Structure of myotoxin II, a catalytically inactive Lys49 phospholipase A2 homologue from Atropoides nummifer venom

Lys49 snake-venom phospholipase A2 (PLA2) homologues are highly myotoxic proteins which, although lacking catalytic activity, possess the ability to disrupt biological membranes, inducing significant muscle-tissue loss and permanent disability in severely envenomed patients. Since the structural basis for their toxic activity is still only partially understood, the structure of myotoxin II, a monomeric Lys49 PLA2 homologue from Atropoides nummifer, has been determined at 2.08 Å resolution and the anion-binding site has been characterized. © 2006 International Union of Crystallography. All rights reserved.

Functional nanostructured catalysts based on the niobates to the dry methane reforming and ethylene homologation reactions

Catalytic activity and selectivity of niobate-based nanostructured materials were investigated. Dry methane reforming (DMR) and ethylene homologation reaction (EHR) were selected as test reactions. KSr 2Nb5O15, Sr2NaNb5O 15 and NaSr2(NiNb4)O15 δ niobate powders were prepared by the high energy ball milling method and calcined in a reductor atmosphere. N2 adsorption isotherms, X-ray diffraction and infrared spectroscopy characterization was performed. Hydrogen pretreated niobates showed from low to moderate catalytic initial activity in DMR's test, nevertheless the materials were deactivated rapidly and the kinetic parameters associated to deactivation were estimated. Otherwise, non-treated catalysts showed a high initial activity in EHR's test and KSr2Nb 5O15 catalyst requires 24 h to the total deactivation with a high selectivity to form propylene. A reaction mechanism to the propylene formation is discussed. © 2012 Elsevier Ltd. All rights reserved.

Production of xylo-oligosaccharides by immobilized-stabilized derivatives of endo-xylanase from Streptomyces halstedii

An endoxylanase from Streptomyces halstedii was stabilized by multipoint covalent immobilization on glyoxyl-agarose supports. The immobilized enzyme derivatives preserved 65% of the catalytic activity corresponding to the one of soluble enzyme that had been immobilized. These immobilized derivatives were 200 times more stable 200 times more stable than the one-point covalently immobilized derivative in experiments involving thermal inactivation at 60 °C. The activity and stability of the immobilized enzyme was higher at pH 5.0 than at pH 7.0. The optimal temperature for xylan hydrolysis was 10 °C higher for the stabilized derivative than for the non-stabilized derivative. On the other hand, the highest loading capacity of activated 10% agarose gels was 75 mg of enzyme per mL of support. To prevent diffusional limitations, low loaded derivatives (containing 0.2 mg of enzyme per mL of support) were used to study the hydrolysis of xylan at high concentration (close to 1% (w/v)). 80% of the reducing sugars were released after 3 h at 55 °C. After 80% of enzymatic hydrolysis, a mixture of small xylo-oligosaccharides was obtained (from xylobiose to xylohexose) with a high percentage of xylobiose and minimal amounts of xylose. The immobilized-stabilized derivatives were used for 10 reaction cycles with no loss of catalytic activity. © 2013 Elsevier Ltd. All rights reserved.

Biochemical, functional, structural and phylogenetic studies on Intercro, a new isoform phospholipase A2 from Crotalus durissus terrificus snake venom

Crotoxin is a neurotoxin from Crotalus durissus terrificus venom that shows immunomodulatory, anti-inflammatory, antimicrobial, antitumor and analgesic activities. Structurally, this toxin is a heterodimeric complex composed by a toxic basic PLA2 (Crotoxin B or CB) non-covalently linked to an atoxic non-enzymatic and acidic component (Crotapotin, Crotoxin A or CA). Several CA and CB isoforms have been isolated and characterized, showing that the crotoxin venom fraction is, in fact, a mixture of different molecules derived from the combination of distinct subunit isoforms. Intercro (IC) is a protein from the same snake venom which presents high similarity in primary structure to CB, indicating that it could be an another isoform of this toxin. In this work, we compare IC to the crotoxin complex (CA/CB) and/or CB in order to understand its functional aspects. The experiments with IC revealed that it is a new toxin with different biological activities from CB, keeping its catalytic activity but presenting low myotoxicity and absence of neurotoxic activity. The results also indicated that IC is structurally similar to CB isoforms, but probably it is not able to form a neurotoxic active complex with crotoxin A as observed for CB. Moreover, structural and phylogenetic data suggest that IC is a new toxin with possible toxic effects not related to the typical CB neurotoxin. © 2013.

Continuous production of xylooligosaccharides in a packed bed reactor with immobilized-stabilized biocatalysts of xylanase from Aspergillus versicolor

The production of xylooligosaccharides (XOS) using a packed-bed enzymatic reactor was studied at lab-scale. For this, a xylanase from Aspergillus versicolor was immobilized on different supports. The optimal derivative was xylanase immobilized on glyoxyl-agarose supports. This derivative preserved 85% of its catalytic activity; it was around 700-fold more stable than the soluble enzyme after incubation at 60. °C and was able to be reused for at least 10 1. h-cycles retaining full catalytic activity. About 18% of oligosaccharides with prebiotic interest (X2-X6) were produced by the glyoxyl derivative in batch hydrolysis. The production of xylobiose was 2.5-fold higher using the immobilized preparation than with soluble enzyme and small concentrations of xylose (<0.1%) were observed only at the end of the reaction. The derivative was employed on a packed bed reactor, and the continuous operation with no recirculation reached 56% and 70% of the end of reaction with flow rates of 60. mL/h and 12. mL/h, respectively. In continuous operation with recirculation at a flow rate of 60. mL/h, the reaction was completed after four hours. © 2013 Elsevier B.V.

Estudos estruturais com fosfolipases A2 e fosfolipases A2 homólogas isoladas no veneno de Bothrops moojeni

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Peptídeos derivados da proteína bacteriana YacG : síntese e estudos de estrutura-função

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Síntese e caracterização de nanocatalisadores 'PtV'/C e 'PtCr'/C para cátodos de células a combustível de baixa temperatura

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Novas estratégias no estudo da eletro-oxidação de etanol: nanocatalisadores multimetálisos e análises dos produtos de reação

Pós-graduação em Química - IQ

Catalisadores 'PT' e 'PTSN' modificados com 'SN''O IND.2' para a oxidação eletroquímica de etanol

Pós-graduação em Química - IQ

Estudos estruturais e filogenéticos com fosfolipases e serino proteases de venenos de serpentes botrópicas nativas e quimicamente modificadas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Sínteses e caracterização de novos catalisadores zeolíticos e sua como suportes inorgânicos para imobilização de lipase produzida por Rhizomucor miehei e seu estudo catalítico na reação de transesterificação do óleo de soja para produção de biodiesel

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

Técnicas de reciclo de protease visando a desfloculação celular de Saccharomyces cerevisiae

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo da ação do extrato bruto de Morus nigra L. (Moreaceae) e frações fenólicas sobre a atividade antimicrobiana e geração de espécies reativas do oxigênio e nitrogênio: in vitro com ensaios químicos, enzumáticos e celular

Pós-graduação em Biociências e Biotecnologia Aplicadas à Farmácia - FCFAR

Espumas cerâmicas produzidas pela conjugação dos processos sol-gel, aeração e emulsificação

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)