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 (k) over bar 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 (k) over bar /k = -1.04 +/- 0.03 for the elastic ratio between the Gaussian and the mean curvature modulus and deduce (k) over bar (m)/k(m) approximate to -0.98 +/- 0.09 for the monolayer elastic ratio, where the latter is based on plausible assumptions for the distance z(0) of the monolayer neutral surface from the bilayer midplane and the spontaneous lipid curvature K-0m. By also analyzing the lateral stress profile sigma(0)(z) of our system, two other lipid types and pertinent data from the literature, we show that determining K-0m and (k) over bar through the first and second moment of sigma(0)(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