An efficient preparation of novel 5-fluoropyrazolin-3-one derivatives from α-trifluoromethylated α-arylacetates

The reactions of α-trifluoromethylated α-arylacetates 1 with 3 equiv of hydrazine, methylhydrazine or benzylhydrazine in 1,4-dioxane at reflux for 24 h afforded the corresponding 5-fluoropyrazolin-3-one derivatives 3a-m in high yields. Similarly, treatment of 1 with 3 equiv of PhNLiNH₂ in THF at −78 °C, followed by warming to room temperature, resulted in the formation of 3n-s in high yields.     

The role of complexing ligands in the formation of non-aggregated nanoparticles of zirconia

The hydrolysis and condensation of zirconium n-propoxide in n-propanol have been chemically controlled via the complexation of the zirconium precursor with acetylacetone. The size of the zirconium oxide-based particles is mainly controlled by the complexation ratio x=[acac]/[Zr]. the mean size increases from nanometric to submicronic range when x decreases from 1 to 0.1. Amorphous colloidal particles are obtained at room temperature. They result from a competitive growth/termination mechanism of zirconium-oxo species in the presence of acac surface capping agents. However non-aggregated nanocrystalline particles of tetragonal zirconia, about 2 nm in diameter are formed upon aging at 60°C when hydrolysis is performed in the presence of paratoluene sulfonic acid (PTSA).     

Control of the Properties of Carbon Nanotubes Synthesized by CVD for Application in Electrochemical Biosensors

Interest in carbon nanotubes (CNT) has grown at a very rapid rate in the last decade. Their interesting physical and chemical properties open attractive possibilities in many application areas. These properties depend on the process conditions during synthesis and on subsequent purification steps. Recent studies have demonstrated that CNT can promote the electron transfer of biomolecules. These exceptional properties make them attractive for use in electrochemical biosensors. Multi walled nanotubes have been synthesized by the Chemical Vapor Deposition (CVD) method using methane as a carbon source and Ni–Al₂O₃–SiO₂ as the catalyst. The influence of the variation of certain reaction parameters such as feed gas composition, catalyst mass, temperature and reaction time in the yield of the CVD process has been established. In addition, the structural and chemical characteristics of the CNTs have been studied and a purification process to eliminate the catalyst and amorphous carbon has been developed that involves a gaseous oxidative process and acid treatment. The efficiency of the purification step has been determined by analytical techniques. Atomic force microscopy, Raman scattering, thermogravimetric analysis, inductively coupled plasma atomic spectroscopy are the characterization techniques employed in this work.     

Fluorescence spectroscopy for monitoring deterioration of extra virgin olive oil during heating

The potential of fluorescence spectroscopy for characterizing the deterioration of extra virgin olive oil (EVOO) during heating was investigated. Two commercial EVOO were analysed by HPLC to determine changes in EVOO vitamin E and polyphenols as a result of heating at 170°C for 3 h. This thermal oxidation of EVOO caused an exponential decrease in hydroxytyrosol and vitamin E (R²=0.90 and 0.93, respectively) whereas the tyrosol content was relatively stable. At the same time, amounts of preformed hydroperoxides (ROOH), analysed by an indirect colorimetric method, decreased exponentially during the heating process (R²=0.94), as a result of their degradation into secondary peroxidation products. Fluorescence excitation spectra with emission at 330 and 450 nm were recorded to monitor polyphenols and vitamin E evolution and ROOH degradation, respectively. Partial least-squares calibration models were built to predict these indicators of EVOO quality from oil fluorescence spectra. A global approach was then proposed to monitor the heat charge from the overall fluorescence fingerprint. Different data pretreatment methods were tested. This study indicates that fluorescence spectroscopy is a promising, rapid, and cost-effective approach for evaluating the quality of heat-treated EVOO, and is an alternative to time-consuming conventional analyses. In future work, calibration models will be developed using a wide range of EVOO samples.     

Self-assembly between silver(I) and di- and tri-2-pyridines with flexible spacer: formation of discrete metallocycle versus coordination polymer

The self-assembly of metallosupramolecules from reactions of flexible 2-pyridyl ligands and silver salts is described. When 1,3-bis(2-pyridyl)propane (L1), tris[(2-pyridyl)methyl]methane (L2), and 1,3-bis(2-pyridyl)-2-tolylpropane (L3) are used in combination with silver ions, novel discrete metallocyclic complexes are formed in crystals. Moreover, the self-assembly of 1,3-bis(2-pyridyl)-2-phenylpropane (L4) with silver nitrate yields a coordination polymer. The examination of its solution shows that this coordination polymer is formed via the solution-based discrete metallocyclic species.     

Estrogen receptor microarrays: subtype-selective ligand binding

We present the first example of a nuclear hormone receptor microarray, using for illustration the ligand-binding domains of the two estrogen receptors, ERalpha-LBD and ERbeta-LBD. The proteins are printed and allowed to attach to aldehyde slides; the efficiency of attachment depends on whether the LBD is liganded with agonists (low attachment) versus liganded with antagonists or unliganded (high attachment). This suggests that attachment is orientation specific and involves principally a single lysine residue. The attached ERs retain good ligand-binding activity that can be assessed using an estradiol-fluorophore conjugate, and specific and ER subtype-selective binding of ligands can be determined conveniently in competitive binding assays. This powerful new, high-throughput technique to study ligand binding to ER-LBDs can be extended to other nuclear hormone receptors and adapted to assay the recruitment of coregulator proteins.     

Decarbopalladation of pi-allylpalladium intermediates formed from palladium-catalyzed arylations of 3-allen-1-ols

[reaction: see text] Unusual palladium-catalyzed arylative fragmentations of acyclic 3-allen-1-ols were observed. Oxidative addition of Pd(0) to aryl halides would form the arylpalladium halides, which added to the central carbon of allenes via carbopalladation to form the pi-allylpalladium intermediates. The pi-allylpalladium intermediates would be reductively eliminated via carbon-carbon cleavage to give the arylated dienes and the alpha-hydroxyalkylpalladium intermediates, which were further reductively eliminated to the corresponding aldehydes.     

Ionizing radiation induces blockade of c-Jun N-terminal kinase-dependent cell death pathway in a manner correlated with p21(Cip/WAF1) induction in primary cultured normal human fibroblasts

During radiotherapy of cancer, neighboring normal cells may receive sub-lethal doses of radiation. To investigate whether such low levels of radiation modulate normal cell responses to death stimuli, primary cultured human fibroblasts were exposed to various doses of gamma-rays. Analysis of cell viability using an exclusion dye propidium iodide revealed that the irradiation up to 10 Gy killed the fibroblasts only to a minimal extent. In contrast, the cells efficiently lost their viability when exposed to 0.5-0.65 mM H(2)O(2). This type of cell death was accompanied by JNK activation, and was reversed by the use of a JNK-specific inhibitor SP600125. Interestingly, H(2)O(2) failed to kill the fibroblasts when these cells were pre-irradiated, 24 h before H(2)O(2) treatment, with 0.25-0.5 Gy of gamma-rays. These cytoprotective doses of gamma-rays did not enhance cellular capacity to degrade H(2)O(2), but elevated cellular levels of p21(Cip/WAF1), a p53 target that can suppress H(2)O(2)-induced cell death by blocking JNK activation. Consistently, H(2)O(2)-induced JNK activation was dramatically suppressed in the pre-irradiated cells. The overall data suggests that ionizing radiation can impart normal fibroblasts with a survival advantage against oxidative stress by blocking the process leading to JNK activation.     

Selective extraction of benzoic acid from landfill leachate by solid-phase extraction and ion-exchange chromatography

In this work a simple method was described for selective extraction of benzoic acid from landfill leachate samples. The samples were submitted to solid-phase extraction (SPE) with XAD-4 resin as the stationary phase and ion-exchange chromatography (IEC) using the ion-exchange resin Amberlyst A-27. The instrumental analysis was performed by gas chromatography with mass spectrometric detection (GC-MSD). Benzoic acid was isolated, identified and quantified. The extraction process is rapid, simple and of low cost. It was also environmental friendly, that is, it was used a minimum amounts of hazardous organic solvents and produced also minimum quantities of residues.     

Kinetics and mechanism of benzylamine additions to ethyl alpha-acetyl-beta-phenylacrylates in acetonitrile

Kinetic studies of the addition of benzylamines to a noncyclic dicarbonyl group activated olefin, ethyl alpha-acetyl-beta-phenylacrylate (EAP), in acetonitrile at 25.0 degrees C are reported. The rates are lower than those for the cyclic dicarbonyl group activated olefins. The addition occurs in a single step with concurrent formation of the Calpha-N and Cbeta-H bonds through a four-center hydrogen bonded transition state.The kinetic isotope effects (kH/kD > 1.0) measured with deuterated benzylamines (XC6H4CH2ND2) increase with a stronger electron acceptor substituent (deltasigmaX > 0) which is the same trend as those found for other dicarbonyl group activated series (1-4), but is in contrast to those for other (noncarbonyl) group activated series (5-9). For the dicarbonyl series, the reactivity-selectivity principle (RSP) holds, but for others the anti-RSP applies. These are interpreted to indicate an insignificant imbalance for the former, but substantial lag in the resonance delocalization in the transition state for the latter series.