Enhancing Free Cyanide Photocatalytic Oxidation by rGO/TiO2 P25 Composites.

Graphene-TiO2 composites have been investigated in various photocatalytic reactions showing successful synergy compared to pristine TiO2. In the present work, graphene oxide (GO) was synthesized by the Hummers method and then reduced graphene oxide-TiO2 composites (rGO/TiO2) were obtained by an in situ GO photoreduction route. X-ray diffraction, FTIR, Raman, UV-vis DRS, and photoluminescence were the main characterization techniques. The obtained composites containing 1 and 3 wt.% rGO were evaluated in the cyanide (50 mg/L) oxidation and Au-cyanide complex (300 mg/L) degradation under UV-A light. The composites showed higher photocatalytic activity than TiO2, mainly with the 1% rGO content. Cyanate and gold nanoparticles, deposited on the photocatalyst's surface, were the main byproducts during the photocatalyst assessment. The improved photocatalytic activity of the composites was attributed to a higher rate of electron transfer and a lower rate of charge recombination due to the chemical interaction of rGO with TiO2.

Bis-cations with two 2,3-diferrocenylcyclopropenium fragments stabilized with diamino-alkanes: Synthesis and cytotoxic activity.

Bis-cations with two 2,3-diferrocenylcyclopropenium fragments 3a-d, and the cis-2-(1,2-diferrocenylvinyl)-2-imidazolinium tetrafluoroborates 4a, d or the cis-2-(1,2-diferrocenylvinyl)-3,4,5,6-tetrahydropyrimidin-2-ium tetrafluoroborates 4b, c were obtained by interactions of 2,3-diferrocenyl-1-ethoxycyclopropenium tetrafluoroborate 1 with bis-1,4-N,N-(2a, d) or bis-1,5-N,N-(2b, c) nucleophiles. The reactions of 3a-d with sodium azide proceed with high regioselectivity, forming tetraferrocenyl-substituted compounds: N,N'-bis-(4',6'-diferrocenyl-1',2',3'-triazin-5'-yl)-piperazine 5a, N,N'-bis-(4',6'-diferrocenyl-1',2',3'-triazin-5'-yl)-N,N'-dialkyl-1,3- or 1,2-alkanediamines 5b-d. Sodium hydrogencyanamide reacts with 3a-d to form N,N'-bis-(1'-aza-1'-cyano-3',4'-diferrocenyl-1',3'-butadien-2'-yl)-piperazine 6a, N,N'-dialkyl-1,3- or 1,2-alkanediamines 6b-d and N-(1'-cyano-3',4'-diferrocenyl-1'-aza-1',3'-butadien-2'-yl)-N,N'-dialkyl-alkanediamines 7a-d. The characterization of new compounds was done by IR, 1H and 13C NMR spectroscopy, mass-spectrometry, elemental analysis, and X-ray diffraction analysis only for the compounds 4b, 4d, and 7a. The biological activity of compounds 5a, 6a, 6b, 6c was assessed regarding anticancer activity against U-251, K-562, SKLU-1, HCT-15, and MCF-7 cell lines. All tested compounds showed good activity but compounds 6a and 6b had the best anticancer activity against U-251 (human glioblastoma) and SKLU-1 (human lung adenocarcinoma) cultures.

Kidney-specific WNK1 isoform (KS-WNK1) is a potent activator of WNK4 and NCC.

Familial hyperkalemic hypertension (FHHt) can be mainly attributed to increased activity of the renal Na+:Cl- cotransporter (NCC), which is caused by altered expression and regulation of the with-no-lysine (K) 1 (WNK1) or WNK4 kinases. The WNK1 gene gives rise to a kidney-specific isoform that lacks the kinase domain (KS-WNK1), the expression of which occurs primarily in the distal convoluted tubule. The role played by KS-WNK1 in the modulation of the WNK/STE20-proline-alanine rich kinase (SPAK)/NCC pathway remains elusive. In the present study, we assessed the effect of human KS-WNK1 on NCC activity and on the WNK4-SPAK pathway. Microinjection of oocytes with human KS-WNK1 cRNA induces remarkable activation and phosphorylation of SPAK and NCC. The effect of KS-WNK1 was abrogated by eliminating a WNK-WNK-interacting domain and by a specific WNK inhibitor, WNK463, indicating that the activation of SPAK/NCC by KS-WNK1 is due to interaction with another WNK kinase. Under control conditions in oocytes, the activating serine 335 of the WNK4 T loop is not phosphorylated. In contrast, this serine becomes phosphorylated when the intracellular chloride concentration ([Cl-]i) is reduced or when KS-WNK1 is coexpressed with WNK4. KS-WNK1-mediated activation of WNK4 is not due to a decrease of the [Cl-]i. Coimmunoprecipitation analysis revealed that KS-WNK1 and WNK4 interact with each other and that WNK4 becomes autophosphorylated at serine 335 when it is associated with KS-WNK1. Together, these observations suggest that WNK4 becomes active in the presence of KS-WNK1, despite a constant [Cl-]i.

The Effect of WNK4 on the Na+-Cl- Cotransporter Is Modulated by Intracellular Chloride.

It is widely recognized that the phenotype of familial hyperkalemic hypertension is mainly a consequence of increased activity of the renal Na(+)-Cl(-) cotransporter (NCC) because of altered regulation by with no-lysine-kinase 1 (WNK1) or WNK4. The effect of WNK4 on NCC, however, has been controversial because both inhibition and activation have been reported. It has been recently shown that the long isoform of WNK1 (L-WNK1) is a chloride-sensitive kinase activated by a low Cl(-) concentration. Therefore, we hypothesized that WNK4 effects on NCC could be modulated by intracellular chloride concentration ([Cl(-)]i), and we tested this hypothesis in oocytes injected with NCC cRNA with or without WNK4 cRNA. At baseline in oocytes, [Cl(-)]i was near 50 mM, autophosphorylation of WNK4 was undetectable, and NCC activity was either decreased or unaffected by WNK4. A reduction of [Cl(-)]i, either by low chloride hypotonic stress or coinjection of oocytes with the solute carrier family 26 (anion exchanger)-member 9 (SLC26A9) cRNA, promoted WNK4 autophosphorylation and increased NCC-dependent Na(+) transport in a WNK4-dependent manner. Substitution of the leucine with phenylalanine at residue 322 of WNK4, homologous to the chloride-binding pocket in L-WNK1, converted WNK4 into a constitutively autophosphorylated kinase that activated NCC, even without chloride depletion. Elimination of the catalytic activity (D321A or D321K-K186D) or the autophosphorylation site (S335A) in mutant WNK4-L322F abrogated the positive effect on NCC. These observations suggest that WNK4 can exert differential effects on NCC, depending on the intracellular chloride concentration.

The ß1-subunit of the MaxiK channel associates with the thromboxane A2 receptor and reduces thromboxane A2 functional effects.

The large conductance voltage- and Ca(2+)-activated K(+) channel (MaxiK, BK(Ca), BK) is composed of four pore-forming α-subunits and can be associated with regulatory ß-subunits. One of the functional roles of MaxiK is to regulate vascular tone. We recently found that the MaxiK channel from coronary smooth muscle is trans-inhibited by activation of the vasoconstricting thromboxane A(2) prostanoid receptor (TP), a mechanism supported by MaxiK α-subunit (MaxiKα)-TP physical interaction. Here, we examined the role of the MaxiK ß1-subunit in TP-MaxiK association. We found that the ß1-subunit can by itself interact with TP and that this association can occur independently of MaxiKα. Subcellular localization analysis revealed that ß1 and TP are closely associated at the cell periphery. The molecular mechanism of ß1-TP interaction involves predominantly the ß1 extracellular loop. As reported previously, TP activation by the thromboxane A(2) analog U46619 caused inhibition of MaxiKα macroscopic conductance or fractional open probability (FP(o)) as a function of voltage. However, the positive shift of the FP(o) versus voltage curve by U46619 relative to the control was less prominent when ß1 was coexpressed with TP and MaxiKα proteins (20 ± 6 mV, n = 7) than in cells expressing TP and MaxiKα alone (51 ± 7 mV, n = 7). Finally, ß1 gene ablation reduced the EC(50) of the U46619 agonist in mediating aortic contraction from 18 ± 1 nm (n = 12) to 9 ± 1 nm (n = 12). The results indicate that the ß1-subunit can form a tripartite complex with TP and MaxiKα, has the ability to associate with each protein independently, and diminishes U46619-induced MaxiK channel trans-inhibition as well as vasoconstriction.

New tricks of an old pattern: structural versatility of scorpion toxins with common cysteine spacing.

Scorpion venoms are a rich source of K(+) channel-blocking peptides. For the most part, they are structurally related small disulfide-rich proteins containing a conserved pattern of six cysteines that is assumed to dictate their common three-dimensional folding. In the conventional pattern, two disulfide bridges connect an α-helical segment to the C-terminal strand of a double- or triple-stranded ß-sheet, conforming a cystine-stabilized α/ß scaffold (CSα/ß). Here we show that two K(+) channel-blocking peptides from Tityus scorpions conserve the cysteine spacing of common scorpion venom peptides but display an unconventional disulfide pattern, accompanied by a complete rearrangement of the secondary structure topology into a CS helix-loop-helix fold. Sequence and structural comparisons of the peptides adopting this novel fold suggest that it would be a new elaboration of the widespread CSα/ß scaffold, thus revealing an unexpected structural versatility of these small disulfide-rich proteins. Acknowledgment of such versatility is important to understand how venom structural complexity emerged on a limited number of molecular scaffolds.

Biochemical, genetic and physiological characterization of venom components from two species of scorpions: Centruroides exilicauda Wood and Centruroides sculpturatus Ewing.

Current literature concerning the taxonomic names of two possibly distinct species of scorpions from the genus Centruroides (sculpturatus and/or exilicauda) is controversial. This communication reports the results of biochemical, genetic and electrophysiological experiments conducted with C. exilicauda Wood of Baja California (Mexico) and C. sculpturatus Ewing of Arizona (USA). The chromatographic profile fractionation of the soluble venom from both species of scorpions is different. The N-terminal amino acid sequence for nine toxins of C. exilicauda was determined and compared with those from C. sculpturatus. Lethality tests conducted in mice support the idea that C. exilicauda venom should be expected to be medically less important than C. sculpturatus. Thirteen genes from the venomous glands of the scorpion C. exilicauda were obtained and compared with previously published sequences from genes of the species C. sculpturatus. Genes coding for cytochrome oxidase I and II of both species were also sequenced. A phylogenetic tree was generated with this information showing important differences between them. Additionally, the results of electrophysiological assays conducted with the venom from both species on the Ca(2+)-dependent K(+)-channels, showed significant differences. These results strongly support the conclusion that C. exilicauda and C. sculpturatus are in fact two distinct species of scorpions.

Mapping the receptor site for ergtoxin, a specific blocker of ERG channels.

We show here that ergtoxin (ErgTx) is a bona fide, specific blocker of the human ether-a-go-go-related gene (HERG) channels. It does not affect the function of either M-eag or M-elk channels. A chimeric construction containing a segment of the P-region of M-eag channel inserted into the HERG channel drastically diminished or completely abolished the inhibitory effect of ErgTx, whereas chimeras of the P-region of HERG channel into M-eag channels recovered the inhibitory effect. From the P-region point mutants of HERG channel assays, only the mutant N598Q shows about 25% decrement of the ErgTx inhibitory effect. ErgTx recognizes the P-region of HERG channels, blocking the channel function with a K(d) in the order of 12 nM.

Obtención de ceftriaxona sódica cristalina / Obtainment of crystaline sodium ceftriaxone

La ceftriaxona sódica es uno de los antibióticos Beta lactámicos pertenecientes a las cefalosporinas aminotiazólicas parenterales de tercera generación, siendo uno de los productos principales de nuestra planta de inyectables.En el marco del proyecto de investigación “Obtención de antibióticos cefalosporánicos estériles” se han desarrollado procedimientos de síntesis de este producto y se contempla la tarea de obtención de ceftriaxona sódica cristalina ya que entre los parámetros establecidos por las monografías oficiales para el control de calidad se encuentra la “cristalinidad”.Nuestro trabajo establece que mediante una cristalización controlada en medio etanol-agua y secando por liofilización se obtiene ceftriaxona sódica cuyo espectro de difracción de rayos X coincide con el del Rocephin, producto líder en el mercado internacional(AU)

Procedimiento alternativo por Espectrofotométria para el monitoreo de la síntesis enzimática de Ceftriaxona

Se propone un método por espectroscopía ultravioleta para el seguimiento de la síntesis enzimática de ceftriaxona basado en la determinación mediante un programa MULTICOMPONENT, que por su repetibilidad, precisión, rapidez y bajo costo constituye un método analítico efectivo que posibilita la evaluación simultánea de la formación del antibiótico y el consumo de los reaccionantes: el ácido 7-amino-3-(2,5-dihidro-6-hidroxi-2-metil-5-oxo-1,2,4-triazín-3-il) tiometil-3-cefem-4-carboxílico y el ácido 2-aminotiazolil-4-il) metoximinoacético. Este procedimiento puede considerarse como un método alternativo al de HPLC, lo cual fue confirmado mediante los estudios de evaluación referentes a la repetibilidad y precisión intermedia, siendo apropiado para el monitoreo de la síntesis enzimática de este antibiótico Cefalosporánico(AU)

Gel de hidróxido de aluminio: análisis comparativo de métodos de separación sólido-líquido que se utilizan en su producción / Aluminum hydroxide: a comparative analysis of the solid-liquid separation methods used in its production

Se analizó de forma comparativa diferentes variantes de separación sólido-líquido para la obtención del gel de hidróxido de aluminio como sedimentación, filtración al vacío (por lotes y continua), filtración a presión y centrifugación. Se presentan las ventajas y desventajas de cada variante incluyendo un análisis técnico-económico de éstas. Se concluye que el uso de un filtro rotatorio al vacío satisface los requerimientos establecidos (AU)

Gel de hidróxido de aluminio: análisis comparativo de métodos de separación sólido-líquido que se utilizan en su producción / Aluminum hydroxide: a comparative analysis of the solid-liquid separation methods used in its production

Se analizó de forma comparativa diferentes variantes de separación sólido-líquido para la obtención del gel de hidróxido de aluminio como sedimentación, filtración al vacío (por lotes y continua), filtración a presión y centrifugación. Se presentan las ventajas y desventajas de cada variante incluyendo un análisis técnico-económico de éstas. Se concluye que el uso de un filtro rotatorio al vacío satisface los requerimientos establecidos

Estudio de la obtención de la Cimetidina en mezclas de etanol- agua / Study of the obtaining of the Cimetidina in mixtures of etanol-water

Se presenta un estudio de cristalización de la Cimetidina utilizando mezclas de etanol -agua a diferentes concentraciones. Se determinó mediante Espectroscopía Infrarroja la distribución de polimorfos A y B en los productos obtenidos. Se encontró que con contenidos de agua mayores al 10 porciento de la mezcla empleada en la cristalización el polimorfo que se obtiene es el B. El estudio realizado permitió además desarrollar un procedimiento semicuantitativo por Espectroscopía Infrarroja para determinar el contenido de polimorfo B en Cimetidina A (AU)

Obtención industrial del polimorfo A de la Cimetidina a partir del polimorfo B / Industrial obtaining of the polimorfe To of the Cimetidine starting from the polimorfe B

Se desarrolló un procedimiento para la obtención de Cimetidina A a partir de la forma cristalina B utilizando como solvente, etanol de producción nacional. Se estudió el disolvente a emplear; la humedad permisible del disolvente; la concentración apropiada de trabajo y la reutilización de los líquidos madres. Los productos fueron analizados por las especificaciones de calidad descritas en la USP 12 y comprobados los mismos mediante espectroscopía infrarroja (IR). Mediante el procedimiento utilizado se obtuvo Cimetidina A calidad farmacéutica tanto a escala de laboratorio como a escala industrial y los resultados obtenidos comprobaron su factibilidad técnica y económica. (AU)

Purificación de furosemida / Purification of furosemide

La furosemida es una materia prima farmacéutica que tiene acción diurética elevada, indicada en todas las formas de edema de origen cardíaco o renal, que puede degradarse por diferentes causas formando productos coloreados. El presente trabajo estudia un método para purificar la furosemida coloreada y obtenerla con la calidad que establecen las farmacopeas actuales. El método en cuestión contempla la suspensión de la furosemida en agua, la adición a ésta de solución de hidróxido de sodio para formar la sal sódica soluble y el tratamiento de esta solución con carbón activado en cantidad de 12 porciento respecto al peso de producto purificado, posterior aislamiento de la sal sódica por cristalización y filtración. Se contempla la redisolución de la misma y su hidrólisis con solución de ácido sulfúrico para restituir y precipitar la furosemida base que luego de filtrada lavada y seca cumple los requisitos de calidad que establece la USP 22. Se reporta la recuperación del producto del líquido madre y su repurificación. (AU)

Procedimiento para la obtención de Cimetidina Polimorfo "A" a partir de Cimetidina Polimorfo "B" impuro / Method for obtaining \"A\" polymorph cimetidine from impure \"B\" polymorph cimetidine

Se describen procedimientos que permiten mediante cristalización en mezclas alcohol etílico-agua (solventes de producción nacional), obtener cimetidina polimorfo a que cumple los requerimientos de la Farmacopea de los EE.UU. a partir de polimorfos A y b impuros. Se estableció que si el contenido de impureza era igual o menor al doble del permitido, podía utilizarse alcohol etilico absoluto con un rendimiento en peso superior al 70 por ciento, pero si el contenido de impurezas estaba entre 2 y 3 veces, era necesario utilizar alcohol etílico con un contenido de agua del 6 por ciento y un rendimiento en peso del 60 al 65 por ciento. Se presentan además los resultados obtenidos durante su comprobación a escala industrial