Characterisation of quaternary mixtures by the apparent content curves method: identification of tocopherols in vegetable oils

A procedure for identification of the compounds in quaternary mixtures has been developed. The proposed procedure is based on the apparent content curves method. From these curves and using the Q parameter, work conditions are selected and quaternary mixtures treated as "pseudoternary" mixtures.A simple strategy to test matrix effects at working wavelengths has been developed, identification limits established and following the identification table quaternary mixtures were easily characterised. The procedure has been applied to the identification of phenols in mixtures by UV-visible spectrophotometry and tocopherols in edible oils by fluorimetry. Results obtained for edible oils are in agreement with the composition obtained by use of the reference method.     

Molecular dynamics simulation on devitrification: isothermal devitrification and thermodynamics of PbF2 glasses

The vitrification and devitrification features of lead fluoride are investigated by means of molecular dynamic simulations. The influence of heating rate on the devitrification temperature as well as the dependence of the glass properties on its thermal history, i.e., the cooling rate employed, is identified. As expected, different glasses are obtained when the cooling rates differ. Diffusion coefficient analysis during heating of glass and crystal, indicates that the presence of defects on the glassy matrix favors the transition processes from the ionic to a superionic state, with high mobility of fluorine atoms, responsible for the high anionic conduction of lead fluoride. Nonisothermal and isothermal devitrification processes are simulated in glasses obtained at different cooling rates and structural organizations occurring during the heat treatments are clearly observed. When a fast cooling rate is employed during the glass formation, the devitrification of a single crystal (limited by the cell dimensions) is observed, while the glass obtained with slower cooling rate, allowing relaxations and organization of various regions on the glass bulk during the cooling process, devitrifies in more than one crystalline plane.     

Chemical composition and evaluation of the antimicrobial activity of the essential oil from leaves of Eugenia platysema

This study describes the qualitative and quantitative chemical composition and evaluates the antibacterial activity of essential oil from Eugenia platysema leaves. Analysis by GC–FID and GC–MS allowed the identification of 22 compounds. Different from the other species of the Eugenia genus, the major compound found in the essential oil was the diterpene phytol (66.05%), being this the first report of the presence of this compound in the essential oils from Eugenia genus. The sesquiterpene elixene was the second most concentrated compound in the studied essential oil (9.16%). The essential oil from E. platysema was tested for its antibacterial activity against cell-walled bacteria and mollicute strains of clinical interest using the microdilution broth assay. The results showed that the essential oil of E. platysema was inactive until 1000 μg mL^?1 against tested bacteria.     

Purification and Characterization of an Ethanol-Tolerant β-Glucosidase from Sporidiobolus pararoseus and Its Potential for Hydrolysis of Wine Aroma Precursors

An extracellular ethanol-tolerant β-glucosidase from Sporidiobolus pararoseus was purified to homogeneity and characterized, and its potential use for the enhancement of wine aroma was investigated. The crude enzymatic extract was purified in four steps (concentration, dialysis, ultrafiltration, and chromatography) with a yield of around 40 % for total activity. The purified enzyme (designated Sp-βgl-P) showed a specific activity of approximately 20.0 U/mg, an estimated molecular mass of 63 kDa after sodium dodecyl sulfate polyacrylamide gel electrophoresis, and isoelectric point of 5.0 by isoelectric focusing. Sp-βgl-P has optimal activity at pH 4.0 and at 55 °C. It was stable in a broad pH range at low temperatures and it was tolerant to ethanol and glucose, indicating suitable properties for winemaking. The hydrolysis of glycosidic terpenes was analyzed by adding Sp-βgl-P directly to the wines. The released terpene compounds were evaluated by gas chromatography/mass spectrometry. The enzymatic treatment significantly increased the amount of free terpenes, suggesting that this enzyme could potentially be applicable in wine aroma improvement.     

An Efficient Synthesis of New 5‐(1‐Aryl‐1H‐pyrazole‐4‐yl)‐1H‐tetrazoles from 1‐Aryl‐1H‐pyrazole‐4‐carbonitriles via [3 + 2] Cycloaddition Reaction

A series of new 5‐(1‐aryl‐1H‐pyrazole‐4‐yl)‐1H‐tetrazoles 4a‐l were synthesized via [3 + 2] cycloaddition reaction from 1‐aryl‐1H‐pyrazole‐4‐carbonitriles 3a‐l , sodium azide and ammonium chloride, using dimethylformamide (DMF) as solvent, in good yields: 64–85%. The structures of these newly synthesized compounds were determined from the IR, ¹H‐ and ¹³C‐NMR spectroscopic data and elemental analyses.     

Synthesis and characterization of novel second-order NLO-chromophores bearing pyrrole as an electron donor group

Two series of novel push–pull 1-(4-(thiophen-2-yl)phenyl)-1H-pyrroles 3–5 were designed to explore the consequence of using different electron accepting moieties linked to the thiophene at the arylthiophene bridge or to the pyrrole heterocycle, which plays the role of donor group. Compound 2 showed a different reactivity behavior in the presence of the Vilsmeier reagent or with tetracyanoethylene (TCNE) giving compounds 4a and 4b functionalized, respectively, at the 2 or on the 3-position of the pyrrole heterocycle. Their optical (linear and first hyperpolarizability), electrochemical, and thermal properties have been examined. Hyper-Rayleigh scattering (HRS) in dioxane solutions using a fundamental wavelength of 1064 nm was employed to evaluate their second-order nonlinear optical properties. Of these systems, thiobarbituric acid derivative 5b functionalized in the thiophene ring exhibits the largest first hyperpolarizability (β=2480×10^?30 esu, T convention) compared to the corresponding compound 4c substituted on the pyrrole heterocycle (β=290×10^?30 esu, T convention). Good to excellent thermal stabilities were also obtained for push–pull compounds 4 and 5 (270–288 °C). This multidisciplinary study shows that modulation of the optical and electronic properties can be achieved by introduction of the acceptor groups in the thiophene of the arylthiophene bridge. The measured molecular first hyperpolarizabilities and the observed electrochemical behavior are quite sensitive to the position of acceptor group on the heterocyclic system (on the thiophene or on the pyrrole ring) as well as the strength of the acceptor moieties. Moreover, the combination of their good nonlinearity and high thermal stability make them good candidates for second-order nonlinear optical applications.     

Energetic features of copper and lead sorption by innovative aminoalcohol-functionalized cobalt phyllosilicates

Inorganic-organic cobalt phyllosilicate hybrids were synthesized by the sol-gel procedure under mild non-hydrothermal conditions with a silicon precursor, formed through individual reactions between the silane 3-glycidoxypropyltriethoxysilane and the aminoalcohols ethanol- or diethanolamine. These procedures generated talc-like phyllosilicates containing pendant organic chains with nitrogen and oxygen basic centres located in the interlamellar region. For organofunctionalized phyllosilicates the lamellar structure obtained through the sol-gel method was confirmed by X-ray powder diffraction, while elemental analysis indicated that the densities of the organic groups attached to the new matrices were 3.31 ± 0.05 and 3.08 ± 0.07 mmol g(-1) for hybrids functionalized with ethanol- and diethanolamines, respectively. Infrared spectroscopy and nuclear magnetic resonance in the solid state for (13)C and (29)Si showed that the organic groups are indeed covalently bonded to the inorganic structures and the process of functionalization did not affect the original structures of the silylating agents employed. The thermally stable hybrids presented well-formed particles with a homogeneous distribution of cobalt and nitrogen atoms. Their abilities for copper removal from aqueous solutions gave maximum capacities of sorption of 2.01 ± 0.11 and 2.55 ± 0.15 mmol g(-1) for phyllosilicates containing ethanol- and diethanolamine groups, respectively. For lead sorption the values of 2.59 ± 0.11 and 2.43 ± 0.12 mmol g(-1) were found for this same sequence. These sorption data were adjusted to the non-linear regression of the Langmuir equation. Energetic features related to the interactions between the cations and the pendant basic centres were determined through calorimetric titrations. The acid-basic interactions reflect the spontaneity of the reactions, which are also enthalpically and entropically favourable for these chelating processes at the solid-liquid interface.     

Diagnosis of dengue infection using a modified gold electrode with hybrid organic-inorganic nanocomposite and Bauhinia monandra lectin

A sensitive and selective biosensor for dengue serotyping was successfully developed. The biosensor uses a novel gold nanoparticles-polyaniline hybrid composite (AuNpPANI) for the immobilization of Bauhinia monandra lectin (BmoLL). The nanocomposite was applied to a bare gold electrode surface by chemical adsorption, and BmoLL was subsequently electrostatically adsorbed to the nanocomposite-modified surface. Atomic force microscopy (AFM), cyclic voltammetry (CV) and electrochemical impedance (EI) techniques were applied to evaluate the immobilization of BmoLL on AuNpPANI. The AFM images for AuNpPANI-BmoLL-DEN systems indicate a homogenous, compact and dense film of the conjugate. In the EI analyses, an obvious difference of the electron transfer resistance between the AuNpPANI-modified electrode and the bare gold electrode was observed. Among three dengue serotypes studied, dengue serotype 2 (DEN2) has higher values for R(CT), and lower values for both n and Q. These are indications of a larger blocking effect and smaller capacitive dispersion, resulting from the higher agglutination of glycoproteins from the DEN2 sera. The selective BmoLL recognition for various dengue serotypes may be attributed to different patterns of glycoproteins in the sera produced by the glycoprotein immunoresponse from patients infected by the dengue virus.