A Controllable Photoresponsive Potassium Transporter

<b>Artificial photoresponsive transport systems are particularly intriguing because they offer the potential for precise spatio-temporal control, rapid response times and minimal toxicity associated with the light. We report here a controllable, photoresponsive, ion-transporting carrier, achieving controllability through a photoregulated</b><b> </b><b><i>β</i></b><b>-cyclodextrin (</b><b><i>β</i></b><b>-CD)-azobenzene host-guest complex. In this complex, a lipid-anchored</b><b> </b><b><i>β</i></b><b>-CD serves as the launch base, tightly immobilizing through host-guest interactions the otherwise freely moving trans-transporter derived from a crown ether-modified trans-azobenzene motif, but rapidly releasing most of it upon 365 nm UV irradiation that converts transporter to its cis-configuration. The launched cis-transporter functions well as a highly efficient potassium transporter, delivering a low EC</b>_{<strong>50</strong>}<b> </b><b>value of 1.51 μM and a drastic transport activity enhancement by ~ 400% relative to the base-bound trans-transporter (EC</b>_{<strong>50</strong>}<b> </b><b>= 7.46 μM), with on-off activities repeatedly regulated by light. In the absence of the base, the on-off activities between cis- and trans-transporters however differ by only 80% (1.35 μM vs 2.45 μM).</b>

人工光响应传输系统极具研究价值，其可实现精准的时空调控、快速响应特性，且光引发的生物毒性极低。本文报道了一种可调控的光响应型离子传输载体，其可控性依托光调控的β-环糊精（β-cyclodextrin，β-CD）-偶氮苯主客体复合物实现。在该复合物中，脂质锚定的β-CD作为触发基底，通过主客体相互作用牢牢固定原本可自由移动的、源自冠醚修饰反式偶氮苯结构基元的反式转运体；但当经365 nm紫外照射将转运体转化为顺式构型时，大部分转运体将被快速释放。被触发释放的顺式转运体可作为高效的钾离子转运体发挥作用，其半数有效浓度（EC₅₀）仅为1.51 μM，相较于基底结合的反式转运体（EC₅₀ = 7.46 μM），转运活性显著提升约400%，且其开关活性可通过光重复调控。而在无基底存在的情况下，顺式与反式转运体之间的活性差异仅为80%（1.35 μM 对比 2.45 μM）。