Investigation of the hydration shell of a membrane in an open system molecular dynamics simulation

Abstract

We analyze structural properties of hydration for a biological membrane with the open boundary adaptive resolution molecular dynamics approach in its latest version. A large region of noninteracting pointlike particles (tracers) acts as a reservoir of molecules and energy for the atomistically resolved membrane-water interface. The drastic simplification of the environment and its simple coupling to the high-resolution region has been successfully tested in a previous work on pure liquid water, and this work represents the method's first application to a system with high structural complexity. The successful results and novel methodology allow us to suggest a complementary view to the controversial question of the definition of the hydration shell for a membrane. The adaptive resolution technique allows for a physically well-founded statistical mechanics definition of the hydration shell by quantifying the minimal size of the region where the atomistic resolution of the molecules is strictly required while the rest of the system plays the role of a generic, structureless thermodynamic reservoir.