Wagner Alexander J, May Sylvio
Department of Physics, North Dakota State University, Fargo, ND 58105-5566, USA.
Eur Biophys J. 2007 Apr;36(4-5):293-303. doi: 10.1007/s00249-006-0089-z. Epub 2006 Sep 19.
We present theoretical work in which the degree of electrostatic coupling across a charged lipid bilayer in aqueous solution is analyzed on the basis of nonlinear Poisson-Boltzmann theory. In particular, we consider the electrostatic interaction of a single, large macroion with the two apposed leaflets of an oppositely charged lipid bilayer where the macroion is allowed to optimize its distance to the membrane. Three regimes are identified: a weak and a high macroion charge regime, separated by a regime of close macroion-membrane contact for intermediate charge densities. The corresponding free energies are used to estimate the degree of electrostatic coupling in a lamellar cationic lipid-DNA complex. That is, we calculate to what extent the one-dimensional DNA arrays in a sandwich-like lipoplex interact across the cationic membranes. We find that, in spite of the low dielectric constant inside a lipid membranes, there can be a significant electrostatic contribution to the experimentally observed cross-bilayer orientational ordering of the DNA arrays. Our approximate analytical model is complemented and supported by numerical calculations of the electrostatic potentials and free energies of the lamellar lipoplex geometry. To this end, we solve the nonlinear Poisson-Boltzmann equation within a unit cell of the lamellar lipoplex using a new lattice Boltzmann method.
我们展示了一项理论研究工作，其中基于非线性泊松 - 玻尔兹曼理论分析了水溶液中带电脂质双层间的静电耦合程度。具体而言，我们考虑单个大的大离子与带相反电荷的脂质双层的两个相对小叶之间的静电相互作用，其中大离子可以优化其与膜的距离。确定了三种情况：弱大离子电荷情况和高大离子电荷情况，中间电荷密度时存在大离子与膜紧密接触的情况将它们分隔开。相应的自由能用于估计层状阳离子脂质 - DNA复合物中的静电耦合程度。也就是说，我们计算夹心状脂质体复合物中一维DNA阵列在阳离子膜间相互作用的程度。我们发现，尽管脂质膜内部的介电常数较低，但对于实验观察到的DNA阵列跨双层的取向有序，静电作用仍可能有显著贡献。我们的近似解析模型通过对层状脂质体几何结构的静电势和自由能的数值计算得到补充和支持。为此，我们使用一种新的格子玻尔兹曼方法在层状脂质体的一个晶胞内求解非线性泊松 - 玻尔兹曼方程。
