RESUMEN
Arsenic is a toxic and carcinogenic contaminant of potential concern. Ettringite [Ca6Al2(SO4)3(OH)12·26H2O] has the ability to incorporate oxyanions as a solid solution with SO42-, which could lower the soluble oxyanion concentrations. Therefore, ettringite containing SO42- and AsO43- has been synthesized. Results indicated that AsO43- could substitute for SO42- inside the channels of ettringite in the form of HAsO42-, and a linear correlation existed between Xinitial solution and Xsolid. The thermodynamic characterization of the solid samples was investigated by means of Visual MINTEQ, a freeware chemical equilibrium model, and the solubility product logK of -48.4 ± 0.4 was calculated for HAsO4-ettringite at 25°C. The Lippmann phase diagram and XHAsO4-XHAsO4,aq plot showed that the solid solution series containing arsenate has HAsO4-poor aqueous solutions in equilibrium. These findings can be helpful to arsenate solidification and arsenate leaching modeling projects.
Asunto(s)
Arseniatos/química , Minerales/química , Arseniatos/síntesis química , Sulfatos/química , TermodinámicaRESUMEN
Improved biotechnological method of receiving the antiviral drug ribavirin by the reaction of transglycosilation by addition of catalytic amounts of sodium arsenate in the reaction mixture. Such approach allows to hydrolyze the amount of the excess natural nucleoside donor--ribose and, as a consequence, to simplify the composition of the reaction mixture and the process of separation of ribavirin. The effect of ribavirin and ozeltamivir carboxylate and their combination on the reproduction of the virus of the influenza A in cell culture and in experiments on laboratory animals (mouse Balb/C). The greatest anti-influenza effect is observed when using a combination of drugs, as compared to each of them taken separately.
Asunto(s)
Virus de la Influenza A/efectos de los fármacos , Gripe Humana/tratamiento farmacológico , Ribavirina/administración & dosificación , Replicación Viral/efectos de los fármacos , Animales , Arseniatos/síntesis química , Arseniatos/química , Perros , Combinación de Medicamentos , Humanos , Gripe Humana/virología , Células de Riñón Canino Madin Darby , Ratones , Oseltamivir/administración & dosificación , Ribavirina/análogos & derivados , Ribavirina/síntesis químicaRESUMEN
The photochemistry of an aqueous suspension of goethite in the presence of arsenite (As(III)) was investigated with X-ray absorption near edge structure (XANES) spectroscopy and solution-phase analysis. Irradiation of the arsenite/goethite under conditions where dissolved oxygen was present in solution led to the presence of arsenate (As(V)) product adsorbed on goethite and in solution. Under anoxic conditions (absence of dissolved oxygen), As(III) oxidation occurred, but the As(V) product was largely restricted to the goethite surface. In this circumstance, however, there was a significant amount of ferrous iron release, in stark contrast to the As(III) oxidation reaction in the presence of dissolved oxygen. Results suggested that in the oxic environment ferrous iron, which formed via the photoinduced oxidation of As(III) in the presence of goethite, was heterogeneously oxidized to ferric iron by dissolved oxygen. It is likely that aqueous reactive oxygen species formed during this process led to the further oxidation of As(III) in solution. Results from the current study for As(III)/goethite also were compared to results from a prior study of the photochemistry of As(III) in the presence of another iron oxyhydroxide, ferrihydrite. The comparison showed that at pH 5 and 2 h of light exposure the instantaneous rate of aqueous-phase As(V) formation in the presence of goethite (12.4 × 10(-5) M s(-1) m(-2)) was significantly faster than in the presence of ferrihydrite (6.73 × 10(-6) M s(-1) m(-2)). It was proposed that this increased rate of ferrous iron oxidation in the presence of goethite and dissolved oxygen was the primary reason for the higher As(III) oxidation rate when compared to the As(III)/ferrihydrite system. The surface area-normalized pseudo-first-order rate constant, for example, associated with the heterogeneous oxidation of Fe(II) by dissolved oxygen in the presence of goethite (1.9 × 10(-6) L s(-1) m(-2)) was experimentally determined to be considerably higher than if ferrihydrite was present (2.0 × 10(-7) L s(-1) m(-2)) at a solution pH of 5.
Asunto(s)
Arseniatos/síntesis química , Arsenitos/química , Compuestos de Hierro/química , Minerales/química , Procesos Fotoquímicos , Concentración de Iones de Hidrógeno , Cinética , Oxidación-Reducción , Oxígeno/química , Solubilidad , Espectroscopía de Absorción de Rayos XRESUMEN
In this study, 5,17-bis-[(N-methylglucamine)methyl]-25,26,27,28-tetrahydroxy-calix[4]arene (3) was synthesized by the treatment of calix[4]arene with a secondary amine N-methylglucamine and formaldehyde. The calixarene derivative (3) was characterized by a combination of FTIR, (1)H NMR and elemental analyses. Followingly, using the macrocyclic building block, the compound 3 was immobilized by [3-(2,3-epoxypropoxy)propyl]trimethoxysilane-modified Fe(3)O(4) magnetite nanoparticles (EPPTMS-MN). The prepared calix[4]arene immobilized material was characterized by a combination of Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and thermogravimetric analyses (TGA). Moreover, the studies regarding the removal of arsenate and dichromate ions from the aqueous solutions were also carried out by using the compound in solid-liquid extraction experiments. It was found that the calix[4]arene-based magnetic material has high extraction ability towards dichromate and arsenate anions in 66% (at pH 1.5) and in 86% (at pH 3.5), respectively.
Asunto(s)
Arseniatos/química , Calixarenos/química , Cromatos/química , Magnetismo , Meglumina/química , Nanopartículas/química , Fenoles/química , Adsorción , Arseniatos/síntesis química , Cromatos/síntesis química , Cromatografía en Capa Delgada , Óxido Ferrosoférrico/química , Concentración de Iones de Hidrógeno , Indicadores y Reactivos , Espectroscopía de Resonancia Magnética , Microscopía Electrónica de Transmisión , Solventes , Espectrofotometría Ultravioleta , Espectroscopía Infrarroja por Transformada de Fourier , TermogravimetríaRESUMEN
A three-dimensional iron arsenate [4,4'-bpyH2]3[Fe9(H2O)6F3(HAsO4)12(AsO4)2].2H2O, 1, has been synthesized using 4,4'-bipyridine as the templating agent under hydrothermal conditions. The structure is formed by FeO6, FeO3F3 octahedral units connected with HAsO4 and AsO4 units, forming one- and two-dimensional units in which the one-dimensional units act as a pillar. The presence of face-shared Fe-dimer units in the one-dimensional unit is noteworthy. Detailed magnetic studies indicate two possible magnetic interactions: antiferromagnetic interactions within the layer and a weak ferromagnetic polarization between the layers at very low temperatures through the Fe-dimer units.
Asunto(s)
Arseniatos , Compuestos Férricos , Magnetismo , Compuestos Organometálicos/química , Compuestos Organometálicos/síntesis química , Arseniatos/síntesis química , Arseniatos/química , Cristalografía por Rayos X , Compuestos Férricos/síntesis química , Compuestos Férricos/química , Modelos Moleculares , Estructura Molecular , TemperaturaRESUMEN
Nanoparticles of iron phosphate, iron arsenate, iron molybdate, and iron vanadate were synthesized within the 8 nm interior of ferritin. The synthesis involved reacting Fe(II) with ferritin in a buffered solution at pH 7.4 in the presence of phosphate, arsenate, vanadate, or molybdate. O2 was used as the oxidant to deposit the Fe(III) mineral inside ferritin. The rate of iron incorporation into ferritin was stimulated when oxo-anions were present. The simultaneous deposition of both iron and the oxo-anion was confirmed by elemental analysis and energy-dispersive X-ray analysis. The ferritin samples containing iron and one of the oxo-anions possessed different UV/vis spectra depending on the anion used during mineral formation. TEM analysis showed mineral cores with approximately 8 nm mineral particles consistent with the formation of mineral phases inside ferritin.
Asunto(s)
Arseniatos/síntesis química , Compuestos Férricos/síntesis química , Ferritinas/química , Hierro/química , Molibdeno/química , Vanadatos/síntesis química , Cinética , Microscopía Electrónica de Transmisión , Minerales/análisis , Oxidantes , Oxígeno , Espectrofotometría UltravioletaRESUMEN
Seafood frequently contains high concentrations of arsenic (approximately 10-100 mg/kg dry weight). In marine algae (seaweed), this arsenic occurs predominantly as ribose derivatives known collectively as arsenosugars. Although it is clear that arsenosugars are not acutely toxic, there is a possibility of arsenosugars having slight chronic toxicity. In general, trivalent arsenicals are more toxic than their pentavalent counterparts, so in this work we examine the hypothesis that trivalent arsenosugars might be significantly more toxic than pentavalent arsenosugars in vitro. We compared the in vitro toxicity of (R)-2,3-dihydroxypropyl-5-deoxy-5-dimethylarsinoyl-beta-D-riboside, a pentavalent arsenosugar, to that of its trivalent counterpart, (R)-2,3-dihydroxypropyl-5-deoxy-5-dimethylarsino-beta-D-riboside. The trivalent arsenosugar nicked plasmid DNA, whereas the pentavalent arsenosugar did not. The trivalent arsenosugar was more cytotoxic (IC50 = 200 microM, 48 h exposure) than its pentavalent counterpart (IC50 > 6000 microM, 48 h exposure) in normal human epidermal keratinocytes in vitro as determined via the neutral red uptake assay. However, both the trivalent and the pentavalent arsenosugars were significantly less toxic than MMA(III), DMA(III), and arsenate. Neither the pentavalent arsenosugar nor the trivalent arsenosugar were mutagenic in Salmonella TA104. The trivalent arsenosugar was readily formed by reaction of the pentavalent arsenosugar with thiol compounds, including, cysteine, glutathione, and dithioerythritol. This work suggests that the reduction of pentavalent arsenosugars to trivalent arsenosugars in biology might have environmental consequences, especially because seaweed consumption is a significant environmental source for human exposure to arsenicals.