Department of Theoretical Physics, Jožef Stefan Institute , 1000 Ljubljana, Slovenia.
School of Physical and Mathematical Sciences, Nanyang Technological University , 21 Nanyang Link, 637371 Singapore.
Langmuir. 2016 Dec 20;32(50):13546-13555. doi: 10.1021/acs.langmuir.6b03614. Epub 2016 Dec 8.
We have studied the electrostatic screening effect of NaCl solutions on the interactions between anionic lipid bilayers in the fluid lamellar phase using a Poisson-Boltzmann-based mean-field approach with constant charge and constant potential limiting charge regulation boundary conditions. The full DLVO potential, including the electrostatic, hydration and van der Waals interactions, was coupled to thermal bending fluctuations of the membranes via a variational Gaussian Ansatz. This allowed us to analyze the coupling between the osmotic pressure and the fluctuation amplitudes and compare them both simultaneously with their measured dependence on the bilayer separation, determined by the small-angle X-ray scattering experiments. High-structural resolution analysis of the scattering data revealed no significant changes of membrane structure as a function of salt concentration. Parsimonious description of our results is consistent with the constant charge limit of the general charge regulation phenomenology, with fully dissociated lipid charge groups, together with a 6-fold reduction of the membranes' bending rigidity upon increasing NaCl concentration.
我们使用基于泊松-玻尔兹曼的均场方法，通过恒电荷和恒电位限制电荷调节边界条件，研究了 NaCl 溶液对流体层状相中阴离子脂质双层相互作用的静电屏蔽效应。全 DLVO 势，包括静电、水合和范德华相互作用，通过变分高斯假设与膜的热弯曲波动耦合。这使我们能够分析渗透压和波动幅度之间的耦合，并同时将它们与通过小角度 X 射线散射实验确定的双层分离的测量依赖性进行比较。对散射数据的高结构分辨率分析表明，膜结构随盐浓度的变化没有明显变化。对我们结果的简约描述与一般电荷调节现象的恒电荷极限一致，脂质电荷基团完全解离，并且随着 NaCl 浓度的增加，膜的弯曲刚度降低 6 倍。
