Simulations of the structural and dynamic effects of double bonds in phospholipid assemblies

The purpose of this study was to explore the effects of unsaturation on the dynamics of the phospholipid dimyristoyl phosphatidylcholine (DMPC). Molecular dynamics simulations (MDS) were used to probe the behavior of both single isolated molecules and monolayers of 16 molecules as a function of selective locations) and number of both trans and/or cis double carbon-carbon bonds. The properties estimated from the MDS of the unsaturated systems were compared to the corresponding fully saturated model systems. It was found that the time-averaged geometry of an isolated DMPC is significantly dependent on the locations and types (cis/trans) of double bonds present in the tails of the molecule. This geometric dependence decreases when the unsaturated DMPC molecule is part of a monolayer. However, some structural alterations seen for one isolated molecule do persist into the monolayer environment.