Dias R S, Pais A A C C, Linse P, Miguel M G, Lindman B
Physical Chemistry 1, Center for Chemistry and Chemical Engineering, Lund University, P.O. Box 124, S-221 00 Lund, Sweden.
J Phys Chem B. 2005 Jun 16;109(23):11781-8. doi: 10.1021/jp050158b.
The adsorption of a single and negatively charged polyion with varying flexibility onto a surface carrying both negative and positive charges representing a charged membrane surface has been investigated by using a simple model employing Monte Carlo simulations. The polyion was represented by a sequence of negatively charged hard spheres connected with harmonic bonds. The charged surface groups were also represented by charged hard spheres, and they were positioned on a hard surface slightly protruding into the solution. The surface charges were either frozen in a liquidlike structure or laterally mobile. With a large excess of positive surface charges, the classical picture of a strongly adsorbed polyion with an extended and flat configuration emerged. However, adsorption also appeared at a net neutral surface or at a weakly negatively charged surface, and at these conditions the adsorption was stronger with a flexible polyion as compared to a semiflexible one, two features not appearing in simpler models containing homogeneously charged surfaces. The presence of charged surface patches (frozen surface charges) and the ability of polarization of the surface charges (mobile surface charges) are the main reasons for the enhanced adsorption. The stronger adsorption with the flexible chain is caused by its greater ability to spatially correlate with the surface charges.
通过使用一个采用蒙特卡罗模拟的简单模型，研究了具有不同柔性的单个带负电荷的聚离子在代表带电膜表面的同时带有负电荷和正电荷的表面上的吸附情况。聚离子由一系列通过谐波键连接的带负电荷的硬球表示。带电表面基团也由带电硬球表示，它们位于略微伸入溶液的硬表面上。表面电荷要么固定在类似液体的结构中，要么可以横向移动。当正表面电荷大量过剩时，出现了具有伸展和平坦构型的强吸附聚离子的经典图像。然而，在净中性表面或弱带负电荷的表面上也会出现吸附，并且在这些条件下，与半柔性聚离子相比，柔性聚离子的吸附更强，这两个特征在包含均匀带电表面的更简单模型中不会出现。带电表面斑块（固定表面电荷）的存在以及表面电荷极化的能力（可移动表面电荷）是吸附增强的主要原因。柔性链更强的吸附是由其与表面电荷在空间上相关的能力更强所致。
