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On line pre-concentration for simultaneous determination of low molecular weight organic acids and inorganic anions in Amazonian river water samples employing ion chromatography with conductivity detection; Pré-concentração em linha para a determinação simultânea de ácidos carboxílicos de baixo peso molecular e ânions inorgânicos em amostras de rios da Amazônia empregando cromatografia de íons com detecção por condutividade elétrica

TUMANG, Cristiane Azevedo; KRUSCHE, Alex Vladimir; VICTORIA, Reynaldo Luis; RICHEY, Jeffrey Edward
Fonte: Instituto Nacional de Pesquisas da Amazônia Publicador: Instituto Nacional de Pesquisas da Amazônia
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
37.038076%
An ion chromatography procedure, employing an IonPac AC15 concentrator column was used to investigate on line preconcentration for the simultaneous determination of inorganic anions and organic acids in river water. Twelve organic acids and nine inorganic anions were separated without any interference from other compounds and carry-over problems between samples. The injection loop was replaced by a Dionex AC15 concentrator column. The proposed procedure employed an auto-sampler that injected 1.5 ml of sample into a KOH mobile phase, generated by an Eluent Generator, at 1.5 mL min-1, which carried the sample to the chromatographic columns (one guard column, model AG-15, and one analytical column, model AS15, with 250 x 4mm i.d.). The gradient elution concentrations consisted of a 10.0 mmol l-1 KOH solution from 0 to 6.5 min, gradually increased to 45.0 mmol l-1 KOH at 21 min., and immediatelly returned and maintained at the initial concentrations until 24 min. of total run. The compounds were eluted and transported to an electro-conductivity detection cell that was attached to an electrochemical detector. The advantage of using concentrator column was the capability of performing routine simultaneous determinations for ions from 0.01 to 1.0 mg l-1 organic acids (acetate...

Sequential IRMPD of XGe(OEt)(4)(-) ions: Gas-phase synthesis of novel oxy-germanium anions

XAVIER, Luciano A.; MALASPINA, Thaciana V.; MORGON, Nelson H.; MENEGON, Jair J.; RIVEROS, Jose M.
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.93583%
The gas-phase ion/molecule reactions of F(-) and EtO(-) with Ge(OEt)(4) yield readily and exclusively pentacoordinated complexes XGe(OEt)(4)(-) (X = F, EtO) at pressures in the 10(-8) T range as observed by FT-ICR techniques. These hypervalent species are prone to undergo sequential fragmentations induced by infrared multiphoton excitation that lead to a variety of germyl and germanate anions. In the case of FGe(OEt)(4)(-), three primary competitive channels are observed in the IRMPD process that can be identified as (EtO)(3)GeO(-), F(EtO)(2)GeO(-) and (EtO)(3)Ge(-). Ab initio calculations have been carried out to characterize the primary fragmentation paths induced by IRMPD and the most favorable structure of the resulting anions. The gas-phase acidity of a number of these germanium-containing ions have been estimated by bracketing experiments and by theoretical calculations. Germanate anions such as (EtO)(3)GeO(-) undergo some interesting reactions with H(2)S to give rise to anions such as (EtO)(3)GeS(-) and (EtO)(2)Ge(OH)S(-). (C) 2010 Elsevier B.V. All rights reserved.; Sao Paulo Science Foundation (FAPESP); Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Brazilian Research Council (CNPq); U.S. Air Force Office of Scientific Research (AFOSR); Air Force Office of Scientific Research (AFOSR); Office of Graduate Education of Brazil (CAPES); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Desenvolvimento de um fotômetro portátil e de procedimentos analíticos automáticos para determinação de ânions e cátions em fontes de captação de águas para uso doméstico e industrial; Development of portable photometer and automatic analytical procedures for anions and cations determination in sources of water captation for domestic and industrial uses

Feres Junior, Mario Almir
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 18/12/2006 PT
Relevância na Pesquisa
36.85517%
Neste trabalho, foi desenvolvido equipamento portátil e procedimentos analíticos automáticos para determinação de cátions e anions em águas usadas para consumo humano e suprimento. Os procedimentos foram baseados no processo de multicomutação em fluxo e detecção fotométrica empregando fotômetro feito no laboratório. Os sistemas de fluxo foram construídos empregando válvulas solenóide, com interface independente de comutação acionadas por computador usando apenas um canal de bombeamento. O sistema proposto foi controlado por um computador rodando um software escrito em QuickBasic 4.5. Os dói fotômetros baseados em LED foram desenvolvidos usando como detectores de radiação foto-transistores e foto-diodos. Nos dois casos a fonte de radiação (LED) e o foto-detector foram acoplados a cela de fluxo obtendo assim, uma unidade compacta. O fotômetro foi projetado para usar um foto-transistor para determinações seqüenciais de nitrato, nitrito, ferro(II), ferro(III) em águas de rios.O fotômetro proposto usa um foto-diodo para determinação de cloreto por turbidimetria, fosfato e amonium por fotometria. A sistema de fluxo foi desenhado associando-se os processos de multicomutação e multisite garantindo redução de reagente e de efluente. O sistema sistema foi empregado para determinação de cloreto...

Arilação seletiva de ânions heterocíclicos ambidentados por sais de difenil iodônio; Seletive arylation of ambident heterocycle anions by diphenyl iodonium salts

Artur, Julio Cesar
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 12/09/2008 PT
Relevância na Pesquisa
36.9643%
A arilação seletiva de compostos orgânicos confere-lhes propriedades com amplas aplicações: em compostos de atividade biológica, inibidora da protease do vírus HIV-1, e de interesse como agroquímicos ou na engenharia de materiais. Em razão disso, novos métodos e reagentes tem sido desenvolvidos com essa finalidade. Sabe-se que a N-arilação de várias aminas, catalisadas por paládio, com haletos de arila e triflatos é tida como ferramenta importante a disposição do químico sintético. Do mesmo modo, publicou-se que a N-arilação de certos -amino ácidos por haletos de arila, procede-se facilmente quando catalisada por CuI. Alternativamente, a literatura cita outros métodos eficientes usando ácidos borônicos, compostos arilbismuto e compostos organochumbo. Neste trabalho foi estudada a arilação seletiva de ânions ambidentados pelo sal de iodo polivalente cloreto de difenil iodônio, em diferentes condições de reação, visando a otimização da síntese: 1) reação térmica (agitação magnética), sem catalisador, e em diferentes solventes, ou mistura de solventes; 2) reação sonoquímica, sem catalisador e em diferentes soluções; 3) reação térmica e sonoquímica na presença de catalisador CuCl (10%). Sacarinato de sódio...

Influencia do PH e de anions na reação de Maillard e na hidrolise de disacarideos

Felix Guillermo Reyes Reyes
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em //1973 PT
Relevância na Pesquisa
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: Foi estudada a hidrolisa da lactose e da sacarose a pH 6,20 e 3,00 era água desionizada en tampão citrato e em tarapao fosfato a 50°C. Cem os mesmos disacarideos a nas mesmas condições da hidrolise, foi também escudada a reação de Maillard com glicina. Os resultados obtidos indicam que a ligação hemiacetalíca da sacarose e triais facilmente hídrolizada do que a da lactose. Foi demonstrado o efeito catalítico de pti e de anions tanto na reação de hidrolise como na reação de Maillard da lactose e da sacarose. A sacarose participa da reação de Maillard através dos seus produtos de hidrolise. Dos resultados obtidos foram feitas correlações entre a velocidade de hidrólise e reação de Maillard dos disacarideos; The hydrolysis of sucrose and lactose vas studied at pH 6,20 and 3,00 in model systems in water. citrate and phosphate buffers at 50ºC The Maillard reaction of lactose arid sucrose with glycine was investigated under the above conditions. The catalytic effect of pH and of the anions present was demonstrated for the hydrolysis as well as for the Maillard reaction. Sucrose was hydrolyzed faster than lactose and the Halliard reaction with sucrose is due to the products of its hydrolysis. The effect of hydrolysis...

Sequential IRMPD of XGe(OEt)(4)(-) ions: Gas-phase synthesis of novel oxy-germanium anions

XAVIER, Luciano A.; MALASPINA, Thaciana V.; MORGON, Nelson H.; MENEGON, Jair J.; RIVEROS, Jose M.
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.93583%
The gas-phase ion/molecule reactions of F(-) and EtO(-) with Ge(OEt)(4) yield readily and exclusively pentacoordinated complexes XGe(OEt)(4)(-) (X = F, EtO) at pressures in the 10(-8) T range as observed by FT-ICR techniques. These hypervalent species are prone to undergo sequential fragmentations induced by infrared multiphoton excitation that lead to a variety of germyl and germanate anions. In the case of FGe(OEt)(4)(-), three primary competitive channels are observed in the IRMPD process that can be identified as (EtO)(3)GeO(-), F(EtO)(2)GeO(-) and (EtO)(3)Ge(-). Ab initio calculations have been carried out to characterize the primary fragmentation paths induced by IRMPD and the most favorable structure of the resulting anions. The gas-phase acidity of a number of these germanium-containing ions have been estimated by bracketing experiments and by theoretical calculations. Germanate anions such as (EtO)(3)GeO(-) undergo some interesting reactions with H(2)S to give rise to anions such as (EtO)(3)GeS(-) and (EtO)(2)Ge(OH)S(-). (C) 2010 Elsevier B.V. All rights reserved.; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

On line pre-concentration for simultaneous determination of low molecular weight organic acids and inorganic anions in Amazonian river water samples employing ion chromatography with conductivity detection

Tumang,Cristiane Azevedo; Krusche,Alex Vladimir; Victoria,Reynaldo Luis; Richey,Jeffrey Edward
Fonte: Instituto Nacional de Pesquisas da Amazônia Publicador: Instituto Nacional de Pesquisas da Amazônia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2009 EN
Relevância na Pesquisa
36.85517%
An ion chromatography procedure, employing an IonPac AC15 concentrator column was used to investigate on line preconcentration for the simultaneous determination of inorganic anions and organic acids in river water. Twelve organic acids and nine inorganic anions were separated without any interference from other compounds and carry-over problems between samples. The injection loop was replaced by a Dionex AC15 concentrator column. The proposed procedure employed an auto-sampler that injected 1.5 ml of sample into a KOH mobile phase, generated by an Eluent Generator, at 1.5 mL min-1, which carried the sample to the chromatographic columns (one guard column, model AG-15, and one analytical column, model AS15, with 250 x 4mm i.d.). The gradient elution concentrations consisted of a 10.0 mmol l-1 KOH solution from 0 to 6.5 min, gradually increased to 45.0 mmol l-1 KOH at 21 min., and immediatelly returned and maintained at the initial concentrations until 24 min. of total run. The compounds were eluted and transported to an electro-conductivity detection cell that was attached to an electrochemical detector. The advantage of using concentrator column was the capability of performing routine simultaneous determinations for ions from 0.01 to 1.0 mg l-1 organic acids (acetate...

New Strategies for Intramolecular Annulations: Intramolecular Additions of Silyloxycyclopropane-Derived Anions; Application to Hydrindenone Syntheses

Marino,J.P.; Stengel,Peter J.; Simonelli,Fabio; Ferreira,J. Tércio B.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/1998 EN
Relevância na Pesquisa
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As an extension to our work on intramolecular annulations via silyloxycyclopropane derived anions, we have investigated the chemistry of cyclopentyl cyclopropane systems, 6-9, in an effort to prepare stereospecifically functionalized hydrindenones. The intramolecular closures of the cyclopropane-derived anions were less stereoselective and more complicated than the corresponding cyclohexyl systems. Nevertheless, modest yields of isomeric hydrinenones such as 20 and 21 were obtained as well as several products derived from a prototropic shift to form the cyclopentanone enolates. These latter products possessed the 5,5-pentalenone systems, 22 and 23.

Unmeasured anions account for most of the metabolic acidosis in patients with hyperlactatemia

Maciel,Alexandre Toledo; Park,Marcelo
Fonte: Faculdade de Medicina / USP Publicador: Faculdade de Medicina / USP
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2007 EN
Relevância na Pesquisa
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PURPOSE: To characterize the different components of metabolic acidosis in patients with hyperlactatemia in order to determine the degree to which lactate is responsible for the acidosis and the relevance that this might have in the outcome of these patients. METHODS: Arterial blood gas, arterial lactate, Na+, K+, Ca2+, Mg2+, Cl-, phosphate, albumin, and creatinine were measured on admission to make a diagnosis of the acid-base disturbances present. Intensive Care Unit and in-hospital mortality were also recorded. RESULTS: A total of 58 patients with hyperlactatemia were included. They usually had a mild acidemia (pH 7.31 ± 0.12) and a significantly high Standard Base Deficit (7.6 ± 6.7 mEq/L). In addition to lactate (4.3 ± 2.3 mEq/L), chloride (106.9 ± 9.5 mEq/L) and unmeasured anions (8.6 ± 5.0 mEq/L) accounted for the metabolic acidosis. Unmeasured anions were primarily responsible for the acidosis in both Intensive Care Unit survivors and nonsurvivors (44.7% ± 26.0% and 46.0% ± 17.5%, respectively, P = 0.871). Lactate contributed in similar percentages to the acidosis in both groups (23.0% ± 11.8% and 24.2% ± 9.7% in Intensive Care Unit survivors and nonsurvivors, respectively; P = 0.753). Correlation between Standard Base Deficit and lactate was found only in Intensive Care Unit nonsurvivors (r = 0.662...

PREPARAÇÃO DE COMPÓSITOS DE POLIANILINA EM MATRIZES DE COPOLÍMEROS ESTIRENO-DIVINILBENZENO E ESTUDOS DE ADSORÇÃO POR TROCA IÔNICA DE ÂNIONS COMPLEXOS DE [FeCl4]- E [CuCl4]2-; PREPARATION FOR SUPPORTING COMPOSITE POLIANYLINE IN MATRIZES OF COPOLYMERS ESTYRENE-DIVINYLBENZENE AND STUDIES OF ADSORPTION BY EXCHANGE IONIC OF COMPLEX ANIONS OF [FeCl4]- AND [CuCl4] 2-

SILVA, Robson Benedito
Fonte: Universidade Federal de Goiás; BR; UFG; Mestrado em Química; Educação em Química Publicador: Universidade Federal de Goiás; BR; UFG; Mestrado em Química; Educação em Química
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
37.093955%
In this work, composites of dispersed polyaniline in beads of styrenedivinybenzene copolymer (Pani/Sty-DVB copopolymer) with different porosities were prepared through in situ polymerization. Materials with high surface areas and high porosities were obtained what explain their properties to adsorve transition metals. SD29 and SD84 copolymers were prepared through suspension polymerization in the presence of inert diluents as toluene/heptane with different DVB ratios to obtain macroporous beads. SD29/Pani and SD84/Pani composites were obtained by swelling the copolymers with aniline/ethanol mixtures (20/80%) before polymerization. Oxidative polymerization of aniline was carried out with ammonium persulfate in the presence of nitric acid at pH extremely acid and temperature range from 0 to 3 oC for 5 hours. All materials were characterized by infrared spectroscopy, porosity measurements, optical microscopy and adsorption capacity. The composite surface areas and pore volumes diminished in relation to original xv copolymers, while apparent density increased due polyaniline incorporation. Pore size distributions did not suffer large variations and all were typical of macroporous structures. Due the high DVB content, SD84/Pani composite and SD84 copolymer presented higher porosity and specific surface area when compared to systems with low reticulation degree. From acid solutions...

Síntese e caracterização de compósitos polianilina/poli(estireno-co-divinilbenzeno) para Adsorção de Ânions [SnCl4]²-; Synthesis and characterization of composite polyaniline/poly(styrene-co-divinylbenzene)-resin for adsorption of anions [SnCl4]²-

Lima, Wolney Arruda de
Fonte: Universidade Federal de Goiás; Brasil; UFG; Programa de Pós-graduação em Química (IQ); Instituto de Química - IQ (RG) Publicador: Universidade Federal de Goiás; Brasil; UFG; Programa de Pós-graduação em Química (IQ); Instituto de Química - IQ (RG)
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
37.007236%
In this work were prepared and characterized polyaniline/poly(styrene-co-divinylbenzene) composites by in situ oxidative polymerization of aniline in the pores of styrene-divinylbenzene copolymers. The aim was to obtain composites with high specific surface areas and total pore volumes for use as adsorbents of complex anions [SnCl4]2-. The copolymers with 29 and 84 % of divinylbenzene (DVB) were called PStyDVB 29 and PStyDVB 84, respectively. They were synthesized by suspension polymerization in the presence of inert diluents like toluene and heptane to obtain mesoporous beads with sizes in the range of 400 to 800 μm. Before the oxidative polymerization, the copolymers were swelled with aniline and ethanol mixture at volumetric ratio 20:80. The oxidative polymerization of aniline in the copolymers was carried out using benzoyl peroxide as an oxidant in the presence of hydrochloric or nitric acid as dopant at 25°C in three polymerization cycles. The materials were characterized by infrared spectroscopy with Fourier transform (FTIR), elemental analysis (CNHS), X ray diffraction, thermogravimetry, nitrogen adsorption (specific surface area and pore volume), Scanning Electron Microscopy and Atomic Absorption spectrophotometry. Elemental analysis indicated that the composite doped with HCl adsorb higher amounts of polyaniline (PANI) than using HNO3. The FTIR spectra and X-ray diffraction patterns of the composites were similar to the ones of the copolymers due the low amounts of PANI incorporated. The copolymers had lower thermal stability than composites...

Enhanced selectivity and sensitivity for inorganic anions using an ion-pairing reagent and sample stacking in capillary zone electrophoresis with direct UV detection

Chen, Zuliang; Owens, Gary; Naidu, Ravendra
Fonte: Springer-Verlag Publicador: Springer-Verlag
Tipo: Artigo de Revista Científica
Publicado em //2003 EN
Relevância na Pesquisa
36.85517%
In this paper, the use of an ion-pairing reagent to improve the separation selectivity of inorganic anions in CZE was demonstrated by the addition of tetramethylammonium hydroxide (TMAOH) to the electrolyte. The separation of inorganic anions (Cl⁻, I⁻, Br⁻, NO2⁻, NO3⁻ and SCN⁻) was performed using co-electroosmotic flow (EOF) with direct UV detection at 185 nm. The parameters affecting the mobility of the tested anions and the EOF such as the electrolyte pH and concentration of TMAOH in the electrolyte were examined to optimise the separation conditions. In addition, sample-stacking techniques were investigated to improve detection sensitivity. Detection sensitivities were improved 5-13-fold using electrokinetic sample stacking. The detection limits ranged from 1-3 µmol L⁻¹. Finally, the proposed method was used for the separation of anions in groundwaters.; ZuLiang Chen, Gary Owens, Ravendra Naidu; © Springer-Verlag 2002

Can collision-induced negative-ion fragmentations of [M-H]- anions be used to identify phosphorylation sites in peptides?

Tran, T.; Wang, T.; Hack, S.; Hoffmann, P.; Bowie, J.
Fonte: John Wiley & Sons Ltd Publicador: John Wiley & Sons Ltd
Tipo: Artigo de Revista Científica
Publicado em //2011 EN
Relevância na Pesquisa
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A joint experimental and theoretical investigation of the fragmentation behaviour of energised [M-H](-) anions from selected phosphorylated peptides has confirmed some of the most complex rearrangement processes yet to be reported for peptide negative ions. In particular: pSer and pThr (like pTyr) may transfer phosphate groups to C-terminal carboxyl anions and to the carboxyl anion side chains of Asp and Glu, and characteristic nucleophilic/cleavage reactions accompany or follow these rearrangements. pTyr may transfer phosphate to the side chains of Ser and Thr. The reverse reaction, namely transfer of a phosphate group from pSer or pThr to Tyr, is energetically unfavourable in comparison. pSer can transfer phosphate to a non-phosphorylated Ser. The non-rearranged [M-H](-) species yields more abundant product anions than its rearranged counterpart. If a peptide containing any or all of Ser, Thr and Tyr is not completely phosphorylated, negative-ion cleavages can determine the number of phosphated residues, and normally the positions of Ser, Thr and Tyr, but not which specific residues are phosphorylated. This is in accord with comments made earlier by Lehmann and coworkers.; T. T. Nha Tran, Tianfang Wang, Sandra Hack, Peter Hoffmann and John H. Bowie

Diagnostic cyclisation reactions which follow phosphate transfer to carboxylate anion centres for energised [M-H]⁻ anions of pTyr-containing peptides; Diagnostic cyclisation reactions which follow phosphate transfer to carboxylate anion centres for energised [M-H](-) anions of pTyr-containing peptides

Tran, T.; Wang, T.; Hack, S.; Bowie, J.
Fonte: John Wiley & Sons Ltd Publicador: John Wiley & Sons Ltd
Tipo: Artigo de Revista Científica
Publicado em //2011 EN
Relevância na Pesquisa
36.795327%
The low-energy negative ion phosphoTyr to C-terminal -CO(2)PO(3)H(2) rearrangement occurs for energised peptide [M-H](-) anions even when there are seven amino acid residues between the pTyr and C-terminal amino acid residues. The rearranged C-terminal -CO(2)PO(2)H(O(-)) group effects characteristic S(N)i cyclisation/cleavage reactions. The most pronounced of these involves the electrophilic central backbone carbon of the penultimate amino acid residue. This reaction is aided by the intermediacy of an H-bonded intermediate in which the nucleophilic and electrophilic reaction centres are held in proximity in order for the S(N)i cyclisation/cleavage to proceed. The ΔG(reaction) is +184 kJ mol(-1) with the barrier to the S(N)i transition state being +240 kJ mol(-1) at the HF/6-31 + G(d)//AM1 level of theory. A similar phosphate rearrangement from pTyr to side chain CO(2)(-) (of Asp or Glu) may also occur for energised peptide [M-H](-) anions. The reaction is favourable: ΔG(reaction) is -44 kJ mol(-1) with a maximum barrier of +21 kJ mol(-1) (to the initial transition state) when Asp and Tyr are adjacent. The rearranged species R(1)-Tyr-NHCH(CH(2)CO(2)PO(3)H(-))COR(2) (R(1)  = CHO; R(2)  = OCH(3)) may undergo an S(N)i six-centred cyclisation/cleavage reaction to form the product anion R(1)-Tyr(NH(-)). This process has a high energy requirement [ΔG(reaction)  = +224 kJ mol(-1)...

Fragmentations of [M-H]⁻ anions of peptides containing Ser sulfate. A joint experimental and theoretical study; Fragmentations of [M-H](-) anions of peptides containing Ser sulfate. A joint experimental and theoretical study

Tran, T.; Wang, T.; Hack, S.; Bowie, J.
Fonte: John Wiley & Sons Ltd Publicador: John Wiley & Sons Ltd
Tipo: Artigo de Revista Científica
Publicado em //2013 EN
Relevância na Pesquisa
36.85517%
RATIONALE: To determine the negative-ion cleavages from [M-H](-) ions of Ser sulfate-containing peptides using experiment and theory in concert. METHODS: Fragmentations were explored using a Waters QTOF2 mass spectrometer in negative-ion electrospray mode, together with calculations at the CAM-B3LYP/6-311++g(d,p) level of theory. Peptides used in this study were: GS(SO3H)(OH) 1 GS(SO3H)(OCH3) 1a GAVS(SO3H)(OH) 2 GAVS(SO3H)(OCH3) 2a GLS(SO3H)(GVA(OH) 3 GLS(SO3H)GDA(OH) 4 GLS(SO3H)GS(SO3H)A(OH) 5. RESULTS: Previously, it has been shown that a peptide containing a Tyr sulfate group shows [(M-H)(-) -SO3] as the base peak. Only a small peak was observed corresponding to HOSO3(-) (formed following rearrangement of the sulfate). A Ser sulfate-containing peptide, in contrast, shows pronounced peaks due to cleavage product anions [(M-H)(-)-SO3] and HOSO3(-). Theoretical calculations at the CAM-B3LYP/6-311++g(d,p) level of theory suggest that rearrangement of a Ser sulfate to give C-terminal CO2SO3H is energetically unfavourable in comparison with fragmentation of the intact Ser sulfate to yield [(M-H)(-)-SO3] and HOSO3(-). [(M-H)(-)-H2SO4] anions are not observed in the spectra of peptides containing Ser sulfate, presumably because HOSO3(-) is a relatively weak gas-phase base (ΔGacid = 1265 kJ mol(-1)). CONCLUSIONS: Experimental and theoretical data suggest that [(M-H)(-)-SO3] and HOSO3(-) product anions (from a peptide with a C-terminal Ser sulfate) are formed from the serine sulfate anion accompanied by specific proton transfer. CID MS/MS/MS data for an [(M-H)(-)-SO3] ion of an underivatised sulfate-containing peptide will normally allow the determination of the amino acid sequence of that peptide. The one case we have studied where that is not the case is GLS(SO3H)GDA(OH)...

Influência da adição de ânions cloreto, fluoreto e sulfato nas propriedades físico-químicas da zircônia sintetizada pelo método Pechini.; Influece of anions chloride, fluoride, sulfate addition on the zirconia\'s physicochemical properties synthesized by the Pechini method.

Entringer, José Marcos Stelzer
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 31/05/2012 PT
Relevância na Pesquisa
37.023823%
Neste trabalho investigou-se a influência da adição dos ânions cloreto, fluoreto e sulfato nas propriedades físico-químicas de nanopós de zircônia sintetizada pelo método Pechini. Análises de fluorescência de Raios-X, difração de Raios-X, espectroscopia no infravermelho, área de superfície específica, espectroscopia Raman, microscopia eletrônica de varredura, análise termogravimétrica, calorimetria diferencial por varredura, amplitude sônica eletrocinética e dilatometria foram realizadas para caracterizar os pós sintetizados. Os resultados obtidos mostraram que o tratamento térmico realizado para a obtenção dos pós retirou os ânions cloreto e fluoreto da composição química final da zircônia enquanto o ânion sulfato permaneceu. Mesmo sendo retirados os ânions cloreto e fluoreto influenciaram no processo de cristalização da zircônia modificando o tamanho de cristalito obtido. A permanência do ânion sulfato na composição química da zircônia se deve à maior energia de ligação com o cátion Zr 4+ assim, observou-se uma maior influência deste ânion no processo de cristalização. Isso permitiu a formação de cristalitos menores e a estabilização da fase tetragonal da zircônia. Em todos os casos...

Anions in metallic matrices model: application to the aluminium crystal chemistry

Vegas, Ángel; Santamaría Pérez, David; Marqués, M.; Flórez, M.; García Baonza, V.; Recio, J. M.
Fonte: International Union of Crystallography Publicador: International Union of Crystallography
Tipo: Artículo Formato: 6080 bytes; image/gif
ENG
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We introduce and discuss an interpretative model of the structure and bonding of inorganic crystals containing metallic elements. The central idea is the conception of the crystal structure of such an inorganic compound as a metallic matrix whose geometric and electronic structures govern the formation and localization of the anions in the lattice. This is the reason for labelling the model anions in metallic matrices (AMM). Taking the AlX3 crystal family (X = F, Cl, OH) as a suitable test-bed class of compounds, we illustrate how this approach gives a direct interpretation of the crystalline structures and explains the variable coordination that Al exhibits in crystalline materials. An exhaustive analysis of the topology of the electron density allows us to provide a quantum-mechanical assessment of the main hypotheses of the AMM model and to uncover, using microscopic arguments, the behavior of anions as chemical pressure agents.; Peer reviewed

Fragmentacions mesolítiques dels radicals anions de benzil fenil èters, benzil fenil tioèters i clorurs de benzil substituïts estudi teòric i per EPR /

Asensio, Francesc Xavier
Fonte: Bellaterra: Universitat Autònoma de Barcelona, Publicador: Bellaterra: Universitat Autònoma de Barcelona,
Tipo: Tesis i dissertacions electròniques; info:eu-repo/semantics/doctoralThesis Formato: application/pdf
Publicado em //2010 CAT; CAT
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Descripció del recurs: el 25 d'octubre de 2010; L'objectiu principal del present estudi és aprofundir, des d'un punt de vista teòric i experimental en els aspectes cinètics i mecanístics de les fragmentacions unimoleculars de radicals anions que evolucionen per donar lloc a radicals i anions. Tractarem de veure el comportament que presenten aquests radicals anions en diferents famílies d'espècies i extreuren conclusions que ens permetin veure quin patró segueixen. El treball s'agrupa en diferents capítols (del capítol 4 al capítol 6), segons el tipus d'enllaç estudiat, i el qual és susceptible de ser fragmentat una vegada generat l'anió radical.; The main purpose of this study is to deeply investigate, in a theoretical and experimental point of view, the kinetics and mechanisms of unimolecular radical anion fragmentations to obtain corresponding radical and anions. We will discuss about the behavior of these radical anions in different families of molecules to achieve concrete reasons to explain these fragmentations. The study is presented in different chapters (from 4 to 6), depending on the type of bond studied which is susceptible to be broken.

Ânions não mensuráveis são responsáveis pela maior parte da acidose metabólica de pacientes com hiperlactatemia; Unmeasured anions account for most of the metabolic acidosis in patients with hyperlactatemia

Maciel, Alexandre Toledo; Park, Marcelo
Fonte: Universidade de São Paulo. Faculdade de Medicina Publicador: Universidade de São Paulo. Faculdade de Medicina
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; ; Formato: application/pdf
Publicado em 01/02/2007 ENG
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OBJETIVO: Caracterizar os diferentes componentes da acidose metabólica de pacientes com hiperlactatemia de modo a verificar o quanto o lactato é responsável pela acidose e a relevância que isso possa ter no prognóstico desses pacientes. MÉTODOS: Gasometria arterial com dosagem de lactato, Na+, K+, Ca2+, Mg2+, Cl-, fosfato, albumina e creatinina séricas foram coletados no momento da admissão para fazer o diagnóstico dos possíveis distúrbios ácido-básicos presentes. Mortalidade na UTI e mortalidade hospitalar foram avaliadas. RESULTADOS: Um total de 58 pacientes com hiperlactatemia foram incluídos. Eles tinham na média uma acidemia leve (pH 7.31 ± 0.12) e o déficit de base significativamente elevado (7.6 ± 6.7 mEq/L). Além do lactato (4.3 ± 2.3 mEq/L), o cloro (106.9 ± 9.5 mEq/L) e os ânions não mensuráveis (8.6 ± 5.0 mEq/L) contribuíram para a acidose metabólica. Os ânions não mensuráveis foram responsáveis pela maior parcela da acidose tanto nos pacientes que tiveram alta da UTI como nos que faleceram (44.7 ± 26.0 % e 46.0 ± 17.5 %, respectivamente, p= 0.871). O lactato contribuiu em percentagens semelhantes para a acidose em ambos os grupos (23.0 ± 11.8 % nos sobreviventes e 24.2 ± 9.7 % nos óbitos...

Supramolecular Anion Recognition by Tetrapyrrolic Macrocycles; Reconhecimento Supramolecular de Ânions por Macrociclos Tetrapirrólicos

Andreia S. F. Farinha; Universidade de Aveiro; Carla M. B. Carvalho; Universidade de Aveiro; João P. C. Tomé; Universidade de Aveiro
Fonte: Revista Virtual de Química Publicador: Revista Virtual de Química
Tipo: ; Formato: binary/octet-stream
Publicado em 08/05/2009 PT
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Anions represent one of the most important species in the natural world and are involved in many crucial chemical processes. Anion coordination chemistry highlights the complexity and importance of anion recognition in almost conceivable biochemical and environmental chemistry processes. This mini review is intended to present recent results achieved in this field, mainly by calix[4]pyrroles and porphyrins. The synthesis and their ability to interact with anionic species will be discussed.   DOI: 10.5935/1984-6835.20090019;  Os ânions representam uma das espécies mais importantes no mundo natural estando presentes em inúmeros processos químicos vitais. A química de coordenação de ânions evidencia a complexidade e importância no reconhecimento e controle destas espécies em processos bioquímicos e ambientais. Esta mini-revisão tem como objetivo apresentar os mais recentes resultados alcançados nesta área, nomeadamente com calix[4]pirróis e porfirinas. A síntese e a sua capacidade para interagirem com espécies aniônicas serão objeto de análise.  DOI: 10.5935/1984-6835.20090019