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De Bettencourt A.M.,University of Evora | Florencio M.H.,FCUL | Henriques F.F.,New University of Lisbon | Portela M.I.,University of Evora | Vilas-Boas L.F.,Institute Tecnologia Quimica e Biologica ITQB
Microchemical Journal | Year: 2011

Arsenic is a type 1 carcinogen and its toxicity is critically dependent on chemical speciation. However, after decades of research, the biogenesis of at least fifty naturally occurring arsenic species is still not well understood.Here, based on experimental work, it is proposed a set of pathways for the formation of multiple arsenic species that might help to clarify the present situation.These are focused on the thiol protein arsenic bond and on its interaction with reactive metabolites. In fact, arsenic bound to glutathione interacting with sulfur adenosyl methionine (SAM), MethylCB12 and AdoCB12, forms a number of complexes that might be key intermediates in arsenic biochemistry. These include dimethylarsino glutathione (DMAG) m/z 412 [M+H]+, synthesized non-enzymatically from glutathione and cacodylate. Trimethylarsonio glutathione (TMAG) m/z 426 [M]+ synthesized from DMA, GSH and SAM, apparently by a classical Challenger methylcarbonium attack. Tetramethyl arsonium ion m/z 135 [M]+ is formed in a third step, apparently by carbanion methylation. The presence of trimethylarsine oxide (TMAO) m/z 137 [M+H]+ is attributed to the hydrolysis of TMAG or TMA, or to carbanion methylation of dimethylarsinoyl glutathione (m/z 428 [M]+) formed from cacodylate and GSH. Cantoni type attacks of DMAG on SAM were unsuccessful, eventually due to competition of the trivalent S+ atom of SAM for the AsIII atom attack. The presence of dimethylarsonio diglutathione (DMADG m/z 717 [M]+), is suggested to result from a GS- attack on dimethylarsenoyl glutathione (m/z 428 [M+H]+). The presence of dimethylarsenoyladenosine (m/z 372 [M+H]+), trimethylarsenosugar adenine (m/z 370 [M]+), and dimethylthioarsenosugar adenine (m/z 388 [M+H]+), is explained by the synthesis of the pecursor dimethylarsonio-adenosine glutathione DMAAG (m/z 661 [M]+), a likely source of oxo-and trimethylated arsenosugars, as well as of thio-arsenosugars by the cleavage of its S-C bond. The results gathered suggest that cell vacuoles might play a major role in arsenic metabolism, and that the dominance of oxo-As sugars, in algae extracts, may be supported by a mechanism of synthesis independent of DMAAG (m/z 661).They also offer an explanation for the reason why arsenobetaine, and tetramethylarsonium are loosely bound to biotic tissues. Four arsenic species new to science, to the best of our knowledge, and a number of known arsenic compounds were synthesized in this work, identified by HPLC-ESI-MSn and FTICR-ESI-MS, and suggestions regarding their mechanisms of synthesis were advanced. These results provide a framework for arsenic biochemistry which may explain the origin of a significant part of arsenic known metabolites. © 2011 Elsevier B.V. Source

Aslanian D.,French Research Institute for Exploitation of the Sea | Moulin M.,FCUL
Geophysical Journal International | Year: 2010

Torsvik et al. recently presented a revised model for the opening of the South Atlantic Ocean. According to these authors, this new plate tectonic model is internally consistent and consistent with globally balanced plate motion solutions and takes into account realistic intraplate deformation. However, this model shows a number of kinematic and geological problems that we underline here, together with some comparisons with the new kinematic model recently proposed by Moulin et al. © 2010 The Authors Journal compilation © 2010 RAS. Source

Leal S.,FCUL | Leal J.P.,ITN
Proceedings - 2013 2nd Experiment@ International Conference, exp.at 2013 | Year: 2013

In the last three years, e-lab a real laboratory remotely controlled via the internet, has been an important educational resource in basic and secondary Portuguese schools in subjects like Physics and Chemistry. Since a pilot study performed in late 2009 that e-lab platform is being used in and outside the classroom contributing to increase students' motivation and interest toward scientific subjects. Currently, the e-lab team is interested in performing remote chemistry experiments, which are more difficult to execute in this kind of environment. At this time, the challenge is to create an experiment focused in a chemical equilibrium reaction. © 2013 IEEE. Source

Jardim M.E.,University of Puerto Rico at San Juan | Peres I.M.,C.C.M.M. | Re P.B.,FCUL | Costa F.M.,C.C.M.M.
Historia, Ciencias, Saude - Manguinhos | Year: 2014

After the Challenger expedition (1872-1878), other nations started to show interest in oceanographic research and organizing their own expeditions. As of 1885, Prince Albert I of Monaco conducted oceanographic campaigns with the collaboration of some of the best marine biologists and physical oceanographers of the day, inventing new techniques and instruments for the oceanographic work. Prince Albert’s scientific activity certainly helped kindle the interest of his friend, Dom Carlos I, king of Portugal, in the study of the oceans and marine life. Both shared the need to use photography to document their studies. This article analyzes the role of scientific photography in oceanography, especially in the expeditions organized by the Portuguese monarch. © 2014, Fundacao Oswaldo Cruz, All right reserved. Source

Loureiro A.,National Laboratory of Energy and Geology | Van Der Neut J.,National Laboratory of Energy and Geology | Alves D.,FCUL | Carvalho J.,FCUL | And 4 more authors.
74th European Association of Geoscientists and Engineers Conference and Exhibition 2012 Incorporating SPE EUROPEC 2012: Responsibly Securing Natural Resources | Year: 2012

When applying seismic interferometry to image sub-vertical salt flanks or structures with large dips from vertical or deviated wells, we are often confronted with poor target illumination. Strong directionalillumination footprints caused by non-ideal placement of sources at the surface degrade the interferometric image quality and may prevent the retrieval of particular dips in the image. The effect of the well's orientation on the interferometric image is investigated. Moreover, a method is presented to estimate the imageable dips in an interferometric image, which can be used to design a more favorable shooting geometry and to gain additional knowledge about the target structures. Source

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