Phos
pholi
pids are essential building blocks of biological membranes. Des
pite a vast amount of very accurate ex
perimental data, the atomistic resolution structures sam
pled by the glycerol backbone and choline headgrou
p in
phoshatidylcholine bilayers are not known. Atomistic resolution molecular dynamics simulations have the
potential to resolve the structures, and to give an arrestingly intuitive inter
pretation of the ex
perimental data, but only if the simulations re
produce the data within ex
perimental accuracy. In the
present work, we simulated
phos
phatidylcholine (PC) li
pid bilayers with 13 different atomistic models, and com
pared simulations with NMR ex
periments in terms of the highly structurally sensitive C鈥揌 bond vector order
parameters. Focusing on the glycerol backbone and choline headgrou
ps, we showed that the order
parameter com
parison can be used to judge the atomistic resolution structural accuracy of the models. Accurate models, in turn, allow molecular dynamics simulations to be used as an inter
pretation tool that translates these NMR data into a dynamic three-dimensional re
presentation of biomolecules in biologically relevant conditions. In addition to li
pid bilayers in fully hydrated conditions, we reviewed
previous ex
perimental data for dehydrated bilayers and cholesterol-containing bilayers, and inter
preted them with simulations. Although none of the existing models reached ex
perimental accuracy, by critically com
paring them we were able to distill relevant chemical information: (1) increase of choline order
parameters indicates the P鈥揘 vector tilting more
parallel to the membrane, and (2) cholesterol induces only minor changes to the PC (glycerol backbone) structure. This work has been done as a fully o
pen collaboration, using
p://nmrlipids.blogspot.fi" class="extLink">nmrlipids.blogspot.fi as a communication platform; all the scientific contributions were made publicly on this blog. During the open research process, the repository holding our simulation trajectories and files (ps://zenodo.org/collection/user-nmrlipids" class="extLink">https://zenodo.org/collection/user-nmrlipids) has become the most extensive publicly available collection of molecular dynamics simulation trajectories of lipid bilayers.