Institute of Complex Systems, ICS-2, Forschungszentrum Jülich, 52425 Jülich, Germany.
Biopolymers. 2012 May;97(5):311-7. doi: 10.1002/bip.22023. Epub 2012 Jan 12.
We explore the properties of adsorption of flexible polyelectrolyte chains in confined spaces between the oppositely charged surfaces in three basic geometries. A method of approximate uniformly valid solutions for the Green function equation for the eigenfunctions of polymer density distributions is developed to rationalize the critical adsorption conditions. The same approach was implemented in our recent study for the "inverse" problem of polyelectrolyte adsorption onto a planar surface, and on the outer surface of rod-like and spherical obstacles. For the three adsorption geometries investigated, the theory yields simple scaling relations for the minimal surface charge density that triggers the chain adsorption, as a function of the Debye screening length and surface curvature. The encapsulation of polyelectrolytes is governed by interplay of the electrostatic attraction energy toward the adsorbing surface and entropic repulsion of the chain squeezed into a thin slit or small cavities. Under the conditions of surface-mediated confinement, substantially larger polymer linear charge densities are required to adsorb a polyelectrolyte inside a charged spherical cavity, relative to a cylindrical pore and to a planar slit (at the same interfacial surface charge density). Possible biological implications are discussed briefly in the end.
我们探索了在三种基本几何形状中带相反电荷的表面之间的受限空间中柔性聚电解质链的吸附特性。为了推导出临界吸附条件，我们开发了一种用于聚合物密度分布本征函数格林函数方程的近似均匀有效解的方法。这种方法在我们最近的研究中也被应用于聚电解质在平面表面上的“反”吸附问题，以及棒状和球状障碍物的外表面上的吸附问题。对于所研究的三种吸附几何形状，该理论给出了引发链吸附的最小表面电荷密度的简单标度关系，这是作为德拜屏蔽长度和表面曲率的函数。聚电解质的封装由朝向吸附表面的静电吸引能与链的熵排斥之间的相互作用控制，该链被挤压在薄缝或小空腔中。在表面介导的限制条件下，与圆柱形孔和平面狭缝（在相同的界面表面电荷密度下）相比，在带电荷的球形腔体内吸附聚电解质需要更大的聚合物线电荷密度。最后简要讨论了可能的生物学意义。
