BPS2026 – Local elasticity profiles unravel the microscopic origin of membrane moduli

Numerous cellular processes such as membrane fission and fusion depend on the energetics of elastic deformation, which include in-plane stretching and out-of-plane bending. These modes of deformation have macroscopic moduli associated with them that are typically measured experimentally or estimated computationally through various methods. The recent curvature-tilt theory of Terzi, Ergüder, and Deserno suggests that there may be at least five macroscopic moduli needed to describe out-of-plane membrane deformations including bending, Gaussian curvature, tilt, splay-tilt, and twist. Within that theory, these moduli have well-defined microscopic origins through various integral moments of microscopic quantities such as the local Young’s modulus. Here, we use the stress-stress fluctuation method to obtain local elasticity profiles from molecular dynamics simulations of coarse-grained (CG) MARTINI lipid membranes. We use these elasticity profiles to estimate locally defined quantities such as the Young’s, area, and shear moduli of the CG membranes. We show that the results from the stress-stress fluctuation formula are in excellent agreement with other methods such as explicit deformation and area fluctuation. We compare the integral moments of the microscopic moduli to values of the macroscopic moduli obtained through analysis of power spectra of large fluctuating membrane simulations. Our results provide for the first time a direct estimation of these important microscopic moduli, which determine the elastic response of a membrane due to any type of deformation.