金属离子-质膜相互作用的分子动力学模拟研究

Molecular dynamics simulation of metal ion-lipid bilayer interactions

为研究植物根表质膜与土壤溶液界面上的双电层结构对金属离子在质膜上吸附以及吸收的影响,从分子水平探讨质膜表面电势下金属离子与质膜的相互作用,建立了质膜与金属溶液的界面模型,采用分子动力学方法模拟了质膜界面K^+、Na^+、Ca^2+、Mg^2+等碱/碱土金属阳离子与Cu^2+、Cd^2+等重金属离子的结合与分布过程。通过对吸附构型、浓度分布等统计分析,发现阳离子在质膜表面主要与质膜头部的羰基和磷酸基团等极性基团结合;二价阳离子吸附作用比一价阳离子更为强烈,并造成质膜表面电势的反转,直接控制着扩散层中离子的分布特征。分子动力学模拟结果与描述界面双电层结构的Gouy-Chapman-Stern(GCS)经典理论很好地吻合,可以从分子水平预测和解释金属阳离子与质膜相互作用的动态过程。

The electric double layer at the soil solution-plant root membrane interface plays an important role in adsorption and uptake of metal ions.Molecular level investigation on the interaction between metal ions and root plasma membrane under the surface potential of membrane was conducted using molecular dynamics(MD)simulation of a model lipid bilayer equilibrating with different electrolyte solutions including K^+,Na^+,Ca^2+,Mg^2+,and heavy metals such as Cu^2+,Cd^2+.Statistical analysis of simulation results,including adsorption con figurations and concentration profiles,revealed that cations mainly binded to the carbonyl and phosphate groups of lipids.The stronger binding for divalent cations than monovalent cations,especially divalent heavy metals,resulted in the sign changes of the surface potential which directly controlled the distribution of ions in the diffuse layer.The molecular dynamics simulation correctly predicted the distribution of ions consistent with the classical Gouy-Chapman-Stern(GCS)model of the electric double layer.We demonstrated that molecular dynamics simulation could quantitatively characterize the dynamic processes of metal ions binding and distribution at the surface of the membrane.