Molecular Dynamics Simulations of the Interaction between Water Molecules and Aggregates of Acetic or Propionic Acid Molecules.

Water adsorption around small acetic and propionic acid aggregates has been studied by means of molecular dynamics simulation in the temperature range of 100-265 K as a function of the water content. Calculations have shown that acetic and propionic acid molecules behave similarly and that both the temperature and the water content have a strong influence on the behavior of the corresponding systems. Two situations have been evidenced for the acid-water aggregates, corresponding either to water adsorption on large acid grains at very low temperatures or to the formation of droplets consisting of acid molecules adsorbed at the surface of water aggregates at higher temperatures and high water content. At low water content and high temperature, only a partial mixing between water and acid molecules has been observed. The results of the present simulations emphasize the need for further experimental and simulation works to achieve a better characterization of the effects of both temperature and humidity on the behavior of organic aerosols in the troposphere.

Encapsulation into carbon nanotubes and release of anticancer Cisplatin drug molecule.

Molecular dynamics simulations have been investigated to study the interactions between single-wall carbon nanotubes and an anticancer agent Pt complex (Cisplatin). The optimized diameter of the vector system has been determined to encapsulate in the best conditions the drug molecules. The simulation results show also that several drug molecules can be adsorbed inside the nanotubes, leading to an increased confinement time. Moreover, our simulations show that the release of the drug near a cell membrane model is favored, opening the way to a natural drug nanocapsule.

Water and formic acid aggregates: a molecular dynamics study.

Water adsorption around a formic acid aggregate has been studied by means of molecular dynamics simulations in a large temperature range including tropospheric conditions. Systems of different water contents have been considered and a large number of simulations has allowed us to determine the behavior of the corresponding binary formic acid-water systems as a function of temperature and humidity. The results clearly evidence a threshold temperature below which the system consists of water molecules adsorbed on a large formic acid grain. Above this temperature, formation of liquid-like mixed aggregates is obtained. This threshold temperature depends on the water content and may influence the ability of formic acid grains to act as cloud condensation nuclei in the Troposphere.