Determination of the Boundary Surface Between the Lipid Bilayer and Water

Abstract

Profiles of various membrane characteristics are traditionally calculated from the middle plane of the membrane towards the surface. In this approach, atomic positions near the membrane surface are determined inaccurately because, strictly speaking, the membrane is nonplanar and can have unevennesses or a variable thickness. However, the profile can also be calculated from the membrane surface. We propose to use the Voronoi boundary surface (a set of adjacent faces of Voronoi regions of membrane atoms and surrounding water) as this surface. It naturally divides the space between the membrane and water. Atomic density and empty intermolecular space profiles calculated relative to this surface reveal new features not seen when the middle plane is used.