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1.
Nucleic Acids Res ; 48(15): 8663-8674, 2020 09 04.
Artigo em Inglês | MEDLINE | ID: mdl-32663277

RESUMO

Divalent metal cations are essential to the structure and function of the ribosome. Previous characterizations of the ribosome performed under standard laboratory conditions have implicated Mg2+ as a primary mediator of ribosomal structure and function. Possible contributions of Fe2+ as a ribosomal cofactor have been largely overlooked, despite the ribosome's early evolution in a high Fe2+ environment, and the continued use of Fe2+ by obligate anaerobes inhabiting high Fe2+ niches. Here, we show that (i) Fe2+ cleaves RNA by in-line cleavage, a non-oxidative mechanism that has not previously been shown experimentally for this metal, (ii) the first-order in-line rate constant with respect to divalent cations is >200 times greater with Fe2+ than with Mg2+, (iii) functional ribosomes are associated with Fe2+ after purification from cells grown under low O2 and high Fe2+ and (iv) a small fraction of Fe2+ that is associated with the ribosome is not exchangeable with surrounding divalent cations, presumably because those ions are tightly coordinated by rRNA and deeply buried in the ribosome. In total, these results expand the ancient role of iron in biochemistry and highlight a possible new mechanism of iron toxicity.


Assuntos
Cátions Bivalentes/metabolismo , Ferro/metabolismo , Clivagem do RNA/genética , Ribossomos/genética , Sítios de Ligação , Cátions Bivalentes/química , Ferro/química , Magnésio/química , Magnésio/metabolismo , Metais/química , Metais/metabolismo , Oxirredução/efeitos dos fármacos , Ribossomos/química
2.
Arch Biochem Biophys ; 690: 108468, 2020 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-32679196

RESUMO

Hsp90 is a ubiquitous, homodimer and modular molecular chaperone. Each Hsp90 protomer has three different domains, named the N-terminal domain (NTD), middle domain (MD) and C-terminal domain (CTD). The Hsp90 molecular cycle involves ATP binding and hydrolysis, which drive conformational changes. Hsp90 is critical for the viability of eukaryotic organisms, including the protozoan that causes the severe form of malaria, Plasmodium falciparum, the growth and differentiation of which are compromised when Hsp90 is inhibited. Here, we characterize the structure of a recombinant P. falciparum Hsp90 (PfHsp90) protein, as well as its MD (PfHsp90MD) and NTD plus MD (PfHsp90NMD) constructs. All the proteins were obtained with high purity and in the folded state. PfHsp90 and PfHsp90NMD interacted with adenosine nucleotides via the NTD, and Mg2+ was critical for strong binding. PfHsp90 behaved mostly as elongated and flexible dimers in solution, which dissociate with a sub-micromolar dissociation constant. The PfHsp90MD and PfHsp90NMD constructs behaved as globular and elongated monomers, respectively, confirming the importance of the CTD for dimerization. Small angle X-ray scattering data were obtained for all the constructs, and ab initio models were constructed, revealing PfHsp90 in an open conformation and as a greatly elongated and flexible protein.


Assuntos
Proteínas de Choque Térmico HSP90/química , Plasmodium falciparum/química , Proteínas de Protozoários/química , Proteínas Recombinantes/química , Adenosina/química , Trifosfato de Adenosina/química , Sítios de Ligação , Reagentes para Ligações Cruzadas/química , Cristalografia por Raios X , Hidrólise , Magnésio/química , Modelos Moleculares , Ligação Proteica , Conformação Proteica , Multimerização Proteica
3.
An Acad Bras Cienc ; 92(2): e20181062, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32638867

RESUMO

The influence of magnesium on roasting vanadium slag was investigated by simulating the roasting process of vanadium by mixing V2O5 and MgO. The calcination products of V2O5 reacted with MgO at different temperatures which were characterized by X-ray diffraction (XRD), Thermogravimetry-differential scanning calorimetry (TG-DSC) and scanning electron microscope (SEM). There were two mass loss intervals, three endothermic peaks and one exothermic peak appearing during the reaction by the integrated thermal analysis as the temperature increased from room temperature to 1273.15 K. The samples of mixed V2O5 and MgO began to melt at 573.15 K and reacted at 773 K, and the shape of the particles changed from block to ovoid or irregular sphere at 773.15 K. With increasing the reaction temperature from 973.15 to 1073.15 K, the intermediate of VO2 was produced, and MgV2O6 was partially decomposed at 1073.15 K. During this process, the particle shape gradually returned to block shape. The conversion rate of vanadium is 99.4% with MgO of 1.65%.


Assuntos
Magnésio/química , Varredura Diferencial de Calorimetria , Minerais , Termogravimetria , Vanádio
4.
Nature ; 583(7814): 66-71, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32612224

RESUMO

Dental enamel is a principal component of teeth1, and has evolved to bear large chewing forces, resist mechanical fatigue and withstand wear over decades2. Functional impairment and loss of dental enamel, caused by developmental defects or tooth decay (caries), affect health and quality of life, with associated costs to society3. Although the past decade has seen progress in our understanding of enamel formation (amelogenesis) and the functional properties of mature enamel, attempts to repair lesions in this material or to synthesize it in vitro have had limited success4-6. This is partly due to the highly hierarchical structure of enamel and additional complexities arising from chemical gradients7-9. Here we show, using atomic-scale quantitative imaging and correlative spectroscopies, that the nanoscale crystallites of hydroxylapatite (Ca5(PO4)3(OH)), which are the fundamental building blocks of enamel, comprise two nanometric layers enriched in magnesium flanking a core rich in sodium, fluoride and carbonate ions; this sandwich core is surrounded by a shell with lower concentration of substitutional defects. A mechanical model based on density functional theory calculations and X-ray diffraction data predicts that residual stresses arise because of the chemical gradients, in agreement with preferential dissolution of the crystallite core in acidic media. Furthermore, stresses may affect the mechanical resilience of enamel. The two additional layers of hierarchy suggest a possible new model for biological control over crystal growth during amelogenesis, and hint at implications for the preservation of biomarkers during tooth development.


Assuntos
Amelogênese , Esmalte Dentário/química , Ácidos/química , Cálcio/química , Carbonatos/química , Cristalização , Teoria da Densidade Funcional , Esmalte Dentário/ultraestrutura , Durapatita/química , Fluoretos/química , Humanos , Magnésio/química , Microscopia Eletrônica de Transmissão e Varredura , Sódio/química , Tomografia , Difração de Raios X
5.
Food Chem ; 328: 127091, 2020 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-32474237

RESUMO

Methanol is highly toxic for human, so methanol detection is valuable especially in water and ethanol medium without complicated and time consuming procedure. In this work, we present a new fluorescence probe for direct detection of methanol in aqueous and ethanol medium based on the ZnS:Mn2+ quantum dot (QDs) and soluble N-methylpolypyrrole (NMPPy) hybrid. Moreover, the number of spectroscopic techniques were used to study the chemical composition and optical properties of the resultant QDs as well as investigation on the sensing mechanism toward methanol. Also, methanol can be determined by using ZnS:Mn2+ QDs/NMPPy hybrid based switchable fluorescence sensing system, with high sensitivity, high selectivity and a very good detection limit of 1 mM with linearity in the concentration range of 25-230 mM (~0.1-0.9% v/v) in aqueous solution. Finally, the ZnS:Mn2+ QDs/NMPPy hybrid as optical sensor was successfully utilized to determine the amount of methanol in real alcoholic beverage samples.


Assuntos
Etanol/química , Metanol/análise , Polímeros/química , Pirróis/química , Pontos Quânticos/química , Espectrometria de Fluorescência/instrumentação , Sulfetos/química , Água/química , Compostos de Zinco/química , Corantes Fluorescentes/química , Humanos , Limite de Detecção , Magnésio/química , Metanol/química
6.
PLoS One ; 15(6): e0234045, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32544208

RESUMO

A study was conducted to determine the impact of applying different sources of Mg, namely kieserite, ground magnesium limestone (GML) and Mg-rich synthetic gypsum (MRSG) on an acid tropical soil, oil palm growth and production. Besides high amount of Mg and Ca, MRSG contains S. Exchangeable Ca in the untreated soil of the plantation was 0.64 cmolc kg-1, but its critical level to sustain oil palm growth was 0.9 cmolc kg-1. MRSG was applied in the plantation as Mg-fertilizer; however, since Ca is also a limiting nutrient, oil palm growth was correlated (r = 0.69) with Ca supplied by the MRSG. Mg needed to sustain oil palm production is normally supplied by kieserite. Its requirement can be met at a lower cost compared to that of the kieserite by using MRSG. Due to MRSG treatment, exchangeable Ca in the soil increased steadily to satisfy the requirement of oil palm for fruit bunches production. From the glasshouse and field study, it was observed that MRSG applied at 1.5 times the recommended rate gave results comparable to that of the kieserite. MRSG treatment resulted in the increase of soil pH to >5 that precipitated Al3+ as inert Al-hydroxides, which eventually enhanced oil palm seedlings growth. Thus, MRSG can also replace GML to increase soil pH and satisfy the Ca and Mg requirement of oil palm. It can be concluded that MRSG has the potential to be used as a source of Mg as well as Ca for oil palm grown on acidic soil.


Assuntos
Sulfato de Cálcio/química , Sulfato de Cálcio/farmacologia , Magnésio/química , Magnoliopsida/efeitos dos fármacos , Magnoliopsida/crescimento & desenvolvimento , Solo/química , Calibragem , Concentração de Íons de Hidrogênio , Plântula/efeitos dos fármacos , Plântula/crescimento & desenvolvimento
7.
PLoS One ; 15(6): e0234981, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32574186

RESUMO

The corrosion behavior of an AZ91D magnesium alloy was investigated under a heterogeneous electrolyte layer by using electrochemical methods and surface analysis techniques. Dynamic polarization curves and morphological characterization were obtained at the center and near the edge zones under the electrolyte layer. The influence of the gas/liquid/solid three-phase boundary zone (TPB) on the corrosion behavior of the AZ91D magnesium alloy was discussed. The corrosion rate changed more significantly near the TPB zone than that at the other zones. The AZ91D alloy exhibited the characteristics of filiform corrosion together with shallow pitting corrosion. Different from the randomly distributed shallow pits, the filiform corrosion preferred to initiate near the TPB region and then progressively expanded adjacent to the edge of the electrolyte layer. The TPB zone played a vital role in determining the corrosion location, the corrosion morphologies and the corrosion rate of the magnesium alloy by influencing the mass transport process of carbon dioxide.


Assuntos
Ligas/química , Eletrólitos/química , Magnésio/química , Corrosão , Técnicas Eletroquímicas/instrumentação , Eletrodos , Propriedades de Superfície , Difração de Raios X
8.
Artigo em Inglês | MEDLINE | ID: mdl-32471142

RESUMO

As an innovative and economical material, hydroxyapatite does little harm to the environment. In this study, a magnesium hydroxyapatite (Mg-HAP) adsorbent was prepared by doping magnesium. Magnesium doping can increase the hydroxyl groups on the surface of Mg-HAP to form more adsorption sites and improve the removal effect of the heavy metal Zn(II) in water. This study was implemented to survey the effect of different sorption elements, including the liquor initial pH, initial concentration, dose of adsorbents, and other factors, on the adsorption effect. The outcomes show that the sorption effect was best at the time that the liquor was weakly acidic (pH = 6); At a pH of 6, the temperature of 25 °C when the optimal dosage of adsorbent is 0.25 g, the maximum adsorption amount is 62.11 mg/g. Through data fitting, the adsorption process can be accurately described as a pseudo-second-order dynamics model and the Langmuir isotherm equation. According to the thermodynamic analysis, the sorption of zinc ions by Mg-HAP belongs to the process of spontaneous endothermic and entropy increase, and the increase of temperature was conducive to adsorption. Material characterization and analysis indicate that surface complexation and dissolution-precipitation was the main mechanism for adsorption of Zn(II).


Assuntos
Durapatita/química , Magnésio/química , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água , Zinco/isolamento & purificação , Adsorção , Concentração de Íons de Hidrogênio , Cinética , Solubilidade , Termodinâmica , Água
9.
Proc Natl Acad Sci U S A ; 117(21): 11217-11219, 2020 05 26.
Artigo em Inglês | MEDLINE | ID: mdl-32393617

RESUMO

Understanding the timing and mechanisms of amino acid synthesis and racemization on asteroidal parent bodies is key to demonstrating how amino acids evolved to be mostly left-handed in living organisms on Earth. It has been postulated that racemization can occur rapidly dependent on several factors, including the pH of the aqueous solution. Here, we conduct nanoscale geochemical analysis of a framboidal magnetite grain within the Tagish Lake carbonaceous chondrite to demonstrate that the interlocking crystal arrangement formed within a sodium-rich, alkaline fluid environment. Notably, we report on the discovery of Na-enriched subgrain boundaries and nanometer-scale Ca and Mg layers surrounding individual framboids. These interstitial coatings would yield a surface charge state of zero in more-alkaline fluids and prevent assimilation of the individual framboids into a single grain. This basic solution would support rapid synthesis and racemization rates on the order of years, suggesting that the low abundances of amino acids in Tagish Lake cannot be ascribed to fluid chemistry.


Assuntos
Aminoácidos , Meteoroides , Sódio/química , Água/química , Aminoácidos/biossíntese , Aminoácidos/síntese química , Colúmbia Britânica , Cálcio/química , Óxido Ferroso-Férrico/química , Concentração de Íons de Hidrogênio , Lagos , Magnésio/química , Estereoisomerismo , Tomografia/métodos
10.
Chemosphere ; 256: 126968, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32428738

RESUMO

The recycling of nutrients from wastewater and their recovery in the form of valuable products is an effective strategy to accelerate the circular economy concept. Phosphorus recovery from wastewater by struvite crystallization (MgNH4PO4·6H2O) is one of the most applied techniques to compensate for the increasing demand and to slow down the depletion rate of phosphate rocks. Using low-cost magnesium sources, such as seawater, improves the financial sustainability of struvite production. In this study, the potential of seawater for struvite crystallization versus the commonly used magnesium source, MgCl2, was tested by crystal growth and kinetic experiments. The impact of ammonium concentration, magnesium concentration and pH on the growth kinetics of struvite in synthetic and real reject water were studied. The results showed that simultaneous precipitation of calcium phosphate was insignificant when using seawater, while presence of struvite seeds diminished it further. Among the supersaturation regulators, pH had the most significant effect on the struvite growth with both MgCl2 and seawater, while high N:P molar ratios further improved the struvite crystal growth by seawater. The N:P molar ratios higher than 6 and Mg:P molar ratios higher than 0.2 are recommended to improve the crystal growth kinetics. It was concluded that seawater is a promising alternative magnesium source and the control of supersaturation regulators (i.e., Mg:P, N:P and pH) is an effective strategy to control the reaction kinetics and product properties.


Assuntos
Modelos Químicos , Água do Mar/química , Estruvita/química , Fosfatos de Cálcio , Cristalização , Cinética , Magnésio/química , Cloreto de Magnésio/química , Compostos de Magnésio/química , Minerais , Fosfatos/química , Fósforo/química , Reciclagem , Águas Residuárias/química
11.
Chemosphere ; 255: 127005, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32416395

RESUMO

Recovering phosphorus from livestock wastewater could partly mitigate the global phosphorus resource crisis. Crystallization is a promising method for removing phosphorus from wastewater, but the costs of calcium- and magnesium-containing reagents are increasing. Cheap, available, efficient materials are required to replace conventional calcium and magnesium reagents. Here, we describe a new approach to removing and recovering phosphorus from livestock wastewater of a large pig farm, containing a high phosphorus concentration. The effects of the pH, stirring speed, stirring time, and extract dose (containing calcium and magnesium) on phosphorus removal from livestock wastewater were investigated. The product was characterized by X-ray diffractometry, Fourier-transform infrared spectroscopy, and scanning electron microscopy. Under optimized conditions (pH 9.0, stirring speed 200 r/m, stirring time 600 s, Ca 207.62 mg/L, Mg 122.86 mg/L), 92% of the phosphorus was removed from livestock wastewater. The product was mainly the hydroxyapatite (Ca5(PO4)3OH) precursor amorphous calcium phosphate but also contained 1.65% (by mass) magnesium ammonium phosphate (MgNH4PO4·6H2O) crystals. The cost of dolomite to treat 1 m3 of high-phosphorus wastewater was 0.20 yuan (45.9%, 25.9%, and 75.9% lower than for pure MgCl2, MgSO4, and CaCl2, respectively) in 2019. Using dolomite to provide calcium and magnesium effectively decreases the crystallization process cost and should encourage the use of crystallization to remove phosphorus from wastewater.


Assuntos
Carbonato de Cálcio/química , Magnésio/química , Fósforo/isolamento & purificação , Águas Residuárias/química , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água/métodos , Animais , Fosfatos de Cálcio/isolamento & purificação , Cristalização , Fazendas , Gado/crescimento & desenvolvimento , Estruvita/isolamento & purificação , Suínos
12.
Chemosphere ; 250: 126416, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32380589

RESUMO

The flavonoid metal-insecticide magnesium-hesperidin complex (MgHP) has recently been considered as a novel insecticide to replace some persistent pesticides. However, it is important to evaluate its action on non-target species, mainly those living in an aquatic environment, as these ecosystems are the final receptors of most chemicals. Reactive oxygen species, antioxidant and oxidative stress biomarkers, genotoxicity as well as cell cycle was evaluated in the liver cell line from zebrafish (Danio rerio; ZF-L) exposed to 0, 0.1, 1, 10, 100 and 1000 ng mL-1 MgHP. MgHP affected cell stability by increasing reactive oxygen species (ROS) in both exposure times (24 and 96 h) at high concentrations. Catalase (CAT) activity decreased after 24 h exposure, and glutathione and metallothionein values increased, avoiding the lipid peroxidation. Genotoxicity increased as MgHP concentration increased, after 24 h exposure, exhibiting nuclear abnormalities; it was recovered after 96 h exposure, evidencing possible stimulation of DNA repair mechanisms. The alteration in the cell cycle (increasing in the Sub-G1 phase and decreasing in the S-phase) was associated with chromosomal instability. In conclusion, the responses of ROS and the antioxidant defense system depended on MgHP concentration and time exposure, while DNA exhibited some instability after 24 h exposure, which was recovered after 96 h.


Assuntos
Ciclo Celular/efeitos dos fármacos , Inseticidas/toxicidade , Fígado/efeitos dos fármacos , Poluentes Químicos da Água/toxicidade , Animais , Antioxidantes/metabolismo , Linhagem Celular , Dano ao DNA , Relação Dose-Resposta a Droga , Ecotoxicologia/métodos , Biomarcadores Ambientais/efeitos dos fármacos , Glutationa/metabolismo , Hesperidina/química , Hesperidina/toxicidade , Inseticidas/administração & dosagem , Inseticidas/química , Peroxidação de Lipídeos/efeitos dos fármacos , Fígado/citologia , Fígado/metabolismo , Magnésio/química , Testes de Mutagenicidade/métodos , Estresse Oxidativo/efeitos dos fármacos , Estresse Oxidativo/fisiologia , Espécies Reativas de Oxigênio/metabolismo , Poluentes Químicos da Água/química , Peixe-Zebra
13.
Phys Chem Chem Phys ; 22(18): 10056-10062, 2020 May 13.
Artigo em Inglês | MEDLINE | ID: mdl-32338264

RESUMO

The brittlestar Ophiocoma wendtii is theorised to employ a technique already used in metallurgy in order to optimise the mechanical properties of calcitic microlenses within their skeletons. These microlenses contain arrays of Mg-rich nanoprecipitates, which are proposed to inhibit crack propagation through the compression of the local host lattice. Here, we employ classical molecular dynamics in order to study the effects of Mg-rich nanoprecipitates on lattice strain, stress distributions and crack propagation in calcite. Our quantitative results on lattice strain and stress induced on the host matrix are compatible with empirical estimates. Simulations of crack propagation demonstrate that the inclusion of a Mg-rich region results in an increase in stress required to fracture the crystal, as well as higher residual stress in the fractured crystal. This is the result of an inhomogeneous stress distribution causing a more disordered fracture, as well as deflections of the crack away from the lowest energy (10.4) surface. The results agree with the proposal that the compression of the host lattice inhibits propagation, and offer insight into other mechanisms through which the nanoprecipitates affect crack propagation.


Assuntos
Carbonato de Cálcio/química , Magnésio/química , Nanoestruturas/química , Estrelas-do-Mar/química , Estresse Mecânico , Animais , Simulação de Dinâmica Molecular
14.
PLoS Genet ; 16(4): e1008750, 2020 04.
Artigo em Inglês | MEDLINE | ID: mdl-32348296

RESUMO

Plasmids, when transferred by conjugation in natural environments, must overpass restriction-modification systems of the recipient cell. We demonstrate that protein ArdC, encoded by broad host range plasmid R388, was required for conjugation from Escherichia coli to Pseudomonas putida. Expression of ardC was required in the recipient cells, but not in the donor cells. Besides, ardC was not required for conjugation if the hsdRMS system was deleted in P. putida recipient cells. ardC was also required if the hsdRMS system was present in E. coli recipient cells. Thus, ArdC has antirestriction activity against the HsdRMS system and consequently broadens R388 plasmid host range. The crystal structure of ArdC was solved both in the absence and presence of Mn2+. ArdC is composed of a non-specific ssDNA binding N-terminal domain and a C-terminal metalloprotease domain, although the metalloprotease activity was not needed for the antirestriction function. We also observed by RNA-seq that ArdC-dependent conjugation triggered an SOS response in the P. putida recipient cells. Our findings give new insights, and open new questions, into the antirestriction strategies developed by plasmids to counteract bacterial restriction strategies and settle into new hosts.


Assuntos
Conjugação Genética , Proteínas Virais/química , Domínio Catalítico , Cristalografia por Raios X , Enzimas de Restrição-Modificação do DNA/genética , Enzimas de Restrição-Modificação do DNA/metabolismo , Escherichia coli/enzimologia , Escherichia coli/genética , Especificidade de Hospedeiro , Magnésio/química , Metaloproteases/química , Pseudomonas putida/enzimologia , Pseudomonas putida/genética , Tetra-Hidrofolato Desidrogenase/genética , Tetra-Hidrofolato Desidrogenase/metabolismo , Proteínas Virais/genética , Proteínas Virais/metabolismo
15.
Sci Rep ; 10(1): 4483, 2020 03 11.
Artigo em Inglês | MEDLINE | ID: mdl-32161377

RESUMO

Protocellular membranes are thought to be composed of mixtures of single chain amphiphiles, such as fatty acids and their derivatives, moieties that would have been part of the complex prebiotic chemical landscape. The composition and physico-chemical properties of these prebiological membranes would have been significantly affected and regulated by their environment. In this study, pertinent properties were systematically characterized, under early Earth conditions. Two different fatty acids were mixed with their respective alcohol and/or glycerol monoester derivatives to generate combinations of binary and tertiary membrane systems. Their properties were then evaluated as a function of multiple factors including their stability under varying pH, varying Mg2+ ion concentrations, dilution regimes, and their permeability to calcein. Our results demonstrate how environmental constraints would have acted as important prebiotic selection pressures to shape the evolution of prebiological membranes. The study also illustrates that compositionally diverse membrane systems are more stable and robust to multiple selection pressures, thereby making them more suitable for supporting protocellular life.


Assuntos
Ácidos Graxos/química , Membranas/química , Origem da Vida , Permeabilidade da Membrana Celular , Cromatografia Líquida , Concentração de Íons de Hidrogênio , Íons , Magnésio/química , Modelos Teóricos
16.
G Ital Cardiol (Rome) ; 21(2 Suppl 1): 52S-59S, 2020 02.
Artigo em Italiano | MEDLINE | ID: mdl-32134409

RESUMO

Bioresorbable scaffolds have emerged as a potential breakthrough for the treatment of coronary artery lesions. The need for drug release and plaque scaffolding is temporary, and leaving a permanent stent once the process of plaque recoil and vessel healing has ended might be superfluous or even deleterious exposing the patient to the risk of very late thrombosis, eliminating vessel reactivity, impairing non-invasive imaging and precluding possible future surgical revascularization. This long-term potential limitation of permanent bare metal stents might be overcome by using a resorbable scaffold. The metallic and antithrombotic properties makes the resorbable magnesium scaffold an appealing technology for the treatment of coronary artery lesions. Notwithstanding this, its mechanical properties substantially differ from those of conventional bare metal stents, and previous experience using polymer-based scaffolds has shown that a standardized implantation technique and optimal patient and lesion selection are key factors for a successful implantation. A panel of expert cardiologists gathered to find a consensus on the best practices for Magmaris implantation in a selected patient population and to discuss the rationale for new potential future indications.


Assuntos
Implantes Absorvíveis , Doença da Artéria Coronariana/terapia , Magnésio/química , Stents Farmacológicos , Humanos , Seleção de Pacientes , Desenho de Prótese
17.
Chemistry ; 26(41): 8958-8968, 2020 Jul 22.
Artigo em Inglês | MEDLINE | ID: mdl-32198779

RESUMO

Ketol-acid reductoisomerase (KARI), the second enzyme in the branched-chain amino acid biosynthesis pathway, is a potential drug target for bacterial infections including Mycobacterium tuberculosis. Here, we have screened the Medicines for Malaria Venture Pathogen Box against purified M. tuberculosis (Mt) KARI and identified two compounds that have Ki values below 200 nm. In Mt cell susceptibility assays one of these compounds exhibited an IC50 value of 0.8 µm. Co-crystallization of this compound, 3-((methylsulfonyl)methyl)-2H-benzo[b][1,4]oxazin-2-one (MMV553002), in complex with Staphylococcus aureus KARI, which has 56 % identity with Mt KARI, NADPH and Mg2+ yielded a structure to 1.72 Šresolution. However, only a hydrolyzed product of the inhibitor (i.e. 3-(methylsulfonyl)-2-oxopropanic acid, missing the 2-aminophenol attachment) is observed in the active site. Surprisingly, Mt cell susceptibility assays showed that the 2-aminophenol product is largely responsible for the anti-TB activity of the parent compound. Thus, 3-(methylsulfonyl)-2-oxopropanic acid was identified as a potent KARI inhibitor that could be further explored as a potential biocidal agent and we have shown 2-aminophenol, as an anti-TB drug lead, especially given it has low toxicity against human cells. The study highlights that careful analysis of broad screening assays is required to correctly interpret cell-based activity data.


Assuntos
Cetol-Ácido Redutoisomerase/metabolismo , Magnésio/química , Mycobacterium tuberculosis/enzimologia , NADP/química , Staphylococcus aureus/metabolismo , Domínio Catalítico , Cristalização , Cristalografia por Raios X , Humanos , Cetol-Ácido Redutoisomerase/química , Mycobacterium tuberculosis/química , NADP/metabolismo , Staphylococcus aureus/química
18.
Food Chem ; 320: 126625, 2020 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-32203839

RESUMO

The cellular antioxidant activity (CAA) assay is wildly used for quantifying antioxidant activities of foods and dietary supplements in vitro. Among various incubation and handling buffers used in different laboratories, the inconsistence in concentrations of ions, particularly calcium and magnesium, has somehow been neglected. We hired the Hank's balanced salt solution with or without calcium and magnesium to perform CAA assay in Caco-2 cells and HepG2 cells, evaluating the impacts of these cations. The absence of calcium and magnesium reduced intracellular ROS level and underestimated the CAA of quercetin, Trolox and catechin. The abnormally high extracellular calcium and magnesium can also produce inaccurate results. Hank's buffer is recommended to ensure the accuracy and reproducibility. It elucidates precautions must be taken on these cations' concentrations of the buffers while conducting CAA determinations on different types of cells and when comparing foods and beverages with various calcium/magnesium contents.


Assuntos
Antioxidantes/farmacologia , Cálcio/farmacologia , Magnésio/farmacologia , Cálcio/química , Linhagem Celular Tumoral , Humanos , Magnésio/química , Quercetina , Reprodutibilidade dos Testes
19.
Chemosphere ; 251: 126326, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32163777

RESUMO

Eutrophication of surface water bodies is a global problem in recent years. Dosing polluted water with oxygen releasing compounds (ORCs), especially those that can remove excessive nutrients simultaneously is regarded as one of the most economical and eco-friendly methods of treating eutrophic waters. In this study, a novel Mg-based ORC was synthesized and characterized as a magnesium hydroxide and hydrogen peroxide complex (MHHPC) with Mg to H2O2 ratio of 2:1. Oxygen-releasing, pH-adjusting and nutrient-removal potentials of MHHPC were evaluated in nano-pure and eutrophic water. The overall performance of MHHPC in preventing the eutrophic water from turning black and odorous was compared with the performance of other ORCs namely, MgO2, CaO2 and the combination of MgCl2 and H2O2. The results showed that MHHPC was capable of constantly releasing oxygen to aqueous phase over a period of one week. Phosphate and ammonia nitrogen in synthetic buffered water can were removed as struvite and other precipitates from the aqueous phase. In the synthetic eutrophic water, all the ORCs tested were able to reduce aqueous ammonia nitrogen below 0.5 mM, while only CaO2 and MHHPC successfully removed the aqueous phosphate. However, CaO2 and MgCl2+H2O2 significantly inhibited microbial activity.


Assuntos
Recuperação e Remediação Ambiental , Magnésio/química , Poluição da Água , Amônia , Eutrofização , Peróxido de Hidrogênio , Nitrogênio , Oxigênio/química , Fosfatos , Fósforo , Estruvita , Água , Purificação da Água
20.
Biomed Eng Online ; 19(1): 12, 2020 Feb 18.
Artigo em Inglês | MEDLINE | ID: mdl-32070352

RESUMO

BACKGROUND: Bone defects are often combined with the risk of infection in the clinic, and artificial bone substitutes are often implanted to repair the defective bone. However, the implant materials are carriers for bacterial growth, and biofilm can form on the implant surface, which is difficult to eliminate using antibiotics and the host immune system. Magnesium (Mg) was previously reported to possess antibacterial potential. METHODS: In this study, Mg was incorporated into poly(lactide-co-glycolic acid) (PLGA) to fabricate a PLGA/Mg scaffold using a low-temperature rapid-prototyping technique. All scaffolds were divided into three groups: PLGA (P), PLGA/10 wt% Mg with low Mg content (PM-L) and PLGA/20 wt% Mg with high Mg content (PM-H). The degradation test of the scaffolds was conducted by immersing them into the trihydroxymethyl aminomethane-hydrochloric acid (Tris-HCl) buffer solution and measuring the change of pH values and concentrations of Mg ions. The antibacterial activity of the scaffolds was investigated by the spread plate method, tissue culture plate method, scanning electron microscopy and confocal laser scanning microscopy. Additionally, the cell attachment and proliferation of the scaffolds were evaluated by the cell counting kit-8 (CCK-8) assay using MC3T3-E1 cells. RESULTS: The Mg-incorporated scaffolds degraded and released Mg ions and caused an increase in the pH value. Both PM-L and PM-H inhibited bacterial growth and biofilm formation, and PM-H exhibited higher antibacterial activity than PM-L after incubation for 24 and 48 h. Cell tests revealed that PM-H exerted a suppressive effect on cell attachment and proliferation. CONCLUSIONS: These findings demonstrated that the PLGA/Mg scaffolds possessed favorable antibacterial activity, and a higher content of Mg (20%) exhibited higher antibacterial activity and inhibitory effects on cell attachment and proliferation than low Mg content (10%).


Assuntos
Antibacterianos/química , Antibacterianos/farmacologia , Magnésio/química , Teste de Materiais , Copolímero de Ácido Poliláctico e Ácido Poliglicólico/química , Copolímero de Ácido Poliláctico e Ácido Poliglicólico/farmacologia , Células 3T3 , Animais , Antibacterianos/toxicidade , Adesão Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Concentração de Íons de Hidrogênio , Camundongos , Copolímero de Ácido Poliláctico e Ácido Poliglicólico/toxicidade , Tecidos Suporte/química
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