Gaussian curvature elasticity determined from global shape transformations and local stress distributions: a comparative study using the MARTINI model
We calculate the Gaussian curvature modulus of a systematically coarse-grained (CG) one-component lipid membrane by applying the method recently proposed by Hu et al. [Biophys. J., 2012, 102, 1403] to the MARTINI representation of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). We find the value /κ = −1.04 ± 0.03 for the elastic ratio between the Gaussian and the mean curvature modulus and deduce m/κm ≈ −0.98 ± 0.09 for the monolayer elastic ratio, where the latter is based on plausible assumptions for the distance z0 of the monolayer neutral surface from the bilayer midplane and the spontaneous lipid curvature K0m. By also analyzing the lateral stress profile σ0(z) of our system, two other lipid types and pertinent data from the literature, we show that determining K0m and through the first and second moment of σ0(z) gives rise to physically implausible values for these observables. This discrepancy, which we previously observed for a much simpler CG model, suggests that the moment conditions derived from simple continuum assumptions miss the effect of physically important correlations in the lipid bilayer.
- This article is part of the themed collection: Lipids & Membrane Biophysics