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Abstract：
We present a method to probe molecular and nanoparticle diffusion within thin, solvated polymer coatings. The device exploits the confinement with well-defined geometry that forms at the interface between a planar and a hemispherical surface (of which at least one is coated with polymers) in close contact and uses this confinement to analyze diffusion processes without interference of exchange with and diffusion in the bulk solution. With this method, which we call plane-sphere confinement microscopy (PSCM), information regarding the partitioning of molecules between the polymer coating and the bulk liquid is also obtained. Thanks to the shape of the confined geometry, diffusion and partitioning can be mapped as a function of compression and concentration of the coating in a single experiment. The method is versatile and can be integrated with conventional optical microscopes; thus it should find widespread use in the many application areas exploiting functional polymer coatings. We demonstrate the use of PSCM using brushes of natively unfolded nucleoporin domains rich in phenylalanine-glycine repeats (FG domains). A meshwork of FG domains is known to be responsible for the selective transport of nuclear transport receptors (NTRs) and their macromolecular cargos across the nuclear envelope that separates the cytosol and the nucleus of living cells. We find that the selectivity of NTR uptake by FG domain films depends sensitively on FG domain concentration and that the interaction of NTRs with FG domains obstructs NTR movement only moderately. These observations contribute important information to better understand the mechanisms of selective NTR transport.
摘要：
我们提出了一种探测分子和纳米颗粒扩散的方法，溶剂化聚合物涂层。该装置利用在紧密接触的平面和半球形表面(其中至少一个用聚合物涂覆)之间的界面处形成的具有明确定义的几何形状的限制,并使用该限制来分析扩散过程,而不干扰与本体溶液的交换和扩散。使用这种方法，我们称之为平面球约束显微镜（PSCM），还获得了关于聚合物涂层和本体液体之间的分子分配的信息。由于有限的几何形状，在单个实验中，扩散和分配可以映射为涂层的压缩和浓度的函数。该方法是通用的并且可以与常规光学显微镜集成;因此它应该在利用功能性聚合物涂层的许多应用领域中得到广泛使用。我们使用富含苯丙氨酸-甘氨酸重复序列（FG结构域）的天然未折叠的核孔蛋白结构域的刷证明了PSCM的使用。已知FG结构域的网状结构负责核转运受体（NTRs）及其大分子货物穿过分离胞质溶胶和活细胞核的核膜的选择性转运。我们发现，FG结构域膜对NTR吸收的选择性敏感地取决于FG结构域浓度，并且NTR与FG结构域的相互作用仅适度地阻碍了NTR的运动。这些观察结果为更好地理解选择性NTR转运的机制提供了重要信息。
