Detection of Catalase Activity by Polyacrylamide Gel Electrophoresis (PAGE) in Cell Extracts from Pseudomonas aeruginosa

Bacteria in nature and as pathogens commonly face oxidative stress which causes damage to proteins, lipids and DNA. This damage is produced by the action of reactive oxygen species (ROS) such as hydrogen peroxide (H2O2), singlet oxygen, superoxide anion and hydroxyl radical. ROS are generated by antimicrobials, environmental factors (e.g., ultraviolet radiation, osmotic stress), aerobic respiration, and host phagocytes during infective processes. Pseudomonas aeruginosa, a versatile bacterium, is a prevalent opportunistic human pathogen which possesses several defense strategies against ROS. Among them, two catalases (KatA and KatB) have been well characterized by their role on the defense against multiple types of stress. In this protocol, KatA and KatB activities are detected by polyacrylamide gel electrophoresis (PAGE). It is also suggested that the detection of KatB is elusive.Fil: Pezzoni, Magdalena. Comisión Nacional de Energía Atómica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Pizarro, R. A.. Comisión Nacional de Energía Atómica; ArgentinaFil: Costa, C. S.. Comisión Nacional de Energía Atómica; Argentin

El Terremoto de Tocopilla de Mw=7.7 (Norte de Chile) del 14 de Noviembre de 2007: Resultados preliminares de la geodesia especial (InSAR)

A Mw 7.7 subduction earthquake occurred on November 14, 2007 in Tocopilla (northern Chile). This region (between 16.5ºS and 23.5ºS) had been identified as major seismic gap (~1000 km length) since the South Peru (Mw= 9.1, 16 August 1868) and the Iquique (Mw=9.0, 10 May 1877) megathrust earthquakes. This gap was reduced to 500 km after the Arequipa (Mw = 8.3, 23 June 2001) and the Antofagasta (Mw = 8.1, 30 July 1995) earthquakes. We compute interferograms using Envisat ASAR images acquired before and after the Tocopilla earthquake to infer the location, geometry and slip of the rupture. Elastic modeling of this data allows us to infer that the 2007 main rupture extended over an area of ~150 x 60 km2, between 35 and 55 km depth, with a mean displacement of ~ 1.3 m. That means that the Tocopilla earthquake ruptured the deeper part of the seismogenic interface, probably within the transition zone. This earthquake released a little portion of the slip deficit accumulated in the seismic gap during the last 130 years (~ 10m). Hence the Tocopilla event may constitute a precursor of a future large thrust event in the current 500 km seismic gap that continues accumulating elastic strain from 1877.Un terremoto de subducción de Mw 7.7 tuvo lugar el 14 de Noviembre de 2007 en Tocopilla (norte de Chile). Esta región (entre 16.5ºS y 23.5º S) había sido identificada como una gran laguna sísmica (de ~ 1000 km de longitud) desde los terremotos del Sur de Perú (Mw = 9.1, 16 de Agosto de 1868) y de Iquique (Mw = 9.0, 10 de Mayo de 1877). La extensión de la laguna se redujo después de los terremotos de Arequipa (Mw = 8.3, 23 de Junio de 2001) y de Antofagasta (Mw=8.1, 30 de Julio de 1995). Hemos calculado interferogramas a partir de imágenes ASAR Envisat adquiridas antes y después del terremoto de Tocopilla para deducir la localización, geometría y deslizamiento asociados a la rotura. La modelización elástica de estos datos indica que la ruptura principal de 2007 se propagó sobre un área de ~150 x 60 km2, entre 35 y 55 km de profundidad, con un deslizamiento medio de ~1.3 m. Esto significa que el terremoto de Tocopilla rompió la parte profunda de la interfase sismogéncia, probablemente dentro de la zona de transición. Este terremoto relajó una porción muy pequeña del déficit de deslizamiento acumulado en la laguna sísmica durante los últimos 130 años (~10 m). Por lo tanto, el evento de Tocopilla podría constituir un precursor de un gran terremoto de subducción en la laguna sísmica actual de 500 km que continua acumulando deformación elástica desde 1877.Depto. de Geodinámica, Estratigrafía y PaleontologíaFac. de Ciencias GeológicasTRUEFrench National Research Agencypu

Influência do óleo lubrificante na transferência de calor em um compressor hermético alternativo

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia Mecânica.No interior de um compressor hermético, o óleo lubrificante tem por função lubrificar as partes móveis, reduzir o vazamento do gás entre o cilindro e o pistão, prevenir a corrosão e o desgaste das partes metálicas, reduzir o acúmulo de contaminantes, amortecer impactos entre os componentes e controlar o campo de temperaturas do compressor por meio da transferência de calor com o gás, com a carcaça e com os demais componentes internos. No presente trabalho, é apresentada uma metodologia de cálculo para se avaliar a influência do óleo lubrificante na transferência de calor de um compressor hermético alternativo. Em alguns compressores, a existência de um padrão de circulação do lubrificante, promovido por um sistema de bombeamento acoplado ao eixo, proporciona uma remoção do calor dos componentes internos, o qual é rejeitado para o ambiente externo por meio da formação de um filme descendente de óleo junto à parede interna da carcaça. O presente modelo propõe equações para o transporte de calor na forma diferencial unidimensional cuja solução fornece o campo de temperaturas no óleo e na carcaça para uma dada condição de operação do compressor. A fim de validar o modelo numérico proposto, um compressor protótipo foi devidamente instrumentado para fornecer valores de temperatura em diversos pontos da carcaça e da parte interna do compressor para diferentes condições de operação. Os testes foram realizados em uma bancada experimental especialmente adaptada para receber o compressor protótipo. Adicionalmente à análise experimental, um modelo térmico global baseado em balanços de massa e energia na forma integral para os componentes internos do compressor foi adaptado e acoplado ao modelo de transferência de calor no óleo e na carcaça. Este modelo permitiu estimar a influência de diversas variáveis relativas ao escoamento do óleo sobre importantes parâmetros do compressor, como temperatura dos componentes, capacidade de refrigeração e potência consumida. De uma forma geral, observa-se que a temperatura dos componentes internos, da carcaça e do óleo no reservatório (cárter) são, em algumas condições, influenciadas pelo padrão de escoamento do óleo no interior da carcaça de forma significativa. Entretanto, grandezas energéticas e de eficiência são pouco afetadas por parâmetros como a vazão total de óleo bombeada, a vazão de óleo que escoa como um filme na parede da carcaça, o volume de óleo presente no cárter do compressor e a fração de óleo que escoa por sobre os componentes internos do compressor

Synthesis and morphological characterization of nanocomposite based on anodic TiO2 nanotubes and poly(N-maleoyl Glycine-CO-Acrylic acid)

Indexación: Scopus.In this study, we examined the synthesis, and characterization of TiO2/poly(N-maleoylglycine-co-acrylic acid) (TiO2/poly(MG-co-AA)) nanocomposite. The nanocomposite was prepared by the dispersion of TiO2 nanotubes in a water solution of the polymer (3% w/w) and then it was lyophilized. The nanocomposite was characterized by FTIR and Raman spectroscopies. The incorporation of TiO2 nanotubes to the polymeric matrix was determined by transmission electron microscopy (TEM) from which TiO2 nanotubes in the inner of copolymer with diameters ranging between 90 and 100 nm were observed. The overall morphology of the previously synthetized nanotubes was determined by scanning electron microscopy (SEM). For the nanocomposite system, the morphology was studied by atomic force microscopy (AFM) from which a grain shape structure was observed. This process resulted in a new nanocompsite material with an average grain diameter estimated by SEM and AFM ranging between 210-240 nm. It was observed that the nanotubes were homogeneously dispersed within the polymeric matrix. The prepared material could be suitable in the design of electronic devices and additionally could have potential applications as biomaterial.https://scielo.conicyt.cl/pdf/jcchems/v62n3/0717-9324-jcchems-62-03-3634.pd

Nasal immunization with the c-terminal domain of bcla3 induced specific igg production and attenuated disease symptoms in mice infected with clostridioides difficile spores

Clostridioides difficile is a Gram-positive, spore-forming bacterium that causes a severe intestinal infection. Spores of this pathogen enter in the human body through the oral route, interact with intestinal epithelial cells and persist in the gut. Once germinated, the vegetative cells colonize the intestine and produce toxins that enhance an immune response that perpetuate the disease. Therefore, spores are major players of the infection and ideal targets for new therapies. In this context, spore surface proteins of C. difficile, are potential antigens for the development of vaccines targeting C. difficile spores. Here, we report that the C-terminal domain of the spore surface protein BclA3, BclA3CTD, was identified as an antigenic epitope, over-produced in Escherichia coli and tested as an immunogen in mice. To increase antigen stability and efficiency, BclA3CTD was also exposed on the surface of B. subtilis spores, a mucosal vaccine delivery system. In the experimental conditions used in this study, free BclA3CTD induced antibody production in mice and attenuated some C. difficile infection symptoms after a challenge with the pathogen, while the spore-displayed antigen resulted less effective. Although dose regimen and immunization routes need to be optimized, our results suggest BclA3CTD as a potentially effective antigen to develop a new vaccination strategy targeting C. difficile spores

Critical Strain Region Evaluation of Self-Assembled Semiconductor Quantum Dots

A novel peak finding method to map the strain from high resolution transmission electron micrographs, known as the Peak Pairs method, has been applied to In(Ga) As/AlGaAs quantum dot (QD) samples, which present stacking faults emerging from the QD edges. Moreover, strain distribution has been simulated by the finite element method applying the elastic theory on a 3D QD model. The agreement existing between determined and simulated strain values reveals that these techniques are consistent enough to qualitatively characterize the strain distribution of nanostructured materials. The correct application of both methods allows the localization of critical strain zones in semiconductor QDs, predicting the nucleation of defects, and being a very useful tool for the design of semiconductor device