Vácha Robert, Berkowitz Max L, Jungwirth Pavel
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.
Biophys J. 2009 Jun 3;96(11):4493-501. doi: 10.1016/j.bpj.2009.03.010.
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.
我们展示了在氯化钠和氯化钾混合水溶液中多组分不对称双层的分子动力学模拟。由于系统的几何结构，我们的模拟中有两个水溶液区域：一个模拟细胞内区域，另一个模拟细胞外区域。离子特异性效应在膜/水溶液界面处很明显。也就是说，在钠和钾浓度相等时，钠离子更强烈地吸附到脂质头部基团的羰基上。为了使这种离子超过膜上的钠含量，需要显著过量的钾浓度。由于内膜层上的负电荷，离子-膜相互作用还导致细胞内区域静电势的浓度依赖性和阳离子特异性行为。此外，在大约100纳秒的时间尺度上观察到了水透过膜的现象。这项研究朝着在细胞内和细胞外环境的生理条件下对真实生物膜进行建模迈出了一步。
