Synthesis,characterization, X-ray structure and preliminary in vitro antitumor activity of the nitrosyl complex fac-[RuCl3(NO)(dppf)], dppf = 1,1′-bis(diphenylphosphine)ferrocene

The reaction of RuCl₃NO · 2H₂O with stoichiometric amount of dppf, 1,1′-bis(diphenylphosphino)ferrocene, afforded the new neutral nitrosyl complex fac-[RuCl₃(NO)(dppf)] which was characterized by spectroscopical, electrochemical and X-ray crystallography techniques as well as elemental analysis. The ν_NO band in the IR spectrum is at 1860 cm⁻¹ (CH₂Cl₂ solution) and in the cyclic voltammogram an irreversible wave was observed at −1.35 V, both are characteristics of a nitrosonium (NO⁺) character for the coordinated NO. Additionally, preliminary in vitro antitumor activity against the MDA-MB-231 breast tumor cell line was carried out for the new complex. The initial results indicated an important activity for fac-[RuCl₃(NO)(dppf)] (IC₅₀ = 10 ± 3 μM ). The complex has a higher cytotoxicity than the precursor complex RuCl₃NO · 2H₂O, the free dppf ligand as well as the reference metallodrug cisplatin.     

Glucose Biosensor Using Glucose Oxidase Immobilized in Polyaniline

A biosensor for glucose utilizing kinetics of glucose oxidase (EC 1.1.3.4.) was developed. The enzyme was immobilized on polyaniline by covalent bonding, using glutaraldehyde as a bifunctional agent. The system showed a linear response up to 2.2 mM of glucose with a response time of 2.5–4.0 min. In addition, the immobilized enzyme had a higher activity between pH 6.5 and 7.5. The system retained 50% of its activity after 30 d of daily use. The optical absorption spectra of the polyaniline/glucose oxidase electrode after glucose had been added to the buffer solution showed that the absorption band around 800 nm had changed considerably when glucose was allowed to react with the electrode. This optical variation makes polyaniline a very promising polymer for use as a support in optical sensor for clinical application.     

The effect of mechanochemical activation on the reactivity in the MgO–Al2O3–SiO2 system

Samples of the MgO–Al₂O₃–SiO₂ ternary system, constituted by 28.5 mol% ofMgO, 28.5 mol% of Al₂O₃ and 43mol%of SiO₂, were activated in a roll mill and calcined at different temperatures. The influence of the grinding time, the used SiO₂ precursor and activation medium, furthermore the mass ratio between the powdered sample and zirconia cylinders was investigated on the reactivity of the MgO–Al₂O₃–SiO₂ ternary system. FTIR spectra and the X-ray powder diffraction patterns indicates the formation of Mg(OH)₂ at 393 K, of forsterite (MgSi₂O₅) and enstatite (MgSiO₃) at 1223 K and of spinel (MgAl₂O₄) between 1223 and 1523 K in some samples. The presence of cordierite (Mg₂Al₂Si₅O₁₈) was observed at 1523 K, a reaction pathway concerning its formation was proposed.     

Automotive Gasoline Quality Analysis by Gas Chromatography: Study of Adulteration

Summary The addition of organic solvents (light aliphatic, heavy aliphatic and aromatic hydrocarbons) in Brazilian gasoline is unfortunately very frequent, and this illicit practice impares gasoline quality. Gas chromatography (GC) and gas chromatography coupled to mass spectrometry (GC-MS) analyses can be used as a procedure to improve the detection of adulterated gasoline. The results showed that adulterated samples and also the type of organic solvent used in adulteration can be detected by comparison of chromatographic profiles (standard samples versus adulterated samples). However, a single GC analysis can detect an adulterated gasoline, and so decrease the number of adulterated samples approved as presenting good quality.     

Low-Temperature Electron Spin Resonance in (TMTSF)2PF6 in the High Pressure Metallic Phase

Abstract

The electron spin resonance of (TMTSF)₂PF₆ has been observed at low fields (H_o < 110 Oe) in the high pressure, metallic phase (p > 6.5 kbar) in the temperature range 1-4^?K. The anisotropy in the g value is similar to that observed at ambient pressure above the metal-insulator transition. The linewidth is very narrow and the spin susceptibility strongly decreases as the superconducting transition is approached from above. We interpret this as evidence for singlet-paired superconductivity. Superconductivity is observed at 1.1 K and the critical field has angular dependence in the be plane. These observations lead us to conclude that (TMTSF)₂PF₆ is a singlet paired superconductor.     

Influence of the addition of Cr in the microstructure and in the phase transformation temperatures of Cu–Al–Be–Nb–Ni alloys

Journal of Thermal Analysis and Calorimetry - Cu–Al–Be polycrystalline SMAs modified with the addition of inoculants show improved ductility, which accredits them for technological...     

First-principles studies of zigzag pristine boron nitride nanotubes doped with one iron atom

Interaction of one iron atom with pristine zigzag boron nitride nanotubes with different diameters, ranging from (8,0) to (12,0), have been investigated using density functional theory calculations. Departing from four initial configurations, considering each of them interacting with the tubes’ walls either from inside or outside, we have analyzed the adsorbate migration to the most favorable positions together with the related binding energies and the equilibrium distances as well as the electronic structure of the final systems. It was observed that the smaller the radius of the tube the lower is the binding energy for all studied structures, and also that the inner configuration is more stable than the outer one for small radius. For the preferred position for the iron atom, it was seen that it varies according to the starting configuration and that the iron-first-nitrogen-neighbor bond length works as a constraint in determining the most favorable position for the adsorbate. Finally, for the electronic structure, it was observed that the presence of the dopant introduces localized levels at the band gap of the nanotubes and that those levels are mostly related to the orbitals 3d and 4s of the iron atom. For the inside case, as a consequence of higher hybridization and a confinement effect, the gap closure is more pronounced for small diameter tubes. For all studied structures, it was observed a net-spin-polarization equal to 4 μ _B.     

On the sign changes of coefficients of general Dirichlet series

Under what conditions do the (possibly complex) coefficients of a general Dirichlet series exhibit oscillatory behavior? In this work we invoke Laguerre's Rule of Signs and Landau's Theorem to provide a rather simple answer to this question. Furthermore, we explain how our result easily applies to a multitude of functions.

     

Lupane triterpenoids,antioxidant potential and antimicrobial activity of Myrciaria floribunda (H. West ex Willd.) O. Berg.

Chemical composition of the methanol extract of Myrciaria floribunda leaves was investigated. The nor-lupane triterpenoids platanic acid and messagenic I acid were identified, along with other known triterpenoids (betulinic aldehyde, ursolic acid acetate and betulinic acid), a new lupane triterpenoid (2α,6α,30-trihydroxybetulinic acid) and the flavonoids catechin, quercetrin and mirycitrin. The structures were determined by spectroscopic methods (NMR, LC-MS, GC-MS). The major isolated compound was betulinic acid. The methanol extract and 2α,6α,30-trihydroxybetulinic acid were evaluated for their DPPH scavenging potential. The tested triterpenoid was one hundred times more active than betulinic acid, but less active than the extract. Screening for antimicrobial activity showed that the methanol extract was active against Staphylococcus aureus and Escherichia coli, but inactive against Candida albicans and Candida krusei, while 2α,6α,30-trihydroxybetulinic acid was inactive to all tested microorganisms.