CH bond activation in aromatic ketones mediated by iridium-tris(pyrazolyl)borate complexes.

Reaction of complex [TpMe2Ir(η4-CH2C(Me)C(Me)C2)] (1) with a series of aromatic ketones at 130 °C renders, by means of a selective ortho-CH activation, Ir(III)-metallacycles 2-5, which display an Ir-H bond. When [TpMe2Ir(C6H5)2N2] (6) is treated with 2-(trifluoromethyl)acetophenone and 2-fluoroacetophenone at 80 °C, the formation of dimeric (7) and trimeric architectures (8) is achieved through the meta- and para-CH activation of the aromatic ketone, respectively. The generation of complexes 2-5 is proposed to occur by the initial formation of Ir(III) η1-ketone adducts as key intermediates, followed by aromatic CH activations and the release of a butadiene ligand. The formation of complexes 7 and 8 involves an assisted process in which a metal center activation of the less sterically hindered C-H bond of the aromatic ketone takes place (releasing a benzene molecule), followed by the coordination of the carbonyl group, which generates the respective dimeric and trimeric structures. Complexes 7 and 8 are efficient catalysts for the transfer hydrogenation of ketones and aldehydes using isopropanol as the hydrogen source. All complexes have been fully characterized by NMR spectroscopy, FT-IR, elemental analysis and, in the cases of 7 and 8, X-ray crystallography. Details of the reaction conditions, isolation of the products, and proposals for the pathways of formation of complexes 2-5 and 7-8 are discussed.

Serine-enriched minimal medium enhances conversion of selenium into selenocysteine by Streptococcus thermophilus.

Selenium is included in selenoprotein sequences, which participate in enzymatic processes necessary to preserve optimal health. Some lactic acid bacteria carry out the biotransformation of inorganic selenium in their metabolism. The complete biochemical mechanism of selenium biotransformation is still unknown; however, it is known that both the selenocysteine synthesis process and its subsequent incorporation into selenoproteins include serine as part of the action of seryl-RNAt synthetase. Therefore, the aim of this work was to determine the effect of serine during the biotransformation of selenium and the subsequence growth of Streptococcus thermophilus in a minimal medium. Two culture media were prepared, one enriched with the minimum inhibitory concentration of selenite (as Na2SeO3) and the other as a mixture of the minimum inhibitory concentration of selenite and serine. The absorbed selenium concentration was measured by inductively coupled plasma, and the selenocysteine identification was performed by reverse-phase HPLC. In the second culture medium, decreases in both times, the adaptation and the logarithmic phase, were observed. According to the results, it was possible to establish that the presence of serine allowed the biotransformation of selenite into selenocysteine by Strep. thermophilus.

The genome of Laccaria bicolor provides insights into mycorrhizal symbiosis.

Mycorrhizal symbioses--the union of roots and soil fungi--are universal in terrestrial ecosystems and may have been fundamental to land colonization by plants. Boreal, temperate and montane forests all depend on ectomycorrhizae. Identification of the primary factors that regulate symbiotic development and metabolic activity will therefore open the door to understanding the role of ectomycorrhizae in plant development and physiology, allowing the full ecological significance of this symbiosis to be explored. Here we report the genome sequence of the ectomycorrhizal basidiomycete Laccaria bicolor (Fig. 1) and highlight gene sets involved in rhizosphere colonization and symbiosis. This 65-megabase genome assembly contains approximately 20,000 predicted protein-encoding genes and a very large number of transposons and repeated sequences. We detected unexpected genomic features, most notably a battery of effector-type small secreted proteins (SSPs) with unknown function, several of which are only expressed in symbiotic tissues. The most highly expressed SSP accumulates in the proliferating hyphae colonizing the host root. The ectomycorrhizae-specific SSPs probably have a decisive role in the establishment of the symbiosis. The unexpected observation that the genome of L. bicolor lacks carbohydrate-active enzymes involved in degradation of plant cell walls, but maintains the ability to degrade non-plant cell wall polysaccharides, reveals the dual saprotrophic and biotrophic lifestyle of the mycorrhizal fungus that enables it to grow within both soil and living plant roots. The predicted gene inventory of the L. bicolor genome, therefore, points to previously unknown mechanisms of symbiosis operating in biotrophic mycorrhizal fungi. The availability of this genome provides an unparalleled opportunity to develop a deeper understanding of the processes by which symbionts interact with plants within their ecosystem to perform vital functions in the carbon and nitrogen cycles that are fundamental to sustainable plant productivity.

Pacientes neurológicos del noreste del Perú con serología positiva por Western Blot a la larva de Taenia solium / Neurological patients in northwestern Peru with positive Western Blot serology to Taenia solium larvae

Obejtivo: Determinar la frecuencia de pacientes con sintomatología neurológica de la zona noroeste del Perú que presentan serología positiva por Western Blot a la larva de Taenia solium. Material y Métodos: El estudio se realizó en 3515 pacientes de cero a noventa años de edad y de ambos sexos con sintomatología neurológica, procedentes de los departamentos de Piura, Lambayeque, Cajamarca, Ancash, La Libertad y algunas poblaciones de la zona selvática (5 a 10º LS; 77a 82º LO). Dichos pacientes fueron atendidos en consultorios privados y en los servicios de neurología de los Hospitales Belén y Regional de Trujillo desde enero de 1997 hasta diciembre de 2001. De cada uno de los pacientes se obtuvo una muestra sanguínea, cuyo suero fue procesado por la técnica de Western Blot, la cual tiene una sensibilidad de 91 por ciento y una especificidad de 100 por ciento. Resultados: Se detectó serología positiva en 562 pacientes, la cual representa una prevalencia de 16 por ciento, siendo el sexo masculino el que presentó mayor porcentaje (58,4 por ciento). Los grupos etáreos con mayor frecuencia de serología positiva fueron los de 41 a 50 años (18,7 por ciento) y 31 a 40 años (17,4 por ciento). Los mayores porcentajes de serología positiva se obtuvo en pacientes procedentes de Piura y Lambayeque. Conclusiones: Los pacientes estudiados presentan una alta frecuencia de serología positiva a la larva de T. solium.

Objective: To determine the frequency of patients presenting with neurological symptoms in Northwestern Peru who have positive Western Blot serology to Taenia solium larvae. Material and Methods: The study was performed in 3515 patients, from zero to ninety years old and from both sexes, who presented with neurological symptoms. Patients came from Piura, Lambayeque, Cajamarca, Ancash, and La Libertad departments, as well as from certain areas in the jungle (5 to 10º southern latitude; 77 to 82º western longitude). Those patients were taken care of in private offices and in Neurology services in Belen and Regional hospitals in Trujillo, from January 1997 to December 2000. A blood sample was obtained from all patients, and the sera were processed using the Western Blot technique, which has 91 percent sensitivity and 100 percent specificity. Results: Positive serological Western Blot tests were detected in 562 patients, representing 16 per cent prevalence, and the infection was more frequent in males (58.4 percent). Age groups more frequently found to have positive serological tests were those form 41 to 50 years old (18.7 percent), and those from 31 to 40 years old (17.4 percent). The maximum percentages for positive serological tests were obtained in patients from Piura and Lambayeque. Conclusions: Patients studied show a high frequency of positive serology for Taenia solium larvae.