Efeitos do benzeno, em ultra alta diluições, frente ao benzolismo experimental agudo em camundongos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Investigação da origem biossintética de cromenos e cromanos em Piper aduncum e Peperomia obtusifolia (Piperaceae)

Pós-graduação em Química - IQ

Dinâmica metabólica em Piper gaudichaudianum: estudo das etapas de ciclização estereosseletiva do ácido gaudichaudianico

Pós-graduação em Química - IQ

Potenciais periódicos: aplicação à espectroscopia do benzeno

Pós-graduação em Física - FEG

Kinetic role of a histidine residue in the T1 copper site of the laccase from Rigidoporus lignosus

Laccases (benzendiol:oxygen oxidoreductases; EC 1.10.3.2) catalyze the oxidation of a broad range of substrates, such as polyphenols, dyes and pollutants, and thus these enzymes are widely applied in industrial, biotechnological and environmental fields. In order to improve their biotechnological applications, a deep knowledge of structural factors involved in controlling their activity, in various experimental conditions and on different substrates, is required. In the present study, a laccase from the mushroom Rigidoporus lignosus was kinetically characterized. In particular, the stability, the effects of pH, ionic strength and fluoride ion concentration on the kinetic parameters were investigated, using three di-hydroxy-benzene isomers (1,2-dihydroxy-benzene, 1,3-dihydroxy-benzene and 1,4-dihydroxy-benzene) as substrates. The catalytic constant values of the laccase showed a bell-shaped pH profile, with the same optimum pH and pK(a) values for all tested substrates. This behavior appears to be due to the presence of an ionizable residue in the enzyme active site. To identify this residue, the enzyme was derivatized with diethylpyrocarbonate to modify accessible histidine residues, which, according to structural data, are present in the active site of this enzyme. The kinetic behavior of the derivatized laccase was compared with that of the native enzyme and the derivatized residues were identified by mass spectrometry. Mass spectrometry and kinetic results suggest the main role of His-457 in the control of the catalytic activity of laccase from R. lignosus. (C) 2013 Elsevier B.V. All rights reserved.

Análise química, citotoxicidade e biocompatibilidade de cimentos de ionômero de vidro

Objetivo: O presente trabalho, dividido em três estudos, teve como objetivo geral identificar e quantificar a liberação de componentes e avaliar a citotoxicidade e a biocompatibilidade de cimentos de ionômero de vidro (CIVs). Método: Para o estudo 1, extratos dos CIVs Vitrebond (VB), Fuji Lining LC (FL), Vitremer (VM), Fuji II LC (FII), Ketac Fil Plus (KF) e Ketac Molar Easymix (KM) foram obtidos pela imersão de corpos-de-prova em meio de cultura celular (DMEM). Esses extratos (n=9 por grupo) foram analisados por eletrodo específico quanto à presença de flúor e por espectrometria de absorção atômica quanto à presença de alumínio e zinco. HEMA e iodobenzeno foram identificados por CG/EM (n=6). Para o estudo 2, células MDPC-23 foram colocadas em contato com os extratos dos CIVs por 24 horas. Em seguida, foram avaliadas a atividade da desidrogenase succínica (SDH) (n=8), a produção de proteína total (PT) (n=8), a atividade da fosfatase alcalina (FAL) (n=8) e a morfologia celular (n=2). Para o estudo 3, tubos de polietileno (n=24 por grupo) foram preenchidos com os CIVs e implantados no tecido subcutâneo de 42 ratos. Como grupo controle foi utilizada a guta-percha. Após 7 ou 15 dias de pós-operatório, metade dos espécimes de cada grupo e período (n=6) foi preparada para análise histológica, e os demais (n=6) para análise da expressão de genes que codificam para IL-1? e TNF-?. Resultados: Os extratos de todos os CIVs apresentaram uma concentração de flúor significativamente maior do que o meio de cultura DMEM (controle), tendo o VB liberado maior quantidade, estatisticamente significante, do que os demais CIVs. O VB foi, também, o único material que liberou quantidades relativamente altas de alumínio e de zinco. O HEMA foi identificado nos extratos de todos os CIVs modificados por resina (VB, FL, VM e FII), e o iodobenzeno... (Resumo completo, clicar acesso eletrônico abaixo)

New reductive addition of hard nucleophiles to 6,7-bis(methylsulfanyl)-1,4-dihydro-1,4-methanonaphthalene-5,8-dione

A new reaction mode of 6,7-bis(methylsulfanyl)-1,4-dihydro-1,4-methanonaphthalene-5,8-dione 1 with the hard nucleophiles sodium benzene- or methane-sulfinate and cyanide, in DMSO, at room temperature, leads to the unexpected hydroquinonoid products 3a-c. All the data are in agreement with a mechanistic pathway involving the initial attack of the hard nucleophile onto the hard carbonyl group, followed by a symbiotic re-attack of the oxygen on the incoming group. In the case of soft nucleophiles, reaction on the olefinic carbon of the enedione system is preferential.

Stretching of BDT-gold molecular junctions: thiol or thiolate termination?

It is often assumed that the hydrogen atoms in the thiol groups of a benzene-1,4-dithiol dissociate when Au-benzene-1,4-dithiol-Au junctions are formed. We demonstrate, by stability and transport property calculations, that this assumption cannot be made. We show that the dissociative adsorption of methanethiol and benzene-1,4-dithiol molecules on a flat Au(111) surface is energetically unfavorable and that the activation barrier for this reaction is as high as 1 eV. For the molecule in the junction, our results show, for all electrode geometries studied, that the thiol junctions are energetically more stable than their thiolate counterparts. Due to the fact that density functional theory (DFT) within the local density approximation (LDA) underestimates the energy difference between the lowest unoccupied molecular orbital and the highest occupied molecular orbital by several electron-volts, and that it does not capture the renormalization of the energy levels due to the image charge effect, the conductance of the Au-benzene-1,4-dithiol-Au junctions is overestimated. After taking into account corrections due to image charge effects by means of constrained-DFT calculations and electrostatic classical models, we apply a scissor operator to correct the DFT energy level positions, and calculate the transport properties of the thiol and thiolate molecular junctions as a function of the electrode separation. For the thiol junctions, we show that the conductance decreases as the electrode separation increases, whereas the opposite trend is found for the thiolate junctions. Both behaviors have been observed in experiments, therefore pointing to the possible coexistence of both thiol and thiolate junctions. Moreover, the corrected conductance values, for both thiol and thiolate, are up to two orders of magnitude smaller than those calculated with DFT-LDA. This brings the theoretical results in quantitatively good agreement with experimental data.

Síntese de nanopartículas de prata suportadas sobre nanotubos de carbono de paredes múltiplas para eletrooxidação de benzeno

Silver nanoparticles (Ag) were deposited on multi-walled carbon nanotube by eletroless. The hybrid Ag/MWCNT was used in the modification of glassy carbon electrode (GC) surface. The electrochemical characterization confirmed the presence of Ag in the nanocomposite has been showed that the synthesis was successful. The GC electrode modified with Ag/MWCNT film was evaluated for electro-oxidation of benzene. The electrochemical behavior presented an improvement on the catalytic surface in relation to non-modified GC electrode. The anodic peak current increased the magnitude in three times when compared with the CG electrode modified only with MWCNT

Redução de consumo de energia eletrica a partir de reaproveitamento de energia termica com uso de ciclo rankine orgânico

This paper is proposed the usage of an Organic Rankine Cycle (ORC) along with waste heat recovery from an inconstant heat source. This method of waste heat recovery with intermittent heat source is part of a technical viability study. This paper also brings up the usage of thermal energy storage as heat source for the ORC. This paper is based on a heat treatment company study in which a natural gas furnace is explored. Data such as mass flow, temperature and specific waste gas heat from this furnace are used through calculations. Calculations are made also based on furnace cycles. This viability study considers a series of working fluids such as ammonia, benzene, R113 and R134a. Results point out that ORC with out thermal storage and using refrigerant fluid ammonia is the best alternative

Avaliação do efeito tóxico do herbicida trifluralina por meio do estudo histológico e histoquímico do intestino médio do diplópodo Rhinocricus padbergi

Currently the use of pesticides in agriculture is widespread due to their high effectiveness in combating pests, weeds and diseases leading to better productivity and economical performance in agricultural area. The use of pesticides affects the whole world and their use is often performed in an improper and indiscriminate way and for long periods. Several studies have been carried out in order to verify the presence of pesticides in nature, with worrying results. The presence of higher levels of pesticides and their degradation products in soil and surface and groundwater have indicated increasing contamination. Among the most widely used pesticides, herbicides are present and among these trifluralin has occupied an important place due to its widespread use; it is an herbicide originated from benzene derivatives belonging to dinitroanilines family; it is classified as belonging to group C, being possibly carcinogenic for humans, present a high persistence in soil as a result of its low mobility and therefore may affect local edaphic fauna. Diplopods belong to a group of invertebrates considered important in the soil dynamics; due to their close contact with it, these animals can be used as bioindicators of substrates toxicity. This study aimed to expose diplopod specimens of the species R. padbergi to different concentrations of trifluralin and therefore it was mounted five bioassays containing soil from the site where animals were collected (control group) and the same soil mixed to different concentrations of trifluralin herbicide (concentration recommended for agriculture use, that is, the dose recommended by the producer 0.0534g/m2, double, haft and quarter of this dose), animals were exposed for 7 and 90 days. During the entire period of exposure (90 days), it was observed that the number of animals in the control bioassay remained stable until the 5th week, presenting only... (Complete abstract click electronic access below)

Efeito fitotóxico e potencial remediador de três espécies vegetais contaminadas com benzeno

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Inorganic elemental analysis and identification of residual monomers released from different glass ionomer cements in cell culture medium

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Identificação e caracterização de fungos melanizados com potencial de degradação de tolueno

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Contaminação do lençol freático por hidrocarbonetos na região de Avaré - SP

Pós-graduação em Engenharia Civil e Ambiental - FEB