Another Piece of the Membrane Puzzle: Extending Slipids Further

To be able to model complex biological membranes in a
more realistic
manner, the force field Slipids (Stockholm lipids) has been extended
to include parameters for sphingomyelin (SM), phosphatidylglycerol
(PG), phosphatidylserine (PS) lipids, and cholesterol. Since the parametrization
scheme was faithful to the scheme used in previous editions of Slipids,
all parameters are consistent and fully compatible. The results of
careful validation of a number of key structural properties for one
and two component lipid bilayers are in excellent agreement with experiments.
Potentials of mean force for transferring water across binary mixtures
of lipids and cholesterol were also computed in order to compare water
permeability rates to experiments. In agreement with experimental
and simulation studies, it was found that the permeability and partitioning
of water is affected by cholesterol in lipid bilayers made of saturated
lipids to the largest extent. With the extensions of Slipids presented
here, it is now possible to study complex systems containing many
different lipids and proteins in a fully atomistic resolution in the
isothermic–isobaric (NPT) ensemble, which
is the proper ensemble for membrane simulations.