Before revision:  The degree of the planarity of the ring system affects the orientation of the methyl groups on the rough side and distribute the lipid chains on the two sides of the sterols differently. Similar to the structural observations, cholesterol also has a stronger influence on the dynamics, and consistently, establishes stronger DPPC-sterol interactions when compared to ergosterol. Although our findings are consistent with some previous simulations as well as recent experiments, they are at odds with some other studies. Therefore, the presented results may shed new lights on the impact of sterols on the saturated lipids bilayers with implications for binary mixtures of lipids as well as lipid rafts .
After revision:  The degree of the planarity of the cholesterol ring region. This planarity combined with an inherent asymmetry in its molecular interactions led to better alignment and hence stronger interaction with saturated acyl chains. Our results show that ergosterol does not have an increased capacity to form ordered lipid domains compared to cholesterol and indicate that the high order demonstrated for fungal plasma membranes must therefore be generated via different mechanisms .