Análise in silico de uma pirofosfatase e de uma tiosterase de uma biblioteca metagenômica de solo de Eucalipto spp

Pós-graduação em Microbiologia Agropecuária - FCAV

Deposição e caracterização de filmes de óxido de cobalto por sputtering reativo

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Formadores de filmes híbridos ureasil-poliéter para proteção da pele e liberação controlada de fármacos

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Catalisadores de cobre suportados em óxidos de zircônio hierarquicamente estruturados para a reação de desidrogenação de etanol

Pós-graduação em Química - IQ

Caracterização de estruturas de óxido de estanho modificado como sensores de gases

Pós-graduação em Química - IQ

Síntese, Caracterização Estrutural e Análise do Potencial Catalítico, para a Preparação de Biodiesel, de Niobatos Não Estequiométricos com Estrutura Tungstênio Bronze

Pós-graduação em Química - IBILCE

Estudos sobre a utilização de pentóxido de nióbio nanoestruturado na produção de biodiesel

In heterogeneous catalysis, numerous elements such as titanium and iron have been studied as nanoscale catalysts, but little is known about the use of niobium in nanocatalysis. The nanostructured particles have intrinsic and different physicochemical characteristics with great potential for use in industrial scale. Brazil having the largest known worldwide niobium reserve has the great challenge of creating pioneering technologies with the metal. Biodiesel is an alternative fuel and renewable substitute for regular diesel. Being biodegradable, non-toxic and have CO2 emissions lower than regular diesel, it contributes to the environment and to the independence from oil. The aim of this work was initially synthesize nanoscale particles of niobium pentoxide (Nanospheres, nanorods, nanofibers, nanocubes) from the sol-gel technique. The characterization of different nanoscale structures obtained was performed using different analytical techniques such as x-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The synthesized nanometer niobium oxide will be used as a heterogeneous catalyst in biodiesel synthesis from commercial soybean oil, checking in detail what the effect of morphology is presented (Nanospheres, nanorods, nanofibers, nanocubes) in the yield of biodiesel synthesis, comparing these results with those already described in literature for the amorphous niobium oxide and other oxide catalysts. The biodiesel obtained was characterized by gas chromatography system equipped with a FID detector

Employing perichromism for probing the properties of carboxymethyl cellulose films: an expedient, accurate method for the determination of the degree of substitution of the biopolymer derivative

The properties of films of carboxymethyl cellulose, CMC, of different degree of substitution, DS, have been examined by the use of perichromic indicators (probes). The film properties that have been determined are: empirical polarity, E-T(33); "acidity", alpha; "basicity", beta; and dipolarity/polarizability, pi*. This has been achieved by employing the following perichromic probes: 4-nitroaniline, 4-nitroanisole, 4-nitro-N,N-dimethylaniline, and 2,6-dichloro-4-(2,4,6-triphenyl-pyridinium-1-yl)phenolate, WB. The correlations between both E-T(33)- or pi* and DS were found to be linear; that between beta and DS is a second order polynomial; no obvious correlation was found between alpha and DS. The polarities of CMC films are in the range of those of butyl alcohols. As models for CMC, we have employed cellulose plus CMC of high DS; oxidized cellulose with degree of oxidation = 0.5; sodium glucuronate. The former model behaved akin to CMC, but the plots of the perichromic properties versus DS showed different slopes/intercepts. FTIR data and molecular dynamics simulations on the solvation of WB have shown that this difference can be traced to more efficient hydrogen bonding between the film of the model and the probe. This affects the intra-molecular charge-transfer energy of the latter, leading to different responses to the variation of DS. Based on the excellent linear correlation between E-T(33) and DS, for CMC from different origins, we suggest that perichromism is a simple, accurate, and expedient alternative for the determination of DS of the biopolymer derivative.

Spectroscopic and Catalytic Characterization of a Functional (FeFeII)-Fe-III Biomimetic for the Active Site of Uteroferrin and Protein Cleavage

A mixed-valence complex, [Fe(III)Fe(II)L1(mu-OAc)(2)]BF4 center dot H2O, where the ligand H(2)L1 = 2-{[[3-[((bis-(pyridin-2-ylmethyl)amino)methyl)-2-hydroxy-5-methylbenzyl](pyridin-2-ylmethyl)amino]methyl]phenol}, has been studied with a range of techniques, and, where possible, its properties have been compared to those of the corresponding enzyme system purple acid phosphatase. The (FeFeII)-Fe-III and Fe-2(III) oxidized species were studied spectroelectrochemically. The temperature-dependent population of the S = 3/2 spin states of the heterovalent system, observed using magnetic circular dichroism, confirmed that the dinuclear center is weakly antiferromagnetically coupled (H = -2JS(1).S-2, where J = -5.6 cm(-1)) in a frozen solution. The ligand-to-metal charge-transfer transitions are correlated with density functional theory calculations. The (FeFeII)-Fe-III complex is electron paramagnetic resonance (EPR)-silent, except at very low temperatures (<2 K), because of the broadening caused by the exchange coupling and zero-field-splitting parameters being of comparable magnitude and rapid spin-lattice relaxation. However, a phosphate-bound Fe-2(III) complex showed an EPR spectrum due to population of the S-tot = 3 state (J= -3.5 cm(-1)). The phosphatase activity of the (FeFeII)-Fe-III complex in hydrolysis of bis(2,4-dinitrophenyl)phosphate (k(cat.) = 1.88 x 10(-3) s(-1); K-m = 4.63 x 10(-3) mol L-1) is similar to that of other bimetallic heterovalent complexes with the same ligand. Analysis of the kinetic data supports a mechanism where the initiating nucleophile in the phosphatase reaction is a hydroxide, terminally bound to Fe-III. It is interesting to note that aqueous solutions of [Fe(III)Fe(II)L1(mu-OAc)(2)](+) are also capable of protein cleavage, at mild temperature and pH conditions, thus further expanding the scope of this complex's catalytic promiscuity.

Direct Access to Oxidation-Resistant Nickel Catalysts through an Organometallic Precursor

The synthesis of nickel catalysts for industrial applications is relatively simple; however, nickel oxidation is usually difficult to avoid, which makes it challenging to optimize catalytic activities, metal loadings, and high-temperature activation steps. A robust, oxidation-resistant and very active nickel catalyst was prepared by controlled decomposition of the organometallic precursor [bis(1,5-cyclooctadiene)nickel(0)], Ni(COD)(2), over silica-coated magnetite (Fe3O4@SiO2). The sample is mostly Ni(0), and surface oxidized species formed after exposure to air are easily reduced in situ during hydrogenation of cyclohexene under mild conditions recovering the initial activity. This unique behavior may benefit several other reactions that are likely to proceed via Ni heterogeneous catalysis.

Recent Advances in the Development of Magnetically Recoverable Metal Nanoparticle Catalysts

The aim of this Account is to provide an overview of our current research activities on the design and modification of superparamagnetic nanomaterials for application in the field of magnetic separation and catalysis. First, an introduction of magnetism and magnetic separation is done. Then, the synthetic strategies that have been developed for generating superparamagnetic nanoparticles spherically coated by silica and other oxides, with a focus on well characterized systems prepared by methods that generate samples of high quality and easy to scale- up, are discussed. A set of magnetically recoverable catalysts prepared in our research group by the unique combination of superparamagnetic supports and metal nanoparticles is highlighted. This Account is concluded with personal remarks and perspectives on this research field.

2-Acetylpyridine- and 2-benzoylpyridine-derived hydrazones and their gallium(III) complexes are highly cytotoxic to glioma cells

2-Acetylpyridine-phenylhydrazone (H2AcPh), its para-chlorophenylhydrazone (H2AcpClPh) and para-nitrophenylhydrazone (H2AcpNO(2)Ph) analogues, the corresponding 2-benzoylpyridine-derived hydrazones (H2BzPh, H2BzpClPh and H2BzpNO(2)Ph) and their gallium(III) complexes were assayed for their cytotoxic activity against U87 (expressing wild-type p53 protein) and T98 (expressing mutant p53 protein) glioma cells. IC50 values against both glioma cells and against the MRC5 (human fetal lung fibroblast) lineage were obtained for the hydrazones, but not for their gallium(III) complexes, due to their low solubility. Hydrazones were highly cytotoxic at nanomolar doses against U87 and T98 cells. The therapeutic indexes (TI = IC50MRC5/IC50glioma) were 2-660 for T98 cells and 28-5000 for U87 cells, indicating that the studied hydrazones could be good antitumor drug candidates to treat brain tumors. (C) 2012 Elsevier Masson SAS. All rights reserved.

Catalyst Recovery and Recycling Facilitated by Magnetic Separation: Iridium and Other Metal Nanoparticles

The immobilization of metal nanoparticles in magnetic responsive solids allows the easy, fast, and clean separation of catalysts; however, the efficiency of this separation process depends on a strong metalsupport interaction. This interaction can be enhanced by functionalizing the support surface with amino groups. Our catalyst support contains an inner core of magnetite that enables the magnetic separation from liquid systems and an external surface of silica suitable for further modification with organosilanes. We report herein that a magnetically recoverable amino-functionalized support captured iridium species from liquid solutions and produced a highly active hydrogenation catalyst with negligible metal leaching. An analogous Ir0 catalyst prepared with use of a nonfunctionalized support shows a higher degree of metal leaching into the liquid products. The catalytic performance in the hydrogenation of alkenes is compared with that of Rh and Pt catalysts.

The 2:1 cycloadducts from [3+2] 1,3-dipolar cycloaddition of nitrile oxide and vinylacetic acid. Synthesis and liquid crystal behaviour

Four liquid crystals (LC) 3,7a-bis(4-alkyloxyphenyl)-7,7a-dihydro-6H-isoxazolo[2,3-d][1,2,4]oxadiazol-6-yl)acetic acid (7a-d) were synthesised and the mesomorphic behaviour reported. The LCs were characterised as 2: 1 bisadducts, which were obtained from a double [3+2] 1,3-dipolar cycloaddition. In the first step, the cycloaddition of 4-alkyloxyphenylnitrile oxide (4a-d) and vinylacetic acid (5) gave the initial unobserved 1:1 cycloadducts 2-[3-(4-alkyloxyphenyl)-4,5-dihydroisoxazol-5-yl]acetic acid (6a-d). In the second step, the addition of a second equivalent of 4 to 6 yielded the 2: 1 bisadducts 7a-d without any traces of 6. All compounds 7a-d were unstable during the transition from the mesophase to the isotropic state upon first heating as evidenced by the large peaks in the differential scanning calorimetry traces. Due to the chemical instability of the compounds upon heating, the transition temperature related to the smectic C to smectic A transitions was acquired by means of an image processing method. X-Ray diffraction experiments were also used to analyse the liquid-crystalline phases. A theoretical calculation was performed using density functional theory (DFT) methods at the PBE1PBE/6-311+G(2d,p) level (with solvent effect) in order to get information about the energetic profile of the 2: 1 cycloaddition. DFT studies revealed that the cycloaddition process is controlled by the HOMO(dipolarophile) - LUMO(1,3-dipole), and that the double [3+2] 1,3-dipolar cycloaddition reaction is quite possible.

N-4-Phenyl-substituted 2-acetylpyridine thiosemicarbazones: Cytotoxicity against human tumor cells, structure-activity relationship studies and investigation on the mechanism of action

N-4-Phenyl 2-acetylpyridine thiosemicarbazone (H2Ac4Ph; N-(phenyl)-2-(1-(pyridin-2-yl)ethylidene) hydrazinecarbothioamide) and its N-4-ortho-, -meta- and -para-fluorophenyl (H2Ac4oFPh, H2Ac4mFPh, H2Ac4pFPh), N-4-ortho-, -meta- and -para-chlorophenyl (H2Ac4oClPh, H2Ac4mClPh, H2Ac4pClPh), N-4-ortho-, -meta- and -para-iodophenyl (H2Ac4oIPh, H2Ac4mIPh, H2Ac4pIPh) and N-4-ortho-, -meta- and -para-nitrophenyl (H2Ac4oNO(2)Ph, H2Ac4mNO(2)Ph, H2Ac4pNO(2)Ph) derivatives were assayed for their cytotoxicity against human malignant breast (MCF-7) and glioma (T98G and U87) cells. The compounds were highly cytotoxic against the three cell lineages (IC50: MCF-7, 52-0.16 nM; T98G, 140-1.0 nM; U87, 160-1.4 nM). All tested thiosemicarbazones were more cytotoxic than etoposide and did not present any haemolytic activity at up to 10(-5) M. The compounds were able to induce programmed cell death. H2Ac4pClPh partially inhibited tubulin assembly at high concentrations and induced cellular microtubule disorganization. (C) 2012 Elsevier Ltd. All rights reserved.