Wetting characteristics of a phospholipid membrane using molecular dynamics simulation

Phospholipid molecules form bilayers in water due to their hydrophilic heads and hydrophobic tails. The electroporation of lipid bilayers (cell membranes) is a phenomenon where membranes are permeabilized by the application of electric fields. At some critical voltage, a dramatic increase in conductivity across the membranes is observed. This phenomenon is widely used in DNA and RNA transfer as well as targeted drug delivery systems. However, the membrane ruptures with a continuous increase in voltage where interaction between lipid and water molecules is an important factor in electroporation behavior. This study characterizes the wettability, of both the head and tail groups of lipid molecules, by calculating the contact angle of a water droplet on a planar phospholipid monolayer using molecular dynamics simulations. The water droplet completely spreads on the hydrophilic heads of the lipid, while forming an average contact angle of 136.05o on the hydrophobic tails. An analysis using the Young's equation suggests that a difference in free energy of 116 mJ/m² contributes to the overall energy barrier for water penetration across the lipid monolayer. We aim to control this permeabilization phenomenon to achieve water desalination.