细胞膜表面电势影响下的重金属与植物根表质膜模型相互作用的分子动力学研究

The root plasma membrane surface potential plays an important role in controlling the adsorption and uptake of heavy metal ions by plant roots, which further accounts for the phytotoxicity of heavy metals. Based on our previous work of developing forcefield for water-soil mineral interface, we propose to develop a consistent polarizable forcefield to accurately describe the interactions of heavy metal ions at the interface of soil solution and plant root plasma membrane(PM). The interactions and binding constants between heavy metals and composites of lipids/ metal binding domain(MBD) of heavy metal transporter proteins under different membrane surface potential will be evaluated by the forcefield and calibrated by NMR and potentiometric titration experiments. The relationship between lipid membrane surface potential and the distribution and adsorption of heavy metals will be elucidated by comparing the ion distributions near the MBD sites on PM calculated from molecular dynamics and the classic Gouy-Chapman-Stern(GCS) electric double layer model(EDL). Systematic studies on the effects of common ions in soil solutions on the membrane surface potential and the adsorption of heavy metals will be taken to further improve GCS model. This study aims to reveal the impact of surface potential on the dynamic properties of heavy metals at the interface between the soil solution and plant root PM at molecular level, and the results from this study will be beneficial towards a better understanding of molecular mechanisms of the transport and uptake of heavy metals by plant root，and provide scientific basis for bioavailability assessments of heavy metals in soils.

细胞膜表面电势对重金属离子在植物根表质膜表面分布、吸收和毒性产生重要的影响。建立重金属-细胞膜分子模型对从分子水平上研究膜表面电势影响下植物重金属吸收规律有重大意义。本研究拟在前期已建立的水-土壤界面分子力场的基础上，开发质膜体系自洽的重金属极化分子力场，建立重金属水-复合体质膜界面分子动力学平台，模拟膜表面电势的影响下重金属在不同电性混合磷脂，磷脂/离子通道MBD区表面的吸附特征和结合强度；与NMR和电位滴定等实验手段相结合，从分子水平上扩充和完善经典GCS模型对重金属与质膜的相互作用的描述，阐明膜表面电势影响重金属在植物根表质膜界面上分布的分子机制；揭示重金属在土壤溶液—植物界面分子水平的迁移规律；为理解和预测重金属在土壤溶液-植物根表界面的迁移和吸收规律，建立量化重金属植物效应的提供重要的依据。

我们按照研究计划，开展了本基金项目的各项研究内容，目前已按计划完成了本基金项目的预期目标。在本基金的资助下，我们共发表科研SCI论文2篇，另有2篇论文在在准备中，完成了本基金预期的成果产出。取得了主要研究成果如下：基于量子化学计算生成了描述重金属在水-质膜界面的分子力场；成功构建复杂质膜/离子通道蛋白MBD多肽片段结构模型，研究溶液化学对重金属在质膜表面吸附的规律，成功地预测了Cd2+, Cu2+等不同类型重金属在质膜表面电势的影响下在混合磷脂的吸附特征和结合强度；与电位滴定等实验手段相结合，从分子水平上扩充和完善了经典GSC模型对重金属与质膜相互作用的定量描述。