Long-wavelength lipid bilayer undulation spectrum by all-atom simulation

Molecular-scale interactions collectively determine the elastic response of membranes, and all-atom models provide the most chemically accurate representation of molecular-scale interactions. However, theoretical considerations and previous coarse-grained simulations suggest that very large all-atom simulations are required to directly observe the continuum regime first described by Canham, Evans, and Helfrich. Here, we present an all-atom simulation of dioleoyl phosphatidylcholine containing 10,330 lipids and approximately 3M atoms. The out-of-plane undulation spectrum clearly reaches the q^-4 scaling regime. Analysis of the long-wavelength intercept and of a fit to a tilt-corrected spectrum yield statistically indistinguishable values for the bending modulus between 21 and 22k_BT.