School of Physical Sciences, University of California , Irvine, California 92697, United States.
J Am Chem Soc. 2014 Jul 16;136(28):9902-5. doi: 10.1021/ja505302q. Epub 2014 Jul 3.
Biological channels embedded in cell membranes regulate ionic transport by responding to external stimuli such as pH, voltage, and molecular binding. Mimicking the gating properties of these biological structures would be instrumental in the preparation of smart membranes used in biosensing, drug delivery, and ionic circuit construction. Here we present a new concept for building synthetic nanopores that can simultaneously respond to pH and transmembrane potential changes. DNA oligomers containing protonatable A and C bases are attached at the narrow opening of an asymmetric nanopore. Lowering the pH to 5.5 causes the positively charged DNA molecules to bind to other strands with negative backbones, thereby creating an electrostatic mesh that closes the pore to unprecedentedly high resistances of several tens of gigaohms. At neutral pH values, voltage switching causes the isolated DNA strands to undergo nanomechanical movement, as seen by a reversible current modulation. We provide evidence that the pH-dependent reversible closing mechanism is robust and applicable for nanopores with opening diameters of up to 14 nm. The concept of creating an electrostatic mesh may also be applied to different organic polymers.
生物通道嵌入细胞膜中，通过响应外部刺激（如 pH 值、电压和分子结合）来调节离子传输。模拟这些生物结构的门控特性对于制备用于生物传感、药物输送和离子电路构建的智能膜至关重要。在这里，我们提出了一种构建能够同时响应 pH 值和跨膜电位变化的合成纳米孔的新概念。在不对称纳米孔的狭窄开口处连接含有可质子化的 A 和 C 碱基的 DNA 寡核苷酸。将 pH 值降低到 5.5 会导致带正电荷的 DNA 分子与带负电的骨架上的其他链结合，从而形成一个静电网格，将孔径封闭到前所未有的几十千兆欧姆的高电阻。在中性 pH 值下，电压切换会导致孤立的 DNA 链发生纳米力学运动，这可以通过可反转的电流调制观察到。我们提供的证据表明，这种 pH 依赖性的可反转关闭机制是稳健的，适用于孔径最大可达 14nm 的纳米孔。创建静电网格的概念也可能适用于不同的有机聚合物。
