title: Molecular model of a cell plasma membrane with an asymmetric multicomponent composition: water permeation and ion effects.
abstract: We present molecular dynamics simulations of a multicomponent, asymmetric bilayer in mixed aqueous solutions of sodium and potassium chloride. Because of the geometry of the system, there are two aqueous solution regions in our simulations: one mimics the intracellular region, and one mimics the extracellular region. Ion-specific effects are evident at the membrane/aqueous solution interface. Namely, at equal concentrations of sodium and potassium, sodium ions are more strongly adsorbed to carbonyl groups of the lipid headgroups. A significant concentration excess of potassium is needed for this ion to overwhelm the sodium abundance at the membrane. Ion-membrane interactions also lead to concentration-dependent and cation-specific behavior of the electrostatic potential in the intracellular region because of the negative charge on the inner leaflet. In addition, water permeation across the membrane was observed on a timescale of approximately 100 ns. This study represents a step toward the modeling of realistic biological membranes at physiological conditions in intracellular and extracellular environments.
authors.affiliation: Institute of Organic Chemistry and Biochemistry, Academy of Sciences of Czech Republic, and Center for Biomolecules and Complex Molecular Systems, 16610 Prague 6, Czech Republic. robert.vacha@uochb.cas.cz
authors.forename: Robert
authors.initials: R
authors.lastname: Vácha
authors.forename: Max L
authors.initials: ML
authors.lastname: Berkowitz
authors.forename: Pavel
authors.initials: P
authors.lastname: Jungwirth
mesh_terms: D002462:Cell Membrane / Q000737:chemistry*; D002463:Cell Membrane Permeability; D003198:Computer Simulation; D008567:Membranes, Artificial; D008956:Models, Chemical; D010713:Phosphatidylcholines / Q000737:chemistry; D010714:Phosphatidylethanolamines / Q000737:chemistry; D010718:Phosphatidylserines / Q000737:chemistry; D011188:Potassium / Q000737:chemistry*; D011189:Potassium Chloride / Q000737:chemistry; D012964:Sodium / Q000737:chemistry*; D012965:Sodium Chloride / Q000737:chemistry; D013109:Sphingomyelins / Q000737:chemistry; D055672:Static Electricity; D013997:Time Factors; D014867:Water / Q000737:chemistry*
chemical_list: D008567:Membranes, Artificial; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D010718:Phosphatidylserines; D013109:Sphingomyelins; C033171:palmitoylsphingomyelin; D014867:Water; C057561:1-palmitoyl-2-oleoylphosphatidylethanolamine; C050294:1-palmitoyl-2-oleoylglycero-3-phosphoserine; D012965:Sodium Chloride; D011189:Potassium Chloride; D012964:Sodium; D011188:Potassium; C028694:1-palmitoyl-2-oleoylphosphatidylcholine