Improvement in the synthesis of (Z)-organylthioenynes via hydrothiolation of buta-1,3-diynes: a comparative study using NaOH or TBAOH as base

Hydrothiolation of symmetrical and unsymmetrical buta-1,3-diynes with sodium organylthiolate anions in reflux, generated in situ by reacting C₄H₉SH with NaOH, afforded (Z)-organylthioenynes in low to good yields (25-80%). By using tetrabutylammonium hydroxide (TBAOH) as base instead of NaOH, the hydrothiolation of buta-1,3-diynes was more rapid and efficient, providing (Z)-organylthioenynes in good to excellent yields (70-95%).     

Purification and Characterization of a Mannose Recognition Lectin from <Emphasis Type="Italic">Oreochromis niloticus</Emphasis> (Tilapia Fish): Cytokine Production in Mice Splenocytes

The aim of this work was to purify and partially characterize a mannose recognition lectin from Nile tilapia (Oreochromis niloticus) serum, named OniL. OniL was isolated through precipitation with ammonium sulfate and affinity chromatography (Concanavalin A–Sepharose 4B). In addition, we evaluated carbohydrate specificity, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS–PAGE) profiles, and in vitro immunomodulatory activity on mice splenocyte experimental cultures through cytotoxic assays and cytokine production. The ammonium sulfate fraction F2 showed the highest specific hemagglutinating activity (331) and was applied to affinity matrix. Adsorbed proteins (OniL) were eluted with methyl-α-d-mannopyranoside. OniL, a 17-kDa protein by SDS–PAGE constituted by subunits of 11 and 6.6 kDa, showed highest affinity for methyl-α-d-mannopyranoside and d-mannose. Immunological assays, in vitro, showed that OniL did not show cytotoxicity against splenocytes, induced higher IFN-γ production and lower IL-10 as well as nitrite release. In conclusion, OniL lectin was successfully purified and showed a preferential Th1 response in mice splenocytes.     

Vinyl acetate polymerization by ionizing radiation

For this work an irradiation system to be used in the polymerization of the vinyl acetate in methylethylketone and in ethyl alcohol solution using the gamma radiation as initiator was projected and built. The molecular weights of the polymers obtained by irradiation with gamma rays in methylethylketone and in ethyl alcohol solution were 33,000 and 44,000 g/mol, respectively. From the characterization by infrared spectroscopy it was possible to verify that the polymers obtained in two studied cases actually correspond to poly(vinyl acetate).     

Basin of attraction of a cusp–fold singularity in 3D piecewise smooth vector fields

Generic one-parameter families of piecewise smooth vector fields on R³${\mathbb{R}}^3$ presenting the so-called cusp–fold singularity are studied. The bifurcation diagrams are exhibited and the asymptotic and structural stabilities are discussed.     

New mixed integer-programming model for the pickup-and-delivery problem with transshipment

In recent years, many important real-world applications are studied as “rich” vehicle routing problems that are variants and generalizations of the well-known vehicle routing problem. In this paper we address the pickup-and-delivery version of this problem and consider further generalization by allowing transshipment in the network. Moreover, we allow heterogenous vehicles and flexible fleet size. We describe mixed integer-programming formulations for the problem with and without time windows for services. The number of constraints and variables in the models are bounded by polynomial size of the problem. We discuss several problem variants that are either captured by our models or can be easily captured through simple modifications. Computational work gave promising results and confirms that transshipment in network can indeed enhance optimization.     

Spectroscopic investigations and computational study of sulfur trioxide–pyridine complex

The Fourier transform infrared (FT‐IR) and FT‐Raman spectra of sulfur trioxide‐pyridine complex were recorded and analyzed. The potential‐dependent surface‐enhanced Raman scattering (SERS) was recorded from an electrochemically roughened silver electrode. The vibrational wave numbers of the compound were computed using the Hartree–Fock/6‐31G* basis and compared with the experimental values. The presence of strong pyridine ring vibrations in the SERS spectrum reveals the interaction between the pyridine ring and the silver surface. The molecule is adsorbed on the silver surface with the pyridine ring in a tilted orientation. The direction of charge‐transfer contribution to the SERS is discussed from the frontier orbital theory. The value of the calculated first hyperpolarizability is comparable to those reported for similar structures, which makes this molecule an attractive object for future studies of nonlinear optics. The optimized geometrical parameters of the title compound are in agreement with similar reported structures. Copyright © 2011 John Wiley & Sons, Ltd.     

Role of the variable active site residues in the function of thioredoxin family oxidoreductases

The enzymes of the thioredoxin family fulfill a wide range of physiological functions. Although they possess a similar CXYC active site motif, with identical environment and stereochemical properties, the redox potential and pK(a) of the cysteine pair varies widely across the family. As a consequence, each family member promotes oxidation or reduction reactions, or even isomerization reactions. The analysis of the three-dimensional structures gives no clues to identify the molecular source for the different active site properties. Therefore, we carried out a set of quantum mechanical calculations in active site models to gain more understanding on the elusive molecular-level origin of the differentiation of the properties across the family. The obtained results, together with earlier quantum mechanical calculations performed in our laboratories, gave rise to a consistent line of evidence, which points to the fact that both active site cysteines play an important role in the differentiation. In contrary to what was assumed, differentiation is not achieved through a different stabilization of the solvent exposed cysteine but, instead, through a fine tuning of the nucleophilicity of both active site cysteines. Reductant enzymes have both cysteine thiolates poorly stabilized, oxidant proteins have both cysteine thiolates highly stabilized, and isomerases have one thiolate (solvent exposed) poorly stabilized and the other (buried) thiolate highly stabilized. The feasibility of shifting the chemical equilibrium toward oxidation, reduction, or isomerization only through subtle electrostatic effects is quite unusual, and it relies on the inherent thermoneutrality of the catalytic steps carried out by a set of chemically equivalent entities all of which are cysteine thiolates. Such pattern of stabilization/destabilization, detected in our calculations is fully consistent with the observed physiological roles of this family of enzymes.     

Investigation of whole blood of SJL/J mice using neutron activation analysis

The Br (0.0022 ± 0.0006 gL⁻¹), Ca (0.113 ± 0.012 gL⁻¹), Cl (3.07 ± 0.36 gL⁻¹), K (2.63 ± 0.14 gL⁻¹), Mg (0.045 ± 0.002 gL⁻¹) and Na (2.09 ± 0.10 gL⁻¹) concentrations were determined in whole blood of SJL/J mice using the Neutron Activation Analysis (NAA) technique. Eleven whole blood samples were analyzed in the IEA-R1 nuclear reactor at IPEN (S?o Paulo, Brazil). These data contribute for applications in veterinary medicine related to biochemistry analyses using whole blood. Moreover, the correlation with human blood estimation allows to checking the similarities for studying muscular dystrophy using this model animal.     

Microstructure development in mixes of calcium aluminate cement with silica fume or fly ash

The most widely identified degradation process suffered by calcium aluminate cement (CAC) is the so-called conversion of hexagonal calcium aluminate hydrate to cubic form. This conversion is usually followed by an increase in porosity determined by the different densities of these hydrates and the subsequent loss of strength. Mixes of calcium aluminate cement (CAC) and silica fume (SF) or fly ash (FA) represent an interesting alternative for the stabilization of CAC hydrates, which might be attributed to a microstructure based mainly on aluminosilicates. This paper deals with the microstructure of cement pastes fabricated with mixtures CAC-SF and CAC-FA and its evolution over time. Thermal analysis (DTA/TG), X-ray diffraction (XRD) and mid-infrared spectroscopy (FTIR) have been used to assess the microstructure of these formulations.