Molecular-dynamic Simulation of Phospholipid Bilayers: Ion Distribution at the Surface of Neutral and Charged Bilayer in the Liquid-Crystalline State

作者：Nesterenko A M^*; Ermakov Yu A

来源：Biologicheskie Membrany, 2012, 29(5): 374-384.

The electric field and ion distribution at the surface of neutral and charged lipid bilayers (BeCL2 and DPPC/DPPS + KCl) were studied with molecular dynamic methods. The contribution of lipid molecules, water and ions to the electric potential are shown to compensate each other significantly in the region of the diffuse double layer and decrease the potential magnitude to zero. It appears that the ion distribution at the charged surface is caused not from the electrostatic ion-medium interaction only. The total energy of this interaction was compared with the potential of mean force of ions. It reveals the difference between cations and anions as the result of their different effect on the water molecule state at the surface. The order parameter of water in the system DPPC + BeCl2 and the Cl- ion distibuton have the extemum at the distance of 10 angstrom from C-alpha atoms of phospholipid glycerin. This position was chosen as membrane "charged surface" for the electrical double layer (EDL) for all lipid systems studied. The potential of mean force of counterions at in EDL allows us to obtain the value of potential at the lipid surface suitable for experimental test of the MD data. This surface potential and surface charge density was found from MD simulation at different electrolyte concentrations and DPPS content of 20, 40 and 60% in the mixture with DPPC and was shown to be in a good agreement with the Gouy-Chapman-Stern model upon fitting parameters close to their experimental values.

• 出版日期2012-10