A structure based model for liposome disruption and the role of catalytic activity in myotoxic phospholipase A(2)S

Venom phospholipase A(2)s (PLA(2)s) display a wide spectrum of pharmacological activities and, based on the wealth of biochemical and structural data currently available for PLA(2)S, mechanistic models can now be inferred to account for some of these activities. A structural model is presented for the role played by the distribution of surface electrostatic potential in the ability of myotoxic D49/K49 PLA(2)s to disrupt multilamellar vesicles containing negatively charged natural and non-hydrolyzable phospholipids. Structural evidence is provided for the ability of K49 PLA(2)s to bind phospholipid analogues and for the existence of catalytic activity in K49 PLA(2)s. The importance of the existence of catalytic activity of D49 and K49 PLA(2)s in myotoxicity is presented. (C) 2003 Elsevier Ltd. All rights reserved.

(5,10,15,20-Tetra(4-pyridil)porphinato)manganes(III) acetate modified by four mu(3)-oxo-triruthenium acetate clusters: synthesis, characterization, electrochemical behavior and catalytic activity

A novel supermolecule constituted by four mu(3)-oxo-triruthenium acetate clusters coordinated to manganese(III)-meso -tetra(4-pyridil)porphyrin acetate ([MnTPyP]CH3COO) has been synthesized. Characterization has been performed by UV-Vis and H-1 NMR spectroscopy. The electrochemical behavior (cyclic voltammetry and spectroelectrochemistry) in N,N'-dimethylformamide has been analyzed in terms of five redox processes: three related to peripheral clusters (Ru-IV,Ru-III,Ru-III/Ru-III,Ru-III,Ru-III/Ru-III,Ru-II,Ru-II) and two centered on the Mn-porphyrin core ((MnP)-P-III/(MnP)-P-II/(MnP2-)-P-II). A direct comparison has been performed between MnTCP and MnTPyP as catalysts for the cyclooctene and cyclohexane oxidation reactions. The improved selectivity exhibited by the supramolecular catalyst for cyclohexane oxidation has been ascribed to electronic effects on the oxomanganese(V) porphyrin species induced by the four peripheral clusters, in the formal (RuRuRuIII)-Ru-IV-Ru-III oxidation state. (C) 2000 Elsevier B.V. S.A. All rights reserved.

Growth of SnO nanobelts and dendrites by a self-catalytic VLS process

This article reports on the growth of SnO nanobelts and dendrites by a carbothermal reduction process. The materials were synthesized in a sealed tube furnace at 1210 degrees C and at 1260 degrees C for 2 h. in a dynamic nitrogen atmosphere of 40 seem. After synthesis, gray-black materials were collected downstream in the tube and the samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDX). The results showed that the gray-black materials were composed of nanobelts, which grew in the [110] direction of the orthorhombic structure of SnO. Some of the belts also presented dendritic growth. The dendrites grew in the (110) planes of the SnO structure, and no defects were observed at the junction between the nanobelts and the dendrites. A self-catalytic vapor-liquid-solid (VLS) process was proposed to explain the growth of the SnO nanobelts and dendrites.

Structure and catalytic mechanism of glucosamine 6-phosphate deaminase from Escherichia coli at 2.1 Å resolution

Background: Glucosamine 6-phosphate deaminase from Escherichia coli is an allosteric hexameric enzyme which catalyzes the reversible conversion of D-glucosamine 6-phosphate into D-fructose 6-phosphate and ammonium ion and is activated by N-acetyl-D-glucosamine 6-phosphate. Mechanistically, it belongs to the group of aldose-ketose isomerases, but its reaction also accomplishes a simultaneous amination/deamination. The determination of the structure of this protein provides fundamental knowledge for understanding its mode of action and the nature of allosteric conformational changes that regulate its function. Results: The crystal structure of glucosamine 6-phosphate deaminase with bound phosphate ions is presented at 2.1 Å resolution together with the refined structures of the enzyme in complexes with its allosteric activator and with a competitive inhibitor. The protein fold can be described as a modified NAD-binding domain. Conclusions: From the similarities between the three presented structures, it is concluded that these represent the enzymatically active R state conformer. A mechanism for the deaminase reaction is proposed. It comprises steps to open the pyranose ring of the substrate and a sequence of general base-catalyzed reactions to bring about isomerization and deamination, with Asp72 playing a key role as a proton exchanger.

Study of utilization of petrol engine equipped with exhaust gas recirculation (EGR) and catalytic converter to reduce consumption and NOx emission

Study of consumption rate and gaseous pollutant emission from engine tests simulating real work conditions, using spark point manually controlled and exhaust gas recirculation (EGR) in diverse proportion levels. The objective of this work is to re-examine the potential of the EGR conception, a well-known method of combustion control, employed together electronic fuel injection and three-way catalytic converter closed-loop control at a spark ignition engine, verifying the performance characteristics and technical availability of this conception to improve pollution control, fuel economy at low torque drive condition and to improve the engine exhaust components useful life. The pollutant emissions and consumption levels under operational conditions simulations were analysed and compared with the expected by concerning theory and real tests performed by EGR equipped engines by factory. Copyright © 2006 Society of Automotive Engineers, Inc.

Structure of a novel class II phospholipase D: Catalytic cleft is modified by a disulphide bridge

Phospholipases D (PLDs) are principally responsible for the local and systemic effects of Loxosceles envenomation including dermonecrosis and hemolysis. Despite their clinical relevance in loxoscelism, to date, only the SMase I from Loxosceles laeta, a class I member, has been structurally characterized. The crystal structure of a class II member from Loxosceles intermedia venom has been determined at 1.7. Å resolution. Structural comparison to the class I member showed that the presence of an additional disulphide bridge which links the catalytic loop to the flexible loop significantly changes the volume and shape of the catalytic cleft. An examination of the crystal structures of PLD homologues in the presence of low molecular weight compounds at their active sites suggests the existence of a ligand-dependent rotamer conformation of the highly conserved residue Trp230 (equivalent to Trp192 in the glycerophosphodiester phosphodiesterase from Thermus thermophofilus, PDB code: 1VD6) indicating its role in substrate binding in both enzymes. Sequence and structural analyses suggest that the reduced sphingomyelinase activity observed in some class IIb PLDs is probably due to point mutations which lead to a different substrate preference. © 2011 Elsevier Inc.

Crystal structure of Jararacussin-I: The highly negatively charged catalytic interface contributes to macromolecular selectivity in snake venom thrombin-like enzymes

Snake venom serine proteinases (SVSPs) are hemostatically active toxins that perturb the maintenance and regulation of both the blood coagulation cascade and fibrinolytic feedback system at specific points, and hence, are widely used as tools in pharmacological and clinical diagnosis. The crystal structure of a thrombin-like enzyme (TLE) from Bothrops jararacussu venom (Jararacussin-I) was determined at 2.48 Å resolution. This is the first crystal structure of a TLE and allows structural comparisons with both the Agkistrodon contortrix contortrix Protein C Activator and the Trimeresurus stejnegeri plasminogen activator. Despite the highly conserved overall fold, significant differences in the amino acid compositions and three-dimensional conformations of the loops surrounding the active site significantly alter the molecular topography and charge distribution profile of the catalytic interface. In contrast to other SVSPs, the catalytic interface of Jararacussin-I is highly negatively charged, which contributes to its unique macromolecular selectivity. © 2012 The Protein Society.

Alkali activated materials based on fluid catalytic cracking catalyst residue (FCC): Influence of SiO2/Na2O and H 2O/FCC ratio on mechanical strength and microstructure

Reuse of industrial and agricultural wastes as supplementary cementitious materials (SCMs) in concrete and mortar productions contribute to sustainable development. In this context, fluid catalytic cracking catalyst residue (spent FCC), a byproduct from the petroleum industry and petrol refineries, have been studied as SCM in blended Portland cement in the last years. Nevertheless, another environmental friendly alternative has been conducted in order to produce alternative binders with low CO2 emissions. The use of aluminosilicate materials in the production of alkali-activated materials (AAMs) is an ongoing research topic which can present low CO2 emissions associated. Hence, this paper studies some variables that can influence the production of AAM based on spent FCC. Specifically, the influence of SiO 2/Na2O molar ratio and the H2O/spent FCC mass ratio on the mechanical strength and microstructure are assessed. Some instrumental techniques, such as SEM, XRD, pH and electrical conductivity measurements, and MIP are performed in order to assess the microstructure of formed alkali-activated binder. Alkali activated mortars with compressive strength up to 80 MPa can be formed after curing for 3 days at 65°C. The research demonstrates the potential of spent FCC to produce alkali-activated cements and the importance of SiO2/Na2O molar ratio and the H2O/spent FCC mass ratio in optimising properties and microstructure. © 2013 Elsevier Ltd. All rights reserved.

Electrochemical behavior of ruthenium-hexacyanoferrate modified glassy carbon electrode and catalytic activity towards ethanol electrooxidation

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Microwave hydrothermal synthesis, characterisation, and catalytic performance of Zn1-xMnxO in cellulose conversion

Wurtzite-type Zn1-xMnxO (x = 0, 0.03, 0.05, 0.07) nanostructures were successfully synthesised using a simple microwave-assisted hydrothermal route and their catalytic properties were investigated in the cellulose conversion. The morphology of the nanocatalysts is dopant-dependent. Pure ZnO presented multi-plate morphology with a flower-like shape of nanometric sizes, while the Zn0.97Mn0.03O sample is formed by nanoplates with the presence of spherical nanoparticles; the Zn0.95Mn0.05O and Zn0.93Mn0.07O samples are mainly formed by nanorods with the presence of a small quantity of spherical nanoparticles. The catalyst without Mn did not show any catalytic activity in the cellulose conversion. The Mn doping promoted an increase in the density of weak acid sites which, according to the catalytic results, favoured promotion of the reaction. © 2013 Institute of Chemistry, Slovak Academy of Sciences.

Effect of the balance between Co(II) and Co(0) oxidation states on the catalytic activity of cobalt catalysts for Ethanol Steam Reforming

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Easily handling penicillin G acylase magnetic cross-linked enzymes aggregates: Catalytic and morphological studies

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

The Identification and Biochemical Properties of the Catalytic Specificity of a Serine Peptidase Secreted by Aspergillus fumigatus Fresenius

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

Structural bases for a complete myotoxic mechanism: Crystal structures of two non-catalytic phospholipases A(2)-like from Bothrops brazili venom

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

Understanding the Function of Conserved Variations in the Catalytic Loops of Fungal Glycoside Hydrolase Family 12

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)