@article {2014|1669, title = {CHARMM36 united atom chain model for lipids and surfactants.}, journal = {J. Phys. Chem. B}, volume = {118}, number = {2}, year = {2014}, month = {jan}, pages = {547{\textendash}556}, publisher = {, Maryland 20742, United States.}, abstract = {Molecular simulations of lipids and surfactants require accurate parameters to reproduce and predict experimental properties. Previously, a united atom (UA) chain model was developed for the CHARMM27/27r lipids (H{\'e}nin, J., et al. J. Phys. Chem. B. 2008, 112, 7008-7015) but suffers from the flaw that bilayer simulations using the model require an imposed surface area ensemble, which limits its use to pure bilayer systems. A UA-chain model has been developed based on the CHARMM36 (C36) all-atom lipid parameters, termed C36-UA, and agreed well with bulk, lipid membrane, and micelle formation of a surfactant. Molecular dynamics (MD) simulations of alkanes (heptane and pentadecane) were used to test the validity of C36-UA on density, heat of vaporization, and liquid self-diffusion constants. Then, simulations using C36-UA resulted in accurate properties (surface area per lipid, X-ray and neutron form factors, and chain order parameters) of various saturated- and unsaturated-chain bilayers. When mixed with the all-atom cholesterol model and tested with a series of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC)/cholesterol mixtures, the C36-UA model performed well. Simulations of self-assembly of a surfactant (dodecylphosphocholine, DPC) using C36-UA suggest an aggregation number of 53 {\textpm} 11 DPC molecules at 0.45 M of DPC, which agrees well with experimental estimates. Therefore, the C36-UA force field offers a useful alternative to the all-atom C36 lipid force field by requiring less computational cost while still maintaining the same level of accuracy, which may prove useful for large systems with proteins.}, keywords = {analogs /\&/ derivatives/chemistry, chemistry, Cholesterol, Dimyristoylphosphatidylcholine, Lipid Bilayers, Lipids, Micelles, Molecular Dynamics Simulation, Phosphorylcholine, Surface-Active Agents}, doi = {10.1021/jp410344g}, author = {Lee, Sarah and Tran, Alan and Allsopp, Matthew and Lim, Joseph B. and J{\'e}r{\^o}me H{\'e}nin and Klauda, Jeffery B.} }