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>