Lipid electropore stabilization process: a comparison between force fields.

RISK, M; CASTELLANI F; FERNÁNDEZ, ML; VERNIER PT

Toulouse

Congreso; 3er World Congress on Electroporation; 2019

Introduction: In this work we analyze the pore stabilization process in lipid bilayers exposed to an external electric field using different force fields. We employ two types of force field, which model the lipids at different levels of detail. The force fields selected are CHARMM36, an all-atom force field, where the parameters for each atom type in the system are explicitly provided, and the GROMOS-OPLS united-atom force field, where all parameters for each atom type are provided except for the nonpolar -CH3 and -CH2- groups in the lipid fatty acid chains, which are treated as a single particle. We simulate the pore opening and stabilization processes, and we evaluate pore size and ion transport for each system. Methods: The simulations were carried out on the GROMACS software platform. Lipid bilayer systems comprised of 128 POPC, and 8926 water molecules for GROMOS-OPLS system and 8933 water molecules for CHARMM36 system, and 22 Na+ and 22 Cl- for CHARMM36 system and 40 Na+ and 40 Cl- for GROMOS-OPLS system were equilibrated, and then a permeabilizing electric field was applied until a pore formed. Stepped values of sustaining electric field (25 MV/m to 100 MV/m) were applied to replicate instances of the porated systems to stabilize the pores for at least 100 ns. Results and Discussion: Pores are stable in these systems for 100 ns with sustaining fields in the range 50 MV/m to 75 MV/m. As previously reported, the stabilized pore radius is a function of the sustaining electric field. Similar pore stabilization behavior is observed with both force fields