Influence of Small Fluorophilic and Lipophilic Organic Molecules on Dipalmitoylphosphatidylcholine Bilayers.

In this study, we investigate the effect of a series of additive molecules with different types of philicities on the structure and dynamics of dipalmitoylphosphatidylcholine (DPPC) bilayers. To this aim, we performed extensive force field molecular dynamics simulations of the systems, using our recently developed perfluoroalkane force field. We found that addition of perfluoro-n-decane and fluorotelomer alcohol at 323 K leads to a phase transition of the membrane from liquid crystalline to the gel phase, whereas the addition of n-decane and partially fluorinated n-decane leaves the liquid crystalline phase intact. The systems in the gel phase show a significantly reduced diffusivity for both DPPC and additive molecules. The addition of nonfluorinated and partially fluorinated n-decane even leads to an increased DPPC diffusivity. While nonfluorinated n-decane and partially fluorinated n-decane are found mainly in the middle of the bilayer, perfluoro-n-decane penetrates significantly deeper into the membrane leaflet. Fluorotelomer alcohol is found almost exclusively inside the leaflet, with its hydroxyl groups forming a strong hydrogen bond network to the ester oxygen atoms in the head group of DPPC. A slight increase in temperature by only 10 K is already sufficient to dynamically overcome this hydrogen bond network, such that no phase transition occurs in that case.