on the thermodynamics of conformational equilibria in proteins and nucleic acids. For obtaining a database for expected pressure effects on free nucleotides and nucleotides bound in macromolecular complexes, the pressure response of 1H chemical shifts and J-coupling constants of the purine 5'-ribonucleotides AMP, ADP, ATP, GMP, GDP, and GTP were studied in the absence and presence of Mg2+-ions. Experiments are supported by quantum-chemical calculations of populations and chemical shift differences in order to corroborate structural interpretations and to estimate missing data for AMP. The preference of the ribose S puckering obtained from the analysis of the experimental J-couplings is also confirmed by the calculations. In addition, the pressure response of the non-hydrolysable GTP analogues GppNHp, GppCH2p, and GTPγS was examined within a pressure range up to 200 MPa. As observed earlier for 31P NMR chemical shifts of these nucleotides the pressure dependence of chemical shifts is clearly non-linear in most cases. In di- and tri-phospho nucleosides, the resonances of the two protons bound to the ribose 5' carbon are non-equivalent and can be observed separately. The gg-rotamer at C4'- C5' bond is strongly preferred and the downfield shifted resonance can be assigned to the H5″ proton in the nucleotides. In contrast, in adenosine itself the frequencies of the two resonances are interchanged.


Assuntos
Espectroscopia de Prótons por Ressonância Magnética , Nucleotídeos de Purina/química , Magnésio/química , Pressão
10.
Mater Sci Eng C Mater Biol Appl ; 104: 109947, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31499970

RESUMO

Due to its good biodegradability and mechanical properties, magnesium alloys are considered as the ideal candidate for the cardiovascular stents. However, the rapid degradation in human physiological environment and the poor biocompatibility seriously limit its application for biomaterials. In the present study, a chitosan/heparinized graphene oxide (Chi/HGO) multilayer coating was constructed on the AZ31B magnesium alloy surface using layer-by-layer (LBL) method to improve the corrosion resistance and biocompatibility. The results of attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), Raman spectrum (RAMAN), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) showed that a dense and compact Chi/HGO multilayer coating was fabricated on the magnesium alloy surface. The results of potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), pH value changes and magnesium ion release suggested that the multilayer coating can significantly enhance the corrosion resistance of the magnesium alloy. Moreover, the Chi/HGO multilayer coating could not only significantly reduce the hemolysis rate and platelet adhesion, but also promote the adhesion and proliferation of endothelial cells. Therefore, the Chi/HGO multilayer coating can simultaneously improve the corrosion resistance and biocompatibility of the magnesium alloys.


Assuntos
Quitosana/química , Materiais Revestidos Biocompatíveis/química , Grafite/química , Heparina/química , Magnésio/química , Ligas/química , Adesão Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Corrosão , Células Endoteliais/efeitos dos fármacos , Humanos , Teste de Materiais/métodos , Microscopia Eletrônica de Varredura/métodos , Adesividade Plaquetária/efeitos dos fármacos , Espectrometria por Raios X/métodos , Espectroscopia de Infravermelho com Transformada de Fourier/métodos , Propriedades de Superfície/efeitos dos fármacos
11.
Mater Sci Eng C Mater Biol Appl ; 104: 109896, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31499977

RESUMO

Zinc alloys have been explored as potential materials for biodegradable vascular stents due to their tolerable corrosion rates and tunable mechanical properties. However, the performances of Zn alloys were not supported with enough toxicity or biological compatibility evaluation, particularly hemocompatibility for vascular scaffolding application. In this work, the hemocompatibility of three zinc alloys (Zn-0.8Cu, Zn-0.8Mn and Zn-0.8Li) was evaluated with 316 L stainless steel and pure zinc as controls. The hemolysis ratios of 316 L stainless steel, pure Zn, Zn-0.8Cu, Zn-0.8Mn and Zn-0.8Li were 0.38 ±â€¯0.08%, 1.04 ±â€¯0.21%, 0.47 ±â€¯0.21%, 0.57 ±â€¯0.14% and 0.52 ±â€¯0.22%, respectively, for direct contact method. Platelets aggregation on the 316 L stainless steel was observed, while the adhered platelets on the Zn alloys exhibited round shape with few pseudopodia spreading. The number of adhered platelets on the three zinc alloys (Zn-0.8Cu, Zn-0.8Mn and Zn-0.8Li) had no statistically difference compared with 316 L stainless steel, while significant fewer than the pure Zn group. None remarkable platelet activation, hematocyte aggregation, coagulation or complement activation was observed in any Zn alloy group. Furthermore, the Zn alloys prolonged prothrombin time and partial thromboplastin time, demonstrating a potential function of anticoagulation. The results demonstrated that Zn alloys presented in this work are indeed meeting the hemocompatible requirements of implant and showing the promise for perspective application as biodegradable stent.


Assuntos
Ligas/química , Materiais Biocompatíveis/química , Lítio/química , Magnésio/química , Zinco/química , Implantes Absorvíveis , Ligas/administração & dosagem , Materiais Biocompatíveis/administração & dosagem , Coagulação Sanguínea/efeitos dos fármacos , Ativação do Complemento/efeitos dos fármacos , Corrosão , Hemólise/efeitos dos fármacos , Humanos , Lítio/administração & dosagem , Teste de Materiais/métodos , Ativação Plaquetária/efeitos dos fármacos , Aço Inoxidável/química , Stents , Zinco/administração & dosagem
12.
BMC Surg ; 19(1): 130, 2019 Sep 09.
Artigo em Inglês | MEDLINE | ID: mdl-31500601

RESUMO

BACKGROUND: The use of surgical metal clips is crucial for ligating vessels in various operations. The currently available metal clips have several drawbacks; they are permanent and interfere with imaging techniques such as computed tomography (CT) or magnetic resonance (MR) imaging and carry the potential risk of endo-clip migration. We recently developed a novel magnesium (Mg) alloy for biodegradable clips that reduces artifacts on CT imaging. This study aimed to examine the tolerance, biodegradability, and biocompatibility of the Mg alloy clips compared with those of standard titanium (Ti) clips in hepatectomy. METHODS: Thirty Wistar rats were divided into two groups based on the clip used (groups A and B). The vascular pedicle, including hepatic artery, portal vein, bile duct, and hepatic vein of the left lateral lobe, was ligated with the Ti clip in group A or the Mg alloy clip in group B, and then the left lateral lobe was removed. The rats were sacrificed at 1, 4, 12, 24, and 36 weeks after surgery. Clinical and histological evaluations were performed. Absorption rate was calculated by measuring the clip volume. RESULTS: Although the Mg alloy clips showed biodegradability over time, there were no significant differences in the serum concentration of Mg between the two groups. The remaining volume ratio of Mg alloy clips was 95.5, 94.3, 80.0, 36.2, and 16.7% at 1, 4, 12, 24, and 36 weeks, respectively. No side effects occurred. Most of the microscopic changes were similar in both groups. CONCLUSIONS: The new biodegradable Mg alloy clips are safe and feasible in vessel ligation for hepatectomy in a rat model and reduce artifacts in CT imaging compared with the standard Ti clips.


Assuntos
Hepatectomia/instrumentação , Magnésio/química , Titânio/química , Ligas , Animais , Ligadura , Imagem por Ressonância Magnética , Masculino , Ratos , Ratos Wistar , Instrumentos Cirúrgicos , Tomografia Computadorizada por Raios X
13.
J Mater Sci Mater Med ; 30(8): 95, 2019 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-31414276

RESUMO

The objective of this study was to investigate the adhesion, proliferation and mineralization of osteoblasts on arginine-glycine-aspartic acid (RGD)- and magnesium ion (Mg+)-decorated zirconia coatings. The zirconia coatings were prepared via a plasma spray; RGD and Mg+ were immobilized via a silane-coupling agent and ion implantation, respectively. This study employed scanning electron microscopy (SEM) to observe the surface morphology of RGD- and Mg+-decorated zirconia coatings; surface roughness and wettability were also measured. The initial adhesion of osteoblasts was measured, and cell morphology and focal adhesion were observed. In addition, the expressions of the integrins a1, a2, a5, av, and ß1 were measured using RT-PCR. A cell count was conducted to measure proliferation. The expressions of ALP and OCN were detected based on a western blot analysis, and mineralized nodules were observed to visualize the mineralization of osteoblasts. A nanoscale surface structure could be found on the Mg+-decorated zirconia coating, and the RGD-decorated zirconia coating showed better wettability (p < 0.05). Cells on the RGD- and Mg+-decorated zirconia coating possessed better spreading properties than did cells on nondecorated surfaces, and more focal adhesion was observed. The higher expressions of the integrins a5, av and ß1 were found on the RGD-decorated zirconia coating (p < 0.05). The western blot results demonstrated that the introduction of Mg+ heightened the expressions of ALP and OCN. More and bigger mineralized nodules were observed on the Mg+- and RGD-decorated zirconia coating, which consisted of small mineralized nodules. RGD- and Mg+-functionalized zirconia coating facilitates the osteogenic reaction of osteoblasts. RGD improves the adhesion of osteoblasts, and Mg+ benefits the mineralization of osteoblasts. In addition, a synergistic effect was found between RGD and Mg+, allowing better performances with regard to adhesion, proliferation and mineralization when the two were used together rather than as separate decorations.


Assuntos
Materiais Revestidos Biocompatíveis/química , Magnésio/química , Oligopeptídeos/química , Osseointegração/fisiologia , Zircônio/química , Animais , Adesão Celular , Diferenciação Celular , Proliferação de Células , Células Cultivadas , Camundongos , Osteoblastos/citologia , Osteoblastos/fisiologia , Osteogênese/fisiologia , Propriedades de Superfície , Tecidos Suporte/química
14.
Artigo em Inglês | MEDLINE | ID: mdl-31397623

RESUMO

The kinetic, isotherm and thermodynamic modeling of the adsorption of arsenite by layered double hydroxide have been performed to analyze the feasibility, efficacy and mechanism of the system. The fast uptake was observed during the initial phase of the process, which reached equilibrium at 240 min following Elovich model. The diffusion kinetic model exhibited that the rate-limiting step of adsorption was controlled by film diffusion as well as intraparticle diffusion. The isotherm modeling revealed the applicability of the Freundlich equation with the Kf values as 8.19-13.99 (mg g-1)(L mg-1)1/n at 283-323 K showing the increasing trend of adsorption capacity, which was further confirmed by the positive value of ΔH0 (9.49 kJ mol-1) demonstrating the endothermic nature of the adsorption process. The spontaneous nature of the adsorption reaction was established by the negative values of ΔG0. Application of the calcined Mg-Fe-LDH adsorbent for the removal of arsenic from real arsenic contaminated groundwater was also successfully performed. The effect of process parameters of the adsorption system was modeled by an artificial neural network (ANN) for adsorption capacity and removal efficiency. The optimized model exhibited high R2, F-value and low values of error functions, establishing the significant applicability of the ANN model.


Assuntos
Arsenitos/química , Carbonatos/química , Água Subterrânea/química , Hidróxidos/química , Ferro/química , Magnésio/química , Adsorção , Arsênico/química , Difusão , Concentração de Íons de Hidrogênio , Cinética , Modelos Químicos , Termodinâmica , Poluentes Químicos da Água/química , Purificação da Água
15.
Molecules ; 24(15)2019 Jul 31.
Artigo em Inglês | MEDLINE | ID: mdl-31370233

RESUMO

The chemical composition and daily mineral intake (DMI) of six macro (calcium, magnesium, sodium, potassium, phosphorous, and chloride) and four microminerals (copper, iron, manganese, and zinc) were determined in four types of Portuguese breads (white wheat, maize, wheat/maize, and maize/rye breads). Samples were processed with microwave assisted digestion and mineral composition was determined with a high-resolution continuum-source atomic absorption spectrometer with flame and graphite furnace. Bread contributes to an equilibrated diet since it is rich in several minerals (0.21 mg/100 g of copper in wheat bread to 537 mg/100 g of sodium in maize/rye bread). Maize/rye bread presented the highest content of all minerals (except phosphorous and chloride), while the lowest levels were mainly found in wheat bread. Median sodium concentrations (422-537 mg/100 g) represented more than 28% of the recommended daily allowance, being in close range of the maximum Portuguese limit (550 mg/100 g). Maize/rye bread exhibited the highest DMI of manganese (181%), sodium (36%), magnesium (32%), copper (32%), zinc (24%), iron (22%), potassium (20%), and calcium (3.0%). A Principal Component Analysis (PCA) model based on the mineral content allowed the differentiation among white wheat, maize, and maize/rye bread. Zinc, magnesium, manganese, iron, phosphorus, potassium, copper, and calcium proved to be good chemical markers to differentiate bread compositions.


Assuntos
Pão/análise , Farinha/análise , Minerais/química , Triticum/química , Pão/normas , Cobre/química , Cobre/isolamento & purificação , Fibras na Dieta/análise , Humanos , Ferro/isolamento & purificação , Magnésio/química , Magnésio/isolamento & purificação , Minerais/isolamento & purificação , Fósforo/química , Fósforo/isolamento & purificação , Portugal , Espectrofotometria Atômica , Zinco/química , Zinco/isolamento & purificação
16.
Carbohydr Polym ; 223: 115062, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31426967

RESUMO

Nata de coco was chemically modified to afford the bacterial cellulose hydrogels carrying terminal alkynes. The resultant hydrogels were then converted into hydrogels carrying lactosides or those carrying α-2,3-sialyllactosides by the Cu+-catalyzed alkyne-azide cyclization. The stable homo association of the hydrogels carrying lactosides was observed in an aqueous solution containing Ca2+, thereby demonstrating the Ca2+-mediated lactoside-lactoside interactions. Ca2+ also stabilized the hetero associations among the hydrogels carrying lactosides and those carrying α-2,3-sialyllactosides, thereby also demonstrating the Ca2+-induced interactions between the lactosides and the α-2,3-sialyllactosides. The sizes of these hydrogels were of the order of ca. 5 mm, and their associations could thus be readily monitored with the naked eye.


Assuntos
Celulose/química , Hidrogéis/química , Oligossacarídeos/química , Polissacarídeos Bacterianos/química , Alquinos/química , Azidas/química , Cálcio/química , Cocos/química , Cocos/microbiologia , Hidrogéis/síntese química , Magnésio/química , Lectinas de Plantas/química , Ricinus/química , Sódio/química
17.
Comput Biol Chem ; 83: 107108, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31442707

RESUMO

Pyrazinamide (PZA) is one of the most potent bacteriostatic drug against tuberculosis, a deadliest disease with high mortality and morbidity rate. PZA metabolizes into its active form pyrazinoic acid (POA) with the help of a metalloenzyme, pyrazinamidase (PZase). Mutagenicity and metal substitution in PZase weakens the binding of PZA with PZase and increases the drug resistance in Mycobacterium tuberculosis. The present study aims at the quantum mechanistic analysis of mutant-metal substituted PZase complexes by studying the mechanics of metals and PZA binding at MCS and catalytic site, respectively. A total of 66 complexes are scrutinised in this study to elucidate the effect of mutations on the enzymatic function of PZase. Among the 10 mutations considered in this study, 7 different mutations i.e. Asp49 → Asn, His51 → Arg, Gly78 → Cys, Asp12 → Gly, Asp12 → Ala, Thr135 → Pro and Asp136 → Gly cause a detrimental effect on the activity of PZase. In addition to this, the substitution of iron with cobalt enhances the enzymatic activity of both wild type and mutant PZase while zinc, magnesium and copper reduce it. Based on these results, it is concluded that upon substitution of iron with zinc, magnesium and copper, PZase cannot function properly. Due to mutations, the reactivity of the drug also reduces as its binding with PZase weakens and this phenomenon enhances the resistance of Mycobacterium tuberculosis against drug.


Assuntos
Amidoidrolases/metabolismo , Magnésio/metabolismo , Metais Pesados/metabolismo , Mycobacterium tuberculosis/enzimologia , Teoria Quântica , Amidoidrolases/química , Amidoidrolases/genética , Antituberculosos/química , Antituberculosos/metabolismo , Antituberculosos/farmacologia , Sítios de Ligação/efeitos dos fármacos , Humanos , Magnésio/química , Metais Pesados/química , Testes de Sensibilidade Microbiana , Modelos Moleculares , Mutação , Mycobacterium tuberculosis/efeitos dos fármacos , Mycobacterium tuberculosis/metabolismo , Pirazinamida/química , Pirazinamida/metabolismo
18.
Environ Sci Pollut Res Int ; 26(29): 30452-30462, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31444717

RESUMO

This study investigates the feasibility of recovery of phosphorus via struvite precipitation from a synthetic anaerobically treated distillery spent wash by optimizing the process using a chemical equilibrium model, namely Visual MINTEQ. Process parameters such as Mg2+, [Formula: see text], and [Formula: see text] ion concentrations and pH were used as inputs into the model. Increasing the molar ratio of [Formula: see text] from 0.8:1 to 1.6:1 at pH 9 led to an increase in phosphate recovery from 88.2 to 99.5%. The model and experimental results were in good agreement in terms of phosphate recovery, indicating that the Visual MINTEQ model can be used to pre-determine the process parameters for struvite synthesis. Increasing the concentration of calcium ion adversely affected the synthesis and purity of struvite, whereas the presence of melanoidins had no significant impact. This study demonstrates that phosphorus recovery through struvite precipitation is a sustainable approach to reclaim phosphorus from high-strength industrial wastewater.


Assuntos
Fosfatos/isolamento & purificação , Estruvita/química , Eliminação de Resíduos Líquidos/métodos , Precipitação Química , Destilação , Indústria Alimentícia , Concentração de Íons de Hidrogênio , Magnésio/química , Modelos Químicos , Fósforo/química , Fósforo/isolamento & purificação , Águas Residuárias/química
19.
Int J Mol Sci ; 20(15)2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31374825

RESUMO

Because Mg-Ca-Zn alloys are biodegradable and obviate secondary implant removal, they are especially beneficial for pediatric patients. We examined the degradation performance of Mg-Ca-Zn alloys depending on the surface modification and investigated the in vivo effects on the growth plate in a skeletally immature rabbit model. Either plasma electrolyte oxidation (PEO)-coated (n = 18) or non-coated (n = 18) Mg-Ca-Zn alloy was inserted at the distal femoral physis. We measured the degradation performance and femoral segment lengths using micro-CT. In addition, we analyzed the histomorphometric and histopathologic characteristics of the growth plate. Although there were no acute, chronic inflammatory reactions in either group, they differed significantly in the tissue reactions to their degradation performance and physeal responses. Compared to non-coated alloys, PEO-coated alloys degraded significantly slowly with diminished hydrogen gas formation. Depending on the degradation rate, large bone bridge formation and premature physeal arrest occurred primarily in the non-coated group, whereas only a small-sized bone bridge formed in the PEO-coated group. This difference ultimately led to significant shortening of the femoral segment in the non-coated group. This study suggests that optimal degradation could be achieved with PEO-coated Mg-Ca-Zn alloys, making them promising and safe biodegradable materials with no growth plate damage.


Assuntos
Implantes Absorvíveis , Ligas/química , Cálcio/química , Lâmina de Crescimento/fisiologia , Magnésio/química , Zinco/química , Animais , Pinos Ortopédicos , Materiais Revestidos Biocompatíveis/química , Eletrólitos/química , Lâmina de Crescimento/ultraestrutura , Teste de Materiais , Oxirredução , Coelhos , Propriedades de Superfície
20.
Environ Sci Pollut Res Int ; 26(27): 28294-28308, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31368068

RESUMO

Stable Hg(II)-containing flue gas has been successfully simulated by the plasma oxidation of Hg(0), and an effective solution for Hg(0) mercury fumes was obtained by combining the plasma with a ceramic nanomaterial. Characterization tests showed that the ceramic nanomaterial was mainly composed of silicon dioxide (SiO2) with other minor constituents, including potassium mica (KAl3Si3O11), iron magnesium silicate (Fe0.24Mg0.76SiO3) and dolomite (CaMg(CO3)2). The nanomaterial had many tube bank structures inside with diameters of approximately 8-10 nm. The maximum sorption capacity of Hg(II) was 5156 µg/g, and the nanomaterial can be regenerated at least five times. During the adsorption, chemical adsorption first occurred between Hg(II) and sulfydryl moieties, but these were quickly exhausted, and Hg(II) was then removed by surface complexation and wrapped into Fe moieties. The pseudo-first-order kinetic model and the Langmuir equation had the best fitting results for the kinetics and isotherms of adsorption. This work suggests that the ceramic nanomaterial can be used as an effective and recyclable adsorbent in the removal of gaseous Hg(II).


Assuntos
Carbonato de Cálcio/química , Ferro/química , Magnésio/química , Mercúrio/análise , Nanoestruturas/química , Dióxido de Silício/química , Adsorção , Silicatos de Alumínio/química , Cerâmica/química , Gases , Cinética , Mercúrio/química , Minerais/química
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA