Carnie S, McLaughlin S
Biophys J. 1983 Dec;44(3):325-32. doi: 10.1016/S0006-3495(83)84306-9.
We have extended the Gouy-Chapman theory of the electrostatic diffuse double layer by considering the finite size of divalent cations in the aqueous phase adjacent to a charged surface. The divalent cations are modeled as either two point charges connected by an infinitely thin, rigid "rod" or two noninteracting point charges connected by an infinitely thin, flexible "string." We use the extended theory to predict the effects of a cation of length 10 A (1 nm) on the zeta and surface potentials of phospholipid bilayer membranes. The predictions of the rod and string models are similar to one another but differ markedly from the predictions of the Gouy-Chapman theory. Specifically, the extended model predicts that a large divalent cation will have a smaller effect on the potential adjacent to a negatively charged bilayer membrane than a point divalent cation, that the magnitude of this discrepancy will decrease as the Debye length increases, and that a large divalent cation will produce a negative zeta potential on a membrane formed from zwitterionic lipids. These predictions agree qualitatively with the experimental results obtained with the large divalent cation hexamethonium. We discuss the biological relevance of our calculations in the context of the interaction of cationic drugs with receptor sites on cell membranes.
我们通过考虑与带电表面相邻的水相中二价阳离子的有限尺寸，扩展了古依-查普曼静电扩散双电层理论。二价阳离子被建模为通过无限细的刚性“杆”连接的两个点电荷，或者通过无限细的柔性“线”连接的两个非相互作用点电荷。我们使用扩展理论来预测长度为10埃（1纳米）的阳离子对磷脂双分子层膜的zeta电位和表面电位的影响。杆模型和线模型的预测彼此相似，但与古依-查普曼理论的预测明显不同。具体而言，扩展模型预测，与点二价阳离子相比，大的二价阳离子对带负电的双分子层膜附近电位的影响较小，这种差异的幅度将随着德拜长度的增加而减小，并且大的二价阳离子将在由两性离子脂质形成的膜上产生负的zeta电位。这些预测与用大二价阳离子六甲铵获得的实验结果在定性上一致。我们在阳离子药物与细胞膜上受体位点相互作用的背景下讨论了我们计算的生物学相关性。
