To understand the relationships between channel size and ion selectivity, we have developed a new type of artificial ion channel based on pore-forming helical polymers consisting of phenanthroline-oxadiazole units with a pore aperture 2.3 Å close to the diameter of the Na⁺ ion (2.04 Å). Successful preparation of high molecular weight helical polymers ( HP1) gives rise to a 4.6 nm long artificial unimolecular transmembrane channel. The transport property of artificial channel HP1 was elaborately investigated by means of vesicle-based kinetic assay and symmetry/asymmetry bilayer membrane (BLM) experiments as well. These results unambiguously demonstrate that HP1 is a Na⁺-selective channel with extremely high transport activity (EC₅₀ = 0.017 mol % relative to lipid). Moreover, the Na⁺/K⁺ selectivity ratio of HP1 reaches 1.9, as determined by asymmetry BLM experiments. Owing to the narrowest 2.3 Å size constraint so far, HP1 transport naked Na⁺ ion across the membrane, which represents a different Na⁺ transport mode from that of natural Na⁺ channels, which transports partially hydrated Na⁺ ions during transmembrane conduction. This study provides crucial insights on the chemical basis of ion selectivity in the field of ion channels.

为了理解通道大小和离子选择性之间的关系，我们开发了一种新型人工离子通道，它基于由菲咯啉-恶二唑单元组成的成孔螺旋聚合物，孔径为 2.3 Å，接近 Na ⁺离子的直径（ 2.04 埃）。成功制备高分子量螺旋聚合物（ HP1) 产生了一个 4.6 nm 长的人工单分子跨膜通道。人工通道的传输特性 HP1还通过基于囊泡的动力学分析和对称/不对称双层膜 (BLM) 实验对 进行了精心研究。这些结果明确表明 HP1是具有极高转运活性的 Na ⁺选择性通道（EC ₅₀  = 0.017 mol % 相对于脂质）。此外，Na ⁺ /K ⁺选择性比为 HP1达到 1.9，由不对称 BLM 实验确定。由于迄今为止最窄的 2.3 Å 尺寸限制， HP1将裸 Na ⁺离子跨膜运输，这代表了与天然 Na ⁺通道不同的 Na ⁺运输模式，后者在跨膜传导过程中运输部分水合的 Na ⁺离子。这项研究为离子通道领域中离子选择性的化学基础提供了重要的见解。