Ejercicios y trozos latinos : primer curso

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Manual de gramática latina

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Molecular Dynamics Simulations of Proton Conduction in Sulfonated Poly(phenyl sulfone)s

Full molecular dynamics was used to simulate separately the diffusion of naked protons and H₃O⁺ hydrated protons across sulfonated poly(phenyl sulfone)s. Simulations were carried out for wet membranes with the following characteristics:  ion-exchange capacity, 1.8 mequiv/g of dry membrane; water uptake, 10−30%; temperature range, 300−360 K. The diffusion coefficient of naked protons is nearly 1 order of magnitude higher than that of the hydrated protons for the membranes with the lower water uptake (10%). For the membranes with higher water uptake the ratio between the diffusion coefficients of the two particles reduces to about half an order of magnitude. The conductivity of the naked protons increases from 21.4 × 10⁻³ to 52.5 × 10⁻³ S/cm when the water uptake increases from 10% to 30%. For hydrated protons the conductivity increases from 1.54 × 10⁻³ to 7.57 × 10⁻³ S/cm. The conductivities obtained through simulations carried out at 300 K for the hydrated proton across membranes with water uptake 18% and 30% are roughly similar to those experimentally measured for a membrane with ion exchange capacity = 1.8 mequiv/g and water uptake = 24.3%. Simulated conductivities of both naked protons and hydrated protons follow Arrhenius behavior.This work was supported by the Comunidad de Madrid through the grant interfaces S-505/MAT-0227, Fondos Europeos de Desarrollo (FEDER), and Fondo Social Europeo (FSE). Financial support was also supplied by the Dirección General de Investigación Científica y Técnica (DGICYT) (grant MAT 2005-05648-C02-02)

Interacción del patógeno humano Bacillus cereus con plantas de interés agronómico

Uno de los grandes retos de la industria agroalimentaria es reducir los continuos casos de intoxicaciones alimentarias causadas por el consumo de frutas y verduras contaminadas con patógenos de humanos, y las consecuentes pérdidas económicas. Bacillus cereus es una bacteria patógena de humanos responsable de intoxicaciones alimentarias que en ocasiones pueden ser letales. El ciclo de vida de esta bacteria se caracteriza por la formación de biopelículas y la esporulación. Las biopelículas son comunidades de bacterias difíciles de erradicar, y para su formación las bacterias ensamblan una matriz extracelular formada principalmente por exopolisacáridos y proteínas. En este trabajo, nos planteamos estudiar las bases moleculares que dirigen la formación de biopelículas en B. cereus, y su posible implicación en la interacción con diferentes plantas hortofrutícolas. Para ello, nos hemos centrado en el análisis de los componentes estructurales de la matriz extracelular, y más concretamente en posibles adhesinas de naturaleza proteica. B. cereus tiene dos ortólogos del gen tasa de B. subtilis que codifica para una proteína que polimeriza en la forma de fibras amiloides y es indispensable para la formación de las biopelículas. Mediante estudios de expresión heteróloga demostramos que el alelo de tasA de B. cereus rescata la formación de biopelículas de una cepa de B. subtilis que carece de su propio tasA. De la misma forma, un mutante de B. cereus en este alelo presenta un fenotipo defectuoso en la formación de biopelículas tanto in vitro como en la interacción con plantas. Finalmente estudios bioquímicos y morfológicos preliminares de esta proteína apuntan a su naturaleza tipo amiloide como su ortólogo de B. subtilis.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

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Comparison Between the Conductivities of Protons Measured Experimentally with the Obtained by Molecular Dynamics Simulations in Sulfonated Polyphenyl Sulfones Membranes

Full Molecular Dynamics was used to simulate separately the diffusion of naked protons and H₃O⁺ hydrated protons across sulfonated polyphenyl sulfones, (sPS). The diffusion coefficient of naked protons is nearly one order of magnitude higher than that of the hydrated protons for the membranes with the lower water uptake (10%). The conductivities simulated at 300 K for the hydrated proton across membranes with water uptake 18% and 30 % are roughly similar to those both experimentally measured for the sPS4 membrane with ion exchange capacity = 1.8 eq/Kg in dry conditions and with water uptake = 24.3 %. The comparison between four sPS membranes shwon the strong dependence of conductivity with the water content into the membranes. In our study, the conductivity of sPS1 with a 3.1% water content decrease two order of magnitude respect the sPS4 with 24.3 of water content. Simulated conductivities of both naked protons and hydrated protons follow Arrhenius behavior.This work was supported by the Dirección General de Investigación Científica y Técnica (DGICYT), Grant MAT-2005-05648-C02-02, and from IMPIVA of Generalitat Valenciana through project IMCITA/2006/030 is gratefully acknowledged. The authors are also grateful to the Instituto de Tecnología Eléctrica (ITE) de la Universidad Politécnica de Valencia for the financial support

The Iturin and Fengycin Families of Lipopeptides Are Key Factors in Antagonism of Bacillus subtilis Toward Podosphaera fusca

Podosphaera fusca is the main causal agent of cucurbit powdery mildew in Spain. Four Bacillus subtilis strains, UMAF6614, UMAF6619, UMAF6639, and UMAF8561, with proven ability to suppress the disease on melon in detached leaf and seedling assays, were subjected to further analyses to elucidate the mode of action involved in their biocontrol performance. Cell-free supernatants showed antifungal activities very close to those previously reported for vegetative cells. Identification of three lipopeptide antibiotics, surfactin, fengycin, and iturin A or bacillomycin, in butanolic extracts from cell-free culture filtrates of these B. subtilis strains pointed out that antibiosis could be a major factor involved in their biocontrol ability. The strong inhibitory effect of purified lipopeptide fractions corresponding to bacillomycin, fengycin, and iturin A on P. fusca conidia germination, as well as the in situ detection of these lipopeptides in bacterial-treated melon leaves, provided interesting evidence of their putative involvement in the antagonistic activity. Those results were definitively supported by site-directed mutagenesis analysis, targeted to suppress the biosynthesis of the different lipopeptides. Taken together, our data have allowed us to conclude that the iturin and fengycin families of lipopeptides have a major role in the antagonism of B. subtilis toward P. fusca.

The Iturin and Fengycin Families of Lipopeptides Are Key Factors in Antagonism of Bacillus subtilis Toward Podosphaera fusca

Podosphaera fusca is the main causal agent of cucurbit powdery mildew in Spain. Four Bacillus subtilis strains, UMAF6614, UMAF6619, UMAF6639, and UMAF8561, with proven ability to suppress the disease on melon in detached leaf and seedling assays, were subjected to further analyses to elucidate the mode of action involved in their biocontrol performance. Cell-free supernatants showed antifungal activities very close to those previously reported for vegetative cells. Identification of three lipopeptide antibiotics, surfactin, fengycin, and iturin A or bacillomycin, in butanolic extracts from cell-free culture filtrates of these B. subtilis strains pointed out that antibiosis could be a major factor involved in their biocontrol ability. The strong inhibitory effect of purified lipopeptide fractions corresponding to bacillomycin, fengycin, and iturin A on P. fusca conidia germination, as well as the in situ detection of these lipopeptides in bacterial-treated melon leaves, provided interesting evidence of their putative involvement in the antagonistic activity. Those results were definitively supported by site-directed mutagenesis analysis, targeted to suppress the biosynthesis of the different lipopeptides. Taken together, our data have allowed us to conclude that the iturin and fengycin families of lipopeptides have a major role in the antagonism of B. subtilis toward P. fusca.