102 research outputs found
A novel framework to study the impact of binding energy distributions on the chemistry of dust grains
The evaporation of molecules from dust grains is crucial to understand some
key aspects of the star- and the planet-formation processes. During the warm-up
phase the presence of young protostellar objects induces molecules to evaporate
from the dust surface into the gas phase, enhancing its chemical complexity.
Similarly, in circumstellar disks, the position of the so-called snow-lines is
determined by evaporation, with important consequences for the formation of
planets. The amount of molecules that are desorbed depends on the interaction
between the species and the grain surface, which is controlled by the binding
energy. Recent theoretical and experimental works point towards a distribution
of values for this parameter instead of the single value often employed in
astrochemical models.We present here a new "multi-binding energy" framework, to
assess the effects that a distribution of binding energies has on the amount of
species bound to the grains. We find that the efficiency of the surface
chemistry is significantly influenced by this process with crucial consequences
on the theoretical estimates of the desorbed species.Comment: Accepted A&
Methadone but not Morphine Inhibits Lubiprostone-Stimulated Cl− Currents in T84 Intestinal Cells and Recombinant Human ClC-2, but not CFTR Cl− Currents
Sphingomyelin Functions as a Novel Receptor for Helicobacter pylori VacA
The vacuolating cytotoxin (VacA) of the gastric pathogen Helicobacter pylori binds and enters epithelial cells, ultimately resulting in cellular vacuolation. Several host factors have been reported to be important for VacA function, but none of these have been demonstrated to be essential for toxin binding to the plasma membrane. Thus, the identity of cell surface receptors critical for both toxin binding and function has remained elusive. Here, we identify VacA as the first bacterial virulence factor that exploits the important plasma membrane sphingolipid, sphingomyelin (SM), as a cellular receptor. Depletion of plasma membrane SM with sphingomyelinase inhibited VacA-mediated vacuolation and significantly reduced the sensitivity of HeLa cells, as well as several other cell lines, to VacA. Further analysis revealed that SM is critical for VacA interactions with the plasma membrane. Restoring plasma membrane SM in cells previously depleted of SM was sufficient to rescue both toxin vacuolation activity and plasma membrane binding. VacA association with detergent-resistant membranes was inhibited in cells pretreated with SMase C, indicating the importance of SM for VacA association with lipid raft microdomains. Finally, VacA bound to SM in an in vitro ELISA assay in a manner competitively inhibited by lysenin, a known SM-binding protein. Our results suggest a model where VacA may exploit the capacity of SM to preferentially partition into lipid rafts in order to access the raft-associated cellular machinery previously shown to be required for toxin entry into host cells
Semliki forest virus as a vector: pros and cons for its use in biopharmaceuticals production
Algunas consideraciones sobre el acceso de los pobres a la tierra en las grandes ciudades de América Latina
Incluye BibliografÃaIntenta despejar ciertos mitos encerrados en la planificación para que las recomendaciones sobre polÃticas de tierra urbana conduzcan a eliminar barreras que se oponen al acceso de los pobres a la tierra
Acceso de los pobres a la tierra en las grandes ciudades de America Latina
Incluye BibliografÃ
Ocho tesis sobre planificación, desarrollo y distribución espacial de la población
Incluye BibliografÃ
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