STRUCTURAL-PROPERTIES OF 1,2-DIACYL-SN-GLYCEROL IN BULK AND AT THE WATER INTERFACE BY MOLECULAR-DYNAMICS

We performed four different molecular dynamics (MD) simulations of 1,2 -dilauroyl-sn-glycerol (DLG) systems at 300 and 360 K: a crystal simul ation, a pure DLG oil phase, a DLG oil phase in contact with a water l ayer, and an oil/monolayer/water simulation. All these systems were si mulated for several nanoseconds in total. We describe the behavior of the DLG molecules in the lipid phase as well as at the aqueous interfa ce. The crystal and pure oil phase tend to converge to the same overal l structure (i.e., an isotropic liquid), as do the systems with an aqu eous interface, although equilibrium for the crystal and monolayer sys tem has not yet been reached compared to their counterpart. The presen ce of an aqueous interface induces layering of the lipid molecules. Th e overall properties like density, hydrogen bonding, and rdf's converg e at the different temperatures. We can conclude that the rearrangemen t of the DLG molecules in these DLG systems is a slow process, but we estimate that the equilibrium for these systems at 360 K, the liquid p hase, will be reached within a few nanoseconds, for the DLG molecules diffuse over nanometers on a nanosecond time scale.