A molecular switch is one of the simplest examples of artificial molecular machines. Even so, the development of molecular switches is still at its very early stage. Currently, building single-molecule switches mostly rely on the molecular junction technique, but many of their performance characteristics are device-dependent. Here, a pH-mediated single-molecule switch based on the combination of an α-hemolysin (αHL) nanopore and a hexacyclen-modified DNA strand is developed. The single-stranded DNA is suspended inside an αHL through biotin-streptavidin linkage and the hexacyclen-modified nucleobase interacts with amino acid residues at positions 111, 113, and 147 to cause current oscillations. Distinct current transitions are observed when pH is tuned back and forth in the range of 3.0–7.4, with a typical “up” level when pH > 6.5 and a “down” level when pH < 4.5. This nanopore-DNA complex possesses membrane-bound advantages and may find applications in single-cell studies where pH could be readily tuned to control ON-OFF functions.

中文翻译：

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用纳米孔-DNA 复合物构建 pH 介导的单分子开关

分子开关是人工分子机器最简单的例子之一。即便如此，分子开关的开发仍处于非常早期的阶段。目前，构建单分子开关主要依赖于分子结技术，但它们的许多性能特征都依赖于器件。在这里，开发了一种基于 α-溶血素 (αHL) 纳米孔和六环素修饰的 DNA 链组合的 pH 介导的单分子开关。单链 DNA 通过生物素-链霉亲和素键悬浮在 αHL 内，六环素修饰的核碱基与 111、113 和 147 位的氨基酸残基相互作用，引起电流振荡。当 pH 值在 3.0-7.4 范围内来回调整时，观察到不同的电流转换，当 pH > 6 时具有典型的“上升”水平。当 pH < 4.5 时为 5 和“下降”水平。这种纳米孔-DNA 复合物具有膜结合的优势，可能会在单细胞研究中找到应用，其中 pH 值可以很容易地调节以控制开关功能。