Pyrazole or tris(pyrazolyl)ethanol oxo-vanadium(IV) complexes as homogeneous or supported catalysts for oxidation of cyclohexane under mild conditions

The oxovanadium(IV) complexes [VO(acac)(2)(Hpz)].HC(pz)(3) 1.HC(pz)(3) (acac= acetylacetonate, Hpz = pyrazole, pz = pyrazoly1) and [VOCl2{HOCH2C(pz)(3)}] 2 were obtained from reaction of [VO(acac)(2)] with hydrotris(1-pyrazolyl)methane or of VCl(3)with 2,2,2-tris(1-pyrazolyl)ethanol. The compounds were characterized by elemental analysis, IR, Far-IR and EPR spectroscopies, FAB or ESI mass-spectrometry and, for 1, by single crystal X-ray diffraction analysis. 1 and 2 exhibit catalytic activity for the oxidation of cyclohexane to the cyclohexanol and cyclohexanone mixture in homogeneous system (TONS up to 1100) under mild conditions (NCMe, 24h, room temperature) using benzoyl peroxide (BPO), tert-butyl hydroperoxide (TBHP), m-chloroperoxybenzoic acid (mCPBA), hydrogen peroxide or the urea-hydrogen peroxide adduct (UHP) as oxidants. 1 and 2 were also immobilized on a polydimethylsiloxane membrane (1-PDMS or 2-PDMS) and the systems acted as supported catalysts for the cyclohexane oxidation using the above oxidants (TONs up to 620). The best results were obtained with mCPBA or BP0 as oxidant. The effects of various parameters, such as the amount of catalyst, nitric acid, reaction time, type of oxidant and oxidant-to-catalyst molar ratio, were investigated, for both homogeneous and supported systems. (C) 2012 Elsevier B.V. All rights reserved.

Homogeneous and heterogenised new gold C-scorpionate complexes as catalysts for cyclohexane oxidation

Gold(III) complexes of type [AuCl2{eta(2)-RC(R'pz)(3)}]Cl [R = R' = H (1), R = CH2OH, R' = H (2) and R = H, R' = 3,5-Me-2(3), pz = pyrazol-1-yl] were supported on carbon materials (activated carbon, carbon xerogel and carbon nanotubes) and used for the oxidation of cyclohexane to cyclohexanol and cyclohexanone, with aqueous H2O2, under mild conditions.

Influ��ncia do per��xido e do uso de diferentes subst��ncias de combate �� dor na inflama����o e na express��o de neuropept��deos pr��-inflamat��rios ap��s o tratamento clareador

Funda����o de Amparo �� Pesquisa do Estado de S��o Paulo (FAPESP)

Influ��ncia da espessura do substrato dental sobre a efic��cia clareadora e citotoxicidade de diferentes protocolos de clareamento

Conselho Nacional de Desenvolvimento Cient��fico e Tecnol��gico (CNPq)

Protection against oxidative stress through SUA7/TFIIB regulation in Saccharomyces cerevisiae

The general transcription factor TFIIB, encoded by SUA7 in Saccharomyces cerevisiae, is required for transcription activation but apparently of a specific subset of genes, for example, linked with mitochondrial activity and hence with oxidative environments. Therefore, studying SUA7/TFIIB as a potential target of oxidative stress is fundamental. We found that controlled SUA7 expression under oxidative conditions occurs at transcriptional and mRNA stability levels. Both regulatory events are associated with the transcription activator Yap1 in distinct ways: Yap1 affects SUA7 transcription up regulation in exponentially growing cells facing oxidative signals; the absence of this activator per se contributes to increase SUA7 mRNA stability. However, unlike SUA7 mRNA, TFIIB abundance is not altered on oxidative signals. The biological impact of this preferential regulation of SUA7 mRNA pool is revealed by the partial suppression of cellular oxidative sensitivity by SUA7 overexpression, and supported by the insights on the existence of a novel RNA-binding factor, acting as an oxidative sensor, which regulates mRNA stability. Taken together the results point out a primarily cellular commitment to guarantee SUA7 mRNA levels under oxidative environments.

Cellular polarity in aging: role of redox regulation and nutrition

Cellular polarity concerns the spatial asymmetric organization of cellular components and structures. Such organization is important not only for biological behavior at the individual cell level, but also for the 3D organization of tissues and organs in living organisms. Processes like cell migration and motility, asymmetric inheritance, and spatial organization of daughter cells in tissues are all dependent of cell polarity. Many of these processes are compromised during aging and cellular senescence. For example, permeability epithelium barriers are leakier during aging; elderly people have impaired vascular function and increased frequency of cancer, and asymmetrical inheritance is compromised in senescent cells, including stem cells. Here, we review the cellular regulation of polarity, as well as the signaling mechanisms and respective redox regulation of the pathways involved in defining cellular polarity. Emphasis will be put on the role of cytoskeleton and the AMP-activated protein kinase pathway. We also discuss how nutrients can affect polarity-dependent processes, both by direct exposure of the gastrointestinal epithelium to nutrients and by indirect effects elicited by the metabolism of nutrients, such as activation of antioxidant response and phase-II detoxification enzymes through the transcription factor nuclear factor (erythroid-derived 2)-like 2 (Nrf2). In summary, cellular polarity emerges as a key process whose redox deregulation is hypothesized to have a central role in aging and cellular senescence.

An��lise voltam��trica da ciprofloxacina ��� aplica����o a medicamentos e a remedia����o

O presente trabalho tem como objectivo o desenvolvimento de um m��todo anal��tico, baseado na voltametria de onda quadrada (SWV), para a an��lise de ciprofloxacina (CIP) em produtos farmac��uticos e em processos de remedia����o. Para o desenvolvimento do m��todo voltam��trico foram utilizadas duas c��lulas voltam��tricas: a c��lula cl��ssica (utilizando um el��ctrodo de trabalho de carbono v��treo - GCE) e um el��ctrodo de carbono impresso (SPCE). Ap��s a optimiza����o dos par��metros da SWV, pH (3,04), frequ��ncia (400Hz), incremento de potencial (6 mV) e amplitude do impulso de potencial (40 mV), procedeu-se a valida����o dos m��todos, obtendo-se zonas lineares entre a concentra����o de CIP e a intensidade de corrente de pico de 5,0��10-6 a 6,0��10-5 mol/L (GCE) e de 1,0��10-5 a 4,0��10-5 mol/L (SPCE) e limites de detec����o de 9,48��10-6 mol/L (GCE) e 2,13��10-6 mol/L (SPCE). Verificou-se que a sensibilidade, a precis��o e a selectividade s��o superiores para o SPCE, sendo por isso esta a c��lula mais adequada para proceder �� an��lise da CIP em produtos farmac��uticos. O SPCE foi aplicado com sucesso �� an��lise de CIP num produto farmac��utico. Para o tratamento de solu����es aquosas contendo a CIP foram testados dois oxidantes: o permanganato de pot��ssio e o per��xido de hidrog��nio. Para o per��xido de hidrog��nio os resultados obtidos foram inconclusivos. No caso do permanganato de pot��ssio, os resultados mostram que a degrada����o da ciprofloxacina depende da concentra����o do oxidante. Para uma concentra����o de CIP de 3,00��10-4 mol/L uma degrada����o r��pida foi obtida com o uso de 6,00��10-3 mol/L de permanganato de pot��ssio. Na aplica����o do permanganato na remedia����o de solos verificou-se que no caso de solos h��micos a ciprofloxacina �� adsorvida pelo solo, n��o sendo poss��vel confirmar a ocorr��ncia da reac����o de degrada����o. No caso de solos arenosos verificou-se que a ciprofloxacina foi rapidamente degradada pelo permanganato de pot��ssio.

Determina����o de germ��nio em alimentos por espectrometria de massa ligada a um plasma acoplada indutivamente (ICP-MS)

Nos dias de hoje existe uma grande preocupa����o da popula����o em fazer uma alimenta����o mais saud��vel, uma alimenta����o que tenha nos seus alimentos elementos que n��o prejudiquem a sa��de mas sim que a tornem mais forte. Um desses elementos que pode trazer benef��cio para a sa��de �� o Germ��nio, elemento de estudo no presente trabalho. Neste trabalho determinou-se a concentra����o de Germ��nio em alguns alimentos. Os alimentos usados foram: espargos, ginseng, cogumelos, rabanete, gengibre, alo�� vera e alho. Para se fazer a decomposi����o das amostras foi usada uma solu����o de ��cido n��trico concentrado (67%) e per��xido de hidrog��nio (30%), de seguida as solu����es resultantes foram analisadas por espectrometria de massa ligado a um plasma acoplado indutivamente (Inductive Coupled Plasma - Mass Spectrometry (ICP-MS)). Esta t��cnica permitiu estudar os tr��s is��topos mais abundantes de germ��nio (Ge70, Ge72 e Ge74). Como principais resultados deste trabalho pode-se referir que o alimento que apresenta uma maior concentra����o de Germ��nio �� o ginseng (243,0 ng/g), seguindo-se o alho (152,6 ng/g). Com concentra����es bastante pr��ximas ficaram os espargos, gengibre e cogumelos com um valor aproximado de 75 ng/g. As concentra����es mais baixas formam encontradas no alo�� vera e rabanete, com valores de 38,16 e 21,85ng/g respectivamente. Com estes resultados podemos concluir que para ter uma alimenta����o rica neste elemento deve-se ingerir ginseng e alho pois dos alimentos estudados s��o os mais ricos em Germ��nio.

Enzymatic determination of choline in milk using a FIA system with potentiometric detection

The development of a FIA system for the determination of total choline content in several types of milk is described. The samples were submitted to hydrochloric acid digestion before injection into the system and passed through an enzymatic reactor containing choline oxidase immobilised on glass beads. This enzymatic reaction releases hydrogen peroxide which then reacts with a solution of iodide. The decrease in the concentration of iodide ion is quantified using an iodide ion selective tubular electrode based on a homogeneous crystalline membrane. Validation of the results obtained with this system was performed by comparison with results from a method described in the literature and applied to the determination of total choline in milks. The relative deviation was always < 5%. The repeatability of the method developed was assessed by calculation of the relative standard deviation (RSD) for 12 consecutive injections of one sample. The RSD obtained was < 0.6%.

Trits(Pyrazol-1-YL)methane metal complexes for catalytic mild oxidative functionalizations of alkanes, alkanes and ketones

This work concerns recent advances (since 2005) in the oxidative functionalization of alkanes, alkenes and ketones, under mild conditions, catalyzed by homoscorpionate tris(pyrazol-1-yl)methane metal complexes. The main types of such homogeneous or supported catalysts are classified, and the critical analysis of the most efficient catalytic systems in the different reactions is presented. These reactions include the mild oxidation of alkanes (typically cyclohexane as a model substrate) with hydrogen peroxide (into alkyl hydroperoxides, alcohols, and ketones), the hydrocarboxylation of gaseous alkanes (with carbon monoxide and potassium peroxodisulfate) into the corresponding Cn+1 carboxylic acids, as well as the epoxidation of alkenes and the Baeyer-Villiger oxidation of linear and cyclic ketones with hydrogen peroxide into the corresponding esters and lactones. Effects of various reaction parameters are highlighted and the preferable requirements for a prospective homogeneous or supported C-scorpionate-M-based catalyst in oxidative transformations of those substrates are identified. (C) 2014 Elsevier B.V. All rights reserved.

Baeyer-Villiger oxidation of Keotones catalysed by rhenium complexes bearing N- Or Oxo-Ligands

Rhenium (I, III-V or VII) complexes bearing N-donor or oxo-ligands catalyse the Baeyer-Villiger oxidation of cyclic and linear ketones (e.g. 2-methylcyclohexanone, 2-methylcyclopentanone, cyclohexanone, cyclopentanone, cyclobutanone and 3,3-dimethyl-2-butanone) into the corresponding lactones or esters, in the presence of aqueous H2O2 (30%). The effects of various reaction parameters are studied allowing to achieve yields up to 54%.

Remedia����o de solos contaminados por compostos farmac��uticos

O recente surgimento de nanopart��culas de ferro valente-zero (nFZV), um material com elevada capacidade de remedia����o de solos por via de reac����es de oxida����o/redu����o pode ser uma op����o vi��vel para a remo����o de f��rmacos do solo. A sua aplica����o j�� �� uma realidade em alguns tipos de solos contaminados por compostos espec��ficos e, com este trabalho, procura-se estudar a sua capacidade de remedia����o de solos contaminados por compostos farmac��uticos, recorrendo-se a uma tecnologia ���verde��� de s��ntese destas nanopart��culas. Esta tecnologia �� bastante recente, ainda n��o aplicada no campo de trabalho, que se baseia no uso de folhas de certas ��rvores para produzir extratos naturais que reduzem o ferro (III) a ferro zero valente, formando nFZV. Desta forma procedeu-se, �� escala laboratorial, ao estudo da efici��ncia das nFZV na degrada����o de um f��rmaco ��� paracetamol ��� e comparou-se com a efici��ncia demonstrada por oxidantes, muito utilizados hoje em dia em casos de remedia����o in situ como o permanganato de pot��ssio, o per��xido de hidrog��nio, o persulfato de s��dio e o reagente de Fenton. O estudo foi efectuado em dois meios diferentes: solu����o aquosa e solo arenoso. De forma muito sucinta, o estudo baseou-se na introdu����o dos oxidantes/nFZV em solu����es/solos contaminados com paracetamol e consequente monitoriza����o do processo de remedia����o atrav��s de cromatografia l��quida de alta efici��ncia. Nos ensaios com solu����es aquosas contaminadas com paracetamol, o permanganato de pot��ssio e o reagente de Fenton revelaram capacidade para degradar o paracetamol, atingindo mesmo um grau de degrada����o de 100%. O persulfato de s��dio tamb��m demonstrou uma capacidade de degrada����o do paracetamol, chegando a atingir 99% de degrada����o, mas apenas recorrendo ao uso de um volume de oxidante elevado quando comparado com os outros dois oxidantes j�� referidos. Por outro lado, o per��xido de hidrog��nio n��o demonstrou qualquer capacidade de degrada����o do paracetamol, pelo que o seu uso n��o passou desta fase. Verificou-se tamb��m que o uso de ferro granulado para o tratamento de ��gua contaminada com paracetamol revelou resultados diferentes dos observados no uso de nFZV, obtendo-se efici��ncias de 87%. Existiram dificuldades anal��ticas na quantifica����o do paracetamol, especificamente relacionadas com o uso do extracto de folhas de amoreira, cuja composi����o continha subst��ncias que causaram dificuldades acentuadas na an��lise dos cromatogramas. Por fim, um pequeno teste de combina����o do reagente de Fenton com os fen��menos de biodegrada����o resultantes dos microrganismos presentes em folhas do extracto de ch�� preto demonstrou que este pode ser uma ��rea que pode e deve ser mais estudada. Desta forma, a utiliza����o das nFZV para o tratamento de ��gua contaminada com paracetamol n��o permitiu a retirada de conclus��es seguras sobre a capacidade que as nFZV produzidas com extractos de folhas de amoreira e de ch�� preto t��m de degrada����o do paracetamol. Nos testes de remedia����o de solos contaminados os resultados demonstraram que, mais uma vez, tanto o permanganato de pot��ssio como o reagente de Fenton se revelam como os melhores oxidantes para a degrada����o do paracetamol, obtendo-se a degrada����o total do paracetamol. Por outro lado, voltou a ser necess��rio uma elevada quantidade de persulfato de s��dio quando comparada com os dois anteriores, para que ocorra a degrada����o desta mesma quantidade de paracetamol, demonstrando mais uma vez que, apesar de n��o ideal, o persulfato demonstra capacidade de degrada����o do paracetamol.

Mitochondria are the main source and one of the targets of Pb (lead)-induced oxidative stress in the yeast Saccharomyces cerevisiae

The yeast Saccharomyces cerevisiae is a useful model organism for studying lead (Pb) toxicity. Yeast cells of a laboratory S. cerevisiae strain (WT strain) were incubated with Pb concentrations up to 1,000 ��mol/l for 3 h. Cells exposed to Pb lost proliferation capacity without damage to the cell membrane, and they accumulated intracellular superoxide anion (O2 .���) and hydrogen peroxide (H2O2). The involvement of the mitochondrial electron transport chain (ETC) in the generation of reactive oxygen species (ROS) induced by Pb was evaluated. For this purpose, an isogenic derivative ��0 strain, lacking mitochondrial DNA, was used. The ��0 strain, without respiratory competence, displayed a lower intracellular ROS accumulation and a higher resistance to Pb compared to the WT strain. The kinetic study of ROS generation in yeast cells exposed to Pb showed that the production of O2 .��� precedes the accumulation of H2O2, which is compatible with the leakage of electrons from the mitochondrial ETC. Yeast cells exposed to Pb displayed mutations at the mitochondrial DNA level. This is most likely a consequence of oxidative stress. In conclusion, mitochondria are an important source of Pb-induced ROS and, simultaneously, one of the targets of its toxicity.

Effect of Cysticercus cellulosae fractions on the respiratory burst of pig neutrophils

Neutrophils, eosinophils and macrophages are cells that interact with invading parasites and naive hosts have been shown to have anti-parasitic activity. The initial reaction of these leukocytes is the generation of reactive oxygen species (ROS) to play in parasite expulsion. The present work was carried out to study the effect of total extract, scolex and membrane fractions from Cysticercus cellulosae on respiratory burst by pig neutrophils. Hydrogen peroxide (H2O2) production by neutrophils incubated with metacestode fractions from C. cellulosae showed an increase of: 190% (total extract), 120% (scolex) and 44% (membrane). High antioxidant catalatic activity (33%, 28%, 28% by total extract, scolex and membrane, respectively) was observed in neutrophils incubated with metacestode fractions, which could be an attempt at self-protection. Scolex and membrane fractions increased the phagocytic capacity of neutrophils (44% and 28%, respectively). On the other hand, total cysticerci did not alter the phagocytosis, possibly due to modifications in membrane function, caused by high ROS production from neutrophils in the presence of total cysticerci. Total fraction from C. cellulosae is toxic for neutrophils as shown by the decrease in phagocytic capacity, probably caused by high levels of ROS formation. The difference in toxicity of total extract, scolex and membrane fractions on neutrophils can be explained by the presence of an antigenic effect of the vesicular fluid in the total extract of C. cellulosae.

Electrochemical characterization of Dps, a DNA-protecting protein

Disserta����o para obten����o do Grau de Mestre em Biotecnologia