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arXiv 1407.3603cond-mat.softphysics.bio-ph
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离子溶液中带电脂双层的弹性和力学不稳定性

Elasticity and mechanical instability of charged lipid bilayers in ionic solutions

Yotam Y. Avital, Niels Grønbech-Jensen, Oded Farago

摘要:

我们使用粗粒度的蒙特卡罗模拟来研究一价和五价反离子溶液中带电膜的弹性性质。两种情况下的仿真结果显示出相反的趋势。抗弯刚度和投影面积的增加与膜电荷密度为单价抗衡离子,而五价离子的减少。这些观察结果可能与脂质电荷的计数器筛选有关。而单价抗衡离子仅弱屏蔽库仑相互作用,这意味着排斥库仑系统,多价抗衡离子凝聚在膜上,并通过空间电荷相关性,使有效的相互作用,由于带电的脂质吸引。在一价和多价反溶液中的带电膜的弹性性质的差异反映在导致它们在高电荷密度下的机械不稳定性的机制中。在前一种情况下,膜开发孔,以减轻静电拉伸应力,而在后一种情况下,膜表现出大的波长弯曲不稳定性。

英文摘要:

We use coarse-grained Monte Carlo simulations to study the elastic properties of charged membranes in solutions of monovalent and pentavalent counterions. The simulation results of the two cases reveal trends opposite to each other. The bending rigidity and projected area increase with the membrane charge density for monovalent counterions, while they decrease for the pentavalent ions. These observations can be related to the counterion screening of the lipid charges. While the monovalent counterions only weakly screen the Coulomb interactions, which implies a repulsive Coulomb system, the multivalent counterions condense on the membrane and, through spatial charge correlations, make the effective interactions due the charged lipids attractive. The differences in the elastic properties of the charged membranes in monovalent and multivalent counterion solutions are reflected in the mechanisms leading to their mechanical instability at high charge densities. In the former case, the membranes develop pores to relieve the electrostatic tensile stresses, while in the latter case, the membrane exhibit large wavelength bending instability.

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