The association of dehydro-epiandrosterone and adenosine triphosphate acid: A DFT study of interactions between prototypic biologically active molecules

International audienceDHEA (dehydro-epiandrosterone) is a neurosteroid whose synthesis inside the brain as well its critical role in brain development, ageing, or memory effects, were recently proved. ATP (adenosine triphosphate acid) is very important as a source of energy in the human organism. The feasibility of an association between ATP and DHEA, investigated here, can be taken as a useful design testing ground in the search for new drugs helping to restore their level. DFT calculations are used to test the association potential of DHEA and ATP. Depending on the initial choice of the method, basis set and starting conformation, a set of quantitative association energies is obtained, the values being in the range -20 to -30 kcal/mol. These results point to the conclusion that such an association should be possible in many instances, and should also be relatively stable against potential perturbations originating from the environment. We use this model as an opportunity for a methodological discussion aiming at the comparative use of two different approaches to assess their performance and physical meaning. The first one is based on plane-waves and pseudo-potentials (with the ABINIT code) while the second one rests on Gaussian-type calculations (with the GAMESS package). The plane-waves approach was chosen as an alternative affording the direct calculation of association energies without the need to apply the so-called basis set superposition error (BSSE) correction. Actually, given a molecular box and a selected energy cut-off, the isolated molecules and the association complex are treated using the same extended basis set. Molecular parameters (geometries, charges and energies) are discussed with respect to the mechanism of association

Theoretical Study at the HF, MP2 and DFT Level of the Electronic Properties of a Complex between Cholesterol and the two Isomers of Pralidoxime (PAM)

International audienceMolecular parameters (interatomic distances and angles, total atomic charge, dipole moments) for cholesterol, for the two isomers of 2-PAM (ee-PAM and ze-PAM) and for their putative electrostatic complexes with the former, have been computed in an ab-initio comparative study involving HF, MP2 and B3LYP calculations. Interest for such a study comes from the potential role of cholesterol to assist in the cell membrane translocation of the very polar PAM, an efficient antidote against organophosphate intoxication, if the latter happens to be complexed to cholesterol at the water-lipid membrane interface. For all calculations the results point to the formation of a weak complex, as shown by the computed heats of formation. It appears also that a weak intramolecular H-bond should be present in the ze-PAM isome

Historia comparada de las Américas : perspectivas de la integración cultural

La presente obra responde al creciente y renovado interés que hoy despierta el tema de la integración cultural en sus múltiples dimensiones. Este volumen reúne veintisiete trabajos preparados por destacados especialistas provenientes de distintos ámbitos académicos, quienes se hicieron eco de la invitación a presentar sus respectivas propuestas y perspectivas, así como a repensar el vínculo entre integración y cultura desde el mirador de la experiencia americana. 'Integración' y 'cultura' constituyen ya en sí mismos dos conceptos de enorme complejidad a través de los que se busca dar cuenta de todo un amplio espectro de procesos, prácticas, discursos, políticas, de vital importancia para la historia de la religión. El estudio de ambos conceptos ha generado a su vez auténticas constelaciones de temas y problemas, y ha dado lugar a reflexiones de muy amplios alcances, líneas de investigación altamente productivas y campos de estudio interdisciplinario en plena etapa de expansión. Así lo confirman los trabajos aquí publicados, que aportan, con gran solvencia, perspectivas de análisis y líneas de discusión de gran riqueza. Una y múltiple, la inquietud por la integración no ha dejado de acompañar a los americanos a lo largo del tiempo. El recorrido histórico, espacial y temático; la reflexión teórica y la preocupación por estrategias concretas; el asomo a miradas de conjunto y a estudios de caso; el particular énfasis en algunos de los posibles nuevos caminos para pensar la integración cultural: muchas de estas perspectivas se hacen presentes en este volumen, a través de reflexiones que confirman que el tema sigue siendo no sólo vigente sino de imperiosa y decisiva actualidad.                                                                         Libro