Triply responsive control of ion transport with an artificial channel creates a switchable AND to OR logic gate

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Abstract

Ion channels are ubiquitous in Nature, performing complex and essential tasks in our bodies. Synthetic chemists have begun to understand how to form artificial channels, which hold great promise as components in artificial cells, and in synthetic biology more widely. Future generations of these systems will be critical in the treatment of channelopathies. Despite advances in synthetic ion transporters, the current generation cannot approach the selectivity and controllability of the biological ion channels they seek to emulate, and multimodal control over activity remains hard to achieve. Herein, we present a synthetic ion channel whose activity can be controlled by three orthogonal stimuli (light, pH, guest/ligand), based on a pillar[5]arene functionalized with photoswitchable ortho-tetrafluoroazobenzene moieties. We demonstrate excellent control over ten photoswitches (E-to-Z 82%, Z-to-E quant.). We show that the most active Z-isomer forms dimeric ion channels in membranes. Single molecule planar bilayer conductance studies show high and low conductance states dependent on irradiation wavelength. We demonstrate that this activity can be modulated over 170-fold by controlling pH, irradiation, and guest addition. We use these three stimuli to design a pH switchable AND to OR logic gate system, creating a powerful addition to the canon of synthetic ion channels.