Kinetics, statistics, and energetics of lipid membrane electroporation studied by molecular dynamics simulations
Kinetics, statistics, and energetics of lipid membrane electroporation studied by molecular dynamics simulations
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DOI：
10.1529/biophysj.108.129437
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发表时间：
2008-08-15
影响因子：
3.4
通讯作者：
Grubmueller, Helmut
中科院分区：
文献类型：
--
作者：
Boeckmann, Rainer A.;de Groot, Bert L.;Grubmueller, Helmut
膜电穿孔是将生物活性物质如药物和基因直接导入活细胞的方法，也是电融合的前一步。虽然已经从实验和模拟中获得了许多关于微观机制的信息，但可能的中间体的存在和性质仍然不清楚。为了阐明中间体的电孔形成的直接比较测得的prepore形成动力学，我们进行了49原子电穿孔模拟的棕榈酰-油酰-磷脂酰胆碱双层的电场强度在0.04和0.7 V/nm之间。一个统计理论的发展，以方便直接比较实验（宏观）prepore形成动力学与（单事件）preporation时间来自模拟，这也使我们能够提取有效数量的脂质参与每个孔形成事件。预孔形成的激活能对所施加的电场的线性依赖关系，实验和模拟之间的定量协议。制备时间的分布符合四态成孔模型。该模型涉及第一中间体，其特征在于两个小叶上的极性脂质头基的差分倾斜，和第二中间体（prepore），其中跨双层的极性链由3-4个脂质头基和几个水分子形成，从而提供了一个微观解释先前从测量的动力学导出的可极化体积。平均孔半径为0.47 +/- 0.15 nm，与脂质囊泡的电导测量和电光实验有利地一致。
Membrane electroporation is the method to directly transfer bioactive substances such as drugs and genes into living cells, as well as preceding electrofusion. Although much information on the microscopic mechanism has been obtained both from experiment and simulation, the existence and nature of possible intermediates is still unclear. To elucidate intermediates of electropore formation by direct comparison with measured prepore formation kinetics, we have carried out 49 atomistic electroporation simulations on a palmitoyl-oleoyl-phosphatidylcholine bilayer for electric field strengths between 0.04 and 0.7 V/nm. A statistical theory is developed to facilitate direct comparison of experimental (macroscopic) prepore formation kinetics with the (single event) preporation times derived from the simulations, which also allows us to extract an effective number of lipids involved in each pore formation event. A linear dependency of the activation energy for prepore formation on the applied field is seen, with quantitative agreement between experiment and simulation. The distribution of preporation times suggests a four-state pore formation model. The model involves a first intermediate characterized by a differential tilt of the polar lipid headgroups on both leaflets, and a second intermediate (prepore), where a polar chain across the bilayer is formed by 3-4 lipid headgroups and several water molecules, thereby providing a microscopic explanation for the polarizable volume derived previously from the measured kinetics. An average pore radius of 0.47 +/- 0.15 nm is seen, in favorable agreement with conductance measurements and electrooptical experiments of lipid vesicles.