Structural modelling of Eu3+-based siloxane-poly( oxyethylene) nanohybrids

The modelling of the local structure of sol-gel derived Eu3+-based organic/inorganic hybrids is reported, based on Small-Angle X-ray Scattering (SAXS), photoluminescence and mid-infrared spectroscopy. The hybrid matrix of these organically modified silicates, classed as di-ureasils and termed U(2000) and U(600), is formed by poly( oxyethylene) (POE) chains of variable length grafted to siloxane domains by means of urea cross-linkages. Europium triflate, Eu(CF3SO3)(3), was incorporated in the two di-ureasil matrices with compositions 400 greater than or equal ton greater than or equal to 10, n is the molar ratio of ether oxygens per Eu3+. The SAXS data for undoped hybrids (n=infinity) show the presence of a well-defined peak attributed to the existence of a liquid-like spatial correlation of siloxane rich domains embedded in the polymer matrix and located at the ends of the organic segments. The obtained siloxane particle gyration radius Rg(1) is around 5 Angstrom (error within 10%), whereas the interparticle distance d is 25 +/-2 Angstrom and 40 +/-2 Angstrom, for U(600) and U(2000), respectively. For the Eu3+-based nanocomposites the formation of a two-level hierarchical local structure is discerned. The primary level is constituted by strongly spatially correlated siloxane particles of gyration radius Rg(1) (4-6 and 3-8 Angstrom, errors within 5%, for U(600())n Eu(CF3SO3)(3), 200 greater than or equal ton greater than or equal to 40, and U(2000)(n)Eu(CF3SO3)(3), 400 greater than or equal ton greater than or equal to 40, respectively) forming large clusters of gyration radius Rg(2) (approximate to 75 +/- 10 Angstrom). The local coordination of Eu3+ in both di-ureasil series is described combining the SAXS, photoluminescence and mid-infrared results. In the di-ureasils containing long polymer chains, U(2000)(n)Eu(CF3SO3)(3), the cations interact exclusively with the carbonyl oxygens atoms of the urea bridges at the siloxane-POE interface. In the hybrids containing shorter chains, U(600)(n)Eu(CF3SO3)(3) with n ranging from 200 to 60, the Eu3+ ions interact solely with the ether-type oxygens of the polymer chains. Nevertheless, in this latter family of hybrids a distinct Eu3+ local site environment involving the urea cross-linkages is detected when the europium content is increased up to n=40.

Structural and functional characterization of myotoxin I, a Lys49 phospholipase A(2) homologue from Bothrops moojeni (Caissaca) snake venom

Myotoxin-I (MjTX-I) was purified to homogeneity from the venom of Bothrops moojeni by ion-exchange chromatography on CM-Sepharose. Its molecular weight, estimated by SDS-PAGE, was 13,400 (reduced) or 26,000 (unreduced). The extinction coefficient (E-1.0 cm(1.0 mg/ml)) of MjTX-I was 1.145 at lambda = 278 nm, pH 7.0, and its isoelectric point was 8.2 at ionic strength mu = 0.1. When lyophilized and stored at 4 degrees C, dimeric, trimeric, and pentameric forms of the protein were identified by SDS-PAGE. This heterogeneous sample could be separated into three fractions by gel filtration on Sephadex 6-50. The fractions were analyzed by isoelectric focusing, immunoelectrophoresis, and amino acid composition, which indicated that heterogeneity was the result of different levels of self-association. Protein sequencing indicated that MjTX-I is a Lys49 myotoxin and consists of 121 amino acids (M-r = 13,669), containing a high proportion of basic and hydrophobic residues. It shares a high degree of sequence identity with other Lys49 PLA(2)-like myotoxins, but shows a significantly lower identity with catalytically active Asp49 PLA(2)s. The three-dimensional structure of MjTX-I was modeled based on the crystal structures of three highly homologous Lys49 PLA(2)-like myotoxins. This model showed that the amino acid substitutions are conservative, and mainly the beta-wing region, and the C-terminal extended random coil. MjTX-I displays local myotoxic and edema-inducing activities in mice, and is lethal by intraperitoneal injection, with an LD50 value of 8.5 +/- 0.8 mg/kg, In addition, it is cytotoxic to myoblasts/ myotubes in culture, and disrupts negatively charged liposomes. In comparison with the freshly prepared dimeric sample, the more aggregated forms showed significantly reduced myotoxic activity. However, the edema-inducing activity of MjTX-I was independent of molecular association. Phospholipase A(2) activity on egg yolk, as well as anticoagulant activity, were undetectable both in the native and in the more associated forms. His, Tyr, and Trp residues of the toxin were chemically modified by specific reagents. Although the myotoxic and lethal activities of the modified toxins were reduced by these treatments, neither its edema-inducing or Liposome-disrupting activities were significantly altered. Rabbit antibodies to native MjTX-I cross-reacted with the chemically modified forms, and both the native and modified MjTX-I preparations were recognized by antibodies against the C-terminal region 115-129 of myotoxin II from B. asper, a highly Lys49 PLA(2)-homologue with high sequencial similarity. (C) 2000 Academic Press.

Density functional theory study on the structural and electronic properties of low index rutile surfaces for TiO2/SnO2/TiO2 and SnO2/TiO2/SnO2 composite systems

The present study is concerned with the structural and electronic properties of the TiO2/SnO2/TiO2 and SnO2/TiO2/SnO2 composite systems. Periodic quantum mechanical method with density functional theory at the B3LYP level has been carried out. Relaxed surface energies, structural characteristics and electronic properties of the (I 10), (0 10), (10 1) and (00) low-index rutile surfaces for TiO2/SnO2/TiO2 and SnO2/TiO2/SnO2 models are studied. For, comparison purposes, the bare rutile TiO2 and SnO2 structures are also analyzed and compared with previous theoretical and experimental data. The calculated surface energy for both rutile TiO2 and SnO2 surfaces follows the sequence (110) < (010) < (101) < (001) and the energy increases as (010) < (101) < (110) < (001) and (010) approximate to (110) < (101) < (001) for SnO2/TiO2/SnO2 and TiO2/SnO2/TiO2 composite systems, respectively. SnO2/TiO2/SnO2 presents larger values of surface energy than the individual SnO2 and TiO2 metal oxides and the TiO2/SnO2/TiO2 system renders surface energy values of the same order that the TiO2 and lower than the SnO2. An analysis of the electronic structure of the TiO2/SnO2/TiO2 and SnO2/TiO2/SnO2 systems shows that the main characteristics of the upper part of the valence bands for all the studied surfaces are dominated by the external layers, i.e., by the TiO2 and the SnO2, respectively, and the topology of the lower part of the conduction bands looks like the core layers. There is an energy stabilization of both valence band top and conduction band bottom for (110) and (010) surfaces of the SnO2/TiO2/SnO2 composite system in relation to their core TiO2, whereas an opposite trend is found for the same surfaces of the TiO2/SnO2/TiO2 composite system in relation to the bare SnO2. The present theoretical results may explain the growth of TiO2@SnO2 bimorph composite nanotape.

Functional and structural analysis of two fibrinogen-activating enzymes isolated from the venoms of Crotalus durissus terrificus and Crotalus durissus collilineatus

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

Functional and Structural Adaptations in the Pancreatic alpha-Cell and Changes in Glucagon Signaling During Protein Malnutrition

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

Density functional theory calculation of the electronic structure of Ba0.5Sr0.5TiO3: Photoluminescent properties and structural disorder

First-principles quantum-mechanical techniques, based on density functional theory (B3LYP level) were employed to study the electronic structure of ordered and deformed asymmetric models for Ba0.5Sr 0.5TiO3. Electronic properties are analyzed and the relevance of the present theoretical and experimental results on the photoluminescence behavior is discussed. The presence of localized electronic levels in the band gap, due to the symmetry break, would be responsible for the visible photoluminescence of the amorphous state at room temperature. Thin films were synthesized following a soft chemical processing. Their structure was confirmed by x-ray data and the corresponding photoluminescence properties measured.

Development of a thermoeconomic methodology for the optimization of biodiesel production - Part I: Biodiesel plant and thermoeconomic functional diagram

This work developed a methodology that uses the thermoeconomic functional diagram applied for allocating the cost of products produced by a biodiesel plant. The first part of this work discusses some definitions of exergy and thermoeconomy, with a detailed description of the biodiesel plant studied, identification of the system functions through Physical Diagram, calculation of the irreversibilities of the plant, construction of the Thermoeconomic Functional Diagram and determination of the expressions for the plant's exergetic functions. In order to calculate the exergetic increments and the physical exergy of certain flows in each step, the Chemical Engineering Simulation Software HYSYS 3.2 was used. The equipments that have the highest irreversibilities in the plant were identified after the exergy calculation. It was also found that the lowest irreversibility in the system refers to the process with a molar ratio of 6:1 and a reaction temperature of 60 °C in the transesterification process. In the second part of this work (Part II), it was calculated the thermoeconomic cost of producing biodiesel and related products, including the costs of carbon credits for the CO2 that is not released into the atmosphere, when a percentage of biodiesel is added to the petroleum diesel used by Brazil's internal diesel fleet (case study). © 2013 Elsevier Ltd. All rights reserved.

Analysing green supply chain management practices in Brazil's electrical/electronics industry using interpretive structural modelling

Industries need to adopt the environmental management concepts in the traditional supply chain management. The green supply chain management (GSCM) is an established concept to ensure environment-friendly activities in industry. This paper identifies the relationship of driving and dependence that exists between GSCM practices with regard to their adoption within Brazilian electrical/electronic industry with the help of interpretive structural modelling (ISM). From the results, we infer that cooperation with customers for eco-design practice is driving other practices, and this practice acts as a vital role among other practices. Commitment to GSCM from senior managers and cooperation with customers for cleaner production occupy the highest level. © 2013 Copyright Taylor and Francis Group, LLC.

Influence of ethanol and glycerol concentration over functional and structural properties of zein-oleic acid films

This study was performed in order to determine the effect of the addition of different concentrations of glycerol and ethanol over functional and structural properties of zein-oleic acid films. Films were prepared from zein and oleic acid formulations, containing: 0, 10, 20 and 30% (w/w) of glycerol as plasticizer and 75, 80, 85, 90 and 95% (v/v) of ethanol as zein solvent. Water vapor permeability (WVP) at 4 and 24 C, opacity, water solubility and structural behavior of the film were assessed. The film water barrier properties, WVP and water solubility, were increased when higher ethanol concentration and lower glycerol concentration were used. Furthermore, WVP at 4 C was lower than WVP at 24 C due to the crystalline solid state of oleic acid at lower temperatures. Likewise, opacity, homogeneity and structure of the composite film were improved as ethanol increased and glycerol lowered. © 2013 Elsevier B.V. All rights reserved.

Changes in plant species composition and functional traits along the successional trajectory of a restored patch of Atlantic Forest

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

Structural and functional characterization of the chaperone Hsp70 from sugarcane. Insights into conformational changes during cycling from cross-linking/mass spectrometry assays

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

Cerrado vegetation and global change: the role of functional types, resource availability and disturbance in regulating plant community responses to rising CO2 levels and climate warming

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Structural and functional characterization of barium zirconium titanate/epoxy composites

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

Structural and functional evidence for membrane docking and disruption sites on phospholipase A2-like proteins revealed by complexation with the inhibitor suramin

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