Structural and Biochemical Characterization of Peroxiredoxin Q beta from Xylella fastidiosa CATALYTIC MECHANISM and HIGH REACTIVITY

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

The co-catalytic effect of chlorpromazine on peroxidase-mediated oxidation of melatonin: enhanced production of N-1-acetyl-N (2)-formyl-5-methoxykynuramine

Accumulating evidence points to relationships between increased production of reactive oxygen or decreased antioxidant protection in schizophrenic patients. Chlorpromazine (CPZ), which remains a benchmark treatment for people with schizophrenia, has been described as a pro-oxidant compound. Because the antioxidant compound melatonin exerts protective effects against CPZ-induced liver disease in rats, in this investigation, our main objective was to study the effect of CPZ as a co-catalyst of peroxidase-mediated oxidation of melatonin. We found that melatonin was an excellent reductor agent of preformed CPZ cation radical (CPZ(center dot+)). The addition of CPZ during the horseradish peroxidase (HRP)-catalyzed oxidation of melatonin provoked a significant increase in the rate of oxidation and production of N-1-acetyl-N-2-formyl-5-methoxykynuramine (AFMK). Similar results were obtained using myeloperoxidase. The effect of CPZ on melatonin oxidation was rather higher at alkaline pH. At pH 9.0, the efficiency of oxidation of melatonin was 15 times higher and the production of AFMK was 30 times higher as compared with the assays in the absence of CPZ. We suggest that CPZ is able to exacerbate the rate of oxidation of melatonin by an electron transfer mechanism where CPZ(center dot+), generated during the peroxidase-catalyzed oxidation, is able to efficiently oxidize melatonin.

Electrochemical characterization of the paste carbon modified electrode with KSr2Ni0.75Nb4.25O15-delta solid in catalytic oxidation of the dipyrone

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

Are light traps baited with kairomones effective in the capture of Lutzomyia longipalpis and Lutzomyia intermedia? An evaluation of synthetic human odor as an attractant for phlebotomine sand flies (Diptera: Psychodidae: Phlebotominae)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

A new oxovanadium(IV)-cucurbit[6]uril complex: Properties and potential for confined heterogeneous catalytic oxidation reactions

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

New geopolymeric binder based on fluid catalytic cracking catalyst residue (FCC)

This paper provides information about the synthesis and mechanical properties of geopolymers based on fluid catalytic cracking catalyst residue (FCC). FCC was alkali activated with solutions containing different SiO2/Na2O ratios. The microstructure and mechanical properties were analysed by using several instrumental techniques. FCC geopolymers are mechanically stable, yielding compressive strength about 68 MPa when mortars are cured at 65 degrees C during 3 days. The results confirm the viability of producing geopolymers based on FCC. (C) 2012 Elsevier B.V. All rights reserved.

Carbon-coated SnO2 nanobelts and nanoparticles by single catalytic step

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Influence of carrion smell and rebaiting time on the efficiency of pitfall traps to dung beetle sampling

Dung beetles (Coleoptera: Scarabaeidae: Scarabaeinae) are very useful insects, as they improve the chemo-physical properties of soil, clean pastures from dung pads, and help control symbovine flies associated with bovine cattle. Their importance makes it fundamental to sample and survey them adequately. The objectives of the present study were to determine the influence of decaying insects trapped in pitfalls on the attractiveness of Moura pig Sus scrofa L. (Suidae) and collared peccary Tayassu tajacu (L.) (Tayassuidae) dung used as baits to lure dung beetles, and to establish how long these baits remain attractive to dung beetles when used in these traps. Some dung beetle species seemed to be able to discriminate against foul smell from decaying insects within the first 24 h, hence decreasing trap efficiency. This was more evident in peccary dung-baited traps, which proved to be the least attractive bait. Attractiveness lasted only 24 h for peccary dung, after which it became unattractive, whereas the pig dung bait was highly attractive for 48 h, after which its attractiveness diminished but was not completely lost.

Preliminary X-ray crystallographic studies of BthTX-II, a myotoxic Asp49-phospholipase A(2) with low catalytic activity from Bothrops jararacussu venom

For the first time, a complete X-ray diffraction data set has been collected from a myotoxic Asp49-phospholipase A(2) (Asp49-PLA(2)) with low catalytic activity (BthTX-II from Bothrops jararacussu venom) and a molecular-replacement solution has been obtained with a dimer in the asymmetric unit. The quaternary structure of BthTX-II resembles the myotoxin Asp49-PLA(2) PrTX-III (piratoxin III from B. pirajai venom) and all non-catalytic and myotoxic dimeric Lys49-PLA(2)s. In contrast, the oligomeric structure of BthTX-II is different from the highly catalytic and non-myotoxic BthA-I (acidic PLA(2) from B. jararacussu). Thus, comparison between these structures should add insight into the catalytic and myotoxic activities of bothropic PLA(2)s.

Crystal structure of a myotoxic Asp49-phospholipase A(2) with low catalytic activity: Insights into Ca2+ -independent catalytic mechanism

A myotoxic Asp49-phospholipase A(2) (Asp49-PLA(2)) with low catalytic activity (BthTX-II from Bothrops jararacussu venom) was crystallized and the molecular-replacement solution has been obtained with a dimer in the asymmetric unit. The quaternary structure of BthTX-II resembles the myotoxic Asp49-PLA2 PrTX-III (piratoxin III from B. pirajai venom) and all non-catalytic and myotoxic dimeric Lys49-PLA(2)s. Despite of this, BthTX-II is different from the highly catalytic and non-myotoxic BthA-I (acidic PLA(2) from B. jararacussu) and other Asp49-PLA(2)s. BthTX-II structure showed a severe distortion of calcium-binding loop leading to displacement of the C-terminal region. Tyr28 side chain, present in this region, is in an opposite position in relation to the same residue in the catalytic activity Asp49-PLA(2)s, making a hydrogen bond with the atom 0 delta 2 of the catalytically active Asp49, which should coordinate the calcium. This high distortion may also be confirmed by the inability of BthTX-II to bind Na+ ions at the Ca2+-binding loop, despite of the crystallization to have occurred in the presence of this ion. In contrast, other Asp49-PLA(2)s which are able to bind Ca2+ ions are also able to bind Na+ ions at this loop. The comparison with other catalytic, non-catalytic and inhibited PLA(2)s indicates that the BthTX-II is not able to bind calcium ions; consequently, we suggest that its low catalytic function is based on an alternative way compared with other PLA(2)s. (c) 2008 Elsevier B.V All rights reserved.

The Intriguing Phospholipases A(2) Homologues: Relevant Structural Features on Myotoxicity and Catalytic Inactivity

Phospholipases A(2) homologues are found in the venom of Crotalinae snakes, being their main action related to myonecrosis induction. Although many studies on these toxins had already been performed, their mechanism of action remains unclear. Here, important aspects about these toxins are reviewed, including their correct biological assembly and how essential is the natural substitution D49K for their catalytic inactivity.

V(2)O(5)/TiO(2) catalytic xerogels raman and EPR studies

Raman spectroscopy and Electron Paramagnetic Resonance (EPR) studies were performed on a series of V(2)O(5)/TiO(2) catalysts prepared by a modified sol-gel method in order to identify the vanadium species. Two species of surface vanadium were identified by Raman measurements, monomeric vanadyls and polymeric vanadates. Monomeric vanadyls are characterized by a narrow Raman band at 1030 cm(-1) and polymeric vanadates by two broad bands in the region from 900 to 960 cm(-1) and 770 to 850 cm(-1). The Raman spectra do not exhibit characteristic peaks of crystalline V(2)O(5). These results are in agreement with those of X-ray Diffractometry (XRD) and Fourier Transform Infrared (FT-IR) previously reported (C.B. Rodella et al., J. Sol-Gel Sci. Techn., submitted). At least three families of V(4+) ions were identified by EPR investigations. The analysis of the EPR spectra suggests that isolated V(4+) ions are located in sites with octahedral symmetry substituting for Ti(4+) ions in the rutile structure. Magnetically interacting V(4+) ions are also present as pairs or clusters giving rise to a broad and structureless EPR line. At higher concentration of V(2)O(5), a partial oxidation of V(4+) to V(5+) is apparent from the EPR results.

Surface characterisation of V(2)O(5)/TiO(2) catalytic system

Samples of the V(2)O(5)/TiO(2) system were prepared by the sol-gel method and calcined at different temperatures. Surface species of vanadium, their dispersion, as well as the structural evolution of the system were analysed by XRD, Raman, EPR, and XPS techniques. The results of XRD showed the evolution of TiO(2) from anatase phase to rutile. phase. The Raman spectra for calcination temperatures up to 500 degreesC showed a good dispersion of vanadium over titania in the form of monomeric vanadyl groups (V(4+)) and polymeric vanadates (V(5+)). At least three families of V4+ ions were identified by EPR investigations. Two kinds of isolated V(4+) species are placed in sites of octahedral symmetry, substituting Ti(4+) in the rutile phase. The third is formed by pairs of V(4+) species on the surface of titania. Above 500 degreesC part of superficial V(4+) is inserted into the,matrix of titania and part is oxidized to V(5+). The XPS results showed that the V/Ti ratio rises with increasing calcination temperature, indicating a smaller dispersion of vanadium.

New catalytic mechanism for human purine nucleoside phosphorylase

Human purine nucleoside phosphorylase has been submitted to intensive structure-based design of inhibitors, most of them using low-resolution structures of human PNP. Recently, several structures of human PNP have been reported, which allowed redefinition of the active site and understanding of the structural basis for inhibition of PNP by acyclovir and immucillin-H. Based on previously solved human PNP structures, we proposed here a new catalytic mechanism for human PNP, which is supported by crystallographic studies and explains previously determined kinetic data. (C) 2004 Elsevier B.V. All rights reserved.