Department of Biomedical Engineering, Department of Chemistry, and Chemistry of Life Processes Institute, Northwestern University, Evanston, Illinois 60208, United States.
Institute of Systems and Physical Biology, Shenzhen Bay Laboratory, Shenzhen 518107, China.
ACS Nano. 2021 Nov 23;15(11):17678-17688. doi: 10.1021/acsnano.1c05543. Epub 2021 Oct 28.
Molecular organizations and charge patterns inside biological nanopores are optimized by evolution to enhance ionic and molecular transport. Inspired by the nuclear pore complex that employs asymmetrically arranged disordered proteins for its gating, we here design an artificial nanopore coated by an asymmetric polyampholyte brush as a model system to study the asymmetric mass transport under nanoconfinement. A nonequilibrium steady-state molecular theory is developed to account for the intricate charge regulation effect of the weak polyampholyte and to address the coupling between the polymer conformation and the external electric field. On the basis of this state-of-the-art theoretical method, we present a comprehensive theoretical description of the stimuli-responsive structural behaviors and transport properties inside the nanopore with all molecular details considered. Our model demonstrates that by incorporating a gradient of pH sensitivity into the polymer coatings of the nanopore, a variety of asymmetric charge patterns and functional structures can be achieved, in a pH-responsive manner that allows for multiple functions to be implemented into the designed system. The asymmetric charge pattern inside the nanopore leads to an electrostatic trap for major current carriers, which turns the nanopore into an ionic rectifier with a rectification factor above 1000 at optimized pH and salt concentration. Our theory further predicts that the nanopore design behaves like a double-gated nanofluidic device with pH-triggered opening of the gates, which can serve as an ion pump and pH-responsive molecular filter. These results deepen our understanding of asymmetric transport in nanoconfined systems and provide guidelines for designing polymer-coated smart nanopores.
生物纳米孔内的分子组织和电荷模式是通过进化优化的，以增强离子和分子的传输。受核孔复合体利用排列不对称的无序蛋白质进行门控的启发，我们设计了一种人工纳米孔，其表面涂有不对称的聚两性电解质刷，作为一个模型系统来研究纳米受限下的不对称质量传输。我们开发了一个非平衡稳态分子理论，以解释弱聚两性电解质复杂的电荷调节效应，并解决聚合物构象和外电场之间的耦合。基于这种最先进的理论方法，我们提出了一个全面的理论描述，包括纳米孔内的刺激响应结构行为和传输特性，同时考虑了所有的分子细节。我们的模型表明，通过在纳米孔的聚合物涂层中引入 pH 敏感性梯度，可以实现多种不对称电荷模式和功能结构，以 pH 响应的方式将多种功能集成到设计系统中。纳米孔内的不对称电荷模式为主要电流载体形成静电陷阱，使纳米孔成为离子整流器，在优化的 pH 值和盐浓度下，整流因子超过 1000。我们的理论进一步预测，纳米孔设计类似于具有 pH 触发门控的双门控纳流控装置，可以作为离子泵和 pH 响应分子过滤器。这些结果加深了我们对纳米受限系统中不对称传输的理解，并为设计聚合物涂层智能纳米孔提供了指导。
