An Arabidopsis Mitochondrial Uncoupling Protein Confers Tolerance to Drought and Salt Stress in Transgenic Tobacco Plants

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Dynamics of glyphosate-induced conformational changes of Mycobacterium tuberculosis 5-enolpyruvylshikimate-3-phosphate synthase (EC 2.5.1.19) determined by hydrogen-deuterium exchange and electrospray mass spectrometry

The enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) catalyzes the reaction between shikimate 3-phosphate and phosphoenolpyruvate to form 5-enolpyruvylshikimate 3-phosphate, an intermediate in the shikimate pathway, which leads to the biosynthesis of aromatic amino acids. EPSPS exists in an open conformation in the absence of substrates and/or inhibitors and in a closed conformation when bound to the substrate and/or inhibitor. In the present report, the H/D exchange properties of EPSPS from Mycobacterium tuberculosis (Mt) were investigated for both enzyme conformations using ESI mass spectrometry and circular dichroism (CD). When the conformational changes identified by H/D exchanges were mapped on the 3-D structure, it was observed that the apoenzyme underwent extensive conformational changes due to glyphosate complexation, characterized by an increase in the content of alpha-helices from 40% to 57%, while the beta-sheet content decreased from 30% to 23%. These results indicate that the enzyme underwent a series of rearrangements of its secondary structure that were accompanied by a large decrease in solvent access to many different regions of the protein. This was attributed to the compaction of 71% of alpha-helices and 57% of beta-sheets as a consequence of glyphosate binding to the enzyme. Apparently, MtEPSPS undergoes a series of inhibitor-induced conformational changes, which seem to have caused synergistic effects in preventing solvent access to the core of molecule, especially in the cleft region. This may be part of the mechanism of inhibition of the enzyme, which is required to prevent the hydration of the substrate binding site and also to induce the cleft closure to avoid entrance of the substrates.

Shikimate Kinase (EC 2.7.1.71) from Mycobacterium tuberculosis: Kinetics and Structural Dynamics of a Potential Molecular Target for Drug Development

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

Hydrogen/deuterium exchange mass spectrometry for characterizing phosphoenolpyruvate-induced structural transitions in Mycobacterium tuberculosis 5-enolpyruvylshikimate-3-phosphate synthase (EC 2.5.1.1)

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

Phosphate closes the solution structure of the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) from Mycobacterium tuberculosis

The 5-enolpyruvylshikimate-3-phosphate synthase catalyses the sixth step of the shikimate pathway that is responsible for synthesizing aromatic compounds and is absent in mammals, which makes it a potential target for drugs development against microbial diseases. Here, we report the phosphate binding effects at the structure of the 5-enolpyruvyl shikimate-3-phosphate synthase from Mycobacterium tuberculosis. This enzyme is formed by two similar domains that close on each other induced by ligand binding, showing the occurrence of a large conformation change. We have monitored the phosphate binding effects using analytical ultracentrifugation, small angle X-ray scattering and, circular dichroism techniques. The low resolution results showed that the enzyme in the presence of phosphate clearly presented a more compact structure. Thermal-induced unfolding experiments followed by circular dichroism suggested that phosphate rigidified the enzyme. Summarizing, these data suggested that the phosphate itself is able to induce conformational change resulting in the closure movement in the M. tuberculosis 5-enolpyruvylshikimate-3-phosphate synthase. (c) 2006 Elsevier B.V. All rights reserved.

The Influence of Solutes on the Enthalpy/Entropy Change of the Actinomycin D Binding to DNA: Hydration, Energy Compensation and Long-Range Deformation on DNA

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Femur bone repair in ovariectomized rats under the local action of alendronate, hydroxyapatite and the association of alendronate and hydroxyapatite

P>An evaluation was made of the local action of alendronate sodium (A), hydroxyapatite (HA) and the association of both substances (A + HA), in different molar concentrations, on the femur bone repair of ovariectomized rats. Ninety-eight animals were divided into seven groups: control (C), starch (S), alendronate 1 mol (A1), alendronate 2 mols (A2), hydroxyapatite 1 mol (HA1), hydroxyapatite 2 mols (HA2) and the association of alendronate + hydroxyapatite (A + HA). Rats weighing about 250 g were ovariectomized and 2.5-mm diameter bone defects were made on the left femur 30 days later. Each experimental group had defects filled with appropriate material, except for group C (control). The animals were killed 7 and 21 days after surgery. Histological, histomorphometric and statistical analyses of bone neoformation in the bone defect site were performed. From the histological standpoint, the major differences occurred after 21 days. All specimens in groups C, S, HA1 and HA2 presented linear closure of the bone defect, and most animals in groups A1, A2 and A + HA showed no bone neoformation in the central area of the defect. No statistically significant difference was found among the experimental groups after 7 days; after 21 days, group HA2 presented the highest amount of neoformed bone. There was no significant difference among groups A1, A2 and A + HA in the two study periods. It was concluded that alendronate, either isolated or in association with hydroxyapatite, had an adverse effect on bone repair in this experimental model. Moreover, the hydroxyapatite used here proved to be biocompatible and osteoconductive, with group HA2 showing the best results.

Fresnel analysis of wave propagation in nonlinear electrodynamics

We study wave propagation in local nonlinear electrodynamical models. Particular attention is paid to the derivation and the analysis of the Fresnel equation for the wave covectors. For the class of local nonlinear Lagrangian nondispersive models, we demonstrate how the originally quartic Fresnel equation factorizes, yielding the generic birefringence effect. We show that the closure of the effective constitutive (or jump) tensor is necessary and sufficient for the absence of birefringence, i.e., for the existence of a unique light cone structure. As another application of the Fresnel approach, we analyze the light propagation in a moving isotropic nonlinear medium. The corresponding effective constitutive tensor contains nontrivial skewon and axion pieces. For nonmagnetic matter, we find that birefringence is induced by the nonlinearity, and derive the corresponding optical metrics.

Compacidade do suporte cerâmico cru versus propriedades do revestimento cerâmico cozido

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

Photosynthetic response of soybean to twospotted spider mite (Acari: Tetranychydae) injury

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Variação da estrutura carpelar em seis espécies de Cassiinae (Leguminosae: Caesalpinioideae)

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

Fechamento epifisário da extremidade distal do rádio de eqüinos da raça Brasileira de Hipismo (BH)

Com o objetivo de avaliar a idade de fechamento epifisário da raça Brasileira de Hipismo (BH), um grupo de 24 cavalos, 12 machos inteiros e 12 fêmeas, teve a região epifisária da extremidade distal do rádio radiografada, mês a mês, em projeção crânio-caudal, a partir dos 18 meses de idade até o fechamento completo. Os dados do experimento foram analisados pelo método ANOVA de uma via, utilizando-se o teste t de Student para comparação entre as médias. Concluiu-se que o fechamento epifisário completo ocorreu aos 25,83 ± 1,58 meses nas fêmeas e aos 28,16 ± 1,40 meses nos machos (p<0,001), observando-se que as primeiras são mais precoces no parâmetro maturidade óssea.

Variação sazonal da fotossíntese, condutância estomática e potencial da água na folha de laranjeira 'Valência'

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

A utilização de diferentes configurações de molas T para a obtenção de sistemas de forças otimizados

OBJETIVO: determinar as características mecânicas de molas T e T com helicóides, quando da incorporação de variações na liga metálica (aço inoxidável e beta-titânio), na intensidade de dobras de pré-ativação (0º e 40º/180º) e na secção transversal do fio utilizado para a construção destas molas (0,017 x 0,025 e 0,019 x 0,025). METODOLOGIA: foram submetidas ao ensaio mecânico 80 molas para fechamento de espaços, sendo estas centralizadas em um espaço de 21mm. As magnitudes de força horizontal, proporção momento/força e relação carga/deflexão produzidas pelos corpos de prova foram quantificadas utilizando-se um transdutor de momentos acoplado ao módulo indicador digital para extensiometria e adaptado a uma máquina universal de ensaios Instron. As molas foram submetidas a uma ativação total de 5mm, sendo registrados os valores a cada 1mm de ativação. No tratamento estatístico dos dados obtidos, foi realizada a análise de variância, sendo esta complementada pelo teste de comparações múltiplas de Tukey, considerando o nível de significância de 5%. RESULTADOS E CONCLUSÕES: os resultados demonstraram que, de maneira geral, as molas T com helicóides produziram menores magnitudes de força horizontal e relação carga/deflexão do que as molas T. Na presença de pré-ativação, as molas produziram altas proporções momento/força, enquanto, na ausência de dobras de pré-ativação, as mesmas geraram baixas proporções momento/força. Dentre todas as variáveis analisadas, aquela que apresentou uma maior influência na força horizontal e na relação carga/deflexão produzidas pelas molas foi a liga metálica. Já a proporção momento/força mostrou ser influenciada em maior grau pela pré-ativação das molas de fechamento.

Bone healing in drill hole defects in spontaneously hypertensive male and female rats' femurs. A histological and histometric study

Objective: the aim of this study was to evaluate the bone healing in spontaneously hypertensive rats (SHR) and compare the results with normotensive rats, evaluating male and female animals.Methods: A bone drill defect was created in the left femur of 24 SHR (12 males and 12 females) and 24 normotensive rats (12 males and 12 females). The animals were divided into two groups and sacrificed 7 and 21 days after the surgical procedure. After the routine laboratory processing, histological and histometric analysis were carried out and data were submitted to ANOVA and Tukey's test (5%).Results: Males and females from the same group had similar histological characteristics. After seven days, all animals presented irregular bone trabeculae. The periosteal osteoblasts were flattened in SHR, and presented a cuboid shape in normotensive animals. After 21 days, the bone defects of all specimens showed a linear closure in all the superficial extension. In addition, SHR presented flattened osteoblasts surrounding the bone trabeculae, while normotensive ones showed cuboidal cells. Statistical analysis of the histometric data indicated similar means between the male and female groups, except for normotensive rats on day 7. In addition, a larger amount of new bone formation was observed in hypertensive when compared to normotensive rats on day 27, in males as well as females.Conclusion: We conclude that bone healing in SHR was more significant than in normotensive ones, as shown by the histological and histometric evaluation 21 days after surgery.