Mapeo de la superficie de energía libre de formación de poros transmembrana

La formación de poros está asociada a una mayor permeabilidad de la membrana y conductividad eléctrica, así como también, al transporte de fármacos y al intercambio de solutos solubles en agua, entre el exterior y el interior de las células. El estudio de los poros transmembrana resulta relevante, especialmente, para comprender los mecanismos por los cuales se producen tales eventos y la energía libre que se pone en juego. Para la estimación adecuada de la energía libre es necesario el uso de variables colectivas (VC), que sean apropiadas. Estas VC son funciones que dependen de la posición que toman las partículas del sistema de estudio y en Dinámica Molecular permiten aplicar técnicas de mejoramiento de muestreo (como Metadinámica).Fil: Moyano, N.. Universidad Nacional de CuyoFil: Klug, J.. Universidad Nacional de CuyoFil: Triguero, C.. Universidad Nacional de CuyoFil: Tribello, G.. Universidad Nacional de CuyoFil: English, N.. Universidad Nacional de CuyoFil: Kohanoff, J.. Universidad Nacional de CuyoFil: Galassi, V.. Universidad Nacional de CuyoFil: Millán, D.. Universidad Nacional de CuyoFil: Del Pópolo, M.. Universidad Nacional de Cuy

Insights into mechanochemical reactions at the molecular level: simulated indentations of aspirin and meloxicam crystals

Although solvent-free mechanochemical synthesis continues to gain ever greater importance, the molecular scale processes that occur during such reactions remain largely uncharacterised. Here, we apply computational modelling to indentations between particles of crystals of aspirin and meloxicam under a variety of conditions to mimic the early stages of their mechanochemical cocrystallisation reaction. The study also extends to the effects of the presence of small amounts of solvent. It is found that, despite the solid crystalline nature of the reactants and the presence of little or no solvent, mixing occurs readily at the molecular level even during relatively low-energy collisions. When indented crystals are subsequently drawn apart, a connective neck formed by a mixture of the reactant molecules is observed, suggesting plastic-like behaviour of the reacting materials. Overall the work reveals some striking new insights including (i) relatively facile mixing of crystals under solvent-free conditions, (ii) no appreciable local temperature increases, (iii) localised amorphisation at the contact region and neck of the reacting crystals, and (iv) small amounts of solvent have relatively little effect during this early stage of the reaction, suggesting that their accelerating effect on the reaction may be exerted at later stages.Fil: Ferguson, Michael. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; Argentina. The Queens University of Belfast; IrlandaFil: Moyano, María Silvina. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; ArgentinaFil: Tribello, Gareth A.. The Queens University of Belfast; IrlandaFil: Crawford, Deborah E.. The Queens University of Belfast; IrlandaFil: Bringa, Eduardo Marcial. Universidad de Mendoza. Facultad de Ingenieria; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; ArgentinaFil: James, Stuart L.. The Queens University of Belfast; IrlandaFil: Kohanoff, Jorge. The Queens University of Belfast; IrlandaFil: del Popolo, Mario Gabriel. The Queens University of Belfast; Irlanda. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; Argentin

Nano-indentation of a room-temperature ionic liquid film on silica: a computational experiment

We investigate the structure of the [bmim][Tf2N]/silica interface by simulating the indentation of a thin (4 nm) [bmim][Tf2N] film by a hard nanometric tip. The ionic liquid/silica interface is represented in atomistic detail, while the tip is modelled by a spherical mesoscopic particle interacting via an effective short-range potential. Plots of the normal force (Fz) on the tip as a function of its distance from the silica surface highlight the effect of weak layering in the ionic liquid structure, as well as the progressive loss of fluidity in approaching the silica surface. The simulation results for Fz are in near-quantitative agreement with new AFM data measured on the same [bmim][Tf2N]/silica interface at comparable thermodynamic conditions.Comment: 24 pages, including 8 fig

Ultrafast structure and dynamics in ionic liquids: 2D-IR spectroscopy probes the molecular origin of viscosity

The viscosity of imidazolium ionic liquids increases dramatically when the strongest hydrogen bonding location is methylated. In this work, ultrafast two-dimensional vibrational spectroscopy of dilute thiocyanate ion ([SCN] -) in 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C4C1im][NTf2]) and 1-butyl-2,3- dimethylimidazolium bis(trifluoromethylsulfonyl)imide ([C4C 1C12im][NTf2]) shows that the structural reorganization occurs on a 26 ± 3 ps time scale and on a 47 ± 15 ps time scale, respectively. The results suggest that the breakup of local ion-cages is the fundamental event that activates molecular diffusion and determines the viscosity of the fluids. © 2014 American Chemical Society