Molecular-dynamic Simulation of DPPC Bilayer in Different Phase States: Hydration and Electric Field Distribution in the Presence of Be2+ Cations

作者：Nesterenko A M^*; Krasilnikov P M; Ermakov Yu A

来源：Biologicheskie Membrany, 2011, 28(5): 397-407.

New molecular-dynamic topology of DPPC bilayer in total atomic OPLS forcefield was developed and used to study the structural characteristics of liquid-crystalline and gel states of lipid bilayer in the absence and in the presence of Na+ and Be2+ cations adsorbed at the interface and different in their affinity. The parameters of bilayer geometry, the amount of surface water, and the electrostatic potential distribution were estimated quantitatively from the simulation in both phase states.. The azimuthal angle of hydrocarbon chains was found nearly the same in the region of each monolayer in gel state. The amount of surface water decreases upon bilayer "freezing" mainly by loss the water molecules not participating in H-bonds between lipid headgroups. The cation absorption was shown to have a small effect on these H-bonded water molecules, whereas Be2+ appeared to retain surface water in the bilayer upon its freezing. The electric potential distribution in the normal direction to the membrane water interface had a similar shape at any bilayer phase state regardless of the presence of the absorbed cations. Analysis of microscopic nature of the electric potential revealed a mutual compensation of the contributions of the main structural components of the system (lipids, water, and ions). The boundary potential increased by 116 mV for pure DPPC, by 212 mV in the presence of Na+, and by 133 mV in the presence of Be2+ upon the phase transition of bilayer to the gel state. The boundary potential difference in the presence of Na+ and Be2+ and its change at the bilayer phase transition are in a good agreement with the experimental data published earlier (Ermakov Yu., 1993).

• 出版日期2011-10