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The role of HBF(4) in electro-catalysis: Arsenic contamination and anion adsorption

SANTOS, Adriano L.; NAGAO, Raphael; OLIVEIRA, Cristiane P.; LIMA, Roberto B. de; VARELA, Hamilton
Fonte: ELSEVIER SCIENCE SA Publicador: ELSEVIER SCIENCE SA
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
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We present in this work a comprehensive investigation of the role played by dissolved tetrafluoroboric acid on the electrochemical response of a polycrystalline platinum electrode in acidic media. HBF(4) from two different suppliers was employed and characterized in terms of the amount of arsenic contamination by Inductively Coupled Plasma-Optical Emission Spectroscopy. The effect of different amounts of HBF(4) on the voltammetric profile of the Pt vertical bar HClO(4)(aq) interface was investigated by means of electrochemical quartz crystal nanobalance (EQCN). Despite the comparable cyclic voltammograms, the presence of arsenic in one of the two HBF(4) used resulted in dramatic variations in the mass change profile, which evidences the deposition/dissolution of arsenic prior to the surface oxidation. For the arsenic-free HBF(4), its effect on the mass change profile was mainly associated to anion adsorption. The impact of dissolved HBF(4) on the electro-oxidation of formic acid was rationalized in terms of two contributions: current enhancement at low potentials due to the arsenic-assisted formic acid electro-oxidation and inhibition at high potentials due to anion adsorption. (C) 2011 Elsevier B.V. All rights reserved.; Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)[2007/06037-2]; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)[2009/00153-6]; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)[2009/16449-1]; Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)[2009/07629-6]; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq)[302698/2007-8]; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq)[306151/2010-3]; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Purification of coagulation factor VIII using chromatographic methods. Direct chromatography of plasma in anion exchange resins

CHENG, Elisabeth; JINZENJI, Daniela; LORTHIOIS, Ana Paula Almeida Aranha; CARVALHO, Roberta Rodrigues de; TANAKA-AZEVEDO, Anita Mitiko; RAW, Isaias; MARTINS, Elizabeth Angelica Leme
Fonte: SPRINGER Publicador: SPRINGER
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.58%
Coagulation factor VIII (FVIII) concentrates are used in the treatment of patients with Hemophilia A. Human FVIII was purified directly from plasma using anion exchange chromatography followed by gel filtration. Three Q-Sepharose resins were tested, resulting in 40% recovery of FVIII activity using Q-Sepharose XL resin, about 80% using Q-Sepharose Fast Flow and 70% using the Q-Sepharose Big Beads. The vitamin K-dependent coagulation factors co-eluted with FVIII from the anion exchange columns. In the second step of purification, when Sepharose 6FF was used, 70% of FVIII activity was recovered free from vitamin K-dependent factors.; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP); Programa de Aprimoramento Profissional (FUNDAP); Programa de Aprimoramento Profissional (FUNDAP); Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Fundacao Butantan; Fundacao Butantan

Anion dopant effects on the structure and performance of polyethersulfone membranes

Mierzwa, José Carlos; Vecitis, Chad; Carvalho, Julia; Arieta, Victor Sartori; Verlage, Marianna
Fonte: ELSEVIER SCIENCE BV; AMSTERDAM Publicador: ELSEVIER SCIENCE BV; AMSTERDAM
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
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In this work, the effect of various casting solution salt dopants with similar cations, but different anions: (NaPO3)(6), Na2SO4, Na2CO3, NaCl, and NaF, on the morphology and performance of polyethersulfone ultrafiltration membranes was evaluated. The phase inversion process was used to produce all membranes using an 18% polyethersulfone in n-methylpyrrolidone casting solution and water as the non-solvent. Scanning electron microscopy (SEM) images of the membrane cross-section and surface pores were used to determine the specific anion effects on membrane morphology. The SEM images depicted significant changes to the membrane internal structure and pore size with respect to the type and concentration of the casting solution anion dopant. Membrane permeability, molecular weight cut-off, alginate retention, and susceptibility to fouling were evaluated using ultrapure water dead-end and ultrapure water, aqueous polyethylene glycol, aqueous sodium alginate, and natural surface water cross-flow filtration tests. Among the anions evaluated, hexametaphosphate doped at 1% w/w to the polymer resulted in the membrane with highest dead-end permeability at 490 LMH-bar (2- to 3-fold greater than the control), greatest alginate retention at 96.5%...

Influência do balanço cátion-aniônico da dieta no desempenho de ovinos.; Influence of dietary cation anion balance on performance in sheep

Del Claro, Gustavo Ribeiro
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 26/06/2003 PT
Relevância na Pesquisa
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O efeito do balanço cátion-aniônico da dieta (BCAD) no desempenho, balanço macromineral (cálcio, fósforo, sódio e potássio), na fermentação ruminal , pH urinário e na concentração sérica de cálcio, foi estudado utilizando-se 25 ovinos machos, da raça Santa Inês, por um período de 75 dias. O delineamento experimental foi em blocos ao acaso, com cinco tratamentos. Para a manipulação do BCAD foram adicionados sulfato de amônio e bicarbonato de sódio, obtendo-se os seguintes tratamentos: -160, -40, 140, 250 e 500 mEq/kg MS. O aumento do BCAD resultou em aumento da IMS, aumento em ganhos diários e eficiência alimentar (P<0,05). O pH ruminal, pH urinário e o volume urinário aumentaram com aumento do BCAD (P<0,05). O perfil de ácidos graxos ruminais não foi afetado pelo BCAD. O BCAD influenciou o metabolismo macromineral principalmente o de cálcio, com a diminução do BCAD o cálcio sérico aumentou. Dietas aniônicas aumentaram a excreção urinária de cálcio, entretanto a retenção não foi afetada.; The dietary cation-anion balance (DCAB) effect in performance, macromineral (calcium, phosphorus and sodium) balance, urinary pH and calcium serum concentration, was studied in 25 males sheeps, from Santa Ines breed...

Preparação e caracterização do ânion Radical naftalenoestabilizado por thf (aplicação na descloração De moléculas organocloradas)

Antonello, Izoldir
Fonte: Universidade Federal de Santa Catarina Publicador: Universidade Federal de Santa Catarina
Tipo: Trabalho de Conclusão de Curso Formato: 39 f.
PT_BR
Relevância na Pesquisa
36.81%
TCC (graduação) - Universidade Federal de Santa Catarina. Centro de Ciências Físicas e Matemáticas. Curso de Química.; O presente trabalho, na busca de uma metodologia limpa e barata para o processo de degradação de moléculas organocloradas (PCBs), apresenta a síntese do ânion radical naftaleno, estabilizado por tetraidrofurano e usando como álcali o sódio. A reação ocorre com conversão completa, com degradação rápida à temperatura ambiente e sobre refrigeração (temperaturas inferiores a -5 °C), a integridade do ânion é mantida. Foram desenvolvidos estudos de UV-Visível e RMN-1H para caracterização do ânion radical naftaleno. No UV-Visível observou-se que as bandas do ânion são deslocadas em relação ao naftaleno, destas, duas aparecem na região do visível, lmáx = 450 e 550 nm. Nos espectros de RMN-1H, pode-se observar a rápida degradação do ânion à temperatura ambiente, pois a obtenção do espectro logo após a síntese apresentava um único pico, característico do ânion (sem distinção dos hidrogênios a e b), mas a obtenção do mesmo após 5 (cinco) dias da síntese, apresentou picos característicos do naftaleno em grande intensidade. O ânion radical foi testado em reações de descloração de padrões de 1...

The superoxide anion donor, potassium superoxide, induces pain and inflammation in mice through production of reactive oxygen species and cyclooxygenase-2

Maioli,N.A.; Zarpelon,A.C.; Mizokami,S.S.; Calixto-Campos,C.; Guazelli,C.F.S.; Hohmann,M.S.N.; Pinho-Ribeiro,F.A.; Carvalho,T.T.; Manchope,M.F.; Ferraz,C.R.; Casagrande,R.; Verri Jr,W.A.
Fonte: Associação Brasileira de Divulgação Científica Publicador: Associação Brasileira de Divulgação Científica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2015 EN
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It is currently accepted that superoxide anion (O2•−) is an important mediator in pain and inflammation. The role of superoxide anion in pain and inflammation has been mainly determined indirectly by modulating its production and inactivation. Direct evidence using potassium superoxide (KO2), a superoxide anion donor, demonstrated that it induced thermal hyperalgesia, as assessed by the Hargreaves method. However, it remains to be determined whether KO2 is capable of inducing other inflammatory and nociceptive responses attributed to superoxide anion. Therefore, in the present study, we investigated the nociceptive and inflammatory effects of KO2. The KO2-induced inflammatory responses evaluated in mice were: mechanical hyperalgesia (electronic version of von Frey filaments), thermal hyperalgesia (hot plate), edema (caliper rule), myeloperoxidase activity (colorimetric assay), overt pain-like behaviors (flinches, time spent licking and writhing score), leukocyte recruitment, oxidative stress, and cyclooxygenase-2 mRNA expression (quantitative PCR). Administration of KO2 induced mechanical hyperalgesia, thermal hyperalgesia, paw edema, leukocyte recruitment, the writhing response, paw flinching, and paw licking in a dose-dependent manner. KO2 also induced time-dependent cyclooxygenase-2 mRNA expression in the paw skin. The nociceptive...

An efficient novel acetate anion receptor based on isatin

Su,Hongyan; Li,Jianwei; Lin,Hai; Lin,Huakuan
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2010 EN
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An anion recognition receptor, a kind of thiourea derivative, was designed and synthesized by combining indoline-2,3-dione and 1,3-diaminothiourea. The anion recognition can be easily monitored by anion complexation induced changes in UV-vis absorption spectra. In particular, the binding ratio between the receptor and fluoride is 1:2 but in the case of dihydrogenphosphate and acetate are 1:1. Moreover, the affinity constants revealed that the receptor can recognize acetate well. Finally, ¹H NMR experiments were carried out to explore the nature of interaction between this new receptor and acetate.

ANION GAP NO SANGUE VENOSO EM EQUINOS

Fan,Luís Carlos Ribeiro; Lopes,Sônia Terezinha dos Anjos; Krause,Alexandre; Costa,Paulo Renato Souza; Dutra,Valeria; Carvalho,Cláudio Baptista de
Fonte: Universidade Federal de Santa Maria Publicador: Universidade Federal de Santa Maria
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/1994 PT
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RESUMO A influência do sangue venoso na determinação do anion gap foi estudada em 50 equinos adultos clinicamente sadios no município de Santa Maria, RS. Os resultados obtidos em mEq/1 foram: sódio 140 ± 2,0; potássio 4,2 ± 0,5; cloreto 102 ± 12 e bicarbonato 26,9 ± 2,0. Conclui-se que o sangue venoso pode substituir o arterial na determinação do anion gap em equinos.

Analysis of the interaction between human kidney anion exchanger 1 and kanadaptin using yeast two-hybrid systems

Wongthida,Phonphimon; Akkarapatumwong,Varaporn; Limjindaporn,Thawornchai; Kittanakom,Saranya; Keskanokwong,Thitima; Eurwilaichitr,Lily; Yenchitsomanus,Pa-thai
Fonte: Sociedade Brasileira de Genética Publicador: Sociedade Brasileira de Genética
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2006 EN
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Kidney anion exchanger adaptor protein (Kanadaptin) is a protein which interacts with the cytoplasmic N-terminal domain of kidney anion exchanger 1 (kAE1) and was first detected in mice using the yeast two-hybrid system and was also found to co-localize with kAE1 in rabbit a-intercalated cells. Impaired trafficking of human kAE1 can result in the kidney disease-distal renal tubular acidosis (dRTA), and defective interaction between human kAE1 and kanadaptin may cause this trafficking impairment and be the basis for dRTA pathogenesis. However, it is unknown whether kAE1 can really interact with kanadaptin in humans. We have thus investigated the interaction between human kAE1 and human kanadaptin by using both Gal4 and LexA yeast two-hybrid systems. It was found that co-expression of Gal4DBD fused to the cytoplasmic N-terminal domain of kAE1 and Gal4AD fused to kanadaptin could not activate the transcription of the ADE2, HIS3 and lacZ reporters in the Gal4 system. A similar result was obtained for the interaction between B42AD fused to the cytoplasmic N-terminal domain of kAE1 and LexA fused to kanadaptin in activation of lacZ transcription in the LexA system. The absence of interaction between the fusion proteins in both yeast two-hybrid systems raises the possibility that kAE1 may not interact with kanadaptin in human cells. Considerably different structures of both kAE1 and kanadaptin in mice and humans may lead to different binding properties of the proteins in these two species.

L(+)-Lactic acid recovery from cassava bagasse based fermented medium using anion exchange resins

John,Rojan P.; Nampoothiri,K. Madhavan; Pandey,Ashok
Fonte: Instituto de Tecnologia do Paraná - Tecpar Publicador: Instituto de Tecnologia do Paraná - Tecpar
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2008 EN
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The properties of the ion exchange resins, Amberlite IRA 402, a strong anion exchange resin and IRA 67, a weak anion exchange resin were determined to evaluate their comparative suitability for lactic acid recovery from fermented cassava bagasse. Data on binding capacities and recovery proved that weak base resin in chloride form was the most favourable ones for lactic acid recovery from aqueous solutions and fermentation media. Fermented media obtained through simultaneous saccharification and fermentation of cassava bagasse starch hydrolysate based medium were used for lactic acid recovery study using weak base resin column. Amberlite IRA 67 had much more efficiency than Amberlite IRA 402 to recover lactic acid. Like in other reports, due to the presence of nutrients and ions other than lactate, the binding capacity was slightly lesser while using fermented media (~93%) instead of aqueous lactic acid solutions (~98%).

Anion Stabilization in Electrostatic Environments

Olivares-Amaya, Roberto; Stopa, Michael P; Andrade, Xavier; Watson, Mark A.; Aspuru-Guzik, Alan
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
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Excess charge stabilization of molecules in metallic environments is of particular importance for fields such as molecular electronics and surface chemistry. We study the energetics of benzene and its anion between two metallic plates. We observe that orientational effects are important at small inter-plate separation. This leads to benzene oriented perpendicular to the gates being more stable than the parallel case due to induced dipole effects. We find that the benzene anion, known for being unstable in the gas-phase, is stabilized by the plates at zero bias and an inter-plate distance of 21 Å. We also observe the effect of benzene under a voltage bias generated by the plates; under a negative bias, the anion becomes destabilized. We use the electron localization function to analyze the changes in electron density due to the bias. These findings suggest that image effects such as those present in nanoscale devices, are able to stabilize excess charge and should be important to consider when modeling molecular transport junctions and charge-transfer effects.; Chemistry and Chemical Biology

Characterization of the TaALMT1 protein as an Al³⁺-activated anion channel in transformed tobacco (Nicotiana Tabacum L.) cells; Characterisation of the TaALMT1 protein as an Al(3+)-activated anion channel in transformed tobacco (Nicotiana tabacum L.) cells

Zhang, W.H.; Ryan, P.; Sasaki, T.; Yamamoto, Y.; Sullivan, W.; Tyerman, S.
Fonte: Japanese Soc Plant Physiologists Publicador: Japanese Soc Plant Physiologists
Tipo: Artigo de Revista Científica
Publicado em //2008 EN
Relevância na Pesquisa
36.81%
TaALMT1 encodes a putative transport protein associated with Al(3+)-activated efflux of malate from wheat root apices. We expressed TaALMT1 in Nicotiana tabacum L. suspension cells and conducted a detailed functional analysis. Protoplasts were isolated for patch-clamping from cells expressing TaALMT1 and from control cells (empty vector transformed). With malate(2-) as the permeant anion in the protoplast, an inward current (anion efflux) that reversed at positive potentials was observed in protoplasts expressing TaALMT1 in the absence of Al(3+). This current was sensitive to the anion channel antagonist niflumate, but insensitive to Gd(3+). External AlCl(3) (50 microM), but not La(3+) and Gd(3+), increased the inward current in TaALMT1-transformed protoplasts. The inward current was highly selective to malate over nitrate and chloride (P(mal) >> P(NO3) >or= P(Cl), P(mal)/P(Cl) >or=18, +/-Al(3+)), under conditions with higher anion concentration internally than externally. The anion currents displayed a voltage and time dependent deactivation at negative voltages. Voltage ramps revealed that inward rectification was caused by the imposed anion gradients. Single channels with conductances between 10 and 17 pS were associated with the deactivation of the current at negative voltages...

Anion-π interactions of hexaaryl[3]radialenes; Anion-pi interactions of hexaaryl[3]radialenes

Evans, J.; Hollis, C.; Hack, S.; Gentleman, A.; Hoffmann, P.; Buntine, M.; Sumby, C.
Fonte: Amer Chemical Soc Publicador: Amer Chemical Soc
Tipo: Artigo de Revista Científica
Publicado em //2012 EN
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Coordination polymers and discrete metallo-supramolecular assemblies of hexaaryl[3]radialene compounds exhibit intriguing structures with short anion to π-centroid distances in the solid-state. Furthermore, these [3]radialene compounds display useful photophysical and electrochemical properties that make them ideal as potential platforms for anion receptors. In this study, hexafluoro[3]radialene was optimized to the MP2/aug-cc-pVTZ level of theory, and its complexes with halide anions were optimized to HF/6-31G++(d,p), MP2/6-31G++(d,p), M06-2X/6-31G++(d,p), and M06-2X/6-311G++(d,p) levels of theory. Hexafluoro[3]radialene was shown to have properties (large positive Qzz and areas of positive electrostatic surface potential) comparable to other compounds that show anion-π interactions. The interaction energies of complexes of hexafluoro[3]radialene with halide anions were calculated and found to be favorable and equivalent to those of fluorinated aromatic compounds. A series of synthetically accessible hexaaryl[3]radialenes were optimized to HF/6-31G++(d,p) theory and their complexes with halides optimized to the M06-2X/6-31G++(d,p) level of theory. The calculated properties of the electron-deficient hexaaryl[3]radialenes also show large positive Qzz quadrupole moments and two areas of positive potential; at the [3]radialene core and the acidic aryl hydrogen atoms. The interaction energies of the complexes of hexaaryl[3]radialenes and halide anions were found to follow the trend F(-) > Cl(-) ≈ Br(-) and correlate with the electron-deficient nature of the [3]radialene. Close contacts were observed between the anion and the radialene core and the aryl hydrogen atoms...

Studies of hexaaryl[3]radialene ligands: synthesis, coordination chemistry and anion interactions.

Hollis, Courtney Ann
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2013
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This thesis describes the synthesis and study of three nitrile substituted hexaaaryl[3]radialene ligands, two of which are new compounds, and three new flexible bis-pyridyl ligands produced as precursors in the attempted synthesis of extended hexaaryl[3]radialenes. The coordination and metallo-supramolecular chemistry of these compounds were investigated with a variety of different metal atoms, primarily silver(I) and copper(I) due to the nature of the soft nitrile donors. Five different coordination modes were observed for hexakis(4 cyanophenyl)[3]radialene with silver(I) and copper(I) including bidentate, tetradentate, and also the first example of this compound acting as a hexadentate ligand. The flexible bis-pyridyl ligands were observed to form predominantly 1-D coordination polymers but also on occasion led to the production of 2-D networks. Mononuclear ruthenium(II) complexes of hexakis(4-cyanophenyl)[3]radialene and hexakis(3-cyanophenyl)[3]radialene are also described, although di- and tri-nuclear complexes were unable to be obtained and thus the nature of any metal-metal interactions within such complexes were unable to be examined. Visible absorption and fluorescence spectroscopy, as well as cyclic voltammetry, were used to examine the properties of the mononuclear radialene complexes as well as dinuclear ruthenium(II) complexes of the [3]radialene precursors 4...

Novel oxidation of aromatic aldehydes catalyzed by Preyssler's anion, [NaP5W30O110]14-

Bamoharram,F. F.; Roshani,M.; Alizadeh,M. H.; Razavi,H.; Moghayadi,M.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2006 EN
Relevância na Pesquisa
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Preyssler's anion, with formula [NaP5W30O110]14-, catalyzes the oxidation of aromatic aldehydes to related carboxylic acids by hydrogen peroxide as oxidizing agent, under microwave irradiation, or at 70 ºC. Both homogeneous and heterogeneous Preyssler's catalysts (as H14[NaP5W30O110 ]) were used and had their activity compared with those of some Keggin structures. Our data indicate that Sodium30-tungsto pentaphosphate, the so-called Preyssler's anion, with high hydrolytic (pH=0-12) and thermal stability is the best catalyst with high yield and good selectivity. Under microwave irradiation, this polyanion supported on SiO2 was found to be an excellent catalyst for aldehydes with low loss factor in 1-2 min (the loss factor is a measure of the ability of the material to dissipate energy). The effects of various parameters, including catalyst type, nature of the substituent in the aldehyde and temperature, on the yield of the carboxylic acids were studied.

The Raman Spectrum of the Squarate (C4O4-2 ) Anion: An Ab Initio Basis Set Dependence Study

Miranda,Sandro G. de; Vazquez,Pedro A. M.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2002 EN
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36.58%
The Raman excitation profile of the squarate anion, C4O4-2 , was calculated using ab initio methods at the Hartree-Fock using Linear Response Theory (LRT) for six excitation frequencies: 632.5, 514.5, 488.0, 457.9, 363.8 and 337.1 nm. Five basis set functions (6-31G*, 6-31+G*, cc-pVDZ, aug-cc-pVDZ and Sadlej's polarizability basis set) were investigated aiming to evaluate the performance of the 6-31G* set for numerical convergence and computational cost in relation to the larger basis sets. All basis sets reproduce the main spectroscopic features of the Raman spectrum of this anion for the excitation interval investigated. The 6-31G* basis set presented, on average, the same accuracy of numerical results as the larger sets but at a fraction of the computational cost showing that it is suitable for the theoretical investigation of the squarate dianion and its complexes and derivatives.

Reactivity of the nitro radical anion from nisoldipine with N-acetylcysteine: EPR spectroscopic and electrochemical evidence

Olea Azar, Claudio; Santander, Paola; Bollo Dragnic, Soledad; Squella Serrano, Juan Arturo; Gunckel, S.; Núñez Vergara, Luis J.
Fonte: Sociedad Chilena de Química Publicador: Sociedad Chilena de Química
Tipo: Artículo de revista
EN
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This paper reports the scavenging of the nitro radical anion of nisoldipine by N-acetylcysteine assessed by cyclic volatammetry (CV) and EPR spectroscopic techniques. Studies by CV on the reactivity of the radical were conducted on the mercury electrode in mixed media at pH 9.0 (0.012 M aqueous citrate buffer/DMF 40/60, 0.1 M TBAI). Interaction rate constant was significantly higher than that on the second order decay rate constant of the radical (ki=4.857[Msec]-1. EPR spectra recorded in situ using DMF/0.1 N NaOH (pH 13) of the nitro radical anion from nisoldipine electrochemically generated was completely inhibited for a 20 mM concentration of N-acetylcysteine

Nitroradical anion formation from some iodo-substituted nitroimidazoles

Núñez Vergara, Luis J.; Barrientos Vargas, Claudia Marjorie; Squella Serrano, Juan Arturo; Bollo Dragnic, Soledad
Fonte: WILEY-V C H VERLAG GMBH Publicador: WILEY-V C H VERLAG GMBH
Tipo: Artículo de revista
EN
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The electrochemical behavior of iodo nitroimidazole derivatives such as 1-methyl-4-iodo-5-nitroimidazole (M-I-NIm) and 1-methyl-2,4-diiodo-5-nitroimidazole (M-I-2-NIm) and the parent compound 1-methyl-5-nitroimidazole (M-NIm), was studied in protic, mixed and non-aqueous media. The electrochemical study was carried out using Differential Pulse Polarography (DPP), Cyclic Voltammetry (CV), Differential Pulse Voltammetry (DPV) and coulometry and as working electrodes mercury and glassy carbon were used. As can be expected, in all media, the effect of introduce iodo as substituent in the nitroimidazole ring produced a decrease of the energy requirements of the nitro group reduction. Certainly, this fact can be explained by the electron withdrawing character of the iodo substituent that acts diminishing the electronic density on the nitro group thus facilitating their reduction. In all the studied media the reduction of M-NIm produced a detectable signal for a nitro radical anion derivative. In the case of M-I-NIm the nitro radical anion was only detectable in both mixed and non-aqueous media. On the other hand the nitro radical anion for the M-I-2-NIm was detected only in non-aqueous medium. When glassy carbon electrode was used as the working electrode in a mixed medium a detectable nitro radical anion derivative appeared for all compounds...

Strategies to isolate transporters that facilitate organic anion efflux from plant roots

Ryan, Peter R; Dong, Bei; Watt, M; Kataoka, T; Delhaize, Emmanual
Fonte: Kluwer Academic Publishers Publicador: Kluwer Academic Publishers
Tipo: Artigo de Revista Científica
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The efflux of organic anions from roots plays an important role in plant nutrition. The release of simple carboxylic anions such as citrate, malate and oxalate have been implicated in mechanisms of aluminium (Al) tolerance and improved acquisition of soil phosphorus. These metabolites are likely to cross cell membranes as multivalent anions and recent evidence indicates that anion-permeable channels facilitate this flow in the Al-dependent efflux of malate and citrate from wheat and maize, respectively. However, the genes encoding these anion channels, or any other protein that facilitates the release of citrate, malate or oxalate have not been isolated. This is an obstacle for the application of biotechnology to combat Al toxicity and to improve P-acquisition efficiency in plants. We discuss several strategies aimed at isolating genes that facilitate organic anion release from plant roots.

The influence of cation, anion and water content on the rate of formation and pore size distribution of zeolite ZSM-5

Petrik,L.
Fonte: South African Journal of Science Publicador: South African Journal of Science
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/2009 EN
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Rapid synthesis and high mesoporosity of ZSM-5 is promoted by altering a fixed molar regime with respect to anion and cation type and water content only. This study shows that merely changing the cation and anion types, accompanying the hydroxide and alumina (Al) sources, respectively, has an impact on the characteristics of ZSM-5. Under identical and replicated preparation and testing conditions, the synthesis time, Al incorporation, product yield, acidity, morphology, pore size distribution and catalytic activity were affected. An ion pair combination of Na+/NO3- allowed the formation of ZSM-5 with enhanced mesoporosity within 3 h in a high-water environment, whereas ZSM-5 prepared with the Na+/SO4(2-) combination had enhanced n-hexane cracking activity. Use of a K+/NO3- ion pair combination in a high-water environment resulted in slower time of formation and larger ZSM-5 crystals with extra-framework Al, loss of acidity, lower surface areas and reduced n-hexane cracking activity. The sulphate anion inhibited the incorporation of Al in ZSM-5 products in low-water environments. Low-water levels increased the time of formation of ZSM-5.